• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.109-112
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• 2007

A new concept of the microlens array is fabricated using a birefringent layer on the concave microlens array. The stacked layers of liquid crystalline polymer (LCP) and the UV epoxy focus an incident light due to the surface relief structure. The ferroelectric liquid crystal layer was added to control the focusing intensity with a fast switching time.

• Smart Structures and Systems
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• v.10 no.6
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• pp.573-591
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• 2012

In this study, a procedure to design an optimal LCVA that maximizes the equivalent damping ratio added to the primary structure subjected to along-wind excitation is proposed. That design procedure does not only consider the natural frequency and damping ratio of the LCVA, but also the proportion of the U-shaped liquid, which is closely related to the participation ratio of the liquid mass in inertial force. In addition, constraints to ensure the U-shape of the liquid are considered in the design process, so that suboptimal solutions that violate the optimal tuning law partly are adopted as a candidate of the optimal LCVA. The proposed design procedure of the LCVA is applied to the control of the 76-story benchmark building, and the optimal proportions of the liquid shape under various design conditions are compared.

• Structural Engineering and Mechanics
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• v.70 no.5
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• pp.563-570
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• 2019

To analyze the seismic reliability of concrete rectangular liquid storage structures (CRLSSs), assuming that the wall thickness and internal liquid depth of CRLSSs are random variables, calculation models of CRLSSs are established by using the Monte Carlo finite element method (FEM). The principal stresses of the over-ground and buried CRLSSs are calculated under three rare fortification intensities, and the failure probabilities of CRLSSs are obtained. The results show that the seismic reliability increases with the increase of wall thickness, whereas it decreases with the increase of liquid depth. Between the two random factors, the seismic reliability of CRLSSs is more sensitive to the change in wall thickness. Compared with the over-ground CRLSS, the buried CRLSS has better reliability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.54-61
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• 2005

Characteristics of sprays injected by gas/liquid coaxial atomizers operated at atmospheric pressure are studied using shadowgraph, mechanical patternator and PDPA. The gas-to- liquid momentum flux ratio(M) and the liquid Reynolds number(Re) are selected as key parameters in characteristics of gas/liquid coaxial sprays from the dimensional analysis. The properties of shear coaxial sprays are compared with those of swirl coaxial sprays through the macroscopic and microscopic analysis. Macroscopic similarities between shear and swirl coaxial sprays are revealed under flow conditions of high momentum flux ratio. Also, empirical correlations between the mean drop diameters(D32) and operating conditions of coaxial sprays are proposed in this paper.

• Earthquakes and Structures
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• v.17 no.2
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• pp.175-189
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• 2019

The aim of the study is to show the results of complex shaking table experimental investigation focused on the response of two models of cylindrical steel tanks under mining tremors and moderate earthquakes, including the aspects of diagnosis of structural damage. Firstly, the impact and the sweep-sine tests have been carried out, so as to determine the dynamic properties of models filled with different levels of liquid. Then, the models have been subjected to seismic and paraseismic excitations. Finally, one fully filled structure has been tested after introducing two different types of damages, so as to verify the method of damage diagnosis. The results of the impact and the sweep-sine tests show that filling the models with liquid leads to substantial reduction in natural frequencies, due to gradually increasing overall mass. Moreover, the results of sweep-sine tests clearly indicate that the increase in the liquid level results in significant increase in the damping structural ratio, which is the effect of damping properties of liquid due to its sloshing. The results of seismic and paraseismic tests indicate that filling the tank with liquid leads initially to considerable reduction in values of acceleration (damping effect of liquid sloshing); however, beyond a certain level of water filling, this regularity is inverted and acceleration values increase (effect of increasing total mass of the structure). Moreover, comparison of the responses under mining tremors and moderate earthquakes indicate that the power amplification factor of the mining tremors may be larger than the seismic power amplification factor. Finally, the results of damage diagnosis of fully filled steel tank model indicate that the forms of the Fourier spectra, together with the frequency and power spectral density values, can be directly related to the specific type of structural damage. They show a decrease in the natural frequencies for the model with unscrewed support bolts (global type of damage), while cutting the welds (local type of damage) has resulted in significant increase in values of the power spectral density for higher vibration modes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.383-390
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• 2020

Since the dynamic behaviors of liquid storage tanks on flexible soil are significantly influenced by the fluid-structure-soil interaction (FSSI), its effects must be rigorously considered for accurate earthquake analysis and seismic design of the storage system. In this study, dynamic analysis is performed for a rectangular liquid storage tank on flexible soil, and its dynamic characteristics are examined by rigorously considering the effects of FSSI. The hydrodynamic force and the interaction force between the structure and soil are evaluated using the finite-element approach. In the evaluations, mid-point integrated finite elements and viscous dampers are considered for energy radiation into the infinite soil. The effective earthquake force is then obtained from free-field analysis. It is thus demonstrated that the earthquake responses of the rectangular liquid storage tank on flexible soil are significantly influenced by the FSSI.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.04a
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• pp.30-32
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• 1996

Although the transport of small molecules through polymer membranes has been extensively studied for a long time, understanding of the transport mechanism is still far from satisfactory. This in turn makes difflcult the search for new membrane materials with the desired transport characteristics. Therefore it is of the utmost interest to study the correlations between a polymer's structure and morphology and its transport properties. Generally, polyurethanes serve as excellent polymer materials for such studies since their physical and chemical properties can be widely and systematically modified by varying the length, composition and chemical structure of the hard and soft segments. In this paper liquid crystalline polyurethanes are presented as new membrane materials for liquld separation and their transport properties with respect to molecular and supermolecular-structure are discussed.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.46-54
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• 1992

In this paper, behavior of rectangular storage structures under earthquake loadings are investigated. Linear sloshing is assumed in this study. The effect of the wall flexibility is considered. Eulerian and lagrangian approaches are presented. The Eulerian approach is carried out by solving the boundary value problem for the fluid motion. In the lagrangian approach, the fluid as well as the storage structure is modelled by the finite element method. The fluid region is discretized by using fluid elements. The (1 $\times$ 1)-reduced integration is carried out for constructing the stiffness matrices of the fluid elements. Seismic analysis of the coupled system is carried out by the response spectra method. The numerical results show that the fluid forces on the wall obtained by two approaches are in good agreements. By including the effect of the wall flexibility, the forces due to fluid motion can be increased very significantly.

• Textile Coloration and Finishing
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• v.5 no.2
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• pp.109-116
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• 1993

Synthesis and liquid-crystallinites of thermotropic polyamides and copolyamides were investigated. Thermotropic polyamides and copolyamides containing a flexible spacer in the backbone were obtained by the two or three components melt polycondensations of 4,4'-dicarboxy-${\alpha}$${\omega}$-diphenoxy alkane as an A components, 4,4'-diacetoamido-3,3' dimethoxybiphenyl as a B, 1,4-diacetoamido-benzene (diacetylated p-phenylenediamine) was used as another amide-group-forming minomer. The content of the amide groups in the thermotropic polyamide and Copolyamide widely varied depending on the structure of the amide-group forming diacetoamido monomers. A polymer (9CLDI) showed a typical nematic texture between 218$^{circle}C$ ($T_m$) and 345$^{circle}C$($T_i$) The melting points of the members of this series of polymers increased with decreasing methylene spacer. The polymer structure and mesmorphic nature were examined by solid and solution ${^13}C$-NMR spectroscopy, cross polarizing microscopy with a hot stage.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1125-1128
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• 2007

The laminating technique for developing flexible liquid crystal display was demonstrated by using a thin UV curable polymer film and a plastic substrate with patterned polymer wall structure. We adopted the rigid wall structure to provide a solid mechanical support for the stable molecular alignment of liquid crystals (LCs) in the device. The cover film was prepared to have an ability of aligning LC molecules by patterning a micro-groove structure using the soft-lithographic process. These two substrates can be assembled tightly by the laminating and one-step UV irradiation process because of the adhesive nature of the used UV curable polymers. Proposed method can be used to fabricate the flexible LC display with simplicity and also be applicable for a cost-effective roll-to-roll process.