Suchergebnisse

As the threats from unmanned aerial vehicles (UAVs) increases gradually, to recognize and classify unknown UAVs have became more and more important in both civil and military security fields. Classification of signal modulation types is one of the basic techniques for specific UAV recognition. In this paper, to represent the hidden features involved in the transmitted signals from UAVs, we propose a two-dimensional squeezing transform (TDST) to characterize the UAV communication signals in a compressed time-frequency plane. The new time-frequency representation, TDST, retains the instantaneous characteristics of the UAV signal, and is with excellent data reduction and noise suppression capabilities. The TDST plane of different modulation types are then considered as input features, and we propose a convolutional neural network (CNN) based on deep-learning to recognize the UAV signals. We design an interception system and consider 10 types of UAV signals with random initial phase, bandwidth and frequency offset. Experimental results demonstrate the effectiveness and superiority of the proposed algorithm.

Abstract. The imminent prediction on a group of strong earthquakes that occurred in Xinjiang, China in April 1997 is introduced in detail. The prediction was made on the basis of comprehensive analyses on the results obtained by multiple innovative methods including measurements of crustal stress, observation of infrasonic wave in an ultra low frequency range, and recording of abnormal behavior of certain animals. Other successful examples of prediction are also enumerated. The statistics shows that above 40% of 20 total predictions jointly presented by J. Z. Li, Z. Q. Ren and others since 1995 can be regarded as effective. With the above methods, precursors of almost every strong earthquake around the world that occurred in recent years were recorded in our laboratory. However, the physical mechanisms of the observed precursors are yet impossible to explain at this stage.

This work is supported by the National Nature Science Foundation of China under the contract number of 61401031, 61605014; the fund from Shunde Government, Guangdong Province, China, under the contract number of 20140401; the 100 Talents Program of Sun Yat-Sen University (76120- 18821104); Chinese Postdoctoral Science Foundation Grant No.2016M591126, and the Fundamental Research Funds for the Central Universities under the contract number of 2016RC18

Sharing lessons from high-performing hospitals facilitates quality improvement. High-performing hospitals have usually been identified using a small number of performance measures. The objective was to analyze how well 1,006 hospitals performed across a broader range of measures. Five measures were developed from publicly available data: adherence to processes of care, 30-day readmission rates, in-hospital mortality, efficiency, and patient satisfaction. For a subset of hospitals, the authors included two survey-based assessments of patient care quality, one by chief quality officers and one by frontline clinicians. In general, there was little correlation among the publicly available measures ( r ≤ .10), though there was notable correlation between objective measures and survey-based measures ( r = .23). Hospitals that performed well on a composite measure calculated from the publicly available measures were often not in the top quintile on most individual measures. This highlights the challenge in identifying high-performing hospitals to learn organizational-level best practices.

Young or forming high-mass stars that are nearby and not within a cluster environment have the potential to provide fundamental insights into star formation. In this paper we report such a candidate (G352.630-1.067), for which we have measured the distance through very long baseline interferometry parallax observations of the associated 6.7 GHz class II methanol maser. We determine the distance to the source to be 0.69 -0.08 +0.10 kpc, which makes it the second nearest highmass star formation region (HMSFR) known, with only the Orion Nebula being closer. This may place this source, not within a Galactic spiral arm, but in the region between the Local and Sagittarius arms, indicating that molecular clouds in interarm regions may also generate high-mass stars. Kinematic association between this source and the Sagittarius Arm suggests that it may be located in a spur extending outward from this arm. Comparison with the known, nearby HMSFRs (distances less than 1 kpc), reveal that G352.630-1.067 is in a more isolated environment than others, hence providing an excellent candidate for investigations of the processes that form individual high-mass stars. We find a good spatial correlation between the 6.7 GHz methanol maser and high angular resolution images of the infrared outflow, suggesting that the class II methanol masers are closely associated with a jet/outflow in this source. © 2019 The American Astronomical Society. ; We thank the anonymous referee for helpful comments that improved the manuscript. This work was supported by the National Natural Science Foundation of China (11590781, 11873002, 11590780), Australian Research Council Discovery project number DP180101061 funded by the Australian Government, and the major scientific research project of Guangdong regular institutions of higher learning (2017KZDXM062).

While the layered 122 iron arsenide superconductors are highly anisotropic, unconventional, and exhibit several forms of electronic orders that coexist or compete with superconductivity in different regions of their phase diagrams, we find in the absence of iron in the structure that the superconducting characteristics of the end member BaPd2As2 are surprisingly conventional. Here we report on complementary measurements of specific heat, magnetic susceptibility, resistivity measurements, Andreev spectroscopy, and synchrotron high pressure x-ray diffraction measurements supplemented with theoretical calculations for BaPd2As2. Its superconducting properties are completely isotropic as demonstrated by the critical fields, which do not depend on the direction of the applied field. Under the application of high pressure, Tc is linearly suppressed, which is the typical behavior of classical phonon-mediated superconductors with some additional effect of a pressure-induced decrease in the electronic density of states and the electron-phonon coupling parameters. Structural changes in the layered BaPd2As2 have been studied by means of angle-dispersive diffraction in a diamond-anvil cell. At 12 GPa and 24.2 GPa we observed pressure induced lattice distortions manifesting as the discontinuity and, hence discontinuity in the Birch-Murnaghan equation of state. The bulk modulus is B0=40(6) GPa below 12 GPa and B0=142(3) GPa below 27.2 GPa. © 2018 American Physical Society. ; We are grateful to the support of the DFG, Deutsche Forschungsgemeinschaft through MO 3014/1-1. A.S. and A.U. are grateful to the support of the RSCF Grant No. 16-12-10507, V.P. acknowledges support by the RSCF Grant No. 16-42-01100. HPCAT operations are supported by DOE-NNSA under Award No. DE-NA0001974 and DOE-BES under Award No. DE-FG02-99ER45775, with partial instrumentation funding by NSF. A.P.S. is supported by DOE-BES, under Contract No. DE-AC02-06CH11357. Y.-W.F. acknowledges the computing center of ECNU and Bridges system of Extreme Science and Engineering Discovery Environment (XSEDE) for providing the computational resources. This work has been supported by Ministry of Education and Science of Russia through NUST "MISiS" Grant No. K2-2017-084 and by the Act 211 of the Government of Russia, contract 02.A03.21.0004.