• Journal of applied mathematics & informatics
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• 제38권3_4호
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• pp.201-209
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• 2020

We introduce and study some basic properties of rough I-convergent of triple sequence spaces and also study the set of all rough I-limits of a triple sequence spaces.

• 한국항공우주학회지
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• 제30권6호
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• pp.21-30
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• 2002

본 연구에서는 영역분할기법에 의하여 예조건화 Navier-Stokes 방정식을 병렬화 하였으며, 병렬화 된 코드의 정확도는 순차 코드의 결과 및 실험 데이터와의 비교를 통하여 확인하였다. 코드의 병렬효율은 Myrinet을 기반의 PC 클러스터와 Fast-Ethernet PC 클러스터에서 살펴보았다. 주된 성능 지표로는 프로세서 수와 네트웍 통신 구성에 따른 속도 향상 비를 살펴보았다. 이 시험에서 Myrinet 환경의 PC 클러스터는 기대한 바와 같이 Fast-Ethernet에 비하여 우수한 성능을 보여 주었다. 문제의 크기에 대한 의존도 시험에서 네트웍 통신 속도는 병렬처리 성능에 중요한 요소이며, Myrinet 기반의 PC 클러스터가 고성능 병렬처리 시스템의 한 가지 대안임을 보여 주었다.

• 한국분말재료학회지
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• 제15권5호
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• pp.371-377
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• 2008

This paper deals with the phase analysis of $MgB_2$ bulk using spark plasma sintering process after ball milling. Mg and amorphous B powders were used as raw materials, and milled by planetary-mill for 9 hours at argon atmosphere. In order to confirm formation of $MgB_2$ phase, DTA and XRD were used. The milled powders were fabricated to $MgB_2$ bulk at the various temperatures by Spark Plasma Sintering. The fabricated $MgB_2$ bulk was evaluated with XRD, EDS, FE-SEM and PPMS. In the DTA result, reaction on formation of $MgB_2$ phase started at $340^{\circ}C$. This means that ball milling process improves reactivity on formation of $MgB_2$ phase. The $MgB_2$ MgO and FeB phases were characterized from XRD result. MgO and FeB were undesirable phases which affect formation of $MgB_2$ phase, and it's distribution could be confirmed from EDS mapping result. Spark Plasma Sintered sample for 5 min at $700^{\circ}C$ was relatively densified and it's density and transition temperature showing super conducting property were $1.87\;g/cm^3$ and 21K.

• 한국환경과학회지
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• 제15권12호
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• pp.1125-1139
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• 2006

The cluster analysis of diurnal precipitation patterns is performed by using daily precipitation of 59 stations in South Korea from 1973 to 1996 in four seasons of each year. Four seasons are shifted forward by 15 days compared to the general ones. Number of clusters are 15 in winter, 16 in spring and autumn, and 26 in summer, respectively. One of the classes is the totally dry day in each season, indicating that precipitation is never observed at any station. This is treated separately in this study. Distribution of the days among the clusters is rather uneven with rather low area-mean precipitation occurring most frequently. These 4 (seasons)$\times$2 (wet and dry days) classes represent more than the half (59 %) of all days of the year. On the other hand, even the smallest seasonal clusters show at least $5\sim9$ members in the 24 years (1973-1996) period of classification. The cluster analysis is directly performed for the major $5\sim8$ non-correlated coefficients of the diurnal precipitation patterns obtained by factor analysis In order to consider the spatial correlation. More specifically, hierarchical clustering based on Euclidean distance and Ward's method of agglomeration is applied. The relative variance explained by the clustering is as high as average (63%) with better capability in spring (66%) and winter (69 %), but lower than average in autumn (60%) and summer (59%). Through applying weighted relative variances, i.e. dividing the squared deviations by the cluster averages, we obtain even better values, i.e 78 % in average, compared to the same index without clustering. This means that the highest variance remains in the clusters with more precipitation. Besides all statistics necessary for the validation of the final classification, 4 cluster centers are mapped for each season to illustrate the range of typical extremities, paired according to their area mean precipitation or negative pattern correlation. Possible alternatives of the performed classification and reasons for their rejection are also discussed with inclusion of a wide spectrum of recommended applications.

• 천문학회보
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• 제36권2호
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• pp.121-121
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• 2011

Thanks to KMTNet's wide field of view, it is time to implement imaging survey of extensive area of clusters of galaxies in the southern sky with modern instrument. As part of potential long-term survey of nearby (D < 50 Mpc) well-known clusters of galaxies, we propose a wide-field and deep survey of Fornax cluster as a first step of the project. By imaging the 400 square deg region (100 fields) enclosed within the five times virial radius of the Fornax cluster, in three SDSSfilters(g', r', i'), we can provide an unprecedented view of structure of Fornax cluster using sample from giant to dwarf galaxies. We will secure galaxies with brightness comparable to the limiting magnitude (r'=23.1 AB mag) of SDSS. Furthermore, we also request extremely deep (limiting surface brightness of ~ 28 mag $arcsec^{-2}$forr'band) survey for the central region (16 square degree, i.e., four fields) of Fornax cluster. This will allow us to detect the diffuse intracluster light (ICL) that permeates clusters as a valuable tool for studying the hierarchical nature of cluster assembly. In order to complete whole survey, about 285 hr observing time (without overhead) is required. By combining data available at other wavelengths, it will offer unique constraints on the formation of large-scale structure and also provide important clues for theories of galaxy formation and evolution. Our proposed survey will be implemented in the close collaboration with researchers in various countries (Germany, Australia, UK, USA) and ongoing project (e.g., SkyMapper).

• 한국의류학회지
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• 제17권2호
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• pp.281-289
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• 1993

Concept of the comfort and fitness becomes a major concern in the basic function of the ready-made clothes. Accordingly a more sophiscated classification of the human morphological characteristics is strongly required for the effective clothing construction. This research was performed to classify and characterize Korean adult males anthropometrically. Sample size was 1290 subjects and their age range was from 19 to 54 years old. Sampling was carried out by the stratified sampling method. Data were collected by the direct anthropometric measurement. 75 variables in total were applied to classify the bodytypes. Data were analyzed by the multivariate method, especially factor and cluster analysis. The high factor loading items extracted by factor analysis were based to determine the variables of the cluster analysis for the similar bodytypes respectively. In the part of the trunk, 19 variables from the data were applied to classify the bodytypes of trunk by Ward's minimum variance method. The groups forming a cluster were subdivided into 5 sets by cross-tabulation extracted by the hierarchical culster analysis. Type 3 and 4 in trunk were composed of the majority of 55.6% of the subjects. The Korean adult males had relatively well-balanced bodytypes in trunk.

• 한국IT서비스학회지
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• 제16권1호
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• pp.119-138
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• 2017

Mobile easy payment is a term for using mobile devices to facilitate financial transactions. Mobile easy payment is a quickly emerging practice, supported by the dramatic increase of mobile phone or device users around the world. The purpose of this study is to classify user's group of the mobile easy payment service by their lifestyle based on I-VALS type and to investigate differences in usage behavior among the user groups. For empirical study, a questionnaire survey was carried out with users of mobile easy payment services using the Internet from June 7 to 10 in 2016. We conducted factor analysis for I-VALS, usage factors, satisfaction factors. We also performed cluster analysis for group classification, and analysis of variance, cross analysis to compare the different usage behavior among the user groups. In analysis results, first three cluster appeared including "ICT task-oriented group", ICT positive and socialities oriented group", "ICT leader-oriented group". Second, it was found significant differences among the clusters about factor of "easy of use", "securities", "universality", "satisfaction". Third, we showed that there were significant differences in time first used the service. Based on these findings, we provide practical implications. Results of our study can be expected to provide the basis of differentiated marketing strategy of mobile easy payment services.

• Membrane and Water Treatment
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• 제13권5호
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• pp.245-257
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• 2022

Water quality characteristics and their spatial variations in the Nakdong River were statistically analyzed by multivariate techniques including correlation analysis, CA, and FA/PCA based on water quality parameters for 17 sites over 2017-2019, yielding PI values for primary factors. Site 10 indicated the highest parameter concentrations, and results of pearson's correlation analysis suggest that non-biodegradable organic matter had been distributed on the site. Five clusters were identified in order of descending pollution levels: I (Ib > Ia) > II (IIa > IIb) > III. Spatial variations started from sub-cluster Ib in which Daegu city and Geumho-river are joined. T-P, PO4-P, SS, COD, and TOC corresponded to VF 1 and 2, which were found to be principal components with strong influence on water quality. Sub-cluster Ib was strongly influenced by NO3-N and T-N compared to other clusters. According to the PIs, water quality pollution deteriorated due to non-biodegradable organic matter, nitrogen- and phosphorus-based nutrient salts in the middle and lower reaches, illustrating worsening water pollution due to inflows of anthropogenic sources on the Geumho-river, i.e., sewage and wastewater, discharged from Site 10, at which there is a concentration of urban, agricultural, and industrial areas.

• 한국의류산업학회지
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• 제14권4호
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• pp.669-676
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• 2012

This study aims to compare the properties of natural dye stuffs, such as color, dyeability, fastness, and marketability, to analyze the differences noted by expert groups regarding the properties of the stuffs, and to make a positioning of the stuffs. A survey of experts in academia, business, and the art of natural dyeing was conducted, with an evaluation of 23 types of the stuff's properties. There is a correlation between the properties of the stuffs, and evaluating dye stuffs differs according to the group to which it belongs. X-axis relates to color and Y-axis refers to fastness in the positioning of the stuff. There are different relationships between properties according to their group. Color is significantly associated with marketability in art experts however, fastness is closely connected with marketability in business. The stuffs can be divided into five clusters. Cluster I includes indigo and persimmon, and is marked by excellent color, dyeability, fastness, and marketability, Cluster II contains safflower and sappan wood, which are excellent colors, yet suffer from low marketability on account of their medium to low fastness. Cluster III includes red, purple, and brown dyes, and onion and rhubarb, and has medium properties. Cluster IV is mugwort and yellow dyes, except onion and rhubarb, and features low properties. Cluster V is loess, featuring medium color and low fastness.

• 대한환경공학회지
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• 제27권3호
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• pp.316-322
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• 2005

폐기물 소각시설 주변토양 중 다이옥신 농도를 분석하여 소각시설로부터 거리와 방향에 따른 농도변화를 고찰하고, 시료에 대한 군집분석을 수행하여 발생원이 수용체에 미치는 영향에 대해 검토 하였다. 토양 중 다이옥신 총 농도 및 I-TEQ 농도는 각각 $31.065{\sim}7,257.499\;pg/g\;d.w.$과 $0.099{\sim}35.191\;pg\;I-TEQ/g\;d.w.$로 나타났다. 조사대상 소각시설 이외의 주변에 소형 소각시설들이 산재해 있어 토양 중 다이옥신 농도와 풍향 및 거리와의 상관성은 약한 것으로 나타났다. 반면 소각시설 배출가스의 영향을 파악하기 위하여 PCDFs와 PCDDs의 비율을 조사한 결과, 소각시설에서 멀어질수록 배출가스에서 높은 비율로 검출되는 PCDFs의 비율이 감소하는 경향을 보였다. 조사대상 소각시설이 주변 토양 중 다이옥신 농도에 미치는 영향권은 500 m 이내인 것으로 판단되었고 먼거리에서 고농도가 검출된 것은 주변에 존재하고 있는 소형 소각시설이나 농약(PCP) 등 다른 오염원에 의한 복합적인 영향을 동시에 받고 있는 것으로 사료되었다. 다이옥신 발생원과 수용체인 토양의 이성체 패턴을 이용한 군집분석 결과, 4개의 그룹으로 나눌 수 있었으며, 각 그룹의 이성체 패턴 비교를 통해 소각시설 배출가스와 농약 등의 발생원이 수용체에 미치는 영향정도에 대해 정성적인 추정이 가능하게 되어 군집 분석이 통계적 수법의 하나로 이용될 수 있을 것으로 사료되었다.