Effect of SiC content on dry sliding wear, corrosion and corrosive wear of Al/SiC nanocomposites

The corrosion, corrosive wear and dry sliding wear of nanocomposites, are extremely complicated and involve various chemical, physical anbd mechanical factors. The aim of this work is to investigate the effects of nanosized SiC content on the hardness, dry sliding wear, corrosion and corrosive wear of Al/SiC nanocomposites synthesized by mechanical milling cold pressing and hot extrusion. The corrosion resistance of these composites in 3%NaCl solution was investigated by electrochemical polarization testing and their dry sliding as well as corrosive wear resistance in the same solution was evaluated using a pin-on-disc tester. The microstructures of the samples and their worn surfaces were examined using scanning electron microscopy. It was shown that the dry sliding wear and corrosion resistance of these nanocomposites were improved with the increase of SiC content. It was concluded that due to the lubrication effect of the solution, both the friction coefficient and frictional heat that might soften the material were reduced. In addition, the improved strength of the nanocomposites combined with their better corrosion resistance contributed to their increased corrosive wear resistance, compared with the base alloy. The prominent wear mechanism in the unreinforced alloy was adhesive wear, in the Al/SiC nanocomposites, the wear mechanism changed to abrasive.

Biocompatibility of vascular stents manufactured using metal injection molding in animal experiments

This study aimed to evaluate the feasibility and safety of a novel stent manufactured by metal injection molding(MIM)in clinical practice through animal experiments.Vessel stents were prepared using powder injection molding technology to considerably improve material utilization.The influence of MIM carbon impurity variation on the mechanical properties and corrosion resistance of 316L stainless steel was studied.In vitro cytotoxicity and animal transplantation tests were also carried out to evaluate the safety of MIM stents.The results showed that the performance of 316L stainless steel was very sensitive to the carbon content.Carbon fluctuations should be precisely controlled during MIM.All MIM stents were successfully implanted into the aortas of the dogs,and the MIM 316L stents had no significant cytotoxicity.The novel intravascular stent manufactured using MIM can maintain a stable form and structure with fast endothelialization of the luminal surface of the stent and ensure long-term patency in an animal model.The novel intravascular stent manufactured using MIM demonstrates favorable structural,physical,and chemical stability,as well as biocompatibility,offering promising application in clinical practice.

Surface Nanocrystallization of Nb-Ti Stabilized 439M Ferritic Stainless Steel

A new nanocrystallization process was designed, which included punching the surface coating to generate dislocation network or cells and recovery treatment to turn the dislocation cells into nano-sized grains. The effort was made to increase the service life of Nb-Ti stabilized 439M stainless steel surface with medium passive ability, particularly to enhance the outmost surface layer by nanocrystallization for improving resistances to corrosion. Electrochemical properties, electron work functions （EWFs）, nano-mechanical properties of the nanocrystallized surfaces were investigated. It was demonstrated that the nanocrystallized 439M stainless steel surface exhibited improved resistance to corrosion in 0.5 mol/L H2 SO4 solution. However, the nanoci＇ystallized 439M stainless steel surface exhibited decreased resistance to corrosion in 3.5% NaCl solution.

中国战略性新兴产业国际贸易网络布局及其优化策略——基于社会网络分析视角

本文基于2014年全球160个经济体的贸易数据,运用社会网络分析方法构建贸易网络模型,从网络中心性、凝聚子群、中间人和网络价值四个维度考察了战略性新兴产业的国际贸易网络布局。研究结果表明,美国和德国在战略性新兴产业贸易网络中占据主导地位。中国战略性新兴产业的入度中心性、中介中心性、参与派系数量,高端装备制造业、生物产业和新能源产业的网络价值低于美国、德国等贸易强国;中国的中间人角色以联络人和代理人为主,话语权和影响力有待增强。根据研究结果,提出如下优化策略:抓住中美贸易战契机,倒逼战略性新兴产业技术升级;巩固优势产业地位,加快推动生物产业和高端装备制造业发展;积极实施贸易平衡发展战略,扩大战略性新兴产业进口。

具有高效发光性能的亚铜卤化物纳米团簇应用于X-射线闪烁体

闪烁体可以将高能辐射转化为可见光,作为一种光电功能材料已经广泛应用于各种放射探测领域.虽然三维Pb基钙钛矿纳米晶可以开发为X射线闪烁体材料,但是其较低的光产额和铅毒性问题在一定程度上限制了其应用.为解决这一问题,本文重点关注零维金属卤化物发光材料,合成了一系列基于孤立[Cu_(4)X_(6)]^(2−)纳米团簇的零维卤化物,并将其开发应用为闪烁体发光材料.在紫外线或蓝光激发下,该卤化物纳米团簇均显示出宽带光发射,发光颜色可覆盖绿色、橙色到红色,并且具有近乎100%的光量子产率和较大的Stokes位移(>1.3 eV).特别突出的是,该类卤化物纳米团簇由于较高的发光量子产率、较小的光学自吸收和较强的X射线衰减效率,表现出优异的X-射线闪烁发光性能,光产额最高可达到24,240 photons MeV−1.材料的闪烁发光强度与X射线剂量呈现线性关系,检测范围较宽,且检测极限(0.7563μGy_(air)s^(−1))远低于常规医学诊断所要求的计量(5.5μGy_(air)s^(−1)).X-射线成像结果表明该纳米团簇余晖衰减时间较短(1.3 ms),空间分辨率较高(14.83 lp mm^(−1)),在医学成像等领域具有潜在的应用价值.该项工作表明,亚铜卤化物纳米团簇具有高效、稳定、无毒、发光效率高等优点,有望成为一种优异的新型闪烁体发光材料.

JNeRF:An efficient heterogeneous NeRF model zoo based on Jittor

Neural radiance fields(NeRFs)for novel-view synthesis have attracted the attention of researchers in computer vision and graphics.Unlike traditional methods using explicit expressions,NeRFs represent a scene as an implicit neural radiance field.When rendering,NeRF queries the color density at every position in the scene through a neural network.NeRF brings a wide range of possibilities for real-world 3D reconstruction and rendering,but problems remain to be solved.Previous works have improved NeRF’s sampling technique,position encoding method,network structure,etc.,but these improvements are difficult to be combined as the different modules are not well decoupled.Recent works have significantly sped up the core GPU computation of NeRF,leaving the deep learning framework as a major computational cost.Thus,it has been suggested to replace the frameworks by pure CUDA programs,but this limits maintainability and extendability.Therefore,we propose JNeRF,a unified,efficient,framework-friendly NeRF model zoo based on Jittor.