Обзор систем параллельной обработки заявок. Часть II

This paper is a continuation of the survey of the “fork-join” queuing systems (in the westernclassification) or the systems with splitting of queries. Interest in such systems is explainedby a wide range of problems that can be solved with their help, since in fact it is a matter ofparallel processing of data and their applications. For example, this may concern the analysis ofdisk arrays, cloud computing, high-performance services and even the process of picking ordersin a warehouse. In the first part of the survey, the main features of the described model (andrelated systems) and its construction were introduced. Also the detailed description of theapproach to obtaining an accurate expression of the average response time in the case of twodevices was presented as well as several methods of approximate analysis of this characteristic(the case when the number of devices is more than two). This part of the survey is devotedto the description of other existing methods for approximating the average response time. Inparticular, the approaches of the approximate analysis of the response time are as follows: thematrix-geometric method, the analysis with the help of order statistics for various types ofdistribution of the service time of subqueries.Данная работа является продолжением обзора методов исследования системы массовогообслуживания вида «fork-join» (в западной классификации) или системы с расщеплениемзапросов. Интерес к рассматриваемой системе объясняется широким спектром задач, которые могут быть решены с её помощью, поскольку фактически речь идёт о параллельнойобработке данных и их приложениях. К примеру, это может касаться анализа работы дисковых массивов, облачных вычислений, высокопроизводительных сервисов и даже процессакомплектации заказов на складе. Если в первой части обзора были описаны особенностипостроения данной модели и родственных ей систем, а также приведено подробное описание подхода к получению точного выражения среднего времени отклика в случае двухприборов и представлено несколько методов приближенного анализа данной характеристики в случае, когда число приборов больше двух, то во второй части обзора представленоописание других существующих методов аппроксимации среднего времени отклика. В частности, к рассматриваемым подходам приближенного анализа времени отклика относятся:матрично-геометрический метод, анализ с помощью порядковых статистик для различныхтипов распределения времени пребывания подзапросов

Dark Energy Fluid with Time-Dependent, Inhomogeneous Equation of State

The four-dimensional Friedman flat universe, filled with an ideal fluid with a linear (oscillating) inhomogeneous equation of state (EoS) depending on time, is studied. The equations of motion are solved. It is shown that in some cases there appears a quasi-periodic universe, which repeats the cycles of phantom-type space acceleration. The appearance of future singularities resulting from various choices for the input parameters is discussed.Comment: 9 pages pdf, 4 figures. To appear in European Physical Journal

A FRW Dark Fluid with a Non-Linear Inhomogeneous Equation of State

A dark Friedman-Robertson-Walker fluid governed by a non-linear inhomogeneous equation of state is considered which can be viewed as a conveniently simple paradigm for a whole class of models which exhibit phase transitions from a non-phantom towards a phantom era (superacceleration transition). From another side, such dark fluid models may describe also quintessence-like cosmic acceleration. Thermodynamical considerations for the processes involved, which are of great importance in the characterization of the global evolution of the corresponding universe, are given too. Connecting the proposed equation of state with an anisotropic Kasner universe with viscosity, we are led to the plausible conjecture of a dark fluid origin of the anisotropies in the early universe.Comment: 11 pages pdf, 2 figures; to appear in Eur. Phys. J.

Анализ системы массового обслуживания с двумя входящими потоками и вероятностным сбросом

The queueing system with two independent flows of requests with different types of priorities is considered. The incoming flows are Poisson flows with different (non equal) rates. The service times of each type requests are independent and exponentially distributed. The priority requests at the end of its service can drop non-priority ones with probability q (renovation probability) or just leaves the system with probability p = 1 - q. For general case the two-dimensional Markov process is introduced and the system of equilibrium equations for steady-state probability distribution is presented. For special case, when drop probability q is equal to one, some probabilistic characteristics as the steady-state probability distribution of priority requests, the probability of idle period are obtained. Also the analytical expressions for some characteristics of non-priority requests, such as probability of being dropped (or serviced), waiting time distribution for non-priority requests (in terms of Laplace-Stieltjes transformation and generating function) and mean waiting time, are obtained.Рассматривается однолинейная система массового обслуживания с накопителем неограниченной ёмкости, в которую поступают два независимых пуассоновских потока заявок с различными интенсивностями и приоритетами. Заявка первого типа (приоритетная), находящаяся на приборе, может в момент окончания обслуживания либо покинуть систему с некоторой ненулевой вероятностью, либо с дополнительной вероятностью сбросить все заявки второго типа (неприоритетные заявки) из накопителя и покинуть систему. Длительности обслуживания заявок обоих типов имеют экспоненциальные распределения с различными значениями интенсивностей обслуживания. Для общего случая построен двумерный марковский процесс, получена система уравнений равновесия для стационарного распределения числа заявок обоих типов в системе. Для частного случая рассматриваемой системы (приоритетные заявки сбрасывают неприоритетные с вероятностью, равной единице) в явном виде представлено стационарное распределение числа приоритетных заявок в системе, вероятность простоя системы. Также получено выражение для вероятности простоя системы. Для неприоритетных заявок найдены вероятность ее сброса из системы приоритетной заявкой, стационарное распределение времени ожидания начала обслуживания (в терминах преобразований Лапласа-Стилтьеса и производящих функций), а также среднее время ожидания начала обслуживания

Обзор систем параллельной обработки заявок. Часть II

This paper is a continuation of the survey of the “fork-join” queuing systems (in the westernclassification) or the systems with splitting of queries. Interest in such systems is explainedby a wide range of problems that can be solved with their help, since in fact it is a matter ofparallel processing of data and their applications. For example, this may concern the analysis ofdisk arrays, cloud computing, high-performance services and even the process of picking ordersin a warehouse. In the first part of the survey, the main features of the described model (andrelated systems) and its construction were introduced. Also the detailed description of theapproach to obtaining an accurate expression of the average response time in the case of twodevices was presented as well as several methods of approximate analysis of this characteristic(the case when the number of devices is more than two). This part of the survey is devotedto the description of other existing methods for approximating the average response time. Inparticular, the approaches of the approximate analysis of the response time are as follows: thematrix-geometric method, the analysis with the help of order statistics for various types ofdistribution of the service time of subqueries.Данная работа является продолжением обзора методов исследования системы массовогообслуживания вида «fork-join» (в западной классификации) или системы с расщеплениемзапросов. Интерес к рассматриваемой системе объясняется широким спектром задач, которые могут быть решены с её помощью, поскольку фактически речь идёт о параллельнойобработке данных и их приложениях. К примеру, это может касаться анализа работы дисковых массивов, облачных вычислений, высокопроизводительных сервисов и даже процессакомплектации заказов на складе. Если в первой части обзора были описаны особенностипостроения данной модели и родственных ей систем, а также приведено подробное описание подхода к получению точного выражения среднего времени отклика в случае двухприборов и представлено несколько методов приближенного анализа данной характеристики в случае, когда число приборов больше двух, то во второй части обзора представленоописание других существующих методов аппроксимации среднего времени отклика. В частности, к рассматриваемым подходам приближенного анализа времени отклика относятся:матрично-геометрический метод, анализ с помощью порядковых статистик для различныхтипов распределения времени пребывания подзапросов

APPLICATION OF TOUCHLESS METHODS FOR MAKING ENTRIES IN DENTAL RECORDS

This review focuses on the current issues of asepsis in dental settings and ways to prevent contact infection using touchless methods of making entries in dental records. Contact transmission is the main route of microbial contamination in dentistry. Various environmental surfaces in dental settings are difficult to disinfect, while contact with the staff's hands with the surfaces of computer equipment is inevitable. Continuous disinfection of the components of the computer hardware in the dental unit can cause damage and significantly reduce their useful life. The disinfection of the keyboard, touch screens, as well as other devices for entering dental records, is especially challenging. Alternative touchless methods for operating computers by dentists and nurses are already applied in various dental settings, such as surgery units, where a high level of sterility is required during operation. The use of such methods not only reduces the time spent by the patient in the dental chair but also excludes the contact of the doctor's hands with hard-to-clean surfaces, minimizing the chance of contact infection transmission

MEASURING OF AIRWAYS RESISTANCE BASED ON INTERRUPTER TECHNIQUE IN PRE-SCHOOLCHILDREN

Authors give information on limits of population norm for expiratory and inspiratory resistance by the interrupter technique indices (RINTexp and RINTinsp accordingly) in 214 healthy children 3–6 years old. Estimation of RINT was performed with spirograph Super Spiro with MicroRint module. Parameters of RINTexp and RINTinsp are similar in boys and girls. RINTexp depends on height of a child. Information on limits of normal rates is presented in this article, and this data can be used in diagnostics of respiratory pathology. Key words: children, age, resistance of airways, RINT, norm.(Voprosy sovremennoi pediatrii — Current Pediatrics. 2010;9(5):30-34

Analysis of Cumulative Distribution Function of the Response Time in Cloud Computing Systems with Dynamic Scaling

One of the key performance measures of cloud computing systems is the response time. However, the mean value of this characteristic does not give the full picture of quality of service. Therefore, we derive the cumulative distribution function (CDF) of the response time in terms of Laplace-Stieltjes transform and use it to evaluate moments of the response time. Moreover, we introduce a simplification of the mathematical model that significantly reduces computing complexity for the response time CDF and provide analysis of approximation accuracy of the simplified model. © 2018, Allerton Press, Inc

Resource queuing systems as models of wireless communication systems

The article presents an overview of the resource queuing systems used for modeling of a wide class of real systems with admittedly limited resources. Despite the objective importance of studying of such systems, there have been very few works devoted to their analysis until recently, which was due to the complexity of constructing a random process to describe their functioning and, accordingly, of obtaining the numerical results. However, in recent years, there has been a significant shift in the study of the resource systems - new methods for their analysis have been proposed, which made it possible to construct recursive algorithms suitable for the numerical calculations. In this regard, the current review reflects only a part of the previously obtained results, namely, it considers the resource systems without waiting space with exponentially distributed service time. The authors consider the models of wireless communication systems based on resource queuing systems, expressions for estimating the main probabilistic, and temporal characteristics and algorithms for their calculation. © 2018 Federal Research Center Computer Science and Control of Russian Academy of Sciences