基于图像识别的结构物变形监测算法研究与应用

当前视频监控已经覆盖了桥梁、隧道等重要交通基础设施的施工、运维全过程,为了进一步挖掘视频监控数据潜在的价值,发挥视频监控主动安全管理的能力,满足交通基础设施结构物安全状态自动识别与管控的需求。利用智能传感、图像识别技术与信息化技术,分析基于图像识别的结构物变形监测方法基本原理,开发基于图像识别的结构物变形监测算法,搭建基于图像识别的结构物变形监测系统,确定图像监控设备的性能与系统软件的功能要求。通过对比分析结构物不同时间下的监控图像特征,通过对特征像素点的变化来测量结构物体表面的变形,为结构物的状态安全提供保障。

地面沉降对公路交通工程的影响

我国的地面沉降灾害在逐年加剧,在一些局部漏斗区已危及到公路交通工程的安全。自1997年起交通部公路科学研究所对国内某重点高速公路的工程结构物进行逐年定期监测,发现工程结构物随地面沉降的持续呈现显著的竖向变形,最大年速率达-20mm/a。

Prediction of Buckling of Plain Knitted Fabric Sheets Subjected to Simple Shear in Wale Direction

Knitted fabric is very different from woven fabric due to its more complicated knitting structures. The buckling of knitted fabric sheets subjected to simple shear in the wale direction is investigated analytically in consideration of the large deformation of fabric sheet in critical configuration. The theory on instability of finite deformation is applied to the analysis. All the stress boundary conditions of knitted fabric sheet are satisfied. An equation to determine the buckling direction angle is derived. It is shown that there are two possible buckling modes, flexural mode and barreling mode. The buckling condition equations for the flexural mode and barreling mode are also obtained respectively. Numerical illustrations reveal that only the flexural mode can actually occur and the barreling mode cannot, which agrees with the experimental observations. For a permitted buckling mode on margin boundaries, the critical value of shear amount and the buckling direction angle can be determined.

Deformation Analysis Due to Early Loading of Concrete Buildings

The building industry has experienced in recent years a strong growth in demand in general and in the case of reinforced concrete buildings this increase has been more marked. This fact has also contributed to accelerate all stages of the production process of these constructions with more pronounced effects on the methodologies used in the constructive steps that influence directly the structural design of the building. Structures loaded at ever earlier ages, in which the strength and deformation properties of materials are not yet sufficiently mature. It is a variable that needs to be taken into account already in the design phase so that the concrete structure behaves within acceptable level of reliability taking into account design code recommendations for service life. To understand the importance of constructive effects and to assess its magnitude in the execution of reinforced concrete buildings, this paper presents result from nonlinear analyses using finite element method adopting an approach commonly referred as staged construction applied to a typical building found in the practice. The effects of creep and shrinkage were considered and the results obtained demonstrate that the strains due to constructive effects can, in certain cases, assume representative values which, if ignored, can lead to important pathologies in the building.

The role of volatiles and coal structural variation in coal methane adsorption

We investigated the role of volatiles in the porous structure of coal samples and the corresponding structural deformations that affect the coals＇ methane adsorption capacity. For this study, the volatiles in coal were gradually removed by extraction. Changes in the crystal, textural, and porous structures were identified by means of thermogravimetric analysis, X-ray diffraction, and N2 adsorption/desorption. Changes in the methane adsorption behavior before and after volatile removal were investigated. It was found that changes in methane adsorption could be attributed to volatile-related deformations in the coal＇s porous structure. Microstructural characterizations indicated that the volatiles could be found in two states within the coal, either trapped in the pores, or cross-linked in the network. The former played an important role in constructing the pore spaces and walls within the coal and affected the accessibility of gases. The latter cross-linked state retained the volatiles within the macromolecular coal structural network. This state affected coal-coal interactions, which was a factor that controlled the crystal structure of coal and contributed to the number of porous deformations.

Microstructure, morphology, crystallization and rheological behavior of impact polypropylene copolymer

Impact polypropylene copolymer (IPC), named polypropylene catalloy, not only possesses excellent impact property, but also presents good rigidity. Its superior performances result from the complicated composition and microstructure. In the present article, recent progress in the studies on microstructure, morphology, crystallization and rheological behavior of IPC is summarized, and findings of the authors and their collaborators are reported. In general, IPC is divided into three components, i.e., ethylene-propylene random copolymer (EPR), a series of different segment lengths ethylene-propylene copolymer (EbP) and propylene homopolymer. The reasonable macromolecular structures of EbP and a multilayered core-shell model of dispersed phase structure in IPC were proposed, in which the dispersed phase consists of an outer EbP shell, an inner EPR layer and an EbP core. It is found that the annealing at melt-state may lead to an abnormal phase inversion, and the phase inversion disappears when temperature cools down to room temperature. The cause of phase inversion is ascribed to the existence of EbP component, which results in the stronger activity of the dispersed phase. The crystalline structure and morphologic results confirm the formation of β-iPP in IPC. Furthermore, it is found that the ethylene content in IPC and cooling rate of the samples have an important influence on the formation of β-iPP. Based on the crystallization kinetics analyzed by Lauritzen-Hoffman theory, crystallization behavior of different IPC samples is discussed and it is proposed that the dilution effect of ethylene propylene copolymer has a more remarkable influence on surface nucleation than on crystal growth. In addition, annealing at high temperature can result in the changes of chain structure for IPC, and this instability is ascribed to the oxidative degradation and crosslink reaction mainly in iPP component.