• 전기의세계
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• 제22권4호
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• pp.25-29
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• 1973

The computation of transmittances between arbitrary input and output nodes is of particular interest in the signal flow graph theory imput. The signal flow matrix [T] can be defined by [X]=-[T][X] where [X] and [Y] are input nose and output node matrices, respectively. In this paper, the followings are discussed; 1) Reduction of nodes by reforming the signal flow matrix., 2) Solution of input-output relationships by means of Gauss-Jordan reduction method, 3) Extension of the above method to the matrix signal flow graph.

• 설비공학논문집
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• 제22권8호
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• pp.573-578
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• 2010

Topological matrix which reflects characteristics of network connectivity has been widely used in efficient solving for complicated flow network. Using topological matrix, one can easily define continuity at each node of flow network and make algorithm to automatically generate continuity equation of matrix form. In order to analyze flow network completely it is required to satisfy energy conservation in closed loops of flow network. Fundamental cycle retrieving algorithm based on graph theory automatically constructs energy conservation equation in closed loops. However, it is often accompanied by NP-complete problem. In addition, it always needs fundamental cycle retrieving procedure for every structural change of flow network. This paper proposes alternative mathematical method to analyze flow network without fundamental cycle retrieving algorithm. Consequently, the new mathematical method is expected to reduce solving time and prevent error occurrence by means of simplifying flow network analysis procedure.

• 한국수자원학회논문집
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• 제30권6호
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• pp.777-785
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• 1997

이 연구는 강우시 산지사면의토양체와 대공극에서 발생하는 지표하 호우류를 구분하여 측정한 후 이들의 수문학적 특성을 밝히고자 수행하였다. 측정 시설은 미국 Georgia 주에 위치한 지질국 산하 Panola 시험유역의 상류 산지사면에 약 20m 길이의 조사구를 암반 깊이까지 파고 2m 간격으로 집수구를 설치하였다. 대공극류는 조사구 토양단면에 있는 13개의 대공극 중 유출이 발생한 6개의 대공극에 집수통을 설치하여 측정하였다. 1996년 3월 6일부터 7일까지 95.5mm의 강우가 내렸으며 이 때 발생한 대공극류와 기질류를 측정하여 분석하였다. 대공국류는 기질류보다 약 10시간 앞서 첨두유출이 발생하므로 유역의 첨두유출을 형성하는데 보다 큰 영향을 미쳤다. 강우가 종료된 후 대공극류는 약 12시간 이내에 멈춘 반면 기질류는 약 3일 이상 지속되어 감수부를 형성하는데 보다 큰 영향을 미쳤다. 기질루와 대공극류의유출량은 집수구에 따라 최대 8,655.3$\ell$에서 최초 17.8$\ell$로 공간적 변이가 매우 크게 나타났으며 이 변이는 지표 지형보다 기반암 표면의 지형과 밀접한 관계가 있었다.

• 자원환경지질
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• 제41권6호
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• pp.731-746
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• 2008

대부분의 분을 흐름 접근 방식을 따르는 다상흐름모델들은 주로 유체나 매질의 비 압축성을 가정하거나 완전한 삼상 오염물을 다루지 않고 이상 유체 (물 또는 공기, 물 또는 불용융성유체)의 거동만을 다룬다. 그러나 본 연구에서는 유체 및 매질의 압축성과 완전한 삼상 오염물을 가정하는, 분율흐름접근방식을 따르는 수학적 지배방정식을 개발하고, 이를 토대로 압축성 유체 및 매질을 고려한 삼상흐름 수치모의프로그램을 개발하였다 개발된 삼상흐름 수치모의프로그램 (Compressible Multiphase Flow Simulator, CMPS)을 검증하기 위해서 기존에 개발된 비압축성 유체 및 매질을 고려한 삼상흐름수치모의 프로그램인 MPS (Suk and Yeh, 2007; Suk and Yeh, 2008) 및 해석해를 통해서 간접적으로 비교 검증하였다. 비교결과 CMPS와 MPS의 결과와 해석해들은 서로 잘 일치하였다. 따라서 CMPS는 압축성 유체 및 매질을 고려한 삼상흐름 수치모의를 구현 할 수 있는 가능성을 가진다.

• Journal of Biosystems Engineering
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• 제32권6호
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• pp.389-394
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• 2007

The power output of the stirling engine is influenced by the regenerator effectiveness. The regenerator effectiveness is influenced by heat transfer and flow friction loss of the regenerator matrix. In this paper, in order to provide basic data for the design of the regenerator matrix, characteristics of working fluid velocities were investigated by a packed method of matrix in the oscillating flow as the same condition of operation in a Stirling engine. As matrices, two different wire screens were used. The results are summarized as follows; 1. When a regenerator is not filled with any wire screen, working fluid velocity of the oscillating flow shows 1.3 times faster than that of one directional flow. 2. When a regenerator is filled with the wire screen of No.50, working fluid velocity of the oscillating flow reveals 2.5 times faster than that of one directional flow. 3. When a regenerator is filled with the wire screen of No. 100, working fluid velocity of the oscillating flow shows 2 times faster than that of one directional flow, regardless of the number of packed wire screens. 4. Working fluid velocity is decreased wire the increase in number of meshes and packed wire screens.

• Journal of Biosystems Engineering
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• 제30권4호
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• pp.195-201
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• 2005

The output of Stirling engine is influenced by the regenerator effectiveness. The regenerator effectiveness is influenced by heat transfer and flow friction loss of the regenerator matrix. In this paper, in order to provide a basic data for the design of regenerator matrix, characteristics of heat transfer and flow friction loss were investigated by a packed method of matrix in the oscillating flow as the same condition of operation in a Stirling engine. As matrices, several kinds of combined wire screen meshes were used. The results are summarized as follows; The packed meshes with high mesh no. in the side of heater part of regenerator showed effective than the packed meshes with low mesh no. in the side of cooler part of regenerator. The temperature difference and pressure drop of the regenerator were not made by the specific surface area of wire screen meshes but by the minimum free-flow area to the total frontal area. Among the No. 150 single screen meshes, 200-60 combined meshes, the 200-150-100 combined meshes showed the highest in effectiveness.

• 대한전기학회논문지:전력기술부문A
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• 제48권9호
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• pp.1081-1087
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• 1999

Load Flow calulation methods can usually be divided into Gauss-Seidel method, Newton-Raphson method and decoupled method. Load flow calculation is a basic on-line or off-line process for power system planning. operation, control and state analysis. These days Newton-Raphson method is mainly used since it shows remarkable convergence characteristics. It, however, needs considerable calculation time in construction and calculation of inverse Jacobian matrix. In addition to that, Newton-Raphson method tends to fail to converge when system loading is heavy and system has a large R/X ratio. In this paper, matrix equation is used to make algebraic expression and then to slove load flow equation and to modify above defects. And it preserve P-Q bus part of Jacobian matrix to shorten computing time. Application of mentioned algorithm to 14 bus, 39 bus, 118 bus systems led to identical results and the same numbers of iteration obtained by Newton-Raphson method. The effect of computing time reduction showed about 28% , 30% , at each case of 39 bus, 118 bus system.

• International Journal of Fluid Machinery and Systems
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• 제5권3호
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• pp.126-133
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• 2012

The transfer matrix and unsteady cavitation characteristics, cavitation compliance and mass flow gain factor, of cavitating inducer were evaluated by CFD using commercial software. Quasi-steady values of cavitation compliance and mass flow gain factor were obtained first by using steady calculations at various flow rate and inlet cavitation number. Then unsteady calculations were made to determine the transfer matrix and the cavitation characteristics. The results are compared with experiments to show the validity of calculations.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 춘계 학술대회논문집
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• pp.219-222
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• 2005

A compressible two-fluid two-phase flow computation model using the stiffened-gas equation of state is formulated. Since the conservation equation system is of mixed type, it gives complex eigenvalues. The sonic speeds obtained from the individual single phase have been simply used in the literature for the fastest wave speeds necessary in the HLL scheme. This method has worked fine but proved to be quite diffusive according to our test. To improve the accuracy, we here propose to utilize the analytic eigenvalues evaluated from an approximate Jacobian matrix lot the fastest wave speeds. The interfacial transfer terms were dropped in constituting the Jacobian matrix for this purpose. The present scheme proved efficient, robust and accurate in comparison with other existing methods. We solved the cavitating flow problem using the present scheme. The result shows more detailed wave structure in the cavitating process caused by the strong expansion waves.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.1074-1077
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• 1997

Newton-Raphson method is mainly used since it shows remarkable convergence characteristics. It, however, needs considerable calculation time in construction and calculation of inverse Jacobian matrix. In this paper a new type of load flow equation is summarized as follows: Since inverse calculation of Jacobian matrix is not needed in the suggested algorithm but using complex bus voltage, the calculation process is simple. With the simple structure, reduction of calculation time is achieved.