The first part of work provides definition of basic parameters of threads, type of threads. Further work includes description of tools, material of tools and cutting forces. The final part of work deals with analysis course of cutting forces, analysis course wear and analysis surface structure of threads.

This thesis deals with the study of production process of threads by screw-taps from the very description of the individual threads through all the available methods of the threads production, thread control function, up to the actual taps, materials, coatings and their distribution. In the experimental part the thesis deals with the question whether it is possible to find an alternative to the standard production of threads using cutting by taps. This alternative seems to be the use of forming taps. The experiment took place under constant cutting conditions and consisted of two parts, one of them was the production of threads into the pre-drilled through holes and the second one was the production of threads into the pre-drilled impassable holes. The result of the experiment was finding the course of the cutting moment depending on the time and the amount of wear of the examined kinds of taps when all the measured values had to be statistically processed and conclusions were then evaluated.

This thesis deals with the study of production process of threads by screw-taps from the very description of the individual threads through all the available methods of the threads production, thread control function, up to the actual taps, materials, coatings and their distribution. In the experimental part the thesis deals with the question whether it is possible to find an alternative to the standard production of threads using cutting by taps. This alternative seems to be the use of forming taps. The experiment took place under constant cutting conditions and consisted of two parts, one of them was the production of threads into the pre-drilled through holes and the second one was the production of threads into the pre-drilled impassable holes. The result of the experiment was finding the course of the cutting moment depending on the time and the amount of wear of the examined kinds of taps when all the measured values had to be statistically processed and conclusions were then evaluated.

En del didaktisk forskning handlar om hur elever lär sig kunskaper effektivt och praktiskt. Ett effektivtsätt att lära ut fysikkunskaper är med hjälp av representationer som text, språk, matematik, grafer ochtekniska verktyg som simulering. Det finns många forskare och elever som hävdar att PhET-simuleringar är ett grundläggande verktyg för att hjälpa till att förbättra och utveckla fysikaliskkonceptuell förståelse.”Rörelse och krafter” är ett centralt innehåll i fysikundervisningen. I detta arbete undersöks därför hursimulering och särskilt PhET-simulering kan bidra till djupare förståelse av det fysikaliska begreppetfjäderkraft (Hooks lag). I den här studien genomfördes kort enskild undervisning för femgymnasieelever och sen användande de PhET-simuleringen för att lösa några problem samtidigt somde berättade hur de tänkte. Datan samlades in genom metoden ”think aloud protocols” ochanalyserades senare med en kvalitativ metod (tematisk analys). I studien undersöktes också vilkainställningar i PhET-simuleringen som var mest och mist hjälpsamma.Resultatet visar att PhET-simuleringen hjälpte eleverna på i huvudsak tre sätt; att ge visualisering avdet fysikaliska begreppet (fjäderkraft), att vara interaktivt (få direkt feedback) och att fokusera på denkonceptuella förståelsen. Eftersom eleverna svarade olika på vilka inställningar som var mest ochminst hjälpsamma, visade detta att eleverna lär sig på olika sätt, beroende på deras tidigare kunskaperoch förutsättningar. Alla deltagarna tyckte att PhET-simuleringen var ett bra sätt att utforskafjäderkraften på egen hand.Elever behöver få vissa förkunskaper från lärare eller pedagoger innan användning av simuleringenannars lär de sig inte effektivt. Lärare måste också förtydliga vilka skillnader det är mellansimuleringen, som är en modell av verkligheten, och verkligheten. Lärare måste lyfta fram skillnadermellan karaktärsdrag för naturvetenskapliga arbetssättet och användning av simulering, annars missar elever detta.

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.

No / A simple method for dynamically adjusting the number of taps of linear equalisers operating in unknown channel conditions is presented. Simulations with various scenarios show that the technique successfully predicts the optimum equaliser length and is capable of adjusting it as the environment changes

The study of tactile illusions like visual illusions can reveal the brain's processing strategies. A famous tactile illusion is the cutaneous rabbit illusion. Fundamental to this illusion is the perceptual length contraction phenomenon: two taps that occur in rapid succession on the forearm are perceived as occurring closer together than they were physically placed. Our lab previously proposed a Bayesian probabilistic model that views perception as a compromise between expectation (prior experience) and sensation (likelihood of sensorineural data given hypothesized tap locations). The model proposes a low-speed prior, an expectation based on experience that objects tend to be stationary or to move slowly on the skin. When the sensation of space is unclear (e.g., taps are weak), the model predicts that expectation will strongly influence perception. Consistent with this prediction, our lab previously showed that the use of weaker taps causes more pronounced perceptual length contraction. Here we report psychophysical tests on 64 participants, which confirmed this finding. Our study also used stimulus sequences consisting of a weak and a strong tap, for which the Bayesian model predicts an asymmetric perceptual length contraction, such that the weaker tap location will be perceived to shift more than the stronger tap. The experimental results confirmed this prediction, providing further support for our Bayesian probabilistic model as an explanation for perceptual length contraction. However, our results revealed a discrepancy in the data at the smaller SOAs, which showed less length contraction than predicted. We hypothesized that participants might overestimate the smaller SOAs, an effect our lab defines as time dilation. Accordingly, in a second study we investigated the effects of varying SOA and lengths on perceived SOA. The model predicts more pronounced time dilation at smaller SOAs and larger lengths. The psychophysical data from 37 participants confirmed the trends predicted by the model. / Thesis / Master of Science (MSc)

This thesis investigates the use of field-programmable gate arrays (FPGAs) to implement a time-to-digital converter (TDC) with on-chip calibration and temperature correction.Using carry-chains on the Xilinx Kintex UltraScale architecture to create a tapped delay line (TDL) has previously been proven to give good time resolution.This project improves the resolution further by using a bit-counter to handle bubbles in the TDL without removing any taps.The bit counter also adds the possibility of using a wave-union approach previously dismissed as unusable on this architecture.The final implementation achieves an RMS resolution of 1.8 ps.