• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.2
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• pp.111-119
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• 2013

It is essential and fundamental to extract boundary information of target object via massive three-dimensional point data acquired from laser scanner. Especially extracting boundary information of manmade features such as buildings is quite important because building is one of the major components consisting complex contemporary urban area, and has artificially defined shape. In this research, extended ${\chi}$-algorithm using geometry information of point data was proposed to extract boundary information of building from three-dimensional point data consisting building. The proposed algorithm begins with composing Delaunay triangulation process for given points and removes edges satisfying specific conditions process. Additionally, to make whole boundary extraction process efficient, we used Sweep-hull algorithm for constructing Delaunay triangulation. To verify the performance of the proposed extended ${\chi}$-algorithm, we compared the proposed algorithm with Encasing Polygon Generating Algorithm and ${\alpha}$-Shape Algorithm, which had been researched in the area of feature extraction. Further, the extracted boundary information from the proposed algorithm was analysed against manually digitized building boundary in order to test accuracy of the result of extracting boundary. The experimental results showed that extended ${\chi}$-algorithm proposed in this research proved to improve the speed of extracting boundary information compared to the existing algorithm with a higher accuracy for detecting boundary information.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2690-2695
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• 2007

This work presents numerical optimization for design of a blade stacking line of a low speed axial flow fan with a fast and elitist Non-Dominated Sorting of Genetic Algorithm (NSGA-II) of multi-objective optimization using three-dimensional Navier-Stokes analysis. Reynolds-averaged Navier-Stokes (RANS) equations with ${\kappa}-{\varepsilon}$ turbulence model are discretized with finite volume approximations and solved on unstructured grids. Regression analysis is performed to get second order polynomial response which is used to generate Pareto optimal front with help of NSGA-II and local search strategy with weighted sum approach to refine the result obtained by NSGA-II to get better Pareto optimal front. Four geometric variables related to spanwise distributions of sweep and lean of blade stacking line are chosen as design variables to find higher performed fan blade. The performance is measured in terms of the objectives; total efficiency, total pressure and torque. Hence the motive of the optimization is to enhance total efficiency and total pressure and to reduce torque.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.33-35
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• 2006

배전 독립사업부제 도입 및 분산전원의 출현으로 배전계통은 계획 및 운영에 있어서도 변화가 일어 날 것이다. 예로, 기존의 방사상 구조의 배전 계통은 분산 전원의 출현으로 부분적인 그물망 구조로 변형될 수 있으며, 사업 구역이나 사업 지역으로 나누어진 배전계통에서는 서로 다른 관리 체제 하에서 운영이 필요하기 때문에 각 배전회사간의 정보 공유 문제가 발생할 수도 있다. 이러한 문제를 해결하기 위해 분화된 배전 계통의 특성을 고려하여 송전계통과 같이 전체 시스템에 대해 조류 계산하지 않고 배전 계통을 몇 개의 영역으로 나누고 다른 영역과의 경계 정보만을 이용하여 자신의 영역에 대한 조류 계산을 수행하는 알고리즘을 제안하였다. 이런 특성을 최대한 반영한 각 영역의 조류 계산은 분산 전원의 투입으로 인한 양방향 조류가 발생하게 되므로 그물망 구조로 된 구역과 기존의 방사상 구조로 된 영역으로 구분할 수 있다. 본 논문에서는 구역 특성에 맞고 배전 계통에 적용 가능한 알고리즘으로 먼저 분리 구역별 조류 계산을 수행한 후 그 다음 경계치 교환으로 배전 계통 전체의 조류 계산을 수행하는 알고리즘을 제안한다. 즉 방사상 구조 영역에서는 back/forward sweep 방법으로 수행하고 그물망 구조 영역에서는 Full Newton-Raphson 방법으로 구분하여 영역의 특성에 맞게 수행하였다.

• Current Optics and Photonics
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• v.1 no.6
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• pp.598-603
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• 2017

Traditional three-dimensional (3-D) laser imaging systems are based on real aperture imaging technology, whose resolution decreases as the range increases. In this paper, we develop a novel 3-D imaging technique based on the synthetic aperture technology in which the imaging resolution is significantly improved and does not degrade with the increase of the range. We consider an imaging laser radar (ladar) system using the floodlight transmitting mode and multi-beam receiving mode. High 3-D imaging resolutions are achieved by matched filtering the linear frequency modulated (LFM) signals respectively in range, synthetic aperture along-track, and the real aperture across-track. In this paper, a novel 3-D imaging signal model is given first. Because of the motion during the transmission of a sweep, the Doppler shift induced by the continuous motion is taken into account. And then, a proper algorithm for the 3-D imaging geometry is given. Finally, simulation results validate the effectiveness of the proposed technique.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10b
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• pp.431-436
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• 2006

외곽선 추적 알고리즘은 영상 인식 및 표현에 있어서 물체의 기본 성질을 파악하는데 중요하다. 따라서 많은 알고리즘들이 연구되어 왔으며, 이중에는 간단한 경계선 추적자 알고리즘(SBF: Simple Boundary Follower)이다. 이외에도 수정된 간단한 경계선 추적자 알고리즘 (MSBF: Modified Simple Boundary Follower), 개선된 간단한 경계선 추적자 알고리즘(ISBF: Improved Simple Boundary Follower), 무어-네이버 추적 알고리즘(MNT: Moore-Neighbor Tracer), 방사형 탐색 알고리즘(RSA: Radial Sweep Algorithm), 그리고 Theo Pavlidis 알고리즘(TPA)이 있다. 이러한 알고리즘들은 추적 경로 특성들이 다르며 각기 장점과 제약성이 있다.외곽선 알고리즘들의 제약성은 크게 두 가지로 나눌 수 있다. 하나는 알고리즘 특성에 따라 외곽선 픽셀간 인접 형태에 따라 추적하지 못하는 경우가 존재할 수 있다는 것이다. 또 다른 하나는 외곽선 추적 알고리즘의 시작과 종료 조건에 따라서 특정 위치 픽셀들을 찾지 못하는 경우도 존재한다는 점이다. 본 논문에서는 이러한 문제점들을 중심으로 외곽선 추적 알고리즘들의 성능을 분석하였다. 또한, ISBF의 시작 조건과 TPA의 인너코너 추적을 개선하는 기법들을 제안하여 이를 해결토록 하였다. 실험 결과 제안한 기법들은 외곽선 추적 성능을 개선하는데 효과적이었다.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.1
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• pp.1-8
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• 2008

Numerical optimization for design of a blade stacking line of a low speed axial flow fan with a fast and elitist Non-Dominated Sorting of Genetic Algorithm(NSGA-II) of multi-objective optimization using three-dimensional Navier-Stokes analysis is presented in this work. Reynolds-averaged Navier-Stokes(RANS) equations with ${\kappa}-{\varepsilon}$ turbulence model are discretized with finite volume approximations and solved on unstructured grids. Regression analysis is performed to get second order polynomial response which is used to generate Pareto optimal front with help of NSGA-II and local search strategy with weighted sum approach to refine the result obtained by NSGA-II to get better Pareto optimal front. Four geometric variables related to spanwise distributions of sweep and lean of blade stacking line are chosen as design variables to find higher performed fan blade. The performance is measured in terms of the objectives; total efficiency, total pressure and torque. Hence the motive of the optimization is to enhance total efficiency and total pressure and to reduce torque.

• Journal of KIISE:Software and Applications
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• v.30 no.1_2
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• pp.58-72
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• 2003

The objects generated by the keyword new in Java are automatically managed by the garbage collector Inside Java Virtual Machine (JVM) not like using the keywords free or delete in C or C++ programming environments. This provides a means of freedom of memory management burden to the application programmers. The garbage collector however. inherently has its own run time execution overhead. Thus it causes the performance degradation of JVM significantly. In order to mitigate the execution burden of a garbage collector, we propose a novel way of dynamic memory management scheme in Java environment. In the proposed method, the application programmers can explicitly manage the objects In a simple way, which in consequence the run-time overhead can be reduced while the garbage collector is under processing. In order to accomplish this, Java application firstly calls the APIs that arc implemented by native Jana, and then calls the subroutines depending on the JVM, which in turn support to keep the portability characteristic Java has. In this way, we can not only sustain the stability in execution environments. but also improve performance of garbage collector by simply calling the APIs. Our simulation study show that the proposed scheme improves the execution time of the garbage collector from 10.07 percent to 52.24 percent working on Mark-and-Sweep algorithm.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.1 s.307
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• pp.31-38
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• 2006

In this paper, we consider one-step-ahead control of waveform parameters (pulse amplitudes and lengths, and FM sweep rate) as well as detection thresholds for optimal range and range-rate tracking in clutter. The optimal control of the combined parameter set minimizes a tracking performance index under a set of parameter constraints. The performance index includes the probability of track loss and a function of estimation error covariances. The track loss probability and the error covariance are predicted using a hybrid conditional average algorithm The effect of the false alarms and clutter interference is taken into account in the prediction. Tracking performance of the one-step-ahead control is presented for several examples and compared with a control strategy heuristically derived from a finite horizon optimization.

• Journal of KIISE
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• v.43 no.1
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• pp.40-46
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• 2016

Digital road map generation is primarily based on artificial satellite photographing or in-site manual survey work. Therefore, these map generation procedures require a lot of time and a large budget to create and update road maps. Consequently, people have tried to develop automated map generation systems using GPS trajectory data sets obtained by public vehicles. A fundamental problem in this road generation procedure involves the extraction of representative trajectory such as main roads. Extracting a representative trajectory requires the base data set of piecewise line segments(GPS-trajectories), which have close starting and ending points. So, geometrically similar trajectories are selected for clustering before extracting one representative trajectory from among them. This paper proposes a new divide- and-conquer approach by partitioning the whole map region into regular grid sub-spaces. We then try to find similar trajectories by sweeping. Also, we applied the $Fr{\acute{e}}chet$ distance measure to compute the similarity between a pair of trajectories. We conducted experiments using a set of real GPS data with more than 500 vehicle trajectories obtained from Gangnam-gu, Seoul. The experiment shows that our grid partitioning approach is fast and stable and can be used in real applications for vehicle trajectory clustering.

• The KIPS Transactions:PartA
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• v.9A no.4
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• pp.441-450
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• 2002

As the size of embedded system software increase bigger and bigger, and it's complexity is grower and grower, the usage of dynamic memory management scheme such collector also has been increased. Using the garbage collector, however, inherently lead us performance degradation. In order to resolve this kind of performance problem in the Java based embedded system. we introduce an explicit dynamic memory free method to the automated dynamic memory management environment. which can be performed by a programmer. In the worst case, the prosed scheme shows the same performance as the case of that only garbage collector is working, since the unclaimed garbage objects will eventually be collected later by the garbage collector. In the best case. our method is free from any runtime overhead because the applications can be implemented without any intervention of the garbage collector. Although the proposed method can be facilitated with all the existing garbage collection algorithms, it shows an outperform in the case of mark-and-sweep algorithm.