• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 845
  • 372
  • 55
  • 45
  • 21
  • 20
  • 20
  • 20
  • 20
  • 20
  • 20
  • 14
  • 5
  • 5
  • 5
  • Tagged with
  • 1589
  • 1589
  • 445
  • 374
  • 372
  • 254
  • 238
  • 215
  • 212
  • 198
  • 194
  • 192
  • 182
  • 180
  • 176
  • 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

An empirical study of the factors affecting individual performance using a modified task-technology fit approach

秦瑀, Chun, Yu, Grace. January 2005 (has links)
published_or_final_version / abstract / Business / Master / Master of Philosophy
72

Understanding online knowledge sharing: an interpersonal relationship perspective

Ma, Wai-kit, Will, 馬偉傑 January 2009 (has links)
published_or_final_version / Education / Doctoral / Doctor of Philosophy
73

Motivated to adopt : understanding the digital effectiveness divide (DED) in volunteerism

Harrison, Yvonne Denise. 10 April 2008 (has links)
No description available.
74

A Study of How the Use of High Depreciation Rates Creates Resistances to the Diffusion of Technological Innovation

Ball, Milton K. 08 1900 (has links)
No description available.
75

The role of digital technologies in human-nature relationships

Verma, Audrey January 2016 (has links)
While technology has widely been formulated as antithetical to nature, there has been an increased adoption of digital set-ups to promote and enact environmental conservation. This thesis thus examined a range of digital technologies more commonly used for nature-related activities (for example, mobile applications for crowdsourcing data, satellite tracking and mapping facilities, and visual imaging equipment such as cameras and sonar devices) with two objectives. First, at an applied level, the research sought to locate the new set-ups being used, and to unfold the technical, practical and relational issues emerging from this use. Second, at a more abstract level, the research aimed to better understand the sociological implications of deploying these technologies, in terms of the definitions of 'nature' being 'produced' and how the devices might be (re)shaping human-nature relationships. Four areas were studied: wildlife monitoring and recording, public engagement efforts by conservation organisations, conflict management, and digital art production. These contexts form the data chapters of this thesis, and the findings result from an inter-disciplinary qualitative social scientific research enquiry, framed by a constructionist perspective. With regard to the first aim, this research found that the technologies used by organisations and practitioners had the capacity to increase public participation as well as the quantity and quality of nature-related data and information, and could contribute to the formulation of environmental conservation strategies. However, these capacities did not come without issues such as the relegation of public participants to passive roles and struggles over legitimacy in terms of production and interpretation of data wrought from new devices. In relation to the second aim, this research found that digital technological set-ups (re)configured the ways in which wildlife in particular was seen and understood, and revealed both enmeshment and persistent binaries along the emotion/cognition and nature/culture axes. These findings highlight the role of emotions in conservation, and point to increasing complexities in how humans define and relate to nature.
76

From Tin to Pewter: Craft and Statecraft in China, 1700-1844

Wang, Yijun January 2019 (has links)
This dissertation examines the transmissions of technology and changes in the culture of statecraft by tracing the itinerary of tin from ore in mines to everyday objects. From the eighteenth century, with the expansion of the Qing empire and global trade, miners migrated from the east coast of China to the southwest frontiers of the Qing empire (1644-1912) and into Southeast Asia, bringing their mining technology with them. The tin from Southeast Asia, in return, inspired Chinese pewter artisans to invent new styles and techniques of metalworking. Furthermore, the knowledge of mining, metalworking, and trade was transferred from miners, artisans, and merchants into the knowledge system of scholar-officials, gradually changing the culture of statecraft in the Qing dynasty. This dissertation explores how imperial expansion and the intensive material exchange brought by global trade affected knowledge production and transmission, gradually changing the culture of statecraft in China. In the Qing dynasty, people used tin, the component of two common alloys, pewter and bronze, to produce objects of daily use as well as copper coins. Thus, tin was not only important to people’s everyday lives, but also to the policy-making of the Qing state. In this way, tin offers an exceptional opportunity to investigate artisans and intellectuals’ approach to technology, while it also provides a vantage point from which to examine how Qing bureaucrats managed the world, a world of human and non-human resources. My dissertation stands at the intersection of the history of science and technology, art history, intellectual history, and the history of global trade. It broadens the scope of the history of science in China by demonstrating how artisans’ practice was crucial to the production of mining treatises. It contributes to the study of science, technology, and society by showing that the transmission of and innovations in technology should be situated in the context of social, cultural, trade, and ecological networks. Finally, I argue that mid-Qing scholars’ efforts to collect practical knowledge changed the culture of governance from Confucian moral didacticism to technocratic epistemology. Qing bureaucrats, Manchu and Han alike, utilized practical knowledge from artisans and merchants in their policy-making process. By emphasizing the entanglement of technology and statecraft, my project contributes to intellectual history and enhances our understanding of the logic of bureaucracy of the Qing empire. My dissertation consists of five chapters. Each chapter uses different methodologies and covers different geographical regions. Chapter One engages with the history of science by demonstrating how scholars translated and codified miners’ vernacular knowledge of mining into mining treatises. Chapter Two examines the semi-autonomous mining community in Yunnan to illustrate that the social organization of miners, which I define as the “social technology” of mining, contributed to the formation of the capital- and labor- intensive mining industry. Chapter Three moves to the island of Bangka (in present-day Indonesia) and focuses on the transmission of mining technology from China to Southeast Asia. Through comparison, I show that the miners in Yunnan and Bangka formed similar (semi-)autonomous social organizations. I argue that it was this social technology that enabled the transmission of Chinese mining technology across geographical regions and laid the foundation for the Chinese dominance of the mining industry in Bangka. The cases of Chinese mining technology in Yunnan and Bangka challenge the modern understanding of technology by showing that technology was not just about tools and machines. Before the 1850s, both Qing bureaucrats and European colonizers considered the social organization of mining to be critical to technological progress. Chapter Four moves back to China to study the formation of Guangdong style pewter. Utilizing visual and material sources, I examine how the introduction of tin from Southeast Asia led to innovations in metallurgy, and how European silver and porcelain inspired stylistic changes. I argue that technology and innovations should be understood in the context of social, economic, material and ecological networks. The final chapter moves to Beijing and Jiangnan area to engage with the institutional history of the Qing empire. Through a case study of monetary reform undertaken in 1740, this chapter reveals that Qing bureaucrats acquired and applied practical expertise to their administrative work. Through their close interactions with artisans and merchants, Qing bureaucrats developed a distinctive vision of statecraft (jingshi). Before the late nineteenth century, the sovereignty of the Qing state was not exercised in the extraction and monopoly over natural resources. Instead, the Qing state relied on the market to acquire most of the natural resources they needed. By focusing on tin, this dissertation shows that the Qing state exercised its political power through material production and paid more attention to the management of skilled labor, capital, and the proper allocation of human and non-human resources.
77

Ensemble Learning Algorithms for the Analysis of Bioinformatics Data

Unknown Date (has links)
Developments in advanced technologies, such as DNA microarrays, have generated tremendous amounts of data available to researchers in the field of bioinformatics. These state-of-the-art technologies present not only unprecedented opportunities to study biological phenomena of interest, but significant challenges in terms of processing the data. Furthermore, these datasets inherently exhibit a number of challenging characteristics, such as class imbalance, high dimensionality, small dataset size, noisy data, and complexity of data in terms of hard to distinguish decision boundaries between classes within the data. In recognition of the aforementioned challenges, this dissertation utilizes a variety of machine-learning and data-mining techniques, such as ensemble classification algorithms in conjunction with data sampling and feature selection techniques to alleviate these problems, while improving the classification results of models built on these datasets. However, in building classification models researchers and practitioners encounter the challenge that there is not a single classifier that performs relatively well in all cases. Thus, numerous classification approaches, such as ensemble learning methods, have been developed to address this problem successfully in a majority of circumstances. Ensemble learning is a promising technique that generates multiple classification models and then combines their decisions into a single final result. Ensemble learning often performs better than single-base classifiers in performing classification tasks. This dissertation conducts thorough empirical research by implementing a series of case studies to evaluate how ensemble learning techniques can be utilized to enhance overall classification performance, as well as improve the generalization ability of ensemble models. This dissertation investigates ensemble learning techniques of the boosting, bagging, and random forest algorithms, and proposes a number of modifications to the existing ensemble techniques in order to improve further the classification results. This dissertation examines the effectiveness of ensemble learning techniques on accounting for challenging characteristics of class imbalance and difficult-to-learn class decision boundaries. Next, it looks into ensemble methods that are relatively tolerant to class noise, and not only can account for the problem of class noise, but improves classification performance. This dissertation also examines the joint effects of data sampling along with ensemble techniques on whether sampling techniques can further improve classification performance of built ensemble models. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
78

Truss climbing robot for space station: design, analysis, and motion control. / CUHK electronic theses & dissertations collection

January 2012 (has links)
近年來,空間機器人被廣泛應用於低地球軌道的空間服務中,其中包括太空船艙內、艙外的活動。因應艙外的活動,空間機器人經常以地面工業用機械臂的形式設計,並擁有相似的關節配置。空間機械臂的關節配置,主要可以分成兩類。第一類是六自由度空間機械臂,例如,太空梭遙控機械手系統SRMS,工程試驗衛星七號RTS-VII '和日本實驗模組遙控器系統JEMRMS 。另一類是七自由度空間機械臂,例如,歐洲機械臂ERA和空間站遠距離機械手系統SSRMS。他們不但能在空間站上完成不同的操作任務,而且能於空間站上進行攀爬。 / 在一個自由飄浮的環境中,空間機械臂的運動會影響太空站的姿態。因此,空間站的姿態穩定對維持太陽能板的接收和系統通訊的信號強度發揮非常重要的作用。大部份太空站姿態穩定的研究都集中於對機械臂的操作運動進行控制。然而,針對機械臂的移動進行優化的研究卻不多。由於空間機械臂的工作空間有限,在空間站上的移動能力是必要的,因此該運動對空間站的影響是無法避免。 / 有見及此,本論文提出一種新型空間站移動技術,從而減低因機械臂移動時對空間站造成的干擾。在維持現有空間機械臂的關節配置下,提出種結合驅動輸和傳統機械手抓優點的新型手抓概念。為了實現這種新型手抓概念,本論文提出了種新型的支架攀爬機械人,名為Frambot' 並在Frambot上實現了新式手抓的設計與應用。Frambot 的設計主要針對不能進行包圍性抓緊的方型析架進行攀爬,手抓的握持力是通過壓縮彈簧而產生,實現低能耗攀爬,提高Ftambot在析架上的工作時間。為了提高Ftambot在析架攀爬時的穩定性,本論文在Ftambot設計了個簡單、不需要傳感器反饋的傾斜修正結構。另外,在Frambot 的平臺上實驗了新式的攀爬運動,從而證明利用驅動輪的原理在析架上進行攀爬的可行性。 / 基於這種新型的手抓,本文為空間機械臂設計出新式空間站移動步履,並分析新式空間站移動步履對空間站造成的干擾。由於傳統的空間機器人系統建模是針對於機械臂的操作運動,因此本文針對機械臂利用驅動輪移動時,對空間站的姿態變化進行建模,並建立一個實驗平臺去對該模型進行驗證。此外,利用空間機械臂的系統模型,對新式的移動步履進行動態運動仿真。透過和傳統的移動步履進行比較,總結出新式的移動步履在空間站的姿態影響和能量需要都是最低的。 / 在一個自由飄浮的環境中,空間機械臂的步履時間越長,對太空站的干擾就越大。另外,空間站的能源是有限的,所以減低空間機臂對空間站的能耗十分重要。本論文考慮到實際的應用,空間機械臂需要移動到空間站上不同的地點完成操作任務,因此提出了空間機械臂在桁架移動時的路徑規規劃方案,目的在於對路徑的總長度和能量需求進行優化。本文提出的路徑規劃演算法,透過利用遺傳演算法,對開型和閉合路徑進行優化。此外,在演算法中引多個新的概念,從而改善遺傳演算法的收斂速度和結果。最後,通過不同類型的仿真,對路徑規劃演算法的性能進行評估。 / The application of space robots has become more popular in performing tasks such as Intra and Extra Vehicular Activities (EVA) in Low Earth Orbit. For EVA, space robots were always designed as a chain-like manipulator with a joint configuration similar to on the earth robotic arm. Based on their joint configuration, they can be classified into two main categories. The first one is the six degrees of freedom (DOF) robotic arm including Shuttle Remote Manipulator System (SRMS), Engineering Test Satellite No. 7 (ETSVII), the Main Arm (MA) and the Small Fine Arm (SFA) of Module Remote Manipulator System (JEMRMS). The other group is the seven-DOF space robotic arm which includes European Robotic Arm (ERA) and Space Station Remote Manipulator System (SSRMS), or Canadarm2. They not only perform manipulation tasks, but also be able to navigate on the exterior of the International Space Station (ISS). / In a free floating environment, motions of a space robotic arm cause the attitude change of a space station because of their dynamic coupling effect. Hence, the stabilization of the space station attitude is important to maintain the electrical energy generated by the solar panels and the signal strength for communication. Most of research in this area focuses on the motion control of a space manipulator through the study of Generalized Jacobian Matrix. Little research has been conducted specifically on the design of locomotion mechanism of a space manipulator. / This dissertation proposes a novel methodology for the locomotion on a space station which aims to lower the disturbance on a space station. Without modifying the joint configuration of conventional space manipulators, the use of a new gripping mechanism is proposed which combines the advantages of active wheels and conventional grippers. To realize the proposed gripping mechanism, this dissertation also presents the design of a novel frame climbing robot (Frambot) which is equipped with the new gripping mechanism, named movable gripper (MovGrip). It is capable of climbing non-enclosable rectangular trusses and the gripping force is generated by the compression of springs. Therefore, the energy consumption in static gripping is zero which allows itself to stay on a truss for a long time. To enhance the climbing stability, a simple and sensor-free auto-tilting correction mechanism is designed. Based on the robot prototype, novel climbing gaits are designed and realized and this verifies the feasibility of using wheels motion in climbing trusses. / With the use of the proposed gripping mechanism, new gaits are designed for space manipulators and the corresponding disturbance on a space station is analyzed. Since conventional modeling of a space station system focuses on manipulation tasks, this dissertation extends the model to formulate the dynamic coupling effect during wheels navigation. To verify the formulations, an experimental platform is designed and developed. Based on the system model, the proposed gaits are simulated and the results are compared with conventional gaits. From the simulation results, it can be concluded that the proposed gaits are better than conventional gaits in terms of minimum dynamic disturbance and energy demand on a space station. / In a free floating environment, the longer a gait is performed, the greater the disturbance is generated on a space station. Also, the energy source of a space station is limited and the minimization of the energy consumption of a robot is important. Therefore, this dissertation also proposes a path planning algorithm which aims to minimize the total traveling distance and energy demand when a space manipulator is commanded to reach a target position for certain missions. For the proposed algorithm, both closed and open paths are considered and the optimizations are based on the conventional genetic algorithm. To enhance the convergent rate and final solutions, several novel concepts are introduced. Different simulation are performed and the results are presented to evaluate the performance of the proposed path planning algorithm. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chung, Wing Kwong. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 164-172). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Related Work --- p.2 / Chapter 1.3 --- Motivation of the Dissertation --- p.9 / Chapter 1.4 --- Organization of the Dissertation --- p.10 / Chapter 2 --- Design Principles of Movable Gripper --- p.12 / Chapter 2.1 --- Preliminary Gripper Design --- p.12 / Chapter 2.2 --- Static Model: Gripping Force --- p.14 / Chapter 2.3 --- Dynamic Model: Tractive Force --- p.19 / Chapter 2.4 --- Anti-slip Strategy --- p.23 / Chapter 2.4.1 --- Vertical Truss Climbing --- p.24 / Chapter 2.4.2 --- Horizontal Truss Climbing --- p.27 / Chapter 2.4.3 --- Right-side-up Truss Climbing --- p.29 / Chapter 2.4.4 --- Arbitrary gripping orientation analysis --- p.31 / Chapter 3 --- Design of a Novel Frame Climbing Robot --- p.36 / Chapter 3.1 --- Introduction --- p.36 / Chapter 3.2 --- Mechanical Design --- p.40 / Chapter 3.2.1 --- Gripper Jaw --- p.42 / Chapter 3.2.2 --- Parallel Gripping Mechanism --- p.43 / Chapter 3.2.3 --- Rotation Axis of Wheels --- p.44 / Chapter 3.2.4 --- Body Linkage --- p.45 / Chapter 3.3 --- Design of Climbing Gaits --- p.48 / Chapter 3.3.1 --- Motion simulation --- p.48 / Chapter 3.4 --- Experiments and Results --- p.52 / Chapter 3.4.1 --- Grasp’s Contact --- p.52 / Chapter 3.4.2 --- Tilting Correction Capability --- p.53 / Chapter 3.4.3 --- Load Carrying Capability --- p.53 / Chapter 3.4.4 --- Performance of Frambot --- p.57 / Chapter 3.5 --- Summary --- p.60 / Chapter 4 --- Modeling Analysis: Robot and Space Station --- p.61 / Chapter 4.1 --- Introduction --- p.61 / Chapter 4.2 --- Modeling of a space station system --- p.62 / Chapter 4.3 --- Kinematics --- p.66 / Chapter 4.4 --- Linear and Angular Momentums --- p.68 / Chapter 4.5 --- Dynamics --- p.69 / Chapter 4.6 --- Modeling Analysis --- p.71 / Chapter 4.7 --- Summary --- p.84 / Chapter 5 --- Modeling Analysis: Disturbance in Space Station --- p.85 / Chapter 5.1 --- Introduction --- p.85 / Chapter 5.2 --- Categories of Locomotion --- p.86 / Chapter 5.2.1 --- Joint Configurations --- p.86 / Chapter 5.2.2 --- Linear Locomotion --- p.87 / Chapter 5.2.3 --- Turning --- p.88 / Chapter 5.2.4 --- Exterior Transition --- p.93 / Chapter 5.3 --- Analysis of Dynamic Disturbance --- p.96 / Chapter 5.3.1 --- Linear Locomotion --- p.97 / Chapter 5.3.2 --- Turning --- p.103 / Chapter 5.3.3 --- Exterior Transition --- p.107 / Chapter 5.4 --- Analysis of Energy Demand --- p.113 / Chapter 5.5 --- Summary --- p.117 / Chapter 6 --- Global Path Planning --- p.122 / Chapter 6.1 --- Shortest Distance Path Planning --- p.124 / Chapter 6.1.1 --- Problem Description --- p.127 / Chapter 6.1.2 --- The Framework of Genetic Algorithm --- p.128 / Chapter 6.1.3 --- Simulation Study and Discussion --- p.135 / Chapter 6.2 --- Minimum Energy Demand Path Planning --- p.144 / Chapter 6.2.1 --- Problem Description --- p.147 / Chapter 6.2.2 --- The Framework of Genetic Algorithm --- p.148 / Chapter 6.2.3 --- Simulation Study and Discussion --- p.154 / Chapter 6.3 --- Summary --- p.159 / Chapter 7 --- Conclusions --- p.160 / Chapter 7.1 --- Contributions --- p.160 / Chapter 7.1.1 --- Design a New Gripping Mechanism for Truss Climbing Robot --- p.160 / Chapter 7.1.2 --- Design and Develop a Novel Truss Climbing Robot --- p.161 / Chapter 7.1.3 --- Formulate and Analyze the Disturbance on a Space Station Under different Gaits --- p.161 / Chapter 7.1.4 --- Develop a Global Path Planning Algorithm for the Minimization of Total Traveling Distance and Energy Demand --- p.162 / Chapter 7.2 --- Recommendation for Future Research --- p.162 / Chapter 7.2.1 --- Design Optimization --- p.162 / Chapter 7.2.2 --- Autonomous Truss Climbing --- p.163 / Chapter 7.2.3 --- Multicriteria Path Planning Algotirhm --- p.163
79

Innovation adoption in naval ship design.

Leopold, Reuven January 1977 (has links)
Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Ocean Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / Ph.D.
80

Success versus survival : the dilemma of high technology firms

McCarthy, Patricia Susan, Plantholt, Barbara Ann, Riordan, Sheila Marie January 1981 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Alfred P. Sloan School of Management, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND DEWEY. / Includes bibliographical references. / by Patricia Susan McCarthy, Barabara Ann Plantholt and Sheila Marie Riordan. / M.S.

Page generated in 0.0418 seconds