2,217 research outputs found
The quadratic electro-optical effect in ferroelectric liquid crystal helical nanostructures: role of the driving voltage shape
No full textRecently it was shown that in deformed helix ferroelectric (DHF) structure, the electrically controlled birefringence of chiral smectic C* phase with subwavelength helix pitch ( is known to be proportional to the square of the electric field E) depends on the cell thickness and on the frequency of applied voltage, given as a Step function of the time. The purpose of the present work is to investigate whether this quadratic effect depends also on the voltage function shape, comparing the electrically controlled birefringence and the Kerr constant in DHF cells with different thickness, driven by STAIR and Step voltage functions
Development of ferroelectric liquid crystals with low birefringence
No full textWe propose an approach for development of ferroelectric liquid crystals (FLC) with low birefringence Δn. Two basic principles have been used to get lowering of Δn: selection of molecules with short chains of conjugation as components for achiral matrix and averaging of local refractive indices by FLC helical structure. FLC mixtures with low birefringence (0.07 < Δn < 0.10 at wavelength 589.3 nm of sodium line) were elaborated and investigated. They consist of an achiral matrix including both nematic and smectic liquid crystal components and of phenylpyrimidine derivatives as chiral dopants. The materials developed can be used for all basic electro-optical FLC modes such as surface stabilised FLC (SSFLC), deformed helix ferroelectrics (DHF) and electrically suppressed helix (ESH). The mixtures developed allow to reduce the FLC cells chromatic retardance variation due to the weaker birefringence dispersion as compared with the known FLC materials to date
The quadratic electro-optical effect in ferroelectric liquid crystal helical nanostructures: role of cell thickness and voltage frequency
No full textIt was reliably proved in recent years both theoretically and experimentally that the electrically controlled birefringence ΔnE of chiral smectic C* phase with subwavelength helix pitch is proportional to the square of the electric field E. The goal of the present work is to investigate the restrictions of the quadratic effect imposed by the thickness of the smectic C* layer between two solid substrates, and by the frequency of applied voltage. It is shown that these restrictions are mainly associated with the dielectric dispersion of the Goldstone mode under various boundary conditions
Premessa a Per d’Arco Silvio Avalle, «Le forme del canto». Interventi di Lino Leonardi, Pietro G. Beltrami, Maria Sofia Lannutti, Arnaldo Soldani
No full textThis collection of essays on medieval poetic metres, edited by Maria Sofia Lannutti following the arrangement conceived by its author, confirms the importance of d'Arco Silvio Avalle's metrical studies. Key issues are the relationship between metrical structure and music in the texts dating back to the origin of romance literatures, the multi-perspective complexity of the approach, and the exemplarity of the methodology used. © 2019 Societa Editrice il Mulino. All rights reserved
Year-Book of the St. Kliment Ohridski University of Sofia. Faculty of Philosophy. Chronological Bibliography 1981-2010
No full textWhen a specialized periodical publication representing a professional community comes out, it is an indication for the authority of the institution. In this sense the Year-book of the St Kliment Ohridski University of Sofia, its oldest periodical publication, coming out with this logo, calls for respect both with its one hundred years history as well as with the quality of the published material. The beginnings were laid in 1905, today the Year-book offers a complex system of the editions of the faculties of the University of Sofia and the specialties and chairs at them.
The teaching of philosophy at the University of Sofia goes back to its very foundation in 1888. In 1950 the Faculty of Philosophy and History was established with three chairs: a chair of philosophy, a chair of history and paedagogics. Since 1972 the chair of History became a Faculty of History, and since 1986 the chair of Paedagogics became a Faculty in its own right, beyond the Faculty of Philosophy. Within the period between 1976 to the 90s of the 20th century the Philosophical faculty assumed its present day shape, providing possibilities for training with a BA degree and MA degree as well as a PhD course in the following principal specialties:
Philosophy 1888
Psychology 1972
Sociology 1976
Political science 1986
Culturology 1991
Library-Information Science 1993
Public administration 1997
European studies 1998
Chair of Rhetorics - 1991 offers optional courses for all specialties of the University as well as training for a MA.
Lecturers and post-graduate student at the Faculty of Philosophy can publish their studies, articles and analyses in the authoritative Year-book of the University of Sofia, Faculty of Philosophy. Over the years its structure has evolved. Together with ‘books’ on philosophy and paedagogics, the new specialties began to bring out ‘books” of their own: namely in Psychology, Sociology, Library-Information Sciences and European studies.
The analytical bibliography of the Year-book of the St.Kliment Ohridski University of Sofia, Faculty of Philosophy is a continuation of the earlier analytical Year-book of the St.Kliment Ohridski University of Sofia, for the 1976-1980 , however the material included here is only from the Year-book of the Faculty of Philosophy. It comes out in separate volumes, following a unified numeration. The period included 1981-2010 comprises vol. 74 - 100.
Books from specialties, which emerged over the 1984-2010 period, are represented in separate series: Book Philosophy, Book Psychology, Book Sociology, Book Library-Information Science, Book European studies. This order is in line with the successive creation of the respective specialties. Book Paedagogics – vol.75 and 76 of the Chair of Paedagogics, vol. 82 and vol. 83 of the Chair in Socio-Political Systems, and vol. 82, vol. 83-84 and 86 of the Problem Research Laboratory on Political Behavior. With a view to give exhaustive information, these books have been presented analytically, regardless the fact that these sections are no longer part of the Faculty of Philosophy, or do not exist separately. The presumption is that previously they were part of its structure.
Within each Book (series) materials are presented chronologically, according to volume. The high academic and professional level of the Year-book of the University of Sofia, Faculty of Philosophy is maintained by an authoritative editorial board for the respective book. It has been a long practice to cite reviewers for each published material. Access to information through the inclusion of additional elements is streamlined in the publication of new specialty ‘Books’. In vol.1 of the specialty European studies mandatory requirements to the author of publications are given, with special emphasis in the rules of citation. Here for the first time, together with a summary in English, given are key-words, drawn from the contents of each publication. A very useful thematic index has been added to vol. 1 of the specialty Library-Information Sciences.
The bibliographical description of the material, published in the Year-book follows the common framework of Bulgarian standard for analytical description. At the same time a substantial difference in this analytical bibliography of the Year-book of the University of Sofia, Faculty of Philosophy from analytical bibliographies up to 1980 is the subject analysis of every publication. The practice of the Year-book of the Faculty of Philosophy at the beginning of the 80s was to present the content of each publication with extended summaries in Russian and English and resumes in English, French, or German. From the 90s the resumes were dropped and only the extended summaries remained, and for the separate Books of the specialties and the separate years they were in Russian and English, and recently only in English. In order to avoid duplication with the summaries of the Year-book, the approach in the bibliography is different. Here it is based on the structure, suggested by the authors themselves. The nature of publications in the Year-book is good ground in this respect. Authors with an established name are those who publish here, with their established style and views on the emphasis in their own papers. Proof of this is the fact that almost every publication has its own internal structure, worked out by the author. It is felt in the respective headings of each section, in many instances with additional subsections, subtitles, and different pagination. The presentation of the content from the point of view of the author is the objective solution for so specific and varied subject matter as publications in the various Books of the Year-book. The style of the authors is preserved in the structure they have chosen for each publication and their preference connected with the names and numbering of the sections. In this way presentation of the contents of publications authentically represents the author’s point of view, concerning his own text.
Publications included in each book have a numeration of their own, beginning with No 1. Each of the books of the Year-book has its own index of author’s names. In this way, authors who have published their works in the respective Book of the Year-book can be noted. Almost everywhere the names of all persons mentioned in the various texts are given in full and as a rule citation is done with family names and initials.
A common alphabetical index has also been compiled, unifying authors and persons with publications from all Books of the Year-book. In this way the total list of publications of lecturers from the Faculty of Philosophy, within the last 30 years is presented. After each name the Book and Number where the respective publication is to be found is given.
Besides a printed edition the Year-book of the University of the University of Sofia has beep prepared as an electronic resource. In this way it has become part of a data-base with material of the Year-books of the respective Faculties, supported by the University Library.
The analytical bibliography of the Year-book of the University of Sofia, Faculty of Philosophy 1981-2010 is a continuation of an year long tradition, presenting the staff of the Faculty of Philosophy before the public through their publications and at the same time allowing students, faculty and specialists effective academic work and research with it
Pedagogical ideas of Sofia Rusova
No full textУ тезах висвітлено педагогічні ідеї Софії Русової, видатного педагога, просвітителя, громадського діяча, автора багатьох досліджень із педагогіки, історії, географії, дошкільної та позашкільної освіти.The theses highlight the pedagogical ideas of Sofia Rusova, an outstanding teacher, educator, public figure, author of many studies on pedagogy, history, geography, preschool and after-school education
Why is unemployment so high in Bulgaria?
No full textThe author seeks to determine the main factors behind poor labor market outcomes in Bulgaria. Unemployment in Bulgaria is high and of long duration. The accumulation of the unemployment stock has been caused by relatively high inflows into unemployment coupled with limited outflows. These features of the Bulgarian labor market are typical of other transition economies in Central Europe and exploring their sources is of broad interest. The author focuses on determinants of and constraints to job creation. He uses data on job creation and job destruction from a survey of employment in all registered firms. He finds that the source of large inflows into unemployment is intensive enterprise restructuring associated with a high pace of job reallocation. However, job creation falls short of job destruction. Three main factors account for the limited job creation and hiring, and thus for low outflows from unemployment: a) The unfriendly business environment, reflected by a low rate of new firm formation, and a relatively small, small and medium enterprise sector. b) Labor market rigidities, including excessive hiring and firing costs. c) Skill and spatial mismatches brought about by enterprise restructuring, as well as low skills and marginalization of the long-term unemployed who cannot successfully compete for new jobs. The author recommends a three pronged strategy to improve labor market performance: (1) removing bureaucratic constraints to entry and expansion of firms; (2) enhancing labor market flexibility through lowering hiring and firing costs; and (3) improving the educational system so as to equip workers with broad and portable skills.Environmental Economics&Policies,Labor Policies,Labor Markets,Public Health Promotion,Health Monitoring&Evaluation,Environmental Economics&Policies,Labor Markets,Health Monitoring&Evaluation,Labor Standards,Banks&Banking Reform
X-ray investigation of new isomeric oxadiazoles
No full textAn x-ray investigation has been performed on five new 2,5- disubstituted 1,2,4-oxadiazoles with reversed structures containing 4-amylbiphenyl-, trans-4-amylcyclohexylphenyl- and 2-halophenyl- as substituents. The aim was to confirm the data about the phase sequence, obtained via polarizing microscopy and differential scanning calorimetry, and to measure the structural parameters. Through x-ray diffraction technique, all substances showed only the nematic mesophase. Moreover, it was proved that some enthalphy variations previously attributed to crystal-crystal transitions are in fact due either to the rearrangement of the lattice or to the coalescence of the grains. However, for some substances, a second crystalline from c' appeared at the melting point, on cooling from the isotropic phase. C' turned out to be different from the starting form C1 of the sample, which had no thermal cycle before
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