• Journal of the Korean Geosynthetics Society
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• v.2 no.1
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• pp.27-37
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• 2003

The factors affecting shear strength and friction characteristics of the fiber-mixed soil can be classified into engineering properties of soil; particle-size, distribution, and particle shape, physical and mechanical properties of fiber; shape, length, diameter, tensile strength, elastic modulus, friction coefficient, and mixed ratio and external factors; confined stress and compaction condition. In this study, a series of shear friction tests and pull-out tests were performed to evaluate the friction properties of fiber-mixed soil according to soil type, fiber type, fiber mixed ratio and compaction degree. The materials and test conditions used in this study are as follows. Soils: SM and ML; mixing fibers: three types of polypropylene fibers(net type 38mm and 60mm, and line type 60mm); reinforcement: geogrid; mixing ratio: 0.2% and 0.3%; degree of compaction : 85% and 95%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.359-363
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• 2005

In SCRamjet engine, combustion occurs in supersonic flow with airbreathing. SCRamjet is characterized by very short combustion time in combustor, so it is very important to be mixing the air and fuel in short duration. Several methods are suggested for mixing enhancement. Among these, cavity is selected to study for enhancement of mixing. The numerical simulation is performed in the case of freestream Mach number of 2.5 and cavity located in front of fuel jet injection. CFD-Fastran, commercial code with three-dimensional Navier-Stokes equation with the Menter SST turbulence model were used. The results are obtained validate experiment results for same condition. Therefore, the numerical results show the mixing enhancement characteristics with a cavity.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.2
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• pp.92-97
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• 2008

Salt wedge into the river from the sea or fresh water flume (fresh wedge) in the ocean from the sea has density current characteristics. However, when temperature and salinity simultaneously determine the density of wedges, one of salinity and temperature can distributed in the reversed profiles against gravity, even though the density profile is stable. In this case, the double diffusive process is critical in determining mixing rate. The present work studies relative contribution of shear driven mechanical mixing component and double diffusive layering process, when warm salty denser water is introduced into the cold fresh lighter water column. Laboratory experiment releases warm salty denser water into cold fresh lighter water controlling discharge amount to achieve the steady state of density current. When longitudinal density rate becomes 15, the released amount ratio of salt and heat changes sharply and in the releasing point, vigorous mixing occurs with increase of discharged amount due to double diffusion. Double diffusion distabilizes gravitational stability and enhances the mixing rate up to $6{\times}10$ times at the lower density ratio comparing to the higher density ratio.

• Computers and Concrete
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• v.15 no.6
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• pp.935-950
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• 2015

The aim of this study is to provide experimental data regarding the compressive, shear and torsional strength of self-compacting concrete (SCC) used in rectangular beams, and then comparing the results with the equations presented by the CSA A23.3-04 and ACI 318-11. In fact, the gathered information in this field is quite useful for calibrating the computer models of other researchers. The other goal of this study was to investigate the effects of silica fume and superplasticizer dosages on the mechanical properties of SCC. In this research, SCC is made based on 16 different type mixing layout. Also two normal concrete (NC) or vibrating concrete are constructed to compare the results of SCC and NC. This work concentrated on concrete mixes having water/binder ratios of 0.45 and 0.35, which contained constant total binder contents of $400kg/m^3$ and $500kg/m^3$, respectively. The percentages of silica fume that replaced cement were 0% and 10%. The superplasticizer dosages utilized in the mixtures were 0.4%, 0.8%, 1.2% and 1.6% of the weight of cement. Beam dimensions used in this test were $30{\times}30{\times}120cm^3$. The results of this research indicated that shear and torsional strength of SCC beams to be used in computer models can be calculated utilizing the equations presented in CSA A23.3-04 and ACI 318-11.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.1
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• pp.93-102
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• 2002

Steel fiber and polymer are used widely for reinforcement material of RC structures because of its excellences of the durability, serviceability as well as mechanical properties. The purpose of this study is to investigate the shear behavior of polymer cement high strength concrete beams mixed with steel fiber. The compressive strength of concrete was based on the 100$\times$200 mm cylinder specimens. The compressive strength of concrete are 320$kgf/cm^2$, 436 $kgf/cm^2$ and 520 $kgf/cm^2$ in the 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns and fracture modes. Also, load-strain and load-deflection examined. During the test cracks were sketched against the load values according to the growth of crack. result are as follows; (1) The failure modes of the specimens are increased in rigidity and durability with mixing steel fiber and polymer. (2) The load of initial crack was similar a theory of shear-crack strength. (3) The deflection and strain at failure load of Polymer-steel fiber high strength concrete beams were increased, improving the brittleness of the high strength concrete.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.285-288
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• 2008

The Present Study describes the numerical investigations concerning a fuel(Hydrogen), inert gas (Nitrogen) or supersonic air stream issued between each other. The basic flow configuration consists of a plane, double shear/mixing layer flow. For the numerical solution, a fully conservative unsteady $2^{nd}$ order time accurate sub-iteration method and a $2^{nd}$ order Total Variation Diminishing(TVD) scheme are used with the finite volume method(FVM). The results are consist of three categories ; single shear layer consist of fuel and supersonic air stream, inert gas stream issued between supersonic air and fuel stream, fuel gas stream issued between supersonic air and fuel stream. The numerical calculations has been carried out in case of 1,2, and 4mm thickness of center stream. The width of total gas stream is 4cm.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.601-608
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• 2000

Steel fiber and Polymer are used widely for the reinforcement material of RC structures because of its excellence of durability, serviceability as well as mechanical properties. Polymer-Steel fibrous high strength concrete beam's input ratio are 1.0%. The shear span-to-depth ratio are 1.5, 2.8 and 3.6, compressive strength of specimens 320kg/㎠, 436kgf/㎠ and 520kgf/㎠ in 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural crack and of diagonal crack, from which crack patte군 and fracture modes are earned. Also, stress-strain, load-strain and load-deflection are examined during the test cracks(shear crack, flexural crack, and diagonal tension crack), when the load values are sketched according to the growth of crack. Result are as follows; (1) The failure modes of the specimens increase in rigidity and durability in accordance with the increase of mixing steel fiber and polymer. (2) The load of initial crack was the same as the theory of shear-crack strength (3) Polymer-Steel fibrous high strength concrete beams have increased the deflection and strain at failure load, improving the brittleness of the high strength concrete. (4) In this result of study, an additional study need to make a need formular because the study is different from ACI formular and Zsutty formular.

• Korea-Australia Rheology Journal
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• v.17 no.3
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• pp.125-130
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• 2005

Coalescence process of binary immiscible fluid mixtures having bimodal size distributions, prepared by mixing two pre-sheared samples at different shear rates, ${\gamma}_{pre1}\;and\;{\gamma}_{pre2}$, under shear flow at a final shear rate, ${\gamma}_f$, are examined by transient shear stress measurements and microscopic observations in comparison with the results for simply pre-sheared samples having narrow size distributions (unimodal distribution samples). Component fluids are a silicone oil (PDMS) and a hydrocarbon-formaldehyde resin (Genelite) and their viscosities are 14.1 and 21.0 $pa{\cdot}sec$ at room temperature $(ca.\;20^{\circ}C)$, respectively. The weight ratio of PDMS: Genelite was 7:3. Three cases, $({\gamma}_{pre1}=7.2sec^{-1},\;{\gamma}_{pre2}=12.0sec^{-1}\;and\;{\gamma}_f=2.4sec^{-1}),\;({\gamma}_{pre1}=0.8sec^{-1},\;{\gamma}_{pre2}=4.0sec^{-1}\;and\;{\gamma}_f=2.4sec^{-1}),\;and\;({\gamma}_{pre1}=7.2sec^{-1},\;{\gamma}_{pre2}=12.0^sec^{-1}\;and\;{\gamma}_f=7.2sec^{-1})$ the first case, transient shear stress did not show any significant difference but domains larger than the initial state are observed at short times. In the latter cases, there exist undershoot of shear stress, reflecting existence of deformed large domains, which is confirmed by the direct observation. It is concluded that coalescence between large and small domains more frequently occur than coalescence between the domains with similar size in the bimodal distribution samples.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.675-682
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• 2013

To verify the effect of inner- and outer-stage gas jets, a shear coaxial injector was designed to analyze the axial velocity profile and breakup phenomenon with an increase in the measurement distance. When the measurement position was increased to Z/d=100, the axial flow showed a fully developed shape due to the momentum transfer, aerodynamic drag effect, and viscous mixing. An inner gas injection, which induces a higher momentum flux ratio near the nozzle, produces the greater shear force on atomization than an outer gas injection. Inner- and Outer-stage gas injection do not affect the mixing between the inner and outer gas flow below Z/d=5. The experiment results showed that the main effect of liquid jet breakup was governed by the gas jet of an inner stage. As the nozzle exit of the outer-stage was located far from the liquid column, shear force and turbulence breaking up of the liquid jets do not fully affect the liquid column. In the case of an inner-stage gas injection momentum flux ratio within 0.84, with the increase in the outer gas momentum flux ratio, the SMD decreases. However, at an inner-stage gas jet momentum flux ratio over 1.38, the SMD shows the similar distribution.

• Proceedings of the Korean Geotechical Society Conference
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• 1992.10a
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• pp.47-54
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• 1992

When marine clay is hydraulically dredged from seabed and pumped into the pond enclosed by contatinment dykes, marine clay is mixed and flocculated with water and then settled. At this time, the fines will interact with the water to form a Bingham plastic slurry which has non-Newtonian characteristics. The dredged slurry has different physical properties depending on settling locations and settling depths in the pond and has few hundred percent of water content and almost nil of shear strenght. In order to make this condition of the dredged slurry the final formation for public use within a short period, sand spreading method to enhance the support capacity of the dredged slurry is developed. In this paper, the effect of sand mixing into the dredged slurry of this method is analyzed based on reference study, laboratory tests and actual construction results.