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Explicit Formulae for Characteristics of Finite-Capacity M/D/1 Queues
서동원 한국전자통신연구원 2014 ETRI Journal Vol.36 No.4
Even though many computational methods (recursiveformulae) for blocking probabilities in finite-capacityM/D/1 queues have already been produced, these areforms of transforms or are limited to single-node queues. Using a distinctly different approach from the usualqueueing theory, this study introduces explicit (transformfree)formulae for a blocking probability, a stationaryprobability, and mean sojourn time under eitherproduction or communication blocking policy. Additionally, the smallest buffer capacity subject to agiven blocking probability can be determined numericallyfrom these formulae. With proper selection of the overalloffered load ρ, the approach described herein can beapplicable to more general queues from a computationalpoint of view if the explicit expressions of random vectorDn are available.
서동원,Yong-il Cho,이영주,Sang-Myeong Lee 대한미생물학회 2019 Journal of Bacteriology and Virology Vol.49 No.4
Macrophages play essential roles in innate immune responses by producing various immune mediators. Therefore, modulating macrophage function is an attractive strategy to treat immune disorders. Aralia cordata var. continentalis (AC), known as “Dokwhal” in Korea, possesses various biological and medicinal functions, including immunomodulation. The present study investigated the effect of the hot water extract of AC (HAC) on RAW264.7 murine macrophages. When these cells were treated with HAC, nitric oxide production and inducible nitric oxide synthase expression was induced dose-dependently. In addition, HAC treatment triggered the secretion of innate immune cytokines, such as TNF-α and IL-6. Phagocytosis, measured by FITC-dextran internalization showed that HAC stimulated the phagocytic activity of macrophages. Furthermore, HAC promoted the production of reactive oxygen species in RAW264.7 cells, determined by CM-H 2 DCFDA. In addition, the immunoblot analysis of intracellular signaling proteins revealed that NF-kB and MAPK signaling pathways, which are important signaling mediators of inflammation, are upregulated by HAC. In conclusion, these findings suggested that HAC can stimulate macrophage activity, and NF-kB and MAPK signaling pathways might be involved in the immunostimulatory effects of HAC.
Optimal Buffer Allocation in Tandem Queues with Communication Blocking
서동원,고성석,정욱 한국전자통신연구원 2009 ETRI Journal Vol.31 No.1
In this letter, we consider an m-node tandem queue (queues in series) with a Poisson arrival process and either deterministic or non-overlapping service times. With the assumption that each node has a finite buffer except for the first node, we show the non-increasing convex property of stationary waiting time with respect to the finite buffer capacities. We apply it to an optimization problem which determines the smallest buffer capacities subject to probabilistic constraints on stationary waiting times.
일반 공정시간과 구조를 갖는 버퍼 공유 분기-접합 생산시스템의 스프레드시트 모형 분석
서동원,Seo, Dong-Won 한국시뮬레이션학회 2019 한국시뮬레이션학회 논문지 Vol.28 No.3
분기-접합 생산시스템은 오랜 기간 동안 연구되어왔지만, 개별 또는 공유 유한 버퍼를 갖고 일반공정시간 분포를 따르는 시스템에 대한 분석은 제한적이다. 일반적으로 대기행렬 이론적 분석법은 유한 버퍼를 갖는 시스템에 대한 분석에는 어려움이 있다. 본 연구에서는 max-plus 대수적 분석법을 활용하여 일반 공정시간을 갖는 버퍼 공유 분기-접합 생산시스템을 분석하였다. 하지만, 이러한 분석법은 특성치 계산의 관점에서는 적절한 방법을 제공하지 못하기 때문에 max-plus 대수로 도출된 표현식과 @RISK 소프트웨어를 활용하여 스프레드시트 시뮬레이션 모형을 개발하였다. 시뮬레이션 실험을 통해 유한 버퍼와 두 가지 차단규칙인 BBS(통신차단)과 BAS(제조차단) 하에서 시스템 대기시간에 대한 몇몇 특성을 비교 분석하였다. For many years, it has been widely studied on fork-join production systems but there is not much literature focusing on the finite buffer(s) of either individuals or shared, and generally distributed processing times. Usually, it is difficult to handle finite buffer(s) through a standard queueing theoretical approach. In this study, by using the max-plus algebraic approach we studied buffer-shared fork-join production systems with general processing times. However, because it cannot provide proper computational ways for performance measures, we developed simulation models using @RISK software and the expressions derived from max-plus algebra. From the simulation experiments, we compared some properties on waiting time with respect to a buffer capacity under two blocking policies: BBS (Blocking Before Service) and BAS (Blocking After Service).
서동원,윤승현,장병윤,Seo, Dong-Won,Yoon, Seung Hyun,Chang, Byeong-Yoon 한국시뮬레이션학회 2013 한국시뮬레이션학회 논문지 Vol.22 No.4
본 연구에서는 네트워크 총 비용 최소화의 관점에서 스마트 노드 자원사용과 네트워크 트래픽 경로를 함께 결정하는 최적화 문제를 고려하였다. 이를 위해, 스마트 노드의 기술 추세와 자원 최적화에 대한 분석방법, 스마트 네트워크의 경제적 효과와 CDN에 대해 살펴보았다. CDN에 대한 분석을 기반으로 혼합정수계획법 모형을 제안하였으며, 이는 기존에 알려진 복제위치선정과 고객요청 분배문제 (RPRDP)와 경로 결정문제가 결합된 형태로 볼 수 있다. 제안된 혼합정수계획법 모형을 구현하고 그 결과를 소개함으로써 제안된 모형의 유효성을 밝혔다. In this research, we dealt with an optimization problem which aims to minimize total cost of resources usage and network routing in a smart node environment. Toward this, we briefly introduced technology trends in smart nodes, methods in resource optimization fields, economic effects of smart network and content delivery (or distribution) network (CDN). Moreover, based on CDN we proposed and implemented a mathematical (mixed integer) programming model to combine replica placement and requests distribution problem (RPRDP) and routing problem. Computational result of an example on RPRDP+Routing problem is also provided.