Subspace-based multitask learning framework for hyperspectral imagery classification

Multimedia Tools and Applications - Subspace-based models have been widely applied for hyperspectral imagery applications, especially for classification. The main principle of these methods is...     

An efficient method of generating vortex electromagnetic wave based on double‐layer transmissive metasurface

A broadband double‐layer transmissive metasurface (TMS) for effective generate vortex electromagnetic wave is presented in this paper. The proposed TMS consists of two types of elements. The first element is composed of a multi‐resonant dipole and four metal vias. The metal vias increase the coupling strength between the upper and lower layers to improve transmission efficiency. On the basis of the first element, the second element adds stubs to ensure sufficient phase shift. The far‐field cross polarisation is eliminated by special element arrangement. Then, a centre‐fed linear polarisation TMS is designed to generate orbital angular momentum beams with mode l = ? 1. The proposed TMS is designed, manufactured and measured to verify the proposed design. The measured results indicate that a maximum gain of 20.8 dBi and narrow divergence angle of ±5° are achieved at 18 GHz. Furthermore, mode purity is higher than 86.1% within the 17 to 19 GHz band. The proposed double‐layer TMS saved costs, reduced weight and without assembly error is a good candidate for OAM generator.     

薄壁弱刚性钛合金结构件制造工艺

随着新型材料冶金技术的发展与进步,钛合金作为“崛起的第三代金属”已完全替代了铝镁合金和钢构件,成为航天飞行器上应用范围最广的材料之一。从某新研制航天飞行器外部结构件用钛合金材料的特性及切削特点入手,针对薄壁弱刚性钛合金结构件在实际加工过程中遇到的诸多难点,提出了相应的解决办法,并重新设计了零件工装。结果表明,改进措施不仅保证了零件质量,而且提高了零件加工效率,使单件零件的生产周期缩短了近10h。     

低碳钢电弧熔覆增材层摩擦磨损及抗腐蚀性能

目的 针对低碳钢零件的破损失效采用TIG焊电弧熔覆增材制造工艺，研究低碳钢电弧熔覆修复使其达到再制造零件性能要求的可行性，为实现TIG焊修复应用提供保证。方法 通过TIG焊熔覆在低碳钢坡口处，对熔覆接头的显微组织进行分析，并测试修复后的增材层表面硬度性能。使用Nanovea Tribometer摩擦磨损仪和NanoveaPS50表面轮廓仪，对基体和增材层进行摩擦性能测试，并表征摩擦磨损后的表面形貌，探究磨损机理。采用电化学工作站对基体和增材层的腐蚀性能进行分析。结果 修复后的增材层显微硬度（220.17HV）高于基体且其摩擦性能和腐蚀性能优于基体，随着磨损载荷的增加，增材层的摩擦系数逐渐降低，磨损机制主要为磨粒磨损和粘着磨损。增材层表面组织均匀细小，在NaCl溶液中点蚀坑小且分散，增材层的腐蚀电流密度（1.8349×10-6 A/cm2）小于基体的腐蚀电流密度（6.5251×10-5 A/cm2），增材层表面的抗腐蚀能力明显提高。结论 电弧熔覆低碳钢可满足低碳钢零部件现场电弧快速修复对再制造性能的要求，实现了低碳钢破损零部件的表面修复与强化。     

Computer-based engineering of thermostabilized antibody fragments

We used the molecular modeling program Rosetta to identify clusters of amino acid substitutions in antibody fragments (scFvs and scAbs) that improve global protein stability and resistance to thermal deactivation. Using this methodology, we increased the melting temperature (T_m) and resistance to heat treatment of an antibody fragment that binds to the Clostridium botulinum hemagglutinin protein (anti-HA33). Two designed antibody fragment variants with two amino acid replacement clusters, designed to stabilize local regions, were shown to have both higher T_m compared to the parental scFv and importantly to retain full antigen binding activity after 2 hr of incubation at 70°C. The crystal structure of one thermostabilized scFv variants was solved at 1.6 Å and shown to be in close agreement with the RosettaAntibody model prediction.