Computer design of a compact cyclotron

Here we present results of the computer design of the structural elements of a compact cyclotron by the example of HITFiL cyclotron selected as the driving accelerator that is under construction at the Institute of Modern Physics (Lanzhou, China). In the article a complex approach to modeling of the compact cyclotron, including calculation of electromagnetic fields of the structural elements and beam dynamics calculations, is described. The existing design data on the axial injection, magnetic, acceleration and extraction systems of the cyclotron are used as a starting point in the simulation. Some of the upgrades of the cyclotron structural elements were proposed, which led to substantial improvement of the beam quality and transmission.     

Tunable self-shifting Bloch modes in anisotropic hexagonal photonic lattices

We study controllable self-shifting Bloch modes in anisotropic hexagonal photonic lattices. The shifting results from a deformed band structure due to deformation of the index distribution in each unit cell. By reconfiguration of the index profile of the unit cell, the direction in which the Bloch modes move can be controlled. Our theoretical predictions are experimentally demonstrated in hexagonal lattices optically induced in an anisotropic nonlinear crystal.     

卷绕式螺旋形薄膜介质脉冲形成线设计

采用模块化结构,设计了一种卷绕式螺旋形薄膜介质脉冲形成线,并且对绝缘材料、电极材料的选择依据进行了分析。基于模块化卷绕式脉冲形成线,研制的重复频率脉冲方波产生器采用4个开关同步触发四级形成线模块,从而实现多模块的电压串联叠加,以达到产生高压的目的。开关采用气体火花间隙开关,每级开关及充放电采用电感隔离。研制的脉冲产生器输出电压220 kV,脉冲宽度182 ns,前沿50 ns,可10 Hz重复频率稳定运行。     

Infrared broadband emission of bismuth–thulium co-doped lanthanum–aluminum–silica glasses

The Bi–Tm co-doped SiO₂–Al₂O₃–La₂O₃ (SAL) glasses, which exhibited a broadband near-infrared (NIR) emission was investigated by the optical absorption and photoluminescence spectra. The super broadband near-infrared emission from 1000 to 2100 nm, which covered the whole O, E, S, C and L bands, was observed in the Bi–Tm co-doped samples, as a result of the overlap of the Bi-related emission band (centered at 1270 nm) and the emission from Tm^{3+ 3}H₄→³F₄ transition (1440 nm) as well as Tm^{3+ 3}F₄→³H₆ transition (1800 nm). Relative luminescence intensity at 1270, 1440 and 1800 nm wavelength varied depending on the mixing ratio of Bi and Tm and the full-width at half-maximum (FWHM) extending from 1000 to 1600 nm could be 400 nm. These results indicated that Bi–Tm co-doped SiO₂–Al₂O₃–La₂O₃ glasses could provide potential applications in tunable lasers as well as the broadband optical amplifiers in WDM system.     

正压流体中具有β效应与地形效应的强迫Rossby孤立波

正压流体中,从有外源的准地转位涡方程出发采用摄动方法和时空伸长变换推导了具有β效应、地形效应和外源的强迫Rossby孤立波方程,得到孤立Rossby波振幅的演变满足带有地形与外源强迫的非齐次 Boussinesq方程的结论. 通过分析孤立Rossby波振幅的演变,指出β效应、地形效应以及外源都是诱导Rossby孤立波产生的重要因素,说明在地形强迫效应和非线性作用相平衡的假定下,Rossby孤立波振幅的演变满足非齐次Boussinesq方程,给出在切变基本气流下地形和正压流体中R     

Size controlled synthesis of semiconductor nanocrystals in a continuous-flow mode microcapillary reactor

A microcapillary reactor with 320 μm inner diameter was utilized for CdSe nanoparticle synthesis. The influence of the reaction temperature and flow rate of precursors on the size and size distribution of prepared CdSe nanoparticles was systematically studied. The as-prepared nanoparticles exhibit sharp excitonic absorption and photoluminescence peak (FWHM 30 nm) with a quantum-yield around 10–40%. The microcapillary reactor was also used for CdSe/ZnS core-shell nanoparticle synthesis in continuous-flow mode. The quantum yield of the core-shell nanoparticles was found to be considerably influenced by the reactor temperature and have a close correlation with the thickness of ZnS shell under growth. An optimized quantum yield up to 70% was obtained for the CdSe/ZnS core-shell nanoparticles.     

小型轻便式流速仪检定系统设计

为满足FP系列流速仪的计量检定需求,提出了一种小型便携式流速仪检定系统的设计方案。根据匀速运动时间等约束条件确定了环形水槽的几何参数。采用FPGA和上位机作为数据处理和控制核心,实现了对伺服电机转速的精确控制。设计了光电编码器和无线摄像机与上位机之间的通信方式,实现了检定装置标准流速值和被检仪器示值的数据读取。对测试数据的处理方法和测控软件的结构框架进行了分析。同时,对实验装置的测量误差进行了分析。结果表明,标准流速值的扩展不确定度为1.28×10-3m/s,检定装置符合量值传递要求,可作为FP系列流速仪计量检定的标准装置。     

矿山多源遥感图像像点位移测试系统设计

针对矿山地形的起伏变化影响对其进行分析研究的准确性,提出矿上多源遥感图像像点位移测试系统的设计方法。结合GPS定位原理,选取遥感图像上某一时刻点作为测试点,对拍摄得到的矿山图像和电子测试系统各触点之间的距离进行计算,进而得到测试点具体坐标位置,将其与测试点真实现场坐标相对比,实现矿山多源遥感图像像点位移的测试。通过实验证明,所设计的测试系统可以高精度实现对遥感图像像点位移的测试,有效减小了矿山地形变化带来的遥感图像研究误差。     

Statistical properties of world investment networks

We have performed a detailed investigation on the world investment networks constructed from the Coordinated Portfolio Investment Survey (CPIS) data of the International Monetary Fund, ranging from 2001 to 2006. The distributions of degrees and node strengths are scale-free. The weight distributions can be well modeled by the Weibull distribution. The maximum flow spanning trees of the world investment networks possess two universal allometric scaling relations, independent of time and the investment type. The topological scaling exponent is 1.17±0.02 and the flow scaling exponent is 1.03±0.01.