Stability of constant retrial rate systems with NBU input*

We study the stability of a single-server retrial queueing system with constant retrial rate, general input and service processes. First, we present a review of some relevant recent results related to the stability criteria of similar systems. Sufficient stability conditions were obtained by Avrachenkov and Morozov (2014), which hold for a rather general retrial system. However, only in the case of Poisson input is an explicit expression provided; otherwise one has to rely on simulation. On the other hand, the stability criteria derived by Lillo (1996) can be easily computed but only hold for the case of exponential service times. We present new sufficient stability conditions, which are less tight than the ones obtained by Avrachenkov and Morozov (2010), but have an analytical expression under rather general assumptions. A key assumption is that interarrival times belongs to the class of new better than used (NBU) distributions. We illustrate the accuracy of the condition based on this assumption (in comparison with known conditions when possible) for a number of non-exponential distributions

Phase separation, ferromagnetism and magnetic irreversibility in La1-xSrxMn1-yFeyO3

The ferromagnetism of LSMFO is attributable to percolation over the system of such particles and generation of large FM clusters, whereas the frustration is governed presumably by a system of smaller weakly-correlated magnetic units, which do not enter the percolative FM clustersyesBelgorod State Universit

Evaluation of competitive strength of building companies based on organization and technical indicators

There are different methods of evaluation of competitive ability of building organizations. We analyzed the main approaches to how assess the competitiveness of organizations and found out some flaws of existing approaches. The article deals with a method based on organizational and technical indicators

Organizational and management mechanism for reforming agricultural organizations based on cooperation and integration of economic systems

In the agricultural sector of Russia, a high proportion of insolvent organizations is currently maintained. Ensuring food independence of the country, the availability of high-quality and affordable food for the population are the main objectives of the development of the domestic agricultural sector. In agriculture, there is growing interest in the formation of universal approaches to the procedure for managing economic entities. The reform of insolvent agricultural producers based on the development of cooperation and integration processes by absorbing economically weak farms by successful agribusiness organizations is one of the methods to achieve these goals. The subject of the research is the methodology and management practice of reforming domestic agricultural organizations based on cooperation and integration of economic systems. Theoretical research and practical material is based on the results of economic activity and the experience of reforming in economic entities. Systemic and process approaches, statistical and economic methods were used mainly in obtaining research results.The purpose and objective of the study is the introduction of progressive methodological approaches to assess the effectiveness of reforming economic entities. The paper presents the conditions and factors, the organizational and managerial mechanism, methods and practical experience in implementing the reform process of insolvent agricultural organizations, as well as an assessment of the production and economic efficiency of reforming on the materials of the agricultural organization. The results of the study confirm the need to replicate the methodology and experience of reforming agricultural organizations through cooperation and integration of economic entities with the provision of state support in all its existing forms for this process. In particular, we propose the formation and legislative consolidation of a system of competitive reform of insolvent agricultural organizations

Developing a modern thermal strengthening technique for regulated fishplate cooling

A modern ecologically friendly technique for fishplate (joint bar) thermal strengthening by regulated water cooling is proposed. The proposed technique can successfully replace the conventional one - oil quenching - due to making the cooling process more controlled by obtaining a uniform temperature distribution over fishplate elements with a different mass such as heads and the wet. The oil quenching process is an out of control fire hazardous one and requires controlling the permanent cooling capability, fishplate flushing after the operation. It is necessary to utilize the oil and to have a special ventilation system. As a mineral oil substitute, the usage of polymer media has been investigated. Within the time, the polymer solution needs to be recycled; the high cost of polymer concentrates also plays an important role. Quenching by water spraying is the most ecological and controlled type of thermal strengthening. The technique was validated by a test bench experiment and implemented in the metallurgical industry. The mechanical properties have been obtained to meet the GOST 4133-73 technical requirements. Moreover, the analysis made showed that when the controlled cooling device is fitted into the line existing due to exclusion of the hardening tank and washing machine from the processing flow it is possible to save energy, exclude the expenditures for acquisition, the preparation of oil and washing mixtures as well as for regeneration of the oils used and washing solutions. © 2014 WIT Press.International Journal of Safety and Security Engineering;International Journal of Sustainable Development and Planning;WIT Transactions on Ecology and the Environmen

The change in the inclination angle of the non-eclipsing binary SS Lacertae: future eclipses

Eclipses in the 14.4-day period double-lined binary SS Lac were observed photographically and visually early in the 20th century, but stopped some 50 or 60 years ago. This has been explained by the presence of a distant third star in the system, which has now been detected spectroscopically with a period of 679 days. The plane of the orbit of the binary is changing relative to the line of sight in response to perturbations from this third object. A recent analysis by Milone et al. (M00) of all photometric material available for the system, including a re-measurement of original Harvard plates, has confirmed earlier reports of changes in the depth of the eclipses as a function of time, which are due to the third star. In this paper we discuss our detailed analysis of the eclipse amplitude measurements, and extract from them information on the change in the inclination angle of the binary over the last century. Our use of a much improved ephemeris for the system by Torres & Stefanik was found to be crucial, and prompted us to re-determine all the amplitudes from the historical data at our disposal, including the Harvard material used by M00. Systematically lower measurements on the branches of the minima were properly accounted for, and we made use of both a linear approximation to the time variation of the inclination angle and a more realistic model based on the theory of three-body interactions ("regression of the nodes" effect). The nodal cycle is found to be about 600 yr, within which TWO eclipse "seasons" occur, each lasting about 100 yr. The non-eclipsing status of the system is expected to continue until the beginning of the 23rd century.Comment: 32 pages, including figures and tables. Accepted for The Astronomical Journal, April 200

Experience of using different schemes corticosteroid therapy for epileptic encephalopathies in children

The article presents the experience of using pulse therapy with dexamethasone and methylprednisolone in the treatment of epileptic encephalopathy on the basis of a prospective study of patients.В статье представлен опыт применения пульс-терапии дексаметазоном и метилпреднизолоном в лечении эпилептических энцефалопатий на основании проспективного исследования пациентов

The usage of surrogacy: bioethical aspect

The aim of the study - to identify bioethical problems of the use of assisted reproductive technologies of surrogacy in legal and social aspects.Цель исследования – выявить биоэтические проблемы применения вспомогательной репродуктивной технологии суррогатного материнства в правовом и социальном аспекта