• Transactions of Materials Processing
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• v.16 no.1 s.91
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• pp.3-8
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• 2007

Novel compression molding system for preform has been developed in this study. The preforms for injection blow molding and injection stretch blow molding are being manufactured by injection molding. However it contains gate mark that affects the bottom crack in the PET bottle. The compression molded preform does not contain gate mark, thus the appearance quality of bottle has been increased and the residual stress near gate(bottom of the bottle) has been reduced. The thickness distributions, haze, and transmittance are well accepted for the preform. Also, flow characteristics of the resin between a core and cavity could be analyzed through computer simulation.

• Transactions of Materials Processing
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• v.24 no.2
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• pp.101-106
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• 2015

Recently, silicone is being used for LED chip lens due to its good thermal stability and optical transmittance. In order to predict residual stresses, which cause optical birefringence and mechanical warpage of silicone, a finite element analysis was conducted for the curing of silicone during molding. For the analysis of the curing process, a dynamic cure kinetics model was derived based on the results of a differential scanning calorimetry (DSC) testing and applied to the material properties for finite element analysis. Finite element simulation results showed that a step cure cycle reduced abrupt reaction heat and showed a decrease in the residual stresses.

• Journal of Powder Materials
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• v.14 no.6
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• pp.410-414
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• 2007

Carbon contamination from the binder resin is an inherent problem with the metal powder injection molding process. Residual carbon in the W-Cu compacts has a strong impact on the thermal and electric properties. In this study, uncertainty was quantified to evaluate determination of carbon in a W-15%Cu MIM body by the combustition method. For a valid generalization about this evaluation, uncertainty scheme applied even to the repeatability as well as the uncertainty sources of each analyse step and quality appraisal sources. As a result, the concentration of carbon in the W-Cu part were measured as 0.062% with expanded uncertainty of 0.003% at 95% level. This evaluation example may be useful to uncertainty evaluation for other MIM products.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.49-54
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• 1999

In this paper. we studied cut off characteristics and fire hazard of residual current protective devices(RCD or ELB) for low voltage. The operative time of RCD with grounding resistance was analyzed by using RCD operating tester. The surface structure and composition of insulator were analyzed by using scanning electron microscope(SEM) and energy dispersive x-ray spectroscopy(EDX). The surface of phenol resin showed network structure and void. The spectra shown in EDX analysis are composed not only of the corresponding elements but also of several new spectra, as CK. OK$\alpha$. MgK, SiK. and CaK, which were absent in original material.

• Journal of the Korean Applied Science and Technology
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• v.15 no.1
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• pp.9-15
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• 1998

Poly(p-anol-formaldehyde) cinnamates(AGEFCs) were synthesized to prepare a photo-sensitive polymer which enabled to be photodimerized via 6-center reaction. The photocharacteristics of the mixture of the AGEFCs and a sensitizer after exposure to light was tested. The yield of the residual film, which was closely related to the sensitivity of the film, was affected by the degree of polymerization of the backbone resin, sensitizers and their concentration. AGEFC-3 revealed a good photosensitive effect such as about 73% yield of residual film at 128 min. of exposed time.

• Journal of the Korean Applied Science and Technology
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• v.13 no.1
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• pp.47-54
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• 1996

Cinnamoyl ester(PGEFC) of poly(phloroglucinol-formaldehyde) glycidyl ether which has photosensitive functional group was prepared to apply to photoresist. Photosensitivity of PGEFC was estimated by the solubility difference in organic solvent before and after exposure to light. The yield of residual film was calculated by immersing the sample-coated quartz plates in the solvent which was used in coating. The yield of the residual film which was closely related to the sensitivity of the film, was affected by the degree of polymerization of the backbone resin, sensitizers and their concentration. The sensitivity was depended upon the degree of polymerization. Most of effective sensitizer for PGEFC among the sensitizers was 2, 6-dichloro-4-nitroaniline.

• Journal of Food Hygiene and Safety
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• v.9 no.1
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• pp.1-13
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• 1994

A Simultaneous determination method was improved for the determination and confirmation of zeranol, zearalenone, as well as their isomers and metabolites, in beef. The analytes were extracted from tissue by CH3CN, hydrolyzed enzymatically(for glucuronide conjugates), cleaned up by a strong basic anion exchange resin combined with a liquid/liquid partitioning, derivatized using MSTFA and confirmed, quantified by GC/MS/SIM with a internal standard, zearalane. The results were as follows : (1) all the estrogens were separated on the GC/MS chromatogram under the extraction method and the chromatographic conditions improved, the retention times of zearalane-TMS2, zearalanone-TMS2, zearalenone-TMS2, zeranol-TMS3, taleranol-TMS3, and $\alpha$-zearalenol-TMS3, $\beta$-zearalenol-TMS3, were 18.49, 19.44, 19.63, 19.71, 19.79 and 19.99, 20.08 minutes, respectively. (2) The calibration curves of residual zeranol, zearalenone and their metabolites showed constantly linear(r=0.99) in the range of 5~20 ng. The minimum detection concentration of residual zeranol, zearalenone and their metabolites was 1 ppb. (3) The total average recovery of residual zeranol, zearalenone and their metabolites from spiked beef was 60.2%(CV=29.7%) at the 1 ppb and 63.5%(CV=26.5) at the 2 ppb, 72.9%(CV=18.2%) at the 4 ppb. (4) The preservation method for 6 estrogens was improved for the fast running time(21 min) and MSTFA was utilized for derivatizing 6 estrogens for improvement of recovery, for good resolution, for characteristic mass spectra unlike Jose's method and Tina's method. The utilization of zearalane as internal standard showed good quantification result for zeranol, zearalenone, as well as their isomers and metabolites, in beef.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.620-631
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• 1996

Bonding of resin to cast alloy has traditionally been provided by mechanical retention. But, chemical bonding methods such as silicoating, tin plating, heat treatment, application of 4-META adhesives, have been developed to overcome the problems of the mechanical bonding methods. Silicoating has been used availaby in fixed prosthodontics, but is also reported to be used in removable prosthodontics. The aim of this study is to measure the tensile bond strength between resin and metal, and compare the effect of the type of metal and the grain size of the aluminum oxide on the bond strength, after metal surface roughening, coating of the opaque resin, and curing of heat-curing resin were performed. The test groups were divided into 4 groups according to the cast alloys and the aluminum oxide particles used. Group 1 : Type 4 gold alloy(DM66) blasted with $$50{\mu}m\;Al_{2}O_3$$ Group 2 : Type 4 gold alloy(DM66) blasted with $$250{\mu}m\;Al_{2}O_3$$, Group 3 : Co-Cr alloy(Nobilium) blasted with $$50{\mu}m\;Al_{2}O_3$$ Group 4 : Co-Cr alloy(Nobilium) blasted with $$250{\mu}m\;Al_{2}O_3$$ * 10 test specimens were made on each group. The specimens were thermocycled, and Instron Universal testing machine was used to measure the tensile bond strength of the finished specimens. The results were as follows : 1. Bond strengths showed that the group of gold alloy blasted with $250{\mu}m$ aluminum oxide particle had higher bond strength, and the group of gold alloy blasted with $50{\mu}m$ aluminum oxide particles had lower bond strength than any of the other groups. 2. Gold alloy had significantly higher bond strength when blasted with $250{\mu}m$ aluminum oxide particles than $50{\mu}m$, but. Co-Cr alloy showed no statistically significant difference between the two particle sizes. 3. When blasted with $50{mu}m$ aluminum oxide particles, Co-Cr alloy showed significantly higher bond strength than gold alloy. And, when blasted with $250{\mu}m$ aluminum oxide particles, gold alloy had significantly higher bond strength than Co-Cr alloy. 4. On the examination of the fractured sites, only the group of Co-Cr alloy blasted with $50{\mu}m$ aluminum oxide particles showed a part of residual opaque resin, but all the samples of the other groups fractured between the resin and the metal.

• Composites Research
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• v.17 no.3
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• pp.1-7
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• 2004

In the vacuum assisted RTM (VARTM) process that has become the center of attention for manufacturing massive composite structures, a good evacuation of air in the fiber preform is recognized as the prime factor. The microvoids, or the dry spots, are formed as a result of improper gate/vent locations and the mold geometry. The non-uniform resin velocity at the flow front leads to the formation of microvoids in the fibers, whereas the air in the microvoids can migrate along with the resin flow during mold filling. The residual air in the internal voids of a composite structure may cause a degradation of the mechanical properties as well as the structural failure. In this study, a unified macro- and micro analysis methods were developed to investigate the formation and transport of air in resin during VARTM process. A numerical simulation program was developed to analyze the three-dimensional flow pattern as well as the macro- and microscopic distribution of air in a composite part fabricated by VARTM process.

• Resources Recycling
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• v.11 no.1
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• pp.9-18
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• 2002

Printed wiring boards(PWBs) of the obsolete computers are composed of various organic and inorganic compounds as well as metals and alloys. As convinced that the valuable metals obtained from the PWBs are effectively utilized as secondary resources when recovered by economical methods, in this study, an investigation for characterizing the physical separation techniques is conducted. For the recovery of them, the sockets and chips dismantled from PWBs by scraping and residual resin boards are subjected to the appropriate separation processes according to the physical properties of each part. In the case of crushed socket scraps size ranged from -2.36 mm to +1.18 mm, approximately 97 wt% of the product obtained by magnetic separation consists of metallic compounds. In the case of chip scraps, 97% of Fe-Ni alloy and 95% of Cu metal are recovered by the combined process of air classification and dry magnetic separation in the size range from -2.36 mm to +0.15 mm. Ball milling is adopted in order to improve the removal efficiency of the thin-printed metallic materials on the residual resin boards and approximately 77% of Cu metal is recovered by zigzag separation after ball milling.