3,274 research outputs found
Error microphone location study for an eight-channel ANC system in free space
© 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling. All rights reserved. The location of error microphones is one key factor that determines the performance of a multichannel active noise control (ANC) system in terms of global sound power reduction when the number and the location of secondary sources are fixed. In a single channel ANC system, the optimal error microphone location is on a line that is nearly perpendicular to the secondary and primary source axis and closer to the secondary source. This paper investigates the optimal location of the error microphones in an 8-channel ANC system in free space. It is demonstrated that good noise reduction performance can be achieved by placing the error microphones between the primary source and secondary sources and closer to the secondary sources in the low frequency range. Experiments conducted on a gearbox for low frequency noise control show that the averaged sound level reduction at the observation locations 2 meters away is 5.2 dB when the error microphones are placed at 0.2 m inside the secondary source surface
Photonic Millimeter Wave Generation and Stabilization in Optically Injected Discrete-mode Semiconductor Lasers subject to Photonic Filter Feedback
Effect of Li-deficiency impurities on the electron-overdoped LiFeAs superconductor
We use transport, inelastic neutron scattering, and angle resolved
photoemission experiments to demonstrate that the stoichiometric LiFeAs is an
intrinsically electron-overdoped superconductor similar to those of the
electron-overdoped NaFe1-xTxAs and BaFe2-xTxAs2 (T = Co,Ni). Furthermore, we
show that although transport properties of the stoichiometric superconducting
LiFeAs and Li-deficient nonsuperconducting Li1-xFeAs are different, their
electronic and magnetic properties are rather similar. Therefore, the
nonsuperconducting Li1-xFeAs is also in the electron overdoped regime, where
small Li deficiencies near the FeAs octahedra can dramatically suppress
superconductivity through the impurity scattering effect.Comment: 5 figures,5 page
Unusually stronger quantum fluctuation with larger spins: Novel phenomena revealed by emergent magnetism in pressurized high-temperature superconductor FeSe
A counter-intuitive enhancement of quantum fluctuation with larger spins,
together with a few novel physical phenomena, is discovered in studying the
recently observed emergent magnetism in high-temperature superconductor FeSe
under pressure. Starting with experimental crystalline structure from our
high-pressure X-ray refinement, we analyze theoretically the stability of the
magnetically ordered state with a realistic spin-fermion model. We find
surprisingly that in comparison with the magnetically ordered Fe-pnictides, the
larger spins in FeSe suffer even stronger long-range quantum fluctuation that
diminishes their ordering at ambient pressure. This "fail-to-order" quantum
spin liquid state then develops into an ordered state above 1GPa due to
weakened fluctuation accompanying the reduction of anion height and carrier
density. The ordering further benefits from the ferro-orbital order and shows
the observed enhancement around 1GPa. We further clarify the controversial
nature of magnetism and its interplay with nematicity in FeSe in the same
unified picture for all Fe-based superconductors. In addition, the versatile
itinerant carriers produce interesting correlated metal behavior in a large
region of phase space. Our study establishes a generic exceptional paradigm of
stronger quantum fluctuation with larger spins that complements the standard
knowledge of insulating magnetism.Comment: 7 pages, 4 figure
Pressure Pulsation Analysis of Oscillating Water Column Rotor Eccentricity Based on the Pulsation Tracking Network Method
An oscillating water column (OWC) is typical of axial rotor turbines, which are used to convert ocean wave energy into electrical energy. This device impacts downstream pressure pulsations when its rotor becomes eccentric. This study compared the details of pressure pulsations downstream of eccentric and non-eccentric rotors under three operating conditions: low flow A, high-efficiency flow B, and high flow C. Computational fluid dynamics (CFD) simulations based on the pulsation tracking network (PTN) method were used for the OWC device to compare the experimental results. The results indicate downstream pressure pulsations were mostly dominated by the blade frequency in non-eccentric low-flow cases. In the other eccentric operating conditions, downstream pressure pulsations were mainly dominated by the 2-, 3.6-, 6-, and 7-times rotation frequencies and the 0.5-times blade frequency. The phase change of downstream pressure pulsations in eccentric and non-eccentric conditions is consistent with the flow direction. The phase change is relatively uniform and steady before eccentricity and becomes turbulent after eccentricity, which affects its steadiness. In this study, the OWC device did not significantly change with or without rotor eccentricity at a 1-time blade frequency intensity; however, at a 1-time rotation frequency, the OWC device showed a significant increase in the pressure pulsation amplitude after rotor eccentricity. The study of the dominant frequency, amplitude, and phase of pressure pulsations in OWC devices with eccentric rotors can help prevent excessive pressure pulsations that can lead to incidents
OPCML Is a Broad Tumor Suppressor for Multiple Carcinomas and Lymphomas with Frequently Epigenetic Inactivation
Background: Identification of tumor suppressor genes (TSGs) silenced by CpG methylation uncovers the molecular mechanism of tumorigenesis and potential tumor biomarkers. Loss of heterozygosity at 11q25 is common multiple tumors including nasopharyngeal carcinoma (NPC). OPCML, located at 11q25, is one of the downregulated genes we identified through digital expression subtraction. Methodology/Principal Findings: Semi-quantitative RT-PCR showed frequent OPCML silencing in NPC and other common tumors, with no homozygous deletion detected by multiplex differential DNA-PCR. Instead, promoter methylation of OPCML was frequently detected in multiple carcinoma cell lines (nasopharyngeal, esophageal, lung, gastric, colon, liver, breast, cervix, prostate), lymphoma cell lines (non-Hodgkin and Hodgkin lymphoma, nasal NK/T-cell lymphoma) and primary tumors, but not in any non-tumor cell line and seldom weakly methylated in normal epithelial tissues. Pharmacological and genetic demethylation restored OPCML expression, indicating a direct epigenetic silencing. We further found that OPCML is stress-responsive, but this response is epigenetically impaired when its promoter becomes methylated. Ecotopic expression of OPCML led to significant inhibition of both anchorage-dependent and -indendent growth of carcinoma cells with endogenous silencing. Conlusions/Significance: Thus, through functional epigenetics, we identified OPCML as a broad tumor suppressor, which is frequently inactivated by methylation in multiple malignancies. © 2008 Cui et al.published_or_final_versio
Anchoring Bias in Online Voting
Voting online with explicit ratings could largely reflect people's
preferences and objects' qualities, but ratings are always irrational, because
they may be affected by many unpredictable factors like mood, weather, as well
as other people's votes. By analyzing two real systems, this paper reveals a
systematic bias embedding in the individual decision-making processes, namely
people tend to give a low rating after a low rating, as well as a high rating
following a high rating. This so-called \emph{anchoring bias} is validated via
extensive comparisons with null models, and numerically speaking, the extent of
bias decays with interval voting number in a logarithmic form. Our findings
could be applied in the design of recommender systems and considered as
important complementary materials to previous knowledge about anchoring effects
on financial trades, performance judgements, auctions, and so on.Comment: 5 pages, 4 tables, 5 figure
An Investigation of Hadronization Mechanism at Factory
We briefly review the hadronization pictures adopted in the LUND String
Fragmentation Model(LSFM), Webber Cluster Fragmentation Model(WCFM) and Quark
Combination Model(QCM), respectively. Predictions of hadron multiplicity,
baryon to meson ratios and baryon-antibaryon flavor correlations, especially
related to heavy hadrons at factory obtained by LSFM and QCM are
reported.Comment: 18 pages, 6 figures. accepted by Sci China Phys Mech Astro
Full-space Cloud of Random Points with a Scrambling Metasurface
With the rapid progress in computer science, including artificial intelligence, big data and cloud computing, full-space spot generation can be pivotal to many practical applications, such as facial recognition, motion detection, augmented reality, etc. These opportunities may be achieved by using diffractive optical elements (DOEs) or light detection and ranging (LIDAR). However, DOEs suffer from intrinsic limitations, such as demanding depth-controlled fabrication techniques, large thicknesses (more than the wavelength), Lambertian operation only in half space, etc. LIDAR nevertheless relies on complex and bulky scanning systems, which hinders the miniaturization of the spot generator. Here, inspired by a Lambertian scatterer, we report a Hermitian-conjugate metasurface scrambling the incident light to a cloud of random points in full space with compressed information density, functioning in both transmission and reflection spaces. Over 4044 random spots are experimentally observed in the entire space, covering angles at nearly 90 degrees. Our scrambling metasurface is made of amorphous silicon with a uniform subwavelength height, a nearly continuous phase coverage, a lightweight, flexible design, and low-heat dissipation. Thus, it may be mass produced by and integrated into existing semiconductor foundry designs. Our work opens important directions for emerging 3D recognition sensors, such as motion sensing, facial recognition, and other applications.113Nsciescopu
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