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Thermodynamics of Solutions
Macháč, Pavel ; Münsterová, Eva (referee) ; Molliková, Eva (advisor)
This bachelor thesis deals with principles of thermodynamics of solutions. The theoretical part is initially concerned with question of solutions generally, such as for example the issue of classification of solutions, expression of solutions composition and a range of mutual solubility. The pivotal part of this document deals with solid solutions, mainly from the thermodynamic point of view. Specifically the issue of thermodynamic activity of components in these solutions is highlighted. There is a detailed description of the ways of determination of the thermodynamic activity, both experimentally and through the use of calculation. Finally there are described the possibilities of the use of the thermodynamic activity, such as for example using it to calculate the other thermodynamic quantities. The practical part of this thesis includes calculation of the thermodynamic activity of components of alloy Bi-Mg at assigned temperature, the partial molar dissolving free enthalpy of components in solution and the calculation of total dissolving free enthalpy of the solution.
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Passivation of Aluminum and Aluminum Alloys in passivation baths without Cr6+ Compounds
Macháč, Pavel ; Tulka,, Jaromír (referee) ; Molliková, Eva (advisor)
This diploma thesis deals with evaluation of efficiency of protection conversion coatings created by passivation metals and alloys in passivation baths without chromium compounds. The theoretical part is initially concerned with question of electrochemical corrosion of metals, consequently there are mentioned different methods of corrosion protection. The main section of theoretical part of this thesis deals with chromate conversion coatings, description of their protective efficiency (including their unique self-healing effect) and then with account of new chromate-free conversion coatings occurring as chromate alternatives, whose usage is constrained because of their content of hexavalent chromium, which is highly toxic, oxidizing and also carcinogenic and thereby very dangerous for human body and the environment. Experimental part of this thesis is concerned with evaluation of efficiency of particular conversion coating which is quite commonly use in some applications as chromate alternative. It is chromate-free conversion coating which is created by passivation of metals or alloys in passivation bath Pragokor BP, which contains zirconium fluorocomplexes and is without any chromium or other toxic or ecologically unhealthy compounds. The influence of sealing of the coating in preparation Pragokor Seal Al and also other surface treatments such as application of conservation wax WAXENG or cold application of zinc coating were tested too. Efficiency of mentioned surface treatments was then evaluated on aluminum and steel by laboratory accelerated and atmospheric corrosion testing.
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Temporal features of Czech fricatives
Homolková, Veronika ; Machač, Pavel (advisor) ; Skarnitzl, Radek (referee)
The thesis is focused on a description of temporal features of Czech central fricatives (f, v, s, z, š, ž, ch [x], h). The duration of fricatives in the intervocalic position is investigated according to the place of articulation and the voicing contrast. These results are contrasted to the preceding comparable researches. Also other contexts that can influence the duration of fricatives are examined (the phonological quantity of the neighbouring vowels, the position of the fricative in the stress unit, the type of speech, the gender of the speaker). The possible reciprocal influences are analysed in relation to the duration of the fricative and the articulation rate. The thesis deals also with the compensation tendencies in the field of duration of sequences "vowel + fricative" or "fricative + vowel". The basis for this research is formed by adequately extensive material of two types - read speeches, acquired advisedly for this analysis, and semi-spontaneous speeches, gained thanks to the Prague Phonetic Corpus (formerly Phonetic-Acoustic Database of Czech), created at the Phonetic Department of the Faculty of Philosophy and Arts, Charles University in Prague. The methodical basis for the thesis is formed by the doctoral thesis of PhDr. Pavel Machač, Ph.D.
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Acoustic properties of monosyllabic words in semi-spontaneous dialogues and read speech
Ondrušková, Lucie ; Volín, Jan (advisor) ; Machač, Pavel (referee)
This thesis investigates temporal characteristics of monosyllabic words (je, se, že) in semi-spontaneous dialogues and read speech. Our material consisted of two sets of recordings from six speakers (three men and three women). The speakers read a text first, and this reading was followed by a recording of a spontaneous dialogue. We investigated differences of temporal characteristics of monosyllabic words between the two types of speech. In addition, we also examined how these characteristics are affected by different variables, which included: position in a stress group, presence of stress, presence of pause and speaker's personality. It was found that the type of speech had a significant influence on duration ratio of sounds in examined words je, že. Word se remained unaffected by the type of speech and generally appeared as a very stable element. The type of speech also influenced variability in duration - this variability proved to be higher in spontaneous speech. The type of speech did not affect average duration of words je, se, že. Position in the stress group also proved to have a significant effect on duration of words. This effect was mainly caused by words which created isolated stress groups - words in such position had longer duration than words in other positions. For words je, se...
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Word-level phonetic variability in public speaking
Kodytková, Carmen ; Machač, Pavel (advisor) ; Zíková, Magdalena (referee)
This thesis concentrates on phonetic variability of words in public speaking. In the first part of the thesis, the aim was to summarize the existing knowledge about the characteristics and principles of spontaneous speech, about phonetic features of Czech speech sounds and about factors that may influence type and degree of reduction. Then we summarize the results of older studies done on other languages (esp. on Dutch and German) and outline a possible application of results from word variability analyses. In the second part of this thesis we look at five Czech words - protože, prostě, myslím, samozřejmě and určitě. We set several groups of variants according to the degree of reduction for each word, we examine stability of their phonetic features and survey whether position (initial, medial, final and I = F) in intonation unit and/or speed of pronunciation of the chosen word has an influence on degree of reduction. Five to eight hierarchical groups of variants were set for each chosen word. Stability of phonetic features in four types of speech sounds (vowels, nasals, unvoiced plosives and unvoiced sibilants) is in line with the existing observations (e.g. Machač, 2004). Speed of pronunciation of the word had an influence on the degree of reduction in words protože, prostě, samozřejmě and určitě,...
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Phonetics in the teaching of German as a foreign language
Holá, Klára ; Berglová, Eva (advisor) ; Machač, Pavel (referee)
This thesis explains the role of phonetics in the teaching of German as a foreign language. The beginning examines the present state - here I try to target in particular the Common European Framework of Reference for Languages and its parts that have to do with phonetics. Next, I explain certain terms with which I work with in most of the thesis. The next chapter concentrates on the role that phonetics play in the teaching of foreign languages. In the practical part of this work I deal with the differences of Czech and German pronunciation. The changes I discovered by comparing both languages became the fundamentals of the phonetic analysis of twenty recordings that obtained a total of 1480 analyzed documents, from which I determined that Czech students have the hardest time pronouncing the following German sounds , , , and . The task of the next analysis was to determine how the pronunciations of these problematic sounds are processed in the following text books: Delfin, Planet and Tangram. The best text book was Tangram, then Delfin and the worst was Planet. Unfortunately, none of the text books emphasize pronunciation and exercising it to a sufficient degree.
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Parametric synthesis and perceptual verification of Czech trills
Koppová, Martina ; Skarnitzl, Radek (advisor) ; Machač, Pavel (referee)
There is a parametric description of American English sounds suitable for parametric synthesis using high-level parametres in the HLSyn system, upon which the Stevens and Bickley system was created as the type of synthesis based on Denis Klatt's formant synthesis and combining the aspects of formant and articulatory synthesis. The aim of this work was to create a parametric description of Czech vibrants, i. e. /r/ and /ř/, synthesize these sounds and examine whether they are considered natural or not in a perception test. The perception test has shown that it is possible to synthesize the simple vibrant /r/ without any problems; the synthesis was based on modification of sounded alveolar explosive parametres and the modification was perceived as natural. However, the fricative vibrant /ř/ proved to be too complicated to be synthesized and even though we tried to follow its development according to real data it was still perceived as unnatural.
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Comparison of some spectral and temporal characteristics of German fricatives [x] and [ç] and Czech fricative [x] and their reflection in perception
Sedláčková, Petra ; Machač, Pavel (advisor) ; Skarnitzl, Radek (referee)
The aim of this diploma thesis is to analyze some of the acoustic characteristics of German fricatives [x] and [ ] and Czech fricative [x]. These sounds will be described and compared partly on the basis of spectral qualities of their noise, expressed by the so-called spectral moments (see chap. 3), and partly on the basis of their temporal characteristics. We assume to find a co-articulatory influence of the preceding vowel on the spectral characteristics of a fricative. We further assume that potential differences in values of the spectral moments, which can be, to a certain extent, considered an acoustic correlation of the place of articulation, can demonstrate a slightly different place of articulation of Czech and German velar fricatives. Using a perception test, we will attempt to explore a possible relation of German "Ich-laut" in the speech of German students of Czech to spectral mean values. The spectral moment measurements along with the perception test results may be found useful in teaching German as a second language for improving one's pronunciation. In practise, it can lead to an improvement in accepting a foreign speaker as an efficient user of the language.
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Electropalatographic study of voicing assimilation in Czech alveolar plosives
Vaněčková, Kateřina ; Skarnitzl, Radek (advisor) ; Machač, Pavel (referee)
The phonological contrast of voicing is based on several phonetic differences which are yet to be satisfactorily explained. The most obvious of them is the presence of vocal cords vibration which has so far been considered crucial in Czech. For capturing the differences in other dimensions, the concept of the strength of articulation, or fortis/lenis contrast have been established. There are some rare cases in languages when the couple of phonemes with the voicing contrast differs also in another feature that cannot be explained by the fortis/lenis dimension correlates. This is the case of Czech alveolar plosives which have been described to differ in their place of articulation: the linguopalatal contact is more anterior for [t] that for [d]. The main aim of this study is to ascertain whether this contrast can indicate the original phoneme in the contexts where the voicing contrast is neutralized due to assimilation. Nevertheless, our electropalatographic data from 7 speakers of Czech show that not only the phonemes do not seem to influence the anteriority of the voicing realisation, but also the very asymmetry of linguopalatal contact in the voicing realisations tends to be neutralised in the segmental context used in our study, that is in coda position in the word-final syllable followed by the...
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