• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.39-42
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• 2004

Carbon nanofiber/Cu composite powder has been fabricated by electroless plating process. Microstructural evolution of the composite powder after heat treatment under vacuum, hydrogen and air environment was investigated. A dispersed carbon nanofiber coated by copper was produced at the as-plated condition. Carbon nanofiber is coated uniformly and densely with the plate shaped copper particles. The copper plates on the carbon nanofiber aggregate during the thermal exposure at elevated temperature in vacuum and hydrogen in order to reduce surface energy. The thermal exposure of the composite powder in air at $400^{\circ}C$ for 3 hours leads to the spherodization of the composite powder owing to oxidation of copper.

• Proceedings of the Safety Management and Science Conference
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• 2011.11a
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• pp.563-571
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• 2011

The purpose of the study was to evaluation of the radiation dose reduction using various automatic exposure control (AEC) systems in different manufactures multi-detector computed tomography (MDCT). We used three different manufacturers for the study: General Electric Healthcare, Philips Medical systems and Siemens Medical Solutions. The general scanning protocol was created for the each examination with the same scanning parameters as many as possible. In the various AEC systems, the evaluation of reduced-dose was evaluated by comparing to fixed mAs with using body phantom. Finally, when we applied to AEC for three manufacturers, the radiation dose reduction decreased each 35.3% in the GE, 58.2% in the Philips, and 48.6% in the Siemens. This applies to variety of the AEC systems which will be very useful to reduce the dose and to maintain the high quality.

• Korean Journal of Digital Imaging in Medicine
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• v.13 no.1
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• pp.7-11
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• 2011

As applications of radiation grow wider from use in the early detection of lesions and preventive diagnosis purposes to the treatment of diseases, the possibilities for patients and working professionals to be exposed to radiation are becoming greater than ever. This can not only directly bring about an increase in patient's individual radiation exposure, but also brings about an increase in the annual radiation dose of working professionals. Therefore, research and countermeasures to reduce radiation dosage are required. In this study, space dosimetry has been divided into two separate measuments with an understanding of the increasing number of angiography procedures: front perspective and side perspective. According to the results of the isodose curve, a way to minimize radiation exposure in working professionals has been suggested. This was made possible by workers through awareness of suitable working positions.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.47 no.3
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• pp.233-236
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• 2021

A mandibular continuity defect can be repaired using either a prosthetic device or autogenous bone. A titanium reconstruction plate can be used with a localized or vascularized flap over the defect of the mandible. Unfortunately, the plate may fail due to plate exposure, screw loosening, fracture, or infection, and will need to be removed. Plate exposure though the skin or mucosa is one of the main reasons for failure. In the present work, the authors introduced a lingually positioned reconstruction plate fabricated via three-dimensional printed bending support. This custom reconstruction plate can avoid plate re-exposure as well as reduce surgical errors and operation time.

• 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.

• Journal of Digital Contents Society
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• v.13 no.3
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• pp.421-429
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• 2012

Lately, the number of interventional radiology is increased by the extension of procedure in medical radiation, and radiation exposure may be appeared differently by interventional radiologists, it is caused increase of radiation dose for radiation worker, patient, and radiologists. This study has done a comparative analysis characteristic of radiation exposure for five radiologists who executed interventional cardiology for 303 patients in S university hospital of Gyeong-Buk from Nov. 1, 2011 to Jan. 31, 2011. The average exposure time of five radiologists was 697.95sec. The average of cumulative DAP(exp) for patients was $52,730mGycm^2$ and the average of total DAP for patients was $104,875.14mGycm^2$. The average of frames for image was 855.52 frames in acquired images, and the average of frames for images was 802.2 frames in exposure images. They were statistically significant differences (p<0.05). Exposure time, cumulative DAP(fluro), cumulative DAP(exp), total DAP, acquired image, and exposure image were high correlation except cumulative DAP(exp), and acquired runs in x-ray exposure characteristics of machine. Exposure time was a great influence on radiologist. It signified that the more exposure time lead to the more radiation dose for radiologist. Radiation dose is related to ability, experience, difficulty, and precision of procedures in interventional procedure. The number of angiography and exposure time is difficult to control by radiologists. Therefore, it is in need of reasonable system which was evaluated the real dose of medical teams in interventional proceedings. We think that self education and training are required to reduce radiation dose for radiologists and radiation workers.

• Journal of Environmental Health Sciences
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• v.44 no.4
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• pp.370-379
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• 2018

Objectives: Bisphenol A (BPA) has been extensively used in a variety of consumer products, resulting in widespread non-occupational human exposure. It is often detected in the human body. Studies have reported many health effects associated with endocrine and metabolic disruptions, including obesity, diabetes, hypertension, and cardiovascular diseases. This study was performed to explain the relationship between BPA exposure and obesity in the Korean adult population. Methods: The second stage of the Korean National Environmental Health Survey (KoNHES) was conducted from 2012 to 2014 with 6,478 persons participating. Using the results of the survey, we analyzed the exposure levels for BPA and the influence on obesity of BPA. Results: In model 1, the volume-based measure concentration of BPA, total, female and the 30s to 60s age group were positively related with BMI. In model 2, creatinine adjusted as a covariate and positive associations for BPA with BMI were observed in the female group and was marginally significantly associated in low body weight group. In model 3, creatinine adjusted (g/g-creatinine), BPA exposure, and BMI were positively related with sex, in females, and there was a marginally significant association with the low body weight group in the BMI categories. BMI was significantly associated with BPA in the female group in all three models. Conclusion: This study added further evidence that exposure to EDCs, include bisphenol A, is related with obesity among the general population. Given the environmental health concerns over BPA, it is necessary to develop comprehensive measures to reduce BPA exposure.

• The Korean Journal of Pain
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• v.27 no.2
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• pp.162-167
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• 2014

Background: Although a physician may be the nearest to the radiation source during C-arm fluoroscope-guided interventions, the radiographer is also near the fluoroscope. We prospectively investigated the radiation exposure of radiographers relative to their location. Methods: The effective dose (ED) was measured with a digital dosimeter on the radiographers' left chest and the side of the table. We observed the location of the radiographers in each procedure related to the mobile support structure of the fluoroscope (Groups A, M and P). Data about age, height, weight, sex, exposure time, radiation absorbed dose (RAD), and the ED at the radiographer's chest and the side of the table was collected. Results: There were 51 cases for Group A, 116 cases for Group M and 144 cases for Group P. No significant differences were noted in the demographic data such as age, height, weight, and male to female ratio, and exposure time, RAD and ED at the side of the table. Group P had the lowest ED ($0.5{\pm}0.8{\mu}Sv$) of all the groups (Group A, $1.6{\pm}2.3{\mu}Sv$; Group M, $1.3{\pm}1.9{\mu}Sv$; P < 0.001). The ED ratio (ED on the radiographer's chest/ED at the side of the table) of Group A was the highest, and the ED radio of Group P was the lowest of all the groups (Group A, $12.2{\pm}21.5%$; Group M, $5.7{\pm}6.5%$; Group P, $2.5{\pm}6.7%$; P < 0.001). Conclusions: Radiographers can easily reduce their radiation exposure by changing their position. Two steps behind the mobile support structure can effectively decrease the exposure of radiographers by about 80%.

• Environmental Analysis Health and Toxicology
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• v.11 no.1_2
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• pp.19-29
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• 1996

Human exposure to volatile compounds in tap water can occur from inhalation and dermal absorption as well as direct ingestion. The relative contribution to total human exposure from these pathways has been considered to be important especially for VOC's (volatile organic compounds). In an attempt to reduce the uncertainty of the risk assessment, it has been suggested that the exposure assessment process could be significantly improved by adopting Monte-Carlo simulation. However, there is no actual data in Korea for each exposure parameter to determine the level of exposure, and the distributional pattern. Therefore, we surveyed water use patterns and behavior related to multi-route exposure to VOC's in household tap water in Korea, and compared these values to the those in western countries. In the first survey, we calculated daily water intake using data from a sample of 1322 persons of several cities in Korea. In the second survey, we obtained questionnaire data on exposure time for showering, bathing and household activities, and tap water intake from 851households in Korea. In the last survey, we measured the exposure parameters (exposure time, water use rate etc.) related to showers, baths, toilets, dish washing, washing and cooking, and tap water intake was surveyed. Also, the subjects were measured their body weight, height and tidal volume, etc. A diary, a flow meter and a measuring cup were used to measure these values as precisely as possible. Average daily water intake was ranged 0.79-1.71 L/day for adults in three surveys. Tap water intake measured by log-sheet during one week in third survey was 1.26 (average), 1.98 L/day (90 percentlie), respectively. These results were comparable with results from EPA (1.4, 2L/day). The average amount of water used by housewives in the third survey was 515.0 $\pm$ 564.6L/day. In usual activity, the amount of water used in the bathroom, the laundry and the kitchen was 140.0 $\pm$ 538.9, 148.0 $\pm$ 174.5, 229.3 $\pm$ 205.4 L/day, respectively. Exposure parameters such as water intake rate, exposure duration, body weight, inhalation rates in surveyed data of Korean people differed from those published from western countries. This could be attributed to variations in lifestyle, dietary habits and physiological characteristics.

• Journal of Preventive Medicine and Public Health
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• v.57 no.2
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• pp.185-196
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• 2024

Objectives: Excess mortality associated with long-term exposure to fine particulate matter (PM_2.5) has been documented. However, research on the disease burden following short-term exposure is scarce. We investigated the cause-specific mortality burden of short-term exposure to PM_2.5 by considering the potential non-linear concentration-response relationship in Korea. Methods: Daily cause-specific mortality rates and PM_2.5 exposure levels from 2010 to 2019 were collected for 8 Korean cities and 9 provinces. A generalized additive mixed model was employed to estimate the non-linear relationship between PM_2.5 exposure and cause-specific mortality levels. We assumed no detrimental health effects of PM_2.5 concentrations below 15 ㎍/m³. Overall deaths attributable to short-term PM_2.5 exposure were estimated by summing the daily numbers of excess deaths associated with ambient PM_2.5 exposure. Results: Of the 2 749 704 recorded deaths, 2 453 686 (89.2%) were non-accidental, 591 267 (21.5%) were cardiovascular, and 141 066 (5.1%) were respiratory in nature. A non-linear relationship was observed between all-cause mortality and exposure to PM_2.5 at lag0, whereas linear associations were evident for cause-specific mortalities. Overall, 10 814 all-cause, 7855 non-accidental, 1642 cardiovascular, and 708 respiratory deaths were attributed to short-term exposure to PM_2.5. The estimated number of all-cause excess deaths due to short-term PM_2.5 exposure in 2019 was 1039 (95% confidence interval, 604 to 1472). Conclusions: Our findings indicate an association between short-term PM_2.5 exposure and various mortality rates (all-cause, non-accidental, cardiovascular, and respiratory) in Korea over the period from 2010 to 2019. Consequently, action plans should be developed to reduce deaths attributable to short-term exposure to PM_2.5.