Synergistic Effect of Triple Ion Beams on Radiation Damage in CLAM Steel

The synergistic effect of triple ion beams is investigated by simultaneous and scquential irradiations of gold, hydrogen and helium ions on the low activation martensitie steel （CLAM） developed in China. The depth profile measurements of the positron annihilation Doppler broadening S parameter are carried out as a function of slow- positron beam energy to examine the produced radiation damage. The synergistic effect of displacement damage and hydrogen and helium on the formation of radiation damage is clearly observed. In the preset case ,this effect suppresses the radiation damage in the CLAM steel due to the helium and/or hydrogen filling of vacancy clusters.     

LASIS高光谱图像的3D-SPECK压缩算法

将三维集合分裂嵌入块编码算法结合感兴趣区域的压缩方案用于大孔径静态干涉成像光谱仪图像压缩.首先,对高光谱干涉图像序列进行三维非对称离散小波变换.其次,定义零块树作为编码单位.采用感兴趣区域方法对不同的编码单位赋予不同的比特率,以保护光谱信息.最后,采用改进的三维集合分裂嵌入块编码算法分别对每个编码单位进行编码.实验结果表明,该方案在8:1压缩比下,获得大于40dB的峰值信噪比,同时有效地保护了光谱信息.该算法复杂度低,实时性好,满足大孔径静态干涉成像光谱仪系统图像压缩要求.     

Effects of Mo promoters on the Cu-Fe bimetal catalysts for the DMC formation from CO2 and methanol

The Mo-promoted Cu-Fe bimetal catalysts were prepared and used for the formation of dimethyl carbonate（DMC） from CO₂ and methanol.The catalysts were characterized by X-ray diffraction（XRD）, temperature programmed reduction（TPR）,laser Raman spectra（LRS）,energy dispersive spectroscopy （EDS） and temperature programmed desorption（TPD） techniques.The experimental results demonstrated that the Mo promoters can decrease the reducibility and increase the dispersion of Cu-Fe clusters.The concentration balance of base-acid sites can be readily adjusted by changing the Mo content.The moderate concentration balance of acid and base sites was in favor of the DMC formation. Under optimal experimental conditions,the highest methanol conversion of 6.99%with a DMC selectivity of 87.7%can be obtained when 2.5 wt%of Mo was loaded.     

CdSe在高压下的电学性质及相变

 利用在金刚石压砧上集成的微电路,原位测量了CdSe多晶粉末在温度为300~450 K、压力达到23 GPa时电阻率随温度和压力的变化关系。实验结果表明：在加压过程中,电阻率在2.6 GPa压力时出现的异常改变,对应着CdSe从纤锌矿向岩盐矿结构的转变,而在6.0、9.8、17.0 GPa等压力处出现的电阻率异常,则是由CdSe中的电子结构的变化所引起的;在卸压过程中,只在约14.0和3.0 GPa压力下观察到了两个电阻率异常点。通过对电阻率随压力变化曲线的模拟,得出了CdSe高压相的带隙随压力的变化关系,据此预测CdSe金属化的压力应在70~100 GPa之间。变温实验结果表明,在实验的温度和压力范围内,CdSe的电阻率均随温度的增加而升高。     

载流子在金属/聚对苯乙炔/金属结构中注入及输运的动力学研究

采用紧束缚的Su-Schrieffer-Heeger模型,利用非绝热动力学方法研究了载流子在金属/聚对苯乙炔(poly(p-phenylene vinylene,简记为PPV))/金属三明治结构中注入与输运的动力学过程.发现由于强的电子-晶格相互作用,注入的电荷在PPV链中形成波包,波包的形成与施加在金属电极上的偏压、PPV链上的电场强度及金属电极与PPV之间的界面耦合强度密切相关.在无外电场的情况下,当偏压达到临界值时电荷能够从金属电极注入到PPV链中并形成波包.随着电场强度的增大,波包能 关键词： 金属/聚对苯乙炔/金属结构 载流子输运 波包     

水下噪声目标被动测距技术研究

运用被动测距声纳中的三元测距技术，通过直接测1、3阵元的时延差来实现时延估计。仿真结果表明，改进的时延估计方法可提高时延估计精度，从而改善测距精度。此外，定义临界距离，并以此为分界点，分别采用K系数分配法和直接测量法对中远程和近程目标进行测距，解决了被动声纳的近程测距模糊问题。将其应用于声纳系统中，可显著提高声纳的被动测距能力，使被动测距声纳可全程测距。     

在太赫兹波段的开口共振环的不同开口形状对透过率频谱的影响

通过对不同开口形状的太赫兹(THz)波段共振环(SRR)的有限时域差分(FDTD)模拟,发现了SRR不同开口形状在发生共振时对开口间距的平均值具有相同的透过率频谱分布的均值效应;并且观察到了在开口边缘很尖的特殊条件下,SRR开口将出现导通现象.此结果可为今后SRR开口工艺设计与质量控制提供参考,也可为SRR工作机理的进一步分析研究提供有关的依据. 关键词： 太赫兹 开口共振环 开口形状 FDTD     

Optimal phase steps of multi-level spiral phase plates

We analyze vortex properties of the optical beams generated by a multi-level spiral phase plate (MLSPP) and find that this kind of beams consists of vortex components with topological charges of L − kM, where k is zero or any integer, M is the level number and L is the intrinsic topological charge of the MLSPP. We proved that the orbital angular momentum of the beams generated by a MLSPP reaches its maximum only if the phase steps (or the ratio of M to L) satisfies some special conditions.     

A New Approach for Controlling Chaos Based on Direct Optimizing Predictive Control

We introduce the predictive control theory into the study of chaos control and propose a direct optimizing predictive control algorithm based on a neural network model. The proposed control system stabilizes the chaotic motion in an unknown chaotic system onto the desired target trajectory. Compared with the existing similar algorithms, the proposed control system has faster response, so it requires much shorter time for the stabilization of the chaotic systems.The proposed approach can control hyperchaos and the algorithm is simple. The convergence of the control algorithm and the stability of the control system can be guaranteed. The theoretic analysis and simulations demonstrate the effectiveness of the algorithm.     

Effect of Structural Relaxation on Deformation Behaviour of Zr-Based Metallic Glass

Structural relaxation through isothermal annealing at temperature below glass transition is conducted on Zr46.75 Ti8.25 CU7.5Ni11Be27.5 （Vitreloy-4） bulk metallic glass. Defect concentration is correlated with the annealing time t according to differential scanning calorimetry thermalgrams. The effects of structural relaxation on mechanical properties and deformation behaviour are investigated by using instrumented nanoindentation. It is found that the as-cast alloy exhibits pronounced serration flow during the loading process of nanoindentation, and the size and number of the serrations decrease with the annealing time. The change of the deformation behaviour with structural relaxation is explained using a free volume model.