• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1661-1667
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• 2009

Post-cure characteristics of a silicone rubber material which is widely used for a LCD lamp holder were investigated using thermogravimetric analysis (TGA). Research was especially focussed on searching for the optimum post-cure conditions in relation to the practical operation environments. The results showed that incipient volatile temperature(Ti) during the process was considered as the most important factor and, thereby, post-curing for 2hrs at $250^{\circ}C$seemed to be a reasonable condition in the practical view-point. Arrhenius plot of shift factors which were empirically determined from the time-temperature-superposition-principle showed good linearity, exhibiting the post-cure mechanism might be proceeded through single mechanism with activation energy of 108.25kJ/mol.

• Elastomers and Composites
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• v.47 no.4
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• pp.336-340
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• 2012

Residual stress in the injection molded part is originated from thermal shrinkage and shear stress during injection molding process. There are many measurement methods of residual stress in the plastic part. Residual stress in opaque products can be measured by chemical cracking test. This method enables the solvent and specimen to react and to cause cracks. Cracks developed according to the level of residual stress. Thus the stresses in plastic part can be quantitatively measured by counting the number of cracks or measuring the size of cracks. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded using PC/PBT and PC/ABS. Solvent for the chemical cracking test was prepared using tetrahydrofuran and methyl alcol with the ratio of 1 to 3. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. Cracks were developed for stress higher than certain level. The number of cracks increased by second order function for stress.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.20 no.2
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• pp.133-138
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• 1998

Choanal atresia may be membrane or bony, unilateral or bilateral. Approximately 90% of the choanal atresia are bony type. Unilateral choanal atresia often eludes the diagnosis because of the absence of subjective symptoms in the neonatal period. However, bilateral choanal atresia presents at birth with cyclic respiratory distress aggravated by feedings. So complete bilateral choanal atresia is considered as a neonatal emergency. Examinations for the diagnosis of chonal atresia include 1) attempt at passing a rubber catheter or probe through the patient s nose, 2) mirror examination of the nasopharynx, 3) digital examination of the nasopharynx, 4) X-ray examination after installation of radiopaque materal into the nasal cavity. But, computed tomography has become accepted method for evaluation of choanal atresia. Surgical repair of choanal atresia is accomplished via transnasal or transpalatal approach. Advantages of the transpalatal approach are improved exposure and the preservation of mucosal flap along the newly formed apertures. On the other hand, the transpalatal approach carries the risk of injury to the greater palatine neurovascular complex, and requires longer operative time. After careful physical and radiographic examinations, we accomplished the surgical repair of the complete bony bilateral choanal atresia via transpalatal approach without complications.