相对论速调管振荡器中两个调制腔耦合系数的计算

 用场方法研究了相对论速调管振荡器中两个调制腔的耦合，解析地得到了两腔耦合系数与腔和波导的尺寸、间隙及两腔之间的距离等参数之间的关系。耦合系数的数值与由耦合与否腔的频率测量确定的实验结果在数量级上符合得较好。     

计算机产生全息图对补偿器检测的技术研究

用一种计算全息板代替补偿器零检验光路中理想的大型非球面,实现对补偿器的定量检验.用于检测补偿器旋转对称的二元反射式全息板根据非球面方程设计,并确定其光程差,再由激光直写(精度可达0.6μm)来制作完成,合成相当于理想非球面反射波前.其检测精度小于λ/10.补偿器的参量由抛物面和三级球差理论确定.     

控制光和信号光频差对太赫兹光非对称解复用器性能的影响

讨论了半导体光放大器中的带间效应，及载流子热效应、谱烧孔效应、双光子吸收以及超快非线性折射等带内效应对半导体光放大器的动态特性的影响，讨论了两种情况：1)保持控制光波长不变而改变信号光频率，2)保持控制光和信号光频率相同而同时改变它们的频率下半导体光放大器的增益、相位动态特性以及太赫兹光非对称解复用器的开关窗口特性。数值结果表明，为了得到较为平坦而窄的开关窗口，控制光波长应与信号光波长相同，且其与半导体光放大器增益谱中心波长的差值应该大一些。     

Improved performance of TiO2 electrodes coated with NiO by magnetron sputtering for dye-sensitized solar cells

TiO₂ electrodes are coated with NiO by DC magnetron sputtering, and their structural, optical and electrochemical performance has been investigated. X-ray diffractometry (XRD), UV-vis spectrophotometry, scanning electron microscopy (SEM), AC impedance, and linear sweep voltammetry (LSV) are used to characterize the TiO₂/NiO electrodes. Their performance is evaluated with a computer controlled electrochemical workstation in combination with three conventional electrodes. The experimental results indicate that the surface modification of TiO₂ electrodes with sputtered NiO reduces trap sites on TiO₂ and improves the electrochemical performance of dye-sensitized solar cells (DSSCs). Sputtering NiO for 7 min, which is about 21 nm thick, on 6.5 μm thick TiO₂ greatly improves the DSSC parameters, and the conversion efficiency increases from 3.21 to 4.16%. Mechanisms of the influence of the NiO coating on electrochemical performance are discussed.     

Structure evolution and stoichiometry control of Pb(Zr, Ti)O3 thick films fabricated by electrospray assisted vapour deposition

Well-crystallized and stoichiometric Pb(Zr, Ti)O₃ (PZT) films, typically ∼5 μm thick, with pure perovskite-type rhombohedral structures have been successfully prepared via an electrospray assisted vapour deposition (ESAVD) method. Control of the deposition temperature within a narrow range of 300-400 °C resulted in films with the most desirable phases. PZT films with close stoichiometric match with the expected composition ratio and uniform element distribution were obtained by adding the appropriate levels of excess Pb in the precursor solutions. The annealed films were uniform, dense, compact and adherent to the substrates. The dielectric constant, ?_r, and loss tangent, tan δ, of the fabricated PZT films measured at 10 kHz were 442 and 0.09, respectively. The ESAVD deposited PZT films showed a remanent polarization, P_r, of 15.3 μC/cm² and coercive field, E_c, of 86.7 kV/cm. These results demonstrate the clear potential of the ESAVD method as a promising technique for the fabrication of thick PZT films.     

Low temperature fired Ni-Cu-Zn ferrite with Bi4Ti3O12

The Ni-Cu-Zn ferrites with different contents of Bi₄Ti₃O₁₂ ceramics (1-8 wt%) as sintering additives were prepared by the usual ceramic technology and sintered at 900 °C to adapt to the low temperature co-fired ceramic (LTCC) technology. The magnetic and dielectric properties of the ferrite can be effectively improved with the effect of an appropriate amount of Bi₄Ti₃O₁₂. For all samples, the ferrite sintered with 2 wt% Bi₄Ti₃O₁₂ has relatively high density (98.8%) and permeability, while the ferrite with 8 wt% Bi₄Ti₃O₁₂ has relatively good dielectric properties in a wide frequency range. The influences of Bi₄Ti₃O₁₂ addition on microstructure, magnetic and dielectric properties of the ferrite have been discussed.     

Possible numbers of ones in the squares of 0–1 matrices with a given rank

For a symmetric 0–1 matrix A, we give the number of ones in A ² when rank(A) = 1, 2, and give the maximal number of ones in A ² when rank(A) = k (3 ≤ k ≤ n). The sufficient and necessary condition under which the maximal number is achieved is also obtained. For generic 0–1 matrices, we only study the cases of rank 1 and rank 2.     

Ultrafast dynamics of BixSb1-x film studied by femtosecond pump-probe technique

The Bi_xSb_1-x film is an important phase change material. The ultrafast dynamics of Bi_xSb_1-x film is studied by the femtosecond pump-probe technique with an 80 fs pulsed laser. Experimental results show that the reflectivity change increases with the fluence of the pump laser. The fast increase of the reflectivity occurs between 100 and 800 fs. Subsequently, the slower recovery of the reflectivity on a time scale of 1.24-18.3 ps is detected. We also found that the reflectivity change can be greatly affected by the ratio between Bi and Sb composition in Bi_xSb_1-x materials with x = 0.2 and 0.88. These experimental results should be helpful for developing new devices with ultrafast dynamics of Bi_xSb_1-x film and ultrafast optical switching.     

Asymptotic stability of traveling waves for delayed reaction-diffusion equations with crossing-monostability

This paper is concerned with the traveling waves for a class of delayed reaction-diffusion equations with crossing-monostability. In the previous papers, we established the existence and uniqueness of traveling waves which may not be monotone. However, the stability of such traveling waves remains open. In this paper, by means of the (technical) weighted energy method, we prove that the traveling wave is exponentially stable, when the initial perturbation around the wave is relatively small in a weighted norm. As applications, we consider the delayed diffusive Nicholson??s blowflies equation in population dynamics and Mackey?CGlass model in physiology.     

高温高压金刚石单晶生长界面的研究

 利用扫描电镜及Auger电子谱技术研究了高温高压下金刚石单晶生长界面的特性，观察到了金刚石单晶表面及金属膜表面的沟槽结构及金刚石-金属、金属-石墨两个主界面间的过渡层结构及界面间C原子电子组态的变化。