有限长管道声衬的参数优化设计研究

本文应用已经过验证的有限长管道声学模型进行声衬参数的优化设计,研究了固定工况下,优化半径、声衬长度和声衬位置对阻抗优化参数的影响,其中声衬长度和声衬位置对阻抗优化参数的影响和应用无限长管道声学模型进行优化设计时的影响明显不同.本文讨论得到的结论对声衬参数优化设计有重要的指导价值.     

飞秒激光泵浦-探测热反射系统的建立与调试

建立了用来研究超快传热现象的飞秒激光泵浦-探测热反射系统.利用该系统测量并得到了在140fs(飞秒)超短脉冲激光加热下, 50 nm金膜的非平衡电子温升引起的反射信号随时间的变化曲线.由于加热光单脉冲能量密度只有5×10-3mJ/cm2,估算最高温升在10 K以内,这有效地减小了由丁物性参数随温度变化而引起的洪差.论文介绍了在系统的调试过程中,各种因素对实验结果的影响,并对实验结果及数据处理方法进行了讨论.     

采用显微图像测量系统实现人体组织典型参数测量

人体组织典型参数的获取对于各类疾病的诊断和治疗有着极其重要的作用。采用高性能显微图像测量系统实现人体组织典型参数在体测量, 对系统研制过程中所涉及的基本原理, 以及图像采集系统、成像系统与图像处理软件等关键性技术问题作了阐述。该显微图像测量系统能快速、有效地完成对人体组织典型图像指标的直接测取和定量分析, 基本实现了人体组织典型参数图像观测的数字化与检测的高智能化。实验结果表明, 采用该系统在体观测人体组织典型参数, 可以实时观测人体组织显微图像, 计算并保存毛细血管网络形态学参数和微血流动力学的各项参数, 同时具有快速简单、精确度高等特点, 可作为医学研究的重要手段之一。     

Hawking Radiation from Topological Kerr Anti-de-Sitter Black Hole with One Rotational Parameter via Covariant Anomalies

Using anomalous viewpoint, we study the Hawking radiation from a kind of topological Kerr Anti-de-Sitter （Kerr-AdS） black hole with one rotational parameter. We employ the covariant gauge and gravitational anomalies. The result supports the Robinson-Wilczek opinion and shows that the Hawking temperature can be correctly determined by cancelling covariant gauge and gravitational anomalies at the horizon.     

Fuzzy Impulsive Control of Permanent Magnet Synchronous Motors

The permanent magnet synchronous motors （PMSMs） may experience chaotic behaviours with systemic parameters falling into a certain area or under certain working conditions, which threaten the secure and stable operation of motor-driven. Hence, it is important to study the methods of controlling or suppressing chaos in PMSMs. In this work, the Takagi-Sugeno （T-S） fuzzy impulsive control model for PMSMs is established via the T-S modelling methodology and impulsive technology. Based on the new model, the control conditions of asymptotieal stability and exponential stability for PMSMs have been derived by the Lyapunov method. Finaily, an illustrated example is also given to show the effectiveness of the obtained results.     

Fibre Optical Parametric Amplification in Defect Bragg Fibres with Zero Dispersion Slow Light Effect

Nonlinearity enhancement by slow light effect and strong light confinement in defect Bragg fibres is demonstrated and anMysed in applications of fibre optical parametric amplifiers. Broadband low group velocity and zero dispersion as well as the strong light confinement by band gap enhances the nonlinear coefficient up to more than one order than the conventional high nonlinear fibres. Moreover, the zero dispersion wavelength of coupled core mode can be designed arbitrarily, under which the phase-matching bandwidth of the nonlinear process can be extended.     

Sinusoidal Steady State Analysis on 4H--SiC Buried Channel MOSFETs

With the combined use of the drift-diffusion （DD） model, experiment measured parameters and small-signal sinusoidM steady-state analysis, we extract the Y-parameters for 4H-SiC buried-channel metal oxide semicon- ductor field effect transistors （BCMOSFETs）. Output short-circuit current gain G and Mason＇s invariant U are cMculated for extrapolating unity current gain frequency in the common-source configuration fT and the maximum frequency of oscillation fmax, respectively. Here fT = 800 MHz and fmax= 5 GHz are extracted for the 4H-SiC BCMOSFETs, while the field effect mobility reaches its peak value 87cm2/Vs when VGs = 4.5 V. Simulation results clearly show that the characteristic frequency of 4H-SiC BCMOSFETs and field effect mobility are superior, due to the novel structure, compared with conventional MOSFETs.     

Phase Transition and High Piezoactivity of Sr Doped Lead-Free （Na0.53K0.422Li0.048） （Nb0.89Sb0.06Wa0.05）O3 Ceramics

Lead-free piezoelectric ceramics （Na0.53K0.422Li0.048 ） （Nb0.89Sb0.06 Ta0.05 ）03 （NKLNST） ＋ x tool SrCO3 are prepared by conventional solid state sintering method. The specimens with pure perovskite structure show tetragonal phase at x 〈 0.01, and become pseudo-cubic phase at x 〉 0.02. A lattice parameter discontinuity is found in the specimens with 0.004 〈 x 〈 0.0075, along with a great improvement in piezoactivity. The 0.004 mol SrCO3 added NKLNST ceramics possesses outstanding performances of kp = 0.53, kt = 0.26, and d33=309 pC/N. Moreover, the Sr^2＋ modification inhibits the gra/n growth, decreases the Curie temperature, and induces a diffuse phase transition.     

Growth Mechanism and Optimized Parameters to Synthesize Nafion-115 Nanowire Arrays with Anodic Aluminium Oxide Membranes as Templates

Nation-115 nanowire arrays are synthesized with an extrusion method using AAO membranes as templates. It is indicated that the vacuum treating of AAO templates before surface decoration plays an important role in obtaining high filling rate of the Nation-115 nanowires in the AAO templates, vchile the concentration of Nafion-115 DMSO solutions does not affect the flling rate greatly. The optimized parameters to synthesize the Nation-115 nanowire arrays are studied. The filling rate of the Nadion-115 nanowires in the AAO templates synthesized with the optimized parameters is about 95% discussed to qualitatively explain the experimental results The growth mechanism of Nafion-115 nanowires is     

Order Parameter Hysteresis on the Complex Network

Collective synchronization is investigated on the small-world network （NW model）. The order parameter is introduced to measure the synchronization of phase. It is found that there are differences between the processes of synchronization and desynchronization. The dependence of order parameter on the coupling strength is shown like a hysteresis loop. The size of the loop demonstrates the non-monotonicity with the change of adding probability, and is relevant to the construction of the network. The area may be maximum, as the adding probability is equal to 0.4. This phenomenon indicates that the clusters in the network play an important role in the processes of synchronization and desynchronization.