873 research outputs found

    Quench characteristics of a stabilizer-free 2G HTS conductor

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    The prospect of medium/high field superconducting magnets using second generation (2G) HTS tapes is approaching reality with continued enhancement in the performance of these conductors. While the cryogenic stability and quench propagation are fundamental issues for the design and safe operation of superconducting magnets, there is insufficient understanding and experimental data for 2G HTS conductors, in particular for the high field scenario at low temperature (<77 K) where the current sharing regime is much larger than in low temperature superconductors. The present work includes a systematic characterization of the relevant thermal-electrical properties used for both qualitative discussion and numerical analysis. Direct measurements of one dimensional adiabatic quench initiation and propagation of a stabilizer-free 2G conductor have been carried out with spatial-temporal recording of temperature and voltage following the deposition of varying local heat pulses to the conductor at different temperatures between 30 K and 77 K carrying different transport currents. The minimum quench energy, and the heat generation in the minimum propagation zone (MPZ) have been obtained as a function of temperature and transport current. The results show quench features unique to HTS such as an increasing MPZ with transport current and higher quench energies at lower temperatures. The experimental results are discussed in the context of current sharing over a large temperature range

    Transport properties of single MgB2 filaments extracted from multifilamentary conductors

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    Using an electrochemical bath copper and nickel metals and alloys are removed in multifilamentary MgB2 conductors to leave single MgB2 filaments surrounded by a Nb sheath. Starting from a 0.55 mm 36 filament diameter conductor, the etched filaments are 60 microns in diameter. Seven wires were characterized by transport critical current measurement, and one investigated further by resistivity when progressively etched. Their radial location in the original multifilamentary wire structure is then used to explore if the critical current is sensitive to the deformation process. The average critical current of the outer layer of filaments is 35% higher than the inner layers. The average filament critical current was 32 A which is within 10 % of the 36 filament wire critical current per filament when adjusted for self field

    Coupled Free Vibrations of Liquid in a Three-Dimensional Rectangular Container with an Elastic Cover

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    The coupled free vibration of liquid and its elastic cover, such as a plate or a membrane, in a three-dimensional rectangular tank is investigated through an analytical scheme based on velocity potential theory for the flow and the linear elastic theory for the cover. For the fluid domain, the velocity potential is expanded into double cosine series along the longitudinal and transverse direction respectively, with the corresponding eigenvalues determined from the impermeable conditions on the side walls. The vertical modes of the potential are obtained from the Laplace equation. The deflection of rectangular cover is expanded into the same double cosine series to match the potential, together with additional terms for satisfying the edge conditions. The polynomials are used for these additional terms which are then expanded into cosine series. For the expansions of the higher-order derivatives of the deflection, the derivatives of these polynomial terms are expanded into cosine series directly, rather than being obtained through differentiating the cosine series of the deflection, to avoid the non-convergent series. Through imposing the boundary conditions on the fluid-plate interface and edge conditions, an infinite matrix equation for the unknown coefficients can be established. The natural frequencies can be obtained when the determinant of the matrix is zero. In practical computation, the infinite matrix equation is truncated into finite size. Results are first provided for natural frequencies. This is followed by the corresponding natural mode shapes and principal strains distribution on the cover. The underlying physics of these results are then provided

    The impact of the Internet on household consumption expenditure: an empirical study based on China Family Panel Studies data

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    This article empirically analyzes the impact of Internet usage on household consumption expenditure based on the China Family Panel Studies (CFPS) data for three periods 2014, 2016, and 2018. The results show that Internet use significantly increases household consumption. This boost persists after adding a series of control variables, accounting for differences in time and region, or changing the measurement of the main explanatory variables. After introducing instrumental variables to overcome potential endogeneity problems and further including the Internet use of the financial decision maker’s spouse for a series of robustness tests, the findings remain robust. The positive boost is even more significant. Finally, heterogeneity analysis is conducted for different consumption types, urban and rural areas, gender of financial decision-makers, and use of other Internet tools

    EMD: an ensemble algorithm for discovering regulatory motifs in DNA sequences

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    BACKGROUND: Understanding gene regulatory networks has become one of the central research problems in bioinformatics. More than thirty algorithms have been proposed to identify DNA regulatory sites during the past thirty years. However, the prediction accuracy of these algorithms is still quite low. Ensemble algorithms have emerged as an effective strategy in bioinformatics for improving the prediction accuracy by exploiting the synergetic prediction capability of multiple algorithms. RESULTS: We proposed a novel clustering-based ensemble algorithm named EMD for de novo motif discovery by combining multiple predictions from multiple runs of one or more base component algorithms. The ensemble approach is applied to the motif discovery problem for the first time. The algorithm is tested on a benchmark dataset generated from E. coli RegulonDB. The EMD algorithm has achieved 22.4% improvement in terms of the nucleotide level prediction accuracy over the best stand-alone component algorithm. The advantage of the EMD algorithm is more significant for shorter input sequences, but most importantly, it always outperforms or at least stays at the same performance level of the stand-alone component algorithms even for longer sequences. CONCLUSION: We proposed an ensemble approach for the motif discovery problem by taking advantage of the availability of a large number of motif discovery programs. We have shown that the ensemble approach is an effective strategy for improving both sensitivity and specificity, thus the accuracy of the prediction. The advantage of the EMD algorithm is its flexibility in the sense that a new powerful algorithm can be easily added to the system

    Baryon density dependence of viscosities of the quark-gluon plasma at hadronization

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    The ϕ\phi meson and Ω\Omega baryon provide unique probes of the properties of the quark-gluon plasma (QGP) at hadronization in relativistic heavy-ion collisions. Using the quark recombination model with the quark phase-space information parameterized in a viscous blastwave, we perform Bayesian inference of the shear and bulk viscosities of the QGP at hadronization with a temperature of T160T\sim 160 MeV by analyzing the ϕ\phi and Ω\Omega data in Au+Au collisions at sNN=\sqrt{s_{\rm NN}}= 19.6-200 GeV and Pb+Pb collisions at sNN=\sqrt{s_{\rm NN}}= 2.76 TeV, corresponding to a baryon chemical potential variation from μB0\mu_B\approx 0 (at sNN=2.76\sqrt{s_{\rm NN}}= 2.76 TeV) to 200200 MeV (at sNN=19.6\sqrt{s_{\rm NN}}= 19.6 GeV). We find that the shear viscosity to enthalpy ratio ηT/(ϵ+P)\eta T/(\epsilon +P) of the QGP at hadronization decreases as μB\mu_B increases, with ηT/(ϵ+P)0.18\eta T/(\epsilon +P)\approx 0.18 at μB=0\mu_B=0 and ηT/(ϵ+P)0.08\eta T/(\epsilon +P)\approx 0.08 at μB=200\mu_B=200 MeV, while the corresponding specific bulk viscosity is essentially constant with ζT/(ϵ+P)=0.020.04\zeta T/(\epsilon + P)=0.02\sim 0.04 for μB<200\mu_B<200 MeV. Our results suggest that the QGP at hadronization (T160T\sim 160 MeV) with finite baryon density is more close to perfect fluid than that with zero baryon density.Comment: 8 pages, 2 figures, 2 table

    Bioinformatics resources for cancer research with an emphasis on gene function and structure prediction tools

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    The immensely popular fields of cancer research and bioinformatics overlap in many different areas, e.g. large data repositories that allow for users to analyze data from many experiments (data handling, databases), pattern mining, microarray data analysis, and interpretation of proteomics data. There are many newly available resources in these areas that may be unfamiliar to most cancer researchers wanting to incorporate bioinformatics tools and analyses into their work, and also to bioinformaticians looking for real data to develop and test algorithms. This review reveals the interdependence of cancer research and bioinformatics, and highlight the most appropriate and useful resources available to cancer researchers. These include not only public databases, but general and specific bioinformatics tools which can be useful to the cancer researcher. The primary foci are function and structure prediction tools of protein genes. The result is a useful reference to cancer researchers and bioinformaticians studying cancer alike

    Distributed 3D-Beam Reforming for Hovering-Tolerant UAVs Communication over Coexistence: A Deep-Q Learning for Intelligent Space-Air-Ground Integrated Networks

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    In this paper, we present a novel distributed UAVs beam reforming approach to dynamically form and reform a space-selective beam path in addressing the coexistence with satellite and terrestrial communications. Despite the unique advantage to support wider coverage in UAV-enabled cellular communications, the challenges reside in the array responses' sensitivity to random rotational motion and the hovering nature of the UAVs. A model-free reinforcement learning (RL) based unified UAV beam selection and tracking approach is presented to effectively realize the dynamic distributed and collaborative beamforming. The combined impact of the UAVs' hovering and rotational motions is considered while addressing the impairment due to the interference from the orbiting satellites and neighboring networks. The main objectives of this work are two-fold: first, to acquire the channel awareness to uncover its impairments; second, to overcome the beam distortion to meet the quality of service (QoS) requirements. To overcome the impact of the interference and to maximize the beamforming gain, we define and apply a new optimal UAV selection algorithm based on the brute force criteria. Results demonstrate that the detrimental effects of the channel fading and the interference from the orbiting satellites and neighboring networks can be overcome using the proposed approach. Subsequently, an RL algorithm based on Deep Q-Network (DQN) is developed for real-time beam tracking. By augmenting the system with the impairments due to hovering and rotational motion, we show that the proposed DQN algorithm can reform the beam in real-time with negligible error. It is demonstrated that the proposed DQN algorithm attains an exceptional performance improvement. We show that it requires a few iterations only for fine-tuning its parameters without observing any plateaus irrespective of the hovering tolerance

    Infollution (Information Pollution) Management, Filtering Strategy, Scalable Workforce, and Organizational Learning: A Conceptual Study

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    Information generation is increasing rapidly on a global scale. The exponential advancement in information technology and communication has accentuated the problem of effective information management. Yet, employees’ cognitive ability to process information has not increased in parallel with information generation. With the exponential rise of information, information pollution (infollution) emerges as a problem on an exponential basis. Infollution is among the greatest challenges of the 21st century. Nevertheless, based on information processing theory and dynamic capability, researchers have conceptualised that agile organisations can cope with information pollution by promoting scalable workforce and organisational learning. By employing coping strategies, filtering has been hypothesised as moderating the association of scalable workplace and organisational learning with infollution management. This research will extend the literature in the domain of information management and agile organisations. It will be particularly useful for information processors to identify quality information for improved decision-making.&nbsp
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