PVDF-based nanocomposites have gained significant focus in capacitors for their excellent dielectric strength, its multi-scale structural inhomogeneity is the bottleneck for improving the energy storage performance. H...PVDF-based nanocomposites have gained significant focus in capacitors for their excellent dielectric strength, its multi-scale structural inhomogeneity is the bottleneck for improving the energy storage performance. Here, the composite components are optimized by the matrix modification,BST(Ba_(0.6)Sr_(0.4)TiO_(3)) ceramic fibrillation and surface coating. A series of PVDF/polymethyl methacrylate/lysozyme@BST nanofibers with continuous gradient distribution(PF-M/m BST nf-g) are prepared by the concentration gradient-biaxial high-speed electrospinning. The finite element simulation and experiment results indicate that the continuous gradient structure is favorable for the microstructure and inhomogeneity of the electric field distribution, significantly increasing the breakdown strength(Eb) and the permittivity(εr), as well as effectively suppressing the interfacial injected charge and leakage current. As a result, the energy storage density(Ue) of 23.1 J/cm^(3)at 600 MV/m with the charge-discharge efficiency(η) of 71% is achieved compared to PF-M(5.6 J/cm^(3)@350 MV/m, 65%). The exciting energy storage performance based on the well-designed PF-M/m BST nf-g provides important information for the development and application of polymer nanocomposite dielectrics.展开更多
In this letter,we demonstrate the effect ofγirradiation on the lateral AlGaN/GaN Schottky barrier diodes(SBDs)with self-terminated recessed anode structure and low work-function metal tungsten(W)as anode.For a compre...In this letter,we demonstrate the effect ofγirradiation on the lateral AlGaN/GaN Schottky barrier diodes(SBDs)with self-terminated recessed anode structure and low work-function metal tungsten(W)as anode.For a comprehensive evaluation of the radiation-resistance performance of the device,the total dose ofγirradiation is up to 100 kGy with irradiation time of 20 h.Attributed to the barrier lowering effect of the W/GaN interface induced byγirradiation observed in the experiment,the extracted turnon voltage(VON)defined at anode forward current of 1 mA decreases from 0.47 to 0.43 V.Meanwhile,benefiting from the reinforced Schottky interface treated by post-anode-annealing,a high breakdown voltage(BV)of 1.75 kV is obtained for theγ-irradiated AlGaN/GaN SBD,which shows the promising application for the deep-space radiation environment and promotes the development of radiation-resistance research for GaN SBDs.展开更多
Peanut is a major cash crop in the world. In recent years, peanut pod rot has become increasingly prevalent,resulting in significant yield and quality losses. Resistance breeding is considered a cost-effective approac...Peanut is a major cash crop in the world. In recent years, peanut pod rot has become increasingly prevalent,resulting in significant yield and quality losses. Resistance breeding is considered a cost-effective approach for managing pod rot. Previous research in the United States identified significant anatomical differences in leaves and shells among peanut cultivars with varying responses to pod rot caused by Pythium myriotylum Drechs. and Rhizoctonia solani Kuhn. However, whether similar anatomical features correlate with resistance to peanut pod rot in Laixi, Qingdao, remained unknown, where the primary causal pathogen for the disease was F. solani. In this study, nine peanut varieties with differing disease reactions to peanut pod rot were planted in the same plots.Paraffin sections of leaves and shells were prepared and stained to evaluate anatomical features, and the main agronomic traits were assessed alongside leaf spot disease ratings. All the four anatomical features, leaf palisade cell number, palisade cell width, index(palisade cell number per mm × cell width in μm), and shell lignin staining area, were measured before the onset of pod rot and were found to be negatively correlated with pod rot scores.Given the consistent and strong correlation of these anatomical features with pod rot resistance and their high heritability estimates, the pre-existing resistance could be identified even in the absence of the disease, which is particularly valuable for fields where pod rot may not occur every year. This study provided useful anatomical indicators for selecting resistance to peanut pod rot, predominantly caused by F. solani.展开更多
A cylindrical chamber with a rotating bottom holds significant potential for application in cell culture bioreactors due to its ability to generate more stable swirling flows.In order to control vortex breakdown withi...A cylindrical chamber with a rotating bottom holds significant potential for application in cell culture bioreactors due to its ability to generate more stable swirling flows.In order to control vortex breakdown within the chamber,this study first establishes a computational fluid dynamics simulation coupled with the level set method.Verified by experimental results in literature,this method accurately simulates the position and shape of vortex breakdown,and also predicts the critical Reynolds numbers for the appearance and detachment of vortex breakdown bubbles from the center.Additionally,it precisely captures the gas-liquid interface and depicts the vortex breakdown phenomenon in the air above the liquid for the first time.Finally,it predicts the impact of physical property of gas-liquid systems on vortex breakdown in response to significant changes in viscosity of microbial process systems.展开更多
The linear elastic hydraulic fracture criterion is not applicable to deep reservoirs when nonlinear behavior is present over an extensive zone at the fracture tip.This study aims to develop a criterion for nonlinear h...The linear elastic hydraulic fracture criterion is not applicable to deep reservoirs when nonlinear behavior is present over an extensive zone at the fracture tip.This study aims to develop a criterion for nonlinear hydraulic fracture considering the fracture process zone(FPZ)and seeks to reveal the causes of nonlinearity during fracture propagation in deep reservoirs.A closing stress profile considering the in-situ stress was established by using the cohesive zone model(CZM)to describe the FPZ at the fracture tip.An analytical model for the FPZ length was derived,while the criterion for nonlinear fracture propagation was proposed.The FPZ fully developed and the fracture began to propagate when the apparent stress intensity at the fracture tip reached the apparent fracture toughness or when the in-situ stress intensity reached the in-situ fracture toughness.The proposed criterion can clearly determine the length of the FPZ,accurately predict the breakdown pressure during fracturing operations,and establish a relationship between these two parameters.It addresses the inherent limitations of conventional linear elastic fracture mechanics(LEFM),which often underestimates fracture toughness and neglects the effects of the FPZ.This research is expected to enhance the fracturing design in deep reservoirs.展开更多
Electrolyte selection for Plasma Electrolytic Oxidation(PEO)of magnesium is important as this determines composition,morphology and properties of resultant coatings that are urgently sought after for protection of Mg ...Electrolyte selection for Plasma Electrolytic Oxidation(PEO)of magnesium is important as this determines composition,morphology and properties of resultant coatings that are urgently sought after for protection of Mg alloys from corrosion and wear in harsh environments.However,electrolyte design is often performed heuristically,which hampers the development and optimisation of new PEO processes.Here,we attempt to achieve a mechanistic understanding of electrochemical and microstructural aspects of anodic films evolution at the prebreakdown stages of PEO treatments of magnesium in aqueous alkaline solutions of NaAlO_(2),Na_(3)PO_(4),Na F and Na_(2)SiO_(3).Systematic studies have shown that magnesium self-passivation by MgO/Mg(OH)_(2)can be compromised by both chemical and mechanical instabilities developed due to side effects of anodic reactions.Stable initiation of PEO process requires maintaining surface passivity in a wide range of p H,which can be achieved only by combining self-depositing passivators with those binding dissolved magnesium into insoluble compounds.展开更多
To delay the vortex breakdown position of the slender delta wing,this study innovativelyproposes the application of control near the Leading-Edge Vortex(LEV)core sweeping path,whichis called Coupled Core Rotation Dual...To delay the vortex breakdown position of the slender delta wing,this study innovativelyproposes the application of control near the Leading-Edge Vortex(LEV)core sweeping path,whichis called Coupled Core Rotation Dual Synthetic Jets(CCR-DSJ)control.The results show that thevortex breakdown points at each angle of attack are moved backward after control,and the max-imum delayed displacement is 32.4%of the root chord at 30°.Besides,there is a linear relationshipbetween the breakdown position and the angle of attack after control,indicating that CCR-DSJcontrol has a significant effect on the pressure gradient of the vortex axis.Furthermore,the lift coef-ficient C_(L)is enhanced after control,with a maximum CLincrement of 0.078 at 27°,and an effectiveincrement interval of[25°,32°].This interval is different from most previous studies,which isdirectly related to the position of the actuators.According to the lift change mechanism,the anglesof attack are divided into three stages:Stage 1(a=15°–25°),Stage 2(a=25°–32°),and Stage 3(a=32°–40°).In conclusion,CCR-DSJ control can significantly change the pressure distribution,thereby offering promising prospects for the flight stage of the slender delta wing.展开更多
The demand for energy-efficient and environmental-friendly power grid construction has made the exploitation of bio-based electrical epoxy resins with excellent properties increasingly important.This work developed th...The demand for energy-efficient and environmental-friendly power grid construction has made the exploitation of bio-based electrical epoxy resins with excellent properties increasingly important.This work developed the bio-based electrotechnical epoxy resins based on magnolol.High-performance epoxy resin(DGEMT)with a double crosslinked points and its composites(Al_(2)O_(3)/DGEMT)were obtained taking advantages of the two bifunctional groups(allyl and phenolic hydroxyl groups)of magnolol.Benefitting from the distinctive structure of DGEMT,the Al_(2)O_(3)/DGEMT composites exhibited the advantages of intrinsically high thermal conductivity,high insulation,and low dielectric loss.The AC breakdown strength and thermal conductivity of Al_(2)O_(3)/DGEMT composites were 35.5 kV/mm and 1.19 W·m-1·K-1,respectively,which were 15.6%and 52.6%higher than those of petroleum-based composites(Al_(2)O_(3)/DGEBA).And its dielectric loss tanδ=0.0046 was 20.7%lower than that of Al_(2)O_(3)/DGEBA.Furthermore,the mechanical,thermal and processing properties of Al_(2)O_(3)/DGEMT are fully comparable to those of Al_(2)O_(3)/DGEBA.This work confirms the feasibility of manufacturing environmentally friendly power equipment using bio-based epoxy resins,which has excellent engineering applications.展开更多
The effect of Cl^(–)and SO_(4)^(2–)on corrosion behavior of pure copper in simulated groundwater was investigated by electrochemical testing techniques,scanning electron microscope/energy dispersive spectroscopy,X-r...The effect of Cl^(–)and SO_(4)^(2–)on corrosion behavior of pure copper in simulated groundwater was investigated by electrochemical testing techniques,scanning electron microscope/energy dispersive spectroscopy,X-ray photoelectron spectroscopy,and X-ray diffraction in 0.1 mol/L NaHCO_(3)solutions.The results indicate that increasing Cl^(-)and SO_(4)^(2–)reduces the corrosion resistance of Cu.Cl^(-)and SO_(4)^(2–)can promote anodic dissolution of Cu and deteriorate the passivation property.The breakdown potential(Eb)of Cu decreases with the increase in Cl^(-)and SO_(4)^(2–).With the increase in immersion time,the polarization resistance in different solutions tends to be stable.After 55 days,polarization resistance(Rp)was almost equal in 0 and 0.01 mol/L Cl^(-)and SO_(4)^(2–)solutions.In 0.05 mol/L Cl^(-)and SO_(4)^(2−)solution,Rp was lower.HCO3–has a certain corrosion effect on Cu and the pits size increased with the increase in Cl^(-)and SO_(4)^(2–).The corrosion products(Cu_(2)(OH)_(2)CO_(3))and CuO were detected in solutions without or at low Cl^(-)and SO_(4)^(2–)contents.The corrosion product after immersion in the solution containing 0.05 mol/L Cl^(-)and SO_(4)^(2–)was Cu_(2)O.展开更多
Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of in...Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of intelligent factories,constantly face dynamic disturbances during the production process,including machine failures and urgent orders.This paper discusses the basic models and research methods of job shop scheduling,emphasizing the important role of dynamic job shop scheduling and its response schemes in future research.A multi-objective flexible job shop dynamic scheduling mathematical model is established,highlighting its complex and multi-constraint characteristics under different interferences.A classification discussion is conducted on the dynamic response methods and optimization objectives under machine failures,emergency orders,fuzzy completion times,and mixed dynamic events.The development process of traditional scheduling rules and intelligent methods in dynamic scheduling are also analyzed.Finally,based on the current development status of job shop scheduling and the requirements of intelligent manufacturing,the future development trends of dynamic scheduling in flexible job shops are proposed.展开更多
Horizontal well intensive fracturing is a critical technology used to stimulate unconventional oil and gas reservoirs.Accurate prediction of wellbore breakdown pressure is conducive to optimal fracturing design and im...Horizontal well intensive fracturing is a critical technology used to stimulate unconventional oil and gas reservoirs.Accurate prediction of wellbore breakdown pressure is conducive to optimal fracturing design and improvement of the reservoir stimulation effect.In this work,the three-dimensional displacement discontinuity method(DDM)is used to characterize fracture deformation and fracture closure after the pumping pressure relief.The influences of key parameters such as the minimum horizontal principal stress,fracture spacing,the Young's modulus,the Poisson's ratio and pumping pressure on the breakdown pressure are analyzed.The results show that,assuming that the fracture half-length is a,the breakdown pressure outside the fracture surface area increases significantly within 2a in the direction of the minimum horizontal principal stress and a in the directions of the vertical stress and maximum horizontal principal stress before pressure relief.The breakdown pressure of the modified zipper-type fracturing in the later stage is lower.When the fracture spacing is small,the fracture breakdown pressure decreases after the modified zipper-type fracturing of two horizontal wells.The fracture breakdown pressure of the first fractured well reaches a maximum when the fracture spacing is a-1.5a,and the breakdown pressure decreases with increasing well spacing.展开更多
The protection effectiveness of traditional Lightning Strike Protection(LSP)for composite rotor blade of helicopter can be diminished due to the explosion risk in overlapping attachment under lightning strike,so a new...The protection effectiveness of traditional Lightning Strike Protection(LSP)for composite rotor blade of helicopter can be diminished due to the explosion risk in overlapping attachment under lightning strike,so a new protection method based on Air Breakdown and insulating adhesive layer(AB-LSP method)was designed to avoid it.In this study,a numerical method was developed to simulate the electrical breakdown,and verified by experiment results.Based on this method,a Finite Element Model(FEM)was established to investigate the effect of two factors(breakdown strength and initial ablation temperature of adhesive layer)on the LSP effectiveness.The results show that the breakdown strength impacts more to the ablation damage in composite than that of high-temperature resistance.Then,another FEM was established to predict the ablation damage by lightning strike in the AB-LSP method protected composite rotor blade.The mechanisms and potential key parameters(magnitude of lightning current,discharge channel location,adhesive layer thickness,and air gap width)that could affect the protection effectiveness were analyzed.The introduction of air breakdown changes the current conduction path and reduces explosion risk.After rational design,this method can offer effective lightning protection for composite helicopter rotor blade and other composite structures.展开更多
Scrap metals are typically covered with surface contaminants,such as paint,dust,and rust,which can significantly affect the emission spectrum during laser-induced breakdown spectroscopy(LIBS)based sorting.In this stud...Scrap metals are typically covered with surface contaminants,such as paint,dust,and rust,which can significantly affect the emission spectrum during laser-induced breakdown spectroscopy(LIBS)based sorting.In this study,the effects of paint layers on metal surfaces during LIBS classification were investigated.LIBS spectra were collected from metal surfaces painted with black and white paints by ablation with a nanosecond pulsed laser(wavelength=1064 nm,pulse width=7 ns).For the black-painted samples,the LIBS spectra showed a broad background emission,emission lines unrelated to the target metals,large shot-to-shot variation,and a relatively low signal intensity of the target metal,causing poor classification accuracy even at high shot numbers.Cleaning the black paint layer by ablating over a wide area prior to LIBS analysis resulted in high classification accuracy with fewer shot numbers.A method to determine the number of cleaning shots necessary to obtain high classification accuracy and high throughput is proposed on the basis of the change in LIBS signal intensity during cleaning shots.For the white-painted samples,the paint peeled off the metal surface after the first shot,and strong LIBS signals were measured after the following shot,which were attributed to the nanoparticles generated by the ablation of the paint,allowing an accurate classification after only two shots.The results demonstrate that different approaches must be employed depending on the paint color to achieve high classification accuracy with fewer shot numbers.展开更多
Demand for high-performance power devices continues to grow with the continuous development of power electronics and high-end field applications.Although packaging materials based on epoxy resins and silica gels have ...Demand for high-performance power devices continues to grow with the continuous development of power electronics and high-end field applications.Although packaging materials based on epoxy resins and silica gels have been widely developed,higher operating temperatures and operating voltages are still critical to the performance of power devices.Here,a composite film containing functionalized meso-porous hollow silica particles(MH-SiO_(2))and polyimide(PI)was prepared by a template method and layer-by-layer coating strategy to address the current bottlenecks in packaging material development.The electrical breakdown strength of the prepared PI/SiO_(2) composite film was 323.41 kV/mm,while the mass fraction of MH-SiO_(2) was only 5%.This indicates that the mesoporous structure can effectively inhibit electron collisions with nano-restricted domains.The simulation results also indicate that the size variation of inorganic fillers and the interaction of organic/inorganic heterogeneous interfaces are the main reasons affecting the performance of the composites.Meanwhile,the PI/SiO_(2) composite films achieved other properties required for practical applications,such as matched coefficient of thermal ex-pansion(CTE)(23.5 ppm/℃),excellent thermal stability(T_(5)%=559.0℃)and low dielectric constant(2.27@1 M Hz).These results highlight the great potential of inorganic phase-specific structural designs for the preparation of high-performance power device packaging materials.展开更多
As a type of charge-balanced power device,the performance of super-junction MOSFETs(SJ-MOS)is significantly influ-enced by fluctuations in the fabrication process.To overcome the relatively narrow process window of co...As a type of charge-balanced power device,the performance of super-junction MOSFETs(SJ-MOS)is significantly influ-enced by fluctuations in the fabrication process.To overcome the relatively narrow process window of conventional SJ-MOS,an optimized structure"vertical variable doping super-junction MOSFET(VVD-SJ)"is proposed.Based on the analysis using the charge superposition principle,it is observed that the VVD-SJ,in which the impurity concentration of the P-pillar gradually decreases while that of the N-pillar increases from top to bottom,improves the electric field distribution and mitigates charge imbalance(CIB).Experimental results demonstrate that the optimized 600 V VVD-SJ achieves a 35.90%expansion of the pro-cess window.展开更多
Space ion electric propulsion has been widely used in the north-south position maintenance and orbit transfer missions for high-orbit satellites.However,unexpected electric breakdown by ion electric propulsion systems...Space ion electric propulsion has been widely used in the north-south position maintenance and orbit transfer missions for high-orbit satellites.However,unexpected electric breakdown by ion electric propulsion systems is still a challenging problem that needs to be solved,as it affects reliability.Based on the analysis of in-orbit and ground test data of ion thrusters from simulation and experimental results,the main influencing factors of induced electric breakdown are clarified and the mechanisms of induced electric breakdown are analyzed.It is found that the main factors inducing breakdown are the voltage and electric field strength between the grids.In addition,by monitoring the waveform of plasma discharge,the temporal characteristics of breakdown can be defined as three stages of“breakdown-spark-loop response”.Thus,three kinds of engineering suppression methods for breakdown of static vacuum with periodic short-term heating,electrode surface polishing and sealing insulation with plasma,add energy suppression circuit are carried out,and the experimental results show that the electric breakdown frequency can be reduced by about 30%.展开更多
Against the backdrop of the global push for environmental protection and the reduction of plastic pollution,the research and development of alternatives to daily disposable plastic products such as straws have become ...Against the backdrop of the global push for environmental protection and the reduction of plastic pollution,the research and development of alternatives to daily disposable plastic products such as straws have become a hot topic in the environmental protection field.Traditional plastic straws are difficult to degrade,imposing a severe burden on the environment.Meanwhile,existing alternatives like paper straws and PLA(polylactic acid)straws also have numerous drawbacks.展开更多
By integrating laboratory physical modeling experiments with machine learning-based analysis of dominant factors,this study explored the feasibility of pulse hydraulic fracturing(PHF)in deep coal rocks and revealed th...By integrating laboratory physical modeling experiments with machine learning-based analysis of dominant factors,this study explored the feasibility of pulse hydraulic fracturing(PHF)in deep coal rocks and revealed the fracture propagation patterns and the mechanisms of pulsating loading in the process.The results show that PHF induces fatigue damage in coal matrix,significantly reducing breakdown pressure and increasing fracture network volume.Lower vertical stress differential coefficient(less than 0.31),lower peak pressure ratio(less than 0.9),higher horizontal stress differential coefficient(greater than 0.13),higher pulse amplitude ratio(greater than or equal to 0.5)and higher pulse frequency(greater than or equal to 3 Hz)effectively decrease the breakdown pressure.Conversely,higher vertical stress differential coefficient(greater than or equal to 0.31),higher pulse amplitude ratio(greater than or equal to 0.5),lower horizontal stress differential coefficient(less than or equal to 0.13),lower peak pressure ratio(less than 0.9),and lower pulse frequency(less than 3 Hz)promote the formation of a complex fracture network.Vertical stress and peak pressure are the most critical geological and engineering parameters affecting the stimulation effectiveness of PHF.The dominant mechanism varies with coal rank due to differences in geomechanical characteristics and natural fracture development.Low-rank coal primarily exhibits matrix strength degradation.High-rank coal mainly involves the activation of natural fractures and bedding planes.Medium-rank coal shows a coexistence of matrix strength degradation and micro-fracture connectivity.The PHF forms complex fracture networks through the dual mechanism of matrix strength degradation and fracture network connectivity enhancement.展开更多
RNA contains diverse post-transcriptional modifications,and its catabolic breakdown yields numerous modified nucleosides requiring correct processing,but the mechanisms remain unknown.Here,we demonstrate that three RN...RNA contains diverse post-transcriptional modifications,and its catabolic breakdown yields numerous modified nucleosides requiring correct processing,but the mechanisms remain unknown.Here,we demonstrate that three RNA-derived modified adenosines,N6-methyladenosine(m6A),N6,N6-dimethyladenosine(m6,6A),and N6-isopentenyladenosine(i6A),are sequentially metabolized into inosine monophosphate(IMP)to mitigate their intrinsic cytotoxicity.展开更多
Modern electric traction networks(ETN)are equipped with automated systems for commercial accounting of power consumption(ASCAPC),which allows solving properly the problems of enhancing the energy efficiency of transpo...Modern electric traction networks(ETN)are equipped with automated systems for commercial accounting of power consumption(ASCAPC),which allows solving properly the problems of enhancing the energy efficiency of transportation processes.Energy efficiency of ETNs is defined as the amount of power losses in ETN components:overhead catenary systems and traction transformers.Due to the instability of traction loads and changes in their location in space,the electric traction network is different from the general network.It is necessary to develop an approach for loss analysis in traction networks and in transformers of traction substations.To solve this prob-lem,a balance-based technique for power loss calculation in traction networks based on ASCAPC data is proposed.First,the balance-based technique presented here breaks down the power consumption of the train by source.Then,calculates technical power losses in 25 and 225 kV traction networks as well as in traction transformers.Last,the technique is implemented in the form of an algorithm tested on real-life data and it is ready for practical use.展开更多
基金the support and funding from the National Natural Science Foundation of China (Nos. 51773164, 5186020071)Ningxia Natural Science Foundation (No. 2023AAC03104)。
文摘PVDF-based nanocomposites have gained significant focus in capacitors for their excellent dielectric strength, its multi-scale structural inhomogeneity is the bottleneck for improving the energy storage performance. Here, the composite components are optimized by the matrix modification,BST(Ba_(0.6)Sr_(0.4)TiO_(3)) ceramic fibrillation and surface coating. A series of PVDF/polymethyl methacrylate/lysozyme@BST nanofibers with continuous gradient distribution(PF-M/m BST nf-g) are prepared by the concentration gradient-biaxial high-speed electrospinning. The finite element simulation and experiment results indicate that the continuous gradient structure is favorable for the microstructure and inhomogeneity of the electric field distribution, significantly increasing the breakdown strength(Eb) and the permittivity(εr), as well as effectively suppressing the interfacial injected charge and leakage current. As a result, the energy storage density(Ue) of 23.1 J/cm^(3)at 600 MV/m with the charge-discharge efficiency(η) of 71% is achieved compared to PF-M(5.6 J/cm^(3)@350 MV/m, 65%). The exciting energy storage performance based on the well-designed PF-M/m BST nf-g provides important information for the development and application of polymer nanocomposite dielectrics.
基金supported in part by the Key Research and Development Projects of Shaanxi Province(Grant No.2024GX-YBXM-082)in part by the Natural Science Basic Research Program of Shaanxi Province(Grant No.2023-JC-JQ-56)+2 种基金in part by the Fundamental Research Funds for the Central Universities(Grant Nos.QTZX23076,XJSJ25014)in part by the funding of the National Key Research and Development Program of China(Grant No.2022YFB3604400)in part by the China Postdoctoral Science Foundation(Grant No.2021TQ0256).
文摘In this letter,we demonstrate the effect ofγirradiation on the lateral AlGaN/GaN Schottky barrier diodes(SBDs)with self-terminated recessed anode structure and low work-function metal tungsten(W)as anode.For a comprehensive evaluation of the radiation-resistance performance of the device,the total dose ofγirradiation is up to 100 kGy with irradiation time of 20 h.Attributed to the barrier lowering effect of the W/GaN interface induced byγirradiation observed in the experiment,the extracted turnon voltage(VON)defined at anode forward current of 1 mA decreases from 0.47 to 0.43 V.Meanwhile,benefiting from the reinforced Schottky interface treated by post-anode-annealing,a high breakdown voltage(BV)of 1.75 kV is obtained for theγ-irradiated AlGaN/GaN SBD,which shows the promising application for the deep-space radiation environment and promotes the development of radiation-resistance research for GaN SBDs.
基金support from Mining Stress Tolerant Early Maturing Peanut Genetic Resources and Breeding Processing Type Peanut Varieties in Xinjiang(2022A02008-3)China Agricultural Research System(CARS-13)+1 种基金Agricultural Science&Technology Innovation Project of Shandong Academy of Agricultural Sciences(CXGC2024D19)Key Research&Development Program of Shandong Province(2024TSGC0532).
文摘Peanut is a major cash crop in the world. In recent years, peanut pod rot has become increasingly prevalent,resulting in significant yield and quality losses. Resistance breeding is considered a cost-effective approach for managing pod rot. Previous research in the United States identified significant anatomical differences in leaves and shells among peanut cultivars with varying responses to pod rot caused by Pythium myriotylum Drechs. and Rhizoctonia solani Kuhn. However, whether similar anatomical features correlate with resistance to peanut pod rot in Laixi, Qingdao, remained unknown, where the primary causal pathogen for the disease was F. solani. In this study, nine peanut varieties with differing disease reactions to peanut pod rot were planted in the same plots.Paraffin sections of leaves and shells were prepared and stained to evaluate anatomical features, and the main agronomic traits were assessed alongside leaf spot disease ratings. All the four anatomical features, leaf palisade cell number, palisade cell width, index(palisade cell number per mm × cell width in μm), and shell lignin staining area, were measured before the onset of pod rot and were found to be negatively correlated with pod rot scores.Given the consistent and strong correlation of these anatomical features with pod rot resistance and their high heritability estimates, the pre-existing resistance could be identified even in the absence of the disease, which is particularly valuable for fields where pod rot may not occur every year. This study provided useful anatomical indicators for selecting resistance to peanut pod rot, predominantly caused by F. solani.
基金National Natural Science Foundation of China(22178228,22178326)
文摘A cylindrical chamber with a rotating bottom holds significant potential for application in cell culture bioreactors due to its ability to generate more stable swirling flows.In order to control vortex breakdown within the chamber,this study first establishes a computational fluid dynamics simulation coupled with the level set method.Verified by experimental results in literature,this method accurately simulates the position and shape of vortex breakdown,and also predicts the critical Reynolds numbers for the appearance and detachment of vortex breakdown bubbles from the center.Additionally,it precisely captures the gas-liquid interface and depicts the vortex breakdown phenomenon in the air above the liquid for the first time.Finally,it predicts the impact of physical property of gas-liquid systems on vortex breakdown in response to significant changes in viscosity of microbial process systems.
基金supported by the National Natural Science Foun-dation of China(No.52434001).
文摘The linear elastic hydraulic fracture criterion is not applicable to deep reservoirs when nonlinear behavior is present over an extensive zone at the fracture tip.This study aims to develop a criterion for nonlinear hydraulic fracture considering the fracture process zone(FPZ)and seeks to reveal the causes of nonlinearity during fracture propagation in deep reservoirs.A closing stress profile considering the in-situ stress was established by using the cohesive zone model(CZM)to describe the FPZ at the fracture tip.An analytical model for the FPZ length was derived,while the criterion for nonlinear fracture propagation was proposed.The FPZ fully developed and the fracture began to propagate when the apparent stress intensity at the fracture tip reached the apparent fracture toughness or when the in-situ stress intensity reached the in-situ fracture toughness.The proposed criterion can clearly determine the length of the FPZ,accurately predict the breakdown pressure during fracturing operations,and establish a relationship between these two parameters.It addresses the inherent limitations of conventional linear elastic fracture mechanics(LEFM),which often underestimates fracture toughness and neglects the effects of the FPZ.This research is expected to enhance the fracturing design in deep reservoirs.
基金supported by the UK EPSRC(grant EP/T024607/1,‘Coat IN’)provided by the Henry Royce Institute for Advanced Materials,funded through the UK EPSRC grants EP/R00661X/1,EP/S019367/1,EP/P025021/1 and EP/P025498/1support from the University of Manchester and Chinese Scholarship Council for his Ph D studies。
文摘Electrolyte selection for Plasma Electrolytic Oxidation(PEO)of magnesium is important as this determines composition,morphology and properties of resultant coatings that are urgently sought after for protection of Mg alloys from corrosion and wear in harsh environments.However,electrolyte design is often performed heuristically,which hampers the development and optimisation of new PEO processes.Here,we attempt to achieve a mechanistic understanding of electrochemical and microstructural aspects of anodic films evolution at the prebreakdown stages of PEO treatments of magnesium in aqueous alkaline solutions of NaAlO_(2),Na_(3)PO_(4),Na F and Na_(2)SiO_(3).Systematic studies have shown that magnesium self-passivation by MgO/Mg(OH)_(2)can be compromised by both chemical and mechanical instabilities developed due to side effects of anodic reactions.Stable initiation of PEO process requires maintaining surface passivity in a wide range of p H,which can be achieved only by combining self-depositing passivators with those binding dissolved magnesium into insoluble compounds.
基金supported by the National Natural Science Foundation of China(Nos.92271110,12072352)the Major National Science and Technology Project,China(No.J2019-Ⅲ-0010-0054)。
文摘To delay the vortex breakdown position of the slender delta wing,this study innovativelyproposes the application of control near the Leading-Edge Vortex(LEV)core sweeping path,whichis called Coupled Core Rotation Dual Synthetic Jets(CCR-DSJ)control.The results show that thevortex breakdown points at each angle of attack are moved backward after control,and the max-imum delayed displacement is 32.4%of the root chord at 30°.Besides,there is a linear relationshipbetween the breakdown position and the angle of attack after control,indicating that CCR-DSJcontrol has a significant effect on the pressure gradient of the vortex axis.Furthermore,the lift coef-ficient C_(L)is enhanced after control,with a maximum CLincrement of 0.078 at 27°,and an effectiveincrement interval of[25°,32°].This interval is different from most previous studies,which isdirectly related to the position of the actuators.According to the lift change mechanism,the anglesof attack are divided into three stages:Stage 1(a=15°–25°),Stage 2(a=25°–32°),and Stage 3(a=32°–40°).In conclusion,CCR-DSJ control can significantly change the pressure distribution,thereby offering promising prospects for the flight stage of the slender delta wing.
基金supported by the China Postdoctoral Science Foundation(No.2023M743622)Natural Science Foundation of Ningbo City(No.2024J109)+2 种基金National Natural Science Foundation of China(Nos.E52307038 and U23A20589)Ningbo 2025 Key Scientific Research Programs(Nos.2022Z111,2022Z160 and 2022Z198)the Leading Innovativeand Entrepreneur Team Introduction Program of Zhejiang(No.2021R01005).
文摘The demand for energy-efficient and environmental-friendly power grid construction has made the exploitation of bio-based electrical epoxy resins with excellent properties increasingly important.This work developed the bio-based electrotechnical epoxy resins based on magnolol.High-performance epoxy resin(DGEMT)with a double crosslinked points and its composites(Al_(2)O_(3)/DGEMT)were obtained taking advantages of the two bifunctional groups(allyl and phenolic hydroxyl groups)of magnolol.Benefitting from the distinctive structure of DGEMT,the Al_(2)O_(3)/DGEMT composites exhibited the advantages of intrinsically high thermal conductivity,high insulation,and low dielectric loss.The AC breakdown strength and thermal conductivity of Al_(2)O_(3)/DGEMT composites were 35.5 kV/mm and 1.19 W·m-1·K-1,respectively,which were 15.6%and 52.6%higher than those of petroleum-based composites(Al_(2)O_(3)/DGEBA).And its dielectric loss tanδ=0.0046 was 20.7%lower than that of Al_(2)O_(3)/DGEBA.Furthermore,the mechanical,thermal and processing properties of Al_(2)O_(3)/DGEMT are fully comparable to those of Al_(2)O_(3)/DGEBA.This work confirms the feasibility of manufacturing environmentally friendly power equipment using bio-based epoxy resins,which has excellent engineering applications.
基金supported by the National Natural Science Foundation of China(No.U22B2065).
文摘The effect of Cl^(–)and SO_(4)^(2–)on corrosion behavior of pure copper in simulated groundwater was investigated by electrochemical testing techniques,scanning electron microscope/energy dispersive spectroscopy,X-ray photoelectron spectroscopy,and X-ray diffraction in 0.1 mol/L NaHCO_(3)solutions.The results indicate that increasing Cl^(-)and SO_(4)^(2–)reduces the corrosion resistance of Cu.Cl^(-)and SO_(4)^(2–)can promote anodic dissolution of Cu and deteriorate the passivation property.The breakdown potential(Eb)of Cu decreases with the increase in Cl^(-)and SO_(4)^(2–).With the increase in immersion time,the polarization resistance in different solutions tends to be stable.After 55 days,polarization resistance(Rp)was almost equal in 0 and 0.01 mol/L Cl^(-)and SO_(4)^(2–)solutions.In 0.05 mol/L Cl^(-)and SO_(4)^(2−)solution,Rp was lower.HCO3–has a certain corrosion effect on Cu and the pits size increased with the increase in Cl^(-)and SO_(4)^(2–).The corrosion products(Cu_(2)(OH)_(2)CO_(3))and CuO were detected in solutions without or at low Cl^(-)and SO_(4)^(2–)contents.The corrosion product after immersion in the solution containing 0.05 mol/L Cl^(-)and SO_(4)^(2–)was Cu_(2)O.
基金supported by the National Key Research and Development Program Project(No.2021YFB3301300).
文摘Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of intelligent factories,constantly face dynamic disturbances during the production process,including machine failures and urgent orders.This paper discusses the basic models and research methods of job shop scheduling,emphasizing the important role of dynamic job shop scheduling and its response schemes in future research.A multi-objective flexible job shop dynamic scheduling mathematical model is established,highlighting its complex and multi-constraint characteristics under different interferences.A classification discussion is conducted on the dynamic response methods and optimization objectives under machine failures,emergency orders,fuzzy completion times,and mixed dynamic events.The development process of traditional scheduling rules and intelligent methods in dynamic scheduling are also analyzed.Finally,based on the current development status of job shop scheduling and the requirements of intelligent manufacturing,the future development trends of dynamic scheduling in flexible job shops are proposed.
基金supported by the National Natural Science Foundation of China,China(No.52074250).
文摘Horizontal well intensive fracturing is a critical technology used to stimulate unconventional oil and gas reservoirs.Accurate prediction of wellbore breakdown pressure is conducive to optimal fracturing design and improvement of the reservoir stimulation effect.In this work,the three-dimensional displacement discontinuity method(DDM)is used to characterize fracture deformation and fracture closure after the pumping pressure relief.The influences of key parameters such as the minimum horizontal principal stress,fracture spacing,the Young's modulus,the Poisson's ratio and pumping pressure on the breakdown pressure are analyzed.The results show that,assuming that the fracture half-length is a,the breakdown pressure outside the fracture surface area increases significantly within 2a in the direction of the minimum horizontal principal stress and a in the directions of the vertical stress and maximum horizontal principal stress before pressure relief.The breakdown pressure of the modified zipper-type fracturing in the later stage is lower.When the fracture spacing is small,the fracture breakdown pressure decreases after the modified zipper-type fracturing of two horizontal wells.The fracture breakdown pressure of the first fractured well reaches a maximum when the fracture spacing is a-1.5a,and the breakdown pressure decreases with increasing well spacing.
文摘The protection effectiveness of traditional Lightning Strike Protection(LSP)for composite rotor blade of helicopter can be diminished due to the explosion risk in overlapping attachment under lightning strike,so a new protection method based on Air Breakdown and insulating adhesive layer(AB-LSP method)was designed to avoid it.In this study,a numerical method was developed to simulate the electrical breakdown,and verified by experiment results.Based on this method,a Finite Element Model(FEM)was established to investigate the effect of two factors(breakdown strength and initial ablation temperature of adhesive layer)on the LSP effectiveness.The results show that the breakdown strength impacts more to the ablation damage in composite than that of high-temperature resistance.Then,another FEM was established to predict the ablation damage by lightning strike in the AB-LSP method protected composite rotor blade.The mechanisms and potential key parameters(magnitude of lightning current,discharge channel location,adhesive layer thickness,and air gap width)that could affect the protection effectiveness were analyzed.The introduction of air breakdown changes the current conduction path and reduces explosion risk.After rational design,this method can offer effective lightning protection for composite helicopter rotor blade and other composite structures.
基金supported by the R&D Center for Valuable Recycling (Global-Top R&D Program)of the Ministry of Environment (No.2016002250003)。
文摘Scrap metals are typically covered with surface contaminants,such as paint,dust,and rust,which can significantly affect the emission spectrum during laser-induced breakdown spectroscopy(LIBS)based sorting.In this study,the effects of paint layers on metal surfaces during LIBS classification were investigated.LIBS spectra were collected from metal surfaces painted with black and white paints by ablation with a nanosecond pulsed laser(wavelength=1064 nm,pulse width=7 ns).For the black-painted samples,the LIBS spectra showed a broad background emission,emission lines unrelated to the target metals,large shot-to-shot variation,and a relatively low signal intensity of the target metal,causing poor classification accuracy even at high shot numbers.Cleaning the black paint layer by ablating over a wide area prior to LIBS analysis resulted in high classification accuracy with fewer shot numbers.A method to determine the number of cleaning shots necessary to obtain high classification accuracy and high throughput is proposed on the basis of the change in LIBS signal intensity during cleaning shots.For the white-painted samples,the paint peeled off the metal surface after the first shot,and strong LIBS signals were measured after the following shot,which were attributed to the nanoparticles generated by the ablation of the paint,allowing an accurate classification after only two shots.The results demonstrate that different approaches must be employed depending on the paint color to achieve high classification accuracy with fewer shot numbers.
基金supported by the National Natural Science Foundation of China(Nos.52377026 and 52301192)the Taishan Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)+1 种基金the Natural Science Foundation of Shandong Province(Nos.ZR2024ME046 and ZR2024QE313)the China Postdoctoral Science Foundation(No.2024M761554).
文摘Demand for high-performance power devices continues to grow with the continuous development of power electronics and high-end field applications.Although packaging materials based on epoxy resins and silica gels have been widely developed,higher operating temperatures and operating voltages are still critical to the performance of power devices.Here,a composite film containing functionalized meso-porous hollow silica particles(MH-SiO_(2))and polyimide(PI)was prepared by a template method and layer-by-layer coating strategy to address the current bottlenecks in packaging material development.The electrical breakdown strength of the prepared PI/SiO_(2) composite film was 323.41 kV/mm,while the mass fraction of MH-SiO_(2) was only 5%.This indicates that the mesoporous structure can effectively inhibit electron collisions with nano-restricted domains.The simulation results also indicate that the size variation of inorganic fillers and the interaction of organic/inorganic heterogeneous interfaces are the main reasons affecting the performance of the composites.Meanwhile,the PI/SiO_(2) composite films achieved other properties required for practical applications,such as matched coefficient of thermal ex-pansion(CTE)(23.5 ppm/℃),excellent thermal stability(T_(5)%=559.0℃)and low dielectric constant(2.27@1 M Hz).These results highlight the great potential of inorganic phase-specific structural designs for the preparation of high-performance power device packaging materials.
基金supported by the National Science Foundation of Guangdong Province under Grant 2023A1515012652School-enterprise cooperation projects of ZTE Corporation.
文摘As a type of charge-balanced power device,the performance of super-junction MOSFETs(SJ-MOS)is significantly influ-enced by fluctuations in the fabrication process.To overcome the relatively narrow process window of conventional SJ-MOS,an optimized structure"vertical variable doping super-junction MOSFET(VVD-SJ)"is proposed.Based on the analysis using the charge superposition principle,it is observed that the VVD-SJ,in which the impurity concentration of the P-pillar gradually decreases while that of the N-pillar increases from top to bottom,improves the electric field distribution and mitigates charge imbalance(CIB).Experimental results demonstrate that the optimized 600 V VVD-SJ achieves a 35.90%expansion of the pro-cess window.
文摘Space ion electric propulsion has been widely used in the north-south position maintenance and orbit transfer missions for high-orbit satellites.However,unexpected electric breakdown by ion electric propulsion systems is still a challenging problem that needs to be solved,as it affects reliability.Based on the analysis of in-orbit and ground test data of ion thrusters from simulation and experimental results,the main influencing factors of induced electric breakdown are clarified and the mechanisms of induced electric breakdown are analyzed.It is found that the main factors inducing breakdown are the voltage and electric field strength between the grids.In addition,by monitoring the waveform of plasma discharge,the temporal characteristics of breakdown can be defined as three stages of“breakdown-spark-loop response”.Thus,three kinds of engineering suppression methods for breakdown of static vacuum with periodic short-term heating,electrode surface polishing and sealing insulation with plasma,add energy suppression circuit are carried out,and the experimental results show that the electric breakdown frequency can be reduced by about 30%.
文摘Against the backdrop of the global push for environmental protection and the reduction of plastic pollution,the research and development of alternatives to daily disposable plastic products such as straws have become a hot topic in the environmental protection field.Traditional plastic straws are difficult to degrade,imposing a severe burden on the environment.Meanwhile,existing alternatives like paper straws and PLA(polylactic acid)straws also have numerous drawbacks.
基金Supported by the National Natural Science Foundation of China(52274014,52421002).
文摘By integrating laboratory physical modeling experiments with machine learning-based analysis of dominant factors,this study explored the feasibility of pulse hydraulic fracturing(PHF)in deep coal rocks and revealed the fracture propagation patterns and the mechanisms of pulsating loading in the process.The results show that PHF induces fatigue damage in coal matrix,significantly reducing breakdown pressure and increasing fracture network volume.Lower vertical stress differential coefficient(less than 0.31),lower peak pressure ratio(less than 0.9),higher horizontal stress differential coefficient(greater than 0.13),higher pulse amplitude ratio(greater than or equal to 0.5)and higher pulse frequency(greater than or equal to 3 Hz)effectively decrease the breakdown pressure.Conversely,higher vertical stress differential coefficient(greater than or equal to 0.31),higher pulse amplitude ratio(greater than or equal to 0.5),lower horizontal stress differential coefficient(less than or equal to 0.13),lower peak pressure ratio(less than 0.9),and lower pulse frequency(less than 3 Hz)promote the formation of a complex fracture network.Vertical stress and peak pressure are the most critical geological and engineering parameters affecting the stimulation effectiveness of PHF.The dominant mechanism varies with coal rank due to differences in geomechanical characteristics and natural fracture development.Low-rank coal primarily exhibits matrix strength degradation.High-rank coal mainly involves the activation of natural fractures and bedding planes.Medium-rank coal shows a coexistence of matrix strength degradation and micro-fracture connectivity.The PHF forms complex fracture networks through the dual mechanism of matrix strength degradation and fracture network connectivity enhancement.
文摘RNA contains diverse post-transcriptional modifications,and its catabolic breakdown yields numerous modified nucleosides requiring correct processing,but the mechanisms remain unknown.Here,we demonstrate that three RNA-derived modified adenosines,N6-methyladenosine(m6A),N6,N6-dimethyladenosine(m6,6A),and N6-isopentenyladenosine(i6A),are sequentially metabolized into inosine monophosphate(IMP)to mitigate their intrinsic cytotoxicity.
基金the state assign-ment of Ministry of Science and Higher Education of the Russian Federation(theme No 123102000012-2“Compre-hensive study of aerodynamic characteristics of plasma systems of thermochemical fuel preparation”,agreement No 075-03-2023-028/1 of 05.10.2023).
文摘Modern electric traction networks(ETN)are equipped with automated systems for commercial accounting of power consumption(ASCAPC),which allows solving properly the problems of enhancing the energy efficiency of transportation processes.Energy efficiency of ETNs is defined as the amount of power losses in ETN components:overhead catenary systems and traction transformers.Due to the instability of traction loads and changes in their location in space,the electric traction network is different from the general network.It is necessary to develop an approach for loss analysis in traction networks and in transformers of traction substations.To solve this prob-lem,a balance-based technique for power loss calculation in traction networks based on ASCAPC data is proposed.First,the balance-based technique presented here breaks down the power consumption of the train by source.Then,calculates technical power losses in 25 and 225 kV traction networks as well as in traction transformers.Last,the technique is implemented in the form of an algorithm tested on real-life data and it is ready for practical use.
