Multiple-tapped-delay-line hardware-linearisation technique based on wire load regulation

This article describes designing, implementation and tuning processes of multiple-tapped-delay-line (MTDL). Obtained MTDL can be implemented in various field-programmable-logic-devices (FPGA) devices and applied for time-to-digital-converters (TDC) construction. The task of tuning process is the tapped-delay-line (TDL) linearisation, and consists of two stages. The first stage depends on selecting an appropriate configurable-logic-block (CLB) for particular delay-segment realization and selecting proper connection between these blocks. The second tuning stage, that is essential from this article viewpoint, depends on inter CLBs connecting wires delay regulation realized directly by load regulation. The Load regulation depends on connecting an appropriate number of unused three-state-buffers or CLB inputs to the wire which delay is adjusted. Depending on the number of inputs connected to the wire its capacitance changes that influences its time-constant and finally changes its time-delay.The MTDL mathematical model, obtained characteristics and results of time-interval (TI) measurements are also presented. The derived TDL model provides information about how the particular wire delay should be changed and in which order the changes should be executed. This makes the designing process predictable and easy to carry out. Presented characteristics confirm the proper operation of presented linearisation technique. The proper operation of the whole measuring module is confirmed by obtained TIs histograms presentation.     

A new algorithm of the nonlinear adaptive interpolation

The paper presents a new algorithm of NonLinearly Adaptive Interpolation （NLAI）. NLAI is based on both the gradients and the curvature of the signals with the predicted subsection, it is characterized by adaptive nonlinear interpolation method with extracting the characteristics of signals, Experimental research testifies the validity of the algorithm using the echoes of the Ground Penetrating Radar （GPR）. A comparison of this algorithm with other traditional algorithms demonstrates that it is feasible.     

半挂车用空气弹簧弹性特性分析

利用有限元软件和实验方法对空气弹簧的弹性特性进行研究.在前处理软件Hypermesh建立空气弹簧的模型并对其进行网格划分,采用Abaqus/Standard模块对空气弹簧载荷-位移特性进行仿真计算,并利用台架试验测试空气弹簧的弹性特性.结果表明:空气弹簧具有变刚度特性,能有效提高车辆的行驶平顺性;两种方法结果基本一致,验证了有限元分析模型的正确性,为该类型空气弹簧的设计开发提供了可靠的理论依据.     

直升机的非线性阻尼特性参数识别

本文研究了直升机的非线性阻尼特性,分析了非线性阻尼特性的描述形式,展示了直升机阻尼特性的试验结果,提出了基于阻尼特性的功量图数据或当量粘性阻尼系数数据的非线性阻尼特性参数识别方法,对直八型直升机的非线性阻尼特性进行了实际的识别研究.     

Using ROC curves to assess the efficacy of several detectors of damage-induced nonlinearities in a bolted composite structure

We offer a comparison of several different detectors of damage-induced nonlinearities in assessing the connectivity of a composite-to-metal bolted joint. Each detector compares the structure's measured vibrational response to surrogate data, conforming to a general model for the healthy structure. The strength of this approach to detection is that it works in the presence of certain types of varying ambient conditions and is valid for structures excited with any stationary process. Here we employ several such detectors using dynamic strain response data collected near the joint as the structure was driven using simulated wave forcing (taken from the Pierson–Moskowitz frequency distribution for wave height). In an effort to simulate in situ monitoring conditions the experiments were carried out in the presence of strongly varying temperatures. The performance of the detectors was assessed using receiver operating characteristic (ROC) curves, a well known method for displaying detection characteristics. The ROC curve is well suited to the problem of vibration-based structural health monitoring applications where quantifying false positive and false negative errors is essential. The results of this work indicate that using the estimated auto-bicoherence of the systems response produced the best overall detection performance when compared to features based on a nonlinear prediction scheme and another based on information theory. For roughly 10% false alarms, the bicoherence detector gives nearly 90% probability of detection (POD). Conversely, for several of the other detectors 5–10% false alarms leads to 70% POD. While the bicoherence (and bispectrum) have been used previously in the context of damage detection, this work represents the first attempt at using them in a surrogate-based detection scheme.     

外差激光干涉仪非线性的细分和消除

通过理论推导得到一个消除外差激光干涉仪非线性的理论,只要改变干涉仪的结构,也就是增加光程倍数,就可以减小激光干涉仪的非线性误差。实验证明,这个方法可以有效地减小双频激光干涉仪的各种非线性误差,不论这个误差是一阶的还是二阶的,也不论是什么原因引起的。它不仅适应于科学实验研究,而且也适应于工业精密测量应用,对纳米测试技术的发展具有实际意义。     

Sea clutter modeling using an autoregressive generalized nonlinear-asymmetric GARCH model

The sea clutter modeling is critical to the radar design and assessment of relevant detection algorithms. In this paper, we investigate a family of generalized autoregressive conditional heteroscedastic (GARCH) processes to model the sea clutter as a time series, in which the current variance is dependent on historical information. The most general model (so-called the ALLGARCH model) provides more flexible variance structures to model non-Gaussian, asymmetry, and nonlinear properties of the clutter. However, after going through the usage of the ALLGARCH model, we find that it is not very suitable because the coefficients of the model, which are numerous, would be difficult to estimate in a real-time operating environment. Meanwhile, we find that some of the coefficients are negligible under almost all kinds of sea environments and weather conditions. Motivated by these observations, we propose a novel GARCH model for sea clutter modeling, which is a generalization of the nonlinear-asymmetric GARCH (NAGARCH) model. Considering the correlation between adjacent clutter returns, autoregressive terms are also introduced. By systematically analyzing practical sea clutter data under different sea environments, we demonstrate that the proposed model achieves comparable fitting effect to some commonly used statistical models. Also, we develop the corresponding generalized likelihood ratio test (GLRT) algorithm for the new model. Numerical simulations exhibit that the proposed detector achieves higher probability of detection, comparing with the AR-GARCH detector.     

Dynamic electrothermal simulation of integrated resistors at device level

This paper presents the dynamic electrothermal simulation of a rectangular resistor integrated on a semi-conductor substrate. Due to the temperature dependence of the electrical conductivity of the resistive sheet, self-heating provokes a coupling between the electrical and thermal problem and gives rise to nonlinear phenomena. We introduce a time stepping iterative method to perform the calculations. The electrical and thermal solvers are based on FEM and Green's functions techniques, respectively. An extensive dynamic analysis of the device will be presented. The results include heating and cooling curves, Nyquist plot (complex locus) of the thermal impedance, time constant spectrum and structure function. Comparisons with the linear case, i.e. a temperature independent resistor, are made and accompanied by analytical approximations if possible. One key observation is that the nonlinearity may easily be overlooked: its detection is only possible in particular characteristics.     

Chirping techniques for enhancing the performance of SOA-based UWB over fiber systems: An experimental demonstration

A phaser-based processing technique was adopted in an UWB over fiber system employing SOA. The target is to simultaneously reduce the ASE noise impact and nonlinear effects inherent to optical amplification. Experimental results prove the effectiveness of chirping in terms of cross correlation and bit error rate.     

自校正前馈调节器在带有时变纯延迟特性的转筒干燥机系统上的应用

分析了转筒干燥机的干燥过程,提出了切合实际的一阶惯性兼时变纯延迟及可测干扰的系统模型。并针对系统所具有的特性提出相应的解决方案,应用K. J. Astrom所提出的自校正调节器原理,在转筒干燥机系统上实现了带有前馈补偿的自校正控制,经仿真结果验证该控制方法是可行的