• Geomechanics and Engineering
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• v.31 no.5
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• pp.519-527
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• 2022

Shear failure in soil is the primary cause of most geotechnical structure failures or instability. Soil water content is a significant factor affecting soil shear strength. In this study, the shear strength of samples with different water contents was tested. The shear strength, cohesion, and internal friction angle decreased with increasing water content. Based on the variation of cohesion and internal friction angle, the water content zone was divided into a high-water content zone and low-water content zone with a threshold water content of 15.05%. Cohesion and internal friction angle have a good linear relationship with water content in both zones. Environmental Scanning Electron Microscopy (ESEM) test presented that the aggregates size of the compacted loess gradually increases with increasing water content. Meanwhile, the clay in the compacted loess forms a matric that envelops around the surface of the aggregates and fills the inter-aggregates pores. A quantitative analysis of bound water and free water under different water contents using a nuclear magnetic resonance (NMR) test was carried out. The threshold water content between bound water and free water was slightly below the plastic limit, which is consistent with the results of shear strength parameters. Combined with the T2 distributions obtained by NMR, one can define a T2 relaxation time of 1.58 ms as the boundary point for bound water distribution without free water. Finally, the effects of bound water and free water on shear strength parameters were analyzed using linear regression analysis.

• Bulletin of the Korean Chemical Society
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• v.2 no.2
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• pp.60-66
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• 1981

The hypothesis that three classes of water exist in hydrogels, namely X water (free water-like), Z-water (bound water-like), and Y water (interfacial water-like), has been verified and generally accepted. To further check the validity of this hypothesis and to study the nature of X, Y, and Z water as conformation changes, several experiments have been done using Tactic Poly(2-hydroxyethyl methacrylate) (P-HEMA) gels. Thermal expansively data for tactic P-HEMA gel was obtained. In each case of isotactic and syndiotactic P-HEMA, the higher water content gels showed an extremely sharp volume change at $0^{\circ}C$, indicating the presence of normal free water-like. Lower water content gels showed no anomalous change in thermal expansion, indicating that the water is bound water-like. The medium water content gels exhibited intermediate behavior. These results were also confirmed by bulk gel conductivity measurments. The differential scanning calorimeter(DSC) experiment was simply introduced to further verify the bound water-like quantities which was obtained by the method of dilatometry and specific conductivity. Observing the amounts of X, Y, and Z water with the change of tacticity, the similar content of bound water-like may be due to the same primary structure of isotactic and syndiotactic polymer and the difference in free and interfacial water-like content may be due to the difference in secondary and tertiary structure of tactic polymer. Therefore, as the polymer conformation varies, the free and interfacial water-like content will be varied. In order to demonstrate these concepts, Russel et al.'s CPK space-filling molecular models of isotactic and syndiotactic P-HEMA was utilized.

• Journal of the Korean Society of Visualization
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• v.9 no.4
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• pp.74-79
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• 2011

In this study the change of free surface vortex is represented at different times according to height of water and with or without curtain wall installation. The air volume fraction is investigated at each condition of water level and the influence about creation of vortex is analyzed. The height of sump intake is taken as 100mm and the water level is divided into 5 steps. The sump model is the TSJ model and the curtain wall is applied by HI standard of America. The results shows that the free surface vortex can be identified on the isotropic surface at air volume fraction 1%~5% and the vortices make an air column from the free surface to the sump intake and are created and destroyed repeatedly. In the higher water level, less air is absorbed into the intake pipe. After curtain wall installation, the suction rate of the air volume fraction is decreased by 6.7%. The result of the vortex motion according to time, works on a cycle.

• Korean Journal Plant Pathology
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• v.10 no.1
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• pp.34-38
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• 1994

Effect of temperature, relative humidity (RH) and free water period on anthracnose development by Colletotrichum gloeosporioides was examined on red pepper fruits. Mycelial growth of C. gloeosporioides was best at 28$^{\circ}C$, but greatly retarded at 32$^{\circ}C$. Minimum inoculum density required for lesion development varied with isolates, but was mostly above 1.0$\times$105 conidia/ml. Optimum temperature for lesion development on fruits was 31$^{\circ}C$. Percentage of lesion development was decreased as incubation temperature decreased. similar trend of temperature response was observed for acervulus formation on the developed lesions. Acervuli were not developed on the lesion as low as at 19$^{\circ}C$. Lesion development and acervuli formation tended to increase as increasing RH, but were greatly inhibited at the RH lower than 88%. More than 2 hours of free water period after inoculation were required for lesion development. Lesion development was increased as free water period increased. This study indicates that anthracnose development by C. gloeosporioides favors the conditions of high temperature above 28$^{\circ}C$, high humidity above 90% RH, and requires free water period longer than 2 hours.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.40-43
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• 2004

The effects of free surface on wake behind a rotating propeller were investigated experimentally in a circulating water channel with the variation of water depth. Instantaneous velocity fields were measured using two-frame PIV technique at tow different blade phases and ensemble-averaged to investigate the phase-averaged flow structure in the wake region. For an isolated propeller, the flow behind the propeller is influenced by the propeller rotation and the free surface. The phase-averaged mean velocity fields show that the potential wake and the viscous wake are formed by the boundary layers developed on the blade surfaces. The interaction between the tip vortices and the slipstream causes the oscillating trajectory of tip vortices. Tip vortices are generated periodically and the slipstream contracts in the near-wake region. The presence of free surface affects the wake structure largely, when the water depth is less than 0.6D. The free surface modifies the vortex structure, especially the tip and trailing vortices and flow structure in slipstreams of the propeller wake behind X/D = 0.3.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.87-99
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• 1992

A mathematical model, UNSATR which predicts the seepage flow through the body of dike especially under the tidal fluctuation has been developed. This model has been revised from UNSAT2 model which was developed on the basis of the saturated-unsaturated theory by Neuman. UNSATR has been verified and applied to the hydraulic model in order to estimated the seepage quantity, the formation of free water surface etc. The results lead to the following conclusions : 1. Seepage rates between the mathematical model and hydraulic model experiment are very similar to each other both in constant and transient water level conditions. 2. The lapsed time to be steady state of the free water surface becomes late as the tidal levels are relatively low mainly due to the seepage flow from the unsaturated zone of the body of dike. 3. Under the transient state of water levels, owing to the flow from the unsaturated domain, streamlines crossing to the free water surface are found and time lag during a falling tide may allow the free water surface inside the body of dike to stand at a high level than the outside water level. 4. The utility and validity of UNSATR model are convinced when the analyses on seepage problems through the porous embankment of the soil structures on the conditions of the steady and unsteady states are carried out.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.647-652
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• 2004

In aqueous tape casting of alumina slurry systems, the relationships between the suspension compositions and the defects of the dried tapes were discussed. The suspensions compositions were controlled with the ratios of the solids, water and organics binder contents. The effects of the thickness of dried tape and kinds of binder system were also examined. In the defect free region, the apparent viscosity showed nearly same value due to the count balancing effect of solid and organic binder content on the apparent viscosity. When water content was constant, increasing solid led to decrease of organic binder content. The defect free region was narrowed with increasing of casting thickness. When linear type acrylic emulsion binders system (D1000 and D 1035) were used, defect free zone formed the belt type in the triangle of solid, water and organic binder content according to the line of constant water contents. However the defect free region was not found in the cross-link type emulsion binder system (D 1050).

• Advances in Traditional Medicine
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• v.8 no.1
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• pp.32-38
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• 2008

Galgeuntang water extract exhibited a strong free radical scavenging activity and reducing power determination. However, a gradual increase in the free radical scavenging activity and reducing power determination was obtained with increasing concentrations. The highest radical scavenging activity was shown by the water extract from Galgeuntang (116.93 ${\mu}g$/mL) and the water extract from Cinnamonum cassia Presl. (95.01 ${\mu}g$/mL). These results of phenolic and flavonoid contents of the extracts indicated that the strong radical scavenging activity of the Cinnamonum cassia Presl. extract might be in part due to the phenolic compounds. The correlation coefficient between TPC and DPPH ($r^2$ = 0.9312), TFC and DPPH ($r^2$ = 0.9677), showed positive correlation among total phenolic/flavonoid contents and antioxidant activity. These results suggest that Galgeuntang has a potential antioxidant activity.

• Journal of Environmental Health Sciences
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• v.28 no.3
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• pp.9-18
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• 2002

This study was to observe the occurrence of heterotrophic bacteria in terms of free chlorine residuals in two different water distribution systems belong to both K and Y water treatment plant. The data analyzed in this study showed that in distribution systems(DS), the free chlorine residuals were decreased from 0.10 to 0.56 ㎎/1 for K, and 0.51 and 0.78 ㎎/l for Y The decay of free chlorine were clearly higher in both March and August than those in January. The HPC in DS were ranged from 0 to 40 CFU/ml for K,0 to 270 CFU/ml for Y, on R2A medium. In particular, Its level was relatively high at consumers' ground storage tanks, taps and point-of-end area of Y, The predominant genera found in the distribution systems were Acinetobacter, Sphingomonas (branch of Pseudomonas), Microroccus, Bacillus, Staphylococcus. The diversity of heterotrophic bacteria was increased in the end-point area. Most of them were either encapsulated cells or cocci of gram-positve. In conclusion, the point-of-end area in distribution systems showed that the longer flow distance from WTP the greater diversity and higher level of heterotrophic bacteria due to the significant decay of free chlorine residuals.

• Journal of Wetlands Research
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• v.24 no.3
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• pp.196-203
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• 2022

This paper contributed to the understanding of the effect of the blade relative position on performance of micro gravitational vortex turbine in free water surface. In a constant vortex flow, the rotation, voltage and current of micro vortex water turbine were measured according to the position change of the blade installed at the relative vortex height (y/h_v) ranging from 0 to 0.778 below the free water surface. The flow rate ranged from 0.0063 to 0.00662 m³/s. The results of the experiments showed that relative positions of the blade affected the performance of vortex water turbine because the distributions of incoming flow velocity and turbulence intensity were changed. The highest amount of the energy generated by the vortex water turbine occurred in the relative vortex height ranging from 0.111 to 0.222. The output power at the relative vortex height of 0.111 was about 2.4 times larger than the relative vortex height of 0.588 below the free water surface.