• Journal of Environmental Health Sciences
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• v.39 no.1
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• pp.32-42
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• 2013

Objectives: Cryptosporidium, a protozoan parasite, has been recognized as a frequent cause of waterborne disease due to its extremely strong resistance against chlorine disinfection. Although there has as yet been no report of a Cryptosporidium outbreak through drinking water in Korea, it is important to estimate the health risk of Cryptosporidium in water supply systems because of the various infection cases in human and domestic animals and frequent detection reports on their oocysts in water environments. Methods: This study evaluated the annual infection risk of Cryptosporidium in tap water using the quantitative microbial risk assessment technique. Exposure assessment was performed upon the results of a national survey on Cryptosporidium on the water sources of 97 large-scale water purification plants in Korea, water treatment efficacy, and daily unboiled tap water consumption. The estimates of the US Environmental Protection Agency on the mean likelihood of infection from ingesting one oocyst were applied for effect assessment. Results: Using probabilistic methods, mean annual infection risk of Cryptosporidiosis by the intake of tap water was estimated to fall within the range of $2.3{\times}10^{-4}$ to $1.0{\times}10^{-3}$ (median $5.7{\times}10^{-4}$). The risk in using river sources was predicted to be four times higher than with lake sources. With 0.5-log higher removal efficacy, the risk was estimated to be $1.8{\times}10^{-4}$, and could then be lowered by one-third. Conclusions: These estimations can be compared with acceptable risk and then used to determine the adequacy and priority of various drinking water quality strategies such as the establishment of new treatment technology.

• Journal of Soil and Groundwater Environment
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• v.12 no.1
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• pp.1-35
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• 2007

In the last decades, the decrease in biological or chemical availability of sorbed contaminants as contact time passed, is generally accepted. This phenomenon so called as "aging" or "sequestration" is known to directly affect risk of the contaminats. This was observed for mainly for hydrophobic organic contaminants (HOCs), but also reported for heavy metals. Aging is known to be directly related to sorption-desorption hysteresis, irreversible sorption, desorption-resistance, nonequilibrium sorption, etc. The decrease in bioavailability due to aging or sequestration indicates realistic decrease in risk potential. Recently a risk-based management concept by scientific evidences but not the simple measurement of contaminant concentration has been attempted to determine environmentally acceptable remedial endpoint. This is because selection of remedial endpoint based on not total concentration but the bioavailability and toxicity of contaminants can reduce both the treatment cost and remedial activities of the contaminated sites. The bioavailability and toxicity of the residual contaminants are highly affected by the fate and transport and also directly affect the exposure pathways and bioaccumulation of contaminants in the living biota. In this paper, scientific feasibility on the risk-based clean-up and management of contaminated sites is reviewed.

• Journal of the Korean Institute of Gas
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• v.25 no.5
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• pp.1-10
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• 2021

Semiconductor Photo Resist (PR) automation equipment uses a mixture of several flammable substances, and when it leaks during the process, it can lead to various accidents, therefore, risk assessment is necessary. This study analyzed the frequency of leakage of Acetone and PGMEA used in PR automation equipment and the frequency at which such leakage could lead to a fire accident through the frequency analysis method, and evaluated the need for additional risk reduction measures in the current facility. Based on the process leak data and ignition probability data of IOGP, leak frequency analysis and ignition probability were derived, and the frequency of actual fire accidents was analyzed by combining them. The frequency of material leakage in semiconductor PR process is 7.30E-03/year, and fire accidents can occur by acetone that exists above the flash point when the material is leaked, the frequency was calculated at the level of 1.24E-05/year. According to the UK HSE, for a major accident occurring with a frequency of 1.24E-05/year, it is defined as "Broadly Acceptable", a level that does not require additional measures for risk reduction when it causes 7 or less deaths, and due to the process operated by two people, no additional risk reduction are required.

• Journal of Korean Neurosurgical Society
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• v.67 no.1
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• pp.60-72
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• 2024

Objective : Recently, robotic-assisted spine surgery (RASS) has been considered a minimally invasive and relatively accurate method. In total, 495 robotic-assisted pedicle screw fixation (RAPSF) procedures were attempted on 100 patients during a 14-month period. The current study aimed to analyze the accuracy, potential risk factors, and learning curve of RAPSF. Methods : This retrospective study evaluated the position of RAPSF using the Gertzbein and Robbins scale (GRS). The accuracy was analyzed using the ratio of the clinically acceptable group (GRS grades A and B), the dissatisfying group (GRS grades C, D, and E), and the Surgical Evaluation Assistant program. The RAPSF was divided into the no-breached group (GRS grade A) and breached group (GRS grades B, C, D, and E), and the potential risk factors of RAPSF were evaluated. The learning curve was analyzed by changes in robot-used time per screw and the occurrence tendency of breached and failed screws according to case accumulation. Results : The clinically acceptable group in RAPSF was 98.12%. In the analysis using the Surgical Evaluation Assistant program, the tip offset was 2.37±1.89 mm, the tail offset was 3.09±1.90 mm, and the angular offset was 3.72°±2.72°. In the analysis of potential risk factors, the difference in screw fixation level (p=0.009) and segmental distance between the tracker and the instrumented level (p=0.001) between the no-breached and breached group were statistically significant, but not for the other factors. The mean difference between the no-breach and breach groups was statistically significant in terms of pedicle width (p<0.001) and tail offset (p=0.042). In the learning curve analysis, the occurrence of breached and failed screws and the robot-used time per screw screws showed a significant decreasing trend. Conclusion : In the current study, RAPSF was highly accurate and the specific potential risk factors were not identified. However, pedicle width was presumed to be related to breached screw. Meanwhile, the robot-used time per screw and the incidence of breached and failed screws decreased with the learning curve.

• Journal of the Ergonomics Society of Korea
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• v.24 no.2
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• pp.65-70
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• 2005

Evaluation of repetitiveness for upper extremity intensive tasks is essential to determine the level of risk for upper extremity musculoskeletal disorders at the workplace. However, experimental data available to establish the acceptable levels of repetitiveness for various postures and forces is lacking. The present study examined the maximum acceptable frequencies(MAFs; motions/min.) of shoulder, elbow, wrist, and index finger motions at different forces(1kgf and 4kgf for shoulder, elbow, and wrist; 0.25kgf and 1 kgf for index finger) in sitting. Seventeen right-handed males in 20s without having any history musculoskeletal disorders participated in the MAF experiment. The participants determined their MAFs for the upper extremity motions by using the self-adjustment method and their work pulse(increase in heart rate; beats/min.) and rating of perceived exertion(RPE) were measured when working at MAF. The MAFs of elbow, wrist, and index finger motions for each force level were about 2, 3, and 6 times the corresponding MAF(9 at the high force and 24 at the low force) of shoulder motion and the MAFs at the low force increased about 2 times those at the high force. The work pulses of elbow, wrist, and index finger motions for each force level were 70%, 50%, and 30% of the corresponding work pulse(17 at the high force and 12 at the low force) of shoulder motion and the work pulses at the low force were about 70 % of those at the high force. Lastly, the RPEs of the upper extremity regions were about level 3(moderate) or below.

• Korean Journal of Radiology
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• v.20 no.5
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• pp.844-853
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• 2019

Objective: To evaluate the learning curve for C-arm cone-beam computed tomography (CBCT) virtual navigation-guided percutaneous transthoracic needle biopsy (PTNB) and to determine the amount of experience needed to develop appropriate skills for this procedure using cumulative summation (CUSUM). Materials and Methods: We retrospectively reviewed 2042 CBCT virtual navigation-guided PTNBs performed by 7 novice operators between March 2011 and December 2014. Learning curves for CBCT virtual navigation-guided PTNB with respect to its diagnostic performance and the occurrence of biopsy-related pneumothorax were analyzed using standard and risk-adjusted CUSUM (RA-CUSUM). Acceptable failure rates were determined as 0.06 for diagnostic failure and 0.25 for PTNB-related pneumothorax. Results: Standard CUSUM indicated that 6 of the 7 operators achieved an acceptable diagnostic failure rate after a median of 105 PTNB procedures (95% confidence interval [CI], 14-240), and 6 of the operators achieved acceptable pneumothorax occurrence rate after a median of 79 PTNB procedures (95% CI, 27-155). RA-CUSUM showed that 93 (95% CI, 39-142) and 80 (95% CI, 38-127) PTNB procedures were required to achieve acceptable diagnostic performance and pneumothorax occurrence, respectively. Conclusion: The novice operators' skills in performing CBCT virtual navigation-guided PTNBs improved with increasing experience over a wide range of learning periods.

• Journal of Environmental Impact Assessment
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• v.5 no.1
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• pp.47-60
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• 1996

Nitrate contamination problems from groundwater supplies have been reported throughout many countries in the world, including Korea. Nitrate salts can induce methemoglobinemia and possibly human gastric cancer. To reduce human health risk from nitrate in groundwater supplies, several nitrate risk-management strategies can be developed based on the acceptable level of human health risk, the reasonableness of nitrate-control cost, and the technical feasibility of nitrate-control methods. However, due to a lack of available information, assessing risk, cost and technical feasibility contains elements of uncertainty. In the present paper, a nitrate risk-management methodology using fuzzy sets in combination with a multiobjective decision-making (MODM) technique is developed to assist decision makers in evaluating, with uncertain information, various nitrate risk-management strategies in order to decide a proper strategy.

• Journal of Environmental Health Sciences
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• v.47 no.4
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• pp.356-365
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• 2021

Background: Concerns have been raised regarding the criteria of groundwater, in particular in Gwangwon-do Province where many residents drink groundwater due to the poor supply of tap water and a high nonconformity rate with water quality criteria nationwide. Objectives: Water quality monitoring and risk assessment were conducted for groundwater in Hoengseong, Gangwon-do Province. Methods: A total of 46 items required for meeting drinking water criteria were analyzed from 258 samples collected from March 2017 through August 2018 (152 sites in 2017 and 106 sites in 2018). Risk assessment was conducted for two non-carcinogens (F^- and NO₃-N), and one carcinogen (i.e., arsenic) based on their high nonconformity to water quality criteria. Results: Water quality analysis revealed that the total proportion of nonconformities was determined to be 27.9%. The nonconformity rate for each content item is as follows: total colony counts (1.6%), total coliform (6.2%), Escherichia coli (1.2%), F^- (8.1%), arsenic (4.7%), NO₃-N (8.1%), pH (1.2%), manganese (0.4%), and turbidity (5.8%). Risk assessment indicated that fluoride induced a hazard quotient greater than 1 with the 95% UCL (Upper Confidence Limit) concentration of the total 258 sites and average, median, and 95% UCL concentrations of nonconformity sites. For NO₃-N, there was no human health risk. For arsenic, the excess cancer risk exceeded the acceptable cancer risk of 1×10^-6 with the average and 95% UCL concentrations of total 258 sites and average, median, and 95% UCL concentrations of nonconformity sites. Conclusions: This study suggests that it is necessary to expand water quality monitoring of groundwater and conduct a more detailed risk assessment in order to establish a health care plan for the residents of Hoengseong, Gangwon-do Province.

• Nuclear Engineering and Technology
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• v.37 no.3
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• pp.273-278
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• 2005

Key concepts in South Korean nuclear safety regulation are safety and risk. Nuclear regulation in South Korea has required reactor designs and safeguards that reduce the risk of a major accident to less than one in a million reactor-years-a risk supposedly low enough to be acceptable. To date, in South Korean nuclear safety regulation has involved the establishment of many technical standards to enable administration enforcement. In scientific lawsuits in which the legal issue is the validity of specialized technical standards that are used for judge whether a particular nuclear power plant is to be licensed, the concept of uncertainty law is often raised with regard to what extent the examination and judgment by the judicial power affects a discretion made by the administrative office. In other words, the safety standards for nuclear power plants has been adapted as a form of the scientific technical standards widely under the idea of uncertainty law. Thus, the improvement of nuclear safety regulation in South Korea seems to depend on the rational lawmaking and a reasonable, judicial examination of the scientific standards on nuclear safety.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1995.11a
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• pp.51-58
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• 1995

The importance of the risk analysis tool has been recognized and its use also has been emphasized by a number of researchers recently The methodology were examined but neither algorithms nor practical applications have been implemented or practiced in Korea. In this paper, the architecture of the Buddy System, one of the automated risk assessment tools. is analyzed in depth to provide the algorithmic understanding and to promote the development of the risk analysis methodology. The Buddy System mainly uses three main factors of vulnerability, threat and countermeasures as a nucleus of the qualatative analysis with the modified loss expectancy value. These factors are identified and assessed by the separation of duties between the end user and security analyst. The Buddy System uses five axioms as its bases of assessment algorithm and the assessed vulnerability level is strictly within these axioms. Since the In-place countermeasures reduce the vulnerability level up to a certain level. the security analyst may use "what if " model to examine the impact of additional countermeasures by proposing each to reduce the vulnerability level further to within the acceptable range. The emphasis on the qualitative approach on vulnerability leveling is very well balanced with the quantitative analysis that the system performance is prominent.prominent.