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Control Techniques of Grid Connected PWM Rectifiers under Unbalanced Input Voltage Conditions
Bejvl, Martin ; Šimek, Petr ; Škramlík, Jiří ; Valouch, Viktor
Current-controlled voltage source converters are widely used in grid-connected applications,for example at ac drives with indirect frequency converters.The structure and parameters of the PLL are developed and proposed in order to cope with the grid containing both the positive and the negative sequence component, and minimize the wrong frequency transients during phase angle steps and also in the start-up stage. The DSC technique was realised. There is also necessary to compensate the negative sequence component in the grid voltage. The negative sequence component of the grid voltage causes ripple of the dc voltage in the intermediate circuit. Several sophisticated topologies of converter current controller were developed, simulated and tested for this purpose. Results of simulation and experimental tests are provided to evaluate different current control schemes and phase locked loop techniques.
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Differences in CO2 Extraction of Vegetable Oils, Essential Oils, and Minor Components from Plants
Sovová, Helena
Significant progress in understanding the phenomena that control supercritical fluid extraction from plants was made in the last years and is reflected in the literature. Combination of chemical engineering approach and botanical knowledge has appeared to be fruitful for the choice of extraction model and even for the prediction of extraction kinetics. This contribution refers to the papers utilizing knowledge of plant microstructure and location of extracted substances together with extraction equilibrium and attempts to specify the differences among extraction kinetics of vegetable oils, essential oils, and other substances. The most abundant substances like vegetable oils in seeds can be regarded in first approximation as non-interacting with plant matrix, in contrast to the minor components whose equilibrium concentration in CO2 is affected by their adsorption on matrix and often also by co-extracted substances.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_C22012102414100 - PDF
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Microalgal Growth Problem for the Photosynthetitc Factory and its Optimization: An Overview and Further Analysis
Čelikovský, Sergej
The overview of the micro-algal growth problem for the photosynthetic factory and its optimal control solution is presented here. First, the model description and its properties like Haldan steady state dynamics, light integration property and the forward invariance of the set of biologically well-de ned states are described. This shows that the model meets basic experimentally based requirements. Further, its optimal control problem is formulated and solved analytically for the one dimensional singular perturbation based reduction. Properties of the optimal control for the reduced model are discussed and compared with some experimental observations. Among them, the general biotechnological paradigm that on large time intervals the optimal solution is, in certain sense, almost constant, is substantiated. As a new original result of this paper, the explicit solvable di erentiable equation for the unsaturated part of the optimal control is derived.
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Kvalitativní analýza a řízení v závislosti na vstupních úodmínkách modelu protiproudé plněné kolony
Akramov, T. A. ; Jiřičný, Vladimír ; Staněk, Vladimír
In recent papers a mathematical model of the transients of the hydrodynamic of counter-current column was formulated. It was used for describing the overshoot phenomenon on the transient profiles of liquid holdup. These overshoots were observed experimentally when the bed was exposed to a sudden increase of either gas or liquid inlet velocity. Another condition for the appearance of the overshoots was that the step change in inlet velocity brings the system in proximity of the flooding point. The formulated model could under some conditions give a good description of the time behavior of the mean liquid holdup. In particular this model is capable of predicting and describing the conditions of the overshoot phenomenon after an imposed change of inlet velocity of liquid or gas. The problem now is to find out the response of the system periodical step changes in inlets velocity of gas or liquid. .
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Power and responsibility of the child
SVOBODOVÁ, Kateřina
This thesis is in the form of literature review. It deals with the development of understanding of the power and the responsibility of the children and the modern concept of education through which the parents try to influence their children so that they would be capable of socialization and long-term functioning in everyday life without conflict with the generally accepted patterns of coexistence. The most important groups influencing social development of individuals are defined in the introduction. I mention briefly below the overall moral development of children, because the control of desire for power and awareness of the responsibilities is included in the overall understanding of the basic principles of human behavior in society. The next section is already about development of application of own power, finding of limits for speeches and actions in contact with other people, and the gradual awareness of the responsibility for own actions. In the connection with the power, It is impossible not to mention the aggression that occurs among children more often nowadays and it is very difficult to solve it. The paper describes the difficulties with which parents can meet during the education. I suggest gradually approaches that help parents in ensuring that children get rid of a feeling of omnipotence and superiority appearing in the vast majority of them and understand that It is important to be responsible. At the end, I briefly notice when a child is seen as a responsible user of her own rights and obligations in terms of the Act. The aim of this thesis was to show that the initial prehension of power and responsibility by children is incompatible with the standards for normal life in society. Parents have to lead children with focused and persistent education to behavior modification and shift the understanding of these concepts.
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Rearing of the zander (Sander lucioperca) stock material under controlled conditions (preliminary results)
Baránek, V. ; Mareš, J. ; Spurný, P. ; Prokeš, Miroslav ; Baruš, Vlastimil ; Němec, M.
The aim of this study was to check the possibilities of exploitation of summer zander (Sander lucioperca) fry for production of stock material under controlled conditions. Two groups of these fish were converted from natural diet to artificial diet using the semi-moist feeding mixtures (variant A) and trout feed (Dan-Ex 1352 - variant B). The average total length of imported fish was 44,3 mm and the average idividual weight was 0,606 g. There were 255 individuals in each tank. The initial stock density was 2,34 g.l-1 (3,86 ks.l-1). The water temperarute during this experiment fluctuated in intervals 21 ů 23 oC. Our simple experiment confirmed possibility of exploitation of summer zander fry to intensive rearing of stock material.
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Possibilities of the application of supplemental and nonconventional methods in prevention and health care in calves
KONRÁDOVÁ, Petra
Diarrheal diseases of calves are one of the most serious risks of rearing calves and cause economic losses. For this reason, the objective of this work was to assess the influence of means of support in operating conditions for the incidence of diarrheal disease in calves in the early post-weaning stages. A company was chosen for this work in which both the company employees and an external veterinarian were willing to collaborate and provide not only information about the breed in question, but also biological material. This company was JINOS - AGRO Veselí nad Lužnicí. The calves were observed in the period of April - June 2009. The calves were housed in separate boxes the second day after birth until the average age of 56 days. After storage, they were divided into 5 groups: 4 based on the chosen means of support, and a single control group. Faeces samples were collected from the calves and subsequently evaluated. The calves to whom were administered means of support were then evaluated to assess the effect thereof on the incidence of diarrhea, the duration of diarrhea, the method of treatment, and the duration of treatment. The results were summarized and analyzed using a statistical program (STATISTICA 7.0.). There was no statistically significant difference found between the individual groups and the experimental group. An evident and statistically significant difference was found only in the case of a difference between the drugs of the 2 experimental groups, specifically between Lactovita and Homeopatika. Based on this observation, it can be stated that there was no evidence supporting the effectiveness of administered means of support for the incidence of diarrheal disease in calves in the early post-weaning stages.
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Design and Development of the Network of Points of the Detailed Minor Horizontal Control using Geodetic and GPS Methods
ŽAHOUREK, Jakub
This thesis deals with "Design and Development of the Network of Points of the Detailed Minor Horizontal Control using Geodetic and GPS Methods" in the cadastral territory Jenín and Horní Kaliště. Using the map basis I conducted the reconnaissance and analysis of the current level of the minor control points in the target territory. Next I stabilized 14 new points of the DMHC, however, this thesis uses only 7 of these 14 points. The work aims to analyze the current level of the minor control and if needed to increase the field density for detailed large-scale mapping. For this purpose I used total station Leica TCR 407 power for the geodetic method and Trimble 4600LS device for the GPS method. Consequently I analyzed the accuracy of both methods.
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Gender and primary school girls
HRONKOVÁ, Martina
The thesis deals with gender issues. It is divided into two parts, theoretical ? based on literature review and practical ? based on research. The theoretical part deals with the concept of gender as a social construct. It is focused on manifestation of gender stereotypes in various aspects of girl?s and woman?s life. The first chapter defines the most important terms (gender, sex, socialization, identity) and is followed by a chapter dealing with gender stereotypes related to female and male social constructs (of femininity and masculinity). The next part describes manifestation of gender roles, (differences and behaviour) in family. The following chapter shows the picture of woman which is presented in the media (magazines for women, advertisement, publications for children). The last chapter describes manifestation of gender roles in school environment. The practical part presents results of the quantitative and qualitative research. The quantitative research is based on questionnaire investigation. The qualitative research was conducted through controlled interviews. Both types of research were focused on gender problems ? whether the girls participating in the research realize the effects of gender roles and how they perceive them. The result of this research is that girls are aware of pressure based on gender differences. They realize the conflict between their wishes and reality, but they fully respect the traditional gender division of the worl into the male and female world and they lead their lives in accordance with the traditional gender stereotypes.
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