Experimental Behaviour of CFRP Strap Strengthened RC Beams Subjected to Sustained Loads

Reinforced concrete (RC) beams strengthened with transverse pre-stressed unbonded carbon-fiber-reinforced polymer (CFRP) straps have shown substantial increases in shear capacity when subjected to short-term static loading. However, understanding the time-dependent behaviour is a further prerequisite in order to better evaluate this strengthening technique and its engineering applications. This paper presents time-dependent experimental results from an un-strengthened RC beam and four RC beams strengthened with CFRP straps. The parameters under consideration included the concrete strength, applied load level and pre-stress level in the CFRP straps. The beams were subjected to sustained loads that were fixed percentages of the short-term failure load. To investigate the development of the external concrete strains, the internal steel shear link strains, the strap strains and the shear crack patterns, the beams were monitored over a period of around 320 days. The long-term beam deformations were also recorded and decomposed into bending and shear components. When compared with an equivalent unstrengthened beam, the presence of the CFRP straps reduced the proportion of the shear deflection. However, in the strengthened beams the shear proportions of the total mid-span deflection were still 24% to 28%, which were not negligible. An analysis using a Mohr’s circle of strain confirmed that the long-term tensile behaviour in the shear span appears to dominate the development of the shear deformation.Cambridge Commonwealth and Overseas Trusts University of Cambridge Department of Engineering Homerton College Emp

Multiplexing of fiber Bragg grating sensors using an FMCW technique

Author name used in this publication: W. JinAuthor name used in this publication: M. S. DemokanVersion of RecordPublishe

Generalized Hamacher aggregation operators for intuitionistic uncertain linguistic sets: Multiple attribute group decision making methods

© 2019 by the authors. In this paper, we consider multiple attribute group decision making (MAGDM) problems in which the attribute values take the form of intuitionistic uncertain linguistic variables. Based on Hamacher operations, we developed several Hamacher aggregation operators, which generalize the arithmetic aggregation operators and geometric aggregation operators, and extend the algebraic aggregation operators and Einstein aggregation operators. A number of special cases for the two operators with respect to the parameters are discussed in detail. Also, we developed an intuitionistic uncertain linguistic generalized Hamacher hybrid weighted average operator to reflect the importance degrees of both the given intuitionistic uncertain linguistic variables and their ordered positions. Based on the generalized Hamacher aggregation operator, we propose a method for MAGDM for intuitionistic uncertain linguistic sets. Finally, a numerical example and comparative analysis with related decision making methods are provided to illustrate the practicality and feasibility of the proposed method

A people-oriented paradigm for smart cities

Most works in the literature agree on considering the Internet of Things (IoT) as the base technology to collect information related to smart cities. This information is usually offered as open data for its analysis, and to elaborate statistics or provide services which improve the management of the city, making it more efficient and more comfortable to live in. However, it is not possible to actually improve the quality of life of smart cities’ inhabitants if there is no direct information about them and their experiences. To address this problem, we propose using a social and mobile computation model, called the Internet of People (IoP) which empowers smartphones to recollect information about their users, analyze it to obtain knowledge about their habits, and provide this knowledge as a service creating a collaborative information network. Combining IoT and IoP, we allow the smart city to dynamically adapt its services to the needs of its citizens, promoting their welfare as the main objective of the city.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Laser-wakefield accelerators as hard x-ray sources for 3D medical imaging of human bone

A bright μm-sized source of hard synchrotron x-rays (critical energy Ecrit > 30 keV) based on the betatron oscillations of laser wakefield accelerated electrons has been developed. The potential of this source for medical imaging was demonstrated by performing micro-computed tomography of a human femoral trabecular bone sample, allowing full 3D reconstruction to a resolution below 50 μm. The use of a 1 cm long wakefield accelerator means that the length of the beamline (excluding the laser) is dominated by the x-ray imaging distances rather than the electron acceleration distances. The source possesses high peak brightness, which allows each image to be recorded with a single exposure and reduces the time required for a full tomographic scan. These properties make this an interesting laboratory source for many tomographic imaging applications

Timing Precision in Population Coding of Natural Scenes in the Early Visual System

The timing of spiking activity across neurons is a fundamental aspect of the neural population code. Individual neurons in the retina, thalamus, and cortex can have very precise and repeatable responses but exhibit degraded temporal precision in response to suboptimal stimuli. To investigate the functional implications for neural populations in natural conditions, we recorded in vivo the simultaneous responses, to movies of natural scenes, of multiple thalamic neurons likely converging to a common neuronal target in primary visual cortex. We show that the response of individual neurons is less precise at lower contrast, but that spike timing precision across neurons is relatively insensitive to global changes in visual contrast. Overall, spike timing precision within and across cells is on the order of 10 ms. Since closely timed spikes are more efficient in inducing a spike in downstream cortical neurons, and since fine temporal precision is necessary to represent the more slowly varying natural environment, we argue that preserving relative spike timing at a similar to 10-ms resolution is a crucial property of the neural code entering cortex

Experimental investigation of time-dependent shear deformation in RC beams strengthened with CFRP straps

Understanding the long-term shear performance of un-strengthened and FRP-strengthened reinforced concrete (RC) beams is important. The shear behaviour under sustained loads impacts the load-sharing between the concrete, internal and external reinforcement. This in turn influences the reliability of a strengthening system over the longer-term. The current work considers RC beams strengthened in shear with transverse pre-stressed unbonded carbon-fibre-reinforced polymer (CFRP) straps. CFRP-strap strengthened beams have previously been shown to exhibit substantial increases in shear capacity when subjected to short-term monotonic loading. However, after diagonal shear cracks occur, shear deformations can start to become significant. To investigate the time-dependent shear behaviour, an un-strengthened control beam and a series of RC beams strengthened with pre-stressed CFRP straps were subjected to sustained loads. Using a detailed measurement scheme, the time-dependent deformations of the experimental beams were recorded over a duration of up to 523 days. The primary objective was to extract the shear components of deflection and to thereby assess the longer-term interactions. The measured shear deformations were found to increase with time and depended on the sustained load level.We gratefully acknowledge Professor Meier’s significant contributions from which we have benefited greatly. Professor Meier’s influence is at the heart of this research and his innovations and leadership have transformed the field of advanced FRP composites

Distinctive Genetic Activity Pattern of the Human Dental Pulp between Deciduous and Permanent Teeth

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Chiral Condensate in Holographic QCD with Baryon Density

We consider the chiral condensate in the baryonic dense medium using the generalized Sakai-Sugimoto model. It is defined as the vacuum expectation value of open Wilson line that is proposed to be calculated by use of the area of world-sheet instanton. We evaluate it in confined as well as deconfined phase. In both phases, the chiral condensate has a minimum as a function of baryon density. In the deconfined phase, taking into account the chiral symmetry restoration, we classify the behavior of chiral condensate into three types. One can set the parameter of the theory such that the results, in low but sufficiently higher density, is in agreement with the expectation from QCD.Comment: 23 pages, 8 figure