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This research paper proposes a hybrid Whale Optimization Algorithm (WOA) variant based on Equilibrium Optimizer (EO), named Equilibrium Whale Optimization Algorithm (EWOA). The major finding lies in an efficient hybridization of bio-inspired (WOA) and physics-based (EO) metaheuristic algorithms. Upon mathematical modelling, EWOA proposes a main architecture that combines WOA's encircling and net-bubble attacking mechanisms via EO's weight balance strategy. The proposed algorithm was tested on 23 classical, 28 constrained CEC 2017, 30 unconstrained CEC 2017, 10 CEC 2019, and 10 CEC 2020 benchmark problems, in comparison with six recently proposed state-of-the-art algorithms (including WOA and EO). EWOA outperforms other algorithms with the best statistical mean performance on 46 out of 101 functions and the most promising clustering data in the graph, respectively. The fact that EWOA could achieve best statistical SD performance on 2 of the total 5 benchmark sets proves that EWOA is competitively robust. EWOA can converge to the optimum before 50% iterations of most benchmark functions, achieving the fastest convergence rate compared to other algorithms. The major contribution thereby lies in the successful development of this hybrid algorithm, which yields better optimization efficiency than the original and other state-of-the-art algorithms in terms of statistics, convergence and clustering. [ABSTRACT FROM AUTHOR]

• Propose a parking-size weibit (PSW) model for the parking choice with emerging shared parking services. • Propose a spatially correlated weibit (SCW) model for the destination choice with spatial information. • Address the spatial similarity and heterogeneity issues in the joint destination and parking choice. • Develop the combined SCW-PSW equilibrium model with an equivalent mathematical programming formulation. • Develop a partial linearization algorithm combined with an iterative balancing scheme for solving the SCW-PSW equilibrium model. This paper proposes a weibit-based equilibrium choice model for investigating the effect of the emerging shared parking services, which have recently received increasing interest, on combined destination location and parking choice behaviors. The model considers the features of shared parking services, including the avoidance of cruising to search for a parking space and limited supply of shared parking spaces. The spatial similarity issues of destination and parking choices, i.e., the correlations among spatially adjacent destination locations and the parking spaces around them, are separately considered through the advanced spatially correlated weibit (SCW) model and parking-size weibit (PSW) model, respectively. Subsequently, an equivalent mathematical programming (MP) formulation of the equilibrium SCW-PSW model is developed, which guarantees the existence and uniqueness of the solutions. Based on the MP formulation, a partial linearization algorithm embedded with the iterative balancing direction-finding scheme and self-regulated averaging line search scheme is developed to solve the proposed equilibrium model. Numerical examples are presented to illustrate the properties of the proposed model and its applicability to analyzing planning scenarios with different shared parking supplies. [ABSTRACT FROM AUTHOR]

In this paper, we extend the classic SIR model to find an optimal lockdown policy to balance between the economy and people's health during the outbreak of COVID-19. In our model, we intend to solve a two phases optimisation problem: policymakers control the lockdown rate to maximise the overall welfare of the society; people in different health statuses take different decisions on their working hours and consumption to maximise their utility. We develop a novel method to estimate parameters for the model through various additional sources of data. We use the Cournot equilibrium to model people's behaviour. The analysis of simulation results provides scientific suggestions for policymakers to make critical decisions on when to start the lockdown and how strong it should be during the whole period of the outbreak. [ABSTRACT FROM AUTHOR]

The projection of the intensity of the epidemics based on their prolonged history remains wanting or lagging altogether. Numerous modeling techniques are being developed to forecast the future of the disease. Various mathematical models have been developed in the literature which assume the spread of infection by considering interaction among the susceptible and infected classes only. In this paper, we propose a more realistic modified SEIR (susceptible–exposed–infected–recovered) model with a time delay in which the origin of infection by interaction within the susceptible and exposed classes is also analyzed. Moreover, various stochastic characteristics, such as population migration and linkages at local levels, are also taken into account to depict more logical population dynamics. We compute the basic reproductive number and investigate the existence and stability of disease-free equilibrium and endemic equilibrium. The effect of crucial parameters influencing disease dynamics on basic reproductive numbers is also being investigated. It has been seen that the basic reproductive number increases with the increase in time delay, contrary to observations in the past. This highlights the significance of the incorporated modified interactions within susceptible and exposed classes along with their factual parameters on the disease dynamics. • We propose a modified SEIR model with time delay. • Interaction within the susceptible and exposed classes is considered. • The parameters like population movement and local connections are incorporated. • The existence and stability of disease-free and endemic equilibrium are examined. • The basic reproductive number and its relation with important parameters is analyzed. [ABSTRACT FROM AUTHOR]

Highlights • A critical review on carbonated water injection (CWI) is provided. • Description, key characteristics, and pros and cons of CWI process are discussed. • Parametric sensitivity analysis identifies important factors/mechanisms in CWI strategy. • Main challenges for research/engineering activities in CWI processes are addressed. • Useful guidelines to design, operate, and optimize CWI operations are recommended. Abstract Carbonated water injection (CWI) is a promising enhanced oil recovery (EOR) technique in which the dissolved CO 2 can transfer to the oil phase to improve the oil mobility and to cause oil swelling, both enhancing the sweep efficiency. In addition to serving as an EOR method, CWI promotes a high storage capacity for geological CO 2 storage. A number of laboratory tests and field applications have confirmed the effectiveness of CWI. This paper provides a comprehensive review of CWI to cover its important aspects/features such as displacement mechanisms and recovery performance at various conditions/properties. In this paper, carbonated water injection process and the properties of CO 2 -brine-oil systems are described. The influences of petrophysical properties, fluid properties, and operational parameters on the performance of CWI are also thoroughly addressed. The pore-scale investigations conducted by several researchers are reported in this review. The theoretical and practical challenges associated with the implementation of CWI are also discussed to unveil the fundamental mechanisms of transport phenomena in CWI. Some of the key points that are deduced from the previous theoretical and engineering works include: the exsolution of CO 2 from carbonated water during pressure drop can provide additional energy for an extra oil recovery; detailed mathematical models capable of capturing the effects of dissolution, gravity, capillary pressure, and relative permeability hysteresis in 2-D and 3-D spatial orientation on the CWI performance have not been systematically developed yet; disparities between model results and experimental results are attributed to the instantaneous equilibrium assumptions in the model development; and the occurrence of asphaltene precipitation during CWI operations has not been highlighted in a majority of research works, while it is expected to happen during the CO 2 exsolution due to the pressure decline. [ABSTRACT FROM AUTHOR]

Abstract Investors often co-invest in the same project together. As the payoff of the project realizes, how to share the total payoff is in consideration. With this inspiration, an investor sharing game is proposed in this paper, where investors’ payoffs relate to their investing amount and the degree of monopoly in the industry market. Economically, the degree of monopoly in the market is introduced in the game by a parameter α that affects the evolutionary process. The distribution of investing amounts is assumed to satisfy the Pareto distribution in terms of the empirical wealth distribution. The simulation on WS small-world networks shows that cooperative behaviors will prosper by the union of investors who invest less amounts in a less monopolized market. The higher power of the Pareto distribution of investing amounts also results in more cooperators in equilibriums. Furthermore, as the degree of monopoly swings, the density of cooperators is higher and more stable in a more random small-world network. The findings may be helpful in understanding the effect of network structure on the emergence of cooperation. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the effect of awareness coverage and delay in controlling infectious diseases. We formulate an SIS model considering individuals’ behavioral changes due to the influences of media coverage and divide the susceptible class into two subclasses: aware susceptible and unaware susceptible. Other model variables are infected human and media campaign. It is assumed that the rate of becoming aware (unaware), from unaware to aware susceptible human (from aware to unaware susceptible human), is a function of media campaign. A time delay is considered for the time that is taken by an unaware (aware) susceptible individual to become aware (unaware). An additional time delay is considered due to the time lag needed in organising awareness campaigns. The model exhibits two equilibria: the disease-free equilibrium and the endemic equilibrium. The disease-free equilibrium is stable if the basic reproduction number is smaller than unity and the endemic equilibrium exhibits a Hopf-bifurcation, in both delayed and non-delayed system, whenever it exists. Analytical and numerical results prove the significance of awareness and delay on the prevalence of infectious diseases. [ABSTRACT FROM AUTHOR]

Abstract We consider periodic smooth solutions for a non-isentropic Euler–Poisson system with small parameters, in which the momentum and energy equations are partially dissipative. When initial data are close to constant equilibrium states, we prove the global-in-time convergence of the system as parameters go to zero. The limit systems are incompressible Euler equations with dissipation, the drift-diffusion system and the energy-transport system. The proof of the results is based on compactness arguments and uniform energy estimates with respect to the time and the parameters. [ABSTRACT FROM AUTHOR]

Radicalization is the process by which people come to adopt increasingly extreme political, social or religious ideologies. When radicalization leads to violence, radical thinking becomes a threat to national security. De-radicalization programs are part of an effort to combat violent extremism and terrorism. This type of initiatives attempt to alter violent extremists radical beliefs and violent behavior with the aim to reintegrate them into society. In this paper we introduce a simple compartmental model suitable to describe de-radicalization programs. The population is divided into four compartments: ( S ) susceptible, ( E ) extremists, ( R ) recruiters, and ( T ) treatment. We calculate the basic reproduction number R 0 . For R 0 < 1 the system has one globally asymptotically stable equilibrium where no extremist or recruiters are present. For R 0 > 1 the system has an additional equilibrium where extremists and recruiters are endemic to the population. A Lyapunov function is used to show that, for R 0 > 1 , the endemic equilibrium is globally asymptotically stable. We use numerical simulations to support our analytical results. Based on our model we assess strategies to counter violent extremism. [ABSTRACT FROM AUTHOR]

Abstract During the design of a stepped spillway it is fundamental to predict the maximum water depth to define wall height. Many experimental and numerical studies have been made on this subject, however the combination of both, in order to enhance aspects related to free-surface characteristics and their numerical prediction, are still uncovered. While experimentally the free-surface position is defined as the line where air-concentration reaches 90%, numerically the free-surface is defined by the equilibrium of volume between the water and air. In this work, the free-surface, captured with a modified version of three-dimensional Volume-of-Fluid model for the combined air–water flow, is compared to the flow depths measured with three ultrasonic sensors in a stepped spillway. This comparison is used to reach an equilibrium between the theoretical definition of the numerical and experimental free-surface position and to propose a numerical procedure to predict the free-surface using the three-dimensional modified Volume-of-Fluid. The numerical model uses the Shear-stress transport k - ω model to calculate the turbulent characteristics of the flow in a uniform and orthogonal mesh. Fit coefficients between experimental and numerical free-surfaces are calculated along with this procedure to obtain the best relation. In non-aerated regions of the flow, free surface should be represented by α = 0.7 while for the aerated region, α = 0.1 should be used instead, both with errors of 2%. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a new third-order RLCM-four-elements-based chaotic circuit, in which the memristor element is equivalently implemented by a diode-bridge cascaded with an inductor. Mathematical model is established and its equilibrium stability is analyzed. The dynamical properties of the memristive chaotic circuit are disposed by MATLAB numerical simulations and confirmed by breadboard experimental measurements. In particular, the antimonotonicity phenomena of coexisting periodic and chaotic bubbles are observed under some specified control system parameters and the evolutions of coexisting bubbles are exhibited with the variations of two control system parameters. The presented memristive chaotic circuit is very simple and only third-order but can emerge complex dynamics with chaos, period, coexisting bifurcation modes, and coexisting bubbles. [ABSTRACT FROM AUTHOR]

Rumor spreading has a profound influence on people’s well-being and social stability. There are many factors influencing rumor spreading. In this paper, we recommended an assumption that among the common mass there are three attitudes towards rumors: to like rumor spreading, to dislike rumor spreading, and to be hesitant (or neutral) to rumor spreading. Based on such an assumption, a Susceptible–Hesitating–Affected–Resistant(SHAR) model is established, which considered individuals’ different attitudes towards rumor spreading. We also analyzed the local and global stability of rumor-free equilibrium and rumor-existence equilibrium, calculated the basic reproduction number of our model. With numerical simulations, we illustrated the effect of parameter changes on rumor spreading, analyzing the parameter sensitivity of the model. The results of the theoretical analysis and numerical simulations illustrated the conclusions of this study. People having different attitudes towards rumors may play different roles in the process of rumor spreading. It was surprising to find, in our research, that people who hesitate to spread rumors have a positive effect on the spread of rumors. [ABSTRACT FROM AUTHOR]

In this paper, a system of neutral functional differential equations in critical case is investigated. Under some suitable assumptions, we prove that every bounded solution of the considered system tends to zero vector as t → + ∞ . An example and its numerical simulations are carried out to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, a mechanical compression heat pump was coupled into the water-heated humidification dehumidification (HDH) desalination system, in which the condenser is applied to heat the seawater while the evaporator is considered to recover the carried heat from the discharged brine. In view of the integration mechanisms between the desalination unit and heat pump, mathematical models based on mass and energy equilibrium are built. Performance of the combined system, including the water production and gained-output-ratio (GOR), at the design conditions are first obtained. Moreover, the relevant influences from the prescribed critical parameters on the performance of the desalination system are simulated and analyzed. The simulation results show that the best performance of the coupled HDH desalination system, appearing as 82.12 kgh −1 for the water production and 5.14 for the GOR, is acquired at the balance condition of the dehumidifier. Two fully coupled cases, in which the heater or cooler is no longer required, when the air mass flow rate is located at 0.17 kgs −1 and 0.35 kgs −1 , are found. During the influence analysis, a best value of pressure ratio, PR = 4, is found due to a highest value of GOR as 5.14 although the relevant value of water production is attained as 106.53 kgh −1 when the pressure ratio is fixed at 5. Furthermore, it is also observed that a lower value of the pinch temperature difference for the condenser, higher values of effectiveness both for the humidification and dehumidification, are effective to elevate the water production and the corresponding thermal efficiency. [ABSTRACT FROM AUTHOR]

The mathematical model of an equilibrium fan-structure in the interface between two elastic blocks, simulating the shear rupture head in a hard rock under high confining pressure, is constructed. The stress–strain state far from the fan-structure is analyzed with the help of a solution of the problem on edge dislocation. The fan length is estimated using this solution. The model of formation of two oppositely directed fans due to the localized action of tangential stress, which pushes two edge dislocations with antiparallel Burgers vectors, is proposed. In complete formulation, the problem on an equilibrium fan-structure in the interface between infinite elastic half-planes is analyzed by means of original method of superposition of dislocations, leading to two nonlinear integral equations in the fan zone. To solve them numerically, the method of successive approximations is applied. Based on this method, fields of stresses and displacements around the equilibrium fan modelling of a deep-seated shear rupture in the seismogenic zone of the Earth’s crust are computed. Such fields can be used, when setting the initial data in the analysis of dynamics of the fan-shaped mechanism. [ABSTRACT FROM AUTHOR]

The compensation behaviors of Fe II Fe III bimetallic oxalates with defects were explored by constructing a diluted spin-2 and spin-5/2 ferrimagnetic Ising model. Within the effective-field theory based on Glauber-type stochastic dynamic, the effects of the concentration of Fe II and Fe III ions on the compensation temperatures have been studied and the two-compensation points were found in Fe II Fe III bimetallic oxalates. The results showed that the compensation behaviors of the compounds were strongly affected by the presence of defects. In addition, the dilution enhanced the magnetization jumps of the compounds which have been found in earlier experimental and theoretical studies. In particular, the dynamic phase transition is absent in the nonequilibrium system with impurities in contrast to the corresponding equilibrium system. [ABSTRACT FROM AUTHOR]

This paper addresses the discrepancies among the common adsorption isotherms of silica-gel/water provided in the literature. It is reported that the Freundlich model and Tòth equation cannot be used to estimate the uptake at relative pressure less than 0.15. In addition, inconsistencies are found among the various models and equations used to describe the uptake of water vapor onto silica-gel. New coefficients for the Dubinin–Astakhov (D–A) model are proposed to eliminate these disagreements. Due to the limited experimental measurements, an experimental setup is designed and built to measure the sorption kinetics and equilibrium uptake of any working pairs. Experimental measurements show that the maximum uptakes of silica gel RD-2060 and Type-RD are 0.38 kg kg −1 and 0.48 kg kg −1 , respectively. Apparent capillary condensation is observed at a relative pressure of 0.4 and 0.35 for silica-gel RD and RD-2060, respectively. Also, it is found that the D–A model can fit the adsorption isotherms of silica-gels appropriately for the entire range of relative pressure when the characteristic energy is set as a function of relative pressure instead of assuming constant values. [ABSTRACT FROM AUTHOR]

This paper describes a fish prey–predator model with a new functional response. The dynamics of the system is discussed mainly from the point of view of permanence and stability. We obtain conditions that affect the persistence of the system. Local asymptotic stability of various equilibrium solutions is explored to understand the dynamics of the model system. The global asymptotic stability of positive interior equilibrium solution is established using suitable Lyapunov functional. We then examine possibilities of the existence of bionomic equilibrium. Lastly, the optimal harvesting policy is obtained by using the Pontryagin’s maximum principle. The objective is to maximize the monetary social benefit as well as conservation of the ecosystem. [ABSTRACT FROM AUTHOR]

In this paper we study nonlinear diffusion problems of the form u t = Δ u + f ( u ) with Robin boundary condition in exterior domain and heterogeneous environment where f ( u ) is a bistable term. First we prove that the radially symmetric solution converges to its equilibrium locally uniformly in the exterior domain. Then we discuss the existence of some certain equilibrium and obtain a spreading–transition–vanishing trichotomy result. Finally the behavior changes with respect to the initial data are presented. [ABSTRACT FROM AUTHOR]

This paper studies the properties of bistability of equilibria, giving rise to periodic oscillations and 2-tori chaotic dynamics in the full three-dimensional structure of the generalized version of the Chamley (1993) endogenous growth model. This complex dynamic phenomenon reflects a particular hopf bifurcation degeneracy that originates in the neighborhood of a so-called Gavrilov–Guckenheimer singularity, with asymptotical stability properties that lead to persistent oscillations under small perturbations, until a chaos frontier is reached. As a consequence, we study all the necessary conditions, and the exact parametric configuration, that allow to locate the economy on the optimal path that avoids this undesired long run indeterminate solution. [ABSTRACT FROM AUTHOR]

Cutting off infected branches has always been an effective method for removing fire-blight infection in an orchard. We introduce a Filippov fire-blight model with a threshold policy: cutting off infected branches and replanting susceptible trees. The dynamics of the proposed piecewise smooth model are described by differential equations with discontinuous right-hand sides. For each susceptible threshold value S T , we investigate the global dynamical behaviour of the Filippov system, including the existence of all the possible equilibria, their stability and sliding-mode dynamics, as we vary the infected threshold level I T . Our results show that model solutions ultimately approach the equilibrium that lies in the region above I T or below I T or on I = I T , or the equilibrium E T = ( S T , I T ) on the surface of discontinuity. Furthermore, control strategies should be taken when the solution of this system approaches the equilibrium that lies in the region above I T . The findings indicate that proper choice of susceptible and infected threshold levels can either preclude an outbreak of fire blight or lead the number of infected trees to a desired level. [ABSTRACT FROM AUTHOR]

On the basis of the complexity of the human body, we explore viral dynamics by using a two-compartment model incorporating the age since infection of infected cells and both virus-to-cell infection and cell-to-cell transmission routes. The basic reproduction number, R 0 , of the system is formulated from two mechanisms: one is the potential trigger from a single infection route in a compartment and the other is the synergistic effect of a viral infection in two compartments. Accordingly, we prove that the infection-free equilibrium is globally asymptotically stable (GAS) if R 0 < 1 , whereas virus persists uniformly with respect to the initial infection if R 0 > 1 . From the viewpoint of a predominant infection route incorporated with another mild infection route, we demonstrate global convergence to the infected equilibrium by applying a theory of perturbation on the globally stable steady state. [ABSTRACT FROM AUTHOR]

We consider two-parameter bifurcation of equilibrium states of an elastic rod on a deformable foundation. Our main theorem shows that bifurcation occurs if and only if the linearization of our problem has nontrivial solutions. In fact our proof, based on the concept of the Brouwer degree, gives more, namely that from each bifurcation point there branches off a continuum of solutions. [ABSTRACT FROM AUTHOR]

Diffusion of particles adsorbed on a homogeneous one-dimensional lattice is investigated using a theoretical approach and MC simulations. The analytical dependencies calculated in the framework of approach are tested using the numerical data. The perfect coincidence of the data obtained by these different methods demonstrates that the correctness of the approach based on the theory of the non-equilibrium statistical operator. [ABSTRACT FROM AUTHOR]

A new method is presented to simulate moving interfaces during diffusion-controlled growth under local equilibrium conditions. The position and compositions of the interface are obtained directly from the equilibrium state of the subsystem around the moving interface, without iterative calculation between diffusion fluxes and solute balance conditions. The method is applicable to general multi-component systems, and it ensures the consistency in compositions and solute balance at the interfaces; Those are ascribed to the presented consideration of subsystem around the interface region in a discretized form. Explicit equations of interface compositions and position in discretized variables are also presented for the simplified ternary systems of two-solution and compound/solution. The validity and usefulness of the method is demonstrated by simulations of the two important ternary systems; The simulation results illustrate the features of diffusion-controlled growth with different alloy compositions and diffusivities of solutes in both systems. [ABSTRACT FROM AUTHOR]

Controlling pest insects is a challenge of main importance to preserve crop production. In the context of Integrated Pest Management (IPM) programs, we develop a generic model to study the impact of mating disruption control using an artificial female pheromone to confuse males and adversely affect their mating opportunities. Consequently the reproduction rate is diminished leading to a decline in the population size. For more efficient control, trapping is used to capture the males attracted by the artificial pheromone. The model, derived from biological and ecological assumptions, is governed by a piecewise smooth system of ODEs. A theoretical analysis of the model without control is first carried out to establish the properties of the endemic equilibrium. Then, control is added and the theoretical analysis of the model enables to identify threshold values of pheromone which are practically interesting for field applications. In particular, we show that there is a threshold above which the global asymptotic stability of the trivial equilibrium is ensured, i.e. the population goes to extinction. Finally, we illustrate the theoretical results via numerical experiments. [ABSTRACT FROM AUTHOR]

The work continues and develops authors’ previous investigation of stability in the small for a two-layer system of inhomogeneous compressible fluids in the uniform gravity field. Here we present a solution of a similar problem in the case of arbitrary non-uniform potential gravity field. The equilibrium stratification of both density and elastic properties of the fluids is supposed arbitrary, as well as the shape of open on top reservoir filled by the fluids. The problem of stability of equilibrium is analyzed as the corresponding problem for the non-linearly elastic bodies, basing on the static energy criterion with regard for the boundary conditions at all parts of the boundary. The crucial element of the analysis is conversion of the quadratic functional of second variation of total potential energy of the system into a “canonical” form that enables to determine its sign. Making use of this canonical form, we obtain almost coinciding with each other necessary and sufficient conditions for stability (those being valid also for an arbitrary number of layers). [ABSTRACT FROM AUTHOR]

We study price competition between heterogeneous matchmakers in a two-sided matching market. It is well known that when two passive matchmakers who provide random matching services compete with entrance fees, there exists no pure-strategy equilibrium. We show that when a passive matchmaker and an active matchmaker, who provides an assortive matching service, compete with entrance fees, there exists a pure-strategy equilibrium. We also provide welfare comparison between the duopoly and a monopoly operating both the passive and active networks. [ABSTRACT FROM AUTHOR]

The paper is devoted to the investigation of intuitively rational choice in a hierarchical game that is a model of election by open sequential veto-voting. Casting a veto against voter’s least preferred alternative (among remaining ones) may not lead to a sophisticated equilibrium. It means that sincere choice (being intuitive) is not rational. There arises the problem of finding conditions under which a sophisticated optimal sequence of actions is intuitively rational. We prove that in the case of strict preference ordering of alternatives, there exists an intuitively rational sophisticated optimal sequence. In the sequence, each voter vetoes an alternative less preferred than the sophisticated equilibrium outcome. Thus, only intuitively rational strategies are to be considered, although complete information about voters’ preferences is still needed. [ABSTRACT FROM AUTHOR]

We develop the open dog-flea model to serve as a check of proposed non-equilibrium theories of statistical mechanics. The model is developed in detail. Then it is applied to four recent models for non-equilibrium statistical mechanics. Comparison of the dog-flea solution with these different models allows checking claims and giving a concrete example of the theoretical models. [ABSTRACT FROM AUTHOR]

Toppling failure is a common mode of instability in layered and blocky rock slopes where rock blocks rotate about their toes and overturn. One of the most important types of toppling failure is slide-toe-toppling. In this failure, rock blocks at the toe of the slope are overturned by the pressure of sliding mass from the upper part of the slope. In the present study, this type of failure is examined through physical and theoretical modeling. The literature on toppling failures is reviewed briefly first and, then, the mechanism of slide-toe-toppling failure is described. To clarify the mechanism of the failure, a series of physical model tests is conducted under static condition by means of a new tilting table apparatus. Then, a theoretical approach is proposed based on limit equilibrium analysis and some new equations are developed for stability analysis of this type of failure. Finally, the results of physical modeling are compared with outcomes of proposed theoretical approach. This comparison shows a good agreement between the theoretical and experimental results. [ABSTRACT FROM AUTHOR]

Soil moisture is an important variable for hillslope and catchment hydrology. There are various computational methods to estimate soil moisture and their complexity varies greatly: from one box with vertically constant volumetric soil water content to fully saturated-unsaturated coupled physically-based models. Different complexity levels are applicable depending on the simulation scale, computational time limitations, input data and knowledge about the parameters. The Vertical Equilibrium Model (VEM) is a simple approach to estimate the catchment-wide soil water storage at a daily time-scale on the basis of water table level observations, soil properties and an assumption of hydrological equilibrium without vertical fluxes above the water table. In this study VEM was extended by considering vertical fluxes, which allows conditions with evaporation and infiltration to be represented. The aim was to test the hypothesis that the simulated volumetric soil water content significantly depends on vertical fluxes. The water content difference between the no-flux, equilibrium approach and the new constant-flux approach greatly depended on the soil textural class, ranging between ∼1% for silty clay and ∼44% for sand at an evapotranspiration rate of 5 mm·d −1 . The two approaches gave a mean volumetric soil water content difference of ∼1 mm for two case studies (sandy loam and organic rich soils). The results showed that for many soil types the differences in estimated storage between the no-flux and the constant flux approaches were relatively small. [ABSTRACT FROM AUTHOR]

In this work we study the bifurcations from the trivial equilibrium of the equation ∂ u ∂ t ( x , t ) = − u ( x , t ) + tanh ( β ( J ∗ u ) ( x , t ) ) , in the space of 2 τ periodic functions. This is accomplished with the help of the equivariant branching lemma , which allows us to take into account the symmetries present in the model. We show that the phenomenon of ‘spontaneous symmetry-breaking’ occurs here, that is, the bifurcating solutions are less symmetric than the trivial one. We also prove that, under certain conditions, these equilibria can be globally continued. [ABSTRACT FROM AUTHOR]

Rectified transport of the active–passive mixture chain is numerically investigated in periodic confined structures. Due to the out-of-equilibrium property of active particles in the chain, the whole chain can be rectified. It is found that the interaction between particles can significantly affect the rectified transport. When all particles in the chain are active, the directed velocity decreases monotonously with increasing the interaction strength. When the particles are mixture, on increasing the interaction strength, the directed velocity firstly decreases to its minimal value, then increases to its maximal value, and finally decreases to zero. In addition, there exist optimal parameters (self-propelled velocity, the natural length of the spring) at which the average velocity is maximal. [ABSTRACT FROM AUTHOR]

We examine public policy toward the use of genetic information by insurers. Individuals engage in unobservable primary prevention and have access to different prevention technologies. Thus, insurance markets are affected by moral hazard and adverse selection. Individuals can choose to take a genetic test to acquire information about their prevention technology. Information has positive decision-making value, that is, individuals may adjust their behavior based on the result of the test. However, testing also exposes individuals to uncertainty over the available insurance contract, so-called classification risk, which lowers the value of information. In our analysis we distinguish between four different policy regimes, determine the value of information under each regime and associated equilibrium outcomes on the insurance market. We show that the policy regimes can be Pareto ranked, with a duty to disclose being the preferred regime and an information ban the least preferred one. [ABSTRACT FROM AUTHOR]

We present a new class of neural network using a variable structure model of neuron (VSMN). From this structure, we generate four models of neurons. For each model, we study different behaviors such as stable or equilibrium, degraded, hole, alternated, oscillator, harmonic, fractal, and chaos behaviors. Then we design different topologies and architectures of neural networks. These architectures are different from the classical ones; each layer of network contains different models of neurons, neurons can take four models by configuration of VSMN. We also present a numerical study describing the behavior of some models of neuron. We illustrate some results to show the efficiency of this new class of neural networks. We show that these neurons put tracks on their stimulators such as: signal track and half bounded region track with two high and low directions. Two applications in chaos and robotic are also given. [ABSTRACT FROM AUTHOR]

In this paper, we propose an SIRS epidemic model with a nonlinear incidence and transfer from infectious to susceptible. Applying LaSalle’s invariance principle and Lyapunov direct method, we establish a threshold dynamics completely determined by the basic reproduction number. [ABSTRACT FROM AUTHOR]

The evaporation of sprinkler droplets is an important phenomenon in fire simulations both for heat removal from the gas and for heat removal from surfaces. In this paper, we address the problems of potential numerical instability and super-saturation that may occur in explicit time integration of the droplet equations. Two novel numerical approaches are developed and evaluated. The first is based on an analytical solution that relaxes the cell composition and temperature toward the equilibrium values. The second method is an implicit solution to the droplet equations. The two approaches are implemented in the Fire Dynamics Simulator (FDS) and verified and validated using both single droplet and practical sprinkler calculations. Ultimately, the implicit approach is deemed the most cost effective for practical fire simulations. [ABSTRACT FROM AUTHOR]

A three-scale diffusion model for textiles was given in Goessens et al. (2015): consisting of a fiber, yarn and room model. To analyze and simplify the model, its characteristic times were investigated in Goessens et al. (2015) [8, 9]. At these times the fiber and yarn model, and the yarn and room model, respectively, tend to reach a partial equilibrium concentration. Here an addition will be made to the model based upon the previous work. An overlap zone is considered between the yarn and room level. Then the overlapping domain decomposition technique is used to calculate the exchange of active ingredient from one level to another in this zone. The mass balance for the system with the overlap zone is calculated and tested in C-language. [ABSTRACT FROM AUTHOR]

This paper presents a study on the development of high-performance finite elements for geometrically nonlinear analysis of frame structures with curved members. Based on the geometrically exact beam theory, a highly efficient and accurate mixed finite element is developed. A new approach is proposed for constructing the independent internal force field by including major terms satisfying equilibrium conditions in the deformed configuration. An element-level equilibrium iteration procedure is employed for the condensation of element internal degrees of freedom during the nonlinear solution. Numerical results are presented to demonstrate the excellent performance of the element developed, and it is shown that even when each structural member is modelled with just one element, accurate solutions can still be achieved. [ABSTRACT FROM AUTHOR]

Virus patches can be disseminated rapidly through computer networks and take effect as soon as they have been installed, which significantly enhances their virus-containing capability. This paper aims to theoretically assess the impact of patch forwarding on the prevalence of computer virus. For that purpose, a new malware epidemic model, which takes into full account the influence of patch forwarding, is proposed. The dynamics of the model is revealed. Specifically, besides the permanent susceptible equilibrium, this model may admit an infected or a patched or a mixed equilibrium. Criteria for the global stability of the four equilibria are given, respectively, accompanied with numerical examples. The obtained results show that the spectral radii of the patch-forwarding network and the virus-spreading network both have a marked impact on the prevalence of computer virus. The influence of some key factors on the prevalence of virus is also revealed. Based on these findings, some strategies of containing electronic virus are recommended. [ABSTRACT FROM AUTHOR]

A predator–prey model was extended to include nonlinear harvesting of the predator guided by its population, such that harvesting is only implemented if the predator population exceeds an economic threshold. The proposed model is a nonsmooth dynamic system with switches between the original predator-prey model (free subsystem) and a model with nonlinear harvesting (harvesting subsystem). We initially examine the dynamics of both the free and the harvesting subsystems, and then we investigate the dynamics of the switching system using theories of nonsmooth systems. Theoretical results showed that the harvesting subsystem undergoes multiple bifurcations, including saddle-node, supercritical Hopf, Bogdanov–Takens and homoclinic bifurcations. The switching system not only retains all of the complex dynamics of the harvesting system but also exhibits much richer dynamics such as a sliding equilibrium, sliding cycle, boundary node (saddle point) bifurcation, boundary saddle-node bifurcation and buckling bifurcation. Both theoretical and numerical results showed that, by implementing predator population guided harvesting, the predator and prey population could coexist in more scenarios than those in which the predator may go extinct for the continuous harvesting regime. They could either stabilize at an equilibrium or oscillate periodically depending on the value of the economic threshold and the initial value of the system. [ABSTRACT FROM AUTHOR]

The supercritical extractions of Monteverdia aquifolia leaves were conducted using neat CO 2 at different temperatures, CO 2 flow rates, and pressures. The highest yield was obtained at 300 bar, 6 mL min-1, and 50 °C. In this condition, extraction kinetics were obtained using mixtures of supercritical CO 2 with ethanol and ethyl acetate. Other studies have proven that leaves are a good source of bioactive and antioxidant compounds. In this way, seeking to better understand obtaining these extracts via the supercritical method, simplified mathematical models were tested regarding their performance to predict the extraction kinetics. Equilibrium isotherms obtained were analytically solved and coupled to a mass balance in the extractor resulting in five simplified models that describe the extraction kinetics. The accuracy of the models was tested in the prediction of the experimental yield and compared to the results of the classic Sovová model. Results obtained demonstrated All five simplified models were able to describe the experimental supercritical extraction, still provide insights, and conduct procedures, to solve problems or optimize a situation. The Halsey-type equilibrium model was the most accurate, even when compared to the Sovová model, with an R2 of 0.981 and a relative mean deviation of 9.7%. Considering that M. aquifolia extracts are already a reality in the herbal medicine industry, the data reported here may contribute to the dissemination of the extraction methodology, as well as to the more effective acquisition of the extract, with its biological effects preserved. [Display omitted] • Monteverdia aquifolia leaves were subjected to supercritical extraction. • 5 simplified kinetic models were proposed to predict the yield. • The simplified models can be used to accurately predict the yield. • The Halsey-type equilibrium model described the process better than the Sovová model. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to improve the numerical evaluation of gas injection enhanced coalbed methane (ECBM) recovery by establishing a new mathematical coalbed methane (CBM) simulation model, in which the two-dimensional Peng–Robinson equation of state (2D PR EOS) model and the Maxwell-Stefan bidisperse pore diffusion (MS-BPD) model for multicomponent gas adsorption and diffusion are implemented. First, the extended Langmuir, ideal adsorbed solution and 2D PR-EOS models were investigated and compared with the experimental data of pure and mixed gas for modeling multicomponent gas adsorption behavior. Then, the MS-BPD model was developed based on the 2D PR-EOS model, bidisperse diffusion mechanisms, and Maxwell-Stefan diffusion theory, which provided an improved simulation of multicomponent gas diffusion behavior. On the basis of previous research, we developed a new CBM simulation model to analyze the effects of injection gas composition on the gas injection ECBM recovery process. The results indicate that mixed-gas injections are able to enhance methane recovery. The optimum composition of injected gas is 75% N 2 and 25% CO 2 , which increases methane recovery by 25% over the pressure depletion production process. This CBM simulation model will provide an effective technical approach for research and development of CBM by gas injection. [ABSTRACT FROM AUTHOR]

This paper deals with a delayed reaction–diffusion predator–prey model with non-smooth harvesting. Sufficient conditions for the local stability of the interior equilibrium and the existence of discontinuous Hopf bifurcations and classical Hopf bifurcations are obtained by using the theory of partial functional differential equations. Finally, numerical simulation results are presented to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

Subaerial sand levels were observed at five southern California beaches for 16 years, including notable El Niños in 1997–98 and 2009–10. An existing, empirical shoreline equilibrium model, driven with wave conditions estimated using a regional buoy network, simulates well the seasonal changes in subaerial beach width (e.g. the cross-shore location of the MSL contour) during non-El Niño years, similar to previous results with a 5-year time series lacking an El Niño winter. The existing model correctly identifies the 1997–98 El Niño winter conditions as more erosive than 2009–10, but overestimates shoreline erosion during both El Niños. The good skill of the existing equilibrium model in typical conditions does not necessarily extrapolate to extreme erosion on these beaches where a few meters thick sand layer often overlies more resistant layers. The modest over-prediction of the 2009–10 El Niño is reduced by gradually decreasing the model mobility of highly eroded shorelines (simulating cobbles, kelp wrack, shell hash, or other stabilizing layers). Over prediction during the more severe 1997–98 El Niño is corrected by stopping model erosion when resilient surfaces (identified with aerial imagery) are reached. The trained model provides a computationally simple (e.g. nonlinear first order differential equation) representation of the observed relationship between incident waves and shoreline change. [ABSTRACT FROM AUTHOR]

A series of fine-grid simulation with two-fluid model (TFM) is performed for bubbling, turbulent and circulating fluidized beds (CFB) with Geldart A particles. The results show that the fine-grid TFM with homogeneous drag seems feasible for simulation of low-velocity, bubbling fluidized beds. However, the fidelity of fine-grid TFM declines with the increase of gas velocity. In particular, the solids flux predicted deviates much from the experimental data of CFB though the clustering phenomenon can be captured with refinement of grid. In contrast, the structure-dependent approach as exemplified by the energy-minimization multi-scale (EMMS)-based multi-fluid model gives better agreement with experimental data. This discrepancy raises the question of the applicability of the local equilibrium assumption underlying the TFM. It also sheds light to the necessity of meso-scale modeling and the critical role of solids flux to evaluate the simulation of CFB. [ABSTRACT FROM AUTHOR]