Bursting phenomena as well as the bifurcation mechanism in a coupled BVP oscillator with periodic excitation

We explore the complicated bursting oscillations as well as the mechanism in a high-dimensional dynamical system.By introducing a periodically changed electrical power source in a coupled BVP oscillator, a fifth-order vector field with two scales in frequency domain is established when an order gap exists between the natural frequency and the exciting frequency.Upon the analysis of the generalized autonomous system, bifurcation sets are derived, which divide the parameter space into several regions associated with different types of dynamical behaviors. Two typical cases are focused on as examples,in which different types of bursting oscillations such as sub Hopf/sub Hopf burster, sub Hopf/fold-cycle burster, and doublefold/fold burster can be observed. By employing the transformed phase portraits, the bifurcation mechanism of the bursting oscillations is presented, which reveals that different bifurcations occurring at the transition between the quiescent states（QSs） and the repetitive spiking states（SPs） may result in different forms of bursting oscillations. Furthermore, because of the inertia of the movement, delay may exist between the locations of the bifurcation points on the trajectory and the bifurcation points obtained theoretically.

Discussion on coupling mechanism of asymmetric CRLH/RH TL coupler

A quasi 0-dB coupler composed of a composite right-/left-handed transmission line (CRLH TL) and a conventional right-handed transmission line (RH TL) is presented. This coupler is shown to exhibit broad bandwidth and tight coupling char- acteristics. The circuit model and S-parameter results are also demonstrated. Another coupler with properly chosen loaded lumped-elements LL and CL in the CRLH TL is proposed to gain further understanding of the coupling mechanism. By adjusting the spacing between the CRLH TL and RH TL from 8 mm to 0.2 mm, it can be shown that backward coupling occurs in the left-handed region.

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.

Coupled effects of climate change and human activities on vegetation dynamics in the Southwestern Alpine Canyon Region of China

The driving effects of climate change and human activities on vegetation change have always been a focal point of research.However,the coupling mechanisms of these driving factors across different temporal and spatial scales remain controversial.The Southwestern Alpine Canyon Region of China(SACR),as an ecologically fragile area,is highly sensitive to the impacts of climate change and human activities.This study constructed a vegetation cover dataset for the SACR based on the Enhanced Vegetation Index(EVI)from 2000 to 2020.Spatial autocorrelation,Theil-Sen trend,and Mann-Kendall tests were used to analyze the spatiotemporal characteristics of vegetation cover changes.The main drivers of spatial heterogeneity in vegetation cover were identified using the optimal parameter geographic detector,and an improved residual analysis model was employed to quantify the relative contributions of climate change and human activities to interannual vegetation cover changes.The main findings are as follows:Spatially,vegetation cover exceeds 60%in most areas,especially in the southern part of the study area.However,the border area between Linzhi and Changdu exhibits lower vegetation cover.Climate factors are the primary drivers of spatial heterogeneity in vegetation cover,with temperature having the most significant influence,as indicated by its q-value,which far exceeds that of other factors.Additionally,the interaction q-value between the two factors significantly increases,showing a relationship of bivariate enhancement and nonlinear enhancement.In terms of temporal changes,vegetation cover shows an overall improving trend from 2000 to 2020,with significant increases observed in 68.93%of the study area.Among these,human activities are the main factors driving vegetation cover change,with a relative contribution rate of 41.31%,while climate change and residual factors contribute 35.66%and 23.53%,respectively.By thoroughly exploring the coupled mechanisms of vegetation change,this study provides important references for the sustainable management and conservation of the vegetation ecosystem in the SACR.

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.

The Driving Mechanism of Oasificationdesertification in Hotan River Basin

[Objective] The main purpose is to reveal the laws and driving mechanism of oasification and desertification in Hotan River Basin during the period of 1972-2010. [Method] The visual interpretation method was used to process TM/ETM＋ image based on field work and investigation of Hotan Oasis. These interpretation dates have been reclassified to desert and oasis. Then, the driving mechanism of desertification and oasification was analyzed. [Result] The analysis indicated that the oasification velocity（91.24 km^2/year） was faster than the desertification’s（77.78 km^2/year）,with a rapid growth of 5.59 km^2/year in oasis area in the mid-lower reaches of the Hotan River. [Coclusion] There existed spatial coupling linked by water consumption between oasification in the middle reaches and desertification in the lower reaches.And the changing trends were opposite not only for the oasis area, but also for the oasification area and oasification velocity between the middle and the lower reaches of the Hotan River Basin. With climatic warming, population growth, economical development, scientific and technological progress, and in particular the implementation of national policies, the cropland area increased and oasis expanded, speeding up the oasification and water consumption in the middle reaches. Hence it is urgent to prevent the Hotan Oasis from exacerbating the current water supply-demand imbalance and prohibit the expansion of arable land to transitional belt between oasis and desert.

A Regional-Scale Method of Forecasting Debris Flow Events Based on Water-Soil Coupling Mechanism

A debris flow forecast model based on a water-soil coupling mechanism that takes the debrisflow watershed as a basic forecast unit was established here for the prediction of disasters at the watershed scale.This was achieved through advances in our understanding of the formation mechanism of debris flow.To expand the applicable spatial scale of this forecasting model,a method of identifying potential debris flow watersheds was used to locate areas vulnerable to debris flow within a forecast region.Using these watersheds as forecasting units and a prediction method based on the water-soil coupling mechanism,a new forecasting method of debris flow at the regional scale was established.In order to test the prediction ability of this new forecasting method,the Sichuan province,China was selected as a study zone and the large-scale debris flow disasters attributable to heavy rainfall in this region on July 9,2013 were taken as the study case.According to debris flow disaster data on July 9,2013 which were provided by the geo-environmental monitoring station of Sichuan province,there were 252 watersheds in which debris flow events actually occurred.The current model predicted that 265 watersheds were likely to experience a debris flow event.Among these,43 towns including 204 debrisflow watersheds were successfully forecasted and 24 towns including 48 watersheds failed.The false prediction rate and failure prediction rate of thisforecast model were 23% and 19%,respectively.The results show that this method is more accurate and more applicable than traditional methods.

ENGINEERING CHARACTERISTICS AND ITS MECHANISM EXPLANATION OF VIBRATORY SYNCHRONIZATION TRANSMISSION

Vibratory synchronization transmission (VST) is a kind of special physicalphenomenon in inertia vibration mechanical systems. For an inertia vibration mechanical systemdriven by one pair of motors runs in step, even the power supply of one motor is cut off, the motorcan continue to keep rotating state under the vibration exciting of the machine body driven by onlyone other motor. And its rotating frequency will be the same as that of the other one. The transientprocess of this wonderful physical phenomenon has not been described quantitatively according tocurrent-existing mechanical models. On the basis of investigation of the engineering characteristicsof VST, a mechanical and electrical coupling mathematical model of a two-shaft inertia vibrationmachine is established. With this model, the transient process of VST is recurred quantitatively andsuccessfully, and a reasonable explanation is given.

Hydro-mechanical coupling mechanism on joint of clay core-wall and concrete cut-off wall

The joint of clay core-wall and concrete cut-off wall is one of the weakest parts in high earth and rockftll dams.A kind of highly plastic clay is always fixed on the joint to fit the large shear deformation between clay core-wall and concrete cut-offwall,so the hydro-mechanical coupling mechanisms on the joint under high stress,high hydraulic gradient,and large shear deformation are of great importance for the evaluation of dam safety.The hydro-mechanical coupling characteristics of the joint of the highly plastic clay and the concrete cut-off wall in a high earth and rockfill dam in China were studied by using a newly designed soil-structure contact erosion apparatus.The experimental results indicate that：1） Shear failure on the joint is due to the hydro-mechanical coupling effect of stress and seepage failure.The seepage failure will induce the final shear failure when the ratio of deviatoric stress to confining pressure is within 1.0-1.2; 2） A negative exponential permeability empirical model for the joint denoted by a newly defined principal stress function,which considers the coupling effect of confining pressure and axial pressure on the permeability,is established based on hydro-mechanical coupling experiments.3） The variation of the settlement before and after seepage failure is very different.The settlement before seepage failure changes very slowly,while it increases significantly after the seepage failure.4） The stress-strain relationship is of a strain softening type.5） Flow along the joint still follows Darcian flow rule.The results will provide an important theoretical basis for the further evaluation on the safety of the high earth and rockfill dam.

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.

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.

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.

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.

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.

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.

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.

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.

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.