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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.
221

Algoritmické a vysokofrekvenční obchodování na kapitálovém trhu / Algorithmic and high-frequency trading on capital market

Kádě, Lukáš January 2019 (has links)
Algorithmic and high-frequency trading on capital market Abstract The subject of this diploma thesis is legal regulation and development of regulation of algorithmic and high-frequency trading on capital market within Community Law but also within several European countries, USA and Japan. The aim of this diploma thesis is to define terms of algorithmic and high-frequency trading, which were not thoroughly regulated until lately, to outline development of legal regulation, to compare different approaches to their regulation in different countries and to assess the phenomenon of algorithmic and high- frequency trading. The diploma theses uses descriptive method to define the fundamental terms and discuss positive legal framework. It also uses deduction for assessment and comparative method to examine different approaches to legal regulation in different countries. The first chapter characterizes capital market as a place in which algorithmic and high- frequency trading takes place, including its historical development, participants and supervisory authorities. The second chapter defines terms of algorithmic and high-frequency trading considering their historical development and both mutual similarities their differences and their characteristics. It also includes an analysis of their key aspects and related...
222

The Influence of High Frequency Hearing Loss on the Distortion Product Otoacoustic Emissions in Tinnitus Subjects with Normal Hearing Thresold (0,25-8kHz)

Fabijańska, Anna, Smurzynski, Jacek, Kochanek, Krzysztof, Bartnik, Grazyna, Raj-Koziak, Danuta, Skarzynski, Henryk 01 January 2012 (has links)
Aim of the study: To evaluate the influence of high frequency hearing loss (>8000 Hz) on distortion product otoacoustic emissions registered in the frequency range from 0,5 to 8 kHz. Material and methods: 280 ears with tinnitus and normal hearing (0.25–8 kHz) divided into 3 groups depending on the degree of high frequency hearing loss: group A – hearing threshold up to 20 dB for 10, 12.5, 14 and 16 kHz (68 ears); group B – hearing threshold 25–40 dB HLfor at least one of four EHfs (93 ears); group C – hearing threshold above 40 dB HL for at least one of four EHFs (119 ears). For each group mean audiogram and DP-gram were obtained and statistical analysis was used for comparison across these groups. Results: Mean DPOAE values in group C were significantly lower in comparison with group A for the frequency range 2–8 kHz, and in comparison with group B were significantly lower for the frequency range 4–8 kHz. Conclusions: High frequency hearing loss (above 8 kHz) has a relevant influence on distortion product otoacoustic emissions registered at frequencies below 8 kHz in tinnitus patients. The greater is hearing loss above 8 kHz, the lower is DPOAE value below 8 kHz.
223

CLEANLINESS ASSESSMENT OF STEEL BARS PRODUCED FROM A HIGH FREQUENCY INDUCTION FURNACE

Hayford, Frank January 2011 (has links)
To stay competitive in the steel industry, steelmakers are utilizing different production methods to reduce production cost without compromising on the quality of their products. In steelmaking, the production process plays a significant role on the steel cleanliness. Recent increasing demands on the cleanliness level therefore require optimization of production process to meet the requirement. Often, the types and distribution of non-metallic inclusions in steel determines the steel cleanliness. In order to optimize the production process, complete assessment of the non-metallic inclusions in the steel is necessary, leading to implementation of measures to control and/or remove non-metallic inclusions in the steel. The present study was performed to investigate the cleanliness level of steel bars produced from a high frequency induction furnace (HF) route at Uddeholms AB. Experimental studies were carried out and characteristics such as number, composition, size distribution and morphology of non-metallic inclusions were investigated. Total oxygen and total nitrogen content were also measured for indirect assessment. Further, the production operations at the HF were observed and evaluated to determine their influence on the inclusion characteristics. The characteristics obtained were compared with characteristics of inclusions in steel bars produced from an electric arc furnace production (EAF) route at Uddeholms AB and a competitor producer sample. The results showed that the level of cleanliness varies from different production routes and is hence dependent on the process at each production route. The number, maximum and mean size of inclusions were found to be higher in the HF route compared to the other routes. More so, there were differences in the types of oxide inclusions observed from each process route. However, sulphide inclusions exhibit similar characteristics from the different process routes. Further, the compositions of oxide inclusions observed from the HF route were found to be closely related to the steel chemistry. More importantly, the types of inclusions formed in the HF route were found to be sensitively affected by the extent of aluminium and calcium contents in the steel. Thus, the oxide inclusion types in the HF samples could be traced to the extent of different additions and operations such as deoxidation and calcium treatment that were carried out during the steelmaking process.
224

High Frequency Magnetic Core Loss Study

Mu, Mingkai 22 March 2013 (has links)
The core used to build power inductors and transformers are soft magnetic materials. When there is alternating external field, the magnetic moments rotate and consume energy, which is the core loss. The core loss depends on the AC flux frequency, amplitude, waveform, DC bias and temperature. These dependences are nonlinear and difficult to predict. How to measure, model and analyze the core loss is a challenge for decades. In this dissertation, two new core loss measurement methods are introduced first. These two methods use the reactive cancellation concept to reduce the sensitivity to phase discrepancy, which will destroy the accuracy in classic two-winding method for high frequency high quality factor sample measurements. By using the new measurement techniques the accuracy can be improved by several orders. The first is for sinusoidal waveforms, and the second is for non-sinusoidal wave. The new methods enable high frequency core loss characterization capability, which will help scientists and engineers on material research and inductor/transformer design. Measurement examples, considerations and error analysis are demonstrated and discussed in detail. With the measurement techniques, the core loss under rectangular AC voltage and DC bias current are investigated. A new core loss model named rectangular extension Steinmetz equation (RESE) is proposed based on the measurement results. The new model is shown to be more accurate than the existing core loss models. Several commercially available MnZn ferrites are characterized and modeled. Other than conventional MnZn ferrite materials, three commercial LTCC ferrite materials are characterized for integrated power supply applications. Based on characterized properties of these LTCCs, a group of new LTCC ferrites are fabricated and tested. The new LTCC is fabricated by laminating commercial LTCC tapes and co-firing. The new LTCC is demonstrated to have over 50% more inductance over the commercial LTCC materials. This work indicates that the power electronics engineers should work with material engineers to get the optimum material for a given application. In the last part, the core loss of the partially saturated lateral flux planar inductor is analyzed. The challenge of the analysis is the complexity of the distribution of bias field and flux density in a highly biased planar inductor. Each point in the core is working at different excitation and bias condition, and the core loss density is very non-uniform. The proposed method combines the characterization tested in previous chapters and the commercial finite element tool. Experiments verified that the calculation errors are within about 10%. In conclusion, the research in this dissertation proposed a complete solution to measure, model and analyze the high frequency core loss. This solution will not only facilitate fundamental research on physics understanding and material innovation, but also development of power electronics and RF applications. / Ph. D.
225

Numerical Analysis of Pulsed Jets in Supersonic Crossflow using a High Frequency Actuator

Castelino, Neil January 2021 (has links)
No description available.
226

Estimation of Cutting Forces in Vibration Assisted Drilling System Using Augmented Kalman Filter

Nadeem, Kashif 04 May 2022 (has links)
Vibration assisted drilling (VAD) is a type of machining process in which high-frequency vibrations with a small amplitude are induced in the cutting tool to improve the cutting process of hard and brittle materials. These vibrations create an unsteady repetitive processing effect which eventually reduce the cutting forces. It is also crucial to measure these forces in some way because their knowledge directly aids in determining the best machining parameters. Direct and indirect methods can be used to measure these forces, but due to serious limitations of direct measurement methods, an indirect measurement method is required which is capable of online monitoring of high-frequency cutting forces. In this thesis, an indirect method is proposed to estimate thrust force and torque from the voltage signal generated by piezoelectric sensor and torsional deflection signal measured through piezoelectric accelerometer. The estimation of two input signals requires a multi-input multi-output (MIMO) model of VAD system which is developed using Receptance Coupling and Substructure Analysis (RCSA) method. Experimental and numerical methods are used to validate the constituent single-input single-output (SISO) transfer functions of the MIMO model. As the estimated forces are distorted by the dynamics of VAD structure, a Kalman Filter is employed to compensate the dynamics. The accuracy and similarity of results is determined by comparing the estimated cutting force values with the force measured from a load cell in time and frequency domain. The reported experimental results confirm the possibility of using Kalman Filter in estimating high-frequency forces generated in VAD process. / Graduate
227

Characteristics of the Audiometric 4,000 Hz Notch (744,553 Veterans) and the 3,000, 4,000, and 6,000 Hz Notches (539,932 Veterans)

Wilson, Richard H., McArdle, Rachel 25 March 2013 (has links)
The purpose of this study was to examine the prevalence and characteristics of audiograms that are notched (1) at 4,000 Hz and (2) at 3,000, 4,000, and/or 6,000 Hz. Bilateral audiograms from 1,000,001 veterans were obtained from Department of Veterans Affairs archives; after "cleaning" algorithms were applied, 744,553 participants (mean age = 63.5 yr) were included in the 4,000 Hz notch analysis (group 1) and 539,932 participants (mean age = 62.2 yr) were included in the 3,000, 4,000, and/or 6,000 Hz notch analysis (group 2). A notch was defined when the threshold at the notch frequency (3,000, 4,000, or 6,000 Hz) minus the 2,000 Hz threshold and the threshold at the notch frequency minus the 8,000 Hz threshold both were greater than or equal to 10 dB. In group 1, 77.1% did not have a notch at 4,000 Hz. In group 2, 65.3% did not have a notch at 3,000, 4,000, or 6,000 Hz; 12.4% had bilateral notches, 11.7% had left ear notches, and 10.7% had right ear notches. The notches were about twice as deep on the low-frequency side of the notch than on the high-frequency side. The mean left ear and right ear notch depths were about the same (23 dB), with mode notch depths in the 15.0 to 17.5 dB range.
228

Characteristics of the Audiometric 4,000 Hz Notch (744,553 Veterans) and the 3,000, 4,000, and 6,000 Hz Notches (539,932 Veterans)

Wilson, Richard H., McArdle, Rachel 25 March 2013 (has links)
The purpose of this study was to examine the prevalence and characteristics of audiograms that are notched (1) at 4,000 Hz and (2) at 3,000, 4,000, and/or 6,000 Hz. Bilateral audiograms from 1,000,001 veterans were obtained from Department of Veterans Affairs archives; after "cleaning" algorithms were applied, 744,553 participants (mean age = 63.5 yr) were included in the 4,000 Hz notch analysis (group 1) and 539,932 participants (mean age = 62.2 yr) were included in the 3,000, 4,000, and/or 6,000 Hz notch analysis (group 2). A notch was defined when the threshold at the notch frequency (3,000, 4,000, or 6,000 Hz) minus the 2,000 Hz threshold and the threshold at the notch frequency minus the 8,000 Hz threshold both were greater than or equal to 10 dB. In group 1, 77.1% did not have a notch at 4,000 Hz. In group 2, 65.3% did not have a notch at 3,000, 4,000, or 6,000 Hz; 12.4% had bilateral notches, 11.7% had left ear notches, and 10.7% had right ear notches. The notches were about twice as deep on the low-frequency side of the notch than on the high-frequency side. The mean left ear and right ear notch depths were about the same (23 dB), with mode notch depths in the 15.0 to 17.5 dB range.
229

Fabrication and Characterization of 2-Port Surface Acoustic Wave (SAW) Resonators for Strain Sensing

Kelly, Liam 29 March 2022 (has links)
This thesis focuses on the theory, fabrication, and characterization of 2-port surface acoustic wave (SAW) resonators, as well as the application of their Fabry-Pérot resonance modes for strain sensing. The thesis includes three articles. In the first article, a fabrication method for high frequency SAW devices using traditional UV photolithography equipment is developed. It is well known that SAW sensors become more sensitive at higher frequencies but realizing high frequency devices requires small features which challenge existing photolithography methods. The proposed process is a modified version of a previously reported tri-layer lift-off photolithography process intended for Si or SiO2 substrates which allows for compatibility with materials that are piezoelectric and pyroelectric, often used as the substrate in SAW devices. The process uses a lithographic tri-layer consisting of layers of lift-off resist (LOR) on the bottom, back anti-reflection coating (BARC) in the middle, and photoresist (PR) on top, improving resolution by a factor of two over traditional lift-off photolithography techniques. We demonstrate the fabrication of a SAW device with an interdigital transducer (IDT) pitch of 4 μm (minimum feature size of 1 μm) on 128o Y-X cut lithium niobate, whose operating frequency is measured as 994.5 MHz. The 2-Port SAW devices that are used in subsequent chapters are fabricated using this process. The second article proposes a method of analyzing acoustic Fabry-Pérot spectra, by analogy with optical cavities, to determine key SAW parameters. In our experiment, 2-port SAW resonators, consisting of two interdigital transducers (IDTs) laterally separated by a free surface cavity length, are used to generate SAWs on 128o Y-X lithium niobate that are trapped between the two IDTs which also act as Bragg reflectors. Fabry-Pérot cavity peaks can be observed through the electrical S11 (reflection) spectrum measured on one IDT, hence a 2-Port resonator is equivalent to an acoustic Fabry-Pérot cavity/resonator. Measurements of the free spectral range and linewidths are then fitted to linear models to obtain the free surface velocity and attenuation of SAW waves, as well as the reflection of interdigital transducers (IDTs), all of which are crucial design parameters. Our method of analyzing Fabry-Pérot spectra provides a convenient method for determining key characteristics of SAW waves and cavities. In the third article, a surface acoustic wave (SAW) strain sensor based on measuring acoustic Fabry-Pérot resonance peaks from a 2-port SAW resonator is demonstrated. A theoretical analysis is proposed to estimate the frequency sensitivity to strain of IDT and cavity resonances and to predict strain distributions in both the cavity and IDT regions of a 2-port SAW resonator bonded to a tapered cantilever beam. The frequency stability of cavity resonance peaks for fabricated 2-port SAW resonators of different cavity length are measured and analyzed to determine the cavity length which exhibits maximum frequency stability. A cross-correlation analysis technique is then introduced to improve the detection of the frequency shift of SAW resonances and enable multimode frequency shift detection. The measured frequency sensitivity to strain of the cavity resonances of a resonator 10 mm in length (operating frequency = 97.7 MHz) was found to be -103.2 ± 0.2 Hz/με while demonstrating excellent linearity (R2 = 0.9999). By considering a minimum signal to noise ratio (SNR) of 3 dB, the device exhibits a minimum strain resolution of only 234 nε.
230

Analysis and Design of Air-Core Transformer Based on Internal Magnetic Flux Density Distribution for High-Frequency Power Converter / 高周波電力変換回路のための内部磁束密度分布に基づく空芯トランスの解析と設計

Hashimoto, Kazuki 23 March 2021 (has links)
京都大学 / 新制・課程博士 / 博士(工学) / 甲第23201号 / 工博第4845号 / 新制||工||1757(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 引原 隆士, 教授 松尾 哲司, 特定教授 中村 武恒 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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