• Journal of the Korean Society of School Health
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• v.21 no.2
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• pp.89-95
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• 2008

Purpose: The purpose of this study is to investigate the heavy metal pollution of playgrounds of elementary schools in the Ulsan Metropolitan City. Soil pollution is one of the most dangerous problems of the utmost concern to both children and teachers. The result of this study would be an educational datum for improving children's health and establishing educational policy. Methods: For the analysis, fifteen representative schools were selected from five sample areas such as Dong-gu, Nam-gu, Jung-gu, Buk-gu and Ulju-gun of the Ulsan city. And from each school playground, soil was extracted from five spots and mingled into one sample. These fifteen samples were pretreated by the microwave extraction method, and the extracted heavy metals(As, Cd, Cu, Pb, Cr⁶⁺, Zn and Hg) were quantified by the ICP(Inductively Coupled Plasma) system. Results: The results of the analysis shows that the level of heavy metal pollution of elementary school playgrounds in Ulsan city did not exceed the permitted limit of each heavy metal. This means that the soil pollution of playgrounds in the Ulsan Metropolitan City is not so serious as it is expected. But it should be added that the soil is not too safe to be ignored.

• Survey Research
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• v.3 no.1
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• pp.25-51
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• 2002

We examine the response patterns to web survey with a series of experiments embedded in a survey of students at the Sookmyung Women's University. A sample of 960 students was sent e-mail invitation to participate in a internet survey, The response rate was 53.9% except partial and overall non-response. Methodological experiments included the use of a pre-notification, reminder notices as well as the type of questionnaire. These factors that manipulate the perceived burden of the task had an effect on the likelihood of accepting the survey invitation. This paper discusses the overall implementation and outcome of the survey, and describes the results of the imbedded design experiments. Also we compared the representative of self-selected and probability sample.

• Korean journal of food and cookery science
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• v.30 no.2
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• pp.119-128
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• 2014

The purpose of this study is to propose the optimum adding rate of freeze-drying beet leaf powder, which has antioxidant components, that have superior DPPH radical extinction effects, in the Sulgidduk, a representative of steamed rice cake, which improve its functionality. According to the measured results on moisture contents and pH levels of Sulgidduk, with added freeze-drying beet leaf powder, the moisture contents have been significantly declined with increasing rates of added beet leaf powder. The pH levels of sample groups are within the range of 6.26-6.13. From the chromatography of measured results, lightness and yellowness have declined and redness have increased along with increasing rates of added beat leaf powder. According to the texture of measured results, the hardness, and chewiness have declined by the increasing the rate of added beet leaf powder. For the storage period, hardness, and chewiness have been inclined, but cohesiveness declines, with increased the storage period, while there are no changes from elasticity. The DPPH contents of Sulgidduk, with added freeze-drying beet leaf powder, inclined by increasing the rates of added beet leaf powder. The sensory test results of color, aroma and fragrance incline with increasing rates of added beet leaf powder. From acceptance test results, the sample group added with 3% receive the highest appraisals.

• Journal of Korea Soil Environment Society
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• v.3 no.2
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• pp.3-12
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• 1998

To analyze of oils in contaminated soils, it is necessary to classify of oils accurately and it has to be selected suitable extraction method and instrumental analysis method in according to the character of sample. In this study, oils are classified into three groups-gasoline, diesel and kerosene-we consider extraction methods and quantitative analysis method of these oils using GC/MS. As the analysis example of real sample, we analyze some gasolines and diesels of some oil refining company and calculate BTEX in gasoline and saturated n-hydrocarbons in diesel. And also, we study the representative quantitative method of each kind of oils.

• Journal of the Korean Dietetic Association
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• v.23 no.4
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• pp.397-407
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• 2017

This study was conducted to explore socio-demographic influences on eating behaviors among adolescents in Korea. Data were obtained from the Eleventh Korea Youth Risk Behavior Web-based Survey (2015 KYRBS), a nationwide representative sample of 3,532,149 middle and high school students. The data were analyzed by descriptive analysis, t-test, and logistic regression based on complex sample design using SPSS 20.0 statistics. The results showed that intake frequency of soda, fast food, and instant noodles was higher in male than female students (P<0.001). Additionally, the frequency of eating breakfast, fruits, vegetables, and milk was higher among high school students than middle school students (P<0.001). Higher levels of economic status were associated with less skipping breakfast. Adolescents with mothers that had higher levels of education were more likely to be frequent consumers of fruits, vegetables, and milk, and to eat breakfast.

• International Journal of Knowledge Content Development & Technology
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• v.10 no.3
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• pp.51-68
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• 2020

The library provides its services to satisfy the user's approach. Naturally, the development of library services may determine by considering the satisfaction of users. It traces users' perceptions regarding subject access highlighting problems in the retrieval of Bengali documents by subject. This study has designed to assess users' attitudes towards the retrievals of Bengali documents in OPAC through subject headings. For a collection of data, a representative sample has drawn from a large and heterogeneous population consisting of users in university libraries of West Bengal using a stratified sampling technique. Subsequently, under each of the universities, users' community was stratified into students, research scholars, and faculty members. Under each stratum, the sample selected on a random basis. The users met personally to collect relevant data, while they came to the library and went on to search OPAC. A structured schedule, prepared for the purpose, was presented before library users and consequently, interviews and interpretations recorded systematically. In this manner, several factors have identified concerning subject searching and retrieval performance for Bengali documents. This study explores the access using subject headings in multilingual information retrieval systems. Moreover, the suitability of subject headings for retrieval of Bengali resources has ascertained from the users' point of view. The findings demand standard principles and rules for the construction of Bengali subject headings to maintain uniformity and consistency.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.717-725
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• 1989

An experimental investigation on the combustion behavior of pulverized coal particles was performed using the cross-section micrography techniques while sample coal particles were collected in-situ from the flow reactor. The coal particles were representative of pulverized bituminous coal undergoing a raped pyrolysis and combustion, however, quenched at the time when the particles were deposited onto a sample plate. The internal structure of coal was observed to change as deposited. Upon injection into a flow reactor, bituminous coal particles showed many holes which represented internal pore formation during the pyrolysis. The relative portion of the remaining matrix of coal was decreasing as the residence time progressed. This direct observation of cross-section of burning particles enabled better understanding of the coal combustion behavior.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1120-1130
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• 2018

An analysis of a pyroprocessing safeguards methodology employing the Pu-to-$^{244}Cm$ ratio is presented. The analysis includes characterization of representative used nuclear fuel assemblies with respect to computed nuclide composition. The nuclide composition data computationally generated is appropriately reformatted to correspond with the material conditions after each step in the head-end stage of pyroprocessing. Uncertainty in the Pu-to-$^{244}Cm$ ratio is evaluated using the Geary-Hinkley transformation method. This is because the Pu-to-$^{244}Cm$ ratio is a Cauchy distribution since it is the ratio of two normally distributed random variables. The calculated uncertainty of the Pu-to-$^{244}Cm$ ratio is propagated through the mass flow stream in the pyroprocessing steps. Finally, the probability of Type-I error for the plutonium Material Unaccounted For (MUF) is evaluated by the hypothesis testing method as a function of the sizes of powder particles and granules, which are dominant parameters to determine the sample size. The results show the probability of Type-I error is occasionally greater than 5%. However, increasing granule sample sizes could surmount the weakness of material accounting because of the non-uniformity of nuclide composition.

• Safety and Health at Work
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• v.13 no.4
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• pp.482-486
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• 2022

Background: This study aimed to estimate the annual prevalence and incidence of urolithiasis stratified by work status based on a large nationwide sample. Methods: This study used data from the National Health Insurance Service-National Sample Cohort from 2002 to 2015. The prevalence and incidence of urolithiasis were estimated based on work status and gender stratification. The risk of urolithiasis among workers was calculated using age-standardized incidence ratio with stratification of work type. Results: The prevalence of urolithiasis was significantly higher in workers than in non-workers, especially men, during the follow-up period. The total estimated number of urolithiasis cases was 41,086 and the overall incidence of urolithiasis was 0.3%. The age-standardized incidence ratio of urolithiasis was significantly higher among the total workers (1.14; 95% confidence interval, 1.13-1.16), self-employed workers (1.08; 95% confidence interval, 1.06-1.11), and paid workers (1.19; 95% confidence interval, 1.17-1.21) than among the non-working population. Conclusions: Workers, especially paid workers and men, were vulnerable to urolithiasis. Further studies are required to investigate the effects of working conditions on urolithiasis.

• The Journal of the Korea Contents Association
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• v.18 no.2
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• pp.468-475
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• 2018

The current system of making course evaluations mandatory in universities in Korea in order to supplement low participation levels is a major hindering factor for the validity of the evaluation results due to students' insincere responses. This study points out the problems in course evaluations that are in the form of surveys and instead proposes a sample course evaluation system that utilizes a sample mean to deduce a population mean, attempting to prove through simulation that this is statistically significant. Thus, small, medium, and large scale courses as well as cyber courses that were available in S University in the fall 2016 semester were set as the population, and each course's evaluation average grade was set as the population mean. Furthermore, we used the average grade and standard deviation of the same courses from the previous year in order to decide the sample number, the reliability level was set as 95%, and the margin of error was set as ${\pm}0.25$. As a result of carrying out a simulation using the data analysis tool R, all the courses (small scale, medium scale, large scale, and cyber) showed to have a reliability level close to 95% including the population mean, and consequently practicality of the representative sample course evaluation system was proven.