Abstract-The article deals with the issues of the security of distributed and scalable computer systems based on the risk-based approach. The main existing methods for predicting the consequences of the dangerous actions of the intrusion agents are described. There is shown a generalized structural scheme of job manager in the context of a risk-based approach. Suggested analytical assessments for the security risk level in the distributed computer systems allow performing the critical t ime values forecast for the situation analysis and decisionmaking for the current configuration o f a distributed computer system. These assessments are based on the number of used nodes and data links channels, the number of act ive security and monitoring mechanisms at the current period, as well as on the intensity of the security threats realization and on the activation intensity of the intrusion prevention mechanis ms. The proposed comprehensive analytical risks assessments allow analyzing the dynamics of intrusions processes, the dynamics of the security level recovery and the corresponding dynamics of the risks level in the distributed computer system. Index Terms-Distributed computer systems, Security analysis, Risk-based approach. NOMENCLATURE α -the average intensity of the security threats for the distributed computer systems resources x1 and x2; β -the average intensity of the security mechanis ms from the group x3 and x4 activation; R 0 -the initial security risk; R(t) -security risks in the distributed computer systems, changing at time t;x 1 -the number of nodes in the distributed computer system;x 2 -the number of data link channels;x 3 -the number of the active security mechanisms; x 4 -the number of the security monitoring tools in the distributed computer systems;x 1max -the maximu m nodes number in a distributed computer system; x 2max -the maximu m number of data link channels; x 3max -the maximu m nu mber of the active security mechanisms;x 4max -the maximu m nu mber o f the security monitoring tools in the distributed computer systems.

In this paper, we present the development of a decentralized mechanism for the resources control in a distributed computer system based on a network-centric approach. Intially, the network-centric approach was proposed for the military purposes, and now its principles are successfully introduced in the other applications of the complex systems control. Due to the features of control systems based on the network-centric approach, namely adding the horizontal links between components of the same level, adding the general knowledge control in the system, etc., there are new properties and characteristics. The concept of implementing of resource control module for a distributed computer system based on a network-centric approach is proposed in this study. We, basing on this concept, realized the resource control module and perform the analysis of its operation parameters in compare with resource control modules implemented on the hierarchical approach and on the decentralized approach with the creation of the communities of the computing resources. The experiments showed the advantages of the proposed mechanism for resources control in compare with the control mechanisms based on the hierarchical and decentralized approaches.One of the main components of resource control system (RCS) of DCS is a scheduler which coordinates the solution of the tasks that arrive for processing to the distributed system by placing them on available computing resources [7]. It is important to meet the requirements of the user and to avoid the idles for the computational resources [8]. In [7] there are identified the following key characteristics of the DCS scheduler: the run time of the task, DCS performance and the response time of the system.In recent years, there was devoted much attention to the study of decentralized resource control techniques for the distributed computer systems to improve the performance of the DCS in the context of its scalability and reliability [9]. In [9] are described the comparative analysis of the existing decentralized distributed computer systems and the mechanisms that are used for resource control. This study contains a comparative analysis of mechanisms of resource control of DCS in different contexts.Additionally, [10,11,12] presents more recent developments of DCS resources control systems, that are implemented on a decentralized basis.The development in [11] uses the exchanges of network messages between DCS compute nodes for the organization of distributed computing. The messages of several types come, each of which provides a specific functions of the algorithm for the resources allocation. This planning framework supports several heuristic algorithms and it also provides the load balancing for the DCS nodes.In [12] there is considered the DCS, which consists of heterogeneous computing elements (CE), which are interconnected by a computer network. In addition to CE, the system has passive nodes, the so-called "Bulletin boards", which are used to allocate users tasks and to collect some service in...

A three-layer plate with thick hard outer layers and a thin soft inner layer was studied. A model is considered on the example of an anti-sandwich panel to describe the mechanical behavior of a plate on the example of a solar panel. A review of the scientific literature was conducted, in which models of both analytical and numerical methods for calculating three-layer plates are displayed. The scientific work uses the method of finite element analysis using a spatial shell element, as well as the theory of single- and multi-layer plates. These elements combine the topology of volumetric elements and the kinematic and structural equations of a classical shell element. Shell elements based on continuum mechanics were used for numerical simulation. The study was carried out under static load under different conditions, and also the self-oscillations of the anti-sandwich were analyzed using the theories of Kirchhoff and Reisner-Mindlin. As part of the scientific work, a study of the mechanical model of a thin solar panel was carried out using finite element analysis taking into account different temperature conditions and comparing the results with existing studies

The paper presents the procedure for calculating and predicting the state of critical structural elements in low-cycle fatigue with allowance for features of the operating conditions. The procedure is based on the nonlocalized damage concept and the allowance for the damage parameter in the system of constitutive equations using fast-rotating parts of laboratory centrifuges as an example. A macro-and microstructural analysis of the material is made, and the static and cyclic tests of the specimens of V95 (7075) aluminum alloy are carried out. The results of the experimental investigations are compared with the theoretical calculations performed based on the finite element method (the ANSYS software package).Introduction. Fast-rotating, multipurpose structural elements have to meet a number of requirements, the main of which are: to ensure the required life and reliability of their operation with a guarantee of trouble-free and safe operation. These requirements should be justified by a high degree of reliability. For this reason, for the purpose of safety, a protective housing is additionally used.High-speed centrifuges with speeds of rotation of up to 15,000 rpm serve for separation of mixtures of different density and often are developed as general-purpose devices. They include different fast-rotating elements, such as rotors, having extensive use. For example, large rotors with the mass of up to 20 kg are used in blood separators.To ensure a safe operation of this kind of structures, the centrifuge protective housing with sufficiently high margin of safety and weight indices is mounted. A reduction in the weight of centrifuges of this type is possible at the expense of the increase in the components of strength of their operational reliability.The centrifuge rotor is a spider with cups. The practice of operation shows that failure of cups occurs in the region of their trunnion mounting and by way of tearing off the bottom. This is supported by the specially performed experimental investigations wherein the loading was accomplished by applying a force to the bottom. To find out the causes of fracture, the analysis of the structure was carried out using microsection techniques, whereas the analysis of the stress-strain state (SSS) was performed using the finite-element method. These investigations testify that the highest stresses are observed at the points of attaching the cups, whereas the separation of the bottom is assisted by a specific structure of a manufacturing origin.Modern experimental and theoretical methods for predicting the life of structures are mainly based on two concepts: a safe operation without macrodefects and a restricted failure model [1][2][3].At present, high-performance diagnostics tools make it possible to bring into service critical structural elements without macrodefects, particularly in those branches of the engineering industry where failure results in serious catastrophic consequences. On this basis, the concept of their safe operation has solid justification, and the

Over the past two decades, upper limb exoskeletons used for service delivery and rehabilitation have attracted attention from the biomedical and engineering sectors. Technology is becoming one of the key solutions for physically weak or disabled people. Mechanical devices were developed to improve the performance and strength of the user. Devices that help the patient during postoperative or post-traumatic rehabilitation after joint damage of various types are orthoses. There are different types of orthoses, such as mechanical, active with EMG functions, exoskeletons, and others. In this work, an overview of various types of orthoses is given, problems of fixing orthoses elements are considered. In the review of the literature related to these studies, the advantages and disadvantages of bolted connections are given. Two contact problems of the orthosis were also considered and the stress-strain state of the bolted joint of the structural elements of the elbow orthosis prototype under study was determined using the FEMAP with NASTRAN software package. Based on the necessary operating conditions, a prototype model of the orthosis was presented.