• Journal of the Korea Society of Computer and Information
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• v.15 no.2
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• pp.19-26
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• 2010

The Windows registry is a hierarchical database where the configuration data of a system or application programs is stored. In this paper, we presented and implemented a registry virtualization algorithm and measured its performance. The registry virtualization algorithm presented in the paper is called Copy-One-level On Write-Open(COOWO) that is a modified version of general Copy On Whte(COW) method to make it suitable for registry virtualization. In this paper, we implemented the proposed algorithm as a dynamically loadable library in Windows and applied it to many Windows application programs. This paper is meaningful since we described a registry virtualization algorithm in detail in situation where we can not find papers that describe the registry virtualization in detail, and we could find the performance of the algorithm can be used in the real applications.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.04a
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• pp.65-69
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• 1999

Switching System(이하 교환 시스템)이 QoS(Quality of Service)를 유지하면서 처리 가능한 최대 동시 호처리 능력을 검증하기 위하여, 수학적 분석을 이용한 해석적 방법, 실제 호를 사용한 통계적 방법 등이 제안되었다. 해석적 방법을 이용해 산출한 교환 시스템의 최번시 동시 호 처리능력(BHCA, Busy Hour Call Attempt)은 단지 수학적인 예측일 뿐이므로 이를 검증하기 위해서 가상 호 발생기가 제안되었다. 이 가상호 발생기는 가입자의 행동을 시스템 하위 프로세서(가입자 정합 Device 제어 프로세서)에서 Simulation하여 가상의 호를 발생시키고, 이를 통해 교환기 최대 동시 호 처리 용량을 시험하기 위한 SW이다. 이 가상호 발생기는 동일한 형태의 호를 동시에 다량으로 발생시킴으로써 교환 시스템의 주 프로세서(Main Processor, MP)의 동시 호 처리 용량을 시험하기 위한 SW이다. ITU-T 권고에 의하면 시스템부하가 90~95%를 넘어 서는 경우는 예외적인 처리(과부하 제어 등)를 권고하고 있으므로 MP 부하 90~95%에서 BHCA를 계산하면 최대 호 처리 용량이라 할 수 있다. 가상 호 발생기는 시스템 개발 초기에 실제 가입자 정합 Device 와 호 발생기 없이도 MP 과부하 지점까지 호를 발생시킴으로써 개발의 시간 및 비용을 절약할 수 있도록 하고, 계획된 시스템 용량을 만족하기 위해 필요한 조치를 교환 시스템 개발 초기에 취할수 있도록 한다. 또한, 과부하 지점에서 MP가 정상 동작하는지 검증하는 도구로 사용 가능하다. 앞으로 이를 더 발전시키면 가상호 발생기를 이용한 다양한 시스템 검증 및 분석에 이용할 수 있을 것이다. 본 논문은 가상호 발생기의 구조와 최대 용량 시험 방법을 소개하고, 더 나아가 호 Traffic에 대한 최대 용량 시험뿐 아니라 QoS를 향상시키기 위한 교환 시스템의 제반 성능 시험 및 분석에 이를 이용하기 위해 개선이 필요함을 서술하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.40 no.1
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• pp.50-58
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• 2003

Recently we have built a VR(Virtual Reality) theater in Kyongju, Korea, which combines the advantages of VR and IMAX theater. The VR theater provides a virtual environment for several hundreds of people at the same time. The VR theater can be characterized by a single shared screen and by multiple inputs from several hundreds of people. In this case, multi-user interaction is different from that of networked VR systems and must be reconsidered. This paper defines the multi-user interaction in such a VR theater as Audience Interaction, and discusses key issues for the implementation of the Audience Interaction. This paper also presents a real implementation example in the Kyongju VR theater.

• Journal of The Korean Association of Information Education
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• v.22 no.1
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• pp.33-40
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• 2018

This study highlights the experiences and lessons learned, through the introduction and production of virtual reality in elementary school classes. We analysed the effects of virtual reality-contents production education using the data from the K.A.P survey, as well as the results from the class using virtual reality. We used Cospaces as a tool for coding the virtual reality content. It was not difficult for students to learn its functions because it could be coded with blockly based programmes. We analysed the results in the practice area. Based on these results, we suggest how to apply this to the elementary school field.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.8
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• pp.491-498
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• 2014

Due to the ossification of current Internet, it is hard to accommodate new service requirements. One of the solutions to this problem is network virtualization. In this paper, we propose a heuristic virtual network embedding method for network virtualization. The proposed method checks whether the candidate substrate nodes in the substrate network have the possibility of satisfying virtual link requirements. It gives priority to the virtual nodes and the substrate nodes, and embeds the node with higher priority first. Also, the proposed method tries to cluster the mapped substrate nodes if possible. We evaluate the performance of the proposed method in terms of time complexity and virtual network acceptance rate.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3B
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• pp.171-182
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• 2003

In this paper, we propose an efficient and simple fair queueing algorithm, called Minimum Possible Virtual Start Time Fair Queueing (MPSFQ), which has O(1) complexity for the virtual time computation while it has good delay and fairness properties. The key idea of MPSFQ is that it has an easy system virtual time recalibration method while it follows a rate-proportional property. MPSFQ algorithm recalibrates system virtual time to the minimum possible virtual start time of all backlogged sessions. We will show our algorithm has good delay and fairness properties by analysis.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.1 s.28
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• pp.55-62
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• 2004

More recently, multiple reference based RTK GPS techniques(VRS ; Virtual Reference System) are becoming increasingly important for many precise GPS applications in many countries to overcome the constrained distance limitations of standard RTK systems. The precision of the position solutions of the rover receiver is closely connected with that of the corresponding virtual reference points(VRPs). The objective of this paper is to investigate the accuracy and performance of the VRPs on the test network have been made in post mode, and the overall analysis results were presented by comparing the solutions for the VRPs from the existing GPS reference station with the true values of the coordinates used to produce the observation data. The results show the reasonable accuracies of VRPs in the network area by using the VRS concept in post mode.

• The KIPS Transactions:PartB
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• v.12B no.2 s.98
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• pp.143-150
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• 2005

The Field is a simulated virtual environment specifically designed to assist elementary students learn the basic scientific inquiry skills such as observation, data collection, and generating and verifying hypothesis. Over the last four years, the Field has been used to teach inquiry learning in the context of mathematics and science in an elementary school. During the studies, it was observed that students suffered from problems in navigation, wayfinding, and data collection. First, this papers discusses the problems and the technical aids we have iteratively developed to address these issues. We will then discuss the impact of the technical aids on the student's behaviors.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06b
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• pp.333-338
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• 2007

시스템 가상머신 환경은 높은 하드웨어 효율성과 높은 보안을 요구하는 시스템에서 그 사용이 점차 늘어나고 있다. 최근 많이 알려진 하이퍼바이저 가상머신 시스템은 높은 아이솔레이션과 보안성을 보장하나 각 게스트 운영체제 별로 운영체제 이미지를 가지기 때문에 하드웨어 효율성이 떨어지는 반면, 컨테이너 기반 가상머신 시스템은 운영체제 이미지의 공유로 인하여 높은 자원 효율성과 확장성을 가진다. 그러나 메모리 자원의 아이솔레이션에 대하여 취약점을 갖는 문제점을 안고 있다. 본 논문에서는 컨테이너 기반 가상머신 시스템에서 동적으로 각 가상머신별로 메모리 사용량 증가에 따른 페이지 히트율-곡선(Hit-Ratio-Curve)을 측정하였다. 이 곡선을 관찰해 보면 각 가상머신의 메모리 필요량을 알 수 있으며 이를 기반으로 메모리 자원을 할당하게 될 경우 효과적으로 메모리 자원의 아이솔레이션을 제공할 수 있게 된다. 본 논문에서는 대표적인 컨테이너 기반 가상머신인 리눅스 VServer가 적용되어 있는 리눅스 2.6.17 커널에 직접 구현하였으며, Lmbench 및 리눅스 커널 컴파일 등을 통하여 오버헤드를 측정하였고 $1.6{\sim}7.2%$의 적은 오버헤드로 이를 측정할 수 있음을 확인하였다.