von Neumann群代数

设G是带左正则表示λ的一个离散群, VN（G）是λ（g）生成的von Neumann群代数。我们刻画了von Neu-mann群代数上的Hardy空间。     

工作休假和休假中止的M/G/1排队模型的适定性

主要研究工作休假和休假中止的M/G/1排队系统,首先将对应于此系统的数学模型转化为抽象Cauchy问题,其次证明对应于此排队模型的主算子生成正压缩C0半群T(t),然后证明T(t)是局部等距的,最后证明此模型存在唯一的非负时间依赖解。     

对位取代酚亚甲基桥三聚物的合成

本文报道通过2, 6-二羟甲基对取代酚和合适的对取代酚的缩合制备一系列对取代酚亚甲基桥三聚物的方法。产率一般为50%左右。     

非对称脉冲超强激光产生的尾场空泡区和超空泡区中的正电子加速

在震荡中心哈密顿原理的(oscillation-center Hamiltonian)框架下,讨论了用非对称圆极化的强激光脉冲激发的尾场和在超空泡区中加速正电子的相关问题.研究内容包括:在超强激光所激发的空泡后区中的尾场正电子加速方法和在超空泡区中的雪梨(snow-plow)正电子加速方法.通过理论分析和数值模拟方法定性地比较了2种正电子加速方法的有效加速性能.结果显示,尾场加速的效果比雪梨加速好,2种加速方法中激光脉冲振幅与被加速正电子的能量之间分别存在着指数关系和线性关系.文中还分析了正电子最大尾场和雪梨加速能量与等离子体密度之间的关系     

Enhancement of electron-positron pairs in combined potential wells with linear chirp frequency

Effect of linear chirp frequency on the process of electron-positron pairs production from vacuum is investigated by the computational quantum field theory. With appropriate chirp parameters, the number of electrons created under combined potential wells can be increased by two or three times. In the low frequency region, frequency modulation excites interference effect and multiphoton processes, which promotes the generation of electron-positron pairs. In the high frequency region, high frequency suppression inhibits the generation of electron-positron pairs. In addition, for a single potential well, the number of created electron-positron pairs can be enhanced by several orders of magnitude in the low frequency region.     

Ultrabright γ-ray emission from the interaction of an intense laser pulse with a near-critical-density plasma

An efficient scheme for generating ultrabright γ-rays from the interaction of an intense laser pulse with a near-critical-density plasma is studied by using the two-dimensional particle-in-cell simulation including quantum electrodynamic effects. We investigate the effects of target shape on γ-ray generation efficiency using three configurations of the solid foils attached behind the near-critical-density plasma: a flat foil without a channel (target 1), a flat foil with a channel (target 2), and a convex foil with a channel (target 3). When an intense laser propagates in a near-critical-density plasma, a large number of electrons are trapped and accelerated to GeV energy, and emit γ-rays via nonlinear betatron oscillation in the first stage. In the second stage, the accelerated electrons collide with the laser pulse reflected from the foil and emit high-energy, high-density γ-rays via nonlinear Compton scattering. The simulation results show that compared with the other two targets, target 3 affords better focusing of the laser field and electrons, which decreases the divergence angle of γ-photons. Consequently, denser and brighter γ-rays are emitted when target 3 is used. Specifically, a dense γ-ray pulse with a peak brightness of 4.6×10²⁶ photons/s/mm²/mrad²/0.1%BW (at 100 MeV) and 1.8×10²³ photons/s/mm²/mrad²/0.1%BW (at 2 GeV) are obtained at a laser intensity of 8.5×10²² W/cm² when the plasma density is equal to the critical plasma density n_c. In addition, for target 3, the effects of plasma channel length, foil curvature radius, laser polarization, and laser intensity on the γ-ray emission are discussed, and optimal values based on a series of simulations are proposed.     

反相高效液相色谱法同时测定食品中14种食品添加剂

采用反相高效液相色谱法研究了一次进样、同时测定食品中苯甲酸、山梨酸、尼泊金甲酯、尼泊金乙酯、尼泊金丙酯、尼泊金丁酯,糖精钠、安赛密,柠檬黄、日落黄、胭脂红、苋菜红、亮蓝及咖啡因等14种食品添加剂的分析方法.实验采用Hypersil ODS柱(4.6×200 mm,5μm,DEAIC)为分离柱,以20 mmol/L乙酸铵(pH 6.8)-甲醇为流动相,用紫外检测器234 nm、254 nm下进行检测,整个分析过程在18 min内完成.被测样品经简单处理后进样,其平均加标回收率为94.5%～99.1%,相对标准偏差小于4.5%.方法适用于食品常规质量检测.     

塔里木盆地克里雅河流域水化学特征及成因分析

为探讨克里雅河流域的水化学特征及其成因,于2014年夏季与2015年冬季实地采集了21个河水、8个地下水和1个高山湖水样品,并对样品的Na+、K+、Mg2+、Ca2+、HCO?3、CI?、SO2?4、NO?3等主要阴阳离子和相关的pH值、电导率、TDS值、硬度等因素进行测定,然后分析了流域水化学的时空变化特征、水化学类...     

激光等离子体相互作用中自生磁场及其空间演化

利用粒子模拟程序,模拟研究了超强激光与等离子体相互作用中的电子束流不稳定性的产生机制,得到了不稳定性所激发的自生磁场的线性增长率与各向异性参数之间的函数关系。观察到了激光与等离子体相互作用时产生的饱和自生磁场在表面领域上的演化过程,发现沿x方向出现的电流比较大时,饱和自生的磁场在z方向的发展比较快,临界面附近较大,但随着深度的增加,逐渐以指数形式减少。     

双荷粒子系统电四极和磁四极电磁辐射的双矢势对偶理论

利用电磁场四维双势法,首先给出了广义Maxwen和d'Alembert方程的解,并进-步给出了场强与四维双势的关系.然后利用有电荷存在时的d'Alembert方程推迟解.求出了带磁荷粒子和双荷粒子(Dyon粒子)的电磁辐射的表达式,并分别给出了电荷和磁荷所激发的电四极和磁四极辐射四维双矢势表达式.最后得到了双荷粒子电四极和磁四极辐射场表达式并对其物理性质进行了讨论.