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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Fluidisation of chocolate under vibration

Bergemann, Nico January 2016 (has links)
The aim of this thesis was to understand how a non-Newtonian fluid like chocolate fluidises under vibration. The problem was approached both experimentally and computationally, employing the finite element method as implemented in oomph-lib. In order to model a non-Newtonian fluid its constitutive behaviour has to be known. For this purpose, rheological measurements on tempered chocolate were performed. The chocolate was modelled using generalised Newtonian models for the viscosity and it was found that the Sisko model provided the best fit to the data. The generalised Newtonian Navier-Stokes equations were implemented within oomph-lib and their validation against analytical solutions yielded excellent agreement. Both the experiments and the computations for a sessile drop of chocolate, which is vibrated vertically, spreading on a layer of the same fluid yielded qualitatively similar results. The parameter which controls the spreading is the acceleration arising from the vibration. The drop rests on the layer and does not spread under gravity and small accelerations. However, as the acceleration increases and exceeds a threshold the drop starts to spread out. For a constant amplitude vibration, the spreading rate increases with increasing frequency and for large frequencies approaches a theoretical spreading law which corresponds to viscous dominated spreading of a Newtonian drop.
2

A Techno-Economic Analysis of Employing Lithium Iron Phosphate Battery Energy Storage System for Peak Demand Reduction of Industrial Manufacturing System

Wong, Alexander T. 21 June 2021 (has links)
No description available.
3

INCIDÊNCIA E SEVERIDADE DE MOFO BRANCO EM SOJA CULTIVADA SOB DIFERENTES DENSIDADES POPULACIONAIS E ESPAÇAMENTOS

Beruski, Gustavo Castilho 02 April 2013 (has links)
Made available in DSpace on 2017-07-25T19:29:58Z (GMT). No. of bitstreams: 1 Gustavo Castilho Beruski.pdf: 1947735 bytes, checksum: 5154fe4925ff733f606b56a918ecfe30 (MD5) Previous issue date: 2013-04-02 / The fungus Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic and polyphagous pathogen with soybean crop as one of the most important hosts. However in order to occur epidemics caused by such a pathogen it is necessary that the climatic conditions, mainly air temperature and relative humidity be favorable to the occurrence and development of the disease. Face with that, the current research aimed to analyze the incidence and severity of S. sclerotiorum on soybean plants grown at Arapoti, PR, Brazil, as a function of different plant populations, between row spacing’s and microclimate. The experiment was conducted in a naturally infested area with 31 sclerotia per square meter. The soybean crop (cv. Apollo RR) was sown on October 18th, 2011. The experimental design adopted herein was a randomized block in a factorial combination with 4 row spacing’s (0.35, 0.45, 0.60, 0.75 m) and 4 plant populations (150, 200, 250; 300 thousands plants per hectare), totaling 16 treatments and 4 replications. Throughout the current study we performed 4assessments of incidence and severity. The local meteorological data were collected by electronical sensors, which were attached to a CR-1000 datalogger (Campbell Scientific Inc.) being programmed to provide readings at each 60 seconds and storing averages at each 30 minutes. In compliance with the data monitored by an automatic weather station we observed that the local climatic conditions were favorable to the incidence and development of the pathogen. Throughout the crop cycle the average air temperature was of 19.5 °C, whereas during the flowering stage of the soybean crop such a variable was of 20.2 °C. The amount of rainfall was high and well distributed over course of the crop growing season, promoting favorable environmental conditions to trigger the development of the white mold in the field.Moreover, the regime of relative humidity and leaf wetness duration lead to favorable conditions to the progress of the disease at the studied site. Among the models used for epidemiological analysis, the molecular and logistic models showed the best adjustment to the data of incidence and severity of white mold on soybean crop, respectively. Pearson correlation coefficients obtained by means of a simple linear regression study between incidence and disease severity degree and local meteorological elements showed a high accuracy for the variables such as mean and maximum temperatures, confirming that these elements had a larger influence on the progress of the disease. As to the other meteorological elements the values of R were low. Yield and weight of thousand grain data did not show significant variations as a function of incidence and severity of white mold for soybean crop grown at the site in study. However, the yield was higher at treatments with reduced spacings,whereas for thousand grain weight higher values at treatments with low population densities were found herein. / O fungo Sclerotinia sclerotiorum (Lib.) de Bary é um patógeno necrotrófico, polífago que tem a planta da soja como um dos seus principais hospedeiros. Porém, para que ocorram epidemias em decorrência desse patógeno é necessário que as condições climáticas, principalmente de umidade e temperatura do ar, sejam favoráveis para a ocorrência e o desenvolvimento da doença. Face ao exposto, o trabalho teve como objetivo analisar a incidência e a severidade de Sclerotinia sclerotiorum na cultura da soja cultivada no município de Arapoti, PR, em função de diferentes densidades populacionais, espaçamentos entre linhas de cultivo e variáveis meteorológicas locais. O experimento foi conduzido no município de Arapoti – PR, em área naturalmente infestada contendo 31 escleródios m-2. A semeadura da soja (cv. Apolo RR) foi realizado no dia 18/10/2011. O delineamento experimental utilizado foi o de blocos casualizados (DBC) em esquema fatorial, sendo combinados 4 espaçamentos entre linhas (0,35; 0,45; 0,60; 0,75 metros) e 4 populações (150; 200; 250; 300 mil plantas ha-1), totalizando 16 tratamentos e 4 repetições. Ao longo do experimento efetuou-se 4 avaliações de incidência e severidade. Os dados meteorológicos locais foram coletados por sensores, os quais foram acoplados a um datalogger CR-1000 (Campbell Scientific Inc.), sendo este programado para efetuar leituras a cada 60 segundos armazenando médias a cada 30 minutos. De acordo com os dados coletados em estação meteorológica automática verificou-se que as condições climáticas locais foram favoráveis a incidência e desenvolvimento do patógeno. Durante o ciclo da cultura, a temperatura média do ar foi de 19,5 °C, já durante a fase de florescimento da cultura da soja esta variável apresentou valores de 20,2 °C. Os índices pluviométricos foram elevados e bem distribuídos ao longo da cultura, favorecendo o desenvolvimento do patógeno no campo. Além disso, os valores de umidade relativa do ar e da duração do período de molhamento foliar também foram favoráveis à ocorrência de mofo branco na cultura da soja. Dentre os modelos utilizados na análise epidemiológica, os modelos Monomolecular e Logístico apresentaram melhores ajustes aos dados de incidência e severidade de mofo branco na cultura da soja, respectivamente. Os coeficientes de correlação de Pearson obtidos através da regressão linear simples entre os dados de incidência e severidade da doença e os elementos meteorológicos locais sob os diferentes tratamentos empregados demonstraram elevada precisão para as variáveis temperaturas média e máxima do ar, confirmando que tais elementos tiveram maior influência no progresso da doença. Já para os demais elementos meteorológicos os valores de R foram reduzidos. Os dados de produtividade e peso de mil sementes não apresentaram oscilações em função das variações nos níveis de incidência e severidade de mofo branco na cultura da soja cultivada na localidade climática estudada. Contudo a produtividade da cultura foi maior nos tratamentos com espaçamentos reduzidos, já a massa de mil grãos apresentou maiores valores em tratamentos com reduzida densidade populacional.
4

Parallel unstructured mesh adaptation and applications

Perez Sansalvador, Julio January 2016 (has links)
In this thesis we develop 2D parallel unstructured mesh adaptation methods for the solution of partial differential equations (PDEs) by the finite element method (FEM). Additionally, we develop a novel block preconditioner for the iterative solution of the linear systems arising from the finite element discretisation of the Föppl-von Kàrmàn equations. Two of the problems arising in the numerical solution of PDEs by FEM are the memory constraints that limit the solution of large problems, and the inefficiency of solving the associated linear systems by direct or iterative solvers. We initially focus on mesh adaptation, which is a memory demanding task of the FEM. The size of the problem increases by adding more elements and nodes to the mesh during mesh refinement. In problems involving a large number of elements, the problem size is limited by the memory available on a single processor. In order to be able to work with large problems, we use a domain decomposition approach to distribute the problem over multiple processors. One of the main objectives of this thesis is the development of 2D parallel unstructured mesh adaptation methods for the solution of PDEs by the FEM in a variety of problems; including domains with curved boundaries, holes and internal boundaries. Our newly developed methods are implemented in the software library oomph-lib, an open-source object oriented multi-physics software library implementing the FEM. We validate and demonstrate their utility in a set of increasingly complex problems ranging from scalar PDEs to fully coupled multi-physics problems. Having implemented and validated the infrastructure which facilitates the finite-element-based discretisation of PDEs in a distributed environment, we shift our focus to the second problem concerning this thesis and one of the major challenges in the computational solution of PDEs: the solution of the large linear systems arising from their discretisation. For sufficiently large problems, the solution of their associated linear system by direct solvers becomes impossible or inefficient, typically because of memory and time constraints. We therefore focus on preconditioned Krylov subspace methods whose efficiency depends crucially on the provision of a good preconditioner. These preconditioners are invariably problem dependent. We illustrate their application and development in the solution of two elasticity problems which give rise to relatively large problems. First we consider the solution of a linear elasticity problem and compute the stress distribution near a crack tip where strong local mesh refinement is required. We then consider the deformation of thin plates which are described by the nonlinear Föppl-von Kàrmàn equations. A key contribution of this work is the development of a novel block preconditioner for the iterative solution of these equations, we present the development of the preconditioner and demonstrate its practical performance.
5

La th��ologie de la lib��ration en Ha��ti : un acteur religieux en politique (1970-2004)

Pr��delus, Mimose 19 June 2012 (has links) (PDF)
Cette ��tude porte sur le mouvement dit de la "��Th��ologie de la lib��ration��" en Ha��ti. A partir d'une approche historique, elle retrace le parcours du mouvement de 1970 �� 2004, en mettant en ��vidence ses r��seaux et ses acteurs.Bien que l'apparition r��elle de ce mouvement soit tr��s r��cente dans la soci��t��, son d��veloppement a ��t��, n��anmoins, fulgurant. Il est perceptible �� travers de nombreuses structures de base comme��: les Communaut��s eccl��siales de base, commun��ment appel��es TKL (Ti Kominote Legliz), les groupements paysans et les centres de formation. Lieu de conscientisation, de fraternit�� et de solidarit��, ces structures ont jou�� un r��le tr��s important, dans les ann��es 80, non seulement dans la redynamisation de l'��glise catholique mais aussi dans la diffusion de la "��Th��ologie de la lib��ration��" en Ha��ti. Leur force a ��t�� d��montr��e sous la dictature tant par leurs prises de position que par leurs actions qui ont largement contribu�� �� la chute du r��gime.A leur t��te se trouvent des pr��tres, issus de milieux sociaux et de Congr��gations divers dont la dictature avait contraint un certain nombre �� l'exil. Si l'exil a ��t�� l'une des sanctions les plus courantes sous la dictature, il ne se r��v��le pas, n��anmoins, la plus efficace puisqu'il a permis le d��veloppement, par ces pr��tres, d'un puissant courant anti-duvali��riste fortement influenc�� par la "��Th��ologie de la lib��ration��", dont les journaux, les revues et les associations de base seront les principaux vecteurs et qui sera �� l'origine du d��part de Jean-Claude Duvalier, le 7 f��vrier 1986. Sa cons��cration est marqu��e par l'��lection, en 1990, de Jean-Bertrand Aristide, l'un d'entre eux. Qui sont ces acteurs��? En quoi consiste leur travail��? Quels sont les principaux r��seaux impliqu��s dans ce mouvement��? Existe-t-il une r��elle convergence de vues entre les id��es de la th��ologie de la lib��ration et celles d��fendues par ses acteurs en Ha��ti ? En quoi les id��es de Jean-Bertrand Aristide concordent-elles avec celles de la "��Th��ologie de la lib��ration��"��? Sa politique pr��sidentielle s'inscrit-elle, ou non, dans la continuit�� de la "��Th��ologie de la lib��ration��" ? Ce sont les principales questions auxquelles cette ��tude tentera de r��pondre.
6

Cognição, linguangens e estereótipos acerca das pessoas deprimidas: estudo em três categorias profissionais

SIEBRA, Gilca Bezerra Alves 14 February 2012 (has links)
Submitted by João Arthur Martins (joao.arthur@ufpe.br) on 2015-04-08T18:30:21Z No. of bitstreams: 2 Tese final.pdf: 3978208 bytes, checksum: cc7d7e00595a7450b2c9fbbe3928f985 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-04-08T18:30:21Z (GMT). No. of bitstreams: 2 Tese final.pdf: 3978208 bytes, checksum: cc7d7e00595a7450b2c9fbbe3928f985 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2012-02-14 / CAPES / Esta tese trata do estudo de prováveis estereótipos quanto a pessoas deprimidas na produção linguística de três categorias: profissionais da área de Saúde, professores de Línguas e outros profissionais. Para tanto, fez-se uma revisão do que seriam linguagem e estereótipos – e sua neurobiologia –, a fim de se estabelecer sua interface. Foi feita uma revisita aos conceitos de crença, categorização social e Modelo de Categoria Linguística, entre outros, e seus pressupostos teóricos. Também foram abordados alguns indícios do que seriam afetividade e depressão, e seus impactos no cotidiano do indivíduo. Discutiu-se a existência inequívoca de estereótipos em produções linguísticas e o que eles revelam, bem como suas possíveis influências no sujeito – produtor e alvo do discurso – exposto a tais estereótipos, em especial naqueles que sofrem de depressão. Foi realizada uma pesquisa com profissionais da área de Saúde (em geral e Mental), professores de Línguas (Português e Inglês) e profissionais de outras áreas (de níveis médio e superior) com o intuito de verificar a possível diferença na ocorrência de vieses linguísticos referentes aos deprimidos e aos não deprimidos (LEB), o que efetivamente se comprovou na codificação linguística mais positiva dos profissionais de Saúde quanto aos deprimidos, apontando ainda para um olhar mais humano desse profissional, indiferente ao fato de se ser ou não deprimido (LEB), ou de se pertencer ou não à sua categoria profissional (LIB). O viés linguístico intergrupal (LIB) nas três categorias investigadas se evidenciou na forma como cada categoria codificou a si própria mais favoravelmente, de acordo com os pressupostos teóricos. Espera-se que este estudo contribua para dirigir um olhar mais atento sobre comportamentos linguísticos baseados em estereótipos e suas possíveis implicações.
7

Generování testovacích vstupů podle stopy programu / Generating Test Inputs Based on Program Trace

Sušovský, Tomáš January 2019 (has links)
This thesis focuses on design and implementation of a tool for automated generation of test inputs for a specified program trace. The aim of the thesis is to make development of testing suites (complying a given advanced coverage criteria) easier and more effective. These kinds of test suites are used in critical applications with code base written in low-level languages like C/C++ with strict restrictions applied. The tool investigates a program model and what conditions must be met to execute program in a way following provided trace. The tool uses advanced SMT-solver tool (software tool specialized for solving satisfiability problem) for generating fitting values. LLVM compiler framework libraries are used for modelling a program. Z3 library is used as a SMT-solver backend. This thesis brings results in architectural and implementation design of a tool capable of test inputs generation based on program analysis and provided program trace to cover.
8

Relevant Factors on the Standardization of Lithium-Ion Batteries (LIBs) Aimed for Recycling and Corresponding Influence on Innovation

Cofre Osses, Aliro, Bechara Bechara, José Luis January 2022 (has links)
Abstract Background:  Electric Vehicles (EVs) have been identified as a sustainable alternative to reduce the world’s dependence on fossil fuels. EV sales are starting to reach significant numbers. Subsequently, the demand for Lithium-Ion Batteries (LIBs), a key component in EVs, has increased. Due to the higher demand, a greater volume of LIBs will enter the waste stream. The waste-management strategies commonly used for the disposal of LIBs create potential risks of soil and air pollution, affecting the sustainability of EVs. The underdeveloped waste-management strategies, and the environmental and social risks related to improper disposal of LIBs, makes the study of second-life strategies of LIBs relevant.  Circular Economy (CE) promotes circular instead of linear flows of materials to reduce environmental impacts and maximize resource efficiency. LIB recycling is gaining popularity since LIBs contain valuable metals such as cobalt and lithium. A major challenge for LIB recycling is developing economical ways to extract and process metals from spent LIBs. The reviewed literature points to aresearch gap formed by the lack of study on the standardization of LIBs aimed to improve LIB recycling. The research gap is relevant because the reviewed literature points to a connection between standardization, innovation, and sustainability. Innovation of LIBs is a driver of sustainable transportation solutions, and the study of LIB standardization is relevant for two reasons. Firstly, standardization may influence further innovations needed to enable sustainable transportation. Secondly, standardization is relevant to achieve better recycling of LIBs and reduce the negative environmental and health effects of improper LIB disposal. Objectives:  During the development of the theoretical framework, two paradoxes were observed. The first paradox is between the dimensions of innovation and sustainability. Innovation acts positively on sustainability by enabling LIB development necessary to include EVs in the transportation sector. On the other hand, improper disposal of LIBs results in pollution affecting sustainability negatively. The second paradox is between the dimensions of standardization and innovation. Academics perceive standardization either as an enabler or as a hinder to innovation. Standardization enables innovation by giving a path and conditions for further technological developments, but standardization could also constrain the freethinking needed in innovation. Considering that innovation of LIBs has been a driver in the development of EVs, often described as a sustainable transportation solution, the study of LIBs’ standardization is relevant in the context of further innovation and higher sustainability goals.  The purpose of this study is to help to fill the gap in existing research on LIB recycling by exploring what factors in the dimensions of standardization, innovation, and sustainability are perceived as relevant for LIBs’ standardization aimed for better recycling. Moreover, the purpose of this thesis is also to explore how these factors influence further innovation of LIBs. Consequently, this thesis seeks to answer the following research question: What factors are perceived to be relevant for standardization of LIBs in the dimensions of standardization, innovation and sustainability aimed to improve recycling, and why? Also, how could these factors influence innovation of LIBs? Methodology:  Research in standardization aimed for recycling of LIBs is in its infancy. Therefore, the research problem is perceived as unstructured and modestly understood. Consequently, an exploratory research design has been selected for this thesis. The chosen research strategy was to conduct a case study focused on automotive firms. The selection of the case was based on four criteria. The first criterion was to select a firm in Sweden. The second criterion was to choose a firm with a defined strategy towards electric vehicles and a track of being innovative. A third criterion behind the selection was the firm’s potential for growth in units sold. The fourth criterion was that the firm should have a publicly known ambition or strategy towards sustainability. Volvo Cars Corporation (VCC) fulfilled all four criteria and was selected as the study case for this thesis. Data was collected by conducting semi-structured interviews with key organizational members involved in work related to second-life strategies of LIBs, development of LIBs, sustainability analysis, andlegislations or standardization. The sampling then focused on informants in the business areas of R&D,which covers these organizational activities. The interview questions were based on factors found to berelevant during the literature review within the dimensions of standardization, innovation, and sustainability. Also, each factor was associated with corresponding attributes. The formulation of the interview questions aimed to explore the relevance of an attribute for the standardization of LIBs aimed for better recycling and to explore how the factor influences innovation. The explored factors in the dimension of standardization were the source of standard, working groups for standardization development, practices during standard development, and design of standards. Meanwhile, the explored factors in the dimension of innovation were network effects and barriers to entry. In the sustainability dimension, the explored factors were exploration-exploitation balance and network effects.  The data analysis for the interviewees was based on first-order categorization of the answers, followed by creating second-order themes. The first-order categories and second-order themes were used for analyzing and assessing the relevance of the explored factors for the standardization of LIBs. Afterward, the second-order and aggregate themes were considered for the analysis of the factors’ influence on innovation. Moreover, the second-order themes have been used to identify new relevant factors to be considered in the standardization of LIBs with an influence in innovation. In this work, those identified relevant factors are referred asidentified elements. Finally, the analysis for the influence of the identified elements on innovation was visualized by the elaboration of a thematic map.  Results & Analysis:  The explored factors of standardization sources, working groups for standardization development, practices during development of standards and design of standards within the dimension of standardization were perceived as relevant and influenced innovation in combination with other identified elements. The most relevant identified elements were maturity, rigid standards, harmonization, flexibility, tacit knowledge, and culture. Maturity and rigid standards were perceived as the dominant among the identified elements by being important to avoid a negative influence on innovation caused by technology lock-in and obsolescence of the developed standards. Regarding identified elements with a positive influence on innovation, harmonization, culture, tacit knowledge, and flexibility are perceived as relevant to innovation by enabling common solutions in harmonized alliances, clarity in scope for the standards, and allowing freedom in the choice of methods. In the case of explored factors in the dimensions of innovation and sustainability, the explored factors of networks effects, entry barriers, and exploration-exploitation were perceived as relevant for the standardization of LIBs. Moreover, the results of the identified elements showed technology lock-in and iiiinefficient products as the biggest influence negatively affecting innovation and sustainability,respectively. The most important identified elements are maturity and investments for the technology lock-in aggregate theme, whereas efficiency, pricing, and environmental impact are identified for the case of inefficient products. Regarding aggregate themes enabling innovation and sustainability, they were presented in the form of resource and process optimization, market dynamics, and holistic view. Among the dominant identified elements enabling innovation are efficiency and specialized facilities.In addition to positive and negative aggregate themes, the aggregate theme of technology path was created. This aggregate theme refers to a technology development path that could influence innovation and or sustainability in potentially different ways: positive, neutral, or negative. The dominant identified elements in this theme are infrastructure, social realm, and consumer preference and awareness. Conclusions:  This thesis explored the relevance of factors in the dimensions of standardization, innovation, and sustainability on LIB standardization and their influence on the innovation of LIBs. The exploration of the factors’ perceived relevance answered the research question and resulted in new identified elementsrelevant to be considered in the standardization of LIBs with an influence on innovation. Consequently, this thesis fulfilled its purpose by helping to fill the gap in the existing research on LIB recycling. The main conclusions for the exploration of factors within the dimension of standardization are two. Firstly, the explored factors are relevant to be considered in the standardization of LIBs. Secondly, the exploration led to the new identified elements with negative and positive influence on innovation. The identified elements of maturity and rigid standards showed a negative influence on innovation in the form of technology lock-in or obsolescence of standards. However, the identified elements of harmonization, flexibility, tacit knowledge, and culture, showed a positive influence on further innovation of LIBs. The main conclusions for the dimensions of sustainability and innovation were that the explored factors are relevant in LIB standardization. Also, high compatibility between LIB manufacturers and recyclers raises challenges towards innovation while supporting sustainability. Also, consumer preferences and their shifts play a central role with negative and positive influence on innovation and sustainability and as a driver to certain segments of standardization.
9

Modélisation électrochimique du comportement d’une cellule Li-ion pour application au véhicule électrique / Electrochemical modeling of lithium-ion cell behaviour for electric vehicles

Falconi, Andrea 05 October 2017 (has links)
Le développement futur des véhicules électriques est lié à l’amélioration des performances des batteries qu’ils contiennent. Parallèlement aux recherches sur les nouveaux matériaux ayant des performances supérieures en termes d'énergie, de puissance, de durabilité et de coût, il est nécessaire développer des outils de modélisation pour : (i) simuler l'intégration de la batterie dans la chaine de traction et (ii) pour le système de gestion de la batterie, afin d'améliorer la sécurité et la durabilité. Soit de façon directe (par exemple, la prévention de surcharge ou de l’emballement thermique) soit de façon indirecte (par exemple, les indicateurs de l’état de charge). Les modèles de batterie pourraient aussi être utilisés pour comprendre les phénomènes physiques et les réactions chimiques afin d'améliorer la conception des batteries en fonction des besoins de l’utilisateur et de réduire la durée des phases de test. Dans ce manuscrit, un des modèles les plus communs décrivant les électrodes poreuses des batteries au lithium-ion est revisité. De nombreuses variantes dans la littérature s’inspirent directement du travail mené par le professeur J. Newman et son équipe de chercheurs à l’UC Berkeley. Pourtant relativement peu d’études analysent en détail les capacités prédictives de ce modèle. Dans ce travail, pour étudier ce modèle, toutes les grandeurs physiques sont définies sous une forme adimensionnelle, comme on l'utilise couramment dans la mécanique des fluides : les paramètres qui agissent de manière identique ou opposée sont regroupés et le nombre total de paramètres du modèle est considérablement réduit. Cette étude contient une description critique de la littérature incluant le référencement des paramètres du modèle développé par le groupe de Newman et les techniques utilisées pour les mesurer, ainsi que l’écriture du modèle dans un format adimensionnel pour réduire le nombre de paramètres. Une partie expérimentale décrit les modifications de protocoles mis en œuvre pour améliorer la reproductibilité des essais. Les études effectuées sur le modèle concernent d’une part l’identification des états de lithiation dans la cellule avec un attention particulière sur la précision obtenue, et enfin une prospection numérique pour examiner l’influence de chaque paramètre sur les réponses de la batterie en décharge galvanostatique puis en mode impulsion et relaxation. / The future development of electric vehicles is mostly dependent of improvements in battery performances. In support of the actual research of new materials having higher performances in terms of energy, power, durability and cost, it is necessary to develop modeling tools. The models are helpful to simulate integration of the battery in the powertrain and crucial for the battery management system, to improve either direct (e.g. preventing overcharges and thermal runaway) and indirect (e.g. state of charge indicators) safety. However, the battery models could be used to understand its physical phenomena and chemical reactions to improve the battery design according with vehicles requirements and reduce the testing phases. One of the most common model describing the porous electrodes of lithium-ion batteries is revisited. Many variants available in the literature are inspired by the works of prof. J Newman and his research group from UC Berkeley. Yet, relatively few works, to the best of our knowledge, analyze in detail its predictive capability. In the present work, to investigate this model, all the physical quantities are set in a dimensionless form, as commonly used in fluid mechanics: the parameters that act in the same or the opposite ways are regrouped and the total number of simulation parameter is greatly reduced. In a second phase, the influence of the parameter is discussed, and interpreted with the support of the limit cases. The analysis of the discharge voltage and concentration gradients is based on galvanostatic and pulse/relaxation current profiles and compared with tested commercial LGC cells. The simulations are performed with the software Comsol® and the post-processing with Matlab®. Moreover, in this research, the parameters from the literatures are discussed to understand how accurate are the techniques used to parametrize and feed the inputs of the model. Then, our work shows that the electrode isotherms shapes have a significant influence on the accuracy of the evaluation of the states of charges in a complete cell. Finally, the protocols to characterizes the performance of commercial cells at different C-rates are improved to guarantee the reproducibility.
10

State-of-health estimation by virtual experiments using recurrent decoder-encoder based lithium-ion digital battery twins trained on unstructured battery data

Schmitt, Jakob, Horstkötter, Ivo, Bäker, Bernard 15 March 2024 (has links)
Due to the large share of production costs, the lifespan of an electric vehicle’s (EV) lithium-ion traction battery should be as long as possible. The optimisation of the EV’s operating strategy with regard to battery life requires a regular evaluation of the battery’s state-of-health (SOH). Yet the SOH, the remaining battery capacity, cannot be measured directly through sensors but requires the elaborate conduction of special characterisation tests. Considering the limited number of test facilities as well as the rapidly growing number of EVs, time-efficient and scalable SOH estimation methods are urgently needed and are the object of investigation in this work. The developed virtual SOH experiment originates from the incremental capacity measurement and solely relies on the commonly logged battery management system (BMS) signals to train the digital battery twins. The first examined dataset with identical load profiles for new and aged battery state serves as proof of concept. The successful SOH estimation based on the second dataset that consists of varying load profiles with increased complexity constitutes a step towards the application on real driving cycles. Assuming that the load cycles contain pauses and start from the fully charged battery state, the SOH estimation succeeds either through a steady shift of the load sequences (variant one) with an average deviation of 0.36% or by random alignment of the dataset’s subsequences (variant two) with 1.04%. In contrast to continuous capacity tests, the presented framework does not impose restrictions to small currents. It is entirely independent of the prevailing and unknown ageing condition due to the application of battery models based on the novel encoder–decoder architecture and thus provides the cornerstone for a scalable and robust estimation of battery capacity on a pure data basis.

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