非合作多基地雷达系统性能仿真分析

针对低RCS（radar cross section）的隐身舰船很难被普通的单基地雷达探测到的问题,提出了采用非合作多基地雷达系统对海上目标进行探测,创建了一个海上场景,其中多艘商船在S波段（3 GHz）发射电磁波,作为机会雷达;一艘护卫舰大小的军舰作为雷达系统接收机,目标假定为一艘货船和一艘隐身军舰。采用专业的电磁软件对海上目标进行仿真,计算普通货船和隐身军舰的双基地RCS数据,建立了MATLAB仿真模型,研究了非合作多基地雷达的探测覆盖范围。使用FEKO的双基地RCS仿真表明,通过改变发射机的数量和发射机到接收机之间的距离,找到一种最优的多基地雷达系统几何结构和系统配置。     

基于双通道注意力的轻量化PCB缺陷检测研究

印刷电路板 (printed circuit board,PCB)在实际生产过程中存在缺陷样式多种多样、缺陷小、缺陷位置难以定位的问题,而一个巨大的模型难以实现实时检测的要求,且大量的深度可分离卷积层建立的轻量级模型也不能达到足够的精度,为此提出一种基于YOLOv5s的PCB缺陷检测算法。 将原始Backbone的Conv模块跟C3模块用GhostConv替换,在Neck部分则引入了一种新的轻量级卷积技术GSConv,减轻模型大小的同时保持精度,GSConv在模型的准确性和速度之间完成了一个极好的权衡,针对许多注意力模块无法关注全局信息同时模型大的问题,提出了多尺度的轻量化双通道注意力模块(double channel depthwise attention module,DWAM),进一步提高模型精度。通过多组实验, 结果表明,改进算法所有类别的平均mAP为99.14%,且模型的GFLOPs为7.194 G,Params为7.175,原始的YOLOv5s平均mAP为96.86%,GFLOPs为6.89 G,Params为6.596,虽然Params以及GFLOPs有所增大,但是还是满足轻量网络的要求,并且精度相对于YOLOv5s提高了2.25%,且对于每个类别的缺陷识别准确率都有改善,大幅减少计算量和模型参数的同时保证了准确率,满足工业检测生产需求的同时便于移动端部署。     

杭州与新加坡的城市社区组织模式比较

我国经济体制的改革对城市社区建设提出了新的要求,因而社区的组织发展与管理已经成为具有挑战性的课题。本文试图对杭州市和新加坡的社区组织管理模式进行比较,着重就城市社区的地域划分、规模组织、职能以及经费来源和服务设施设置等几个方面比较。     

Short-term bacterial community composition dynamics in response to accumulation and breakdown of Microcystis blooms

Short-term bacterial community composition (BCC) dynamics in response to accumulation and breakdown of Microcystis blooms were examined by conducting in situ mesocosm experiments with varying levels of Microcystis sp. biomass, ranging from 15 to 3217 μg/L as measured by chlorophyll-a concentration in the freshwater water column. The BCC was assessed by means of terminal restriction fragment length polymorphism (T-RFLP) of 16S ribosomal RNA genes followed by cloning and sequencing of selected samples. The results showed that the composition of both free-living and particle-attached bacterial communities changed during the accumulation and breakdown phases of a Microcystis bloom, and differences were also evident with different levels of Microcystis biomass. The relative abundance of bacteria affiliated with Micrococcineae and Legionellales increased in general after amendment with Microcystis. Significant correlation between the relative abundance of Micrococcineae and breakdown of Microcystis biomass was also observed. Canonical correspondence analysis (CCA) showed that the changes in the free-living and particle-attached bacterial community were mostly related to the changes in the concentrations of chlorophyll-a, dissolved organic carbon (DOC), dissolved oxygen (DO) and pH, which were mainly induced by the breakdown of Microcystis biomass. Overall, our study revealed the following: i) accumulation of Microcystis blooms and their breakdown have strong impacts on bacterial community composition; ii) there might be saprophytic association between Micrococcineae and decomposition of Microcystis biomass; iii) it is necessary to reveal potential associations between Legionellales organisms and Microcystis blooms in eutrophic freshwater lakes.     

应用有限元方法优选预应力网壳结构布索方案

以某预应力网壳结构为研究对象，根据该预应力网壳结构的实际结构特征及受力状况建立了精确的有限元计算模型，利用ADINA软件对其进行了有限元分析，通过对预应力网壳结构不同布索方案的研究，验证了该结构设计应用的合理性和现实意义。     

Pipe failure rate prediction in water distribution networks using multivariate adaptive regression splines and random forest techniques

ABSTRACT

This paper presents the results of a comparison between multivariate adaptive regression splines (MARS) and random forest (RF) techniques in pipe failure prediction in two water distribution networks. In this regard, pipe diameter, pipe length, pipe installation depth, pipe age and average hydraulic pressure are considered as input variables. Results show that the RF outperforms the MARS which is found as an accurate pipe failure rate predictor. The proposed models are further evaluated through dividing the data into three parts of lower, medium and higher pipe failure rate values. According to the equations produced by MARS technique, three variables of pipe diameter, pipe age and average hydraulic pressure are distinguished as the most effective variables in predicting pipe failure rate in the first case study. Four variables of pipe diameter, pipe length, pipe age and average hydraulic pressure are determined as the most effective variables in the second case study.     

“新工科”视角下土木类大学生学习共同体构建

以互联网、人工智能、云计算等为新兴技术的新经济形态蓬勃发展,新型工科建设给工程教育带来了机遇和挑战。土木类专业作为传统专业,面临着专业知识跟不上社会发展和产业需求、跨学科跨专业融合不够等问题,亟需改造和升级。河海大学土木与交通学院以学生为中心,以第二课堂为落脚点,实现教育教学横纵向深度融合,系统设计与构建线上虚拟空间、线下共享空间并行,实践情境体验空间付诸实际行动的“两并行一实践”的学生学习共同体,在要求土木类工程科技人才行业专精的基础上,培养学生创新实践能力、跨界整合能力和多元发展能力,助力新工科从理念到行动的全新转变。     

某大型山水休闲度假区给水工程规划与设计

以某大型山水休闲度假区给水工程为例,依据相关规范,并结合该度假区的用水特点及该地区的用水规律,对其用水量的确定进行了分析,详细阐述了其供水方案的设计过程,最后对给水管网的布置进行了规划设计,为类似给水工程的规划设计提供了依据。     

关于建筑桩基检测技术规范的商榷及修订建议

分析了建筑桩基检测技术规范中安全系数取值、单桩极限承载力取值、工程缺陷桩的处理及承载力检测中受检桩的选择等条款在工程检测过程中出现的问题,针对这些问题提出了一些修正建议,以供主编单位修订时参考借鉴。     

小空间火灾多元探测装置和实现方法研究

针对小空间火灾探测方法单一、误报漏报率高、采集数据处理简单的问题，提出1 种小空间火灾多元探测装置及方法，能够实现对火灾的烟雾、CO 气体、温度、火焰等的多元探测，多角度多方位采集火灾信号，利用信息融合技术和算法，寻找特征信息之间的规律，对数据信息进行分析解析、优化组合，运用人工神经网络和模糊推理方法，采取反复的样本训练将探测数据的误差降到最低，从而准确地判断火灾所处的阶段和类型，及时有效地采取灭火抑制措施。研究结果证明，小空间火灾多元探测方法能够满足小空间的火灾探测要求，减少了公共财产的损失，对火灾探测的进一步研究具有重要意义。