• Journal of the Korean Geophysical Society
• /
• v.2 no.2
• /
• pp.143-152
• /
• 1999

We have studied a denoising technique involving wavelet transform for improving the quality of geophysical data during the preprocessing stage. To assess the effectiveness of this technique, we have made synthetic data contaminated by random noises and compared the results of denoising with those obtained by conventional low-pass filtering. The low-pass filtering of the sinusoidal signal having a sharp discontinuity between the first and last sample values shows apparent errors related to Gibbs' phenomena. For the case of bump signal, the low-pass filtering induces maximum errors on peak values by removing some high-frequency components of signal itself. The wavelet transform technique, however, denoises these signals with much less adverse effects owing to its pertinent properties on locality of wavelet and easy discrimination of noise and signal in the wavelet domain. The field data of gravity tide are denoised by using soft threshold, which shrinked all the wavelet coefficients toward the origin, and the G-factor is determined by comparing the denoised data and theoretical data.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
• /
• v.23 no.2
• /
• pp.76-81
• /
• 2012

Objectives : Childhood is a critical period involving various developmental tasks that need to be accomplished. Childhood depression has overall negative implications for certain areas of development, including cognition, emotion, social skills, academic achievement, and ability to cope with stress. Yet, because depression can be "masked" by accompanying behavioral problems, early detection and diagnosis of childhood depression is somewhat challenging. In this study, using the Korean version of the Child Behavior Checklist (K-CBCL), we evaluated the association between children's self reports on depression and parents' assessment of children's behaviors. Methods : Subjects were recruited from the S city, a cohort comprising a non-random convenience sample of 226, 10-year-old ethnic Koreans in their fourth year of elementary school and their parents. All participants underwent several tests, including Children's Depression Inventory (CDI) and K-CBCL. Results : A total of 226 children, including 166 boys (73.5%) and 60 girls (26.5%), participated in the study. The average CDI for the participants was 14.57 (SD=7.54). Two items on the K-CBCL, total scale of adjustment scale and social withdrawal problems, showed a close association with the CDI. Conclusion : Although much remains to be elucidated, after controlling for covariates, the results of this study suggested that behavioral problems observed in children may be closely associated with depression.

• Journal of the Korean Chemical Society
• /
• v.6 no.1
• /
• pp.25-28
• /
• 1962

The colorimetric estimation, by dithiol method, of the solubility of tin dissolved from the container the tin plate in some canned marine foods has been made on 200 cans of sample on the market. Some of them contained more than 150 ppm of Sn concentration were as follows; (1) ca. 50% of squid can, (2)ca. 30% of mackerel can, (3) ca. of saury can, (4) naught of crab, whale, clam(Japanese hard clams), fish meat ball, and Turbo cornutus one. (1) It had the tendency of increasing Sn concentration according to lowering or arising the value of pH. (2) No significant difference in Sn concentration was caused by the variation of the sort of tinning as H-D or E-T. (3) The longer the period of the storage the higher Sn concentration was found, and the concentration more than 150 ppm of Sn was generally found among the cans stored more than twelve months. (4) The concentration of Sn in the liquid was higher than in solid portion, and most of dissolved Sn was distributed in the liquid portion.

• Journal of the Korean Data and Information Science Society
• /
• v.27 no.1
• /
• pp.111-120
• /
• 2016

In usual, the discontinuous variance function was estimated nonparametrically using a kernel type estimator with data sets split by an estimated location of the change point. Kang et al. (2000) proposed the Gasser-$M{\ddot{u}}ller$ type kernel estimator of the discontinuous regression function using the adjusted observations of response variable by the estimated jump size of the change point in $M{\ddot{u}}ller$ (1992). The adjusted observations might be a random sample coming from a continuous regression function. In this paper, we estimate the variance function using the Nadaraya-Watson kernel type estimator using the adjusted squared residuals by the estimated location of the change point in the discontinuous variance function like Kang et al. (2000) did. The rate of convergence of integrated squared error of the proposed variance estimator is derived and numerical work demonstrates the improved performance of the method over the exist one with simulated examples.

• Journal of the Korean Data and Information Science Society
• /
• v.21 no.2
• /
• pp.231-240
• /
• 2010

If only fixed effects exist in a 4 $\times$ 4 balanced incomplete block design, powers of FR statistic for testing a main effect show the highest level with a few replications. Under the exponential and double exponential distributions, FR statistic shows relatively high powers with big differences as compared with the F statistic. Further in a traditional balanced incomplete block design, powers of FR statistic having a fixed main effect and a random block effect show superior preference for all situations without regard to the effect size of a main effect, the parameter size and the type of population distributions of a block effect. Powers of FR statistic increase in a high speed as replications increase. Overall power preference of FR statistic for testing a main effect is caused by unique characteristic of a balanced incomplete block design having one main and block effect with missing observations, which sensitively responds to small increase of main effect and sample size.

• Journal of Environmental Health Sciences
• /
• v.30 no.2
• /
• pp.173-183
• /
• 2004

The purpose of the present study was to assess food hygiene and safety knowledge, attitudes, and practices of food-service personnel in school food-service programs and to find factors affecting their knowledge, attitudes, and practices. A self-administered questionnaire was offered to a random sample of 40 kitchen employees in elementary schools in one region of Korea, with 37 completing the survey, a response rate of 92.5%. The survey was carried out over a two-month period (April-May, 2001). Knowledge score of the employees was high with a mean/standard deviation of 4.75/0.32 on a 5.0-point scale. They had significantly lower attitude score (4.55$\pm$0.33) and practice score (4.55$\pm$0.45) compared to the score of knowledge (p＜0.05). Logistic regression analysis showed that (1) the employees＇ education level and work experience in school food-service programs affected their knowledge, (2) age, level of living, monthly income, and housing type affected their attitudes, and (3) monthly income, level of living, housing type, and work experience in school food-service programs affected their practices. Pearson＇s correlation analysis confirmed that the knowledge and attitude scores were significantly correlated (r=0.598, p＜0.001). The results indicate that the knowledge, attitude, and practice levels of the employees regarding the food hygiene and safety were better than expected, however, the results suggest a need for the adoption of approaches which take account of socio-economic and environmental influences on behavior to improve and maintain their practice level. The food-handling practices of school food-service employees need to be monitored routinely in order to ensure that safe food is served to our school children.

• Imaging Science in Dentistry
• /
• v.46 no.2
• /
• pp.109-115
• /
• 2016

Purpose: Sinus elevation procedures have become a routine and reliable way to gain bone volume in the edentulous maxilla for dental implant placement. Presence of bony septations and pathology in the maxillary sinus often cause complications leading to graft or implant failure or both. The aim of this study was to retrospectively evaluate the prevalence of pathology, direction of the septa, and sinus width measured at 2 mm, 5 mm, and 10 mm from the sinus floor in maxillary sinuses using cone-beam computed tomography (CBCT). Materials and Methods: Seventy-two sinuses from 36 random preoperative CBCT scans referred for implant therapy were retrospectively evaluated for the number, prevalence, and direction of bony septations and presence of pathology. Width of the sinus was also measured at 2 mm, 5 mm, and 10 mm from the sinus floor to account for the amount of bone available for implant placement. Results: Maxillary sinus septa were found in 59.7%. Presence of a single septum was noted in 20 sinuses (27.7%), followed by two septa in 17 sinuses. The most common direction of the septum was the transverse direction. Retention pseudocyst and mucosal thickening were the most commonly seen abnormality/pathology. Conclusion: Based on the high prevalence of septa and sinus pathology in this sample, a preoperative CBCT scan might be helpful in minimizing complications during sinus augmentation procedures for dental implant therapy.

• Korean Journal of Health Education and Promotion
• /
• v.26 no.4
• /
• pp.49-62
• /
• 2009

Objectives: Few studies have focused on health behaviors and health status among teachers even though these are one of principles and values of WHO's Health Promoting Schools. In this study, we described health behaviors and health status among teachers and explored the differences of these by personal and school characteristics. Methods: A stratified and random cluster sampling design was used to obtain a cross-sectional sample. A total of 59 elementary, middle and high schools in Seoul and Gyeonggi areas were included in which 333 teachers (males 40.6%, females 59.4%) participated in this survey. Chi-square tests were conducted with SPSS 17.1. Results: Overall, health behaviors and health status among teachers were better than the general public according to Korea National Health and Nutrition Examination Survey. Male and middle/high school teachers had higher prevalence of alcohol dependence and of driving under the influence of alcohol. Also, their rate of wearing seat belts were lower compare to female. In other hand, female, health and nutrition teachers, rural school teachers had lower prevalence of meeting recommended levels of physical activity. Underweight were more prevalent to them in contrast to male with higher prevalence of obesity. In addition, teachers of health promoting schools were not likely to ride on a car with a drunk driver. They also have a lower prevalence of skipping breakfast and have higher positive perception of health for themselves. Conclusion: Teachers' health should be given higher concerns as a key component of school based health promotion. Gender and age specific programs should be considered to develop health promoting programs for them.

• Transactions on Electrical and Electronic Materials
• /
• v.5 no.6
• /
• pp.223-226
• /
• 2004

The PZT thin films are one of well-known materials that has been widely studied for ferroelectric random access memory (FRAM). We etched the PZT thin films by $CF_{4}/(Cl_{2}+Ar)$ plasma and investigated improvement in etching damage by $O_{2}$ annealing. The maximum etch rate of the PZT thin films was 157 nrn/min and that the selectivity of the PZT thin films to Pt was 3.1 when $CF_{4}(30{\%})$ was added to a $Cl_{2}(80{\%})/Ar(20{\%})$ gas mixing ratio. To improve the ferroelectric properties of PZT thin films after etching, the samples were annealed for 10 min at various temperatures in $O_{2}$ atmosphere. After $O_{2}$ annealing, the remanent polarization of the asdeposited films was $34.6{\mu}/cm^{2}$ and the sample annealed at 650, 550, and $450^{\circ}C$ was 32.8, 22.3, and $18.6{\mu}/cm^{2}$, respectively. PZT thin films with $O_{2}$ annealing at $450^{\circ}C$ retained $77{\%}$ of their original polarization at 106 cycles. Also as the annealing temperature increased, the fatigue properties improved. And the leakage current was decreased gradually and almost recovered to the as-deposited value after the annealing at $450^{\circ}C$.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.3D
• /
• pp.355-361
• /
• 2011

In order to properly evaluate ITS services exposed in SMART Highway project, a confident dynamic origin-destination (OD) is inevitably needed. This paper used WAVE communication information as a part of call and response (C&R) communication which constitutes core part of the technology for constructing OD. This information includes node information and vehicle information (e.g., latitude and longitude) as well as trajectory data and sample path volume date calculated using node information and vehicle information. A procedure developed to construct a dynamic OD and to validate OD is consist of 1) making toy network and one-hour 00 (random distribution), 2) collecting link information and vehicle information, 3) constructing five-minute OD, and 4) validating estimated OD result using traffic volume and travel time simultaneously. The constructed OD is about 84.79% correct within less than 20% error range for 15min traffic volume, and about 85.42%, within less than 20% error rate of 15 min travel time. Some limitations and future research agenda have also been discussed.