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Bifurcations and chaos control in a discrete-time biological model

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International Journal of Biomathematics 2020年第4期13卷 1-31页

作者： A.Q.Khan T.khalique Department of mathematics University of Azad Jammu and Kashmir muzaffarabad 13100 Pakistan

In this papcr,bifurcations and chaos control in a discrete-time Lotka-Volterra predator-prey model have been studied in *** is shown that for all parametric values,model hus boundary equilibria:P00(0,0),Px0(1,0),and the unique positive equilibrium point:P^+xy(d/c,r(c-d)/bc) if c>*** Linearization method,we explored the local dynamics along with different topological classifications about *** also explored the boundedness of positive solution,global dynamics,and existence of prime-period and periodic points of the *** is explored that flip bifurcation occurs about boundary equilibria:Poo(0,0),P.o(1,0),and also there exists a flip bifurcation when parameters of the discrete-time model vary in a small neighborhood of P^+xy(d/c,r(c-d)/bc).Further,it is also explored that about P^+xy(d/c,r(c-d)/bc) the model undergoes a N-S bifurcation,and meanwhile a stable close invariant curves *** the perspective of biology,these curves imply that betwecn predator and prey populations,there exist periodic or quasi-periodic *** simulations are presented to illustrate not only main results but also reveals the complex dynamics such as the orbits of period-2,3,13,15,17 and *** maximum Lyapunov exponents as well as fractal dimension are computed numeri-cally to justify the chaotic behaviors in the ***,feedback control method is applied to stabilize chaos existing in the model.

关键词： Lotka-Volterra model bifurcations and chaos center manifold theorem numerical simulation

Serological surveillance for SARS-coV-2 antibodies among students,faculty and staff within a large university system during the pandemic

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World Journal of Virology 2025年第1期14卷 99-107页

作者： marcos G Pinheiro Gabriela G O Alves maria Eduarda R conde Sofia L costa Regina c S Sant’Anna Isa m F Antunes mônica c carneiro Fabio S Ronzei Julia c Scaffo Felipe R Pinheiro Lialyz S Andre Helvecio c Povoa Valéria T Baltar Fabíola Giordani Eduarda S Hemerly Gisele c Alexandre Karla c de Paula márcio Watanabe Antonio claudio L da Nóbrega Jackeline christiane P Lobato Fabio Aguiar-Alves Laboratory of molecular Epidemiology and Biotechnology Rodolpho Albino University LaboratoryFluminense Federal UniversityNiterói 24241000Rio de JaneiroBrazil Estácio de SáUniversity Nova Friburgo 28611135Rio de JaneiroBrazil Pathology Program Medicine schoolFluminense Federal UniversityNiterói 24070090Rio de JaneiroBrazil Department of Pharmaceutical Sciences Lloyd L.Gregory School of PharmacyPalm Beach Atlantic UniversityWest Palm BeachFL 33401United States Health Institute of Nova Friburgo Fluminense Federal UniversityNova Friburgo 28613001Rio de JaneiroBrazil Department of Epidemiology and Biostatistics Institute of Collective Health(ISC)Fluminense Federal UniversityNiterói 24033900Rio de JaneiroBrazil Institute of Physical Education Fluminense Federal UniversityNiterói 24020005Rio de JaneiroBrazil Department of Statistics Fluminense Federal UniversityNiterói 24210200Rio de JaneiroBrazil Department of Physiology and Pharmacology Fluminense Federal UniversityNiterói 24210130Rio de JaneiroBrazil

BAcKGROUND At the end of December 2019,the world faced severe acute respiratory syndrome-coronavirus 2(SARS-coV-2),which led to the outbreak of coronavirus disease 2019(cOVID-19),associated with respiratory *** virus has shown significant challenges,especially for senior citizens,patients with other underlying illnesses,or those with a sedentary *** tests conducted early on have helped identify how the virus is transmitted and how to curb its *** study hypothesis was that the rapid serological test for SARS-coV-2 antibodies could indicate the immunoreactive profile during the cOVID-19 pandemic in a university *** To conduct active surveillance for serological expression of anti-SARS-coV-2 antibodies in individuals within a university setting during the cOVID-19 *** This sectional study by convenience sampling was conducted in a large university in Niteroi-RJ,Brazil,from march 2021 to July *** study population consisted of students,faculty,and administrative staff employed by the university.A total of 3433 faculty members,60703 students,and 3812 administrative staff were invited to *** were gathered through rapid serological tests to detect immunoglobulin(Ig)m and IgG against ***χ²or Fisher's exact test was used to conduct statistical analysis.A 0.20 significance level was adopted for variable selection in a multiple logistic regression model to evaluate *** A total of 1648 individuals were enrolled in the *** proportion of cOVID-19 positivity was 164/1648(9.8%).The adjusted logistic model indicate a positive association between the expression of Igm or IgG and age[odds ratio(OR)=1.16,95%cI:1.02-1.31](Pcontact with a cOVID-19-positive case(OR=3.49,95%cI:2.34-5.37)(Pceived the cOVID-19 vaccine(OR=2.33,95%cI:1.61-3.35)(Pcial isolation(OR=0.59,95%cI:0.41-0.84)(P<0.004).The likelihood of sho

关键词： Serological surveillance SARS-coV-2 antibodies cOVID-19 Serological rapid test Risk factors for cOVID-19

Butt-welding Residual Stress of Heat Treatable Aluminum Alloys

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Journal of materials Science & Technology 2007年第2期23卷 217-222页

作者： c.m. cheng Department of Industrial Education National Taiwan Normal University Taipei Taiwan China　

This study, taking three types of aluminum alloys 2024-T351, 6061-T6 and 7075-T6 as experimental materials, conducted single V-groove GTAW （gas tungsten arc welding） butt-welding to analyze and compare the magnitude and differences of residual stress in the three aluminum alloys at different single V-groove angles and in restrained or unrestrained conditions. The results show that the larger the grooving angle of butt joint, the higher the residual tensile stress. Too small grooving angle will lead to dramatic differences due to the amount of welding bead filler metal and pre-set joint geometry. Therefore, only an appropriate grooving angle can reduce residual stress. While welding, weldment in restrained condition will lead to a larger residual stress. Also, a residual stress will arise from the restraint position. The ultimate residual stress of weldment is determined by material yield strength at equilibrium temperature. The higher the yield strength at equilibrium temperature, the higher the material residual stress. Because of its larger thermal conductivity, aluminum alloy test specimens have small temperature differential. Therefore, the residual tensile stress of all materials is lower than their yield strength.

关键词： Residual stress Hole-drilling strain-gage method Aluminum alloy Single-V groove

Detection of Breaking Waves Using X-Band Pulse Radar in the Nearshore Region

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china Ocean Engineering 2013年第4期27卷 549-556页

作者： Y.c.Lin c.c.chang m.c.Lee H.c.chan J.m.Leu Department of Hydraulic and Ocean Engineering National Cheng-Kung University Department of Soil and Water conservation National Chung Hsing University Department of Hospitality management Taiwan Shoufu University

An X-band pulsed Doppler microwave radar has been used to determine the characteristics of breaking waves. Field experiments were conducted at the Shuang-Si estuary in the north of Taiwan in the winter of 2005. Analyses on maxima radar cross section and Doppler frequency shift are done to characterize wave breaking zones. Based on observations of breaking waves, the wave breaking zones are shown to be located at water depths of 1.8 to 2.2 m in the experimental site. In general, the results indicate that a radar system has the potential to delineate the spatial variation of breaking waves clearly and that this is sufficient to achieve a measurement operation for near-shore air-sea interaction events.

关键词： radar Doppler effect wave breaking coastal zone

mixing features in an electromagnetic rectangular micromixer for electrolyte solutions

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Journal of Hydrodynamics 2017年第4期29卷 668-678页

作者： m.m.Wen c.N.Kim Department of mechanical Engineering Graduate School Kyung Hee University Department of mechanical Engineering College of Engineering Kyung Hee University

In this study, a new magnetohydrodynamic（mHD） mixer for electrolyte solutions with pumping function is reported, and the mixing performance of the device for two different electrolyte solutions is numerically examined in a uniform magnetic field. Application of different potentials to different electrodes allows the current to be induced. The combination of the induced current and magnetic field yields Lorentz force, resulting in the fluid motion. The numerical simulation for the flows in the device is carried out with commercial software cFX. The validity of cFX code for the present numerical model is presented. The mixing performance of the fluids is investigated in many different cases with different combinations of input voltage of the electrode. This study shows that the mixing performance can be enhanced by applying spatially alternating positive and negative voltages to the electrodes. The present simulation results show that with a magnetic field intensity lower than 0.5 T, a voltage difference smaller than 2.0 V, and an electric conductivity of electrolyte solution of 1.5 S/m the pumping capabilities ranging 1.6×10^（-7）-3.6×10^（-6） kg/s and the mixing indexes higher than 0.90 can be obtained with sophisticated designs of the micromixer.

关键词： mixer electrolyte solution Lorentz force cFX

Hard rock tunnel boring machine penetration test as an indicator of chipping process efficiency

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Journal of Rock mechanics and Geotechnical Engineering 2017年第4期9卷 611-622页

作者： m.c. Villeneuve Department of Geological Sciences University of Canterbury Christchurch 8140 New Zealand

The transition from grinding to chipping can be observed in tunnel boring machine(TBm) penetration test data by plotting the penetration rate(distance/revolution) against the net cutter thrust(force per cutter) over the full range of penetration rates in the *** penetration test data to the geological and geomechanical characteristics of rock masses through which a penetration test is conducted provides the ability to reveal the efficiency of the chipping process in response to changing geological *** test data can also be used to identify stress-induced tunnel face *** research shows that the strength of the rock is an important parameter for controlling how much net cutter thrust is required to transition from grinding to *** also shows that the geological characteristics of a rock will determine how efficient chipping occurs once it has *** particular,geological characteristics that lead to efficient fracture propagation,such as fabric and mica contents,will lead to efficient *** findings will enable a better correlation between TBm performance and geological conditions for use in TBm design,as a basis for contractual payments where penetration rate dominates the excavation cycle and in further academic investigations into the TBm excavation process.

关键词： Penetration rate Grinding chipping Geological characteristics Face stability

Hydrodynamics of the interceptor on a 2-D flat plate by cFD and experiments

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Journal of Hydrodynamics 2015年第6期27卷 919-933页

作者： mANSOORI m. FERNANDES A.c. Department of Naval and Ocean Engineering Federal University of Rio de Janeiro

Nowadays, the use of interceptor by both partial and total dynamic lift crafts is quite common. In this article, a lot of evidence is given regarding the effectiveness of interceptor. The interceptor, when placed at the stern region, changes the pressure distribution around the craft. Its presence affects drag force, lifting force and the position of pressure＇s center leading to a new trim. This study focuses on hydrodynamic effects of interceptors on a 2-D fiat plate based on both computational fluid dynamic （cFD） and experimental approaches. The Reynolds average Navier-Stokes （RANS） equations are used to model the flow around a fixed flat plate with an interceptor at different heights and attack angles. Based on finite volume method and SImPLE algorithm which uses static structures, this model can be analyzed and the RANS results can be compared with the experimental data obtained in the current channel of the laboratory of waves and current of cOPPE/UFRJ （LOc in Portuguese acronym）. According to the results, the increase of pressure at the end of the flat plate was proportional to the interceptor height. In addition, the existence of interceptors can significantly increase the lift force coefficient at high angles of attack also proportional to the interceptor height. The presence of interceptor at the end of the fiat plate increased both the lift coefficient and the drag coefficient but hydrodynamic drag did not grow as fast as the lift coefficient did. The lift coefficient increased much more. Furthermore, the results showed that the interceptor effectiveness is proportional to the boundary layer thickness at the end of the fiat plate. As the interceptor was inside the boundary layer alterations of flow speed led to changes in boundary layer thickness, directly affecting interceptor＇s efficiency. Optimum choice of interceptor height had a great effect on its efficiency, and in choosing it the flow speed and length of the boat must be taken into consideration.

关键词： interceptor craft 2-D fiat plate lifting coefficient Reynolds average Navier-Stokes (RANS) pressure distribution,computational fluid dynamic drag

A code-independent technique for computational verification of fluid mechanics and heat transfer problems

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Acta mechanica Sinica 2008年第4期24卷 387-397页

作者： m.Garbey c.Picard Department of computer Science University of Houston Houston TX 77204 USA

The goal of this paper is to present a versatile framework for solution verification of PDE＇s. We first generalize the Richardson Extrapolation technique to an optimized extrapolation solution procedure that constructs the best consistent solution from a set of two or three coarse grid solution in the discrete norm of choice. This technique generalizes the Least Square Extrapolation method introduced by one of the author and W. Shyy. We second establish the conditioning number of the problem in a reduced space that approximates the main feature of the numerical solution thanks to a sensitivity analysis. Overall our method produces an a posteriori error estimation in this reduced space of approximation. The key feature of our method is that our construction does not require an internal knowledge of the software neither the source code that produces the solution to be verified. It can be applied in principle as a postprocessing procedure to off the shelf commercial code. We demonstrate the robustness of our method with two steady problems that are separately an incompressible back step flow test case and a heat transfer problem for a battery. Our error estimate might be ultimately verified with a near by manufactured solution. While our pro- cedure is systematic and requires numerous computation of residuals, one can take advantage of distributed computing to get quickly the error estimate.

关键词： Solution verification PDE's Navier Stokes ·Heat transfer. Aposteriori estimate·Distributed computing

modelling mechanical Properties in Native and Biomimetically Formed Vascular Grafts

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Journal of Bionic Engineering 2009年第4期6卷 371-377页

作者： m.mandru c.Ionescu m.chirita University of medicine and Pharmacy Faculty of Biomedical EngineeringUniversity street 16700115 IasiRomania Ghent University Department of Electrical energySystems and AutomationTechnologiepark 913B9052GentBelgium

The paper presents a detailed analysis of experimental data in order to characterize the elastic properties of *** analysis would provide a good basis for evaluation of biomimetic vascular *** the latter needs to exhibit similar properties of native tissue,it is important to accurately characterize the biomimetic sample in a large range of applied stresses. The stress-strain properties vary according to the specific pathology(***,aneurism)and the tissue graft must be chosen *** models are proposed in this paper on the stress-strain *** extension for frequency-domain analysis is provided for one of the *** comparison between vascular grafts and native tissue for carotid and thoracic arteries in pigs are in good agreement with results from *** proposed experimental method offers suitable parameters for identifying models which characterize both elasticity and stiffness properties of the analyzed tissues(stress-strain).The proposed models show good performance in characterizing the intrinsic material properties.

关键词： biomimetic biomaterials vascular graft native and artificial tissues stress-strain modeling