Teses / dissertações sobre o tema "DIM method"
Siga este link para ver outros tipos de publicações sobre o tema: DIM method.
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "DIM method".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
1
Helvacı, Deniz Keskin Mustafa Erol. "Dim barajının dinamik analizi /". Isparta : SDÜ Fen Bilimleri Enstitüsü, 2009. http://tez.sdu.edu.tr/Tezler/TF01235.pdf.
Texto completo da fonte
2
Gomez, Arturo, e Gema Rueda. "DIM : A systematic and lightweight method for identifying dependencies between requirements". Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3280.
Texto completo da fonteResumo:
Dependencies between requirements are a crucial factor for any software development since they impact many project areas. Nevertheless, their identification remains a challenge. Some methods have been proposed but none of them are really applicable to real projects due to their high cost or low accuracy. DIM is a lightweight method for identifying dependencies proposed on a previous paper. This paper presents an experiment comparing the sets of dependencies found by DIM and a method based on pair-wise comparison. The experiment was executed using a requirement specification for an open source project. These requirements were extracted by reverse engineering. Our results have provided evidence confirming that DIM finds more dependencies and its results (the dependencies identified) do not depend on the profile of the practitioner applying it. Another important result is that DIM requires fewer resources when applied, since it does not rely on pair-wise comparisons and it can be easily automated.Avda. Espana 101 P6 Bj-E 28341, Madrid, Spain. Telephone number: +34627770492
3
Tenanguena, Nongni Fresnelle. "Modélisation de la formation des ions moléculaires dans les plasmas froids de gaz rares". Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSES080.
Texto completo da fonteResumo:
Les ions moléculaires, en particulier les ions dimères de gaz rares, ont une influence très importante sur le comportement des plasmas de gaz rares utilisés dans de nombreux domaines. Par conséquent, l'analyse et la compréhension de leur formation sont d'une grande importance pour la modélisation macroscopique de ces plasmas. L'objectif principal de ce travail est de calculer les constantes de réaction de formation des dimères dans les plasmas froids utilisant des gaz rares comme porteurs sur une large gamme de champs électriques réduits. Pour ce faire, nous avons utilisé des données mésoscopiques (sections efficaces) obtenues à partir de données microscopiques (potentiels d'interaction) pour l'argon afin de fournir des constantes de réaction pour la formation d'Ar_2^+. En outre, pour effectuer nos calculs, nous avons pris en compte les six états électroniques des ions Ar_2^+. Ces six états électroniques sont classés dans deux états de structure fine de l'ion atomique, l'état fondamental (_ ^2)P_(3/2) et l'état excité (_ ^2)P_(1/2). Une approche de trajectoire quasi-classique basée sur l'approche dynamique nonadiabatique du champ moyen et le modèle Diatomics In Molecules (DIM) des interactions des collisions complexes utilisés dans les études précédentes pour calculer les sections efficaces de collision ont été utilisés dans le présent travail. Ces sections efficaces de collision alimenteront un code Monte Carlo adapté et optimisé pour le calcul de données auxiliaires telles que les distributions d'énergie de collision qui sont importantes pour fournir des constantes de réactions de recombinaison ternaire thermiques moyennées des états fondamental et excité de l'ion dimère. Les constantes de réaction de recombinaison ternaire ainsi calculées sont comparées aux mesures expérimentales et théoriques disponibles dans la littérature. Les résultats que nous avons obtenus sont proches de ces valeurs expérimentales et théoriques pour des valeurs sélectionnées de champs électriques réduits, E/N = 1, 50 et 100 Td, dans les conditions standard de température T = 300 K et de pression P = 10^5 Pa. Ainsi, ces résultats devraient être utiles pour régler les générateurs de plasma froid pour des applications spécifiquesMolecular ions, in particular, dimeric rare-gas ions have a very important influence on the behavior of rare gas plasmas used in multiple fields. Therefore, the analysis and understanding of their formation are of great importance for the macroscopic modeling of these plasmas. The main objective of this work is to perform calculations of the rate constants of dimers ion formation in cold plasmas using rare gases as carriers over a wide range of reduced electric fields. To do so we have used mesoscopic data (cross sections) obtained from microscopic data (interaction potentials) for argon to provide reaction rate constants of the formation of Ar_2^+. Further, to perform our calculations we have considered all six lowest-lying electronic states of the Ar_2^+ ions. These six electronic states are classified in two fine structure states of the atomic ion, the ground state (_ ^2)P_(3/2) and the excited state(_ ^2)P_(1/2). A quasi-classical trajectory approach based on the nonadiabatic mean-field dynamics approach and Diatomics In Molecules (DIM) model of the interactions in collision complexes used in preceding studies to calculate the collision cross sections that we will use in the present work. These collision cross sections will feed a Monte Carlo code adapted and optimized for the calculation of auxiliary data such as collision energy distributions which are important to provide averaged, thermal ternary recombination rate constants of ground and excite states of the dimer ion. The ternary recombination rate constants calculated in this way are compared with the experimental measurements and theoretical available in the literature. The results we have obtained, are close to these experimental and theoretical values for selected values of reduced electric fields, E/N = 1, 50, and 100 Td, with standard conditions of temperature T = 300 K and pressure P = 10^5 Pa. Thus, these results are expected to be helpful in tuning cold plasma generators for specific applications
4
Pikhartová, Karolína. "Analýza vlivu Luhačovické přehrady na okolí". Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-399633.
Texto completo da fonteResumo:
This thesis deals with the influence of the Luhačovice dam on the surroundings, mainly on the price of recreational facilities. Firstly, the thesis addresses terminology, issues concerning dams and valuation methods suitable for these issues. Secondly, the thesis describes the current condition of the dam and its surroundings, the facilities situated in the surroundings and operation costs. The thesis presents a novel method of finding the average price of cottages in given area and comparing it with average prices of recreational facilities in other selected areas. The thesis concludes with an evaluation of the average prices and the economic and security influence of the dam on its surroundings.
5
Katre, Aanandita Ramakant. "Developing Methods for Prediction and Reduction of Springback using a Practical Method to Estimate E-Modulus". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500028074848847.
Texto completo da fonte
6
Kovářová, Lucie. "Měření deformace statorového kroužku turbodmychadla při teplotním zatížení". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401547.
Texto completo da fonteResumo:
The thesis is about deformation measurement of the nozzle ring in variable nozzle turbine mechanism under temperature load. In the first part, there is a brief description of the turbocharger. In the second part, methods of deformation measurement are mentioned there. The main part of the thesis includes component testing of selected measuring methods and their application for measuring deformation of the nozzle ring on the turbocharger. Test is done on a gas stand which simulates the thermal load conditions of the turbocharger, same which is exposed to on the engine.
7
Lee, Haegyun. "Level-set finite element simulation of free-surface flow". Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/168.
Texto completo da fonte
8
Chaumeil, Florian. "Using DEM-CFD method at colloidal scale". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8066.
Texto completo da fonteResumo:
The aim of this work is to look into the applicability of Discrete Element Modelling (DEM) coupled to Computational Fluid Dynamics (CFD) to simulate micro-scale colloidal particles immersed in fluid. Numerical methods were implemented through the commercial framework of EDEM2.3. As opposed to dissolved matter, which behaves as a continuum within the fluid medium, particulate matter is made of discrete entities that interact amongst themselves, and with the fluid and any physical boundaries. Particulate matter is ubiquitous in many purification processes that would beneficiate from having an easy way to model particle dynamics immersed in water. In an effort to understand better the dynamics of particle deposition under surface forces and hydraulic forces, a micro-scale numerical model was built adopting both a mechanistic and a statistical approach to represent the forces involved in colloidal suspension. The primary aim of the model was to simulate particle aggregation, deposition and cluster re-suspension in real world micro-systems. Case studies include colloidal flocculation in a constricted tube, and colloidal fouling around membrane filtration feed spacers. This work used a DEM-CFD coupling method that combined the DEM particle flow simulation with hydrodynamics forces from a velocity field computed through CFD. It also implemented boundary-particle and particle-particle interactions by enabling the modelling of surface and interfacial forces. Two kinds of coupling method were considered: two-way and one-way coupling. Two-way coupling is suitable for high particle concentration flow where particle loading affects the hydrodynamics. One-way coupling is suitable for dispersed particle configuration where the flow field is assumed to be undisturbed by the particles. The advantages and drawbacks of both techniques for micron-size particles were investigated. EDEM 2.3 was customised with plug-ins to implement Van der Waals forces and Brownian forces and its post-processing features offered the ability to investigate easily the microparticles behaviour under the influence of fluid forces. In this context, DEM-CFD modelling using EDEM 2.3 represents an improvement on previously published works as it enables higher visibility and reproducibility along with increasing the number of potential users of such modelling. Emphasis was given in presenting original findings and validation results that illustrate DEMCFD applicability, with respect to modelling of hydraulically mediated colloidal surface interaction; while highlighting factors that limit the ability of the technique. For instance, the effect of particle disturbance on the surrounding medium currently proves difficult to model.
9
Sharp, Jacqueline Emily U'Ren. "Applicability of the Mathews Stability Method to Open Stope Stability Assessment at Olympic Dam Mine". Thesis, University of Canterbury. Geological Sciences, 2011. http://hdl.handle.net/10092/5520.
Texto completo da fonteResumo:
Olympic Dam underground mine is located in South Australia approximately 520km north-north-west of Adelaide. The copper-gold-uranium deposit is extracted by open stope mining. The empirical Mathews stability method has been applied to open stope stability forecasting at Olympic Dam for the more than 20 years. This method adjusts the rock tunneling quality index (Q’) to allow for a rock stress factor, the orientation of any discontinuity and the orientation of the geometric surface formed by the excavation.
The applicability of the Mathews stability method at Olympic Dam was analysed by assessing the volume of over break outside the stope design profile. It was found that 41% of all stope surface predictions were correct, and that 59% (by difference) of all predictions were therefore incorrect. This was found to be primarily due to the method as applied at Olympic Dam, rather than the inherent errors of the Mathews stability method. However there are a number of weaknesses in the Mathews stability method including the inability to identify structural weaknesses in the rock mass, to allow for different stress concentrations around irregular shaped stopes and to account for stope relaxation.
A high resolution non-linear, Hoek Brown, numerical model is capable of providing displacement, velocity and strain rates for points within a rock mass. Velocity is the modelled rate of displacement of the points within the rock mass relative to the stope profile. An existing numerical model of this sort at Olympic Dam was used to investigate the relationship of the velocity of points moving toward a stope, and the probability of them becoming over break. It was found that with increasing rates of velocity the probability of a point becoming over break increased.
The identified limitations of the application of the Mathews stability method are not enough to justify removing the method from the stope design process at Olympic Dam. With the implementation of recommended improvements such as, increasing the frequency of window mapping collection, live stress measurements and detailed post-mining assessment of stopes, an increase in the methods reliability can be expected. These improvements should be incorporated in conjunction with the continued trial of velocity as a stope performance indicator at Olympic Dam.
10
Vítek, Pavel. "Vlastnosti svarových spojů po žárovém zinkování". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229350.
Texto completo da fonteResumo:
The project elaborated in frame of Master's studies branch 2303T002 presents a study of welded joints for hot-dip galvanizing. On the basis of literature study it is assumed that zinc influences the properties of welded joints. Samples were made of high strength steels DOMEX and wear-resistant steels HARDOX which were welded using MAG. Subsequently, half of the samples treated with zinc. The evaluation is used tear test and test Vickers hardness. Finally, the project is the comparison of the measured values of galvanized steel and steel without zinc.
11
Torkelsson, Olle, e Markus Dauksz. "DFMA : A Methodology Study and Method Development". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-9562.
Texto completo da fonteResumo:
Volvo Cars Corporation (VCC) is devoted to Lean and Six Sigma, and has lately considered an imple-mentation of Design for Manufacturing and Assembly (DFMA) with the purpose of improving their product design process and production. The goal for this project work is therefore to investigate if DFMA is a beneficial method for VCC to use, how DFMA can be used and suggest a DFMA method. A literature study is performed as a starting point to understand DFMA methods and its possibilities. Scientific articles, technical books and online sources is used during the study in order to gather in-formation regarding DFMA implementations, application areas, approaches and potential risks that need to be eliminated for a successful implementation. In order to map the product development and manufacturing processes of VCC interviews are per-formed. The interviews also gathered information regarding what VCC employees thinks of DFMA and how they wish to use it. This information is compiled into a demand specification where the de-mands are weighted after importance by the interviewees. After the pre-study, three idea generation sessions is performed with three different focus groups. The generated ideas are then evaluated and classified. The remaining ideas are classified with the purpose of enabling the possibility to use a morphological chart to build whole concepts from the single ideas. Three concepts are chosen amongst the generated concepts. These concepts are then evaluated against the weighted demand specification. The concept considered most suitable is further devel-oped which resulted in a proposed DFMA method for VCC. A case study on a product is performed in order to communicate, test and evaluate the final DFMA method. The project is rounded off with discussions regarding DFMA and the suggested method from sustain-ability point of view and how to motivate usage. All results and discussions from the project are handed over to the company, enabling further research on a possible implementation of DFMA in the organization.Volvo Cars Corporation arbetar hängivet efter metoderna Lean och Sex Sigma och har avsikt att im-plementera Design for Manufacturing and Assembly (DFMA) i syfte att förbättra deras produkt- och produktutvecklingsprocess. Målet med detta arbete är att undersöka om DFMA är en värdefull me-tod för VCC att använda och hur metoden kan tänkas användas och implementeras inom organisat-ionen. Som utgångspunkt för att förstå DFMA metoden och dess möjligheter genomförs en litteraturstudie. Under studien granskades aktuella vetenskapliga artiklar, tekniska böcker och webbkällor i syfte att samla information om DFMA-implementeringar, användningsområden, tillvägagångsätt och potenti-ella risker som behövs elimineras för en lyckad implementation av metoden. Vidare utförs intervjuer i syfte att kartlägga produktutvecklings- och tillverkningsprocessen samt samla information om hur anställda ställer sig till, och önskar använda DFMA. Denna information sammanställs sedan till en kravspecifikation där kraven i sin tur viktas av intervjuobjekten efter hur viktiga de anses vara. Tre idégenereringssessioner utförs därefter med tre olika fokusgrupper. Dessa idéer gallras sedan ut och klassificeras för att sedan kombineras med hjälp av en morfologisk tabell i syfte att bygga kon-cept av de enskilda idéerna. Tre koncept väljs ut bland de genererade koncepten. Dessa koncept utvärderas sedan mot varandra med kravspecifikationen som bedömningsskala. Det koncept som bedöms som mest lämpligt vidare-utvecklas och en föreslagen metod för VCC tas fram. För att testa och illustrera den slutgiltiga meto-den genomförs en fallstudie på en produkt. Arbetet rundas av med diskussioner kring DFMA och den föreslagna metoden ur både hållbarhets-synpunkt och motivationssynpunkt. Samtliga resultat och diskussioner överlämnas sedan till företa-get för att möjliggöra vidare undersökningar kring en eventuell implementation av DFMA.
DFMA FMEA DFM DFA Lean Produktdesign Metodutveckling
12
Tsuruta, Naoki. "Improved Particle Method with High-Resolution and Computational Stability for Solid-Liquid Two-Phase Flows". 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188536.
Texto completo da fonte
13
Charatpangoon, Bhuddarak. "SEISMIC SAFETY EVALUATION OF EARTH DAM AND POSSIBLE REHABILITATION METHODS". 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/192169.
Texto completo da fonte
14
Tichý, Richard. "Beitrag zur numerischen Untersuchung der Bewegungs- und Beanspruchungsprofilen in einer Kugelmühle unter Verwendung von physikalisch begründeten Stoßparametern". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2011. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-69915.
Texto completo da fonteResumo:
Die am häufigsten für die Zerkleinerung des Zementklinkers eingesetzte Kugelmühle stellt eine relativ einfache Maschine dar, in der sehr komplizierte dynamische Wechselwirkungen herrschen. Die direkte Messung der Beanspruchungsintensitäten ist heutzutage immer noch eine schwierige Aufgabe. In der vorliegenden Arbeit sind die Spektren der Beanspruchungsgrößen sowie einige spezifische integrale Größen mit der Methode der diskreten Elemente (DEM) untersucht worden. Eine besondere Aufgabe bestand in der Ermittlung der Parameter des viskoelastischen Kontaktmodells und der den Zementklinker charakterisierenden mechanischen Größen. Die reale Abbildung der Stoßvorgänge wurde anhand vereinfachter Modelle der Messprüfstände validiert. Mit den ermittelten Parametern sind numerische Untersuchungen durchgeführt worden, mit denen ihre Auswirkung auf die Zielgrößen bestimmt wurde. In Hinsicht auf eine mögliche konstruktive Weiterentwicklung sind Simulationen mit festgelegten betrieblichen und zu variierenden konstruktiven Parametern durchgeführt worden.
15
Vadluga, Vaidas. "Simulation of dynamic deformation and fracture behaviour of heterogeneous structures by discrete element method". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080213_082157-83281.
Texto completo da fonteResumo:
Research area and topicality of the work. Mechanical properties and their evolution under loading are the most significant factors for the development of various mechanical structures, technologies and equipment. It seems to be natu-ral that deeper understanding of the behaviour of existing and design of new materials presents a challenge in different research areas.
It should be noted, that all the materials are heterogeneous in meso- and
micro- scales. They exhibit essential differences, compared to the macroscopic continuum behaviour. Basically, both experimental and numerical simulation methods are extensively applied for investigation purposes.
Experimental techniques, capable of giving a realistic view of the inside of the material and extracting the real data, are very expensive. Therefore, the nu-merical simulation tools are extensively used as an alternative for investigation purposes. They have considerable advantages allowing the reproduction of multiple experiments and providing comprehensive data about ongoing phe-nomena.
Recently, numerical technologies have become highly multidisciplinary subjects. They comprise phenomenological and statistical ideas, while mathe-matical models employ the relations of continuum mechanics, classical discre-tization methods and molecular dynamics. The Discrete Element Method (DEM) is one of new methods. It is aimed at simulating the dynamic behaviour of the contacting particles. Variable topology of the system of particles is an... [to full text]Tyrimų sritis ir darbo aktualumas. Kuriant modernias ��vairios paskirties mechanines sistemas, technologijas ir įrangą, svarbiomis tampa jas sudarančios medžiagos. Savaime suprantama, kad žinomos ir naujai kuriamos medžiagos dabar kur kas išsamiau nagrinėjamos daugelyje mokslo šakų, įskaitant ir me-džiagų mechaniką. Visos medžiagos mezo- ir mikrostruktūros požiūriu yra ne-vienalytės. Jų mikroskopinės savybės skirtingos, lyginant su įprastu kontinuu-mu. Medžiagų savybėms tirti dažniausiai taikomi eksperimentiniai metodai. Eksperimentiniais metodais ištirti medžiagos struktūras ir jose vykstančius procesus ir įvertinti tam tikras jų savybes labai brangu. Tai viena priežasčių, kodėl skaitinis modeliavimas tampa realia tyrimų alternatyva. Skaitinį eksperi-mentą galima kartoti daug kartų, valdant bandinio parametrus, išlaikant tas pa-čias sąlygas, ir stebėti reiškiniui būdingus rodiklius visame tūryje. Šiuolaikiniai modeliavimo metodai yra kompleksiniai. Jie jungia fenome-nologines ir statistines idėjas, o matematiniai modeliai sudaromi taikant konti-nuumo mechanikos ir jų diskrečiųjų modelių bei molekulinės dinamikos pri-klausomybes. Diskrečiųjų elementų metodas (DEM) taip pat priskiriamas šiuo-laikinių metodų kategorijai. Jis skirtas kontaktuojančių dalelių sistemų dinami-niam modeliavimui. Kintanti dalelių sistemos topologija – būdingas metodo požymis. Pastaruoju metu DEM jau taikomas kontinuumui modeliuoti ir praktikoje aktualiems irimo uždaviniams spręsti. Reikia pastebėti... [toliau žr. visą tekstą]
16
Zhou, Yu. "Simulation of High-velocity Penetration for Rigid Projectile into Plain Concrete Target using Discrete Element Method". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/31325.
Texto completo da fonteResumo:
Penetration of high velocity is of concern for both civilian and military research for decades, and computerized simulation is the scholarâ s focus in recent years. This study presents a study on the Discrete Element Method (DEM) simulation of plain concrete targetâ s behavior under high-velocity penetration of rigid projectile.
In this thesis, different types of research works including empirical, analytical and numerical methods in penetration by the previous scholars were carefully reviewed. A DEM-based concrete model was established by using software PFC3D. The major micro-variables of the simulation program were calibrated according to the required macro-mechanical parameters. Meanwhile, their correlations within the concrete range were studied, with the sensitivity analysis and the corresponding regression equations.
With the established digital concrete model, penetration simulation tests were carried out. The results of penetration depth versus impact velocity were compared with the experimental and empirical calculated results from Forrestalâ s work in 1994. A good agreement was obtained. Some other simulation studies, like projectile mass, geometry, penetrating acceleration, concrete response stress, strain, and strain-rate were also conducted to study the constitutive properties in this thesis.Master of Science
17
Alsuleimanagha, Zaid, e Jing Liang. "Dynamic analysis of the Baozhusi dam using FEM". Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171817.
Texto completo da fonteResumo:
High magnitude earthquakes have devastating effects that leads to severe human and material losses; when affecting concrete gravity dams, seisms devastate the surrounding habitat through sudden release of reservoir. Dam safety is therefore a significant issue to be accounted in order to prevent the failure of dams located in seismic regions. The Baozhusi dam, the case study of this thesis, was exposed to 8.0 Ms (at the Mercalli scale) Wenchuan earthquake 2008 with intensity of (0.148 g) at the dam site. The earthquake intensity exceeded the design level of the dam (0.1 g); yet, the Baozhusi dam was not severely damaged as showed by tests. The present study case is a modeling and analyzing of the dynamical behavior of the Baozhusi dam during the earthquake duration. The results show that the horizontal component of the ground motion predominate the dynamic response of the dam. It is confirmed that the horizontal component of the ground motion crossed the dam at its axis and therefore minimizing the damages on the concrete gravity dam.
18
Spross, Johan. "A Critical Review of the Observational Method". Licentiate thesis, KTH, Jord- och bergmekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144207.
Texto completo da fonteResumo:
Building a sustainable structure in soil or rock that satisfies all predefined technical requirements implies choosing a rational and effective construction method. An important aspect is how the performance of the structure is verified. For cases when the geotechnical behaviour is hard to predict, the existing design code for geotechnical structures, Eurocode 7, suggests the so-called “observational method” to verify that the performance is acceptable. The basic principle of the method is to accept predefined changes in the design during construction, in order to accommodate the actual ground conditions, if the current design is found unsuitable. Even though this in theory should ensure an effective design solution, formal application of the observational method is rare. It is therefore not clear which prerequisites and circumstances that must be present for the observational method to be applicable and be the more suitable method. This licentiate thesis gives a critical review of the observational method, based on, and therefore limited by, the outcome of the performed case studies. The aim is to identify and highlight the crucial aspects that make the observational method difficult to apply, thereby providing a basis for research towards a more applicable definition of the method. The main topics of discussion are (1) the apparent contradiction between the preference for advanced probabilistic calculation methods to solve complex design problems and sound, qualitative engineering judgement, (2) the limitations of measurement data in assessing the safety of a structure, (3) the fact that currently, no safety margin is required for the completed structure when the observational method is applied, and (4) the rigidity of the current definition of the observational method and the implications of deviations from its principles. Based on the review, it is argued that the observational method can be improved by linking it to a probabilistic framework. To be applicable, the method should be supported by guidelines that explain and exemplify how to make the best use of it. The engineering judgement is however not lost; no matter how elaborate probabilistic methods are used, sound judgement is still needed to define the problem correctly. How to define such a probabilistic framework is an urgent topic for future research, because this also addresses the concerns regarding safety that is raised in the other topics of discussion.För att i berg eller jord kunna konstruera en anläggning, som uppfyller satta tekniska krav, krävs det att man väljer en rationell och effektiv konstruktionsmetod. En viktig aspekt i detta val är hur man verifierar konstruktionens funktion avseende exempelvis bärförmåga eller stadga. För fall när konstruktionens beteende svårt att förutsäga, erbjuder gällande standard (Eurokod 7) den så kallade observationsmetoden. Denna metod tillåter i förväg förberedda förändringar i designen under konstruktionstiden, om observationer av konstruktionens beteende indikerar att så behövs. På så vis anpassas konstruktionen till de faktiska förhållandena i marken. Trots att detta tillvägagångssätt i teorin borde ge en rationell design, används metoden sällan. Det råder därför oklarheter om vilka förutsättningar och omständigheter som krävs för att observationsmetoden ska kunna användas och dessutom utgöra den bästa lösningen. I denna licentiatuppsats granskas observationsmetoden och dess användbarhet. Målet med licentiatuppsatsen är att belysa de aspekter som kan utgöra svårigheter när observationsmetoden används. Dessa identifierades under arbetet med några fallstudier. Licentiatuppsatsen ger därmed en utgångspunkt för fortsatt forskning för att ta fram en mer användbar definition av observationsmetoden. De viktigaste aspekterna som diskuteras i uppsatsen är (1) den skenbara motsatsen mellan användandet av sannolikhetsbaserade beräkningsmetoder för att lösa komplexa dimensioneringsfrågor och kvalitativa ingenjörsmässiga bedömningar, (2) de begränsningar som finns när man använder mätdata för att utvärdera konstruktioners säkerhet, (3) att det för tillfället saknas krav på säkerhetsmarginal mot brott för konstruktioner som byggts med observationsmetoden, och (4) vad svårigheten att uppfylla Eurokodens strikta definition innebär för metodens användbarhet. Utifrån resultatet av granskningen dras slutsatsen att observationsmetoden kan förbättras genom att ge den ett sannolikhetsbaserat ramverk. För att förenkla användningen bör riktlinjer och anvisningar utformas. Även om metoden utvecklas mot en högre grad av beräkningskomplexitet, kommer ingenjörsmässiga bedömningar också framgent att vara viktiga, eftersom en avgörande aspekt är hur problemställningen formuleras. Med ett sannolikhetsbaserat ramverk ökar möjligheten att lösa de frågeställningar kring säkerhet som också diskuteras i uppsatsen.
QC 20140415
19
Kováříková, Sabina. "Využití DIC při měření zbytkových napětí metodou vrtání otvoru". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-418191.
Texto completo da fonteResumo:
This thesis deals with measurement of residual stress by hole drilling method. This method is based on drilling a hole and measurement of deformation in the area around this hole. Measured deformations are then converted to residual stresses by using calibration coefficients. The deformation around the drilled hole is measured by optical non contact method called digital image correlation (DIC). First part of the thesis is focused on current state of research. The thesis contains evaluation of residual stresses by using different methods and evaluation of used methods.
20
Cibis, Anna. "Erklärt die Methodenwahl höhere Suizidraten bei Männern?" Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-144278.
Texto completo da fonteResumo:
Suizid gehört in den meisten Ländern weltweit zu den zehn führenden Todesursachen und wird laut Studien der WHO im Jahr 2020 2,4% des weltweiten „Burden of Disease“ ausmachen (1998:1,8%). Auch Suizidversuche, deren Zahl auf das 10-20fache der Suizide geschätzt wird, stellen eine starke Belastung und einen hohen Kostenfaktor für die Gesundheitssysteme dar. Bezüglich der vollendeten Suizide sind Männer ungefähr 2 bis 3mal so häufig betroffen wie Frauen, bei Suizidversuchen verhält es sich umgekehrt. Mit dem Ziel, dieses Phänomen zu verstehen und effektivere Suizidpräventionsmethoden zu finden, wurden diverse Gründe für die Geschlechtsunterschiede diskutiert und beforscht. Die geschlechtsspezifische Methodenwahl, verschiedene Rollenmodelle, Suchterkrankungen und soziale Unterstützung werden unter anderem als Gründe benannt. Das Ziel dieser Dissertation ist zu untersuchen, ob die Geschlechtsunterschiede in Suizidraten alleine durch die Wahl letalerer Suizidmethoden durch Männer erklärt werden können. Es wird in vielen Studien angenommen, dass Männer zu harten Suizidmethoden wie Erschießen oder Erhängen und Frauen zu weichen Suizidmethoden wie Vergiften neigen. Anhand eines Datensatzes zu Suiziden und Suizidversuchen soll die methodenspezifische „Case Fatality“ (Suizide/Suizide+Suizidversuche) ermittelt werden. Die Hypothese lautet, dass unterschiedliche „Case Fatality rates“ darauf hinweisen, dass über die Methodenwahl hinaus weitere zentrale Gründe die höheren männlichen Suizidraten erklären bzw. dass gleiche „Case Fatality rates“ annehmen lassen, dass die Methodenwahl der Hauptgrund für die Geschlechtsunterschiede ist. In dem Artikel, welcher den Kern der Dissertation ausmacht, wird gezeigt, dass die Methodenwahl bei Männern nicht der ausschlaggebende Faktor für höhere Suizidraten ist. Vielmehr scheinen Männer einzelne Suizidmethoden mit einer höheren Letalität durchzuführen. Auch nach der Kontrolle von Alterseinflüssen zeigt sich dieses Ergebnis signifikant, speziell bei den Methoden Erhängen und Vergiften, Beispiele für eine harte und eine weiche Methode. Dies weist darauf hin, dass dahinterstehende Gründe, z.B. die Intention zu sterben, eine größere Rolle spielen und in zukünftigen Studien weiter beforscht werden solltenBackground: In most countries worldwide suicide rates are higher for males whereas attempted suicide rates are higher for females. The aim is to investigate if the choice of more lethal methods by males explains gender differences in suicide rates. Methods: Data on completed and attempted suicides were collected (n=3235, Nuremberg and Wuerzburg, years 2000–2004). The research question was analyzed by comparing the methodspecific case fatality (= completed suicides /completed+attempted suicides) for males and females. Results: Among the events captured, men chose high-risk methods like hanging significantly more often than women ( =−0.27; pb0.001). However, except for drowning, case fatalities were higher for males than for females within each method. This was most apparent in “hanging” (men 83.5%, women 55.3%; =−0.28; pb0.001) and “poisoning by drugs” (men 7.2%, women 3.4%; =−0.09; pb0.001). Limitations: The sample size (n=3235) was not enough for comparing method and gender specific case fatalities with a fine-meshed stratification regarding age. Conclusions: Higher suicide rates in males not only result from the choice of more lethal methods. Other factors have to be considered
21
Busta, Michal. "Analýza namáhání vybraných konstrukčních částí bagru při provozu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443770.
Texto completo da fonteResumo:
This thesis is focused on the issue of computational modeling of soil harvesting while using the compact excavator from the company DOOSAN BOBCAT EMEA s.r.o.. The solution consists in creating two computational models in Rocky DEM and Ansys Mechanical. Rocky DEM software is used to solve the disconnection of soil by excavator components using the discrete element method. The outcome includes courses of forces and moments during the particular time of the individual joints of the model that was used. The obtained courses are then applied as an external load to the joint of a selected structural part of the analyzed model using a kinematic model in ANSYS Mechanical. The kinematic model consists of simplified geometry models of individual parts of the excavator arm, and a more detailed geometry model of the analyzed part of the arm. All the parts are connected to each other by rotational bonds representing joints. A static structural analysis of the mechanical stress is performed in ANSYS Mechanical for the prepared model during the simulated process. Finally, the selected structural part is assessed with respect to the elastic limit and fatigue strength.
22
Durieux, Johan Hendrik. "Development of a practical methodology for the analysis of gravity dams using the non-linear finite element method". Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-06232009-152815/.
Texto completo da fonte
23
Hedman, Stefan. "Smooth and non-smooth approaches to simulation of granular matter". Thesis, Umeå universitet, Institutionen för fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-50584.
Texto completo da fonteResumo:
Granular matter is defined as a collection of particle grains, such as sand.This type of matter have different characteristics (solid, liquid and gas) depending on the energy level per grain. There are several approaches to modeling and numerical simulations of granular matter. They are used by different groups for different purposes, and the choice between the approaches is based on knowledge and tradition rather than what might be best for the purpose. The key questions are when to use what method and what physical quality is lost depending on the choice.Two regimes of discrete element granular simulations emerge: smooth and non-smooth. To compare the efficiency and physical quality of the two approaches, four physics softwares are examined including Bullet Physics, LMGC90, AgX and LIGGGHTS. Test scenes are setup in each software and the results are compared to each other or to the results of other work.The thesis is performed at UMIT Research Lab at Umeå University.
24
Johnstone, Mical William. "Calibration of DEM models for granular materials using bulk physical tests". Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4655.
Texto completo da fonteResumo:
From pharmaceutical powders to agricultural grains, a great proportion of the materials handled in industrial situations are granular or particulate in nature. The variety of stesses that the matierals may experience and the resulting bulk behaviours may be complex. In agricultural engineering, a better understanding into agricultural processes such as seeding, harvesting, transporting and storing will help to improve the handling of agricultural grains with optimised solutions. A detailed understanding of a granular system is crucial when attempting to model a system, whether it is on a micro (particle) or macro (bulk) scale. As numerical capabilities are ever increasing, the Discrete Element Method (DEM) is becoming an increasingly popular numerical technique for computing the behaviour of discrete particels for both industrial and scientific applications. A look into the literature shows a lack of validation of what DEM can predict, specifically with respect to bulk behaviour. In addition, when validation studies are conducted, discrepancies between bulk responses in physical tests and numerical predictions using measured particles properties may arise. The aire of this research is to develop a methodology to calibrate DEM models for agricultural grains using data meaured in bulk physical tests. The methodology will have a wider application to granular solids in general and will advance understanding in the area of DEM model calibration. A contrasting set of granular materials were used to develop the methodology including 3 inorganic solids (single and paired glass beads, and polyethylene terephthalate pellets) and two organic materials (black eyes beans and black kidney beans). The developed methodology consists of three steps: 1. The development of bulk physical tests to measure the bulk responses that will be used to calibrate the DEM models, 2. The creation of the numerical dataset that will describe how the DEM input parameters influence the bulk responses , and 3. The optimisation of the DEM parameters using a searching algorithm and the results from Step 1 and 2. Two laboratory devices were developed to provide calibration data for the proposed methodology: a rotating drum and an confined compression test. These devices were chosen as they can produce bulk responses that are repeatable and easy to quantify, as well as generate discriminating results in numerical simulations when DEM parameters are varied. The bulk response determined from the rotating drum device was the dynamic angle of repose Ør formed when the granular material in a 40% filled drum is rotating at a speed of 7 rpm. the confined compression apparatus was used to determine the bulk stiffness of a system by monitoring the change in void ratio from the stress applied during a loading and unloading cycle. The gradient of the loading and unloadng curves termed λ and κ respectively were chosen as the bulk responses to calibrate the DEM models. The experimental results revealed that the dynamic Ør was significantly influences by the particle aspect ration and boundary conditions. The stiffness parameters were found to be predominantly influences by the initial packing arrangement. The numerical dataset describing how the DEM input parameters influence the numerical bulk responses was created by simulating the bulk physical tests, varying selected DEM parameters and monitoring the effects on bulk parameters. To limit the number of simulations required, design of experiment (DOE) methods were used to determine a reduced factorial matrix of simulations. In additions, an extensive parametric investigation on the non-optimised parameters as well as a scaling sensitivity study was carried out. The final step in determining the optimised parameters is to use a searching algorithm to infer the DEM parameters based on the numerical dataset and used the experimental results as calibration data. To perform a comparative study, tow searching algorithms were explored: the first was a simple method based on Microsoft Excel's Solver algorithm coupled with a weighted inverse distance method. The second made used of the statistical analysis program Statistica. It was shown that the Excel Solver algorithm is simpler and quicker to use but for the present first implementation, could only perform an optimisation based on two bulk responses. Statistica required the creation of a staistical model based on the numerical dataset before using the profiling and desirability searching technique, but was able to optimise the parameter using all three bulk responses. A verification and validation of the optimisation methodology was conducted using the optimised parameters for the black eyed beans. A verification was cnducted by simulating the two calibration experiments using the optimsed parameters and comparing these with the experiments. In addition, a validation was peformed by predicting the response of ta shallow footing penetration on a bed of black eyed beans. It was found that DEM simulations using optimised parameters predicted vertical stress on the footing during penetration to an acceptable degree of accuracy for industrial applications (<10%) at penetration depths up to 30mm.
25
Brown, Nicholas John. "Discrete element modelling of cementitious materials". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8011.
Texto completo da fonteResumo:
This thesis presents a new bonded particle model that accurately predicts the wideranging behaviour of cementitious materials. There is an increasing use of the Discrete Element Method (DEM) to study the behaviour of cementitious materials such as concrete and rock; the chief advantage of the DEM over continuum-based techniques is that it does not predetermine where cracking and fragmentation initiate and propagate, since the system is naturally discontinuous. The DEM’s ability to produce realistic representations of cementitious materials depends largely on the implementation of an inter-particle bonded-contact model. A new bonded-contact model is proposed, based on the Timoshenko beam theory which considers axial, shear and bending behaviour of inter-particle bonds. The developed model was implemented in the commercial EDEM code, in which a thorough verification procedure was conducted. A full parametric study then considered the uni-axial loading of a concrete cylinder; the influence of the input parameters on the bulk response was used to produce a calibrated model that has been shown to be capable of producing realistic predictions of a wide range of behaviour seen in cementitious materials. The model provides useful insights into the microscopic phenomena that result in the bulk loading responses observed for cementitious materials such as concrete. The new model was used to simulate the loading of a number of deformable structural elements including beams, frames, plates and rings; the numerical results produced by the model provided a close match to theoretical solutions.
26
Pierce, Ian. "Applying the Material Point Method to Identify Key Factors Controlling Runout of the Cadia Tailings Dam Failure of 2018". Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104218.
Texto completo da fonteResumo:
This thesis examines the 2018 failure of the Northern Tailings Storage Facility at Cadia Valley Operations, located in New South Wales, Australia. First, the importance of examining and understanding failure mechanisms and post failure kinematics is described. Within which we understand that in the current state of affairs it is exceedingly difficult, or nigh impossible to perform without the use of large strain analyses, which have yet to permeate into the industry to a significant degree. Second, the initial construction and state of the dam just prior to failure is defined, with the materials and their properties laid out and discussed in depth as well as our means of modeling their behavior. Third, we validate and discuss our results of the base model of the dam based on key topographic features from initial and post-failure field measurements. After validation, we examine the influences of each of the different materials on the runout, comparing final topographies of different simulations with the actual final topography observed. This study was a valuable method of validating the Material Point Method as a means of modeling large deformations, as well as demonstrating its powerful applications towards catastrophic disaster prevention. The study validates and provides a greater understanding of the event of the Cadia Tailings Storage Facility Failure, and presents a framework of steps to perform similar examination on future tailings dams as a means of providing risk management in the event of failure.Master of Science
Tailings dams are structures integral to the life cycle of mining and mineral processing. After mining and the processing of mined materials, the leftover material, known as "tailings" are pumped and stored behind these structures, usually indefinitely. These structures are unique because they are usually expanded as additional storage space for these materials is required. Over the past several decades, the rate at which catastrophic or serious tailings dam failures occur out of failures has been on the rise. Because of this, it becomes necessary to better understand the failure and post-failure movements of the dam. This thesis presents one such failure, the Cadia Tailings Dam Failure of 2018, which is located in New South Wales, Australia. It applies the Material Point Method, a numerical method which allows for largestrain deformations, to examine the post-failure mechanism and interpret various influences by the different materials on the final runout. Because of this, the paper provides insights on the importance of understanding large strain analyses, discussing and presenting the incidents of the failure. The model used for reference is validated using topographic and field data taken after the failure, allowing for a comparison with future models which vary the geometry and material characteristics of the event. A procedural plan is proposed to apply to future analyses, allowing for the analysis to be applied to other events and tailings dam structures, for further insight on influences of variability and material properties on post-failure topography and geometry.
27
Sukcharoenpong, Anuchit. "Shoreline Mapping with Integrated HSI-DEM using Active Contour Method". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406147249.
Texto completo da fonte
28
Potgieter, Andrew. "A Parallel Multidimensional Weighted Histogram Analysis Method". Thesis, University of Cape Town, 2014. http://pubs.cs.uct.ac.za/archive/00000986/.
Texto completo da fonteResumo:
The Weighted Histogram Analysis Method (WHAM) is a technique used to calculate free energy from molecular simulation data. WHAM recombines biased distributions of samples from multiple Umbrella Sampling simulations to yield an estimate of the global unbiased distribution. The WHAM algorithm iterates two coupled, non-linear, equations, until convergence at an acceptable level of accuracy. The equations have quadratic time complexity for a single reaction coordinate. However, this increases exponentially with the number of reaction coordinates under investigation, which makes multidimensional WHAM a computationally expensive procedure. There is potential to use general purpose graphics processing units (GPGPU) to accelerate the execution of the algorithm. Here we develop and evaluate a multidimensional GPGPU WHAM implementation to investigate the potential speed-up attained over its CPU counterpart. In addition, to avoid the cost of multiple Molecular Dynamics simulations and for validation of the implementations we develop a test system to generate samples analogous to Umbrella Sampling simulations. We observe a maximum problem size dependent speed-up of approximately 19 for the GPGPU optimized WHAM implementation over our single threaded CPU optimized version. We find that the WHAM algorithm is amenable to GPU acceleration, which provides the means to study ever more complex molecular systems in reduced time periods.
29
Jeong, Gi Young. "Tensile Properties of Loblolly Pine Strands Using Digital Image Correlation and Stochastic Finite Element Method". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29563.
Texto completo da fonteResumo:
Previous modeling of wood materials has included many assumptions of unknown mechanical properties associated with the hierarchical structure of wood. The experimental validation of previous models did not account for the variation of mechanical properties present in wood materials. Little research has explored the uncertainties of mechanical properties in earlywood and latewood samples as well as wood strands. The goal of this study was to evaluate the effect of the intra-ring properties and grain angles on the modulus of elasticity (MOE) and ultimate tensile strength (UTS) of different orientation wood strands and to analyze the sensitivity of the MOE and UTS of wood strands with respect to these variables.
Tension testing incorporating digital image correlation (DIC) was employed to measure the MOE and UTS of earlywood and latewood bands sampled from growth ring numbers 1-10 and growth ring numbers 11-20. A similar technique adjusted for strand size testing was also applied to measure the MOE and UTS of different orientation wood strands from the two growth ring numbers. The stochastic finite element method (SFEM) was used with the results from the earlywood and latewood testing as inputs to model the mechanical property variation of loblolly pine wood strands. A sensitivity analysis of the input parameters in the SFEM model was performed to identify the most important parameters related to mechanical response.
Modulus of elasticity (MOE), Poisson ratio, and ultimate tensile strength (UTS) from earlywood and latewood generally increased as the growth ring number increased except for the UTS of latewood, which showed a slight decrease. MOE and UTS from radial, tangential, and angled grain orientation strands increased as the growth ring numbers increased while MOE and UTS from cross-grain strands decreased as the growth ring number increased. Shear modulus of wood strands increased as the growth ring number increased while shear strength decreased as the growth ring number increased. Poisson ratio from radial and angled grain strands decreased as the growth ring number increased while Poisson ratio from tangential and cross grain orientation strands increased as the growth ring number increased.
The difference of average MOE from different grain strands between experimental results and SFEM results ranged from 0.96% to 22.31%. The cumulative probability distribution curves from experimental tests and SFEM results agreed well except for the radial grain models from growth ring numbers 11-20. From sensitivity analysis, earlywood MOE was the most important contributing factor to the predicted MOE from different grain orientation strand models. From the sensitivity analysis, earlywood and latewood participated differently in the computation of MOE of different grain orientation strand models. The predicted MOE was highly associated with the strain distribution caused by different orientation strands and interaction of earlywood and latewood properties. In general, earlywood MOE had a greater effect on the predicted MOE of wood strands than other SFEM input parameters.
The difference in UTS between experimental and SFEM results ranged from 0.09% to 11.09%. Sensitivity analysis showed that grain orientation and growth ring number influenced the UTS of strands. UTS of strands from growth ring numbers 1-10 showed strength indexes (Xt, Yt, and S) to be the dominant factors while UTS of strands from growth ring numbers 11-20 showed both strength indexes and stress components (Ï 1, Ï 2, and Ï 12) to be the dominant factors. Grain orientations of strands were a strong indicator of mechanical properties of wood strands.Ph. D.
30
Tang, Wee-Hua. "EFFICIENT INTEGRAL EQUATION METHOD FOR 2.5D MICROWAVE CIRCUITS IN LAYERED MEDIA". UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_diss/345.
Texto completo da fonteResumo:
An efficient integral equation method based on a method of moment (MoM) discretization of the Mixed-Potential Integral Equation (MPIE) for the analysis of 2.5D or 3D planar microwave circuits is presented. The robust Discrete Complex Image Method (DCIM) is employed to approximate the Greens functions in layered media for horizontal and vertical sources of fields, where closed-form formulations of the z-integrations are derived in the spectral domain. Meanwhile, an efficient and accurate numerical integration technique based on the Khayat-Wilton transform is used to integrate functions with 1/R singularities and near singularities. The fast iterative solver - Quadrature Sampled Pre-Corrected Fast Fourier Transform (QSPCFFT) - is associated with the MoM formulation to analyze electrically large, dense and complex microwave circuits.
31
Garza-Delgado, Abelardo. "A study of casting distortion and residual stresses in die casting". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196175848.
Texto completo da fonte
32
Rangelova, Sandra. "Methods for assessing the consistency of the New National Height Model". Thesis, KTH, Fastigheter och byggande, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299788.
Texto completo da fonteResumo:
Digital Elevation Models (DEM) are a simple representation of the Earth’s surface. DEMs play an important role in the field of remote sensing and GIS and are used as basis for mapping and analysis for a vest majority of scientific applications. There are many ways of producing DEMs, however the direct geo-referencing technology has made Airborne Laser Scanning (ALS) a preferred technology for the acquisition of accurate surface models over broad areas. ALS uses LiDAR (Light Detection and Ranging) which uses light in a form of pulsed laser to measure distances. Before the introduction of the DEM called Ny Nationell Höjdmodell (NNH), the highest level of height data over Sweden was the GSD-altitude data (Geographical Sweden Data). The NNH was a project by Lantmäteriet, where between 2009-2019 the entire Sweden was laser scanned. The product was a new height model called Laser Data NH with positional accuracy of 0,1 m in height and relative accuracy of 0,15 m. This project focuses on testing few methods for consistency assessment between the overlapping strips using linear features. Linear features are extracted for each overlapping area, based on intersection between planar patches extracted from gable rooftops. The first method of this study computes the distance between the overlapping areas without linear features, using two approaches: cloud-to-cloud distance and mesh-to-cloud distance. The second method computes the transformation shifts and rotations needed for the linear features to align by registering the strips with both levelled and not levelled registration. In the third method, distances and angles are measured between the lines, to further analyze how well the strips fit together. The distances are measured as distance between a mid-point of one line in the first LiDAR strip and the line on the second LiDAR strip, for all linear features. The distances were measures both as 3D distances and separately as horizontal and vertical distances. As a final step a hypothesis testing was performed to determine whether the distances and angles between the lines are significant or whether any systematic error is present in the point cloud. Based on the results obtained from the first method, significant distance between the point clouds was obtained. The results from the mesh-to-cloud distance yielded better result with higher uncertainty. According to the second method significant distances between the linear features were obtained based on the registration. The mean absolute error of the registrations showed an error at a dm level, with a minimal rotation in the vertical plane for the coalignment for the levelled registration. The third method showed a mean distance between the linear features of 20 cm. Moreover, this method showed a significant inconsistence between the linear features in the vertical plane based on the high standard uncertainty.Digitala höjdmodeller (DEM) är en enkel representation av jordens yta. DEM spelar en viktig roll inom fjärranalys och GIS och används som grund för kartläggning och analys för en majoritet av vetenskapliga tillämpningar. Det finns många sätt att producera DEM, men den direkta georefereringstekniken har gjort Airborne Laser Scanning (ALS) till en föredragen teknik för förvärv av exakta ytmodeller över breda områden. ALS använder LiDAR (Light Detection and Ranging) som använder ljus i form av pulserande laser för att mäta avstånd. Före introduktionen av Ny Nationell Höjdmodell (NNH) var den högsta nivån av höjddata över Sverige GSD-höjddata (Geographical Sweden Data). NNH var ett projekt av Lantmäteriet, där mellan 2009-2019 laserscannades hela Sverige. Produkten var en ny höjdmodell som heter Laserdata NH med positionsnoggrannhet på 0,1 m i höjd och relativ noggrannhet på 0,15 m. Detta projekt fokuserar på att testa få metoder för konsekvensbedömning mellan de överlappande remsorna med hjälp av linjära funktioner. Linjära funktioner extraheras för varje överlappande område, baserat på skärningspunkten mellan plana fläckar extraherade från gaveltak. Den första metoden för denna studie beräknar avståndet mellan de överlappande områdena utan linjära funktioner, med två metoder: moln-till-moln-avstånd och nät-till-moln-avstånd. Den andra metoden beräknar de transformationsförskjutningar och rotationer som behövs för att de linjära särdragen ska kola genom att registrera remsorna med både nivellerad och inte nivellerad registrering. I den tredje metoden mäts avstånd och vinklar mellan linjerna, för att ytterligare analysera hur bra remsorna passar ihop. Avstånden mäts som avstånd mellan en mittpunkt på en linje i den första LiDAR-remsan och linjen på den andra LiDAR-remsan, för alla linjära funktioner. Avstånden var mått både som 3D -avstånd och separat som horisontella och vertikala avstånd. Som ett sista steg utfördes en hypotesprovning för att avgöra om avstånden och vinklarna mellan linjerna är signifikanta eller om det finns något systematiskt fel i punktmolnet. Baserat på resultaten från den första metoden erhölls ett betydande avstånd mellan punktmolnen. Resultaten från mask-till-moln-avståndet gav bättre resultat med högre osäkerhet. Enligt den andra metoden erhölls betydande avstånd mellan de linjära särdragen baserat på registreringen. Det genomsnittliga absoluta felet för registreringarna visade ett fel på en dm -nivå, med en minimal rotation i det vertikala planet för samlinjering för den jämnade registreringen. Den tredje metoden visade ett medelavstånd mellan de linjära särdragen på 20 cm. Dessutom visade denna metod en signifikant inkonsekvens mellan de linjära särdragen i det vertikala planet baserat på hög standardosäkerhet.
33
O'Connor, Mark J. "Evaluation of TIN extraction methods for various terrain textures". Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-09182008-063345/.
Texto completo da fonte
34
Jacobi, Christoph Alexander. "Methodenlehre der Normwirkung : die Normwirkung als Massstab der Rechtsgewinnung /". Baden-Baden : Nomos, 2008. http://d-nb.info/990130010/04.
Texto completo da fonte
35
Spross, Johan. "Toward a reliability framework for the observational method". Doctoral thesis, KTH, Jord- och bergmekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192825.
Texto completo da fonteResumo:
Constructing sustainable structures in rock that satisfy all predefined technical specifications requires rational and effective construction methods. When the geotechnical behaviour is hard to predict, the European design code, Eurocode 7, suggests application of the observational method to verify that the performance is acceptable. The basic principle of the method is to accept predefined changes in the design during construction to comply with the actual ground conditions, if the current design is found unsuitable. Even though this in theory should ensure an effective design solution, formal application of the observational method is rare. Investigating the applicability of the observational method in rock engineering, the aim of this thesis is to identify, highlight, and solve the aspects of the method that limit its wider application. Furthermore, the thesis aims to improve the conceptual understanding of how design decisions should be made when large uncertainties are present. The main research contribution is a probabilistic framework for the observational method. The suggested methodology allows comparison of the merits of the observational method with that of conventional design. Among other things, the thesis also discusses (1) the apparent contradiction between the preference for advanced probabilistic calculation methods and sound, qualitative engineering judgement, (2) how the establishment of limit states and alarm limits must be carefully considered to ensure structural safety, and (3) the applicability of the Eurocode definition of the observational method and the implications of deviations from its principles.För att kunna konstruera en anläggning i berg, som uppfyller satta tekniska krav, krävs det en rationell och effektiv konstruktionsmetod. När konstruktionens beteende är svårt att förutsäga, erbjuder den europeiska standarden Eurokod 7 den så kallade observationsmetoden. Denna metod tillåter i förväg förberedda förändringar i designen under konstruktionstiden, om observationer av konstruktionens beteende indikerar att så behövs. På så vis anpassas konstruktionen till de faktiska förhållandena i marken. Trots att detta tillvägagångssätt i teorin ger en rationell design, används metoden sällan i enlighet med Eurokod 7. Denna doktorsavhandling undersöker tillämpbarheten av observa-tionsmetoden när man bygger i och på berg. Målet är att belysa de aspekter som begränsar dess användning och i dessa fall föreslå förbättringar som ökar tillämpbarheten. I ett vidare perspektiv syftar avhandlingen även till att förbättra den konceptuella förståelsen för hur beslut bör fattas i designprocessen när det finns stora osäkerheter. Avhandlingen visar hur observationsmetoden kan användas i ett sannolikhetsbaserat ramverk. Metodiken ger användaren möjlighet att jämföra för- och nackdelarna med observationsmetoden och konventionell dimensionering. Avhandlingen diskuterar bland annat även (1) den skenbara motsatsen mellan användandet av sannolikhetsbaserade beräkningsmetoder för att lösa komplexa dimensioneringsfrågor och kvalitativa ingenjörsmässiga bedömningar, (2) hur larmgränser och brottgränstillstånd bör definieras för att ge tillräcklig säkerhetsmarginal, samt (3) hur Eurokod 7:s strikta definition av observationsmetoden påverkar dess användbarhet.
QC 20160926
36
Fanelli, Maddalena. "UNDERSTANDING AGGLOMERATE DISPERSION: EXPERIMENTS AND SIMULATIONS". online version, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1119374160.
Texto completo da fonte
37
Sultan, Abdullah Emad. "Alternative Methods for Sealing Overlapping Steel Members with Narrow Gaps During Galvanizing". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83182.
Texto completo da fonteResumo:
Narrow gaps in overlapping structural steel surfaces are problematic when being hot-dip galvanized due to the potential for trapped cleaning solutions between the surfaces. A seal-weld is often used to prevent the cleaning solutions from penetrating this gap. However, these welds are not necessary used for strength, and add fabrication costs because of the additional weld. The purpose of this research is to provide alternatives, which fall under two major categories, to the seal-weld fabrication process. The first one was motivated by the steel fabrication industry and uses a commercial silicone caulk to seal the narrow gap instead of a seal-weld. The second was motivated by the galvanizing industry and increases the narrow gap to a minimum of 3/32 in. to allow free flowing of the liquids including viscous molten zinc. 45 specimens in six different overlapping configurations were tested. Three experimental tasks were performed as part of this research: two different types of silicone caulks were used to partially substitute the seal-weld to prevent fluid penetration; an accelerated corrosion test was performed to determine the long-term corrosion resistance of each configuration; and a coating layer evaluation was performed to investigate the bond of the metallurgical layer between the steel and the coating. Results indicate that silicone only partially prevented the penetration of the cleaning solutions into the gap but performed poorly when fully galvanized. Also, the accelerated corrosion and coating investigations indicated that the suggested caulks and the 3/32 in. gap were not as efficient as the seal-weld solution.Master of Science
38
Polwaththe, Gallage Hasitha Nayanajith. "Numerical modelling of deformation behaviour of red blood cells in microvessels using the coupled SPH-DEM method". Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/91719/1/Hasitha%20Nayanajith_Polwaththe%20Gallage_Thesis.pdf.
Texto completo da fonteResumo:
This thesis developed an advanced computational model to investigate the motion and deformation properties of red blood cells in capillaries. The novel model is based on the meshfree particle methods and is capable of modelling the large deformation of red blood cells moving through blood vessels. The developed model was employed to simulate the deformation behaviour of healthy and malaria infected red blood cells as well as the motion of red blood cells in stenosed capillaries.
39
Nasato, Daniel Schiochet. "Desenvolvimento de acoplamento númerico entre o método dos elementos discretos (DEM) e o método dos elementos finitos". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266925.
Texto completo da fonteResumo:
Orientadores: José Roberto Nunhez, Nicolas SpogisDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-17T20:12:44Z (GMT). No. of bitstreams: 1 Nasato_DanielSchiochet_M.pdf: 8429075 bytes, checksum: 08b5ea34c892e0a82506be022a1613ee (MD5) Previous issue date: 2011
Resumo: Este trabalho propõe um acoplamento entre o método dos elementos discretos (DEM), utilizado para simular o manuseio de materiais particulados, e o método dos elementos finitos (FEM), utilizado para estimar respostas estruturais a uma dada condição de carregamento. O acoplamento é de 1 via, onde as forças na estrutura calculadas pelo software de DEM são passadas ao software de FEM. Foi proposta uma validação numérica a fim de avaliar a precisão do acoplamento em passar as forças do software de DEM para o software de FEM. Apenas efeitos estáticos são avaliados neste primeiro teste. Uma validação experimental foi realizada utilizando-se medidas em um tanque de mistura, permitindo assim a captura de efeitos dinâmicos das partículas. Com o modelo desenvolvido e validado, foram realizadas simulações em um equipamento industrial utilizando os softwares de DEM e FEM e o acoplamento desenvolvido, como parte de um projeto realizado com uma empresa do setor de mineração
Abstract: This work proposes a coupling between the discrete element method (DEM), used to simulate bulk materials handling, and the finite element method (FEM), used to simulate structural response to a certain loading condition. It is a one-way coupling, where the forces in the structure calculated by the DEM software are sent to the FEM software. It was proposed a numerical validation in order to evaluate the precision of the coupling to pass the forces from the DEM to the FEM software. Only static effects are evaluated in this initial test. An experimental validation was done using data measured from a mixing tank, allowing dynamic effects to be considered. With the model developed and validated simulations were done in industrial equipment using DEM and FEM software and the developed coupling, as part of a project with a mining sector company
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
40
Daryusi, Ali. "Beitrag zur Ermittlung der Kerbwirkung an Zahnwellen mit freiem und gebundenem Auslauf". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1240915811153-56748.
Texto completo da fonteResumo:
Durch die zunehmende technologische Entwicklung des Getriebe-, Gelenkwellen-, Werkzeugmaschinen-, Kraftfahrzeug-, sowie Landmaschinenbaus steigen die zu übertragenden Leistungen und Drehmomente enorm. Dies führt zu einem wachsenden Bedarf an formschlüssigen Profilwellenverbindungen und deren erhöhter Lebensdauer und Genauigkeit. Hierbei bilden die Zahnwellenverbindungen (ZWVen) mit Evolventenflanken nach DIN 5480 /N1/ den Regelfall für eine Vielzahl der Anwendung. Abhängig von Festigkeitsüberlegungen, Herstellungsverfahren und Platzbedarf treten in der Praxis nahezu ausschließlich die folgenden zwei Grundtypen auf. Es handelt sich dabei zum Ersten um die Zahnwelle (ZW) mit freiem Auslauf.Die zweite Geometrievariante ist die Zahnwelle mit gebundenem Auslauf, die eine nach DIN 471 /N2/ genormte Sicherungsringnut (SRN) enthalten kann. Zahnwellenverbindungen dienen zur Übertragung großer, wechselnder und stoßartiger Drehmomente ohne zusätzliches Verbindungselement durch die Profilierung der Welle und Nabe. Axiale Verschiebbarkeit unter Last, Profilverschiebungsmöglichkeit, einfache Montage und Demontage sowie die Herstellung mit hochleistungsfähigen umformenden und spanenden Massenfertigungsverfahren, die die Herstellungskosten verhältnismäßig niedrig halten, sind technisch bedeutsame Eigenschaften, die zum ansteigenden Einsatz von ZWVen führen (z.B. /N1/, /Vil84/, /Koh86/ und /Wes96/). Starke Kerbwirkung und erhebliche Überdimensionierung benachbarter Gestaltungszonen sind die wesentlichen Schwachpunkte der Profilverbindungen. Eine große Anzahl (ca. 80 %) von Ausfällen im Maschinenbau ist auf Schäden an Achsen und Wellen infolge konstruktiv bedingter Kerben zurückzuführen (z.B. /N3/ und /Hai89/). Speziell im Bereich der hochbeanspruchten Profilwellen-Verbindungen kommt es auf Grund der starken Querschnittsveränderungen und der häufig angewandten Ausläufe und Formelemente, z. B. Zahn- und Keilwellen zu Kerbwirkungen, die erhebliche örtliche Spannungskonzentrationen sowohl im Zahnfußbereich und Zahnlückenauslauf als auch im Bereich der Verbindung selbst verursachen. Diese Beanspruchungskonzentrationen sind fast in der Hälfte aller Zahnwellenbrüche die häufigste Ursache für Dauerbrüche (Ermüdungs- bzw. Schwingungsbrüche) und für Schäden (bleibende Verformung, Anriss, Gewaltbruch) infolge Maximalbelastung. Hier trifft die Lastüberhöhung am Welle-Nabe-Verbindungsrand mit dem Steifigkeitssprung des Verzahnungsendes auf der Welle zusammen /Die93/. Die erwähnten Schadensfälle belegen, dass der heutige Kenntnisstand über eine beanspruchungsgerechte Auslegung von Zahnwellen noch recht lückenhaft ist. Deshalb sind neue Erkenntnisse über Form- bzw. Kerbwirkungszahlen bei Einzel- und Mehrfachkerben von scharf und weniger scharf gekerbten Zahnwellen mit Auslauf für eine treffsichere Festigkeitsberechnung erforderlich und stellen damit die Hauptschwerpunkte dieser Arbeit dar. Das vorliegende Forschungsprojekt, welches sich erstmals mit der Ermittlung der Beanspruchungen in torsions-, und biegebelasteten Zahnwellen mit freiem und gebundenem Auslauf befasst, wurde im Rahmen der Forschungsvereinigung für Antriebstechnik e.V. (FVA) unter der Nummer T 467 und dem Forschungsthema „ Ermittlung der Kerbwirkung bei Profilwellen für die praktische Getriebeberechnung von Zahnwellen“ initiiert und untersucht.
41
Krenzer, Knut. "Entwicklung eines zustandsabhängigen DEM-Stoffmodells zur Nachbildung von Mischprozessen für Frischbeton". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-226677.
Texto completo da fonteResumo:
In der vorliegenden Dissertation wird ein Simulationsmodell für die Diskrete Elemente Methode vorgestellt, das in der Lage ist, das Materialverhalten während des Mischprozesses von Frischbeton nachzubilden. Zur realitätsnahen Abbildung des Materialverhaltens während des gesamten Mischprozesses ist zum einen die korrekte, prozessabhängige Modellierung der Feuchtigkeitsverteilung im Mischgut notwendig. Zum anderen definiert sich das lokale Materialverhalten durch den aktuellen Feuchtegrad und die Materialzusammensetzung der Mischung und muss im Simulationsmodell Berücksichtigung finden. Zur korrekten Modellierung der Feuchteverteilung wurde der Flüssigkeitstransfer zwischen unterschiedlich feuchten Kontaktpartnern (Partikeln) im Simulationsmodell realisiert. Der Flüssigkeitstransfer ist dabei abhängig vom Feuchtegrad der beiden Kontaktpartner, ihrer relativen Positionierung zueinander und der Viskosität der zu transferierenden Flüssigkeit. Zudem spielt die Partikelgröße eine entscheidende Rolle bei der Flüssigkeitsaufnahmefähigkeit eines Partikels und bei der Geschwindigkeit des Flüssigkeitstransfers. Zur Repräsentation des Flüssigkeitsanteils aller Partikel im Simulationsmodell erhält jedes Partikel eine zusätzliche Partikelvariable. Feuchte Feststoffpartikel lassen sich somit als zweischichtige Partikel repräsentieren, die eine äußere Flüssigkeitsschicht und einen inneren Feststoffkern besitzen. Die Modellierung des Materialverhaltens basiert auf einer Unterteilung in drei verschiedene Kraftkomponenten, die in Abhängigkeit der lokalen Feuchtegrade Anwendung finden. Die erste Kraftkomponente umfasst Reibungs-, Dämpfungs- und Federkräfte, die bei trockenen Feststoffkontakten zum Einsatz kommen. Die zweite Kraftkomponente besteht aus zusätzlichen Flüssigkeitsbrückenkräften, die bei leicht angefeuchteten Materialien wirken. Die Flüssigkeitsbrückenkräfte sind abhängig von Flüssigkeitsvolumen, Flüssigkeitszusammensetzung, Partikelgröße und Abstand der Kontaktpartner. Die dritte Kraftkomponente umfasst die viskosen Kräfte, die bedingt durch die Flüssigkeitsschichten zwischen den Kontaktpartnern auftreten. Die viskosen Kräfte in Tangentialrichtung basieren auf dem Bingham-Modell, das häufig für zementgebundene Suspensionen eingesetzt wird. Die Anwendung des Bingham-Modells setzt die Kenntnis der rheologischen Kenngrößen Fließgrenze und plastische Viskosität voraus, die aus der lokalen Zusammensetzung der Flüssigkeitsschicht approximiert werden müssen. Die Grundlage für diese Approximation bilden sowohl Modelle aus der Literatur als auch experimentelle Untersuchungen, die im Rahmen dieser Arbeit durchgeführt wurden. Auch die Definitionen der materialabhängigen Flüssigkeitsaufnahmemengen und -geschwindigkeit sowie die Berechnung der zustandsabhängigen Flüssigkeitsbrückenkräfte basieren auf theoretischen Modellen und experimentellen Untersuchungen. Die Experimente sollen die entsprechenden theoretischen Modelle stützen, die materialspezifischen Modellparameter bestimmen und zusätzliche Daten außerhalb des Gültigkeitsbereichs der Modelle liefern. Alle Einzelaspekte der Flüssigkeitsaufnahme, des -transfers und des feuchteabhängigen Materialverhaltens werden in der Simulation implementiert und anhand der Nachbildung der Experimente überprüft. Das Zusammenspiel aller Modellaspekte wird anhand der Simulation eines experimentell durchgeführten Betonmischprozesses in einem Zwangsmischer für zwei Rezepturen mit unterschiedlichen w/z-Werten ohne Verwendung von Zusatzstoffen und -mitteln validiert. Während des Mischprozesses wurde die Leistungsaufnahme des Mischers erfasst und mit der aus dem Drehmoment abgeleiteten Leistungsausnahme aus der Simulation verglichen. Dabei zeigte sich eine gute qualitative Übereinstimmung des zeitlichen Leistungsverlaufs, der das realistische Durchlaufen der verschiedenen Phasen der Materialzustände widerspiegelt. Als zusätzliches Vergleichskriterium wurde nach dem Mischprozess das Setz- bzw. Setzfließmaß ermittelt. Auch hier zeigte sich eine gute qualitative Übereinstimmung zwischen Experiment und Simulation. Damit konnte die grundsätzliche Anwendbarkeit des Modells zur Nachbildung des Materialverhaltens während des Frischbetonmischprozesses anhand einer ausgewählten Betonrezeptur demonstriert werdenIn this thesis a simulation model for the Discrete Element Method is presented, which is capable to simulate the material behavior during the mixing process of fresh concrete. For the realistic modeling of the material behavior during the entire mixing process two major aspects have to be integrated in the model. On the one hand the correct, process-dependent representation of the moisture distribution within the mix is necessary. Second, the local material behavior defined by the current degree of humidity and the mix composition must be taken into account in the simulation model. For a correct simulation of the humidity distribution representation the fluid transfers between different wet contact partners (particles) was realized in the contact model. The fluid transfer is dependent on the moisture level of the two contact partners, their relative positioning to each other and the viscosity of the liquid to be transferred. In addition, the particle size plays a crucial role in the water absorption capacity of a particle and in the water transfer velocity. For the representation of the liquid content of each particle, all particles in the simulation model have an additional particle variable. Wetted solid particles can thus be represented as two-layered particles having an outer liquid layer and an inner solid core. The modeling of the material behavior is based on a subdivision into three different force components, which are applied dependent on the local moisture degree. The first force component comprises friction, damping and spring forces, which are used in dry solid contacts. The second force component consists of additional liquid bridge forces acting in weakly wetted materials. The liquid bridge forces are defined as a function of liquid volume, liquid composition, particle size and the distance of the contact partners. The third force component covers the viscous forces that occur due to the fluid layers between the contact partners. The viscous forces in the tangential direction are based on the Bingham model, which is commonly used for cementitious suspensions. The application of the Bingham model assumes knowledge of the rheological parameters yield stress and plastic viscosity, which need to be approximated from the local composition of the liquid layer. The basis of this approximation is provided by models of literature and experimental investigations that have been carried out in this work. Also, the definitions of the material-dependent fluid absorption volume and the liquid transfer velocity as well as the computation of the state-dependent liquid bridge forces are based on theoretical models and experimental studies. Experiments are supposed to support the relevant theoretical models, determine the material-specific model parameters and provide additional information outside the scope of the models. All aspects of the fluid absorption, fluid transfer and the moisture-dependent material behavior are implemented in the simulation and verified by the remodeling of the experiments. The interplay of all aspects of the model is validated by the simulation of an experimentally investigated concrete mixing process in a compulsory mixer for two concrete recipes with different w/c ratios without using additives and admixtures. During the mixing process the power consumption of the mixer was recorded and compared with the approximated power consumption in the simulation, deduced from the torque data. Thereby a good qualitative agreement of the power curve was achieved, which reflects a realistic pass through the various phases of the material states during the mixing process. As an additional comparison criterion the slump or the slump flow was determined after the mixing process. Again, a good qualitative agreement between experiment and simulation was achieved. Thus the basic applicability of the model to simulate the material behavior during the fresh concrete mixing process is demonstrated using a selected concrete mix
42
Vaquer, Charles. "Optimisation du dimensionnement et comportement des matrices frettees". Toulouse 3, 1988. http://www.theses.fr/1988TOU30024.
Texto completo da fonte
43
Sekula, Peggy [Verfasser], e Martin [Akademischer Betreuer] Schumacher. "Statistical modelling for risk assessment in pharmacoepidemiology: the case-crossover method = Statistische Modellierung zur Risikobeurteilung in der Pharmakoepidemiologie: die case-crossover-Methode". Freiburg : Universität, 2012. http://d-nb.info/1123471053/34.
Texto completo da fonte
44
Liu, Haoyu. "System reliability calibrations for the Direct Design Method of planar steel frames with partially restrained connections". Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20858.
Texto completo da fonteResumo:
The system-based design approach for steel structures using advanced structural analysis, referred to as the Direct Design Method (DDM), has gained much research interest from the scientific community, and has been permitted in a number of steel structural specifications such as American specification AISC360 and Australian standard AS4100. Unfortunately, even the most sophisticated nonlinear analysis method cannot predict the actual performance of a structure with certainty due to ever-present uncertainties in the demands imposed to the structure and structural resistance. To fulfill the goal of assuring a prescribed level of structural reliability in the DDM, a resistance factor applied at the system level (system resistance factor) is used in the DDM. The system resistance factor needs to be determined based on a system reliability calibration procedure. This thesis examines the role of connection behaviors and the associated uncertainties on the system reliabilities of semi-rigid frames designed by the DDM. Probabilistic models of connection properties (connection stiffness and strength) are established for five types of commonly used connections based on the connection test data compiled from the literature, including the single web angle connection, double web angle connection, top and seat angle connection (with or without webangle), and extended end plate connection. The popular three-parameter-power model is used to compute the “nominal” moment-rotation response of the connections, to normalize the test data. By comparing the test-to-nominal results, the mean-to-nominal ratio and coefficient of variation of connection stiffness/strength are estimated, and incorporated in the system reliability analyses. Six series of typical planar steel frames with partially restrained beam-column connections are selected for conducting system reliability calibrations for the DDM. For each model frame, different types of connections with different stiffness and strength are considered, including the extended end plate connections, top and seat withe double web angle connections, and double web angle connections. First, the design strength of the frame given by the DDM and AISC LRFD are compared. Then, system reliability evaluations are performed for two most common design load combinations, i.e., combined wind and gravity loads, and gravity load only combination. Different loading scenarios are considered (wind-to-gravity load ratio, live-to-dead load ratio). The effects of connection type, connection stiffness and strength on the system reliability and system resistance factor are investigated. The relationship between the system resistance factor and frame reliability is established, which can serve as a basis for the code writers to choose the appropriate system resistance factors for the DDM of semi-rigid frames.
45
Barrett, Benjamin Joseph. "Field Validation of an Advanced Autonomous Method of Exterior Dam Inspection Using Unmanned Aerial Vehicles". BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7463.
Texto completo da fonteResumo:
The maintenance of infrastructure is critical to the well-being of society. This work focuses on a novel method for inspecting the exterior of dams using unmanned aerial vehicles (UAVs) in an automated fashion. The UAVs are equipped with optical sensors capturing still images. The resulting images are used to generate three-dimensional (3D) models using Structure from Motion (SfM) computer software. The SfM models are then used to inspect the exterior of the dam. As typical dam inspections entail completing a checklist of inspection items with varied degrees of precision (e.g. a concrete spillway may be finely inspected for cracking or joint deterioration while the general stability and water-tightness of a large embankment may be observed from a distance), a targeted inspection is also needed for the UAV method. In conjunction with the work presented in this thesis, a novel algorithm was developed which uses camera view planning across multiple proximity levels to generate a set of camera poses (positions and orientations) which can be collected in an autonomous UAV flight that facilitates generation of SfM models having tiered model quality for targeted inspection of infrastructure features. In this thesis, this novel algorithm and accompanying mobile application (referred to together as the novel advanced autonomous method) were field validated at Tibble Fork Dam, UT. The advanced autonomous method was compared to two other common image acquisition methods—basic autonomous and manual piloted—based on the SfM models produced from the collected image sets. The advanced autonomous method was found to produce models having tiered quality needed for efficient targeted inspection (25% and 50% higher resolution in medium and high priority target areas). The advanced autonomous method was found to produce models having on average 38% higher precise point accuracy (1.3cm) and 53% tighter surface reproducibility (for repeat inspections) (1.9cm) than basic autonomous and manual piloted image acquisition methods. The advanced autonomous method required on average 167% longer flight time and 38% fewer images than the other two methods, resulting in increased field time but decreased processing load. Additionally, viability of the advanced autonomous method for practical dam inspection was assessed through a case study inspection of Tibble Fork Dam using the collected SfM model and corresponding still images. The SfM model and corresponding images were found fully adequate for performing 94% of the inspection tasks and partially adequate for the remaining tasks. In consideration of this and other practical implementation factors such as time and safety, the method appears highly viable as an alternate to or supplement with traditional on-foot visual exterior inspection of dams such as Tibble Fork Dam. Suggestions for future work include adjustments to the optimization framework to improve field efficiency, development of a framework for cooperative inspection using UAV swarms, and development of a more automated workflow that would allow fully-remote dam inspections.
46
Fonner, Adam M. "An Investigation on Syndiotactic Polystyrene Aerogel Coating of Macroporous Fabric via Dip Coating Method". University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron15550203400871.
Texto completo da fonte
47
Duncan, Susan Cromwell. "Improving the prediction of differential item functioning: a comparison of the use of an effect size for logistic regression DIF and Mantel-Haenszel DIF methods". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/5876.
Texto completo da fonteResumo:
Psychometricians and test developers use DIF analysis to determine if there is possible bias in a given test item. This study examines the conditions under which two predominant methods for determining differential item function compare with each other in item bias detection using an effect size statistic as the basis for comparison. The main focus of the present research was to test whether or not incorporating an effect size for LR DIF will more accurately detect DIF and to compare the utility of an effect size index across MH DIF and LR DIF methods. A simulation study was used to compare the accuracy of MH DIF and LR DIF methods using a p value or supplemented with an effect size. Effect sizes were found to increase the accuracy of DIF and the possibility of the detection of DIF across varying ability distributions, population distributions, and sample size combinations. Varying ability distributions and sample size combinations affected the detection of DIF, while population distributions did not seem to affect the detection of DIF.
48
Shah, Ritesh Lalit. "Optimized upper bound analysis of polymer coated metal rod extrusion through conical die". Texas A&M University, 2003. http://hdl.handle.net/1969.1/5907.
Texto completo da fonteResumo:
Extrusion is a metal forming process used extensively in industry to produce different
structural, mechanical, electrical, architectural, automotive and aerospace application
parts. Currently after extrusion, the rod is subjected to environmental wear due to long
storage time and hence requires an additional cleaning process before further use. This
cleaning process can be eliminated by extruding a polymer coated metal rod workpiece
such that the polymer coating is sustained on the final product after the extrusion
process.
In the present research study a new upper bound analytical model is developed to predict
the forces required to conduct extrusion of a polymer coated metal rod successfully. The
search for the lower upper bound power functional is modeled as a non linear
optimization problem. Optimizing the functional also determines the set of constraints
defining the shape of rigid plastic deformation boundaries and the final coating
thickness. Also an upper bound analytical model was developed to predict forces for
failure of the polymer coating during the extrusion. Both the analytical models for successful and failed extrusion are compared to obtain critical die angle which can
provide tooling and process design guidelines. Finite element analysis simulations were
modeled using commercially available software package, ABAQUS. Predictions of FEA
simulations were in good agreement with published results and with the predictions of
analytical model developed in this study.
49
Morrissey, John Paul. "Discrete element modelling of iron ore pellets to include the effects of moisture and fines". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8270.
Texto completo da fonteResumo:
Across industry the majority of raw materials handled are particulate in nature, ranging in size and properties from aggregates to powders. The stress regimes experienced by the granular solids vary and the exhibited bulk behaviours can be complex and unexpected. The prevalence of granular solids makes them an area of interest for industry and researchers alike as many challenges still remain, such as dealing with complex cohesive behaviour in materials, which often gives rise to handling difficulties. Storage and transportation are an important part of the process chain for industries where particulate solids are commonplace. Failure to properly account for the cohesive nature of a particulate solid can be costly as it can easily lead to blockages in a silo such as ratholing or arching near the outlet during discharge. The cohesive strength of a bulk material depends on the consolidation stress it has experienced. As a result, the stress history in the material leading up to a handling scenario needs to be considered when evaluating its handling behaviour. The Discrete Element Method (DEM) has been extensively used to simulate the behaviour of granular materials, however the majority of the focus has been on noncohesive systems. For cohesive solids, it is crucial that the stress history dependent behaviour is adequately captured. Many of the contact models commonly used in DEM simulations to simulate cohesive granular materials such as the JKR model or liquid bridge models are elastic in nature and may not capture the stress history dependent behaviour observed in cohesive particulate solids. A comprehensive study on the effect of cohesion arising from the addition of moisture on the behaviour of two types of LKAB iron ore fines (KPBO and KPRS) has been carried out. The addition of moisture to the sample has been found to have a significant effect on both kinds of fines. KPRS fines were found to have a much higher unconfined strength and flow function at higher moisture contents, and also show a greater increase in cohesion with the addition of moisture, while at moisture contents of less than 2% the KPBO fines demonstrate higher unconfined yield strength. The KPBO fines were also found to achieve a significantly looser initial packing at much lower moisture content when compared to the KPRS fines. The lateral pressure ratio has also been evaluated. In this study a mesoscopic adhesive contact model that accounts for contact plasticity and stress history dependency in the bulk solid, the Edinburgh Elasto-Plastic Adhesion (EEPA) mode, has been presented and mathematically verified. A parametric study of the DEM contact model parameters was conducted to gain a deeper understating of the effect of input parameters on the simulated cohesive bulk behaviour. The EEPA contact model has been used to predict an experimental flow function of KPRS iron ore fines. The contact model has demonstrated the ability to capture the stress history dependent behaviour that exists in cohesive granular solids. The DEM simulations provide a very close match to the experimental flow functions, with the predicted unconfined strengths found to be within the standard deviations of the experimental results. Investigations into the failure mode predicted by the DEM simulations show that the samples are failing from the development of shear planes similar to those observed experimentally. The effect of increasing levels of adhesion has been explored for a flat bottomed silo where the level of adhesion has been varied. The DEM simulations were found to capture the major phenomena occurring in silo discharge including the various flow zones associated with a flat bottomed silo. Funnel flow, the effective transition and mass flow which are associated with a mixed flow pattern were observed in the model silo. The location of the effective transition height was identified: above this was mass flow. The velocity determined from the discharge rate was found to be in excellent agreement with the velocity profiles found in the zones of mass flow. A high velocity core flow zone was observed above the outlet where velocities were greater than 1.25 times the mass flow velocity, VMF. The level of adhesion in the silo was found to affect the discharge rate - a reduced flow rate was found until the eventual blockage of the silo at a high level of adhesion was found. As the level of adhesion increased the probability of arching also increased, and the formation of intermittent arching behaviour was noted in the cases with higher levels of adhesion in the system. The development of both temporary and permanent cohesive arches over the silo outlet were also observed with stopped flow from the silo.
50
Thakur, Subhash Chandra. "Mesoscopic discrete element modelling of cohesive powders for bulk handling applications". Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9777.
Texto completo da fonteResumo:
Many powders and particulate solids are stored and handled in large quantities across various industries. These solids often encounter handling and storage difficulties that are caused by the material cohesion. The cohesive strength of a bulk material is a function of its past consolidation stress. For example, high material cohesive strength as a result from high storage stresses in a silo can cause ratholing problems during discharge. Therefore, it is essential to consider the stress-history dependence when evaluating such handling behaviour. In recent years the Discrete Element Method (DEM) has been used extensively to study the complex behaviour of granular materials. Whilst extensive DEM studies have been performed on cohesionless solids, much less work exists on modelling of cohesive solids. The commonly used DEM models to model adhesion such as the JKR, DMT and linear cohesion models have been shown to have difficulty in predicting the stress-history dependent behaviour for cohesive solids. DEM modelling of cohesive solid at individual particle level is very challenging. To apply the model at single particle level accurately would require one to determine the model parameters at particle level and consider the enormous complexity of interfacial interaction. Additionally it is computationally prohibitive to model each and every individual particle and cohesion arising from several different phenomena. In this study an adhesive elasto-plastic contact model for the mesoscopic discrete element method (DEM) with three dimensional non-spherical particles is proposed with the aim of achieving quantitative predictions of cohesive powder flowability. Simulations have been performed for uniaxial consolidation followed by unconfined compression to failure using this model. Additionally, the scaling laws necessary to produce scale independent predictions for cohesionless and cohesive solids was also investigated. The influence of DEM input parameters and model implementation have been explored to study the effect of particle (meso-scale) properties on the bulk behaviour in uniaxial test simulation. The DEM model calibration was achieved using the Edinburgh Powder Tester (EPT) – an extended uniaxial tester to measure flowability of bulk solids. The EPT produced highly repeatable flowability measurements and was shown to be a good candidate for DEM model calibration. The implemented contact model has been shown to be capable of predicting the experimental flow function (unconfined compressive strength versus the prior consolidation stress) for a limestone powder which has been selected as a reference solid in the Europe wide PARDEM research network. Contact plasticity in the model is shown to affect the flowability significantly and is thus essential for producing satisfactory computations of the behaviour of a cohesive granular material. The model predicted a linear relationship between a normalized unconfined compressive strength and the product of coordination number and solid fraction. Significantly, it has been found that contribution of adhesive force to the limiting friction has a significant effect on bulk unconfined strength. Failure to include the adhesive contribution in the calculation of the frictional resistance may lead to under-prediction of unconfined strength and incorrect failure mode. The results provide new insights and propose a micromechanical based measure for characterising the strength and flowability of cohesive granular materials. Scaling of DEM input parameters in a 3D simulation of the loading regimes in a uniaxial test indicated that whilst both normal and tangential contact stiffness (loading, unloading, and load dependent) scales linearly with radius of the particle, the adhesive forces scales with the square of the radius of the particles. This is a first step towards a mesoscopic representation of a cohesive powder that is phenomenological based to produce the key bulk characteristics of a granular solid and the results indicate that it has potential to gain considerable computational advantage for large scale DEM simulations. The contact model parameters explored include particle contact normal loading stiffness, tangential stiffness, and contact friction coefficient. The DEM model implementation parameters included numerical time step, strain rate, and boundary condition. Many useful observations have been made with significant implications for the relative importance of the DEM input parameters. Finally the calibration procedure was applied to a spray dried detergent powder and the simulation results are compared to whole spectrum of loading regime in a uniaxial experiment. The experimental and simulation results were found to be in reasonable agreement for the flow function and compression behaviour.