550 research outputs found
Estimation of Dynamic Mixed Double Factors Model in High Dimensional Panel Data
The purpose of this article is to develop the dimension reduction techniques
in panel data analysis when the number of individuals and indicators is large.
We use Principal Component Analysis (PCA) method to represent large number of
indicators by minority common factors in the factor models. We propose the
Dynamic Mixed Double Factor Model (DMDFM for short) to re ect cross section and
time series correlation with interactive factor structure. DMDFM not only
reduce the dimension of indicators but also consider the time series and cross
section mixed effect. Different from other models, mixed factor model have two
styles of common factors. The regressors factors re flect common trend and
reduce the dimension, error components factors re ect difference and weak
correlation of individuals. The results of Monte Carlo simulation show that
Generalized Method of Moments (GMM) estimators have good unbiasedness and
consistency. Simulation also shows that the DMDFM can improve prediction power
of the models effectively.Comment: 38 pages, 2 figure
Study of blasting vibration safety security criterion method based on response spectrum
AbstractBased on lots of blasting vibration monitoring data, correlation analysis on blasting vibration velocity response spectrum SR and blasting seismic waves with each signal characteristic, research that SR has damage and associated influence on building structure vibration. Research found that SR can reflect the values of the comprehensive effect of blasting vibration, and the dynamic characteristics of the influence of structural vibration. According to the research results, this paper puts forward with SR as blasting vibration safety assessment criterion of new methods
Experimental study on thermal runaway risk of 18650 lithium ion battery under side-heating condition
Radio emission of tidal disruption events from wind-cloud interaction
Winds can be launched in tidal disruption event (TDE). It has been proposed
that the winds can interact with the cloud surrounding the black hole, produce
bow shocks, accelerate electrons, and produce radio emission. We restudy the
wind-cloud interaction model. We employ the properties of winds found by the
radiation hydrodynamic simulations of super-Eddington circularized accretion
flow in TDEs. We can calculate the peak radio emission frequency, the
luminosity at the peak frequency, and their time-evolution based on the TDEs
wind-cloud interaction model. We find that the model predicted peak radio
emission frequency, the luminosity at peak frequency, and their time evolution
can be well consistent with those in TDEs AT2019dsg and ASASSN-14li. This
indicates that in these two radio TDEs, the wind-cloud interaction mechanism
may be responsible for the radio emission.Comment: 11 pages, 10 figures, accepted to MNRA
Evolution of H9N2 influenza viruses from domestic poultry in Mainland China
AbstractH9N2 viruses have circulated in domestic poultry in Mainland China since 1994, and an inactivated vaccine has been used in chickens to control the disease since 1998. The present study analyzed 27 H9N2 avian influenza viruses that were isolated from chickens and ducks from 1996 to 2002. Infection studies indicated that most of the viruses replicate efficiently but none of them is lethal for SPF chickens. However, these viruses exhibit different phenotypes of replication in a mouse model. Five viruses, including 4 early isolates and one 2000 isolate, are not able to replicate in mice; 14 viruses replicate to moderate titers in mouse lungs and cause less than 5% weight loss, while other 8 viruses could replicate to high titers in the lungs and 7 of them induce 10–20% weight loss of the mice on day 5 after inoculation. Most of the viruses isolated after 1996 are antigenically different from the vaccine strain that is currently used in China. Three viruses isolated in central China in 1998 are resistant to adamantanes. Phylogenetic analysis revealed that all of the viruses originated from CK/BJ/1/94-like virus and formed multiple genotypes through complicated reassortment with QA/HK/G1/97-, CK/HK/G9/97-, CK/SH/F/98-, and TY/WI/66-like viruses. This study is a description of the previously uncharacterized H9N2 avian influenza viruses recently circulating in chickens and ducks in Mainland China. Our findings suggest that urgent attention should be paid to the control of H9N2 influenza viruses in animals and to the human's influenza pandemic preparedness
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