爆轰波对碰驱动平面锡飞层的动力学及动载行为特征研究

强冲击下的物质变形、破坏及诱发的轻重介质混合问题,是内爆压缩科学和工程应用领域的研究重点.本文针对爆轰波对碰条件下的复杂加载动力学过程及其动载破坏形态特征,开展数值模拟研究与极曲线理论分析.设计了爆轰波对碰驱动平面锡飞层的计算模型,获得了爆轰加载动力学过程及波系相互作用物理图像,分析了锡飞层对碰区自由表面速度历史的典型特征.给出了锡飞层中折射激波对碰发生马赫反射的临界条件,解读了三波结构的传播行为,阐明了对碰区内存在"一维正冲击"区域,一维区外存在单次斜冲击向两次斜冲击过渡的复杂加载动力学过程,提出了对碰区冲击动力学模型,揭示了影响对碰区动载行为特征的机理.数值模拟结果与极曲线理论分析结果相互印证,符合较好.本文的研究成果,将为深入理解和解读对碰区特殊的物质破坏及混合现象提供重要的理论支撑.     

C2轴手性双胍催化叶立德和不饱和吖内酯的串联反应研究

本文成功合成了4种基于联二萘酚骨架的手性双胍-酰胺类催化剂,并将其应用于邻羟基苯甲醛亚甲胺叶立德与不饱和吖内酯的1,3-偶极环加成和分子内串联反应。研究表明,在室温下以CHCl_3作为溶剂、轴手性胍(1b,10(mol)%)作为催化剂,反应12h,能以较好的收率(73%～88%)和较高的对映选择性(72%～86%)得到苯并吡喃衍生物。     

界面偶极如何影响有机与钙钛矿太阳电池的能带结构与性能

界面能带结构是指界面处电子能带的弯曲和倾斜。它能显著影响载流子的产生、注入、分离、传输、复合和收集等过程,是半导体光电子器件性能的重要影响因素。因此,优化界面能带结构、调控器件性能与工作机理是光电子器件领域的核心课题之一。如果将一组相距很近的正负点电荷肩并肩排列所组成的偶极层插入器件界面,电势能穿过偶极层时会发生突变,将能有效调控界面能带结构和载流子运动过程。     

气液界面超分子手性分布的原位二次谐波研究

界面超分子手性因其在材料、催化、生物等领域的应用前景得到了人们的广泛关注。卟啉(porphyrin)衍生物因具有强的π-π堆垛能力、生物兼容性和出色的电子性能,常用于构建界面超分子结构。卟啉衍生物的表面超分子手性研究多数在固体基底上进行。利用二次谐波线二色谱方法分析卟啉衍生物在空气/水界面形成的超分子结构,通过界面层不同位置处产生的S偏振二次谐波强度随入射基频光偏振态的变化研究界面超分子结构的手性分布。实验表明,卟啉衍生物TPPS吸附在两亲分子CTAB在空气/水界面上形成的单层后会形成超分子结构,该结构具有手性,且手性的二维分布是非均匀的。     

高频强场中Kramers-Henneberger变换在狄拉克方程中的应用

在强激光场中,通过Kramers-Henneberger(KH)变换和高频近似可以将狄拉克方程的求解从一个含时问题转换成一个稳态问题来研究。以氢原子为例,详细研究了相对论框架下该稳态问题中的有效库仑势的特点,并和非相对论框架下的结果进行了比较。研究发现,由于相对论有效质量的引入,有效库仑势的分布范围并不像非相对论条件下随着激光场强度的增强单调变大,而是增加到一定值后不再变化。另外,通过比较偶极近似和非偶极近似下有效库仑势的分布,发现对高频强场,偶极近似不再适用。     

极谱法测定矿石及冶金渣中铍含量

矿石及冶金渣试样与过氧化钠在700℃熔融,用温水浸取,以一定量盐酸酸化后定容。分取部分试样溶液使其中铍(Ⅱ)与铍试剂Ⅲ在EDTA、氯化铵和氨水底液中,生成稳定的配合物,该配合物于-0.80V(vs.SCE)处产生一灵敏的吸附波,其峰电流的二阶导数与铍(Ⅱ)的质量浓度在0.004~0.20mg·L-1范围内呈线性关系,检出限(3S/N)为0.3μg·L-1。方法用于了7个矿石及冶金渣样品的分析,所得测定值与认定值一致。方法的加标回收率在96.0%~105%之间,相对标准偏差(n=6)在1.3%~9.7%之间。     

Synthesis and thermal properties of novel calix[4]arene derivatives containing 1,2,3-triazole moiety via K2CO3-catalyzed 1,3-dipolar cycloaddition reaction

Two calix[4]arene derivatives containing 1,2,3-triazole moiety were synthesized via K2CO3-catalyzed1,3-dipolar cycloaddition reaction between calix[4]arene-based azide and active methylene compounds in good yields.The structures of the two compounds synthesized herein were fully confirmed by 1HNMR,,（13）C NMR,and MS（ESI）.The thermal analysis showed that the mass losses of the synthesized compounds 4 and 5 containing 1,2,3-triazole groups are similar to each other.     

面向脑机接口的犹他神经电极技术

A human brain is composed of a large number of interconnected neurons forming a neural network. To study the functional mechanism of the neural network, it is necessary to record the activity of individual neurons over a large area simultaneously. Brain-computer interface (BCI) refers to the connection established between the human/animal brain and computers/other electronic devices, which enables direct interaction between the brain and external devices. It plays an important role in understanding, protecting, and simulating the brain, especially in helping patients with neurological disorders to restore their impaired motor and sensory functions. Neural electrodes are electrophysiological devices that form the core of BCI, which convert neuronal electrical signals (carried by ions) into general electrical signals (carried by electrons). They can record or interfere with the state of neural activity. The Utah Electrode Array (UEA) designed by the University of Utah is a mainstream neural electrode fabricated by bulk micromachining. Its unique three-dimensional needle-like structure enables each electrode to obtain high spatiotemporal resolution and good insulation between each other. After implantation, the tip of each electrode affects only a small group of neurons around it even allowing to record the action potential of a single neuron. The availability of a large number of electrodes, high quality of signals, and long service life has made UEA the first choice for collecting neuronal signals. Moreover, UEA is the only implantable neural electrode that can record signals in the human cerebral cortex. This article mainly serves as an introduction to the construction, manufacturing process, and functioning of UEA, with a focus on the research progress in fabricating high-density electrode arrays, wireless neural interfaces, and optrode arrays using silicon, glass, and metal as that material of construction. We also discuss the surface modification techniques that can be used to reduce the electrode impedance, minimize the rejection by brain tissue, and improve the corrosion resistance of the electrode. In addition, we summarize the clinical applications where patients can control external devices and get sensory feedback by implanting UEA. Furthermore, we discuss the challenges faced by existing electrodes such as the difficulty in increasing electrode density, poor response of integrated wireless neural interface, and the problems of biocompatibility. To achieve stability and durability of the electrode, advancements in both material science and manufacturing technology are required. We hope that this review can broaden the scope of ideas for the development of UEA. The realization of a fully implantable neural microsystem can contribute to an improved understanding of the functional mechanisms of the neural network and treatment of neurological diseases.     

基于极课大数据的初中化学组卷及试卷评价

为了提高组卷质量,基于极课大数据建立初中化学校本题库,根据双向细目表,利用该系统的出卷功能进行组卷。采用SPSS软件对试卷难度、区分度、信度和效度进行综合分析和评价,可知基于极课所出试卷各项评价指标较优秀,符合考试要求,试卷质量高。