Adaptive synchronization between two different chaotic systems with unknown parameters

A unified mathematical expression describing a class of chaotic systems is presented, for which the problem of adaptive synchronization between two different chaotic systems with unknown parameters has been studied. Based on Lyapunov stability theory, an adaptive synchronization controller is designed and analytic expression of the controller and the adaptive laws of parameters are developed. The adaptive synchronizations between Lorenz and Chen systems, a modified Chua's circuit and Rössler systems are taken as two illustrative examples to show the effectiveness of the proposed method.     

Linear Study of a Large-orbit Coaxial-waveguide Cyclotron Autoresonance Maser Amplifier

A linear theory based on Maxwell-Vlasov equations and the Laplace transform is presented to describe the large-orbit coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier. A 35-GHz, TE_5,1-mode large-orbit coaxial-waveguide CARM amplifier is specifically analyzed. Good agreement between the linear theory and the nonlinear simulations is found in the exponentially growing region of the wave. Results show that the operating magnetic field and the electron-beam energy and average radius substantially affect the power, and especially, a small beam current may be unsuitable to a large-orbit CARM amplifier operation.     

Enhanced nonlinear effects in photonic crystal fibers

Photonic crystal fibers are a new class of single-material optical fibers with wavelength-scale air holes running down the entire fiber length. Photonic crystal fibers were first developed in 1996 and have subsequently been the focus of increasing scientific and technological interest in the field of fiber optics. The manufacturing, principles, basic properties, and some applications of photonic crystal fibers are briefly described in this paper. A review of our recent work on the nonlinear effects in photonic crystal fibers is presented, and special emphasis is placed on such effects as supercontinuum generation, frequency conversion, and solitons observed when femtosecond light pulses propagate in these fibers.     

Excited state absorption and stimulated emission of Nd3+ in crystals. Part 2: YVO4, GdVO4, and Sr5(PO4)3F

3+ ion in the crystals YVO₄, GdVO₄, and Sr₅(PO₄)₃F. The measurements were performed in the spectral region of the main laser transitions ⁴F_3/2→⁴I_9/2, ⁴F_3/2→⁴I_11/2, and ⁴F_3/2→⁴I_13/2by a continuous wave pump and probe technique. The calibrated gain and ESA spectra are presented and possible implications of ESA on the laser performance are estimated. It is shown that ESA can be a small loss factor to the laser emission near 1060 nm but does considerably diminish the effective emission cross sections near 1340 nm especially in Nd:YVO₄ and Nd:GdVO₄. Received: 29 January 1998/Revised version: 8 May 1998     

新疆十字花科部分杂草种于微形态的研究

本文对新疆的十字花科9属9种杂草种子形状、大小、颜色及内部特征进行了描述，对种子外形、种皮进行电镜扫描，发现种皮微形态特征在种与种之间有明显的差异，并根据种皮微形态特征编制了分种检索表．     

Preparation of polymer microspheres from solutions

Polymer microspheres are obtained by the dropwise addition of a precipitant, containing a polymeric stabilizer, into a polymer solution, containing a polymeric stabilizer. The polymer and stabilizer concentrations, the stirring speed, and the precipitation temperature determine the size and size uniformity of the microspheres. Seven polymer microspheres of polyimide, poly(ether imide), poly(ether ketone), poly(phenylene oxide), polysulfone, poly(vinylidene fluoride), and cellulose diacetate have been prepared with dimethylacetamide as the solvent, with water as the precipitant, and with poly(vinyl alcohol) as the stabilizer. The size and size uniformity of the obtained microspheres are d = 2.3–25.7 μm and ? = 0.15–0.50, respectively (? = σ/d, where ? is the dispersion coefficient, d is the average diameter, and σ is the standard deviation of the diameter). © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 159–165, 2003     

类MgB2硼化物晶体电子结构比较研究

应用准确的第一原理方法 ,对 8种类MgB2 超导体结构的二硼化物进行了电子结构比较研究 ,发现其中的超导体具有特殊的能带属性 .对其在高压下态密度的变化情况做了对照 .     

频域标定飞秒脉冲干涉自相关迹及钛宝石振荡器实时啁啾监测

采用频域处理的方法首次在频域标定飞秒激光脉冲干涉自相关迹的时间扫描.计算被测脉冲的均方根宽度和啁啾参数，并以此为依据在实验中优化钛宝石振荡器的调节从而获得接近变换极限的115fs脉冲.该方法只涉及到数值积分和快速傅里叶变换，在实验中完全可以用于实时监测振荡器的运行情况. 关键词： 频域标定 钛宝石振荡器 飞秒脉冲 干涉自相关迹     

Isolation and characterization of beta-hydroxypropionic acid- and hydroxyacetic acid-uroporphyrin I in the urine of a patient with congenital erythropoietic porphyria by high performance liquid chromatography and liquid secondary ion mass spectrometry

beta-Hydroxypropionic acid- and hydroxyacetic acid-uroporphyrin I have been isolated from the urine of a patient with congenital erythropoietic porphyria by reversed phase high performance liquid chromatography. The compounds were characterized by their chemical behaviour and confirmed by liquid secondary ion mass spectrometry.