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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.
1

NUMERICAL COMPUTATIONS FOR ADIABATIC PARTICLE MOTION : Numeriska beräkningar för adiabatisk partikelrörelse

Dao, David January 2013 (has links)
Axisymmetric mirrors have no collision free radial transport, but such magnetic fields may have problems with plasma stability (the tearing instability in particular). There are some means to improve plasma stability in axisymmetric mirrors by magnetic expander tanks or axisymmetric divertors, but plasma stability can still be a challenge in axisymmetric mirrors. An alternative is to use quadrupolar magnetic fields as a robust method to overcome the stability issues. A price may then be increased radial transport if the magnetic field design is done without strict consideration of asymmetries, which could result from manufacturing errors.The computations have been done with a hybrid reactor scenario in mind. Such a case have less demands for confinement, but the demands are still challenging. Confinement for about 200 longitudinal bounces is required in a hybrid reactor. The computations carried out here have confirmed that axial asymmetry may become dangerous for plasma confinement in quadrupolar mirror machines. Asymmetry in the range of a few percentage relative error will almost surely result in a too strong radial leakage (at least without a radial electric field). The computational results made in this paper may suggest that if the manufacturing error is kept below 0.15% relative error throughout the plasma confinement region, there is then a some margin for sufficient radial confinement quality. Such accuracies ought to be possible to achieve in the manufacturing process, possible combined with compensating magnetic fields to maintain a precise magnetic field design. The precision requirements in the design is still a bit challenging.
2

Ultra-Thin AMC for Gain-Enhancement of a 94 GHz Antenna-On-Chip

Yu, Yiyang 04 1900 (has links)
The surge in transistor scaling and integration processes has driven the growth of wireless technology, especially low-cost millimeter-wave systems. Based on mainstream Silicon technology, System-on-Chip (SoC) has become an attractive approach to achieve the required high level of on-chip integration for modern wireless systems. However, the low resistivity (ρ=10 Ω-cm) and high relative permittivity (εr=11.9) of the silicon substrate are unsuitable for hosting antennas on it, because the Radio Frequency (RF) power is lost in the lossy silicon substrate, and some of it gets radiated in a certain undesired direction due to the surface waves. This has caused such antennas, typically known as Antenna-on-chip (AoC), to be poor radiators. Introducing an on-chip artificial magnetic conductor (AMC) between the substrate and the antenna can isolate the silicon substrate from the antenna and provide in-phase reflection, thereby improving the radiation performance. However, the drawback of conventional on- chip AMC is its relatively large thickness, which is extremely difficult to achieve on the thin silicon dioxide layer of typical CMOS processes (~10-15 μm). To resolve this problem, the embedded guiding structures have been designed between the periodic structure layer and the ground plane to realize an ultra-thin AMC which is suitable for thin oxide stack up of typical CMOS processes. Specifically, a patch-based AMC with embedded guiding structures has been designed for an on-chip monopole antenna operating at 94 GHz. The performance of the AMC has been studied for different resistivity substrates (from 10-3 to 103 Ω-cm). The AMC-backed on- chip antenna has been fabricated through an in-house CMOS-compatible process. The adhesion of the metallic layer to the substrate has been improved without using a seed layer, which is typically a low conductivity metal and has a negative impact on the radiation of the AoC. The measured input impedance and radiation performance of the AMC-backed AoC are fairly consistent with the simulations. It provides 5.85 dBi gain with the return loss of 16 dB at 94 GHz. According to the author’s best knowledge, this is the thinnest AMC-based AoC design in the literature.
3

Pulsed laser generation and optical fibre detection of thermoelastic waves in arterial tissue

Beard, Paul Christopher January 1996 (has links)
No description available.
4

The study of errors in synchros and resolvers using numerical methods

Burke, D. M. January 1991 (has links)
No description available.
5

Průvodcovské služby v lokalitách UNESCO / Guiding services in the UNESCO locations

Písařová, Markéta January 2010 (has links)
The master thesis contains an analysis of guiding services in all the UNESCO locations in the Czech Republic. There is a special emphasis on the current situation in Prague because the position of the capital city in the incoming tourism is unquestionable. A part of the analysis is formed with a brief comparison of Prague with Vienna and Budapest.
6

Guiding the Eye: A Non-photorealistic Solution for Controlling Viewer Interest

Piedra, Pedro A. 2010 December 1900 (has links)
In film and still photography, depth of field control is often employed to control viewer interest in an image. This technique is also used in computer animation, but, in a medium where artists have near infinite control, must we rely on replicating photorealism? This research is a viable, non-photorealistic solution to the problem of directing viewer interest. Vision is directed by reducing superfluous visual information from parts of the image, which do not directly affect the depictive meaning of that image. This concept is applied to images and animations rendered from three-dimensional, computergenerated scenes, where detail is defined as visual information pertaining to the surface properties of a given object. A system is developed to demonstrate this concept. The system uses distance from a user-defined origin as the main mechanism to modulate detail. This solution is implemented within a modeling and shading environment to serve as a non-photorealistic, functional alternative for depth of field. This approach is conceptually based on a model of human vision, specifically, the relationship between foveal and peripheral vision, and is artistically driven by various works in the disciplines of painting and illustration, that through the careful manipulation of detail, control interest and understanding within the image. The resulting images and animations produced by this system provide viable evidence that detail modulation can be used to control effectively viewer interest in an image eliminating the need to use photographic techniques like depth of field.
7

Guiding operators' attention with the help of a visual aid system

Zhou, Jiayang January 2019 (has links)
In the cutting age of industrial 4.0, automation has developed rapidly in all aspects. The emergence of the modern industrial control room has provided a new horizon to the large operation. However, the problem facing the operators is too many screens that they need to monitor at the same time which could result in fatal mistakes such as missing important alerts or failing to act on important information. With that being said, this thesis explores the possibilities of developing a visual aid system to help guide operators’ attention. With the knowledge gained from a literature review and previous efforts from ABB, a visual aid system has been developed with implementations such as unreadable screen and blinking cue guiding the operators’ attention. An experiment to evaluate the solution has also been designed and conducted with 29 participants. Both quantitative data and qualitative data have been collected and analyzed. The results suggest a strong benefit in using such a visual aid to help guide operators’ attention.
8

Planning and Teaching Compliant Motion Strategies

Buckley, Stephen J. 01 January 1987 (has links)
This thesis presents a new high level robot programming system. The programming system can be used to construct strategies consisting of compliant motions, in which a moving robot slides along obstacles in its environment. The programming system is referred to as high level because the user is spared of many robot-level details, such as the specification of conditional tests, motion termination conditions, and compliance parameters. Instead, the user specifies task-level information, including a geometric model of the robot and its environment. The user may also have to specify some suggested motions. There are two main system components. The first component is an interactive teaching system which accepts motion commands from a user and attempts to build a compliant motion strategy using the specified motions as building blocks. The second component is an autonomous compliant motion planner, which is intended to spare the user from dealing with "simple" problems. The planner simplifies the representation of the environment by decomposing the configuration space of the robot into a finite state space, whose states are vertices, edges, faces, and combinations thereof. States are inked to each other by arcs, which represent reliable compliant motions. Using best first search, states are expanded until a strategy is found from the start state to a global state. This component represents one of the first implemented compliant motion planners. The programming system has been implemented on a Symbolics 3600 computer, and tested on several examples. One of the resulting compliant motion strategies was successfully executed on an IBM 7565 robot manipulator.
9

Smart Parking Assisting System

Garisa, Shankara Sree Vatsava, Konanki Rangaiahgari, Dinesh Chakravarthi January 2022 (has links)
Cars and other automobiles are used for transportation every single day all over the world. Almost ninety percent of the households have access to at least one car. Along with this, the chance of getting into an accident has also risen. Our objective is to deal with the case of parking. Everyone must have felt anxiety about the distances while sitting inside the car. Oneway or the other way, it always leads to property damage, etc. It will be difficult for people who spend lavish money on their vehicles to see the damage. In our project, we designed a system that aids drivers with information about distances between the vehicle and a wall or obstacle. It will be even more helpful if the driver has an idea of the distance between the wall and the vehicle by visual representation not as a text because of natural instinct. A hardware setup is fixed to the walls of the garage after analyzing all the possible scenarios including skewed parking which only guides the driver. This system uses sensors like ultrasonic to get information about the distances and an LED strip to guide the driver about the distances. Depending on the distances the LED will indicate either red or green and also the number of glowing LEDs. The two signals to the LED are pre-calibrated after considering the garage spacing. This system can effectively remove the chance of accidents while parking a vehicle in the garage.
10

Analysis of Side-Polished Few-Mode Optical Fiber

Ray, Taylor J. 29 April 2019 (has links)
Side-polished fiber allows access to the evanescent field propagating in the cladding of a few-mode fiber. This cladding mode is analyzed and experimentally validated to further the design of a novel class of fiber optic devices. To do this, specific modes are excited in the polished fiber using a phase-only spatial light modulator to determine spatial mode distribution. Each mode is excited and compared to the expected field distribution and to confirm that higher order modes can propagate through side-polished fiber. Based on each mode’s distribution, a side-polished fiber can be designed so that perturbations on the polished portion of the fiber effect each mode independently. By carefully analyzing the effects of identical perturbations on each mode, it is determined that each mode can be isolated based on the geometry of the polished fiber and careful alignment of the mode field. This research has the potential to advance the development of novel fiber-based sensors and communications devices utilizing mode-based interferometry and mode multiplexing. / M.S. / Fiber optic devices have seen significant advancement since the realization of the laser and low-loss optical fiber. Modern day fiber optics are commonly utilized for high-bandwidth communications and specialized sensing applications. Utilizing multiple modes, or wave distributions, in a fiber provides significant advantages towards increasing bandwidth for communications and provides potential for more accurate sensing techniques. Significant research has been conducted in both the sensing and communication field, but mode-domain devices have the capability to significantly advance the field of fiber optic devices. This thesis demonstrates the potential for side-polished fiber geometry to effect each mode independently, thus allowing side-polished fiber to be utilized for realizing novel devices such as multiplexing devices and fiber optic sensors.

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