Dynamics of Information Flow between the Chinese A-Share Market and the U.S. Stock Market: From the 2008 Crisis to the COVID-19 Pandemic Period

The relationship between the Chinese market and the US market is widely concerned by researchers and investors. This paper uses transfer entropy and local random permutation (LRP) surrogates to detect the information flow dynamics between two markets. We provide a detailed analysis of the relationship between the two markets using long-term daily and weekly data. Calculations show that there is an asymmetric information flow between the two markets, in which the US market significantly affects the Chinese market. Dynamic analysis based on weekly data shows that the information flow evolves, and includes three significant periods between 2004 and 2021. We also used daily data to analyze the dynamics of information flow in detail over the three periods and found that changes in the intensity of information flow were accompanied by major events affecting the market, such as the 2008 financial crisis and the COVID-19 pandemic period. In particular, we analyzed the impact of the S&P500 index on different industry indices in the Chinese market and found that the dynamics of information flow exhibit multiple patterns. This study reveals the complex information flow between two markets from the perspective of nonlinear dynamics, thereby helping to analyze the impact of major events and providing quantitative analysis tools for investment practice.     

3-(噁唑-5-基)吲哚类天然产物生物活性及其衍生物的合成研究进展

3-(噁唑-5-基)吲哚类天然产物如Pimprinine,Streptochlorin等,广泛存在于海洋微生物中,因其具有多样的生物活性,在医药和农药领域中很有研究潜力.3-(噁唑-5-基)吲哚类天然产物的合成方法有很多研究报道,在吲哚结构上构建噁唑环是合成此类天然产物的关键.总结了已报道的3-(噁唑-5-基)吲哚类天然产物的生物活性,并对构建3-(噁唑-5-基)吲哚骨架的合成方法及部分主要反应机理进行了综述,探讨了3-(噁唑-5-基)吲哚类骨架作为一种优势活性结构在未来的应用前景.     

描述复合型疲劳裂纹扩展路径的等效模型

复合型裂纹的扩展路径不同于Ⅰ型裂纹,会沿着与初始裂纹面不同的方向扩展,扩展路径的准确预测对扩展速率的评估具有重要的作用.采用最大周向应力准则和最小应变能密度准则进行扩展路径的预测时,开裂角的误差会使裂纹不断偏离实际路径,造成最终结果的较大偏差.论文将复合裂纹在扩展过程中的弯折裂纹简化为直线裂纹,对简化过程中所产生的误差进行定量分析,并在此基础上提出了一种描述复合型裂纹扩展路径的等效修正模型.将此模型写入ABAQUS扩展有限元模块,实现了基于等效修正模型的疲劳裂纹扩展程序.通过对含中心斜裂纹板的疲劳裂纹扩展试验,验证了该模型的有效性,预测的开裂角与试验结果基本一致,所得到的载荷循环次数低于试验值,对含裂纹结构的寿命评估偏于保守.     

基于传输线等效法的双腔体屏蔽系数快速算法

传输线等效法（TLM）是一种常用的开孔腔屏蔽系数快速计算方法,在孔缝耦合系数的计算中考虑了孔缝处的场模式,提高了TLM算法在高频段计算屏蔽系数（SE）的准确性。继而将TLM算法推广到开孔双金属腔屏蔽系数的计算,通过将外腔体中任意位置的电压等效为内孔缝处的辐射电压源,计算得到内腔体中任意位置上的屏蔽系数,解决了已有文献中方法的不足。该算法计算结果与CST仿真结果吻合较好。     

新型双阈值高g值MEMS惯性开关（英）

在保证引信勤务安全性和正常发射可靠性前提下,为实现引信小型化而设计了一种新型无源双阈值高g值MEMS惯性开关,其主要包括能够识别两种典型加速度环境（载荷1:15 000g-300 ms,载荷2：3000g-3 ms）的环境识别模块M1和为后续电路可靠供电的通电模块M2。环境识别模块M1主要通过控制带有Z型齿的质量块与对应L型挡块之间的碰撞来确定质量块的运动位移,进而控制通电模块M2的工作情况。基于两种典型加速度环境对MEMS惯性开关进行了动力学仿真并优化,仿真结果表明所设计的开关在载荷1环境下保持断开,而在载荷2环境下可靠闭合。     

Application of Nanomaterials to Enhance Polymerase Chain Reaction

Polymerase Chain Reaction (PCR) is one of the most common technologies used to produce millions of copies of targeted nucleic acid in vitro and has become an indispensable technique in molecular biology. However, it suffers from low efficiency and specificity problems, false positive results, and so on. Although many conditions can be optimized to increase PCR yield, such as the magnesium ion concentration, the DNA polymerases, the number of cycles, and so on, they are not all-purpose and the optimization can be case dependent. Nano-sized materials offer a possible solution to improve both the quality and productivity of PCR. In the last two decades, nanoparticles (NPs) have attracted significant attention and gradually penetrated the field of life sciences because of their unique chemical and physical properties, such as their large surface area and small size effect, which have greatly promoted developments in life science and technology. Additionally, PCR technology assisted by NPs (NanoPCR) such as gold NPs (Au NPs), quantum dots (QDs), and carbon nanotubes (CNTs), etc., have been developed to significantly improve the specificity, efficiency, and sensitivity of PCR and to accelerate the PCR reaction process. This review discusses the roles of different types of NPs used to enhance PCR and summarizes their possible mechanisms.     

激光冲击与渗碳复合工艺改善12CrNi3A钢磨损性能

为了提高12CrNi3A钢渗碳层质量及其抗磨损性能,提出了激光冲击与渗碳不同顺序复合的工艺方法。球磨实验结果表明,相比渗碳处理,激光冲击后渗碳试样的比磨损率降低了51%,而渗碳后激光冲击强化试样的比磨损率降低了13%,说明激光冲击后渗碳的复合工艺能更好地改善抗磨损性能。在摩擦系数差别不大的情况下,抗磨损性能的提升与显微硬度提高、微观组织变化有关,从这两方面讨论抗磨损性能提升的机理。研究表明:激光冲击强化可促进渗碳的过程,强化后渗碳形成的渗碳层结构致密,大量细小碳化物形成,固溶强化、第二相强化作用增强,显微硬度增大,从而提高抗磨损性能;而渗碳后激光冲击强化只使渗层表面发生了形变强化,与渗碳工艺相比,显微硬度略有提高,抗磨损性能提高有限。     

变分模态分解在爆破信号趋势项去除中的应用

爆破工程中,信号趋势项的准确去除对提高爆破振动信号分析的精度具有重要意义。针对经验模态分解（empirical mode decomposition,EMD）识别法存在的模态混叠和端头效应等缺陷,提出了基于变分模态分解（variational mode decomposition,VMD）去除信号趋势项的方法,即VMD法。叙述了VMD法识别爆破信号趋势项原理,并进行了仿真实验,结果表明：趋势项频率对分解效果的影响相对较小,当趋势项频率处于1～5 Hz之间时,频率对分解效果的影响基本保持不变;振幅对分解效果影响显著,且振幅越小,VMD法的分解效果越差。当趋势项振幅超过原始爆破信号最大振幅的1/3时,VMD法分解效果较好。最后,应用VMD法和EMD法对含有趋势项的实测爆破振动信号进行处理,认为相比于EMD法,VMD法处理后的信号基本一致且不存在端点效应,在爆破信号趋势项去除领域中具有更加广泛的适用性。

     

反应型次氯酸荧光探针

生物体内的次氯酸是氯离子和过氧化氢(H2O2)由髓过氧化物酶(MPO)催化生成的,是生物体内最重要的活性氧(ROS)之一,在生理过程中发挥了至关重要的作用.但是,过量的次氯酸会导致一系列生理疾病,因此有效的识别和检测次氯酸备受研究者们的青睐.与传统检测方法相比,荧光探针具有选择性好、灵敏度高、可实时监测等诸多优势,因此...     

利用界面激基复合物发射大致估算稀土配合物LUMO能级

研究了一种利用无荧光稀土配合物与同一受体材料形成的界面激基复合物的发射来大致估算其最低未占据轨道(LUMO)能级简单方法.镥、钆、钪三种稀土配合物与星形爆炸物形成的激基复合物发射峰位分别在590,607和656 nm,与此相对应LUMO能级计算结果大致为3.0,3.06,3.21 eV.