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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.
101

Information management environment for engineering design in multi-location companies : four case studies in China

Zhang, Shuai January 2019 (has links)
Information management systems are being developed and introduced to engineering design activities to help companies reuse their information. This trend has been identified in multi-location companies, which operate design departments at various locations. Investigating how multi-location companies can configure their information management environment to fulfil engineers' information needs in design process opens up a research topic for us. A well configured information management environment will require a clear understanding of what designers need from it. A literature review has identified that only a few studies have observed the way in which design practitioners work in an industrial environment; and since these studies were all conducted 10 or 20 years ago within a specific context, their findings may no longer reflect current practice. The first phase of this research investigates the information needs of designers in the vehicle industry, and the different approaches and resources that they currently adopt to fulfil these needs. The findings of this first phase of research are then used to identify further industry-based studies. The second phase of the research focuses on the structures and operations of information management for engineering design. A case study of four multi-location companies was conducted to understand their information management environments (IMEs). Primary data was collected in fieldwork visits to the companies. Inductive grounded coding was applied to analyse the data, revealing the constructs of information management environments at the case companies studied. The analyses identified strategic orientations, structures, organisational enablers and individuals' capabilities in case companies' IMEs. A new classification of IMEs was proposed to understand their structural and operational features. The analyses have implications for how companies should configure their IMEs. The studies reported in this dissertation contribute to theory by providing an understanding of the configuration of IMEs in companies and proposing ways of configuring IMEs in practice. Researchers in the domain of information systems can develop a good understanding of how professional practitioners interact with information environments so that they can propose information management systems or methods that make tangible improvements. This study also helps engineers map out the information environment that they search to acquire information. Chief engineers or managers in companies who are in charge of information management can benefit from the understanding of their own information environment and use the proposed model as a guide to configure their own information management environments. The study also suggests future research directions, such as identifying and proposing the indicators that can be used to measure the performance of information management.
102

A model-driven approach to scenario-based requirements engineering /

Sun, Ximeng, 1979- January 2007 (has links)
No description available.
103

A model-driven approach to design engineered physical systems /

Sen, Sagar. January 2006 (has links)
No description available.
104

Deformations in Concrete Cantilever Bridges : Observations and Theoretical Modelling

Takács, Peter F. January 2002 (has links)
<p>The thesis deals with the deformation problem of segmental, cast-in-place concrete cantilever bridges. This type of bridge has shown some propensity to develop larger deflections than those were predicted in the design calculation. Excessive deflections may lead to deterioration of aesthetics, serviceability problems and eventually early reconstruction of the bridge. Also in the construction stages the deflections have to be properly compensated to achieve the smooth camber in the completed bridge deck.</p><p>Deformation prediction in concrete cantilever bridges is not as reliable as it would be necessary due to several factors. The high degree of uncertainty in creep and shrinkage prediction in concrete constitutes the major difficulty. Other factors are the complex segmental construction procedure and the sensitivity of the deformations to variations in the construction schedule, the uncertainty in estimating the frictional loss of prestress and relaxation in the prestressing tendons and uncertainty in estimating model parameters such as temperature and relative humidity.</p><p>The doctoral study was initiated with the objective to improve deformation prediction in segmentally cast concrete cantilever bridges and to establish guidelines for deformation analysis based on advanced numerical methods.</p><p>A database on observed deformations in three modern long span concrete cantilever bridges in Norway has been established. Two of the bridges were partly constructed from lightweight aggregate concrete. The deformations have been monitored since the construction stages up to the present time. The measurements cover the construction stages and the service life of 14, 8 and 3 years, respectively for the three bridges. The measured deformations are deflections in the superstructure and in one of the bridges, also strain measurements in the piers and the superstructure.</p><p>A sophisticated numerical model was created for deformation analysis. The numerical model realistically simulates the segmental construction procedure and the entire life span of the bridge. The effects of the segmental construction method, temporarily supports and constraints and changes in the structure system during construction are taken into account. The model considers the different concrete age from segment to segment, the sequential application of permanent loads and prestressing and the effect of temporary loads. The prestressing tendons are individually modelled with their true profile taking into account the variation of the effective prestressing force along the length of the tendon and with time.</p><p>The finite element model consists of beam elements which are based on an advanced beam element formulation. The beam model was verified against a robust two-and-a-half dimensional shell model concerning its general performance and some specific issues. The comparison confirmed the accuracy of the beam model. Existing experimental data on creep and shrinkage in lightweight aggregate concrete and high strength concrete were evaluated in comparison with theoretical models. The main focus was on the CEB-FIP Model Code 1990 and its subsequent extensions. The findings were considered in the numerical studies.</p><p>Deformations of the three bridges were computed. The CEB-FIP Model Code 1990 material model was used for concrete for the most part. The elastic moduli were taken from test results where they were available. The creep coefficient and the shrinkage strain of the lightweight aggregate concrete were assumed equal to those of normal density concrete of the same strength. The agreement between the calculated and the measured deformations were satisfactory in view of the large uncertainty involved in theoretical prediction. While moderate differences were observed in most cases, no clear overall tendency toward underor overestimation was found. In subsequent numerical studies, the sensitivity of the deformations to variations in various model parameters was investigated. The B3 model was compared to the CEB-FIP Model Code 1990 in the analysis of one of the bridges, where the latter model showed somewhat better agreement with the measurements.</p><p>The last part of the work concerned a robust probabilistic analysis which was based on a Monte Carlo simulation. The objective of the probabilistic analysis was to estimate the statistical properties of the deformation responses. With the distribution function of a given deformation response being known, the confidence limit for the deformation can be determined. It is recommended to design the bridge for the long-time deflection which represents a certain confidence limit (e.g. the 95 % confidence limit) of the response rather than its mean. Such way the risk that the bridge will suffer intolerable deflection over its life span can be minimised.</p>
105

Ballistic Penetration and Perforation of Steel Plates

Børvik, Tore January 2001 (has links)
<p>Situations involving impact, i.e. the collision between two or more solids, were at one time primarily of concern to the military. Nowadays, as safety is highlighted within most branches of industry, the field of impact dynamics covers a wide range of situations and is of interest to engineers from a large number of different disciplines. This is in particular true for the oil, transport, space, military, nuclear and metal forming industry. </p><p>This thesis describes an experimental and numerical investigation on the ballistic penetration and perforation of Weldox 460F steel plates, and consists of eight independently published parts that are linked together through a synopsis. The thesis was generated from a project in progress on the behaviour of structural components subjected to impact loading conditions. </p>
106

Ballistic Penetration and Perforation of Steel Plates

Børvik, Tore January 2001 (has links)
Situations involving impact, i.e. the collision between two or more solids, were at one time primarily of concern to the military. Nowadays, as safety is highlighted within most branches of industry, the field of impact dynamics covers a wide range of situations and is of interest to engineers from a large number of different disciplines. This is in particular true for the oil, transport, space, military, nuclear and metal forming industry. This thesis describes an experimental and numerical investigation on the ballistic penetration and perforation of Weldox 460F steel plates, and consists of eight independently published parts that are linked together through a synopsis. The thesis was generated from a project in progress on the behaviour of structural components subjected to impact loading conditions.
107

Deformations in Concrete Cantilever Bridges : Observations and Theoretical Modelling

Takács, Peter F. January 2002 (has links)
The thesis deals with the deformation problem of segmental, cast-in-place concrete cantilever bridges. This type of bridge has shown some propensity to develop larger deflections than those were predicted in the design calculation. Excessive deflections may lead to deterioration of aesthetics, serviceability problems and eventually early reconstruction of the bridge. Also in the construction stages the deflections have to be properly compensated to achieve the smooth camber in the completed bridge deck. Deformation prediction in concrete cantilever bridges is not as reliable as it would be necessary due to several factors. The high degree of uncertainty in creep and shrinkage prediction in concrete constitutes the major difficulty. Other factors are the complex segmental construction procedure and the sensitivity of the deformations to variations in the construction schedule, the uncertainty in estimating the frictional loss of prestress and relaxation in the prestressing tendons and uncertainty in estimating model parameters such as temperature and relative humidity. The doctoral study was initiated with the objective to improve deformation prediction in segmentally cast concrete cantilever bridges and to establish guidelines for deformation analysis based on advanced numerical methods. A database on observed deformations in three modern long span concrete cantilever bridges in Norway has been established. Two of the bridges were partly constructed from lightweight aggregate concrete. The deformations have been monitored since the construction stages up to the present time. The measurements cover the construction stages and the service life of 14, 8 and 3 years, respectively for the three bridges. The measured deformations are deflections in the superstructure and in one of the bridges, also strain measurements in the piers and the superstructure. A sophisticated numerical model was created for deformation analysis. The numerical model realistically simulates the segmental construction procedure and the entire life span of the bridge. The effects of the segmental construction method, temporarily supports and constraints and changes in the structure system during construction are taken into account. The model considers the different concrete age from segment to segment, the sequential application of permanent loads and prestressing and the effect of temporary loads. The prestressing tendons are individually modelled with their true profile taking into account the variation of the effective prestressing force along the length of the tendon and with time. The finite element model consists of beam elements which are based on an advanced beam element formulation. The beam model was verified against a robust two-and-a-half dimensional shell model concerning its general performance and some specific issues. The comparison confirmed the accuracy of the beam model. Existing experimental data on creep and shrinkage in lightweight aggregate concrete and high strength concrete were evaluated in comparison with theoretical models. The main focus was on the CEB-FIP Model Code 1990 and its subsequent extensions. The findings were considered in the numerical studies. Deformations of the three bridges were computed. The CEB-FIP Model Code 1990 material model was used for concrete for the most part. The elastic moduli were taken from test results where they were available. The creep coefficient and the shrinkage strain of the lightweight aggregate concrete were assumed equal to those of normal density concrete of the same strength. The agreement between the calculated and the measured deformations were satisfactory in view of the large uncertainty involved in theoretical prediction. While moderate differences were observed in most cases, no clear overall tendency toward underor overestimation was found. In subsequent numerical studies, the sensitivity of the deformations to variations in various model parameters was investigated. The B3 model was compared to the CEB-FIP Model Code 1990 in the analysis of one of the bridges, where the latter model showed somewhat better agreement with the measurements. The last part of the work concerned a robust probabilistic analysis which was based on a Monte Carlo simulation. The objective of the probabilistic analysis was to estimate the statistical properties of the deformation responses. With the distribution function of a given deformation response being known, the confidence limit for the deformation can be determined. It is recommended to design the bridge for the long-time deflection which represents a certain confidence limit (e.g. the 95 % confidence limit) of the response rather than its mean. Such way the risk that the bridge will suffer intolerable deflection over its life span can be minimised.
108

Full- and Model Scale Study of Wind Effects on a medium-rise Building in a built up Area

Snæbjörnsson, Jónas Thór January 2002 (has links)
The present study deals with full- and model scale study of wind effects on a medium-rise building in a built up area. Most low-rise building experiments have been based on an isolated building placed in a relatively uniform terrain. Similarly, the very tall buildings often extend out from their environment in a similar fashion. However, buildings are constructed in various shapes and placed in different types of terrain and topography. Therefore, despite a number of studies made in the past, there are still problems that remain unsolved. As the majority of office- and residential buildings in populated areas fall in the intermediate height category, it should be of interest to examine the wind effects acting upon such a building, as well as its dynamic response. For this purpose, an experimental program was initiated utilising a combination of full-scale measurements and wind tunnel studies, where the fluctuating wind actions are evaluated from recorded simultaneous point pressure fluctuations. Recent improvements in experimental techniques and data handling enable a more detailed information gathering that should eventually lead to an improved understanding of the pressure field around buildings. The investigation studies, experimentally, the wind induced dynamic loading and response of a multi-story building of intermediate height. The presented work evolves on one hand around experimental data acquisition in both full- and model scale, whereas on the other it evolves around basic data reduction, understanding and interpretation of the acquired data. The objective of the study is, in a way, to attempt to provide a sound wind loading chain a la Davenport [29], in the form of data that would facilitate the study of the links connecting the main parameters i.e. Wind – Load – Response. This entails the definition of the relevant wind parameters, the description of the aerodynamic loading process, such as the time-dependent variations of pressure fluctuations on the building surface, and an investigation of the wind induced response of a medium-rise building. Information on the study-building and the experimental setup and procedures is given, for both full-scale and model scale. The full-scale and model scale data are systematically compared through the evaluation of descriptive parameters of both wind turbulence and surface pressures. In general, the evaluated full-scale parameters are found to be in qualitatively good agreement with the model scale parameters. However, the investigation revealed some characteristic differences between full-scale and model scale behaviour. These differences are largely related to the fact that significant variability is found to be inherent in the fullscale data, whereas considerably less variability seems to be associated with the wind tunnel data.
109

A Quantitative Study of the Application of Design Patterns in Java

Hahsler, Michael January 2003 (has links) (PDF)
Using design patterns is a widely accepted method to improve software development. There are many benefits of the application of patterns claimed in the literature. The most cited claim is that design patterns can provide a common design vocabulary and therefore improve greatly communication between software designers. Most of the claims are supported by experiences reports of practitioners, but there is a lack of quantitative research concerning the actual application of design patterns and about the realization of the claimed benefits. In this paper we analyze the development process of over 1000 open source software projects using version control information. We explore this information to gain an insight into the differences of software development with and without design patters. (author's abstract) / Series: Working Papers on Information Systems, Information Business and Operations
110

Design of Rear Suspension Mechanisms of Mountain Bikes

Chen, Cheng-Sheng 14 July 2000 (has links)
­^¤åºK­n The purpose of this work is to provide a design procedure of rear suspension mechanisms of mountain bikes by using the concept of engineering design method. First, the conditions and particularities of mountain biking are investigated and the performance specification of rear suspension mechanisms is set by focusing the investigations on the requirements of rear suspension mechanisms. Second, the requirements and constraints of generating different types of rear suspension mechanisms are developed and the systematic process of creative mechanism design is followed. Third, the different types of rear suspension mechanisms resulted from creative mechanism design are analyzed to realize the property of each type of rear suspension mechanisms and the procedure of kinematic design is developed by using the algorithm of heuristic combinatorial optimization method. Finally a computer aided design program written in Visual BASIC 6.0 programming language is developed to be the powerful tool of performance analysis and kinematic design of rear suspension mechanisms.

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