An experimental investigation of retro-reinforced clay brick arches

This paper describes the laboratory testing of eight 2.95m span segmental profile clay brick arches. Seven of the arches were strengthened with longitudinal intrados (soffit) reinforcement; the eighth was left unreinforced as an experimental control. Three of the arches also contained reinforcement to resist inter-ring shear. The barrel of each arch consisted of 3 rings of brickwork laid in stretcher bond; the compressive strength of the mortar used in the arch construction varied from 1.7 to 6.2 MPa. In each case a full width line load was applied incrementally to the arch extrados at quarter span until collapse occurred. Surface crack development and the vertical deflection profile of each arch were recorded at each load increment. In all cases, the longitudinal reinforcement was found to delay the onset of cracking and to increase the load carrying capacity. As expected, premature failure by ring separation was found to occur in the arches constructed with the weakest mortar without inter-ring reinforcement. Radial dowels were found to be the most effective means of preventing ring separation. The effect of the longitudinal reinforcement was found to be greatest in the arches where measures were taken to prevent ring separation

Paradigm shift: a case study of transnational collaboration for a high-profile design competition in Shanghai, China

This conference is organised in conjunction with the Design and Construction Management Students Day and Competition (Organised in collaboration with BuHU, CIB TG53 and CIB W104), Design and Construction Management Industry Day (Organised in collaboration with BOSS RE&H students society)The topic of this paper centers on the paradigm shift in transnational design collaboration for high-profile design competitions which are fiercely contested in major Chinese cities. In view of the fact that most writings on design competitions prefer some successful stories rather than the equally instructive ones telling why others fail, this paper will look at the issues from a different perspective by providing an unusual case of collaboration. The intention is to offer some original insights into understanding the emerging situation which probably constitutes one of the future trends in design competitions. By reviewing the current performance of design competitions which greatly influence the development of collaboration paradigm, this paper investigates a collaboration case with an emerging form, a controversial process and mixed outcomes. Questionnaire survey and case study are used in this study. Despite a single case investigation, there are strong reasons to believe that it serves as a precursor of a major shift over the coming decades in the evolution of transnational collaboration in high-profile design competitions in China.postprintThe International Conference on Changing Roles, New Roles; New Challenge, Rotterdam, The Netherlands, 5-9 October 2009. In CRO9 International Conference on Changing Roles, New Roles; New Challenges, 2009, p. 131-14

Polaronic effect in the x-ray absorption spectra of La1-x Ca x MnO3 manganites.

X-ray absorption spectroscopy (XAS) is performed to study changes in the electronic structures of colossal magnetoresistance (CMR) and charged ordered (CO) La1-x Ca x MnO3 manganites with respect to temperature. The pre-edge features in O and Mn K-edge XAS spectra, which are highly sensitive to the local distortion of MnO6 octahedral, exhibit contrasting temperature dependence between CMR and CO samples. The seemingly counter-intuitive XAS temperature dependence can be reconciled in the context of polarons. These results help identify the most relevant orbital states associated with polarons and highlight the crucial role played by polarons in understanding the electronic structures of manganites

Nature of band-gap states in V-doped TiO2 revealed by resonant photoemission

Band-gap states in V-doped TiO2 have been studied by photoemission spectroscopy over a range of photon energies encompassing the Ti 3p and V 3p core thresholds. The states show resonant enhancement at photon energies significantly higher than found for Ti 3d states introduced into TiO2 by oxygen deficiency or alkalimetal adsorbates. This demonstrates that the gap states relate to electrons trapped on dopant V cations rather than host Ti cations

Circular-polarization reconfigurable monopole antenna with enhanced boresight gain for GNSS applications

A circular-polarization (CP) reconfigurable monopole antenna with enhanced boresight-gain for GNSS applications is proposed. The antenna consists of two meandered monopoles placed perpendicular to each other, a feeding network using the Wilkinson power divider, two switchable 90°-phase-shifters, a defected ground structure (DGS) and a metallic reflector. The metallic reflector is placed at the back of the antenna to improve efficiency and boresight gain. Simulation results show that the metallic reflector can substantially increase the efficiency and boresight-gain of the antenna by about 20% and 5 dB, respectively, in the operating band, yet retaining the impedance bandwidth and axial-ratio bandwidth.postprin

Planar Monopoles with Different Radiator Shapes for UWB Body-centric Wireless Communications

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Frequency-Reconfigurable MIMO Monopole Antenna with Wide-Continuous Tuning Range

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Developing a Tailored RBS Linking to BIM for Risk Management of Bridge Projects

Purpose – The purpose of this paper is to address the current theoretical gap in integrating knowledge and experience into Building Information Model (BIM) for risk management of bridge projects by developing a tailored Risk Breakdown Structure (RBS) and formalising an active link between the resulting RBS and BIM. Design/methodology/approach – A three-step approach is used in this study to develop a tailored RBS for bridge projects and a conceptual model for the linkage between the RBS and BIM. First, the integrated bridge information model is in concept separated into four levels of contents (LOCs) and six technical systems based on analysis of the Industry Foundation Classes specification, a critical review of previous studies and authors’ project experience. The second step develops a knowledge-based risk database through an extensive collection of risk data, a process of data mining, and further assessment and translation of data. A critical analysis is conducted in the last step to determine on which level the different risks should be allocated to bridge projects and to propose a conceptual model for linking the tailored RBS to the four LOCs and six technical systems of BIM. Findings – The findings suggest that the traditional method and BIM can be merged as an integrated solution for risk management by establishing the linkage between RBS and BIM. This solution can take advantage of both the traditional method and BIM for managing risks. On the one hand, RBS enables risk information to be stored in a formal structure, used and communicated effectively. On the other hand, some features of BIM such as 3D visualisation and 4D construction scheduling can facilitate the risk identification, analysis, and communication at an early project stage. Research limitations/implications – A limitation is that RBS is a qualitative technique and only plays a limited role in quantitative risk analysis. As a result, when implementing this proposed method, further techniques may be needed for assisting quantitative risk analysis, evaluation, and treatment. Another limitation is that the proposed method has not yet been implemented for validation in practice. Hence, recommendations for future research are to: improve the quantitative risk analysis and treatment capabilities of this proposed solution; develop computer tools to support the solution; integrate the linkage into a traditional workflow; and test this solution in some small and large projects for validation. Practical implications – Through linking risk information to BIM, project participants could check and review the linked information for identifying potential risks and seeking possible mitigation measures, when project information is being transferred between different people or forwarded to the next phase. Originality/value – This study contributes to the theoretical development for aligning traditional methods and BIM for risk management, by introducing a new conceptual model for linking RBS to BIM

The hidden horizon and black hole unitarity

We motivate through a detailed analysis of the Hawking radiation in a Schwarzschild background a scheme in accordance with quantum unitarity. In this scheme the semi-classical approximation of the unitary quantum - horizonless - black hole S-matrix leads to the conventional description of the Hawking radiation from a classical black hole endowed with an event horizon. Unitarity is borne out by the detailed exclusive S-matrix amplitudes. There, the fixing of generic out-states, in addition to the in-state, yields in asymptotic Minkowski space-time saddle-point contributions which are dominated by Planckian metric fluctuations when approaching the Schwarzschild radius. We argue that these prevent the corresponding macroscopic "exclusive backgrounds" to develop an event horizon. However, if no out-state is selected, a distinct saddle-point geometry can be defined, in which Planckian fluctuations are tamed. Such "inclusive background" presents an event horizon and constitutes a coarse-grained average over the aforementioned exclusive ones. The classical event horizon appears as a coarse-grained structure, sustaining the thermodynamic significance of the Bekenstein-Hawking entropy. This is reminiscent of the tentative fuzzball description of extremal black holes: the role of microstates is played here by a complete set of out-states. Although the computations of unitary amplitudes would require a detailed theory of quantum gravity, the proposed scheme itself, which appeals to the metric description of gravity only in the vicinity of stationary points, does not.Comment: 29 pages, 4 figures. Typos corrected. Two footnotes added (footnotes 3 and 5

An ISM/UWB antenna with offset feeding and slotted ground plane for body-centric communications

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