Controllable synthesis of high aspect ratio Mg_2B_2O_5 nanowires and their applications in reinforced polyhydroxyalkanoate composites

Highly pure magnesium borate （Mg2B2O5） nanowires with an average diameter of - 30 nm, an average length of 15 μm, and a high aspect ratio of - 500 have been synthesized on a large scale via a two-step method. MgBO2（OH） nanowires with high aspect ratios were first prepared via a PVP-assisted hydrothermal technique. Using these nanowires as precursors, single crystalline Mg2B205 nanowires were synthesized by post-annealing treatment at a relatively low temperature of 700 ℃. The important effect of the MgBO2（OH）-Mg2B2O5 conversion process on the morphology of the Mg2B2O5 nanowires was investigated and it was indicated that the recrystallization process plays an important role in the protection of the one-dimensional （1D） nanostructure. Moreover, the rigidity and the toughness of the Mg2B2O5 nanowire- reinforced PHA composites were tremendously improved compared to those of the pure PHA. Our results demonstrate the effectiveness of Mg2B2O5 nanowires for reinforcement applications in polymer composites.     

New 3-mode bosonic operator realization of SU（2） Lie algebra： From the point of view of squeezing

We consider the quantum mechanical SU(2) transformation e2λ JzJ± e-2λJz= e±2λJ± as if the meaning of squeezing with e±2λbeing squeezing parameter. By studying SU(2) operators(J±,Jz) from the point of view of squeezing we find that(J±,Jz) can also be realized in terms of 3-mode bosonic operators. Employing this realization, we find the natural representation(the eigenvectors of J+ or J-) of the 3-mode squeezing operator e2λ Jz. The idea of considering quantum SU(2) transformation as if squeezing is liable for us to obtain the new bosonic operator realization of SU(2) and new squeezing operators.     

溶胶凝胶法制备圆柱形大孔二氧化硅反蛋白石结构晶体

利用溶胶凝胶法在不同直径的毛细管表面制备了圆柱形二氧化硅反蛋白石多孔结构.利用扫描电子显微镜表征了其形貌,发现胶体晶体的类(111)面结构整体为圆柱形,平行于毛细管表面.透射光谱结果表明,二氧化硅多孔结构在[111]方向具有典型的光子带隙效应,与布拉格理论相符合,有望应用到光通讯和传感领域.     

Image reconstruction tomography with only a method for laminar optical single Monte-Carlo simulation

Laminar optical tomography （LOT） is a new mesoscopic functional optical imaging technique. Currently, the forward problem of LOT image reconstruction is generally solved on the basis of Monte-Carlo （MC） methods. However, considering the nonlinear nature of the image reconstruction in LOT with the increasing number of source positions, methods based on MC take too much computation time. This letter develops a fast image reconstruction algorithm based on perturbation MC （pMC） for reconstructing the absorption or scattering image of a slab medium, which is suitable for LOT or other functional optical tomography system with narrow source-detector separation and dense sampling. To calculate the pMC parameters, i.e., the path length passed by a photon and the collision numbers experienced in each voxel with only one baseline MC simulation, we propose a scheme named as the trajectory translation and target voxel regression （TT＆TVR） based on the reciprocity principle. To further speed up the image reconstruction procedure, the weighted average of the pMC parameters for all survival photons is adopted and the region of interest （ROI） is extracted from the raw data to save as the prior information of the image reconstruction. The method is applied to the absorption reconstruction of the layered inhomogeneous media. Results demonstrate that the reconstructing time is less than 20 s with the X - Y section of the sample subdivided into 50 × 50 voxels, and the target size quantitativeness ratio can be obtained in a satisfying accuracy in the source-detector separations of 0.4 and 1.25 mm, respectively.     

Numerical Simulation on the Production Mechanism of Surface-Wave Plasmas Sustained along a Metal Rod

For interpreting the production mechanism of surface-wave plasmas sustained along a metal rod, electromagnetic simulation on the electromagnetic field distributions and particle-in-cell/Monte Carlo collision （PIC/MCC） simulation of the ionization process are present. The results show that the enhanced electric field of surface plasmon polaritons （SPPs） can be excited in the ion sheath layer between the negative-voltage metal rod and the surface-wave plasmas, which is responsible for maintaining the plasma discharge. Moreover, the spatio-temporal evolutions of plasma density and electric fields are simulated by the PIC/MCC model. It is further suggested that the expanded ion sheath layer can extend the length of plasma domain by increasing the plasma absorbed energy from SPPs.     

航空发动机尾气静电带电机理分析与试验研究

航空发动机工作时燃烧室内发生复杂的物理化学变化,生成大量带电粒子,导致发动机尾气静电带电;理论分析了发动机喷流尾气中带电粒子产生演化过程和带电影响因素,讨论对比了多种测试原理与传感器方案,确立了非接触式静电感应测试方案,研制了共轴喇叭状静电传感器和静电监测系统,开发了自动测试软件并对某型航空发动机进行了机载尾气静电带电试验研究,验证了测试平台的有效性,成功获得了大量喷流尾气静电信号;研究结果表明:航空发动机正常工作时喷流尾气中带电粒子总体显正极性,平均体电荷密度约为0.077 nC/m³,发动机等效充电电流为2.26 nA。     

磺硝酚偶氮若丹宁固相萃取光度法测定生物样品中的汞

在 p H2 .0的氯乙酸 -氢氧化钠缓冲介质与吐温 - 80存在下 ,磺硝酚偶氮若丹宁 (NSPAR)与汞反应生成 2∶ 1稳定络合物 ,可被 Waters Sep- Pak C18小柱固相萃取 ,氮 -氮二甲基甲酰氨 (DMF)洗脱后光度法测定 ,λmax=5 5 0 nm,体系摩尔吸光系数ε=8.12× 10 4L· mol-1· cm-1。汞含量在 0 .0 5— 4 .0μg/m L内符合比耳定律 ,用于生物样品中汞含量的测定 ,结果令人满意     

光声光谱技术在层状物质的逐层分析研究中的应用——Ⅰ.光声相位精细谱技术

本文提出光声相位精细谱法(PAPFS)。通过对层状物初始态光声相位扫描和对由此产生的PAPFS曲线的解析,可获取各层与光学热学和空间坐标相关的有价值的信息。本文用该法对彩色相纸作了逐层分析,并将结果与电镜作了比较。与PAPFS相关的层状物光声理论将在本文第Ⅱ部分中涉及。     

高速传输系统CAD/CAM齿形误差最优化算法

本文提出了一种CAD/CAM齿形误差的最优化算法。本算法收敛速度快、拟合误差小,能够按照预定设计要求对齿形精度加以控制,实现最优化自动搜索,同时给出数值计算结果。     

基于RBR和PCA的2.4米风洞故障诊断系统应用研究

为解决2.4米风洞试验装备的故障监测与诊断（FDD）问题,设计了一种基于规则推理（RBR）和主元分析（PCA）的并行故障诊断系统。对试验流程和因果关系较强的单一装备故障,采用RBR诊断方法;而对控制过程和重要传感器的故障,通过构建PCA模型,根据平方预报误差（SPE）实现系统故障的诊断。运行效果表明：该系统实时性好、诊断结果与实际相符合、且对过程故障具有较强的针对性。