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Analysis of reproduction and milk yield of dairy cattle
STEJSKAL, Petr
The diploma thesis is focused on reproduction and milk yield of a herd of Czech Fleckvieh and Red Holstein cattle on Velká Chyška farm. Milk yield together with the reproduction makes a basement of every breeding and its analysing is very useful for the breeder. The aim of the thesis was to split the herd according to the lactation into four groups (1, 2, 3, 4 and more lactations) and according to the percentage of blood of Czech Fleckvieh and Red Holstein cattle into three groups (C1- C 75-100 %, C2- C 51-74 % and R- R 51-100 %). To observe the indicators of milk yield and especially to observe yield in standardized lactation, index of persistence of the lactation line and whole-life yield of these cows. Next, to focus on the reproductive indicators: the insemination interval, the service period and the interval itself. Gathered information was recorded into tables and then statistically evaluated. Also, all groups were mutually compared. Needed information was gathered from GEA Dairy plan program and the milk cow cards. Milk cows, which started the lactation in period from 10. 10. 2014 to 30. 2. 2015, were included into the analyzed group. Generally, 155 pieces of livestock participated here. The milk yield indicators were evaluated as excellent. The groups of cows C1 and C2 cows with dominant percentage of blood of Czech Fleckvieh breed, showed significantly better-than-average results when compared with the yield check. The group with dominant percentage of blood of Red Holstein breed (R) exceeded the results from the yield check of the Czech republic as well, but not as in such extent as in case of C1 and C2 groups. In comparison of the groups together, no statistically important results were found. Statistically, only influence of lactation order to the yield in standardized lactation and also influence of lactation order to the index of persistence of lactation line was proved. Reproductive indicators were different in comparison from the yield; they were on very low levels. The service period and the period itself were evaluated as unsatisfactory in all groups and a problem with reproductive management was proved. In comparison of the groups together, no statistically important differences were found as well. Based on the found results and their analysis, conclusions for the breeding practice came about.
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Mechanical Properties of solder joint
Meliš, Josef ; Starý, Jiří (referee) ; Stejskal, Petr (advisor)
This thesis deals with the differences between the mechanical properties of surface conditionings of the printed circuit boards and various types of soldering pastes. The practical part of the thesis describes all the steps necessary to conduct the experiment. The experiment will evaluate the measured mechanical strength of the solder joint for each surface conditioning, the types of solders, the increase in thickness of the intermetalic layer during long-term aging and the change in the structure of the solder joint.
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Solder Joint Reliability Prediction
Stejskal, Petr ; Skočil, Vlastimil (referee) ; Hovorka, Ladislav (referee) ; Kazelle, Jiří (advisor)
The thesis deals issue of the solder joint reliability and diagnostics. The manufacturing technology of electronics currently features a very high level of perfection. A large number of electrical devices ends its functional life due to solder joint failure. The objective of presented research consists studies of processes taking place in the solder joint due to soldering and after soldering. To this end, I will employ several methods of diagnostics. Noise based methods of solder joint measurement was evaluated. Based on a detailed study and understanding of processes it can be solder joint reliability predicted.
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Inspection of PCB with SMT by using comparative method
Hejdiš, Roman ; Stejskal, Petr (referee) ; Starý, Jiří (advisor)
The first part of the bachelor´s thesis discuss AOI, types of AOI, its utilization and importance in the industrial production. The second part is devoted to realization of simple comparative inspection method. There were testing effects of ambient light to record photographs of PCB and also artificial light was used. There was problems indication of PCB lit and PCB fixturing. At last, there are discussed some technical problems of this simple comparative method.
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Reliability of lead free solder joint
Paško, Martin ; Knotek, Tomáš (referee) ; Stejskal, Petr (advisor)
This thesis deals with voids formation in lead-free soldered joint. In theoretical part are described types of voids, voids formation, effect on join reliability, effect reflow profile on voids formation and effect of surface finish on voids formation. In practical part is investigated a effect of thermal stress on voids growth.
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Laser diode soldering
Straka, Michal ; Holík, Milan (referee) ; Stejskal, Petr (advisor)
This work deals with the laser diode soldering. The theoretical part summarizes general and acquired findings about soldering technology and materials that occur in this process. It also describes factors that affect the reliability of solder joints. It is closely focused to the shaping of the solder joint and structure of intermetallic layer. The practical part of this work is focused on the design of equipment for laser diode soldering and subsequent shaping of the samples. The quality of soldered joint is compared against the quality of joint created using re-flow technology - remelting in in-line smelter. The structure and thickness of the intermetallic layer, the number and shape of the voids in the solder joints are compared.
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