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Study on the Growth of Monoclinic VO<sub>2</sub> Phase Applicable for Thermochromic Ceramic Tile
Jung, DaeYong,Kim, Ungsoo,Cho, Wooseok The Korean Ceramic Society 2015 한국세라믹학회지 Vol.52 No.5
Vanadium dioxide ($VO_2$) of monoclinic phase exhibits Metal Insulator Phase Transition (MIPT) phenomenon involving a sharp change in electrical and optical properties at $68^{\circ}C$. Solution-based process is applied to form uniform $VO_2$ coating layer on ceramic tiles. This can selectively block the near-infrared light to possibly reduce the energy loss and prevent dew condensation caused by the temperature difference. Heat treatment conditions including temperature and dwell time were examined to obtain a monoclinic $VO_2$ single phase. Both rutile and monoclinic $VO_2$ phases were observed from in the tiles post-annealed below $700^{\circ}C$. Desired monoclinic $VO_2$ single phase was grown in the tiles heat treated at $750^{\circ}C$. Nano facets of irregular size were observed in the monoclinic $VO_2$ phase involving the phase-transition. Grain growth of monoclinic $VO_2$ phase was observed as a function of dwell time at $750^{\circ}C$.
Task Balanced Workflow Scheduling Technique considering Task Processing Rate in Spot Market
Jung, Daeyong,Lim, JongBeom,Gil, JoonMin,Lee, Eunyoung,Yu, Heonchang Hindawi Limited 2014 Journal of applied mathematics (JAM) Vol.2014 No.-
<P>Recently, the cloud computing is a computing paradigm that constitutes an advanced computing environment that evolved from the distributed computing. And the cloud computing provides acquired computing resources in a pay-as-you-go manner. For example, Amazon EC2 offers the Infrastructure-as-a-Service (IaaS) instances in three different ways with different price, reliability, and various performances of instances. Our study is based on the environment using spot instances. Spot instances can significantly decrease costs compared to reserved and on-demand instances. However, spot instances give a more unreliable environment than other instances. In this paper, we propose the workflow scheduling scheme that reduces the out-of-bid situation. Consequently, the total task completion time is decreased. The simulation results reveal that, compared to various instance types, our scheme achieves performance improvements in terms of an average combined metric of 12.76% over workflow scheme without considering the processing rate. However, the cost in our scheme is higher than an instance with low performance and is lower than an instance with high performance.</P>
Fabrication of pure monoclinic VO<sub>2</sub> nanoporous nanorods via a mild pyrolysis process
Jung, Daeyong,Kim, Ungsoo,Cho, Wooseok Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.6
<P><B>Abstract</B></P> <P>This paper describes a method for the synthesis of high quality monoclinic VO<SUB>2</SUB> powder under mild pyrolysis conditions. Vanadyl ethylene glycolate (VEG) precursor powder was synthesized first and the pyrolysis temperature necessary to prevent oxidation into V<SUB>2</SUB>O<SUB>5</SUB> was analyzed with the thermal analysis as below 253°C. VO<SUB>2</SUB>(M) powder with the highest purity and crystallinity was synthesized at a heat treatment temperature of 190°C for 1h in an air flux of 10L/min. The microstructure analysis showed porous nanorods whose spherical nanoparticles with 20–50nm diameters were agglomerated in the finally synthesized VO<SUB>2</SUB>(M) powder. However, the nanopores disappeared with grain growth of nanoparticles in the VO<SUB>2</SUB>(M) powder, which underwent peroxidation after high temperature heat treatment. The final product, VO<SUB>2</SUB>(M) powder, showed a change in the reversible crystal structure at the transition temperature through the crystalline analysis. In addition, thermal analysis revealed a reversible Metal Insulator Phase Transition (MIPT) phenomenon at about 83°C (heating) and 55°C (cooling). This study confirmed that with a fabrication process using a low pyrolysis temperature, short duration and air atmosphere, mass production is possible and it is suitable for large area application.</P>
A Workflow Scheduling Technique Using Genetic Algorithm in Spot Instance-Based Cloud
( Daeyong Jung ),( Taeweon Suh ),( Heonchang Yu ),( Joonmin Gil ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.9
Cloud computing is a computing paradigm in which users can rent computing resources from service providers according to their requirements. A spot instance in cloud computing helps a user to obtain resources at a lower cost. However, a crucial weakness of spot instances is that the resources can be unreliable anytime due to the fluctuation of instance prices, resulting in increasing the failure time of users` job. In this paper, we propose a Genetic Algorithm (GA)-based workflow scheduling scheme that can find the optimal task size of each instance in a spot instance-based cloud computing environment without increasing users` budgets. Our scheme reduces total task execution time even if an out-of-bid situation occurs in an instance. The simulation results, based on a before-and-after GA comparison, reveal that our scheme achieves performance improvements in terms of reducing the task execution time on average by 7.06%. Additionally, the cost in our scheme is similar to that when GA is not applied. Therefore, our scheme can achieve better performance than the existing scheme, by optimizing the task size allocated to each available instance throughout the evolutionary process of GA.
Estimated Interval-Based Checkpointing (EIC) on Spot Instances in Cloud Computing
Jung, Daeyong,Lim, JongBeom,Yu, Heonchang,Suh, Taeweon Hindawi Limited 2014 Journal of applied mathematics (JAM) Vol.2014 No.-
<P>In cloud computing, users can rent computing resources from service providers according to their demand. Spot instances are unreliable resources provided by cloud computing services at low monetary cost. When users perform tasks on spot instances, there is an inevitable risk of failures that causes the delay of task execution time, resulting in a serious deterioration of quality of service (QoS). To deal with the problem on spot instances, we propose an estimated interval-based checkpointing (EIC) using weighted moving average. Our scheme sets the thresholds of price and execution time based on history. Whenever the actual price and the execution time cross over the thresholds, the system saves the state of spot instances. The Bollinger Bands is adopted to inform the ranges of estimated cost and execution time for user's discretion. The simulation results reveal that, compared to the HBC and REC, the EIC reduces the number of checkpoints and the rollback time. Consequently, the task execution time is decreased with EIC by HBC and REC. The EIC also provides the benefit of the cost reduction by HBC and REC, on average. We also found that the actual cost and execution time fall within the estimated ranges suggested by the Bollinger Bands.</P>
클라우드 컴퓨팅에서 비용-효율적 스팟 인스턴스를 위한 시간 문턱치 기반의 검사점 기법
정대용 ( Daeyong Jung ),유헌창 ( Heonchang Yu ),길준민 ( Joon-min Gil ) 한국정보처리학회 2011 한국정보처리학회 학술대회논문집 Vol.18 No.2
클라우드 환경에서 스팟 인스턴스(spot instance)는 사용자가 제시한 입찰 가격으로 클라우드 내의 자원을 활용하도록 해 준다. 그러나 사용자의 입찰 가격이 클라우드 자원 가격보다 높으면 작업 실패가 발생하고 이로 인해 작업 완료 시간의 지연과 서비스 품질의 저하를 야기한다. 이 문제에 효과적으로 대처하기 위해, 본 논문에서는 시간 문턱치 기반의 검사점(time threshold-based checkpointing) 기법을 제안하고, 시뮬레이션을 통하여 작업 수행 시간과 비용 절감 관점에서 기존 기법과 비교·분석한다.
정대용 ( Daeyong Jung ),최숙경 ( Sookkyong Choi ),이정하 ( Jungha Lee ),정광식 ( Kwang Sik Chung ),유헌창 ( Heonchang Yu ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.2
스팟 인스턴스(Spot instance)는 클라우드 환경에서 사용자가 제시한 입찰 가격으로 클라우드 내의 자원을 이용하여 작업을 수행할 수 있게 하는 새로운 방식이다. 사용자는 자신의 입찰 금액이 클라우드 내의 스팟 인스턴스 가격을 초과하는 한 인스턴스를 실행할 수 있다. 그러나 입찰 가격이 스팟 가격보다 낮다면 작업 실패가 발생하고, 이로 인해 작업 완료 시간은 지연되며 서비스 품질은 저하된다. 이 문제를 해결하기 위해, 본 논문에서는 스팟 인스턴스에서 사용자 비드가 초과되어 작업 수행이 중지된 VM에 대하여 체크포인트 기법과 VM 이주(migration) 기법을 이용함으로써 작업 대기 시간을 줄이는 방법을 제안한다. 이는 작업 중인 스팟 인스턴스에서 작업 실패가 발생할 경우 다른 인스턴스로 이주하여 작업을 재수행하는 기법이다. 실험 결과는 제안하는 VM 이주 기법이 작업을 수행할 수 있는 스팟 인스턴스의 가용성을 증가시킬 수 있음을 보여준다.
정대용 ( Daeyong Jung ),진성호 ( Sungho Chin ),정광식 ( Kwangsik Chung ),유헌창 ( Heonchang Yu ),길준민 ( Joonmin Gil ) 한국정보처리학회 2010 한국정보처리학회 학술대회논문집 Vol.17 No.1
모바일 그리드 환경에서 작업 처리를 위해 노드로 활용되는 모바일 장치는 무선 인터넷 연결과 모바일 장치의 배터리 용량 등의 제약으로 인해 모바일 그리드 환경에서의 작업 처리는 기존 그리드 컴퓨팅 환경에 비해 신뢰성이 낮고 결함이 발생할 확률이 높다. 따라서 모바일 장치의 신뢰성을 고려한 작업 분배 방법이 요구된다. 이 논문에서는 모바일 장치의 신뢰성을 고려한 작업 분배 스케줄링을 제안하고자 한다. 제안 기법에서는 노드의 신뢰성을 바탕으로 작업량과 복제 개수를 서로 달리 설정하여 신뢰성이 우수한 노드에게 더 많은 작업량을 할당하고 작업 복제 개수를 적게 설정하도록 한다. 제안 기법의 타당성을 보이기 위한 성능 평가에서는 제안 기법이 기존 기법에 비해 성능이 향상됨을 보여준다.