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Measurements of current density distribution in e-beam writer
Bok, Jan ; Kolařík, Vladimír
An e-beam writer with a variable shaped beam needs a bright and stable source of electrons but also a homogeneous square beam segment. This is the starting element out oif wich smaller rectangular-shaped variable-sized patterns are selected (stamps). Current inhomogeneity of the starting element would cause and different current density of various stamps that negatively impacts the exposure quality. This problem implies the necessity of analysing and monitoring the current density distribution in the staring beam element.
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Stress-free and stress-assisted aging of NiTi shape memory alloys
Dlouhý, Antonín ; Bojda, Ondřej ; Fiala, J.
The present work investigates coherent Ni4Ti3 precipitates in a Ti-50,7at%Ni shape memory alloy after different thermo-mechanical treatments. The study is based on the quantitative TEM (transmission electron microscopy) image analysis using the ACC (Adaptive Contrast Control) programme. The attention is given to a number, size and volume fraction of individual crystallographic variants of the Ni4Ti3 precipitates. Preliminary results suggest that, after common heat treatments, the precipitation of Ni4Ti3 particles is inhomogeneous not only as far as the density of particles in the original B2 grains is concerned but also with respect to the distribution of the crystallographic particle variants. The possible influence of the heterogeneous Ni4Ti3 precipitation on the characteristics of the martensitic transformations B2-R-B19’ is discussed.
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Genetická struktura populací lína Tinca tinca (Linnaeus, 1758)
Lajbner, Zdeněk ; Linhart, Otomar ; Kotlík, Petr
The tench is an important fish for aquaculture, which is undergoing intensive domestication, but only few studies have examined genetic structure of its populations. We present first results of a phylogeographic study based on DNA sequence data for four nuclear genes and one mitochondrial DNA gene from throughout the tench geographical distribution, including some of the known transfers outside its native Eurasian range. The multiple gene dataset revealed a strong phylogeographic partitioning between the western and eastern parts of the species range with a wide zone of overlap in Europe. Tench in European aquaculture largely represent mixtures of the two evolutionary lineages. We will discuss the likely historical processes underlying these findings. We suggest that human-mediated dispersal may have played an important role in shaping the present phylogeographic pattern.
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Arctic tundra dendrochronology
Lehejček, Jiří ; Svoboda, Miroslav (advisor) ; Monika, Monika (referee)
Historically unprecedented environmental change in the Arctic ecosystems is often given into the context of its past and possible future development. In the region where instrumental meteorological observations are scarce archives need to be investigated in order to address this issues. The comprehensive synthesis one of the archives: long-live circumpolar evergreen Juniperus communis L. shrub is presented here. 20 individuals from southwest Greenland were investigated at the cell anatomy level to understand the ecology of the species and unhide its potential for environmental and climate reconstructions. The findings are as follows:
i) Stop of exponential cross-sectional conduit-lumen widening with increasing age is in contrast with conduit-lumen nature of trees. This indicates that shrubs do not need to saturate their water and nutrient demands via traits of classical hydraulic conductivity law but rather developed different mechanisms. Extreme weather conditions result in prostrate growth form. However, different weather factors probably influence shrub growth differently: While snow and wind act mechanically (a), temperature influences the form of growth physiologically (b). a) So long as the young shrub stem has high resilience to bend back to an upright position after snow melt and so long as it can withstand the wind during the vegetation season it most likely grows upright and the conduit-lumens widen. b) Temperature, resp. freeze-thaw events are responsible for the shrubs preference of safety (finite size of conduit-lumens) over hydraulic efficiency, thus not allowing for more primary growth. All of these (and other) factors are apparently working together and the transition of vertical to more horizontal growth is gradual. As a consequence, the conduit-lumen sizes may not have to be further increased (due to ecophysiological restrictions possibly also must not) because water is no longer transported against gravity.
ii) Observed age/growth trend has to be taken into consideration for further employment of the wood anatomical parameter in paleoenvironmental studies. That is, shrub cell parameters can only be used for this purposes if correctly detrended. This allows for more accurate as well as longer reconstructions because youth trend was often neglected in reconstructions based on shrub annual-rings.
iii) The south-western Greenland Ice-Sheet (GrIS) melt rates reconstruction is presented for the whole 20th century. This part of GrIS is considered as the most active. According to the presented reconstruction current GrIS melt rates are not uncommon for the last century being comparable to first decades of 20th century. This finding is particularly important contribution to the debate on Atlantic meridional overturning circulation (AMOC). Too high fresh water inputs into the Northern Atlantic from GrIS melting may slow down or even stop the AMOC which would result in more continental climate in Europe. Presented results indicate that this threshold lies higher than observed current melt rates of GrIS.
Fascinating Juniperus comunnis species has shown to be able to address many ecological as well as environmental open questions and due to its longevity and abundant distribution has a great potential to become an important player in the Arctic research.
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Mapování teplotního a rychlostního pole ve volném proudu horkého plynu
Gregor, Jan ; Jakubová, I. ; Mendl, T. ; Šenk, J.
In the paper the measurements on hot gas mixture free jet are analyzed. The main interest is oriented on the analysis of the distribution of the individual species in the jet based on the vector form of the continuity and momentum equation. In the continuity equation the diffusion member is involved. To simplify the problem, the temperature and velocity fields are approximated by suitable functions. The calculation process is applied on the jet generated by a hybrid water stabilized plasma torch with argon added into the chamber of a plasma heater.
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Studium difuzního proudu na hranici oblouku pomocí elektrických sond
Chumak, Oleksiy ; Hrabovský, Milan ; Kavka, Tetyana ; Kopecký, Vladimír
Electric probes were used for investigation of an intermediate layer between the arc and anode surface in regions outside the main current channel. Distributions of a diffuse current and the potential were measured. Resistance and heating of the intermediate layer by diffuse current were evaluated.It was found that not only the value of diffuse current strongly depends on distance from the arc but also the shape of the distribution and the position of the maximum of the current change with the distance. These trends can be explained by expanding of the plasma jet. Evaluated equivalent intermediate layer resistance shows widening of the conductive region in a stream wise direction. Variation of resistivity of the intermediate layer is much higher than variation of the potential drop on the layer. That means that distributed current as well as Joule heating of the layer are generally controlled by distributed resistance.
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Is genetic diversity congruent with morphological diversity across the distributional range of the Melampyrum subalpinum group (Orobanchaceae)?
CHLUMSKÝ, Jan
Allozymes were used to assess the genetic structure of 27 populations of Melampyrum subalpinum group and an artificial pollination experiment was carried out to examine the possibility of autogamy. Genetic variation was generally congruent with the known morphological variation of the group. The results corresponded with the central-marginal concept. Allelic enrichment due to hybridization with M. nemorosum was observed in some Austrian populations. Czech and Slovak populations do not differ from Austrian populations. The high inbreeding coefficient and the pollination experiment do not contradict the possibility of autogamy.
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Diffraction on Spatial and/or Deep Objects
Hrabec, Aleš ; Petráček, Jiří (referee) ; Kotačka, Libor (advisor)
This discourse deals with a theoretical study of the radiation passage through a diffraction screen with non-zero size in the propagation direction of the radiation, i.e. the radiation passage through a three-dimensional object. Without any loss of generality, we solve the problem for cylindrical cavity in metal. The task exceeds evidently standard scalar theory of diffraction, thus we solve the problem using a waveguiding theory. Following the principles of the electromagnetic theory, we derive required formulae to determine mode distribution at the entry of the cavity. Further, we solve numerically the radiation propagation through the cavity, then we actually seek for radiation distribution at the very end of the cavity. This yields, with a help of the discrete Fourier transform, an intensity distribution of Fraunhofer diffraction pattern, consequently compared with an intesity distribution of the radiation pattern of Fraunhofer diffraction on infinitely thin circular opening having the radius of the cylinder cavity under study. A comparison of such patterns results to a conclusion, that the cavity length has a significatn influence on the diffraction pattern and more importantly, that the scalar diffraction theory appears incorrect for a coherent light passage through cavities longer than their radius squared. Similarly, the same conclusion is inversely proportional to a wavelength of the interacting radiation. Finally, we mention an existence of the so called "focal regime", when the radiation repeatedly exhibits roughly one order increased intensity on the symmetry axis of the cavity.
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SUBWAY - Logistic solution for central and eastern Europe
Benschová, Šárka ; Pernica, Petr (advisor) ; Grossová, Petra (referee)
Subway is the leading fast food franchise chain having over 29.700 branches in 87 countries and differentiating itself among other fast foods by serving healthy food. The chain's focus for further development is concentrated on the countries in Central Europe (Czech Republic, Poland, Hungary and Croatia) and its 47 branches. However, the concept of supply chain in this region is disunited and leads to unfair high costs and high requirements from the branch management. Therefore there is an urgent need to unite the logistic system. The idea is that all the branches in the region will keep two or three local suppliers providing delivery of vegetables, drinks and local specialties; other goods will be distributed by single logistics company in the form of consolidated supply. The new logistic concept for provision of availability of products needed for proper work of all Subway branches in Central and Eastern Europe in context of integration, unification and simplification of logistic chains and its effective management is suggested in the work from the logistic service provider point of view. The task is solved in three parts -- transportation of goods from the producers to the warehouse, its delivery to individual branches, and warehouses itself including the cost calculations. The analysis of supplier's location and the location of supplied branches conclusion follows on locating the warehouse unit near Prague. The kinds of goods could be divided into frozen, cooled, dry and non-food goods. The consumption of individual kinds of goods is specified and the process of supplying the warehouse, means of transport, number of drivers, consolidation on distribution routes and its frequency is suggested. The supply of 47 branches will be done with special means of transport with combined shipping space enabling separate transport of individual kinds of goods by using the mobile screens; on 5 routes always between 7:00 to 23:00 in every country on the same day. The warehouse is a key place for delivery consolidation according to the needs of individual branches in accordance with FIFO principle. About 70 different articles of goods are stocked in three parts; respectively in truss racks with longitudinal filling with capacity of 168 pallet spaces in the height of 4 pallets. The manipulation is provided by low-lift and high-lift trucks. The limit warehouse is rectangular with the area of 122.4 m2, Monthly cost are 485,- Kč for pallet space, the costs in the frozen and cooled warehouse are higher by 15,-Kč per pallet space, that is 500,- Kč. The total costs to supply all the Subway branch restaurants in the whole region is the total sum of costs for good acquisition, its transfer from suppliers to the warehouse, warehouse operations and distribution of goods to individual branches.
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Usability of connectivity metrics as predictors of species distribution
Kučera, Michal ; Šímová, Petra (advisor) ; Krčílková, Šárka (referee)
The aim of this thesis is to evaluate whether connectivity indices are usable for bird prediction.
The study area contains of the whole country but is divided into separate squares with area of
133 km 2 each, where the presence or absence of the bird species is known. The dependence is
tested on landscape connectivity indices presented by prof. S. Saura. The land cover contains
of Corine land cover 2012 data. The results will be evaluated with logistic regression approach
on sample data including 4 different dispersal distances (500 m, 1 000 m, 2 000 m and 3 000
m) and 10 specific bird species typical for given land cover. The corelation between land cover
area presence of the bird is also tested.
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