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81.
OSCILLATION THEOREMS FOR A CLASS OF SECOND ORDER NEUTRAL DIFFERENTIAL EQUATIONS OF EMDEN-FOWLER TYPE
Some oscillation theorems are established by the averaging technique for a class of second order neutral differential equations of Emden-Fowler type. Our results essentially improve some known results in the previous literature. 相似文献
82.
本文引入了两类具有六个同构块的苯系异构物,每类包含八个本质不同的异物构物,我们能够依据于它们所含克勒结构数目对这八个异构物勒结构数目对这八个异构物进行全序比较。 相似文献
83.
本文通过将高阶非线性自治微分方程转化为Lurie型控制系统的方法,借助于Popov的频率判据,得到了它们全局渐近稳定的判别准则,推广了文[1]的结果. 相似文献
84.
M.D. Gil García F. Cañada Cañada M.J. Culzoni L. Vera-Candioti G.G. Siano H.C. Goicoechea M. Martínez Galera 《Journal of chromatography. A》2009,1216(29):5489-5496
An analytical method for the simultaneous determination of seven non-steroidal anti-inflammatory drugs (naproxen, ketoprofen, diclofenac, piroxicam, indomethacin, sulindac and diflunisal) and the anticonvulsant carbamazepine in river and wastewater is reported. The method involves pre-concentration and clean-up by solid-phase microextraction using polydimethylsiloxane/divinylbenzene fibers, followed by liquid chromatography with diode array detection analysis. Owing to the fact that river water samples did not contain interferences and no sensitivity changes due to sample matrix were observed, external calibration was implemented. Standardization was also applied in order to carry out the prediction step by preparing only two diluted standards that were subjected to the pre-concentration step and a set of standards prepared in solvent. For the analysis of wastewater samples, in contrast, it was necessary to implement standard addition calibration in combination with the multivariate curve resolution-alternating least squares (MCR-ALS) algorithm, which allowed us to overcome matrix effect and exploit the second order advantage. Recoveries ranging from 72% to 125% for all pharmaceuticals proved the accuracy of the proposed method in river water samples. On the other hand, wastewater sample recoveries ranged from 83% to 140% for all pharmaceuticals, showing an acceptable performance – considering this sample contains no modeled interferences. 相似文献
85.
86.
Ziauddin Ahmed Carsten Müller Jaya J. Johnston Kevin Nguyen Christopher P. J. Schubert Karina Abitaev 《Liquid crystals》2019,46(6):896-904
We investigate the origins of ‘de Vries-like’ liquid crystalline behaviour by introducing an ethynyl spacer in the core of the tricarbosilane-terminated 5-phenylpyrimidine mesogens QL16-6 and QL17-6. The rationale for this structural change is based on the assumption that an ethynyl spacer would create more free volume in the core sub-layer and therefore decrease the orientational order parameter S2 in the SmA phase. The tricarbosilane-terminated mesogens WL41-5 and WL42-6 with a 5-(phenylethynyl)pyrimidine core in either a normal or inverted orientation were synthesised, and their mesomorphic and ‘de Vries-like’ properties characterised using polarised optical microscopy, differential scanning calorimetry, birefringence measurements, small–angle (SAXS) and 2D X-ray scattering. Reduction factors R derived from SAXS and optical tilt angle measurements suggest that neither WL41-5 (R = 0.49) nor WL42-6 (R = 0.80) exhibit ‘de Vries-like’ properties. The S2(T) profiles show an increase in orientational order with decreasing temperature and a sharp discontinuity at the SmA-SmC transition, which is consistent with ‘de Vries-like’ behaviour. However, the Leff(T) profiles suggest an increase in interdigitation that reduces the positive effect of increasing S2 in compensating for the molecular tilt. 相似文献
87.
Jieni Li Henan Li Lai Liu Huizhen Yao Bingbing Tian Chenliang Su Haizhe Zhong Ye Wang Lifu Zhang Yumeng Shi 《化学:亚洲杂志》2019,14(16):2861-2868
Organometallic halide perovskites have attracted great research interest as light‐active materials for use in optoelectronics. Here, we report a high‐performance photoconductor based on a methylammonium lead iodide (MAPbI3) film that was prepared from a methylamine‐treated MAPbI3/PbI2 perovskite film. An ultrahigh responsivity of 3.6 A W?1 and detectivity of 5.4×1012 Jones were obtained for the film under 0.5 mW cm?2 white‐light illumination. In addition, under 420 nm light irradiation, the film exhibited its highest responsivity and detectivity of 30 A W?1 and 2.4×1014 Jones, respectively. The excellent photo‐response performance results from the improved electronic quality and suppressed nonradiative recombination channels of the treated perovskite thin film. 相似文献
88.
Jin‐Yun Wang Chen‐Sheng Lin Min‐Yi Zhang Guo‐Liang Chai Wen‐Dan Cheng 《International journal of quantum chemistry》2012,112(3):759-769
Geometrical structures of the investigated endohedral metallofullerenes Sc3N@C2n (2n = 68, 70, 78, and 80) were optimized at the B3LYP/6‐31G* level. The analyses of electronic structures display that the contribution of fullerene cage to the lowest unoccupied molecular orbital decreases as the cage size increases. Based on the optimized structures, the time‐dependent density functional theory combined with the sum‐over‐states method was used to investigate their nonlinear optical properties. Calculated third‐order polarizabilities γ and two‐photon absorption (TPA) cross‐section δ do not present the monotone variation with the size of fullerene cage, with largest γ of 0.48 × 10?34 esu for Sc3N@C78 in static state, and largest δ of 12.374 GM for Sc3N@C70 in the wavelength of 902.5 nm. However, the obtained TPA resonant peaks shift red with the size of fullerene cage. By analyzing the electronic origin of the third‐order optical properties, it is found that the charge transfers from the fullerene cage to the encapsulated Sc3N cluster make important contributions to the studied properties. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
89.
气固相法合成的Ti-ZSM-5催化剂上苯乙烯氧化反应的宏观动力学 总被引:1,自引:0,他引:1
采用TiCl4气固相同晶取代法制得的Ti-ZSM-5作催化剂,对H2O2氧化苯乙烯反应的宏观动力学进行了研究,考察了催化剂、苯乙烯和H2O2用量及反应温度对苯乙烯氧化反应速率的影响.结果表明,催化剂Ti-ZSM-5和底物苯乙烯对苯乙烯氧化反应速率的贡献均为一级,而H2O2为1/2级;苯乙烯氧化反应的表观活化能Ea=48.14kJ/mol.当以丙酮为溶剂,在n(PhCH∶CH2)/n(H2O2)=7.91,催化剂用量为20g/L,反应温度为343K的条件下,反应360min时,苯乙醛选择性和H2O2利用率分别可达91.9%和88.6%. 相似文献
90.
统计质量保证技术在分析测试实验室内部质量控制中的应用 总被引:5,自引:1,他引:5
对通过统计质量保证(SQA)技术进行分析测试实验室内部质量控制(IQC)的方法作了初探。研究结果表明,SQA技术的应用能保证实验室始终处于统计受控状态,确保测试数据的有效性,有利于分析测试实验室质量保证活动的开展。 相似文献