• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.143-151
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• 2020

Recently, research on self-healing concrete has been actively conducted, and various methods have been attempted for use in the maintenance of structures. However, contrary to the technical development of self-healing concrete, the method for evaluating the performance is insufficient. Although surface observation and permeability experiments are widely used to observe the healing of cracks, microscopic observation of surface may be insufficient to assess the overall performance. Also, permeation experiments should consider the losses caused by the dissolution of self-healed product and viscosity of water. Although a gas diffusion experiment have been proposed to overcome the shortcomings of these two test methods, verification has not been made on specimens with actual healing. Therefore, in this study, gas diffusion experiments were performed on the mortar specimens that had healed, and the adequacy of self-healing evaluation by the gas diffusion experiment was verified.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.357-366
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• 1986

The flow characteristics of two-dimensional turbulent offset jet which is discharged parallel to a solid wall has been studied experimentally and numerically. In the experiment, 3-hole pitot tube and 2 channel constant temperature hot-wire anemometer are used to measure local mean velocity, turbulence intensity and Reynolds stress while scannivalve is used to measure the wall pressure distribution. It is confirmed experimentally that local mean velocity is closely related to wall pressure distribution. It is also verified that for large Reynolds numbers and fixed step height there exists a similarity in the distribution of wall pressure coefficient. The maximum values of turbulence intensity occur in the top and bottom mixing layers and the magnitude of Reynolds stress becomes large in the lower mixing layer than in the top mixing layer due to the effect of streamline curvature and entrainment. In the numerical analysis, standard k-.epsilon. model based on eddy viscosity model and Leschziner and Rodi model based on algebraic stress model are adopted. The numerical analyses predict shorter reattachment lengths than the experiment, and this difference is judged to be due mainly to the problem of turbulence model constants and numerical algorithm. This also causes the inconsistency between the two results for other turbulence quantities in the recirculation region and impingement region, which constitutes a subject of a continued future study.

• Journal of Life Science
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• v.18 no.2
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• pp.162-166
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• 2008

The production of heteropolysaccharide-7 (PS-7) by Beijerinckia indica (B. indica L3) was evaluated in shaker flask culture. The medium optimization was studied using response surface methodology (RSM). A five-level three-factor central composite design was employed to determine the maximum PS-7 yield at optimum levels for whey lactose, glucose and ammonium nitrate contents. The validity of the model could be determined by the regression coefficient, $R^2$. The values of $R^2$ were 0.72, 0.64 and 0.85 in PS-7, DCW and viscosity, respectively. The optimal medium combinations of whey lactose, glucose and ammonium nitrate concentrations on the PS-7 production were whey lactose (2%), glucose (1 %) and ammonium nitrate 5 mM, respectively. The result indicated that PS-7 production was affected significantly by the addition of glucose to whey lactose based on medium and C/N ratio.

• Applied Biological Chemistry
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• v.33 no.4
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• pp.301-306
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• 1990

The Physical and chemical properties or dry acorn starch(DS), detannined acorn starch (DTS) and defatted and detannined acorn starch(Drn) were investigated. Ail acorn starch sample, observed by a scanning electron microscope, showed a hemispherical shape ud its size was about $5{\sim}10{\mu}m$ in diameter. It had a little change on the pasting temperature of DS, DTS and DFTS but peak viscosity of DTS was somewhat higher than that of n. Flow behavior of gelatinized starch pastes showed a pseudoplastic behavior and flow behavior index was lower than unit. The consistency coefficient showed concentraion and temperature dependency. The activation energies of DS, DTS and DFTS were $2.09{\sim}3.58Kcal/g\;{\cdot}\;mol and time dependent characteristic of acorn starch samples showed thixotrpic behavior.

• Applied Biological Chemistry
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• v.33 no.4
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• pp.293-300
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• 1990

The physical and chemical properties of dry acorn starch(DS), defatted acorn starch (DFS) and reincorporated acorn starch(RIS) were investigated. Swelling power and solubility of all starch sample, were exhibited two stage behavior. It had a little change on the pasting temperature of DS and DFS but the peak viscosity and breakdown value of DFS was somewhat higher than those of DS and RIS. Flow behavior of gelatinized starch pastes showed a pseudoplastic behavior and flow behavior index was lower than unit The consistency coefficient showed concentration and temperature dependency. The activation energies of DS, DFS and RIS were from $1.70Kca1/g\;{\cdot}\;mol$ to $3.75Kca1/g\;{\cdot}\;mol$.

• Journal of Biosystems Engineering
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• v.32 no.3
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• pp.166-172
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• 2007

Egg quality indices are related with freshness, size of air chamber, loss of weight, and viscosity of the yolk and the protein. However, since the described quality parameters require measured in a destructive way, it is not suitable to inspect the egg quality with complete enumeration. Therefore, this study was performed to investigate the potential of image analysis method for evaluation of internal egg quality. Samples of 90 fresh eggs were collected immediately after laying and stored up to 24 days. Five eggs were randomly drawn from each storage condition (packing vs unpacking) at a regular interval and loss of weight, specific gravity and size of air chamber were measured. The image analysis for nondestructive measurement of size of air chamber was also studied. Results showed that the egg weight and gravity gradually decreased with increasing of storage days, while the size of air chamber linear increased caused by evaporation of water through the shell. A relationship a between conventional method and the image analysis method for measuring the size of air chamber was developed with the correlation coefficient of 0.928. The new finding implied that image analysis might provide a useful nondestructive tool to assess internal egg quality.

• Structural Engineering and Mechanics
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• v.52 no.6
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• pp.1069-1084
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• 2014

The long-term performance of plates resting on viscoelastic foundations is a major concern in the analysis of soil-structure interaction. As a powerful mathematical tool, fractional calculus may address these plate-on-foundation problems. In this paper, a fractionalized Zener model is proposed to study the time-dependent behavior of a uniformly loaded rectangular thin foundation plate. By use of the viscoelastic-elastic correspondence principle and the Laplace transforms, the analytical solutions were obtained in terms of the Mittag-Leffler function. Through the analysis of a numerical example, the calculated plate deflection, bending moment and foundation reaction were compared to those from ideal elastic and standard viscoelastic models. It is found that the upper and lower bound solutions of the plate response estimated by the proposed model can be determined using the elastic model. Based on a parametric study, the impacts of model parameters on the long-term performance of a foundation plate were systematically investigated. The results show that the two spring stiffnesses govern the upper and lower bound solutions of the plate response. By varying the values of the fractional differential order and the coefficient of viscosity, the time-dependent behavior of a foundation plate can be accurately captured. The fractional differential order seems to be dependent on the mechanical properties of the ground soil. A sandy foundation will have a small fractional differential order while in order to simulate the creeping of clay foundation, a larger fractional differential order value is needed. The fractionalized Zener model is capable of accounting for the primary and secondary consolidation processes of the foundation soil and can be used to predict the plate performance over many decades of time.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.211-221
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• 2002

The purpose of this study was to analyze the commercial paste opaque products currently available in domestic of foreign as well as domestic, such as Duceram Plus(DU; Ducera Dental GmbH, Germany), VMK 95(VM; Vita Co., Germany), Noritake EX-3(EX; Noritake Co., Japan) and Ceramax(CE; Alphadent Co., Korea). They were characterized in thermal expansion coefficient, particle size distribution, viscosity and solvent using thermomechanical analyzer, particle size analyzer, rheometer and infrared spectrophotometer. Experimental results are as follows; Firstly, thermal expansion coefficients were determined $13.9{\times}10-6/^{\circ}C$ for DU, $14.3{\times}10-6/^{\circ}C$ for VM, $13.3{\times}10-6/^{\circ}C$ for EX, and $14.0{\times}10-6/^{\circ}C$ for CE. Secondly, percent of partice size below $1{\mu}m$ were 12% for DU, VM and CE, and 13% for EX, percent between $1{\mu}m$ and $5{\mu}m$ were 42% for DU, 42% for VM, 38% for EX, and 61 % for CE, percent between $5{\mu}m$ and $10{\mu}m$ were 21 % for DU, 24% for VM, 20% for EX, and 18% for CE, and over $10{\mu}m$ were 25% for DU, 22% for VM, 29% for EX, 9% for CE. Thirdly, the basic composition of the solvent in all of the commercial paste opaques were determined as ethylene glycol from FT-IR investigation. Lastly, measured viscosities were 1798 cp for DU, 536 cp for VM, 1110 cp for EX, and 721 cp for CE.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.602-607
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• 1993

These studies were conducted to investigates the changes in physicochemical characteristics of Charbori (waxy-barley) and Olbori (normal) during kernel maturation. 1000-kernel weight increased as the barley matured and as the original moisture decreased. The amount of total nitrogen per endosperm was similar in both cultivars. 1000-kernal weight had a correlation coefficient of $r=-0.871^{**}$ with water soluble nitrogen and of $r=-0.894^{**}$ with nitrogen solubility index. At maturity, the starch content of Olbori was 26% higher than Chalbori. Amylose content ranged from 20.4 to 24.7% in Olbori and from 9.9 to 12.9% in Chalbori as the kernel matured. ${\beta}-glucan$ viscosity was no differences at the early stages of development, but at 40 days after heading, was greatly differences between Chalbore and Olbori, 7.9 kand 5.8 cST, respectively. Gelatinization characteristics and other properties of the starch by Amylograph were compared with those of Olbori and Chalbori. The Chalbori starch usually had a lower initial temperature and setback.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.179-190
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• 2003

The grout based on solution type makes it difficult to get the improvement of ground strength and the effefct of water curtain because it has lower strength and durability than suspension type. Nowadays, the technology of particle acceleration, that enhance the material permeability, such as grout based on solution type, and inexpensive grout, is being required. For these reasons, in this study, using wet milling system, we evaluated physical properties of manufactured factors such as water-cement ratio of particles before being milled, optimum milling capacity by controlling milling time and rpm, viscosity of materials, permeation coefficient, and unconfined compressive strength. Also, using micro wet milling apparatus which could manufacture ordinary Portland cement and high speed shear mix which could forcefully separate conglomerate particles in situ, we performed electrical resistivity investigation and falling head permeability tests to analyze differences of grouting effects. From these results, we found that the permeability of the applied equipment was much superior, and in the case of using high speed shear mixer, particles of grout material were well separated.