Stability of HDE model with sign-changeable interaction in Brans-Dicke theory

We consider the Brans-Dicke (BD) theory of gravity and explore the cosmological implications of the sign-changeable interacting holographic dark energy (HDE) model in the background of Friedmann-Robertson-Walker (FRW) universe. As the system's infrared (IR) cutoff, we choose the future event horizon, the Granda-Oliveros (GO) and the Ricci cutoffs. For each cutoff, we obtain the density parameter, the equation of state (EoS) and the deceleration parameter of the system. In case of future event horizon, we find out that the EoS parameter, $w_{D}$, can cross the phantom line, as a result the transition from deceleration to acceleration expansion of the universe can be achieved provided the model parameters are chosen suitably. Then, we investigate the instability of the sign-changeable interacting HDE model against perturbations in BD theory. For this purpose, we study the squared sound speed $v_s^2$ whose sign determines the stability of the model. When $v_s^2<0$ the model is unstable against perturbation. For future event horizon cutoff, our universe can be stable (${v}^{2}_s>0$) depending on the model parameters. Then, we focus on GO and Ricci cutoffs and find out that although other features of these two cutoffs seem to be consistent with observations, they cannot leads to stable dominated universe, except in special case with GO cutoff. Our studies confirm that for the sign-changeable HDE model in the setup of BD cosmology, the event horizon is the most suitable horizon which can passes all conditions and leads to a stable DE dominated universe.Comment: 19pages, 22figure

Revisiting Agegraphic Dark Energy in Brans-Dicke Cosmology

We explore a spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) universe which is filled with agegraphic dark energy (ADE) with mutual interaction with pressureless dark matter in the background of Brans-Dicke (BD) theory. We consider both original and new type of agegraphic dark energy (NADE) and further assume the sign of the interaction term can change during the history of the Universe. We obtain the equation of state parameter, the deceleration parameter and the evolutionary equation for the sign-changeable interacting ADE and NADE in BD theory. We find that, in both models, the equation of state parameter, $w_D$, cannot cross the phantom line, although they can predict the Universe evolution from the early deceleration phase to the late time acceleration, compatible with observations. We also investigate the sound stability of these models and find out that both models cannot show a signal of stability for different model parameters.Comment: 10 pages, 14 figure

A Note on Tsallis Holographic Dark Energy

We explore the effects of considering various infrared (IR) cutoffs, including the particle horizon, Ricci horizon and Granda-Oliveros (GO) cutoffs, on the properties of Tsallis holographic dark energy (THDE) model, proposed inspired by Tsallis generalized entropy formalism \cite{THDE}. Interestingly enough, we find that for the particle horizon as IR cutoff, the obtained THDE model can describe the accelerated universe. This is in contrast to the usual HDE model which cannot lead to an accelerated universe, if one consider the particle horizon as IR cutoff. We also investigate the cosmological consequences of THDE under the assumption of a mutual interaction between the dark sectors of the Universe. It is shown that the evolution history of the Universe can be described by these IR cutoffs and thus the current cosmic acceleration can also been realized. The sound instability of THDE models for each cutoff are also explored, separately.Comment: 12 pages, 31 figure

Ghost dark energy in the DGP braneworld

We investigate the ghost model of dark energy in the framework of DGP braneworld. We explore the cosmological consequences of this model by determining the equation of state parameter, $\omega_D$, the deceleration and the density parameters. We also examine the stability of this model by studying the squared of the sound speed in the presence/absence of interaction term between dark energy and dark matter. We find out that in the absence of interaction between two dark sectors of the Universe we have $\omega_D\rightarrow -1$ in the late time, while in the presence of interaction $\omega_D$ can cross the phantom line $-1$. In both cases the squared of sound speed $v_s^2$ does not show any signal of stability. We also determine the statefinder diagnosis of this model as well as the $\omega_D-{\omega}^{\prime}_{D}$ plane and compare the results with the $\Lambda$CDM model. We find that $\omega_D-{\omega}^{\prime}_{D}$ plane meets the freezing region in the absence of interaction between two dark sectors, while it meets both the thawing and the freezing regions in the interacting case.Comment: 14 pages, 18 figure

Design, modeling and control of a soft gripper with TCP actuator using image processing

Artificial muscles have gained importance due to their high deformability, which is used in soft robots. In this article, to further exploit and understand the behavior of TCP muscles, as well as to control these muscles more easily, we mathematically model the stimulus, which includes a model to understand the temperature behavior of muscles with changes in flow and amount of displacement due to changes in temperature and amount of external force. is. By designing a soft gripper and applying the necessary restrictions, we get the force needed to move this gripper. Then we obtain the inematic model of the finger to obtain the bending angle due to the displacement of the muscle which is connected to the fingers and gripper by the cable. We also check the muscle's ability to perform this movement. In the next step, programming and implementation of a simple model of turning on and off the heating and cooling system to create expansion and contraction in the muscle is done by image processing on the Arduino controller to control the system. Using the obtained models and taking into account different and important values in the models, we extracted the related diagrams and checked and compared them. From these results, we can point out the changes in the temperature behavior and movement of the muscle with the change in the input current as well as the type of alloy used, the controllability of the muscle, and the ability of the muscle to move the gripper