• Journal of the Korea Society of Computer and Information
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• v.15 no.11
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• pp.11-20
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• 2010

XML view is proposed to integrate between XML data and heterogeneous data over distributed environment and global XML view is used to search distributed heterogeneous data. At this time, standard query language for user is XQuery and the method for processing global XQuery queries over distributed environment is one of the new research topics. One of the basic and simple methods to process distributed SQL queries is that generates local queries for processing a global query and constructs the result of the global query from the results of the local queries. However, the syntax of XQuery differs from SQL because the XQuery contains some special expressions like FOR clauses for querying to semi-structured data, of course, FOR clauses are not used in SQL. Therefore, there are some problems to adopt the method for processing global SQL queries for generating local XQuery queries. This paper defines some problems when generates local XQuery queries for processing global XQuery queries and proposes a method for generating local XQuery queries considered these problems. Also we implement and evaluate a Global XQuery Processor which uses our method.

• The Korean Journal of Applied Statistics
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• v.28 no.5
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• pp.1035-1046
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• 2015

Variance components models incorporate various random factors in the form of linear models. There are two experimental Layouts for the classification of factors under variance components models: nested classification and crossed classification. We consider two-way variance components models and investigate the effect of experimental Layout on the performance of model selection criteria AIC and BIC. The effect of experimental Layout is studied through a simulation study with various combinations of parameters in a systematic fashion. The simulation study shows differences in performance of model selection methods between the two classification. There is a particular tendency to prefer the smaller model than the true model when the variance component of a nested factor becomes relatively larger than a nesting factor that is persistent even when the sample size is not small.

• Journal of Internet Computing and Services
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• v.8 no.1
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• pp.133-142
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• 2007

Large database processing is one of the most important technique in the information society, Since most large database is regionally distributed, the distributed database processing has been brought into relief. Communications and data compressions are the basic technologies for large database processing. In order to maximize those technologies, the execution time for the task, the size of data, and communication time between processors should be considered. In this paper, the dataflow scheme and vertically layered allocation algorithm have been used to optimize the distributed large database processing. The basic concept of this method is rearrangement of processes considering the communication time between processors. The paper also introduces measurement model of the execution time, the size of output data, and the communication time in order to implement the proposed scheme.

• Smart Media Journal
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• v.8 no.4
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• pp.46-52
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• 2019

The size of data generated and collected at industrial sites or in public institutions is growing rapidly. The existing data processing server often handles the increasing data by increasing the performance by scaling up. However, in the big data era, when the speed of data generation is exploding, there is a limit to data processing with a conventional server. To overcome such limitations, a distributed cluster computing system has been introduced that distributes data in a scale-out manner. However, because distributed cluster computing systems distribute data, inefficient use of network bandwidth can degrade the performance of the cluster as a whole. In this paper, we propose a scheme that compresses data when transmitting data in a Hadoop cluster considering network bandwidth. The proposed scheme considers the network bandwidth and the characteristics of the compression algorithm and selects the optimal compression transmission scheme before transmission. Experimental results show that the proposed scheme reduces data transfer time and size.

• Journal of the Korea Society of Computer and Information
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• v.15 no.1
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• pp.71-81
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• 2010

In a typical web environment, it is difficult to determine the update and re-computation status of WebView content or the transition of WebView processing included in web page. If an update to one of data is performed before a read operation to that, we could get a wrong result due to the incorrect operation and increase a complexity of the problem to process. To solve this problem, lots of researchers have studied and most of these problems at the single user environment is not problems. However, the problems at a distributed environment might be occurred. For this reason, in this paper, we proposed the extended state transition graph and algorithms for each status of WebView for explaining WebView state in the distributed environment and analyze the performance of using the materialized WebView and not. Additionally, also analyze the timing issues in network and effectiveness which follows in size of WebView contents.

• Journal of the Korea Society of Computer and Information
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• v.14 no.1
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• pp.107-115
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• 2009

The cryptological key which is used in WiMAX environment is used at regular intervals by mobile nodes (laptop computer, PDA, cell-phone) which is in the range of base station coverage. But it is very weak at local attack like man-in-the-middle when the mobile node is off the range of base station or enters into the range to communicate with base station because the communication section is activated wirelessly. This paper proposes a distribution key building protocol which can reuse security key used by nodes to reduce cryptological security attack danger and communication overhead which occurs when mobile node tries to communicate with base station. The proposed distribution key establishing protocol can reduce overhead which occurs between base station and mobile node through key reusing which occurs during the communication process and also, makes security better than IEEE 802.16 standard by creating shared key which is required for inter-certification through the random number which node itself creates.

• Journal of the Korea Society of Computer and Information
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• v.25 no.8
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• pp.1-8
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• 2020

In this paper, we propose a gene family based RNA-seq read distribution method in means to accelerate the overal transcriptome assembly computation time. To measure the performance of our transcriptome sequence data distribution method, we evaluated the performance by testing four types of data sets of the Arabidopsis thaliana genome (Whole Unclassified Reads, Family-Classified Reads, Model-Classified Reads, and Randomly Classified Reads). As a result of de novo transcript assembly in distributed nodes using model classification data, the generated gene contigs matched 95% compared to the contig generated by WUR, and the execution time was reduced by 4.2 times compared to a single node environment using the same resources.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.799-802
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• 2003

컴퓨터 보급 증가와 인터넷 발전으로 다양한 종류와 다량의 디지털 데이터들이 제작, 유포되고 있다. 디지털 컨텐츠는 기존 아날로그 컨텐츠와 비교할 때 생성, 가공, 유통, 분배 등의 측면에서 많은 장점을 갖는 반면, 원본과 동일한 복사본을 쉽게 생성할 수 있는 특징 때문에 디지털 창작물에 대한 저작권 보호가 중요시 본다. 본 논문에서는 디지털 컨텐츠 보호 기술로 각광 받고 있는 DRM(Digital Rights Management)기술에서 컨텐츠 유통 시 개인키가 노출될 경우 비인가자에 의한 컨텐츠 불법접근이 가능해지는 취약성에 대한 개선책으로 PDMS (Publlic-Key Distributed Management System ： 개인키 분산관리 시스템)를 확장 적용하는 방안에 대하여 논한다.

• Journal of Advanced Navigation Technology
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• v.18 no.5
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• pp.468-475
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• 2014

The recommend system is getting more difficult real time recommend by lager preference data set, computing power and recommend algorithm. For this reason, recommend system is proceeding actively one's studies toward distribute processing method of large preference data set. This paper studied distribute processing method of large preference data set using hadoop distribute processing platform and mahout machine learning library. The recommend algorithm is used Co-occurrence Matrix similar to item Collaborative Filtering. The Co-occurrence Matrix can do distribute processing by many node of hadoop cluster, and it needs many computation scale but can reduce computation scale by distribute processing. This paper has simplified distribute processing of co-occurrence matrix by changes over from four stage to three stage. As a result, this paper can reduce mapreduce job and can generate recommend file. And it has a fast processing speed, and reduce map output data.

• Journal of the Korea Convergence Society
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• v.2 no.2
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• pp.35-45
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• 2011

Recently, with the increasement of the interest about global warming, pollutions, and so on, a number of distributed generations(DGs) such as photovoltaic(PV) and wind power(WP), are interconnected with distribution systems. However, installing of DGs makes power flow changes such as directions, one-direction to bi-direction, and increasing/decreasing of fault current. Therefore, it may cause the critical problems. This paper proposes an evaluation algorithm for bi-directional protection coordination and presents an evaluation system for protection coordination based on this algorithm. Additionally, the result shows that the existing method may cause critical problems, and also the effectiveness of proposed method is verified.