To see the other types of publications on this topic, follow the link: SMC Method.
Dissertations / Theses on the topic 'SMC Method'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'SMC Method.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
GONZATO, LUCA. "Application of Sequential Monte Carlo Methods to Dynamic Asset Pricing Models." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2020. http://hdl.handle.net/10281/295144.
Full textAbstract:
In questa tesi si considera l’applicazione di metodi Monte Carlo sequenziali per modelli di asset pricing di tipo dinamico. Il primo capitolo della tesi presenta una panoramica generale sui metodi Monte Carlo sequenziali. Nello specifico, partendo da metodi Monte Carlo standard si giunge fino allo stato dell’arte per quanto riguarda i metodi Monte Carlo sequenziali.
Il secondo capitolo costituisce una review della letteratura sui metodi di simulazione esatta per processi di Hawkes. Dall’analisi svolta si evince che lo schema proposto da Dassios e Zaho (2013) performa meglio degli altri algoritmi, incluso il più noto metodo “thinning” proposto da Ogata (1981). Questo capitolo serve inoltre come introduzione ai processi di salto di tipo auto eccitante, che saranno oggetto di studio del Capitolo 3.
Nel terzo capitolo, quindi, viene proposto un nuovo modello diffusivo con salti auto eccitati per descrivere la dinamica del prezzo del petrolio. Il modello viene stimato implementando una recente metodologia di tipo Monte Carlo sequenziale utilizzando dati spot e futures. Dalla stima viene confermata la presenza di salti auto eccitati nel mercato del petrolio; questo conduce ad un migliore adattamento del modello ai dati e a migliori performance in termini di previsione dei futures rispetto ad un modello con intensità costante. Inoltre, vengono calcolate e discusse due strategie di copertura ottimali basate sul trading di contratti futures. La prima strategia è basata sulla minimizzazione della varianza, mentre la seconda tiene in considerazione anche la skewness. Viene infine proposto un confronto tra le due strategie in termini di efficacia della copertura
Nel quarto capitolo si considera la stima di modelli a volatilità stocastica a tempo continuo basati su processi di Wishart, osservando portafogli di opzioni come in Orlowski (2019). In questo contesto la funzione di verosimiglianza non è nota esplicitamente, quindi verrà stimata ricorrendo a metodi Monte Carlo sequenziali. A questo proposito, i processi latenti vengono marginalizzati e la stima della verosimiglianza viene effettuata adattando metodi Monte Carlo sequenziali “controllati”, recentemente proposti da Heng et. Al. (2019). Dai risultati numerici si mostra come la metodologia proposta dia risultati decisamente migliori rispetto a metodi standard. Pertanto, l’elevata stabilità della metodologia proposta permetterà di costruire algoritmi per la stima congiunta di processi latenti e parametri utilizzando un approccio Bayesiano. Quest’ultimo step si traduce nel costruire un così detto SMC sampler, il quale è attualmente in fase di studio.<br>In this thesis we consider the application of Sequential Monte Carlo (SMC) methods to continuous-time asset pricing models. The first chapter of the thesis gives a self-contained overview on SMC methods. In particular, starting from basic Monte Carlo techniques we move to recent state of the art SMC algorithms.
In the second chapter we review existing methods for the exact simulation of Hawkes processes. From our analysis we infer that the simulation scheme of Dassios and Zaho (2013) outperforms the other algorithms, including the most popular thinning method proposed by Ogata (1980). This chapter serves also as introduction to self-exciting jump processes, which are the subject of Chapter 3.
Hence, in the third chapter we propose a new self-exciting jump diffusion model in order to describe oil price dynamics. We estimate the model by applying a state of the art SMC sampler on both spot and futures data. From the estimation results we find evidence of self-excitation in the oil market, which leads to an improved fit and a better out of sample futures forecasting performance with respect to jump-diffusion models with constant intensity. Furthermore, we compute and discuss two optimal hedging strategies based on futures trading. The optimality of the first hedging strategy proposed is based on the variance minimization, while the second strategy takes into account also the third-order moment contribution in considering the investors attitudes. A comparison between the two strategies in terms of hedging effectiveness is provided.
Finally, in the fourth chapter we consider the estimation of continuous-time Wishart stochastic volatility models by observing portfolios of weighted options as in Orlowski (2019). In this framework we don't know the likelihood in closed-form; then we aim to estimate it using SMC techniques. To this end, we marginalize latent states and perform marginal likelihood estimation by adapting the recently proposed controlled SMC algorithm (Heng et. Al. 2019). From the numerical experiments we show that the proposed methodology gives much better results with respect to standard filtering techniques. Therefore, the great stability of our SMC method opens the door for effective joint estimation of latent states and unknown parameters in a Bayesian fashion. This last step amounts to design an SMC sampler based on a pseudo-marginal argument and is currently under preparation.
2
Esteras, Bejar Miguel. "Development of methods for the study of the role of the Smc5-Smc6 complex in DNA stability." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11072.
Full textAbstract:
The Structural Maintenance of Chromosomes (SMC) proteins play a number of crucial roles in the metabolism of chromosomes. The Smc5-Smc6 complex is the least well understood of the complexes formed by SMC proteins. Hitherto, the Smc5-Smc6 complex has been linked to protein post-translational modification by sumoylation and restart of collapsed replication forks by homologous recombination between sister chromatids (SCR). However, a detailed characterization of the roles of the Smc5-Smc6 complex is missing. The objective of this study is to characterize the function of the Smc5-Smc6 complex in DNA repair by SCR, and to identify sumoylation substrates of MMS21, a E3-sumoligase subunit of the Smc5-Smc6 complex. Recent studies suggest that DNA single-strand nicks are transformed to doublestrand breaks in a replication-dependent manner, and this triggers SCR. I developed an assay for the activation of SCR based on the expression of a site-specific nickase. Unfortunately, a stable site-specific nick was observed in only 30% of the population. This percentage was insufficient for the study of the molecular role of the Smc5-Smc6 complex during SCR. However, this assay could be used to confirm and further characterize the activation of SCR upon replication-induced DNA damage. To study the role of sumoylation within the Smc5-Smc6 activity, I have developed a proteome-wide approach for the in vivo identification of sumoylation-sites by mass spectrometry. This technique can be used for the identification of MMS21 substrates and for the mapping of their sumo-acceptor lysines. The mapping of sumo-acceptor sites allows the generation of sumo-specific mutant proteins that can be used to study the function of sumoylation. More than 360 sumo-acceptor lysines, belonging to 245 different proteins, were identified. In vivo sumoylation at these lysines was verified by MS-independent methods. In addition, I developed a SILAC-based mass spectrometry assay for the quantitative study of site-specific sumoylation.
3
McFarland, James. "Investigation of carbon nanotube growth using a nozzle CVD method." Pomona College, 2006. http://ccdl.libraries.claremont.edu/u?/stc,4.
Full textAbstract:
This work uses a modification of the chemical vapor deposition (CVD) technique to study the effects of source gas flow geometry (and the corresponding parameters) on carbon nanotube growth. Our approach is to flow the carbon-containing source gas through a nozzle, projecting the gas stream onto targeted regions of the substrate. This technique not only allows the potential for localized nanotube growth, but also offers an interesting opportunity to provide an experimental test of theoretical nanotube growth models.
4
Strapko, Jaroslav. "Měření teplotních profilů SMD pouzder." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218369.
Full textAbstract:
Diploma thesis mainly deals with temperature management and calculation of temperature profile in oven by using SMD packages (PLCC, 1206) of different thermal capacitance on testing PCB. Above all shows theoretical consecution of temperature profile calculation in oven by using known mathematical method like the lumped capacitance method or finite difference method. Theoretical solution and measured values are compared. Diploma thesis also deals with fixation methods of thermocouples K type on assembly, comparison methods based on known and subexperiment, determines the deficiencies of methods. This thesis can perform as theoretical as well as experimental resource to prediction of temperature profiles of PCB´s with different assembly density.
5
Wang, Shu. "Thermodynamic properties predictions using the COSMO-SAC solvation method." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 366 p, 2007. http://proquest.umi.com/pqdweb?did=1362532041&sid=24&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
6
Inoue, Shinichiro. "Ion assisted methods of deposition of SiC." Thesis, University of Salford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308174.
Full text
7
Zhang, Yixia. "Refined non-conforming linear and nonlinear finte [sic] element analysis." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22753060.
Full text
8
Saarikko, Jukka Olavi. "A multi-method empirical study of the Finnish SME restructurings." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500475.
Full textAbstract:
The ultimate purpose of the study was to find out differences between successful and unsuccessful Finnish SME restructurings. By contrast to previous research, the population of the study was homogeneous, insolvent Finnish small and middle-sized enterprises. In addition to that, a significant sample was achieved with the questionnaire survey which made it possible to generalize the findings. A theoretical sampling plan for the qualitative phase was conducted to build theories of success and failure on SME restructurings in Finland. In order to find out differences between cases, extremes were selected from both success and failure cases in three different size groups of firms: micro firms, small firms and middle-sized firms (six firms in total). Multiple sources of data, both primary and secondary were collected and analysed. Triangulation was conducted to ascertain the validity of findings within and across different research methods. With the help of a multi-method research tool and the approach of the resource-based view of the firm, rich and interesting findings were made. With the findings made by both quantitative and qualitative research methods, a process model of successful restructurings was built. The model includes three basic steps: situation analysis, concentration on the core and the restructuring strategy. These basic factors are affected by six basic forces: reasons for failure, resources of the firm, competitive position of the firm, industry development, stakeholder management, and aspirations of owners and management. The ongoing change management process is in the core of the process model. Numerous other important ingredients that affected the success of restructuring processes were found, for example: the experience of the administrator and the finding that all the problems of the troubled firm must be resolved without delay and the restructuring strategy must be in line with the resources of the troubled firm. The debtrestructurings seemed only to give the troubled firm short-term help. From the creditors' point of view, the going-concern value of the troubled firm should exceed the liquidation value of the firm. Such a position is not going to be achieved without major changes in the business of the troubled firm.
9
Yang, James J. "A statistical method for identifying informative genes in micorarrays [sic]." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001199.
Full text
10
Zhang, Yixia, and 張義霞. "Refined non-conforming linear and nonlinear finte [sic] element analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242704.
Full text
11
Roberts, Adam E. "A Phan-type theorem for orthgonal [sic] groups." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1124723065.
Full text
12
Pringle, Matthew. "Fnite [sic] element modelling of two-component, solid-liquid mixtures /." *McMaster only, 2001.
Find full text
13
Carballo, Jose M. "Residual Stress Analysis in 3C-SiC Thin Films by Substrate Curvature Method." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1590.
Full textAbstract:
Development of thin films has allowed for important improvements in optical, electronic and electromechanical devices within micrometer length scales. In order to grow thin films, there exist a wide variety of deposition techniques, as each technique offers a unique set of advantages. The main challenge of thin film deposition is to reach smallest possible dimensions, while achieving mechanical stability during operating conditions (including extreme temperatures and external forces, complex film structures and device configurations). Silicon carbide (SiC) is attractive for its resistance to harsh environments, and the potential it offers to improve performance in several microelectronic, micro-electromechanical, and optoelectronic applications. The challenge is to overcome presence of high defect densities within structure of SiC while it is grown as a crystalline thin film. For this reason is important to monitor levels of residual stress, inherited from such grown defects, and which can risk the mechanical stability of SiC- made thin film devices.
Stoney's equation is the theoretical foundation of the curvature method for measuring thin film residual stress. It connects residual film stress with substrate curvature through thin plates bending mechanics. Important assumptions and vii simplifications are made about the film-substrate system material properties, dimensions and loading conditions; however, accuracy is reduced upon applying such simplifications. In recent studies of cubic SiC growth, certain Stoney's equation assumptions are violated in order to obtain approximate values of residual stress average. Furthermore, several studies have proposed to expand the scope of Stoney's equation utility; however, such expansions demand of more extensive substrate deflection measurements to be made, before and after film deposition.
The goal of this work is to improve the analysis of substrate deflection data, obtained by mechanical profilometry, which is a simple and inexpensive technique. Scatter in deflection data complicates the use of simple processes such as direct differentiation or polynomial fitting. One proposed method is total variation regularization of differentiation process; and results are promising for the adaptation of mechanical profilometry for complete measurement of all components of non-uniform substrate curvature.
14
Angioni, Margherita. "The Role of the Internet in the Process of Internationalization of SMEs: A Mixed Method Analysis on the Furniture Sector." Doctoral thesis, Urbino, 2019. http://hdl.handle.net/11576/2663935.
Full text
15
Cabrera, Carlos Andres Cuenca. "Ductile failure prediction using phenomenological fracture model for steels: calibration, validation and application." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-27082018-075853/.
Full textAbstract:
The present thesis shows the analysis, calibration, and application of the stress modified criticai strain criterion to predict ductile failure for an A285 steel. To obtain the mechanical behavior of the material, experimental tests were carried out by implementation of 5 different types of geometries: smooth round bar, notched round bar (R=1 , 2, 3 mm), and, deep and shallow cracked SE(B) specimens. Then, for the calibration process of the mechanical properties finite element models were generated, using 30 solid elements with 8 nodes (C308), matching the geometry and the properties of the tested specimens. To calibrate the elastoplastic behavior was used the experimental and numerical response obtained from the smooth and notched round bar specimens; and, for the damage calibration was used the responses obtained from both deep and shallow crack SE(B) specimens. Once the mechanical properties were calibrated, then there were obtained the SMSC criterion factors represented by the equation ..... and, the damage condition which is represented by the displacement at failure (.......) and exponential factor (....). This calibrated model was able to recover the SE(B) experimental responses that validate the use of the characterized material in a complex structure. Then, the fully characterized material was applied in two pipelines which have externai initial circumferential elliptical crack; being the first one pipe with shallow crack and the second one with deep crack. Finally, both pipes were submitted to tension loads to predict the ductile damage behavior, obtaining the necessary load to the crack start growing, and the evolution of the failure.<br>A presente dissertação apresenta o processo de análise, calibração e aplicação das propriedades mecânicas, incluindo o comportamento elastoplástico e de dano, para o aço A285, utilizando o critério \"Stress modified criticai strain\" (SMCS). Para obter o comportamento mecânico do material, testes experimentais foram realizados com a implementação de 5 tipos diferentes de geometrias: barra cilíndrica sem entalhe, barra cilíndrica com entalhe (R = 1, 2, 3 mm) e corpos de prova SE(B) com trinca inicial profunda e rasa. Para o processo de calibração das propriedades mecânicas foram gerados modelos de elementos finitos, utilizando elementos sólidos 30 com 8 nós (C3D8), que representam de forma adequada a geometria e as propriedades dos corpos de prova testados. Para calibrar o comportamento elastoplástico e iniciação do dano, utilizou-se a resposta experimental e numérica obtida para as amostras de barra cilíndrica com e sem entalhe; e, para a calibração da evolução do dano, foram utilizadas as respostas obtidas para os espécimes SEB de trincas profundas e rasa. Este modelo calibrado foi capaz de recuperar as respostas experimentais dos corpos de prova SE(B), o que valida o uso do material caracterizado em uma estrutura complexa. Uma vez calibradas as propriedades mecânicas, foram obtidos os fatores do critério SMSC representados pela equação ....... , e, a condição de dano que é representada pelo deslocamento na falha .... e o fator de amolecimento exponencial .... . Depois, o material totalmente caracterizado foi aplicado em dois dutos que possuem trinca elíptica circunferencial inicial externa; sendo o primeiro tubo com trinca superficial e o segundo com trinca profunda. Finalmente, ambos os tubos foram submetidos a cargas de tensão para prever o comportamento do dano dúctil, obtendo a carga necessária para o início do crescimento da trinca e a evolução da falha.
16
Benassi, Romain. "Nouvel algorithme d'optimisation bayésien utilisant une approche Monte-Carlo séquentielle." Phd thesis, Supélec, 2013. http://tel.archives-ouvertes.fr/tel-00864700.
Full textAbstract:
Ce travail de thèse s'intéresse au problème de l'optimisation globale d'une fonction coûteuse dans un cadre bayésien. Nous disons qu'une fonction est coûteuse lorsque son évaluation nécessite l'utilisation de ressources importantes (simulations numériques très longues, notamment). Dans ce contexte, il est important d'utiliser des algorithmes d'optimisation utilisant un faible nombre d'évaluations de cette dernière. Nous considérons ici une approche bayésienne consistant à affecter à la fonction à optimiser un a priori sous la forme d'un processus aléatoire gaussien, ce qui permet ensuite de choisir les points d'évaluation de la fonction en maximisant un critère probabiliste indiquant, conditionnellement aux évaluations précédentes, les zones les plus intéressantes du domaine de recherche de l'optimum. Deux difficultés dans le cadre de cette approche peuvent être identifiées : le choix de la valeur des paramètres du processus gaussien et la maximisation efficace du critère. La première difficulté est généralement résolue en substituant aux paramètres l'estimateur du maximum de vraisemblance, ce qui est une méthode peu robuste à laquelle nous préférons une approche dite complètement bayésienne. La contribution de cette thèse est de présenter un nouvel algorithme d'optimisation bayésien, maximisant à chaque étape le critère dit de l'espérance de l'amélioration, et apportant une réponse conjointe aux deux difficultés énoncées à l'aide d'une approche Sequential Monte Carlo. Des résultats numériques, obtenus à partir de cas tests et d'applications industrielles, montrent que les performances de notre algorithme sont bonnes par rapport à celles d'algorithmes concurrents.
17
Esguerra, Mark. "An investigtion [sic] of developmentally appropriate methods in teaching drawing." [Denver, Colo.] : Regis University, 2006. http://165.236.235.140/lib/MEsguerra2007.pdf.
Full text
18
Worley, Joseph Charles. "Equipping pastors to vary their their [sic] methods of preaching." Theological Research Exchange Network (TREN), 1995. http://www.tren.com.
Full text
19
Islas, Michael E. "Efficiency improvement techniques for high voltage capacitor carging [sic] methods." Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002899.
Full text
20
Slavětínský, Radek. "Analýza cloudových řešení Business Intelligence pro SME." Master's thesis, Vysoká škola ekonomická v Praze, 2017. http://www.nusl.cz/ntk/nusl-358847.
Full textAbstract:
The thesis is focused on the analysis of presently offered products supporting Business Intelligence (BI) which are affordable for small and medium-sized enterprises (SMEs). Current BI solutions available to SMEs are mostly offered via Cloud computing, specifically in the form of Software as a Service (SaaS) as it requires low initial acquisition costs. The objectives of this thesis are to analyse the work in applications for BI in cloud that can be used by SMEs and to analyse in detail the comparison the worldwide extended reporting tools distributed as SaaS in the lower price category. The theoretical part provides a description of the Cloud computing and the BI system. In the practical part are selected following products: IBM Watson Analytics, Qlik Sense Cloud, Zoho Reports, Tableau Public and Microsoft Power BI. Practical testing of these applications was based on evaluation of the selected metrics with weights calculated by using the Fuller's triangle. Analyses and the information form the basis for comparison of selected applications. The contribution of this thesis is in discovering the strengths and weaknesses of these BI solutions. The output of this thesis can be used as a source for the selection of BI applications for SMEs.
21
Zhang, Jing. "The correlation among three hand srength [sic] measurement methods : hand dynamometer." Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1020143.
Full textAbstract:
The purpose of this study was to determine the correlation among three hand strength measurement methods: Hand dynamometer, MDD (Middle Digital Extension Isokinetic Dynamometer), and Cybex. Five students (2 males, 3 females) from Ball State University were asked to participate in this study. Both right and left lower arm data were collected from these subjects. A Cybex 340 (Lumax Cor.) was employed to determine wrist flexion and extension isokinetic peak torque, total work, and power at 30 degrees/second and 60 degrees/second. A MDD was used to determine third digit eccentric torque, work, and power. A hand dynamometer (Lafayette Instrument Co., Model 76618) was used to determine grip force. Pearson product moment correlation coefficients were used to determine correlation among these variables. Significant correlations were noted between isometric grip strength and isokinetic 30 and 60 degrees/second wrist flexion power, as well as between isometric grip strength and isokinetic 30 degrees/second wrist extensor power. The results of this study indicate there is very little relationship between the three clinically used measurement tools.<br>School of Physical Education
22
Poskovic, Emir. "Innovative magnetic materials for the new applications in electrical machines." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3424784.
Full textAbstract:
Permanent magnets play a key role as a component in a wide range of devices utilised by many industries; they are widely used in several electromechanical applications to convert energy, including actuators, motors and sensors, home appliances, office automation equipment, speakers, aerospace, wind generators and more.
Traditionally the adopted PMs were obtained from Rare Earth components, such as NdFeB, with high magnetic performance, but expensive. The research of alternative permanent magnets, in many cases has brought to choose the ferrites, mainly due to their low cost, but sometimes with significant design modifications of the final circuit, and possible increment of the weight.
Permanent magnets can roughly be divided into two categories: sintered (metallic) and bonded, these last representing a valid alternative to the first. Bonded magnets consist of two components: a hard magnetic powder and a non-magnetic binder; the powder may be hard ferrite, NdFeB, SmCo, and is mixed with binders for compression or injection moulding. The benefits lie in the adoption of polymeric binders to prepare the magnetic mixture: the resulting magnetic characteristic can be then “tuned” by adopting different percentages of the plastic binder. Moreover, the realisation process is simpler and cheaper than that of sintered materials, and no special protective treatment is needed.
The majority of the magnetic circuits are made with soft magnetic materials. Commonly laminated steels are adopted but recently the use of Soft Magnetic Composite (SMC) materials has increased representing a new solution to design the electrical machines with respect to traditional electrical steels.
SMC materials are realized with pure Iron grains coated and insulated by means of a layer that should be organic or inorganic. With respect to traditional laminated steel, these materials present different advantages: the capability to lead the magnetic flux in all directions, the volume reduction, the possibility to realize components with new complex shapes and geometries, and the reduction of iron losses, mainly the eddy currents, at medium and high frequency. On the other hand, the mechanical performances, in terms of strength, are in general weak.
Furthermore, a new material typology is introduced: the Hybrid Magnetic Composites (HMC), which are obtained with a combination of soft and hard magnetic materials mixed with a binder. The basic idea is that such materials should reflect the performance of AlNiCo magnets, low coercivity and adequate remanence, typically used in sensors applications.
Prototypes of traditional and unconventional rotating machines, such as assisted reluctance motors, brushless DC motors, axial flux machines and electromechanical frequency converters, have been studied in own laboratories and tested to evaluate the results coming from the adoption of the proposed materials in substitution of the commonly adopted (and expensive) Rare Earth sintered magnets. Different type of electrical machines can adopt innovative magnetic materials with the aim to improve their performance.
Induction motors are very useful and robust machines; on the other hand, such type of machines does not have a high dynamic behaviour. The DC motors can be easily controlled, but the presence of the brushes causes limitations on the efficiency, thermal restrictions and reduced life. The axial flux motors (AFM) have high efficiencies but the construction of the machines is very complex. The synchronous reluctance machines (SRM) have a lower cost compared to brushless ones.
In general, the reluctance electrical machines don’t use permanent magnets. In this way, they have a reduction in the costs and allow a high overload capability. On the other hand, the lower power factor and power density, compared to PM synchronous motor (PMSM), are the main disadvantages. The filling of flux barriers with the permanent magnets allows the overcoming of these drawbacks. However, the regular ferrite and NdFeB sintered magnets cannot fill the flux barriers with complex geometries. For this reason, the use of bonded magnets can be a solution for a better utilization and design of flux barriers.
Therefore different prototypes have been prepared and analyzed in our laboratories using SMC materials. Several experiments have been performed using dedicated test benches, where magnetic, energetic and mechanical aspects have been considered.
On the other hand, with regard to HMCs, various magnets have been made in our laboratories, and different properties have been investigated: the effect of Iron content in the material and, also the binder content effect has been analysed.
23
Čedo, Žlebič. "Uticaj jednosmerne struje na karakteristike podešljivih feritnih komponenti." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=110180&source=NDLTD&language=en.
Full textAbstract:
U okviru doktorske disertacije, realizovane su podešljive feritne komponente sa jezgrima koja su proizvedena od komercijalno dostupnih ESL 40011 feritnih traka čije se induktivnosti podešavaju primenom jednosmerne struje. Rad realizovanih podešljivih feritnih komponenti je verifikovan u kolu DC-DC konvertora podizača napona. U disertaciji je predložena merna metoda koja omogućava ispitivanje uticaja jednosmerne struje na karakteristike SMD induktora postavljenih u realnom okruženju. Metoda je verifikovana na komercijalno dostupnim SMD induktorima.<br>As part of this thesis variable ferite components with cores produced from comercialy available ESL 40011 ferite tapes manufactured in Low Temperature Co-fired Ceramic technology are implemented. Inductivity of the components is varied by applying DC current. Functionality of the implemented ferite components is verified in a circuit of DC-DC boost converter. This thesis proposes a measurement method which enables examining the influence of DC current on the characteristics of SMD inductors in real environment. The method is verified on comercialy available SMD inductors
24
Wiskel, J. Barry. "A study of the manufacturing method and related mechanical properties of SiC reinforced aluminum." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26343.
Full textAbstract:
A study involving manufacturing and tensile testing was conducted to elucidate the mechanical properties of a SiC fibre reinforced aluminum. Areas analyzed included production methods, failure mechanisms, tensile behaviour and interfacial bonding.
A well dispersed fibre distribution in the as cast composite was difficult to obtain. This arises from the high degree of intermingling of fibres in the as-received tows. The poor distribution can lead to incomplete fibre utilization and increase composite susceptibility to delamination damage.
The strength of the composites tested were below that expected from a rule of mixtures (ROM) value. Fibre damage incurred during manufacturing and by the formation of aluminum carbide on the fibre surface are possible causes for this anomaly. Also, fibre/(matrix plastic deformation) interaction can lead to premature composite failure especially at the low volume fractions of fibres being analyzed.
On a microscopic level good bonding between the fibre and matrix was observed. This adhesion was attributed to the formation of aluminum carbide at the fibre/matrix interface.
Synergistic strengthening of the matrix was observed for several tensile samples. This phenomena may be attributed to fibre distribution altering the aluminum matrix deformation behaviour.<br>Applied Science, Faculty of<br>Materials Engineering, Department of<br>Graduate
25
Afrifa, Godfred Adjapong. "Working capital management and AIM listed SME companies profitability : a mixed research method approach." Thesis, Bournemouth University, 2013. http://eprints.bournemouth.ac.uk/20968/.
Full textAbstract:
This research was undertaken to achieve two main objectives. The first objective was to investigation whether working capital management (WCM) is associated with profitability of Alternative Investment Market (AIM) listed Small and Medium Enterprise (SME) companies. The second objective was to investigate through a questionnaire survey the WCM practices of AIM listed SMEs and their effect on profitability from the perspective of financial directors. These two objectives were met by the use of a mixed research method approach. The study employed two research methods by collecting both quantitative and qualitative data. The financial data analysis is based on the annual reports of 160 AIM listed SMEs over a six year period (960 firm years) for the period 2005 to 2010. The findings of the panel data regression analysis show that SMEs with shorter inventory holding period, shorter accounts receivable period and shorter accounts payable period are more profitable. However, no evidence was found that cash conversion cycle has any effect on profitability of AIM listed SME companies. Under the control variables the corporate governance factors including: board size, Chief Executive Officer (CEO) age, CEO tenure and directors remuneration were found to be statistically significant in explaining the profitability of AIM listed SME companies. Also, the following company specific characteristics were found to have statistically significant effect on AIM listed SME companies’ profitability: company age, company size, asset tangibility, gross working capital efficiency and working capital requirement. In terms of the WCM practices, a questionnaire analysis was used. Questionnaires were sent to 248 companies to examine the WCM practices of AIM listed SME companies from the view point of financial directors. The analysis employed both t-test and one-way Analysis of Variance (ANOVA). The findings of the t-test and one-way ANOVA analysis indicate that there are significant differences in the perception of financial directors about each component of WCM. First, there are differences in the educational level and work experience of financial directors and their attitude towards WCM. Second, there are differences in the importance attached to the effect of each component of WCM to profitability. Third, the results indicate significant differences in the way AIM listed SME companies set target level and strategy pursued for each component of WCM.
26
Armour, Arthur David 1964. "Adaptive random search evaluated as a method for calibration of the SMA-NWSFS model." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278394.
Full textAbstract:
Random search methods are becoming more widely used to estimate model parameters. Their ability to globally search a parameter space makes them attractive for solving problems that have multi-local optima, as are non-linear hydrologic models such as Conceptual Rainfall-Runoff (CRR) models. The investigation of this thesis is on the ability of the Adaptive Random Search (ARS) to find the global optimum of the CRR model known as the Soil Moisture Accounting Model of the National Weather Service River Forecast System (SMA-NWSRFS) and compares its performance to that of the Uniform Random Search (URS). Research results indicate that, although the ARS was slightly more efficient than the URS, neither strategy demonstrated an ability to converge to the globally optimum parameter set. Factors which inhibit the convergence include model structure characteristics and an insufficient number of points searched. Ways for random search techniques to identify and address these problems are discussed.
27
Putaala, J. (Jussi). "Reliability and prognostic monitoring methods of electronics interconnections in advanced SMD applications." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526207605.
Full textAbstract:
Abstract In the interest of improving reliability, electrical monitoring methods were utilized to observe the degradation of electronics interconnections while simultaneously characterizing accelerated testing-induced changes in test structures by means of optical examination, X-ray, scanning acoustic microscopy and scanning electron microscopy. To improve the accuracy of lifetime prediction for the PCSB interconnections investigated in this work, a modified Engelmaier’s solder joint lifetime prediction model was recalibrated. The results show that with most of the presented lead-free (SAC387, SAC405, SAC-In) solder and structure combinations with a large global thermal mismatch (ΔCTE > 10 ppm/°C), lifetime was adequate in the presented TCT ranges of 0‒100 °C and −40‒125 °C, while the amount of non-preferred crack types, i.e. ceramic cracks, was minimized. Degradation of interconnections was characterized using RF measurements both during TCT and intermittently during TCT breaks. A grounded coplanar waveguide was arranged either in a straight back-to-back configuration or together with a filter module with a passband at 22‒24 GHz—both with two transitions—and characterized during cycling breaks up to 25 GHz and 30 GHz, respectively. Besides off-cycle measurements, in-cycle measurements were done on an antenna structure with an in-band at 10‒11 GHz, up to 14 GHz. The results show that the signal response was initially affected at some frequencies as short-duration (< 1 s) glitches in the monitored signal when measured during cycling in 0‒100 °C TCT. Later on the degradation could be observed in the whole frequency band as TCT was continued. Development of the semi-empirical lifetime prediction model for PCSB interconnections showed the temperature range dependency of the correction term to be a second order polynomial instead of a logarithmic one. For components with PCSB BGA, promising prediction results were achieved which differed from the realized lifetime by less than 0.5% at best<br>Tiivistelmä Elektroniikkaliitosten rikkoontumisen seurantaan tarkoitettuja sähköisiä monitorointimenetelmiä kehitettiin samanaikaisesti karakterisoimalla testauksella liitoksiin aikaansaatuja muutoksia optisesti, akustisella mikroskoopilla sekä röntgen- ja pyyhkäisyelektronimikroskoopeilla. Liitosten eliniän ennustamiseen soveltuva muokattu Engelmaierin malli kalibroitiin PCSB-liitosten elinikäennusteen tarkkuuden parantamiseksi. Tulosten perusteella useimmille tässä työssä käytetyille lyijyttömille (SAC387, SAC405, SAC-In) juotteille ja suuren termisen epäsovituksen (ΔCTE > 10 ppm/°C) rakenneyhdistelmille eliniät lämpösyklaustesteissä 0‒100 °C ja −40‒125 °C alueilla olivat riittävät ja haitallisimpien murtumien, eli keraamimurtumien, määrä saatiin minimoiduksi. RF-mittauksia käytettiin liitosten vikaantumisen seurantaan sekä lämpösyklauksen aikana että syklausten välillä. Maadoitettua koplanaarista aaltojohtoa käytettiin joko suoraan perättäiskytkennässä tai suodatinmoduulin kanssa, jonka päästökaista oli 22–24 GHz. Rakenteet karakterisoitiin syklausten välillä 25 GHz ja 30 GHz asti tässä järjestyksessä. Näiden mittausten lisäksi 10–11 GHz kaistalla toimivaa antennirakennetta karakterisoitiin syklauksen aikana 14 GHz asti. Tulokset osoittavat, että signaalivasteen muutos ilmenee aluksi joillakin taajuuksilla lyhyinä, alle 1 s mittaisina häiriöpiikkeinä, 0‒100 °C syklauksen aikana. Syklauksen edetessä vasteen huononeminen havaitaan myöhemmin koko mittausalueella. Puolikokeellista elinikäennustemallia tarkasteltaessa havaittiin, että PCSB-liitosten lämpötila-alueesta riippuvia korjauskertoimia kuvasivat logaritmisen riippuvuuden sijaan parhaiten toisen asteen polynomifunktiot. PCSB BGA ‒rakenteille saadun ennusteen ja toteutuneen eliniän välinen ero oli pienimmillään alle 0.5 %
28
Santesmasses, Ruiz Didac 1978. "Selenoproteins across the tree of life: Methods and applications." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/565634.
Full textAbstract:
La selenocïsteina és coneguda com a l'aminoàcid 21. Les selenoproteïnes incorporen selenocïsteina en resposta a codons UGA específics mitjançant un mecanisme de recodificació, el qual és present en els tres dominis de la vida, però no en tots els organismes. Els programes estàndard per a la predicció de gens consideren UGA només com a codó stop, per aquesta raó l'anotació de selenoproteínes és, generalment, incorrecte. Hem desenvolupat mètodes computacionals per a la predicció de selenoproteïnes. Mitjançant l'aplicació d'aquestes i altres eines, hem caracteritzat selenoproteïnes a través de l'Arbre de la Vida, on hem observat una evolució dinàmica en la utilització de selenocïsteina en els diferents llinatges. Hem caracteritzat l'abundància i distribució de selenoproteïnes en el microbioma humà. Hem caracteritzat les selenoproteïnes presents a Lokiarchaeota, les quals presenten trets eucariòtics. Finalment hem dedicat especial atenció als insectes, en els quals una progressiva reducció en el nombre de selenoproteïnes culminà en múltiples extincions de selenoproteïnes en esdeveniments evolutius independents.<br>Selenocysteine is known as the 21st amino acid. Selenoproteins incorporate selenocysteine in response to specific UGA codons through a recoding mechanism, which present in the three domains of life, but not in all organisms. Standard gene prediction programs consider UGA only as stop, and selenoproteins are normally misannotated. We have developed computational methods for prediction of selenoproteins. By applying these and other tools, we have characterized selenoproteins across the Tree of Life, showing a diverse evolution of the utilization of selenocysteine in different lineages. We have characterized the abundance and distribution of selenoproteins in the human microbiota. We characterized the selenoproteins in Lokiarchaeota, which have some eukaryotic-like features. Finally we gave special attention to insects, in which a progressive reduction in the number of selenoproteins culminated in multiple independent selenoprotein extinctions.
29
Costa, Gonçalo José Rodrigues. "Experimental investigation of EDM parameters on machining AIMg10 15%SiC composite based on Taguchi method." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11347.
Full textAbstract:
Mestrado em Engenharia Mecânica<br>O objetivo do estudo é investigar os efeitos da corrente de pico, servo voltagem, pulso on-time
e pulso off-time na perfuração por electroerosão da liga de Alumínio Magnésio reforçado com
carbonetos de silício e determinar a sua influência num grupo de parâmetros de saída, que
incluem a taxa de remoção de material, desgaste do elétrodo, sobre corte radial e conicidade.
Para melhor entender o problema experimental e todas as questões que este inclui, em
primeiro lugar, foi feita uma revisão da literatura que abrange todos os princípios, tecnologias
e aplicações do processo de electroerosão. Os dados para esta pesquisa foram recolhidos no
laboratório de tecnologias não convencionais na "Gheorghe Asachi" Universidade Técnica de
Iasi. O design de experiencias foi escolhido através do metodo Taguchi, nomeadamente o
array L9. O primeiro objetivo desta pesquisa é encontrar a combinação ideal dos níveis de
parâmetros através do método de Taguchi. O segundo objetivo é encontrar a contribuição da
cada parâmetro de entrada para cada parâmetro de saída usando o método de análise estatística
Análise da Variância. Objetivo final é desenvolver um modelo matemático para prever os
valores de saída experimentais, através do software GW-Basic. Os resultados mostraram que
os parâmetros com uma maior influência sobre a taxa de remoção de material e desgaste dos
elétrodos foram a servo voltagem e corrente de pico, com 49% e 24% em relação ao primeiro
parâmetro e 84% e 10% em relação ao segundo. O sobre corte radial foi mais influenciado
pela corrente de pico e pelo pulso on-time, com 29% e 35%. Relativamente a conicidade,
os parâmetros com mais influência foram corrente de pico e o pulso on-time, com 47% e
33% em termos de contribuição. Além disso, os níveis de combinação ótima de parâmetros
associadas com a taxa de remoção de material, desgaste dos elétrodos, sobre corte radial e
conicidade foram também obtidos. As respostas em estudo podem ser previstas usando os
modelos matemáticos com um erro médio de 2% para a taxa de remoção de material, 16%
para o desgaste do elétrodo, de 2% para sobre corte radial e 2% para a conicidade.<br>The purpose of this study is to investigate the effects of peak current, servo voltage, pulse on−
time and pulse off − time on electrical discharge drilling of an aluminum magnesium reinforced
with particles of silicone carbide and determine their influence on a range of output
parameters such as material removal ratio, electrodewear,radial over cut and taper. To
better understand the experimental problem and all issues that it includes, firstly, was done
a literature review that covers all the electrical discharge machining principals, technologies
and applications.The data for this research was collected on the “non conventional“ machining
technologies laboratory at “Gheorghe Asachi” Technical University of Iasi. The design of experiments
was chosen by Taguchi method, namely, orthogonal array L9.The first goal of this
research is to find the optimum parameter level combination through the Taguchi method.
The second goal is to find the contribution of the each parameter for each output using the
statistic method Analysis of variance. Final goal was to find a mathematical model to predict
the experimental output values, through a software GW-Basic. The results shows that
the parameters with more influence on material removal ratio and electrode wear responses
were servo voltage and peak current, with 49% and 24% regarding the first output and 84%
and 10% the second. Radial over cut was more influenced by peak current and pulse on-time,
with 29% and 35%, concerning the taper, the parameters with more influence were also peak
current and pulse on-time but with 47% and 33% of contribution. In addition, the optimal
combination levels of machining parameters associated with material removal rate, electrode
wear, radial over cut and taper were also drawn. Responses in study can be predicted using
the Mathematical models with a average error of 2% for material removal rate, 16% for
electrode wear, 2% for radial over cut and 2% for taper.
30
Savchenko, Dariya, Bela Shanina, E. Kalabukhova, Andreas Pöppl, J. Lancok, and Evgeny Mokhov. "The spin relaxation of nitrogen donors in 6H SiC crystals as studied by the electron spin echo method." AIP Publishing, 2016. https://ul.qucosa.de/id/qucosa%3A21289.
Full textAbstract:
We present the detailed study of the spin kinetics of the nitrogen (N) donor electrons in 6H SiC wafers grown by the Lely method and by the sublimation “sandwich method” (SSM) with a donor concentration of about 10 17cm-3 at T=10–40K. The donor electrons of the N donors substituting quasi-cubic “k1” and “k2” sites (Nk1,k2) in both types of the samples revealed the similar temperature dependence of the spin-lattice relaxation rate (T1 -1), which was described by the direct one-phonon and two-phonon processes induced by the acoustic phonons proportional to T and to T9, respectively. The character of the temperature dependence of the T1 -1 for the donor electrons of N substituting hexagonal (“h”) site (Nh) in both types of 6H SiC samples indicates that the donor electrons relax through the fast-relaxing centers by means of the cross-relaxation process. The observed enhancement of the phase memory relaxation rate (Tm -1) with the temperature increase for the Nh donors in both types of the samples, as well as for the Nk1,k2 donors in Lely grown 6H SiC, was explained by the growth of the free electron concentration with the temperature increase and their exchange scattering at the N donor centers. The observed significant shortening of the phase memory relaxation time Tm for the Nk1,k2 donors in the SSM grown sample with the temperature lowering is caused by hopping motion of the electrons between the occupied and unoccupied states of the N donors at Nh and Nk1,k2 sites. The impact of the N donor pairs, triads, distant donor pairs formed in n-type 6H SiC wafers on the spin relaxation times was discussed.
31
Simon, Tom. "Temperaturbestimmung an IGBTs und Dioden unter hohen Stoßstrombelastungen." Master's thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-166595.
Full textAbstract:
Diese Arbeit beschäftigt sich mit drei verschiedenen Temperaturmessmethoden VCE, VGTH sowie über die Messung der thermsichen Impedanz mit 10ms langen Lastimpulsen und vergleicht die Messergebnisse mit zwei Simulatoren. Dabei wird ein Schaltungs- sowie ein Halbleitersimulator verwendet und das bisherige Simulationsmodell angepasst.
32
Calminder, Tobias, and Martin Carlshamre. "The Transition towards Product-Service Systems : A Business Development Method for Small and Medium-Sized Manufacturing Enterprisees." Thesis, Linköping University, Department of Management and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15656.
Full textAbstract:
<p>The increasing competition on today’s globalized markets creates drivers for new business models in order to create competitive advantage. By integrating services with the physical product, unique offers that aim at fulfilling customer needs rather than just providing physical goods can be created. This type of offers, in the literature often referred to as Product-Service Systems (PSS), are more difficult to imitate than pure products. Furthermore, the focus on fulfilling customer needs rather than just providing physical goods can reduce the use of resources, decreasing both costs and the environmental impact of the offer. From the customers’ point of view, PSS offers can bring increased flexibility and reduced risk. The development of successful PSS offers requires structured methods. Much of the research within the area, and consequently models and guidelines, has focused on large companies. However, since small and medium-sized enterprises (SMEs) constitute the foundation of economic growth in all developed countries, there is an important gap in the existing research within this area. One research initiative to fill this gap is the ongoing IPSE project (Integrated Product and Service Engineering), which aims at developing a methodology for efficient development of PSS offers in manufacturing SMEs. The methodology developed in the IPSE project is however at a conceptual level that is not applicable for the management in smaller companies. This thesis hence aims at <em>developing a concrete and useful business development method applicable for the management in manufacturing SMEs, with the focus on generation of PSS offer concepts</em>.</p><p>Based on earlier research within the PSS area, with the emphasis on the IPSE methodology, a concrete business development method for the generation of PSS concepts was created, which was then tested on three SMEs in order to verify and improve the method. The method consists of the three steps <em>internal analysis</em>, <em>external analysis </em>and <em>planning of the new PSS offer. </em>Each step contains a number of tools to be used in order to analyze different aspects of the business context. After analyzing the studies of the three case studies a revised method was developed, which was then summarized in managerial guidelines to be used by managers in manufacturing SMEs. The revision of the method mainly regarded simplifications of some of the tools in order to ease the use and increase the applicability.</p><p>The method proved to be useful and concepts could be generated for all the case companies. The method thoroughly examined the possibilities of creating PSS offers, even though it was found that it was also useful for the development of conventional business offers. Since the drivers for the case companies were specific threats or opportunities that would require changes in the offer, rather than a purpose in itself to integrate more services in the offer, this implies that the method can be useful as general business development method for manufacturing SMEs.</p><p>An important learning from our studies is that the day-to-day business is strongly focused by the managers in manufacturing SMEs, leaving little time for long-term business development. As stated by a manager in the case companies:</p><p><em>“It is like running beside the bicycle, but we do not have the time to get on it.”</em></p><p><em></em>The developed method can work as a tool for structuring the information needed in the business development process and hence reducing the time needed. However, if the reduction in time needed for long-term business development is enough to get the managers on their bikes is a question assigned to further studies.</p><p> </p>
33
Guo, Yu-yau. "Behavioral modeling and simulaitons [sic] of mixed-signal integrated circuits with process variations and physical defects /." View online ; access limited to URI, 2003. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3115630.
Full text
34
Gause, L. Arnold. "An evaluation of the Columbia Ministry, Education, and Training Center (C-MET) an alternative method of theological education /." Theological Research Exchange Network (TREN), 1993. http://www.tren.com.
Full text
35
Dyckman, Theodore R. (Theodore Robert) 1978. "Benchmark characterization for reusable launch vehicle onboard trajectory generation using a Legendre psuedospectral [sic] optimization method." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82221.
Full text
36
Quintanilla-Anicama, Mario, Johana Congona-Garcia, Edgardo Carvallo-Munar, Iliana Macassi-Jauregui, and Luis Cardenas. "Combined method redesign for the packing area in a peruvian bakery sme provider of national food programs." Springer, 2021. http://hdl.handle.net/10757/656013.
Full textAbstract:
In the bakery industry, it is sought to have zero defective products. It is in the packing; where it is evident, as the last area of the production chain, all the defects generated. Therefore, a combined redesign method is proposed, which consists in the use of Economy of Movement, Ergonomics, Poka Yoke and Method Engineering to reduce defective products in SMEs in the bakery industry. The losses of these generate a reduction of 29.50% for crushed bread and 19.67% of bread on the floor, reducing with the use of this method to 16.20% and 8.38% respectively.
37
Simmons, Kate D. "Improving the spelling skills of elementary students with mild learning and behavior problems a comparison between an explict [sic] rule-based method and traditional method /." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Dissertations/SIMMONS_KATE_27.pdf.
Full text
38
von, Axelson Jens. "On development of production methods for transfer to SMEs." Doctoral thesis, KTH, Industriell produktion, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4502.
Full textAbstract:
The main problem in this thesis is: How should research and development results regarding production methods be represented for better adoption by SMEs? Manufacturing SMEs in Sweden have in general low profit margins and risk to go bankrupt. Different production methods could facilitate the needed performance improvement. Networking provides an arena where research and development needs could be determined and effective transfer activities could be carried through. How new production methods could be characterized and represented are presented. Several case studies, surveys and literature studies have been carried through. The results from these studies have been analyzed and compared to literature on the production method diffusion process – Dissemination-Clustering-Transfer. This analysis has resulted in a specification of requirements on how new production methods should be presented for better adoption by SMEs. One suggestion to the specification of requirements, the DFMTsme process, is described. The process is based on a repeated development procedure and follows a six-step development process in five phases. It is concluded that the DFMTsme process works. The research project is finally reviewed due to verification, validation and the contribution to knowledge. Implications for actors in the production method diffusion process as well as for policy makers are discussed.<br>QC 20100729
39
Poller, Tilo. "Thermal and thermal-mechanical simulation for the prediction of fatigue processes in packages for power semiconductor devices." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-154320.
Full textAbstract:
The knowledge about the reliability of power electronics is necessary for the design of converters. Especially for offshore applications it is essential to know, which fatigue processes happen and how the lifetime can be estimated. Numerical simulation is an important tool for the development of power electronic systems. This thesis analyse the thermal and thermal-mechanical behaviour of packages for power semiconductor devices with the help of simulations. One topic is the evaluation of different thermal models. The main focus is on the description of the thermal cross-coupling between the devices and the influence to the lifetime estimation. The power module is a well established package for power semiconductor devices. It will be explained how the heating period of power cycles influences the failure mode of this package type. Additionally, it will evaluated how SiC devices and DAB substrates influence the power cycling capability. The press-pack is in focus for high power applications as the package short-circuits during an electrical failure without external auxiliary systems. However, the knowledge about the power cycling behaviour is currently limited. With the help of simulations this behaviour will be analysed and possible weak points will be also derived. In the end of the work it will be discussed, how the lifetime can be estimated with help of FEM simulations<br>Für die Entwicklung von Umrichtern ist die Kenntnis über die Zuverlässigkeit der Leistungselektronik ein wichtiges Kernthema. Insbesondere für Offshore-Anwendungen ist das Wissen über die stattfindenden Ermüdungsprozesse und die Abschätzung der zu erwartenden Lebensdauer der Bauteile essentiell. Hierfür hat sich die Simulation als ein wichtiges Werkzeug für die Entwicklung und Lebensdauerbewertung von leistungselektronischen Anlagen etabliert. In der folgenden Arbeit wird das thermische und das thermisch-mechanische Verhalten der Leistungselektronik mittels Simulationen untersucht. Hierzu wird ein Vergleich zwischen verschiedenen thermischen Modellen für Leistungsbauelemente durchgeführt. Schwerpunkt ist die Beschreibung der thermischen Kopplung zwischen den Chips und deren Einfluss auf die Lebensdauerabschätzung. Ein weiterer Schwerpunkt ist das Leistungsmodul, welches sich als ein Standardgehäuse etabliert hat. Dazu wird erklärt, wie die Variation der Einschaltzeit im aktiven Lastwechseltest den Fehlermodus dieses Gehäusetyps beeinflusst. Weiterhin wird untersucht, wie SiC als Leistungshalbleiter und DAB als Substrat die Zuverlässigkeit beein- flusst. Der Press-Pack ist für Hochleistungsapplikationen von hohem Interesse, da dieses Gehäuse im elektrischen Fehlerfall ohne äußere Unterstützung kurzschliesst. Jedoch ist das Wissen über diese Gehäusetechnologie unter aktiven Lastwechselbedingungen sehr limitiert. Mit Hilfe von Simulationen wird dieses Verhalten untersucht und mögliche Schwachpunkte abgeleitet. Am Ende der Arbeit werden Möglichkeiten untersucht, wie Mithilfe von FEM Simulationen die Lebensdauer von Leistungsmodulen evaluiert werden kann
40
Cho, Harngid. "Financing methods that drive innovation in biotech and pharmaceuticals : the meagfund [sic] IPO model." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90227.
Full textAbstract:
Thesis: M. Fin., Massachusetts Institute of Technology, Sloan School of Management, Master of Finance Program, 2014.<br>Title as it appears in the MIT commencement exercises program, June 6, 2014: Financing methods that drive innovation in biotechnology: the megafund IPO model Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 91-92).<br>Current research has shown that a mega fund and securitization approach using debt financing can not only mitigate risk in investments in cancer but can also align research and development in the right direction for new and innovative breakthrough therapies. We propose a new application of this megafund biopharma model - the megafund IPO model. There are almost arbitrage-like opportunities for investors where there are heavily discounted investments opportunities which are generated in IPO's. However, these events driven investments are only for the institutional investor and hence pooling capital into a more scalable mega fund structure could generate returns that are not otherwise possible while encouraging innovation in biomedicine. The investment vehicle is attractive to investors because of the significant amount of alpha that the fund can generate on de-risked basis. Risk is mitigated by the fact that there is an arbitrage like opportunity for the institutional investor in events driven investments for the mispricing of an IPO. We examine a back-testing of ten years examining a long only strategy and later also look at a case study of Monashee Investment Management that currently most closely resembles the megafund IPO model.<br>by Harngid Cho.<br>M. Fin.
41
Lind, Sofia. "Adaptation of eco-design methods for SMEs in India : Experiences from the electronics industry." Thesis, Linköping University, Department of Water and Environmental Studies, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9195.
Full textAbstract:
<p>This thesis presents guidelines for how eco-design methods can be adapted to facilitate the introduction of ecologically responsible manufacturing in small and medium sized enterprises (SMEs) in the Indian electronics industry. It also investigates the major opportunities and obstacles for eco-design to become a natural part of product design. This is urgent both from environmental and economic perspectives since the SMEs pollute a lot in proportion to their share of the total industrial production, and at the same time they are vulnerable for the increasing environmental demands on product design. The European Union recently introduced their directive on the Restriction of the Use of certain Hazardous Substances in Electrical and Electronic Equipment (RoHS) which bans certain hazardous chemicals in electric and electronic device. For many producers that supply to the European market this was a wake up clock to start thinking about environmental aspects related to production.</p><p>The study was carried out as an interview and questionnaire study at three SMEs in the electronics industry. Additional interviews were held with informants in different organisations. It was concluded that for SMEs in the Indian electronics industry qualitative and semi-quantitative eco-design methods should be chosen before quantitative methods. Eco-design methods should resemble traditional methods that are already used in the companies. For the product developers to be able to work with eco-design more education and other solutions are needed to raise the environmental knowledge. Support and commitment from top management is also imperative. Methods should be developed to encourage the establishment of multi functional teams and early integration of environmental aspects in design projects.</p><p>The external demands on environmentally responsible manufacturing are expected to increase in the future. This will most likely have a positive influence on the environmental awareness in the industry, just as the RoHS directive has had. However, there are still economic and technical barriers that need to be bridged for SMEs in India to be able to work with eco-design. More cooperation and communication between academics, policy makers and the industry is needed to make it happen.</p>
42
Kapsalis, Alexandra, and Roy Khazzaka. "Införande av digitalt mätsystem i tillverkande SME företag : MeasurLink." Thesis, KTH, Hållbar produktionsutveckling (ML), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276685.
Full textAbstract:
Kvaliteten på produkterna som tillverkas av SME företag har hög betydelse för deras konkurrenskraft. Att kunna producera skräddarsydda artiklar med hög kvalitet samt kunna leverera i tid och enligt specifikation är några av de vanligaste krav stora företag ställer som kunder. Tillverkande SME företag differentierar sig gentemot konkurrenter genom att digitalisera sina processer. Behovet av digitala verktyg kan dock också anses vara en överlevandsfaktor ty kundernas krav blir allt högre desto mer automatiserade kundernas fabriker blir. Att övergå till en digitaliserad kvalitetsäkringsprocess för SME:er är inte enkelt. En del av problematiken kopplad till övergången mot en digitaliserad kvalitetssäkringsprocess är saknaden av IT kunskap och de begränsade medlen som SME bolag har. Syftet med arbetet är att analysera användandet av digitala mätverktyg som kan användas i kvalitetssäkringsprocessen hos tillverkande SME företag samt analysera hur denna implementation kan utföras på bästa möjliga sätt. För att nå detta syfte svarade arbetet på följande frågeställningar: 1) Vilka processer för kvalitetssäkring använder tillverkande SME företag i dagsläget? 2) Hur kan digitala verktyg implementeras för att assistera kvalitetsäkringsprocessen hos tillverkande SME företag? 3) Vilka utmaningar finns det vid implementation av digitala stödverktyg för kvalitetssäkring i tillverkande SME företag? Arbetet är baserat på teorier om olika kvalitetssäkringsprocesser. Exempel på dessa är Lean, TQM och Six Sigma. Metoden som användes var en fallstudie på företaget Marcus Komponenter AB i Järna utanför Södertälje. I fallstudien användes det digitala mätsystemet MeasurLink som tillhandahålls av Mitotoyo, för att digitalisera kvalitetssäkringsprocessen av de tillverkade produkterna. Datainsamlingen i arbetet har utförts med hjälp av tre olika kvalitativa datainsamlingsmetoder; dokumentinsamlingsmetodik, intervjuer och observationer. Resultatet av arbetet visar på att företaget bör följa en handlingsplan så att de kan förbereda sig för att kunna implementera ett digitalt mätsystem fullskaligt i hela produktionen. Resultatet är viktigt ty det visar på att företag bör ha uppnått en viss mognadsgrad för att kunna implementera digitala mätsystem. Sammanfattningsvis har slutsatsen dragits att en storskalig implementation av MeasurLink vid närvarande inte är möjlig. Däremot kan implementationen utföras i mindre skala vid en teststation. När företaget byggt upp ett standardiserat arbetssätt kring mätning och dataanalys med hjälp av MeasurLink kan en fullskalig implementation genomföras.<br>The quality of products manufactured by SME companies is of high importance for their competitiveness. Being able to produce tailor-made items of high quality and being able to deliver on time and according to specification are some of the most common requirements large companies place as customers. Manufacturing SME companies differentiate themselves from competitors by digitalizing their processes. However, the need for digital tools can also be considered as a survival factor, as the demands of customers become higher the more automated customers' factories become. Switching to a digitalized quality assurance process for SMEs is not easy. Part of the problems associated with the transition to a digitalized quality assurance process is the lack of IT knowledge and the limited resources that SME companies have. The purpose of this bachelor’s thesis is to analyze the use of digital measuring tools that can be used in the quality assurance process in manufacturing SME companies. As well as to analyze how this implementation can be carried out in the best possible way. To achieve this goal, this thesis answered the following research questions: 1) What quality assurance processes do SME manufacturing companies currently use? 2) How can digital tools be implemented to assist the quality assurance process of manufacturing SMEs? 3) What are the challenges in implementing digital quality assurance tools in manufacturing SMEs? The thesis is based on theories of different quality assurance processes. Examples of these are Lean, TQM and Six Sigma. The method used was a case study at the company Marcus Komponenter AB in Järna outside Södertälje. In the case study, the digital measurement system MeasurLink provided by Mitotoyo was used to digitalize the quality assurance process of the manufactured products. The data collection has been carried out using three different qualitative data collection methods; document collection, interviews and observations. The result of the thesis shows that the company should follow an action plan so that they can prepare in order to be able to implement a digital measurement system full-scale throughout the production. The result is important because it shows that companies should have achieved a certain degree of maturity in order to be able to implement digital measurement systems. In summary, the conclusion of the case study was that a large-scale implementation of MeasurLink is currently not possible. However, the implementation can be done in a smaller scale, at a test station. Once the company has built up a standardized method of measurement and data analysis using MeasurLink, a full-scale implementation can be performed.
43
Gumprecht, Daniela. "Spatial Methods in Econometrics. An Application to R&D Spillovers." Department of Statistics and Mathematics, WU Vienna University of Economics and Business, 2005. http://epub.wu.ac.at/290/1/document.pdf.
Full textAbstract:
In this paper I will give a brief and general overview of the characteristics of spatial data, why it is useful to use such data and how to use the information included in spatial data. The first question to be answered is: how to detect spatial dependency and spatial autocorrelation in data? Such effects can for instance be found by calculating Moran's I, which is a measure for spatial autocorrelation. The Moran's I is also the basis for a test for spatial autocorrelation (Moran's test). Once we found some spatial structure we can use special models and estimation techniques. There are two famous spatial processes, the SAR- (spatial autoregressive) and the SMA- (spatial moving average process) process, which are used to model spatial effects. For estimation of spatial regression models there are mainly two different possibilities, the first one is called spatial filtering, where the spatial effect is filtered out and standard techniques are used, the second one is spatial two stage least square estimation. Finally there are some results of a spatial analysis of R&D spillovers data (for a panel dataset with 22 countries and 20 years) shown. (author's abstract)<br>Series: Research Report Series / Department of Statistics and Mathematics
44
Bernardin, Frederick E. "Application of Semi-Grand Canonical Monte Carlo (SGMC) methods to describe non-equilibrium polymer systems." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42428.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007.<br>Includes bibliographical references.<br>Understanding the structure of materials, and how this structure affects their properties, is an important step towards the understanding that is necessary in order to apply computational methods to the end of designing materials to fit very specific needs. Such needs include specific optical and mechanical properties. In polymers, the ability to easily create orientation through a variety of processes allows the production of materials that, while chemically similar, exhibit a wide variety of optical and mechanical properties. The ability to illuminate the connections between structure and optical or mechanical properties depends on the ability to reliably interpret a wide variety of experimental measurements. I assert that thermodynamic consistency and energy minimization is an integral part of this endeavor; reliable analyses of structure and properties are built upon the foundation of a minimum-free-energy ensemble of configurations that reproduces the experimental results. This project encompasses three goals, which make up this thesis: 1) to show how sets of experimental measurements are integrated into simulations to produce thermodynamically consistent, minimum-free-energy ensembles; 2) to show how these ensembles can characterize the conformations of macromolecules, which are not available from direct simulation; 3) to show how dynamic processes, which create inhomogeneous systems can be incorporated, along with experimental structural measurements, into thermodynamically consistent, minimum-free-energy ensembles. To achieve the first of these goals, we describe the application of the Semi-Grand Canonical Monte Carlo (SGMC) method to analyze and interpret experimental data for non-equilibrium polymer melts and glasses. Experiments that provide information about atomic-level ordering, e.g. birefringence, are amenable to this approach.<br>(cont.) Closure of the inverse problem of determining the structural detail from limited data is achieved by selecting the lowest-free-energy ensemble of configurations that reproduces the experimental data. The free energy is calculated using the thermodynamic potential of the appropriate semi-grand canonical (SGC) ensemble ... , as defined by the experimental data. To illustrate the method we examine uniaxially oriented polyethylene melts of average chain length up to C400. The simulation results are analyzed for features not explicitly measured by birefringence, such as the density, torsion angle distribution, molecular scale orientation and free energy, to understand more fully the underlying features of these non-equilibrium states. The stress-optical rule for polyethylene is evaluated in this way. The second goal is achieved through multi-scale modeling, which requires the selection and preservation of information crucial to understanding the behavior of a system at appropriate length and time scales. For a description of processed polymers, such a model must successfully link rheological properties with atomic-level structure. We propose a method for the calculation of an important rheological state descriptor, the configuration tensor <QQ>, from atomistic simulations of oligomers. The method requires no adjustable parameters and can describe anisotropic polymer conformations at conditions of significant deformation. We establish the validity of the atomistic-to-macromolecular scaling by comparing the consistency of macromolecular predictions of <QQ> among different polyethylene (PE) oligomer systems. We use this method with the previously reported Semi-Grand Canonical Monte Carlo (SGMC) method to deduce macromolecular and atomic-level structural information interchangeably for systems with flow-induced orientation. Introducing the ability to model arbitrary points in a dynamic process fulfills the third goal elaborated above.<br>(cont.) Because the characteristic relaxation times of processed polymer chains often span several orders of magnitude, it is commonly the case that partial relaxation of the chains is frozen into the final product. We report results of molecular simulations by the Semi-grand Canonical Monte Carlo (SGMC) method to study the orientation-dependent elasticity of glassy polystyrene as a function of both the system-average degree of orientation and the degree of relaxation of chain ends at a constant average degree of orientation, in accord with the tube model of Doi and Edwards. Our simulations reproduce quantitatively the experimentally observed changes in the tensile modulus E33 as a function of both average orientation and inhomogeneity of the orientation due to partial relaxation. The results show that the partial relaxation of the polymer chains is sufficient to explain the observed variation of mechanical properties for samples that differ in processing history, yet have the same observed birefringence.<br>by Frederick E. Bernardin, III.<br>Ph.D.
45
Celik, Ertugrul. "Integrating EMS into SCM : A Case Study of Methods, Benefits and Barriers at Sandvik Tooling." Thesis, Högskolan i Gävle, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-21299.
Full textAbstract:
Purpose – The aim of this research is to explore the benefits and barriers of integrating EMS to SCM in Sandvik Tooling. While exploring that, it is intended to gain insights into the methods employed to integrate the systems and find out the type of integration used in practice. Design/methodology/approach – Explorative case study method is employed in this research paper. Primary data is obtained through semi-structured interviews and observations. Triangulation, respondent validation, peer review are the principal strategies employed to ensure validity and reliability of this study. Findings – Sandvik Tooling employed a composite view of integration in which verbal and documented forms of information exchanged together with novel solutions to provide integration throughout supply chain on the basis of common goals and vision, shared values and resources. Integration is provided with a balanced mixture of interactions and collaborations. Benefits of integration are categorized as environmental, economic, and organizational benefits. On the other side, barriers are presented as internal and external barriers. Practical Implications – This research paper has significant practical contributions to businesses with presenting the ways to integrate and analyze these two systems and demonstrate barriers to overcome and benefits to take advantage of. Originality/value – Environmental management systems and supply chain management topics received considerable interest among researchers in recent decades. However there is a lack of research about how these two systems can be integrated and what kind of integration will best define this integration type. Analyzing barriers and benefits of integration process will also advance and contribute our knowledge in this research area.
46
Zaidi, Mohammed. "Experimental Testing and Reliability Analysis of Repaired SMA and Steel Reinforced Shear Walls." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35357.
Full textAbstract:
Superelastic Shape Memory Alloys (SMAs) are being explored as alternative reinforcing materials to traditional deformed steel reinforcement for seismic applications. The main advantage is the ability of the SMA to recover large nonlinear strains, which promotes the self-centering phenomenon. The primary objective of this research is to present the performance, before and after repair, of slender reinforced concrete shear walls, one reinforced internally with SMAs in the boundary zones within the plastic hinge region and other control wall reinforced with conventional steel only. The repair procedure included removal of damaged concrete within the plastic hinge region, replacing fractured and buckled reinforcement, followed by shortening of the SMA reinforcement in the boundary zones of SMA wall. The removed concrete was replaced with self-consolidating concrete, while the concrete above the plastic hinge region remained intact.
The SMA reinforced concrete shear wall (before and after repair) exhibited stable hysteretic response with significant strength, and displacement and energy dissipation capacities. In addition, the walls exhibited pinching in the hysteretic response as a result of minimizing the residual displacements due to the restoring capacity of the SMA reinforcement. The results demonstrate that SMA reinforced components are self-centering, permitting repairing of damaged areas. Furthermore, the SMA reinforcement is re-usable given its capacity to reset to its original state. The length of the SMA bars in the original and repaired wall, in addition to the presence of starter bars in the original wall, were significant factors in the location of failure of the walls.
The conventional steel wall prior to repair was unstable due to large residual displacements experienced during the original test. After repair the wall exhibited ratcheting in hysteretic response but with significant strength. The conventional wall, before and after repair, dissipated more energy than the SMA wall. This was the result of the wider hysteretic loops with reduced punching, but at the cost of large residual displacements. The starter bars in the conventional wall before repair controlled the location of failure, while the presence of couplers in the plastic hinge region was the main factor in determining the failure location in the repaired conventional wall.
47
Краснов, В. А., С. Ю. Ерохин та А. Н. Деменский. "Формирование внутренних дефектов в p-n структурах SiC для перспективных источников одиночных фотонов". Thesis, Сумский государственный университет, 2017. http://essuir.sumdu.edu.ua/handle/123456789/64503.
Full textAbstract:
Для современных оптических технологий требуются источники одиночных фотонов, работающие при комнатной температуре. Поэтому очень важным является направление исследований, связанное с изучением излучательной рекомбинации через внутризонные состояния в p-n структурах SiC. В частности, формирование точечных дефектов типа VSi позволяет реализовать состояние доминирования прямых оптических переходов в процессах рекомбинации носителей заряда через энергетические уровни дефектов.
48
Enmark, Martin. "Fundamental Investigations of Supercritical Fluid Chromatography." Doctoral thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-37913.
Full textAbstract:
This thesis aims at a deeper understanding of Supercritical Fluid Chromatography (SFC). Although preparative SFC has started to replace Liquid Chromatography (LC) in the pharmaceutical industry - because of its advantages in speed and its less environmental impact - fundamental understanding is still lacking. Therefore there is no rigid framework to characterize adsorption or to understand the impact of changes in operational conditions. In Paper I we demonstrated, after careful system verification, that most methods applied to determine adsorption isotherms in LC could not be applied directly in SFC. This was mainly due to operational differences and to the fact that the fluid is compressible which means that everything considered constant in LC varies in SFC. In Paper II we showed that the most accurate methods for adsorption isotherm determination in LC, the so called plateau methods, do not work properly for SFC. Instead, methods based on overloaded profiles should be preferred. In Paper III a Design of Experiments approach was successfully used to quantitatively describe the retention behavior of several solutes and the productivity of a two component separation system. This approach can be used to optimize SFC separations or to provide information about the separation system. In Paper IV severe peak distortion effects, suspected to arise from injection solvent and mobile phase fluid mismatches, were carefully investigated using experiments and simulations. By this approach it was possible to examine the underlying reasons for the distortions, which is vital for method development. Finally, in Paper V, the acquired knowledge from Paper I-IV was used to perform reliable scale-up in an industrial setting for the first time. This was done by carefully matching the conditions inside the analytical and preparative column with each other. The results could therefore provide the industry with key knowledge for further implementation of SFC.<br>This thesis aims at a deeper understanding of Supercritical Fluid Chromatography (SFC). Although preparative SFC has started to replace Liquid Chromatography (LC) in the pharmaceutical industry - because of its advantages in speed and its less environmental impact - fundamental understanding is still lacking. Therefore there is no rigid framework to characterize adsorption or to understand the impact of changes in operational conditions. In Paper I-II it was demonstrated why most methods applied to determine adsorption isotherms in LC could not be applied directly for SFC. Methods based on extracting data from overloaded profiles should be preferred. In Paper III a Design of Experiments approach was successfully used to quantitatively describe the behavior of several solutes in a separation system. This approach can be used to optimize SFC separations or to provide information about the separation system. In Paper IV severe peak distortion effects often observed in SFC were carefully investigated and explained using experiments and simulations. Finally, in Paper V, the prerequisites for performing reliable and predictable scale-up of SFC were investigated by small and large scale experiments.<br><p>Paper 4 ("Evaluation of scale-up from analytical to preparative...") ingick som manuskript med samma titel i avhandlingen. Nu publicerad. </p>
49
Xu, Yingjie. "Prediction of properties and optimal design of microstructure of multi-phase and multi-layer C/SiC composites." Phd thesis, Université de Technologie de Belfort-Montbeliard, 2011. http://tel.archives-ouvertes.fr/tel-00625953.
Full textAbstract:
Carbon fiber-reinforced silicon carbide matrix (C/SiC) composite is a ceramic matrixcomposite (CMC) that has considerable promise for use in high-temperature structuralapplications. In this thesis, systematic numerical studies including the prediction of elasticand thermal properties, analysis and optimization of stresses and simulation ofhigh-temperature oxidations are presented for the investigation of C/SiC composites.A strain energy method is firstly proposed for the prediction of the effective elastic constantsand coefficients of thermal expansion (CTEs) of 3D orthotropic composite materials. Thismethod derives the effective elastic tensors and CTEs by analyzing the relationship betweenthe strain energy of the microstructure and that of the homogenized equivalent model underspecific thermo-elastic boundary conditions. Different kinds of composites are tested tovalidate the model.Geometrical configurations of the representative volume cell (RVC) of 2-D woven and 3-Dbraided C/SiC composites are analyzed in details. The finite element models of 2-D wovenand 3-D braided C/SiC composites are then established and combined with the stain energymethod to evaluate the effective elastic constants and CTEs of these composites. Numericalresults obtained by the proposed model are then compared with the results measuredexperimentally.A global/local analysis strategy is developed for the determination of the detailed stresses inthe 2-D woven C/SiC composite structures. On the basis of the finite element analysis, theprocedure is carried out sequentially from the homogenized composite structure of themacro-scale (global model) to the parameterized detailed fiber tow model of the micro-scale(local model). The bridge between two scales is realized by mapping the global analysisresult as the boundary conditions of the local tow model. The stress results by global/localmethod are finally compared to those by conventional finite element analyses.Optimal design for minimizing thermal residual stress (TRS) in 1-D unidirectional C/SiCcomposites is studied. The finite element models of RVC of 1-D unidirectional C/SiCIIcomposites with multi-layer interfaces are generated and finite element analysis is realized todetermine the TRS distributions. An optimization scheme which combines a modifiedParticle Swarm Optimization (PSO) algorithm and the finite element analysis is used toreduce the TRS in the C/SiC composites by controlling the multi-layer interfaces thicknesses.A numerical model is finally developed to study the microstructure oxidation process and thedegradation of elastic properties of 2-D woven C/SiC composites exposed to air oxidizingenvironments at intermediate temperature (T<900°C). The oxidized RVC microstructure ismodeled based on the oxidation kinetics analysis. The strain energy method is then combinedwith the finite element model of oxidized RVC to predict the elastic properties of composites.The environmental parameters, i.e., temperature and pressure are studied to show theirinfluences upon the oxidation behavior of C/SiC composites.
50
Gao, Xiang. "Using methods of optimization programming and meta-analysis to evaluate current Unite [sic] States nutritional recommendations /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2005.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 2005.<br>Adviser: Katherine L. Tucker. Submitted to the School of Nutrition Science and Policy. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;