• Carbon letters
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• v.6 no.2
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• pp.106-110
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• 2005

In this work, the effects of atmospheric oxygen plasma treatment of carbon fibers on mechanical interfacial properties of carbon fibers-reinforced epoxy matrix composites was studied. The surface properties of the carbon fibers were determined by acid/base values, Fourier-transform infrared spectrometer (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses. Also, the crack resistance properties of the composites were investigated in critical stress intensity factor ($K_{IC}$), and critical strain energy release rate mode II ($G_{IIC}$) measurements. As experimental results, FT-IR of the carbon fibers showed that the carboxyl/ester groups (C=O) at 1632 $cm^{-1}$ and hydroxyl group (O-H) at 3450 $cm^{-1}$ were observed for the plasma treated carbon fibers, and the treated carbon fibers had the higher O-H peak intensity than that of the untreated ones. The XPS results also indicated that the $O_{1S}/C_{1S}$ ratio of the carbon fiber surfaces treated by the oxygen plasma led to development of oxygen-containing functional groups. The mechanical interfacial properties of the composites, including $K_{IC}$ (critical stress intensity factor) and $G_{IIC}$ (critical strain energy release rate mode II), were also improved for the oxygen plasma-treated carbon fibersreinforced composites. These results could be explained that the oxygen plasma treatment played an important role to increase interfacial adhesions between carbon fibers and epoxy matrix resins in our composite system.

• Research in Community and Public Health Nursing
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• v.6 no.2
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• pp.183-196
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• 1995

The purpose of this study was to construct a substantive theory about the substantials of stress of Korean Wives in the community. The subjects were 10 wives. In the process of data analysis, 'burden' was found to be the core phenomenon. And the properties of burden were 'burden of domestic economy', 'a sence of duty about the esteemed family of her husband', 'role burden in a family and her work place', and 'burden of conception'. Twenty five hypotheses were derived from the integration of categories. It is as follows : 1. The stronger the difference as perceiced by subjects, the stronger the burden will be. 2. The stronger the dissatisfaction, the stronger the burden will be. 3. The stronger the trouble, the stronger the burden will be.4. The stronger the worry, the stronger the burden will be. 5. The stronger the forcible demand, the stronger the burden will be. 6. The stronger the regret, the stronger the burden will be. 7. The rarer the communication, the stronger the burden will be. 8. The stronger the fatigue, the stronger the burden will be. 9. The stronger the anger, the stronger the burden will be. 10. The stronger the worrisome feeling, the stronger the burden will be. 11. The stronger the unbearable feeling, the stronger the burden will be. 12. The stronger the resentment. the stronger the burden will be. 13. The stronger the sence of insufficiency, the stronger the burden will be. 14. The stronger the estrangement, the stronger the burden will be. 15. The stronger the attachment, the stronger the burden will be.

• Journal of Preventive Medicine and Public Health
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• v.37 no.1
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• pp.44-50
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• 2004

Objectives : This study was conducted in order to investigate the professionalism, job stress and job satisfaction in western and oriental doctors in Korea. Methods : The authors conducted a survey using a self-administered questionnaire, conducted between August and September, 2001. The study subjects were 457 western doctors and 161 oriental doctors practicing at local clinics in Daegu City. Results : For the professionalism scale, the score for belief in service to the public of western doctors was significantly higher than that of oriental doctors (p<0.05) whereas the scores for sense of calling to the field and feeling of autonomy were higher in oriental doctors (p<0.01). For the job stress scale, the scores for work factor, and clinical responsibility/decision factor of western doctors were significantly higher than those of oriental doctors (p<0.01). Of the western doctors, 59.7% expressed satisfaction with their job as a doctor, 69.5% responded that the role of a doctor was appropriate to their aptitude, and 61.8% answered that they wouldn't consider other kinds of job even if offered. In case of oriental doctors, these responses were 83.1%, 82.5%, and 82.3%, respectively. Conclusions : The job stress scores of western doctors were higher than those of oriental doctors, but the job satisfaction was lower. The reasons for the above results are not clear. Further studies are required to understand the characteristics of job stress and job satisfaction in doctors.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.432-461
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• 1995

The basic principles in the design of Class II amalgam cavity preparations have been modified but not changed in essence over the last 90 years. The early essential principle was "extension for prevention". Most of the modifications have served to reduce the extent of preparation and, thus, increase the conservation of sound tooth structure. A more recent concept relating to conservative Class II cavity preparations involves elimination of occlusal preparation if no carious lesion exists in this area. To evaluate the ideal ClassII cavity preparation design, if carious lesion exists only in the interproximal area, three cavity design conditions were studied: Rodda's conventional cavity, simple proximal box cavity and proximal box cavity with retention grooves. In this study, MO amalgam cavity was prepared on maxillary first premolar. Three dimensional finite element models were made by serial photographic method. Linear, eight and six-nodal, isoparametric brick elements were used for the three dimensional finite element model. The periodontal ligament and alveolar bone surrounding the tooth were excluded in these models. Three types model(B option, Gap option and R option model) were developed. B option model was assumed perfect bonding between the restoration and cavty wall. Gap option model(Gap distance: $2{\mu}m$) was assumed the possibility of play at the interface simulated the lack of real bonding between the amalgam and cavity wall (enamel and dentin). R option model was assumed non-connection between the restoration and cavty wall. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed the displacement, 1 and 2 direction normal stress and strain with FEM software ABAQUS Version 5.2 and hardware IRIS 4D/310 VGX Work-station. The results were as followed. 1. Rodda's cavity form model showed greater amount of displacement with other two models. 2. The stress and strain were increased on the distal marginal ridge and buccopulpal line angle in Rodda's cavity form model. 3. The stress and strain were increased on the central groove and a part of distal marginal ridge in simple proximal box model and proximal box model with retention grooves. 4. With Gap option, Rodda's cavity form model showed the greatest amount of the stress on distal marginal ridge followed by proximal box model with retention grooves and simple proximal box model in descending order. 5. With Gap option, simple proximal box model showed greater amount of stress on the central groove with proximal box model with retention grooves. 6. Retention grooves in the proximal box played the role of supporting the restorations opposing to loads.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.3
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• pp.215-227
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• 2022

In the digital transformation paradigm, IT employee work as a key human resource to accept new technologies and to lead their organization to be settled them efficiently. However, due to relatively short term of their job life and high turnover rate, the companies and the organizations are still experiencing problem the lack of IT manpower or turnover. In this study, it attempted to analyze the relationship between IT employee's technostress factors such as techno-overload, techno-complexity, techno-uncertainty, techno-invasion, and techno-insecurity and job burnout through stress coping. To reveal the structural relationship between main variables, the survey was conducted on 318 IT employees. An EFA, CFA, and reliability analysis were performed to confirm reliability and validity, and the structural equation model was conducted to testify research hypotheses. The main results are as follows. First, it was found that techno-uncertainty and techno-insecurity had the significant positive effect on problem focused coping(PFC). And, techno-complexity, techno-uncertainty, and techno-insecurity were found to have a significant positive effect on emotion focused coping(EFC). Second, in the relationship between stress coping and job burnout, it was found that EFC had a significant positive effect on burnout. Third, in the relationship between technostress and burnout, techno-uncertainty and techno-invasion were found to have a significant positive effect on burnout. In addition, it was found that the mediator effect of stress coping between techno-overload and techno-complexity through EFC. Therefore, these outputs are expected to suggest how to motivate IT employees who work as key role in efficient management on IT assets and strengthen competitiveness in digital transformation paradigm.

• Korea journal of population studies
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• v.19 no.1
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• pp.139-159
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• 1996

This study comparatively examines a causal model of employee attatchment which focuses on employee's organizational commitment and intent to stay with an organization. This study is based on two separate studies of employee attachment among teachers : the U.S. case of the Chicago Public Schools (CPS) and the South Korean case of the Seoul Educational District (SED). The main purpose of this study is to replicate in Korea the CPS study. A revised model based on the unique characteristics of Korean teachers is also developed and estimated. The Price Mueller model of employee attachment provides the basic theoretical framework for this study. It includes five general classes of variables : 1) employee responses to work variables : job satisfaction, commitment, and intent to stay; 2) psychological stress variables: role ambiguity, role conflict, work overload, and quality of students; 3) social structural variables: autonomy, routinization, distributive justice, and legitimacy; 4) economic structural variables: pay, job security, promotional opportunities, and job opportunities; and 5) work orientation variables : career commitment, normative commitment, work motivation, affectivity, work values, and met expectations. The data was collected through questionnaire survey and a sample of 649 secondary school teachers in Seoul, South Korea, was included in the final analysis. Covariance structure analysis (LISREL) was used to estimate the causal model. The results indicate that the endogenous variables of job satisfaction and commitment play a considerably less important role than in the U.S. model in mediating the effects of the exogenous variables on intent to stay, and the model fails to explain the majority of the variance in intent to stay. In addition, the new variables added to the revised Korean model do not bave significant effects on intent to stay. The structural characteristics of the employment relationship and labor markets associated with Korean teachers forced mobility and closed external markets - are largely accountable for the major differences between the Korean and the U.S. cases. The study suggests that conceptual and empirical work on what produces employee attachment under these structural constraints needs to receive more attention in future studies.

• Korean Journal of Health Education and Promotion
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• v.21 no.1
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• pp.1-23
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• 2004

The purpose of this study is to examine the effects of job-related characteristics on alcohol consumption among female workers. The Data was collected from a sample of 1,000 female workers by a stratified proportional quota sampling method derived from those who were working in Seoul. Drinking behavior pattern includes total amount of pure alcohol consumed during the last month (AC) measured by graduated quantity-frequency. Job-related characteristics (JRC) were measured by job-related stress, work characteristics, and organizational structure including length of working hours, number of times dining out together with workers per year, number of staff to supervise, employment status, occupational category, and proportion of female workers to male counterpart. Confounding variables include sociodemogrphic and socio-cultural attitudes toward alcohol expectancy, subjective norm of drinking, and gender-role attitude. Hierarchical multiple regression models show that the variability of AC was accounted for by some JRC including number of times dining together and employment status, with confounding variables held constant. However, the relationship between AC and JRC varied across occupational categories. Some implications were discussed in terms of health policy for female workers and further study for female drinking behavior.

• Steel and Composite Structures
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• v.22 no.1
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• pp.45-61
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• 2016

The domestic and foreign scholars conducted many studies on mechanical properties of wave web steel beam and high-strength spiral stirrups confined concrete columns. Based on the previous research work, studies were conducted on the anti-seismic property of the end plate bolt connected wave web steel beam and high-strength spiral stirrups confined concrete column nodes applied with pre-tightening force. Four full-size node test models in two groups were designed for low-cycle repeated loading quasi-static test. Through observation of the stress, distortion, failure process and failure mode of node models, analysis was made on its load-carrying capacity, deformation performance and energy dissipation capacity, and the reliability of the new node was verified. The results showed that: under action of the beam-end stiffener, the plastic hinges on the end of wave web steel beam are displaced outward and played its role of energy dissipation capacity. The study results provided reliable theoretical basis for the engineering application of the new types of nodes.

• Structural Engineering and Mechanics
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• v.64 no.5
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• pp.527-541
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• 2017

In this work, a new hyperbolic shear deformation beam theory is proposed based on a modified couple stress theory (MCST) to investigate the bending and free vibration responses of functionally graded (FG) micro beam made of porous material. This non-classical micro-beam model introduces the material length scale coefficient which can capture the size influence. The non-classical beam model reduces to the classical beam model when the material length scale coefficient is set to zero. The mechanical material properties of the FG micro-beam are assumed to vary in the thickness direction and are estimated through the classical rule of mixture which is modified to approximate the porous material properties with even and uneven distributions of porosities phases. Effects of several important parameters such as power-law exponents, porosity distributions, porosity volume fractions, the material length scale parameter and slenderness ratios on bending and dynamic responses of FG micro-beams are investigated and discussed in detail. It is concluded that these effects play significant role in the mechanical behavior of porous FG micro-beams.

• Transactions of Materials Processing
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• v.17 no.1
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• pp.52-58
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• 2008

Tube hydroforming process is generally consisted with pre-bending, preforming and hydroforming processes. Among forming defects which may occur in tube hydroforming such as buckling, wrinkling and bursting, the wrinkling and bursting by local instability under excessive tensile stress mode were mainly caused by thinning phenomenon in the manufacturing process. Thus the accurate prediction and suitable evaluation of the thinning phenomenon play an important role in designing and producing the successfully hydroformed parts without any failures. In this work, the formability on hydroformed part for automobile, i.e. engine cradle, was evaluated using finite element analysis. The initial tube radius, loading path with axial feeding force and internal pressure, and preformed configuration after preforming process were considered as the dominant process parameters in total tube hydroforming process. The effects on these process parameters could be confirmed through the numerical experiments with respect to several kinds of finite element simulation conditions. The degree of enhancement on formability with each process parameters such as initial tube radius, loading path and preform configuration were also compared. Therefore, it is noted that the evaluation approach of the formability on hydroformed parts for lots of industrial fields proposed in this study will provide one of feasible methods to satisfy the increasing practical demands for the improvement of the formability in tube hydroforming processes.