• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.05a
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• pp.145-152
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• 1998

실내에서 가스폭발시 피해를 예측하기 위해서 폭발 화염면의 전파를 수치해석을 통해 해석했다. 확산방정식에 의해 가스누출에 의한 실내의 가스확산분포를 구했으며 문헌에서 선택한 누출의 초기조건을 사용했다. 화염온도를 계산하기 위해 각 가스 혼합비에 따른 엔탈피와 화학식에 대한 reduced mechanism을 사용했으며 문헌에서 찾은 각 가스의 농도별 층류 연소속도를 혼합가스의 층류연소속도에 적용시켰다. k-$\varepsilon$ 모델에서 turbulance energy를 층류연소속도와 결합시켜 난류화염 전파속도를 모델링 했다. 화염면의 전파를 분석하기 위해 실내의 위치에는 직각, 화염면의 전파에는 원통좌표계를 사용했다. 유리창의 파손에 의한 화염전파면의 변화에 따른 압력상승 요인을 해석하였으며 창문의 크기에 따라서 점화위치에 따른 실내 압력상승의 영향이 서로 다르게 나타나는 결과를 얻었다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.73-79
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• 1996

우리나라와 같이 철도의 운행위치와 소음 피해를 받는 수음자 간의 거리가 인접되어 있는 경우, 소음의 전파특성은 과도형상을 나타내는 구간에 속하게 되어 전파중에 나타나는 지표면의 다양한 물리적, 현상과 경계면 등의 이피던스 값등이 많은 영향을 끼치게 된다. 본 연구에서는 철도소음의 소음원 자체에 대한 모델링 기법과, 자유공간을 전파할 때 나타나는 거리감쇠 효과 등을 고려한 음향학적인 연속선음원 및 유한 불연속 선음원 등에 대한 검토가 이루어졌고, 특히, 소음원의 크기에 비교하여 수음자의 위치에 따라 저감되는 음향전파특성을 설명하였다. 또한, 유한한 길이를 가지고 있는 철도차량의 소음원 모델을 이용하여 향후 국내에서 운행되리라 예상되는 고속철도의 음향파워를 산출하였다. 산출된 음향파워로부터 철도변의 소음분포를 도출하였으며 고속철도의 경우 운행시 소음피해가 어느 정도인지를 예상하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.6
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• pp.614-619
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• 1997

In this paper, radio-wave propagation characteristics in a rectangular corridor are investigated using a tunnel model of reduced dimensions. Measurements were carried out on vertical polarization characteristics in the frequency range from 2 GHz to 10 GHz. The experimental results for the propagation constant in tunnel model agree satisfactorily with theoretical prediction. It is shown that model method is applicable in determining the propagation characteristics in tunnel.

• Annual Conference of KIPS
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• 2009.04a
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• pp.1281-1284
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• 2009

무선통신에서는 다양한 서비스, 높은 신뢰도와 함께 빠른 전송속도를 요구한다. 이러한 요구를 만족시키기 위해서 LDPC 부호와 MIMO 기술이 활발히 연구 중에 있다. 본 논문에서는 LDPC와 결합된 STC 모델을 설명하고, 여러개의 송신안테나로부터 송신되어 결합된 신호를 분리하기 위해 사용되는 Log-Likelihood Computation을 기존의 방식과 제안하는 저 계산량 알고리즘을 통한 방식을 비교, 분석하여 기존의 방식과 근접한 BER 성능을 유지 하면서 계산량 감소를 확인한다.

• The Journal of Korean Association of Computer Education
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• v.5 no.4
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• pp.61-69
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• 2002

Software documents consist of a number of logical objects and relationships between them, and a lot of versions are generated during software development. When an object is changed, it is desirable to easily identify the change and the range of change propagation for efficient software development and maintenance. However, it is difficult to identify it in a coarse-grained object management model. To solve this problem, fine-grained object management is required. In this paper, I propose a consistency management model for fine-grained software objects based on operation history applied to edit software objects. This paper presents a formal model for consistency management at the fine-grained level. Consistency between documents is managed using dependency between objects and kinds of the operations applied to the objects so that unnecessary change propagation can be avoided.

• Journal of Korean Society for Geospatial Information Science
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• v.9 no.2 s.18
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• pp.17-27
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• 2001

Buffering is one of the popular spatial analytical functions widely used in many proximity analyses. The buffeting inevitably entails a new polygon of specified edge that is simulated by rolling a ball around the buffering object. While buffering, the error on the buffering object propagates to the new buffered object. In this paper the error propagation behavior during the buffering operation is analyzed based on a pilot project for two different data models: polyline and spline curve. Thus, the error on the buffered objects are classified, mathematically defined, and measured. For measurements, the pilot project is designed and performed using a test site that is a lake boundary at Wisconsin, USA.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.315-322
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• 2010

The phase-screen and the split-step Fourier migrations, which are implemented in both the frequency-wavenumber and frequency-space domains by using one-way scalar wave equation, allow imaging in laterally heterogeneous media with less computing time and efficiency. The generalized-screen migration employs the series expansion of the exponential, unlike the phase-screen and the split-step Fourier migrations which assume the vertical propagation in frequency-wavenumber domain. In addition, since the generalized-screen migration generalizes the series expansion of the vertical slowness, it can utilize higher-order terms of that series expansion. As a result, the generalized-screen migration has higher accuracy in computing the propagation with wide angles than the phase-screen and split-step Fourier migrations for media with large and rapid lateral velocity variations. In this study, we developed a 2D prestack generalized-screen migration module for imaging a complex subsurface efficiently, which includes various dips and large lateral variations. We compared the generalized-screen propagator with the phase-screen propagator for a constant perturbation model and the SEG/EAGE salt dome model. The generalized-screen propagator was more accurate than the phase-screen propagator in computing the propagation with wide angles. Furthermore, the more the higher-order terms were added for the generalized-screen propagator, the more the accuracy was increased. Finally, we compared the results of the generalizedscreen migration with those of the phase-screen migration for a model which included various dips and large lateral velocity variations and the synthetic data of the SEG/EAGE salt dome model. In the generalized-screen migration section, reflectors were positioned more accurately than in the phase-screen migration section.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.112-118
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• 2008

In the present study, the dependence of ultrasonic phase velocity on porosity and frequency in cancellous bone was predicted using the Biot model and the modified Biot-Attenborough (MBA) model for propagation in fluid-saturated porous media. It was also compared with previously published measurements in human and bovine cancellous bones in vitro. It was shown that the phase velocity in cancellous bone decreased with increasing porosity and frequency The dependence of phase velocity on propagation angle in cancellous bone as predicted using the Schoenberg model together with the Biot model and tile MBA model which were modified to include the effect of angle. The theoretical models used in the present study advance our understanding of the interaction between ultrasound and cancellous bone and can be expected to be usefully employed for the diagnosis of osteoporosis.

• Fire Science and Engineering
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• v.30 no.6
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• pp.37-42
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• 2016

The present study has been performed to examine the feasibility of a flame spread model on the design fire scenario for fire risk analysis. Thermo-Gravimetric analysis and sample burning test were conducted to obtain the material properties of a single couch covered with synthetic leather material and a series of FDS calculations applying with the measured material properties were performed for different grid sizes. The overall fire growth characteristics predicted by the fire model were quite different from the results of a real scale fire test and the initial peak value of the HRR and total released energy showed the results within a 30% discrepancy for the computational grids used in the present study. The current model has some limitations in predicting the fire growth characteristics, such as fire growth rate and the time to the maximum HRR. This study shows that the fire model may be applicable to creating the design fire scenario through continuous model improvement and detailed material properties.

• Annual Conference on Human and Language Technology
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• 2018.10a
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• pp.185-188
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• 2018

띄어쓰기와 문장 경계 인식은 그 성능에 따라 자연어 분석 단계에서 오류를 크게 전파하기 때문에 굉장히 중요한 문제로 인식되고 있지만 각각 서로 다른 자질을 사용하는 문제 때문에 각각 다른 모델을 사용해 순차적으로 해결하였다. 그러나 띄어쓰기와 문장 경계 인식은 완전히 다른 문제라고는 볼 수 없으며 두 모델의 순차적 수행은 앞선 모델의 오류가 다음 모델에 전파될 뿐만 아니라 시간 복잡도가 높아진다는 문제점이 있다. 본 논문에서는 띄어쓰기와 문장 경계 인식을 하나의 문제로 보고 한 번에 처리하는 다중 클래스 분류 시스템을 통해 시간 복잡도 문제를 해결하고 다중 손실 선형 결합을 사용하여 띄어쓰기와 문장 경계 인식이 서로 다른 자질을 사용하는 문제를 해결했다. 최종 모델은 띄어쓰기와 문장 경계 인식 기본 모델보다 각각 3.98%p, 0.34%p 증가한 성능을 보였다. 시간 복잡도 면에서도 단일 모델의 순차적 수행 시간보다 38.7% 감소한 수행 시간을 보였다.