In order to gain a deeper understanding of the effect of pulsed current on the mechanical properties and size effect of nanocrystalline Ni foils,nanocrystalline Ni foils with different grain thickness-to-grain size ra...In order to gain a deeper understanding of the effect of pulsed current on the mechanical properties and size effect of nanocrystalline Ni foils,nanocrystalline Ni foils with different grain thickness-to-grain size ratios(λ)were prepared using pulsed electrodeposition in this paper and unidirectional tensile experiments were carried out at room temperature with different currents and their applied directions.The experimental results show that the nanocrystalline Ni foil produces an obvious electroplasticity effect after applying the current field,and when 300<λ<1100,the current weakens the size effect of nanocrystalline Ni foils to a certain extent,and the angle between the current direction and the deformation direction also affects the mechanical response of nanocrystalline Ni foils,and when the angle between the current direction and the deformation direction is 0°,electroplasticity effect is the best,and the current has the most significant effect of abating the size effect of the material.The mechanism of unidirectional tensile deformation of nanocrystalline Ni foils under the effect of pulsed current was analyzed using TEM and TKD.It was found that the applied pulse current increased the activity of the nanocrystalline boundaries,promoted the movement of dislocations,and reduced the tendency of dislocation entanglement.The higher the peak current density and the smaller the angle between the direction of the current and the direction of deformation,the smaller the grain boundary orientation difference,the more dispersed the grain orientation,and the lower the density of geometrically necessary dislocations(GND)in the deformed nanocrystalline foil,the more significant the effect on material plasticity improvement.展开更多
The electrically assisted(EA)deformation process has received considerable attention in recent years,ac-companied by research on current-induced deformation mechanisms.However,there are still challenges in eliminating...The electrically assisted(EA)deformation process has received considerable attention in recent years,ac-companied by research on current-induced deformation mechanisms.However,there are still challenges in eliminating thermal effects,which have prevented a comprehensive understanding of the underlying current-induced mechanisms.Opting for a single crystal(SC)in research provides advantages in decou-pling the nonthermal effect of electric current at smaller scales and eliminating the complex interactions that exist in polycrystalline materials.Therefore,the innovation of this work lies in decoupling the non-thermal effect of electric current and conducting a comprehensive analysis of anisotropic deformation and mechanisms within a Ni-based SC with different crystallographic axes and various current directions dur-ing electrically assisted tensile simulation.A significant tension axis direction in the SC during EA tension was induced by the combination of a higher current direction factor(|cosθ|)and a dimensionless factor for the current density(|J^(α)/J_(0)^(α)|)along the[100]axis.The stress drop within the SC due to the nonthermal effect of electric current generally increased with increasing current direction.This was attributed to the increased dislocation density differences and decreased temperature.The increased stress anisotropy of the SC at a current direction of 45°was attributed to fewer activated(111)slip systems and the pinning effect of more dislocations within these systems.This study advances our understanding of the thermal and nonthermal effects of electric current and offers valuable insights for the informed application of EA deformations in industrial and aerospace settings with SC superalloys.展开更多
A macroscopic thermal field calculation and a microstructure simulation are performed to investigate the directional solidification of a nickel-based superalloy with applied direct current in this study.The heat effec...A macroscopic thermal field calculation and a microstructure simulation are performed to investigate the directional solidification of a nickel-based superalloy with applied direct current in this study.The heat effects of electric current passing through the solidification interface as Joule heat and Peltier heat are investigated in the calculations.The calculated result shows that the Joule heat improves the temperature gradient in the solidification interface,while the effect of Peltier heat is negligible for macroscopic thermal field.The directional growth of dendrites under the influence of Joule heat is investigated with simulation.It is found that under the influence of Joule heat,the dendrites are provided with self-adjustment ability of coordinating growth to achieve flat interface in macroscale during directional solidification with the direct electric current.This interesting phenomenon is brought by the crowdedly passing through the dendrite of electric current in the solidification interface for the large difference of the electrical resistivity between solid state and melt of the superalloy.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
The integration of large-scale new energy and high-capacity DC transmission leads to a reduction in system inertia.Grid-forming renewable energy sources(GF-RES)has a significant improvement effect on system inertia.Co...The integration of large-scale new energy and high-capacity DC transmission leads to a reduction in system inertia.Grid-forming renewable energy sources(GF-RES)has a significant improvement effect on system inertia.Commutation failure faults may cause a short-term reactive power surplus at the sending end and trigger transient overvoltage,threatening the safe and stable operation of the power grid.However,there is a lack of research on the calculation method of transient overvoltage caused by commutation failure in high-voltage DC transmission systems with grid-forming renewable energy sources integration.Based on the existing equivalent model of highvoltage DC transmission systems at the sending end,this paper proposes to construct a model of the high-voltage DC transmission system at the sending end with grid-forming renewable energy sources.The paper first clarifies the mechanism of overvoltage generation,then considers the reactive power droop control characteristics of GF-RES,and derives the transient voltage calculation model of theDC transmission system with GF-RES integration.It also proposes a calculation method for transient overvoltage at the sending-end converter bus with GF-RES integration.Based on the PSCAD/EMTDC simulation platform,this paper builds an experimental simulation model.By constructing three different experimental scenarios,the accuracy and effectiveness of the proposed transient overvoltage calculation method are verified,with a calculation error within 5%.At the same time,this paper quantitatively analyzes the impact of grid strength,new energy proportion,and rated transmission power on transient overvoltage from three different perspectives.展开更多
Interconnection planning involving bi-directional converters(BdCs)is crucial for enhancing the reliability and robustness of hybrid alternating current(AC)/direct current(DC)microgrid clusters with high penetrations o...Interconnection planning involving bi-directional converters(BdCs)is crucial for enhancing the reliability and robustness of hybrid alternating current(AC)/direct current(DC)microgrid clusters with high penetrations of renewable energy resources(RESs).However,challenges such as the non-convex nature of BdC efficiency and renewable energy uncertainty complicate the planning process.To address these issues,this paper proposes a tri-level BdC-based planning framework that incorporates dynamic BdC efficiency and a data-correlated uncertainty set(DcUS)derived from historical data patterns.The proposed framework employs a least-squares approximation to linearize BdC efficiency and constructs the DcUS to balance computational efficiency and solution robustness.Additionally,a fully parallel column and constraint generation algorithm is developed to solve the model efficiently.Numerical simulations on a practical hybrid AC/DC microgrid system demonstrate that the proposed method reduces interconnection costs by up to 21.8%compared to conventional uncertainty sets while ensuring robust operation under all considered scenarios.These results highlight the computational efficiency,robustness,and practicality of the proposed approach,making it a promising solution for modern power systems.展开更多
Background Pain sensitivity is critical for preventing non-suicidal self-injury(NSSI)behaviours;however,individuals engaging in such behaviours often exhibit decreased pain sensitivity,which may undermine this natural...Background Pain sensitivity is critical for preventing non-suicidal self-injury(NSSI)behaviours;however,individuals engaging in such behaviours often exhibit decreased pain sensitivity,which may undermine this natural safeguard.The dorsolateral prefrontal cortex(DLPFC)is a key region involved in pain regulation,and recent approaches using transcranial direct current stimulation(tDCS)to target the DLPFC have shown potential for modulating pain processing and restoring normal pain perception for individuals engaging in NSSI behaviours.Aims This study aimed to explore the immediate and short-term effects of a single session of tDCS on pain sensitivity in individuals with NSSI,as well as its secondary effects on mood and NSSI-related factors.Methods In this randomised,double-blind,parallel,sham-controlled clinical trial,participants with a history of NSSI were randomly assigned to receive either active or sham tDCS.The intervention consisted of a single 20 min tDCS session targeting the left DLPFC.The primary outcome was pain sensitivity,measured by the pressure pain threshold(PPT)and heat pain score(HPS).Secondary and additional outcomes included NSSI urges,NSSI resistance,self-efficacy in resisting NSSI,mood-related variables and exploratory cognitive-affective processes such as rumination,self-criticism and self-perceived pain sensitivity,assessed at baseline,immediately post-intervention,and at 24 hours,1 week and 2 weeks follow-ups.Results For the primary outcomes,no significant differences between groups were observed for pain sensitivity(PPT,padj=0.812;HPS,padj=0.608).However,an exploratory sensitivity analysis treating each trial as an individual observation revealed a significant effect on HPS(padj=0.036).For the secondary and additional outcomes,although there were initial improvements in joyful feelings and reductions in negative affect at 2 weeks post-intervention,these effects did not remain significant after multiple comparison corrections.Notably,reductions in rumination were statistically significant at both 1-week and 2-week follow-ups(1 week,p_(adj)=0.040;2 weeks,p_(adj)=0.042).There were no significant effects on NSSI urges,NSSI resistance,self-efficacy in resisting NSSI or self-criticism.Conclusions A single session of tDCS over the left DLPFC did not produce significant changes in pain sensitivity in individuals with NSSI.A sensitivity analysis indicated an effect on heat pain sensitivity,possibly reflecting changes in brain activity,warranting confirmation through neuroimaging.These findings suggest that tDCS warrants further investigation for its potential to influence pain-related cognitive-affective processes in individuals with NSSI.展开更多
BACKGROUND Schizophrenia is a chronic psychiatric condition with complex symptomatology,including debilitating auditory hallucinations.Transcranial direct current stimulation(tDCS)has been explored as an adjunctive tr...BACKGROUND Schizophrenia is a chronic psychiatric condition with complex symptomatology,including debilitating auditory hallucinations.Transcranial direct current stimulation(tDCS)has been explored as an adjunctive treatment to alleviate such symptoms.AIM To evaluate the therapeutic efficacy of tDCS in schizophrenia.METHODS Adhering to PRISMA guidelines,we systematically searched PubMed,Embase,Web of Science,and the Cochrane Library on September 19,2023,for randomized controlled trials examining the efficacy of tDCS in schizophrenia,with no language or time restrictions.We included studies that compared tDCS with a control condition and reported clinically relevant outcomes.Data extraction and quality assessments were performed by independent evaluators using the Cochrane Collaboration's risk of bias tool.Statistical heterogeneity was evaluated,and a random-effects model was applied due to moderate heterogeneity(I2=41.3%).RESULTS Nine studies comprising 425 participants(tDCS group:219,control group:206)were included.The meta-analysis demonstrated a significant reduction in auditory hallucination scores following tDCS treatment(weighted mean difference:-2.18,95%confidence interval:-4.0 to-0.29,P<0.01).Sensitivity analysis confirmed the robustness of the results,with no significant influence from individual studies.Additionally,publication bias was not detected,supporting the reliability and generalizability of the findings.These results underscore the efficacy of tDCS as a therapeutic intervention for auditory hallucinations in schizophrenia.CONCLUSION tDCS significantly reduces auditory hallucinations in schizophrenia,suggesting its potential as an effective adjunctive treatment for managing this disabling symptom.The findings highlight the practical significance of tDCS in clinical settings,particularly for patients with treatment-resistant auditory hallucinations.展开更多
Herein,the effect of direct current(DC)attached the mold on refining the microstructure and alleviating the central segregation of a tin–bismuth(Sn–10 wt.%Bi)alloy ingot during the solidification process has been in...Herein,the effect of direct current(DC)attached the mold on refining the microstructure and alleviating the central segregation of a tin–bismuth(Sn–10 wt.%Bi)alloy ingot during the solidification process has been investigated.The experiment used a self-made device,which can achieve the effect of refining the solidified structure and alleviate the segregation of the metal casting.Numerical simulations were performed to calculate the Lorentz force,Joule heating and induced melt vortex flow for the magneto-hydrodynamic case.Our results show that the maximum velocity of the global electro-vortex reached 0.017 m s^(–1).The DC-induced electro-vortex was found to be the primary reason of refining the equiaxed grain and alleviating the segregation of theβ-Sn crystal boundary.The grain refining effect observed in these experiments can be solely attributed to the forced melt flow driven by the Lorentz force.DC field attached the mold can lead to grain refinement and alleviate the segregation of the ingot via a global vortex.The technology can be applied not only to opened molds,but also toward improving the quality in closed molds.展开更多
BACKGROUND Postoperative delirium(POD),an acute neuropsychiatric complication in elderly surgical patients,manifests as attention and cognitive disturbances that may last 24-72 hours after surgery,potentially progress...BACKGROUND Postoperative delirium(POD),an acute neuropsychiatric complication in elderly surgical patients,manifests as attention and cognitive disturbances that may last 24-72 hours after surgery,potentially progressing to dementia.Transcranial direct current stimulation(tDCS),a non-invasive neuromodulation technique,enhances cortical excitability and cognitive function by modulating brain networks and synaptic plasticity.Elderly patients undergoing major laparoscopic surgery face elevated POD risks due to prolonged anesthesia and pneumoperitoneum-induced cerebral hypoperfusion.This study investigates whether pre-anesthesia tDCS can reduce POD incidence in this population.AIM To investigate the effect of preoperative tDCS on reducing the incidence of POD in elderly patients undergoing major laparoscopic surgery.METHODS In this study,we enrolled 220 elderly patients who underwent major laparoscopic surgery between April 2024 and December 2024.Patients were randomly assigned to the active-tDCS(group A)and sham-tDCS(group S)groups.A single session of tDCS or sham stimulation was administered 30 minutes before anesthesia induction.The primary outcome was the incidence of POD during within 3 days postoperatively.RESULTS A total of 201 patients were included in the final analysis,with 100 patients in group A and 101 in group S.The incidence of POD within 3 days postoperatively was 7.0%in group A,which was significantly lower than 22.8%in group S.On postoperative day 1,the Self-Rating Anxiety Scale and Self-Rating Depression Scale scores significantly differed between the two groups,but the pain scores showed no significant difference.CONCLUSION A single session of preoperative tDCS can reduce the incidence of POD in elderly patients undergoing major laparoscopic surgery and can also reduce postoperative anxiety and depression in these patients.展开更多
The sub-forum on standardization of new energy and direct-current diversified applications was held on July 9,which gathered leaders and experts to discuss how to thoroughly implement the national green power direct c...The sub-forum on standardization of new energy and direct-current diversified applications was held on July 9,which gathered leaders and experts to discuss how to thoroughly implement the national green power direct connection policy proposed in the transformation of the energy landscape,pool wisdom to tackle bottlenecks in the industrialization of DC technology,and leverage the role of standardization in coordinating and regulating the diversified applications of DC technology.It was designed to promote the establishment of a collaborative,open,and advanced global standards system for DC technology.展开更多
Accurate quantification of the spin–orbit torques(SOTs) is critical for the identification and applications of new spin-orbitronic effects. One of the most popular techniques to quantify the SOTs is the “switching a...Accurate quantification of the spin–orbit torques(SOTs) is critical for the identification and applications of new spin-orbitronic effects. One of the most popular techniques to quantify the SOTs is the “switching angle shift”, where the applied direct current is assumed to shift, via domain wall depinning during anti-domain expansion, the switching angle of a perpendicular magnetization in a linear proportional manner under a large rotating magnetic field. Here, we report that, for the most commonly employed perpendicular magnetization heterostructures in spintronics(e.g., those based on FeCoB, Co, and Co/Ni multilayers), the switching angle shift considerably misestimates the SOT within the domain wall depinning analysis of the slope of linear-in-current scaling and may also have a non-zero residual value at zero direct current. Our experiments and simulations unveil that the switching angle shift is most likely dominated by chiral asymmetric nucleation rather than expansion of anti-domains. The in-plane field from external magnets and current-induced SOTs lowers the perpendicular nucleation field and thus reduces the required switching angle, ultimately leading to an underestimation of SOTs by domain wall depinning analysis. These results have advanced our understanding of magnetization switching in spintronic devices.展开更多
Effect of direct current electric field （DCEF） on corrosion behaviour of copper printed circuit board （PCB-Cu）, Cl-ion migration behaviour, dendrites growth under thin electrolyte layer was investigated using pote...Effect of direct current electric field （DCEF） on corrosion behaviour of copper printed circuit board （PCB-Cu）, Cl-ion migration behaviour, dendrites growth under thin electrolyte layer was investigated using potentiodynamic polarization and scanning electron microscopy （SEM） with energy dispersive spectrometer （EDS）. Results indicate that DCEF decreases the corrosion of PCB-Cu;Cl-ions directionally migrate from the negative pole to the positive pole, and enrich on the surface of the positive pole, which causes serious localized corrosion; dendrites grow on the surface of the negative pole, and the rate and scale of dendrite growth become faster and greater with the increase of external voltage and exposure time, respectively.展开更多
The combined effects of direct current pulsed magnetic field （DC-PMF） and inoculation on pure aluminum were investigated, the grain refinement behavior of DC-PMF and inoculation was discussed. The experimental resul...The combined effects of direct current pulsed magnetic field （DC-PMF） and inoculation on pure aluminum were investigated, the grain refinement behavior of DC-PMF and inoculation was discussed. The experimental results indicate that the solidification micro structure of pure aluminum can be greatly refined under DC-PMF. Refinement of pure aluminum is attributed to electromagnetic undercooling and forced convection caused by DC-PMF. With single DC-PMF, the grain size in the equiaxed zone is uneven. However, under DC-PMF, by adding 0.05% （mass fraction） Al5Ti-B, the grain size of the sample is smaller, and the size distribution is more uniform than that of single DC-PMF. Furthermore, under the combination of DC-PMF and inoculation, with the increase of output current, the grain size is further reduced. When the output current increases to 100 A, the average grain size can decrease to 113 μn.展开更多
To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direc...To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direct current method, we propose a new mesh refinement and recoarsement method for a two-dimensional point source. We introduce the mesh refinement and mesh recoarsement into the traditional structured mesh subdivision. By refining the horizontal grids, the singularity owing to the point source is minimized and the topography is simulated. By recoarsening the horizontal grids, the number of grid cells is reduced significantly and computational efficiency is improved. Model tests show that the proposed method solves the singularity problem and reduces the number of grid cells by 80% compared to the uniform grid refinement.展开更多
An empirical expression for the direct tunneling (DT) current is obtained.This expression can be used to calculate the DT current for nMOSFETs with ultra thin oxide when the oxide thickness is considered as an adjust...An empirical expression for the direct tunneling (DT) current is obtained.This expression can be used to calculate the DT current for nMOSFETs with ultra thin oxide when the oxide thickness is considered as an adjustable parameter.The results have good agreement with the experimental data.And the oxide thickness obtained is less than the value acquired from the capacitance voltage( C V )method.展开更多
A direct tunneling model through gate dielectric s in CMOS devices in the frame of WKB approximation is reported.In the model,an im proved one-band effective mass approximation is used for the hole quantization, wher...A direct tunneling model through gate dielectric s in CMOS devices in the frame of WKB approximation is reported.In the model,an im proved one-band effective mass approximation is used for the hole quantization, where valence band mixing is taken into account.By comparing to the experiments, the model is demonstrated to be applicable to both electron and hole tunneling c urrents in CMOS devices.The effect of the dispersion in oxide energy gap on the tunneling current is also studied.This model can be further extended to study th e direct tunneling current in future high-k materials.展开更多
Noninvasive brain stimulation techniques offer promising therapeutic and regenerative prospects in neurological diseases by modulating brain activity and improving cognitive and motor functions.Given the paucity of kn...Noninvasive brain stimulation techniques offer promising therapeutic and regenerative prospects in neurological diseases by modulating brain activity and improving cognitive and motor functions.Given the paucity of knowledge about the underlying modes of action and optimal treatment modalities,a thorough translational investigation of noninvasive brain stimulation in preclinical animal models is urgently needed.Thus,we reviewed the current literature on the mechanistic underpinnings of noninvasive brain stimulation in models of central nervous system impairment,with a particular emphasis on traumatic brain injury and stroke.Due to the lack of translational models in most noninvasive brain stimulation techniques proposed,we found this review to the most relevant techniques used in humans,i.e.,transcranial magnetic stimulation and transcranial direct current stimulation.We searched the literature in Pub Med,encompassing the MEDLINE and PMC databases,for studies published between January 1,2020 and September 30,2024.Thirty-five studies were eligible.Transcranial magnetic stimulation and transcranial direct current stimulation demonstrated distinct strengths in augmenting rehabilitation post-stroke and traumatic brain injury,with emerging mechanistic evidence.Overall,we identified neuronal,inflammatory,microvascular,and apoptotic pathways highlighted in the literature.This review also highlights a lack of translational surrogate parameters to bridge the gap between preclinical findings and their clinical translation.展开更多
Interface traps generated under hot carrier (HC) stress in LDD nMOST's are monitored by the direct current current voltage (DCIV) measurement technique and charge pumping (CP) technique.The measured and analyzed...Interface traps generated under hot carrier (HC) stress in LDD nMOST's are monitored by the direct current current voltage (DCIV) measurement technique and charge pumping (CP) technique.The measured and analyzed results show that the D peak in DCIV spectrum,which related to the drain region,is affected by a superfluous drain leakage current.The band trap band tunneling current is dominant of this current.展开更多
The investigation on bubble behavior in electric field helps to analyze the mechanism of electric enhancement of boiling heat transfer. Experiments were performed to investigate the bubble deformation in direct curre...The investigation on bubble behavior in electric field helps to analyze the mechanism of electric enhancement of boiling heat transfer. Experiments were performed to investigate the bubble deformation in direct current （DC） electric field with bubbles attached to the orifice. The air bubbles were slowly generated in the transformer oil pool at different orifices, so that the effect of flow on bubble shape was eliminated. The results showed that the bubbles were elongated and the departure volume decreased when the electric field was intensified. The major and minor axes, aspect ratio and departure volume increased with increasing the orifice diameter. Both the electric field and orifice size have great influence on bubble behavior. The bubble deformation was also simulated to compare with the experimental results. The numerical and experimental data qualitatively agree with each other.展开更多
基金Project(51975167)supported by the National Natural Science Foundation of China。
文摘In order to gain a deeper understanding of the effect of pulsed current on the mechanical properties and size effect of nanocrystalline Ni foils,nanocrystalline Ni foils with different grain thickness-to-grain size ratios(λ)were prepared using pulsed electrodeposition in this paper and unidirectional tensile experiments were carried out at room temperature with different currents and their applied directions.The experimental results show that the nanocrystalline Ni foil produces an obvious electroplasticity effect after applying the current field,and when 300<λ<1100,the current weakens the size effect of nanocrystalline Ni foils to a certain extent,and the angle between the current direction and the deformation direction also affects the mechanical response of nanocrystalline Ni foils,and when the angle between the current direction and the deformation direction is 0°,electroplasticity effect is the best,and the current has the most significant effect of abating the size effect of the material.The mechanism of unidirectional tensile deformation of nanocrystalline Ni foils under the effect of pulsed current was analyzed using TEM and TKD.It was found that the applied pulse current increased the activity of the nanocrystalline boundaries,promoted the movement of dislocations,and reduced the tendency of dislocation entanglement.The higher the peak current density and the smaller the angle between the direction of the current and the direction of deformation,the smaller the grain boundary orientation difference,the more dispersed the grain orientation,and the lower the density of geometrically necessary dislocations(GND)in the deformed nanocrystalline foil,the more significant the effect on material plasticity improvement.
基金National Science Fund for Distinguished Young Scholars(No.52225505)the National Sci-ence and Technology Major Project(No.J2019-VII-0014-0154)+1 种基金the National Natural Science Foundation of China(No.52005412)the Tianjin Natural Science Foundation of China-Multi-input key projects(No.22JCZDJC00650)for financial supports given to this research.
文摘The electrically assisted(EA)deformation process has received considerable attention in recent years,ac-companied by research on current-induced deformation mechanisms.However,there are still challenges in eliminating thermal effects,which have prevented a comprehensive understanding of the underlying current-induced mechanisms.Opting for a single crystal(SC)in research provides advantages in decou-pling the nonthermal effect of electric current at smaller scales and eliminating the complex interactions that exist in polycrystalline materials.Therefore,the innovation of this work lies in decoupling the non-thermal effect of electric current and conducting a comprehensive analysis of anisotropic deformation and mechanisms within a Ni-based SC with different crystallographic axes and various current directions dur-ing electrically assisted tensile simulation.A significant tension axis direction in the SC during EA tension was induced by the combination of a higher current direction factor(|cosθ|)and a dimensionless factor for the current density(|J^(α)/J_(0)^(α)|)along the[100]axis.The stress drop within the SC due to the nonthermal effect of electric current generally increased with increasing current direction.This was attributed to the increased dislocation density differences and decreased temperature.The increased stress anisotropy of the SC at a current direction of 45°was attributed to fewer activated(111)slip systems and the pinning effect of more dislocations within these systems.This study advances our understanding of the thermal and nonthermal effects of electric current and offers valuable insights for the informed application of EA deformations in industrial and aerospace settings with SC superalloys.
基金Item Sponsored by National Natural Science Foundation of China[No.50931004]the National Basic Research Program of China[No.2010CB631205]
文摘A macroscopic thermal field calculation and a microstructure simulation are performed to investigate the directional solidification of a nickel-based superalloy with applied direct current in this study.The heat effects of electric current passing through the solidification interface as Joule heat and Peltier heat are investigated in the calculations.The calculated result shows that the Joule heat improves the temperature gradient in the solidification interface,while the effect of Peltier heat is negligible for macroscopic thermal field.The directional growth of dendrites under the influence of Joule heat is investigated with simulation.It is found that under the influence of Joule heat,the dendrites are provided with self-adjustment ability of coordinating growth to achieve flat interface in macroscale during directional solidification with the direct electric current.This interesting phenomenon is brought by the crowdedly passing through the dendrite of electric current in the solidification interface for the large difference of the electrical resistivity between solid state and melt of the superalloy.
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supported by Key Natural Science Research Projects of Colleges and Universities in Anhui Province(2022AH051831).
文摘The integration of large-scale new energy and high-capacity DC transmission leads to a reduction in system inertia.Grid-forming renewable energy sources(GF-RES)has a significant improvement effect on system inertia.Commutation failure faults may cause a short-term reactive power surplus at the sending end and trigger transient overvoltage,threatening the safe and stable operation of the power grid.However,there is a lack of research on the calculation method of transient overvoltage caused by commutation failure in high-voltage DC transmission systems with grid-forming renewable energy sources integration.Based on the existing equivalent model of highvoltage DC transmission systems at the sending end,this paper proposes to construct a model of the high-voltage DC transmission system at the sending end with grid-forming renewable energy sources.The paper first clarifies the mechanism of overvoltage generation,then considers the reactive power droop control characteristics of GF-RES,and derives the transient voltage calculation model of theDC transmission system with GF-RES integration.It also proposes a calculation method for transient overvoltage at the sending-end converter bus with GF-RES integration.Based on the PSCAD/EMTDC simulation platform,this paper builds an experimental simulation model.By constructing three different experimental scenarios,the accuracy and effectiveness of the proposed transient overvoltage calculation method are verified,with a calculation error within 5%.At the same time,this paper quantitatively analyzes the impact of grid strength,new energy proportion,and rated transmission power on transient overvoltage from three different perspectives.
基金supported by the National Natural Science Foundation of China(72271213)the Shenzhen Science and Technology Program(JCYJ20220530143800001 and RCYX20221008092927070)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(2024A1515240024)the National Key Research and Development Program of China(2022YFB2403500).
文摘Interconnection planning involving bi-directional converters(BdCs)is crucial for enhancing the reliability and robustness of hybrid alternating current(AC)/direct current(DC)microgrid clusters with high penetrations of renewable energy resources(RESs).However,challenges such as the non-convex nature of BdC efficiency and renewable energy uncertainty complicate the planning process.To address these issues,this paper proposes a tri-level BdC-based planning framework that incorporates dynamic BdC efficiency and a data-correlated uncertainty set(DcUS)derived from historical data patterns.The proposed framework employs a least-squares approximation to linearize BdC efficiency and constructs the DcUS to balance computational efficiency and solution robustness.Additionally,a fully parallel column and constraint generation algorithm is developed to solve the model efficiently.Numerical simulations on a practical hybrid AC/DC microgrid system demonstrate that the proposed method reduces interconnection costs by up to 21.8%compared to conventional uncertainty sets while ensuring robust operation under all considered scenarios.These results highlight the computational efficiency,robustness,and practicality of the proposed approach,making it a promising solution for modern power systems.
基金supported by National Natural Science Foundation of China(82471564)YT is supported by National Natural Science Foundation of China(32322035,32171078).
文摘Background Pain sensitivity is critical for preventing non-suicidal self-injury(NSSI)behaviours;however,individuals engaging in such behaviours often exhibit decreased pain sensitivity,which may undermine this natural safeguard.The dorsolateral prefrontal cortex(DLPFC)is a key region involved in pain regulation,and recent approaches using transcranial direct current stimulation(tDCS)to target the DLPFC have shown potential for modulating pain processing and restoring normal pain perception for individuals engaging in NSSI behaviours.Aims This study aimed to explore the immediate and short-term effects of a single session of tDCS on pain sensitivity in individuals with NSSI,as well as its secondary effects on mood and NSSI-related factors.Methods In this randomised,double-blind,parallel,sham-controlled clinical trial,participants with a history of NSSI were randomly assigned to receive either active or sham tDCS.The intervention consisted of a single 20 min tDCS session targeting the left DLPFC.The primary outcome was pain sensitivity,measured by the pressure pain threshold(PPT)and heat pain score(HPS).Secondary and additional outcomes included NSSI urges,NSSI resistance,self-efficacy in resisting NSSI,mood-related variables and exploratory cognitive-affective processes such as rumination,self-criticism and self-perceived pain sensitivity,assessed at baseline,immediately post-intervention,and at 24 hours,1 week and 2 weeks follow-ups.Results For the primary outcomes,no significant differences between groups were observed for pain sensitivity(PPT,padj=0.812;HPS,padj=0.608).However,an exploratory sensitivity analysis treating each trial as an individual observation revealed a significant effect on HPS(padj=0.036).For the secondary and additional outcomes,although there were initial improvements in joyful feelings and reductions in negative affect at 2 weeks post-intervention,these effects did not remain significant after multiple comparison corrections.Notably,reductions in rumination were statistically significant at both 1-week and 2-week follow-ups(1 week,p_(adj)=0.040;2 weeks,p_(adj)=0.042).There were no significant effects on NSSI urges,NSSI resistance,self-efficacy in resisting NSSI or self-criticism.Conclusions A single session of tDCS over the left DLPFC did not produce significant changes in pain sensitivity in individuals with NSSI.A sensitivity analysis indicated an effect on heat pain sensitivity,possibly reflecting changes in brain activity,warranting confirmation through neuroimaging.These findings suggest that tDCS warrants further investigation for its potential to influence pain-related cognitive-affective processes in individuals with NSSI.
文摘BACKGROUND Schizophrenia is a chronic psychiatric condition with complex symptomatology,including debilitating auditory hallucinations.Transcranial direct current stimulation(tDCS)has been explored as an adjunctive treatment to alleviate such symptoms.AIM To evaluate the therapeutic efficacy of tDCS in schizophrenia.METHODS Adhering to PRISMA guidelines,we systematically searched PubMed,Embase,Web of Science,and the Cochrane Library on September 19,2023,for randomized controlled trials examining the efficacy of tDCS in schizophrenia,with no language or time restrictions.We included studies that compared tDCS with a control condition and reported clinically relevant outcomes.Data extraction and quality assessments were performed by independent evaluators using the Cochrane Collaboration's risk of bias tool.Statistical heterogeneity was evaluated,and a random-effects model was applied due to moderate heterogeneity(I2=41.3%).RESULTS Nine studies comprising 425 participants(tDCS group:219,control group:206)were included.The meta-analysis demonstrated a significant reduction in auditory hallucination scores following tDCS treatment(weighted mean difference:-2.18,95%confidence interval:-4.0 to-0.29,P<0.01).Sensitivity analysis confirmed the robustness of the results,with no significant influence from individual studies.Additionally,publication bias was not detected,supporting the reliability and generalizability of the findings.These results underscore the efficacy of tDCS as a therapeutic intervention for auditory hallucinations in schizophrenia.CONCLUSION tDCS significantly reduces auditory hallucinations in schizophrenia,suggesting its potential as an effective adjunctive treatment for managing this disabling symptom.The findings highlight the practical significance of tDCS in clinical settings,particularly for patients with treatment-resistant auditory hallucinations.
基金the National Natural Science Foundation of China(51974155)the Outstanding Young Scientific and Technological Talents Project of University of Science and Technology Liaoning(2023YQ07)+4 种基金the University of Science and Technology Liaoning Young Foundation(2018QN06)National Natural Science Foundation of China(51774178)the National Key Research and Development Program(2021YFB3702005)the Central Government Guides Local Science and Technology Development Fund Projects(2023JH6/100100046)the Liaoning Provincial Department of Education Basic Research Projects for Universities(JYTQN2023242).
文摘Herein,the effect of direct current(DC)attached the mold on refining the microstructure and alleviating the central segregation of a tin–bismuth(Sn–10 wt.%Bi)alloy ingot during the solidification process has been investigated.The experiment used a self-made device,which can achieve the effect of refining the solidified structure and alleviate the segregation of the metal casting.Numerical simulations were performed to calculate the Lorentz force,Joule heating and induced melt vortex flow for the magneto-hydrodynamic case.Our results show that the maximum velocity of the global electro-vortex reached 0.017 m s^(–1).The DC-induced electro-vortex was found to be the primary reason of refining the equiaxed grain and alleviating the segregation of theβ-Sn crystal boundary.The grain refining effect observed in these experiments can be solely attributed to the forced melt flow driven by the Lorentz force.DC field attached the mold can lead to grain refinement and alleviate the segregation of the ingot via a global vortex.The technology can be applied not only to opened molds,but also toward improving the quality in closed molds.
文摘BACKGROUND Postoperative delirium(POD),an acute neuropsychiatric complication in elderly surgical patients,manifests as attention and cognitive disturbances that may last 24-72 hours after surgery,potentially progressing to dementia.Transcranial direct current stimulation(tDCS),a non-invasive neuromodulation technique,enhances cortical excitability and cognitive function by modulating brain networks and synaptic plasticity.Elderly patients undergoing major laparoscopic surgery face elevated POD risks due to prolonged anesthesia and pneumoperitoneum-induced cerebral hypoperfusion.This study investigates whether pre-anesthesia tDCS can reduce POD incidence in this population.AIM To investigate the effect of preoperative tDCS on reducing the incidence of POD in elderly patients undergoing major laparoscopic surgery.METHODS In this study,we enrolled 220 elderly patients who underwent major laparoscopic surgery between April 2024 and December 2024.Patients were randomly assigned to the active-tDCS(group A)and sham-tDCS(group S)groups.A single session of tDCS or sham stimulation was administered 30 minutes before anesthesia induction.The primary outcome was the incidence of POD during within 3 days postoperatively.RESULTS A total of 201 patients were included in the final analysis,with 100 patients in group A and 101 in group S.The incidence of POD within 3 days postoperatively was 7.0%in group A,which was significantly lower than 22.8%in group S.On postoperative day 1,the Self-Rating Anxiety Scale and Self-Rating Depression Scale scores significantly differed between the two groups,but the pain scores showed no significant difference.CONCLUSION A single session of preoperative tDCS can reduce the incidence of POD in elderly patients undergoing major laparoscopic surgery and can also reduce postoperative anxiety and depression in these patients.
文摘The sub-forum on standardization of new energy and direct-current diversified applications was held on July 9,which gathered leaders and experts to discuss how to thoroughly implement the national green power direct connection policy proposed in the transformation of the energy landscape,pool wisdom to tackle bottlenecks in the industrialization of DC technology,and leverage the role of standardization in coordinating and regulating the diversified applications of DC technology.It was designed to promote the establishment of a collaborative,open,and advanced global standards system for DC technology.
基金supported by the National Key Research and Development Program of China (Grant No.2022YFA1204000)partly by the National Natural Science Foundation of China (Grant Nos.12274405,12304155,and 12393831)the Beijing Natural Science Foundation (Grant No.Z230006)。
文摘Accurate quantification of the spin–orbit torques(SOTs) is critical for the identification and applications of new spin-orbitronic effects. One of the most popular techniques to quantify the SOTs is the “switching angle shift”, where the applied direct current is assumed to shift, via domain wall depinning during anti-domain expansion, the switching angle of a perpendicular magnetization in a linear proportional manner under a large rotating magnetic field. Here, we report that, for the most commonly employed perpendicular magnetization heterostructures in spintronics(e.g., those based on FeCoB, Co, and Co/Ni multilayers), the switching angle shift considerably misestimates the SOT within the domain wall depinning analysis of the slope of linear-in-current scaling and may also have a non-zero residual value at zero direct current. Our experiments and simulations unveil that the switching angle shift is most likely dominated by chiral asymmetric nucleation rather than expansion of anti-domains. The in-plane field from external magnets and current-induced SOTs lowers the perpendicular nucleation field and thus reduces the required switching angle, ultimately leading to an underestimation of SOTs by domain wall depinning analysis. These results have advanced our understanding of magnetization switching in spintronic devices.
基金Project(50871044)supported by the National Natural Science Foundation of ChinaProject(2012M511207)supported by the Postdoctoral Science Foundation of ChinaProject(10122011)supported by the Science Research Foundation of Wuhan Institute Technology,China
文摘Effect of direct current electric field （DCEF） on corrosion behaviour of copper printed circuit board （PCB-Cu）, Cl-ion migration behaviour, dendrites growth under thin electrolyte layer was investigated using potentiodynamic polarization and scanning electron microscopy （SEM） with energy dispersive spectrometer （EDS）. Results indicate that DCEF decreases the corrosion of PCB-Cu;Cl-ions directionally migrate from the negative pole to the positive pole, and enrich on the surface of the positive pole, which causes serious localized corrosion; dendrites grow on the surface of the negative pole, and the rate and scale of dendrite growth become faster and greater with the increase of external voltage and exposure time, respectively.
基金Projects(51074031,51271042,50874022)supported by the National Natural Science Foundation of ChinaProject(2013M530913)supported by the China Postdoctoral Science FoundationProject(DUT12RC(3)35)supported by the Fundamental Research Funds for the Central Universities of China
文摘The combined effects of direct current pulsed magnetic field （DC-PMF） and inoculation on pure aluminum were investigated, the grain refinement behavior of DC-PMF and inoculation was discussed. The experimental results indicate that the solidification micro structure of pure aluminum can be greatly refined under DC-PMF. Refinement of pure aluminum is attributed to electromagnetic undercooling and forced convection caused by DC-PMF. With single DC-PMF, the grain size in the equiaxed zone is uneven. However, under DC-PMF, by adding 0.05% （mass fraction） Al5Ti-B, the grain size of the sample is smaller, and the size distribution is more uniform than that of single DC-PMF. Furthermore, under the combination of DC-PMF and inoculation, with the increase of output current, the grain size is further reduced. When the output current increases to 100 A, the average grain size can decrease to 113 μn.
基金financially supported by the National Natural Science Foundation of China(No.41574127 and 41174104)the National Key Technology R&D Program for the 13th five-year plan(No.2016ZX05018006-006)
文摘To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direct current method, we propose a new mesh refinement and recoarsement method for a two-dimensional point source. We introduce the mesh refinement and mesh recoarsement into the traditional structured mesh subdivision. By refining the horizontal grids, the singularity owing to the point source is minimized and the topography is simulated. By recoarsening the horizontal grids, the number of grid cells is reduced significantly and computational efficiency is improved. Model tests show that the proposed method solves the singularity problem and reduces the number of grid cells by 80% compared to the uniform grid refinement.
文摘An empirical expression for the direct tunneling (DT) current is obtained.This expression can be used to calculate the DT current for nMOSFETs with ultra thin oxide when the oxide thickness is considered as an adjustable parameter.The results have good agreement with the experimental data.And the oxide thickness obtained is less than the value acquired from the capacitance voltage( C V )method.
文摘A direct tunneling model through gate dielectric s in CMOS devices in the frame of WKB approximation is reported.In the model,an im proved one-band effective mass approximation is used for the hole quantization, where valence band mixing is taken into account.By comparing to the experiments, the model is demonstrated to be applicable to both electron and hole tunneling c urrents in CMOS devices.The effect of the dispersion in oxide energy gap on the tunneling current is also studied.This model can be further extended to study th e direct tunneling current in future high-k materials.
基金funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation):project ID 431549029-SFB 1451the Marga-und-Walter-Boll-Stiftung(#210-10-15)(to MAR)a stipend from the'Gerok Program'(Faculty of Medicine,University of Cologne,Germany)。
文摘Noninvasive brain stimulation techniques offer promising therapeutic and regenerative prospects in neurological diseases by modulating brain activity and improving cognitive and motor functions.Given the paucity of knowledge about the underlying modes of action and optimal treatment modalities,a thorough translational investigation of noninvasive brain stimulation in preclinical animal models is urgently needed.Thus,we reviewed the current literature on the mechanistic underpinnings of noninvasive brain stimulation in models of central nervous system impairment,with a particular emphasis on traumatic brain injury and stroke.Due to the lack of translational models in most noninvasive brain stimulation techniques proposed,we found this review to the most relevant techniques used in humans,i.e.,transcranial magnetic stimulation and transcranial direct current stimulation.We searched the literature in Pub Med,encompassing the MEDLINE and PMC databases,for studies published between January 1,2020 and September 30,2024.Thirty-five studies were eligible.Transcranial magnetic stimulation and transcranial direct current stimulation demonstrated distinct strengths in augmenting rehabilitation post-stroke and traumatic brain injury,with emerging mechanistic evidence.Overall,we identified neuronal,inflammatory,microvascular,and apoptotic pathways highlighted in the literature.This review also highlights a lack of translational surrogate parameters to bridge the gap between preclinical findings and their clinical translation.
文摘Interface traps generated under hot carrier (HC) stress in LDD nMOST's are monitored by the direct current current voltage (DCIV) measurement technique and charge pumping (CP) technique.The measured and analyzed results show that the D peak in DCIV spectrum,which related to the drain region,is affected by a superfluous drain leakage current.The band trap band tunneling current is dominant of this current.
基金the National Key Basic Research Program of China (G2000026301)Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, China
文摘The investigation on bubble behavior in electric field helps to analyze the mechanism of electric enhancement of boiling heat transfer. Experiments were performed to investigate the bubble deformation in direct current （DC） electric field with bubbles attached to the orifice. The air bubbles were slowly generated in the transformer oil pool at different orifices, so that the effect of flow on bubble shape was eliminated. The results showed that the bubbles were elongated and the departure volume decreased when the electric field was intensified. The major and minor axes, aspect ratio and departure volume increased with increasing the orifice diameter. Both the electric field and orifice size have great influence on bubble behavior. The bubble deformation was also simulated to compare with the experimental results. The numerical and experimental data qualitatively agree with each other.
