• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.982-989
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• 2005

In this study, a series of laboratory tests based on 'Unit-cell concept' are performed to investigate improvement characteristics of clay ground in sand compaction pile method. Settlement reduction characteristics of composite ground and improvement characteristics of clay part could be qualified. In these procedure, the new strain-compression index($C_{\epsilon}$) of composite ground are adopted to show compressibility of composite ground according to the area replacement ratio, which is similar to the compression index($C_c$) in pure clay ground. Also, using normalization of reduction of water content in composite ground to the initial water content, improvement characteristics of clay part are investigated.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.38 no.5 s.118
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• pp.9-15
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• 2006

Wet compaction test (WCT) is a fiber evaluation method where wet fibers are compressed at one side of a cylinder and water drains out from the other side. The consistency of the fiber furnishes and their pressures are recorded during the test. In the previous study we found that WCT results always gave better coefficients of determination in fiber furnish drainage, and paper properties (density, tensile, tear, and burst strength) than those of WRV (water retention value). Fiber freeness and fiber length correlated well with drainage and tear strength of the furnishes, respectively; however, their correlations were very much improved by combining the WCT results. In this study, we used the WCT test for fractionated fiber furnishes to see whether improvement of the WCT is possible. We found that strength properties such as breaking length and burst index were correlated better with the fractionated long fiber furnishes. Drainage was greatly affected by the presence of short fiber furnishes. We used bleached chemical pulps (SwBKP, HwBKP), recycled pulp (OCC), and mechanical pulp (BCTMP) as fiber furnishes in this study. Fiber fractionation can be performed on-line in these days by using multifractor and WCT can be used as an on-line test in papermachine in the future.

• Journal of Korean Society of Forest Science
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• v.77 no.1
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• pp.65-72
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• 1988

This study was conducted to examine the effects of trampling intensity and frequency on the change of forest bed soil and vegetation by experimental trampling. 23 experimental lanes($0.3{\times}5.0m$) were established at non-trampled Quercus acutissima stand in Suweon, Gyunggi-Do, Korea. And soil compaction and ground vegetation were examined during and after 4 weeks trampling. Increasing in trampling intensity resulted in decreasing increment rate of soil compaction and after 400 passes of trampling, soil hardness showed $11.32kg{\cdot}cm^{-2}$, (23.8mm) which affected root growth badly. At the same trampling intensity, soil compaction was high where trampling was spread over a longer period of time. The difference of soil compaction by trampling frequency was not significant below 200 passes, but 16X(every other day trampling) type resulted in the highest soil compaction over 400 passes of trampling intensity. The relative coverage of vegetation was more severely decreased than the relative density by trampling, 16X type of Trampling frequency resulted in most servere vegetational change and difference among trampling frequencies showed significance in case of 200 passes, contrasting to soil compaction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.7
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• pp.590-596
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• 2008

The ultrasonic velocities of sintered aluminum with varying density were measured in order to deduce the mechanical properties for optimum design of the sintered aluminum. Specimens with different densities were prepared by the plasma activated sintering machine. The density distribution of sintered aluminum becomes partially inhomogeneous because of the friction between the powder and the die during compaction. The elastic moduli are increased as the ultrasonic velocity is increased. Furthermore, Poisoon's ratio is depending on not only the density but also the size and distribution of voids. As the specimen's thickness increases, the center frequency in the frequency spectrum of the reflection wave is shifted to the low frequency. The attenuation coefficient of ultrasonic wave is decreased inversely as the density increased.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.385-386
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• 2006

For attaining optimum fatigue resistance of PM steels, high density levels are necessary. In this work, sintered steels Fe-1.5%Mo-0.6%C and Fe-1.5%Cr-0.2%Mo-0.6%C were produced with density levels of 7.1 to $7.6\;g.cm^{-3}$. Ultrasonic fatigue testing with 20 kHz was performed in push-pull mode up to 10E9 cycles. It was shown that the fatigue endurance strength is strongly improved by higher density levels, but also higher sintering temperatures are beneficial. The Cr-Mo steels proved to be superior to the plain Mo alloyed, due to a more favourable as-sintered matrix microstructure.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.5
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• pp.132-144
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• 2001

Iln order to figure out criteria of bentonite for using as impervious material of waste landfill, laboratory experiments were performed to reveal the geotechnical properties of soil-bentonite mixtures such as compaction test, direct shear test, unconfined compression test, triaxial compression test, consolidation test and permeability test. The results of the study are summarized as follows ; 1. Based on the compaction test, optimum moisture content increased with the increase of bentonite content, but maximum dry density decreased. 2. In unconfined compression test, the maximum strength of the soil-bentonite mixtures appeared at 10% bentonite content. The correlation equation between stress($\sigma$) and strain($\varepsilon$) of the soil-bentonite mixtures is given by ; $\sigma=\frac{a\cdot\varepsilon}{\varepsilon^n+b}$ 3. In shear test of the mixtures. the shear strength showed an increasing trend with increase of bentonite content and the maximum shear strength appeared at 10% bentonite content. 4. In consolidation test, the coefficient of compressibility $(a_v)$$(m_v)$$(C_v)$

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.1
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• pp.79-85
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• 1999

Use of soils with crushed expanded polystyrene(EPS) satisfied both recycling of industrial waste and development of new light-weight fill materials. Objectives of the study were to make the mixed the mixed soils with the crushed EPS and to suggest the most rational mixing ration as a fill material. A series of laboratory tests was performed to investigate the relationship between miximum dry density and optimum moisture contenr and to find the variation of CBR for mixtures with 3 soils and 2 sizes of the crushed EPS. Results of the test showed that the sizes fo the curshed EPS had a little effect on the properties of mixed soils. But gradatiion of soils and mixing ration with the crushed EPS were important factors to characterize compaction properties of the mixed soils.

• Journal of Biomedical Engineering Research
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• v.27 no.3
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• pp.94-100
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• 2006

The effectiveness of the treatment of intracranial aneurysms with endovascular coiling depends on coil packing density, the location of aneurysm, its neck dimensions with respect to the aneurysm dome, and its size with respect to the surrounding tissue. Clinical data also suggests that the aneurysm neck size is the main predictor of aneurysm recanalization. In this study, the force impinging on the aneurysm neck in an idealized aneurysm was calculated by using a three dimensional finite volume method for the non-Newtonian incompressible laminar flow. To quantify the effect of neck size on the impingement force, calculations were performed for aneurysm neck diameters (Da) varying from 10% to 100% of the parent artery diameter (Dp). Also, maximum impingement forces were represented by a function of the ratio of the aneurysm neck to the diameter of the parent vessel. The results show that the hemodynamic forces exerted on the coil mass at the aneurysm neck due to the pulsatile blood flow are larger for wide necked aneurysms.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.557-558
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• 2006

In all conventional sintered PM products, the pores present are of two types, primary and secondary. Primary pores forming during compaction and latter during sintering, due to penetration of formed liquid through the matrix grain boundary. Effect of carbon addition on diffusion of Cu in SH737-2Cu system was investigated. After compaction and transient liquid phase sintering at $1120^{\circ}C$ and $1180^{\circ}C$, samples were characterized for densification, showing rise in sintering density and reduction in swelling on carbon addition. Quantitative microstructural characterization (shape factor and pore size) revealed bimodal distribution for 0% carbon, more rounded pores for 0.9% carbon and higher sintering temperature, and pore coarsening at higher sintering temperature.

• Transactions of Materials Processing
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• v.12 no.5
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• pp.457-464
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• 2003

In the powder compact melting technique, proper precursor fabrication is very important because density distribution after foaming and foamability are determined during precursor fabrication process. The fabrication of the precursor has to be performed very carefully because any residual porosity or other defects will lead to poor results in further processing. In order to evaluate the effect of the compaction parameters on the kinetics of the foaming process, a series of experiments were performed. In this study, aluminium foams with a closed cell structure were fabricated by using both the powder compact method and the induction heating process. A proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of precursor. To establish the foamable precursor fabrication conditions, effects of process parameters such as the titanium hydride content (0.3∼1.5 wt.%), pressing pressure of the foamable precursor (50∼150kN) on the pore morphology were investigated.