• Nuclear Engineering and Technology
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• 제40권5호
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• pp.365-374
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• 2008

Dependability-critical systems, such as digital instrumentation and control systems in nuclear power plants, necessitate engineering techniques and tools to provide assurances of their safety and reliability. Determining system reliability at the architectural design phase is important since it may guide design decisions and provide crucial information for trade-off analysis and estimating system cost. Despite this, reliability and system engineering remain separate disciplines and engineering processes by which the dependability analysis results may not represent the designed system. In this article we provide an overview and application of our approach to build architecture-based, dynamic system models for dependability-critical systems and then automatically generate dynamic fault trees (DFT) for comprehensive, tool-supported reliability analysis. Specifically, we use the Architectural Analysis and Design Language (AADL) to model the structural, behavioral and failure aspects of the system in a composite architecture model. From the AADL model, we seek to derive the DFT(s) and use Galileo's automated reliability analyses to estimate system reliability. This approach alleviates the dependability engineering - systems engineering knowledge expertise gap, integrates the dependability and system engineering design and development processes and enables a more formal, automated and consistent DFT construction. We illustrate this work using an example based on a dynamic digital feed-water control system for a nuclear reactor.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.1132-1139
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• 2006

Railway risk is evaluated by a method of linking event trees and fault trees as the general PSA(Probabilistic Safety Assessment) model for the risk assessment of complex systems. Accident scenarios causing undesirable events are modeled by event trees comprised of several accident sequences. Each branch located in the accident progression of the event tree is modeled by an fault tree or can be represented by some value too simply. We usually evaluate the frequency of the whole sequence by adding them after calculating the frequency of each sequence at a time. However, since there are quite a number of event trees and fault trees in the railway risk assessment model, the number of sequence to evaluate increases and preparation for the risk assessment costs much time all the more. Also, it may induce errors when analysts perform the work of quantification. Therefore, the systematic maintenance and control of event trees and fault trees will be essential for the railway risk assessment. In this paper we introduce an integrated assessment method using one-top model and develop a risk assessment tool for the maintenance and control of the railway risk model.

• 한국항해항만학회지
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• 제36권7호
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• pp.571-575
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• 2012

Berthing and unberthing maneuver is essential work for marine pilots and securing the safety against risks during the maneuver is more important than anything else. Moreover, the maneuvering environment in ports and harbors has changed rapidly and got worse due to development of a new port, the advent of a new type or large-sized ship, and the rapid increase in harbor traffic. As one of measures taken to cope with such changes in the maneuvering environment and for each pilot to improve his own maneuvering ability, this paper developed laptop-based ship-handling simulator which is readily available anytime and anywhere. This paper is to develop a conning display for ship's maneuvering and electronic chart based display widely used nowadays to represent a model ship's movement. The displays were arranged appropriately considering pilot age, easy handling by mouse, using a maximum screen, proper arrangement of rudder, engine, thruster, tug etc and representation of information. Up to now thirteen (13) model ships were developed based on real-ship, whose mathematical model is Japanese MMG & pilots' low speed maneuver.

• Nuclear Engineering and Technology
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• 제31권5호
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• pp.465-475
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• 1999

The objective of the present work is to assess the analysis capability of two wall film condensation models, the default and the alternative models, of RELAP5/MOD3.2 on condensation experiments in the presence of noncondensable gas in a vertical tube of PCCS of CP-1300. In the calculation of a base case the default model of RELAP5/MOD3.2 under-predicts the heat transfer coefficients, and Its alternative model over-predicts them throughout the condensing tube, Also, both models over-predict the void fractions. The nodalization study shows that the variation of the node number does not change both modeling results of RELAP5/MOD3.2 Sensitivity study for varying input parameters shows that the inlet steam-air mixture flow rate, the inlet air mass fraction, and the inlet saturated steam temperature give significant changes of their heat transfer coefficients Run statistics show that the grind time of the default model is always higher than that of the alternative model by about 23%.

• 한국식품위생안전성학회지
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• 제18권4호
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• pp.202-210
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• 2003

두부는 양질의 단백질을 주성분으로 한 대중 식품으로 소비량이 계속 증가하고 있다. 두부는 변질 발생 가능성이 높은 고위험 식품에 해당되지만, 두부제조업체는 82.4%가 종업원 5인 이하 소규모로 체계적인 식품안전관리를 기대하기 어려운 실정이다. HACC(Hazard Analysis Critical Control Point : 위해요소 중점관리제도)는 식품안전성과 비용절감을 ㅎ율적으로 확보할 수 있는 체계적, 지속적인 공정관리 방법이다. 본 연구는 두부제조업체의 실정에 맞는 HACCP시스템을 개발하여 적용하고 그 성과를 확인함으로써 두부 HACCP 시스템의 일반적 모델을 확정하고 다른 중소업체 및 대기업으로 이를 확산시키려고 시행하였다. 규모별 4개 두부제조업체를 대상으로 판 두부와 포장 판 두부의 HACCP 계획을 Codex의 HACCP 적용 지침에 따라 현장 실부자와 협력하여 수립하였다. HACCP 팀 편성, HACCP 범위 및 목적의 설정, 제품 기술 및 사용자 의도의 결정, 공정도 작성 및 현장 검증, 위해 분석 및 예방책 식별, CCP(중요관리점)의 식별, CL(관리할계기준) 설정, CCP 모니터링 시스템 수립, 개선조치 설정, 검증절차 수립, 기록 및 문서화의 순서로 HACCP 계획을 작성하였다. 공정 중 CCP는 선별 공정, 냉각 공정, 열처리 공정(판 두부는 제외)으로 결정하였고, 각각의 HACCP 계획에 따라 관리하였다. 제정된 HACCP시스템을 3개월간 시행한 후 그 성과를 HACCP 적용 이전과 이후의 미생물 검사를 통하여 확인하였다. 검사결과 HACCP 적용 이전의 판두부 플라스틱 상자, 포장재, 완제품의 일반 세균수가 HACCP 적용 이후에 크게 감소되었다.(P<0.1) 두부제조업체의 실정에 맞는 HACCP 시스템을 적용함으로써 위생관리 및 식품안정성 확보에 큰 성과가 있음이 확인되었다.

• 한국직업건강간호학회지
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• 제25권1호
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• pp.65-74
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• 2016

Purpose: The purpose of this study is to predict industrial accident rate using time series analysis. Methods: The rates of industrial accident and occupational injury death were analyzed using industrial accident statistics analysis system of the Korea Occupational Safety and Health Agency from 2001 to 2014. Time series analysis was done using the most recent data, such as raw materials of Economically Active Population Survey, Economic Statistics System of the Bank of Korea, and e-National indicators. The best-fit model with time series analysis to predict occupational injury was developed by identifying predictors when the value of Akaike Information Criteria was the lowest point. Variables into the model were selected through a series of expertises' consultations and literature review, which consisted of socioeconomic structure, labor force structure, working conditions, and occupational accidents. Results: Indexes at the meso- and macro-levels predicting well occurrence of occupational accidents and occupational injury death were labor force participation rate for ages 45-49 and budget for small scaled workplace support. The rates of industrial accident and occupational injury death are expected to decline. Conclusion: For reducing industrial accident continuously, we call for safe employment policy of economically active middle aged adults and support for improving safety work environment of small sized workplace.

• 한국환경보건학회지
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• 제35권6호
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• pp.500-509
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• 2009

Passive samplers have been used for many years for the sampling of organic vapors in work environment atmospheres. Currently, all passive samplers used in domestic occupational monitoring are foreign products. This study was performed to evaluate variable parameters for the development of passive organic samplers, which include the geometry of the device and diffusive length for the sampler design. Four prototype diffusive lengths; A-1(4.5 mm), A-2(7.0 mm), A-3(9.5 mm), A-4(12.0 mm) were tested for adsorption performances to a chemical mixture (benzene, toluene, trichloroethylene, and n-hexane) according to the US-OSHA's evaluation protocol. A dynamic vapor exposure chamber developed and verified by related research was used for this study. The results of study are as follows. The results in terms of sampling rate and recommended sampling time test indicate that the most suitable model was A-3 (9.5 mm diffusive lengths on both sides) for passive sampler design in time weighted average (TWA) assessment. Sampling rates of this A-3 model were 45.8, 41.5, 41.4, and 40.3 ml/min for benzene, toluene, trichloroethylene, and n-hexane, respectively. The A-3 models were tested on reverse diffusion and conditions of low humidity air (35% RH) and low concentrations (0.2 times of TLV). These conditions had no affect on the diffusion capacity of samplers. In conclusion, the most suitable design parameters of passive sampler are: 1) Geometry and structure - 25 mm diameter and 490 $mm^2$ cross sectional area of diffusion face with cylindrical form of two-sided opposite diffusion direction; 2) Diffusive length - 9.5 mm in both faces; 3) Amount of adsorbent - 300 mg of coconut shell charcoal; 4) Wind screen - using nylon net filters (11 ${\mu}m$ pore size).

• Safety and Health at Work
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• 제10권1호
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• pp.39-46
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• 2019

Background: As of now, the impact of low back pain (LBP) and its chronic state, chronic low back pain (CLBP), on mental health-related quality of life (HRQOL) has never been investigated among police officers. The present investigation aims at studying this relationship using a biopsychosocial model. Methods: Between May and October 2014, a Web-based cross-sectional study was conducted among Quebec police officers (Quebec, Canada). Mental HRQOL was measured using the role emotional (RE) and the mental health (MH) domains of the SF-12v2 Health Survey. The impact of CLBP on mental HRQOL (as opposed to acute/subacute LBP or no LBP) was studied with a multivariate linear regression model. Results: Of the 3,589 police officers who participated in the study, 1,013 (28.4%) reported CLBP. The mean age of respondents was $38.5{\pm}8.7years$, and 32.0% were females. The RE (44.1/100) and MH (49.0/100) mean scores of the CLBP group were comparable with the scores found in populations suffering from cancer or heart diseases. Compared to officers without LBP, the presence of CLBP was significantly associated with lower RE (${\beta}$: -0.068; p = 0.003) and MH (${\beta}$: -0.062; p = 0.002) scores. These relationships were not found in the acute/subacute LBP group. Conclusion: Our results underscore how frequent CLBP is among police officers and how burdensome it is. Considering the importance of good physical and mental health for this occupational population, police organizations should be aware of this issue and contribute to the efforts toward CLBP prevention and management in the workplace.

• Safety and Health at Work
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• 제15권1호
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• pp.59-65
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• 2024

Background: Different job strain formulations based on the Job Demand-Control model have been developed. This study evaluated longitudinal associations between job strain and psychological distress and whether associations were influenced by six formulations of job strain, including quadrant (original and simplified), subtraction, quotient, logarithm quotient, and quartile based on quotient, in randomly selected Japanese workers. Methods: Data were from waves I and II of the Survey of Midlife in Japan (MIDJA), with a 4-year followup period. The study sample consisted of 412 participants working at baseline and had complete data on variables of interest. Associations between job strain at baseline and psychological distress at follow-up were assessed via multivariable linear regression, and results were expressed as β coefficients and 95% confidence intervals including R² and Akaike information criterion (AIC) evaluation. Results: Crude models revealed that job strain formulations explained 6.93-10.30% of variance. The AIC ranged from 1475.87 to 1489.12. After accounting for sociodemographic and behavioral factors and psychological distress at baseline, fully-adjusted models indicated significant associations between all job strain formulations at baseline and psychological distress at follow-up: original quadrant (β: 1.16, 95% CI: 0.12, 2.21), simplified quadrant (β: 1.01, 95% CI: 0.18, 1.85), subtraction (β: 0.39, 95% CI: 0.09, 0.70), quotient (β: 0.37, 95% CI: 0.08, 0.67), logarithm quotient (β: 0.42, 95% CI: 0.12, 0.72), and quartile based on quotient (β: 1.22, 95% CI: 0.36, 2.08). Conclusion: Six job strain formulations showed robust predictive power regarding psychological distress over 4 years among Japanese workers.

• 한국지반신소재학회논문집
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• 제15권4호
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• pp.25-32
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• 2016

지반공학에서 평면변형율을 가정하는 2차원 사면안정해석은 일반적으로 널리 사용되고 있다. 이 가정은 사면활동이 넓은 영역에 걸쳐서 발생되는 가정이므로 3차원 효과가 무시된다. 대다수 연구에서 2차원해석의 최소안전율값은 3차원해석에 비하여 작게 평가되는 보수적인 결과를 나타낸다. 최근에는 컴퓨터의 소프트웨어와 하드웨어를 포함한 해석방법의 발달로 3차원해석에 대한 요구가 커지고 있다. 본 논문에서는 원호모드, 병진모드사면을 이용하여 유한요소에 의한 2, 3차원해석 및 2차원 한계평형해석을 통하여 수치해석을 실시하였다. 해석결과 매개변수(요소망크기, 체적팽창각(dilatency angle), 경계조건, 응력이력, 모델차원)에 따른 사면안정해석에 미치는 영향을 분석하였다. 해석결과 2차원 해석보다 3차원 해석에 의한 사면의 안전율 값은 항상 크게 평가되며, W 뱡향 경계조건이 롤러지지인 경우, 사면폭에 의한 결과 차이는 없는 것으로 조사되었다.