• Honam Mathematical Journal
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• v.45 no.2
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• pp.359-379
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• 2023

In the present paper, we study translation hypersurfaces in E⁴. In this context, firstly we obtain first, second and third Laplace-Beltrami (LB^I, LB^II and LB^III) operators of the translation hypersurfaces in E⁴. By solving second and third order nonlinear ordinary differential equations, we prove theorems that contain LB^I-minimal, LB^II-minimal and LB^III-minimal translation hypersurfaces in E⁴.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.819-821
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• 1998

Arachidic acid(AA) was used as LB films and its dielectric and conduction characteristics were investigated. The relative dielectric constant(${\varepsilon}_{LB}$) of AA LB films obtained from capacitance-frequency properties was about $3.5{\sim}4.1$. And the conductivity(${\sigma}_{LB}$) of AA LB films obtained from Current-Voltage characteristics was about $2.6{\times}10^{-15}[S/cm]$. Also, the conduction mechanism of current in LB films was dependant on Schottky type and the barrier height obtained from Schottky plot was about 1.4[eV].

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.211-214
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• 2003

The tribological properties of amphiphilic monolayers and composite multilayer on silicon surface were investigated using micro-tribometer and Auger Electron Spectroscopy. Langmuir-Blodgett (LB) monolayers from behenic acid. 2.4-heneicosanedione(HD) and its copper complex((HD)$_2$Cu) were fabricated on silicon surface and the composite multilayer of 5-bilayer of (HD)$_2$Cu was fabricated on the surface of octadecyltrichlorsilane (OTS) self-assembled monolayer(SAM). We observed that LB monolayers and the composite multilayer exhibited a steady and excellent friction response when compared with the OTS SAM. These LB mono and multilayer also showed much higher wear-resistance than the OTS SAM.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.511-514
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• 1987

Langmuir-Blodgett (LB) films of TCNQ(tetracyanoquinodimethane) with alkyl radical($C_{12}TCNQ$) were prepared on the sample of Al/LB film/Al type where Al are electrode, and polarization in LB film and dipolar moment of molecules in the films were measured by TSC. $Al_2O_3$ layer was yielded on the electrode by natural oxidation in air. According to the cooperation of $Al_2O_3$ dielectric layer and the polarization of $C_{12}TCNQ$-LB film, the macroscopic electrical field was yielded in LB film and $Al_2O_3$ layer. The field strength in $C_{12}TCNQ$-LB films was evaluated at about $1{\times}10^6{\sim}5{\times}10^6\;V/cm$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.320-323
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• 2000

We attempted to fabricate polyurethane derivatives (PU-CN, PU-DCM) LB films by using LB method. Also, we investigated the monolayer behavior at the air-water interface by surface pressure-area ($\pi$-A) isotherms. And, the surface morphologies and the physicochemical properties of LB films were investigated by atomic force microscopy (AFM) and UV-vis spectroscopy, respectively. Also, the electrical properties of polyurethane derivatives LB films were investigated by using the conductivity and the dielectric constant. In the AFM images, we conclude that surface morphology of PU-DCM LB films is smooth and homogeneous and has optimal hydrophobicity and good stability, whereas PU-CN LB films give rougher surfaces with more excess material. In the I-V characteristics, the conductivity is different as to the polyurethane derivatives, it is considered that this phenomena could be described by the difference of lumophore pendant which was adhered at PU main chain.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.657-665
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• 2011

LB-DECK, a precast concrete panel type, is a permanent concrete deck form used as a formwork for cast-in-place concrete pouring at bridge construction site. LB-DECK consists of 60 mm thick concrete slab and 125 mm height Lattice-girders partly embedded in the concrete slab. These decks have been applied to the bridges, which girder spacings are short enough to resist longitudinal cracking caused by construction loads. This paper presents experimental research work conducted to evaluate the cracking load of LB-DECKs designed for long span bridge decks. Twenty four non-composite beams and four composite beams are fabricated considering three design variables of thickness of concrete slab, height of lattice-girder, and diameter of top-bar. Static loads controlled by displacements are applied to test beams to obtain cracking and ultimate loads. Vertical displacements at the center of beams, strains of top-bar, crack propagation in concrete slab, and final failure modes are carefully monitored. The obtained cracking loads are compared to the analytical results obtained by elastic analyses. Long-term analyses using age-adjusted effective modulus method (AEMM) are also conducted to investigate the effects of concrete shrinkage on the cracking loads. Based on the test results, the tensile strength and the design details of LB-DECKs are discussed to prevent longitudinal cracking of long span bridge decks.

• Journal of the Korean Chemical Society
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• v.37 no.3
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• pp.302-308
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• 1993

Monolayers of calcium palmitate were deposited on a piezoelectric quartz crystal plate by the Langmuir-Blodgett(LB) technique, and it was found from frequency changes of the quartz crystal deposited LB films. The usual carbonyl absorbance at 1704 cm$^{-1}C$ was replaced by the split band in the 1540~1590 cm$^{-1}C$. The two absorptions at 1580 cm$^{-1}C$ and 1540 cm$^{-1}C$ were assigned to the antisymmetric stretching vibration of the calcium carboxylate group and the hydrated species due to the lowering carbonyl stretching frequency by hydrogen bonding$^1$ respectively. Besides, it was demonstrated by X-ray diffraction analysis. The swelling behaviour of LB films in water phase at 23$^{\circ}C$ was observed from the frequency change of the LB films deposited quartz crystal with time. Calcium palmitate LB films has been found to swell substantially in water without flaking, whereas hexadecanol LB films hardly swelled in water. Amount of swelling of calcium palmitate LB films was equivalent to 47 wt.${\%}$ of the dry LB films, which means that ca. 7 water molecules were incorporated per calcium palmitate amphiphile. Chemical structure of calcium palmitate LB film was estimated as [CH$_3$(CH$_2$)$_{14}$COO]$_2$Ca${\cdot}$XH$_2$O, and the hydration number was 1.

• Korean Journal of Food Science and Technology
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• v.39 no.6
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• pp.681-687
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• 2007

This study was designed to examine the suitable characteristics of potential probiotic bacteria. Possible probiotic bacteria, including Lactobacillus acidophilus DDS-1, Lb. acidophilus B-3208, Bifidobacterium bifidum KCTC 3357, Lb. plantarum, Leuconostoc mesenteroides ssp. mesenteroides ATCC 8293, and Lactococcus lactis ssp. lactis ATCC 7962 were selected. We then measured their acid and bile tolerances, adhesion properties in the gastrointestinal tract, antimicrobial activity against pathogenic bacteria, and immunomodulation activity. The acid tolerances of Lb. acidophilus DDS-1, Lb. acidophilus B-3208, Lb. plantarum, and Leu. mesenteroides ssp. mesenteroides ATCC 8293, in PBS (pH 2.5) for 2 hr, were high enough that 50% of the inocula survived. The bile tolerances of all bacteria, except Lc. lactis ssp. lactis ATCC 7962, were also observed at a 3% oxgall concentration in MRS broth. The results of the adhesion property assay showed that the total binding affinities of Lb. acidophilus DDS-1, Lb. acidophilus B-3208, and B. bifidum were about three times higher than those of the other bacteria. In testing their antimicrobial activities against pathogens, Lb. acidophilus B-3208, B. bifidum KCTC 3357, and Lb. plantarum inhibited the growth of pathogenic bacteria. For their immunomodulation activity, the cell wall fractions from Lb. acidophilus DDS-1 and Lb. acidophilus B-3208 showed the highest bone marrow cell proliferation activities. However, the cell wall fractions of Lb. acidophilus DDS-1 and B. bifidum, and the cytosol fraction of Lc. lactis ssp. lactis ATCC 7962 showed higher macrophage stimulation activities than those of the other bacteria. Since Lb. acidophilus DDS-1 and Lb. acidophilus B-3208 satisfy the requirements for probiotics, they can be considered suitable probiotic bacteria.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.683-693
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• 2013

In this study, the mixing characteristics in lid-driven cavity flows were studied numerically by using a hybrid lattice Boltzmann method (HLBM). First, we compared the numerical results from single-relaxation-time (LB-SRT) and multi-relaxation-time (LB-MRT) models to examine their reliability. In most of the cavity flow, the results from both the LB-SRT and the LB-MRT models were in good agreement with those using a Navier-Stokes solver for Re=100-5000. However, the LB-MRT model was superior to the LB-SRT model for the simulation of higher Reynolds number flows having a geometrical singularity with much lesser spatial oscillations. For this reason, the LB-MRT model was selected to study the mass transport in lid-driven cavity flows, and it was demonstrated that mass transport in the fluid was activated by a recirculation zone in the cavity, which is connected from the top to the bottom surfaces through two boundary layers. Various mixing characteristics such as the concentration profiles, mean Sherwood (Sh) numbers, and velocity were computed. Finally, the detailed transport mechanism and solutions for the concentration profile in the cavity were presented.

• Polymer(Korea)
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• v.24 no.1
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• pp.90-96
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• 2000

Organic electroluminescent (EL) device was fabricated with Alq$_3$ as an emitting material and PDPMA ultra thin film prepared by Langmuir-Boldgett technique as a polymer hole transport layer. A stable condensed PDPMA monolayer was obtained using arachidic acid as a surface active material. The thickness and absorbance of PDPMA LB film increased line-arly with the layer numbers. The organic multilayered device consisted of ITO/PDPMA LB film (19 layers)/Alq$_3$/Al emitted green light with brightness of 2500 cd/m$^2$ at a DC 14 V Especially, the drive voltage of EL device having PDPMA LB film of 15 layers exhibited the value as low as 4 V. The effects of thickness control and molecular orientation in the PDPMA LB film on EL performance were discussed.