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Search Results: 1 - 10 of 127066 matches for " Tiantian Li "
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Global Stability Analysis of a Delayed SEIQR Epidemic Model with Quarantine and Latent  [PDF]
Tiantian Li, Yakui Xue
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.410A2011

In this paper, we study a kind of the delayed SEIQR infectious disease model with the quarantine and latent, and get the threshold value which determines the global dynamics and the outcome of the disease. The model has a disease-free equilibrium which is unstable when the basic reproduction number is greater than unity. At the same time, it has a unique endemic equilibrium when the basic reproduction number is greater than unity. According to the mathematical dynamics analysis, we show that disease-free equilibrium and endemic equilibrium are locally asymptotically stable by using Hurwitz criterion and they are globally asymptotically stable by using suitable Lyapunov functions for any \"\" Besides, the SEIQR model with nonlinear incidence rate is studied, and the \"\" that the basic reproduction number is a unity can be found out. Finally, numerical simulations are performed to illustrate and verify the conclusions that will be useful for us to control the spread of infectious diseases. Meanwhile, the \"\" will effect changing trends of \"\"\"\" in system (1), which is obvious in simulations. Here, we take \"\" as an example to explain that.

Optimal mean-variance investment strategy under value-at-risk constraints
Jun Ye,Tiantian Li
Quantitative Finance , 2010,
Abstract: This paper is devoted to study the effects arising from imposing a value-at-risk (VaR) constraint in mean-variance portfolio selection problem for an investor who receives a stochastic cash flow which he/she must then invest in a continuous-time financial market. For simplicity, we assume that there is only one investment opportunity available for the investor, a risky stock. Using techniques of stochastic linear-quadratic (LQ) control, the optimal mean-variance investment strategy with and without VaR constraint are derived explicitly in closed forms, based on solution of corresponding Hamilton-Jacobi-Bellman (HJB) equation. Furthermore, some numerical examples are proposed to show how the addition of the VaR constraint affects the optimal strategy.
On the basis of the morphology of the T-wave alternans: A Poincare mapping method research  [PDF]
Hui Guo, Jie Zhao, Fei Li, Tiantian Li
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.64064

Presently T-wave alternans (TWA) has become a clinical index of non-invasive diagnosis for heart sudden death prediction, and detecting T-wave alternate accurately is particularly important. This paper introduces an algorithm for detecting TWA using Poincare mapping method which is a technique for nonlinear dynamic systems to display periodic behavior. Sample series of beat to beat cycles were selected to prepare Poincare mapping method. Vector Angle Index (VAI), which is the mean of the difference between θi (the angle between the line connecting the i point to the origin and the X axis) and 45 degrees was used to present the presence or absence of TWA. The value of 0.9 rad ≤ VAI ≤ 1.03 rad is accepted as a level determinative for presence of TWA. VAI via Poincare mapping method (PM) is used for correlation analysis with T-wave alternans voltage (Vtwa) by way of the spectral method (SM). The cross-correlation coefficient between Vtwa and VAI is γ = 0.8601. The algorithm can identify the absence and presence of TWA accurately and provide idea for further study of TWA-PM.

Effects of a Nurse-Led Educational Intervention for Chinese Adult Patients with Psoriatic Arthritis: A Case-Control Study  [PDF]
Bishan Cai, Tiantian Xin, Aizhen Yan, Luna Wu, Li Wang
Open Journal of Nursing (OJN) , 2016, DOI: 10.4236/ojn.2016.62012
Abstract: The aim of this study was to evaluate the effect of an individual nurse-led educational intervention for patients with psoriatic arthritis (PsA). This was a case-control study. The case group consisted of six individual educational sessions delivered by a nurse. A total of 40 patients with PsA joined in this study: the case group (n = 20) and the control group (n = 18). After a 6-week intervention, the case group had significantly better management for the severity of arthritis symptoms (p < 0.05), better psychological well-being and significant lower levels of anxiety (p < 0.05), and depression score (p < 0.01), and reported better improvement of physical and psychological domain of quality of life (QOL) (both p values < 0.05) than the control group. In conclusion, this nurse-led individual education intervention has statistically significant benefits for the management of clinical symptoms of arthritis and for psychological well-being and QOL in patients with PsA.
Study on the Corrosion Inhibition Characteristic of ZH and ZG Mannich Base Inhibitors  [PDF]
Shusheng Zhou, Kehua Li, Tiantian Tang, Dongpo Shi
Open Journal of Yangtze Oil and Gas (OJOGas) , 2017, DOI: 10.4236/ojogas.2017.23011
Abstract: ZG/ZH Mannich bases (acid corrosion inhibitors) were synthesized with benzaldehyde, 2-aminothiazole, acetophenone/cyclohexanone as raw materials, and selecting the appropriate proportion of reaction time, temperature and ratio of raw materials.The corrosion inhibition performance of two kinds of Mannich bases on N80 steel was investigated by means of mass loss method and electrochemical technique. The result of mass loss method showed that two kinds of inhibitors both had excellent effect on N80 steel in 15% hydro-chloric acid solution. Electrochemical technique showed that both ZG and ZH were a mainly anodic-controlling composite corrosion inhibitor, and their corrosion inhibition effect was further confirmed by AC impedance technique. The adsorption behavior between inhibitiors and the steel surface both abides by the Langmuir isotherm model.
Darboux Transformation and New Multi-Soliton Solutions of the Whitham-Broer-Kaup System  [PDF]
Tiantian Xu
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.61003
Abstract: Through a variable transformation, the Whitham-Broer-Kaup system is transformed into a parameter Levi system. Based on the Lax pair of the parameter Levi system, the N-fold Darboux transformation with multi-parameters is constructed. Then some new explicit solutions for the Whitham-Broer-Kaup system are obtained via the given Darboux transformation.
Symmetry protected skyrmions in 3D spin-orbit coupled Bose gases
Guanjun Chen,Tiantian Li,Yunbo Zhang
Physics , 2015, DOI: 10.1103/PhysRevA.91.053624
Abstract: We present a variational study of pseudo-spin $1/2$ Bose gases in a harmonic trap with weak 3D spin-orbit coupling of $\bmsigma\cdot\mathbf{p}$ type. This spin-orbit coupling mixes states with different parities, which inspires us to approximate the single particle state with the eigenstates of the total angular momentum, i.e. superposition of harmonic $s$-wave and $p$-wave states. As the time reversal symmetry is protected by two-body interaction, we set the variational order parameter as the combination of two mutually time reversal symmetric eigenstates of the total angular momentum. The variational results essentially reproduce the 3D skyrmion-like ground state recently identified by Kawakami {\it et al.}. We show that these skyrmion-like ground states emerging in this model are primarily caused by $p$ wave spatial mode involving in the variational order parameter that drives two spin components spatially separated. We find the ground state of this system falls into two phases with different density distribution symmetries depending on the relative magnitude of intraspecies and interspecies interaction: Phase I has parity symmetric and axisymmetric density distributions, while Phase II is featured with special joint symmetries of discrete rotational and time reversal symmetry. With the increasing interaction strength the transition occurs between two phases with distinct density distributions, while the topological 3D skyrmion-like spin texture is symmetry protected.
Coupled spin-vortex pair in dipolar spinor Bose-Einstein condensates
Tiantian Li,Su Yi,Yunbo Zhang
Physics , 2015, DOI: 10.1103/PhysRevA.92.063603
Abstract: We investigate the ground-state and magnetic properties of a dipolar spin-1 Bose-Einstein condensate trapped in a symmetric double-well potential. In particular, we focus on the spin-vortex states by assuming that each potential well is highly pancake shaped. We show that the presence of the double-well potential gives rise to two different spin configurations for the spin-vortex pair states. We also study the response of the coupled spin-vortex pair to static transverse magnetic fields.
Interspecies singlet pairing in a mixture of two spin-1 Bose condensates
Jie Zhang,Tiantian Li,Yunbo Zhang
Physics , 2011, DOI: 10.1103/PhysRevA.83.023614
Abstract: We study the ground state properties of a mixture formed by two spin-1 condensates in the absence of an external magnetic field. As the collisional symmetry between interspecies bosonic atoms is broken, the interspecies coupling interaction ($\beta $) and interspecies singlet pairing interaction ($\gamma $) arise. The ground state can be calculated using the angular momentum theory analytically for $\gamma =0$. The full quantum approach of exact diagonalization is adopted numerically to consider the more general case as $\gamma \neq 0$. We illustrate the competition between the two interspecies interactions and find that as singlet pairing interaction dominates (or the total spin vanishes), there are still different types of singlet formations which are well determined by $\beta $.
The Impact of Irrigation on Bacterial Community Composition and Diversity in Liaohe Estuary Wetland The Impact of Irrigation on Bacterial Community Composition and Diversity in Liaohe Estuary Wetland
LI Tiantian,HU Hong,LI Zhengyan,ZHANG Jianye,LI Dong
- , 2018,
Abstract: In this study, the sequencing of 16S ribosomal DNA was used to characterize the soil bacterial community composition and diversity in Liaohe estuarine wetland. Soil samples were taken from different locations in the wetland dominated by reed. Moreover, the soil quality parameters were evaluated(p H, moisture, organic matter, total nitrogen, available nitrogen, total phosphorus, available phosphorus). The results showed that the organic matter and nutrient contents were significantly higher in irrigated wetland than those in natural wetland. Major phylogenic groups of bacteria in soil samples including Proteobacteria, Acidobacteria, Gemmatimonadetes, Actinobacteria and Cyanobacteria were analyzed and we found that Proteobacteria was the most abundant in the community, and the phylum Acidobacteria was more abundant in irrigated wetland. Beta diversity analyses indicated that the soil bacterial community was mainly affected by sampling sites rather than seasons. In general, the bacterial community in natural wetland was not significantly different with that in artificial irrigated wetland. Artificial hydraulic engineering irrigated according to the water requirement rule of reed, increased the production of reeds, changed the way of wetland soil material input, but the diversity of bacterial community kept stable relatively
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