Дисертації: "Simulations STM"

1

Lesnard, Hervé. "Structure électronique de molécules aromatiques sur une surface sondée par STM : apports récents des simulations." Lyon, École normale supérieure (sciences), 2009. http://www.theses.fr/2009ENSL0553.

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Mes travaux théoriques concernent les potentialités du microscope STM pour induire deux types d’excitations locales, soit vibrationnelle soit électronique, sur des molécules aromatiques isolées adsorbées sur des surfaces. La spectroscopie vibrationnelle sous le microscope à effet tunnel (IETS pour «Inelastic Electron Tunneling Spectroscopy») est une technique récente qui mesure le spectre vibrationnel d’une seule molécule déposée sur une surface conductrice. A partir d’une tension seuil, on peut exciter une vibration moléculaire qui se traduit par un pic dans la dérivée de la conductance par rapport à la tension et la perte d’énergie de l’électron tunnel: c’est le signal vibrationnel inélastique. Pour des spectres mesurés sur Cu(100) de radicaux issus de la perte d’hydrogènes du benzène comme le phényl et le benzyne (groupe de W. Ho, Irvine), nos simulations du signal inélastique atteignent un niveau de comparaison quantitative permettant l’identification du radical. D’autre part, en dupliquant l’étude pour la déshydrogénation de la pyridine, nous montrons que l’hétéroatome en substitution ne modifie que l’intensité des signaux inélastiques. Enfin, nous montrons que les règles de sélection se rationalisent en tenant compte de la symétrie des états électroniques avant et après couplage électron-vibration et de l’état vibrationnel. Ensuite, nous nous intéressons à la réactivité électro-induite du biphényl sur Si(100) étudiée par STM (groupe de G. Dujardin, Orsay) qui montre une sélectivité régie par la polarité de l’impulsion de tension. D Par un calcul exhaustif de tous les chemins possibles, nous montrons que les barrières cinétiques de diffusion et de déshydrogénation fournissent la preuve que la sélectivité observée en fonction de la polarité d’impulsion de tension ne peut pas être attribuée directement à différentes énergies d'activation
The subject of my theoretical work deals with the capabilities of the STM tool to induce two types of local excitations, either vibrational or electronic on single adsorbed aromatic molecules on surfaces. Concerning vibrational excitations, the changes in tunneling conductance at vibrational thresholds have recently been used as an Inelastic Electron Tunneling Spectroscopy (IETS). We study the STM-induced dehydrogenation of benzene on Cu(100), where the reaction products could be either phenyl or benzyne fragments (group of W. Ho, Irvine). We demonstrate that they are solely identified with their theoretical IETS fingerprints being in quantitative agreement with the IETS measurements. We similarly investigate the dehydrogenation of pyridine and show that one heteroatom in the aromatic ring affects the magnitude of the IETS signatures. Conversely, we rationalize our findings in terms of inelastic propensity rules that couple the symmetry of the electronic scattering states and the molecular vibrators. In a second part, we study the electron-induced reactions of individual biphenyl molecules on a Si(100) surface, which have been investigated by using the tip of the STM as an atomic size source of electrons (group of G. Dujardin, Orsay). Selected types of molecular reactions are produced, depending on the polarity of the surface voltage during STM excitation. We determine all possible reaction pathways on the silicon surface, providing evidence that the observed selectivity as a function of the surface voltage polarity cannot be ascribed to different activation energies

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2

Vu, Van Binh. "Theoretical studies of novel graphene based nanostructures." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP039.

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Depuis sa découverte, le graphène est devenu un centre de recherche et d'intérêt important en raison de ses caractéristiques mécaniques, thermiques et électriques exceptionnelles. Néanmoins, l'absence de bande interdite dans le graphène constitue un obstacle aux applications dans les domaines de l'optique, de la nanoélectronique et de la spintronique. L'ingénierie de la bande interdite impliquant la nanostructuration du graphène a été développée au fil des ans, par exemple par confinement quantique, pour surmonter cette limitation. Ce travail théorique est consacré à la modification des réponses électroniques, optiques et de microscopie/spectroscopie à effet tunnel (STM/STS) en fonction de la taille du système de nouveaux matériaux de carbone tels que les nanomeshs de graphène (GNM), les boîte quantiques de graphène de forme/taille contrôlée (GQD) et les nanorubans de graphène (GNR), afin de comparer et d'analyser les données expérimentales. Ces nouveaux matériaux carbonés sont théoriquement déposés sur des surfaces d'or Au(111) dans une simulation STM réalisée à l'aide du formalisme des fonctions de Green hors équilibre (NEGF) basé sur la méthode DFT Fireball afin d'étayer les données expérimentales. En ce qui concerne les GQD, nous simulons leur spectre d'absorption en utilisant la correction GW et les équations de Bethe-Salpeter (BSE), si possible, pour les comparer directement aux données expérimentales. Dans le cas contraire, leurs propriétés optiques sont obtenues par une approche inférieure, l'approche Tight-Binding (TB). Les impacts des agrégations et des impuretés sur leurs réponses optiques sont également explorés en étudiant la bicouche torsadée des GQDs via la méthode TB. En outre, les changements dans les propriétés électroniques de ces nouveaux matériaux de carbone en fonction de la taille de leur système sont extraits à l'aide de la méthode TB. La performance de la méthode TB est vérifiée par des simulations DFT et GW. Enfin, d'autres matériaux de faible dimension, les nouvelles structures bicouches de nitrure de bore hexagonal torsadées à près de 30° (hBN-TBLs), sont également étudiées dans cette thèse. Les méthodes DFT et TB réalisent les structures électroniques et optiques de nouveaux hBN-TBLs plus loins de 30° afin d'obtenir les paramètres d'ajustement pour le modèle TB. Ces paramètres sont ensuite utilisés pour prédire des hBN-TBL plus proches de 30°, ce qui est difficilement réalisable par DFT
Since its discovery, graphene has become a focal point of extensive research and interest because of its exceptional mechanical, thermal, and electrical characteristics. Nevertheless, the absence of a bandgap in graphene constitutes a barrier to applications in optics, nanoelectronics, and spintronics. Bandgap engineering involving the nanostructuration of graphene has been developed over the years, such as by quantum confinement, to overcome this limitation. This theoretical work is dedicated to the change of electronic, optical, and scanning tunneling microscopy/spectroscopy (STM/STS) responses as a function of system size of new carbon materials like graphene nanomeshes (GNMs), shape/size controlled graphene quantum dots (GQDs) and graphene nanoribbons (GNRs), in order to compare and analyze experimental data. These new carbon materials are theoretically deposited on gold Au(111) surfaces in STM simulation performed using the Non-equilibrium Green's function (NEGF) formalism based on the Fireball DFT method to support the experimental data. Concerning GQDs, we simulate their absorption spectrum using the GW approximation and the Bethe-Salpeter equations (BSE), if possible, to compare directly with the experiment data. Otherwise, their optical properties are achieved by a lower approach, the Tight-Binding (TB) approach. Also, the impacts of aggregations and impurities on their optical responses are explored by studying the twisted bilayer of the GQDs via the TB method. Moreover, the changes in these new carbon materials' electronic properties as a function of their system size are extracted using the TB method. The performance of the TB method is verified by DFT and GW simulations. Finally, other low-dimensional materials, new close-to 30° twisted hexagonal boron nitride bilayer structures (hBN-TBLs), are also studied in this thesis. DFT and TB methods perform the electronic and optical structures of further 30° hBN-TBLs to obtain the fit parameters for the TB model. These parameters are then used to predict closer to 30° hBN-TBLs, which are hardly to be obtained by DFT

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3

Parditka, Bence. "Investigation of diffusion and solid state reactions on the nanoscale in silicon based systems of high industrial potential : experiments and simulations." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4348/document.

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La première partie de mes résultats concerne les phénomènes de diffusion induits par des effets de contrainte. Nous avons étudié ces effets d’un point de vu théorique, afin de comprendre le rôle de la contrainte dans la diffusion. Les résultats montrent que l’effet de contrainte ne semble pas induire d’effet mesurable sur le coefficient cinétique à l’interface, cependant le taux de mélange semble diminuer. La seconde partie concerne des mesures expérimentales, par EXAFS et GIXRF utilisées sur des empilements Ta/a-Si/Ni/a-Si/Ta/substrat permettant de suivre la formation des phases ainsi que la croissance, à une température donnée, et ce jusqu’à la formation de la phase Ni2Si et au delà. La troisième partie concerne le système Cu-Si. Nous avons suivi les premiers stades de la formation de la phase Cu3Si, en utilisant les techniques XRD, APT, SNMS, ainsi qu’un profilomètre et une mesure de résistance quatre points sur différents échantillons réalisés par pulvérisation. Dans le cas de l’empilement Cu/a-Si/substrat, la formation de phases a suivi une cinétique linéaire. Nous avons notamment mis en évidence la formation très rapide d’une phase qui apparait directement après le premier recuit très court, démontrant ainsi le rôle déterminant de la préparation des échantillons dans l’étude des processus de formation de phases. La quatrième partie s’intéresse au silicène : cette structure bidimensionnelle de silicium dite en « nid d’abeilles », réalisée sur un substrat d’argent et qui présente de grandes similitudes avec le graphène. En utilisant de façon complémentaire les techniques AES-LEED-STM, nous avons déterminé la limite de solubilité du silicium dans l’argent
Diffusion and related solid state reaction phenomena have been studied in four different material couples. The first section of the results concerned the diffusion related stress effects. We analyzed the question theoretically, for planar model geometry, to find the role of stress in diffusion. We obtained that stress effects do not have any measurable effects on the kinetic coefficient of the interface shift. However, the intermixing rate decreases. The second section we performed EXAFS and GIXRF experiments on sandwich structured Ta/a- Si/Ni/a-Si/Ta/substrate samples and followed the phase formation and growth at a given temperature at which the Ni2Si phase has formed and continued to grow. The third section we obtained in the Cu-Si system. We followed the early stages of phase formation of the Cu3Si phase under different circumstances. We performed XRD, APT, SNMS, profilometer and 4 wire resistance measurements on sputtering deposited samples. We found that in case of the Cu/a-Si/substrate samples the phase formation was followed by a linear kinetics. Secondly, prior to the linear phase growth, we observed an extremely fast phase formation that appeared immediately after the very first and shortest annealing, which showed that the preparation sequence of the sample is a crucial point in phase formation processes. The fourth section deals with the silicene. It is the honeycomb structured formation of Si atoms with properties similar to graphene. We investigated the dissolution of Si into Ag. We performed a combination of AES, LEED, STM measurements. We determined the dissolution limit of Si in Ag from data obtained from the AES measurements

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4

Boukari, Khaoula. "De la molécule unique au tapis supramoléculaire sur surface de silicium passivée : Simulations numériques à l'échelle atomique." Thesis, Mulhouse, 2013. http://www.theses.fr/2013MULH8858/document.

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Ma thèse porte sur l’étude par simulations numériques à l’échelle atomique de l’adsorption de molécules uniques et d’auto-assemblages moléculaires sur la surface de silicium Si(111) dopée bore notée Si(111) (√(3 ) x√3)R30°-B. Après un premier chapitre de présentation des méthodes de calcul, puis un chapitre consacré à la surface Si(111)-B, la thèse se divise en deux grandes parties : l’une concernant l’adsorption de molécules uniques et l’autre consacrée à l’adsorption de tapis moléculaire.La première partie concerne l’adsorption de molécules uniques sur la surface de Si(111) (√(3 ) x√3)R30°-B. Nous avons plus particulièrement étudié trois molécules présentant des mécanismes d’adsorption différents : la molécule de pyridile-azobenzène, une molécule de la famille des porphyrines (Cu-TBPP) et deux molécules appartenant à la famille des phtalocyanines (H2Pc et CuPc). Dans chaque étude, nous avons effectué une étude énergétique, structurale et électronique. Dans la plupart des cas, nous avons complété l’étude par un calcul d’image STM pour comparer avec les résultats expérimentaux. A partir de cette étude, nous avons montré que les molécules interagissent différemment avec la surface via des interactions électrostatiques, des liaisons datives, des liaisons ioniques et un mécanisme de cycloaddition. La deuxième partie de la thèse est dédiée à l’étude de l’auto-assemblage de molécules organiques sur la surface Si(111) (√(3 ) x√3)R30°-B. L’auto-assemblage moléculaire est une technique permettant la fabrication d’architectures hautement organisées à l’échelle atomique. Nous avons étudié trois molécules différentes formant un auto-assemblage sur la surface de Si(111)-B : 1,3,5-tri(4-bromophényle benzène) notée TBB, 1,3,5-tri(4-iodophényle benzène) notée TIB et 1,3,5-triphenylbenzene notée THB. Comme la formation d’un réseau auto-organisé est la conséquence d’un équilibre entre les interactions molécule-molécule et molécules-substrat, nous avons évalué les énergies d’interaction mises en jeu en utilisant différentes approximations (LDA, GGA et GGA+D). Nous avons étudié, ensuite, les propriétés électroniques de ces assemblages par le calcul des densités d’états projetées, de la différence de la densité de charge, du Laplacien de la charge ou de la fonction ELF. Afin de comparer nos résultats avec les résultats expérimentaux, nous avons effectué un calcul d’image STM en utilisant deux approches : l’approche de Tersoff-Hamann et l’approche multidiffusion proposée par le code bSKAN. Dans une dernière étape, nous avons étudié la recroissance de molécules de fullerène C60 sur le réseau auto-organisé de molécules de TBB déposées sur la surface Si(111) (√(3 ) x√3)R30° -B. Nous avons effectué une étude énergétique des molécules de C60 qui se déposent préférentiellement dans les nanopores de forme hexagonale en accord avec les expériences STM
My thesis presents the study of the adsorption of single molecules and molecular self-assembly, by numerical simulations at the atomic scale, on a boron doped silicon surface denoted Si(111)(√(3 ) x√3)R30°-B. After presenting the calculation methods and describing the surface model, this thesis is made of two parts: the first one is about the adsorption of single molecules and the second one is devoted to the formation of supramolecular network. In the first part, I studied the adsorption of single molecules on the silicon surface doped boron Si (111)(√(3 ) x√3)R30°-B. I have investigated the adsorption mechanisms of three different molecules: a molecule of pyridyl-azobenzene, a molecule of the family of porphyrin (Cu-TBBP) and two molecules which belong to the family of phtalocyanine (H2Pc and CuPc). For every molecule, I conducted energetic, structural and electronic studies. In most of the cases, I completed this work by calculating STM images in order to compare with experimental results. The second part of this thesis deals with the study of self assembly of organic molecules on the surface of Si(111)(√(3 ) x√3)R30°-B. Molecular self assembly is a technique which allows the formation of highly organized architectures at the atomic scale. I have studied three different molecules forming self assembly on the surface of Si (111)(√(3 ) x√3)R30°-B : 1,3,5-tri(4-bromophenyl benzene) denoted TBB, 1,3,5-tri(4-iodophenyle benzene) denoted TIB et 1,3,5-triphenylbenzene denoted THB. As the formation of a self organized network is a result of equilibrium between molecule-molecule interaction and molecule-substrate one, I have evaluated the interaction energies by using different approximations (LDA, GGA and GGA+D). Then, I have studied the electronic properties of these assemblies by calculating the projected density of states, the charge difference and the Laplacien of the charge or the ELF function (Electronic Localization Function). In order to compare our results with experimental ones, STM images calculations were performed by using two different approaches: the approach of Tersoff-Hamann and the multi-scattering approach proposed by bSKAN code. Finally, I have studied the growth of C60 molecules on the self organized network formed by the TBB molecules deposited on the Si (111)(√(3 ) x√3)R30°-B surface. The energetic study shows that C60 molecules are adsorbed preferentially in the hexagonal nanopores in agreement with the STM observations

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Robinson, Michael C. "A study of the diffusion of Pb on Au(111) using scanning tunneling microscopy (STM), with a comparison to embedded atom method (EAM) and surface embedded atom method (SEAM) simulations." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ52846.pdf.

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6

Laird, Rob. "Sim City : the simulation of ideology /." Title page, table of contents and introduction only, 2005. http://web4.library.adelaide.edu.au/theses/09AR/09arl188.pdf.

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7

Watcharasukarn, Montira. "Travel Adaptive Capacity Assessment Simulation (TACA Sim)." Thesis, University of Canterbury. Mechanical Engineering, 2010. http://hdl.handle.net/10092/5119.

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More than 95% of fuel used for personal transportation is petroleum-based (Environment and Development Division (EDD), 2005). The peak and decline of world oil production is producing price and uncertainty pressures that may cause significant travel behaviour change in the future. Current travel behaviour has developed during conditions of low cost fuel and government investment in private vehicle mobility. Current urban forms and land use have also been developed during a period of growth in vehicle travel demand. Research that explores the long term (permanent oil supply reduction period) implications of reduced fuel demand on private travel behaviour is needed. Local and national government investments in transport infrastructure and urban development will be used and require maintenance for decades. Research is needed to assess long-term mode choice and car travel demand as a function of urban form and demographic indicators. This type of travel behaviour adaptive potential should be relevant to transport planning decision making. Literature review shows that there are a few available long-term planning methods, models, or tools in transportation engineering for future oil depletion. Transportation engineers need information of how current travel demand patterns may change over the lifetime of infrastructure investments in response to oil supply depletion. Behaviour change data for long term future situations would be difficult to obtain using traditional survey methods because most people have never experienced oil depletion situations. This research proposes that immersing people into the situation of oil depletion through sharp price rise would be necessary to generate relevant behaviour change decisions. The thesis is that the long term behaviour change can be assessed by characterising current adaptive capacity. Adaptive capacity is defined in this thesis as the travel demand pattern with maximum fuel reduction without reducing participation in activities. The reasons why people might change travel demand to reduce fuel use is not part of the definition. This research also proposed that an immersive sim game environment could be used to prompt behaviour change decisions relating to fuel price shocks. Research into sim game surveys and travel behaviour surveys was used to inform the design of a Transport Adaptive Capacity Assessment (TACA) Sim survey tool. The TACA Sim survey was designed to assess capacity to adapt travel behaviour to reduce fuel use, and to characterise the potential for mode change. Participants experience the TACA Sim survey as a self assessment or transport energy audit. The survey provides a personal feel, focuses on the usual weekly activities, and provides feedback to participants about their fuel use and car dependence. Participants supply their normal travel activities over a week, and three weeks of sim play includes a steep fuel price rise while people are allowed to change their travel behaviour in response. The TACA Sim survey was evaluated through a case study of surveys of staff and students at the University of Canterbury. A second version of the TACA survey was developed that surveyed the one week of normal travel, but then probed adaptive capacity by asking a simple question after each travel activity was entered “Could you get to the activity another way?” The sim game travel adaptive capacity is compared with the available alternative adaptive behaviour for participants in a case study at the University of Canterbury. The results of the case study show that the participants responded well with the simulated situation. This reflects that the TACA Sim is successful in helping participants to perceive the situation of fuel price rise and think about their alternatives to car travel. Asking people “Could you get to the activity another way?” was found to effectively probe their adaptive capacity which agreed well with the virtual reality survey. The virtual reality survey yields more details of what people can do such as moving house, chaining trips, combining trips and buying a more efficient vehicle. The web-based TACA survey has been developed and deployed in two further research projects.

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Deniz, Ertan. "Dds Based Mil-std-1553b Data Bus Interface Simulation." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614852/index.pdf.

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This thesis describes distributed simulation of MIL-STD-1553B Serial Data Bus interface and protocol based on the Data Distribution Service (DDS) middleware standard. The data bus connects avionics system components and transports information among them in an aircraft. It is important for system designers to be able to evaluate and verify their component interfaces at the design phase. The 1553 serial data bus requires specialized hardware and wiring to operate, thus it is expensive and complex to verify component interfaces. Therefore modeling the bus on commonly available hardware and networking infrastructure is desirable for evaluation and verification of component interfaces. The DDS middleware provides publish-subscribe based communications with a number of QoS (Quality Of Service) attributes. DDS makes it easy to implement distributed systems by providing an abstraction layer over the networking interfaces of the operating systems. This thesis takes the advantage of the DDS middleware to implement a 1553 serial data bus simulation tool. In addition, the tool provides XML based interfaces and scenario definition capabilities, which enable easy and quick testing and validation of component interfaces. Verification of the tool was performed over a case study using a scenario based on the MIL-STD-1760 standard.

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Petersson, Jenny. "3D-simulation som avprovningsmetod : Inriktat mot tights för sportutövning." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-14789.

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Denna studie om 3D-avprovning för sport-tights är en kandidatuppsats i designteknik. Företaget studien är utvecklad för jobbar med sportkläder och har i dagsläget ett intresse av att använda sig av 3D-simulering som avprovningsmetod. Vid utveckling av tights anpassade för träning skickas i dagsläget flera prototyper mellan företaget och leverantören innan produkten kan börja produceras. För att framtagningen av produkten ska ta mindre tid, bli mer miljövänlig och kosta mindre undersöker studien om 3D-avprovning är applicerbart i företagets process för produktframtagning. För att kontrollera validiteten i 3D-avprovning av tights gjordes tre undersökningar med syfte att få förståelse för skillnaderna mellan en fysisk och en virtuell avprovning. Undersökningarna fokuserar på grundstorleken Small och den största storleken Extra Large. Studien visar att 3D-simulering till viss del är en fungerande avprovningsmetod för tights när det kommer till att kontroll av designen. För att kontrollera plaggens rörelsevidd är metoden i denna studie ej fungerande. Studiens deltagare visade en positiv inställning till att använda sig av metoden i deras produktframtagningsprocess men då främst som ett komplement till fysiska avprovningar tidigt i designprocessen.
This study on 3D fitting for sports tights is a Final Bachelor Degree Thesis in design technology. The company the study is developed for works with sportswear and currently has an interest in using 3D simulation as a fitting method. For the development of tights adapted for training, several prototypes are currently being sent between the company and the supplier before the product can start to be produced. In order for the production of the product to take less time, become more environmentally friendly and cost less, the study investigate if 3D fitting is applicable in the company's product development process. To check the validity of 3D fitting of tights, three surveys were made with the purpose of understanding the differences between physical and virtual testing. The studies focus on the base size Small and the largest size Extra Large. The study shows that 3D simulation is partially functional testing method for tights when it comes to controlling the design. In order to control the ease, the method in this study is not working. The participants of the study showed a positive attitude to use the method in their product development process, but mainly as a complement to physical fittings early in the design process.

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Holt, Jennifer A. "THz Systems: Spectroscopy and Simulation." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417536443.

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11

Abuelyaman, Eltayeb Salih. "Sequential circuits fault simulation using fan out stem based techniques." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184466.

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This dissertation describes a new simulation technique for an automatic test generation system, SCIRTSS version 4.0 (Sequential Circuit Test Sequence System). This test generation system is driven by the hardware compiler AHPL, a Hardware Programming Language, and an intelligent heuristic-based search for test vector generation. Using a fault-injection gate-level simulator and the generated test vector, all the faulty states of the circuit are simulated in parallel and the simulator is thus able to find all detected faults by a particular input sequence. The major objective of this research was to develop a faster replacement for the existing simulation process. The philosophy of divide and conquer is used in the development of the new simulation technique. Sequential networks are divided into combinational sub-networks, and, if necessary, the combinational sub-networks are further reduced into fan-out free regions. Thus, the problem is reduced to a relatively simple combinational one. In addition to the classical faults, the new simulator attempts to detect CMOS stuck-open faults. Several circuits were tested under SCIRTSS 4.0 using both the existing and the new simulation techniques. The results are listed in this paper to verify superiority of the new simulation technique.

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Baca, Dawnielle C. "DATA ACQUISITION, ANALYSIS, AND SIMULATION SYSTEM (DAAS)." International Foundation for Telemetering, 1994. http://hdl.handle.net/10150/608561.

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International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California
The Data Acquisition, Analysis, and Simulation System (DAAS) is a computer system designed to allow data sources on spacecraft in the Flight System Testbed (FST) to be monitored, analyzed, and simulated. This system will be used primarily by personnel in the Flight System Testbed, flight project designers, and test engineers to investigate new technology that may prove useful across many flight projects. Furthermore, it will be used to test various spacecraft design possibilities during prototyping. The basic capabilities of the DAAS involve unobtrusively monitoring various information sources on a developing spacecraft. This system also provides the capability to generate simulated data in appropriate formats at a given data rate, and to inject this data onto the communication line or bus, using the necessary communication protocol. The DAAS involves Serial RS232/RS422, Ethernet, and MIL-STD-1553 communication protocols, as well as LabVIEW software, VME hardware, and SunOS/UNIX operating systems.

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St-Georges, Kim. "Modélisation et simulation du phénomène de diffusion des progiciels de gestion intégrée au sein de réseaux industriels." Mémoire, École de technologie supérieure, 2007. http://espace.etsmtl.ca/230/1/ST%2DGEORGES_Kim.pdf.

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Le phénomène de concurrence internationale auquel les entreprises font face aujourd'hui les pousse à optimiser leur gestion d'information. Les systèmes de gestion intégrée, soit les systèmes ERP (Enterprise Resource Planning), permettent ainsi aux entreprises d'optimiser leur gestion d'information en intégrant une grande quantité d'information en temps réel selon une structure d'affaire complexe. Actuellement, une panoplie de systèmes ERP sont disponibles et plusieurs éditeurs se livrent concurrence pour offrir un progiciel toujours plus performant. Afin de se tailler une place parmi la concurrence, il est donc important pour les éditeurs de bien comprendre la dynamique de diffusion des systèmes ERP au sein des différents réseaux industriels. Malgré le fait que la théorie de la diffusion couvre depuis longtemps ces comportements de propagation par réseautage dans le segment des innovations logicielles, aucun modèle ne quantifie, ni ne décrit de façon dynamique par l'entremise de la simulation ce type phénomène. En réponse à cette problématique, le présent mémoire propose un modèle de propagation de progiciels de gestion intégrée au sein de réseaux d'affaires, en tenant compte des caractéristiques du réseau et de l'influence de la publicité dans son ensemble. Le modèle proposé dans ce mémoire est basé sur un modèle à influence mixte. Il utilise la modélisation par événements discrets. Le modèle présenté nous a permis de décrire la diffusion de systèmes ERP sous un angle épidémiologique, en plus de suivre le développement à chaque période de l'évolution du phénomène de diffusion, et ce, pour chacune des entreprises du réseau. Il ne s'agit là que d'une base à la modélisation de ce type de phénomène, limité à rexploration du sujet par la structure du réseau et certaines caractéristiques principales de bases. L'étude se limite également à la propagation de systèmes ERP par adoption complète d'une solution et, par conséquent, ne tient pas compte des adoptions partielles de multiples systèmes ERP

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14

Öman, Love. "Examination of a Damaged Slitting Knife using Scanning Electron Microscopy and Finite Element Simulations." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-86126.

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At voestalpine Precision Strip AB, the slitting process is used frequently. Slitting is a commonly applied manufacturing technique during sheet metal processing that aims to split large coils of sheet metal into narrower widths. The coiled sheets are uncoiled and transferred to a slitter, where they pass between rotating circular knives that produce long and straight cuts, splitting the wide sheet into desired widths. However, during operation, their slitting knives are occasionally damaged. This means that the knives must be replaced, which wastes both time and money. The goal of this project is therefore to examine the damage of a degraded slitting knife. A scanning electron microscope (SEM) is used to analyse the fracture surface and the microstructure of the knife. Further analysis of the knife is a Vickers hardness test to determine the knife’s hardness. Moreover, finite element (FE) simulations of the slitting process are performed in FE software Abaqus to understand the stresses that the knives are subject to during operation. The results show that the Mises stress reaches a maximum value of around 2250 MPa, which is approximately 75% of the materials yield stress in compression. The SEM images show clear signs of smooth cleavage zones in the fracture area, indicating that the knife has failed by a brittle fracture. Furthermore, the images reveal possible signs of fatigue. The hardness test proved that the knife is very hard with a hardness of 802,2 HV. Plenty of carbides were revealed by the microstructure test – mainly two types. MC vanadium carbides and M6C carbides mainly consisting of tungsten and molybdenum, which explains the hardness of the knife. To draw further conclusions on the damage of slitting knives in the future, there needs to be proper documentation of the slitting process. This involves taking note of the knife setup, the sheet material and its thickness, as well as the lifetime of the knives as failure occurs.

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15

Tang, Yi. "SUNSHINE: Integrate TOSSIM and P-Sim." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/40721.

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Simulators are important tools for wireless sensor network (sensornet) design and evaluation. However, existing simulators only support evaluations of protocols and software aspects of sensornet design. Thus they cannot accurately capture the significant impacts of various hardware designs on sensornet performance. To fill in the gap, we proposed SUNSHINE, a scalable hardware-software cross-domain simulator for sensornet applications. SUNSHINE is the first sensornet simulator that effectively supports joint evaluation and design of sensor hardware and software performance in a networked context. SUNSHINE captures the performance of network protocols, software and hardware through the integration of two modules: a network simulator TOSSIM [1] and hardware-software simulator P-Sim composed of an instruction-set simulator SimulAVR [2] and a hardware simulator GEZEL [3]. This thesis focuses on the integration of TOSSIM and P-Sim. It discusses the integration design considerations and explains how to address several integration challenges: time conversion, data conversion, and time synchronization. Some experiments are also given to demonstrate SUNSHINEâ s cross-domain simulation capability, showing SUNSHINE's strength by integrating simulators from different domains.
Master of Science

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16

Babaji, G. A. "Some plant stem properties and overland flow hydraulics : a laboratory simulation." Thesis, Cranfield University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293314.

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17

Hogg, Glynn A. "Multi-stem mechanised harvesting operation analysis : application of discrete-event simulation." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1973.

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Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2009.
In this study, a multi-stem harvesting operation was observed and time studies carried out on its machines. A stump-to-mill simulation model (System 1) of this system was subsequently built using a commercial simulation software package (Arena 9) and data from the time studies were incorporated into the model. Following this, another two stump-to-mill multistem models (Systems 2 and 3) were built using the same simulation software package and parameterised input data. These two models represented hypothetical systems which were tested against System 1 and against one another in terms of machine balance within the system, production rate and cost. System 2 used identical equipment to System 1, but practised alternative operating methods. Some of System 3’s machines and operating methods differed from those in Systems 1 and 2. The objectives of the study were to: 1. Determine whether or not commercial simulation software can be used to adequately model forest harvesting operations. 2. Gauge potential system balance, production and/or cost improvement/s achievable through application of simulation-based operation adjustments. 3. Define beneficial equipment operation and application practises for multi-stem systems. 4. Through construction and use of the commercial software package in producing forest harvesting operation models, evaluate the software’s usability in terms of its applicability to and ease of use in such models, as well as its ability to meet forestrybased user requirements.

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18

Lüder, Stephan, Marcel Graf, Birgit Awiszus, Thoufeili Taufek, and Yupiter HP Manurung. "Methoden und Herausforderungen bei der numerischen Simulation des selektiven Laserschmelzens (SLM)." Technische Universität Chemnitz, 2019. https://monarch.qucosa.de/id/qucosa%3A34096.

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Additive Fertigungsverfahren stellen in den letzten Jahren einen Megatrend dar, da sich mit diesen Verfahren endkonturnahe Werkstücke mit hohem Materialausnutzungsgrad herstellen lassen. Die auch als 3D-Druck bekannt gewordenen additiven Fertigungsverfahren sind jedoch nicht auf die Prototypenfertigung aus Kunststoffen begrenzt. Beim selektiven Laserschmelzen werden metallische Werkstoffe im Pulverbettverfahren mittels Laserstrahl aufgeschmolzen und somit schichtweise aufgebaut. Das Verfahren findet bereits in der Luft- und Raumfahrt, der Medizintechnik, aber auch in der Automobilindustrie und im Maschinenbau Anwendung für Prototypen, Einzelanfertigungen oder Kleinstserien. Des Weiteren ermöglicht es auch die Herstellung von Werkstücken mit besonders hoher Komplexität, die mit spanenden Verfahren nicht herstellbar sind, und bietet dadurch neue Gestaltungsmöglichkeiten bei der Konstruktion. Innerhalb des Vortrags werden nach der Vorstellung des Verfahrens verschiedene Methoden zur numerischen Simulation des selektiven Laserschmelzens von Edelstahl (1.4404) am Beispiel der kommerziellen Software Simufact Additive erläutert. Dazu werden der mechanische und thermo-mechanische Lösungsansatz betrachtet sowie die Methode zur Kalibrierung der Simulationen erläutert. Die Erläuterung eines voll transienten thermo-mechanischen Ansatzes erfolgt unter Verwendung der Software MSC Marc. Des Weiteren wird der Einfluss der Orientierung des Werkstücks im Herstellungsprozess auf resultierende Spannungen, Verzug sowie mechanische Eigenschaften analysiert und mit experimentellen Untersuchungen untersetzt.

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19

Stapelfeldt, Thim Frederik [Verfasser], and Roland [Akademischer Betreuer] Wiesendanger. "Simulation of the SP-STM induced magnetization switching of nanowires and nanoislands / Thim Frederik Stapelfeldt. Betreuer: Roland Wiesendanger." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1054422486/34.

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20

Vigano, Andre De Souza. "Simulation of an SP8T 18 GHz RF Switch Using SMT PIN Diodes." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2259.

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Radio frequency (RF) and microwave switches are widely used in several different applications including radar, measurement systems, telecommunications, and other areas. An RF switch can control a radar’s transmit vs. receive mode, select the operating band, or direct an RF signal to different paths. In this study, a single pole eight throw (SP8T) switch using only Surface Mount (SMT) components is designed and simulated in Keysight’s Advanced Design System (ADS). Single pole eight throw is defined as one input and eight possible outputs. A star network configuration with series-shunt PIN diode switches is used to create the 8-way RF switch. There are other commercially available SP8T switches from MACOM, Skyworks, Analog Devices, and other vendors that operate around this bandwidth. However, this design uses SMT components and series-shunt diode configurations to create a device in the GHz range and power handling in the high 20 to 30 dBm range. This study modeled components in ADS, including the PIN diodes and the bias tees. The project also analyzed multiple layouts, finalizing the optimal design to meet specifications. The insertion loss, bandwidth, isolation, return loss, power handling, and switching speed are analyzed in the final design. Key specifications for this design are determined by comparing to other commercially available SP4T and SP8T switches from MACOM, Skyworks, Analog Devices, and other vendors, as well as developing an operational switch over the 2-18 GHz bandwidth. Additional specifications include limiting insertion loss to 2.0 dB maximum and maximizing isolation to 30 dB minimum. Switching speed and power handling specifications are also set to 20 ns and 23 dBm, respectively. Future projects will work on design fabrication and improvements to the manufactured switch.

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21

Susin, Marcos José. "Estudo e desenvolvimento de um atuador planar de armadura sem núcleo ferromagnético." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/150579.

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Este trabalho apresenta a proposta de topologia para um atuador planar sem núcleo ferromagnético na armadura, sua análise teórica em termos de forças de tração que nele atuam, seu desenvolvimento e resultados teóricos e experimentais obtidos como base em um protótipo construído. O atuador planar tem características inovadoras: uma armadura estacionária sem ferro com enrolamentos ortogonais e dois carros acoplados magneticamente um ao outro com quatro ímãs permanentes de NdFeB de alto produto energético. A armadura desse estator é composta por enrolamentos planares multifases colocados de tal maneira que dois enrolamentos ortogonais independentes são produzidos e assim definem duas forças de propulsão ortogonais. Cada carro possui uma culatra de aço que suporta os ímãs permanentes e que está ligada a uma estrutura de suspensão mecânica para permitir o movimento bidirecional sobre a área definida pela armadura. Esse tipo de atuador pode ser usado em aplicações que requerem o movimento em qualquer direção ao longo de um plano. O protótipo desenvolvido neste trabalho foi testado com a finalidade de validar suas características estáticas de operação com relação à análise numérica e o modelo analítico. Os valores de densidade de fluxo magnético no entreferro e de força planar de propulsão, obtidos através de ensaios, apresentaram uma boa aproximação em relação aos valores obtidos através da simulação numérica e do modelo analítico. Para os ensaios de força normal este trabalho preocupou-se em analisar numérica e experimentalmente os resultados, que também apresentaram valores convergentes e satisfatórios para os itens propostos. Para os ensaios do atuador planar com regulagem de entreferro de 12 mm e 24 mm foram encontradas sensibilidades médias da força planar de propulsão de 7,19 N/A e 4,13 N/A respectivamente.
This work presents a proposal of topology of a planar actuator with an ironless armature core, its theoretical analysis in terms of the driving forces that acting on the actuator, its development, the theoretical and experimental results obtained for an implemented prototype. Such planar actuator has innovative features: a stationary and ironless armature core with orthogonal planar windings and two cars magnetically coupled to each other by means of four high energy-product NdFeB permanent magnets. The stator of the actuator comprehends an ironless core with two sets of multiphase windings placed in such a way that two independent orthogonal windings form the armature in a way that allows the yielding of two orthogonal propulsion forces. Each car has a back iron which supports two permanent magnets and is supported by a suspension structure to allow bidirectional movement of the coupled cars. This type of actuator can be used in applications that require the movement in any direction over a plane. The prototype of this study was tested in order to validate their static characteristics of operation with respect to the numerical analysis and the analytical model. The values of magnetic flux density in the air gap and the planar propulsion force obtained through testing, showed a good agreement with the values obtained by numerical simulation and analytical model. The normal force tests showed good agreement with the results of the numerical analysis. The tests of planar actuator with air gaps of 12 mm and 24 mm were found to produce an average sensitivity of the planar propulsion force of 7.19 N/A and 4.13 N/A respectively.

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22

Zhang, Fangyi. "Learning real-world visuo-motor policies from simulation." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/121471/1/Fangyi%20Zhang%20Thesis.pdf.

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This thesis explores how simulation can be used to create the large amount of data required to teach a robot certain hand-eye coordination skills. It advances the state-of-the-art of deep visuo-motor policy learning by introducing a new modular architecture, a novel reinforcement learning exploration strategy, and adversarial discriminative transfer.

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23

Pant, Gaurav, I. Felician Campean, Aleksandrs Korsunovs, Daniel Neagu, and Oscar Garcia-Afonso. "Hybrid Dynamic Modelling of Engine Emissions on Multi-Physics Simulation Platform." SAE, 2020. http://hdl.handle.net/10454/18376.

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Yes
This paper introduces a hybrid dynamic modelling approach for the prediction of NOx emissions for a Diesel engine, based on a multi-physics simulation platform coupling a 1-D air path model (GT-Suite) with in-cylinder combustion model (CMCL Stochastic Reactor Model Engine Suite). The key motivation for this research was the requirement to establish a real time stochastic simulation capability for emissions predictions early in engine development, which required the replacement of the slow combustion chemistry solver (SRM) with an appropriate surrogate model. The novelty of the approach in this research is the introduction of a hybrid approach to metamodeling that combines dynamic experiments for the gas path model with a zonal optimal space-filling design of experiments (DoEs) for the combustion model. The dynamic experiments run on the virtual Diesel engine model (GT- Suite) was used to fit a dynamic model for the parameters required as input to the SRM. Optimal Latin Hypercubes (OLH) DoE run on the SRM model was used to fit a response surface model for the NOx emissions. This surrogate NOx model was then used to replace the computationally expensive SRM simulation, enabling real time simulations of transient drive cycles to be executed. The performance of the proposed approach was validated on a simulated NEDC drive cycle against experimental data collected for the engine case study, which proved the capability of methodology to capture the transient trends for the NOx emissions. The significance of this work is that it provided an efficient approach to the development of a global model with real time transient modelling capability based on the integration of dynamic and local DoE metamodeling experiments.
The full-text of this article will be released for public view at the end of the publisher embargo on 12 Aug 2021.

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24

Mo, Yamin. "Terra - An Open Digital Twin Framework for Simulation-to-Real AI Development." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25799.

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The development of artificial intelligence (AI) based robot policies such as embodied visual AI is a rapidly emerging field that promises to fully automate robot sensing and control, reducing the need for expert knowledge and information about system dynamics. The recent surge in the availability of digital simulation environments has helped to alleviate the data scarcity problem faced by AI training and yielded many tasks for embodied AI to explore. In contrast to conventional computer vision databases (e.g. ImageNet, COCO), they provide interactive environments tailored to the training of embodied AI agents (e.g. virtual robots). Despite their success, there remain several unaddressed issues. First, these environments primarily focus on in-simulation policy training and are not well suited for real-world performance evaluation. Second, current platforms do not model the dynamics of the physical environment on-the-fly, limiting their potential for the development of robot navigation policies in challenging environments. Third, the associated real-world evaluation environments are both expensive and limited to large interior scenes. This limits access to the physical environments, subsequently making sim-to-real policy evaluation difficult. Fourth, current simulations rely on third party robots for policy training and evaluation, which can be costly while limiting the robot’s customizability and optimisation for the associated task and environment. To tackle these issues, we propose a novel robot-centred smart digital twin framework called Terra. Terra leverages the power of digital twin (DT) systems (digital replicas of the physical world), commonly used for monitoring and evaluating physical systems. Terra includes a comprehensive DT representation which encodes useful real-time dynamics of both the physical world and the robot agent deployed therein. The DT is updated through a multi-view, multi-modality perception module, which obtains high-level semantics, delivering a precise description of the current status of the physical environment and the robot agent. By mapping the perceived results to the virtual replica of the physical environment, Terra actively updates the action policy and sends it back to the agent, forming an integral and real-time information feedback loop. In practice, to help demonstrate the proposed framework's effectiveness and feasibility, we deliberately set up a challenging unordered physical environment with many obstacles and a custom robot tasked with a simple navigation task. Our physical scene is inexpensive and small, while our novel low-cost robot is customised for the environment. Experiment results show that the proposed Terra framework successfully enables the robot to accomplish a simple navigation task, demonstrating its suitability for real-world robot performance evaluation.

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25

Wallace, Peter Duncan. "SMT goes ABMS : developing strategic management theory using agent-based modelling and simulation." Thesis, Durham University, 2009. http://etheses.dur.ac.uk/258/.

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For the emerging complexity theory of strategy (CTS), organizations are complex adaptive systems able to co-evolve with their dynamic environments through interaction and response, rather than purely analysis and planning. A promising approach within the CTS context, is to focus on a strategic logic of opportunity pursuit, one in which the distributed decision-makers behave audaciously despite unpredictable, unstable environments. Although there is only emergent support for it, intriguingly organizations can perform better when these decision-makers ‘throw caution to the wind’ even at their own possible expense. Since traditional research methods have had difficulty showing how this can work over time, this research adopts a complementary method, agent-based modelling and simulation (ABMS), to examine this phenomenon. The simulation model developed here, CTS-SIM, is based on quite simple constructs, but it introduces a rich and novel externally driven environment and represents individual decision-makers as having autonomous perceptions but constrainable decision-making freedom. Its primary contribution is the illumination of core dynamics and causal mechanisms in the opportunity-transitioning process. During model construction the apparently simple concept of opportunity-transitioning turns out to be complex, and the apparently complex integration of exogenous and endogenous environments with all three views of opportunity pursuit in the entrepreneurship literature, turns out to be relatively simple. Simulation outcomes using NetLogo contribute to CTS by confirming the positive effects on agent performance of opportunistic transitioning among opportunities in highly dynamic environments. The simulations also reveal tensions among some of the chosen variables and tipping points in emergent behaviours, point to areas where theoretical clarity is currently lacking, provoke some interesting questions and open up useful avenues for future research and data collection using other methods and models. Guidance through numerous stylized facts, flexible methods, careful documentation and description are all intended to inspire interest and facilitate critical discussion and ongoing scientific work.

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26

Lundstedt, Moa, and Sofie Hronek. "Förbättring av produktionsmiljö med hjälp av automation : Med Discrete Event Simulation som verktyg." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-35743.

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In order to meet the expectations of today’s market and compete in the global world we live in, many companies are facing changes. A low cost production and high quality is not enough to be competitive. Companies must also satisfy the external customers’ claims, which to a great extent imply demands on an increased productivity. It is not enough to look to the external customers. The people working within the production system are the internal customers and the production system must be designed to suit their needs. Increased productivity can be stressful for operators, especially in the automotive industry, where heavy and frequent lifting is part of the daily work. The increased competition can thus in the long run lead to consequences for operator health as a result of heavy, and frequent, lifting. Due to this, more companies are looking over the possibilities to automate parts of their production process. The purpose of this thesis is to explore, using simulation tools, how automation of heavy lifting can affect productivity and work environment in processing or manufacturing processes. The research questions that will be answered are: o In what way does automation affect productivity in processing processes? o How can simulation tools act as an aid in designing automation? o What impact does automation have on the operator’s ergonomic work environment? To answer these questions, a literature study has been conducted in three main areas: production development, automation and simulation. A case study was carried out in a processing cell within the heavy vehicle industry, which currently does not have an approved ergonomic working environment. The company wanted to implement a robot and the purpose was to investigate how ergonomics and productivity was affected. The comparison was made using a simulation created in the ExtendSim software. The purpose of the simulation was to compare the current production system with a layout where a robot was implemented in the system. From this thesis, the conclusions were drawn that automation can affect a company’s productivity in a positive way provided that the preparatory planning is carried out thoroughly. The thesis shows that a simulation tool can be helpful from a number of aspects when automation is to be designed, and not least that it can undoubtedly be positive for the operator’s ergonomic work environment to automate parts of the production that includes heavy and frequent lifting.

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27

Abelsson, Anna. "Simulering som lärande inom prehospital akutsjukvård." Doctoral thesis, Karlstads universitet, Institutionen för hälsovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-48243.

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Den prehospitala akutsjukvården är ett komplext kunskapsfält som innebär att vårdaren skall kunna bemöta patient och närstående, bedöma skada, sjukdom och den aktuella situationen samt avgöra vilka vårdåtgärder som skall prioriteras. Patientens lidande kan lindras genom att vårdaren tränar färdigheter i ett prehospitalt kontext. Detta främjar en god och säker vård samt stärker patientens möjligheter till överlevnad. Resultatet visar på behovet av simulering inom prehospital akutsjukvård. Med simulering lär sig vårdaren att hantera realistiska, dynamiska och komplexa vårdsituationer, vilket skapar kunskaper, färdigheter och erfarenheter av omhändertagande av patient drabbad av högenergitrauma. Simuleringens utformning och miljö skapar förutsättningar för lärandet vilket framkommer i interventionsstudien. Utifrån resultatet i föreliggande forskning utvecklas en modell för lärande med hjälp av simulering.
The overall aim of the research was to deepen the understanding of learning through simulation in prehospital emergency care. Method: In this research, qualitative and quantitative methods are used as well as integrative literature studies (I, II). Qualitative data from the interview studies (III, V) were analyzed by phenomenographic methodology. Quantitative data from the intervention study (IV) were analyzed using descriptive and analytical statistics. Results: Research on simulation and learning within the prehospital trauma care context is relatively rare (I). Simulation of realistic scenarios where the caregivers are exposed to stress contributes to strengthen caregiver knowledge, skills and experience (II). Caregivers request simulation opportunities regarding critical and emergency situations (III). They describe that learning through regular simulation provides in-depth knowledge and skills in the care of a patient exposed to high-energy trauma (V). Interventions with repeated simulation opportunities related to the care of the patient exposed to high-energy trauma give some improvement in care provided at the site of the accident (IV). Conclusion: Through simulation, the caregivers develop knowledge and skills and receive enhanced confidence in the care of an injured and sick patient. The research suggests several areas with potential for improvement with regard to the care of patients exposed to high-energy trauma. A model has been developed for systematic trauma simulation.

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28

Szekely, Tamas. "Stochastic modelling and simulation in cell biology." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:f9b8dbe6-d96d-414c-ac06-909cff639f8c.

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Modelling and simulation are essential to modern research in cell biology. This thesis follows a journey starting from the construction of new stochastic methods for discrete biochemical systems to using them to simulate a population of interacting haematopoietic stem cell lineages. The first part of this thesis is on discrete stochastic methods. We develop two new methods, the stochastic extrapolation framework and the Stochastic Bulirsch-Stoer methods. These are based on the Richardson extrapolation technique, which is widely used in ordinary differential equation solvers. We believed that it would also be useful in the stochastic regime, and this turned out to be true. The stochastic extrapolation framework is a scheme that admits any stochastic method with a fixed stepsize and known global error expansion. It can improve the weak order of the moments of these methods by cancelling the leading terms in the global error. Using numerical simulations, we demonstrate that this is the case up to second order, and postulate that this also follows for higher order. Our simulations show that extrapolation can greatly improve the accuracy of a numerical method. The Stochastic Bulirsch-Stoer method is another highly accurate stochastic solver. Furthermore, using numerical simulations we find that it is able to better retain its high accuracy for larger timesteps than competing methods, meaning it remains accurate even when simulation time is speeded up. This is a useful property for simulating the complex systems that researchers are often interested in today. The second part of the thesis is concerned with modelling a haematopoietic stem cell system, which consists of many interacting niche lineages. We use a vectorised tau-leap method to examine the differences between a deterministic and a stochastic model of the system, and investigate how coupling niche lineages affects the dynamics of the system at the homeostatic state as well as after a perturbation. We find that larger coupling allows the system to find the optimal steady state blood cell levels. In addition, when the perturbation is applied randomly to the entire system, larger coupling also results in smaller post-perturbation cell fluctuations compared to non-coupled cells. In brief, this thesis contains four main sets of contributions: two new high-accuracy discrete stochastic methods that have been numerically tested, an improvement that can be used with any leaping method that introduces vectorisation as well as how to use a common stepsize adapting scheme, and an investigation of the effects of coupling lineages in a heterogeneous population of haematopoietic stem cell niche lineages.

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29

Diktas, Emine Guncem. "A multi-analytical protocol combining EDXRF, SEM+EDS, μXRD and Monte Carlo simulations applied to analyse non-destructively portuguese corroded copper coins". Master's thesis, Universidade de Évora, 2018. http://hdl.handle.net/10174/24464.

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Performing quantitative analyses on archaeological and cultural heritage metallic artefacts is challenging due to their complex multi-layered internal structure. “Layers” may include a) Original metal and/or alloy substrate (gold, silver, bronze etc.) b) Surface patinas enriched in corrosion products sulphides, oxides and/or chlorides compounds c) Protective treatments applied in past conservation interventions d) Soil derived incrustations from archaeological burial environment. To obtain compositional data on the metal substrate, usually these layers have to be removed but this not always possible due to the inherent fragility of the corroded artefacts as it is the case in particular with copper objects such as coins. The setting up of a non-destructive protocol is therefore important. In this study, a protocol combining SEM-EDS, μXRD, EDXRF and Monte Carlo simulations has been tested on a series of Portuguese coins from the 12th to the 19th centuries found at Largo das Olárias and Travessa do Jordão in Lisbon. 1. Analyze non-destructively the corrosion patterns and patinas developed on the surface Portuguese Copper coins from a Lisbon archaeological site (Largo das Olarias) SEM+EDS, μXRD and portable EDXRF 2. Apply the mineralogical and chemical data obtained during the analytical sessions to run Monte Carlo simulations of EDXRF spectra 3. Assess the feasibility of the combined non-destructive protocol in obtaining a reliable quantitative estimation of the metal substrate composition without the need to remove the surface corrosion patinas; RESUMO: Realizar análises quantitativas em artefactos metálicos arqueológicos de património cultural é um desafio devido à sua estrutura interna com múltiplas camadas. Essas ‘’Camadas’’ podem incluir: a) Substrato original de metal e / ou liga (ouro, prata, bronze etc.) b) Patinas de superfície enriquecidas em produtos de corrosão compostos de sulfetos, óxidos e / ou cloretos c) Tratamentos de protecção aplicados em intervenções de conservação passadas d) Incrustações derivadas do solo do ambiente de enterro arqueológico. Para obter dados de composição sobre o substrato metálico, geralmente essas camadas devem ser removidas, porém isso nem sempre é possível devido à fragilidade inerente aos artefactos corroídos, como é o caso em particular de objectos de cobre como as moedas. A criação de um protocolo não destrutivo é, portanto, importante. Neste estudo, um protocolo que combina as simulações SEM-EDS, μXRD, EDXRF e Monte Carlo foi testado numa série de moedas portuguesas dos séculos XII ao XIX encontradas num Largo das Olárias e Travessa do Jordão em Lisboa. 1. Analisar de forma não destrutiva os padrões de corrosão e patinas desenvolvidas na superfície de moedas de cobre portuguesas de um sítio arqueológico de Lisboa SEM + EDS, μXRD e EDXRF portátil. 2. Aplicar os dados mineralógicos e químicos obtidos durante as sessões analíticas para executar simulações Monte Carlo dos espectros EDXRF. 3. Avaliar a viabilidade do protocolo não destrutivo combinado na obtenção de uma estimativa quantitativa confiável da composição do substrato metálico sem a necessidade de remover as patinas de corrosão superficial.

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Ekblom, Jonas, and John Andersson. "Value-at-Risk : Historisk simulering som konkurrenskraftig beräkningsmodell." Thesis, Linköping University, Department of Management and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12599.

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Value-at-Risk (VaR) is among financial institutions a commonly used tool for measuring market risk. Several methods to calculate VaR exists and different implementations often results in different VaR forecasts. An interesting implementation is historical simulation, and the purpose of this thesis is to examine whether historical simulation with dynamic volatility updating is useful as a model to calculate VaR and how this differs in regard to type of asset or instrument. To carry out the investigation six different models are implemented, which then are tested for statistical accuracy through Christoffersens test. We find that incorporation of volatility updating into the historical simulation method in many cases improves the model. The model also generates good results compared to other commonly used models, especially if the volatility is predicted through a GARCH(1,1) updating scheme.

Value-at-Risk (VaR) är ett bland finansiella institutioner vanligt mått för att mäta marknadsrisk. Det finns ett flertal olika sätt att beräkna VaR, vilka ofta ger olika resultat beroende på förutsättningar. Ett av dessa är historisk simulering, och syftet med denna uppsats är att undersöka huruvida historisk simulering med dynamiskt uppdaterande volatilitet är en användbar modell för beräkning av VaR och hur dess lämplighet beror på valt tillgångsslag eller instrument. För att besvara detta implementeras sex olika modeller för beräkning av VaR, vilka sedan testas med hjälp av Christoffersens test. Vi finner att inkorporering av dynamisk volatilitet i historisk simulering i många fall medför en förbättring av modellen ifråga om statistisk riktighet. Vidare kan historisk simulering med dynamiskt uppdaterande volatilitet anses vara konkurrenskraftig i jämförelse med andra vanligt använda modeller, framförallt då volatiliteten skattas genom GARCH(1,1).

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Rajasimha, Harsha Karur. "Insights Into Mitochondrial Genetic and Morphologic Dynamics Gained by Stochastic Simulation." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29961.

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MtDNA mutations in mammalian cells are implicated in cellular ageing and encephalomyopathies, although mechanisms involved are not completely understood. The mitochondrial genetic bottleneck has puzzled biologists for a long time. Approximate models of genetic bottleneck proposed in the literature do not accurately model underlying biology. Recent studies indicate mitochondrial morphology changes during cellular aging in culture. In particular, the rates of mitochondrial fission and fusion are shown to be in tight balance, though this rate decreases with age. Some proteins involved in mitochondrial morphology maintenance are implicated in apoptosis. Hence, mitochondrial genetic and morphologic dynamics are critical to the life and death of cells. By working closely with experimental collaborators and by utilizing data derived from literature, we have developed stochastic simulation models of mitochondrial genetic and morphologic dynamics. Hypotheses from the mitochondrial genetic dynamics model include: (1) the decay of mtDNA heteroplasmy in blood is exponential and not linear as reported in literature. (2) Blood heteroplasmy measurements are a good proxy for the blood stem cell heteroplasmy. (3) By analyzing our simulation results in tandem with published longitudinal clinical data, we propose for the first time, a way to correct for the patient's age in the analysis of heteroplasmy data. (4) We develop a direct model of the genetic bottleneck process during mouse embryogenesis. (5) Partitioning of mtDNA into daughter cells during blastocyst formation and relaxed replication of mtDNA during the exponential growth phase of primordial germ cells leads to the variation in heteroplasmy inherited by offspring from the same mother. (6) We develop a “simulation control” for experimental studies on mtDNA heteroplasmy variation in cell cultures. Hypothesis from the mitochondrial morphologic dynamics model: (7) A cell adjusts the mitochondrial fusion rate to compensate for the fluctuations in the fission rate, but not vice versa. A deterministic model for this control is proposed. Contributions: extensible simulation models of mitochondrial genetic and morphologic dynamics to aide in the powerful analysis of published and new experimental data. Our results have direct relevance to cell biology and clinical diagnosis. The work also illustrates scientific success by tight integration of theory with practice.
Ph. D.

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Sarabian, Mohammad. "Experimental Investigations and Direct Numerical Simulations of Rigid Particles in ShearFlows of Newtonian and Complex Fluids." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1582821437191013.

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Magnusson, Anton. "Hardware-In-the-Loop simulation of a small scale prototype of a Wave Energy Converter." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-20698.

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Renewable energy sources are a hot topic, both when it comes to climate change and the constant increase in demand of electricity due to population growth and a more electrified society. One such energy source is wave energy - an energy source with great potential but still relatively new with the need for further development. Blekinge Institute of Technology (BTH) together with Ocean Harvesting Technologies (OHT) have made a collaboration to build a scaled Hardware-In-the-Loop (HIL) system of a power take-off (PTO) based on OHTs wave energy converter, InfinityWEC. The purpose is to teach the students at BTH about hydrodynamic and HIL simulations. A manual will also be written to help students perform the lab activities. A model of the HIL system will first be implemented in Matlab/Simulink, both with and without the WEC-Sim hydrodynamic simulation toolbox and simulations will be run to predict the system's behaviour. To parametrize the hydrodynamic model, the open-source Boundary Element Method (BEM) code, NEMOH, is used. The HIL system consists of electric motors, connected mechanically to each other with a coupling. One of the motors is the actuator, which applies torque to the second motor according to the simulated hydrodynamic loads on the buoy. The second motor on the other hand applies a torque according to the load connected to it or torque-controlled according to a selected control strategy. In this thesis two different types of loading is used: 1) resistive load without control of the generator drive, 2) resistive and capacitive load with reactive control of the generator drive. The load resistance can be changed within a limited range as well as the sea state. Data that can be collected are the position and angular velocity of the motors, the currents to and from the two motors and the voltage over the load capacitance. The project concluded that the compensation needed for the motors to get the true hydrodynamic force has little effect when using reactive control and that a protective capacitor is be needed between the actuator motor and the power supply to protect it from reverse current. Finally, this work demonstrated the effectiveness of HIL systems to execute simulations to test and validate PTO systems in wave energy converters. The advantages are that one can create representative wave loading without the presence of water and with ease test different sea states.
Förnybara energikällor är ett hett ämne, både när det gäller klimatförändringar och den ständiga ökningen av efterfrågan av el på grund av befolkningsökning och ett mer elektrifierat samhälle. En sådan energikälla är vågenergi - en energikälla med stor potential men fortfarande relativt ny med behov av vidareutveckling. Blekinge Tekniska Högskola (BTH) vill tillsammans med Ocean Harvesting Technologies (OHT) konstruera ett skalat Hardware-In-The-Loop (HIL) system av power take-off (PTO) baserat på OHT:s vågenergiomvandlare, InfinityWEC. Syftet är att lära eleverna på BTH om hydrodynamik och HIL-simuleringar. En manual kommer också att skrivas för att hjälpa eleverna att utföra labbaktiviteterna. En modell av HIL-systemet kommer först att konstrueras i Matlab/Simulink, både med och utan WEC-Sim hydrodynamisk simuleringsverktygslåda och simuleringar kommer att köras för att förutsäga systemens beteende. För att bestämma de nödvändiga parametrarna för hydrodynamiska modellen används Boundary Element Method koden NEMOH. HIL-systemet består av elmotorer, som är mekaniskt anslutna till varandra med en koppling. En av motorerna är ställdonet, som tillämpar vridmoment på den andra motorn enligt de simulerade hydrodynamiska belastningarna på bojen. Den andra motorn tillämpar ett vridmoment enligt belastningen som är kopplad till den eller är moment reglerad enligt en vald kontrollstrategi. I denna avhandling används två olika typ av belastning: 1) resistiv belastning utan kontroll av generatorndrivdonet, 2) resistiv och kapacitive belastning med reaktiv kontroll av generatorndrivdonet. Belastningsmotståndet kan ändras inom ett visst intervall och lika så havstillståndet. Data som kan samlas in är motorernas position och vinkelhastighet, strömmen till och från de två motorerna och spänningen över last kapasitatorn. I projektet drogs slutsatsen att den kompensation som behövs för motorerna för att få den riktiga hydrodynamiska kraften har liten påverkan reaktiv kontroll används och att det behövs en skyddande kondensator mellan ställdonsmotorn och strömförsörjningen för att skydda den mot bakström. Slutligen visade detta arbete hur effektiva HIL-system är för att utföra simuleringar för att testa och validera PTO-system i vågenergiomvandlare. Fördelarna är att man kan skapa representativ vågbelastning utan närvaro av vatten och med lätthet testa olika havstillstånd.

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Kolozsvari, Nicoleta. "Sim one, do one, teach one: considerations in designing training curricula for surgical simulation." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103718.

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Background: Although there is value in the use of simulation for the acquisition of fundamental surgical skills through goal-directed practice in a safe environment, there is little evidence guiding educators on how to best implement simulation within surgical skills curricula. This thesis reviews the application of the expert-performance model in surgery and the role of simulation in surgical skills acquisition. The focus is on implementation of deliberate practice, highlighting the principles of proficiency-based training, part-task training and overtraining. In a randomized controlled trial, we investigated the impact of part-task training by examining whether practicing a basic laparoscopic simulator task (peg transfer, PT) facilitates learning of a more complex skill (intracorporeal suture, ICS). We examined overtraining by comparing ICS learning and PT retention in subjects that had standard PT training (passing proficiency) to subjects who overtrained on PT (expert proficiency). Methods: Surgically naïve subjects were randomized to one of three PT training groups: control, standard training, and overtraining. All participants then trained in ICS. The learning curves for ICS were analyzed by estimating the learning plateau and rate using nonlinear regression. Skill retention was assessed by retesting participants one month after training. Results: Part-task training: ICS learning plateau rose with increasing PT training and there was a trend toward higher initial ICS scores and faster learning rates with increasing PT training. Overtraining: At retention, there were no differences in PT scores. Overtrained participants saved time in learning ICS compared to controls, but PT overtraining took longer than the time saved on ICS training. Conclusion: In surgically naïve subjects, part-task training with peg transfer alone was associated with slight improvements in the learning curve for intracorporeal suturing. However, overtraining with peg transfer did not improve skill retention and peg training alone was not an efficient strategy for learning intracorporeal suturing.
Contexte: Bien qu'il y ait un intérêt à utiliser la simulation pour développer des aptitudes fondamentales en chirurgie, par la pratique ciblée réalisée dans un environnement sécuritaire, il n'y a toutefois que peu de consignes indiquant aux éducateurs comment intégrer adéquatement la simulation dans les programmes d'acquisition de compétences chirurgicales. Cette thèse analyse l'application du modèle de performance d'expert en chirurgie ainsi que le rôle de simulation dans l'acquisition de compétences chirurgicales. Ce document est centré sur la mise en place de la pratique délibérée en mettant l'accent sur les principes d'entrainement basé sur des compétences, l'entrainement à l'exécution de tâches partielles et le surentraînement. Dans une étude aléatoire contrôlée, nous avons étudié ces principes pour déterminer 1) si pratiquer une tâche psychomotrice de base (le transfert sur planche à chevilles, TPC) sur un simulateur FLS facilite l'acquisition de compétences plus complexes (la suture intracorporelle, SIC) et 2) nous avons comparé l'impact, sur la rétention de TPC et de l'apprentissage de SIC, de l'entrainement à un niveau d'expert et de l'entraînement à un niveau de passage. Méthodes: Des novices en chirurgie ont été aléatoirement distribués dans trois groupes d'entraînement : un groupe contrôle, un groupe d'entraînement standard et un groupe de surentraînement. Tous les participants se sont alors entraînés à réaliser des SIC. Les courbes d'apprentissage pour les SIC ont été analysées par régression non linéaire, pour estimer le plateau et les taux d'apprentissage. La rétention de compétences a été déterminée en réévaluant des participants un mois après l'entraînement. Résultats: Le plateau d'apprentissage des SIC a monté avec l'augmentation de l'entrainement au TPC. Aussi, il y a eu une tendance croissante des scores initiaux des SIC et les taux d'apprentissage ont été plus rapides avec l'augmentation de l'entraînement au TPC. Pour la rétention, il n'y a eu aucune différence entre les scores de TPC. De plus, quoique les participants surentraînés au TPC ont nécessité moins de temps pour l'entrainement des SIC comparativement au groupe de contrôle, le surentraînement au TPC a pris plus de temps que le temps qu'il n'en a gagné lors de l'entraînement aux SIC. Conclusion: Chez les novices en chirurgie, lorsque réalisé seul, l'entrainement au transfert sur planche à cheville, pour la réalisation de tâches partielles, a été associé à une faible élévation de la courbe d'apprentissage pour les sutures intracorporelles. Toutefois, le surentraînement au transfert sur planche à cheville n'a pas amélioré la rétention de compétence. Enfin, l'entrainement sur planche à cheville seul ne s'est avéré être une stratégie efficace pour apprendre à réaliser des sutures intracorporelles.

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Johnson, Michael S. "Advancements in the Solid-state Impact-ionization Multiplier (SIM) Through Theory, Simulation and Design." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2636.

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This dissertation outlines the study and development of a Solid-state Impact-ionization Multiplier (SIM). The SIM is a stand-alone current amplifier designed with optical detection systems in mind. The SIM amplifies signals utilizing impact ionization as a source of gain. The SIM is fabricated on silicon in order to take advantage of its favorable impact ionization coefficients. Utilizing silicon in impact ionization based gain devices makes low noise and high gains attainable. Because it is a stand-alone device, it can be wired to an arbitrary current source making it capable of receiving an input from photodiodes of any material. This makes it possible to amplify a signal from a photodiode that has been optimized for a given wavelength. In this way, the SIM attempts to separate the absorption and multiplication portions in modern day optical detection/amplification devices such as in Avalanche Photodiodes (APDs). This flexibility allows it to be utilized in many different systems. The SIM has gone through several iterations in the last few years. Each change has been with the purpose of increasing gain, frequency response or yield. The progression of the device has come at the hand of much thought, theory, simulation, fabrication, and testing. One of the challenges encountered in its development has been gain controllability due to poor carrier confinement and premature breakdown. Increased gain control was developed through simulation and fabrication of a confining oxide layer. Yield and difficulties in consistent fabrication were also addressed by altering the input metallization and doping processes. The frequency response of the device has been the largest challenge in device development. Issues such as space charge, floating node voltage, edge effects and low signal amplification have caused limitations. Successes and attempts at overcoming these, and other, challenges is the basis of this dissertation of work.

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Євсєєв, В. В., Н. П. Демська та Ю. М. Олександров. "Моделювання виробничої лінії SMT-монтажу в кібер-фізичних виробничих системах". Thesis, Кременчуцький національний університет імені Михайла Остроградського, 2022. https://openarchive.nure.ua/handle/document/20422.

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Industry 4.0 визначає бачення і принципи функціонування Smart Manufacturing. Таке підприємство використовує модульну структуру, кібер-фізичні системи контролюють фізичні та інформаційні процеси, створюючи своєрідну віртуальну копію реального світу, де приймають децентралізовані рішення. За допомогою Internet of Things (IoT) кібер-фізичні системи з'єднуються і взаємодіють одна з однією та людьми в реальному часі.

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Krepkin, Konstantin. "The Role of Cooperation in Pre-tumor Progression: A Cellular Population Dynamics Model." Yale University, 2010. http://ymtdl.med.yale.edu/theses/available/etd-03042010-195339/.

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Competition among cells has long been recognized as an important part of the evolutionary process of tissue leading up to the development of cancer. However, the role of cellular cooperation in cancer has been largely ignored. In this work, we investigated the role of cooperation in early tumor progression using a mathematical and agent-based modeling approach. We hoped to learn whether cooperation between cells in spatially organized tissue has a significant role in hastening tumor development, and to uncover general principles governing such cooperation. We focused on the early stages of tumor development given the critical importance of this time period and since we hypothesized that cooperation will have its greatest influence during these early phases. In our model, stem cells were placed into an array of 50 x 20 cell patches, with each patch carrying a maximum of 64 cells. The stem cells' potential to replicate or leave the stem cell compartment through apoptosis or differentiation were governed by modified versions of the Lotka-Volterra equation of ecology. The cells could also acquire mutations in two oncogenes and three tumor suppressor genes. We explored two different cooperation strategies, one in which a cell could acquire the ability to send a cooperative signal that improved the fitness of its immediate neighbors, and one in which a cell could acquire the ability to take advantage of a cooperative signal already in the environment. Cooperation could be acquired through mutation or assigned in advance. We ran simulations of the model in MATLAB. We found that cooperation is a very robust property. Once a small number of cooperative cells is introduced into a cell population, they rapidly proliferate to the point of being the major constituent of the cell population. Cooperation leads to an increased growth rate of the aggregate cell population, with the growth rate rising in parallel with the cooperative cell fraction. Interestingly, cooperation does not seem to have an effect on cell heterogeneity, counter to what we initially suspected. We also found that cooperative cells have a wider spatial influence than non-cooperating cells. The cooperative cells or their descendant are, on average, present in more patches than corresponding non-cooperative cells at each point in time. Further analysis showed that cooperation is particularly important in the very early pre-tumor stage, when tissue is morphologically and histologically normal, and during times of extensive cell death, such as when tissue experiences necrosis, repeated bouts of inflammation, or cancer treatment. In conclusion, we found that cooperation may play an important role in early tumor progression that is complementary to the competitive interactions among cells that are driven by mutations in tumor suppressors and oncogenes. Cooperation may also be a critical force during later stages of tumor progression when there is significant cell turnover. Our results have implications for cancer prevention and tumor therapeutic strategies.

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Blanc, Guylaine. "Selection assistee par marqueurs (sam) dans un dispositif multiparental connecte - application au maÏs et approche par simulations." Phd thesis, INAPG (AgroParisTech), 2006. http://pastel.archives-ouvertes.fr/pastel-00003478.

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L'avènement des marqueurs moléculaires dans les années 80 a ouvert de nouvelles perspectives pour l'identification de locus impliqués dans la variation de caractères quantitatifs (QTL). De nombreuses études, notamment théoriques, ont montré que l'utilisation en sélection des marqueurs associés aux QTL (la Sélection Assistée par Marqueurs, SAM) pourrait permettre un gain d'efficacité par rapport à la sélection conventionnelle. En génétique végétale, la plupart des expériences de détection de QTL sont réalisées dans des populations issues du croisement entre deux lignées pures. Ainsi, beaucoup de moyens se retrouvent concentrés sur une base génétique étroite. Pourtant la probabilité de détecter des QTL est plus importante dans des populations avec une base génétique large, impliquant plus de deux parents car la diversité génétique est plus importante. Dans un contexte multiparental, le cas des populations multiparentales connectées, c'est-à-dire issues de croisements ayant un des parents en commun, présente un intérêt majeur puisque les connexions entre populations permettent pour un effectif global donné d'augmenter la puissance de détection des QTL, de comparer pour chaque QTL l'intérêt relatif de plusieurs allèles, et d'étudier leurs éventuelles interactions avec le fonds génétique. En termes de SAM, on peut penser que les marqueurs seront particulièrement intéressants dans un tel contexte pour diriger les croisements entre individus, afin de contrôler les recombinaisons entre les différents génomes parentaux et d'aider à la sélection d'individus qui cumulent les allèles favorables provenant des différents parents de départ. Aussi l'objectif de ce programme est-il de valider l'intérêt d'un schéma de SAM dans un dispositif multiparental connecté. Un croisement diallèle entre quatre lignées de maïs a permis de générer 6 populations de 150 plantes F2 chacune. La détection de QTL sur ce dispositif de 900 individus a été réalisée pour différents caractères grâce à MCQTL qui permet de prendre en compte les connexions entre populations. La comparaison des QTL détectés population par population et ceux détectés sur le dispositif complet en prenant en compte les connexions ou non, montre que l'analyse globale du dispositif en prenant en compte les connexions entre populations permet un gain de puissance substantiel et conduit à une meilleure précision de la localisation des QTL. A partir de ces résultats nous avons mis en place trois cycles de sélection sur marqueurs dans deux schémas présentant des objectifs distincts : i. obtenir un matériel plus précoce, pour le premier ii. augmenter le rendement tout en conservant une humidité des grains constante à la récolte pour le second. Pour pouvoir suivre la transmission des allèles parentaux aux QTL au cours des générations, un programme de calcul de probabilités d'identité par descendance adapté au dispositif à été développé. L'évaluation expérimentale du progrès génétique nous a permis de mettre en évidence, après 3 cycles de sélection, un gain significatif de précocité de 3 jours pour le schéma floraison et un gain significatif de 3.2 quintaux de rendement pour le schéma rendement. Parallèlement, nous avons comparé par simulation différents schémas de sélection, en nous basant sur le dispositif expérimental mis en place (nombre et effet des QTL, h²

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Blanc, Guylaine. "Sélection assistée par marqueurs (SAM) dans un dispositif multiparental connecté : application au maïs et approche par simulations." Paris, Institut national d'agronomie de Paris Grignon, 2006. http://www.theses.fr/2006INAP0039.

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40

Coulston, John Wesley. "SIMULATING FOREST STANDS BY RESAMPLING ONE-ACRE STEM MAPS: SPATIAL CHARACTERISTICS OF RESULTS." NCSU, 1999. http://www.lib.ncsu.edu/theses/available/etd-19990323-181716.

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The purpose of this research is to generate forest stands for sampling simulations on anoperational level. In this research, a simulated forest stand consists of x and y coordinates ofstems and their attributes. One-acre stem maps are mapped stem locations and attributes from thefield. The simulation procedure is a two step process. The first step is to create discrete samplesfrom a one-acre stem map. Secondly, the discrete samples are selected randomly withreplacement and placed adjacently until a simulated forest stand of desired size and shape is built. The simulated forest stands are then compared with the one-acre stem map from which they werecreated by their respective average clump size, spatial point pattern, and spatial variability of stemdiameter. Average clump size is estimated using stem counts from grids of contiguous quadrats(Greig-Smith, 1952). Spatial point pattern is classified based on the mean and variance of first,second, third, and fourth nearest neighbor distances (Smith, 1977). The spatial variability of stemdiameter is assessed using the robust semi-variogram estimator (Cressie et al., 1980) The abilityof the simulation procedure to reproduce the above mentioned spatial characteristics is related tothe second order stationarity of stem diameter in the one-acre stem map. In this case, secondorder stationarity is the premise that the mean stem diameter is constant in the one-acre stem mapand the variance is only dependant on stem separation distance. Stem locations, the speciespercentages, and the coefficient of variation of stem diameter should be assessed to determine theapplicability of this simulation procedure for a particular one-acre stem map.

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Mohamood, Fayez. "DLL-Conscious Instruction Fetch Optimization for SMT Processors." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10560.

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Simultaneous multithreading (SMT) processors can issue multiple instructions from distinct processes or threads in the same cycle. This technique effectively increases the overall throughput by keeping the pipeline resources more occupied at the potential expense of reducing single thread performance due to resource sharing. In the software domain, an increasing number of Dynamically Linked Libraries (DLL) are used by applications and operating systems, providing better flexibility and modularity, and enabling code sharing. It is observed that a significant amount of execution time in software today is spent in executing standard DLL instructions, that are shared among multiple threads or processes. However, for an SMT processor with a virtually-indexed based cache implementation, existing instruction fetching mechanisms can induce unnecessary false cache misses caused by the DLL-based instructions, which were intended to be shared. This problem is more conspicuous when multiple independent threads are executing concurrently in an SMT processor. This work investigates an often-neglected form of contention between running threads in the I-TLB and I-cache caused by DLLs. To address these shortcomings, we propose a system level technique involving a light-weight modification in the microarchitecture and the OS. By exploiting the nature of the DLLs in our new architecture, we are able to reinstate physical sharing of the DLLs in an SMT machine. Using Microsoft Windows based applications, our simulation results show that the optimized instruction fetching mechanism can reduce the number of DLL misses up to 5.5 times and improve the instruction cache hit rates by up to 62%, resulting in upto 30% DLL IPC improvements and upto 15% overall IPC improvements.

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42

Saro, Alexandro. "Galactic population in cosmological hierarchical models." Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3066.

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2007/2008
Il lavoro di ricerca è stato orientato allo studio delle proprietà delle strutture su grande scala dell'Universo. In particolar modo si sono studiate le proprietà ottiche e fisiche di popolazioni sintetiche di galassie in ammassi di galassie in ambito cosmologico all'interno dello scenario gerarchico. Abbiamo affrontato il problema della formazione galattica seguendo due approcci complementari. Una linea di ricerca svolta è stata indirizzata allo studio della popolazione galattica in ammassi di galassie, utilizzando simulazioni idrodinamiche cosmologiche. A tale scopo si sono analizzate simulazioni realizzate con il codice Tree+SPH GADGET2 (Springel 2005) che include processi fisici quali cooling, formazione stellare ed un trattamento dettagliato dei processi di arricchimento chimico associato ai processi di nucleosintesi stellare (Tornatore et al. 2007). Dall'analisi comparata delle osservazioni tra le proprietà ottiche e fisiche di galassie in ammasso ed i risultati di codici spettro-fotometrici applicati alle simulazioni realizzate, è possibile trarre importanti informazioni sulla formazione e sull'evoluzione della componenente barionica tutta ed in particolar modo della popolazione galattica. In particolar modo sono state confrontate le proprietà fisiche e luminosità ottiche e infrarosse delle osservazioni con quelle delle galassie predette dai modelli numerici identificate tramite l'utilizzo di software specifici per il riconoscimento di sottostrutture gravitazionalmente legate (Saro et al. 2006). Sempre nell'ambito di questa linea di ricerca abbiamo studiato i processi coinvolti nella formazione delle galassie centrali d'ammasso ad alto redshift () (Saro et al. 2009), comparando le predizioni numeriche con le più recenti osservazioni ottenute tramite telescopi spaziali (Miley et al. 2006, Hatch et al. 2007), includendo in maniera autoconsistente nel calcolo delle luminosità l'assorbimento da polvere, la quale gioca un ruolo cruciale in regioni ad alto tasso di formazione stellare. Altro aspetto dell'attività di ricerca è stato rivolto allo studio ed al confronto delle predizioni delle proprietà della popolazione galattica in ammassi di galassie attraverso due diversi metodi d’indagine: simulazioni idrodinamiche cosmologiche dirette e modelli semianalitici (SAM), nei quali la popolazione galattica è invece riprodotta tramite apposite ”ricette” a partire dall’analisi dei “merging trees” degli aloni di materia oscura (p.es. De Lucia et al. 2006). Tali metodi presentano vantaggi e svantaggi complementari. Se da un lato infatti le simulazioni dirette permettono uno studio più accurato della dinamica e di seguire in dettaglio la fisica al prezzo però di enormi costi computazionali, dall'altro i modelli semianalitici permettono uno studio dello spazio dei parametri ed una statistica irragiungibile tramite le sole simulazioni. Parte di tale ricerca è stata svolta anche presso il Max Planck Institute for Astrophysics (MPA) di Garching (Monaco) in Germania in collaborazione con Klaus Dolag e Gabriella de Lucia grazie ad una borsa europea EARA - Marie Curie della durata di tre mesi, successivamente estesa per ulteriori due mesi. Lo scopo di quest’indagine si sviluppa su due fronti: confrontare le predizioni dei modelli semianalitici basati su merger trees di simulazioni con fisica diversa e confrontare le predizioni dei modelli semianalitici con quelle che si ottengono direttamente dalle simulazioni. Da un lato, infatti, confrontando le predizioni del modello semianalitico basato su merger trees di simulazioni di sola Dark Matter con le predizioni dello stesso modello semianalitico basato però su merger trees di simulazioni di Dark Matter e Gas, possiamo quantificare e valutare quanto considerare o trascurare processi fisici quali la pressione d'ariete modifichi l'evoluzione e la dinamica della popolazione galattica (Saro et al. 2008). Dall'altro, il confronto tra la popolazione galattica predetta direttamente da simulazioni idrodinamiche cosmologiche e quella predetta dai modelli semianalitici basati sugli stessi merger trees, permette di capire meglio i limiti e le differenze tra queste due tecniche nello studio della formazione di galassie in ambito cosmologico. In particolare tale confronto è stato effettuato con una fisica “semplificata” per poter quantificare l'importanza delle singole assunzioni. Nella fattispecie abbiamo considerato solo cooling e star formation, ed abbiamo trascurato processi fisici quali l'arrichimento chimico e il feedback. In questo modo sono state messe in luce le differenti trattazioni del cooling, della formazione stellare e degli effetti mareali nella creazione di una popolazione stellare intracluster (Saro et al. 2009, in prep).
XXI Ciclo
1980

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43

Agouzoul, Asmaâ. "Nouvelles méthodes numériques pour la simulation de l’impression 3D métallique." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0004.

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Le procédé SLM offre de nouvelles perspectives en termes de conception de pièces. Cependant, les phénomènes thermo-mécaniques liés au procédé sont responsables des contraintes résiduelles et de la distorsion de la pièce fabriquée. La simulation numérique est un outil intéressant pour mieux cerner les phénomènes physiques à l’œuvre et leur impact sur la qualité de la pièce. Dans cette thèse, nous proposons différentes approches qui permettent de réaliser les simulations à moindre coût, en utilisant des algorithmes de réduction de modèles. Les résultats sont comparés à ceux obtenus par la méthode des éléments finis. Une méthode inverse d’identification rapide de la contrainte inhérente à partir d'abaques numériques est proposée. L'approche Proper Generalised Décomposition (PGD) est utilisée pour la construction de cet abaque. Nous explorons aussi les avantages qu'offre une implémentation de la PGD sur GPU
Selective Laser Melting offers new perspectives in terms of part design and simplification of complex assemblies. However, severe thermo-mechanical conditions arise and are responsible for local plastic deformation, residual stresses and distortion of the manufactured component. Numerical simulation is an interesting tool for process understanding the physical phenomena and their impact on the quality of the part. In this thesis, we propose different approaches to perform simulations at a lower cost, by using model reduction algorithms. The results are compared with those obtained by the finite element method. A reverse analysis in order to identify the inherent strain responsible for the measured elastic springback makes possible to build offline numerical abacus. Therefore, we use a multi-parametric reduced order model using the so called Proper Generalised Decomposition (PGD) to construct this abacus. We also explore the benefits of an implementation of PGD on GPU

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44

Vincent, Timothy John. "Computational Modeling and Simulation of Thermal-Fluid Flow and Topology Formation in Laser Metal Additive Manufacturing." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1512398718245784.

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45

Prill, Torben. "Caractérisation et modélisation de structures carbonées nanoporeuses." Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0073/document.

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L'objectif de la thèse présentée ici est l'optimisation de matériaux carbonésnanoporeux au moyen de la “conception de matériaux virtuels”. En ce qui concerne cette échelle de travail (~ 10nm), la Nanotomographie FIB-SEM est la seule technique d'imagerie donnant accès à une information sur la géométrie tridimensionnelle. Cependant, pour l'optimisation du comportement, l'espace des pores doit être reconstruit à partir des données tirées des images obtenues. Jusqu'à présent ce problème n'était pas résolu. Pour pouvoir le maîtriser, on a développé une simulation d'images FIB-SEM. Les images FIB-SEM simulées peuvent être utilisées pour la vérification et la validation des algorithmes de segmentation. En utilisant les données d'image simulées, un nouvel algorithme pour la reconstruction de l'espace des pores à partir des données FIB-SEM a été développé.Deux études de cas avec des carbones nanoporeux utilisés pour le stockage d'énergie sont présentées, en utilisant les nouvelles techniques pour la caractérisation et l'optimisation des électrodes Li-ion de type EDLC'S (« electric double-layer capacitors », soit supercondensateurs). L'espace des pores reconstruit est modélisé géométriquement à l'aide de la géométrie stochastique. Enfin, on a simulé les propriétés électriques des matériaux enutilisant des structures modélisées et simulées
The aim of the work presented here is to optimize nanoporous carbon materials by means of 'virtual material design'. On this length scale (~ 10nm) Focused Ion Beam – Scanning Electron Microscopy Nanotomography (FIB-SEM) is the only imaging technique providing three dimensional geometric information. Yet, for the optimization, the pore space of the materials must be reconstructed from the resulting image data, which was a generally unsolved problem so far.To overcome this problem, a simulation method for FIB-SEM images was developed. The resulting synthetic FIB-SEM images could then be used to test and validate segmentation algorithms. Using simulated image data, a new algorithm for the morphological segmentation of the highly porous structures from FIB-SEM data was developed, enabling the reconstruction of the three dimensional pore space from FIB-SEM images.Two case studies with nanoporous carbons used for energy storage are presented, using the new techniques for the characterization and optimization of electrodes of Li-ion batteries and electric double layer capacitors (EDLC's), respectively. The reconstructed pore space is modeled geometrically by means of stochastic geometry. Finally, the electrical properties of the materials were simulated using both imaged real and modeled structures

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46

Alipčenkov, Timur. "Řízení dodavatelských řetězců a jejich optimalizace." Master's thesis, Vysoká škola ekonomická v Praze, 2007. http://www.nusl.cz/ntk/nusl-12411.

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Dissertation work comes with a summary of logistics evolution in the sphere of Supply Chain Management and focuses readers attention on the processes inside of supply chain. However dissertaion work is not just a huge methodological part, it also comes with an optimization part. Reader meets imaginary company trying to optimize a part of its distribution process by using modification of distribution technology "Hub and Spoke". Optimization computational procedure also consist of Traveller Salesman Problem (TSP). Fictional data for three days of testing where prepared by using MS Excel function of random numbers. For longer testing period dissertation work uses simulation technology represented by SIMPROCESS software.

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47

Dusselier, Hallie E. "Understanding 20th Century Antarctic Pressure Variability and Change in Multiple Climate Model Simulations." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1469189473.

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48

Nosek, Jakub. "Analýza teplotního chování procesu aditivní výroby mikro-prutových struktur z materiálu AlSi10Mg." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443192.

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Using Additive manufacturing it is possible to manufacture complicated components, that cannot be manufactured using conventional methods. The typical example is the lattice structure. Fabrication of these structures is complicated, and it is different from the fabrication of bulk parts. Using numerical simulation which can reflect process parameters it is possible to analyze the thermal behaviour of vertical and inclined struts fabrication. Results show that the diameter of struts influences weld track width. This influence is caused by preheating the powder material by previous scanning paths. The final geometry of inclined struts is made in more scanning layers. In this work influence of the start and endpoint of trajectory is described.

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49

Jirsák, Petr. "Informační podpora manažerského rozhodování v logistice (SCM) - simulace." Doctoral thesis, Vysoká škola ekonomická v Praze, 2009. http://www.nusl.cz/ntk/nusl-72788.

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The thesis is focused on SCM and information support for supply chain managers with emphasis on modelling and simulation. The first main aim of the work is to verify the method for applicability in SCM problem solution. The second main aim is to analyse supply chains by means of modelling and simulation and find the most suitable supply chains for the area of The New economics. The third main aim is to analyse behaviour of supply chains under changing factors on which the supply chains are initially modelled. The output of this work is applicable in the theory, practice and education

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50

Monavari, Benyamin. "SHM-based structural deterioration assessment." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/132660/1/Benyamin%20Monavari%20Thesis.pdf.

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This research has successfully developed an effective methodology to detect and locate deterioration as well as estimate its severity in the presence of environmental and operational (E&O) variations and high level of measurement noise. It developed a novel data normalization procedure to diminish the E&O variations and high level of noise content; and developed thirteen time-series based deterioration indicators to detect deterioration. The proposed methods were verified utilising measured data from different numerically simulated case studies and laboratory tests, and their efficiency is demonstrated using data acquired from a real-world instrumented building.

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