The load response to voltage and frequency changeshas a considerable impact on the behaviour of the powersystem. Thus, the selection of a load model structure andits corresponding parameters is an important task in orderto study and predict the system behaviour. Currently,the Nordic Transmission System Operators (TSO) use theZIP load model, as it provides an easy and flexible way ofrepresenting the load. The main goal of the thesis has beento test two approaches for deriving ZIP model parameters,namely the component-based and measurement-basedapproaches. The former approach uses predefined parametervalues, and information on the loads electricityconsumption, whereas the latter uses measurement dataand curve-fitting techniques. In order to evaluate themethodology, a case study has been performed, wherethe two aggregation approaches were applied on anevaluation point. It was found that the aggregation bymeans of the component-based approach may result in ZIPparameters lacking physical significance. ZIP parameterswithout physical significance pose a challenge for systemplanners, who may have difficulties in accepting thesevalues as they are less intuitive than physically significantones. Furthermore, the results of the measurement-basedapproach indicate that the ZIP model has some limitationwhen it comes to the sudden load changes that it canaccommodate. This has been the case with the measuredreactive power in the case study. Based on the resultsof applying the methodology, it can be concluded thatthe component-based and measurement-based approachesprovide useful information when understanding powersystem loads. / Lastens svar på spänning och frekvensförändringarhar en betydande inverkan på elkraftsystemet. Sålundaär valet av en lastmodell och dess parametrar viktigt föratt kunna studera och förutsäga systemets beteende. Förnärvarande använder de nordiska stamnätsägarna (TSO)ZIP lastmodellen, eftersom det ger ett enkelt och flexibeltsätt att representera lasten. Huvudsyftet med den häravhandlingen har varit att testa två metoder för att ta framZIP modellparametrar, nämligen en komponent-baseradoch en mätnings-baserade metod. Den tidigare metodenanvänder fördefinierade parametervärden, och informationom lasternas elförbrukning, medan den senare användermätdata och kurvanpassningstekniker. För att utvärderametoden har en fallstudie genomförts där de två metodernaapplicerades på en utvärderingspunkt. Det konstateradesatt den komponent-baserade metoden kan resultera i ZIPparametrar som saknar fysisk betydelse. ZIP parametrarutan fysisk betydelse utgör en utmaning för systemplanerare,som kan ha svårt att acceptera dessa värden eftersom deär mindre intuitiva än fysiskt betydande sådana. Dessutomindikeras det, att ZIP modellen har begränsningar när detgäller att representera stora steg i den uppmätta effektenssvar, då den mätnings-baserade metoden används. Dettaär fallet för den reaktiva effekten i fallstudien. Baserat påresultaten av tillämpningen av metoden, kan man dra slutsatsenatt den komponent-baserade och mätnings-baserademetoden ge användbar information när man vill förståkraftsystems laster.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Road Tra c legislation prescribes constraints on the forces/loads which vehicles may exert on the road at contact surfaces or load points. These constraints have bearing on speci c contact surfaces or groups of contact surfaces. The constraints are in the form of maximum force values and maximum ratios, which may exist between forces. The forces exerted by a vehicle on the road is determined by a combination of the vehicle's own mass, dimensional characteristics, and the mass and position of its cargo. The mass and position of the cargo can be modelled by only considering its centroid. The centroid's position is linked to a certain cargo arrangement. It is necessary, in terms of legal constraints, to distinguish between legally permissable- and non-permissable arrangements. Methods are proposed in this dissertation to determine the borders for the position of the centroid according to cargo-mass, for a variety of vehicle con gurations. The determination of borders for the position of the centroid is the result of a three part process. Firstly, the legal limits are translated to mathematical inequalities that must be satis ed for the forces at contact surfaces. Secondly, conservative parametric estimates for the forces, in terms of the position and the mass of the centroid of a given vehicle, must be derived. Finally these estimates are incorporated into the load constraints and an enclosed permissable area for the centroid is found. These position constraints are suitable inputs to solution methods of various cargo arrangement problems. Linear programmes which can solve certain general arrangement problems by utilising the position constraints on the centroid, were successfully developed. Solutions are presented for the arrangement of pallet-freight, as well as the arrangement of cargo units with asymetrical centroids over the length or width of a vehicle's cargo area. / AFRIKAANSE OPSOMMING: Padvervoerwetgewing skryf grense op kragte/laste voor wat voertuie by kontakoppervlakke of laspunte, op die pad mag uitoefen. Hierdie voorskrifte het betrekking op spesi eke laspunte en groepe van laspunte. Die voorskrifte is in die vorm van maksimum laswaardes by laspunte en maksimum ratio's wat tussen sekere laste mag bestaan. Die laste wat 'n voertuig op die pad uitvoer word bepaal deur 'n kombinasie van die voertuig se eie massa, dimensionele eienskappe, sowel as sy vrag se massa en posisie. Die vrag se massa en posisie kan gemodelleer word deur slegs die massamiddelpunt daarvan te beskou. Die massamiddelpunt se posisie word gekoppel aan 'n bepaalde vragrangskikking. Dit is nodig om, in terme van wetlike voorskrifte, te kan onderskei tussen wetlik toelaatbare en -ontoelaatbare rangskikkings. Metodes word in hierdie proefskrif voorgestel waarmee daar grense vir die posisie van die vragmassamiddelpunt bepaal kan word na gelang van die vragmassa, vir 'n verskeidenheid van voertuigkon gurasies. Die bepaling van grense vir die posisie van die vragmassamiddelpunt is die resultaat van 'n drieledige proses. Eerstens word die wetlike beperkings herlei na wiskundige ongelykhede waarbinne laste by kontakoppervlakke moet val. Tweedens word konserwatiewe parametriese beramings vir die laste verkry in terme van die ligging en massa van die vragmassamiddelpunt vir 'n gegewe voertuig. Laastens word hierdie beramings in die lasbeperkings opgeneem om 'n afgebakende toelaatbare gebied vir die vragmassamiddelpunt se posisie te verkry. Hierdie posisiebeperkings is geskik om as inset te dien in die oplossingmetodes van 'n verskeidenheid van vragrangskikkingsprobleme. Line^ere programme wat sekere algemene rangskikkingsprobleme kan oplos deur die aanwending van posisiebeperkings op die vragmassamiddelpunt, is suksesvol ontwikkel. Oplossings word aangebied vir die rangskikking van paletvrag, asook die rangskikking van vrageenhede met asimmetriese massamiddelpunte oor die lengte of breedte van 'n voertuig se vragarea.

Este trabalho se propõe a analisar os efeitos produzidos pela inundação do solo em estacas escavadas, isoladas, submetidas a esforços de compressão. Os resultados obtidos referem-se à execução de três provas de carga lentas em estacas com diâmetros de 0,40 m e 0,50 m (2 provas de carga distintas) e comprimentos de 10,0 m, submetidas anteriormente a uma série de carregamentos (duas provas de carga rápidas e duas lentas). Os resultados relativos aos deslocamentos medidos no topo das estacas e os obtidos pela instrumentação instalada ao longo do fuste são então comparados com a sequência dos resultados anteriores, para avaliação do efeito de umedecimento no comportamento \"carga x recalque\" e nos mecanismos de transferência de carga. É feita ainda uma descrição minuciosa do processo utilizado para inundação do solo e uma breve consideração sobre os efeitos da não reposição de cargas em ensaios lentos, de longa duração. / This work intends to analyze the effects produced by the flooding of the soilexcavated piles, isolated, subjected to compression efforts. The results refer to the execution of three slow load tests on piles with diameters of 0.40 m and 0.50 m (2 distinct load tests) and 10.0 m lengths, submitted previously to a number of shipments (two slow and two quick load). The results concerning offsets measured at the top of the stakes and those obtained by the instrumentation installed along the forend are then compared with the sequence of the previous results, to evaluate the effect of damping in behavior \"load x settlement\" and load transfer mechanisms. It was also made a thorough description of the process used to flood the ground and a brief consideration of the effects of non-replacement of loads in slow, long-term trials.

Este trabalho se propõe a analisar os efeitos produzidos pela inundação do solo em estacas escavadas, isoladas, submetidas a esforços de compressão. Os resultados obtidos referem-se à execução de três provas de carga lentas em estacas com diâmetros de 0,40 m e 0,50 m (2 provas de carga distintas) e comprimentos de 10,0 m, submetidas anteriormente a uma série de carregamentos (duas provas de carga rápidas e duas lentas). Os resultados relativos aos deslocamentos medidos no topo das estacas e os obtidos pela instrumentação instalada ao longo do fuste são então comparados com a sequência dos resultados anteriores, para avaliação do efeito de umedecimento no comportamento \"carga x recalque\" e nos mecanismos de transferência de carga. É feita ainda uma descrição minuciosa do processo utilizado para inundação do solo e uma breve consideração sobre os efeitos da não reposição de cargas em ensaios lentos, de longa duração. / This work intends to analyze the effects produced by the flooding of the soilexcavated piles, isolated, subjected to compression efforts. The results refer to the execution of three slow load tests on piles with diameters of 0.40 m and 0.50 m (2 distinct load tests) and 10.0 m lengths, submitted previously to a number of shipments (two slow and two quick load). The results concerning offsets measured at the top of the stakes and those obtained by the instrumentation installed along the forend are then compared with the sequence of the previous results, to evaluate the effect of damping in behavior \"load x settlement\" and load transfer mechanisms. It was also made a thorough description of the process used to flood the ground and a brief consideration of the effects of non-replacement of loads in slow, long-term trials.

<p><!-- --></p><p>In the wake of the economic growth of the Chinese market the past couple of decades, the energy consumption has surged. One of the biggest consequences of the increased energy consumption is a massive increase in CO₂ emission. In fact, China has overtaken the U.S. as the biggest emitter of CO₂. In light of this energy-saving technology gets more important to implement. District heating is one of the solutions used with success in parts of China where heating is required. In this paper, an energy recovery technology has been examined for two climate zones in China namely a mechanical ventilation system using a flat-plate counter-flow heat exchanger. Beijing is located in a cold zone while Hong Kong is located in a zone with hot summers and mild winters. Cooling load calculations were conducted manually using the RTS - method developed by ASHRAE and heating load calculations were conducted for Beijing using Swedish guidelines stated in BBR. Further, the energy recovery unit (VM1) that was provided by Systemair AB was tested using a rig where different outdoor conditions were simulated. This data was then used to evaluate the potential for energy recovery in a model apartment located in the two zones. As expected, significant differences were obtained when comparing the performance for the two locations.</p><p> </p> / Redan avklarad

<p>The purpose of this master thesis was to study if the drain efficiency of power amplifiers can be maintained at power back off using a technique called load modulation.</p><p>The amplifier classes studied are E, F and D-1. The target figure was to obtain a 10 to 12 dB dynamic range of amplitude with reasonable efficiency. Studies of power amplifiers have been made to understand how power is generated. Several different load modulation networks have been evaluated. Attempts to derive design equations for the modulation networks have also been done.</p><p>The thesis work was carried out with simulations in ADS 2006. As active devices commercially available bare-die transistor models have been used. The power rating of the dies are 15 W.</p><p>A dynamic range of amplitude of over 15 dB has been achieved with drain efficiency greater than 60 percent. The peak output power is in the 40 – 45 dBm range.</p>

No description available.

Improvements in quality of life, population growth, and environmental restrictions associated with the burning of fossil fuels will accentuate the need for renewable energy and energy geo-storage. A salient characteristic of these systems is that they impose numerous cycles of effective stress, temperature, and humidity on the surrounding geomaterials. This thesis quantifies future energy consumption based on realizable scenarios and explores the behavior of geomaterials subjected to mechanical and thermal cycles in view of energy-related applications. The long-term behavior of geotechnical systems subjected to a large number of mechanical load cycles is studied with a new numerical scheme based on a hybrid finite element formulation. The numerical scheme satisfies initial conditions as well as fundamental characteristics of soil behavior, such as threshold strain, terminal density, and long-term ratcheting. Numerical results show that shallow foundations subjected to repetitive loading experience strain accumulation and stress redistribution. On the other hand, the long-term behavior of energy piles, exposed geomembranes on slopes, and jointed rock masses subjected to cyclic thermal changes is studied using a combination of numerical, analytical, and experimental methods. Results show that thermal cycles lead to the gradual accumulation of plastic displacements, which may be amplified by thermally-induced wedging in jointed rock masses. In general, cumulative effects caused by repetitive loads increase with the number of cycles, the static factor of safety, the amplitude of the cyclic excitation, and the magnitude of the cyclically-induced displacement with respect to the critical elastic displacement.

<!-- --> In the wake of the economic growth of the Chinese market the past couple of decades, the energy consumption has surged. One of the biggest consequences of the increased energy consumption is a massive increase in CO2 emission. In fact, China has overtaken the U.S. as the biggest emitter of CO2. In light of this energy-saving technology gets more important to implement. District heating is one of the solutions used with success in parts of China where heating is required. In this paper, an energy recovery technology has been examined for two climate zones in China namely a mechanical ventilation system using a flat-plate counter-flow heat exchanger. Beijing is located in a cold zone while Hong Kong is located in a zone with hot summers and mild winters. Cooling load calculations were conducted manually using the RTS - method developed by ASHRAE and heating load calculations were conducted for Beijing using Swedish guidelines stated in BBR. Further, the energy recovery unit (VM1) that was provided by Systemair AB was tested using a rig where different outdoor conditions were simulated. This data was then used to evaluate the potential for energy recovery in a model apartment located in the two zones. As expected, significant differences were obtained when comparing the performance for the two locations. / Redan avklarad

The purpose of this master thesis was to study if the drain efficiency of power amplifiers can be maintained at power back off using a technique called load modulation. The amplifier classes studied are E, F and D-1. The target figure was to obtain a 10 to 12 dB dynamic range of amplitude with reasonable efficiency. Studies of power amplifiers have been made to understand how power is generated. Several different load modulation networks have been evaluated. Attempts to derive design equations for the modulation networks have also been done. The thesis work was carried out with simulations in ADS 2006. As active devices commercially available bare-die transistor models have been used. The power rating of the dies are 15 W. A dynamic range of amplitude of over 15 dB has been achieved with drain efficiency greater than 60 percent. The peak output power is in the 40 – 45 dBm range.