• Geotechnical Engineering
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• v.11 no.4
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• pp.49-62
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• 1995

Soil nailing has been widely rosed during the last two decades to stabilize sheep excavated slopes in several countries. In thin study, the discrete element method has been applied to evaluate the stability of the reiuorced slope. This method is capable of not only estimat ins tensile and sheer stresses mobilized in nails but also providing individual safety factors of soil and nails, It has been assumed that the nailed slope be comprised of slices connected with elastoplastic twinkler springs. A reasonable mechanism is applied for representing the behavior between nails and adj scent soils. Taking into account for the bequence of construction the developed method well predicts the measured tensile forces developed in nails so that it is possible to appropriately evaluate the overall safety factor.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.87-95
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• 2003

In this paper, the discrete element method was applied to evaluate the stability of composite cover and lining system of landfill. This method is capable of estimating the distribution of tensile force and shear stress mobilized in each liner component and its interfaces, based on a relationship of force and displacement. It was assumed that the cover soil and geomembrane were comprised of slices connected with elastoplastic Winkler springs and tensile spring respectively. Parametric study using this method was performed and compared with other techniques based on limit equilibrium method fur the example analysis.

• Journal of Drive and Control
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• v.16 no.1
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• pp.7-13
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• 2019

The objective of this study was to present a damped pneumatic suspension, a bike fork suspension, which can adapt itself to incoming road excitations is presented in this paper. It consists of a hydraulic damper and a pneumatic spring in parallel with a linear spring. The study also proposed a variable and switchable orifice, in the hydraulic damper, to select appropriate damping property. Hydraulic-pneumatic circuit model for the bike fork suspension was established based on AMESim, in order to predict its performance. In addition, elastic-damping characteristics of the fork such as spring constant and viscous damping coefficient were computed and compared, for validation, with those evaluated by experiment using the universal test machine. Through simulation analysis and test, it was established that the hydraulic-pneumatic circuit model is effective and practical for development of future MTB suspensions.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.306-308
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• 2003

본 논문은 variable optical attenuator(VOA)에 응용하기 위한 comb actuator를 설정하기 위해, 요구되는 조건에 가장 적합한 comb actuator를 설계하기 위한 방법을 제시한다. VOA 응용을 위한 comb actuator 설계에서 고려되어야 하는 조건들은 comb actuator의 performance(변위, 공진 주파수), 구동 전압 그리고 공정의 한계(최소 선폭, 최소 간격, 두께) 등이다. 이러한 조건들이 정해지면, 이 조건들을 comb actuator의 구동력과 지지빔 스프링에 의한 복원력에 대입하여 두 힘이 평형일 때의 조건으로부터 comb finger의 수와 구동부의 질량 및 지지빔의 길이 등의 선계 변수들을 정할 수 있다. 그리고 comb actuator의 질량으로 부터 구동부의 면적을 구할 수 있고, 이러한 조건에서 구한 지지빔의 면적과 비교하여 적절한 구동부의 면적을 설정한다. 이상의 내용을 조합해서 요구된 조건이 comb actuator 설계에 적합한지의 여부를 확인했고, VOA 응용을 위한 요구 조건에 맞는 comb actuator 설계를 했다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1559-1566
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• 1994

Using the finite element method, the contact force, contact band width and temperature distribution of lip seals analyzed for the interference including some nonlinearities such as material nonlinearity, geometrical nonlinearity and nonlinear contact boundary condition. The calculated results showed that the contact stress concentrated on the contact zone between the garter spring and the rubber toward the flex side, the contact edge of lip seals. The high contact forces due to the increased interference separate the sealing gap between the lip edge and the rotating shaft. This may lead to leak the sealed oil.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.480-483
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• 2010

착륙장치는 완충장치를 이용하여 항공기 착륙 시의 충격을 흡수하는 역할을 한다. 여러 방식의 완충장치가 있으나, Oil에 의한 감쇠력과 Gas에 의한 스프링력을 이용하여 에너지를 흡수하는 유공압 방식이 가장널리 사용되고 있다. 착륙장치 성능해석에서는 다양한 착륙조건에 대한 Dynamic simulation을 통해 최적의 Orifice 형상과 Gas spring 특성을 결정하고, 설계에 필요한 착륙하중을 구하게 된다. 이 논문에서는 상용 프로그램인 VI-Aircraft를 이용한 착륙장치 성능해석 과정을 소개한다. 유공압 완충장치의 모델링 및 Landing simulation 결과를 분석하고, 이에 따른 완충효율 최적화 과정을 제시한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.6
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• pp.599-607
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• 2011

In this paper, a reaction-force compensation system for an XY linear motion stage, without an additional external isolation structure or extra motors, is developed. This system consists of a movable magnet track, a spring, a dummy weight, and a dedicated sensor module that measures the relative positions of the movable magnet track with respect to the motor coil. The reaction force compensation system is modeled, and simulations are carried out to optimize design parameters such as the moving distance of the magnet track, the transmission force, the dummy weight, and the allowed size of the mechanism. An XY linear motion stage is built, incorporating the reaction force compensation system, and the performance of the system is verified experimentally. For acceleration and deceleration values of 10 m/$s^2$, 85% of the reaction force is absorbed by the reaction force compensation system.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.49-63
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• 1989

Wave drift forces which are small in magnitudes compared to the first order wave exciting forces can cause very large motion of a vessel in waves. In this paper a theoretical and experimental analysis is made of the mean and slowly varying wave dirft forces on the semi-submersible platform. Theoretical calculations are performed by using near field method with three dimensional diffraction theory and model tests are carried out in regular and irregular waves with a 1/60 semi model. Test results are compared with theoretical calculations and the mooring spring effects in the test are discussed.

• Computational Structural Engineering
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• v.10 no.3
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• pp.125-131
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• 1997

Most dynamic systems have are known to various random properties in excitation and system parameters. In this paper, a procedure for response analysis is proposed for the linear dynamic system with random properties in both excitation and system parameters. The system parameters and responses with random properties are modeled by perturbation technique, and then response analysis is formulated by probabilistic and vibration theories. And probabilistic FEM is also used for the calculation of mean response which is difficult by the proposed response model. As an applicative example, the transient response is considered for systems of single degree of freedom with random mass and spring constant subjected to stationary white-noise excitation and the results are compared to those of numerical simulation.

• Journal of the Korean Society for Railway
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• v.15 no.1
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• pp.48-61
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• 2012

It is of great importance to assure the running safety, ride comfort and serviceability in designing the floating slab track for mitigation of train-induced vibration. In this paper, for this, analyzed are the system requirements for the running safety, ride comfort and serviceability, and then, the behavior of train and track at the floating slab track including the transition zone to the conventional concrete slab track according to several main design variables such as system natural frequency, arrangement of spring at transition, spacing of spring isolators, damping ratio and train speed, using the dynamic analysis technique considering the train-track interaction. The results of this study demonstrate that the discontinuity of the support stiffness at the transition results in a drastic increase of the dynamic response such as wheel-rail interaction force, rail bending stress and rail uplift force. Hence, it is efficient to decrease the spacing of springs or to increase the spring constants at the transition to obtain the running safety and serviceability. On the other hand, the vehicle body acceleration as a measure of ride comfort is little affected by the discontinuity of the stiffness at the transition, but by the system tuning frequency; thus, to obtain the ride comfort, it is of great significance to select the appropriate system tuning frequency. In addition, the effects of damping ratio, spacing of springs and train speed on the dynamic behavior of the system have been discussed.