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Termodynamické re-modelování systému Cu-Ni-Sn
Zemanová, Adéla ; Kroupa, Aleš
The Cu-Ni-Sn system is an important alloy system in lead-free soldering. In the scope project COST 531 the binary data for the Ni-Sn system required modification. The high temperature form of Ni3Sn, which has a DO3 structure, was modeled as BCC_A2 in the COST 531 thermodynamic database for compatibility with Cu-Sn system. The reassessment of this phase was carried out with the help of Parrot module in the ThermoCalc software and very good agreement was reached comparing the partial quantities from previous data and new model of this phase. Nevertheless it was also necessary to remodel the description of the Cu-Ni-Sn ternary system. The reassessment was based on the work of Miettinen who was primarily concerned with copper-rich compositions and experimental data for lower temperature.
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Study of Glycine-NBDCl Derivate Stability
Koudelková, Lenka ; Kubíček, Vladimír (advisor) ; Lázníčková, Alice (referee)
Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of biophysics and physical chemistry Candidate: Lenka Koudelková Consultant: Ing.Vladimír Kubíček, CSc. Title of Thesis: Study of glycine-NBDCl derivate stability In this thesis the stability of glycine-NBDCl derivative under three different conditions (heat+light, heat+dark, cool+dark) is studied by HPLC with fluorimetric detection. Ater being stabilized by hydrochloric acid the derivatives exhibit a better stability, but the concentrations found during several weeks are too scattered. In addition an alternative chromatographic conditions were proposed for the HPLC analysis. Acetonitrile with hydrogen phosphate buffer (pH 7,0) in ratio 70:30 on an Atlantis column gave symetric peaks with a short time of elution.
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FEM modeling of thermo-mechanical interaction in rubber block
Pešek, Luděk ; Půst, Ladislav ; Šulc, Petr
The FEMLAB code based on weak formulation of PDE’s problem was used at a solution of feedback thermo-mechanical interaction in damping bodies by finite element method. In our approach structural motion and heat conduction equations are solved interactively as time dependent problems. The conservative energy law, i.e. equality of heat energy density and dissipation energy density, realizes the coupling between the equations. The dissipation energy density is computed according to the assumed damping model. In the contribution the results, such as temperature versus strain distribution, of thermo-mechanical processes in case of a plane strain deformation under static compression and cyclic dynamic loading concerning mechanical energy lost modeled as proportional damping, heat generation, heat transfer between rubber and outer steel parts, cooling problem and changing stiffness and damping coef.
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TEM and SEM study of precipitation hardened Cu-Co alloys after severe plastic deformation
Buršík, Jiří ; Svoboda, Milan ; Král, Petr ; Dvořák, Jiří ; Sklenička, Václav
The paper reports on preliminary results of microstructural study of Cu-2wt.%Co alloy processed by ECAP. The experimental alloy was cast and annealed at 1273 K for 10 hours followed by water cooling, resulting in the solid solution (the initial state). Further heat treatment was then applied to produce two-phase material with fine distribution of precipitates. ECAP was then conducted at room temperature on both the initial and the precipitation hardened states. Resulting microstructures were studied and characterized by microhardness testing, TEM observations and texture analysis by means of electron backscatter diffraction (EBSD) technique in SEM.
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Development of HPLC method for assesment of stability of amorphous compounds
Číhalová, Daniela ; Solich, Petr (advisor) ; Sklenářová, Hana (referee)
Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of Analytical Chemistry Candidate: Daniela Číhalová Supervisor: Prof. RNDr. Petr Solich, CSc., Prof. Seppo Auriola, MSc. Marko Lehtonen Title of diploma thesis: Development of HPLC method for assessment of stability of amorphous compounds Solid materials can be found in many diverse forms which are distinguishable by different properties. In my thesis, I focus on amorphous solids, their properties, significance, occurrence and, most of all, characterization. The most widely used methods are introduced and described, focusing on their practical use in characterizing polymorphic and amorphous compounds. During the preparation of an amorphous solid, rapid heating and cooling down occurs and therefore degradation can be expected. To prove thermal stability, an HPLC method has been developed and validated for the determination of concentration decrease of an active pharmaceutical ingredient in amorphous state of 8 compounds. The compounds (benzocaine, chlorpropamide, clotrimazole, furosemide, piroxicam, salicylic acid, thiosalicylic acid, and tolbutamide) were determined separately. The method was carried out on a reversed-phase column (1.8µm, 50 × 4.6 mm) maintained at 40řC. The mobile phase was acetonitrile-water containing...
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Climate change and plant transpiration
Šír, Miloslav ; Tesař, Miroslav ; Lichner, Ľ. ; Syrovátka, O.
The article shows how the plant transpiration cools the boundary level of the atmosphere. In a summer day, when the heat input is 5 to 6 kWh/m2 per day, in the mountainous and submontane areas of the Czech Republic (600 to 1400 m a.s.l.) the plant transpiration decreases: (1) maximum temperature of plant cover from 47 to 25 degrees C, (2) maximum temperature of boundary level of the atmos-phere from 29 to 21 degrees C, (3) maximum temperature of the soil in the depth of 15 cm from 15 to 8 degrees C. The cooling caused by plant transpiration substantially af-fects the energy balance of the land surface. Insufficient transpiration caused an increment of thermal energy of about 23
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Heating systems in buildings with low energy consumption for heating
Juráček, Martin ; Topič, Jan (referee) ; Počinková, Marcela (advisor)
This work is processed like a proposal of heating for a part of seminar centre in Hostětín names Veronika. This current object is built in passive standard. In a part of building there is heating which it is suggested with help by singletube heating system. There is intake of air by recuperator without heating or cooling of air. Heat source is boiler room functional on renewable. Target of this work is analyze of current singletube heating system and find out cause it´s incompletely functionality. Further, design a new heating system which it suppose to be singletube and doubletube heating system.
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Microstructure Characterization and Faigue Behavior of Beta Phase Containing Gama-TiAl Alloy
Petrenec, Martin ; Beran, Přemysl ; Šmíd, Miroslav ; Chlupová, Alice ; Kuběnová, Monika
The microstructure and fatigue properties of Ti–44Al–7.8Nb – 0.2Ni (at.%) alloy after graded cooling heat treatment were investigated. Different techniques as SEM, TEM and FIB were used for characterization of microstructure. Quantification of phase volume fraction was measured by neutron diffraction method. After graded cooling heat treatment the structure consists of fully lamellar uniform grains which contain lamellar phases /2 and cubic phases (ordered B2 and disordered phases) at grain boundary and interlamellar spaces. The foils for TEM were prepared using FIB technique and observed in TEM in order to identify B2 phase by selected electron diffraction. Low cycle fatigue behaviour at 750 °C shows stable fatigue crack propagation due the presence of plastic beta and B2 phases.
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