• Explosives and Blasting
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• v.36 no.2
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• pp.1-9
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• 2018

In this paper, AUTODYN blasting simulation of single blast hole were conducted to evaluate the blasting effects of Polymer Gel. The coupling mediums used as the filling material around an explosive charge were air and gelatin. each simulation case was D I(decoupling index) 1.0, 1.25, 1.56 with air or polymer gel coupling materials. In order to evaluate blast effects full charge model was used as a reference for evaluation of blasting effects. The results of numerical analysis showed that fragmentation of a limestone model of were much more fractured by polymer gel medium than by air medium. As expected, the transmitted peak pressure was higher polymer gel coupled model than in air medium.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1577_1578
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• 2009

본 논문은 Electro Magnetic Topology(EMT)를 이용하여 전자장과 전송선로의 커플링 영향에 대해 해석한다. 본 논문은 BLT 방정식을 이용하여 외부 소스에 의해 영향을 받는 전송 선로의 해를 주파수 영역에서 구하였다. 위의 해석 방법을 양단에 저항 부하가 있는 2선 전송 선로에 적용하여, 외부에서 평면파 소스가 인가되었을 때의 각 전송 선로 종단에서의 전류의 파형을 Mode Matching(MoM), Finite Difference Time Domain(FDTD) 결과와 비교함으로 정확성을 확인하였다.

• Explosives and Blasting
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• v.35 no.3
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• pp.9-14
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• 2017

Coupling effects of the stemming materials for single borehole were studied by AUTODYN analysis and compared to understand the role of different stemming materials on transmitting the pressure from blasthole to the surrounding rocks. Five different material properties, air, sand, water, 10% and 20% gelatin were selected. Authors assumed that high pressure detected in borehole means better fragmentation. Simulations show that these coupling materials lead to different level of pressure in the blasting hole and 20% gelatin turns out to be highest among them. Results show that gelatin can be used as better coupling material than sand or water.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.149-157
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• 1999

A powerful numerical method that can be used for that purpose is the Discontinuous Deformation Analysis (DDA) method developed by Shi in 1988. In this method, rock masses are treated as systems of finite and deformable blocks. Large rock mass deformations and block movements are allowed. Although various extensions of the DDA method have been proposed in the literature, the method is not capable of modeling water-block interaction that is needed when modeling surface or underground excavation in fractured rock. This paper presents a new extension to the DDA method. The extension consists of hydro-mechanical coupling between rock blocks and water flow in fractures. A example of application of the DDA method with the new extension is presented. The results of the present study indicate that fracture flow could have a destabilizing effect on the tunnel stability.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.163-173
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• 2003

In this paper, a numerical comparison of predictions by limit equilibrium analysis and 3D analysis is presented for slope/pile system. Special attention is given to the coupled analysis based on the explicit finite difference code, FLAC 3D. To this end, an internal routine (FISH) was developed to calculate a factor of safety for a file reinforced slope according to shear strength reduction technique. The case of coupled analyses was performed for stabilizing piles in slope in which the pile response and slope stability are considered simultaneously. In this study, by using these methods, the failure surfaces and factors of safety were compared and analyzed in several cases, such as toe, middle and top of the slope, respectively. Furthermore, the coupled method based on shear strength reduction technique was verified by the comparison with other analysis results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.707-713
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• 2013

Coupling bolts have replaced conventional fitted bolts in applications where the operator's safety during assembly/disassembly is of concern or where the cost of process interruption is significant. Coupling bolts have been installed on rotating flange couplings in a wide range of marine and power applications worldwide. Their use has been approved by all leading international and national classification societies and regulatory bodies. A coupling bolt is a hydraulically tensioned fitted bolt that creates a stable and rigid link between coupling flanges and simplifies assembly and disassembly. We measure the bolt dimensions for reverse engineering and study the standard of assembly-load using a mechanical formula in order to localize a coupling bolt for a shaft in a power plant. We experimentally obtain the friction coefficient and confirm the condition of bolt sets through structure analysis. We show the variation of contact pressure for the shape parameter in order to consider the result when redesigning a bolt.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1048-1056
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• 2001

Decoupling capacitors are commonly used to reduce the effect of SSN propagated through parallel power and ground planes in high-speed multilayer printed circuit boards (PCBs). In this paper, we introduced a simple high frequency measurement and proposed a wideband (50 MHz ∼3 GHz) equivalent circuit model for decoupling capacitor considering high frequency parasitic effects. The proposed model can be easily combined with the SPICE model of power supply planes far SSN analysis. The circuit simulations with the proposed model show good agreement with the measurement results. Also, we expect to accurately analyze the noise reduction effect as a function of value and location using the proposed model of decoupling capacitor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.91-95
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• 1992

현재 대부분의 공작기계에서는 모터의 동력을 주축으로 전달하기 위해서 커플링, 밸트,기어 등을 사용하고 있지 만 주축이 고속회전할 수록 커플링 구동방법에서는 주축과 모터의 미스얼라인먼트에 의한 진동과 소음이 커지고 벨트 구동방법에서는 원심력에 의한 벨트 장력의 증가 및 벨트의 파손현상, 벨트와 풀리간의 미끄럼현상 등이 발생하며, 기거 구동방법에서는 기어간의 금속접촉에 의한 진동과 소음이 증대하게 된다. 본 연구에서는 모터내장형 주축의 동특성을 체계적으로 해석하기 위해서 유한요소모델을 도입하였다. 특히 공작기계 주축은 세장비가 비교적 작기 때문에 Timoshenko보 이론으로 모델화하였고, 여러장의 얇은 철심용 강판들도 적층된 내장형 모터의 회전부(rotor)는 굽힘변형 및 전단변형에 대해서 상당 수준의 강성효과를 나타내기 때문에 질량효과 외에도 그 강성효과를 수학적 모델에서 고려하였다, 또한 진동실험 결과로 부터 모터회전부의 강성특성을 규명하는 방법을 제시하였으며, 제안된 규명방법의 유용성은 모터내장형 주축에 대한 모드매개변수의 이론값과 실험값을 비교함으로써 입증하였다.

• The KSFM Journal of Fluid Machinery
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• v.17 no.4
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• pp.70-75
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• 2014

In this paper a analysis method is presented to obtain the steady state dynamic response from the finite element based equations of a rotor-bearing system with initial deflection. The method has been applied to analyze the dynamic response of the two-shaft rotor-bearing system with rigid coupling offset in a heavy duty gas turbine-generator. Bumps in the dynamic response of each rotor system have been observed at each critical speed due to the effect of initial deflection for rigid coupling offset. And, the dynamic responses have been shown to reduce for operating condition changes from cold to hot.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1126-1127
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• 1999

연산자 분리 시영역 모델을 이용하여 광섬유 커플러 ADM(add-drop multiplexer)의 필터링 효과를 분석하였다. 이 모델은 방향성 결합기나 브래그 격자를 포함하는 소자의 해석에 유용하다. 본 논문에서는 비대칭 구조를 고려했으며 결합계수, 코어의 반경, 개구수, 굴절율 변조 등의 파라미터를 이용하여 최적의 필터링 효과를 얻기 위한 구조를 설계하였다.