Applications of computer vision on tile alignment inspection

Subjective visual inspection is the main quality measure for tile alignment acceptance because of a lack of standard operation procedures in Taiwan. Without quantitative specifications for tile alignment, inspectors can easily manipulate the outcome; therefore, fine craftsmanship is not valued, resulting in considerable quality variation in tile installation works. This paper proposes an automated tile installation quality assurance prototype system that uses computer vision technologies. The system receives digital images of finished tile installation and has the images processed and analyzed to capture the geometric characteristics of the finished tile surface. The geometric characteristics are subsequently evaluated to determine the quality level of the tiling work. Application of the proposed automated system can effectively improve the tile alignment inspection practice and simultaneously reduce improper manipulation during acceptance procedures.     

Effects of anchoring tensile stresses in axially loaded plates and sections

Thin-walled compression members are commonly designed on the assumption that the loaded edges remain straight. Under this assumption, tensile stresses develop in the most flexible parts of the component plates at advanced local buckling deformation, and thus are assumed to be ‘anchored’ at the ends. However, current design rules for plate elements, such as the Winter formulae, are partly based on tests in which the load was applied by use of rigid platens that did not permit tensile stresses to develop. There exists an apparent inconsistency between the assumption of straight loaded edges and the use of a design curve calibrated from tests in which the loaded edges of component plates may not have remained straight.This paper addresses this apparent inconsistency by comparing finite element solutions for the conditions of straight loaded edges and loading by use of a contact surface between the plate edge and a non-deformable rigid body end platen, where there is no constraint for the plate edge to remain in contact with the rigid body. Solutions are provided for a single half-wavelength of unstiffened and stiffened plate elements simply supported along three and four edges, respectively. The effect of multiple half-wavelengths is also investigated, as is the effect of interaction between elements in practical sections comprising stiffened and unstiffened elements.     

全站仪配CAD定线在路网改造项目中的应用

针对路网项目中受征地拆迁条件的影响 ,线形调整余地不大的具体情况 ,介绍了用全站仪配CAD定线的方法。指出该方法简便易行 ,经实践检验能有效提高工效。     

异型拱桥顶系梁安装吊杆的施工分析与监测

针对全钢异型拱桥的受力特点,提出一种简单适用的顶系梁安装吊杆的施工方法。通过对1座机耕桥工程实例的计算分析及现场监测比较发现,该方法可以简单快捷地使吊杆获得合理的初张力,并使主梁线形满足设计要求。成桥后,顶升点附近的吊杆索力远大于其他吊杆索力,并承担了全桥主要恒载及活载。     

一种基于 Sobel 算子的小波与 IHS 遥感影像融合算法

针对IHS图像融合算法中颜色畸变比较明显的问题,提出一种新的基于小波与IHS相结合的遥感影像算法.经IHS变换的多光谱影像Mul的I分量与全色影像Pan由二维离散小波分解,对小波高频和低频分量采用不同融合规则:低频分量采用绝对值加权平均的方法,把两者的低频系数按其权值比例合成到新的分量I1中;高频系数采用基于区域分块的Sobel算子的绝对值取大. 实验结果与IHS法、传统小波与IHS结合法相比较,该算法能获取更多的光谱信息,人眼视觉效果也较好.     

Evaluation of image-based modeling and laser scanning accuracy for emerging automated performance monitoring techniques

Accurate and rapid assessment of the as-built status on any construction site provides the opportunity to understand the current performance of a project easily and quickly. Rapid project assessment further identifies discrepancies between the as-built and as-planned progress, and facilitates decision making on the necessary remedial actions. Currently, manual visual observations and surveying are the most dominant data capturing techniques but they are time-consuming, error-prone, and infrequent, making quick and reliable decision-making difficult. Therefore, research on new approaches that allow automatic recognition of as-built performance and visualization of construction progress is essential. This paper presents and compares two methods for obtaining point cloud models for detection and visualization of as-built status for construction projects: (1) A new method of automated image-based reconstruction and modeling of the as-built project status using unordered daily construction photo collections through analysis of Structure from Motion (SfM); (2) 3D laser scanning and analysis of the as-built dense point cloud models. These approaches provide robust means for recognition of progress, productivity, and quality on a construction site. In this paper, an overview of the newly developed automated image-based reconstruction approach and exclusive features which distinct it from other image-based or conventional photogrammetric techniques is presented. Subsequently the terrestrial laser scanning approach carried out for reconstruction and comparison of as-built scenes is presented. Finally the accuracy and usability of both of these techniques for metric reconstruction, automated production of point cloud models, 3D CAD shape modeling, and as-built visualizations is evaluated and compared on eight different case studies. It is shown that for precise defect detection or alignment tasks, image-based point cloud models may not be as accurate and dense as laser scanners' point cloud models. Nonetheless image-based point cloud models provide an opportunity to extract as-built semantic information (i.e., progress, productivity, quality and safety) through the content of the images, are easy to use, and do not need add burden on the project management teams by requiring expertise for data collection or analysis. Finally image-based reconstruction automatically provides photo alignment with point cloud models and enables image-based renderings which can remarkably impact automated performance monitoring and as-built visualizations.     

Digital image analysis of fluid inclusions

Fluid inclusions commonly exist in the cracks of rock masses. From a microscopic point of view, the fluid inclusion plane (FIP) is the crack plane while the fluid inclusion line (FIL) is the intersecting line between a specific plane (horizontal or different) and the FIP. These microscopic compositions or structures not only provide valuable information on the deformations and/or fractures of rocks but also reflect the trend, length and width of cracks. This paper presents the digital image analysis of fluid inclusions in rocks and discusses the characteristics of FILs. For the image analysis, the original digital images photographed by the microscope equipped with a digital camera on a heating–freezing platform were first converted into grayscale images and then broken into blocks using quadtree decomposition and region segmentation. For each block, the inflection point, derivative, frequency and color-based methods were used to detect the edges of fluid inclusions. To better define the boundaries of fluid inclusions, the dilation, erosion, seed filling, boundary connection and smoothing techniques were used to, respectively, extend edges, connect discontinuous points, fill pores in the outlines, eliminate irrelative parts in neighboring positions, smoothen projecting parts around the outlines and aggregate smaller inclusions into larger ones. After the boundaries of fluid inclusions were defined, the blocks were re-assembled and the edge points and lines of fluid inclusions were then defined in a global coordinate system. Based on the geometrical properties of the fluid inclusions, such as the centroid positions, areas and long-axis directions, FILs and their configuration parameters (such as length, mean width and abundance) were obtained with the least-squares method. All of these procedures were coded into a program and could be automatically run. The digital image analyses of fluid inclusions may provide valuable information about the relationships between the FIL networks and the crack properties.     

A sequential exploration algorithm for the design optimization of horizontal road alignment

Most computer-aided optimization procedures for horizontal alignment optimization of roads require the use of information such as horizontal points of intersection (PIs) to determine an alignment. In these methods, to obtain parameters such as the radius of the curve corresponding to a specific PI, the previous and next PIs must be known. In this paper, a sequential exploration algorithm (SEA) is proposed, and the algorithm continuously explores the entire optimization space through certain steps. Only the parameters of the previous node are required to determine the current node's parameters during the exploration process, avoiding the tight coupling between PIs in traditional optimization algorithms. Furthermore, the proposed SEA does not require assumptions about the positions and numbers of the PIs, and it can design near-optimal road alignments that match geometric restrictions and automatically take transition curves into account. Another feature of the proposed algorithm is that it directly optimizes the geometric element parameters based on the actual milepost, and it is a fully collaborative optimization approach that does not require secondary optimization nesting during the optimization process. Analyses comparing the optimization effects of different algorithms are performed on a numerical case, that is, a problem of avoiding obstacles, and two actual cases from the literature, that is, a new road design problem and an existing road reconstruction problem. It is discovered that the proposed SEA results in an approximately 3% to 10% improvement in optimization effects when compared to two current cutting-edge optimization algorithms. This work offers a new perspective on road alignment optimization by merging discrete and continuous optimizations, with a discrete component handling optimization accuracy and a continuous component handling real optimization.     

Einfluss des Verlustfaktors auf die Schalldämmung von Lochsteinmauerwerk

Effect of loss factor on the sound insulation of hollow block masonry. Sound insulation is known to depend on the loss factor. In solid construction elements the loss factor is largely determined by the energy transfer to adjacent construction elements via the edges, so that the installation conditions influence the sound insulation. This effect is taken into account in the calculation models of EN 12354 through the so‐called in‐situ correction, whereby the overall loss factor of a component tested in the laboratory is converted to an expected loss factor in a real building. This paper illustrates how the loss factor correction should be applied for vertically perforated bricks with possible resonance frequencies from around 800 Hz. It was found that the correction can basically be applied in the same way as for homogeneous masonry, but only up the first resonance frequency of the brick. For higher frequencies the sound insulation was found to be independent of the installation conditions, so that in this range no loss factor correction should be applied.     

Image-based 3D scene reconstruction and exploration in augmented reality

Augmented Reality (AR) is an integrated technique of image processing and display system of complex information, which involves real-time computing, motion tracking, pattern recognition, image projection, database linking, feature extraction, and coordinate transformation. In this study, such techniques through Structure From Motion (SFM), Clustering Views for Multi-View Stereo (CMVS), Patch-based Multi-View Stereo (PMVS), and Poisson surface reconstruction were smoothly integrated into a 3D reconstruction system with comparative efficiency in computation. The system can be applied to regular images taken by amateur cameras, smart phones, tablet PCs, and other mobile devices, without need of a priori internal and external camera parameters. To verify the ability of the established reconstruction system, indoor and outdoor objects at various scales, such as a helmet (a small object), a corridor (an indoor medium object), an arbor (outdoor medium object), and a building (outdoor large object) were tested. Through tracking and registration, the reconstructed 3D models were loaded in an AR environment to facilitate displaying, interacting, and rendering that provides AR applications in construction design and management for better and qualitative communication in economical and handy ways.     

武昌车站改扩建工程钢柱筒吊装技术

武昌车站改扩建工程候车室采用新型的焊接敞口槽形钢箱梁形式,为了实现混凝土柱与钢梁连接的转换,选用了钢板拼焊而成的钢柱筒结构.钢柱筒重达8t且有众多钢筋从钢柱筒中的两层加劲板穿过,施工难度较大.为了使钢筋能顺利穿过钢柱筒,采用钢导向管的安装方式,安装迅速且安全,取得了良好的效果.同时对先装钢柱筒与后装钢柱筒这两种安装方法进行对比,选用后装钢柱筒的方法进行施工.经过实践检验,安装方法成功有效.具体施工过程中使用独臂拔杆吊装钢柱筒,可以解决部分位置的钢柱筒无法采用大型机械设备安装的问题.     

国家体育场(鸟巢)钢结构桁架柱安装技术

国家体育场(鸟巢)的构件截面均为箱形截面,且空间位置复杂。其桁架柱截面大,单体重量重,整根柱吊装难度大。通过合理设计施工器械,精确计算施工数据,采取分段安装、双机抬吊等施工方法,按时保量地完成了桁架柱的安装。     

青岛北客站复杂巨型倒三角箱型构件高空安装技术

青岛北客站站房屋脊主梁为高5m、宽3.8m,带有大量接口、孔洞及拉杆的复杂巨型倒三角箱型构件。构件设计独特新颖,位于站房中轴线之上,结构上所有屋盖结构都以此为中心建造,且由于截面异形、尺寸巨大、施工条件复杂等因素,施工难度极大。通过研究此巨型构件安装过程中的吊装计算、安装方法、工况分析及安全质量措施,探讨巨型钢构件高空安装技术。     

A Von Neumann-Morgenstern interpretation of the weighting factors in a valuewise-independent utility function

The possible eventualities in decision problems are often multi-attributed. The task of assigning utility functions to such eventualities can be considerably simplified if the property of valuewise-independence extends over the utility field or can be assumed to do so. This allows component utility functions to be constructed and the composite utility function assembled from these components with appropriate scaling. The component utility functions are often scaled between zero and unity and weighting factors attached to each to restore the correct scaling.

The interpretation of these weighting factors has often been misleading and the various methods suggested for their determination have not been related to the fundamental notions of utility theory, the Von Neumann-Morgenstern axioms. The object of this paper is to demonstrate that the determination and interpretation of these weighting factors can be achieved in terms of the utility axioms. This connection might also facilitate the construction of appropriate utility functions.     

Free-form thick layer object manufacturing technology for large-sized physical models

Large-sized free-form objects of different materials are widely used in various industrial applications. Currently, layered rapid prototyping technologies are not suitable for the fabrication of this kind of objects, due to the necessity of a large number of layers and the limitations in size. This paper reports a novel approach of layered manufacturing that is more appropriate for the fabrication of these large objects. A method of thick-layered object manufacturing is presented, which is based on a higher order approximation of the shape and application of a flexible curved cutting tool.The method allows the production of physical prototypes, which need little or no finishing. In order to meet the designer's intend, as closely as possible, some feasible system characteristics are introduced. The process is ordered in a sequential way and provides a highly automated process. A hierarchical decomposition of the CAD geometry takes place into components, segments, layers and sectors, based on morphological analysis. This method enables the manufacturing and the re-assembly of the parts to produce the physical prototypes without affecting the requested functionality. Due to the possibility of obtaining multiple solutions in the physical model, much attention must be paid to the efficiency of the process.     

Spiral Spline Curves for Highway Design

Techniques for automating the design of highways are examined. It is accepted design practice to reduce the straight-line parts of the horizontal alignment of a designed center line as much as possible. This can be accomplished manually by using clothoid templates. This article describes the use of spiral splines that behave in a manner such that the horizontal alignment may be automatically designed as a composition of clothoid segments. The resulting methods are suitable for microcomputer implementation.     

Evaluation of round-robin testing using the PASLINK test facilities

The IQ-TEST Thematic Network has carried out round-robin tests at ten of the PASLINK outdoor test cell facilities. A round-robin test generally produces a clear picture of the overall quality of certain test procedures carried out by the participating organisations. For practical considerations, each organisation constructed its own components according to strict instructions regarding the selection of materials, manufacture and instrumentation. Two components of different levels of complexity were designed: (1) an opaque, homogeneous wall with a removable central section, and (2) a window, which is used to replace the central section of the first component. Using recommended dynamic test procedures and appropriate identification methods, each participant determined the thermal performance of the components. Good agreement between sites was achieved for the U-value of the opaque wall. A range of U-values was obtained for the window; however, the variation can be largely accounted for by variations in the boundary conditions between sites, e.g. wind speed and ambient temperature. For future components the test sequence and analysis methods should account for such non-linear behaviour, in order to estimate thermal and solar performance characteristics for appropriate standardised boundary conditions.     

Two algorithms for reconstructing vertical alignments exploring the neural dynamics model of Adeli and Park

Vertical alignment reconstruction obtains alignment parameters by fitting geometric components to a set of measured points representing the profile of an existing road or railroad, which is essential in alignment consistency analysis and maintenance to ensure safety and comfort. The neural dynamics model of Adeli and Park is explored and improved for reconstructing vertical alignments with constraints. The structure of the dynamics model is modified to include three layers: parameter layer, intermediate layer, and energy layer. The number of nodes in the parameter or intermediate layers corresponds to the number of independent parameters defining a vertical alignment. The number of nodes in the energy layer is the sum of the number of deviations and the number of constraints in the alignment reconstruction problem. The coefficients connecting nodes between the parameter layer and the intermediate layer determine the integral operations, which define the Levenberg–Marquardt algorithm of the dynamics model (LMADM) and the steepest descent algorithm of the dynamics model (SDADM). Both the LMADM and SDADM methods satisfy the Lyapunov stability theorem, but the LMADM method outperforms the SDADM method in its objective function value and computation time. Experiment results demonstrate that there are multiple local optima for a vertical alignment reconstruction, and the solutions obtained by the LMADM method are the best obtained so far, compared with those reported in the literature, with 57.1% and 23.4% decreases of the mean squared error for the highway and the railroad examples, respectively.