• Journal of KIISE:Computer Systems and Theory
• /
• v.29 no.1
• /
• pp.22-34
• /
• 2002

In this paper, we consider ring embeding problem in faulty (n,k) star graphs which is recently proposed as an alternative interconnection network topology, By effectively utilizing such strategies as series of dimension expansions and even distribution of faulty nodes into sub-stars in graph itself. we prove that it is possible to construct a maximal fault-free ring excluding only faulty nodes when the number of faults is no more than n-3 and $n-k{\geq}2$, and also propose an algorithm which can embed the corresponding ring in (n.k)-star graphs This results will be applied into the multicasting applications that the underlying cycle properties on the multi-computer system.

• The Journal of Korean Association of Computer Education
• /
• v.17 no.6
• /
• pp.115-122
• /
• 2014

One of the problems with current youth generations is increasing rate of violence and suicide in their school lives, and this study aims at the design of a sentiment analysis system to prevent suicide by uising big data process. The main issues of the design are economical implementation, easy and fast processing for the users, so, the open source Hadoop system with MapReduce algorithm is used on the HDFS(Hadoop Distributed File System) for the experimentation. This study uses word count method to do the sentiment analysis with informal data on some sns communications concerning a kinds of violent words, in terms of text mining to avoid some expensive and complex statistical analysis methods.

• Journal of the Korean Society for Railway
• /
• v.13 no.6
• /
• pp.570-576
• /
• 2010

This paper presents the use of the Petri Net Method for modeling railway tracks. The Petri Net is defined as having the characteristics of a parallel, asynchronous, distributed, inconclusive, statistical, etc. information handling system and is a graphical mathematical modeling tool to study the specifics of active movement. It's proven use can be seen at the Korean type Light Rail testing tracks where they modelled the Petri Net method using the train track encasing the segment, track, turnout, and platform as a singular factor and even though two trains either travelling in the same or opposite directions on a single test track equipped with a sidetrack can travel with the guarantee that the two will not collide.

• Convergence Security Journal
• /
• v.19 no.3
• /
• pp.21-28
• /
• 2019

As the number of websites managed by organizations or organizations increases, so does the number of web application servers and containers. In checking the status of the web service of the web application server and the container, it is very difficult for the person to check the status of the web service after accessing the physical server at the remote site through the terminal or using other accessible software It. Previous research on crawler-related research is hard to find any reference to the processing of data from crawling. Data loss occurs when the crawler accesses the database and stores the data. In this paper, we propose a method to store the inspection data according to crawl - based web application server management without losing data.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.5A
• /
• pp.561-570
• /
• 2008

Time synchronization is essential for a number of network applications such as high speed communication and parallel/distribution processing systems. As the era of ubiquitous computing is ushered in, the high precise time synchronization in wireless networks have been required in. This paper presents the design ana the implementation of the high precision time synchronization in wireless networks using ZigBee. To achieve high precision requirements, we have tried to analyze and reduce error factors such as the latency and jitters of a protocol stack on wireless environments. In addition, this paper includes some experiments and performance evaluations of our system. The result is that we established for nodes in a network to maintain their elects to within a 50 nanosecond offset from the reference clock.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.10a
• /
• pp.115-117
• /
• 2017

R has become a popular analytics platform as it provides powerful analytic functions as well as visualizations. However, it has a weakness in which scalability is limited. As an alternative, the RHadoop package facilitates distributed processing of R programs under the Hadoop platform. This paper investigates usefulness of the RHadoop package when analyzing healthcare big data that is widely open in the internet space. To do this, this paper has compared analytic performances of R and RHadoop using the medical treatment records of year 2015 provided by National Health Insurance Service. The result shows that RHadoop effectively enhances processing performance of healthcare big data compared with R.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.217-217
• /
• 2023

상수도관망은 사용자에게 고품질의 물을 안정적으로 공급하는 것을 목적으로 하며, 이를 평가하기 위한 지표 중 하나로 압력을 활용한다. 최근 스마트 센서의 설치가 확장됨에 따라 기계학습기법을 이용한 실시간 데이터 기반의 분석이 활발하다. 따라서 어디에서 데이터를 수집하느냐에 대한 센서 위치 결정이 중요하다. 본 연구는 eXtreme Gradient Boosting(XGBoost) 모델을 활용하여 대규모 상수도관망 내 센서 위치를 최적화하는 방법론을 제안한다. XGBoost 모델은 여러 의사결정 나무(decision tree)를 활용하는 앙상블(ensemble) 모델이며, 오차에 따른 가중치를 부여하여 성능을 향상시키는 부스팅(boosting) 방식을 이용한다. 이는 분산 및 병렬 처리가 가능해 메모리리소스를 최적으로 사용하고, 학습 속도가 빠르며 결측치에 대한 전처리 과정을 모델 내에 포함하고 있다는 장점이 있다. 모델 구현을 위한 독립 변수 결정을 위해 압력 데이터의 변동성 및 평균압력 값을 고려하여 상수도관망을 대표하는 중요 절점(critical node)를 선정한다. 중요 절점의 압력 값을 예측하는 XGBoost 모델을 구축하고 모델의 성능과 요인 중요도(feature importance) 값을 고려하여 센서의 최적 위치를 선정한다. 이러한 방법론을 기반으로 상수도관망의 특성에 따른 경향성을 파악하기 위해 다양한 형태(예를 들어, 망형, 가지형)와 구성 절점의 수를 변화시키며 결과를 분석한다. 본 연구에서 구축한 XGBoost 모델은 추가적인 전처리 과정을 최소화하며 대규모 관망에 간편하게 사용할 수 있어 추후 다양한 입출력 데이터의 조합을 통해 센서 위치 외에도 상수도관망에서의 성능 최적화에 활용할 수 있을 것으로 기대한다.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.110-115
• /
• 2010

Recently the deeply underground tunnels have been increased along the subway railroads of urban area compared to the past subway railroads. The Shin-Gum-Ho subway station (the Fifth lines, the depth : 46m) which is the third among the deep subway stations in the Korea was chosen as the model of deeply underground stations, and attempted to do simulation of fire. This station consists of three entrance, the basement first floor (B1), the basement second floor (B2), the basement eighth floor or platform (B8) and escalators and stairs from B2 to B8. The total number of grid was about 9,000,000 to make simulation of fire and smoke from the platform to entrance in this research, and the grid system was divided into 19 blocks to increase the efficiency of this simulation. The FDS (Fire Dynamics Simulation) was chosen to make the simulation of fire, and the model of turbulent flow was LES (Large Eddy Simulation). Each block is processed in a CPU using parallel processing of MPI (Message Passing Interface). The resource of CPU for this simulation is a ten of Intel 3.0 GHz Dual CPU (20 CPU).

• The Korean Journal of Applied Statistics
• /
• v.29 no.6
• /
• pp.1077-1094
• /
• 2016

Apache Spark is a fast and general-purpose cluster computing package. It provides a new abstraction named resilient distributed dataset, which is capable of support for fault tolerance while keeping data in memory. This type of abstraction results in a significant speedup compared to legacy large-scale data framework, MapReduce. In particular, Spark framework is suitable for iterative machine learning applications such as logistic regression and K-means clustering, and interactive data querying. Spark also supports high level libraries for various applications such as machine learning, streaming data processing, database querying and graph data mining thanks to its versatility. In this work, we introduce the concept and programming model of Spark as well as show some implementations of simple statistical computing applications. We also review the machine learning package MLlib, and the R language interface SparkR.

• Journal of Broadcast Engineering
• /
• v.2 no.1
• /
• pp.56-64
• /
• 1997

An HDTV frame has 4~6 times more pixels than a DTV frame. In order to encode the HDTV image in real time, parallel processing architectures have been widely used in many HDTV codec developments. That is, an HDTV Image is divided into several subbands and each subband is encoded in parallel using some DTV level encoders. In this paper, we adopt an HDTV codec architecture which divides an HDTV frame into 4 subbands and propose a new scene change detection algorithm using local variance. In addition, a new adaptive multichannel rate control scheme which allocate target bits adaptively to each subband of the HDTV image based on the activities of subband images is suggested in this paper. The activities of subband images are calculated at scene change detection part and reused at the adaptive rate control part. The simulation results show that the proposed scene change detection algorithm detects the scene change of HDTV video very accurately. Also the suggested adaptive multichannel rate control scheme shows better performance than the rate control method which allocates target bits equally to each subbands of the HDTV image.