针对图像中用户选定的感兴趣区域ROI(Regions of interest)的保护,提出形状自适应离散小波变换SA-DWT(ShapeAdaptive DWT)是实现感兴趣区域二维水印算法的有效工具。水印图像(一幅灰度图像)经压缩后生成可以嵌入的水印序列,同时SA-DWT...针对图像中用户选定的感兴趣区域ROI(Regions of interest)的保护,提出形状自适应离散小波变换SA-DWT(ShapeAdaptive DWT)是实现感兴趣区域二维水印算法的有效工具。水印图像(一幅灰度图像)经压缩后生成可以嵌入的水印序列,同时SA-DWT变换作用于ROI区域,通过选择变换系数的嵌入位置和嵌入准则实现水印信息的嵌入;最后提取水印信号,通过重构恢复水印图像。攻击实验表明该算法可以抵抗常见的图像攻击手段,ROI区域得到了有效保护。展开更多
The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a...The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a back- ward curved impeller of 500 turn tip diameter and 24.5 mm width and its design flow coefficient is Фd=0.0535. Three different low solidity diffuser vane shapes namely uncarnbered aerofoil, constant thickness flat plate and circular arc cambered constant thickness plate were chosen as the variants for diffuser vane shape and all the three shapes have the same thickness to chord ratio （t/c=0.1）. Flow coefficient, polytropic efficiency, total head coeffi- cient, power coefficient and static pressure recovery coefficient were chosen as the parameters for evaluating the effect of diffuser vane shape on the stage performance. The results show that there is reasonable improvement in stage efficiency and total head coefficient with the use of the chosen diffuser vane shapes as compared to conven- tional vaneless diffuser. It is also noticed that the aero foil shaped LSD has shown better performance when com- pared to flat plate and circular arc profiles. The aerofoil vane shape of the diffuser blade is seen to be tolerant over a considerable range of incidence.展开更多
文摘针对图像中用户选定的感兴趣区域ROI(Regions of interest)的保护,提出形状自适应离散小波变换SA-DWT(ShapeAdaptive DWT)是实现感兴趣区域二维水印算法的有效工具。水印图像(一幅灰度图像)经压缩后生成可以嵌入的水印序列,同时SA-DWT变换作用于ROI区域,通过选择变换系数的嵌入位置和嵌入准则实现水印信息的嵌入;最后提取水印信号,通过重构恢复水印图像。攻击实验表明该算法可以抵抗常见的图像攻击手段,ROI区域得到了有效保护。
文摘The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a back- ward curved impeller of 500 turn tip diameter and 24.5 mm width and its design flow coefficient is Фd=0.0535. Three different low solidity diffuser vane shapes namely uncarnbered aerofoil, constant thickness flat plate and circular arc cambered constant thickness plate were chosen as the variants for diffuser vane shape and all the three shapes have the same thickness to chord ratio （t/c=0.1）. Flow coefficient, polytropic efficiency, total head coeffi- cient, power coefficient and static pressure recovery coefficient were chosen as the parameters for evaluating the effect of diffuser vane shape on the stage performance. The results show that there is reasonable improvement in stage efficiency and total head coefficient with the use of the chosen diffuser vane shapes as compared to conven- tional vaneless diffuser. It is also noticed that the aero foil shaped LSD has shown better performance when com- pared to flat plate and circular arc profiles. The aerofoil vane shape of the diffuser blade is seen to be tolerant over a considerable range of incidence.
