• 한국CDE학회논문집
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• 제7권2호
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• pp.75-80
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• 2002

This paper details a robust and efficient algorithm for point classification with respect to a polygon in 2D real number domain. The concept of tolerance makes this algorithm robust and consistent. It enables to define‘on-boundary’ , which can be interpreted as either‘in-’or‘out-’side region, and to manage rounding errors in floating point computation. Also the tolerance is used as a measure of reliability of point classifications. The proposed algorithm is based on a ray-intersection technique known as the most efficient, in which intersections between a ray originating from a given test point and the boundary of a region are counted. An odd number of intersections indicates that the point is inside region. For practical examples the algorithm is most efficient because most edges of the polygon region are processed by simple bit operations.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1997년도 제8회 학술강연회논문집
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• pp.43-51
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• 1997

Steady and unsteady numerical simulations are conducted for the experiments performed to investigate the ram accelerator flow field by using the expansion tube facility in Stanford University. Navier-Stokes equations for chemically reacting flows are analyzed by fully implicit and time accurate numerical methods with Jachimowski's detailed chemistry model for hydrogen-air combustion involving 9 species and 19 reaction steps. Although the steady state assumption shows a good agreement with the experimental schlieren and OH PLIF images for the case of $2H_2$+$O_2$+$17N_2$, it fails in reproducing the combustion region behind the shock intersection point shown in the case of $2H_2$+$O_2$+$12N_2$, mixture. Therefore, an unsteady numerical simulation is conducted for this case and the result shows all the detailed flow stabilization process. The experimental result is revealed to be an instantaneous result during the flow stabilization process. The combustion behind the shock intersection point is the result of a normal detonation formed by the intersection of strong oblique shocks that exist at early stage of the stabilization process. At final stage, the combustion region behind the shock intersection point disappears and the steady state result is retained. The time required for stabilization of the reacting flow in the model ram accelerator is found to be very long in comparison with the experimental test time.

• 대한기계학회논문집
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• 제19권8호
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• pp.1832-1843
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• 1995

Tool interference is one of the most critical problems in sculptured surface machining. When machining cavities and concaves, the tool frequently overcuts the portions of the surface, which cause inaccuracy in machining. So tool interference-free paths must be generated for rough cutting more efficiently. In this paper a software using SSI(Surface/Surface intersection) algorithm is developed for eliminating tool interference which occurs in an offset surface in 3-dimensional free form surface modeling. this work consists of two stages : using the offset data, the intersection curves are rapidly checked by this algorithm at the first stage. CL(cutter location) data are obtained by deleting the loop section of intersected offset patches at the second stage. This algorithm can reduce the amount of memory required to store machining data and also easily check region which have the possibility of intersection. Also, This software is verified to be useful in machining a curved object on a DNC milling machine.

• 문화기술의 융합
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• 제1권1호
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• pp.79-85
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• 2015

최근 모바일 장치를 이용한 개인용 GPS 사용이 늘어나면서 모바일 장치로부터 수집한 GPS 데이터를 정제, 가공하여 사용자에게 위치추적, 공공안전, 위치기반정보 등을 제공해 주는 위치 기반 서비스 사업이 증가하고 있다. 하지만 위성 신호의 특성 상 반사 굴절이 잘 되는 고층 건물이나 실내에서는 사용이 거의 불가능기 때문에 GPS 오차를 보정해 줄 필요가 있다. 본 논문은 교차점 기반 구역 인덱싱을 이용해 사용자의 GPS 정보를 보정하여 정제된 궤적을 생성하는 방법을 제시한다. 이를 이용하여 모바일 장치를 이용한 사용자 이동 궤적을 분석하고, 다수의 사용자로 부터 입력받은 궤적의 유사성 식별을 통해 선호 경로를 추천하는 방법을 제안한다.

• 전력전자학회논문지
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• 제18권4호
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• pp.322-332
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• 2013

Conventional single-phase series quasi Z-source voltage compensator can not compensate for voltage sag less than 50% that frequently occurs in the industrial field. In this study, single-phase series quasi Z-source voltage sag-swell compensator which can compensate the voltage variation of entire range is proposed. The proposed system is composed of two quasi Z-source AC-AC converters connected in series with output terminal stage. Voltage sag less than 50% could be compensated by the intersection switching control of the upper converter duty ratio and of the upper converter duty ratio. Also the compensation voltage and its flowchart for each compensation mode are presented for entire sag-swell region. To confirm the validity of the proposed system, a DSP(DSP28335) controlled experimental system was manufactured. As a result, the proposed system could compensate for the voltage sag/swell of 20% and 60%. Finally, voltage compensation factor and THD(Total Harmonic Distortion) according to voltage variation and load change were measured, and voltage quality shows a good results.

• 디지털산업정보학회논문지
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• 제14권4호
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• pp.169-176
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• 2018

In this study, we propose a new Fire Flame Region Extraction using Block Homogeneity Segmentation method of the Fire Image with irregular texture and various colors. It is generally assumed that fire flame extraction plays a very important role. The Color Image with fire flame is divided into blocks and edge strength for each block is computed by using modified color histogram intersection method that has been developed to differentiate object boundaries from irregular texture boundaries effectively. The block homogeneity is designed to have the higher value in the center of region with the homeogenous colors or texture while to have lower value near region boundaries. The image represented by the block homogeneity is gray scale image and watershed transformation technique is used to generate closed boundary for each region. As the watershed transform generally results in over-segmentation, region merging based on common boundary strength is followed. The proposed method can be applied quickly and effectively to the initial response of fire.

• 제어로봇시스템학회논문지
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• 제14권8호
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• pp.848-855
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• 2008

In this paper, we describe correspondence among multiple images taken by multiple cameras. The correspondence among multiple views is an interesting problem which often appears in the application like visual surveillance or gesture recognition system. We use the principal axis and the ground plane homography to estimate foot of human. The principal axis belongs to the subtracted silhouette-based region of human using subtraction of the predetermined multiple background models with current image which includes moving person. For the calculation of the ground plane homography, we use landmarks on the ground plane in 3D space. Thus the ground plane homography means the relation of two common points in different views. In the normal human being, the foot of human has an exactly same position in the 3D space and we represent it to the intersection in this paper. The intersection occurs when the principal axis in an image crosses to the transformed ground plane from other image. However the positions of the intersection are different depend on camera views. Therefore we construct the correspondence that means the relationship between the intersection in current image and the transformed intersection from other image by homography. Those correspondences should confirm within a short distance measuring in the top viewed plane. Thus, we track a person by these corresponding points on the ground plane. Experimental result shows the accuracy of the proposed algorithm has almost 90% of detecting person for tracking based on correspondence of intersections.

• ETRI Journal
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• 제29권5호
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• pp.697-699
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• 2007

Spatiograms are histograms augmented with spatial means and covariances to capture a richer description of the target. We present a particle filtering framework for region-based tracking using spatiograms. Unlike mean shift, the framework allows for non-differentiable similarity measures to compare two spatiograms; we present one such similarity measure, a combination of a recent weighting scheme and histogram intersection. Experimental results show improved performance with the new measure as well as the importance of global spatial information for tracking. The performance of spatiograms is compared with color histograms and several texture histogram methods.

• Steel and Composite Structures
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• 제18권4호
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• pp.1045-1062
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• 2015

Concrete-filled circular t steel tubular joints (CFSTJs) in practice are frequently subjected to fluctuated loadings caused by wind, earthquake and so on. As fatigue crack is sensitive to such cyclic loadings, assessment on performance of CFSTJs with crack-like defect attracts more concerns because both high stress concentration at the brace/chord intersection and welding residual stresses along weld toe cause the materials in the region around the intersection to be more brittle. Once crack initiates and propagates along the weld toe, tri-axial stresses in high gradient around the crack front exist, which may bring brittle fracture failure. Additionally, the stiffness and the load carrying capacity of the CFSTJs with crack may decrease due to the weakened connection at the intersection. To study the behaviour of CFSTJs with initial crack, experimental tests have been carried out on three full-scale CFCST T-joints with same configuration. The three specimens include one uncracked joint and two corresponding cracked joints. Load-displacement and load-deformation curves, failure mode and crack propagation are obtained from the experiment measurement. According to the experimental results, it can be found that he load carrying capacity of the cracked joints is decreased by more than 10% compared with the uncracked joint. The effect of crack depth on the load carrying capacity of CFCST T-joints seems to be slight. The failure mode of the cracked CFCST T-joints represents as plastic yielding rather than brittle fracture through experimental observation.

• 융합신호처리학회논문지
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• 제3권1호
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• pp.1-7
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• 2002

본 논문에서는 사용자가 질의영상을 선택할 때 영상전체 뿐만 아니라 영상내의 다양한 물체에 대해 질의를 원하는 물체영역만을 간단히 선택, 추출하여 그와 유사한 물체를 영상 데이터베이스 내에서 검색할 수 있는 내용기반 영상검색 시스템을 구현하였다. 질의영상으로부터 개선된 HSV변환을 통해 히스토그램을 구한 뒤 질의영상의 대표색상을 이용한 컬러 히스토그램 인터섹션방법으로 신속하게 1차 유사도 측정을 하여 후보영상들을 검색한다. 그리고 밴디드 컬러 오토코릴로그램을 이용한 2차 유사도 측정을 수행하여 최종 검색된 영상을 구하였는데 각각의 단점을 보완할 수 있는 2개의 검색방법들을 결합함으로써 소환성(recall) 및 정확성(precision)을 개선하였다. 또한 영상데이터베이스내의 영상들을 특성 라이브러리내에 자통 색인화하여 이를 통해 빠른 영상검색이 가능하였다.