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71.
Relationship between grain boundary diffusion in nanocrystals and amorphous microstructure
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Lin‐lin Sun Jun Wang Hong‐chao Kou Jin‐shan Li Ping‐xiang Zhang 《Surface and interface analysis : SIA》2016,48(12):1341-1344
The effects of microstructure on diffusion behaviors of Ni in Zr48Cu36Ag8Al8 alloy were investigated by transmission electron microscope and secondary ion mass spectrum. The temperature dependence of Ni diffusivities in Zr48Cu36Ag8Al8 alloy with different states (metallic glass, nanocrystals and coarse crystals) has been measured in the temperature range of 693–723 K. The results show that diffusion behavior is microstructure dependence, and the relations between the microstructure and diffusion are discussed. The activity energy of the grain boundary diffusion in nanocrystals calculated by the Suzuoka solution is about 1.433 eV/atom. It is equivalent with that of metallic glass, which is attributed to the similar microstructure between the two. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
72.
固体力学中侵入问题的若干新进展 总被引:6,自引:0,他引:6
本文主要介绍了固体力学中侵入问题近10余年来的发展情况。重点综述了侵入断裂实验及理论研究的新成果;讨论了动静态侵入断裂的关系;简述了侵入方法在测定材料断裂韧性方面的应用。 相似文献
73.
针对WebGIS中存在的系统不稳定、难以扩展及可维护性差等问题,提出一种基于组件的多层WebGIS模型,并论述了如何基于J2EE框架实现该体系结构。实际的系统设计与开发工作表明,基于新体系结构的WebGIS具有较好的集成性与可扩展性,从而缩短了开发周期,降低了开发成本。 相似文献
74.
A four-level double-ladder atomic system with two upper states coupled to the excited state by a standing-wave trigger field is explored to generate photonic bandgap (PBG) structure. With the assistance of spontaneously generated coherence (SGC) from the two decay pathways, we can obtain single or double fully developed PBG when the trigger field is far away from resonance or resonant. While in the absence of SGC, the atomic medium becomes strong absorptive to the probe field, and therefore the resulting PBGs are severely malformed or even cannot be opened up. Numerical results show that the PBG structure is originated from the third-order cross Kerr nonlinear modulation between the probe and trigger fields. This mechanism differs from the recent schemes based on linear modulation. 相似文献
75.
The characters of self-assembly core/shell nanoparticles of amphiphilic hyperbranched polyethers (HP-g-PEO) as drug carriers
were investigated. The HP-g-PEO consisting of hydrophobic HP-g-PEO core and hydrophilic poly(ethylene glycol) arms was prepared
by the cation ring-opening polymerization. A series of HP-g-PEO samples with different degree of branching (DB) were synthesized
under various reaction temperatures. Nanoparticles (NP) were obtained by self-assembly of HP-g-PEO in aqueous media. The structure
of resulting HP-g-PEO was characterized by IR, 13CNMR and GPC. Dynamic light scattering and transmission electron microscopy were applied to characterize the sizes and size
distributions of NP. The results demonstrated that the mean diameters of NP were less than 100 nm, which exhibited uniform
spherical formations and narrow size distributions. Using hydrophobic drug Probucol (PRO) as model drug, the particle sizes
of drug loaded NP were larger than relative blank NP. The drug loading efficiency (LE) and incorporation efficiency (IE) of
these NP were achieved to 35 and 89%, respectively. The in vitro release of PRO from the NP exhibited a sustained release
and the cumulative drugs released for more than 600 h. The most important factor to affect drug release was the value of DB
of HP-g-PEO. With the DB of HP-g-PEO increasing, the size and size distribution of NP decreased as well as the release rate.
However, the small DB was beneficial to the LE of NP. Nanoparticle size and size distribution, LE, IE, and drug release rate
were slightly affected by the initial solution concentration of polyethers. The co-incorporated hydrophilic drug had influence
slightly on the release of drug from drug loaded NP. The results of in vitro drug release suggested that the core/shell NP
performed good controlled release behaviors with potential practice as novelty drug delivery vehicles. 相似文献
76.
应用一般系统论的思想和方法,分析了基于系统动态平衡和系统模型网络式描述的统一的建模和求解方法,以及系统状态变量X与结构关系R的影响形式和函数描述,并提出了系统变化过程中系统模式的概念和一种矩阵描述方法。最后,讨论了基于网络模型的模型管理系统设计和初步应用情况。 相似文献
77.
寇夏莲 《西北大学学报(自然科学版)》1991,(4)
本文介绍了一种直接面向机器的、采用特殊方法进行存贮空间分配的新型软件开发工具NST,其基础是IBM PC/XT的核心软件CC-BIOS。NST的研制对改变我国目前微机闲置率高等状况有很大的价值,对“系统软件国产化”也有很深远的意义。 相似文献
78.
寇培林 《陕西师范大学学报(自然科学版)》1994,(1)
应用费马原理推导出主截面内的非常光线通过两种各向异性媒质分界面时的反射定律和折射定律. 相似文献
79.
80.
对金工实习进行全面改革,建立了新的运行机制,组建并培育出一支结构合理的教学队伍.改革传统的实习模式和实习内容,为培养学生的创新能力,建立了四个平台,使学生通过金工实习在劳动素养、工程素质、严谨的科学态度和工作作风、团队协作精神等方面得到训练. 相似文献