Transient thermo-mechanical coupling simulation of wet brake friction disk on tracked vehicle

The transient finite element technique is applied, and a transient heat conduction model of wet brake friction disk is established. For obtaining the accurate heat flow density mathematic model and avoiding possibly instable thermoelastic stress produced by the non uniform contact pressure of friction pair, a test method is applied to collect accurate contact pressure between the dual sheet steel and friction disk in the combining process. And then the heat-flow density and transient ther mo mechanical coupling simulation are analyzed. At the same time all possible boundary conditions are considered, such as the heat generation, heat conduction problem, relation between friction and contact, variation in load and heat change problem etc. The simulation results show that the me chanical model of thermo mechanical coupling can express well the dynamic characteristics of fric tion disk, and gives perfect reference for more study on thermoelastic distortion of brake friction pairs.

A mechanically coupled MEMS filter with high-Q width extensional mode resonators

This work presents a novel radio frequency(RF)narrowband Si micro-electro-mechanical systems(MEMS)filter based on capacitively transduced slotted width extensional mode(WEM)resonators.The flexibility of the plate leads to multiple modes near the target frequency.The high Q-factor resonators of around 100000 enable narrow bandwidth filters with small size and simplified design.The 1-wavelength and 2-wavelength WEMs were first developed as a pair of coupled modes to form a passband.To reduce bandwidth,two plates are coupled with aλ-length coupling beam.The 79.69 MHz coupled plate filter(CPF)achieved a narrow bandwidth of 8.8 kHz,corresponding to a tiny 0.011%.The CPF exhibits an impressive 34.84 dB stopband rejection and 7.82 dB insertion loss with near-zero passband ripple.In summary,the RF MEMS filter presented in this work shows promising potential for application in RF transceiver front-ends.

Anisotropic strength,deformation and failure of gneiss granite under high stress and temperature coupled true triaxial compression

The anisotropic mechanical behavior of rocks under high-stress and high-temperature coupled conditions is crucial for analyzing the stability of surrounding rocks in deep underground engineering.This paper is devoted to studying the anisotropic strength,deformation and failure behavior of gneiss granite from the deep boreholes of a railway tunnel that suffers from high tectonic stress and ground temperature in the eastern tectonic knot in the Tibet Plateau.High-temperature true triaxial compression tests are performed on the samples using a self-developed testing device with five different loading directions and three temperature values that are representative of the geological conditions of the deep underground tunnels in the region.Effect of temperature and loading direction on the strength,elastic modulus,Poisson’s ratio,and failure mode are analyzed.The method for quantitative identification of anisotropic failure is also proposed.The anisotropic mechanical behaviors of the gneiss granite are very sensitive to the changes in loading direction and temperature under true triaxial compression,and the high temperature seems to weaken the inherent anisotropy and stress-induced deformation anisotropy.The strength and deformation show obvious thermal degradation at 200℃due to the weakening of friction between failure surfaces and the transition of the failure pattern in rock grains.In the range of 25℃ 200℃,the failure is mainly governed by the loading direction due to the inherent anisotropy.This study is helpful to the in-depth understanding of the thermal-mechanical behavior of anisotropic rocks in deep underground projects.

Peridynamic modeling and simulation of thermo-mechanical de-icing process with modified ice failure criterion

De-icing technology has become an increasingly important subject in numerous applications in recent years.However,the direct numerical modeling and simulation the physical process of thermomechanical deicing is limited.This work is focusing on developing a numerical model and tool to direct simulate the de-icing process in the framework of the coupled thermo-mechanical peridynamics theory.Here,we adopted the fully coupled thermo-mechanical bond-based peridynamics(TM-BB-PD)method for modeling and simulation of de-icing.Within the framework of TM-BB-PD,the ice constitutive model is established by considering the influence of the temperature difference between two material points,and a modified failure criteria is proposed,which takes into account temperature effect to predict the damage of quasi-brittle ice material.Moreover,thermal boundary condition is used to simulate the thermal load in the de-icing process.By comparing with the experimental results and the previous reported finite element modeling,our numerical model shows good agreement with the previous predictions.Based on the numerical results,we find that the developed method can not only predict crack initiation and propagation in the ice,but also predict the temperature distribution and heat conduction during the de-icing process.Furthermore,the influence of the temperature for the ice crack growth pattern is discussed accordingly.In conclusion,the coupled thermal-mechanical peridynamics formulation with modified failure criterion is capable of providing a modeling tool for engineering applications of de-icing technology.

COUPLED THERMO MECHANICAL FEM ANALYSIS OF TWIST COMPRESSION DEFORMATION PROCESS

3-D rigid-viscoplastic FEM of compressible materials was applied to analyze the deformation behavior during twist compression forming of axisymmetrical body at high temperatures. When calculating the temperature fields, considering the thermo mechanical coupling effect between temperature and deformation, 2-D FEM and CNG methods were adopted, and the up winding technique was used to avoid the influences of numerical instability on calculated results.

Coupling effect of the conductivities of Li ions and electrons by introducing LLTO@C fibers in the LiNi0.8Co0.15Al0.05O2 cathode

To probe the coupling effect of the electron and Li ion conductivities in Ni-rich layered materials(LiNi0.8Co0.15Al0.05O2,NCA),lithium lanthanum titanate(LLTO)nanofiber and carbon-coated LLTO fiber(LLTO@C)materials were introduced to polyvinylidene difluoride in a cathode.The enhancement of the conductivity was indicated by the suppressed impedance and polarization.At 1 and 5 C,the cathodes with coupling conductive paths had a more stable cycling performance.The coupling mechanism was analyzed based on the chemical state and structure evolution of NCA after cycling for 200 cycles at 5 C.In the pristine cathode,the propagation of lattice damaged regions,which consist of high-density edge-dislocation walls,destroyed the bulk integrity of NCA.In addition,the formation of a rock-salt phase on the surface of NCA caused a capacity loss.In contrast,in the LLTO@C modified cathode,although the formation of dislocation-driven atomic lattice broken regions and cation mixing occurred,they were limited to a scale of several atoms,which retarded the generation of the rock-salt phase and resulted in a pre-eminent capacity retention.Only NiO phase“pitting”occurred.A mechanism based on the synergistic transport of Li ions and electrons was proposed.

Fluid-solid coupling model for studying wellbore instability in drilling of gas hydrate bearing sediments

As the oil or gas exploration and development activities in deep and ultra- deep waters become more and more, encountering gas hydrate bearing sediments （HBS） is almost inevitable. The variation in temperature and pressure can destabilize gas hydrate in nearby formation around the borehole, which may reduce the strength of the formation and result in wellbore instability. A non-isothermal, transient, two-phase, and fluid-solid coupling mathematical model is proposed to simulate the complex stability performance of a wellbore drilled in HBS. In the model, the phase transition of hydrate dissociation, the heat exchange between drilling fluid and formation, the change of mechanical and petrophysical properties, the gas-water two-phase seepage, and its interaction with rock deformation are considered. A finite element simulator is developed, and the impact of drilling mud on wellbore instability in HBS is simulated. Results indicate that the re- duction in pressure and the increase in temperature of the drilling fluid can accelerate hydrate decomposition and lead to mechanical properties getting worse tremendously. The cohesion decreases by 25% when the hydrate totally dissociates in HBS. This easily causes the wellbore instability accordingly. In the first two hours after the formation is drilled, the regions of hydrate dissociation and wellbore instability extend quickly. Then, with the soaking time of drilling fluid increasing, the regions enlarge little. Choosing the low temperature drilling fluid and increasing the drilling mud pressure appropriately can benefit the wellbore stability of HBS. The established model turns out to be an efficient tool in numerical studies of the hydrate dissociation behavior and wellbore stability of HBS.

Mechanics analysis of a wheelchair robot with wheel-track coupling mechanism

A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities whether on flat ground or stairs and obstacles in the city. The wheel- track coupling mechanism is designed and the stability of the bodywork of the wheelchair robot on the stairs is analyzed. In order to obtain the stability of wheelchair robot when it climbs obstacles, centroid projection method is applied to analyze the static stability, stability margin is proposed to provide the stability under some dynamic forces, and the push rod rotation angle in terms of the guaranteed stability margin is given. Finally, the dynamic model of the wheelchair robot based on Lagrange equation is established, which can be a theoretical foundation for the wheelchair control system design.

Coupling Mechanism of Saturated Concrete Subjected to Simultaneous Fatigue Loading and Freeze-thaw Cycles

The coupling mechanism of saturated concrete subjected to simultaneous 4-point fatigue loading and freeze-thaw cycles was, for the first time, experimentally studied by strain technology. The coupling strain, temperature strain and fatigue strain of concrete specimens were measured at the same time from one sample with stain analysis method and the relationship among these three kinds of strains was studied by fitting data to present coupling mechanism at macro level. The results showed that there was no interaction between fatigue strain and temperature strain and the coupling strain could be written by linear superposition of temperature strain and fatigue strain.

The coupling mechanism between the suitable space and rural settlements considering the effect of mountain hazards in the upper Minjiang River basin

Some settlements were located in unsuitable regions due to limited land resources in mountainous areas,some settlements were even even constructed in areas prone to geological hazards in Southwest China.Therefore,it was important to evaluate the spatial appropriateness of a region and determine the areas that were unsuitable for settlements,and then find out the settlements located in unsuitable regions.It will assist in decision making associated with the relocation of settlements.Furthermore,it will be the key to ensure the safety of inhabitants and promoting sustainable development in mountainous areas.This study explored the coupling mechanism between suitable space and rural settlements in the upper Minjiang River basin,which is an ecologically fragile area with high-frequency of natural hazards.Firstly,we identified relief degree of land surface(RDLS),elevation,and disaster risk as the limiting factors.Then,by determining the thresholds of these limiting factors,we recognized the suitable areas for inhabitation in the upper Minjiang River basin with GIS.Finally,using the distribution map of rural settlements and that of suitable space,the distribution of rural settlements located at unsuitable area was obtained by coupling relationship analysis.Consequently,an in-depth understanding of this relationship was achieved as follows:(1)The suitable space of the upper Minjiang River basin is 13.7 thousand km2,accounting for 54.9%of the total land space;(2)There were 196 settlements located in the unsuitable area,the total area of these settlements was 125.27 km2,and there were 68000 people in these settlements,accounting for 17.65%of the total population;(3)There were 65 settlements located near mountain hazard areas,accounting for 4.9%of the total.These findings suggest that it was necessary to carefully investigate settlements with risks and develop targeted relocation policies to help find the most effective way of using land safely and to good effect.The details are as follows:(1)Fully consider the safety of residents:For the 196 settlements distributed in the unsuitable region,the government should undertake a point-by-point survey and classify these settlements into different categories for relocation;(2)For the 65 settlements closely related with mountain hazards,professional geological prospecting teams should be organized to conduct a field survey at each point;(3)Besides considering the safety of residents during the relocation process,it is necessary to pay more attention to the cultural customs of inhabitants and livelihood sustainability.

Tunable terahertz transmission behaviors and coupling mechanism in hybrid MoS_(2)metamaterials

A hybrid metamaterial with the integration of molybdenum disulfide(MoS_(2))overlayer is proposed to manipulate the terahertz(THz)wave.The simulated results indicate that the introduction of MoS_(2) layer could significantly modify the resonant responses with large resonance red-shift and bandwidth broadening due to the depolarization field effect,especially for the structure on the small permitivity substrate.Additionally,the wide-band modulator in off-resonant region and a switch effect at resonance can be achieved by varying the conductivity of MoS_(2) layer.Further theoretical calculations based on the Lorentz coupling model are consistent with the simulated results,explicating the response behaviors originate from the coupling between MoS_(2) overlayer and the metastructure.Our results could provide a possibility for active control THz modulator and switchable device based on the MoS_(2) overlayer and advance the understanding of the coupling mechanism in hybrid structures.

Numerical simulation and experimental validation of multiphysics field coupling mechanisms for a high power ICP wind tunnel

We take the established inductively coupled plasma(ICP) wind tunnel as a research object to investigate the thermal protection system of re-entry vehicles. A 1.2-MW high power ICP wind tunnel is studied through numerical simulation and experimental validation. The distribution characteristics and interaction mechanism of the flow field and electromagnetic field of the ICP wind tunnel are investigated using the multi-field coupling method of flow, electromagnetic, chemical, and thermodynamic field. The accuracy of the numerical simulation is validated by comparing the experimental results with the simulation results. Thereafter, the wind tunnel pressure, air velocity, electron density, Joule heating rate, Lorentz force, and electric field intensity obtained using the simulation are analyzed and discussed. The results indicate that for the 1.2-MW ICP wind tunnel, the maximum values of temperature, pressure, electron number density, and other parameters are observed during coil heating. The influence of the radial Lorentz force on the momentum transfer is stronger than that of the axial Lorentz force. The electron number density at the central axis and the amplitude and position of the Joule heating rate are affected by the radial Lorentz force. Moreover, the plasma in the wind tunnel is constantly in the subsonic flow state, and a strong eddy flow is easily generated at the inlet of the wind tunnel.

Synchronization in multilayer networks through different coupling mechanisms

In recent years,most studies of complex networks have focused on a single network and ignored the interaction of multiple networks,much less the coupling mechanisms between multiplex networks.In this paper we investigate synchronization phenomena in multilayer networks with nonidentical topological structures based on three specific coupling mechanisms:assortative,disassortative,and anti-assortative couplings.We find rich and complex synchronous dynamic phenomena in coupled networks.We also study the behavior of effective frequencies for layers I and II to understand the underlying microscopic dynamics occurring under the three different coupling mechanisms.In particular,the coupling mechanisms proposed here have strong robustness and effectiveness and can produce abundant synchronization phenomena in coupled networks.

Coupling Mechanism between Tamm Plasmon Polaritons and Monolayer WS_(2) Embedded in Metal/Dielectric Bragg Reflector Hybrid Architecture

To reveal and utilize the interaction between Tamm plasmon polaritons(TPPs)and two-dimensional materials are promising for exploiting next-generation optoelectronic devices.Herein,the coupling mechanism between metal TPPs and monolayer WS_(2) along with its differences from that between metal TPPs and graphene was studied in detail by using the transfer matrix method.The experimental results show that it is difficult to excite TPPs at the boundary between monolayer WS_(2) and dielectric Bragg reflector(DBR)such that the strong coupling mainly stems from the interaction between metal TPPs and exciton in monolayer WS_(2).However,the coupling in graphene/DBR/metal hybrid structure derives from the interaction between two different TPP resonance modes.Thus,evolutions of Rabi splitting with various structural parameters including spacer thickness,incident angle and DBR period greatly differ from those observed in graphene/DBR/metal hybrid structure.In addition,the discrepancies induced via metal Ag and Au films as well as the possible influence mechanism were also discussed.

Extraction algorithm for longitudinal and transverse mechanical information of AFM

The atomic force microscope(AFM)can measure nanoscale morphology and mechanical properties and has a wide range of applications.The traditional method for measuring the mechanical properties of a sample does so for the longitudinal and transverse properties separately,ignoring the coupling between them.In this paper,a data processing and multidimensional mechanical information extraction algorithm for the composite mode of peak force tapping and torsional resonance is proposed.On the basis of a tip–sample interaction model for the AFM,longitudinal peak force data are used to decouple amplitude and phase data of transverse torsional resonance,accurately identify the tip–sample longitudinal contact force in each peak force cycle,and synchronously obtain the corresponding characteristic images of the transverse amplitude and phase.Experimental results show that the measured longitudinal mechanical characteristics are consistent with the transverse amplitude and phase characteristics,which verifies the effectiveness of the method.Thus,a new method is provided for the measurement of multidimensional mechanical characteristics using the AFM.

Epidemic Spreading–Information Dissemination Coupling Mechanism in Heterogeneous Areas

With COVID-19 continuing to rage around the world,there is a spread of epidemic-related information on social networking platforms.This phenomenon may inhibit or promote the scale of epidemic transmission.This study constructed a double-layer epidemic spreading–information dissemination network based on the movements of individuals across regions to analyze the dynamic evolution and coupling mechanism of information dissemination and epidemic transmission.We also proposed measures to control the spread of the epidemic by analyzing the factors affecting dynamic transmission.We constructed a state probability equation based on Markov chain theory and performed Monte Carlo simulations to demonstrate the interaction between information dissemination and epidemic transmission.The simulation results showed that the higher the information dissemination rate,the larger the scale of information dissemination and the smaller the scale of epidemic transmission.In addition,the higher the recovery rate of the epidemic or the lower the infection rate of the epidemic,the smaller the scale of information dissemination and the smaller the scale of epidemic transmission.Moreover,the greater the probability of individuals moving across regions,the larger the spread of the epidemic and information.Finally,the higher the probability of an individual taking preventive behavior,the smaller the spread of the epidemic and information.Therefore,it is possible to suppress epidemic spread by increasing the information dissemination rate,epidemic recovery rate,and probability of individuals taking preventive behavior,while also reducing the infection rate of the epidemic and appropriately implementing regional blockades.

Carbon,nitrogen and phosphorus coupling relationships and their influencing factors in the critical zone of Dongting Lake wetlands,China

Wetland is a transition zone between terrestrial and aquatic ecosystems,and is the source and sink of various biogenic elements in the earth’s epipelagic zone.In order to investigate the driving force and coupling mechanism of carbon(C),nitrogen(N)and phosphorus(P)migration in the critical zone of lake wetland,this paper studies the natural wetland of Dongting Lake area,through measuring and analysing the C,N and P contents in the wetland soil and groundwater.Methods of Pearson correlation,non-linear regression and machine learning were employed to analyse the influencing factors,and to explore the coupling patterns of the C,N and P in both soils and groundwater,with data derived from soil and water samples collected from the wetland critical zone.The results show that the mean values of organic carbon(TOC),total nitrogen(TN)and total phosphorus(TP)in groundwater are 1.59 mg/L,4.19 mg/L and 0.5 mg/L,respectively,while the mean values of C,N and P in the soils are 18.05 g/kg,0.86 g/kg and 0.52 g/kg.The results also show that the TOC,TN and TP in the groundwater are driven by a variety of environmental factors.However,the concentrations of C,N and P in the soils are mainly related to vegetation abundance and species which influence each other.In addition,the fitted curves of wetland soil C-N and C-P appear to follow the power function and S-shaped curve,respectively.In order to establish a multivariate regression model,the soil N and P contents were used as the input parameters and the soil C content used as the output one.By comparing the prediction effects of machine learning and nonlinear regression modelling,the results show that coupled relationship equation for the C,N and P contents is highly reliable.Future modelling of the coupled soil and groundwater elemental cycles needs to consider the complexity of hydrogeological conditions and to explore the quantitative relationships among the influencing factors and chemical constituents.

Coupled Thermo-Mechanical Modeling of Long Cone-Shaped Forging Based on Rigid Visco-Plastic FEM

Based on synthetically considering the coupled thermo mechanical relations between temperature and deforming, a numerical simulation of the forging process for the special long cone shaped workpiece of Al 5.44Mg 2.15Li 0.12Zr alloy at high temperature was conducted by using the rigid visco plastic finite element method. The relations between the total load and the displacement during the forging, and the distributions of stress, strain, temperature and strain rate, which can provide useful information for the process design, are obtained.

Research on the Coupling Mechanism of Creative Spirit Cultivation and Scientific and Technological Innovation Development

Migration and innovation is the driving force of scientific and technological development.By analyzing the coupling relationship between the two,this paper finds out the common elements shared by the two factors,and constructs the coupling guarantee mechanism between them,so as to provide suggestions for the coordination,win-win and synchronous benign development of the spirit of makers and the development of scientific and technological innovation,and promote the sustainable development of the national innovation system.

Light Inducing the Geometric Conversion of NiO_(6) to Trigger a Faster Oxygen Evolution Reaction Pathway:The Coupled Oxygen Evolution Mechanism

Developing highly active and robust oxygen evolution reaction(OER)electrocatalysts is still a critical challenge for water electrolyzers and metal-air batteries.Realizing the dynamic evolution of the intermediate and charge transfer during OER and developing a clear OER mechanism is crucial to design high-performance OER catalysts.Recently in Nature,Xue and colleagues revealed a new OER mechanism,coupled oxygen evolution mechanism(COM),which involves a switchable metal and oxygen redox under light irradiation in nickel oxyhydroxide-based materials.This newly developed mechanism requires a reversible geometric conversion between octahedron(NiO_(6))and square planar(NiO_(4))to achieve electronic states with both“metal redox”and“oxygen redox”during OER.The asymmetric structure endows NR-NiOOH with a nonoverlapping region between the dz^(2) orbitals and a_(1g)^(*)bands,which facilitate the geometric conversion and enact the COM pathway.As a result,NR-NiOOH exhibited better OER activity and stability than the traditional NiOOH.