Academic literature on the topic 'Chvění'

This thesis encompasses measuring and rating of vibrations in electric machines. The theoretical part begins with a short description of possible causes of vibrations, which is followed by a discussion about what consequences the vibrational effects have on electrical devices. Then there is a description of available vibration sensors. The bigger part is then devoted to analysis of vibratory signal in both time and frequency domains. The practical part is divided into two chapters. The first one describes laboratory demonstration of control drive with DC motor, which is expanded by measurement of vibrations. The second chapter deals with measurement and analysis of said vibrations in the demonstration.

This master's thesis deals with vibrodiagnostics and its use for monitoring of the vibration transmission during grinding of large shafts at Siemens Electric Machines s.r.o. based in Drásov. Diagnostic system for machine tools testing was designed as well as a measurement methodology, which is used to detect the vibration transfer from the grinding spindle to the workpiece. Influences that affect the quality of the ground surface were determined, based on evaluation of measured data. The last part is dedicated to a proposal of a diagnostic and measuring system.

The diploma work deals with a mathematical description of vibration and its generation when machining. Moreover, some techniques of modal parameters measurement in the theoretical part are included. The practical part is designed and based on the measured natural frequencies of the machine with specific tool and materials. In conclusion, a lobe diagram stability for semiautomatic lathe SPN 12 CNC and selected machining operation is specified by means of apparatus.

This diploma thesis is concerning about summarizing and describing types of vibrations, their causes and influences to the machining. The stable conditions of machining were pointed out. The experiment was conducted in which the frequency response function of specific milling machine was measured. Than the stability lobe diagram was constructed.

The theoretical part of the thesis deals with materials used in the aircraft industry with a focus on aluminium alloys. Then it describes high speed machining, its characteristics and its comparison with conventional machining. The following chapters describe strategies of machining thin-walled parts and a description of vibration that occurs during machining. The practical part deals with selection appropriate tool geometry, machining of thin-walled parts and evaluation of their deflection during machining.

Este estágio foi realizado durante cinco meses na Unidade I do Centro Hospitalar de Vila Nova de Gaia/Espinho (CHVNG/E), em que colaborei no Serviço de Equipamentos e Electromedicina (SEE). Pretendeu-se efectuar um levantamento rigoroso dos equipamentos de electromedicina localizados nos blocos operatórios para apoiar a concepção da planificação da manutenção preventiva para o ano de 2011. Durante o estágio, além da construção do mapa de equipamentos dos blocos operatórios, foi possível elaborar as fichas de manutenção do que é efectuado em cada manutenção. Elaborou-se um total de 16 fichas de reparação preventiva para cada equipamento abrangendo 377 equipamentos de electromedicina dos blocos operatórios. A constante aquisição de novos equipamentos permitiu verificar e compreender como se desenrola o processo de compra, recepção, facturação e inventariação do equipamento hospitalar. Processos de renovação de contratos levaram a uma verificação da existência e do local dos equipamentos do Centro Hospitalar. Adquiriu-se também experiência no domínio do processo de abate de equipamentos relevante devido à constante substituição de equipamentos hospitalares. Verificou-se que o software utilizado para a gestão do hospital apresentava diversas lacunas relativas à gestão da manutenção. Estas falhas foram identificadas e criaram-se ferramentas alternativas de apoio à manutenção. As ferramentas criadas, e os resultados daí obtidos, permitiram alterar 43,3% dos contratos de manutenção dos equipamentos através da alteração de Contrato de Assistência Técnica Anual para o Regime de Ordem de Trabalho ou Manutenção Interna. Foram obtidas economias substantivas, mas cujo montante é informação confidencial. The study reported here was performed at the Unit I of the Centro Hospitalar de Vila Nova de Gaia/Espinho, EPE during a five-month internship, where I’ve collaborated within the Service of Electromedicine and Equipments. With the objective to support the creation of a preventive maintenance plan for 2011, an extensive survey of all electro-medical equipments existing in the Operating Rooms was executed. In order to accomplish this purpose, a list of equipments in each operating room was elaborated and the maintenance procedures for each medical service were organized. A total of sixteen documents on equipment´s preventive repair were created for the 377 electro-medical machines actually on use. Due to the permanent acquisition of new equipment, it was possible to verify and to understand the flow of the purchasing, receiving, invoicing and inventorying process of these hospitalar equipments. Furthermore, the update of external technical assistance contracts represents an additional source of information about the equipments existence and location. During my internship, I have also acquired relevant experience in the bureaucratic process of equipments elimination that is very significant due to the constant replacement of hospitalar equipments. Important gaps concerning the equipments maintenance were revealed and alternative tools were created. These new tools and the results obtained with them allowed to adjustments in 43,1% of the maintenance contracts. These contracts have been transferred from Annual Technical Assistance Contracts to the Regime of the Work Order or Internal Maintenance Contracts with considerable cost savings. These cost savings amount is confidential.

Introdução: A estenose valvular aórtica (EA) representa uma redução da área de abertura sistólica da válvula aórtica, sendo a EA degenerativa relacionada com a idade, a etiologia mais comum em adultos. Este trabalho pretende estudar o capítulo da EA, nomeadamente o seu novo tratamento – Substituição percutânea da válvula aórtica (TAVI). A implantação da válvula aórtica por via percutânea é um procedimento emergente no tratamento dos doentes com EA severa, sendo uma possível alternativa ao tratamento cirúrgico. A evolução da técnica e dos materiais tem simplificado e generalizado a sua utilização. Métodos: Para elaborar a revisão bibliográfica, procedeu-se a uma análise e compilação de informação actualmente existente. Relativamente à análise da casuística do Centro Hospitalar de Vila Nova de Gaia (C.H.V.N.G), para determinar o número de casos de EA tratados com a TAVI, procedeu-se à análise retrospectiva dos processos clínicos. Os dados recolhidos são referentes aos pacientes submetidos a este tipo de intervenção nas datas compreendidas entre 30 de Agosto de 2007 a 28 de Fevereiro de 2011. A selecção dos pacientes incluídos neste tratamento implicou alguns factores como: doente com EA grave (área <0,7cm²/ m²) sintomáticos e recusados para cirurgia de substituição valvular. Foi utilizado em todos eles o dispositivo CoreValve, uma prótese auto-expansível de pericárdio porcino, montada numa estrutura de nitinol e entregue num cateter. Resultados: Ecocardiograficamente, a maioria dos pacientes apresentaram gradientes médio e máximo de pressão Ventrículo Esquerdo - Aorta (VE-Ao) aumentados (53,2±12,7 mmHg e 88,8± 19,2 mmHg, respectivamente) e área média da válvula aórtica (AVA) diminuída (0,52±0,10 cm²). 59% apresentaram Insuficiência Mitral (IM) grau ≤ I e 41% grau II. Mais de 50% tinha Insuficiência Aórtica (IA) ≤I e 3% tinha uma IA de grau III. Vinte e sete apresentaram Hipertensão pulmonar (HTP) (designada por uma PSAP> 40mmHg). Após a TAVI, a AVA média aumentou para 1,63±0,23 cm² e os gradientes médio e máximo diminuíram para 18,5±4,5 mmHg e 21,36±10,1 mmHg, respectivamente. Dos 59 pacientes seguidos, 14 já faleceram, 42 permanecem vivos e os 3 restantes deixaram de ter qualquer contacto com o Hospital. Conclusão: Verificou-se que a aplicação da TAVI é maior no sexo feminino, sendo no entanto desejável a todos os pacientes com comorbilidades e factores que os impedem de seguir a via de tratamento comum – substituição cirúrgica da válvula aórtica (AVR). Pode ser então uma técnica eficaz na melhoria da qualidade de vida dos doentes com EA, sendo uma potencial alternativa válida em doentes com EA severa sintomática.<br>Introduction: The aortic valve stenosis (AS) represents a decreasing of the aortic valve´s systolic opening area, being the age related degenerative AS the most common etiology in adults. This bibliographical revision aims to study the AS chapter, namely its new way of treatment – Transcatheter Aortic Valve Implantation (TAVI). The percutaneous aortic valve implantation is an emerging procedure in the healing of patients with severe AS, being a possible alternative to surgical treatment. The whole technique and materials development has simplified and generalized its use. Methods: In order to prepare the bibliographical revision, an analysis was done and a compilation from the currently available data as well. For the analysis of the sample of Centro Hospitalar de Vila Nova de Gaia (C.H.V.N.G), it was done the retrospective analysis of the clinical processes so as to determine the number of the EA cases treated with TAVI. The data collected refer to the patients undergoing this type of intervention, from August 31st 2007 to February 28th 2011. The selection of patients included in this treatment involved several factors such as: symptomatic patients with severe AS (area <0,7cm²/ m²) who were refused to surgical valve replacement. A device called CoreValve was used in all of them, consisting of a porcine pericardium self-expandable prosthesis, applied on a nitinol frame and delivered in a catheter. Results: Through the ecocardiography, most of the patients had an increased mean and maximum Left Ventricle – Aorta pressure gradients (VE-Ao) (53,2±12,7 mmHg e 88,8± 19,2 mmHg, respectively) and a decreased average area of the aortic valve (AVA) (0,52±0,10 cm²). 59% had grade ≤ I mitral regurgitation (MI) and 41% grade II MI. More than a half had grade ≤I aortic regurgitation (AI) and 3% had a grade III AI. Twenty seven patients had pulmonar hypertension (HTP) (represented by a PSAP (Pulmonary artery systolic pressure) >40mmHg). After the TAVI procedure, the AVA increased to 1,63±0,23 cm² and the mean and maximum transvalvular gradients decreased to 18,5±4,5 mmHg e 21,36±10,1 mmHg, respectively. From the 59 treated patients, 14 have already died, 42 are still alive and the remaining 3 no longer had any contact with the Hospital. Conclusion: It was found that the TAVI´s application is higher in females; however, it´s recommended to all patients with comorbidities and factors that prevent them from following the lead of the common treatment – surgical aortic valve replacement. It may be then an effective technique to improve AS patients’ quality of life, being a powerful alternative in patients with severe symptomatic AS.