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1.
针对双重化智能站域保护在检修、故障退出、灾变恢复等多种场景下可靠性不充分的问题,提出远程备用智能保护一体化中心(Remote Duplicate Configuration Smart-Protection Center,RDCSPC)继电保护新架构,需研究RDCSPC的动作逻辑情况。根据其与双重化智能站域保护之间的配合关系,使用Hierarchical Petri net Simulator(Hi PS)软件分别建立RDCSPC在热备用、冷备用工作模式下的时序Petri网(PN)模型并对之进行动态仿真分析,同时,采用PN矩阵分析法对所建立的时序PN模型进行描述验证。模型验证结果表明:所建立的时序PN模型可以有效的描述RDCSPC的动作逻辑。  相似文献   
2.
Modal analysis is an important tool in the structural dynamics community; it is widely utilised to understand and investigate the dynamical characteristics of linear structures. Many methods have been proposed in recent years regarding the extension to nonlinear analysis, such as nonlinear normal modes or the method of normal forms, with the main objective being to formulate a mathematical model of a nonlinear dynamical structure based on observations of input/output data from the dynamical system. In fact, for the majority of structures where the effect of nonlinearity becomes significant, nonlinear modal analysis is a necessity. The objective of the current paper is to demonstrate a machine learning approach to output‐only nonlinear modal decomposition using kernel independent component analysis and locally linear‐embedding analysis. The key element is to demonstrate a pattern recognition approach which exploits the idea of independence of principal components from the linear theory by learning the nonlinear manifold between the variables. In this work, the importance of output‐only modal analysis via “blind source” separation tools is highlighted as the excitation input/force is not needed and the method can be implemented directly via experimental data signals without worrying about the presence or not of specific nonlinearities in the structure.  相似文献   
3.
以非接触式机械密封为原型,建立磁流体端面动压润滑试验装置,研究转速、被密封介质压力、磁场强度对液膜润滑特性的规律;同时基于Muijderman窄槽理论,建立磁流体动压润滑特性的解析计算方法,并将解析计算结果与试验结果进行对比分析。结果表明:随转速和被密封介质压力增大,摩擦扭矩、泵送量均增大,而膜厚均减小;随着磁场强度增大,摩擦扭矩增大,泵送量和膜厚减小;相比于转速和密封介质压力,磁场强度对磁流体的动压润滑性能的影响尤为显著,因而当工况变化时可以通过调节磁场强度使密封性能始终保持在最佳工作范围。解析计算方法得到的结果与试验结果基本趋势一致,即验证了试验方法的可靠性,也表明提出的解析计算方法可用于流体动压润滑性能的预测。  相似文献   
4.
页岩油探井现场地质评价实验流程与技术进展   总被引:1,自引:0,他引:1  
页岩油勘探钻完井过程中需要及时对页岩含油性及页岩油的可动性进行快速评价,而已有的现场评价技术主要适用于常规砂岩储层,难于满足页岩非均质性描述的需求,迫切需要建立针对性的实验技术序列。根据页岩油探井现场快速地质评价客观需求,结合实验仪器的客观技术指标,提出了现场实验项目、取样保存和实验技术流程,并开展了现场技术方法实验和应用研究,研制磁流体变密度岩石总体积测试装置,解决了易松散形变页岩难于取柱塞样而无法及时获取物性参数的难题,建立了无固定形状页岩物性分析技术;采用液氮冷冻密闭粉碎制样技术避免轻烃损失,岩石热解分析数据更为真实;优化现场测试项目之间以及现场和实验室分析项目之间的衔接,实验支撑更为高效。新技术在江汉盆地潜江组、济阳坳陷沙河街组和鄂尔多斯盆地延长组七段应用效果显著,为陆相页岩油勘探快速地质评价提供了科学依据。同时也需要指出,中国目前页岩油勘探现场实验技术还不完善,还没有相应的规范标准,下一步攻关方向应该是,在完善现场实验技术和应用技术的基础上,形成规范的方法技术体系,搭建页岩油勘探快速地质评价技术平台。  相似文献   
5.

Summary

With the advances of cloud computing, business and scientific‐oriented jobs with certain workflows are increasingly migrated to and run on a variety of cloud environments. These jobs are often with the property of deadline constraint and have to be completed within limited time. Therefore, to schedule a job with workflow (short for workflow) with deadline constraint is increasingly becoming a crucial research issue. In this paper, we, based on previous work, propose an agent‐based workflow scheduling mechanism to schedule workflows that are with deadline constraint into federated cloud environment.

Design and Methods

We add a workflow agent into the original framework to schedule the deadline‐constraint workflow. The workflow agent can smoothly schedule workflows to the cloud system according to their required resource and automatically monitor their execution. In order to accurately predict the execution time of each task to meet deadline constraint on certain VM with given resource, we inherit the use of rough set theory to estimate execution time of task in our previous work.

Result and Discussion

A heuristic algorithm that is embedded into the workflow agent is also proposed because the problem had been shown to be NP‐complete. The mechanism also adopts dynamic job dispatching method to reduce the usage of VM and to improve the resource utilization. We also conducted experiments to evaluate the efficiency and effectiveness.

Conclusion

The experimental results show that the prediction time is very close to the real execution time and can efficiently schedule multiple scientific workflows to meet the deadline constraints simultaneously.  相似文献   
6.
This article studies control and performance enforcement for a class of uncertain dynamical systems that consist of actuated and unactuated portions physically interconnected to each other. The proposed approach stabilizes the overall interconnected system in the presence of unknown physical interconnections as well as system uncertainties. Performance guarantees are enforced, individually, on the actuated as well as unactuated portions of the interconnected system via this approach. For enforcing these performance guarantees, a set-theoretic model reference adaptive control approach is used, in conjunction with linear matrix inequalities, to restrict the respective system error trajectories of the actuated and unactuated dynamics inside a priori, user-defined compact sets. The efficacy of the proposed approach is demonstrated using simulations.  相似文献   
7.
Both planning and design phase of large infrastructural project require analysis, modelling, visualization, and numerical analysis. To perform these tasks, different tools such as Building Information Modelling (BIM) and numerical analysis software are commonly employed. However, in current tunnel engineering practice, there are no systematic solutions for the exchange between design and analysis models, and these tasks usually involve manual and error-prone model generation, setup and update. In this paper, focussing on tunnelling engineering, we demonstrate a systematic and versatile approach to efficiently generate a tunnel design and analyse the lining in different practical scenarios. To this end, a BIM-based approach is developed, which connects a user-friendly industry-standard BIM software with effective simulation tools for high-performance computing. A fully automatized design-through-analysis workflow solution for segmented tunnel lining is developed based on a fully parametric design model and an isogeometric analysis software, connected through an interface implemented with a Revit plugin. The IGA-Revit interface implements a reconstruction algorithm based on sweeping teachnique to construct trivariate NURBS lining segment geometry, which avoids the burden to deal with trimmed geometries.  相似文献   
8.
采用NbC/Si材料组合设计多层膜Laue透镜,总膜厚为40μm,利用衍射动力学理论分析多层膜Laue透镜对硬X射线的衍射效率及聚焦分辨率。通过两种方法提高多层膜Laue透镜的分辨率。第一种方式是减小膜层的最外层宽度,该方法要求结构必须是楔型结构,制备极其困难。第二种方法是使用多层膜Laue透镜的高级次,该方法在不增加制备难题的前提下能有效提高分辨率。通过使用多层膜Laue透镜的-3级次,对10keV硬X射线获得了分辨率为6.72nm,衍射效率为49.31%的聚焦光斑。  相似文献   
9.
在Gleeble-3500热模拟试验机上对2.25Cr1Mo0.25V钢进行等温压缩试验,得到变形温度在900~1200℃、应变速率在0.001~10 s-1、变形量为60%时的高温流动应力-应变曲线。结合金相实验,研究2.25Cr1Mo0.25V钢在不同变形条件下微观组织的演变规律,建立2.25Cr1Mo0.25V钢在高温塑性变形过程中的动态再结晶数学模型。将模型与有限元结合,对热压缩过程的组织演化进行数值模拟,模拟结果与试验结果的相对误差小于11%,验证了模型的正确性。  相似文献   
10.
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