一种新型声学超材料平板对机械波吸收性能的模拟与实验研究

基于质量-弹簧微结构通过光学振动模式对机械波进行选择性吸收的原理, 本文设计了一个由集中质量与弹性薄膜构成的二维声学超材料等效平板结构. 利用有限元法对等效平板代表性胞元的振动特性模拟结果表明, 二维超材料平板结构表现出与质量-弹簧微结构相同的振动模式. 基于模拟结果, 制作加工了一个正方形超材料平板, 并通过Polytec扫描式激光测振仪(PSV)对其振动特性进行了试验测试, 结果表明, 本文设计制作的超材料平板可以对频率157.5 Hz的机械波进行选择吸收.     

螺旋波纹波导回旋行波管注波互作用非线性理论

螺旋波纹波导回旋行波管与采用光滑圆波导的回旋管相比,有较大的带宽。介绍了该类回旋行波管的非线性注波互作用理论。计算结果表明该理论计算结果与实际实验报道的结果基本符合,相应的电子效率达到29%,饱和增益达到37 dB,工作磁场0.21 T,电压185 kV,电流19 A。     

Toward higher-order passive harmonic mode-locking of a soliton fiber laser

We report >13 MHz/mW pump power efficiency in increasing the repetition rate of passive harmonic mode-locking by engineering the soliton pulse energy in Er fiber lasers incorporating carbon nanotube saturable absorber. Stable pulses with a ～5 GHz repetition rate and 40 dB of super-mode suppression are demonstrated with only ～400 mW pump power in a single-clad fiber laser.     

Modifying optical properties of ZnO nanowires via strain-gradient

We conduct systematical cathodolumiuescence study on red-shift of near-band-edge emission energy in elastic bent ZnO nanowires with diameters within the exciton diffusion length （- 200 nm） in liquid nitrogen temperature （81 K）. By charactering the emission spectra of the nanowires with different; local curvatures, we find a linear relationship between strain-gradient and the red-shift of near-band-edge emission photon energy, an elastic strain-gradient effect in semiconductor similar to the famous flexoelectric effect in liquid crystals. Our results provide a new route to understand the inhomogeneous strain effect on the energy bands and optical properties of semiconductors and should be useful for designing advanced nano-optoelectronic devices.     

Synthesis and Property of Flame Retardant Epoxy Resins Modified with 2-（Diphenylphosphinyl）-l,4-benzenediol

2-（Diphenylphosphinyl）-1,4-benzenediol（DPO-HQ） was synthesized by the reaction of diphenylphos- phine oxide（DPO） with 1,4-benzoquinone（BQ）, and characterized by Fourier transform infrared（FTIR）, and nuclear magnetic resonance（1H NMR, 13C NMR, 31p NMR） spectrometries. The thermal stability of DPO-HQ was investi- gated by thermogravimetric analysis（TGA）. Flame retardant epoxy resin was synthesized based on DPO-HQ. The thermal properties and burning performance of cured epoxy resins were measured by differential scanning calorime- try（DSC）, thermogravimetric analysis（TGA）, limited oxygen index（LOI） and vertical burning test（UL-94V）. The morphologies of cured epoxy resins after combustion were investigated by scanning electron microscopy（SEM） and electron probe microanalysis（EPMA）. Moreover, the thermal stability（both in air and in N2） of DPO-HQ and its cured epoxy resin was compared with that of 10-（2,5-dihydroxyphenyl）-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10- oxide（DOPO-HQ） and its cured epoxy resin. The thermal stability of DPO-HQ is comparable with that of DOPO-HQ, while the thermal stability of cured epoxy resin based on DPO-HQ is better than that based on DOPO-HQ.     

电解质对TiO2纳米管阵列膜光生阴极保护效应的影响

基于光电化学测试考察了光电解池中电解质(NaNO₃, NaCl, Na₂SO₄, Na₂S和NaOH)的种类和浓度对阳极氧化法制备的锐钛矿型TiO₂膜电极光电性能的影响, 并解释了其作用机理.结果表明, 电解质捕获空穴的能力顺序为Na₂S>NaOH>Na₂SO₄>NaCl>NaNO₃.Na₂S和NaOH在溶液中具有协同作用, 当两者组成混合溶液并且浓度均为0.5 mol/L时, 更有利于TiO₂膜光生电子-空穴对的分离和光电转化性能的提高.当0.5 mol/L NaCl溶液中的403不锈钢(403SS)与0.5 mol/L Na₂S+0.5 mol/L NaOH混合溶液中的TiO₂膜电极耦连时, 光照膜电极可使403SS的电极电位负移约650 mV, 具有良好的光生阴极保护效应.当切断光源时, 在该混合液中TiO₂膜也能对403SS起到一定的阴极保护作用.     

Wavy structures in compressible mixing layers

Semi-periodic structures namely inclined wavy structures(IWS) are experimentally observed in compressible mixing layers at two convective Mach numbers(Mc=0.11 and 0.47). Flow structures are visualized by the laserinduced planar laser Mie scattering(PLMS) technique. Two methods are developed to investigate the spatial distribution and geometry of IWS:(1) the dominant mode extraction(DME) method, to extract the dominant modes of IWS from the streamwise gray-level fluctuation, and(2) the phase tracking(PT) method, to identify the shape of IWS. The results suggest that pressure perturbations account for the formation of IWS in the initial mixing region and the joint efect of dilatation and coherent vortices enhances IWS in the welldeveloped region. The large transverse(cross-flow) scale of the IWS and their relation to coherent vortices(CV) indicate that the disturbance originated from CV in the mixing center propagates far into the free streams. The DME and the PT method are shown to be the efective tools to study the geometrical features of wavy structures in compressible shear flows.     

顶空进样-气相色谱法检测乳制品中硫氰酸盐的含量

建立了顶空进样气相色谱法测定乳制品中硫氰酸盐含量的方法。乳制品中硫氰酸盐用水提取,然后用乙酸锌溶液沉淀蛋白质,将提取液离心,取上清液加入氯胺T将硫氰酸离子衍生为氯化氰,顶空进样,经BP10(14%氰丙基苯基聚硅氧烷)气相色谱柱分离,电子捕获检测器(ECD)检测,外标法定量,同时对衍生剂用量、顶空加热时间和保温温度进行了优化。结果表明: 硫氰酸盐在0.005～0.1 mg/L内线性关系良好,相关系数(r)为0.997,定量限(以信噪比(S/N)≥10计)为0.1 mg/kg。在1.0、2.0、10.0 mg/kg 3个添加水平下进行了回收率和精密度试验,加标回收率为90.0%～110.0%,相对标准偏差(RSD, n=10)为4.98%～7.89%。该方法操作简便、快速、稳定性好,可用于乳制品中硫氰酸盐的测定,能满足日常检测要求。应用该法对市售的18种乳制品进行了检测,发现所测乳制品皆含有硫氰酸盐,含量大约在0.5～10 mg/kg。     

浅谈测控专业基本技能实训的探索与实践

为了贯彻测控专业"以就业为导向,以素质教育为核心,以技术应用能力培养为主线"的实训教学理念,本文总结了本校测控专业在电工专题实习方面的探索,通过对最小单片机系统的元器件认知、焊接、调试等过程的训练,培养了学生工程意识和团队精神,增强了实践情感和实践观念,为更好地训练学生的动手能力和工程素质奠定了基础.     

利用傅里叶模方法分析厚层光刻胶内衍射光场

建立了描述厚层光刻胶内衍射光场形成过程的物理模型,并利用傅里叶模方法模拟计算和分析了其内部衍射光场分布。该方法考虑了其界面反射、透射及光刻胶复折射率在空间上的缓慢变化对衍射光场的影响,采用该方法模拟光刻胶内衍射光场具有数值计算结果准确、计算速度快的优点。对厚层光刻胶折射率在几种特殊分布情况下衍射光场分布的数值模拟表明,衍射光场与其复折射率的空间分布有关。由于厚层光刻胶折射率在空间上呈缓慢变化的特点,为降低其数值计算量和编程难度,可以将厚层光刻胶近似为折射率随曝光时间变化的光栅。