• YAKHAK HOEJI
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• v.35 no.6
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• pp.461-465
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• 1991

Silica-based gel filtration chromatography has been used to characterize molecular weight of proteins. However, the molecular weight measured by this method was distorted by protein-silica interactions like hydrophobic and electrostatic forces. Therefore, we characterized protein-silica interaction using two forms of phytochrome (124 kDa) having different hydrophobicity and surface charge. PH and ionic strength affected the retention time of phytochrome suggesting that electrostatic force is the major interaction between protein and silica surface.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.897-919
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• 2015

In this study, the effects of ground shocks due to explosive loads on the dynamic response of historical masonry bridges are investigated by using the multi-point shock response spectrum method. With this purpose, different charge weights and distances from the charge center are considered for the analyses of a masonry bridge and depending on these parameters frequency-varying shock spectra are determined and applied to each support of the two-span masonry bridge. The net blast induced ground motion consists of air-induced and direct-induced ground motions. Acceleration time histories of blast induced ground motions are obtained depending on a deterministic shape function and a stationary process. Shock response spectrums determined from the ground shock time histories are simulated using BlastGM software. The results obtained from uniform and multi-point response spectrum analyses cases show that significant differences take place between the uniform and multi-point blast-induced ground motions.

• Food Science and Biotechnology
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• v.15 no.2
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• pp.163-167
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• 2006

Pectin was enzymatically extracted from industrial lemon pomace by using an endo-polygalacturonase from Aspergillus niger as a processing aid and compared to pectin extraction by hot hydrochloric acid. The yield of pectin was 17.6 and 20.2% with enzymatic and acidic treatments, respectively. The molecular weight distribution did not vary greatly between the samples extracted with enzyme or acid. Large differences in charge density were observed, however, when the samples were analyzed by anionic-exchange chromatography. Pectin extracted by the enzymatic treatment indicated higher charge density than that obtained by hydrochloric acid. The higher charge density could due to the presence of endogenous lemon pectinesterase, which was activated at low pH 4.5 in situ conditions during the process of enzymatic extraction, leading to low methoxylated pectin with a higher charge density.

• Journal of Environmental Science International
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• v.11 no.2
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• pp.93-102
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• 2002

Using a simple continuous optical technique, coupled with measurements of zeta potential, the flocculation characteristics of kaoline suspensions of different content(15, 35 and 55 NTU) by several cationic polyelectrolytes, has been examined. The optimum mixing is obtained under a constant stirring of 200 rpm, differently from a general flocculation test. The charge density of a polyelectrolyte is important in determining the optimum dosage and in the removal of kaoline particles. The optimum dosage is less for the polyelectrolyte of higher charge density and is the same regardless of kaoline content. At the dosage, the removal of kaoline particles is higher for the polyelectrolyte of higher charge density and zeta potential of kaoline particles reaches to near zero. The rate of adsorption and flocculation rate have been found to be affected by charge density and molecular weight of a polyelelctrolyte and the content of kaoline particles.

• Macromolecular Research
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• v.17 no.11
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• pp.894-900
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• 2009

This study examined the charge carrier photogeneration and hole transport properties of blends of poly (9-vinylcarbazole) (PVK), $\pi$-conjugated polymer, with different weight proportions (0~29.4 wt%) of (PEA)$VOPO_4{\cdot}H_2O$ (PEA: phenethylammonium cation), a novel organic-inorganic hybrid material, using IR, UV-Vis, and energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), steady state photocurrent (SSPC) measurement, and atomic force microscopy (AFM). The SSPC measurements showed that the photocurrent of PVK was reduced by approximately three orders of magnitude by the incorporation of a small amount (~12.5 wt%) of (PEA) $VOPO_4{\cdot}H_2O$, suggesting that hole transport occurred through the PVK carbazole groups, whereas a reverse trend was observed at high proportions (>12.5 wt%) of (PEA)$VOPO_4{\cdot}H_2O$, suggesting that transport occurred via (PEA)$VOPO_4{\cdot}H_2O$ molecules. The transition to a trap-controlled hopping mechanism was explained by the difference in ionization potential and electron affinity of the two compounds as well as the formation of charge percolation threshold pathways.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.262-267
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• 2000

This paper describes a weight in motion(WIM) sensor to measure the weight of a vehicle in motion. The main sensing element of the WIM sensor is the PVDF(Polyvinylidene fluoride) film that shows rapid response to an external excitation. Due to the property of rapid response, it is possible to measure the weight of a vehicle in motion with high speed. In the development of the WIM sensor, the dominant target value was the uniformity of the sensor. To increase the uniformity, We employed shrinkable tube made of rubber to enhance the uniformity, and performed the rolling of the brass tube repeatedly. The uniformity of the sensor was examined experimentally. It was comparable to that of a WIM sensor of the MSI which was the benchmark of this development. This paper also describes the mechanical modeling of the sensor and the suitable charge amplifier for the sensor.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.313-317
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• 2005

Synthetic gene carriers such as poly-cationic polymers easily form complexes with plasmid DNA which contains negative charge. Chitosan is a polysaccharide that demonstrates much potential as a gene delivery system. The ability of depolymerized chitosan to condense DNA was determined using electrophoresis. Dynamic laser scattering and scanning electron microscopy were used to examine the size and the morphology of the chitosan/DNA complex. Parameters such as chitosan molecular weight and charge density influenced the complex size and the DNA amount condensed with chitosan. The cell viabilities in the presence of chitosan ranged between 84-108% of the control in all experiments. Gene expression efficacy using chitosan/DNA complex was enhanced in 293 cells relative to that using naked DNA, although it was lower than that using lipofecamine. Transfection efficacy using low molecular weight chitosan (Mw=8,517) was higher than those of the control and the other chitosan (MW=4,078). The low molecular weight chitosan (MW=8,517) with a high charge density (18.32 mV) fulfilled the requirements for a suitable model gene delivery system with respect to the condensing ability of DNA, complex formation, and transfection efficacy.

• Journal of Adhesion and Interface
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• v.21 no.4
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• pp.129-134
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• 2020

Understanding charge trapping at the interface between conjugated semiconductor and polymer dielectric basically gives insight into the development of long-term stable organic field-effect transistors (OFET). Here, the charge transport properties of OFETs using polymer dielectric with various molecular weights (MWs) have been investigated. The conjugated semiconductor, pentacene exhibited morphology and crystallinity, insensitive to MWs of polymethyl methacrylate (PMMA) dielectric. Consequently, transfer curves and field-effect mobilities of as-prepared devices are independent of MWs. Under bias stress in humid environment, however, the drain current decay as well as transfer curve shift are found to increase as the MW of PMMA decreases (MW effect). The charge trapping induced by MW effect is irreversible, that is, the localized charges are difficult to be delocalized. The MW effect is caused by the variation in the density of polymer chain ends in the PMMA: the free volumes at the PMMA chain ends act as charge trap sites, corresponding to drain current decay depending on MWs of PMMA.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2008.10a
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• pp.291-298
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• 2008

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1215-1217
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• 1993