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STRAIN ENGINEERING OF THE ELECTRONIC STRUCTURE OF 2D MATERIALS
del Corro, Elena ; Peňa-Alvarez, M. ; Morales-García, A. ; Bouša, Milan ; Řáhová, Jaroslava ; Kavan, Ladislav ; Kalbáč, Martin ; Frank, Otakar
The research on graphene has attracted much attention since its first successful preparation in 2004. It possesses many unique properties, such as an extreme stiffness and strength, high electron mobility, ballistic transport even at room temperature, superior thermal conductivity and many others. The affection for graphene was followed swiftly by a keen interest in other two dimensional materials like transition metal dichalcogenides. As has been predicted and in part proven experimentally, the electronic properties of these materials can be modified by various means. The most common ones include covalent or non-covalent chemistry, electrochemical, gate or atomic doping, or quantum confinement. None of these methods has proven universal enough in terms of the devices' characteristics or scalability. However, another approach is known mechanical strain/stress, but experiments in that direction are scarce, in spite of their high promises.\nThe primary challenge consists in the understanding of the mechanical properties of 2D materials and in the ability to quantify the lattice deformation. Several techniques can be then used to apply strain to the specimens and thus to induce changes in their electronic structure. We will review their basic concepts and some of the examples so far documented experimentally and/or theoretically.
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HYDROGEN ABSORPTION IN A-Co30Fe55B15
Čermák, Jiří ; Král, Lubomír ; Roupcová, Pavla
Hydrogen solved in amorphous alloys (AAs) influences their magnetic characteristics. AAs are also perspective\nas additives that can improve hydrogen storage kinetic in certain types of ball-milled hydrogen storage\nmaterials (HSMs). Therefore, knowledge of hydrogen solubility and hydrogen sorption kinetics in AAs are of a\ngreat importance for aimed design both AAs with optimal magnetic parameters and HSMs with desired sorption\ncharacteristics. In the present paper, amorphous alloy Co30Fe55B15 (an example of the type a-TM1xTM2y Bz ;\nTM - transition metal) was investigated. Hydrogen concentration c H was measured by Sieverts method in\ntemperature interval from T = 150 °C to T = 350 °C under hydrogen pressure p up to 6 MPa. It was found that\nc H was an increasing function of p and its maximum value was typically 0.5 wt.% H2 at 350 °C and 6 MPa.\nHowever, when the alloy was preliminary hydrogen charged (PHC), the pressure dependence of total c Htot in\nthe first absorption cycle(s) is non-monotonous in dependence on PHC conditions. For the sake of comparison,\nthe same absorption characteristics were measured also in Mg2Ni intermetallic that is a common constituent\nin Mg-based HSMs. Comparing Co30Fe55B15 and Mg2Ni, it was concluded that Co30Fe55B15 shows lower\nhydrogen solubility, but much better absorption kinetics.
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Fytochemical potencial of polyfenols contain in berries
KRUMPHANZLOVÁ, Iva
This thesis sums up findings on polyphenols and their positive influence on human health. In these fytochemicals, unlike in micronutrients, recommended daily amount cannot be estimated. Micronutrient deficiency in food can cause deficiency symptoms, while in polyphenol deficiency, the deficiency does not occur. When they are present in sufficient amount in food, it is considered functional food, which is important for civilization illnesses prevention. At the beginning of the theoretical part, the polyphenol classification from pharmacological and chemical point of view is represented. On the basis of this classification important role of antioxidants and flavonoids is described. Special attention is being paid to resveratrol, which is populardue to its well known "French paradox". The following part considers the polyphenol influence on human health. The way in which polyphenols protect our body from certain diseases is explained in detail. Most of the health benefits are supported by studies conducted on animals. These studies are also mentioned and described in this paper. In the theoretical part the process of absorption and the polyphenols safety for human body is also explained. Polyphenol sources are listed in the last subchapter. The work is mainly aimed at blueberry fruits (Vaccinium myrtillus) and vine grapes (Vitis vinifera). Other berries are briefly mentioned as well, such as cranberries, raspberries, blackberries and currant. The goal of this work is to create a diet that would provide a functional daily amount of polyphenols. This amount can be compared to 120 ml of native blueberries. Only products, consumable without cooking, are used in this diet. The second goal is to chart, which food products are adequate source of polyphenols. On the basis of these goals, research inquiries were defined. Research inquiry No. 1: What amount of polyphenols is contained in berries, especially blueberries. Research inquiry No. 2: Which food products (without cooking) are ideal to be included in diet, to provide adequate daily amount of polyphenols. To asses polyphenol content in blueberries, analysis of polyphenol content acquired through GEOMED program from Nemocnice České Budějovice a.s., department of clinical pharmacology, was used. Assessments were made using the HPLC method (high performance liquid chromatography) in cooperation with the biological centre AV ČR in České Budějovice. Thanks to this analysis, the first inquiry can be answered. An interesting phenomenon is discovered, that frozen blueberries have higher polyphenol content then cooled ones. Malvidin (malvidin-3-6"-acetoyl glycoside) was chosen as priority anthocyan since it is most represented in the blueberry. Remaining information about polyphenol content in certain food products were drawn on Joseph Maroon´s book, MD, FACS (2010). The practical part involves a diet for 14 days, which meets the given requirements. The results clearly show that it is possible to create a diet rich in polyphenols. A list of blueberry products accessible to everyone is included. Blueberry dairy products, jams, beverages, fruit salads and fruit pyre have been analysed. The list shows which product contains the most polyphenols. The required amount can be achieved by the proper combination of given products. The ideal one proved to be 200 ml of red wine and one blueberry dairy product (with the malvidin value higher than 64). Findings in this paper will serve to promote polyphenol awareness and itseffects. This diet can be used in nursing homes, where their positive influence on equilibrium can be applied. It can also be used in spas and other alimentation related facilities.
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Cut Languages in Rational Bases
Šíma, Jiří ; Savický, Petr
We introduce a so-called cut language which contains the representations of numbers in a rational base that are less than a given threshold. The cut languages can be used to refine the analysis of neural net models between integer and rational weights. We prove a necessary and sufficient condition when a cut language is regular, which is based on the concept of a quasi-periodic power series. We show that any cut language with a rational threshold is context-sensitive while examples of non-context-free cut languages are presented.
Fulltext: content.csg -  PDF
Plný tet: v1236-16 - PDF
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Natural houses in gardens
Formánková, Kristýna ; Kunt, Miroslav (advisor)
Thesis discusses natural houses which are supposed to be part of our lives in the future. These houses may be for someone and they might prefer smarter building with non-recyclable materials when choosing a new housing. But it is necessary to think about our future and sustainable development. We also need to tell ourselves what is really a priority for our planet. There comes a time when they will prefer building materials which can be used somehow after some time or be recycled. This is related to the design of the garden. It is designed to fulfil an ornamental, economic and social function. The garden is an integral part of each house, therefore it is important for each element used to be creating the garden as a linked harmonious whole. The study deals with the concept of a natural houses home in accordance with the maximum use of the garden.
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Effect of snowpack on runoff generation during rain on snow event.
Juras, Roman ; Máca, Petr (advisor) ; Ladislav , Ladislav (referee)
During a winter season, when snow covers the watershed, the frequency of rain-on-snow (ROS) events is still raising. ROS can cause severe natural hazards like floods or wet avalanches. Prediction of ROS effects is linked to better understanding of snowpack runoff dynamics and its composition. Deploying rainfall simulation together with hydrological tracers was tested as a convenient tool for this purpose. Overall 18 sprinkling experiments were conducted on snow featuring different initial conditions in mountainous regions over middle and western Europe.
Dye tracer brilliant blue (FCF) was used for flow regime determination, because it enables to visualise preferential paths and layers interface. Snowpack runoff composition was assessed by hydrograph separation method, which provided appropriate results with acceptable uncertainty. It was not possible to use concurrently these two techniques because of technical reasons, however it would extend our gained knowledge. Snowmelt water amount in the snowpack runoff was estimated by energy balance (EB) equation, which is very efficient but quality inputs demanding. This was also the reason, why EB was deployed within only single experiment.
Timing of snowpack runoff onset decrease mainly with the rain intensity. Initial snowpack properties like bulk density or wetness are less important for time of runoff generation compared to the rain intensity. On the other het when same rain intensity was applied, non-ripe snowpack featuring less bulk density created runoff faster than the ripe snowpack featuring higher bulk density. Snowpack runoff magnitude mainly depends on the snowpack initial saturation. Ripe snowpack with higher saturation enabled to generate higher cumulative runoff where contributed by max 50 %. In contrary, rainwater travelled through the non-ripe snowpack relatively fast and contributed runoff by approx. 80 %.
Runoff prediction was tested by deploying Richards equation included in SNOWPACK model. The model was modified using a dual-domain approach to better simulate snowpack runoff under preferential flow conditions. Presented approach demonstrated an improvement in all simulated aspects compared to the more traditional method when only matrix flow is considered.
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Design of Experiment for Non-Stationary Processes of Production
Jadrná, Monika ; Macák, Tomáš (advisor)
The doctoral thesis is concerned with the services sector and the area of mass production. Particularly, the optimization of the product portfolio of the travel agency and the optimization of production rounds of ammunition.
The theoretical part deals with the current overview of discussed topic. Further, the terminology and methods of the decision-making process are defined to support decision making. The theoretical basis of research focused on the choice of appropriate input variables in the area of services, and on the choice of a particular material option in the production area and appropriate equipment for the production. The theoretical part forms the basis for the practical part of the thesis.
For the doctoral thesis was chosen an enterprise operating in the defined sector. Product portfolio for the services sector is optimised using Fuzzy logic and Fuzzy sets so that the enterprise can maintain its competitiveness in todays highly ambitious market. Product portfolio for manufacture is optimised for achieving desired properties of the product.
The main aim of the thesis is to propose a new methodological approach for the management of selected business processes in their nonstationary time course. The aim of the practical implementation is to verify the functionality of the proposed methodological approach, both in the area of services and in the field of mass production.
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