• Journal of KIISE:Databases
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• v.31 no.6
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• pp.664-674
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• 2004

The trajectory preservation property that stores only one trajectory in a leaf node is the most important feature of an index structure, such as the TB-tree for retrieving object's moving paths in the spatio-temporal space. It performs well in trajectory-related queries such as navigational queries and combined queries. But, the MBR of non-leaf nodes in the TB-tree have large amounts of dead space because trajectory preservation is achieved at the sacrifice of the spatial locality of trajectories. As dead space increases, the overlap between nodes also increases, and, thus, the classical range query cost increases. We present a new split policy and entry relocation policies, which have no deterioration of the performance for trajectory-related queries, for improving the performance of range queries. To maximally reduce the dead space of a non-leaf node's MBR, the Maximal Area Reduction (MAR) policy is used as a split policy for non-leaf nodes. The entry relocation policy induces entries in non-leaf nodes to exchange each other for the purpose of reducing dead spaces in these nodes. We propose two algorithms for the entry relocation policy, and evaluate the performance studies of new algorithms comparing to the TB-tree under a varying set of spatio-temporal queries.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.110-116
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• 2013

With the recent development of wireless network technologies, there have been increasing usage of variouse position base servies. Position based services basically collect position information of moving object for the utilization of them in real life. Accordingly, new index structures are required to efficiently retrieve the consecutive positions of moving objects. In the paper, we consider volume of Extended Minimum Bounding Rectangles(EMBR) to be determined by average size of range queries. We proposed the methode that split efficiently moving object with long distance between location, and split moving object for decrease searching space an Estimated-Split algorithm that minimizes the volume of MBRs is designed and simulated. Our experimental evaluation confirms the effectiveness and efficiency of our proposed splitting policy.

• 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.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.776-778
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• 2003

이동체 데이터베이스에서 대용량 궤적 정보를 효율적으로 검색학기 위해서는 색인이 필요하다. 특히 궤적을 선택하는 과정과 선택된 궤적의 일부분을 추출하는 과정으로 이루어진 복합 질의를 효율적으로 처리하기 위해서는 궤적 보존을 지원하는 TB-tree와 같은 색인 구조가 적합하다. 그러나, TB-tree는 공간적인 인접성을 고려하지 않아 비단말 노드의 겹침과 사장 영역이 매우 커 영역 질의의 비용이 증가하는 문제가 있다. 이 논문에서는 복합 질의 및 영역 질의를 효율적으로 처리하기 위하여, TB-tree에서 사장 영역을 감소시킬 수 있는 최대 영역 감소 정책을 제시한다. 최대 영역 감소 정책을 공간 활용도를 최대로 유지하면서 사장 영역을 점진적으로 감소시키는 삽일 및 분할 정책으로서 TB-tree의 비단말 노드의 겹침을 줄여 영역 질의의 비용을 감소시킨다.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.477-486
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• 2020

The purpose of this study was to evaluate the effects of reconstruction filters, X-ray source trajectories and intervals in the quality of digital tomosynthesis (DT) images, and the results was clinically validated. The filtered back-projection was implemented by using Ramp, Shepp-Logan, Cosine, Hamming, Hann and Blackman filters, and the X-ray source trajectories were simulated with 1 × 36, 2 × 18, 3 × 12, 4 × 9 and 6 × 6 arrays. The X-ray source intervals were 5, 10, 20, 30 and 40 mm. The depth resolution, spatial resolution and noise of DT image were evaluated by measuring artifact spread function (ASF), full width at half maximum (FWHM) and signal-to-noise ratio (SNR), respectively. The results showed that the spatial resolution and noise properties of DT images were maximized by the Ramp and Blackman filters, respectively, and the depth resolution and noise properties of the DT images obtained with a 1 × 36 X-ray source trajectory were superior to the other trajectories. The depth resolution and noise properties of DT images improved with an increase of X-ray source intervals, and the high X-ray source intervals degraded the spatial resolution of DT images. Therefore, the characteristics of DT images are highly dependent on reconstruction filters, X-ray source trajectories and intervals, and it is necessary to use optimal imaging parameters in accordance with diagnostic purpose.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06c
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• pp.52-54
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• 2006

RFID를 이용하는 물류 시스템에서 태그 객체의 위치 추적을 위해서는 태그 객체의 궤적을 모델링하고 효율적으로 검색하기 위한 색인 구성이 필수적이다. 태그 객체의 궤적은 리더의 인식 영역에 들어오고 나가는 두 점을 연결한 시공간 선분으로 표현할 수 있다. 그러나 태그 객체가 리더의 인식영역 밖으로 벗어나게 되면 태그 객체의 궤적을 표현 할 수 없으므로 위치 추적이 불가능하게 되는 문제를 가진다. 이러한 문제를 해결하기 위하여 리더의 비 인식 영역에서 GPS를 이용한 태그 객체의 위치 추적을 병행할 필요가 있다. 본 논문에서는 RFID 시스템과 LBS 시스템을 연동한 환경에서 태그 궤적을 표현하기 위한 위치 추적 시스템의 모델을 제시하고. 제시된 모델에서 태그 객체의 위치 추적을 효율적으로 처리하기 위한 색인 구조를 제안한다. 제안된 색인 구조는 태그 객체의 현재 위치뿐만 아니라 과거 궤적을 효율적으로 처리하기 위한 새로운 삽입 및 분할 알고리즘을 제안하여 노드가 차지하는 영역을 최소화한다.

• Journal of KIISE:Databases
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• v.34 no.1
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• pp.59-69
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• 2007

The trajectory of a tag in RFID system is represented as a interval that connects two spatiotemporal locations captured when the tag enters and leaves the vicinity of a reader. Whole trajectories of a tag are represented as a set of unconnected interval because the location of the tag which left the vicinity of a reader is unknown until it enters the vicinity of another reader. The problems are that trajectories of a tag are not connected. It takes a long time to find trajectories of a tag because it leads to searching the whole index. To solve this problem, we propose a technique that links two intervals of the tag and an index scheme called SLR-tree. We also propose a sharing technique of link information between two intervals which enhances space utilization of nodes, and propose a split policy that preserves shared-link information. And finally, we evaluate the performance of the proposed index and prove that the index processes history queries efficiently.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1302-1304
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• 2015

컴퓨터 비전에서 다수의 보행자 궤적을 생성하는 문제는 여전히 어려운 문제이다. 전경에서 추출된 보행자 윤곽은 음영과 밝기 등의 문제로 윤곽이 명확하지 않고, 보행자들이 서로 다른 방향으로 움직이며 상호작용을 한다. 이로 인해 보행자를 식별하고 궤적을 생성하기에는 다소 어려움이 있다. 우리는 의사결정 트리를 사용하여 보행자 영역의 병합과 분할 상황을 개별 분리된 보행자로 검출한다. 검출된 개별 보행자는 점 대응 알고리즘으로 각 보행자의 궤적을 생성한다. 우리는 수정된 $A^*$ 검색 알고리즘으로 새로운 휴리스틱 점 대응 알고리즘을 소개한다. 우리의 실험은 PETS2010 데이터 세트로 구현되고 실험했다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.8 no.3
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• pp.15-26
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• 1971

The paper presents a new method for analyzing oscillation regions of transistor oscillators. In transistor feedback oscillators oscillation region appears as a circle in feedback impedance complex plane. When the resistive component of feedback impedance is fixed and the reactive component of feedback impedance is varied or vice versa, the locus of maximum negative output conductance becomes hyperbola. In transistor crystal oscillators oscillation region is determined by two circles which make real part and imaginary part of input impedance zero in load impedance complex plane. When the resistive compoment of load impedance is fixed and the reactive colnponent of load impedance is varied or vice versa, the loci of maximum or minimum resistive component of input impedance become straight lines.

• Journal of Broadcast Engineering
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• v.5 no.1
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• pp.41-49
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• 2000

In this paper, we propose a new method of indexing and searching based on object-specific features at different semantic levels for video retrieval. A moving trajectory model is used as an indexing key for accessing the individual object in the semantic level. By tracking individual objects with segmented data, we can generate motion trajectories and set model parameters using polynomial curve fitting. The proposed searching scheme supports various types of queries including query by example, query by sketch, and query on weighting parameters for event-based video retrieval. When retrieving the interested video clip, the system returns the best matching event in the similarity order.