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Search Results: 1 - 10 of 43209 matches for " Lixin Xu "
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A Study on Chinese Regional Scientific Innovation Efficiency with a Perspective of Synergy Degree  [PDF]
Lixin Xu, Min Cheng
Technology and Investment (TI) , 2013, DOI: 10.4236/ti.2013.44027
Abstract: From the perspective of the process of regional scientific innovation, the regional scientific innovation system is divided into two sub-systems of technology output and economic output. We utilize the chain-DEA method to assess scientific innovation and each sub-system’s efficiencies of 30 Chinese provinces from 2001 to 2011. Results suggest that the scientific innovation and each sub-system’s efficiencies need to be improved, unequilibrium in different regions exists evidently, each sub-system efficiency of one district varies a lot and the synergy degree remains low. Next, we compute the synergy degree of the two sub-systems using the synergy degree model. By employing linear regression model, an obvious positive correlation is demonstrated between the synergy and the scientific innovation efficiency. At last, based on the results of this study and real situations of Chinese scientific innovation, some suggestions are put forward accordingly.
An Empirical Study on the Effects of Equity Incentive of the Listed Corporations in the SME Board of China
—An Empirical Analysis Based on the View of Earnings Management
 [PDF]

Lixin Xu, Wenqin Cui
Technology and Investment (TI) , 2014, DOI: 10.4236/ti.2014.51004
Abstract:

Currently, most researches are focusing on Shanghai & Shenzhen exchange, and few researches have been done on the SME board. Besides, while studying the effect of equity incentive, most of the researchers have ignored the earnings management triggered by stock ownership incentive. This paper takes the SME board companies which have implemented stock ownership incentive as the research object. We have used earnings management to modify the company performance and carried out an empirical research to study the effect of stock ownership incentive. Our result shows that without earnings management to modify the company performance, stock ownership incentive is positively related to company performance. Taking the earnings management into account, the positive correlation relationship between stock ownership incentive and company performance will be weakened, and stock ownership incentive will stimulate earnings management.

Holographic Dark Energy Model with Hubble Horizon as an IR Cut-off
Lixin Xu
Physics , 2009, DOI: 10.1088/1475-7516/2009/09/016
Abstract: The main task of this paper is to realize a cosmic observational compatible universe in the framework of holographic dark energy model when the Hubble horizon $H$ is taken as the role of an IR cut-off. When the model parameter $c$ of a time variable cosmological constant (CC) $\Lambda(t)=3c^{2}H^{2}(t)$ becomes time or scale dependent, an extra term enters in the effective equation of sate (EoS) of the vacuum energy $w^{eff}_{\Lambda}=-c^2-d\ln c^{2}/3d\ln a$. This extra term can make the effective EoS of time variable CC cross the cosmological boundary and be phantom-like at present. For the lack of a first principle and fundamental physics theory to obtain the form $c^2$, we give a simple parameterized form of $c^2$ as an example. Then the model is confronted by the cosmic observations including SN Ia, BAO and CMB shift parameter $R$. The result shows that the model is consistent with cosmic observations.
Time Variable Cosmological Constant from Renormalization Group Equations
Lixin Xu
Physics , 2009, DOI: 10.1142/S0217732310031762
Abstract: In this paper, a time variable cosmological constant (CC) from renormalization group equations (RGEs) is explored, where the renormalization scale $\mu^2=R^{-2}_{CC}=Max(\dot{H}+2H^2,-\dot{H})$ is taken. The cosmological parameters, such as dimensionless energy density, deceleration parameter and effective equation of state of CC etc, are derived. Also, the cosmic observational constraints are implemented to test the model's consistence. The results show that it is compatible with cosmic data. So, it would be a viable dark energy model.
Cosmological Model-independent Gamma-ray Bursts Calibration and its Cosmological Constraint to Dark Energy
Lixin Xu
Physics , 2010, DOI: 10.1088/1475-7516/2012/04/025
Abstract: As so far, the redshift of Gamma-ray bursts (GRBs) can extend to $z\sim 8$ which makes it as a complementary probe of dark energy to supernova Ia (SN Ia). However, the calibration of GRBs is still a big challenge when they are used to constrain cosmological models. Though, the absolute magnitude of GRBs is still unknown, the slopes of GRBs correlations can be used as a useful constraint to dark energy in a completely cosmological model independent way. In this paper, we follow Wang's model-independent distance measurement method and calculate their values by using 109 GRBs events via the so-called Amati relation. Then, we use the obtained model-independent distances to constrain $\Lambda$CDM model as an example.
Constraints to Holographic Dark Energy Model via Type Ia Supernovae, Baryon Acoustic Oscillation and WMAP
Lixin Xu
Physics , 2012, DOI: 10.1103/PhysRevD.85.123505
Abstract: In this paper, the holographic dark energy (HDE) model, where the future event horizon is taken as an IR cut-off, is confronted by using currently available cosmic observational data sets which include type Ia supernovae, baryon acoustic oscillation and cosmic microwave background radiation from full information of WMAP-7yr. Via the Markov Chain Monte Carlo method, we obtain the values of model parameter $c= 0.696_{- 0.0737- 0.132- 0.190}^{+ 0.0736+ 0.159+ 0.264}$ with $1,2,3\sigma$ regions. Therefore one can conclude that at lest $3\sigma$ level the future Universe will be dominated by phantom like dark energy. It is not consistent with positive energy condition, however this condition must be satisfied to derive the holographic bound. It implies that the current cosmic observational data points disfavor the HDE model.
Spherical Collapse of a Unified Dark Fluid with Constant Adiabatic Sound Speed
Lixin Xu
Physics , 2013, DOI: 10.1140/epjc/s10052-013-2344-7
Abstract: In this paper, we test the spherical collapse of a unified dark fluid (UDF) which has constant adiabatic sound speed. By choosing the different values of model parameters $B_s$ and $\alpha$, we show the nonlinear collapse for UDF and baryons which are considered for their formation of the large scale structure of our Universe. The analyzed results show that larger values of $\alpha$ and $B_s$ make the structure formation faster and earlier.
Constraints on the Holographic Dark Energy Model from Type Ia Supernovae, WMAP7, Baryon Acoustic Oscillation and Redshift-Space Distortion
Lixin Xu
Physics , 2013, DOI: 10.1103/PhysRevD.87.043525
Abstract: In this paper, we use the joint measurement of geometry and growth rate from matter density perturbations to constrain the holographic dark energy model. The geometry measurement includes type Ia supernovae (SN Ia) Union2.1, full information of cosmic microwave background (CMB) from WMAP-7yr and baryon acoustic oscillation (BAO). For the growth rate of matter density perturbations, the results $f(z)\sigma_8(z)$ measured from the redshift-space distortion (RSD) in the galaxy power spectrum are employed. Via the Markov Chain Monte Carlo method, we try to constrain the model parameters space. The jointed constraint shows that $c=0.750_{- 0.0999- 0.173- 0.226}^{+ 0.0976+ 0.215+ 0.319}$ and $\sigma_8=0.763_{- 0.0465- 0.0826- 0.108}^{+ 0.0477+ 0.0910+ 0.120}$ with $1,2,3\sigma$ regions. After marginalizing the other irrelevant model parameters, we show the evolution of the equation of state of HDE with respect to the redshift $z$. Though the current cosmic data points favor a phantom like HDE Universe for the mean values of the model parameters in the future, it can behave like quintessence in $3\sigma$ regions.
Confronting DGP Braneworld Gravity with Cosmic Observations after Planck Data
Lixin Xu
Physics , 2013, DOI: 10.1088/1475-7516/2014/02/048
Abstract: The normal branch of Dvali-Gabadadze-Porrati braneworld gravity with brane tension is confronted by the currently available cosmic observations from the geometrical and dynamical perspectives. On the geometrical side, the type Ia supernova as standard candle, the baryon acoustic oscillation as standard ruler and the cosmic microwave background measurement from the first released 15.5 months data were used to fix the background evolutions. On the dynamical side, the redshift space distortion data will be used to determine the evolution of the matter perturbation. Through a Markov chain Monte Carlo analysis, we found the dimensionless crossover scale $\Omega_{r_c}=1/(4H^2_0r^2_{c})=0.00183_{-0.00183}^{+0.000338}$ in a spatially flat normal branch of Dvali-Gabadadze-Porrati braneworld. This result suggests that the crossover scale $r_c$ should be around $12H^{-1}_0$ which is consistent with the previous result $r_c>3H^{-1}_0$ and greater. It also implies that the five-dimensional gravity effect is weak to be observed in $H^{-1}_0$ scale.
Constraints on Dark Matter annihilation and Its Equation of State after Planck Data
Lixin Xu
Physics , 2013, DOI: 10.1142/S0217732314400045
Abstract: In this paper, the annihilation of dark matter $f_d\epsilon_0$ with nonzero equation of state $w_{dm}$ was studied by using the currently available cosmic observations which include the geometric and dynamic measurements. The constrained results show they are anti-correlated and are $w_{dm}=0.000390_{-0.000753}^{+0.000754}$ and $f_d\epsilon_0=1.172_{-1.172}^{+0.243}$ respectively in $1\sigma$ regions. With the including of possible annihilation of dark matter, no significant deviation from $\Lambda$CDM model was found in the $1\sigma$ region.
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