Prediction of the crack condition of highway pavements using machine learning models

Departments of Transportation regularly evaluate the condition of pavements through visual inspections, nondestructive evaluations, image recognition models and learning algorithms. The above methodologies, though efficient, have drawn attention due to their subjective errors, uncertainties, noise effects and overfitting. To improve on the outcomes of the shallow learning models already used in pavement crack prediction, this paper reports on an investigation of the use of recursive partitioning and artificial neural networks (ANN; deep learning frameworks) in predicting the crack rating of pavements. Explanatory variables such as the average daily traffic and truck factor, roadway functional class, asphalt thickness, and pavement condition time series data are employed in the model formulation. Overall, it is observed that the recursive partitioning (regression tree – R² > 0.8 and classification tree – R² > 0.6) and ANN (continuous response – R² > 0.8 and categorical response – R² > 0.6) are compelling machine learning models for the prediction of the crack ratings based on their goodness-of-fit statistics, mean absolute deviation (MAD < 0.4) and the root mean square errors (RMSE between 0.30 and 0.65).     

微机械差动电容压力传感器的研究

文中介绍以Ｎ型单昌硅为基底,利用微机械加工研制而成的一种中央上举开放式差动电容压力传感器的结构及其设计。     

进口工业设备液压润滑系统管道的安装

重点介绍了进口大型冶金、加工设备的液压润滑系统管路安装时,如何与国内技术标准,施工方法打结合以达到设备所要求的精度以及施工时应注意的问题。     

浅谈建筑给排水设计中的常见问题与解决措施

随着人民生活水平的不断提高,我国建筑业的迅速发展,为满足居民对高品质住宅的需求,要求建筑设计和施工具有更多的适应性、灵活性,要求赋予住宅更高的科技含量和文化内涵.建筑给排水设计技术也日趋完善,给排水设计是建筑设计的一个很重要的方面,,同时与人们的日常生活也是密切相关,因此其设计过程中应本着实用、安全、经济的原则.现对其的发展现状进行了介绍及常见问题时行了分析探讨,并提出一些解决办法.     

Distribution of respiratory droplets in enclosed environments under different air distribution methods

The dispersion characteristics of respiratory droplets are important in controlling transmission of airborne diseases indoors. This study investigates the spatial concentration distribution and temporal evolution of exhaled and sneezed/coughed droplets within the range of 1.0 − 10.0μm in an office room with three air distribution methods, specifically mixing ventilation (MV), displacement ventilation (DV), and under-floor air distribution (UFAD). The diffusion, gravitational settling and deposition mechanism of particulate matter were accounted by using an Eulerian modeling approach with one-way coupling. The simulation results indicate that exhaled droplets up to 10μm in diameter from normal human respiration are uniformly distributed in MV. However, they become trapped in the breathing zone by thermal stratifications in DV and UFAD, resulting in a higher droplet concentration and an increased exposure risk to other room occupants. Sneezed/coughed droplets are more slowly diluted in DV/UFAD than in MV. Low air speed in the breathing zone in DV/UFAD can lead to prolonged human exposure to droplets in the breathing zone.     

高边坡压力分散型预应力锚索施工工艺研究

压力分散型预应力锚索由于具有较多优点而在复杂高边坡加固工程中应用越来越广泛，施工中结合边坡岩体性质和设备条件科学合理的选择施工工艺是其取得理想效果的关键环节。本文结合金丽温高速公路17标段工程实例，从施工组织、现场试验、钻孔、注浆、张拉、监测等方面对压力分散型预应力锚索施工工艺作了详细论述，为类似工程提供一些借鉴经验。     

锈蚀钢筋混凝土梁抗弯刚度评估方法研究

为合理评估锈蚀钢筋混凝土梁的变形能力,对影响锈蚀混凝土梁抗弯刚度退化的因素进行系统分析,明确锈蚀引起粘结力退化使裂缝间受拉钢筋应变趋于均匀和钢筋应变与混凝土应变不协调是影响锈蚀混凝土梁抗弯刚度计算模型建立的关键因素;抛弃传统的平截面假定,采用刚度解析法对粘结力退化后构件截面刚度进行了理论分析,引进综合应变系数考虑裂缝间钢筋应变趋于均匀和应变不协调的影响,建立了锈蚀钢筋混凝土梁抗弯刚度的计算模型;通过有限元数值分析,确定了综合应变系数与粘结强度退化系数的关系;经试验验证,模型计算结果与试验结果吻合较好。     

深圳机场1号航站楼改扩建工程的空调设计

介绍了该航站楼空调设计的特点,重点阐述了空调方式、防排烟、空调自控及节能等方面的设计.分析了变频控制在空调节能运行中的重要性,强调了排风系统在通风空调系统中的作用.     

Experimental study on the influence of soluble salt content on unsaturated mechanical characteristics of undisturbed Ili loess

Bulletin of Engineering Geology and the Environment - Due to the perennial influence by west wind climate, the loess in Ili, China, is obviously different from that in the loess plateau of the...     

The role of UV-B on the degradation of PCDD/Fs and PAHs sorbed on surfaces of spruce (Picea abies (L.) Karst.) needles

Photodegradation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs) sorbed on surfaces of spruce (Picea abies (L.) Karst.) needles was investigated. The role of sunlight and, in particular, the role of short wavelength UV-B radiation were studied in a sun simulator under controlled environmental conditions. The photodegradation of PCDD/Fs and PAHs follows first-order kinetics. Simulated sunlight containing UV-B induced two phases of photodegradation kinetics for PCDD/Fs, whereas no distinct phases of the kinetics were observed for PAHs. UV-B radiation plays a much more important role on the photodegradation for PCDD/Fs than that for PAHs. Direct photolysis dominates the photodegradation of PCDD/Fs and PAHs.