• Korean Journal of Remote Sensing
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• v.23 no.6
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• pp.559-566
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• 2007

The generation of precise digital elevation model (DEM) is very important in coastal area where time series are especially required. Although a LIDAR system is useful in coastal regions, it is not yet popular in Korea mainly because of its high surveying cost and national security reasons. Recently, precise DEM has been made using radar interferometry and waterline methods. One of these methods, spaceborne imaging radar interferometry has been widely used to measure the topography and deformation of the Earth. We acquired ALOS PALSAR FBD mode (Fine Beam Dual) data for evaluating the quality of interferograms and their coherency. We attempted to construct DEM using ALOS PALSAR pairs - One pair is 2007/05/22 and 2007/08/22, another pair is 2007/08/22 and 2007/10/22 with respective perpendicular baseline of 820 m, 312m and respective height sensitivity of 75 m and 185m at southern of Ganghwa tidal flat, Siwha- and Hwaong-lake over west coastal of Korea peninsula. Ganghwa tidal flat has low coherence between 0.3 and 0.5 of 2007/05/22 and 2007/08/22 pair. However, Siwha-lake and Hwaong-lake areas have a higher coherence value (From 0.7 and 0.9) than Ganghwa tidal area. The reason of difference coherence value is tidal condition between tidal flat area (Ganghwa) and reclaimed zone (Siwha-lake and Hwaong-lake). Therefore, DEM was constructed by ALOS PALSAR pair over Siwha-lake and Hwaong-lake. If the temporal baseline is enough short to maintain the coherent phases and height sensitivity is enough small, we will be able to successfully construct a precise DEM over coastal area. From now on, more ALOS PALSAR data will be needed to construct precise DEM of West Coast of Korea peninsular.

• Korean Journal of Remote Sensing
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• v.25 no.4
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• pp.383-389
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• 2009

The main objective of the research is a feasibility study on the intertidal zone using a X-band radar satellite, TerraSAR-X. The TerraSAR-X data have been acquired in the west coast of Korea where large tidal flats, Ganghwa and Yeongjong tidal flats, are developed. Investigations include: 1) waterline and backscattering characteristics of the high resolution X-band images in tidal flats; 2) polarimetric signature of halophytes (or salt marsh plants), specifically Suaeda japonica; and 3) phase and coherence of interferometric pairs. Waterlines from TerraSAR-X data satisfy the requirement of horizontal accuracy of 60 m that corresponds to 20 cm in average height difference while current other spaceborne SAR systems could not meet the requirement. HH-polarization was the best for extraction of waterline, and its geometric position is reliable due to the short wavelength and accurate orbit control of the TerraSAR-X. A halophyte or salt marsh plant, Suaeda japonica, is an indicator of local sea level change. From X-band ground radar measurements, a dual polarization of VV/VH-pol. is anticipated to be the best for detection of the plant with about 9 dB difference at 35 degree incidence angle. However, TerraSAR-X HH/TV dual polarization was turned to be more effective for salt marsh monitoring. The HH-HV value was the maximum of about 7.9 dB at 31.6 degree incidence angle, which is fairly consistent with the results of X-band ground radar measurement. The boundary of salt marsh is effectively traceable specifically by TerraSAR-X cross-polarization data. While interferometric phase is not coherent within normal tidal flat, areas of salt marsh where the landization is preceded show coherent interferometric phases regardless of seasons or tide conditions. Although TerraSAR-X interferometry may not be effective to directly measure height or changes in tidal flat surface, TanDEM-X or other future X-band SAR tandem missions within one-day interval would be useful for mapping tidal flat topography.

• Journal of Preventive Medicine and Public Health
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• v.25 no.3 s.39
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• pp.247-268
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• 1992

This study was conducted to evaluate the effect of VDT work on eyes and vision among workers in a TV manufacturing plant. The study subjects consisted of 264 screen workers and 74 non-screen workers who were less than 40 years old male and had no history of opthalmic diseases such as corneal opacities, trauma, keratitis, etc and whose visual acuity on pre-employment health examination by Han's test chart was 1.0 or above. The screen workers were divided into two groups by actual time for screen work in a day : Group I, 60 workers, lesser than 4 hours a day and group II, 204 workers, more than 4 hours a day. From July to October 1992 a questionnaire was administered to all the study subjects for the general charateristics and subjective eye symptoms after which the opthalmologic tests such as visual acuity, spherical equivalent, lacrimal function, ocular pressure, slit lamp test, fundoscopy were conducted by one opthalmologist. The proportion of workers whose present visual acuity was decreased more than 0.15 in comparison with that on the pre-employment health examination by Han's test chart was 20.6% in Group II. 15.0% in Group I and 14.9% in non-screen workers. However, the differences in proportion were not statistically significant. The proportion of workers with decreased visual acuity was not associated with the age, working duration, use of magnifying glass and type of shift work (independent variables) in all of the three groups. However, screen workers working under poor illumination had a higher proportion of persons with decreased visual acuity than those working under adequate illumination (P<0.05) . The proportion of workers whose near vision was decreased was 27.5% in Group II, 18.3% in Group I, and 28.4% in non-screen workers and these differences in proportion were not statistically significant. Changes of near vision were not associated with 4 independent variables in all of the three groups. Six out of seven subjective eye symptoms except tearing were more common in Group I than in non-screen workers and more common in Group II than in Group I (P<0.01). Mean of the total scores for seven subjective symptoms of each worker(2 points for always, 1 point for sometimes, 0 point for never) was not significantly different between workers with decreased visual acuity and workers with no vision change. However, mean of the total scores for Group II was higher than those for the Group I and non-screen workers (P<0.01). Total eye symptom scores were significantly correlated with the grade of screen work, use of magnifying glass, and type of shift work. There was no independent variable which was correlated with the difference in visual acuity between the pre-employment health examination and the present state, the difference between far and near visions, lacrimal function, ocular pressure, and spherical equivalent. Multiple linear regression analysis for the subjective eye symptom scores revealed a positive linear relationship with actual time for screen work and shift work(P<0.01). In this study it was not observed that the VDT work decreased visual acuity but it induces subjective eye symptoms such as eye fatigue, blurred vision, ocular discomfort, etc. Maintenance of adequate illumination in the work place and control of excessive VDT work are recommended to prevent such eye symptoms.

• Journal of agricultural medicine and community health
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• v.25 no.2
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• pp.397-411
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• 2000

The present study was conducted to analyze the degree of changes in knowledge and attitude toward health, arid health promoting activities after providing health education intervention for a year to elementary school children, to examine the factors effecting knowledge, attitude and health promoting practices for obesity and diet, and to analyze whether changes are present in health level according to changes in knowledge on health and health promoting activities. After conducting a pre-survey rio 354 subjects of 3rd and 4th grade students and their mothers in the city area of Kyungju, in April, 1999, 301. responses with the responding rate of 85% were obtained. Final analysis was done with 231 pairs of a student and his/her mother who could be followed up after a year among 301 pairs of the respondents, excluding those students who transferred, those who were excused from school early, those who did not take abdominal fat measurements, and those students and mothers respondents whose survey was incomplete. Based on the changes before and after the intervention, the scores on knowledge about obesity and diet showed a significant difference in normal weight group, and the scores on the attitude toward obesity and diet increased significantly in obesity group but decreased significantly in normal weight group(p<0.01). The scores of practicing health promoting activities were significantly increased in both groups, and although the waist-hip ratio (WHR) did not change in obesity group, the rate increased significantly in normal weight group(p<0.01). As for changes on the knowledge of obesity and diet before and after the intervention while dividing the scores into 3 levels based on the scores of the pre-survey and compared to changes in the scores one year after, in the case of the changes in the scores in the 1st third, the score on the knowledge about obesity and diet changed from 1.3 in the pre survey to 3.7 after the intervention, showing significant increase(p<0.01) The scores of practicing health promoting activities for obesity and diet were significantly increase in all three levels(p<0.01), and the degree of changes in the scores was 7.0 points in the 1st third, 4.4 points for the and third and 1.8 points for the 3rd third, showing a significant difference among the three levels(p<0.01). It was shown that the increase in BMI in those students whose mothers have the education level higher than university was significantly higher than the increase in BMI in those students whose mothers have the education level under high school, and those students whose mothers are in their 30's showed higher changes in practicing health promoting activities for obesity and diet. When the scores of mothers' knowledge and attitude toward obesity and diet were compared by dividing the scores into tertile, the score of students' knowledge changed significantly according to the scores of mothers' attitude toward obesity and diet. In multiple regression analysis on changes in the scores of knowledge about obesity and diet, the student variables of the degree of awareness on the seriousness of obesity, and the scores of previous knowledge on diet and obesity were selected the significant variables, and among the mother variables, the degree of guiding the child on diet and the education level were the significant variables. In multiple regression analysis to analyze the factors effecting changes in the attitude toward obesity and diet, the student variables of the BMI, scores of previous knowledge on obesity and diet, and scores on the previous attitude toward obesity and diet were shown to be significant. In multiple regression analysis on the factors effecting changes in health promoting activities for obesity and diet, the student variables of the BMI, scores on the previous attitude toward obesity and diet, and changes in the scores of obesity and diet were selected the significant variables.