• Composites Research
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• v.29 no.6
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• pp.358-362
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• 2016

Mechanical properties of static and dynamic behavior became important since the use of conical composite tubes in large structures such as aerospace, planes, and submarines as well as leisure goods such as bicycle frames, fishing rods, and golf shafts. In the past, the mechanical property prediction model for static behavior was studied using vibration, bending, and buckling. But there is a need to study how fiber orientation error affects mechanical properties of conical composite structure because the model assumes constant fiber orientation angle. The purpose of this study is to derive an equation that can predict the static behavior of conical composite tube for bicycle frames by considering fiber orientation error with respect to various design parameters.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.524-532
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• 2018

In this study, two types of amino acids-based anionic biosurfactants such as potassium cocoyl glutamate (CTK) and sodium cocoyl glutamate (CTN) were synthesized from coconut oils and the structure elucidation of CTK and CTN was carried out by using FT-IR, $^1H-NMR$ and $^{13}C-NMR$ spectrophotometries. Measurements of interfacial properties such as static and dynamic surface tensions and emulsification activity showed that both CTK and CTN were surface-active and effective in lowering the interfacial free energy. In particular, the CTK surfactant was found to be more efficient in reducing the interfacial free energy since the larger number of CTK molecules was preferentially adsorbed at the air-water interface due to the higher hydrophobicity and larger mobility of CTK than those of using CTN, indicating possible uses in cosmetics and household products formulation.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2494-2504
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• 2014

P38 mitogen activated protein (MAP) kinase is an important anti-inflammatory drug target, which can be activated by responding to various stimuli such as stress and immune response. Based on the conformation of the conserved DFG loop (in or out), binding inhibitors are termed as type-I and II. Type-I inhibitors are ATP competitive, whereas type-II inhibitors bind in DFG-out conformation of allosteric pocket. It remains unclear that how these allosteric inhibitors stabilize the DFG-out conformation and interact. Organosilicon compounds provide unusual opportunity to enhance potency and diversity of drug molecules due to their low toxicity. However, very few examples have been reported to utilize this property. In this regard, we performed docking of an inhibitor (BIRB) and its silicon analog (Si-BIRB) in an allosteric binding pocket of p38. Further, molecular dynamics (MD) simulations were performed to study the dynamic behavior of the simulated complexes. The difference in the biological activity and mechanism of action of the simulated inhibitors could be explained based on the molecular mechanics/generalized Born surface area (MM/GBSA) binding free energy per residue decomposition. MM/GBSA showed that biological activities were related with calculated binding free energy of inhibitors. Analyses of the per-residue decomposed energy indicated that van der Waals and non-polar interactions were predominant in the ligand-protein interactions. Further, crucial residues identified for hydrogen bond, salt bridge and hydrophobic interactions were Tyr35, Lys53, Glu71, Leu74, Leu75, Ile84, Met109, Leu167, Asp168 and Phe169. Our results indicate that stronger hydrophobic interaction of Si-BIRB with the binding site residues could be responsible for its greater binding affinity compared with BIRB.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.448-455
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• 2007

In 1992, the first design standard of quake proof bridge was established. However, most bridge structures which were constructed without considering earthquake in former times need performance of quakeproof property. Quakeproof analysis in current bridges, is based on analysis of load base which just has strength over the load of simple structures but is not checked through simple comparison of strength performance of structures so that we would like to check that ADRS method is reasonable or not using ADRS method(Accleration-Displacement Response Spectrum Method), a analysis method based on displacement of object of performance test. As the result of that, the capacity spectrum method can avoid complex dynamic analysis in analysis based on loads and it efficiently applies to design verification with normal checking for quakeproof performance and aimed performance of new structures. However we can not consider effects of high modes and it has problem that does not consider falling of performance in structures by repeated load.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.15-24
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• 2000

The dielectric relaxation of high-dielectric capacitors could be understood as a dynamic property of the capacitor in the time domain, which is regarded as a primarily important charge loss mechanism during the refresh time of DRAMs. Therefore, the equivalent circuit of the dielectric relaxation of the high-dielectric capacitor is essentially required to investigate its effects on DRAM. Nevertheless, There is not any theoretical method which is generally applied to realize the equivalent circuit of the dielectric relaxation. Recently, we have developed a novel procedure for the circuit modeling of the dielectric relaxation of high-dielectric capacitor utilizing the frequency domain. This procedure is a general method based on theoretical approach. We have also verified the feasibility of this procedure through experimental process. Finally, we successfully investigated the effect of dielectric relaxation on DRAM operation with the obtained equivalent circuit through this new method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.970-976
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• 2007

This paper presents a novel polar transmitter architecture with a 2-bit sigma-delta modulator. In the proposed architecture, the 2-bit sigma-delta modulator is introduced to suppress quantization noise of conventional sigma-delta modulator. The power amplifier configuration is also modified in a binary form to accommodate the 2-bit digitized envelope signal. The Ptolemy simulation results of the proposed structure show that the spectral property is greatly improved in full transmit band of EDGE system. The fine quantization scheme of the 2-bit modulator lowers the noise level by 10dB without increasing the over-sampling ratio, which may be obtained if the over-sampling ratio increases twofold. Dynamic range is also enhanced up to 5dB owing to the new form of the power amplifier in the transmitter.

• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.135-141
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• 2009

For more reliable estimation of soil-structure interaction and seismic source and attenuation properties, site amplification function should be considered. This study use the Nakamura's method (1989) for estimating site amplification though various methods for the same purpose have been proposed. This method was originally applied to the surface waves of background noise and therefore there are some limitation for applications to general wave energy. However, recently this method has been extended and applied to the S wave energy successfully. This study applied the method to the coda wave energy which is equivalent to the backscattered S wave energy. We used more than 60 observed ground motions from 5 earthquakes which occurred recently, with magnitude range from 3.6 to 5.1 Each station showed characteristic site amplification property in low-, high- and resonance frequency ranges. In the case of comparing these results to those from S wave energy, lots of information to the site classification work can be gained. Moreover, removal of site amplification can give us more reliable seismic source parameters.

• Membrane and Water Treatment
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• v.8 no.1
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• pp.51-71
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• 2017

Antimicrobial polyethersulfone ultrafiltration membranes containing zerovalent iron ($Fe^0$) and magnetite ($Fe_3O_4$) nanoparticles were synthesized via phase inversion method using polyethersulfone (PES) as membrane material and nano-iron as nanoparticle materials. Zerovalent iron nanoparticles (nZVI) were prepared by the reduction of iron ions with borohydride applying an inert atmosphere by using $N_2$ gases. The magnetite nanoparticles (nMag) were prepared via co-precipitation method by adding a base to an aqueous mixture of $Fe^{3+}$ and $Fe^{2+}$ salts. The synthesized nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering analysis. Moreover, the properties of the synthesized membranes were characterized by scanning electron microscopy energy dispersive X-ray spectroscopy and atomic force microscopy. The PES membranes containing the nZVI or nMag were examined for antimicrobial characteristics. Moreover, amount of iron run away from the PES composite membranes during the dead-end filtration were tested. The results showed that the permeation flux of the composite membranes was higher than the pristine PES membrane. The membranes containing nano-iron showed good antibacterial activity against gram-negative bacteria (Escherichia coli). The composite membranes can be successfully used for the domestic wastewater filtration to reduce membrane biofouling.

• Earthquakes and Structures
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• v.11 no.6
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• pp.1077-1099
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• 2016

One of the main shortcomings in the current passive base isolation system is lack of adaptability. The recent research and development of a novel adaptive seismic isolator based on magnetorheological elastomer (MRE) material has created an opportunity to add adaptability to base isolation systems for civil structures. The new MRE based base isolator is able to significantly alter its shear modulus or lateral stiffness with the applied magnetic field or electric current, which makes it a competitive candidate to develop an adaptive base isolation system. This paper aims at exploring suitable control algorithms for such adaptive base isolation system by developing a close-loop semi-active control system for a building structure equipped with MRE base isolators. The MRE base isolator is simulated by a numerical model derived from experimental characterization based on the Bouc-Wen Model, which is able to describe the force-displacement response of the device accurately. The parameters of Bouc-Wen Model such as the stiffness and the damping coefficients are described as functions of the applied current. The state-space model is built by analyzing the dynamic property of the structure embedded with MRE base isolators. A Lyapunov-based controller is designed to adaptively vary the current applied to MRE base isolator to suppress the quake-induced vibrations. The proposed control method is applied to a widely used benchmark base-isolated structure by numerical simulation. The performance of the adaptive base isolation system was evaluated through comparison with optimal passive base isolation system and a passive base isolation system with optimized base shear. It is concluded that the adaptive base isolation system with proposed Lyapunov-based semi-active control surpasses the performance of other two passive systems in protecting the civil structures under seismic events.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.6
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• pp.896-904
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• 2013

Cattle breeds have a striking effect on milk, including milk composition and technological characteristics. This study aims to compare milk composition, acidification activity, viscosity, milk dispersion system stability and casein molecular weight among three buffalo breeds in China. The technological characteristics of milk produced by three cattle breeds of river buffalo (Murrah), crossbreed 1st generation ($F_1$), crossbreed multiple generation ($F_H$, $H{\geq}3$) buffaloes were investigated. Cattle breeds showed evident effect on milk protein, fat and total solids content, but little effect on most of buffalo casein molecular weight. Milk fat, protein content and the viscosity of buffalo milk from river buffalo were lower than those of $F_1$ and $F_H$, so was the buffer capacity. The viscosity was negatively correlated to temperature and concentration. Results of stability coefficient showed that milk dispersion system had the best dynamic stability characteristics under pH 6.6 and 6 times dilution, while zeta potential of Murrah milk was slightly higher than that of hybrid offspring ($F_1$, $F_H$). SDS-PAGE results showed that buffalo ${\alpha}_s$-casein had a slightly faster mobility than standard ${\alpha}_s$-casein; while buffalo ${\beta}$-casein showed a slightly slower mobility than standard ${\beta}$-casein. There is no clear differences in molecular weight of ${\alpha}_s$-, ${\beta}$-, and ${\kappa}$-casein among Murrah, $F_1$ and $F_H$.