• 한국통신학회논문지
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• 제38B권3호
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• pp.199-206
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• 2013

본 논문에서는 이전 연구에서 능동형 RFID 시스템의 태그 수집 성능 향상을 위해 제안된 인식 슬롯 스캔 기반 태그 수집 알고리즘의 단점을 개선하는 수정된 태그 수집 알고리즘을 제안한다. 기 제안된 인식 슬롯 스캔 기반 태그 수집 알고리즘은 태그 수집 과정에서 모든 태그들로부터 정해진 크기의 데이터를 수집하는 상황에 최적화 되어 있기 때문에 태그들이 다양한 크기의 데이터를 가지는 환경에 적용할 경우 제대로 된 성능 향상을 가져오지 못한다. 본 논문에서 새롭게 제안하는 개선된 태그 수집 알고리즘은 먼저 인식 슬롯 스캔 단계에서 각 태그로부터 자신이 가진 데이터를 전송하는데 필요한 슬롯 크기 정보를 획득하고 이를 활용하여 태그 수집 단계를 수행함으로써, 기 제안된 알고리즘의 문제점을 해결하고 모든 환경에서 능동형 RFID 태그 수집의 성능을 효율적으로 향상시키도록 설계되었다. 성능 평가를 위해 수행한 시뮬레이션 결과는 제안하는 개선된 태그 수집 알고리즘이 태그들이 동일한 데이터 크기를 가지는 환경에서는 기 제안된 알고리즘과 거의 동일한 성능을 보이고, 태그들이 다양한 데이터 크기를 가지는 환경에서는 기 제안된 알고리즘과 달리 ISO/IEC 18000-7 표준의 태그 수집 성능을 크게 향상시킴을 보여주었다.

• 한국통신학회논문지
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• 제21권5호
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• pp.1089-1095
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• 1996

가변블록 변환부호화는 변환부호화에 적용되는 블럭의 크기를 다르게 하여 코딩의 효율을 좋게 한다. 변환블록의 크기는 블럭의 활성도에 따라 적응된다. 즉, 블럭의 활성도가 크면 블럭의 크기는 작아지고, 반대로 활성도가 작으면 블럭의 크기가 커진다. 본 논문에서는 블럭의 활성도로서 분산값 대신에 변환계수의 고주파 에너지를 이용하였다. 컴퓨터 시뮬레이션 결과, 제안한 방법이 분산값을 이용한 방법보다는 약 1~5dB, MAD를 이용한 방법보다는 약 0.5~3dB정도의 성능개선을 보여주었다.

• 전자공학회논문지A
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• 제33A권5호
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• pp.31-43
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• 1996

In this paper, we analyze the delay characteristics of the multimdedia traffic in B-ISDN, and propose a weighted variable-size window estimator considering the QoS characteristics of the media and the variable delay characteristics of the networks, and present a delay estimator-based synchronization protocol for the efficient synchronization in ATM-based B-ISDN. The proposed estimator assigns a high weight value to recent cells arrived in the receiver, and suitably adjusts window size in order to efficiently adapt to delay variation by the prameter to detect the delay variation of the networks. The proposed synchronization protocol estimates end-to-end delay by the weighted variable-size window estimator, and dynamically schedules th evirtual channel of the transmitter to playout multimedia data on time in the receiver. Also, we evaluate the performance of the delay estimator, which is the most importnat functional element in our proposed synchronization protocol, by the simulation and analyze the results of the simulation.

• 산업경영시스템학회지
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• 제38권4호
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• pp.132-141
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• 2015

We focus on the fire scheduling problem (FSP), the problem of determining the sequence of targets to be fired at, for the objective of minimizing makespan to achieve tactical goals. In this paper, we assume that there are m available weapons to fire at n targets (> m) and the weapons are already allocated to targets. One weapon or multiple weapons can fire at one target and these fire operations should start simultaneously while the finish time of them may be different. We develop several dominance properties and a lower bound for the problem, and suggest a branch and bound algorithm implementing them. Also, In addition, heuristic algorithms that can be used for obtaining an initial upper bound in the B&B algorithm and for obtaining good solutions in a short time were developed. Computational experiments are performed on randomly generated test problems and results show that the suggested algorithm solves problems of a medium size in a reasonable amount of computation time. The proposed lower bound, the dominance properties, and the heuristics for upper bound are tested in B&B respectively, and the result showed that lower bound is effective to fathoming nodes and the dominance properties and heuristics also worked well. Also, it is showed that the CPU time required by this algorithm increases rapidly as the problem size increases. Therefore, the suggested B&B algorithm would be limited to solve large size problems. However, the employed heuristic algorithms can be effectively used in the B&B algorithm and can give good solutions for large problems within a few seconds.

• Journal of Communications and Networks
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• 제7권1호
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• pp.87-92
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• 2005

This paper presents basic queueing analysis contributing to teletraffc theory, with commonly accessible mathematical tools. This paper studies queueing systems with bulk arrivals. It is assumed that the number of arrivals and the expected number of arrivals in each bulk are bounded by some constraints B and (equation omitted), respectively. Subject to these constraints, convexity argument is used to show that the bulk-size probability distribution that results in the worst mean queue performance is an extremal distribution with support {1, B} and mean equal to A. Furthermore, from the viewpoint of security against denial-of-service attacks, this distribution remains the worst even if an adversary were allowed to choose the bulk-size distribution at each arrival instant as a function of past queue lengths; that is, the adversary can produce as bad queueing performance with an open-loop strategy as with any closed-loop strategy. These results are proven for an arbitrary arrival process with bulk arrivals and a general service model.

• 한국통신학회논문지
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• 제28권9B호
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• pp.783-792
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• 2003

We consider a finite-buffer discrete-time queueing system with fixed-size bulk-service discipline: Geo/ $G^{B}$1/K＋B. The main purpose of this paper is to present a performance analysis of this system that has a wide range of applications in Asynchronous Transfer Mode (ATM) and other related telecommunication systems. For this purpose, we first derive the departure-epoch probabilities based on the embedded Markov chain method. Next, based on simple rate in and rate out argument, we present stable relationships for the steady-state probabilities of the queue length at different epochs: departure, random, and arrival. Finally, based on these relationships, we present various useful performance measures of interest such as the moments of number of packets in the system at three different epochs and the loss probability. The numerical results are presented for a deterministic service-time distribution - a case that has gained importance in recent years.s.

• 한국IT서비스학회지
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• 제2권1호
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• pp.75-83
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• 2003

Among EC areas. the B2B EC market is being spotlighted as an important interesting research area considering its size and the potential impact on companeies and the whole society. In comparison with private consumers in B2C EC. business buyers in B2B EC have to precisely keep track of the purchase records. and integrate them with the buyer's e-procurement system, which might have been implemented as a part of integrated ERP (Enterprise Resource Planning) systems. There are three approaches for such integration between ERP and e-marketplace in B2B EC; Two previous approaches are Inside-Out approach and Outside-In approach. And a newly, one is b-cart approach. In this paper, we try to survey these three approaches and make a comparison analysis. From this research. we identify that the b-cart approach is the most efficient framework in integrating ERP with e-marketplace in B2B EC.

• 펄프종이기술
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• 제39권4호
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• pp.29-37
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• 2007

The effects of latex particle size, basis weight of base paper and coating color concentration on the printing quality of coated paper were investigated. Coating colors were prepared with five types of latexes having different particle sizes. Coated papers were produced with high solid coating colors and with low solid coating colors in a industrial coater, respectively. In high solid coating colors, rheology modifier was used and GCC content was high. It was concluded that, in order to control binder migration and hence print mottle, latex particle sizes shall be controlled as well as formation, sizing degree and roughness of basis paper.

• 전자공학회논문지B
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• 제32B권12호
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• pp.1680-1686
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• 1995

GAs, effective stochastic search algorithms based on the model of natural evolution and genetics, have been successfully applied to various optimization problems. When population size is not large, GAs often suffer from the phenomenon of premature convergence in which all chromosomes in the population lose the diversity of genes before they find the optimal solution. In this paper, we propose that a new heuristic that maintains the diversity of genes by adding some chromosomes with random mutation and selective mutation into population during evolution. And population size changes dynamically with supplement of new chromosomes. Experimental results for several test functions show that when population size is rather small and the length of chromosome is not long, this method is effective.

• Environmental Engineering Research
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• 제19권4호
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• pp.345-354
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• 2014

In this paper, effects of physical configurations and operating conditions on bubble column performance were analyzed in terms of bubble hydrodynamic and mass transfer parameters. Bubble column with 3 different dimensions and 7 gas diffusers (single / multiple orifice and rigid / flexible orifice) were applied. High speed camera and image analysis program were used for analyzing the bubble hydrodynamic parameters. The local liquid-side mass transfer coefficient ($k_L$) was estimated from the volumetric mass transfer coefficient ($k_La$) and the interfacial area (a), which was deduced from the bubble diameter ($D_B$) and the terminal bubble rising velocity ($U_B$). The result showed that the values of kLa and a increased with the superficial gas velocity (Vg) and the size of bubble column. Influences of gas diffuser physical property (orifice size, thickness and orifice number) can be proven on the generated bubble size and the mass transfer performance in bubble column. Concerning the variation of $k_L$ coefficients with bubble size, 3 zones (Zone A, B and C) can be observed. For Zone A and Zone C, a good agreement between the experimental and the predicted $K_L$ coefficients was obtained (average difference of ${\pm}15%$), whereas the inaccuracy result (of ${\pm}40%$) was found in Zone B. To enhance the high $k_La$ coefficient and absorption efficiency in bubble column, it was unnecessary to generate numerous fine bubbles at high superficial gas velocity since it causes high power consumption with the great decrease of $k_L$ coefficients.