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Hello, Gaëtan. "Modélisation numérique de la rupture ductile par la méthode des équations intégrales de frontière." Compiègne, 2009. http://www.theses.fr/2009COMP1832.
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Les travaux menés durant cette thèse ont comme objectif principal le développement d'une stratégie numérique robuste pour la simulation de la rupture ductile dans des tôles minces en alliages d'aluminium. L'approche numérique retenue appartient à la classe des méthodes discontinues où les fissures résultant de l'endommagement sont représentées explicitement au moyen d'entités géométriques. Dans ce cadre de la mécanique non-linéaire de la rupture, l'atteinte de l'objectif fixé repose en premier lieu sur l'aptitude à simuler efficacement le comportement d'une tôle fissurée en présence de non-linéarités matérielles. Cette problématique est traitée au moyen d'une représentation continue du modèle par équations intégrales associée à sa discrétisation numérique par la méthode des éléments de frontière. L'extension de la formulation BEM élastoplastique aux milieux fissurés généraux se fonde sur l'approche BEM duale. Le second enjeu essentiel consiste ensuite à pouvoir déterminer l'évolution du dommage à partir de la connaissance des champs mécaniques locaux. La modélisation de l'endommagement s'appuie ainsi sur le modèle local découplé de Rice/Tracey qui s'avère à la fois adapté à la classe de tôles étudiées et pratique à implémenter dans le contexte du code de calcul C++ BEM développé. Le couplage de ces deux composantes rend alors possible la simulation effective de courbes de résistance à la rupture pour des panneaux aéronautiquesThe main goal of the works carried out during this ph-D thesis consists in developing a robust numerical strategy for the simulation of the ductile tearing phenomenon occurring in thin sheets of aluminiumalloys. The selected numerical approach belongs to the class of discontinuous methods where the cracks resulting of the damage are explicitly represented as geometrical entities. Within this framework of the non-linear fracture mechanics, reaching our aim first requires to be able to simulate efficiently the behaviour of a cracked metal sheet enduring material non-linearities. This issue is handled by the mean of a continuous description of the model based on integral equations associated to their discretized counterpart relying on the boundary element method. The extension of the elastoplastic BEM formulation to general cracked media is based on the dual BEM approach. To fulfill our initial aim, the evolution of the damage parameters has to be determined from the accurate evaluation of local mechanical fields provided by the BEM code. The modelization of the damage is hence based on the uncoupled local model of Rice/Tracey which suits to the metal sheets encountered and is easily integrated into the developed C++ BEM libraries. The coupling of these two components enables the effective simulation of resistance curves for the fracture of aeronautical panels
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Wojcik, Randolph Frank. "Dual energy scanning beam X -radiography." W&M ScholarWorks, 2004. https://scholarworks.wm.edu/etd/1539623461.
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Dual energy X-radiography is a method first developed in the mid-1970's by which one uses the information contained in the energy spectrum of the transmitted X-ray flux through an object. With this information one can distinguish the types of materials present in a radiograph and thus allow a computer to subtract them from the image enhancing the contrast of the remaining materials. Using this method, one can see details, which would have been hidden by overlying structures of other materials such as seen in radiographs of parts, made up of mixtures of metals and composites. There is also great interest in this technique for medical imaging of the chest where images of the organs are significantly improved by subtracting the bones. However, even with the enhanced capabilities realized with this technique, the majority of X-radiography systems only measures the bulk transmitted X-ray intensity and ignores the information contained in the energy spectrum. This is due to the added expense, time requirements, and registration problems incurred using standard radiographic methods to obtain dual energy radiographs. This dissertation describes a novel method which overcomes these problems and allows one to perform inexpensive, near real time, single shot dual energy X-radiography. The work of this thesis resulted in US patent #5,742,660.
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Semsir, Emine Zeynep. "Adaptive Beam Control Of Dual Beam Phased Array Antenna System." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610695/index.pdf.
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In this study, the Dual Beam Phased Array Antenna System designed for COST260* project is upgraded to have the abilities of beam steering, tracking and direction finding by providing the necessary computer codes using C++ Programming Language. The functions of new prototype are tested to verify the operation.
*COST260 project was an adaptive phased array receiving antenna system for satellite communication, which was operating at 11.49-11.678 GHz band.
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McKinnon, Hamish Alexander. "Improved Hydrogen Production from Biomass Gasification in a Dual Fluidissed Bed Reactor." Thesis, University of Canterbury. Chemical and Process Engineering, 2009. http://hdl.handle.net/10092/4459.
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Biomass gasification is a technology under development that presents a means of generating hydrogen using renewable energy. While many forms of gasification have been investigated, steam gasification using a dual fluidised bed (DFB) reactor has been shown to efficiently produce high hydrogen content producer gas. The aims of this research were to increase the hydrogen yield from the 100kW DFB gasifier installed at the University of Canterbury, and thereby improve the current state of the art of gasifier operation.
Calcium carbonate-based minerals such as calcite and dolomite were shown to be able to improve hydrogen production by absorbing carbon dioxide in the producer gas, promoting the water gas shift reaction. Bed material mixtures of olivine and calcite were the most effective at improving gasifier performance, increasing producer
gas yield by 20%, increasing cold gas efficiency by 6% and increasing hydrogen yield by 85%. In addition, the carbon monoxide content was reduced and the ratio of hydrogen to carbon monoxide in the producer gas was ideal for Fisher-Tropsch synthesis of liquid fuels.
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Frejowski, Tom. "Design of a dual beam optical trap." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123212.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 29-30).
Dual beam optical traps use radiation pressure from two counterpropagating laser beams to manipulate microscopic particles. Typical traps use optical fibers to guide those beams. This thesis proposes a design for the coaxial alignment of optical fibers that allows for the fibers to translate along a common axis while maintaining alignment. Additionally, this design enables the optical fibers and trapping samples to be quickly and easily swapped out for different experiments. A full optical trapping setup was constructed using this design and successfully demonstrated the trapping of multiple polystyrene microspheres.
by Tom Frejowski.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Lee, Jung Kyu, and Flaviis Franco De. "DUAL-BAND SWITCHED BEAM SYSTEM WITH HIGH FREQUENCY RATIO (1:1.8) FOR TELEMETRY APPLICATIONS." International Foundation for Telemetering, 2006. http://hdl.handle.net/10150/603932.
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ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, CaliforniaIn this paper, we propose a dual-band switched beam system operating at 4.05 and 7.4 GHz. This system comprise of a dual frequency Butler matrix feeding a microstrip antenna array. Very good agreement is shown between measured and simulated data. The system can provide a tilted beam of ±13° and ±48° at the lowest frequency band and ±9° and ±27° at the higher frequency band.
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Rieger, Anne. "Analyse der Stimulationsparameter bei atrialer "Dual-site"-Stimulation." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972319921.
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Vilches, Freixas Gloria. "Dual-energy cone-beam CT for proton therapy." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI099/document.
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La proton thérapie est une modalité de traitement du cancer qu’utilise des faisceaux de protons. Les systèmes de planification de traitement actuels se basent sur une image de l’anatomie du patient acquise par tomodensitométrie. Le pouvoir d’arrêt des protons relatif à l’eau (Stopping Power Ratio en Anglais, SPR) est déterminé à partir des unités Hounsfield (Hounsfield Units en Anglais, HU) pour calculer la dose absorbée au patient. Les protons sont plus vulnérables que les photons aux modifications du SPR du tissu dans la direction du faisceau dues au mouvement, désalignement ou changements anatomiques. De plus, les inexactitudes survenues de la CT de planification et intrinsèques à la conversion HU-SPR contribuent énormément à l’incertitude de la portée des protons. Dans la pratique clinique, au volume de traitement s’ajoutent des marges de sécurité pour tenir en compte ces incertitudes en détriment de perdre la capacité d’épargner les tissus autour de la tumeur. L’usage de l’imagerie bi-énergie en proton thérapie a été proposé pour la première fois en 2009 pour mieux estimer le SPR du patient par rapport à l’imagerie mono-énergie. Le but de cette thèse est d’étudier la potentielle amélioration de l’estimation du SPR des protons en utilisant l’imagerie bi-énergie, pour ainsi réduire l’incertitude dans la prédiction de la portée des protons dans le patient. Cette thèse est appliquée à un nouveau système d’imagerie, l’Imaging Ring (IR), un scanner de tomodensitométrie conique (Cone-Beam CT en Anglais, CBCT) développé pour la radiothérapie guidée par l’image. L’IR est équipé d’une source de rayons X avec un système d’alternance rapide du voltage, synchronisé avec une roue contenant des filtres de différents matériaux que permet des acquisitions CBCT multi-énergie. La première contribution est une méthode pour calibrer les modèles de source et la réponse du détecteur pour être utilisés en simulations d’imagerie X. Deuxièmement, les recherches ont évalué les facteurs que peuvent avoir un impact sur les résultats du procès de décomposition bi-énergie, dès paramètres d’acquisition au post-traitement. Les deux domaines, image et basée en la projection, ont été minutieusement étudiés, avec un spéciale accent aux approches basés en la projection. Deux nouvelles bases de décomposition ont été proposées pour estimer le SPR, sans avoir besoin d’une variable intermédiaire comme le nombre atomique effectif. La dernière partie propose une estimation du SPR des fantômes de caractérisation tissulaire et d’un fantôme anthropomorphique à partir d’acquisitions avec l’IR. Il a été implémentée une correction du diffusé, et il a été proposée une routine pour interpoler linéairement les sinogrammes de basse et haute énergie des acquisitions bi-énergie pour pouvoir réaliser des décompositions en matériaux avec données réelles. Les valeurs réconstruits du SPR ont été comparées aux valeurs du SPR expérimentales déterminés avec un faisceau d’ions de carboneProton therapy is a promising radiation treatment modality that uses proton beams to treat cancer. Current treatment planning systems rely on an X-ray computed tomography (CT) image of the patient's anatomy to design the treatment plan. The proton stopping-power ratio relative to water (SPR) is derived from CT numbers (HU) to compute the absorbed dose in the patient. Protons are more vulnerable than photons to changes in tissue SPR in the beam direction caused by movement, misalignment or anatomical changes. In addition, inaccuracies arising from the planning CT and intrinsic to the HU-SPR conversion greatly contribute to the proton range uncertainty. In clinical practice, safety margins are added to the treatment volume to account for these uncertainties at the expense of losing organ-sparing capabilities. The use of dual-energy (DE) in proton therapy was first suggested in 2009 to better estimate the SPR with respect to single-energy X-ray imaging. The aim of this thesis work is to investigate the potential improvement in determining proton SPR using DE to reduce the uncertainty in predicting the proton range in the patient. This PhD work is applied to a new imaging device, the Imaging Ring (IR), which is a cone-beam CT (CBCT) scanner developed for image-guided radiotherapy (IGRT). The IR is equipped with a fast kV switching X-ray source, synchronized with a filter wheel, allowing for multi-energy CBCT imaging. The first contribution of this thesis is a method to calibrate a model for the X-ray source and the detector response to be used in X-ray image simulations. It has been validated experimentally on three CBCT scanners. Secondly, the investigations have evaluated the factors that have an impact on the outcome of the DE decomposition process, from the acquisition parameters to the post-processing. Both image- and projection-based decomposition domains have been thoroughly investigated, with special emphasis on projection-based approaches. Two novel DE decomposition bases have been proposed to estimate proton SPRs, without the need for an intermediate variable such as the effective atomic number. The last part of the thesis proposes an estimation of proton SPR maps of tissue characterization and anthropomorphic phantoms through DE-CBCT acquisitions with the IR. A correction for X-ray scattering has been implemented off-line, and a routine to linearly interpolate low-energy and high-energy sinograms from sequential and fast-switching DE acquisitions has been proposed to perform DE material decomposition in the projection domain with real data. DECT-derived SPR values have been compared with experimentally-determined SPR values in a carbon-ion beam
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De, la Rey Jandri. "Energy efficiency in dual fluidised bed fast pyrolysis." Diss., University of Pretoria, 2015. http://hdl.handle.net/2263/57516.
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The Combustion Reduction Integrated Pyrolysis System (CRIPS) is a dual fluidised bed fast pyrolyser that was developed at the University of Pretoria for the conversion of biomass waste to biofuels. The dual fluidised bed design allows in situ catalytic upgrading of bio-oil, by providing the conditions required for the regeneration and decoking of catalysts. The first version of the CRIPS process (CRIPS 1) emphasised the need for an energy balance approach to model the pyrolysis process rather than a mass balance. CRIPS 1 experienced severe energy losses and as a result very poor performance was observed. The energy balance was set up in the enthalpy reference level since no shaft work was produced and the entire process was operated under constant atmospheric conditions. The enthalpy balance approach was set up to analyse the process performance and energy efficiencies of a CRIPS process and possibly the bio-oil energy content and yield that could be expected from such a process. The approach was used to derive the bio-oil properties and energy efficiencies for a number of scenarios based on the CRIPS process. The Higher Heating Value (HHV) of the bio-oil was derived using the total energy balance of the CRIPS process. The validity of the approach was confirmed by comparing the derived bio-oil HHV from CRIPS 1 of 14,2 MJ/kg with that of similar processes, in the range of 17-23 MJ/kg, as well as comparison to the operating data and process yields. The enthalpy balance approach was able to accurately model the operation of CRIPS 1 using energy and mass balances and therefore the approach was used in the design of CRIPS 2 to limit heat losses and improve the process efficiency by recovering heat from the exhaust of the combustor. The heat recovery resulted in significant improvements in the efficiency of CRIPS 2 (74%) compared to CRIPS 1 (33%). The final design of the CRIPS 2 process featured an annular design in which the combustion bed is located in a refractory cylinder, with the pyrolysis bed around the refractory. The design allowed for the addition of a heat exchanger inside the combustor which is responsible for the increase in efficiency.Dissertation (MEng)--University of Pretoria, 2015.
tm2016
Chemical Engineering
MEng
Unrestricted
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Diawara, Bandiougou. "Caractérisation quantitative de la microstructure de l'acier 16MND5 des cuves de réacteurs nucléaires à eau pressurisée." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENI063.
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Ce travail de thèse concerne l’acier 16MND5 des cuves des Réacteurs à Eau Préssurisée (REP).L’étude vise à caractériser de manière quantitative la microstructure et à comprendre l’effet desparamètres influents (vitesse de refroidissement, température de revenu …) sur sa formation. D’unpoint de vue expérimental, l’étude est menée grâce à l’utilisation des techniques d’observationcomme la métallographie, le MET, MEB et l’EBSD, et la réalisation de traitements thermiquescontrôlés (dilatométrie notamment).Ces observations visent à identifier les différents constituants de l’acier et de déterminer lesgrandeurs quantitatives les caractériser (tailles, fractions volumiques des différentes phases ainsique leurs orientations cristallographiques).Nous avons dans un premier temps caractérisé de manière complète et quantitative, lamicrostructure de l’acier 16MND5 à l’état de réception (trempé et revenu). L’étude a permis demontrer qu’il existe un gradient de microstructure entre la peau interne et le coeur de l’épaisseur dela virole. La microstructure à coeur est constituée de ferrite proeutectoïde, de bainite et d’amas decarbures, tandis qu’en peau interne on est en présence de bainite et d’amas de carbures.Une campagne d’essais de dilatométrie a été réalisée afin de simuler la microstructure brute detrempe de l’acier 16MND5 et d’observer l’effet de la vitesse de refroidissement, des températuresde transformation sur la microstructure des aciers de cuve. Ces essais ont révélé que lamicrostructure de l’acier 16MND5 après refroidissement est constituée de bainite, d’îlots demartensite et d’austénite résiduelle (M-A) enrichie en carbone. Ce sont ces îlots M-A qui donnentnaissance aux amas de carbures lors du revenu final.L’effet de la composition chimique de cet acier a été étudié grâce à l’utilisation d’une tôle ayant unecomposition chimique plus riche en carbone et en éléments d’alliages. Ce travail a montré quel’augmentation des teneurs en carbone et en éléments d’alliages modifiaient la morphologie et lacristallographie de la ferrite.L’étude des comportements mécaniques des constituants présents en peau interne, quart épaisseur etmi épaisseur a été réalisée grâce à des essais de résilience sur des éprouvettes de mini charpy. Cetteétude a permis de montrer qu’à basse température (-120°C) la peau interne présente de meilleurespropriétés de résilience que le quart et la mi épaisseur de la virole. Des examens de la surfacelatérale des éprouvettes de Charpy ont montré que la présence de ferrite proeutectoïde favorise lagermination de micro-fissures de clivageReactor pressure vessel is the second security barrier of the nuclear reactor and it is elaboratedwith a low carbon steel ( C-0.16%). Due to the large size of the ferrule there is temperatureand cooling rate gradient, which lead to microstructure gradient. To develop predictive modelit is necessary to well describe the microstructure which depend to the processing parameters.We focuse our work in investigating the effect of the processing parameters (cooling rate,chemical composition...) on the final microstructure during phase transformation.To get these informations and better describe the microstructure, we have used someexperimental technics like SEM, EBSD, TEM and Optical Microscopy. The steel used is alow carbon steel with a composition of C-0.16%, Mn-1.32%, Ni-0.72%, Mo-0.49%, Si-0.23%, Cr-0.23%, P-0.010%, S-0.004%. The material has been tempered in the range 635°C-660°C after cooling. Three positions have been chosen for examinations, because the coolingrate is not the same between the center and the edge of the material. The results of theobservations made in the different scale, indicate that the microstructure is mainly baniticwith bainitic ferrite and cementite precipitates. Examinations of the precipitates withextractive replicas in TEM reveal that morphology of cementite particles is complex they arecylinder-shaped particles, short bars particles and skeletal particles. OrientationsRelationships (OR) have been determined between ferrite and cementite particles with thinfoils in TEM by using Selected Area Diffraction, in a large number areas the Isaichev andBagaryatskii OR have been observed, a little Pitsch Petch OR have been obtained. The EBSDmap shows that the bainitic ferrite morphologies are both lath like and polygon. Themisorientations inside the laths are very small (0.5° misorientation point to point) andbetween laths we have the range 49-60° misorientation. The profile of misorientationsbetween point to point indicates higher frequency for the range 49-60°. Charpy test have beenperformed to analyze the effect of the microstructure on the fracture energy at lowtemperature. The results show that the fracture energy decreases when the content ofproeutectoid ferrite is high
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Folkeson, Björn. "Propensity of bed materials used in dual fluidized beds to retain ash-forming elements from biomass fuels." Thesis, SLU, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-239002.
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The main aim of this work was to investigate the propensity of bed materials to retain ash-forming elements from biomass under conditions relevant to dual fluidized bed gasification (DFBG). The investigation was carried out in a laboratory-scale bubbling fluidized bed reactor in which biomass was gasified with steam and the unconverted char was combusted in the temperature range 800–900 ° C. Three bed materials (sand, olivine and bauxite) and two biomass fuels (forestry residue and wheat straw) were studied. From the results obtained and literature on the ash transformation chemistry during thermal conversion of biomass, it was found that the extent to which ash-forming elements from biomass are retained on bed materials depend among other factors on (1) the abundance of ash-forming elements in the fuel, (2) the ability of the bed material to react and form compounds with ash-forming elements and (3) the atmosphere surrounding the fuel in the reactor. For example, Ca, P and K (which were among the most abundant ash-forming elements in the forestry residues) were also the main ashforming elements retained on sand, olivine and bauxite during thermal conversion of the forestry residues. However, the retention of these elements differed on the three bed materials. With respect to reactor atmosphere, Ca and P were retained on olivine primarily during char combustion while the retention of K on olivine was somewhat similar during gasification and char combustion. In addition to the experimental results, the effect of the retention of ash-forming elements on bed agglomeration tendency and the composition of the product gas is discussed as well as the relevance of the obtained results for the DFBG process.
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Gao, Tian. "Mode-I Fracture in Bonded Wood: Studies of Adhesive Thermal Stability, and of the Effects of Wood Surface Deactivation." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31697.
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This work included two separate studies; the common theme in each was the use of mode-I fracture testing to evaluate wood adhesion.
In the first study, mode-I fracture testing was used to compare the thermal stability of polyurethane (PUR) and resorcinol-formaldehyde (RF) wood adhesives. Bonded specimens for both adhesives were subjected to prolonged thermal exposure, and fracture testing was subsequently conducted after re-equilibration to standard test conditions. It was found that both PUR and RF suffered a significant fracture energy loss after heat treatment, and that RF was more thermally stable than PUR, as expected. However, both adhesives suffered significant thermal degradation, and fracture testing did not distinguish the RF system as being clearly superior to PUR. Dynamic mechanical analysis (DMA) was also used to analyze and compare the thermal softening of PUR and RF in terms of the decline in storage modulus. DMA results indicated that PUR specimens suffered greater stiffness loss due to simple thermal softening. Because fracture testing indicated that both adhesives suffered significant degradation, the DMA results suggested that the generally superior fire resistance of RF adhesives is born from greater high temperature stiffness; whereas the more compliant PUR suffers greater immediate softening during thermal exposure. In other words, both systems suffer from thermal degradation, but the more highly cross-linked RF system suffers less thermal softening and therefore maintains a greater load carrying capacity during fire exposure.
In the second study, mode-I fracture testing was used to test the effects of wood surface thermal deactivation (surface energy reduction) on the adhesion between southern pine wood (Pinus spp.) and polyethylene (PE). Pine specimens were progressively surface deactivated by 185°C heat treatments for periods of 5, 15, and 60 minutes. Control and deactivated pine laminae were subsequently hotpressed/bonded using PE film as the adhesive. Mode-I fracture testing was conducted under the assumption of linear elasticity, however load/displacement test curves suffered from a severe degree of nonlinearity believed to be caused by PE bridging behind the advancing crack tip. Instead of applying a nonlinear data analysis, a standard linear elastic analysis was conducted and deemed acceptable for comparative purposes within this study. Under dry conditions (unweathered specimens), 5 and 15 minute thermal treatments resulted in progressively worse adhesion (lower fracture energies) when compared to control surfaces; but the 60 minute heat treatment improved adhesion relative to 5 and 15 minute treatments, and showed a trend of improving adhesion as surface deactivation became more extreme. Simulated-weather resistance was also studied and it was determined that the highest degree of surface deactivation slightly improved weather durability in comparison to control surfaces. Overall, the findings here were similar to those in a previously published work- thermal deactivation of wood surfaces shows promise as a method to improve adhesion between wood and nonpolar polyolefins.Master of Science
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Göransson, Kristina. "Internal Tar/CH4 Reforming in Biomass Dual Fluidised Bed Gasifiers towards Fuel Synthesis." Doctoral thesis, Mittuniversitetet, Avdelningen för kemiteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-22984.
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Production of high-quality syngas from biomass gasification in a dual fluidised bed gasifier (DFBG) has made a significant progress in R&D and Technology demonstration. An S&M scale bio-automotive fuel plant close to the feedstock resources is preferable as biomass feedstock is widely sparse and has relatively low density, low heating value and high moisture content. This requires simple, reliable and cost-effective production of clean and good syngas. Indirect DFBGs, with steam as the gasification agent, produce a syngas of high content H2 and CO with 12-20 MJ/mn3 heating value. The Mid Sweden University (MIUN) gasifier, built for research on synthetic fuel production, is a dual fluidised bed gasifier. Reforming of tars and CH4 (except for methanation application) in the syngas is a major challenge for commercialization of biomass fluidised-bed gasification technology towards automotive fuel production. A good syngas from DFBGs can be obtained by optimised design and operation of the gasifier, by the use of active catalytic bed material and internal reforming. This thesis presents a series of experimental tests with different operation parameters, reforming of tar and CH4 with catalytic bed material and reforming of tar and CH4 with catalytic internal reformer. The first test was carried out to evaluate the optimal operation and performance of the MIUN gasifier. The test provides basic information for temperature control in the combustor and the gasifier by the bed material circulation rate. After proven operation and performance of the MIUN gasifier, an experimental study on in-bed material catalytic reforming of tar/CH4 is performed to evaluate the catalytic effects of the olivine and Fe-impregnated olivine (10%wtFe/olivine Catalyst) bed materials, with reference to non-catalytic silica sand operated in the mode of dual fluidised beds (DFB). A comparative experimental test is then carried out with the same operation condition and bed-materials but when the gasifier was operated in the mode of single bubbling fluidised bed (BFB). The behaviour of catalytic and non-catalytic bed materials differs when they are used in the DFB and the BFB. Fe/olivine and olivine in the BFB mode give lower tar and CH4 content together with higher H2+CO concentration, and higher H2/CO ratio, compared to DFB mode. It is hard to show a clear advantage of Fe/olivine over olivine regarding tar/CH4 catalytic reforming. In order to significantly reduce the tar/CH4 contents, an internal reformer, referred to as the FreeRef reformer, is developed for in-situ catalytic reforming of tar and CH4 using Ni-catalyst in an environment of good gas-solids contact at high temperature. A study on the internal reformer filled with and without Ni-catalytic pellets was carried out by evaluation of the syngas composition and tar/CH4 content. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases from 25 g/m3 down to 5 g/m3 and the CH4 content from 11% down below 6% in the syngas. The MIUN gasifier has a unique design suitable for in-bed tar/CH4 catalytic reforming and continuously internal regeneration of the reactive bed material. The novel design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas composition.Gasification-based Biorefinery for Mechanical Pulp Mills
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Benawra, Jashil Singh. "Developing dual beam methods for the study of polymers." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611359.
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Theunissen, W. H. "Reconfigurable contour beam synthesis using a mechanical FEM surface description of dual offset reflector antenna surfaces." Thesis, University of Pretoria, 1999. http://hdl.handle.net/2263/26784.
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Schäffer, Benno. "Dual Energy CT-Kolonographie als präoperatives Staging bei kolorektalen Neoplasien." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-163992.
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Jaini, Rajiv. "Mass-transfer correlations for the dual bed colloidal suspension reactor." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50210.
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To meet the growing energy world demands, and in conjunction, lower CO2 production levels, near zero emission energy sources must be pushed to the forefront as alternatives to fossil fuels. Photoelectrochemical (PEC) cells are a potential alternative to fossil fuels and have recently generated much interest because of their potential to electrolyze water into hydrogen fuel from sunlight. But in order to be competitive with fossil fuels, understanding the mass-transfer limitations in PEC systems is critical. This work focuses on the addressing the mass-transfer limitations in a conceptually novel PEC cell reactor, the Dual Bed Colloidal Suspension Reactor (DBCSR).
Mass-transfer correlations for the DBCSR are presented. The correlations are based on experimental data obtained using two fabricated diffusion cells. The working correlation representative of both cells is given.
An analysis of the orientation of the gas sparger suggests that the transport phenomena in both cells is not the same, and therefore using two correlations to represent similar systems is justified. An energy analysis is presented that shows that gas sparging is a low energy consumption option to mitigate mass-transfer limitations. Future work is suggested for better understanding the mass-transfer behavior in the DBCSR.
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Schulz, Jana [Verfasser]. "Rolle von Dual-Oxidase 2 bei akuter Dünndarmmukositis / Jana Schulz." Mainz : Universitätsbibliothek der Johannes Gutenberg-Universität Mainz, 2021. http://d-nb.info/1238223753/34.
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Xu, Dongli, Weibin Zhou, and Leilei Peng. "Cellular resolution multiplexed FLIM tomography with dual-color Bessel beam." OPTICAL SOC AMER, 2017. http://hdl.handle.net/10150/623268.
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Fourier multiplexed FLIM (FmFLIM) tomography enables multiplexed 3D lifetime imaging of whole embryos. In our previous FmFLIM system, the spatial resolution was limited to 25 mu m because of the trade-off between the spatial resolution and the imaging depth. In order to achieve cellular resolution imaging of thick specimens, we built a tomography system with dual-color Bessel beam. In combination with FmFLIM, the Bessel FmFLIM tomography system can perform parallel 3D lifetime imaging on multiple excitation-emission channels at a cellular resolution of 2.8 mu m. The image capability of the Bessel FmFLIM tomography system was demonstrated by 3D lifetime imaging of dual-labeled transgenic zebrafish embryos. (C) 2017 Optical Society of America
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Fatehi, Pouladi Soheil. "Phosphorus Removal from Domestic Wastewater Using Dual Reactive Materials Polonite® and Absol®." Thesis, KTH, Miljögeokemi och ekoteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95429.
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Private wastewater treatment facilities release tons of phosphorus to the aquatic environment due to the insufficient removal efficiency in conventional soil infiltration systems. Reactive filter materials have demonstrated promising P removal rates. Laboratory-scale column experiments were carried out using Absol® and Polonite® in dual infiltration media and results were compared with Polonite® functioning as the only layer of reactive filter material. Two sets of experiments were arranged with layer lengths of 5 cm and 15 cm which were operated for 50 and 119 days respectively. Columns with an additional layer of Absol® demonstrated very good average removal rates of 85.99 % and 99.13 % in both experiments while the effluent in the former exceeded the maximum allowed P concentration shortly after half of the total time of the experiment. On the other hand, O-P concentration in collected samples from dual filter media with 15 cm layers of Absol® and Polonite® (column B1) was as low as 0.04 mg/l after 119 days of operation exhibiting high potentials for Absol® in local wastewater treatment. Levels of pH in treated samples showed a decreasing trend in all columns which was similarly simultaneous with high removal rates observed in B1.
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Akemeier, Dieter [Verfasser]. "Nano-prototyping and 3D bioimaging with dual beam microscopy / Dieter Akemeier." Bielefeld : Universitätsbibliothek Bielefeld, 2012. http://d-nb.info/1047666421/34.
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Older, Julia K. (Julia Katherine) Carleton University Dissertation Physics. "Beam hardening correction for standard computed tomography using dual-material decomposition." Ottawa, 1991.
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Engelhard, Nils [Verfasser]. "Mikrostrukturelle Bildgebung bei Wirbelkörperkompressionsfrakturen mit der Dual-Energy-Computertomographie / Nils Engelhard." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2021. http://d-nb.info/1234982218/34.
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McGrow, Anja. "Prozedurales Lernen bei Zwangsstörungen." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2011. http://dx.doi.org/10.18452/16277.
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Das aktuelle Modell zur Pathophysiologie der Zwangserkrankung (OCD) geht von fronto-striatalen Dysfunktionen aus. Damit werden Beeinträchtigungen im prozeduralen Lernen, das anhand der Serial Reaction Time Task (SRTT) erfasst werden kann, in Verbindung gebracht. Die Befunde zu Defiziten von OCD-Patienten in der SRTT sind widersprüchlich, was auf Unterschiede im methodischen Vorgehen sowie die zusätzliche Auslastung des Arbeitsgedächtnisses durch die Vorgabe einer Gedächtnisaufgabe zurückgeführt wird. Weiterhin ist unklar, ob die vermutete fronto-striatale Dysfunktion und die Defizite im prozeduralen Lernen kennzeichnend für OCD sind oder auch bei anderen Störungsbildern auftreten. Die prozedurale Lernleistung von OCD-Patienten wurde mit der Lernleistung von gesunden Probanden, Patienten mit einer Angststörung und Patienten mit einer Depression verglichen. Weiterhin wurde die prozedurale Lernleistung unter der Vorgabe der SRTT alleine (single-task) und bei gleichzeitiger Vorgabe einer Gedächtnisaufgabe (dual-task) untersucht. OCD-Patienten zeigten im Vergleich zu gesunden Probanden Defizite im prozeduralen Lernen – sowohl unter der single-task als auch unter der dual-task Bedingung. Im Vergleich zu Patienten mit einer Angststörung zeigte sich lediglich in der dual-task Bedingung eine tendenzielle Beeinträchtigung der OCD-Patienten. Keine Unterschiede ergaben sich in der prozeduralen Lernleistung zwischen OCD-Patienten und Patienten mit einer Depression. Die stärkste Beeinträchtigung der prozeduralen Lernleistung in den verschiedenen Symptomdimensionen (Kontrolle, Waschen, Symmetrie, Horten) der OCD zeigte sich in der Dimension Horten. Außerdem waren die Defizite im prozeduralen Lernen stärker bei Patienten mit einem früheren Beginn der Zwangsstörung ausgeprägt. Die Befunde stehen im Einklang mit bisherigen Ergebnissen, wonach bei OCD eine Beeinträchtigung im prozeduralen Lernen vorliegt, was für die Annahme einer fronto-striatalen Dysfunktion bei OCD spricht.Obsessive-compulsive disorder (OCD) is seen as a disease that implicates fronto-striatal dysfunctions. These dysfunctions are hypothesized to be related to neuropsychological deficits. One of the putative deficits regards procedural learning, which can be assessed by using the serial reaction time task (SRTT). So far, the results regarding procedural learning in OCD patients are inconsistent, which is attributed to differences in methods, like the implementation of a secondary task (dual-task condition) using a concurrent working memory load. Moreover, it is still uncertain whether the fronto-striatal dysfunctions and the deficits in procedural learning are specific to OCD or if they can also be found in other mental illnesses. Procedural learning performance as measured with the SRTT was compared in OCD patients, healthy subjects, patients with anxiety disorder and depression. Additionally, procedural learning was examined under single- (SRTT) and dual-task (SRTT plus a secondary task) conditions. In comparison with healthy subjects, procedural learning was impaired in OCD patients – both in the single- and in the dual-task condition. Yet in the dual task condition, procedural learning was diminished in both groups. Compared to patients with anxiety disorder, OCD patients were impaired in procedural learning only in the dual-task condition, while there was no difference between OCD and depression in procedural learning. Regarding the different symptom dimensions of OCD (checking, washing, symmetry, hoarding), patients high on the dimension hoarding exhibited the most distinct impairment. Moreover, deficits in procedural learning were more pronounced in OCD patients with an earlier age at illness onset. The results confirm previous findings and add supportive evidence for performance deficits in procedural learning and the fronto-striatal dysfunction model of OCD.
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Bell, Christa. "Investigation of catalytic partial oxidation of methane using platinumnickel dual bed reactors." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99756.
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The catalytic partial oxidation of methane to produce synthesis gas using a platinum/nickel dual bed reactor has been shown to have high conversions and selectivity of synthesis gas products, hydrogen and carbon monoxide. In this work the relative length of the platinum and nickel in the dual bed reactor is investigated experimentally and a model describing the nickel portion of the dual bed catalyst is developed. The model uses simplified flow conditions, experimentally determined temperature profiles and an elementary reaction mechanism to describe the nickel bed of the reactor. The rate parameters of the elementary reaction in the mechanism are determined using theoretical methods. Unity Bond Index - Quadratic Exponential Potential (UBI-QEP) is used to determine the activation energy and thermodynamic consistency is forced to produce a set of preexponential factors.
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Lim, Mook Tzeng. "Hydrodynamics of a Cold Model of a Dual Fluidized Bed Gasification Plant." Thesis, University of Canterbury. Chemical and Process Engineering, 2012. http://hdl.handle.net/10092/6287.
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Biomass energy is increasingly used to reduce the dependence on fossil fuels and reduce the impact of greenhouse gas emissions on global warming. Fluidized bed
gasification converts solid biomass into gaseous fuels that can be used for combustion or liquid fuels synthesis. The efficiency of biomass gasification is directly affected by the fluidized bed hydrodynamics. For example, the solids recirculation rate through the system is an important parameter that affects the heat and mass transfer rates. In this study, a cold model of a dual fluidized bed (DFB) biomass gasification plant was designed using scaling laws, and was constructed to investigate the hydrodynamics of
industrial DFBs. A DFB consists of a bubbling fluidized bed (BFB), where biomass is gasified to produce syngas, and a circulating fluidized bed (CFB) where the residues of
gasification are combusted. The investigation was divided into Phase I and II. In Phase I, an operational map was developed for the CFB to define operational boundaries for
steady state operation of the plant. An empirical model was developed to predict the solids mass flow rate out of the CFB riser, which is an empirical function of the exit
opening width, the CFB diameter, and a newly introduced aerodynamic factor. The correlation coefficient, R2 for the empirical function was 0.8327. The aerodynamic
factor accounts for the particle inertia and clustering effects at the exit of the CFB riser. Results from Phase I also showed that increasing the fluidizing velocities increased the solids circulation rate and affected the pressure drop over various points in the CFB plant
due to redistribution of solids with the system. A critical assessment was performed on published correlations found in the literature to determine how accurately they predicted
the hydrodynamics in the CFB riser. By comparing predicted and experimental results, the correlations were found to be inaccurate for the conditions and configuration of the
CFB tested in this study. For example, the solids velocity was not accurately predicted by published correlations due to unaccounted particle clustering effects. The main issue
with the published correlations was a lack of generality, so that the correlations only applied for predicting fluidizing behaviour in the equipment they were developed in. In Phase II, an operational map was developed for the DFB, which incorporated both the CFB and the BFB. Experiments with a binary mixture representing sand and char in an industrial gasifier showed a blocking effect in the connecting chute between the CFB and BFB by the material representing char, which was larger and less dense than the material representing sand. A computational fluid dynamics (CFD) based design tool for modelling the cold model CFB cyclone was developed and validated by comparing the predicted and experimental cyclone pressure drop. The correlation coefficient for the CFD pressure drop prediction was 0.7755. The design tool contained information about the grid resolution and the time step required for modelling the cyclone accurately.
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Pearson, Robert Anthony. "An array-fed dual reflector antenna for limited sector electronic beam scanning." Thesis, University College London (University of London), 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715430.
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Myeong-Heom, Park. "Effect of Grain Size on Mechanical Properties of Dual Phase Steel Composed of Ferrite and Martensite." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225592.
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Kim, Jae-Keun. "Synthesis and characterisation of titanium nitride films using a dual ion beam technique." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292883.
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Hsu, Shih-Hsun. "Dual-band beam scanning reflectarrays and novel wideband and polarization diversified planar antennas." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2948.
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Reyes-Ramirez, Paula Andrea. "Hydrodynamic study of a dual fluidized bed system at room and elevated temperatures." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45126.
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Gasification with in-situ CO₂ looping cycle is a promising technology to produce energy while reducing CO₂ emissions. An alternative reactor concept to carry out the integrated process is a Dual Fluidized Bed (DFB). In this reactor, a solid sorbent is continuously circulated between two vessels to undergo multiple carbonation and sorbent regeneration. A comprehensive understanding of the fluidization characteristics of lime-based sorbents (commonly used for CO₂ capture), solids transport between the vessels, and operational analysis of DFB are important for the design and scale-up of the integrated process.
In this study, the hydrodynamic behaviour of limestone of mean diameter 438 µm in a DFB consisting of a riser interconnected via a loop-seal and a downcomer to a bubbling fluidized bed (BFB) was investigated at temperatures up to 250°C. The effects of operating parameters influencing the performance and stability of the system such as riser superficial gas velocity (2.5-6.5 m/s), aeration velocity (1 to 7Umf) and solids circulation flux (25-139 kg/m²･s) on the pressure profiles and cross-sectional average solids holdup in the riser were determined at room temperature. Further experimental work was conducted in the same DFB facility, and employing the same limestone particles to study the effect of scale on hydrodynamics, while increasing the bed temperature. Gas leakage between the coupled fluidized beds and its relationship with operating conditions, was also measured based on a gas tracer technique.
Stable operation of the DFB was obtained under the conditions evaluated. The cross-sectional solids holdup in the riser was found to increase with increasing solids mass flux and decreasing riser gas velocity. The DFB riser operated within the fast fluidization and the dilute-phase transport regimes with the transition point characterized by the presence of accumulative choking. Analysis of the pressure profiles revealed that the pressure head in the loop-seal is an important parameter to obtain high solids circulation flux. Furthermore, the pressure in the BFB was found to influence the rate of leakage of riser product gas into this reactor. Smoother fluidization was obtained at elevated temperatures. The results showed that solids holdup in riser decreased with increasing temperature.
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Dong, Xue. "Novel methods for scatter correction and dual energy imaging in cone-beam CT." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51903.
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Excessive imaging doses from repeated scans and poor image quality mainly due to scatter contamination are the two bottlenecks of cone-beam CT (CBCT) imaging. This study investigates a method that combines measurement-based scatter correction and a compressed sensing (CS)-based iterative reconstruction algorithm to generate scatter-free images from low-dose data. Scatter distribution is estimated by interpolating/extrapolating measured scatter samples inside blocked areas. CS-based iterative reconstruction is finally carried out on the under-sampled data to obtain scatter-free and low-dose CBCT images. In the tabletop phantom studies, with only 25% dose of a conventional CBCT scan, our method reduces the overall CT number error from over 220 HU to less than 25 HU, and increases the image contrast by a factor of 2.1 in the selected ROIs. Dual-energy CT (DECT) is another important application of CBCT. DECT shows promise in differentiating materials that are indistinguishable in single-energy CT and facilitates accurate diagnosis. A general problem of DECT is that decomposition is sensitive to noise in the two sets of projection data, resulting in severely degraded qualities of decomposed images. The first study of DECT is focused on the linear decomposition method. In this study, a combined method of iterative reconstruction and decomposition is proposed. The noise on the two initial CT images from separate scans becomes well correlated, which avoids noise accumulation during the decomposition process. To fully explore the benefits of DECT on beam-hardening correction and to reduce the computation cost, the second study is focused on an iterative decomposition method with a non-linear decomposition model for noise suppression in DECT. Phantom results show that our methods achieve superior performance on DECT imaging, with respect to noise reduction and spatial resolution.
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Carlini, Gianluca. "Artefatti di ricostruzione nella tomografia computerizzata con raggi X." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16933/.
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Gli artefatti da ricostruzione sono problemi comuni nella tomografia computerizzata con raggi X. Essi possono degradare la qualità di una immagine al punto da renderla inutilizzabile. Scopo dell’elaborato è l’analisi di diversi tipi di artefatti, a partire dai fenomeni che li causano, fino ad arrivare ai metodi impiegati per eliminarli o quantomeno ridurli. A tal fine si è proceduto ad una approfondita ricerca bibliografica e allo studio dei testi scientifici fondamentali riguardo all’argomento. Particolare attenzione è stata rivolta al fenomeno fisico del Beam Hardening, che è tra le maggiori cause di artefatti grafici, e di cui si sono viste diverse metodologie di correzione. Sono stati poi trattati gli artefatti dovuti all’apparato di misura e gli artefatti dovuti al paziente. Per quanto riguarda le tecniche di correzione, oltre ai procedimenti di più vecchia concezione e ormai consolidati, si è dato largo spazio alle metodologie innovative, di recente applicazione e ancora oggetto di studio e ricerca, come la Dual-Energy CT e la ricostruzione iterativa. Si è visto come la ricostruzione iterativa garantisca risultati di gran lunga superiori in merito alla qualità dell’immagine ricostruita, rispetto alla canonica Filtered Back-Projection, in particolare per quanto riguarda la Low-dose CT, di grande interesse in campo medico.
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Gülden, Jakob [Verfasser], and Barbara [Akademischer Betreuer] Mayer. "Duale Expression ausgewählter Biomarker beim kolorektalen Karzinom und seinen Lebermetastasen: prognostische Wertigkeit und therapeutische Konsequenz / Jakob Gülden ; Betreuer: Barbara Mayer." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1214593259/34.
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Bull, Douglas Rutherford. "Performance Improvements to a Fast Internally Circulating Fluidised Bed (FICFB) Biomass Gasifier for Combined Heat and Power Plants." Thesis, University of Canterbury. Chemical and Process Engineering, 2008. http://hdl.handle.net/10092/1952.
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This thesis describes the development and experimental testing of a 100 kW dual fluidized bed biomass gasifier (also called a Fast Internally Circulating Fluidized Bed (FICFB) biomass gasifier). This steam-blown gasifier is being studied for its suitability within combined heat and power plant systems for the New Zealand forest products industry. This advanced design of gasifier has the ability to generate producer gas with a lower heating value (LHV) of 11.5-13.4 MJ/Nm3, which is two to three times higher than yielded by conventional gasification systems. This is accomplished because the gasification and combustion processes occur in two physically separated reactors.
Several modifications to the gasifier were required after it was first constructed in order to achieve stable and reliable operation. Producer gas yields were measured through the use of helium as a tracer gas. A new simultaneous producer gas and tar sampling system was developed, allowing accurate samples to be obtained in a matter of minutes.
Experimental testing included a cold testing exercise which provided valuable information on the circulation behaviour of the bed material and char within the gasifier. This helped in achieving stable and reliable operation of the plant. Producer gas yields of 14.6 Nm3/h were recorded with a fuel (radiate pine wood pellets) feed rate of 18.9 kgdry/h. The cold gas efficiency ranged from 16-40 % with limited heat recovery in place, but depended noticeably on the plant operating conditions especially gasification temperature.
The amount of polycyclic aromatic hydrocarbon (PAH) tars measured in the producer gas ranged between 0.9-4.7 g/Nm3 with naphthalene and acenapthylene being the most abundant compounds. The moisture content of the producer gas was determined to be 0.9-1.2 g/gdry gas. It was found that a steam to biomass ratio of 0.45-0.7 kg/kgdry was most favourable for generating a 12-13.4 MJ/Nm3 producer gas while limiting the amount of steam generation. Gasification temperatures above 750 °C encouraged higher producer gas yields and higher cold gas efficiencies. The catalytic bed material olivine (forsterite olivine) was found to increase the producer gas yield by approximately 20 % compared to the non-catalytic bed material greywacke. The use of olivine meant higher cold gas efficiencies were achieved for a given wood feed rate.
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Glass, Susanne [Verfasser]. "Effektivität verschiedener Gerinnungstests bei Patienten mit mono- und dualer Thrombozytenaggregationshemmung vor Herz-Operation / Susanne Glass." Gießen : Universitätsbibliothek, 2017. http://d-nb.info/1143461657/34.
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Maier, Alexander Andreas [Verfasser], and Mühlen Constantin von [Akademischer Betreuer] Zur. "Ein duales molekulares Kontrastmittelverfahren charakterisiert den myokardialen Ischämie-Reperfusionsschaden nichtinvasiv in der Magnetresonanztomographie bei Mäusen." Freiburg : Universität, 2016. http://d-nb.info/1134966008/34.
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Taylor, Kevin B. "Dual-beam multiple-wavelength light transmittance measurement for particle sizing in rocket motor plumes." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA272491.
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Meinel, Jan. "Spezifische Effekte visueller und kognitiver Ablenkung bei der Kraftfahrzeugführung." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2013. http://dx.doi.org/10.18452/16678.
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In vier Laborexperimenten wurde versucht, auf der Grundlage der Theorie multipler Ressourcen visuelle und kognitive Ablenkung bei der Kraftfahrzeugführung getrennt zu erfassen. Um die Vorhersagen der Theorie prüfen zu können, sind die zu erwartenden Ablenkungseffekte zuvor mit Hilfe des Computational Model of Task Interference geschätzt worden. Die Experimente 1 und 2 wurden als einfache, visuell ablenkende Reaktionsaufgaben an einem PC realisiert, bei denen die Versuchspersonen unter visueller und unter kognitiver Ablenkung auf den Wechsel von Verkehrszeichen reagierten. Entgegen der Hypothese wurde in Versuch 1 die Reaktionsleistung in der Primäraufgabe durch visuelle Ablenkung nicht stärker beeinträchtigt als durch kognitive Ablenkung. Die Wiederholung des Experiments mit überarbeiteten Aufgaben ergab in Versuch 2 eine hypothesenkonforme Trennung zwischen visueller und kognitiver Ablenkung. Die Experimente 3 und 4 bestanden aus einer kognitiv beanspruchenden Navigationsaufgabe, die ebenfalls an einem PC unter visueller und kognitiver Ablenkung vollzogen wurde. Die Navigationsaufgabe zeichnete sich dadurch aus, dass visuelle und motorische Störeinflüsse der ablenkenden Zweitaufgaben zum Messzeitpunkt ausgeblendet wurden, um ausschließlich kognitive Interferenzen zu erheben. Weder im dritten Versuch noch in Versuch 4 mit einer zeitlichen Zuspitzung der Navigationsaufgabe konnte gezeigt werden, dass kognitive Ablenkung eine kognitiv beanspruchende Navigationsaufgabe stärker beeinträchtigt als visuelle Ablenkung. Die anderslautende Interferenzvorhersage des Computational Model of Task Interference hat sich nicht bestätigt. Die Ergebnisse dieser Arbeit legen nahe, dass visuelle und kognitive Ablenkung nicht als getrennt messbare Phänomene aufgefasst werden können. Einer dementsprechenden Auslegung der Theorie multipler Ressourcen muss für den hier gewählten experimentellen Zugang der Ablenkungsmessung widersprochen werden.Based on multiple resource theory, four laboratory experiments were undertaken in an effort to independently measure visual and cognitive distractions during motor vehicle operation. In order to verify the predictions of the theory, the expected distraction effects were previously assessed with the aid of the computational model of task interference. Experiments 1 and 2 were performed as simple, visually distracting reaction tasks at a computer workstation, during which the test persons reacted to changing traffic signs while being subjected to visual and cognitive distractions. Contrary to the hypothesis, during experiment 1, the reaction performance in the primary task was not impaired more severely through visual distraction than through cognitive distraction. Repetition of the experiment with modified tasks in experiment 2 revealed a hypothesis-confirming separation between visual and cognitive distractions. Experiments 3 and 4 consisted of a cognitively challenging navigation task, which was also performed at a computer workstation with the interference of visual and cognitive distractions. During the navigation task, the visual and motor interferences of the distracting secondary tasks were omitted at the time of measurement in order to record only the cognitive interferences. Neither during the third experiment, nor during experiment 4, which involved an added time-pressure element to the navigation task, was it possible to demonstrate that cognitive distraction impairs a cognitively challenging navigation task to a greater extent than a visual distraction. The contrary interference prediction of the computational model of task interference was not confirmed. The results of this study suggest that visual and cognitive distractions cannot be regarded as separately measurable phenomena. A corresponding interpretation of multiple resource theory must therefore be rejected for the experimental approach selected here with regard to distraction measurement.
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Abdalla, Karim Yousif [Verfasser]. "Vergleich von Quantitativer Computertomographie und Dual-Energy XRay Absorptiometry bei postmenopausalen Frauen / Karim Yousif Abdalla." Ulm : Universität Ulm. Medizinische Fakultät, 2014. http://d-nb.info/1053705689/34.
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Schäffer, Benno [Verfasser], and Anno [Akademischer Betreuer] Graser. "Dual Energy CT-Kolonographie als präoperatives Staging bei kolorektalen Neoplasien / Benno Schäffer. Betreuer: Anno Graser." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1046503049/34.
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Chung, I. L., and 鐘瑜隆. "Derivation of dynamic stiffness and flexibility using dual BEM." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/98288357462317429405.
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碩士國立海洋大學
河海工程學系
88
Concept of dynamic stiffness and dynamic flexibility plays an important role in structural dynamics. Many approaches, e.g., finite element method and boundary element method, can be utilized to determine the stiffness and flexibility. In this thesis, dual BEM was considered. In an analytical study, the stiffness and flexibility of simple structures, rod, beam and membrane structures, are exactly determined. It is found that spurious eigenvalues are embedded and can be cancelled out with each other in the stage of calculating the stiffness. Also, the numerical instability of zero divided by zero occurs. To deal with this problem, additional independent equations from the real and imaginary information of dual formulation are added to the system to raise the rank of matrix in a similar way of CHIEF and CHEEF method. After adding the sufficient equations, the true and spurious solutions can be separated simultaneously and the least square solution for the overdetermined system can be obtained. For the special case of static flexibility, the pseudo-inverse or truncated singular value decomposition (TSVD) technique is employed to find the inverse of a singular matrix. For the problem of general geometrical shape, analytical study is not straightforward. A numerical program was developed to determine the stiffness and flexibility. Also, the spurious solution can be filtered out. Two examples, the circular and square cases were demonstrated to show the validity of the proposed method.
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Wu, Ping-Hsueh, and 吳秉學. "Design of Beam-Steerable Dual-Beam Reflectarray." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/mb2vyt.
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碩士國立臺灣大學
電信工程學研究所
105
A novel beam-steerable dual-beam reflectarray antenna system is presented. It consists of hexagonal unit cells arranged in a honeycomb lattice structure. Each unit cell is formed by a conductor-backed strip dipole loaded with a varactor diode for adaptively adjusting its reflection phase. To find the appropriate phase distribution for the unit cells, an ideal analysis algorithm is proposed and integrated with the reflectarray structure. Each row of the reflectarray can be considered as a linear subarray and is optimized by the ideal analysis. In each subarray, the even and odd numbers of the unit cells are configured respectively for the two targeted beams, and optimized separately. To account for the imperfect periodic boundary condition of the prototype reflectarray, a method is proposed to correct the reflection phases of the unit cells at the outer rim of the reflectarray. At last, a Genetic-Algorithm-based (GA-based) phase correction method is proposed and is adopted to correct the preliminary reflection phase of each unit cell obtained from the ideal analysis. The operating frequency range of the proposed reflectarray is limited by the operating frequency/bandwidth of the unit cell in use and the available tuning range of the varactor diode. Moreover, the total area of the prototype reflectarray is limited by the fabrication process and the maximum size of the available dielectric slab, and the number of unit cells in the reflectarray is limited by number of I/O ports of the DAQ interface (as will be detailed in Section 3 of Chapter 2). Therefore, a 91-element beam-steerable dual-beam reflectarray operating at 5.8 GHz with configured hexagonal unit cell is proposed, fabricated, and tested. The angle between the dual beams can be up to 60. Moreover, if the angle is not less than 30, the reflected field is better. The maximal gain of the proposed beam-steerable reflectarray is between 7.1 dBi and 12.1 dBi and the aperture efficiency can reach 66%. The loss of one of the targeted beams is lower than 3 dB in the bandwidth from 5.77 GHz to 5.83 GHz.
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Heimann, Michael. "Sakkadenanalysen bei Stilling-Türk-Duane Syndrom." 1988. http://catalog.hathitrust.org/api/volumes/oclc/18199635.html.
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Chang, Jiang-Ren, and 張建仁. "Applications of Domain Partitioning on Vibration Problems Using the Dual BEM." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/96264786650582428260.
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博士國立海洋大學
河海工程學系
87
In this dissertation, the alternatives of dual boundary element methods in conjunction with the domain partitioning have been proposed to solve the free vibration problems in one- and two-dimensional examples, and to solve the forced vibration problems in one-dimensional ones both for analytically and numerically. The results show that even the complex formulations of the dual boundary element methods are chose, the spurious eigenvalues and resonance arise when the domain partition is used and subsequent parallel treatments are needed. The causes and mechanism of those spurious phenomena are clearly illustrated by some well-designed worked examples analytically and numerically. Finally, the methods to filter out those spurious eigenvalues and resonance existing in the domain partitioning formats and subsequent iteration schemes for parallel treatments are also proposed here, respectively. The results of current dissertation deserve to be a clue for the dynamic analysis on the large or complicated structures when the parallel treatments are needed to introduce.
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Swart, Stephen David. "Design, modelling and construction of a scalable dual fluidised bed reactor for the pyrolysis of biomass." Diss., 2012. http://hdl.handle.net/2263/29849.
Full textAbstract:
The pyrolysis of biomass is a thermochemical process in which woody biomass is converted to several high-value products such as bio-oil, bio-char and syngas. The forestry sector has shown particular interest in this process as a large quantity of biomass is produced as an underutilised by-product in this sector annually. Dual fluidised beds (DFBs) have been identified as a feasible reactor system for this process. However, little attention has been given to the optimisation or to the design of a scalable DFB for the pyrolysis of biomass process. Therefore, the objective of the current project was the design, modelling and construction of a scalable dual fluidised bed system for the pyrolysis of biomass. In order to achieve this objective, several tasks were performed, which included the following: - A literature study was done in order to obtain a theoretical foundation for the current project.
- A novel dual fluidised bed reactor system was designed, which included the block flow diagram and the process and instrumentation diagram for the system.
- A cold unit of the system was built in order to test the performance of the system.
- A comprehensive model for the system was developed, which included mass and energy balance considerations, hydrodynamics and reaction kinetics.
- A complete pilot-scale system of the proposed design was built and tested at the University of Pretoria.
- The current research offers the opportunity for the forestry sector to shift its focus from the production of traditional wood products, such as pulp and paper, to products such as specialised chemicals.
- The bio-oil produced in the dual fluidised bed system can be upgraded to renewable liquid fuels, which may help reduce the dependence of the infrastructure on fossil fuels.
- The dual fluidised bed system provides an opportunity for capturing and removing CO2 from the atmosphere in the form of bio-char. It is therefore considered to be a carbon-negative process, and may help reduce the concentration of greenhouse gases.
- The bio-char produced in the dual fluidised bed system can be used to feed nutrients back to plantation floors in the forestry sector, thereby aiding the growth of further plantations.
Dissertation (MEng)--University of Pretoria, 2013.
Chemical Engineering
unrestricted
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Sholes, Kevin R. "Dual-reference-beam holographic particle image velocimetry." 1999. http://catalog.hathitrust.org/api/volumes/oclc/45317786.html.
Full textAbstract:
Thesis (Ph. D.)--University of Wisconsin--Madison, 1999.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 97-100).
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Yang, Kun-Ta, and 楊坤達. "Fiber-Optical Dual-Beam Trapping and Manipulation." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/87410494014731590117.
Full textAbstract:
碩士國立陽明大學
生醫光電工程研究所
93
A. Three-dimensional mapping of optical force field In this study, We have successfully trapped and manipulated a wide range of micro-particles including micron-size silica beads in water, red blood cells (RBC) and Chinese hamster ovary cells (CHO cell) in PBS solution. We report the first direct experimental mapping of the three-dimensional optical force field on a wide range of micro-particles confined in a counter-propagating dual-beam trap. The basic principle of our approach is based on the tracking of the Brownian motion of the trapped particle followed by statistical analysis of the particle position distribution. We used the trapping beams scattered by the trapped particle along two orthogonal directions (mutually orthogonal to each other and also to the trapping beams) in conjunction with a pair of quadrant photo-detectors (QPD) to significantly facilitate high-speed (20 KHz) three-dimensional tracking. Position tracking over two mutually orthogonal planes intrinsically provides one set of redundant data for cross-checking the experimental results. From the position distribution of the Brownian motion of the trapped particle, we calculate the optical force constants of the 3-D optical force field for the trapping of Chinese hamster ovary cells (CHO cell), red blood cells (RBC) and different sizes of silica particles. B. Optical trap-and-stretch “Optical Stretcher” was demonstrated by Guck et al (Biophysical Journal, August 2001) by inspecting a set of images of a RBC (red blood cell) trapped in a pair of counter-propagating trapping beams with varying optical power. Following the approach reported by Guck and with some important modifications of his experimental configuration, we have demonstrated for the first time, simultaneous trapping, stretching, and real-time quantitative monitoring of the deformation of a red blood cell in a fiber-optical dual-beam trap. This study will also provide a deeper insight into the elasticity of the membrane of cells. The capability to monitor quantitatively (and in real-time) the stress-strain relationship of a living cell (CHO cell) in response to the environmental changes may lead to important biomedical applications. The ultimate goal of these cell elasticity studies with optical stretcher is to distinguish dysplastic cells from early cancer cells and to monitor the progress of cancer from preinvasive to invasive.
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Chen, Wei-Chih, and 陳韋誌. "A study of free terms and rigid body modes in the dual BEM." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/60613697439712259641.
Full textAbstract:
碩士國立海洋大學
河海工程學系
89
The dual boundary integral formulations play an important role for the potential or plane elasticity problem. In this thesis, we derived the free terms on a smooth boundary by using the bump-contour approach surrounding the singularity. The jump terms using the limiting approach in conjunction with the degenerate kernels are also derived. The scalar (Laplace equation) and vector (Navier equation) problems are considered for the two and three-dimensional cases. The definition of the Hadamard principal value for hypersingular integral at the collocation point of a smooth boundary is extended to a generalized sense in comparison with the conventional definition. Moreover, the concept of rigid body modes in BEM was employed to determine the stiffness matrix and to solve for the degenerate scale problem. In deriving the stiffness, e.g., a rod, a beam and a circular membrane, the role of rigid body modes and complementary solutions is examined. Finally, the spurious mode is extracted by using the Fredholm alternative theorem and the singular value decomposition updating technique. By adopting the rigid body mode and spurious mode, the degenerate scale problem can be solved in the matrix operation.
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Chen, Chao-yuh, and 陳朝鈺. "Concentration of CO2 by dual-bed PSA process." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/74651936632117981734.
Full textAbstract:
碩士國立中央大學
化學工程學系
85
The global climate is greatly changed by greenhouse effect . The major cause for greenhouse effect is the emission of CO2 from burning of fossil fuel. The recovery of CO2 from flue gas is the first important step in solving CO2 problem. Two vacuum swing adsorption processes(VSA) are explored by simulation in this study. The feed gas contains 16% CO2 and 84% N2. This study used the equilibrium model without the consideration of pressure drop, and assumed instantaneous equilibrium between the solid and gas phases. It is considered Nonisothermal operation.The method of line with adaptive grid points is used in simulation. The estimation of the spatial derivatives by upwind difference is used to reduce the PDEs into ODEs, and cubic spline approximation is utilized to estimate flow rate in the adsorptive bed. Finally, the integration with respect to time is achieved by program LSODE of ODEPACK.The influence of operation parameters has been studied by the simulation program. The simulation results is expected to help the experimental runs.