• 한국대기환경학회지
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• 제13권1호
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• pp.51-63
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• 1997

Total suspended particulate matters in the ambient air were analyzed for eight chemical elements (Ca, Co, Cu, Fe, Mn, Pb, Si, and Zn) using an x-ray fluorescence spectrometry (XRF) at the Kyung Hee University - Suwon Campus during 1989 to 1994. To use these data as basis for source identification study, membership of each sample was selected to represent one of the well defined sample groups. The data sets consisting of 83 objects and 8 variables were initially separated into two groups, fine (d$_{p}$<3.3 ${\mu}{\textrm}{m}$) and coarse particle groups (d$_{p}$>3.3 ${\mu}{\textrm}{m}$). A hierarchical clustering method was examined to obtain possible member of homogeneous sample classes for each of the two groups by transforming raw data and by applying various distances. A disjoint principal component analysis was then used to define homogeneous sample classes after deleting outliers. Each of five homogeneous sample classes was determined for the fine and the coarse particle group, respectively. The data were properly classified via an application of logarithmic transformation and Euclidean distance concept. After determining homogeneous classes, correlation coefficients among eight chemical variables within all the homogeneous classes for calculated and meteorological variables (temperature. relative humidity, wind speed, wind direction, and precipitation) were examined as well to intensively interpret environmental factors influencing the characteristics of each class for each group. According to our analysis, we found that each class had its own distinct seasonal pattern that was affected most sensitively by wind direction.ion.

• 한국경영과학회지
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• 제38권4호
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• pp.11-33
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• 2013

We analyzed the structures and properties of the global financial market networks using social network analysis approach. The Minimum Spanning Tree (MST) lengths and networks of the global financial markets based on the correlation coefficients have been analyzed. Firstly, similar to the previous studies on the global stock indices using MST length, the diversification effects in the global multi-asset portfolio can disappear during the crisis as the correlations among the asset class and within the asset class increase due to the system risks. Second, through the network visualization, we found the clustering of the asset class in the global financial markets network, which confirms the possible diversification effect in the global multi-asset portfolio. Meanwhile, we found the changes in the structure of the network during the crisis. For the last one, in terms of the degree centrality, the stock indices were the most influential to other assets in the global financial markets network, while in terms of the betweenness centrality, Gold, Silver and AUD. In the practical perspective, we propose the methods such as MST length and network visualization to monitor the change of the correlation risk for the risk management of the multi-asset portfolio.

• 한국항행학회논문지
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• 제13권2호
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• pp.252-256
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• 2009

본 논문에서는 산재되어있는 비상등을 운용관리센터에서 항시 점검 및 관리할 수 있고, 데이터 병목현상에 구애받지 않는 안정된 데이터 통신이 가능한 클러스터 구조형 감시망을 이용하여 비상등감시장치를 설치함에 있어 비상등 위치에 구애받음 없이 비상등의 감시장치를 설치할 수 있고, 감시 통신망을 구축함에 있어 게이트웨이로 지정된 감시장치가 고장나더라도 사각지대 없이 비상등의 상태를 감시 및 관리가 가능한 비상등관리시스템을 제안한다.

• 대한기계학회논문집B
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• 제21권8호
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• pp.1024-1033
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• 1997

The past several years have witnessed an ever-increasing acceptance and adoption of parallel processing, both for high performance scientific computing as well as for more general purpose applications. Furthermore with increasing needs to perform the complex flow calculations in an efficient manner, the use of the message passing model on distributed networks has emerged as an important alternative to the expensive supercomputers. This work attempts to provide a generic framework to enable the parallelization of all CFD-related works using the master-slave model. This framework consists of (1) input geometry, (2) domain decomposition, (3) grid generation, (4) flow computations, (5) flow visualization, and (6) output display as the sequential components, but performs computations for (2) to (5) in parallel on the workstation clustering. The flow computations are parallized by having multiple copies of the flow-code to solve a PDE on different spatial regions on different processors, while their flow data are exchanged across the region boundaries, and the solution is time-stepped. The Parallel Virtual Machine (PVM) is used for distributed communication in this work.

• 한국분말재료학회지
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• 제1권1호
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• pp.42-51
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• 1994

6061Al-SiCP metal matrix composite materials(MMCs) were fabricated by injecting SiCP particles directly into the atomized spray. The main attraction of this technique is the rapid fabrication of semi-finished, composite products in a combined atomization, particulate injection(10 $\mu\textrm{m}$, 40 $\mu\textrm{m}$, SiCP) and deposition operation. Conclusions obtained are as follows; The microstructure of the unreinforced spray formed 6061Al alloy consisted of relatively fine(50 $\mu\textrm{m}$) equiaxed grains. By comparision, the microstructure of the I/M materials was segregated and consisted of relatively coarse(150 $\mu\textrm{m}$) grains. The probability of clustering of SiCP particles in co-sprayed metal matrix composites increased it ceramic particle size(SiCP) was reduced and the volume fraction was held constant. Analysis of overspray powders collected from the spray atomization and deposition experiments indicated that morphology of powders were nearly spherical and degree of powders sphercity was deviated due to composite with SiCp particles. Interfacial bonding between matrix and ceramics was improved by heat treatment and addition of alloying elements(Mg). Maximum hardness values [Hv: 165 kg/mm2 for Al-10 $\mu\textrm{m}$ SiCp Hv--159 kg/mm2 for Al-40 $\mu\textrm{m}$SiCp] were obtained through the solution heat treatment at $530^{\circ}C$ for 2 hrs and aging at $178^{\circ}C$, and there by the resistance were improved.

• 한국수산과학회지
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• 제43권5호
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• pp.521-531
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• 2010

This study examined the community structure and temporal variation of the macro-crustaceans on Jangbong tidal flat, Incheon, Korea. Macro-crustaceans on this tidal flat were collected using a modified otter trawl from November 1999 to January 2001. The macro-crustaceans comprised 32 species, 7,741 individuals, and 29,211.3 gWWt during the study period. The Jangbong tidal flat was dominated numerically by three shrimp (Palaemon carinicauda, Crangon affinis, and Metapenaeus joyneri) and two portunid crabs (Charybdis japonica and Portunus trituberculatus). The macro-crustacean assemblages were divided into two different season and species groups based on the q-mode and r-mode clustering methods. In terms of q-mode, they consisted of a winter species group from December through April and a summer species group from May through November. The r-mode analysis showed that the species group visiting the tidal flat in winter was dominated numerically by palaemonid and crangonid shrimps, while a species group characterized by an abundance of portunid crabs and penaeid shrimps was more frequent in spring, summer, and autumn. In conclusion, our study revealed distinct temporal variation in the tidal flat use by macro-crustaceans around Jangbong Island, Incheon, Korea.

• Journal of Information Technology Applications and Management
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• 제26권3호
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• pp.43-59
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• 2019

The goal of this paper is to investigate changes in North Korea's domestic and foreign policies through automated text analysis over North Korean new year addresses, one of most important and authoritative document publicly announced by North Korean government. Based on that data, we then analyze the status of text mining research, using a text mining technique to find the topics, methods, and trends of text mining research. We also investigate the characteristics and method of analysis of the text mining techniques, confirmed by analysis of the data. We propose a procedure to find meaningful tendencies based on a combination of text mining, cluster analysis, and co-occurrence networks. To demonstrate applicability and effectiveness of the proposed procedure, we analyzed the inaugural addresses of Kim Jung Un of the North Korea from 2017 to 2019. The main results of this study show that trends in the North Korean national policy agenda can be discovered based on clustering and visualization algorithms. We found that uncovered semantic structures of North Korean new year addresses closely follow major changes in North Korean government's positions toward their own people as well as outside audience such as USA and South Korea.

• 정보학연구
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• 제1권1호
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• pp.13-26
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• 1998

대부분의 정보검색시스템들은 부적절한 색인어들에 의해 가끔 사용자의 의도에 맞지 않는 전혀 다른 검색 결과가 나타난다. 그것은 시스템이 색인어들을 검색하기 위해 그 의미가 아닌, 단지 용어로서만 고려하기 때문이다. 검색 정확도의 증진을 위해 색인어는 연관된 용어 사용 빈도와 역 빈도 사용으로 검색되고 동시 발생어는 원시 문서로부터 추출된다. 결과적으로 색인어는 계산된 상호 정보들을 사용함으로써 그들의 세맨틱에 의해 클러스팅된다. 이 논문은 재현율의 감소없이 클라이언트 사용자 모듈로부터 피드백에 따라 세분된 세맨틱 정보를 사용하여 부적절한 검색 결과를 거절함으로써 검색 효율을 높일 수 있도록 설계하였다.

• 한국산업융합학회 논문집
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• 제23권4_2호
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• pp.683-691
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• 2020

In the era of super-aged societies, research and development (R&D) projects related to aging are very important agenda for establishing the direction of future R&D planning and technological competitiveness in the country. In order to respond promptly to this agenda, it is essential to establish a national-level convergence R&D policy. In this study, we utilized the global R&D funding project data from major nations (US, Europe, Japan), and then standardized them with the same fields. To analyze the current status of global R&D related to aging, we performed cluster analysis based on the co-occurrence matrix to explore convergence R&D areas in the US, Europe, and Japan related to aging. In addition, comparative analysis by country suggested that different points on the interdisciplinary area and the convergence of aging-related R&D by each country. These results provide fundamental understandings for the status of convergence in aging-related global R&D, the current technology trends, and establish the direction and strategy of R&D policy.

• 한국직업건강간호학회지
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• 제28권4호
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• pp.221-229
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• 2019

Purpose: The aim of this study was to identify core keywords and topic groups of workplace bullying researches in the past 10 years for better understanding research trend. Methods: The study was conducted in four steps: 1) collecting abstracts, 2) extracting and cleaning semantic morphemes, 3) building co-occurrence matrix and 4) analyzing network features and clustering topic groups. Results: 437 articles between 2010 and 2019 were retrieved from 5 databases (RISS, NDSL, Google scholar, DBPIA and Kyobo Scholar). Forty-one abstracts from these articles were extracted, and network analysis was conducted using semantic network module. The most important core keywords were 'turnover', 'intention', 'factor', 'program' and 'nursing'. Four topic groups were identified from Korean databases. Major topics were 'turnover' and 'organization culture'. Conclusion: After reviewing previous research, it has been found that turnover intention has been emphasized. Further research focused on various intervention is needed to relieve workplace bullying in nursing field.