Photoassociation Reactions H＋D^＋ and H^＋ ＋D in Ultrashort Pulse Laser Fields

The photoassociation reactions H＋D^＋ and H＋ ＋D induced by the one- and two-colour laser pulses are theoretically studied. The reactions occur through two channels： （i） H（1S）＋D^＋ →HD^＋, and （ii） H^＋ ＋D（1S）→HD^＋. The reaction probability through channel （ii） is higher than through channel （i）. The populations of the products H^＋ ＋D and HD＋ and the ratio of H^＋ ＋D to HD＋ can be controlled by laser pulses. The two-colour laser pulses can more efficiently lower the dissociation probability and therefore enhance the yield ratio of the product HD＋.     

A Comparison between AlN Films Grown by MOCVD Using Dimethylethylamine Alane and Trimethylaluminium as the Aluminium Precursors

Aluminium nitride (AlN) films grown with dimethylethylamine alane (DMEAA) are compared with the ones grown with trimethylaluminium (TMA). In the high-resolution x-ray diffraction Ω scans, the full width at half maximum (FWHM) of (0002) AlN films grown with DMEAA is about 0.70 deg, while the FWHM of (0002) AlN films grown with TMA is only 0.11 deg. The surface morphologies of the films are different, and the rms roughnesses of the surface are approximately identical. The rms roughness of AlN films grown with DMEAA is 47.4nm, and grown with TMA is 69.4nm. Although using DMEAA as the aluminium precursor cannot improve the AlN crystal quality, AlN growth can be reached at low temperature of 673K. Thus, DMEAA is an alternative aluminium precursor to deposit AlN film at low growth temperatures.     

Autler-Townes Splitting in Photoelectron Spectrum of Three-Level Li2 Molecule in Ultrashort Pulse Laser Fields

The Autler-Townes （AT） splitting in femtosecond photoelectron spectrum of three-level Li2 molecules is theoretically investigated using time-dependent quantum wave packet method. With proper femtosecond laser pulses, three peaks of the AT splitting can be observed in the photoelectron spectrum. The AT splitting stems from rapid Rabi oscillation caused by intense ultrashort laser pluses. The effects of laser parameters on the molecular ionization dynamics are also discussed.     

高压串级延迟击穿开关在快前沿脉冲触发源中的应用

 报导了一种高压串级延迟击穿（DBD）开关在快脉冲触发源中的应用，介绍了脉冲源的电路结构和工作原理，并将DBD开关成功应用于快前沿脉冲触发源，获得了明显的脉冲陡化效果。串级DBD开关的级数为15级，直流击穿电压45 kV，脉冲工作电压60 kV，脉冲前沿由95 ns减小到21.5 ns，脉冲宽度50 ns。     

真实尾流的光学特性

在实验室对模拟尾流气泡幕研究的基础上,设计了用于真实尾流测试的水下实验系统通过对千湖1号船在不同航速下尾流的几何特征进行观察和分析计算,得到了尾流深度、宽度与航速的关系,并且对尾流的水面宽度以及散开角进行了估计.在5km/h,10km/h和15km/h的航速下对尾流不同几何部位的激光透射强度进行了测量,结果与理论计算基本一致.从透射光的相对强度来分析实验结果,可以认为自然光的影响是一个次要因素.     

氧化铁-氧化锌体系的结构及其催化活性

铁酸盐是丁烯氧化脱氢制丁二烯的优良催化剂,本文联合X光衍射、穆斯鲍尔能谱和电子顺磁共振等三种方法对ZnFe₂O₄、ZnCrFeO₄和ZnCrFeO₄/SiO₂等三种铁酸盐进行晶相,铁的价态、化学环境以及顺磁中心考察,并关联其氧化脱氢催化活性,以试图能认识这类催化剂的活性本质,本文还探讨了在丁烯氧化脱氢生成丁二烯反应中催化活性中心的可能结构。     

Modelling of massive particulates for breakwater engineering using coupled FEMDEM and CFD

The seaward slope of many breakwaters consists of thousands of interlocking units of rock or concrete comprising a massive granular system of large elements each weighing tens of tonnes. The dumped quarry materials in the core are protected by progressively coarser particulates. The outer armour layer of freely placed units is intended to both dissipate wave energy and remain structurally stable as strong flows are drawn in and out of the particulate core. Design guidance on the mass and shape of these units is based on empirical equations derived from scaled physical model tests. The main failure mode for armour layers exposed to severe storms is hydraulic instability where the armour units of concrete or rock are subjected to uplift and drag forces which can in turn lead to rocking, displacement and collisions sufficient to cause breakage of units. Recently invented armour unit designs making up such granular layered system owe much of their success to the desirable emergent properties of interlock and porosity and how these combine with individual unit structural strength and inertial mass. Fundamental understanding of the forces governing such wave-structure interaction remains poor. We use discrete element and combined finite-discrete element methods to model the granular solid skeleton of randomly packed units coupled to a CFD code which resolves the wave dynamics through an interface tracking technique. The CFD code exploits several methods including a compressive advection scheme, node movement, and general mesh optimization. We provide the engineering context and report progress towards the numerical modelling of instability in these massive granular systems.     

求解广义中立型系统的线性多步方法的NGP_G-稳定性

建立了广义中立型延迟系统理论解渐近稳定的充分条件 ,分析了用线性多步方法求解广义中立型延迟系统数值解的稳定性 ,在一定的Lagrange插值条件下 ,证明了数值求解广义中立型系统的线性多步方法NGPG_稳定的充分必要条件是线性多步方法是A_稳定的·     

层状粘接结构超声检测信号的同态解卷积脱粘界面定征

本文利用建立的多层粘接结构超声无损检测信号的卷积模型,推导出了检测信号的解析表达式,并用同态滤波解卷积方法有效地提取出粘接结构的系统响应,进而由其中界面多次反射响应的位置、幅度和包络等特征参数,实现了脱粘二界面（指空气脱粘）的定征和识别。仿真和实验数据的处理结果表明本文方法对脱粘检测的应用有积极的意义。     

Bi_2O_3-Li_2O玻璃的热致变色研究

发现氧化和氧化锂所形成的玻璃有着明显的热致变色现象 .温度系数随氧化含量的增加而上升 ,反映了热致变色现象主要来源于氧化 .这种热致变色现象与半导体同样 ,来源于玻璃中的电子 声子相互作用而产生的随温度变化的光学能隙 .氧化重金属氧化物玻璃中高电子密度和低声子能量的化学键是产生强电子 声子相互作用的主要原因