• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.3-4
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• 2008

본 논문에서 k-means 군집화 알고리즘을 효율적으로 적용하는 방법을 제안했다. 제안하는 알고리즘의 특징을 속도 향상을 위해 예측 데이터를 이용한 것이다. 군집화 알고리즘의 각 단계에서 군집을 변경할 데이터만 최인접 군집을 계산함으로써 계산 시간을 줄일 수 있었다. 제안하는 알고리즘의 성능 비교를 위해서 KMHybrid 와 비교했다. 제안하는 알고리즘은 데이터의 차원이 큰 경우에 KMHybrid 보다 높은 속도 향상을 보였다.

• Journal of the Korean Society of Radiology
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• v.17 no.5
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• pp.633-640
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• 2023

With the recent development of static and dynamic modulated brachytherapy methods in brachytherapy, which use radiation shielding to modulate the dose distribution to deliver the dose, the amount of parameters and data required for dose calculation in inverse treatment planning and treatment plan optimization algorithms suitable for new directional beam intensity modulated brachytherapy is increasing. Although intensity-modulated brachytherapy enables accurate dose delivery of radiation, the increased amount of parameters and data increases the elapsed time required for dose calculation. In this study, a GPU-based CUDA-accelerated dose calculation algorithm was constructed to reduce the increase in dose calculation elapsed time. The acceleration of the calculation process was achieved by parallelizing the calculation of the system matrix of the volume of interest and the dose calculation. The developed algorithms were all performed in the same computing environment with an Intel (3.7 GHz, 6-core) CPU and a single NVIDIA GTX 1080ti graphics card, and the dose calculation time was evaluated by measuring only the dose calculation time, excluding the additional time required for loading data from disk and preprocessing operations. The results showed that the accelerated algorithm reduced the dose calculation time by about 30 times compared to the CPU-only calculation. The accelerated dose calculation algorithm can be expected to speed up treatment planning when new treatment plans need to be created to account for daily variations in applicator movement, such as in adaptive radiotherapy, or when dose calculation needs to account for changing parameters, such as in dynamically modulated brachytherapy.

• Journal of Internet Computing and Services
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• v.13 no.3
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• pp.75-82
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• 2012

In this paper, an improved community detection algorithm based on the modularity is proposed. The existing algorithm does not consider the information that the nodes have in checking the possible modularity increase, hence the computation may be inefficient. The proposed algorithm computes the node degree (weight) and sorts them in non-increasing order. By checking the possible modularity value increase for the nodes in the nonincreasing order of node weights, the algorithm finds the final solution more quickly than the existing algorithm does. Through the computational experiments, it is shown that the proposed algorithm finds a modularity as good as the existing algorithm obtains.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.405-412
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• 1999

We propose an effective algorithm, which can predict the detailed behavior of the intensity-modulated high speed optical signal after propagating through an optical fiber. The alogrithm is based on the SSF (Split Step Fourier) Method, however, the step size is automatically calibrated in each calculation step to reduce the number of calculations within given round-off error bound. Applying the algorithm to the 2.5 Gbps 100 km transmission and 10 Gbps 40 km transmission simulations, we achieved the calculation time reduction by maximum 1/120 and 1/56 of the calculation time by using the SSF fixed step algorithm previously known. The root-mean-square of the round-off error was kept within -30 dB compared to the signal level throughout the calculation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.8
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• pp.1531-1536
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• 2016

In this paper, we propose a fast motion estimation algorithm which is important in performance of video encoding. Even though so many fast algorithms for motion estimation have been published due to its tremendous computational amount of for full search algorithm, efforts for reducing computations in motion estimation still remain. In the paper, we propose an algorithm that reduces unnecessary computations only, while keeping prediction quality the same as that of the full search. The proposed algorithm does not calculate block matching error for each candidate at once to find motion vectors but divides the calculation procedure into several steps and calculates partial sum of block errors. By doing that, we can estimate the minimum error point early and get the enhancement of calculation speed by reducing unnecessary computations. The proposed algorithm uses smaller computations than conventional fast search algorithms with the same prediction quality as full search.

• Journal of Information Technology and Architecture
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• v.9 no.4
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• pp.455-464
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• 2012

Due to the recent data explosion, methods which can meet the requirement of large data analysis has been studying. This paper proposes MRIterativeBUC algorithm which enables efficient computation of large data cube by distributed parallel processing with MapReduce framework. MRIterativeBUC algorithm is developed for efficient iterative operation of the BUC method with MapReduce, and overcomes the limitations about the storage size and processing ability caused by large data cube computation. It employs the idea from the iceberg cube which computes only the interesting aspect of analysts and the distributed parallel process of cube computation by partitioning and sorting. Thus, it reduces data emission so that it can reduce network overload, processing amount on each node, and eventually the cube computation cost. The bottom-up cube computation and iterative algorithm using MapReduce, proposed in this paper, can be expanded in various way, and will make full use of many applications.

• Journal of the Institute of Convergence Signal Processing
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• v.18 no.2
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• pp.62-67
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• 2017

In this paper, we propose a fast motion estimation algorithm which is important in performance of video encoding. Even though so many fast algorithms for motion estimation have been published due to tremendous computational amount of full search algorithm, efforts for reducing computations of motion estimation still remain. In the paper, we propose an algorithm that reduces unnecessary computations only, while keeping prediction quality the same as that of the full search. The proposed algorithm does not calculate block matching error for each candidate directly to find motion vectors but divides the calculation procedure into several steps and calculates partial sum of block errors for candidates with high priority. By doing that, we can find the minimum error point early and get the enhancement of calculation speed by reducing unnecessary computations. The proposed algorithm uses smaller computations than conventional fast search algorithms with the same prediction quality as the full search algorithm.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.127-129
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• 2007

최적조류계산(Optimal Power Flow:OPF)은 전력계통에서 여러 가지 제약 조건을 만족하면서 경제적이고 안전하게 계통을 운영하기 위한 기법이다. 종래의 계산방법에는 비선형 계획법, 선형계획법 같은 수치해석적인 방법을 사용하였다. 그러나, 이러한 방법들은 전역 최저해를 구하기 위해서는 목적함수가 convex해야 한다. 또한, 계통 규모가 클 경우, 최적해 수렴이 안 되거나 수렴이 되더라도 시간이 많이 걸리는 단점이 있다. 최근에는 이러한 문제를 극복하고자 여러 가지 진화연산기법들이 최석조류계산 문제에 적용되고 있다. 본 논문에서 최근에 등장한 PSO알고리즘을 수정한 MPSO알고리즘은 이용한 최적조류계산 기법을 소개하고, 제안한 방법의 유용성을 보이기 위하여 IEEE 30,118 모선 계통의 최적 조류계산 문제에 적용하였다.

• Progress in Medical Physics
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• v.10 no.2
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• pp.103-114
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• 1999

In this study, as a preliminary study for developing a full 3D photon dose calculation algorithm, We developed 2.5D photon dose calculation algorithm by extending 2D calculation algorithm to allow non-coplanar configurations of photon beams. For this purpose, we defined the 3d patient coordinate system and the 3d beam coordinate system, which are appropriate to 3d treatment planning and dose calculation. and then, calculate a transformation matrix between them. For dose calculation, we extended 2d "Clarkson-Cunningham" model to 3d one, which can calculate wedge fields as well as regular and irregular fields on arbitrary plane. The simple Batho's power-law method was implemented as an inhomogeneity correction. We evaluated the accuracy of our dose model following procedures of AAPM TG#23; radiation treatment planning dosimetry verifications for 4MV of Varian Clinac-4. As results, PDDs (percent depth dose) of cubic fields, the accuracy of calculation are within 1% except buildup region, and $\pm$3% for irregular fields and wedge fields. And for 45$^{\circ}$ oblique incident beam, the deviations between measurements and calculations are within $\pm$4%. In the case of inhomogeneity correction, the calculation underestimate 7% at the lung/water boundary and overestimate 3% at the bone/water boundary. At the conclusions, we found out our model can predict dose with 5% accuracy at the general condition. we expect our model can be used as a tool for educational and research purpose.. purpose..

• Journal of KIISE:Software and Applications
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• v.32 no.8
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• pp.808-818
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• 2005

We devise a differential fixpoint computation method and develop a new worklist algorithm based on it. Compared with other differential methods, our method can deal with non-distributive systems and adopt any worklist scheduling policy satisfying restrictions imposed by differential evaluation. As a practical application, we present an interpretation framework and implement constant and alias analysis and memory lifetime analysis based on it. Our experiment shows that our method can save computation and worklist scheduling is also important in differential fixpoint evaluations.