Effect of rock mechanical properties on electromagnetic radiation mechanism of rock fracturing

The influence of rock mechanical properties on the electromagnetic radiation(EMR)mechanism of rock fracturing is an important research topic in solid mechanics and earthquake prediction.In this study,an EMR model of rock fracturing considering the fracture factor,elastic modulus,Poisson’s ratio,radiation distance and crack length is derived based on the Hertz oscillator array assumption.An experimental system,including an electromagnetic shielding module,an EMR signal induction and transmission module,a signal recording module and a loading module,is developed to understand the EMR characteristics of four different rocks.The validity of the EMR theoretical model is verified and the relationships between the rock cracking morphology and the EMR waveform,amplitude and frequency are revealed.It is found that rock mechanical properties have obvious influences on the EMR waveform,amplitude and frequency during rock fracturing.This study provides a better understanding on the EMR mechanism of rock fracturing and can help to improve the accuracy of rock disaster prediction based on EMR.

Simulation study of the dynamic characteristics of the electromagnetic flame-proof mechanism

Since the overloads of the electromagnetic flame-proof mechanism under different working conditions are complex and hard to be verified,a numerical simulation method of this mechanism working process is proposed with the combination of Adams and Simulink.First,a simulation model of electromagnetic flame-proof mechanism was established,which includes the safety pin,the spring,and the exciting coils and so on.Then,the model was imported to Adams taking constraints into consideration,which include the contacts,kinematic pairs and the spring.The co-simulation model was established through the union of Adams and Simulink.The model was tested via simulations,and the obtained results were analyzed finally.The results show that the method can simulate the dynamic process of the electromagnetic flame-proof mechanism during the service process and under the normal power supply condition,and therefore the motion displacements of the electromagnetic pin under different working conditions can be obtained through simulations.It can verify the mechanism＇s designing rationality,thus laying the foundation for the physical prototype testing and reducing the repetition of the product＇s design process.

Mechanism of Electromagnetic Flow Control Enhanced by Electro-Discharge in Water

Pulsed discharge utilized to achieve large current density in the electromagnetic flow control is numerically studied. A mathematic discharge model is established to calculate the plasma channel, and an actuator is designed to generate the Lorentz force in the micro plasma channel. During the discharge process, the resistance in the channel decreases rapidly and a large current density appears between the discharge electrodes. After the actuator is applied in the leading edge of a flat plate, the separation region and downstream turbulent boundary layer on the plate disappear. Meanwhile, a skin-friction drag force reduction is achieved.

Introduction to Synchronized Kinematic and Electromagnetic Mechanics

Introduction to fundamental physics according to the parallel harmonization of kinematic and electromagnetic mechanics, in accordance with Wilhelm Wien’s project, which involved the integration in kinematic mechanics of the mass increase of the electron as a function of its velocity, as measured by Walter Kaufmann with his bubble-chamber experiments, and analyzed and confirmed by H. A. Lorentz and all the leading edge physicists who then re-analyzed this data.

Dynamic interactions of an integrated vehicle–electromagnetic energy harvester–tire system subject to uneven road excitations

An investigation is undertaken of an integrated mechanical-electromagnetic coupling system consisting of a rigid vehicle with heave, roll, and pitch motions, four electromagnetic energy harvesters and four tires subject to uneven road excitations in order to improve the passengers' riding comfort and harvest the lost engine energy due to uneven roads. Following the derived mathematical formulations and the proposed solution approaches, the numerical simulations of this interaction system subject to a continuous sinusoidal road excitation and a single ramp impact are completed. The simulation results are presented as the dynamic response curves in the forms of the frequency spectrum and the time history, which reveals the complex interaction characteristics of the system for vibration reductions and energy harvesting performance. It has addressed the coupling effects on the dynamic characteristics of the integrated system caused by: (1) the natural modes and frequencies of the vehicle; (2) the vehicle rolling and pitching motions; (3) different road excitations on four wheels; (4) the time delay of a road ramp to impact both the front and rear wheels, etc., which cannot be tackled by an often used quarter vehicle model. The guidelines for engineering applications are given. The developed coupling model and the revealed concept provide a means with analysis idea to investigate the details of four energy harvester motions for electromagnetic suspension designs in order to replace the current passive vehicle isolators and to harvest the lost engine energy. Potential further research directions are suggested for readers to consider in the future.

Ultrathin flexible electrospun carbon nanofibers reinforced graphene microgasbags films with three-dimensional conductive network toward synergetic enhanced electromagnetic interference shielding

In recent years,graphene-based composite films have been greatly developed in the field of electromagnetic shielding interference(EMI).However,it is still a huge challenge to prepare graphene-based composite films with excellent mechanical properties,conductivity and electromagnetic shielding properties.In this work,we adopted a facile and effective method by annealing the alkali-treated polyacrylonitrile(aPAN)nanofibers reinforced graphene oxide(GO)composite films at 2000°C to obtain graphene-carbon nanofibers composite films(GCFs).Microscopically,carbon nanofibers(CNFs)were intercalated into the graphene sheets,and microgasbags structure was formed during the heat treatment process.The special structure makes GCFs have superior tensile strength(10.4 MPa)at 5%strain.After repeated folding over1000 times,the films still demonstrate excellent structural integrity and flexibility performance.Interestingly,the graphene-based composite films with 10 wt%a PAN nanofibers exhibit an extremely low density of about 0.678 g/cm^(3)and excellent electrical conductivity of 1.72×10^(5)S/m.Further,an outstanding electromagnetic shielding effectiveness(SE)of 55–57 d B was achieved,and the corresponding value of the specific SE/thickness can reach 67,601–70,059 d B·cm^(2)/g,which is the highest among reported graphenebased shielding materials.The significant electromagnetic shielding performance is due to the synergistic enhancement effect brought by the excellent conductivity of carbon nanofibers and graphene,the formed effective conductive network and the microgasbags structure.Electromagnetism simulation further clarified that the underlying mechanism should be mainly attributed to the conduction loss and multiple reflections caused by the special structure of GCFs.This work will provide new solutions for low density,high flexibility and excellent electromagnetic shielding properties materials in the next generation of foldable and wearable electronics.