• 한국의류산업학회지
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• 제22권2호
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• pp.250-260
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• 2020

The purpose of the present study was to explore the most effective body region and cooling temperature to alleviate heat strain of workers in hot environments. We developed liquid cooling hood, vest, sleeves and socks and applied the water temperatures of 10, 15, 20, and 25℃ through the liquid cooling garments in a hot and humid environment (33℃ air temperature and 70% RH air humidity). A healthy young male participated in a total of 16 experimental trials (four cooling garments × four cooling temperatures) with the following protocol: 10-min rest, 40-min exercise on a treadmill and 10-min recovery. The results showed that rectal temperature, mean skin temperature, and ratings of perceived exertion during exercise; heart rate and diastolic blood pressure during recovery; and total sweat rate were lower for the vest condition than other garment conditions(p < .05). However, there was no differences in mean skin temperature among the four cooling garments when we compared the values converted by covering area(%BSA). When we classified the results by cooling temperature, there were no consistent differences in thermoregulatory and cardiovascular responses among the four temperatures, but 25℃ water temperature was evaluated as being the most ineffective cooling temperature in terms of subjective responses. In conclusion, the results indicated that wearing cooling vest with < 20℃ cooling temperature can alleviate heat strain of workers in hot and humid environments. If the peripheral body regions are cooled with liquid cooling garments, larger cooling area with lower cooling temperature than 10℃ would be effective to reduce heat strain of workers. Further studies with a vaild number of subjects are required.

• 한국토양비료학회지
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• 제46권2호
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• pp.117-121
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• 2013

Single or co-inoculation of phosphate solubilizing bacterial and fungal strains (Burkholderia anthina and Aspergillus awamori respectively) was performed separately to assess their synergistic and antagonistic interactions and the potential to be used as bio-inoculants. Co-inoculation was found to release the highest content of soluble phosphorus (1253 ${\mu}g\;ml^{-1}$) into the medium, followed by single inoculation of fungal strain (1214 ${\mu}g\;ml^{-1}$) and bacterial strain (997 ${\mu}g\;ml^{-1}$). However, there was no significant difference between single inoculation of fungal strain and co-inoculation of fungal and bacterial strain in terms of the phosphorous release. The highest pH reduction, organic acid production and glucose consumption were observed in the sole A. awamori inoculated culture medium. According to the plant growth promotion bioassays, co-inoculation of the microbial strains resulted in 21% and 43% higher shoot and root growth of the mung bean seedlings respectively as compared to the respective controls. Therefore, co-inoculation of B. anthina and A. awamori showed better performance in stimulating plant growth than that in inoculation of each strain alone. However, assessment period of the present study being short, we recommend in engaging further experimentation under field conditions in order to test the suitability of the strains to be used as bio-inoculants.

• 한국기계가공학회지
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• 제18권9호
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• pp.72-80
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• 2019

In this task, the tool dynamometer design and manufacture, and the Ansys S/W structural analysis program for tool attachment that satisfies the cutting force measurement requirements of the tool dynamometer system are used to determine the cutting force generated by metal cutting using 3-axis static structural analysis and the LabVIEW system. The cutting power in a cutting process using a milling tool for processing metals provides useful information for understanding the processing, optimization, tool status monitoring, and tool design. Thus, various methods of measuring cutting power have been proposed. The device consists of a strain-gauge-based sensor fitted to a new design force sensing element, which is then placed in a force reduction. The force-sensing element is designed as a symmetrical cross beam with four arms of a rectangular parallel line. Furthermore, data duplication is eliminated by the appropriate setting the strain gauge attachment position and the construction of a suitable Wheatstone full-bridge circuit. This device is intended for use with rotating spindles such as milling tools. Verification and machining tests were performed to determine the static and dynamic characteristics of the tool dynamometer. The verification tests were performed by analyzing the difference between strain data measured by weight and that derived by theoretical calculations. Processing test was performed by attaching a tool dynamometer to the MCT to analyze data generated by the measuring equipment during machining. To maintain high productivity and precision, the system monitors and suppresses process disturbances such as chatter vibration, imbalances, overload, collision, forced vibration due to tool failure, and excessive tool wear; additionally, a tool dynamometer with a high signal-to-noise ratio is provided.

• Smart Structures and Systems
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• 제7권4호
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• pp.241-262
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• 2011

Cast iron pipe has been used as a water distribution technology in North America since the early nineteenth century. The first cast iron pipes were made of grey cast iron which was succeeded by ductile iron as a pipe material in the 1940s. These different iron alloys have significantly different microstructures which give rise to distinct mechanical properties. Insight into the non-destructive structural condition assessment of aging pipes can be advantageous in developing mitigation strategies for pipe failures. This paper examines the relationship between the small-strain and large-strain properties of exhumed cast iron water pipes. Nondestructive and destructive testing programs were performed on eight pipes varying in age from 40 to 130 years. The experimental program included microstructure evaluation and ultrasonic, tensile, and flexural testing. New applications of frequency domain analysis techniques including Fourier and wavelet transforms of ultrasonic pulse velocity measurements are presented. A low correlation between wave propagation and large-strain measurements was observed. However, the wave velocities were consistently different between ductile and grey cast iron pipes (14% to 18% difference); the ductile iron pipes showed the smaller variation in wave velocities. Thus, the variation of elastic properties for ductile iron was not enough to define a linear correlation because all the measurements were practically concentrated in single cluster of points. The cross-sectional areas of the specimens tested varied as a result of minor manufacturing defects and levels of corrosion. These variations affect the large strain testing results; but, surface defects have limited effect on wave velocities and may also contribute to the low correlations observed. Lamb waves are typically not considered in the evaluation of ultrasonic pulse velocity. However, Lamb waves were found to contribute significantly to the frequency content of the ultrasonic signals possibly resulting in the poor correlations observed. Therefore, correlations between wave velocities and large strain properties obtained using specimens manufactured in the laboratory must be used with caution in the condition assessment of aged water pipes especially for grey cast iron pipes.

• Tribology and Lubricants
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• 제37권6호
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• pp.224-231
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• 2021

Recently, the waterproofing performance of high-voltage connectors in automotive vehicles has attracted increased interest. In this study, an optimal cross-sectional shape was derived to obtain uniform contact pressure and strain by considering stress relaxation problems caused by initial tension when mounting a seal. A high strain of 52.1 was distributed in the round region, owing to excessive initial tension. The finite element method (FEM) analysis indicated that the strain corresponding to the optimal initial tensile was 11. We adopted six design factors to optimize the seal cross-section and three factors as the main design factors. An orthogonal arrangement table was prepared using Minitab. FEM analyses of 16 study models were conducted to determine the optimized model. The contact pressure of the optimization model is the most evenly distributed while satisfying the waterproof performance of 0.47 MPa. Compared to the initial model, the difference in strain decreases from 35.5% to 19.6%. Finally, the derived cross-sectional shape can reduce the strain of the round region by 33.8% and the differences in the contact pressure at the upper and lower surfaces by 42% and 76%, respectively.

• 한국가금학회지
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• 제17권1호
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• pp.7-15
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• 1990

본 연구는 재래형 유색계통계와 상업용 백색 산난계의 혈중 지질과 단백질 함양을 비교하기 위하여 재래형 유색계통계로서 황갈색계 10수, 녹흑색학 13수, 백색계 7수, 오골계 10수를, 개량형으로서 상업용 백색산난계(Nick chick) 30수를 선정하여 동일한 사료를 1개월 간 급이한 다음 혈청중 Cholesterol, triglyceride 및 protein 함양을 측정한 결과를 요약하면 다음과 같다. 1. 혈청 cholesterol 함양은 상업용 백색산난계 ($172.50\pm$13.45 mg/100 $m\ell$)에서 고도의 유의차(P＜0.01)를 보였고 유색계통보다는 백색계통계에서 다소 높았고 유색계통간은 비슷했다. 2. 혈청 triglyceride 함양은 재래형 유색계간에는 차이가 없으나 상업용 산난계에서 유의성을 나타냈다. (p＜0.01) 3. 혈청 protein 합양은 상업용 산란계에서 $6.24\pm$0.23 mg/100 $m\ell$으로서 재래형보다 유의하게 높게 나타났다. (p＜0.01) 이상과 같이 재내형 유색계통보다 상업용 산난계에서 혈중 지질과 protein 농도가 높은 것은 닭의 개량정도에 의한 차이로서 상업용 산란계는 섭취한 사료의 영양소 흡수율이 높았기 때문인 것으로 사료된다.

• 한국구조물진단유지관리공학회 논문집
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• 제18권2호
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• pp.64-73
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• 2014

본 연구에서는 철골 골조 구조물의 안전성 모니터링을 위하여 계측한 변형률을 통해 구조물에 작용한 하중을 식별하는 알고리즘을 제안한다. 기존의 시스템 식별 연구에서 구조물의 강성 등을 변수화한 것과는 다르게, 본 연구에서는 구조물에 작용한 하중과 이로 인해 구조물에 발생하는 변형률 간의 관계를 행렬로 정의하고, 이 행렬 및 작용한 하중을 변수화 한다. 계측한 변형률과 변수를 통해 추정한 변형률 사이의 차이를 오차함수로 설정하고 이를 최소화시키기 위해 최적화 알고리즘 중 하나인 유전자 알고리즘을 적용한다. 구해진 변수와 계측 변형률을 통해 작용한 하중을 식별하고 구조물의 하중 변화 시 미계측 지점의 응답을 추정한다. 본 연구에서 제안하는 하중 식별 알고리즘을 검증하기 위해 3차원 철골 골조 구조물의 정적 가력 실험을 수행하였고, 계측한 변형률을 통해 가해진 하중을 낮은 오차 수준으로 식별할 수 있었다. 또한, 하중 조건 변화 시, 계측한 변형률을 통해 모니터링 대상이 되는 미계측 지점의 변형률을 0.17~3.13%의 오차 범위로 추정하였다. 본 연구가 제안하는 식별법이 철골 구조물의 보다 현실적인 안전성 모니터링에 효과적으로 적용될 것으로 기대된다.

• Nuclear Engineering and Technology
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• 제5권1호
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• pp.55-64
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• 1973

압축변형시킨 순천(0.007% 탄소포함)을 8$0^{\circ}C$이하에서 저온열처리(ageing)한 후, 열처리시간에 따라 증가하는 저항복점(lower yield point)의 변화를 압축시험으로 측정하여 그 strain ageing 효과를 조사했다. 본 실험에서 압축변형된 순철의 strain ageing 속도는 저항복응력의 증가가 그치고 중가의 60% 정도에 이를 때까지 열처리시간의 2/3승에 비례했으나, 이미 알려진 인장변형의 경우에서보다 느렸다. 이 60%의 증가는 순철을 6$0^{\circ}C$에서 약 5시간 열처리함으로써 얻었다. 압축변형된 순철의 strain ageing을 위한 활성화에너지는 열처리의 초기단계(6$0^{\circ}C$에서 약 30분)에서 21,500 cal/mole이었는데, 이것은 인장변형의 경우에서 알려진 것보다 대략 10%가 큰 값이다. 이 증가는 잔유응력에 의해 결정내에 형성되는 strain field로 설명되었다. 열처리공정의 둘깨단계(6$0^{\circ}C$에서 약 5시간까지 계속되는)에서는 그 활성화에너지가 다소 감소되는 경향이 있었다.

• Journal of Yeungnam Medical Science
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• 제6권1호
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• pp.47-57
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• 1989

T. verrucosum에 의한 피부사상균증의 임상 및 병리조직학적 경과를 이해하여 진단과 치료에 도움이 되고자, 환자와 그 감염원으로 추정되는 한우에서 채취한 T. verrucosum을 Sabouraud 포도당 한천배지에서의 성장속도를 비교하고, 기니픽에 접종한 후 다음과 같은 결과를 얻었다. Sabouraud 포도당 한천배지에서의 성장속도는 한우주가 환자주에 비해 빨랐으며 $25^{\circ}C$보다 $37^{\circ}C$에서 더 빨리 자랐으나, 환자주는 온도에 따른 차이가 없었다. 홍반과 인설이 6일 경부터 증가하여 14-16일경에 황선과 유사한 병변을 형성하였으며 이후 점차 감소하여 30일 경에는 부분적인 탈모를 남기고 치유되었다. 환자주와 한우주에서 병변의 진행과정은 큰 차이가 없었으며 그 정도에서는 환자주에서 한우주보다 약간 더 심하게 나타났다. 병리조직학적인 변화는 접종 3일째에 극세포증과 혈관의 확장 및 증식이 나타나기 시작하여 12일 경에 최고에 도달했으며 이때에 과각화증, 이상각화증, 표피내 미세농양, 해면증과 더불어 진피의 혈관증식 및 확장, 세포침윤이 가장 심하였고 이러한 표피와 진피의 변화는 25일 경까지 지속된후 감소되어 33일째는 가벼운 과각화증과 극세포증을 보였으며 진피내에는 부분적으로 약간의 혈관 확장과 단핵구의 침윤을 나타내었다. PAS 염색상 접종 6일에 균사가 각질층하부와 모낭개구부에서 보인 후 9일째는 외내측 모근초와 모간에서도 관찰되었으며 21일째는 완전히 소실되었다. Trichophytin 피부반응검사에서는 평균 $9.83{\pm}1.17$일에 24마리의 기니픽 모두에서 양성반응을 나타내었다. 이상의 결과로 미루어 볼 때 T. verrucosum에 의한 피부사상균증은 조기에 세포면역을 유도하여 특히 모낭에 심한 염증을 일으키며 병변의 빠른 치유와 연관이 있을 것으로 사료된다.

• Fibers and Polymers
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• 제2권3호
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• pp.141-147
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• 2001

The effect of compositions of isophorone diisocyanate (IPDl)/4.4'-diphenylmethane diisocyalate (MDI) and polypropylene oxide diol (PPG, $M_w$: 3000)/1,4-butane diol (BD) on the properties of UV-cured polyurethane acrylate films based on 2-hydroxyethyl acrylate (HEA) was examined. UV-curable polyurethane acrylates were formulated from the prepolymer. trimethylol propane triacrylate (TMPTA) as a reactive diluent, and 1-hydroxycyclohexyl ketone (Irgacure 184) as a photoinitiator. Dynamic mechanical thermal properties and elastic properties of UV-cured polyurethane acrylates was fecund to depend on the chemical composition of IPDl/MDl and PPG/BD. As the BD content increased, the tensile storage modulus of all series samples increased significantly. The storage modulus increased in the order of samples A (IPDI based samples)> samples B (IPDI/MDl (7/3 molar ratio) based samples) > samples C (IPDI/MDl (5/5 molar ratio) based samples at the same composition. Two distinct louts modulus peaks for all samples are observed owing to the softs segment glass transition temperature ($T_gh$) and hard segment glass transition temperature ($T_gh$). The difference between $T_gh$, and $T_gh$, (Δ$T_g$) increases in the order of A > B > C at the same composition. In cycle test, the initial onset strain (%) was found to decrease with increasing BD content in PPG/BD and with increasing MDI content in IPDI/MDl.