A two-dimensional integrodi erential equation resulting from the use of potential harmonics expansion in the many-body Schr odinger equation is used to study ground-state properties of selected few-body nuclear systems. The equation takes into account twobody correlations in the system and is applicable to few- and many-body systems. The formulation of the equation involves the use of the Jacobi coordinates to de ne relevant global coordinates as well as the elimination of center-of-mass dependence. The form of the equation does not depend on the size of the system. Therefore, only the interaction potential is required as input. Di erent nucleon-nucleon potentials and hyperon-nucleon potentials are employed to construct the Hamiltonian of the systems. The results obtained are in good agreement with those obtained using other methods. / Physics

Este trabalho apresenta um estudo de medições e simulações de fluxo harmônico na Usina Solar Fotovoltaica do Estádio Mineirão em Belo Horizonte/MG. O objetivo foi verificar o comportamento dos inversores solares fotovoltaicos na geração de harmônicos e a atenuação ocorrida pela agregação de múltiplos inversores. Para isso, foram realizadas medições em seis pontos estratégicos da usina investigada, por meio de analisadores de qualidade de energia, o que possibilitou a verificação do comportamento da usina em horários distintos e condições climáticas diversas. Foi avaliada a injeção de harmônicos no sistema elétrico pelos inversores e comparados os valores com os limites previstos em normas, procedimentos e recomendações vigentes. Além disso, o modelo completo da usina foi desenvolvido e simulado utilizando os softwares OpenDSS, ANAH e PowerFactory para análise harmônica e sua validação com os dados de medição. Os resultados obtidos indicam boa conformidade das medições e adequações dos modelos desenvolvidos. / This work presents a study of harmonic measurements and flow simulations in Photovoltaic Solar Plant of the Mineirao Stadium in Belo Horizonte/MG. The objective was to verify the behavior of photovoltaic solar inverters in the generation of harmonics and the attenuation occurred by the aggregation of multiple inverters. For this, measurements were performed on six strategic points of the investigated plant through power quality analyzers, allowing the verification of the plant's behavior at different times and different climates. It was evaluated the injection of harmonics in the electrical system for inverters and compared the values with the limits laid down in standards, procedures and current recommendations. In addition, the complete model of the plant was developed and simulated using the OpenDSS, ANAH and PowerFactory softwares to harmonic analysis and its validation with the data measurement data. The results indicate good agreement between measurement and developed models.

Nuclear reactor design requires the calculation of integral core parameters and power and radiation profiles. These physical parameters are obtained by the solution of the linear neutron transport equation over the geometry of the reactor. In order to represent the fine structure of the nuclear core a very small geometrical mesh size should be used, but the computational capacity available these days is still not enough to solve these transport problems in the time range (hours-days) that would make the method useful as a design tool. This problem is traditionally solved by the solution of simple, smaller problems in specific parts of the core and then use a procedure known as homogenization to create average material properties and solve the full problem with a wider mesh size. The iterative multi-level solution procedure is inspired in this multi-stage approach, solving the problem at fuel-pin (cell) level, fuel assembly and nodal levels. The nested geometrical structure of the finite element representation of a reactor can be used to create a set of restriction/prolongation operators to connect the solution in the different levels. The procedure is to iterate between the levels, solving for the error in the coarse level using as source the restricted residual of the solution in the finer level. This way, the complete problem is only solved in the coarsest level and in the other levels only a pair of restriction/interpolation operations and a relaxation is required. In this work, a multigrid solver is developed for the in-moment equation of the spherical harmonics, finite element formulation of the second order transport equation. This solver is implemented as a subroutine in the code EVENT. Numerical tests are provided as a standalone diffusion solver and as part of a block Jacobi transport solver.

No description available.

A two-dimensional integrodi erential equation resulting from the use of potential harmonics expansion in the many-body Schr odinger equation is used to study ground-state properties of selected few-body nuclear systems. The equation takes into account twobody correlations in the system and is applicable to few- and many-body systems. The formulation of the equation involves the use of the Jacobi coordinates to de ne relevant global coordinates as well as the elimination of center-of-mass dependence. The form of the equation does not depend on the size of the system. Therefore, only the interaction potential is required as input. Di erent nucleon-nucleon potentials and hyperon-nucleon potentials are employed to construct the Hamiltonian of the systems. The results obtained are in good agreement with those obtained using other methods. / Physics / M.Sc. (Physics)

The project contains adventurous research, with an aim to understand and design a planar Gunn diode with a novel integrated circuit configuration to extract the 2nd harmonic. This will potentially enhance the Gunn diode as a high frequency source towards frequencies in excess of 600 GHz. The RF performance from the above integrated circuit was achieved by design and simulation of radial and diamond stub resonators, which were used to short the fundamental oscillation frequency while allowing the second harmonic frequency to pass through to the load. The diamond stub resonator is a new configuration offering a number of advantages which include a higher loaded quality factor and occupies 55% less chip area than a comparable radial stub resonator. The designed novel circuits with integrated planar Gunn diode were fabricated using microwave monolithic integrated circuits (MMIC) technology at the James Watt Nanofabrication centre in Glasgow University. Full DC and microwave characterisation of the diodes and integrated circuits with diodes was carried out using a semiconductor analyser, network analyser (10 MHz to 110GHz) and spectrum analyser (10 MHz to 125GHz). The microwave measurements were carried out at the high frequency RF laboratories in Glasgow University. Both GaAs and InP based Gunn diodes were characterised and RF characterisation work showed that higher fundamental frequencies could be obtained from Gunn diodes fabricated on InGaAs on a lattice matched InP substrate. Planar Gunn diodes with an anode to cathode spacing of 4 microns giving a fundamental frequency of oscillation of 60 GHz were fabricated as an integrated circuit with coplanar waveguide (CPW) circuit elements to extract the second harmonic. A second harmonic frequency of 120 GHz with an RF output power of -14.11 dBm was extracted with very good fundamental frequency suppression. To the authors knowledge this was the first time second harmonic frequencies have been extracted from a planar Gunn diode technology. Aluminium gallium arsenide (AlGaAs) planar Gunn diodes were also designed with an integrated series inductor to match the diode at the fundamental frequency to obtain higher RF output powers. Devices with a 1 micron anode to cathode separation gave the highest fundamental oscillation frequency of 121 GHz the highest reported for a GaAs based Gunn diode and with an RF output power of -9 dBm. These circuits will have potential applications in secure communications, terahertz imaging etc.

Examensarbetet går ut på att utreda hur störningsnivån varierar över tid i elnätet samt ett antal olika ställen inom Norrlands universitetssjukhus, Umeå. Elektrisk fältmätning ingick också i arbetet för att undersöka om det fanns ett samband mellan det elektriska fältet och övertoner i sjukhusets elnät. Examensarbetet presenterar grundläggande teori om elnät, elkvalité och parametrar som beskriver elkvalité, t.ex. övertoner, flimmer och transienter. Förslag på hur övertonshalten kan reducera tas även upp. Mätningarna av elkvalitets parametrar genomfördes med ett antal mätinstrument. Insamlat mätdata analyserades i några olika programvaror. Undersökningen visar att övertonshalten varierade mycket över dygnet och var högst på intensivvårdsavdelning där maxvärdet på spänningsövertonshalten THDu var 4,01%. Ström, spänning och frekvens var inte stabila, dvs. transienter och flimmer har uppstått under mätningen. Analysen av mätdata visar att den totala spänningsövertonshalten THDu var under 5% och inte överskred gränsvärdet 8% som anges i standarden SS-EN 50 160. / The aim of the thesis was to examine whether the level of disturbance in the power grid vary between different types of care environment over time at University Hospital of Umeå. Electric field measurement was also included in the thesis to investigate whether there was a connection between the electric field and harmonics in the hospital’s power grid. The thesis presents basic theory about power grid, power quality and parameters which describe power quality, such as, harmonics, flicker and transients. Suggestions on how to reduce the harmonic content will also be discussed. The measurements of the power quality parameters were performed by using different measuring equipment. The data were analyzed using different software. The study shows that the harmonic content often varied and was highest in intensive care unit, where the maximum value of the harmonic voltage distortion THD was 4,01%. The measurement shows that current, voltage and frequency were not stable, that is transients and flicker occurred several times during the measurement. The analysis of the data shows that the harmonic voltage distortion THDu was below 5% and never above the limit 8% which is specified in the standard SS-EN 50 160.

Time-Interleaved Analog to Digital Converters (TI ADC) consist of several individual sub-converters operating at a lower sampling rate, working in parallel, and in a circular loop. Thereby, they are increasing the sampling rate without compromising on the resolution during conversion, at high sampling rates. The latter is the main requirement in the area of radio frequency sampling. However, they suffer from mismatches caused by the different characteristics in each sub-converter and the TI structure. The output of the TI ADC under consideration contains a lot of harmonics and spurious tones due to the non-linearities mismatch between the sub-converters. Therefore, previously extensive frequency planning was performed to avoid the input signal from coinciding with these harmonic bins. More importance has been given to digital calibration in recent years where algorithms are developed and implemented outside ADC in a Digital signal processor (DSP), whereas the compensation is done in real time. In this work, we model the distortions and the harmonics present in the TI ADC output to get a clear understanding of the TI ADC. A post-correction block is developed for the cancellation of the characterized harmonics. The suggested method is tested on the TI ADCs working at radio frequencies, but is valid also for other types of ADCs, such as pipeline ADCs and sigma-delta ADCs.

Datahallar behöver reservkraft av god kvalitet för att garantera upprätthållandet av dess funktion. Laster i en datahall kommer att generera ström och spänningsövertoner som kan skapa problematik med elkvaliteten. Coromatic är intresserade av att veta mer hur dessa laster påverkar reservkraftsgeneratorn. En mätning utfördes på en datahall under ett funktionsprov. Resultatet blev att halten av THD ökade, främst är det 3:e övertonen som är framträdande. Mätvärdena för THDV ligger under gränsvärdena för SS-EN 50160 och 61000-2-2, men gränsvärdena för 3:e ton ligger långt över. Ingen åtgärd föreslås i nuläget för att hantera problemet. Denna avhandling har gett värdefull information till Coromatic att ta i beaktande vid utförande av nya reservkraftsanläggningar. / A facility full with computers needs backup-power to guarantee the function. Loads in this facility will produce current and voltage harmonics that can pollute and cause trouble with the quality of electricity. Coromatic are interested in knowing more about how these loads can affect the generator. A measurement was performed on a facility when they ran a functional test. The results indicated that THD increased, the third harmonic turned out to be the single harmonic with the highest value. The value is within the boundaries for THDV according to SS-EN 50160 and 61000-2-2, except for the third harmonic. Its value was far too high. No action is propsed to deal with the problem at the moment. This thesis has provided Coromatic with valuable information too consider when they building new systems.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / This thesis presents the design and implementation of a Neutral-Point-Clamped (NPC) shunt Active Filter (AF) for non-linear loads. A NPC shunt AF is an attractive solution for AFs at the medium volage level, because it eliminates the need for cosly injection transformers. The balance of the capacitors of the direct current (dc) bus of the NPC inverter needs to maintained for stable and satisfactory operation though. Modulation techniques and their associated balancing techniques of the NPC inverter are analysed and discussed in the shunt AF setup. Specifically, the effect of Power Factor (PF), harmonics and unbalance of non-linear loads are considered. The practical design and implementation of the NPC shunt AF is presented. Practical and simulation results are presented which validates the presented theory.