Com base nos pressupostos teórico-metodológicos variacionistas (LABOV, 2006 [1966]; 2008 [1972]; 1999; 2001; 2010) e em alguns conceitos caros à terceira onda (ECKERT, 2012) da Sociolinguística, este trabalho objetiva estudar a comunidade de fala sul-mineira de Itanhandu. Itanhandu se localiza em uma região de tríplice divisa entre os estados de Minas Gerais, São Paulo e Rio de Janeiro. Além dessa posição geográfica singular, os itanhanduenses revelam possuir com as capitais fluminense e paulista uma relação de identificação maior do que possuem com a própria capital de seu estado, o que parece influenciar o falar local, sobretudo na realização de (-r). O estudo de Itanhandu iniciou-se com uma coleta de 36 entrevistas sociolinguísticas na cidade, que possibilitaram constatar a presença não só de retroflexos, pronúncia considerada a mais prototípica na comunidade, mas também de tepes e fricativos, variantes comumente associadas às capitais de São Paulo e do Rio de Janeiro, respectivamente. Diante da verificação da ocorrência de tais variantes em Itanhandu, aventou-se a hipótese de que elas estariam correlacionadas aos dois grupos de identificação presentes na cidade, um que se compõe de itanhanduenses que gostam de morar lá e não desejam se mudar ou que tenham saído dela, mas desejam voltar; e outro que se define por itanhanduenses que desejam tentar a vida fora de Itanhandu ou que já se mudaram e não desejam retornar. Entretanto, a análise quantitativa dos dados mostra que as variantes não prototípicas em Itanhandu estão mais ligadas ao tempo de permanência que os itanhanduenses passaram fora de sua cidade natal, ou seja, pronúncias tepes e fricativas são menos correlatos de uma questão identitária e mais de um fenômeno que se dá naturalmente em um processo de acomodação linguística (GILES, 1973) pelo qual passam os itanhanduenses que moram em outras cidades, principalmente localizadas nos estados de São Paulo e Rio de Janeiro. Além disso, este trabalho também investiga a existência de graus de retroflexão em Itanhandu. Retroflexos fortes, ou seja, mais duradouros e intensos, opõem-se a retroflexos fracos, ou melhor, mais curtos e com intensidade reduzida. A análise quantitativa dos dados mostra que tal variação correlaciona-se, principalmente, a variáveis linguísticas: são os grupos de fatores Classe Morfológica da Palavra com (-r) e Frequência do Item Lexical com (-r) os que mais explicam a existência de tal fenômeno em Itanhandu. Por fim, esta dissertação mostra a complexidade da identidade itanhanduense, composta não só de relações sociais, econômicas e linguísticas estabelecidas com cidades paulistas e fluminenses, mas também a partir das vivências individuais dos itanhanduenses, das cidades em que eles já moraram, da forma com que se relacionam com Itanhandu e com os itanhanduenses, das posturas que assumem diante de fatos da vida cotidiana e, principalmente, diante de fatos da realidade linguística da comunidade de fala em que se inserem. / Based on variationist theory and methods (LABOV, 2006 [1966]; 2008 [1972]; 1999; 2001; 2010), including third wave sociolinguistics (ECKERT, 2012), this masters thesis focuses Itanhandu, a town in Southern Minas Gerais, located near the border between Minas Gerais and São Paulo e Rio de Janeiro. Itanhanduenses tend to identify themselves with the capitais of these two states more than with Belo Horizonte, the capital of Minas Gerais. Such identification has an influence in their local speech, especially when it comes to variable (-r). In a sample of 36 sociolinguistic interviews collected in Itanhandu, there are fricative and tap ocurrences of (-r), aside from the retroflex which is prototypical in the community. The fricative and tap variants are commonly associated with the capitals São Paulo and Rio de Janeiro, respectively. The main initial hypothesis is that this case of variation correlates with how Itanhanduenses identify themselves: those who like to live in Itanhandu and do not wish to move to another city (and those who have moved out but would like to return to Itanhandu); and those who would like to leave their birth town (including those who live somewhere else and would not like to move back to Itanhandu). The quantitative analyses suggest that fricative and tap occurrences of (-r) are less correlated to these subgroups, and more strongly associated with how long a period Itanhanduenses spend outside of their birth town. There seems to be a process of accomodation (GILES, 1973) in the speech of those Itanhanduenses who have lived in other cities, especially in the states of São Paulo and Rio de Janeiro. This thesis also looks into degrees of (-r) retroflexion. Strong retroflex (lengthier and more intense) and weak retroflex (shorter and less intense) are analyzed as a variable, which correlates more strongly to linguistic factors: Word Class and Word Frequency. This thesis shows that the Itanhanduense identity is composed not just by social, economic and linguistic relations to São Paulo and Rio de Janeiro, but also by individual experiences, both in Itanhandu itself and in other cities. Such experiences are revealed in stances taken during the sociolinguistic interviews, in relation to facts of their day-to-day life, including their linguistic experiences.

[pt] O fenômeno de estabilidade de tensão vem despertando grande interesse acadêmico e das principais empresas de energia elétrica do mundo desde que começou a ser observado em sistemas reais, no final da década de setenta. Sua ocorrência está relacionada ao carregamento excessivo das linhas de transmissão. Modelar transformador com tap variável adequadamente é fundamental em análises de estabilidade de tensão, tanto no que diz respeito às informações fornecidas ao operador referentes às margens de estabilidade de tensão, quanto aos efeitos de ações de controle de tensão. O modelo de transformador com tap variável utilizado mundialmente consiste de uma impedância, obtida através do ensaio em curto-circuito e com tap nominal, em série com um transformador ideal. Esta tese mostra que, em estudos de estabilidade de tensão, o uso desse modelo leva a resultados qualitativamente errados. Para demonstração, utiliza-se um circuito pequeno e os conceitos de máxima potência transmitida, impedância equivalente da carga, e efeito do controle de tensão. Propõe-se um novo modelo coerente com os resultados obtidos em laboratório, com as leis de circuitos elétricos e com a teoria de estabilidade de tensão. Esse modelo pode ser utilizado em qualquer estudo em regime permanente. Através de diversas simulações computacionais, diferenças quantitativas e principalmente qualitativas foram obtidas comparando-se os resultados dos dois modelos. / [en] The voltage stability phenomenon is of interest since it began to be observed in real systems in the late seventies. It happens due to excessive loading of transmission lines. The modeling of tap-changing transformers is fundamental in voltage stability analysis, in terms of the information provided to the operator about voltage stability margins and the effects of voltage control actions. The model for tap-changing transformers currently in widespread use consists of an impedance, measured in a short-circuit test with a nominal tap, in series with an ideal transformer. The use of this model in voltage stability studies leads to qualitatively incorrect results, as shown in this thesis. For demonstration purpose a small circuit and the concepts of maximum load, equivalent load impedance and voltage control effects are used. An improved model that takes into account laboratory results, circuit laws and voltage stability theory is proposed. This model can be used in any steady-state study. It gives results that are not only more accurate than those obtained with the conventional model, but also, as shown in this thesis, qualitatively different.

Der Ausbau dezentraler Energieanlagen wie fotovoltaischen Anlagen beeinflusst die Netzzustände signifikant. Dabei ist unsicher, wo und in welchem Maße deren Ausbau zukünftig erfolgt. Es ist nun an den Netzbetreibern gleichzeitig die aktuellen Herausforderungen zu meistern und die Netzplanung und -regelung für die Zukunft zu aktualisieren. Eine statistische Methode wird entwickelt, die Verteilnetzplanung unter Einsatz von quasi-stationär modellierten ”Smart Grid”-Lösungen wie Blindleistungsreglern und regelbaren Ortsnetztransformatoren ermöglicht. Durch Stichprobenverfahren werden Unsicherheiten wie Ort, Größe und Leistungsprofile der Energieanlagen in das Netzmodell eingebunden. Diese als probabilistischer Lastfluss bekannte Methode wird durch Gütemaße im Bereich geringer Kombination evaluiert. Beispiele probabilistischer Netzplanung werden an Netztopologien präsentiert. / Development of distributed energy units such as photovoltaic systems affects grid states significantly. It is uncertain, where and to what extent the development of these units is carried out in the future. It is now up to the distribution system operator to cope with todays grid challenges and to update grid planning and control for the future. A statistical method is developed, which incorporates quasi-stationary modeled ”smart grid” solutions such as reactive power controllers and on-load tap-changers. Uncertainties such as location, size and power profiles of energy systems are integrated into the grid model by sampling. This method is known as probabilistic load flow and is evaluated by quality measures at low combinations. Examples on probabilistic grid planning of different grid topologies are presented.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Voltage regulation still is a problem faced by power utilities currently. In addition to the series impedance and the significant load variation of the distribution grids, the main causes of voltage regulation problems, the requirements for the enhancement of power quality by the electricity regulatory agencies, increasing energy consumption, the inclusion of distributed generation and the development of the smart grids tends to increase the complexity of the distribution systems. One of the most used methods for voltage regulation in alternating current systems is the employment of tap changer on transformers, this method allows voltage regulation by varying the transformation ratio, modifying the value of the secondary voltage. The application of these devices is primarily performed by manual commutation mechanical devices in distribution systems, and by automatic electromechanical on load tap changers in substations. In the case of manual devices, operating costs and the impossibility of automatic voltage regulation are limiting factors, while in the case of electromechanical devices the limitations are mainly related to the costs of employment and maintenance. Currently, the increase of voltage and current operating levels of semiconductor devices has allowed envision the application of semiconductor switches instead of the mechanical switches employed nowadays. However, due to the operating characteristics of these devices, a detailed analysis of the commutation process is necessary, in order to allow the proper design of the devices involved in the commutation and protection process of the electronic tap changer. In this context, this work presents the analysis, design and implementation of an electronic on load tap changer applied to a single-phase distribution transformer, proposed as an alternative to the existing mechanical and electromechanical tap changers. Such a system enables the automatic voltage regulation, avoiding the insulation oil degradation, resulting from the commutation process, and also the elimination of movable parts, the main cause of defects in current automatic commutation devices. In addition to allowing steady state voltage regulation, the system allows the regulation for momentary voltage sags, since they occur in the transformer operating range. The analysis of the commutation process is presented, allowing the design of the electronic switches, as well as the protection system to be employed. Experimental results show the correct voltage regulation for different kinds of load, demonstrating the potential application of electronic on load tap changers in the current distribution systems and in future smart grids. / A regulação dos níveis de tensão é um problema ainda enfrentado pelas companhias concessionárias de energia elétrica atualmente. Além da impedância série e da significativa variação de carga das linhas de distribuição, principais causas dos problemas de regulação, a maior exigência dos agentes reguladores do sistema elétrico para a melhoria da qualidade de energia, o aumento do consumo de energia, a inclusão de geração distribuída e o desenvolvimento das redes inteligentes (smart grids), tendem a aumentar a complexidade dos sistemas de distribuição. Um dos métodos mais empregados na regulação de tensão em sistemas de corrente alternada é a aplicação de comutadores de taps em transformadores. Este método permite a regulação da tensão através da variação da relação de transformação, modificando o valor da tensão secundária. A aplicação desta solução é feita, majoritariamente, através de dispositivos mecânicos de comutação manual nos sistemas de distribuição e de dispositivos automáticos eletromecânicos de comutação sob carga em subestações. No caso dos dispositivos manuais, os custos operacionais e a impossibilidade da regulação automática de tensão são fatores limitantes, enquanto que no caso dos dispositivos eletromecânicos, os limitantes estão relacionados principalmente aos custos de implantação e de manutenção. Atualmente, o aumento dos níveis de tensão e corrente de operação dos dispositivos semicondutores tem permitido vislumbrar a aplicação de chaves semicondutoras em substituição às chaves mecânicas empregadas. Entretanto, devido às características de funcionamento destes dispositivos, uma análise detalhada do processo de comutação do sistema é necessária, de modo a permitir um adequado projeto dos dispositivos envolvidos no processo de comutação e proteção dos comutadores eletrônicos de taps. Neste contexto, o presente trabalho apresenta a análise, projeto e implementação de um comutador eletrônico de taps aplicado a um transformador de distribuição monofásico, proposto como alternativa aos comutadores mecânicos ou eletromecânicos existentes. Tal sistema permite a regulação automática da tensão, eliminando o desgaste do óleo isolante, resultante do processo de comutação sob carga e também a eliminação de partes móveis, principal causa de defeitos nos comutadores automáticos atuais. Além de permitir a regulação da tensão em regime permanente, o sistema possibilita a regulação para afundamentos de tensão momentâneos, desde que estejam na faixa de operação do transformador. A análise do processo de comutação do dispositivo estudado é apresentada, permitindo o projeto das chaves eletrônicas, bem como do sistema de proteção a ser empregado. Resultados experimentais demonstram a correta regulação de tensão do sistema desenvolvido, dentro dos limites de operação do transformador, para diferentes tipos de carga, evidenciando a potencialidade dos comutadores eletrônicos de taps em aplicações nas atuais redes de distribuição e nas futuras redes inteligentes.

The use of treated waste water for irrigation of vegetable crops is on the increase in Botswana especially in the Glen Valley farms, a peri-urban settlement of Gaborone city. However, the effects of this practice on heavy metals uptake by vegetable crops are uninvestigated. Chromium and nickel have been reported to be accumulating in Gaborone crop soils and cultivating vegetables in these soils with treated waste water could potentially lead to an increased bio-availability of the heavy metals in the vegetable crops. The main aim of this study was therefore to compare the uptake of chromium and nickel in tomato plants, a vegetable grown in sludge amended Glen Valley soils, to those grown in sludge absent Glen Valley soils using treated waste water at different pH values and tap water for irrigation. The high water uptake and high water consumption rate of tomato plants made it suitable for this study. Twenty five pots each containing 2.5 kg sludge amended Glen Valley soils and 5 pots each containing 2.5 kg sludge absent soils were utilized. Fresh treated waste water in a 50 L plastic container on a need by need basis was used. For the control experiments 5 pots each containing 2.5 kg standard commercial soils and fresh tap water were used. The potted tomato plants were cultivated from early May to middle of October 2009. One leaf and one fruit from each tomato plant was harvested and tested in this study. The highest uptakes of chromium (0.819 mg/L) and nickel (0.327 mg/L) were experienced in the leaves where the tomato plant were cultivated in standard commercial soil and irrigated with tap water at pH 7.0. The least uptake of chromium (0.052 mg/L) and that of nickel (-0.030 mg/L) was found in the fruits, where the tomatoes were grown in sludge amended Glen Valley soil and irrigated with normal Glen Valley treated waste water at pH 8.5. Increasing the pH of the treated waste water from 5.0 to 6.0 caused increased bio-accumulation of chromium and nickel in the leaves and the fruits of the tomato plants. Normal treated waste water (pH 8.5) and treated waste water at pH 9.0, however, reduced the chromium and the nickel uptake by the tomato plants. Treated waste water at pH 10.0 bio-accumulate more chromium and more nickel in the leaves and fruits of tomato plants. The pH variation experiments suggested that the fruit tissues accumulated more chromium and the leaf tissues accumulated more nickel. The mean chromium uptake in the tomato plants exceeded the Food and Agriculture Organization permissible limits but the Botswana Bureau of Standards effluent limit was not exceeded. The mean nickel concentrations were below the threshold limits for both local and international standards. Statistical analysis showed no significant difference between the mean chromium and the mean nickel concentration in the leaves and the fruits of the tomatoes at the 5% significant level. It can be concluded from this study that cultivating tomatoes with sludge amended Glen Valley soil combined with normal treated waste water at pH 8.5 could reduce the uptake of chromium and nickel uptake in tomato plants. However, an increase in the uptake of chromium and nickel in the leaves and fruits of the tomato plants could be triggered at slightly low pH (pH 5.0 and pH 6.0) and high pH (pH 10.0) of the treated waste water. It is recommended that the current practices of using treated waste water combined with sludge amended Glen Valley soil to cultivate tomatoes at the Glen Valley farm is good practice and should be continued. Nonetheless, further studies need to be carried out at the farm to establish possible phytotoxicity effects of these heavy metals on tomatoes when using treated waste water combined with sludge amended and sludge absent soils. / Dissertation (MSc)--University of Pretoria, 2011. / Chemical Engineering / unrestricted

Magister Educationis - MEd / This study investigated 1) the conceptions on capacitors held by a group teachers in the Western Cape; 2) the effect of a dialogical argumentation instructional model on the teachers’ conceptions on the capacitor; and 3) the teachers’ perceptions on the implementation of this instructional model. The theoretical framework of the study was based on Toulmin’s Argumentation Pattern (TAP) and Ogunniyi’s Contiguity Argumentation Theory (CAT). The objective was to retrain science teachers in their awareness and understanding of the Nature of Science and Indigenous Knowledge Systems thereby enhancing their ability and efficacy in integrating science and Indigenous Knowledge Systems. The study involved workshop activities that included the teachers’ Reflective Diary, interview sessions, and video-taped lesson observations. The study adopted a Case Study approach and the data was analysed both quantitatively and qualitatively. The findings of the study showed that: 1) the teachers held varying conceptions of the capacitor; 2) the teachers’ conceptions of the capacitor improved after being exposed to the Dialogical Argumentation Instructional Model and 3) the teachers were dominantly in favour of the Dialogical Argumentation Instruction Model as a teaching method to be introduced at schools. The implications of the findings for school science and pedagogy were highlighted for closer observation.

The Master´s thesis solves question about sanitation installations in factory in Přelouč. The theoretical part deals with pumping technique and pumping of wastewater. The work also focuses on possible solutions of the given specialization. The project part solves the sanitation installation of this factory in the selected variant. It is a large hall with administrative part.

Thesis (MEng (Electrical Engineering)--Cape Peninsula University of Technology, 2019 / The purpose of an electrical power system is to supply electrical energy to the customers. Power transformers are required to transform the system voltage from generation to transmission and distribution levels. Protection and control systems must ensure that power system high voltage equipment such as transformers operate and deliver save, reliable and secure electricity supply. The aim of the project research work is to develop and implement a strategy, methods and algorithms for monitoring, protection and voltage control of parallel power transformers based on IEC 61850-9-2 process bus standard. NamPower is a power utility in Namibia. The IEC 61850 protocol for electrical substation automation system is used for the protection and control of 5 power transformers operated in parallel in an existing substation system. The IEC 61850-9-2 process bus standard is however not used in regards of Sampled Values (SV). Protection and control devices are connected to a substation communication network, routers and switches using fibre optic linked Ethernet. Inductive Current Transformers (CTs) and Voltage Transformers (VTs) secondary circuits are hardwired to Intelligent Electronic Devices (IEDs) and fibre optic links are not used for this purpose at process level communication. The research focuses on the implementation of the IEC 61850 standard with Merging Units (MUs) and sampled values to improve the existing implemented protection and control system at NamPower. This includes substation communication networks and MUs used for transformer protection, voltage regulator control and cooling fan control. At the present the CTs located at the transformer bushings and switchgear and the VTs located at the switchgear are hardwired to the inputs on protection and control IEDs. The research focuses on issues with the copper wires for voltage and currents signals and how these issues can be eliminated by using the MUs and the SV protocol. The MUs which are considered in this Thesis is to improve the voltage regulator control and the control of the cooling fan motors. The voltage regulator control IED is situated at the tap change motor drive of the On-Load Tap Changer (OLTC). The IED of each transformer is required to regulate the voltage level of the secondary side bus bar it is connected to. All the regulating IEDs are required to communicate with each other and collectively to control the bus bar voltage depending on the switching configuration of the parallel transformers. The control circuit for controlling the cooling fan motors is hardwired. Temperature analogue signal input into a programmable automation controller IED can be used for controlling the transformer cooling fans. A strategy, methods and algorithms for transformer protection, voltage regulator control and cooling fan motor control of parallel power transformers need to be developed and implemented based on IEC 61850-9-2 process bus. Power utilities and distributors can benefit from interpretation of the IEC 61850-9-2 standard and implementing MUs and SV in substations. MUs can be included in the power transformer protection, automation and control systems. A cost reduction in high voltage equipment, substation installation and commissioning costs and better performance of protection and control system are anticipated.

In this paper numerical flow calculations with respect to the annular gaps with added radial grooves normaly used on the spools of directional control valves were carried out. The impact of various annular gap geometries and radial grooves during variable pressure conditions, and while using different hydraulic fluids, on the flows through annular gaps were investigated for different flow regimes. Samples with different geometries and numbers of radial groves on the spool of the directional control valve were also made for the purpose of carrying out flow measurements. The two different hydraulic fluids that were used in the numerical simulations and for the flow measurements were a hydraulic mineral oil and tap water. The results of the numerical calculations for the different models of the radial grooves with axially symmetric geometries show their impact on the internal leakage with respect to three different regimes of flow. The results of the numerical calculations based on the use of a hydraulic oil show a trend that was established by the experimental investigation.

In view of the fact that most of the synthetic refrigerants, in case of leakage or release, are harmful to the environment by contributing in global warming or depleting stratospheric ozone layer, many research works have been done recently to find alternative refrigerants posing no or negligible threat to the environment. Among alternative refrigerants, ammonia, a natural refrigerant with zero Global Warming Potential (GWP) and Ozone Depletion Potential (ODP), can be a sensible choice.Although ammonia has been used for many years in large industrial systems, its application in small units is rare. In this project a small heat pump with about 7 kW heating capacity at -5 °C and +40 °C evaporation and condensation temperatures is designed and built to work with ammonia as refrigerant. The heat pump is expected to produce enough heat to keep a single-family house warm in Sweden and to provide tap hot water for the house. After successful completion of this project, it is planned to install the heat pump in a house to test it throughout a heating season to study its performance in real working conditions.Since ammonia is flammable and toxic in high concentrations, the refrigerant charge is tried to be kept low in the heat pump to reduce the risk of fire or poisoning in case of unwanted release of refrigerant to the surroundings. The compact design of the heat pump helps reducing the refrigerant charge. Besides, considering the limited space normally reserved for installation of a heat pump in a house, the compact design of the heat pump is necessary.