• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.31-36
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• 2003

A field reconstruction scheme for a cell centered finite volume method on unstructured meshes is developed. Regardless of mesh quality, this method is exact within a machine accuracy if the solution is linear, which means it has full second order accuracy. It does not have any limitation on cell shape except convexity of the cells and recovers standard discretization stencils at structured orthogonal grids. Accuracy comparisons with other popular reconstruction schemes are performed on a simple example.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.187-189
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• 2004

하드웨어와 응용 프로그램의 다양한 요구를 만족시키기 위한 운영체제의 재구성 능력이나 기능 확장에 대한 필요성은 최근 들어 급증하고 있다. 운영체제의 재구성을 지원하기 위해서 개선되어야 할 부분 가운데 가장 정적이라고 할 수 있는 부분은 인터럽트 처리와 같은 저수준 입출력 부분이다. 이러한 인터럽트 처리는 하드웨어와 밀접한 부분으로써 운영체제의 설계목적에 따라서 설러 가지 방식으로 구성되어왔으나 각 운영체제에 의존적이며 처리방식이 고정적이라는 한계를 가진다. 본 논문에서는 다양한 형태의 인터럽트 처리 방식을 지원할 수 있는 동적 재구성이 가능한 인터럽트 처리 방식과 그 구조를 제안한다. 제안하는 방식은 커널 컴포넌트들의 동적인 확장과 재구성을 지원하는 커널 컴포넌트 스와핑과 인터포지션 기법을 사용하여 M3K 커널에 구현되었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8C
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• pp.729-740
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• 2002

This paper studies the issues arising in the virtual topology reconfiguration phase of Multi-wavelength Routed Optical Networks. This reconfiguration process means to change the virtual topology in response to the changing traffic patterns in the higher layer. We formulate the optimal reconfiguration policy as a multi-stage decision-making problem to maximize the expected reward and cost function over an infinite horizon. Then we propose a new heuristic algorithm based on node-exchange to reconfigure the virtual topology to meet the traffic requirement. To counter the continual approximation problem brought by heuristic approach, we take the traffic prediction into consideration. We further propose a new heuristic reconfiguration algorithm called Prediction based Multi-stage Reconfiguration approach to realize the optimal reconfiguration policy based on predicted traffic. Simulation results show that our reconfiguration policy significantly outperforms the conventional one, while the required physical resources are limited.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.679-685
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• 2017

Computed tomography has widely been used to diagnose patient disease, and patient dose also increase rapidly. To reduce the patient dose by CT, various techniques have been applied. The iterative reconstruction is used in view of image reconstruction. Image quality of the reconstructed section image through algebraic reconstruction technique, one of iterative reconstruction methods, was examined by the normalized root mean square error. The computer program was written with the Visual C++ under the parallel beam geometry, Shepp-Logan head phantom of $512{\times}512$ size, projections of 360, and detector-pixels of 1,024. The forward and backward projection was realized by Joseph method. The minimum NRMS of 0.108 was obtained after 10 iterations in the regularization parameter of 0.09-0.12, and the optimum image was obtained after 8 and 6 iterations for 0.1% and 0.2% noise. Variation of optimum value of the regularization parameter was observed according to the phantom used. If the ART was used in the reconstruction, the optimal value of the regularization parameter should be found in the case-by-case. By finding the optimal regularization parameter in the algebraic reconstruction technique, the reconstruction time can be reduced.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.285-295
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• 2023

With the development of technology, efforts to reduce the exposure dose received by patients in CT scans are continuing with the development of new reconstruction techniques. Recently, deep learning reconstruction techniques have been developed to overcome the limitations of repetitive reconstruction techniques. This study aims to evaluate the usefulness of images according to reconstruction techniques in pediatric chest CT images. Patient study conducted a study on 85 pediatric patients who underwent chest CT scan at P-Hospital in Gyeongsangnam-do from January 1, 2021 to December 31, 2022. The phantom used in the Phantom Study is the Pediatrics Whole Body Phantom PBU-70. After the test, the images were reconstructed with FBP, ASIR-V (50%) and DLIR (TF-Medium, High), and the images were evaluated by obtaining SNR and CNR values by setting ROI of the same size. As a result, TF-H of deep learning reconstruction techniques had the lowest noise value compared to ASIR-V (50%) and TF-M in all experiments, and SNR and CNR had the highest values. In pediatric chest CT scans, TF images with deep learning reconstruction techniques were less noisy than ASiR-V images with adaptive statistical iterative reconstruction techniques, CNR and SNR were higher, and the quality of images was improved compared to conventional reconstruction techniques.

• Progress in Medical Physics
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• v.26 no.1
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• pp.28-35
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• 2015

In this study, we investigated the effects of an iterative reconstruction algorithm and an automatic exposure control (AEC) technique on image quality and radiation dose through phantom experiments with coronary computed tomography (CT) angiography protocols. We scanned the AAPM CT performance phantom using 320 multi-detector-row CT. At the tube voltages of 80, 100, and 120 kVp, the scanning was repeated with two settings of the AEC technique, i.e., with the target standard deviations (SD) values of 33 (the higher tube current) and 44 (the lower tube current). The scanned projection data were reconstructed also in two ways, with the filtered back projection (FBP) and with the iterative reconstruction technique (AIDR-3D). The image quality was evaluated quantitatively with the noise standard deviation, modulation transfer function, and the contrast to noise ratio (CNR). More specifically, we analyzed the influences of selection of a tube voltage and a reconstruction algorithm on tube current modulation and consequently on radiation dose. Reduction of image noise by the iterative reconstruction algorithm compared with the FBP was revealed eminently, especially with the lower tube current protocols, i.e., it was decreased by 46% and 38%, when the AEC was established with the lower dose (the target SD=44) and the higher dose (the target SD=33), respectively. As a side effect of iterative reconstruction, the spatial resolution was decreased by a degree that could not mar the remarkable gains in terms of noise reduction. Consequently, if coronary CT angiogprahy is scanned and reconstructed using both the automatic exposure control and iterative reconstruction techniques, it is anticipated that, in comparison with a conventional acquisition method, image noise can be reduced significantly with slight decrease in spatial resolution, implying clinical advantages of radiation dose reduction, still being faithful to the ALARA principle.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04b
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• pp.196-198
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• 2002

클러스터링 데이터베이스는 높은 가용성과 확장성을 갖으며, 예상치 못한 클라이언트 질의의 증가나 질의 패턴의 변경에 따른 작업부하의 편중에 효율적으로 대처할 수 있는 구조이다. 특히 온라인 확장 기법은 트랜잭션 처리를 중지하지 않고 새로운 노드를 클러스터에 추가하여 데이터를 재구성함으로써 임의의 노드에 질의가 집중되는 문제를 해결할 수 있다. 정적으로 구성된 시스템만으로는 두 대 이상의 서버에 작업량이 집중될 경우 재배치 시 서버 간의 데이터 이동의 반복 현상이 발생되며. 이로 인해 네트웍의 부하와 함께 실시간 트랜적션의 처리에 있어서 응답 시간이 지연되는 문제점이 발생한다. 따라서 본 논문에서는 데이터 이동의 반복 현상을 해결하기 위해 클러스터링 데이터베이스에서 온라인 확장을 고려한 CSB+ 트리 색인의 온라인 재구성 기법을 제안한다. 제안된 기법은 온라인 확장을 통한 동구 노드의 확장으로 데이터 이동의 반복을 막고 새롭게 추가된 노드를 통해 빠르고 효율적인 데이터의 분산을 수행한다 또한 각 시스템의 내부를 CS$B^{+}$ 트리로 구성하여 데이터의 재주성시에도 실시간 트랜잭션에 대한 빠른 응답 시간을 보장한다.

• Annual Conference of KIPS
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• 2005.11a
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• pp.1195-1198
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• 2005

Radio Frequency Identification(RFID)를 이용한 물류 시스템은 바코드를 대체할 시스템으로 주목받고 있다. 이러한 RFID 를 이용한 물류 시스템이 실제로 적용하는 데에는 매우 큰 설치 비용이 문제로 제기된다. 이를 해결하기 위해 무선으로 연결되는 이동형 RFID 리더를 이용한다. 한편 동기화 모드 및 비동기화 모드로 전송되는 RFID 데이터의 특성과 기존의 라우팅 기법의 브로드캐스트에 따른 오버헤드를 줄이기 위해 재구성 가능한 클러스터 기반의 라우팅 기법이 적합하다. 따라서 RFID 창고 관리 시스템을 위한 재구성 가능한 클러스터 기반의 라우팅 기법을 제안한다.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2005.11a
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• pp.339-342
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• 2005

동적 부분 재구성은 FPGA 칩에 구현된 디자인에서 변경이 필요한 부분만 재구성하여 줌으로써 실시간적 재구성을 가능하게하는 방법이다. 동적 부분 재구성에 대한 많은 연구를 통하여 게이트 수준의 부분 재구성이 가능하지만, 설계 복잡도가 큰 시스템을 설계시에 게이트 수준의 부분 재구성 방법은 부적적하다. 본 논문에서는 Xilinx에서 제고하는 버스 매크로를 사용하여 모듈 기반의 부분 재구성 기법에 대하여 기술하며, 곱셈기, 레지스터, 그리고 ripple carry adder로 구성된 회로에서 ripple carry adder를 carry lookahead adder로 재구성한다.

• The Journal of the Korea Contents Association
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• v.6 no.9
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• pp.9-18
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• 2006

We completed a new cluster system based on WDM by proposing a virtual topology reconfiguration schemes. The key idea of the proposed scheme is to construct a set with the longest chains of requests of connecting nodes which need to be assigned a wavelength. All the sets have no common factor, that is, there is no duplicated link among the requests of connecting. After making the set satisfying this condition, we could assign a wavelength to per corresponding set. We could reconfigure a virtual topology with this scheme collectively. we compared our scheme to existing approaches by the OWns simulation tool. As the results, we gained improved performances, reducing 10% of blocking rate and improving 30% of ADM utilization in terms of the blocking probability and the ADM utilization.