Multiplicity of Homoclinic Solutions for Second Order Hamiltonian Systems with Local Conditions at the Origin

In this paper,the multiplicity of homoclinic solutions for second order non-autonomous Hamiltonian systems ü(t)-L(t)u(t)+▽_uW(t,u(t))=0 is obtained via a new Symmetric Mountain Pass Lemma established by Kajikiya,where L ∈C(R,R^N×N) is symmetric but non-periodic,W ∈C¹(R×R^N,R)is locally even in u and only satisfies some growth conditions near u=0,which improves some previous results.     

Testing the Intercept of a Balanced Predictive Regression Model

Testing predictability is known to be an important issue for the balanced predictive regression model. Some unified testing statistics of desirable properties have been proposed, though their validity depends on a predefined assumption regarding whether or not an intercept term nevertheless exists. In fact, most financial data have endogenous or heteroscedasticity structure, and the existing intercept term test does not perform well in these cases. In this paper, we consider the testing for the intercept of the balanced predictive regression model. An empirical likelihood based testing statistic is developed, and its limit distribution is also derived under some mild conditions. We also provide some simulations and a real application to illustrate its merits in terms of both size and power properties.     

A Highly Selective Fluorescent Probe for the Detection of Nitroreductase Based on a Naphthalimide Scaffold

The development of fluorescent probes for nitroreductase (NTR) has received intense attention because of its biological significance and wide application. In this work, a novel fluorescent probe for the detection of NTR in aqueous solution was designed and synthesized on a 1,8-naphthalimide scaffold. In the presence of NTR and nicotinamide adenine dinucleotide (NADH) under physiological conditions, the probe was converted into a 4-hydroxy-1,8-naphthalimide derivative and exhibited a sharp fluorescence enhancement at 550 nm, with a high selectivity for NTR over various analytes. The detection limit for NTR was determined to be 9.8 ng/ml by this probe. Due to its low signal background, this probe showed?>?70-fold fluorescence enhancement. Theoretical calculations revealed that the reason for the fluorescence quenching of this probe is the photoinduced electron transfer (PET) from both the nitrobenzene and morpholine groups to the naphthalimide fluorophore.

     

化学发光法大气氮氧化物浓度自动分析仪中光信号探测模块温控系统设计

化学发光法是测量低浓度的大气氮氧化物含量的有效方法,可用于24h连续自动分析的大气环境监测系统。然而该方法需要高温转换室、高压臭氧发生模块、高温反应室等模块,使得仪器内的环境分布极为复杂,仪器在长时间运行后容易出现灵敏度下降、信噪比降低等现象。针对上述现象,设计了用于仪器的光信号探测模块的温度控制系统。该温控系统基于PID控制原理,通过AVR单片机ATMEGAl6对半导体制冷片（Ther—mo—ElectricCooling,TEC）的闭环控制来实现温度的精密控制。实验结果表明,该系统可以使光信号探测模块的温度控制在5℃±0．1℃,光电倍增管的暗噪声从25℃时的363个／s下降到5℃时的8个／s光子数,噪声波动标准差也从22降到3,能够很好地满足系统对信号探测稳定性的要求。     

Structure and electrochemical performance of LiCoO2 cathode material in different voltage ranges

LiCoO₂ sample prepared by high-temperature solid state calcination shows a typical hexagonal structure with a single phase and fine particle size distribution. The high-voltage electrolyte with additive fluoroethylene carbonate (FEC) has been used. Electrochemical results show that the initial discharge capacities of the prepared LiCoO₂ cathode are 157.7, 169.5, 191.0, and 217.5 mAh g^?1 in the voltage ranges of 3.0–4.3, 3.0–4.4, 3.0–4.5, and 3.0–4.6 V, respectively. The capacity increases, while the initial coulombic efficiency and capacity retention decrease with increasing the charge cutoff voltage. The capacity retention is only 10.4 % after 200 cycles at 1C rate in the voltage range of 3.0–4.6 V. X-ray diffraction measurements confirm structural changes of the layered material in the different voltage ranges. A phase transition from the O3 to the H1-3 phase can be observed when LiCoO₂ is charged above 4.5 V. The AC impedance analysis indicates that the resistances (R _(sf+b), R _ct) of the prepared LiCoO₂ rapidly increase when the cell is charged to higher voltage. The amount of dissolved Co into the electrolyte also greatly increases with increasing the charge cutoff voltage.     

PERIODIC SOLUTIONS OF NEUTRAL FUNCTIONAL DIFFERENTIAL EQUATIONS

1 IntroductionThe problem of periodic solutions of nonlineax dtherential equations has been one Of thecenter problem to the tI1eory of differelltial equatiol1, it 11as wide application baCkground(8uchas fOrce oscillatioll of telecomnmnication, periodic euvironment in econondc system, etc.), soit has been a popular subject in the research work. In this paperl we discuss the problem ofperiodic solutions of the fOllowing nolllinear lleutral functional differential equatiollsd,dtD(ft xt) = f(f, …     

Crystal structure,dielectric and piezoelectric properties of Ta/W codoped Bi3TiNbO9 Aurivillius phase ceramics

Aurivillius phase Bi₃Ti_1−xTa_xNb_1−xW_xO₁₂ high temperature piezoceramics were prepared by a conventional solid state reaction method. The crystal structure, dielectric, electrical conduction and piezoelectric properties were systematically studied. Pure or modified Bi₃TiNbO₉ ceramics revealed the presence of only two-layered Aurivillius phase, indicating that Ta/W doping entered into the B-site of pseudo-perovskite structure and formed solid solutions. The Curie temperature had a strong reliance on the structural distortion. Furthermore, Ta/W dopants act as a donor doping, decrease the number of oxygen vacancies and facilitate the domain wall motion. As a result, Ta/W modifications significantly increase the DC resistivity and piezoelectric properties. Bi₃Ti_0.98Ta_0.02Nb_0.98W_0.02O₁₂ ceramics possess the optimum d₃₃ value (∼12.5 pC/N) together with a high T_C point (∼893 °C). Moreover, the resonance–antiresonance spectra demonstrate that the Ta/W-BTN ceramics are indeed piezoelectric in nature at 600 °C. The d₃₃ value of BTTNW-2 ceramic remains ∼12.2 pC/N after annealing at 700 °C. These factors suggest that the BTTNW-based ceramic is a promising candidate for ultra-high temperature sensor applications.     

Nd:YVO4自受激拉曼激光器调Q锁模特性

利用Nd:YVO4激光晶体的自受激拉曼效应,结合Cr:YAG被动锁模技术和倍频技术,实现了结构紧凑的1176 nm和588 nm黄光锁模激光输出。激光器为LD端面泵浦,三镜折叠腔结构,并且采用了透过率为10%的输出镜。Nd:YVO4晶体长度为10 mm,Nd3+离子掺杂质量分数为0.2%,Cr:YAG晶体的初始透过率为67%。10 W激光泵浦时,1176 nm激光平均输出功率为123 mW,调Q包络宽度为6 ns,调Q包络内的锁模脉冲重复频率高达1 GHz。588.2 nm 黄光的平均输出功率为8 mW。     

Polymer Optical Fiber Photosensitivities and Highly Tunable Fiber Gratings

In this paper, recent progress in the investigation of photosensitivities of polymer optical fibers and the development of polymer optical fiber grating is reported. Photosensitivities in various polymer fibers, including doped and undoped, multimode and single-mode polymer fibers, have been experimentally characterized and evaluated for fiber grating application. In particular, the wavelength dependence of material absorption and photosensitivity has been found essential to the fabrication of polymer optical fiber grating. Based on the results of photosensitivity research, polymer optical fiber gratings have been successfully fabricated. More importantly, polymer optical fiber grating has been demonstrated highly tunable, with a tuning range more than 70 nm. The unique feature of high tunability in polymer optical fiber grating has great potential in various applications including optical fiber WDM systems and fiber sensor systems. Several important issues that remain to be investigated will also be discussed.