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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.
51

Measuring the contact pressure during sheet metal forming of automotive components

Andersson, Andreas January 2020 (has links)
The competition in the car market in the world is continuously intensifying. To gain an advantage in the market while making a profit, each car manufacturer needs a strong focus on always improving in the technology development. It is not just technology of the cars that need development, but it is equally important to improve the manufacturing processes itself. In the end, this will result in more appealing products for the customer at a competitive cost. The aim and scope of this master thesis is to get a deeper understanding of the forces in the stamping die during sheet metal forming in manufacturing. By using strain gauges and microcontrollers, the forces during the entire forming process could be measured and analyzed. The relationship between the force on the pressure pins in the die and the length of the pressure pins was also investigated by adding shims on the pressure pins. A modular system using Arduino Uno with 3D-printed parts was developed to measure the forces in the blank holder during sheet metal forming. An Arduino software system and TeraTerm was found the most appropriate for collecting and organizing data from the strain gauge sensors and microcontrollers. Tests were then conducted using different settings of the press, and these showed that the forces in the blank holder were uneven. Adding shims to the pins so that they were all of equal length evened out the forces in the blank holder. Another test showed that adding more shims to only one of the pins increased the force in that pin, and that adding 0.5mm of shims to that pin more than doubled the maximum force. The system developed in this thesis can measure the forces in the blank holder during the sheet forming process at a lower speed of production. This system can also detect different force settings in the press. Lastly, it can also detect a difference in force for different pressure pin lengths. / Konkurrensen på bilmarknaden i världen intensifieras kontinuerligt. För att få en fördel påmarknaden samtidigt som de gör vinst måste varje biltillverkare ha ett starkt fokus på att alltid förbättrateknikutvecklingen. Det är inte bara bilens teknik som behöver utvecklas, utan det är lika viktigt attförbättra tillverkningsprocesserna i sig. I slutändan kommer detta att resultera i mer attraktiva produkterför kunden till ett konkurrenskraftigt pris. Syftet och omfattningen av detta examensarbete är att få en djupare förståelse av krafterna ipressverktyget under plåtformningprocessen. Genom att använda töjningsgivare och mikrokontrollerkunde krafterna under hela formningsprocessen mätas och analyseras. Förhållandet mellan kraften påmothållarpinnarna i verktyget och längden på pinnarna undersöktes också genom att lägga till shims påpinnarna. Ett modulsystem som använde Arduino Uno med 3D-printade delar utvecklades för att mätakrafterna i formen under formningsprocessen. Ett Arduino-mjukvarusystem och TeraTerm bedömdesvara det mest lämpliga för att samla in och organisera data från töjningssensorer och mikrokontroller. Tester genomfördes sedan med olika inställningar i pressen, och dessa visade att krafterna ipressverktyget var ojämna. Genom att lägga till shims på pinnarna så att de alla var lika långa utjämnadeskrafterna i pressverktyget. Ett annat test visade att genom att lägga till fler shims på endast en avmothållarpinnarna ökade kraften i pinnen. Genom att tillägg till 0,5 mm shims på den pinnen mer änfördubblade den maximala kraften. Systemet som utvecklats i denna rapport kan mäta krafterna i pressverktygets mothållarpinnarunder formningsprocessen vid en lägre produktionshastighet. Detta system kan också upptäcka olikakraftinställningar i pressen. Slutligen kan den också upptäcka skillnader i kraft vid olika längder påmothållarpinnarna.
52

マシニングセンタを用いたスレッドミルのヘリカル補間運動に基づく雌ねじ切り加工法に関する研究 / マシニング センタ オ モチイタ スレッド ミル ノ ヘリカル ホカン ウンドウ ニ モトズク メネジキリ カコウホウ ニカンスル ケンキュウ

松井 翔太, Shota Matsui 22 March 2021 (has links)
本報は,雌ねじ切り工具であるスレッドミルを使用した雌ねじ切り加工を研究対象としている.スレッドミル加工の特性やねじ精度について,切削力や加工温度を計測し解析することで検討をおこないその結果を記載している.計測には無線ホルダやサーボドライブユニット等の最新のIoT技術も使用することで,近年増加傾向にあるIoT技術の適応も試みた. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University
53

Coordination of Cell Fate Specification and Cell Movements by Morphogenetic Gradients

Xue, Yongqiang 22 January 2021 (has links)
No description available.
54

Development of Medical Equipment to make Colonoscopy Procedures Safer for Physicians: Control Head Holder and Splatter Shield

Shanbhag, Rajesh Ravindra January 2014 (has links)
No description available.
55

John-Stromberg Inequality for Certain Anisotropic BMO Spaces

Hu, Yingfeng 01 June 2018 (has links)
No description available.
56

[en] REGULARITY TRANSMISSION BY APPROXIMATION METHODS: THE ISAACS EQUATION / [pt] TEORIA DE REGULARIDADE POR MÉTODOS DE APROXIMAÇÃO: A EQUAÇÃO DE ISAACS

MIGUEL BELTRAN WALKER URENA 30 April 2020 (has links)
[pt] A equação de Isaacs é um exemplo importante de equação elíptica totalmente não-linear, aparecendo em uma grande variedade de disciplinas. Um fato de interesse particular é que tais equações são dirigidas por operadores não convexos. Portanto, são compatíveis com a teoria de EvansKrylov e apresentam delicados desafios quando se trata de sua teoria da regularidade. Descrevemos uma série de resultados recentes sobre a teoria da regularidade da Equação de Isaacs. Estas cobrem estimativas nos espaços Hölder e Sobolev. Argumentamos através de um método genuinamente geométrico, importando informações de uma equação de Bellman relacionada. / [en] Isaacs equation is an important example of fully nonlinear elliptic equation, appearing in a wide of disciplines. Of particular interest is the fact that such equations are driven by nonconvex operators. Therefore, it falls off the scope of the Evans-Krylov theory and poses additional, delicate, challenges when it comes to its regularity theory. We describe a series of recent results on the regularity theory of the Isaacs equation. These cover estimates in Holder and Sobolev spaces. We argue through a genuinely geometrical method, by importing information from a related Bellman equation.
57

Resistência térmica de diferentes espoligotipos de Mycobacterium bovis à pasteurização lenta (65ºC) em leite experimentalmente inoculado / Thermal Death Kinetics (65°C) of some Mycobacterium bovis spoligotypes recently isolated from bovines

Felipe, Tatiane Hoshida 11 December 2009 (has links)
A pasteurização do leite é obrigatória no Brasil e o sistema lento (65ºC/30 minutos) é o mais empregado na fabricação de queijos. Os parâmetros de tempo e temperatura empregados no mundo foram definidos após estudos sobre a resistência térmica do Mycobacterium tuberculosis e da Coxiella burnetti, reconhecidos como os microrganismos patogênicos, não formadores de esporos e que eventualmente podem estar presentes no leite cru, que apresentam a maior resistência térmica. Entretanto, não há estudos sobre a resistência térmica do M. bovis que circula nos bovinos no Brasil. Este estudo propôs-se a avaliar a resistência térmica (65ºC) de cinco espoligotipos de M. bovis, isolados de bovinos abatidos no estado de São Paulo, em leite integral experimentalmente contaminado. Leite UHT foi contaminado com M. bovis e, então, submetido a tratamento térmico em banho-maria a 65ºC por 30 minutos. Cada espoligotipo foi testado 3 vezes. As amostras foram retiradas do banho nos tempos 0 (o momento em que o leite atingiu 65ºC), 5, 10, 15, 20, 25 e 30 correspondendo ao tempo, em minutos, de tratamento térmico. O leite contaminado também foi analisado, para quantificação da carga inicial. O controle do processo envolveu o acompanhamento da temperatura do leite (um tubo com termômetro) e análise das enzimas fosfatase alcalina e peroxidase ao final do tratamento; para tal, amostras de leite cru foram tratadas juntamente com as amostras-teste. Para quantificação, foi realizada a diluição decimal seriada seguida da semeadura em duplicata em meio Stonebrink-Leslie (37ºC/45dias). Os resultados mostraram que foi na fase de aquecimento que ocorreu a maior taxa de morte. Houve diferença de resistência entre os espoligotipos ao processo que simulou a pasteurização lenta e o BR024 foi o mais resistente. Conclui-se que houve diferença da eficácia da pasteurização, de acordo com o espoligotipo testado, mas que os resultados precisam ser melhor investigados. / Milk pasteurization is mandatory in Brazil and the Low Temperature Long Time - LTLT - Pasteurization (62 to 65°C/30 min.) is normally used for cheese making. Permitted parameters were based on the reports of Myconbacterium bovis/tuberculosis inactivation made up to that time. Since then, just a few studies have been done to determine if the M. bovis in circulation nowadays among bovine population still presents the same pattern of inactivation. In this way, this study verified the behavior of recently isolated M. bovis against LTLT Pasteurization parameters reproduced in water bath. M. bovis isolated from bovines slaughtered in São Paulo State, Brazil. When milk reached 65°C the 0 tube was removed and refrigerated while the others taken out after 5, 10, 15, 20, 25 and 30 minutes and cooled. For controlling heat treatment a thermometer was adapted to one tube with 5 ml each of raw milk which were submitted together to heat treatment and used for analysis of peroxidase and alkaline phosphatase enzymes after 30 minutes of heat treatment. Milk samples were submitted to serial decimal dilution in peptone water (0.1%) and inoculated in the Stonebrink-Leslie media. After 45 days at 37°C, colonies were counted and the result expressed in CFU/ml. The results showed that heating phase determined more inactivation than the holding phase. The resentence was different between the spoligotypes that simulated the low pasteurization and BR024 was more resentence. The results enable us to speculate that in the worst scenario of natural contamination of the milk.
58

Smallholder farmers' perceptions on climate variability in relation to climatological evidence in the Molemole Municipality (Limpopo Province) South Africa

Rapholo, Maropene Tebello Dinah January 2018 (has links)
Thesis (MSc. (Geography)) -- University of Limpopo, 2018 / In spite of the widespread scientific debate on the impacts of climate variability, not much is known about smallholder farmers’ perceptions towards climate variability and the impacts thereof on their agricultural practices. This is especially true for smallholder farmers in Sub-Saharan Africa in general and South Africa in particular. Literature contends that an understanding of the farmers’ perceptions of climate change and variability is indispensable for effective policy formulations and adaptive strategies. This current study posits that discrepancies between farmer perceptions and climatological evidence will negatively impact on farmer adaptation options and outcomes. The objectives of the study were to; (1) assess climate variability in Molemole Local Municipality, Limpopo Province, (2) investigate farmers’ perceptions of climate variability, (3) compare farmers’ perceptions of climate variability with climatological data and (4) appraise farmers’ adaptive strategies to climate variability. A total of 125 farmers from Botlokwa Village participated in the study. The village was selected because it is the largest village in the municipality and it comprises mainly of rural farmers that are involved in rain-fed subsistence agriculture. In addition, the village receives limited government intervention and is in close proximity to a functional climate station (Polokwane Airport Weather Station). Based on purposive sampling, focus group discussions and a three-part closed ended questionnaire was administered to the farmers. Mean annual temperature and rainfall data (30 years) was used to assess climate variability in the study area. Farmers’ perceptions to climate variability was assessed using descriptive statistics based on summary counts of the responses with Statistical Package for Social Science (SPSS) program. Logistic regression analysis was used to compare differences in perception (mean responses). Comparison of farmers’ perceptions of climate variability against climatological evidence was restricted to mean annual temperature and rainfall data over the past 5 – 10 years). To appraise farmers’ adaptive strategies, the Adaptation Strategy Index (ASI) and the Weighted Average Index (WAI) were employed. vi Farmers’ perceptions of climate variability were consistent with recorded meteorological data. Based on the ASI and WAI computations, use of indigenous knowledge systems (IKS) and crop management approaches were highly important adaptation strategies while the use of insurance and subsidies were least employed by the farmers. The results from the study also showed that the age of the household head, gender, level of education, farming experience and access to information on climate variability were crucial factors in influencing the likelihood of farmers to perceive climate variability. Given the overwhelming dependence on IKS for weather forecast, and adaptation to climate variability, it is recommended that IKS take centre stage in government initiatives and policies on climate change and variability, especially for smallholder farmers in rural settings. Sensitisation on the use of technology such as cellular phones to receive weather forecast is also recommended.
59

Comparing the performance of storage phosphor plate and insight film for the detection of proximal caries depth.

Crombie, Karima. January 2008 (has links)
<p><font face="Arial"> <p align="left">The aim of this study is to compare proximal caries depth on unenhanced storage phosphor plate images and conventional film images. The phosphor plate images were then copied by increasing and decreasing both contrast and brightness respectively. The enhanced phosphor plate images were compared with the unenhanced storage phosphor plate images and conventional film images for the detection of proximal caries diagnosis.</p> </font></p>
60

Application of a Network Model for Complex Fenestration Systems

Rogalsky, Christine Jane January 2011 (has links)
In the fight to reduce carbon emissions, it is easy to see the necessity of reducing energy consumption. Buildings consume a large amount of energy, and have significant potential for energy savings. One tool for realising these potential savings is building simulation. To be able to use building simulation, accurate models for windows are needed. The models include individual layer models, to determine the solar and longwave radiative behaviours, as well as whole-system models to determine heat flows through the various layers of fenestration systems. This thesis looks at both kinds of models for incorporating windows into building simulations. A new network whole-system model is implemented, and integrated into the California Simulation Engine building simulation software. This model is also used as the calculation engine for a stand-alone rating tool. Additionally, a measurement technique used to measure off-normal solar properties of drapery materials, as part of developing shading layer models, is investigated using a Monte Carlo simulation. The network model uses a very general resistance network, allowing heat transfer between any two layers in a complex fenestration system (CFS), whether they are adjacent or not, between any layer and the indoor or outdoor side, or between the indoor and outdoor sides, although this last case is unlikely. Convective and radiative heat transfer are treated using the same format, resulting in increased stability. This general resistance network is used to calculate indices of merit for the CFS using numerical experiments. This approach requires fewer iterations to solve than previous solution methods, and is more flexible. The off-normal measurement technique which was investigated used a sample holder inserted into an integrating sphere. This is a non-standard way of using an integrating sphere, and early analyses did not provide conclusive information as to the effect of the sample holder. A Monte Carlo analysis confirmed the amount of beam attenuation as being 20% for the sample holder used in the experiments. Also con firmed was the effectiveness of dual-beam integrating spheres in correcting for the presence of a sample holder. The stand-alone rating tool which uses the general network framework, incorporates an easy-to-use visual interface. This tool models multiple types of shading layers with no restrictions on how they are combined. Users can easily change any one layer to see the effects of different arrangements. Users may specify any combination of indoor and outdoor ambient and mean radiant temperatures, insolation, and beam/diffuse split.

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