• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권4호
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• pp.1501-1518
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• 2016

This paper presents an effective management of VM (Virtual Machine) for heterogeneous cloud using Common Deployment Model (CDM) brokering mechanism. The effective utilization of VM is achieved by means of task scheduling with VM placement technique. The placements of VM for the physical machine are analyzed with respect to execution time of the task. The idle time of the VMis utilized productively in order to improve the performance. The VMs are also scheduled to maintain the state of the current VM after the task completion. CDM based algorithm maintains two directories namely Active Directory (AD) and Passive Directory (PD). These directories maintain VM with proper configuration mapping of the physical machines to perform two operations namely VM migration and VM roll back. VM migration operation is performed from AD to PD whereas VM roll back operation is performed from PD to AD. The main objectives of the proposed algorithm is to manage the VM's idle time effectively and to maximize the utilization of resources at the data center. The VM placement and VM scheduling algorithms are analyzed in various dimensions of the cloud and the results are compared with iCanCloud model.

• 물과 미래
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• 제28권6호
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• pp.229-236
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• 1995

강수의 물리과정에 입각한 호우모형이 전일권(1994)에 의하여 개발되었다. 본 논문에서 이를 수정하였다. 본는 연구 모형에서 구성한 주요 부분은 포화증기압, 구름두께, 운정기압에 관한 것이다. 기존 모형과 달리 본 연구 모형의 입력자료로써 위성에 의해 측정된 운정기온과 알베도를 사용하였다. 본 연구에서 기존의 포화증기압 방정식보다 현실에 가까운 방정식을 획득하였으며 기존 방정식의 단점을 해결하였다. 또한 운정기온과 운정기압 추정에 사용된 매개변수가 소거되었으며 계산시간도 단축되었다. 본 연구 모형을 전주지점의 호우사상에 적용하여 검증한 결과 모형의 출력인 총강우량과 강우 패턴이 실측치에 잘 부합되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권10호
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• pp.1712-1732
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• 2011

Cloud provides dynamically scalable virtualized computing resources as a service over the Internet. To achieve higher resource utilization over virtualization technology, an optimized strategy that deploys virtual machines on physical machines is needed. That is, the total number of active physical host nodes should be dynamically changed to correspond to their resource usage rate, thereby maintaining optimum utilization of physical machines. In this paper, we propose a pattern-based prediction model for resource provisioning which facilitates best possible resource preparation by analyzing the resource utilization and deriving resource usage patterns. The focus of our work is on predicting future resource requests by optimized dynamic resource management strategy that is applied to a virtualized data center in a Cloud computing environment. To this end, we build a prediction model that is based on user request patterns and make a prediction of system behavior for the near future. As a result, this model can save time for predicting the needed resource amount and reduce the possibility of resource overuse. In addition, we studied the performance of our proposed model comparing with conventional resource provisioning models under various Cloud execution conditions. The experimental results showed that our pattern-based prediction model gives significant benefits over conventional models.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제20권12호
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• pp.664-669
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• 2014

클라우드 컴퓨팅 패러다임이 성행하면서 IaaS, PaaS, SaaS 유형의 클라우드 서비스가 나타나고 있다. 제공되는 클라우드 서비스의 다양화로 인해 클라우드 테넌트(사용자)의 요구사항에 적합한 클라우드 서비스를 중개하는 기술인 서비스 브로커 기술이 최근 들어 관심을 받고 있다. 클라우드 서비스를 중개하기 위해서 다양한 클라우드 서비스의 체계적인 등록, 분석, 검색을 지원할 수 있는 클라우드 서비스 명세 모델이 필요하다. 본 논문은 다양한 유형의 클라우드 서비스를 명세하기 위한 가변성 기반의 클라우드 서비스 분석 모델(SAM)을 제시한다. SAM은 소프트웨어 프로덕트 라인의 가변성 개념을 적용하여 클라우드 서비스를 명세할 때 기능, 품질, 가격 측면에서 나타날 수 있는 가변점에 가변값을 바인딩함으로써 클라우드 서비스의 공통성과 가변성을 나타낸다. 또한, SAM을 이용하여 테넌트에게 클라우드 서비스를 중개하는 브로커로서의 가상 클라우드 뱅크의 구조를 제안한다.

• 경영정보학연구
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• 제17권1호
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• pp.1-18
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• 2015

최근 많은 IT 기업들이 클라우드 서비스 시장에 진입하면서 출시되는 클라우드 서비스의 숫자가 크게 늘어나고 있다. 이러한 이유로 발생하는 클라우드 서비스 선택의 문제들을 해결하고, 기술적인 역량이 부족한 클라우드 서비스 사용자들의 서비스 초기화와 운용을 돕기 위해서 클라우드 서비스 중개업 회사들이 크게 주목받고 있다. 본 연구에서는 원 클라우드 서비스 제공자들과 클라우드 서비스 중개업 회사들 간의 협업을 대표적인 사례들인 국내의 NCloud24와 미국의 RightScale을 통해 보았다. 두 회사의 비즈니스 모델을 비즈니스 모델 캔버스를 사용하여 분석하였으며, 클라우드 서비스 중개업 회사들의 출현을 IaaS(Infrastructure-as-a-Service) 클라우드 서비스 회사들의 언번들링(Unbundling) 과정으로 해석하였다. 그리고 두 사례간의 차이점을 비교하고, 이를 바탕으로 향후 국내 클라우드 서비스 중개업이 나아가야 할 방향에 대하여 조망하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권7호
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• pp.3375-3400
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• 2018

With the advent of database-as-a-service (DAAS) and cloud computing, more and more data owners are motivated to outsource their data to cloud database in consideration of convenience and cost. However, it has become a challenging work to provide security to database as service model in cloud computing, because adversaries may try to gain access to sensitive data, and curious or malicious administrators may capture and leak data. In order to realize privacy preservation, sensitive data should be encrypted before outsourcing. In this paper, we present a secure and practical system over encrypted cloud data, called QSDB (queryable and secure database), which simultaneously supports SQL query operations. The proposed system can store and process the floating point numbers without compromising the security of data. To balance tradeoff between data privacy protection and query processing efficiency, QSDB utilizes three different encryption models to encrypt data. Our strategy is to process as much queries as possible at the cloud server. Encryption of queries and decryption of encrypted queries results are performed at client. Experiments on the real-world data sets were conducted to demonstrate the efficiency and practicality of the proposed system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권11호
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• pp.5269-5286
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• 2018

Task scheduling is one of the key issues in improving system performance and optimizing resource management in cloud computing environment. In order to provide appropriate services for heterogeneous users, we propose a novel task scheduling strategy with service differentiation, in which the delay sensitive tasks are assigned to the rapid cloud with high-speed processing, whereas the fault sensitive tasks are assigned to the reliable cloud with service restoration. Considering that a user can receive service from either local SaaS (Software as a Service) servers or public IaaS (Infrastructure as a Service) cloud, we establish a hybrid queueing network based system model. With the assumption of Poisson arriving process, we analyze the system model in steady state. Moreover, we derive the performance measures in terms of average response time of the delay sensitive tasks and utilization of VMs (Virtual Machines) in reliable cloud. We provide experimental results to validate the proposed strategy and the system model. Furthermore, we investigate the Nash equilibrium behavior and the social optimization behavior of the delay sensitive tasks. Finally, we carry out an improved intelligent searching algorithm to obtain the optimal arrival rate of total tasks and present a pricing policy for the delay sensitive tasks.

• 대한기계학회논문집A
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• 제30권8호
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• pp.906-915
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• 2006

This study concerns an advanced 3D surface reconstruction method that the vertices of surface model can be completely matched to the unstructured point cloud measured from arbitrary complex shapes. The concept of bounding voxel model is introduced to generate the mesh model well-representing the geometrical and topological characteristics of point cloud. In the reconstruction processes, the application of various methodologies such as shrink-wrapping, mesh simplification, local subdivision surface fitting, insertion of is isolated points, mesh optimization and so on, are required. Especially, the effectiveness, rapidity and reliability of the proposed surface reconstruction method are demonstrated by the simulation results for the geometrically and topologically complex shapes like dragon and human mouth.

• 한국IT서비스학회지
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• 제13권3호
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• pp.201-219
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• 2014

This paper considers service deployment and priority optimization for multiple service-oriented applications sharing reusable services, which are deployed as multiple instances in the cloud. In order to handle variations in the workloads of the multiple applications, service instances of the individual reusable services are dynamically provisioned in the cloud. Also service priorities for each application in a particular reusable service are dynamically adjusted. In this paper, we propose an analytic performance model, based on a queueing network model, to predict the expected sojourn times of multiple service-oriented applications, given the number of service instances and priority disciplines in individual reusable services. We also propose a simple heuristic algorithm to search an optimal number of service instances in the cloud and service priority disciplines for each application in individual reusable services. A numerical example is also presented to demonstrate the applicability of the proposed performance model and algorithm to the proposed optimal decision problem.

• 대한기계학회논문집
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• 제8권6호
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• pp.544-552
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• 1984

본 연구에서는 Chiu et al.의 집단연소이론에 대한 비정상집단연소모델(non- steady group combustion model)을 개발, 정지된 액적군에서 초기 액적들의 분포상태, 즉 초기액적들의 크기, 수밀도 및 액적군의 크기에 따른 연소시간, 연소형태 및 특성 과 화염의 성질등을 비정상 상태하에서 이론적인 모델을 통하여 고찰한다.