• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.817-824
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• 2000

It is essential to analyze structural vibrations due to turbulent wall pressure fluctuations over a body surface which moves through a fluid, because the vibrations can be a severe source of noise affecting to passengers in airplanes and SONAR performance. Generally, this kind of problems have been solved for very simplified models, e.g. plates, which can be applied to the wavenumber domain analysis. In this paper, a finite element modeling of the wall pressure fluctuations over arbitrary smooth surfaces is investigated. It is found that the modeled wall pressure fluctuation at nodes becomes uncorrelated at higher frequencies and at lower flow speeds, and the response is over-estimated due to the aliased power. Finally, the frequency range available for uncorrelated loading model and two power correction schemes are presented.

• 한국지반공학회지:지반
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• 제13권5호
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• pp.125-132
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• 1997

토석류는 다양한 크기의 흙 입자와 물이 고루 섞여 점성을 가진 유체처럼 하방향으로 이동한다는 사실이 관찰되었다. 이 관찰로부터 토석류를 비선행적인 점도를 가진 비뉴톤 유체처럼 거동하는 것으로 간주할 수 있다. 이 논문에서는 토석류의 레올로지적 특성을 규명하기 위해 산사태 현장에서 채취한 시료를 가지고 점도계를 사용하여 일련의 점도시험을 수행하였다. 그 결과, 토석류는 비뉴톤 유체 중 빙함 소성 모델로 거동한다는 사실이 밝혀졌다. 이 모델을 이용하면 토 석류의 이동을 예측할 수 있다.

• 한국전산유체공학회지
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• 제20권4호
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• pp.36-43
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• 2015

Accurate prediction of supersonic transition is required for the heat transfer estimation over supersonic double compression ramp flows. Correlation-based transition models were assessed for a supersonic double ramp problem. Numerical results were compared with experimental data from RWTH Aachen University. A parametric study on the nose bluntness was performed using a selected transition model. As the nose bluntness increases, the boundary layer thickness is increased and the triple point of shock interactions moves downstream. The peak magnitude of the heat transfer is consequently decreased with the nose bluntness.

• Journal of Ship and Ocean Technology
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• 제6권1호
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• pp.1-15
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• 2002

A new concept for launching free-fall lifeboats, proposed by Yokohama National University is described in this paper. It has been pointed out that, using the conventional single-skid free-fall system, the potential for dangerous lifeboat motions (in which the lifeboat moves backward or jerks on the surface after entering the water) increases with the fall height of the lifeboat. One of the principal causes of this undesirable motion is vertical rotation of the lifeboat during its restricted fall at the edge of the launching skid. Thus a new "double-skid"launching concept is proposed to effectively eliminate the rotation of the lifeboat at the skid end and to enable the lifeboat to move smoothly after entering the water. In order to evaluate the performance of the proposed method, a series of model experiments and numerical simulations is carried out in which two lifeboat models with overall lengths of 1 meter and 6 meters are used. The effects of design parameters such as skid angle and skid height are investigated, and an example of the implementation of this new system at the stern of a large merchant ship is illustrated.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1740-1746
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• 2008

The present study performed numerical investigation to analyze the smoke behavior in the rescue station by using the commercial CFD code (FLUENT Ver 6.3). The present study adopted a 10MW ultrafast mode for simulation, and it also used the MVHS(Modify Volumetric Heat Source) model modified from the original VHS(Volumetric Heat Source) model in order to treat the product generation and the oxygen consumption under the stoichiometric state. In addition, the present simulation includes the species conservation equation for the materialization of heat source and the estimation of smoke movement. From the results, the smoke flows are moving along the ceiling because of thermal buoyancy force and as time goes, the smoke gradually moves downward at the vicinity of the entrance. Moreover, without using ventilation, it is found that the smoke flows no longer spread across the cross-passages because the pressure in the non-accident tunnel is higher than that in the accident tunnel.

• 한국통신학회논문지
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• 제12권2호
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• pp.176-188
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• 1987

본 논문은 역필터링을 이용하여 이동에 의해 흐려진 영상을 복원하는 기법에 관한 논문이다. 적절한 역필터를 설계하기 위하여 저하과정(Degradation Process)을 정확히 모델링하여 그의 역특성을 갖는 필터를 구해내야 한다. 고속으로 이동하는 물체의 영상은 Blurring되는데, 이것은 수학적으로 시간에 대한 영상의 적분으로 모델링될 수 있으며, 공간좌표상 방향성 방형 윈도우(Rectangular Window)를 상승(Convolution)하는 것으로 분석된다. 본 논문에서는 주파수 영역에서 이를 분석하여, 이동방향을 고려한 역 Sinc 함수 특성을 갖는 필터를 이용하여 흐려진 영상을 복원하는 기법을 연구한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.247-252
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• 2001

In this paper, dynamic modeling and its analysis for the PIG flow through $90^{\circ}$ curved pipe with compressible and unsteady flow are studied. The PIG dynamics model is derived by using Lagrange equation under assumption that it passes through 3 different sections in the curved pipeline such that it moves into, inside and out of the curved section. The downstream and up stream flow dynamics including the curved sections are solved using MOC. The effectiveness of the derived mathematical models is estimated by simulation results for a low pressure natural gas pipeline including downward and upward curved sections. The simulation results show that the proposed model and solution can be used for estimating the PIG dynamics when we pig the pipeline including curved section.

• 한국자기학회지
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• 제5권4호
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• pp.294-298
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• 1995

A shielded magnetoresistive (SMR) head which has double MR films and linearizes each other has been designed and studied by applying the transmission-line model. We have analyzed the yoke efficiency, bias efficiency and read efficiency of the SMR head. The read efficiency strongly depends on the height of the sensor and slightly on the other geometric parameters. The yoke and bias efficiencies vary with gap length, insulated layer thickness and relative permeability. A quasi-index reduction in the signal flux is observed when the displacement moves away from the medium.

• 약학회지
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• 제33권2호
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• pp.87-100
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• 1989

Salicylic acids as anti-inflammatory agents were analyzed by ab initio, quantum chemical methods to study the possible modes of binding to the receptor. As the result of multiple regression analysis of reactivity indices and interpretation of normalized frontier orbital charges of drugs, potency seems to be related to energy of HOMO and LUMO at the 5 position of benzene ring, and in the 5-phenyl substituted case, the para position of substituting ring is important. The binding occurs first at the positive site of its receptor. The charge density exhibited by the frontier orbitals suggests that charge moves from receptor site to carboxyl group. The electrostatic orientation effect makes an important contribution to the binding of the active molecules to their receptors. Also the electrostatic potential model may be able to rationalize the source of activity or inactivity of the drugs under investigation.

• Journal of Positioning, Navigation, and Timing
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• 제8권3호
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• pp.107-117
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• 2019

When a vehicle moves with a high rotation rate, it is not easy to measure the angular velocity using an off-the-shelf gyroscope. If the angular velocity is estimated using the extended Kalman filter in the gyro-free inertial navigation system, the effect of the accelerometer error and initial angular velocity error can be reduced. In this paper, in order to improve the navigation performance of the gyro-free inertial navigation system, an angular velocity estimation method is proposed based on an extended Kalman filter with an accelerometer random bias error model. In order to show the validity of the proposed estimation method, angular velocities and navigation outputs of a vehicle with 3 rev/s rotation rate are estimated. The results are compared with estimates by other methods such as the integration and an extended Kalman filter without an accelerometer random bias error model. The proposed method gives better estimation results than other methods.