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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.
271

Field Emission Microscopy of Al-Deposited Carbon Nanotubes: Emission Stability Improvement and Image of an Al Atom-Cluster

Saito, Yahachi, Matsukawa, Tomohiro, Asaka, Koji, Nakahara, Hitoshi 03 1900 (has links)
No description available.
272

Near-Field Characterization of FM Transmitter Devices in Mobile Phone Applications

Khatun, MST Afroza January 2008 (has links)
Mobile Phone, without this we can’t think to pass a day in presence. We have found a rapid increase of mobile phone users from a few years ago till now. Day by day the modern technologies allow the mobile phone to become smaller, cheaper, and more reliable. This also creates new possibilities for applications and integrations of the classical broadcast systems and modern mobile phone technologies. One example is the FM transmitter in mobile phone. The FM transmitter in a mobile phone is a “cool” feature which allows listening to the music content in phone on a car or home radio.   This thesis work deals with the near field characterization of FM transmitters in mobile phone applications. The RF scientists and engineers neglect the near field zone because typical RF links operate at distances of many wavelengths away where near field effects are totally insignificant. But in this work we are interested in the near field properties of the FM transmitter. We measured the field intensity at near field and estimated the field strength at the far field region at 3 meters. To measure the field intensity and the effective radiated power we used HR1 near field scanner. As this is a new measurement approach, we made the validation of this system by measuring a reference dipole antenna at 880MHz and then compare the measured results to the CST simulation results. A basic phone model of FM transmitter has been created by CST simulation and a prototype has been made which was also used as our DUT. After validation of the near field measurement system we measured our DUTs (3 models-one cable fed prototype and two active devices) with the near field system and estimate the effective radiated power and field intensity at 3 meter. Furthermore, we measured our DUTs at 3 meter with a far field measurement system with optical fiber connection. A feasible relation between field strength and measured power was defined in order to correlate the near field scanner results with the far field measurement system.   This paper also provides a short design guide line for built in FM antennas by relating the antenna size and placement to input power and the field strength in mobile phone FM transmitter application
273

Design of an in-field Embedded Test Controller

Shah, Ghafoor, Arslan, Saad January 2011 (has links)
Electronic systems installed in their operation environments often require regular testing. The nanometer transistor size in new IC design technologies makes the electronic systems more vulnerable to defects. Due to certain reasons like wear out or over heating and difficulty to access systems in remote areas, in-field testing is vital. For in-field testing, embedded test controllers are more effective in terms of maintenance cost than external testers. For in-field testing, fault coverage, high memory requirements, test application time, flexibility and diagnosis are the main challenges. In this thesis, an Embedded Test Controller (ETC) is designed and implemented which provides flexible in-field testing and diagnostic capability with high fault coverage. The ETC has relatively low memory requirements for storing deterministic test data as compared to storing complete test vectors. The test patterns used by the ETC are stored separately for each component of the device under test, in system memory. The test patterns for each component are concatenated during test application according to a flexible test command. To address test application time (which corresponds to down time of the system), two different versions of the ETC are designed and implemented. These versions provide a trade off between test application time and hardware overhead. Hence, a system integrator can select which version to use depending on the cost factors at hand. The ETC can make use of an embedded CPU in the Device Under Test (DUT), for performing test on the DUT. For DUTs where no embedded CPU is available, there is the additional cost of a test specific CPU for the ETC. To access the DUT during the test application, the IEEE 1149.1 (JTAG) interface is used. The ETC generates test result that provides information of failing ICs and patterns. The designed and implemented versions of the ETC are validated through experimentations. An FPGA platform is used for experimental validation of the ETC versions. A set of tools are developed for automating the experimental setup. Performance and hardware cost of the ETC versions are evaluated using the ITC'02 benchmarks.
274

Using photovoltaic effect of Hg lamp on contactless electroreflectance spectroscopy to study transition mechanism of c-plane ZnO

Cheng, An-hao 05 July 2011 (has links)
Photo reflectance¡]PR¡^ and Contactless electroreflectance¡]CER¡^spectra of Zn and O-faces of a c-plane ZnO bulk have been measured at room temperature, respectively. It was found that the phase of PR is the same as that of CER for the Zn-face and they are inverted for the O-face. This indicates a polarization induced field existing in the c- plane ZnO bulk due to nonzero spontaneous polarization. In addition, a mercury lamp was focused on the ZnO sample in the CER measurements to provide a photovoltaic voltage to reduce electric field in the sample. The CER spectrum with Hg lamp is more blue-shifted and its amplitude is smaller than that without Hg lamp. Hence, the type of transitions was classified as excitonic transition. The A, B, and C excitonic transition energies were obtained by fitting experimental spectra.
275

An Analysis of the Magnetic Field of Transmission Lines and its Suppression Approaches

Su, Feng-chi 26 June 2006 (has links)
This thesis presents a computational analysis of the magnetic field of low-frequency power transmission lines, and the approaches to its suppression. First, according to the structure of Taiwan's three-phase A.C. transmission network, this research calculated the distribution of conducting wires' magnetic field under specific configuration by applying the theories of Near-field effect, Biot Savart's law, and double complex number. Second, this research explored the features of various approaches to magnetic field suppression with magnetic-field vector analyses and Matlab simulations. Finally, two magnetic-field cancellation methods, the ¡§circuit space arrangement¡¨ and ¡§time phase permutations¡¨ were adopted to investigate their magnetic effects under various structures and combinations of transmission lines. This study reveals that the magnetic field can be effectively suppressed by using appropriate configuration of transmission lines in space and phase. By applying the result to the design and construction of transmission lines, we can meet not only the requirements of magnetic field reduction, but also the needs of the least cost.
276

Analysis and Control of a Single-side Permanentmagnet Axial-flux Motor with Aluminum Stator Core

Wong, Wun-Siane 10 September 2007 (has links)
This thesis presents a systematic scheme to design the propulsive force and axial force control of a single-sided permanent-magnet axial-flux motor with aluminum stator core (SPAMA) through the detailed mathematical model and operational analysis. According to the rotating magnetic field theory combining with the recoil line characteristics of permanent magnet and the magnetic equivalent circuit, appropriate projection of the stator currents to achieve the propulsive force and axial force control can be realized. From these evaluations, a feasible operational guidance for SPAMA field oriented control (FOC) framework can be successfully developed. Finally, based on our system model and simulation results, the steady-stay characteristics of the machine can be observed.
277

Variational particle-antiparticle bound states in the scalar Yukawa model /

Ding, Bingfeng. January 2000 (has links)
Thesis (Ph. D.)--York University, 2000. Graduate Programme in Physics. / Typescript. Includes bibliographical references (leaves 100-105). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ59128
278

The Organizational Field of Crowdfunding : Emergence and Special Characteristics

Hammar, Corrie January 2015 (has links)
Crowdfunding is an online fundraising technique, where individuals or groups ask for contributions from a large number of people, i.e. “the crowd”. Crowdfunding first appeared in 2003 and has doubled its financial scope every year since 2011. Yet, very little is known about it, especially from a societal perspective. In this thesis I have attempted to understand how the organizations surrounding crowdfunding have structured themselves into an organizational filed, and also how “the crowd” might have granted this field special characteristics. This since “the crowd” is an element not earlier taken into consideration when studying field emergence. I have conducted a content analysis with data from 170 crowdfunding platforms and 190 media articles. I found that several events coincided in 2009 and opened up for the emergence of the crowdfunding field, and also that the understanding of crowdfunding’s purpose has shifted since 2003, from culture projects to start-ups. Regarding the special characteristic of the field it seems like the online nature enabled a fierce structuration pace, and also that “the crowd” constitutes an entity that cannot be captured by our traditional understanding of fields. The results suggest that when “the crowd” takes on functions in a field, the functions become invisible, and this has implications for future research regarding organizational fields.
279

Polymer Dynamics: A Self-Consistent Field-Theoretic Approach

Grzetic, Doug 08 December 2011 (has links)
We develop a self-consistent field theory of polymer dynamics, based on a functional integral approach, which is analogous to the existing equilibrium self-consistent field theory for polymers. We apply a saddle-point approximation to the exact dynamical theory, which generates a set of mean-field equations for the time-dependent density and mean force field. We also develop a method of treating the single-chain dynamics exactly, subject to this mean-field, resulting in a functional Fokker-Planck equation that must be solved along with the mean-field equations in a self-consistent manner. To test the self-consistency, we apply the theory to the simple but non-trivial case of np Brownian particles in one dimension interacting via a short-range repulsion in a harmonic external potential. Results for the non-interacting case agree with the literature. The interacting case demonstrates physically sensible interaction-dependent dynamics, such as an increased broadening of the density field when the repulsion is increased. We also examine the dynamics of a binary system with two distinct particle species. We calculate the center-of-mass trajectories for colliding distributions of species A and B, and observe that when the difference of repulsion strengths between like and unlike species chi is greater than a threshold value (between chi = 0.3 and chi = 0.4), the two species do not mix (indicating the onset of phase segregation).
280

Autumn field-feeding patterns of the wild mallard duck (Anas platyrhynchos)

Ball, Garth 31 September 1983 (has links)
Sixteen adult male and 8 adult female post moult mallards were equipped with radio transmitters, in a two year study (1977-6AHY-M and 4AHY-F; 1978-10AHY-M and 4AHY-F). Field-feeding was monitored at a lure crop and on adjacent grain fields. Ninety-two percent of the mallards radio-equipped were recorded at a field-feeding site at least once with 71% recorded field-feeding within one week. There was no significant difference in field-feeding activity between males and females. In the morning during periods of rain, mallards field-fed 0.55h longer, arriving 0.30h later and departing 0.9h later than mallards field-feeding during clear weather. The morning field-feeding period was longer in duration than the evening foeld-feeding period. Light intensity was the dominant climatological variable contributing to the arrival of mallards in the morning during periods of no rain (multiple R2=68.1%) and rain (R2=69.5%). Light appeared to act as an initiating cue for morning feeding activity. A high correlation existed between duration of stay during periods of no rain (r=0.815) and rain (r=0.860) suggesting that mallards remained longer at a field-feeding site in the morning by departing later, not arriving earlier. Light intensity was also the dominant climatological variable contributing to the arrival of mallards in the evening amongst those mallards which field-feed in both the morning and evening (R2=78.1%) and those which field-fed in the evening only (R2=63.3%). In addition, light intensity was the only contributing factor in the evening for all mallards departing a field-feeding site (R2=72.7%). Mallards were never recorded field-feeding longer than 15 minutes after there was non measurable light...

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