冷变形低碳马氏体钢的回火塑性

研究回火温度对15钢冷变形低碳马氏体塑性的影响.获得板条马氏体的试样经大量冷拔变形后在200～600℃进行了回火处理并测试了抗拉强度和伸长率.结果表明,随回火温度的提高拉伸强度连续降低,且伸长率在200～500℃范围内始终保持不变,当回火温度超过500℃后伸长率才开始急剧上升.而未冷变形的低碳马氏体钢在同温度范围回火时其伸长率随回火温度的提高连续增长.透射电镜分析结果表明,这种冷变形低碳马氏体的回火特性是,由于马氏体再结晶晶界上大量析出渗碳体所致.     

碳化硅颗粒增强铝基复合材料的重熔和铸造工艺特征

介绍了SiC颗粒增强铸造铝基复合材料的铸锭重熔、除气和铸造过程的特征。由于颗粒的存在 ,这些工艺过程和普通铝合金有一定的差异。在铸锭重熔时 ,需要控制熔炼温度和对熔体施加搅拌 ,以防止颗粒反应和下沉。普通铝合金采用的熔盐和气体除气工艺不适合于复合熔体的除气精炼 ,而真空除气具有很好的效果。复合熔体具有高的粘度 ,流动性较差 ,在大气自由重力浇注时容易卷入气体而导致铸件气孔缺陷。为了防止铸件缺陷的形成 ,复合材料在大气自由重力浇注下的浇注系统需要设计集气、集渣冒口和阻流口等特殊组元。真空差压浇注工艺大大简化了浇注系统 ,降低了材料消耗 ,同时消除了大气自由重力浇注时容易产生的铸造缺陷。通过该工艺可获得形状复杂、表面光洁、尺寸精确的铝基复合材料精密铸件     

利用扫描声学显微镜对金属-陶瓷复合涂层亚表层相分布的研究

利用声学显微技术这一无损检测手段对等离子喷涂的金属－陶瓷复合涂层进行了亚表层显微结构的观察，通过分析涂层材料的声波信号，得出了金属相和陶瓷相分布区域的结论，并为涂层表面的背散射电子像和断面的金相观察等手段所证实。     

虚拟仪器技术在机械传动系统扭矩和功率测试中的应用

利用虚拟仪器技术,实现了机械传动系统扭矩和功率的自动测量.文章介绍了该测试系统的结构、功能和系统的软硬件构成以及它们的实现方法.这种测量方法以灵活的软件功能代替固化硬件,提高了系统的可靠性和测量精度.     

人像照片的美感质量评价

随着机器学习理论和图形图像处理技术的不断发展,在计算机视觉和计算美学领域中人们越来越关注如何建立自动评价和判断图片美感质量的系统.该系统将可用来补充和完善原有对照片只有主观美感质量评价的这一问题.对人像照片美感质量的客观评价进行研究,提出了25种能够较好反映人像类照片美感质量的特征,并使用支持向量机、Adaboost、随机森林等多种分类器来进行机器学习和评价,对提出的特征值集合进行十交叉检验并探讨了哪些特征对美感评价有较强影响等问题.最后,通过与现有研究结果进行对比分析后得出,当采用所提出的25种特征进行人像照片美感质量评价和分类时有更高的准确率,即使用于机器学习的训练数据集数目较少时仍能保持较高的准确率.     

基于自适应蚁群遗传混合算法的 PID 参数优化

针对遗传算法易重复迭代、蚁群算法易陷入停滞的缺点,提出基于自适应蚁群遗传混合算法的 PID 参数优化。先用遗传算法获得 PID 参数的初值,再用改进后的蚁群算法自适应调整路径选择概率和信息素更新规则,最终搜索出 PID 参数的最优值。仿真结果表明,对于给定的被控对象,相比于 GA 和 ACS 算法,该算法搜索出的 Kkp、Kki 、Kkd 最优,系统响应时间短,动态性和稳定性佳,说明该方法整定出的 PID 参数值具有最优性。对于其他的控制对象和过程也具有参考价值。     

Feature scalability for a low complexity face recognition with unconstrained spatial resolution

Automatic face recognition (FR) based applications in low computing power constrained systems, such as mobile and smart camera, have become particularly interesting topic in recent years. In this context, we present computationally efficient FR framework underpinning the so-called feature scalability algorithm. The proposed framework aims at implementing robust FR systems under low-computing power restriction and varying face resolution. Key beneficial property of our proposed FR framework based on feature scalability is to require low computational complexity without sacrificing a level of FR performance. To do this, using feature scalability algorithm enables to directly estimate the features (from pre-enrolled gallery images) that are well matched with the feature of an input probe image with different resolution (generally lower resolution) without any complex process. In addition, our method is helpful for relieving storage shortage problem as it does not require a large amount of training and gallery images with different face resolutions. Results show that our proposed feature scalability algorithm can be seamlessly embedded into state-of-the-art feature extraction methods extensively used for FR by achieving impressive recognition performance. Also, according to the results on computational complexity measurement, the proposed method is proven to be useful for substantially saving FR operation time.     

Global Output‐Feedback Stabilization for Stochastic Nonlinear Systems with Function Control Coefficients

This paper investigates the global output‐feedback stabilization for a class of stochastic nonlinear systems with function control coefficients. Notably, the systems in question possess control coefficients that are functions of output, rather than constants; hence, they are different from the existing literature on stochastic stabilization. To solve the control problem, an appropriate reduced‐order observer is introduced to reconstruct the unmeasured system states before a smooth output‐feedback controller is designed using the backstepping method, which guarantees that the closed‐loop system is globally asymptotically stable in probability. This paper combines the related results in the deterministic and stochastic setting and gives the first treatment on the global output‐feedback stabilization for the stochastic nonlinear systems with function control coefficients. A simulation example is given also to illustrate the effectiveness of the proposed approach.     

Interference coordination based on random fractional spectrum reuse in femtocells toward Internet of Things

Femtocell is featured with a low-power and low-cost cellular access in indoor environments, and thus offers an effective yet flexible way to implement information exchange over Internet of Things. In femtocell networks, the dense deployment of home eNodeBs causes severe inter-cell interferences and imposes heavier load on the scarce frequency spectrum. In this paper, we propose an inter-femtocell interference coordination scheme to enable random and fractional reuse of frequency resources in a 3D in-building scenario. Specifically, we consider the regular femtocell deployment, where all the femtocells are divided into two groups and two neighboring femtocells will be classified into different group. Each group is initially allocated with a half of frequency resources. To more sufficiently utilize the spectrum, either group of femtocell is allowed to transmit over the frequency assigned to the other group of femtocell in a random way at the cost of introducing some interferences, i.e., reuse based on a specified probability. This probability is determined by maximizing the geometric mean of users’ average throughput, such that the fairness among users is guaranteed simultaneously. Moreover, an equivalent scheme generated from full frequency reuse between two femtocells groups is also given. Here, either group of femtocell will avoid transmitting over fractional frequency randomly with a certain probability and the interference to the adjacent femtocell can be reduced. The simulation results show that the proposed schemes could obtain the larger system average rate and edge user performance compared with the baseline schemes. Moreover, the geometrical average throughput per user achieved by our method is highest, and a more fair resources allocation can be realized .     

CH395与 SPI 接口的以太网模块设计

伴随着物联网的高速发展,以太网已经成为很多嵌入式系统中的一个重要模块。针对很多无自带以太网模块的低成本单片机控制器,本设计采用 CH395芯片连接 dsPIC33系列单片机的 SPI 接口实现以太网模块,该方案开发难度小,占用单片机硬件资源少,是一种可靠的设计方案。