近红外漫反射光谱法测定玉米秸秆NDF与ADF含量

应用主成分空间和傅里叶变换近红外光谱技术,采用偏最小二乘回归法(PLS),在国内首次建立了适合不同品种类型、不同生长发育时期和不同部位且适配范围广的近红外漫反射光谱(NIRS)测定玉米秸秆中性洗涤纤维(NeutralDetergentFiber,NDF)和酸性洗涤纤维(AcidDetergentFiber,ADF)含量的稳定校正模型。结果表明,采用一阶导数 矢量归一化预处理和一阶导数 多元散射校正预处理,谱区均为7502～5450cm-1和4601～4247cm-1,所建立的NDF与ADF校正模型,其校正和预测效果最佳。其校正决定系数(R2cal)均大于094,交叉验证和外部验证决定系数(R2cv,R2val)为092～096,各项误差(RMSEE,RMSECV和RMSEP)为149%～181%。该结果对青贮玉米秸秆材料快速鉴定和筛选具有重要的意义。     

大块金属玻璃Zr41Ti14Cu12.5Ni10Be22.5的流变行为研究

采用静态拉伸方法在连续升温条件下动态地测量了大块金属玻璃Zr41Ti14Cu12.5Ni10Be22.5（Vit1）的黏度随温度的变化关系.在应变速率与温度的关系曲线中，观测到了与玻璃转变和晶化过程相联系的多个应变速率峰.在玻璃转变温度Tg以上，大块金属玻璃Zr41Ti14Cu12.5Ni10Be22.5的过冷液体呈现Newton流体特征，其黏度与温度的关系符合Vogel Fulcher-Tammann (VFT)关系式，拟合得到脆度D*＝36，VFT温度T0＝319K，脆度参数m＝30，这说明Zr41T 关键词： 大块金属玻璃 应变速率 剪切黏度 自由体积     

基于ANSYS的高温超导混合磁轴承悬浮力分析

基于商用电磁场有限元软件ANSYS以及Bean临界态模型,对由圆柱形高温超导块材、永磁体和超导线圈组成的新型高温超导混合磁轴承的电磁场分布及悬浮力进行了仿真分析,研究了超导线圈对高温超导混合磁轴承悬浮力的影响,同时还通过实验测试了悬浮力。结果表明:仿真与实验具有较好的一致性,使用软件仿真方便可行,其结果较为准确可靠,可为高温超导混合磁轴承的设计和优化提供理论依据。     

一种投影式激光方向测量方法

为了在激光告警中实现全方位角度探测,且达到一定的探测精度,提出了一种投影式激光方向测量方法.通过计算激光照射在参量给定的遮光板上形成的投影量.求解在探测器上由不同探测象限产生的不同的探测电流的比值.再根据投影面积的比值与角度一一对应的关系可事先编码的原理.由对应程序判断激光入射方向.在软件Matlab仿真中计箅得到产生最小分辨率的四个极限角度分别为(0°,90°)、(33°,21°)、(33°,69°)、(45°,90°),并由实验得到最小分辨电压为0.05 V.通过仿真计算与实验数据证明该设计可达到最小识别角度1°的探测要求.     

整齐排列的氧化锌纳米针阵列的场发射性能

采用简单的热蒸发方法,不使用任何催化剂,在硅基底上制备出了两种垂直于基底、整齐排列的氧化锌纳米针阵列.它们具有均匀的分布以及一致的取向和高度.场发射性能研究表明它们同时具有较低的开启和阈值场强,稳定的发射电流和长时间维持发射的能力.较低的开启和阈值场强来源于它们较高的长径比和较细的尖端;稳定发射电流和长时间维持发射的能力来源于它们在基底上均匀一致的分布以及由于较粗的根部带来的与基底的良好接触.实验结果表明整齐的氧化锌针状纳米结构阵列是一种理想的平面场发射材料. 关键词： 氧化锌 热蒸发 阵列场发射 屏蔽效应     

Synchronization and coherent combining of two pulsed fiber lasers

We demonstrate a scalable architecture for coherent combining of pulsed fiber lasers.A new method for generating synchronous pulsed fiber lasers by direct phase modulation is proposed and investigated.It is shown that phase modulated mutually coupled laser array can be a steady synchronous pulsed fiber laser source.The synchronous pulsed fiber lasers are coherently combined with an invariable phase difference of π in adjacent lasers.Neither active phase control nor polarization control is taken in our experiment.     

为学生打开自主学习的空间--一个高中物理教学案例与思考

现在，整个教育界都在提倡创新教育和自主探究式学习．笔者曾经尝试着在课堂上渗透让学生自主学习的思想，努力创设情景给学生多一些创新的机会，允许并鼓励他们在课堂上提出自己的看法．但课堂教学，特别是在目前仍受考试压力影响的高中课堂中，教师和学生依然面临着升学压力．无奈的现实很难在课堂上落实这些“理念”．毕竟学生这么多、课时这么少、教学任务又如此之重，作出一个教学决定又要考虑方方面面的因素，     

Linear and nonlinear optical properties of ZnO nanorod arrays

Polarization-dependent linear absorption, second-harmonic generation （SHG） and 3rd-order nonlinearities of wellaligned ZnO nanorod arrays have been investigated with ps pulses. The depressed spectral width and the enhanced intensity of reflective SHG along the long axis of ZnO nanorods were observed by using p-polarized pulses, which is explained by the optical confinements. The nonlinear absorption coefficient measured with s-polarization reached the maximum 4.0×10^4cm/GW at the wavelength -750nm, which revealed a large two-photon resonance absorption attributed to the quantum confined exciton when the polarization is vertical to the long axis of ZnO nanorod.     

Versatile Nitro-Fluorophore as Highly Effective Sensor for Hypoxic Tumor Cells: Design, Imaging and Evaluation

Based on the characteristics of a nitro-group, which can be partially or totally reduced to an amino-group in hypoxic cells, two series of hypoxic sensors containing 7H-Benzimidazole [2,1-a]benz[de]isoquinolin-7-one cores with nitro groups in different positions were designed, synthesized and evaluated. The target compounds exhibited significantly different fluorescence characteristics (fluorescence enhancement or quenching). The strong fluorescences of some partially reduced compounds could be explained through the examination of their infrared spectra, which showed a restriction of the nitro-group vibration. These compounds exhibited significant hypoxic–oxic fluorescence differences not only in numerical values but also in their fluorescent imaging properties as reported for the first time.      

Analysis of photonic band gaps in a two-dimensional photonic crystal with centrifugal core-shell rods

The absolute photonic band gap (PBG) in two-dimensional (2D) photonic crystal with excentric core-shell rods is studied in this paper. The core rod shifts away from the core-shell rod center, and its position is decided by two new introduced parameters — the shift angle θ and the offset ρ. We use the FDTD algorithm to calculate the photonic bands of the photonic crystal, and analyze how the offset and shift angle affect the photonic bang gap of excentric core-shell photonic crystal for different core rod size. It has been shown that the variation of the photonic band gap is quite peculiar.