• International Journal of CAD/CAM
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• 제6권1호
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• pp.29-40
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• 2006

The paper presents an optimization system which integrates a parametric design tool, 3D diffraction-radiation analysis and hydrodynamic performance assessment based on short and long term wave statistics. Controlled by formal optimization strategies the system is able to design offshore structure hulls with superior seakeeping qualities. The parametric modeling tool enables the designer to specify the geometric characteristics of the design from displacement over principal dimensions down to local shape properties. The computer generates the hull form and passes it on to the hydrodynamic analysis, which computes response amplitude operators (RAOs) for forces and motions. Combining the RAOs with short and long-term wave statistics provides a realistic assessment of the quality of the design. The optimization algorithm changes selected shape parameters in order to minimize forces and motions, thus increasing availability and safety of the system. Constraints ensure that only feasible designs with sufficient stability in operation and survival condition are generated. As an example the optimization study of a semisubmersible is discussed. It illustrates how offshore structures can be optimized for a specific target area of operation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.240-243
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• 2005

A design procedure using spatial Fourier transform is presented for a structural-acoustic coupled radiator that can emit sound in the desired direction with high power and low side lobe level. The design procedure consists of three steps. Firstly, the structural-acoustic coupled radiator is chosen to obtain strong coupling between structural vibration and acoustic pressure. The radiator is composed by two spaces which are separated by a wall. Spaces can be categorized as reverberant finite space and unbounded semi-infinite space, and the wall are composed of two plates and an opening. The velocities on the wall are predicted. Secondly, directivity and energy distribution of radiator are predicted in wave number domain using spatial Fourier transform. Finally, optimal design variables are calculated using a dual optimal algorithm. Its computational example is presented including the directivity and resulting pressure distribution using proposed procedure.

• 한국철도학회논문집
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• 제17권1호
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• pp.7-13
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• 2014

팬터그래프와 전차선 사이의 이선을 유발하는 주요 요인은 팬터그래프로 인하여 전차선에 야기되는 파동의 전파와 반사 그리고 열차 진행방향의 전차선로 강성변화이다. 본 논문의 목적은 200km/h급 일반철도와 300km/h급 고속철도에서 이선을 효과적으로 줄이기 위하여 앞서 언급하였던 두 가지 요인 중에서 어느 쪽을 중요하게 고려해야 하는지를 분석하는 것이다. 고속철도 경우에는 파동의 전파와 반사가 강성 변화에 비하여 집전성능에 영향을 더 크게 미친다. 증속을 위해서는 드로퍼 경량화와 전차선 고 장력 부여를 위한 고 강도 전차선 개발이 필요하다. 파동전파속도를 향상하기 위하여 조가선의 장력을 증가시키면 오히려 집전성능을 악화할 수 있음에 유의해야 한다. 200km/h급 일반철도의 경우에는 전차선로 강성 변화가 파동 전파 및 반사에 비하여 집전성능에 영향을 더 미치므로 강성변화를 완화시키기 위하여 경간길이 축소, 전차선로의 장력 증가 및 드로퍼배치 최적화가 필요하다.

• 한국해안해양공학회지
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• 제14권2호
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• pp.95-107
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• 2002

신뢰성설계법의 적용성을 확대하기 위하여 혼성제 직립 케이슨의 활동에 대한 신뢰성 해석이 수행되었다. 충격쇄파 효과를 고려한 결정론적 설계법에 의하여 단면의 안전성이 자세히 해석되었으며, 특히 신뢰성 해석의 결과를 직접 결정론적 설계법의 결과와 연결시키기 위한 연구가 시도되었다. 해석 결과에 의하면 현재의 결정론적 설계 법에서 적용되고 있는 안전율은 약간 안전 측에 속한다. 또한 동일한 입사조건과 안전율에 대하여 수심이 증가함에 따라 신뢰지수는 감소하는 경향을 보이고 있다. 한편 방파제가 그 기능을 수행하는데 지장이 없을 것으로 예상되는 목표 파괴확률을 설정하고 그 목표 범위내에서 가장 최적의 파괴 확률을 산정하였는데, 입사조건에 따라 약간 씩 다른 최적의 안전율이 추정되었다. 마지막으로 혼성제 케이슨의 단면 결정에 영향을 주는 변수들의 변화에 따른 민감도 분석이 수행되었다. 해석 결과에 의하면 입사각, 주기의 영향이 크게 나타났으며 하상의 경사나 마운드의 두께에 대한 영향의 정도는 상대적으로 낮게 평가되었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.297-306
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• 2014

The paper presents the numerical analysis of wave run-up over rubble-mound breakwaters covered by antifer units using a technique integrating Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD) software. Direct application of Navier-Stokes equations within armour blocks, is used to provide a more reliable approach to simulate wave run-up over breakwaters. A well-tested Reynolds-averaged Navier-Stokes (RANS) Volume of Fluid (VOF) code (Flow-3D) was adopted for CFD computations. The computed results were compared with experimental data to check the validity of the model. Numerical results showed that the direct three dimensional (3D) simulation method can deliver accurate results for wave run-up over rubble mound breakwaters. The results showed that the placement pattern of antifer units had a great impact on values of wave run-up so that by changing the placement pattern from regular to double pyramid can reduce the wave run-up by approximately 30%. Analysis was done to investigate the influences of surface roughness, energy dissipation in the pores of the armour layer and reduced wave run-up due to inflow into the armour and stone layer.

• Structural Engineering and Mechanics
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• 제53권3호
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• pp.393-410
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• 2015

Two dimensional numerical models and physical models have been developed to study the highly nonlinear interactions between waves and breakwaters, but several of these models consider the effects of the structural dynamic responses and the shape of the breakwater axis on the wave pressures. In this study, a multi-material Arbitrary Lagrangian Eulerian (ALE) method is developed to simulate the nonlinear interactions between nonlinear waves and elastic seawalls on a coastal rubble mound breakwater, and is validated experimentally. In the experiment, a solitary wave is generated and used with a physical breakwater model. The wave impact is validated computationally using a breakwater - flume coupling model that replicates the physical model. The computational results, including those for the wave pressure and the water-on-deck, are in good agreement with the experimental results. A local breakwater model is used to discuss the effects of the structural dynamic response and different design parameters of the breakwater on wave loads, together with pressure distribution up the seawall. A large-scale breakwater model is used to numerically study the large-scale wave impact problem and the horizontal distribution of the wave pressures on the seawalls.

• 대한기계학회논문집B
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• 제23권2호
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• pp.234-242
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• 1999

Flow phenomena such as the pressure transients Inside a high-speed railway tunnel and the Impulsive waves at the exit of the tunnel are closely associated with the characteristics of the entry compression wave, which is generated by a train entering the tunnel. Tunnel entrance hood may be an effective means for alleviating the Impulsive waves and pressure transients. The objective of the current work is to explore the effects of the train nose shape and the entrance hood on the characteristics of the entry compression wave. Numerical calculations using the method of characteristics were applied to one-dimensional, unsteady, compressible flow field with respect to high-speed railway/tunnel systems. Two types of the entrance hoods and various train nose shapes were employed to reveal their influences on the entry compression wave for a wide range of train speeds. The results showed that the entry compression wave length increases as the train nose becomes longer and the train speed becomes lower. The entry compression wave length in the tunnel with hood becomes longer than that of no hood. Maximum pressure gradient in the compression wavefront reduces by the entrance hood. The results of the current work provide useful data for the design of tunnel entrance hood.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.198-207
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• 2010

Many methods and techniques have been developed to obtain the accurate design parameters in soft soils. In particular, several researchers suggest the techniques to get the void ratio for understanding the soil behavior. The objective of this paper verifies the accuracy of the proposed analytical solution for determining the void ratio based on the elastic wave velocities. The paper covers the theories of Wood, Biot, Gassmann and Foti proposed chronological order. The total theory represents the wave propagation in fully saturated medium. To verify the proposed analytical solution, the laboratory and field tests are carried out. After measuring the elastic wave, the void ratios are assessed using proposed equation. The volume based void ratios are also obtained for comparing with the estimated value by several equations. The values estimated by volume, Gassmann and Biot are show good similarity. However, the void ratios based on Wood and Foti methods have a slightly different trend. This study suggests that the theories of Biot and Gassmann may be a useful equation for assessing the void ratio using elastic wave velocities in the field.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.1133-1136
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• 2002

We designed and fabricated a low local oscillation (LO) power V-band CPW mixer module using a CPW-to-waveguide transition technology for the application of millimeter-wave wireless communication systems. The mixer was designed using a unique gate mixing architecture to achieve simultaneously a low LO input power, a high conversion gain, and good LO-RF isolation characteristics. The fabricated mixer exhibited a high conversion gain of 2 dB at a low LO power of 0 dBm. For data transmission of the 60 ㎓ wireless LNA systems, we fabricated a CPW-to-waveguide converter module of WR-15 type and mounted the fabricated mixer in the converter module. The fabricated V-band mixer exhibited a higher conversion gain and a lower LO input power than other reported V-band mixers.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2002년도 종합학술발표회 논문집 Vol.12 No.1
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• pp.25-28
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• 2002

In this paper, a micromachined millimeter-wave end-gap band-pass filter (BPF) is presented. The millimeter-wave BPF is designed using 3D design software, Zeland IE3D with the center frequency of 60 GHz, band width of 3 GHz, ripple of 1㏈ and insertion loss of 2.5dB. This type of micromachined BPF can be used in millimeter-wave circuit.