• 정보학연구
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• 제1권2호
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• pp.65-79
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• 1998

본 논문에서는 ATM 망으로 입력되는 트래픽(CBR/VBR)의 QoS 특성을 만족시키기 위한 버퍼할당 및 버퍼관리 메카니즘을 제안하였다. 본 논문에서 제안하는 ATM 망의 트래픽 처리방식은 입력되는 트래픽의 특성에 따라 버퍼를 각각 할당하는 방식을 사용하는 경로분리 메카니즘을 기본으로하며 임계치를 설정하여 버퍼관리 메카니즘의 셀처리 스케줄링 및 알고리즘, 그리고 서비스 크래스의 특성에 따라 요구되는 평균 셀지연과 셀손실을 고찰하였고, CBR/VBR 버퍼의 임계치가 셀지연이나 셀손실에 많은 영향을 미치는 것을 확인할 수 있었다.

• 대한조선학회논문집
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• 제44권1호
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• pp.16-25
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• 2007

Studies of unsteady-airfoil flows have been motivated mostly by efforts to avoid. or reduce such undesirable effects as flutter, noise and vibrations, dynamic stall. In this paper, we carry out a computational study of viscous flows around a two-dimensional oscillating airfoil to investigate unsteady effects in these important and challenging flows. A fully implicit incompressible RANS solver has been used for calculating unsteady viscous flows around an airfoil. The cell-centered End order finite volume method is utilized to discretize governing equations. in order to ease the flow computation for fluid region changing in time, improve the qualify of solution and simplify the grid generation for an oscillating airfoil flow, the computational method adopts a moving and deforming grid generation technique based on the multi-block grid topology. The numerical method is applied for calculating viscous flows of an oscillating NACA 0012 in uniform flow. The computational results are compared with available experimental data. Computed results are compared with experimental data and flow characteristics of the experiment are reproduced well In the computed results.

• 한국정밀공학회지
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• 제24권11호
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• pp.44-51
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• 2007

Condenser tubes are mainly produced by precision extrusion with a porthole die and are used in the flow pass of refrigerant cooling systems in automobiles. The recent technical trend of condenser tube requires the tube to be of more multi cellizing, high strength and small size, and to increase the heat transfer area and heat efficiency. Hence, this paper is shown that the results of FE-simulation are in good agreement with the experimental ones. Finally, the extrusion die shape is proposed through analysis of FE-simulation and performance of trial extrusion. Chamber shape dimension and initial temperatures of die is adjusted analysis results. And the possibility of extrusion is estimated that forming load, welding pressure and stress analysis of die in this paper. The validity of simulated results was verified into extrusion experiments on the condenser tubes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4291-4310
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• 2015

This paper investigates the traffic offloading over unlicensed bands for two-tier multi-mode small cell networks. We formulate this problem as a Stackelberg game and apply a hierarchical learning framework to jointly maximize the utilities of both macro base station (MBS) and small base stations (SBSs). During the learning process, the MBS behaves as a leader and the SBSs are followers. A pricing mechanism is adopt by MBS and the price information is broadcasted to all SBSs by MBS firstly, then each SBS competes with other SBSs and takes its best response strategies to appropriately allocate the traffic load in licensed and unlicensed band in the sequel, taking the traffic flow payment charged by MBS into consideration. Then, we present a hierarchical Q-learning algorithm (HQL) to discover the Stackelberg equilibrium. Additionally, if some extra information can be obtained via feedback, we propose an improved hierarchical Q-learning algorithm (IHQL) to speed up the SBSs' learning process. Last but not the least, the convergence performance of the proposed two algorithms is analyzed. Numerical experiments are presented to validate the proposed schemes and show the effectiveness.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1915-1919
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• 1991

The efficiency of automated assembly line is increased by realizing the automation of each assembly cell, monitoring the line information and developing the real-time line control system it. which production flow is controllable. In this paper, the several modules which are important factors when constructing automated real-time control system, such as, line control S/W module, real-time model change module, error handling module and line production management S/W module, are developed. For developing these important programming modules, real-time control and multi-tasking techniques are integrated. In this paper, operating method of real-time line control in PCB automated assembly line is proposed and for effective control of production line by using multi-tasking technique, proper operating method for relating real-time line control with multi-tasking is proposed by defining the levels of signals and tasks. CIM-Oriented modular programming method considering expandability and flexibility will be added for further research in the future.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.659-665
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• 2008

The 1-D numerical study of the interior ballistics has been conducted. The unsteady compressible 1-D CFD code using SIMPLER algorithm and QUICK scheme has been developed. The mathematical model of the two-phase flow has been established for the behavior of the interior ballistics. The moving boundary due to the projectile motion as the physical phenomena of the interior ballistics results in the varied control volume. In order to analyze the moving boundary, the numerical codes, which apply the ghost-cell extrapolation method and the Lagrangian method respectively, have been developed. The ghost-cell extrapolation method has been used in the Eulerian coordinate system. The Lagrangian method has been used in Non-Eulerian coordinate system. These codes have been verified through the analysis of the free piston motion problem in the tube. Through this study, the basic techniques of the numerical code for the multi-dimensional two-phase flow of the interior ballistics have been obtained.

• IMMUNE NETWORK
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• 제21권4호
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• pp.31.1-31.16
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• 2021

Gastric cancer (GC) is the fourth most common cause of cancer-related death globally. The classification of advanced GC (AGC) according to molecular features has recently led to effective personalized cancer therapy for some patients. Specifically, AGC patients whose tumor cells express high levels of human epidermal growth factor receptor 2 (HER2) can now benefit from trastuzumab, a humanized monoclonal Ab that targets HER2. However, patients with HER2^negative AGC receive limited clinical benefit from this treatment. To identify potential immune therapeutic targets in HER2^negative AGC, we obtained 40 fresh AGC specimens immediately after surgical resections and subjected the CD45⁺ immune cells in the tumor microenvironment to multi-channel/multi-panel flow cytometry analysis. Here, we report that HER2 negativity associated with reduced overall survival (OS) and greater tumor infiltration with neutrophils and non-classical monocytes. The potential pro-tumoral activities of these cell types were confirmed by the fact that high expression of neutrophil or non-classical monocyte signature genes in the gastrointestinal tumors in The Cancer Genome Atlas, Genotype-Tissue Expression and Gene Expression Omnibus databases associated with worse OS on Kaplan-Meir plots relative to tumors with low expression of these signature genes. Moreover, advanced stage disease in the AGCs of our patients associated with greater tumor frequencies of neutrophils and non-classical monocytes than early stage disease. Thus, our study suggests that these 2 myeloid populations may serve as novel therapeutic targets for HER2^negative AGC.

• 대한기계학회논문집B
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• 제21권2호
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• pp.252-263
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• 1997

Steady-state two-dimensional natural convective heat transfer in horizontal cylindrical annuli was studied by solving the governing equations based on the primitive variables. Emphasis was put on the occurrence of the multiple solutions at a given set of parameter values, and on the determination of the bifurcation points at which those multiple solutions begin to branch out. The multicellular flow pattern from the results of melting process in an isothermally heated horizontal cylinder for high Rayleigh numbers, was used as initial guesses for the field variables. This was succeeded in new bifurcation point to tetracellular solutions for an identical set of parameter variables of previous works. The close examination of flow pattern transition around bifurcation point was also conducted. It was found that the mechanisms of flow transition are different depending on the critical Rayleigh number of bifurcation point.

• 한국전산유체공학회지
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• 제13권4호
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• pp.86-95
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• 2008

For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.

• 대한산업공학회지
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• 제24권1호
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• pp.23-35
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• 1998

This article presents a network flow analysis to form flexible machine cells with minimum intercellular part moves and a neural network model to form part families. The operational sequences and production quantity of the part, and the number of cells and the cell size are taken into considerations for a 0-1 quadratic programming formulation and a network flow based solution procedure is developed. After designing the machine cells, a neural network approach for the integration of part families and the automatic assignment of new parts to the existing cells is proposed. A multi-layer backpropagation network with one hidden layer is used. Experimental results with varying number of neurons in hidden layer to evaluate the role of hidden neurons in the network learning performance are also presented. The comprehensive methodology developed in this article is appropriate for solving large-scale industrial applications without building the knowledge-based expert rule for the cellular manufacturing environment.