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991.
992.
Radiation-induced wood-polymer composites have been prepared using some tropical commercial woods. These included Kapur (Dryobalanop sp.), Kempas (Koompassia sp.), Red Seraya (Shorea sp.), White Seraya (Parashorea sp.), and Jelutong (Dyera sp.). The wood specimens were modified by impregnation with monomers and followed by exposure to gamma radiation. Monomer systems used were methyl methacrylate, methyl methacrylate with 5% dioxane, acrylonitrile, 60:40 styrene-acrylonitrile comonomer, vinyl acetate, and vinylidene chloride. The resulting composite specimens exhibited significant increases in hardness and compressive strength, the extent of which appeared to depend on the amount and type of polymer present. Dimensional stability increased when the woods were impregnated with polymethyl methacrylate and improved further to about 35% on addition of a swelling agent, dioxane. Wood-polyvinylidene chloride composites gave high fire resistance as opposed to wood-polymethyl methacrylate which showed increased flammability. A 4-fold decrease in weight loss was observed in the fire-tube and crib tests conducted. The impregnated polymers were not totally resistant to termites. The polymers, not being nutrients, reduced the number of survivals after a 90-d test period. Polystyrene-acrylonitrile appeared toxic to the termites. 相似文献
993.
The novel C2‐symmetric sulfur‐containing chiral bis(oxazoline) compound has been synthesized and characterized by X‐ray crystallography. Highly enantioselective and diastereoselective cyclopropanation reactions have been performed using the copper‐bis(oxazoline) catalyst. 相似文献
994.
A trefoil-shaped liquid crystal containing an aromatic hetero-nucleus has been synthesized by the reaction of cyanuric chloride with 3,6-didecanoyl carbazole (DDC). The molecular structure was characterized by 1H NMR and 13C NMR spectroscopy, mass spectroscopy and elemental analysis. The core consists of 1,3,5-triazine directly linked to three carbazole groups. The trefoil-shaped conformation is suggested by molecular modelling. The mesophase was investigated using DSC, X-ray diffraction and polarizing optical microscopy. The X-ray diffraction pattern of a sample cooled slowly from the isotropic state showed sharp peaks in the small angle and wide angle regions implying the existence of a columnar phase with interand intra-columnar ordering. An unusual reticular texture similar to a cholesteric texture was observed. 相似文献
995.
996.
997.
In this paper, the effect of temporal separation of two Geiger mode avalanche photodiodes and the variation of time bin widths on detection probabilities in LADAR system using two Geiger mode avalanche photodiodes (GmAPDs) was investigated. The system is implemented by using two GmAPDs with a beam splitter and applying comparative process to their ends. Then, the timing circuitry receives the electrical signals only if each GmAPD generates the electrical signals simultaneously. Although this system decreases the energy of a laser-return pulse scattered from the target, it is highly effective in reducing the false alarm probability because of the randomly distributed noise on the time domain. The temporal separation of two GmAPDs and the variation of the time bin widths result in the variation of detection probabilities. The experiments were performed to verify the effect of temporal separation of two GmAPDs and the variation of time bin widths on the detection probability in the LADAR system. As a result, the optimal temporal difference and the optimal time bin width were. Using these optimal values, a clear 3D image could be obtained by the simple acquisition of the raw time-of-flight data with high SNR. 相似文献
998.
Charles Ng Xiangju Kong Dr. Dongxia Wu Dr. Min Song Dr. Xiaohong Shi Xiaochun Xu Wei‐Han OuYang Rongxian He Prof. Xing‐Zhong Zhao Tom Lee Prof. F. Charles Brunicardi Dr. Mitch André Garcia Prof. Antoni Ribas Prof. Roger S. Lo Prof. Hsian‐Rong Tseng 《Angewandte Chemie (International ed. in English)》2013,52(12):3379-3383
999.
1000.
Based on the analysis and the discussion of the influence of thermal ionization energy and various scatterings on magnetoresistance(MR) of p-type diamond films, a revised model of valence band split-off over temperature is put forward, and a corresponding calculation formula is given for the MR of p-type diamond films (Corbino discs). It is shown that the theoretical calculation that the MR of diamond films changes with temperature is consistent with the experiment. The influence of Fermi energy level on MR of diamond films is discussed. Additionally, the thermal effect mechanism of MR in p-type diamond films is also explored. 相似文献