• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.662-667
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• 2009

상수도시설은 준공후 관련지자체에 이관 관리하는 시설로서 사용관종이 현재 다양하게 생산 보급되고 있어 관종 선정시 다각적인 측면에서 검토하여 채택하여야 한다. 최근 한국토지공사에서 사용하고 있는 상수도 관종은 대부분 택지개발계획 등 인허가 당시부터 관리주체인 지자체 등과의 협의과정을 거쳐 선정되는 경우가 많아 자재선택에 한계성이 있다. 이를 극복하기 위해서는 자재 성능에 대한 공사내 명확한 기준이 제시되어야 한다. 따라서 본 연구에서는 배수관과 급수관용으로 최근 사용되고 있는 관종에 대한 특성을 분석하고, 각각의 관종에 대하여 기본통수성, 내구성, 시공성, 경제성, 외부환경인자로 구분하여 성능평가근거를 제시하였다. 제시된 평가근거를 바탕으로 각 관종의 항목별 평가등급을 부여하고, 이를 통해 좀 더 구체적인 상수관 자재선정 기준을 제시하고자 하였다. 이러한 작업을 뒷받침하기 위한 과정으로 전국 주요 상수관 제조업체를 대상으로 설문조사를 실시하였으며, 다양한 관종에 대한 평가자료를 분석하였다. 본 연구는 상수도관 다양한 성능평가항목 및 기준을 통해 자재성능검토를 수행하였고, 상수관 자재선정기준 제시를 위한 기초자료를 구축하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 1992.07a
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• pp.411-418
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• 1992

The purpose of this study is to develop dynamic-stochastic models that can forecast the inflow into reservoir during low/drought periods and flood periods. For the formulation of the models, the discrete transfer function is utilized to construct the deterministic characteristics, and the ARIMA model is utilized to construct the stochastic characteristics of residuals. The stochastic variations and structures of time series on hydrological data are examined by employing the auto/cross covariance function and auto/cross correlation function. Also, general modeling processes and forecasting method are used the model building methods of Box and Jenkins. For the verifications and applications of the developed models, the Chungju multi-purpose reservoir which is located in the South Han river systems is selected. Input data required are the current and past reservoir inflow and Yungchun water levels. In order to transform the water level at Yungchon into streamflows, the water level-streamflows rating curves at low/drought periods and flood periods are estimated. The models are calibrated with the flood periods of 1988 and 1989 and hourly data for 1990 flood are analyzed. Also, for the low/drought periods, daily data of 1988 and 1989 are calibrated, and daily data for 1989 are analyzed.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.2
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• pp.246-254
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• 2017

In this paper, cooling characteristics of seeker windows were examined using the Sinda-Fluint software. Various cooling methods were considered to satisfy the limit temperature of the cooled seeker window which would be exposed to excessive aerodynamic heating conditions by varying coolant type and mass flow rate of coolant. Due to the enhanced heat transfer between the coolant and the seeker window, internally cooled seeker window which uses liquid coolant showed lowered temperature distribution in the window compared to internally cooled seeker window which uses gas coolant. External film cooled seeker window also showed good cooling characteristics because it reduces the convective heat flux to the seeker window fundamentally. It was also confirmed that the temperature and the temperature gradient of seeker windows were significantly reduced for the cases which use external film cooling additionally to the gas and liquid cooled seeker window.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.158-165
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• 1994

A fiber optic voltage sensor is demonstrated with a new signal processing scheme that displays the magnitude and the waveform of applied voltage with immunity from the signal frequency change. The sensor is based on a Mach-Zehnder interferometer with a PZT phase modulator as a sensing element. We observed a linear relationship between applied voltage and the number of fringe shift during a half cycle of the ac signal. The temperature dependence of the sensor output is experimentally evaluated over the temperature range from $-20^{\circ}C to 80^{\circ}C$. It is demonstrated that the detrimental polarization modulation effect can be overcome by using polarization maintaining fibers or a half-wave plate. plate.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1141-1148
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• 2016

This paper proposed a heart attack predictive monitoring system using QRS pattern of ECG for wearable healthcare. It detects abnormal heart pattern with a ECG (X, Y) coordinate pattern DB on wearable monitoring smart watch. We showed the acute heart failure prevention system and method with a proposed scheme. Especially, It proved the method which can do first aid in gold time through abnormal heart analysis with a digital ECG(X, Y) pattern information when acute heart failure occurs.

• Journal of Korean Institute of Industrial Engineers
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• v.3 no.1
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• pp.39-47
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• 1977

Most of the current literature on inventory theory has been devoted to the study of single stage models. A class of inventory problems which is of great interest is the multistage inventory system which involves a series and hierarchical sequence of stations. This study analyzes some aspect of the series type and multi-stage inventory system, using the fixed cycle ordering which bas a modificatory control function in the system equations. The objective of this study is to clarify the dynamic behavior of the system. The author has derived the theoretical formulas of variation of ordering quantity and stock fluctuation of each stage due to power spectral density function. Influence of parameters such as, (1) intensity of autocorrelation of demand sequence ($\lambda$), (2) forecasting exponential smoothing factors of each stage (${\alpha}_1,\;{\alpha}_2,\;{\alpha}_3$) and (3) production control factor of the 3rd stage ($\gamma$), as operators of the system on the variation of ordering quantity and stock fluctuation of the system. is also clarified. As a result of this study, the relations between the variation of ordering quantity, stock fluctuation and the parameters of the system, have been found. The principles and the theorical analysis presented here will be applicable to more complex type of discrete control systems in constructing the specific condition of the system to minimize inventory variances.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.187-194
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• 2001

Spray impingement and fuel film formation models were developed and incorporated into the computational fluid dynamics code. STAR-CD. The spray/wall interaction process was modeled by considering the change of behaviour with surface temperature conditions and the fuel film formation. We divided the behaviour of fuel droplets after impingement into rebound, spread and splash using the Weber number and the parameter K. The Spray impingement model accounts for mass conservation, energy conservation and heat transfer to the impinging droplets. The fuel film formation model was developed by integrating the continuity, Navier-Stokes and energy equations along the direction of fuel film thickness. Validation of the models was conducted using previous diesel spray experimental data and the present experimental results for the gasoline spray impingement. In all the cases, the prediction compared reasonably well with the experimental results. The spray impingement and fuel film formation models have been applied to the spray/wall impingement in high speed direct injection diesel engines.

• Proceedings of the KAIS Fall Conference
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• 2007.11a
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• pp.367-370
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• 2007

한국수자원공사에서 개발한 유출모의 모형인 RRFS의 입력자료로 사용되는 소유역별 각 용수에 대한 회귀율은 생공용수의 경우에는 65%, 농업용수의 경우에는 35%로 하여 일괄적으로 입력되어 있으나 이러한 값은 대략적으로 추정된 값이다. 따라서 본 연구에서는 금강수계내 전체에 대한 용수체계도를 대청댐 상류, 청주권, 대전권, 대청댐 하류 및 하구언권으로 구분하여 각 권역별로 작성하여 유출체계에 의한 메커니즘을 도시하였다. 본 연구에서는 체계적인 용수이용별 물이용수급현황 분석을 통해 물이용현황을 파악하는 것에 목적을 삼고 용수계통도 작성을 통한 권역별 용수체계를 분석하고자 하였다. 금강유역내 총 14개의 소유역에 대한 용수계통도 작성을 통해 용수수급현황을 분석하고, 궁극적으로 용수수급현황도를 작성하고자 각 권역별 하천 수계현황 조사, 용수사용현황 조사, 주요 용수시설물 현장조사 및 용수계통도를 작성하였다.

• Journal of the Korean GEO-environmental Society
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• v.3 no.4
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• pp.19-27
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• 2002

Prediction of exact soil loss yield has as important engineering meaning as prediction of exact flow measurement in a stream. The quantity of soil loss in a stream should be considered in planning and management of water resources and water quality such as design and maintenace of hydraulic structures : dams, weirs and seawalls, channel improvement, channel stabilization, flood control, design and operation of reservoirs and design of harbors. In this study, the soil loss of Sap-gyo reservoir watershed is simulated and estimated by RUSLE model which is generally used in the estimation of soil loss. The parameters of RUSLE model are selected and estimated using slope map, landuse map and soil map by GIS. These parameters are applied to RUSLE's estimating program. And soil loss under probability rainfall in different frequencies are estimated by recent 30 years of rainfall data of Sap-gyo reservoir watershed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.342-348
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• 2017

In this paper, film cooling characteristics at supersonic free stream conditions were examined experimentally by applying an IR-thermography. Film cooling experiments were carried out in a free-jet facility at Mach number of 3.0 and with unit Reynolds number of $42.53{\times}10^6$ and $69.35{\times}10^6$ using wedge shaped film cooling model which has a converging film cooling nozzle. Film cooling efficiency was calculated by measuring the surface temperature of PEEK(Polyether Ether Ketone) and the effects of angle of attack and blowing ratios on the film cooling efficiency were examined. The measured wall temperature was significantly reduced by the film cooling flow compared with the results without the film cooling flow. The usefulness of film cooling was also confirmed by the surface heat flux calculated using the surface temperature history of PEEK. As the blowing ratio increases the protected area of PEEK was also expanded along the direction of free stream and film cooling flow.