Application and Analysis of Computer Vision Algorithms in Graphics and Image Processing

After decades of research by researchers, there have been many mature algorithms and systems that can meet the requirements for the application of computer vision algorithms in many fields. There are applications of computer algorithms in many industries, such as car navigation, video detection, industrial production and other industries. Most industries have synchronization requirements in terms of time, that is, real-time. Because of the limitation on the amount of calculation, many realtime vision systems will use the local window algorithm, but the image quality generated by the local algorithm and the image quality generated by the global algorithm have a large gap. According to the latest research results, if you use precisely adjusted matching calculation and collection methods, the local algorithm is as good as the global algorithm in terms of matching rate. This article mainly takes UAV as the research object, and studies the UAV's processing function of graphics and image based on computer vision algorithm. The research content mainly includes the single passage of the UAV in different environments of straight lines, corners, and slopes, and the passage of the UAV in the overall process. Through the application of computer vision algorithms in the UAV's graphics and image processing process, the experimental data is analyzed and the corresponding conclusions are drawn

Numerical simulation of ram extrusion in short-fiber-reinforced fresh cementitious composites

This is the author's accepted manuscript. The final published article is available from the link below. First published in JoMMS in 4(10), 2009, published by Mathematical Sciences Publishers.A series of ram extrusion tests was carried out on a short-fiber-reinforced, semisolid, fresh cementitious composite. An elastoviscoplastic constitutive model is proposed for the extrudable fresh cementitious composite. It features the associative flow rule, a nonlinear strain rate-hardening law, and the von Mises yield criterion. The model is then implemented in ANSYS/LS-DYNA explicit finite element code. Various ram extrusion processes of the fresh cementitious composite were simulated. It has been found that the extrusion load versus imposed displacement predictions agree well with the experimental results. The fresh paste flow, through the die entry and the die-land, is then interpreted in light of the evolution of the deformation and distribution of state variables, mainly based on numerical results and the ram extrusion mechanism. The effects of extrusion ratio and extrusion velocity on extrusion load are also investigated, based on the mechanical properties of the fresh cementitious composite. The study indicates that the numerical procedure established, together with the constitutive model proposed, is applicable for describing ram extrusion of short-fiber-reinforced fresh cementitious composites, which might provide a numerical rheometric tool from which ram extrusion of elastoviscoplastic paste-like materials can be examined and quantified.Hong Kong Research Grant Council and China Ministry of Science and Technology

Finite-Element Analysis of Shear-off Failure of Keyed Dry Joints in Precast Concrete Segmental Bridges

This article has been made available through the Brunel Open Access Publishing Fund.The structural behaviour of precast concrete segmental bridges is largely dependent on the behaviour of the joints between segments. The current practice is to use small keys that are usually unreinforced, distributed over the height of the web and the flange of concrete segments and these keys are normally dry. In this study, a numerical analysis model was established based on ABAQUS finite element code to investigate structural behaviour of keyed dry joints under direct shear. The concrete damage plasticity model along with the pseudo-damping scheme were incorporated to analyse the system for microcracks and to stabilize the solution, respectively. The numerical model is calibrated by full-scale experimental results published elsewhere. It was found that the predicted ultimate load, cracking evolution history, and final crack pattern agree reasonably well with experiment results. The validated numerical model was then employed for parametric study on factors affecting shear behaviour of keyed dry joints, in this case confining pressure. It has been found that shear capacity predicted by AASHTO diverges from that predicted by numerical analysis at high confining pressure because the contribution of friction in the total shear capacity reduces with the increase in confining pressure. Hence, it is recommended to reduce the friction coefficient used in AASHTO code when high confining pressure is applied. Moreover, the propagation of inclined crack is arrested at high confining pressure due to the fact that the fracture propagation direction is governed by the criterion of the maximum energy release rate

β-Elemene alleviates bone cancer-related pain in rats by modulating N-methyl-D-aspartate receptor 2B subunit

Purpose: To investigate the effect of β-elemene on bone cancer-related pain (BCRP) and its underlying mechanism in a rat model.Methods: A rat model of BCRP was established by injection of Walker 256 cells into the medullary cavity in adult male Sprague-Dawley rats. The effects of β-elemene on pain-related behaviours were assessed by paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL). Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to analyse the transcription and translation levels of N-methyl-D-aspartate receptor 2B subunit (NR2B), respectively.Results: This study found that PWMT and PWTL were significantly decreased in rats as evidence of successful establishment of a rat model of BCRP. Behavioral test showed that β-elemene treatment could attenuate pain-related behaviours. This analgesic effect began 1 h after drug injection, reached the highest value at 2 h, declined at 4 h, and disappeared by 24 h. qRT-PCR and western blotting indicated that intrathecal administration of β-elemene down-regulated mRNA and protein levels of NR2B.Conclusion: The results show that β-elemene alleviates behaviours related to pain in a rat model of BCRP probably by modulating NR2B, thus indicating a new potential treatment method for cancerrelated pain.Keywords: β-Elemene, Bone cancer, Pain relief, N-methyl-D-aspartate receptor 2B subunit (NR2B), Sensitisatio

Influence of Early Oven Curing on the Alkali Activated Binders with Reactive Magnesia Replacement

Magnesia is widely used an expansive agent in construction materials due to its delayed hydration, which will compensate for the thermal shrinkage. This study investigates the influence of magnesia and early oven curing on the mechanical performance and microstructures of alkali-activated natural clay samples under different curing regimes after 28 days. Microstructural analysis and pH measurements were conducted to assess the strength of the samples. Results indicate that the strength was greatly improved (in comparison with the control samples) by the incorporation of magnesia due to the formation of nesquehonite. Meanwhile, oven curing is an effective method in the fast strength development in alkali-activated natural clay. The results also demonstrated the possibility of CO2 curing in the strength development of the magnesia-modified alkali-activated natural clay. Keywords: magnesia, natural clay, oven curing, compressive strength, microstructur

Nonlinear three–dimensional finite–element modelling of reinforced–concrete beams: Computational challenges and experimental validation

Three–dimensional nonlinear finite–element models have been developed to investigate the loading–unloading–reloading behaviour of two reinforced–concrete beams under four–point bending using explicit dynamics in ABAQUS. The damaged–plasticity model proposed by Lubliner and collaborators was employed for the plain concrete, and elastic–perfectly plastic models were employed for the steel reinforcement. A perfect bond was assumed between the steel rebars and concrete, whereby the bond–slip behaviour, as well as damage along crack patterns, were modelled through concrete damage. The influence of the shape of the tension–softening law on the numerical load–deflection response was studied by considering bi–linear, exponential and linear post–failure stress–displacement and stress–strain relationships. The effect of modelling steel rebars with truss or beam elements was also investigated. Structured meshes of linear hexahedral elements either with incompatible modes or with reduced integration, and unstructured meshes of either linear or ‘modified’ quadratic tetrahedral elements were considered. In terms of load–deflection curves, both the structured and the unstructured meshes gave results in very good agreement with test results. In terms of crack patterns, results predicted by the structured meshes exhibited some mesh bias, which was less pronounced with the unstructured meshes. In the post–yield phase, if a geometrically nonlinear model is used, discrepancies were found when truss elements were used for steel rebars, whereas good agreement was found if the bending stiffness of the rebars is included using beam elements. This is a non–obvious result that may be important to consider when studying the progressive collapse of RC structures

Manufacturing cement-based materials and building products via extrusion: From laboratory to factory

Manufacturing is critical to the economies of the UK and many other countries in the rest of the world. However, manufacturing of cement-based materials and building products predominantly remains based on old batch processing such as casting and pressing technologies and this may limit the applications and performance of the materials and products formed. In this paper, research is reported on transforming manufacturing of precast cement-based materials and building products from in batches to continuous processes via extrusion. Techniques used for producing plastic products are transferred into manufacturing cement-based building products like flat and corrugated sheet tiles, down pipes, door/window frames, door panels, solid wall/facade panels, honeycomb wall/facade panels etc. at laboratory and factory scales. In combination with sustainable cementitious materials with low carbon and low energy as matrix, this enables sustainable building products with key characteristics required by the 21st century can be manufactured via extrusion. The cement-based building products extrusion technique has been successfully transferred to industry. For instance, fibre reinforced cement-based partition wall panels, with a honeycomb cross section as large as 600 mm wide and 90 mm high, have been produced by a continuous extrusion process in a precast concrete products factory in Hangzhou, China.European Commission Seventh Framework Programme, (grant agreement no. 262954) and from the Hong Kong Research Grants Council through grants 6091/00E, 6226/01E, 6273/03E and 6167/06

Environmental assessment of magnesium oxychloride cement samples: A case study in Europe

This study is the first in the literature to systematically assess the environmental impacts of magnesium oxychloride cement (MOC) samples, which are regarded as a more eco-friendly construction material than Portland cement. The environmental impacts of MOC samples prepared with various molar ratios of MgO/MgCl2∙6H2O and sources of reactive magnesia were obtained via a life cycle assessment (LCA) approach (from cradle to grave), and the obtained outcomes were further compared with the counterparts associated with the preparation of Portland cement (PC) samples. Meanwhile, a sensitivity analysis in terms of shipping reactive magnesia from China to Europe was performed. Results indicated that the preparation of MOC samples with higher molar ratios led to more severe overall environmental impacts and greater CO2 sequestration potentials due to the difference of energies required for the production of MgO and MgCl2∙6H2O as well as their various CO2 binding capacities, whereas in terms of CO2 intensities, the molar ratios in MOC samples should be carefully selected depending on the strength requirements of the applications. Furthermore, various allocation procedures and MgO production processes will greatly influence the final outcomes, and allocation by mass is more recommended. Meanwhile, the environmental impacts associated with the transportation of reactive magnesia from China to Europe can be ignored. Finally, it can be concluded that MOC concrete is no longer a type of ‘low-carbon’ binder in comparison with PC concrete in terms of CO2 emissions, and in view of the single scores and mixing triangles for weighing, MOC concrete can only be identified as a type of more sustainable binder than PC concrete when the main component MgO in MOC samples is obtained through the dry process route rather than the wet process route