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

DIM : A systematic and lightweight method for identifying dependencies between requirements

Gomez, Arturo, Rueda, Gema January 2010 (has links)
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
2

Iterative Damage Index Method for Structural Health Monitoring

You, Taesun 2009 December 1900 (has links)
Structural Health Monitoring (SHM) is an effective alternative to conventional inspections which are time-consuming and subjective. SHM can detect damage early and reduce maintenance cost and thereby help reduce the likelihood of catastrophic structural events to infrastructure such as bridges. After reviewing the Damage Index Method, an Iterative Damage Index Method (IDIM) is proposed to improve the accuracy of damage detection. These two damage detection techniques are compared numerically and experimentally using measurements from two structures, a simply supported beam and a pedestrian bridge. The dynamic properties for the numerical comparison are extracted by modal analysis in ABAQUS, while the dynamic characteristics for the experimental comparison are obtained with the Wireless Sensor Network and the Time Domain Decomposition. In both the numerical and experimental phases, the accuracy of damage predictions from each method is quantified. Compared to the traditional damage detection algorithm, the proposed IDIM is shown to be less arbitrary and more accurate when applied to both structures. The proposed IDIM has the potential to improve SHM.
3

The Effects Of Assumption On Subspace Identification Using Simulation And Experiment Data

Kim, Yoonhwak 01 January 2013 (has links)
In the modern dynamic engineering field, experimental dynamics is an important area of study. This area includes structural dynamics, structural control, and structural health monitoring. In experimental dynamics, methods to obtain measured data have seen a great influx of research efforts to develop an accurate and reliable experimental analysis result. A technical challenge is the procurement of informative data that exhibits the desired system information. In many cases, the number of sensors is limited by cost and difficulty of data archive. Furthermore, some informative data has technical difficulty when measuring input force and, even if obtaining the desired data were possible, it could include a lot of noise in the measuring data. As a result, researchers have developed many analytical tools with limited informative data. Subspace identification method is used one of tools in these achievements. Subspace identification method includes three different approaches: Deterministic Subspace Identification (DSI), Stochastic Subspace Identification (SSI), and Deterministic-Stochastic Subspace Identification (DSSI). The subspace identification method is widely used for fast computational speed and its accuracy. Based on the given information, such as output only, input/output, and input/output with noises, DSI, SSI, and DSSI are differently applied under specific assumptions, which could affect the analytical results. The objective of this study is to observe the effect of assumptions on subspace identification with various data conditions. Firstly, an analytical simulation study is performed using a sixdegree-of-freedom mass-damper-spring system which is created using MATLAB. Various conditions of excitation insert to the simulation test model, and its excitation and response are iv analyzed using the subspace identification method. For stochastic problems, artificial noise is contained to the excitation and followed the same steps. Through this simulation test, the effects of assumption on subspace identification are quantified. Once the effects of the assumptions are studied using the simulation model, the subspace identification method is applied to dynamic response data collected from large-scale 12-story buildings with different foundation types that are tested at Tongji University, Shanghai, China. Noise effects are verified using three different excitation types. Furthermore, using the DSSI, which has the most accurate result, the effect of different foundations on the superstructure are analyzed.
4

Reduction of coupled field models for the simulation of electrical machines and power electronic modules / Réduction de modèles couplés Electro-Thermo-Hydrauliques pour la simulation de machines électriques et de modules électroniques de puissance

Abid, Fatma 11 June 2015 (has links)
Dans le domaine automobile, les modules électroniques de puissance des produits mécatroniques voient leur puissance sans cesse s'accroître, tout en étant confinés dans des volumes de plus en plus réduits. Au cours de leur fonctionnement, les composants semi-conducteurs et leur assemblage subissent ainsi des contraintes électro-thermo-mécaniques sévères, susceptibles d'entraîner leur destruction et de provoquer la défaillance du produit. L'étude de la fiabilité et le calcul de la durée de vie de tels produits dépendent des températures de jonction calculées au niveau des puces des composants de puissances. De surcroît, le contexte d'applications embarquées requiert de maîtriser, outre les paramètres électriques et mécaniques, les paramètres thermiques tels que les températures de jonctions et les puissances dissipées au niveau des composants, qu'il est nécessaire de réguler et contrôler en temps réel afin d'assurer le bon fonctionnement du produit. L'objectif de cette thèse est ainsi de proposer une méthode d'identification de modèles réduits dans le but d'estimer le comportement thermique des modules électroniques de puissance, en se fondant uniquement sur les données d'entrées et les résultats issus d'une simulation numérique d'un modèle détaillé du système étudié. Dans cette thèse, une nouvelle méthode d'identification, nommée « Kernel Identification Method », est développée. Cette méthode a été validée sur une application industrielle traitant d'un problème thermique couplé solide/fluide dont le comportement est essentiellement régi par de la convection forcée. Une étude exploratoire portant sur l'identification de problèmes non linéaires où la convection naturelle joue le rôle dominant est ensuite proposée. A cet effet, deux méthodes d’identification non-paramétrique sont proposées : (i) une première méthode basée sur l’extension de la méthode Kernel Identification Method ; et (ii) une deuxième méthode basée sur la variante dite « Unscented » du filtre de Kalman. / In automotive applications, the thermal dissipation of power electronics modules in mechatronic products is constantly increasing, whereas these products are confined in increasingly reduced volumes. During their operation, the semiconductor components and their environment are then submitted to severe electro-thermo-mechanical stresses that could cause their damage and lead to the product failure. The reliability and lifetime prevision of such products depend on the temperature junction located at the chip of power components. Furthermore, in order to ensure the safe operation of embedded applications, it is essential to perform a real-time control of thermal parameters such as the junction temperatures and power dissipated on the power components, in addition to the electrical and mechanical parameters. The objective of this thesis is to develop an identification method aimed at producing reduced thermal models to estimate the thermal behaviour of power electronic modules. Designed in a non-intrusive framework, this method post-processes the input data and the results produced by the numerical simulation of a detailed of the system under study. In this thesis, a new identification method, called "Kernel Identification Method" is developed. It has been validated on an industrial application dealing with a thermally coupled solid / fluid problem mainly governed by forced convection. An exploratory study of nonlinear problems identification where the natural convection plays the dominant role is then proposed. To this end, two identification methods of nonparametric nature are proposed: (i) a method based on the extension of the Kernel Identification Method; and (ii) a second method based on the "unscented" variant of the Kalman filter.
5

The value of personalised consumer product design facilitated through additive manufacturing technology

Abdul Kudus, Syahibudil I. January 2017 (has links)
This research attempted to discover how Additive Manufacturing (AM) can best be used to increase the value of personalised consumer products and how designers can be assisted in finding an effective way to facilitate value addition within personalisable product designs. AM has become an enabler for end-users to become directly involved in product personalisation through the manipulation of three-dimensional (3D) designs of the product using easy-to-use design toolkits. In this way, end-users are able to fabricate their own personalised designs using various types of AM systems. Personalisation activity can contribute to an increment in the value of a product because it delivers a closer fit to user preferences. The research began with a literature review that covered the areas of product personalisation, additive manufacturing, and consumer value in product design. The literature review revealed that the lack of methods and tools to enable designers to exploit AM has become a fundamental challenge in fully realising the advantages of the technology. Consequently, the question remained as to whether industrial designers are able to identify the design characteristics that can potentially add value to a product, particularly when the product is being personalised by end-users using AM-enabled design tools and systems. A new value taxonomy was developed to capture the relevant value attributes of personalised AM products. The value taxonomy comprised two first-level value types: product value and experiential value. It was further expanded into six second-level value components: functional value, personal-expressive value, sensory value, unique value, co-design value, and hedonic value. The research employed a survey to assess end-users value reflection on personalised features; measuring their willingness to pay (WTP) and their intention to purchase a product with personalised features. Thereafter, an experimental study was performed to measure end-users opinions on the value of 3D-printed personalised products based on the two value types: product value and experiential value. Based on the findings, a formal added value identification method was developed to act as a design aid tool to assist designers in preparing a personalisable product design that embodies value-adding personalisation features within the product. The design method was translated into a beta-test version paper-based design workbook known as the V+APP Design Method: Design Workbook. The design aid tool was validated by expert designers. In conclusion, this research has indicated that the added value identification method shows promise as a practical and effective method in aiding expert designers to identify the potential value-adding personalisation features within personalisable AM products, ensuring they are able to fully exploit the unique characteristics and value-adding design characteristics enabled by AM. Finally, the limitations of the research have been explained and recommendations made for future work in this area.
6

A Historic-contextual Approach For The Identification Of The Built Heritage In Historic Urban Areas: Case Of Galata District In Istanbul

Topcu, Hicran 01 July 2004 (has links) (PDF)
ABSTRACT A HISTORIC-CONTEXTUAL APPROACH FOR THE IDENTIFICATION OF BUILT HERITAGE IN HISTORIC URBAN AREAS: CASE OF GALATA DISTRICT IN ISTANBUL Top&ccedil / u, Hicran Ph.D., Department of Architecture, Restoration Supervisor: Prof. Dr. &Ouml / m&uuml / r Bakirer July 2004, 230 pages The recent developments in the urban conservation theory has introduced a contextual perspective that gives further emphasis to the cultural integrity of the historic urban area which is created through the physical and non-physical relationships between the urban context and its components. In this perspective, the conventional identification tools of the urban conservation - the separate designation of the buildings and areas- come to be questioned, and re-formulated according to the demands created by this new holistic-contextual understanding of the heritage conservation. In this thesis, it is aimed to formulate a historic-contextual method for the identification of the built heritage. Re-establishing the links between the historic urban context and its components, and turning the inherent character of the area into an effective tool for the conservation of the area, we claim that such an approach would provide the necessary interface between the conservation and development, responding the requirements of both and providing a common base both for the action and research. The thesis comprises a conceptual part focusing on the historic-contextual aspects of the built heritage and a case study for the experimentation of the defined methodology. The case study is realized in the Galata district in Istanbul, which represents one of the richest examples in Turkey from the aspect of the availability of historic sources.
7

Dialogue essais - simulation et identification de lois de comportement d’alliage à mémoire de forme en chargement multiaxial / Coupled experimental-numerical study and identification of multiaxial SMA constitutive behavior

Echchorfi, Rachid 06 September 2013 (has links)
Les travaux présentés ont consisté à développer des stratégies d'identification performantes des paramètres des lois de comportement superélastique des Alliages à Mémoire de Forme (AMF). L'objectif est de disposer d'une solution complète de caractérisation, d'identification, et de simulation de structures en AMF soumises à des sollicitations complexes. Une base de données expérimentale unifiée pour un alliage de NiTi superélastique a été établie pour une multitude de trajets de déformation multiaxiaux et à différentes températures : en traction homogène, en compression, en traction-compression et en traction-traction. Une caractérisation expérimentale a été développée sur une plate-forme multiaxiale assemblée au laboratoire durant ce travail. L'emploi de la corrélation d'images a permis d'enrichir la base de données expérimentale en déterminant pour chaque essai les champs cinématiques. Cette collection d'essais a permis de montrer l'importante différence de comportement observée entre les directions de laminage et transverse, bien que le matériau soit faiblement texturé. Des procédures d'identification du comportement thermomécanique des AMF ont été mises en place, basées sur la construction et minimisation d'une fonction objectif régularisée. La première est basée sur l'exploitation des courbes contrainte-déformation moyennes sous chargement homogène et unixial. La seconde exploite la richesse des champs de déformations mesurés en essai hétérogène. Les deux stratégies ont permis d'identifier les huit paramètres gouvernant le comportement superélastique du modèle de Chemisky et al. (Chemisky et al. 2011). Des différences entre les jeux de paramètres identifiés sont caractéristiques des effets d'anisotropie observés. Le succès de cette stratégie démontre sa pertinence et est encourageant pour l'identification de paramètres de lois de comportement anisotropes. / In this work, efficient identification strategies were developed to determine the characteristic parameters of the thermomechanical behavior of pseudoelastic Shape Memory Alloys (SMA). The aim is to obtain a complete solution for characterization, identification and numerical simulation of SMA structures undergoing multiaxial loading paths. A unified experimental database has been constructed to characterize the behavior of superelastic NiTi SMAs. This database includes tension, compression, tension-tension and tension-compression multiaxial tests at different temperatures. A characterization methodology has been developed on a multiaxial testing setup, which has been assembled in the laboratory during this Ph.D. project. Vital information about the strain fields for each test is added to the experimental database through the use of Digital Image Correlation. A significant difference in the thermomechanical behavior between the rolling and transverse directions has been observed, even when the specimens are not strongly textured. Two strategies were developed that rely on the minimization of a regularized cost function for identification of thermomechanical constitutive law parameters. The first identification procedure is based on uniaxial homogeneous tests at different temperatures. In the other strategy the information of strain fields of heterogeneous tests are utilized. In each case, the eight material parameters of the constitutive law of Chemisky et al. (Chemisky et al. 2011) have been identified. A difference between the identified parameters in the rolling and transverse direction is noted and corresponds to the effect of anisotropy. Nevertheless, the capabilities of the relevant identification strategies shall allow the determination of the parameters of anisotropic constitutive laws.
8

Diagnostic vibratoire des systèmes mécaniques par subspace fitting / Vibration diagnosis of mechanical systemes by subspace fitting

Gautier, Guillaume 03 July 2015 (has links)
Dans ce mémoire, une méthode subspace fitting (SF) destinée à l’identification des paramètres mécaniques et l’évaluation de l’état de santé de structures vibrantes, est présentée. La méthode SF s’attache à extraire, à partir des méthodes d’identification par sous-espaces (4SID), une matrice d’observabilité du système et de la corréler, au sens de la norme, à une matrice d’observabilité théorique. L’originalité de ce travail est de construire la matrice d’observabilité théorique sur la base d’un modèle éléments finis (EF) de la structure considérée. En ajustant les paramètres inconnus du modèle EF, les propriétés mécaniques de la structure vibrante sont identifiées. Les coûts de calcul d’une telle procédure sont réduits en considérant une méthode de réduction de modèle basée sur la position des excitations et des capteurs. La méthode est évaluée pour l’identification des fréquences propres d’une structure vibrante. Des applications numériques et expérimentales s’attachent à montrer la pertinence d’une telle approche. En particulier, il est mis en évidence que la méthode SF permet d’identifier précisément les fréquences propres d’une structure, pour des niveaux de bruit importants. / In this thesis, a subspace fitting (SF) method is presented for the identification of mechanical parameters and assessment of the health condition of vibrating structures. The SF method attempts to extract, from subspace identification methods (4SID), a system observability matrix of the system and correlate them with a theoretical observability matrix. The originality of this work is to obtain the theoretical observability matrix from a finite element model (EF) of the structure. By adjusting unknown parameters of the FE model, the mechanical properties of the vibrating structure are identified. Computational costs of such a procedure are reduced by considering a model reduction method based on the excitations and sensors location. The method is evaluated for the identification of natural frequencies of a vibrating structure. Numerical and experimental applications are assessed to show the relevance of such an approach. In particular, it is highlighted that the SF method can accurately identify the natural frequencies of a structure to high noise levels.
9

Algorithms for knowledge discovery using relation identification methods

Tomczak, Jakub January 2009 (has links)
In this work a coherent survey of problems connected with relational knowledge representation and methods for achieving relational knowledge representation were presented. Proposed approach was shown on three applications: economic case, biomedical case and benchmark dataset. All crucial definitions were formulated and three main methods for relation identification problem were shown. Moreover, for specific relational models and observations’ types different identification methods were presented. / Double Diploma Programme, polish supervisor: prof. Jerzy Świątek, Wrocław University of Technology
10

A Study Of Tremor In Parkinsons Disease Using Signals From Wrist-Worn Inertial Measurement Sensors

Aditya Ajay Shanghavi (19739650) 25 September 2024 (has links)
<p dir="ltr">Parkinson’s Disease (PD) is the second most common neurodegenerative disorder with tremor being its primary motor symptom. Although the MS-UPDRS is the current clinical method for evaluating the severity of tremors in PD, it has several drawbacks resulting from the subjective, visual-based examination, and the ordinal scale used to rate the tremors. Since, the MS-UPDRS is agnostic to the etiology of the tremor, age related increase in naturally occurring physiological tremors may confound the precise rating of PD tremors. However, replacing the judgment of the neurologist in determining the holistic progression of PD and treatment protocol is neither feasible nor advisable. This research used lightweight, wearable, non-invasive sensors to detect, analyze, and differentiate changes in wrist kinematics due to physiological and PD tremors. Findings reveal key differences and similarities in composition between these different types of tremors. Dominant frequency analysis using a data-based approach shows interesting parallels with the frequency range found in literature for these tremors. Finally, using features of tremor signal obtained from the sensors, a novel Tremor Severity Score rating scale was created that shows greater sensitivity in differentiating rest and postural tremors as well as medication effects on these tremors in PD patients compared to the MS-UPDRS. This study offers a simple method for objectively evaluating Parkinsonian tremors, identifying kinematic distinctions between rest and postural tremors, analyzing the effect of anti-parkinsonian medication on these tremors, and sensitively scoring tremors. These objective methods could be valuable for early diagnosis and distinguishing between different tremor causes in both clinical and telehealth settings, as well as for investigating the effects of various treatment methods on tremors.</p>

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