Improved average consensus algorithm based distributed cost optimization for loading shedding of autonomous microgrids

This paper addresses a new distributed cost optimization (DCO) method for load shedding (LS) of an islanded microgrid considering cost. A two-layer improved average consensus algorithm (IACA) of multi-agent system (MAS) is proposed, and the consensus characteristic of which is analyzed in detail. With the global information discovered in the first layer of the IACA, the DCO of LS can be solved by using the synchronization processing of the IACA in the second layer. PSCAD/EMTDC-based simulation models are built to study the value settings of consensus constants and the performances of the proposed DCO method. Simulation results verified the convergence improvement of the IACA and the effectiveness of the proposed DCO.     

LS-DYNA在工程抗震中的应用

介绍了LS—DYNA软件以及在工程抗震中应用的特点，列举了该软件在高层建筑、地下工程、边坡、土石坝工程抗震分析中的应用以及对人工震源模拟的适用性。     

慢走丝线切割单点放电温度场有限元分析

建立了慢走丝电火花线切割单脉冲放电模型,利用有限元分析了单脉冲放电温度场分布。计算出该条件下工件放电凹坑几何特征,与实际切割条件下的材料去除率进行了对比,并根据电火花线切割的加工特点进行了修正。讨论了不同峰值电流和脉冲宽度条件下,蚀除凹坑体积与材料去除率(MRR)的变化规律,并分析了峰值电流和脉冲宽度对MRR的交互作用。分析结果表明:考虑实际加工的相关因素,模拟的单脉冲放电的MRR经修正后可以近似表征实际连续切割时的MRR;单个凹坑的蚀除量随着电流和脉宽的增大而增大,并且电流和脉宽的交互作用随着它们取值的增大而更加明显。     

Preparation and studies of transparent conductive monolayers of multiwall carbon nanotubes on quartz and flexible polymer with the use of modified Langmuir technique

An improved Langmuir method is described and applied to produce transparent, conductive and flexible single layer of multiwall carbon nanotubes. This paper presents properties of multiwall carbon nanotubes spread on water subphase and in a form of Langmuir–Schaefer layers on a quartz plate and on flexible polymeric foil. The results show very high homogeneity of the monolayers on a very large area obtained with the use of the proposed modified Langmuir method and indicate their relatively high radiation transmission and electrical conductivity. Laser scanning confocal and scanning electron microscopic images of the layers are presented. The microscopic visualization of the nanolayers is supported by spectroscopic studies (transmittance, photoacoustics) in the range from ultraviolet to mid-infrared. Moreover, electric measurements (current versus voltage characteristics) of the carbon material on the polymeric foil are presented.The obtained results of the investigated multiwall carbon nanotubes are discussed in a view of potential application in optoelectronics.     

数字时钟电路的设计与仿真

数字时钟设计既是电子教学中最为典型的综合性实验之一,也在商业领域有着极为广泛地应用。文中介绍了一种以74LS190同步可预置的十进制可逆计数IC为主功能芯片,联合其他逻辑门器件共同实现数字时钟功能的电路。该电路包含4个子模块,分别是1Hz脉冲产生电路、计数电路、手动校时电路和整点报时电路。设计过程中利用EWB5.0软件仿真,既提高了设计效率,又节约了设计成本。经验证,该电路工作稳定可靠,达到了预期的效果。     

Numerical simulation of impact behaviour of structures with response adapted to the intensity of shock

This study presents an alternative approach for the absorption of impact energy that uses the internal pressurization of structures in the framework of a crash‐adaptive response. Numerical simulations were conducted on axial impact of thin‐walled tubular structures with circular cross section that serve as an approximation to a front crash box of a motor vehicle. The main objective of this work consists in studying the effect of internal pressurization of tubular structures in a crashworthiness application, as well as the possibility to obtain a reduction in wall thickness thus improving weight efficiency. A numerical study is presented for an internal pressure of 20 bar and tubular structures of circular section and 1.14 mm thickness. Numerical simulations were performed recurring to LS‐DYNA explicit dynamics software while considering for the material a stainless steel alloy that is a material with interest for crashworthiness applications and manufacturing requisites due to its balance between strength, ductility and energy absorption. The results obtained allow concluding that recurring to internal pressurization it is feasible to reduce the wall thickness and have an impact resistance identical to the original while improving overall efficiency.     

一种改进的基于LS的OFDM盲同步算法

在基于LS(lease squares)的OFDM盲同步算法基础上,提出了一种性能优良的OFDM盲同步算法。采样周期取为原算法采样周期的M倍,计算出抽样点处的判决函数值,然后对相邻的判决函数值进行前后移动平均,定时点取为使移动平均值为最小时对应的那2个抽样点的中间位置。仿真结果表明:该算法不仅减少了计算量,而且在复杂的多径衰落信道中,定时和频偏估计性能也有大的改善。     

AT89S51单片机实验系统的开发与应用

针对传统单片机实验系统依赖于仿真器调试,实验成本高且效率低,不适应现代科技的开发要求的问题,为改善单片机实验系统的性能,采用在系统编程（ISP）的方法,利用AT89S51芯片设计了一种单片机实验系统。实验表明系统结构简单,实用性强,达到了工科类高职生快速掌握单片机的基础知识的预期效果。     

基于隐枚举的输电网规划局部搜索策略

提出了求解输电网规划问题的局部搜索策略。针对去掉当前规划方案中的一条支路后可能出现的元件过负荷、出现孤立节点和对系统无任何影响3种情况,分别定义了局部节点集、局部支路集和有效局部支路集,并由此定义了当前规划方案的邻域。通过变换,将局部搜索问题转化为0-1规划问题,采用0-1隐枚举法求解。结合了输电网规划问题特点的剪枝策略能够有效减少枚举过程中需要评估的节点数量,提高搜索效率。算例结果表明,所提的局部搜索策略能够显著改善全局优化算法的局部寻优能力,加快收敛速度。     

Selection of minimal tripping times for distance protection using fault trees with time dependencies

Correct coordination between protection relays is an essential requirement to maintain stability and integrity of electrical power systems. Time settings of protection relays have to be adapted to time characteristics of electrical power systems and time settings of other protections. In the paper, fault trees with time dependencies (FTTD) are used for selecting time delay settings of remote back-up distance protections. In FTTD, events and gates are characterized by time parameters, which are derived from time characteristics of protection devices and the inherent delays of protection equipment. Two case studies are presented. First, the coordination of protections for the simple transmission line composed of two identical sections is studied. Next, the transmission line that contains two sections of different lengths and transformer between them is analyzed. In both cases, formulae for time delays of protections are derived. According to calculations executed for the first case, our method gives time delays that often are significantly smaller than values suggested by generally recommended and accepted rules.