• Textile Coloration and Finishing
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• v.31 no.4
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• pp.323-331
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• 2019

Sorghum is a rich source in phytochemicals, such as tannins, phenolic acids, anthocyanins, phytosterols and policosanols. Sorghum has been known to have antimicrobial, antiinflammatory, antioxidant properties. In this study, poly(vinyl alcohol)(PVA)-sorghum extract(SE) composite nanoweb was produced by electrospinning and its characteristics including bioactivities were investigated. The SE had antimicrobial and antiinflammatory activities as well as a reduced cytotoxicity. The PVA-SE nanoweb had a highly enhanced antimicrobial activity compared to PVA nanoweb. The amount of proinflammatory cytokine released from macrophages treated with the PVA-SE nanoweb was reduced. The PVA-SE nanoweb can be a potential candidate for medical and cosmeceutical materials providing antimicrobial and antiinflammatory activities with a low degree of cytotoxicity.

• Journal of the Korean Ceramic Society
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• v.51 no.1
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• pp.19-24
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• 2014

Three-layer porous alumina-mullite composites with a symmetric gradient porosity are prepared using a controlled freeze/gel-casting method. In this work, tertiary-butyl alcohol (TBA) and coal fly ash with an appropriate addition of $Al_2O_3$ were used as the freezing vehicle and the starting material, respectively. When sintered at $1300-1500^{\circ}C$, unidirectional macro-pore channels aligned regularly along the growth direction of solid TBA were developed. Simultaneously, the pore channels were surrounded by less porous structured walls. A high degree of solid loading resulted in low porosity and a small pore size, leading to higher compressive strength. The sintered porous layered composite exhibited improved compressive strength with a slight decrease in its porosity. After sintering at $1500^{\circ}C$, the layered composite consisting of outer layers with a 50 wt% solid loading showed the highest compressive strength ($90.8{\pm}3.7MPa$) with porosity of approximately 26.4%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.294-298
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• 2008

The ionic polymer-metal composite actuators with selectively grown multiple electrodes were developed to mimic the swimming locomotion of a fish. The developed method is based on combining electroplating with the electroless chemical reduction using the patterned mask. The advantages of this fabrication method are that the initial compositing between the polymer and platinum particles can be assured by the chemical reduction method, and the thickness of each electrode can be controlled easily and rapidly by electroplating. By using the fabricated actuator with a multiple degree of freedom, the oscillatory wave of the flexible membrane actuator was generated and a twisting motion was also realized to verify the possibility of mimicking the fish-like locomotion. The frequency response function was analyzed to investigate the natural frequency and the damping factor by a mechanical shaker and direct electrical excitation through the swept-sine method. Present results show that this novel method can be a promising technique to easily pattern each of multiple electrodes and to implement the biomimetic motion of the polymer actuators with good mechanical bending performance.

• Journal of Environmental Science International
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• v.21 no.4
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• pp.507-515
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• 2012

To improve the mechanical properties of hydroxyapatite (HA)/waterborne polyurethane (WBPU) composites, the hydroxyl group of HA was modified by urethane reactions: the hydroxyl groups of HA were reacted with aliphatic or cyclic diisocyanate, and then the modified HAs were extended by adding polyol and/or ${\varepsilon}$-caprolactone. Composites were prepared by the prepolymer process method: the modified HA was directly pured into the urethane reaction of isocyanate and polyol. The properties of modified HA/WBPU composites were investigated by thermogravimetric analysis, tensile strength, and water resistance. The results showed that the reactivity of aliphatic diisocyanate to the hydroxy group of HA was faster than that of cyclic one. Comparing to those of pure HA/WBPU composite films, the thermal stability, water resistance, and mechanical properties of the modified composite films increased with a degree of modification of HA.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1785-1795
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• 2001

A multi-layered brick element fur the finite element method is developed for analyzing the three-dim-ensionally layered composite structures subjected to both thermal and mechanical boundary conditions. The element has eight nodes with one degree of freedom for the temperature and three for the display-ements at each node, and can contain arbitrary number of layers with different material properties with-in the element; the conventional element should contain one material within an element. Thus the total number of nodes and elements, which are needed to analyze the multi-layered composite structures, can be tremendously reduced. In solving the global equation, a partitioning technique is used to obtain the temperature and the displacements which are caused by both the mechanical boundary conditions and temperature distributions. The results by using the developed element are compared wish the commercial package, ANSYS and the conventional finite element methods, and they are in good agreement. It is also shown that the Number of nodes and elements can be tremendously reduced using the element without losing the numerical accuracies.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1365-1381
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• 1990

A $C^{0}$ continuous displacement finite element method based on a higher-order shear deformation theory is employed in the prediction of the transient response of laminated composite plates subjected to low-velocity impact. A modified contact law was applied to calculate the contact force during impact. The discrete element chosen is a nine-noded quadrilateral with 5 degree-of-freedom per node. The Wilson-.theta. time integration algorithm is used for solving the time dependent equations of the impactor and the central difference method was adopted to perform time integration of the plate. Numerical results, including the contact force history, deflection, and velocity history, are presented. Comparisons of numerical results using a higher order theory and a first-order theory show that using a higher order theory provides more accurate results. Effects of boundary condition, impact velocity, and mass of the impactors are also discussed.d.

• International Journal of CAD/CAM
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• v.12 no.1
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• pp.20-28
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• 2012

Finite Element Analysis (FEA) is often used to identify local stress/strain concentrations where a component is likely to fail. In order to reduce the degree of strain concentration, component thickness can be increased in those regions, or a stronger material can be used. In short fiber reinforced composite materials, strength and stiffness can be increased through proper fiber alignment. The field-aided microtailoring (FAiMTa) process is one promising method for doing this. FAiMTa uses principles of dielectrophoresis to preferentially align particles or fibers within a matrix. To achieve the preferred fiber orientation, an interdigitated electrode network must be integrated into the mold halves which can be fabricated by additive manufacturing (AM) processes. However, the process of determining the preferred fiber arrangements and electrode locations can be very challenging. This paper presents algorithms to semi-automate the interdigitated electrode design process. The algorithm has been implemented in the Solidworks CAD system and is demonstrated in this paper.

• Journal of the Korean Ceramic Society
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• v.37 no.2
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• pp.122-127
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• 2000

The thermal expansion, thermal stability, mechanical strength and infrared radiative property of Al2TiO5-clay composites, prepared from synthesized Al2TiO5 and clay, were investigated to develop a material for far infrared radiators. The emittance of composites containing 10~50 wt% clay, heated at 1,20$0^{\circ}C$ for 3 h, increased with increasing clay content and emittance was about 0.3 and 0.92 in the ranges of 3,400~2,500 cm-1 and 2,500~400cm-1, respectively. The bulk density and bending strength of the Al2TiO5-clay composites increased with increasing clay content. 50 wt% Al2TiO5-50 wt% clay composite, heat-treated at 1,20$0^{\circ}C$, had an adequate strength for infrared radiators; 80 MPa. The degree of thermal expansion hysteresis decreased with increasing clay content and the mean thermal expansion coefficient increased with increasing clay content. The thermal expansion coefficient of 50 wt% Al2TiO5-50 wt% clay composite heated at 1,20$0^{\circ}C$ was 5.78$\times$10-6/$^{\circ}C$.

• BMB Reports
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• v.37 no.6
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• pp.648-656
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• 2004

This paper deals with the development of a predictive probabilistic model, a composite dependency-reflecting model (CDRM), which was designed to detect core promoter regions and transcription start sites (TSS) in vertebrate genomic DNA sequences, an issue of some importance for genome annotation. The model actually represents a combination of first-, second-, third- and much higher order or long-range dependencies obtained using the expanded maximal dependency decomposition (EMDD) procedure, which iteratively decomposes data sets into subsets on the basis of dependency degree and patterns inherent in the target promoter region to be modeled. In addition, decomposed subsets are modeled by using a first-order Markov model, allowing the predictive model to reflect dependency between adjacent positions explicitly. In this way, the CDRM allows for potentially complex dependencies between positions in the core promoter region. Such complex dependencies may be closely related to the biological and structural contexts since promoter elements are present in various combinations separated by various distances in the sequence. Thus, CDRM may be appropriate for recognizing core promoter regions and TSSs in vertebrate genomic contig. To demonstrate the effectiveness of our algorithm, we tested it using standardized data and real core promoters, and compared it with some current representative promoter-finding algorithms. The developed algorithm showed better accuracy in terms of specificity and sensitivity than the promoter-finding ones used in performance comparison.

• Composites Research
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• v.17 no.3
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• pp.38-44
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• 2004

The electromagnetic interference (EMI) shielding is very essential for commercial and military purposes. We fabricated multi-walled carbon nanotube (MWNT)/epoxy composites and studied the electromagnetic characteristics of the composites before we study the characteristics of MWNT-added glass fiber-reinforced composites. After setting up the fabrication process, we measured the permittivity of MWNT/epoxy composites with process variables and MWNT concentrations in X-band (8.2GHz~12.4GHz). We also observed re-aggregation phenomenon of MWNTs and investigated its effect on the permittivity. The permittivity of the composites was influenced by the degree of dispersion of MWNTs and increased almost linearly as MWNT concentration increases.