The formed surface characteristics of SiCf/SiC composite in the nanosecond pulsed laser ablation

For the advantages of high-temperature resistance, corrosion resistance and ultra-high hardness, SiC_f/SiC composite is becoming a preferred material for manufacturing aero-engine parts. However, the anisotropy and heterogeneity bring great challenges to the processing technology. In this study, a nanosecond pulsed laser is applied to process SiC_f/SiC composite, where the influence of the scanning speed and laser scanning direction to the SiC fibers on the morphology of ablated grooves is investigated. The surface characteristics after ablation and the involved chemical reaction of SiC_f/SiC are explored. The results show that the increased laser scanning speed, accompanied by the decreasing spot overlap rate, leads to the less accumulation of energy on the material surface, so the ablation effect drops. In addition, for the anisotropy of the SiC_f/SiC material, the obtained surface characteristics are closely dependent on the laser scanning direction to the SiC fibers, resulting in different groove morphology. The element composition and phase analysis of the machined surface indicate that the main deposited product is SiO₂ and the carbon substance. The results can provide preliminary technical support for controlling the machining quality of ceramic matrix composites.     

单片机应用系统综合实验装置的设计

单片机原理与应用作为电子技术类学科中的必修课程具有很强实践性,要求学生掌握实际应用能力,为此研制了基于单片机系统通信为基础的实验板,依据单片机应用系统特点,可完成SPI、I^2C、UART串行通信以及并行总线方式通信。实验板有利于学生更好地了解和掌握单片机应用系统设计的方法,有利于学生进行自主设计和内容拓展。做到培养学生的学习能力、提高学生的学习兴趣、发挥学生的创造性。     

Controlling Au electrode patterns for simultaneously monitoring electrical actuation and shape recovery in shape memory polymer

This paper presents an effective approach to achieve efficient electrical actuation and monitoring of shape recovery based on patterned Au electrodes on shape memory polymer (SMP). The electrically responsive shape recovery behavior was characterized and monitored by the evolution change in electrical resistance of patterned Au electrode. Both electrical actuation and temperature distribution in the SMP have been improved by optimizing the Au electrode patterns. The electrically actuated shape recovery behavior and temperature evolution during the actuation were monitored and characterized. The resistance changes could be used to detect beginning/finishing points of the shape recovery. Therefore, the Au electrode not only significantly enhances the electrical actuation performance to achieve a fast electrical actuation, but also enables the resistance signal to detect the free recovery process.     

Ag–Cu–BTC prepared by postsynthetic exchange as effective catalyst for selective oxidation of toluene to benzaldehyde

A mixed-node MOF catalyst Ag–Cu–BTC was prepared by postsynthetic exchange (PSE) method. It is believed that PSE method can realize isomorphous replacement of Ag ion to framework Cu ion in Cu–BTC successfully. The catalytic performance of Ag–Cu–BTC was investigated via selective oxidation of toluene to benzaldehyde by molecular oxygen in the absence of solvent and initiator. This catalyst exhibits good catalytic performance: on the premise of keeping highly selective catalysis of Cu–BTC for toluene oxidizing to benzaldehyde, the introduction of Ag (Ag content is 2.76 wt.%) can promote toluene conversion from 6.5% to 12.7%.     

一种动态Q值多标签识别算法的性能分析

EPCglobal组织发布的第二代超高频射频识别空中接口协议EPC-C1G2协议可同时识别多个标签,该协议采用时槽ALOHA算法来解决多标签识别时产生的碰撞问题。文章首先介绍了EPC-C1G2协议多标签碰撞解决所需的参数和命令,指出协议中的Q值决定了解决碰撞时所用的时槽数。时槽数越多,标签越不容易碰撞,但识别时间越长,因此,恰当地选择Q值可以在标签识别时间和识别标签数之间找到最佳点。文中同时给出了一种动态Q值算法,该算法可根据标签碰撞解决的实际情况动态调整Q值,使标签识别更高效。文章最后对这种多标签识别流程的性能进行了仿真分析。     

嵌入式PLC系统的设计与实现

基于Linux操作系统和ARM嵌入式平台设计并实现了一种嵌入式PLC系统,详细介绍了该系统的硬件组成及开发系统、运行系统的软件设计方法。该系统已在某高校电化学工作站平台上进行了实用性测试,结果表明,该系统操作步骤简单易掌握,控制较为灵活,但仍需进一步改进其电磁兼容性和健壮性。     

多能互补系统综合效益最大化控制

针对光伏发电出力随机性大,波动较强等问题,提出了一种多能互补系统综合效益最大化控制策略,控制双向DC-DC逆变器实现蓄电池、超级电容器和氢燃料电池充放电,保证直流母线电压的稳定。然后利用蓄电池和超级电容器所具有的能量互补特点,实现对储能系统的优化管理。采用光伏与混合储能协调互补的方法,可以减少储能系统的容量、降低蓄电池循环充放电的次数、延长储能装置的使用寿命,并获得较好的光伏波动平抑效果,相比于常规的控制方法,减少了运行投资成本,具有显著的经济效益。     

基于Ziegler-Nichols优化算法的火电机组负荷频率PID控制研究

随着风电和光伏接入电网的规模不断扩大,电网负荷峰谷差逐渐增加,电网的频率控制出现超调量过大、调节速度过慢等一系列问题。本文针对互联电力系统的负荷分配以及频率控制问题,提出考虑发电机组分配系数的互联电力系统负荷频率控制方法。首先,建立单个区域包含多个火电机组的两区域电网自动发电控制（AGC）系统仿真模型,根据各发电机组的煤耗特性建立经济性目标函数,并且获得最优的出力分配系数;然后,基于联络线功率和频率偏差控制（TBC-TBC）的控制模式,采用经Ziegler-Nichols相关算法优化后的PID控制,并对优化后PID控制器的鲁棒性进行分析研究;最后,基于两区域系统仿真模型,在一定的负荷扰动工况下进行仿真验证。仿真结果表明:该分配方法能够有效节省煤耗,本文算法优化后的PID控制器在频率恢复速度方面具有一定的优势,并且鲁棒性良好。     

基于恢复价值动态评估的配电网恢复控制决策

配电网停电后,停电场景、恢复进程和应急情况下的负荷职能等均会影响负荷恢复供电的紧急程度,通常根据待恢复对象自身的恢复价值静态设置其重要等级或重要度,这制约了有限恢复资源的精细化管理.为此,考虑冷负荷启动特性与负荷间职能耦合关系对负荷单位恢复价值的影响,考虑间歇性电源出力的可控性对电源恢复价值的影响,结合母线恢复为周边其他待恢复对象带来的潜在恢复价值,同时计及系统供电缺额、恢复代价和恢复操作的不确定性,提出了综合恢复收益、代价和风险的负荷及电源母线恢复价值动态评估方法.以此为基础,建立了配电网供电恢复多进程优化模型及分区并行恢复决策方法.最后,通过仿真分析验证了所提策略能够有效提高恢复资源的利用率.