• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.22-26
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• 2014

This paper introduces homogeneous liquid crystal (LC) orientations on chemically modulated polystyrene (PS) surfaces using various ion beam (IB) exposure time. Transparent PS was replaced with conventional polyimde material. Especially, PS has higher transparent property than conventional polyimide thin film and it means PS is more suitable material for producing high brightness mobile LCD. As a non-contact process, IB bombardment process induced LC orientation in the direction parallel to the IB process. Through x-ray photoelectron spectroscopy, it was shown that the chemical compositional changes of the IB-irradiated PS surfaces were determined as a function of IB exposure time. Using this analysis, the optimal IB bombardment condition was determined at IB exposure time of up to 15 s. Moreover, thermal stability on IB-irradiated PS surfaces were carried out which showed that a relatively high IB exposure time induced a thermally stable LC alignment property. And it has a highly potential of mobile high transparent mobile LCD such as smart phone display and mobile information device.

• Carbon letters
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• v.26
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• pp.18-24
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• 2018

Pollution of chloride ion-reinforced concrete can trigger active corrosion processes that reduce the useful life of structures. Multifunctional materials used as a counter-electrode by electrochemical techniques have been used to rehabilitate contaminated concrete. Cement-based pastes added to carbonaceous material, fibers or dust, have been used as an anode in the non-destructive Electrochemical Chloride Extraction (ECE) technique. We studied the performance of the addition of Carbon Fiber (CF) in a cement-graphite powder base paste used as an anode in ECE of concretes contaminated with chlorides from the preparation of the mixture. The experimental parameters were: 2.3% of free chlorides, 21 days of ECE application, a Carbon Fiber Volume Fraction (CFVF) of 0.1, 0.3, 0.6, 0.9%, a lithium borate alkaline electrolyte, a current density of $4.0A/m^2$ and a cement/graphite ratio of 1.0 for the paste. The efficiency of the ECE in the traditional technique using metal mesh as an anode was 77.6% and for CFVF of 0.9% it was 90.4%, with a tendency to increase to higher percentages of the CFVF in the conductive cement-graphite paste, keeping the pH stable and achieving a homogeneous ECE in the mass of the concrete contaminated with chlorides.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.941-948
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• 2009

The present study aims at the examination of the effects of 1 mol% NiO addition on the reaction, microstructure development, resultant electrical properties, and especially the bulk trap and interface state levels of $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=0.5, 1.0, and 2.0) systems (ZBS). The samples were prepared by conventional ceramic process, and characterized by density, XRD, SEM, I-V, impedance and modulus spectroscopy (IS & MS) measurement. The sintering and electrical properties of Ni-doped ZBS (ZBSN) systems were controlled by Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$) was decomposed more than $100^{\circ}C$ lowered in ZBS (Sb/Bi=1.0) by Ni doping. The reproduction of pyrochlore was suppressed by the addition of Ni in ZBS. Between two polymorphs of $Zn_7Sb_2O_{12}$ spinel ($\alpha$ and $\beta$), microstructure of ZBSN (Sb/Bi=0.5) composed of a-spinel was more homogeneous than $Sb/Bi{\geq}1.0$ composed of $\beta$-spinel phase. In ZBSN, the varistor characteristics were not improved drastically (non-linear coefficient $\alpha\;=\;6{\sim}11$) and independent on microstructure according to Sb/Bi ratio. Doping of Ni to ZBS seemed to form ${V_0}^{\cdot}$ (0.33 eV) as dominant bulk defect. From IS & MS, especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature.

• Preventive Nutrition and Food Science
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• v.15 no.1
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• pp.57-66
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• 2010

Passion fruit fiber pectin gels represent a new alternative pectin source with potential for food and non-food applications on a commercial scale. Pectic polysaccharides were extracted from passion fruit (Passiflora edulis) fiber using citric acid as a clean catalyst and autoclaved for 20 to 60 min at $121^{\circ}C$. The best condition of pectin yield with the highest molecular weight was obtained with 1.0% of citric acid (250 mg/g dry passion fruit fiber pectin) for 20 min of autoclaving. Spectroscopic analyses by Fourier transform infrared, enzymatic degradation reactions, and ion-exchange chromatography assays showed that passion fruit pectin extracted for 20 min was homogeneous high methoxylated pectin (70%). Gel permeation analysis confirmed that the pectin extract obtained by autoclaving by 20 min showed higher molecular weights than those autoclaved for 40 and 60 min. Passion fruit pectin extracted for 20 min was enzymatically modified with fungal pectinmethylesterase to create restructured gels. Short autoclave treatment (20 min) with citric acid as extractant resulted in a significant increase of gel strength, improving pectin extraction in terms of functionality. The treatment of solubilized material (pectic polysaccharides) in the presence of insoluble material (cellulose and hemicellulose) with pectinmethylesterase and calcium led to the creation of a stiffer passion fruit fiber pectin gel, while syneresis was not observed.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.55-64
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• 2009

Recently, concrete track is replacing ballast track for efficient and economic maintenance of track. It considerably offer less maintenance, a longer service life and reduced life-cycle costs. With the aim of achieving high-quality track construction work, of developing tools for quality assurance in new construction and for later technical inspection of material condition, a quality strategy has to be developed. For these purpose, NDT which is using the seismic wave has carried out in situ studies in the test construction section. The used NDT are SASW test, impact echo test and continuous impact echo test. The test is performed 5,353 times on 49 pre-cast concrete track panels to verify the stiffness structure and grouting efficiency of the track structure. To conclude, because of the non-homogeneous characteristic of concrete material. it is restricted to apply the elastic wave test at some aspect. However it is possible to acquisite a sufficient reliability about structural stiffness and grouting efficiency of concrete track.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.267-274
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• 2010

Unlike the structure which has a homogeneous material property, a composite structure is coupled with materials which have different properties, namely, steel and concrete. At actual modeling, the real behavior cannot be predicted without consideration of those material characteristics. Therefore, by putting the interface element between concrete and steel, a slip of steel and concrete is made predictable. Interface element can be used properly not by an ordinary constitutive relation, but by a non-linear constitutive relation considering actual adhesion and slip. A contact surface between plate-shape steel box and concrete is described by using this interface element. Furthermore, because the general 8 node conforming element is inappropriate for describing a bending buckling behavior of steel box, the EAS(Enhanced Assumed Strain) solid-shell element is used to describe a bending behavior of plate-shape steel box.

• Earthquakes and Structures
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• v.10 no.5
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• pp.1143-1179
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• 2016

Offshore wind turbines are considered as a fundamental part to develop substantial, alternative energy sources. In this highly flexible structures, monopiles are usually used as support foundations. Since the monopiles are large diameter (3.5 to 7 m) deep foundations, they result in extremely stiff short monopiles where the slenderness (length to diameter) may range between 5 and 10. Consequently, their elastic deformation patterns under lateral loading differ from those of small diameter monopiles usually employed for supporting structures in offshore oil and gas industry. For this reason, design recommendations (API and DNV) are not appropriate for designing foundations for offshore wind turbine structures as they have been established on the basis of full-scale load tests on long, slender and flexible piles. Furthermore, as these facilities are very sensitive to rotations and dynamic changes in the soil-pile system, the accurate prediction of monopile head displacement and rotation constitutes a design criterion of paramount importance. In this paper, the Fourier Series Aided Finite Element Method (FSAFEM) is employed for the determination of static impedance functions of monopiles for OWT subjected to horizontal force and/or to an overturning moment, where a non-homogeneous soil profile has been considered. On the basis of an extensive parametric study, and in order to address the problem of head stiffness of short monopiles, approximate analytical formulae are obtained for lateral stiffness $K_L$, rotational stiffness $K_R$ and cross coupling stiffness $K_{LR}$ for both rough and smooth interfaces. Theses expressions which depend only on the values of the monopile slenderness $L/D_p$ rather than the relative soil/monopile rigidity $E_p/E_s$ usually found in the offshore platforms designing codes (DNV code for example) have been incorporated in the expressions of the OWT natural frequency of four wind farm sites. Excellent agreement has been found between the computed and the measured natural frequencies.

• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.117-121
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• 2010

$SnO_2-(1-x)P_2O_5-xB_2O_3$ glass system were prepared by melt-quenching technique in the compositional series containing 50, 55 and 60 mol% of $SnO_2$. Local structure of the glasses was investigated by Raman and FT-IR measurements. A large glass-forming region was found at the phosphate side of the ternary system with homogeneous glasses containing up to 5~25 mol% of $B_2O_3$. According as content of $B_2O_3$ increases, theraml expansion coefficient of glass decreased but transition temperature and softening temperature increased. Because these phenomenon changed local structure of glass. According as content of $B_2O_3$ increases, quantity of bridging oxygen increased. Also, according as content of $SnO_2$ increases, confirmed that quantity of non-bridging oxygen increases.

• Korean Journal of Social Welfare Studies
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• no.37
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• pp.171-197
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• 2008

This study focuses on the following question; self-supporting training program increases participants' income compare to non-participants who have similar characteristics. This question is based on counterfactual assumption. In other words, this study concentrates on what the outcomes would have been if the participants were to be absent. This study adopts a quasi-experimental design. To overcome previous study's methodological weaknesses, especially selection bias, I applied matching procedure based on a propensity-score matching. Matching process was performed by using 'MatchIt' software. The major findings are as follows From Least Squares Regression analysis, I found the poor's income are significantly different according to age, pre-intervention earning, material status, and participation of training. Since the poor have homogeneous education level, education variable was not statistically significant. From the Simulation Quantities of Interest analysis, I also found that treatment group's expected incomes are lower than control's expected incomes. In other words, participation of training has a negative effect on the participants' earnings.

• Advances in aircraft and spacecraft science
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• v.8 no.4
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• pp.345-372
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• 2021

The analysis of nonlinear vibrations, buckling, post-buckling, flutter boundary determination and post-flutter behavior of a homogeneous curved plate assuming cylindrical bending is conducted in this article. Other assumptions include simply-supported boundary conditions, supersonic aerodynamic flow at the top of the plate, constant pressure conditions below the plate, non-viscous flow model (using first- and third-order piston theory), nonlinear structural model with large deformations, and application of mechanical and thermal loads on the curved plate. The analysis is performed with constant environmental indicators (flow density, heat, Reynolds number and Mach number). The material properties (i.e., coefficient of thermal expansion and modulus of elasticity) are temperature-dependent. The equations are derived using the principle of virtual displacement. Furthermore, based on the definitions of virtual work, the potential and kinetic energy of the final relations in the integral form, and the governing nonlinear differential equations are obtained after fractional integration. This problem is solved using two approaches. The frequency analysis and flutter are studied in the first approach by transferring the handle of ordinary differential equations to the state space, calculating the system Jacobin matrix and analyzing the eigenvalue to determine the instability conditions. The second approach discusses the nonlinear frequency analysis and nonlinear flutter using the semi-analytical solution of governing differential equations based on the weighted residual method. The partial differential equations are converted to ordinary differential equations, after which they are solved based on the Runge-Kutta fourth- and fifth-order methods. The comparison between the results of frequency and flutter analysis of curved plate is linearly and nonlinearly performed for the first time. The results show that the plate curvature has a profound impact on the instability boundary of the plate under supersonic aerodynamic loading. The flutter boundary decreases with growing thermal load and increases with growing curvature.