• Smart Structures and Systems
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• v.8 no.2
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• pp.173-190
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• 2011

As a practical and effective seismic resisting technology, the base isolation system has seen extensive applications in buildings and bridges. However, a few problems associated with conventional lead-rubber bearings have been identified after historical strong earthquakes, e.g., excessive permanent deformations of bearings and potential unseating of bridge decks. Recently the applications of shape memory alloys (SMA) have received growing interest in the area of seismic response mitigation. As a result, a variety of SMA-based base isolators have been developed. These novel isolators often lead to minimal permanent deformations due to the self-centering feature of SMA materials. However, a rational design approach is still missing because of the fact that conventional design method cannot be directly applied to these novel devices. In light of this limitation, a displacement-based design approach for highway bridges with SMA isolators is proposed in this paper. Nonlinear response spectra, derived from typical hysteretic models for SMA, are employed in the design procedure. SMA isolators and bridge piers are designed according to the prescribed performance objectives. A prototype reinforced concrete (RC) highway bridge is designed using the proposed design approach. Nonlinear dynamic analyses for different seismic intensity levels are carried out using a computer program called "OpenSees". The efficacy of the displacement-based design approach is validated by numerical simulations. Results indicate that a properly designed RC highway bridge with novel SMA isolators may achieve minor damage and minimal residual deformations under frequent and rare earthquakes. Nonlinear static analysis is also carried out to investigate the failure mechanism and the self-centering ability of the designed highway bridge.

• Elastomers and Composites
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• v.39 no.1
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• pp.3-11
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• 2004

Plasma treatment is frequently used to increase surface functionality and surface activity. It enables to improve various surface properties such as catalytic selectivity, printability, and interfacial adhesion between various materials. Surface or the ethylene-vinyl acetate (EVA) is exposed under an atmospheric pressure plasma torch (APPT), generated by dielectric barrier discharge (DBD), and the treated surfaces are systemically investigated. Argon, air, and oxygen are used as a processing gas. Properties of the treated EVA surfaces are investigated by the zeta-potential measurements and surface free energies. It is shown that the plasma treatment leads to a drastic increase of surface functional groups of EVA, as the increase of its adhesion energy ($G_{IC}$). Therefore, it is concluded that the APPT process is an effective means to improve adhesion of EVA and polyurethane (PU).

• Elastomers and Composites
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• v.47 no.2
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• pp.162-167
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• 2012

Surface modification of macromolecules renders a progressive and favorable method to enhance the properties of polymeric materials and improves conductivity, wettability, stability, adhesion, antibacterial properties, etc. of polymeric surfaces without deterioration of the polymer bulk properties. Polyolefins such as polyethylene and polypropylene were grafted with maleic anhydride(MAH) as a functional monomer in solution. Evidence for grafting was shown with FTIR measurement. The grafting ratio was determined from chemical titration. The higher MAH loading, the lower contact angle(${\theta}$) was obtained. With the increasing content of MAH, melting temperature($T_m$) of maleic anhydride grafted polymer decreased while decomposition temperature($T_d$) of maleic anhydride grafted polymer increased.

• Elastomers and Composites
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• v.47 no.2
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• pp.141-147
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• 2012

Silicone resin has no water-absorbing function because it is a strong hydrophobic polymer. However, addition of super absorbent polymer gives much better absorbency than that of conventional silicone resin. In this study, we developed novel silicone materials with water-absorbing function by choosing three types of amorphous acrylic super absorbent polymers with different particle sizes, determining the mixing ratio of the three polymers and applying the mixtures into two-component type silicone material for medical purpose. The change in the mechanical properties such as tensile strength, tear strength, compressive strength and hardness was investigated by varying the particle size and content ratio of the added super absorbent polymers while preparing the silicone resins. The absorbency of the silicone resins was measured over time. Additionally, the particle shape of the super absorbent polymers as well as the distribution within the silicone resin was observed using an optical microscope.

• Elastomers and Composites
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• v.44 no.1
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• pp.22-33
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• 2009

Recently, elastomer-nanocomposites reinforced with low volume fraction of nanofillers have attracted great interest due to their fascinating properties. The incorporation of nanofillers, such as, layered silicate clays, carbon nanotubes, nanofibers, calcium carbonate, metal oxides or silica nanoparticles into elastomers improves significantly their mechanical, thermal, dynamic mechanical, barrier properties, flame retardancy, etc. The properties of nanocomposites depend greatly on the chemistry of polymer matrices, nature of nanofillers, and the method in which they are prepared. The uniform dispersion of nanofillers in elastomer matrices is a general prerequisite for achieving desired mechanical and physical characteristics. In this paper, current developments in the field of elastomer nanocomposites reinforced with layered silicates, silica, carbon nanotubes, nanofibers and various other nanoparticles have been addressed.

• Elastomers and Composites
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• v.48 no.1
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• pp.2-9
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• 2013

We synthesized polyethylene, poly(ethylene-co-1-decene), poly(ethylene-co-p-methylstyrene), and poly(ethylene-ter-1-decene-ter-p-methystyrene) using a rac-$Et(Ind)_2ZrCl_2$ metallocene catalyst and a methylaluminoxane cocatalyst system. The materials were characterized using nuclear magnetic spectroscopy and fourier transform infrared spectroscopy. To identify suitable reaction conditions for terpolymerization, we studied the effects of catalyst content, cocatalyst/catalyst molar ratio, polymerization time, and polymerization temperature. As the catalyst content increased, the catalytic activity and the molecular weight of the terpolymers increased. The catalytic activity sharply increased but little change was observed after a polymerization time of 30 min. The increase in the cocatalyst/catalyst molar ratio resulted in a decrease in the molecular weight of the terpolymers and an increase in the catalytic activity to some degree. The catalytic activity increased with increasing polymerization temperature, while the molecular weight of the terpolymers decreased.

• Journal of Adhesion and Interface
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• v.13 no.1
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• pp.1-8
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• 2012

The effect of the grafting ratio on the mechanical property and adhesion property of the grafted EPDM modified with methacrylic acid (MA) was investigated. The storage modulus of MA-grafted EPDM was maintained higher than that of cross-linked EPDM vulcanizate by sulfur, but it was observed that the storage modulus was decreased at elevated temperature because of the weakened secondary bonding. When the functional group for hydrogen bonding was introduced in EPDM, it had excellent mechanical properties by the aggregate between grafted EPDM molecules and crystallinity of MA. The bonding strength between EPDM and other rubbers was very low because EPDM has nonpolar property and low molecular interaction to others. The bonding strength was increased as increasing grafting ratio and it was excellent enough to break the rubber during the peel test when the grafting ratio was more than 10%.

• International Journal of Human Ecology
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• v.11 no.1
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• pp.23-33
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• 2010

Articles from The New York Times and magazines including Consumer Digest, Journal of Home Economics, Scholastic, Time and Woman's Home Companion were analyzed in this study and focused on the following research questions: How did the social situation influence American women's adoption of pants during World War II? How were the social opinions of women's adoption of pants? How did American women's adoption of pants and the social opinions on women's pants represent the process of change in the definition of femininity during World War II? Women were encouraged to wear pants in work places because many women had to work in defense industries and farms. Women had to wear pants during the winter to keep warm in order to conserve oil, rubber, and other materials. In addition, wearing men's clothes became a fashion trend among college women during this period. However, practicality was often not the primary thing alone to consider in women's fashion. Femininity was still important in women's fashion. There were criticisms over the women's adoption of pants. Regulations against pants were imposed on women, while there were women who wanted to dress like ladies even at defense industries. An abrupt change in women's gender roles and the increased adoption of trousers aroused social ambivalence about the traditional definition of femininity. Even though many women returned to their homes after the war, the social demand of practicality in women's day-time clothes during the war offered women the experience of comfort and practicality in pants. These experiences contributed to paving the way for more women to adopt pants and helped establishing a new definition of femininity after the war.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.9
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• pp.103-110
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• 2008

In terms of electrical safety, environmental impact assessment and revision of domestic regulation are needed for the electric facilities. In this paper, risk of electric facilities is assessed by the spot measures and analysis in dust generation area. Adhesion dust in a surface of insulated materials cause electrical accidents. In a mechanism of these accidents, when the dust lie on electric facilities, a leakage current is flowed and the surface of insulated material is carbonized. Hereafter, electrical fire is generated due to Joule's heat. As the results, dusts are found in protection devices or panel board and sampled dusts vary in sampled amounts and conductivity severally. For the most part, sodium is detected but zinc and calcium are detected in case of reclaimed rubber factory by the ICP-AES(Inductively Coupled Plasma-Atomic Emission Spectroscopy). In a sewerage, the ingredients such as sodium, magnesium, iron, calcium, aluminium, etc are detected uniformly. So that, results of the spot measures and analysis of dusts are become the important data for the assessment of electrical hazard in dust generation area.

• Polymer(Korea)
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• v.37 no.6
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• pp.722-729
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• 2013

In order to enhance the thermal conductivity of poly(dimethyl siloxane) (PDMS), boron nitride (BN) and carbon nanotubes (CNTs) were incorporated as the thermally conductive fillers. The amount of BN was increased from 0 to 100 phr (parts per hundred rubber) and the amount of CNTs was increased from 0 to 4 phr at a fixed amount of the boron nitride (100 phr). The thermal conductivity of the composites increased with an increasing concentration of BN, but the incorporation of CNTs had only a slight effect on the enhancement of thermal conductivity. Unexpectedly, the thermal degradation of the composites was accelerated by the addition of CNTs in 100 phr BN filled PDMS. Activation energy for thermal decomposition of the composites was calculated using the Horowitz-Metzger method. The curing behavior, electrical resistivity, and mechanical properties of PDMS filled with BN and CNTs were investigated.