• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.625-633
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• 2015

In this study, a coupled probabilistic framework is developed to assess wind risk on apartment buildings by using the convolution of wind hazard and fragility functions. In this framework, typhoon induced extreme wind is estimated by applying the developed Monte Carlo simulation model to the climatological data of typhoons affecting Korean peninsular from 1951 to 2013. The Monte Carlo simulation technique is also used to assess wind fragility function for 4 different damage states by comparing the probability distributions of the window system's resistance performance and wind load. Wind hazard and fragility functions are modeled by the Weibull and lognormal probability distributions based on simulated wind speeds and failure probabilities. The modeled functions are convoluted to obtain the wind risk for the different damage levels. The developed probabilistic framework clearly shows that wind risk are influenced by various important characteristics of terrain and apartment building such as location of building, exposure category, topographic condition, roof angle, height of building, etc. The risk model presented in this paper can be used as tools to predict economic loss estimation and to establish wind risk mitigation plan for the existing building inventory.

• Journal of Radiation Protection and Research
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• v.39 no.1
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• pp.30-37
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• 2014

Recently High-Definition Reference Korean-Man (HDRK-Man) and High-Definition Reference Korean-Woman (HDRK-Woman) were constructed in Korea. The HDRK phantoms were designed to represent respectively reference Korean male and female to calculate effective doses for Korean by performing Monte Carlo dose calculation. However, the Monte Carlo dose calculation requires detailed knowledge on computational human phantoms and Monte Carlo simulation technique which regular researchers in radiation protection dosimetry and practicing health physicists do not have. Recently the UFPE (Federal University of Pernambuco) research group has developed, and opened to public, an online Monte Carlo dose calculation system called CALDOSE_X(www.caldose.org). By using the CALDOSE_X, one can easily perform Monte Carlo dose calculations. However, the CALDOSE_X used caucasian phantoms to calculate organ doses or effective doses which are limited for Korean. The present study developed an online reference Korean dose calculation system which can be used to calculate effective doses for Korean.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.326-328
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• 2008

본 논문의 목표는 실제 시스템과 가장 유사한 이중여자 유도발전기(Doubly-Fed Induction Generator)의 시뮬레이터를 구현하고 실험을 통해서 그것을 검증하는 것이다. 바람의 속도를 2D 룩업 테이블을 이용하여 데이터화 한 후 터빈 모델의 입력으로 인가한다. 터빈 모델의 파라미터는 실험용 이중여자 유도발전기의 것과 동일하게 설정하여 실제 시스템과 유사하게 하였다. 지금까지는 이중여자 유도발전기를 모사하기 위하여 매트랩(Matlab) 등을 이용하였지만 실제와 다소 다르다는 문제와 구현하기 힘들다는 문제를 가지고 있었다. 하지만 본 논문에서는 심플로러(Simplorer)를 이용하여 쉽고 정확한 시뮬레이터를 구현하였다. 터빈과 이중여자 유도발전기는 기어를 이용하여 직결함으로써 실제 시스템과 매우 가깝게 모사하였으며 이중여자 유도발전기의 회전자를 여자시키기 위해 이산 캐리어 변조 방법을 이용하여 매트릭스 컨버터를 구동하였다. 그리고 실험을 통해서 시뮬레이터의 결과와 실험 결과의 비교 및 검증을 한다. 궁극적으로 어떤 지역의 바람의 품질과 발전량 등 중요한 정보를 얻기 위해 실제 크기의 발전기를 설치하지 않고 본 논문에서 개발한 시뮬레이터를 이용하여 쉽게 그 정보들을 얻을 수 있다.

• Journal of Energy Engineering
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• v.6 no.1
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• pp.87-95
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• 1997

A chemical heat pump based on the reversible reactions between metal chlorides and ammonia gas is attractive alternative to compression system and liquid absorption systems in cooling and refrigerating fields. The advantages of chemical heat pump are no regulatory constants due to CFC refrigerants, utilization of gas, industrial waste heat, electricity, fuel oil etc. as heat sources and wide applications to energy storage system, large-scale energy managements for industrial process. The scale-up of chemical heat pump from laboratory prototype to pilot plants necessitates the interpretation of system performance and evaluation of dynamic behavior in the chemical reactor. This study contains the prediction of performance of chemical refrigerator according to operating condition, the dynamic simulations through reactor modelling, which is used for the calculation of reactive medium temperature and the conversion variation with reactor cooling temperature, and the effect survey of block parameters on the power of refrigerator.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.3
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• pp.38-44
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• 2003

In this study, a performance model of the smart UAV propulsion system with ducts, tip jets and variable main nozzle, which has flight capability of the rotary wing mode for the take-off/landing and low speed forward flight as well as the fixed wing mode for high speed forward flight, has been newly developed With the proposed model, steady-state performance analysis was performed at various flight modes such as rotary wing mode, fixed wing mode, compound ing mode and altitude as well as at flight speed conditions. In investigation of performance analysis. it was noted that the operational capability of the propulsion system was limited due to the duct losses depending on each flight mode, and the limitation with the altitude variation case had much greater than that with the flight speed variation case.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.53-61
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• 2006

Axisymmetric numerical thermal analysis for a 3-dimensional regenerative cooling system in a rocket engine is carried out. To predict the accurate heat transfer with the stiff temperature distribution, several tests have been conducted for the grid size, the properties variation of the coolant and the combustion gas depending on temperature. The axisymmetric heat flux model is defined using fin efficiencies and is designed to be equivalent to the heat flux of the 3-dimensional coolant channel. For comparison purpose, the 1-dimensional analysis using Bartz equation is also conducted. The performance of the present model in predicting the cooling characteristics of a 3-dimensional regenerative cooling system is compared with the 3-dimensional results of RTE(Rocket Thermal Evaluation). It is found that the present method predicts much closer results to those of RTE code than 1-dimensional analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.76-83
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• 2004

A Propulsion System of the CRW(Canard Rotor Wing) type UAV(Unmanned Aerial Vehicle) was composed of the turbojet engine to generate the propulsive exhaust gas, and the duct system including main and rotary ducts, the nozzle subsystem including main and tip jet nozzle for three flight modes such as lift/landing mode, low speed transition flight mode and high speed forward flight mode. Transient simulation performance utilized the ICV (Inter-component volume) method and simulated using the SIMULINK. Transient performance analysis was performed on 3 cases. Fuel flow schedules to accelerate from Idle to maximum rotational speed were divided into the step increase of the most severe case and ramp increase cases to avoid the overshoot of turbine inlet temperature, and variations of thrust and the turbine inlet temperature were investigated in some transient analysis cases.

• Korean Journal of Optics and Photonics
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• v.19 no.3
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• pp.237-241
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• 2008

An all-optical encryption system built on the basis of electrical logic circuit design principles is proposed, using semiconductor optical amplifier (SOA) exclusive or (XOR) logic gates. Numerical techniques (steady-state and dynamic) were employed in a sequential manner to optimize the system parameters, speeding up the overall design process. The results from both numerical and experimental testbeds show that the encoding/decoding of the optical signal can be achieved at a 10 Gbps data rate with a conventional SOA cascade without serious degradation in the data quality.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.129-132
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• 2008

For the development of the 30tonf level LOx/kerosene liquid rocket engine, turbopump-gas generator closed-loop coupled tests are performed. To simulate engine operation conditions, combustion chamber was substituted by flow control orifices. In simulated engine system operation environment, chill-down procedure, startup characteristics, nominal operability of turbopump+gas generator coupled Test Plant are confirmed. Turbopump and gas generator are confirmed to operate well in simulated engine environment. The control system for regulating power and mixture ratio of Test Plant are also successfully confirmed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.1
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• pp.88-97
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• 2016

A closed loop thermal control system simulates space thermal environment to verify the satellites' functionality in extremely cold/hot temperature. It is composed of a cryogenic blower, thermal shroud, heater, cryogenic valves. This paper presents an overview of closed loop thermal control system's design parameter and test results for control parameter. A capacity of blower is calculated through energy balance equation and an advantage/disadvantage for a shroud material and a type was analysed. The thermal control system is controlled by a constant density of fluid in the system. A requested performance of closed loop thermal control system was verified by measuring a homogeneity and stability of shroud through control parameter such as density and RPM of blower.