• 한국화재소방학회논문지
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• 제32권5호
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• pp.34-39
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• 2018

본 연구에서는 구획 공간 화재 시 발열량이 급격히 변하는 조건에서 스프링클러헤드의 손실인자 변화에 따른 작동시간을 분석하였다. 이를 위해서 내화보드로 구성된 구획 공간의 크기가 폭 0.3 m, 세로 0.5 m, 길이 3.0 m인 구조물을 제작하고 헵탄(n-Heptane) 풀 화재 실험을 수행하여 구획 공간 내부의 온도 분포, 헵탄의 질량감소율 그리고 발열량을 산출하였다. 또한, Fire Dynamics Simulator (FDS) Version 6.5를 사용하여 실험 조건과 동일한 발열량을 가정하고 스프링클러헤드의 설치위치 및 손실인자(C-factor) 변화에 따른 작동 시간을 분석하였다. 그 결과 반응시간지수(Response Time Index, RTI)가 $100(m{\cdot}s)^{0.5}$이고 작동온도가 $72^{\circ}C$인 스프링클러는 화원 상층부의 기류 온도가 $100^{\circ}C$에서 $300^{\circ}C$로 상승하고, 기류의 속도가 약 0.7 m/s인 경우 C-factor = 0과 1일 때 스프링클러의 작동시간은 최소 30 s~60 s, C-factor = 3일 때 62 s에서 최대 92 s, C-factor = 5일 때 120 s 이상으로 나타났다.

• Geomechanics and Engineering
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• 제33권2호
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• pp.141-154
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• 2023

This study investigated the effect of water retention characteristics between aged and fresh Municipal Solid Waste (MSW) on the stability of the landfill. A series of transient numerical modeling for the slope of an MSW landfill was performed considering the variation of water retention characteristics due to leachate circulation. Four different scenarios were considered in this analysis depending on how to obtain hydraulic conductivity and the aging degree of materials. Unsaturated hydraulic properties of the MSW used for the modeling were evaluated through modified hanging column tests. Different water retention properties and various landfill conditions, such as subgrade stiffness, leachate injection frequency, and gas and leachate collection system, were considered to investigate the pore water distribution and slope stability. The stability analyses related to the factor of safety showed that unsaturated properties under those varied conditions significantly impacted the slope stability, where the factor of safety decreased, ranging between 9.4 and 22%. The aged materials resulted in a higher factor of safety than fresh materials; however, after 1000 days, the factor of safety decreased by around 10.6% due to pore pressure buildup. The analysis results indicated that using fresh materials yielded higher factor of safety values. The landfill subgrade was found to have a significant impact on the factor of safety, which resulted in an average of 34% lower factor of safety in soft subgrades. The results also revealed that a failed leachate collection system (e.g., clogging) could result in landfill failure (factor of safety < 1) after around 298 days, while the leachate recirculation frequency has no critical impact on stability. In addition, the accumulation of gas pressure within the waste body resulted in factor of safety reductions as high as 24%. It is essential to consider factors related to the unsaturated hydraulic properties in designing a landfill to prevent landfill instability.

• 터널과지하공간
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• 제29권5호
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• pp.356-366
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• 2019

다양한 TBM 성능 예측 모델이 개발되었기만 대부분 관입율 예측에 한정되어 있다. 일부 모델들이 수식과 그래프를 이용하여 TBM 가동율을 추정하는 방법을 제시하기도 하지만, TBM 가동율에 대한 연구는 매우 드문 편이다. TBM 가동율은 TBM 장비의 종류, 운영, 유지보수, 지질 조건, 시공자의 경험 등에 영향을 받는다. 본 연구에서는 100여개 이상의 사례 분석을 통해서 TBM 가동율과 RMR, 암종 등의 지반 조건, TBM의 종류, 터널의 연장 및 직경 등과의 관계를 조사하였다. 단순 및 다중 회귀분석을 수행하여 TBM 가동율 예측모델을 개발하였다. 암종 등의 지반조건, TBM의 종류, 터널의 연장 및 직경 등을 설명 변수로 갖는 회귀모델은 낮은 상관계수를 나타내었다. RMR을 설명변수로 갖는 회귀모델이 더 높은 상관계수를 나타내었다.

• 한국직업건강간호학회지
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• 제14권2호
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• pp.108-117
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• 2005

Purpose: This paper was attempted to focused on the analysis of job stress and job satisfaction according to the moderating effects of social support. Method: Data collected from 302 staff nurses in 2 general hospitals, with self-reporting questionnaires(Wolfgang's HPSI, modified Hagihara's social support, and MSQ). Descriptive statistics, Cronbach's alpha, Pearson correlation, ANOVA, and moderated regression analysis were used. Result: The subjects exhibited significantly highest level of 'the work and patients' conditions'. The perceived job stress was negatively correlated with supervisor and co-workers' support, and job satisfactions. Also supervisor and coworkers' support were positively correlated with job satisfactions. The main factor that affected the job satisfactions was 'work and patient conditions' and it was explained 35.5% out of the total variance of the job satisfactions with 'the work load and disturbing factor', 'supervisor support' and 'co-workers' support'. Supervisor support moderated the relationships between 'the patient care responsibilities and career development factor' and satisfaction. Conclusion: For developing the stress management program for hospital nurses, 'the work and patients' conditions', and the strategies of strengthening 'supervisor and co-workers' support' should be considered. In addition to, it may be considered to examine the effects of social support on the other criterion variables.

• 화약ㆍ발파
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• 제23권3호
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• pp.75-82
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• 2005

여러 발파공학자들이 현지 암반의 지역적 특성을 고려한 발파를 위해 적용할 수 있는 나름대로의 방법론들을 개발하고 있는 실정이다. 그러나 대부분의 방법론들이 지역적인 암반 특성을 반영할 수 있도록 체계화되어 있지 못할 뿐만 아니라 발파자의 관찰과 경험에만 주로 의존한다는 단점이 있다. 본 연구에서는 현지암반의 고유한 공학적 특성을 고려할 수 있도록 Lilly가 제안한 발파지수(blastability index) 개념을 도입하여 발파설계 인자를 도출할 수 있도록 시도하였다. 발파지수 산정 시에는 암반 자체의 공학적 특성뿐만 아니라 절리분포 특성도 반영이 되므로 현지 여건에 부합될 수 있는 발파암 분류가 가능하고, 합리적인 발파설계를 수행하는 데에 도움이 될 것으로 기대된다.

• 한국터널지하공간학회 논문집
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• 제16권2호
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• pp.125-133
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• 2014

본 연구에서는 지반 및 현장조건을 고려한 TBM 선정방법을 제시하였다. 지반, 환경, 가격조건별로 TBM 선정에 영향을 미치는 인자와 굴착장비를 선정 분류 하였다. 선정된 영향인자와 장비 간 가중치를 AHP기법을 적용하여 산정하였다. 선정된 영향인자의 분석결과 기본요소에서는 지반조건이 가장 중요한 영향요소로 확인되었으며, 세부요소로서 암반조건에서는 강도, 토사지반조건에서는 수압이 가장 중요한 인자로 확인되었다. 주변 환경조건에서는 시공성에 영향을 줄 수 있는 주변구조물 인접여부가 중요한 인자로 확인되었다. 마지막으로 도출된 각 영향인자별 가중치를 토대로 굴착현장에 적용 가능한 TBM을 선정하고 도출결과와 실제 현장에 적용된 장비의 비교를 통하여 본 연구에서 제안하는 방법에 대한 검증이 이루어 졌다.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2188-2197
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• 2022

To ensure the safety margin of a reactor pressure vessel (RPV) under normal operating conditions, it is regulated through the pressure-temperature (P-T) limit curve. The stress intensity factor (SIF) obtained by the internal pressure and thermal load should be obtained through crack analysis of the nozzle corner crack in advance to generate the P-T limit curve for the nozzle. In the ASME code Section XI, Appendix G, the SIF via the internal pressure for the nozzle corner crack is expressed as a function of the cooling or heating rate, and the wall thickness, however, the SIF via the thermal load is presented as a polynomial format based on the stress linearization analysis results. Inevitably, the SIF can only be obtained through finite element (FE) analysis. In this paper, simple prediction equations of the SIF via the thermal load under, cool-down and heat-up conditions are presented. For the Korean standard nuclear power plant, three geometric variables were set and 72 cases of RPV models were made, and then the heat transfer analysis and thermal stress analysis were performed sequentially. Based on the FE results, simple engineering solutions predicting the value of thermal SIF under cool-down and heat-up conditions are suggested.

• 대한기계학회논문집B
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• 제30권4호
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• pp.381-388
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• 2006

The objective of this study is to predict the etching characteristics using spray characteristics for the optimization on the etching process of Lead-Frame. The etching characteristics such as etching factor, uniformity were investigated on the actual operating conditions. The correlation between the etching characteristics and the spray ones obtained by measurement were analyzed to simulate the etching characteristics according to actual conditions of lead-frame etching process. These conditions of lead-frame process were spray pressure, distance from nozzle tip to substrate, pipe pitch, and nozzle pitch. To improve the etching characteristics in the lead-frame process, effects of the various operating conditions should be understood in detail. The spray characteristics obtained by experiment using PDA system were simulated by the Monte-Carlo method. The etching process model was coded by Java language. It was found that simulation results generally agreed well with the measured results of etching characteristics in lead-frame etching process. The optimal operating parameters were successfully found under variable conditions.

• 한국안전학회지
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• 제28권4호
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• pp.8-13
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• 2013

Fatigue crack growth tests were conducted on urban railway wheel steel under mode I and mixed-mode conditions. Fatigue crack growth rates were evaluated in terms of equivalent stress intensity factor ranges, using both the extended and projected crack lengths. The equivalent stress intensity factor range with the growth rate results obtained under mode I loading conditions can be used to predict the crack growth rate under mixed-mode loading conditions. Extended crack length rather than projected crack length is appropriate for the prediction of the crack growth rate under the mixed-mode loading conditions.

• 한국식품조리과학회지
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• 제25권6호
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• pp.725-738
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• 2009

The purpose of this study was to investigate the effects of working conditions on internship satisfaction. Hotel & Restaurant management students at universities in Jeonju participated in this study. Out of 156 questionnaires, 149 were analyzed using SPSS 17.0 and descriptive analysis, frequency test, factor analysis, reliability test, chi-square, t-test, ANOVA, duncan's multiple regression analysis, correlation analysis and regression analysis were used. Based on the result of the conducting factor analysis, the working conditions were classified into 2 factors: work suitability and work environment. Internship satisfaction was classified into 3 factors: internship preference, education and work satisfaction, company satisfaction. Cronbach's alpha was calculated for the reliability of the survey instrument. Consequently, the working conditions were shown to affect internship satisfaction. Among the working conditions, work suitability had a lower effect on internship satisfaction than work environment. At the resort used in this study, the salary level was high, but the level of work environment, internship preference, and company satisfaction was low. The students wanted attend an internship program at the desired place to be hired and found that it was more important to be assigned to the desired department than having a higher salary.