한국의 중산간지역 구분에 관한 연구

張宇煥,崔奎燮 韓國農業政策學會 1998 농업경영정책연구 Vol.25 No.2

청피홍심무 현탁배양에서 세포생장과 색소생산에 미치는 요인

최규환,채영암 서울大學校 農業生命科學大學 農業開發硏究所 1996 서울대농학연구지 Vol.21 No.1

공간 영역 질의의 선택률 추정을 위한 향상된 면적 균등 분할 방법

황환규,문현수 강원대학교 정보통신연구소 2000 정보통신논문지 Vol.4 No.-

Selectivity estimation of queries in relational databases has been studied extensively. Although relational selectivity estimation problems are well studied in the database literature, spatial selectivity estimation problems are not well understood. In this paper we examine selectivity estimation in spatial databases. In particular, we focus on spatial range queries over two-dimensional rectangular data. We propose and implement an improved equi-area partition for selectivity estimation of spatial range queries. We present a detailed experimental study comparing the proposed techniques and the currently used equi-area and nonequi-area partition for selectivity estimation.

새로운 데이타베이스 응용을 위한 대형 데이타 관리 기법에 관한 고찰

황환규,김상욱 강원대학교 정보통신연구소 1997 정보통신논문지 Vol.1 No.-

Previous DBMSs have been built based on the simple assumption that a date item can reside on a disk page since traditional database applications such as bank service systems, business automation systems, and office automation systems have dealt with only small data items. However, with the advent of new advanced multimedia applications frequently dealing with large data items, this assumption is no longer acceptable. For supporting such new applications, DBMSs have to provide the additional facilities for managing large data items whose size are larger than that of a page. Recently, some researches have been performed aiming at this issue through developing advanced DBMSs and storage systems. In this paper, we discuss recent research results on large data management. We first present design considerations for large data management techniques. Next, we introduce the five techniques employed in commercial DBMSs and advanced storage systems such as WiSS, Exodus, Starburst, and EOS, and then compare those techniques focusing on (1) data structures, (2) algorithms, and (3) advantages and disadvantages. We also introduce domestic research activities, and finally suggest future research directions related to this issue.

CSPAM: 닫힌 빈발 시퀀스 패턴을 위한 효과적인 가지치기 전략

황환규 강원대학교 정보통신연구소 2009 정보통신논문지 Vol.13 No.-

Sequential pattern mining finds all of the frequent sequences satisfying a minimum support threshold in a large database. However, when mining long frequent sequences, or when using very low support thresholds, the performance of currently reported algorithms often degrades dramatically. In this paper we present a novel algorithm, CSPAM (Closed Sequential PAttern Mining), using only closed frequent sequences which are small subset of very large frequent sequences. When systematically exploring the search space of closed frequent sequences, we present two novel pruning strategies, which prune the unpromising parts of search space effectively. The experimental results show that the proposed method outperforms the previous algorithms.

로케트 工學에 관한 硏究 : 第1報 : 亞音速 亂流流動에서 飛行翼模型의 剝離現象 Ⅰst Report : Separation of Airfoils in Subsonic Turbulent Flow

朴煥奎,金鍾一,金鎭興,李茂錫,朴吉文,鄭洛奎,李行男,李東起 조선대학교 동력자원연구소 1984 動力資源硏究所誌 Vol.6 No.2

Separation, pressure and velocity distributions were studied fully developed two dimensinonal, incompressible flow over a flat airfoil in subsonic wind tunnel. Velocity and turbulence were measured with a two channel constant temperature hot wire anemometer and pressure with a pitot tube and pressure tranducer system. The experimental results were obtained as follow: (1) Turbulent intensity of shear layer just outside the separation point is considered to affect the size of separation bubble. (2) Static pressure coefficient is separated into three regions according to its value change. (3) Separation point is varied with the change of attack angle. (4) Velocity distributions and boundary layers normal to airfoil surface are changed as variation of attack angle of airfoil.

텔레비젼이 어린이의 價値觀 形成에 미치는 影響硏究

朴正圭,全煥盛 청주대학교 사회과학연구소 1984 한국사회과학연구 Vol.2 No.-

Ⅰ. The Purpose of the Study The purpose of this study is to search for the relationships betwen children's television viewing behaviors and their value orientations by controlling the socio-demographics and social-psychological factors as inter-mediating variables. As is well known, almost all of the studies of television impact on children have focused on antisocial behavioral effects through examining only the relationship between TV and children's behaviors without considering the third variable on which relationships between the two former variables are dependent. These kinds of approaches have been criticized in terms of studying the child as an individual system rather than within a system. More recently, some researchers suggest that environment-related and psychological variables must be considered in the studies on the relationships between TV and children. With these problems in mind, the following research questions were examined in this study: 1. What are the relationships between children's television viewing behaviors (such as TV viewing hours, types of favorite programs, channel selector, contingent behaviors while TV viewing, etc.) and their social-psychological factors such as affinity, perceived reality of TV contents, children's perception of their parents' authority and generosity, etc. with their demographics? 2. What are the relationships between children's value orientations and their' television viewing behaviors? 3. What are the similarities or differences between children's value orientations and those depicted in children's favorite TV programs? Ⅱ. Research Method For this research, we used a social survey research method with self-administered questionnaires. Total sample of 1020 children from the 4th to 6th grades were selected nationally on a cluster-randomsampling basis from one of the large-sized cities (Seoul), one of the middle sized cities (Cheong-ju) and three rural areas. While each area was selected on a purposive sampling basis, Sample Schools and classes were selected on a multi-stage stratified random-sampling method. Questionnaires were distributed, filled in and collected together afterwards in each sample class. For final analysis, 90.5% of the samples (N=923) turned out to be valid. For the statistical analysis, complex Chi-square, production moment correlation and multiple regression analysis methods were used according to the statistical purposes. Ⅲ. Summary of Significant Research Findings A. Children's TV Viewing Behaviors: 1. In relation to children's week day TV viewing hours, only the age (grade) variable turned out to be significant. The results show that there are more heavy viewers among 5th grade (12 year old) children than 4th or 6th grade. 2. But for the weekend TV viewing hours, children who are in the categories of large-sized city, small-sized family and 5th grade tend to be heavier viewers than the other categories of children. 3. In regressing TV viewing hours with nine independent variables-degree of necessity of TV perceived by children, TV affinity, perceived reality of TV contents, frequency of communication with their father, types of parents, parents attitudes toward children's TV viewing, usefulness of TV for children's study, parents' generosity, and children's study hours-- the total explanatory power of independent variables was only 2.8% of total variances. So it can be assumed that these nine independent variables do not contribute much to determine children's television viewing hours. But multiple regression analysis shows the ranks of contribution among independent variables to the dependent variable. 4. It was found that 76.5% of the respondents were engaged in some other activities (contingent behaviors) such as working, doing homework, playing, reading comics or newspapers, eating and communicating with family while viewing television. These results suggest that most of the children do not watch TV attentively always. 5. The results show that 33.8% of the respondents are viewing TV alone but 66.2% of the respondents are viewing TV with some of their family members. While children in Seoul and male children tend to watch alone, rural children tend to watch with their brothers or sisters, and female children tend to watch with their mother. 6. When there are some conflicts in channel selecting, the power of channel control are in the order of father, child-himself, elder brothers and younger brothers. These results mean that there is a kind of ranking order to control the TV channel in each family. 7. Even when the child himself does not control the channel, 65% of the repondents continue to watch TV programs that they want to watch in the following ways: they endure watching the program even though they want to watch other programs, or go to some other place watch what they want to, or cry for watching what they want to. 8. It was found that 15.2% of the respondents perceived the types of their panental guidance to their TV viewing as lassez-faire, 37.7% as conditioned lassez-faire, 40.7% as controlled and 6.4% as prohibitive. In the case of the conditioned-lassez-faire type, children can watch TV freely as long as they do their homework, but under the controlled type parents, programs or hours which children can watch are restricted or indicated. The types of parental guidances to children's TV viewing have a certain impact on children't viewing behaviors. The results show that children under lassez-faire type tend to be heavier viewers. 9. Children often discuss about what they have watched on TV with their friends and these tendencies are higher among rural children than among children in Seoul. 10. In regard to program preferences, children usually like programs for children especially television cartoons. But the degree of preference for adult programs are increasing in the case of the large city and in older children. Over all results show that children's TV viewing is largely dependent on preferences for TV cartoons. 11. The major reasons to watch television indicated by children are in the order of entertainment, learning, and information. 12. According to the multiple regression analysis, affinity and respectively, reality of television can be explained at the level of only 3.3% and 4.8% by nine independent variables each. The equations of regresion are as follows: Y (TV affinity) = 1.11 + 0.95×1 (reality) + 0.36×2 (parents' attitude to children's TV viewing) + 0.21×3 (TV viewing hours) = 0.33×4 (frequency of communication with father) + 0.39×5 (usefulness for studying) + 0.51×6 (type of parents) + 0.16×7 (generosity of parents) - 0.16×8 (study hours) - 0.93×9 (necessity of TV) + E and Y (TV reality) = 0.73 + 0.90×1. (necessity of TV) + 0.92×2 (affinity) + 0.19×3 (TV viewing hours) + 0.22×4 (type of parents) - 0.25×5 (study hours) + 0.26×6 (generosity of parents) + 0.12×7 (frequency of communication with father) + 0.91×8 (usefulness for studying) + 0.54×9 (parents' attitude to children's TV viewing) + E. 13. It was found that children themselves perceived the psychological effects of identification, arousal, and retention to be higher than those of behavioral effects of imitation or modeling. 14. Pearson product-moment correlation analysis suggests .that there were positive correlations between necessity of TV/usefulness for studying (r=0.42, p<0.0001), weekday TV viewing/weekend TV viewing (r=0.34, p<0.001), TV reality/necessity of TV (r=0.17, p< 0.001), parents, generosity/frequency of communication with father (r=0.16, p<0.001) weekend TV viewing/necessity of TV (r=0.14, p<0.001), TV reality/affinity (r=0.12, p<0.001), and negative correlations between type of parents/generosity (r= -0.12, p<0.001), type of parents/necessity of TV (r=-0.006, p<0.05), and frequency of communication with father/TV affinity (r=-0.06, p<0.05). B. Children's Life-Style and Value Orientations 1. The research shows what children in Korea study about 2 hours and 18 minutes a day on the average, and girls and children living in cities study harder than boys and children living in the rural areas. 2. Children's major consultants when they have difficult problems are according to the following order: older brothers and sisters, their friends, and their fathers. The selection of consultant is related to the TV viewing hours; on weekdays, heavy viewers tend to consult their older brothers and sisters and light viewers ask their mother's advice, while on the weekend, heavy viewers tend to consult their mother but light viewing children tend to select their fathers as their consultant. These differences in viewing hours reflect the differences in life style. Therefore, it is understood that the family life pattern has an important impact on children's TV viewing behaviors. 3. The most favored jobs that children want to have in the future are … in order of preference … school teachers, scientists, athletes, and medical doctors. These prefered future jobs are closely related to weekend TV viewing. According to the research, while the heavy viewers mostly want to be scientists in the future, the light viewers prefer to be school teachers. This suggests that TV viewing has some impact on children's orientations toward occupation. Those orientations are also influenced by such variables as family structures, resident conditions and sex. Considered from this point of view, future studies on the relationships between children's value and TV viewing have to be made in the direction of measuring the degree of contribution that TV makes to the children. 4. The research also shows the fact that children's most admired personal model figures are their parents, and the image of their parents as objects of respect is high in the rural area and low in the urban area. And more children,living in big cities tend to select their respectable model figures from politicians and scientists, compared with those in the rural area. 5. Considered in terms of the amount of TV viewing, light viewers tend to place their highest values on the family and individual factors such as life, health and happiness. However, heavy viewers are inclined to think more of universal and social value such as freedom than light viewers do. Also the heavy viewers. tend to place their highest value on love, filial piety, patriotism and friendship in order to get along with others in the world. From the overall research results, we can come to the conclusion that children's value orientations are not made only by TV but are more influenced by fundamental social agents such as home and school.

액체 크로마토크래피에서 벤젠 유도체류의 분리 최적화

김인환,김창만,황규탁,김상태 대구대학교 기초과학연구소 1997 基礎科學硏究 Vol.14 No.1

The iterative regression optimization method using two parameters is applied to the separation of benzene derivatives in liquid chromatography. Also, the effect of separation selectivity with elution strength in liquid chromatography was investigated. The parameters examined are the concentration of methanol and acetonitrile. It was obtained an efficient optimization using a small number of initial experiments. The optimum solvent, which gives complete separation of benzene derivatives, was determined as follows MeOH : ACN : H₂O = 49:14 : 37

상간이동촉매 존재하의 여러 유기용매에서 Phenethyl Bromide와 칼륨염들과의 치환반응에 관한 연구

황규탁,김인환,김정성,임태훈 대구대학교 기초과학연구소 1996 基礎科學硏究 Vol.13 No.-

The catalytic effects and the degree of substitution for the reactions of phenethyl bromide with potassium salts in a solid-liquid two-phase system under phase transfer catalysts were investigated in aprotic nonpolar solvent (toluene) and in aprotic polar sovent (DMF) at 35 캜 Tetrabutylanmionium bromide(TBAB), tetrapropylammonium bromide(TPAB), 18-crown-6-ether-(CR), dicyclohexyl-18-crown -6-ether-(DCHC) were used as phase transfer catalyst. In these reactions, the degree of substitution were increased in a aprotic polar solvent than in aprotic nonpolar solvent. TBAB, DCHC showed more excellent catalytic effects than that of TPAB, CR. These results was considered to be attributed to the hydrophobic interaction of the catalysts with in organic layer. From all of the observed results, the strength of nucleophilicity showed the following trend: Cl-KOS > SCN- > CH3COO- > C6HsC0oo

B+트리를 위한 벌크로드

황환규,김상욱 江原大學校 産業技術硏究所 1995 産業技術硏究 Vol.15 No.-

In this paper, we propose a bulk-load algorithm for B' -trees, the most widely used index structures in database systems. The main characteristic of our algorithm is to simultaneously process all the keys to be placed on each B' -tree page when accessing the page. This avoids the overhead for accessing the same page multiple times, which results from applying the B' -tree insertion algorithm repeatedly. For performance evaluation, we analyze our algorithm in terms of the number of disk accesses. The results show that the number of disk accesses excluding those in the redistribution process in identical to the number of B' -tree pages. Considering that the redistribution process is an unavoidable preprocessing step for bulk-loading, our algorithm requires just one disk access per B' -tree page, and therefore turns out to be optimal. We also present performance tendancy according to the changes of parameter values via simulation.