碳纤维/环氧树脂复合材料层压板冲击凹坑的回弹特性

冲击凹坑的回弹特性对飞机复合材料结构低速冲击损伤的目视检出概率有至关重要的影响。采用T800碳纤维/M21环氧树脂复合材料单向预浸丝束自动铺贴和热压罐固化工艺制造了层压板试件。试件引入1 mm左右的冲击凹坑后分成4组,分别在室温环境、湿热环境、重复载荷及湿热和重复载荷联合作用的条件下测量冲击凹坑在不同时间的回弹量,以研究湿热环境和重复载荷对冲击凹坑回弹的影响。结果表明:湿热环境可显著提高冲击凹坑的末期回弹量,但其影响过程较缓慢,因而对凹坑初始回弹速率影响不显著;重复载荷也可提高冲击凹坑末期回弹量,但其影响相对较小,其使冲击凹坑的初始回弹速率有明显提高;湿热环境和重复载荷联合作用对冲击凹坑末期回弹量的影响高于重复载荷和湿热环境的单独影响,凹坑初始回弹速率与重复载荷单独影响下几乎相同。      

盘管式冰蓄冷箱蓄冷机理实验研究

考察测定了蓄冷吕水箱内水温下降规律、水温及冰层温度分布、载冷剂温度变化、制冷机性能变化,对盘管设置和载冷剂温度提出了结论性意见。     

超高层建筑电梯群节能控制方案设计

提出一种基于能量回馈原理设计的超高层建筑电梯群的节能控制方案.对4台电梯变频器直流侧并联控制系统进行设计,并分析其工作原理;设计控制系统的主电路并阐述其工作原理.     

如何减少GPS测量垂线偏差对进洞观测方向的影响

本文用理论及数据说明近洞的ＧＰＳ点与进洞点，近距而高差大时，进洞点投点的垂线偏差，将影响隧洞横向正确贯通。     

Recycling Bacteria for the Synthesis of LiMPO4 (M = Fe,Mn) Nanostructures for High‐Power Lithium Batteries

In this work, a novel waste‐to‐resource strategy to convert waste bacteria into a useful class of cathode materials, lithium metal phosphate (LiMPO₄; M = Fe, Mn), is presented. Escherichia coli (E. coli) bacteria used for removing phosphorus contamination from wastewater are harvested and used as precursors for the synthesis of LiMPO₄. After annealing, LiFePO₄ and LiMnPO₄ nanoparticles with dimensions around 20 nm are obtained. These particles are found to be enveloped in a carbon layer with a thickness around 3–5 nm, generated through the decomposition of the organic matter from the bacterial cell cytoplasm. The battery performance for the LiFePO₄ is evaluated. A high discharge capacity of 140 mAh g^?1 at 0.1 C with a flat plateau located at around 3.5 V is obtained. In addition, the synthesized particles display excellent stability and rate capabilities. Even under a high C rate of 10 C, a stable discharge capacity of 75.4 mAh g^?1 can still be achieved.     

Anti-Swelling,High-Strength,Anisotropic Conductive Hydrogel with Excellent Biocompatibility for Implantable Electronic Tendon

As hydrogels rapidly advance for diverse technologies, their practical applications as implantable artificial tendon becomes promising, yet challenging. It requires similar anisotropic fibril structures, matching water content, high mechanical strength, good biocompatibility, and stable performance under physiological conditions. Furthermore, the capabilities of real-time joint motion monitoring and implant condition are extremely important for the precise assessment of rehabilitation processes. However, it is challenging to realize all these properties simultaneously. Herein, this work reports an intelligent implantable artificial tendon based on strong and conductive anisotropic hydrogel, by coupling prestretching-induced ordered structure with drying-enabled strengthening. The fiber structure fixed during drying/rehydration produces a dense and stable network with a hierarchically anisotropic structure. The resulting anisotropic hydrogel presents excellent anti-swelling ability (<3%), high tensile strength (3.71 MPa), and toughness (9.86 MJ m⁻³) upon hydration, at a tendon-matching water content of 72.5 wt%. The in vitro and in vivo tests demonstrate its excellent biocompatibility with significant protein resistance. With reliable strain sensing, the hydrogel can act as an intelligent artificial tendon to restore and real-time monitor joint motion in an in vitro model. The SD rats with tendon defects display restored motor function after implantation of the hydrogel as tendon substitutes, facilitating malfunction tissue therapeutics and rehabilitation.     

电子产品在焊接过程中的可靠性探究

制备了一种新型Sn-9Zn-2.5Bi-1.5In钎料,开发了一套波峰焊氮气保护系统,考察了该钎料在不同氧含量的环境下的焊接质量. 结果表明,开发的氮气保护系统通过增加氮气流量可以将焊接区域内的动态氧含量降低到0.06%以下. 降低焊接区氧含量,可显著减少桥连、填充不良、气孔3类缺陷的数量,将不良率控制在0.20%以内. 在氧含量0.50%的临界值以下,该钎料可在锡炉设定温度为225 ℃的条件下进行低温焊接,焊接效果满足规模化生产需求. 通过能谱分析发现氧化物表面Zn元素含量比Sn-9Zn-2.5Bi-1.5In钎料升高84.9%,Zn元素的易氧化倾向是导致钎料形成大量氧化渣的主要原因. 降低焊接区域的氧含量可以有效抑制氧化渣的形成.采用氮气保护的方法可以解决Sn-Zn钎料在高氧环境下易出现的焊接缺陷问题,从而实现225 ℃低温波峰焊.     

基于单尺度Retinex与改进的K-均值聚类的涡流热成像缺陷检测

在利用涡流红外热成像技术检测金属材料损伤缺陷时,因热波属于衰减波,且热波三维热扩散等问题,导致采集的红外图像中缺陷部位模糊.针对该问题,提出一种基于单尺度Retinex与改进的K-均值聚类的缺陷检测方法,用于处理红外图像特征增强、图像分割和边缘特征提取等问题.该方法首先利用单尺度Retinex(single-scale Retinex,SSR)对红外热图像进行图像增强,强化缺陷特征,然后利用改进的K-均值聚类算法对图像进行分割,最后采用数学形态学算法处理图像,去除缺陷图像中无用信息,并利用Canny算子检测出缺陷边缘.实验结果证明,该方法有效地检测出金属材料试件缺陷,并提取出完整清晰的缺陷边缘.