• 수산해양기술연구
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• 제43권1호
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• pp.1-11
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• 2007

It is the basic studies for productivity improvement and laborsaving of purse seine fishery. Because the seine shape is apt to be transformed in seine shooting process due to the effect of tide, this study is intended to establish 4 steps, whose flow velocity are 0, 2, 4 and 6cm/sec, in flume tank and perform the experiment to review the character. We used two model seines designed on the scale of 1 to 180 based on the power block seine, which is the mackerel purse seine generally used in the near sea of Jeju Island and triplex seine, which is the mackerel purse seine of one boat system fishing expected in the future, for the experiment, analyzed of the sinking movements on the two seines and its results are as follows. In the setting over the flow velocity 6cm/sec, experiment was impossible because of flying and transformation of seine were severe. The sinking movements of P seine and T seine generally showed linear phenomenon and the sinking speed showed gentle curve shape. Sinking tendency was distinguished by existence of flow velocity. When there is flow velocity, it showed the phenomenon that it sinking by similar type. Although sinking depth and sinking speed did not show distinguished classification, P seine shows bigger than T seine. When there was in flow velocity, the elapsed time(Et) and sinking depth (PDp, TDp) of P seine and T seine can be shown such experimental equations as PDp=(0.21V+4.96)Et-(0.62V-0.10) and TDp=(0.19V+4.95)Et-(0.72V+0.34). When there was in flow velocity, the elapsed time and siking speed (PSp, TSp) of P seine and T seine can be shown such experimental equations as $PSp=-0.11Et^2+1.42Et+1.75\;and\;TSp=-0.11Et^2+1.41Et+1.37$.

• 대한기계학회논문집B
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• 제21권7호
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• pp.911-918
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• 1997

The turbulent viscous wake flows behind a single airfoil, two-dimensional stationary blade row and three-dimensional rotating blade row were calculated, and the numerical results were compared with experimental ones. The numerical technique was based on the SIMPLE algorithm using three turbulent closure models, standard k-.epsilon. model(WFM), low Reynolds number k-.epsilon. model(LRN) and Reynolds stress model (RSM). In the case of a single airfoil, WFM, LRN and RSM presented fairly good velocity distributions in the wake compared with experimental data. In the case of the stationary blade row, LRN and RSM presented better results than WFM for wake velocity distribution, and especially LRN showed best results among these three turbulent models. In the case of the rotating blade row, WFM and LRN showed fairly good agreement with experimental data of the three-dimensional velocity component distributions in the range from hub to mid span region. LRN was also superior to WFM in accuracy of prediction for the wake velocity distribution as same with the cases of a airfoil and the stationary blade row.

• 대한조선학회논문집
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• 제42권5호
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• pp.448-457
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• 2005

The experiment was performed at the large wind tunnel of the Chungnam National University to measure the velocity distribution around the stern of a Liquefied Natural Gas Carrier model. The data, mean velocity vectors of turbulent shear flows at the stern and near-wake including the propeller plane, were obtained by a five-hole Pilot tube for the double body model fixed inside the wind tunnel test section. The present result of the double body model shows a close agreement with the result of the lowing tank experiment performed by the KRISO for the same ship model. The characteristics of the LNG stern flow are discussed based on the measured velocity distribution. The data can be very useful for the validation of some numerical methods in computational fluid dynamics.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.575-586
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• 2008

The main objective of this paper is to develop an improved model for the analysis of liquefaction potential and to predict excess pore pressure (EPP) using the proposed model that can simulate behavior of saturated sand under earthquake loading conditions. The damage concept is adopted for the development of the proposed model. For the development of the model, a general formulation based on experimental results and damage potential using cumulative absolute velocity (CAV) is proposed for a more realistic description of dynamic responses of saturated sand. Undrained dynamic triaxial tests are conducted using earthquake loading conditions. Based on test results, the NCER-NCW function in terms of $w_d$ and CAV is developed. Procedure for the evaluation of EPP and determination of model parameters for the proposed model is presented as well. For the determination of initial liquefaction, the minimum curvature method using the NCS-NCW curve is proposed. It is observed that predicted initial liquefaction using the proposed method agrees well with measured initial liquefaction. From results of additional undrained dynamic triaxial tests, it is seen that predicted EPP generation using the proposed model agrees well with measured results for earthquake loading cases.

• Ocean Systems Engineering
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• 제2권2호
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• pp.83-97
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• 2012

In the present work, design procedure and computer simulation of an AUV are documented briefly. The design procedure containing the design of propulsion system and CFD simulation of hydrodynamics behavior of the hull leads to achieve an optimum mechanical performance of AUV system. After designing, a comprehensive one dimensional model including motor, propeller, and AUV hull behavior simulates the whole dynamics of AUV system. In this design, to select the optimum AUV hull, several noses and tails are examined by CFD tools and the brushless motor is selected based on the first order model of DC electrical motor. By calculating thrust and velocity in functional point, OpenProp as a tool to select the optimum propeller is applied and the characteristics of appropriate propeller are determined. Finally, a computer program is developed to simulate the interaction between different components of AUV. The simulation leads to determine the initial acceleration, final velocity, and angular velocity of electrical motor and propeller. Results show the final AUV performance point is in the maximum efficiency regions of DC electrical motor and propeller.

• 한국철도학회논문집
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• 제8권4호
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• pp.337-341
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• 2005

Algorithm for passenger flow analysis based on DEM(Discrete Element Method) is newly developed. In the new algorithm, there are many similarity between multi phase flow and passenger flow. The velocity component of 1st phase corresponds to the direction vector of cell, each particle to each passenger, volume fraction to population density and the momentum equation of particle to the walking velocity equation of passenger, etc. And, the walking velocity of passenger is also represented by the function of population density. Key algorithms are developed to determine the position of passenger, population density and numbering to each passenger, To verify the effectiveness of new algorithm, passenger flow analysis for simple railway station model is conducted. The results for passenger flow in the model station are satisfying qualitatively and quantitatively.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.245-248
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• 1998

This paper proposes a sensorless velocity estimator using the reduced-order state equation of induction motor based on Kalman Filter. The electrical transients in the stator voltage equations of induction motor are neglected in the reduced-order model. The advantage of using the reduced-order model is to reduce the required number of numerical integrations for filtering the rotor speed. As changing the operating points and the parameters of the induction motor in simulation studies, the behavior of the sensorless velocity estimator as predicted by the reduced-order state equation of induction machine is compared with the behavior predicted by the complete state equation of induction machine.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 춘계학술대회
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• pp.189-192
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• 2021

항적추적 기술에 딥러닝 기반 LSTM(Long Short-Term Memory) 모델을 적용하는 연구로서 기존의 항적추적기술의 경우, 항공기의 등속, 등가속, 급기동, 선회(3D) 비행 등 비행 특성에 따른 칼만 필터 기반의 LMIPDA를 활용한 실시간 항적 추적 시 등속, 등가속, 급기동, 선회(3D) 비행 가중치가 자동으로 변경된다. 이러한 과정에서 등속 비행 중 급기동 비행과 같이 비행 특성이 변경될 때, 항적 손실 및 항적 추적 성능이 하락하여 비행 특성 가중치 변경성능을 향상시킬 필요성이 있다. 본 연구는 레이더의 오차 모델이 적용된 시뮬레이터의 Plot과 표적을 딥러닝 기반 LSTM(Long Short-Term Memory) 모델을 적용하여 학습시키고, 칼만 필터를 활용한 항적추적 결과와 딥러닝 기반 LSTM(Long Short-Term Memory) 모델을 적용한 항적추적결과를 비교함으로써 미리 비행 특성의 변경과정을 예측하여 등속, 등가속, 급기동, 선회(3D) 비행 가중치변경을 신속하게 함으로써 항적추적성능을 향상하기 위한 연구이다.

• Geomechanics and Engineering
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• 제15권4호
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• pp.987-995
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• 2018

In this study, a relationship between small-strain shear modulus ($G_{max}$) and overconsolidation ratio (OCR) based on shear wave velocity ($V_S$) measurement was established to identify the stress history of centrifuge model ground. A centrifuge test was conducted in various centrifugal acceleration levels including loading and unloading sequences to cause various stress histories on centrifuge model ground. The $V_S$ and vertical effective stress were measured at each level of acceleration. Then, a sensitivity analysis was conducted using testing data to ensure the suitability of OCR function for the tested cohesionless soils and found that OCR can be estimated based on $V_S$ measurements irrespective of normally-consolidated or overconsolidated loading conditions. Finally, the developed $G_{max}$-OCR relationship was applied to centrifuge models constructed and tested under various induced stress-history conditions. Through a series of tests, it was concluded that the induced stress history on centrifuge model by compaction, g-level variation, and past overburden load can be analysed quantitatively, and it is convinced that the OCR evaluation technique will contribute to better interpret the centrifuge test results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.2838-2858
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• 2019

Traditional channel models for vehicle-to-vehicle (V2V) communication usually assume fixed velocity in static scattering environment. In the realistic scenarios, however, time-variant velocity for V2V results in non-stationary statistical properties of wireless channels. Dynamic scatterers with random velocities and directions have been always utilized to depict the non-stationary statistical properties of the channel. In this paper, a non-stationary geometry-based cooperative scattering channel model is proposed for multiple-input multiple-output (MIMO) V2V communication systems, where a birth-death process is used to capture the appearance and disappearance dynamic properties of moving scatterers that reflect the time-variant time correlation and Doppler spectrum characteristics. Moreover, our model has more straight and concise to study the impact of the vehicular traffic density on channel characteristics and thus avoid complicated procedure in deriving the analytical expressions of the channel parameters and functions. The numerical results validate our analysis and demonstrate that setting important parameters of our model can appropriately build up more purposeful measurement campaigns in the future.