Interpretation of Oxygen K pre-edge peak in complex oxides

A controversial pre-edge peak has often been observed at the O K-edge in absorption spectra from complex oxides. We study this feature in both K(2)O-SiO(2) glass and MgAl(2)O(4) spinel crystals. Our time-resolved energy-loss spectroscopy (EELS) results indicate that the pre-edge peak is due to radiation damage, rather than from any intrinsic feature of the material. It is assigned to the pi* peak due to the O-O interaction.     

Clean and metal-contaminated Si(110) surfaces studied by RHEED,XPS and STM

We have studied the atomic structure of clean and metal-contaminated Si(110) surfaces in real space with Scanning Tunnelling Microscopy (STM) and compared the results with Reflection High Energy Electron Diffraction (RHEED) data taken on samples from the same wafer. On clean Si(110) surfaces flat reconstructed regions coexist with (15 17 1), (15 173) and related facets. The surface consists of periodically-alternating high and low terraces, with a height difference corresponding to the interlayer spacing (0·19 nm). This structure is found in two domains, with terrace edges aligned along the and directions respectively. Atomic scale zig-zag chains can be recognized on the terraces. Contamination of the surface with Ni or Cu results in the formation of reconstructions with drastically different unit cells, all orientated along [001] and . The transition proceeds via a disordered 5×1-like intermediate phase for Ni coverages around 0·007 ML.     

A simple method to deposit palladium doped SnO2 thin films using plasma enhanced chemical vapor deposition technique

This work presents a simple method to deposit palladium doped tin oxide (SnO(2)) thin films using modified plasma enhanced chemical vapor deposition as a function of deposition temperature at a radio frequency plasma power of 150 W. Stannic chloride (SnCl(4)) was used as precursor and oxygen (O(2), 100 SCCM) (SCCM denotes cubic centimeter per minute at STP) as reactant gas. Palladium hexafluroacetyleacetonate (Pd(C(5)HF(6)O(2))(2)) was used as a precursor for palladium. Fine granular morphology was observed with tetragonal rutile structure. A peak related to Pd(2)Sn is observed, whose intensity increases slightly with deposition temperature. Electrical resistivity value decreased from 8.6 to 0.9 mΩ cm as a function of deposition temperature from 400 to 600 °C. Photoelectron peaks related to Sn 3d, Sn 3p3, Sn 4d, O 1s, and C 1s were detected with varying intensities as a function of deposition temperature.     

多层焊填充层焊道图像处理及边缘提取

结合二维小波变换方法与数学形态学方法对多层焊填充层焊道图像进行处理,实现对焊道边缘及坡口边缘的提取。首先通过对图像进行小波变换获取明区及暗区信息,鉴于坡口边缘及焊道边缘两端暗区及明区的峰值绝对值大于其他位置,将图像小波变换结果进行二值化处理,取对应峰值的位置信息。然后根据图像明区及暗区的峰值所处位置特征采用图像形态学方法对其进行处理,最后提取焊道及坡口边缘。采用该方法获取的边缘与实际焊道及坡口边缘吻合。     

一种提高测角精度的线交叉寻峰算法

为了提高测量精度,提出了一种适用于前后沿对称脉冲波形的线交叉寻峰算法。该算法利用对脉冲前、后沿的采样数据估计直线位置线的参数,并计算2条直线位置线的交点,实现脉冲峰值位置的估计。该方法能有效减小参考点和计数脉冲频率引起的测量误差。由于为线性算法,且对采样率要求低,易于工程实现。计算机仿真结果验证了所提出方法的有效性。     

采用子图像抽取尺度变换的边缘检测方法

针对工业尺寸检测中现场采集图像模糊但目标占有空间尺度较大这一特点,利用低分辨率采样下图像高频特征失真较大而低频特征失真较小的原理,提出了一种通过图像抽取获得多幅不同尺度子图像分别进行边缘检测后,综合各子图像边缘与原图像边缘来提取大尺度弱边缘的算法。试验结果表明,本算法能有效地检测出图像中的大尺度弱边缘。     

硫化锌基底上减反膜的镀制

硫化锌是红外波段重要的光学材料 ,在许多光电系统应用中 ,要求镀制适当的减反膜增加其透过率。介绍了硫化锌基底上的减反膜 ,该设计是用薄的氧化钇层作为与硫化锌的结合层 ,用一氧化硅和锗分别作为低、高折射率膜料的膜堆组成的。这种五层膜满足环境稳定性标准 ,在 3μm～ 5 μm波段的某应用范围内平均透过率即可达 96% ,并在 4.2 μm处有超过 98%的峰值透过率。     

Position stabilization of EELS spectra

The position of the zero-loss peak in electron energy-loss spectra was sensed with a double photo diode. A signal, proportional to the disturbances from a central position, was amplified and fed back into a deflection coil in order to compensate for the origin of the disturbances. Thus, slow variations of the position of characteristic edges in the EEL spectrum could be reduced by a factor 100, and 60 Hz oscillations could be reduced by a factor 5.     

Electron energy-loss near-edge structures of 3d transition metal oxides recorded at high-energy resolution

Near-edge fine structures of the metal L(2,3) and O K-edges in transition metal-oxides have been studied with a transmission electron microscope equipped with a monochromator and a high-resolution imaging filter. This system enables the recording of EELS spectra with an energy resolution of 0.1eV thus providing new near-edge fine structure details which could not be observed previously by EELS in conventional TEM instruments. EELS-spectra from well-defined oxides like titanium oxide (TiO(2)), vanadium oxide (V(2)O(5)), chromium oxide (Cr(2)O(3)), iron oxide (Fe(2)O(3)), cobalt oxide (CoO) and nickel oxide (NiO) have been measured with the new system. These spectra are compared with EELS data obtained from a conventional microscope and the main spectral features are interpreted. Additionally, the use of monochromised TEMs is discussed in view of the natural line widths of K and L(2,3) edges.     

Towards automated diffraction tomography. Part II--Cell parameter determination

Automated diffraction tomography (ADT) allows the collection of three-dimensional (3d) diffraction data sets from crystals down to a size of only few nanometres. Imaging is done in STEM mode, and diffraction data are collected with quasi-parallel beam nanoelectron diffraction (NED). Here, we present a set of developed processing steps necessary for automatic unit-cell parameter determination from the collected 3d diffraction data. Cell parameter determination is done via extraction of peak positions from a recorded data set (called the data reduction path) followed by subsequent cluster analysis of difference vectors. The procedure of lattice parameter determination is presented in detail for a beam-sensitive organic material. Independently, we demonstrate a potential (called the full integration path) based on 3d reconstruction of the reciprocal space visualising special structural features of materials such as partial disorder. Furthermore, we describe new features implemented into the acquisition part.     

Real-Time Front Vehicle Detection Algorithm Based on Local Feature Tracking Method

This paper proposes an algorithm that extracts features of back side of the vehicle and detects the front vehicle in real-time by local feature tracking of vehicle in the continuous images.The features in back side of the vehicle are vertical and horizontal edges,shadow and symmetry.By comparing local features using the fixed window size,the features in the continuous images are tracked.A robust and fast Haarlike mask is used for detecting vertical and horizontal edges,and shadow is extracted by histogram equalization,and the sliding window method is used to compare both side templates of the detected candidates for extracting symmetry.The features for tracking are vertical edges,and histogram is used to compare location of the peak and magnitude of the edges.The method using local feature tracking in the continuous images is more robust for detecting vehicle than the method using single image,and the proposed algorithm is evaluated by continuous images obtained on the expressway and downtown.And it can be performed on real-time through applying it to the embedded system.     

BTA深孔钻切削过程实验研究

通过BTA深孔钻削加工过程的实验，探讨了其切削机理，主要研究了BTA钻头切削部几何角度和切削用量对切屑变形的影响。实验结果显示，中心切削刃切下的切屑变形最大，各切削刃对切屑变形的影响趋势基本相同。本实验研究丰富了深孔加工的切削机理，为优化深孔加工的切削参数奠定了基础。     

Electrochemically induced adsorption of radio-labeled DNA on gold and HOPG substrates for STM investigations.

In a scanning tunneling microscope (STM) electrochemical cell we have studied the effects of electrode potential on both the surface topography and the adsorption of deoxyribonucleic acid (DNA) to graphite and gold surfaces. Images of the surface of highly oriented pyrolytic graphite (HOPG), of the same area, in response to a positive increase in surface potential show degradation of the step edges with little change in the crystal plane. Images of the same area of a gold surface demonstrate the formation of and the progressive increase in nodular structures on the crystal planes, in response to increased potential, with little effect on the step edges. Using radio-labeled DNA we monitored electrochemical absorption onto HOPG and gold surfaces. Although at no applied potential and at negative surface potentials some DNA was bound, at positive potentials 3 to 5 times more DNA was incorporated onto both surfaces. DNA adsorbed to a surface at a positive potential was not removed by reversing the potential.     

Determination of chromium valence over the range Cr(0)–Cr(VI) by electron energy loss spectroscopy

Chromium is a redox active 3d transition metal with a wide range of valences (−2 to +6) that control the geochemistry and toxicity of the element. Therefore, techniques that measure Cr valence are important bio/geochemical tools. Until now, all established methods to determine Cr valence were bulk techniques with many specific to a single, or at best, only a few oxidation state(s). We report an electron energy loss spectroscopy (EELS) technique along with an extensive suite of affined reference spectra that together, unlike other methods, can determine Cr valence (or at least constrain the possible valences) at high-spatial resolution (tens-of-nanometer scale) across a wide valence range, Cr(0)–Cr(VI). Fine structure of Cr-L_2,3 edges was parametrized by measurement of the chemical shift of the L₃ edge and the ratio of integrated intensity under the L₃ and L₂ edges. These two parameterizations were correlated to Cr valence and also the dⁿ orbital configuration which has a large influence on L-edge fine structure. We demonstrate that it is not possible to unambiguously determine Cr valence from only one fine-structure parameterization which is the method employed to determine metal valence by nearly all previous EELS studies. Rather, multiple fine-structure parameterizations must be used together if the full range of possible Cr valences is considered. However even with two parameterizations, there are limitations. For example, distinguishing Cr(IV) from Cr(III) is problematic and it may be difficult to distinguish low-spin Cr(II) from Cr(III). Nevertheless, when Cr is known to be divalent, low- and high-spin dⁿ orbital configurations can be readily distinguished.     

Cavitation at a fluid-solid boundary by an incident P-wave

In this paper a strong incident P-wave in a solid producing tensile tractions at a fluid-solid interface is considered. Tensile tractions at the interface lead to cavitation, and the fluid separates from the solid by the appearance of bubbles. These bubbles run along the interface with a constant velocity. It is shown that the angles of reflection and refraction are not affected by separation, but that the reflected and refracted waves undergo a phase shift that depends on the extent of separation and contain higher frequencies. It is found that the slopes of the leading edges of the bubbles are continuous, while those at the trailing edges are discontinuous. Correspondingly, the normal tractions vanish at the leading edges but have jump discontinuities at the trailing edges.     

非导电工程陶瓷电火花磨削技术

开发出双电极同步伺服跟踪电火花磨削新技术,该技术突破了传统的机械磨削和电解电火花机械复合磨削方法,利用导电磨轮与紧贴非导电工程陶瓷工件表面作自动伺服进给运动的薄片辅助电极间的放电实现电火花磨削。对非导电的Al2O3工程陶瓷进行加工试验,给出加工参数如脉冲宽度、脉冲间隔、峰值电压、峰值电流、磨轮转速以及铜片电极厚度等对材料去除率和表面粗糙度的影响规律关系。试验结果表明,该种新型加工技术具有效率高、表面质量好、成本低和对环境无污染等优点。     

Extended fine structure in electron energy loss spectra of MgO crystallites

EXAFS-like features in energy loss spectra (known as EXELFS) were observed by using an imaging energy filter built into an electron microscope. Single crystal micro-platelets of MgO were used as test samples. Extended fine structures were obtained reproducibly in the energy range up to 150 eV beyond the OK, MgK and MgL edges. Comparison with single scattering calculations for the K edges showed a fair agreement, indicating the feasibility of this type of analysis.     

Volume-weighted mean particle volume estimation using different measurement methods

The use of the ‘point-sampled intercepts’ method on histopathological material is evaluated for the main purpose of comparing different methods of intercept length measurements. The volume-weighted mean nuclear volume—nuclear —of the carcinoma of the ampulla of Vater is calculated using three methods for measuring intercept lengths: a semiautomatic image analyser, an equidistant I_o-ruler and a logarithmic -ruler. Rulers of several classes and lengths are used, and the results of the nuclear estimations are compared. The equidistant I_o-ruler is more accurate than the logarithmic -ruler. With a greater number of ruler classes and with adjustment of ruler length to the greatest nuclear intercept lengths, the systematic deviation from the true value of the nuclear is smaller. The nuclear parameter has great power to differentiate intestinal carcinoma from normal tissue.     

Absolute x-ray energy calibration over a wide energy range using a diffraction-based iterative method

In this paper, we report a method of precise and fast absolute x-ray energy calibration over a wide energy range using an iterative x-ray diffraction based method. Although accurate x-ray energy calibration is indispensable for x-ray energy-sensitive scattering and diffraction experiments, there is still a lack of effective methods to precisely calibrate energy over a wide range, especially when normal transmission monitoring is not an option and complicated micro-focusing optics are fixed in place. It is found that by using an iterative algorithm the x-ray energy is only tied to the relative offset of sample-to-detector distance, which can be readily varied with high precision of the order of 10(-5) -10(-6) spatial resolution using gauge blocks. Even starting with arbitrary initial values of 0.1 A?, 0.3 A?, and 0.4 A?, the iteration process converges to a value within 3.5 eV for 31.122 keV x-rays after three iterations. Different common diffraction standards CeO(2), Au, and Si show an energy deviation of 14 eV. As an application, the proposed method has been applied to determine the energy-sensitive first sharp diffraction peak of network forming GeO(2) glass at high pressure, exhibiting a distinct behavior in the pressure range of 2-4 GPa. Another application presented is pair distribution function measurement using calibrated high-energy x-rays at 82.273 keV. Unlike the traditional x-ray absorption-based calibration method, the proposed approach does not rely on any edges of specific elements, and is applicable to the hard x-ray region where no appropriate absorption edge is available.