• KSBB Journal
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• v.15 no.6
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• pp.605-608
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• 2000

Oligodeoxynucleotides (ODNs) were separated by high-performance membrane chromatography (HPMC), a combined system of chromatography and membrane. The separation mechanism involved anion-exchange, and the stationary phase was cation CIM (Convective Interaction Media) DEAE disk (16${\times}$3 mm). Two types of mobile phase were used, buffer A (20mM Tris-HCl, pH 7.4) and buffer B (buffer A + 1M NaCl). As the amount of NaCl dissolved in buffer linearly increased, the retention time shortened, which enabled a gradient elution mode. Based on the number of theoretical plates and resolution observed, the optimum mobile phase and operating condition (Buffer A/Buffer B=50/50 - 20/80 vol%, gradient time 2 min) were experimentally determined. In this experimental condition, ODNs were separated within 2 min at a mobile phase flow rate of 6 ml/min.

• Membrane and Water Treatment
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• v.13 no.6
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• pp.291-301
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• 2022

In this study, cement/PVDF hollow-fiber hybrid membranes were prepared via a mixed process of diffusion-induced phase separation and hydration. The presence of X-ray diffraction peaks of Ca(OH)₂, an AFt phase, an AFm phase, and C-S-H phase confirmed the hydration reaction. Good hydrophilicity was obtained. The cross-sectional and surface morphologies of the hybrid membranes showed that an asymmetric pore structure was formed. Hydration products comprising parallel plates of Ca(OH)₂, fibrous ettringite AFt, and granulated particles AFm were obtained gradually. For the hybrid membranes cured for different time, the pore-size distribution was similar but the porosity decreased because of blocking of the hydration products. In addition, the water flux decreased with hydration time, and carbon retention was 90% after 5 h of rejection treatment. Almost all the Zn²⁺ ions were adsorbed by the hybrid membrane. The above results proved that the obtained membrane could be alternative as basement membrane for separation application.

• Steel and Composite Structures
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• v.50 no.4
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• pp.429-441
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• 2024

This paper studies the free vibration behavior of trapezoidal shaped coupled double-layered graphene sheets (DLGS) system using first-order shear deformation theory (FSDT) and incorporating nonlocal elasticity theory. Two nanoplates are assumed to be bonded by an interlayer van der walls force and surrounded by an external kelvin-voight viscoelastic medium. The governing equations together with related boundary condition are discretized using a mapping-differential quadrature method (DQM) in the spatial domain. Then the natural frequency of the system is obtained by solving the eigen value matrix equation. The validity of the current study is evaluated by comparing its numerical results with those available in the literature and then a parametric study is thoroughly performed, concentrating on the series effects of angles and aspect ratio of GS, viscoelastic medium, and nonlocal parameter. The model is used to study the vibration of DLGS for two typical deformation modes, the in-phase and out-of-phase vibrations, which are investigated. Numerical results indicate that due to Increasing the damping parameter of the viscoelastic medium has reduced the frequency of both modes and this medium has been able to overdamped the oscillations and by increasing stiffness parameters both in-phase and out-of-phase vibration frequencies increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.174-174
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• 2004

본 논문에서는 4변이 고정된 정사각형 알루미늄 평판의 진동 진폭을 측정하기 위하여, 기존의 위상 이동 ESP떼 스트로보스코프식 조사를 적용한 스트로보스코픽 ESPI 기법을 이용하였다. 일반적으로 시간평균 ESPI를 이용하면 진동하고 있는 대상체의 정성적인 진동 패턴을 측정할 수 있다. 그러나 시간평균 ESPI로는 진동하고 있는 대상체의 두께방향으로의 진폭량을 측정하기는 어렵다. 또한 일반적인 위상이동법을 적용시킬 경우, 대상체가 진동을 하게 됨으로써 정확한 진동 진폭을 측정하기 어렵다.(중략)

• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.110-114
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• 2003

In this study is proposed the advanced elasto-plastic analytical method which can identify complex structural behaviors on the splice part of steel structures such as sliding and plastic contact problem between splice plates and blots. Compliated boundary conditions and various manufacturing defects are considered in various analytical cases. In the design or repair phase the plastic behavior and ultimate strength of splice parts should be very carefully verified to extend the service life of steel structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.9
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• pp.1166-1174
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• 2000

This work presents a two-dimensional quasi-steady state model to study the fluid flow and heat transfer in high-power density welding process of thin AISI-304 stainless steel plates. The enthalpy method and the finite volume method were used for a numerical analysis of the mushy region phase change as well as the heat flow at the weld pool and the heat-affected zone. The results show that the mushy region distributed around the weld pool becomes wider downstream and the surface heat losses by convection and radiation can be significant factors in welding process especially when a welding speed is relatively low.

• Journal of the Korean Graphic Arts Communication Society
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• v.16 no.1
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• pp.1-11
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• 1998

Recently the study of the application of liquid crystal in industrial fields has developed rapidly. It is well known that the encapsulated liquid crystal is advantageous than raw liquid crystal for protection of surface pollution. This paper describes a new class of thermal sensor. It is that the liquid crystal polymer composite(LCPC) films consisting of a continuous LC phase embedded in a three-dimensional network of polymer matrix are formed by photopolymerization-induced phase separation. In this works, it has been demonstrated that consiste of a 8:2 mixture of chiral nematic liquid crystal and HX-620 has the greatest domain and it was best discoloration.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.21.1-21.1
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• 2011

Controlling the morphology of a metal nanocrystal is critical to modern materials chemistry because its physical and chemical properties can be easily and widely tuned by tailoring the size and shape. Combined with ease of synthesis and processing, metal nanocrystals with desired morphologies and thus properties are promising candidates for a wide variety of applications in catalysis, sensing, imaging, electronics, and photonics, and medicine. In this talk, I would like to introduce my recent research results on the shape-controlled synthesis of metal nanocrystals using a simple aqueous method. This water-based system provides a number of merits such as simplicity, convenience, and the potential for large-scale production and enables us to synthesize metal nanocrystals with a rich variety of shapes such as truncated octahedron, cubes, bars, octahedrons, and thin plates. The ability to control the shape of metal nanocrystals provides a great opportunity to systematically investigate their catalytic and optical properties.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.12
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• pp.22-27
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• 2015

Conoscopic holography, which consists of two linear polarizers and two wave plates, and an uniaxial crystal, is incoherent holographic technology for three-dimensional display. In the uniaxial crystal, the wave from object divides into extraordinary and ordinary waves and phase difference between two waves is caused by the different refractive index of two waves. Four intensity patterns, which are made by phase difference, are obtained using LCLV(liquid crystal light valve) and conoscopic holography system. By combining four intensity patterns, the complex hologram without bias and conjugate image. In this paper, we propose the optimized system, which consists of a wave plate and a linear polarizer, and uniaxial crystal. In the proposed system, it doesn't need LCLV. By adjusting the azimuth angle of a linear polarizer and a wave plate, we derive four intensity patterns in recording plane. We demonstrate theoretically that the complex hologram with bias and a conjugate image is obtained using the proposed system.

• Steel and Composite Structures
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• v.33 no.5
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• pp.653-661
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• 2019

In this paper aeroelastic behavior of 3-phase nano-composite beam-plate with double delaminations is investigated. It is tried to study the effect of carbon nano-tubes (CNTs) on critical flutter pressure of reinforced damaged nano-composite structures. In this case, the CNTs are appending to the polymer matrix uniformly. The Eshelby-Mori-Tanaka model is used to obtain the effective material properties of 3-phase nano-composite beam-plate. To investigate the aeroelastic behavior of delaminated beam-plate subjected to supersonic flow, it is assumed that the damaged segments are forced to vibrate together. The boundary conditions and auxiliary conditions at edges of delaminated segments are used to predict critical flutter pressure. The influence of CNTs and different delamination parameters such as delamination length, axial position and its position through thickness are investigated on critical flutter pressure.