Holstein 分子晶体模型能带结构的温度依赖性

研究了温度对Holstein分子晶体模型能带结构的影响,结果表明固体的能带宽度和禁带宽度都与电子和热声子相互作用以及热膨胀密切相关.对一维Li原子品格链,在所选定的参数下,1s和2s的能带宽度随着温度的增加而变窄,两带之间的禁带宽度变宽,这些结果与实验结果在定性上是一致的.显然,研究能带结构的温度依赖性对于理解固体的光学和输运性质都是十分重要的.     

微型光纤光谱仪的波长定标分析

为了提高光纤光谱仪的测量精度,采用标准汞氩灯谱线和最小二乘法的3阶线性拟合,取得了完整的波长定标方案。结果表明,算术平均误差小于0.167nm,标准差小于0.217nm,波长与像素的拟合相关程度较高;定标后波长不确定度优于0.11nm,误差小于0.15nm,波长重复性可达0.01nm。这一结果对提高光谱仪实际应用中的测量精度是非常有益的。     

计算机技术在桥式自动采样系统中的研究与应用

本论文主要介绍了利用计算机和PLC控制系统,实现对矿粉等各种粉末原材料样品的自动采集实现的方法,并着重介绍了自动采样系统地组成以及控制功能,该系统组成主要有Siemens 300系列PLC控制系统,MicroMaster440系列变频器,绝对式编码器,三相异步电机及其他各种辅助设备。该系统的实现解决了原料厂人工采集样品的现状,在更好的完成生产的需要的同时,实现故障率低、准确、效率高、节省劳动力等诸多优点,使职工的工作环境大大提高,其重要性随着生产应用将更加突出。     

基于偏振不敏感超材料的全光可调谐太赫兹慢光效应研究

太赫兹(terahertz,THz) 慢光效应可以有效地提升THz脉冲数据传输的安全性和存储性,而一般THz慢光器件对入射THz波偏振态变化敏感。本文设计了一种超材料结构,其微结构单元由一个十字型谐振器和4个U型谐振器构成。研究表明:基于超材料的THz慢光效应对线偏振光和圆偏振光均不敏感。通过对超材料结构的参数优化,获得到了最大群折射率为1 618的慢光效应。另外,本文在超材料微结构层和SiO₂衬底之间嵌入了一层二硫化钼(MoS₂)薄膜,当MoS₂的载流子浓度从1.7×10¹⁷ cm-3增大到5.1×10¹⁹ cm-3时,群折射率从1 566减小到26。实现了偏振不敏感全光可调谐的THz慢光效应。该研究有望为偏振不敏感和全光可调谐的THz慢光器件设计提供崭新的研究思路。     

Significant Strain‐Induced Orbital Reconstruction and Strong Interfacial Magnetism in TiNi(Nb)/Ferromagnet/Oxide Heterostructures via Oxygen Manipulation

Dynamical manipulation of oxygen ion (O^2?) at metal/oxide heterointerfaces is widely demonstrated to tailor numerous physical and chemical properties and facilitate creating novel functionalities significantly. The traditional works mainly focus on electric control of O^2? dynamical behavior and related interface characteristics. Here, an alternative strategy is reported to modulate O^2? transport and interfacial magnetism via a significant strain induced by shape memory effect, which is different from the conventional magnetoelastic coupling mechanism. By driving the martensite to austenite transition in TiNi(Nb) shape memory alloy substrates, a significant and tunable strain is exerted on Pt/Co/MgO heterostructure, which promotes interfacial O^2? migration in a nonvolatile manner. The O^2? migration induces an orbital reconstruction of Co to tune the orbital magnetism noticeably, which strengthens the interfacial magnetic anisotropy energy by two times to a striking value of 0.95 erg cm^?2. Besides, the overall magnetic anisotropy is broadly tunable from in‐plane to perpendicular direction by an elaborate strain engineering with changing Co thickness. This work develops a nonelectrical oxygen manipulation for tailoring ion‐controlled interfacial properties universally and also clarifies the magnetoionic coupling origin for enriching the oxygen‐related orbital physics and functional device applications.     

基于NB-IoT的智慧工地人脸识别系统

生物特征是人的内在属性,具有很强的稳定性和个体差异性,是身份验证的理想依据。利用人脸特征是较为直接的手段,相比其他生物特征,人脸有直接、友好、方便等特点,易被为用户接受。数字工地指挥安全监控平台上的人脸识别系统,可以分为人脸识别设备和数字工地指挥安全监控平台两部分。其中,人脸识别设备可用于人脸识别和数据采集,以NB-Iot无线传输形式传输数据,在平台上将人脸识别库与匹配初始人员信息的数据库应用相互关联,以促进工地统计,使管理工作更便捷。     

基于MOBILE的JK触发器设计

介绍了一种新型量子逻辑单元电路——单稳双稳转换逻辑单元及其工作原理,在此基础上探讨并设计了以MOBILE为基本单元电路的具有同步置位复位功能的边沿型JK触发器电路,从而丰富了量子电路中触发器的类型     

无线用户环路技术及其应用

本文在分析无线用户环路的特点和关键技术的基础上,介绍了它的实现方法、系统结构及其应用,并就有关技术方案和标准的选用提出了作者自己的看法。     

Impacts of a jet''s exit flow pattern on mixing and combustion performance

The influence of modifying a jet's exit flow pattern on both the near and far-field turbulent mixing processes and on the resulting combustion performance, is explored. This reveals that, in contradiction to some common assumptions, increasing the coherence of large-scale motions can decrease molecular mixing rates, and yet can still be beneficial in some applications.

Even relatively minor changes to the exit flow pattern of a non-reacting round jet, through changes to the nozzle profile are found to propagate downstream into the far field, apparently through the underlying turbulent structure. Importantly, while a jet from a smoothly contracting nozzle is found to have higher rates of entrainment, mean spread and mean decay of the scalar field than does a long pipe jet, it has a lower rate of molecular mixing. That is, increased large-scale mixing does not necessarily result in increased fine-scale mixing. A range of devices are reviewed which enhance, or stimulate the large-scale, coherent motions in an emerging jet using acoustic, mechanical or fluidic methods. The available evidence suggests that those methods which induce instantaneously asymmetric flow structure are more effective at increasing the near-field spreading than are those which induce instantaneously axisymmetric flow structure. Only limited data are available of the effects of such near-field changes on the far-field properties. Nevertheless, the available data reveal a clear trend that this near-field flow undergoes a transition to a far-field state whose spread and decay is comparable with that of a steady jet, albeit being indelibly altered by the near-field excitation. It also suggests that “self-exciting” devices (i.e. that are not externally forced), cause a net reduction in the total entrainment relative to the unexcited jet, due to the losses induced by the device itself. Nevertheless, the changes which they can impart to the flow, such as redistributing the turbulent energy from the fine to the larger scales, can be beneficial for combustion in applications where high radiant heat transfer is desirable.

Precessing and flapping jets are found to cause an increase in flame volume relative to an equivalent simple jet (SJ), implying lower molecular mixing rates. However, importantly, this decrease in mixing is achieved with no increase in the flame length. Rather the width to length ratio of these flames is increased significantly. This is of practical significance because the length of a flame is often the limiting dimension in industrial systems. The reduced strain-rates lead to an increased presence of soot within the flame, while not, in general, significantly influencing the emission of soot from the flame. The increased volume of soot leads to increased radiation, which in turn acts to reduce flame temperature, so lowering thermal NO_x emissions through a global residence time–temperature reduction. For example, in full-scale cement kilns these burner nozzles are found to reduce NO_x emissions by around 40–60% and increase fuel efficiency (or output) by around 5–10%.