加权分数傅里叶变换在采样重构中的应用

针对频域非带限信号的重构问题,提出了一种基于加权分数傅里叶变换的采样与重构算法,并利用信号加权分数傅里叶变换在加权分数域的特性,得到了信号可完全重构的条件.理论分析和仿真结果表明,在满足给定误差的条件下,该算法能够以低于香农重构所需的采样率实现对信号的恢复,且简单易行,可利用FFT快速算法实现.     

钽内标X射线荧光光谱法测定钨精矿中WO_3

提出了以钽为内标波长色散X射线荧光光谱法测定钨精矿中WO3的新方法。以Na2B4O7和Li2B4O7(质量比65:35)的混合物作为熔剂,Ta2O5为内标,同时加入LiNO3为氧化剂,在1200℃下进行熔融制样,最后将本方法应用于实际样品的分析,结果表明,以钽作为内标测定WO3,不仅可以在很大程度上降低实验操作和仪器测量带来的偏差,也可以消除基体效应的影响。方法用于测定白钨精矿和黑钨精矿中WO3,其准确度和精密度优于重量分析法。     

常见饮料中咖啡因的拉曼光谱定性检测

利用激光拉曼光谱仪在微弱光信号检测方面的优点,用测试范围200nm-800nm,测试精度0．1nm的激光拉曼光谱仪对几种常见饮料进行测试,将265nm处咖啡因特征峰作为判断依据,定性检出饮料中含有咖啡因。     

Analysis of distances between inclusions in finite binary stochastic materials

A generalized probability density function (PDF) describing the distribution of inter-inclusion distances in finite, isotropic, binary stochastic materials with fixed diameter inclusions has been developed and tested. The new probability density function explicitly accounts for edge effects present in finite two- and three-dimensional stochastic materials. The generalized PDF is shown to include factors that are dependent on both the geometry of the material region as well as the statistical properties of the material. A discussion of the properties and application of this newly developed PDF is provided along with supporting numerical results for case studies in one- and two-dimensions. These numerical results demonstrate the ability of the newly derived PDF to correctly account for edge effects in finite stochastic materials, while still reproducing the expected distribution within the bulk material region.     

Reconstruction of band-limited signals from multichannel and periodic nonuniform samples in the linear canonical transform domain

Linear canonical transforms (LCTs) are a family of integral transforms with wide application in optical, acoustical, electromagnetic, and other wave propagation problems. This paper addresses the problem of signal reconstruction from multichannel and periodic nonuniform samples in the LCT domain. Firstly, the multichannel sampling theorem (MST) for band-limited signals with the LCT is proposed based on multichannel system equations, which is the generalization of the well-known sampling theorem for the LCT. We consider the problem of reconstructing the signal from its samples which are acquired using a multichannel sampling scheme. For this purpose, we propose two alternatives. The first scheme is based on the conventional Fourier series and inverse LCT operation. The second is based on the conventional Fourier series and inverse Fourier transform (FT) operation. Moreover, the classical Papoulis MST in FT domain is shown to be special case of the achieved results. Since the periodic nonuniformly sampled signal in the LCT has valuable applications, the reconstruction expression for the periodic nonuniformly sampled signal has been then obtained by using the derived MST and the specific space-shifting property of the LCT. Last, the potential applications of the MST are presented to show the advantage of the theory.     

采用树脂透镜的掌纹图像采集光学系统设计

为了获得高分辨率、高对比度和低畸变的掌纹图像,同时实现系统的轻量化和高性价比,本文基于全反射原理,采用树脂材料设计了一款由6片镜构成双远心光路的掌纹采集光学系统。树脂材料的选用减轻了光学系统的总重量;基于光的全反射原理的系统设计增强了掌纹图像的对比度;选择双远心光学结构,便于对倾斜物面所产生的梯形畸变进行矫正。对所设计光学系统的成像质量分析表明,该系统所有视场的光学传递函数（MTF）在Nyquist频率228 lp/mm处均达0.55以上,畸变〈0.14%。设计的光学系统可以采集120 mm×160 mm的手掌区域,实际手掌面上的分辨率达到500dpi,采集的掌纹图像分辨率达到8.0×106 pixel,满足了实际采集的要求。     

基于相关序列脉冲的布里渊光时域反射测量系统解码方法研究

布里渊光时域反射测量(BOTDR)系统空间分辨率和传感距离存在相互制约的关系.相关序列脉冲编码技术可用于解决这一矛盾,但直接对编码脉冲的布里渊散射采样信号进行解码,会因采样时间间隔小于编码单位脉冲宽度而导致解码信号的失真,从而降低了系统空间分辨率和测量精度.分析了直接互相关解码对BOTDR系统空间分辨率的影响,提出一种...     

Heavy quarkonia spectra and their decays in a relativistic quark model

Using the phenomenological relativistic harmonic model (RHM) for quarks, we have obtained the masses of S wave charmonium and bottomonium states. The full Hamiltonian used in the investigation has Lorentz scalar plus vector confinement potential, along with the confined one gluon exchange potential (COGEP). A good agreement with the experimental masses for the ground and the radially excited states is obtained both for the triplet and singlet S wave mesons. The decay properties of the ground state charmonium and bottomonium are investigated.     

A class of weighted estimators for additive hazards model in case-cohort studies

Case-cohort sampling is a commonly used and efficient method for studying large cohorts. In many situations, some covariates are easily measured on all cohort subjects, and surrogate measurements of the expensive covariates also may be observed. In this paper, to make full use of the covariate data collected outside the case-cohort sample, we propose＇a class of weighted estimators with general time-varying weights for the additive hazards model, and the estimators are shown to be consistent and asymptotically normal. We also identify the estimator within this class that maximizes efficiency, and simulation studies show that the efficiency gains of the proposed estimator over the existing ones can be substantial in practical situations. A real example is provided.     

威布尔分布族刻度参数的经验Bayes检验函数的收敛速度

本文研究了在"加权线性损失"下,威布尔分布族刻度参数经验Bayes (EB)检验问题.利用概率密度函数的递归核估计,构造了刻度参数的经验Bayes检验函数,并获得了它的收敛速度,在适当的条件下,收敛速度的阶可任意接近O(n^-1),推广了文献的结果.最后给出一个有关本文主要结果的例子.