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排序方式: 共有26条查询结果,搜索用时 15 毫秒
1.
高温扫描隧道显微镜(HT-STM)可以实时原位地捕捉到表面原子的熔化相变过程.在这一原位变温实验中,快速可靠地识别出每帧STM图像中的熔融相十分关键.传统的手工统计方法存在效率低下、随意性大等问题.我们发展出一套基于数学形态学的算法,来自动快速地识别.与人工方法相比,该算法消除了人为主观误差,使确定的边界更加准确、光滑,处理效率提高了266倍.  相似文献   
2.
吴夏  魏征 《物理学报》2017,66(15):150202-150202
具有特殊催化、磁性和化学活性的三元合金团簇已成为基础科学研究的热点问题.确定其稳定结构是研究团簇性质的重要前提.针对大尺寸Cu-Au-Pd团簇结构优化,提出了内核构建的方法改进了自适应免疫优化算法的效率(称为AIOA-IC算法).采用基于紧束缚势二阶矩近似的多体Gupta势函数来描述三元合金团簇原子间相互作用.为测试算法效率优化了原子数为60的Ag-Pd-Pt团簇稳定结构.结果显示新得到的结构比文献报道的团簇结构势能量值更低,由此可知AIOA-IC算法具有更强的势能面搜索能力.运用该算法研究了38及55原子Cu-Au-Pd团簇的稳定结构.所研究的38原子Cu-Au-Pd团簇包含了五折叠、六折叠和截角八面体结构,并且原子成分比例影响了团簇的结构类型.而55原子Cu-Au-Pd团簇均为完整二十面体结构,序列参数显示Cu,Au和Pd原子分层现象明显.对于147原子Cu_(12)Au_(93)Pd_(42)团簇完整二十面体结构,中心原子为Au,内层和次外层分别被12个Cu原子和42个Pd原子占据,最外层则被92个Au原子占满.通过原子半径及表面能分析了Cu,Pd和Au原子分别倾向于分布在内层、次外层和最外层的规律.  相似文献   
3.
Capillary forces are significantly dominant in adhesive forces measured with an atomic force microscope (AFM) in ambient air, which are always thought to be dependent on water film thickness, relative humidity, and the free energy of water film. We study the nature of the pull-off force on a variety of surfaces as a function of tip velocity. It is found that the capillary forces are of relatively strong dependence on tip velocity. The present experiment is expected to provide a better understanding of the work mechanism of AFM in ambient air.  相似文献   
4.
The experimental relationship between width and amplitude of the non-destructive threshold pulse for Pt tip of a scanning tunneling microscope (STM) on graphite surface have been studied strictly and systematically in a wide range of pulse width for the first time. The threshold curve of amplitude versus width indicates that the amplitude of threshold pulse will increase with the decrease of the pulse width. A more rigorous explanation is suggested to interpret the dependence of threshold pulse amplitude on width. Fitted with the experimental data,a new empirical formula is given, extrapolated from which the threshold pulse amplitude will rise to 50 V when the pulse width decreases to 10ns.  相似文献   
5.
Adhesion elastic contact and hysteresis effect   总被引:1,自引:0,他引:1       下载免费PDF全文
魏征  赵亚溥 《中国物理》2004,13(8):1320-1325
In this paper, we study the relationship between the pull-off force and the transition parameter (or Tabor number) as well as the variation of the pull-off radius with the transition parameter in the adhesion elastic contact. Hysteresis models are presented to describe the contact radius as a function of external loads in loading and unloading processes. Among these models, we verified the hysteresis model from Johnson-Kendall-Roberts theory, based on which the calculated results are in good agreement with experimental ones.  相似文献   
6.
Tian-Long Li 《中国物理 B》2021,30(12):120702-120702
A novel instrument that integrates reflection high energy electron diffraction (RHEED), electron energy loss spectroscopy (EELS), and imaging is designed and simulated. Since it can correlate the structural, elemental, and spatial information of the same surface region via the simultaneously acquired patterns of RHEED, EELS, and energy-filtered electron microscopy, it is named correlative reflection electron microscopy (c-REM). Our simulation demonstrates that the spatial resolution of this c-REM is lower than 50 nm, which meets the requirements for in-situ monitoring the structural and chemical evolution of surface in advanced material.  相似文献   
7.
The dissipation of energy during the process of contact and separation between a tip and a sample is very important for understanding the phase images in the tapping mode of atomic force microscopes(AFMs). In this study, a method is presented to measure the dissipated energy between a tip and a sample. The experimental results are found to be in good agreement with the theoretical model, which indicates that the method is reliable.Also, this study confirms that liquid bridges are mainly produced by extrusion modes in the tapping mode of AFMs.  相似文献   
8.
建立起一套工作于真空环境下的基于脉冲电压扫描隧道显微镜(STM)的单原子识别预研究装置.该装王主要由脉冲发生器、真空系统和STM系统三部分组成,能够在5×10-5Pa的真空环境下进行快脉冲STM实验.利用此装置,进行了单个快脉冲诱导的石墨表面超大周期结构的脉冲实验以及脉冲偏压不破坏STM针尖和样品表面的阈值实验.  相似文献   
9.
3-酞酰亚胺-2-氧-正丁醛双缩硫代氨基脲(5)具有明显的抑制沙眼衣原体、细菌和大鼠瓦克癌256的作用。对各型沙眼和某些病毒性皮肤病均有肯定的疗效。本文报道了该化合物的合成方法,即以丁酮为原料经溴化得到了3-溴代丁酮-(2)(1),1与酞酰亚胺钾盐缩合得2,再经溴化得3。由于溴化反应条件不同,可得其它的溴化物(6,8,9)。3用二甲基亚砜氧化成α-酮醛(4)。我们对氧化反应进行了一些探讨,除酞丁安(5)外,还分到三个副产物,经鉴定分别为:α-酞酰基丙酰甲基二甲基溴化锍(10),三甲基溴化锍(11)及酞酰亚胺。4可不经分离直接与硫代氨基脲缩合而得酞丁安。  相似文献   
10.
采用高能电子束辐照方法获得了一系列从20kGy到1000kGy大剂量辐照范围的超高分子量聚乙烯纤维(UHMWPE fiber)。通过凝胶含量测试和溶胶流变性能测试定性和定量表征了辐照过程的交联和裂解效应,利用差示扫描量热仪(DSC)和X射线衍射仪(XRD)表征了辐照产物的结晶性能,并且利用热机械分析仪(TMA)表征了辐照纤维在高温恒温条件下的热尺寸稳定性。结果表明,高能电子束辐照对于UHMWPE纤维具有交联和裂解两种作用;大剂量辐照下会造成纤维熔点和熔融热焓降低,法线方向晶粒平均尺寸有明显变小;辐照交联大大提高了纤维的热尺寸稳定性。  相似文献   
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