• 한국안전학회지
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• 제18권3호
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• pp.8-13
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• 2003

Equivalent Reynolds equation of truncated cone type SFD bearing using nonnewtonian EV fluid is derived. The 3 nondimensional oil film pressures and its forces are obtained with axial and circumferential pressure gradient of bearing respectively, and dynamic characteristics for the stability of rotor-bearing system are obtaind through the governing equation for an elastic rotational shaft. It is shown that EV fluid is less sensitive to the changes of oil-film than newtonian fluids for dynamic characteristics. Therefore, results show that it is better to use an EV fluid with truncated cone type SFD bearing for the vibration control of rotational machines.

• 비파괴검사학회지
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• 제30권3호
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• pp.200-206
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• 2010

In ultrasound-excited thermography, the injected ultrasound to an object is transformed to heat and the appearance of defects can be visualized by thermography camera. The advantage of this technology is selectively sensitive to thermally active defects. Despite the apparent simplicity of the scheme, there are a number of experimental considerations that can complicate the implementation of ultrasound excitation thermography inspection. Factors including acoustic horn location, horn-crack proximity, horn-sample coupling, and effective detection range all significantly affect the detect ability of this technology. As conclusions, the influence of coupling pressures between ultrasound exciter and specimen was analyzed, which was dominant factor in frictional heating model.

• 한국안전학회지
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• 제32권4호
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• pp.53-58
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• 2017

The rebound hammer test and the measurement of ultrasonic pulse velocity(UPV) have been widely used for the physical properties & condition evaluation of reinforced & prestressed concrete structures for a long time, but the acoustoelastic effects by the prestressing in the prestressed concrete structures on the rebound number and ultrasonic pulse velocity have not been studied clearly. Therefore, this study investigated the data distribution of the rebound numbers and ultrasonic pulse velocities in reinforced and prestressed concrete slabs of $3000{\times}3000mm$ with a thickness of 250 mm. Also, the Kolmogorov-Smirnov goodness-of-fit test was done in order to identify statistical consistency and reliability. The statistical analysis results show that the rebound number and ultrasonic pulse velocities increased about 1.9% and 2.5%, respectively when prestressing was applied. As expected, the UPV shows better statistical reliability and potential for in situ evaluation than the RB because the RB are more sensitive to testing posture, surface condition, temperature and humidity so on. The experimental data in this study can be used for the condition assessment of reinforced and prestressed concrete structures by the rebound number and ultrasonic pulse velocity.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1321-1329
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• 2016

To get an insight into the operating characteristics of the passive residual heat removal system of molten salt reactors, a two-phase natural circulation test facility was constructed. The system consists of a boiling loop absorbing the heat from the drain tank, a condensing loop consuming the heat, and a steam drum. A steady-state experiment was carried out, in which the thimble temperature ranged from $450^{\circ}C$ to $700^{\circ}C$ and the system pressure was controlled at levels below 150 kPa. When reaching a steady state, the system was operated under saturated conditions. Some important parameters, including heat power, system resistance, and water level in the steam drum and water tank were investigated. The experimental results showed that the natural circulation system is feasible in removing the decay heat, even though some fluctuations may occur in the operation. The uneven temperature distribution in the water tank may be inevitable because convection occurs on the outside of the condensing tube besides boiling with decreasing the decay power. The instabilities in the natural circulation loop are sensitive to heat flux and system resistance rather than the water level in the steam drum and water tank. RELAP5 code shows reasonable results compared with experimental data.

• 한국식품과학회지
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• 제46권1호
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• pp.7-12
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• 2014

Flutianil은 흰가루병에 높은 방제효과를 가지는 thiazolidine계 살균제로서 고추, 피망, 오이, 참외에 대해 flutianil의 사용등록이 신청됨에 따라 농산물 중 flutianil 잔류량을 측정하기 위한 검사법을 개발하였다. Flutianil 잔류물은 acetonitrile로 추출하여 포화식염수와 dichloromethane을 이용한 액-액분배과정을 수행하였고, silica 카트리지를 이용하여 clean-up을 실시한 후 GC-ECD를 통해 기기분석을 수행하였으며, GC-MS로 재확인하였다. flutianil 표준품의 직선성은 상관계수($R^2$)가 0.999이상으로 우수하였고 고추, 피망, 감귤, 감자, 현미, 대두에 대한 flutianil의 회수율을 측정한 결과, 76.5-108.0%의 범위로 10% 미만의 표준오차를 나타내었으며, 분석법의 검출한계는 0.004 mg/kg, 정량한계 0.02 mg/kg이었다. 이는 코덱스 가이드라인(CAC/GL 40)인 회수율 70-120%, 분석오차 10 미만에 적합함을 보여주어 분석법의 정확성을 확인하였다. 본 연구에서 개발한 시험법은 flutianil 분석을 위한 신속, 정확한 시험법으로, 국내에서 유통되는 농산물 중 flutianil 잔류물의 안전관리를 위한 공정시험법으로 활용될 예정이다.

• 한국산업보건학회지
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• 제30권4호
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• pp.331-341
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• 2020

Objectives: This study was conducted to evaluate perceptions of safety and risk among Korean industrial hygienists and the change between before and after the Sewol Ferry Disaster in 2014. Two surveys with questionnaires composed of 51 questions were completed by attendees of the Korea Industrial Hygiene Association(KIHA) conference. Methods: One was conducted at the 2013 KIHA Fall Conference(N=181) and the other was from the 2014 KIHA Summer Conference(N=123). Between these two surveys was the Sewol Ferry Disaster on April 14, 2014, which was believed to seriously affect safety and risk perceptions in Korea. Results: It was revealed that industrial hygienists' awareness of safety rules strengthened after the Sewol Ferry Disaster(p<0.05). It was apparent that people over the age of 30 were more sensitive to social safety. There was no significant difference in the evaluation and attitude regarding governmental safety policy between the years of 2013 and 2014. The credibility of public organizations responsible for the disaster management system decreased. The self-evaluation of respondents' safety level also decreased. This trend shows mainly in the younger generation. It was evaluated that the overall social safety level decreased and the anxiety level increased. The score on social safety on a ±5 Likert scale was 0.68 in the 2013 survey and -0.33 in the 2014 survey(p<0.05). It was reported that the most serious threat factors for accident or disaster were 'building collapse > illegalities and corruption > side effects of radiation therapy >accidents in normal activity > occupational disease,' in order. They picked 'safety ignorance > hurry-up habits and culture > focusing on short-term benefit > easy-going attitude > insufficient safety education' for the causes of low social safety levels in 2013. In 2014, they were 'safety ignorance > easy-going attitude > focusing on short-term benefit > insufficient safety education > hurry-up habits and culture'. Conclusions: This study has some limitations because it was originally not designed to survey attitudes prior to the Sewol Ferry disaster in 2013. In addition, the survey targets are industrial hygienists who are familiar with occupational disease and injury.

• 대한기계학회논문집A
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• 제37권4호
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• pp.521-527
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• 2013

본 논문에서는 3 차원 유한요소해석을 통해 표면균열이 있는 직관에 내압, 굽힘, 그리고 비틀림의 단일 또는 복합하중이 작용하는 경우의 응력확대계수를 연구하였다. 두 가지 결함평가코드(API-579-1, RCC-MR A16)를 각각 유한요소해석 결과와 비교하여 코드 간의 차이 및 해석의 신뢰성을 확인하였다. 응력확대계수는 적분 경로에 독립적이기 때문에 민감하지 않다고 알려져 있는데 3 차원 유한요소해석을 통해 요소 수에 대한 민감도를 확인하였다. 또한 균열형상의 정의방법에 따른 유한요소해석 결과의 차이와 두 가지 결함평가코드를 사용한 결과의 차이를 확인하였다.

• 한국식품위생안전성학회지
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• 제18권2호
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• pp.79-86
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• 2003

대부분의 식중독은 단체 급식으로부터 발생하는 경우가 많으며, 특히 위생상태와 연관되어 식중독을 야기 시키는 병인 물질 중 포도상 구균은 많은 부분을 차지하고 있다 따라서 본 연구에서는 서부경남지역의 5개 초등학교 급식시설에서 총 98개의 샘플 중 A 급식소의 식수, D 급식소의 손, E 급식소의 냉장고와 앞치마에서 4개의 포도상 구균을 분리하였다. 분리된 균주들은 1개의 메티실린 저항성 혈장응고 효소 음성 황색포도상구균(Methicilline Resistant Coagulase Negative Staphylococcus aureus； MRCPS)과 3개의 메치실린 민감성 혈장응고효소 양성 황색포도상구균 (Methicilline sensitive Coagulase positive Staphylococcus aureus； MSCPS)으로 구분되었다. 한편 포도상 구균은 내열성 내독소로서, 이 중 가장 문제가 되는 내독소 B(enterotoxin B)를 검색하기 위한 PCR을 실시한 결과, A 장소의 식수, D 장소의 손, E 장소의 냉장고와 앞치마에서 분리된 균주로부터 477bp의 생성물을 갖는 sob gene을 확인할 수 있었다. 이들 분리된 황색포도상구균에 대한 항생제 민감성 실험에서는 ampicillin과 penicillin에 대하여 전체적으로 저항성을 가졌으며, 특히 A 식수에서 분리된 균주는 옥사실린 저항성(oxacilline resistant)균주로 나타나 MRSA(methicilline resistant staphylococcus aureus)균주로 확인되었다.

• 한국식품위생안전성학회지
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• 제3권1호
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• pp.19-26
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• 1988

Most of meat spoilage bacteria area Gram negative, which are very sensitive to freezing ; for instance , 90% of E. coli cells are killed or sub-lethally injured by freezing at -3$0^{\circ}C$, and the freeze-injury rate is dependent upon freezing rate. Since the injured bacterial cells are sensitive to selective agents, they fail to multiply in selective media. Injured bacterial cells are, however, capable of spontaneous repair at appropriate environmental and nutritional conditions . Enumeration of injured bacterial cells involves artificial induction of repair at these conditions. Cubic beef samples(3$\times$3$\times$3cm) were frozen at -6$0^{\circ}C$, -4$0^{\circ}C$, or -18$^{\circ}C$. The samples frozen at each temperature were thawed at 4$^{\circ}C$, 2$0^{\circ}C$, or by microwave . After these respective freezing an thawing treatments, the percentage of sub-lethally injured total coliforms out of total surviving ones was measured and compared. The results were as follows: 1. The interaction between freezing and thawing on injury rate was not significant. 2. The injury rates(as means of all three thawing treatments post-freezing) by freezing at -6$0^{\circ}C$, -4$0^{\circ}C$, or -18$^{\circ}C$ were 32.2$^{\circ}C$ and 19.2$^{\circ}C$ respectively . 3. The injury rates(as means of all three freezing treatments)by thawing at 4$^{\circ}C$, 2$0^{\circ}C$, or by microwave were 49.3%, 11.7% and 21.0% respectively. The highest injury rate was caused by freezing at -6$0^{\circ}C$ and subsequent thawing at 4$^{\circ}C$. However since the injury rates by freezing treatment were not significantly different, freezing at -18$^{\circ}C$ and subsequent thawing at 4$^{\circ}C$ can also be recommended , from an economic perspective.

• 한국미생물·생명공학회지
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• 제9권3호
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• pp.117-121
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• 1981

분리 정제한 황색색소의 안정성을 검토하기 위하여 in vivo 및 in vitro 시험을 한 결과는 다음과 같다. 1. Mouse를 이용한 안정성 시험은 경구 투여시 LSD$_{50}$은 체중 20g당 0.13245g이었다. 2. 본 색소를 이용한 발열성물질 시험결과 발열 한도량은 체내투여시 kg 당 5 mg이었다. 3. 본 색소를 이용한 histamin 물질 시험은 혈압강하물질 표준품으로 비교할 때 시험동물 당 10 mg까지 안정하였다. 4. 본 색소의 병원성균에 대한 감수성 시험결과 500 mcg/$m\ell$ 농도에서 Bacillus subtilis(ATCC 6633), Sarcina lutea (ATCC 8341) 및 Staphylococcus aureus(ATCC 6538-P)에 대하여 미량의 저해 작용을 나타내었다.