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Search Results: 1 - 10 of 29259 matches for " Tao Tang "
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On discrete least square projection in unbounded domain with random evaluations and its application to parametric uncertainty quantification
Tao Tang,Tao Zhou
Mathematics , 2014,
Abstract: This work is concerned with approximating multivariate functions in unbounded domain by using discrete least-squares projection with random points evaluations. Particular attention are given to functions with random Gaussian or Gamma parameters. We first demonstrate that the traditional Hermite (Laguerre) polynomials chaos expansion suffers from the \textit{instability} in the sense that an \textit{unfeasible} number of points, which is relevant to the dimension of the approximation space, is needed to guarantee the stability in the least square framework. We then propose to use the Hermite/Laguerre {\em functions} (rather than polynomials) as bases in the expansion. The corresponding design points are obtained by mapping the uniformly distributed random points in bounded intervals to the unbounded domain, which involved a mapping parameter $L$. By using the Hermite/Laguerre {\em functions} and a proper mapping parameter, the stability can be significantly improved even if the number of design points scales \textit{linearly} (up to a logarithmic factor) with the dimension of the approximation space. Apart from the stability, another important issue is the rate of convergence. To speed up the convergence, an effective scaling factor is introduced, and a principle for choosing quasi-optimal scaling factor is discussed. Applications to parametric uncertainty quantification are illustrated by considering a random ODE model together with an elliptic problem with lognormal random input.
Characteristics of Dry Cold Air Intrusion in a Typical Strong Storm  [PDF]
Yanjing Tang, Bo Liao, Tao Wei
Journal of Geoscience and Environment Protection (GEP) , 2019, DOI: 10.4236/gep.2019.74015
Abstract: Taking a typical strong storm in Guizhou on April 5, 2017 for example, the diagnosis analysis used the water vapor cloud and the initial field of EC thin grid, including physical quantity, surface and upper air meteorological observation, as well as radar observation data. For the environment parameter analysis, small CAPE value tended to underestimate storm intensity on potential forecast stage, strong vertical wind shear revealed the strong dry cold air was the important intensity factors of the storm. The water vapor cloud map can be used to monitor the most important features, the dry zone, the wet zone and the boundary between them. When dry intrusion is found, it can be used as one of the bases for the development of heavy rain. Dry cold air intrusion on high-level was traced by water vapor images. And in this process, the analyses revealed the role of dry cold air’s influence on intensity of the storm.
IL-33 Attenuates Anoxia/Reoxygenation-Induced Cardiomyocyte Apoptosis by Inhibition of PKCβ/JNK Pathway
Tao Rui, Qizhu Tang
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056089
Abstract: Background Interleukin-33 (IL-33) is a new member of the IL-1 cytokine family. The objectives of present study are to assess whether IL-33 can protect cardiomyocytes from anoxia/reoxygenation (A/R)-induced injury and the mechanism involved in the protection. Methods Cardiomyocytes derived from either wild type or JNK1?/? mice were challenged with an A/R with or without IL-33. Myocyte apoptosis was assessed by measuring caspase 3 activity, fragmented DNA and TUNEL staining. In addition, cardiomyocyte oxidative stress was assessed by measuring DHR123 oxidation; PKCβII and JNK phosphorylation were assessed with Western blot. Results Challenge of cardiomyocytes with an A/R resulted in cardiomyocyte oxidative stress, PKCβII and JNK phosphorylation, and myocyte apoptosis. Treatment of the cardiomyocytes with IL-33 attenuated the A/R-induced myocyte oxidative stress, prevented PKCβII and JNK phosphorylation and attenuated the A/R-induced myocyte apoptosis. The protective effect of the IL-33 did not show in cardiac myocytes with siRNA specific to PKCβII or myocytes deficient in JNK1. Inhibition of PKCβII prevented the A/R-induced JNK phosphorylation, but inhibition of JNK1 showed no effect on A/R-induced PKCβII phosphorylation. Conclusions Our results indicate that IL-33 prevents the A/R-induced myocyte apoptosis through inhibition of PKCβ/JNK pathway.
Numerical investigations on the finite time singularity in two-dimensional Boussinesq equations
Z. Yin,Tao Tang
Physics , 2006,
Abstract: To investigate the finite time singularity in three-dimensional (3D) Euler flows, the simplified model of 3D axisymmetric incompressible fluids (i.e., two-dimensional Boussinesq approximation equations) is studied numerically. The system describes a cap-like hot zone of fluid rising from the bottom, while the edges of the cap lag behind, forming eye-like vortices. The hot liquid is driven by the buoyancy and meanwhile attracted by the vortices, which leads to the singularity-forming mechanism in our simulation. In the previous 2D Boussinesq simulations, the symmetricial initial data is used. However, it is observed that the adoption of symmetry leads to coordinate singularity. Moreover, as demonstrated in this work that the locations of peak values for the vorticity and the temperature gradient becomes far apart as $t$ approaches the predicted blow-up time. This suggests that the symmetry assumption may be unreasonable for searching solution blow-ups. One of the main contributions of this work is to propose an appropriate asymmetric initial condition, which avoids coordinate singularity and also makes the blow-up to occur much earlier than that given by the previously simulations. The shorter simulation time suppresses the development of the round-off error. On the numerical side, the pseudo-spectral method with filtering technique is adopted. The resolutions adopted in this study vary from $1024^2$, $2048^2$, $4096^2$ to $6144^2$. With our proposed asymmetric initial condition, it is shown that the $4096^2$ and $6144^2$ runs yield convergent results when $t$ is fairly close to the predicted blow-up time. Moreover, as expected the locations of peak values for the vorticity and the temperature gradient are very close to each other as $t$ approaches the predicted blow-up time.
Resolving Small-scale Structures in Two-dimensional Boussinesq Convection by Spectral Methods with High Resolutions
Z. Yin,Tao Tang
Physics , 2005,
Abstract: Two-dimensional Boussinesq convection is studied numerically with very fine spatial resolutions up to 4096^2. Our numerical study starts with a smooth asymmetric initial condition, which is chosen to make the flow field well confined in the computational domain until the blow-up time (T_c). Our study shows that the vorticity will blow up at a finite time with |\omega|_{max} \~{(T_c-t)}^{-1.61} and |\nabla \theta|_{max} ~ {(T_c - t)}^{-3.58}.
Efficient routing strategies in scale-free networks with limited bandwidth
Ming Tang,Tao Zhou
Computer Science , 2011, DOI: 10.1103/PhysRevE.84.026116
Abstract: We study the traffic dynamics in complex networks where each link is assigned a limited and identical bandwidth. Although the first-in-first-out (FIFO) queuing rule is widely applied in the routing protocol of information packets, here we argue that if we drop this rule, the overall throughput of the network can be remarkably enhanced. We proposed some efficient routing strategies that do not strictly obey the FIFO rule. Comparing with the routine shortest path strategy, the throughput for both Barab\'asi-Albert (BA) networks and the real Internet, the throughput can be improved more than five times. We calculate the theoretical limitation of the throughput. In BA networks, our proposed strategy can achieve 88% of the theoretical optimum, yet for the real Internet, it is about 12%, implying that we have a huge space to further improve the routing strategy for the real Internet. Finally we discuss possibly promising ways to design more efficient routing strategies for the Internet.
Analysis of Reflection Properties of High Power Microwave Propagation in Mixture-Atmosphere  [PDF]
Tao Tang, Cheng Liao, Qingmin Gao, Pengcheng Zhao
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.29070
Abstract: A simple theoretical modeling is made to describe the reflection features of the high power microwave (HPM) in the mixture-atmosphere. The time-space dependent mixture-atmosphere is generated by ionization of the neutral molecules in atmosphere. Reflection will occur when HPM propagates in such mixture-atmosphere. The reflection characteristic of the HPM propagation in the mixture-atmosphere is investigated by FDTD numerical experiments in inhomogeneous medium, the influence on the reflection for different HPM parameters is concluded. An additional stability conditions for the FDTD difference scheme of the HPM mixture-atmosphere propagation model are presented.
Down Regulation of Survivin Gene and Up Regulation of p53 Gene expression by siRNA Induces Apoptosis in human Hepatocellular Carcinoma cell Line HepG2  [PDF]
Yun-Hua Lu, Cong Tang, Wei Wang, Tao Xi
Journal of Biomedical Science and Engineering (JBiSE) , 2009, DOI: 10.4236/jbise.2009.21010
Abstract: Survivin gene may be a good target for cancer gene therapy because it is over expressed in a variety of human tumors including human hepatocellular carcinoma but not in differen- tiated adult tissues. To explore the effects of the siRNA of survivin gene inducing apoptosis in human hepatocellular cancer cells, three siRNAs cpusiRNA1, cpusiRNA2 and cpusiRNA3 were designed and transferred into human hepatocellular carcinoma cell line HepG2 (HepG2) by lipofection. MTT test showed that the growth of HepG2 decreased when it was transfected with 25nM, 50nM, 100nM, 150nM, 200nM, 400nM siRNA respectively after 48 hours. And the change of mRNA and protein of survivin gene and p53 gene had been detected by RT-PCR and Western blot. Cells presented an increase in apoptosis index was assayed by flow cytometry. Small interfering RNA can exert a knockdown of survivin gene expression and up regulation of p53 gene to induce apoptosis and to inhibit the growth of HepG2.
An Immunity-Based IOT Environment Security Situation Awareness Model  [PDF]
Yuanquan Shi, Tao Li, Renfa Li, Xiaoning Peng, Pengju Tang
Journal of Computer and Communications (JCC) , 2017, DOI: 10.4236/jcc.2017.57016
Abstract: To effectively perceive network security situation under IOT environment, an Immunity-based IOT Environment Security Situation Awareness (IIESSA) model is proposed. In IIESSA, some formal definitions for self, non-self, antigen and detector are given. According to the relationship between the antibody-concentration of memory detectors and the intensity of network attack activities, the security situation evaluation method under IOT environment based on artificial immune system is presented. And then according to the situation time series obtained by the mentioned evaluation method, the security situation prediction method based on grey prediction theory is presented for forecasting the intensity and security situation of network attack activities that the IOT environment will be suffered in next step. The experimental results show that IIESSA provides a novel and effective model for perceiving security situation of IOT environment.
Analysis of Influence Factors of Tide-Dominated Estuaries Based on Deposition Numerical Simulation  [PDF]
Tao Tang, Jixin Huang, Yanshu Yin, Wenjie Feng
Open Journal of Yangtze Oil and Gas (OJOGas) , 2018, DOI: 10.4236/ojogas.2018.32012
Abstract: Tide-dominated estuaries sedimentary reservoir is a hot area of sedimentology research in recent years, and the important target of oil and gas exploration is one of the relatively few sedimentary systems. Based on the study of underground reservoirs, outcrop and modern sedimentation, scholars believe that the estuary is a sedimentary system formed by transgressive system tract, which is composed of a complex subfacies environment with obvious changes. Its formation is influenced by many factors. The purpose of this paper is to simulate the deposition process of estuaries by Delft-3D software, and to reveal the main controlling factors of estuarine reservoir formation. The factors are as follows. 1) The size of the river flow has a destructive effect on the formation of the estuarine sand bar in the estuary, but the effect is small. 2) Tidal energy plays a constructive role in estuarine sand bars in estuaries, and it is also the main force for the formation of estuarine reservoirs. 3) The composition of the sediments has an obvious influence on the formation of the estuarine reservoir, and the content of the mud is an important factor for the retention of the estuarine sand bar.
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