• 한국통계학회:학술대회논문집
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• 한국통계학회 2005년도 춘계 학술발표회 논문집
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• pp.203-207
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• 2005

A loss system where two types of customers arrive in accordance with two independent Poisson processes is considered. An efficient recursive formula is developed for calculating the loss probability when the number of servers is large. Some practical examples regarding the performance evaluation of telecommunications networks are discussed.

• 상하수도학회지
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• 제23권6호
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• pp.855-864
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• 2009

The main object of this work was to determine the influence of periodic chemical backwash on filtration resistance in membrane filtration system. In this work Hermia's models were used to investigate the fouling mechanisms involved in the microfiltration of $0.45{\mu}m$ filtered sewage feed. Batch microfiltration experiments were performed at transmembrane pressure 0.4 bar and different feed SCOD concentration (9~67 mgSCOD/L). The results showed that the best fit to experimental data corresponded to the intermediate blocking model followed by the standard and complete blocking model for all the experimental conditions tested. From the simulation results of filtration performance, it was found that in order to maintain sustainable operation of membrane filtration system, irreversible foulant component accumulated continuously on membrane surface and/or pore must be effectively removed. In addition, it was verified that periodic chemical backwash using NaOCl or NaOH effectively improved filtration performance of membrane.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.149-152
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• 2000

In this paper, the reverse link performance of an imperfect power controlled DS/CDMA cellular system that uses a base station array antenna which can effectively remove the multiple access interference is analyzed considering both beam forming algorithm and power control error in shadowing. The blocking probability of the DS/CDMA cellular system based on array parameters, Eb/No and statistics of interference is derived, and then the system capacity corresponding to a certain blocking probability is calculated. On the assumption that the blocking probability is set 1 ％, the system capacity using MCGM algorithm with 12 antenna arrays is increased about 59 % than that using 8 antenna arrays when power control error is 2.5 ㏈.

• 경영과학
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• 제9권1호
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• pp.3-15
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• 1992

In this paper, we study a manufacturing system of serial stages with general service times, in which the production of each stage and the coordination of stages are controlled by Kanban discipline. This Kanban discipline is modeled as a Discrete Event Dynamic System and a system of recursive equations is applied to study the dynamics of the system. The recursive relationship enables us to compare this Kanban discipline with the other blocking disciplines such as transfer blocking, service blocking, block-and-hold b, and block-and-hold K, and the Kanban is shown to be superior to the other disciplines in terms of makespan and throughput. As a special case, two stages Kanban system is modeled as $C_2/C_2/1/N$ queueing system, and a recursive algorithm is developed to calculate the system performance. In optimizing the system performance, the stochastic optimization approach of Robbins-Monro is employed via perturbation analysis, the way to estimate the stochastic partial derivative based on only one sample trajectory of the system, and the required commuting condition is verified. Then the stochastic convexity result is established to provide second-order optimality condition for this parametric optimization problem.

• 정보처리학회논문지A
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• 제8A권2호
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• pp.125-132
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• 2001

IBM developed the MPI-IO, we call it MPI-2, on the General Parallel File System. We designed and implemented various Matrix Multiplication Benchmarks to evaluate its performances. The MPI-IO on the General Parallel File System shows four kinds of data access methods : the non-collective and blocking, the collective and blocking, the non-collective and non-blocking, and the split collective operation. In this paper, we propose benchmarks to measure the IO time and the computation time for the data access methods. We describe not only its implementation but also the performance evaluation results.

• 한국경영과학회지
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• 제25권1호
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• pp.85-92
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• 2000

Channel management is critical in designing a cellular mobile system that offers high capacity and high quality. In this paper, an integrated channel management scheme is proposed, which consists of a dynamic channel allocation scheme and an admission control scheme. The dynamic channel allocation scheme allocates a call request the channel which minimizes the impact on its interfering cell, and consists of two types of channel allocation strategies : nominal channel allocation strategy and non-nominal channel allocation strategy. The admission control scheme named the variable cutoff priority scheme reserves some frequency channels for handoff cells in each cell the number of which varies according to the blocking probability of handoff class in that cell. Computationl tests are performed to evaluate the performance of the proposed scheme in terms of overall blocking probability, defined by the weighted value of the blocking probabilities of new calls and handoff calls. The results show that the proposed scheme yields better performance than other compared schemes.

• ETRI Journal
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• 제8권3호
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• pp.29-43
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• 1986

어떤 고장이 시스팀의 기능을 완전히 마비시키는 것이 아니라 그 성능이 저하된 상태에서 운용할 수 있는 degradable system에서는 고전적인 신뢰도 모형을 적용하기가 어려우며, 여기서 성능과 신뢰도는 매우 밀접한 관련이 있다. 본고에서는 성능신뢰도(Performance reliability)에 대한 개념 및 모형화 방법에 대해 살펴보고 실제로 TDX-1의스위치 네트워크인 SWCD의 성능을 해석하여 성능신뢰도를 구하였다. SWCD의 성능척도인 통화성공률에 영향을 미치는 요인으로는 스위치 네트워크 내에서의 blocking, T-SW 및 S-SW의 고장, 그리고 T-SW 및 S-SW의 고장으로 인해 DLC 와 TLC의 가용한 서비스 채널이 감소함으로써 발생하는 DLC 및 TLC에서의 blocking등을 들 수 있는데 이 요인들을 고려하여 SWCD의 성능을 해석하였으며, SWCD에 요구되는 표준성능(Normalized performance) 이 0.99라 할 때 single unit라고 가정한 경우 SWCD의 성능 신뢰도는 MTUO(Mean Time to Unreliable Operation)가 3076.7시간이었다. 또한 성능을 해석하는 과정에서 디지틀 스위치 네트워크인 SWC만의 최대 발신 통화처리 용량을 구한 결과, 스위치 네트워크 내에서의 blocking 확률에 대한 최대 허용치를 $10^-3$으로 하였을 때 약 1,700Erlang이었다.

• 통합자연과학논문집
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• 제11권1호
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• pp.1-8
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• 2018

HEMA, AA, MMA, and EGDMA as crosslinking agent and AIBN as an initiator, and 2,4-dihydroxybenzophenone, 2-ethylhexyl-trans-4-methoxy-cinnamate, 2-hydroxy-4-(methacryloyloxy)benzophenone as additives at 0.1-1.0% ratios were used to manufacture hydrophilic ophthalmic lenses through thermal polymerization before their physical properties were measured. The results showed that the samples containing of 2,4-dihydroxybenzophenone and 2-ethylhexyl-trans-4-methoxy-cinnamate resulted in a decrease of the UV blocking performance after high-pressure sterilization whereas the sample containing 2-hydroxy-4-(methacryloyloxy)benzophenone showed no change in the UV blocking performance. It is judged that this is induced by presence or absence of an acyl functional group in benzophenone.

• 대한전자공학회논문지
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• 제25권6호
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• pp.663-671
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• 1988

In this paper, in order to reduce the blocking effect of block coded images, we propose the method considering the lowpass and bandpass components of Granrath's human visual model. This method consists of two-stage enhancement procedure. The first step is lowpass filtering which smooths out the blocking effect, and the second step is a high frequency enhancement procedure to increase the contrast decreased by the lowpass filtering in the first step. In the first step, the one-dimensional Gaussian filter which aligthns parallel to the edge direction is considered to preserve the edge in the block and the two-dimensional Gaussian filter is used to smooth out the blocking effect near the block boundaries. In the second step, the lowpass and bandpass components of the Granrath's model are considered to increase contrast in a restored image. The performance comparison of the proposed method and the existing mehtods is made by a computer simulation with several block coded images. We can see that the enhancement in the subjective quality of images of the proposed method is more significant than the enhancement in the subjective quality of images of the proposed method is more significant than the existing methods, though the proposed method does not show better performance on the PSNR gain, the poor measure of picture quality for block coded images.

• 정보처리학회논문지C
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• 제10C권4호
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• pp.485-492
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• 2003

본 논문에서는 ATM 스위치에서 복수개의 입력버퍼를 사용하는 경우 HOL 블록킹에 의한 성능 저하의 영향을 최소화하기 위하여 입력버퍼 방식을 개선한 그룹형 버퍼 방식의 새로운 스위치구조를 제안한다. 스위치 내부 구조는 네트워크의 구조적 특성에 따라 분할된 서브 네트워크들을 단계별로 재귀적 방법으로 그룹화하여 구성된다. 이것은 블록된 셀을 전송하기 위하여 그룹간에 추가적인 경로와 버퍼를 제공하게 함으로써 HOL 블록킹에 의한 영향을 감소시킬수 있으며, 따라서 스위치의 성능이 향상되는 결과를 나타낸다. 처리율, 셀 손실율, 지연, 시스템 파워 등의 척도를 고려한 시뮬레이션을 통하여 기존의 모델과 비교, 분석하였다.