• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 609
  • 124
  • 124
  • 111
  • 71
  • 50
  • 20
  • 18
  • 17
  • 14
  • 12
  • 10
  • 8
  • 5
  • 4
  • Tagged with
  • 1390
  • 356
  • 221
  • 157
  • 156
  • 141
  • 135
  • 124
  • 124
  • 113
  • 110
  • 98
  • 95
  • 87
  • 85
  • 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

Vision-based Navigation for Mobile Robots on Ill-structured Roads

Lee, Hyun Nam 16 January 2010 (has links)
Autonomous robots can replace humans to explore hostile areas, such as Mars and other inhospitable regions. A fundamental task for the autonomous robot is navigation. Due to the inherent difficulties in understanding natural objects and changing environments, navigation for unstructured environments, such as natural environments, has largely unsolved problems. However, navigation for ill-structured environments [1], where roads do not disappear completely, increases the understanding of these difficulties. We develop algorithms for robot navigation on ill-structured roads with monocular vision based on two elements: the appearance information and the geometric information. The fundamental problem of the appearance information-based navigation is road presentation. We propose a new type of road description, a vision vector space (V2-Space), which is a set of local collision-free directions in image space. We report how the V2-Space is constructed and how the V2-Space can be used to incorporate vehicle kinematic, dynamic, and time-delay constraints in motion planning. Failures occur due to the limitations of the appearance information-based navigation, such as a lack of geometric information. We expand the research to include consideration of geometric information. We present the vision-based navigation system using the geometric information. To compute depth with monocular vision, we use images obtained from different camera perspectives during robot navigation. For any given image pair, the depth error in regions close to the camera baseline can be excessively large. This degenerated region is named untrusted area, which could lead to collisions. We analyze how the untrusted areas are distributed on the road plane and predict them accordingly before the robot makes its move. We propose an algorithm to assist the robot in avoiding the untrusted area by selecting optimal locations to take frames while navigating. Experiments show that the algorithm can significantly reduce the depth error and hence reduce the risk of collisions. Although this approach is developed for monocular vision, it can be applied to multiple cameras to control the depth error. The concept of an untrusted area can be applied to 3D reconstruction with a two-view approach.
102

A Study on the Concept of Unknown and Problem-Solving Process Among Different Graders in Concrete Situations

Chuang, Sung-chieh 20 July 2005 (has links)
The aim of this study is to explore different graders¡¦ concept of unknown and performance in solving equations in concrete situations. In recent years of early algebra research in the United States (Carraher, Schliemann, & Schwartz, in press), it was found that through systematic teaching, low and middle graders¡¦ algebra performance was better than the same or even higher graders without teaching. Therefore, semi-structured interview was adopted to collect data on three cases: a second-grader, a fifth-grader and a seventh-grader who were using textbooks that follow Grade one-nine Integrated Coordinate Curriculum in SY89. The interview questions included addition and subtraction CHANGE problems, as well as multiplication and division EQUAL GROUPS problems; with natural numbers below 20, and given in four types: one-step, two-steps mixed, relating two unknowns and comparing two unknowns. Data analysis was conducted by referring to three sources of data: protocols from interviews, children¡¦s problem-solving records and interviewer¡¦s observation records. Research findings were: all three cases that received guidance could use equations to express problems; ¡§Undoing¡¨ was the most frequently used problem-solving strategy; both second and fifth graders could simplify expressions by number properties in concrete situations; both fifth and seventh graders could check if answers were reasonable; the meaning of equal sign developed from ¡§finding the results of¡¨ to ¡§equality in measures¡¨; and, individual differences in ¡§trial and error substitution¡¨ among three cases. Such results were consistent to that of Carraher. It is suggested that, introducing early algebra in the elementary school is helpful to children¡¦s learning of formal algebra in the junior high school.
103

Pool boiling on nano-finned surfaces

Sriraman, Sharan Ram 10 October 2008 (has links)
The effect of nano-structured surfaces on pool boiling heat transfer is explored in this study. Experiments are conducted in a cubical test chamber containing fluoroinert coolant (PF5060, Manufacturer: 3M Co.) as the working fluid. Pool boiling experiments are conducted for saturation and subcooled conditions. Three different types of ordered nano-structured surfaces are fabricated using Step and flash imprint lithography on silicon substrates followed by Reactive Ion Etching (RIE) or Deep Reactive Ion Etching (DRIE). These nano-structures consist of a square array of cylindrical nanofins with a longitudinal pitch of 1 mm, transverse pitch of 0.9 mm and fixed (uniform) heights ranging from 15 nm - 650 nm for each substrate. The contact angle of de-ionized water on the substrates is measured before and after the boiling experiments. The contact-angle is observed to increase with the height of the nano-fins. Contact angle variation is also observed before and after the pool boiling experiments. The pool boiling curves for the nano-structured silicon surfaces are compared with that of atomically smooth single-crystal silicon (bare) surfaces. Data processing is performed to estimate the heat flux through the projected area (plan area) for the nano-patterned zone as well as the heat flux through the total nano-patterned area, which includes the surface area of the fins. Maximum heat flux (MHF) is enhanced by ~120 % for the nanofin surfaces compared to bare (smooth) surfaces, under saturation condition. The pool boiling heat flux data for the three nano-structured surfaces progressively overlap with each other in the vicinity of the MHF condition. Based on the experimental data several micro/nano-scale transport mechanisms responsible for heat flux enhancements are identified, which include: "microlayer" disruption or enhancement, enhancement of active nucleation site density, enlargement of cold spots and enhancement of contact angle which affects the vapor bubble departure frequency.
104

A study of parents¡¦ selection of cross district school settings on aboriginal elementary students

Tu, Chih-Hsiung 20 August 2009 (has links)
This study explores the reasons for why aboriginal parents decide for their children to cross district to school with a specific focus on three school district of Paiwaness tribes in Pingtung County. The area we research is undeveloped and the researcher is himself Paiwanese. It aims to explore why aboriginal parents choose to leave the school in tribes, discover the problems that parents and children encounter , how they handle the problems and the adaptations for children. The study adopts semi-structured questionnaire to conduct in-depth interviews. Purposive sampling was used to identify interviews and there were ten aboriginal parents were interviewed. The conclusions of the research are as the following:. 1.The main reasons for crossing district schooling include lack of peer-learning competitive in tribes, adaption in mainstream society and parents¡¦ positive discipline. 2.Poor marketing strategy of tribal school administrator, and local indigenous teachers¡¦ background and their negative image within daily lives affected parents¡¦ trust toward tribal school. 3.The decision of cross district schooling for children is influenced by parents¡¦ learning experience and opinions of family numbers. 4.The main consideration of cross district schooling for parents is to get household register of school district easily without comparing the ideas between the two different kinds of schools. 5.The problems they faced include driving the children to school, cultural learning of Paiwanese and learning tribal lives. But the main solution is passive pattern for parents. 6.The results of cross district school choice are satisfied mostly with parents¡¦ expectation but there is still a gap.
105

Physical design automation of structured high-performance integrated circuits

Ward, Samuel Isaac 06 February 2014 (has links)
During the last forty years, advancements have pushed state-of-the-art placers to impressive performance placing modern multimillion gate designs in under an hour. Wide industry adoption of the analytical framework indicates the quality of these approaches. However, modern designs present significant challenges to address the multi objective requirements for multi GHz designs. As devices continue to scale, wires become more resistive and power constraints significantly dampen performance gains, continued improvement in placement quality is necessary. Additionally, placement has become more challenging with the integration of multi-objective constraints such as routability, timing and reliability. These constraints intensify the challenge of producing quality placement solutions and must be handled carefully. Exasperating the issue, shrinking schedules and budgets are requiring increased automation by blurring the boundary between manual and automated placement. An example of this new hybrid design style is the integration of structured placement constraints within traditional ASIC style circuit structures. Structure aware placement is a significant challenge to modern high performance physical design flows. The goal of this dissertation is to develop enhancements to state-of-the-art placement flows overcoming inadequacies for structured circuits. A key observation is that specific structures exist where modern analytical placement frameworks significantly underperform. Accurately measuring suboptimality of a particular placement solution however is very challenging. As such, this work begins by designing a series of structured placement benchmarks. Generating placement for the benchmarks manually offers the opportunity to accurately quantify placer performance. Then, the latest generation of academic placers is compared to evaluate how the placers performed for these design styles. Results of this work lead to discoveries in three key aspects of modern physical design flows. Datapath placement is the first aspect to be examined. This work narrows the focus to specifically target datapath style circuits that contain high fanout nets. As the datapath benchmarks showed, these high fanout nets misdirect analytical placement flows. To effectively handle these circuit styles, this work proposes a new unified placement flow that simultaneously places random-logic and datapath cells. The flow is built on top of a leading academic force-directed placer and significantly improves the quality of datapath placement while leveraging the speed and flexibility of existing algorithms. Effectively placing these circuits is not enough because in modern high performance designs, datapath circuits are often embedded within a larger ASIC style circuit and thus are unknown. As such, the next aspect of structured placement applies novel data learning techniques to train, predict, and evaluate potential structured circuits. Extracted circuits are mapped to groups that are aligned and simultaneously placed with random logic. The third aspect that can be enhanced with improved structured placement impacts local clock tree synthesis. Performance and power requirements for multi-GHz microprocessors necessitate the use of a grid-based clock network methodology, wherein a global clock grid is overlaid on the entire die area followed by local buffered clock trees. This clock mesh methodology is driven by three key reasons: First, full trees do not offer enough performance for modern microprocessors. Second, clock trees offer significant power savings over full clock meshes. Third, local clock trees reduce the local clock wiring demands compared to full meshes at lower level metal layers. To meet these demands, a shift in latch placement methodology is proposed by using structured placement templates. Placement configurations are identified a priori with significantly lower capacitance and the solutions are developed into placement templates. Results through careful experimentation demonstrate the effectiveness of these approaches and the impact potential for modern high-speed designs. / text
106

New Product Forecasting with Structured Analogy Method in the Fashion Industry : Case Studies with the Fashion Footwear Products

Torlakcik, Tugce January 2015 (has links)
Fashion and the contemporary environment as a whole, is a complex environment that requires retailers and wholesalers to adapt to the changes that constantly occurring. This adaptation is in a bid to ensure that more profits than loses are realized by the company. For this reason, companies have to use various methods to determine the best ways to improve their products. Companies resolve to introduction of new product to the market but the acceptance of new products to the fashion industry is not an assured factor but rather a gamble. This is mainly because of the industry’s characteristics. The main aim of this thesis is to analyze the methods that may be used to improve the accuracy of new products. The fashion industry has characteristics that may be considered as challenges because for instance, when a product is launched, one has to determine whether it is by a reputable designer or whether it is a trend, and with the fashion industry, trends are mainly turned into such by celebrities who introduce a certain design to the world for adoption. These challenges or characteristics are carefully analyzed and examined with the necessity of the introduction of new products analyzed. Data collection, being the main backbone of this thesis and multiple-case study method, is used to answer the research question as “How can structured analogy method be used to improve the forecast accuracy for the footwear products in the fashion industry “.Samples for case study have been chosen from footwear category. Structured analogy method is used to determine the accuracy of the information gathered from literature review.
107

Advanced analysis of structured packing via computational fluid dynamics simulation

Owens, Scott Allen, 1982- 08 February 2011 (has links)
This research explored the use of CFD simulations to study single phase flows through structured packing. Flow rates were chosen to approximate those used in the vapor phase of industrial distillation columns. The results were evaluated against experimental results obtained with the same packing model and packed height. Several novel methods were employed to quickly obtain high validity results. A high-fidelity, digital copy of an actual packing element was created in seven hours through CT scanning. The meshing strategy employed adaptive, polyhedral meshing algorithms which resulted in high quality volume meshes with 80 percent less mesh elements than would be required with traditional tetrahedral meshing. Meshing and computation were performed on the TACC clusters. The permitted meshing with up to 57 million volume cells in less than 30 hours while simulations employing a realizable k-[epsilon] model converged in approximately two days using up to 544 processors. Nitrogen simulation predictions were found to be, on average, 7 percent below experimental measurements with water simulations showing considerably more error (~40%). The error is likely attributable a discrepancy between the simulation and experimental geometries. This discrepancy is due to an oversight in sample preparation and not a flaw in the CT scanning process of geometry creation. The volume of data generated in CFD simulation was found to be very valuable for understanding and benchmarking packing performance. Streamlines and contour plots were used to analyze the variation in performance both locally and throughout the packing stack. Significant variation was observed in flow pattern, velocity distribution, and pressure profiles throughout the column. However, the joint regions were found to be most adverse to column energy efficiency. / text
108

“How useful and applicable is the program The Underwear Rule for Greek parents? Parents' perspectives on the advantages and problems with the program: an interview study”

Michailidou, Kyriaki January 2015 (has links)
Child sexual abuse is a burning issue raising concern because of the statistics which indicate that one in five children are victims of some kind of abuse. The protective program, the “Underwear Rule” was launched by the European Council in order to inform and equip parents, caregivers and children towards this sensitive issue. The program is addressed to all European countries in the exact same form and content, with only differentiation the language. This study tries to examine theoretically and empirically the applicability of the “Underwear Rule” to Greek parents, in the sense that each country has its own cultural background and cast of mind, which differentiate the acceptance and the applicability of the Rule. This relates mainly to prior research of Kirana exploring Greek parents’ perspective towards sexual education, as well to Babatsiko’s research about developing national protective programs corresponding to local and cultural demands. An interview study has been carried out, focusing on parents’ point of view about the Underwear Rule. The analysis is based on the subjective experiences and thoughts of seven parents whose children are in the age-target group covered by the Underwear Rule. The parents’ interviews have been analyzed thematically. Overall this study argues that The Underwear Rule is a good protective program, but parents would like improvements and enrichment in order the burning topic of child sexual abuse to be covered more effectively
109

The Influence of Interviewee Social Skill and Impression Management on Structured Employment Interview Outcomes

Schneider, Leann 09 August 2012 (has links)
The purpose of this thesis was to investigate the influence of interviewee social skill on the use and effectiveness of impression management (IM), as well as interviewers’ perceptions of the use of IM during the employment interview. One hundred and nine participants completed mock employment interviews for developmental purposes. An antecedent model whereby IM partially mediated the effect of social skill on interview performance was supported for observer-coded self-promotion. In contrast, a moderator model was supported for self-reported deceptive IM, as interviewees were more likely to positively influence their interview performance with the use of deceptive IM when they were high on social skill. In addition, although interviewers were mostly inaccurate in their perceptions of deceptive IM, social skill did not moderate the amount of agreement between self- and interviewer-ratings of IM. Implications for research and practice are discussed. / Social Sciences and Humanities Research Council of Canada
110

Bi-metallic Catalyst for Hydrogen Sorption of Magnesium Hydride

Zahiri-Sabzevar, Beniamin Unknown Date
No description available.

Page generated in 0.0458 seconds