• Journal of the Korean GEO-environmental Society
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• v.14 no.12
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• pp.5-12
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• 2013

In this study, weathered granite model tests were performed to investigate the variation of volumetric water content and matric suction by the adsorption and desorption processes of artificial rainfall. It has been compared with numerical analysis in unsaturated condition. As the results, the behaviors of volumetric water content and matric suction were distinguished by the seepage distance separated into higher, middle and lower area, and the drainage layer located at the bottom of the experimental device. In the adsorption process, the instantaneously large change of matric suction and water content were related to the increase of permeability in soil. However, in the desorption process, the change of matric suction and water content were gradually small because of the decrease of permeability. The volumetric water content and matric suction showed the difference according to the seepage distance, however the typical characteristic curves were made by the adsorption and desorption processes.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.41-49
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• 2003

Rainfall-induced landslides in a weathered granite soil slope usually happen on shallow slip surfaces above the groundwater table. The pore-water pressure of soil above the groundwater table is usually negative. This negative pore-water pressure (or matric suction) has been found to make a large contribution to the slope stability. Therefore, the variation of in-situ matric suction profiles with time elapse in a soil slope should be understood. In this study, a field measurement program was carried out from June to August, 2001 in order to monitor in-situ matric suctions and volumetric water contents in a weathered granite soil slope. Finite-element transient seepage analyses are also conducted using SEEP/W. The influence of climatic conditions on the variation of in-situ matric suctions could be found to decrease rapidly with the change of depth. It could be found that decrement of matric suction induced by precipitation is affected not only by the amount and duration of rainfalls but also by the initial matric suction just prior to rainstorms. The soil-water characteristic from the field monitoring tends toward the wetting path of SWCC obtained from the laboratory test.

• Journal of the Korean Geotechnical Society
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• v.28 no.2
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• pp.33-42
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• 2012

The purpose of this study is to determine the effect of soil grain size and its distribution on soil-water characteristic. To do this, soil-water characteristic tests were conducted on Saemangeum silt using the axis translation technique. For comparison, the test was also conducted on Jumunjin sand. Using the test results, the soil-water characteristic curves (SWCCs) of Saemangeum silt and Jumunjin sand were predicted by Van Genuchten model. By comparison and analysis between two SWCCs, the silt shows higher values of matric suction, water content, and air entry value than the sand. On the other hand, the sand has higher values of Van Genuchten model parameters of ${\alpha}$, $n$, $m$ than the silt. It indicates that the SWCC is significantly dependent on the structure of soils. In other words, if a soil has relatively high grain size and poor grain size distribution curve, the values of saturated volumetric water content, residual volumetric water content, and air entry value are small, and the variation of volumetric water content is high in accordance with the matric suction variation, and consequently it shows a narrow range of funicular region.

• Journal of the Korean GEO-environmental Society
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• v.11 no.5
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• pp.53-60
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• 2010

The comprehensive tests on unsaturated weathered granite soils are carried out to obtain the soil-water characteristic curve that is the one of the essential requisites to study the unsaturated soil. The weathered granite soils were obtained at Palgong mountain in Daegu. The existing test results have been carried out without overburden pressures and volume changes. In this study, the volumetric pressure plate extractor is improved to consider two factors such as overburden pressure and volume change. The applied overburden pressures were 0, 25, 50, 75, 100kPa and volume changes were measured at each phase. he results of this study are summarized as follows: As the overburden pressure increases, the volumetric water content decreases at the same matric suction and the air entry value increases and gradient of curve at the transition zone and the size of the hysteresis loops decreases. As the overburden pressure increases, the degree of saturation increases at the same matric suction and degree of saturation of the wetting curve is higher than that of dry curve. The SWCC with volume changes are slightly larger than those without volume changes. The general equation proposed by Fredlund & Xing(1994) to fit the experimental result of the SWCC indicates good agreement. The empirical parameters a, n, m as overburden pressure show similar inclination as the existing results.

• Journal of the Korean Society of Radiology
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• v.8 no.5
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• pp.231-240
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• 2014

The purpose of this study were to analyze that the Seoul neuropsychological screening battery (SNSB) for the evaluating cognitive assessment of the Parkinson's disease patients with mild cognitive impairment (PD-MCI) and the changes of the cerebral ventricle volume in the brain magnetic resonance imaging (MRI), and we has been bring forward the guideline to determine the diagnostic criteria for the PD-MCI. To achieve this, we was diagnosed with Parkinson's disease patients (PD-MCI group: 34 patients; Parkinson's disease with normal cognition, PD-NC group: 34 patients) to perform the SNSB test for the attention, language, memory, visuospatial, and frontal/executive functions and the brain MRI. Additionally, to compared the change of the cerebral ventricle volume, we performed the brain MRI for the 32 normal control (NC) group. The volumetric analysis for a specific cerebral ventricle performed by using Freesurfer Ver. 5.1 (Massachusetts general Hospital, Boston MA, USA). As a results, compared to the PD-NC group, the PD-MCI group were statistically significant reduction in the ability to perform the memory and the visuospatial function (p<0.05). The volumetric changes for a specific cerebral ventricle were statistically significant variation in the left and right lateral ventricle, left and right inferior lateral ventricle, and 3rd ventricle. Although, in order to compared the objectification, the normalized percentage applied to the volumetric changes showed to extend the PD-MCI group than the PD-NC group. Specially, the left and right ventricle extension for the PD-MCI patients conspicuously had showed a quantitative linear relationship between the memory and the visuospatial function for the SNSB (r>0.5, p<0.05). Therefore, we were able to judge the diagnostic criteria of the PD-MCI through that can observe the volumetric variation of the specific cerebral ventricle by using Freesurfer in brain MRI, and to analyze the correlation between the SNSB.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.523-535
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• 2008

A simulated rainfall system was built, and the unsaturated characteristics were examined by execution of simulated rainfall system test and soil water characteristic curve cell test(SWCC Cell Test) under the various rainfall and slope conditions. With the results, the applicability of infiltration behavior under rainfall and soil water characteristic curve models to the unsaturated weathered granite soil was examined. At the results of comparison the volumetric water content and matric suction measured in the wetting process(under rainfall) with those in the drying process(leaving as it was) of the simulated rainfall system, the volumetric water content showed a difference of $2{\sim}5%$ and matric suction of about $3{\sim}10\;kPa$, indicating the occurrence of hysteresis. In addition, the difference was relatively larger in matric suction than in the volumetric water content, and this tells that the hysteresis behavior is larger in matric suction. When the soil water characteristic curve derived from measurements in simulated rainfall system test were compared with those from the soil water characteristic curve cell test, both methods produced soil water characteristic curves close each other in the wetting process and the drying process, but in both, there was a difference between results obtained from in the wetting process and those from in the drying process. Thus, when soil water characteristic curves are rationally applied to the design and stability analysis considering of the properties of unsaturated soil, it is considered desirable to apply the soil water characteristic curve of the wetting process to the wetting process, and that of the drying process to the drying process.

• Journal of the Korean Geotechnical Society
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• v.39 no.5
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• pp.13-26
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• 2023

This study examined the soil-water characteristic curve (SWCC), considering the volume change, using wetting curves on the field monitoring data of a wireless sensor network. Special attention was given to evaluating the landslide vulnerability by deriving a matric suction suitable for the actual site during the wetting process. Laboratory drying SWCC and shrinkage laboratory tests were used to perform the combined analysis of landslide and debris flow. The results showed that the safety factor of the wetting curve, considering the volume change of soil, was lower than that of the drying curve. As a result of numerical analyses of the debris flow simulation, more debris flow occurred in the wetting curve than in the drying curve. It was also found that the landslide analysis with the drying curve tends to overestimate the actual safety factor with the in situ wetting curve. Finally, it is confirmed that calculating the matric suction through SWCC considering the volume change is more appropriate and reasonable for the field landslide analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.657-666
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• 2017

In this study, factor analysis was performed to reduce the friction in the elevation motion of a stand for a 50-inchtelevision. Pipe type cross-section control was used for accurate positioning control of the piston rod. The pipe type was also compared with a labyrinth-type crosssection for the orifice. The frictional force was then reduced using gas seal lip technology. Specifications were chosen, and a volume compensation experiment was carried out using an apparatus for compensating the volume of the cylinder, which is compressed by the volume of the piston rod. Based on CAE and experimental considerations, the labyrinth-type orifice is preferred for reducing friction. For the gas seal lip technology, outer and inner diameters of ${\Phi}20$ and ${\Phi}8$ for the hollow rod were more appropriate when assuming the weight of a 50-inch television to be 30kgf. The third is that the result of total consideration in stability problem and performance of volume compensation for specification decision and volume compensation experiment is determined the final speculation of hollow rod ?8x?4 and riveting system. The last is that the labyrinth orifice is not founded that of the ${\O}0.4{\sim}0.6$ orifice both tests on 300 mm intervals.

• Journal of the Korean Institute of Landscape Architecture
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• v.37 no.3
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• pp.54-60
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• 2009

The purpose of this study is to analyze the impacts of three-dimensional land cover on changing urban air temperatures and to explore some strategies of urban landscaping towards mitigation of heat build-up. This study located study spaces within a diameter of 300m around 24 Automatic Weather Stations(AWS) in Seoul, and collected data of diverse variables which could affect summer energy budgets and air temperatures. The study also selected reflecting study objectives 6 smaller-scale spaces with a diameter of 30m in Chuncheon, and measured summer air temperatures and three-dimensional land cover to compare their relationships with results from Seoul's AWS. Linear regression models derived from data of Seoul's AWS revealed that vegetation volume, greenspace area, building volume, building area, population density, and pavement area contributed to a statistically significant change in summer air temperatures. Of these variables, vegetation and building volume indicated the highest accountability for total variability of changes in the air temperatures. Multiple regression models derived from combinations of the significant variables also showed that both vegetation and building volume generated a model with the best fitness. Based on this multiple regression model, a 10% increase of vegetation volume decreased the air temperatures by approximately 0.14%, while a 10% increase of building volume raised them by 0.26%. Relationships between Chuncheon's summer air temperatures and land cover distribution for the smaller-scale spaces also disclosed that the air temperatures were negatively correlated to vegetation volume and greenspace area, while they were positively correlated to hardscape area. Similarly to the case of Seoul's AWS, the air temperatures for the smaller-scale spaces decreased by 0.32% ($0.08^{\circ}C$) as vegetation volume increased by 10%, based on the most appropriate linear model. Thus, urban landscaping for the reduction of summer air temperatures requires strategies to improve vegetation volume and simultaneously to decrease building volume. For Seoul's AWS, the impact of building volume on changing the air temperatures was about 2 times greater than that of vegetation volume. Wall and rooftop greening for shading and evapotranspiration is suggested to control atmospheric heating by three-dimensional building surfaces, enlarging vegetation volume through multilayered plantings on soil surfaces.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.24-24
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• 2003

최근 자동차 산업이 발달함에 따라 철강업계와 자동차 회사에서는 전에 많이 사용하던 내연 무도금강판 대신 부식에 저항력이 강한 도금강판을 사용한 이후로 냉연강판의 가공 시에 야기되지 않았던 많은 문제점들이 나타났다 자동차용 강판의 경우 판재의 체적에 비하여 금형과 판재의 접촉면적이 큰 프레스 공정에서는 판재의 표면에 작용하는 마찰력의 크기가 판재의 스탬핑 성형성에 큰 영향을 미친다. 이는 마찰특성이 비록 재료고유의 성형한계에서는 영향을 미치지 못하나 스탬핑 공정에 있어서 금형과의 접촉면에서 마찰력의 크기가 패널의 변형률분포를 변화시켜 스탬핑 성형성에 큰 영향을 주는 것이다. 따라서 본 연구는 자동차용 도금강판의 표면 거칠기에 따른 판재의 표면 마찰 특성 변화를 알아보았다. 소재의 기계적 특성 측정은 UTM을 사용하였고, 도금층은 XRD, SEM을 이용하여 상분석 하였으며, 표면 거칠기는 AFM(Atomic Force Microscope), SJ-400(Mitutoyo)을 사용하여 표면 거칠기를 측정하였다. 또 드로잉 하중을 비드부에서의 굽힘-굽힘 풀림 소성변형에 의한 변형력 성분과 마찰력 성분으로 분리하여 강판의 쿠롬 마찰계수를 DBS(Draw bead simulation)로 측정하였다.