• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1146-1154
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• 2010

A virtual machine lease service in the cloud computing environment has been implemented using the open source cloud computing platform, OpenNebula. In addition, a web-based cloud user interface is developed for both convenient resource management and efficient service access. The present virtual machine allocation scheme adopted in OpenNebula has performance reduction problem because of not considering CPU allocation scheduler of the virtualization software. In order to address this problem we have considered both the priority of the idle CPU resources of the cluster and credit scheduler of Xen, which resulted in performance improvement of the OpenNebula virtual machine scheduler. The experimental results showed that the proposed allocation scheme provided more virtual machine creations and more CPU resource allocations for cloud service.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.2
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• pp.141-148
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• 2006

This paper suggests method of safe security S/W by verifying and its result of formal verification tool. We will survey many formal verification tools and compare features of these tools. And we will suggest what tool is appropriate and methodogoly of developing safe security S/W. The Z/EVES is the most appropriate tool. This paper proposes formal verification of ACS by using RoZ tool which is formal verification tool to create UML model. The specification and verification are executed using Z/EVES tool. These procedures can find weak or wrong point of developed S/W.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.3
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• pp.173-180
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• 2001

고가용도 클러스터 시스템에서 가동되는 인터넷 기반 소프트웨어의 복잡도가 증가됨에 따라 소프트웨어의 설계, 구현, 또는 그 밖의 여러 가지 원인과 관련된 결함으로 인하여 시스템 서비스의 오동작 또는 수행 중단으로 이어지는 사례가 늘어나고 있다. 특히 대량 트랜잭션을 처리하는 인터넷 기반 컴퓨팅 소프트웨어는 빈번한 통신 두절과 데이터 유실로 인하여, 이들이 탑재된 클러스터 시스템의 결함 발생이 더욱 심각할 가능성이 높다. 본 연구는 소프트웨어 재활 결함 허용 기법을 활용하여, 별도의 추가되는 하드웨어 없이도 가용도를 개선할 수 있다는 '소프트웨서 재활 기법을 적용한 다중계 시스템 가용도 분석'에 관한 논문에서 언급된 문제점들에 대한 해결 방안을 제시하였으며, 구체적으로는 1) 주서버의 고장 발생시 여분서버로의 작업전이(switchover) 상태를 클러스터 시스템 모델링에 포함시켰으며, 2) 작업전이 상태와 재활(rejuvenation) 상태에서 머무는 시간을 지수분포 대신에 k-stage Erlangian 분포를 사용하여 확정시간(deterministic time)을 표현할 수 있도록 하였다. 즉 본 논문에서는 고가용도 cold standby 클러스터 시스템의 운영 상태에 대한 상태전이도(state transition diagram)에서, 임의의 상태에서 머무는 시간분포가 memoryless 성질을 만족하지 않아도 되는 semi-Markov 프로세스 문제를 해결하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.8
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• pp.730-740
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• 2000

The software rejuvenation method for highly available multiplex systems uses a pro-active fault-tolerant approach to handle system failures. The software rejuvenation prevents failures from occurring, while the previous methods recover from failures after happening. Especially, since the software aging proceeds fast in the software used for the multimedia mobile computing due to the loss of communications or data, the preventive method from failures using software rejuvenation can be used for the multimedia mobile computing. In this paper, according to the operational parameters such as rejuvenation period, rejuvenation time, failure rate and repair rate of the servers, number of running servers, duration of running time, and type of running modes, we calculate steady-state probabilities, downtime, availability, and cost of the multiplex systems using software rejuvenation method. We validate the closed-form solutions of the mathematical model by experiments based on various operational parameters and find that the software rejuvenation method can be adopted as preventive fault-tolerant technique. The failure rate and unstable rate of the servers are essential factors for the decision making of the rejuvenation policies.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1375-1380
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• 2014

SaaS at a cloud computing is a framework to provide a software as a service. Depending on the difference of the tenant and the use, if the service provider re-establish a service, they are required resources In terms of costs and managerial. So we propose a technique for analysis of software structure using the process algebra to reuse existing software. A process algebra analyze the structure of the software, express in different languages and verify that it can be reused. CCS in a process algebra is useful to convert the business process or XML, by using this, we structure a process as process view and propose meta storage for comparison and management a structured document.

• Journal of The Korean Association of Information Education
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• v.20 no.6
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• pp.607-616
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• 2016

Computational thinking is complexity and independent subject matter being capable to learn concept of computer science and providing methodology of problem solving. Also many experts have said that computational thinking will be grow essential tool in the further developing information society. Thus our country has been trying to introduce it in the K12 informatics subject matter education. Therefore we proposed a introducing method of computational thinking being appropriated of a character of it in the informatics curriculum. To do this, we analyzed character and worthy of it, advanced model cases introducing it into the curriculum. And we proposed that introduced case of it into curriculum is divided 3 cases archiving computational thinking itself, being connected aim of general subject matter with it and computer science education. According to this advanced cases, this study selected permeative style of computational thinking with the informatics subject matted curriculum. This method is divided achievement criterion into contents and means. also we proposed that contents area of informatics subject matter achievement criterion is composed Computing System, Information Life, Software and means area can be filled with subset of computational thinking. This introducing method can make informatics subject matter education settle subject matter helping problem solving through computer system beyond character of technology oriented subject matter.

• Journal of Convergence for Information Technology
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• v.7 no.1
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• pp.61-66
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• 2017

As the fourth industrial revolution becomes more popular and advanced services such as artificial intelligence and Internet of Things technology are widely commercialized, awareness of the importance of software is spreading. Recently, software education has been taught not only in elementary school and college but also in college. Also, there is a growing interest in computational thinking needed to solve problems through computing methodology and model. The purpose of this study is to design an app inventor course for non-majors software education based on computational thinking. As a result of the study, six detailed competencies of computational thinking were derived, and six detailed competencies were mapped to the app inventor learning elements. In addition, based on the computational thinking modeling, I designed an app inventor class for students who participated in IT curriculum of university liberal arts curriculum.

• The KIPS Transactions:PartD
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• v.15D no.3
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• pp.361-374
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• 2008

In the latest intelligent computing environments, the self-adaptive software, as new software paradigm, which modifies its own behavior in response to changes in its operating environment is needed. To develop the self-adaptive software, it is necessary to analyze and design the context of software as well as the structure and the behavior of software. We need more efforts for self-adaptive software development than for traditional software development because we need more activities and technologies like context modeling and adaptation to develop the self-adaptive software. In this paper, we present the product line architecture for self-adaptive software and templates of artifacts to improve the efficiency of development through a reuse methodology. The artifacts of the architecture support the systematic reuse activities of core assets by expressing the commonality and variability of product line.

• Journal of Advanced Navigation Technology
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• v.11 no.3
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• pp.259-265
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• 2007

Systematic components for implementing ubiquitous computing, for example, electronic devices, electric home appliances, and controllers, etc, are consist of not only circuits but also softwares expected to do some special system-controlling functions, and these softwares used to be called like as embedded software. Because embedded software is a core component controlling systems, the codes or control flows should be protected from being opened to the public or modified. Embedded software security can be divided into 2 parts: first is the unauthorized access to development site and embedded software, second is the unauthorized disclosure or modification. And this research is related to the first aspect of them.This paper proposes some security check requirements related to embedded software development site by analyzing the ALC_DVS.1 of the ISO/IEC 15408 and Base Practices (BPs) of the ISO/IEC 21827. By applying this research, we expect to protect unauthorized modification of embedded software indirectly.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.10
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• pp.261-268
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• 2021

Cloud computing is a computing paradigm in which users can utilize computing resources in a pay-as-you-go manner. In a cloud system, resources can be dynamically scaled up and down to the user's on-demand so that the total cost of ownership can be reduced. The Modeling and Simulation (M&S) technology is a renowned simulation-based method to obtain engineering analysis and results through CAE software without actual experimental action. In general, M&S technology is utilized in Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD), Multibody dynamics (MBD), and optimization fields. The work procedure through M&S is divided into pre-processing, analysis, and post-processing steps. The pre/post-processing are GPU-intensive job that consists of 3D modeling jobs via CAE software, whereas analysis is CPU or GPU intensive. Because a general-purpose desktop needs plenty of time to analyze complicated 3D models, CAE software requires a high-end CPU and GPU-based workstation that can work fluently. In other words, for executing M&S, it is absolutely required to utilize high-performance computing resources. To mitigate the cost issue from equipping such tremendous computing resources, we propose HEMOS-Cloud service, an integrated cloud and cluster computing environment. The HEMOS-Cloud service provides CAE software and computing resources to users who want to experience M&S in business sectors or academics. In this paper, the economic ripple effect of HEMOS-Cloud service was analyzed by using industry-related analysis. The estimated results of using the experts-guided coefficients are the production inducement effect of KRW 7.4 billion, the value-added effect of KRW 4.1 billion, and the employment-inducing effect of 50 persons per KRW 1 billion.