Радянський союз і українсько-польська війна

Трофимович Володимир Васильович - доктор історичних наук, професор, завідувач кафедри історії Національного університету «Острозька академія» (м. Острог)

Shielding of a moving test charge in a quantum plasma

The linearized potential of a moving test charge in a one-component fully degenerate fermion plasma is studied using the Lindhard dielectric function. The motion is found to greatly enhance the Friedel oscillations behind the charge, especially for velocities larger than a half of the Fermi velocity, in which case the asymptotic behavior of their amplitude changes from 1/r^3 to 1/r^2.5. In the absence of the quantum recoil (tunneling) the potential reduces to a form similar to that in a classical Maxwellian plasma, with a difference being that the plasma oscillations behind the charge at velocities larger than the Fermi velocity are not Landau-damped.Comment: 9 pages, 11 figures. v3: Fixed typo, updated abstrac

О ПРОБЛЕМАХ ИНЕРЦИОННОСТИ И ЧУВСТВИТЕЛЬНОСТИ ПРИ МАТЕМАТИЧЕСКОМ МОДЕЛИРОВАНИИ ТЕПЛОВОЙ РАБОТЫ ОБЖИГОВОЙ ПЕЧИ ДЛЯ ПОЛУЧЕНИЯ ИСКУССТВЕННОГО ГРАФИТА

The method of mathematical simulation has been used for examination of the effect of relationship of thermal time lag of the container (with stock material and fill) and susceptibility of the control system on the temperature pattern of stock material for obtaining artificial graphite; also the effect of computational time step value in time (Δτ) on the results of mathematical simulation has been studied. The results of simulation at any fill bed thickness are shown not to depend practically on Δτ for infinitelyfast system for control of roasting furnace, and at finite susceptibility of the control system the temperature oscillations, being generated by the system with decreasing thermal time lag of the container (fill bed depth), penetrate ever deeper and deeper inside it, however you can detect it with help of computational method only at small Δτ – because big time steps show smoothed pattern with monotonous trends that corresponds to the reality only at significant fill bed depth. The degree of convergence of iteration calculation algorithm is high enough if Δτ is significantly more or significantly less than the period of modeled periodic processes; if these values are of the same order the algorithm can run into a cyclic path or the demanded amount of iterations can increase by some orders.Методом математического моделирования исследовано влияние соотношения термической инерционности контейнера (с заготовкой и пересыпкой) и чувствительности системы регулирования на температурное поле заготовки для получения искусственного графита, а также изучено влияние величины расчетного шага по времени (Δτ) на результаты математического моделирования. Показано, что для безынерционной системы управления обжиговой печью результаты моделирования при любой толщине слоя пересыпки практически не зависят от Δτ, а при конечной чувствительности системы управления порождаемые ею температурные колебания с уменьшением термической инерционности контейнера (толщины слоя пересыпки) все глубже проникают внутрь него, однако обнаружить это расчетным путем можно только при малых Δτ – большие шаги по времени позволяют получить сглаженную картину с монотонными тенденциями, соответствующими реальности только при значительной толщине слоя пересыпки. Установлено также, что скорость сходимости итерационного алгоритма расчета достаточно высока, если Δτ существенно больше или существенно меньше периода моделируемых периодических процессов; если же эти величины одного порядка, то алгоритм может зацикливаться или требуемое количество итераций может возрасти на несколько порядков

Advanced EFL learners' beliefs about language learning and teaching: a comparison between grammar, pronunciation, and vocabulary

This paper reports on the results of a study exploring learners’ beliefs on the learning and teaching of English grammar, pronunciation and vocabulary at tertiary level. While the importance of learners’ beliefs on the acquisition process is generally recognized, few studies have focussed on and compared learners’ views on different components of the language system. A questionnaire containing semantic scale and Likert scale items probing learners’ views on grammar, pronunciation and vocabulary was designed and completed by 117 native speakers of Dutch in Flanders, who were studying English at university. The analysis of the responses revealed that (i) vocabulary was considered to be different from grammar and pronunciation, both in the extent to which an incorrect use could lead to communication breakdown and with respect to the learners’ language learning strategies, (ii) learners believed in the feasibility of achieving a native-like proficiency in all three components, and (iii) in-class grammar, pronunciation and vocabulary exercises were considered to be useful, even at tertiary level. The results are discussed in light of pedagogical approaches to language teaching

Vowel reduction in word-final position by early and late Spanish-English bilinguals

Vowel reduction is a prominent feature of American English, as well as other stress-timed languages. As a phonological process, vowel reduction neutralizes multiple vowel quality contrasts in unstressed syllables. For bilinguals whose native language is not characterized by large spectral and durational differences between tonic and atonic vowels, systematically reducing unstressed vowels to the central vowel space can be problematic. Failure to maintain this pattern of stressed-unstressed syllables in American English is one key element that contributes to a ?foreign accent? in second language speakers. Reduced vowels, or ?schwas,? have also been identified as particularly vulnerable to the co-articulatory effects of adjacent consonants. The current study examined the effects of adjacent sounds on the spectral and temporal qualities of schwa in word-final position. Three groups of English-speaking adults were tested: Miami-based monolingual English speakers, early Spanish-English bilinguals, and late Spanish-English bilinguals. Subjects performed a reading task to examine their schwa productions in fluent speech when schwas were preceded by consonants from various points of articulation. Results indicated that monolingual English and late Spanish-English bilingual groups produced targeted vowel qualities for schwa, whereas early Spanish-English bilinguals lacked homogeneity in their vowel productions. This extends prior claims that schwa is targetless for F2 position for native speakers to highly-proficient bilingual speakers. Though spectral qualities lacked homogeneity for early Spanish-English bilinguals, early bilinguals produced schwas with near native-like vowel duration. In contrast, late bilinguals produced schwas with significantly longer durations than English monolinguals or early Spanish-English bilinguals. Our results suggest that the temporal properties of a language are better integrated into second language phonologies than spectral qualities. Finally, we examined the role of nonstructural variables (e.g. linguistic history measures) in predicting native-like vowel duration. These factors included: Age of L2 learning, amount of L1 use, and self-reported bilingual dominance. Our results suggested that different sociolinguistic factors predicted native-like reduced vowel duration than predicted native-like vowel qualities across multiple phonetic environments