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371.
372.
为提高40Cr钢表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备Fe基涂层,利用HT-500摩擦磨损实验机测定干摩擦条件下,基体和熔覆层的摩擦因数随温度变化的规律。利用表面粗糙度轮廓仪测量磨痕的深度和宽度,SEM观察熔覆层以及磨痕的显微组织形貌,使用HV-1000型显微硬度仪检测基体和熔覆层结合部分的硬度。研究结果表明:熔覆层平均显微硬度值达到373.8HV(0.2);显著高于基体硬度198.4HV(0.2)。在干摩擦条件下,随着温度升高,磨损过程逐渐变平缓,平均摩擦因数降低,磨损率增加,耐磨性下降;在350~400 ℃之间,熔覆层磨损性能优于基体。 相似文献
373.
374.
Lilian Huang Zefeng Zhang Jianhong Xiang 《Mathematical Methods in the Applied Sciences》2020,43(4):1857-1867
This paper is devoted to investigate a class of complex chaotic systems and a linear correlation between the real and imaginary component of complex variables in these systems is found. Based on this linear relationship, a simplified law is proposed. First, complex Lorenz system is given to show the linear correlation, then it is simplified. Second, a simplified law is proposed to determine whether the complex system can be simplified, and the complex Lü system and hyperchaotic complex Lü system are used to verify the simplified law. Finally, a new synchronization control is proposed to synchronize complex Lorenz system and real Lorenz system. The theoretical analysis and numerical simulation prove the feasibility and better performance of this method. 相似文献
375.
Hongyun Meng Jianhong Liao Yongheng Zhou Qingmao Zhang 《Optics & Laser Technology》2009,41(3):300-302
A metallic cardiovascular stent cutting system based on fiber laser was designed in this study. In order to achieve the cutting of stent, the main modules and the key technologies were analyzed and achieved. Then with the cutting system, the kerf width size was studied for different cutting parameters including laser output power, pulse length, repeat frequency, cutting speed and assisting gas pressure. Finally, a high quality of cutting of 316L stainless steel cardiovascular stent was achieved. 相似文献
376.
Wenhe Wang Qiang Gao Xiaoyu Li Jianhong Wang Chaopeng Wang Yinghui Zhang Xianhe Bu 《中国化学快报》2019,30(1):75-78
A Tb3+ based coordination polymer (NKU-115) with free N sites was successfully constructed, featuring strong green light emission and selective quenching response toward Fe3+ in aqueous solution. 相似文献
377.
Qi Hu Guomin Li Xiufang Liu Bin Zhu Xiaoyan Chai Qianling Zhang Jianhong Liu Chuanxin He 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4362-4366
Recently, metal‐free, heteroatom‐doped carbon nanomaterials have emerged as promising electrocatalysts for the oxygen evolution reaction (OER), but their synthesis is a tedious process involving energy‐wasting calcination. Molecular electrocatalysts offer attractive catalysts for the OER. Here, phytic acid (PA) was selected to investigate the OER activity of carbons in organic molecules by DFT calculations and experiments. Positively charged carbons on PA were very active towards the OER. The PA molecules were fixed into a porous, conductive hydrogel with a superhydrophilic surface. This outperformed most metal‐free electrocatalysts. Besides the active sites on PA, the high OER activity was also related to the porous and conductive networks on the hydrogel, which allowed fast charge and mass transport during the OER. Therefore, this work provides a metal‐free, organic‐molecule‐based electrocatalyst to replace carbon nanomaterials for efficient OER. 相似文献
378.
By means of first-principles calculations within the generalised gradient approximation (GGA), phase stability, elastic properties and electronic structures of B2 CoX (X = Ti, Zr and Hf) compounds as a function of pressure have been investigated. The formation energy indicates that CoTi is the most stable phase in these three B2 phases under different pressures. The elastic properties of B2 Co (X = Ti, Zr and Hf), calculated via the Voigt–Reuss–Hill (VRH) approximation, increase with increasing pressure. The mechanical anisotropies are characterised by the universal anisotropy index (AU) and the Zener anisotropy index (AZ). The sound velocities, Debye temperatures and melting temperature under applied pressure are also evaluated. Electronic structure show that the changes in the charge distribution are moderate under applied pressure, resulting in the general characteristics of the bonding between X (X = Ti, Zr and Hf) and Co remain unchanged. 相似文献
379.
Jianhong Yang Lei Gang & Jianwei Yang 《advances in applied mathematics and mechanics.》2014,6(5):663-679
In this paper, we consider a two-scale stabilized finite volume method for the two-dimensional
stationary incompressible flow approximated by the lowest equal-order element pair $P_1-P_1$
which does not satisfy the inf-sup condition. The two-scale method consists of solving a small non-linear system
on the coarse mesh and then solving a linear Stokes equations on the fine mesh. Convergence of the optimal
order in the $H^1$-norm for velocity and the $L^2$-norm for pressure is obtained. The error analysis shows
there is the same convergence rate between the two-scale stabilized finite volume solution and the usual
stabilized finite volume solution on a fine mesh with relation $h =\mathcal{O}(H^2)$. Numerical experiments completely
confirm theoretic results. Therefore, this method presented in this paper is of practical importance in
scientific computation. 相似文献
380.
高效液相色谱-离子阱质谱法测定尿液中β2-受体激动剂及β-受体阻断剂 总被引:1,自引:0,他引:1
建立了尿液中23种β2-受体激动剂及5种β-受体阻断剂的高效液相色谱-离子阱质谱(HPLC-IT-MS)测定方法。尿液样品采用冷冻高速离心沉淀蛋白,上清液过ExtrelutTM硅藻土柱,用乙酸乙酯洗脱后,洗脱液经旋转蒸发仪浓缩并复溶待测。HPLC分离采用AtlantisT3-150 mm色谱柱,以甲醇和含0.1%甲酸的水溶液为流动相梯度洗脱,IT-MS采用电喷雾离子源在多反应离子监测模式下测定。定量分析选择9种经过氘代同位素标记的β2-受体激动剂为内标。各化合物的线性范围为0.005~0.16 mg/L,尿液中的检出限均能达到0.2 μg/L。空白尿液样品中不同加标水平的回收率为57.1%~127.1%,相对标准偏差为1.1%~31.1%。该方法简便快速,灵敏度高,适用于人或动物尿液中23种β2-受体激动剂及5种β-受体阻断剂的定性和定量分析。 相似文献