• International Journal of Aeronautical and Space Sciences
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• v.11 no.2
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• pp.145-153
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• 2010

In this work, the comprehensive structural dynamics codes including DYMORE and CAMRAD II are used to validate the higher harmonic control aeroacoustic rotor test (HART) II data in descending flight condition. A total of 16 finite elements along with 17 aerodynamic panels are used for the CAMRAD II analysis; whereas, in the DYMORE analysis, 10 finite elements with 31 equally-spaced aerodynamic panels are utilized. To improve the prediction capability of the DYMORE analysis, the finite state dynamic inflow model is upgraded with a free vortex wake model comprised of near shed wake and trailed tip vortices. The predicted results on aerodynamic loads and blade motions are correlated with the HART II measurement data for the baseline, minimum noise and minimum vibration cases. It is found that an improvement of solution, especially for blade vortex interaction airloads, is achieved with the free wake method employed in the DYMORE analysis. Overall, fair to good correlation is achieved for the test cases considered in this study.

• Journal of the Korea Safety Management & Science
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• v.7 no.5
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• pp.107-117
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• 2005

Zohar(1980) emphasized the influence of social, organizational, and psychological context in occupational safety and health study. With this research trend, Neal, Griffin, and Hart(2000) developed a sequential safety climate model. In this paper, author examined the usability of their model the relationships among safety climates, safety knowledge, safety motivation, and safety performance(safety compliance and safety participation). The author conducted a survey to 207 manufacturing workers, and the chief results of statistical analysis are as follows : 1) the leadership has positive effects on safety knowledge and motivation, 2) the precaution activities has only positive on safety knowledge, 3) the safety system has only on safety motivation, 4) the safety knowledge and motivation have positive effects on safety compliance and participation.

• 전기의세계
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• v.2
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• pp.1-5
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• 1949

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.52-62
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• 2009

A three-dimensional compressible Navier-Stokes solver, KFLOW, using overlapped grids has recently been developed to simulate unsteady flow phenomena over helicopter rotor blades. The blade-vortex interaction is predicted for a descending flight using measured blade deformation data. The effects of computational grid resolution and azimuth angle increments on airloads were examined, and computed airloads and vortex trajectories were compared with HART-II wind tunnel data. The current method predicts the BVI phenomena of blade airloads reasonably well. It is found from the present study that a peculiar distribution of vorticity of tip vortices in an approximate azimuth angle range of 90 to 180 degrees can be explained by physics of the shear-layer interaction as well as the dissipation of numerical schemes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.6
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• pp.516-525
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• 2015

In this paper, the acoustic pressure of a helicopter rotor in hovering and low speed descent flight is predicted and compared with experimental data. Ffowcs Williams-Hawkings equation is used to predict the acoustic pressure. Two different wind tunnel test data are used to validate the predicted results. Boeing 360 model rotor test results are used for the low-frequency noise in hover, and HART II test results are employed for the mid-frequency noise, especially BVI noise, in low speed descent flight. A simple free-wake model as well as the state-of-the-art CFD/CSD coupling method are adopted to perform the analysis. Numerical results show good agreement against the measured data for both low-frequency and mid-frequency harmonic noise signal. The noise carpet results predicted using the FFT(Fast Fourier Transform) shows also reasonable correlation with the measured data.

• Korean Architects
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• no.2 s.96
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• pp.63-83
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• 1977

• Journal of the Korean Institute of Telematics and Electronics
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• v.12 no.6
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• pp.9-13
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• 1975

Employing indefinite admittance matrix analysis method, a novel synthesis procedure of general active-RC filters using 2 operational amplifiers has been shown in this paper. With this procedure, a stable active-RC bandpass filter hart been designed, which provides for independent adjustment of the uning and band-width control. The predicted and actual performance is in good agreement.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.2
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• pp.56-64
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• 2006

Rapid progress in many branches of technology has led to a demand on new materials such as high strength light weight alloys, powdered alloys and composite materials. The hydrostatic extrusion is essentially a method of extruding a clad rod through a die. In order to investigate the effect of the process conditions such as friction heat, deformation and clad thickness on the clad extrusion process, viscoplastic finite element simulations were conducted. A specific model for theoretical analysis used in this study is The single scalar variable version of Hart's model. An experiment also has been carried out using 1.5MN hydrostatic extruder with variable speed ram, LVDT and load cell for comparison. It is found that the hydrostatic extrusion pressure considering the effect of heat dissipation in this theoretical work was closer to the experimental pressure than the isothermal hydrostatic extrusion pressure.

• 대한핵의학회:학술대회논문집
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• 1991.05a
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• pp.141.2-142
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• 1991

• Composites Research
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• v.35 no.5
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• pp.340-346
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• 2022

In this study, an optimal structural design of composite helicopter blades is performed using the genetic algorithm-based optimizer PSGA (Particle Swarm assisted Genetic Algorithm). The blade sections consist of the skin, spar, form, and balancing weight. The sectional geometries are generated using the B-spline curves while an opensource code Gmsh is used to discretize each material domain which is then analyzed by a finite element sectional analysis program Ksec2d. The HART II blade formed based on either C- or D-spar configuration is exploited to verify the cross-sectional design framework. A numerical simulation shows that each spar model reduces the blade mass by 7.39% and 6.65%, respectively, as compared with the baseline HART II blade case, while the shear center locations being remain close (within 5% chord) to the quarter chord line for both cases. The effectiveness of the present optimal structural design framework is demonstrated, which can readily be applied for the structural design of composite helicopter blades.