FDTD Method in the Analysis of Lithium Niobate Modulator

The Mach-Zehnder traveling-wave lithium niobate modulator is simulated by time domain finite difference (FDTD)method for different device geometry. The result is comparable to the reported value by finite element method.     

Smoothing minimally supported frequency wavelets: Part II

The main purpose of this paper is to give a procedure to “mollify” the low-pass filters of a large number ofMinimally Supported Frequency (MSF) wavelets so that the smoother functions obtained in this way are also low-pass filters for an MRA. Hence, we are able to approximate (in the L ² -norm) MSF wavelets by wavelets with any desired degree of smoothness on the Fourier transform side. Although the MSF wavelets we consider are bandlimited, this may not be true for their smooth approximations. This phenomena is related to the invariant cycles under the transformation x ↦2x (mod2π). We also give a characterization of all low-pass filters for MSF wavelets. Throughout the paper new and interesting examples of wavelets are described.     

Electronic structures and nonlinear optical properties of trinuclear transition metal clusters M-(mu-S)-M' (M = Mo,W; M' = Cu,Ag, Au)

A series of trinuclear metal clusters MS4(M'PPh3)2(M'PPh3) (M = Mo, W; M' = Cu, Ag, Au) have been studied using the density functional theory (DFT) method. The static polarizabilities and hyperpolarizabilities of the model clusters have been calculated using the finite-field (F-F) method. The model clusters, divided into two groups, are alike in the structure of two fragments of rhombic units M-(mu-S)2-M' (M = Mo, W; M' = Cu, Ag, Au), perpendicular to each other, which are joined by sharing the bridge metal M. It is the charge transfer from one of these moieties to the other in these characteristic sulfido-transitional metal cores that is responsible for the polarizabilities and hyperpolarizabilities. This kind of electronic delocalization, different from that of the planar pi-system, is interesting and warrants further investigation. The structural effects on properties are important. In these models, considerable third-order nonlinearities are exhibited. The element substitution effect of Mo and W is weak, while that of Cu and Ag is relatively substantial. An overall order is gamma xxxx(Mo-Ag) > gamma xxxx(W-Ag) > gamma xxxx(Mo-Au) > gamma xxxx(W-Au) > gamma xxxx (Mo-Cu) > gamma xxxx(W-Cu) and gamma av(Mo-Ag) approximately gamma av(W-Ag) > gamma av(Mo-Au) approximately gamma av(W-Au) approximately gamma av (Mo-Cu) approximately gamma av(W-Cu).     

A novel thin-layer chromatography-based method for Brazilin quantification

JPC – Journal of Planar Chromatography – Modern TLC - Brazilin, a constituent of the Chinese medicine heartwood, exhibits pronounced anti-tumor effects. To date, brazilin quantification...     

Improvement on peak-to-trough ratio of sampled fiber Bragg gratings with multiple phase shifts

Via a cascaded structure, the peak-to-trough ratio is considerably improved for sampled fiber Bragg gratings （SFBGs） based on multiple-phase-shift （MPS） technique. This cascaded filter is composed of two identical SFBGs which are inserted with the increasing or decreasing arrangement of phase shifts. With this inverse arrangement of MPS in grating design, the phase fluctuation of individual SFBG can be compensated, and as a result an excellent phase matching condition is realized. In this way, the peak-to- trough ratio in reflection spectra is improved from 6 to 12 dB when multiplication factor m = 4, and from 5dBto 10dBwhenm=8.     

超耐候乳胶漆的研究

以常用工艺制备乳胶漆，严格按照国标GB／T9755～2001《合成树脂乳液外墙涂料》，测试了乳胶漆的耐水性、耐碱性、耐擦洗性和耐候性，研究了不同类型乳液、不同颜料体积分数（PVC）、不同粉体对乳胶漆的影响。结果表明，使用硅丙乳液、PVC为0．49％且颜料为金红石型钛白粉时，乳胶漆的耐候性最好。     

Inhibition effect of pomelo peel extract for N80 steel in 3.5% NaCl saturated with CO2 solution

Research on Chemical Intermediates - Pomelo peel extract (PPE) has been evaluated as a corrosion inhibitor for N80 steel in 3.5% NaCl saturated with CO2 solution using weight loss measurements,...     

Non-ionic, thermo-responsive DEA/DMA nanogels: synthesis, characterization, and use for DNA separations by microchip electrophoresis

While organically bridged alkoxysilane precursors such as bis(triethoxysilyl)ethane (BTESE) find increasing use in materials synthesis, their polymerization still has not been subject to detailed kinetic investigations. One factor complicating the measurement and interpretation of the behavior of these monomers is their tendency to aggregate during polymerization into small clusters or particles. Here, the phase behavior and kinetics of BTESE during polymerization in acidic water-ethanol solutions are investigated in situ using (29)Si NMR spectroscopy. Based on macroscopic observation of the colloidal stability of the reacting solutions, a ternary pseudo-phase diagram is constructed and solutions that seem from a macroscopic point of view to be favorable for kinetic investigation are probed in situ using (29)Si NMR. However, even when the solutions remain optically clear, the polymerization mixtures are sometimes prone to gradual loss of NMR signal. The rate of signal loss is found to be dependent on the initial composition as well as the pH of the reacting mixtures. We speculate that this phenomenon is caused by microphase separation of reaction intermediates formed early in the polymerization process. This phenomenon is likely to affect the formation and distribution of oligomers in the solution that eventually react together to form a material.