• 한국컴퓨터정보학회논문지
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• 제16권5호
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• pp.153-162
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• 2011

최소 절단 문제는 공급처 S에서와 수요처 T로의 흐름 용량이 최소가 되는 지점들을 절단하는 문제이다. 망의 병목지점을 찾는 방법은 대부분 유동망을 계산하여 최소 절단값을 찾는 유동-기반 알고리즘이 적용되고 있다. 이 알고리즘은 최소절단은 제시하지 않는 단점이 있다. 본 논문은 유동망을 구하지 않고 망으로부터 직접 최대 수용량을 가진 정점을 인접한 S 또는 T로 병합하는 방법으로 최소 절단값을 찾는 간단한 알고리즘이다. 13개의 한정된 그래프에 적용한 결과 제안된 알고리즘은 간단하면서도 정확하게 최소 절단 값 $_{\min}c$(S, T)을 찾을 수 있었다.

• 대한기계학회논문집B
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• 제35권4호
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• pp.379-383
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• 2011

본 연구에서는 두 종류의 다공성 유리막을 이용하여 전기삼투 펌프를 제작하였다. 전기삼투 펌프의 성능은 탈이온수와 1 mM 나트륨 테트라붕산염 데카수화물 완충액을 이용하여 최대유량, 최대전류 그리고 최대압력의 항으로 표현하였다. 최대유량과 최대전류는 ROBU 사의 다공성 유리막의 높은 공극률에 기인하여 DURAN 사의 다공성 유리막 보다 높은 값을 가졌다. 그러나 최대압력은 비슷하였다. 열역학적 효율은 ROBU 사의 다공성 유리막이 DURAN 사의 다공성 유리막보다 2 배 정도 높은 값을 가졌으며, 최대유량당 최대전류 역시 ROBU 사의 다공성 유리막이 높은 값을 가졌다. 그러나 최대압력당 최대전류는 DURAN 사의 다공성 유리막에서 더 높은 값을 가졌다. 본 연구에서는 ROBU 사의 다공성 유리막은 낮은 출력으로 높은 유량을 구현할 수 있고, DURAN 사의 다공성 유리막은 낮은 출력으로 높은 압력을 구현할 수 있음을 확인하였다.

• Advances in aircraft and spacecraft science
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• 제10권2호
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• pp.141-158
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• 2023

In current research work, the aerodynamics performance of a newly designed large flying V aircraft is numerically investigated. Three Flying V configurations, with V-angles of 50°, 70° and 90° that represent the minimum, moderate, and maximum configurations respectively, were designed and modeled to assess their aerodynamic performance at cruise flight conditions. The unstructured mesh was developed using ICEM CFD and Ansys-Fluent was used as an aerodynamic solver. The developed models were numerically simulated at cruise flight conditions with a Mach number equal to 0.15. K-ω SST turbulence model was chosen to account for flow turbulence.The authors performed steady flow simulations.The results obtained from the experimentation reveal that the maximum main angle configuration of 90° had the highest C_Lmax value of 0.46 compared to other configurations. While the drag coefficient remained the same for all three configurations, the 50° V-angle configuration achieved the maximum stall angle of 35°. With limited stall delay benefits, the flying V possesses no sufficient stability, due to the flow separation detected at whole elevon and winglet suction side areas at AoA equal and higher than 30°.

• 설비공학논문집
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• 제4권3호
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• pp.183-190
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• 1992

The Collins cryocooler is numerically analysed with the optimization technique, and the optimum operating and design conditions are searched. This paper shows that liquefied helium quantity has an external maximum w.r.t. the total mass flow rate, the mass flow rates through expander and the capacities of heat exchangers. The liquefied helium quantity increases as the compressor exit pressure of the cryocooler does. The maximum quantity of liquefied helium and the maximum coefficient of performance have been found to exist in extremum, depending on the ratios of each heat exchanger capicities to the total one. At the optimum condition, the capacity of heat exchanger in high temperature region is larger than that in low temperature region.

• 한국산업정보학회논문지
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• 제4권2호
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• pp.81-87
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• 1999

본 연구에서는 단일 공정의 생산시스템을 대상으로 n개 작업에 있어서의 시간/비용의 트레이드-오프에 있어서 작업순서의 평가기준과 자원할당 비용의 평가기준을 동시에 고려한 2목적 스케쥴링 문제들을 제안한다. 우선 가공작업의 총체류시간(total flow time)과 납기(due date)의 평가기준에 관한 2목적의 유효스케쥴을 구하는 해법을 제안한다. 그리고 이러한 평가기준과 이에 관련된 자원할당의 비용을 동시에 최소화하는 2목적의 해법을 제안한다.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2019년도 제59차 동계학술대회논문집 27권1호
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• pp.143-144
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• 2019

최대 엔트로피(Maximum Entropy)는 실증적 데이터에서 관찰된 잠재적인 여러 유용한 특징들을 기반으로 최대 엔트로피를 갖는 추정된 분포를 구축하기 위한 접근법이다. 본 논문에서는 네트워크상의 데이터 전송 시 혼잡한 흐름을 효율적으로 분류하기 위해 최대 엔트로피 알고리즘을 기반으로 한 새로운 네트워크 흐름 분류 모델을 제안한다. 제안한 알고리즘이 기존의 방법들 보다 높은 분류 정확도를 나타내는 것을 목표로 네트워크 서비스 시 효율성을 높이고자 한다.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2002년도 추계 학술발표회 논문집
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• pp.119-124
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• 2002

We consider a multi-state flow network consisted of undirected links and focus on how to find efficiently the union of minimal paths transmitting a required flow when minimal paths are known.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 춘계학술대회
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• pp.111-114
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• 1994

Three component velocity measurements with a refractive index-matching technique was used to investigate the flow characteristics in the atrio-pulmomnary (AP) Fontan connection under the steady flow condition. A strong swirl was observed in the extra-cardiac conduit and the main pulmonary artery (MPA). Maximum velocity magnitude in the MPA was about 0.8 m/s near the posterior wall at 6 liter/min. Swirling motion of the flow as well as geometric abnormalities of the connection are important factors in energy loss across Fontan connections.

• 대한기계학회논문집
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• 제18권4호
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• pp.1019-1030
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• 1994

Natural convection heat transfer from a horizontal ice cylinder immersed in quiescent cold pure water was studied experimentally. The experiment was conducted for the ambient water temperatures ranging from $2.0^{\cric}C$ to $10.0^{\circ}C$. The flow fields around an ice cylinder and its melting shapes were visualized and local Nusselt numbers obtained. Especially, its attention was focused on the density maximum effects and stagnation point Nusselt number. From the visualized photographs of flow fields, three distinct flow patterns were observed with the ambient water temperature variation. The melting shapes of ice cylinder are various in shape with flow patterns. Steady state upflow was occured at the range of $2.0^{\circ}C \leq T_{\infty} \leq 4.6^{\circ}C$ and steady state downflow was occured at $T_{\infty} \geq 6.0^{\circ}C$. In the range of $4.7^{\circ}C < T_{\infty} < 6.0^{\circ}C$, three-dimensional unsteady state flow was observed. Especially, the melting shapes of ice cylinder have formed the several spiral flutes for the temperatures ranging from $5.5^{\circ}C$ to $5.8^{\circ}C$. For upflow regime, the maximum stagnation point Nusselt number exists at $T_{\infty} = 2.5^{\circ}C$ and as the ambient water temperature increases the Nusselt number decreases. At ambient water temperature of about $5.7^{\circ}C$, Nusselt number shows its minimum value.

• 한국재료학회지
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• 제9권6호
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• pp.551-555
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• 1999

The deposition condition to obtain stoichiometric $Ta_2$O\ulcorner films, which is still controversial, using magnetron reactive sputtering was studied. The films were deposited by varying $O_2$gas flow rate with sputtering power and Ar gas flow rate of 200W and 60 sccm fixed. At the conditions of $O_2$ gas flow rate over 20 sccm, amorphous Tantalum oxide films with the refractive index of 2.1 and dielectric constant of 25 were deposited. Among those films, the capacitors dielectric properties of the film deposited at the condition of $O_2$ gas flow rate 50 sccm was best, the leakage current was 1$\times$10\ulcornerA/$\textrm{cm}^2$ at the electric field strength of 0.5 MC/cm and the breakdown field strength was over 2.0 MV/cm. This result could be explained from the analysis comparing with a standard sample using RBS because the composition of the film deposited at this condition was closest to the stoichiometric $Ta_2$O\ulcorner. The result of XPS analysis convinced that this film was stoichiometric $Ta_2$O\ulcorner film. A maximum cathode voltage was observed when $O_2$gas flow rate was 30 sccm. This shows that the Schiller's proposition that one can obtain stoichiometric films at the condition of maximum cathode voltage is not correct and more oxygen than that of the maximum voltage condition is necessary to deposit the stoichiometric Ta$_2$O\ulcorner films.