• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.710-719
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• 2002

This study investigates a nonlinear inverse convection problem for a laminar-forced convective flow between two parallel plates. The upper plate is exposed to unknown heat flux while the lower plate is insulated. The unknown heat flux is determined using temperature measured on the lower plate. The thermophysical properties of the fluid are temperature dependent, which renders the problem nonlinear. The sequential gradient method is applied to this nonlinear inverse problem in order to solve the problem efficiently. The function specification method is incorporated to stabilize the sequential estimation. The corresponding adjoint formalism is provided. Accuracy and stability have been examined for the proposed method with test cases. The tendency of deterministic error is investigated for several parameters. Stable solutions are achieved eve]1 with severely impaired measurement data.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.636-651
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• 2000

In these days, SNCF replace the connector wire (M-T type) with a dropper has a equivalent role and function of the one in general lines of TGV, and change the connector wire (T-T-M-M-T-T, T-T-M-M-T type, etc) into a New one has more flexible cable in parallel lines (air section air joint, etc) of TGV. The Connector wire has many problems according to a flow of excessive circulation current (or traction current) and a sudden rise of temperature on catenary when electric locomotive is running in high speed. To solve the question at issue of the connector wire in high speed railway catenary system of Fiance, SNCF return their operating experience in TGV lines to design and execution of catenary system Therefore, we have to deal with the question in design and execution of catenary system for kyoungbu HSR line because we will spend a lot of time and more money for maintenance than for construction of that.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.4
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• pp.318-323
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• 2004

When a strong electric field is applied between a sharply curved electrode and a blunt surface, the corona may result in a gas movement in the electrode gap which is directed toward the blunt surface. That is called the corona wind. It enhances heat and mass transfer between the surface and the surrounding gas. Moreover such enhancement causes no noise or vibration, which can be applied in complex, isolated geometries, and allows simple control of surface temperatures. This paper examines the relationship between the corona wind and the relative humidity. The facility consists of high voltage power supply thin tungsten wire, plate electrode, multimeter, microammeter and flow meter. Gas velocity is a linear function of voltage, relative humidity and is proportional to the square root of the current. The maximum velocities for the positive and negative corona discharge are 1.9 m/s (2.74 CMM/m), 1.5 m/s(2.15 CMM/m), respectively.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1267-1271
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• 2009

In the present study, performance characteristics on environment change of A/C applied fin-tube and PF heat exchangers were experimentally investigated. Capacity and COP changing an outlet air velocity, an indoor/outdoor temperature and a relative humidity were obtained. Air－enthalpy calorimeter was used. As the air velocity, indoor temperature and relative humidity increase, capacity and COP increase. PF A/C has smaller refrigerant weight than the fin-tube A/C. The performance of PF-2 A/C with the squarer fin was more excellent than that of PF-1 A/C with the triangler fin.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.71-79
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• 2016

This paper introduces the design method of the centrifugal turbo fan and the process of developing the design program of it. The developed design program confirmed the applicability by experimental performance data. Here, we proposed new velocity coefficients and considered various losses such as impeller inlet loss, vane passage flow loss, casing pressure loss, recirculation loss power, and disk friction loss power. Especially, the inlet and outlet widths of the impeller were newly determined by reflecting the experimental results. As a result, this fan design program shows a good performance result regardless of the types of impeller and is expected to be a very useful design tool.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1949-1950
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• 2008

Activation battery that are required to deliver short pulses to power, for instance, pyrotechnic devices required during jettison payload separation. Activation battery contains 24 Sony US18650 cells configured as 3 strings in parallel, with each string containing 8 series connected cells. This allows to meet voltage and capacity requirements specified for the mission. In this paper design description and specifications of Activation battery are presented. Qualification test flow and results are also shown to make sure the performance in the predicted space environment. Electrical performance was proven on real equipment load assembly.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1661-1662
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• 2008

After steam turbines in power plant drives generator and maintains it at rated speed using high temperature and high pressure steam energy, they regulate the output of generator when synchronized in parallel with the power system. By the way, as the steam flow into turbine can not be reduced fast even though the electrical load is lost, the turbine gets into dangerous situation due to the increase of its speed. At this time, the duty of the turbine governor is "how to limit the speed within its overspeed trip setpoint and escape from danger." In order to implement this purpose, there are various ways different from valve position control. So, in this paper, the various methods for overspeed protection are introduced in comparison with valve position control.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.193-200
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• 1999

An unstructured implicit Euler solver is parallelized on a Cray T3E. Spatial discretization is accomplished by a cell-centered finite volume formulation using an unpwind flux differencing. Time is advanced by the Gauss-Seidel implicit scheme. Domain decomposition is accomplished by using the k-way N-partitioning method developed by Karypis. In order to analyze the parallel performance of the solver, flows over a 2-D NACA 0012 airfoil and a 3-D F-5 wing were investigated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.101-111
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• 1988

This thesis investigated the variation of the seepage line of earth structure when the water level rises and drawdowns and compare this with the hither to published formula. And, analysised by a vector in embankment model's seepage velocity of followed rises and drawdowns. And, by the experimental method find difference point per follow drawdown and rises in the same model.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.1-6
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• 2000

In this study, We evaluated the Performance of PFC and the system performance of large size air-conditioner applying to outdoor condenser. PFC can meet the same cooling capacity in 40.42% of volume to fin-tube condenser. Although the fin-tube condenser requires 3600g of refrigerant charging, PFC requires 1700g, 1800g, 1900g, 2000g refrigerant charging for each 2.0mm, 2.5mm, 3.0mm and 3.5mm fin pitches. Difference of condensing and evaporation pressure is the biggest point 2.0mm fin pitch and the smallest point 2.5mm fin pitch.