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Search Results: 1 - 10 of 113676 matches for " Hai Zhang "
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Architecture of Network and Client-Server model
Hai Zhang
Computer Science , 2013,
Abstract: With the development of Internet technology, the Web is becoming more and more important in our lives so that it has even become an essential element. The application of the Web has never been limited to computers; it has been opened to all kinds of intelligent digital devices like mobile ones. In this paper, we discuss the main and substantial difference between UDP and TCP, and how to implement Client-Server model. We also discuss the efficiency of multi-thread server and its relationship with internet.
Analysis of Temporal and Spatial Distribution and Large-Scale Circulation Features of Extreme Weather Events in Shanxi Province, China in Recent 30 Years  [PDF]
Yanmeng Li, Hai Zhi, Dongfeng Zhang
Journal of Geoscience and Environment Protection (GEP) , 2019, DOI: 10.4236/gep.2019.73009
Abstract: Extreme weather events such as persistent high temperatures, heavy rains or sudden cold waves in Shanxi Province in China have brought great losses and disasters to people’s production and life. It is of great practical significance to study the temporal and spatial distribution characteristics of extreme weather events and the circulation background field. We selected daily high temperature data (≥35°C), daily minimum temperature data and daily precipitation data (≥50 mm) from 109 meteorological stations in Shanxi Province, China from 1981 to 2010, then set the period in which the temperature is ≥35°C for more than 3 days as a high temperature extreme weather event, define the station in which 24 hour cumulative precipitation is ≥50 mm precipitation on a certain day (20 - 20 hours, Beijing time) as a rainstorm weather, and determine the cold air activity with daily minimum temperature dropped by more than 8°C for 24 hours, or decreased by 10°C for 48 h, and a daily minimum temperature of ≤4°C as a cold weather process. We statistically analyze the temporal and spatial characteristics and trends of high temperature, heavy rain and cold weather and the circulation background field. We count the number of extreme weather events such as persistent high temperatures, heavy rains and cold weather frosts in Shanxi, and analyze the temporal and spatial distribution characteristics, trends and general circulation background of extreme weather events. We analyze and find out the common features of the large-scale circulation background field in various extreme weather events. Through the study of the temporal and spatial distribution characteristics of extreme weather events in Shanxi, including persistent high temperature, heavy rain or sudden cold wave frost weather, we summarize the large-scale circulation characteristics of such extreme weather events. It will provide some reference for future related weather forecasting.
A Semi-Implicit Scheme of Lattice Boltzmann Method for Two Dimensional Cavity Flow Simulation  [PDF]
Lei Zhang, Jun Yao, Hai Sun, Jianguang Zhang
Open Journal of Fluid Dynamics (OJFD) , 2015, DOI: 10.4236/ojfd.2015.51002
Abstract: The calculation sequence of collision, propagation and macroscopic variables is not very clear in lattice Boltzmann method (LBM) code implementation. According to the definition, three steps should be computed on all nodes respectively, which mean three loops are needed. While the “pull” scheme makes the only one loop possible for coding, this is called semi-implicit scheme in this study. The accuracy and efficiency of semi-implicit scheme are discussed in detail through the simulation of lid-driven cavity flow. Non-equilibrium extrapolation scheme is adopted on the boundary of simulation area. The results are compared with two classic articles, which show that semi-implicit scheme has good agreement with the classic scheme. When Re is less than 3000, the iterations steps of semi-scheme can be decreased by about 30% though comparing the semi-implicit scheme with standard scheme containing three loops. As the Re increases into more than 3400, the standard scheme is not converged. On the contrary, the iterations of semi-implicit scheme are approximately linear to Re.
Regulation of Protein Function by Residue Oxidation
Xing-Hai Zhang
Proteomics Insights , 2012, DOI: 10.4137/PRI.S3327
Abstract: A majority of extant life forms require O2 to survive and thrive. Oxidation is inevitably one of the most active cellular processes and one constant challenge that living organisms must face. Generation of oxidants including reactive oxygen species is a natural consequence of cellular metabolism of all biological systems during normal life cycle under different environments. These oxidants oxidize many biological macromolecules such as proteins and affect their functions. Oxidation of specific amino acids in proteins may cause damage to protein structure and impair function, or may also activate protein activities and promote cellular metabolism. As an example, the reversible oxidation of cysteine and methionine residues has a profound impact on protein function and cellular process. A recent study that examines the effect of Met oxidation on Ser phosphorylation in a mitochondrial enzyme, pyruvate dehydrogenase, provides another demonstration that protein oxidation is an important regulatory mechanism for organisms to deal with developmental and environmental challenges throughout life processes.
A Framework of Learner Development Ecosystem for Designing a Ubiquitous Educational Informational Infrastructure
Hai Zhang,Takanori Maesako
Journal of Software , 2009, DOI: 10.4304/jsw.4.2.124-131
Abstract: The methodology of designing ubiquitous learning environments has recently started to attract considerable attention in various disciplines. From the viewpoint of researchers of educational technology, this paper proposes a new framework of a learner development ecosystem for designing a ubiquitous learning environment, which is built on the theory of social constructivism proposed by Vygotsky, the theory of ecology of human development by Bronfenbrenner and the knowledge spiral theory by Nonaka. We argue that a practical ubiquitous learning environment should be regarded as a complex, dynamic ecosystem within which a learner’s knowledge is continuously developed in the shape of spiral. Based on this framework, we suggest a technical infrastructure and the implementation of ubiquitous learning in a real world context.
Quantum Creation of Closed Universe with Both Effects of Tunneling and Well
De-Hai Zhang
Physics , 2000,
Abstract: A new ''twice loose shoe'' method in the Wheeler-DeWitt equation of the universe wave function on the cosmic scale factor a and a scalar field $\phi$ is suggested in this letter. We analysis the both affects come from the tunneling effect of a and the potential well effect of $\phi$, and obtain the initial values $a_0$ and $\phi_0$ about a primary closed universe which is born with the largest probability in the quantum manner. Our result is able to overcome the ''large field difficulty'' of the universe quantum creation probability with only tunneling effect. This new born universe has to suffer a startup of inflation, and then comes into the usual slow rolling inflation. The universe with the largest probability maybe has a ''gentle'' inflation or an eternal chaotic inflation, this depends on a new parameter q which describes the tunneling character.
Future Destiny of Quintessential Universe and Constraint on Model from Deceleration Parameter
De-Hai Zhang
Physics , 1999,
Abstract: The evolution of the quintessence in various stages of the universe, the radiation-, matter-, and quintessence-dominated, is closely related with the tracking behavior and the deceleration parameter of the universe. We gave the explicit relation between the equation-of-state of the quintessence in the epoch of the matter-quintessence equality and the inverse power index of the quintessence potential, obtained the constraint on this potential parameter come from the present deceleration parameter, i.e., a low inverse power index. We point out that the low inverse power-law potential with a single term can not work for the tracking solution. In order to have both of the tracker and the suitable deceleration parameter it is necessary to introduce at least two terms in the quintessence potential. We give the future evolution of the quintessential universe.
The First Acoustics Peak CMBR and Cosmic Total Density
De-Hai Zhang
Physics , 2000,
Abstract: Boomerang measured the first peak in CMBR to be at location of $l_D=196\pm 6$, which excites our strong interesting in it. A widely cited formula is $l_D\simeq 200\Omega_T^{-0.50}$ to estimate the cosmic total density. Weinberg shows it is not correct and should be $l_D\propto \Omega_T^{-1.58}$ near the interest point $(\Omega_m,\Omega_\Lambda)=(0.3,0.7)$. We show further that it should be $l_D\propto \Omega_T^{-1.43}\Omega_m^{-0.147}$ or $\Omega_T^{-1.92}\Omega_\Lambda^{0.343}$ near the same point in the more veracious sense if we consider the effect from the sound horizon. We draw a contour graph for the peak location, show that the recent data favor to a closed universe with about $\Omega_T\simeq 1.03$. If we insist on obtaining a flat universe, a point $(0.36,0.64)$, i.e., more matter and less vacuum energy, is still possible, which has a more right-side first peak $l_D=208$ in CMBR and a smaller acceleration parameter $-q_0=0.10$ for the $z=0.4$ redshift SNIa.
The Eventual Quintessential Big Collapse of the Closed Universe with the Present Accelerative Phase
De-Hai Zhang
Physics , 2001,
Abstract: Whether our universe with present day acceleration can eventually collapse is very interesting problem. We are also interesting in such problems, whether the universe is closed? Why it is so flat? How long to expend a period for a cycle of the universe? In this paper a simple ``slow-fast'' type of the quintessence potential is designed for the closed universe to realize the present acceleration of our universe and its eventual big collapse. A detail numerical simulation of the universe evolution demonstrates that it divides the seven stages, a very rich story. It is unexpected that the quintessential kinetic energy is dominated in the shrink stage of the universe with very rapid velocity of the energy increasing. A complete analytic analysis is given for each stage. Some very interesting new problems brought by this collapse are discussed. Therefore our model avoids naturally the future event horizon problem of the present accelerative expanding universe and maybe realize the infinite cycles of the universe, which supplies a mechanism to use naturally the anthropic principle. This paper shows that the understanding on the essence of the cosmological constant should contain a richer content.
The Cosmological Constant as a Residual Energy in the Chaotic Inflationary Model
De-Hai Zhang
Physics , 1999,
Abstract: A new idea of the cosmological constant is proposed in this paper. Due to the horizon is limited, the quantum fluctuation of the inflaton field is not zero, a nonzero vacuum energy is remained as a residual inflationary energy of an unusual potential, however the true stable vacuum energy is zero fortunately. A unified model of the cosmological constant and the chaotic inflation is proposed, which satisfies almost all cosmological phenomenology and will can be tested by data of the cosmic large scale structure.
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