IGBT在铜端环焊接领域的应用

通过对超音频感应电加热铜端环焊接设备的研究,介绍了大功率IGBT在水泵转子铜端环焊接设备中的应用,拓展了感应电加热设备的应用范围。通过对铜端环焊接设备基本技术方案的确定,重点解决了IGBT串联谐振、感应器以及冷却方法,解决其设备的稳定性和实用性研究,将其推向市场,适应工业化生产的要求。     

Effects of ultraviolet–ozone treatment on organic-stabilized ZnO nanoparticle-based electron transporting layers in inverted polymer solar cells

Electron transporting layers (ETLs) in inverted polymer solar cells (I-PSCs) were fabricated by spin coating a colloidal dispersion of ZnO nanoparticles (NPs), and the effects of ultraviolet–ozone (UVO) treatment on the ZnO NP ETLs were investigated. The brief UVO treatment (<5 min) could considerably improve the performance of the resulting I-PSCs (∼30% increase in power conversion efficiency); whereas, excessive UVO treatment (>10 min) caused significant degradation. The characterization of the ZnO ETLs as a function of the UVO treatment duration revealed that brief treatment can remove the residual organic stabilizer molecules on the surface of the ZnO films by UV induced decomposition mechanism. However, excessive treatment can generate additional defects on/within the ZnO films, which can induce charge recombination. This effect was further confirmed by the thermal treatment of the ZnO ETLs at a high temperature (280 °C) at which the organic surfactants could be removed. Flexible I-PSCs were also fabricated using indium doped tin oxide coated plastic substrates and the usefulness of the room temperature UVO treatment was further confirmed in view of its potential applicability in flexible devices.     

Delivery of iPS‐NPCs to the Stroke Cavity within a Hyaluronic Acid Matrix Promotes the Differentiation of Transplanted Cells

Stroke is the leading cause of adult disability with ≈80% being ischemic. Stem cell transplantation has been shown to improve functional recovery. However, the overall survival and differentiation of these cells is still low. The infarct cavity is an ideal location for transplantation as it is directly adjacent to the highly plastic peri‐infarct region. Direct transplantation of cells near the infarct cavity has resulted in low cell viability. Here, neural progenitor cells derived from induce pluripotent stem cells (iPS‐NPC) are delivered to the infarct cavity of stroked mice encapsulated in a hyaluronic acid hydrogel matrix to protect the cells. To improve the overall viability of transplanted cells, each step of the transplantation process is optimized. Hydrogel mechanics and cell injection parameters are investigated to determine their effects on the inflammatory response of the brain and cell viability, respectively. Using parameters that balanced the desire to keep surgery invasiveness minimal and cell viability high, iPS‐NPCs are transplanted to the stroke cavity of mice encapsulated in buffer or the hydrogel. While the hydrogel does not promote stem cell survival one week post‐transplantation, it does promote differentiation of the neural progenitor cells to neuroblasts.     

Adhesion and Surface Interactions of a Self‐Healing Polymer with Multiple Hydrogen‐Bonding Groups

The surface properties and self‐adhesion mechanism of self‐healing poly(butyl acrylate) (PBA) copolymers containing comonomers with 2‐ureido‐4[1H]‐pyrimidinone quadruple hydrogen bonding groups (UPy) are investigated using a surface forces apparatus (SFA) coupled with a top‐view optical microscope. The surface energies of PBA–UPy4.0 and PBA–UPy7.2 (with mole percentages of UPy 4.0% and 7.2%, respectively) are estimated to be 45–56 mJ m^?2 under dry condition by contact angle measurements using a three probe liquid method and also by contact and adhesion mechanics tests, as compared to the reported literature value of 31–34 mJ m^?2 for PBA, an increase that is attributed to the strong UPy–UPy H‐bonding interactions. The adhesion strengths of PBA–UPy polymers depend on the UPy content, contact time, temperature and humidity level. Fractured PBA–UPy films can fully recover their self‐adhesion strength to 40, 81, and 100% in 10 s, 3 h, and 50 h, respectively, under almost zero external load. The fracture patterns (i.e., viscous fingers and highly “self‐organized” parallel stripe patterns) have implications for fabricating patterned surfaces in materials science and nanotechnology. These results provide new insights into the fundamental understanding of adhesive mechanisms of multiple hydrogen‐bonding polymers and development of novel self‐healing and stimuli‐responsive materials.     

基于Kippo蜜罐的SSH暴力破解行为分析

SSH是相对于传统协议而言安全可靠的远程服务协议,然而现今针对于SSH的暴力破解攻击已经严重威胁了其安全性.为了研究SSH暴力破解攻击行为特征,提高系统和服务的安全性,采取了不同于传统网络防护的被动防御策略,搭建了基于Kippo蜜罐的主动防御系统,并基于此,利用Kippo蜜罐的日志记录,对攻击者及其攻击行为特征进行了多方面的详细分析,从而提出了SSH服务的安全建议与加固措施,在一定程度上增强了针对SSH暴力破解攻击的防御能力,提高了安全性.     

利用多数据处理方法提高LIBS谱信号质量

基于分段光谱特征值提取法和小波变换算法等多个数据预处理方法,分别针对分段基线差异及光谱噪声等严重影响激光诱导击穿光谱(LIBS)信号质量的主要影响因素,开展光谱信号预处理研究.基于实验室LIBS实验装置,通过实验验证,基于多通道光谱仪不同波段光谱特征值提取,提出了一种简单易行的多组数据中特征值点连接的方法,有效地提高了LIBS光谱信号的基线平直度,并得出以小波变换算法进行LIBS谱线信号去噪的最佳算法参数.在上述工作的基础上,使用基于误差反向传播的人工神经网络方法,实现了纯铜和不锈钢等物质种类的有效识别,研究结果表明,综合利用多数据处理方法进行LIBS技术中光谱信号处理可以有效提高谱线分析和识别的质量.     

Unraveling the Dynamic Nanoscale Reducibility (Ce4+ → Ce3+) of CeOx–Ru in Hydrogen Activation

The interaction of molecular hydrogen with ceria is of important relevance for heterogeneous catalysis related to green chemistry and renewable energy. Here, the complex structural transformations of a well‐defined cerium oxide model catalyst are followed in situ and in real time when exposed to a reactive H₂ environment. By using electron spectromicroscopy and diffraction with chemical and structural sensitivities, it is demonstrated that the transition from CeO₂ to crystalline Ce₂O₃ occurs through a mixture of transient, coexisting phases on the nanoscale. The findings establish a clear relationship between structure and functionality for hydrogen dissociation over ceria(111), bearing profound implications on the nature of the reduction (Ce⁴⁺ → Ce³⁺) and mechanism for H₂ scission.     

纳米结构镁的制备及其储氢性的研究进展

氢能的利用越来越受到人们的重视,而氢的储存和运输限制了其广泛的实际应用。镁基合金作为一种固体储氢材料,在储氢领域显示出巨大的潜力。但是,吸放氢温度高,释氢速率慢,阻碍了其工程应用。为了提高镁基合金的储氢能力,目前的研究主要集中在合金成分的优化和加工工艺的改进方面,而纳米细化是最有前途的方法之一。详细介绍了纳米镁的各种制备工艺,包括高能球磨、物理气相沉积、氢化化学气相沉积、液相化学合成和模板法,并分析了各种方法的优缺点。阐述了纳米结构和元素掺杂对镁基合金储氢性能的影响。本研究为储氢领域的材料开发和制备工艺的改进提供参考。     

Correlations among stress corrosion cracking,grain-boundary microchemistry,and Zn content in high Zn-containing Al–Zn–Mg–Cu alloys

The correlations among the corrosion behaviour, grain-boundary microchemistry, and Zn content in Al–Zn–Mg–Cu alloys were studied using stress corrosion cracking (SCC) and intergranular corrosion (IGC) tests, combined with scanning electron microscopy (SEM) and high-angle angular dark field scanning transmission electron microscopy (HAADF-STEM) microstructural examinations. The results showed that the tensile strength enhancement of high Zn-containing Al–Zn–Mg–Cu alloys was mainly attributed to the high density nano-scale matrix precipitates. The SCC plateau velocity for the alloy with 11.0 wt.% Zn was about an order of magnitude greater than that of the alloy with 7.9 wt.% Zn, which was mainly associated with Zn enrichment in grain boundary precipitates and wide precipitates-free zones. The SCC mechanisms of different Zn-containing alloys were discussed based on fracture features, grain-boundary microchemistry, and electrochemical properties.