Dissertations / Theses on the topic 'Low latitude current system'
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Tsunomura, Satoru. "On the Contribution of Global Scale Polar-originating Ionospheric Current Systems to Geomagnetic Disturbances in Middle and Low Latitudes." 京都大学 (Kyoto University), 1999. http://hdl.handle.net/2433/182006.
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Yokoyama, Yoshihiro. "Characteristics of the mesoscale field-aligned currents in the dusk sector of the auroral oval based on data from the Swarm satellites." Kyoto University, 2021. http://hdl.handle.net/2433/261602.
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Shao, Hui. "System design and power management for ultra low energy applications using energy harvesting techniques /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?ECED%202009%20SHAO.
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FINARDI, ILARIA. "Traceable low-current measurements towards the realisation of the ampere in the new SI." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2745712.
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Grundmark, Sofia. "The current tax system on the Swedish residential market – problems and possible solutions." Thesis, KTH, Fastigheter och byggande, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150794.
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Idag präglas den svenska bostadsmarknaden av en trögrörlighet som bland annat beror på höga flyttrelaterade skatter. Dessa flyttrelaterade skatter består av reavinstskatt, stämpelskatter, expeditionsavgifter och uppskovsränta. Många hushåll anser det idag vara för dyrt att flytta och avstår därför. Detta leder till att flyttkedjor stannar upp och arbetsmarknaden påverkas negativt eftersom många hushåll drar sig för att flytta och många tackar därför nej till arbeten som kräver en flytt. Detta beteende leder till att den individuella välfärden och hela Sveriges ekonomiska välfärd drabbas negativt. Detta är ett aktuellt och omtalat ämne och många rapporter har skrivits och det finns många förslag på förbättringar till dagens system. Många har som syfte att ge förslag på olika åtgärder som skulle leda till ett bättre system på bostadsmarknaden och många har gjort beräkningar på hur resultat av bland annat en minskning av reavinstskatten skulle se ut. Det är dock i detta examensarbete första gången som en siffra över hur hög en fastighetsskatt skulle behöva vara för att kunna ersätta dagens alla flyttrelaterade skatter redovisas. Detta arbete har som syfte att se över dagens flyttrelaterade skattesystem och uppmärksamma eventuella problem med dagens situation. En litteraturstudie redovisas för att en bredare inblick ska ges och utifrån litteraturstudien kommer sedan ett antal förslag till förbättringar av dagens flyttrelaterade skattesystem att sammanfattas. Sedan kommer en utredning av hur mycket dagens flyttrelaterade skatter faktiskt genererar i pengar till staten att redovisas och sist kommer beräkningen över hur hög en fastighetsskatt skulle behöva vara för att kunna ersätta dagens flyttrelaterade skatter. Slutsatserna visar på att en del av problemen med dagens flyttrelaterade skattesystem kan lösas med en rad olika åtgärder som flera författare har utrett. Beräkningarna över hur hög en fastighetsavgift skulle behövara vara för att kunna ersätta dagens flyttrelaterade skatter visar på att alla bostadsägare årligen ska betala 5900 kronor eller 0,47 % av sitt taxeringsvärde i skatt, oavsett om man äger ett småhus eller en bostadsrättslägenhet.The Swedish housing market is presently characterized by low mobility. This could partly be a result of the high taxes on moving from one house to another. Not only is there a capital-gains tax on moving, but also a stamp duty, a service charge and an interest charge on postponed capital gains tax. Many households consider the price of moving too high, making them reluctant to move. This will have a negative effect on the labour market due to the fact that people will be less willing to move to places where labour is needed. This type of behaviour will ultimately affect both the wealth of the individual and Sweden’s economy in a negative way. The purpose of this thesis is to examine the current tax-system and emphasize the problems with it. Firstly, a literature study will be presented to give a wide perspective of the subject. This will be the basis for a number of suggestions that will resolve the problem with low mobility on the housing market. After this, an investigation of how much money the taxes on moving actually generate to the government. Lastly, a calculation of how high a real estate tax would have to be in order to replace the taxes on moving. The conclusions of this paper suggest that there are a number of actions that can be taken in order to resolve some of the problems with the tax system on the Swedish housing market. The calculations show that the taxes on moving could be replaced by a real estate tax where the homeowners would pay 5900 SEK or 0,47% of the assess value of the home yearly, instead of paying taxes only when moving.
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Baggu, Murali Mohan. "Advanced control techniques for doubly fed induction generator-based wind turbine converters to improve low voltage ride-through during system imbalances." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Baggu_09007dcc806684bd.pdf.
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Thesis (Ph. D.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 27, 2009) Includes bibliographical references (p. 126-130).
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MOSCA, CARMELO. "Methodologies for Frequency Stability Assessment in Low Inertia Power Systems." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2895393.
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Geury, Thomas. "Smart matrix converter-based grid-connected photovoltaic system for mitigating current and voltage-related power quality issues on the low-voltage grid." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/243967.
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The increasing penetration of distributed energy resources, in particular Photovoltaic (PV) production units, and the ever-growing use of power electronics-based equipment has led to specific concern about Power Quality (PQ) in the Low-Voltage (LV) grid. These include high- and low-order current harmonics as well as voltage distortion at the point of common coupling. Solutions to overcome these issues, meeting international grid codes, are being proposed in the context of smart energy management schemes.This work proposes a novel three-phase topology for a PV system with enhanced PQ mitigation functionality, tackling the corresponding control challenges.First, a single-stage current-source inverter PV system with active filtering capability is preferred to the more common two-stage voltage-source inverter topology with additional voltage-step-up converter. The system also guarantees a nearly unitary displacement power factor in the connection to the grid and allows for Maximum Power Point Tracking (MPPT) with direct control of the PV array power. The grid-synchronised dq-axis grid current references are generated for the mitigation of nonlinear load low-order current harmonics, without the need for additional measurements. Active damping is used to minimise grid-side filter losses and reduce high-order harmonics resulting from the converter switching.Results on a 500W laboratory prototype confirm that active damping reduces the switching harmonics in the grid currents and active filtering properly mitigates the low-order current harmonics. The MPPT algorithm works effectively for various irradiance variations. Second, a PV system with a novel Indirect Matrix Converter (IMC)-based unified power quality conditioner topology is developed for enhanced current and voltage compensation capability, with compactness and reliability advantages. PQ issues such as current harmonics, and voltage sags, swells, undervoltage and overvoltage are mitigated by the shunt and series converters, respectively.The more common Space Vector Modulation (SVM) method used in IMCs is developed for this specific topology. In particular, a new shunt converter modulation method is proposed to additionally control the PV array current with zero switching vectors, resulting in a specific switching sequence.A direct sliding mode control method is also studied separately for the shunt and series converters, so that the zero-vector modulation method of the shunt converter can be used, with no sensitive synchronisation of the switching signals; this contrasts with the SVM method. A new dc link voltage modulation method with 12 voltage zones, instead of 6, is proposed to help overcome the limitation in the choice of shunt converter switching vectors due to the positive dc link voltage constraint.Results are obtained for the direct method on a 1 kW laboratory prototype with optimised IMC dc link connection and alternative shunt converter switching transitions to guarantee a positive dc link voltage. Current and voltage compensation capabilities are confirmed by tests in various operating conditions.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Carbonell, Cortés Carla. "Customizing a low temperature system for microwave transmission measurements. Quantum transport in thin TiN films and nanostructures." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/83635.
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The work presented in this thesis consists of two distinct parts.
The first years of my work focused on the development and improvement of a new equipment built to study magnetic and electrical properties, particularly applying microwaves in reflection and transmission conditions. The sample space in conventional cryostats with superconducting magnets is usually smaller than 10-mm-diameter. Our equipment consists of a hollow cylindrical cryostat having a 33-mm-diameter hole all along its vertical axis. These characteristics enable the measurement of large samples and the use of big resonant cavities to get to a wider microwave (MW) range, particularly in transmission measurements.
The cryostat has a superconducting magnet made of a solenoid that applies a magnetic field from -5 T to 5 T, and a temperature controller that works in the range 1.8 - 300 K. The system is cooled down with nitrogen and helium and the temperature can be controlled with the precision required by each experiment using a heater and a needle valve.
Different probes for a wide range of experiments in our cryostat have been developed in order to be as versatile as possible. Following this idea each one has been divided in two halves that can be combined as it is preferred in each experiment. Each probe is made of a 8-to-10-mm-diameter stainless steel tube that is used to protect and give some stiffness to the measuring device. A coaxial cable and different waveguides are added to these stainless steel jackets, so we end up having nine halves, four upper parts that can be combined with five lower parts. There are three waveguides working in the frequency ranges 33-50 GHz (WR22), 50-75 GHz (WR15) and 75-110 GHz (WR10), and a coaxial cable that maintains the fundamental mode at a frequency of 60 GHz. In the extra lower part a 16-pin Fischer connector is added at the bottom in order to be able to perform more resistance experiments. Once the probes have been built, they have been tested to make sure the system is able to reach high vacuum and to be cooled down. Problems found along the way have been solved and at the end all the probes work properly.
Different sample holders have been designed and built according to the needs in each experiment. The system has been tested by reproducing experimental results with Mn12-acetate, as quantum tunneling and magnetic avalanches, and by obtaining new results on microwave transmission in thin TiN films.
The second part of the thesis focuses on the measurements of thin TiN films in a dilution refrigerator working with a mixture of 3He and 4He that enables experiments at a few tens of millikelvins. The cryostat also contains a superconductor magnet which can apply a magnetic field up to 5 T.
Low-temperature transport properties of nanoperforated superconducting TiN films have been experimentally studied. Resistance measurements have been performed in the critical region of the superconductor-insulator transition (SIT), applying the magnetic field perpendicular to the plane of the structure or the dc current through the sample.
SIT is a transition from a superconductor to an insulator state by localizing the Cooper pairs. The evolution of the SIT with temperature, magnetic field and dc current has been investigated in detail.
Characteristic parameters have been determined for as-cast thin films using the theory of quantum corrections to conductivity. Disorder-driven and field-induced SITs have been measured. Commensurability effects have been observed down to the lowest experimental temperature, and are emphasized in the more disordered samples. The SIT has been observed for a dc current applied across the sample as changes in the curvature at zero bias current. Experiments prove that electronic transport in the nanoperforated samples is mediated by Andreev conversion. Finally, the existence of the superinsulator state has been experimentally proved.El treball que es presenta en aquesta tesi consta de dues parts ben diferenciades. La primera pretén el desenvolupament d’un equip experimental concebut per a l’estudi de propietats magnètiques i elèctriques en materials diversos i, en especial, el treball amb radiació de microones en condicions de reflexió i transmissió. La segona s’ha centrat en les mesures de transport d’una capa fina superconductora de nitrur de titani (TiN) de 5 nm de gruix en un criòstat de dilució.
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Latzo, Curtis Thomas. "Approaches to Arc Flash Hazard Mitigation in 600 Volt Power Systems." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3198.
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ABSTRACT
Federal regulations have recognized that arc flash hazards are a critical source of potential injury. As a consequence, in order to work on some electrical equipment, the energy source must be completely shut-down. However, power distribution systems in mission critical facilities such as hospitals and data centers must sometimes remain energized while being maintained. In recent years the Arc Flash Hazard Analysis has emerged as a power system tool that informs the qualified technician of the incident energy at the equipment to be maintained and recommends the proper protective equipment to wear. Due to codes, standards and historically acceptable design methods, the Arc Flash Hazard is often higher and more dangerous than necessary.
This dissertation presents detailed methodology and proposes alternative strategies to be implemented at the design stage of 600 volt facility power distribution systems which will decrease the Arc Flash Hazard Exposure when compared to widely used code acceptable design strategies. Software models have been developed for different locations throughout a power system. These software model simulations will analyze the Arc Flash Hazard in a system designed with typical mainstream code acceptable methods. The model will be changed to show implementation of arc flash mitigation techniques at the system design level. The computer simulations after the mitigation techniques will show significant lowering of the Arc Flash Hazard Exposure.
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Bolgár, Robert. "Posouzení možností regulace napětí v distribučních sítích nn." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220155.
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This paper deals with possible ways of voltage regulation. Theoretical part includes a search of published methods and the available voltage regulators. Acquired theoretical knowledge has been applied in the development of mathematical models of two selected controllers applied to the testing network. The result of this work is a summary of the outcomes of dynamic simulations with two selected regulators at various locations in testing network. Comparing the results of dynamic simulation for two selected states was chosen the most appropriate regulator and its optimal location in testing network.
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Pic, Axel. "Numerical and experimental investigations of self-heating phenomena in 3D Hybrid Bonding imaging technologies." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI054.
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Dans cette thèse, les phénomènes d’auto-échauffement ont été étudié pour guider la conception de circuits intégrés 3D de nouvelle génération. Grâce à des études expérimentales et numériques, la dissipation thermique dans des imageurs 3D par collage hybride a été analysée et l’impact de l’augmentation de température résultante a été évalué. Premièrement, afin de développer des modèles précis, les propriétés thermiques des matériaux utilisés dans les circuits intégrés ont dû être déterminées. Différents films minces diélectriques impliquant des oxydes, des nitrures et des composés low-k ont été étudiés. Pour ce faire, la microscopie thermique à sonde locale (SThM) et la méthode électrothermique 3ω, sensibles à la conductivité thermique effective faible et élevée, ont été mises en œuvre. Dans un deuxième temps, des modèles éléments finis de circuits intégrés 3D ont été développés. Une méthode numérique nécessitant homogénéisations et approches multi-échelles a été proposée pour surmonter des grands rapports de forme inhérents à la microélectronique. La procédure numérique a été validée en comparant les calculs et les mesures expérimentales effectuées par SThM, la thermométrie résistive et la microscopie infrarouge sur une puce de test par collage hybride simplifiée. Il a été montré que la dissipation de chaleur est principalement limitée par la conductance du puit thermique ainsi que les pertes par l'air. Enfin, des études numériques et expérimentales ont été réalisées sur des imageurs 3D par collage hybride fonctionnels. Le champ de température a été mesuré par SThM et comparé aux calculs par éléments finis à la surface de la matrice. Les résultats numériques ont montré que la température de la surface des pixels est égale à celle du Front-End-Of-Line de l’imageur. L'influence de l'échauffement sur les performances optiques de l'imageur a été déduite de cette analyse. Cette étude a permis également d'évaluer les différentes méthodes numériques et expérimentales pour la caractérisation de la dissipation de chaleur en microélectroniqueIn this PhD thesis, self-heating phenomena are studied for guiding the design of next-generation 3D Integrated Circuits (ICs). By means of experimental and numerical investigations, associated heat dissipation in 3D Hybrid Bonding imagers is analyzed and the impact of the resulting temperature rise is evaluated. First, in order to develop accurate models, the thermal properties of materials used in ICs are to be determined. Different dielectric thin films involving oxides, nitrides, and low-k compounds are investigated. To do so, Scanning Thermal Microscopy (SThM) and the 3ω electrothermal method, sensitive to low and large effective thermal conductivity, are implemented. In a second step, finiteelement models of 3D ICs are developed. A numerical method involving homogenization and a multiscale approach is proposed to overcome the large aspect ratios inherent in microelectronics. The numerical procedure is validated by comparing calculations and experimental measurements performed with SThM, resistive thermometry and infrared microscopy on a simplified Hybrid Bonding test chip. It is shown that heat dissipation is mainly limited by the heat sink conductance and the losses through air. Finally, numerical and experimental studies are performed on fully-functional 3D Hybrid Bonding imagers. The temperature field is measured with SThM and compared with finite-element computations at the die surface. The numerical results show that the temperature of the pixel surface is equal to that of the imager Front-End-Of-Line. The influence of the temperature rise on the optical performance of the imager is deduced from the analysis. The study also allows assessing the various numerical and experimental methods for characterizing heat dissipation in microelectronics
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Chen, Her-Yuan, and 陳鶴元. "The simulation of low latitude ionospheric tomography by using ITS system." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/eqs26p.
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碩士國立中央大學
太空科學研究所
94
The Low Latitude Ionospheric Tomographic Network (LITN) suitable for the study of lare scale ionosphere structure , especially in the Taiwan area , we can study the large scale electron density variation in the equatorial anomaly region . In the past, NCU had begun to set up LITN . It consisted of six ground-based receivers spanning 20∘along Taiwan meridian (121∘E) to receiver beacon signals from the US Naval Navigation Satellite System (NNSS) with receiver JMR-1 in order to carry out the large scale experiments on two-dimensional ionospheric imaging by computerized tomography until the decommission of NNSS satellites in late 1997.Since July 2003, NCU has purchased 4 ITS30 receivers from North West Research Associates, Inc. (NWRA) and set them in Pingtung , Nantou and Taoyuan in Taiwan for the reestablishment of the NEW LITN with the hope to promote the receiving stations to other countries such as Philippines , Indonesia and so on in the near future . In this thesis, We have applied STK ,IRI-model to determine the location of LEO satellite and initial electron number density . In addition, the simulation study of GPS/MET and real data inversion with the ITS receiver were accomplished. A comparison is made between our results and dynasonde data, some possible explanation were discussed. After Formosat-3, which consist of six LEO satellites and one more frequency band (1066.67MHz), entered into their orbits, we can get more data for the inversion of CIT study.
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黃耀賢. "Impact of Current Harmonic on Distribution Design in Low Voltage Distribution System." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/25717421368607398202.
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碩士國立臺灣科技大學
電機工程系
89
The three phases four wires 220/380V grounded Y connected con-figuration is mostly used for low voltage distribution system in Taiwan. Meanwhile the three phases four wires 110/220 V-V connected configu-ration is widely used for commercial and residencial regions to supply single phase home appliances and other equipments. The electrical engi-neers were used to design low voltage distribution system with reducing the rating of the neutral wire based on the considerations that electric loads were distributed evenly and the unbalance condition was not very serious. Recently, a large number of power electronic control equipments were used in industrial applications, the current harmonic contents became to be the major concerns affect the power quality of the distribution sys-tems and the electric safety. It may cause electric fire hazards when the total current flowing in the neutral wire exceeds the rated ampacity of the neutral wire. The research was devoted to discuss the effects and harmfulness due to current harmonics caused by higher harmonic loads in the distribution system. The various connections model of the dis-tribution transformer and Y/ connected configurations of the loads were proposed firstly, then we simulate and analyze the effects caused by current harmonics by Pspice, a commercial simulation software, in order to evaluate the distribution safety quantitively. Finally, many strategies were proposed to solve the current harmonics problems caused by lighting luminaries as an example to discuss the effectiveness of the strategies proposed.
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Anand, Raj R. "Kalman Filter Estimation Of Ionospheric TEC And Differential Instrumental Biases Over Low Latitude Using Dual Frequency GPS Observations." Thesis, 2006. http://hdl.handle.net/2005/426.
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The low latitude tropical ionosphere has been investigated by various researchers
using Global Positioning System (GPS). Presently for many civil aviation applications, the ionospheric modeling of the tropical region has gained importance, in particular for flight safety. Since ionosphere is dispersive in nature, dual frequency (L1 = 1575.42 MHz and L2 = 1227.60 MHz) GPS observations can be used to obtain Ionospheric Total Electron Content (TEC). Since TEC varies with local time and geomagnetic latitude, an Ionospheric Modeling Technique using spatial linear approximation of vertical TEC over receiver station has been implemented following Sardon et al. The effects of all the
systematic errors due to the satellite plus the receiver (SPR) instrumental biases can reach upto several nanoseconds. (1 TEC is 1016 electrons/m2, 1 ns = 2.86 TEC and
1 TEC = 0.16 m). Hence, to have an accurate estimation of ionospheric TEC, the
instrumental biases must also be estimated. This thesis describes a heuristic adaptive
Kalman Filtering scheme developed to estimate the TEC, the constants in the
linearisation scheme, as well as the above total instrumental biases.
The Kalman filter implementation is basically an optimization problem of
minimizing the Cost Function J based on the difference between the model output and the
measurement, called as the ‘innovation’, scaled by its covariance. In order to obtain the best possible results using the Kalman Filter approach, it is essential to provide
appropriate values for the initial state, process and measurement noise covariances (P0, Q and R) respectively, which in general may not be known. Usually manual tuning of the filter parameter is carried out without using the above cost function J! The filter
estimates can be highly sensitive to the above chosen statistics and thus these will have to be estimated carefully. Hence, we have utilized the Adaptive Kalman Filtering procedure of Myers and Tapley extended by Gemson and Ananthasayanam. The minimization is carried out by simultaneously estimating the above statistics and the unknown
parameters, which include the TEC and the instrumental bias. In addition, A Constant
Gain Kalman Filter approach using Genetic Algorithm (GA) has also been developed for
the above requirement. It is observed that the steady state gains in KF and AKF
approaches are in good match with the constant gains obtained from Genetic Algorithm.
Using the above Adaptive Kalman Filtering technique and Constant Gain Kalman Filter approach, vertical TEC values and SPR biases have been estimated from the IGS receiver observations stationed at ISTRAC/ISRO, Bangalore, India. A diurnal TEC variation over Bangalore for a period of one year for 2003 and January 2004 is estimated and reported in this thesis. This approach has also been applied to study the behaviour of
the ionosphere over low latitude IGS station at Fortaleza, Brazil data during the great
magnetic storm on the 15th July 2000 and the results were found to be consistent with the
results of Basu et al. In addition, Using Constant Kalman filter, the TEC enhancement
over Indian region has been estimated for the October 2003 Ionospheric storm, and the
results were found to be consistent with the reported results in the literature.
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Liu, Jia-En, and 劉佳恩. "Development of Position Control System for Three-phase Permanent-magnet Synchronous Motors with Low Current Harmonics." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/auw7md.
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碩士國立臺灣科技大學
電機工程系
104
The thesis focuses on the development of position control system for three-phase permanent-magnet synchronous motor (PMSM) with reduced current harmonics strategy. A three-leg three-phase inverter is adopted as the driving circuit of three-phase PMSM. Voltage space vector pulse-width modulation method is used for increasing the utility ratio of dc-link voltage. As for the feedback of the rotor positions and rotational speed, the resolver and resolver to digital converter, which not only detect the absolute position of the rotor, but also improve the resolution of feedback signals are used. Whereas, for the current harmonics mitigation control, fast fourier transform is introduced for analyzing the harmonic distortion of back electro-motive-force (EMF). Through transferring harmonic components of back EMF to quadrature- and direct-axis, and compensating them with current controllers, the harmonic distortion of current can be improved. In addition, position controller of adjustable proportional gain which can reduce the steady-state error of position in the same response time is proposed. In the steady state, the direct-axis current is used for locking rotor. This can stop the response of position from being affected by noise of feedback elements to cause rotor vibration. Additionally, An anti-interference control strategy is proposed to yield electromagnetic torque instantaneously to resist disturbing forces exerted on the rotor, resulting in no position overshoot in the steady state, thereby enhancing the interference immunity of the system. The 32-bit digital signal processor, TMS320F28069, is adopted as the control core. The control strategy is completed by software program for cost reduction and reliability enhancement. The experimental results of current harmonics mitigation control show that the total harmonic distortion of three phase current is reduced from 5.30% to 2.31%, The corresponding torque ripple is reduced from 15.28% to 5.98%. Whereas, the experimental results of position closed-loop control system indicate that properly adjusting the proportional gain of position controller reduces the steady-state error of position from to . In conclusion, the feasibility of the proposed control strategy has been verified by the experimental results.
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Chang, Wan-Siang, and 張萬祥. "Analysis of the Ground Current Characteristics of Low Voltage Distribution System in the Large High-Tech Plants." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/95049630923487737844.
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碩士中原大學
電機工程研究所
92
Abstract In the large high-tech plants, the distribution system has many cables, wires and apparatus being allocated everywhere. Some currents from the system will flow into ground to form the so-called ground currents which flow through everywhere of grounding system in the plant to interfere the sensitive equipments and systems and even producing hazards. It is necessary to understand the characteristics of ground current for preventing the hazards and interference. For this, the thesis investigate the characteristics of ground currents which include the distributions of ground current, the ground potential rise and conductor current distributed on the grounding system (ground-grid) , and the magnetic fields, step voltage and touch voltage distributed on the ground surface. The affections of these characteristics on personnel and sensitive equipments and systems are also evaluated briefly. The distribution systems in the large high-tech plants usually include very high voltage (VHV), high voltage and low voltage distribution systems in which the low voltage distribution system is the subject of the study due to with large ground current and close relations with the sensitive equipments. The root causes of ground current and its affections are first described. Then, the circuit model to represent the typical three-phase five-wire (3 5W) distribution system is constructed for analyzing the ground current distribution. All the ground points, self and mutual impedances of three-phase cables, neutral wires, equipment grounding wires and the cable tray are considered in the circuit model. Various conditions including single-point and multi-point grounding of neutral lines, the different grounding impedances of cable tray, the use of equipment grounding wires and the load unbalances are taken into account in the analysis of ground current distribution. According to the ground current data from the circuit model, the other characteristics of ground current mentioned above are analyzed by a software called “CDEGS” which is based on the electromagnetic field analysis of grounding system. Finally, the affections of ground current characteristics are evaluated briefly by comparing between the data obtained from simulation and the tolerance values. The study results show that the ground currents due to low voltage distribution at normal operation will not damage the personnel but may interfere the sensitive equipments and systems. Especially, very high levels of ground currents, ground potential rises and magnetic fields due to neutral line with multi-point grounding and unbalanced loading should be prevented for protecting the sensitive equipments and systems from interferences. It is also necessary to refer the conductor currents of ground-grid and the ground current at each ground point for determining the grounding points and locations of sensitive equipments and systems. Keywords：Large high-tech plants, low voltage distribution systems, ground current, ground potential rise, magnetic field
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Huang, Shi-Yuan, and 黃世源. "Design and Implementation of FSK Demodulation System Application for RFID and Current Feedback Low-Dropout Voltage Regulator." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/fzp2dm.
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碩士國立臺北科技大學
電腦與通訊研究所
96
The major research of this thesis can be divided into two parts. The first part of the thesis is to implement a FSK demodulation system for RFID. We proposed an analog demodulation system and a digital demodulation system. The both systems use the same AC-DC converter which provides DC power for demodulation circuit. The analog demodulation circuit is composed of a multiplexer, a phase frequency detector, a charge pump, and a current controlled oscillator. The digital demodulation circuit is composed of a multiplexer, a phase frequency detector, a charge pump, and a shift register. The two demodulation systems are implemented by 3.3V TSMC 0.35μm CMOS 2P4M process. The chip area of analog demodulation system is 0.34mm2 without PAD, and the chip area of digital demodulation system is 0.36mm2 without PAD. In the second part of this thesis, we presented a current feedback low-dropout voltage regulator. We adopted a simple circuit architecture and replaced voltage feedback by current feedback. Therefore, the characteristics of the proposed LDO are low quiescent current and fast transient response. The LDO is implemented by 3.3V TSMC 0.35μm CMOS 2P4M process. The chip area of LDO is 0.25mm2 without PAD.
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Ting, Chen-ya, and 丁振亞. "Protective Coordination Tests and Benefit Assessment for the Current-limiting Circuit Breaker in the Low Voltage Distribution System." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/bz8aj6.
Full textAbstract:
碩士國立臺北科技大學
電機工程系所
102
The objective of this thesis is to study the protective coordination between upstream and downstream circuit-breakers during short-circuit fault and influence of voltage sags on various sensitive equipments in the low-voltage distribution system in the high-tech plants. Noncurrent-limiting and current-limiting circuit breakers mixed as an upstream or downstream, and two combination in series connection are tested in the laboratory. The test is to verify the fast trip characteristics of current-limiting circuit breakers that can not only interrupt the currents within the first half cycle with prospective limited currents but also ensure the total selectivity between upstream and downstream current-limiting circuit breakers. In addition, the voltage sag magnitude and duration can be obtained from the test to certify that the use of current-limiting circuit breakers can meet the requirement of SEMI F47. All of these tests are very important to certify that the current-limiting circuit breakers with total selectivity is a useful solution for designers to plan protective coordination for the low voltage distribution system of high-tech plants.
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Chen, Jia-Ming, and 陳家銘. "Development of sensorless inverter-fed compressor drive system using a DC-link current sensor with torque compensation at low speed operation." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/91562963814538295895.
Full textAbstract:
碩士國立中央大學
電機工程學系
101
The objective of this thesis is to develop a sensorless permanent magnet synchronous motor (PMSM) drive for inverter-fed compressor drive system. First, a saliency back-EMF based speed estimation method combining with space vector pulse width modulation (SVPWM) is developed for sensorless control in order to achieve sinusoidal driven PMSM drive system. Then, to achieve cost savings, three-phase current signals are reconstructed by using only one DC-link current sensor. Three-phase current signals are reconstructed using the relationship between DC-link current and the inverter power components conduction states. Moreover, a load torque feedforward compensation method is implemented to improve the dynamic performance using traditional proportional-integral speed controller under external load disturbances. Furthermore, a Microchip DSP is adopted to develop the proposed inverter-fed drive system. Finally, some experimental results are given to verify the feasibility of the proposed sensorless control scheme.
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Xiang, Alice. "Current state of the American healthcare system - why exorbitant spending results in low international health rankings and how to ameliorate this paradox." Thesis, 2015. https://hdl.handle.net/2144/16292.
Full textAbstract:
The United States spends more than any other nation on healthcare by an exceedingly significant amount. The United States also ranks very poorly on health outcomes when compared to other economically developed nations. The reason why the United States spends so much more than other nations is because they spend more in all categories of healthcare. Hospital admissions and overnight stays are more expensive, medical staff salaries are higher than in other nations, procedures and treatments are ordered more frequently and cost more than in other nations, prescription drugs prices are multiple times greater in the U.S., the multi-payer private and public insurance payment schemes are time consuming and complex, and administrative costs are significantly higher in the U.S. than in other countries. These complexities and high costs create inefficiencies in America's healthcare system that can interfere with the quality of care provided. The major reasons why the United States is lacking in health outcome rankings can be attributed to an underdeveloped primary care sector and an underfunded social services sector, which make it difficult to coordinate care and practice preventative medicine. America's history of uninsured citizens lacked access to care so the U.S. saw repeats of emergency admissions and expensive hospitalizations for chronic conditions. These problems are preventable with a more robust primary care sector, increased access to care, and advocating public health awareness. Current reforms such as the Affordable Care Act are making strides in the positive direction by creating Accountable Care Organizations, increasing access to care, and regulating an online insurance marketplace. However, continued research and assessments of these new methods of delivering care are necessary in the near future to see if pilot studies can be scaled up on a national level.
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Tsai, Yu-Ching, and 蔡宇清. "Low-Power QVCO using Current-Reused Technique and Back-Gate Coupling, Wideband QVCO with frequency divider and Integer-N Frequency Synthesizer for MB-OFDM UWB system." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/67239966097555766306.
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