The adaptive da/dN method: a solution to the problem of processing crack growth data

The standard fatigue data‐processing procedure, published in ASTM E647, is not adapted to the use of modern crack length measurement techniques. Because the use of this standard is usually required by journals, the raw data are often reduced to only a few data points. This way valuable information is simply thrown away and mathematical errors are unintentionally made. More importantly, the fact that no satisfactory reduction method exists, has led to destandardization of the processing procedure. Therefore, a new standard processing method is desired. In this paper a new data‐processing method, referred to as the ‘adaptive da/dN method’, is proposed and discussed. This method is suitable for both optical and modern (electrical or automated) measurement techniques as well as modern (computer‐assisted or ‐controlled) processing techniques. The adaptive da/dN method is validated both by data generated with a certain amount of scatter as well as actual experimental data. It shows a more accurate behaviour than the ASTM standards for all data types.     

A distributed controller approach for delay-independent stability of networked control systems

This article introduces a novel distributed controller approach for networked control systems (NCS) to achieve finite gain L₂ stability independent of constant time delay. The proposed approach represents a generalization of the well-known scattering transformation which applies for passive systems only. The main results of this article are (a) a sufficient stability condition for general multi-input-multi-output (MIMO) input-feedforward-output-feedback-passive (IF-OFP) nonlinear systems and (b) a necessary and sufficient stability condition for linear time-invariant (LTI) single-input-single-output (SISO) systems. The performance advantages of the proposed approach are reduced sensitivity to time delay and improved steady state error compared to alternative known delay-independent small gain type approaches. Simulations validate the proposed approach.     

基于彩色CCD的摩擦焊接温度场测量系统

根据彩色CCD三基色测温原理,设计了摩擦焊接的温度场测量系统.采用CCD摄像头对焊接界面进行高速、连续拍摄,得到温度场图像,DSP对图像进行预处理后,对温度进行计算,然后使用伪彩色增强方法,通过不同颜色来反映焊接界面各部分的动态温度分布状况.为提高测量的精度,通过黑体炉实验对计算公式中的参数进行标定,并根据实验数据进行了插值修正.TMS320DM647的高速运算能力和丰富的片上资源保证了测量的实时性,伪彩色处理后的温度场图像可以方便、直观地反映出温度场的分布.     

Crack growth in a naturally corroded bridge steel

This paper summarises the findings of an international collaborative programme that focuses on the problem of the growth of cracks that arise from natural corrosion in bridge steels. The experimental data presented in this paper confirm that the bridge steel da/dN versus ΔK relationship is similar to that seen by the high‐strength aerospace steels D6ac and 4340. It is then shown that the methodology developed to predict the growth of small naturally occurring cracks in aerospace materials can also be used to compute the growth of cracks that arise because of natural corrosion in bridge steels.     

Continuous wave excitation two-photon fluorescence microscopy exemplified with the 647-nm ArKr laser line

We report on efficient two-photon fluorescence imaging in beam scanning microscopy by exciting UV dyes at the 647-nm line of a continuous wave ArKr mixed gas laser. For a numerical aperture of 1.4 (oil), we used an illumination power of up to 210 mW at the sample. High-resolution images were obtained for DAPI-labelled cell nuclei within 4–60 s. Our method is a simple two-photon alternative to UV confocal imaging with the potential of becoming a very useful feature of laser scanning microscopy.     

非接触式智能识别卡系统的设计

针对接触式智能识别卡系统的缺陷,文章提出了一种采用射频技术的非接触式智能识别卡系统的设计方案,详细介绍了非接触式智能识别卡系统的组成、工作原理、读卡器软硬件的设计。     

Enhancement effect of terbium complex luminescence by binding to silver nanoparticles in the solution

The lanthanides displaylarge Stokes shifts,narrowe-mission bandwidths,and long emission lifeti mes.Due tothese characteristics,lanthanides complexes are widelyusedin high-sensitivity i mmunoassays andin DNA hy-bridization assay[1-3].A major problem concer…