非对称双原子分子在输运扩散中的取向效应

本文建立了同时具有化学势梯度和温度梯度的非平衡系统,研究非对称双原子分子的输运扩散行为.研究发现,双原子分子在非平衡输运中具有取向效应.浓度梯度与温度梯度使双原子分子在输运中产生的大小原子取向的方向刚好相反,沿着梯度的正方向,前者使小原子在前,后者使大原子在前.通过最小熵产生原理,解释了取向的物理机制.研究结果对于深刻理解非平衡条件下物质的输运与其形态的关系具有理论意义.     

Closed-form breakdown voltage/specific on-resistance model using charge superposition technique for vertical power double-diffused metal–oxide–semiconductor device with high-κ insulator

An improved vertical power double-diffused metal–oxide–semiconductor(DMOS) device with a p-region(P1) and high-κ insulator vertical double-diffusion metal–oxide–semiconductor(HKP-VDMOS) is proposed to achieve a better performance on breakdown voltage(BV)/specific on-resistance(Ron,sp) than conventional VDMOS with a high-κ insulator(CHK-VDMOS).The main mechanism is that with the introduction of the P-region,an extra electric field peak is generated in the drift region of HKP-VDMOS to enhance the breakdown voltage.Due to the assisted depletion effect of this p-region,the specific on-resistance of the device could be reduced because of the high doping density of the N-type drift region.Meanwhile,based on the superposition of the depleted charges,a closed-form model for electric field/breakdown voltage is generally derived,which is in good agreement with the simulation result within 10% of error.An HKP-VDMOS device with a breakdown voltage of 600 V,a reduced specific on-resistance of 11.5 m?·cm~2 and a figure of merit(FOM)(BV~2/Ron,sp)of 31.2 MW·cm~(-2) shows a substantial improvement compared with the CHK-VDMOS device.     

世界上最老的生命究竟有多老?

 如果你像一棵13000年帕默氏栎树那样静观人类的万年演变,你会有什么感觉?如果你更高寿地活到10万岁,看自然变迁,看人类一代又一代的生生死死,又会是什么感觉?     

低应力软岩复合顶板大变形煤巷支护技术

 低应力软岩复合顶板煤巷,虽然埋深较浅,围岩自重应力水平不高,但因顶底板岩层岩性及结构的特殊性,巷道围岩具有软岩的特性。以黑沟煤业有限公司主采4-2煤层回采巷道为工程背景,对该地质条件下巷道支护技术进行研究,结果表示,锚杆支护产生的夹持作用可提高巷道浅部围岩完整程度及深部围岩承载能力,缩小浅部围岩的破坏范围;锚索支护能够提高深部围岩与浅部围岩的整体性,减缓围岩的整体沉降运动趋势;金属网与钢带可加强对表面围岩的约束作用,限制破坏区向深部发展和表面围岩的冒落变形,减小顶板岩层的变形;底角锚杆能够促使应力峰值向深部的转移,减轻垂直应力向水平应力的转化程度,控制巷道底臌变形。上述支护方式的综合运用,可实现复合软岩大变形煤巷的有效支护。     

Wavefront reconstruction algorithm for wavefront sensing based on binary aberration modes

We propose a new algorithm for wavefront sensing based on binary intensity modulation. The algorithm is based on the fact that a wavefront can be expended with a series of orthogonal and binary functions, the Walsh series. We use a spatial light modulator(SLM) to produce different binary-intensity-modulation patterns which are the simple linear transformation of the Walsh series. The optical fields under different binary-intensity-modulation patterns are detected with a photodiode.The relationships between the incident wavefront modulated with the patterns and their optical fields are built to determinate the coefficients of the Walsh series. More detailed and strict relationship equations are established with the algorithm by adding new modulation patterns according to the properties of the Walsh functions. An exact value can be acquired by solving the equations. Finally, with the help of phase unwrapping and smoothing, the wavefront can be reconstructed. The advantage of the algorithm is providing an analytical solution for the coefficients of the Walsh series to reconstruct the wavefront. The simulation experiments are presented and the effectiveness of the algorithm is demonstrated.     

基于开尔文滴水起电器的废水处理系统

基于开尔文滴水起电原理提出了一种利用高压静电场对废水进行氧化的废水处理系统.为了提高对废水的氧化杀菌效率,研究了影响起电效果的因素,并根据实验数据优化了废水处理系统的结构.经过验证实验表明,提出的高压静电场废水处理系统,能有效将亚甲基蓝溶液氧化,体现了氧化杀菌的能力,且无需输入外界能源,具有环保、无二次污染的优势.     

基于计算机视觉的微球缺陷检测及分类方法

惯性约束聚变试验中,对大批量的聚变靶球的表面质量进行检测和分类是一项重要的工作。传统的人工检测分类方法效率低,精度差,难以满足实际需要。提出了一种基于计算机视觉的缺陷检测及分类方法。该方法在获取待测微球的显微图像之后,通过设置兴趣区域提取圆内部的像素点,并以此绘制灰度直方图。然后计算其累积分布函数,经归一化处理之后对分布函数进行分段线性拟合。最终根据拟合后的分布函数,提出均匀性和透光性两个参数用于定量表示微球的表面质量,很好地实现了光滑、粗糙和畸形三种类型的微球的分类。实验结果表明,该检测分类方法的准确率均在90%以上,处理1280960分辨率的包含20个微球的图像平均只需300 ms,准确高效,可扩展性强。     

用于飞秒时间分辨分子反应动力学研究的千赫兹离子/电子速度成像仪

A new velocity map imaging spectrometer is constructed for molecular reaction dynamics studies using time-resolved photoelectron/ion spectroscopy method.By combining a kHz pulsed valve and an ICCD camera,this velocity map imaging spectrometer can be run at a repetition rate of 1 kHz,totally compatible with the fs Ti:Sapphire laser system,facilitating time-resolved studies in gas phase which are usually time-consuming.Time-resolved velocity map imaging study of NH₃ photodissociation at 200 nm was performed and the time-resolved total kinetic energy release spectrum of H+NH₂ products provides rich information about the dissociation dynamics of NH₃.These results show that this new apparatus is a powerful tool for investigating the molecular reaction dynamics using time-resolved methods.     

平头弹丸正撞下钢筋混凝土靶板厚度方向的开裂

主要针对钢筋混凝土靶板在受到平头弹丸撞击下发生的厚度方向开裂的问题进行研究,并提出了一个弹丸低速撞击有限厚度板的二阶段模型。模型中第一阶段为侵彻阶段,弹丸受到混凝土介质的侵彻阻力由静阻力和速度效应引起的动阻力组成;模型中第二阶段为开裂阶段,钢筋混凝土靶板发生动态剪切破坏的最大承载力可以通过静态剪切破坏最大承载力乘以一个动态增强因子得到。该模型可以用来预测钢筋混凝土靶板发生厚度方向开裂破坏的临界能量。模型预测与实验结果吻合较好。     

环糊精柱结合液质联用方法测定果蔬中烯酰吗啉异构体残留量

基于乙二胺-β-环糊精的包结分离作用,建立了一种快速、简便的检测5种果蔬（黄瓜、葡萄、莴苣、茄子和土豆）中烯酰吗啉顺反-异构体的LC/MS方法。果蔬中残留的烯酰吗啉异构体用QuEChERS方法提取,然后用自组装的N-丙基乙二胺（PSA）、石墨化炭黑（GCB）和磁性四氧化三铁纳米粒子（MNPS）复合物进行快速净化。由于乙二胺-β-环糊精柱能与顺、反烯酰吗啉异构体形成稳定性不同的包结物,环糊精柱能高效分离几何异构体,结合液质联用技术,通过选择离子监测灵敏地测定5种果蔬中的顺、反烯酰吗啉异构体残留量。考察了不同柱温对烯酰吗啉异构体分离度的影响以及电喷雾离子化等优化条件。采用0.1%甲酸-乙腈（1090,v/v）作流动相,流速0.5mL·min^-1,在20℃的柱温下,烯酰吗啉顺反异构体在环糊精柱上的分离度（Rs）为2.2,分析时间在10min内。烯酰吗啉顺反异构体的质谱定量离子m/z 388.20->301,Q1电压是-18ev,碰撞能量（CE）-21ev以及Q3电压是-20ev,碰撞能量（CE）-32ev。对于反式-和顺式-烯酰吗啉分别在0.125²0μg·kg^-1和0.375⁶0μg·kg^-1范围存在良好的线性关系（r>0.999）。它们的最低检出限（LODs,S/N=3）分别为0.035⁰.066和0.015⁰.069μg·kg^-1。基质样品的加标回收率均在76%¹09.0%之间,对反式-烯酰吗啉的日内精密度和日间精密度在3.2%⁸.2%和2.9%⁹.9%范围,而对于顺式-烯酰玛琳的日内精密度和日间精密度在1.1%⁶.9%和2.3%¹0.1%范围。该方法简便、快速和准确,适用于果蔬中烯酰吗啉顺、反异构体的含量测定。