• Journal of KIISE:Computer Systems and Theory
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• v.26 no.10
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• pp.1185-1193
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• 1999

최적 스택 필터는 시그널 또는 영상의 임의의 특성 정보를 보존하고자 하는 요구조건에 의해 강제된 구조적 제약 하에서 최대의 잡음제거 효과를 얻을 수 있다. 그리고 임계치 분할 특성과 양의 부울 함수에 기반한 이진 영역에서의 처리 특성은 이 필터가 높은 병렬성을 갖고 있음을 보여준다. 본 논문에서는 두 개의 병렬 계산 모델 MCC(Mesh-Connected Computer)와 CCC(Cube-Connected Computer)에서 최적 스택 필터를 위한 1차원 병렬 알고리즘을 개발한다. 최적 스택 필터의 실행 시간은 주로 이진 median 연산에 의해 결정되고 본 논문에서 제안된 알고리즘은 선형 분리성에 의해 이 연산을 구현한다. 이를 바탕으로, M 레벨의 1-D 시그널의 길이가 L이고 윈도우 폭이 N이라고 가정할 때, 제안된 알고리즘은 {{{{root M times root M`` MCC에서 O(L sqrt{M}`) 시간에 그리고 M 개의 PE를 갖는 CCC에서 O(L log M)시간에 수행될 수 있다. 또한 잡음을 더욱 효과적으로 제거하기 위해 윈도우 폭 N을 증가시킬 때, 제안된 병렬 알고리즘의 계산 시간은 일정하게 유지됨을 보인다.Abstract An optimal stack filter achieves the maximum noise attenuation under the structural constraints imposed by the requirement of preserving certain signal or image features. And the filter provides a high parallelism due to the principles of threshold decomposition and binary processing based on positive Boolean functions(PBFs). In this paper, we develop an one-dimensional parallel algorithm for the optimal stack filter on two parallel computation models, MCC(Mesh-Connected Computer) and CCC(Cube-Connected Computer). The running time of the optimal stack filter depends mainly on the binary median operation and our algorithm realizes this operation by the linear separability. Based on this scheme, our parallel algorithm can be performed in {{{{O(L sqrt{M}`) MCC and inO(L log M) time on CCC with M PEs, when the length of M``-valued 1-D signal is L`` and window width is N`` Also, we show that the computation time of our parallel algorithm keeps constant when the window width N increases in order to achieve the best noise attenuation.

• The KIPS Transactions:PartA
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• v.10A no.3
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• pp.181-188
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• 2003

We propose a heuristic on-line scheduling algorithm for the IRIS (Increasing Reward with Increasing Service) tasks, which has low computation complexity and produces total reward approximated to that of previous on-line optimal algorithms. The previous on-line optimal algorithms for IRIS tasks perform scheduling on all tasks in a system to maximize total reward. Therefore, the complexities of these algorithms are too high to apply them to practical systems handling many tasks. The proposed algorithm doesn´t perform scheduling on all tasks in a system, but on (constant) W´s tasks selected by a predefined task selection policy. The proposed algorithm is based on task selection policies that define how to select tasks to be scheduled. We suggest two simple and intuitive selection policies and a generalized selection policy that integrates previous two selection policies. By narrowing down scheduling scope to only W´s selected tasks, the computation complexity of proposed algorithm can be reduced to O(Wn). However, simulation results for various cases show that it is closed to O(W) on the average.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.2
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• pp.87-93
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• 2002

A new approach of constructing a suffix tree $T_s$for the given string S is to construct recursively a suffix tree $ T_0$ for odd positions construct a suffix tree $T_e$ for even positions from $ T_o$ and then merge $ T_o$ and $T_e$ into $T_s$ To construct suffix trees for integer alphabets in linear time had been a major open problem on index data structures. Farach used this approach and gave the first linear-time algorithm for integer alphabets The hardest part of Farachs algorithm is the merging step. In this paper we present a new and simpler merging algorithm based on a coupled BFS (breadth-first search) Our merging algorithm is more intuitive than Farachs coupled DFS (depth-first search ) merging and thus it can be easily extended to other applications.

• Journal of the Korea Society of Computer and Information
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• v.18 no.12
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• pp.75-82
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• 2013

This paper proposes a $O(n^2)$ polynomial time algorithm to obtain optimal solution for Traveling Salesman problem that is a NP-complete because polynomial time algorithm has been not known yet. The biggest problem in a large-scale Traveling Salesman problem is the fact that the amount of data to be processed is $n{\times}n$, and thus as n increases, the data increases by multifold. Therefore, this paper proposes a methodology by which the data amount is first reduced to approximately n/2. Then, it seeks a bi-directional route at a random point. The proposed algorithm has proved to be successful in obtaining the optimal solutions with $O(n^2)$ time complexity when applied to TSP-1 with 26 European cities and TSP-2 with 46 cities of the USA. It could therefore be applied as a generalized algorithm for TSP.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.167-170
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• 2006

Most wavelength assignment algorithms assume that every node has infinite ADMs and I/O blocking is excluded. Furthermore wavelengths continue to occur intermittently in the network using existing algorithms. This can result in increased link blocking under dynamic traffic circumstances. In audition, it can create time-complexity problems such as O(W $N^3$) in the worst case scenario. In this paper, we propose a new wavelength assignment algorithm which has time-complexity of O(W $N^2$) and considers both I/O and link blocking. The basic idea is to maximize the number of links where wavelengths will be assigned continuously after present assignment. As a result, the number of intermittent wavelengths is minimized, and blocking probabilities are decreased.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.87-92
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• 2005

This study showed the possibility of the medical treatment by thermal feedback as the laser medical treatment had given by design of the digital I/O interfaces of the electronic shutter to control the laser beam and the temperature controlled algorithm. The electronic shutter is economical and that is designed to be automatically controlled within the range of an extent temperature by such development of its driving interfaces and the controlled algorithm of the electronic shutter. The possibility of local therapy for the patients by the treatment of the laser beam within an extent temperature controlled, is proposed by improvement of the problems on the current treatment methods such as radiotherapy, high frequency treatment or medical therapy of drug stuffs which even kill the normal cells.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.1
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• pp.1-5
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• 2020

Solar power generation systems require maximum power point tracking (MPPT) control to operate PV panels at their maximum power point (MPP). Most conventional MPPT algorithms are based on the slope-tracking concept. A typical slope-tracking method is the perturb and observe (P&O) algorithm. The P&O algorithm measures the current and voltage of a PV panel to find the operating point of the voltage at which the calculated power is maximized. However, the measurement error of the sensor causes irregularity in the calculation of the generated power and voltage control. This irregularity leads to the problem of not finding the correct MPP operating point. In this work, the power output of a PV panel based on the P&O algorithm is simulated by considering the insolation profiles from typical clear and cloudy weather conditions and the errors of current and voltage sensors. Simulation analysis suggests the optimal control period and perturbation voltage of MPPT to maximize its target efficiency under real weather conditions with sensor tolerance.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.5
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• pp.333-337
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• 2007

Flash Translation Layer(FTL) which enables NAND Flash memory-based storage system to be used as a block device is designed considering only characteristics of NAND Flash memory. However, since FTL precesses I/O requests which survived against buffer replacement algorithm, FTL algorithm has tight relationship with buffer replacement algorithm. Therefore, if we do not consider both FTL and buffer replacement algorithms, it is difficult to predict the actual I/O performance of the computer systems that have Flash memory-based storage system. The necessity of FTL and buffer replacement algorithm co-design arises here. In this work, we implemented I/O performance evaluation tool, IPSiNS, which simulates both the buffer replacement and FTL algorithms, simultaneously.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.1
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• pp.1-8
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• 2019

In this study, a maximum power point tracking (MPPT) algorithm based on the perturb and observe (P&O) method with variable step size is proposed to improve the dynamic response characteristic of MPPT, using the existing P&O method. The proposed algorithm, which we verified by simulation and experiment, can track the maximum power point (MPP) through duty control and consisted of three operation modes, namely, constant voltage mode, fast mode, and variable step mode. When the insolation is constant, the voltage variation of the operating point at the MPP is reduced through the step size reduction of the duty in the variable step mode. Consequently, the vibration of the operating point is reduced, and the power generation efficiency is increased. When the insolation changes, the duty and the photovoltaic (PV) voltage are kept constant through the constant voltage mode. The operating point then rapidly tracks the new MPP through the fast-mode operation at the end of the insolation change. When the MPP is reached, the operation is changed to the variable step mode to reduce the duty step size and track the MPP. The validity of the proposed algorithm is verified by simulation and experiment of a PV system composed of a PV panel and a boost converter.

• Journal of the Korea Society of Computer and Information
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• v.20 no.5
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• pp.107-112
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• 2015

This paper proposes a simplified algorithm devised to obtain optimal solution to the marriage problem. In solving this problem, the most widely resorted to is the Gale-Shapley algorithm with the time complexity of $O({\mid}V{\mid}^2{\mid}E{\mid})$. The proposed algorithm on the other hand firstly constructs a $p_{ij}$ matrix of inter-preference sum both sexes' preference over the opposite sex. Secondly, it selects $_{min}p_i$ from each row to establish ${\mid}p_{.j}{\mid}{\geq}2,j{\in}S$, ${\mid}p_{.j}{\mid}=1$, $j{\in}H$, ${\mid}p_{.j}{\mid}=0$, $j{\in}T$. Finally, it shifts $_{min}\{_{min}p_{ST},p_{SH}+p_{HT\}$ for $_{min}P_{ST}$ of $S{\rightarrow}T$ and $p_{SH}+p_{HT}$, $p_{HT}<_{min}p_{ST}$ of $S{\rightarrow}H$, $H{\rightarrow}T$. The proposed algorithm has not only improved the Gale-Shapley's algorithm's complexity of $O({\mid}V{\mid}^2{\mid}E{\mid})$ to $O({\mid}V{\mid}^2)$ but also proved its extendable use on unbalanced marriage problems.