Flame Enhancement and Quenching in Fluid Flows

We perform direct numerical simulations (DNS) of an advected scalar field which diffuses and reacts according to a nonlinear reaction law. The objective is to study how the bulk burning rate of the reaction is affected by an imposed flow. In particular, we are interested in comparing the numerical results with recently predicted analytical upper and lower bounds. We focus on reaction enhancement and quenching phenomena for two classes of imposed model flows with different geometries: periodic shear flow and cellular flow. We are primarily interested in the fast advection regime. We find that the bulk burning rate v in a shear flow satisfies v ~ a*U+b where U is the typical flow velocity and a is a constant depending on the relationship between the oscillation length scale of the flow and laminar front thickness. For cellular flow, we obtain v ~ U^{1/4}. We also study flame extinction (quenching) for an ignition-type reaction law and compactly supported initial data for the scalar field. We find that in a shear flow the flame of the size W can be typically quenched by a flow with amplitude U ~ alpha*W. The constant alpha depends on the geometry of the flow and tends to infinity if the flow profile has a plateau larger than a critical size. In a cellular flow, we find that the advection strength required for quenching is U ~ W^4 if the cell size is smaller than a critical value.Comment: 14 pages, 20 figures, revtex4, submitted to Combustion Theory and Modellin

Polariton Dispersion Law in Periodic Bragg and Near-Bragg Multiple Quantum Well Structures

The structure of polariton spectrum is analyzed for periodic multiple quantum well structures with periods at or close to Bragg resonance condition at the wavelength of the exciton resonance. The results obtained used to discuss recent reflection and luminescent experiments by M. H\"{u}bner et al [Phys. Rev. Lett. {\bf 83}, 2841 (1999)] carried out with long multiple quantum well structures. It is argued that the discussion of quantum well structures with large number of wells is more appropriate in terms of normal modes of infinite periodic structures rather then in terms of super- and sub- radiant modes.Comment: replaced with a new version, an error in one of the equations is correcte

Solution combustion synthesis of α-Al2O3 using urea

The processes involved in the solution combustion synthesis of α-Al2O3 using urea as an organic fuel were investigated. The data describing the influence of the relative urea content on the characteristic features of the combustion process, the crystalline structure and the morphology of the aluminium oxide are presented herein. Our data demonstrate that the combustion of stable aluminium nitrate and urea complexes leads to the formation of α-alumina at temperatures of approximately 600-800 °C. Our results, obtained using differential thermal analysis and IR spectroscopy methods, reveal that the low-temperature formation of α-alumina is associated with the thermal decomposition of an α-AlO(OH) intermediate, which was crystallised in the crystal structure of the diaspore. © 2012 Elsevier Ltd and Techna Group S.r.l

Методический подход к оценке уровня адаптивности организационных структур управления компаниями

Purpose: to present and justify a methodical approach to assessing the level of adaptability of organizational management structures to the conditions of a dynamically changing external environment.Methods: a wide range of general scientific methods is used – system analysis, synthesis, graphical interpretation of data. During the study, the method of expert assessments was used to assess the level of adaptability. In order to classify the types of management structures depending on their adaptability, a cluster analysis was carried out.Results: the article presents an approach to the definition of the concepts of "adaptation" and "adaptability" in relation to management structures. In order to develop a methodical approach to assessing the level of adaptability of organizational structures, the types of their adaptation were systematized, the main characteristics of the structures were identified and the scale was developed to assess the level of their adaptability. The use of the expert method made it possible to assess the level of adaptability of the main types of organizational structures to the conditions of a changing business space and rank them depending on this level. As a result of the cluster analysis, all the studied types of management structures were classified depending on their adaptability.Conclusions and Relevance: the developed methodical approach to assessing the level of adaptability of management structures made it possible to determine the adaptive properties of both hierarchical and organic management structures, assess their level of adaptability and identify the most adaptive among them. It has been established that the basis for the successful development of companies in the conditions of turbulent business space is the use of organic structures or changing individual parameters of hierarchical structures in order to increase their adaptability. Adaptation can be carried out using any structure, both traditional hierarchical and organic, by forming new management structures or increasing the adaptability of existing ones. Further research in this area should be devoted to the development of an effective mechanism for adapting management structures to the conditions of a changing business space.Цель статьи – представить и обосновать методический подход по оценке уровня адаптивности организационных структур управления компаниями к условиям динамично меняющейся внешней среды.Методы. Использован широкий спектр общенаучных методов – системного анализа, синтеза, графической интерпретации данных. При проведении исследования для оценки уровня адаптивности использовался метод экспертных оценок. С целью классификации видов структур управления в зависимости от их адаптируемости был проведен кластерный анализ.Результаты работы. В статье представлен подход к определению понятий «адаптация» и «адаптивность» применительно к структурам управления. С целью разработки методического подхода к оценке уровня адаптивности организационных структур проведена систематизация видов их адаптации, выявлены основные характеристики структур и разработана шкала оценки уровня их адаптивности. Использование экспертного метода позволило оценить уровень адаптивности основных видов организационных структур к условиям изменяющегося бизнес-пространства, и проранжировать их в зависимости от этого уровня. В результате проведения кластерного анализа все исследуемые виды структур управления были классифицированы в зависимости от их адаптируемости.Выводы. Разработанный методический подход к оценке уровня адаптивности структур управления позволил определить адаптивные свойства как иерархических, так и органических структур управления, оценить уровень их адаптивности и выявить среди них самые адаптивные. Установлено, что основой успешного развития компаний в условиях турбулентности бизнес-пространства является использование органических структур или изменение отдельных параметров иерархических структур с целью повышения их адаптивности. Адаптация может осуществляться при использовании любой структуры, как традиционной иерархической, так и органической, путем формирования новых структур управления или повышения адаптивности уже существующих. Дальнейшие исследования в этой сфере должны быть посвящены разработке действенного механизма адаптации структур управления к условиям изменяющегося бизнес-пространства

Lecture-Conversation in Methodological Instrumentation of Russian as a Foreign Language Teacher

The article justifies the urgency of development of lectures-conversations when presenting the theoretical material of the training courses to foreigners. Attention is drawn to the difficulties of foreign students in listening the lecture in its traditional understanding as a monologue of the teacher. The importance of a methodical understanding of the theoretical presentation of the material in question-answer form is emphasised. Scientific novelty and practical significance of research results is seen in the fact that the issues are described from the point of view of the purpose of their performance to the students, the positive effect of the issue, the shortcomings of the question. It is assumed that within this form of classes the teacher can introduce new material, systematize theoretical information studied by students, consolidate students’ knowledge in the subject area, take into account communicative and personal aspects of adaptation of foreign students in Russian educational environment. On the original author’s material of lecture-conversation on theoretical grammar the kinds of questions are demonstrated that are appropriate to use in dialogue with foreign students. Methodological training for teachers in the formulation of various types of questions is proposed. It is concluded that the systematic use of lecture-conversation in teaching practice will contribute to overcoming the communicative and psychological difficulties of foreign students listening to lectures in a foreign language (Russian) that meets the modern trends of multicultural education

Microbiological diagnostics of pyoinflammatory abdominal diseases

The aim of the work was to establish the significance of complex bacteriological research in the diagnostics of acute appendicitis and to determine an optimal material for the research based on the findings. We examined 19 patients with acute phlegmonous or acute gangrenous appendicitis (males, aged 18-60 years). We performed bacteriological research of abdominal exudate (n = 19) and biopsy specimen (n = l9) of appendix wall taken before opening the lumen of the intestine. Both abdominal exudate and appendix wall specimen were taken at the same time. Aerobic and anaerobic microorganisms were detected and identified, antimicrobial susceptibility was tested. In total, we detected 25 strains of aerobic and 13 strains of anaerobic microorganisms. It has been established that a bioptate was most informative for testing (68.4 %); the parallel study of an abdominal exudate gave positive results in 21.1 % of cases. In the structure of clinically significant microflora dominated E. coli (43.3 %), then went nonfermentative gram-negative bacteria (13.3 %) and Bacteroides spp. (16.7 %). We marked growing resistance of detected strains of gram-negative bacteria to some antibiotics. For instance, 62 % of detected E. coli strains were resistant to ampicillin, 25 % - to ciprofloxacin. 92 % of strains were resistant to cefepime, 93 % -to ceftriaxone, 77 % - to Amoxiclav, 67 % - to gentamicin, 90 % - to tobramycin. From one bioptate a strain of E. coli ESBL was separated. The study of intraoperative bioptate of appendix wall increases effectiveness of microbiological diagnostics in comparison with the abdominal exudate research

Effects of inhomogeneous broadening on reflection spectra of Bragg multiple quantum well structures with a defect

The reflection spectrum of a multiple quantum well structure with an inserted defect well is considered. The defect is characterized by the exciton frequency different from that of the host's wells. It is shown that for relatively short structures, the defect produces significant modifications of the reflection spectrum, which can be useful for optoelectronic applications. Inhomogeneous broadening is shown to affect the spectrum in a non-trivial way, which cannot be described by the standard linear dispersion theory. A method of measuring parameters of both homogeneous and inhomogeneous broadenings of the defect well from a single CW reflection spectrum is suggested.Comment: 27 pages, 6 eps figures; RevTe

Studying of immunophysiological properties of Yersinia Pestis strains with various plasmid composition

Data of Yersinia pestis plasmid structure influence on its adhesive properties and phagocytic activity of peritoneal macrophages in vitro are represented. It is shown that Y. pestis strains of diverse subspecies differing by a plasmid profile, particularly by one of the plasmids (pYP, pYV) lacking, possess low adhesive activity and promote the increase of laboratory animal phagocyte absorbing capacity

Combustion in thermonuclear supernova explosions

Type Ia supernovae are associated with thermonuclear explosions of white dwarf stars. Combustion processes convert material in nuclear reactions and release the energy required to explode the stars. At the same time, they produce the radioactive species that power radiation and give rise to the formation of the observables. Therefore, the physical mechanism of the combustion processes, as reviewed here, is the key to understand these astrophysical events. Theory establishes two distinct modes of propagation for combustion fronts: subsonic deflagrations and supersonic detonations. Both are assumed to play an important role in thermonuclear supernovae. The physical nature and theoretical models of deflagrations and detonations are discussed together with numerical implementations. A particular challenge arises due to the wide range of spatial scales involved in these phenomena. Neither the combustion waves nor their interaction with fluid flow and instabilities can be directly resolved in simulations. Substantial modeling effort is required to consistently capture such effects and the corresponding techniques are discussed in detail. They form the basis of modern multidimensional hydrodynamical simulations of thermonuclear supernova explosions. The problem of deflagration-to-detonation transitions in thermonuclear supernova explosions is briefly mentioned.Comment: Author version of chapter for 'Handbook of Supernovae,' edited by A. Alsabti and P. Murdin, Springer. 24 pages, 4 figure