基于OTA和CCCII的电流模式可调谐滤波器

设计了一种新颖的双二阶电流模式通用滤波器结构,该滤波器仅包含有源器件OTA、CCCII和接地电容,电路结构简单,与VLSI工艺兼容,便于集成,可实现同时低通、高通、带通、带阻、全通等滤波功能;Q和ω0可以互相不影响的独立调节。采用PSPICE软件仿真分析了所提电路的性能。

基于偏振、波长和位置复用的多功能全息液晶元件

为了实现大信息容量、多功能的全息显示,本文提出了基于偏振/位置/波长参数进行复用的液晶全息显示器件,并分别对各个参数的复用进行了探索和验证。首先,通过GS算法计算出多个特定衍射条件和目标图像的全息图。接着,利用全息叠加原理将多个全息图进行叠加并得到基于几何相位的复用全息图。最后,基于光控取向技术制作了多个复用液晶器件并对其有效性进行了验证。实验结果表明,通过该方法可以设计显示对应多个偏振、位置和波长全息图像的液晶器件,且基于液晶聚合物和塑料衬底的器件在弯曲时仍可实现清晰的图像显示。此外,提出了波长复用的动态可调全息液晶盒,该器件具有良好的电可调谐能力并在445~638 nm的可见光波段实现了显示图像的开/关状态的切换。得益于全息叠加机制的灵活性和液晶材料的特性,我们的策略为低成本、易设计的多通道全息液晶器件提供了新的视角,设计的基于液晶的复用器件在柔性显示、成像复用和信息存储等方面具有广阔的应用潜力。

基于光敏材料的达曼光栅的制备

图形化取向层通常可用来调制光学性质,如偏振,相位和强度.光取向技术是用于制备图形化取向结构的最有前景的技术之一.通过将图形化光取向技术与向列相液晶相结合,可以制作电可调谐液晶器件.使用向列相液晶E7制作并测试了可调谐达曼光栅(DG),并评估其性能.实验结果表明:对于制备的DG,衍射效率为76.8%,均匀度为0.11.通过在DG加电压(10V),从开启状态到关闭状态的切换时间是70us,从关闭状态返回到开启状态是3.4ms.所设计的DG具有可调谐,低成本,偏振无关,快速可切换的优点.

Identification of Intermediates in Pyridine Pyrolysis with Molecular-beam Mass Spectrometry and Tunable Synchrotron VUV Photoionization

The pyrolysis of pyridine （5.26% pyridine in argon） was performed with tunable synchrotron vacuum ultraviolet photoionization and molecular-beam mass spectrometry technique at the temperature range of 1255-1765 K at 267 Pa. About 20 products and intermediates, containing major species H2, HCN, C2H2, C5H3N, C4H2, and C3H3N, were identified by near-threshold measurements of photoionization mass spectra and their mole fractions vs. temperatures were estimated. The major reaction pathways are analyzed based on the experimental observations.

Tunable Self-assembled Weak Polyelectrolyte Brushes

The authors have investigated the pH and ionic strength response of self-assembled layers formed by adsorption of amphiphilic weak polyelectrolytes. Using the SFA （Surface Forces Apparatus） the authors measured force-distance profiles of poly （isoprene）-poly （acrylic acid） block copolymers adsorbed on mica. Also by Atomic Force Microscopy the authors captured single polyelectrolyte molecule adsorbed on a surface. The effect of salt concentration （Cs） and pH upon the height of the brush layers was explored mainly by measuring the forces between two adsorbed polyelectrolyte brushes. At pH = 4 our results are in good agreement with the scaling prediction L0 ∝Cs-1/3 Changing the pH from 4 to 10 causes a remarkable swelling of the polymer layer, but only a weak dependence on salt concentration was detected at the higher pH. This can be attributed to the degree of dissociation, which depends on the local pH value. At low pH the polyelectrolyte chains have a low charge density, while on increasing the pH the degree of dissociation rises, and the increased charge density is followed by swelling of the adsorbed layer. The local concentration of ions in the brush is now greater than that of pH = 4 and approximately equivalent to 0.3 M. So the swelling is only weakly dependent on salt concentration in the range 0.01-1.0 M. The results demonstrate the tunable nature of such self-assembled polyelectroiyte brushes whose height and range of interactions, can be systematically controlled by adjusting the pH and ionic strength of the medium.

Experimental Study of Premixed Stoichiometric Ethylene/Oxygen/Argon Flame

A comprehensive experimental study of the premixed ethylene/oxygen/argon flame at 2.667 kPa with a stoichiometric equivalence ratio （Ф=1） was performed with the tunable synchrotron photoionization and molecular-beam sampling mass spectrometry techniques. The isomers of most observed species in the flame were unambiguously identified by measurements of the photoionization etticiency spectra, e.g. C3H4, C2H4O and C4H4. The mole fraction profiles of species up to C7H8 were measured by scanning the burner position at the selected photon energies near ionization thresholds, and the flame temperature profile was obtained by using Pt/Pt-13%Rh thermocouple. Compared with the previous studies, a lot of new flame species： C3H2, C3H3, C3H5, C2H6O, C4H2, C4H4, C4H6, C3H4O, C3H6O, C3H8O, C5H6, C4H8O and C7H8, were observed. A series of free radicals in the flame are detected to be CH3, C2H3, C2H5, HCO, C3H3 and C3H5. Based on the experimental work, a reduced reaction mechanism was developed including 40 species and 223 reactions. Modeling and measurements agree well for the major species and most intermediates. A detailed kinetic model is desired for this flame.

Realization of a tunable analog predistorter using parallel combination technique for laser driver applications

This paper describes a new approach for designing analog predistorters that can compensate for the nonlinear distortion of laser drivers in a radio-over-fiber （RoF） system. In contrast to previous works, this paper analyzes the transfer characteristics of CMOS transistors, by combining parallel currents of CMOS transistors in various W/L and negative bias voltages to realize the tunable analog predistortion function. The circuit is fabricated by a standard 0.18txm CMOS technology. The core circuit current consumption is only 15mA and the entire driver circuit works in a band-pass from 1 - 2.2GHz. Experimental results of two-tone tests have shown that with an analog predistortoer the IIP3 of the laser driver circuit has an improvement of 4.91 dB.

NiaSi2O5（OH）4 Multi-Walled Nanotubes with Tunable Magnetic Properties and Their Application as Anode Materials for Lithium Batteries

Highly crystalline and thermally stable pure multi-walled Ni3Si2O5（OH）4 nanotubes with a layered structure have been synthesized in water at a relatively low temperature of 200-210 ℃ using a facile and simple method. The nickel ions between the layers could be reduced in situ to form size-tunable Ni nanocrystals, which endowed these nanotubes with tunable magnetic properties. Additionally, when used as the anode material in a lithium ion battery, the layered structure of the Ni3Si2O5（OH）4 nanotubes provided favorable transport kinetics for lithium ions and the discharge capacity reached 226.7 mA.h.g-1 after 21 cycles at a rate of 20 mA.g-1, Furthermore, after the nanotubes were calcined （600 ℃, 4 h） or reduced （180℃ 10 h）, the corresponding discharge capacities increased to 277.2 mA.h.g-1 and 308.5 mA.h.g-1, respectively.

Tunable synthesis solid or hollow Au-Ag nanostructure, assembled with GO and comparative study of their catalytic properties

In this work, we demonstrated a simple and efficacious two-step method for the synthesis of Ag@Au core-shell nanoparticles （Ag@AuNPs） and the Ag/Au hollow nanocages （Ag/AuNCs） with Ag nanoparticles （AgNPs） as seeds by adjusting pH, and the preparation of hybrid Ag@AuNPs- or Ag/AuNCs-graphene oxide nanocomposites （Ag@AuNPs-GO or Ag/AuNCs-GO） based on the self-assembly. It was noticed from the elec- trostatic assembly experiment that the loading amount of Ag/AuNCs on GO nanosheet was more than that of Ag@AuNPs. The as-synthesized hybrid materials were characterized by transmission electron microscopy, atomic force microscopy, ξ-potential, high-angle annular dark- field scanning transmission electron microscopy, thermo- gravimetric analyzer and X-ray diffraction. Catalytic activities of Ag@AuNPs, Ag/AuNCs and Ag/AuNCs-GO nanostructures were investigated in the reduction of 4-, 3-or 2-nitrophenol to 4-, 3- or 2-aminophenol, and on the basis of comparative kinetic studies the following trend was obtained for the related catalytic activity： Ag/AuNCs- GO 〉 Ag/AuNCs 〉 Ag@AuNPs. These observations were attributed to the simultaneous effects of surface area available for catalytic reaction and composition of the hybrid nanostructures.

Multiferroics and magnetoelectric effects in charge ordered compounds

The coexistence of magnetic ordering and ferroelectricity, ing on the origin of ferroelectricity, multiferroic materials known as multiferroics, has drawn a lot of research effort. Depend can be classified into different groups. In this paper, we review re cent progress in the field of multiferroics induced by different forms of charge ordering. In addition to a general description of charge order and electronic ferroelectricity, we focus on two specific systems： （1） charge order with frustration in RFe2O4 （R=Lu, Yb） system; （2） charge ordered perovskite manganites of the type （R1-xCax）MnO3 （R=La, Pr）. The charge ordering can be tuned by external electric fields, which results in pronounced magnetoelectric effects and strong dielectric tunability. Other materials and possible candidates with charge order induced multiferroics are also briefly summarized.

Enhanced and tunable fluorescent quantum dots within a single crystal of protein

The design and synthesis of bio-nano hybrid materials can not only provide new materials with novel properties, but also advance our fundamental understanding of interactions between biomolecules and their abiotic counterparts. Here, we report a new approach to achieving such a goal by growing CdS quantum dots （QDs） within single crystals of lysozyme protein. This bio-nano hybrid emitted much stronger red fluorescence than its counterpart without the crystal, and such fluorescence properties could be either enhanced or suppressed by the addition of Ag（I） or Hg（II）, respectively. The three-dimensional incorporation of CdS QDs within the lysozyme crystals was revealed by scanning transmission electron microscopy with electron tomography. More importantl~ since our approach did not disrupt the crystalline nature of the lysozyme crystals, the metal and protein interactions were able to be studied by X-ray crystallography, thus providing insight into the role of Cd（II） in the CdS QDs formation.

A simplified tunable frequency interval optical frequency comb generator using a single continuous-wave laser

We propose and demonstrate a simplified and tunable frequency interval optical frequency comb(OFC) generator based on a dual-drive Mach-Zehnder modulator(DD-MZM) using a single continuous-wave(CW) laser and low-power radio frequency(RF) driven signal. A mathematical model for the scheme is established. The 21-and 29-mode OFCs with frequency interval ranging from 6 GHz to 40 GHz are obtained under DD-MZM driven by a low-power RF signal within a maximum bandwidth of 1.12 THz. The generated OFCs exhibit spectral flatnesses of less than 0.5 d B and 0.8 d B within bandwidths of 160 GHz and 400 GHz, respectively.