• Proceedings of the Korean Quaternary Association Conference
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• 2005.06a
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• pp.7-11
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• 2005

The soil erosion processes have estimated using spatial distribution of 137Cs radionuclide in Granite and Sedimentary Hillslopes in South Korea. The local variability of 137Cs inventory indicates that was related positively to organic matter content, clay content and water content and negatively to hydraulic permeability and slope gradient for bulk samples in different landforms within Granite and Sedimentary rock basins. The vertical variability of 137Cs inventory shows that most of 137Cs concentration and organic matter were accumulated between 0 and 2cms and gradually decrease with soil depth in incremental samples in both basins. The vertical variability of 137Cs inventories shows that 137Csinventories increase as we go to toward downslope in both basins. Finally, the soil loss values indicate that hillslope erosion processes are more intensive in Granite rock basin than those in Sedimentary rock basin.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.73-76
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• 2001

We have simulated the effect of fracture characteristics on reduction of effective permeability of the fractured rocks due to in-situ bacteria growth. A nutrient is injected continuously for growth of in-situ bacteria. We used a power law for fracture length distribution and a fBm for fracture aperture spatial distribution. The results show that in-situ bacteria growth reduces the Permeability hyperbolically, but the porosity of backbone fracture does not change significantly. It shows that reduction of the permeability proceeds at faster speed for smaller value of length exponent(a) and for larger value of Hurst exponent(H). The fracture length distribution has stronger effect on speed of reduction than the aperture spatial distribution. The time needed to reduce permeability is inversely proportional to the hydraulic gradient.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.134-142
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• 1997

The stability of an embankment Impounding a water reservoir is highly depend upon the location of seepage line with the embankment. To evaluate the accurate safety factor of an embankment, it is important to illustrate the seepage phenomenon. Of particular interest is the stability following a rapid change (drawdown) of reservoir level Seepage forces in embankments are easily determined if frictional forces are expressed in relation to hydraulic gradient Ⅰ. If a piezometer is inserted into a body of embankment, the level to which free water rises is a measure of the energy at that point. From model test result, it is possible to calculate safety factors of earth embankment. To assure the validity of this research, tests were conducted with numerical experimental models. And the experiment models were constructed with slopes of 1:1.0, 1:1.5, 1:2.0, 1:2.5. Analysis of experimental results, seepage force was analyzed according to downstream time, internal friction angle and cohesion, respectively.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1999.10a
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• pp.77-80
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• 1999

In this study, to evaluate the performance of leachate collection and removal system, the clogging of geotextile filter was tested and simulated for HELP. As a result of clogging test, the all permeability of geotextiles were decreased rapidly in several day. Also, $Ca^{2+}$ and CODcr concentrations were decreased during test. In model simulation for HELP, Daily discharge volume was shown insignificant change with the filter clogging. however, this result may effect on increasing of the hydraulic gradient in waste layer.r.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.4
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• pp.360-364
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• 2011

Backlash is common in mechanical and hydraulic systems and severely limits overall system performance. In this paper, the development of an adaptive control scheme for systems with unknown backlash is presented. An adaptive backlash inverse based controller is applied to a plant that has an unknown backlash in its input. The harmful effects of backlash are presented. Compensation for backlash by adding a discrete adaptive backlash inverse structure and the gradient-type adaptive algorithm, which provides the estimated backlash parameters, are also presented. The supposed adaptive backlash control algorithms are applied to an aircraft with unknown backlash in the actuator of control surfaces. Simulation results show that the proposed compensation scheme improves the tracking performance of systems with backlash.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.109-116
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• 1988

This study was aimed at determining a regime of flow through rubble mound dike consisted of all sized quarrystons, and deriving a relationship between hydraulic gradient (I) and mean flow velocity (V) through the dike. The analysis was carried out with the data observed after final gap closing of the Haenam Sea dike from May, 6 to May, 14, 1987. The resu]ts are summarized as follows: 1. The regime of flow would be defined as the turbulent flow. 2. As to the relationships, two kinds of formula that are exponential and binomial were obtained. Exponential formula: I=2.099V 1.2888 Binomial formula: I=0.6113V+5.5235V$^2$ 3. Correlation coefficient of the former was 0.824 and that of the latter was 0.821, and the deviations between observed data and estimated were 0.0070 and 0.0064 respectively. 4. Comparing the correlation coefficient, both the equations have the same correlation coefficients, but in case of the deviation the binomial equation was better than the exponential equation. Therefore, the binomial equation is proposed for analyzing the flow through rubble mound dike.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.529-536
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• 2002

The purpose of this paper os to present and discuss some of flow and drain observed in modelling results. Because dredged fill ground of Yul-Chon located in the south coast of Korea is very soft, this ground should be improved after operation of surface stabilization. There are surface stabilization method such as chemical stabilization, desiccation, horizontally vacuum drain, replacement, and geosynthetics. In Yul-Chon, PTM(Progressive Trenching Method) is adopted to provide the necessity condition of surface desiccation. In the case trench in the dredged soft ground is formed by PTM equipment, pore water in the ground is drained through trench. There, drain and desiccation of surface ground increase, and bearing capacity is improved. In this research, when trench in the dredged soft ground is formed by PTM equipment, permeable characteristics and drain efficiency of pore-water are analyzed using SEEP/W software package. Results show variation of total head, pressure head, flux, hydraulic gradient, and flow quantity.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1999-2004
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• 2004

Experiments were conducted to investigate the flow characteristics of water through rectangular PDMS microchannels with a hydraulic diameter ranging from 66.67 to 200 ${\mu}m$. In the experiments, the flow rate and pressure drop across the microchannels were measured at steady states. The experimental results were compared with the predictions from the conventional laminar flow theory. A significant difference between the experimental data and the theoretical predictions was found. Experimental results indicate that the pressure gradient and flow friction in microchannels are higher than those from the conventional laminar flow theory. This may be attributed to the fact that there exists effect of surface roughness of the microchannels. In this study, a surface roughness model is implemented to interpret the experimental data. A good agreement between the experimental data and the numerical predictions with a surface roughness model were found.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.399-406
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• 2000

In this study, using the CRS consolidation tests on reconstituted marine clay, the characteristics of C$\sub$v/, k, e and $\varepsilon$, the anisotropic characteristics of specimen according to the rate of strain were estimated. Also, the validity of the Wissa et al.(1971) consolidation theory on CRS(Constant Rate of Strain) consolidation tests were reviewed. From that results, it was shown that the value of C$\sub$v/, k and u$\sub$b/ was increased as the rate of strain was increased. While the difference of the value( C$\sub$v/, k and u$\sub$b/) between vertically reconstituted specimen and horizontally reconstituted specimen became small as the rate of strain was increased. It is known that k is different due to the hydraulic gradient(i) during the CRS consolidation tests. The subject of this study is to distinguish steady state from transient state in CRS consolidation tests. Consequently, the difference of the value(C$\sub$v/ and k) is higher in case of vertically reconstituted specimen than horizontally reconstituted specimen.

• Geotechnical Engineering
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• v.6 no.2
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• pp.21-34
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• 1990

Laboratory experiments are performed for staple fibre -nonwoven geotextiles which have been widely used in Korea to investigate the filter characteristics of soil/geoteztile system under alternating flow conditions. It is experimentally examined the effects of various design factors such as alternating hydraulic gradient, alternating period, vertical load, gradation and density of foundation soil on the filter structure, vertical permeability and soil retention of soil/geoteztile systems. Based on the experimental results, alternating flow filtration criteria- retention criteria and permeability criteria-for staple fibre-nonwoven geotextiles made in Korea are suggested.