• Journal of Energy Engineering
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• v.1 no.1
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• pp.76-86
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• 1992

A three-dimensional model has been developed for pulverized coal combusters and gasifiers. Coal devolatilization, heterogeneous char oxidation, gas particle interchange, radiation, gas phase oxidation, primary and secondary stream mixing, and heat losses are considered. A finite difference method was used to solve the ordinary non-linear differential equations. The effects of primary and secondary stream flow ratio and coal particle size are investigated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.143-155
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• 2006

SPT-Uphole tomography method was introduced for the evaluation of near subsurface shear wave velocity (Vs) distribution map. In SPT-Uphole method, SPT (Standard Penetration Test) which is common in geotechnical site investigation was used as a source and several surface geophones in line were used as receivers. Vs distribution map which is the triangular shape around the boring point can be developed by tomography inversion. To obtain the exact travel time information of shear wave component, a procedure using the magnitude summation of vertical and horizontal components was used based on the evaluation of particle motion at the surface. It was verified that proposed method could give reliable Vs distribution map through the numerical study using the FEM (Finite Element Method) model. Finally, SPT-Uphole tomography method was performed at the weathered soil site where several boring data with SPT-N values are available, and the feasibility of proposed method was verified in the field.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.5 no.3
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• pp.117-126
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• 2012

This study configuration Vector Control System which is stable and has outstanding Dynamic Characteristics in Very Low Speed Region and Low Speed Region, and proposes Instantaneous Speed Observer and Very Low Speed Control method using Reduced-Dimensional State Observer. The Observer proposed in this system, by appling Reduced-Dimensional State Observer to Load-Torque estimation and using for speed estimation, implements system composition simply and is capable of accurate Instantaneous Speed estimation in Very Low Speed Region. Also, this study reduces influence by System Noise and suggests an induction motor speed control system which is effective in Load Disturbance, modeling error, estimation noise and so on without changing pole of an Observer.

• Fire Science and Engineering
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• v.22 no.2
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• pp.63-69
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• 2008

The characteristics of the spread of a forest fire are generally related to the attributes of combustibles, geographical features, and meteorological conditions, such as wind conditions. The most common methodology used to create a prediction model for the spread of forest fires, based on the numerical analysis of the development stages of a forest fire, is an analysis of heat energy transmission by the stage of heat transmission. When a forest fire breaks out, the analysis of the transmission velocity of heat energy is quantifiable by the spread velocity of flame movement through a physical and chemical analysis at every stage of the fire development from flame production and heat transmission to its termination. In this study, the formula used for the 1-D surface forest fire behavior prediction model, derived from a numerical analysis of the surface flame spread rate of solid combustibles, is introduced. The formula for the 1-D surface forest fire behavior prediction model is the estimated equation of the flame spread velocity, depending on the condition of wind velocity on the ground. Experimental and theoretical equations on flame duration, flame height, flame temperature, ignition temperature of surface fuels, etc., has been applied to the device of this formula. As a result of a comparison between the ROS(rate of spread) from this formula and ROSs from various equations of other models or experimental values, a trend suggesting an increasing curved line of the exponent function under 3m/s or less wind velocity condition was identified. As a result of a comparison between experimental values and numerically analyzed values for fallen pine tree leaves, the flame spread velocity reveals a prediction of an approximately 10% upward tendency under wind velocity conditions of 1 to 2m/s, and of an approximately 20% downward tendency under those of 3m/s.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.85-98
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• 2009

The tau-p inversion algorithm is widely employed to generate starting models with most computer programs, which implement refraction tomography. This algorithm emphasises the vertical resolution of many layers, and as a result, it frequently fails to detect even large lateral variations in seismic velocities, such as the decreases which are indicative of shear zones. This study demonstrates the failure of the tau-p inversion algorithm to detect or define a major shear zone which is 50m or 10 stations wide. Furthermore, the majority of refraction tomography programs parameterise the seismic velocities within each layer with vertical velocity gradients. By contrast, the Generalized Reciprocal Method (GRM) inversion algorithms emphasise the lateral resolution of individual layers. This study demonstrates the successful detection and definition of the 50m wide shear zone with the GRM inversion algorithms. The existence of the shear zone is confirmed by a 2D analysis of the head wave amplitudes and by numerous closely spaced orthogonal seismic profiles carried out as part of a later 3D refraction investigation. Furthermore, an analysis of the shot record amplitudes indicates that a reversal in the seismic velocities, rather than vertical velocity gradients, occurs in the weathered layers. The major conclusion reached in this study is that while all seismic refraction operations should aim to provide as accurate depth estimates as is practical, those which emphasise the lateral resolution of individual layers generate more useful results for geotechnical and environmental applications. The advantages of the improved lateral resolution are obtained with 2D traverses in which the structural features can be recognised from the magnitudes of the variations in the seismic velocities. Furthermore, the spatial patterns obtained with 3D investigations facilitate the recognition of structural features such as faults which do not display any intrinsic variation or 'signature' in seismic velocities.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1330-1339
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• 2022

3D object detection generally aims to detect relatively large data such as automobiles, buses, persons, furniture, etc, so it is vulnerable to small object detection. In addition, in an environment with limited resources such as embedded devices, it is difficult to apply the model because of the huge amount of computation. In this paper, the accuracy of small object detection was improved by focusing on local features using only one layer, and the inference speed was improved through the proposed knowledge distillation method from large pre-trained network to small network and adaptive quantization method according to the parameter size. The proposed model was evaluated using SUN RGB-D Val and self-made apple tree data set. Finally, it achieved the accuracy performance of 62.04% at mAP@0.25 and 47.1% at mAP@0.5, and the inference speed was 120.5 scenes per sec, showing a fast real-time processing speed.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.613-613
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• 2012

ADCP는 매우 상세한 유속 및 하상자료를 측정할 수 있어 하천의 수리학적 계측에 많은 가능성을 열어주고 있다. 하지만 현재까지 대부분 하천 단면에서의 유량 측정에 국한되어 운영되고 있는 실정이다. 본 연구에서는 ADCP가 제공하는 원자료인 3차원 유속과 하상자료를 유량 외의 평균유속장 및 하상 계측에 활용될 수 있도록 하는 후처리 소프트웨어 개발을 통해 ADCP가 하천의 흐름해석 및 2차원 및 3차원 수치모델의 검보정 등에 활용될 수 있는 가능성을 보이고자 한다. 따라서 계측 방식도 하천의 단면뿐만 아니라 하도에 따른 지그재그 방식의 자료를 포괄한다. ADCP 자료의 후처리는 제작사에서 제공하는 소프트웨어가 유량 제공에 초점을 맞춰 다른 분야에의 활용을 위해 별도의 후처리 소프트웨어의 제작이 필요하나 자료구조가 까다롭고 수십에서 수백 개의 파일을 동시에 처리할 수 있는 툴의 개발은 용이하지 않아 ADCP를 흐름분석 등에 활용하고자하는 연구자나 관계 기관종사자들에 한계로 작용하였다. 또한 제작사 (RDI, SonTek)에 따라 원자료의 구조가 완전히 달라 한꺼번에 처리하는 데 많은 문제가 있어왔다. 본 연구를 통해 개발된 툴은 두 제작사의 ADCP 원자료 포맷으로 구성된 다수의 관측 파일도 동시에 처리할 수 있다. 또한 GIS 기반에서 ADCP 자료의 위치를 표출할 수 있어 지형정보와 결부된 흐름장 해석이 가능하게 한다. ADCP 3차원 속도자료는 매우 정밀한 공간에서 측정되는 부분이 장점인 반면에 지나치게 정밀하고 또한 난류 등이 포함되어 원자료 만으로 흐름장을 분석하는 데 한계가 있다. 따라서 본 연구에서는 다양한 공간평균방법을 제공하여 2차원 및 3차원 공간에서의 공간보간된 평균유속장을 볼 수 있게 하였다. 이러한 방식은 2,3차원 수치모델의 격자에 ADCP 유속자료를 보간할 수 있어 모델 검보정에도 활용될 수 있다. ADCP 원자료 및 후처리된 결과는 GIS, Excel, Google Earth 파일 형태 등으로 제공될 수 있어 추후 활용가능성을 높였다.

• Geophysics and Geophysical Exploration
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• v.20 no.2
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• pp.72-77
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• 2017

We calculated 3D frequency- and Laplace-domain wavefields using time-domain modeling and Fourier transform or Laplace transform. We adopted OpenACC and GPU for an efficient parallel calculation. The OpenACC makes it easy to use GPU accelerators by adding directives in conventional C, C++, and Fortran programming languages. Accordingly, one doesn't have to learn new GPGPU programming languages such as CUDA or OpenCL to use GPU. An OpenACC program allocates GPU memory, transfers data between the host CPU and GPU devices and performs GPU operations automatically or following user-defined directives. We compared performance of 3D wave propagation modeling programs using OpenACC and GPU to that using single-core CPU through numerical tests. Results using a homogeneous model and the SEG/EAGE salt model show that the OpenACC programs are approximately 53 and 30 times faster than those using single-core CPU.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.296-299
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• 2009

본 논문은 차분진화 알고리즘을 이용한 다중 손상된 RC 슬라브 교량에 대한 시스템 인식(System Identification)기법을 소개한다. 제안된 기법을 이용하여 이동하중에 의한 교량의 동적응답을 기반으로 손상유무, 위치, 크기가 추정된다. ABAQUS를 이용한 손상된 3차원 슬라브 모델을 실험대상으로 하여, 모델로부터 동적응답을 찾아내었다. 차분진화 알고리즘(Differential Evolutioinary algorithm)을 기반으로 동적응답과 Bi-variate Gaussian 함수로 강성저하된 2차원 유한요소 MZC모델을 이용하여 손상된 위치와 크기, 이동하중의 크기와 속도가 추정되었다. 차분진화 알고리즘을 이용한 RC교량의 손상위치와 이동하중에 대한 추정은 3%이내의 오차를 보였고, 이로부터 제안된 방법의 효율성과 정확성이 검증되었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.2
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• pp.70-80
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• 2000

Princeton Ocean Model (POM) is modified to construct a three-dimensional, semi-implicit hydro¬dynamic model with a wetting-and-drying scheme. The model employs semi-implicit treatment of the barotropic pressure gradient terms and the vertical mixing terms in the momentum equations, and the velocity divergence term in the vertically-integrated continuity equation. Such treatment removes the external mode and thus the mode splitting scheme in POM, allowing the semi-implicit model to use a larger time step. Applied to hypothetical systems, both the semi-implicit model and POM give nearly the same results. The semi-implicit model, however, runs approximately 4.4 times faster than POM showing its improved computational efficiency. Applied to a hypothetical system with intertidal flats, POM employing the mode splitting scheme produces noises at the intertidal flats, that propagate into the main channel resulting in unstable current velocities. Despite its larger time step, the semi-implicit model gives stable current velocities both at the intertidal flats and main channel. The semi-implicit model when applied to Kyeonggi Bay gives a good reproduction of the observed tides and tidal currents throughout the modeling domain, demonstrating its prototype applicability.