DUST-ACOUSTIC SHOCK WAVES INTHE SHEATH OF DUSTY PLASMAS

The effect of dust charging and influence of its fluctuation on dust-acoustic shock waves in the sheath region of the dusty plasma is investigated. By employing the reductive perturbation technique, the Burgers' equation is derived. The weak shock wave solution is obtained and discussed in this dust-charge-fluctuation system.     

DUST-ACOUSTIC SHOCK WAVES IN THE SHEATH OF DUSTY PLASMAS

The effect of dust charging and influence of its fluctuation on dust-acoustic shock waves in the sheath region of the dusty plasma is investigated. By employing the reductive perturbation technique, the Burgers' equation is derived. The weak shock wave solution is obtained and discussed in this dust-charge-fluctuation system.     

Electron-Positron Pair Production in an Arbitrary Polarized Ultrastrong Laser Field

Electron-positron pair production in an arbitrary polarized ultrastrong laser field is investigated in the first order perturbation approximation in which the Volkov states are used for convenient calculation of scattering amplitude and cross section. It is found surprisingly that the optimal pair production depends strongly on the polarization. For some cases of field parameters, the optimal field is elliptically polarized or evenly circularly polarized one, rather than the usual linear polarization as indicated by previous works. Some insights into pair generation are given and some interesting unexpected features are also discussed briefly.     

2-取代硫醚(砜)-5-(4-硝基或4-甲氧苯基)-1,3,4-噻二唑类化合物的合成及抑菌活性

以4-硝基苯甲酸和4-甲氧基苯甲酸为起始原料,经酯化、酰肼化、成钾盐、闭环、硫醚化合成7个新化合物5.在乙醇中钼酸铵催化过氧化氢氧化合成了10个2-取代磺酰-5-(4-硝基或4-甲氧苯基)-1,3,4-噻二唑砜化合物6.所有化合物结构经过1HNMR,13CNMR,IR和元素分析确证.初步生物活性试验结果表明,在500μg·mL-1浓度下化合物5d对小麦赤霉病菌、辣椒枯萎菌、苹果腐烂菌的抑制率分别为99.0%,100.0%,100.0%;化合物6j在50μg·mL-1的浓度下对小麦赤霉病菌、辣椒枯萎菌、苹果腐烂菌的也有较好的抑制活性,其抑制率分别为47.7%,46.4%和50.6%.     

DETERMINATION OF FLOQUET STATES AND QUASI-ENERGY BY CORRELATION FUNCTION

The Floquet spectrum generated by the use of time correlation function has been developed to extract the Floquet functions with Fourier transform method for wave function at integral multiples of optical period. The quasi-energy position and ionization width of those Floquet states have also been determined by least-squares fit method. Numerical calculation shows that the Fourier transform method is powerful and the resultant Floquet functions are in excellent agreement with that obtained by orthogonality projection method developed in our previous work.     

三维热权函数法和多虚拟裂纹扩展技术

热权函数法直接利用温度场与热权函数的乘积的积分来求应力强度因子(SIF)的过渡过程，它可以免除对每一时刻进行热弹性力学有限元或边界元应力分析，计算效率大大提高。本文给出了三维热权函数法的基本方程，并提出了求解三维热权函数法基本方程的多虚拟裂纹扩展法(MVCE法)。在MVCE法中，可以引入无穷多个虚拟裂纹扩展模式；虚拟裂纹扩展模式与应力强度因子的插值直接相联系，所得到的方程组的系数矩阵是一个三对角矩阵，具有良好的计算性能。它对于裂纹前缘SIF分布急剧变化的情况，有良好的数值模拟能力。实例计算表明，MVCE法具有权高的计算效率，并具有很高的计算精度。     

纯水中超痕量无机及有机阴离子的毛细管电泳法同时测定

以钼酸钠-十六烷基三甲基氢氧化铵(CTAH)缓冲液体系为背景电解质溶液,建立了纯水中超痕量无机和有机阴离子 (Cl-、SO2-4、NO-3、F-、HCOO-、CH3COO-、C2O2-4)同时分析的毛细管电泳方法.考察了背景缓冲液组成对分离的影响,优化了进样方式和进样条件.在优化条件下,方法检出限为0.3 ～0.6 μg/L,RSD小于7%.采用所建立方法,实现了西安脉冲堆一回路水中6种阴离子的分析,分析结果相对标准偏差小于10%,加标回收率为82% ～120%.     

甘油对冰晶生长抑制作用的分子动力学模拟

采用分子模拟方法研究了正交晶系冰晶(020)生长面在不同浓度甘油水溶液中的生长情况. 通过统计分析氢键数、 密度分布函数、 均方根偏差和原子间径向分布函数研究了水分子和甘油分子的动态行为. 结果表明, 甘油分子在水溶液中可与水分子形成大量氢键, 这使水分子间的氢键作用受到抑制, 降低了水分子的扩散性, 致使冰晶不易成核和生长; 另外, 一些甘油分子可代替水分子吸附在晶面上, 甚至占据晶格位点, 这种行为打破了冰晶的对称性并且降低了冰晶的生长速率. 因此, 甘油可同时在晶面和液相中抑制冰晶的生长.     

氨氮标准样品测定中影响因素的探讨

氨氮作为环境监测的一项重要指标,在一定程度上反映了水体被污染的状况。氨氮在水中通常以游离氨或铵盐形式存在,测定方法有纳氏比色法、苯酚-次氯酸盐(或水杨酸-次氯酸盐)比色法和容量法等。纳氏比色法因操作简便、灵敏,而被作为测定氨氮的首选经典方法,但是在分析过程中,实验     

氨氦标准样品测定中影响因素的探讨

氨氮作为环境监测的一项重要指标，在一定程度上反映了水体被污染的状况。氨氮在水中通常以游离氨或铵盐形式存在，测定方法有纳氏比色法、苯酚一次氯酸盐（或水杨酸一次氯酸盐）比色法和容量法等。纳氏比色法因操作简便、灵敏，而被作为测定氨氮的首选经典方法，但是在分析过程中，实验室环境、试验用水、显色温度和pH等因素对测定结果都会产生影响。