• The Transactions of the Korean Institute of Electrical Engineers
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• 제36권3호
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• pp.171-178
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• 1987

A study of two phase chopper system with four separate groups of DC motors in powering. A novel two phase chopper system with four separate groups of DC motors which applies the principles of two phase chopper with two separate groups of DC motors is dealt with this article. The main circuit consists of eight sets of chopping parts, four diodes and four separate groups of DC motors. Four groups of DC motors are driven through the series and parallel connections to each other in accordance with the operating conditions of the choppers. Although the proposed chopper circuit requires more circuit elements than the conventional two phase chopper system with combined output or two phase chopper system with two separate groups of DC motors, it has the following advantages` (1). It is possible to drive twice as much motors as conventional system does, using esisting receiving-and equipments and motors. (2). It is possible to control load voltage continuously from 0 to source voltage by changing time-ratio from 0 to 1. (3). Load current division becomes equalized. Therefore it is possible to drive not only series motors but also shunt and separately exited motors. (4). When smoothing reactor L is small, harmonic components of the proposed circuit is not so large. Therefore, the value of L can be determined from viewpoints of allowable value of ripple-ratio and current unbalance factor.

• International Journal of Reliability and Applications
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• 제3권3호
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• pp.125-132
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• 2002

Sometimes we have two groups of inbred lines and there are only interest in gca comparisons within two groups of lines of sizes$\P_1$ and $\P_@$, not between two groups. For example, suppose there two Lab, each of the 2 Labs have obtained the best line. For this purpose we now give a method of constructing block designs for diallel cross experiments and we will explain how to calculate efficiency. Then we show the efficiencies in the table.

• Journal of the Korean Mathematical Society
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• 제56권3호
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• pp.739-750
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• 2019

We proved that finite p-groups in the title coincide with finite p-groups all of whose non-abelian subgroups are generated by two elements. Based on the result, finite p-groups all of whose subgroups of class 2 are minimal non-abelian (of the same order) are classified, respectively. Thus two questions posed by Berkovich are solved.

• Korean Journal of Crystallography
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• 제16권1호
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• pp.11-20
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• 2005

Six basic symmetries and five Bravais lattices existing in the two-dimensional lattice are derived and then ten two-dimensional point groups are classified by each of five Bravais lattices. Finally seventeen two-dimensional space groups belonging to the ten point groups are studied.

• Journal of the East Asian Society of Dietary Life
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• 제8권2호
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• pp.116-125
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• 1998

This study was designed to find out the anti-cancer effects of two herbs using a folk remedy in Korea-The two herbs were A: Equisetum arvense L. (Seddugi), B: Eunymus alatus Siebold. (Hwasalnamoo) The experiment for the anti-cancer effects were conducted in mice and experimental groups were divided into normal(NO), standard (ST) and two other(A,B) groups for each herb and each of the two experimental groups consisted of three sub-groups(I, II, III) according to three different quantity doses of a folk remedy using five times and ten times the quantity of a commonly used in a folk remedy. The water soluble extracts of two herbs were orally administered to mice during six weeks followed by inoculation of the sarcoma-180 tumor cells into the peritoneal cavity. During experimental periods, the contents of ascites, abdominal organs were observed histopathologically. The results of effects on anticancer were as follows : 1. The survival time was significantly prolonged by the two herbs, especially in groups AII & BII.2. Body weight, circumference of the abdomen and contents of ascites at the time of sacrifice were noted and significantly decreased in groups AI, AII & BII. 3. Anti-cancer effects evaluated by the invasiveness and thickness of the tumor cells were noted in groups AIII & BII.

• Child Health Nursing Research
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• 제3권2호
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• pp.178-189
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• 1997

This study was done to compare the breast-feeding primiparas' perceptions of their babies with bottle-feeding primiparas' at 2-3 days after delivery. The subjects of this study included 42 breast-feeding mothers and 56 bottle-feeding mothers. Data were collected by using the Neonatal Perception Inventory(NPI) devised by Broussard (1963) and added by Lee, Ja Hyung(1986) from December, 1996 to June, 1997. The results of this study are as follows, 1. Primiparas' perceptions of their babies according to their general characteristics. 1) There was no significant difference in mothers' perceptions according to mothers' age and whether they have a job or not. 2) There was a difference in mothers' perceptions according to their educational level (P<0.1). 2. The comparisons of breast-feeding mothers' perceptions of their babies with bottle-feeding mothers'. 1) There was no significant difference in the two groups' perceptions of other babies 2) There was no significant difference in the two groups' perceptions of their own babies. (1) Breast-feeding mothes' general perceptions of their own babies were better than bottle-feeding mothers', but there was no significant difference between the two groups. (2) Breast-feeding mothers' perceptions about the basic needs of their own babies were better than bottle-feeding mothers', and there was a significant difference between the two groups (P<0.05). (3) Breast-feeding mothers'perceptions about the sense and motor abilities of their own babies were better than bottle-feeding mothers', but there was no significant difference between the two groups. (4) Breast-feeding mothers' perceptions about the necessary care of their own babies were lower than bottle-feeding mothers', but there was no significant difference between the two groups. 3) There was no significant difference between the two groups' positive-negative perceptions of their babies (1) 69% of breast-feeding mothers and 69.9% of bottle-feeding mothers had positive perceptions about general conditions, but there was no significant difference between the two groups (2) 57.1% of breast-feeding mothers and 46.4% of bottle-feeding mothers had positive perceptions about the needs of babies, but there was no significant difference between the two groups. (3) 50% of breast -feeding mothers and 48.2% of bottle-feeding mothers had positive perceptions about the sense and motor abilities of babies, but there was no significant difference between the two groups. (4) 57.1% of breast-feeding mothers and 60.7% of bottle-feeding mothers had positive perceptions about the necessary care for babies, but there was no significant difference between the two groups. 3. 54.8% of breast-feeding mothers tried to feed their own babies on the 1st day after delivery. 83.3% of breast-feeding mothers chose the feeding method for themselves. Only 9.5% of breast-feeding mothers took recomendations for breast-feeding from nurses. 78.6% of breast-feeding mothers had no chance to learn about breast-feeding. 69% of breast-feeding mothers complained about the difficulties of breast-feeding. The most serious problems were : 'insufficient milk supply', 'lack of knowledge about feeding technique' and 'problems with nipples'.

• Journal of the Korean Home Economics Association
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• 제31권1호
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• pp.153-162
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• 1993

The purpose of this study is to demonstrate the physical consciousness of two groups, the high school girl(335) and the female college students(246), about their actual somatotype and cognitive comatotype, and to investigate it in comparison with the R hrer Index, the BMI Index, and the Broca-Katsura Index to find if there is any difference between the two groups. The results are as follows; A. In the light of cognitive somatotype by self-evaluation:(1) both high school girls and female college students recognized their weight and somatotype as normal and balanced with no significant difference between them. (2) bout groups indicated that their answers were the results of their own self-evaluation, and it was shown that there was a significant difference between the two groups. B. According to the actual somatotype based on Index. (1) it was shown there was a significant difference between the cognitive somatotype and the actual one of the tow respective groups when based on the Broca Katsura Index. (3) there was a significant difference between the cognitive somatotype and the actual one of the two respective groups when based on the Rohrer Index. Finally, it was shown that there was a significant difference between the two groups.

• Journal of the Korean Society for Library and Information Science
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• 제19권
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• pp.189-241
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• 1990

This study identified cognitive styles of online searchers in terms of Field Dependence (FD) and Field Independence (FI) dimension and determined whether searching performance was affected by FD / FI cognitive differences between online searchers and the extent to which searching performance was affected by the FD / FI dimension of cognitive style. This study used a quasi experimental design with 41 student subjects using the Lockheed DIALOG system and ERIC ONT AP database. Cognitive styles of student subjects were measured by using GEFT (Group Embedded Figure Test) and the subjects were divided into two cognitive groups- FD and FI based on the GEFT scores. Each subject was assigned two predetermined searches which had different search goals-a 'high precision search' and a 'high recall search.' Search performance of the two cognitive groups on the two problems was compared in order to see how these two groups responded to achieving different search goals in terms of search strategy, search inputs, and resulting search outputs. The major findings of this study were: 1. The pattern of approaching a search problem regardless of whether it was a high precision search or a high recall search was not significantly different between the two cognitive groups. 2. The FI group tended to use significantly more terms for the high recall search than the FD group but slightly less time than the FD group. However, significant differences in connect time between the two groups were not revealed. 3. For both search problems the FI group achieved a significantly higher success rate than the FD group. The FI group were significantly more successful searchers than the FD group. As for unit / cost, although the FI group were more cost effective than those of the FD group for both searches, these differences were too small to be statistically significant. 4. Mean differences of the search performance variables between the FD / FI groups were consistent across the two types of search questions. The FI group seemed to be equally effective for both types of search questions. In conclusion, the differences found in number of terms used and success rate between the two cognitive groups apparently resulted from different cognitive styles.

• Journal of the Korean Mathematical Society
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• 제59권4호
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• pp.805-819
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• 2022

We describe the structure of finite p-groups in which all normal closures of non-normal subgroups have two orders for p > 2.

• Journal of the Korean Ceramic Society
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• 제27권5호
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• pp.693-697
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• 1990

TIACA has two different side groups(ligands) as iso-propoxy groups and acetylacetonate groups. These two side groups have different hydrolysis rates. The two different rates of hydrolysis confer unique properties on TIACA, which are stability in aqueous solution and easy preparation of TiO2 and its multi components gels without precipitation. Their hydrolysis rates were monitored with I.R. and U.V. spectrophotometer.