柴胡中微量元素的初级形态及溶出特性研究

按照传统的中药煎煮方法对柴胡中铜、锌、铁、锰、钙、镁6种元素进行提取;用0.45μm微孔滤膜分离提取液中的可溶态和悬浮态;采用火焰原子吸收光谱法对柴胡中微量元素的初级形态进行了测定.结果显示:柴胡中6种元素的提取率在21.1%-45.8%之间,悬浮态在水煎液中的比率在4.3%-12.0%之间.方法的加标回收率在96.7%-104.0%之间,相对标准偏差小于1.8%.     

液Zn对Fe_2Al_5涂层侵蚀的相变过程研究

本文对Fe2Al5涂层在液态Zn中的侵蚀相变过程进行了研究,实验结果表明:在侵蚀初期,靠界面张力平衡的作用,先发生热侵蚀,在试样表面形成热蚀沟,当热蚀沟达到一定程度后,液Zn与Fe2Al5相由不浸润变为浸润;同时Zn原子扩散进入Fe2Al5相并形成Fe2Al5-Znx固溶体相(η相);随着侵蚀时间的增加,发生在腐蚀界面上的液Zn对Fe2Al5涂层的侵蚀过程是恒温相变过程,相变过程使Fe2Al5涂层发生定向熔化.相变的驱动力来自于相成分的改变所引起的各相自由能的变化及各相间的相平衡的重新建立.     

线性指数危险率模型的贝叶斯判别分析

设有两个总体Π0和Π1，其危险率为具有不同参数的线性函数。对于待观测的寿命样本X，给出了相应的判别分析问题的Bayes停止判决法则，其中损失函数包括试验费用和误判损失两部分。      

不同荷载水平及速率下超软土水相核磁共振试验研究

大规模建设中面临越来越多的淤泥等超软土地基处理,其目的是尽可能排出超软土体中的水而使土体固结,以改善其物理力学性能.静动力排水固结法试图利用高能量冲击而将超软土中部分结合水转换为自由水,进而实现更多水的排出而有效固结.然而,目前还不十分清楚能造成这种水相变化的冲击荷载究竟要达到何种水平及速率.为此,在模拟条件的、淤泥土的不同类型荷载水平及速率试验基础上,进行核磁共振水相测试,探索了典型荷载水平及速率下这种超软土中结合水可转化为自由水的条件及规律,主要为:1)对应于通常工程荷载的较低能量真三轴试验荷载速率与水平(1.6 MPa/s与100 kPa及以下),淤泥类超软土中非自由水不能转化为自由水.2)对应于静动力排水固结法条件的高速冲击荷载下(每击荷载水平3787 kPa,速率631.2 MPa/s),非自由水可转化为自由水;且冲击总能量越大(遍数及击数越多),就越易析出自由水.3)约束样品的侧限刚度对非自由水转化为自由水的影响可忽略.     

Grammian and Pfaffian solutions as well as Pfaffianization for a (3+1)-dimensional generalized shallow water equation

Based on the Grammian and Pfaffian derivative formulae, Grammian and Pfaffian solutions are obtained for a (3+1)-dimensional generalized shallow water equation in the Hirota bilinear form. Moreover, a Pfaffian extension is made for the equation by means of the Pfaffianization procedure, the Wronski-type and Gramm-type Pfaffian solutions of the resulting coupled system are presented.     

高效外腔倍频产生426 nm激光的实验研究

利用与铯原子吸收线对应的852 nm半导体激光作为基频光,泵浦基于周期极化磷酸钛氧钾(PPKTP)晶体的环形腔,进行高效外腔谐振倍频并产生426 nm激光.在理论分析小角度环形腔内的热透镜效应基础上,发现晶体中等效热透镜中心位置并非在晶体的几何中心.在理论分析的基础上,实验上通过精密平移台精细调节PPKTP晶体在腔内位置,使得等效热透镜中心位置与谐振腔的腰斑位置重合,进而减小晶体热透镜效应导致的模式失配对倍频效率的影响.在泵浦功率为515 mW时产生了428 mW的426 nm激光输出,对应的倍频转换效率为83.1%.此高效倍频过程为制备与铯原子吸收线相匹配的非经典光场提供有效泵浦光,为推动量子非经典光场的应用以及量子信息科学的发展奠定基础.     

利用手持技术探究浓度对化学平衡的影响

为便于学生深入理解化学平衡知识点,借助手持技术,在教材的基础上,从定性探究单一浓度对Fe3+-SCN-平衡体系化学平衡移动的影响转化为定量探究多个浓度对化学平衡移动的影响,同时还探究了加入晶体后对化学平衡移动的影响。并通过对实验现象及图表的分析得出了随着加入硫氰化钾的浓度和质量的增加,化学平衡往正反应方向移动的程度增加的结论。     

A Note on Exact Solutions to Linear Differential Equations by the Matrix Exponential

It is known that the solution to a Cauchy problem of linear differential equations: $$x'(t)=A(t)x(t), \quad {with}\quad x(t_0)=x_0,$$ can be presented by the matrix exponential as $\exp({\int_{t_0}^tA(s)\,ds})x_0,$ if the commutativity condition for the coefficient matrix $A(t)$ holds: $$\Big[\int_{t_0}^tA(s)\,ds,A(t)\Big]=0.$$ A natural question is whether this is true without the commutativity condition. To give a definite answer to this question, we present two classes of illustrative examples of coefficient matrices, which satisfy the chain rule $$ \frac d {dt}\, \exp({\int_{t_0}^t A(s)\, ds})=A(t)\,\exp({\int_{t_0}^t A(s)\, ds}),$$ but do not possess the commutativity condition. The presented matrices consist of finite-times continuously differentiable entries or smooth entries.     

Alkylation reactions of benzothiazoles with N,N-dimethylamides catalyzed by the two-component system under visible light

Eosin Y/K₂S₂O₈ catalyzed C2-alkylation reactions of benzothiazoles with N,N-dimethylamides under visible light have been developed. The reactions completed smoothly in the presence of Eosin Y as the photocatalyst and K₂S₂O₈ as the oxidant under solvent-free conditions in open air. This green and simple method provides an alternative route for the synthesis of C2-alkylation of benzothiazoles and tolerates a number of functional groups to afford moderate to excellent yields.     

Reduced nonlocal integrable mKdV equations of type (−λ, λ) and their exact soliton solutions

We conduct two group reductions of the Ablowitz–Kaup–Newell–Segur matrix spectral problems to present a class of novel reduced nonlocal reverse-spacetime integrable modified Korteweg–de Vries equations. One reduction is local, replacing the spectral parameter with its negative and the other is nonlocal, replacing the spectral parameter with itself. Then by taking advantage of distribution of eigenvalues, we generate soliton solutions from the reflectionless Riemann–Hilbert problems, where eigenvalues could equal adjoint eigenvalues.