• Journal of Ocean Engineering and Technology
• /
• v.18 no.4 s.59
• /
• pp.46-51
• /
• 2004

The surface layer in dredged and reclaimed marine clay is improved by mixing of shallow soils and hardening agents, which is made of cement, containing some other special admixtures. Tests in both laboratory and field settings are performed to investigate the improvement effect and strength properties of cement-stabilized soils. The test results show that the hardening agent sufficiently improves the soil properties of the surface layer, while increasing the load-carrying capacity. The strength of cement-stabilized soils depends, primarily, on water-to-cement ratio and curing temperature. That is, the higher curing temperature and the longer curing time, the higher the strength in cement-stabilized soils. The high ratio of water-ta-cement results in a lower strength.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2004.03b
• /
• pp.659-666
• /
• 2004

Dynamic compaction has evolved as an acceptable method of site improvement by treating poor soils in situ. The method is often an economical alternative for utilizing shallow foundations and preparing subgrades for construction when compared with conventional solutions. In general, the installation purpose of dynamic compaction are to increase bearing capacity and decrease differential settlement within a specified depth of improvement. This method involves the s systematically dropping large weights onto the ground surface to compact the underlying ground. The weights used on dynamic compaction projects have been typically constructed of steel plates, sand or concrete filled steel shells, and reinforced concrete. Typically, weights range from 5-20 ton and base configurations are, circular or octagonal. In this study, the effective depth of improvement is evaluated based on the numerical analysis code, the dynamic analysis of FLAC-3D program, in order to analyze the influence parameters ; ground conditions, maximum applied load and the area of compaction plate.

• Proceedings of the IEEK Conference
• /
• 2000.11b
• /
• pp.41-44
• /
• 2000

Ultra large scale integrated circuit(ULSI) & complementary metal oxide semiconductor(CMOS) circuits require gate electrode materials such as meta] silicides, titanium-silicide for gate oxides. Many previous authors have researched the improvements sub-micron gate oxide quality. However, little has been done on the electrical quality and reliability of ultra thin gates. In this research, we recommend novel shallow trench isolation structure and two step TiSi$_{2}$ formation for sub 0.1${\mu}{\textrm}{m}$ gate oxide.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.5
• /
• pp.1383-1393
• /
• 2014

Recently, with rapid improvement in computer hardware and theoretical development in the field of computational fluid dynamics, high-order accurate schemes also have been applied in the realm of computational hydraulics. In this study, numerical solutions of 1D shallow water equations are presented with TVD Runge-Kutta discontinuous Galerkin (RKDG) finite element method. The transcritical flows such as dam-break flows due to instant dam failure and transcritical flow with bottom elevation change were studied. As a formulation of approximate Riemann solver, the local Lax-Friedrichs (LLF), Roe, HLL flux schemes were employed and MUSCL slope limiter was used to eliminate unnecessary numerical oscillations. The developed model was applied to 1D dam break and transcritical flow. The results were compared to the exact solutions and experimental data.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.2
• /
• pp.335-341
• /
• 1994

Laboratory model test results for bearing capacity of a square shallow foundation supported by a sand layer reinforced with layers of geogrid have been presented. Use of geogrids provides an economical and time efficient method for improving load-settlement, and strength characteristics of weak soils. Especially the geogrid reinforced soil will be necessary in the case of foundations supporting machines, embankments for railroads, and foundations of structures in earthquake-prone areas. Based on the present model test results, the bearing capacity ratio (BCR) with respect to the ultimate bearing capacity (UBC), at levels of limited settlement of the shallow foundation. has been determined. Also, it appears that significant improvement in the UBC of medium sands can be achieved by reinforcing elements which shows promise for future work.

• Tribology and Lubricants
• /
• v.31 no.5
• /
• pp.213-220
• /
• 2015

This study evaluates the effect of grooves on the stem part of a plunger on the lubrication characteristics of a fuel injection pump (FIP) by using hydrodynamic lubrication analysis. The current study uses the two-dimensional Reynolds equation to evaluate the changes in lubrication characteristics with variations in clearance, viscosity, and grooves for a laminar, incompressible, and unsteady state flow. This study investigates the lubrication characteristics by comparing the dimensionless minimum film thickness or the film parameter, which is the ratio of the minimum film thickness to surface roughness. The analysis method for the groove section differs depending on the depth of the groove. For instance, in the case of a shallow groove, the film thickness equation considers the depth of the groove, while in the case of a deep grove, it considers the flow continuity. The lubrication characteristics of the FIP are more sensitive to changes in the groove width than to changes in other design variables. Moreover, the application of a groove is more effective under low viscosity conditions. The smaller the distance from the edge of the stem part to the first groove in the case of shallow grooves, the better are the lubrication characteristics of the FIP. In contrast, in the case of deep grooves, the lubrication characteristics of the FIP improve as the distance increases. The application of shallow grooves is more effective for improving the lubrication characteristics than the application of deep grooves.

• Geotechnical Engineering
• /
• v.14 no.6
• /
• pp.33-44
• /
• 1998

Preliminary study has been conducted to analyse the co-relation between shallow landslides frequently occurring in rainy seasons and the water infiltration into the slope. The change of stress state due to partial saturation of a soil and hence the reduction of its shear strength have been reviewed. The variation of the safety factor of an infinite planar slope in accordance with various water infiltration scenarios has been estimated by limit equilibrium method to explain the mechanism of shallow slope failure. Numerical analysis under the same condition as those of some models dealt with in the previous method has been carried out by using FLAC, a finite difference program, and the results have been compared with the ones obtained by limit equilibrium method. Both results proved to be identical, which implies the ability of the numerical approach to the problems related to the stability analysis of unsaturated slope with the irregular geometry. Further improvement, however, should be made to apply the present analysis procedure to general slopes since it deals with a simple one.

• Geomechanics and Engineering
• /
• v.28 no.6
• /
• pp.547-557
• /
• 2022

Dune sands are poorly graded collapsible soils lacking fines. This experimental study explored the technical feasibility of sustainable invigoration of fine waste materials to improve the geotechnical properties of dune sand. The fine waste considered in this study is fine marble waste. The fine waste powder was mixed with dune sand at different contents (5, 10,15, 20, 25, 50%), where the gradation, void ratio, compaction, and shear strength characteristics were assessed for each fine marble waste -dune sand blend. The geotechnical properties of the dune sand-fine marble waste mix delineated in this study reveal the enhancement in compaction and gradation characteristics of dune sand. According to the results, the binary mixture of dune sand with 20% of fine marble waste gives the highest maximum dry density and results in shear strength improvement. In addition, a numerical study is conducted for the practical application of the binary mix in the field and tested for an isolated shallow foundation. The elemental analysis of the fine marble waste confirms that the material is non-contaminated and can be employed for engineering applications. Furthermore, the numerical study elucidated that the shallow surface replacement of the site with the dune sand mixed with 20% fine marble waste gives optimal performance in terms of stress generation and settlement behavior of an isolated footing. For a sustainable mechanical performance of the fine marble waste mixed sand, an optimum dose of 20% fine marble waste is recommended, and some correlations are proposed. Thus, for improving dune sand's geotechnical characteristics, the addition of fine marble waste to the dune sand is an environment-friendly solution.

• The KSFM Journal of Fluid Machinery
• /
• v.11 no.6
• /
• pp.38-45
• /
• 2008

Development of high efficiency turbine with good performance is one of the main topics in the field of developing wave energy converter. For the development and improvement of the turbine performance, the effect of wave condition on the turbine performance should be considered in detail. Also, water depth is an important factor because incident wave power to the turbine is considerably influenced by the wave particle amplitude of motion and the amplitude is closely related with the water depth. Therefore, in this study, the effect of water depth on the performance of a direct drive turbine(DDT) for wave energy converter is investigated using the DDT which is installed in two types of wave channel. The experimental results show that the DDT captures more wave energy under the condition of relatively shallow water depth. When the water depth is shallow, the horizontal water particle amplitude of motion becomes wider and thus, the water power toward the turbine becomes larger.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.723-725
• /
• 1998

STI CMP process are substituting gradually for LOCOS(Local Oxidation of Silicon) process to be available below sub-0.5um technology and to get planarized. The other hand, STI CMP process(especially STI CMP with RIE etch back process) has some kinds of defect like Nitride residue, Torn Oxide defect, etc. In this paper, we studied how to reduce Torn Oxide defects after STI CMP with RIE etch back process. Although Torn Oxide defects which occur on Oxide on Trench area is not deep and not sever, Torn oxide defects on Moat area is sometimes very deep and makes the yield loss. We did test on pattern wafers witch go through Trench process, APCVD process, and RIE etch back process by using an REC 472 polisher, IC1000/SUV A4 PAD and KOH base slurry to reduce the number of torn defects and to study what is the root causes of torn oxide defects.