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The Global ETD Search service is a free service for researchers
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Showing 421 to 429 of 429 (0.025 seconds)| 421 |
異常渦電流損を考慮したモータの鉄損予測手法に関する研究 / イジョウ ウズデンリュウソン オ コウリョ シタ モータ ノ テッソン ヨソク シュホウ ニカンスル ケンキュウ吉岡 卓哉, Takuya Yoshioka 22 March 2020 (has links)
近年、自動車の電動化が加速しており、車両駆動を担うモータのさらなる効率向上が求められている。高効率モータ設計に向けて、主な損失の１つである鉄損予測の精度向上が求められている。本論文では、鉄損を構成する各種損失の中から、実用的なモデル化手法が確立していない、異常渦電流損に関して、磁気測定から影響を与える諸因子を検討した。また、得られた知見に基づき、モータ鉄損予測にあたり、実用的なモデルを開発した。 / In recent years, electrification of automobiles has accelerated, and further improvement in efficiency of motors that drive the vehicles is required. For high-efficiency motor design, it is important to improve the accuracy of iron loss estimation, which is one of the main losses in the motor. In this paper, we investigated influencing factors of excess loss, which is one element that consists iron loss and has not been established as practical estimating modeling, from the magnetic measurement. In addition, based on the obtained knowledge, a practical model was developed for motor iron loss estimation. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University
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On magnetic amplifiers in aircraft applicationsAustrin, Lars January 2007 (has links)
In the process of designing an electric power supply system for an aircraft, parameters like low weight and low losses are important. Reliability, robustness and low cost are other important factors. In the Saab Gripen aircraft, the design of the primary power supply of the electric flight control system was updated by exchanging a switching transistor regulator to a magnetic amplifier (magamp). By introducing a magamp design, weight was saved and a more reliable power supply system at a lower cost was achieved. In this particular case, with the power supply of the electric flight control system in the Saab Gripen fighter, advantage could be taken of a specific permanent magnet generator (PM-generator). The frequency of the generator offered the perfect conditions for a magamp controller. A key parameter in designing magnetic amplifiers (magamps) is low losses. New amorphous alloys offer new possibilities of the technique in designing magnetic amplifiers, because of their extremely low losses. The core losses are evaluated by studying the equations and diagrams specifying the power losses. The core losses are evaluated and compared with the copper losses in the process of optimizing low weight and low losses. For this an engineering tool is developed and demonstrated. Evaluations of the hysteresis characteristics for the magnetic alloys, as well as modeling and simulation of the core losses, are presented in this work. The modeling of the core losses includes hysteresis losses, eddy current losses and excess losses as well as copper losses. The losses are studied dynamically during realistic operational conditions. The model can be used for any generic analysis of hysteresis in magnetic circuits. Applications of magnetic amplifiers in aircrafts have been demonstrated to be a feasible alternative / QC 20101103
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Shear Modulus Degradation of Liquefying Sand: Quantification and ModelingOlsen, Peter A. 13 November 2007 (has links) (PDF)
A major concern for geotechnical engineers is the ability to predict how a soil will react to large ground motions produced by earthquakes. Of all the different types of soil, liquefiable soils present some of the greatest challenges. The ability to quantify the degradation of a soil's shear modulus as it undergoes liquefaction would help engineers design more reliably and economically. This thesis uses ground motions recorded by an array of downhole accelerometers on Port Island, Japan, during the 1995 Kobe Earthquake, to quantify the shear modulus of sand as it liquefies. It has been shown that the shear modulus of sand decreases significantly as it liquefies, apparently decreasing in proportion to the increasing excess pore water pressure ratio (Ru). When completely liquefied, the shear modulus of sand (Ru = 1.0) for a relative density of 40 to 50% is approximately 15% of the high-strain modulus of the sand in its non-liquefied state, or 1% of its initial low-strain value. Presented in this thesis is an approach to modeling the shear modulus degradation of sand as it liquefies. This approach, called the "degrading shear modulus backbone curve method" reasonably predicts the hysteretic shear stress behavior of the liquefied sand. The shear stresses and ground accelerations computed using this method reasonably matches those recorded at the Port Island Downhole Array (PIDA) site. The degrading shear modulus backbone method is recommended as a possible method for conducting ground response analyses at sites with potentially liquefiable soils.
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Intermittent hypoxia elicits a unique physiological coping strategy in Fundulus killifishBorowiec, Brittney G. January 2019 (has links)
Fish encounter daily cycles of hypoxia in the wild, but the physiological strategies for coping with repeated cycles of normoxia and hypoxia (intermittent hypoxia) are poorly understood. Contrastingly, the physiological strategies for coping with continuous (constant) exposure to hypoxia have been studied extensively in fish. The main objective of this thesis was to understand how Fundulus killifish cope with a diurnal cycle of intermittent hypoxia, an ecologically relevant pattern of aquatic hypoxia in the natural environment. To do this, I characterized the effects of intermittent hypoxia on hypoxia tolerance, oxygen transport, metabolism, and the oxidative stress defense system of killifish, and compared these effects to fish exposed to normoxia, a single cycle of hypoxia-normoxia, and constant hypoxia.
Specifically, I studied the following topics: (i) how acclimation to intermittent hypoxia modifies hypoxia tolerance, and the hypoxia acclimation response of Fundulus heteroclitus (Chapter 2), (ii) metabolic adjustments occurring during a hypoxia-reoxygenation cycle (Chapter 3), (iii) how acclimation to intermittent hypoxia alters O2 transport capacity and maximal aerobic metabolic rate (Chapter 4), (iv) the effects of hypoxia and reoxygenation on reactive oxygen species and oxidative stress (Chapter 5), and (v) variation in hypoxia tolerance and in the hypoxia acclimation responses across Fundulus fishes (Chapter 6).
Killifish rely on a unique and effective physiological strategy to cope with intermittent hypoxia, and that this strategy is distinct from both the response to a single bout of acute hypoxia-reoxygenation (12 h hypoxia followed by 6 h reoxygenation) and to chronic exposure to constant hypoxia (24 h hypoxia per day for 28 d). Key features of the acclimation response to intermittent hypoxia include (i) maintenance of resting O2 consumption rate in hypoxia followed by a substantial increase in O2 consumption rate during recovery in normoxia, (ii) reversible increases in blood O2 carrying capacity during hypoxia bouts, (iii) minimal recruitment of anaerobic metabolism during hypoxia bouts, and (iv) protection of tissues from oxidative damage despite alterations in the homeostasis of reactive oxygen species and cellular redox status. Of these features, (i) is unique to intermittent hypoxia, (ii) also occurs in fish exposed to acute hypoxia-reoxygenation, and (iii) and (iv) are observed in both fish acclimated to intermittent hypoxia as well as those acclimated to constant hypoxia.
This is the most extensive investigation to date on how fish cope with the energetic and oxidative stress challenges of intermittent hypoxia, and how these responses differ from constant hypoxia. This thesis adds substantial insight into the general mechanisms by which animals can respond to an ecologically important but poorly understood feature of the aquatic environment. / Dissertation / Doctor of Philosophy (PhD) / Oxygen levels in the aquatic environment are dynamic. Many fishes routinely encounter changes in oxygen content in their environment. However, we have very little understanding of how cycles between periods of low oxygen (hypoxia) and periods of high oxygen (normoxia) affect the physiology of fish. This thesis investigated how Fundulus killifish cope with daily cycles between hypoxia and normoxia (intermittent hypoxia) by modifying oxygen transport, metabolism, and oxidative stress defense systems. I found that killifish rely on a unique and effective physiological strategy to cope with intermittent hypoxia, and that this strategy is distinct from how they respond to a single bout of hypoxia (followed by normoxia) and to a constant pattern of only hypoxia. This is the most extensive investigation to date on how fish respond to the challenges of intermittent hypoxia, an understudied but ecologically important type of aquatic hypoxia.
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台灣股票市場的長期超額報酬與股票風險溢酬值 / The Equity Excess Return and Risk Premium of Taiwan Stock Market簡瑞璞, Chien, Dennis Jui-Pu Unknown Date (has links)
已實現投資報酬率與無風險利率之差、被稱為超額報酬，而股票的預期報酬率超過無風險利率的部份則為股票風險溢酬，是許多資產評價模型的重要依據，例如資本資產定價模型。有不同的理論架構解釋說明風險溢酬值，例如；股票風險溢酬的迷思、短期損失的憎惡、生還存留因素和回歸與偏離平均值等等。
研究台灣股市的超額報酬與股票風險溢酬，有助投資大眾和企業理性面對股市的預期報酬和風險，對台股才有合理的期望報酬值。分析1967年迄2003年的台灣金融市場，計算過去37年長期的幾何平均年報酬率，以臺灣證券交易所發行量加權股價指數為台股市場報酬率，已實現台股實質年報酬率為6.71%。無風險報酬率使用第一銀行的一年期定期存款利率，實質台幣存款年利率為3.07%，消費者物價指數年增率則為4.80%。以年資料計算的台股實質超額報酬，算術和幾何值分別為12.48%和3.63%(年)，計算月資料算術平均和幾何平均值分別為0.77%和0.25%(月)。過去37年長期的台股超額報酬現象未較歐美市場的情況更加明顯，也比一般市場的預期報酬率低。
因資料取得的限制、台股的理論超額報酬方面，1991年迄2003年的近十三年來，經固定股利成長模式和盈餘成長模式的兩種計算方式，台股的實質超額報酬分別為 0.6%和-4.3%，此時期台股的投資報酬率比起台幣存款並不突出、且是低超額報酬。同期的已實現的實質超額報酬值；算術平均1.69%和幾何平均-3.35%。評估目前台股風險溢酬，將十分接近過去37年長期歷史資料得到的超額報酬數值，算術年均值為12.48%(年)和0.77%(月)，幾何平均分別為3.63%(年)和0.25%(月)，低風險溢酬是當前台灣股票市場的一般現象。 / The difference between the observed historical investment return and the risk-free interest rate is the excess return. The equity risk premium, ERP is the expected rate of return on the aggregate stock market in excess of the rate of risk-free security. ERP is one of important factor of many asset-pricing models, including Capital Asset Pricing Model, CAPM. There were many theories and factors to explain the equity risk premium; equity premium puzzle, myopic loss aversion, survivorship bias, mean reversion & aversion and etc.
Studying the value of Taiwan equity excess return and risk premium is fundamental for investors and institutions evaluating the expected market investment return and risk. Analyzing the data from year 1967 to 2003 for thirty-seven years long holding period, Taiwan Stock Exchange Capitalization Weighted Stock Index as Taiwan stock market return, the realized real return was 6.71%. One-year bank time deposit rate as NT dollars risk-free asset rate and real interest rate was 3.07% and consumer price index, CPI annual growth rate was 4.80%. The historical real yearly excess return was 12.45% for arithmetic mean and 3.63% geometric mean; the historical real monthly excess return was 0.77% for arithmetic mean and 0.25% geometric mean. Taiwan realized equity excess returns were not higher than the returns in the developed countries and were also lower than the market's expectation.
Due to the limits of available data, the theoretical equity excess returns that were calculated on two theoretical models; Constant Growth Dividend Discount Model (dividend yield model) and earnings yield model were 0.6% and -4.3% from year 1991 to year 2003. Comparing the same period of historical realized excess returns of 1.69% for arithmetic mean and -3.35% geometric mean, Taiwan stock market returns were not spectacular. The current equity risk premium of Taiwan stock market is low and should be near the level of the long historical realized equity excess return.
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A Multi-Factor Stock Market Model with Regime-Switches, Student's T Margins, and Copula DependenciesBerberovic, Adnan, Eriksson, Alexander January 2017 (has links)
Investors constantly seek information that provides an edge over the market. One of the conventional methods is to find factors which can predict asset returns. In this study we improve the Fama and French Five-Factor model with Regime-Switches, student's t distributions and copula dependencies. We also add price momentum as a sixth factor and add a one-day lag to the factors. The Regime-Switches are obtained from a Hidden Markov Model with conditional Student's t distributions. For the return process we use factor data as input, Student's t distributed residuals, and Student's t copula dependencies. To fit the copulas, we develop a novel approach based on the Expectation-Maximisation algorithm. The results are promising as the quantiles for most of the portfolios show a good fit to the theoretical quantiles. Using a sophisticated Stochastic Programming model, we back-test the predictive power over a 26 year period out-of-sample. Furthermore we analyse the performance of different factors during different market regimes.
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Ocenenie doménového mena / Valuation of Domain NameDávidová, Lucia January 2011 (has links)
The main goal of this work is to evaluate the market value of the Internet domain, Fotečky.cz, at the 1st in January 2012, for the purpose of subsquent selling the domain on the market to the potential buyer. To correct evaluation, method of multi-period excess earnings and method of the license analogy are used.
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Validation and application of advanced soil constitutive models in numerical modelling of soil and soil-structure interaction under seismic loadingKowalczyk, Piotr Jozef 23 September 2020 (has links)
This thesis presents validation and application of advanced soil constitutive models in cases of seismic loading conditions.
Firstly, results of three advanced soil constitutive models are compared with examples of shear stack experimental data for free field response in dry sand for shear and compression wave propagation. Higher harmonic generation in acceleration records, observed in experimental works, is shown to be possibly the result of soil nonlinearity and fast elastic unloading waves. This finding is shown to have high importance on structural response, real earthquake records and reliability of conventionally employed numerical tools. Finally, short study of free field response in saturated soil reveals similar findings on higher harmonic generation.
Secondly, two advanced soil constitutive models are used, and their performance is assessed based on examples of experimental data on piles in dry sand in order to validate the ability of the constitutive models to simulate seismic soil-structure interaction. The validation includes various experimental configurations and input motions. The discussion on the results focuses on constitutive and numerical modelling aspects. Some improvements in the formulations of the models are suggested based on the detailed investigation.
Finally, the application of one of the advanced soil constitutive models is shown in regard to temporary natural frequency wandering observed in structures subjected to earthquakes. Results show that pore pressure generated during seismic events causes changes in soil stiffness, thus affecting the natural frequency of the structure during and just after the seismic event. Parametric studies present how soil permeability, soil density, input motion or a type of structure may affect the structural natural frequency and time for its return to the initial value. In addition, a time history with an aftershock is analysed to investigate the difference in structural response during the earthquake and the aftershock.
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Le train de vie en droit privé / Standard of living in private lawMartinez, Michaël 19 October 2016 (has links)
Locution issue du langage courant, le « train de vie » a été importée dans la sphère juridique dès la fin des années 1930 pour lutter contre la fraude fiscale. Depuis les années 1960 et surtout 2000 elle est utilisée dans toutes les branches du droit privé. Elle n’a pourtant reçu aucune définition. Partant de ce constat, la première partie de cette thèse s’intéresse au contenu juridique de la notion de train de vie. Elle y est définie comme la jouissance, à titre habituel d’une certaine quantité de biens et de services, caractérisant à la fois un niveau de vie et une habitude de vie. Il ressort de cette définition que tant les biens que les services peuvent être le support du train de vie, que cette notion s’apprécie en jouissance et non en propriété et qu’une condition de durée doit être remplie. La seconde partie de cette thèse s’intéresse aux effets qui sont attachés au train de vie. Il est toujours utilisé en tant que point de référence mais n’est pas toujours invoqué par la même personne. Ainsi, le train de vie peut être soit opposé à son bénéficiaire par un tiers, soit opposé par son bénéficiaire à un tiers. Dans le premier cas, il est un point de référence permettant d’identifier une disproportion, à laquelle sont attachées des conséquences juridiques néfastes pour le bénéficiaire du train de vie. Dans le second cas, il sert de point de référence pour apprécier et traiter une situation de rupture patrimoniale. Caractérisant une situation économique habituelle, le train de vie est doté d’une certaine inertie,qui nécessite qu’il ne soit pas arrêté brutalement. Il est alors de nature à conférer des droits à son bénéficiaire. / An expression usually found in everyday language, the « train de vie », or standard of living, wasbrought into the legal sphere as early as the late 1930’s in a bid to fight fiscal fraud. Since the 1960’s, and evenmore so since the 2000’s, it is found in all branches of private law. It has, however, never been defined.Therefore, the first part of this thesis looks into the legal content of the idea of « train de vie ». It is definedhere as the enjoyment of a certain quantity of goods and services that has come to be the habitual, markingboth a standard of living and a life habit. This definition of the expression leads to the conclusion that as goodsand services can support of the « train de vie », this is a notion that is to be assessed in enjoyment and not inpropriety, and that a condition of length of time is to be fulfilled. The second part of this thesis focuses on theeffects attached to the « train de vie ». It is still used as a reference point but not always invoked by the sameperson. Therefore, the “train de vie” can either be set against it’s beneficiary by a third party, or by it’sbeneficiary against a third party. In the first case, it becomes a point of reference allowing to identify a lack ofproportion, unto which are attached legal consequences unfavorable to the beneficiary of the « train de vie ».In the second case, it serves as a point of reference to asses and deal with a situation of a patrimonial break.Charaterizing a habitual economic situation, le “train de vie” is endowed with a measure of inertia, whichrequires that it not by stopped suddenly. It is thusfore of a nature to create rights for it’s beneficiary.
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