• 한국가시화정보학회:학술대회논문집
• /
• 2002.11a
• /
• pp.117-120
• /
• 2002

An experimental research has been carried out for flow control of the shock wave/turbulent boundary-layer interaction utilizing aeroelastic mesoflaps. Various shapes and thicknesses of the mesoflap are tested to achieve different deflections of the flap, and ail the results are compared to the solid-wall reference case without flow-control mechanism. Quantitative variation of skin friction has been measured downstream of the interactions using the laser interferometer skin friction meter, and qualitative skin friction distribution has been obtained by observing the interference fringe pattern on the oil-film surface. A strong spanwise variation in the fringe patterns with a narrow region of separation near the centerline is noticed to form behind the shock structure, which phenomenon is presumed partially related to three-dimensional flow structures associated with both the sidewalls and the bottom test surface. The effect of the shape of the cavity is also observed and it is noticed that the shape of the cavity is not negligible.

• 한국태양에너지학회:학술대회논문집
• /
• 2009.04a
• /
• pp.109-114
• /
• 2009

The dominant heating system used in Korean residential apartment buildings is a hydronic radiant floor heating system, known as the Ondol system. The most common control strategy applied to this traditional hydronic radiant system is a simple on-off control that intermittently supplies "hot water of a fixed temperature" at a "constant flow rate" to each room. However, the current problems with the aforementioned control are as follows: (1) since the simple on-off control is usually based on a one point measured temperature (a signal from a thermostat installed in a living room) in each dwelling unit, heating energy use for unoccupied rooms as well as a difference in temperatures between spaces (master bedroom, living room, bedroom1, bedroom2) can occur occasionally. (2) the most widely used residential water splitter has static valves, and is thus not able to change the flow rate to each room depending on the space heating load. In other words, the ratio of flow rates to rooms is fixed after construction, resulting in over- or under-heating and an improper use of energy. The aim of this paper is therefore to investigate the differences in the system's performance between control strategies in terms of the flow rate control and sensor location. It is shown that energy savings of control strategies are strongly influenced by occupant schedule.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.368-373
• /
• 2005

This paper presents a new framework for the traffic flow control based on integrated model descriptions as the Hybrid Dynamical System (HDS).

• Journal of Haehwa Medicine
• /
• v.15 no.2
• /
• pp.263-272
• /
• 2006

Purpose Brain vessles have autoregulation function, so even when perfusion pressure drops, cerebral blood flow remain stable by vasodilation. Latest research on this reserve of cerebral vessels is being done using TCD, which measures the reserve of the vessels. We did a research comparing cerebral vessel and peripheral vessel reserve between Taeumin, who are more likely to suffer CVA, and the normal. We observed blood flow of Internal carotid artery siphon and radial indicis artery of the two group with TCD. Method We picked 20 people out of patients diagnosed as cerebral infarction at Cheon-An Oriental hospital of Daejeon University. They were diagnosed as Taeumin with QSCCII questionnaire and constitutional differentiation. Using TCD, we measured highest blood flow rate, mean blood flow and asymmetric counting blood flow of Internal carotid artery siphon and radial indicis artery at rest. And then we measured again after stimulating cerebral vessels, by triggering hypercapnia by self apnea and peripheral vessels by palm heating. Result At rest, mean blood flow rate of Internal carotid artery siphon showed significant decrease compared to control group. Blood flow rate of Internal carotid artery siphon after hypercapnia showed significant decline in highest blood flow rate and mean blood flow compared to control group. Cerebral vessel reaction after the hypercapnia induction showed great change in experiment group than the control group. Peripheral vessel reaction after palm heating showed significant decline in experiment group compared to control group. Conclusion In conclusion, measuring the alteration of blood flow used in diagnosing cerebral infarction, is more sensitive when vessel stimulation is done. Non-invasive TCD is effective especially in case of Taeumin who are more likely to suffer vascular disorder than others.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.119-122
• /
• 2002

In general, Liquid Injection Thrust Vector Control(LITVC) is accomplished by injecting a liquid into the supersonic exhaust flow through holes in the wall of the propulsion nozzle. This injection flow field is highly complicated and detailed flow physics associated with the secondary flow injection should be known far the practical design and use of the LITVC system. The present study aims at understanding the LTTVC flow field and obtaining fundamental design parameters for LITVC. The experimentations were performed in a supersonic blow-down wind tunnel. Compressed, dry air was used for both the main exhaust and injection flows but the pressures of these two flows were controlled independently. The location of the injection holes was changed and the pressures of the two streams were also changed between 2.0 and 15.0 bar. The effectiveness of LITVC was discussed in details using the results of the pressure measurements and flow visualizations

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2012.05a
• /
• pp.443-446
• /
• 2012

A thrust control valve of a liquid rocket engine plays a role to increase or decrease the thrust of an LRE by modulating the flow rate of propellant into a gas-generator. This paper deals with a flow regulator that has functions of not only modulating thrust but also maintaining constant flow rate regardless of pressure change at inlet or outlet of the flow regulator. A direct acting flow regulator was fabricated and tested for the comparison of experimental and simulation results under steady-state conditions. The drawbacks and limitations of the flow regulator were analyzed. Also the new design of a flow regulator was proposed.

• Journal of Drive and Control
• /
• v.16 no.4
• /
• pp.1-8
• /
• 2019

The HPM (High-speed Power Matching) system is an electro-hydraulic control system. It directly controls the swash plate of the pump by selecting four-loop logic based on joystick signals, pump flow, and pressure signal to improve the efficiency and controllability of construction machines. In the NFC (Negative Flow Control) system, a typical pump control system using conventional open center type MCV, the loss is continuously generated by flow through the center bypass line even when the excavator is not in operation. Also, due to the slow response of the pump that indirectly controls the flow rate using the pressure regulator, peak pressure occurs at the start or stop of the operation. Conversely, the HPM system uses an MCV without center-by-pass flow path and the swash plate of a pump for the HPM is controlled by a high-speed proportional flow control valve. As a result, the HPM system minimizes energy loss in standby state of the excavator and enables peak pressure control through rapid electro-hydraulic control of a pump. In this paper, the concept of the HPM system algorithm is introduced and the hydraulic system efficiency is compared with the NFC system using the excavator SAT (System Analysis Tool).

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.4 no.2
• /
• pp.313-322
• /
• 2000

The ATM Forum has been focusing on flow control mechanism for ABR traffic management. The goal of this activity is to efficiently manage the leftover network bandwidth and fairly distribute it among contending ABR VC so that communication links can be optimally utilized. ABR traffic is difficult to predict traffic shape because it has bursts and variable behavior. Also it's sensitive to lose but not to delay. This behavior makes difficult to UPC function in network and cause of congestion in switch, thus performance is degraded. To resolve this problem, various flow control mechanism has been worked in the ATM Forum. Especially, the rate-based flow control mechanism for ABR traffic has been standardized in the ATM Forum, Sept. 1994. Thus, various flow control mechanism has been working which likes EFCI, ER, VS/VD. VS/VD control is superior than existed ER control because it isolate different networks from each other. In this paper, we propose an expanded VS/VD flow control algorithm and compare with existed VS/VD flow control algorithm. Simulation result shows that this algorithm improve a problem in aspect of delay and fairness.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.1
• /
• pp.110-118
• /
• 2008

It is essential for the valid design of a marine flow-control valve to exactly know its flow characteristics. The present study has numerically investigated the flow characteristics inside a marine throttle-type globe valve using a kind of commercial CFD code, CFX10.0, with an adoption of the SST (Shear-Stress Transport) turbulence model. To validate the numerical approach, the flow coefficients are compared with the experimental ones. Results show that the globe valve is effective in the control of flow rate according to the opening ratio in case of the forward-direction flow, whereas it is effective in the flow shutoff in case of the reverse-direction flow. Around the inlet of the valve, a recirculation region is formed due to the blunt body shape, the turbulence intensity becomes strengthened and then an abrupt pressure loss occurs.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.5
• /
• pp.121-128
• /
• 2000

Simple design methods were developed to control the coolant flow rates through cylinder head gasket holes. Applying the concept of flow through an obstruction the ratio of intake to exhaust side flow rates could be easily controlled while maintaining the flow rates per cylinder of the original model. Flow distribution in the coolant passage of the original model was calculated by CFD and the flow rates at the gasket holes were modified based on the calculation results. The calculated flow rated of the modified gasket holes were reasonably close to target values. For more accurate control of the flow rate distribution, a design method with iterative CFD calculations was also suggested. The final size of gasket holes for the target flow rates were obtained just after a few optimization iterations. These methods can be very useful for the optimization of heat transfer characteristics in engine cylinder head and block.