• Title/Summary/Keyword: 점성학

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Ability to Resist Chloride Ion Penetration and Dry Shrinkage Evaluation of Magnesium Phosphate Ceramics (인산마그네슘 세라믹의 염소 이온 투과 저항성 및 길이변화 특성에 관한 성능 평가)

  • Ko, Jeong-Won;Yang, Wan-Hee;Park, Dong-Cheol
    • Journal of the Korea Institute of Building Construction
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    • v.17 no.4
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    • pp.341-348
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    • 2017
  • The performance degradation of concrete pavement by winter deicer is very serious in Korea, and its maintenance and rehabilitation brings a high expense. Therefore, a suitable method for rehabilitation of such concrete pavement and repair material of proper performance are required. In this study, the properties of compressive strength, ability to resist chloride ion penetration, and properties of dry shrinkage of magnesium phosphate ceramics were assessed to evaluate its applicability as a repair material for concrete pavement in Korea. As a result, the mortar flow showed a normal level of 190 mm, but the viscosity was high and the self-flow ability was poor. The setting time was 12 minutes, leading very rapid-hardening, and thus a prompt work was required. The compressive strength of mortar was 38.4MPa in 2 hours, 73.8MPa in 24 hours, and 111.0MPa in 28 days, showing a significant level. As a result of the test to chloride ion penetration resistance, mortar showed 143 Coulombs, and concrete showed 172.6 Coulombs, which fell under very low level. The drying shrinkage of MPC concrete in 40 days was below $60{\times}10-6$, and comparing with normal cement concrete, it showed the level below 1/10 of other concrete to secure an excellent volume stability. As above, magnesium phosphate ceramics has excellent strength performance, chloride ion penetration resistance, and volume stability, and this in the future shall be used in construction under the consideration of working time or workability, requiring further improvement for such performance.

Effect of Appearance, Viscosity and Texture Characteristics on Rice Palatability in Some Rice Varieties (쌀의 외관, 호화특성 및 물성 차이에 따른 품종별 분류)

  • Ha, Ki-Yong;Choi, Yoon-Hee;Choung, Jin-Il;Noh, Gwang-Il;Ko, Jae-Kwon;Ree, Jae-Kil;Kim, Chung-Kon
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.51 no.spc1
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    • pp.21-24
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    • 2006
  • We analyzed factors which related with rice quality at seven varieties. The whiteness of Daeyabyeo, Hopyeongbyeo and Koshihikari were higher than those of other rice varieties. In the hardness of brown rice, Ilpumbyeo was the lowest, and Sindongjinbyeo was the highest among varieties. The hardness cooked rice of Hopyeongbyeo were significantly low, and cohesiveness of those were significantly high. but adhesiveness, viscosity and gumminess of Ko-shihikari was high than other cooked rice varieties. The palatability of Daeyabyeo and Hopyeongbyeo were higher than those of Ilpunbyeo and Ungwangbyeo. Varieties which were known as having good palatability were higher in the breakdown, while setback and consistency were low. In those varieties, factors of upper were correlated with palatability, so this were supposed to determine palatability.

Characteristics of Wheat Flour Dough and Noodles with Barnyard Millet (Echinochloa spp.) (식용피 첨가에 의한 밀가루 반죽 및 국수의 특성)

  • Lee, Yun Sang;Yoon, Hyang-Sik;Lee, Sang-Yeong;Lee, Joung-Kwan;Park, Chul Soo;Seo, Woo Duck;Woo, Sun-Hee;Song, In Gyu
    • The Korean Journal of Food And Nutrition
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    • v.25 no.4
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    • pp.706-712
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    • 2012
  • The effects of barnyard millet (Echinochloa spp.) content (10~30%) on wheat flour dough and noodle properties were investigated. As the amount of barnyard millet increased, the particle size and ash content of mixed flour increased, while lightness tended to decrease. The gelatinization characteristics of millet flour showed higher peak viscosity, holding strength, final viscosity, and setback compared with wheat flour. There was significant positive correlation between protein content and sedimentation volume, as well as between protein content and water absorption. As the amount of barnyard millet increased, hardness, springiness and cohesiveness of wet noodles tended to decrease. From the results of sensory evaluation, composite flours (addition up to 20% barnyard millet) were rated with a quality score for taste and overall acceptance which was comparable with the control flour.

Demulsification of Petroleum Emulsion by Streptomyces sp. 8321 (Streptomyces sp. 8321에 의한 석유 유상액의 탈유화)

  • Ko, Sung-Hwan;Lee, Deuk-Soo;Kim, Sang-Jin;Lee, Hong Kum
    • Korean Journal of Microbiology
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    • v.34 no.3
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    • pp.162-168
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    • 1998
  • The characteristics of demulsification of petroleum emulsion by Streptomyces sp. 8321 were investigated. Demulsification ability of Streptomyces sp. 8321 appeared to be confined within the spores. Spore surface hydrophobicity was increased with culture age stimulating the demulsification ability. Over $1.1{\times}10^8spores/ml$ completely demulsified kerosene-0.2% Triton X-100 (2:1) emulsion. Among the low viscosity hydrocarbons, hydrocarbons with longer chain such as n-hexadecane and diesel were more rapidly demulsified. However, only 20-30% of the emulsion with high viscosity hydrocarbons was demulsified after 24 hours. Oil-in-water emulsions made by Corexit, Finalsol and BP series surfactants were completely demulsified within one minute. Demulsification rate ($t_{1/2}$) of oil-in-water emulsions made by Corexit 7664, 8667, Triton X-100 and Tween 80 decreased as their concentration increased. In case of water-in-oil emulsion made by Seagreen, $t_{1/2}$ was over 24 hours. Therefore, demulsification ability of Streptomyces sp. 8321 was more effective on oil-in-water emulsions.

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Model on the Contact Lens Movement from Eye-lid Blinking (순목 작용에 의한 콘택트 렌즈의 운동 모델)

  • Kim, Daesoo
    • Journal of Korean Ophthalmic Optics Society
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    • v.9 no.1
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    • pp.145-159
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    • 2004
  • A mathematical model and its computer solution program were proposed to analyze the motion of contact lenses which are being subject to lid-blinking. The equation was derived by incorporating an acceleration induced lid's force exerting on the contact lens, the viscous damping resistance in the tear layer beneath the lens and the sliding frictional force between the lid and the contact lens surface into the formulation of differential equation describing the vibration. The model predicts the time-dependent displacement from the equilibrium postion during/after the blinking. During the blinking, as the time for the completion of one cycle of blinking decreases the off-the-equilibrium displacement of contact lens increases while the decrease of diameter in the contact cause the opposite effect. It is found that lid pressure exerting on the lens cause an insignificant lens displacement from the equilibrium position. After blinking the frequency of damped oscillation of contact lens decreases as the diameter of lens increases, due to the incresed surface while the reduced blinking time does not cause a significant frequency change. This is because that driving force for the contact lens movement posterior to blinking is the capillary-induced force not the lid force.

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Uplift Capacity of Shallow Foundation for Greenhouse (온실용 얕은기초의 인발저항력 검토)

  • Yun, Sung Wook;Choi, Man Kwon;Lee, Si Young;Kang, Dong Hyeon;Moon, Sung Dong;Yu, Chan;Yoon, Yong Cheol
    • Journal of Bio-Environment Control
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    • v.24 no.3
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    • pp.187-195
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    • 2015
  • In this study, a field test of uplift load was carried out using 15 greenhouse foundations fabricated in full scale on a sand soil to examine the uplift capacity of plastic film greenhouse and glasshouse foundations for disasterproof standard. As a result, the maximum uplift capacity of the target greenhouse foundations was shown to be in the range from 11.6kN to 82.4kN according to the differences between the forms and sizes of the foundation. As a result of the examination of the applicability using the field uplift load test result of the theoretical equation proposed for maximum uplift capacity calculation of greenhouse foundations, we found that in general, the conventional theoretical equation for the calculation provided numerical values close to the field test results. However, the soil considered in this study was a sand; thus, in the future, verifying the conventional theoretical equation for the uplift capacity calculation of a cohesive soil would be necessary.

Simulation of Solid Particle Sedimentation by Using Moving Particle Semi-implicit Method (고체 입자형 MPS법을 이용한 토사물 퇴적 시뮬레이션)

  • Kim, Kyung Sung;Yu, Sunjin;Ahn, Il-Hyuk
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.1
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    • pp.119-125
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    • 2018
  • The particle based computational fluid dynamics (CFD) method, which follow Lagrangian approach for fluid dynamics, fluid particle behavior by tracking all particle calculation physical quantities of each particle. According to basic concept of particle based CFD method, it is difficult to satisfy continuum theory and measure influences from neighboring particle. Article number density and weight function were used to solve aforementioned issue. Difficulties continuum mean simulate non-continuum particles such as solid including granular and sand. In this regard, the particle based CFD method modified solid particle problems by replacing viscous and surface tension forces friction and drag forces. In this paper, particle interaction model for solid particle friction model implemented to simulate solid particle problems. The broken dam problem, which is common to verify particle based CFD method, used fluid or solid particles. The angle of repose was observed in the simulation results the solid particle not fluid particle.

Model on the Capillary Action-Induced Dynamics of Contact Lens (모세관 작용에 의한 콘택트 렌즈의 운동 모델)

  • Kim, Dae-Soo
    • Journal of Korean Ophthalmic Optics Society
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    • v.6 no.2
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    • pp.85-97
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    • 2001
  • A mathematical model was proposed to analyze the damped motion of contact lens which is initially displaced from the equilibrium position. The model incorporates the differential equations and their numerical solution program, based on the formulations of restoring force arising from the capillary action in the tear-film layer between the lens and cornea. The model predicts the capillary action induced surface tension, time dependence of displacement of lens when it is released from the equilibrium position. It seems that the motion of lens is similar to the typical over-damped oscillation caused by the large viscous friction in the liquid layer between the cornea and lens. The effect of variables such as base curves, lens diameters and thickness of tear film layer were illustrated by the computer simulation of the derived program. The time required for the lens to return to the original position increases as the liquid layer thickness increases and it decreases as the diameter of lens increases. With the certain value of base curve the time interval is found to be minimum. The free vibrations of lenses were also simulated varying the parameters such as base curve, diameter, layer thickness. The resonant frequencies are inversely proportional to the liquid layer thickness and it increases as the lens diameter increases. The resonant frequency of lens has a maximum when the diameter is of certain value. If the external impulse or force of the same frequency as the natural frequency of contact lens acted on the cornea in vivo it may cause an excessive movement and thus it might cause the distortion 10 the lens or be pulled off the eye.

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A Preliminary Study for the Prediction of Leaking-Oil Amount from a Ruptured Tank (파손된 기름 탱크로부터의 유출양 산정을 위한 기초 연구)

  • Kim Wu-Joan;Lee Young-Yeon
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.4 no.4
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    • pp.21-31
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    • 2001
  • When an oil-spilling accident occurs at sea, it is of the primary importance to predict the amount of oil leakage for the swift response and decision-making. The simplest method of oil-leakage estimation is based on the hydrostatic pressure balance between oil inside the tank and seawater outside of leakage hole, that is the so-called Torricelli equilibrium relation. However, there exists discrepancy between the reality and the Torricelli relation, since the latter is obtained from the quasi-steady treatment of Bernoulli equation ignoring viscous friction. A preliminary experiment has been performed to find out the oil-leaking speed and shape. Soy-bean oil inside the inner tank was ejected into water of the outer tank through four different leakage holes to record the amount of oil leakage. Furthermore, a CFD (Computational Fluid Dynamics) method was utilized to simulate the experimental situation. The Wavier-Stokes equations were solved for two-density flow of oil and water. VOF method was employed to capture the shape of their interface. It is found that the oil-leaking speed varies due to the frictional resistance of the leakage hole passage dependent on its aspect ratio. The Torricelli factor relating the speed predicted by using the hydrostatic balance and the real leakage speed is assessed. For the present experimental setup, Torricelli factors were in the range of 35%~55% depending on the aspect ratio of leakage holes. On the other hand, CFD results predicted that Torricelli factor could be 52% regardless of the aspect ratio of the leakage holes, when the frictional resistance of leakage hole passage was neglected.

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Preliminary Study on Factor Technology of Selective Catalytic Reduction System in Marine Diesel Engine (선박용 디젤엔진 SCR 시스템 요소 기술에 관한 기초 연구)

  • Park, Yoon-Yong;Song, Ha-Cheol;Ahn, Gi-Ju;Shim, Chun-Sik
    • Journal of Navigation and Port Research
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    • v.40 no.4
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    • pp.173-181
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    • 2016
  • From 2016, controls on reduction of NOx and SOx emissions from the vessels that are operated in the emission control area were tightened. The selectivity catalytic reduction system of the denitrification equipment which NOx among the above controlled materials is very effective and used commercially very much. But it has the disadvantage that CSR is activated at high temperatures. Therefore, the SCR and SCR activation instrument that can react even at low temperatures by using micro-nano bubbles so that the above problems can be minimized were developed. And the computational fluid dynamics technique was used by ANSYS-CFX package to prepare the plan that improves the SCR system's efficiency. Simulation for the viscous flow analysis of the SCR system was executed by applying the Navier-Stokes equation to it as a governing equation. For the SCR system's shape, 3D modeling was done by using CATIA V5. SCR jet nozzle's position was checked by changing it to the intervals of 1/3, 1/2, and 2/3 from the inlet of the vent pipe to compare the SCR system's efficiency. And the number of nozzles was compared and analyzed by simulating 4, 6, and 8 holes to check an effect of the number on the SCR system's efficiency. The simulation result has found that the closer nozzles are to the inlet of the vent pipe and the more nozzles are, the more efficiency is improved.