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A Mathematical Programming Approach for Cloud Service Brokerage
장병윤,윤승현,서동원,Chang, Byeong-Yun,Abate, Yabibal Afework,Yoon, Seung Hyun,Seo, Dong-Won The Korea Society for Simulation 2014 한국시뮬레이션학회 논문지 Vol.23 No.4
클라우드 컴퓨팅은 가정과 비즈니스 컴퓨팅에 있어 빠르게 확산되고 있다. 이러한 변화에 따라 수년 내에 다양한 클라우드 서비스를 제공하는 클라우드 서비스 공급자의 수가 폭발적으로 증가할 것으로 예측된다. 하지만 클라우드는 하나의 독립체가 아니고 서로 단절되어 있는 많은 응용 프로그램(SaaS)과 기반시설(IaaS), 상이한 플렛폼 서비스(PaaS)들의 집합으로 볼 수 있다. 클라우드 중개방법(brokering mechanism)은 산재되어 있는 서비스들의 집합을 통합하고 편리하게 유용한 서비스를 다양한 사용자에게 제공할 수 있게 하기 때문에 서로 상이한 클라우드 시장을 하나의 통상적 서비스로 변환시키는데 있어 필수적이다. 따라서 CSBs(클라우드 서비스 중개자들)는 사용자와 CSP(클라우드 서비스 제공자)사이의 거리를 최소화하고 예약과 on-demand 서비스의 비용을 최소화하는 운영전략을 찾을 필요가 있다. 이를 위하여 본 연구에서는 클라우드 서비스의 비용과 품질을 최적화하기 위해 예약 접근법을 고려한 수리적 모형을 제안한다. Cloud computing is fast becoming the wave of the future for both home and business computing. Because of this growing acceptance, we can expect an explosion of diverse cloud service providers in the coming years. However, the cloud is not a single entity, rather it is a set of many disconnected islands of application (SaaS), infrastructure (IaaS), and different platform (PaaS) services. Cloud brokering mechanisms are essential to transform the heterogeneous cloud market into a commodity-like service. Cloud service brokers (CSBs) are the new form of business entities to help to aggregate the scattered set of cloud services and make conveniently available to their diverse users. CSBs can reserve a certain percentage of their clients' (users') demand and satisfy the remaining portion in an on-demand basis. In doing so, they need to minimize cost of both reserved and on-demand instances as well as the distance of a link between the cloud service provider (CSP) and the user. The study proposes a reservation approach with a mixed integer model to optimizes the cloud service cost and quality.
커먼레일 단기통 디젤엔진에서 EGR율에 따른 연소 및 배기특성
허정윤(Jeong Yun Heo),윤승현(Seung Hyun Yoon),박성욱(Sung Wook Park),이창식(Chang Sik Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
The purpose of this work is an experimental investigation of combustion and emission characteristics in DI diesel engine applied high EGR rate as known general method of low-temperature combustion. In order to analyze theeffect of EGR rate variation, single-cylinder DI diesel engine was operated under various EGR rate conditions. In addition, injection timing conditions was variously controlled to investigate the effect of injection timing in DI diesel engine using the EGR system. NOx emissions were decreased, as a result, by increasing EGR rate. Soot emissions were generally increased under applied EGR conditions. However, soot emissions were decreased in a few injection timings under high EGR rate conditions. The results showed that the charge could have a premix period sufficiently due to be increased the ignition delay period by decreased oxygen concentrations in combustion chamber under the high EGR rate.
직접분사식 단기통 디젤엔진에서 다단분사에 따른 연소 및 배기특성
허정윤(Jeong Yun Heo),차준표(Junepyo Cha),윤승현(Seung Hyun Yoon),이창식(Chang Sik Lee) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
The purpose of this work is an experimental investigation combustion and emission characteristics in DI diesel engine applied multiple injection strategy. In order to analyze the effect of multiple injection, single-cylinder DI diesel engine was operated under electrically controlled fuel injection system. In this study, multiple injections were injected as two types of multiple injection that were defined as the pilot injection and the post injection. The pilot injection and the post injection was injected 30% of total fuel injections mass quantity. The results of multiple injection were compared to those of single injection and each multiple injection types. To investigate for a low speed engine and middle range load, the experimental conditions were conducted under a fixed engine speed and constant stoichiometric ratio condition. The combustion results show that each multiple injections decreases peak heat release rates but increases indicated mean effective pressure. The emissions results that pilot injection increases emissions but post injection reduces NOx, HC and CO emissions.