• Journal of Korea Water Resources Association
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• v.30 no.2
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• pp.119-129
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• 1997

A three-dimensional numerical model for the simulation of meso-scale local circulation is developed and it is applied to the land and sea breezes which take place around Ulsan. The surface temperature and moisture on the land are determined by means of the surface heat budget with a layer of vegetation considered. The vertical diffusion coefficients of momentum, heat and specific humidity at the surface layer are obtained by the lever-2 model of the turbulence closure proposed by Yamada (1982). This model proved to be effective in simulating the structure of the land and sea breezes around Ulsan.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.137-160
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• 2015

The one-way (two-way) flexural strength of RCC prisms (circular slabs) reinforced with glass fiber textiles is addressed. To this end, alkaline-resistant glass fiber textiles with three surface weights were used in the composite, the matrix concrete was designed with zero/nonzero slump, and the textiles were used with/without an intermediate layer provided by epoxy resin and sand mortar. Prisms were tested under a four-point loading apparatus and circular slabs were placed on simple supports under a central load. Effects of the amount and geometry of reinforcement, matrix workability, and the intermediate layer on the ultimate load and deflection were investigated. Results revealed that, with a specific reinforcement amount, there is an optimum textile tex for each case, depending on the matrix mix design and the presence of intermediate layer. Similar results were obtained in one-way and two-way bending tests.

• Membrane and Water Treatment
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• v.9 no.4
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• pp.245-253
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• 2018

The aim of this study is to investigate the membrane fouling in a thermophilic membrane bioreactor (TMBR) operated different sludge retention times (SRTs). For this purpose, TMBR was operated at four different SRTs (10, 30, 60 and 100 days). Specific cake resistance (${\alpha}$), cake resistance, gel resistance, total resistance, MFI (modified fouling index) and FDR (flux decrease ratio) were calculated for all SRTs. It was observed that flux in the membrane increases with rising SRT although the sludge concentrations in the TMBR increased. The steady state flux was found to be 31.78; 34.70; 39.60 and 43.70 LMH ($Liter/m^2/h$) for the SRTs of 10, 30, 60 and 100 days respectively. The concentrations of extracellular polymeric substance (EPS) and soluble microbial product (SMP) decreased with increasing SRT. The membrane fouling rate was higher at shorter SRT and the highest fouling rate appeared at an SRT of 10 d. Both the sludge cake layer and gel layer had contribution to the fouling resistance, but the gel layer resistance value was dominant in all SRTs.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.130-131
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• 2017

The combined waterproofing technique, which forms the waterproofing layer of two or more substances, is characterized by forming a waterproof layer, which is characterized by the formation of waterproof layers and the thickness of the waterproofing layer is inherently formed. In this study, it is intended to verify the integrity of the material through the manufacture of materials for special purpose waterproofing methods, primarily for the manufacture of composite waterproofing materials and composite waterproofing methods using cement materials and materials.

• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.249-256
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• 2017

We design Ge-Al multilayer assemblies as anode materials for Li-ion batteries, in which Ge and Al thin films are alternately deposited by a radio sputtering method. By sandwiching Ge layers between Al layer, the cyclability, rate capability, and capacity of Ge are improved significantly. The success of the Ge-Al multilayer is attributed to the Al films. To maintain the integrity of electrical contact, Al acts as an elastic layer, which can expand or shrink with the Ge film upon lithiation or delithiation. In addition, the presence of the Al film on the surface can prevent direct contact of Ge and electrolyte, thereby reducing the growth of a SEI layer. Importantly, with high electrical and ionic conductivities, the Al film provides efficient electrical and ionic routes for electrons and Li-ions to access the Ge film, promoting a high specific capacity and high rate capability for Ge.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.127-132
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• 2013

In this paper, we design the physical layer of Guardian modem for wireless public networks. The physical layer is composed of a dual-band RF (Radio Frequency) transceiver and a baseband-processor with quasi-orthogonal codes. The 2.4/5GHz dual-band RF transceiver can overcome the communication difficulty of dense 2.4GHz band for wireless public environment. Also the quasi-orthogonal code can reduce the required ASIC (Application Specific Integrated Circuit) design area. Finally, we analyze the performance of the developed system in viewpoint of data rate, BER (Bit Error Rate), PER (Packet Error Rate). Moreover we verify the performance of the dual-band RF communication.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.606-607
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• 2006

A porous material with a surface layer was fabricated using glass abrasive sludge and expanding agents. The glass abrasive sludges were mixed with expanding agents and compacted into pellets. These pellets were sintered in the range of $700-900^{\circ}C$ for 20min. The sintered porous materials had a surface layer with smaller pores and inner parts with larger pores. The surface layer and pores controlled the absorption ratio and physical properties.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.69-83
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• 1995

A great number of experimental data indicating shock-induced separation(SIS) in internal or external supersonic flows were reviewed to make clear the mechanism of SIS and to present the criterion of turbulent boundary layer separation. The interesting conclusions were obtained for the considerably wide range of flow geometries that the incipient separation is almost independent of the flow geometries, and that it is relatively unaffected by changes in gas specific heat, and boundary layer Reynolds number, Furthermore, the pressure rise necessary to separate boundary layer in external flows was found to be applicable to SIS in overexpanded propulsion nozzles. This is due to the fact that the SIS phenomenon caused by the interaction between shock waves and turbulent boundary layers is processed through a supersonic deceleration. This is, the SIS in almost all of interacting flow fields is governed by the concept of free interaction, and criterion of SIS is only a Function of upstream Mach number.

• Interaction and multiscale mechanics
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• v.3 no.2
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• pp.157-171
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• 2010

In this paper, a theoretical method has been developed for the electric double layer interaction under condition of the variable dielectric permittivity of water. Using Poisson-Boltzmann equation (PBE), for one plate and two plates having similar or dissimilar constant charge or constant potential, we have investigated the electric double layer potential, its gradient and the disjoining pressure as well as the effect of variation of dielectric permittivity on these parameters. It has been assumed that plates are separated by a specific distance and contain a liquid solution in between. It is shown that reduction of the dielectric permittivity near the interfaces results in compression of electric double layers and affects the potential and its gradient which leads to a decreased electrostatic repulsion. In addition, it is shown that variation of dielectric permittivity in the case of higher electrolyte concentration, leads to a greater change in potential distribution between two plates.

• Coupled systems mechanics
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• v.12 no.4
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• pp.337-364
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• 2023

The Rayleigh wave propagation is considered in the structure of the functionally graded piezoelectric material (FGPM) layer over the elastic substrate. The elastic substrate loosely bonds the layer through a corrugated interface, whereas its upper boundary is also corrugated but stress-free. Additionally, the solutions for the FGPM layer and substrate are derived using the fundamental variable separable approach to convert the partial differential equation to an ordinary differential equation. The results with boundary conditions lead to dispersion relations for the electrically open and electrically short cases in the determinant form. The outcomes have been numerically analyzed using a specific model. The findings were presented in the form of graphs, which were created using Mathematica 7. Graphs are plotted for variations in wavenumber and phase velocity. The outcomes may help measure interface defects and design Surface Acoustic Wave (SAW) devices.