• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.7
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• pp.497-505
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• 2022

Performance and hub vibratory load analyses for a lift-offset coaxial rotor are conducted using a rotorcraft comprehensive analysis code, CAMRAD II. The lift-offset coaxial rotor is trimmed to match the total rotor thrust(lift-offset coaxial rotor's thrust) or the individual rotor thrust(upper and lower rotor thrusts, respectively) in this study. The individual rotor's lift and torque, and effective rotor lift to drag ratio for the total rotor are investigated for various advance ratios and lift-offset values. The two result sets with different trim methods are similar to each other and they are correlated well with the wind-tunnel test results. Therefore, the present study using CAMRAD II validates successfully the aeromechanics modeling and analysis techniques for the lift-offset coaxial rotor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.12
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• pp.1011-1018
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• 2021

This numerical study conducts the modeling and the hover performance analyses of coaxial co-rotating rotor(or stacked rotor), using a rotorcraft comprehensive analysis code, CAMRAD II. The important design parameters such as the index angle and axial spacing for the coaxial co-rotating rotor are varied in this simulation study. The coaxial co-rotating rotor is trimmed using the torque value of the upper rotor of the previous coaxial counter-rotating rotor or the total thrust value of the previous coaxial counter-rotating rotor in hover. The maximum increases in the rotor thrust is 1.84% for the index angle of -10° when using the torque trim approach. In addition, the maximum decreases in the rotor power is 4.53% for the index angle of 20° with the thrust trim method. Thus, the present study shows that the hover performance of the coaxial co-rotating rotor for e-VTOL aircraft can be changed by the index angle.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.477-478
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• 2009

• Proceeding of EDISON Challenge
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• 2016.11a
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• pp.35-43
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• 2016

본 연구에서는 EDISON의 해석자를 활용하여 선박의 최적 운항 자세 도출과 같은 실용적 문제 해석뿐 만 아니라 자유 수면 및 대칭 경계 조건이 수직한 몰수 익형 주위 유동에 미치는 영향을 분석하는 학술적 연구를 수행하였다. 선박의 자세에 따른 저항 변화를 분석한 결과 0.5m 선수 트림에서 선체 저항이 가장 작은 것으로 나타났으며, 이는 유동 가속에 의한 선수 어깨부의 낮은 압력 및 선미부에서의 압력 회복에 의한 것이다. 반면, 1.0m 선미 트림에서 선체 저항이 가장 큰 것으로 나타났는데, 평형 상태보다 선미부의 압력 회복이 약하기 때문이다. 또한 자유 수면과 대칭 경계 조건이 날개 성능에 미치는 영향을 분석한 결과, 비현실적 대칭경계 조건으로 인해 날개 양력이 13%~16% 크게 나타났으므로 대칭경계조건을 사용할 경우에는 이러한 오차를 감안해야 한다.

• Journal of Ocean Engineering and Technology
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• v.30 no.2
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• pp.134-140
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• 2016

An envelope protection system is a control system that allows a submarine to operate freely using its own operational envelope without exceeding the structural limit, dynamic limit, and control input limit. In this paper, an envelope protection system for the pitch angle of a submarine is designed using a dynamic trim algorithm. A linear quadratic regulator and artificial neural network are used for the true dynamics approximation. A submarine maneuvering simulation program developed using experimental data is used to validate the designed envelope protection system. Simulation results show the effectiveness of the designed envelope protection system.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.1
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• pp.64-69
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• 2005

In spite of many efforts, in the design of high speed fishing vessel the sea-keeping performance improvement without neglection of resistance-propulsion performance by hull form itself has its limitations. In this paper, the development of sea-keeping improving appendage pitching and trim improver for high speed planing hull on behalf of the hull form of fishing vessel has been introduced. The developed appendage verified its effectiveness in the full scale test and also has been proved the better resistance performance in the model test and full scale test.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.74-85
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• 2010

In order to formulate the compounded polypropylene(C-PP) which is suitable to an automotive door trim panel, 9 sorts of properties were measured after manufacturing the C-PP using an extruder and an injection machine with polypropylene(PP), ethylene-octene rubber(EOR) and talc. Mixture design, especially extreme vertices design, in DOE with MINITAB - commercial software was used to analyze the data. The relations between each property and each component, for example, $y=0.00907222x_1+0.00870556x_2+0.0155722x_3$ for specific gravity, were found out by the regression analysis and the variance analysis. The optimized formulation of the C-PP for an automotive door trim panel was acquired at PP(77.6962), EOR(11.0238) and talc(10.2800) by use of the response optimizer(mixture) in MINITAB.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.86-91
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• 2008

To present the design procedure of discretized 8-bit tent map executing the transformation of tent function which is one of the chaotic functions, first, the truth table of discretized tent map was written, and then according to the simplified Boolean algebra equations obtained from the truth table, the discretized map is implemented with the exclusive logic gate as a real hardware. The discretized tent map circuit which provides the feedback circuit for generating the period-8 states relevant to the 8-bit finite precision is also designed and presented in this paper. Furthermore, it might be used stream cipher system with a new key-stream circuit for generate of chaotic binary sequence.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.689-692
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• 2010

일반형 자동차 내장부품은 외부가 플라스틱 사출 성형한 형태로 사용되지만, 고급 차종은 내장재의 미감이나 질감을 위하여 사출물 표면에 엠보싱 무늬가 형성된 표피재가 수지에 추가로 부착되어 제작된다. 부착하는 방법은 한 장비에서 저압 사출 후 플라스틱이 완전 응고 전에 표피재를 넣고 압입하는 저압 사출법과 표피재 수지를 기 사출된 제품위에 놓고 압착시키는 압착법이 있으나 이 두 방법 모두 엠보싱 무늬가 형성된 표피재를 넣고 작업하기 때문에 고온 압착시 기존 무늬가 찌그러지고 코너 부위가 경화되어 기존의 질감을 얻지 못하며, 치수 공차가 변형되어 불량률이 증가하므로 이를 시급히 개선할 새로운 제조 기술의 필요성이 대두된다. 본 연구는 가열 압착기로 지그 및 금형을 새로 개발하여 도어 트림 제조시, 기 사출물을 금형 쪽으로 기 조직을 삽입한 후 엠보싱 무늬가 없는 원소재 표피재로 상부 금형 쪽으로 소재조직을 진공으로 흡입하여 무늬를 성형한 후 하강시켜, 기 사출물에 압착시키는 가열 압착으로 엠보싱무늬의 손상을 방지하는 금형을 제안하였으며 그에 대한 해석, 설계, 실험을 통하여 성능을 평가 분석 하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.9
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• pp.88-93
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• 2003

This Paper described the simulation program development for helicopter. In the design of flight control system to accomplish some special missions like UAV, it is important to minimize the execution time obtaining a linear model from nonlinear model that is used for design of controller. The first step for this kind of purpose is to complete a nonlinear model that contains full dynamic characteristics. The second step is to get the trim values that are obtained from the nonlinear model by solving an algebraic equation. And then stability and control derivatives are derived through hovering to forward flight by numerical perturbation that will be used for linear model for a specified flight condition. The software program(HeliSim) is developed by using MATLAB GUI and will provide easy modeling procedure. The suggested method in this paper is much more simpler than any other method like a fully scale helicopter model. The advantage of our suggested method will reduce the computational time due to simple formula to extract a linear model from nonlinear model that will be beneficially used for flight control system of unmanned helicopter by some reduction of computational load.