Cr-C-O氢渗透阻挡层的适用条件研究

将具有阻挡层的试样封装在具有不同CO2压力的石英管中加热,然后对阻挡层表面进行观察和XPS分析,并用相对灵敏度因子法对X射线光电子能谱分析结果进行了计算分析。结果表明：700℃加热后,在0．03MPaCO2条件下的阻挡层被破破坏;300—500Pa的CO2条件下的阻挡层完好,其中的C-H键和-OH键的量随保温时间的增长和CO2压力的增高而增高;阻挡层能够在300—500Pa的CO2、700℃的封闭小空间中连续工作300小时。     

Manganese and chromium doping in atomically thin MoS2

Recently, two-dimensional materials have been attracting increasing attention because of their novel properties and promising applications. However, the impurity doping remains a significant challenge owing to the lack of the doping strategy in the atomically thin layers. Here we report on the chromium (Cr) and manganese (Mn) doping in atomically-thin MoS₂ crystals grown by chemical vapor deposition. The Cr/Mn doped MoS₂ samples are characterized by a peak at 1.76 and 1.79 eV in photoluminescence spectra, respectively, compared with the undoped one at 1.85 eV. The field-effect transistor (FET) devices based on the Mn doping show a higher threshold voltage than that of the pure MoS₂ while the Cr doping exhibits the opposite behavior. Importantly, the carrier concentration in these samples displays a remarkable difference arising from the doping effect, consistent with the evolution of the FET performance. The temperature-dependent conductivity measurements further demonstrate a large variation in activation energy. The successful incorporation of the Mn and Cr impurities into the monolayer MoS₂ paves the way towards the high Curie temperature two-dimensional dilute magnetic semiconductors.     

Water permeation across nanochannels with defects

Defects are common in fabricated nanochannels. In this paper, water permeation across a single-walled carbon nanotube with defects was studied using molecular dynamics simulations. It is found that the impact on water permeation is negligible when the density of the defects is small, while a significant reduction in water permeation is observed when the density of the defects is high. These findings should be helpful in both understanding water permeation across nanochannels and designing efficient artificial nanochannel.     

碱土元素和稀土元素复合合金化镁合金研究现状及进展

本文介绍了碱土、稀土元素在镁合金中的主要作用及作用机理,简述了碱土、稀土复合合金化的主要发展趋势和研究方向.指出稀碱土镁合金是我国镁合金发展的重要研究方向.     

大罐露天连续发酵在酒精生产中的应用

一个企业要在社会主义经济市场中立于不败之地,没有规模经济是不行的,没有规模经济不能参与竞争,企业就无法生存.企业要生存要发展要靠经济规模,要靠科技进步高新技术的应用才能取得好的经济效益.     

Characteristics of force chains in frictional interface during abrasive flow machining based on discrete element method

Abrading is a very important sub-technology of the surface treatment technology with vast applications in the industry. This study aims at analyzing the inherent laws of friction systems during abrading. In particle flow code modeling, the abrading process can be simplified to the movement of particles in a parallel-plate shear friction system. In this study, the PFC2D software is used to construct the particle flow friction system with the set of parallel plates and the model parameters according to the abrading processing equipment and processing materials, control the simulation of a single variable, and compare the output data to estimate the impact of change of parameters on the force chain. The simulation results show that the shear dilatancy can be divided into three stages:plastic strain, macroscopic failure, and granular recombination stages. The distribution and load rates of the weak force chains depend on the load, velocity, friction coefficient between granules, granular diameter, and number of granular layers. The number of granular layers and the load increase cause the direction of the force chain to be oriented with the vertical direction, and the force chains move toward the horizontal direction as the velocity increases. The increase in load does not cause the shear dilatancy stage to occur; the velocity, friction coefficient between granules, and granular diameter increase cause the shear dilatancy to occur gradually.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0236-7     

Negligible particle-specific antibacterial activity of silver nanoparticles

For nearly a decade, researchers have debated the mechanisms by which AgNPs exert toxicity to bacteria and other organisms. The most elusive question has been whether the AgNPs exert direct "particle-specific" effects beyond the known antimicrobial activity of released silver ions (Ag(+)). Here, we infer that Ag(+) is the definitive molecular toxicant. We rule out direct particle-specific biological effects by showing the lack of toxicity of AgNPs when synthesized and tested under strictly anaerobic conditions that preclude Ag(0) oxidation and Ag(+) release. Furthermore, we demonstrate that the toxicity of various AgNPs (PEG- or PVP- coated, of three different sizes each) accurately follows the dose-response pattern of E. coli exposed to Ag(+) (added as AgNO(3)). Surprisingly, E. coli survival was stimulated by relatively low (sublethal) concentration of all tested AgNPs and AgNO(3) (at 3-8 μg/L Ag(+), or 12-31% of the minimum lethal concentration (MLC)), suggesting a hormetic response that would be counterproductive to antimicrobial applications. Overall, this work suggests that AgNP morphological properties known to affect antimicrobial activity are indirect effectors that primarily influence Ag(+) release. Accordingly, antibacterial activity could be controlled (and environmental impacts could be mitigated) by modulating Ag(+) release, possibly through manipulation of oxygen availability, particle size, shape, and/or type of coating.     

基于魔方的并联机构运动支链构造及综合方法

提出了1种基于魔方的并联机构运动支链构造及综合方法,该方法不仅能够直观反映出运动支链中运动副的数量,还能展现出相邻运动副之间的轴线关系,有利于机构创新工作者,根据具体的需求综合出最优的机构构型。首先介绍了并联机构,魔方以及魔方与运动副和运动副轴线之间的相互联系;其次通过魔方的各种变换来构造出各种运动支链,并借助螺旋理论分析运动支链的末端运动特征;而后根据运动支链的末端运动特征状况进行整理、分类,组建运动支链库;最后,根据实际的需求,在运动支链库中选择合适的运动支链,构造出一系列同等运动形式的并联机构,并对其进行评估,从而得到最优的并联机构构型。     

Light concentration and redistribution in polymer solar cells by plasmonic nanoparticles

We propose an optoelectronic model to investigate polymer solar cells with plasmonic nanoparticles. The optical properties of the plasmonic active layers, approximated by the effective medium theory, are combined with the organic semiconductor model. The simulation suggests the enhancement on short-circuit photocurrent is due to light concentration and redistribution by particle plasmons.