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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
471

Design podtlakového chodícího pásu / Design of the vacuum treadmill

Havránek, Jakub January 2011 (has links)
The diploma thesis concerns with the design of the vac- uum treadmill. The aim was to create a vision of this machine for the near future. As the final result we en- counter a brand new conception, consisting of the outer stable base, inner tilting base, upper frame with steel handle, control panel and airtight bellows. The design includes 3 different colour schemes. The first part of the thesis analyses the historical de- velopment and construction and design solutions. The second part describes this particular design project in detail, including its development.
472

Oduhličení a odplynění vysokolegovaných chromových ocelí ve vakuu / Decarburisation and degassing of high-alloyed Cr steels under vacuum

Ertelt, Tomáš January 2014 (has links)
The work deals with the investigation of the effects of vacuum degassing and decarburization in high alloyed stainless steel. The reason for this is to increase corrosion resistance and mechanical properties. The theoretical part is devoted to the analysis of options to reduce carbon, nitrogen, hydrogen and manganese at atmospheric pressure and in vacuum. In experimental part there is the description of melting, calculation of conditions facilitating reduction of oxide inclusions as a function of the gas pressure in the furnace and the evaluation of the influence of vacuum on the content reduction of carbon, nitrogen and manganese.
473

Komora pro elektronové svařování / Working chamber of electron beam welder

Červinka, Petr January 2015 (has links)
The submitted work deals with the design of the working chamber of the electron beam welders. This vacuum chamber of the cubic shape, with a volume of approx. 100 litres will be used in the ÚPT of the AV ČR v.v.i. during building an experimental welding with electron gun performance 2 kW with accelerating voltage 60 kV. The theoretical part is about the theory of electron welding, electron beam welders of basic sections of the facility, and about possibilities of the technology for welding working chambers. In the practical part of the thesis is being thought out the design of the working chamber (construction chamber in design software), the strength test of construction chamber in the software ANSYS and the design of appropriate methods of welding. The sample of the material which is the stainless steel 17240, from which the chamber will be made, have been used in methods of welding TIG and MAG that was verified by the suitability of the chosen methods of welding.
474

Oduhličení austenitických ocelí a jeho vliv na vlastnosti materiálu / Decarburization of austenitic steels and its influence on material properties

Vítek, Radovan January 2015 (has links)
This master´s thesis deals with theoretical study of decarburization of austenitic steels. Mathematical model, which analyse numerical calculations, was compared with experiments. Obtained results were discussed considering validity of model and performed aproximations.
475

Photoexcitation et relaxation de cyanopolyynes en phase gazeuse dans le domaine de l'ultraviolet du vide / Photoexcitation and relaxation of gas-phase cyanopolyynes in the vacuum ultraviolet range

Lamarre, Nicolas 29 June 2016 (has links)
Ce travail de thèse, essentiellement de nature expérimentale, s’inscrit dans le domaine de la physique moléculaire en phase gazeuse avec des applications en astrophysique. Il porte sur l’étude de la photoexcitation et de la relaxation de molécules de la famille des cyanopolyynes qui sont détectées dans plusieurs objets du milieu interstellaire (nuages moléculaires, comètes) et dans les atmosphères planétaires comme celle de Titan. Ces composés participent à la chimie du carbone dans ces milieux en interagissant avec le rayonnement interstellaire ou avec le flux solaire dans le domaine spectral de l’ultraviolet du vide (VUV). La structure électronique excitée de plusieurs cyanopolyynes neutres a été étudiée avec la spectroscopie d’absorption par transformée de Fourier. Ces expériences ont permis d’identifier les états de Rydberg et de mesurer la section efficace absolue de photoabsorption. Parmi les processus de relaxation ouverts suite à la photoexcitation VUV, les voies d’ionisation et d’ionisation dissociative ont été explorées de façon détaillée à l’aide du rayonnement synchrotron SOLEIL ou du rayonnement laser du Centre Laser de l'Université Paris-Sud. Des informations variées (potentiels d’ionisation vers les premiers états électroniques, fréquences vibrationnelles, couplages vibroniques, etc) ont été obtenues sur les cations de cyanopolyynes via l’utilisation de la spectroscopie de photoélectrons de seuil et de la spectroscopie de photoélectrons d’énergie cinétique nulle. Enfin, la détection par spectrométrie de masse des fragments cationiques issus de l’ionisation dissociative a permis de mesurer leur énergie d’apparition et de déterminer leur voie de formation à l’aide de calculs DFT menés par un collaborateur. / This PhD thesis presents essentially an experimental work dealing with gas-phase molecular physics with astrophysical applications. The goal of the PhD is the study of the photoexcitation and relaxation of cyanopolyyne molecules that have been detected in different interstellar objects (molecular clouds, comets), and in planetary atmospheres (e.g. Titan). These molecules contribute to the carbon chemistry of these media by interacting with the interstellar radiation or with the solar flux in the vacuum ultraviolet range (VUV). The excited electronic structure of neutral cyanopolyynes was studied by absorption spectroscopy with a VUV Fourier-transform spectrometer. These experiments allowed us to identify the Rydberg states, and to measure the absolute photoabsorption cross section.Among the different open relaxation processes following a VUV photoexcitation, ionisation and dissociative ionisation have been investigated in detail using SOLEIL synchrotron radiation or laser sources of Centre Laser de l’Université Paris-Sud. Data on the ionisation potentials toward the first electronic states, vibrational frequencies, vibronic couplings, etc. were obtained on cyanopolyyne cations with the use of threshold photoelectron spectroscopy and zero-kinetic-energy photelectron spectroscopy. Finally, cationic species created by dissociative ionisation of cyanopolyynes were detected by mass spectrometry. The threshold energies were measured and the formation channel of these fragments was determined with the help of DFT calculations performed by a collaborator.
476

Equipamento de ordenha, manejo e fatores de risco para patologias não infecciosas das tetas de vacas leiteiras

Gouvêa, Fábio Lucas Rezende de January 2019 (has links)
Orientador: José Carlos de Figueredo Pantoja / Resumo: Os objetivos deste estudo foram descrever características do equipamento e manejo de ordenha, características morfológicas das tetas, prevalência de patologias não infecciosas, e identificar fatores de risco para tais patologias. Quarenta rebanhos foram visitados para realização de levantamento de dados produtivos e de manejo, avaliação estática do equipamento de ordenha, avaliação dinâmica de parâmetros de vácuo coletados no conjunto de ordenha e dos procedimentos adotados pelos colaboradores. Houve grande heterogeneidade nas dimensões das tetas avaliadas. A prevalência de edema, anel de base, cianose, hemorragia petequial e hiperqueratose grave foi 7,81%, 45,47%, 14,69%, 0,63% e 11,88%, respectivamente. Formato e posição da teta foram associados à observação de hiperqueratose. Paridade, extração automática do conjunto, nível de vácuo e duração da fase B do ciclo de pulsação foram associados à prevalência de edema. Paridade, formato da teta e tempo de ordenha foram associadas à prevalência de anel de base. Fluxo de leite bimodal, extração automática, condição da teteira, sobreordenha, nível de vácuo na cabeça da teteira e comprimento da fase B foram associados à prevalência de cianose. Práticas indesejáveis, tais como uso de teteiras desgastadas, falta de manutenção do equipamento, ausência de extração automática, longo tempo de ordenha e sobreordenha e rotina de trabalho sequencial foram mais frequentemente observadas em rebanhos com até 50 vacas, destacando dificuldades té... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objectives of this study were to describe characteristics of milking equipment and management, teat morphological characteristics, prevalence of noninfectious pathologies, and to identify risk factors for such pathologies. Forty herds were visited to collect production and management data, evaluation of the milking equipment, dynamic evaluation of vacuum parameters collected from the milking cluster, and milking procedures adopted on the farms. There was great heterogeneity in teat dimensions. The prevalence of edema, ring at the teat base, cyanosis, petechial hemorrhage, and severe hyperkeratosis was 7.81%, 45.47%, 14.69%, 0.63%, and 11.88%, respectively. Teat shape and position were associated with teat-end hyperkeratosis. Parity, automatic extraction of clusters, vacuum level, and length of the pulsation cycle´s B phase were associated with prevalence of edema. Parity, teat shape and milking duration were associated with prevalence of ring at the teat base. Bimodal milk flow, automatic extraction, liner condition, overmilking, vacuum at the mouthpiece chamber, and phase B´s length were associated with prevalence of cyanosis. Undesirable practices, such as the use of worn liners, lack of equipment maintenance, lack of automatic extraction, long milking and overmilking times, and sequential working routine were most often observed in small herds (< 50 cows), highlighting technical and structural difficulties faced by producers. Results of this study contribute to improve... (Complete abstract click electronic access below) / Mestre
477

Trends in Vacuum Technology and Pneumatics in the Context of Digitalization

Schmalz, Kurt, Winter, Albrecht January 2016 (has links)
Digitalization is finding it’s way into production and machine-building. Autonomous, sefoptimizing and highly interconnected units will determine the functionality of machines and production facilities. Communication and automation layout will fundamentally change, data will be more and more the base for new business modells. Innovation is determining pneumatics and handling technology. The innovation topics performance improvement, modular and mechatronic design of systems, sustainability and efficiency are keeping pneumatics and vacuum technology on the pathway of success. But is the technology field also prepared for the tremendous challenges caused by the digitalization? This paper is focusing on the significance of digitalization for fluid technology, especially for pneumatics and vacuum technology. The new concepts of digitalization and autonomization are based on the Internet of Things with open Communication of cyber-physical systems. These cyber-physical systems are able to react autonoumously. Cyber-physical systems can collect, interpret and analys data and transfer it into valuable information. Based on these data, cyberphysical systems will provide services to all participants of the smart factory. There will be a digital image inside the factory cloud, which is the base of new business models. Systems of pneumatics, vacuum technology and hydraulics will play a core role in this world. They are placed directly at the interface to the real technical process, they have direct contact with the workpieces, they are collecting multitude of sensor data and are evaulating it, they have functionality like Condition Monitoring and Energy Efficiency optimization on board and are able to communicate with the world of automation. This paper will show, that the innovation trends of the last years are supporting the way towards digitalization and Industrial Internet of Things. There are already a lot of different approaches to establish vacuum and pneumatic systems as adequate elements of the digitalized world. It will also be shown, that fluid technology still is facing tremendous challenges It will be not sufficient to equip the systems with more functionality and better communication. It will be essential, that from the interpretation and correlation of data will be derived valuable services with real customer benefit. This should happen under control of the vendors of smart field devices in fluid technology. Then it will be possible to turn this new kind of value generation also into new business models.
478

Optimization of pneumatic vacuum generators – heading for energy-efficient handling processes

Kuolt, Harald, Gauß, Jan, Schaaf, Walter, Winter, Albrecht January 2016 (has links)
In current production systems, automation and handling of workpieces is often solved by use of vacuum technology. Most production systems use vacuum ejectors which generate vacuum from compressed air by means of the Venturi effect. However, producing vacuum with compressed air is significantly less efficient than using other principles. To minimize the energy costs of pneumatic vacuum generation or to make full use of the energy available, it is important that the inner contour of the nozzle is shaped precisely to suit the specific application - also the system\'s flow conduction needs to be optimal and the flow losses have to be minimized. This paper presents a method for optimally designing pneumatic vacuum generators and producing them economically even at very low lot sizes in order to keep the operation costs low and address other concerns (such as noise emissions) as well.
479

Promotion of sustainable renovation in the built environment : An early stage techno-economic approach

Gohardani, Navid January 2012 (has links)
According to the Swedish Government's set targets for energy use and environmental quality imposed by the European Union, the total energy per heated unit area in residential and commercial buildings will have to be decreased by 20% in 2020 and 50% by 2050 in relation to the annual consumption of 1995. The building sector should additionally be completely independent of fossil fuels for energy usage, with the increasing sector of renewable energy continuously growing until 2020. In its current state, the number of multistory buildings and single-family houses in Sweden exceeds 4 000 000 units. In order to attain the set goals, renovation of the existing housing stock is a necessity given its current relatively slow turnover. As a result of the Swedish Million Unit Program undertaken during 1965−1974, about 750 000 apartments are currently in need of renovation in order to meet today's building standards. Simultaneously, new buildings are built with energy efficiency in mind. In this study an early stage methodology is developed for building refurbishment that takes advantage of a multi-faceted approach. The methodology comprises of multiple dimensions related to a techno-economic, environmental and building occupancy approach. The work presented herein includes a thorough literature review of decision making tools within the built environment and identifies major research efforts in sustainable refurbishment. The technical aspect of this study deals with the proper identification of high-efficient insulation materials that would serve one of the set purposes of energy efficiency when utilized within building envelopes. Further, results are shown for case studies, in which economic investments in Vacuum Insulation Panels (VIPs) and a coupled heat and moisture transport for predefined configurations of VIPs with supplementary insulation of balcony slabs and wall cross-sections are considered. The developed methodology also examines simulations of the total energy consumption utilizing a set of different insulation materials such as mineral wool and VIPs, for a number of locations in Northern and Southern Europe. The research findings of this study identify several aspects of a new developed tool for decision making, to be used in sustainable renovation and refurbishment. / <p>QC 20120918</p>
480

Carbon and Oxygen reduction during vacuum annealing of stainless steel powder

Mallipeddi, Dinesh January 2012 (has links)
Stainless steel family grades are very famous for their combined corrosion resistance and high mechanical properties. These properties can be improved further by decreasing the content of impurities like carbon and oxygen. The main purpose of this research work is to study the possibility of stainless steel powder decarburization by vacuum annealing. The influence of different process parameters like treatment time, temperature, fraction size and depth of the powder layer on the decarburization process was analyzed. The investigation results showed that it is possible to achieve extra low values of carbon and oxygen in steel powder by processing it with optimum process parameters.

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