共查询到16条相似文献,搜索用时 140 毫秒
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固体物料的管道水力输送技术广泛应用于国民经济众多领域,针对固体物料的多样性,复杂性以及管道固液两相流动的特点,阐述了固液两相流动与单相流动的主要差异,研究内容,研究方法和实验手段,简要介绍了江河湖库疏浚工程中管道固液两相流动的研究。 相似文献
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目前,国内的管道环焊缝数字射线检测设备仅能实现静态成像,曝光时间过长,成像结果由多张图像组成,增加了判读工作量和图像评定难度。管道环焊缝X射线数字成像动态采集系统解决了这些问题,采集面板在电机的驱动下沿着轨道匀速行驶,采集图像无缝无重叠地连续实时显示,最终形成一幅完整的管道焊缝扫查图。针对数字射线动态数据采集系统的TDI原理、TDI扫查的时钟同步源、CMOS平板探测器中偏置电压的刷新和面板校准等问题进行详细说明,完成了X射线数字成像动态采集软件的设计和编程,并在管径813 mm、壁厚12.5 mm的管道环焊缝上进行检测试验,采集图像中缺陷清晰可见。 相似文献
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管道瞬变流动控制策略可采用主动控制及被动控制两种方案,综述了包括阀门程控法、最优化方法以及最优控制方法等在内的主动控制策略实现方法及其研究进展。目前,主动控制策略主要应用于简单短管道、简单水力管网等距离较短的系统,它在油气长距离管道输送的运行与控制领域具有广阔应用前景。 相似文献
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分析并提出了管路固体物料输送的一种新的观点,认为在管路输送中应当以输送率而不是输送能耗作为界定管路输送流速的标准,推导出了管道物料输送流速的确定方法,并且在国家重点工程中应用,取得了良好经济效益。 相似文献
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Deep neural networks (DNNs) have recently demonstrated the capability to predict traffic flow with big data. While existing DNN models can provide better performance than shallow models, it is still an open issue of making full use of spatial-temporal characteristics of the traffic flow to improve their performance. In addition, our understanding of them on traffic data remains limited. This paper proposes a DNN based traffic flow prediction model (DNN-BTF) to improve the prediction accuracy. The DNN-BTF model makes full use of weekly/daily periodicity and spatial-temporal characteristics of traffic flow. Inspired by recent work in machine learning, an attention based model was introduced that automatically learns to determine the importance of past traffic flow. The convolutional neural network was also used to mine the spatial features and the recurrent neural network to mine the temporal features of traffic flow. We also showed through visualization how DNN-BTF model understands traffic flow data and presents a challenge to conventional thinking about neural networks in the transportation field that neural networks is purely a “black-box” model. Data from open-access database PeMS was used to validate the proposed DNN-BTF model on a long-term horizon prediction task. Experimental results demonstrated that our method outperforms the state-of-the-art approaches. 相似文献
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Due to the interdependency between multiple infrastructure systems, the performance of a facility may depend on the resources or supplies received from other facilities. However, cross-system interdependence has seldom been studied in the location design context, probably due to the lack of a concise model describing interdependence across heterogeneous systems. This paper proposes a new heterogeneous flow scheme to describe cross-system interdependence. This scheme has two features distinguished from existing models in describing an interdependent facility location problem. First, it is a simple linear model upon which a compact facility location model can be built. Secondly, it relaxes the need to maintain flow conservation between different systems and is suitable in describing heterogeneous systems that take in and output different resources or services. Built on this scheme, this paper proposes a reliable location design model for a nexus of interdependent infrastructure systems. This model aims to locate the optimal facility locations in multiple heterogeneous systems to balance the tradeoff between the facility investment and the expected nexus operation performance. Different from other reliable facility location models, this expected performance captures interdependence among heterogeneous systems due to the resource input-output relationships. The consideration of continuous partial capacity losses complements the reliable location literature that mainly focuses on binary disruptions. Two numerical examples are conducted for investigating features and applications of the proposed model. The results indicate that with a standard off-the-shelf integer programming solver, the proposed model is able to solve optimal facility location design for problem instances of realistic scales to the near-optimum solutions with optimality gap assurance. Sensitivity analyses of key parameters indicate that improving facility capacity and reducing interdependency between systems can mitigate impacts of facility capacity losses and reduce the overall system cost. 相似文献
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《运输规划与技术》2012,35(8):868-880
ABSTRACTAnalysis of elevator traffic in high rise buildings is critical to the performance evaluation of elevator group control systems (EGCS). Elevator dispatching methods or parking algorithms in an EGCS can be designed or modified according to analyses of traffic flow. However, interpretation of traffic flow based solely on numerical data may not be explicit and transparent for EGCS experts as well as for other non-expert building administration. In this study, we present a model for visualization and analysis of elevator traffic. First, we present an alternative approach for traffic analysis which we call route visualization. In the proposed approach, we initially decompose elevator traffic into its component parts and investigate each component independently. Then, using superposition of components we obtain a reconstructed model of overall traffic. This modeling approach provides component-based traffic analysis and representation of routes with intensities through data visualization. In the second part we introduce a multi-dimensional analysis of time parameters in ECGS. This approach provides a comparative analysis of several control algorithms such as dispatch or park algorithms for different combinations of traffic components. 相似文献
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Local departments of transportation and metropolitan planning organizations have been collecting traffic data for many decades.
However, these data are rarely exploited to their full potential. In this paper, we describe an exploratory visualization
toolkit for large traffic flow databases. The visualization toolkit is based on the concept of the traffic cube: an extension
of the data cube in data mining. The traffic cube organizes traffic flow data across different spatial and temporal dimensions
and with respect to user-specified aggregation levels. The toolkit allows the user to perform data cube operations to select,
summarize and cross-tabulate the traffic data prior to visualization as two-dimensional space-time plots. We demonstrate a
prototype system using MATLAB, ArcGIS and MS Access database software. Example visualizations of a large database of hourly
traffic flows along major highways in the state of Utah (USA) over a 10-year period illustrate the potential for the toolkit
to reveal patterns about traffic flows and trends hidden in the database. 相似文献