为方便有效地进行简支梁的损伤识别,基于对称集中加载和结构静力位移数据的采集,以梁体的局部抗弯刚度和剪切刚度为损伤识别参数,通过理论推导提出了一个基于中心差分曲率指标的损伤识别新指标——临近差分曲率差值D;(difference of nea...为方便有效地进行简支梁的损伤识别,基于对称集中加载和结构静力位移数据的采集,以梁体的局部抗弯刚度和剪切刚度为损伤识别参数,通过理论推导提出了一个基于中心差分曲率指标的损伤识别新指标——临近差分曲率差值D;(difference of nearby difference curvature, DNDC),并建立了相应的损伤识别方法。结果表明,D;指标方法可通过损伤后简支梁的D;值图形形态来直观形象地展示出损伤位置信息,进而可通过简便的计算得到用局部刚度相对变化量来代表的简支梁损伤程度。展开更多
为减少低剂量计算机断层扫描(computed tomography,CT)重建图像时出现的大量条形伪影,提出一种基于差分曲率自适应正则化的低剂量CT重建算法。将差分曲率应用到原有的投影域惩罚加权最小二乘法(penalized weight least square,PWLS)中,...为减少低剂量计算机断层扫描(computed tomography,CT)重建图像时出现的大量条形伪影,提出一种基于差分曲率自适应正则化的低剂量CT重建算法。将差分曲率应用到原有的投影域惩罚加权最小二乘法(penalized weight least square,PWLS)中,差分曲率对图像的边缘、平滑区域以及斜坡结构具有良好的检测性能,可有效地控制平滑区域和边缘区域的扩散程度,自适应地去除重建图像中的条形伪影。实验结果表明,该算法能有效抑制条形伪影的产生,较好保持图像的边缘和细节信息。展开更多
The gradient image is always sensitive to noise in image detail enhancement. To overcome this shortage, an improved detail enhancement algorithm based on difference curvature and contrast field is proposed. F...The gradient image is always sensitive to noise in image detail enhancement. To overcome this shortage, an improved detail enhancement algorithm based on difference curvature and contrast field is proposed. Firstly, the difference curvature is utilized to determine the amplification coefficient instead of the gradient. This new amplification function of the difference curvature takes more neighboring points into account, it is therefore not sensitive to noise. Secondly, the contrast field is nonlinearly amplified according to the new amplification coefficient. And then, with the enhanced contrast field, we construct the energy functional. Finally, the enhanced image is reconstructed by the variational method. Experimental results of standard testing image and industrial X-ray image show that the proposed algorithm can perform well on increasing contrast and sharpening edges of images while suppressing noise at the same time.展开更多
The effect of the microstrip bend on the propagation characteristics of a microstrip line was investigated based on the Finite-Difference Time-Domain(FDTD)method.The dispersive characteristics of a microstrip line wit...The effect of the microstrip bend on the propagation characteristics of a microstrip line was investigated based on the Finite-Difference Time-Domain(FDTD)method.The dispersive characteristics of a microstrip line with a bend are quite different from that of a uniform straight microstrip line.The effect of bend discontinuity on propagation constants deceases exponentially with the distance form the corner of the bend.This can be explained by the fact that the higher order modes excited by the bend discontinuities have intrinsic properties of exponentially decay with the distance from the bend discontinuities.This effect can be negligible(less than five percent)when the distance is beyond ten times of conductor strip width.The S parameters and propagation constants comparison between unmitered and mitered bends are also presented.The proposed method which takes advantage of the FDTD algorithm and the Root Mean Square Deviation(RMSD)analysis is also an effective way for analyzing the dispersion characteristics of other planar transmission lines.展开更多
We study the ordinary differential equations related to rotationally symmetric pseudo-Khler metricsof constant scalar curvatures. We present various solutions on various holomorphic line bundles over projectivespaces ...We study the ordinary differential equations related to rotationally symmetric pseudo-Khler metricsof constant scalar curvatures. We present various solutions on various holomorphic line bundles over projectivespaces and their disc bundles, and discuss the phase change phenomenon when one suitably changes initialvalues.展开更多
文摘为减少低剂量计算机断层扫描(computed tomography,CT)重建图像时出现的大量条形伪影,提出一种基于差分曲率自适应正则化的低剂量CT重建算法。将差分曲率应用到原有的投影域惩罚加权最小二乘法(penalized weight least square,PWLS)中,差分曲率对图像的边缘、平滑区域以及斜坡结构具有良好的检测性能,可有效地控制平滑区域和边缘区域的扩散程度,自适应地去除重建图像中的条形伪影。实验结果表明,该算法能有效抑制条形伪影的产生,较好保持图像的边缘和细节信息。
基金National Natural Science Foundation of China(No.61271357)International S&T Cooperation Program of Shanxi Province(No.2013081035)
文摘The gradient image is always sensitive to noise in image detail enhancement. To overcome this shortage, an improved detail enhancement algorithm based on difference curvature and contrast field is proposed. Firstly, the difference curvature is utilized to determine the amplification coefficient instead of the gradient. This new amplification function of the difference curvature takes more neighboring points into account, it is therefore not sensitive to noise. Secondly, the contrast field is nonlinearly amplified according to the new amplification coefficient. And then, with the enhanced contrast field, we construct the energy functional. Finally, the enhanced image is reconstructed by the variational method. Experimental results of standard testing image and industrial X-ray image show that the proposed algorithm can perform well on increasing contrast and sharpening edges of images while suppressing noise at the same time.
基金supported by basic research item of National Key Lab of Electronic Measurement Technology and National Natural Science Foundation of China(No.60876028,60633060)
文摘The effect of the microstrip bend on the propagation characteristics of a microstrip line was investigated based on the Finite-Difference Time-Domain(FDTD)method.The dispersive characteristics of a microstrip line with a bend are quite different from that of a uniform straight microstrip line.The effect of bend discontinuity on propagation constants deceases exponentially with the distance form the corner of the bend.This can be explained by the fact that the higher order modes excited by the bend discontinuities have intrinsic properties of exponentially decay with the distance from the bend discontinuities.This effect can be negligible(less than five percent)when the distance is beyond ten times of conductor strip width.The S parameters and propagation constants comparison between unmitered and mitered bends are also presented.The proposed method which takes advantage of the FDTD algorithm and the Root Mean Square Deviation(RMSD)analysis is also an effective way for analyzing the dispersion characteristics of other planar transmission lines.
基金supported by National Natural Science Foundation of China (Grant Nos.10425101, 10631050)National Basic Research Program of China (973 Project) (Grant No. 2006cB805905)
文摘We study the ordinary differential equations related to rotationally symmetric pseudo-Khler metricsof constant scalar curvatures. We present various solutions on various holomorphic line bundles over projectivespaces and their disc bundles, and discuss the phase change phenomenon when one suitably changes initialvalues.
