改进的EEMD算法及其在多项流检测中的应用

针对应用集合经验模态分解(ensemble empirical mode decomposition,EEMD)方法难以提取强噪声背景下滚动轴承微弱故障特征的问题,提出了将最小熵反褶积(minimum entropy deconvolution,MED)和小波阈值去噪与EEMD相结合的改进方法. 先采用MED对滚动轴承振动信号降噪,增强冲击特征;然后利用基于EEMD的小波阈值去噪方法处理降噪后信号得到一组固有模态分量(intrinsic mode function,IMF),并依据相关系数准则剔除虚假分量;对重构后信号进行Teager能量算子解调分析,提取其微弱故障特征. 通过仿真信号和实验台信号验证了该改进方法的有效性.

     

镁合金表面磁控溅射沉积铝膜的力学性能

采用直流磁控溅射法在镁合金上沉积铝膜,在高真空下对铝膜进行加热后处理.用X射线衍射仪(XRD)分析膜层为纯铝多晶态,扫描电子显微镜(SEM)观察铝膜晶粒细小.采用纳米压痕/划痕仪对铝膜的厚度、临界附着力、硬度和弹性模量进行了测试,并且用辉光放电光谱仪(GDS)测试了镁合金表面铝膜的成分和性能随薄膜深度的分布.结果表明,铝膜的厚度随后处理温度的升高而降低,其表面硬度和弹性模量高于镁合金基体并且随深度增加而逐渐降低.铝膜与镁合金基体间存在一个过渡层,结合良好且表现出一定的弹塑性能,有利于镁合金表面的防护.     

广域复杂流体系统中基于无线传感网的数据保存关键技术研究进展

流体系统包括城市供水管网、天然气供给管网等,是具有经济和社会价值的重要基础设施。它们具有分布地域广、结构复杂、规模庞大、难以检测等特点,在出现泄漏、污染等异常时难以快速发现和准确定位。随着传感器技术、通信技术、微机电技术等的发展,利用无线传感网来对系统进行监测成为研究热点。由于在流体系统中通信困难,数据被监测到后很难实时传送给用户,只能暂时保存在传感器节点(简称节点)上,等待适当的时刻再进行上传。但是,节点具有体积微小、易损坏、存储容量小、通信能力弱、能量有限等特点,如何可靠地存储大量的数据是一个难点问题。目前,已有部分工作对这个问题进行了研究。为了解该领域研究的进展,文中对相关工作进行了细致地分析、对比、归纳和总结,介绍了它们的优缺点,并对未来的研究方向进行了探讨。     

热轧纯铝板带道次温降近似计算法

推荐基于轧件厚度减缩系数KH的热轧道次温降计算公式,与实测数据对比,能较好地均衡符合实测结果,能为优化热轧压下规程例行条件.     

出钢过程钢水净化工艺优化研究

介绍了转炉在出钢过程强化钢水净化的工艺,实验结果表明:该工艺能在较短时间内降低钢水及熔渣氧化性,利用出钢过程良好的动力学条件进行脱硫,从而提高了LF精炼炉的精炼效果,显著提高了钢水纯净度.通过对工艺的优化和完善,可使部分钢种不经LF炉处理也能满足品种钢性能的要求,进而缓解LF炉作业压力,减少了LF增碳增硅的几率,提高了低碳低硅钢的成分命中率.     

Can a Large Number of Transplanted Mesenchymal Stem Cells Have an Optimal Therapeutic Effect on Improving Ovarian Function?

Mesenchymal stem cells (MSCs) are next-generation treatment in degenerative diseases. For the application of mesenchymal stem cell therapy to degenerative disease, transplantation conditions (e.g., optimized dose, delivery route and regenerating efficacy) should be considered. Recently, researchers have studied the mode of action of MSC in the treatment of ovarian degenerative disease. However, the evidence for the optimal number of cells for the developing stem cell therapeutics is insufficient. The objective of this study was to evaluate the efficacy in ovarian dysfunction, depends on cell dose. By intraovarian transplantation of low (1 × 10⁵) and high (5 × 10⁵) doses of placenta-derived mesenchymal stem cells (PD-MSCs) into thioacetamide (TAA)-injured rats, we compared the levels of apoptosis and oxidative stress that depend on different cell doses. Apoptosis and oxidative stress were significantly decreased in the transplanted (Tx) group compared to the non-transplanted (NTx) group in ovarian tissues from TAA-injured rats (* p < 0.05). In addition, we confirmed that follicular development was significantly increased in the Tx groups compared to the NTx group (* p < 0.05). However, there were no significant differences in the apoptosis, antioxidant or follicular development of injured ovarian tissues between the low and high doses PD-MSCs group. These findings provide new insights into the understanding and evidence obtained from clinical trials for stem cell therapy in reproductive systems.     

N-Functionalization of 5-Aminotetrazoles: Balancing Energetic Performance and Molecular Stability by Introducing ADNP

5-aminotetrazole is one of the most marked high-nitrogen tetrazole compounds. However, the structural modification of 5-aminotetrazole with nitro groups often leads to dramatically decreased molecular stability, while the N-bridging functionalization does not efficiently improve the density and performance. In this paper, we report on a straightforward approach for improving the density of 5-aminotetrazole by introducing 4-amino-3,5-dinitropyrazole. The following experimental and calculated properties show that nitropyrazole functionalization competes well with energetic performance and mechanic sensitivity. All compounds were thoroughly characterized using IR and NMR spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). Two energetic compounds (DMPT-1 and DMPT-2) were further confirmed by implementing single-crystal X-ray diffraction studies. Compound DMPT-1 featured a high crystal density of 1.806 g cm⁻³, excellent detonation velocity (v_D = 8610 m s⁻¹), detonation pressure (P = 30.2 GPa), and impact sensitivity of 30 J.     

数字阵列雷达用电源模块的研究与实现

针对数字阵列雷达中的关键部件数字阵列模块（DAM）提出分布式供电方案,分析了DAM用电源模块的设计难点,针对DAM用电源模块的关键技术—补偿环路设计、脉冲调制输出技术和电磁兼容设计进行了详细讨论,给出了变换器的传递函数、补偿网络的选择和零极点配置方法以及储能解耦电容的设计依据,模块实验结果完全达到设计要求,充分证明了设计方法的正确性。为了实现小体积和良好的散热能力,文中介绍了模块的结构工艺和热设计。模块批量生产结果稳定可靠,证明了技术方案的有效性。     

一种新型PIR人体探测技术研究

为了提高被动式红外(PIR,passive infrared)探测器的工作性能,从改进PIR探测器空间布局和信号处理入手,提出一种基于复合式布局的PIR探测器人体探测的新方法.采用双PIR探测器复合式布局,通过GA算法得到其最优布局.当人体在探测区域内运动时,两探测器同时多角度检测人体移动情况.验证实验结果表明,提出的新检测方法能使设计的PIR探测器有效且可靠地检测和识别人体的移动情况.该检测方法适用于基于PIR传感的人体移动的智能检测和识别系统.     

KM250/1600型快开隔膜压滤机控制系统自动化改造

介绍了快开压滤机的结构和工作原理;根据实际生产状况,对压滤机控制系统进行了改造,实现了联机自动化控制,取得了显著效果。