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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.
141

Methodology development for parametric CAD modeling in CATIA V5 to aid simulation driven design using turbine volute as a case study

Luu, ViChi January 2015 (has links)
This report is the documentation of a master’s thesis which was conducted at Scania CV AB in Södertälje. In this study, the benefits, challenges and conditions of using parametric CAD-models for aiding CFD-simulations and performance-optimization in the product development within internal combustion engines have been assessed. The goal of the thesis included developing and proposing a methodology for design engineers at Scania which will aid them in creating parametric CAD-models which are robust, flexible, comprehensible and intelligent. The study also included assessing the benefits and pre-requisites of such methodology with both practical and theoretical approaches. The ultimate goal of this entire study was to create value for the organization by reducing lead-time in the design process while promoting the production of high quality products. A case-based approach was applied in the study in which modeling strategies resulting from practical investigations and analyzing existing methodologies were implemented on a CAD-model representing the gas-volume of a turbine volute. The chosen strategies were evaluated and subsequently documented as a part of the methodology or discarded depending on its support for the parameterization. The final methodology itself was evaluated based on the quality of the parameterized CAD-model, the time required to create the model and its compatibility to the present design process at Scania CV AB. Finally the methodology was discussed with respect to the different evaluations, and the defined research questions were discussed and answered. The results of the thesis revealed that if parametric CAD-models are made in a structured, standardized and conscious manner, they are able to be highly robust and flexible which gives the models the ability to assume a big set of different forms. The methodology is recommended to be tested in a pilot project and be implemented through internal courses at the company. It was concluded that a methodology which aids the design engineers in creating parametric CAD-models will be the key towards implementing parametric CAD-models in the company and also enabling the many benefits of parameterization, which includes reduced lead-time, enhanced component performance, increased knowledge about the component, and promotion of collaboration among engineers. It was also concluded that parametric models are best suited when the existing design freedom is big and when the time permits performance analyses via optimizations, while challenges include ensuring that the model is parameterized correctly with respect to the CFD-engineers’ wishes while taking into account the requirements from other disciplines. Therefore it is very important to establish a communication between the different engineers. Ultimately, when parametric models are established in the organization, they are recommended to be implemented eventually in both short-term and long-term projects within Scania for its beneficial properties.
142

Learning curves and engineering assessment of emerging energy technologies : onshore wind

Mukora, Audrey Etheline January 2014 (has links)
Sustainable energy systems require deployment of new technologies to help tackle the challenges of climate change and ensuring energy supplies. Future sources of energy are less economically competitive than conventional technologies, but there is the potential for cost reduction. Tools for modelling technological change are important for assessing the deployment potential of early-stage technologies. Learning curves are a tool for assessing and forecasting cost reduction of a product achieved through experience from cumulative production. They are often used to assess technological improvements, but have a number of limitations for emerging energy technologies. Learning curves are aggregate in nature, representing overall cost reduction gained from learning-by-doing. However, they do not identify the actual factors behind the cost reduction. Using the case study of onshore wind energy, this PhD study focuses on combining learning curves with engineering assessment methods for improved methods of assessing and managing technical change for emerging energy technologies. A third approach, parametric modelling, provides a potential means to integrate the two methods.
143

The influence of mooring dynamics on the performance of self reacting point absorbers

Ortiz, Juan Pablo 08 June 2016 (has links)
The design of a mooring system for a floating structure is a significant challenge; the choice of line structure and layout determine highly non-linear hydrodynamic behaviors that, in turn, influence the dynamics of the whole system. The difficulty is particularly acute for Self-Reacting Point Absorber Wave Energy Converters (SRPA WEC) as these machines rely on their movements to extract useful power from wave motions and the mooring must constrain the SRPA WEC motion without detracting from power production. In this thesis this topic has been addressed in an innovative way and new ideas on how these devices should be moored were investigated. As part of the study, an optimization routine was implemented to investigate the optimal mooring design and its characteristics. In this process, different challenges were faced. To evaluate the different mooring configurations, a high fidelity representation of the system hydrodynamics is necessary which captures the non-linearities of the system. Unfortunately, high-fidelity modeling tends to be very computationally expensive, and for this reason previous studies based mooring design largely relies on simplified representations that only reflect part of the mooring design space since some physical and hydrodynamic properties are dropped. In this work, we present how a full hydrodynamic time domain simulation can be utilized within a Metamodel-Based Optimization to better evaluate a wider range of mooring configurations spanning the breadth of the full design space. The method uses a Metamodel, defined in terms of the mooring physical parameters, to cover the majority of the optimization process a high fidelity model is used to establish the Metamodel in a pre-processing stage. The method was applied to a case study of a two-body heaving SRPA WEC. Survivability constrains where introduce into the model using a new statistical approach which reduces the execution time, and allowed the optimization routine. The analysis results lead to the conclusion that for SRPA WEC the mooring loads have a significant impact on how the body reacts with the waves, affecting both the energy that enter the system as well as the energy that is extracted as power. This implies that, in some cases, the mooring lines need to be considered in early stages of the designs as opposed to an afterthought, as is typically done. Results indicate that an optimal mooring design can result in a 26% increase in total annual power production. In addition, the mooring lines impact on mitigating parasitic pitch and roll were analyzed. It was established that in regular waves, the mooring lines can reduce the parametric excitations and improve the power extraction up to 56% for a particular sea state. By applying a computationally efficient iterative design approach to a device's mooring, parasitic motions and suboptimal device operation can be reduced, ultimately making WECs a more competitive source of energy. / Graduate / 0346 / 0537 / 0548 / 0547 / jortiz@uvic.ca
144

Intracavity terahertz optical parametric oscillators

Walsh, David A. January 2011 (has links)
This thesis describes the design and implementation of several novel, nanosecond pulsed, intracavity optical parametric oscillators for the generation of terahertz radiation. The application of the intracavity approach in the context of terahertz optical parametric oscillators has been demonstrated for the first time, and the pump wave energy required was thereby reduced by an order of magnitude. The terahertz wave was tunable from under 1THz up to 3THz with a free running linewidth of ~50GHz and pulse energies up to ~20nJ (pulses were a few nanoseconds in duration). The terahertz beam profile was of Gaussian shape and could be focussed down to 2.3 times the diffraction limited spot size (M² values of 2.3 and 6.7 in the components of the beam parallel and perpendicular to the silicon prism array output coupler respectively). Developments of this intracavity source with regard to the linewidth are also reported. Implementation of etalons in the optical (laser and OPO) cavities was shown to be a promising technique that brings the terahertz linewidth down below 1GHz (close to the transform limit of nanosecond pulses) while retaining the tuning range and beam characteristics of the free running system. Close to Fourier transform limited pulses were obtained (<100MHz linewidth) via an injection seeding technique, although with significantly increased system complexity. A deleterious effect caused by the mode beating of a multimode host laser was also discovered, in that sidebands were induced on the seeded downconverted wave. This has wider implications in the field of intracavity OPOs. Finally, quasi-phasematching techniques implementing periodically poled lithium niobate were investigated as a way to lower the downconversion threshold energy requirement (by collinear propagation of the optical waves), and also to extract the terahertz wave rapidly from the (highly absorbing in the terahertz region) lithium niobate crystal. The existence of two phasematching solutions arising from the bidirectionality of the grating vector was identified as a serious design constraint in the context of an OPO where either solution can build up from noise photons, and so prefers the solution with the lowest walkoff of the downconverted waves - possibly resulting in unextractable terahertz radiation. Quasi-phasematching with an orthogonal grating vector (with identical but opposite phasematching solutions) was demonstrated and cascaded downconversion processes observed and characterised. These cascaded processes are permitted by the collinearality of the optical waves and may allow efficiency improvements through overcoming the quantum defect limit. This research has resulted in four peer reviewed papers in respected journals, and the intracavity terahertz OPO has been licensed to a company who have commercialised the technology (M Squared Lasers, Glasgow).
145

Versatile photonic processor based on fiber optical parametric amplifiers

Liang, Yu, 梁羽 January 2009 (has links)
published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy
146

Parametric estimating for early electric substation construction cost

Wall, Darden Lee 15 September 2010 (has links)
Developing accurate construction estimates is critical for electric utilities to make reliable financial plans for their future. Parametric estimating is just one of several techniques available to help estimate the cost of a construction project. Other estimating methods may have some advantages over parametric estimating in the latter stages of a project but parametric estimating is possibly the most accurate method in the very early stages of a project. This report delves into the analysis and development of a parametric equation for use primarily in the very early stages of a construction project. The result of this research is a functional equation that can be used for estimating future electric substation construction cost with a fair level of confidence. / text
147

Modelling transport, accessibility and productivity in Öresund

Petersen, Tom January 2004 (has links)
<p>This licentiate thesis is about the provision of transportinfrastructure and the regional impacts of such provision.Three different techniques have been investigated that can beused for the assessment and forecasting of the effects ofinfrastructure: transport demand models and parametric andnon-parametric econometric estimation techniques. The maininterest is focused around the regional effects of theÖresund fixed link, which was opened on July 1, 2000.</p><p>The thesis is a collection of three papers plus a generalintroduction: papers 1 and 2 are concerned with the effect ofaccessibility in the transport networks on productivity on anindividual firm level. In paper 1, a translog cost function,extended with an accessibility variable, is estimated for 24business aggregates using panel data techniques and tests on adataset covering single workplaces in Scania over the years1990–98. The results are not conclusive, and cannot beused for forecasting of the after-situation. In paper 2, anon-parametric method, propensity score matching, is applied onthe same dataset to test if productivity differs in highaccessibiliby areas compared to those with low accessibility,while controlling for other differences between firms. Theresult here is the same as in the first paper: for no businessthere is a significant difference in productivity that can berelated to accessibility. In paper 3, a framework for theexternal validation of models of transport, landuse andenvironment is developed, with a focus on transport forecastmodels. The scenario assumptions and forecast results ofearlier models are presented and compared. A before-and-afterdatabase under construction for the Öresund region is alsopresented, to be used for validation of such models.</p><p><b>Key words:</b>infrastructure assessment, validation,Öresund, transport demand models, regionalconsequences.</p>
148

ICT and economic growth : a dynamic non-parametric approach

Wang, Bin January 2010 (has links)
One of important issues of the policymakers is to improve output and/or productivity growth associated with information and communication technology (ICT) adoption, where total factor productivity (TFP) growth related with ICT in the 1990s appeared in the US but not in the UK (Jorgenson and Stiroh, 2000; Oliner and Sichel, 2000). The general agreement is that ICT can raise output and/or productivity growth via an increase in productivity growth in the ICT-producing sectors due to rapid technological progress, through capital deepening driven by high levels of investment in ICT equipments, and via increases in efficiency in ICT-using sectors that successfully adopt this new technology by ICT spillover effects (David, 1990). Due to the small size of ICT-producing industries and relatively low level of ICT investments in the UK (Colecchia and Schreyer, 2001; Daveri, 2002; Vijselaar and Albers, 2002), the utilization of ICT spillover effects was crucial to improving output and/or productivity growth for the UK. However, in most of the previous studies, while many concluded ICT spillover effects existed in the US, they had mixed results as to whether ICT spillover effects existed in the UK (Schreyer, 2000; Basu et al., 2003; Inklaar et al., 2005; Jorgenson et al., 2005). The objective of this thesis is to contribute to the existing literature by investigating the existence of ICT spillover effects in the US and the UK and exploring the reasons for the different effects between them. This thesis argues that the mixed findings in the previous studies are due to the ignorance of the General-purpose technology (GPT) theory and weakness in methodology. Thus, the first step is to build a new framework of measuring ICT spillover effects to solve the problems from the existing studies. The main ignorance of the GPT theory is the lack of guidance for the proxy of co-invention related to ICT investments and for the length of lag. The new framework no longer has this ignorance because it uses efficiency as a proxy of co-invention and captures the length of lag by years with negative return on ICT capital. The methodology employed in the previous studies was inappropriate mainly because of the small sample size taken in the ICT study, the two-stage approach used to explore the effect of the environmental variables on efficiency and the linear and concavity assumptions on the frontiers without taking account of ICT as a GPT. The new framework uses Bayesian technique, one-stage approach and non-parametric frontiers to avoid these three drawbacks. In addition, the new framework introduces the persistent level of inefficiency, using a first-order autoregressive (i.e. AR(1)) structure of inefficiency itself, as one of factors that influence ICT spillover effects. In order to model the new framework which takes into account the non-parametric frontiers for capturing negative return of ICT capital, an AR(1) structure of inefficiency, the small sample size and factors that influence ICT spillover effects, this thesis has developed two non-parametric dynamic stochastic frontier analysis (SFA) models with an AR(1) structure and performed the analysis via Bayesian inference. The first model was a semi-parametric dynamic stochastic frontier with a time-variant non-parametric frontier at the basic level along with a time-invariant linear function for the technical inefficiency at the higher-level. The second model relaxed the time-invariant linear functional form for technical inefficiency at the higher level. The results of the new framework showed strong ICT spillover effects in the US with a lag of about 6-8 years during 1982-83 to 1988-89, while relatively weaker ICT spillover effects in the UK. This can be evidenced by the fact that the UK has been in the process of organizational adjustment up to 2000 due to a longer lag. Thus, in the 1990s, there was a lack of TFP growth in the UK. Related to the different ICT spillover effects between the US and the UK, the results from the new framework suggested that the various persistent levels of inefficiency between the two countries was important, apart from the different levels of ICT investment between them mentioned in the previous studies (Inklaar, O Mahony and Timmer, 2003). JEL Classifications: C51, E13, O30, O33
149

Design and Structural Analysis of a Robotic Arm

Eranki, Venkata Krishna Prashanth, Reddy Gurudu, Rishank January 2017 (has links)
Automation is creating revolution in the present industrial sector, as it reduces manpower and time of production. Our project mainly deals around the shearing operation, were the sheet is picked manually and placed on the belt for shearing which involves risk factor. Our challenge is designing of pick and place operator to carry the sheet from the stack and place it in the shearing machine for the feeding. We have gone through different research papers, articles and had observed the advanced technologies used in other industries for the similar operation. After related study we have achieved the design of a 3-jointed robotic arm were the base is fixed and the remaining joints move in vertical and horizontal directions. The end effector is also designed such that to lift the sheet we use suction cups were the sheet is uplifted with a certain pressure. Here we used Creo-Parametric for design and Autodesk-Inventor 2017 to simulate the designed model.
150

Study of Numerical Model Parameters and Crack Tip of a Packaging Materials

Kodavati, Venkata Seshank, Buraga, Devi Prasad January 2017 (has links)
Packaging industries widely use Low-Density Polyethylene (LDPE) in manufacturing different types of containers to store the food products. They are difficult to model numerically in order to have similar experimental response. This research deals with the study of numerical material model parameters of continuum LDPE. It is carried out with the help of experiments along with the numerical simulation of LDPE. Study of stress-strain distribution at crack tip and elements close to the tip is carried out in the LDPE material with the pre-existing center crack with varying lengths. By implementing an optimization algorithm and automating the simulation with the help of python code, we obtain a set of parameters. This obtained data for the material can be used directly for numerical simulation in the future without carrying out additional experimental studies. After implementing the optimization algorithm is also validated, against the results that were close to the experimental response.

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