• Journal of Korean society of Dental Hygiene
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• v.9 no.1
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• pp.141-151
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• 2009

Cognitive degree of musculoskeletal symptoms and existence (or non-existence) of experience was conducted following dental hygienists' health habits, heath state and working environment targeting dental hygienists who were working for the dental clinics in Masan-si, Changwon-si and Jinhae-si in Gyeongsangnam-do for one year or more. The research findings were as follows. 1. Cognitive degree of musculoskeletal symptom following general characteristics was the highest among the subjects who were 40 years old or above. 2. As for the education level, cognitive degree of musculoskeletal symptoms was high while prevalence was low, which were statistically significant when the education level was higher. 3. Cognitive degree of musculoskeletal symptom was high when the subjects exercised, and cognitive degree of musculoskeletal symptom and prevalence were significantly high when they are engaged in leisure activities or hobbies. 4. Prevalence of musculoskeletal symptoms was statistically high if they are afflicted with disease, if they feel burdened by their job, if they suffer from considerable physical fatigue, if they feel chronic fatigue or if they feel that their health state is poor. 5. Cognitive degree of musculoskeletal symptom and prevalence were higher, which was statistically significant, when the number of years worked was higher. 6. Cognitive degree of musculoskeletal symptom was higher, but prevalence was lower when the time that they were seated was longer. This research demonstrated that the musculoskeletal disorders related to their job that afflicts the dental hygienists is not caused by one element, but it is possible to see that the musculoskeletal disorders results from the interaction of the diverse elements that are interrelated such as the subjects' characteristics and health habits and heath state, working environment and so forth including inappropriate work related movements. To this, dental hygienists need to improve their health habits so that they can form proper health habits that will ensure health in every day life on their own with the improvement of their every day life habit and positive self-evaluation to act on the health promotion behaviors, education and publicity, and measures to prevent and to manage musculoskeletal disorders in overall need to bepursued after in an active manner.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.615-627
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• 2017

The purpose of this study is to identify the physical and psycho-social effects of self-foot reflexology on female college students wearing high heels. The research design used was the nonequivalent control group pretest-posttest design. A total of sixty-eight participants were assigned to the experimental group (n=35) or control group (n=33). Data were collected at baseline and after 6 weeks and 10 weeks. The data were analyzed using descriptive statistics, the chi-square test, t-test, and repeated measures ANOVA with the SPSS WIN 20.0 program. In the analysis of the physical effects of self-foot reflexology, there were significant interactions of group by time in terms of the lower extremity edema and fatigue (p<.05). In the analysis of the psycho-social effects of self-foot reflexology, there were significant interactions of group by time in terms of the perceived health status and self-efficacy (p<.05), except for health promoting behavior. Self-foot reflexology was effective in reducing lower extremity edema and fatigue and in improving the perceived health status and self-efficacy. Consequently, self-foot reflexology as a nursing intervention was found to be a method of providing female college students wearing high heels with physical and psycho-social relief.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.251-258
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• 2011

Steel pipe piles have been used as various deep foundation materials for a long time. Recent increase in steel material cost has made engineers reluctant in using it even with its good quality and ease of construction. Therefore when constructing with steel pipe pile, the decision to reuse the excessive pile length that is cut off from the designed pile head elevation after pile driving can be cost saving. This has caused many constructors to reuse the pile leftovers with new piles, but the absence of quantitative structural capacity behaviors of steel pipe pile after pile driving or appropriate countermeasures and standards in reusing steel pipe pile has resulted in wrong applications, pile structural integrity problems, inappropriate limitation of reusable pile length, etc. The structural performance analysis between a new pile and a pile that has undergone working state and ultimate state stress level during pile driving was performed in this research by means of comparing the results between the dynamic pile load test, tensile load test, charpy energy test and fatigue test for high strength steel of $440N/mm^2$ yield strength. Test results show that under working load conditions the yield strength variation is less than 2% and for ultimate load conditions the variation is less than 5% for maximum total blow count of 3000. The results have been statistically analyzed to check the sensitivity of each factors involved. From the test results, reusability of steel pipe pile lies not in the main pipe yield strength deviation but in the reduction of absorb energy, strength changes and quality control at the welded section, shape deformation and local buckling during pile driving.

• Research in Community and Public Health Nursing
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• v.11 no.1
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• pp.127-145
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• 2000

The objectives of this study are to identify health behaviors and health problems. and the relations between health behaviors and health problems of female workers in the retail business. The number of subjects were 200 female workers of 6 department stores in Seoul and Kyonggi area, whose jobs last more than 6 months as retail employees. The data was collected during 2 months from July 1 to August 30, 1998. The Cornell Medical Index Health Questionnaire(CMI) was used to measure their health problems, while health behaViorn were investigated in terms of 'smoking', 'alcohol', exercise', 'diet', and 'sleeping'. The data were analyzed with frequency. percentage, t-test, ANOVA test, and $X^2-test$ by SPSS PC+ program. The results of this study are as follows: 1. Out of health problems. Digestive symptoms occupied the highest percent number. nervous ones the second and cardiovascular ones the third among physical health problems of retail female workers. The most frequent mental health problem was 'adequacy' and the next, 'tension' and 'anger', 2, Health problems according to general characteristics of subjects were shown that the younger or the unmarried complained more than the older or the married, especially in the items of 'eye and ear', 'respiratory system', 'cardiovascular system', 'digestive tract', 'nervous system', 'adequacy', and 'depression'. The longer working duration they have had, the more they complained of 'respiratory system' and 'adequacy'. The lower academic careers complained of 'nervous' than the higher ones with statistical significance. 3. The analysis of daily health clinic notes showed that respiratory complaints were the highest percent, successively followed by digestive tract, nervous one, external injury, musculoskeletal system, urinary-reproductive system and others. 4. The level of their health practice was generally low in smoking, diet habit and alcohol intake, exercise, sleeping, very low especially in smoking, diet, alcohol intake, and exercise among them all. 5. Present smokers and ones with past experience complained of physical and mental health problems of 'respiratory system', 'digestive tract', 'skin', 'nervous', 'urinary-reproductive system', 'fatigability', adequacy', 'depression', 'anxiety', 'anger' and 'tension', than non smokers, with statistical difference. Workers without having breakfast and with irregular diet had more complaints on 'digestive tract', 'adequacy' and 'tension', than those who had regular dietary habit. The less the subjects slept, the more they complained of eye and ear, cardiovascular system. The subjects who drank alcohol complained more digestive problem. However, whether they exercise or not did not affect physical and mental health problems in a significant manner. 6. The subjects' age and marital status were statistically significant relating to health behaviors, as the younger or unmarried recorded a low level of health practice in smoking, drinking, dietary habit. Based on the results, the suggestions are made as follows: 1. Health education program on smoking, alcohol intake, diet habit is needed to improve health problems and health behavior of female retail workers. 2. The unmarried workers of late teen and twenties, who are transitional period from teenagers to adulthood are important targets for health promotion program especially for maternal health. 3. Better working environment with sufficient time and facilities for workers to relax is required to promote female sales workers' health. 4. Further research is required to identify the relation between workers' visual fatigue and intense lights for the display of goods.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3046-3051
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• 2011

The third-rail system is an important device supplying power directly to the Maglev train through physical contact with the collecting shoe. It is directly related to safety and reliability for the running of Maglev. However, most the third-rail system used in Korea depend on foreign product or technologies, Korea Urban Maglev in the development of appropriate power feeding is urgent. In particular, the turnout section is the weakness point in the system because bending force by turnout section movement and fatigue caused by repetitive motion as well as the expansion by temperature, the forces by Maglev collecting shoe is added th the third-rail. Therefore, this paper proposes the third-rail system appropriate for Korean Urban Maglev of turnout section. To verify the structural stability of POSCO ICT third-rail system, the finite element analysis and physical testing was performed. The third-rail is fixed on each side of the turn-out section steel structure by epoxy insulation supporter and the integral behaviors are occurred. Therefore, the maximum horizontal displacements of each support are investigated and then, it is applied to finite element model of the third-rail to investigate the moments and stress. Also, the bending test about one million times and Expansion Joint for the third-rail was performed. The third-rail system safety and reliability was identified by test line on Korea Institute of Machinery & Materials in Deajeon for under the actual usage environment such as the Maglev and turn-out operation.

• Ocean Systems Engineering
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• v.2 no.2
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• pp.99-113
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• 2012

Steel Catenary Risers (SCR) are the simplest and often the most economic solution compared to other riser types such as flexible pipe, riser towers, top tensioned risers, etc. The top of a SCR is connected to the host platform riser porch. The other end of the SCR connects to flowlines from subsea wells. The riser touchdown point (TDP), which is the location along the riser where contact with the sea floor first occurs, exhibits complex behaviors and often results in compression and fatigue related issues. Heave dynamic responses of semisubmersibles in extreme and operating sea states are crucial for feasibility of SCR application. Recent full field measurement results of a deep draft semisubmersible in Hurricane Gustav displayed the considerable discrepancies in heave responses characteristics between the measured and the simulated results. The adequacy and accuracy of the simulated results from recognized commercial software should be examined. This finding raised the awareness of shortcomings of current commercial software and potential risk in mega investment loss and environmental pollutions due to SCR failures. One main objective of this paper is to attempt to assess the importance and necessity of accounting for viscous effects during design and analysis by employing indicator of viscous parameter. Since viscous effects increase with nearly third power of significant wave height, thus newly increased metocean criteria per API in central Gulf of Mexico (GoM) and even more severe environmental conditions in Western Australia (WA) call for fundamental enhancements of the existing analysis tools to ensure reliable and robust design. Furthermore, another aim of this paper is to address the impacts of metocean criteria and design philosophy on semisubmersible hull sizing in WA and GoM.

• Explosives and Blasting
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• v.28 no.1
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• pp.1-10
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• 2010

In blasting for lighting, fatigue behaviors of pillars such as destruction and deformation may occur due to blasting vibration and flyrock, which may cause collapses of cavities. This study aims to identify dynamic behavior of pillars to maintain efficient safety of cavities in large drafts. when they collide with flyrocks under blasting for the excavation. For the purpose, we compared ground vibration around pillar when flyrock collided with the pillar and that when explosive blast happened for the excavation. we conducted fragmentation analysis of the flyrock and compared impact vibration obtained from empirical equation with ground vibration obtained from regression analysis of real vibration data. also we compared those with results analyzed from numerical analysis.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.409-416
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• 2012

Recently, surface modification technology is of importance to improve the wear resistance and the corrosive resistance for high accurate mechanical parts such as LM guide, Ball Screw and Roller Bearing etc., Those has generally featured on rolling contact mechanism to improve not only the wear and the friction, but also the accuracy and the corrosion performances. For surface modifications of high accurate mechanical parts, normally thermal spray, PVD, CVD and E.P. processes have been used with many materials such as DLC, raydent, W, Ni, Ti etc. Diamondlike carbon (DLC) films possess a combination of attractive properties and have been largely employed to modify the tribological behaviors such as friction, wear, corrosion, fretting fatigue, biocompatibility, etc. However, for rolling contact mechanism mechanical parts DLC films are needed to study for commercial benefit. Rolling contact mechanism has features on effects of cyclic motions and stresses, and also not simply sliding motions. The papers focused on the performance test of wear and corrosive resistance according to Me-DLC film thickness. And also, its thickness effect of wear analysis was carried out through the simulation of the maximum shear stress under the rolling contact surface. As the results, Me-DLC films have more potential to improve the wear resistance for high precision mechanical parts than raydent films.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.259-267
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• 1997

Wind tunnel test results and their interpretations focused on the behavior of girder, which were performed to study the aerodynamic stability of a self-anchored suspension bridge with lateral sag of main cable, are presented in this paper The shape of the girder which has the best aerodynamic stability was selected based on the section model test under uniform and turbulent flow conditions. Good performance of the selected section was confirmed in the full bridge model test. Measured flutter derivatives are presented for further study. Buffeting response was investigated to check the fatigue problem and serviceability of the bridge but it was found to be acceptable from the engineering point of view. Even though the drag coefficient of the girder had high value, the amplitude of the lateral vibration was found to be very low. This may be due to the restraint provided by the lateral sag of the cables.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.2
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• pp.94-100
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• 2004

In order to improve the wear resistance of Ti-6Al-4V alloy, plasma carburization treatment was newly carried out without consumption of its good specific strength and fatigue life over the temperature. Effect of the plasma carburization was analyzed and compared with the non-treated alloy by microstructural observation, structure characterization and mechanical test. The plasma treated alloy formed a carburized layer of about $150{\mu}m$ in depth from the surface, where a fine and hard particles of TiC and $V_4C_3$ were homogeneously dispersed through the layer. The steady-static creep behaviors of Ti-6Al-4V alloy, using the constant stress creep tester, were investigated over the temperature range of $510{\sim}550^{\circ}C$(0.42~0.44Tm) and the stress range of 200~275 MPa. Stress exponent(n) was decreased from 9.32 of non-treatment specimen to 8.95 of carburized, however, the activation energy(Q) increased from 238 to 250 kJ/mol with the same condition as indicated above. From the above results, it can be concluded that the static creep deformation for Ti-6Al-4V alloy was controlled by the dislocation climb over the ranges of the experimental conditions.