• 대한기계학회논문집A
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• 제21권7호
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• pp.1081-1088
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• 1997

The purpose of this work is to investigate the working limit of carbon steel and forging condition of cold forging. The fracture criteria which was proposed by Oyane and Osakada was used. Compression test, hardness study and tension test by Oyane's creteria, microstructure study by Osakada's were carried out. The results were compared with each other. It was found that working limit on compressive hydrostatic stress is increased in comparison with that of tensile stress field and can be forecasted the fracture limit of closed cold forging.

• 대한치과의사협회지
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• 제55권1호
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• pp.42-52
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• 2017

The purpose of this study is to evaluate the preferred method of root canal length determination and the apical limit for canal instrumentation among endodontic teachers of dental school. A questionnaire on the preferred method of root canal length determination and the apical limit for canal instrumentation was designed and distributed to endodontic teachers of various dental schools. The response rate was 90%. The most preferred method of root canal length determination was Electronic apex locator (EAL)(89%). The most favoured apical limit for canal instrumentation was 0.5 to 1.0 mm short of the radiographic apex(78%). The most preferred method of using EAL was that the working length is taken at 'APEX' mark and then distracted 0.5mm from that length.(41%). When there is no agreement between radiographic measurement and EAL measurement, 74% of respondents chose the length of EAL measurement. The majority of endodontic teachers from Korean dental schools preferred EAL to radiograph method in determining root canal length.

• 대한조선학회논문집
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• 제47권4호
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• pp.589-597
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• 2010

The indoor noise of the naval vessel is very important considering hearing protection, improvement of working environment and easily communication between crews. When the environment of the naval vessel suffering from the noise is considered, it is very important to be quiet in the living area where the crews have a rest sufficiently. In addition, the noise of the working area should be reduced in order to increase working efficiency. Therefore, in this research, the satisfactions about the indoor noise are survey for crews working in a naval vessel. Through this survey, the relationship between the indoor noise and crew's satisfaction about it can be found. As a result, the limit of sound pressure level which almost all crew can be satisfied with the indoor noise about their living and working area is suggested base on the survey in this research.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 춘계학술대회논문집
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• pp.203-210
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• 1995

The rapid progress of automobile industry has led to a demand for sheet metal products and the new forming technology for complex product is required. In Deep Drawing process of steel sheet, especially stainless steel sheet at room temperture, some intermediate annealing need to be added to lessen strain hardening effect. The present study is concerned with the wram deep drawing of stainless steel sheet. In order to reduce the number of working process. the limit drawing ration is considered as main parameter. In this study, the effect of process variables such a sblank holder force, working temperature and lubricant on limit drawing ration is investigated . Experiments are carried out for the hemisherical and sqare shape at room and warm temperature respectively. The drawing loads and thickness deviation accoring to process variables measured . As the result of apploying those experimental data to the commerical butt product, the number of process can be reduced and good quality of products can be obtained.

• 한국산업보건학회지
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• 제24권4호
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• pp.556-565
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• 2014

Objectives: This study is aimed at inquiring into the grasp of real condition of working environment and improvements by calculating the hypertension distribution consequent on job stress risk and exposure level of alleviating factors. In addition, this study is intending to estimate the hypertension distribution through socio-demographic factors and level of stressors occurring at working environment, such as high workload, low control, low support, job insecurity, long working hours, low income. Methods: This study estimated the hypertension distribution using the tertiary Korean Working Conditions Survey data, and conducted comparative analysis according to the category of individual questionnaire items using odds ratio. Result: As a result of study, it was found that in the event that working environment satisfaction is low and business & an immediate superior's attitudes are negative, the hypertension distribution was high. Particularly, it was found that physical risk factor musculoskeletal risk factor, and mental risk factor in a workplace were all increasing the hypertension distribution. Conclusions: With the aged workers' labor market participation ratio increasing, hypertension could be a major issue in the field of Occupational Safety and Health. Thus, it's necessary that the relevant employer should lower the hypertension distribution through creation of pleasant working environment and inducement of workers to improve in the relations with their superiors. As for the uppermost limit of this study, there is a limit to clarifying the mechanism of hypertension through multivariate statistics analysis because it's difficult to establish causal relationship by individual questionnaire item as the working conditions survey is made by cross-sectional study. In the follow-up research, this study is going to do research on the mechanism of hypertension through questionnaire supplementation and in-depth analysis.

• 한국보육지원학회지
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• 제16권1호
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• pp.75-98
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• 2020

Objective: This study aimed to examine the influences of household chaos on self-control of young children and to investigate whether teachers' limit-setting styles had moderating effects. Methods: The participants were 184 children (83 boys and 101 girls), at age 3 -5, their mothers and teachers working at daycare centers located in Seoul and Gyeonggi-do. The data were analyzed by descriptive statistics, Pearson's correlation, and hierarchical regression. Moderating effects were examined using the Mplus8.0 program. Results: The results indicated that household chaos as well as teacher's permissive and logical limit-setting styles had significant effects on self-control of preschoolers. The lower the level of household chaos was, the higher the level of self-control of preschoolers was. The level of self-control was more likely to be high when teachers used logical limit-setting with detailed explanation to children whereas it was lower when they used more permissive limit-setting. In addition, teachers' logical limit-setting moderated the relation between household chaos and self-control of preschoolers. That is, the effects of household chaos on preschoolers' self-control were mitigated when the level of logical limit-setting was high compared to when it was low. Conclusion/Implications: The results suggested that both household chaos and teachers' limit-setting styles play important roles in increasing self-control of preschoolers.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.28-35
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• 2005

It is now well recognized that the ultimate limit state approach is a much better basis for design and strength assessment of ships and offshore structures since it is difficult to determine the realistic margin of safety using the traditional allowable working stress approach on the basis of linear elastic method solutions together with buckling strengthchecks adjusted by a simple plasticity correction. This paper outlines ALPS theory for ultimate limit state assessment of ship structures. ALPS is a computer software which stands for nonlinear Analysis of Large Plated Structures. Application examples of ALPS program to ultimate limit state assessment of plates, stiffened panels and ship hull girders are presented. A benchmark study is made by a comparison with the ALPS solutions with other methods including class rule formulae, nonlinear finite element methods and experimental results. Future trends on ultimate limit state assessment of ship structures are addresse[1]

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.291-295
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• 2003

The occurrence of ductile fracture is the working limit of many metal forming processes. It is necessary to predict the criteria and to apply the condition in a process design. Over the years. the way for clarifying conditions have been studied and presented. However such a way needs lots of experiments and analysis. In this study, in order to determine the critical damage value of a used material Cu 4N, it was performed a tensile test and FEM analysis by using DEFORM 2D. For applying the obtained critical damage value it was also performed a upsetting test by using DEFORM 2D. The way of determining a critical damage value which is presented in this study will make possible to find easily it which is one of the working limit factor. And the way of determining a critical damage value will make possible to find in multi-pass drawing process.

• Bulletin of the Korean Chemical Society
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• 제29권9호
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• pp.1742-1746
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• 2008

Catechol and caffeine were simultaneously analyzed with a bismuth-immobilized carbon nanotube paste electrode (BPE) using square wave (SW) stripping voltammetry. Optimum analytical conditions were determined. Simultaneous working ranges of 100-1,500 $mgL^{-1}$ for caffeine and 5-75 $mgL^{-1}$ for catechol were obtained. In the separated cell systems, a working range of 0.1-2.1 $mgL^{-1}$ catechol with a correlation coefficient of 0.9935, and a working range of 10-210 $mgL^{-1}$ caffeine with a correlation coefficient of 0.9921 were obtained. A detection limit (S/N) of 0.15 $mgL^{-1}$ (7.7 ${\times}$ $10^{-7}$ M) and a detection limit of 0.02 $mgL^{-1}$ (1.82 ${\times}$ $10^{-7}$ M), respectively, manifested for catechol and caffeine. It was found that three macro-type electrode systems could be implanted in fish and rat neuro cells. For both ions, the ion currents were observed. The physiological impulse conditions and the neuronal thinking current were also obtained.

• 한국소음진동공학회논문집
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• 제12권6호
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• pp.437-444
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• 2002

This paper is to provide the basic way of a acoustical evaluation and efficient control noise by investigating the limits of perceptual loudness of living environment and by finding out any correlation between Physical characteristics of noise and psychoacoustic parameters. The limits of perceptual loudness were selected by the subjects in a chamber for residential and working environment. And the noise sources were analyzed to find out whether there is any correlation with Zwicker parameters and ACF factors. In this study especially, to set up the domestic evaluation grade about floor impact noise. we'd like to suggest the loudness Perception research result as fundamental resource for setting up the evaluation grade through the result that is based on annoyance. In the result of this research, upper limit of heavy-weight impact noise was L-60, and lower limit of it was L-50. On the other hand, upper limit of light-weight impact noise was L-70, and lower limit of it was L-55. It seemed that the loudness of noise from vacuum cleaner noise does not affect its perceived noisiness. Noises implicated In human such as floor walking noise and talking sound, are the most irritating noise in office environment.