• Korean Journal of Acupuncture
• /
• 제25권3호
• /
• pp.29-41
• /
• 2008

Objectives : The aim of this study is to examine the effects of SSP(silver-spike point) therapy, applied to acupuncture points, on the middle cerebral arteries blood flows of sample group(tention-type headache patients, n=12) and control group(non tension-type headache patients, n=12), and on the reduction of their headaches, when applied to acupuncture points. Methods : We stimulated 6 acupuncture points for headache with the SSP(three times a week for three weeks), and measured VAS(visual analogue scale) and the blood flow of the middle cerebral arteries with TCD(transcranial doppler ultrasonography). Results : The blood flow of the middle cerebral artery and VAS of the sample group and the control group were compared four times(initial, 1weeks, 2weeks, 3weeks) and significant differences in the measurements were found at 3 weeks(p<.05). The blood flow of the middle cerebral artery of the sample group was significantly increased, and VAS was significantly decreased in both groups. Conclusions : The silver-spike-point low-frequency electrical-stimulation treatment, applied to acupuncture points, can significantly increase the blood flow of the middle cerebral arteries in headache patients and can thus alleviate their headaches.

• 설비공학논문집
• /
• 제18권2호
• /
• pp.129-136
• /
• 2006

Optimal design of an air-to-liquid finned plate heat exchanger is considered theoretically in this study. Based on existing correlations for the pressure loss and the heat transfer in channel flows, the optimal configuration of the plate heat exchanger including the optimal plate pitch and the optimal fin pitch is obtained to maximize the heat transfer within the limit of the pressure drop for a given flow depth of the plate heat exchanger. It is found that the optimal fin pitch is about one ninth of the optimal plate pitch. In the optimal configuration, the flow and thermal condition in the channels is just at the boundary between the laminar developing and laminar fully developed states. It is also found when reducing the flow depth of plate heat exchangers for compactness, the heat transfer performance can be maintained exactly the same if the geometric parameters such as the plate thickness, plate pitch, fin thickness, and fin pitch are reduced proportional to the square root of the flow depth as long as the flow keeps laminar within the heat exchangers.

• 대한기계학회논문집B
• /
• 제30권8호
• /
• pp.722-730
• /
• 2006

In this study, the flow characteristics of a FPN (Fountain Pen Nano-Lithography) using active membrane pumping are investigated. The FPN has integrated chamber, micro channel, and high capacity reservoir for continuous ink feed. The most important aspect in this probe provided control of fluid injection using active membrane pumping in chamber. The flow rates in channel by capillary force are theoretically analyzed, including the control of the mass flow rates by the deflection of the membrane. The above results are compared with the numerical simulations that calculated by commercial code, FLUENT. The velocity of the fluid in micro channel shows linear behaviors. And the mass flows are proportional to the second order function of the pumping pressure that is imposed to the membrane.

• 대한전자공학회논문지TC
• /
• 제41권2호
• /
• pp.31-40
• /
• 2004

Diff-Sew는 개별적으로 구분된 다른 트레픽에 대해서 다른 종류의 네트워크 서비스를 제공하기 위한 메카니즘이며 이용자들에게 양질의 서비스를 제공하기 위한 방법을 제시하고 있다. DS는 토큰 버켓 방법을 사용하여 고정된 호스트들에게 제공되기 때문에 이동성을 가지는 서비스나 개별적인 트레픽에 대한 차등적인 서비스를 제공할 방안이 존재하지 않는다 본 논문에서는 트래픽컨테이너(TC)를 위해서 WFQ 방법과 변방 노드들과 경계 라우터들 내부에서 제어가 가능한 AggF(Aggregate Flow)를 모니터링하여 스케쥴링하는 방법을 제시한다. 이 방법은 트래픽 비율(traffic rate)을 유동적으로 제어가 가능하며 대역폭의 효율적인 이용성을 제공하고 있다.

• 한국통신학회논문지
• /
• 제29권12B호
• /
• pp.1052-1062
• /
• 2004

지금의 high-speed TCP 프로토콜은 공정성과 TCP friendliness에 심각한 문제가 있으며, 이는 high-speed TCP의 도입에 있어 중요한 문제가 된다. 본 논문에서는 high-speed TCP의 버스터한 특성을 줄여 TCP friendliness와 공평성 향상시키는 방안으로 high-speed TCP에 pacing 적용을 제시하고 성능 분석을 수행하였다. Pacing은 TCP 송신원의 수정만으로 적용 가능하며 TCP 혼잡 제어 방식과는 독립적으로 동작하기 때문에 도입이 쉽다는 장점을 가진다. 시뮬레이션 결과 제안된 방안은 high-speed TCP의 버스터한 특성을 효과적으로 줄이고 성능 저하 없이 기존의 high-speed TCP에 비해 향상된 TCP friendliness와 RTT에 따른 공정성을 제공함을 보였다.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1999년도 춘계 학술대회논문집
• /
• pp.155-161
• /
• 1999

The three-dimensional turbulent cascade flows with and without endwall fences are numerically investigated by solving the incompressible Navier-Stokes equations with a high-Reynolds number $k-{\varepsilon}$ turbulence closure model. A projection method based algorithm is used in the finite-volume formulation, with the second order upwind-differencing scheme for the convective terms. First, assessments on accuracy of the present method are made by comparing the static pressure distributions at the mid-span of the cascade with measured data, and also by confirming the experimental observations on the choice of an optimal fence height for the secondary flow control. In understanding the three-dimensional nature of the secondary flow in turbine cascade, the limiting streamline patterns and the static pressure contours at the suction surface of the blade as well as on the cascade endwall are employed to visualize the effectiveness of the endwall fence for the secondary flow control. Analysis on the streamwise vorticity contour maps along the cascade with the three-dimensional representation of their iso-surfaces reveals the strucuture of the complicated vortical flow in the turbine cascade with endwall fence, and also leads to an understanding on formation of the counter-rotating streamwise vortex over the endwall fence, in explaining the mechanisms of controlling the secondary flow and also for the proper selection of an optimal fence height.

• 한국시뮬레이션학회:학술대회논문집
• /
• 한국시뮬레이션학회 1997년도 춘계 학술대회 발표집
• /
• pp.23-28
• /
• 1997

We discuss development of a simulator for automated manufacturing systems (AMSs) which have sophisticated automated material handling equipments and complicated work flows. The simulator is designed to satisfy the following requirements. A user should be able to easily configure or specify an AMS through a graphical user interface (GUI) and minimal data input. The user should be able to model diverse and complied control logic for automated material handling systems like automated guided vehicle (AGV) systems, robot workcell systems and conveyor systems as well as complicated job flow program. Real time animation is desired. Finally, the simulator should be easily maintained and extended. To satisfy the requirements, we use an object-oriented paradigm for modeling, designing, and programming of the simulator. We use an object-oriented modeling framework to design the modeling elements library, and take the process interaction approach for scheduling processes and events. To model a user-defined diverse control logic, we also develop a script language and its interpreter. We explain design and implementation strategies. We implement the simulator using Visual C++ 4.2 and Open GL on Windows NT and the Windows95. Some modeling examples will be demonstrated.

• 항공우주기술
• /
• 제1권2호
• /
• pp.51-56
• /
• 2002

위성 추진계는 궤도 천이와 수정 및 제어에 사용된다. 저궤도 위성의 단기추진제 공급 시스템은 추력기 연소실로 연료를 밀어내어 공급한다. 추력기에 의해 생성되는 추력은 연소실로 공급되는 연료량에 종속된다. 만약 위성에 탑재된 명령기로부터 추력기 밸브에 개폐 신호가 주어지면 밸브는 개방되거나 닫힌다. 개방된 추력기 밸브를 통해 연료가 유입될 때 밸브의 자동에 의한 순간적인 흐름 단절은 압력파에 의한 비정상 압력을 발생시킨다. 이 논문에는 래칭 밸브와 추력제어 밸브의 작동에 의한 다목적실용위성 2호 추진계의 비정상 압력이 예측되어 있다. 시간-종속 유체질량 및 운동량 방정식은 특성곡선해법(MOC)으로 계산된다.

• 대한조선학회논문집
• /
• 제48권6호
• /
• pp.544-551
• /
• 2011

The internal flows of moonpool usually causes huge added resistance on drillships, and those are very complex to analyze. Therefore, not only experimental approaches but also numerical simulations are required for better investigations when dealing with the hydrodynamic problems of moonpool. In the present research, numerical simulations are used to find out why the resistance increases by moonpool on a running drillship. That is, the three-dimensional numerical simulations and model tests are carried out to examine the characteristics of internal flow and added resistance by changing the section of the moonpool in both longitudinal and transverse directions. Finally, based on the present studies, an optimized shape of the moonpool is suggested, which effectively reduces added resistance, and that is confirmed with three-dimensional numerical simulations and model tests.

• 한국통신학회논문지
• /
• 제17권10호
• /
• pp.1117-1130
• /
• 1992

본 논문에서는 컴퓨터 망을 통한 분산 시스템의 효율적인 프로세스 관리 및 메시지 전송을 위한 프로세스 그룹 통신에 관하여 연구한다. 메시지 전송중 장애가 발생할 수 있는 단일 프로세스 그룹에 대하여 송수신 메시지의 순서호를 유지하면서 흐름 제어를 실시하는 멀티캐스트 프로토콜을 제안한다. 프로세스 그룹을 형성하는 구성원들은 그룹 구성원 관계 서비스를 이용하여 실행중 그룹을 탈퇴할 수도 있고, 또한 새로운 구성원의 가입도 언제든지 가능하도록 하였다. 메세지 배달은 벡터 타임 논리적 타임 스템프를 이용하여 필요하다면 메세지 배달지연을 행하고, 구성원 변경에 대응하기 위한 가상적 동기화를 실시한다. 결론적으로 본 논문에서 제안되는 멀티캐스트 프로토콜은 메세지들의 인과적 배달순서를 유지하면서, 또한 과잉 밀집 현상등을 방지하기 위한 흐름제어 기법을 적용하여 신뢰성과 메세지 전송 효율성을 갖도록 설계하였다.