As a case study on aspect ratio behavior, Kaolin, zeolite, TiO2, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 pai media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D50, ~6 μm are shifted to submicron size, D50 ~0.6 μm, after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.

Glutathione S-transferase (GST) is a key gene involved in multiple stress tolerance in all living organisms, though it is still to be disclosed the gene function in teff grass [Eragrostis tef (Zucc.)Trotter].The objectives of this study were to clone and molecular characterization of GST gene in teff grass. We characterized GST1 from teff grass (EtGST1), it composed of a 645-bp open reading frame (ORF) that encoded 195 amino acid residue. Further, we transformed EtGST1 in E.coli BL21 (DE3) cells. This recombinant EtGST1 in E.coli BL21(DE3) induced at 37°C temperature. In addition, Growth of cells overexpressing EtGST1 rapidly increased in the presence of polyethylene glycol (5%), heat (46°C), NaCl (0.6%), and arsenic (1 mM) than that of cells harboring an empty vector. These results suggest that EtGST1 would be suitable candidate for improving tolerance in forages and/or grasses species against multiple abiotic stresses.

This study analyzed variations of learning stress by comparing the salivary cortisol levels of students who participated in Earth Science inquiry activities. The cortisol concentrations between the pre- and post-inquiries of the sample of 34 university students, who had taken the course of ‘Basic Earth Science and Experiments’, were analyzed. The Earth Science inquiries consisted of geology and astronomy activities. The observational geology activities consisted of a session of ‘structure contours and map patterns’ and the cognitive astronomy activities consisted of a session of ‘representations of horizontal and equatorial coordinates’. These Earth Science inquiry activities were found to cause students to have anxiety, and the thought processes that these activities involved were found to cause learning stress. The variations in cortisol concentrations of students increased by 1.6±5.9 ng mL−1 after conducting observational activities in geology compared with 2.1±6.2 ng mL−1 after doing cognitive activities in astronomy. The analysis of the observational activities in the geology inquiry activities indicated that they were consistent with low levels of learning stress. Conversely, the analysis of the cognitive activities in the astronomy inquiry activities showed significant individual variations in cortisol concentrations. Furthermore, individual differences in cognitive ability were reflected in the astronomy inquiry activities. While students, who received high scores, exhibited low levels of stress in the geology inquiry activities, they showed high levels of stress in the astronomy inquiry activities. It was concluded that, in the case of students with high scores in the study, the level of learning stress increased due to the raised anxiety in cognitive inquiry activities. In contrast, students, who received low scores in the study, exhibited high levels of stress in the geology inquiry activities, and low levels of stress in the astronomy inquiry activities.

To improve life time of machine components, higher alloy grade materials are used by adding more metal alloy components and content. Also production processes are further complicated and subdivided such as the forging, preliminary heat treatment, quality heat treatment, rough machining and finished machining process. Those reasons become major cause of large stress in the materials, and the residual stress generated during the manufacturing process causes fatal defects, such as crack, surface tear, warping and deformation of the products. It is necessary to evaluate the residual stress on the entire processes, from forging process to final finished machining process. Also in order to avoid those problems caused by residual stresses, it is necessary to know in advance what process is important to be controlled and what parameters affect residual stress. By the hole drilling method, residual stress was measured in each manufacturing process step. In this study, the hardness of the surface, the cutting force test and the metal analysis were performed to clarify the influence of manufacturing process parameters.

Fatigue crack growth retardation of 304 L stainless steel is studied using a neutron diffraction method. Three orthogonal strain components(crack growth, crack opening, and through-thickness direction) are measured in the vicinity of the crack tip along the crack propagation direction. The residual strain profiles (1) at the mid-thickness and (2) at the 1.5 mm away from the mid-thickness of the compact tension(CT) specimen are compared. Residual lattice strains at the 1.5 mm location are slightly higher than at the mid-thickness. The CT specimen is deformed in situ under applied loads, thereby providing evolution of the internal stress fields around the crack tip. A tensile overload results in an increased magnitude of the compressive residual stress field. In the crack growth retardation, it is found that the stresses are dispersed in the crack-wake region, where the highest compressive residual stresses are measured. Our neutron diffraction mapping results reveal that the dominant mechanism is by interrupting the transfer of stress concentration at the crack tip.

쑥은 세포 손상과 위염 회복에 효능이 있는 유파틸 린을 가지고 있는 약용작물이다. 본 연구의 목적은 강 화쑥의 온실에서의 주년 생육 특성을 분석하고, 환경 스트레스를 처리하여 유파틸린의 함량을 증대시키는 것이다. 유리 온실에서 강화쑥을 육묘 6주, 정식 후 8 주간 재배하여 생육 특성과 유파틸린 함량을 비교하였 다. 광합성은 상대적으로 고광도인 1,200μmol·m-2·s-1에 서도 포화되지 않았다. 생육속도는 정식 후 2주후에 최고에 도달하였고 정식 후 8주부터 감소하기 시작하 였다. 강화쑥은 다년생 숙근초로 계절 변화에 민감하게 반응하여 봄 여름의 영양 생장기에는 높은 생육과 성 분 함량을 나타내었으나, 가을과 겨울에는 개화 및 월 동으로 인하여 생육 및 유파틸린 성분 함량이 크게 감 소하였다. 따라서 강화쑥의 주년 재배를 위하여는 이를 억제하기 위한 야파 처리의 적용이 필수적인 것으로 판단되었다. 2종류의 스트레스와 1종류의 eliciter를 처 리하였다. 건조 스트레스는 수확 전 5, 6, 7, 8 일간 관수을 중단하였고, 염류 스트레스는 수확 3일전 양액 에 염화나트륨 추가하여 2, 4, 6, 8dS·m-1 농도로 하였 고, 메틸자스모네이트는 수확 3일전 12.5, 25, 50, 100μM 농도로 엽면 시비하였다. 건조 스트레스 처리 구 중 7일 및 8일간 관수를 중단한 경우와 메틸자스모 네이트를 25μM 엽면 시비한 경우 유파틸린 함량이 증 가하였다. 염류 스트레스 처리구에서는 유파틸린 함량 증대가 발견되지 않았다. 본 연구 결과는 환경 처리를 통해 유용 성분의 증대가 가능하고 의약 원료로써 강 화쑥의 생산성과 품질을 크게 향상시킬 수 있음을 증 명하였다.

The purpose of this study was to examine the relationship of fatigue and stress in seafarers. Ninety healthy adults were recruited and cumulative fatigue, stress index and stress resistance of seafarers were measured using autonomic nervous system analysis device (SA-6000; Medicoa Co. Ltd. Korea). The stress index had a significant correlation with the degree of resistance (p<.01). Cumulative fatigue and the stress index had a strong positive correlation (r=.781) with the stress resistance, cumulative fatigue had a strong negative correlation (r=.782) (p<0.01). Furthermore, the stress index had a strong negative correlation with the degree of resistance (r=.924) (p<.01). The present study indicate that there are significant correlation between the cumulative fatigue and stress index, cumulative fatigue and stress resistance, as well as stress index and stress resistance in the seafarers (p<.01).

본 연구는 서울지역에 위치한 영유아 복지시설 종사자 148명을 대상으로 직무스트레스, 교사효능감, 교사-영유아 상호작용을 분석하고, 직무스트레스와 교사효능감이 교사-영유아의 상호작용에 미치는 영향을 검증하였다. 분석 결과 연구대상자의 직무스트레스 중 업무 과부하가 가장 높은 수준을 보였으며, 교사효능감의 경우 일반적 교수 효능감이 개인적 교수 효능감보다 높게 나타났다. 교사-영유아 상호작용의 경우 적극적인 활동 참여가 가장 높았으며 기타 하위영역들 또한 비교적 높은 수준을 보였다. 직무스트레스와 교사효능감이 교사-영유아 상호작용에 미치는 영향을 분석한 결과 직무스트레스 중 원장 지도력 및 행정적 지원 부족 변인이 교사-영유아 상호작용에 가장 크게 부적 영향을 미치는 것으로 나타났다. 교사효능감의 경우 교사-영유아 상호작용의 전 하위영역에 걸쳐 긍정적 영향을 미치는 것으로 나타났다. 곧 교사효능감이 높을수록 교사-영유아 상호작용은 증가하는 것으로 나타났으며, 교사효능감이 교사-영유아 상호작용을 설명하는 수준 또한 매우 높게 나타나 강력한 영향 요인임을 알 수 있었다. 이를 토대로 종사자의 직무스트레스 중 원장지도력 및 행정적 지원의 수준을 높일 수 있는 방안 마련, 교사효능감의 수준을 높일 수 있는 제도 마련의 필요성을 제시하였다.

Numerical analysis has been performed to investigate the stress distribution characteristics of auxiliary axle system in a compact special vehicle. Structural and running stability of compact special vehicle is largely affected by auxiliary axle system installation. Structural characteristics of stress and deformation distributions with safe factor in the auxiliary axle system are analyzed. It can be seen that maximum stress happens near the local axle position, and deformation is also predicted. Simulation results are also compared with experimental test data. These results from this study could be applicable for optimal design of diverse axle systems in the compact special vehicle.

섬유강화 복합재료는 열팽창 계수의 방향성을 갖고 있을 뿐만 아니라 제작과정 온도와 실제 사용온도 사이의 차이 때문에 필연적으로 열응력 효과를 받게 된다. 이러한 열응력에 의한 파손현상은 실제 항공우주산업에서의 응용이 증대되고 있는 두 꺼운 복합 적층판의 경우에 더욱 현저한 현상으로 적층판의 역학적 기능 및 파단강도에 큰 영향을 미치게 된다. 본 연구에서 는 복잡한 재질로 구성되고 높은 세장비를 가진 블레이드 날개 구조의 차원축소 및 열 응력 복원 이론을 소개하고 3차원 유 한요소모델과 비교결과를 통해 효율성과 정확성을 입증한다. 또한 차원을 축소한 모델링을 구성하고 복원이론를 이용하여 열적 환경에 적용된 복합재 보 단면의 열응력을 차원 복원하고 시각적으로 형상화하는 효율적인 복원해석 과정을 소개하고 자 한다.