一种新的图象展开算法

本文提出了一种对被压缩并产生几何畸变的图象进行展开的算法,它不仅可使图象的几何畸变获得了很好的矫正,而且使图象的灰度分布得到了恢复,图象边缘细节更清晰,实践已证明了该算法的高效性能.     

钙钛矿（GaTiO3）高压相变及等温压缩

 高温高压条件下对钙钛矿（Perovstsite）多晶进行了研究，在金刚石压砧设备上压力条件最高达38 GPa，YAG莱塞加热温度近1 000 ℃以上，用红宝石荧光校压系统进行压力标定。实验结果表明静水压条件X射线就位测量，GaTiO₃(Ⅰ)由斜方晶系在10 GPa时直接向六方GaTiO₃(Ⅱ)结构相变，体积变化为1.6％；1 000 ℃加热及其非静水压条件下GaTiO₃(Ⅰ)由斜方晶系首先转变为四方晶系GaTiO₃(Ⅲ)转变压力为8.5 GPa，体积变化为0％，继续增加压力导15 GPa，GaTiO₃(Ⅲ)向GaTiO₃(Ⅱ')转化成六方晶系，体积变化亦为1.6％。三种高压相，在压力降到一个大气压时都会消失，所以是逆转化的非淬火相。等温压缩在标准静水压条件下进行，压力应小于10.4 GPa，K₀'=5.6时，K₀=(210±7)GPa，此数据是根据Birch-Murnaghan状态方程求得的体模量。     

A method for constructing radial wave packets with application to target distortion in electron-atom collisions

It has been shown that an analysis of radial stationary state wave functions of a particle in terms of their loops leads to such continuous, single-valued and finite functions which represent a practically convenient form of the radial wave packets of that particle at various positions. The radial wave packets have been used to investigate target distortion in electron-atom collisions. The distortion of the target is defined in terms of quantum-mechanical probabilities given by the wave packets. A closed expression which depends upon the position of the colliding electron, is obtained for the potential energy of the target in the field of the colliding electron.     

36单元高功率双层径向线螺旋阵列天线功率容量

 对36单元高功率双层径向线螺旋阵列天线的功率容量进行了研究。讨论了真空状态下的微波击穿和真空与大气交界面的微波击穿，以这两种状态下的击穿阈值为依据，论证了阵列天线实现1 GW高功率微波辐射的可行性。采用有限元软件数值模拟了中心频率为4.0 GHz的阵列天线的功率容量，给出了模拟结果并分析了功率容量降低的原因；提出了提高阵列天线功率容量的技术途径。结果表明：改进的高功率双层径向线螺旋阵列天线可以实现1 GW高功率微波的发射。     

中国散裂中子源/快循环同步加速器电源系统数字化控制方案

在中国散裂中子源工程中, 需要设计1台1.6GeV快循环同步质子加速器. 加速器的磁铁电源系统驱动9套怀特电路. 这9套电源的输出都是带直流偏置的交流电流源. 在每个重复加速周期内, 电流(磁场)必须保证相位和幅值精度. 数字控制技术的可靠性、温度漂移抑制、高集成性等等使得它在越来越广泛地应用于控制电路的设计中. 为了达到中国散裂中子源电源系统苛刻的指标, 本文提出了一种数字化控制方案.     

非线性负载谐波电流测量及功率因数的研究

对典型单相非线性负载电流的谐波用2种方法进行分析:用余弦脉冲函数式表述出负载电流波形,对此函数式进行积分运算得出有功功率;又用谐波分析仪测量出此电流的10奇次谐波有效值,计算出了电流总谐波畸变率.给出了负载的广义功率因数为位移功率因数与畸变功率因数乘积的结论.指出了传统意义的功率因数与广义功率因数的区别,对谐波畸变率对广义功率因数的影响进行了讨论.     

Acoustic array tracking performance under moderately complex environmental conditions

The direction-of-arrival (DOA) tracking performance of microphone arrays having aperture sizes ranging from 0.3 to 34 m is examined for an experiment involving a vehicle traversing a moderately complex terrain. A segment of the vehicle’s path was obscured behind a small, 6.7-m high, vegetated hill. The combination of the hill and upwind propagation created an acoustic shadow during this segment. DOA tracks were estimated with a minimum-variance distortionless response (MVDR) beamformer operating in two frequency bands: 25-60 Hz and 60-105 Hz. In the lower frequency band, array sizes between 1 and 8 m gave the best results, with DOA errors between 2° and 5°. Furthermore, in this band shadowing from the hill and wind refraction had a minimal affect on DOA error. In the higher frequency band, the acoustic shadow zone produced a distinct interval of high DOA error, with the 8-m array giving the best overall performance. Modeling of the beamforming process shows that high DOA errors corresponded to MVDR wavenumber patterns that are degraded by distortions to the propagating wavefronts. Our experimental results indicate that small acoustic arrays with apertures less than 0.3 m, operating at frequencies above 100 Hz, should be considered line of sight sensors. Given the moderate complexity of the test conditions, it is anticipated that the observed effects are likely to be present in most attempts to localize outdoor sound sources.     

Crystal structure of [Mn2(III)(salpa)2Cl2(H2O)2] (H2salpa = 1-(salicylaldeneamino)-3-hydroxypropane)

The manganese complex, (Mn₂(III)(salpa)₂Cl₂(H₂O)₂], has been prepared and its structure determined using x-ray crystallography. The dimer is a di-₂-alkoxo complex which is a six-coordinate manganese dimer with unsupported alkoxide bridges and a rare example of a chloride- and water-containing manganese dimer. The complex crystallizes in the monoclinic space group P2₁/c with a = 9.315(5), b = 11.130(4), c = 11.637(5) Å, = 104.33(3)°, V = 1169.0(9) ų, and Z = 2. The structure comprises discrete binuclear clusters in which the metal atoms are bridged by two alkoxo oxygens of the salpa^2– ligands. The Mn—O and Mn—N distances are in good agreement with those found for other manganese(III) Schiff base complexes. The Mn—Cl and Mn—O3 distances are 2.585(2) and 2.371(2) Å, respectively, and the Mn ··· Mn distance is 3.001(1) Å. In the crystal, there are two types of hydrogen bonding between the H₂O molecule and the Cl atom with Cl ··· H(H₂O) distance of 2.33(6) (intramolecule: –1 + x, y, –1 + z) and 2.68(6) Å (intermolecule: –1 + x, 0.5–y, –0.5 + z).     

Colossal Negative Thermal Expansion in Electron‐Doped PbVO3 Perovskites

Colossal negative thermal expansion (NTE) with a volume contraction of about 8 %, the largest value reported so far for NTE materials, was observed in an electron‐doped giant tetragonal perovskite compound Pb_1?xBi_xVO₃ (x=0.2 and 0.3). A polar tetragonal (P4mm) to non‐polar cubic structural transition took place upon heating. The coefficient of thermal expansion (CTE) and the working temperature could be tuned by changing the Bi content, and La substitution decreased the transition temperature to room temperature. Pb_0.76La_0.04Bi_0.20VO₃ exhibited a unit cell volume contraction of 6.7 % from 200 K to 420 K. Interestingly, further gigantic NTE of about 8.5 % was observed in a dilametric measurement of a Pb_0.76La_0.04Bi_0.20VO₃ polycrystalline sample. The pronounced NTE in the sintered body should be attributed to an anisotropic lattice parameter change.