• Economic and Environmental Geology
• /
• v.45 no.6
• /
• pp.623-641
• /
• 2012

The Janggun lead-zinc-silver deposit is hydrothermal-metasomatic deposit. We have sampled wallrock, hydrother-maly-altered rock and lead-zinc-silver ore vein to study the element dispersion during wallrock alteration. The hydrothermal alteration that is remarkably recognized at this deposit consists of rhodochrositization and dolomitization. Wallrock is dolomite and limestone that consisit of calcite, dolomite, quartz, phlogopite and biotite. Rhodochrosite zone occurs near lead-zinc-silver ore vein and include mainly rhodochrosite with amounts of calcite, dolomite, kutnahorite, arsenopyrite, pyrite, chalcopyrite, sphalerite, galena and stannite. Dolomite zone occurs far from lead-zinc-silver ore vein and is composed of mainly dolomite and minor calcite, rhodochrosite, pyrite, sphalerite, chalcopyrite, galena and stannite. The correlation coefficients among major, trace and rare earth elements during wallrock alteration show high positive correlations(dolomite and limestone = $Fe_2O_3(T)$/MnO, Ga/MnO and Rb/MnO), high negative correlations(dolomite = MgO/MnO, CaO/MnO, $CO_2$/MnO, Sr/MnO; limestone = CaO/MnO, Sr/MnO). Remarkable gain elements during wallrock alteration are $Fe_2O_3(T)$, MnO, As, Au, Cd, Cu, Ga, Pb, Rb, Sb, Sc, Sn and Zn. Remarkable loss elements are CaO, $CO_2$, MgO and Sr. Therefore, elements(CaO, $CO_2$, $Fe_2O_3(T)$, MgO, MnO, Ga, Pb, Rb, Sb, Sn, Sr and Zn) represent a potential tools for exploration in hydrothermal-metasomatic lead-zinc-silver deposits.

• Computers and Concrete
• /
• v.6 no.2
• /
• pp.133-153
• /
• 2009

Discrete element modeling (DEM) in concrete technology is concerned with design and use of models that constitute a schematization of reality with operational potentials. This paper discusses the material science principles governing the design of DEM systems and evaluates the consequences for their operational potentials. It surveys the two families in physical discrete element modeling in concrete technology, only touching upon probabilistic DEM concepts as alternatives. Many common DEM systems are based on random sequential addition (RSA) procedures; their operational potentials are limited to low configuration-sensitivity features of material structure, underlying material performance characteristics of low structure-sensitivity. The second family of DEM systems employs concurrent algorithms, involving particle interaction mechanisms. Static and dynamic solutions are realized to solve particle overlap. This second family offers a far more realistic schematization of reality as to particle configuration. The operational potentials of this family involve valid approaches to structure-sensitive mechanical or durability properties. Illustrative 2D examples of fresh cement particle packing and pore formation during maturation are elaborated to demonstrate this. Mainstream fields of present day and expected application of DEM are sketched. Violation of the scientific knowledge of to day underlying these operational potentials will give rise to unreliable solutions.

• Computers and Concrete
• /
• v.7 no.5
• /
• pp.469-482
• /
• 2010

This paper investigates the concrete permeability through a numerical and statistical approach. Concrete is considered as a random heterogeneous composite of three phases: aggregates, interfacial transition zones (ITZ) and matrix. The paper begins with some classical bound and estimate theories applied to concrete permeability and the influence of ITZ on these bound and estimate values is discussed. Numerical samples for permeability analysis are established through random aggregate structure (RAS) scheme, each numerical sample containing randomly distributed aggregates coated with ITZ and dispersed in a homogeneous matrix. The volumetric fraction of aggregates is fixed and the size distribution of aggregates observes Fuller's curve. Then finite element method is used to solve the steady permeation problem on 2D numerical samples and the overall permeability is deduced from flux-pressure relation. The impact of ITZ on overall permeability is analyzed in terms of ITZ width and contrast ratio between ITZ and matrix permeabilities. Hereafter, 3680 samples are generated for 23 sample sizes and 4 contrast ratios, and statistical analysis is performed on the permeability dispersion in terms of sample size and ITZ characteristics. By sample theory, the size of representative volume element (RVE) for permeability is then quantified considering sample realization number and expected error. Concluding remarks are provided for the impact of ITZ on concrete permeability and its statistical characteristics.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.12 no.3
• /
• pp.133-141
• /
• 2007

A finite element model is developed for the extended Boussinesq equations that is capable of simulating the dynamics of long and short waves. Galerkin weighted residual method and the introduction of auxiliary variables for 3rd spatial derivative terms in the governing equations are used for the model development. The Adams-Bashforth-Moulton Predictor Corrector scheme is used as a time integration scheme for the extended Boussinesq finite element model so that the truncation error would not produce any non-physical dispersion or dissipation. This developed model is applied to the problems of solitary wave propagation. Predicted results is compared to available analytical solutions and laboratory measurements. A good agreement is observed.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 1999.04a
• /
• pp.53.1-56
• /
• 1999

The vibration behavior of glass-fabric reinforced plastic(GFRP) composite beams subjected to various transverse impacts has been investigated as a function of fiber orientation and void fraction. Theoretical results of resonant frequency damping coefficient and modal amplitude dispersion using the Euler-beam theory were obtained along with the finite element analysis which were compared with experimental ones Consequently it was shown that the transverse vibration characteristics were largely affected by fiber orientation and void fraction.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 2002.08a
• /
• pp.287-293
• /
• 2002

조석을 수치모의하기 위해 North carolina 대학의 R.A. Luettich와 Notre Dame 대학의 J.J. Westerink가 개발한 ADvanced CIRCulation model for oceanic, coastal and estuarine waters(ADCIRC) 유한요소모형 (Luettich, et al., 1992)은 수심 적분된 2 차원 모형(2DDI)과 3차원 모형(3DL)으로 구성되어 있는데, 그 중 2차원 ADCIRC 유한요소모형은 천수방정식에서 연속방정식과 운동방정식을 합성하여 수면변위에 대해 하나의 식으로 표현한 파동방정식(wave equation)을 지배방정식으로 사용하고 있다. (중략)

• Journal of the Korean Society for Nondestructive Testing
• /
• v.26 no.6
• /
• pp.411-416
• /
• 2006

The critical subject of transverse crack detection in a rail head is treated in this paper. Conventional bulk wave ultrasonic techniques oftenfail because of shelling and other surface imperfections that shield the defects that lie below the shelling. A guided wave inspection technique is introduced here that can send ultrasonic energy along the rail under the shelling with a capability of finding the deleterious transverse crack defects. Dispersion curves are generated via a semi analytical finite element technique along with a hybrid guided wave finite element technique to explore the most suitable modes and frequencies for finding these defects. Sensor design and experimental feasibility experiments are also reported.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.05a
• /
• pp.335-338
• /
• 2003

A finite element-based, integrated process model has been developed and applied to predict the detailed, three-dimensional aspects of the thermo-mechanical behavior occurring in the slab caster considering inclusion removal from molten steel by argon bubble flotation. Gas bubbles are simulated using the dispersion model calculating the volume fraction, and the bubble capture effect is included by a source term in the transport equation for particles. The process model is applied to the investigation of the effect of various process parameters on the inclusion removal in the molten steel.

• Journal of Power System Engineering
• /
• v.15 no.3
• /
• pp.18-24
• /
• 2011

In this study, the reflection of the L(0,2), axially symmetric guided elastic wave from defects in pipes above ground is examined using finite element method. Phase and group velocity dispersion curves for the pipe were presented for the selection of the excitation mode. Some simple signal processing was applied to determine the amplitude of each of the reflected waves and to calculate the reflection coefficient. The results show the reflection coefficient of this mode is very close to a linear function of the circumferential extent of the defect. The motivation for the work was the development of a technique for inspecting chemical plant pipelines, but the study addresses the nature of the reflection function and its general applicability.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1955-1960
• /
• 2003

Static mixers have found a large range of applications, including blending, reaction, dispersion, heat transfer and mass transfer. All static mixers have in common a straight pipe or transfer tube into which individual elements are inserted to cut, fold, twist and re-combine the mixing fluid. The operations virtually ensure uniformity in composition, concentration, viscosity and temperature. The objective of this study is to perform the experimental investigations of mixing characteristics for three mixing element types. The resulting mixing patterns were recorded with a digital camera. OPTIMAS was used to analysis the visualized images. The results clearly indicated that the mixing characteristics was highly influenced by the mixer types or mixing mode.