A viscoelastic metamaterial beam for integrated vibration isolation and energy harvesting

Locally resonant metamaterials have low-frequency band gaps and the capability of converging vibratory energy in the band gaps at resonant cells.It has been demonstrated by several researchers that the dissipatioin of vibratory energy within the band gap can be improved by using viscoelastic materials.This paper designs an integrated viscoelastic metamaterial for energy harvesting and vibration isolation.The viscoelastic metamaterial is achieved by a viscoelastic beam periodically arrayed with spatial ball-pendulum nonlinear energy harvesters.The nonlinear resonator with an energy harvesting function is achieved by placing a free-rolling magnetic ball in a spherical cavity with an additional induction coil.The dynamic equations of viscoelastic metamaterials under transverse excitation are established,and the energy harvesting and vibration isolation characteristics within the dispersion relation of viscoelastic metamaterials are analyzed.The results show that the vibrations of the main body of the viscoelastic metamaterial beam are significantly suppressed in the frequency range of the local resonance band gap.At the same time,the elastic waves are limited in the nonlinear resonator with an energy harvesting function,which improves the energy output.Finally,an experimental platform of viscoelastic metamaterial vibration is established for validation purposes.

Nonlinear energy harvesting based on a modified snap-through mechanism

A modified snap-through mechanism is used in an electromagnetic energy harvester to improve its effectiveness. It mainly comprises three springs that are configured so that the potential energy of the system has two stable equilibrium points. In particular, the small vibration behavior of the harvester around one of the equilibriums is of interest. A multi-scale method(MSM) is used to analyze the frequency response curve. Two snap-through mechanisms are considered. One has both horizontal and vertical springs. The other has only horizontal springs. The frequency response curves of these two classes are compared under the same excitation and electric loading conditions. The latter exhibits more bending of the frequency response curve than the former one. The results are also validated by some numerical work. The averaged power subject to the Gaussian white noise is calculated numerically, and the results demonstrate that bi-stable energy harvesting with only horizontal springs can outperform the mechanism with both horizontal and vertical springs for the same distance between two equilibriums.

Chemical Fertilizer Reduction and High Yield Cultivation Technique for Peanut

For a long time,the amount of fertilizer applied to peanuts in China has been much higher than that of other main peanut producing countries.At the same time of increasing production,chemical fertilizers have also brought many adverse effects,which have brought potential threats to the sustainable development of peanut production.While continuously increasing the yield,reducing the amount of chemical fertilizer has become an urgent problem to be solved in peanut production of China.Based on the research results of our team,this paper appropriately absorbed the latest research progress of chemical fertilizer reduction in related fields,and established the cultivation technique for peanut fertilizer reduction and high yield under different cultivation modes,to realize the synchronization of fertilizer reduction and yield increase for peanut production.The technique includes two parts:common technology and different cultivation mode fertilization schemes.The former includes crop rotation,proper deep tillage,application of organic fertilizer,selection of nutrient-efficient varieties,topdressing of foliar fertilizer,etc.,the latter includes film mulching spring peanut,continuous cropping field,acidified soil,peanuts interplanting with wheat,and summer direct sowing,etc.This technique provides a technical support for the chemical fertilizer reduction of peanut production in China.

An Investigation into the Isolation Performance of Mono-and Bi-stable Systems

Motivated by the need for improving the isolation performance, many research studies have been performed on isolators with nonlinear characteristics. Based on the shape of their phase portrait, such devices can be configured as either a mono-or bi-stable isolator. This paper focuses on investigating the relative performance of these two classes under the same excitations. Force transmissibility is used to measure the isolation performance, which is defined in terms of the RMS of the ratio of the transmitted force to the excitation force. When the system is subjected to harmonic excitation, it is found that the maximum reduction of the force transmissibility in the isolation range using Quasi-Zero stiffness is achieved. When the system is subjected to random excitation, it has the same effect of Quasi-Zero stiffness. Further, optimum damping can be changed with stiffness and has minimum value.

High-yield and High-efficiency Standardized Cultivation Technique for Wheat Interplanting with Peanuts

Through wheat interplanting with peanuts,it is able to make full use of the light and heat resources in the growing season to achieve high yield of both wheat and peanuts in two seasons of one year.Wheat interplanting with peanuts is one of the main cultivation methods of wheat and oil crop double cropping system,and has very broad development prospects in the Huang-Huai-Hai region.This paper summarized high-yield the high-efficiency and standardized cultivation techniques for wheat interplanting with peanuts,including crop rotation,proper deep ploughing,balanced fertilization,rational matching of fine varieties,interplanting at suitable time,sowing according to certain specification,and enhancing the field management.This can be used as reference for high-yield and high-efficiency standardized cultivation technique for wheat interplanting with peanuts.