• Title/Summary/Keyword: JRC

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An Experimental Study for the Scale Effects on Shear Behavior of Rock Joint (절리면 전단거동의 크기효과에 관한 실험적 연구)

  • Lee, Sang-Eun
    • Journal of the Korean GEO-environmental Society
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    • v.7 no.3
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    • pp.31-41
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    • 2006
  • The scale effect of specimens on the shear behavior of joints is studied by performing direct shear tests on six different sizes in Granite. The peak and residual shear stress, shear displacement, shear stiffness, and dilation angle are measured with the different normal stress(0.29~2.65MPa) and roughness parameters. It is also shown that both the joint roughness coefficient(JRC) and the joint compression strength(JCS) reduce with increasing joint length. A series of shear tests show about 56~67% reduction in peak shear stress, and about 18~44% in residual shear stress, respectively as the contact area of joint increases from 12.25 to $361cm^2$. Also the variation of dilation angle is $27^{\circ}$ at normal stress of 0.29 MPa and $6^{\circ}$ at normal stress of 2.65 MPa, respectively. The envelopes considering scale effect for JRC are made for the peak shear strength of rock joint in comparison with the Barton's equation.

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Analysis of Random Properties for JRC using Terrestrial LiDAR (지상라이다를 이용한 암반사면 불연속면거칠기에 대한 확률특성 분석)

  • Park, Sung-Wook;Park, Hyuck-Jin
    • The Journal of Engineering Geology
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    • v.21 no.1
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    • pp.1-13
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    • 2011
  • Joint roughness is one of the most important parameters in analysis of rock slope stability. Especially in probabilistic analysis, the random properties of joint roughness influence the probability of slope failure. Therefore, a large dataset on joint roughness is required for the probabilistic analysis but the traditional direct measurement of roughness in the field has some limitations. Terrestrial LiDAR has advantagess over traditional direct measurement in terms of cost and time. JRC (Joint Roughness Coefficient) was calculated from statistical parameters which are known from quantitative methods of converting the roughness of the material surface into JRC. The mean, standard deviation and distribution function of JRC were obtained, and we found that LiDAR is useful in obtaining large dataset for random variables.

Effect of Age-related Changes in Taste Perception on Dietary Intake in Korean Elderly (노인의 영양상태에 미각변화가 미치는 영향)

  • 김화영
    • Journal of Nutrition and Health
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    • v.30 no.8
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    • pp.995-1008
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    • 1997
  • This study was performed to investigate the change in taste perception during aging and its effects on dietary intake in Korean elderly. The subjects were female aged 65 through 90 in the Anyang area, and college women were included as a comparison group . Dietary intake of the elderly(n=155) and young subjects (n=38) was measured by a 3 day diet record. The taste threshold and 'just right' concentrations(JRC) for sweet and salty tastes were assessed by sensory evaluation . Sucrose solution (0.0.,0.4,0.6,0.8,1.0, 1.2%) and salt solution(0, 0.02, 0.03,0.06,0.09,0.12,0.15%) were used to establish thresholds. for JRC assessment, four suprathreshold sucrose concentrations of 5, 8, 11 and 14% in orange-pineapple flavored juice and salt concentrations of 0.20, 0.34, 0.50and 0.75% in beef stock were prepared. Mean intakes of energy, protein , vitamin A, thiamin , riboflavin, niacin ,calcium and iron of the elderly were below the Korean Recommended Dietary allowances. The elderly showed higher taste thresholds than young subjects of both sweet and salty tastes consumed less calories. Needs to bespecified. The older subjects having high threshold or JRCs for sweet and salty tastes consumed fewer calories from protein and fat. Pearson correlation coefficients was between JRC for sweet and salty tastes 0.54(p<0.01). The correlation coefficients between tastes threshold and nutrient intakes were very low for both age groups. Unlike the college women, in the elderly the JRC of sweet taste of the orange-pineapple juice were negatively correlated with intakes of energy, protein, fats, thiamin , riboflavin , niacin ,vitamin C , iron and consumption of meat and egg food groups (p<0.01). In summation age-related alterations in sweet and salty taste perception were observed in the elderly and dietary intakes of the elderly see to be influenced by these taste perception changes.

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Effects of Job-related Characteristics on Alcohol Consumption among Female Workers in Korea (직업관련 특성이 여성의 음주소비에 미친 영향)

  • 김명순;김광기
    • Korean Journal of Health Education and Promotion
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    • v.21 no.1
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    • pp.1-23
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    • 2004
  • The purpose of this study is to examine the effects of job-related characteristics on alcohol consumption among female workers. The Data was collected from a sample of 1,000 female workers by a stratified proportional quota sampling method derived from those who were working in Seoul. Drinking behavior pattern includes total amount of pure alcohol consumed during the last month (AC) measured by graduated quantity-frequency. Job-related characteristics (JRC) were measured by job-related stress, work characteristics, and organizational structure including length of working hours, number of times dining out together with workers per year, number of staff to supervise, employment status, occupational category, and proportion of female workers to male counterpart. Confounding variables include sociodemogrphic and socio-cultural attitudes toward alcohol expectancy, subjective norm of drinking, and gender-role attitude. Hierarchical multiple regression models show that the variability of AC was accounted for by some JRC including number of times dining together and employment status, with confounding variables held constant. However, the relationship between AC and JRC varied across occupational categories. Some implications were discussed in terms of health policy for female workers and further study for female drinking behavior.

A study on the determination of shear strength and the support design of pre-failed rock slope (일차파괴된 암반사면의 전단강도 및 보강설계법 고찰)

  • 조태진;김영호
    • Tunnel and Underground Space
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    • v.5 no.2
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    • pp.104-113
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    • 1995
  • Shear strength of the discontinuity on which the pre-failure of rock slope was occurred during surface excavation was measured through the direct shear test using core samples obtained in-situ. Internal friction angle was increased as the roughness of discontinuity surface(JRC) was increased. Results of the tilt test using core samples of higher JRC also showed very similar trend as those of the direct shear test. When the samples replicated from natural cores were used int he tilt test, results of friction angles showed almost perfect continuation of the residual friction angles from the direct shear test. However, when the gouge material existed in the discontinuity the internal friction angle strongly depended upon the rate of filling thickness to the height of asperity irrespective of the JRC. Based on the results of both direct shear test and tilt test internal friction angle and cohesion of discontinuity, which reflect the in-situ conditions fo pre-sliding failure and also can be used for the optimum design of support system, were assessed. Two kinds of support measures which were expected to increase the stability of rock slope were considered; lowering of slope face angle and installation of rock cable. But, it was found that the first method might lead to more unstable conditions of rock slope when the cohesion of discontinuity plane was negligibly low and in that case the support systems of any kind which could exert actual resisting force were needed to ensure the permanent stability of rock slope.

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Probabilistic Analysis for Rock Slope Stability Due to Weathering Process (풍화작용에 따른 암반사면 안정성의 확률론적 해석)

  • Park, Hyuck-Jin;Woo, Ik;Um, Jeong-Gi
    • Economic and Environmental Geology
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    • v.42 no.4
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    • pp.357-366
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    • 2009
  • Since weathering weakens the rock fabric and exaggerates any structural weakness, it affects mechanical properties as well as physical and chemical properties of rock. Weathering leads to a decrease in density, strength, friction angle and cohesion, and subsequently it affects negatively on the stability of rock slope. The purpose of the study is to investigate the changes of the rock slope stability caused by discontinuities which have different weathering grades. For that, the discontinuity samples which are divided into two different weathering grades are obtained from the field and tested their mechanical properties such as JCS, JRC and residual friction angle. In order to evaluate the effects on the stability of slope due to weathering, the deterministic analysis is carried out. That is, the factors of safety for planar failure are calculated for rock masses which have two different weathering grades, such as fresh and weathered rock mass. However, since the JRC and friction angle values are widely scattered and the deterministic analysis cannot consider the variation, the factors of safety cannot represent properly the stability of the rock slope. Therefore, the probabilistic analysis has been used to consider the scattered values. In the deterministic analysis, the factors of safety for the fresh discontinuity and weathered discontinuity are 1.25 and 1.0, respectively. The results indicate the fresh discontinuities are stable for planar failure and the weathered discontinuities are marginally stable. However, the probabilities of failure for the fresh discontinuity and weathered discontinuity are 25.6% and 45.9%, respectively. This shows that both discontinuities are analyzed as unstable in the probabilistic analysis.

Microbiological Characteristics, Enzyme Activity, and Physiological Functionality of Unrecorded Wild Yeasts from the Wolsung Valley of South Deogyu Mountain and Jinjamcheon in Daejeon, Korea (남덕유산 월성계곡과 대전광역시 진잠천주변 등으로부터 선발된 국내 미기록 야생효모들의 균학적 특성과 주요 효소활성 및 생리활성)

  • Jeong-Su Moon;Min-Young An;Mal-Geum Park;Jong-Soo Lee
    • The Korean Journal of Mycology
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    • v.51 no.1
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    • pp.39-49
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    • 2023
  • This study aimed to screen and investigate the microbiological characteristics, enzyme activity, and physiological functionality of unrecorded wild yeasts from the Wolsung valley of South Deogyu mountain and Jinjamcheon in Daejeon city, Korea. Candida sorboxylosa WSC25-4 (NNIBRFG47336), Arxula adeninivorans WSC6-3 (NNIBRFG47335), Farysizyma taiwaniana JRC6-2 (NNIBRFG47339), Saturnispora dispora JTS19-1 (NNIBRFG47334), Vanderwaltozyma polyspora JJCH5-3 (NNIBRFG47337), and Vanrija fragicola SW-9 (NNIBRFG47338) have not been previously recorded. None of these formed spores or pseudo-mycelium, and four strains, including C. sorboxylosa WSC25-4, were global in shaped. Except for V. polyspora JJCH5-3, all strains grew well in the yeast extract-peptone-dextrose (YPD), potato-dextrose and yeast malt extract media. A. adeninivorans WSC6-3 and S. dispora JTS19-1 grew well in 40% glucose-containing YPD medium and V. fragicola SW-9 in 5% NaCl-containing YPD medium. The supernatant of A. adeninivorans WSC6-3, F. taiwaniana JRC6-2, and V. fragicola SW-9 exhibited 58.0, 59.0, and 59.0% of glucoamylase activity, respectively. C. sorboxylosa WSC25-4 also produced extracellular alkaline protease. Antioxidant activity of the supernatant from F. taiwanian JRC6-2 was high (79.8%), while the other five unrecorded yeasts demonstrated elevated antiaging superoxide dismutase (SOD)-like activity (99%). Anti-gout xanthin oxidase inhibitory activity of S. dispora JTS19-1 and V. fragicola SW-9 was also elevated at 79 and 80%, respectively.

The Engineering Properties of Shear Strength of Rock Joints in Korea (국내에 분포하는 주요 암석의 절리면 전단강도에 대한 공학적 성질)

  • 김대복;이상근;이정인
    • Journal of the Korean Geotechnical Society
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    • v.17 no.4
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    • pp.301-315
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    • 2001
  • 본 연구에서는 최근 5년간 국내 각 지역에서 채취한 802개의 절리면 시료에 대하여 전단시험을 실시하여 얻은 결과를 이용하여, 절리면의 여러 공학적 성질들을 조사, 연구하였다. 절리면 전단시험에서 얻어진 최대마찰각 및 잔류마찰각을 지체구조별, 암종별로 분류하고 통계적으로 구하였으며, Barton의 전단강도식의 입력변수인 JRC, JCS를 측정하고 Barton식의 적용성에 대해서도 검토하였다. 그 결과 설계의 기초자료로 활용할 수 있는 지역별, 주요 암종별 최대마찰각, 잔류마찰각을 제시하였다. 또한, JRC, JCS, 수직응력에 따른 마찰각과 전단강성 및 팽창각의 변화를 분석하였다. 마지막으로, Barton의 식에서 구한 이론적 전단강도와 이 실험에서 얻어진 전단강도를 비교한 결과, Barton의 경험식은 높은 상관도로 암석 절리면 전단강도를 예측할 수 있음을 확인하였다.

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Investigation on the effect of eccentricity for fuel disc irradiation tests

  • Scolaro, A.;Van Uffelen, P.;Fiorina, C.;Schubert, A.;Clifford, I.;Pautz, A.
    • Nuclear Engineering and Technology
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    • v.53 no.5
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    • pp.1602-1611
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    • 2021
  • A varying degree of eccentricity always exists in the initial configuration of a nuclear fuel rod. Its impact on traditional LWR fuel is limited as the radial gap closes relatively early during irradiation. However, the effect of misalignment is expected to be more relevant in rods with highly conductive fuels, large initial gaps and low conductivity filling gases. In this paper, we study similar characteristics in the experimental setup of two fuel disc irradiation campaigns carried out in the OECD Halden Boiling Water Reactor. Using the multi-dimensional fuel performance code OFFBEAT, we combine 2-D axisymmetric and 3-D simulations to investigate the effect of eccentricity on the fuel temperature distribution. At the same time, we illustrate how the advent of modern tools with multi-dimensional capabilities might further improve the design and interpretation of in-pile separate-effect tests and we outline the potential of such an analysis for upcoming experiments.