• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.47-55
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• 2007

In this study, applicability of electrical conductivity monitoring technique for containment barrier such as soil-bentonite wall was evaluated. Laboratory tests including permeability tests and column tests were performed to understand variations in electrical conductivity at different bentonite contents, hydraulic conductivities, and heavy metal concentrations. The electrical conductivity of compacted soil-bentonite mixtures was found to increase proportionally with bentonite content. Accordingly, the hydraulic conductivity of compacted soil-bentonite mixtures which decreases linearly with increasing bentonite content was found to have an inversely proportional relationship with the electrical conductivity. In column tests, electrical conductivity breakthrough curves and concentration breakthrough curves were simultaneously obtained. These results indicated that electrical conductivity measurement can be an effective means of detecting heavy metal transport at the desired locations within barriers and verifying possible contaminant leakage. Experimental results obtained from this study showed that the electrical conductivity measurement can be a promising tool for monitoring of containment barrier.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.249-256
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• 2013

In accordance with the US Nuclear Regulatory Commission (US NRC), Regulatory Guide 1.20, the reactor vessel internals comprehensive vibration assessment program (RVI CVAP) has been developed for an Advanced Power Reactor 1400 (APR1400). The purpose of the RVI CVAP is to verify the structural integrity of the reactor internals to flow-induced loads prior to commercial operation. The APR1400 RVI CVAP consists of four programs (analysis, measurement, inspection, and assessment). Thoughtful preparation is essential to the measurement program, because data acquisition must be performed only once. The optimized design of a vibration and stress measurement system for the RVI CVAP is essential to verify the integrity of the APR1400 RVI. We successfully designed a vibration and stress measurement system for the APR1400 RVI CVAP based on the design materials, the hydraulic and structural analysis results, and performance tests of transducers in an extreme environment. The measurement system designed in this paper will be utilized for the APR1400 RVI CVAP as part of the first construction project in Korea.

• Journal of Soil and Groundwater Environment
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• v.13 no.2
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• pp.36-43
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• 2008

A method estimating unsaturated hydraulic conductivity using Guelph permeameter was developed and applied to the Ddanseom area of Kimhae in Nakdong River basin where the facilities producing bank-filtrated groundwaters are currently under construction. It is believed that the hydraulic conductivity values obtained from this study are useful in determination of recharges through unsaturated zone or from the river. The distribution of the surface hydraulic conductivity shows that sediments are finer downstream, implying the downstream part of Ddanseom has the higher potential of groundwater production.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.362-371
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• 2013

We conducted hollow cylinder tensile strength tests and Brazilian tests in Seokmo granite to measure tensile strength necessary for estimating the magnitude of the maximum horizontal principal stress in hydraulic fracturing stress measurements. Two different pressurization rates were used in hollow cylinder tests. Tensile strengths were determined to be higher at higher pressurization rate, which suggests that tensile strength should be measurement at the same rate used in actual in situ hydraulic fracturing tests. Considering the effect of pressurization rate and specimen size on tensile strength, the hollow cylinder tests and Brazilian tests yield similar results each other. This demonstrates that Brazilian tests can be utilized to produce representative tensile strengths for interpretation of hydraulic fracturing test results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.5
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• pp.521-528
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• 2009

One of reliability measurements of vehicle is estimated by driving mileage but the reliability of component, such as an hydraulic clutch system, is defined from the number of successful operational cycle. Relationship between these reliability measurement variables(mileage and cycle) should be examined first of all in the reliability estimation of components. Relationship between mileage and cycles is commonly known as linear function. However, the gradient depends on the operational environmental condition. Therefore, estimation of mission profile variable should be done with correlation analysis at the same time. In this paper, we derive mission profile variable of an hydraulic clutch system by field vehicle test and suggest the determination process of durability test parameters of CMC(Clutch Master Cylinder) with mission profile variable.

• Korean Journal of Soil Science and Fertilizer
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• v.16 no.1
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• pp.14-19
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• 1983

Comparison and evaluation of various wellknown methods to determine the saturated hydraulic conductivity of soil were attempted in order to choose a convenient and reliable method applicable, at least, to Bonryang sandy loam (coarse loamy over sandy, mixed, mesic family of Typic Udifluvents). Three experimental methods, inversed auger hole, infiltrometer, and core sample method, were used for this purpose. The results were summarized as follows: 1. The inversed auger hole method was highly correlated with the infiltrometer method while the core sample method was poorly correlated with other two methods. 2. The inversed auger hole method was proved to be convenient and reliable method to measure the hydraulic conductivity of upland coarse textured soils in situ. 3. The hydraulic conductivity determined by the infiltrometer method converged to a constant value after 80 to 100 minutes from starting of measurement. 4. The conductivity determined by the inversed auger hole method approached to a constant value at 5 or 6th run of measurement. 5. The hydraulic conductivity determined by the core sample method was greatly under estimated in comparison with the values obtained by other two methods.

• Tunnel and Underground Space
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• v.26 no.4
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• pp.304-315
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• 2016

In this study, the current horizontal stress characteristics of the Tertiary rock formations in the Pohang Basin are investigated on the basis of the in-situ rock stress measurements at depths from 75 m to 716 m of the 3 test boreholes in the Doumsan area, Pohang. The deep hydraulic fracturing stress measurement results indicated that the horizontal stress components in the test site appear far lower than the average ones by the linear fit for the data set measured from the other domestic sites. But, borehole scanning revealed clearly that lots of small and large scale borehole failures occurred due to the low strength characteristics of the existing rocks. To obtain more accurate and overall information on the horizontal stress direction, the integrated analysis combining the hydraulic fracturing stress measurement and borehole scanning data set were additionally carried out. The analysis results showed that in the upper sedimentary and the lower volcanic rock formation, the dominant orientations of the current maximum horizontal stress components were appeared in the range of $80^{\circ}{\sim}100^{\circ}$ (N80E~N80W) and $120^{\circ}{\sim}140^{\circ}$ (N60W~N40W), respectively. From this study result it was found that the maximum horizontal stress directions have a tendency to rotate in a clockwise direction as the rock formation changes with depth in the test site.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1668-1679
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• 2004

The design of an axial piston pump for electro-hydrostatic transmission systems requires accurate information where and how much the internal friction and flow losses are produced. This study is particularly focused on the friction losses of a bent-axis type hydraulic piston pump, aiming at finding out which design factors influence its torque efficiency most significantly. To this end, the friction coefficients of the pump parts such as piston heads, spherical joints, shaft bearings, and valve plate were experimentally identified by a specially constructed tribometer. Applying the experimental data to the equations of motion for pistons as well as to the theoretical friction models for the pump parts, the friction torques produced by them were computed. The accuracy of the computed results was confirmed by the comparison with the practical input torque of the pump. In this paper, it is shown that the viscous friction forces on the valve plate and input shaft bearing are the primary source of the friction losses of the bent-axis type pump, while the friction forces and moments on the piston are of little significance.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.166-174
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• 2008

Recently, the automotive industry has been developing rapidly. With the progress parts of the automobile components need high quality and the reliability. Among them, braking unit is essential device, and acquire the reliability through the performance test of brake. This study was aimed to design the performance-test-bench to measure the drag torque which has effect on caliper in braking unit. In this progressive technology, it is vital importance to use hydraulic and pneumatic, and to combine test bench with instrumentation engineering technology. This system to construct the design of hydraulic and pneumatic circuit, interface technique between sensors and personal computer, data acquisition and display design, and integrated control are very important technology. Moreover, reliable data are obtained through vacuum system and hydraulic and pneumatic system by using of booster and brake master cylinder which are actually applied to automobile. Then, data signal detector sensors for speed, pressure and torque is attached on this system. Therefore, in this study, we designed a performance-test-bench by and we also made an total control system using personal computer which is more progressive and flexible method than existing PLC control.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.3
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• pp.36-46
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• 1993

The purposes of this study are to develop three-layered Green-Ampt infiltration model considering temporal variation of physical properties of soil and to evaluate the model with field experiment on bare-tilled and soybean-growing soil plots under natural rainfalls. Infiltration tests were conducted on a sandy loam soil. The model has three-layered soil profile including a surface crust, a tilled layer, a subsoil and considers temporal variation of porosity, hydraulic conductivity, capillary pressure head on a tilled layer by natural rainfalls and canopy density variation of crop. Field measurement of porosity, average hydraulic conductivity and average capillary presure head on a tilled layer were conducted by soil sampler and air-entry permeameter at regular intervals-after tillage. It was found that temporal variation of porosity and average hydraulic conductivity might be expressed as a function of cumulative rainfall energy and average capillary pressure head might be expressed as a function of porosity of a tilled soil. The model was calibrated by an optimization technique, Hooke and Jeeves method using hourly surface runoff data. With the calibrated parameters, the model was verified satisfactorily.