384,329 research outputs found

    Comment on "Modified Coulomb Law in a Strongly Magnetized Vacuum"

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    This is a comment on Phys. Rev. Lett. 98, 180403 (2007) [arXiv:0704.2162].Comment: 1 page, comment on arXiv:0704.2162, published versio

    Improved thermal performance of a large laminated lithium-ion power battery by reciprocating air flow

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    The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Thermal safety issues are increasingly critical for large-size laminated Lithium-Ion Batteries (LIBs). Despite a number of investigations conducted on the Battery Thermal Management System (BTMS) with reciprocating air-flow cooling, large laminated power LIBs are still not sufficiently investigated, particularly in the view of battery thermal characteristics. The present study investigates the thermal behaviors of an air-cooled NCM-type LIB (LiNi1−x−yCoxMnyO2 as cathode) from an experimental and systematic approach. The temperature distribution was acquired from different Depth of Discharge (DOD) by the infrared imaging (IR) technology. A reciprocating air-flow cooling method was proposed to restrict the temperature fluctuation and homogenize temperature distribution. Results showed that there was a remarkable temperature distribution phenomenon during the discharge process, the temperature distribution was affected by direction of air-flow. Forward air-flow (from current collector side to lower part of battery) was always recommended at the beginning of the discharge due to the thermal characteristics of the battery. After comprehensive consideration on battery temperature limit and cooling effect, the desired initial reversing timing was about 50% DOD at 3 C discharge rate. Different reversing strategies were investigated including isochronous cycles and aperiodic cycles. It was found that the temperature non-uniformity caused by heat accumulation and concentration was mitigated by reciprocating air-flow with optimized reversing strategy

    Cosmological model of the interaction between dark matter and dark energy

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    In this paper, we test the dark matter-dark energy interacting cosmological model with a dynamic equation of state wDE(z)=w0+w1z/(1+z)w_{DE}(z)=w_{0}+w_{1}z/(1+z), using type Ia supernovae (SNe Ia), Hubble parameter data, baryonic acoustic oscillation (BAO) measurements, and the cosmic microwave background (CMB) observation. This interacting cosmological model has not been studied before. The best-fitted parameters with 1σ1 \sigma uncertainties are δ=0.022±0.006\delta=-0.022 \pm 0.006, ΩDM0=0.213±0.008\Omega_{DM}^{0}=0.213 \pm 0.008, w0=1.210±0.033w_0 =-1.210 \pm 0.033 and w1=0.872±0.072w_1=0.872 \pm 0.072 with χmin2/dof=0.990\chi^2_{min}/dof = 0.990. At the 1σ1 \sigma confidence level, we find δ<0\delta<0, which means that the energy transfer prefers from dark matter to dark energy. We also find that the SNe Ia are in tension with the combination of CMB, BAO and Hubble parameter data. The evolution of ρDM/ρDE\rho_{DM}/\rho_{DE} indicates that this interacting model is a good approach to solve the coincidence problem, because the ρDE\rho_{DE} decrease with scale factor aa. The transition redshift is ztr=0.63±0.07z_{tr}=0.63 \pm 0.07 in this model.Comment: 6 pages, 6 figures, published in A&

    Periodicities in Solar Coronal Mass Ejections

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    Mid-term quasi-periodicities in solar coronal mass ejections (CMEs) during the most recent solar maximum cycle 23 are reported here for the first time using the four-year data (February 5, 1999 to February 10, 2003) of the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). In parallel, mid-term quasi-periodicities in solar X-ray flares (class >M5.0) from the Geosynchronous Operational Environment Satellites (GOES) and in daily averages of Ap index for geomagnetic disturbances from the World Data Center (WDC) at the International Association for Geomagnetism and Aeronomy (IAGA) are also examined for the same four-year time span. Several conceptual aspects of possible equatorially trapped Rossby-type waves at and beneath the solar photosphere are discussed.Comment: Accepted by MNRAS, 6 figure

    The structural response of a rail accelerator

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    The transient response of a 0.4 by 0.6 cm rectangular bore rail accelerator was analyzed by a three dimensional finite element code. The copper rail deflected to a peak value of 0.08 mm in compression and then oscillated at an amplitude of 0.02 mm. Simultaneously the insulating side wall of glass fabric base, epoxy resin laminate (G-1o) was compressed to a peak value of 0.13 mm and rebounded to a steady state in extension. Projectile pinch or blowby due to the rail extension or compression, respectively, can be identified by examining the time history of the rail displacement. The effect of blowby was most significant at the side wall characterized by mm size displacement in compression. Dynamic stress calculations indicate that the G-10 supporting material behind the rail is subjected to over 21 MPa at which the G-10 could fail if the laminate was not carefully oriented. Results for a polycarbonate resin (Lexan) side wall show much larger displacements and stresses than for G-10. The tradeoff between the transparency of Lexan and the mechanical strength of G-10 for sidewall material is obvious. Displacement calculations from the modal method are smaller than the results from the direct integration method by almost an order of magnitude, because the high frequency effect is neglected