Visibility of wavelet quantization noise

The discrete wavelet transform (DWT) decomposes an image into bands that vary in spatial frequency and orientation. It is widely used for image compression, measures of the visibility of DWT quantization errors are required to achieve optimal compression. Uniform quantization of a single band of coefficients results in an artifact that we call DWT uniform quantization noise; it is the sum of a lattice of random amplitude basis functions of the corresponding DWT synthesis filter. We measured visual detection thresholds for samples of DWT uniform quantization noise in Y, Cb, and Cr color channels. The spatial frequency of a wavelet is r2^-λ, where r is the display visual resolution in pixels/degree, and λ is the wavelet level. Thresholds increase rapidly with wavelet spatial frequency. Thresholds also increase from Y to Cr to Cb, and with orientation from lowpass to horizontal/vertical to diagonal. We construct a mathematical model for DWT noise detection thresholds that is a function of level, orientation, and display visual resolution. This allows calculation of a “perceptually lossless” quantization matrix for which all errors are in theory below the visual threshold. The model may also be used as the basis for adaptive quantization schemes     

用于平板显示制造中的真空设备——BOC Edwards特有的模块组合系统

在过去的10年内,平板显示业(FPD)迅猛发展,以满足对高品质的显示设备,如显示器,电视机,手机和掌上电脑(PDA)等的需求。显示行业研究机构的最新统计表明:显示器的销售由2003年的440亿美元增至2006年的730亿美元,预计2009年将达到900亿美元。而产能的扩张更令人惊讶:以每年42%的增长率,从2005年的39000m2玻璃到2009年预计的121000m2。为了使平板显示器能更普遍地使用,降低生产成本是关键。FPD行业已经通过增加玻璃尺寸非常成功地降低了每块面板的成本。这个增长比率每年都在递增,从2000年的0.35m(23代)到2006年的4.4m(27代),6年内翻了10番…     

Coherence of VCSEL's for holographic interconnects

Temporal and spatial coherence measurements were conducted on the emission from AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSEL's). Results of both CW and pulsed conditions from devices of 8- and 15-μm diameter are reported. Coherence length of 0.6 mm for multi-mode and ~75 cm for single-mode were obtained. Thermal chirp reduces the single-mode coherence to 16 mm for 5 ns pulses. For holograms smaller than 0.6 mm in size the density of information that can be read by the VCSEL's is diffraction-limited by the size of the holographic element     

Wind speed variability across the UK between 1957 and 2011

By using surface data from 57 UK meteorological stations, a national [British Atmospheric Data Centre (BADC)‐57] and regional wind index for the UK has been calculated for the period 1983–2011. For a subset of seven stations, an additional national index (BADC‐7) has been calculated for the period 1957–2011. The indices show an annual variability of 4% over their respective periods, corresponding to a variation in typical wind turbine capacity factor of 7%. These indices are compared with indices calculated from other sources, namely an index generated using a gridded dataset of observed values interpolated across the UK, an index calculated from an area bounding the UK using the ERA‐40 re‐analysis dataset, indices calculated from bilinear interpolation of the ERA‐40 re‐analysis dataset to the 57 and 7 stations and another independent UK wind index. The indices show variation in trends, with all showing some level of decline with the exception of that generated using the ERA‐40 re‐analysis dataset averaged over the UK, which shows a significant increase. The various indices show varying degrees of agreement with correlation coefficients, after trends are removed, ranging between 0.611 and 0.979. The effect of changes in site exposure, instrument bias and measuring height was considered for the BADC‐7 and BADC‐57 indices. The change in instrument measurement height appears to have a significant biasing effect, and it is likely that this along with changes in exposure at urban sites has caused the decline in annual wind speeds observed for some of the indices. There does not appear to be evidence for significant changes in large‐area (mesoscale) surface roughness. The correlation between annual mean wind speeds at the seven surface station sites used to calculate the BADC‐7 index is seen to be quite weak, indicating very localized variations in inter‐annual variability. When regional differences in the index are investigated, it is seen that wind speeds show a very slight decline across the UK in all regions except the south‐east, which shows a slight increase. The greatest decrease is seen in the north‐west. These changes are in the same direction as the tentative predictions given by climate models for future changes in wind speed across the UK, although the uncertainty is large given the large degree of inter‐annual variation. Copyright © 2013 John Wiley & Sons, Ltd.     

(Vinylaryloxy)acetic acids. A new class of diuretic agents. 3. ((2-Nitro-1-alkenyl)aryloxy)acetic acids

A series of [(2-nitro-1-alkenyl)aryloxy]acetic acids was synthesized and tested in dogs for saluretic and diuretic activity. A number of these compounds exhibit a high order of activity on iv or po administration; representative of these is (E)-[2,3-dichloro-4-(2-nitropropenyl)phenoxy]acetic acid (5). The most highly active compounds are qualitatively similar in action to [2,3-dichloro-4-(2-methylenebutyryl)phenoxylacetic acid (ethacrynic acid) in causing a prompt increase in the excretion of water and of sodium and chloride ions in approximately equimolar amounts but are three to five times as potent. Potassium ion excretion is increased but less markedly than sodium excretion.