石英晶体板非线性高频振动的拓展伽辽金法分析

针对考虑几何和材料非线性的石英晶体板厚度剪切振动和弯曲振动的方程组,利用扩展伽辽金法对该方程组进行转化和求解,分别获得了强烈耦合的厚度剪切振动模态和弯曲振动模态的频率响应关系,绘制了不同振幅比和不同驱动电压影响下的频率响应曲线图。数值计算结果表明可以选取石英晶片的最佳长厚比尺寸来避免两种模态的强烈耦合。驱动电压的变化将引起石英晶体谐振器厚度剪切振动频率的明显改变,必须将振动频率的漂移值控制在常用压电声波器件的允许值之内。扩展伽辽金法对石英晶体板非线性振动方程组的求解为非线性有限元分析和偏场效应分析奠定了基础。     

Theoretical study on the mechanism for the excited-state double proton transfer process of an asymmetric Schiff base ligand

Excited-state double proton transfer (ESDPT) in the 1-[(2-hydroxy-3-methoxy-benzylidene)-hydrazonomethyl]-naphthalen-2-ol (HYDRAVH₂) ligand was studied by the density functional theory and time-dependent density functional theory method. The analysis of frontier molecular orbitals, infrared spectra, and non-covalent interactions have cross-validated that the asymmetric structure has an influence on the proton transfer, which makes the proton transfer ability of the two hydrogen protons different. The potential energy surfaces in both S₀ and S₁ states were scanned with varying O-H bond lengths. The results of potential energy surface analysis adequately proved that the HYDRAVH₂ can undergo the ESDPT process in the S₁ state and the double proton transfer process is a stepwise proton transfer mechanism. Our work can pave the way towards the design and synthesis of new molecules.     

Conformational change-modulated spin transport at single-molecule level in carbon systems

Controlling the spin transport at the single-molecule level, especially without the use of ferromagnetic contacts, becomes a focus of research in spintronics. Inspired by the progress on atomic-level molecular synthesis, through first-principles calculations, we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups, contacted by atomic carbon chain electrodes. It is found that, by rotating the functional group, the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states. Moreover, the transition between spin-up and spin-down polarized states can also be achieved, operating as a dual-spin filter. Further analysis shows that, it is the spin-dependent shift of density of states, caused by the rotation, that triggers the shift of transmission peaks, and then results in the variation of spin polarization. Such a feature is found to be robust to the length of the nanoflake and the electrode material, showing great application potential. Those findings may throw light on the development of spintronic devices.     

CdS/Si nanofilm heterojunctions based on amorphous silicon films:Fabrication,structures,and electrical properties

Shortening the distance between the depletion region and the electrodes to reduce the trapped probability of carriers is a useful approach for improving the performance of heterojunction.The CdS/Si nanofilm heterojunctions are fabricated by using the radio frequency magnetron sputtering method to deposit the amorphous silicon nanofilms and Cd S nanofilms on the ITO glass in turn.The relation of current density to applied voltage(I-V)shows the obvious rectification effect.From the analysis of the double logarithm I-V curve it follows that below~2.73 V the electron behaviors obey the Ohmic mechanism and above~2.73 V the electron behaviors conform to the space charge limited current(SCLC)mechanism.In the SCLC region part of the traps between the Fermi level and conduction band are occupied,and with the increase of voltage most of the traps are occupied.It is believed that Cd S/Si nanofilm heterojunction is a potential candidate in the field of nano electronic and optoelectronic devices by optimizing its fabricating procedure.     

构建核壳结构增强Ho~(3+)离子在镥基纳米晶中的红光上转换发射

本文主要以具有六方相结构的NaLuF_4:Yb~(3+)/Ho~(3+)/Ce~(3+)纳米晶体为核,采用外延生长法构建具有同质结构的NaLuF_4:Yb~(3+)/Ho~(3+)/Ce~(3+)@NaLuF_4:Yb~(3+)核壳纳米晶体.借助X-射线衍射仪及透射电子显微镜对样品的晶体结构、形貌及尺寸进行表征.在近红外光980nm激光激发下,通过构建核壳结构及有效调控外壳中敏化离子Yb~(3+)离子的掺杂浓度,实现Ho~(3+)离子在NaLuF_4纳米晶体中的红光发射增强.实验结果表明:在相同的激发条件下,具有核壳结构的NaLuF_4:Yb~(3+)/Ho~(3+)/Ce~(3+)@NaLuF_4:Yb~(3+)纳米晶体的红光发射均得到了增强,同时,当外壳中Yb~(3+)离子的掺杂浓度为10.0%时,其上转换红光发射强度最强,为NaLuF_4:Yb~(3+)/Ho~(3+)/Ce~(3+)晶体核红光发射强度的5.8倍.根据其光谱特性及发光动力学过程,讨论了同质壳及壳中敏化离子掺杂浓度变化对其发光特性的影响规律.这种具有较强红光发射的核壳结构纳米晶体在生物医学、防伪编码、多色显示等领域具有较大的应用前景.     

组织忘却对组织惰性的影响研究—–环境动态性与创新导向的调节作用

组织惰性是客观存在于组织机体内的消极行为表现, 对组织的可持续发展产生阻碍作用. 如何克服组织惰性、提升组织效率是组织惰性研究的关键问题. 本文主要探讨了组织忘却对组织惰性的影响作用. 以长三角地区的260个调查样本为研究对象, 对组织忘却与组织惰性的关系进行了分析, 并探讨了环境动态性、创新导向以及环境动态性和创新导向交互在两者之间的调节作用. 结果表明 组织忘却对组织惰性具有显著的负向作用, 环境动态性和创新导向均显著正向地调节了两者之间的负向作用, 环境动态性和创新导向的交互对两者之间的关系具有调节作用, 但调节作用最强的情况出现在环境动态性或创新导向单方面较强, 而非环境动态性和创新导向两者均强时.     

pH控制硫酸锰骨架的演化及其晶体结构

在DMF/H2O/CH3OH的混合体系中,反应温度为170℃,Mn SO4·4H2O盐溶液在p H=5和7的条件下,加热72小时,最终得到了结构不同的硫酸锰骨架[Mn2(SO4)3]·(H3O)2(1)和[Mn3(SO4)2(OH)2(H2O)2](2)。化合物结构通过单晶X-射线和红外光谱所表征,相应的晶胞参数:化合物1,立方晶系,空间群:P213,a=10.2009(12),V=1061.49(37)3,Goo F=1.158,Flack parameter 0.02(2),R1=0.0186(I2sigma);化合物2,四方晶系,空间群:Pbcm,a=7.3214(15),b=9.984(2),c=13.291(3),V=971.5(4)3,Goo F=1.063,R1=0.0227(I2sigma);单晶X射线分析显示化合物1是一个三维单手性硫酸锰骨架,化合物2是一个非手性羟基硫酸锰骨架。实验结果说明,p H值对硫酸锰骨架的改变起重要作用。     

基于P31荧光粉的像增强器余辉测量方法研究

荧光屏余辉在高帧频速光子计数等系统应用中起着决定性作用。GJB 7351-2011《超二代像增强器通用规范》荧光屏余辉试验方法中规定光脉冲作为激励源，该方法中光脉冲激励源停止后光源照度下降缓慢，造成在短余辉粉（μs级）和中余辉粉（ms级）的余辉时间测量中测试结果不准。针对该问题，提出了一种在光照持续工作状态下，用光电阴极电压脉冲信号作为激励源的荧光屏余辉测试方法，该方法中光电阴极超快响应时间（一般为1 ns左右）和脉冲电压信号的较短边沿时间（一般可控制在10 ns以内）特性改善了激励源自身时间响应对荧光屏余辉测试结果准确性带来的影响。基于该方法建立了一套微光像增强器荧光屏余晖测量装置，对P31荧光粉的国产三代微光像增强器余辉进行了重复性测量，对测量不确定度进行了误差分析，其扩展不确定度为3.2%，达到了传统光电测试仪器的准确度要求，可满足微光像增强管荧光屏余辉测量的要求。该研究成果为更高性能产品提供了一种检测手段。     

一种非正交对称条带束流位置监测器设计

介绍了一种条带束流位置监测器(BPM)的设计与仿真方法。在国家同步辐射实验室"太赫兹近场高通量材料物性测试系统"工程项目中,针对波荡器出口处真空室非正交对称性的问题,设计了矩形真空室和跑道形真空室下的两种非正交对称性条带BPM,并与传统的圆形真空室下条带BPM进行对比。基于边界元法,利用MATLAB软件分别对三种真空室下的条带BPM进行建模和仿真。仿真结果表明:相对于传统的圆形真空室下条带BPM,矩形和跑道形真空室下条带BPM灵敏度提高了30%,阻抗匹配误差相对降低了20%,束流位置拟合误差降低了80%。考虑加工精度,矩形真空室下的条带BPM更适用于该工程。