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941.
用于近红外光谱仪的平场全息凹面光栅的模拟与设计 总被引:3,自引:0,他引:3
针对近红外光谱分析属于微弱信号与多元信息处理的特点,基于全息凹面光栅理论,采用光学设计软件CODE V,从初始结构出发,利用软件强大的全局优化功能,设计出一种用于近红外光谱仪的平场全息凹面光栅,成功地减小了像 差,解决了宽光谱、窄谱面展宽的矛盾,并充分利用了光谱信息,是一种高效率的分光光学系统结构。利用CODE V软件,不需要求解复杂的高级像差方程,能对结果进行迅速评价,并可在设计中同时兼顾平场和提高分辨率的要求,极大地 提高了工作效率。最后,给出了实例,设计出的全息凹面光栅工作波长范围为900~1700 nm、直径ф=25 mm、F/#=1.5,对设计结果分析表明:在宽度为50 μm缝光源再现情况下,理论分辨率优于6.3 nm。 相似文献
942.
膜结构对金纳米线阵列表面增强拉曼散射的影响 总被引:1,自引:0,他引:1
金纳米线阵列作为表面增强拉曼散射的基底能够产生有效的增强效应,金纳米线阵列通过金线之间的电场耦合产生增强的拉曼信号。在实验中,制备出金纳米线阵列与金纳米刷,两种样品结构不同,金纳米刷的一面带有金膜。用巯基吡啶作为探针分子,金纳米刷的SERS实验显示出很好的增强效应,增强因子为106,不同位点的SERS谱具有区域不均一的特征。而相同实验条件下的金纳米线阵列的增强因子只有102。光学吸收谱表明这两种结构均发生了共振吸收增强电场,对其结构的分析表明,这两种结构具有不同的电场局域化分布,同时金纳米刷中金线上端强烈的电场耦合,这是其具有更好的增强效用的原因。同时,4-MP的表面增强拉曼谱的变化特征体现了化学增强效应的影响。 相似文献
943.
944.
945.
We consider the anti-plane shear deformation of a three-phase inhomogeneity-coating-matrix composite containing a coated non-elliptical inhomogeneity whose surrounding matrix is subjected to the action of a screw dislocation and uniform remote anti-plane shear stresses. Our objective is to establish conditions under which the inhomogeneity maintains an internal uniform stress field. Our analysis, which is based on a carefully chosen conformal mapping function, clearly indicates that such an internal uniform stress distribution can be achieved independently of the action of the screw dislocation, which influences the shape of the inhomogeneity depending on its proximity to the dislocation. In fact, we find that when the screw dislocation is located far from the coated inhomogeneity, the corresponding material interfaces become two confocal ellipses as reported previously in the literature. A simple criterion for the convergence of the series in the conformal mapping function is established. 相似文献
946.
Investigation of current transport parameters of Ti/4H-SiC MPS diode with inhomogeneous barrier
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The current transport parameters of 4H-SiC merged PiN Schottky(MPS) diode are investigated in a temperature range of 300-520 K.Evaluation of the experimental current-voltage(I-V) data reveals the decrease in Schottky barrier height Φ b but an increase in ideality factor n,with temperature decreasing,which suggests the presence of an inhomogeneous Schottky barrier.The current transport behaviours are analysed in detail using the Tung’s model and the effective area of the low barrier patches is extracted.It is found that small low barrier patches,making only 4.3% of the total contact,may significantly influence the device electrical characteristics due to the fact that a barrier height of 0.968 eV is much lower than the average barrier height 1.39 eV.This shows that ion implantation in the Schottky contact region of MPS structure may result in a poor Ti/4H-SiC interface quality.In addition,the temperature dependence of the specific on-resistance(R on sp),T 2.14,is determined between 300 K and 520 K,which is similar to that predicted by a reduction in electron mobility. 相似文献
947.
948.
锦屏Ⅰ级水电站右岸建基面发育有大量的绿片岩,它们是水电站建设中重大工程地质问题研究中需要注意的对象之一。为了研究它们的迹长分布规律,利用3D激光扫描工艺,对锦屏Ⅰ级水电工程右岸建基面高差50m范围内的绿片岩出露区域进行了扫描,获得了准确的绿片岩出露的迹长数据,从而使绿片岩迹长分布研究成为可能。研究发现,迹长数据样本最集中分布于0~3m的区间; 随着迹长的增加,落在子区间内的条数(频数)递减; 在0~9m的各个子区间内,样本呈正态分布。整体而言,实测迹长样本数据服从对数正态分布。 相似文献
949.
Leandro Luetkmeyer Maria Inês Bruno Tavares Gisele C. X. Valle José de Souza Nogueira 《Macromolecular Symposia》2007,258(1):108-112
Summary: The focus of this work was to characterize the molecular dynamic of High Impact Polystyrene (HIPS - 5% PB), wood - A (Vochysia divergens) and B (Erisma uncinatum) - and their composites, using solid state nuclear magnetic resonance (NMR), by measuring the proton spin-lattice relaxation time (T1H) using a low field NMR, and by thermal analysis as Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). DSC and TGA measurements show that both woods present the same molecular behavior. On the other hand, the spin-lattice relaxation time observed that the water is interfering in the packing and arrangements of cellulose chains due to inter and intra hydrogen molecular interactions, promoting the T1H values changed to high values. T1H shows that the sample B presents a higher rigidity than sample A. However, HIPS presents higher T1H values comparing to wood types. Analyzing the relaxation data for the composites, the values indicate that composites present an interaction between both components. 相似文献
950.
Density functional approximation for van der Waals fluids: based on hard sphere density functional approximation
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A universal theoretical approach is proposed which enables all hard
sphere density functional approximations (DFAs) applicable to van der
Waals fluids. The resultant DFA obtained by combining the universal
theoretical approach with any hard sphere DFAs only needs as input a
second-order direct correlation function (DCF) of a coexistence bulk
fluid, and is applicable in both supercritical and subcritical
temperature regions. The associated effective hard sphere density can
be specified by a hard wall sum rule. It is indicated that the value
of the effective hard sphere density so determined can be universal,
i.e. can be applied to any external potentials different from the
single hard wall. As an illustrating example, the universal
theoretical approach is combined with a hard sphere bridge DFA to
predict the density profile of a hard core attractive Yukawa model
fluid influenced by diverse external fields; agreement between the
present formalism's predictions and the corresponding simulation data
is good or at least comparable to several previous DFT approaches.
The primary advantage of the present theoretical approach combined
with other hard sphere DFAs is discussed. 相似文献