• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1398-1400
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• 1996

In this paper, a method of the decision of the road direction for ALV(Autonomous Land Vehicle) road following by region-based segmentation is presented. The decision of the road direction requires extracting road regions from images in real-time to guide the navigation of ALV on the roadway. Two thresholds to discriminate between road and non-road region in the image are easily decided, using knowledge of problem region and polygonal approximation that searches multiple peaks and valleys in histogram of a road image. The most likely road region of the binary image is selected from original image by these steps. The location of a vanishing point to indicate the direction of the road can be obtained applying it to X-Y profile of the binary road region again. It can successfully steer a ALV along a road reliably, even in the presence of fluctuation of illumination condition, bad road surface condition such as hidden boundaries, shadows, road patches, dirt and water stains, and unusual road condition. Pyramid structure also saves time in processing road images and a real-time image processing for achieving navigation of ALV is implemented. The efficacy of this approach is demonstrated using several real-world road images.

• Bulletin of the Korean Chemical Society
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• 제7권3호
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• pp.224-228
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• 1986

A nonlinear theory is presented for the fluctuations of intermediates in the Brusselator near the critical point caused by diffusion. The method used is the two time scaling method different from the conventional method in the sense that a slight nonlinear effect is included in the initial time region where the linear approximation is conventionally valid. The result obtained by the nonlinear theory shows that fluctuations close to the critical point approach the value of a stable steady state or deviate infinitely from an unstable steady state, as time goes to infinity, while the linear theory gives approximately time-independent fluctuations. A brief discussion is given for the correlation at a time between fluctuating intermediates when the system approaches a stable steady state.

• 융합보안논문지
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• 제18권4호
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• pp.62-71
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• 2018

4차 산업혁명 시대에 가상현실 기술의 급속한 성장은 국방 분야에서도 ICT 융합과 더불어 군사훈련체계의 과학화를 가속 시키고 있다. 최근 육군에서는 사격장 소음문제에 따른 민원증가, 사격장 안전사고 예방, 그리고 훈련비용 절감과 같은 민감한 사안을 해결하기 위해 모의 사격훈련 시뮬레이터 연구개발이 활발하게 진행되고 있다. 본 논문에서는 기존의 사격훈련시뮬레이터의 기술적 한계점을 살펴보고 이를 극복하기 위해 훈련자 중심의 공간 동기화 기법과 미소각 근사 수정질점탄도모델을 제안한다. 자체 개발한 정밀사격 시뮬레이터 MARS(medium range assault rifle shooting simulator)에 조성된 혼합현실(mixed reality) 환경에서 반응조끼(haptic vest)를 착용한 훈련자는 가상적군과 양방향 교전간 실시간 피격을 경험할 뿐만 아니라 실제 탄도궤도가 적용된 정밀사격훈련을 수행하게 되어 훈련 결과에 따른 신뢰 높은 훈련평가를 받을 수 있게 되었다.

• 한국통신학회논문지
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• 제23권9A호
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• pp.2333-2344
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• 1998

We present a two step approach for estimating the motionand sturcture parameters from region orrespondences in two frames. Given four or more region corresondences on the same planar surface, the motion and planar orientation parameters are first linearly estimated based on second-order approximation of the displacement field of the image plane. Then, using this linear estimate as an initial guess, a nonlinear estimate is obtained by iteratively minimizing an objective function using the exact experession of the displacement field. The objective function involves the centroids of corresponding regions and relationships among low-order moments. Through simulations, we show that the two-step region-based approach gives robust estimates. The performance of nonlinear region-based estimation is compared with that of linear region-based and point-based methods. Experimental results for two image pairs, on esynthetic and one real, ar epresented to show the practical applicability of our approach.

• 천문학회보
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• 제37권2호
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• pp.77.2-77.2
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• 2012

We have studied the physical properties of X-ray point sources in galaxy clusters for years based on the archival observations using the most sophisticated space X-ray observatory, Chandra X-ray Observatory. Because the ultimate goal of the study is comparing the physical properties of X-ray point sources found in galaxy clusters to those in X-ray blank fields; blank fields are the regions in the sky where any noticeable cosmic diffuse X-ray emission is not observed, an important key issue regarding this study is picking out the point sources related with galaxy clusters. However we do not have red-shift information of all the X-ray point sources. Therefore as a first order approximation we will consider the point sources with smaller projected cluster-centric distance than the adopted size of galaxy clusters. As a first step of this study we perform X-ray surface photometry of ~600 galaxy clusters based on ~800 Chandra ACIS observations. We carefully investigate the radial structures of diffuse X-ray emission in 3 different energy bands. Based on the highly accurate surface photometry we determine the characteristic size of diffuse X-ray emission (i.e., the boundary of X-ray emission). We also investigate the cosmological evolution of this characteristic size of galaxy clusters. General discussion regarding the two dimensional morphology of galaxy clusters will be presented.

• 한국정보통신학회논문지
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• 제10권3호
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• pp.459-466
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• 2006

열성능 평가를 위한 수치해석에서는 온도, 압력, 건도, 체적, 엔탈피, 엔트로피 등의 열역학적 성질들의 수치값이 필요하다. 그러나 이러한 성질들을 포함하고 있는 증기표를 그대로 사용할 수 없기 때문에, 효과적으로 모델링하여야 한다. 이러한 관점에서 함수근사 특성을 가진 신경회로망을 하나의 대안으로 검토하였다. 신경 회로망은 포화증기 영역과 과열증기 영역에 대해서 따로 구성하였다. 포화증기 영역에 대해서는 하나의 입력으로 7개의 출력을 얻을 수 있도록 하였으며, 각각 10개와 20개의 노드를 가진 은닉층을 구성 하였다. 과열증기 영역에 대해서는 2개의 입력으로 3개의 출력을 얻을 수 있도록 하였으며, 각각 15개와 25개의 노드를 가진 은닉층을 구성하였다. 제안된 모델은 온도, 엔탈피, 엔트로피의 백분율오차가 대부분 ${\pm}0.005%$, 압력이나 비체적의 백분율오차도 대부분 ${\pm}0.025%$ 범위 내로 수렴시킬 수 있었다. 이 성공적인 결과로부터 증기 표를 함수근사하는데 있어서 신경회로망이 아주 강력한 수단이 될 수 있음을 확인할 수 있었다.

• 한국CDE학회논문집
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• 제15권3호
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• pp.178-188
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• 2010

This paper addresses the problem of determining if two surfaces intersect tangentially or transversally in a mathematically consistent manner and approximating an intersection curve. When floating point arithmetic is used in the computation, due to the limited precision, it often happens that the decision for tangential and transversal intersection is not clear cut. To handle this problem, in this paper, interval arithmetic is proposed to use, which provides a mathematically consistent way for such decision. After the decision, the intersection is traced using the validated ODE solver, which runs in interval arithmetic. Then an iterative method is used for computing the accurate intersection point at a given arc-length of the intersection curve. The computed intersection points are then approximated by using a B-spline curve, which is provided as one instance of intersection curve for further geometric processing. Examples are provided to demonstrate the proposed method.

• 한국자기공명학회논문지
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• 제7권1호
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• pp.16-24
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• 2003

Nuclei with the spin quantum number not smaller than unity have not only the nuclear magnetic moment but also the electric quadrupole moment. The quadrupole moment couples with the electric field gradient (EFG) to produce the nuclear quadrupole interaction. It is well known that two independent parameters, i.e. the quadrupole coupling constant (QCC) and the asymmetry parameter ($\eta$) together with the principal axis directions can fully describe the interaction and are very sensitive to the local symmetry and structure of the solid. In order to obtain quantitative estimates of the EFG tensor for various simple ionic configurations surrounding the nucleus under consideration, we employ the simple point charge approximation and apply the calculated results to some real crystals. General agreement is rather satisfactory.

• 자원ㆍ환경경제연구
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• 제11권2호
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• pp.321-333
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• 2002

Approximating bottled water consumption distribution is complicated by zero observations in the sample. To deal with the zero observations, a mixture model of bottled water consumption distributions is proposed and applied to allow a point mass at zero. The bottled water consumption distribution is specified as a mixture of two distributions, one with a point mass at zero and the other with full support on the positive half of the real line. The model is empirically verified for household bottled water consumption survey data. The mixture model can easily capture the common bimodality feature of the bottled water consumption distribution. In addition, when covariates were added to the model, it was found that the probability that a household has non-consumption significantly varies with some variables.

• 한국음향학회지
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• 제20권5호
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• pp.61-68
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• 2001

본 논문에서는 목적함수에 대한 구배계산을 위한 해석적인 방법과 차분근사법을 점배열음원과 최적화 알고리즘(DFP법: davidon-fletcher-powell)을 조합한 적응형 초음파 트랜스듀서의 지향성 최적화에 적용하였다. 위의 두 방법에 대한성능을 비교하기 위하여 준이상 빔 (quasi-ideal beam)과 회전 빔을 목적지향성으로 설정하였다. 수치적인 실험 결과, 차분근사법은 부엽 (side lobe) 레벨의 억압능력은 물론 수렴과정에서의 안정성, 수렴속도, 적응성 면에서 해석적인 계산법에 비해 탁월함을 나타내었다.