• 제목/요약/키워드: High shear rate

검색결과 353건 처리시간 0.058초

풍화된 암반에 근입된 현장타설말뚝의 하중전이 기구 (Load Transfer Mechanism of Drilled Shafts in Weathered Rock)

  • 권오성;조성민;정성준;김명모
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2005년도 춘계 학술발표회 논문집
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    • pp.57-64
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    • 2005
  • Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of the rock socketed pile should be well known. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanisms of drilled shaft socketed into weathered rock was investigated. For that, 5 cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the field test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The side shear resistance of the pile in moderately weathered rock reached to yielding point at a few millimeter displacements, and after that, the rate of resistance increment dramatically decreased. However, that in the highly /completely weathered rock did not show the obvious yielding point, and gradually increased showing the hyperbolic pattern until with the relatively high displacement (>10 mm). The end bearing-displacement curves showed linear increase at least until with the base displacement of approximately 10 mm, regardless rock mass conditions.

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Formation, Breakage and Reformation of Humic Flocs by Inorganic and Organic Coagulants

  • Kam, Sang-Kyu;Lee, Min-Gyu;Kang, Kyung-Ho;Xu, Mei-Lan
    • 한국환경과학회지
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    • 제17권3호
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    • pp.275-285
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    • 2008
  • The floc formation, breakage and reformation of humic acid by inorganic (alum and PAC) and organic coagulants (cationic polyelectrolytes) at several conditions (pH, ionic strength and floc breakage time) were examined and compared among the coagulants at different conditions using a continuous optical monitoring method, with controlled mixing and stirring conditions. For alum, the shapes of formation, breakage and reformation curves at different pH (5 and 7) were different, but the shapes and the sizes of initial floc and reformed floc were nearly the same in the absence and presence of electrolytes at pH 7. For PAC, similar shapes of the curves were obtained at different pH and ionic strength, but the sizes were different, except for those of reformed flocs at different pH. However, for these coagulants, reformed flocs after floc breakage, occurred irreversibly for all the conditions used in this study. For organic coagulants, the time to attain the initial plateau floc size, the extent of floc strength at high shear rate and reversibility of reformed floes were different, depending floc formation mechanism. Especially, for the cationic polyelectrolyte forming humic flocs by charge neutralization or electrostatic patch effect mechanism, reformed flocs occurred reversibly, regardless of pH and floc breakage time, but occurred irreversibly in the presence of electrolytes.

전자레인지 가열시 분쇄 돈육 패티의 지방함량과 가열특성과의 상관관계에 관한 연구 (The Relationship between Fat Level and Quality Properties of Ground Pork Patties Cooked by Microwave Energy)

  • 최지훈;정종연;최윤상;이의수;김천제
    • 한국축산식품학회지
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    • 제28권3호
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    • pp.295-300
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    • 2008
  • This study was carried out to elucidate the relationship between different fat levels (0%, 5%, 10%, 15%, 20%, and 25%) and the quality of ground pork patties cooked to reach an internal temperature of $75^{\circ}C$ in a microwave oven. The relationship between fat level and cooking rate of pork patties cooked by microwave energy was highly significant ($R^2=0.72$), and had a low determination coefficient ($R^2=0.55$). The relationship between fat level and total cooking loss of pork patties cooked by microwave energy was also very significant, with a high correlation coefficient of $R^2=0.89$. The correlation coefficient between fat level and cooking drip loss of patties cooked by microwave energy was 0.92, which was highly significant. Although the correlation coefficient between fat level and evaporation loss had a negative value ($R^2=-0.63$), there was a highly significant relationship between fat level and shear force of pork patties cooked by microwave energy.

지상기반 라이다의 측정 오차에 영향을 미치는 요인 분석 (Analysis of Factors Influencing the Measurement Error of Ground-based LiDAR)

  • 강동범;허종철;고경남
    • 한국태양에너지학회 논문집
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    • 제37권6호
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    • pp.25-37
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    • 2017
  • A study on factors influencing measurement error of Ground-based LiDAR(Light Detection And Ranging) system was conducted in Kimnyeong wind turbine test site on Jeju Island. Three properties of wind including inclined angle, turbulence intensity and power law exponent were taken into account as factors influencing the measurement error of Ground-based LiDAR. In order to calculate LiDAR measurements error, 2.5-month wind speed data collected from LiDAR (WindCube v2) were compared with concurrent data from the anemometer on a nearby 120m-high meteorological mast. In addition, data filtering was performed and its filtering criteria was based on the findings at previous researches. As a result, at 100m above ground level, absolute LiDAR error rate with absolute inclined angle showed 4.58~13.40% and 0.77 of the coefficients of determination, $R^2$. That with turbulence intensity showed 3.58~23.94% and 0.93 of $R^2$ while that with power law exponent showed 4.71~9.53% and 0.41 of $R^2$. Therefore, it was confirmed that the LiDAR measurement error was highly affected by inclined angle and turbulence intensity, while that did not much depend on power law exponent.

Cu-Sn 삽입금속을 이용한 DP강의 아크 브레이징 접합부의 미세조직과 인장특성 (Microstructure and Tensile Strength Property of Arc Brazed DP steel using Cu-Sn Insert Metal)

  • 조욱제;조영호;윤중길;강정윤
    • Journal of Welding and Joining
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    • 제31권1호
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    • pp.58-64
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    • 2013
  • The following results were obtained, microstructures and tensile properties in arc brazed joints of DP(dual phase) steel using Cu-5.3wt%Sn insert metal was investigated as function of brazing current. 1) The Fusion Zone was composed of ${\alpha}Fe+{\gamma}Cu$ and Cu23Sn2. The reason for the formation of these solid solutions. Despite, Fe & Cu were impossible to solid solution at room temperature. It's melting & reaction to something of insert metal & Base Metal (DP Steel) by Arc. Brazing Process has faster cooling rate then Cast Process, Supersaturated solid solution at room temperature. 2) The increase Hardness of Fusion Zone was directly proportional to the rise of welding current. Because, ${\alpha}Fe+{\gamma}Cu$ phase (higher hardness than the Cu23Sn2.(104.1Hv < 271.9Hv)) Volume fraction was Growth, due to increasing the amount of base metal melting by High current. 3) The results of tensile shear test by Brazing, All specimens happen to fracture in Fusion Zone. On the other hand, when Brazing Current increasing tend to rise tensile load. but it was very small, about 26-30% of the base metal. 4) The result of fracture analysis, The crack initiate at Triple Point for meet to Upper B.M/Under B.M/Fusion Zone. This Crack propagated to Fusion zone. So ruptured by tensile strength. The Reason to in the fusion zone fracture, Fusion zone by Brazing of hardness (strength) was very lower then the base metal (DP steel). In addition the Fusion Zone's thickness in triple point was thin than the base metal's thickness in triple point.

High-precision modeling of uplift capacity of suction caissons using a hybrid computational method

  • Alavi, Amir Hossein;Gandomi, Amir Hossein;Mousavi, Mehdi;Mollahasani, Ali
    • Geomechanics and Engineering
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    • 제2권4호
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    • pp.253-280
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    • 2010
  • A new prediction model is derived for the uplift capacity of suction caissons using a hybrid method coupling genetic programming (GP) and simulated annealing (SA), called GP/SA. The predictor variables included in the analysis are the aspect ratio of caisson, shear strength of clayey soil, load point of application, load inclination angle, soil permeability, and loading rate. The proposed model is developed based on well established and widely dispersed experimental results gathered from the literature. To verify the applicability of the proposed model, it is employed to estimate the uplift capacity of parts of the test results that are not included in the modeling process. Traditional GP and multiple regression analyses are performed to benchmark the derived model. The external validation of the GP/SA and GP models was further verified using several statistical criteria recommended by researchers. Contributions of the parameters affecting the uplift capacity are evaluated through a sensitivity analysis. A subsequent parametric analysis is carried out and the obtained trends are confirmed with some previous studies. Based on the results, the GP/SA-based solution is effectively capable of estimating the horizontal, vertical and inclined uplift capacity of suction caissons. Furthermore, the GP/SA model provides a better prediction performance than the GP, regression and different models found in the literature. The proposed simplified formulation can reliably be employed for the pre-design of suction caissons. It may be also used as a quick check on solutions developed by more time consuming and in-depth deterministic analyses.

기계편용 장식사 니트소재의 물성 및 감성 평가 (Physical and Hand Properties of the Knitted Fabrics From Machine Knitting Fancy Yarns)

  • 박기윤;박명자
    • 한국의상디자인학회지
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    • 제10권2호
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    • pp.125-138
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    • 2008
  • For physical and hand property evaluation of fabrics, the knitted fabrics from 11 types of machines knitting fancy yarns, boucle (M1), knot (M2), snarl (M3), and slub (M4), tamtam (M5), tubular (M6), fur 1 (M7), bead (M8), fur 2 (M9), fur 3 (M10), and ladder (M11) yarns, were prepared with 7-10 G plain stitch. Washing test and pilling test had also been carried out. For hand properties by objective sensibility evaluation, 17 items of sir mechanical properties using KES-FB (Kawabata Evaluation System) had been measured. Then hand values of knitted fabrics were calculated with a calculation formula, namely KN-402-KT. Finally the total hand values were obtained through KN-301-WINTER. As a result of physical properties and objective evaluation for machines knitting fancy fabrics, most of them shrank in the direction of wale and course after the washing test, in which their shrinkage rate had a maximum of 3.5%. Therefore, the washing test indicated that the shrinkage ratio of knitted fabrics had a minor change. The results of the pilling test are mostly 4-5th grade, and all of the machines knitting fancy fabrics showed good results in the pilling resistance. In hand properties and objective sensibility evaluation, twisted fancy yarns, such as boucle (M1), knot (M2), snarl (M3), and slub (M4), were superior to bonding rigidity (B) and shear rigidity (G). The surface property between course and wale differs in all samples and course direction is tougher than wale direction. FUKURAMI (fullness and softness) of all samples have high values, besides NUMERI (smoothness) of tamtam (M5) and boucle (M1), which were rather good. Most samples except fur 1 (M7) had low KOSHI (stiffness) value. The total hand value (THV) of twisted yarns was low. This study proves that manufacturers, who plan knitting yarn products and knit fashion, can apply these data to develop machines knitting yarns and knits that fit the consumers' demands.

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여자만의 해수교환 (The Exchange of Sea Water in Yeoja Bay)

  • 이명철
    • 수산해양기술연구
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    • 제19권1호
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    • pp.33-39
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    • 1983
  • 폐쇄적인 지형구조를 보이는 여자만에서 환경조사 및 어장관리를 위한 해양물리학적 기초자료를 얻기 위하여, 1982년 10월 30일부터 11월 6일까지 만구에서 실시한 측류판추적 및 유속계에 의한 측류자료를 사용하여 해수교류 및 교환량을 추정하고 그 해수교환특성을 알아보았다. 여자만의 평균용적(1.96km super(3))에 대하여 유입량은 43%(조차, 320cm), 유출량은 42%(조차, 304cm)였다. 이로부터 얻은 항류성분은 약 3.7$\times$10 super(7)m super(3)로서 대부분이 담수유출량으로 해석된다. 물질수송에 기여한다고 생각되는 평균해수교환량은 만의 용적(2.33km super(3); 평균고조면 3.1m 기준)에 대하여 썰물 때 1.97$\times$10 super(6) cm super(2)/sec, 밀물 때 1.69$\times$10 super(6) cm super(2)/sec였다. 썰물 때 확산계수가 큰 것은 교환능률이 컸음에 기인하여, 썰물 때 shear분산효과가 크다고 생각된다.

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고온 비대칭압연이 알루미늄 합금의 미세조직과 성형성에 미치는 영향 (Effects of Hot Asymmetric Rolling on Microstructure and Formability of Aluminum Alloys)

  • 정무섭;이종범;한준현
    • 한국재료학회지
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    • 제29권10호
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    • pp.647-655
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    • 2019
  • In order to analyze the effect of hot asymmetric rolling on the microstructure and texture of aluminum alloy and to investigate the effect of the texture on the formability and plastic anisotropy of aluminum alloy, aluminum 6061 alloy is asymmetrically rolled at room temperature, $200^{\circ}C$, $350^{\circ}C$, and $500^{\circ}C$, and the results are compared with symmetrically rolled results. In the case of asymmetric rolling, the equivalent strain (${\varepsilon}_{eq}$) is greatest in the upper roll part where the rotational speed of the roll is high and increases with increasing rolling temperature. The increase rate of the mean misorientation angle with increasing temperature is larger than that during symmetrical rolling, and dynamic recrystallization occurs the most when asymmetrical rolling is performed at $500^{\circ}C$. In the case of hot symmetric rolling, the {001}<110> rotated cube orientation mainly develops, but in the case of hot asymmetric rolling, the {111}<110> orientation develops along with the {001}<100> cube orientation. The hot asymmetric rolling improves the formability (${\bar{r}}$) of the aluminum 6061 alloy to 0.9 and reduces the plastic anisotropy (${\Delta}r$) to near zero due to the {111}<110> shear orientation that develops by asymmetric rolling.

인젝터 리세스와 추진제 공급유량이 메탄-산소 확산화염의 가연한계와 구조에 미치는 영향 (Effects of the Recess and Propellants Mass Flow on the Flammability Limit and Structure of Methane-Oxygen Diffusion Flame)

  • 홍준열;배성훈;김정수
    • 한국추진공학회지
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    • 제22권1호
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    • pp.28-35
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    • 2018
  • 전단 동축형 인젝터를 통해 분사된 기체메탄-기체산소 확산화염의 가연한계와 구조분석을 위해 인젝터 리세스와 추진제 공급유량에 따른 연소실험이 수행되었다. 연구 결과, 추진제 운동량 플럭스 비가 증가함에 따라 높은 산화제 레이놀즈 수 구간에서도 안정적인 부착화염이 관찰되었으며, 인젝터 리세스는 화염의 형태와 가연한계에 큰 영향을 미치지 않음을 확인하였다. 자발광 기법을 통해 가시화된 부착화염은 추진제 분사조건이 변함에도 불구하고 항상 일정한 지점에서 최대 OH 라디칼 방사강도를 나타내었으며, 그 강도는 리세스에 의해 심하게 감소함을 확인하였다.