• Journal of the Korean Mathematical Society
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• v.38 no.6
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• pp.1107-1116
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• 2001

In this paper, we study the rationality of the Reidemeister zeta function of an endomorphism of a group extension. As an application, we give sufficient conditions for the rationality of the Reidemeister and the Nielsen zeta functions of selfmaps on an exponential solvmanifold or an infra-nilmanifold or the coset space of a compact connected Lie group by a finite subgroup.

• Bulletin of the Korean Chemical Society
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• v.7 no.1
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• pp.55-58
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• 1986

Analytical capability of surface-enhanced Raman scattering has been evaluated. Silver films prepared by homogeneous chemical reduction were used as the substrate. Detection limits for p-nitrobenzoic acid, thiophenol and rhodamine 6G were around $10{\sim}100\;pg$.

• MALSORI
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• no.25_26
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• pp.3-26
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• 1993

The goals of the present study were (3) to collect and analyze sets of fundamental frequency (F0) and formant frequency (F1, F2, F3) data of Korean diphthongs from ten linguistically homogeneous speakers of Korean males, and (2) to make a comparative study of Korean monophthongs and diphthongs. Various definitions, kinds, and previous studies of diphthongs were examined in the introduction. Procedures for screening subjects to form a linguistically homogeneous group, time point selection and formant determination were explained in the following section. The principal findings were as follows: 1. Much variation was observed in the ongliding part of diphthongs. 2. F2 values of (j) group descended while those of [w] group ascended, 3. The average duration of diphthongs were about 110 msec, and there was not much variation between speakers and diphthongs. 4. In a comparative study of monophthongs and diphthongs, Fl and F2 values of the same offgliding part at the third time point almost converged. 5. The gliding of diphthongs was very short beginning from the h-noise. Perceptual studies using speech synthesis are desirable to find major parameters for diphthongs. The results of the present study wi11 be useful in the area of automated speech recognition and computer synthesis of speech.

• Journal of the Korean Society of Food Culture
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• v.24 no.5
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• pp.457-466
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• 2009

The purpose of this study was to identify and compare the dimensions and patterns of the perception of traditional food for Koreans living in Yanbian, Mongolia and Uzbekistan. Items representing the perception of traditional food were combined into a dimension and a pattern based on underlying perception of the Koreans living in the area. Any difference in the perception of the Koreans living in these areas likely reflects their different dimensions and patterns. Thus, it is important to determine if Koreans living in Yanbian, Mongolia and Uzbekistan should be treated as a homogeneous group when defining their perceptional structure of traditional food. Factor and cluster analysis of the data generated in this study revealed two different dimensions and patterns for each group of Koreans living in Yanbian, Mongolia and Uzbekistan. However, the structure of the dimensions and patterns of the perception of traditional food differed, indicating that Koreans within and between the countries are not a homogeneous group. Similarities and differences in perceptional dimensions and patterns among Yanbian, Mongolian and Uzbekistan-Koreans are also discussed. Moreover, future implications for food and nutrition specialists, especially for those who have an interest in Korean traditional food in Asia and those who have an interest in globalization of Korean traditional food are provided.

• Journal of the Korean Chemical Society
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• v.47 no.1
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• pp.72-78
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• 2003

In this study, the effects of grouping by extraversion and introversion in POE learning applied to elementary science class on students' achievement, the perception of learning environment and the attitude toward science instruction were investigated. Ninety-five 5th graders were assigned to the control group and the experimental groups, and taught about acid and base for 9 class hours. In the experimental groups, the homogeneous small group was composed of four introverts or four extroverts, and the heterogeneous small group was composed of two introverts and two extroverts. Two-way ANCOVA results revealed that the homogeneous group performed better than the control group in the application subtest of the achievement test. Significant difference in learning difficulty was found between the heterogeneous group and the control group. In the attitude toward science class, significant interaction effect was found between the instruction and the extraversion/introversion.

• Journal of The Korean Association For Science Education
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• v.27 no.3
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• pp.180-189
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• 2007

This study investigated the influences of reciprocal peer tutoring (RPT) strategy on middle school students' science achievement, self-efficacy, perception of instruction by grouping method and science achievement level. Eighth graders from a middle school in Seoul were assigned to comparison, homogeneous RPT, and heterogeneous RPT groups. The students were taught about 'separation of mixtures' for 8 class hours. After the instructions, a science achievement test consisting of three subtests (knowledge, understanding, and application), a self-efficacy test, and a questionnaire about the perception of instruction were administered. The analysis of the results revealed that the scores of heterogeneous RPT group, regardless of the students prior science achievement level, were significantly higher than those of the other groups in the knowledge and understanding subtests, and the self-efficacy test. The scores of homogeneous RPT group were significantly higher than those of the comparison group in the knowledge subtest but not in the understanding subtest and the self-efficacy test. The low-level students in heterogeneous RPT group performed better in the science achievement test and the application subtest than those in the other groups. The high-level students in RPT groups performed better in the science achievement test than those in comparison group. However, there was no significant difference for the application subtest scores of the high-level students of the three groups. Most students in RPT groups perceived positively on the instructions. The students in heterogeneous RPT group and low-level students especially showed more positive perception of the instruction than those in homogeneous RPT group and high-level students.

• Journal of The Korean Association For Science Education
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• v.22 no.3
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• pp.508-516
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• 2002

This study investigated the influences of group composition in cooperative computer-assisted instruction (CAI) upon students' conceptual understandings, application abilities, learning motivations, and the perceptions of involvement. Seventh graders (N=97) were selected from a co-ed middle school in Seoul, and taught about 'motion of molecules' for 5 class hours. In the two treatment groups with cooperative CAI strategy, homogeneous and heterogeneous small groups were organized by the previous science achievement. Traditional instructions were administered to the comparison group. Two-way ANCOVA results revealed that the scores of the conception test for the treatment groups were significantly higher than those for the comparison group. However, there was no difference between the homogeneous and the heterogeneous groups. The scores of the three groups did not differ significantly in the application test and the learning motivation test. However, the perceptions of involvement for the treatment groups were more positive than those for the comparison group.

• Journal of Photoscience
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• v.9 no.2
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• pp.356-358
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• 2002

Regioselective 3$^1$-$^{18}$ O-labelling of chlorophyll derivatives possessing a 3-formyl group such as methyl (pyro) pheophorbide-d (3, 4) was carried out efficiently by a simple one-step procedure; by stirring a homogeneous solution of tetrahydrofuran and H$_2$$^{18}$ O containing a small amount of trifuluoroacetic acid.

• Journal of applied mathematics & informatics
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• v.40 no.5_6
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• pp.831-842
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• 2022

In this work we classified translation invariant surfaces with zero Gaussian curvature in the 3-dimensional Sol Lie group endowed with Lorentzian metric.

• Journal of Korean Institute of Industrial Engineers
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• v.25 no.2
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• pp.162-172
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• 1999

For VBR video traffic, Motion-Picture Experts Group(MPEG) coding algorithm was adopted as the standard coding algorithm by International Telecommunication Union(ITU). In this paper, we propose a traffic model of an MPEG coded video traffic in frame level and cell level, and develop an approximate model for evaluating performance of a ATM multiplexer with homogeneous MPEG video sources by considering burst-level variation of aggregated traffics. For homogeneous MPEG video traffics which are frame-synchronized, the performance of the ATM multiplexer is influenced by source correlation at the multiplexing time. When sources are highly correlated, we decompose the aggregated cell streams by the frame-type and model multiplexing process during a frame time as n*D/D/1/K queueing model and suggest an approximate method for obtaining CLP of the ATM multiplexer. In the case that sources are highly correlated, the solution has the meaning of the upper bounds of performance of the ATM multiplexer. For the verification of our model, we compare the solution of our model with simulation resets. As the number of sources increases. The CLP obtained from our model approaches to simulation results, and gives upper bounds of simulation results.