Dynamic model and performance analysis of landing buffer for bionic locust mechanism

The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are used to replace the leg muscles to achieve a buffering effect. To reveal the dynamic performance in the buffering process of the bionic locust mechanism, a dynamic model is established with different modes of landing and buffering. In particular, to analyze the buffering process conveniently, an equivalent vibration dynamic model of the bionic locust mechanism is proposed.Given the support forces of the ground to the leg links, which can be obtained from the dynamic model, the spring forces of the legs and the impact resistance of each leg are the important parameters affecting buffering performance, and evaluation principles for buffering performance are proposed according to the aforementioned parameters. Based on the dynamic model and these evaluation principles, the buffering performances are analyzed and compared in different modes of landing and buffering on a horizontal plane and an inclined plane. The results show that the mechanism with the ends of the legs sliding can obtain a better dynamic performance. This study offers primary theories for buffering dynamics and an evaluation of landing buffer performance,and it establishes a theoretical basis for studies and engineering applications.

Highly Sensitive Temperature Sensor Based on Coupled-Beam AIN-on-Si MEMS Resonators Operating in Out-of-Plane Flexural Vibration Modes

This paper reports a type of highly sensitive temperature sensor utilizing AlN-on-Si resonators with coupled-beam structures of double-and triple-ended-tuning-fork(D/TETF).For both resonators,the out-of-plane flexural mode is adopted as it favors the effect of thermal mismatch between the composite layers inherent to the AlN-on-Si structure and thus helps attain a large temperature coeficient of resonant frequency(TCF).The analytical model to calculate TCF values of D/TETF AIN-on-Si resonators is provided,which agrees well with the finite-element simulation and experimental results.The resonant temperature sensor is built by closing the loop of the AlN-on-Si resonator,a transimpedance amplifer,a low-pass flter,and a phase shifter to form an oscillator,the output frequency of which shifts proportionally to the ambient temperature.The measured sensitivities of the temperature sensors using D/TETF resonators are better than-1000 ppm/℃in the temperature range of 25℃~60℃,showing great potential to fulfll the on-chip temperature compensation scheme for cofabricated sensors.

Entropic destruction of heavy quarkonium with hyperscaling violation

We study the entropic destruction of heavy quarkonium in strongly coupled theories with an anisotropic scaling symmetry in time and a spatial direction.We consider Lifshitz and hyperscaling violation theories,which are covariant under a generalized Lifshitz scaling symmetry with the dynamical exponent z and hyperscaling violation exponentθ.It is shown that the entropic force depends on the parameters of these theories.In particular,increasing z decreases the entropic force,thus reducing the quarkonium dissociation,while increasingθhas the opposite effect.

Holographic Schwinger effect in a rotating strongly coupled medium

We perform a potential analysis on the holographic Schwinger effect in a rotating deformed AdS blackhole background.We calculate the total potential of a quark-antiquark(QQ)pair in an external electric field and evaluate the critical electric field from Dirac-Born-Infeld action.It is shown that the inclusion of angular velocity decreases the potential barrier,thus enhancing the Schwinger effect,which contrasts with the effect of the confining scale.Moreover,increasing the angular velocity decreases the critical electric field,above which these pairs are produced freely without suppression.Furthermore,we conclude that QQ pair production would be easier in a rotating medium.

Entropic destruction of heavy quarkonium in a rotating hot and dense medium from holography

Previous studies have indicated that the peak of the quarkonium entropy at the deconfinement transition can be related to the entropic force,which would induce the dissociation of heavy quarkonium.In this study,we investigated the entropic force in a rotating hot and dense medium using AdS/CFT correspondence.It was found that the inclusion of angular velocity increases the entropic force,thus enhancing quarkonium dissociation,while chemical potential has the same effect.The results imply that the quarkonium dissociates easier in rotating medium compared with the static case.

Holographic Schwinger effect in a soft wall AdS/QCD model

We perform a potential analysis for the holographic Schwinger effect in a deformed AdS5 model with conformal invariance broken by a background dilaton.We evaluated the static potential by analyzing the classical action of a string attached to a rectangular Wilson loop on a probe D3 brane located at an intermediate position in the bulk AdS space.We observed that the inclusion of the chemical potential tends to enhance the production rate,which is opposite to the effect of the confining scale.In addition,we calculated the critical electric field based on the Dirac-Born-Infeld(DBI)action.

Jet quenching parameter from a soft wall AdS/QCD model

We study the effect of chemical potential and nonconformality on the jet quenching parameter in a holographic QCD model with conformal invariance broken by background dilaton.The presence of chemical potential and nonconformality both increase the jet quenching parameter,thus enhancing the energy loss,consistently with the findings of the drag force.