• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 91
  • 19
  • 17
  • 17
  • 8
  • 8
  • 5
  • 4
  • 4
  • 4
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 211
  • 41
  • 24
  • 22
  • 20
  • 19
  • 19
  • 17
  • 16
  • 15
  • 15
  • 14
  • 13
  • 13
  • 13
  • 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

The rotation process and interfaces of the nano NiO and Ag grains

Ji, Yi-jen 24 June 2010 (has links)
A nanofilm rotation method is developed to study the rotation of nanograins and the formation of various low energy interfaces. Epitaxial NiO and Ag nanofilms are prepared by ion beam sputtering onto the (100), (110), (111) and (112) surfaces of NaCl single crystal. By overlapping of the above films with an angle difference, and annealing at relatively low temperatures the nanograins are induced to rotate till a stable interface is reached. The rotation process and the stable interfaces are determined by transmission electron microscopy. Many new interfaces between mixed planes are found, and their orientation relationships and structures are analyzed. The rotation speed increase with temperature and is fast above 200oC.
72

A study of the interface formed by ZrO2/ NiO planes and by Ag mixed planes

Wu, Kuang-yao 08 July 2010 (has links)
none
73

Dual-mode ZnO thin films for piezoelectric transducers

Mao, Chun-Kai 09 August 2012 (has links)
The purpose of this thesis is to study the c-axis inclined ZnO films to produce dual-mode thin-film piezoelectric transducer. The cantilever beam vibration theory as a power generation mode in adopted to verify that the transducer is in suitable for the application in the environment for low-frequency vibration. In order to develop dual-mode thin-film piezoelectric transducer, this study uses radio-frequency magnetron sputtering method with off-axis growth to deposit ZnO films on Pt/Ti/stainless steel substrate(SUS304), the effects of deposition parameters on the characteristict of ZnO films are studied. Because zinc oxide thin-film is grown with c-axis tilt, so the piezoelectric transducer exhibits longitudinal-mode and shear-mode characteristics. The physical characteristics of ZnO thin films were obtained by the analyses of the scanning electron microscopy (SEM) and X-ray diffraction (XRD) to discuss the surfaces, cross section and crystallization of ZnO thin films. Finally, the vibration test equipment in used for the measurement of electrical properties. The open and loaded voltages of the transducers were obtained by the measurement system. The optimal deposition parameters for ZnO thin films are sputtering pressure of 5 mTorr, RF power of 150W, substrate temperature of room temperature and oxygen concentration of 50%, which were determined by physical characteristics and voltage analysis. Under the optimal parameters, the ZnO thin-films are deposited with maximum shear-mode and tilting angles of 35¢X.The transducer was one-sid loaded with a piece of metal of 0.5 g load to enhance the cantilever vibration amplitude. As the input vibration of 65 Hz and vibration amplitude of 1mm were set, the maximum output power was obtained. The maximum open circuit voltage of 19.4 V was obtained. When the output of the transducers was recetified and filtered through a 1NN5711 Schottky diode bridge rectifier and a 33nF capacitor, the maximum power of 2.05£gW/cm2 was achieved with the load resistance of 5M£[.
74

Enhancing Posterior Pelvic Tilt Exercise By Providing Motivation Inducing Feedback To The Patient

Tomsuk, Emrah 01 May 2008 (has links) (PDF)
The aim of this study is to develop a set-up that can be used by patients performing posterior pelvic tilt exercises to assess and improve the effectiveness of the exercise by visual feedbacks. Lifetime of low back pain prevalence is between %60 and %90. In other words almost everyone encounters the problem of low back pain sometime during their life. Therapeutic and protective exercises are the most important components of treatment for the low back pain. People who have mechanical based low back pain due to postural disorders, have weakness of abdominal and back muscles. Posterior pelvic tilt exercises are one of the effective types of exercises to solve this problem. These can be done standing against a wall or lying on a surface. These exercises are advised to patients generally as home exercise programs. However most patients cannot do their exercises effectively due to lack of training and control. In posterior pelvic tilt exercise, the patient is asked to straighten his/her lumbar lordosis and exert as much pressure as possible to the surface he/she is lying on. It is believed that the efficiency of the exercise is correlated with the amount of this pressure. Entertaining visual feedback may increase patient&amp / #8217 / s motivation and consequently quality of the exercise. In this experimental set-up, pressure variations were determined by three receivers which were placed under the back of the patient to provide feedback for proper posterior pelvic tilt exercises. By means of this experimental set-up training for these exercises was achieved easily and the quality of exercises was improved.
75

Flight Control Of A Tilt Duct Uav With Emphasis On The Over Actuated Transition Flight Phase

Unlu, Tugba 01 October 2009 (has links) (PDF)
In the thesis, automatic flight control system is designed for Tilt Duct Unmanned Aerial Vehicle (UAV). The vehicle is a Vertical Take-Off Landing (VTOL) type with two symmetric rotors on the wings, one aft rotor on the aft body. It behaves like a helicopter but with higher speeds in forward flight. Transition flight of the aircraft from hover to cruise or take-off to forward flight is the primary concern of the thesis study with the nonlinearities and instabilities encountered, together with the over-actuated controls in this mode. A nonlinear simulation code is developed including nonlinear equations of motion together with the nonlinear aerodynamics, environmental eects, and rotor dynamics. Trim and linearization codes are also developed. Trim conditions for the transition flight phase are calculated for two different transition scenarios. Linear controllers are developed and nonlinear controller is designed for the transition mode. Nonlinear controller uses the state dependent Ricatti equation SDRE approach by using extended linearization. Two loop approach is used in order to increase controllability. In the inner loop, attitude rates are fed back and SDRE approach is used to calculate the feedback gain matrix online. In the outer loop, vehicle attitude is controlled using the eigenvalue assignment. Blended inverse algorithm based control allocation method is used in control of the over-actuated transition phase. This algorithm is shown to be quite effective among different methods in not only generating necessary forces needed for the control, but also allocating with more control authority on the desired actuator.
76

Biomechanical responses to seated full body tilt and their relationship to clinical application

Sonenblum, Sharon Eve 19 August 2009 (has links)
The overall goal of this research is to improve the use of seated tilt to increase function, health and quality of life for people using power wheelchairs. Specifically, the objective of this dissertation is to evaluate the biomechanical responses to seated full body tilt and their relationships to the actual use of tilt-in-space wheelchairs. In the first phase of this study, researchers remotely monitored how 45 fulltime power wheelchair users used their tilt-in-space systems. Participants spent an average of 12.1 hours in their wheelchair each day. They spent more than 2 hours seated at positions greater than 15° and performed tilts of 5° or greater every 27 minutes, but rarely performed tilts past 30°. Two distinct types of tilt behavior were identified: uni-modal (staying at a single position more than 80% of the time) and multi-modal (staying at a single position less than 80% of the time). Participants in the multi-modal group tilted significantly more frequently (4 times per hour) than the uni-modal group, and did not have a single typical position. Participants without sensation were more likely to exhibit uni-modal behavior. In the second phase of this study, researchers used interface pressure measurements and laser Doppler flowmetry to study changes in localized loading and superficial blood flow at the ischial tuberosities across different amounts of tilt. Eleven participants with spinal cord injuries were studied in a laboratory setting. Results showed that biomechanical responses to tilt were highly variable. Pressure reduction at the ischial tuberosity was not present at 15°, but did occur with tilts to 30° and greater, and could be explained by the tilt position and upright pressure. Unlike pressure, blood flow increased with all tilts from an upright position, but did not increase when tilting from 15° to 30°. Only 4 of 11 participants had a considerable increase (≥10%) in blood flow at 30° tilt, whereas 9 participants did during maximum tilt (i.e., 45°-60°). Based on the results of this study, tilting for pressure reliefs as far as the seating system permits is recommended to maximize the potential for significant blood flow increases and pressure relief.
77

Essays in Financial Economics

Zhang, Fan January 2014 (has links)
This dissertation presents three essays. The first essay finds that the household risky ratio, the ratio of high risk assets over low risk assets directly owned by households, is a strong negative predictor of the equity premium on the US stock market. The predictability is robust to definition of the asset classes, first versus second half of sample, and the finite-sample bias of Stambaugh (1999). The predictability is stronger than, and not subsumed by popular predictors like price-earnings ratios, yield spread, equity share of issues, or consumption-wealth ratios. The main predictive power is decomposed into three similar parts: 1) the household tilt of risky assets, which is novel and generally orthogonal to known predictors; 2) a valuation ratio component; and 3) an issuance component of high risk versus low risk assets. / Economics
78

Modified Design of a Precision Planter for a Robotic Assistant Farmer

2014 February 1900 (has links)
Modified design of a planter to be attached to a mobile robot, was the main objective of this project. This research project was part of a larger project, called “Developing robotics assisted technology for farming”. The main motivation for this research project is the fact that mobile robot, is an electric powered vehicle with limited power and pulling force. Thus, a customized planter with a customized connection mechanism should be designed. Besides, it should require less draft force compared to existing planters so that it can be pulled by the mobile robot. The developed planter should have the same efficiency as the existing planters in seeding. To find the forces between soil engagement tool (disc coulter) and soil, experiments were designed and performed in the Linear Soil Bin at University of Saskatchewan. Disc and tilt angle of a disc coulter was changed and draft, vertical and side forces applied to it were measured to find the disc and tilt angle combinations that results in minimum draft force. Experiments showed that 7° disc angle and 25° tilt angle provides the least draft force compared to other disc angle and tilt angle combinations. Then, using the knowledge obtained from literature and the soil bin experiments, a planter was designed conceptually and in detail, based on the existing CNH planter. For further analyses computer modeling was performed. The whole planter was modeled in 3D, using SolidWorks. Stress analysis was performed in ANSYS Workbench to calculate safety factor of the designed parts. Two prototypes were fabricated and were attached to the mobile robot for field tests. Tests were performed in indoor settings to measure the total draft force required to pull developed planters. Draft force was very close to the value that was calculated in design stage. Results showed that an average of 460 N pulling force is required to pull one row planter for 50 mm depth of cut, which can be compared to n existing CNH corn planter that requires a pulling force of between 900 N to 1300 N. Seed drop accuracy and function of the developed planters in opening and closing a packed soil in presence of residue, were also observed in outdoor tests.
79

ARE MEASUREMENTS OF HIP EXTENSION AND ANTERIOR PELVIC TILT TAKEN FROM STATIC PHOTOGRAPGHS DURING A CONSTRAINED FORWARD LUNGE TEST VALID AND RELIABLE IN HEALTHY ADULT RUNNERS?

Gray, Jason 10 August 2011 (has links)
The aim of this study was to determine the concurrent validity, test-retest intra-rater reliability, and test-retest inter-rater reliability of photographic measures of anterior pelvic tilt range of motion (APT ROM) and hip extension ROM range of motion (HE ROM) during a constrained forward lunge test (CFLT) in healthy adult runners. Measurements of start, end, and range of motion (ROM) variables for APT and HE motion were taken from an Optorak kinematic measurement system and from printed photographs extracted from digital video footage using a protractor. A total of 13 healthy adult male and female recreational runners participated in the study. Measures of APT ROM and HE ROM were found to be valid compared to Optorak measures, with intraclass correlation coefficients (ICC) of 0.94 and 0.99 respectively, and limits of agreement of -1.42 ± 1.99 degrees and 0.41 ± 2.13 degrees respectively. APT ROM and HE ROM demonstrated high between-day intra-rater reliability with ICCs ranging from 0.75 to 0.91 and within-day inter-rater reliability with ICCs ranging from 0.86-0.90. For between day intra-rater measurements smallest detectable differences (SDDs) ranged from 5.59 to 4.12 for APT ROM and from 9.08 to 11.08 for HE ROM. The present study suggests that photographic measurements of APT ROM and HE ROM during a CFLT are valid and reliable in healthy adult runners; however, these measurements display a low sensitivity with respect to detecting changes between trials.
80

A-Coord input: augmented pen-based interactions by combining auxiliary input channels

Hasan, Mohammad Khalad 10 April 2012 (has links)
Pen-based interactions are becoming widely popular on a variety of devices, including tabletPCs, mobile devices and tabletop systems. The digital pens and tablets have evolved considerably and served users in creative industries. A digital pen can sense various auxiliary inputs, such as tilt, pressure and roll. Researchers have explored properties of each channel in isolation of another. Since the human wrist and fingers can operate multiple input channels simultaneously, a natural progression warrants examination of controllability when these channels are operated simultaneously. In this thesis, I explore a class of interaction techniques, a-coord input, which requires users to control two auxiliary channels simultaneously. Through experiments, I explore the design space of a-coord input and investigate the effect of changing the order in which the channels are combined. Furthermore, I investigate its effectiveness for discrete and continuous selection tasks. Finally, this thesis shows the value of a-coord input through several applications.

Page generated in 0.0463 seconds