Measurement of piezoelectric modulus by pulsed excitation of piezoelectric ceramic elements

The possibility of measuring the piezoelectric modulus by exciting piezoelectric ceramic components with a radio pulse is considered. It is shown that there is a relation between the piezoelectric modulus and the rate of change of the current envelope at the beginning of the transient. Theoretical relations are derived. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 71–72, October, 2006.     

C/Cu(Fe)复合材料制备工艺及性能研究

利用三步电沉积法制备C／Cu（Fe）复合材料预制丝，将预制丝缠绕成毛坯，采用真空热压法制备C／Cu（Fe）复合材料．研究表明，真空热压工艺对复合材料力学性能有很大影响，通过力学性能试验和对拉伸断口形貌的分析，得出了制备C／Cu（Fe）复合材料的最佳工艺．     

Magnetic Perovskite Superlattices Grown by Pulsed Laser Deposition

Magnetic multilayers of (SrRuO₃) _m (SrMnO₃) _n were grown artificially using the pulsed laser deposition technique on (001)-oriented SrTiO₃ substrates. The temperature and magnetic field dependent reisistivity of the superlattices consisting of ferromagnetic (FM) SrRuO₃ and antiferromagnetic (AFM) SrMnO₃ are studied as a function of the SrRuO₃ unit cells. We observed a pinned/biased moment instead of the biased field in the superlattices and we redefine the structure as AFM/FM(Pin)/FM(Free)/FM(Pin) units below a critical field.     

堆泵浦3He-Ar-Xe激光体系小信号增益与效率实验研究

介绍了CFBR-Ⅱ堆泵浦3He-Ar-Xe体系1.73μm波长激光小信号增益和泵浦效率的实验研究.在脉冲峰热中子注量率为6.9×1014cm-2.s-1、3He、Ar、Xe气体的比例为80.219.30.5,总压强为8.3×104Pa时,采用透射率从1.7%到10%的6个谐振腔输出镜均获得了激光输出.在谐振腔输出镜透射率为7%时,得到了激光脉冲峰功率为45mW,其对应的激光泵浦效率为1%.在此基础上,利用Rigroa分析方法拟合出3He-Ar-Xe体系激光的小信号增益为0.24%/cm,饱和光强为36W/cm2.     

周期性脉冲流体对滴流床反应器性能的影响

用铜铬催化剂催化的过氧化氢分解反应作为液体限制反应的例子来研究周期性脉冲流体对滴流床反应器性能的影响.初步研究表明:当催化剂非完全润湿时,周期性脉冲流体能够提高反应器的性能;当催化剂完全润湿时,周期性脉冲流体不能提高反应器的性能,甚至还会产生不利影响.     

直流电沉积CdS纳米线的研究

在磷酸溶液中，采用二次铝阳极氧化法得到了多孔铝阳极氧化膜(AAO)．以AAO为模板，选用直流电沉积方法在孔内组装CdS半导体纳米线，溶去模板后，获得粗细均一、直径约为100nm、长度约为1．5μm的纳米线，与AAO模板的孔径一致．该方法在制备过程中，无需对AAO模板进行去除阻挡层、喷金或预镀金属等处理过程，而是直接在纳米孔内电沉积CdS，形成CdS半导体纳米线阵列．该方法工艺简单，操作方便，容易获得半导体CdS的一维纳米材料．TEM和XRD测试结果表明，CdS纳米线为六方晶型结构．对CdS纳米线的生长机理还进行了初步的分析和探讨．     

Pulsed Laser Precision Length Measurements

The paper discusses mode locking use in pulsed lasers for precision measurement of large lengths.     

A pulsed neural network model of spectro-temporal receptive fields and population coding in auditory cortex

The existence of spectro-temporal receptive fields and evidence for population coding in auditory cortex motivate the development of such models, that explicitly operate in the time-frequency domain and are based on a pulsed neural network. In presenting such a model, a formal connection of the fields of Time Frequency Analysis and Pulsed Neural Networks is established. The resulting neural time-frequency signal representation is shown to be representable as a signal-dependent overcomplete dictionary. It is derived from neural population coding. Signal decomposition and filtering effects are presented, indicating obvious technical applications of the proposed model. This revised version was published online in June 2006 with corrections to the Cover Date.     

Study on characteristics of Ni-W-B composites containing CeO2 nano-particles prepared by pulse electrodeposition

Ni-W-B composites containing CeO2 nano-particles on the surface of 45 steel were prepared by pulse electrodeposition,and the in-fluence of pulse frequency,pulse duty circle and heat treatment temperature on the structures and properties were investigated.The results in-dicated that the pulse co-deposition of Ni,W,B and CeO2 nano-particles led to Ni-W-B/CeO2 composites possessing higher microhardness and better wear resistance when heat-treated at 400 oC for 1 h.The microhardness of 636 HV and the deposition rate of 0.0281 mm/h of the as-deposited alloy were the highest at pulse frequency of 1000 Hz,pulse duty circle of 10% and pulse average current density of 10 A/dm2.The composites were mainly in the amorphous state and were partially crystallized as-deposited,and the crystallization trend was strength-ened when heat-treated at 400 oC.Decreasing pulse duty cycle from 75% to 10% was favorable to the refinement in grain structures and im-provement of microstructures.The crystal sizes of the composites were smaller by means of pulse electrodeposition.     

Experimental investigation on the plasma morphology of ablative pulsed plasma thruster with tongue-shaped and flared electrodes

Ablative pulsed plasma thrusters(APPTs) are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites. In order to understand the physical mechanism of APPTs, high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the electrodes. The plume images and spectra at different times and positions are experimentally recorded, and the spatial distribution, composition, and trajectory of plasmas can be concluded through analyzing them. With the increase of the distance from the ablation surface, two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.