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Search Results: 1 - 10 of 70583 matches for " YU Zhen "
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Empirical Analysis of the Spread of University Students’ Amative Behavior  [PDF]
Xiaoling Yu, Zhen Jia, Cuiping Zhang
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.48A019

We used a questionnaire to obtain data about 664 university students’ amative behavior in a campus. Then we studied dissemination rules of university students’ amative behavior on campus social network. We found the amative behavior changes over time by focusing on the analysis of love group’s influence to single people and single group’s affected degree. Meanwhile, we compared the influence of single and multiple social relationships to the spread of amative behavior, and the result shows diversity of social relationships is a significant effect factor in spreading process.

Logistic Mapping-Based Complex Network Modeling  [PDF]
Xiaoling Yu, Zhen Jia, Xiangguo Jian
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.411210

In this paper, a new topological approach for studying an integer sequence constructed from Logistic mapping is proposed. By evenly segmenting [0,1] into N non-overlapping subintervals which is marked as \"\", representing the nodes identities, a network is constructed for analysis. Wherein the undirected edges symbolize their relation of adjacency in an integer sequence obtained from the Logistic mapping and the top integral function. By observation, we find that nodes’ degree changes with different values of \"\" instead of the initial value—X0, and the degree distribution presents the characteristics of scale free network, presenting power law distribution. The results presented in this paper provide some insight into degree distribution of the network constructed from integer sequence that may help better understanding of the nature of Logistic mapping.

Design of Monitoring System on QDQ2-1 Type Water Electrolysis Hydrogen Equipment  [PDF]
Tao Jiang, Ping Yu, Yu Liu, Jiajia Zhang, Shuyong Zhen
Open Journal of Safety Science and Technology (OJSST) , 2016, DOI: 10.4236/ojsst.2016.63006
Abstract: In order to solve the deficiencies of the prior detection method on QDQ2-1 type water electrolysis hydrogen equipment, the key state parameters of hydrogen plant, such as hydrogen storage pressure, the operating voltage and the temperature of the tank, can be monitored in remote online by making full use of modern communications technology and data collection [1]. Once the hydrogen plant is abnormal, the alarm can be issued in time. The multi-point real-time automatic monitoring [2] mode can be realized in the hydrogen production process. The safe operation of hydrogen production work can be greatly improved by the advanced monitoring mode.
A High Resolution Method for Fluid Prediction Based on Geostatistical Inversion
Zhen Yu,Jing He
International Journal of Geophysics , 2013, DOI: 10.1155/2013/845646
A High Resolution Method for Fluid Prediction Based on Geostatistical Inversion
Zhen Yu,Jing He
International Journal of Geophysics , 2013, DOI: 10.1155/2013/845646
Abstract: In order to predict the fluid in thin layer precisely, this paper proposed a high-resolution method for fluid prediction. The method used geostatistical inversion with lithology masks to calculate water saturation. We applied this method to theoretical model and real data. The result was compared with that of prestack AVA simultaneous inversion for fluid prediction. It showed that this method had high resolution both in vertical and lateral directions for fluid prediction and could also predict the fluid in thin layer efficiently. 1. Introduction Nowadays the main target of geological exploration has changed from a simple constructed oil and gas reservoir to complex structure reservoir and lithology reservoir. The need of precise exploration is increasing. The precise prediction for thin-layer fluid becomes an urgent problem for oil and gas exploration. Conventional fluid prediction is mainly based on AVO technology, including AVO analysis [1, 2], prestack AVA simultaneous inversion [3, 4], elastic impedance inversion [5, 6], and other methods. However, these methods do analysis mainly based on seismic data, and their vertical resolution is limited. So it cannot precisely predict the fluid in thin layer and cannot meet the needs of precise exploration. In this paper, in order to solve this issue, we presented a high-resolution method for fluid prediction. The method used geostatistical inversion with lithology masks to calculate water saturation. The result was compared with that of prestack AVA simultaneous inversion. 2. Method 2.1. Geostatistical Inversion with Lithology Masks Geostatistical inversion is based on geological information (including seismic, drilling, and logging). It applies random function theory and geostatistics (histogram analysis, variogram analysis, etc.) and combines with traditional seismic inversion technique. It can generate multiple optional inversion results with the same probability [7–9]. It includes stochastic simulation and stochastic inversion. Stochastic simulation includes sequential Gaussian simulation, sequential indicator simulation, and other simulation methods. The geostatistical inversion with lithology masks mentioned in this paper contained two parts: sequential Gaussian simulation with lithology masks and stochastic inversion. 2.1.1. Sequential Gaussian Simulation with Lithology Masks The basic principle of sequential Gaussian simulation is the application of Kriging algorithm for locally estimating the geological variables, which is using a set of values at grid points where it is known (it is generally the
State Transitions in Bright Galactic X-ray Binaries: Luminosities Span by Two Orders of Magnitude
Wenfei Yu,Zhen Yan
Physics , 2009, DOI: 10.1088/0004-637X/701/2/1940
Abstract: Using X-ray monitoring observations with the ASM on board the RXTE and the BAT on board the Swift, we are able to study the spectral state transitions occurred in about 20 bright persistent and transient black hole and neutron star binaries. We have confirmed that there is a correlation between the X-ray luminosity corresponding to the hard-to-soft transition and the X-ray luminosity of the following soft state. This correlation holds over a luminosity range spanning by two orders of magnitude, with no indication of a flux saturation or cut-off. We have also found that the transition luminosity correlates with the rate of increase in the X-ray luminosity during the rising phase of an outburst or flare, implying that the origin of the variation of the transition luminosity is associated with non-stationary accretion in both transient sources and persistent sources. The correlation between the luminosity corresponding to the end of the soft-to-hard transition and the peak luminosity of the preceding soft state is found insignificant. The results suggest that the hysteresis effect of spectral state transitions is primarily driven by non-stationary accretion when the mass accretion rate increases rather than the mass accretion rate decreases. Our results also imply that Galactic X-ray binaries can reach more luminous hard states during outbursts of higher luminosities and of similar rise time scales as those observed. Based on the correlations, we speculate that bright hard state beyond the Eddington luminosity will be observed in Galactic binaries in the next century. We also suggest that some ultra-luminous X-ray sources in nearby galaxies, which stay in the hard states during bright, short flares, harbor stellar-mass compact stars.
Fourth-order split monopole perturbation solutions to the Blandford-Znajek mechanism
Zhen Pan,Cong Yu
Physics , 2015, DOI: 10.1103/PhysRevD.91.064067
Abstract: The Blandford-Znajek (BZ) mechanism describes a physical process for the energy extraction from a spinning black hole (BH), which is believed to power a great variety of astrophysical sources, such as active galactic nuclei (AGNs) and Gamma ray bursts (GRBs). The only known analytic solution to the BZ mechanism is a split monopole perturbation solution up to $O(a^2)$, where $a$ is the spin parameter of a Kerr black hole. In this paper, we extend the monopole solution to higher order $\sim O(a^4)$. We carefully investigate the structure of the BH magnetosphere, including the angular velocity of magnetic field lines $\Omega$, the toroidal magnetic field $B^\phi$ as well as the poloidal electric current $I$. In addition, the relevant energy extraction rate $\dot E$ and the stability of this high-order monopole perturbation solution are also examined.
Analytic properties of force-free jets in the Kerr spacetime- I
Zhen Pan,Cong Yu
Physics , 2015, DOI: 10.1088/0004-637X/812/1/57
Abstract: Blandford-Znajek (BZ) mechanism describes a process extracting rotation energy from a spinning black hole (BH) via magnetic field lines penetrating the event horizon of central BH. In this paper, we present a perturbation approach to study force-free jets launched by the BZ mechanism, and its two immediate applications: (1) we present a high-order split monopole perturbation solution to the BZ mechanism, which accurately pins down the energy extraction rate $\dot E$ and well describes the structure of BH magnetosphere for all range of BH spins ($0\leq a\leq 1$); (2) the approach yields an exact constraint for the monopole field configuration in the Kerr spacetime, $I = \Omega (1-A_\phi^2)$, where $A_\phi$ is the $\phi-$component of the vector potential of electromagnetic field, $\Omega$ is the angular velocity of magnetic field lines and $I$ is the poloidal electric current. The constraint is of particular importance to benchmark the accuracy of numerical simulations.
Highly-collimated, magnetically-dominated jets around rotating black holes
Zhen Pan,Cong Yu
Physics , 2014,
Abstract: In this paper, we propose a general method for perturtative solutions to Blandford-Znajek mechanism. Instead of solving the nonlinear Grad-Shafranov equation directly, we introduce an alternative way to determine relevant physical quantities based on the horizon boundary condition and the convergence requirement. Both the angular velocity $\Omega$ of magnetic field lines, the toroidal magnetic field $B^\phi$ and the total electric current $I$ are self-consistently specified according to our method. As an example, stationary axisymmetric and force-free jet models around rotating black holes are self-consistently constructed according to the method we proposed. This jet solution distinguishes itself from prior known analytic solutions in that it is highly collimated and asymptotically approaches a magnetic cylinder. This jet solution is helically twisted, since toroidal magnetic field is generated when the black hole spin is taken into account. For a given magnetic flux threading the black hole, the jet power and energy extraction rate of the collimated jet are compared with previous solutions. We find that our new solution agrees better with current state-of-the-art numerical simulation results. Some interesting properties of the collimated jet and effects of field line rotation on the jet stability are also briefly discussed.
X-ray outbursts of low-mass X-ray binary transients observed in the RXTE era
Zhen Yan,Wenfei Yu
Physics , 2014, DOI: 10.1088/0004-637X/805/2/87
Abstract: We have performed a statistical study of the properties of 110 bright X-ray outbursts in 36 low-mass X-ray binary transients (LMXBTs) seen with the All-Sky Monitor (2--12 keV) on board the {\it Rossi X-ray Timing Explorer} ({\it RXTE}) in 1996--2011. We have measured a number of outburst properties, including peak X-ray luminosity, rate of change of luminosity on a daily timescale, $e$-folding rise and decay timescales, outburst duration, and total radiated energy. We found that the average properties such as peak X-ray luminosity, rise and decay timescales, outburst duration, and total radiated energy of black hole LMXBTs, are at least two times larger than those of neutron star LMXBTs, implying that the measurements of these properties may provide preliminary clues as to the nature of the compact object of a newly discovered LMXBT. We also found that the outburst peak X-ray luminosity is correlated with the rate of change of X-ray luminosity in both the rise and the decay phases, which is consistent with our previous studies. Positive correlations between total radiated energy and peak X-ray luminosity, and between total radiated energy and the $e$-folding rise or decay timescale, are also found in the outbursts. These correlations suggest that the mass stored in the disk before an outburst is the primary initial condition that sets up the outburst properties seen later. We also found that the outbursts of two transient stellar-mass ULXs in M31 also roughly follow the correlations, which indicate that the same outburst mechanism works for the brighter outbursts of these two sources in M31 that reached the Eddington luminosity.
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