• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.4
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• pp.269-275
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• 2004

Photovoltaic(PV) system has been studied and watched with keen interest due to a clean and renewable power source. But, the output power of PV system is not only unstable but uncontrollable, because the maximum power point tracking (MPPT) of PV system is still hard with the tracking failure under the sudden fluctuation of irradiance. Authors suggest that the optimal voltage for MPPT be obtained by only solar cell temperature. Having an eye on that the optimal voltage point of solar cell is in proportion to its panel temperature, with operating the power converter whose operating point keeps its input voltage to the optimal voltage imagined by the surface's temperature of PV panel, the maximum power point becomes tenderly possible to be tracked. In order to confirm the availability of the proposed control scheme. And both control methods are simulated not only on the various angle of sampling time of switching control, but also with the real field weather condition. As the results of that, the conversion efficiency between PV panel and converter of the proposed control scheme was much better than that of the power comparison MPPT control, and what is better, the output voltage of PV panel was extremely in stable when the optimal voltage for MPPT is obtained by only solar cell temperature.

• Women's Health Nursing
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• v.19 no.4
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• pp.285-294
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• 2013

Purpose: The study was done to survey feminine hygiene and vaginal douche practices in middle-aged women to obtain basic information for public health education. Methods: With a descriptive survey design, 134 middle-aged women who have menstrual period were recruited via convenience sampling. Survey contents were from the study by Czerwinski (2000) regarding feminine hygiene and vaginal douching practices. After obtaining IRB approval, a self-administered structured questionnaire was distributed to study participants. Results: Mean age of middle-aged women was 46.88 years old. Fifty-six percent of the women practiced vaginal douching. Women performed douching with water (68%), commercial products (13%), soap (12%), and vinegar-mixed water (6%) for clean and fresh feeling, removal of unpleasant odor, and removal of vaginal discharge. Vaginal douche practice was significantly related to a history of vaginitis. Conclusion: The study results indicate that most of the women practiced inadequate feminine hygiene especially in douching, suggesting that is important to develop education programs on feminine hygiene practices for women of all ages, especially regarding douching and hand washing before and after changing pads or tampons.

• Korean journal of food and cookery science
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• v.15 no.4
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• pp.327-337
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• 1999

This study was conducted on a sampling of 700 mixed college students from seven different schools nationwide by written questionnaire to evaluate the value system of convenience foods among Korean college students. Korean students put value on the following categories of convenience foods in order; convenience, taste, price, appearance, appliance to daily life, variety, locality, nutritional value, originality, improvement required, cleanliness and tradition. Significant differences between the sexes occurred in categories as cleanliness and convenience, since females considered convenience foods as convenient but not so clean (safe to eat). This study also conducted factor analysis on 24 individual convenient foods. Noodles laid emphasis on nutritional value; where refrigerated foods, ready to eat (RE) side dishes, on-the-spot kimbab, and sandwiches focused on cleanliness. Noodles. cereal, and instant soup focused on price. Frozen pizza, noodles, retort, RE meat, ham, fish cakes were dependent on locality and traditionality. Noodles, instant food, and packed kimchi scored highly on convenience. Frozen fried rice, retort, instant porridge, instant rice, RE meat, cereal, instant soup, and RE side dishes on consumption on a regular basis. Cereal, refrigerated foods, and RE side dishes laid emphasis on taste. Noodles, instant rice, cereal, ham, and RE side dishes focused on variety. Retort, RE meat, ramen, cereal, ham, and on the spot sandwiches looked to originality, while canned foods was recognized as ‘needing improvement’.

• Ocean and Polar Research
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• v.43 no.4
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• pp.335-352
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• 2021

Trace elements in the ocean have been known as essential micronutrients for the primary production of phytoplankton and the growth of marine organisms. The GEOTRACES program beginning in the mid-2000 provided a new understanding of the distribution, origin and behavior of trace elements in the ocean, together with the establishment of both clean seawater sampling and trace element analysis techniques. The Indian Ocean, one of the major oceans, is relatively the least explored area, despite playing an important role in global climate variability. Although trace element observations have recently been conducted in the Indian Ocean by Japanese-and Indian scientists, relatively not much study has been done compared to the Atlantic, Pacific and Polar Regions. Recently, together with the launch of R/V Isabu, a 5,000-ton grade large- and comprehensive research vessel, the observations of trace elements has been conducted in the Indian Ocean for the first time in Korea since 2018. In this paper, we introduce the key results of currently conducted GEOTRACES expedition in the Indian Ocean to present future trace element research directions in the Indian Ocean, and also reviewed the preliminary results in the Indian Ocean studies from Korea. In the 2020s, new Indian Ocean GEOTRACES projects are planned around European countries, and it is time for Korea to prepare for the next phase of the trace element study in the Indian Ocean in line with these international trends.

• Journal of Soil and Groundwater Environment
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• v.12 no.4
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• pp.16-24
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• 2007

An investigation on the polluted sediments in the Lake Sihwa and the benthos that inhabited on the sediments was conducted. Cost effective remediation alternatives were derived form the results of the investigation. The sediment samples taken from four sampling points out of thirteen showed relatively high heavy metal (particularly copper) concentrations which exceeded the Effects Range Low (ERL) of the National Oceanic and Atmospheric Administration, USA. The four sampling points were located in front of industrial complexes. Although the heavy metals appeared to have affected the growth of the benthos, the concentration of it did not exceed the criteria of dredging that were developed by Netherlands or the State of Washington, USA. However, contamination by organic matters and sulfur compounds was severe, which exceeded the criteria of dredging that were established in Japan. The sediments taken from the four sampling points which were contaminated with heavy metals showed higher organic matter content in general. The organic matters in the sediments depleted oxygen in summer, which appeared to be fatal to the benthos. A comprehensive analysis on the sediments, benthos, and other environmental impact from the contaminated sediments drew a conclusion that the benthonic environment of the Lake Sihwa needed a stepwise remediation, giving a particular emphasis on the clean up of the sediments upstram of the Lake which could cause odor problems to the nearby residential area.

• Particle and aerosol research
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• v.13 no.3
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• pp.105-110
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• 2017

Real-time measurements of fine particles from stack emission gases are necessary due to the needs of continuous environmental monitoring of PM10 and PM2.5. The porous tube dilutor using hot and cold dilutions was developed to measure fine particles without condensable particles from highly humid emission gases and compared to the commercialized ejector-type dilutor. Particle size distributions were measured at the emission gases from a diesel engine and a coal-fired boiler. The porous tube dilutor could successfully measure the accumulation mode particles including relatively large particles more than $3{\mu}m$ without nuclei particles, while the ejector dilutor detected some condensable particles and could not detect large particles. The porous tube dilutor could successfully remove the already condensed water droplet particles generated by a humidifier in a $30m^3$ chamber.

• Journal of Korean society of Dental Hygiene
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• v.10 no.3
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• pp.523-530
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• 2010

Objectives : In order to provide basic data necessary for developing oral health education plane for school continued oral health education by understanding knowledge and activities of oral health. Methods : This study was performed against 324 students at 5th grade of 2 elementary schools in Iksan-si, Jellabuk-do selected through convenience sampling, who were in mixed dentition period that might experience dental caries of permanent tooth. Results : As results, For the knowledge level on oral health by questions, it was found that the case that the elementary school students had correct knowledge on oral health was 'chocolates, snacks, and candies were foods that might often cause dental caries' and 95.8% of the students recognized it well. It was found that for 'must do toothbrushing before going to bed', 'during toothbrushing, I clean my tongue', and 'Proper time necessary for toothbrushing is about 3 minutes', 89.3%, 93.2%, and 89.3% of the students knew the, respectively. When oral health knowledge level by groups was divided into 3 groups and observed, they were classified into Low (0-4 points), Mid (5-7 points), and High (8-10 points). It was found that the knowledge level of each group was High 64.1%, Mid 33.9%, and Low 2.0% and it was identified that the high group took the largest ratio. It was suggested also for oral health knowledge level depending on their father's academic background that there was a statistically significant difference in the group higher than university graduate(p<.05). It was found for oral health knowledge level depending on parents' dental condition that an answer that both parents were good was high and there was a statistically significant difference. But post-analysis resulted that there was no apparent difference among groups. It was found that the ratio of respondents who answered for toothbrushing method 'toothbrush should be moved and rotated downward for the upper teeth and upward for the lower teeth to clean the teeth and gum' were 33.2% of male students and 29.4% of female students and showed statistically significant difference (p<0.05). It was found also that the ratio of respondents who answered to use a toothbrush for about 3 months' were 29.4% of male students and 25.5% of female students and showed statistically significant difference (p<0.05). Conclusions : Oral health program through the elementary school students and their parents for the development of proper oral health care education programs continue to be made should be considered.

• Microbiology and Biotechnology Letters
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• v.31 no.2
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• pp.177-181
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• 2003

Eleven bacterial strains which are able to utilize terephthalic acid as a carbon and an energy source for growth were isolated from the soil of 7 water quality evaluation points in Kyonggi area of Korea. Phthalic acid isomer degrading activity of the isolates from the 4 contaminated points was higher than those from the 3 clean points. Among 11 isolates, 4 isolates which have high terephthalic acid degrading activity and degrade two phthalic acid isomers were identified by partal 16S rDNA sequence determination. One of them was identified as Pseudomonas putida, and the others as Comamonas testosteroni. Thus a large number of phthalic acid isomer degrading bacteria in domestic soil were inferred as C. testosteroni. On the basis of these results, the PCR detection of C. testosteroni in soil was applied to monitor soil contamination by phthalic acid isomers. The DNA of C. test-osteroni extracted from 4 g soil was directly detected by PCR with C. testosteroni specific primer pair. The amount of PCR products was different according to sampling sites and more PCR products were obtained from contaminated sites than those from clean sites (Gulpo-chun＞Anyang-chun＞Hwangguji-chun>Shin-chun＞Huk-chun＞Pukhan-river>Kapyeong-chun). This result was coincided with that of the viable cell counts for terephthalic acid degrading bacteria.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.2
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• pp.201-208
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• 2011

Recently, a real-time, pocket-sized aethalometer (microAeth$^{(R)}$ model AE51) has been developed by Magee Scientific Inc. for measuring the concentration of black carbon in the atmosphere. In this study, two aethalometers, models AE-16 and AE-51, which measure the optical absorption of carbon particles at infrared 880 nm, were operated at time interval of 5-min between January 9 and February 10, 2010 at an urban site of Gwangju, to compare the accuracy of black carbon (BC) concentrations reported from the AE-51 model and to investigate reasonable sampling time of filter media in the AE-51. The air samples in the AE-51 and AE-16 models are collected on T60 (Teflon coated glass fiber) filter media (filter spot area: 0.07 $cm^2$) and quartz fiber roll-tape filter (filter spot area: 1.67 $cm^2$), respectively. Real-time measurement results indicate that when the filters were clean, the AE-51 BC was greater than or similar to the AE-16 BC data. However as the filter spots become darker, the AE-16 BC concentrations were higher than the AE-51 BC data and the difference in the BC concentrations from two AE models becomes gradually increased. Relative error in the AE-51 and AE-16 BC concentrations showed significance difference depending on used time of the filter in the AE-51 model, weather pattern, levels of air pollution, etc, ranging from 11.5% (used time of the filter in AE-51: 1,595 min) to 52.5% (used time of the filter in AE-51: 2,085 min). When considering the used time of one filter ticket in the AE-51 model and difference (or relative error %) between AE-16 and AE-51 BC concentrations, it is recommended that the standard sampling time per one filter ticket within the AE-51 model be less than approximately 24 hr (1,440 min) under the normal weather conditions except for severe haze and mist events.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.3
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• pp.457-464
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• 2017

The large breeding of algae in rivers has caused the algal bloom and has becoming a serious national problem for the safety of water sources. Therefore, in order to supply stable water resources through securing clean water, it is necessary to develop technology for prevention of water pollution caused by algal bloom. The purpose of this study is to improve the water quality management ability of river by applying the algal bloom detection technique using UAV. Unmanned aerial images were acquired for the Dodong in the middle region of the Nakdong River where algal bloom are frequent. In addition, the phytoplankton concentration was acquired through the sampling of algal bloom and the examination of water quality. Correlation between phytoplankton concentrations and the results of applying the algal bloom index to the Unmanned aerial images showed a strong positive correlation. The remote sensing method suggested in this study is expected to improve the initial response capability of river water pollution.