Studies of the anodic dissolution of aluminium alloys containing tin and gallium using imaging with a high-speed camera

Imaging with a high-speed camera at a resolution of 10–20 μm has been used for the direct observation of the anodic dissolution of aluminium alloys containing Sn and Ga. The imaging allows confirmation that hydrogen bubble evolution occurs from the Sn inclusions within rounded pits during both open circuit corrosion and anodic dissolution. Using microelectrodes with only a few Sn inclusions in their surface, it is shown that the evolution of H₂ is not continuous and may be correlated with a potential oscillations between −1.50 V (where H₂ evolution occurs) and significantly less negative potentials (where no H₂ is evolved). It is proposed that this potential shift is associated with pH changes resulting from H₂ evolution itself.     

Time-resolved X-ray tomography of a fluidized bed

This paper discusses first results of bubbles moving through a fluidized bed imaged with an X-ray Tomographic Scanner. The scanner is made of 3 medical X-ray sources equipped with 30 CdWO₄ detectors each. The fluidized bed has a diameter of 23 cm and is filled with Geldart B powder. The scanner measures the attenuation in a thin slice perpendicular to the column axis at a sampling frequency of 2500 Hz.The data collected during 2 s are reconstructed using the SART algorithm with a one-step-late correction. The reconstructions show the distribution of the bubbles in the 2-dimensional cross-section. By stacking these images, a 3-dimensional view of the bubbles in the column is represented.     

Time-resolved fluorescence of excimer-forming polymers in solution

The kinetics of excited dimer (excimer) formation in small molecules, and in excimer-forming polymers, is discussed. The use of time-resolved fluorescence to study molecular order, and heterogeneity, segmental motion and energy migration in synthetic polymers in solution is described with respect to p-phenylene diacrylic acid, a cross-linkable commercial polymer, and copolymers of methyl methacrylate and 1-vinyl naphthalene, respectively.     

Time-resolved cathodoluminescence and photoluminescence of nanoscale oxides

The nanostructured oxide materials such as ZnO, ZrO₂, and Y₃Al₅O₁₂ (YAG) are perspective materials for transparent scintillating and/or laser ceramics. The luminescence properties of single crystals, nanopowders and ceramic were compared. Nominally pure and rare-earth doped nanopowders and ceramics have been studied by means of time-resolved luminescence spectroscopy.The fast blue luminescence band was studied in ZnO ceramics sintering from different raw materials.The luminescence centres of ZrO₂:Y were compared in a single crystal, ceramic and nanopowder.It is shown that ceramic sintering parameters have a strong influence on time-resolved luminescence characteristics in cerium-doped YAG.     

Time-resolved fluorescence spectroscopy of crude oils and condensates

A pulsed laser fluorescence spectroscopy system, previously developed for coal characterization, was used to characterize thirteen crude oils and condensates. From time-resolved fluorescence spectra, three individual components (fluorophores) with decay times in the nanosecond and sub-nanosecond range were resolved. A good correlation was obtained between the fluorescence decay times of these components and API gravity. The fluorescence decay of normal crude oil was different from biodegraded crude oil. Two of the three resolved component spectra and decay times resembled those of anthracene and pyrene in solution.     

静电喷雾沉积半径的预测模型

静电喷雾法制备薄膜是近年来新兴的纳米材料制备工艺之一,因其具有工艺简单、材料利用率高和表面适应性强等优点而受到广泛关注。喷涂面积作为评价喷涂质量和生产效率的重要指标,由于易受外加电压、溶液性质、喷涂距离等参数的影响,在相关的生产过程中难以精确控制。为了解决这一问题,本文提出了一种预测静电喷雾沉积半径的数学模型。通过高斯定律将静电喷雾羽流等效为空间电荷场,随后对羽流外侧液滴进行受力分析,得出喷雾羽流在不同位置处的膨胀半径,即为静电喷雾的沉积半径。对比发现,模型与相关结果吻合良好。相比传统的拉格朗日方法和实验方法,该模型可快速预测各种工况下的喷涂面积,为工业生产操作和雾化器设计提供指导。     

Time-resolved two-photon photoemission at metal—dielectric interfaces

We review the influence of rare-gas layers on image-potential states at metal surfaces. Experiments on Xe, Kr, and Ar on Cu(100) and on Xe/Ru(0001) that use the technique of time-resolved two-photon photoemission are discussed. The energetic position of the electron affinity, the geometry of the adsorbate layer, and dielectric screening are the factors that influence the dynamical and energetic properties of the states. Theories on various levels are compared, including 1- and 3-dimensional models and the GW approximation of many-body theory. We also present new results on buried interface states that exist in the band gaps of both the Cu(100) substrate and a thick adsorbed Ar layer.     

Colour measurement by video camera

If video cameras could be used to measure colours directly, many technical and commercial possibilities would opened up. Christine Connolly, William Leung and Jim Nobbs describe how this is now close to being a reality.     

Time-resolved synchrotron X-ray study of chain-folded crystallization of long paraffins

The examination of the crystallization of strictly uniform ultra-long n-alkanes was resumed with the view of exploring the onset of chain-folding, as laid out previously in ref. 1. The present study, largely on C₂₄₆H₄₉₄, centred on the initial stages of crystallization in the melt, registered in situ by time-resolved small-angle X-ray scattering using a synchrotron X-ray source. The salient new feature was the identification of transient initial fold lengths which were non-integer fractions (NIF) of the chain length. This NIF structure transforms subsequently into forms with integer fraction (IF) fold lengths. In the present study the latter have the extended chain (E) and once-folded (F2) configurations, while NIF has a fold length between the two. The NIF → IF transformation occurs either by lamellar thickening or thinning, or by both. It was found that the NIF state had a more disordered layer surface as compared to the final E and F2 structures, the latter being the states on which the conclusions in ref. 1 had been drawn, which accordingly should apply to the transformed material. Implications of these and several other findings for some central issues in polymer crystallization are briefly discussed. The existence of an initial NIF phase focusses attention to the importance of the fastest kinetic pathway as the determining factor for chain-folded crystal growth with particular attention to the initial chain deposition probability, a line made accessible by the present alkanes.     

Optical investigation of high-speed aerosol-microjets

Aerosol-jets are generated by the expansion of an aerosol-gas mixture from different types of micro-nozzles. The particle velocity is measured by means of a Fabry-Perot laser Doppler anemometer, whereas the geometrical structure of the jet will be investigated by direct optical observation. Comparative measurements show that Laval-nozzles are more suitable for the generation of rapid, intense aerosol-jets than simple orifices, because the internal energy of the carrier gas may be transformed more perfectly into one-directional kinetic energy. Moreover, the particles gain high velocities due to the smooth acceleration process.     

Time-resolved X-ray scattering studies of creep in oriented UHMWPE films

The change in the crystalline structure of oriented melt-crystallised and gel-cast UHMPWPE (Stamylan) films of various draw ratios during creep upon constant load has been followed in real time using synchrotron X-ray diffraction techniques at the synchrotron radiation source ANKA (Angstroemquelle Karlsruhe) at Forschungszentrum Karlsruhe (Germany). The shift of (002) Bragg reflections with time of loading and change in their halfwidth are observed for all the samples investigated. The analysis of the data shows a difference in the behaviour of loaded gel-cast and melt-crystallised films. The longitudinal crystallite sizes in the former grow with time, while in the latter they become smaller. Besides, the splitting of a (002) profile in WAXS patterns of melt-crystallised samples (including unstressed samples) was revealed. Several possible causes of this splitting are suggested. One of them is the co-existence of strained crystallites in monoclinic and orthorhombic crystalline modifications.The observed phenomena is discussed in terms of coherent disposition of crystallites in microfibrils, one-dimensional diffraction on taut-tie molecules, probable pulling-out of the molecules from crystallites upon creep and inhomogeneity of stress distributions.     

Time-resolved GISAXS and cryo-microscopy characterization of block copolymer membrane formation

Time-resolved grazing-incidence small-angle X-ray scattering (GISAXS) and cryo-microscopy were used for the first time to understand the pore evolution by copolymer assembly, leading to the formation of isoporous membranes with exceptional porosity and regularity. The formation of copolymer micelle strings in solution (in DMF/DOX/THF and DMF/DOX) was confirmed by cryo field emission scanning electron microscopy (cryo-FESEM) with a distance of 72 nm between centers of micelles placed in different strings. SAXS measurement of block copolymer solutions in DMF/DOX indicated hexagonal assembly with micelle-to-micelle distance of 84–87 nm for 14–20 wt% copolymer solutions. GISAXS in-plane peaks were detected, revealing order close to hexagonal. The d-spacing corresponding to the first peak in this case was 100–130 nm (lattice constant 115–150 nm) for 17 wt% copolymer solutions evaporating up to 100 s. Time-resolved cryo-FESEM showed the formation of incipient pores on the film surface after 4 s copolymer solution casting with distances between void centers of 125 nm.     

A high-speed twisting mechanism

Conclusions A study of the construction of the electrical drive for twisting mechanisms with a gasmagnetic suspension of the rotor has confirmed the advisability of using it for texturizing man-made fibers.The type of electrical drive developed ensures a high operating rotational frequency at a low vibration and noise level.Translated from Khimicheskie Volokna, No. 4, pp. 47–48, July–August, 1983.     

Time-resolved Infrared Absorption Study of Photochemical Reactions Over Metal Oxides

The present account describes how photochemical reactions over metal oxides are traced by time-resolved infrared (IR) absorption spectroscopy. The ac-coupled amplification of the IR signal allows detection of transient absorbance changes as small as 10⁻⁶ with a time resolution of 50 ns. Band-gap excited electrons in TiO₂ and NaTaO₃ present a structureless absorption of IR light from 3000 to 1000 cm⁻¹. Reaction-perturbed decay of this absorption evidences the assignment to photoexcited electrons, not to holes. The efficiency of the water splitting reaction on NaTaO₃-based catalysts correlates with the quantity of electrons detected by the IR absorption. A short-lived intermediate state of 2-propanol oxidation on TiO₂ is identified by its vibrational band at 1640 cm⁻¹ superposed on the structureless absorption of electrons. Ru dye (N3) on a TiO₂ film is irradiated with a 532-nm light pulse to simulate dye-sensitized solar cells. The neutralization rate of dye cations and the decay rate of electrons injected in the film are quantified, leading to a three-state model which describes the relaxation of injected electrons. These results demonstrate the ability of this method in tracing photochemical kinetics over metal oxides.     

Try camera gamut again: Not for size,but for camera and profile evaluation

Hunt and Pointer call into question the utility of the camera color gamut (at least by my definition). Such doubt may be partly due to the connection of gamut with a size metric. Quite apart from gamut size, the sets that define my gamut definition are essential to the evaluation of digital cameras in conjunction with their profiles. The output‐device gamut; emphasized by Hunt and Pointer is also important, but appears at another stage of color management. © 2007 Wiley Periodicals, Inc. Col Res Appl, 33, 82–83, 2008     

DVDCAM摄影机的使用及其后期编辑

使用可记录DVD进行视频记录的摄像机已经开始进入普及阶段,但是一次拍摄可能有不满意的地方,这就需要将视频信息进行编辑处理,本文将详细介绍DVD光盘摄像机的使用和后期编辑。拍摄前的准备