• Journal of the Korean Electrochemical Society
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• v.4 no.3
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• pp.104-108
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• 2001

Naphthalene derived mesophase pitch WP) was spun into short fibers by using melt-blown technology. The pitch fibers oxidative stabilization were carried out heating rates of $2^{\circ}C/min,\;5^{\circ}C/min\;and\; 10^{\circ}/min$. The heating rate was a key factor to maximate the capacity of the Li-ion secondary battery through controlling the morphology of the graphitized fiber. The diameters of the melt-blown fibers prepared were in the range of $4{\mu}m\~16{\mu}m$ with functions of air jet speed, air temperature and the temperature of the nozzle. The graphitized fibers of $10{\mu}m$ diameters showed various morphological structure with heating rate of the stabilization. Radial, radial-random and skin-core cross-sectional structure of the fibers were observed at the respective heating rate of $2^{\circ}C/min\;5^{\circ}C/min\;and\;10^{\circ}C/min$. Most crystalline structure of graphite was obtained from the fiber stabilized at heating rate of $10^{\circ}C/min$ exhibiting the best anode performance with 400 mAh/g of capacitance and $96.8\%$ of charge/discharge efficiency.

• Journal of Korean society of Dental Hygiene
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• v.16 no.6
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• pp.969-978
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• 2016

Objectives: The purpose of the study was to examine the expected role and competency of future public health dental hygienist. Methods: This study was cross-sectional design. One dental hygienist per 16 cities and provinces was selected from the list of Korea Society of public dental hygienists. After signing in the informed consent, the interview was carried out. Transcripts were made after each interview. Six researchers recorded meaningful contents in the transcripts. They classified and integrated the information that they had recorded commonly or not. Their opinions were converged by conference. Two supervisors verified results whether they were derived from actual recordings for the reliability of the results. The records were confirmed once again and corrected into common message. Results: The main difficult subjects in public health official examination were public health, English, and medical legislation to pass the examine. The preliminary certificates included public health related certificate, computer certificate, and driver's license. In the personality aspect, creativity, activeness, cooperation and good responsibility were very important trait to public health official. Among 16 interviews, 9 were positive and 5 were negative about the future prospects of a public dental hygienist. Conclusions: The future of public health dental hygienist will be positive. Throughout effort to prepare for the public health official, the public health dental hygienist will be expanded and in many ways the dental hygienists will take the charge of the important parts of the public health administration in the near future.

• Journal of International Academy of Physical Therapy Research
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• v.5 no.1
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• pp.661-667
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• 2014

This study is a cross-sectional study for conscripts with chronic low back pain, where it is designed to investigate general characteristics that conscripts with chronic low back pain carry, and it is also aimed to analyze the correlation as well as discrepancy within pain, depression and body mass index depending on their ranks. In this study, 90 Korean conscripts with chronic low back pain participated. And in order to analyze general characteristics as well as pain, depression and body mass index of the subjects, this study adopted a survey questionnaire upon general characteristics, and it also employed Visual Analogue Scacle(VAS) and Center for Epidemiological Studies Depression(CES-D) Scale which have proven their credibility, where BMI values for the subjects were calculated based on 'Asian Pacific standard' Body Mass Index(BMI). From the general characteristics exhibited by the subjects through this study, average age and average height of the subjects were $20.78{\pm}1.41$ and $175.97{\pm}5.34$ respectively; and corporals displayed the highest ratio of 42% with the chronic low back pain while 40% of the total subjects experienced the duration of the illness less than 6 to 9 months. Moreover, 57.8% of all subjects were reportedly suffering moderate pain, and 48% exhibited depression while 49% carried BMI value between 18.5 and $22.9kg/m^2$(normal range). Based on the analysis of correlation among pain, depression, discrepancy of BMI depending on the ranks and each independent variable, it appears that there is no significant difference amongst the ranks, and there is no correlation between independent variables; however, it was obvious that all groups divided by the ranks had a moderate pain(45-74mm), depression(${\geq}16$) and BMI value in normal range(18.5-22.9).

• Tunnel and Underground Space
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• v.29 no.6
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• pp.480-507
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• 2019

This paper aims at optimizing the auxiliary ventilation system in large-opening limestone mines with unducted fans. An extensive CFD and also site study were carried out for optimization at the blind entries. The fan location, operating mode, and layout are the parameters for optimization. Since the jet stream discharged from the auxiliary fan is flowing faster than 15 m/s in most of the cases, the stream collides with floor, sides or roof and even with the jet stream generated from the other fan placed upstream. Then, it is likely to lose a large portion of its inertial force and then its ventilation efficiency drops considerably. Therefore, the optimal fan installation interval is defined in this study as an interval that maximizes the uninterrupted flowing distance of the jet stream, while the cross-sectional installation location can be optimized to minimize the energy loss due to possible collision with the entry sides. Consequently, the optimization of the fan location will improve ventilation efficiency and subsequently the energy cost. A number of different three-dimensional computational domains representing a full-scale underground space were developed for the CFD study. The velocity profiles and the CO concentrations were studied to design and optimize the auxiliary ventilation system without duct and at the same time mine site experiments were carried out for comparison purposes. The ultimate goal is to optimize the auxiliary ventilation system without tubing to provide a reliable, low-cost and efficient solution to maintain the clean and safe work environment in local large-opening underground limestone mines.

• The Korean Journal of Applied Statistics
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• v.33 no.3
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• pp.281-296
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• 2020

Repeated outcomes from the same subjects are referred to as longitudinal data. Analysis of the data requires different methods unlike cross-sectional data analysis. It is important to model the covariance matrix because the correlation between the repeated outcomes must be considered when estimating the effects of covariates on the mean response. However, the modeling of the covariance matrix is tricky because there are many parameters to be estimated, and the estimated covariance matrix should be positive definite. In this paper, we consider analysis of multivariate longitudinal data via two modeling methodologies for the covariance matrix for multivariate longitudinal data. Both methods describe serial correlations of multivariate longitudinal outcomes using a modified Cholesky decomposition. However, the two methods consider different decompositions to explain the correlation between simultaneous responses. The first method uses enhanced linear covariance models so that the covariance matrix satisfies a positive definiteness condition; in addition, and principal component analysis and maximization-minimization algorithm (MM algorithm) were used to estimate model parameters. The second method considers variance-correlation decomposition and hypersphere decomposition to model covariance matrix. Simulations are used to compare the performance of the two methodologies.

• 한국해양학회지
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• v.30 no.4
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• pp.237-249
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• 1995

To understand the cross-sectional structures of temperature, salinity and current across the Korea Strait, field measurements were carried out for the period of May 2 to 20, 1994. Using the R/V Tam Yang, detailed CTD profiles and ADCP records were obtained and used to examine the mean and variability field on two time scales (15 days and 25 hours). A sharp coastal front in the middle of the Korea Strait exists across which two different water masses, i.e., warm and saline water in the eastern side and cold and less saline water in the western side are neighboring. We observed highly variable field of T and S apparently caused by the westward movement of warm and saline water mass. Short-term fluctuations of T and S in the middle layer are remarkable and their importance was analysed as the first Eigen mode accounting for more than 50% of total variances. The currents in th Korea Strait are strongly influenced by tidal currents with spring and neap variation whose maximum speed ranges 80-90 and 60-70 cm/s respectively near the central portion of the channel. Strong southward tidal current could even mask the Tsushima Current completely. Results of harmonic analysis show that the magnitudes of semidiurnal, diurnal and mean components of currents are comparable to each other at spring and neap tide conditions. The volume transport across the western channel of the Korea Strait were estimated to be 2.1 Sv at neap tide condition and 3.4 Sv at spring tide condition.

• Journal of Preventive Medicine and Public Health
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• v.24 no.4 s.36
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• pp.496-506
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• 1991

A cross-sectional study was conducted to investigate the effect of long term noise exposure on blood pressure among steel mill workers. The workers participated in periodic medical examinations performed from August 27 to September 6 in 1990. Examined were 1,034 workers with high-level noise exposure(average $91.8{\pm}5.2dB(A)$) and 390 workers with low-level noise exposure(average $75.2{\pm}4.6dB(A)$). No significant difference was found in systolic or diastolic flood pressure between the two exposure groups. Prevalence of hypertension (${\geq}160mmHg\;systolic\;or{\geq}100mmHg\;diastolic$) was higher in a younger age group (${\leq}40$ years old) of high-level noise exposure than of low-level noise exposure. However, the difference was not statistically significant. Furthermore, in younger ages, prevalence of hypertension appeared to be higher in the hearing loss group (${\geq}25dB\;at\;1000Hz\;or{\geq}40dB$ at 4000Hz in at least one ear) than in the normal hearing group. From multiple regression analysis, hearing loss, body mass index, age, alcohol and family history of hypertension were proven to be predictors of diastolic blood Pressure (p<0.02). When regression was performed for each age group, hearing loss was a strong predictor of diastolic pressure in the younger age group (p<0.01).

• Journal of Preventive Medicine and Public Health
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• v.38 no.4
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• pp.391-400
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• 2005

Objective : This study examined the socioeconomic differentials for the health and health related behaviors among South Korean middle school students. Methods : A nationwide cross-sectional interview survey of 3,449 middle school second-grade students and their parents was conducted using a stratified multi-stage cluster sampling method. The response rate was 93.3%. The socioeconomic position indicators were based on self-reported information from the students and their parents: parental education, father's occupational class, monthly family income, out-of-pocket expenditure for education, housing ownership, educational expectations, educational performance and the perceived economic hardships. The outcome variables that were measured were also based on the self-reported information from the students. The health measures included self-rated health conditions, psychological or mental problems, the feelings of loneliness at school, the overall satisfaction of life and the perceived level of stress. The health related behaviors included were smoking, alcohol drinking, sexual intercourse, violence, bullying and verbal and physical abuse by parents. Results : Socioeconomic differences for the health and health related behaviors were found among the eighth grade boys and girls of South Korea. However, the pattern varied with gender, the socioeconomic position indicators and the outcome measures. The prevalence rates of the overall dissatisfaction with life for both genders differed according to most of the eight socioeconomic position indicators. All the health measures were significantly different according to the perceived economic hardship. However, the socioeconomic differences in the self-rated health conditions and the psychosocial or mental problems were not clear. The students having higher socioeconomic position tended to be a perpetrator of bullying while those students with lower socioeconomic position were more likely to be a victim. Conclusions : The perceived economic hardships predicted the health status among the eighth graders of South Korea. The overall satisfaction of life was associated with the socioeconomic position indicators. Further research efforts are needed to explore the mechanisms on how and why the socioeconomic position affects the health and health related behaviors in this age group.

• Journal of Preventive Medicine and Public Health
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• v.30 no.4 s.59
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• pp.729-740
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• 1997

To determine the relationship between hypertension and nutrient intake cross-sectional study were performed in a rural area. Adult resident over 30-year-old age were measured blood pressure and body mass index(BMI), and interviewed about food in-take for the previous 24 hours. 250 men and 297 women participated the survey. Significant correlation was showen in men between mean systolic blood pressure and protein density. Significant correlation with mean diastolic blood pressure was showen on protein density, protein energy(%), calcium density and energy-adjusted protein in men. We analysed risk factor for hypertension adjust the effect of age, BMI, sex and family history by multiple logistic regression. Protein density(odds ratio=3.18), fat density(odds ratio=1.94) and energy-adjusted protein(odds ratio=1.01) intake were positively associated with hypertension but sodium density(odds ratio=0.73) was showen to have inverse relationship.

• Journal of Preventive Medicine and Public Health
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• v.30 no.4 s.59
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• pp.779-790
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• 1997

The Association between myofascial pain syndrome and some tests was assessed in a cross-sectional study of 904 female telephone operators using video display terminals(VDTs). 105 cases were diagnosed as Myofascial pain syndrome with symptom questionnaire, laboratory examination and physician's physical examination and 550 controls were defined to show only musculoskeletal symptoms using NIOSH symptom criteria. Data on demographics, musculoskeletal symptom and visual analogue scale(VAS) were obtained by questionnaire. Anthropometric measurements, pressure pain threshold, Grip & Pinch strength and laboratory test were conducted. No significant difference between case and control at comparing of demographics, occupational history and body measurements were observed. But, Grip strength, pressure pain threshold and VAS showed the statistical difference between case and controt. Age, pressure pain threshold of Rt. Upper trapezius and VAS were associated with myofascial pain syndrome in multivariate logistic regression analysis. This results suggest that, to diagnose of myofascial pain syndrome, the consideration of the objective aspects among patients' subjective symptom complaints through the VAS and pressure pain threshold is required.