• 천문학회보
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• 제36권2호
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• pp.106.2-106.2
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• 2011

The two competing theories of star formation are based on turbulence and ambipoar diffusion. I will first briefly explain the two theories. There have been analytical (or semi-analytic) models, which estimate star formation rates in a turbulent cloud. Most of them are based on the log-normal density PDF (probability density function) of the turbulent cloud without self-gravity. I will first show that the core (star) formation rate can be increased significantly once self-gravity of a turbulence cloud is taken into account. I will then present the evolution of molecular line profiles of HCO+ and C18O toward a dense core that is forming inside a magnetized turbulent molecular cloud. Features of the profiles can be affected more significantly by coupled velocity and abundance structures in the outer region than those in the inner dense part of the core. During the evolution of the core, the asymmetry of line profiles easily changes from blue to red, and vice versa. Finally, I will introduce a method for incorporating ambipolar diffusion in the strong coupling approximation into a multidimensional magnetohydrodynamic code.

• 정보보호학회논문지
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• 제25권6호
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• pp.1377-1383
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• 2015

클라우드 서비스 이용자의 증가로 클라우드 스토리지상에 개인이 생성한 중요한 파일이 다수 존재한다. 즉, 클라우드 사용 흔적은 주요 증거가 될 수 있기에 조사할 필요성이 있다. 클라우드 서비스를 조사하는 방법에는 스토리지 서버 공급자(CSP:Cloud Service Provider)를 이용하여 조사하는 방법과 클라이언트를 조사하는 방법이 있다. 이 중 본 논문에서는 클라이언트 컴퓨터를 조사할 수 있는 도구(Cloud Artifact)를 개발하였다. Cloud Artifact는 Google Drive, Dropbox, Evernote, N드라이브, Daum 클라우드, Ucloud, LG Cloud, T 클라우드, iCloud 9가지 클라우드 서비스 아티팩트를 수집 및 분석한다.

• International Journal of Internet, Broadcasting and Communication
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• 제13권1호
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• pp.180-186
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• 2021

In cloud computing service it is important to share the system resource among multiple instances according to user requirements. In particular, the issue of efficiently distributing I/O resources across multiple instances is paid attention due to the rise of emerging data-centric technologies such as big data and deep learning. However, it is difficult to evaluate the I/O resource distribution of a Linux container, which is one of the core technologies of cloud computing, since conventional I/O benchmarks does not support features related to container management. In this paper, we propose a new I/O performance benchmarking framework that can easily evaluate the resource distribution of Linux containers using existing I/O benchmarks by supporting container-related features and integrated user interface. According to the performance evaluation result with trace-replay benchmark, the proposed benchmark framework has induced negligible performance overhead while providing convenience in evaluating the I/O performance of multiple Linux containers.

• 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.

• Journal of Internet Technology
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• 제19권6호
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• pp.1741-1752
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• 2018

The best known software developers all offer cloud storage services. Microsoft offers Onedrive to its users, Apple offers iCloud Drive and Google offers Google Drive or GDrive. The battle between these software developers is ongoing and they will always strive to give the best services to their users. It is not only technology that is evolving, however, but also ways in which security can be breached and data abused. The security of information on the Internet is increasingly at risk and there are many threats to cloud storage platforms. This research used the mobile forensics approach to help in identifying and analyzing user behavior that may occur while using GDrive application for cybercrime. The novelty of comparison and analyzing methods performed in this research can help to find remnant data from all activities performed by GDrive users in Android smartphones. Hence, this proposed method can assist investigators in finding remnant data on GDrive client and can provide knowledge for legal practitioners.

• International Journal of Computer Science & Network Security
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• 제23권5호
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• pp.65-72
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• 2023

Cloud Computing is one of the current research areas in computer science. Recently, Cloud is the buzz word used everywhere in IT industries; It introduced the notion of 'pay as you use' and revolutionized developments in IT. The rapid growth of modernized cloud computing leads to 24×7 accessing of e-resources from anywhere at any time. It offers storage as a service where users' data can be stored on a cloud which is managed by a third party who is called Cloud Service Provider (CSP). Since users' data are managed by a third party, it must be encrypted ensuring confidentiality and privacy of the data. There are different types of cryptographic algorithms used for cloud security; in this article, the algorithms and their security measures are discussed.

• International Journal of Computer Science & Network Security
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• 제23권5호
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• pp.89-94
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• 2023

Cloud-based technology is used in different organizations around the world for various purposes. Using this technology, the service providers provide the service mainly SaaS, PaaS and while the cloud service consumer consumes the services by paying for the service they used or accessed by the principle of "pay per use". The customer of the services can get any services being at different places or locations using different machines or electronic devices. Under the conditions of being well organized and having all necessary infrastructures, the services can be accessed suitably. The identified problem in this study is that cloud providers control and monitor the system or tools by ignoring the calculation and consideration of various faults made from the cloud provider side during service delivery. There are currently problems with ignoring the consumer or client during the monitoring and mentoring system for cloud services consumed at the customer or client level by SLA provisions. The new framework was developed to address the above-mentioned problems. The framework was developed as a unified modeling language. Eight basic components are used to develop the framework. For this research, the researcher developed a prototype by using a selected cloud tool to simulate and java programming language to write a code as well as MySQL to store data during SLA. The researcher used different criteria to validate the developed framework i.e. to validate SLA that is concerned with a cloud service provider, validate what happened when the request from the client-side is less than what is specified in SLA and above what is specified in SLA as well as implementing the monitoring mechanism using the developed Monitoring component. The researcher observed that with the 1st and 3rd criteria the service level agreement was violated and this indicated that if the Service level agreement is monitored or managed only by cloud service prover, there is a violation of LSA. Therefore, the researcher recommended that the service level agreement be managed by both cloud service providers and service consumers in the cloud computing environment.

• Journal of Astronomy and Space Sciences
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• 제35권1호
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• pp.19-30
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• 2018

The analysis of the high-resolution spectra of 31 Magellanic Clouds Cepheid variables enabled the identification of thorium lines. The abundances of thorium were found with spectrum synthesis method. The calculated thorium abundances exhibit correlations with the abundances of other chemical elements and atmospheric parameters of the program stars. These correlations are similar for both Clouds. The correlations of iron abundances of thorium, europium, neodymium, and yttrium relative to the pulsational periods are different in the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC), namely the correlations are negative for LMC and positive or close to zero for SMC. One of the possible explanations can be the higher activity of nucleosynthesis in SMC with respect to LMC in the recent several hundred million years.

• 한국환경과학회지
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• 제4권1호
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• pp.13-18
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• 1995

In order to examine the effect on the insolation of cloud cover, we analyzed the data of the insolation, cloud cover and surface air pressure in Pusan during the period of 1991. 10 - 1993.1. At first, we investigate the atmospheric transmissivity A(t) using the Beer's law at clear skies. The atmospheric transmissivity is characterized by cold season high and warn season low. From this atmospheric transmissivity, the empirical formula that shows the variation of the insolation due to the cloud cover is obtained. The result formula is I : l0 A(tn)·( 0.7-0.05×m ). 1 is the insolation that reaches the surface when cloud cover is m and to is solar constant. Although the result is some rough it seems meaningful that the estimation of insolation can be made only from the routine data.

• International Journal of Contents
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• 제10권1호
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• pp.62-67
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• 2014

Usually, cloud storage systems are developed based on DFS (Distributed File System) for scalability and reliability reasons. DFSs are designed to improve throughput than IO response time, and therefore, they are appropriate for batch processing jobs. Recently, cloud storage systems have been used for update intensive applications such as OLTP and so on. However, in DFSs, in-place update operations are not carefully considered. Therefore, when updates are frequent, I/O performance of DFSs are degraded significantly. DFSs with RAID techniques have been proposed to improve their performance and reliability. Their performance degradation caused by frequent update operations can be more significant. In this paper, we propose an in-place update method for DFS RAID exploiting a differential logging technique. The proposed method reduces the I/O costs, network traffic and XOR operation costs for RAID. We demonstrate the efficiency of our proposed in-place update method through various experiments.