等衍射长度超短脉冲贝塞耳-高斯光束的传输特性

使用复解析信号法,研究了衍射长度与频率无关的超短脉冲贝塞耳－高斯光束在自由空间中的传输,推导出了解析表达式并进行了理论和计算分析.结果表明：在无衍射长度内,等衍射长度超短脉冲贝塞耳.高斯光束的横向光强分布扩展很小.在无衍射长度之外,横向光强分布有显著扩展.但是,在无衍射长度内轴上脉冲波形仍有展宽.随传输距离增加轴上蓝移单调增加逐渐达到一渐近值.随横向距离增加轴外光谱移动由蓝移变为红移.     

基于单片机的超声冲击装置频率跟踪控制和恒幅控制

对超声波冲击以提高焊接接头疲劳强度的装置进行了研究,研制出一台可用于实际冲击处理的样机。该样机以单片机为核心,采用自适应带通滤波器提取超声换能器工作的基波信号,在此基础上获得电流和电压的相位差,根据相位差用模糊控制方法来实现自动频率跟踪;通过电流控制执行机构的输出端振幅,使之恒定不变,对超声冲击处理的质量进行控制。该装置能够适应超声冲击这种负载变化十分剧烈的场合,并可实现准确的频率跟踪和保证冲击处理的质量及效率。     

“强光一号”预脉冲气体开关特性研究

 对“强光一号”加速器预脉冲气体开关特性进行了初步研究,估算开关固有电容等电气参数,给出了开关的直流自击穿特性。在此基础上,针对“强光一号”加速器预脉冲的特点,选取加速器中的预脉冲开关的工作间距及工作气压,在开关间距为24mm,气压为6.0×10⁵Pa时,成功的抑制了预脉冲。     

Studies on Microbial Biosensor for DL-Phenylalanine and Its Dynamic Response Process

Abstract

A biosensor for the determination of DL-phenylalanine, based on immobilized bacteria P. Vulgaris in calcium alginate gel coupled with an amperometric oxygen electrode, was designed and constructed. The effect of the culture medium, the response character of the electrode and its kinetic mechanism were studied, and the activity of phenylalanine deaminase was tested by biochemical method. The biosensor exhibited longer lifetime, higher sensitivity and faster response to the Phe in the linear range of 2.5×10^?5 to 2.5×10^?3 M for the optimum analytical performance. The relationship between the response velocity and the substrate concentration was also discussed. The results indicate that the dynamic response process of the reaction catalyzed by bacteria is similar to that by isolated enzymes. The apparent Michaelis constant. K_m ^app the apparent activation energy. E_a and the temperature coefficient, Q₁₀ for deaminase in the immobilized bacterial membrane were calculated to be 2.0×10^?3 M, 49.5kJ/mol and 1.86 respectively.     

Hilbert series of invariants, constant terms and Kostka-Foulkes polynomials

A problem that arose in the study of the mass of the neutrino led us to the evaluation of a constant term with a variety of ramifications into several areas from Invariant Theory, Representation Theory, the Theory of Symmetric Functions and Combinatorics. A significant by-product of our evaluation is the construction of a trigraded Cohen Macaulay basis for the Invariants under an action of SL_n(C) on a space of 2n+n² variables.     

Surfaces with high contact number and their characterization

The notion of contact number of a Euclidean submanifold was introduced in an earlier article (Proc. Edinb. Math. Soc. 47:69–100, 2004) as the highest order of contact of geodesics and normal sections on the submanifold. It was proved in (Proc. Edinb. Math. Soc. 47:69–100, 2004) that the contact number relates closely with the notions of isotropic submanifolds and holomorphic curves. One important problem concerning contact number is to construct Euclidean submanifolds with high contact number. The purpose of this article is thus to construct Euclidean surfaces with high contact number and to provide simple geometric characterization of such surfaces. Mathematics Subject Classification (2000) Primary 53C40, 53A10 Secondary 53B25, 53C42     

Topological conjugacy to given constant length substitution minimal systems

We find necessary and sufficient conditions for a symbolic dynamical system to be topologically conjugate to any given constant length substitution minimal system, thus extending the results in Coven et al. (2008) for the Morse and Toeplitz substitutions.     

Weibull分布场合具有非常数形状参数恒加试验的参数估计

本文讨论了Weibull分布场合恒加寿命试验的点估计和近似区间估计，利用模拟方法说明所给方法的有效性。     

空调水系统的压力分析及定压点的选择

根据伯努利方程分析讨论了空调水系统采用膨胀水箱定压时,定压点选在回水管最高点和循环水泵吸入口位置对水系统压力分布的影响,该分析对于系统的安全运行提供了充足的理论依据。     

Kinetic performance limits of constant pressure versus constant flow rate gradient elution separations. Part II: experimental

We report on a first series of experiments comparing the selectivity and the kinetic performance of constant flow rate and constant pressure mode gradient elution separations. Both water-methanol and water-acetonitrile mobile phase mixtures have been considered, as well as different samples and gradient programs. Instrument pressures up to 1200 bar have been used. Neglecting some small possible deviations caused by viscous heating effects, the experiments could confirm the theoretical expectation that both operation modes should lead to identical separation selectivities provided the same mobile phase gradient program is run in reduced volumetric coordinates. Also in agreement with the theoretical expectations, the cP-mode led to a gain in analysis time amounting up to some 17% for linear gradients running from 5 to 95% of organic modifier at ultra-high pressures. Gains of over 25% were obtained for segmented gradients, at least when the flat portions of the gradient program were situated in regions where the gradient composition was the least viscous. Detailed plate height measurements showed that the single difference between the constant flow rate and the constant pressure mode is a (small) difference in efficiency caused by the difference in average flow rate, in turn leading to a different intrinsic band broadening. Separating a phenone sample with a 20-95% water-acetonitrile gradient, the cP-mode leads to gradient plate heights that are some 20-40% smaller than in the cF-mode in the B-term dominated regime, while they are some 5-10% larger in the C-term dominated regime. Considering a separation with sub 2-μm particles on a 350 mm long coupled column, switching to the constant pressure mode allowed to finish the run in 29 instead of in 35 min, while also a larger peak capacity is obtained (going from 334 in the cF-mode to 339 in the cP-mode) and the mutual selectivity between the different peaks is fully retained.