• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.563-566
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• 2000

Sampling rate conversion widely used in subband coding, A/D and D/A transitions etc. is an important techniques Nyquist filters and the filter banks have been used for the sampling converter. However, they need many memories and, whenever the sampling rate is changed, it is necessary to design filters. So the objective of this paper is to present a new kernel that is quick to evaluate and has a good stopband performance.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.925-928
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• 1993

In this paper the caracteristics of the fuzzy flip-flop which was proposed as a fuzzy sequential circuit is firstly mentioned. Secondly the circuit construction of typical fuzzy flip-flip circuits using VHDL (Very high speed integrated circuit Hardware Description Language) compiler and simulator is presented. Finally the possibility of the application of the fuzzy sequential circuit will be mentioned.

• Bulletin of the Korean Mathematical Society
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• v.53 no.2
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• pp.615-640
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• 2016

We consider the fourth-order $Schr{\ddot{o}}dinger$ equation with focusing inhomogeneous nonlinearity ($-{\mid}x{\mid}^{-2}{\mid}u{\mid}^{\frac{4}{n}}u$) in high space dimensions. Extending Glassey's virial argument, we show the finite time blowup of solutions when the energy is negative.

• Composites Research
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• v.33 no.5
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• pp.268-274
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• 2020

This paper analyzed the degradation behaviors of silica nano epoxy composite based on the isoconversional method. The size of the silica nano particle was about 12 nm and the particles were mixed by three different weight ratios to make the degradation test samples. The thermogravimetric analyses were performed under six different temperature increase rates to measure the weight changes. Four different methods, Friedman, Flynn-Wall-Ozawa, Kissinger and DAEM (Distributed Activation Energy Method), were employed to calculate the activation energies depending on the conversion ratios, and their calculation results were compared. The results represented that the activation energy was increased when the silica nano particles were mixed up to 10%, indicating the definite contribution of the particles to the degradation behavior enhancements. However, the enhancement was not proportional to the particle mixture ratio by demonstrating the similar activation energies between 10% and 18% samples. The calculation results by the different methods were also compared and discussed.

• Polymer(Korea)
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• v.27 no.3
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• pp.176-182
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• 2003

The fluorine-containing epoxy resin, 2-trifluorotoluene diglycidylether (FER) was prepared by reaction of 2-chloro-${\alpha}$,${\alpha}$,${\alpha}$-trifluorotoluene with glycerol diglycidylether in the presence of pyridine catalyst. Curing behavior of FER/DDM system was investigated using dynamic and isothermal DSC. Cure activation energy (Ea) was determined by Flynn-Wall-Ozawa's equation. The rheological properties of FER/DDM system were studied under isothermal condition using a rheometer. Cross-linking activation energy (Ec) was determined from the Arrhenius equation based on gel time and curing temperature. As a result, the chemical structure of FER was confirmed by FT-IR, $\^$13/C NMR, and $\^$19/F NMR spectroscopy. The cure activation energy of FER/DDM system was 55.4 kJ/mol and conversion and conversion rate were increased with the curing temperature. The cross-linking activation energy of FER/DDM system was 41.6 kJ/mol and gel time was decreased with the curing temperature.

• Elastomers and Composites
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• v.35 no.4
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• pp.272-280
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• 2000

The experimental kinetics was analyzed for commercial rubbers such as NR, IR, BR, SBR 1500, and SBR 1700. Kinetic analysis for the commercial rubbers was performed using a thermogravimetric method, which the activation energies of NR obtained by Kissinger, Friedman, ana Ozawa's method were 195.0, 198.3, and 186.3 kJ/mol, respectively. whereas that of SBR 1500 were 246.4, 247.5, and 254.8 kJ/mol, respectively. It was shown that the yield of pyrolytic oil was generally increased with increasing the final temperature. Considering the effect of heating rate. it was found that the yield of pyrolytic oil was not consistent for each sample. The number average molecular weight of pyrolitic oil of SBR 1500 was in the range of 740-2486. The calorific value of SBR 1500 was 39-40 kJ/g, and it might be a considerable energy potential although it was lower than the conventional fuel such as kerosene, diesel, light fuel, and heavy fuel.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.548-556
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• 1999

The thermal degradation of polyethylene has been studied using a nonisothermal thermogravimetric technique under a nitrogen atmosphere condition at several heating rates from 10 to $50^{\circ}C/min$. To obtain information on the kinetic parameters, the dynamic thermogravimetric analysis curve and its derivative have been analyzed by a variety of analytical methods such as Kissinger, Freeman-Carroll, Flynn-Wall, Coats-Redfern, Chatterjee-Conrad, Friedman, Horowitz-Metzger, Ozawa and Denq methods. The comparative works for the kinetic results obtained from various methods should be performed to determine the kinetic parameters, because three are tremendous differences in the calculated kinetic parameters depending upon the mathematical method taken in the analysis. From this work, it was found that the apparent activation energy of HDPE was larger than those of LDPE and LLDPE.

• Polymer(Korea)
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• v.27 no.1
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• pp.33-39
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• 2003

In this study, the bisphenol-based DGEBA/GEBS blend systems were studied in cure kinetics, thermal stabilities, and fracture toughness of the casting specimen. The content of DGEBA/DCEBS was varied in 100 : 0, 90 : 10, 80 : 20, 70 : 30, and 60 : 40 wt%. The cure activation energies ($E_a$) of the blend systems were determined by Ozawa's equation. The thermal stabilities, including initial decomposed temperature (IDT), temperatures of maximum rate of degradation ($T_{max}$), and integral procedural decomposition temperature (IPDT) of the cured specimen were investigated by thermogravimetric analysis (TGA). For the mechanical interfacial properties of the specimens, the critical stress intensity factor ($K_{IC}$) test was performed and their fractured surfaces were examined by using a scanning electron microscope (SEM). As a result, $E_a$, IPDT, and $K_{IC}$ show maximum values in the 20 wt% DGEBS content compared with the neat DGEBA resins. This was probably due to the fact that the elevated networks were farmed by the introduction of sulfonyl groups of the DCEBS resin.

• Elastomers and Composites
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• v.49 no.2
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• pp.144-148
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• 2014

Compression set (CS) and weight loss by thermal degradation of the ACM rubber composite sample prepared for an automotive part were measured simultaneously at several given temperatures of $150^{\circ}C$, $160^{\circ}C$, $170^{\circ}C$, and $180^{\circ}C$. Using the relationship between them, thermal life of the sample could be predicted at a given operating temperature by applying Toops method which is based on the analysis of non-isothermal TGA thermograms. Conversion by weight loss showed a linear relationship with CS changes, exhibiting 4.2% at CS 40%. Activation energy of thermal degradation was calculated as 120.2 kJ/mol at 4.2% of weight loss from Flynn-Wall-Ozawa analysis. When the expected life was set as time to reach CS 40% at $120^{\circ}C$, the life time of the sample was calculated as 9,700 hrs when Toops method was applied.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.178-185
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• 2019

Three spherical quaternary composites composed of metal/metal oxide/high explosive/oxidizer were prepared by a crystallization/agglomeration process. From the characteristics of composites by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the shortening of the decomposition zone of high explosives in the quaternary composite was observed, which may be attributed to the autocatalytic reaction caused by $ClO_2$ or HCl which are ammonium perchlorate (AP) degradation products. The activation energy analysis showed that the activation energy abruptly decreases at the end of the decomposition zone of high explosives, and it was considered to be caused by $HNO_2$ which is common in decomposition products of high explosives. The activation energy predicted from complex pyrolysis results by the distributed activation energy model (DAEM) showed much better in accuracy than those by model-fitting methods such as Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa models.