西门子S7-300在铅蓄电池生产中的应用

设计了一种基于西门子PLC的铅蓄电池生产控制系统,实现铅蓄电池化成液位、温度、压力等参数的智能控制.对西门子可编程控制器应用于铅蓄电池生产的设计思想做了介绍,重点论述了控制系统的硬件设计与软件编程.现场运行情况表明:该控制系统工作可靠,操作方便,大大提高了劳动生产率.     

Normal sintering and electric properties of (K,Na,Li)(Nb,Sb)O3 lead-free piezoelectric ceramics

0.94(K₀₅Na_0.5)NbO₃?0.03LiNbO₃?0.03LiSbO₃ (KNLNS) lead-free piezoelectric ceramics were prepared by conventional mixed oxide route with normal sintering method. The samples were sintered at different temperatures with KNLNS powder atmosphere to prevent volatilization of alkali metal oxides at high temperature. The effects of sintering temperature on the density, structure and electric properties of KNLNS ceramics were studied. X-ray diffraction (XRD) results showed that the crystal structure of the crushed KNLNS ceramic powders were pure perovskite phase with tetragonal phase structure when sintered at T????1080°C. However a K₃Li₂Nb₅O₁₅ phase with tetragonal tungsten bronze structure began to appear when the sintering temperature was higher than 1080°C. The optimum sintering temperature was 1080°C which was determined by measuring the density of the samples. Scanning electron microscope (SEM) observation indicated that the sintering temperature had a great effect on the microstructure of the samples. The KNLNS ceramics under the optimum sintering temperature showed excellent electric properties: ???=?4.29 g/cm³, ?? _r?=?826, tan???=?0.049, d ₃₃?=?190 pC/N, k _p?=?0.30, and T _c?=?385°C. The results show that the KNLNS ceramics are promising candidate for lead-free piezoelectric ceramics.     

Hydrothermal degradation of polybenzimidazole coating

The usefulness of a room-temperature film-forming polybenzimidazole (PBI) resin as a high-temperature anti-corrosion coating for carbon steel in geothermal environments was evaluated. PBI displayed thermal stability at temperatures up to 600 °C. However, when its film was exposed to 300 °C brine, it underwent hydrolysis, which causes the opening and breakage of imidazole rings in the PBI structure, followed by the formation of two hydrolysate derivatives, biphenyl tetra-amine and benzodicarboxylic acid. This shortcoming lowered the film's maximum effectiveness in minimizing the rate of transportation through it of corrosive electrolytes in hydrothermal environments. As a result, the PBI coating film was hydrothermally degraded, and it delaminated from the underlying steel substrates after a 14-day exposure.     

Cellular automata computations and secret key cryptography

In this paper, cellular automata (CAs) are used to design a symmetric key cryptography system based on Vernam cipher. CAs are applied to generate a pseudo-random numbers sequence (PNS) which is used during the encryption process. The quality of PNSs highly depends on the set of applied CA rules. Rules of radius r=1 and 2 for nonuniform one-dimensional CAs have been considered. A new set of rules has been discovered using an evolutionary technique called cellular programming. This set provides very high quality encryption, and the system is very resistant to attempts of breaking the cryptography key.     

User interface features influencing overall ease of use and personalization

This study examines user perceptions of gathering information on, locating, and buying compact discs through Web-based interfaces. A group of part-time MBA students in Hong Kong performed a specific set of tasks using the Web sites of two vendors of compact discs. The tasks were selected to be general enough to apply to a variety of on-line shopping situations. As they performed tasks, they answered questions regarding their perceptions of several user interface features as well as their perceptions of overall ease of use. User interface features associated with a perception of overall ease of use were identified, as were differences based on personal characteristics of respondents. Also, differences in perceptions of interface features that might be due to personal characteristics, such as age and sex, were identified. The methodology and results help identify user interface features that a designer should emphasize and features for which personalization is likely to be beneficial.     

Preparation of carbonized fiber web from electrospinning of isotropic pitch

The petroleum-based isotropic pitch precursor (IPP) with a broad molecular weight distribution was electrospun. After the dimethylformamide (DMF) soluble fraction was cut off from the IPP, the DMF insoluble pitch (DIP) solution in tetrahydrofuran (THF) was electrospun into web, and then it was stabilized, carbonized. Cutting out the DMF soluble fraction from the IPP improved the spinnability in comparison with the IPP solution itself at the same spinning conditions. The prepared fibers showed dumb-bell like cross-sectional shape indicating incompletion of the splitting in the spinning process with the fiber size of 4–6 μm in long axis and 2–3 μm in short axis. The fibers were randomly layered to be a web. The electrical conductivity of the web increased from 63 to 83 S/cm with an increase in carbonization temperature from 1000 to 1200 °C, and are high enough conductivity for applications to various kinds of electrodes.     

Residual stresses and magnetic properties of alumina–nickel nanocomposites

Nanocomposites were produced by infiltration of alumina preforms with a nickel-nitrate solution, followed by reduction and sintering. Multiple infiltration and reduction steps resulted in nanocomposites with varying Ni particle concentrations. The strain in the nickel particles was evaluated from X-ray diffraction, and correlated with the magnetic properties of the nanocomposites.     

Apatite formation on titania–vaterite powders in simulated body fluid

Titania–hydroxyapatite composites were prepared by soaking compacts of a powder mixture consisting of crystalline titania and calcium carbonate (vaterite) to form apatite in simulated body fluid (SBF). The apatite crystal formed on compacts in SBF at 37 °C within 2 days. The apatite-forming ability of the mixtures was much higher than that of titania crystals such as anatase or rutile on their own. Calcium carbonate (vaterite), which has high solubility in the aqueous solution, plays an important role in the apatite formation; the dissolution is suggested to increase the supersaturation of the apatite in SBF. Formation of titanium hydroxide groups, which may induce the apatite formation, is drastically promoted on the powder-compacts by the soaking in SBF, independently of the structures of the titania crystals (anatase or rutile). The apatite formation on the compact of the titania–calcium carbonate (vaterite) powder mixture containing the anatase phase occurs in a shorter period than that on the one of titania (rutile)–calcium carbonate (vaterite). Crystalline titania (anatase phase) is suggested to be particularly effective in inducing the apatite nucleation.     

Robust digital image watermarking method against geometrical attacks

This paper proposes a new image watermarking scheme which is robust to RST attacks with cropping by improving Fourier–Mellin transform based watermarking (FMW). The proposed scheme reorders and modifies function blocks of FMW for improvement of realization and performance. Unlike FMW, our method uses log-polar map (LPM) in the spatial domain for scaling invariance, while translation invariance is provided by the use of an invariant centroid (IC) as the origin of LPM. IC is a gravity center of a central area on gray scale image that is invariant although an image is attacked by RST. For this, its calculation method is proposed. Also since LPM includes the property which transforms rotation of Cartesian coordinates system into a cyclic shift, 2-D DFT is performed on the LPM image and the magnitude spectrum extracted to provide a domain that is rotation invariant. The resulting domain, which is invariant to RST, is then used as the watermark-embedding domain. Furthermore, to prevent the watermarked image from degrading due to the coordinate system conversion, only LPM image of watermark signal is inverse mapped to Cartesian coordinates and add to the original image. Experimental results demonstrate that the proposed scheme is robust to RST attacks.