TMS320F28335与交流永磁伺服驱动器的接口方法

在伺服控制系统中,控制芯片、伺服驱动器和伺服电机的接口电路对于提高控制精度有重要的影响,文章主要研究了一种连接TI的TMS320F28335 DSC芯片、安川交流伺服驱动器SGDM-04A-DA和交流永磁伺服电机SGMAH-04AAA41的连接电路,实验证明,这种接口方法能够实现TMS320F28335 DSC芯片对伺...     

Photoluminescent properties of LiInO2 nanocrystals

Synthesis and luminescence properties of LiInO₂ nanocrystals by the sol–gel process were investigated. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectroscopy and absorption spectra. The well-crystallized tetragonal LiInO₂ can be obtained by heat treatment above 600 °C from XRD. The excitation wavelengths at about 246 nm were associated with charge transfer between In and O with In³⁺ ions in octahedral coordination. The PL spectra excited at 246 nm have a broad and strong emission band maximum at 391 nm, corresponding to the self-activated luminescence. The optical absorption spectra of the 600 °C sample exhibited the band gap energies of 3.7 eV.     

Fabrication and tribological behavior of superhydrophobic zinc surface based on oleic acid

A zinc substrate was firstly immersed in an aqueous solution of N, N-dimethylformamide (DMF) solution and then chemically modified with oleic acid to generate a superhydrophobic surface. The morphological features, chemical composition and superhydrophobicity of the resultant superhydrophobic surface were analyzed by means of scanning electron microscopy, Fourier transform infrared microscopy and water contact angle (WCA) measurements, respectively, and the tribological behavior of films was evaluated by sliding the superhydrophobic films against a steel ball under 0.5 N normal load using a reciprocating ball-on-plate tribo-tester. It was found that the as-obtained superhydrophobic surface on the roughened (oxidized) zinc substrate had a WCA as high as 155°, and effectively reduced friction and largely increased antiwear life, due to the combined beneficial effects of nanotexturing of DMF treatment and nanolubrication of self-assembled oleic acid overcoat.     

燃煤灰渣水化反应动力学测定方法研究

煤粉炉粉煤灰、沸腾炉渣和循环流化床固硫灰渣是3种具有代表性的燃煤灰渣.采用氢氧化钙变化量和化学结合水量表征方法,对燃煤灰渣的水化反应动力学进行研究.研究发现,由于燃煤灰渣中游离CaO的存在,用Ca(OH)2反应变化量研究其水化反应动力学时存在较大的干扰和误差;而用化学结合水量法则不受燃煤灰渣中游离CaO和SO3含量的影响,且与28d抗压强度比方法所得结果相一致.结果表明,随着龄期增长,固硫灰渣或沸腾炉渣-水泥胶凝系统中,水化产物生成量明显高于粉煤灰-水泥胶凝系统;燃煤灰渣的火山灰活性与其CaO或SO3含量不存在必然联系.     

Hysteretic behaviour of square tubular T-joints with chord reinforcement under axial cyclic loading

The stiffness of hollow section tubular joints is weak in the chord radial direction, and thus failure frequently occurs at the weld toe in the form of brittle fracture caused by crack propagation due to cyclic loading. To avoid such brittle failure, the chord at the intersection can be reinforced by increasing the chord thickness. With the chord reinforced, the failure position can be transferred to the chord intersection, and hence the cracking along the weld toe is prevented. To verify the efficiency of the proposed reinforcing method, both experimental test and finite element analysis are carried out on reinforced and un-reinforced square tubular T-joints subjected to quasi-static cyclic loads. The hysteretic curves, ductility ratio, energy dissipation and failure mode of the two full-scale specimens are studied experimentally, and it is found that the hysteretic curves of both specimens are plump, which show the T-joints can absorb much energy when they are subjected to seismic action. However, the enclosed area of the hysteretic curves of the reinforced T-joint is larger than that of the un-reinforced specimen because the chord reinforcement can prevent the fracture failure as well as improving the bearing capacity. The failure performance of the reinforced and un-reinforced specimens also show that a T-joint with chord reinforcement is more advantageous in resisting seismic action. Finally, the effect of the reinforced chord length and thickness on the hysteretic behaviour of square tubular T-joints is also investigated from a parametric study.     

圆CFRP-钢管混凝土压弯构件滞回性能试验研究

进行了12个圆CFRP-钢管混凝土压弯构件的滞回性能试验研究。试验结果表明,CFRP对圆钢管混凝土有很好的环向约束和纵向增强作用,钢管的局部屈曲得到了延缓或消除。所有试件的跨中荷载-挠度曲线和弯矩-曲率曲线均较为饱满,表现出很好的滞回性能。在加载后期,无轴压力试件的承载力无下降,而有轴压力试件的承载力明显下降。对试验结果的分析表明,钢管和CFRP在纵向和环向都可以协同工作;同一点的纵向应变和环向应变异号;试件的挠曲线均近似为正弦半波曲线。计算表明,强度退化不显著,轴压比和纵向CFRP增强系数的增大可以提高试件的抗弯承载力和刚度,同时减缓刚度退化,但会降低试件的延性和累积耗能,而轴压比在一定范围内对试件的抗震性能是有利的。     

多元减灾语境下的重点结构概念设计

针对重点结构设施的设防需求,提出以多元减灾为目标的重点结构概念设计。阐明结构全寿命期安全的两个不同层面(即可靠性和鲁棒性),指出多元减灾可以从改善结构鲁棒性入手。分析了能量原理用于抗灾分析的普遍适用性,在此基础上,提出从增进结构本身的消能能力同时减少外界潜在的能量释放两方面开展和检验结构概念设计。最后,结合案例,给出从结构体型与空间布置、选材、结构体系、施工方案四方面实施多元减灾概念设计的主、被动措施,以期降低重点结构在灾害状况下发生不相称破坏的风险。     

混凝土软化本构关系对双K断裂参数的影响

混凝土裂缝扩展的双K断裂准则,用于描述混凝土结构裂缝的起裂、稳定扩展和失稳断裂。其相应的双K断裂参数K_ICⁱⁿⁱ、K_IC^un可通过简便的实验和基于虚拟裂缝扩展粘聚力的解析方法确定。已取得的研究结果表明,起裂韧度K_ICⁱⁿⁱ的解析解与所确定的混凝土软化本构关系有关。对于简单实用的双线性软化本构曲线而言,参数σ_s、w_s、w₀的取值直接影响软化本构关系的确定。根据本课题组新近所做楔入劈拉实验,经分析对比得到了与实测结果相符合、为确定双K断裂参数所使用的双线性软化本构曲线的相应参数。     

Migration of soluble cadmium species in nickel-cadmium cells

It has been shown that migration of cadmium species, in the separator region of the nickel-cadmium cell, is most likely to occur via a diffusion contro     

基于组件特征与多注意力融合的车辆重识别方法

为提升车辆重识别算法的性能,提出一种基于车辆组件特征与多注意力融合的特征学习方法.首先,修改深度残差网络以获取具有丰富语义信息的特征图,同时应用语义分割网络将车辆图像划分为车辆正面、背面、顶面、侧面及背景区域,以实现组件特征提取并消除视角变化的影响.然后,设计多注意力融合模块,基于面积注意力与特征注意力实现组件特征的自适应融合.最后,在多任务学习框架下,优化车辆重识别的三元组损失与辅助分类任务的交叉熵与焦点损失,对网络参数进行训练.在多个数据集上的实验结果表明,提出的方法在大多数性能指标上均超越了现有方法.进一步的消融实验证明了多注意力融合模块与多任务损失函数在特征提取上的有效性.