• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.147-154
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• 2008

The purpose of this study is to critically evaluate the structural performance of an innovative new shear resistance connecting structure of precast member. Joints such as shear resistance connecting structure require special attention when designing and constructing precast segmental structures. An experimental and analytical study was conducted to quantify performance measures and examine one aspect of detailing for developed shear resistance connecting structure. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. A joint element is used to predict the inelastic behavior of the joints between segmental members. Future work by the authors will do a model test of precast segmental prestressed concrete bridge columns with this shear resistance connecting structure, and examined both the structural behavior and seismic performance.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.105-115
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• 2009

Numerical analysis of shear walls governed by flexural behavior is conducted for the seismic control performance of proposed friction dampers installed at the center of coupling beams. Control effectiveness of shear walls connected by beams with the proposed dampers are compared for single shear wall with same flexural rigidity. Average responses of the shear walls with the dampers are found with seven scaled-downed earthquakes based on KEC 2005 design spectrum. Slip load is the most important design parameter. It is designed to be 5, 10, 20, 30, 60, 90% of total vertical shear force at damper location to prevent damper slip in specific stories. Nonlinear time-history analysis is conducted by using SeismoStruct analysis program. Seismic control performance of the dampers is evaluated for base shear, energy dissipation, curvature and top-floor displacement. Results show that the dampers are the most effective in reducing the responses when their total slip load is 30% of total vertical shear force.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.51-57
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• 2004

An intelligent performance diagnostic computer program of a gas turbine using the NN(Neural Network) was developed. Recently on-condition performance monitoring of major gas path components using the GPA(Gas Path Analysis) method has been performed in analyzing of engine faults. However because the types and severities of engine faults are various and complex, it is not easy that all fault conditions of the engine would be monitored only by the GPA approach Therefore in order to solve this problem, application of using the NNs for learning and diagnosis would be required. Among then, a BPN (Back Propagation Neural Network) with one hidden layer, which can use an updating learning rate, was proposed for diagnostics of PT6A-62 turboprop engine in this work.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.2171-2180
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• 1991

An analysis model for off-design performance of radial inflow turbines with or without variable area guide vane is developed, where two important factors in loss models, total pressure ratio between variable area guide vane exit and scroll casing inlet and rotor loss coefficient are determined without experimental data. The analysis results show that the predicted trends with or without variable area guide vane are consistent with the experimental observations. The comparison of present method with the well-known NASA off-design performance analysis program shows that the mass flow rate and static efficiency by present analysis are in good agreement with those by the NASA program. Therefore, this method can be used to predict off-design performance of radial inflow turbines with validity of the loss models used by present analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.12
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• pp.1201-1207
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• 2012

This study was performed to develop a high-efficiency submersible nonclogging pump impeller. Toward this end, we simulated the effect of some parameters such as the outlet position of a blade ($h_I$), outlet width of a blade ($b_2$), and hub profile on the pump efficiency by using the commercial codes ANSYS CFX and BladeGen. The results showed that the pump efficiency was proportional up to $h_I$= 38 mm and $b_2$= 55 mm. It remained constant over these values. However, the head and shaft power were proportional to $h_I$ and $b_2$ in the simulated ranges. The effects of hub profile changes on the pump efficiency were relatively small compared to those of the other parameters.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.151-160
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• 2022

Owing to the recent increase in the frequency of explosion accidents, blast resistive design has garnered attention to reduce the damage of important structural elements. However, domestic research on the blast resistive structures is still insufficient, and domestic design guideline against blast loads are not documented yet. In this study, a numerical study on the RC blast resistive walls, where the test variable was the presence of FRP sheet, was performed using LS-DYNA program. Based on the numerical results, displacement-time hysteretic curve, pressure-impulse diagram, and fragility curve of the test specimens were derived. It was shown that the FRP sheet strengthening method is efficient to improve the blast resistive performance of the RC wall. Also, the strengthening effect of FRP sheet on the RC wall was stronger when the magnitude of the blast load was greater.

• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.76-85
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• 2024

Recently, from a global perspective, the use of small unmanned aerial vehicles in terrorism and warfare is increasing, and the need for anti-drone shooting training targeting small UAVs is increasing. However, in reality, there are many cases in Korea where anti-drone shooting training is restricted, due to complaints such as noise. In this paper, we describe the development and testing of an electric-powered direct strike type high-speed, low-noise small aerial target drone. To achieve the flight speed and endurance required for shooting training, target drone sizing was performed, and aerodynamic performance analysis was conducted using a CFD program. Based on the performance analysis, the motor propulsion system was selected and a variable pitch propeller system was designed, and performance tests were performed on a ground test rig. Finally, the target flight speed, flight time, and flight noise level were confirmed through flight tests.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.697-703
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• 2017

A teflon ionization modeling has been conducted to predict the performance of a PPT(Pulsed Plasma Thruster). One dimensional unsteady circuit model and Teflon ablation model were implemented. The Saha equation was adapted to predict the ionization of Carbon and Fluorine gas. The lumped circuit model including a resistance and a inductance model of a plasma was adapted to predict the magnitude of a discharge current. Numerical simulation results had good agreements with pervious research. The degree of current change according to PPT operating voltage was examined.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.289-291
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• 2005

고도화, 정보화시대를 맞이하여 대형인버터, 컴퓨터 등 전력풀질을 저하시키는 비선형 부하의 보급이 확대되고 있으며, 이들 비선형부하에 의한 전력품질 저하시 공정제어기, 마이크로프로세서 등과 같이 전력품질에 매우 민감한 기기의 오동작 등으로 경제적 피해가 증대되고 있다. 따라서 중요부하 및 계통을 보호하기 위한 전력전자 기술을 응용한 전력품질 보상기기 적용이 필요하다. 이에 본 연구에서는 전력품질 향상기기 성능평가 텐 실증기술 개발을 위한 전력풀질 실증시험장 구축 및 전력풀질 향상기기 실계통 적용시 효과분석을 위한 해석기법을 확보하고자 하였다. DSTATCOM, DVR, SSTS 등 전력품질 향상기기의 성능평가를 위해서 실계통에서 발생되는 외란을 모의할 수 있는 외란발생장치 등 시험설비와 전력품질 향상기기 및 실증시험설비를 제어하는 S/W와 시험결과를 분석하기 위한 전력품질 측정 및 분석시스템을 구축하였다. 순간전압강하, 순간전압 상승 파형을 외란발생장치를 구현하고 전력품질 향상기기의 보강효과를 분석하였다. 또한 전력품질 향상기기(DVR, DSTATCOM, SSTS)와 부하 등 시험설비에 대하여 EMTDC 프로그램용 모델 및 해석기법을 개발하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.267-270
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• 2003

An intelligent performance diagnostic computer program of a gas turbine using the NN(Neural Network) was developed. Recently on-condition performance monitoring of major gas path components using the GPA(Gas Path Analysis) method has been performed in analyzing of engine faults. However because the types and severities of engine faults are various and complex, it is not easy that all fault conditions of the engine would be monitored only by the GPA approach. Therefore in order to solve this problem, application of using the NNs for learning and diagnosis would be required. Among then, a BPN (Back Propagation Neural Network) with one hidden layer, which can use an updating learning rate, was proposed for diagnostics of PT6A-62 turboprop engine in this work.