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Differences and Correlations of Morphological and Hemodynamic Parameters between Anterior Circulation bifurcation and Side-wall Aneurysms

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Current Medical Science 2024年第2期44卷 391-398页

作者： Kai-kai GUO Chang-ya LIU Gao-hui LI Jian-ping XIANG Xiao-chang LENG Yi-ke CAI Xue-bin HU Department of Neurosurgery Union HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430022China Department of Emergency Longhua HospitalShanghai University of Traditional Chinese MedicineShanghai 200032China Artery Flow Technology Co. Ltd.Hangzhou 310051China

Objective:The objective of this research was to explore the difference and correlation of the morphological and hemodynamic features between sidewall and bifurcation aneurysms in anterior circulation arteries,utilizing computational fluid dynamics as a tool for analysis.Methods:In line with the designated inclusion criteria,this study covered 160 aneurysms identified in 131 patients who received treatment at Union Hospital of Tongji Medical College,Huazhong University of Science and Technology,China,from January 2021 to September 2022.Utilizing follow-up digital subtraction angiography(DSA)data,these cases were classified into two distinct groups:the sidewall aneurysm group and the bifurcation aneurysm group.Morphological and hemodynamic parameters in the immediate preoperative period were meticulously calculated and examined in both groups using a three-dimensional DSA reconstruction model.Results:No significant differences were found in the morphological or hemodynamic parameters of bifurcation aneurysms at varied locations within the anterior circulation.However,pronounced differences were identified between sidewall and bifurcation aneurysms in terms of morphological parameters such as the diameter of the parent vessel(Dvessel),inflow angle(θF),and size ratio(SR),as well as the hemodynamic parameter of inflow concentration index(ICI)(P0.5,Pbifurcation aneurysms emphasize the importance to contemplate variances in threshold values for these parameters when evaluating the risk of rupture in anterior circulation aneurysms.Whether it is a bifurcation or sidewall aneurysm,these disparities should be considered.The morphological parameter SR has the potential to be a valuable clinical tool for promptly distinguishing

关键词： sidewall bifurcation unruptured aneurysms computational fluid dynamics

Research on the Stability Analysis Method of DC Microgrid Based on bifurcation and Strobe Theory

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Energy Engineering 2024年第4期121卷 987-1005页

作者： Wei Chen Nan Qiu Xusheng Yang School of Electrical Engineering and Information Engineering Lanzhou University of TechnologyLanzhou730050China

During the operation of a DC microgrid,the nonlinearity and low damping characteristics of the DC bus make it prone to oscillatory instability.In this paper,we first establish a discrete nonlinear system dynamic model of a DC microgrid,study the effects of the converter sag coefficient,input voltage,and load resistance on the microgrid stability,and reveal the oscillation mechanism of a DC microgrid caused by a single source.Then,a DC microgrid stability analysis method based on the combination of bifurcation and strobe is used to analyze how the aforementioned parameters influence the oscillation characteristics of the system.Finally,the stability region of the system is obtained by the Jacobi matrix eigenvalue method.Grid simulation verifies the feasibility and effectiveness of the proposed method.

关键词： DC microgrid bifurcation nonlinear dynamics stability analysis oscillation characteristics

Stability and bifurcation analysis of a size-stage-structured cooperation model

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International Journal of Biomathematics 2024年第1期17卷 61-80页

作者： Yajing Li Zhihua Liu Laboratory of Mathematics and Compler Systems(Ministry of Education)School of Mathematical Sciences Beijing Normal University Beijing 100875 P.R.China

In this paper,we propose a size-stage-structured cooperation model which has two distinct life stages in facultative cooperator.The primary feature of this model is to consider size structure,stage structure and obligate and facultative symbiosis at the same time in a cooperation system.We use the method of characteristic to show that this new model can be reduced to a threshold delay equations(TDEs)model,which can be further transformed into a functional differential equations(FDEs)model by a simple change of variables.Such simplification allows us to apply the classical theory of FDEs and establish a set of sufficient conditions to investigate the qualitative analysis of solutions of the FDEs model,including the global existence and uniqueness,positivity and boundedness.What's more,we use the geometric criteria to get the conclusions about stability and Hopf bifurcation of positive equilibrium because the coefficients of the characteristic equation depend on the bifurcation parameter.Finally,numerical simulations are carried out as supporting evidences of our analytical results.Our results show that the presence of size structure and stage structure plays an important role in the dynamic behavior of the model.

关键词： Cooperation model size-structured threshold-type delay stability bifurcation

Some properties of Melnikov functions near a cuspidal loop

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Science China Mathematics 2024年第4期67卷 767-786页

作者： Junmin Yang Maoan Han School of Mathematical Sciences Hebei Normal UniversityShijiazhuang 050024China Department of Mathematics Zhejiang Normal UniversityJinhua 321004China

In this paper,we consider the first-order Melnikov functions and limit cycle bifurcations of a nearHamiltonian system near a cuspidal loop.By establishing relations between the coefficients in the expansions of the two Melnikov functions,we give a general method to obtain the number of limit cycles near the cuspidal loop.As an application,we consider a kind of Liénard systems and obtain a new estimation on the lower bound of the maximum number of limit cycles.

关键词： Melnikov function nilpotent cusp limit cycle bifurcation

Dynamics of a delay-induced prey-predator system with interaction between immature prey and predators

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International Journal of Biomathematics 2024年第2期17卷 139-176页

作者： Soumik Pandey Abhijit Sarkar Debashis Das Sarbani Chakraborty Department of Mathematics West Bengal State University Barasat-7000126West BengalIndia Department of Basic Science&Humanities JIS College of Engineering Kalyani-741235West BengalIndia

In biological pest control systems,several pests(including insects,mites,weeds,etc.)are controlled by biocontrol agents that rely primarily on predation.Following this biocontrol management ecology,we have created a three-tier prey-predator model with prey phase structure and predator gestation delay.Several studies have demonstrated that predators with Holling type-II functional responses sometimes consume immature prey.A study of the well-posedness and local bifurcation(such as saddle-node and transcritical)near the trivial and planer equilibrium points is carried out.Without any time lag,the prey development coeficient has a stabilizing impact,while increasing attack rate accelerates instability.Energy transformation rate and handling time are shown to cause multiple stability switches in the system.Numerical results demonstrate time delay is the key destabilizer that destroys stability.Our model can replicate more realistic events by including time-dependent factors and exploring the dynamic behavior of nonautonomous systems.In the presence of time delay,sufficient conditions of permanence and global attractivity of the nonautonomous system are derived.Finally,MATLAB simulations are performed to validate the analytical findings.

关键词： Holling type-II functional response stage-structure bifurcation time delay seasonality

Dynamics and data fitting of a time-delayed SIRS hepatitis B model with psychological inhibition factor and limited medical resources

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International Journal of Biomathematics 2024年第2期17卷 263-298页

作者： Ximei Wang Xinzhi Ren Yan Wu Yong Li School of Information and Mathematics Yangtze University Jingzhou 434023 P.R.China School of Mathematics and Statistics Southwest University Chongqing 400715 P.R.China School of Mathematics and Statistics Lanzhou University Lanzhou 734000 P.R.China

Hepatitis B is an infectious disease worthy of attention.Considering the incubation period,psychological inhibition factor,vaccine,limited medical resources and horizontal transmission,an SIRS model is proposed to describe hepatitis B transmission dynamics.In order to describe the behavior changes caused by people's psychological changes,the non-monotonic incidence rate is adopted in the model.We use the saturated treatment rate to describe the limited medical resources.Mathematical analysis shows the existence conditions of the equilibria,forward or backward bifurcation,Hopf bifurcation and the Bogdanov-Takens bifurcation.During the observation of the case data of hepatitis B in China,it is found that there are mainly three features,periodic outbreaks,aperiodic outbreaks,and periodic outbreaks turns to aperiodic outbreaks.According to the above features,we select three different representative regions,Jiangxi,Zhejiang province and Beijing,and then use our model to fit the actual monthly hepatitis B case data.The basic reproduction numbers that we estimated are 1.7712,1.4805 and 1.4132,respectively.The results of data fitting are consistent with those of theoretical analysis.According to the sensitivity analysis of Ro,we conclude that reducing contact,increasing treatment rate,strengthening vaccination and revaccinating can effectively prevent and control the prevalence of hepatitis B.

关键词： Hepatitis B SIRS model psychological inhibition factor limited medical resources bifurcation data fitting

Influence of toxic substances on dynamical behavior of a delayed diffusive predator-prey model

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International Journal of Biomathematics 2024年第2期17卷 177-200页

作者： Honglan Zhu Xuebing Zhang Hao Zhang Business School Huaiyin Institute of Technology Huai'an 223003P.R.China College of Mathematics and Statistics Nanjing University of Information Science and Technology Nanjing210044 P.R.China Jiangsu Key Laboratory of Trafic and Transportation Security Huaiyin Institute of Technology Huaian 223003P.R.China

In this paper,we propose and investigate a delayed diffusive predator-prey model affected by toxic substances.We first study the boundedness and persistence property of the model.By analyzing the associated characteristic equation,we obtain the conditions for the existence of steady state bifurcation,Hopf bifurcation and Turing bifurcation.Furthermore,we also study the Hopf bifurcation induced by the delay.Finally,our theoretical results are verified by numerical simulation.The numerical observation results are in good agreement with the theoretically predicted results.Theoretical and numerical simulations indicate that toxic substances have a great impact on the dynamics of the system.

关键词： Toxicant delay diffusion bifurcation spatial pattern

Dynamical behaviors of a constant prey refuge ratio-dependent prey-predator model with Allee and fear effects

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International Journal of Biomathematics 2024年第1期17卷 227-250页

作者： Soumitra Pal Pijush Panday Nikhil Pal A.K.Misra Joydev Chattopadhyays Department of Mathematics Institute of Science Banaras Hindu University Varanasi 221005India Department of Mathematical and Statistical Sciences University of Alberta EdmontonAB T6G 2G1Canada Department of Mathematics Visva-Bharati Santiniketan 731235India Agricultural and Ecological Research Unit Indian Statistical Institute 203 B.T.RoadKolkata 700108India

In this paper,we consider a nonlinear ratio-dependent prey-predator model with constant prey refuge in the prey population.Both Allee and fear phenomena are incorporated explicitly in the growth rate of the prey population.The qualitative behaviors of the proposed model are investigated around the equilibrium points in detail.Hopf bifurcation including its direction and stability for the model is also studied.We observe that fear of predation risk can have both stabilizing and destabilizing effects and induces bubbling phenomenon in the system.It is also observed that for a fixed strength of fear,an increase in the Allee parameter makes the system unstable,whereas an increase in prey refuge drives the system toward stability.However,higher values of both the Allee and prey refuge parameters have negative impacts and the populations go to extinction.Further,we explore the variation of densities of the populations in different bi-parameter spaces,where the coexistence equilibrium point remains stable.Numerical simulations are carried out to explore the dynamical behaviors of the system with the help of MATLAB software.

关键词： Predator-prey system Allee effect fear effect prey refuge bifurcation population density

bifurcation analysis of dual-sidestay landing gear locking performance considering joint clearance

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Chinese Journal of Aeronautics 2022年第7期35卷 209-226页

作者： Kui XU Yin YIN Yixin YANG Hong NIE Xiaohui WEI State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Sidestay lock mechanism is an important part of landing gear system,and the locking performance can be analyzed based on changes in its stability.However,during numerical continuation analysis of fully-rigid dual-sidestay landing gear without clearance,it has been found that the appearance of bifurcation points does not necessarily imply that both sidestay links can be locked synchronously.This problem reveals the limitations of fully-rigid model with ideally-articulated in solving dual-sidestay mechanisms with extremely high motion sensitivity.Therefore,this study proposes a bifurcation analysis method for synchronous locking of dual-sidestay landing gears,which takes into consideration the joint clearance.For in-depth analysis of this problem,we initially build kinematic and mechanical models of a landing gear mechanism that consider joint clearance.Then,the models are solved based on continuation.The fundamental causes of synchronous locking are discussed in detail,and the number of bifurcation points is found to be closely related to whether the landing gear is completely locked.Finally,the effects of structural parameters on the synchronous locking are analyzed,and the feasible region of parameters satisfying synchronous locking condition is given,which agrees well with the test results.

关键词： bifurcation Clearance Dual-sidestay landing gear Numerical continuation Synchronous locking