• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.12
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• pp.1657-1668
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• 1998

In the analysis of a mushy solidification system with natural convection using a fixed grid method, the enthalpy method has been used to account for the release of latent heat. The variable viscosity, Darcy source, and hybrid methods have been employed for the velocity suppression in a mushy region. The choice of the values of solid viscosity and permeability constant in conjunction with the Darcy source term plays an important role in forming the location and shape of the phase boundaries. In this work the effects of these major parameters related to steady-state behavior in the system of mushy solidification are investigated through a simple test problem. The effective specific heat based on the spatial gradients of the enthalpy and temperature is adopted for the treatment of the release of latent heat. The effects of the Prandtl and Rayleigh numbers on the shape of mushy region are examined using the hybrid method.

• The Journal of Asian Finance, Economics and Business
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• v.1 no.1
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• pp.23-30
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• 2014

The aim of this research is theoretical and methodological approaches to the necessity of formation of innovation clusters as growth poles on the basis of statistical analysis and identification of specialization. In this research, we used methods, which will allow to analyze of innovative processes and to identify of prospective branches of specialization of the formation of innovative clusters in the spatial context. Keeping with the previous literature, the present study is determined by the novelty of the problem, concerning the formation and development of innovative clusters as growth poles, as well as large specifics of problems in our country in the framework of use of innovative clusters. An analysis was showed that Kazakhstan's regions have substantial differences in the groups of regions for most of the indicators have presented form a tightly located clusters and in the ratings of innovative susceptibility and innovative activity. This research has some practical implications, which have proved that innovative clusters become platforms as growth poles for introduction of advanced technologies, development of innovative companies, thereby providing a certain stability of the economy of the regions.

• Journal of Computing Science and Engineering
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• v.7 no.1
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• pp.53-66
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• 2013

Bounding the worst-case DRAM performance for a real-time application is a challenging problem that is critical for computing worst-case execution time (WCET), especially for multicore processors, where the DRAM memory is usually shared by all of the cores. Typically, DRAM commands from consecutive DRAM accesses can be pipelined on DRAM devices according to the spatial locality of the data fetched by them. By considering the effect of DRAM command pipelining, we propose a basic approach to bounding the worst-case DRAM performance. An enhanced approach is proposed to reduce the overestimation from the invalid DRAM access sequences by checking the timing order of the co-running applications on a dual-core processor. Compared with the conservative approach, which assumes that no DRAM command pipelining exists, our experimental results show that the basic approach can bound the WCET more tightly, by 15.73% on average. The experimental results also indicate that the enhanced approach can further improve the tightness of WCET by 4.23% on average as compared to the basic approach.

• Journal of Korea Multimedia Society
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• v.8 no.9
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• pp.1216-1226
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• 2005

In this paper, a preventive transmission rate decision algorithm, called PTRD, is proposed for the transmission of live video over networks with dynamic bandwidth allocation capability. Frame analyzer predicts the bit-rates of future frames before encoding by analyzing the source information such as spatial variances and the degree of scene changes. By using the predicted bit-rates, transmission rate bounds are derived from the constraints of encoder and decoder buffers. To resolve the problem of renegotiation cost increment due to frequent renegotiations, the PTRD algorithm is presented to decide transmission rates considering the elapsed time after the recent renegotiation and the perceived video quality. From the simulation results, compared to the normalized LMS based method, PTRD is shown to achieve high channel utilization with low renegotiation cost and no delay violation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.758-763
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• 2006

In various fields of basic science and engineering, in order to present signals and systems exactly and acquire useful information from spatial and timely changes, many researches have been processed. In these methods, the Fourier transform which represents signal as the combination of the frequency component has been applied to the most fields. But as transform not to consider time information, the Fourier transform has its limitations of application. To overcome this problem, a variety of methods including the wavelet transform have been proposed. As transform to represent signal by using the changing window, according to scale parameter in time-scale domain, the wavelet transform is capable of multiresolution analysis and defines various functions according to the application environments. In this paper, to detect features of signal we analyzed wavelet the spectrum by using the basis function of the fourier transform.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.613-620
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• 1985

An analysis on the thermal instability of horizontal Blasius flow in the form of longitudinal vortices has been carried out by introducing the 3-dimensional spatial dependence of the disturbance quantities. The stability problem has been simplified significantly by considering the limiting case of infinite Prandtl number and by skilfully replacing the boundary conditions at infinity with the interface conditions at the edge of the thermal boundary layer (or by simply confining the thermal disturbances in the thermal boundary layer). The advantage of this approach is that the critical values marking the onset of thermal instability can be readily obtained as solutions of the eigenvalues problems formulated by a 6*6(or a 5*5) determinant. Present analysis provides reasonable explanations on the existing experimental and theoretical data. Especially, the heat transfer correlation based on the present analysis agrees well with the existing experimental data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.856-867
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• 2006

This paper proposes a new algorithm for opportunistic scheduling that take advantage of both multiuser diversity and power control. Motivated by the multicast RTS and priority-based CTS mechanism of OSMA protocol, we propose an opportunistic packet scheduling with power control scheme based on IEEE 802.11 MAC protocol. The scheduling scheme chooses the best candidate receiver for transmission by considering the SINR at the nodes. This mechanism ensures that the transmission would be successful. The power control algorithm on the other hand, helps reduce interference between links and could maximize spatial reuse of the bandwidth. We then formulate a convex optimization problem for minimizing power consumption and maximizing net utility of the system. We showed that if a transmission power vector satisfying the maximum transmission power and SINR constraints of all nodes exist, then there exists an optimal solution that minimizes overall transmission power and maximizes utility of the system.

• Journal of Information Technology Services
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• v.11 no.sup
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• pp.61-74
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• 2012

As the retail industry has been challenged by stiff competition, the retailer becomes more interested in better understanding consumers' in-store behavior to gain and sustain competitive advantage. Consumers' shopping paths provide valuable clues to understanding customers' in-store behavior, which has been a long standing research issue in business. This study is to explore the shopping path patterns in a grocery using RFID technology and clustering method. To this end, we designed the RFID systems, affixing active RFID tags to the bottom of grocery carts. The tag emit signal that is received by receptors installed at various location throughout the store. The RFID systems provide the time and location of the cart while consumers shop around the store. The point of sale data are matched with the cart movement records to provide a complete picture of each shopping path. To find the distinctive patterns of consumers' shopping paths, we proposed the distance-index matrix using dijkstra method and normalization method to conduct the clustering in order to handle the problem in measuring the similarity among shopping paths, which is raised by the spatial nature of consumer movement in a grocery. After analyzing the RFID data obtained in one of the groceries in a major Korean retailer, we could successfully identify several distinctive patterns of shopping paths, which prove to provide the valuable implications for store management.

• Journal of Information Processing Systems
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• v.16 no.2
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• pp.406-420
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• 2020

In order to make up the deficiencies of the existing research results which cannot effectively deal with the nearest neighbor query based on the line segments in obstacle space, the k nearest neighbor query method of line segment in obstacle space is proposed and the STA_OLkNN algorithm under the circumstance of static obstacle data set is put forward. The query process is divided into two stages, including the filtering process and refining process. In the filtration process, according to the properties of the line segment Voronoi diagram, the corresponding pruning rules are proposed and the filtering algorithm is presented. In the refining process, according to the relationship of the position between the line segments, the corresponding distance expression method is put forward and the final result is obtained by comparing the distance. Theoretical research and experimental results show that the proposed algorithm can effectively deal with the problem of k nearest neighbor query of the line segment in the obstacle environment.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.2 s.32
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• pp.51-63
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• 2005

With the emerging mobile technologies, applications based on GIS are also getting more attention recently. But it is known to have some limitations in being served in different types of mobile devices and platforms. While information services are limited by data format and data exchange between platforms, the eXtensible Markup Language(XML) is getting focused as the most promising technology as the solution to such problems. Geographic Markup Language(GML) is based on XML technology and is being frequently mentioned recently as the solution to service problem on different mobile devices as well as the internet. In this study, we suggested the framework to use the GML in order to transfer and represent geographical data through the on-line or wireless platforms. We compared different application types which are currently used with GML and proposed to improve GIS services using the GML in geographical data transfer and description.