• KEPCO Journal on Electric Power and Energy
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• v.3 no.2
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• pp.119-125
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• 2017

Regarding the implementation of ROMM project (Rehabilitation, Operation, Maintenance & Management), which is one of overseas development projects, it is very important to diagnose the exact current status of aged thermal power plant. However, when people visit the power plant for the purpose of prediagnosis to implement the ROMM project, most target power plants for diagnosis, in general, are under operation. This can be a big interference factor to diagnose the exact current status of power plants. Therefore, in order to solve such interference factor, based on the 30 years of know-how in the field, the present study has developed a regression curve for a simple life time assessment and the calculation of rehabilitation cost that may be used as a reference relatively for the quantitative diagnosis on the status of a relevant power plant even during the operation of the power plant.

• Journal of Applied Reliability
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• v.9 no.4
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• pp.291-302
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• 2009

Accelerated and field degradation tests are performed for reliability assessment of an anticorrosive paint for steel structures. Test data were analyzed to obtain the degradation model and the life time distributions of the paint. A power law degradation model and lognormal performance distribution were used to predict the lifetime of the anticorrosive paint and the method of finding an acceleration factor is provided.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.163-167
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• 2017

The service life extension of the missile can reduce the replacement cost of the missile, maintain the combat power, and consist of the lifetime assessment of the shelf-life(energetic) items, the maintenance of the missile and upgrade of the related components. This technology should be developed together with the missile system and advanced sustainedly. It is a converging technology that combines various fields of expertise and long-term experiences and databases.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.2
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• pp.37-42
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• 2016

While datacenter operation cost increases with electricity price rise, many researchers study low-power processor based supercomputers to reduce power consumption of datacenters. Reliability of low-power processors for supercomputers can be of concern since the reliability of many low-power processors are assessed based on mobile use conditions. This paper assessed the reliability of low-power processor packages based on supercomputer use conditions. Temperature cycling was determined as a critical failure cause of low-power processor packages through literature surveys and failure mode, effect and criticality analysis. The package temperature was measured at multiple processor load conditions to examine the relationship between processor load and package temperature. A physics-of-failure reliability model associated with temperature cycling predicted the expected lifetime of low-power processors to be less than 3 years. Recommendations to improve the lifetime of low-power processors were presented based on the experimental results.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.72-81
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• 2015

Objectives: The aim of this study was to investigate the exposure and risk assessment of residents near asbestos mines in Korea. Methods: To assess asbestos types and airborne concentrations, air monitoring was performed in the neighborhoods of Kwangcheon (KC) and Sinsuk (SS) mines, which were leading South Korean mines in the past. In addition, activity-based-sampling (ABS) of residents' particular activities were conducted in order to estimate the Excess Lifetime Cancer Risks (ELCRs) for the residents. Conclusions: The average concentration of airborne asbestos in KC was 0.0014 f/cc and 0.0015 f/cc by PCM and TEM, respectively. In SS it was equal at 0.0012 f/cc by PCM and TEM. No statistically significant difference was found in the average concentration of airborne asbestos between the two mines. The average asbestos concentration of ABS was 0.0048 f/cc (PCM) and 0.0042 f/cc (TEM) in KC, while it was 0.0137 f/cc (PCM) and 0.0125 f/cc (TEM) in SS. It was found that the average asbestos concentration of ABS in SS was statistically significantly higher than that of KC (p<0.01). The results of ELCRs by scenario in KC showed that the scenarios of bicycle, car, weed control, weed whacking, child playing in the dirt, and physical training fell within $1{\times}0^{-6}-1{\times}10^{-4}$, which is the acceptable range of ELCR. The scenarios of motorcycle, walker, digging, and field sweeping, however, exceeded the acceptable range. In SS, only the scenario of car fell within the acceptable range, while all of the other scenarios exceeded the acceptable range.

• Journal of Environmental Science International
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• v.17 no.1
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• pp.45-56
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• 2008

This study was to assess the lifetime cancer and non-cancer risk of exposure of worker and user at public facilities in Korea to volatile organic compounds (VOCs). We measured the concentrations of two aldehydes and five VOCs in indoor air at 424 public buildings that 8 kinds of public facilities (70 movie theaters, 86 offices, 86 restaurants, 70 academies, 22 auditoriums, 30 PC-rooms, 30 singing-rooms and 30 bars) all over the country. There were estimated the human exposure dose and risks with averages of the using-time and frequency for facility users and office workers, respectively. Carcinogens (formaldehyde, acetaldehyde, and benzene) were estimated the lifetime excess cancer risks (ECRs). non-carcinogens (toluene, ethylbenzene, xylene, and styrene) were estimated the hazard quotients (HQs). The average ECRs of formaldehyde and benzene for facility worker and user were $1{\times}10^{-3}{\sim}1{\times}10^{-4}\;and\;1{\times}10^{-4}{\sim}1{\times}10^{-5}$ level, respectively, in all facilities. HQs of four non-carcinogens did not exceed 1.0 for all subjects in all facilities. The estimated ECRs for restaurant and auditorium were the highest, and the PC-room and bar were the next higher facilities. Furthermore, people in a smoking facility had the highest cancer risk. Higher ECRs of formaldehyde and benzene were observed in indoor smoking facilities such as restaurant and auditorium. Higher HQs of toluene and xylene were observed at the restaurant and office building.

• Environmental Analysis Health and Toxicology
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• v.25 no.1
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• pp.57-68
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• 2010

This study assessed the lifetime cancer and non-cancer risk of aldehydes and volatile organic compounds exposure of young children at child-care facilities and indoor playgrounds in Korea. The samples were collected at various children's facilities (40 day-care houses, 42 child-care centers, 44 kindergartens, and 42 indoor playgrounds) in summer (Jul~Sep, 2007), winter (Jan~Feb, 2008) and Spring (Mar~Apr, 2008) periods, and analyzed by GC-MS. We estimated the lifetime excess cancer risks (ECRs) of formaldehyde, acetaldehyde, benzene, chloroform, CCI4 and tetrachloroethylene, and the hazard quotients (HQs) of Non-carcinogens (toluene, xylene, benzaldehyde and formaldehyde). Formaldehyde evaluated both cancer and non-cancer risk. The average ECRs of formaldehyde for young children were $1\times10^{-4}{\sim}1\times10^{-5}$ level in all facilities. HQs of four non-carcinogens did not exceed 1.0 for all subjects in all facilities.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.6
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• pp.2317-2322
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• 2015

Background: Despite the increasing number of screening examinations performed for cervical cancer utilizing the Papanicolaou smear test (Pap test), few studies have examined whether this strategy is cost-effective in Korea. Objective: This study was conducted to evaluate the cost-effectiveness of cervical cancer screening strategies incorporating the Pap test based on age at the start and end of screening as well as screening interval. Materials and Methods: We designed four alternative screening strategies based on patient age when screening was started (20 or 30 years) and discontinued (lifetime, 79 years). Each strategy was assessed at screening intervals of 1, 2, 3, or 5 years. A Markov model was developed to determine the cost-effectiveness of the 16 possible cervical cancer screening strategies, and this was evaluated from a societal perspective. The main outcome measures were average lifetime cost, incremental quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratio (ICER). Results: Compared with various strategies comprising younger starting age, discontinuation age, and longer screening intervals, strategies employing annual screening for cervical cancer starting at a target age of 30 years and above were the most cost-effective, with an ICER of 21,012.98 dollars per QALY gained (with a Korean threshold of 30,000,000 KRW or US$27,272). Conclusions: We found that annual screening for cervical cancer beginning at a target age of 30 years and above is most cost-effective screening strategy. Considering the potential economic advantages, more intense screening policies for cervical cancer might be favorable among countries with high rates of cervical cancer and relatively low screening costs.

• Tribology and Lubricants
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• v.34 no.2
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• pp.49-54
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• 2018

Hydraulic reciprocating seal has been widely used to prevent fluid leakage in hydraulic systems. Also, hydraulic reciprocating seal plays a significant role to provide lubricant film at contacting interface to minimize tribological problems due to sliding with counter material. To predict lifetime of hydraulic reciprocating seal, quantitative understanding of wear characteristics with respect to operating conditions such as normal force and sliding speed is needed. In this work, effect of sliding speed on wear of polyurethane (PU) hydraulic reciprocating seal were experimentally investigated using a pin-on-disk tribo-tester. The wear characteristics of PU specimens were quantitatively determined by comparing the confocal microscope data before and after test. It was found that the wear rate of PU specimens decreased from $4.9{\times}10^{-11}mm^3$ to $1.1{\times}10^{-11}mm^3/Nm$ as sliding speed increased from 120 mm/s to 940 mm/s. Also, it was observed that the friction decreased slightly as the sliding speed increased. Improvement of lubrication state with increasing sliding speed was likely to be responsible for this enhanced friction and wear characteristics. This result also suggests that decrease in sliding distance between PU elastomer and counter materials at lower sliding speed is preferred. Furthermore, the quantitative assessment of wear characteristics of PU specimen may be useful in prediction of lifetime of PU hydraulic reciprocating seal if the allowed degree of wear for failure of the seal is provided.

• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.289-302
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• 2017

The key risk analysis technologies for the re-entry of space objects into Earth's atmosphere are divided into four categories: cataloguing and databases of the re-entry of space objects, lifetime and re-entry trajectory predictions, break-up models after re-entry and multiple debris distribution predictions, and ground impact probability models. In this study, we focused on reentry prediction, including orbital lifetime assessments, for space situational awareness systems. Re-entry predictions are very difficult and are affected by various sources of uncertainty. In particular, during uncontrolled re-entry, large spacecraft may break into several pieces of debris, and the surviving fragments can be a significant hazard for persons and properties on the ground. In recent years, specific methods and procedures have been developed to provide clear information for predicting and analyzing the re-entry of space objects and for ground-risk assessments. Representative tools include object reentry survival analysis tool (ORSAT) and debris assessment software (DAS) developed by National Aeronautics and Space Administration (NASA), spacecraft atmospheric re-entry and aerothermal break-up (SCARAB) and debris risk assessment and mitigation analysis (DRAMA) developed by European Space Agency (ESA), and semi-analytic tool for end of life analysis (STELA) developed by Centre National d'Etudes Spatiales (CNES). In this study, various surveys of existing re-entry space objects are reviewed, and an efficient re-entry prediction technique is suggested based on STELA, the life-cycle analysis tool for satellites, and DRAMA, a re-entry analysis tool. To verify the proposed method, the re-entry of the Tiangong-1 Space Lab, which is expected to re-enter Earth's atmosphere shortly, was simulated. Eventually, these results will provide a basis for space situational awareness risk analyses of the re-entry of space objects.