Generalized modeling and experimental research on the transient response of supercapacitors under compressive mechanical loads

Supercapacitors(SCs)have been successfully used in electric vehicles or military equipment systems for their high power density.However,the mechanical impacts from vehicle crashes and missile penetration probably cause performance fluctuations or failure of SCs,which may threaten the safety of systems using SCs.In this paper,a generalized circuit model to analyze the transient process of SCs under mechanical loads is proposed.The circuit model simultaneously takes capacitance change,internal short-circuit and resistance change into account,an extra resistor-capacitor circuit(RCC)is added to simulate the nonlinear behavior during charging and discharging.Subsequently,the relationships between pressure and fundamental circuit parameters are determined by static methods.By taking the static test data into the circuit model,the transient response of different types of SCs under particular mechanical loading conditions is predicted.Finally,the influences of some crucial parameters on the voltage responses of SCs are revealed based on the simulations,which provide references for designing and optimizing mechanical load-resistant or self-sensing SCs in specific application scenarios.

Analytical analysis of hollow CORC cable under thermo-mechanical loads

According to engineering experience,the axial shrinkage caused by the refrigerant seriously endangers the performance of long‐distance conductor on round core(CORC)cables.Since outage maintenance of high‐temperature superconducting(HTS)cables is inevitable,providing appropriate compensation for cyclic temperature is one of the key technologies in the actual application of power cables.Therefore,this paper presents an analytical solution for hollow CORC cables under thermo‐mechanical loads.First,regarded as an axisymmetric composite structure,the radial temperature distribution of CORC cable under Dirichlet boundary or mixed boundary conditions was calculated.Then,assuming cable ends were axially fixed,a recursive method without variables is used to evaluate its displacement,strains,and stresses.Then,an algebraic method with axial strain as a variable is developed to analyze the mechanical behavior of the CORC cable more directly.Finally,concluded from the above derivation,a matrix equation is constructed based on continuity equations and boundary conditions,which applies to isotropic and orthotropic materials with orientations.Calculation results show that the analytical solution agrees with finite element method(FEM)results.Compared to the trial results of a 360 m CORC cable,the calculation error of axial shrinkage is within 1.63 cm,and the relative error is within 6.1%.In addition,the recursive method is the fastest to calculate axial strain,while the matrix method has a significant efficiency advantage in calculating the stresses and strains of each layer.

The effect of mechanical loads on the degradation of aliphatic biodegradable polyesters

Aliphatic biodegradable polyesters have been the most widely used synthetic polymers for developing biodegradable devices as alternatives for the currently used permanent medical devices.The performances during biodegradation process play crucial roles for final realization of their functions.Because physiological and biochemical environment in vivo significantly affects biodegradation process,large numbers of studies on effects of mechanical loads on the degradation of aliphatic biodegradable polyesters have been launched during last decades.In this review article,we discussed the mechanism of biodegradation and several different mechanical loads that have been reported to affect the biodegradation process.Other physiological and biochemical factors related to mechanical loads were also discussed.The mechanical load could change the conformational strain energy and morphology to weaken the stability of the polymer.Besides,the load and pattern could accelerate the loss of intrinsic mechanical properties of polymers.This indicated that investigations into effects of mechanical loads on the degradation should be indispensable.More combination condition of mechanical loads and multiple factors should be considered in order to keep the degradation rate controllable and evaluate the degradation process in vivo accurately.Only then can the degradable devise achieve the desired effects and further expand the special applications of aliphatic biodegradable polyesters.

Failure transition of shear-to-dilation band of rock salt under triaxial stresses

Great potential of underground gas/energy storage in salt caverns seems to be a promising solution to support renewable energy.In the underground storage method,the operating cycle unfortunately may reach up to daily or even hourly,which generates complicated pressures on the salt cavern.Furthermore,the mechanical behavior of rock salt may change and present distinct failure characteristics under different stress states,which affects the performance of salt cavern during the time period of full service.To reproduce a similar loading condition on the cavern surrounding rock mass,the cyclic triaxial loading/unloading tests are performed on the rock salt to explore the mechanical transition behavior and failure characteristics under different confinement.Experimental results show that the rock salt samples pre-sent a diffused shear failure band with significant bulges at certain locations in low confining pressure conditions(e.g.5 MPa,10 MPa and 15 MPa),which is closely related to crystal misorientation and grain boundary sliding.Under the elevated confinement(e.g.20 MPa,30 MPa and 40 MPa),the dilation band dominates the failure mechanism,where the large-size halite crystals are crushed to be smaller size and new pores are developing.The failure transition mechanism revealed in the paper provides additional insight into the mechanical performance of salt caverns influenced by complicated stress states.

A multiscale 3D finite element analysis of fluid/solute transport in mechanically loaded bone

The transport of fluid, nutrients, and signaling molecules in the bone lacunar–canalicular system(LCS) is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching(FRAP) approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30–50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis(FEA)approach. An intact murine tibia was first re-constructed from micro CT images into a three-dimensional(3D)linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform(FEBio) to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex.Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces(shear and drag forces) for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.

Electric potential and energy band in ZnO nanofiber tuned by local mechanical loading

Recent success in strain engineering has triggered tremendous interest in its study and potential applications in nanodevice design. In this paper, we establish a coupled piezoelectric/semiconducting model for a wurtzite structure ZnO nanofiber under the local mechanical loading. The energy band structure tuned by the local mechanical loading and local length is calculated via an eight-band k·p method, which includes the coupling of valance and conduction bands. Poisson's effect on the distribution of electric potential inversely depends on the local mechanical loading. Numerical results reveal that both the applied local mechanical loading and the local length exhibit obvious tuning effects on the electric potential and energy band. The band gap at band edges varies linearly with the applied loading. Changing the local length shifts the energy band which is far away from the band edges. This study will be useful in the electronic and optical enhancement of semiconductor devices.

Wireless Network Security Using Load Balanced Mobile Sink Technique

Real-time applications based on Wireless Sensor Network(WSN)tech-nologies are quickly increasing due to intelligent surroundings.Among the most significant resources in the WSN are battery power and security.Clustering stra-tegies improve the power factor and secure the WSN environment.It takes more electricity to forward data in a WSN.Though numerous clustering methods have been developed to provide energy consumption,there is indeed a risk of unequal load balancing,resulting in a decrease in the network’s lifetime due to network inequalities and less security.These possibilities arise due to the cluster head’s limited life span.These cluster heads(CH)are in charge of all activities and con-trol intra-cluster and inter-cluster interactions.The proposed method uses Lifetime centric load balancing mechanisms(LCLBM)and Cluster-based energy optimiza-tion using a mobile sink algorithm(CEOMS).LCLBM emphasizes the selection of CH,system architectures,and optimal distribution of CH.In addition,the LCLBM was added with an assistant cluster head(ACH)for load balancing.Power consumption,communications latency,the frequency of failing nodes,high security,and one-way delay are essential variables to consider while evaluating LCLBM.CEOMS will choose a cluster leader based on the influence of the fol-lowing parameters on the energy balance of WSNs.According to simulatedfind-ings,the suggested LCLBM-CEOMS method increases cluster head selection self-adaptability,improves the network’s lifetime,decreases data latency,and bal-ances network capacity.

Evaluation of the weakening behavior of gas on the coal strength and its quantitative influence on the coal deformation

The coal strength and deformation properties are key factors affecting safe coal mining and highefficiency coalbed methane(CBM)development.In this paper,reconstituted coal samples are chosen to investigate the weakening behavior of gas on coal strength,meanwhile,its effects on coal deformation are quantitatively evaluated.The results indicate that the weakening degree of gas on coal strength is closely related to the confining stress and gas pressure.Compared with non-gas-saturated coals,the maximum weakening ratios of adsorbed gas to coal strength are 10.58%,18.12%,8.55%and 14.65%under the conditions of confining stress CS=3 MPa and gas pressure GP=1 MPa,CS=3 MPa and GP=2 MPa,CS=4 MPa and GP=1 MPa,and CS=4 MPa and GP=2 MPa,respectively.Furthermore,the maximum weakening ratios of free gas to coal strength are 18.27%,36.54%,14.79%and 29.58%,respectively,under above four conditions.The maximum coal bulk strain decreases as particle sizes of coal powders increase,and it has a maximum value of 0.0227 and a minimum value of 0.0191 in particle size ranges of 0.01–0.041 and 0.5–1 mm.Under the same conditions,the coal bulk strain increases with increasing gas pressure,revealing that coal deformation properties can be enhanced by gas.

Mechanotransduction of stem cells for tendon repair

Tendon is a mechanosensitive tissue that transmits force from muscle to bone.Physiological loading contributes to maintaining the homeostasis and adaptation of tendon,but aberrant loading may lead to injury or failed repair.It is shown that stem cells respond to mechanical loading and play an essential role in both acute and chronic injuries,as well as in tendon repair.In the process of mechanotransduction,mechanical loading is detected by mechanosensors that regulate cell differentiation and proliferation via several signaling pathways.In order to better understand the stem-cell response to mechanical stimulation and the potential mechanism of the tendon repair process,in this review,we summarize the source and role of endogenous and exogenous stem cells active in tendon repair,describe the mechanical response of stem cells,and finally,highlight the mechanotransduction process and underlying signaling pathways.

Failure mechanism and stability control of a large section of very soft roadway surrounding rock shear slip

The measured data and simulation test phenomenon of surrounding rock deformation and failure at the project site indicate that shear failure which firstly occurs in surrounding rock, block slip and second shear failure are the root cause of deformation and damage of supporting structure of the surrounding rock at a large scale. We derived limit load of surrounding rock shear slip failure and reasonable support resistance of given load by means of shear slip line field theory, discussed the main factors which influence the limit load of surrounding rock. Shear slip line field and limit load of circular tunnel surrounding rock were obtained by means of physical simulation test, which agreed well with the theoretical analysis results. Based on the theoretical analysis and physical simulation test, the cause deformation and failure at large scale of Xinshanghai No. 1 coal mine big section ingate was analyzed, and the shear failure resistance and block slip in surrounding rock were proposed as the core technical supporting ideas. Proper range of supporting resistance which came from calculation was suggested. The support scheme which is mainly composed of large grouting anchor, sprayed anchor net support technique and full-face grille concrete finally ended the dilemma of repeated failure and mending of ingate and created critical conditions for smooth production in the coal mine.

In vitro calcification studies on bioprosthetic and decellularized heart valves under quasi-physiological flow conditions

The lifespan of biological heart valve prostheses available in the market is limited due to structural alterations caused by calcium phosphate deposits formed from blood plasma in contact with the tissues.The objective of this work is to present a comparative methodology for the investigation of the formation of calcium phosphate deposits on bioprosthetic and tissue-engineered scaffolds in vitro and the influence of mechanical forces on tissue mineralization.Based on earlier investigations on biological mineralization at constant supersaturation,a circulatory loop simulating dynamic blood flow and physiological pressure conditions was developed.The system was appropriately adapted to evaluate the calcification potential of decellularized(DCV)and glutaraldehyde-fixed(GAV)porcine aortic valves.Results indicated that DCV calcified at higher,statistically nonsignificant,rates in comparison with GAV.This difference was attributed to the tissue surface modifications and cell debris leftovers from the decellularization process.Morphological analysis of the solids deposited after 20 h by scanning electron microscopy in combination with chemical microanalysis electron-dispersive spectroscopy identified the solid formed as octacalcium phosphate(Ca8(PO4)6H2·5H2O,OCP).OCP crystallites were preferentially deposited in high mechanical stress areas of the test tissues.Moreover,GAV tissues developed a significant transvalvular pressure gradient increase past 36 h with a calcium deposition distribution similar to the one found in explanted prostheses.In conclusion,the presented in vitro circulatory model serves as a valuable prescreening methodology for the investigation of the calcification process of bioprosthetic and tissue-engineered valves under physiological mechanical load.

Harnessing wrinkling morphologies of graphene on soft substrates for mechanically programmable interfacial thermal conductance

Strain engineering has been leveraged to tune the thermal properties of materials by introducing stress and manipulating local atomic vibrations,which poses a detrimental threat to the mechanical integrity of materials and structures and limits the capability to regulate thermal transport.Here,we report that the interfacial thermal conductance of graphene on a soft substrate can be regulated by harnessing wrinkling and folding morphologies of graphene,which could be well controlled by managing the prestrain applied to the substrate.These obtained graphene structures are free of significant in-plane mechanical strain and only have infinitesimal distortion to the intrinsic thermal properties of graphene.The subsequent thermal transport studies with pumpprobe non-equilibrium molecular dynamics(MD)simulation show that the thermal conductance between graphene structures and the substrate is uniquely determined by the morphological features of graphene.The atomic density of interfacial interactions,energy dissipation,and temperature distribution are elucidated to understand the thermal transport across each graphene structure and substrate.We further demonstrate that the normalized thermal conductance decreases monotonically with the increase of the equivalent mechanical strain,showing the capability of mechanically programmable interfacial thermal conductance in a broad range of strains.Application demonstrations in search of on-demand thermal conductance are conducted by controlling the geometric morphologies of graphene.This study lays a foundation for regulating interfacial thermal conductance through mechanical loading-induced geometric deformation of materials on a soft substrate,potentially useful in the design of flexible and stretchable structures and devices with tunable thermal management performance.

Statistical analysis of mechanical properties of biological soft tissue under quasi-static mechanical loading

The mechanical properties of biological soft tissues are inextricably linked to the field of health care,and their mechanical properties can be important indicators for diagnosing and detecting diseases;they can also be used to analyze the causes of organ diseases from a pathological point of view and thus guide the deployment of medical solutions.As an effective method to characterize the mechanical properties of materials,mechanical loading experiments have been successfully applied to the mechanical properties of materials,including tension,compression,pure shear,and so on.Under quasi-static loading,when the material is a biological soft tissue material between a solid and an ideal fluid,its viscoelastic properties strongly respond to the force stimulus,and the stress-strain-time in the elastic phase will have obvious disturbance characteristics.Therefore,the existing statistical methods are often difficult to quantitatively describe the mechanical properties of materials.Therefore,this study proposes an Interval Capture Point based on the principle of integration.The experimental data based on this method can characterize its nonlinear mechanical properties well,especially when the loading speed is extremely low and the soft materials show strong disturbance characteristics.The proposed method can still accurately characterize the hyperelastic and viscoelastic properties of the mechanical properties of biological soft tissues under quasi-static loading.

Mechanically conditioned cell sheets cultured on thermo-responsive surfaces promote bone regeneration

Cell sheet-based scaffold-free technology holds promise for tissue engineering applications and has been extensively explored during the past decades.However,efficient harvest and handling of cell sheets remain challenging,including insufficient extracellular matrix content and poor mechanical strength.Mechanical loading has been widely used to enhance extracellular matrix production in a variety of cell types.However,currently,there are no effective ways to apply mechanical loading to cell sheets.In this study,we prepared thermo-responsive elastomer substrates by grafting poly(N-isopropyl acrylamide)(PNIPAAm)to poly(dimethylsiloxane)(PDMS)surfaces.The effect of PNIPAAm grafting yields on cell behaviours was investigated to optimize surfaces suitable for cell sheet culturing and harvesting.Subsequently,MC3T3-E1 cells were cultured on the PDMS-g-PNIPAAm substrates under mechanical stimulation by cyclically stretching the substrates.Upon maturation,the cell sheets were harvested by lowering the temperature.We found that the extracellular matrix content and thickness of cell sheet were markedly elevated upon appropriate mechanical conditioning.Reverse transcription quantitative polymerase chain reaction and Western blot analyses further confirmed that the expression of osteogenic-specific genes and major matrix components were up-regulated.After implantation into the critical-sized calvarial defects of mice,the mechanically conditioned cell sheets significantly promoted new bone formation.Findings from this study reveal that thermo-responsive elastomer,together with mechanical conditioning,can potentially be applied to prepare high-quality cell sheets for bone tissue engineering.

Dynamic mechanical loading facilitated chondrogenic differentiation of rabbit BMSCs in collagen scaffolds

Mechanical signals have been played close attention to regulate chondrogenic differentiation of bone marrow mesenchymal stem cells(BMSCs).In this study,dynamic mechanical loading simulation with natural frequencies and intensities were applied to the 3D cultured BMSCs–collagen scaffold constructs.We investigated the effects of dynamic mechanical loading on cell adhesion,uniform distribution,proliferation,secretion of extracellular matrix(ECM)and chondrogenic differentiation of BMSCs–collagen scaffold constructs.The results indicated that dynamic mechanical loading facilitated the BMSCs adhesion,uniform distribution,proliferation and secretion of ECM with a slight contraction,which significantly improved the mechanical strength of the BMSCs–collagen scaffold constructs for better mimicking the structure and function of a native cartilage.Gene expression results indicated that dynamic mechanical loading contributed to the chondrogenic differentiation of BMSCs with higher levels of AGG,COL2A1 and SOX9 genes,and prevented of hypertrophic process with lower levels of COL10A1,and reduced the possibility of fibrocartilage formation due to down-regulated COL1A2.In conclusion,this study emphasized the important role of dynamic mechanical loading on promoting BMSCs chondrogenic differentiation and maintaining the cartilage phenotype for in vitro reconstruction of tissue-engineered cartilage,which provided an attractive prospect and a feasibility strategy for cartilage repair.

Overexpression of mechanical sensitive miR-337-3p alleviates ectopic ossification in rat tendinopathy model via targeting IRS1 and Nox4 of tendon-derived stem cells

Tendinopathy,which is characterized by the ectopic ossification of tendon,is a common disease occurring in certain population,such as athletes that suffer from repetitive tendon strains.However,the molecular mechanism underlying the pathogenesis of tendinopathy caused by the overuse of tendon is still lacking.Here,we found that the mechanosensitive miRNA,miR-337-3p,had lower expression under uniaxial cyclical mechanical loading in tendon-derived stem cells(TDSCs)and negatively controlled chondro-osteogenic differentiation of TDSCs.Importantly,downregulation of miR-337-3p expression was also observed in both rat and human calcified tendons,and overexpressing miR-337-3p in patellar tendons of rat tendinopathy model displayed a robust therapeutic efficiency.Mechanistically,we found that the proinflammatory cytokine interleukin-1^was the upstream factor of miR-337-3p that bridges the mechanical loading with its downregulation.Furthermore,the target genes of miR-337-3p,NADPH oxidase 4,and insulin receptor substrate 1,activated chondro-osteogenic differentiation of TDSCs through JNK and ERK signaling,respectively.Thus,these findings not only provide novel insight into the molecular mechanisms underlying ectopic ossification in tendinopathy but also highlight the significance of miR-337-3p as a putative therapeutic target for clinic treatment of tendinopathy.

Mechanical regulation of bone regeneration during distraction osteogenesis

Distraction osteogenesis(DO)is a mechanobiological process of regenerating bone tissue by tension stress.DO is used clinically to lengthen bones or to treat critical size bone defects.Although DO provides satisfactory results in many cases,the prolonged period of treatment remains a major challenge that needs to be overcome.Various attempts have been devoted to accelerating bone regeneration during DO.One common approach is manipulation of the applied mechanical loading by altering distraction strategies.In this article,we reviewed relevant in vivo animal studies exploring the effects of changing mechanical environments,by varying distraction parameters(e.g.,rate and frequency)or adding compression loading,on bone regeneration in DO.We further presented how the mechanically-regulated bone regeneration process during DO could be simulated by in silico models incorporating mechano-regulatory tissue differentiation rules.A comprehensive review of those in vivo and in silico studies may not solely provide important references for development of improved DO protocols in clinic,but also promote a deeper understanding of the mechanobiological mechanism of bone regeneration.

Investigations on MBSE modelling and dynamic performance assessment of an electrical trimmable horizontal stabilizer actuator

With the development of power-by-wire technology for more electric aircraft,the electromechanical actuator(EMA)has the advantages to replace the conventional hydraulic servo actuator in some aerospace flight controls.Conventional hydraulically powered trimmable horizontal stabilizer actuation(THSA)system is nowadays developed to be electrically supplied.Given their safety-criticality,no-back mechanism and redundant load paths are utilized to meet the flight control requirements.However,rare literatures have introduced these functions and addressed the virtual prototyping activities from system-level point of view.This paper proposed such a model of a THSA system with dual electric power sources and fault-tolerant mechanical load paths.The nonlinear effects of components are considered with realism,and system-level simulation test is conducted to support the model-based system engineering(MBSE)approach.The models are developed with a power view instead of a pure signal view.Focusing on the friction effect and compliance effect with backlash or preload,some improved and novel approaches are adopted for these crucial components and validated via experimental results.Meanwhile,the implemented systemlevel model enables injection of crucial faults.Finally,the simulation of the proposed model shows that it is an efficient resource to investigate the actuator’s dynamic performance,to virtually prove that the actuator meets the fail/safe constraint,and to demonstrate the soundness of the fault monitoring functions.