A torsional resonance mode AFM for in-plane tip surface interactions

Changing the method of tip/sample interaction leads to contact, tapping and other dynamic imaging modes in atomic force microscopy (AFM) feedback controls. A common characteristic of these feedback controls is that the primary control signals are based on flexural deflection of the cantilever probes, statically or dynamically. We introduce a new AFM mode using the torsional resonance amplitude (or phase) to control the feedback loop and maintain the tip/surface relative position through lateral interaction. The torsional resonance mode (TRmode™) provides complementary information to tapping mode for surface imaging and studies. The nature of tip/surface interaction of the TRmode facilitates phase measurements to resolve the in-plane anisotropy of materials as well as measurements of dynamic friction at nanometer scale. TRmode can image surfaces interleaved with TappingMode™ with the same probe and in the same area. In this way we are able to probe samples dynamically in both vertical and lateral dimensions with high sensitivity to local mechanical and tribological properties. The benefit of TRmode has been proven in studies of water adsorption on HOPG surface steps. TR phase data yields approximately 20 times stronger contrast than tapping phase at step edges, revealing detailed structures that cannot be resolved in tapping mode imaging. The effect of sample rotation relative to the torsional oscillation axis of the cantilever on TR phase contrast has been observed. Tip wear studies of TRmode demonstrated that the interaction forces between tip and sample could be controlled for minimum tip damage by the feedback loop.     

SLS快速成形技术中激光加工参数对制件性能的影响

以AFS--320MZ快速成形机为例，研究了基于选择性激光烧结(SLS)快速成形制造中激光功率密度、扫描速度、扫描间距、扫描方式和铺粉密度等加工参数对制件性能的影响。     

滑动轴承两种油膜边界条件的比较

本文对滑动轴承计算中两种常用的油膜边界条件进行了比较，一种是雷诺边界条件，另一种即质量守恒边界条件。对于前者，常采用负压力归零法进行计算，对于后者，大多采用Elrod算法。本文通过改变Elrod算法中的变量θ的定义，对Elrood算法进行改进，建立一新的通用方程，可自动确定动态边界，并在稳态工况下，将两种边界条件的计算结果与实验数据进行比较，发现根据质量守恒边界条件采用本文新改进的算法计算所得结果与实验数据十分吻合，同时，计算结果表明，空穴并不总是降低轴承的承载力，在稳态工况下，当空穴压力为较大的负压力时，轴承的承载能力反而有明显提高。     

Structural studies of pulsed-laser deposited nanocomposite metal-oxide films

Pulsed laser deposition in vacuum has been used to develop metal-oxide nanocomposite films with well controlled structural quality. Results for the copper–aluminium oxide (Cu:Al₂O₃) system are used to illustrate the main morphological and structural features of these films. High resolution transmission electron microscopy (TEM) analysis shows that the films consist of Cu nanocrystals with average dimensions that can be controlled between 2 nm and 10 nm embedded in an amorphous Al₂O₃ matrix. It is observed that the in-plane shape of the nanocrystals evolves from circular to elongated, and the number of nanocrystals per unit area decreases as their size increases. This evolution is explained in terms of nucleation at the substrate surface and coalescence during the later stages of growth. The thermal stability of the films has been studied by in situ TEM annealing and no transformation could be observed up to about 800 °C when partial crystallization of the Al₂O₃ starts.     

可变论域的模糊自整定控制方法

该文将模糊控制中的“可变论域”思想和参数模糊自整定方法相结合，提出一种“可变论域”的模糊自整定控制方法，并将它成功应用在转台的速率控制中，为模糊控制在工程中的应用提供了一种新的、简单易行的途径。     

虚拟样机技术在飞行器设计中的应用

论述利用虚拟样机技术设计飞行器的意义,分析虚拟样机技术的实现方法,探讨虚拟样机技术在飞机系统优化设计中的应用。     

Neural network based expert system for induction motor faults detection

Early detection and diagnosis of incipient induction machine faults increases machinery availability, reduces consequential damage, and improves operational efficiency. However, fault detection using analytical methods is not always possible because it requires perfect knowledge of a process model. This paper proposes a neural network based expert system for diagnosing problems with induction motors using vibration analysis. The short-time Fourier transform (STFT) is used to process the quasi-steady vibration signals, and the neural network is trained and tested using the vibration spectra. The efficiency of the developed neural network expert system is evaluated. The results show that a neural network expert system can be developed based on vibration measurements acquired on-line from the machine.     

双圆弧弧齿锥齿轮传动的切齿啮合分析

基于双圆弧齿轮的齿形特点 ,结合弧齿锥齿轮的加工原理 ,进行双圆弧弧齿锥齿轮的切齿啮合分析 ,得到了切齿啮合过程中的啮合方程、产形轮齿面方程以及双圆弧弧齿锥齿轮的通用齿面方程表达式     

吉林省和龙火车站滑坡地质灾害防治措施概述

本文通过对吉林省和龙火车站滑坡特征的描述,详细论述了三种防治滑坡的方法,即地表水汇流排泄、微型抗滑桩和地下水排泄的防治方法.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@PAM@NTA-Ni<Superscript>2+</Superscript> Magnetic Composite Nanoparticles for Highly Specific Separation of His-tagged Proteins

A facile approach has been developed to synthesize Fe₃O₄@PAM (polyacrylamide) nanoparticles (NPs) with carboxyl groups on the surfaces by copolymerization with acrylamide and acrylic acid in Fe₃O₄ NPs aqueous suspension. Nitrilotriacetic acid (NTA) was conjugated to the magnetic NPs via well-known carboniimide chemistry using EDC and NHS. The Ni²⁺ ions loaded on the surface of NPs provide abundant docking sites for immobilization of His-tagged green fluorescent proteins (His-tagged GFP). The high magnetic property of Fe₃O₄@PAM@NTA-Ni²⁺ allows an easy separation of the NPs from solution under an external magnetic field, with high His-tagged protein binding capacity (42 μg protein/mg of NPs). The NPs can be recycled for at least four times without significant loss of binding capacity to proteins. These materials show great potential to separate His-tagged protein with low-cost purification at industrial scale.