• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1083-1092
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• 2016

In this paper, the performance of the optical code-division multiple access (OCDMA) technology on a plastic optical fiber (POF) access network, which had received much attention due to its low weight, large core diameter, flexibility, easy installation, and especially its high bandwidth, is analyzed. Recently, POF was a very attractive candidate for transmission media in an access network based on OCDMA technology. But the conventional OCDMA system only allows finite units to transmit and access simultaneously according to the number of channels which are restricted by BER, and so, in this paper, to resolve this problem a novel multi-priority reservation protocol is also proposed. By using this reservation scheme and a distributed arbitration algorithm, channel collision and destination conflict could be avoided. And this protocol can efficiently support the transmission of multimedia messages that require the different time-delay. The network throughput and average delay using various system parameters have been investigated by numerical analysis and simulation experiments. These results shows that the multi-priority reservation protocol in this POF access network based on OCDMA technology is valid and efficient.

• Korean Journal of Health Education and Promotion
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• v.17 no.2
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• pp.229-237
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• 2000

The purpose of this study was to be useful in working out plans for improving national health by identifying public workers' knowledge of and attitude to smoking, actual conditions of smoking within nonsmoking areas, and related factors. For the purpose, the questionnaire was carried out with 761 public officials of the division manager-level and lower working in Taegu Metropolitan City Hall in september, 1998. The results are summarized as follows; Smokers of the subject group accounted for 55.1％, and the smoking rate had a significant relation with age and religion. In view of the time when smokers started smoking, smokers who started smoking after graduation from a high school accounted for 70.6％. Smokers who smoke one pack of cigarettes per day and a cigarette to its two-thirds length was the most. In the smoking place of smokers at home, 54.9％ of the smokers responded that they smoke in an outdoor space The rate of smoking in an office was 68.3％ and the rate of smoking within the nonsmoking areas of other public institutions was 43.0％. The results of multiple regression analysis with the actual state of smoking within the nonsmoking area of other public institutions as an independent variable revealed that smokers who check for a nonsmoking area before smoking in the public institutions and who do not smoke in an office do not smoke within the nonsmoking areas of other public institutions. In conclusion, more smoking and health education for public workers is needed to reduce the rate of national smoking and allow people to have a good smoking attitude, and it is required to arrange an institutional system who can strictly control public workers' smoking in their offices or public places and to stress a function of surveillance and monitoring by nonsmokers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.275-284
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• 2019

This study was conducted to evaluate the health promotion behavior level, health beliefs, and self-efficacy of individuals preparing for civil service examinations, as well as the main factors that influence their health promotion behavior. The study subjects were 290 individuals who were preparing for civil service examinations in Noryangjin, where there are a lot of private institutions that provide training for the examinations. Data were collected by questionnaire surveys conducted from December 1 to 19, 2017. With the use of SPSS ver. 23, descriptive statistics, t-tests, one-way ANOVA, correlation analysis, and stepwise multiple regression were conducted. On average, the score for health promotion behavior practice was $2.37{\pm}0.45points$, health beliefs $3.13{\pm}0.45points$, and self-efficacy $3.55{\pm}0.74points$. Health promotion behavior was significantly positively correlated with perceived severity and perceived benefits, which are sub factors of health beliefs (r=.60, p<.001; r=.55, p<.001), while it was significantly negatively correlated with perceived barriers, which are a sub factor of health beliefs (r=.32, p<.001). The factors that influenced health promotion behavior were perceived health condition and perceived barriers, and the explanatory power of health promotion behavior was 25.1% (F=13.58, p<.001). In general, respondents studied for the examinations for a long time and were under severe job pressure; accordingly, they need to have quality meals, regular exercise, and regular medical check-ups to enhance health promotion behavior to control their stress.

• Journal of Korea Water Resources Association
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• v.57 no.3
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• pp.151-164
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• 2024

In water treatment plants supplying potable water, the management of chlorine concentration in water treatment processes involving pre-chlorination or intermediate chlorination requires process control. To address this, research has been conducted on water quality prediction techniques utilizing AI technology. This study developed an AI-based predictive model for automating the process control of chlorine disinfection, targeting the prediction of residual chlorine concentration downstream of sedimentation basins in water treatment processes. The AI-based model, which learns from past water quality observation data to predict future water quality, offers a simpler and more efficient approach compared to complex physicochemical and biological water quality models. The model was tested by predicting the residual chlorine concentration downstream of the sedimentation basins at Plant, using multiple regression models and AI-based models like Random Forest and LSTM, and the results were compared. For optimal prediction of residual chlorine concentration, the input-output structure of the AI model included the residual chlorine concentration upstream of the sedimentation basin, turbidity, pH, water temperature, electrical conductivity, inflow of raw water, alkalinity, NH₃, etc. as independent variables, and the desired residual chlorine concentration of the effluent from the sedimentation basin as the dependent variable. The independent variables were selected from observable data at the water treatment plant, which are influential on the residual chlorine concentration downstream of the sedimentation basin. The analysis showed that, for Plant, the model based on Random Forest had the lowest error compared to multiple regression models, neural network models, model trees, and other Random Forest models. The optimal predicted residual chlorine concentration downstream of the sedimentation basin presented in this study is expected to enable real-time control of chlorine dosing in previous treatment stages, thereby enhancing water treatment efficiency and reducing chemical costs.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.6
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• pp.575-582
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• 2016

Seoul city has high population density as well as high traffic congestion, which are vulnerable to exposure of environmental pollutions caused by car traffic. However, recent studies are only on local regions about road traffic and air pollution or health effect of road traffic on residents. Thus, comprehensive study data are needed in terms of overall Seoul regions. In this study utilized the nitrogen dioxide concentration through the national air pollution monitoring network data, 2012 to 2013. It also divided regions into high and low exposure districts via the Origin destination data developed by the Korea transport institute to quantify and evaluate the effect of transport policies and analyzed a correlation of asthma symptoms with high and low exposure districts through raw data of community health survey from the Korea centers for disease control and prevention. Based on the collected data, the pearson's correlation analysis was conducted between air pollution substance concentration and high exposure district and multiple logistic regression analysis was conducted to determine the effect of traffic environment and factors on asthma symptoms of residents. Accordingly, the following results were derived. First, the high exposure district was higher concentrations of nitrogen dioxide ($NO_2$) as per time compared to those of the low exposure district (p<0.01). Second, analysis on correlation between average daily environmental concentration in the air pollution monitoring network and road traffic showed that nitrogen dioxide had a significant positive correlation (p<0.01) with car traffic and total traffic as well as with truck traffic (p<0.05) statistically. Third, an adjusted odds ratio about asthma doctor's diagnosis in the high and low exposure districts was analyzed through the logistic regression analysis. With regard to an adjusted model 2 (adjusted gender, age, health behavior characteristics, and demographic characteristics) odds ratio of asthma doctor's diagnosis in the high exposure district was 1.624 (95% CI: 1.269~2.077) compared to that of the low exposure district, which was significant statistically (p<0.001).

• The Journal of Engineering Geology
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• v.25 no.1
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• pp.83-91
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• 2015

Few studies have investigated soil management policy and soil erosion measurement, whereas the occurrence of climate change requires the establishment of robust soil management systems and appropriate control of soil erosion. In this study, we developed a smart sensor for real-time quantitative measurements of soil erosion at the watershed scale. The smart sensor consists of an ultrasonic sensor, a rainfall meter, a solar cell, an RTU (remote terminal unit),and a CDMA (code division multiple access) and it was programmed to take a measurement every 30 minutes. The depths measured by the smart sensor were compared with data from terrestrial LiDAR. Experimental results showed a strong correlation in the depth of soil erosion between LiDAR and the ultrasonic sensor for the period from 22 August to 11 October 2013. Furthermore, the correlation coefficient between soil erosion depth (mm) and soil erosion volume (m³) was 0.9063 in the lower region of the watershed and is 0.9868 in the upper region. The proposed ultrasonic sensor technique can provide high-quality data for soil conservation and management systems in the future.

• Journal of Preventive Medicine and Public Health
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• v.39 no.2
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• pp.141-148
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• 2006

Objectives : We wanted to evaluate the medical underutilization for benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS) among Korean elderly men and we wanted to determine their associated factors. Methods : This study was conducted on 239 men with LUTS and 116 men with BPH who were compatible with the diagnostic criteria from a total of 641 participants. These participants were over 50 years old and they were randomly chosen in a community-based study for estimating the prevalence of BPH. Using a self-reported questionnaire, we surveyed the sociodemographics, health status, quality of life, lower urinary tract symptoms, medical utilization and reasons for not seeking treatment. Results : Only 27.6% of the men with LUTS and 31.0% of the men with BPH reported having visited a doctor for urinary symptoms. The reasons for not visiting a doctor were, in order of responses from the group with LUTS: 'considered the symptoms as a part of the normal ageing process', 'not enough time to visit a doctor', 'financial difficulty' and 'the symptoms were not severe or bothersome'. Regarding BPH, the responses were the same as those of the group with LUTS however, 'financial difficulty' placed second. Among the men with experience of visiting a doctor for urinary symptoms, 33.3% of those with LUTS and 28.1% of those with BPH were not treated. The most common reason in both groups was 'the symptoms were not severe to be treated'. On a multiple logistic regression analysis, the larger size household (odds ratio (OR) 3.03, 95% confidence interval (CI)=1.40-6.54) and an unsatisfactory quality of life related with urinary symptoms (OR 2.98, 95% CI=1.23-7.21) were associated with medical utilization in the group of LUTS. For BPH, the current employment status was related with the medical utilization (OR 2.80, 95% CI=1.10-7.11), in addition to the larger size household (OR 3.24, 95% CI=1.14-9.21). Conclusions : Many men with urinary symptoms do not visit a doctor. This medical underutilization for people with LUTS and BPH may be associated with economic status in Korea.

• Korean Journal of Remote Sensing
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• v.21 no.4
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• pp.287-302
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• 2005

Digital Elevation Models (DEMs) were generated by ERS-l/2 and JERS-1 SAR interferometry in Daejon area, Korea. The quality of the DEM's was evaluated by the Ground Control Points (GCPs) in city area where GCPs were determined by GPS surveys, while in the mountain area with no GCPs, a 1:25,000 digital map was used. In order to minimize errors due to the inaccurate satellite orbit information and the phase unwrapping procedure, a Differential InSAR (DInSAR) was implemented in addition to the traditional InSAR analysis for DEM generation. In addition, DEMs from GTOPO30, SRTM-3, and 1:25,000 digital map were used for assessment the resolution of the DEM generated from DInSAR. 5-6 meters of elevation errors were found in the flat area regardless of the usage and the resolution of DEM, as a result of InSAR analyzing with a pair of ERS tandem and 6 pairs of JERS-1 interferograms. In the mountain area, however, DInSAR with DEMs from SRTM-3 and the digital map was found to be very effective to reduce errors due to phase unwrapping procedure. Also errors due to low signal-to-noise ratio of radar images and atmospheric effect were attenuated in the DEMs generated from the stacking of 6 pairs of JERS-1. SAR interferometry with multiple pairs of SAR interferogram with low resolution DEM can be effectively used to enhance the resolution of DEM in terms of data processing time and cost.

• Laboraroty Animal Research
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• v.34 no.4
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• pp.248-256
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• 2018

O-2-$^{18}F$-fluoroethyl-l-tyrosine ($[^{18}F]FET$) has been widely used for glioblastomas (GBM) in clinical practice, although evaluation of its applicability in non-clinical research is still lacking. The objective of this study was to examine the value of $[^{18}F]FET$ for treatment evaluation and prognosis prediction of anti-angiogenic drug in an orthotopic mouse model of GBM. Human U87MG cells were implanted into nude mice and then bevacizumab, a representative anti-angiogenic drug, was administered. We monitored the effect of anti-angiogenic agents using multiple imaging modalities, including bioluminescence imaging (BLI), magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET/CT). Among these imaging methods analyzed, only $[^{18}F]FET$ uptake showed a statistically significant decrease in the treatment group compared to the control group (P=0.02 and P=0.03 at 5 and 20 mg/kg, respectively). This indicates that $[^{18}F]FET$ PET is a sensitive method to monitor the response of GBM bearing mice to anti-angiogenic drug. Moreover, $[^{18}F]FET$ uptake was confirmed to be a significant parameter for predicting the prognosis of anti-angiogenic drug (P=0.041 and P=0.007, on Days 7 and 12, respectively, on Pearson's correlation; P=0.048 and P=0.030, on Days 7 and 12, respectively, on Cox regression analysis). However, results of BLI or MRI were not significantly associated with survival time. In conclusion, this study suggests that $[^{18}F]FET$ PET imaging is a pertinent imaging modality for sensitive monitoring and accurate prediction of treatment response to anti-angiogenic agents in an orthotopic model of GBM.