颗粒滚动摩擦系数对堆积特性的影响

为探讨颗粒摩擦系数对堆积特性的影响,利用离散单元法,模拟静摩擦系数固定时,变化滚动摩擦系数对椭球形颗粒堆积角及堆积体的影响.利用自制斜面仪测定了颗粒静摩擦系数,并对滚动摩擦系数与堆积角建立线性方程.结果表明,滚动摩擦系数对颗粒堆积特性有显著影响,颗粒堆积角随滚动摩擦系数增大而增大,边界圆与连续圆间的间隙随滚动摩擦系数增大而减小.依据颗粒堆积过程中旋转动能的变化可以阐述上述结果,建立的滚动摩擦系数与堆积角的线性方程可为具体颗粒物料滚动摩擦系数的获取提供数值测量思路.模拟堆积的过程可为散体物料一些不易测量的参数进行虚拟实验标定.     

叠加态下3色场波形优化增大谐波辐射截止能量及强度

在He~+离子1s态和2s态的叠加态作为初始态时,提出一种优化3束激光场来增大谐波截止能量和强度的方法.结果表明:在叠加初始态下,谐波强度要比基态初始态下增强3个数量级以上.随后,在3色场波形优化下,谐波截止能量又得到增大,进而获得一个高强度、高光子能量的谐波光谱连续区.通过叠加光谱连续区上最后100次的谐波可以获得一个27 as的孤立阿秒脉冲.     

Self-screening of the polarized electric field in wurtzite gallium nitride along [0001] direction

The strong polarization effect of GaN-based materials is widely used in high-performance devices such as white-light-emitting diodes (white LEDs), high electron mobility transistors (HEMTs), and GaN polarization superjunctions. However, the current researches on the polarization mechanism of GaN-based materials are not sufficient. In this paper, we studied the influence of polarization on electric field and energy band characteristics of Ga-face GaN bulk materials by using a combination of theoretical analysis and semiconductor technology computer-aided design (TCAD) simulation. The self-screening effect in Ga-face bulk GaN under ideal and non-ideal conditions is studied respectively. We believe that the formation of high-density two-dimensional electron gas (2DEG) in GaN is the accumulation of screening charges. We also clarify the source and accumulation of the screening charges caused by the GaN self-screening effect in this paper and aim to guide the design and optimization of high-performance GaN-based devices.     

1,8-二羟基-3-甲基-苯并［d,e］蒽酮的2D NMR研究

从中药芦荟(Aloe vera)中分离得到一个蒽酮类新化合物. 通过UV、IR、HREI-M S、¹H NMR和¹³C NMR及2D NMR(¹H-¹H COSY、HMBC、HMQC和J -resolved)方法， 鉴定其结构为：1,8- 二羟基-3-甲基-苯并［d,e］蒽酮. 文章的侧重点在于讨论该化合物的¹H和¹³C NMR信号的全归属.     

油田注水系统拓扑布局优化的混合遗传算法

以投资最小为目标函数,建立了注水系统拓扑布局优化数学模型.根据模型特点,将优化问题分为两层,分别采用遗传算法和非线性优化方法进行求解.并对遗传算法的操作过程进行了改进,调整了适应函数,改进了交叉和变异操作,结合了模拟退火算法,在操作过程中使约束条件得到满足,减少了不可行解的产生,使遗传算法的优化性能得到了提高.优化算例说明了该方法的有效性.     

稳定直线型硝酮加-O-·2 合物的构型因素解析

对生命体系中的氧自由基, Spin trapping-ESR方法是公认的特征分析手段[1].然而, 对超氧阴离子自由基(O-·2)而言, 其自由基加合物稳定性差.对此,人们通过改变硝酮的取代基团, 设计出更为有效的O-·2捕获探针[2,3].     

基于Fe3O4@Ag壳核结构磁性纳米复合物的对杀螟硫磷的电化学传感

制备一种壳核结构的Fe3O4@Ag磁性纳米粒子,将该纳米粒子通过壳聚糖（CS）修饰在玻碳电极（GCE）表面,制备了对杀螟硫磷有灵敏电化学传感的Fe3O4@Ag/CS/GCE。应用透射电镜（TEM）和紫外可见光谱（UV-VIS）,对Fe3O4@Ag纳米粒子进行表征。运用电化学交流阻抗（EIS）、循环伏安法（CV）和时间电流法（I-T）来研究杀螟硫磷电化学特性。研究发现,在1.74×10-7～3.27×10–4 mol/L浓度范围内,该传感器可以实现对杀螟硫磷的快速检测,检测限为5.7×10-8 mol/L（S/N=3）     

油水两液相一维非等温渗流的传递分析

在求解油水两液相非等温渗流的温度场、压力场基础上,以驱动功、驱动功率、驱动阻力、驱动速率为特征参数,对该过程进行(火用)传递分析。数值模拟的结果表明:含水通过降低油的相对渗透率、从而增大驱动阻力、减小驱动功率, 最终导致原油产量降低。     

基因组重排问题的一个近似算法

分子生物学中基因无方向的反向基因组重排问题在数学上已被证明是一个NP困难问题．基于断点图的概念，给出一个时间复杂性为O(max{b^(π)，nb(π)})，空间复杂性为0(n)的求其近似最优解的算法．其中n为基因组中基因个数，π=(π1,π2，…，πn)表示n个基因的一种排列，b(π)表示排列π中的断点数．数据实验的结果表明，该近似算法可以求得较好的结果．     

Lattice Boltzmann Simulation for the Optimized Surface Pattern in a Micro-Channel

Based on the Bhatangar-Gross-Krook （BGK） models, numerical simulation using the lattice Boltzmann model is performed to investigate the optimized surface pattern in a micro-channel. In order to simulate the practical situation correctly, a slip/no-slip boundary condition is applied with making several assumptions. To assess the validity and efficiency of the model, one benchmark problem with considering the surface patterns is studied. Numerical results show the value of rms velocity Vrms increases with the increasing ratio β and larger Reynolds number Re, higher fluctuation of the rms oscillating velocity. Furthermore, the results show that a good mixing effect can be obtained when Re is large enough and the ratio β is about 1.618,which is the appropriate choice, i.e. the well known golden section phenomenon.