Дисертації з теми "Coefficient of resistance"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Coefficient of resistance.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Coefficient of resistance".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Seo, Scott Y. "Development of techniques to determine temperature coefficient of resistance." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123270.
Анотація:
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (page 27).
The focus of this thesis was to develop a simple, repeatable method for characterizing the relationship of different materials' electrical resistance with respect to temperature. A measurement of this relationship is the temperature coefficient of resistance (TCR). Determining the TCR allows a material to be used as a temperature probe and can be utilized in thermal conductivity measurements. The test apparatus and measurement setup proved capable of determining the temperature coefficients of resistance of a copper-alloy wire and a carbon film resistor, giving TCR values of 0.0036 1/K and -0.00014 1/K, which was consistent with their published values. The work of this project aims to aid in the development of a micro-cooling system, which uses polycarbonate for its heat exchanger at cryogenic temperatures. A potential carbon film temperature probe was tested, but was found to be unfit for the intended use as a temperature probe on a polycarbonate surface due to catastrophic failures in the film, most likely caused by the different thermal expansion rates of the carbon and polycarbonate. Further research should be conducted to first find a more suitable temperature probe for polycarbonate and then conduct tests at cryogenic temperatures.
by Scott Y. Seo.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering
2
Liu, Gengshen. "Measurement of ship resistance coefficient from simple trials during a regular voyage." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14391.
3
Griškevičius, Mečislavas. "High Temperature Effect On Resistance Of Timber Structures." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101119_134602-29128.
Анотація:
The present dissertation and its main subjects inquires into the pine and oak timber strength property changes-temperature relations. It also explores the behaviour of slender timber elements in axial compression at higher temperatures; and the comparative analysis of obtained results.
The work seeks to accomplish the following major tasks: to obtain test data about the influence of high temperature on the properties of different natural – pine and oak – timber; to investigate the behaviour of slender timber elements under axial compression exposed to fire. Taking into account the investigated real fire effect to correct accordingly the existing in LST EN 1995-1-2 procedure for the fire resistance calculation of timber slender elements in compression.
The dissertation consists of an introduction, five chapters, general conclusions, a list of references, a list of author’s publications on the dissertation subject, and 2 Annexes.
Chapter 1 provides a literature review. It focuses on the publications inquiring into the loss of strength properties by timber at higher temperatures, the fire resistance of timber structures in compression. The chapter ends with the formulation of conclusions and the adjustment of research tasks.
Chapter 2 offers the methodology of the research on strength properties of timber at higher temperatures, and the schemes of the developed testing equipment.
Chapter 3 presents the procedure of the research on the behaviour of slender timber elements... [to full text]Disertacijoje nagrinėjami pušinės ir ąžuolinės medienos stipruminių savybių pokyčių temperatūriniai sąryšiai bei medinių centriškai gniuždomų liaunų elementų elgsena veikiant aukštesnėms temperatūroms. Pagrindiniai tyrimo objektai yra Lietuvos spygliuočių ir lapuočių medienos savybių pokyčiai didėjant temperatūrai ir centriškai gniuždomų liaunų medinių elementų elgsenos veikiant kaitrai eksperimentiniai tyrimai bei rezultatų lyginamoji analizė. Darbe spręsti tokie pagrindiniai uždaviniai: gauti eksperimentinius duomenis apie aukštos temperatūros poveikį skirtingos natūralios – pušinės ir ąžuolinės – medienos savybėms, atlikti centriškai gniuždomų liaunų medinių elementų elgsenos ugnyje tyrimus. Atsižvelgiant į tyrinėtą tikrovišką gaisro poveikį patikslinti esamą EN 1995-1-2 medinių liaunų gniuždomų elementų atsparumo ugniai skaičiavimo metodiką. Disertaciją sudaro įvadas, penki skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai ir du priedai. Pirmasis skyrius skirtas literatūros apžvalgai. Jame pateikta darbų, kuriuose nagrinėjamas aukštesnės temperatūros veikiamos medienos, stipruminių savybių mažėjimas ir kuriuose pateikiami gaisro sąlygomis gniuždomų medinių elementų laikomosios galios tyrimų rezultatai. Pabaigoje formuluotos išvados ir disertacijos tikslai ir uždaviniai. Antrajame skyriuje pateikta medienos stipruminių savybių aukštesnėse temperatūrose tyrimo metodika ir sukurtų nestandartinių bandymo įrenginių schemos... [toliau žr. visą tekstą]
4
LaBranche, Adrienne Janel. "Creeping Bentgrass, Kentucky Bluegrass and Tall Fescue Responses to Plant Growth Stimulants Under Deficit Irrigation." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/32000.
Анотація:
A four-year drought, increasing population and shifting climate has spurred water conservation practices within Virginia. Creeping bentgrass (Agrostis palustris â L93â ), Kentucky bluegrass (Poa pratensis â Midnightâ ), and tall fescue (Festuca arundinacea) Dominion blend were evaluated under deficit irrigation and upon exogenous application of plant growth stimulants (PGS), seaweed extract (SWE) + humic acid (HA), glycinebetaine (GB) and a commercial SWE product (PP). The objectives were to determine crop coefficients (Kc) for creeping bentgrass fairways and tall fescue home lawns, to determine if PGS application allowed for more water conservation, and to determine if they impacted physiological function and/or root morphology.
A preliminary greenhouse experiment was conducted with creeping bentgrass and Kentucky bluegrass irrigated with 100%, 85% and 70% of evapotranspiration (ET). The study determined that an additional deficit irrigation level should be included for the field study and that GB application and 100% and 85% ET irrigation level produced the greatest creeping bentgrass root mass.
The two â year field study evaluated creeping bentgrass and tall fescue. Tall fescue home lawns could be irrigated every five days with a Kc of 0.55 or once a week with a Kc of 0.70. Creeping bentgrass fairways could be irrigated every four days with a Kc of 0.85. Glycinebetaine application increased bentgrass rooting after planting and showed osmoprotectant properties.
Another greenhouse study evaluated five GB rates on bentgrass and tall fescue. No differences were found between the five rates and concluded that the rate utilized in the field study may be appropriate for turfgrass application.Master of Science
5
Iyalla, Ibiyekariwaripiribo. "Computational fluid dynamics modelling of pipeline on-bottom stability." Thesis, Robert Gordon University, 2017. http://hdl.handle.net/10059/2721.
Анотація:
Subsea pipelines are subjected to wave and steady current loads which cause pipeline stability problems. Current knowledge and understanding on the pipeline on-bottom stability is based on the research programmes from the 1980’s such as the Pipeline Stability Design Project (PIPESTAB) and American Gas Association (AGA) in Joint Industry Project. These projects have mainly provided information regarding hydrodynamic loads on pipeline and soil resistance in isolation. In reality, the pipeline stability problem is much more complex involving hydrodynamic loadings, pipeline response, soil resistance, embedment and pipe-soil-fluid interaction. In this thesis Computational Fluid Dynamics (CFD) modelling is used to investigate and establish the interrelationship between fluid (hydrodynamics), pipe (subsea pipeline), and soil (seabed). The effect of soil types, soil resistance, soil porosity and soil unit weight on embedment was examined. The overall pipeline stability alongside pipeline diameter and weight and hydrodynamic effect on both soil (resulting in scouring) and pipeline was also investigated. The use of CFD provided a better understanding of the complex physical processes of fluid-pipe-soil interaction. The results show that the magnitude of passive resistance is on the average eight times that of lateral resistance. Thus passive resistance is of greater significance for subsea pipeline stability design hence the reason why Coulomb’s friction theory is considered as conservative for stability design analysis, as it ignores passive resistance and underestimates lateral resistance. Previous works (such as that carried out by Lyons and DNV) concluded that soil resistance should be determined by considering Coulomb’s friction based on lateral resistance and passive resistance due to pipeline embedment, but the significance of passive resistance in pipeline stability and its variation in sand and clay soils have not be established as shown in this thesis. The results for soil porosity show that increase in pipeline stability with increasing porosity is due to increased soil liquefaction which increases soil resistance. The pipe-soil interaction model by Wagner et al. established the effect of soil porosity on lateral soil resistance but did not attribute it to soil liquefaction. Results showed that the effect of pipeline diameter and weight vary with soil type; for sand, pipeline diameter showed a greater influence on embedment with a 110% increase in embedment (considering combined effect of diameter and weight) and a 65% decrease in embedment when normalised with diameter. While pipeline weight showed a greater influence on embedment in clay with a 410% increase. The work of Gao et al. did not completely establish the combined effect of pipeline diameter and weight and soil type on stability. Results also show that pipeline instability is due to a combination of pipeline displacement due to vortex shedding and scouring effect with increasing velocity. As scoring progresses, maximum embedment is reached at the point of highest velocity. The conclusion of this thesis is that designing for optimum subsea pipeline stability without adopting an overly conservative approach requires taking into consideration the following; combined effect of hydrodynamics of fluid flow on soil type and properties, and the pipeline, and the resultant scour effect leading to pipeline embedment. These results were validated against previous experimental and analytical work of Gao et al, Brennodden et al and Griffiths.
6
Milesi, Paul. "Interactions between waves and new generations of brakewaters with small footprint." Thesis, Ecole centrale de Marseille, 2019. http://www.theses.fr/2019ECDM0003/document.
Анотація:
De nos jours, le respect de l'environnement est une obligation dans le cadre de travaux maritimes. Les caissons en béton verticaux à plaques poreuses sont souvent la solution technique privilégiée pour agrandir les ports existants et / ou améliorer l'agitation des bassins. L'empreinte au sol est réduite et la demande en matériaux de carrière est moins importante par rapport aux digues en enrochement classiques. Récemment, des systèmes alternatifs aux caissons en béton verticaux ont été conçus. Les structures amortisseuses de la houle à enrochements verticalisés sont constituées d'une structure métallique entourant des blocs. Ce type de structure offre des avantages environnementaux, une perméabilité aux courants et une bonne performance hydrodynamique. Ce travail de thèse visait à développer un nouveau code 3D-BEM facile à utiliser et intégrant les écoulements en milieux poreux. Des géométries innovantes sont testées comme des gabions espacés avec une chambre d’expansion ou un mélange de plaques poreuses et de milieux poreux.La description des écoulements dans un milieu poreux est une question complexe. Navier-Stokes moyenné au sens de Reynolds (RANS) est le processus mathématique communément utilisé pour modéliser les écoulements en milieux poreux. Ce dernier est considéré comme un milieu continu homogène. L'équation bien connue de Forchheimer étendue décrit les forces volumiques appliquées à l'écoulement par un milieu poreux à travers des coefficients de résistance et d'inertie. Ces recherches ont été l’occasion d’examiner ces coefficients, notamment celui d'inertie mal connu dans le cas d’un milieu poreux. Il joue un rôle majeur pour les écoulements à très faible KC se produisant dans les couches internes des digues poreuses. Une analyse de la littérature sur les écoulements de milieux poreux a été entreprise. Le code numérique appelé Diffra3D a été développé. Il a ensuite été utilisé pour rechercher des coefficients de résistance de milieux poreux à l'aide de données provenant de trois campagnes expérimentales : un test de sloshing sur hexapode et deux études classiques de transmission/réflexion en canal à houle. Celles-ci ont également été l'occasion de tester et de calibrer le code. De nouvelles géométries de structures poreuses ont ensuite été testées expérimentalement et numériquement.Deux nouvelles valeurs de coefficients de résistance d'un milieu poreux sont proposées pour les écoulements à très faibles KC. Certaines caractéristiques intéressantes concernant le coefficient d'inertie CM d'un milieu poreux sont également développées. Ce sujet de recherche mériterait encore d’être approfondi pour tenter de trouver une ou plusieurs loi(s) empirique(s) décrivant l’évolution du coefficient d'inertie dans ce régime spécifique d’écoulement. Le code Diffra3D fonctionne de façon satisfaisante pour modéliser les écoulements en milieu poreux. Il est cependant limité aux vagues à faibles cambrures. Tout l'enjeu est de bien caractériser le milieu poreux étudié. L'utilisation de Diffra3D a permis de montrer que les structures poreuses verticales innovantes, telles que les gabions espacés, ont entièrement leur place en tant que digues amortisseuses de la houle respectueuses de l'environnement. Elles pourraient être couramment utilisées dans le futurNowadays the respect of the environment is an obligation in maritime works. Vertical concrete caissons with porous plates are often the number one technical solution to enlarge existing ports and/or to improve the agitation of the basins. The footprint is reduced and the demand in quarry materials is less important compared to classical riprap breakwaters. Recently, alternative systems to vertical concrete caissons have been designed. Vertical riprap breakwaters are made of a metal framework enclosing blocks. This kind of structure offers environmental benefits, permeability for currents and a good hydrodynamic performance. This thesis work looks at developing a new 3D-BEM code that is easy to use and integrates porous media. Innovative geometries are tested like spaced gabions with damping chamber or a mix of porous plates and porous media.Describing flows in porous media is an complex issue. Volume averaging method is the common mathematical process used to model porous media flows without drawing every grain of a porous medium. The well-known extended Forchheimer equation describes the volumetric forces applied to the flow by a porous medium through resistance and inertial coefficients. These researches were the occasion to look into this coefficients, especially the one of poorly understood inertia in the case of a porous medium. It plays a major role in very low-KC flows currently occurring in porous breakwaters apart from armour layer.First, a literature review on porous media flows was undertaken. In parallel, the numerical code called Diffra3D was produced. It was then used to look for resistance coefficients of porous media through data coming from three experimental campaigns : one sloshing test on hexapode and two classical reflection-transmission studies in a wave tank. These campaigns were also the occasion to test and calibrate the code. New geometries of porous structures were then tested experimentally and numerically. Two new values of resistance coefficients of a porous medium are proposed. Some interesting features concerning the inertia coefficient CM of a porous medium are also developed. In simulations, we observe that the hydrodynamic behaviour of porous structures in low-KC flows is very sensitive to the coefficient of inertia. This research topic would still deserve further studies in order to find empirical law(s) for the inertia coefficient of a porous medium. The code Diffra3D performs well to model porous media flows. However, it is limited to waves with low steepness. The challenge is to properly characterise the porous medium. This research has shown that innovative porous structures like spaced gabions have proven their place as environmentally-friendly damping breakwaters. They may be commonly used in the future
7
Hutama, Chapin. "Effect of Inclusion of Nanofibers on Rolling Resistance and Friction of Silicone Rubber." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1556118372072796.
8
Piskoř, Martin. "Konstrukce zařízení pro měření valivého odporu pneumatiky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254428.
Анотація:
The aim of this thesis is a construction concept of tyre rolling resistance measuring device. The first part deals with the rolling resistance. It describes its causes, its influential factors and it also includes rolling resistance identification methods. The second part deals with construction design of the rolling resistance measuring device itself. It contains stress analysis, and fatigue analyses as well. It includes selection of transducers used for tyre rolling resistance measuring and also measurement error analyses. The last part focuses on estimated financial requirements connected with producing and assembling the designed measuring device.
9
Pinheiro, Francisco NascÃlio. "Development of a New Prototype Thermal Desalination with Heat Recovery Triggered by Source Controlled of Electric Energy." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11517.
Анотація:
CoordenaÃÃo de AperfeiÃoamento de NÃvel SuperiorSolar thermal desalination plants operate with variable heat source, solar radiation, which complicates the identification of the influence of process variables and of the constructive geometric parameters. In operation, brackish or salt water is heated in a storage tank, where it evaporates and condenses on the walls of a lower metal tray (first stage) installed above the tank. By condensing, the steam transfers heat to the salt water of this first stage and the condensate is collected on the outside of the tank. This work aims to develop a new prototype desalination unit with thermal controllable operating parameters for operation in transient and steady states. In the prototype, the heating of the water to be desalinated is done by electrical resistance with controllable source, allowing the variation of the desired heating power. Sensors of the type PT-100 were installed, especially specified for the dimensions of the storage tank for measuring water temperature at different positions in the tank. The mass of water in the tank is measured by a precision balance. With the measurements, graphics of water temperature of the tank during the heating, the cooling and the steady state were constructed. Also, the Global Coefficient of Heat Transfer was measured for phases of heating, cooling and steady state. Finally, desalination was found by the electrical conductivity of the used water.
Dessalinizadores solares tÃrmicos operam com fonte variÃvel de calor, a radiaÃÃo solar, o que dificulta a identificaÃÃo da influÃncia das variÃveis de processo e dos parÃmetros geomÃtricos construtivos. Em seu funcionamento, Ãgua salobra ou salgada à aquecida em um tanque de armazenamento, onde evapora e condensa nas paredes inferiores de uma bandeja metÃlica (primeiro estÃgio) instalada acima do tanque. Ao condensar, o vapor transfere calor para a Ãgua salgada desse primeiro estÃgio e o condensado à coletado no exterior do tanque. O presente trabalho tem como objetivo o desenvolvimento de um novo protÃtipo de dessalinizador tÃrmico com parÃmetros operacionais controlÃveis para funcionamento em regimes transiente e permanente. No protÃtipo, o aquecimento da Ãgua a ser dessalinizada à feito por resistÃncia elÃtrica com fonte de tensÃo controlÃvel, permitindo a variaÃÃo desejÃvel da potÃncia de aquecimento. Foram instalados sensores do tipo PT-100, especialmente especificados para as dimensÃes do tanque de armazenamento, para mediÃÃes de temperaturas da Ãgua em diferentes posiÃÃes no tanque. A massa de Ãgua no tanque à medida por balanÃa de precisÃo. Com as mediÃÃes realizadas, foram construÃdos grÃficos de temperatura da Ãgua do tanque durante os regimes constante de aquecimento e resfriamento. Foi tambÃm medido o Coeficiente Global de TransferÃncia de Calor para as fases de aquecimento, regime permanente e resfriamento. Por fim, foi constatada a dessalinizaÃÃo por medidas de condutividade elÃtrica da Ãgua utilizada.
10
Nekulová, Pavla. "Součinitel tření povrchu vozovky a Skid Resistance Index." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226945.
Анотація:
This diploma thesis deals with the relation between the longitudinal friction coefficient dependence on measuring speed and the value of road surface macrotexture MPD. Results of longitudinal friction coefficient and value of MPD measurement on 73 sections are included in this thesis. The results were compared by regression analysis and its outcome was used for determination of formula that enable calculation of longitudinal friction coefficient for any operating speed when longitudinal friction coefficient for 60 km/h and value of macrotexture are known. The evaluation scale for skid resistance index (SRI) was also determined in this thesis. It could be used for evaluation of skid resistance independently of the type of device used for friction coefficient measurement.
11
Kuijpers, Stephan Robert. "Phonon wave-packet dynamics at modelled grain boundaries." Kyoto University, 2018. http://hdl.handle.net/2433/235089.
12
Ait, Hssaine Bouchra. "Spatialisation des flux d'énergie et d'eau : combinaison de la modélisation des échanges de surface-atmosphère et de la télédétection optique, thermique et micro-ondes." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30093.
Анотація:
Une estimation précise de l'évapotranspiration (ET) à grand échelle est une priorité pour comprendre les interactions sol-atmosphère, particulièrement dans les zones semi-arides. La télédétection fournit des informations très pertinentes à grande échelle pour alimenter les modèles d'ET. Généralement, trois variables dérivées de la télédétection sont utilisées pour déterminer la distribution spatiale de l'ET : l'humidité du sol en surface (SM) dérivée des données micro-ondes, la température de surface (LST) dérivée des données infrarouges thermiques et les indices de végétation (ou fraction de couvert fc,) issus des réflectances visible/proche infrarouge. Cependant, très peu d'études ont tenté de combiner les trois variables dans un même modèle ET. Dans ce contexte, l'objectif principal de cette thèse est d'améliorer l'estimation de l'ET en combinant la modélisation par télédétection optique /micro-ondes à multiples résolutions et la modélisation des échanges surface-atmosphère. Dans la première partie, le modèle de bilan d'énergie à double source (TSEB) basé sur les données de LST, fc et le coefficient de Priestley Taylor (αPT) qui relie l'ET au le rayonnement net est testé sur une zone hétérogène à Niamey, Niger (Wankama). Les prédictions du modèle en terme de flux de chaleur latente (LE) et sensible (H) sont comparées aux données acquises par un scintillomètre à grande ouverture (LAS) installé sur un transect d'environ 3,2 km couvrant trois types de végétation (mil, savane et jachère). Les résultats obtenus pour H et LE sont pertinents. Cependant, une surestimation des flux simulés à la fin de la saison est remarquée. Ce qui est principalement due à la valeur de αPT (fixé généralement à 1,26). Dans la 2ème partie, un nouveau modèle appelé TSEB-SM dérivé du formalisme TSEB a été développé en utilisant, en plus des données LST et fc, les données de SM comme une contrainte supplémentaire sur l'évaporation du sol. Une calibration innovante est proposée pour extraire trois paramètres clés : le coefficient de Priestley Taylor (αPT) et les paramètres (arss and, brss) de la résistance du sol. En pratique, arss et brss sont extraits à l'échelle saisonnière à partir des données SM et LST avec fc inférieur à un seuil donné fc,thres(fc,thres = 0.5), tandis que αPT est inversé à la échelle journalière à partir des données SM et LST pour fc> fc,thres. Le modèle TSEB-SM est testé sur une parcelle de blé inondée et 2 parcelles de blé irriguées en goutte-à-goutte en utilisant les données in-situ collectées lors de deux expériences expérimentales en 2002-2003 et en 2016-2017 dans le bassin versant du Tensift. L'insertion de la résistance du sol dans le modèle TSEB améliore l'estimation de l'évaporation du sol et, par conséquent, améliore la partition de l'ET. L'analyse de la série temporelle indique que αPT suit principalement la phénologie de la culture de blé, avec une valeur maximale correspondant au développement complet de la biomasse verte et une valeur minimale atteinte à la récolte. Finalement, TSEB-SM est appliqué à l'état réel en utilisant les données MODIS LST et fc à 1 km de résolution et les données SM issu de satellite SMOS (Soil Moisture and Ocean Salinity) désagrégées à l'aide d'un algorithme de désagrégation (DisPATCh) à 1 km de résolution. L'approche est validée sur une période de quatre ans (2014-2018) sur une parcelle de blé pluvial dans le bassin du Tensift, au Maroc. La parcelle a été semée pour la saison agricole 2014-2015 (S1), 2016-2017 (S2) et 2017-2018 (S3), alors qu'elle n'était pas labouré (sol nu) pendant la saison 2015-2016 (B1). La contrainte appliquée sur l'évaporation du sol en utilisant le SM dérivé des données SMOS est l'un des principaux facteurs de contrôle de la fraction évaporative, ce qui permet de déterminer avec plus de précision la partition LE/H. De plus, αPT inversé augmente après les événements pluvieux, suggérant un lien avec la disponibilité en eau du sol dans la zone racinaireA precise estimate of evapotranspiration (ET) at the landscape scale remains a priority to understand land-atmosphere-interactions, especially over semi-arid lands. Regarding data availability over large areas and at multiple scales, remote sensing observations provide very relevant information to feed ET models. Commonly, there are three main variables, derived from remote sensing, that can be used to determine the spatial distribution of ET: the surface (0-5 cm) soil moisture (SM) derived from microwave data, the land surface temperature (LST) derived from thermal infrared radiances and vegetation indices (or fractional vegetation cover fc) derived from visible/near infrared reflectances. However, very few studies have attempted to combine all three variables within a single ET model. In this context, the main objective of this thesis is to improve the estimation of ET by combining multi-resolution optical/microwave remote sensing and surface-atmosphere exchange modelling. In the first part, the thermal-based two-source energy balance (TSEB) model based on LST, fc and the Priestley Taylor (PT) coefficient (αPT) relating ET to the net radiation is tested over an heterogeneous watershed in Niamey, Niger (Wankama catchment). The model predictions of area-averaged latent (LE) and sensible (H) heat fluxes are compared to data acquired by a Large Aperture Scintillometer (LAS) set up over a transect about 3.2 km-long and spanning three vegetation types (millet, fallow and degraded shrubs). The results obtained for H and LE are relevant. However, an overestimation of simulated fluxes is recorded at the end of the season. This is mainly due to the fixed maximum value for αPT (generally set to 1.26). In the second part, a new model named TSEB-SM derived from the TSEB formalism is developed by using, in addition to LST and fc data, the near-surface SM as an extra constraint on soil evaporation. An innovative calibration procedure is proposed to retrieve three key parameters: the Priestley Taylor coefficient (αPT) and the parameters (arss and, brss) of a soil resistance formulation. In practice, arss and brss are retrieved at the seasonal time scale from SM and LST data with fc lower than a given threshold fc,thres(fc,thres is set to 0.5), while αPT is retrieved at the daily time scale from SM and LST data for fc> fc,thres. TSEB-SM model is tested over 1 flood- and 2 drip-irrigated wheat fields using in situ data collected during two field experiments in 2002-2003 and 2016-2017 in the Tensift watershed, central Morocco. The coupling of the soil resistance formulation with the TSEB formalism improves the estimation of soil evaporation, and consequently, improves the partitioning of ET. Analysis of the retrieved time series indicates that the daily αPT mainly follows the phenology of winter wheat crop with a maximum value coincident with the full development of green biomass and a minimum value reached at harvest. Finally, TSEB-SM is applied in real-life using 1 km resolution MODIS LST and fc data and the 1 km resolution SM data disaggregated from SMOS (Soil Moisture and Ocean Salinity) observations by using a disaggregation algorithm (DisPATCh). The approach is validated during a four-year period (2014-2018) over a rainfed wheat field in the Tensift basin, central Morocco. The field was seeded for the 2014-2015 (S1), 2016-2017 (S2) and 2017-2018 (S3) agricultural season, while it remained under bare soil conditions during the 2015-2016 (B1) wheat seasons. The constraint applied on the soil evaporation by using the SM derived from SMOS data is one of the main controlling factors of the evaporative fraction, which helps determine with more accuracy the LE/H partitioning. Moreover, the retrieved αPT increases after rainfall events, suggesting a relationship with the soil water availability in the root zone
13
Ondrák, Adam. "Program na výpočet tahových ztrát." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-449798.
Анотація:
This work deals with the creation of a program for calculating the tensile losses of an in-dustrial boiler. The work is divided into four parts. The first part of the thesis deals with a theoretical introduction to the issue of pressure losses. The second part deals with all equations and procedures by which the program was created, as well as the limitations and conditions of using a given type of equation. The third part consists of a sample calculation of pressure loss-es of a real boiler. Furthermore, in the third part, the correctness of the program function is checked, where the measured losses on the real device were compared with the losses calcu-lated by the program. The fourth part deals with the influence of the boiler's parameters on its pressure losses, where the individual losses were graphically represented and compared to determine the sensitivity analysis. The output of this work is a functional program that has been optimized for ease of use and requires almost no knowledge of the user.
14
Babenko, Maksims. "A Study of Heat Transfer at the Cavity-Polymer Interface in Microinjection Moulding. The effects of processing conditions, cavity surface roughness and polymer physical properties on the heat transfer coefficient." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14745.
Анотація:
This thesis investigates the cooling behaviour of polymers during the microinjection moulding process. The work included bespoke experimental mould design and manufacturing, material characterisation, infra-red temperature measurements, cooling analysis and cooling prediction using commercial simulation software. To measure surface temperature of the polymers, compounding of polypropylene and polystyrene with carbon black masterbatch was performed to make materials opaque for the IR camera. The effects of addition of carbon black masterbatch were analysed using differential scanning calorimetry and Fourier transform infrared spectroscopy. Sapphire windows formed part of the mould wall and allowed thermal measurements using an IR camera. They were laser machined on their inside surfaces to generate a range of finishes and structures. Their topographies were analysed using laser confocal microscope. The surface energy of sapphire windows was measured and compared to typical mould steel, employing a contact angle measurement technique and calculated using Owens-Wendt theory. A heating chamber was designed and manufactured to study spreading of polymer melts on sapphire and steel substrates. A design of experiments approach was taken to investigate the influence of surface finish and the main processing parameters on polymer cooling during microinjection moulding. Cooling curves were obtained over an area of 1.92 by 1.92 mm of the sapphire window. These experiments were conducted on the Battenfeld Microsystem 50 microinjection moulding machine. A simulation study of polymer cooling during the microinjection moulding process was performed using Moldflow software. Particular interest was paid to the effect of the values of the interfacial heat transfer coefficient (HTC) on the simulated cooling predictions. Predicted temperature curves were compared to experimentally obtained temperature distributions, to obtain HTC values valid for the material and processing parameters.
15
Erwe, Martin. "Testuppställning för uppmätning av rullmotstånd." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235840.
Анотація:
När en lastbil färdas på väg utsätts den för ett antal krafter. Däckens rullmotstånd utgör ungefär 36 till 60 % av färdmotståndet. Att kunna validera rullmotståndet vid egen testning är värdefullt för en fordonstillverkare som Scania. Däcktillverkare tillhandahåller en konstant rullmotståndskoefficient men det är oklart om den går att använda i beräkningar för Scanias testsetup.Provningen går ut på att undersöka om testuppställningen möjliggör uppmätning av däckens rullmotstånd på chassidynamometer med momentnav. För den experimentella delen av examensarbetet har en kvantitativ datainsamlingsmetod använts för vidare maskinell analys och manuellt utföra statistisk undersökning. Testdriven utveckling (TDD) har tillämpats för att utifrån testresultaten kunna arbeta iterativt.Vid testningen går rullmotståndskoefficienten upp, ner eller ligger stabilt. Detta beror på att Kistler (Kistler momentnav består av två fälgar som innehåller universalsensorer för att kunna mäta vridmoment) har elektrisk drift som korrelerar till spridning av uppmätt rullmotståndskoefficient. Kistler momentnav är inte repeterbart på grund av drift. Det är möjligt att kompensera för den elektriska driften i Kistler momentnav och beräkna rullmotståndskoefficienten baserat på sista analyspunkten från körningarna.Mätvärden från Kistler momentnav har spridning. Genom att beräkna medelvärde för rullmotståndskoefficienten fås bättre noggrannhet. Medelvärde indikerar att rullmotståndskoefficienten har inget eller litet hastighetsberoende.Det går att använda Kistler momentnav och chassidynamometer 2 som testuppställning för att mäta upp av däckens rullmotståndkoefficient. Det är möjligt för Scania att fortsätta använda denna testuppställning för att bland annat undersöka fler däck.When a long haul truck travels on a road it’s subjected to a number of forces. The tires rolling resistance is approximately 36 to 60% off the total travel resistance. Being able validate the rolling resistance during own testing is valuable to vehicle manufacturers like Scania. The tire manufacturers provide a constant rolling resistance coefficient but it’s unclear if it can be used in calculations for Scanias test setup.The purpose of the testing is to investigate if the test setup enables measuring the tires rolling resistance on a chassis dynamometer with torque wheels. For the experimental part of the degree project, a quantitative data collection methodology has been used for further machine analyzation and manually performing statistical analysis. Test driven development (TDD) has been applied to work iterative based on the test results.During testing the value of the rolling resistance coefficient went up, down or was stable. This is dependent on the electrical drift Kistler have (Kistler torque wheel consists of two rims that contain universal sensors to measure torque), that correlated with the distribution of the measured rolling resistance coefficient. It’s possible to compensate for the electrical drift in Kistler torque wheel and calculate the rolling resistance coefficient based on the last analyzation point from the tests.The measurements from Kistler torque wheel are distributed. By calculating the average of the rolling resistance coefficients a higher degree of accuracy is obtained. The average indicates that the rolling resistance coefficient have no or a small speed dependency.It’s possible to use Kistler torque wheel and chassis dynamometer 2 as a test setup to measure the rolling resistance of the tires. It’s possible for Scania to continue using this test setup to investigate more tires.
16
Prachař, Roman. "Jízdní odpory vozidel." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-232514.
Анотація:
his thesis deals with the analysis of particular road resistances that affect the car. It describes their importance and factors that influence their size. This thesis defines steps that determine particular quantities that are necessary to assess road resistances. Describing, it qualifies transfer and sizes of driving force that is needed to overcome total road resistance, measuring methods of road range tests upon appropriation of road resistances and influence of road resistances on economy of traffic. Practical part discusses the plan and course of realized measuring of selected sample of cars. Final part deals with the evaluation of measured values of realized measuring.
17
Wong, Min Hao. "The development of scratch test methodology and characterization of surface damage of polypropylene." Texas A&M University, 2003. http://hdl.handle.net/1969.1/1194.
Анотація:
A new scratch test methodology is proposed. The new test methodology is
developed based on the principles of materials science and solid mechanics, which
include the consideration of material parameters, use of microscopy for image
analysis and the finite element method (FEM). The consistency and reproducibility of
test results are shown using a new scratch test device on two sets of neat and talcfilled
polypropylene (PP) systems. Three different test conditions, i.e., linear load
increase under constant rate, constant load under constant rate, and linear rate increase
under constant load, have been conducted to determine the most effective, informative
test conditions for evaluation of scratch resistance of polymers. Experimental
observations and FEM results show a good qualitative correlation. The unique
advantages of the new scratch test method for evaluating scratch resistance of
polymers are discussed. A systematic study of surface damage effected by a
progressive scratching load is performed on model polypropylene (PP) systems. Mar-scratch
and stress -whitening transitions can be readily observed, and the
corresponding critical loads determined. Distinctive scratch hardnesses and surface damage features are
found for different material systems. Visibility of scratched surface is quantified
using gray level analysis via a flatbed scanner and a commercial image analysis tool.
It is found that the onset of scratch visibility can be determined accurately and
reproducibly using the custom -built scratcher under progressive loading condition.
Talc particles are found to be responsible for the increased light scattering, leading to
greatly increased visibility. The observed scratch visibility is also found to be related
to the measured frictional force profiles. Approaches for producing scratch
resistant PP are discussed.
18
Smith, Jacob A. "Electrical Performance of Copper-Graphene Nano-Alloys." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1550675878730599.
19
Ainegren, Mats. "Roller skis' rolling resistance and grip characteristics : influences on physiological and performance measures in cross-country skiers." Doctoral thesis, Mittuniversitetet, Institutionen för teknik och hållbar utveckling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-16446.
Анотація:
The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski with a μS similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a (similar) higher μS.The part of the thesis which focused on skiing economy and efficiency as a function of skill, age and gender, showed that the elite cross-country skiers had better skiing economy and higher gross efficiency (5-18 %) compared with the recreational skiers, and the senior elite had better economy and higher efficiency (4-5 %) than their junior counterparts, while no differences could be found between the genders.Syftet med denna avhandling var att undersöka fristils- och klassiska rullskidors rullmotståndskoefficienter (μR) och klassiska rullskidors statiska friktionskoefficienter (μS) samt effekter av olika μR och μS på längdskidåkares prestation vid rullskidåkning på rullande band. Syftet var även att undersöka s.k. åkekonomi och mekanisk verkningsgrad mellan motionärer och kvinnliga och manliga junior- och seniorlängdskidåkare på elitnivå.Experimenten visade att under en period av 30 minuters kontinuerligt rullande, på rullande band, så sjönk μR signifikant (p<0.05) till 60-65 % och 70-75 % av initiala värden, för fristils- respektive klassiska rullskidor. Undersökandet av olika normalkrafter, hastigheter och lutningars påverkan på μR resulterade i en signifikant, negativ korrelation för μR som funktion av normalkraft, medan olika hastigheter och lutningar endast medförde små förändringar av μR.Studien som undersökte fysiologiska effekter av olika μR visade, vid submaximala konstanta arbetsbelastningar, att yttre effekt, syreupptagning, hjärtfrekvens och blodlaktat förändrades signifikant vid ~50 % förändring av μR. Försökspersonernas frekvens och sträcka per frekvens samt skattning av upplevd ansträngning resulterade dock i mestadels icke signifikanta eller små förändringar. Protokollen med successivt ökande arbetsbelastning (maxtest) resulterade i signifikant förändrad tid till utmattning, vid ~50 % förändring av μR. Detta inträffade utan signifikant skillnad i maximal syreupptagning, hjärtfrekvens och blodlaktat, vilket även mestadels gällde för skattning av upplevd ansträngning.Experimenten som undersökte klassiska rullskidors μS visade att dessa erhöll värden som är fem till åtta gånger högre än vad som rapporterats från studier av μS på snö med fästvallade skidor.Den efterföljande studien som undersökte fysiologiska och biomekaniska influenser av olika μS visade, vid submaximala konstanta arbetsbelastningar, att åkekonomin försämrades (~14 % högre syreförbrukning), hjärtfrekvensen ökade, den framåtdrivande kraften från benen på rullskidorna minskade samt att det blev kortare tid till utmattning (~30 %), vid maxtest, när skidåkarna använde rullskidor med en μS i likhet med vad som rapporterats för skidåkning på snö. För arbetsförsöken med olika rullskidor av olika fabrikat med en högre, och likartad, μS förelåg ingen skillnad i de undersökta variablerna.Studien som undersökte åkekonomi och mekanisk verkningsgrad som funktion av prestationsnivå, ålder och kön, visade att elitskidåkarna hade bättre åkekonomi och verkningsgrad (5-18 %) i jämförelse med motionärerna, att seniorerna hade bättre åkekonomi och verkningsgrad (4-5 %) än juniorerna och att ingen skillnad kunde konstateras mellan könen.
20
Ghanbarpourgeravi, Morteza. "Investigation of Thermal Performance of Cylindrical Heatpipes Operated with Nanofluids." Doctoral thesis, KTH, Skolan för industriell teknik och management (ITM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202566.
Анотація:
Nanofluids as an innovative class of heat transfer fluids created by dispersing nanometre-sizedmetallic or non-metallic particles in conventional heat transfer fluids displayed the potential toimprove the thermophysical properties of the heat transfer fluids. The main purpose of this study is toinvestigate the influence of the use of nanofluids on two-phase heat transfer, particularly on thethermal performance of the heat pipes. In the first stage, the properties of the nanofluids were studied,then, these nanofluids were used as the working fluids of the heat pipes. The thermal performance ofthe heat pipes when using different nanofluids was investigated under different operating conditionsexperimentally and analytically. The influences of the concentration of the nanofluids, inclinationangles and heat loads on the thermal performance and maximum heat flux of the heat pipes wereinvestigated.This study shows that the thermal performance of the heat pipes depends not only on thermophysicalproperties of the nanofluids but also on the characteristics of the wick structure through forming aporous coated layer on the heated surface. Forming the porous layer on the surface of the wick at theevaporator section increases the wettability and capillarity and also the heat transfer area at theevaporator of the heat pipes.The thermal performance of the heat pipes increases with increasing particle concentration in all cases,except for the heat pipe using 10 wt.% water/Al2O3 nanofluid. For the inclined heat pipe, irrespectiveof the type of the fluid used as the working fluid, the thermal resistance of the inclined heat pipes waslower than that of the heat pipes in a horizontal state, and the best performance was observed at theinclination angle of 60o, which is in agreement with the results reported in the literature. Otheradvantages of the use of nanofluids as the working fluids of the heat pipes which were investigated inthis study were the increase of the maximum heat flux and also the reduction of the entropy generationof the heat pipes when using a nanofluid.These findings revealed the potential for nanofluids to be used instead of conventional fluids as theworking fluid of the heat pipes, but the commercialization of the heat pipes using nanofluids for largescale industrial applications is still a challenging question, as there are many parameters related to thenanofluids which are not well understood.QC 20170228
21
Suárez, Yannick Vália Romero. "Estudo da resistência ao escoamento em canais de fundo fixo." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/3/3147/tde-22032006-223408/.
Анотація:
O problema da previsão da resistência ao escoamento em canais tem atraído a atenção dos engenheiros há longo tempo. Durante os últimos decênios a resistência ao escoamento em canais abertos de fundo fixo tem sido amplamente investigada, usando rugosidade artificial nas superfícies de canais experimentais. A adoção do coeficiente de rugosidade para um canal natural significa estimar a resistência de este ao escoamento. A utilização de um valor incorreto deste coeficiente pode ter grandes impactos na estimação da vazão e em conseqüência no dimensionamento dos projetos de obras hidráulicas. Apresenta-se, mediante pesquisa bibliográfica, os métodos de cálculo para avaliação do coeficiente de rugosidade ou coeficiente de resistência, dando ênfase a aqueles desenvolvidos para canais naturais com rugosidade de grande escala, sem os efeitos do transporte de sedimentos. Em modelo físico avaliam-se os efeitos da distribuição, tamanho e forma dos elementos geométricos na resistência ao escoamento. Espera-se que os resultados da pesquisa proporcionem ao engenheiro os critérios necessários para a avaliação do coeficiente de rugosidade. Os métodos diretos de medição de vazões nos rios nem sempre podem ser levados a cabo em rios de montanha , especialmente na época de cheia, devido às grandes declividades (i>1%), material de grandes dimensões no leito (pedras, seixos, matacões), submersão relativa menor do que 1, condições estas de escoamento que podem ser perigosas para os equipamentos de medição. Em tais circunstâncias é necessário o uso de métodos indiretos. A aplicação das relações de resistência ao escoamento em rios de montanha torna-se difícil pelos escassos conhecimentos na avaliação do coeficiente de resistência. Faz-se uma comparação das diferentes formulações existentes da resistência ao escoamento com dados de um rio dos Andes peruanos, determinando-se uma equação de ajuste.The flow resistance estimation problem in channels has attracted the engineer's attention for a long time. During the last decades the flow resistance in open channels with rigid bed has been research with the use of artificial roughness in bed flumes. Adapting a natural channel roughness coefficient means the estimation of the corresponding resistance to flow. The use of an incorrect value in this coefficient might produce a big impact in the discharge estimation, as well as in the hydraulic work project. The calculation methods to estimate the roughness coefficient or resistance coefficient are showed through this bibliographic research, attaching importance to those developed for channels with large scale roughness; this without the sediment transport effects into account. The distribution, size and shape effects of the geometric elements in the flow resistance are evaluated in a physical model. It is expected that the research results provide the engineer with the required criteria to estimate the roughness coefficient. The direct methods of the discharge measurement in rivers can not always take place in mountain rivers, owing to the following reasons: high gradients (i>1%), big dimension material (cobbles and boulders), relative submergence lower than unit; flow conditions that might be dangerous for the measuring equipment. Under these circumstances it is necessary the use of indirect methods. The application of flow resistance relations in mountain rivers turns very difficult, due to the limited knowledge in resistance coefficient evaluation. In the following research has been made a comparison of the different existing flow resistance equations in mountain rivers, for a river in the Peruvian Andes by establishing a fitting curve.
22
Alshawaf, Hussain M. J. A. A. M. A. "A Novel Thermal Method for Pipe Flow Measurements Using a Non-invasive BTU Meter." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/101528.
Анотація:
This work presents the development of a novel and non-invasive method that measures fluid flow rate and temperature in pipes. While current non-invasive flow meters are able to measure pipe flow rate, they cannot simultaneously measure the internal temperature of the fluid flow, which limits their widespread application. Moreover, devices that are able to determine flow temperature are primarily intrusive and require constant maintenance, which can shut down operation, resulting in downtime and economic loss. Consequently, non-invasive flow rate and temperature measurement systems are becoming increasingly attractive for a variety of operations, including for use in leak detection, energy metering, energy optimization, and oil and gas production, to name a few. In this work, a new solution method and parameter estimation scheme are developed and deployed to non-invasively determine fluid flow rate and temperature in a pipe. This new method is utilized in conjunction with a sensor-based apparatus--"namely, the Combined Heat Flux and Temperature Sensor (CHFT+), which employs simultaneous heat flux and temperature measurements for non-invasive thermal interrogation (NITI). In this work, the CHFT+ sensor embodiment is referred to as the British Thermal Unit (BTU) Meter. The fluid's flow rate and temperature are determined by estimating the fluid's convection heat transfer coefficient and the sensor-pipe thermal contact resistance. The new solution method and parameter estimation scheme were validated using both simulated and experimental data. The experimental data was validated for accuracy using a commercially available FR1118P10 Inline Flowmeter by Sotera Systems (Fort Wayne, IN) and a ThermaGate sensor by ThermaSENSE Corp. (Roanoke, VA). This study's experimental results displayed excellent agreement with values estimated from the aforementioned methods. Once tested in conjunction with the non-invasive BTU Meter, the proposed solution and parameter estimation scheme displayed an excellent level of validity and reliability in the results. Given the proposed BTU Meter's non-invasive design and experimental results, the developed solution and parameter estimation scheme shows promise for use in a variety of different residential, commercial, and industrial applications.MS
23
Laporte, Julie. "Etude et modélisation de l'endurance électrique de micro-contacts soumis à des sollicitations de fretting-usure : caractérisation de nouveaux dépôts base Argent." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC034/document.
Анотація:
L’instrumentation de plus en plus poussée des systèmes mécaniques (aéronautique, automobile,…) impose une utilisation croissante des connecteurs électriques. Cependant, leur environnement de fonctionnement (sollicitations chimiques et vibratoires) peut entrainer une dégradation plus ou moins sévère des contacts électriques limitant ainsi le passage du courant. Pour limiter cette dégradation et assurer la stabilité des connexions, des revêtements d’or sont couramment appliqués au niveau des contacts. Cependant, la conjecture économique et le coût très élevé de l’or nécessite de trouver une alternative moins chère. Parmi les métaux conducteurs, l’argent est aujourd’hui le meilleur candidat. L’objectif de cette thèse est donc d’étudier la réponse électrique et l’endommagement de dépôts argent soumis à des sollicitations de fretting. Pour cela, ces travaux de recherche ont été abordés selon trois axes. Le premier axe a permis une étude complète d’un contact homogène argent/argent afin d’identifier les mécanismes de dégradation responsables de la rupture électrique aussi bien en fretting qu’en glissement alterné. Il a aussi été possible, par une approche énergétique, de mettre en place un modèle prédictif permettant d’extrapoler les durées de vie du contact selon différents paramètres de chargement. Une étude complémentaire a également montré l’impact d’une atmosphère corrosive à base de soufre sur les contacts électriques en argent. Le second axe a permis, quant à lui, d’étudier le comportement tribologique et électrique de nouveaux matériaux à base d’argent développés dans le but de remplacer les dépôts dorés. L’analyse de ces contacts homogènes a permis de mettre en évidence les mécanismes de dégradation et les comportements mécaniques des contacts soumis à des environnements humides. Dans le dernier axe, une étude a été menée sur ces mêmes matériaux à base d’argent mais en configuration hétérogène contre un dépôt d’or afin d’identifier le comportement tribologique et électrique de ces contacts quand ils sont composés par des matériaux avec des propriétés similaires ou opposéesAdvanced instrumentation in mechanical systems (aeronautical, automobile etc…) goes hand in hand with an ever increased use of electrical connectors. However, the unfavorable operating environment (chemical attack and vibrational loads) causes more or less severe degradation of electrical contacts, which in turn perturbs their electrical conductivity. Gold plating is usually applied in electrical contacts in order to limit damage and to ensure connector stability. However, economic constraints and the high cost of gold require cheaper alternatives. Amongst conductive metals, silver is the best candidate. Hence, the purpose of this PhD project is to investigate the electrical response and the degradation of silver coatings when subjected to fretting loadings. The study is divided into three main research axes. The first axis consists in realizing a complete study of a homogeneous silver/silver contact in order to identify the degradation mechanisms that are responsible for the electrical failure, both in fretting loadings and reciprocating sliding. It was possible to formalize a predictive model, using an energy density approach, allowing to extrapolate the lifetime of the contact as a function of various loading parameters. A complementary study also showed the impact of a corrosive sulfur atmosphere on these electric contacts. As part of the second research axis, an investigation of the tribological and electrical behavior of novel silver-based materials, solely synthesized as a gold replacement, was performed. The analysis of these homogeneous contacts allowed to explain the degradation mechanism and the mechanical behavior of these contacts when subjected to a wet environment. In the last research axis a study was led on the same silver-based materials but in a heterogenous configuration against a gold coating in order to identify the tribological and electrical behavior of these contacts when composed by materials with similar or opposite properties
24
Sýs, Tomáš. "Komplexní analýza funkce distribučního systému typu U." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443219.
Анотація:
Fluid flow maldistribution plays a key role in equipment used in process and energy industries, although its evaluation is often underestimated or fully neglected. Uneven flow distribution may cause thermal or mechanical load on the tube bundle, and in extreme scenarios, it can also have an adverse effect on the process efficiency. This thesis aims to find the optimal computational tools for flow distribution prediction suitable for the initial stage of the equipment design process and to identify suitable settings of these tools for their subsequent industrial deployment. The results of simplified analytical models, detailed numerical simulations, and experimental measurements were compared for the dividing header and the U-type distribution system. It was found that the results provided by simplified mathematical models, the solution of which is also significantly less time-consuming compared to detailed CFD simulations, best correspond to the measured experimental values in all modeled configurations. For arrangements with higher lateral resistance coefficient, both computational approaches provide approximately equally accurate results. However, for arrangements with lower lateral resistance coefficient, the deviation of the results obtained by CFD calculations from the experimental data is significantly larger.
25
Alanazi, Mohammed Awwad. "Non-invasive Method to Measure Energy Flow Rate in a Pipe." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/103179.
Анотація:
Current methods for measuring energy flow rate in a pipe use a variety of invasive sensors, including temperature sensors, turbine flow meters, and vortex shedding devices. These systems are costly to buy and install. A new approach that uses non-invasive sensors that are easy to install and less expensive has been developed. A thermal interrogation method using heat flux and temperature measurements is used. A transient thermal model, lumped capacitance method LCM, before and during activation of an external heater provides estimates of the fluid heat transfer coefficient h and fluid temperature. The major components of the system are a thin-foil thermocouple, a heat flux sensor (PHFS), and a heater. To minimize the thermal contact resistance R" between the thermocouple thickness and the pipe surface, two thermocouples, welded and parallel, were tested together in the same set-up. Values of heat transfer coefficient h, thermal contact resistance R", time constant �[BULLET], and the water temperature �[BULLET][BULLET], were determined by using a parameter estimation code which depends on the minimum root mean square RMS error between the analytical and experimental sensor temperature values. The time for processing data to get the parameter estimation values is from three to four minutes. The experiments were done over a range of flow rates (1.5 gallon/minute to 14.5 gallon/minute). A correlation between the heat transfer coefficient h and the flow rate Q was done for both the parallel and the welded thermocouples. Overall, the parallel thermocouple is better than the welded thermocouple. The parallel thermocouple gives small average thermal contact resistance average R"=0.00001 (m2.�[BULLET][BULLET]/W), and consistence values of water temperature and heat transfer coefficient h, with good repeatability and sensitivity. Consequently, a non-invasive energy flow rate meter or (BTU) meter can be used to estimate the flow rate and the fluid temperature in real life.MS
26
Tomala, Daniel. "Návrh letounu podle předpisu FAR 103." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-227917.
Анотація:
This diploma work considers conceptual design of aircraft in accordance in FAR 103 regulation. On the base of statistical dates has been made basic geometrical and aero-dynamical concept of a single occupant aircraft. For conception have been chosen optimal driving force and bases calculations of the load pressure and dimensions are included.
27
Kebapci, Basak. "Development Of High Performance Uncooled Infrared Detector Materials." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613070/index.pdf.
Анотація:
This thesis reports both the optimizations of the vanadium oxide (VOx) thin film as an active infrared detector material by the magnetron sputtering deposition method and its use during fabrication of proper resistors for the microbolometers. Vanadium oxide is a preferred material for microbolometers, as it provides high TCR value, low noise, and reasonable resistance, and a number of high-tech companies have used this material to obtain state-of-the-art microbolometer arrays. This material is first used in microbolometers by Honeywell, who provides its recipe with license agreements, and there is not much information in the literature for its deposition recipe. This is the first study at METU for development of vanadium oxide thin film for microbolometers.
The VOx material deposition studies started by identifying the deposition parameters of the magnetron sputtering system in order to obtain proper VOx resistors for the readout electronics. The obtained recipe includes high temperature deposition
conditions of VOx, however, this causes a diffusion problem on the electrodes, preventing to obtain a good contact to VOx. Also, high oxygen level in the depositions makes a contamination on the electrodes. A number of studies were done to determine a proper electrode material which is proper with the deposition conditions of the VOx.
Characterization of the vanadium oxide samples is done by XRD and XPS measurements to see the relation between the phases and resistivity of the vanadium oxide. It is known that V2O5 phase provides a high TCR and resistivity value, and the XRD results show that this phase is dominant in the highly-oxygen doped or annealed resistors. The TCR and noise measurements are done using resistors implemented with the developed VOx film, after the etching processes of the both VOx and the electrodes are optimized. The contamination on the electrodes is prevented by the help of a newly designed process. The TCR measurement results show that annealing of the resistors affect the TCR values, i.e., increasing the annealing duration increases the TCR values of the resistors. Two different resistors with different deposition conditions are annealed to see the effect of annealing, where TCR results of the resistors are -0.74%/K and -0.8 %/K before annealing. The TCR values of these resistors increase to -1.6 %/K and -4.35 %K, respectively, after annealing in same conditions, showing that both the deposition conditions and annealing change the TCR significantly. Although good TCR values are obtained, the noise values of the VOx resistors are much higher than the expected values, which suggest a further study to determine the cause of this noise.
28
Kotas, Jakub. "Parní turbína - návrh potrubní trasy kondenzátu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417534.
Анотація:
The master thesis deals with the design, tracing and dimensioning of condensate pipeline. In the beginning, a preliminary calculation of heat balance is done. It is followed by a description of the main condensate system supplemented by the computational design of pipeline and the calculation of pressure losses in this pipeline. The crucial part of the thesis is the calculation of pressure losses, which is done in two ways. The first approach to calculation of pressure losses in the pipeline is calculated using values of representative resistance coefficient for pipe ele-ments using Idelchik literature and for individual types of valves using values from datasheets of Siemens Energy suppliers. In the second approach to calculation representative resistance coefficients for pipe elements and individual types of valves CRANE literature are used. Then both approaches of choosing representative resistance coefficients are compared and evaluated. Based on the calculated values, a suitable pump is selected at the end of the master thesis.
29
Ardila, Miguel Angel Narvaez. "Influência da natureza e topografia da superfície na micro-abrasão e micro-abrasão-corrosão." Universidade Federal de Uberlândia, 2017. http://dx.doi.org/10.14393/ufu.te.2018.24.
Анотація:
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorCNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
O trabalho tem como objetivo contribuir ao entendimento do efeito das caraterísticas superficiais no desgaste abrasivo com e sem efeito corrosivo. Utilizou-se o equipamento de micro-abrasão-corrosão desenvolvido no Laboratório de Tribologia e Materiais (LTM). Foi utilizado nos testes: amostras de aço inoxidável austenítico AISI 304, partículas abrasivas de sílica e velocidade de rotação de 150 rpm. Para a parte corrosiva foi usada solução eletrolítica com 1N de H2SO4. Para a influência da topografia de superfície do corpo de prova o aço AISI 304 foi preparado em lixas de carbeto de silício de granulometria #80 e #4000, e com disposições de lixamento perpendicular e paralelo com respeito ao sentido de rotação da esfera. Esferas de zircônia (Ø 25,4 mm) foram usadas como contra-corpos. Para avaliar a influência da natureza e evolução topográfica da superfície do contra-corpo usaram-se cinco contra-corpos esféricos (Ø 25,4 mm): um cerâmico (nitreto de silício, Si3N4), um metálico (aço AISI 52100) e três polímeros termoplásticos (polipropileno, PP, poliacetal, POM, e poliamida 6,6, PA 6,6); para os testes de micro-abrasão-corrosão foram usados um cerâmico (Si3N4) e um polímero termoplástico (PP). Foi acompanhada a evolução topográfica ao longo dos testes nos contra-corpos por meio de interferometria e perfilometría. O deslizamento das partículas abrasivas foi predominante nas calotas geradas em todos os testes realizados. A topografia de superfície do corpo e contra-corpo mostrou ter relação com a taxa de desgaste na micro-abrasão e micro-abrasão-corrosão. Topografia de superfície com parâmetros de rugosidade maiores apresentam maiores taxas de desgaste, tendo maior sensibilidade na micro-abrasão-corrosão. Atribuiu-se que, com maiores valores dos parâmetros de rugosidade, consegue-se maior efetividade no arraste e participação de partículas abrasivas no contato.
The aim of this work is to contribute to the understanding of the effect of surface characteristics on abrasive wear with and without corrosive effect. The micro-abrasion-corrosion apparatus developed at the Tribology and Materials Laboratory (LTM) was used. The following tests were used: AISI 304 austenitic stainless steel test specimens (body), silica abrasive particles and rotational speed of 150 rpm. For the corrosive analysis, an 1N H2SO4 electrolytic solution was used. For the influence of the surface topography of the specimen, the AISI 304 steel was grinded using silicon carbide (SiC) (#80 and # 4000), and tested with perpendicular and parallel arrangements with respect to the direction of rotation of the sphere. Zirconia balls (Ø 25.4 mm) were used as counter bodies. In order to analyze the influence of the nature and topographic evolution of the counter-body surface, five spherical counter bodies (Ø 25.4 mm) were used in the micro-abrasion tests: one ceramic (silicon nitride, Si3N4), one metal (AISI steel 52100) and three thermoplastic polymers (polypropylene, PP, polyacetal, POM and polyamide 6.6, PA 6.6); For the micro-abrasion-corrosion tests one ceramic (silicon nitride) and one thermoplastic polymer (PP) were used. The topographic evolution of the counter bodies was monitored along the tests through interferometry and profilometry. The grooving of the abrasive particles was predominant in the wear scars generated in all tests performed. The surface topographies of the body and counter-body showed to have relation with the wear rate in the micro-abrasion and micro-abrasion-corrosion tests. Higher roughness parameters induced higher wear rates, and show greater sensitivity in micro-abrasion-corrosion. It was attributed that higher values of the roughness parameters achieved greater effectiveness in the drag and participation of abrasive particles in the contact.
Tese (Doutorado)
30
Popoola, Oludélé Olusègun. "Amorphisation et précipitation superficielles induites par implantation ionique dans les alliages NiTi équiatomiques : application aux propriétés tribologiques." Poitiers, 1988. http://www.theses.fr/1988POIT2292.
Анотація:
Mise en evidence par microscopie electronique en transmission, spectrometrie sims et photoelectron d'une amorphisation superficielle et de la formation de fins precipites cristallins tin::(x) dans le cas d'une implantation, d'azote. Influence de la temperature et de la dose d'ion sur l'epaisseur de la couche. Correlation entre la microstructure d'implantation et les proprietes tribologiques. Le coefficient de frottement se trouve reduit et la resistance a l'usure se trouve amelioree de facon durable. L'initiation et la propagation des processus de degradation sont ainsi ralenties
31
Eroglu, Numan. "Development Of High Performance Active Materials For Microbolometers." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613533/index.pdf.
Анотація:
This thesis reports the development of Vanadium Tungsten Oxide (VWO) film as an active detector material for uncooled infrared detectors by using the reactive DC magnetron co-sputtering method. VWO is a doped form of the Vanadium Oxide (VOx) which is known as a prominent material for uncooled infrared detectors with its high TCR, low resistivity, and low noise properties.
VOx is a widely preferred material for commercialized uncooled infrared detectors along with its drawbacks. Fabrication is fairly difficult due to its unstable material properties and the need for low process temperatures for a monolithic, CMOS compatible surface micromachining process. Hence, a new material with high performance and easier fabrication is needed. This thesis is the first study at METU on the development of high-performance VWO as an active detector material for uncooled infrared detectors.
Deposition studies of VWO primarily started by measuring the effects of deposition parameters upon the magnetron sputtering system. Because the high effectiveness of the tungsten doping has been obtained for the doping level below 10% according to literary information, maximum vanadium (V) deposition rate together with minimum tungsten (W) deposition rate has been initially aimed.
TCR of the VWO films has been measured between -2.48 %/K and -3.31 %/K, and the variation of noise corner frequency from 0.6 kHz to 8 kHz has been observed. In addition to these results of VWO, a favorable VOx recipe which has the highest performance done at METU in terms of resistance, TCR, noise and uniformity has also attained during the studies. Structural characterization of VWO is achieved using XPS, XRD, and AFM characterization techniques.
Other than the sputtering parameters, post-annealing process and oxygen plasma exposure was examined as well. A general observation of the post-annealing is that it decreases not merely the TCR but also the noise of the deposited film. A short-period oxygen plasma exposure has a constructive effect on the noise behavior.
Fabricated vanadium tungsten oxide with sandwich type resistor structure shows very close but better bolometric properties when compared with the yttrium barium copper oxide (YBCO), which is another material being studied in scope of other theses at METU.
XPS, XRD and AFM characterization methods have been used for the structural characterization of vanadium-tungsten-oxide.
32
Landrum, Evan. "Anisotropic parameters of mesh fillers relevant to miniature cryocoolers." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28159.
Анотація:
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Ghiaasiaan, S. Mostafa; Committee Member: Desai, Prateen; Committee Member: Jeter, Sheldon; Committee Member: Kirkconnell, Carl.
33
Dašková, Jaroslava. "Závislost protismykových vlastností povrchů vozovek na ohladitelnosti kameniva a dopravním zatížení." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-233819.
Анотація:
Road safety is a complex problem. It is influenced mainly by the driver, the vehicle and the road surface. This thesis is focused on the road surface properties and especially skid resistance that directly affect the braking distance and keeping the vehicle in the horizontal curves and thus traffic accidents. The thesis deals with the durability of pavement surface skid resistance, the type of pavement layers and aggregate polishing used in wearing course. The aim of this thesis was to develop the methodology for improvement of road surfaces skid resistance durability and implementation of functional test for their assessment.
34
Weerasekara, Aruna Bandara. "Electrical and Optical Characterization of Group III-V Heterostructures with Emphasis on Terahertz Devices." Digital Archive @ GSU, 2007. http://digitalarchive.gsu.edu/phy_astr_diss/16.
Анотація:
Electrical and optical characterizations of heterostructures and thin films based on group III-V compound semiconductors are presented. Optical properties of GaMnN thin films grown by Metalorganic Chemical Vapor Deposition (MOCVD) on GaN/Sapphire templates were investigated using IR reflection spectroscopy. Experimental reflection spectra were fitted using a non - linear fitting algorithm, and the high frequency dielectric constant (ε∞), optical phonon frequencies of E1(TO) and E1(LO), and their oscillator strengths (S) and broadening constants (Γ) were obtained for GaMnN thin films with different Mn fraction. The high frequency dielectric constant (ε∞) of InN thin films grown by the high pressure chemical vapor deposition (HPCVD) method was also investigated by IR reflection spectroscopy and the average was found to vary between 7.0 - 8.6. The mobility of free carriers in InN thin films was calculated using the damping constant of the plasma oscillator. The terahertz detection capability of n-type GaAs/AlGaAs Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) structures was demonstrated. A threshold frequency of 3.2 THz (93 µm) with a peak responsivity of 6.5 A/W at 7.1 THz was obtained using a 0.7 µm thick 1E18 cm−3 n - type doped GaAs emitter layer and a 1 µm thick undoped Al(0.04)Ga(0.96)As barrier layer. Using n - type doped GaAs emitter layers, the possibility of obtaining small workfunctions (∆) required for terahertz detectors has been successfully demonstrated. In addition, the possibility of using GaN (GaMnN) and InN materials for terahertz detection was investigated and a possible GaN base terahertz detector design is presented. The non - linear behavior of the Inter Pulse Time Intervals (IPTI) of neuron - like electric pulses triggered externally in a GaAs/InGaAs Multi Quantum Well (MQW) structure at low temperature (~10 K) was investigated. It was found that a grouping behavior of IPTIs exists at slow triggering pulse rates. Furthermore, the calculated correlation dimension reveals that the dimensionality of the system is higher than the average dimension found in most of the natural systems. Finally, an investigation of terahertz radiation efect on biological system is reported.
35
Klus, Lukáš. "Armatury v otopných soustavách." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372198.
Анотація:
The theme of this diploma thesis is fittings of heating systems and it is divided into three parts. The first part deals with this topic on theoretical level. In the second part, there is a calculations and drawings that deals with heating and water heating of the apartment building in Uherské Hradiště. This part is solved in two variants concerning hydraulic balancing and regulation of the heating system. The last part of the thesis is an experimental solution and processing of pressure loss results of selected valves. These results are compared with the values reported by the manufactures of the valve.
36
Morison, Colin. "The resistance of laminated glass to blast pressure loading and the coefficients for single degree of freedom analysis of laminated glass." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4651.
Анотація:
For terrorist explosions or accidental explosions in urban areas, the greatest threat of death and serious injury comes from the effects of glass fragments. Laminated glazing has been proven by trials and experience of actual events to eliminate the risk of significant fragment injury to people behind the glazing, and also to provide substantial protection from blast injury effects, provided that after cracking it remains as a continuous membrane substantially attached to the supporting frame. However, design of laminated glazing is currently based on extrapolation from testing, with limited understanding of the material behaviour that underlies the behaviour under blast loading. This thesis presents an investigation into the application of a simplified method of dynamic analysis for laminated glass, the development of parameters derived from the properties of the materials in laminated glass and the behaviour of laminated glass systems that can be applied to the design of laminated glazing to resist blast loading. The development of the single degree of freedom method for analysis of dynamic response is reviewed from its inception use for analysis of glazing, through its adaptation for reinforced concrete analysis, to its modern use for analysis of glazing. Although the principles of the method are widely applicable, some procedures established for elastic-plastic reinforced concrete analysis in the 1950s are not appropriate for glazing, and should be treated with care. Coefficients for analysis of reinforced concrete date from approximate analyses in the 1950s and 60s and are not accurate. New calculations using advanced yield line models and finite element analysis have been used to provide alternative coefficients for rectangular panels supported on four edges. The elastic analyses for reinforced concrete are linear because they are based on small-deflection theory. Deflections of most uncracked glass panes exceed the limits of this theory. The development of practical non-linear large-deflection analyses in the 1980s was dependent on numerical methods and computer analysis, but they have previously only been applied to resistance and cracking. New non-linear finite element analyses refine the existing resistance data, and data from the same calculations has been used to derive large deflection single degree of freedom parameters for dynamic analysis and to assess the reaction distribution. The cracking of glass arises from small flaws in its surface, and can be very variable in its onset. In addition, the strength is sensitive to the loading rate. Statistical approaches have been based on quasi-static tests, either assuming a normal distribution, or using a more complex Weibull distribution. However, statistical refinement gains little, as strengths then need to be increased for the faster loading under blast. Back-analysis of extensive blast tests had been used to establish deterministic lower bound design cracking strengths for different types of glass. These have been applied in this thesis for design, and back-analysis of blast trials indicates that the design cracking strengths are lower bound. Formulae for a monolithic pane with equivalent behaviour to a laminated glass pane are proposed that would allow the large deflection analysis to be applied to laminated glass up to cracking of the final ply. The results of some blast trials of uncracked laminated glass are reported which are consistent with an equivalent monolithic analysis. They indicate that laminated glass under blast can be taken as fully composite to temperatures approaching 20ºC, but that it is not fully composite at 29ºC or above. Unfortunately, there is currently no data to indicate the performance in the critical temperature range between. After laminated glass cracks, the resistance is provided by an interlayer of the viscoelastic polymer, Polyvinyl Butyral. Though research is ongoing, non-linear viscoelastic material models for finite element analyses have not yet been developed to the point that they can reproduce the full range of behaviour observed in the tensile tests over the range of temperatures and elongation rates which are reported in the thesis. Instead, the results of the tensile tests are fitted to a simple bilinear material model by back-analysis of the tensile tests to give three stiffness and strength parameters that vary with temperature and strain rate. Non-linear finite element analyses of PVB membranes corresponding to two series of laminated glass blast trials are used to produce single degree of freedom parameters for membrane response. The blast trials are reported, and back-analysis of the deflection histories is used to estimate the ratio of the PVB material strain rates and the observed laminated glass strain rates for the best-fit calculated response. This ratio, found to have a mean value of 3.8, is expected to reflect the stiffening of PVB by attached glass fragments, together with other factors. However, the scatter in the data is large, so the reliability of this figure should be viewed with this in mind. Laminated glass providing blast protection is normally maintained close to room temperature, so a design based on a room temperature of 23ºC is proposed, using single degree of freedom data that is a composite of the uncracked data up to cracking and the membrane data after that point. For normal laminated glazing where the observed strain rate is expected to be about 10 /s, design membrane properties based on a PVB strain rate of 40 /s are proposed, but this may need to be modified for other cases. Typical design cases for marginal behaviour are analysed on this basis, and also for material properties at temperatures 6ºC higher and lower than 23ºC, to assess the sensitivity of the design to likely temperature variations. These indicate that a margin of 16-21% may be needed on deflection limits to allow for temperature increases, but that the calculated deflections would still be below the maximum deflections observed in the trials without PVB failure. The analyses indicate that the peak reactions are unlikely to be sensitive to temperature. However, they indicate that a margin of safety of 2.4 will need to be incorporated in the design anchorage strength to resist in-plane tension in the PVB membrane at reduced temperature. The thesis develops an improved design method under blast loading for laminated glass and double glazing incorporating laminated glass, although some of the values used in the method should be considered tentative. The thesis also indicates a level of anchorage strength sensitivity to temperature reductions that needs to be taken into account in practical glazing designs.
37
Morison, C. "The resistance of laminated glass to blast pressure loading and the coefficients for single degree of freedom analysis of laminated glass." Thesis, Engineering Systems Department, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4651.
Анотація:
For terrorist explosions or accidental explosions in urban areas, the greatest threat of
death and serious injury comes from the effects of glass fragments.
Laminated glazing has been proven by trials and experience of actual events to
eliminate the risk of significant fragment injury to people behind the glazing, and also
to provide substantial protection from blast injury effects, provided that after cracking
it remains as a continuous membrane substantially attached to the supporting frame.
However, design of laminated glazing is currently based on extrapolation from
testing, with limited understanding of the material behaviour that underlies the
behaviour under blast loading.
This thesis presents an investigation into the application of a simplified method of
dynamic analysis for laminated glass, the development of parameters derived from the
properties of the materials in laminated glass and the behaviour of laminated glass
systems that can be applied to the design of laminated glazing to resist blast loading.
The development of the single degree of freedom method for analysis of dynamic
response is reviewed from its inception use for analysis of glazing, through its
adaptation for reinforced concrete analysis, to its modern use for analysis of glazing.
Although the principles of the method are widely applicable, some procedures
established for elastic-plastic reinforced concrete analysis in the 1950s are not
appropriate for glazing, and should be treated with care. Coefficients for analysis of
reinforced concrete date from approximate analyses in the 1950s and 60s and are not
accurate. New calculations using advanced yield line models and finite element
analysis have been used to provide alternative coefficients for rectangular panels
supported on four edges.
The elastic analyses for reinforced concrete are linear because they are based on
small-deflection theory. Deflections of most uncracked glass panes exceed the limits
of this theory. The development of practical non-linear large-deflection analyses in
the 1980s was dependent on numerical methods and computer analysis, but they have
previously only been applied to resistance and cracking. New non-linear finite
element analyses refine the existing resistance data, and data from the same
calculations has been used to derive large deflection single degree of freedom
parameters for dynamic analysis and to assess the reaction distribution.
The cracking of glass arises from small flaws in its surface, and can be very variable
in its onset. In addition, the strength is sensitive to the loading rate. Statistical
approaches have been based on quasi-static tests, either assuming a normal
distribution, or using a more complex Weibull distribution. However, statistical
refinement gains little, as strengths then need to be increased for the faster loading
under blast. Back-analysis of extensive blast tests had been used to establish
deterministic lower bound design cracking strengths for different types of glass. These
have been applied in this thesis for design, and back-analysis of blast trials indicates
that the design cracking strengths are lower bound.
Formulae for a monolithic pane with equivalent behaviour to a laminated glass pane
are proposed that would allow the large deflection analysis to be applied to laminated
glass up to cracking of the final ply. The results of some blast trials of uncracked
laminated glass are reported which are consistent with an equivalent monolithic
analysis. They indicate that laminated glass under blast can be taken as fully
composite to temperatures approaching 20ºC, but that it is not fully composite at 29ºC
or above. Unfortunately, there is currently no data to indicate the performance in the
critical temperature range between.
After laminated glass cracks, the resistance is provided by an interlayer of the
viscoelastic polymer, Polyvinyl Butyral. Though research is ongoing, non-linear
viscoelastic material models for finite element analyses have not yet been developed
to the point that they can reproduce the full range of behaviour observed in the tensile
tests over the range of temperatures and elongation rates which are reported in the
thesis. Instead, the results of the tensile tests are fitted to a simple bilinear material
model by back-analysis of the tensile tests to give three stiffness and strength
parameters that vary with temperature and strain rate.
Non-linear finite element analyses of PVB membranes corresponding to two series of
laminated glass blast trials are used to produce single degree of freedom parameters
for membrane response. The blast trials are reported, and back-analysis of the
deflection histories is used to estimate the ratio of the PVB material strain rates and
the observed laminated glass strain rates for the best-fit calculated response. This
ratio, found to have a mean value of 3.8, is expected to reflect the stiffening of PVB
by attached glass fragments, together with other factors. However, the scatter in the
data is large, so the reliability of this figure should be viewed with this in mind.
Laminated glass providing blast protection is normally maintained close to room
temperature, so a design based on a room temperature of 23ºC is proposed, using
single degree of freedom data that is a composite of the uncracked data up to cracking
and the membrane data after that point. For normal laminated glazing where the
observed strain rate is expected to be about 10 /s, design membrane properties based
on a PVB strain rate of 40 /s are proposed, but this may need to be modified for other
cases.
Typical design cases for marginal behaviour are analysed on this basis, and also for
material properties at temperatures 6ºC higher and lower than 23ºC, to assess the
sensitivity of the design to likely temperature variations. These indicate that a margin
of 16-21% may be needed on deflection limits to allow for temperature increases, but
that the calculated deflections would still be below the maximum deflections observed
in the trials without PVB failure. The analyses indicate that the peak reactions are
unlikely to be sensitive to temperature. However, they indicate that a margin of safety
of 2.4 will need to be incorporated in the design anchorage strength to resist in-plane
tension in the PVB membrane at reduced temperature.
The thesis develops an improved design method under blast loading for laminated
glass and double glazing incorporating laminated glass, although some of the values
used in the method should be considered tentative. The thesis also indicates a level of
anchorage strength sensitivity to temperature reductions that needs to be taken into
account in practical glazing designs.
38
Machala, David. "Vývoj nového samonosného zateplovacího systému s ohledem na dynamické namáhání." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226705.
Анотація:
This diploma thesis deals with suggestion of self-supporting insulating system that can be used for objects which insulating is more or less complicated. In this thesis are theoretically processed information about insulation systems while focus is on their structure, composition and principle of operation. Further, there is theoretically designed self-supporting insulating system which is practically built after theoretically composed testing for finding its basic properties. The most appropriate process of realization is formulated at the end after evaluation of the individual tests.
39
Khedekar, Mayur. "Temperature Based Estimation of the Time-Resolved Massflux of ICE Exhaust Gas Flow." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300050.
Анотація:
The aim ofthe study was to provideinformation and experience gained with fine wire thermocouples (TCs)or resistance wire thermometers (RWTs) temperature signals to estimate the timeresolved heat transfercoefficient. Constant current method was assumed in the study and medium used in this study was air. Here the heat balance equation has been described, different Nucorrelations and further discusses potential hurdles and difficulties one may encounter while calculating heat transfer coefficient. As asolution, the use of an appropriate heatbalance equation and lowpass filter was suggested as this provides a more accurate fitting. The investigation was carried out for Reynolds number (Re) 103 to 107 and Prandlt number (Pr) 0.734. The impact of the Re and Pr on the Nusselts number (Nu) around a cylinder was represented and all the results were compared with GT-POWER engine simulation software.Syftet med studien var att tillhandahålla information och erfarenhet från fina trådtermoelement (TC) eller motståndstrådstermometrar (RWT) temperatursignaler för att uppskatta den tidsupplösta värmeöverföringskoefficienten. Metoden med konstant flöde antogs i studien och mediet som användes i denna studie var luft. Här har värmebalansekvationen beskrivits, olika Nu-korrelationer och diskuterat ytterligare potentiella hinder och svårigheter man kan stöta på vid beräkning av värmeöverföringskoefficienten. Som en lösning föreslogs användning av en lämplig värmebalansekvation och lågpassfilter eftersom detta ger en mer exaktpassform. Undersökningen genomfördes för Reynoldsnummer (Re) 103 till 107 och Prandlt nummer (Pr) 0,734. Effekten av Re och Pr på Nusselts-numret (Nu) runt en cylinder representerades och alla resultat jämfördes med GT-POWER-motorns simuleringsprogram.
40
Holeček, Dominik. "Studium užitných vlastností termoreflexních izolací pro stavebnictví." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392345.
Анотація:
The diploma thesis is partly dedicated to energetic efficiency of buildings and describes possibilities how to evaluate energetic efficiency of buildings in the Czech Republic. We also get to know with distribution of thermal insulators by material base and use in construction. There are also mentioned methods how to determine thermal insulations characteristics of heat insulations, so called heat conductivity coefficient. The last and the crucial chapter of theoretic part is dedicated to thermal-reflective insulations. There are mentioned some of the basic characteristics of insulations, material composition and heat transfer mechanism in their structure as well. Practical part describes measurement of thermal resistance of chosen samples of thermal-reflective insulations per measuring device on the principal of Hot Box method. In the next step was determined emissivity of aluminium foils which forms the surface of chosen samples of thermal-reflective insulations. In the end of thesis are defined possibilities of use thermal-reflective insulations in building structures especially in passive and low-energy buildings in climatic conditions of the Czech Republic.
41
Mobe, Nompumelelo Thelma. "The influence of canopy cover and cultivar on rates of water use in apple orchards in the Western Cape Province, South Africa." University of the Western Cape, 2020. http://hdl.handle.net/11394/8156.
Анотація:
Philosophiae Doctor - PhDWater availability and climate related issues are some of the greatest crop production risks to irrigated agriculture in arid regions. In South Africa, for example, the increasing frequency and severity of droughts related to climate change and the growing competition for limited water resources among different users threaten the sustainability and growth of irrigated agriculture, especially the water-intensive fruit industry. Major fruit such as apples (Malus domestica Borkh) are produced entirely under irrigation in South Africa. As a result, there has been considerable research to accurately quantify the water requirements of fruit tree orchards in order to maximize water productivity.
42
Freitas, Ana Carolina Carneiro de. "Forças, momentos e coeficiente de atrito em teste de três pontos e em teste de resistência ao deslizamento com braquetes autoligáveis e fios 0.014\" utilizando um novo dispositivo." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-24052016-154250/.
Анотація:
O objetivo principal do estudo é comparar o teste em 3 pontos com braquetes com o teste de resistência ao deslizamento utilizando um novo dispositivo que realiza a mensuração simultânea do coeficiente de atrito, das forças e dos momentos nos braquetes de ancoragem e da força de desativação no braquete desalinhado, exercidos por fios ortodônticos. Os objetivos secundários foram desenvolver o dispositivo e comparar, no teste em 3 pontos: (i) a influência, nas grandezas e no coeficiente de atrito cinético, da variação da simetria nas distâncias inter-braquetes, do tipo de braquete de ancoragem (canino ou 2º pré-molar), do deslocamento (3 ou 5mm) do braquete central, do sentido do desalinhamento (vestibular ou lingual) do braquete central e da marca de fio-braquete; (ii) as 3 formas de cálculo do coeficiente de atrito cinético; (iii) os 10 ciclos, para vestibular ou lingual, para verificar se eles são semelhantes ou não entre si. Foram utilizados braquetes autoligáveis (dentes 13, 14 e 15) e fios 0.014\'\' NiTi e CuNiTi das marcas Aditek e Ormco. O teste de resistência ao deslizamento foi realizado no desalinhamento lingual, nos dois deslocamentos e na configuração simétrica. O teste em 3 pontos com braquetes foi realizado no desalinhamento lingual e vestibular, nos dois deslocamentos e na configuração simétrica e assimétrica. Por meio da ANOVA, foram comparados, entre os dois tipos de teste: (A) as grandezas e o coeficiente de atrito e (B) o coeficiente de atrito gerado apenas no braquete de 2º pré-molar. Utilizando-se do mesmo teste estatístico foram comparados, no teste em 3 pontos com braquetes: (A) na configuração simétrica, algumas grandezas e o coeficiente de atrito advindos da variação da marca de fio-braquete, do deslocamento, do desalinhamento e do tipo de braquete; (B) algumas grandezas e o coeficiente de atrito gerados na configuração simétrica e assimétrica; (C) os valores das 3 formas de cálculo do coeficiente de atrito na configuração simétrica; e (D) algumas grandezas e o coeficiente de atrito encontrados nos 10 ciclos. Resultados: (A) a maioria dos valores das grandezas e do coeficiente de atrito gerados pelos dois tipos de teste foram diferentes estatisticamente; (B) o braquete de 2º pré-molar apresentou valores de coeficiente de atrito diferentes entre os dois tipos de teste; (C) na configuração simétrica, as variáveis foram estatisticamente significantes na maioria dos casos para as grandezas analisadas e para o coeficiente de atrito; (D) houve diferença entre a configuração simétrica e assimétrica; (E) o coeficiente de atrito baseado nas duas normais e na força de atrito se aproximou mais da realidade clínica e foi sensível à variação da geometria da relação fio-braquete; e (F) os 10 ciclos para lingual foram semelhantes entre si em 70% dos casos e os 10 ciclos para vestibular foram diferentes em 57% dos casos. Conclusões: o teste em 3 pontos com braquetes é diferente do teste de resistência ao deslizamento; a variação das configurações geométricas e da marca de fio-braquete pode influenciar nos valores das grandezas e do coeficiente de atrito cinético; os 10 ciclos para lingual foram mais semelhantes entre si que os 10 ciclos para vestibular.The main objective of the study is to compare the three-bracket bending test with the resistance to sliding test using a new device that performs simultaneous measurement of coefficient of friction, the forces and moments on the anchor brackets and deactivation force in misaligned bracket, exercised by orthodontic wires. Secondary objectives were to develop the device and compare, in the three-bracket bending test: (i) the influence, on the physical quantities and on the kinetic friction coefficient, of the variation of the symmetry in the inter-bracket distance, of the type of anchor bracket (canine or 2nd premolar), of displacement (3 or 5mm) and misalignment (buccal or lingual) of the central bracket, and of the wire and bracket brand; (ii) the three ways to calculate the coefficient of kinetic friction; (iii) the 10 cycles, for buccal or lingual, to see if they are similar or not. Self-ligating brackets were used (teeth 13, 14 and 15) and wires 0.014 \'\' NiTi and CuNiTi of Aditek and Ormco brands. The resistance to sliding test was conducted on the lingual misalignment, on both displacements and on symmetrical configuration. The three-bracket bending test was held at the lingual and vestibular misalignment, at both displacements and at the symmetrical and asymmetrical configuration. Through ANOVA, were compared, between the two types of tests: (A) the quantities and the coefficient of friction and (B) the coefficient of friction generated only in the second premolar bracket. Using the same statistical test were compared, in three-bracket bending test: (A) in symmetrical configuration, the quantities and the coefficient of friction arising from the variation in the wire and bracket brands, displacement, misalignment and the type of bracket; (B) the quantities and the coefficient of friction generated by the symmetric and asymmetric configuration; (C) the values of the three ways of calculating friction coefficient; and (D) the quantities and the coefficient of friction encountered in 10 cycles. Results: (A) most of the values of the quantities and the coefficient of friction generated by the two types of test were statistically different; (B) the 2nd premolar bracket showed different friction coefficient values between the two types of test; (C) in the symmetrical configuration, the variables were statistically significant in the most of cases for quantities and the friction coefficient; (D) was found difference between symmetric and asymmetric configuration; (E) the friction coefficient based on both normal forces and frictional force was closer to the clinical reality and was sensitive to variations in the geometry of the wire-bracket relationship; and (F) the 10 cycles for lingual were similar in 70% of cases and the 10 cycles for buccal desalignment were different in 57% of cases. Conclusions: The three-bracket bending test is different from the resistance to sliding test; the variation of geometric configurations and wire and bracket brands may influence the values of the quantities and the coefficient of kinetic friction; the 10 cycles for lingual were more similar to each other than the 10 cycles for buccal.
43
Ripard, Valentin. "Tribological characterization of greased drive-shaft : Evaluation of constant velocity joint durability." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI083.
Анотація:
La modification des besoins clients amène les constructeurs automobiles vers de nouveaux challenges. En effet, en Europe notamment, les véhicules rehaussés type SUV (Sport Utility Vehicle) sont de plus en plus populaires. Or, ces véhicules impliquent une modification de l’implantation des transmissions mécaniques. Ces dernières possèdent alors une angularité plus élevée que pour des berlines par exemple. Cette modification a alors 2 impacts : l’augmentation du glissement dans la transmission mais aussi son influence sur la durabilité des composants. La modification de l’angularité est un des enjeux majeurs de ces dernières années pour les constructeurs. En effet, son augmentation influe sur le rendement des transmissions. Or, avec des normes environnementales de plus en plus contraignantes mais aussi une hausse du prix du pétrole, cet axe d’amélioration représente un facteur d’attractivité pour les constructeurs. De plus, la durabilité des organes reste primordiale. Une voiture se doit d’avoir une transmission fiable ne nécessitant, pour le cas des joints homocinétiques, aucun entretien durant la vie du véhicule. C’est sur cet axe que les travaux suivants ont majoritairement porté. L’objectif de ce manuscrit est de comprendre le mécanisme d’usure des joints homocinétiques côté boîte dits tripode. Une analyse de la cinématique a d’abord été menée afin de reproduire les contacts sur des bancs d’essais. Elle s’est appuyée sur des données issues de la bibliographie mais aussi une simulation de la dynamique des solides. De plus, la création en fabrication additive d’un banc d’observation a permis d’évaluer de façon expérimentale le glissement dans cet organe de transmission. Par la suite, une caractérisation des graisses de transmission utilisée dans le groupe PSA a été effectuée afin de connaître les coefficients de frottement induisant le niveau de vibrations de la transmission pour un client. Ces derniers sont essentiels pour juger l’efficacité énergétique de l’organe. Enfin, une étude de l’usure a permis d’expliquer les mécanismes de défaillance de la lubrification avec des graisses proposant des propriétés mécaniques. Cela permet alors de comprendre les données-clés afin de choisir une graisse assurant une durabilité maximale des organes de transmission et remplissant alors un des deux enjeux cités ci-dessus. Pour le futur, un banc de caractérisation des lubrifiants spécialement conçu pour les contacts de joint tripode a été créé. Il permettra ainsi de caractériser de façon plus complète les lubrifiants du futur pour cet organe essentiel d’une voitureNew customer desires are leading car manufacturers to new challenges. Indeed, enhanced vehicles like SUV (Sport Utility Vehicle) becomes more and more popular, especially in Europe. These vehicles involve some modification over the usual mechanical transmissions designs. This vehicle type has a higher angularity than sedans for example. This desire modification has 2 impacts: the increase of slipping in the transmission and its influence on the durability of the components. The angularity modification remains one of the major lines of research in recent years for car manufacturers. Its increasing influences efficiency. Indeed, this axis of improvement is attractive for manufacturers due to new environmental standards but also an increase in oil price. In addition, a car must have a reliable transmission that does not require, in the case of constant velocity joints, any maintenance during vehicle life. The following work will focus on this objective. The main goal of this manuscript is to understand the wear mechanism of the tripod constant velocity joint (CVJ). An analysis of the kinematics was first conducted to reproduce contacts on test rigs. It relied on data from the bibliography but also a simulation of solid dynamics. In addition, the design of a new observation rig using additive manufacturing made it possible to experimentally reproduce slipping in tripod. Furthermore, a characterization of greases used in Groupe PSA transmissions was performed in order to know the friction coefficients inducing the shudder level of the CVJ. These are also essential in order to judge the efficiency of the component. Finally, a wear investigation is performed to explain the possible lubrication failure mechanisms with greases proposing different mechanical behaviour. This approaches enables the transmission designer to choose a grease ensuring maximum durability of transmission components. Looking ahead, a lubricant characterization rig specially designed for tripod joint contacts has been designed. It will thus allow a more complete characterization of further lubricants to this essential vehicle component
44
Hejný, Lukáš. "Tepelně technické vlastnosti rámu okenní výplně a připojovací spáry." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-234552.
Анотація:
This thesis deals with the solution problem of fitting a window in the wall, especially for passive houses. It provides options to optimize the window connection joints, improve the thermal transmittance of the window frame, thereby reducing the total heat loss through the window. In the first part of the thesis is a research literature on the windows and heat technical and physical mechanisms. Are described equations and physical processes taking place in the windows and related building structures. This section describes the basic points in history, technical description of windows, etc. and present ways of assembly Installation the window and the influence of the thermal properties of the heat loss. The next part deals with the description of the work and the results obtained in the course of doctoral study. Describes the main objectives of the dissertation thesis, calculations and simulations of temperature fields and the results of the calculated values. Furthermore are described and analyzed measurement data and compared with the calculated values. At the end dissertation thesis are given opportunities to improve the current solution regarding the heat transfer coefficient of the frame, the optimal way of installation fillers windows in the perimeter wall and improve the thermal properties of the connecting joint.
45
Fiedler, Holger. "Preparation and characterization of Carbon Nanotube based vertical interconnections for integrated circuits." Doctoral thesis, Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-149474.
Анотація:
(ULSI) causes an increase of the resistance of the wiring system by increased scattering of electrons at side walls and grain boundaries in the state of the art Cu technology, which increases the RC delay of the interconnect system and thus degrades the performance of the device. The outstanding properties of carbon nanotubes (CNT) such as a large mean free path, a high thermal conductance and a large resistance against electromigration make them an ideal candidate to replace Cu in future feature nodes. The present thesis contributes to the preparation and properties of CNT based vertical interconnections (vias). In addition, all processes applied during the fabrication are compatible to ULSI and an interface between CNT based vias and a Cu metallization is studied. The methodology for the evaluation of CNT based vias is improved; it is highlighted that by measuring the resistance of one multiwall CNT and taking into account the CNT density, the performance of the CNT based vias can be predicted accurately. This provides the means for a systematic evaluation of different integration procedures and materials. The lowest contact resistance is obtained for carbide forming metals, as long as oxidation during the integration is avoided. Even though metal-nitrides exhibit an enhanced contact resistance, they are recommended to be used at the bottom metallization in order to minimize the oxidation of the metal-CNT contact during subsequent processing steps. Overall a ranking for the materials from the lowest to the highest contact resistance is obtained: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Furthermore the impact of post CNT growth procedures as chemical mechanical planarization, HF treatment and annealing procedures after the CNT based via fabrication are evaluated. The conductance of the incorporated CNTs and the applicable electrical transport regime relative to the CNT quality and the CNT length is discussed. In addition, a strong correlation between the temperature coefficient of resistance and the initial resistance of the CNT based vias at room temperature has been observedDie kontinuierliche Miniaturisierung der charakteristischen Abmessungen in hochintegrierten Schaltungen (ULSI) verursacht einen Anstieg des Widerstandes im Zuleitungssystem aufgrund der erhöhten Streuung von Elektronen an Seitenwänden und Korngrenzen in der Cu-Technologie, wodurch die Verzögerungszeit des Zuleitungssystems ansteigt. Die herausragenden Eigenschaften von Kohlenstoffnanoröhren (CNT), wie eine große mittlere freie Weglänge, hohe thermische Leitfähigkeit und eine starke Resistenz gegenüber Elektromigration machen diese zu einem idealen Kandidaten, um Cu in zukünftigen Technologiegenerationen zu ersetzen. Die vorliegende Arbeit beschreibt die Herstellung und daraus resultierenden Eigenschaften von Zwischenebenenkontakten (Vias) basierend auf CNTs. Alle verwendeten Prozessierungsschritte sind kompatibel mit der Herstellung von hochintegrierten Schaltkreisen und eine Schnittstelle zwischen den CNT Vias und einer Cu-Metallisierung ist vorhanden. Insbesondere das Verfahren zur Evaluierung von CNT Vias wurde durch den Einsatz verschiedener Methoden verbessert. Insbesondere soll hervorgehoben werden, dass durch die Messung des Widerstandes eines einzelnen CNTs, bei bekannter CNT Dichte, der Via Widerstand sehr genau vorausgesagt werden kann. Dies ermöglicht eine systematische Untersuchung des Einflusses der verschiedenen Prozessschritte und der darin verwendeten Materialien auf den Via Widerstand. Der niedrigste Kontaktwiderstand wird für Karbidformierende Metalle erreicht, solange Oxidationsprozesse ausgeschlossen werden können. Obwohl Metallnitride einen höheren Kontaktwiderstand aufweisen, sind diese für die Unterseitenmetallisierung zu empfehlen, da dadurch die Oxidation der leitfähigen Schicht minimiert wird. Insgesamt kann eine Reihenfolge beginnend mit dem niedrigsten zum höchsten Kontaktwiderstand aufgestellt werden: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Desweiteren wurde der Einfluss von Verfahren nach dem CNTWachstum wie die chemischmechanische Planarisierung, eine HF Behandlung und einer Temperaturbehandlung evaluiert, sowie deren Einfluss auf die elektrischen Parameter des Vias untersucht. Die Leitfähigkeit der integrierten CNTs und die daraus resultierenden elektrischen Transporteigenschaften in Abhängigkeit der CNT Qualität und Länge werden besprochen. Ebenso wird die starke Korrelation zwischen dem Temperaturkoeffizienten des elektrischen Widerstandes und des Ausgangswiderstandes der CNT basierten Vias bei Raumtemperatur diskutiert
46
Fiedler, Holger. "Preparation and characterization of Carbon Nanotube based vertical interconnections for integrated circuits: Preparation and characterization of Carbon Nanotube based verticalinterconnections for integrated circuits." Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2013. https://monarch.qucosa.de/id/qucosa%3A20091.
Анотація:
(ULSI) causes an increase of the resistance of the wiring system by increased scattering of electrons at side walls and grain boundaries in the state of the art Cu technology, which increases the RC delay of the interconnect system and thus degrades the performance of the device. The outstanding properties of carbon nanotubes (CNT) such as a large mean free path, a high thermal conductance and a large resistance against electromigration make them an ideal candidate to replace Cu in future feature nodes. The present thesis contributes to the preparation and properties of CNT based vertical interconnections (vias). In addition, all processes applied during the fabrication are compatible to ULSI and an interface between CNT based vias and a Cu metallization is studied. The methodology for the evaluation of CNT based vias is improved; it is highlighted that by measuring the resistance of one multiwall CNT and taking into account the CNT density, the performance of the CNT based vias can be predicted accurately. This provides the means for a systematic evaluation of different integration procedures and materials. The lowest contact resistance is obtained for carbide forming metals, as long as oxidation during the integration is avoided. Even though metal-nitrides exhibit an enhanced contact resistance, they are recommended to be used at the bottom metallization in order to minimize the oxidation of the metal-CNT contact during subsequent processing steps. Overall a ranking for the materials from the lowest to the highest contact resistance is obtained: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Furthermore the impact of post CNT growth procedures as chemical mechanical planarization, HF treatment and annealing procedures after the CNT based via fabrication are evaluated. The conductance of the incorporated CNTs and the applicable electrical transport regime relative to the CNT quality and the CNT length is discussed. In addition, a strong correlation between the temperature coefficient of resistance and the initial resistance of the CNT based vias at room temperature has been observed.Die kontinuierliche Miniaturisierung der charakteristischen Abmessungen in hochintegrierten Schaltungen (ULSI) verursacht einen Anstieg des Widerstandes im Zuleitungssystem aufgrund der erhöhten Streuung von Elektronen an Seitenwänden und Korngrenzen in der Cu-Technologie, wodurch die Verzögerungszeit des Zuleitungssystems ansteigt. Die herausragenden Eigenschaften von Kohlenstoffnanoröhren (CNT), wie eine große mittlere freie Weglänge, hohe thermische Leitfähigkeit und eine starke Resistenz gegenüber Elektromigration machen diese zu einem idealen Kandidaten, um Cu in zukünftigen Technologiegenerationen zu ersetzen. Die vorliegende Arbeit beschreibt die Herstellung und daraus resultierenden Eigenschaften von Zwischenebenenkontakten (Vias) basierend auf CNTs. Alle verwendeten Prozessierungsschritte sind kompatibel mit der Herstellung von hochintegrierten Schaltkreisen und eine Schnittstelle zwischen den CNT Vias und einer Cu-Metallisierung ist vorhanden. Insbesondere das Verfahren zur Evaluierung von CNT Vias wurde durch den Einsatz verschiedener Methoden verbessert. Insbesondere soll hervorgehoben werden, dass durch die Messung des Widerstandes eines einzelnen CNTs, bei bekannter CNT Dichte, der Via Widerstand sehr genau vorausgesagt werden kann. Dies ermöglicht eine systematische Untersuchung des Einflusses der verschiedenen Prozessschritte und der darin verwendeten Materialien auf den Via Widerstand. Der niedrigste Kontaktwiderstand wird für Karbidformierende Metalle erreicht, solange Oxidationsprozesse ausgeschlossen werden können. Obwohl Metallnitride einen höheren Kontaktwiderstand aufweisen, sind diese für die Unterseitenmetallisierung zu empfehlen, da dadurch die Oxidation der leitfähigen Schicht minimiert wird. Insgesamt kann eine Reihenfolge beginnend mit dem niedrigsten zum höchsten Kontaktwiderstand aufgestellt werden: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Desweiteren wurde der Einfluss von Verfahren nach dem CNTWachstum wie die chemischmechanische Planarisierung, eine HF Behandlung und einer Temperaturbehandlung evaluiert, sowie deren Einfluss auf die elektrischen Parameter des Vias untersucht. Die Leitfähigkeit der integrierten CNTs und die daraus resultierenden elektrischen Transporteigenschaften in Abhängigkeit der CNT Qualität und Länge werden besprochen. Ebenso wird die starke Korrelation zwischen dem Temperaturkoeffizienten des elektrischen Widerstandes und des Ausgangswiderstandes der CNT basierten Vias bei Raumtemperatur diskutiert.
47
Pozděnová, Barbora. "Srovnání nákladů rodinných domů s nosnou konstrukcí z tenkostěnných ocelových profilů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227475.
Анотація:
The aim of this thesis is to find the best option of the building technology for a house. The thesis is divided into two sections – theoretical and practical. The theoretical section consists of three parts. The first part deals with theory of costs and pricing. Second part specifies types of the budgeting used in Czech Republic and the last part is focused on description of the selected construction systems used for building a house. Second section deals with description and the layout of the house, for which three budgets are set with a respect to the used option of the construction system. Furthermore, a comparison of the technical parameters as well as the costs analysis according to the TSKP is made. Finally, the optimal variant is selected with respect to the price and technical properties.
48
Žiūkaitė, Monika. "Verslo ciklų įtakos ūkio sektoriams vertinimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2011~D_20140627_165142-60001.
Анотація:
Viso pasaulio ir atskirų valstybių ekonomika pasižymi tuo, jog pagaminamos produkcijos kiekis kasmet kinta ir ilgu laikotarpiu būna nepastovus. Vienais metais produkcijos pagaminama daugiau, kitais mažiau. Pradėjusi mažėti gamybos apimtis sukelia daugybę šalutinių efektų: ima mažėti įmonių pajamos ir pelnai, mažiau pinigų lieka investicijoms, mažėja produktyvumas, didėja prekių atsargos sandėliuose, galiausiai tenka atleisti dalį darbuotojų ar sumažinti darbo užmokestį. Žmonės, gaunantys mažesnes pajamas, išleidžia mažiau pinigų ir taip priverčia įmones dar labiau riboti savo išlaidas. Tokiu būdu patenkama į užburtą ratą, kai priežastys tampa pasekmėmis ir jos tarpusavy kartojasi, tačiau ne visos ūkio šakos vienodai stipriai reaguoja į ekonomikos svyravimus. Darbo objektas – skirtingų ūkio sektorių jautrumas verslo ciklams. Darbo tikslas – nustatyti individualų skirtingų ūkio sektorių jautrumą verslo ciklams. Darbo uždaviniai: • Išanalizuoti verslo ciklo sąvoką, siekiant suvokti jo įtaką visai ekonomikai ir įmonėms • Nustatyti ciklinių svyravimų priežastis bei pasekmes, kurios atsiranda ekonomikai esant žemiausioje verslo ciklo fazėje • Remiantis moksliniais darbais bei specializuotų agentūrų informacija, išnagrinėti verslo ciklų indikatorius, nustatant jų reikšmę verslo ciklų analizėje • Išanalizuoti įmonėje dėl ekonomikos cikliškumo susidarantį užburtą ratą, kuris leistų suprasti procesus, vykstančius ciklų metu • Remiantis mokslininkų tyrimais, nustatyti daugiausiai ir... [toliau žr. visą tekstą]The economy of all the world and different counties is characterized by the annual changes of production volume, that in the long-term is erratic. One year the amount of production is higher, others lower. The decrease in volume of production causes many side effects such as declining corporate earnings and profits, less money for investment, declining productivity, increasing inventory of goods in warehouses, then it leads firing workers or reducing wages. People with lower levels of income, spend less money and that makes companies even more to limit their costs. In this way, we get into the vicious circle, where causes become results and they inter-repeat, but not all economic sectors equally respond to economic fluctuations. Object – different economic sectors sensitivity to business cycles. The aim – to identify the individual sensitivity of different economic sectors to business cycles. Objectives: • To explore the concept of the business cycle, in order to understand it‘s impact on the economy and companies. • To find out the causes and the consequences of the cyclical fluctuations, that appears then the economy is in the lowest stage of the business cycle. • On the basis of scientific works and information of the specialized agencies, to analyze the business cycle indicators determining their value in business cycle analysis. • To analyze a vicious circle in the company, forming because of cycles of economy, which would allow to understand the processes during the... [to full text]
49
Šot, Petr. "Ověření tepelně-izolační vlastnosti termoreflexních fóliových izolací." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226729.
Анотація:
The master´s thesis deals with verification of thermal insulating property of thermoreflection foil insulations. The teoretical part of thesis focuses on the energy demand of buildings, the problems of heat transfer material, terms required for study of thermoreflection thermal insulation and experimental methods for determination of thermal insulating properties of insulators. In the next part the chapter is accompanied by an overview of the most common insulation materials which used in construction. The last part of teoretical part is devoted to the description of thermoreflect formation and analysis of the spread of thermal insulating layers of thermoreflection thermal insulation. The first part of thesis is devoted to the use of thermoreflection therm insulation in buildings. The second part of thesis is devoted to the design, assembly and calibration of the measuring device that uses a method of protected warm chamber. It is declared as a binding method of detection of the heat transfer performance of thermoreflection thermal insulation. The developed measuring device allows detection of endpoints in some direction of propagation of heat. Measurment of heat transfer coefficient devoted the third part of practical part. This part contains a description of the samples used for the measurement of the heat transfer coefficient. In the fourth chapter of the practical part are presented the results of the heat transfer coefficient measurments on selected samples of thermoreflection foil insulation. It is shown the characteristic of heat transfer coefficient of individual samples, the dependence of the heat transfer coefficient on the position of the sample in the measuring device and the recommendation of an appropriate use of sample in the works for the climatic conditions of the Czech republic. The work concludes the chapter of comparing and evaluating of all samples with practical recommendations.
50
Hásová, Eva. "Využiti ozonu při čistění odpadních vod." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216450.
Анотація:
Diploma thesis will be dealt with the utilization of ozone wastewater treatment. Experimental part will be focused on study of ozone utilization in two different reactors (bubble column, jet loop reactor). Reactors will be compared by overall mass transfer coefficient and saturation concentration. Ozonization will be applied because of biological resistent and toxic compound 2-mercaptobenzothiazole disposal. Changes of biological decomposition will be measured and assessed by respirometric measurements.