Nonlinear adaptive IIR digital filter for linear system modeling

The structure and adaptive algorithm of a nonlinear adaptive IIR digital filter is presented. It does not need stability monitoring in the adaptive process, which has always been a computational burden and disturbs the adaptive process in linear adaptive IIR filtering. The individual parameter adaptation scheme is incorporated into the adaptive algorithm to optimally adjust each parameter at every iteration to improve convergence speed. Simulation results are conducted for linear IIR system modeling     

Study of synthetic diamonds by dynamic nuclear polarization-enhanced13C nuclear magnetic resonance spectroscopy

Four I_b-type synthetic diamond crystals were studied by dynamic nuclear polarization (DNP)-enhanced high resolution solid state¹³C nuclear magnetic resonance (NMR) spectroscopy. The home built DNP magic-angle-spinning (MAS) NMR spectrometer operates at a field strength of 1.9 T and the highest DNP enhancement factor of synthetic diamonds came near to 10³. Comparing with I_b-type natural diamonds, the¹³C NMR linewidths of synthetic diamonds in static spectra are broader. The¹³C spin-lattice relaxation time and DNP polarization time of synthetic diamond are shorter than those of I_b-type natural diamond. From the hyperfine structure of the DNP enhancement curve, four kinds of nitrogen-centred free radicals could be identified in synthetic diamond.     

神经网络A／D转换器电路的两种改进方法

本文对Ｈｏｐｆｉｅｌｄ神经网络Ａ／Ｄ转换器电路进行了分析。对照转换条件及电路的稳态方程，讨论了输出状态与参考输入必须满足的条件。在此基础上提出了两种改进Ａ／Ｄ转换电路的途径：（１）对原电路选择适宜的参考输入；（２）根据Ｈｏｐｆｉｅｌｄ线性规划网络提出的一种新电路。文中还给出了ＰＳＰＩＣＥ模拟计算，所得结果与理论分析吻合。     

Nd：MgO：LiNbO_3光波导的特性

用质子交换法制备了Ｎｄ：ＭｇＯ：ＬｉＮｂＯ３波导。通过测量平面波导的二次离子质谱，得到了波导的原子组分分布，并测量了Ｎｄ：ＭｇＯ：ＬｉＮｂＯ３晶体的吸收谱线，最后利用端面耦合，分别得到了条波导内和衬底内激光诱导的荧光谱线。     

阿尔芬波加热托卡马克等离子体的能量平衡问题

本文用“剖面不变性”确定等效电子热导系数,研究了TCA装置上阿尔芬波加热的能量平衡,结果与实验符合很好。证明本文所用的方法对不同装置、不同加热方式都适用。     

振荡奇异积分的L~p有界性

文中讨论了振荡奇异积分:其中对满足一定凸性条件的P以及Ω∈L~q(S~(n-1))(q>1),证明了T在L~P(R~n)上有界,p>1.     

Mössbauer study of magnetic ordering and superconductivity in YBa2(Cu1−xFex)3O7

We have made superconducting samples of the Y?Ba?Cu?O system with Fe substituted for the Cu. The percentage of Fe substituted varied from 2 to 100. The samples have been verified by x-ray diffraction to be single-phase 1–2–3 compounds. The 6% Fe substitution reduces T_c from 94 K to 80 K. The room temperature Mössbauer spectrum shows two pairs of doublets, indicating there are two distinct Cu sites in the sample. The most surprising result is that magnetic ordering of the Fe coexists with superconductivity of the material at 4.2 K.     

杂多阴离子的NMR和ESR研究——P-V-W Keggin阴离子的31P、51V、17O-NMR谱

本文合成了六种含有P-V-W和V-V-W Keggin结构的杂多阴离子,并研究了它们的³¹P、⁵¹V、¹⁷O-NMR谱,对于PV_xW_12-xO₄₀^(x+3)-(x=1~4)阴离子,当x=1时,³¹P和⁵¹V-NMR谱只有一条线,并且此线化学位移和pH无关。当x ≥ 2时,谱线数目随着x迅速增加,其原因是几何异构体的数目和类型迅速增加。它们的化学位移δ_p,和δ_v。依赖于溶液的酸性和x,即δ_p,随pH值和x增加而减少,而δ_v,却随pH和x的增加而增加。最后简短讨论了桥氧上质子化的影响。     

强激光系统中铜镜微变形实验研究

利用泰曼干涉仪及图像处理系统对强激光作用下不同冷却结构镜片包括空腔、环形通道几何结构铜镜的变形进行了实验研究，对其变形规律、变形机理作了探讨和分析。设计了一种新型多层冷却结构铜镜。将这几种铜镜的变形作比较．结果表明新结构铜镜不仅热变形小．而且由冷却流体压力引起的附加变形也很小．为有效控制强激光系统中镜片表面变形提供了有效途径。