• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.73-81
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• 1997

This study was to find the best adhesive condition comparing mechanical property in case of hot-melt adhesion using glue-gun, ultrasonic welding with adhesion and only ultrasonic welding in order to adhere thermoplastic resin of polyethylene (PE) in which reliable adhesion was resulted in case of ultrasonic welding with same materials of PE. The best welding condition were acquired at welding time 1 second, welding pressure 250kPa for PE-PE where welding time and welding pressure were increased in accordance with the increase of material strength. At the best ultrasonic welding conditions, bonding strength of PE-PE welding was about 21MPa of which material have tensile strength of 24MPa. Through the analysis of microscophic test for ultrasonic welding structure, it was distinguished between well welded structure with higher intermolecule flow and bad welded structure with lower flow, of which result is mostly correspond with the result of tensile strength test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1997-2000
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• 2005

In this work, the effects of orthogonal ribs on warpage of plastic structure through injection molding process were investigated. Three kinds of injection molds were prepared to perform injection molding experiments of orthogonal stiffened plastic plate. The warpage of each injection molded specimen was measured using 3D CMM. And plastic injection molding analysis with commercial code was performed for the presented model. Numerical results of injection molding analysis were compared with those of experiments. It was shown that orthogonal ribs have a significant effect on the warpage of the structure in both cases of experiment and numerical analysis.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.110-118
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• 1995

The filling phase analysis of the injection molding process for thermoplastics was applied to predict pressure, themperature and shear stress in the test mold, and the results were compared with the experiment using 30% glass fiber added ABS resin. The finite difference method was used in the analysis considering the effects of heat transfer between molten polymer and mold wall, and also frictional heating by shear flow. The analysis results were considered as a method to improve the quality and the productivity of injection molding process. Using the analysis results, the molding factors such as mold-ability of polymers, performance of injection molding machine, positioning of gate and dimendsioning of runner in the injection molding process can be estimated at the design stage of mold for good quality and productivity.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.983-988
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• 2004

In the present study, the effects of orthogonal ribs on structural warpage during injection molding process were investigated. Basic ribbed models for the evaluation of degree of warpage were introduced and designed. Injection molds for these models are manufactured based on the full 3D CAD/CAM technology and specimens are prepared for experiment. Numerical analysis using commercial plastic injection molding analysis software was also performed to compare the results with experimental ones. The variations of materials and parameters such as injection time, mold temperature, melt temperature, holding time were considered in the present work. It was shown that orthogonal ribs have significant effect on the reduction of warpage during the injection molding process.

• Asian Journal of Turfgrass Science
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• v.10 no.3
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• pp.263-270
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• 1996

This experiment was conducted to investigate the loss of various herbicides by means of vola-tility from the turfgrass field and the hare ground with the different soil moisture contents and temperatures. Different herbicides were applied at the rates of 375 g a.i. /l0a of pendimethalin,250 g a.i. /l0a of napropamide, and 96.4 g a.i. /l0a of dicamba with 200 \ulcorner/10a of spray volume in the turfgrass(Zoysia japonica cut off 5cm) grown in pots(265.8 $cm^2$) and bared soil. The pots were placed in the growth chamber with 10,000 lux of light intensity(12h per day) at 25 and 35˚C for 7days. Amberlite XAD polymeric resin(20/50 mesh) was used as sampling media for herbicide airborne residues. Air flow was maintained at 10 \ulcorner /min by vacuum pump regulated with a factory calibrated flow meter. Herbicide airborne residues were extracted from the XAD resin with 300 ml of 1:1 acetone and hexane. The extracts were concentrated by rotary evaporation at 35˚C and dissolved in 1 ml MeCN for HPLC analysis. The airborne losses of the herbicide applied in the turfgrass and bare soil increased as the temperature and soil moisture contents were increased, regardless of the kinds of herbicide. Higher airborne residues was observed in the turfgrass pots than the bare soil pots. Pendimethalin and dicamba with higher vapor pressure gave rise to the increased loss of airborne herbicides, showing that 6.26 and 6.4% of average airborne loss in pendimethalin and dicamba, respectively, compared to 0.56% in napropamide. The amount of airborne losses in turfgrass was highest at one day after application and then a declined trend was observed as the time was prolonged. Key words. Herbicides, Turfgrass field, Bare ground, Volatility.

• Journal of The Korean Digital Architecture Interior Association
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• v.12 no.3
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• pp.59-66
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• 2012

Autoclaved Lightweight Concrete(ALC) features such as a high performance insulation, the fire resistance, the advantage of easy handing construction, and lightweight panels applied the curtain wall system. ALC materials are certified as non-toxic environmental and eco-friendly productions. But ALC external panels mixed with blast furnace slag pounder and silica fume have to be coated with a stucco compound or plaster because of resisting the ambient environment. This study is that mixing tests to evaluate a performance analysis of exterior paints to be make-up pigments(organic or inorganic) coated with panel surface. Testing compared by KS F 2476; flow test, KS F 2426; compression strength test, KS F 2762; bond strength test. In results, the case of the inorganic binder, ratio of alumina cement : anhydrite is 90:10 to 80:20 at the highest level of intensity. In the case of the organic binder, adhesive strength rating at surface of ALC, the pullout strength is below 0.5 $N/mm^2$ but the normal concrete is over 2.0$N/mm^2$. A contents ratio of EVA resin is more than 3% and then bond strength is effectively.

• Restorative Dentistry and Endodontics
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• v.44 no.4
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• pp.37.1-37.10
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• 2019

Objectives: This study evaluated the bond strength of various fiberglass post cementation techniques using different resin-based composites. Materials and Methods: The roots from a total of 100 bovine incisors were randomly assigned to 5 treatment groups: G1, post + Scotchbond Multi-Purpose (SBMP) + RelyX ARC luting agent; G2, relined post (Filtek Z250) + SBMP + RelyX ARC; G3, individualized post (Filtek Z250) + SBMP; G4, individualized post (Filtek Bulk-Fill) + SBMP; G5, individualized post (Filtek Bulk-Fill Flow) + SBMP. The samples were subjected to the push-out (n = 10) and pull-out (n = 10) bond strength tests. Data from the push-out bond strength test were analyzed using 2-way analysis of variance (ANOVA) with the Bonferroni post hoc test, and data from the pull-out bond strength test were analyzed using 1-way ANOVA. Results: The data for push-out bond strength presented higher values for G2 and G5, mainly in the cervical and middle thirds, and the data from the apical third showed a lower mean push-out bond strength in all groups. No significant difference was noted for pull-out bond strength among all groups. The most frequent failure modes observed were adhesive failure between dentine and resin and mixed failure. Conclusions: Fiberglass post cementation using restorative and flowable bulk-fill composites with the individualization technique may be a promising alternative to existing methods of post cementation.

• Journal of Korean Society of Forest Science
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• v.79 no.4
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• pp.424-430
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• 1990

The variation of needle, cone and seed characteristics and of allelic frequency in isoenzyme, ADH, ME and PGI, according to different resin duct index in Pinus densiflora, Pinus thunbergii and their hybrids was analyzed. The results obtained were as follows : 1. With increase of number of resin ducts, morphological characteristics such as needle length, needle sheath length, cone size, seed size, seed wing size, 1000 seeds weight, etc. tended to he increased, while number of stomata row in needle to be decreased. 2. As the results of discriminant analysis for the morphological characteristics of needle, cone and seed, most individuals are generally coincided with number of resin duct mostly in Pinus densiflora were not. 3. According to the canonical discriminant function obtained from the morphological characteristics in Pinus densiflora, Pinus thunbergii and their hybrids including introgressive hybrid, the resin duct index, 1000 seeds weight, cone size and neelde sheath length characterized fairly their species. 4. With increase of resin duct index, hybrid index tended to be higher. The results obtained from the discriminant analysis and the hybrid index were nearly same each other. 5. With increase of number of resin duct, the allelic frequencies for isoenzyme, ADH-$B_2$, ME-$A_2$ and PGI-$B_1$. $B_2$ tended to increase but those of ADH-$B_3$, ME-$A_4$, and PGI-$B_3$, to decrease. It is thought that this increase of frequency for the former four isoenzymes was resulted in introgressive gene flow from Pinus thunbergii to Pines densiflora and accordingly the frequency of latter three isoenzymes tended to decrease.

• Journal of Technologic Dentistry
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• v.39 no.2
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• pp.83-91
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• 2017

Purpose: The objective of this study was to evaluate influence of mechanical properties of gingival shade composite resins(GSCRs) according to thermocycling treatment. Methods: The material utilized in this study was Crea.lign(CGR), Twiny flow(TGF) and Twiny(TGP). Total sixty specimens were fabricated with a dimension of $25{\times}2{\times}2mm$ according to the ISO 4049. After fabrications, specimens of before and after thermocycling(to $55^{\circ}C$ from $5^{\circ}C$) were stored in the distilled water for 24 hours at the $37^{\circ}C$. Three-point flexural test was performed in universal testing machine(Instron 5966, USA) at a crosshead speed of 1 mm/min. Flexural strength, flexural modulus and work of fracture according to the thermocycling were analyzed using a one-way ANOVA analysis. Surface analysis of GSCRs after thermocycling evaluated using the scanning electron microscope. Results: : The highest FS was measured in TGP group of NTC group and lowest in CGR group after TC. After TC, FS and FM decreased in CGR and TGP groups, but TGF increased. There was a statistically significant difference between FS and WOF in GSCRs(p<0.05). But FM did not show any significant difference after TC (p>0.05). The strength of the characteristic exceeded the flexural strength required by ISO 4049(> 80 MPa). Weibull modulus(m) showed the highest reliability in the TGP group (m = 14.22), and the reliability of the TGF and TGP groups after TC decreased. Conclusion: Thermocycling treatment is important factor influence of mechanical properties with gingival shade composite resins. Therefore, we recommended that mechanical properties need to get useful information and accuracy for life-span expectancy according to the thermocycling treatment.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.24-30
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• 2013

Today, the modification of carbon foam for high performance remains a major issue in the environment and energy industries. One promising way to solve this problem is the optimization of the pore structure for desired properties as well as for efficient performance. In this study, using a sol-gel process followed by carbonization in an inert atmosphere, hollow spherical carbon foam was prepared using resorcinol and formaldehyde precursors catalyzed by 4-aminobenzoic acid; the effect of carbonization temperature and re-immersion treatment on the pore structure and characteristics of the hollow spherical carbon foam was investigated. As the carbonization temperature increased, the porosity and average pore diameter were found to decrease but the compression strength and electrical conductivity dramatically increased in the temperature range of this study ($700^{\circ}C$ to $850^{\circ}C$). The significant differences of X-ray diffraction patterns obtained from the carbon foams carbonized under different temperatures implied that the degree of crystallinity greatly affects the characteristics of the carbon form. Also, the number of re-impregnations of carbon form in the resorcinol-formaldehyde resin was varied from 1 to 10 times, followed by re-carbonization at $800^{\circ}C$ for 2 hours under argon gas flow. As the number of re-immersion treatments increased, the porosity decreased while the compression strength improved by about four times when re-impregnation was repeated 10 times. These results imply the possibility of customizing the characteristics of carbon foam by controlling the carbonization and re-immersion conditions.