基于安全自动装置控制的火电机组改进超速保护

为解决传统的火电机组超速保护控制特性无法适应不同形态故障对电网、机组的影响,完善其控制策略,加强电网稳定性、提高机组设备安全性,提出一种基于安全自动装置控制的火电机组超速保护。该保护利用区域稳控系统实现信息采集、处理和命令分发,实现了安全自动装置与超速保护两者的精确配合,可达到防止同一供电区域内的多台火电机组超速保护同时动作的目的。分析结果表明,该保护在有效提高电网稳定性的同时,也确保了机组原有的安全屏障不受削弱,可操作性强,为解决孤网系统高频问题另辟蹊径。     

弹塑性缓冲限位与滞变-摩擦并联隔震体系参数分析

针对弹塑性缓冲限位与滞变-摩擦并联隔震体系,建立了隔震系统的恢复力模型和隔震体系的运动方程;根据缓冲限位装置的作用机理,定义了隔震层与缓冲限位装置软碰撞和脱离接触过程中的软碰撞拐点和恢复力拐点,给出了拐点时刻的缓冲限位装置位移和恢复力的计算公式,编制了相应隔震体系的非线性分析程序,分析了缓冲限位装置的缓冲限位距离、弹性刚度、屈服位移等关键参数对隔震体系的影响。研究表明：弹塑性缓冲限位距离的合理取值范围为60～100 mm;缓冲限位装置与滞变 摩擦隔震装置的设计参数完全相同,但缓冲限位装置的设置数量为滞变 摩擦隔震装置数量的一半;与仅滞变 摩擦隔震情况相比,并联隔震体系隔震层位移控制效果在30%以上;与无控情况相比,并联隔震体系的上部结构层间位移控制效果在40%以上。     

Nonlinear seismic assessment of isolated high-speed railway bridge subjected to near-fault earthquake scenarios

Abstract

An iterative framework is introduced in this present study to detect seismic isolation precursors of the shortcut calculation method for the isolated benchmark high-speed railway RC bridge. The spatial finite element (FE) analysis model of a benchmark isolated high-speed railway reinforced concrete (RC) bridge system under high-speed railway vehicles is set up based on the equivalent linear method. The vehicle with two bogies is assumed to be represented by a 3?D discrete rigid multi-body system with 23 degrees of freedoms (DOFs). The present study compares the nonlinear seismic response of a high-speed railway bridge with and without isolation bearings. Numerical results demonstrate that the isolation system with the optimal parameters can simultaneously reduce the deck displacement and the internal force of the isolated railway bridge under near-fault (NF) ground motions with various peak accelerations and peak velocity ratios, to ensure the adequate isolation efficiency of isolated structures. Specifically, the study shows that the seismic response of the seismically isolated bridge (IB) and the running safety indexes of the train are primarily dominated by the contents around the fundamental frequency of the train-bridge system subjected to the earthquakes.     

地方煤矿隔爆设施安装方法探讨

通过对地方煤矿隔爆设施现状的深入了解，结合地方煤矿生产布局和开采条件等实际情况，阐述了适合地方煤矿的隔爆水袋和岩粉棚安装的基本要求、方法及特点。     

非连续体吸波平板的设计制备及吸波机理分析

通过吸波体内导电媒质的“孤岛”化设计, 制备了单层非连续体平板吸波材料, 并分析了不同炭黑含量和不同试样厚度对吸波效能的影响以及电磁波的损耗机理。发现随着CB/ ABS 颗粒中炭黑含量和试样厚度的增加, 在8～18 GHz 频段内, 非连续体试样的反射损耗增加。当炭黑质量含量达到30 %时, 平板的反射损耗在8. 5～18 GHz 宽频范围内都超过- 10 dB , 在15～18 GHz 均高于- 15 dB。当试样厚度达到20 mm 时, 其反射损耗在8～18 GHz 频率范围内超过- 15 dB。结果表明, 非连续体试样较热压致密试样吸波效能有较大提高, 是很有潜力的吸波结构。      

基础隔震建筑中应用变刚度保护装置的地震反应分析

长周期的地面运动会使隔震建筑物发生类共振而导致隔震支座失稳破坏。在这种情况下,可以利用附加的弹簧改变建筑物的周期,减小隔震层的变形,使之限制在允许的范围内,同时使上部结构的层间剪力不明显增大。按照多质点结构分析模型推导了不发生附加、右侧附加、左侧附加弹簧的运动方程,编制了相应的分析程序。通过对模型实例分析,论证了变刚度保护装置在限制支座大变形中的作用,讨论了在工程设计中如何选取变刚度保护装置的适宜参数。     

大型预应力U型薄壳渡槽施工过程仿真分析

针对预应力U型薄壳渡槽的施工问题,采用单元“生和死”的技术及“时程”分析的方法进行了仿真计算,得出了预应力U型薄壳渡槽在张拉纵、环向预应力锚索、装配横杆、造槽机移位过跨等受载过程中槽身混凝土的力学行为变化规律.在上述一系列的施工过程中,施加预压应力效果较好,采用造槽机施工对槽身损伤小,为渡槽的设计和施工提供了依据.     

图的分数[a,b]-因子存在的一个条件

图G的孤立韧度定义为I(G)=min｛｜S｜/i(G-S):S!V(G),i(G-S)≥2｝,若G不是完全图;否则,令I(G)=∞。论文给出了图的分数[a,b]-因子的存在性与图的孤立韧度的关系。证明若δ(G)≥I(G)≥a-1+a/b,则图G有分数[a,b]-因子,其中a相似文献   

Synthesis of pH-responsive isolated soy protein/carboxymethyl chitosan microspheres for sustained pesticide release

In order to improve the utilization rate of avermectin (AVM), a complex was prepared by electrostatic self-assembly using isolated soy protein (ISP) and carboxymethyl chitosan (CMCS) for loading AVM to obtain ISP/CMCS@AVM microspheres. The encapsulation efficiency (EE), sustained release property, ultraviolet (UV) protective ability, and toxicity of the microspheres were evaluated, and the release kinetics of AVM from the microsphere at different pHs were investigated. The results demonstrated that the average particle size of ISP/CMCS@AVM was 283.95 nm, and the EE reached 88.42% for AVM after denaturation. After 70 h of exposure to UV light, the residual rate of AVM in ISP/CMCS@AVM was 78.12%, which was significantly higher than 35.18% in the AVM emulsion. Moreover, the formulation imparted pH sensitivity and sustained-release property to AVM and was consistent with the Korsmeyer–Peppas model, controlled by Fick diffusion. Finally, the insecticidal toxicity of ISP/CMCS@AVM did not differ significantly from that of unmodified AVM. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48358.     

基于深度学习的高压隔离开关分合状态检测算法研究

高压隔离开关的正常工作是电力系统稳定运行的前提。为正确识别隔离开关的分合状态,提出一种轻量化改进型YOLOv5s目标检测算法。首先,针对隔离开关数据集,采用二次优化K-means++聚类算法重新获取锚框参数。然后,将模型中的损失函数由CIOU替换为具有更强收敛性能的EIOU,加快模型训练的收敛速度。最后,在模型主干特征提取网络的最后一层添加CBAM注意力模块,加强模型特征提取能力。在此基础上,采用通道稀疏化剪枝的方法对改进后的模型进行轻量化处理,减小模型体积和算力消耗。实验结果表明,改进后的模型识别平均精度均值到达97.4%,轻量化处理后的模型大小为3.92 MB,使得模型更加容易部署到移动端设备完成实时检测。