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GLOBAL STABILITY OF AN EPIDEMIC MODEL FOR VECTOR-BORNE DISEASE

Journal of Systems Science & Complexity 2010年第2期23卷 279-292页

作者： Hongzhi YANG Huiming WEI Xuezhi LI Faculty of Science Xi'an Jiaotong University Xi'an 710049 China. State Key Laboratory of Multiphase Flow in Power Engineering Xian Jiaotong University Xi'an 710049China Department of Mathematics Xinyang Normal University Xinyang 464000 China. Department of Mathematics Xinyang Normal University Xinyang 464000 China

This paper considers an epidemic model of a vector-borne disease which has the vectormediated transmission only. The incidence term is of the bilinear mass-action form. It is shown that the global dynamics is completely determined by the basic reproduction number Ro. If Ro ≤ 1, the diseasefree equilibrium is globally stable and the disease dies out. If Ro 〉 1, a unique endemic equilibrium is globally stable in the interior of the feasible region and the disease persists at the endemic equilibrium. Numerical simulations are presented to illustrate the results.

关键词： Basic reproduction number endemic equilibrium epidemic model global stability vectorborne disease.

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Bubble packing method based unstructured grid generation of curved-edge polygon with its application

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Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2009年第11期43卷 109-113页

作者： Wu, Lilong Zhou, Gaoling Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

An algorithm for bubble packing method based unstructured grid generation of a curved-edge polygon is developed to avoid bubble departure from a curved boundary during dynamic bubble movement. The curve boundary is mapped into a straight line to allow bubble adding and moving. Then the bubble position is mapped into the curve boundary by the arc-length parameterization method. Combined with conventional methods, a new method to judge a point in a given curved-edge polygon is proposed. Local grid refinement is realized by adding different size bubbles to the real and artificial vertices and setting the bubble's radius by the weighted average method. Moreover, the SIMPLE algorithm on unstructured collocated grid systems is developed and applied to simulate the lid-driven flow in a polar cavity. The numerical simulation results agree well with the experimental data under different Reynolds numbers.

关键词： Reynolds number

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Life cycle assessment of a 1000 MW supercritical pulverized coal power plant under partial loads 31

Life cycle assessment of a 1000 MW supercritical pulverized ...

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31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2018

作者： Han, Xiaoqu Chen, Nana Karellas, Sotirios Liu, Ming Liu, Jiping Yan, Junjie Kakaras, Emmanuel State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China Laboratory of Steam Boilers and Thermal Plants National Technical University of Athens Athens Greece

ISBN: (纸本)9789729959646

With increasing share of renewable energy sources, pulverized coal (PC) power plants have to participate in peak load regulations frequently and operate in partial loads regularly. The energy efficiency and eco-efficiency are both affected significantly in this manner. Therefore, an overall concept for the estimation of environmental impacts from PC plants under nominal and partial loads should be established in life cycle assessment (LCA) methodology. In the present work, a 1000 MW supercritical coal-fired unit, which is the main force for power supply in China, was modeled using commercial simulation tools (GSE and SimaPro). The aim is to investigate the environmental impacts under different working conditions from the perspective of LCA. Moreover, a partial load feedwater heating system with ejector in a coal-fired power unit was proposed and investigated. Model validation and LCA analysis under nominal load show that GWP and PCOP are the main environmental impacts of PC plants. But AP and EP are also serious concerns. Under partial loads, the AP and EP increase significantly, resulted from the reduction in NOx removal efficiency. It is thereby concluded that the mechanisms of formation, migration, and removal of different kinds of pollutant emissions influence the LCA results significantly. Therefore, operation optimization was carried out based on the guidelines of the LCA framework, to reduce the environmental impacts of PC power plants under partial loads. It is indicated that through the integration of an ejector, the NOx removal efficiency at extremely low load (30%) can be maintained at a high level. The environment impact potentials can thus be reduced effectively. © 2018 University of Minho. All rights reserved.

关键词： Emission control

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Effects of velocity ratio on turbulent mixing layer

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第11期30卷 1882-1884页

作者： Guo, Fu-De Chen, Bin Wang, Zhi-Wei Guo, Lie-Jin Zhang, Xi-Min State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In present paper, the effect of velocity ratio on plane mixing layer is experimentally investigated with Particle Image Velocimetry (PIV). The velocity ratio between low- and high-speed side are 0.25, 0.33 and 0.50, respectively. The Reynolds number based on the velocity difference of two streams and hydraulic diameter of the channel ranges from 15840~132000. The results indicate that the maximum mean Reynolds stress on the same cross section increases with Reynolds number increasing but decreases with velocity ratio increasing at the equal Reynolds number. The mean vorticity increases with Reynolds number increasing on the same cross-section and increases with the velocity ratio increasing at the equal Reynolds number. The maximum non-dimensional mean vorticity decreases according to an exponential law along the stream-wise direction, and the decreasing speed of maximum mean vorticity increases with the velocity ratio increasing.

关键词： Reynolds number

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Simulation of turbulent mixing layer flow by vortex method

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Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2010年第11期44卷 87-91页

作者： Ma, Mingxian Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Turbulent mixing layer flow was simulated by the discrete vortex method, and viscosity was modeled by the random walk method and the solid wall was represented by the vortex sheet in the simulation. The predictions of the profiles of mean velocity and turbulent flow parameters agree well with experimental data. The results show that the peak value of Reynolds shear stress increases but the fluctuations of the peak value occur because of vortex-pairing, and vorticity peak value increases in the downstream direction. Then the effect of Reynolds number on the distribution of the turbulent flow parameters at the same velocity ratio was explored. It seems that the peak values of Reynolds shear stress under different Reynolds numbers will increase at the similar slope in the downstream direction. The average vorticity peak value will decrease in the downstream direction, and the decrease rate will increase with Reynolds number. In addition, the vorticity peak value in each section will increase nearly linearly with Reynolds number.

关键词： Vorticity

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Experimental Study on the Characteristics of Effervescent Atomization

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2019年第4期40卷 834-838页

作者： Wang, Wen-Jie Zheng, Xue-Bo Bai, Bo-Feng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In this paper, the characteristics of effervescent atomization are studied experimentally. A high speed camera was used to record the bubbling process and the change of the flow regime in the mixing chamber. Three typical flow regimes were observed, namely, bubble flow, transition flow and annular flow. The particle size of the spray droplet was measured by a laser particle sizer. The droplet diameter distribution curve under typical flow regimes was obtained. Bubble flow and annular flow showed a single peak distribution, while transition flow showed a bimodal distribution. The effects of parameters such as gas-liquid ratio (GLR), liquid mass flow rate and orifice diameter on droplet size were studied. The results showed that the larger the GLR, the larger the liquid mass flow rate and the smaller the orifice diameter, the smaller the SMD. The instability of the atomization process is analyzed. The larger the GLR and the smaller the orifice diameter, the greater the instability. © 2019, Science Press. All right reserved.

关键词： Atomization

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The explosion limit of dimethyl ether, methane and their mixtures

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第8期30卷 1267-1270页

作者： Chen, Xin Bi, Sheng-Shan Wu, Jiang-Tao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The explosion limits of dimethyl ether, methane and different mixtures of dimethyl ether and methane were measured under the temperature ranging from room temperature to 80C and the pressure ranging from 0.1 to 0.3 MPa. In addition, the effects of temperature and pressure on the explosion limit were analyzed, and the accuracies of some theoretical calculation models of explosion limit were tested with the experimental results.

关键词： Methane

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flow visualization of erythrocytes motion and deformation in microchannel

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2010年第4期31卷 621-624页

作者： Guo, Fang Xiang, Hao Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The dimension of erythrocyte is close to capillary diameter and in microcirculation blood should be treated as a two-phase flow system, i.e., erythrocytes suspended in plasma. The rheological property of erythrocytes will significantly influence the hemodynamics. In our experiment, the motion and deformation of erythrocytes in a microfluidic chip with rectangular cross-section microchannel was captured by optical microscope and high speed CCD camera. The aggregation, deformation and common movement forms of erythrocytes were observed under different viscosity, hematocrit and velocity. It was found that erythrocytes behaved a regular biconcave disc shape at low velocity and low-to-medium viscosity, and always rolled and rotated themselves in their movement. At high velocity and medium viscosity, RBCs elongated obviously along the flow direction and presented a flat oval shape together with a tank-treading motion (TTM).

关键词： Microfluidic chips

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Maximum drag reduction and scale up of surfactant solution

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2013年第9期34卷 1675-1678页

作者： Ma, Ning Xu, Na Wei, Jin-Jia Long, Yan Huang, Chong-Hai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Turbulent drag reducing characteristics of CTAC/NaSal aqueous solution (CTAC had same mass concentration with NaSal.) were investigated in a two-dimensional channel of 30 mm height and 375 mm width, which was made of transparent acrylic resin. The measured drag reduction data were scaled up by using Hoyt's scaling method and were compared with other reported drag reduction data for different channel sizes. It could be concluded that both the critical temperature and critical Reynolds number at which turbulent drag reduction of surfactant solution occurred increased with concentration. There was a maximum drag-reduction about 60% for the measured CTAC/NaSal solutions. The Hoyt's scale-up method correlated well the experimental data for different channel heights when the SIS (shearing induced structure) was established very well in surfactant solutions.

关键词： Drag reduction

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Constructing built-in electric fields in bimetallic selenide heterojunctions to bidirectional catalyze polysulfide conversion for flexible lithium-sulfur batteries

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Chemical engineering Journal 2025年 516卷

作者： Fangchao Han Shichao Zhang Dezhi Yan Yalan Xing Jun Xia Xianggang Guan Qiang Lu Puheng Yang Xiaomeng Wu Qianfan Zhang School of Materials Science and Engineering Beihang University Beijing 100191 PR China Chinese Acad Sci Inst Proc Engn State Key Lab Multiphase Complex Syst POB 353 Beijing 100190 PR China Shanghai Institute of Space Power Sources/State Key Laboratory of Space Power Sources PR China

Parasitic shuttle effects and sluggish kinetics severely limit the practical applications of lithium-sulfur (Li–S) batteries. Developing conducting catalysts with high catalytic activity is effective strategy to address such issues. Electronic engineering as tuning strategy can optimize the electronic structure and enhance the redox reaction kinetics. Herein, NiSe 2 -CoSe 2 hollow microspheres with abundant heterogeneous interfaces were synthesized as sulfur cathode catalysts. DFT calculations show that heterostructure can promote electron redistribution and form built-in electric field (BIEF), which causes the directional transfer of electrons. Additionally, NiSe 2 -CoSe 2 has optimized adsorption energy, which can effectively suppress shuttle effect. Meanwhile, electrochemical tests further confirmed bidirectional catalytic ability. Benefiting the merits, S/NiSe 2 -CoSe 2 -GO-CNF (S/NiCo-GN) achieved an initial discharge specific capacity of 1353.35 mAh g −1 at 0.2C and stable 1000 cycles at 1C with a capacity decay rate of only 0.044 % per cycle. Moreover, S/NiCo-GN also achieved high areal capacity of 1.688 mAh cm −2 at 0.5C under high loading (∼2.5 mg cm −2 ) and lean electrolyte (∼10 μL mg −1 ) conditions. The flexible pouch cell further demonstrated its high safety, good thermal stability, and robust mechanical stability. This work provides guiding methods for the design of efficient catalysts, which can contribute to the realisation of high-performance Li–S batteries.

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