• Proceedings of the Korean Geotechical Society Conference
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• 2000.02a
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• pp.1-11
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• 2000

The use of Compaction Grouting evolved in 1950's to correct structural settlement of buildings. Over the almost 50 years, the technology has been developed and is currently used in wide range of applications. Compaction Grouting, the injection of a very stiff, 'zero-slump' mortar grout under relatively high pressure, displaces and compacts soils. It can effectively repair natural or man-made soil strength deficiencies in variety of soil formations. Major applications of Compaction Grouting include densifying loose soils or fill voids caused by sinkholes, poorly compacted fills, broken utilities, improper dewatering, or soft ground tunneling excavation. Other applications include preventing liquefation, re-leveling settled structures, and using compaction grout bulbs as structural elements of minipiles or underpinning. In this paper, on the basis of the case history constructed in this year, a study has been performed to analyze the basic mechanism of the Compaction Grouting. Also, the effectiveness of the ground improvement and the bearing capacity of the Compaction Pile has been verified by the Cone Penetration Test(CPT) and Load Test. Relatively uniform Compaction grouting column could be maintained by planning the Quality Control in the course of grouting. And, the Quality Control Plan has been conceived using grout pressure, volume of grout and drilling depth.

• Tribology and Lubricants
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• v.1 no.1
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• pp.46-58
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• 1985

The basic mechanism of lubrication between the piston ring and the cylinder wall is developed theoretically under the assumption of a reciprocating and dynamically loaded slider-bearing pair of parabolic form and smooth plane. A numerical computation for the prediction in cyclic variations of film thickness, net lubricant flow and frictional behaviour is attempted, and the influenec on the performance characteristics due to the ring height, ring face radius of curvature and the degree of offset, is also examined. The computational procedures develeped for a single ring system are extended and applied further to the complex problem of a ring pack system. It is well known that the ring pressure which is the total load on a ring, can be obtained from either an experimental measurement or a gas flow analysis. In this work, the latter of a gas low analysis method was used to calculate the pressures. It is remarked that the work done was focused on the role of flow continuity and lubricant starvation within the ring pack lubrication.

• Journal of the Korean Geosynthetics Society
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• v.7 no.4
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• pp.25-36
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• 2008

This paper presents the results of numerical investigation on support mechanism of geogrid-encased stone columns for use in soft ground. A number of cases were analyzed using a axial-and 3D stress-pore pressure coupled model that can effectively model construction sequence and drainage as well as reinforcing effects of geogrid-encased stone columns. The results indicated that the geogrid encasement tends to significantly improve the load carrying of a stone column. Also revealed was that such a confinement effect depends on encasement length and stiffness of geogrid. It is also shown that there exist critical encasement length and stiffness of geogrid for a given condition.

• Geomechanics and Engineering
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• v.23 no.3
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• pp.289-300
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• 2020

With the rapid development of the distributed strain sensing (DSS) technology, the strain becomes an alternative monitoring parameter to analyze slope stability conditions. Previous studies reveal that the horizontal strain measurements can be used to evaluate the deformation pattern and failure mechanism of soil slopes, but they fail to consider various influential factors. Regarding the horizontal strain as a key parameter, this study aims to investigate the stability condition of a locally loaded slope by adopting the variable-controlling method and conducting a strength reduction finite element analysis. The strain distributions and factors of safety in different conditions, such as slope ratio, soil strength parameters and loading locations, are investigated. The results demonstrate that the soil strain distribution is closely related to the slope stability condition. As the slope ratio increases, more tensile strains accumulate in the slope mass under surcharge loading. The cohesion and the friction angle of soil have exponential relationships with the strain parameters. They also display close relationships with the factors of safety. With an increasing distance from the slope edge to the loading position, the transition from slope instability to ultimate bearing capacity failure can be illustrated from the strain perspective.

• Steel and Composite Structures
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• v.34 no.3
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• pp.441-452
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• 2020

Within the French CIFRE research project COMINO, an innovative type of composite beam was developed for buildings that need fire resistance with no additional supports in construction stage. The developed solution is composed of a steel U-shaped beam acting as a formwork in construction stage for a reinforced concrete part that provides the fire resistance. In the exploitation stage, the steel and the reinforced concrete are acting together as a composite beam. This paper presents the investigation made on the load bearing capacity of this new developed steel-concrete composite section. A full-scale test has been carried out at the Laboratory of Structural Engineering of the University of Luxembourg. The paper presents the configuration of the specimen, the fabrication process and the obtained test results. The beam behaved compositely and exhibited high ductility and bending resistance. The shear connection in the tension zone was effective. The beam failed by a separation between the slab and the beam at high deformations, excessive shear forces conducted to a failure of the stirrups in this zone. The test results are then compared with good agreement to analytical methods of design based on EN 1994 and design guidelines are given.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.12
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• pp.1173-1179
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• 2007

In recent years, research to machine large-surface micro-features has become important because of the light guide panel of a large-scale liquid crystal display and the bipolar plate of a high-capacity proton exchange membrane fuel cell. In this study, in order to realize the systematic design technology and performance improvements of an ultra-precision machine for machining the large-surface micro-features, a structural characteristic analysis was performed using its virtual prototype. The prototype consisted of gantry-type frame, hydrostatic feed mechanisms, linear motors, brushless DC servo motor, counterbalance mechanism, and so on. The loop stiffness was estimated from the relative displacement between the tool post and C-axis table, which was caused by a cutting force. Especially, the causes of structural stiffness deterioration were identified through the structural deformation analysis of sub-models.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.68-75
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• 2000

This paper presents the construction of an ultra-precision machining system and machining experiments using the developed system. The system is composed of air bearing system, granite bed, air pad, and linear feeding mechanism. The cutting conditions have great effect on the surface quality in ultra-precision machining. the ultra-precision machining is mainly processed by several ${\mu}{\textrm}{m}$ depth of cut and feed rate. For this, tools with sharper cutting edge and less tool wear are needed. To satisfy these requirement, diamond is generally used as a tool material for ultra-precision machining. In order to evaluate the cutting characteristics of the PCD and MCD tools on the aluminum alloy, the machining experiments performed using the developed system.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.34-39
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• 2002

The surfaces of machine components in sliding contact such as bearing, gears and pistons etc. frequently operate under the condition of mixed lubrication due to high load, high speed and slip. These machine components often undergo the inception of scuffing in practical application. The scuffing failure is a critical problem in modern machine components, especially for the requirement of high efficiency and small size. However, it is difficult to find a universal mechanism to explain all scuffing phenomena because there are so many factors affecting the onset of scuffing. In this study, scuffing experiments are conducted using Acoustic Emission(AE) measurement by an indirect sensing approach to detect scuffing failure. Acoustic Emission(AE) signal has been widely utilized to monitor the interaction at the friction interface. Using AE signals we can get an indication about the state of the friction processes, about the quality of solid and liquid layers eon the contacting surfaces in real time. The FFT(Fast Fourier Transform)analyses of the AE signal are used to understand the interfacial interaction and the relationship between the AE signal and the state of contact is presented

• The Journal of Internal Korean Medicine
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• v.22 no.1
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• pp.73-78
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• 2001

After examining and analysing the medicinal herbs of fifty-three experimental papers, we studied their effects on immediate tumors in specific cancers. We did not study the influence on the life span of general cancerous cells. We looked to see if the combined usage of medicinal herbs and anticancer agents inhibited the tumor cell's growth. The serum test and blood cell count test showed if the medicinal herbs inhibited the side effects of the anticancer agent. The test showed that more than 80 percent of used medicinal herbs, brought anticancer activities. However, anticancer experimental studies using medicinal herbs have draw-backs. First, it is difficult to choose a prescription using the standards of Oriental Medicine because we are testing a mouse not a man. Second, because we only observed the indirect effect on the whole physiological regulation caused by the synergic effects of the complex prescription, we are not able to understand the detailed mechanism of the herbs. Therefore; if the anticancer effect of the herbs is proved by the experiment, we need to research the concrete medical action of medicinal herbs and the immunological analysis of herbal medicines on the body.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.108-111
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• 2000

FeS/FeS$_2$ minerals have been known to be potentially useful reductant to the removal of common organic contaminants in groundwater and soil. This research is aimed at improving our understanding of factors affecting the pathways and rates of reductive transformation of Hexachloroethane by catalytical iron minerals in natural system. Hexachloroethane is reduced by FeS/FeS$_2$ minerals under anaerobic condition to tetrachloroethylene and trichloroethylene with pentachloroethyl radical as the intermediate products. The kinetics of reductive transformations of the Hexachloroethane have been investigated in aqueous solution containing FeS, FeS$_2$. The proposed reduction mechanism for the adsorbed nitrobenzene involves the electron donor-acceptor complex as a precursor to electron transfer. The adsorbed Hexachloroethane undergo a series of electron transfer, proton transfer and dehydration to achieve complete reduction. It can be concluded that the reductive transformation reaction takes place at surface of iron-bearing minerals and is dependent on surface area and pH. Nitrobenzene reduction kinetics is affected by reductant type, surface area, pH, the surface site density, and the surface charge. FeS/FeS$_2$-mediated reductive dechlorination may be an important transformation pathway in natural systems.