• Journal of Environmental Health Sciences
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• v.46 no.3
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• pp.335-343
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• 2020

Objectives: The Korean Ministry of Environment has identified cases of people suspected of suffering lung disease potentially caused by polyhexamethylene guanidine (PHMG) used in humidifier disinfectants (HDs). Exposure assessment for the HDs was conducted using a questionnaire during face-to-face interview. The main purposes of this study were to develop a methodology to effectively classify levels of exposure to HDs based on a questionnaire. Methods: We first identified the overall participants' exposure characteristics by HD exposure levels; Second, we selected misclassified subjects and investigated characteristics of overestimated and underestimated subjects, focusing on exposure cases to PHMG-containing HDs. An inhalation reference concentration (RfC) for PHMG was produced on the basis of inhalation toxicity values. We made a cross-tabulation of the exposure classes (Exposure classes 1-to-4) by clinical classes based on the RfC. When the value of the exposure class minus the clinical class was 0 or 1, we assumed these were true values. When the value was ≥2 and ≤ -2, we assigned these cases to the overestimation group and underestimation group, respectively. Results: The overestimated group may have already recovered and responded excessively due to psychological anxiety or in order to receive compensation. On the other hand, relatively high mortality rates and surrogate responses for those under 10 years of age may have resulted in inaccurate exposure assessment for underestimated groups. For the characteristics of exposure, it was shown that for the underestimated group, the exposure was relatively weaker than the overestimated group, even though a high overall clinical rating was determined. Conclusions: This study may suggest ways to reduce bias and overcome the limitations of current HD exposure assessment.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.1
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• pp.21-27
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• 2015

Hydrogen production from commercial diesel fuels is an attactive option for energy generation purpose due to the low cost and good availability of diesel fuels. However, in order to utilize commercial diesel fuels, the sulfur contents must be removed down to approximately 0.1 ppm level to protect the fuel cell catalysts from poisoning. Commercial catalysts $CoMo/Al_2O_3$ and $NiMo/Al_2O_3$ were tested for HDS (Hydrodesulfurization) of model diesel and commercial diesel. The experimental conditions were $250-400^{\circ}C$ and LHSV (Liquid Hourly Space Velocity) $0.27-2.12hr^{-1}$. $NiMo/Al_2O_3$ was found to be more effective than $CoMo/Al_2O_3$ in removing sulfur from model diesel. Based on the experimental results of model diesel, commercial diesel fuel purchased from a local petrol station was tested for HDS using $NiMo/Al_2O_3$. The GC-SCD (Gas Chromatography Sulfur Chemiluminescence Detector) results showed that the DMDBT (Dimethyldibenzothiophene) derivatives were fully removed from the commercial diesel fuel proving that HDS with $NiMo/Al_2O_3$ is technically feasible for industrial applications.

• Journal of Environmental Health Sciences
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• v.45 no.1
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• pp.71-81
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• 2019

Objectives: The lung injuries by exposure to the humidifier disinfectants (HDs) were reported in 2011, Korea. For the HD victims, environmental exposure level and clinical diagnosis were conducted to determine the levels of damage by HDs. Methods: The exposure assessment to the HDs from 1st to 4th questionnaire surveys were carried out for 5,245 victims. And the affecting factors of exposure levels were analyzed by characterizing exposure and demographic information. By using of exposure concentration and cumulative time, exposure levels were classified and compared by percentage of clinical diagnosis classes. The high exposure and low clinical diagnosis rating groups, and low exposure and high clinical diagnosis rating groups were analyzed to overcome the limitation of past exposure assessment such as recall bias. Results: Among the all applicants damaged by the humidifier disinfectants, survivors were 4,028 and the dead were 1,217. And male and female were 2,675, and 2,547, respectively. In case of occurrence age of lung disease, under 10 years was majority age group (1,536) and followed by thirties (917). Pregnant women and fetuses were 339 and 439, respectively. And the damages by exposure to the HDs were concentrated on these susceptible populations in groups with low exposure and high clinical diagnosis rating. On the other hand, the groups classified by high exposure and low clinical diagnosis rating were shown different characterization. Conclusions: The questionnaire survey on past exposure may be uncertain due to recall bias. However, the relationship between classified exposure levels and clinical diagnosis ratings might be shown positive correlation if the exposure assessment errors were analyzed and controlled.

• Journal of Environmental Health Sciences
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• v.49 no.3
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• pp.159-168
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• 2023

Background: An ongoing environmental exposure assessment of humidifier disinfectants (HDs) has been conducted since November 2011 among individuals who experienced HD exposure-related adverse health effects. It is being performed in order to determine and quantify exposure to humidifier disinfectants in victims and their families. To date, the assessment has encompassed Cycles I-to-V. There is no report summarizing the characteristics of the subjects from the overall cycles. Objectives: We intended to examine the individual characteristics related to demographics, HD usage, and HD exposure using integrated data from Cycles I-to-V of the environmental exposure assessment of HDs and the changes with the cycles. Methods: We included 7,543 individuals who participated in Cycles I-to-V of the environmental exposure assessment of HDs. We summarized the participants' characteristics regarding their demographics (e.g., sex, education level, and age), HD usage history (e.g., product name, ingredient, and frequency of HD use), and HD exposure (e.g., daily time of HD use, cumulative time of HD use, and exposure intensity). In addition, their characteristics were compared across the cycles of the exposure assessment. Results: Among the 7,543 participants from Cycles I-to-V, there were more male participants than females (51.05% overall), except for Cycles I and III. Across all cycles, a higher proportion of survivors was observed than deceased individuals. While PHMG was the most prevalent ingredient in HDs throughout all the cycles, its proportion gradually decreased over the course of the examination cycles. Participants in Cycle I reported longer daily times of HD use compared to those in the subsequent cycles. On the other hand, cumulative time of HD use was shorter in the earlier cycles than in the later cycles. Conclusions: Using the integrated data from the full cycles of the environmental exposure assessment, this study identified changes in demographic characteristics as well as the HD exposure characteristics between the participants across different cycles.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.368-373
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• 2005

This paper presents a new framework for the traffic flow control based on integrated model descriptions as the Hybrid Dynamical System (HDS).

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2747-2752
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• 2003

This paper has develops a new framework to understand the human’s driving maneuver based on the expression as HDS focusing on the driver’s stopping maneuver. The driving data has been collected by using the three-dimensional driving simulator based on CAVE, which provides three-dimensional visual information. In our modeling, the relationship between the measured information such as distance to the stop line, its first and second derivatives and the braking amount has been expressed by the PWPS model, which is a class of HDS. The key idea to solve the identification problem was to formulate the problem as the MILP with replacing the switching conditions by binary variables. From the obtained results, it is found that the driver appropriately switches the ‘control law’ according to the following scenario: At the beginning of the stopping behavior (just after finding the stopping point), the driver decelerate the vehicle based on the acceleration information, and then switch to the control law based on the distance to the stop line.

• Journal of Haehwa Medicine
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• v.15 no.1
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• pp.1-9
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• 2006

For this study, we carried out dementia assessment examination of 74 patients with memory disturbance who have come to Cheongju oriental hospital of Daejeon university from April 2005 to February 2006. This study classified the patients as none-dementia(ND), questionable dementia(QD), and dementia(DA) groups and analyzed the result of examination. As a result, the following conclusion was drawn. 1. Among the 3 groups, there was no significant differences in the sex distribution. But according to age distribution, the age of QD and DA groups showed significant difference from that of ND group. 2. MMSE-K and HDS-K scores showed the significant differences among all groups, and 7 MS result showed the significant difference between ND and the other groups. 3. The DA group significantly got lower scores than ND group in the items of the MMSE-K, Orientation, Registration, Recall, Attention, Copy two pentagons and Comprehension. Especially, significant difference also was shown in the orientation item between QD and DA groups. 4. The scores in the items of 7 MS, Benton temporal orientation, Enhanced cued recall and Clock drawing showed significant difference among all groups. Category fluency score showed significant difference between ND and the other groups. 5. The results of Brain CT and clinical chemistry test didn't show significant difference among all groups.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.9
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• pp.423-428
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• 2006

We have been carried out the two-beam interference method to form the diffraction grating on chalcogenide $AS_{40}Se_{15}S_{35}Ge_{10}$ thin films for Holography Data Storage (HDS). In the present work, we have been formed holographic diffraction gratings using He-Ne laser (632.8nm) under different Polarization state combinations (intensity polarization holography, phase polarization holography). It was obtained the diffraction grating efficiency by 11st order intensity and investigated the formed grating structure using Atomic Force Microscopy (AFM). As the results, it is shown that the diffraction efficiency of (P: P) polarized recording was maximum 2.4% and we found that its value was rather higher than that of other-polarized recordings. From the results, it is confirmed that the efficient holographic grating formation on amorphous chalcogenide $AS_{40}Se_{15}S_{35}Ge_{10}$ films depend on both the spatial variation of intensity and the polarization state of the incident field pattern.

• Korean Journal of Adult Nursing
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• v.16 no.1
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• pp.123-134
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• 2004

Purpose: The purpose of this study was to examine the effect of use of a horticultural program on the cognitive function, activities of daily living, and hand grip strength of institutionalized dementia patients. Method: Twenty three study participants completed a five week protocol comprised of one week of baseline and four weeks of treatment. The study design was a one group repeated measurement study. For the first and fifth week of the study period, data was collected with 3 instruments: Korean Version of Hasegawa Dementia Scale (HDS-K), Katz's ADL index, hand grip strength. Data analysis was conducted by SPSS version 10.0. Result: Total HDS-K score(p=.000), Activities of daily living(p=.013) and hand grip strength(p=.001) was significantly improved after treatment compared to the baseline. Conclusion: The horticultural program was effective for improving cognitive function, ADL and hand grip strength of the dementia patients. Repeated studies utilizing a control group are needed, using various durations, plants and processes, to confirm these results and to standardize the horticultural program protocol.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.10-14
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• 2015

In holographic data storage systems, data is recorded and read by page on a volume of storage medium, and it can increase transmission rate and storage capacity because of two-dimensional page-oriented data processing by charge-coupled devices. However, HDS suffers two-dimensional intersymbol interference unlike conventional data storages. In this paper, we propose a preprocessing method of decreasing ISI before read data in HDS pass to detector. This method has some advantage when we collaborate with the preprocessing for reducing misalignment error and modulation code.