• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 춘계종합학술대회
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• pp.385-388
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• 1999

Non-local impact ionization 현상의 해석에 사용될 수 있는 새로운 local model이 제시되었다. 새로운 모델은 임의의 점에서 가상의 선형 전기장과 path integral로 계산되는 유효전기장의 값을 이용한다. 이 모델은 불순물 농도, 전자 및 홀 농도, 전기장의 기울기 둥의 local 변수만을 이용함으로써 기존의 drift-diffusion 소자 시뮬레이터에 쉽게 적용될 수 있다. 결과를 Monte Carlo 시뮬레이션과 비교하여 새로운 모델이 non-local 현상을 잘 설명하는 것을 확인할 수 있었다.

• Tribology and Lubricants
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• 제19권6호
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• pp.357-364
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• 2003

The sub­surface stress field beneath the gear's contact surface caused by the contact pressure in lubricated condition has been calculated. To evaluate the influence of the clearance shape on the stress field, two kinds of tooth profile models were chosen. One is the conventional cylinder contact model and the other is the new numerical model. Love's rectangular patch solution was used to obtain the sub­surface stress field. The analysis results show that the sub­surface stress is quite dependent on both the contact pressure and the profile model. The maximum effective stress of the new model is lower than that of the old model. The depth where the maximum effective stress occurs in the new model is not proportional to the intensity of the external load.

• Computers and Concrete
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• 제26권4호
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• pp.343-350
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• 2020

Concrete-filled steel tubular (CFST) members have been widely used in engineering, and their tube diameters have become larger and larger. But there is no research on the thermal field of large-diameter CFST structure. These studies focused on the thermal field of the large-diameter CFST structure under solar radiation. The environmental factors and the actual placement position were considered, and the finite element model (FEM) of the thermal field of CFST members under solar radiation (SR) was established. Then the FEM was verified by practical experiments. The most unfavorable temperature gradient model in the cross-section was proposed. The testing results showed that the temperature field of the large-diameter CFST member section was non-linearly distributed due to the influence of SR. The temperature field results of CFST members with different pipe diameters indicated that the larger the core concrete diameter was, the slower the central temperature changed, and there was a significant temperature difference between the center and the boundary. Based on the numerical model, the most unfavorable temperature gradient model in the section was proposed. The model showed that the temperature difference around the center of the circle is small, and the boundary temperature difference is significant. The maximum temperature difference is 15.22℃, which appeared in the southern boundary area of the specimen. Therefore, it is necessary to consider the influence of SR on the thermal field of the member for large-diameter CFST members in actual engineering, which causes a large temperature gradient in the member.

• 한국자기학회지
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• 제26권5호
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• pp.159-167
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• 2016

초등학교 6학년 과학교과 영구자석 주위의 자기장에 대한 학습에서 나타나는 학생들의 자기장 개념 유형을 조사하였다. 그리고 학생들의 영구자석 주위의 자기장에 대한 오개념 개선을 위한 나침반을 사용하는 대안실험을 제안하였으며 학생들의 인지양식에 따른 효과를 비교하였다. 영구자석 주위에 철가루를 뿌려 관찰한 자기장에 대해 부분 분포 모형, 극 분리 모형, 균질 분포 모형, 장 모형의 4가지 개념 모형이 나타났으며, 영구자석과 나침반을 이용하여 자기장을 관찰한 실험에서는 철가루 실험에서 나타났던 자기장 모형들이 연속, 변형, 복잡화되었는데 극 분리 모형, 복합 균질 분포 모형, 장 모형의 3가지 자기장 개념 모형으로 나타났다. 대안실험을 통해서 올바른 자기장 개념의 형성 비율이 장의존적인 학생들에게 유의미하게 높은 것으로 나타났다.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2006년도 추계학술발표회
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• pp.131-135
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• 2006

이 연구의 목적은 지구 내부의 동적 코어에서 공간과 시간에 따라서 발생하는 지구 자기장 구조와 그에 따른 경년 자차변화를 모델링하고 연구하는 것이다. 지구의 주 자장과 경년 자차변화에 대한 구형 조화 모델은, 외부 간섭자장이나 내부의 불균일 등이 없다는 가정 하에 안정되고 왜곡되지 않은 지구상 어떠한 위치에서의 지구자장의 구조와 세기를 나타낼 수 있다. 이 연구에서는 선박용 디지털 컴퍼스를 이러한 지구자장 에 적용하는 경우를 고려해 지구의 원 조화 모텔에 대한 실제 적용방법과 절차를 기술하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권2호
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• pp.120-131
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• 2007

A comprehensive short channel analytical model has been proposed for High Electron Mobility Transistor (HEMT) to obtain higher cut-off frequency maintaining the reliability of the device. The model has been proposed to consider generalized doping variation in the directions perpendicular to and along the channel. The effect of field plates and different gate-insulator geometry (T-gate, etc) have been considered by dividing the area between gate and the high band gap semiconductor into different regions along the channel having different insulator and metal combinations of different thicknesses and work function with the possibility that metal is in direct contact with the high band gap semiconductor. The variation obtained by gate-insulator geometry and field plates in the field and channel potential can be produced by varying doping concentration, metal work-function and gate-stack structures along the channel. The results so obtained for normal device structure have been compared with previous proposed model and numerical method (finite difference method) to prove the validity of the model.

• 천문학회보
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• 제46권1호
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• pp.41.3-42
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• 2021

Conventional global magnetic field maps, such as daily updated synoptic maps, have been constructed by merging together a series of observations from the Earth's viewing direction taken over a 27-day solar rotation period to represent the full surface of the Sun. It has limitations to predict real-time farside magnetic fields, especially for rapid changes in magnetic fields by flux emergence or disappearance. Here, we construct accurate synchronic magnetic field maps using frontside and AI-generated farside data. To generate the farside data, we train and evaluate our deep learning model with frontside SDO observations. We use an improved version of Pix2PixHD with a new objective function and a new configuration of the model input data. We compute correlation coefficients between real magnetograms and AI-generated ones for test data sets. Then we demonstrate that our model better generate magnetic field distributions than before. We compare AI-generated farside data with those predicted by the magnetic flux transport model. Finally, we assimilate our AI-generated farside magnetograms into the flux transport model and show several successive global magnetic field data from our new methodology.

• 한국대기환경학회지
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• 제14권3호
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• pp.219-228
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• 1998

In the present investigation, a numerical model developed for the prediction of the wind flow over complex terrain is validated by comparing with the field experiments. For the solution of the Reynolds - Averaged Clavier- stokes equations which are the governing equations of the microscale atmospheric flow, the model is constructed based on the finite-volume formulation and the SIMPLEC pressure-correction algorithm for the hydrodynamic computation. The boundary- fitted coordinate system is employed for the detailed depiction of topography. The boundary conditions and the modified turbulence constants suitable for an atmospheric boundary- layer are applied together with the k- s turbulence model. The full- scale experiments of Cooper's Ridge, Kettles Hill and Askervein Hill are chosen as the validation cases . Comparisons of the mean flow field between the field measurements and the predicted results show good agreement. In the simulation of the wind flow over Askervein Hill , the numerical model predicts the three dimensional flow separation in the downslope of the hill including the blockage effect due to neighboring hills . Such a flow behavior has not been simulated by the theoretical predictions. Therefore, the present model may offer the most accurate prediction of flow behavior in the leeside of the hill among the existing theoretical and numerical predictions.

• 한국도로학회논문집
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• 제18권1호
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• pp.73-83
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• 2016

PURPOSES : The purpose of this study is to develop a method for improving the accuracy of analysis results obtained from a two-dimensional (2-D) numerical analysis model of continuously reinforced concrete pavement (CRCP). METHODS : The analysis results from the 2-D numerical model of CRCP are compared with those from more rigorous three-dimensional (3-D) models of CRCP, and the relationships between the results are recognized. In addition, the numerical analysis results are compared with the results obtained from field experiments. By performing these comparisons, the calibration factors used for the 2-D CRCP model are determined. RESULTS : The results from the comparisons between 2-D and 3-D CRCP analyses show that with the 2-D CRCP model, concrete stresses can be overestimated significantly, and crack widths can either be underestimated or overestimated by a slight margin depending on the assumption of plane stress or plane strain. The behaviors of crack width in field measurements are comparable to those obtained from the numerical model of CRCP. CONCLUSIONS : The accuracy of analysis results from the 2-D CRCP model can be improved significantly by applying calibration factors obtained from comparisons with 3-D analyses and field experiments.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1674-1681
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• 2015

This paper presented an improved analytical method for calculating armature-reaction field in the surface-mounted permanent magnet machines accounting for opening slots. The analytical model is divided into two types of subdomains. The current of the armature is centralized in the center of the slots. The field solution of each subdomain is obtained by applying the interface and boundary conditions of the model. Two 30-pole/36-slot prototype machines with different slot-opening width are used for validation. The FE (finite element) results confirm the validity of the analytical results with the proposed model. The investigation shows that the wider the slot-opening width is, the smaller the peak value of radial and circumferential components of flux density, and the analytical armature-reaction field produced by centralized current in the slots is similar with the armature-reaction field produced by distributed current in the slots in the FE.