真空灭弧室 配电开关 断路器和接触器的高可靠性元件

自从20世纪50年代中期将真空灭弧室(VI)用作配电操作开关、断路器和接触器的电流分断元件以来,其作用逐步增强.在电路的开断和配电保护领域,该电气产品已经占统治地位.真空灭弧室甚至被引入到电力输送中的通断产品的领域上.真空灭弧室受到追捧的原因有:结构紧凑、适用范围广、成本低、极好的电寿命和机械寿命,以及使用方便.其中,最重要的优点是公认的高可靠性.     

The.assessment of relative electron gun performance The assessment of relative electron gun performance Comments on the paper entitled “ Digital computer studies of electron guns for electron microscopes “†

A method of comparing the basic performance of electron guns is described. The method is applied to some recently computed results on two versions of an electron gun which has a hairpin-filament cathode.     

Microbial characterisation and stability of a farmhouse natural fermented milk from Spain

This work reports the microbial characterisation of a farmhouse natural fermented milk (NFM) with good sensorial properties produced in Spain. Culturing and denaturing gradient gel electrophoresis (DGGE) analyses showed thatLactococcus lactissubsp.lactis and L. lactissubsp.cremoris(approximate levels of 10⁹ cfu/mL) were dominant in this NFM, whileLactobacillus plantarumappeared at a lower level (10⁶–10⁷ cfu/mL). Repetitive extragenic palindromic (REP)‐PCR typing of the isolates identified single strains each ofLc. lactissubsp.lactis, Lc. lactissubsp.cremorisandLb. plantarum. These three strains formed a stable microbial association which has been maintained for at least some decades.     

The biodiversity and evolution of lactic flora during ripening of the Iranian semisoft Lighvan cheese

Ninety‐five isolated strains of Lactic acid bacteria (LAB) were identified from Lighvan cheese. The LAB evolution showed the dominance of lactococci and lactobacilli in the first stage and substitution of these genera by enterococci at the end of ripening. The most predominant strains were Enterococcus faecium (22.44%), Lactococcus lactis ssp. lactis (20.4%), Lactobacillus plantarum (18.36%) and E. faecalis (14.28%), respectively. Eleven and 51 different carbohydrate fermentation profiles were observed according to API 20 STREP and API 50 CH, respectively. API 20 STREP dendogram showed identical fermentation profiles of some E. faecalis and E. faecium strains, indicating that these strains might be well adapted to the whole cheese manufacture.     

Software image alignment for X-ray microtomography with submicrometre resolution using a SEM-based X-ray microscope

Improved X-ray sources and optics now enable X-ray imaging resolution down to ∼50 nm for laboratory-based X-ray microscopy systems. This offers the potential for submicrometre resolution in tomography; however, achieving this resolution presents challenges due to system stability. We describe the use of software methods to enable submicrometre resolution of approximately 560 nm. This is a very high resolution for a modest laboratory-based point-projection X-ray tomography system. The hardware is based on a scanning electron microscope, and benefits from inline X-ray phase contrast to improve visibility of fine features. Improving the resolution achievable with the system enables it to be used to address a greater range of samples.     

Chlorophyll distribution in Lake Kinneret determined from Landsat Thematic Mapper data

Chlorophyll distribution in Lake Kinneret was estimated at a time of low chlorophyll concentrations (3-7 mgm^?3). Landsat Thematic Mapper (TM) data were acquired three days after the acquisition of high spectral resolution radiometric measurements in the range 400 to 750 nm, chlorophyll and suspended matter concentrations, and Secchi disk transparency at 22 stations. The radiometric data were used to create an algorithm for estimation of chlorophyll concentration from the TM data. The radiance in channel TM3 (620-690 nm) was primarily dependent upon non-organic suspended matter concentration. Radiance in this channel was substracted from radiance in TM1 (450-520 nm) to correct for the additional radiance caused by scattering of non-pigmented suspended particles and (TM1 – TM3)/TM2 was found to be a useful index for estimating chlorophyll concentration. The concentrations calculated from atmospherically corrected TM data were compared to chlorophyll extracted from lake water samples. The estimation error of chlorophyll concentration was less than 0.85 mgm^?3.     

MONOLITHIC-SUPPORTED NICKEL CATALYSTS: I. METHANATION ACTIVITY RELATIVE TO PELLET CATALYSTS

The catalytic activity and selectivity of pellet and monolithic supported Ni/A1₂O₃ for methanation of carbon monoxide were investigated to determine the role of support geometry in catalyst performance. Turnover numbers, CO conversion versus temperature data, and product distributions were measured at space velocities from 15,000 to 50,000 hr^-1 and pressures of 140 to 2500 kPa. The data show that monolithic supported nickel is significantly more active and selective for methane production at both low and high CO conversions compared to nickel catalysts beads and pellets. Monolithic supported methanation catalysts apparently operate with a higher effectiveness and rate of mass transfer than do catalyst beads or pellets. Because of its superior activity, selectivity and tow pressure drop at high space velocities, monolithic nickel may be the ideal catalyst for use in a high throughput recycle methanator     

Solutions of the Equations for Space-charge Electron Flow with a Magnetic Field at the Cathode for Beams of Non-uniform Current Density†

After a discussion of the space-charge equations, a solution is given from which the critical conditions are obtained for flows like Brillouin flow but with a magnetic field at the cathode. Results for confined flows are derived; it is shown that, compared with a beam of uniform current density, much more current can be put into a beam of given boundary voltage if the current density increases strongly with radius. Confined ribbon beams are also considered.     

X-ray omni microscopy

The science of wave‐field phase retrieval and phase measurement is sufficiently mature to permit the routine reconstruction, over a given plane, of the complex wave‐function associated with certain coherent forward‐propagating scalar wave‐fields. This reconstruction gives total knowledge of the information that has been encoded in the complex wave‐field by passage through a sample of interest. Such total knowledge is powerful, because it permits the emulation in software of the subsequent action of an infinite variety of coherent imaging systems. Such ‘virtual optics’, in which software forms a natural extension of the ‘hardware optics’ in an imaging system, may be useful in contexts such as quantitative atom and X‐ray imaging, in which optical elements such as beam‐splitters and lenses can be realized in software rather than optical hardware. Here, we develop the requisite theory to describe such hybrid virtual‐physical imaging systems, which we term ‘omni optics’ because of their infinite flexibility. We then give an experimental demonstration of these ideas by showing that a lensless X‐ray point projection microscope can, when equipped with the appropriate software, emulate an infinite variety of optical imaging systems including those which yield interferograms, Zernike phase contrast, Schlieren imaging and diffraction‐enhanced imaging.     

Analysis of Judge Performance in Wine-Quality Evaluations

The use of correlation coefficients, F-statistics and LSDs was described for measuring judge performance in terms of agreement, reliability, discrimination, stability, and variability. The technique was applied to a number of wine-quality evaluation experiments. It was shown that a single analysis of variance of all judges' scores in an experiment will often be inappropriate. Further, it was demonstrated that judges' performances varied over time. It was, therefore, recommended that each judge's performance be monitored continually and that when judges were unreliable and nondiscriminating, they would be ignored in drawing conclusions from the experiment. The analysis for wine differences should be based on a separate analysis of each set of homogeneous judges as determined from the measures for agreement, reliability, and variability.