• Title, Summary, Keyword: Low normal stress

Search Result 279, Processing Time 0.044 seconds

Anisotropic Shear Strength of Artificially Fractured Rock Joints Under Low Normal Stress (낮은 수직응력 하에서 인공 절리면의 전단 이방성에 관한 연구)

  • 곽정열;이상은;임한욱
    • Tunnel and Underground Space
    • /
    • v.13 no.3
    • /
    • pp.169-179
    • /
    • 2003
  • Anisotropic shear strength of rock joints is studied based on the artificially fractured specimens using experimental and analytical methods. Series of direct shear tests are performed to obtain the strength, stiffness and friction angle of joints under various low normal stresses and shearing directions. The results of shear strength and stiffness show anisotropic value according to shearing direction under low normal stress specially less than 2.45 MPa. But, the effect of joint roughness on strength decreases with increasing normal stress. To estimate more effectively the peak shear strength under low normal stress, the modified Barton's equation is suggested.

Study on the Comparison of Emotion between the Mothers with Low-birth Weights and Normal Infants and the Effect of Home Visiting for the Low-birth Weights (저체중출생아 어머니와 정상신생아 어머니의 정서와 지지 비교 및 보건소 저체중출생아 가정방문간호의 효과에 대한 연구)

  • Bang, Kyung-Sook;Kim, Yong-Soon;Park, Jee-Won
    • Korean Parent-Child Health Journal
    • /
    • v.5 no.1
    • /
    • pp.75-89
    • /
    • 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.

  • PDF

Investigation into the Worst Stress Condition for an Accelerated Life Test of a Compressor in Refrigerators - Acceleration Factor and the Reducible Test Time under Low Temperature - (냉장고용 압축기의 가속수명시험을 위한 가혹조건 탐색 - 저온 가혹조건에서의 가속계수와 단축 시험기간 -)

  • Jung, Y.M.;Joo, W.J.;Jeong, S.K.
    • Journal of the Korea Society For Power System Engineering
    • /
    • v.16 no.2
    • /
    • pp.43-48
    • /
    • 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.

Analysis of Coaxial Magnetic Gear with Low Gear Ratios for Application in Counter Rotating Systems

  • Shin, H.M.;Chang, J.H.
    • Journal of Magnetics
    • /
    • v.20 no.2
    • /
    • pp.186-192
    • /
    • 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.

The Relationship between Perceived Stress and Coping Strategies in Patients with Chronic Low Back Pain (만성요통 환자들에서 스트레스지각과 대응전략 간의 관계)

  • Shin, Yoon-Sik;Koh, Kyung-Bong
    • Korean Journal of Psychosomatic Medicine
    • /
    • v.10 no.1
    • /
    • pp.18-26
    • /
    • 2002
  • Objectives : The object of this study was to investigate the relationship between coping strategies and perceived stress or pain discomfort in patients with chronic low back pain. 80 patients with chronic low back pain and 100 normal controls participated in this study. Methods: Global assessment of recent stress (GARS) scale and Stress Response Inventory (SRI) were used to measure perception for stressors and stress responses. Coping scale and pain discomfort scale were used to measure coping strategies and pain perception. Results : Scores of perceived stress related to work or job, interpersonal relationship, changes in relationship, sickness or illness and the total scores on the GARS scale were significantly higher in those with chronic low back pain than normal controls. Scores of the SRI fatigue subscale scored significantly higher in those with chronic low back pain than normal controls. No significant difference was found on total scores of the pain discomfort scale between those with chronic low back pain and normal controls. The patients with chronic low back pain scored significantly higher on planful problem solving and positive reappraisal than normal controls. In the patient group, pain perception had significant positive correlations with total scores of the SRI and scores of stress perception related to illness or injury. The extent of escape-avoidance showed significant negative correlations with age, whereas the extent of distancing or escape-avoidance had significant negative correlations with the level of education. Significant difference was also found in accepting responsibilities between male subjects and females. However, no significant correlations were found between coping strategies and perceived stressors, stress responses or pain perception. Conclusion : The results suggest that patients with chronic low back pain were more likely to use more active coping strategies than normal controls, though the former had more perception for stressors than the latter. It was also found that coping strategies used by the patients were associated with sociodemographic factors, but that they were not associated with perceived stressors, stress responses or pain perception.

  • PDF

Analysis of reliability test results of low-pass filter assembly (저역필터 어셈블리에 대한 신뢰성시험 결과의 해석)

  • Baik, Jaiwook
    • Journal of Applied Reliability
    • /
    • v.14 no.1
    • /
    • pp.45-51
    • /
    • 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.

The Subsurface Stress Field Caused by Both Normal Loading and Tangential Loading

  • Koo Young- Phi;Kim Tae-Wan;Cho Yong-Joo
    • Journal of Mechanical Science and Technology
    • /
    • v.19 no.11
    • /
    • pp.1967-1974
    • /
    • 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.

Oxidative Stress in Extrahepatic Tissues of Rats Co-Exposed to Aflatoxin B1 and Low Protein Diet

  • Rotimi, Oluwakemi A.;Rotimi, Solomon O.;Oluwafemi, Flora;Ademuyiwa, Oladipo;Balogun, Elizabeth A.
    • Toxicological Research
    • /
    • v.34 no.3
    • /
    • pp.211-220
    • /
    • 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.

Variations of Catecholamine Contents in Rat Urine by Environmental Stress (환경 Stress에 의한 횐쥐뇨중 catecholamine의 변화)

  • 김형석
    • Environmental health and toxicology
    • /
    • v.3 no.3_4
    • /
    • pp.9-15
    • /
    • 1988
  • The word of stress crime from Latin language as stringere and it was used in medical fields from 1935. According to Selye, all the biological bodies reveal physilolgical changes when some stimulation exceed normal levels, and consequently the pituitary gland and adrenal systems are activated. Jacob expressed that stress is the loss of homeostasis by physical, chemical, and emotional stimulation. When biological organisms receive extreme stress the amount of catecholamine excretion are increase. Author investigated the catecholamine contents in rat urine after giving the low temperature stress, noise stress, and water immersion stress. The 24 hours rat urine was collected by adding 1 ml 6 N-HCl and the sample is passed through Bio-Rex 70 samples treatment column to extract catecholamine and detected the catecholamine with HPLC-fluorescence detetor. The highest epinephrine concentration was 67.14 ng in water immersion stress condition and the dopamine concentration of 221.37 ng was shown in the low temperature stress condition.

  • PDF

Effect of Coicis Semen on Starvation Stress in Mice (억이인이 생쥐의 기아 Stress에 미치는 영향)

  • 홍서영;임형호;이태희
    • The Journal of Korean Medicine
    • /
    • v.24 no.3
    • /
    • pp.23-34
    • /
    • 2003
  • Objective : In 2001, the rate of obesity in Korea reached 30.6%. There are many therapeutic ways to reduce body weight, such as low and very low calorie diet, exercise therapy, behavior modification therapy, etc. However, in many cases the patients feel stress under obesity treatment because of starvation. This study was aimed to evaluate the anti-starvation stress effect of Coicis Semen on mice. Methods : First, the mice were divided into 6 groups : Normal (group with no starvation), Control (administrated normal saline 6 times before starting 36 hours starvation), and Samples A, B, C, and D (administrated 0.25, 0.5, 1.0, 3.0 g/kg Coicis Semen respectively 6 times before starting 36 hours starvation). Then the plasma corticosterone level and rectal temperature were measured. The norepinephrine, dopamine, DOPAC (dihydroxy-phenylacetic acid), 5-HT (5-hydroxytryptamine) and 5- HIAA (5-hydroxy-indole-acetic acid) in the hypothalamus were measured by the HPLC method. Result : I. The rectal temperature in Sample group D showed a significant difference (P<0.05) compared with the Control group. 2. The DOPAC in Sample groups A, C and D showed the significant difference (P<0.05) compared with the Control group. Conclusion : It might be recognized that Coicis Semen has an anti-starvation stress effect.

  • PDF