• Progress in Medical Physics
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• v.25 no.4
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• pp.205-209
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• 2014

Medical polymers require sterilization and must be able to maintain material properties for a specified shelf life. Sterilization can be achieved by using gamma or e-beam exposure. In this study, accelerated aging tests of poly(ether-block-amide) (PEBA) copolymer samples is presented. PEBA copolymer samples with different polyether content that result in Shore hardness of 35D to 72D, were sterilized using e-beam radiation followed by accelerated aging at $55^{\circ}C$. E-beam sterilization effect on molecular weight and mechanical property has performed and analyzed. The average molecular weight significantly reduced as a result of ageing. The enlarged proportion of low molecular weight chains in the aged samples is consistent with the generation of degradation products produced by oxidative chain scission. Also E-beam materials have shown decreased tensile strength and elongation. Overall, this study demonstrated that the medical grade PEBA was significantly affected by radiation exposure over aging time, particularly at high irradiation doses. For medical use in case of radiation sterilization required, it is recommended to avoid Pebax material. If Pebax material must be in use for medical device, recommend to use alternate sterilization method such as Ethylene Oxide sterilization.

• The Journal of Engineering Geology
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• v.14 no.1
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• pp.61-69
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• 2004

Building stones are used mainly as a material for making decoration and sculpture, and consequently they must have predominant physical properties extensively. Among various physical properties, the coefficient of pore dominates the usefulness of building stones, so the plans were made for establishing the quality classification of building stones with respect to the nature of pore. For this study, bore-hole core samples according to the depth of the biotite granites and the granitic gneiss were applicated. From the related chart between porosity and absorption ratio, Mungyeong granitic gneiss($Gn_1$) shows the widest phase of distribution in the range of measurement values, and the values decrease in the order of Pocheon granite($Gr_2$) and Mungyeong granite($Gr_1$) in the range. The strength of each rock mass varies with the degree of alteration. Also in correlation between compressive strength and tensile strength, the range of measurement values decrease in the order of $Gn_1$, $Gr_2$and $Gr_1$. Porosity is adopted as a representative physical property for establishing the quality classification of building stones, and then relative evaluation was made with regard to various physical properties. From the related chart between porosity(n)-specific gravity(G), absorption ratio(Ab), compressive strength(${\sigma}_{c}$), tensile strength(${\sigma}_{t}$), shore hardness(Hs) and Young's modulus($E_{t}$), standard of each grade is established.