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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.
71

Dynamics and control of flexible manipulators

Vakil, Mohammad 24 July 2008
Flexible link manipulators (FLM) are well-known for their light mass and small energy consumption compared to rigid link manipulators (RLM). These advantages of FLM are even of greater importance in applications where energy efficiency is crucial, such as in space applications. However, RLM are still preferred over FLM for industrial applications. This is due to the fact that the reliability and predictability of the performance of FLM are not yet as good as those of RLM. The major cause for these drawbacks is link flexibility, which not only makes the dynamic modeling of FLM very challenging, but also turns its end-effector trajectory tracking (EETT) into a complicated control problem. <p>The major objectives of the research undertaken in this project were to develop a dynamic model for a FLM and model-based controllers for the EETT. Therefore, the dynamic model of FLM was first derived. This dynamic model was then used to develop the EETT controllers. <p>A dynamic model of a FLM was derived by means of a novel method using the dynamic model of a single flexible link manipulator on a moving base (SFLMB). The computational efficiency of this method is among its novelties. To obtain the dynamic model, the Lagrange method was adopted. Derivation of the kinetic energy and the calculation of the corresponding derivatives, which are required in the Lagrange method, are complex for the FLM. The new method introduced in this thesis alleviated these complexities by calculating the kinetic energy and the required derivatives only for a SFLMB, which were much simpler than those of the FLM. To verify the derived dynamic model the simulation results for a two-link manipulator, with both links being flexible, were compared with those of full nonlinear finite element analysis. These comparisons showed sound agreement. <p>A new controller for EETT of FLM, which used the singularly perturbed form of the dynamic model and the integral manifold concept, was developed. By using the integral manifold concept the links lateral deflections were approximately represented in terms of the rotations of the links and input torques. Therefore the end-effector displacement, which was composed of the rotations of the links and links lateral deflections, was expressed in terms of the rotations of the links and input torques. The input torques were then selected to reduce the EETT error. The originalities of this controller, which was based on the singularly perturbed form of the dynamic model of FLM, are: (1) it is easy and computationally efficient to implement, and (2) it does not require the time derivative of links lateral deflections, which are impractical to measure. The ease and computational efficiency of the new controller were due to the use of the several properties of the dynamic model of the FLM. This controller was first employed for the EETT of a single flexible link manipulator (SFLM) with a linear model. The novel controller was then extended for the EETT of a class of flexible link manipulators, which were composed of a chain of rigid links with only a flexible end-link (CRFE). Finally it was used for the EETT of a FLM with all links being flexible. The simulation results showed the effectiveness of the new controller. These simulations were conducted on a SFLM, a CRFE (with the first link being rigid and second link being flexible) and finally a two-link manipulator, with both links being flexible. Moreover, the feasibility of the new controller proposed in this thesis was verified by experimental studies carried out using the equipment available in the newly established Robotic Laboratory at the University of Saskatchewan. The experimental verifications were performed on a SFLM and a two-link manipulator, with first link being rigid and second link being flexible.<p>Another new controller was also introduced in this thesis for the EETT of single flexible link manipulators with the linear dynamic model. This controller combined the feedforward torque, which was required to move the end-effector along the desired path, with a feedback controller. The novelty of this EETT controller was in developing a new method for the derivation of the feedforward torque. The feedforward torque was obtained by redefining the desired end-effector trajectory. For the end-effector trajectory redefinition, the summation of the stable exponential functions was used. Simulation studies showed the effectiveness of this new controller. Its feasibility was also proven by experimental verification carried out in the Robotic Laboratory at the University of Saskatchewan.
72

End of life scenarios for the Re-load pallets-how different waste scenarios impacts the life cycle environmental impact comparison with other pallet type

Ali, Azhar January 2011 (has links)
Increasing consumption and transportation gears the use of transport utilities which cause environmental effects over the globe. Environmental performance of three different types of pallets such as Re-load, plastic and corrugated fibreboard pallets are evaluated in this project. LCA tool is used to assess and compare their environmental performance in all phase of their life cycle but more focusing on end of life phase.   This study gives more emphasis to waste treatment options such as incineration, landfilling and recycling. Three different end of life scenarios have been used in this study such as 100% incineration, 100% landfilling and 100% recycling.   This study includes results of all the phases of all three types of pallets which are analysed in this report. More detailed results could be seen in excel sheets. Results of impact analysis tells that landfilling contributes to 14793 Kg CO2 of global warming potential in case of corrugated pallets. Incineration contributes to 12148.6 Kg CO2 of global warming potential. Recycling contributes to 7136 Kg CO2 of global warming. Re-load pallets show the major contribution of global warming is from landfilling approx 813.2 Kg CO2 of global warming potential. Recycling and incineration contribute to 438 Kg CO2 and 726.7 Kg CO2 of global warming potential respectively. In plastic case incineration contributes the most to global warming approximate 1183.8 Kg CO2 of global warming potential. Landfilling and recycling contribute almost the same approximate 932.6 Kg CO2 of global warming potential and 924.5 Kg CO2 of global warming potential respectively. Acidification impact show corrugated pallets cause high emissions when they are treat with landfilling and give negative values of incineration. In Eutriphication impact corrugated pallets are considered better in a sence they are inbetween 150 and 100 kg of PO-4. Re-load pallets give the least values when they are applied to different end of life scenarios.   According to the results recycling could be replace other waste treatment options because of less impact through out the end of life. Secondly, Reload pallets represent a environmental friendly product which can be improved more after this study. Lack of LCI data is the major problem in this study because it is not easily accessible and it is very time consuming part of this study. Results might be different if more data is available.   This study can be helpful for further study, for instance more replaceable scenarios will show different results for all three types of pallets. Moreover, it helps to compare more pallet types which are already in the market or propose to come in the market.
73

Means-end Search for Hidden Objects by 6.5-month-old Infants: Examination of an Experiential Limitation Hypothesis

Menard, Karen January 2005 (has links)
Three experiments were conducted to investigate the hypothesis that young infants? failures to search for occluded objects arises, not from deficiencies in their object representations, but from limitations in experience with the physical world. Successful means-end search is typically found at 8 months of age and is traditionally taken as the hallmark of object permanence. However, recent evidence suggests that infants much younger than 8 months of age are able to represent and reason about objects that are no longer visible. In Experiment 1, successful means-end search was found for 8. 5-, but not 6. 5-month-old infants in a traditional task, but younger infants showed successful search ability when the task was made familiar to them in Experiment 2 (i. e. , when the toy and occluder are first presented as a single composite object), and when they were given the opportunity to watch a demonstration of the solution to the task in Experiment 3. These results are taken as evidence for the ?experiential limitation? hypothesis and suggest that young infants are more apt at solving manual search tasks than previously acknowledged.
74

Dynamics and control of flexible manipulators

Vakil, Mohammad 24 July 2008 (has links)
Flexible link manipulators (FLM) are well-known for their light mass and small energy consumption compared to rigid link manipulators (RLM). These advantages of FLM are even of greater importance in applications where energy efficiency is crucial, such as in space applications. However, RLM are still preferred over FLM for industrial applications. This is due to the fact that the reliability and predictability of the performance of FLM are not yet as good as those of RLM. The major cause for these drawbacks is link flexibility, which not only makes the dynamic modeling of FLM very challenging, but also turns its end-effector trajectory tracking (EETT) into a complicated control problem. <p>The major objectives of the research undertaken in this project were to develop a dynamic model for a FLM and model-based controllers for the EETT. Therefore, the dynamic model of FLM was first derived. This dynamic model was then used to develop the EETT controllers. <p>A dynamic model of a FLM was derived by means of a novel method using the dynamic model of a single flexible link manipulator on a moving base (SFLMB). The computational efficiency of this method is among its novelties. To obtain the dynamic model, the Lagrange method was adopted. Derivation of the kinetic energy and the calculation of the corresponding derivatives, which are required in the Lagrange method, are complex for the FLM. The new method introduced in this thesis alleviated these complexities by calculating the kinetic energy and the required derivatives only for a SFLMB, which were much simpler than those of the FLM. To verify the derived dynamic model the simulation results for a two-link manipulator, with both links being flexible, were compared with those of full nonlinear finite element analysis. These comparisons showed sound agreement. <p>A new controller for EETT of FLM, which used the singularly perturbed form of the dynamic model and the integral manifold concept, was developed. By using the integral manifold concept the links lateral deflections were approximately represented in terms of the rotations of the links and input torques. Therefore the end-effector displacement, which was composed of the rotations of the links and links lateral deflections, was expressed in terms of the rotations of the links and input torques. The input torques were then selected to reduce the EETT error. The originalities of this controller, which was based on the singularly perturbed form of the dynamic model of FLM, are: (1) it is easy and computationally efficient to implement, and (2) it does not require the time derivative of links lateral deflections, which are impractical to measure. The ease and computational efficiency of the new controller were due to the use of the several properties of the dynamic model of the FLM. This controller was first employed for the EETT of a single flexible link manipulator (SFLM) with a linear model. The novel controller was then extended for the EETT of a class of flexible link manipulators, which were composed of a chain of rigid links with only a flexible end-link (CRFE). Finally it was used for the EETT of a FLM with all links being flexible. The simulation results showed the effectiveness of the new controller. These simulations were conducted on a SFLM, a CRFE (with the first link being rigid and second link being flexible) and finally a two-link manipulator, with both links being flexible. Moreover, the feasibility of the new controller proposed in this thesis was verified by experimental studies carried out using the equipment available in the newly established Robotic Laboratory at the University of Saskatchewan. The experimental verifications were performed on a SFLM and a two-link manipulator, with first link being rigid and second link being flexible.<p>Another new controller was also introduced in this thesis for the EETT of single flexible link manipulators with the linear dynamic model. This controller combined the feedforward torque, which was required to move the end-effector along the desired path, with a feedback controller. The novelty of this EETT controller was in developing a new method for the derivation of the feedforward torque. The feedforward torque was obtained by redefining the desired end-effector trajectory. For the end-effector trajectory redefinition, the summation of the stable exponential functions was used. Simulation studies showed the effectiveness of this new controller. Its feasibility was also proven by experimental verification carried out in the Robotic Laboratory at the University of Saskatchewan.
75

The studies of investor sentiment proxy variables

Huang, Kuo-chan 24 June 2004 (has links)
More and more events and anomalies that have happened in recent years cannot be explained by traditional models, which leads to a pervasive doubt of the effectiveness of the efficient market hypothesis. In particular, over ninety percent of Taiwan¡¦s stock market investors are individuals, and the noise trading phenomenon is very common and has a great effect upon the return of stock. Hence, the measure of investor sentiment formed by noise traders becomes a task for the researcher studying the factors which effect the stock return in Taiwan. The objective of this paper is to find the investor sentiment proxy variables which can be a significant factor in explaining stock return. This analysis adopts the arbitrage pricing model of the macroeconomic factors. The sample contains data for most listed stocks on the Taiwan Stock Exchange from 1984 to 2002. By combining the stock or company characteristic related to the noise traders¡¦ perception, including market value, stock and etc., and phenomenons effect by investor sentiment, including closed-end fund discount, initial returns on IPOs, and number of IPOs to the arbitrage pricing model , we found that closed-end fund discount and initial returns on IPOs are significant and appropriate to investor sentiment proxy variables. However, the number of IPOs is not significant enough
76

The Effect of the Cutter Attitude on the Surface Roughness

Sung, Yi-Fang 30 July 2003 (has links)
The technology of multi-axis machining has been applied extensively to the manufacturing of dies, molds, and various aerospace components. For machining mechanical parts with complex, sculptured surfaces, the use of multi-axis machine tools is probably the only one solution for avoiding tool-part collision during machining. Since cutting force will be changed by cutter attitudes, the machined surface characteristic can also be affected by cutter attitudes. In this thesis, the major concern is focused on investigating the effect of the cutter attitude on machined surface roughness. Based on the relationship between the cutter incline angle and the enveloped condition in cutting, the correlation of the mean chip thickness and the cutter incline angle is observed. To identify the relationship between the cutter attitude and the workpiece surface roughness, experimental verification is performed by milling aluminum alloy material. By fixing the cutting depths and the width of tool paths, different spindle rotational speeds and cutter incline angles are taken to machine the workpieces. And then, the machined surfaces are measured for their surface roughness. Form the experimental results, it shows that the surface roughness will reach a peak value at a special cutter incline angle. The tendency between the surface roughness and the incline angle agrees with that between the mean chip thickness and the cutter attitude approximately.
77

Proteomic analysis of hemodialysis tube binding proteins

Ho, Ya-wen 20 January 2010 (has links)
Hemodialysis is widely used for kidney failure patients, it is well known that oxidative stress is induced during hemodialysis process. To figure out what kind of proteins may adhere to the hemodialysis tube, and were those proteins oxidized during dialysis process. In this study, proteins adhere to hemodialysis membrane are eluted and examined by protein two-dimensional gel electrophoresis and MALDI-TOF technique. The two-dimensional gel electrophoresis results demonstrate 153 proteins binding to hemodialysis tube including Vsm-Rho GEF, Fibroblast growth factor 23, Prothrombin, Glomulin and Nucleobindin-1. The oxidation detection shows that some tube binding proteins are oxidized including MAP4K3 protein and Sulfiredoxin-1, and the oxidation level of hemodialysis tube binding proteins are higher then serum proteins. In conclusion, we find out 20 novel proteins which bind to hemodialysis tube and 5 novel proteins which oxidized during hemodialysis. And protein oxidation level was related to inflammation where high CRP levels were detected.
78

The destiny of the world a study on the end of the universe in the light of ancient Egyptian texts.

ElSebaie, Sherine M. January 2000 (has links) (PDF)
Thesis (M.A.)--University of Toronto, 2000. / Canadian theses = Thèses canadiennes. Description based on web page; title from title screen (viewed 15 Mar. 2004). Includes bibliographical references.
79

Organizational decision making : the Fuzzy Front End

Alas, José Ernesto 08 February 2012 (has links)
Decision-makers have many defined and widely accepted tools in place to manage projects and programs. However, can the same be said for the very early stages of projects? This research investigates what researchers are now referring to as the Fuzzy Front End of Innovation, which is defined as the territory leading up to organizational-level absorption and commercialization of the innovation process. Despite all of the actions in establishing new operational efficiencies and project management guidelines to improve New Product Development (NPD), a formalized model does not exist for the screening and filtering of the most exceptional opportunities. The ALAS Fuzzy Front End of Innovation Process Model is proposed to help manage the innovation process. This model is based on an in-depth literature review and respondent interview data. As a secondary topic this thesis will look to understand and propose the organizational structure required to support pre-phase Fuzzy Front End activities, governance and management’s role. This will not be a discussion on organizational types within development or engineering organizations (i.e.: matrix, product, platform organizational structures) but rather from the findings propose a structure that helps define who the key stake holders are in approving or rejecting development efforts. / text
80

For their patients : a grounded theory study of hospice nurses responding to their patients' suffering

Sacks, Jodi Lee 23 June 2014 (has links)
The purpose of this study was to develop an inductive theory describing the process that hospice nurses use to identify and respond to their patients' suffering. Additionally, the study sought to describe the coping strategies that hospice nurses used when working with patients they considered to be suffering. By examining nurses' responses to suffering, this study is the first step in developing effective interventions to alleviate patient suffering and mitigate its consequences on the nurses caring for those patients. Additionally, by knowing the different strategies that nurses use to cope when working with suffering patients, nurse administrators could institute educational programs, build supportive environments, and develop policies to support nurses as they deal with these difficult clinical situations. This is especially important in a hospice environment where the registered nurse is the focal point for ensuring ongoing patient assessment and implementation of the interdisciplinary plan of care by the various team members. Charmaz (2006) description of grounded theory methodology guided the study design and analysis. Participants identified and responded to their patients' suffering within the context of the nurse-patient relationship. Phases of the relationship included: preparation, establishment, cultivation, maintenance, and letting go. The participants gained insight into the psychosocial and existential aspects of the patient's psyches by cultivating the nurse-patient relationship. Within this relational context, the participants used a four-phase process: observation, issue assessment, suffering, and intervention to respond to their patient's suffering. In addition to pain and other signs of physical suffering, the participants identified other aspects of suffering: role losses, the patient's fear of the impending death, the patient's aloneness, and the patient's feelings of guilt or regret. Interestingly, suffering also was considered a family affair and could involve the loss of self-identity. While the participants recognized the importance of self-care, often they had difficulty naming strategies used to respond and cope with their patients' suffering. Clinical supervision and emotional support through mentoring and practical guidance need to be further developed to help nurses cope with the complexity of feelings that arise when caring for dying people. / text

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