Sz\`{a}sz-Mirakjan 算子拟中插式的点态逼近等价定理

Recently some classical operator quasi-interpolants were introduced to obtain much faster convergence. A.T. Diallo investigated some approximation properties of Szasz-Mirakjan Quasi-Interpolants, but he obtained only direct theorem with Ditzian-Totik modulus wφ^2r （f, t）. In this paper, we extend Diallo＇s result and solve completely the characterization on the rate of approximation by the method of quasi-interpolants to functions f ∈ CB[0, ∞） by making use of the unified modulus wφ^2r（f, t） （0≤λ≤ 1）.     

爆破动载作用下新喷射混凝土累积损伤效应的模型实验

利用模型实验的手段模拟了巷道的爆破掘进,并在实验中辅以声波测试,通过分析声波波速和声波波形的变化规律,研究了新喷射混凝土在多次爆破动载作用下的累积损伤效应。实验结果表明,爆破次数、与掌子面之间的距离和爆破药量均会影响喷射混凝土的累积损伤,这种影响体现在声波波速和波形2个方面:爆破次数增加、距离减小和药量增加,则声速降低值越大,波形变化越明显,即累积损伤值越大;爆破次数和距掌子面的距离均与累积损伤呈非线性关系,其中距离与爆破损伤之间的非线性关系可以用二次多项式进行较好的拟合;第一次爆破对声速和波形影响最大,造成的单次损伤值也最大;在小药量爆破的情况下,测试面的最大累积损伤值达到了0.1268,表明爆破近区喷射混凝土的损伤是需要关注的重点。     

基于光谱成像与光谱分析的壁画鉴赏研究

针对壁画鉴赏中对科学分析方法的需求,根据光谱成像及光谱分析方法在壁画处理中的特点与优势,重点讨论了光谱成像技术在壁画鉴赏处理中的应用,其可以辅助传统的专家经验鉴定方法,提供更丰富客观的画作信息,实现作品的鉴赏分析。光谱成像与分析方法是一类重要的科学分析方法,因其具有非接触、破损少甚至无破损、科学、准确、可量化等特点,可应用于壁画修复、信息提取、颜料分析、特征增强、鉴赏分析等。首先,从技术实现角度出发给出具体的鉴赏应用方向。然后,基于光谱特征分析、主成分分析、独立分量分析、相关性判别、人机交互处理等方法,对实际观测的韩休墓壁画进行实验处理,验证技术应用的实验效果,最后,结合应用实验提出包括规范化采集、图谱特征分析、图谱处理系统等关键技术还需进一步解决。实验结果表明,利用光谱成像分析技术可以实现壁画颜料信息的判读,隐藏信息的提取、弱信息的增强,不同属性的分类识别,同时,还可以综合特殊需求,开展画作图谱探索性研究,如壁画处理中的涂改小孩分析、画作修复等。     

A Frictional Heat Model of Planetary Roller Screw Mechanism Considering Load Distribution

Planetary roller screw (PRS), with higher thrust, higher load capacity, and higher speed, is the best choice of the transmission component of the servo system. However, spinning sliding of rollers and support bearings can cause frictional moments and frictional heat, which is an undesirable phenomenon. Besides, frictional heat will further result in high temperature that causes deterioration of lubrication and eventually lead to destruction of the mechanism. Therefore, it is important to predict frictional moments which result in frictional heat. In order to predict the magnitude of frictional heat of PRS mechanism and study the influence of structural parameters of thread and operating conditions on frictional heat, first, a frictional moment model of bearings is built, and frictional moments models of PRS considering the elastic hysteresis of material, the spinning sliding of the rollers, the viscosity of lubricating oil and the differential sliding of thread raceways are established in this paper, respectively. Second, heat generation models of bearing and PRS are presented, respectively. Finally, relationships between frictional heat in terms of operating conditions of PRS, contact angle, and helix angle of roller thread are investigated. The achievements of this project will provide theoretical basis for the design of PRS with lower frictional moments and higher transmission efficiency.     

内掺氮富勒烯N_2@C_(60)的几何结构和电子性质的密度泛函计算研究

采用密度泛函理论中的广义梯度近似对内掺氮富勒烯N2@C60的几何结构和电子性质进行计算研究.发现在N2@C60中,氮倾向以分子形式存在于C60中心处.键长分析、能级图、态密度图和电荷分析表明内掺氮分子对C60几何结构和电子结构带来的影响甚微.     

目标激光脉冲一维距离成像研究

根据激光雷达方程及粗糙面脉冲波束散射理论,提出了目标激光脉冲后向散射回波功率即激光一维距离像的计算表达式,并获得斜板、球和圆锥一维距离像的具体形式.数值计算结果与粗糙平板和圆锥激光脉冲回波强度实验数据比较,两者符合良好.数据分析表明,激光一维距离像曲线能够较好反映目标的纵向几何外形信息.我们着重讨论了入射激光脉冲宽度与目标径向尺寸对距离像的影响.上述研究可为激光波段的目标特征提取和识别提供理论依据.     

TiN对Co基合金激光熔覆层组织与性能的影响

采用5 kW CO2激光器在低碳钢表面熔覆Co基合金涂层及TiN/Co基合金复合涂层,研究了两种涂层的组织、显微硬度以及滑动磨损性能。结果表明,Co基合金涂层主要组成相为-γCo,-εCo,Cr23C6等,TiN/Co基合金复合涂层组成相为-γCo,-εCo,Cr23C6,TiN和TiC等。Co基合金涂层由发达的-γCo枝晶和其间共晶组织所组成,TiN/Co基合金涂层典型组织为等轴固溶体以及细小的共晶组织。TiN对熔覆层的组织有显著的改善作用,促使其组织细化,树枝晶向等轴晶转化,同时可显著提高Co基合金涂层的显微硬度及耐磨性能。     

Compact beam collimator for laser diode bar

A compact beam collimator for a laser diode (LD) bar fabricated by a simple method is presented. It consists of a single set of microlenses and a cylindrical lens, which are fabricated from SiO₂ rods using a fiber-drawing tower. The principle and parameter optimization of this device are investigated numerically using ZEMAX software and illustrated experimentally for a specific LD bar. It is shown that the output beam is well collimated in both the fast-axis and slow-axis directions; the beam quality is greatly enhanced via the redistribution of intensity in the two directions and by eliminating the fill factor for the LD bar.     

Nonuniformity correction algorithm with nonlinear model for infrared focal plane arrays

For the detector in infrared focal plane arrays (IRFPA) with a large dynamic range of response, a nonlinear model of response curve of the detector in IRFPA is introduced in this paper. With the model, the Kalman-filter nonuniformity correction (NUC) algorithm with linear model, developed by Torres and Hayat, is extended. In the extended algorithm, the raw image is translated into a linearized one firstly by directly employing a logarithm-based transformation. Then the linearized image is corrected by the Kalman-filter NUC algorithm with linear model, and the corrected linearized image is obtained. Finally the uniformity image of the original one is achieved by fulfilling an exponent transformation to the corrected linearized image. The presented algorithm not only inherits the advantage of the original algorithm that resolves the problem of the temporal drift in the gain and the bias in each detector by updating NUC parameters with information of the current scene, but also reduce the influence of the detector nonlinear response to the NUC performance, so it is suitable for IRFPA under large response-range. The NUC ability of the presented algorithm is demonstrated by experiments with real infrared image sequences.     

Slowing polar molecules using a wire Stark decelerator

We have designed and implemented a new Stark decelerator based on wire electrodes, which is suitable for ultrahigh vacuum applications. The 100 deceleration stages are fashioned out of 0.6 mm diameter tantalum and the array's total length is 110 mm, approximately 10 times smaller than a conventional Stark decelerator with the same number of electrode pairs. Using the wire decelerator, we have removed more than 90% of the kinetic energy from metastable CO molecules in a beam.