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91.
M.H. YEOW.K. LEE 《Journal of sound and vibration》2002,257(4):653-665
An investigation into non-linear asymmetric vibrations of a clamped circular plate under a harmonic excitation is made. We re-examined a primary resonance studied by Sridhar, Mook and Nayfeh, in which the frequency of excitation is near the natural frequency of an asymmetric mode of the plate. We corrected their solvability conditions and found that in the absence of internal resonance, the steady state response can have not only the form of standing wave but also the form of travelling wave, which is a remarkable contrast to their conclusion. 相似文献
92.
CHAOTIC DYNAMICS OF REPEATED IMPACTS IN VIBRATORY BOWL FEEDERS 总被引:2,自引:0,他引:2
I. HANY. LEE 《Journal of sound and vibration》2002,249(3):529-541
The vibratory bowl feeder is widely used to convey small engineering parts, and can be considered as a typical non-linear dynamic system experiencing repeated impacts with friction. This paper presents a simplified model and analysis for the dynamic behavior of a single part on the vibrating track of the bowl feeder. While the previous studies are restricted to the sliding regime, the presented analysis is focused on the hopping regime where the high conveying rate is available. The periodic and chaotic regions in the hopping regime are identified through numerical simulation and experimental analysis. It is verified experimentally that the conveying rate in the chaotic region is roughly independent of variations of external parameters. The dynamic effects from the variation of several physical parameters are examined and the important features for the effective design of the vibratory feeder are presented. This research holds much potential for leverage over design problems of a wide range of mechanisms and tools with repeated collisions. 相似文献
93.
LEE BADGER 《Natural Resource Modeling》2003,16(1):1-19
ABSTRACT. A global model of population‐resource interaction is proposed consisting of two first order ordinary differential equations. In it the population growth rate increases due to increasing technology, then declines due to declining resources. When the model is fit to twentieth century data it predicts that global population will peak and then decline while already declining global resources bottom out; both will eventually stabilize slightly above their lows. Because of the uncertainty of model parameters and resource data, the values and times of these peaks and lows are uncertain, but the qualitative behavior of the model transcends this uncertainty. Actual best‐fit values of population include a peak of nearly nine billion about year 2050 and a peak rate of decline of 0.3% about year 2100. Global resources bottom out at 70% of optimum around year 2100. Variability and sensitivity analyses are also provided. 相似文献
94.
95.
癌症严重威胁着人类健康, 因此, 急需开发高效的诊断和治疗方法. 基于光敏剂和近红外激光的光学诊疗将诊断和治疗集于一体, 与传统的手术治疗和化学治疗相比, 光学诊疗显示出无创性和高空间选择性的优点. 有机小分子染料具有确定且易于修饰的化学结构、 良好的重现性和优异的生物相容性, 与无机和聚合物材料相比, 它是一类具有前景的可用于光学诊疗的光敏剂. 本文总结了基于传统小分子染料、 给体-受体(D-A)共轭小分子和聚集诱导发光(AIE)分子等有机小分子的纳米粒子在光学诊疗中的应用. 此外, 对于光学诊疗用有机小分子染料纳米粒子未来的挑战和前景也进行了展望. 相似文献
96.
建立了一种可同时测定锂离子电池电解液中13种有机磷阻燃剂含量的气相色谱-串联质谱分析方法,以乙酸乙酯为萃取溶剂,超声萃取锂离子电池电解液中的有机磷阻燃剂,萃取液经浓缩、定容、过滤后进行气相色谱-串联质谱分析,外标法定量。结果显示,13种有机磷阻燃剂在一定浓度范围内线性良好,相关系数不低于0.999 3,方法的检出限(S/N=3)为0.3~30μg/kg,定量下限(S/N=10)为1~100μg/kg。在低、中、高3个加标水平下的平均回收率为80.4%~94.6%,相对标准偏差(RSD)为3.8%~10%。该方法简单快捷,灵敏度高,定量下限低,可满足锂离子电池电解液中有机磷阻燃剂含量日常检测需要。 相似文献
97.
We present and demonstrate a polarization-insensitive mechanically induced long-period fiber grating (MLPG) for EDFA gain flattening. By forming a 90° fiber rotator in the middle of the MLPG the PDL of the MLPG was substantially reduced. The PDL-compensated MLPG was able to flatten the ASE spectrum of an EDFA successfully without deterioration of the polarization characteristics. 相似文献
98.
DE-CHAO WANG FOO-TIM CHAU EDMOND P. F. LEE ALEXANDER KAI-MAN LEUNG JOHN M. DYKE 《Molecular physics》2013,111(6):995-1005
Geometry optimization and harmonic vibrational frequency calculations at the CASSCF, MP2 and CCSD(T) levels with basis sets up to 6-311G(2df) quality were carried out on the X1Σ+states of FCN and ClCN and the X2Π and A2Σ+ states of their cations. Adiabatic ionization energies were calculated up to the CCSD(T)/6-311G(3df)//CCSD(T)/6-311G(2d) level. Some B3LYP calculations were performed also for the ground states of the neutral molecules and the cations. Franck-Condon simulations were performed for the first two bands in the He I photoelectron spectra of FCN and ClCN by employing the ab initio computed geometries and frequencies. By comparing the observed and the simulated spectra obtained from different CN and CX (X = F or Cl) ionic bond lengths chosen on the basis of the ab initio computed values, the following structural parameters are obtained for the two lowest-lying states of FCN+ and ClCN+ (the method of deriving the uncertainties is described): 相似文献
99.
B. HRIBAR LEE V. VLACHY L. B. BHUIYAN C. W. OUTHWAITE M. MOLERO 《Molecular physics》2013,111(19):2969-2980
Monte Carlo simulation and theoretical results on some aspects of thermodynamics of mixtures of electrolytes with a common species are presented. Both charge symmetric mixtures, where ions differ only in size, and charge asymmetric but size symmetric mixtures at ionic strength ranging generally from I = 10?4 to 1.0 M, and in a few cases up to I = 2 M, are examined. The theoretical methods explored are: (i) the symmetric Poisson-Boltzmann theory, (ii) the modified Poisson-Boltzmann theory and (iii) the hypernetted-chain integral equation. The first two electrolyte mixing coefficients w 0 and w 1 of the various mixtures are calculated from an accurate determination of their osmotic pressure data. The theories are seen to be consistent among themselves, and with certain limiting laws in the literature, in predicting the trends of the mixing coefficients with respect to ionic strength. Some selected relevant experimental data have been analysed and compared with the theoretical and simulation trends. In addition the mean activity coefficients for a model mimicking the mixture of KC1 and KF electrolytes are calculated and hence the Harned coefficients obtained for this system. These calculations are compared with the experimental data and Monte Carlo results available in the literature. The theoretically predicted Harned coefficients are in good agreement with the simulation results for the model KC1-KF mixture. 相似文献
100.
A new hybrid organic-inorganic monolithic cartridge was synthesized and used as the selective sorbent for the extraction and purification of quercetin and myricetin from Chamaecyparis obtusa via a solid-phase extraction method.The morphology of the monolithic material was examined by field emission-scanning electron microscopy and a Brunauer-Emmett-Teller(BET) test.The adsorption capacity of the obtained material for quercetin and myricetin was investigated by fitting the adsorption data to four different adsorption equations,of which the LangmuirFreundlich isotherm was selected as the most suitable model.Under optimized conditions,good calibration curves were observed at nine concentrations ranged from 0.5 μg/mL to 100.0 μg/mL of quercetin and myricetin.The extraction recovery ranged from 74.5% to 84.6% and the inter-and intra-day relative standard deviations were <6%.This type of hybrid monolith has potential for the separation and purification of bioactive compounds from natural plant extracts. 相似文献