Switched wave packets: A route to nonperturbative quantum control

The dynamic Stark effect due to a strong nonresonant but nonionizing laser field provides a route to quantum control via the creation of novel superposition states. We consider the creation of a field-free "switched" wave packet through adiabatic turn-on and sudden turn-off of a strong dynamic Stark interaction. There are two limiting cases for such wave packets. The first is a Raman-type coupling, illustrated by the creation of field-free molecular axis alignment. An experimental demonstration is given. The second case is that of dipole-type coupling, illustrated by the creation of charge localization in an array of quantum wells

Are you talking to me? An analysis of journalism conversation on social media

Social media has become a key medium for discussion and dissemination of news stories, fuelled by the low barrier to entry and the ease of interaction. News stories may be propagated through these networks either by official news organisation accounts, by individual journalists or by members of the public, through link sharing, endorsing or commenting. This preliminary research aims to show how computational analysis of large-scale data-sets allows us to investigate the means by which news stories are spread through social media, and how the conversation around them is shaped by journalists and news organisations. Through the capture of more than 11 million tweets relating to 2303 Twitter accounts connected to journalism and news organisations, we are able to analyse the conversation within and around journalism, examining who spreads information about news articles and who interacts in the discussion around them. Capturing the tweets of news organisations and journalists and the replies and retweets of these micro-blogs allows us to build a rich picture of interaction around news media

Seismic assessment of the Matera cathedral

This paper presents the seismic assessment of the Cathedral of Matera, in southern Italy, to determine the capacity of the structure when subjected to earthquakes. This church dates back to the 13th century and is one of the most representative monuments of the Apulian Romanesque architecture. Within the context of the evaluation of the seismic response of the cathedral, modal identification tests were performed in order identify and characterize the main dynamic properties of the structure. The results of these tests were used to develop a representative finite element model, which is able to provide the response to seismic actions. A pushover analysis was performed to characterize the seismic behavior of the structure. The results of the seismic analyses on the cathedral show that its vulnerability is high, being the transversal direction the less stiff and resistant. Elements as the nave and the façade, along with the bell tower, might be the most vulnerable to seismic actions. Additionally, it was observed that components as the trusses of the central nave strongly modify the seismic response and capacity of the structure. Apparently, the structure might not be able to withstand a strong earthquake from the region or might present several damage after one. Hence, it is recommendable to perform further studies about the seismic behavior, especially of the most vulnerable elements.The authors would like to acknowledge the University of Minho for supporting the experimental campaign. Thanks is also extended to Dr. Nuno Mendes, University of Minho, for his guidance and help for performing the in-situ tests on the cathedral. The authors would also like to thank to the ELARCH project number 552129-EM-1-2014-1-IT-ERASMUS MUNDUS-EMA 21 for funding the graduate studies of the first author

INCEFA-PLUS Programme Overview and Update

INCEFA-PLUS is a five year project supported by the European Commission HORIZON2020 programme which commenced in mid 2015. 16 organisations from across Europe have combined forces to deliver new experimental data and a fatigue assessment procedure which will support the development of improved guidelines for assessment of environmental fatigue damage to ensure safe operation of nuclear power plants. Prior to the start of INCEFA-PLUS, an in-kind study was undertaken by several European organisations with the aim of developing the current state of the art for this technical area. This study identified three experimental variables which required further study in order to support improved assessment methodology for environmental fatigue, namely the effects of mean stress/strain, hold time and surface finish. Within INCEFA-PLUS, the effects of these three variables, plus strain amplitude, on fatigue endurance of austenitic stainless steels in light water reactor environments are therefore being studied experimentally. The data obtained will be collected and standardised in an online environmental fatigue database. In order to facilitate the exchange of fatigue data a standardized data format will be developed in the framework of a CEN workshop, to which international participants are welcome to participate. The outcome of the workshop will be a pre-normative document, a CEN Workshop Agreement (CWA) which will set a standard for enabling the exchange of fatigue data not only within the project but within the fatigue community. Based on the data generated and the resulting improvement in understanding, it is planned that INCEFAPLUS will develop and disseminate methods for including the new insights into assessment procedures for environmental fatigue degradation. This will take better account of the effects of mean strain, hold time and surface finish. This paper will provide more details on the background to this project and the way the project is organized to meet its objectives. Details will be provided as to how uncertainties due to variations in testing practice and specimen preparation have been minimized. Additionally, the choices associated with testing for the effects of surface finish, hold time and mean stress will be described along with the status of decisions so far within the project. The paper will also report current status of the project and when findings are likely to be disseminated

A Computer Vision-Based Approach for Non-contact Modal Analysis and Finite Element Model Updating

Computer vision-based techniques for modal analysis and system identification are rapidly becoming of great interest for both academic research and engineering practice in structural engineering. For instance, this is particularly relevant in fields such as bridge or tall building monitoring, where the large size of the structure would require an expensive sensor network, and for the characterisation of very slender, highly-flexible structural components, where physically-attached sensors cannot be deployed without altering the mass and stiffness of the system under investigation. This study concerns the latter case. Here, an algorithm for the full-field, non-contact extraction and processing of useful information from vibrational data is applied. Firstly, video acquisition is used to capture rapidly very spatially- and temporally-dense information regarding the vibrational behaviour of a high-aspect-ratio (HAR) prototype wing, with high image quality and high frame rate. Video processing is then applied to extract displacement time histories from the collected data; in turn, these are used to perform Modal Analysis (MA) and Finite Element Model Updating (FEMU). Results are benchmarked against the ones obtained from a single-point laser Doppler vibrometer (LDV). The study is performed on the beam-like spar of the wing prototype with and without the sensors attached to appreciate the disruptive effects of sensor loading. Promising results were achieved

Fermi Surface and Quasiparticle Excitations of overdoped Tl2Ba2CuO6+d by ARPES

The electronic structure of the high-T_c superconductor Tl2Ba2CuO6+d is studied by ARPES. For a very overdoped Tc=30K sample, the Fermi surface consists of a single large hole pocket centered at (pi,pi) and is approaching a topological transition. Although a superconducting gap with d_x^2-y^2 symmetry is tentatively identified, the quasiparticle evolution with momentum and binding energy exhibits a marked departure from the behavior observed in under and optimally doped cuprates. The relevance of these findings to scattering, many-body, and quantum-critical phenomena is discussed.Comment: Revised manuscript, in press on PRL. A high-resolution version can be found at http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/Tl2201_LE.pdf and related material at http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/articles.htm

Strongly aligned coastal boulders on Ko Larn island (Thailand): a proxy for past typhoon-driven high-energy wave events in the Bay of Bangkok

© 2019 Institute of Australian Geographers Recent studies of elevated carbonate boulder deposits on several rock islands near Bangkok have indicated that Thailand\u27s capital city may not be as protected from typhoon strikes as previously thought. Here, new evidence is presented for past high-energy wave (HEW) events in the form of statistically significant patterns of boulder alignment on exposed rocky shorelines of Ko Larn island. The long-axis orientations of 193 coastal sandstone boulders were analysed across four study sites. Several scenarios for the unimodal, bimodal, and polymodal patterns found can be envisaged. Either the most recent HEW event was the strongest—in which case most clasts were rearranged unimodally (one observation site), or the strongest HEW event was earlier and subsequent weaker ones realigned only smaller boulders to produce bimodal or polymodal patterns (three observation sites). Inferred northeastward or eastward onshore flow directions are consistent with palaeo-typhoons penetrating into the Bay of Bangkok on northwestward curving tracks. The calculated minimum flow velocities required to transport all sampled boulders are 5.5–7.8 m s−1, similar to other findings throughout the Asia-Pacific region. It was observed that the absence of a fitted boulder geomorphology lends credence to the earlier proposed time frame of 150–200 years between typhoon phases in the upper Gulf of Thailand. The current work has provided additional insights into the characteristics of past HEW events that have a possibility of reoccurring again at some time in the future. Our findings continue to raise awareness for a reassessment of the risks of coastal hazards for the Chao Phraya River delta and densely populated Bangkok, for which storm surge modelling should be an urgent priority, so as to give better perceptions on how typhoon-driven marine incursion would impact the city

A multivariate interval approach for inverse uncertainty quantification with limited experimental data

© 2018 Elsevier Ltd This paper introduces an improved version of a novel inverse approach for the quantification of multivariate interval uncertainty for high dimensional models under scarce data availability. Furthermore, a conceptual and practical comparison of the method with the well-established probabilistic framework of Bayesian model updating via Transitional Markov Chain Monte Carlo is presented in the context of the DLR-AIRMOD test structure. First, it is shown that the proposed improvements of the inverse method alleviate the curse of dimensionality of the method with a factor up to 105. Furthermore, the comparison with the Bayesian results revealed that the selection ofthe most appropriate method depends largely on the desired information and availability of data. In case large amounts of data are available, and/or the analyst desires full (joint)-probabilistic descriptors of the model parameter uncertainty, the Bayesian method is shown to be the most performing. On the other hand however, when such descriptors are not needed (e.g., for worst-case analysis), and only scarce data are available, the interval method is shown to deliver more objective and robust bounds on the uncertain parameters. Finally, also suggestions to aid the analyst in selecting the most appropriate method for inverse uncertainty quantification are given