• Journal of Korean Medicine Rehabilitation
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• v.29 no.4
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• pp.15-27
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• 2019

Objectives This study was performed to evaluate anti-obesity effects of Crataegus pinnatifida (CP) on high-fat-diet induced obese mice. Methods The experimental animals were divided into four groups: normal diet (NOR) group, high fat diet (HFD) group, HFD+Xenical (XEN) group, and HFD+CP (CP) group. NOR group was fed a normal diet and the other three groups were fed high fat diet during the experiment. After the first two weeks of diet, XEN group and CP group were administered with XEN or CP for seven weeks, respectively. After that, we measured body weight, liver weight, fat weight, food intake, and serum concentrations of lipids and liver enzymes. Also the liver, intestine, fat tissue was removed to estimate the obesity-related mRNA expressions and the stool sample was collected to analyze the gut microbiota. Results We found that body weight, fat weight, and triglyceride level were decreased significantly in CP group compared to HFD group. Also CP significantly suppressed gene expressions associated with lipogenesis and inflammation, and increased gene expressions of browning of white adipose tissue and mitochondrial biogenesis. Moreover, it shifted the microbial diversity closer to that of NOR group and increased Firmicutes/Bacteriodetes ratio. Conclusions These results suggest that CP decrease body weight, fat weight and serum triglyceride. Also it inhibit inflammation and adipogenesis, altering gut microbial diversity and abundance. In conclusion, CP could be used as a therapeutic drug for obesity via gut microbiota modulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.11
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• pp.2764-2783
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• 2012

Network virtualization supports future Internet environments and cloud computing. Virtualization can mitigate many hardware restrictions and provide variable network topologies to support variable cloud services. Owing to several advantages such as low cost, high flexibility, and better manageability, virtualization has been widely adopted for use in network virtualization platforms. Among the many issues related to cloud computing, to achieve a suitable cloud service quality we specifically focus on network and performance isolation schemes, which ensure the integrity and QoS of each virtual cloud network. In this study, we suggest a virtual network platform that uses Xen-based virtualization, and implement multiple virtualized networks to provide variable cloud services on a physical network. In addition, we describe the isolation of virtual networks by assigning a different virtualized network ID (VLAN ID) to each network to ensure the integrity of the service contents. We also provide a method for efficiently isolating the performance of each virtual network in terms of network bandwidth. Our performance isolation method supports multiple virtual networks with different levels of service quality.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.55-64
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• 2008

Recently virtualization becomes one of the most popular research topics. and a lot of software products which is related to virtualization have been released accordingly. Server virtualization, which virtualize physical servers to supply many virtual servers, provides very efficient way to build network-based servers. In this paper, we design and implement virtual desktop service which is based on server virtualization. We also propose load balancing scheme for the virtual desktop service. The proposed virtual desktop service and its load balancing scheme provides a cost-effective way to build high-performance remote desktop service.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2462-2472
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• 2014

Recently, the computing paradigm has been changing and VoIP technology is being revisited to support various services. In this paper, we have designed and implemented the system of software PBX open source Asterisk, hardware platform, and mobile devices to support secured voice service based on VoIP. Specially, we designed the various platform from single board to servers based on XenServer in hardware platform. And we verified the delay test of network traffics and the secured voice communication test based on this platform.

• Smart Media Journal
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• v.6 no.3
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• pp.29-40
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• 2017

Lately weight for smartphone mounted to function for NFC is increasing, rapidly. Because of this, NFC related technology is made by many companies. We developed Gallery-Auction for security enhancements and new services of NFC-based 2 factor electronic payment system. Enhanced security features development of user authentication module through fingerprint recognition to apply FIDO authentication technology and developed electronic contract voice service of Gallery-Auction using TTS(Text to Speech). Therefore we enhanced convenient and simple authentication method and security through NFC mobile electronic payment.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.2
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• pp.113-118
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• 2013

The current GPU virtualization techniques incur large overheads when executing application programs mainly due to the fine-grain time-sharing scheduling of the GPU among multiple Virtual Machines (VMs). Besides, the current techniques lack of portability, because they include the APIs for the GPU computations in the VM monitor. In this paper, we propose a low overhead and high performance GPU virtualization approach on a heterogeneous HPC system based on the open-source Xen. Our proposed techniques are tailored to the bio applications. In our virtualization framework, we allow a VM to solely occupy a GPU once the VM is assigned a GPU instead of relying on the time-sharing the GPU. This improves the performance of the applications and the utilization of the GPUs. Our techniques also allow a direct pass-through to the GPU by using the IOMMU virtualization features embedded in the hardware for the high portability. Experimental studies using microbiology genome analysis applications show that our proposed techniques based on the direct pass-through significantly reduce the overheads compared with the previous Domain0 based approaches. Furthermore, our approach closely matches the performance for the applications to the bare machine or rather improves the performance.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1691-1693
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• 2010

본 논문에서는 OpenNebula 기반의 클라우드 컴퓨팅 환경을 구축하고 클러스터 노드에 설치되는 하이퍼바이저로 Xen을 이용하여 클라우드 컴퓨팅 기반 컴퓨터 교육 시스템을 구축하였다. 전체 시스템은 Front-End 1대와 클러스터 노드 2대로 구성되며, 시스템 사용자는 원격 접속을 이용하여 가상 머신에 접근이 가능하다. 관리자는 Web를 통해 클러스터 노드와 가상 머신을 관리할 수 있으며, 컴퓨터 실습수업의 형태에 따라 각기 다른 OS와 응용 소프트웨어가 설치된 가상머신을 생성하여 사용자들에게 제공할 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.770-771
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• 2009

리눅스 커널을 VMM(Virtual Machine Monitor)로 만들어 주는 KVM의 메모리 관리 기법을 분석한다. Xen과의 차이점과 KVM의 구조를 알아보고 KVM에서의 메모리 관리 기법에 대해 분석하였다. 또한 CPU의 가상화 기능인 Intel VT-x가 어떻게 적용되었는지 분석한다.

• Journal of KIISE:Computer Systems and Theory
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• v.37 no.1
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• pp.35-42
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• 2010

Guest operating systems running over the virtual machines share a variety of resources. Since CPU is allocated in a time division manner it consequently leads them to having the unknown physical time. It is not regarded as a serious problem in the server virtualization fields. However, it becomes critical in embedded systems because it prevents guest OS from executing real time tasks when it does not occupy CPU. In this paper we propose a hypercall to register a timer service to notify the timer request related real time. It enables hypervisor to schedule a virtual machine which has real time tasks to execute, and allows guest OS to take CPU on time to support real time. The following experiment shows its implementation on Xen-Arm and para-virtualized Linux. We also analyze the real time performance with response time of test application and frames per second of Mplayer.

• KIISE Transactions on Computing Practices
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• v.24 no.3
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• pp.129-137
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• 2018

NVMe(Non-Volatile Memory Express) SSD(Solid State Drive) is a high-performance storage that makes use of flash memory as a storage cell, PCIe as an interface and NVMe as a protocol on the interface. It supports multiple I/O queues which makes it feasible to process parallel-I/Os on multi-core environments and to provide higher bandwidth than SATA SSDs. Hence, NVMe SSD is considered as a next generation-storage for data-center and cloud computing system. However, in the virtualization system, the performance of NVMe SSD is not fully utilized due to the bottleneck of the software I/O stack. Especially, when it uses I/O stack of the hypervisor or the host operating system like Xen and KVM, I/O performance degrades seriously due to doubled-I/O stack between host and virtual machine. In this paper, we propose a new I/O engine, called Direct-AIO (Direct-Asynchronous I/O) engine, that can access NVMe SSD directly for I/O performance improvements on QEMU emulator. We develop our proposed I/O engine and analyze I/O performance differences between the existed I/O engine and Direct-AIO engine.