不同管路元件流动声发射信号熵值量化分析方法

针对流体在流经不同管路元件时产生的噪声会造成管道损伤在线监测精准性下降的问题,引入了小波能量熵与时频熵两种熵值量化分析方法,通过计算流体流动声信号的熵值对流动过程中不同管路元件的流动状态进行量化,从而判断损伤是否发生以及损伤所处的管路元件部位.在此基础上,设计了管路流动声发射测试实验,采集了不同压力下直管、弯头入口、弯头出口、三通、变径管小头共5种管路元件的声发射信号,对所采集的声发射信号逐一采用时频熵及小波能量熵的方法分析计算.测试实验结果表明,时频熵与小波能量熵均能很好地区分不同管路元件的流动状态差异,且时频熵对同一管路元件压力变化时的流动状态有着较高的量化精度.     

The Role of Chronic Inflammation in Various Diseases and Anti-inflammatory Therapies Containing Natural Products

Chronic inflammation represents a long-term reaction of the body's immune system to noxious stimuli. Such a sustained inflammatory response sometimes results in lasting damage to healthy tissues and organs. In fact, chronic inflammation is implicated in the development and progression of various diseases, including cardiovascular diseases, respiratory diseases, metabolic diseases, neurodegenerative diseases, and even cancers. Targeting nonresolving inflammation thus provides new opportunities for treating relevant diseases. In this review, we will go over several chronic inflammation-associated diseases first with emphasis on the role of inflammation in their pathogenesis. Then, we will summarize a number of natural products that exhibit therapeutic effects against those diseases by acting on different markers in the inflammatory response. We envision that natural products will remain a rich resource for the discovery of new drugs treating diseases associated with chronic inflammation.     

基于Buck电路的BLDCM调速系统设计

为了获得转速平稳、调节快速的无刷直流电机(BLDCM)输出,对BLDCM控制和驱动系统进行了设计。分析了BLDCM的运行原理和转矩波动原因,并采用Buck电路直接驱动解决了转矩波动的问题。针对传统PID调速慢、精度低以及参数调节困难等问题,采用了BP神经网络对PID进行参数调节。在MATLAB/Simulink仿真平台上搭建了系统的各个模块并进行仿真。结果表明,所设计的系统调节速度快,控制过程中超调小,转速平稳,转矩波动减小。     

基于分段式虚拟阻抗的改进下垂控制

当线路电阻在线路阻抗中的影响不能忽略时,系统的有功功率和无功功率会发生耦合,会降低下垂控制的性能和系统无功功率的分配精度,为此本文提出了基于分段虚拟阻抗的改进下垂控制策略.以无功功率比值为依据,分段设计自适应线路虚拟阻抗,减小线路阻抗差异,增大无功功率分配精度;在无功功率-电压下垂控制中加入自适应电压补偿环节以补偿电压跌落;最后,通过仿真和实验验证自适应分段虚拟阻抗和电压补偿环节的有效性.     

粉煤灰空心微珠强化厚型钢结构防火涂料的制备及性能

将小粒径粉煤灰空心微珠(FAC)作为隔热填料掺入厚型钢结构防火涂料中,研究了FAC掺量对涂料理化性能及耐火性能的影响.结果显示:FAC掺量为8％时得到的防火涂料整体性能最优,灼烧3 h的背温低于市售防火涂层.利用数据模型对防火涂料耐火试验过程参数进行计算,求得固定和平均这2种形式的等效热阻,再以其模拟钢构件受火过程的温升情况,结果与实测基本一致.探讨了涂层表现出耐火性的原因.     

Boron Nitride Nanosheets Strengthened PVA/Borax Hydrogels with Highly Efficient Self-Healing and Rapid pH-Driven Shape Memory Effect

Self-healing hydrogels often possess poor mechanical properties which largely limits their applications in many fields. In this work, boron nitride nanosheets are introduced into a network of the poly(vinyl alcohol)/borax (PVA/borax) hydrogels to enhance the mechanical properties of the hydrogel without compromising the self-healing abilities. The obtained hydrogels exhibit excellent mechanical properties with a tensile strength of 0.410 ± 0.007 MPa, an elongation at break of 1712%, a Young's Modulus of 0.860 ± 0.023 MPa, and a toughness of 3.860 ± 0.075 MJ m⁻³. In addition, the self-healing efficiency of the hydrogels is higher than 90% within 10 min at room temperature. Benefiting from the excellent self-healing properties, the shapeability of the hydrogel fragments is observed using different molds. In addition, the hydrogels display rapid pH-driven shape memory effects and can recover to their original shape within 260 s. Overall, this work provides a new approach to hydrogels with integrated excellent mechanical properties, self-healing abilities, and rapid pH-driven shape memory effects.     

Effect of ammonia concentrations on SCC of α-brass under mode III loading

Stress corrosion cracking (SCC) of α-brass in ammonia solution was studied under mode III loading. The results showed that SCC occurred on the principal stress planes where shear stresses are zero. No SCC occurred on the maximum shear stress plane. Ammonia concentration affected fracture behaviour. When the concentration was low, many cracks with spacing of 10–150 μm were found on 45 ° planes, i.e., the principal stress planes. When the concentration was high, the cracks on 45 ° planes were not clearly visible because of serious general corrosion.     

鞍钢鲅鱼圈4038m3高炉高比例使用中块焦炭生产实践

针对鞍钢股份有限公司鲅鱼圈钢铁分公司4038 m3高炉高比例使用中块焦炭后出现的风量萎缩、顺行变差,尤其是高炉休送风恢复过程中炉缸活跃性差、煤气流中心通道打不开、频繁崩滑料现象,提出采取合理匹配上下部调剂、组织好炉前渣铁排放、小焦布料制度以及改善休风料结构等措施.实践后,高炉实现了中块焦比为90 kg/t情况下的长期稳定顺行,休送风恢复未出现超时现象,适应了高比例使用中块焦炭的生产.     

中空螺旋状不锈钢冷却水喷头的熔模精密铸造

采用熔模精密铸造工艺，生产中空螺旋状不锈钢冷却水喷头，其工艺要点是，采用热型重力浇注，在高温下进行自由浇注。同时采用先慢后快，流量由小到大的浇注方法。结果表明：铸件表面光洁，无砂眼、气孔等缺陷，铸件合格率高于90％；在实际使用中，雾化区域直径大于1．5m，雾化率大于90％，喷雾效果稳定良好；盐雾试验2000h没有锈蚀，具有优良的耐磨性和耐腐蚀性。     

Effect of laser fluences on the structure of carbon nitride films deposited by direct current plasma assisted pulsed laser ablation

Carbon nitride films were deposited by direct current plasma assisted pulsed laser ablation of a graphite target under a nitrogen atmosphere at room temperature. The surface morphology, composition and bonding structure of the deposited films were characterized by atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, Raman, and X-ray photoelectron spectroscopy (XPS). The effect of laser fluences in the range 0.5–3 J/cm² on the surface morphology, composition and bonding structure of the carbon nitride films were systematically studied. As laser fluence is increased, AFM results show a great decrease in the surface roughness of carbon nitride films. FTIR and XPS results indicate an increase in the N/C ratio and the content of N atoms bonded to sp³ C, as well as a decrease in the content of H atoms and the content of N atoms boned to sp² C in the deposited films, and Raman spectra indicate an increase in the content of disordered sp² C atoms and the sp² cluster size. The increase in the film density and the decrease in the particle fraction contribute to the decrease of surface roughness with increasing laser fluence.