• 터널과지하공간
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• 제13권3호
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• pp.169-179
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• 2003

암석의 절리면 전단강도의 이방성을 연구하기 위하여 인공절리면을 형성한 시편에 대한 실험을 실시하고 그 결과를 분석하였다. 즉 낮은 수직응력 상태에서 전단 방향에 따른 전단강도, 전단강성 및 마찰각을 구하기 위한 실험을 실시하였다 그 결과 낮은 수직응력하에서 전단 강도 및 강성은 전단 방향에 따라 이방성을 보이며, 특히 수직응력 2.45 MPa미만에서 뚜렷하였다. 그리고 수직응력이 증가할수록 절리면의 이방성 효과는 감소하였다. 따라서 낮은 수직응력 하에서 전단강도 및 강성값을 보다 정확히 구하기 위해서 Barton의 식에 전단방향을 고려한 보정함수 F(a)를 반영하여 새로이 수정식을 제안한다.

• 부모자녀건강학회지
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• 제5권1호
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• pp.75-89
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• 2002

This study was conducted to compare the emotional state between the mothers with low-birth-weights and mothers with normal infants, and to analyze the effects of home visiting for the low-birth-weights in one city. Data were collected from 51 mothers with low-birth-weights and 90 mothers with normal infants to compare emotional state, and from 26 mothers with low-birth weights to evaluate the effect of home visiting care. Summaries of results were as follows; 1. In mothers with low-birth-weights, social support form others was significantly lower than those of mothers with normal infants. Although the differences were not significant, mothers with low-birth-weights have more stress and child rearing burden, and less maternal self-esteem than those of mothers with normal infants. 2. Mothers with low-birth-weights, the more burden, postpartum depression, and the less husbands' support they felt. When they had lower maternal self-esteem and lower husbands' support, child rearing burden was higher. Also there was significant negative correlation between maternal self-esteem and postpartum depression. 3. In mothers with low-birth-weights, the score of post-intervention stress, care-giving burden, and postpartum depression were somewhat decreased, and maternal self-esteem was increased than pre-intervention data, although they were not statistically significant. 4. Mothers' satisfaction on the home-visiting care was considered to be high. In summary, mothers with low-birth-weights had lower social support even though they experienced more stress than mothers with normal infants. Therefore, public health nurse in community should pay more attention to them.

• Journal of Magnetics
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• 제20권2호
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• pp.186-192
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• 2015

This paper describes the electromagnetic and mechanical characteristics of coaxial magnetic gear (CMG) with a low gear ratio. The analysis models are restricted to a CMG with a gear ratio of less than 2. The electromagnetic characteristics including transmitted torque and iron losses are presented according to the variation of the gear ratio. The pole pairs of high speed rotor are chosen as 6, 8 and 10 by considering the torque capability. As the gear ratio approaches 1, both iron losses on the ferromagnetic materials and eddy current losses on the rotor permanent magnets are increased. The radial and tangential forces on the modulating pieces are calculated using the Maxwell stress tensor. When the maximum force is exerted on the modulating pieces, the mechanical characteristics including stress and deformation are derived by structural analysis. In CMG models with a low gear ratio, the maximum radial force acting on modulating pieces is larger than that in CMG models with a high gear ratio, and the normal stress and normal deformation are increased in a CMG with a low gear ratio. Therefore, modulating pieces should be designed to withstand larger radial forces in CMG with a low gear ratio compared to CMG with a high gear ratio.

• 정신신체의학
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• 제10권1호
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• pp.18-26
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• 2002

연구목적: 본 연구의 목적은 만성요통 환자에서 스트레스지각 및 통증지각과 대응전략 간의 관계를 알아보고자 하는데 있다. 본 연구에는 만성요통 환자 80명과 정상대조군 100명이 참여하였다. 방법: 스트레스인자 및 스트레스반응에 대한 지각은 각각 스트레스인자 지각척도 (Global Assessment of Recent Stress Scale) 및 스트레스반응 척도(Stress Response Inventory)를, 대응전략 및 통증지각은 각각 대응척도(The Way of Coping-revised) 및 통증지각척도(Pain Discomfort Scale)를 이용하여 평가하였다. 결과: 만성요통환자들이 정상대조군보다 일 및 직장, 대인관계, 대인관계의 변화, 질병 및 상해에 관련된 스트레스인자 지각점수, 전체 스트레스인자지각 정수가 각각 유의하게 더 높았다. 스트레스반응점수에서는 피로점수가 정상대조군보다 환자군에서 유의하게 더 높았으나, 통증지각에서는 양군 간에 유의한 차이를 보이지 않았다. 대응전략에서는 환자군이 정상대조군에 비해 계획적 문제해결 및 긍정적 재평가를 더 많이 사용하였다. 환자군에서 통증지각은 전체 스트레스반응 점수, 질병 및 상해에 관련한 스트레스인자지각 점수와 각각 유의한 양상관성을 보였다. 도피 회피 점수는 연령과 유의한 음상관성을, 거리감두기 및 도피-회피 점수는 유의한 양상관성을 보였다. 한편 책임수용은 여자가 남자보다 더 유의하게 많이 사용하였다. 그러나 대응전략과 스트레스인자지각 및 스트레스반응 통증지각 간에는 각각 유의한 상관성을 보이지 않았다. 결론: 이상의 결과들은 만성요통환자들이 정상인에 비해 스트레스인자에 대한 지각이 더 높으나, 더 적극적인 대응을 하고 있음을 시사한다. 또한 환자군에서 사용하는 대응전략은 스트레스인자지각, 스트레스반응, 통증지각과 연관성을 보이지 않는 반면 사회인구학적 특정들과 연광성이 높음을 시사한다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권1호
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• pp.45-51
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• 2014

Thermal shock tests at two stress levels were performed to see the life (cycles) of LPF ASSY (low pass filter assembly) at normal stress level. In this case Coffin-Manson relationship is generally used to describe the relationship between the temperature difference and the life, together with the Weibull distribution describing the life at each stress level. So for given data Coffin-Manson is fitted to predict the life at normal stress level. However, different types of models are appropriate for this type of test. Hence, a more appropriate model such as General log-linear model which can also incorporate the duration at the highest and lowest temperatures and acceleration time will be introduced.

• Structural Engineering and Mechanics
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• 제76권2호
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• pp.153-162
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• 2020

Aiming at the mechanical and structural characteristics of the contact zone composite rock, the shear tests and numerical studies were carried out. The effects of the differences in mechanical properties of different materials and the normal stress on shear properties of contact zone composite samples were analyzed from a macro-meso level. The results show that the composite samples have high shear strength, and the interface of different materials has strong adhesion. The differences in mechanical properties of materials weakens the shear strength and increase the shear brittleness of the sample, while normal stress will inhibit these effect. Under low/high normal stress, the sample show two failure modes, at the meso-damage level: elastic-shearing-frictional sliding and elastic-extrusion wear. This is mainly controlled by the contact and friction state of the material after damage. The secondary failure of undulating structure under normal-shear stress is the nature of extrusion wear, which is positively correlated to the normal stress and the degree of difference in mechanical properties of different materials. The increase of the mechanical difference of the sample will enhance the shear brittleness under lower normal stress and the shear interaction under higher normal stress.

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.1967-1974
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• 2005

The subsurface stress field caused by both normal loads and tangential loads has been evaluated using the rectangular patch solution. The effect of tangential loading on the subsurface stress field has been investigated in detail for both the cylinder-on-cylinder contact and a spur gear teeth contact. For the cylinder-on-cylinder contact, the subsurface stress fields are moved more to the direction of tangential loads and the positions where the maximum stress occur are getting closer to the surface with the increasing tangential loads. The subsurface stress fields of the gear teeth contact are expanded more widely to the direction of tangential loads with the increasing tangential loads. The friction coefficient of a gear teeth contact is low because they are operated in a lubricated condition, and therefore surface tractions in the EHL condition hardly affect on the subsurface stress field.

• 대한의생명과학회지
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• 제26권4호
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• pp.249-255
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• 2020

Radiation therapy is one of the primary options for the treatment of malignant tumors. Even though it is an effective anti-cancer treatment, it can cause serious complications owing to radiation-induced damage to the normal tissue around the tumor. It was recently reported that normal stem cell response to the genotoxic stress of ionizing radiation can boost the therapeutic effectiveness of radiation by repairing damaged cells. Therefore, we focused on annexin A-1 (ANXA1), one of the genes induced by low-dose irradiation, and assessed whether it can protect adipose-derived stem cells (ADSCs) against oxidative stress-induced damage caused by low-dose irradiation and improve effectively cell survival. After confirming ANXA1 expression in ADSCs transfected with an ANXA1 expression vector, exposure to hydrogen peroxide (H2O2) was used to mimic cellular damage induced by a chronic oxidative environment to assess cell survival under oxidative conditions. ANXA1-transfected ADSCs demonstrated that increased viability compared with un-transfected cells and exhibited enhanced anti-oxidative properties. Taken together, these results suggest that ANXA1 could be used as a potential therapeutic target to improve the survival of stem cells after low-dose radiation treatment.

• 동력기계공학회지
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• 제16권2호
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• pp.43-48
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• 2012

Generally accelerated life test is well known as one method to reduce reliability qualification test period. This test is conducted under the higher stress condition than normal condition. So it can save the test time by calculating the acceleration factor from the relationship between the worst stress condition and normal condition. This paper investigates the worst stress condition for the accelerated life test to increase the acceleration factor. Especially, we focused on the method to obtain effective acceleration factors under the worst stress condition. Moreover, we considered how to decide the worst stress condition by looking for the operating limit of this system. The acceleration factor can be estimated from the ratio of the kinematic viscosity in the normal condition and the worst stress condition, the lowest temperature, by using Arrhenius relationship. Through some experiments for a refrigerator's compressor, we were able to confirm how to increase acceleration factors and how to reduce the reliability qualification test period with minimum samples.

• Toxicological Research
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• 제34권3호
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• pp.211-220
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• 2018

Early life exposure to aflatoxin B1 (AFB1) and low protein diet through complementary foods during weaning is common in parts of Africa and Asia. This study evaluated the effect of co-exposure to AFB1 and low protein diet on the extrahepatic tissues of rats. Twenty-four three-week old weanling male albino rats were used for this study and were randomly assigned into four groups: group 1 served as control and was fed normal protein diet (20% protein), group 2 was fed low protein diet (5% protein), group 3 was fed normal protein diet + 40 ppb AFB1 while group 4 received low protein diet + 40 ppb AFB1, all for eight weeks. Afterward, biomarkers of anemia (packed cell volume (PCV), hemoglobin) and kidney function (urea, uric acid, and creatinine) were determined in the blood while biomarkers of oxidative stress were determined in the tissues spectrophotometrically. Co-exposure to AFB1 and low protein diet significantly (p < 0.05) decreased body weight gain and PCV, increased biomarkers of kidney functions and induced oxidative stress in the tissues studied. There was significant (p < 0.05) reduction in glutathione concentration while TBARS was significantly increased in the tissues. Co-exposure to AFB1 and low protein diet had additive effects on decreasing the weight gain and potentiation effect of kidney dysfunction in the rats. The co-exposure also decreased antioxidant enzymes and increased oxidant status in the tissues. Our results demonstrate that this co-exposure has deleterious health effects on extrahepatic tissues and should be a public health concern especially in developing countries where AFB1 contamination is common.