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991.
Ching Hsuan Lin Chu Nan Hsiao Chun Hung Li Chun Shan Wang 《Journal of polymer science. Part A, Polymer chemistry》2004,42(16):3986-3995
A 2,6‐dimethylphenol‐dipentene dicyanate ester ( DPCY ) was synthesized from the reaction of 2,6‐dimethylphenol‐dipentene adduct and cyanogen bromide. The proposed structure was confirmed by Fourier transform infrared (FTIR), elemental analysis, mass, and nuclear magnetic resonance (NMR) spectra. DPCY was then cured by itself or cured with bisphenol A dicyanate ester ( BADCY ). Thermal properties of cured epoxy resins were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric analysis (DEA), and thermogravimetric analysis (TGA). These data are compared with those of BADCY . The cured DPCY exhibits a lower dielectric constant (2.61 at 1 MHz), dissipation factor (29.3 mU at 1 MHz), thermal stability (5% degradation temperature and char yield are 429 °C and 17.64%, respectively), glass transition temperature (246 °C by TMA and 258 °C by DMA), coefficient of thermal expansion (33.6 ppm before Tg and 134.1 ppm after Tg), and moisture absorption (0.95% at 48 h) than those of BADCY , but higher moduli (5.12 GPa at 150 °C and 4.60 GPa at 150 °C) than those of the bisphenol A system. The properties of cured cocyanate esters lie between cured BADCY and DPCY , except for moduli. Moduli of some cocyanate esters are even higher than those of cured BADCY and DPCY . A positive deviation from the Fox equation was observed for cocyanate esters. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3986–3995, 2004 相似文献
992.
The core-modified 5,20-phenyl-10,15-tolyl-thia-p-benziporphyrin (SBzP) can be prepared from the condensation of 1,4-bis(α-hydroxyl-benzyl)benzene with 5,10-ditolyl-16-thia-5,10,15,17-tetrahydrotripyrrin using BF3·OEt2 as catalyst. Spectroscopic studies suggest an aromatic macrocycle with a rapid flipping phenylene ring. SBzP exhibits a tilted phenylene ring and crystal packing shows dimeric structure with two SBzP rings linked by hydrogen bonding and π-π interaction. TFA acidified SBzPH22+ has a saddle-shaped dication porphyrin ring with two solvated trifluoroacetate and two solvated trifluoroacetic acid linked by hydrogen bondings. 相似文献
993.
Albert Y. C. Hung 《Journal of Polymer Science.Polymer Physics》2003,41(7):679-686
The effect of the repeated unit length on the substantially increasing molecular motion and entropy change (?TΔSm) of polymer blends was investigated with solid‐state 13C NMR and differential scanning calorimetry within a miscible window. The hydrogen‐bonding strength, from the formation of the phenolic–polyester interaction, was not high enough to overcome the breaking‐off of the self‐association of the phenolic. With respect to the increasing repeated unit length, the polyester resonance intensity of the solid‐state 13C NMR spectra was weakened because of the reduction in the cross‐polarization efficiency in highly mobile samples. The glass‐transition temperature of the blend and the proton spin–lattice relaxation time from NMR experiments were also reduced. The effect of the reduced hydrogen‐bonding strength on blending brought about a tendency of higher entropy (?TΔSm) and higher molecular mobility of the blend. Accordingly, poly(decamethylene adipate) possessed the longest repeated unit length and exhibited the most mobile one in this phenolic/polyester blend family. The molecular segmental motion and entropy progressively increased while the repeated unit length of the guest polymers increased within a miscible window. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 679–686, 2003 相似文献
994.
Zhengchun Xu Yueguang Jiao Shien-Kuei Liaw Fu-Chun Hung TAO Qin Hanyi Zhang Yili Guo Xiaoping Zheng 《光学学报》2003,23(Z1)
Two array waveguide grating (AWGs) based fiber ring lasers are experimentally demonstrated. Either of them achieves wavelength discrete tuning of 32 nm, or yields simultaneously lasing up to four channels with -7 dBm output power for each channel. 相似文献
995.
Jih‐Jung Chen Chang‐Yih Duh Hung‐Yi Huang Ih‐Sheng Chen 《Helvetica chimica acta》2003,86(6):2058-2064
A new pyridone alkaloid, 5,6‐dihydro‐5‐hydroxy‐1H‐pyridin‐2‐one ( 1 ), and a new ester, sintenin (=3‐(3,4‐dimethoxyphenyl)propyl 3‐(3,4‐dimethoxyphenyl)propanoate 2 ), together with three known compounds, 5,6‐dihydro‐1H‐pyridin‐2‐one ( 3 ), d‐sesamin (=5,5′‐(3a,4,6,6a‐tetrahydro‐1H,3H‐furo[3,4‐c]furan‐1,4‐diyl)bis[1,3‐benzodioxole]; 4 ), and (E)‐phytol (=3,7,11,15‐tetramethylhexadec‐2‐en‐1‐ol; 5 ) have been isolated from the whole plant of Piper sintenense. The structures of the two new compounds were determined through spectral analyses. Among twenty isolates obtained so far, four compounds exhibited effective cytotoxicities against P‐388, HT‐29, or A549 cell lines in vitro. 相似文献
996.
997.
This paper considers the partitioning of all transportation problem instances into a finite number of equivalent classes. Combinatoric properties of each class, in both primal and dual spaces, are investigated. The problem instances are partitioned into convex regions by degeneracy hyperplanes. Properties of adjacent regions are fully developed. It turns out that adjacency relations are much more complex in the primal space than in the dual space. Finally, algorithms based on the simplex method are classified according to how they behave in each class. 相似文献
998.
Hsu CH Hung SC Wu CY Wong CH 《Angewandte Chemie (International ed. in English)》2011,50(50):11872-11923
Carbohydrates have been shown to play important roles in biological processes. The pace of development in carbohydrate research is, however, relatively slow due to the problems associated with the complexity of carbohydrate structures and the lack of general synthetic methods and tools available for the study of this class of biomolecules. Recent advances in synthesis have demonstrated that many of these problems can be circumvented. In this Review, we describe the methods developed to tackle the problems of carbohydrate-mediated biological processes, with particular focus on the issue related to the development of the automated synthesis of oligosaccharides. Further applications of carbohydrate microarrays and vaccines to human diseases are also highlighted. 相似文献
999.
Dual optical sensor for oxygen and temperature based on the combination of time domain and frequency domain techniques 总被引:1,自引:0,他引:1
In measuring specific conditions in the real world, there are many situations where both the oxygen concentration and the temperature have to be determined simultaneously. Here we describe a dual optical sensor for oxygen and temperature that can be adapted for different applications. The measurement principle of this sensor is based on the luminescence decay times of the oxygen-sensitive ruthenium complex tris-4,7-diphenyl-1,10-phenanthroline ruthenium(III) [Rudpp] and the temperature-sensitive europium complex tris(dibenzoylmethane) mono(5-amino-1,10-phenanthroline)europium(III) [Eudatp]. The excitation and emission spectra of the two luminophores overlap significantly and cannot be discriminated in the conventional way using band pass filters or other optical components. However, by applying both the frequency and time domain techniques, we can separate the signals from the individual decay time of the complexes. The europium complex is entrapped in a poly(methyl methacrylate) (PMMA) layer and the ruthenium complex is physically adsorbed on silica gel and incorporated in a silicone layer. The two layers are attached to each other by a double sided silicone based tape. The europium sensing film was found to be temperature-sensitive between 10 and 70 °C and the ruthenium oxygen-sensitive layer can reliably measure between 0 and 21% oxygen. 相似文献
1000.
Wen-Liang Hung Miin-Shen Yang E. Stanley Lee 《Mathematical and Computer Modelling》2011,53(9-10):1776-1787
Cellular manufacturing is a useful way to improve overall manufacturing performance. Group technology is used to increase the productivity for manufacturing high quality products and improving the flexibility of manufacturing systems. Cell formation is an important step in group technology. It is used in designing good cellular manufacturing systems. The key step in designing any cellular manufacturing system is the identification of part families and machine groups for the creation of cells that uses the similarities between parts in relation to the machines in their manufacture. There are two basic procedures for cell formation in group technology. One is part-family formation and the other is machine–cell formation. In this paper, we apply a fuzzy relational data clustering algorithm to form part families and machine groups. A real data study shows that the proposed approach performs well based on the grouping efficiency proposed by Chandrasekharan and Rajagopalan. 相似文献