Error Analysis of Liquid Holdup Measurement in Gas-Liquid Annular Flow Through Circular Pipes Using High-Speed Camera Method

Accurate measurement of gas-liquid phase fraction is essential for the proper modelling of the pressure drop, heat transfer coefficient, mass transfer rate and interfacial area in two-phase flows. In this paper, taking the issue of optical distortion into account, an analytical model was proposed to estimate and correct the liquid holdup in gas-liquid annular flow through a circular pipe using high-speed camera method. The error in the liquid holdup measurement generated from different refractive indices among transparent circular pipe, liquid film and air core was firstly theoretically analyzed based on the geometric optics. Experimental tests were then carried out to identify the difference as well as to validate the proposed model. Results indicated that the prediction of the liquid holdup has a good performance with the experimental data (i.e., mean relative error is 4.1%) and the measured liquid holdup is larger than the real one. It was found that the measured liquid holdup is larger than the real one. Generally, when the real liquid holdup gets smaller, the discrepancy between the measured liquid holdup by image and the real liquid holdup becomes more significant. Thus, after measuring the liquid holdup from the images, the value of the measured liquid holdup must be corrected by the present model in order to obtain the real liquid holdup.     

不同驾驶操作方法下的汽车运行燃料消耗量分析

为了规范汽车驾驶操作,提高汽车行驶的经济性,本文按照汽车驾驶操作的流程,针对驾驶员普遍存在的驾驶节能操作认识误区,对汽车起步、换挡变速、加减速、车速控制和变更车道等驾驶操作开展研究,并利用实际道路试验和发动机台架试验进行燃料消耗量对比分析,总结了"轻踩缓抬"加速踏板、保持经济车速行驶、一脚离合配合换挡、避免"频繁变更车道、急加速和急减速"等驾驶节能操作方法。本文的研究将为广大驾驶员朋友和道路运输企业开展驾驶节能操作训练提供借鉴。     

Detecting Premature Ventricular Contraction in Children with Deep Learning

Premature ventricular contractions (PVCs) are abnormal heart beats that indicate potential heart diseases. Diagnosis of PVCs is made by physicians examining long recordings of electrocardiogram (ECG), which is onerous and time-consuming. In this study, deep learning was applied to develop models that can detect PVCs in children automatically. This computer-aided diagnosis model achieved high accuracy while sustained stable performance. It could save time and repeated efforts for physicians, enabling them to focus on more complicated tasks.This study is a first step toward children’s PVC auto-detection in clinics. Further study will improve the model’s performance with optimized structure and more data in different sources, while facing the challenges of the variety and uncertainty of children’s ECG with heart diseases.     

生命周期评价在汽车能源与排放评估中的应用

本文对国内外生命周期评价在汽车能源与排放评估中的应用现状进行综述,并对汽车生命周期评价未来的发展趋势进行了展望,能够从方法上实现对汽车节能减排效果的科学评价,为我国汽车及其替代燃料的发展提供决策依据。     

三峡库区下洛碛库段消落带生态护岸方案

三峡库区重庆渝北区下洛碛土质库段消落带因近岸采砂形成水下深槽,受江水冲刷库岸造成岸坡崩塌导致库岸线不断后移,区内生境已呈现不可逆转的破坏。为寻求一种兼顾环境、生态与经济的综合治理方案,通过现场勘察,在查明消落带地形地貌、岩土体特征、水文地质特征等的基础上,提出传统斜坡生态护岸和特拉锚垫生态护岸2种方案,并从施工工艺、护岸效果、生态恢复效果、施工周期、施工场地条件和后期养护成本共6个方面对比了2种方案的优缺点。结果表明,特拉锚垫生态河道系统护坡方案因其施工工艺简单、植物易活绿化覆盖率高、满足岸坡对江水侵蚀作用的防治需求等优势,更适合类似下洛碛库段消落带的江河湖泊和库区消落带土质和硬质岸坡的生态修复需求,可推广应用。     

日本超低地板轻轨车的开发

仅采用国外产品或用国外技术制造的车辆,不能实现日本国内路面电车的超低地板化."ARUNA车辆(株)"独立开发了"little Dancer"系列车辆.这种车辆采用日本国产转向架、机电设备,是日本独自开发的首批纯国产超低地板轻轨车.介绍这种系列车辆的开发经过及车辆的技术概况.     

旋喷桩法在老桥桩基缺陷加固中的应用

文章结合工程实例,从方案的选择、原理、工艺流程、施工要点、质量检验方法等六个方面详细介绍了旋喷桩对老桥有缺陷桩基础的加固处理方法,该方法对维修基础缺陷来说是简单、经济和行之有效的,值得类似工程借鉴。     

趋势预测法在公路工程造价管理系统中的应用研究

将数量统计趋势预测的数学方法应用于公路工程造价管理系统中,采用分段曲线拟合,选择最优的模型预测造价发展趋势,实现造价预测功能,为提高公路建设投资效益提供有效技术支持。     

浅析我国国债发行制度的弊端

国债是连接财政政策和货币政策的桥梁,而我国的国债发行制度存在种种弊端,不利于经济的发展。本文从建国后中国的国债发行历史和现状中找寻国债发行制度存在的弊端,建议从国债的发行额度、发行对象、发行方式、发行时间及发行凭证形式等制度安排上减少风险,减少成本,增加效益,为国债发行制度的完善指明方向。