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991.
对比研究了货车心盘用ZG25MnNb钢、AAR-C级钢及经过表面强化处理的锻钢20Mn、锻钢Q345和铸钢ZG25的耐磨性能;采用金相显微镜分析了材料金相结构对其耐磨性能的影响。结果表明,对货车心盘用钢材进行表面强化能够显著改善其耐磨性能ZG25MnNb钢和经表面强化处理的锻钢20Mn的耐磨性较优;表面硬度高而组织细小的材料组成的摩擦副的耐磨性较好。 相似文献
992.
For the system of multilayer dynamics of fluids in porous media, the second order upwind finite difference fractional steps schemes applicable to parallel arithmetic are put forward. Some techniques, such as calculus of variations, energy method, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates are adopted. Optimal order estimates are derived to determine the error in the second order approximate solution. These methods have already been applied to the numerical simulation of migration-accumulation of oil resources. 相似文献
993.
994.
提出了超大单元、结点归一化相对距离判别法这一快速三维自动剖分技术,针对大型水工建筑物的特点,给出了几种常遇问题的实用处理方法;还给出了适合工程实际的超大面判断立体消隐图绘制法和基于Autolisp语言及Auto-CAD的立体图处理方法. 相似文献
995.
基于文献中报道的试验结果,本文考虑非均匀的畴变过程区,它包含一个位于中心的饱和区和环绕饱和区的渐变区.为了描述外加应力引起的部分铁弹畴变,本文采用一个显式的基于最小能量原理的非均匀畴变准则.考虑离面极化的压电陶瓷,假设其初始极化矢量平行于离面方向.畴变后的电畴位于面内,具体方位由最大释放功来确定.基于非均匀畴变准则,本文给出了裂尖处非均匀畴变区几何及畴变体积分数的分布.并在静止裂纹和稳态扩展裂纹两种特殊情况下计算了铁弹畴变对裂尖处应力强度因子的影响.结果表明:(1) 静止裂纹尖端处的畴变减小了材料的起裂强度;(2) 准静态稳态裂纹附近的畴变增加了材料的断裂强度.且理论预测的R曲线渐近值与试验结果定量吻合. 相似文献
996.
氮化物陶瓷颗粒增强铜基复合材料的干摩擦磨损性能研究 总被引:4,自引:0,他引:4
采用粉末冶金工艺制备了纯铜以及AlNp/Cu和TiNp/Cu系列铜基复合材料,研究了2种复合材料在不同颗粒含量、不同载荷及滑动速度等条件下与45^#钢对摩时的干摩擦磨损性能,用扫描电子显微镜观察其磨损表面形貌,用能谱仪分析了磨损表面的元素组成.结果表明:与纯铜相比,AlNpCu及TiNp/Cu复合材料的耐磨性能显著提高,随着氮化物颗粒含量增加,2种复合材料的磨损率先下降而后趋于稳定;载荷与滑动速度提高引起的热效应使得纯铜及其复合材料的磨损率增高;由于TiNp的硬度高于AlNp以及本身具有一定的自润滑性能,使得TiNp/Cu复合材料的耐磨减摩性能优于AlNp/Cu复合材料. 相似文献
997.
998.
High‐contrast Noninvasive Imaging of Kidney Clearance Kinetics Enabled by Renal Clearable Nanofluorophores 下载免费PDF全文
Dr. Mengxiao Yu Dr. Jinbin Liu Xuhui Ning Prof. Dr. Jie Zheng 《Angewandte Chemie (International ed. in English)》2015,54(51):15434-15438
Noninvasive imaging of kidney clearance kinetics (KCK) of renal clearable probes is key to studying unilateral kidney function diseases, but such imaging is highly challenging to achieve with in vivo fluorescence. While this long‐standing challenge is often attributed to the limited light penetration depth, we found that rapid and persistent accumulation of conventional dyes in the skin “shadowed” real fluorescence signals from the kidneys and prevented noninvasive imaging of KCK, which, however, can be addressed with renal clearable nanofluorophores. By integrating near infrared emission with efficient renal clearance and ultralow background interference, the nanofluorophores can increase kidney‐contrast enhancement and imaging‐time window by approximately 50‐ and 1000‐fold over conventional dyes, and significantly minimize deviation between noninvasive and invasive KCK, laying down a foundation for translating in vivo fluorescence imaging in preclinical noninvasive kidney function assessments. 相似文献
999.
Dr. Junhe Ma Qing Cao Dr. Sarah M. McLeod Keith Ferguson Ning Gao Prof. Alexander L. Breeze Dr. Jun Hu 《Angewandte Chemie (International ed. in English)》2015,54(16):4764-4767
An NMR‐based approach marries the two traditional screening technologies (phenotypic and target‐based screening) to find compounds inhibiting a specific enzymatic reaction in bacterial cells. Building on a previous study in which it was demonstrated that hydrolytic decomposition of meropenem in living Escherichia coli cells carrying New Delhi metallo‐β‐lactamase subclass 1 (NDM‐1) can be monitored in real time by NMR spectroscopy, we designed a cell‐based NMR screening platform. A strong NDM‐1 inhibitor was identified with cellular IC50 of 0.51 μM , which is over 300‐fold more potent than captopril, a known NDM‐1 inhibitor. This new screening approach has great potential to be applied to targets in other cell types, such as mammalian cells, and to targets that are only stable or functionally competent in the cellular environment. 相似文献
1000.
Two‐Dimensional Covalent Organic Frameworks for Carbon Dioxide Capture through Channel‐Wall Functionalization 下载免费PDF全文
Ning Huang Dr. Xiong Chen Prof. Dr. Rajamani Krishna Prof. Dr. Donglin Jiang 《Angewandte Chemie (International ed. in English)》2015,54(10):2986-2990
Ordered open channels found in two‐dimensional covalent organic frameworks (2D COFs) could enable them to adsorb carbon dioxide. However, the frameworks’ dense layer architecture results in low porosity that has thus far restricted their potential for carbon dioxide adsorption. Here we report a strategy for converting a conventional 2D COF into an outstanding platform for carbon dioxide capture through channel‐wall functionalization. The dense layer structure enables the dense integration of functional groups on the channel walls, creating a new version of COFs with high capacity, reusability, selectivity, and separation productivity for flue gas. These results suggest that channel‐wall functional engineering could be a facile and powerful strategy to develop 2D COFs for high‐performance gas storage and separation. 相似文献