• 한국재료학회지
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• 제24권7호
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• pp.375-380
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• 2014

Solar cells exhibit different power outputs in different climates. In this study, the temperature dependence of open-circuit voltage(V-oc), short-circuit current(I-sc), fill factor(FF) and the efficiency of screen-printed single-crystal silicon solar cells were studied. One group was fabricated with homogeneously-doped emitters and another group was fabricated with selectively-doped emitters. While varying the temperature (25, 40, 60 and $80^{\circ}C$), the current-voltage characteristics of the cells were measured and the leakage currents extracted from the current-voltage curve. As the temperature increased, both the homogeneously-doped and selectively-doped emitters showed a slight increase in I-sc and a rapid degradation of V-oc. The FF and efficiency also decreased as temperature increased in both groups. The temperature coefficient for each factor was calculated. From the current-voltage curve, we found that the main cause of V-oc degradation was an increase in the intrinsic carrier concentration. The temperature coefficients of the two groups were compared, leading to the idea that structural effects could also affect the temperature dependence of current-voltage characteristics.

• 영어어문교육
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• 제12권1호
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• pp.257-286
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• 2006

This paper investigates the effects of small group collaborative transcription activities on the improvement of university students' English listening ability. Based on the results of pre-tests, a class of 42 students was subdivided into 11 small homogeneous groups of three to four students. Each group was provided with 7 different news items to be transcribed. Means were compared between pre-test and post-test scores, followed by comparison of transcription errors in content and function words. Finally, students' perception and attitudes about the use of small group transcription for improving listening skills were qualitatively analysed and compared with pre- and post test results. It was found that post test scores highly correlated with improvement of listening ability. It was also found that groups of high degree of collaboration showed improvement in listening ability while lack of collaboration contributed to loss of interests in listening. Students who see process more important were found to make more contribution to the group success than those who place more emphasis on the results.

• 한국경영과학회지
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• 제23권4호
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• pp.171-186
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• 1998

While one main stream of research in GDSS (Group Decision Support System) is to investigate how GDSS affects decision-making performances of groups according to task types, support features, meeting facilitation modes and meeting environments. little study h3s been done about how group characteristics affect group decision processes and outcomes depending upon GDSS is provided or not. So far, most GDSS research has considered group characteristics (e.g. personality homogeneity) as given and did not include it as control variables in experiments. Therefore, the objective of this study is to investigate how members of two different groups perceive the use of GDSS in group meetings through lab experiments. The two groups are homogeneous and heterogeneous groups in terms of members' personality mix. This research found that the effect of GDSS is a function of groups' personality homogeneity in regards of the satisfaction on decision process and the communication thoroughness. The support of GDSS and the group homogeneity are proved to influence participant's perception about some dependent variables such as satisfaction on decision process.

• 한국지리정보학회지
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• 제20권3호
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• pp.42-51
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• 2017

대설은 우리나라의 법적 자연재해 중 하나이다. 최근 기상현상에 의한 사회경제적 영향력을 함께 예보하는 영향예보가 부각되고 있으며, 이를 위해서는 먼저 각 지역의 기후적 특징을 분석할 필요가 있다. 본 연구에서는 영향예보의 기반마련을 위해 자기조직화지도를 활용하여 적설동질지역을 구분하여 지역별 적설 특징을 분석했다. 연구결과 적설동질지역은 7개 군집으로 나타났으며, 강설량 및 관측일수, 최대강설량을 이용하여 각 그룹의 특징을 구분했다. 대관령, 강릉시, 정읍시는 강설량이 많은 지역으로, 경상도는 강설량이 적은 지역으로 구분되었다. 선행연구와 비교결과 대표적인 지역이 잘 구분되었으나 강설의 특징은 차이가 있는 것으로 나타났다. 본 연구의 결과는 각 지역의 영향예보를 위한 정책결정에 기초자료로 활용될 수 있다.

• Macromolecular Research
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• 제17권7호
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• pp.506-515
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• 2009

We synthesized a series of polystyrene derivatives containing various side chain terminal moieties, such as phenoxymethyl, 4-methoxyphenoxymethyl, 4-fluorophenoxymethyl, 4-methylphenoxymethyl, and 4-trifluoromethoxyphenoxymethyl groups, using polymer analogous reactions, in order to investigate the effect of the side group on their liquid crystal (LC) alignment behaviors. The polymers containing 4-fluorophenoxymethyl, 4-methylphenoxymethyl, or 4-trifluoromethoxyphenoxymethyl side groups had lower surface energy values and the LC cells fabricated using the unrubbed films of these polymers showed homeotropic LC alignment behavior. The LC cells fabricated using the rubbed films of the polymers containing phenoxymethyl or 4-fluorophenoxymethyl groups showed homogeneous planar LC alignment behavior in which the LCs were aligned perpendicular to the rubbing direction. This homogeneous planar and perpendicular alignment behavior was ascribed to the favorable anisotropic interactions between the LC molecules and the side groups preferentially oriented perpendicular to the rubbing direction.

• 한국군사과학기술학회지
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• 제9권2호
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• pp.51-59
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• 2006

The purpose of this paper is to present reliability analysis procedures for repairable systems and apply the procedures for assessing the reliabilities of two subsystems of a specific group of military equipment based on field failure data. The mean cumulative function, M(t), the average repair rate, ARR(t), and analytic test methods are used to determine whether a failure process follows a renewal or non-renewal process. For subsystem A, the failure process turns out to follow a homogeneous Poisson process, and subsequently, its mean time between failures, availability, and the necessary number of spares are estimated. For subsystem B, the corresponding M(t) plot shows an increasing trend, indicating that its failure process follows a non-renewal process. Therefore, its M(t) is modeled as a power function of t, and a preventive maintenance policy is proposed based on the annual mean repair cost.

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.259-265
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• 1992

Cyclic voltammetric behavior of symmetric (dimethyl, diheptyl, dioctyl, dibenzyl) and asymmetric (methyloctyl, methyldodecyl, methylbenzyl) viologens was investigated in homogeneous aqueous solution and sodium dodecyl sulfate (SDS) micellar media. In SDS-free 0.1 M NaCl solutions, the reduction potential is less negative as the chain length of alkyl substituent is longer. This is due to the stabilization of the reduced cationic radical and neutral form of viologen by adsorption on electrode surface. The adsorbed species show the "aging-effect". With the exceptions of methyldodecyl viologen and methylbenzyl viologen, the viologens show strong tendency of conproportionation reaction between viologen dications and neutral forms. In cases of methyldodecyl viologen and methylbenzyl viologen, the conproportionation reaction is kinetically disfavored, though it is thermodynamically favorable. SDS micelles dissolve the adsorbed species and the viologens exhibit two reversible redox processes in SDS micellar solutions. The reduction potentials of viologens in SDS micellar solutions depend little on the length of alkyl chain. Benzyl-substituted viologens are more easily reduced than the alkyl substituted viologens, presumably due to electron-withdrawing character of benzyl group.

• 국제초고층학회논문집
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• 제11권4호
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• pp.331-346
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• 2022

Reproducing the horizontally homogeneous atmospheric boundary layer in computational wind engineering is essential for predicting the wind loads on structures. One of the important issues is to use fully developed inflow conditions, which will lead to the consistence problem between inflow condition and internal roughness. Thus, by analyzing the previous results of computational fluid dynamic modeling turbulent horizontally homogeneous atmospheric boundary layer, we modify the past hypotheses, detailly derive a new type of inflow condition for standard k-ε turbulence model. A group of remedial approaches including formulation for wall shear stress and fixing the values of turbulent kinetic energy and turbulent dissipation rate in first wall adjacent layer cells, are also derived to realize the consistence of inflow condition and internal roughness. By combing the approaches with four different sets of inflow conditions, the well-maintained atmospheric boundary layer flow verifies the feasibility and capability of the proposed inflow conditions and remedial approaches.

• International journal of advanced smart convergence
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• 제2권2호
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• pp.23-26
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• 2013

Social networking services that connect a person to other people are attracting people's attention and various types of services are provided on the Internet. Library has been playing a role of social media by providing us with materials such as books and magazines, and with a place for reading, studying, getting lectures, etc. In this paper, we present a method for finding candidates of groups of the library's patrons who share interest areas by utilizing the loan records, which are obtainable in every library. Such a homogeneous group can become a candidate for a study group, a community for exchange ideas, and other activity group. We apply the method to a collection of loan records of a university library, find some problems to be solved, and propose measures for more detailed solutions. Even though the potential group finding problem still remains a lot of issues to be solved, its potential importance is very high and thus to be studies even more for future applications.

• International Journal of Internet, Broadcasting and Communication
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• 제6권1호
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• pp.5-8
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• 2014

Social networking services that connect a person to other people are attracting our attention and various types of on-the-network services are provided. Library has been playing a role of social media by providing with materials such as books and magazines, and with a place for reading, studying, getting lectures, etc. In this paper, we present a method for finding candidates of groups of the library's patrons who share interest areas by utilizing the loan records, which are obtainable by every library. Such a homogeneous group can become a candidate for a study group, a community for exchange ideas, and other activity group. We apply the method to a collection of loan records of a university library, find some problem to be solved, and propose measures for more detailed solutions. Even though the potential group finding problem still remains a lot of problems to be solved, its potential importance is very high and thus to be studies even more for future applications.