Статьи журнала - Программные системы: теория и приложения
Все статьи: 418
A note on migration perturbation and convergence rates to a steady state
Статья научная
Using tools developed in the Markov chains literature, we study convergence times in the Leslie population model in the short and middle run. Assuming that the population is in a steady state and reproduces itself period after period, we address the following question: how long will it take to get back to the steady state if the population distribution vector was affected by some shock as, for instance, the “brain drain”? We provide lower and upper bounds for the time required to reach a given distance from the steady state.
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A picture of common subsequence length for two random strings over an alphabet of 4 symbols
Статья научная
The maximal length of longest common subsequence (LCS) for a couple of random finite sequences over an alphabet of 4 characters was considered as a random function of the sequences lengths and 𝑛; Exact probability distributions tables are presented for all couples of length in a range 2
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An FPGA packet communication protocol
Статья научная
When creating computer boards with FPGA or application-specific chips, it is often needed to connect several chips. Existing available buses do not have all the properties required by the authors' task at hand: packet transmission, using a small number of GPIO pins, sufficient bandwidth.We describe a packet communication protocol that uses GPIO pins and has bandwidth up to 10 MB/s at a frequency of 20 MHz.
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Analytical design of controllers for discrete-continuous systems with linear control
Статья научная
The study focuses on a certain kind of discrete-continuous systems (DCS): the linear hybrid DCS with state-dependent coefficients. The authors proposed a problem similar to the analytical design of optimal controllers (ADOC). For this study, we generalized the Krotov sufficient optimality conditions. The paper includes several examples.
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Approximate optimal control synthesis for nonuniform discrete systems with linear-quadratic state
Статья научная
Nonuniform discrete systems linear-quadratic over its state are the subject of intense study in optimal control theory. This work presents an approximate optimal control synthesis method in this class based on Krotov’s sufficient optimality conditions and illustrates it with a simple example.
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Статья научная
This paper is devoted to the study of interrelated thermal processes in a submersible electric motor of a pumping unit located in an oil-producing well and flowed around by a water-oil-gas reservoir mixture, taking into account the heat exchange of the flow with the rocks surrounding the well. To describe these processes, mathematical and numerical models are developed. The numerical model and algorithms are implemented in a software that allows to study temperature fields and various thermal effects using computational experiments with simultaneous visualization of the results of computations. It is shown, in particular, that the transient thermal processes in the system “motor - three-phase flow - rocks”, when the motor is turned off due to its heating to the maximum permissible temperature depend on the physical and geometrical characteristics of each element of the system and are characterized by a non-trivial temperature profiles in rocks. Calculated estimates of the duration (on the order of tens of minutes) of the cooling stage of the motor after it is turned off and its heating stage when it is turned on again correspond to the real times of these processes in producing oil wells.
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Clustering of handwritten digits by Kohonen neural network
Статья научная
Clustering of handwritten digits is carried out for sixty thousand images contained in the training sample of the MNIST database. For clustering, the Kohonen neural network is used. For each handwritten digit, the optimal number of clusters (no more than 50) is determined. When determining the distance between objects (images of handwritten digits), the Euclidean norm is used. Checking the correctness of building clusters is carried out using data from the test sample of the MNIST database. The test sample contains ten thousand images. It is concluded that the images from the test sample belong to the "correct digit" cluster with a probability of more than 90{\%}. For each digit, an F-measure is calculated to evaluate the clusters. The best F-measures are obtained for digits 0 and 1 (F-mean is 0.974). The worst values are obtained for the number 9 (F-mean is 0.903). A cluster analysis is also carried out, which allows drawing conclusions about possible errors in recognition by the Kohonen neural network. Intersections of clusters for images of handwritten digits are constructed. Examples of intersections of clusters are given, as well as examples of images that are incorrectly recognized by the neural network.
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Desktop Grid корпоративного уровня
Статья научная
В работе рассказывается о системах Desktop Grid корпоративного уровня, их возможностях, отличительных особенностях и приложениях. Даны примеры реализации систем промежуточного программного обеспечения, предназначенных для организации корпоративных Desktop Grid.
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Detecting states of ion channels on the cell membrane using neural networks
Статья научная
The problem of automating the process of analyzing the open states of channels on the membrane of a neuron of a living organism is considered. Taking into account that the registration of the electrical activity of the cell was made by the patch clamp method at various values of the applied potential, a division into intervals with a constant potential is carried out. Further, to eliminate noise, a notch filter, low-frequency and high-frequency Chebyshev filters are applied to the data. A neural network is applied to the normalized data, based on the results of which the data is changed and re-processed by the same neural network. As a result of the algorithm, the dynamics of channel states was obtained, which makes it possible to register up to several open channels simultaneously.
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Etherbox: протокол для управления модульной сенсорной сетью
Ред. заметка
Протокол прикладного уровня Etherbox предназначен для взаимодействия управляющего компьютера с узлами сенсорной сети в форме исполняемых программ виртуальной машины, что позволяет обеспечить гибкость в управлении, необходимую для сенсорных сетях с модульной конструкцией узлов. В статье описаны принципы функционирования сенсорной сети, использующей протокол Etherbox, в сравнении с сетями, использующими протоколы MQTT-SN и CoAP. Рассматривается архитектура программного обеспечения снесорных узлов и управляющего компьютера.
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Existence of global fundamental solution to a class of Fokker-Planck equations
Ред. заметка
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Статья научная
A hybrid method of global optimization NNAICM-PSO is presented. It uses neural network approximation of inverse mappings of objective function values to coordinates combined with particle swarm optimization to find the global minimum of a continuous objective function of multiple variables with bound constraints. The objective function is viewed as a black box.The method employs groups of moving probe points attracted by goals like in particle swarm optimization. One of the possible goals is determined via mapping of decreased objective function values to coordinates by modified Dual Generalized Regression Neural Networks constructed from probe points.The parameters of the search are controlled by an evolutionary algorithm. The algorithm forms a population of evolving rules each containing a tuple of parameter values. There are two measures of fitness: short-term (charm) and long-term (merit). Charm is used to select rules for reproduction and application. Merit determines survival of an individual. This two-fold system preserves potentially useful individuals from extinction due to short-term situation changes.Test problems of 100 variables were solved. The results indicate that evolutionary control is better than random variation of parameters for NNAICM-PSO. With some problems, when rule bases are reused, error progressively decreases in subsequent runs, which means that the method adapts to the problem.
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Local competing in interpolation problems
Статья научная
A simple example illustrates the insufficiency of the known approaches to interpolation in the problem of recovering a function from a few given specific values that clearly convey the form. A local choice between polynomial and rational local interpolants, which minimizes the local interpolant's errors at the nearest external nodes from one or different sides, complements the known approaches. It combines the extreme computational simplicity of local interpolants with the thorought selection of them. The principles of constructing the algorithm are formulated in general terms for mappings of metric spaces. They provide accurate (with rare exceptions) reconstruction of mappings that locally coincide with some of the given possible interpolants. In the one-dimensional case, the two-stage algorithm guarantees the continuity of the interpolant and accurately reconstructs {[itemindent=1cm] polynomials of small degree, simple rational functions with a linear denominator, broken lines of long links with knots at the ends } when these requirements do not contradict each other. An additional parameter allows you to replace the exact restoration of polylines with the required smoothness of interpolation.
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Memory-efficient sensor data compression
Статья научная
We treat scalar data compression in sensor network nodes in streaming mode (compressing data points as they arrive, no pre-compression buffering). Several experimental algorithms based on linear predictive coding (LPC) combined with run length encoding (RLE) are considered. In entropy coding stage we evaluated (a) variable-length coding with dynamic prefixes generated with MTF-transform, (b) adaptive width binary coding, and (c) adaptive Golomb-Rice coding. We provide a comparison of known and experimental compression algorithms on 75 sensor data sources. Compression ratios achieved in the tests are about 1.5/4/1000000 (min/med/max), with compression context size about 10 bytes.
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Methods for anchoring boundary nodes when smoothing a triangular surface mesh
Статья научная
In numerical modeling tasks that use surface meshes, remeshing is often required. However, while remeshing, distortion can occur. The accumulation of distortions can lead to the collapse of the solution. Smoothing algorithms are used to maintain the quality of the mesh during the calculation. When performing smoothing using methods that shift the mesh nodes, the border nodes are usually fixed to avoid distortion. However, simply fixing the nodes can lead to more severe distortion. This paper presents methods for working with boundary nodes to control such nodes during the smoothing process. Algorithms for working with pseudo-3D surface meshes, which are of particular interest, are also considered
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Статья научная
Using the integral-equation-based in-house guaranteed-convergence numerical code, we study the effect of a circular air hole on the frequency, threshold gain and directionality of emission of the whispering-gallery modes of a two-dimensional model of circular-disk microcavity laser. It is shown that a small hole can enhance the directionality greatly and leave the threshold gain intact, if the disk`s refractive index is large enough and the hole`s location is chosen properly. This location should be close to the area, in which the same uniform disk, if illuminated with a plane wave, would display a broadband focusing in the form of a hot spot called a photonic jet.
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Modern server ARM processors for supercomputers: A64FX and others. Initial data of benchmarks
Статья обзорная
A comparative analysis of~the performance of~ARM server processors used on~supercomputers or also aimed at~high-performance computing (HPC) is given. Fujitsu A64FX, Marvell ThunderX2 and Huawei Kunpeng 920 were selected for the initial performance analysis. The HPC performance review focuses primarily on~benchmarks and applications for the A64FX, which supports longer vectors than other ARM processors and has higher peak performance. The performance of~the A64FX is compared against corresponding data for Intel Xeon Skylake and Cascade Lake, and AMD EPYC with Zen 2 and 3 (Roma and Milan), as well as Nvidia V100 and A100 GPUs. A~short set of~potential pros and cons of~the A64FX microarchitecture has been formulated. Comparison of~performance data obtained using different compilers for A64FX. Features have been formed when A64FX usually gives advantages in~performance over x86-64, and when it concedes to x86-64. It is clear that the use of~A64FX in~supercomputers can grow further. There is an assumption that x86-64 hegemony in~HPC will decrease, in~particular, due to the increased use of~server ARM processors. But the analysis of~A64FX and new AArch64 processors expected in~the near future showed that A64FX will not necessarily lead in~this process.
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Статья научная
This article is devoted to applying mathematical models in the differential diagnosis of venous diseases based on microwave radiometry data. A modified approach for transforming feature space in thermometric data is described. After constructing features, a multiclass classification problem is solved in several ways: by reducing to binary classification problems using “one versus rest” and “one versus one” methods and building a multivariate logistic regression model. The best classification model achieved an average balanced accuracy score of 0.574. A key feature of the approach is that classification result can be explained and justified in terms understandable to a diagnostician. This article presents the most significant patterns in thermometric data and the accuracy with which they can identify different classes of diseases.
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