Interfacial structure and crystallographic studies of transformations in βt$́and β CuZn alloys—II. martensitic formation of α1′ plates in β′

A TEM study of the interphase boundary structure of 9R orthorhombic α₁' martensite formed in β′ CuZn alloys shows that it consists of a single array of dislocations with Burgers vector parallel to 〈110〉_β′ and spaced about 3.5 nm apart. This Burgers vector lies out of the interface plane; hence the interface dislocations are glissile. Unexpectedly, though, the Burgers vectors of these dislocations are not parallel when referenced to the matrix and the martensite lattices. This finding is rationalized on published hard sphere models as a consequence of relaxation of a resultant of the Bain strain and lattice invariant shear displacements within the matrix phase.     

The progressive wear of tubes: The volumes of the intersections of cylinders with each other and with flats

It is shown that cylinders can wear against each other or against flats in only a very few ways, each of which can be defined geometrically. For each geometry the volume of any intersection varies with a few easily measured dimensions. When dealing with a wear scar on a tube it is relatively easy to relate the volume already lost as a fraction of the volume that must be removed before any particular depth is reached. The results are presented graphically so that calculations can be reduced to a minimum and the results made as widely applicable as possible.The methods developed here have already been employed to predict the lifetimes of irreplaceable tubes showing wear scars. Amongst other possible uses of these methods, one discussed in this paper is a better way of calculating specific wear rates in wear testing using crossed cylinder geometries.     

Dimensional synthesis of planar triads: Motion generation with prescribed timing for six precision positions

In this paper, the complex number method is applied to the dimensional synthesis of planar triads, for six precision positions, and motion generation with prescribed timing. A triad is a series of three binary links which can be part of many linkages. The solution for the displacement equation of the triad is developed through the use of compatibility equations. An interactive computer program which allows the user to find an appropriate triad from the Triad-Burmester curves for a specified motion is outlined. A numerical example to show the application of the triad program to the dimensional synthesis of an eight-bar linkage is included.     

QPQ技术中渗氮时间对合金铸铁组织及摩擦性能的影响

采用OM、SEM、硬度测试、摩擦磨损试验等方法研究了QPQ技术中渗氮时间对合金铸铁组织与摩擦性能的影响。结果表明,QPQ处理后,合金铸铁表面形成的渗层物相主要由Fe_2-3N、Fe₂O₃和FeO组成。渗层厚度的平方与渗氮时间存在线性关系,在580 ℃渗氮盐浴条件下,氮元素在合金铸铁中的扩散激活能为70.07 kJ/mol。在90~150 min渗氮时间内,随着渗氮时间延长,渗层的表面硬度值由522 HV0.05降低至441 HV0.05,当渗氮时间延长至180 min,表面硬度值回升至455 HV0.05。与未处理试样相比,QPQ处理的试样具有更小的摩擦因数,并且QPQ处理后试样表面的犁沟显著变浅,表面的金属剥落也得到明显改善,且随着渗氮时间的增加,渗层厚度增加且稳定材料。经180 min渗氮处理的QPQ试样具有最优综合性能,表面硬度值为455 HV0.05,摩擦因数为0.32。     

One-pot synthesis of PdBi/reduced graphene oxide catalyst under microwave irradiation used for formic acid electrooxidation

The Pd and PdBi nanoparticles dispersed on the reduced graphene oxide (Pd/rGO and PdBi/rGO) have been synthesized through one-pot reaction under the irradiation of microwave and the obtained composites have been characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, and their electrocatalytic activities have also been evaluated. It is found that the PdBi_0.05/rGO catalyst exhibits higher activity and better stability toward formic acid electrooxidation compared with Pd/C and Pd/rGO. The excellent electrocatalytic performance indicates that the addition of appropriate amount of Bi can greatly enhance the activity and stability of Pd catalysts for the formic acid oxidation.     

Boosting hydrogen evolution under simulated sunlight via constructing close electron transfer interface between 1D CdxZn1-xS nanorod and 2D MoS2@MoOy nanosheet

Designing an efficient non-noble metal photocatalyst, which utilizes solar energy, has great potential to produce clean energy hydrogen. The microstructural refinement of 1D Cd_0.2Zn_0.8S nanorod was induced by doping with 2D MoS₂@MoO_y layer during microwave hydrothermal treatment. The maximum H₂ production rate of the composite prepared at optimum conditions was 186 mmol g⁻¹ h⁻¹, which increased by 34.8% compared with that of Cd_0.2Zn_0.8S (138 mmol g⁻¹ h⁻¹). The apparent quantum yields of the optimized composite were 10.3% and 15.6% at 365 and 420 nm, respectively. The tight S-scheme heterojunction contributed to the separation of photogenerated electron-hole pairs effectively, as confirmed by the characterization analysis of ·OH and ·O⁻₂ radicals, surface potential under illumination and darkness and in situ XPS spectra. Moreover, the active species of sulfur coordinated-Mo⁵⁺ as low-coordinate center promoted the dissociation of water and decreased the over potential of H₂ production. Furthermore, the optimal composite showed excellent stable catalytic activity for hydrogen evolution, and the H₂ production rate was 176.7 mmol g⁻¹ h⁻¹ after five cycles (95% of the first cycle). Overall, this work provides a promising strategy for improving the effectiveness of H₂ production by preparing non-noble metal composite photocatalysts.     

Monocular-vision-based method for online measurement of pose parameters of weld stud

With the rapid development of stud welding technology, weld studs are extensively used in automobile industry. A weld stud differs from a regular stud in that it has special external features. This study develops a novel non-contact, fast, and high-precision method based on monocular vision for measuring the position and attitude parameters of a weld stud. Under this method, the measuring principle for the weld stud’s position and attitude parameters is derived and an accurate mathematical model is set up. Based on this mathematical model, a precise calibration method for the projective transformation’s corresponding relationship parameters is developed and an optimal observation condition is then introduced as the constraint into the measurement process so as to enhance the location precision. The experiment results show that the proposed method is fast and accurate, and it satisfies the requirement of online, flexible, fast, and high-precision measurement of weld studs’ pose parameters in automobile and other manufacturing industries.     

Rise of cyborg microrobot: different story for different configuration

By integrating organic parts achieved through evolution and inorganic parts developed by human civilisation, the cyborg microrobot is rising by taking advantage of the high flexibility, outstanding energy efficiency, extremely exquisite structure in the natural components and the fine upgradability, nice controllability in the artefact parts. Compared to the purely synthetic microrobots, the cyborg microrobots, due to the exceptional biocompatibility and biodegradability, have already been utilised in in situ diagnosis, precise therapy and other biomedical applications. In this review, through a thorough summary of recent advances of cyborg microrobots, the authors categorise the cyborg microrobots into four major classes according to the configuration between biomaterials and artefact materials, i.e. microrobots integrated inside living cell, microrobots modified with biological debris, microrobots integrated with single cell and microrobots incorporated with multiple cells. Cyborg microrobots with the four types of configurations are introduced and summarised with the combination approaches, actuation mechanisms, applications and challenges one by one. Moreover, they conduct a comparison among the four different cyborg microrobots to guide the actuation force promotion, locomotion control refinement and future applications. Finally, conclusions and future outlook of the development and potential applications of the cyborg microrobots are discussed.Inspec keywords: medical robotics, cellular biophysics, mobile robots, molecular biophysics, polymers, microrobotsOther keywords: locomotion control refinement, actuation force promotion, combination approaches, biological debris, living cell, artefact materials, biomaterials, biomedical applications, biodegradability, exceptional biocompatibility, natural components, energy efficiency, human civilisation, purely synthetic microrobots, cyborg microrobot     

空间机器人基于比例因子识别的自校正反馈神经网络容错算法设计

针对执行器发生部分失效故障的空间机器人,提出一种基于比例因子识别的自校正反馈神经网络容错算法.首先,针对无故障系统设计一种常规的神经网络控制算法;然后,利用比例因子观测器对真实的比例因子进行识别;最后,将该神经网络控制算法与识别的比例因子相结合,得到一种具有容错功能的自校正反馈神经网络控制算法.控制器与观测器的稳定性判据均由Lyapunov函数法严格给出,并通过数值仿真表明所提出控制策略的可行性.     

多孔储液介质自润滑机理研究进展

多孔储液介质是启发自关节软骨的仿生摩擦材料,因具有良好的自润滑性能,在工业生产中发挥着重要作用。早期多孔储液介质多是针对不同基体材料及骨架结构进行优化设计,或是根据单因素理想边界建立润滑数值模型,对多孔储液介质的润滑机理缺乏系统的理论描述,限制了其大规模的工业应用。根据不同的结构形式和润滑机理,将多孔储液介质分为有限直孔储液介质和随机多孔储液介质,总结了有限直孔储液介质中空化现象、流体运动、惯性效应、气-液耦合对润滑性能的影响,论述了基于渗流力学、流-固耦合作用的随机多孔储液介质自润滑理论的发展,以及多孔储液介质的应用现状。分析和讨论了多孔储液介质自润滑机理研究的难点问题,对推动多孔储液介质润滑机理的研究和工程实践应用具有重要的参考意义。