Este trabalho apresenta resultados de testes com processo de usinagem para diferentes ferramentas de torneamento. Foram realizados ensaios para avaliar a diferença de comportamento quantoa esforçosde cortee acabamentosuperficialem operaçãode torneamento para um mesmo tipo de ferramenta, com variação na superfície de saída, sendo uma com quebra cavaco com outra de superfície de saída lisa. O material usinado foi aço ao carbono 1045 recozido, testado para duas diferentes velocidades, variando-se também a profundidade de corte e avanço para cada ensaio. Os testes foram executados em um torno mecânico convencional, onde as variáveis do processo foram coletadas com um sistema de aquisição de dados, através de um dinamômetro piezoelétrico para avaliação das forças de corte e um rugosímetro portátil para medida da rugas idade superficial. Observou-se nos resultados, uma forte diminuição dos esforços quando aplicada a ferramenta sinuosa com quebra-cavaco, bem como melhoria nas características do cavaco. Em relação à rugas idade superficial houve uma pequena melhora quando utilizada a ferramenta com superfície de saída lisa, situação decorrente das condições de remoção do cavaco. / This wark presents the results af machiningpracess tests with different turning tools. Tests were done to evaluate behaviors differenceson cutting efforts and surface finishing in turning operations to a same type of tool, with a variation on rake face, where one had a chipbreaker groove and the other are flat. The machining material was 1045 annealed carbon steel, tested to two different cutting speeds, changing also the depth of cut and the feed rate for each case. The tests were done in a conventionallathe, where the process variances were collected by a data acquisition system, through a piezoelectric dynamometer to evaluate the cut efforts and a portable rugosimeter to measure the surface roughness. The results show a strong reduction of the efforts when grooved tools with chip-breaker were applied as well an improvement on the chip characteristics. In relation to the surface roughness, it was observed a slight improvement when the tlat tool was used, because ofthe conditions of chip remova!.

Este trabalho apresenta resultados de testes com processo de usinagem para diferentes ferramentas de torneamento. Foram realizados ensaios para avaliar a diferença de comportamento quantoa esforçosde cortee acabamentosuperficialem operaçãode torneamento para um mesmo tipo de ferramenta, com variação na superfície de saída, sendo uma com quebra cavaco com outra de superfície de saída lisa. O material usinado foi aço ao carbono 1045 recozido, testado para duas diferentes velocidades, variando-se também a profundidade de corte e avanço para cada ensaio. Os testes foram executados em um torno mecânico convencional, onde as variáveis do processo foram coletadas com um sistema de aquisição de dados, através de um dinamômetro piezoelétrico para avaliação das forças de corte e um rugosímetro portátil para medida da rugas idade superficial. Observou-se nos resultados, uma forte diminuição dos esforços quando aplicada a ferramenta sinuosa com quebra-cavaco, bem como melhoria nas características do cavaco. Em relação à rugas idade superficial houve uma pequena melhora quando utilizada a ferramenta com superfície de saída lisa, situação decorrente das condições de remoção do cavaco. / This wark presents the results af machiningpracess tests with different turning tools. Tests were done to evaluate behaviors differenceson cutting efforts and surface finishing in turning operations to a same type of tool, with a variation on rake face, where one had a chipbreaker groove and the other are flat. The machining material was 1045 annealed carbon steel, tested to two different cutting speeds, changing also the depth of cut and the feed rate for each case. The tests were done in a conventionallathe, where the process variances were collected by a data acquisition system, through a piezoelectric dynamometer to evaluate the cut efforts and a portable rugosimeter to measure the surface roughness. The results show a strong reduction of the efforts when grooved tools with chip-breaker were applied as well an improvement on the chip characteristics. In relation to the surface roughness, it was observed a slight improvement when the tlat tool was used, because ofthe conditions of chip remova!.

Sulphur hexafluoride gas is the dominant insulation and interruption material in high voltage gas insulated substation. Its usage remains a concern of transmission system operators owing to the global warming potential of the gas. The work carried out in this thesis aims to find the environment-friendly materials that can replace SF6. These candidates are required to have a strong dielectric strength for high voltage busbar insulation and well arc extinguishing capability necessary for high voltage circuit breaker.A range of alternative insulation types including CF3I gas and its mixture, high pressure air and solid insulating foam are considered as substitute of SF6. Theoretical studies on the dimensions of busbars used in substations are carried out for these options. The dimension of the dielectric system and its ampacity of respect system are calculated using heat transfer models considering their boiling point and proper working pressure which is related with the dielectric strength of some gas.On the other hand, SF6 gas circuit breaker is extremely popular on the medium and high voltage power networks owning to its effective arc extinguishing performance. It would be ideal if a substitute material could be found for SF6 as an interruption material. Biodegradable oil PTFE ablation, other gas candidates including N2, CF3I are investigated as possible replacement of SF6 through literature study.The usage of vacuum circuit breaker is eventually capable to operate in high voltage transmission system. Simulations have been carried out with software ATP/EMTP to investigate the influence of different characteristics of vacuum circuit breaker including chopping current level, the dielectric strength of vacuum gap and the opening time. And then the probability of overvoltages when vacuum circuit breakers installed is studied by statistical study in MATLAB.

The master thesis is focused on the calculation of electrodynamic forces acting on the contacts of the moulded case circuit breaker Siemens 3VA5 from OEZ Letohrad. This work is divided into ten chapters. In the introductory chapter it is described why it is important to deal with the calculation of the electrodynamic forces and the design of the current path. The second chapter describes the problem of the origin and effect of electrodynamic forces on individual parts of the electrical device. The third chapter describes the parameters, properties and design of the 3VA5 Siemens circuit breaker. The fourth chapter describes the Finite Element Methods. The fifth chapter describes how to create a 3D current path model in Solidworks. The sixth to ninth chapter is focused on the stationary calculation of moments in the program Ansys Maxwell by means of Magnetostatic Analysis and on the calculation of the total repulsive force between contacts with the influence of ferromagnetic materials. The last chapter is focused on dynamic calculation of moments and forces acting on contacts in a certain time interval.

This diploma thesis explains the principle of SCADA systems and describes the DLMS/COSEM protocol. In the next part, it shortly describes the Modbus protocol and details the pros and cons of the Modbus protocol in comparison with the DLMS/COSEM protocol. In the next part, an open-source automated scanner was created. This scanner detects devices in a laboratory network. As the next step, the automated scanner finds out open ports and active services, which run on these devices, and tries to attack HTTP, SSH, and Telnet services. Next, the program checks, whether the found device is a smart-meter device and if it is compatible with DLMS/COSEM protocol. If yes, it checks, if the service is vulnerable to DOS attack and breaker disconnection. Scanner’s findings are presented in a newly created web application. NMAP, Masscan, and Metasploit open-source programs are used in the automated scanner. The whole automated scanner is optimized for the HW device Raspberry Pi with the operating system Raspbian Buster Lite installed. This work also describes the testing of the scanner on the laboratory environment and the results are evaluated afterwards.

DC circuit breakers must be able to arrest overcurrent conditions to prevent electrical equipment and wiring from causing building fires or other hazards from occurring. With more DC renewable sourced structures such as Cal Poly’s DC House, an inexpensive and reliable protection system is necessary to ensure safe energy transfer to the loads. One method of protecting a system is preventing excessive amounts of current to be drawn by the load when the surrounding components are rated at a lesser value. DC circuit breakers act as a monitoring system and barely presents an effect on the voltage or power. With most DC circuit breakers on the market being mechanical, the response time to an overload condition is limited to the speed the contacts can disconnect. The examination of response timing and overcurrent limiting is explored in this thesis when using a solid state based DC circuit breaker. The system is designed to handle 600 W, where the operating voltage is 48 V and the maximum allowable current is 12.5 A. The solid state DC circuit breaker has the capability of arresting excessive currents within 30 µs and can be reset through a single pole single throw switch.

Master´s thesis deals with modern cutting tools for grooving and cutting-off. The main part of this project is analysis of forces in the process of grooving by using two types of chip breaker and their influence on the shape of the chip.

No description available.

This article studies the possibility of perpetrator trauma in Edwidge Danticat's The Dew Breaker. The article gives a brief historical background of the political violence in Haiti that occurred under the Duvalier dictatorship and focuses specifically on the role of Tonton Macoutes, the violent enforcers of much of Duvalier's oppression. Drawing on trauma theory, the article argues that perpetrators have been very little studied within trauma studies because of the possible moral implications of giving research time to individuals who have often chosen their own path of violence. Along with theorists such as Kali Tal and Dominick LaCapra, this article investigates the difficult position of perpetrators who are also victims or those who have been traumatized in the act of violence. The paper finally argues that perpetrators may benefit from the opportunity to work through their trauma in the same way that victims work through trauma as a means of healing. In making this argument, this article shows the need for trauma theorists to study perpetrators in addition to current studies on victims and also shows an in depth study of the main character and primary perpetrator in The Dew Breaker.

The vehicle industry must reduce emissions to lessen their environmental impact. Using electric motors for propulsion and batteries for energy storage decreases the pollution and greenhouse gases emitted by heavy commercial vehicles such as trucks and buses. As they often travel long distances, a large energy storage is needed, and it needs to be possible to recharge it quickly. The fast recharging requires high power chargers with high voltage and high current, and that in turn necessitates a suitable overcurrent protection system to avoid damageif a fault would occur. Possible technologies for this overcurrent protection system are investigated in this thesis, and the different solutions are evaluated based on important metrics. A solid state breaker is found to be a promising technology that limits the current quickly and reliably. The evaluation including computer simulations shows that the technology is feasible, but some aspects of the circuit design need to be executed carefully like the inductance, the sampling frequency of the current measurement, and the design of the snubber circuit.