• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 46
  • 29
  • 24
  • 10
  • 10
  • 3
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 146
  • 16
  • 16
  • 15
  • 15
  • 12
  • 11
  • 9
  • 9
  • 9
  • 9
  • 9
  • 8
  • 8
  • 8
  • 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.
71

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

Tatiane Hoshida Felipe 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.
72

Market participation of smallholder sunflower farmers in Sekhukhune District of Limpopo Province, South Africa

Mathagu, Hangwelani Tshilidzi January 2016 (has links)
Thesis (MSc. Agriculture (Agricultural Economics)) -- University of Limpopo, 2016 / The study focused on the market participation of the smallholder sunflower farmers of Sekhukhune District in Limpopo Province of South Africa. A total of 100 smallholder sunflower farmers of Sekhukhune were randomly selected for the study. Data was gathered through the use of structured questionnaires with open-ended questions. The data was analysed using the Logistic Regression model on SPSS 26.0 (statistical package for social sciences). The probability of the smallholder sunflower farmers participating in markets was determined significantly by gender of household head, farm size, level of education, marketing experience, distance to the market, ownership of vehicle and stakeholder availability. Recommendations were made with regard to that of training, monitoring, funding, Government support, access to production land and the involvement of organizations with the smallholder sunflower farmers. Training should be provided for the smallholder sunflower farmers because farmers are always faced with new technology and market changes, there should be a budget that is put aside for the funding of the smallholder farmers, monitoring programs should be implemented in order to monitor the progress of the smallholder farmers, increased access to production land for farming, government support through financial and input support, smallholder farmers should get involved with organizations that can help them with training and funding, and the government should implement policies that are commodity based. Key words: smallholder farmers, market participation, Logistic Regression Model, sunflower, Limpopo province
73

Kryogenní cela pro studium vodního ledu v mikroskopu ESEM / Cryogenic cell for study of water ice in ESEM microscope

Krutil, Vojtěch January 2020 (has links)
The presented thesis focuses on designing a cryogenic cell for the study of water ice in an environmental scanning electron microscope (ESEM). This cell allows the study ice in the temperature range 80 K – 300 K in a nitrogen gas environment with a pressure of up to 400 Pa. The cell is cooled by a flow cooling system, where liquid or gaseous nitrogen is used as a refrigerant. The cell consists of a double-walled vessel with vacuum insulation, a flow-through heat exchanger, a sample well, and a cooled cell lid. The heat exchanger was designed to be able to dissipate the heat load at the level of 1 W. The exchanger is equipped with an electric resistance heater with an output of approximately 60 W, enabling heating of the sample at speeds of up to 100 K·min-1. The design also includes an LN2 gateway located on the door of the vacuum chamber of the microscope, to which the capillaries of the heat exchanger for the intake and outlet of refrigerant are connected. During the experimental verification of the cryogenic cell in the test vacuum chamber with a pressure of GN2 ~ 400 Pa, the limit temperature of 77.5 K on the sample well was reached.
74

Depozice CaF2 ultratenkých vrstev na grafenový substrát / The deposition of CaF2 ultrathin layers on graphene substrate

Caesar, Radek January 2020 (has links)
This master’s thesis is focused on preparation and analysis of ultrathin CaF2 (calcium fluoride) films on a graphene substrate. CaF2 was deposited in UHV conditions at substrate temperatures in the range from 20 °C to 400 °C. The material was deposited on Si(111) with a native SiO2 layer and on a substrate with a CVD graphene layer. The deposited films were analyzed by XPS, AFM and SEM. Moreover four different sample holders for deposition purposes were designed in this work.
75

Untersuchung von additiv gefertigten Prägeformen mit graduellen Eigenschaften hinsichtlich ihres Prägeverhaltens

Mohrich, Maximilian 16 July 2021 (has links)
Ziel dieser Masterarbeit ist die Untersuchung neuartiger Prägeformkonzepte hinsichtlich ihres Prägeverhaltens. Die Konzepte weisen lokal unterschiedliche Materialeigenschaften auf, die zu einer verbesserten Ausprägung von Karton führen sollen. Die Konzepte sollen anhand der Prägeergebnisse und der Abformgenauigkeit evaluiert werden. Dabei ist ein weiteres Ziel der Arbeit, Methoden zur Quantifizierung der Abformgenauigkeit zu finden. Die Herstellung der Konzepte erfolgt mithilfe eines additiven Fertigungssystems, welches mehrere Materialien in einem Bauvorgang verarbeiten kann. Zur Datengewinnung werden Oberflächenscans der geprägten Kartonproben und Werkzeuge durchgeführt. Auf Grundlage dieser Scans werden drei Methoden zur Ermittlung der Abformgenauigkeit vorgeschlagen. Abschließend werden die Werkzeuge anhand der Prägeergebnisse und der ermittelten Abformgenauigkeit bewertet. Weiterhin werden die vorgeschlagenen Methoden miteinander verglichen und deren Vor- und Nachteile diskutiert. Dies gibt Auskunft darüber, unter welchen Bedingungen der Einsatz welcher Methode sinnvoll erscheint.:1. Einleitung 2. Theoretische Grundlagen 2.1 Umformprozesse 2.1.1 Prägen von Faserwerkstoffen 2.1.2 Einsatz von Niederhaltern beim Umformen von Blechen 2.1.2.1 Tiefenziehen 2.1.2.2 Tiefen 2.1.3 Einsatz von Niederhaltern beim Umformen von Karton 2.1.3.1 Ziehen und Pressformen 2.1.3.2 Hydroformen 2.2 Multi-Material-Verarbeitung in der additiven Fertigung 2.2.1 Materialextrusion 2.2.2 Badbasierte Photopolymerisation 2.2.3 Material Jetting 2.2.4 Pulverbettbasiertes Schmelzen 2.2.5 Workflow und Datenvorbereitung 2.3.6 Geeignete Dateiformate 2.3 Soll-Ist-Vergleich von 2.5D-Oberflächendaten 2.3.1 Berechnung von Flächeninhalten und Volumen 2.3.2 Registrierung und Abstandsberechnung von Punktwolken 3. Versuche und Messungen 3.1 Herstellung der Prägeformkonzepte 3.1.1 Beschreibung der Konzepte 3.1.2 Fertigungstechnologie und Materialwahl 3.1.3 Datenvorbereitung für die Polyjet-Fertigung 3.2 Prägeversuche und Datenverarbeitung 3.2.1 Prägeversuche 3.2.2 Oberflächenscan am Keyence 3D-Makroskop 3.3 Ermittlung der Abformgenauigkeit 3.3.1 Flächen- und Volumenberechnung in MatLab & CloudCompare 3.3.2 Abformgenauigkeit nach ICP-Algorithmus & Abstandsberechnung 4. Ergebnisse und Diskussion 4.1 Betrachtung der Prägewerkzeuge 4.2 Betrachtung der Kartonprägungen 4.2.1 Prägeergebnisse nach Flächeninhalt der Profilschnitte 4.2.2 Einfluss der Faserlaufrichtung auf Kartonprägungen 4.2.3 Prägeergebnisse nach Volumen der Punktwolken 4.3 Betrachtung der Abformgenauigkeit 4.3.1 Abformgenauigkeit nach Flächeninhalt & Volumen 4.3.2 Abformgenauigkeit nach ICP-Algorithmus & Abstandsberechnung 4.4 Bewertung der Methoden zur Ermittlung der Abformgenauigkeit 4.5 Beurteilung des Bedienereinflusses bei der Datenverarbeitung am Keyence 5. Zusammenfassung und Ausblick Literaturverzeichnis Eidesstattliche Erklärung / The aim of this master thesis is to investigate novel embossing die concepts with regard to their embossing behavior. The concepts have locally different material properties, which should lead to an improved embossing of cardboard. The concepts are to be evaluated on the basis of the embossing results and the impression accuracy. A further aim of the work is to find methods for quantifying the impression accuracy. The concepts will be manufactured using an additive manufacturing system that can process multiple materials in a single build process. Surface scans of the embossed cardboard samples and tools are performed to obtain data. Based on these scans, three methods are proposed to determine the impression accuracy. Finally, the tools are evaluated based on the embossing results and the determined impression accuracy. Furthermore, the proposed methods are compared with each other and their advantages and disadvantages are discussed. This provides information on the conditions under which the use of which method appears to be sensible.:1. Einleitung 2. Theoretische Grundlagen 2.1 Umformprozesse 2.1.1 Prägen von Faserwerkstoffen 2.1.2 Einsatz von Niederhaltern beim Umformen von Blechen 2.1.2.1 Tiefenziehen 2.1.2.2 Tiefen 2.1.3 Einsatz von Niederhaltern beim Umformen von Karton 2.1.3.1 Ziehen und Pressformen 2.1.3.2 Hydroformen 2.2 Multi-Material-Verarbeitung in der additiven Fertigung 2.2.1 Materialextrusion 2.2.2 Badbasierte Photopolymerisation 2.2.3 Material Jetting 2.2.4 Pulverbettbasiertes Schmelzen 2.2.5 Workflow und Datenvorbereitung 2.3.6 Geeignete Dateiformate 2.3 Soll-Ist-Vergleich von 2.5D-Oberflächendaten 2.3.1 Berechnung von Flächeninhalten und Volumen 2.3.2 Registrierung und Abstandsberechnung von Punktwolken 3. Versuche und Messungen 3.1 Herstellung der Prägeformkonzepte 3.1.1 Beschreibung der Konzepte 3.1.2 Fertigungstechnologie und Materialwahl 3.1.3 Datenvorbereitung für die Polyjet-Fertigung 3.2 Prägeversuche und Datenverarbeitung 3.2.1 Prägeversuche 3.2.2 Oberflächenscan am Keyence 3D-Makroskop 3.3 Ermittlung der Abformgenauigkeit 3.3.1 Flächen- und Volumenberechnung in MatLab & CloudCompare 3.3.2 Abformgenauigkeit nach ICP-Algorithmus & Abstandsberechnung 4. Ergebnisse und Diskussion 4.1 Betrachtung der Prägewerkzeuge 4.2 Betrachtung der Kartonprägungen 4.2.1 Prägeergebnisse nach Flächeninhalt der Profilschnitte 4.2.2 Einfluss der Faserlaufrichtung auf Kartonprägungen 4.2.3 Prägeergebnisse nach Volumen der Punktwolken 4.3 Betrachtung der Abformgenauigkeit 4.3.1 Abformgenauigkeit nach Flächeninhalt & Volumen 4.3.2 Abformgenauigkeit nach ICP-Algorithmus & Abstandsberechnung 4.4 Bewertung der Methoden zur Ermittlung der Abformgenauigkeit 4.5 Beurteilung des Bedienereinflusses bei der Datenverarbeitung am Keyence 5. Zusammenfassung und Ausblick Literaturverzeichnis Eidesstattliche Erklärung
76

Návrhy na zlepšení personálních činností v organizaci / The Proposals of the Improvement of Personal Procedures in the Organization

Šimeček, Filip January 2010 (has links)
This master’s thesis deals with personal management and personal procedures within the organization. In the concrete, it is applied to the public service – Municipality Office of the city district Brno-Zabovresky. The thesis contains also the analysis of the personal procedures of the organization mentioned and possible proposals and methods for their improvement.
77

Výroba opěrného držáku objemovým tvářením / Production of supporting holder by solid forming

Kopecký, Martin January 2008 (has links)
This diploma thesis has been elaborated within the Master's study of department 2307 that submits a production proposal of supporting holder by solid forming. The used material of the forging is steel ČSN 12050 with yearly production of 100 000 pieces. The forging has been performed using drop forging method by two operations at the crank forging press LZK 1000, with induction heating of semi-finished product and flash trimming at the trimming press LKOA 200. For this method have been performed required technological calculations, geometric design of the die and assigning production machines needed for this technology. A part of this study is an economical evaluation where have been stated production expenses and prices of the forging of assigned component.
78

Výroba nosného tělesa objemovým tvářením / Production of carrying body by solid forming

Dvořák, Jan January 2009 (has links)
This diploma thesis has been elaborated within the Master's study that submits a production proposal of carrying body by solid forming. The forging has been performed using drop orging method at the crank forging press LZK 1000. Heating is inductive and flash trimming has been peformed in the trimming press LKOA 200. The used material of the forging is steel CSN 14 220. Production series is 100 000 pieces. A part of this thesis is calkulations, geometric design and economical evaluation.
79

Manipulátor nástrojových držáků a hlav / Tool holders and machining heads manipulator

Neudert, Pavel January 2009 (has links)
Neudert Pavel Goal of this work is preparing different variants of manipulator for changing the tool holder. The report contains choose of optimal solution and specific design solution of manipulator, including technical report and economical conclusions.
80

Výroba tělesa držáku objemovým tvářením / Production of holder body by solid forming

Tichý, Pavel January 2009 (has links)
TICHÝ Pavel: Production of a holder body by solid forming. A Graduation Thesis of Master´s Studies, the 5th Year of Study, the School-year 2008/2009, FSI VUT Brno, Department of Machining, May 2009, Pages No. 80, Appendixes No. 9. The Graduation Thesis, elaborated in the framework of engineering studies, presents the technology of a body holder production carried out by solid forming. The material of the forged piece is steel Ck55 (12 060), the semi-finished product is of the 65 and its length is 12m. A yearly production is 122 000 pieces. Based on the studies of possible production technologies, the technology of production by die forging has been chosen, while a drop forging technology on a hammer HO630 and product-trim on a trimming press S160 have been used. For this option, the required technological calculations, the design of the die, the specification of production machines, which are necessary for forging process realization, have been carried out. An inspection of the propose forging by a private forge and a change in the geometry of the die have been carried out. A part of the study is a simulation forming process which is made in the software QFORM.

Page generated in 0.0367 seconds