Element Scheme Research Articles

Effects of Orientations, Roughnesses, and Cavities on Stress-Corrosion Coupled Damage in Magnesium

Orientations, roughnesses, and cavities of crystals are typical factors influencing the servicing reliability of metals in corrosive environments. A phase-field scheme for modeling stress-corrosion coupled damage (SCCD) is developed. The effects of the crystal factors on SCCD are numerically simulated using the incremental-iterative scheme of the user-defined finite elements. The impacts of orientations, roughnesses, and cavities on the corrosion rate of magnesium (Mg) in corrosive environments are discussed quantitatively. It is found that crystal textures and surface roughnesses can significantly influence the diffusion-controlled corrosion rate. Strong basal texture and a smooth surface of the crystal can significantly enhance the corrosion resistance of Mg. The cavity, as a typical crystal defect, is capable of inducing the damage path and modulating the corrosion rate. The design of crystal-scale features, such as orientations, roughnesses, and cavities, is promising for the enhancement of the resistance to SCCD.

A fifth order WENO scheme for numerical simulation of shallow granular two-phase flow model

In this article, a weighted essentially non-oscillatory (WENO) scheme is implemented to simulate two-phase shallow granular flow (TPSF) model. The flow is assumed to be incompressible and it is regarded as shallow layer of granular and liquid material. The mathematical model consists of two phases, that is, solid and liquid. Each phase has its continuity and momentum equation. The presence of the equations are coupled together involving the derivatives of unknowns which make it more challenging to solve. An efficient numerical technique is needed to tackle the numerical complexities. Our main intrigue is the numerical approximation of the above-mentioned solid-liquid model. The weighted essentially non-oscillatory (WENO) scheme of order 5 is utilized to handle the shock waves and contact discontinuities appear in the solution. The results are compared with the results already available in the literature by conservation element and solution element (CESE) scheme. It is observed the WENO scheme produces less errors as compared to CESE scheme and also effectively handle the shocks.

An analytical method for solving the problem of heat network load flow

The author aimed to develop an analytical solution to the problem of the load flow of a six-, eleven- and twelve-circuit heat network, as well as to solve the problem of optimisation of a multi-circuit heat network, including the choice of the objective function and the determination of a number of variable technical parameters. For accelerating the optimisation process, the method of decomposition of the heat network graph was used. Decomposition involves is cutting the network graph at some nodes for the transition of a multi-circuit scheme to a branched scheme in the form of a tree. Optimisation of each branched circuit was carried out by the dynamic programming method, as a result of which new values of the variable parameters were obtained at the current iteration. Next, the author returned to the multi-circuit scheme to solve the load flow problem and calculate the value of the objective function. The iterative convergence of the decomposition method was not mathematically proven. The author proposed a method for splitting the graph, which eliminates the decomposition procedure when optimising a heat network. The following methods were applied: mathematical modelling of the hydraulic circuit, graph splitting method and the analytical method for solving the algebraic equation of the fourth degree. The following results were achieved: a scheme of the minimum element of a multi-circuit heat network was determined, the possibility of series and parallel circuits of minimum elements was shown, and analytical dependencies for the problem of load flow of a heat network of these schemes were obtained. The proposed analytical solution of the load flow problem for a multi-circuit heat network allows the problem of calculating a complex network to be reduced to the calculation of several minimum elements, which significantly reduces the amount of computational work when modelling a hydraulic circuit. The provided examples show that the calculation error does not exceed 3%.

Dynamic data reshaping for 3D mesh animation compression

Effective compression of 3D mesh animation data has been increasingly used in a variety of multimedia systems including virtual reality, gaming, remote transmission, display and storage. In this work, we propose a spectral clustering-based dynamic reshaping model that is performed on spatio-temporal segments to enhance the compression of 3D mesh sequences. After the lossy compression of spatio-temporal segments through Principal Component Analysis (PCA), we first compute a spectral clustering of all the PCA elements. Then, we introduce three novel reshaping schemes (namely, Row-wise matrix scheme, Arch-wise matrix scheme, and Curl-wise matrix scheme) of the PCA elements within each cluster. Through extensive experiments and comparisons, we show our model can substantially improve the compression performances on various 3D mesh sequences.

ORGANIZATIONAL MECHANISMS OF EFFICIENT LOGISTICS FORMATION VEGETABLE MARKET OF UKRAINE

Topicality. The vegetable market is one of the strategic markets of Ukraine, which ensures national food security. Fundamentally important tasks for its reproductive development are to ensure access of individual producers, who grow 87% of vegetable products, to the profitable link of distribution and sale of products by introducing organizational mechanisms for the formation of efficient market logistics. Aim and tasks. The purpose of this article is to improve the organizational mechanisms for the formation of efficient logistics of the vegetable market of Ukraine. Research results. During the study, the main indicators and parameters of the vegetable market of Ukraine were analyzed. The main directions and drivers of development of the vegetable market are established, problems of the given market and ways of the decision are defined. The article analyzes the content analysis of the category �vegetable market� on the basis of management-coordination, reproduction, object-subject, elemental and structural approaches; the scheme of elements and tools that ensure the functioning of the vegetable market according to the structural-institutional approach is built. The territorial boundaries of the vegetable market are studied, the author 's model of the quality infrastructure of the vegetable market of Ukraine is given. The comparative characteristics of parameters and types of products of the vegetable market of Ukraine and their influence on the logistical support of the market are given, the model of formation of logistic expenses under the influence of factors of internal and external environment is formed. The prospects of development of the vegetable market of Ukraine in the context of implementation of the European experience are outlined, the comparative characteristic of organizational mechanisms of development of logistics of the vegetable market of Ukraine is carried out, namely: wholesale trade, cooperation, interaction of individual producers with processing enterprises. Conclusion. The logistic chains of formation of commodity batches of vegetable products are offered and constructed, namely: perspective logistic chain on the basis of reproductive function ����, completed cooperative logistic chain of vegetable market, logistic chain of contractual relations between production cooperative and processing enterprises. large consignments of vegetable products and providing the population with vegetable products. The formed scheme of the vegetable market of Ukraine on the basis of interaction of individual producers with the processing enterprises will allow to keep perishable products of the given market at the expense of their processing and preservation. And the constructed scheme of organizational mechanisms of production and distribution of vegetable market products on the basis of "export-oriented approach" will allow to carry out market exchange through integration into European and world markets.

Models and forms of public and private partnership in modern conditions

In economics many attempts are made to reveal the essence of such concepts as the model and form of public and private partnership. In addition, in modern practice, in the process of searching for the most optimal variant of interaction between the state and private structures, there is a wide variety of forms, types and models of public private partnership. Throughout the entire period of transformation of the economy of Kazakhstan, many of them were underestimated, despite the fact that they cover the basic aspects of society and ensure their harmonious development. For quite a long time, the state cannot fully implement many major infrastructure projects. Various forms and models of partnership between the state and private entities could help to solve these problems. Moreover, in the context of innovative development, this type of interaction between government and business will receive a new impetus in the development and application of new forms of public private partnership that meet modern realities. It should be noted that the conditions of contractual relations in our country are usually extremely complex and unstable. All this requires the creation of a contractual procedure that would include the entire general scheme of the main elements of such contracts, taking into account their features.

Stabilization for Equal-order Polygonal Finite Element in Incompressible Fluid Flow Computation

This paper presents an adapted stabilisation method for the equal-order mixed scheme of finite elements on convex polygonal meshes to analyse the high velocity and pressure gradient of incompressible fluid flows that are governed by Stokes equations system. This technique is constructed by a local pressure projection which is extremely simple, yet effective, to eliminate the poor or even non-convergence as well as the instability of equal-order mixed polygonal technique. In this research, some numerical examples of incompressible Stokes fluid flow that is coded and programmed by MATLAB will be presented to examine the effectiveness of the proposed stabilised method.

ФОРМАЛЬНІ ОПИСИ СКЛАДНИХ ДИНАМІЧНИХ СИСТЕМ І СПЕЦИФІКАЦІЇ СИМУЛЯТОРІВ, ПОБУДОВАНИХ ЗАСОБАМИ МОВ МОДЕЛЮВАННЯ

The concept of developing parallel modeling languages (PML) of complex dynamic systems (CDS) based on the analogy between the principles of operation of serial languages (SL) and MIMD parallelism provides for the purpose of "Functional element of the SL block diagram - MIMD process", which transforms the SL specifications of serial simulators (block diagrams) in the structure of virtual parallel simulators. Virtuality is due to the atypical for MIMD-systems "fine granulation" of the processes generated by this purpose and the connections between the processes, which must be appropriate to the connection schemes of the functional elements of SL simulators. The architecturally relevant implementation of a parallel simulator of any CDS is related to the form of its mathematical description and the corresponding Simulation model. CDS with concentrated parameters are described by systems of ordinary differential equations (ODE) of the first order, systems of equations of different orders, systems of differential-algebraic equations (DAE-Problem), and in network CDS there are sums of derivatives from different variables. CDS with distributed parameters are described by systems of differential equations in partial derivatives, so the development of Simulation-models is associated with the approximation of equations by spatial coordinates and the formation of ODE systems. For these forms of description Simulation-models and corresponding SL-specifications in the form of block diagrams of SL-elements are considered, which is the basis for construction of virtual MIMD-simulators of two possible levels of granulation of processes: the basic level " SL-element - process" provides MIMD-processes "Shallow granulation", in which there is uneven loading of processes and an unfavorable relationship between the volume of computational operations and data exchange operations between processes; The level "Group of SL-elements - process" corresponds to the stage of simulator development, in which the specifications use the composition of SL-elements according to a certain principle, for example, "One equation Simulation model - Group of SLelements to solve the equation - Coarse granulation process"

Depth of Schemes Embedded in a Unit Cube and Implementing Typical Boolean Functions

A class of schemes of functional elements in the standard basis of conjunction, disjunction, and negation elements is considered. For each scheme Σ from this class, in addition to depth D(Σ), its dimension R(Σ) is determined and found to be equal to the minimum dimension of the unit (Boolean) cube that allows isomorphic embedding Σ. In addition to results obtained earlier, it is proved that within the considered model inequality $$D({\Sigma _f}) \ge n + \frac{n}{{{{\log }_2}n}} - O(\frac{n}{{{{({{\log }_2}n)}^2}}})$$ is satisfied for typical function f of n variables and for any scheme of functional elements Σf implementing it, such that R(Σf) = O(n), n = 1,2,.... New and more accurate lower estimates of the depth of the schemes implementing the typical functions and having linear dimensions are thus obtained.

Проект будівництва етнопарку в селі Червонокозацьке Запорізької області

Зелений туризм – нове спрямування у світовому та вітчизняному туризмі. В Україні, зокрема і в Запорізькому регіоні, є величезний потенціал для розвитку зеленого туризму. Тому в с. Червонокозацьке, у 52 км від Запоріжжя, планують створити "Парк історичних та етнографічних періодів". Ініціатором цього проекту є Інеса Носенко, голова запорізького центру "Мазал-тов", яка запросила викладачів та студентів Хортицької національної навчально-реабілітаційної академії взяти участь у проектуванні оформлення ділянок-садів у стилях, властивих різноманітним етносам. Розроблений проект "Парку історичних та етнографічних періодів" за умови реалізації дасть змогу створити колоритний, цікавий ландшафтний об'єкт, який буде комфортним місцем відпочинку для місцевих, міських мешканців, туристів зі всієї України та з-за кордону. Водночас він стане ландшафтним музеєм просто неба. Відвідування садів-ділянок, оформлених у різноманітних стилях сучасної ландшафтної архітектури, дасть змогу доторкнутися до культури різних народів та епох. "Античний сад" – один із таких цікавих, загадкових і привабливих куточків, який занурить відвідувачів у атмосферу давньої Греції, познайомить з архітектурою і рослинністю сонячного Пелопонесу. Майбутній Парк має привернути увагу вітчизняних та зарубіжних туристів, інвесторів, меценатів, що сприятиме економічному розвитку регіону, забезпечить нові робочі місця для місцевих мешканців і покращить естетичний та санітарно-екологічний стан території проектування.

Pore pressure cohesive zone modelling of complex hydraulic fracture propagation in a permeable medium

A pore pressure cohesive zone method (PCZM) is proposed to simulate the complex hydraulic fracturing process in a permeable poroelastic medium. A shared node scheme of the cohesive elements is developed to consider the arbitrary fracture propagation and fluid flow at the intersection. The fracture propagation is based on a bilinear cohesive law, while the tangential flow within the fracture is controlled by the lubrication equation. The fluid leak-off within the cohesive element is calculated according to the distribution of pressure. Three models are given to verify the capability of the PCZM in simulating the complex fracturing process. The effects of the approaching angle, cementing strength, in situ stress and natural fracture on the fracture geometry are investigated. These studies indicate that the proposed PCZM can accurately predict complex hydraulic fractures (HFs) and provide a useful way to study HF mechanisms.

Development of a 10-kV regional compensation dynamic voltage restorer with multiple functions

ABSTRACTThe first 10-kV regional compensation dynamic voltage restorer (DVR) has been installed in a 110-kV substation in Shenzhen power grid, to protect plenty of sensitive loads in a wide area simultaneously from the disturbances caused by voltage sags. The location selection and performance indicators of the DVR are determined based on the voltage sag statistic results in recent years of Shenzhen power grid. The implementation schemes of main circuit elements, such as the energy storage unit, inverter and LC filter are presented. To further improve the DVR’s cost-effectiveness, a novel virtual impedance control strategy is proposed to provide the DVR with a function of a Fault Current Limiter (FCL) or a Series Compensator (SC) besides the function of voltage sag compensation. Simulation and field experimental results are provided to show the correctness and effectiveness of the main circuit design and control system development of the 10-kV DVR.

Development of municipal-private partnership in the system of municipal crediting of Ukraine

The object of research is the processes of formation and development of municipal-private partnership (MPP) in the system of communal lending in Ukraine. One of the most problematic places of the object of study is the lack of a unified definition of MPP in the scientific economic literature and current legislation. In the course of the study, general scientific and special methods are used, namely: abstract-logical to generalize the theoretical foundations of the emergence and development of MPP; analysis, synthesis, logical generalization to substantiate the prerequisites for development, the subject-objective characteristics of MPP, the means of increasing the effectiveness of such a partnership. Systematization of the conceptual and categorical apparatus with respect to the definition of the MPP essence allows to conclude that there is no single definition in the scientific literature. The author has provided his own MPP interpretation as a tool to ensure the development of long-term mutually beneficial cooperation of local governments with business structures and the public. With the help of MPP, a policy of regional and municipal socio-economic development is being implemented, and infrastructure and other projects that are socially important for the development of territorial units are co-financed.A systematic analysis of the problems of the development of small private entrepreneurship in Ukraine allowed to justify the direction of their elimination. The obtained results allow to determine the specific features of the MPP and its distinctive features from the state-private partnership (SPP). It is established that attracting private investors requires the development of an appropriate regulatory framework, restoring confidence in the instruments of local loans and the activities of local governments. To do this, it is necessary to ensure the openness and transparency of the MPP implementation projects by creating online platforms through which private investors can receive the necessary information. The construction of the scheme of the constituent elements of the MPP functioning allows to establish the subject-object composition, to determine the prerequisites for the development of such a partnership and its effectiveness. Thanks to this, it is possible to obtain a budgetary, social, environmental effect at the level of administrative-territorial units and the development of a system of communal lending in Ukraine.

Метод розрахунку динаміки процесу конверсії природного газу

We have proposed a new scheme of reaction element for the realization of the process of natural gas reforming. We have developed a mathematical model of its dynamics, where the dense bed of catalyst granules with the reacting gas mixture in its cavities is considered as a quasihomogeneous substance with certain effective physical characteristics. An iteration algorithm for the solution of equations of our model and two programs for its realization have been developed. We also present an example of calculating the change in the flow rates of components of the reacting gas mixture and calorific value of the reformed fuel along the apparatus length.

Convergence Analysis for Mixed Finite Element Method of Positive Semi-definite Problems

A mixed element-characteristic finite element method is put forward to approximate three-dimensional incompressible miscible positive semi-definite displacement problems in porous media. The mathematical model is formulated by a nonlinear partial differential system. The flow equation is approximated by a mixed element scheme, and the pressure and Darcy velocity are computed at the same time. The concentration equation is treated by the method of characteristic finite element, where the convection term is discretized along the characteristics and the diffusion term is computed by the scheme of finite element. The method of characteristics can confirm strong computation stability at the sharp fronts and avoid numerical dispersion and nonphysical oscillation. Furthermore, a large step is adopted while small time truncation error and high order accuracy are obtained. It is an important feature in numerical simulation of seepage mechanics that the mixed volume element can compute the pressure and Darcy velocity simultaneously and the accuracy of Darcy velocity is improved one order. Using the form of variation, energy method, $L^2$ projection and the technique of priori estimates of differential equations, we show convergence analysis for positive semi-definite problems. Then a powerfu tool is given to solve international famous problems.

A space–time CESE scheme for shallow water magnetohydrodynamics equations with variable bottom topography

The dynamics of thin layer incompressible and electrically conducting fluids is described by shallow water magnetohydrodynamics equations (SWMHD), for which the evolution is nearly two dimensional and the magnetic equilibrium lies in the third direction. In this article, a space–time conservation element and solution element (CESE) scheme is extended for numerical investigation of one- and two-dimension shallow water magnetohydrodynamics (SWMHD) with variable bottom topography. The presence of non-conservative terms and the inclusion of variable bottom topography on the right hand side of SWMHD equations poses some major challenges for any numerical scheme. The proposed CESE scheme differs from the previous techniques because of global and local flux conservation in a space–time domain without restoring to interpolation and extrapolation. To check the validity of the scheme, a number of test problems are considered. The results are also compared with the already existing results in the literature by central-upwind scheme.

An innovative H ∞ –norm based worst case scenario approach for dynamic compliance optimization with applications to viscoelastic beams

A novel frequency---based definition of dynamic compliance is introduced within the framework of Hź---norm based structural dynamics in the presence of load uncertainties. The system itself is supposed to depend on a vector of design parameters with respect to which an optimal design is pursued. A three-step worst-case-scenario is then developed that finds the minimum-compliance structure capable of accounting for the entire norm---bounded load sets. Once the problem is initialized, the current worst load is found that is used as input to the minimization of the structural compliance and the procedure is repeated until convergence. Numerical examples are eventually proposed that deal with viscoelastic beams discretized via a truly---mixed finite---element scheme.

DETERMINATION OF ENERGY LOSSES BY SHOCK ABSORBER IN A FREIGHT CAR AT CRASH MODE

Purpose. The purpose of this work is to determine the energy losses in the shock absorber of the freight car whose wheel-set moves in the derailed state on the track panel depending on the axle load and structural parameters of spring suspension. Methodology. On the basis of spring suspension construction analysis and operating principle of the friction shock absorber of the freight car bogie the authors provide the method for determining the energy absorbed by it. The calculations take the maximum values of the absorber elements displacement and the regulatory values of spring suspension parameters. Findings. The authors obtained the calculated formula for determining the energy absorbed by shock absorber for regulation-set mounting schemes of elastic bogie elements depending on the axial load. The mentioned curves are parabolic. Originality. The work examines the crash mode of the wheel-set movement on the track panels after its derailment. It is shown that the energy dissipation in the shock absorbers is the reason for increase in resistance to rolling stock movement. The formulas for calculating the amount of energy dissipated in the shock absorber with a maximum displacement of its elements are derived. This energy depends on the axle load and structural parameters of spring suspension. Practical value. The proposed method allows setting the value of the additional resistance to motion that occurs in crash mode which makes it possible to increase the accuracy of traction calculations.

Taut String Model: Getting the Right Energy versus Getting the Energy the Right Way

The initial boundary value problem of the transverse vibration of a taut string is a classic that can be found in many vibration and acoustics textbooks. It is often used as the basis for derivations of elementary numerical models, for instance finite element or finite difference schemes. The model of axial vibration of a prismatic elastic bar also serves in this capacity, often times side-by-side with the first model. The stored (potential) energy for these two models is derived in the literature in two distinct ways. We find the potential energy in the taut string model to be derived from a second-order expression of the change of the length of the string. This is very different in nature from the corresponding expression for the elastic bar, which is predictably based on the work of the internal forces. The two models are mathematically equivalent in that the equations of one can be obtained from the equations of the other by substitution of symbols such as the primary variable, the resisting force and the coefficient of the stiffness. The solutions also have equivalent meanings, such as propagation of waves and standing waves of free vibration. Consequently, the analogy between the two models can and should be exploited, which the present paper successfully undertakes. The potential energy of deformation of the string was attributed to the seminal work of Morse and Feshbach of 1953. This book was also the source of a misunderstanding as to the correct expression for the density of the energy of deformation. The present paper strives to settle this question.

FEATURES OF THE RESEARCH WORK ELEMENTS DEFORMABILITY OF RAILWAY TRACK

Purpose. The scientific paper is supposed the determination of basic physical and structural conditions in modeling life cycle of the elements of the railway line for the study of deformation processes as the basis of normative base of the track at the condition of railway safety. Methodology. To achieve the aim principles of the elasticity theory and wave propagation process in the description of the interaction between the track and rolling stock were used. Findings. The basic physical and structural conditions under which it is necessary to carry out the simulation of the life cycle of the elements of the railway line for the study of deformation processes were determined. The basic physical and structural principles of drawing the design schemes of railway track elements for the process assessment of the track deformation work were formulated. The decision correctness and the possibility of the problem solution are proved. Originality. The study of the track reliability questions motivates the development of new models, allow considering it for some developments. There is a need to identify the main physical and structural conditions for assembly design schemes based on assessment and prediction of possible track state changes during its operation. The paper presents the basic principles of physical and structural drafting design schemes of railway line items for which Huygens’ principle is implemented. This principle can be performed only when the four dimensional space: the volume changing over time is considered. Practical value. Analytical models applied in determining the parameters of strength and resistance lines, fully satisfy the task, but can not be used to determine the parameters of track reliability. One of the main impossibility factors of these models is quasidynamic approach. Therefore, as a rule, receive and examine not only dynamic process of a railway track, but also its consequences. Besides, these models are related to flat ones, and it also adds some complexity in results comparing with an experiment, as well as the process is not easy to distinguish the impact of volume in its limited parts. The use of numerical methods extend the posibilities, and it also make it impossible for the consideration of the dynamic process, as well as it is impossible to introduce processes, causing the reaction to stress load. Thus the basic physical and constructive approaches in modeling make it possible to consider the dynamic process of localized both in time and in space directly.