• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.68-73
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• 2000

In this study, tlhe relationships of high school students' abilities to solve chemistry problems with cognitive variables (logical thinking ability, mental capacity. and learning strategy) and affective variables(self-efficacy, self-concept of ability, learning goal, and attitude toward science) were investigated. The proportion of variance due to the variables for algorithmic and conceptual problem solving ability was studied by a multiple regression analysis. The results indicated that, among the cognitive variables, the logical thinking ability significantly predicted the algorithmic problem solving ability, and the learning strategy was the best predictor of conceptual problem solving ability although not significant. Among the affective variables studied, the self-concept of alility was the significant predictor of both algorithmic and conceptual problem solving abilities. The seif-efficacy was significantly correlated with conceptual problem solving ability, but it had no predictive power.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.45-54
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• 1991

The closed forms of mass matrix with rotational inertia matrix are developed for free vibration analysis in space structures containing linearing tapered members with cross section of thin-walled tube. The exact displacement functions are used for formulating mass matrix. The very small slopes of the tapered member are used in usual practice, such that the series expansion forms of these are also developed to avoid numerical failure in vibration analysis. Significant improvements of accuracy and efficiency of free vibration analysis are achieved by using the mass matrices developed in this study. Frequencies of free vibration of tapered members are compared with solutions based upon stepped representation of beam element.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1935-1946
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• 2013

In this study, the behavior characteristics of bent pile structures with varying cross-section was examined through the measured results of field load test. A framework for determining the bending stress is calculated based on the stresses in the circumference of the pile using 3D finite element analysis. It is found that the bending stress near the pile-column joint changes rapidly and fracture zones occurs easily at variable cross-sections in bent pile structures. Also, the optimized column-pile diameter ratio was analyzed through the relationship between the column-pile diameter ratio and lateral crack load ratio. Based on this study, the optimized column-pile diameter ratio can be obtained near the inflection point of the curve between the column-pile diameter ratio and lateral crack load ratio. Therefore, a present study by considering the optimized variable cross-section condition would be improved bent pile structures design.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.615-627
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• 1998

In order to determine the maximum shear force, the maximum bending moment, the maximum pure torsion. the maximum warping torsion, and the maximum bimoment for the curved girder grid bridges, it is important to find the location of live load applied to the curved girder grid bridges, so that the influence line can be estimated. The fundamental differential equation concerning the behaviour with warping effects for the curved girder is developed by Vlasov. In this paper, the influence line of shear force, bending moment, pure torsion, warping torsion, and bimoment due to unit vertical load and unit torsional moment for curved I-girder grid bridges with variable and constant cross section are obtained by using the finite difference method and compared with respectively.

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.143-152
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• 2006

An automatic observation system has been constructed at Chungbuk National University for the purpose of monitoring the bright and long period variable stars effectively. We improved the control part of 40cm telescope of the LX200 and developed n observing software ObsTool II so that the telescope, CCD camera and dome can be controlled in one software. ObsTool II is a COM (Common Object Module) based software, which can be easily reprogrammed in case that a new telescope or CCD camera is installed. Because this system has an additional function in which the telescope can switch the variable, comparison, and check stars respectively as like a photoelectric observation, we can observe the variable star even if the CCD view field does not contain the comparison star with the variable star. In order to check the system stability a W UMa type variable V523 Cas and a magnetic cataclysmic variable TT Ari have been observed with the constructed system and the results have been discussed in context with the possibility of a further application of our automatical observation system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1013-1021
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• 1994

The stiffness and mass matrices are developed for free torsional vibration analysis in linearly tapered thin-walled I-beams that takes into account the effect of warping torsion. The approximate shape functions are used for formulating stiffness and mass matrices. Significant improvements of accuracy and efficiency of free vibration analysis are achieved by using the stiffness and mass matrices developed in this study. Frequencies of free vibration of tapered members are compared with solutions based upon stepped representation of beam element and also are verified with model tests. The stiffness and mass matrices presented in this study can be used for the free vibration analysis of tapered and prismatic thin walled I-beams and space structures involving warping torsion.

• Korean Journal of Environment and Ecology
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• v.15 no.2
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• pp.104-117
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• 2001

경상북도 낙동상 상류부에 위치한 하천변 식물군락에 대해 식물사회적 조사를 하였다. 그 결과 아래처럼 10군강에 속하는 30군락단위와 상급단위 미결정의 1군락단위를 식별하였다. 특히, 과거에 인위적 영향을 반영하여 쑥군강에 속하는 군집 군락이 가장 많이 출현하였다. A. 관목식물군락-A-1나도버들군장, 버드나무군단: 버드나무-왕버들군집, 버드나무군집, 시무나무군집, 갯버들군집, 눈갯버들군집, 선버들군집, A-2 찔레꽃 군강: 국수나무군락, 구기자나무군락: A-3 상급단위 미결정의 군락: 누리장나무군락; B, 초본식물군락 B-1 가래군강: 노랑어리연꽃군집, 마름군락, B-2 좀개구리밥군강: 좀 개구리밥-개구리밥군랍, B-3 가막사리군강: 고마리군집, 미꾸라지낚시-여뀌군집, 개기장-여뀌군집, B-4 갈대군강; 창포군집, 갈풀-미나리군집, 달뿌리풀군집, 물억새군집, 갈대군락, B-5 쑥군강:물쑥군집, 쑥군락, 물봉선군락, 왕고들빼기-환삼덩굴군집, 칡-환삼덩굴군집, 수크려군랑, B-6 명아주군강: 물피군락, 바랭이군란, 큰개여뀌군락, B-7 억새군강: 억새군락, B-8 질경이군강: 비노리-질경이군락, 이들 식생단위는 거의가 일본의 것과 공통하고 있어 한국에 고유한 하천변 식생은 매우 드물다는 사실을 나타내었다. 한편 하천에는 고유한 군강의 군집, 군락은 하류에서 상류로 감에 따라 양적으로 증가 하였으마, 귀화식물의 수는 그 반대였다. 또, 각 군락과 환경과의 관계, 하천변 식생의 복원생태 및 자연보호 등에 관해 상세히 논하였다.

• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.419-424
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• 2010

Through the process of state estimation in the electric railway substation, this paper presents a new method for improving the reliability of the measurements corrupted by gauge error. Unlike the case of commercial power systems, it has been difficult to perform the state estimation by using the usual methods in the electric railway substation. At some of the monitoring points in the substation, most often, it is hard to define the measurement functions by use of the states or as we set up a new states set with the change of system topology, some of the measurement functions become part of the states themselves, which leads to poor results. To resolve the problems in the existing method caused by the relations between the states and the measurement functions at the monitoring points, the proposed method in this paper exploits the equality constraints. They can be derived numerously and concisely from the current and the voltage attributes of the Scott transformer and the buses connecting conditions, etc. We have proofed the effectiveness of the proposed method by the test on a standard sample substation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.4
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• pp.353-361
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• 2001

A new stereoscopic codec. structure using MPEG-2 multiview profile is presented in this paper. In the suggested codec., the left image is coded with motion estimation in the base layer and the right image is coded with disparity estimation in the enhancement layer. Since it is possible to calculate rough motion of the right image sequence with disparity and motion of the left image sequence, motion compensation of the enhancement layer is performed without motion estimation. To apply this mathod to MVP codec., the prediction mode of base layer and enhancement layer is restricted, and B picture mode in the base layer is removed. Since the proposed codec. does not perform motion estimation in the enhancement layer encoding and prediction mode of base layer is restricted, it's structure is simple and reduces the encoding time. We compared the SNR of encoded image with three different structured codec., and the experimental results show suggested codec. have comparable result.

• Journal of Families and Better Life
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• v.25 no.4
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• pp.43-55
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• 2007

The Purpose of this study was to investigate the ecological variables on adolescent's sociometric popularity. Independent variables were organism(sex, age, aggression, self-esteem, impulsiveness, prosocial behavior, dominance), microsystem(parenting style, family support, friends relationship, teacher support), mesosystem(family-peer relationship, family-school relationship), and exosystem(positive community environment, social support of extended family, school's policy). The subjects were 835 - 1st and 2nd graders of two middle and two high schools in Daegu. Adolescent's sociometric popularity and ecological variables were measured with questionnaire. Adolescent's sociometric popularity was measured with sociometric popularity questionnaire. Organism variables were measured with sex, age, aggression, self-esteem, impulsiveness, prosocial behavior and dominance questionnaire. Microsystem variables were measured with parenting style, family support, friends relationship and teacher support questionnaire. Mesosystem variables were measured with family-peer relationship and family-school relationship questionnaire. Exosystem variables were measured with positive community environment, social support of extended family and school's policy questionnaire. The data analyzed by frequency, percentage, mean, cronbach's $\alpha$, and multiple regression. The major findings were as follows: First, adolescent's sociometric popularity was affected by age, overt aggression, academic self-esteem, social self-esteem, and impulsiveness of organism variables. Second, adolescent's sociometric popularity was affected by mother's affectional parenting, mother's control parenting, and attachment to friends of microsystem variables. Third, adolescent's sociometric popularity was affected by family - peer relationship and family - school relationship of mesosystem variables. Fourth, adolescent's sociometric popularity was affected by appraisal support of extended family, after-school activity, and circle activity of exosystem variables.