城市轨道交通车站客流状态采集范围

随着城市化进程的不断推进,迅猛增加的轨道交通客流对客运组织管理提出了更高的要求.目前,虽然多样化的视频采集设备已广泛应用于地铁客流监测中,但是对视频监测范围缺乏统一的标准规范导致监控设备布设随意性大、客流采集无法满足监测需求,鉴于此,开展了对轨道交通车站客流状态数据采集范围的研究.首先,阐述了客流状态采集范围的概念和影...     

双共识混合链跨异构域身份认证方案

针对目前基于区块链的身份认证方案存在节点性能损耗严重的问题,提出一种基于双共识混合链的跨异构域身份认证方案。采用多因子分析方法对基于综合性能的Raft共识算法进行优化,实现了对节点综合性能的合理评估;选出综合性能优异的节点作为跨域节点,可避免因跨域节点性能不佳而引起的系统故障。该方案结合实用拜占庭容错共识机制并引入监督节点,增强了认证系统的拜占庭容错能力,解决了因恶意节点导致的域内错误认证问题。利用SM9广播密码算法对认证过程中的通信数据进行加密,实现了系统的双向认证和保密通信,确保了系统的安全性。实验表明：该方案的双共识认证机制相较于单一共识认证机制,具有较强的拜占庭容错能力和较高的吞吐量,不但能使系统更加安全稳定,而且减少了单对单加解密计算操作,降低了系统的计算开销和时间开销。     

难加工合金材料复杂曲面磁性磨料光整加工技术

磁性磨料光整加工技术是一种非常重要的光整加工技术,与低频振动和超声振动相结合,可实现高精度、高质量和高效率的光整加工。介绍了磁性磨料光整加工、振动辅助磁性磨料光整加工及超声辅助磁性磨料光整加工技术的原理和特点及相关的国内外研究现状。根据难加工合金材料复杂曲面的特点,提出实现复杂曲面磁性磨料光整加工,需要就以下问题开展进一步研究和探索:通过提高加工间隙的磁通量密度及磁能与其他能量复合来提高光整加工效率;建立复杂曲面磁性磨粒光整加工过程控制函数;探讨在磁极工具的空间几何约束作用下复杂曲面磁性磨料光整加工工艺的规划方法等。     

柴北缘陆相页岩压裂返排液水化学和同位素特征

为陆相页岩压裂返排液污染含水层的精准识别,依托柴北缘第1口陆相页岩气勘探井——柴页1井,对比分析页岩气开发区背景地下水、压裂返排液和常规油田卤水(COB)的水化学和同位素特征,探讨压裂返排液污染含水层的标识.研究结果表明:①柴北缘地区极度干旱的气候条件、含水层矿物组成以及陆相页岩的沉积环境,导致海相页岩气田常用的返排液...     

采用谐振腔微扰法的NiZn铁氧体介电常数测量

谐振腔微扰法广泛用于材料微波介电性能的测量,它与常规的测量方法相比,具有样品尺寸小、计算公式简单的优点,在近似计算频率、谐振腔品质因数、材料的介电常数等方面具有较高的应用价值.采用谐振腔微扰法,测量不同配方NiZn铁氧体在微波频段的复介电常数,计算得到介电常数的虚部ε″和实部ε',进而分析Ni和Zn的含量对NiZn铁氧体材料介电常数的影响.     

无水哌嗪合成工艺放大

目的研究放大实验的工艺参数。方法以无水哌嗪合成的小试研究工艺条件为依据,对无水哌嗪合成过程进行工艺计算,以空速为放大参数,采用半经验半理论的放大方法。结果实验得到预热器温度180℃,反应温度360℃,原料流量25L/h,放大条件下合成无水哌嗪的最佳工艺条件。在最佳工艺条件下乙二胺的转化率为91.19%,哌嗪(PA)收率为65.34%,三乙烯二胺(TE-DA)收率为25.74%。结论放大实验结果与小试实验结果吻合良好。     

New material of microfossils from the Ediacaran Doushantuo Formation in the Zhangcunping area, Yichang, Hubei Province and its zircon SHRIMP U-Pb age

The Zhangcunping area is located at the north limb of the Huangling anticline in Yichang, Hubei Province. Here, the sedimentary succession of the Ediacaran Doushantuo Formation is similar with that in the Weng’an area, Guizhou Province. A large number of new microfossils (mainly acanthoacritarchs) from the Doushantuo Formation in this area are reported in this paper. The fossil assemblage shows similarity as the phosphatized biota of the Doushantuo Formation at Weng’an, Guizhou Province and the silicified biota of the Doushantuo Formation at the Yangtze Gorges, which suggests that the Zhangcunping area is a key for correlation of the Doushantuo Formation between the Weng’an area, Guizhou Province and the Yangtze Gorges. Besides, a new zircon SHRIMP U-Pb age (614.0±7.6 Ma) is first obtained from a horizon underneath the exposed surface in the middle of the Doushantuo Formation in the Zhangcunping area. This age not only provides a new datum for subdivision of the Ediacaran Doushantuo Formation, but also indicates that the age of the exposed surface in the middle of the Doushantuo Formation in the Yangtze Platform should be posterior to 614.0±7.6 Ma. Due to the horizon of the Weng’an biota situated above the exposed surface, the age of the Weng’an biota should be posterior to 614.0±7.6 Ma as well. Supported jointly by the Basic Foundation of scientific research work from Ministry of Science and Technology of the People’s Republic of China (Grant No. J0716), Science and Technology of China for fundamental work (Grant No. 2006FY120300-2), National Natural Science Foundation of China (Grant Nos. 40772013 and 40672022) and China Geological Survey (1212010611801-3)     

结构-地基相互作用的频域计算模型

基于比例边界有限元法（SBFEM）建立了结构-无限地基相互作用分析的频域透射边界,这种透射边界精确满足Sommerfeld辐射条件.该方法的特点是可以根据精度需要从低阶到高阶逐步递推计算无限域刚度矩阵,应用简单且十分方便.针对文献中比较常用的各种无限地基计算模型的适应性进行了一定的研究分析.结合无限地基上重力坝的地震响应,对无限地基迟滞效应的影响进行了对比分析,由对比结果可以看出考虑无限地基影响时的坝体最大拉应力分布比常用的无质量地基模型的计算结果约小15%;考虑迟滞效应时最大应力计算结果比不考虑迟滞效应时的计算结果增加了约25%.     

Optimization criteria for the performance of heat and mass transfer in indirect evaporative cooling systems

The wide application of evaporative cooling techniques in which the optimization criteria form the theoretical basis for improving evaporative cooling performance is essential for energy conservation and emission reduction.Based on exergy analysis and the entransy dissipation-based thermal resistance method,this contribution aims to investigate the effects of flow and area distributions in the optimization of the performance of indirect evaporative cooling systems.We first establish the relationships of exergy efficiency,entransy dissipation-based thermal resistance and cooling capacity of a typical indirect cooling system.Using the prescribed inlet parameters,the heat and mass transfer coefficients and the circulating water mass flow rate,we then numerically validate that when the cooling capacity reaches a maximum,the entransy dissipation-based thermal resistance falls to a minimum while the exergy efficiency is not at an extreme value.The result shows that the entransy dissipation-based thermal resistance,not the exergy efficiency,characterizes the heat transfer performance of an evaporative cooling system,which provides a more suitable method for evaluating and analyzing the indirect cooling system.     

Sr-Nd isotope stratification along water depth: An example from Datong hydrological station of Yangtze River

This study examines the effects of hydrologic sorting and mixing of sources on the Sr-Nd isotopic compositions of suspended sediments at different water depths. The samples were collected from three layers (surface, middle and bottom) at Datong hydrological station of Yangtze River during the flood season of 2010. Our results show that, 87 Sr/ 86 Sr values decrease from surface to bottom, ranging from 0.730332 to 0.720857. ε Nd (0) values range from 14.75 to 10.09, with surface sediments being the most negative. The isotope composition at the middle layer can best represent the mean isotopic composition of the total suspended sediments transported by a river. It is believed that the stratification of Sr-Nd isotope is attributable to mixing of sediments from different sources due to hydrological sorting. Sediments from the upper stream are found to be coarser, and tend to contribute more to the lower water column. Although Sr-Nd isotope is a well acknowledged tool to trace sediment provenance, the current study suggests that the grain size of the samples and the sampling locations should be taken into consideration when applying this method to provenance study.