一种基于EMD的共振解调改进方法

针对传统共振解调方法中共振频带需要人为确定和故障轴承振动信号信噪比低的缺陷,提出了一种基于EMD算法的共振解调改进方法。该方法首先对轴承振动信号进行EMD分解,然后自适应地筛选出高频固有振动频率附近的基本模式分量（IMF）,并对单分量进行滤波处理,最后重构选取滤波后的基本模式分量,并对重构信号进行包络解调分析,得到故障特征频率和故障类型。滚动轴承故障诊断表明,改进方法不仅能够自适应地确定共振频带,而且可以有效地提取故障特征,识别故障类型。     

Assessing a soft twin tunneling numerical model using field data

Using a five-floor building affected by the Yangtze River highway tunnels in Wuhan as the engineering background, we have constructed a free-field model and a coupled model to study the soil, lining, foundations and upper structure, and analyze the rules of movements of building foundation and ground induced by single tunnel and twin tunnel excavation with the Finite Element Analysis method. It is shown that for the coupled model, the longitudinal displacement of each foundation increases slowly when the tunnel face gets close to the foundation section and then increases fast when the tunnel face moves away from the foundation during the single and twin tunneling. For a single tunnel, the surface settlements are overestimated by the free-field and coupled tunnel. This might be crucial in urban areas. Regarding the maximum settlements and the width of the settlement trough, the difference between the free-field model and the coupled model is quite obvious. This comparison with the field measurement value reveals that the coupled model seems to be superior to the free-field model. These results are of instructive significance for design and excavation.     

Screening of the effective cellulose-degradable strain and its application in the production of cellulose bioethanol

Strains from the cellulose-containing environment were collected. Primary screening(by filter-paper Hutchison solid culture medium and sodium carboxymethylcellulose solid culture medium) and reelection(by filter-paper inorganic salt culture medium and sodium carboxymethylcellulosc Congo red coltnre medium) indicated that five strains obtained were best suited for high performance cellulose degradation. Determination of sodium carboxymethylcellulose activity(CMCA) and filter paper activity(FPA) was accomplished for each of the five. The strongest of the five in CMCA and FPA was applied to the production of cellulose bioethanol by separate hydrolysis and fermentation(SHF) and simultaneous saccharification and fermentation(SSF) respectively.     

A novel approach to design robust fault detection filter for networked control systems

In this paper, an approach for designing robust fault detection filter (RFDF) of networked control systems (NCSs) with unknown inputs is studied. The design aims at implementing the optimal trade-off between robustness of unknown inputs (including the item produced by networked-induced delay) and sensitivity of fault. The key design issue is to introduce an optimal fault detection filter based on NCSs with the control law compensation as the reference residual model of NCSs and to formulate the RFDF design as a model-matching problem. By applying H _∞ optimization technique, linear matrix inequality (LMI) approach is given to solve the model-matching problem. The validity of the proposed approach is shown by a numerical example.      

基于非线性规划法的最小阻力船型优化设计

为了获得阻力性能优良船型,以兴波阻力理论为基础,利用非线性规划法并结合CAD技术研究最小阻力船型的优化设计.以总阻力为目标函数,总阻力用兴波阻力和平板摩擦阻力之和来表达,设计变量取船型修改函数的参数,在保证必要的排水量为基本约束条件下,选取Wigley船型为初始船型,分别对船体的首部和全船线型进行优化设计.通过将改良船型的阻力性能、船体线型和基于Michell积分法的优化计算结果相比较,证实了在相同的设计参数和约束条件下,采用Rankine源法进行船型优化结果更可靠.     

改善时速160 km以下铁路隧道养护维修条件的应对措施初步研究

时速160 km及以上的隧道断面既受控于建筑限界,同时受控于空气动力学效应,断面较大,能够满足大型机械养护维修作业需要;而时速160 km以下的隧道断面,由于隧道内道砟槽宽度小,不能满足大型机械养护维修作业要求,笔者观察了目前隧道维修养护作业环境条件,指出繁忙干线铁路特别是重载铁路隧道内大型机械养护取代人工养护作业的必要性和紧迫性,从加宽隧道断面道砟槽宽度、铺设无砟轨道等方面入手,分析了改善时速160km以下铁路隧道养护维修条件的应对措施,并进行经济性分析,研究结论中明确了加大隧道断面的标准。     

STPA安全分析技术在全自动无人驾驶中的应用

随着城市轨道交通列车运行自动化等级越来越高,信号系统实现的功能越来越复杂,系统之间的信息交互也越来越多。而经典功能安全分析技术更多关注的是组件失效引发的事件链,忽略了组件间复杂交互导致的不安全控制行为。为此引入基于系统理论的事故模型和过程（STAMP）致因模型的安全分析技术——系统理论过程分析STPA方法。针对全自动无人驾驶中的自动洗车功能,构建控制结构,识别子系统间交互存在的不安全控制行为和致因场景,确定风险规避措施,从而保证复杂功能的安全性。     

青藏铁路GSM-R网络优化浅析

GSM-R系统的首次创新使用是在青藏铁路,目前借着中国高速铁路建设迅速发展的契机正迎来空前的发展。随着通信业务的不断发展,用户对通信的需求也变得多样化,对通信系统的安全及质量要求也日益提高,因此,如何利用既有网络资源最大限度地优化GSM-R网络,使得网络提供最优通信服务和获得最佳效益将成为一项长期而艰巨的任务。文章就青藏铁路安全运营十年及期间GSM-R网络维护人员不断科学创新、采取多种有效手段对网络进行持续不断的优化,确保青藏线GSM-R系统持续稳定及网络服务质量不断提升的大量基础性工作予以总结分析,以期和广大GSM-R网络维护优化人员相互交流、共同进步。     

凤凰山水电站溢洪道消能结构优化设计研究

凤凰山水电站位于山区转平原入口的冲积扇上,枢纽消能防冲的方案设计关系到建筑物的安全和下游河床河岸的稳定。为改善其消能段的水流流态,提高效能效率,通过整体水工模型试验,在原设计方案的基础上,对消能段结构进行优化。实际效果表明,推荐方案下消能段水流流态有了明显改善,下泄水流能够平顺地与天然河床相衔接,水流流态平顺,河势稳定,满足工程设计和施工的要求。     

ATIS 环境下随机动态路网行程时间可靠性0

为评价随机动态道路网络系统在ATIS 环境下的行程时间可靠性,将出行者群 体划分为装载和未装载信息接收设备两类,并假设他们均遵循随机动态用户最优原则 (SDUO)进行动态路径选择,运用动态均衡理论建立了基于路径的混合SDUO 不动点模 型,并证明该模型至少存在一个不动点.使用离散随机变量序列描述需求的随机动态变 化,基于Monte Carlo 模拟和对角化相继平均算法(MSA),提出了ATIS 环境下随机动态路 网的行程时间可靠性评价方法.随后通过算例验证了可靠性评价方法的可行性. 数值结果 表明：OD 行程时间可靠性随出发时段动态变化,且在动态情形下,扩大ATIS 市场占有率 并不能进一步提高可靠性,反而可能会导致可靠性下降.