Characterization and estimation of refractive index profile of laser-written photopolymer optical waveguides

In this study, channel waveguides fabricated in photopolymer films by direct-writing using a low-power CW laser, are used as phase objects in a simple plane-wave diffraction setup, and the refractive index modulation profiles of the waveguides are characterized using the recorded diffraction patterns. Index profiles are modeled by piece-wisely combining two Gaussian functions representing the central and the tail regions. Measured diffraction patterns are matched with patterns generated using the model. This simple model makes it possible to design various channel waveguides embedded into polymer substrates. The proposed model is tested on three distinctive waveguide profiles written on the same Acrylamide/Polyvinyl Alcohol based photopolymer with different exposures.     

Asymmetric electrical properties in Pt/Ba0.5Sr0.5Ti0.99Co0.01O3/Nb-doped SrTiO3 capacitors

Ba_0.5Sr_0.5Ti_0.99Co_0.01O₃ (BSTC) thin films have been fabricated with pulsed laser deposition on Nb-doped SrTiO₃ (STN) substrate. In Pt/BSTC/STN capacitor, we systematically investigated the capacitance, leakage current and polarization versus bias voltage characteristics, and found that curves of capacitance versus voltage and leakage current versus voltage were not symmetric, and polarization hysteresis loop exhibited large relaxation of the remnant polarization at negatively poled state. A detailed analysis of capacitance data demonstrated a difference of the built-in voltage between top Pt/BSTC interface (V_b,t=2.5 V) and bottom BSTC/STN interface (V_b,b=1.1 V). Such different built-in voltages lead to the presence of an internal electric field, which results in asymmetric electric characteristics in Pt/BSTC/STN capacitor.     

掺Bi钨酸镉单晶体发光特性的研究

用坩埚下降法(Bridgman)生长出了Bi离子掺杂的CdWO₄单晶.测定了晶体不同部位的吸收光谱、发射光谱和X射线电子能谱(XPS).Bi离子的掺入引起CdWO₄晶体的吸收边从345 nm红移到399 nm.在311 nm, 373 nm,808 nm和980 nm光的激发下,分别观测到中心波长为470 nm,528 nm,1078 nm和较弱的1504 nm四个不同发射带.Bi:CdWO₄单晶的XPS谱分别与Bi₂ 关键词： Bi离子 荧光光谱 X射线电子能谱 4单晶')" href="#">CdWO₄单晶     

内锥式流量计数值模拟及优化设计

多相流过程参数的准确测量在石油化工与冶金工业等工业过程中十分重要。内锥式流量计作为一种新型差压流量计在多相流测量中逐渐受到关注,它能在较短的直管段条件下对流体实现准确的测量,但其结构尚存在优化的空间,需进行深入研究。本文对传统内锥式流量计做结构变形和优化研究,利用计算流体力学(CFD)方法对DN50 mm水平管道中内锥变形体的流场进行数值模拟,分析在不同结构参数下锥体的水力特性以优化结构。数值仿真结果表明,综合内锥式流量计在取压点、永久压损及测量精确度等因素,优化后的结构可以显著降低永久压损,提高测量重复性和精确度。     

Unusual resistive switching induced by voltage in La0.7Sr0.3MnO3 thin films

The hysteretic and reversible resistive-switching effect was observed in La_0.7Sr_0.3MnO₃ films at room temperature. The resistive switching was found to be most obvious in films fabricated at 30 Pa oxygen pressure, and more distinct in films fabricated on SrTiO₃ substrates than those fabricated on LaAlO₃ substrates. Moreover, La_0.7Sr_0.3MnO₃ films fabricated at a certain oxygen pressure with indium electrodes showed double ‘8’ type current-voltage loops. Some of the results are explained by considering the influence of the interface effect, electrodes and oxygen vacancies, but the mechanism of the double ‘8’ type current-voltage loops remains an open question.     

Generalized dressing method for the extended two-dimensional Toda lattice hierarchy and its reductions

In this paper, we solve the extended two-dimensional Toda lattice hierarchy (ex2DTLH) by the generalized dressing method developed in Liu-Lin-Jin-Zeng (2009). General Casoratian determinant solutions for this hierarchy are obtained. In particular, explicit solutions of soliton-type are formulated by using the τ-function in the form of exponential functions. The periodic reduction and one-dimensional reduction of ex2DTLH are studied by finding the constraints. Many reduced systems are shown, including the pe...     

Transmission of 10 GHz, 3.5 ps Optical Pulses Over 100-km Standard Fiber Using Mid-span Spectral Inversion

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大型水电工程物资调运建模及算法

根据小湾水电工程物资供应管理的实际情况,提出了物资调运的三级节点概念模型,论述了物资采购与调运的数学模型,并给出了具体算法。模型已应用于该工程物资调运决策支持系统中,运行实践表明,该模型能够辅助调度人员制定合理的物资采购与调运方案。     

Olefin‐Directed Palladium‐Catalyzed Regio‐ and Stereoselective Oxidative Arylation of Allenes

An olefin‐directed palladium‐catalyzed oxidative regio‐ and stereoselective arylation of allenes to afford 1,3,6‐trienes has been established. A number of functionalized allenes, including 2,3‐ and 3,4‐dienoates and 3,4‐dienol derivatives, have been investigated and found to undergo the olefin‐directed allene arylation. The olefin moiety has been proven to be a crucial element for the arylating transformation.     

Formal Asymmetric Catalytic Thiolation with a Bifunctional Catalyst at a Water–Oil Interface: Synthesis of Benzyl Thiols

The enantioselective conjugated addition of tritylthiol to in situ generated ortho‐quinone methides (o‐QMs) is catalyzed by an acid–base bifunctional squaramide organocatalyst. The transformation proceeds with high yield (up to 99 %) and stereoselectivity (up to 97:3 e.r.) using water as solvent under mild conditions. The catalyst system provides a new strategy for the synthesis of optically active benzyl mercaptans. Control experiments suggested that o‐QMs are generated by the tertiary amine moiety of the squaramide organocatalyst and that the water–oil biphase is crucial for achieving high reactivity and stereoselectivity.