Relationships between the accumulative damage and dielectric properties of woven BN-coated Hi-Nicalon™ SiC fibre-reinforced SiC matrix composites

The accumulative damage behaviour of BN-coated Hi-Nicalon™ SiC fibre-reinforced SiC matrix composite was examined under tensile cyclic loading at room and elevated temperatures. The accumulative damage occurring during the cyclic loading was quantitatively characterised using the damage parameter obtained by the hysteresis loop curves. The damage parameter increased with increasing applied stress beyond the matrix cracking stress, and it subsequently retained a nearly constant value until just before fracture. Moreover, the dielectric constant, dielectric loss and loss tangent of the composite were measured before and after the fracture in the frequency range 1–1000 MHz. The dielectric properties had similar frequency dependency before and after the fracture. However, the dielectric constant, dielectric loss and loss tangent were lower in the post-fractured specimens than in the pristine ones. The reduction of the dielectric properties was associated with the accumulative damage stored in the specimens. In addition, the relationships between the dielectric properties and the damage parameter were described in detail.     

In2O3:Ga and In2O3:P-based one-electrode gas sensors: Comparative study

Gas sensing characteristics of one-electrode sensors based on the In₂O₃ ceramics doped by gallium and phosphorus have been discussed. In₂O₃-based ceramic was prepared by sol–gel technology. Ozone, CO, CH₄ and H₂ were used as tested gases. The doping concentration effect on the sensor parameters such as magnitude of response, operating temperature, response and recovery times, sensitivity to the air humidity, and selectivity have been analyzed. It was shown that In₂O₃ doping by Ga and P could be used for the sensor performance optimization. It was assumed that the appearance of the second phase (InPO₄ and Ga₂O₃) and the change of structural parameters, taking place during doping process, were the main factors controlling the change of operating characteristics in In₂O₃:P and In₂O₃:Ga-based sensors.     

Alcohol consumption detection through behavioural analysis using intelligent systems

We describe in this paper a new methodology for blood alcohol content (BAC) estimation of a subject. Rather than using external devices to determine the BAC value of a subject, we perform a behaviour analysis of this subject using intelligent systems. We monitor the user’s actions in an ordinary task and label those data to various measured BAC values. The obtained data-set is then used to train learning systems to detect alcoholic consumption and perform BAC estimation. We obtain good results on a mono-user base, and lower results with multiple users. We improve the results by combining multiple classifiers and regression algorithms.     

一种基于环形振荡器的轻量级高效率的真随机数发生器

真随机数发生器(TRNG)作为芯片中重要的安全组件,在现代加密系统中扮演着越来越重要的角色。对于TRNG的设计,关键是需要熵提取器可以在恶劣的环境变化(如工艺波动、电压和温度(PVT))下稳定地生成熵值。基于Xilinx FPGA平台提出了一种基于环形振荡器的低成本,高效率真随机数发生器。TRNG一方面通过快速进位逻辑来提高熵提取的效率,另一方面通过优化电路结构和延迟,在以相对较低的资源开销情况下实现可观的吞吐量和随机性。TRNG分别在多块Xilinx Virtex6 FPGAs和Xilinx Spartan6 FPGAs上进行验证,实验数据测试结果表明,所提出的TRNG能够在广泛的PVT范围内表现出良好的鲁棒性,且生成的随机比特流不仅以相当高P值通过NIST SP800-22统计测试套件,而且可以通过最新的NIST SP800-90B测试。     

固结磨料研磨单晶蓝宝石亚表面损伤的预测

目的 为了准确预测工件亚表面损伤，合理确定材料去除量，优化固结磨料研磨单晶蓝宝石的工艺参数。方法 针对固结磨料研磨特点和单晶蓝宝石特性，采用离散元模拟技术，建立单晶蓝宝石材料的离散元模型，仿真固结磨料对材料研磨的动态过程，分析载荷作用下材料单元颗粒间裂纹的产生和扩展规律，研究磨粒切入深度对亚表面损伤的影响，预测固结磨料研磨单晶蓝宝石亚表面裂纹的数量和深度，并借助化学腐蚀法验证预测结果。结果 采用粒度分别为W14、W28、W50、W65的金刚石固结磨料垫，其对应的研磨单晶蓝宝石亚表面损伤层深度预测值分别为3.75、5.28、7.62、10.92 μm，预测的裂纹数量分别为199、236、526、981条，对应的实验实测值分别为3.79、5.88、8.76、11.44 μm。固结磨料垫中的磨料粒径越大，单晶蓝宝石亚表面损伤层的深度越大，裂纹数量越密集。对比发现腐蚀实验的实测值和理论预测值基本一致，验证了预测结果模型的正确性。结论 采用离散元法可以快速有效地预测固结磨料研磨单晶蓝宝石亚表面损伤层的裂纹数量和深度，为研磨工艺参数的优化和后续抛光工艺参数的制定提供指导。     

一种双臂激光测距系统设计和误差分析

长度是 7 个基本物理量之一,在人们工作和生活中有着广泛的应用场景。 本文提出了一种由两个激光测距传感器构成 的双臂激光测距系统,可以通过非接触方式测量仪器与空间中任意一点以及空间中任意两点之间的距离,还具备测量阴角、阳 角和二维垂直度的功能。 本系统测量误差从理论上被分析,并通过 MATLAB 软件进行了仿真。 实际的实验测试表明,测量距 离在 1 m 以内时绝对误差能控制在 1 mm 以内,测量距离在 50 m 以内时相对误差能控制在 1‰的数量级。 同时,重复性测量实 验和测量不确定度评定验证了本系统的误差指标,也为本系统的改进指明了方向。 本仪器还具有功耗低、成本低和便于便携化 等优势,因此有着广阔的应用前景。     

改进的线性自抗扰永磁同步电机转速控制器设计

基于线性自抗扰控制(linear active disturbance rejection controller, LADRC)在永磁同步电机(permanent magnet synchronous motor, PMSM)转速、电流复合控制中无法应对q轴电流突变和参数整定存在缺陷,提出一种改进的自抗扰控制器。首先,分析常规LADRC在转速、电流复合控制的设计方法,并对其核心参数进行剖析。其次,基于常规LADRC用最速控制综合函数(fhan)代替比例微分(the proportion of differential, PD)进行控制律设计,提高系统控制性能并优化参数配置方式;同时基于该函数特性,设计电流外环控制器,利用电流偏差反馈算法对q轴电流进行限幅控制,避免电流冲击过大损伤硬件。通过搭建实验平台测试,实验结果显示改进的LADRC能有效应对q轴电流冲击,同时具有与传统LADRC相当的抗扰能力,并且对扰动的瞬态响应时间缩短20 ms,表明改进的LADRC具有更高的安全性能和良好的抗扰能力。     

An improved adaptive genetic algorithm based on hormone modulation mechanism for job-shop scheduling problem

An improved adaptive genetic algorithm (IAGA) for solving the minimum makespan problem of job-shop scheduling problem (JSP) is presented. Though the traditional genetic algorithm (GA) exhibits implicit parallelism and can retain useful redundant information about what is learned from previous searches by its representation in individuals in the population, yet GA may lose solutions and substructures due to the disruptive effects of genetic operators and is not easy to regulate GA’s convergence. The proposed IAGA is inspired from hormone modulation mechanism, and then the adaptive crossover probability and adaptive mutation probability are designed. The proposed IAGA is characterized by simplifying operations, high search precision, overcoming premature phenomenon and slow evolution. The proposed method by employing operation-based encoding is effectively applied to solve a dynamic job-shop scheduling problem (DJSP) and a complicated contrastive experiment of JSP in manufacturing system. Meanwhile, in order to ensure to create a feasible solution, a new method for crossover operation is adopted, named, partheno-genetic operation (PGO). The computational results validate the effectiveness of the proposed IAGA, which can not only find optimal or close-to-optimal solutions but can also obtain both better and more robust results than the existing genetic algorithms reported recently in the literature. By employing IAGA, machines can be used more efficiently, which means that tasks can be allocated appropriately, production efficiency can be improved, and the production cycle can be shortened efficiently.     

New robust stability analysis for genetic regulatory networks with random discrete delays and distributed delays

This paper investigates the delay-probability-distribution-dependent stability problem of stochastic genetic regulatory networks (GRNs) with random discrete time delays and distributed time delays which exist in both translation process and feedback regulation process. The information of the probability distribution of the discrete time delays is considered and transformed into parameter matrices of the GRN models. By introducing a new Lyapunov functional which takes into account the ranges of delays and employing some free-weighting matrices, some new delay-probability-distribution-dependent stability criteria are established in the form of linear matrix inequalities (LMIs) to guarantee the GRNs to be asymptotically stable in the mean square. In addition, when estimating the upper bounds of the derivative of Lyapunov functionals, we carefully handle the additional useful terms about the distributed delays, which may lead to the less conservative results. The new criteria are applicable to both slow and fast time delays. Finally, numerical examples are given to illustrate the effectiveness of our theoretical results and less conservativeness of the proposed method.     

Mixed H∞ and passive filtering for switched Takagi-Sugeno fuzzy systems with average dwell time

This paper investigates the mixed H_∞ and passive filtering problem for switched Takagi-Sugeno (T-S) fuzzy systems with average dwell time (ADT) in both continuous-time and discrete-time contexts. To deal with this problem, a new performance index is proposed for switched systems. This new performance index can be viewed as the mixed weighted H_∞ and passivity performance index. Based on this new performance index, the weighted H_∞ filtering problem and the passive filtering problem for switched T-S fuzzy systems can be solved in a unified framework. Combining the multiple Lyapunov functions approach with a matrix decoupling technique, new sufficient conditions for the existence of mixed weighted H_∞ and passive filters are obtained for switched T-S fuzzy systems. All these conditions are expressed in terms of linear matrix inequalities (LMIs). The desired filters can be constructed by solving these LMIs. Finally, numerical examples and practical examples are provided.