Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into...Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.展开更多
This article investigates the robust current tracking control problem of three-phase grid-connected inverters with LCL filter under external disturbance by a dynamic state feedback control method.First,this paper cons...This article investigates the robust current tracking control problem of three-phase grid-connected inverters with LCL filter under external disturbance by a dynamic state feedback control method.First,this paper constructs an internal model to learn the information of the states and input of the grid-connected inverter under steady state.Second,by utilizing the internal model principle,the paper turns the tracking control problem into the robust stabilization control problem based on some appropriate coordinate transformations.Then,The paper designs a dynamics state feedback control law to deal with this robust stabilization problem,and thus the solution of the robust current tracking control problem of three-phase grid-connected inverters can be obtained.This control method can ensure the asymptotic stability of the closedloop system.Finally,the paper illustrates the effectiveness of the proposed control approach through several groups of simulations,and compares it with the feedforward control method to verify the robustness of the proposed control method to uncertain parameters.展开更多
To elucidate the accelerated degradation mechanisms of metallic interconnects in operational solid oxide fuel cells,the oxidation behavior of FSS430 ferritic stainless steel under the coupling of simultaneous electric...To elucidate the accelerated degradation mechanisms of metallic interconnects in operational solid oxide fuel cells,the oxidation behavior of FSS430 ferritic stainless steel under the coupling of simultaneous electrical current and high-temperature exposure is investigated.Isothermal thermogravimetric analysis was employed to quantify oxidation kinetics,complemented by microstructural characterization using X-ray diffraction,scanning electron microscopy with energy-dispersive spectroscopy and transmission electron microscopy.Experimental results demonstrate that the applied current dramatically enhances oxidation rates,increasing specific mass gain from 0.25 mg/cm^(2)(0 A/cm^(2))to 5.20 mg/cm^(2)(0.2 A/cm^(2))and oxide scale thickness from 1.87 to 15.62μm after 200 h.This acceleration originates from current-induced electromigration forces that promote cationic transport through the oxide layer.The quantitative relationships between current density and oxidation parameters are established,enabling predictive modeling of interconnector degradation in solid oxide fuel cell(SOFC)systems.展开更多
Exercise produces a decrease in pain sensitivity via an effect called exercise-induced hypoalgesia(EIH).Transcranial direct current stimulation(tDCS),acting on similar analgesic mechanisms as EIH,represents a potentia...Exercise produces a decrease in pain sensitivity via an effect called exercise-induced hypoalgesia(EIH).Transcranial direct current stimulation(tDCS),acting on similar analgesic mechanisms as EIH,represents a potential complementary intervention that may amplify the effects of exercise on pain.This study aimed to explore if anodal tDCS could enhance the effect of exercise on pain compared to exercise alone.A total of 35 healthy participants aged 19–37 years completed a familiarisation session followed by two separate sessions where active and sham tDCS was applied in a randomised cross-over design.The familiarisation session involved familiarisation to the pain assessment and exercise tasks,while the subsequent tDCS sessions involved pain sensitivity assessment,exercise and either anodal tDCS or sham tDCS.tDCS doses were applied at 2 mA over the primary motor cortex for 10 min,with the reference electrode placed over the contralateral supraorbital area.The exercise task involved a sustained isometric grip strength contraction at 35%of maximal voluntary contraction(MVC)until volitional exhaustion.Pain sensitivity was evaluated as pressure pain threshold before tDCS,after tDCS,and after exercise.Across both tDCS conditions,pain threshold was higher after exercise when compared to pre-and post-tDCS measurement.This increase in pain threshold did not differ between active and sham tDCS conditions.Our findings suggest that the hypoalgesic effects of active anodal tDCS over the motor cortex prior to exercise are no greater than the effects of sham tDCS prior to exercise.展开更多
To address the issues of high costs and low component utilization caused by the independent configuration of hybrid DC circuit breakers(HCBs)and DC power flow controllers(DCPFCs)at each port in existing DC distributio...To address the issues of high costs and low component utilization caused by the independent configuration of hybrid DC circuit breakers(HCBs)and DC power flow controllers(DCPFCs)at each port in existing DC distribution networks,this paper adopts a component sharing mechanism to propose a composite multi-port hybrid DC circuit breaker(CM-HCB)with DC power flow and fault current limitation abilities,as well as reduced component costs.The proposed CM-HCB topology enables the sharing of the main breaker branch(MB)and the energy dissipation branch,while the load commutation switches(LCSs)in the main branch are reused as power flow control components,enabling flexible regulation of power flow in multiple lines.Meanwhile,by reconstructing the current path during the fault process,the proposed CM-HCB can utilize the internal coupled inductor to limit the current rise rate at the initial stage of the fault,significantly reducing the requirement for breaking current.A detailed study on the topological structure,steady-state power flow regulation mechanism,transient fault isolation mechanism,control strategy and characteristic analysis of the proposed CM-HCB is presented.Then,a Matlab/Simulink-based meshed three-terminal DC grid simulation platform with the proposed CM-HCB is built.The results indicate that the proposed CM-HCB can not only achieve flexible power flow control during steady-state operation,but also obtain current rise limitation and fault isolation abilities under short-circuit fault conditions,verifying its correctness and effectiveness.Finally,a comparative economic analysis is conducted between the proposed CM-HCB and the other two existing solutions,confirming that its component sharing mechanism can significantly reduce the number of components,lower system costs,and improve component utilization.展开更多
The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corr...The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.展开更多
In order to explore the influence of soil resistivity on stray current in power supply system of urban rail transit,we establish an equivalent circuit model of the rail-to-ground structure based on resistance network ...In order to explore the influence of soil resistivity on stray current in power supply system of urban rail transit,we establish an equivalent circuit model of the rail-to-ground structure based on resistance network method first.After measuring the soil resistivity of a real subway system,a simulation model is established in Matlab to obtain the stray currents at different soil resistivities.Then the influence of soil resistivity on stray current is analyzed.Afterwards,to verify the rationality and reliability of the simulation model,we design a test circuit to measure the stray current and rail-to-ground voltage in a real subway system,and a comparison of the experimentally measured results and simulation results is presented.The results show that the stray current is the maximum when the soil resistivity is 211.57Ω·m;when the soil resistivity is 768.47Ω·m,the stray current is the minimum,that is,the smaller the soil resistivity,the greater the stray current.Therefore,the resistivity should be increased as much as possible when ramming the track foundation in urban rail transit system.展开更多
In contrast to the conventional direct current railway electrification system(DC-RES),the medium voltage direct current(MVDC)-RES is considered promising for long-distance high-speed corridors.In the MVDC-RES,traction...In contrast to the conventional direct current railway electrification system(DC-RES),the medium voltage direct current(MVDC)-RES is considered promising for long-distance high-speed corridors.In the MVDC-RES,traction substations(TSSs)are placed much farther and train loads are much heavier than in the conventional DC-RES.Hence,the MVDC-RES brings a drastic change in catenary voltage,TSS spacing,and train loading,which affects rail potential and stray current.In this connection,this work performs some significant quantitative analysis of rail potential and stray current in the MVDC-RES environment.An MVDC simulation model is proposed and different grounding schemes are analyzed for a single-train and two TSSs scenario as well as for a multi-train multi-TSS scenario.According to the simulation and analysis,the maximum values of rail potential and stray current at MVDC-RES distances and the maximum safe distance between adjacent TSSs are determined.展开更多
Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete ...Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete under the action of stray current and sulphate.The deterioration law of concrete under the action of stray current and sulphate was studied by microscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD).The microstructure of corroded concrete was observed to determine the phase composition of erosion products.The damage performances such as quality,strength,and dynamic elastic mode of corroded concrete were performed.The experimental results show that,under the action of stray current,the products of sulfate-eroded concrete are mainly gypsum,ettringite,and thaumasite;the stray current accelerates the hydration process of cement and the erosion of concrete by sulfate;when the concrete pores are filled with the erosion product,there is an increase of approximately 10% in the concrete compressive strength and dynamic elastic modulus;and the concrete compressive strength is more sensitive to the stray current electrification period than the current intensity.展开更多
The rail transit in sulfate-rich areas faces the combined effects of stray current and salt corrosion;however,the sulfate ion transport and concrete degradation mechanisms under such conditions are still unclear.To ad...The rail transit in sulfate-rich areas faces the combined effects of stray current and salt corrosion;however,the sulfate ion transport and concrete degradation mechanisms under such conditions are still unclear.To address this issue,novel sulfate transport and mesoscale splitting tests were designed,with a focus on considering the differences between the interfacial transition zone(ITZ)and cement matrix.Under the influence of stray current,the ITZ played a pivotal role in regulating the transport and mechanical failure processes of sulfate attack,while the tortuous and blocking effects of aggregates almost disappeared.This phenomenon was termed the“stray current-induced ITZ effect.”The experimental data revealed that the difference in sulfate ion transport attributed to the ITZ ranged from 1.90 to 2.31 times,while the difference in splitting strength ranged from 1.56 to 1.64 times.Through the real-time synchronization of splitting experiments and microsecond-responsive particle image velocimetry(PIV)technology,the mechanical properties were exposed to the consequences of the stray currentinduced ITZ effect.The number of splitting cracks in the concrete increased,rather than along the central axis,which was significantly different from the conditions without stray current and the ideal Brazilian disk test.Furthermore,a sulfate ion mass transfer model that incorporates reactivity and electrodiffusion was meticulously constructed.The embedded finite element calculation exhibited excellent agreement with the experimental results,indicating its reliability and accuracy.Additionally,the stress field was determined utilizing analytical methods,and the mechanism underlying crack propagation was successfully obtained.Compared to the cement matrix,a stray current led to more sulfates,more microstructure degradation,and greater increases in thickness and porosity in the ITZ,which was considered to be the essence of the stray current-induced ITZ effect.展开更多
The influence of the direction and magnitude of direct(DC)stray current on the disbonding performance of epoxy powder coating was studied by using electrochemical impedance spectroscopy and scanning electron microscop...The influence of the direction and magnitude of direct(DC)stray current on the disbonding performance of epoxy powder coating was studied by using electrochemical impedance spectroscopy and scanning electron microscopy technology.The results show that the application of DC stray current could accelerate the anodic dissolution.The peeling degree of the coating increases as the magnitude of positive DC stray current interference increases in the range of 2–8V.With 16V positive stray current disturbance,the degree of coating disbonding decreases.With the application of negative stray current,the coating peeling becomes more serious,and the degree of peeling increases as the DC stray current increases.展开更多
According to the service environment of subway structure,experiment is carried out to simulate influence of different loading levels to reinforcement corrosion of R.C element affected by stray current and chlorine sal...According to the service environment of subway structure,experiment is carried out to simulate influence of different loading levels to reinforcement corrosion of R.C element affected by stray current and chlorine salt solution. The current density of the corrosion is measured with the linear polarization resistance method,together with the qualitative analysis and quantitative calculation. Experiment shows that rebar corrosion current density increase accordingly with the increase of loading level. The quantitative relations and the time of rust corrosion of reinforcement are obtained.展开更多
With the rapid development of urban rail transit,there have been an urgent problem of excessive stray current.Because the stray current distribution is random and difficult to verify in the field,we designed an improv...With the rapid development of urban rail transit,there have been an urgent problem of excessive stray current.Because the stray current distribution is random and difficult to verify in the field,we designed an improved stray current experimental platform by replacing the simulated aqueous solution with a real soil environment and by calculating the transition resistance by measuring the soil resistivity,which makes up for the defects in the previous references.Firstly,the mathematical models of rail-drainage net and rail-drainage netground were established,and the analytical expressions of current and voltage of rail,drainage net and other structures were derived.In addition,the simulation model was built,and the mathematical analysis results were compared with the simulation results.Secondly,the accuracy of the improved stray current experimental platform was verified by comparing the measured and simulation results.Finally,based on the experimental results,the influence factors of stray current were analyzed.The relevant conclusions provide experimental data and theoretical reference for the study of stray current in urban rail transit.展开更多
The Allan variance analysis method is used to identify the stochastic noise in the stray current sensor. The stray current characteristic is firstly introduced. Then the optical configuration and the signal processing...The Allan variance analysis method is used to identify the stochastic noise in the stray current sensor. The stray current characteristic is firstly introduced. Then the optical configuration and the signal processing method of the stray current sensor are illustrated. Moreover, the cause of the stochastic noise in the stray current sensor is analyzed. The calculation method of the stochastic noise coefficient is presented in detail. And the feasibility of the stochastic noise identification with the Allan variance analysis method is evaluated. Furthermore, the zero-drift signal acquisition experiment is conducted to identify the stochastic noise in the stray current sensor. According to the experimental result, the bias instability noise, the quantization noise and the white noise are identified as the major stochastic noise. Finally, the experiment on the direct-current signal acquisitions is conducted, whose results indicate that the signal drift of the measured direct-current is mainly caused by the major stochastic noise. And the suppression methods of the major stochastic noise are proposed.展开更多
On the basis of analyzing the influencing factors and harmfulness of stray current, and discussing the existing problems of monitoring and prevention system for stray current, the integrated monitoring and prevention ...On the basis of analyzing the influencing factors and harmfulness of stray current, and discussing the existing problems of monitoring and prevention system for stray current, the integrated monitoring and prevention system for stray current in metro was developed. A net system of distributed computers for monitoring was set up. It can monitor the distribution of stray current in metro and the corrosion of the metal structure in the whole line. According to the situation of monitoring it can also control the drainage of its tank to reach the best effect and eliminate the negative effect of polarity drainage. By using the new type unilateral electric device, the problem of burning the rail by electric arc can be avoided. The unilateral electric device can be connected with the monitoring net system directly to realize the monitor in line and improve the reliability of the device.展开更多
Detection method and evaluation standards are introduced in storage tank detection of DC stray current disturbance and AC stray current disturbance. Taking an oil storage tank as an example, this paper evaluates its o...Detection method and evaluation standards are introduced in storage tank detection of DC stray current disturbance and AC stray current disturbance. Taking an oil storage tank as an example, this paper evaluates its operating status under interference sources and provides the basis and references for its corrosion protection system reform and safe operation.展开更多
The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow ...The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.展开更多
Advanced OER/HER electrocatalytic alternatives are crucial for the wide adaptation of green hydrogen energy.Herein,Ru/NiMnB spherical cluster pillar(SCP),denoted as Ru/NiMnB,is synthesized using a combination of elect...Advanced OER/HER electrocatalytic alternatives are crucial for the wide adaptation of green hydrogen energy.Herein,Ru/NiMnB spherical cluster pillar(SCP),denoted as Ru/NiMnB,is synthesized using a combination of electro-deposition and hydrothermal reaction.Systematic investigation of Ru doping in the NiMnB matrix revealed significant improvements in electrocatalytic performance.The Ru/NiMnB SCPs demonstrate superior OER/HER activity with low overpotentials of 150 and 103 mV at 50mA/cm^(2)in 1 M KOH,making them highly competitive with state-of-the-art electrocatalysts.Remarkably,the Ru/NiMnB SCPs exhibit a low 2-E cell voltage of 2.80 V at ultra-high current density of 2,000 m A/cm^(2)in 1 M KOH,outperforming the standard benchmark electrodes of RuO_(2)||Pt/C,thereby positioning Ru/NiMnB as one of the best bifunctional electrocatalysts.These SCPs exhibit exceptional high-current characteristics,stability and corrosion resistance,as evidenced by continuous operation at 1,000 mA/cm^(2)high-current density for over 150 h in 6 M KOH at elevated temperatures under harsh industrial conditions.Only a small amount of Ru incorporation significantly enhances the electrocatalytic performances of NiMnB,attributed to increased active sites and improved intrinsic properties such as conductivity,adsorption/desorption capability and reaction rates.Consequently,Ru/NiMnB SCPs present a promising bi-functional electrode concept for efficient green H_(2)production.展开更多
This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven second...This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven secondary sources,taking as an example ion acceleration by target normal sheath acceleration.The Pearson linear correlation of maximum return current amplitude and proton spectrum cutoff energy is found to be in the range from~0.70 to 0.94.kA-scale return currents rise in all interaction schemes where targets of any kind are charged by escaping laser-accelerated relativistic electrons.Their precise measurement is demonstrated using an inductive scheme that allows operation at high repetition rates.Thus,return currents can be used as a metrological online tool for the optimization of many laser-driven secondary sources and for diagnosing their stability.In particular,in two parametric studies of laser-driven ion acceleration,we carry out a noninvasive online measurement of return currents in a tape target system irradiated by the 1 PW VEGA-3 laser at Centro de Láseres Pulsados:first the size of the irradiated area is varied at best compression of the laser pulse;second,the pulse duration is varied by means of induced group delay dispersion at best focus.This work paves the way to the development of feedback systems that operate at the high repetition rates of PW-class lasers.展开更多
BACKGROUND Diabetic gastroparesis(DGP)disrupts gastric motility.Electroacupuncture(EA)at Zusanli(ST36)may alleviate DGP symptoms via neural pathways.AIM To investigate how EA current intensities at ST36 regulate neura...BACKGROUND Diabetic gastroparesis(DGP)disrupts gastric motility.Electroacupuncture(EA)at Zusanli(ST36)may alleviate DGP symptoms via neural pathways.AIM To investigate how EA current intensities at ST36 regulate neural pathways and improve gastric motility in DGP models.METHODS A DGP model was established using intraperitoneal injection of streptozotocin.Gastrointestinal motility was measured in rats after 2 weeks of continuous EA at ST36.Current intensity was selected as 0.5 mA,1 mA,and 3 mA.Gastric electrodynamics were detected by recording and analyzing the number of gastric discharges.The gastric emptying rate and propulsion rate of the small intestine were measured to assess dynamic gastrointestinal function.Hematoxylin-eosin staining was conducted to measure histopathological changes in the gastric sinus.Reverse transcription-polymerase chain reaction was conducted to determine mRNA levels of Rho guanine nucleotide-binding protein A and Rho-associated coiled-coil forming protein kinase.Western blotting was conducted to determine the expression levels of choline acetyltransferase,tyrosine hydroxylase,Rho guanine nucleotide-binding protein A,and Rho-associated coiled-coil forming protein kinase.Immunofluorescence staining in the stomach was conducted to detect the distribution of C-kit,an interstitial cell of Cajal marker.An enzymelinked immunosorbent assay was conducted to detect serum levels of acetylcholine and norepinephrine.RESULTS Treatment with EA improved gastric emptying and gastric smooth muscle disorders in rats with DGP,mitigated pathological damage,and restored the function of interstitial cells of Cajal.In addition,different current intensities of EA affected gastrointestinal function of rats with DGP.The 0.5 mA,1 mA,and 3 mA EA groups all improved gastrointestinal function.0.5 mA EA increased acetylcholine levels by increasing protein expression of choline acetyltransferase(P<0.05),thereby upregulating vagus nerve activity and enhancing parasympathetic nerve regulation.3 mA EA increased norepinephrine levels(P<0.05)by increasing protein expression of tyrosine hydroxylase,thereby activating the sympathetic nervous pathway.1 mA coordinated the function of the vagus and sympathetic nerves to improve gastrointestinal motility.CONCLUSION EA with ST36 improved gastric motility in rats with DGP.0.5 mA EA activated the vagus nerve,while 3 mA EA regulated gastrointestinal motility by activating the sympathetic nerves.展开更多
基金National Key Research and Development Program of China(2021YFB3700801)。
文摘Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.
基金Supported by the Fundamental Research Funds for the Central Universities(2024ZYGXZR047)the National Natural Science Foundation of China(62373156)the Guangdong Basic and Applied Basic Research Foundation(2024A1515011736)。
文摘This article investigates the robust current tracking control problem of three-phase grid-connected inverters with LCL filter under external disturbance by a dynamic state feedback control method.First,this paper constructs an internal model to learn the information of the states and input of the grid-connected inverter under steady state.Second,by utilizing the internal model principle,the paper turns the tracking control problem into the robust stabilization control problem based on some appropriate coordinate transformations.Then,The paper designs a dynamics state feedback control law to deal with this robust stabilization problem,and thus the solution of the robust current tracking control problem of three-phase grid-connected inverters can be obtained.This control method can ensure the asymptotic stability of the closedloop system.Finally,the paper illustrates the effectiveness of the proposed control approach through several groups of simulations,and compares it with the feedforward control method to verify the robustness of the proposed control method to uncertain parameters.
基金supported by Natural Science Foundation of Wuhan(2024040701010051)Natural Science Foundation of Hubei(2023AFB111)and National Natural Science Foundation of China(52401108).
文摘To elucidate the accelerated degradation mechanisms of metallic interconnects in operational solid oxide fuel cells,the oxidation behavior of FSS430 ferritic stainless steel under the coupling of simultaneous electrical current and high-temperature exposure is investigated.Isothermal thermogravimetric analysis was employed to quantify oxidation kinetics,complemented by microstructural characterization using X-ray diffraction,scanning electron microscopy with energy-dispersive spectroscopy and transmission electron microscopy.Experimental results demonstrate that the applied current dramatically enhances oxidation rates,increasing specific mass gain from 0.25 mg/cm^(2)(0 A/cm^(2))to 5.20 mg/cm^(2)(0.2 A/cm^(2))and oxide scale thickness from 1.87 to 15.62μm after 200 h.This acceleration originates from current-induced electromigration forces that promote cationic transport through the oxide layer.The quantitative relationships between current density and oxidation parameters are established,enabling predictive modeling of interconnector degradation in solid oxide fuel cell(SOFC)systems.
文摘Exercise produces a decrease in pain sensitivity via an effect called exercise-induced hypoalgesia(EIH).Transcranial direct current stimulation(tDCS),acting on similar analgesic mechanisms as EIH,represents a potential complementary intervention that may amplify the effects of exercise on pain.This study aimed to explore if anodal tDCS could enhance the effect of exercise on pain compared to exercise alone.A total of 35 healthy participants aged 19–37 years completed a familiarisation session followed by two separate sessions where active and sham tDCS was applied in a randomised cross-over design.The familiarisation session involved familiarisation to the pain assessment and exercise tasks,while the subsequent tDCS sessions involved pain sensitivity assessment,exercise and either anodal tDCS or sham tDCS.tDCS doses were applied at 2 mA over the primary motor cortex for 10 min,with the reference electrode placed over the contralateral supraorbital area.The exercise task involved a sustained isometric grip strength contraction at 35%of maximal voluntary contraction(MVC)until volitional exhaustion.Pain sensitivity was evaluated as pressure pain threshold before tDCS,after tDCS,and after exercise.Across both tDCS conditions,pain threshold was higher after exercise when compared to pre-and post-tDCS measurement.This increase in pain threshold did not differ between active and sham tDCS conditions.Our findings suggest that the hypoalgesic effects of active anodal tDCS over the motor cortex prior to exercise are no greater than the effects of sham tDCS prior to exercise.
基金funded by Youth Talent Growth Project of Guizhou Provincial Department of Education(No.Qianjiaoji[2024]21)National Natural Science Foundation of China(No.62461008 and No.52507211)Guizhou Provincial Key Technology R&D Program(No.[2024]General 049).
文摘To address the issues of high costs and low component utilization caused by the independent configuration of hybrid DC circuit breakers(HCBs)and DC power flow controllers(DCPFCs)at each port in existing DC distribution networks,this paper adopts a component sharing mechanism to propose a composite multi-port hybrid DC circuit breaker(CM-HCB)with DC power flow and fault current limitation abilities,as well as reduced component costs.The proposed CM-HCB topology enables the sharing of the main breaker branch(MB)and the energy dissipation branch,while the load commutation switches(LCSs)in the main branch are reused as power flow control components,enabling flexible regulation of power flow in multiple lines.Meanwhile,by reconstructing the current path during the fault process,the proposed CM-HCB can utilize the internal coupled inductor to limit the current rise rate at the initial stage of the fault,significantly reducing the requirement for breaking current.A detailed study on the topological structure,steady-state power flow regulation mechanism,transient fault isolation mechanism,control strategy and characteristic analysis of the proposed CM-HCB is presented.Then,a Matlab/Simulink-based meshed three-terminal DC grid simulation platform with the proposed CM-HCB is built.The results indicate that the proposed CM-HCB can not only achieve flexible power flow control during steady-state operation,but also obtain current rise limitation and fault isolation abilities under short-circuit fault conditions,verifying its correctness and effectiveness.Finally,a comparative economic analysis is conducted between the proposed CM-HCB and the other two existing solutions,confirming that its component sharing mechanism can significantly reduce the number of components,lower system costs,and improve component utilization.
基金Project(BE2010043) supported by the Technology Support Program of Jiangsu Province,ChinaProject(CXZZ13_0928) supported by the Graduate Education Innovation Project of Jiangsu Province,China
文摘The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.
基金National Natural Science Foundation of China(Nos.51476073,51266004)Natural Science Foundation of Gansu Province(No.1308RJZA199)。
文摘In order to explore the influence of soil resistivity on stray current in power supply system of urban rail transit,we establish an equivalent circuit model of the rail-to-ground structure based on resistance network method first.After measuring the soil resistivity of a real subway system,a simulation model is established in Matlab to obtain the stray currents at different soil resistivities.Then the influence of soil resistivity on stray current is analyzed.Afterwards,to verify the rationality and reliability of the simulation model,we design a test circuit to measure the stray current and rail-to-ground voltage in a real subway system,and a comparison of the experimentally measured results and simulation results is presented.The results show that the stray current is the maximum when the soil resistivity is 211.57Ω·m;when the soil resistivity is 768.47Ω·m,the stray current is the minimum,that is,the smaller the soil resistivity,the greater the stray current.Therefore,the resistivity should be increased as much as possible when ramming the track foundation in urban rail transit system.
文摘In contrast to the conventional direct current railway electrification system(DC-RES),the medium voltage direct current(MVDC)-RES is considered promising for long-distance high-speed corridors.In the MVDC-RES,traction substations(TSSs)are placed much farther and train loads are much heavier than in the conventional DC-RES.Hence,the MVDC-RES brings a drastic change in catenary voltage,TSS spacing,and train loading,which affects rail potential and stray current.In this connection,this work performs some significant quantitative analysis of rail potential and stray current in the MVDC-RES environment.An MVDC simulation model is proposed and different grounding schemes are analyzed for a single-train and two TSSs scenario as well as for a multi-train multi-TSS scenario.According to the simulation and analysis,the maximum values of rail potential and stray current at MVDC-RES distances and the maximum safe distance between adjacent TSSs are determined.
基金Funded by the National Natural Science Foundation of China (Nos.51590914 and 52078415)the Science and Technology Program of Shaanxi Province (Nos.2019KW-047, 20JY034, and SGSNXA00XGJS20015 60)the China Scholarship Council (No.202008610268)。
文摘Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete under the action of stray current and sulphate.The deterioration law of concrete under the action of stray current and sulphate was studied by microscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD).The microstructure of corroded concrete was observed to determine the phase composition of erosion products.The damage performances such as quality,strength,and dynamic elastic mode of corroded concrete were performed.The experimental results show that,under the action of stray current,the products of sulfate-eroded concrete are mainly gypsum,ettringite,and thaumasite;the stray current accelerates the hydration process of cement and the erosion of concrete by sulfate;when the concrete pores are filled with the erosion product,there is an increase of approximately 10% in the concrete compressive strength and dynamic elastic modulus;and the concrete compressive strength is more sensitive to the stray current electrification period than the current intensity.
基金supported by the State Major Program of National Natural Science Foundation of China(52090082)the National Key Research and Development Program of China(2022YFB2602200)the National Natural Science Foundation of China(52178423 and 52378398).
文摘The rail transit in sulfate-rich areas faces the combined effects of stray current and salt corrosion;however,the sulfate ion transport and concrete degradation mechanisms under such conditions are still unclear.To address this issue,novel sulfate transport and mesoscale splitting tests were designed,with a focus on considering the differences between the interfacial transition zone(ITZ)and cement matrix.Under the influence of stray current,the ITZ played a pivotal role in regulating the transport and mechanical failure processes of sulfate attack,while the tortuous and blocking effects of aggregates almost disappeared.This phenomenon was termed the“stray current-induced ITZ effect.”The experimental data revealed that the difference in sulfate ion transport attributed to the ITZ ranged from 1.90 to 2.31 times,while the difference in splitting strength ranged from 1.56 to 1.64 times.Through the real-time synchronization of splitting experiments and microsecond-responsive particle image velocimetry(PIV)technology,the mechanical properties were exposed to the consequences of the stray currentinduced ITZ effect.The number of splitting cracks in the concrete increased,rather than along the central axis,which was significantly different from the conditions without stray current and the ideal Brazilian disk test.Furthermore,a sulfate ion mass transfer model that incorporates reactivity and electrodiffusion was meticulously constructed.The embedded finite element calculation exhibited excellent agreement with the experimental results,indicating its reliability and accuracy.Additionally,the stress field was determined utilizing analytical methods,and the mechanism underlying crack propagation was successfully obtained.Compared to the cement matrix,a stray current led to more sulfates,more microstructure degradation,and greater increases in thickness and porosity in the ITZ,which was considered to be the essence of the stray current-induced ITZ effect.
基金supported by“Civil Aviation Safety Capacity Building Fund(Construction of safety evaluation system for multibranch complex annular apron pipe network)”“the Fundamental Research Funds for the Central Universities(19CX05007A).”
文摘The influence of the direction and magnitude of direct(DC)stray current on the disbonding performance of epoxy powder coating was studied by using electrochemical impedance spectroscopy and scanning electron microscopy technology.The results show that the application of DC stray current could accelerate the anodic dissolution.The peeling degree of the coating increases as the magnitude of positive DC stray current interference increases in the range of 2–8V.With 16V positive stray current disturbance,the degree of coating disbonding decreases.With the application of negative stray current,the coating peeling becomes more serious,and the degree of peeling increases as the DC stray current increases.
基金National Natural Science Foundation of China (Granted No.50808005)National"11-5"Science and Technology Supporting Program(Granted No.2006BAJ27B04)Major Program of Beijing Municipal Natural Science Foundation(Granted No.8100001)
文摘According to the service environment of subway structure,experiment is carried out to simulate influence of different loading levels to reinforcement corrosion of R.C element affected by stray current and chlorine salt solution. The current density of the corrosion is measured with the linear polarization resistance method,together with the qualitative analysis and quantitative calculation. Experiment shows that rebar corrosion current density increase accordingly with the increase of loading level. The quantitative relations and the time of rust corrosion of reinforcement are obtained.
基金supported by National Natural Science Foundation of China(Nos.51476073,51266004)Natural Science Foundation of Gansu Province(No.138RJZA199).
文摘With the rapid development of urban rail transit,there have been an urgent problem of excessive stray current.Because the stray current distribution is random and difficult to verify in the field,we designed an improved stray current experimental platform by replacing the simulated aqueous solution with a real soil environment and by calculating the transition resistance by measuring the soil resistivity,which makes up for the defects in the previous references.Firstly,the mathematical models of rail-drainage net and rail-drainage netground were established,and the analytical expressions of current and voltage of rail,drainage net and other structures were derived.In addition,the simulation model was built,and the mathematical analysis results were compared with the simulation results.Secondly,the accuracy of the improved stray current experimental platform was verified by comparing the measured and simulation results.Finally,based on the experimental results,the influence factors of stray current were analyzed.The relevant conclusions provide experimental data and theoretical reference for the study of stray current in urban rail transit.
基金Project(2017QNA13)supported by Fundamental Research Funds for the Central Universities,ChinaProject(PAPD)supported by Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘The Allan variance analysis method is used to identify the stochastic noise in the stray current sensor. The stray current characteristic is firstly introduced. Then the optical configuration and the signal processing method of the stray current sensor are illustrated. Moreover, the cause of the stochastic noise in the stray current sensor is analyzed. The calculation method of the stochastic noise coefficient is presented in detail. And the feasibility of the stochastic noise identification with the Allan variance analysis method is evaluated. Furthermore, the zero-drift signal acquisition experiment is conducted to identify the stochastic noise in the stray current sensor. According to the experimental result, the bias instability noise, the quantization noise and the white noise are identified as the major stochastic noise. Finally, the experiment on the direct-current signal acquisitions is conducted, whose results indicate that the signal drift of the measured direct-current is mainly caused by the major stochastic noise. And the suppression methods of the major stochastic noise are proposed.
文摘On the basis of analyzing the influencing factors and harmfulness of stray current, and discussing the existing problems of monitoring and prevention system for stray current, the integrated monitoring and prevention system for stray current in metro was developed. A net system of distributed computers for monitoring was set up. It can monitor the distribution of stray current in metro and the corrosion of the metal structure in the whole line. According to the situation of monitoring it can also control the drainage of its tank to reach the best effect and eliminate the negative effect of polarity drainage. By using the new type unilateral electric device, the problem of burning the rail by electric arc can be avoided. The unilateral electric device can be connected with the monitoring net system directly to realize the monitor in line and improve the reliability of the device.
文摘Detection method and evaluation standards are introduced in storage tank detection of DC stray current disturbance and AC stray current disturbance. Taking an oil storage tank as an example, this paper evaluates its operating status under interference sources and provides the basis and references for its corrosion protection system reform and safe operation.
基金supported in part by Natural Science Foundation of Jiangsu Province under Grant BK20230255Natural Science Foundation of Shandong Province under Grant ZR2023QE281.
文摘The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.
基金Core Research Institute Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2018R1A6A1A03025242)in part by the research grant of Kwangwoon University in 2024。
文摘Advanced OER/HER electrocatalytic alternatives are crucial for the wide adaptation of green hydrogen energy.Herein,Ru/NiMnB spherical cluster pillar(SCP),denoted as Ru/NiMnB,is synthesized using a combination of electro-deposition and hydrothermal reaction.Systematic investigation of Ru doping in the NiMnB matrix revealed significant improvements in electrocatalytic performance.The Ru/NiMnB SCPs demonstrate superior OER/HER activity with low overpotentials of 150 and 103 mV at 50mA/cm^(2)in 1 M KOH,making them highly competitive with state-of-the-art electrocatalysts.Remarkably,the Ru/NiMnB SCPs exhibit a low 2-E cell voltage of 2.80 V at ultra-high current density of 2,000 m A/cm^(2)in 1 M KOH,outperforming the standard benchmark electrodes of RuO_(2)||Pt/C,thereby positioning Ru/NiMnB as one of the best bifunctional electrocatalysts.These SCPs exhibit exceptional high-current characteristics,stability and corrosion resistance,as evidenced by continuous operation at 1,000 mA/cm^(2)high-current density for over 150 h in 6 M KOH at elevated temperatures under harsh industrial conditions.Only a small amount of Ru incorporation significantly enhances the electrocatalytic performances of NiMnB,attributed to increased active sites and improved intrinsic properties such as conductivity,adsorption/desorption capability and reaction rates.Consequently,Ru/NiMnB SCPs present a promising bi-functional electrode concept for efficient green H_(2)production.
基金funding from the European Union’s Horizon 2020 research and innovation program through the European IMPULSE project under Grant Agreement No.871161from LASERLAB-EUROPE V under Grant Agreement No.871124+6 种基金from the Grant Agency of the Czech Republic(Grant No.GM23-05027M)Grant No.PDC2021120933-I00 funded by MCIN/AEI/10.13039/501100011033by the European Union Next Generation EU/PRTRsupported by funding from the Ministerio de Ciencia,Innovación y Universidades in Spain through ICTS Equipment Grant No.EQC2018-005230-Pfrom Grant No.PID2021-125389O A-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER,UEby“ERDF A Way of Making Europe”by the European Unionfrom grants of the Junta de Castilla y León with Grant Nos.CLP263P20 and CLP087U16。
文摘This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven secondary sources,taking as an example ion acceleration by target normal sheath acceleration.The Pearson linear correlation of maximum return current amplitude and proton spectrum cutoff energy is found to be in the range from~0.70 to 0.94.kA-scale return currents rise in all interaction schemes where targets of any kind are charged by escaping laser-accelerated relativistic electrons.Their precise measurement is demonstrated using an inductive scheme that allows operation at high repetition rates.Thus,return currents can be used as a metrological online tool for the optimization of many laser-driven secondary sources and for diagnosing their stability.In particular,in two parametric studies of laser-driven ion acceleration,we carry out a noninvasive online measurement of return currents in a tape target system irradiated by the 1 PW VEGA-3 laser at Centro de Láseres Pulsados:first the size of the irradiated area is varied at best compression of the laser pulse;second,the pulse duration is varied by means of induced group delay dispersion at best focus.This work paves the way to the development of feedback systems that operate at the high repetition rates of PW-class lasers.
基金Supported by National Natural Science Foundation of China,No.82205298Natural Science Foundation of Hunan Province,No.2023JJ30462+1 种基金Hunan Provincial Department of Science and Technology,No.2023SK2045,No.22JBZ007,No.Z2023XJYQ07,No.B2024007,and No.Z2023JB012024 Graduate Innovation Topics,No.2024CX031.
文摘BACKGROUND Diabetic gastroparesis(DGP)disrupts gastric motility.Electroacupuncture(EA)at Zusanli(ST36)may alleviate DGP symptoms via neural pathways.AIM To investigate how EA current intensities at ST36 regulate neural pathways and improve gastric motility in DGP models.METHODS A DGP model was established using intraperitoneal injection of streptozotocin.Gastrointestinal motility was measured in rats after 2 weeks of continuous EA at ST36.Current intensity was selected as 0.5 mA,1 mA,and 3 mA.Gastric electrodynamics were detected by recording and analyzing the number of gastric discharges.The gastric emptying rate and propulsion rate of the small intestine were measured to assess dynamic gastrointestinal function.Hematoxylin-eosin staining was conducted to measure histopathological changes in the gastric sinus.Reverse transcription-polymerase chain reaction was conducted to determine mRNA levels of Rho guanine nucleotide-binding protein A and Rho-associated coiled-coil forming protein kinase.Western blotting was conducted to determine the expression levels of choline acetyltransferase,tyrosine hydroxylase,Rho guanine nucleotide-binding protein A,and Rho-associated coiled-coil forming protein kinase.Immunofluorescence staining in the stomach was conducted to detect the distribution of C-kit,an interstitial cell of Cajal marker.An enzymelinked immunosorbent assay was conducted to detect serum levels of acetylcholine and norepinephrine.RESULTS Treatment with EA improved gastric emptying and gastric smooth muscle disorders in rats with DGP,mitigated pathological damage,and restored the function of interstitial cells of Cajal.In addition,different current intensities of EA affected gastrointestinal function of rats with DGP.The 0.5 mA,1 mA,and 3 mA EA groups all improved gastrointestinal function.0.5 mA EA increased acetylcholine levels by increasing protein expression of choline acetyltransferase(P<0.05),thereby upregulating vagus nerve activity and enhancing parasympathetic nerve regulation.3 mA EA increased norepinephrine levels(P<0.05)by increasing protein expression of tyrosine hydroxylase,thereby activating the sympathetic nervous pathway.1 mA coordinated the function of the vagus and sympathetic nerves to improve gastrointestinal motility.CONCLUSION EA with ST36 improved gastric motility in rats with DGP.0.5 mA EA activated the vagus nerve,while 3 mA EA regulated gastrointestinal motility by activating the sympathetic nerves.
