• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.450-453
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• 2004

The present study is a basic experiment on the estimation of the compression strength of high strength concrete, aiming at estimating the compression strength of mass test pieces of high strength concrete by giving the temperature hysteresis of the mass test pieces to managerial test pieces. Thus, this study made concrete test pieces in an optimal mix ratio for each strength level, and also created adiabatic curing tank and managerial test pieces. Then it carried out comparative analysis in relation to core strength and suggested equipment and a technique that can control the strength of high strength concrete mass more conveniently and accurately.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.274-280
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• 2006

The study is to analyze dynamo test results for various commercial pads in order to verify the performance of brake disk with CV-NCM cast iron. The developed brake disk will apply to 200 km/h tilting trains that is being developed as one part of project for speed-up on Korean existing railroad. The test program is made out suitably for braking condition and performance of test equipment by referring UIC 541-3. Two kinds of resin pad and one kind of foreign sintered pad suitable for 200 km/h trains are used as various commercial pad for the dynamo test. The data aquisition for the maximum and smallest temperature, hot spot, etc. on disk and pad is performed by using the thermocouples and thermal imaging cameras. From this research, we obtained braking characteristics between CV-NCM cast iron disk and pad of various material and will be utilized usefully as basis data of performance optimization of developing sintered pad.

• 방사성폐기물학회지
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• 제13권2호
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• pp.99-112
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• 2015

본 연구에서는 고준위폐기물 처분시 완충재로 사용되는 벤토나이트의 열적 거동을 평가하기 위해 실내실험장치를 제작하였다. 그리고 실험 결과를 검증하기 위해 유한요소해석 프로그램인 ABAQUS를 이용한 열해석을 실시하였다. 그리고 실험기간 동안의 계절변화를 감안하여 외부대기 온도에 따른 벤토나이트의 열적거동을 평가하였다. 해석결과, 스테인리스스틸이 포함된 case3 해석모델의 결과가 실험결과와 1℃ 내외의 오차를 보이며 거의 일치함을 볼 수 있었다. 그리고 계절에 따른 벤토나이트 온도 해석을 수행한 결과, 시간에 따른 온도분포 경향이 일치함을 확인하였다. 이러한 열해석을 통해 완충재를 둘러싸고 있는 물질의 열전도도와 외부대기의 온도가 벤토나이트 완충재의 열적 거동에 큰 영향을 주는 요소임을 확인할 수 있었다. 향후 열원을 포함한 벤토나이트 완충재의 수분 포화 특성 실험이 실시 될 예정이므로, 실험에 대한 검증과 예측을 위해 보다 적합한 수치해석모델 개발에 대한 연구가 필요할 것이다.

• 대한영양사협회학술지
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• 제7권1호
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• pp.56-64
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• 2001

The study was conducted to assess sanitary concepts of employees and needs of HACCP-based sanitation training program for elementary school foodservice operations. Subjects consisted of 370 foodservice employees. Foodservice employees' demographic characteristics were surveyed, and their food sanitation knowledge was tested. Food sanitation knowledge included 4 dimensions of foodborne disease & food microbiology; sanitary management in food product flows; personal hygiene management; and equipment & facility sanitation management. The data were analysed using the SPSS package for descriptive analysis, t-test and ANOVA test. The average sanitation knowledge score was 9.5 out of 15. The working periods of foodservice employees were singnificantly(p<01) related to food sanitation knowledge dimensions. Correct answering rate of 4 sanitation management dimensions were 74.4% in foodborne disease & food microbiology; 536% in sanitary management in food product flows; 78.7% in personal hygiene management; and 50.5% in equipment & facility sanitation management. 6 items in 4 sanitation knowledge dimensions under mean score were identified. Those items were temperature danger zone, thawing method of frozen foods, cooking & holding temperature, proper sampling & storage methods, proper storing methods in refrigerator, and proper washing & sanitizing method for utensils. Identified 6 items were included in 12 critical control points developed for the elementary school generic HACCP plan, and should be emphasized in implementing HACCP-based sanitation training program.

• 마이크로전자및패키징학회지
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• 제12권1호
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• pp.65-71
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• 2005

At present, Electronic industries push ahead to eliminate the Pb(Lead) -a hazardous material-from all products. Especially, we have performed to select the optimum standard composition of lead free alloy for the application to products for about 3 years from 2000. These days, we have the chance for applying to the mass-production. This project constructed the system for applying the lead free solders on consumer electronic products, which is one of the major products of the LG Electronics. To select the lead free solders with corresponding to the product features, we have passed through the test and applied with Sn-3.0Ag-0.5Cu alloy system to our products, and for the application to the high melting temperature composition, we secured the thermal resistance of the many parts and substrate and optimized the processing conditions. We have operated the temperature cycling test and the high temperature storage test under the standards to confirm the reliability of the products. On these samples, we considered the consequence of our decision by the operating test. For the long life time of the product, we have operated the temperature cycling test at $-45^{\circ}C\;-\;+125^{\circ}C$, 1 cycle/hour, 1000 cycles. Also we have tested the tin whisker growth about lead free plating on lead finish. We have analyzed with the SEM, EDS and any other equipment for confirming the failure mode at the joint and the tin whisker growth on lead free finish.

• 한국의류산업학회지
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• 제24권5호
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• pp.655-665
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• 2022

This study evaluated the validity of a newly developed mobility protocol examining the comfort functions and requirements of personal protective equipment (PPE) for COVID-19 healthcare workers. Eight males (age: 24.7 ± 3.0 y, height: 173.4 ± 2.3 cm, and body weight 69.9 ± 3.7 kg) participated in the following three PPE conditions: (1) Plastic gown ensemble, (2) Level D ensemble, and (3) Powered air purifying respirator (PAPR) ensemble. The mobility protocol consisted of 10 different tasks in addition to donning and doffing. The 10 tasks were repeated twice at an air temperature of 25oC with 74% RH. The results showed significant differences among the three PPE conditions in mean skin temperature, local skin temperatures (the forehead, thigh, calf, and foot), clothing microclimate (the chest and back), thermal sensation, thermal comfort, and humidity sensation, while there were no significant differences in heart rate or total sweat rate. At rest, the subjects felt less warm and more comfortable in the PAPR than in the Level D condition (P<0.05). However, subjective perceptions in the PAPR and Level D conditions became similar as the tasks progressed and mean skin and leg temperature became greater for the PAPR than the Level D condition (P<0.05). An interview was conducted just after completing the mobility test protocol, and suggestions for improving each PPE item were obtained. To sum up, the mobility test protocol was valid for evaluating the comfort functions of PPE for healthcare workers and obtaining requirements for improving the mobility of each PPE item.

• 전기전자학회논문지
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• 제23권3호
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• pp.1088-1091
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• 2019

본 논문에서는 생활권역별 환경안전 실시간 모니터링 시스템을 제안한다. 제안하는 시스템은 고정형 및 이동형 측정장비를 활용하여 방사선, 미세먼지, 생활기본정보(온도) 등을 측정 하도록 설계된다. 고정형 및 이동형 측정장비로부터 수신한 데이터를 저장하는 웹 데이터베이스를 구성한다. 또한 수신한 데이터를 PC에 디스플레이하기 위한 웹 프로그램과 휴대폰에 디스플레이 위한 웹 프로그램을 개발한다. 제안된 시스템의 성능을 평가하기 위하여 공인시험기관에서 실험한 결과는 방사선 측정범위는 세계 최고 수준과 버금가는 $10{\mu}Sv/h{\sim}10mSv/h$의 범위에서 측정이 되었고, 정확도는 ${\pm}6.7%{\sim}8.7%$의 측정 불확도가 측정되어 국제 표준인 ${\pm}15%$ 이하에서 정상동작 됨이 확인되었다. 4계절을 보유한 우리나라의 온도변화 특성에 따라 $-20^{\circ}C{\sim}50^{\circ}C$의 구간에 대해 온도 시험을 수행하였으며 온도변화에 대응하여 정상동작 됨이 확인되었다. 복사전자파 내성 시험의 경우에 적합 판정으로 안정성이 확보되었다. 시제품 제작이후 약 4개월 동안 일반환경 및 고온과 저온 환경에서 제품을 테스트한 결과, 구성된 센서의 보증기간 및 운영테스트 시 작동 및 기록되는 데이터를 기반으로 약 5년 이상의 내구성이 확인되었다. 미세먼지 센서에 대한 측정범위와 정확도는 대기환경 측정 기업을 통하여 상대성 비교 테스트를 진행하고 대기질 측정 기록부를 통하여 성능수준이 유사함을 확인하였다.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1652-1656
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• 2022

Fire tests were conducted on cables using fire-retardant paint employed in nuclear power plants that transmit electrical power, control and instrument signals. The failure criteria of various power and control cables coated with fire retardant coating at three different coating thicknesses (~0.5 mm, 1.0 mm & 1.5 mm) were studied under direct flame test using Container Fire Test Facility (CFTF) based on standard tests for bare cables. A direct flame fire test was conducted for 10 min with an LPG ribbon burner rated at ten by fixing the cable samples in a vertical cable track. Inner sheath temperature was measured until ambient conditions were achieved by natural convection. The cables are visually evaluated for damage and the mass loss percentage. Cable functionality is ascertained by checking for electrical continuity for each sample. The thickness of cable coating on fire exposure is also studied by comparing the transient variation of inner sheath temperature along the Cable length. This study also evaluated the adequacy of fire-retardant coating on cables used for safety-critical equipment in nuclear power plants.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.198-201
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• 2009

As a way to improve the safety of automotives and to reduce the weight of vehicles, new forming technologies and advanced materials are in high demand in the automotive industry. However, the advanced strength steel has inferior formability and large springback. In order to overcome such drawbacks, the hot press forming process (HPF) has been being applied for forming of automotive sheet parts. In this work, new equipment was suggested to measure unlimited displacement range compared to previous one which was able to measure only up to 10mm displacement range. The external extensometer connected with grips by wire was applied to equipment so that total strain range was measured up to failure also in high temperature. And the finite element analysis was conducted to characterize the mechanical properties of the HPF steel. Finally, the flow curves were represented by utilizing the Johnson-Cook type equation both in uniform and post-uniform deformation regions.

• 한국항공운항학회지
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• 제27권3호
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• pp.15-23
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• 2019

This paper contains analyses and development processes of the requirements to detect the possible intermittent failure in an old avionics backplane. Interconnections for signal transmission between electronic components, such as Pin-to-PCB, FPCB-to-FPCB, pin-to-FPCB, and pint-to-wire, were selected as the main cause of intermittent failure by analyzing target equipment and documents. The possibility of detecting intermittent failures occurring in the target equipment is verified by physics-of-failure analyses. In order to verify the occurrence of intermittent failures and their detectability, latching continuity circuit testers were manufactured and accelerated life tests were performed by applying temperature and vibration cycle in consideration of flight conditions. Through the above process, the detection requirements for the major intermittent failure in the target avionics backplane was developed.