Software & Systems

Articles of journal № 3 at 2012 year.

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51. Nearest neighbour search algorithm [№3 за 2012 год]
Author: Гусев Д.И.
Visitors: 12368
The article describes special algorithm for nearest neighbor search in the set of particles in Euclidean space. The algorithm presents the set of particles in the form of linear list data structure; in this list nearest neighbors are placed close to each other, according to sequence numbering of such elements, so, next search of neighboring pair is made through comparison of the next point with following points (according to sequence number) in the list of elements. The algorithm provides search of all neighbors among N particles in O(N2  k) time, where k2 – density coefficient of particle distribution. The article gives experimental dependencies of coefficient k vs. particle distribution density in two-dimensional space, where this feature changes up to 20 units. In described experiments the algorithm has highest effectiveness, when the particles have high concentration: when the concentration is 80 %, it shall be needed, average, 1,3 operations in order to find next pair of neighbors; with concentration 40 % – 1,5 operations; with concentration 20 % – 2,5 operations and 3–4,5 operations with concentration 10–5 %, accordingly. The algorithm is effectively implemented with programming software, which makes it attractive for use.

52. Parallel algorithms designed for the strength analysis of hydrogen-charged structures [№3 за 2012 год]
Authors: Федотов В.П., Spevak L.F., Nefedova O.A.
Visitors: 9638
The work provides a model for estimation of hydrogen brittleness for flat elements used in metal structures with defects. It is known that defective metal parts the hydrogen concentration is distributed fairly uneven – defect area is surrounded with molecular hydrogen of high concentration under high pressure. This model can be used for analysis of destruction process of a metal structure that is exposed to intensive external action. In this case, internal pressure in defects grows quickly, and this leads to destruction of such elements. The model uses algorithm of coupled diffusion-deformation problem. Coupled problem includes equations that describe hydrogen diffusion process in high field, and mechanic equations for stress and deformation tensors that consider diffusion process. Solution of deformation problem in linear elasticity theory is made with modified boundary element method. Collection of the hydrogen around defect area is described by convective diffusion in the field of high mechanical stress. Diffusion problem can be solved with modified boundary element method. Solution of the coupled problem can be obtained step by step in time. In final stage of calculation, each step produces value of molecular hydrogen pressure in every defect and then destruction condition of boundaries is checked. For reduction of computing time, parallelizing procedure was performed. The program was designed with this algorithm. This program can be implemented on multiprocessor computing system. This algorithm was illustrated by solution of two-dimensional problem of hydrogen diffusion around the defect – pores for the metal sample exposed to external tension stress. Calculation outputs are shown in charts.

53. Parallel design algorithm for description of the mass transfer in a pore [№3 за 2012 год]
Authors: Поветкин А.Д., Чан Хыу Куе, Koltsova E.M.
Visitors: 9201
Here is described a model using molecular dynamics approach that describes gas transfer in small pores. Two types of the mass transfer that happen in a pore were taken into account: Knudsen diffusion and molecular diffusion. Two cases of interaction are mentioned that describe molecular movement and interaction. First case describes the variant, where molecules move according to classic mechanics law and where they interact with each other and a wall, on the principle of perfectly elastic collision. It is assumed that the particles can collide with the pore’s wall in two ways: mirror and diffusion, and for each specific collision this way is defined at random fashion, and the ratio of collisions according to both ways presents one of the features of the model. The second case describes molecular interaction using intermolecular potential of Lennard-Jones interaction. Calculation of molecular movement was made with parallel algorithms. Parallel computing is made with the use of CUDA technology. Information about particle features is stored in 3-D array. Number of array cells corresponds to number of particles in the system. Each array cell contains information about particle: coordinates, velocity vector, speed up vector and its type. One dimension array of particle type exists separately. Number of array elements equals to number of types of existing particles. Cells contain information about each substance that is present in the system: particle’s mass and radius, coefficient of molecular interaction potential. The array was arranged with bubble sort algorithm adapted for parallel operation and extended for 3-D case. The article contains basic computation flow charts.

54. Creation of software system on the basis of spatial object interaction diagram [№3 за 2012 год]
Authors: Prokhorov S.A., Kulikovskikh I.M.
Visitors: 10230
The article looks into the possibility of software system creation for data analysis within Data Mining systems with a staged platform of data analysis. In this regard a new solution is provided for software products creation focused on incremental processing of the initial information in the form of a spatial object interaction diagram, which will allow time and resource expenditures required to obtain the final software product to be reduced. The developed spatial diagram is built on the basis of the following fundamental notions: functional transformation space, functional enhancement space, characteristic enhancement space, key of transition from one space to the other at multiple levels. On the basis of the developed spatial diagram the structural diagram of software system for correlation and spectral data mining was created, while this kind of analysis, according to the research at the market of the analogous products, is unique in terms of the class of current problems. Mathematical models taken as a basis for this software product are based on Fourier orthogonal decomposition of functional characteristics, and for implementation of a hidden level of data analysis the analytical processing technique was created, which consists in functioning management and implementation of created search mechanisms for hidden regularities. Using spatial object integration diagram reduces the labour intensity of software development for automated systems of scientific research, control and data processing, and can be recommended to the designers of automated systems – programmers, as well as to the analysts involved in designing of complex software systems.

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