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The recently developed formalism of nonlinear fluctuating hydrodynamics (NLFH) has been instrumental in unraveling many new dynamical universality classes in coupled driven systems with multiple conserved quantities. In principle,...
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The recently developed formalism of nonlinear fluctuating hydrodynamics (NLFH) has been instrumental in unraveling many new dynamical universality classes in coupled driven systems with multiple conserved quantities. In principle, this formalism requires knowledge of the exact expression of locally conserved current in terms of local density of the conserved components. However, for most nonequilibrium systems an exact expression is not available and it is important to know what happens to the predictions of NLFH in these cases. We address this question here in a system with coupled time evolution of sliding particles on a fluctuating energy landscape. In the disordered phase this system shows short-ranged correlations, the exact form of which is not known, and so the exact expression for current cannot be obtained. We use approximate expressions based on mean-field theory and corrections to it, to test the prediction of NLFH using numerical simulations. In this process we also discover important finite size effects and show how they affect the predictions of NLFH.We find that our system is rich enough to show a large variety of universality classes. From our analytics and simulations we have been able to find parameter values which lead to diffusive, Karder-Parisi-Zhang (KPZ), 5/3 Lévy, and modified KPZ universality classes. Interestingly, the scaling function in the modified KPZ case turns out to be close to the Pr?hofer-Spohn function, which is known to describe usual KPZ scaling. Our analytics also predict the golden mean and the 3/2 Lévy universality classes within our model but our simulations could not verify this, perhaps due to strong finite size effects.
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Considering the disadvantages of the traditional high-gain DC-DC converter such as big size, high voltage stress of switches, and large input current ripple, a novel high-gain interleaved boost converter with coupled-inductor and ...
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Considering the disadvantages of the traditional high-gain DC-DC converter such as big size, high voltage stress of switches, and large input current ripple, a novel high-gain interleaved boost converter with coupled-inductor and switched-capacitor was proposed correspondingly and the operation principle together with the steady-state analysis of this converter was also described. Besides, a new control approach-dynamic sliding mode evolution PWM controller (DSME PWM) for the novel topological converter based on both dynamic evolution and sliding mode control was also presented. From the simulation results and experimental validation the proposed converter can fulfill high-gain boost, low ripple of both the input current and the output voltage. Furthermore, MPPT technique can be also achieved in a short time by simulation. The efficiency and stability of the converter proposed in this paper can be improved.
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In this paper, a Filippov type model is proposed for the predator-prey system. The smooth subsystems of the proposed model admit regular and virtual equilibrium points and their dynamics is explored. The tangent points, boundary e...
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In this paper, a Filippov type model is proposed for the predator-prey system. The smooth subsystems of the proposed model admit regular and virtual equilibrium points and their dynamics is explored. The tangent points, boundary equilibrium and pseudo-equilibrium are obtained on discontinuity boundary. Equation of sliding motion is obtained using the Filippov's convex method and sliding mode dynamics is discussed. It has been shown that the Filippov system admits pseudo-equilibrium, only if virtual equilibrium of two subsystems coexist. The value of threshold parameter is computed for which tangent point and boundary equilibrium collide. The two parameter bifurcation diagram is drawn to show the existence of regular and virtual equilibrium points in different regions. The existence of boundary equilibrium bifurcation is investigated through numerical simulation, as value of threshold parameter varies.
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This paper proposes a model of West Nile Virus (WNV) including threshold control policies concerning the culling of mosquitoes and birds under different conditions. Two thresholds are introduced to estimate whether and which contr...
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This paper proposes a model of West Nile Virus (WNV) including threshold control policies concerning the culling of mosquitoes and birds under different conditions. Two thresholds are introduced to estimate whether and which control strategy should be implemented. For each mosquito threshold level C-Im the dynamical behaviour of the proposed non-smooth system is investigated as the bird threshold level C-Ib, varies, focusing on the existence of sliding domains, the existence of pseudo-equilibria, real or virtual of the endemic equilibria, global stability of these steady states, and the most interesting case of the occurrence of a novel globally asymptotically stable pseudo-attractor. The model solutions ultimately converge to a real equilibrium or a pseudo-equilibrium (if it exists), or a pseudo-attractor if no equilibrium is real and no pseudo-equilibrium exists. Here within, we show that the free system has a single stable endemic equilibrium under biologically reasonable assumptions, and show that when the control system has: (1) a bird-culling threshold that is above the bird equilibrium, culling has no advantage; (2) a bird culling threshold that is below the bird equilibrium, but a mosquito-culling threshold that lies above the mosquito equilibrium, the infected bird population can be reduced but the infected mosquito population will remain the same; (3) a bird-culling threshold and a mosquito-culling threshold that both lie below their respective equilibrium values of the free system, then both the infected bird and mosquito populations can be reduced to lower levels. The results suggest that preset levels of the number of infected birds and infected mosquitoes can be maintained simultaneously when threshold values are chosen properly, which provides a possible control strategy when an emergent infectious disease cannot be eradicated immediately. (C) 2018 Elsevier Ltd. All rights reserved.
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The paper considers sliding manifold design for higher-order sliding mode (HOSM) in linear systems. In this case, the sliding manifold must meet two requirements: to achieve the desired dynamics in HOSM and to provide the appropri...
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The paper considers sliding manifold design for higher-order sliding mode (HOSM) in linear systems. In this case, the sliding manifold must meet two requirements: to achieve the desired dynamics in HOSM and to provide the appropriate relative degree of the sliding variable depending on the SM order. It is shown that in the case of single-input systems, a unique sliding manifold can be determined that satisfies these two requirements, whereas in multi-input case, such a manifold exists only in systems satisfying specific structural constraints. Theoretically obtained results are validated through numerical examples and illustrated by digital simulations.
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The numerical method was used to study bubble sliding characteristics and dynamics of R134a during subcooled flow boiling in a narrow gap. In the numerical method, the volume of fraction (VOF) model, level set method, Lee phase ch...
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The numerical method was used to study bubble sliding characteristics and dynamics of R134a during subcooled flow boiling in a narrow gap. In the numerical method, the volume of fraction (VOF) model, level set method, Lee phase change model and the SST k ? ω turbulent model were adopted for the construction of the subcooled flow boiling model. In order to explore bubble sliding dynamics during subcooled flow boiling, the bubble sliding model was introduced. The bubble velocity, bubble departure diameter, sliding distance and bubble sliding dynamics were investigated at 0.2 to 5 m/s inlet velocities. The simulation results showed that the bubble velocity at the flow direction was the most important contribution to bubble velocity. Additionally, the bubble velocity of 12 bubbles mostly oscillated with time during the sliding process at 0.2 to 0.6 m/s inlet velocities, while the bubble velocity increased during the sliding process due to the bubble having had a certain inertia at 2 to 5 m/s inlet velocities. It was also found that the average bubble velocity in flow direction accounted for about 80% of the mainstream velocities at 0.2 to 5 m/s. In the investigation of bubble sliding distance and departure diameter, it was concluded that the ratio of the maximum sliding distance to the minimum sliding distance was close to two at inlet velocities of 0.3 to 5 m/s. Moreover, with increasing inlet velocity, the average sliding distance increased significantly. The average bubble departure diameter obviously increased from 0.2 to 0.5 m/s inlet velocity and greatly reduced after 0.6 m/s. Finally, the investigations of the bubble sliding dynamics showed that the surface tension dominated the bubble sliding process at 0.2 to 0.6 m/s inlet velocities. However, the drag force dominated the bubble sliding process at 2 to 5 m/s inlet velocities.
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We investigate the fracture toughness of slide-ring (SR) gels, in which polymer chains are cross-linked by ring molecules, at various strain rates to evaluate the sliding speed of the cross-linking points. SR gels show a drastic d...
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We investigate the fracture toughness of slide-ring (SR) gels, in which polymer chains are cross-linked by ring molecules, at various strain rates to evaluate the sliding speed of the cross-linking points. SR gels show a drastic decrease of the fracture energy at crack velocities higher than a critical value, since the sliding motion of the rings cannot catch up with the high deformation rates. From the critical transition velocity, we estimated the characteristic time scale of the sliding dynamics to be micro-seconds under the single-layer fracture assumption.
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This study investigated the dynamic sliding friction of polyurethane (PU) rubber samples on an inclined smooth transparent polymethylmethacrylate (PMMA) surface with a thin layer of silicone oil. The sliding velocity increased dur...
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This study investigated the dynamic sliding friction of polyurethane (PU) rubber samples on an inclined smooth transparent polymethylmethacrylate (PMMA) surface with a thin layer of silicone oil. The sliding velocity increased during the initial stages of sliding and approached a constant value toward the latter stages. To describe the changes in velocity observed, the present study developed an analytical model based on Couette flow with no pressure gradient and indicated that the model could predict important changes in velocity. These findings suggest that dynamic friction force is dependent on both the sliding velocity and the contact area, and that the behavior is similar to that given by Stokes' law, which describes the falling velocity of a particle in a viscous fluid. (C) 2015 Elsevier Ltd. All rights reserved.
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This paper presents a new algorithm for designing dynamic sliding-mode controllers. The proposed controller is based on dynamic sliding manifolds to circumvent the difficulties associated with the conventional sliding mode control...
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This paper presents a new algorithm for designing dynamic sliding-mode controllers. The proposed controller is based on dynamic sliding manifolds to circumvent the difficulties associated with the conventional sliding mode controllers in the face of non-minimum phase systems. Unlike previous works, a proper and easy to implement algorithm is presented for designing the dynamic sliding manifold which facilitates the design of the controller. The output tracking problem in nonlinear non-minimum phase systems with matched and unmatched disturbances and matched nonlinearities is addressed. Then, the performance of the dynamic sliding mode controller is significantly improved by combining the given dynamic sliding manifold with online parameter adaptation. Simulations results are presented to demonstrate the effectiveness of the proposed sliding mode controller in terms of performance, robustness and stability.
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摘要 :AbstractThis paper presents a sliding cable element for multibody system analysis. Unlike the existing literature on sliding cables developed using the finite element approach, the novelty of this approach is the use of the config...
展开AbstractThis paper presents a sliding cable element for multibody system analysis. Unlike the existing literature on sliding cables developed using the finite element approach, the novelty of this approach is the use of the configuration of the attached rigid bodies as the generalized coordinates, rather than the traditional nodal displacements. The generalized force vector, and its related tangent stiffness and damping matrix, of the sliding cable and that of the classical cable element are analytically derived. It can also be found that the proposed sliding cable element can degenerate to the existing element formulated using the finite element approach. This allows us to use less generalized coordinates to address a system that contains few rigid or flexible body but with many pulleys. Then, this sliding cable element is employed to investigate the deployment of clustered tensegrity. Both quasi-static and dynamic analyses are carried out. Two representative examples show the effectiveness of the proposed element. The dynamic results also show that the motion characteristics of the system differ from the quasi-static solutions as the actuation speed increases. To achieve a fast actuation speed for deploying such systems, quasi-static analysis seems inadequate, and the dynamic effect must be taken into account. Under this background, the proposed element, coupled with the multibody dynamic methodology used in this work, does provide a powerful tool for analyzing the mechanical properties of such systems.]]>
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