• Advanced Composite Materials
• /
• 제18권3호
• /
• pp.265-285
• /
• 2009

Off-axis compressive deformation behavior of a unidirectional CFRP laminate at high temperature and its strain-rate dependence in a quasi-static range are examined for various fiber orientations. By comparing the off-axis compressive and tensile behaviors at an equal strain rate, the effect of different loading modes on the flow stress level, rate-dependence and nonlinearity of the off-axis inelastic deformation is elucidated. The experimental results indicate that the compressive flow stress levels for relatively larger off-axis angles of $30^{\circ}$, $45^{\circ}$ and $90^{\circ}$ are about 50 percent larger than in tension for the same fiber orientations, respectively. The nonlinear deformations under off-axis tensile and compressive loading conditions exhibit significant strain-rate dependence. Similar features are observed in the fiber-orientation dependence of the off-axis flow stress levels under tension and compression and in the off-axis flow stress differential in tension and compression, regardless of the strain rate. A phenomenological theory of viscoplasticity is then developed which can describe the tension-compression asymmetry as well as the rate dependence, nonlinearity and fiber orientation dependence of the off-axis tensile and compressive behaviors of unidirectional composites in a unified manner. It is demonstrated by comparing with experimental results that the proposed viscoplastic constitutive model can be applied with reasonable accuracy to predict the different, nonlinear and rate-dependent behaviors of the unidirectional composite under off-axis tensile and compressive loading conditions.

• Asia pacific journal of information systems
• /
• 제16권4호
• /
• pp.179-202
• /
• 2006

The objective of this study is to identify the impacts of communication reinforcement on performance of learning in Web-PBL. Communication reinforcement is defined as the combination of information sharing and co-construction. As factors facilitating communication reinforcement, we propose learner's characteristics, task characteristics, and group characteristics. Learner's characteristics are collaboration-orientation, openness, holistic approach, and online community-orientation which reflects e-learning environment. Collaboration-oriented tasks as group projects were developed and given to groups with 5-6 members. The group characteristics are categorized into 'horizontal' and 'vertical', according to the patterns of communication between a group leader and members. To verify empirically the proposed research model, an experimental design was performed to learners who took on-line and off-line courses with group projects. We found important results as follows; First, field dependence has positive impacts on information sharing, and online community-orientation has positive impacts on co-construction. These results correspond with prior studies on relationship between field dependence and collaborative learning. Second, collaboration-oriented task directly impacts on information sharing, and indirectly affects co-construction, This result implicates that information sharing is pre-requisite of co-construction. Third, 'horizontal' was identified as a factor giving positive effects on information sharing and co-construction. This result implies that horizontal communication is very important to facilitate communication reinforcement.

• Fibers and Polymers
• /
• 제6권3호
• /
• pp.206-218
• /
• 2005

Structural studies of series of 'as spun' and drawn PEEK fibers have been carried out using X-ray diffraction and optical microscopy techniques. The analysis of results suggest that fibers produced at a constant draw ratio with increasing draw temperatures show enhanced orientation and crystalline behaviour. The resolved equatorial and meridional traces provide additional structural parameters in terms of crystallinity, crystallite size, and crystallite thickness. It is concluded that drawing at a temperature below $T_g(i.e.,\;144^{\circ}C)$ results in poorly oriented non-crystalline materials, whereas drawing above $T_g$ results in highly oriented semi crystalline materials. Additional drawing proved to increase the overall orientation with slight improvements in lateral order of the chain molecules. Quantitative analysis revealed that the crystallite size increases with increasing drawing temperature. The results also revealed the increased crystallite size upon additional drawing. Crystalline orientation parameter, $_c$, suggests almost perfect orientation. In all cases, the amorphous orientation is found to be lower than the overall orientation parameter obtained from the optical birefringence. As a result of additional drawing, crystalline orientation was found to increase slightly but the increase in the orientation of non-crystalline material was found to be substantial. An average crystalline density was determined from the orthorhombic unit cell dimensions. It was found to vary as a result of processing conditions. It was also found that the value of the maximum birefringence shows heavy dependence on the chain conformation.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 2004년도 요약집 춘계학술발표대회
• /
• pp.320.2-320.2
• /
• 2004

• 융합정보논문지
• /
• 제9권4호
• /
• pp.100-108
• /
• 2019

연구의 목적은 대학생의 스마트폰 의존도가 진로태도성숙에 미치는 영향과 그 경로에서 대인관계 문제의 매개효과를 분석하는데 있다. 이를 위해 서울과 수도권에 소재한 4개 대학의 학생들을 대상으로 설문을 진행하여 총 221부로 실증적인 검증을 위해 구조방정식을 실행하였다. 그 결과 첫째, 대학생의 일상생활 장애와 가상세계 지향이 높으면 대인관계 문제에 정적인 영향을 주는 것으로 나타났다. 둘째, 대학생의 일상생활 장애와 가상세계 지향이 높으면 진로태도성숙에 부적인 영향을 미치는 것으로 나타났다. 셋째, 대학생의 대인관계 문제는 진로태도성숙에 부적인 영향을 미치며, 스마트폰 의존도와 진로태도성숙 관계에서 모두 완전매개하고 있음을 파악하였다. 따라서 본 연구결과는 대학생의 진로태도성숙을 증진시키는 다양한 프로그램의 개발과 적용에 기초자료로 사용될 수 있음을 시사하였다.

• 보건교육건강증진학회지
• /
• 제12권2호
• /
• pp.146-161
• /
• 1995

This study is an effort to bring our attention to social dependence on alcohol, focusing on previous studies of drinking behaviors. Although drinking behavior and problems must be understood in a biopsychosocial framework, a certain aspect is often ignored in alcohol research. A few attention has been paid to social aspect of alcohol abuse or dependence. Social processes of drinking behavior deserve to have same attention as other aspects, psychological and physical aspects of the behavior. Literature show that the interdependence among group members exists to regulate individual's drinking behavior. Such social interactions tend to control drinking level for individual in terms of amounts, frequency, and preference. The drinking level tends to be dependent on desires for heavy drinkers, ignoring variabilities of individual's sensitivity to alcohol. However, such a heavy-oriented tendency in drinking behavior may have different patterns which are function of normative orientation of alcohol. negotiation among group members, and ethnoreligious characteristics. Perspectives from conflict tradition and symbolic interactionism are welcomed to illuminate multi-dimentional aspects of social dependence. Policy implication were discussed from public health perspective.

• 한국의류학회지
• /
• 제29권5호
• /
• pp.715-726
• /
• 2005

The purpose of this study was to identify the effects of the sensation seeking and body image on female adolescents' clothing behavior and hair style attitude. The data was collected from 390 high school girls living in Seoul, via a self·administered questionnaires, and were analyzed by frequency, factor analysis, reliability test, Pearson's correlation, and multiple regression. The results of this study was as follows : 1) Three factors of body images were self appearance evaluation, appearance orientation and fitness orientation. Five factors of clothing attitudes were fashion/clothing interest, clothing exhibition, social approval, psychological dependence on clothing and fashion leadership. And three factors of hair style attitudes were interest in hair style, individuality in hair style and dependency on hair designer. 2) As the result of analyzing the effects of sensation seeking and body image on clothing behavior, fashion/clothing interest was explained by appearance orientation and fitness orientation, and clothing exhibition by sensation seeking and appearance orientation, and social approval by appearance orientation, self appearance evaluation and body cathexis, and fashion leadership by appearance orientation, fitness orientation and self appearance evaluation, and clothing conformity to the self-entertainer by appearance orientation, sensation seeking and fitness orientation, and appearance related delinquency by sensation seeking, appearance orientation, fitness orientation, self appearance evaluation. 3) As the result of analyzing the effects of sensation seeking and body image on hair style attitudes, interest in hair style was explained by the factors such as appearance orientation, sensation seeking, fitness orientation, and body cathexis, and individuality in hair style by appearance orientation, sensation seeking and self appearance evaluation, and dependency on hair designer by body cathexis.

• 대한기계학회논문집
• /
• 제19권6호
• /
• pp.1460-1468
• /
• 1995

The objective of this paper is to evaluate the material properties of SA106 Gr. C carbon steel and its associated weld manufactured for main steam system of Yonggwang 3,4 nuclear generating stations. A total of 43 tensile and 35 fracture toughness tests were performed and the effects of various parameters such as pipe size, crack plane orientation, test temperature, welding on material properties were discussed. Test results show that the effects of crack plane orientation, test temperature, and welding on fracture toughness were significant while the effects of pipe size, specimen orientation and test temperature on tensile properties were negligible. Especially the dependence of J-R curves on the crack plane orientation appears to be the characteristics of carbon steel.

• 한국전기전자재료학회논문지
• /
• 제15권6호
• /
• pp.539-542
• /
• 2002

The effect of the superconducting film thickness on the surface resistance has been investigated. Superconducting YBCO thin films have been grown on MgO substrates by pulsed laser deposition. The dependence of the orientation of YBCO film on thickness has been investigated by X-ray diffraction technique. X-ray diffraction indicated that the film orientation was changed by increasing the film thickness and by changing the substrate temperature. The microwave properties of the films with mixed orientations of a-axis and c-axis will be reported for the applications of microwave devices.

• 천문학회지
• /
• 제29권spc1호
• /
• pp.53-54
• /
• 1996

Based on the database of 128 disk galaxies (66 SO, 62 S and Irr) mailnly compiled from Kent and Gunn (1982) and Doi et a1.(1995) which is complete down to m < 15.6 mag within a radius of $3^{\circ}$, the orientation of spin vectors of disk galaxies of the Coma cluster has been analyzed. The results confirm the morphological dependence of the orientation of disk galaxies found from the analsis of the Virgo cluster. Common features of orientation of disk galaxies of both clusters are outlined.