• Ocean and Polar Research
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• 제37권2호
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• pp.119-125
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• 2015

This paper focuses on the efficient arrangement plan of buoyancy modules, which plan is used to secure the safe operation and structural stability of a marine riser. The marine riser is connected between a vessel and seabed devices. The movement of the vessel and the seabed devices are affected by the motion of the riser. The riser of a deep-seabed integrated mining system exerts a strong influence on the healthy transfer of minerals. So, buoyancy modules must be equipped to compensate for the problem which is the structure stability and the dynamic motion. Installation locations and quantities of the buoyancy modules are determined by real sea experiments. But this is not easy to do because in real sea experimental conditions the cost is expensive as well as being, time-consuming and dangerous. Therefore, the locations and quantities should be determined by numerical simulation. This method is called simulation-based design. The dynamic analysis models of the riser and the buoyancy modules are built into the commercial software of DAFUL.

• 한국CDE학회논문집
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• 제17권3호
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• pp.149-155
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• 2012

The ankle over-pronation causes the mechanical overloading transferred to proximal areas (i.e. knees or hips) over time. Thus, the over-pronation is recognized as a contributory factor in a wide variety of musculo-skeletal pathologies in lower extremities. Commonly, over-pronated ankles are treated using specially designed insoles that support medial heels and correct the posture of lower limbs. However, the biomechanical effects of the insoles are not yet fully understood, so there still are controversies whether such insoles really have clinical significance. In this study, in order to verify the effects of insoles and determine the best shape of the insoles, we examined how the medio-lateral knee joint reaction force changes due to insole conditions through a case study about a subject. As a result, it is revealed that the medial heel post, which drastically reduced the peak medio-lateral knee joint reaction force, has significant effects on the gait of the over-pronated patients. However, in case that the arch support is combined together, the positive effect of the medial heel post may rather decrease.

• 한국산학기술학회논문지
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• 제14권11호
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• pp.5323-5329
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• 2013

스마트폰의 슬림화를 위한 방법으로 스마트폰의 두께 방향이 아닌 너비 방향으로 진동하는 수평 선형 진동 모터를 여러 회사에서 현재 개발 중이다. 진동 모터 개발과정 중 수학적 모델링을 이용한 방법은 진동을 예측하기 위한 효율적인 방법 중 하나이다. 하지만 실제 수평 선형 진동모터에서는 Lorentz Force에 의한 수평 힘과 진동자 내의 자석과 브라켓 사이에 작용하는 자력에 인한 인력과 진동자 중력에 의한 수직 힘이 발생하여 진동자는 수평 선형 운동이 아닌 비틀림 운동을 하게 된다. 즉, 진동자에 수평 힘만 고려되어져 이상적인 운동으로 가정하는 수학적 모델링은 해석 오차의 발생 원인 중 하나이다. 따라서, 본 논문은 상용 동역학 해석 프로그램인 "DAFUL"을 이용한 진동 모터의 동적해석을 제시한다. 이 해석 프로그램은 진동자에 작용하는 수평, 수직 힘을 모두 고려할 수 있어 실제 진동모터의 움직임에 가까운 운동을 구현하여 수학적 모델링이 가지는 한계를 극복할 수 있다. 또한 "DAFUL"을 이용하여 해석 결과를 검증하기 위해 실험을 행하였고, 각각의 데이터를 비교 및 분석하여 결과를 확인하였다.

• 한국산학기술학회논문지
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• 제19권9호
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• pp.84-90
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• 2018

철도차량의 거동을 해석하기 위하여 다물체 동역학 모델을 구성함에 있어 현가시스템을 구성하는 스프링, 댐퍼와 같은 현가요소에 대한 스프링강성이나 감쇠계수와 같은 물성치 파악은 매우 중요하다. 그 중 1차, 2차 현가시스템에 주로 활용되고 있는 코일스프링에 대한 동역학 모델을 구성함에 있어 축방향 강성은 도면이나 설계자료에 명확하게 명시되어 있지만 횡방향에 대한 물성은 명시되어 있지 않아 동역학 해석 모델 구성에 어려움을 안고 있다. 따라서 본 논문에서는 철도차량의 현가시스템에 폭 넓게 적용되고 있는 코일스프링에 대한 횡강성을 해석하기 위한 모델에 대하여 검토하고자 한다. 코일스프링 시료에 대한 횡강성을 해석하고자 유한요소해석 방법을 수행하였고 Krettek와 Sobczak의 코일스프링 횡강성 해석모델을 적용하여 수치해석을 수행하였다. 그리고 코일스프링 시료를 대상으로 횡강성 특성시험을 수행하여 해석모델과의 적합성을 검토하였다. 시험결과와 비교한 결과, Krettek와 Sobczak의 코일스프링 횡강성 해석모델을 적용하고 보정계수를 수정한 결과가 시험결과에 근사한 결과를 얻을 수 있었다.

• 한국기계가공학회지
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• 제17권1호
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• pp.130-137
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• 2018

In long freight trains, there is a brake time delay in the neighboring freight cars that causes damage and fractures of couplers, especially the knuckle of them. If there is a problem for couplers in the cars, this could cause a derailment and lead to damage of human life and property damage. In this study, maximum forces on the couplers are studied when a long freight car brakes, with brake delay time and coupler gap. We have made a dynamic model of 50 freight cars and couplers, applying contact between couplers and a characteristic curve for expressing force and displacement of buffers with SIMPACK, a multi-body dynamics program. We use EN 14531-2 from the British Standards Institution, a standard of freight car brakes for the verification of the dynamic model. We also use a simplified method to analyze the dynamic model of 50 freight cars. With changing coupler gap and brake delay time, we do comparative analysis with AAR M-201 from the Association of American Railroads, a standard of AAR couplers. From this result, we find that the standard on fatigue limit is satisfied, such that the brake delay time is within 0.06 second if the coupler gap of the AAR coupler is within 20 millimeters.

• 한국기계가공학회지
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• 제16권5호
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• pp.91-98
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• 2017

This study was conducted to optimize the spring constant and the damping coefficient, which are design parameters of the tractor cabin suspension system, to minimize the ride vibration. A 3D tractor MBD (multi-body dynamics) model with a cabin suspension system was developed using a dynamic analysis program (Recurdyn). Using the developed model and optimization algorithm, the spring constant and the damping coefficient, which are the design parameters of the cabin suspension for the tractor, was were optimized so thatto minimize the maximum overshoot for the vertical displacement of the cabin was minimized. The percent maximum overshoot of the tractor cabin was simulated for the 13 initial models, which were obtained using the ISCD-II method, and for the 3 additional SAO models presented in the optimization algorithm software. The model that represents with the smallest percent maximum overshoot among the 16 models was selected as the optimized model. The percent maximum overshoot of the optimized model was about approximately 5% lower than that of the existing model.

• 한국해양공학회지
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• 제26권2호
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• pp.48-57
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• 2012

This paper deals with numerical analyses in the context of estimations of hydrodynamic motions and dynamic loads for a floating type offshore platform using some exclusive simulation code such as code for the simulation of a floating type of offshore crane based on multi-body dynamics, along with the commercial code AQWA. Verifications of numerical models are carried out by comparing the RAO results from the simulation code. In the verification analyses, hydrodynamic motions are examined in the frequency domain for the floating type offshore platform according to the mooring lines. Both the hydrodynamic motions and dynamic loads are estimated for floating type offshore platforms equipped with the catenary type and taut mooring lines. A review and comparison are carried out for the numerically estimated results. The structural safety of the connection parts in an offshore structure such as a floating type offshore platform is one of the most important design criteria in view of fatigue life. The dynamic loads in the connecting area between a floating type offshore platform and its mooring lines are estimated in detail according to variations in the mechanical properties of the mooring lines. The dynamic tension load on the mooring lines is also estimated.

• 한국항공우주학회지
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• 제32권5호
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• pp.24-29
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• 2004

본 논문에서는 저속통제기로부터 비상 시 분리되는 외부연료탱크 및 LAU-131 로켓발사기의 분리안전성을 보이기 위하여 수행한 자유낙하 풍동시험, MSAP을 이용한 해석과 비행 시험의 연구결과를 종합하였다. 자유낙하형의 bomb rack을 사용하는 비행시험 중의 분리안 전성의 확인과 MSAP의 보정용 자료 생성을 위하여 수행한 아음속풍동을 이용한 자유낙하 시험의 결과에 대하여 기술하였다. 보정된 MSAP으로 자유낙하형과 사출형의 bomb rack 을 사용하였을 때의 분리안전성 해석을 수행하였다. MSAP 해석 결과를 이용한 상관관계 해석을 통하여 자유낙하형의 bomb rack을 사용할 경우의 투하 안전성도 보였다. 또한, 실기 비행시험을 통하여 투하시험을 수행하였으며 이를 해석결과와 비교하였다. 마지막으로, 풍동 시험, 해석결과 및 비행시험의 결과를 종합하여 저속통제기의 안전투하영역을 확정하였다.

• Journal of Power Electronics
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• 제15권4호
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• pp.1047-1053
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• 2015

A time-domain simulation tool to predict the dynamic power output of wind turbines in an offshore wind farm was developed in this study. A wind turbine model consisting of first or second order transfer functions of various wind turbine elements was combined with the Ainslie's eddy viscosity wake model to construct the simulation tool. The wind turbine model also includes an aerodynamic model that is a look up table of power and thrust coefficients with respect to the tip speed ratio and pitch angle of the wind turbine obtained by a commercial multi-body dynamics simulation tool. The wake model includes algorithms of superposition of multiple wakes and propagation based on Taylor's frozen turbulence assumption. Torque and pitch control algorithms were implemented in the simulation tool to perform max-Cp and power regulation control of the wind turbines. The simulation tool calculates wind speeds in the two-dimensional domain of the wind farm at the hub height of the wind turbines and yields power outputs from individual wind turbines. The NREL 5MW reference wind turbine was targeted as a wind turbine to obtain parameters for the simulation. To validate the simulation tool, a Danish offshore wind farm with 80 wind turbines was modelled and used to predict the power from the wind farm. A comparison of the prediction with the measured values available in literature showed that the results from the simulation program were fairly close to the measured results in literature except when the wind turbines are congruent with the wind direction.

• 대한기계학회논문집A
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• 제37권1호
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• pp.17-23
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• 2013

지하철 전동차에는 2 차 현가장치인 공기스프링의 횡강성 저하특성을 보강하기 위해 대차와 차체 사이에 횡댐퍼를 설치하게 되는데, 이 횡댐퍼는 주행 시 차체의 횡진동을 감소시키는 역할을 수행한다. 그러나, 횡댐퍼의 감쇠력이 저하될 경우 전동차의 주행안정성과 승차감이 함께 악화되며, 차체의 횡방향 운동이 증가되는 요인으로 작용하게 된다. 본고에서는 전동차 주행 시 비정상적으로 발생하는 충격에 대하여 그 원인을 살펴보고 해결방안을 마련하고자 횡댐퍼의 감쇠력에 따른 차체의 횡변위를 동역학 시뮬레이션을 통해 검토하였으며, 그에 따라 충격에 의한 이상진동 및 소음의 발생 유무를 파악하였다. 그로부터 충격이 발생되지 않는 적정 감쇠력을 구하고자 하였다.