The mid-subtropical forest is one of the biggest sections of subtropical forest in China and plays a vital role in mitigating climate change by sequestering carbon.Studies have examined carbon storage density(CSD) dis...The mid-subtropical forest is one of the biggest sections of subtropical forest in China and plays a vital role in mitigating climate change by sequestering carbon.Studies have examined carbon storage density(CSD) distribution in temperate forests. However, our knowledge of CSD in subtropical forests is limited. In this study, Jiangle County was selected as a study case to explore geographic variation in CSD. A spatial heterogeneity analysis by semivariogram revealed that CSD varied at less than the mesoscale(approximately 2000–3000 m). CSD distribution mapped using Kriging regression revealed an increasing trend in CSD from west to east of the study area.Global spatial autocorrelation analysis indicated that CSD was clustered at the village level(at 5% significance).Some areas with local spatial autocorrelation were detected by Anselin Local Moran's I and Getis-Ord G*. A geographically weighted regression model showed different impacts on the different areas for each determinant. Generally, diameter at breast height, tree height, and stand density had positive correlation with CSD in Jiangle County, but varied substantially in magnitude by location.In contrast, coefficients of elevation and slope ranged from negative to positive. Based on these results, we propose certain measures to increase forest carbon storage,including increasing forested area, improving the quality of the current forests, and promoting reasonable forest management decisions and harvesting strategies. The established CSD model emphasizes the important role of midsubtropical forest in carbon sequestration and provides useful information for quantifying mid-subtropical forest carbon storage.展开更多
Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0....Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3BiFeO_(3)-x%Mn(x=0,0.5,1.5,2,3)thin films via sol-gel method.Mn ions of divalent valence combine with oxygen vacancies,forming defect complex,which results in marked decline in leakage current and obvious enhancement in breakdown strength.A high energy storage density~47.6 J cm^(-3)and good efficiency~65.68%are simultaneously achieved in 2%Mn doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor.Moreover,the 2%Mn-doped thin film exhibits excellent thermal stability in wide operating temperature range(35–115℃)and strong fatigue endurance behaviors after 108 cycles.The above results demonstrate that 2%Mn-doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor with superior energy storage performances is a potential candidate for electrostatic energy storage.展开更多
Metallised film capacitors(MFC)can operate under much higher voltage compared to the foil capacitor due to their self-healing(SH)properties,which caters to their application with high energy storage density requiremen...Metallised film capacitors(MFC)can operate under much higher voltage compared to the foil capacitor due to their self-healing(SH)properties,which caters to their application with high energy storage density requirement.Excellent results were achieved on the enhancement of the energy storage density of the dielectric material,whereas the SH properties of the modified material were less concerned.In the present study,the simultaneous improvement of the energy storage density and the SH properties were proposed,by constructing double-layer metallised films of polypropylene(PP)and pol-ymethyl methacrylate(PMMA).The breakdown strength of the PP/PMMA first increased and then decreased with the rising thickness of the PMMA layer.The dielectric constant was also raised because of the introduced ester groups.The highest energy storage density of 5.93 J/cm3 was obtained,which was 62.47%higher than the neat PP,whereas the dielectric loss was maintained around 0.01.The SH properties of PP/PMMA were systematically evaluated,that the SH energy decreased with the increasing PMMA ratio,and the equivalent conductivity at the SH point of the PP/PMMA decreased to only 1%of the neat PP,which largely benefit the stability of the MFC with reduced tem-perature rise.展开更多
In this study,the authors proposed a promising structure design,the micro-crosslinked polypropylene(PP),to enhance the high-temperature energy storage density.With the grafting of 1,6,7,12-tetrachlorinated perylene-N-...In this study,the authors proposed a promising structure design,the micro-crosslinked polypropylene(PP),to enhance the high-temperature energy storage density.With the grafting of 1,6,7,12-tetrachlorinated perylene-N-2-aminoethyl acrylate-Nʹ-dodecylamine-3,4,9,10-tetracarboxylic bisimide(PTCDA)onto PP molecules,the obtained PP-g-PTCDA achieved a superior energy storage density of 2.34 J/cm^(3)at 120℃ with the discharge efficiency above 90%,which was 585%higher than that of neat PP.The great enhancement,on the one hand,originated from the micro-crosslinked structure,since the restricted molecular motion can lead to the suppression of electrons'hopping across the molecular chains.On the other hand,deep traps were also introduced in PP-g-PTCDA,which restricted the electrons'hopping along the molecular chains simultaneously.This work provided an orientation to enhance the energy storage density at an elevated temperature of 120℃.展开更多
Ensuring reliable and safe operation of high-power electronic devices necessitates the development of high-quality dielectric nano-capacitors with high recoverable energy density(URec)and efficiency(η)at low applied ...Ensuring reliable and safe operation of high-power electronic devices necessitates the development of high-quality dielectric nano-capacitors with high recoverable energy density(URec)and efficiency(η)at low applied electric fields(E)/voltages.In this work,we demonstrate ultra-high URec andηat low E<500 kV/cm in as-grown epitaxial relaxor ferroelectric(RFE)PMN-33PT films,rivaling those typically achieved in state-of-the-art RFE and antiferroelectric(AFE)materials.The high energy storage properties were achieved using a synergistic strategy involving large polarization,a giant built-in potential/imprint(five times higher than the coercive field),and AFE like behavior.The structural,chemical,and electrical investigations revealed that these achievements mainly arise from the effects of strain,dipole defects,and chemical composition.For instance,at low E,the capacitors exhibit under 160 kV/cm(i.e.,8 V)and 400 kV/cm(i.e.,20 V),respectively,an ultra-highΔP(45μC/cm^(2)and 60μC/cm^(2)),UE=URec/E(21 J·MV/cm^(2)and 17 J·MV/cm^(2)),and UF=URec/(1-η)(20 J/cm^(3)and 47 J/cm^(3))with a robust charge-discharge fatigue endurance and outstanding frequency and thermal stability.Additionally,the designed films exhibit outstanding energy storage performance at higher E up to 2 MV/cm(ΔP≈78μC/cm^(2),UE≈17.3 J·MV/cm^(2)and UF≈288 J/cm^(3))due to their low leakage current density.展开更多
The NaNbO_(3) antiferroelectrics have been considered as a potential candidate for dielectric capacitorsapplications. However, the high-electric-field-unstable antiferroelectric phase resulted in low energystorage den...The NaNbO_(3) antiferroelectrics have been considered as a potential candidate for dielectric capacitorsapplications. However, the high-electric-field-unstable antiferroelectric phase resulted in low energystorage density and efficiency. Herein, good energy storage properties were realized in (1-x)NaNbO_(3)- xNaTaO_(3) ceramics, by building a new phase boundary. As a result, a high recoverable energy density(Wrec) of 2.2 J/cm3 and efficiency (h) of 80.1% were achieved in 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic at300 kV/cm. The excellent energy storage performance originates from an antiferroelectric-paraelectricphase boundary with simultaneously high polarization and low hysteresis, by tailoring the ratio ofantiferroelectric and paraelectric phases. Moreover, the 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic also exhibitedgood temperature and frequency stability, together with excellent charge-discharge performance. Theresults pave a good way of designing new NaNbO_(3)-based antiferroelectrics with good energy storageperformance.展开更多
Inspired by increasing demand of advanced pulsed power capacitors,the development of lead-free dielectric ceramic capacitors with high energy storage density and temperature-insensitive performance are extremely cruci...Inspired by increasing demand of advanced pulsed power capacitors,the development of lead-free dielectric ceramic capacitors with high energy storage density and temperature-insensitive performance are extremely crucial.Herein,the lead-free relaxor ferroelectric ceramics based on(1-x)(Na_(0.5)Bi_(0.5))0.6Sr_(0.4)TiO_(3-x)Sr_(0.7)La_(0.2)ZrO_(3)[abbreviated as(1-x)NBST-xSLZ]are prepared by the solid-state reaction route.The large recoverable energy density(Wrec)of 3.45 J/cm^(3)and efficiency(h)of 90.1%are simultaneously realized in 0.86NBST-0.14SLZ ceramic due to increased breakdown strength.Furthermore,both the Wrec and h of 0.86NBST-0.14SLZ ceramic display superior of thermal stability(20e180C),frequency stability(1e1000 Hz),and cycle stability(10^(4))within a satisfactory range of variation.In addition,the 0.86NBST-0.14SLZ ceramic can also achieve a large current density(CD)of 625 A/cm^(2),an ultrahigh power density(PD)of 50 MW/cm^(3)and a fast discharge rate(t0.90)of 160.8 ns at 160 kV/cm.These results demonstrate that the 0.86NBST-0.14SLZ ceramic could be a highly competitive and ecofriendly relaxor ferroelectric material for next-generation pulsed power capacitors.展开更多
We introduce a technique for increasing density in optical data storage systems. This technique is based on the use of a superresolving filter at the pupil of a confocal readout system. The main characteristic of this...We introduce a technique for increasing density in optical data storage systems. This technique is based on the use of a superresolving filter at the pupil of a confocal readout system. The main characteristic of this confocal readout system is that the light beam traverses twice through the pupil filter. We describe how to analyze the system performance for general filters, but we focus the study on filters with no focus displacement. Although the storage density attainable depends on the filter characteristics, we show that the storage density can be easily duplicated.展开更多
The Ba_(0.3)Sr_(0.6)Ca_(0.1)TiO_(3)(BSCT)powder was prepared through the solid-state reaction.And then preparing ceramic samples with quantitative doped-Bi_(2)O_(3)·3TiO_(2) and diferent doped-MgO.X-ray diffracto...The Ba_(0.3)Sr_(0.6)Ca_(0.1)TiO_(3)(BSCT)powder was prepared through the solid-state reaction.And then preparing ceramic samples with quantitative doped-Bi_(2)O_(3)·3TiO_(2) and diferent doped-MgO.X-ray diffractometer(XRD)and scanning electron microscopy(SEM)were used to investigate the phase compositions,distribution and morphology of the ceramic samples.SM-11J49 capacitance measurement instrument and CS2674A pressure tester were used to measure the dieletric properties of the samples.The results show that the compactness and the dielectric constant of the ceramics increases first and then decreases when the doped MgO content was changed from 1.5 to 4.5 wt.%.The trend of breakdown strength is characterized by M-shaped pattern with the increase of doped-MgO content.Calculation results demonstrate that when the doped-MgO content is 2.0%,the samples have the highest energy storage density.展开更多
In this work,the dependency of the polarization(P)-electric field(E)loop area A of lead free ferro-electrics Na_(0.5)Bi_(0.5)TiO_(3)(NBT), K_(0.5)Bi_(0.5)TiO_(3)(KBT),and Na_(0.25)K_(0.25)Bi_(0.5)TiO_(3)(NKBT)on the a...In this work,the dependency of the polarization(P)-electric field(E)loop area A of lead free ferro-electrics Na_(0.5)Bi_(0.5)TiO_(3)(NBT), K_(0.5)Bi_(0.5)TiO_(3)(KBT),and Na_(0.25)K_(0.25)Bi_(0.5)TiO_(3)(NKBT)on the amplitude(E0)of the electric field is studied.Based on the nature of the hysteresis loop with increasing E0,the lnA versus lnE0 graph is divided into three stages and the scaling exponents of each stage are estimated.In the third stage,NBT,KBT,and NKBT show different shapes of P-E loops(square,slanted and pinched,respectively).Although,almost similar slopes in the third stage are obtained from the lnA versus lnE0 graphs of KBT and NKBT,the formation of pinched P-E loop of NKBT is discussed based on the current-time curve under a complete cycle of the applied electric field.The shape of the P-E loop also affects the recoverable energy storage density(Wrec)of the material.Similar to the scaling of A,the variation of lnWrec with lnE0 of NBT,KBT and NKBT are examined.Interestingly,three stages are only noticed in the lnWrec-lnE0 curve of pinched P-E loop(NKBT),whereas lnWrec linearly increases with lnE0 for square and slanted P-E loop.Such type of behavior of Wrec of NKBT is explained based on the reversible domain switching mechanism of the pinched P-E loop.展开更多
Dielectric films are critical components in the fabrication of capacitors. However, their reliance on petroleum-derived polymers presents significant environmental challenges. To address this issue, we report on a hig...Dielectric films are critical components in the fabrication of capacitors. However, their reliance on petroleum-derived polymers presents significant environmental challenges. To address this issue, we report on a high-performance biomass-based dielectric material derived from vanillin(VA), a renewable aromatic aldehyde. Vanillin was first esterified to synthesize vanillin methacrylate(VMA), which was then copolymerized with methyl methacrylate(MMA) via free-radical polymerization to yield P(VMA-MMA). By crosslinking the aldehyde groups in VMA with the amine groups in the polyether amine D400(PEA), we fabricated a series of P(VMA-MMA)@PEA dielectric films with precisely tunable crosslinking densities. The unique molecular structure of vanillin, featuring both a benzene ring and an ester group, facilitates strong δ-π interactions and dipolar polarization, synergistically enhancing energy storage density while minimizing dielectric loss. At an optimal P(VMA-MMA) ratio of 1:10and 80% theoretical crosslinking degree, the dielectric constant reaches 3.4 at 10^(-3 )Hz, while the breakdown strength reaches 670.2 MV/m. Furthermore, the film exhibits an energy storage density of 7.1 J/cm3at 500 MV/m while maintaining a charge-discharge efficiency exceeding 90%.This study demonstrates a green and reliable strategy for designing biomass-based dielectric materials and opens new avenues for the development of eco-friendly energy-storage technologies.展开更多
Conventionally,interface effects between polymers and fillers are essential for determining the breakdown strength and energy storage density of polymer-based dielectric composites.In this study,we found that interfac...Conventionally,interface effects between polymers and fillers are essential for determining the breakdown strength and energy storage density of polymer-based dielectric composites.In this study,we found that interface effects between different fillers have similar behavior.BN and Ba TiO3 fiber composite fillers with three different interface bonding strengths were successfully achieved by controlling composite processes(BT-fiber/BN<BT-fiber@BN<BT-fiber&BN),and introduced into a polyimide(PI)matrix to form composite films.Considerably enhanced breakdown strength and energy storage density were obtained in BT-fiber&BN/PI composites owing to strong interface bonding,compared to other two composite fillers,which are well supported by the data from the finite element simulation.Specifically,PI composites with only 3 wt%BT-fiber&BN possess an optimized energy storage density of approximately 4.25 J/cm^(3)at 4343 k V/cm.These results provide an effective way for adjusting and improving the energy storage properties of polymer-based composites.展开更多
Optimizing the high-temperature energy storage characteristics of energy storage dielectrics is of great significance for the development of pulsed power devices and power control systems.Selecting a polymer with a hi...Optimizing the high-temperature energy storage characteristics of energy storage dielectrics is of great significance for the development of pulsed power devices and power control systems.Selecting a polymer with a higher glass transition temperature(T_(g))as the matrix is one of the effective ways to increase the upper limit of the polymer operating temperature.However,current high-T_(g)polymers have limitations,and it is difficult to meet the demand for high-temperature energy storage dielectrics with only one polymer.For example,polyetherimide has high-energy storage efficiency,but low breakdown strength at high temperatures.Polyimide has high corona resistance,but low high-temperature energy storage efficiency.In this work,combining the advantages of two polymer,a novel high-T_(g)polymer fiber-reinforced microstructure is designed.Polyimide is designed as extremely fine fibers distributed in the composite dielectric,which will facilitate the reduction of high-temperature conductivity loss for polyimide.At the same time,due to the high-temperature resistance and corona resistance of polyimide,the high-temperature breakdown strength of the composite dielectric is enhanced.After the polyimide content with the best high-temperature energy storage characteristics is determined,molecular semiconductors(ITIC)are blended into the polyimide fibers to further improve the high-temperature efficiency.Ultimately,excellent high-temperature energy storage properties are obtained.The 0.25 vol%ITIC-polyimide/polyetherimide composite exhibits high-energy density and high discharge efficiency at 150℃(2.9 J cm^(-3),90%)and 180℃(2.16 J cm^(-3),90%).This work provides a scalable design idea for high-performance all-organic high-temperature energy storage dielectrics.展开更多
SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum ...SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum and kaolin as the raw materials,Co_(2)O_(3)as the additive via pressureless graphite-buried sintering method in this study.Influences of Co_(2)O_(3)on the microstructure and properties of SiC composite ceramics for solar absorber and storage integration were studied.The results indicate that sample D2(5wt%Co_(2)O_(3))sintered at 1480℃exhibits optimal performances for 119.91 MPa bending strength,93%solar absorption,981.5 kJ/kg(25-800℃)thermal storage density.The weight gain ratio is 12.58 mg/cm2after 100 h oxidation at 1000℃.The Co_(2)O_(3)can decrease the liquid phase formation temperature and reduce the viscosity of liquid phase during sintering.The liquid with low viscosity not only promotes the elimination of pores to achieve densification,but also increases bending strength,solar absorption,thermal storage density and oxidation resistance.A dense SiO_(2) layer was formed on the surface of SiC after 100 h oxidation at 1000℃,which protects the sample from further oxidation.However,excessive Co_(2)O_(3)will make the microstructure loose,which is disadvantageous to the performances of samples.展开更多
Dielectric and energy storage properties of PbOSrO-Na_(2)O-Nb_(2)O_(5)-SiO_(2)(PSNNS) thin films with annealing temperature from 700 to 850 ℃ were investigated by measuring their capacitance-electric filed curve and ...Dielectric and energy storage properties of PbOSrO-Na_(2)O-Nb_(2)O_(5)-SiO_(2)(PSNNS) thin films with annealing temperature from 700 to 850 ℃ were investigated by measuring their capacitance-electric filed curve and hysteresis loops.The results show that the highest dielectric constant and energy density are 81.2 and 17.0 J·cm^(-3),respectively,which is obtained in the sample with annealing temperature of 800 ℃.Annealed from 700 to800 ℃,the dielectric constant and energy storage performance of PSNNS films are continuously improved.However,with annealing temperature up to 850 ℃,their dielectric constant decreases,which might be related with the removal of interfacial defects as a function of annealing temperature.Defect is one of the causes of space charge phenomenon,resulting in the increase in dielectric constant.Moreover,the micro structure analysis by X-ray diffraction(XRD) and transmission electron microscope(TEM) indicates that the change of crystallization phase and interfacial polarization takes responsibility to the results.展开更多
Rapid urbanization has led to dramatic changes in urban forest structures and functions, and consequently affects carbon(C) storage in cities. In this study, field surveys were combined with high resolution images to ...Rapid urbanization has led to dramatic changes in urban forest structures and functions, and consequently affects carbon(C) storage in cities. In this study, field surveys were combined with high resolution images to investigate the variability of C storage of urban forests in Changchun, Northeast China. The main objectives of this study were to quantify the C storage of urban forests in Changchun City, Northeast China and understand the effects of forest type and urbanization on C storage of urban forests. The results showed that the mean C density and the total C storage of urban forests in Changchun were 4.41 kg/m2 and 4.74 × 108 kg, respectively. There were significant differences in C density among urban forest types. Landscape and relaxation forest(LF) had the highest C density with 5.41 kg/m2, while production and management forest(PF) had the lowest C density with 1.46 kg/m2. These differences demonstrate that urban forest type is an important factor needed to be considered when the C storage is accurately estimated. Further findings revealed significant differences in different gradients of urbanization, and the mean C density decreased from the first ring(6.99 kg/m2) to the fourth ring(2.87 kg/m2). The total C storage increased from the first ring to the third ring. These results indicate that C storage by urban forests will be significantly changed during the process of urbanization. The results can provide insights for decision-makers and urban planners to better understand the effects of forest type and urbanization on C storage of urban forests in Changchun, and make better management plans for urban forests.展开更多
Extensive usage of highly conductive carbon materials with large specific surface area(e.g.,carbon nanotubes,CNTs)in lithium ion batteries(LIBs),especially as current collector of anodes,suffers from low initial coulo...Extensive usage of highly conductive carbon materials with large specific surface area(e.g.,carbon nanotubes,CNTs)in lithium ion batteries(LIBs),especially as current collector of anodes,suffers from low initial coulombic efficiency(ICE),large interfacial resistance,and severe embrittlement,as the large specific surface area often results in severe interfacial decomposition of the electrolyte and the formation of thick and fluffy solid electrolyte interphase(SEI)during cycling of LIBs.Herein,we demonstrate that when the CNT-based current collector and Na foil(which are being stacked intimately upon each other)are being placed in Na+-based organic electrolyte,local redox reaction between the Na foil and the electrolyte would occur spontaneously,generating a thin and homogeneous NaF-based passivating layer on the CNTs.More importantly,we found that owing to the weak solvation behaviors of Na+in the organic electrolyte,the resulting passivation layer,which is rich in NaF,is thin and dense;when used as the anode current collector in LIBs,the pre-existing passivating layer can function effectively in isolating the anode from the solvated Li+,thus suppressing the formation of bulky SEI and the destructive intercalation of solvated Li+.The relevant half-cell(graphite as anode)exhibits a high ICE of 92.1%;the relevant pouch cell with thus passivated CNT film as current collectors for both electrodes(LiCoO_(2)as cathode,graphite as anode)displays a high energy density of 255 Wh kg^(-1),spelling an increase of 50%compared with that using the conventional metal current collectors.展开更多
Temperate and high-latitude forests are carbon sinks and play pivotal roles in offsetting greenhouse gas emissions of CO2.However,uncertainty still exists for subtropical forests,especially in monsoon-prevalent easter...Temperate and high-latitude forests are carbon sinks and play pivotal roles in offsetting greenhouse gas emissions of CO2.However,uncertainty still exists for subtropical forests,especially in monsoon-prevalent eastern Asia.Earlier studies have depended on remote sensing,ecosystem modeling,carbon fluxes,or single period forest surveys to estimate carbon sequestration capacities,and the results vary significantly.This study was designed to utilize multi-period forest survey data to explore spatial-dynamics of biomass storage in subtropical forests of China.Jiangxi province,a region with over 60%subtropical forest cover,was selected as the case study site and is located in central east China.Based on forest inventory data 1984-2013,and the stock-difference and biomass expansion factor methods,the carbon storage and density,of arboreal forests,economic forests,bamboo forests,woodlands and shrubberies were estimated.The results show that carbon storage increased from 159.1 Tg C in 1988 to 276.1 TgC in 2013,making up 3.1-3.8%of carbon stored throughout China.Among the four types of forests,the amount of carbon stored was as follows:arboreal forest>economic forest>bamboo forest>woodland and shrubbery.Arboreal forests accounted for 64.0-79.4%of the total.Forest carbon density increased from 21.2 Mg C ha-1 in 1984 to26.2 Mg C ha-1 in 2013,equal to 61.2-70.2%of the average carbon density of China’s forests in the same period.Forest carbon storage in Jiangxi will reach 355.5 Tg C and 535.8 Tg C in 2020 and 2030,respectively,and forest carbon density is predicted to be 31.9 Mg C ha-1and 46.4 Mg C ha-1,respectively.As one of the few studies using multi-period data tracking biomass dynamics in Jiangxi province,the findings of this study may be used as a reference for other research.Using Jiangxi as a case study underlies the fact that subtropical forests in China have great carbon sequestration potential and have fundamental significance to offset global environmental change effects.展开更多
Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on...Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on compact and portable pulsed power supplies,the National Key Laboratory of Transient Physics(NKLTP)recently developed a pulsed power supply consisting of a set of compact pulse-forming units(PFU),each with a capacitor energy storage of 220 kJ.This integrated PPS comes with a complete system configuration,a miniature compact structure,a high rate of repetition,and high power,with energy storage density exceeding 1.2 MJ/m^(3).This paper describes the device-level design of the unit,the system layout,the control system,the thermal management system,and the experimental results of the pulsed power supply.The experimental results verified the good reliability of the PPS at high repetition rates with each unit module delivering an output current of more than 100 kA.Additionally,flexible current pulse shapes can be formed by setting the charging voltage and the trigger sequence of the PFUs.The pulse forming network(PFN)developed from these PFUs was successfully applied to electromagnetic launch.展开更多
CO_(2) hydrate-based sequestration in submarine sediments shows great potential for carbon emission reduction.Considering the proportional relationship of CO_(2) and water for hydrates formation,their existing ratio l...CO_(2) hydrate-based sequestration in submarine sediments shows great potential for carbon emission reduction.Considering the proportional relationship of CO_(2) and water for hydrates formation,their existing ratio largely determines the CO_(2) sequestration density and phase state.Here,this work focuses on determining the optimal ratio of CO_(2) to seawater in sediments simulated with 20-40 mesh(0.42-0.85 mm) quartz sand,in order to maximize CO_(2) hydrate conversion in sediments.The results show that the conversion rate of CO_(2) hydrate increases with the initial water saturation,reaching 15.3%at 80% initial water saturation.The optimal CO_(2) hydrate formation occurs at 30% initial water saturation,with the corresponding CO_(2) storage density in hydrate form of 33.09 kg·m^(-3) and the hydrate saturation of 22.3%.However,CO_(2) hydrate conversion rate is <10%,which implies that most CO2 still exists in liquid state,despite the presence of free water.The total CO_(2) sequestration density is negatively correlated with the initial water saturation,and at 10% initial water saturation,398.73 kg·m^(-3) of CO_(2) is sequestered,of which only 18.02 kg·m^(-3) is hydrated.Additionally,the lower initial water saturation corresponds to the shorter time to achieve t_(90) of CO_(2) consumption,and the water conversion rate to hydrate reaches 90% at 10% initial water saturation.In summary,adjusting the volume ratio of liquid CO_(2) to seawater can effectively increase the sequestration amount of CO_(2) hydrates,but methods to increase CO_(2) conversion to hydrate still need to be established.展开更多
基金supported by Science and Technology Major Project of the Hall of Science and Technology of Fujian (No. 2012NZ0001)the Project of National Natural Science Fund of China (No.30671664)
文摘The mid-subtropical forest is one of the biggest sections of subtropical forest in China and plays a vital role in mitigating climate change by sequestering carbon.Studies have examined carbon storage density(CSD) distribution in temperate forests. However, our knowledge of CSD in subtropical forests is limited. In this study, Jiangle County was selected as a study case to explore geographic variation in CSD. A spatial heterogeneity analysis by semivariogram revealed that CSD varied at less than the mesoscale(approximately 2000–3000 m). CSD distribution mapped using Kriging regression revealed an increasing trend in CSD from west to east of the study area.Global spatial autocorrelation analysis indicated that CSD was clustered at the village level(at 5% significance).Some areas with local spatial autocorrelation were detected by Anselin Local Moran's I and Getis-Ord G*. A geographically weighted regression model showed different impacts on the different areas for each determinant. Generally, diameter at breast height, tree height, and stand density had positive correlation with CSD in Jiangle County, but varied substantially in magnitude by location.In contrast, coefficients of elevation and slope ranged from negative to positive. Based on these results, we propose certain measures to increase forest carbon storage,including increasing forested area, improving the quality of the current forests, and promoting reasonable forest management decisions and harvesting strategies. The established CSD model emphasizes the important role of midsubtropical forest in carbon sequestration and provides useful information for quantifying mid-subtropical forest carbon storage.
基金the National Natural Science Foundation of China under Grant No.51332003 and 51372171。
文摘Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3BiFeO_(3)-x%Mn(x=0,0.5,1.5,2,3)thin films via sol-gel method.Mn ions of divalent valence combine with oxygen vacancies,forming defect complex,which results in marked decline in leakage current and obvious enhancement in breakdown strength.A high energy storage density~47.6 J cm^(-3)and good efficiency~65.68%are simultaneously achieved in 2%Mn doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor.Moreover,the 2%Mn-doped thin film exhibits excellent thermal stability in wide operating temperature range(35–115℃)and strong fatigue endurance behaviors after 108 cycles.The above results demonstrate that 2%Mn-doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor with superior energy storage performances is a potential candidate for electrostatic energy storage.
基金National Natural Science Foundation of China,Grant/Award Number:52107025。
文摘Metallised film capacitors(MFC)can operate under much higher voltage compared to the foil capacitor due to their self-healing(SH)properties,which caters to their application with high energy storage density requirement.Excellent results were achieved on the enhancement of the energy storage density of the dielectric material,whereas the SH properties of the modified material were less concerned.In the present study,the simultaneous improvement of the energy storage density and the SH properties were proposed,by constructing double-layer metallised films of polypropylene(PP)and pol-ymethyl methacrylate(PMMA).The breakdown strength of the PP/PMMA first increased and then decreased with the rising thickness of the PMMA layer.The dielectric constant was also raised because of the introduced ester groups.The highest energy storage density of 5.93 J/cm3 was obtained,which was 62.47%higher than the neat PP,whereas the dielectric loss was maintained around 0.01.The SH properties of PP/PMMA were systematically evaluated,that the SH energy decreased with the increasing PMMA ratio,and the equivalent conductivity at the SH point of the PP/PMMA decreased to only 1%of the neat PP,which largely benefit the stability of the MFC with reduced tem-perature rise.
基金National Natural Science Foundation of China,Grant/Award Numbers:52077163,52107025。
文摘In this study,the authors proposed a promising structure design,the micro-crosslinked polypropylene(PP),to enhance the high-temperature energy storage density.With the grafting of 1,6,7,12-tetrachlorinated perylene-N-2-aminoethyl acrylate-Nʹ-dodecylamine-3,4,9,10-tetracarboxylic bisimide(PTCDA)onto PP molecules,the obtained PP-g-PTCDA achieved a superior energy storage density of 2.34 J/cm^(3)at 120℃ with the discharge efficiency above 90%,which was 585%higher than that of neat PP.The great enhancement,on the one hand,originated from the micro-crosslinked structure,since the restricted molecular motion can lead to the suppression of electrons'hopping across the molecular chains.On the other hand,deep traps were also introduced in PP-g-PTCDA,which restricted the electrons'hopping along the molecular chains simultaneously.This work provided an orientation to enhance the energy storage density at an elevated temperature of 120℃.
基金supported by the Slovenian Research Agency(Nos.P2-0091,J2-2510,N2-0187,N2-0149,and P1-0125)the Swiss National Science Foundation(Lead Agency Grant No.192047)the Region Hauts-de-France(Projects TERRA(AAP STARS-N°21002758)and TRANSITION(CPER MANIFEST-N°22006563)).
文摘Ensuring reliable and safe operation of high-power electronic devices necessitates the development of high-quality dielectric nano-capacitors with high recoverable energy density(URec)and efficiency(η)at low applied electric fields(E)/voltages.In this work,we demonstrate ultra-high URec andηat low E<500 kV/cm in as-grown epitaxial relaxor ferroelectric(RFE)PMN-33PT films,rivaling those typically achieved in state-of-the-art RFE and antiferroelectric(AFE)materials.The high energy storage properties were achieved using a synergistic strategy involving large polarization,a giant built-in potential/imprint(five times higher than the coercive field),and AFE like behavior.The structural,chemical,and electrical investigations revealed that these achievements mainly arise from the effects of strain,dipole defects,and chemical composition.For instance,at low E,the capacitors exhibit under 160 kV/cm(i.e.,8 V)and 400 kV/cm(i.e.,20 V),respectively,an ultra-highΔP(45μC/cm^(2)and 60μC/cm^(2)),UE=URec/E(21 J·MV/cm^(2)and 17 J·MV/cm^(2)),and UF=URec/(1-η)(20 J/cm^(3)and 47 J/cm^(3))with a robust charge-discharge fatigue endurance and outstanding frequency and thermal stability.Additionally,the designed films exhibit outstanding energy storage performance at higher E up to 2 MV/cm(ΔP≈78μC/cm^(2),UE≈17.3 J·MV/cm^(2)and UF≈288 J/cm^(3))due to their low leakage current density.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.11864004 and 52072080)The author also thanks to the fund(Grant No.20KF-16)from the Key Laboratory of New Processing Technology for Nonferrous Metal&Materials,Ministry of Education/Guangxi Key Laboratory of Optical and Electronic Materials and Devices,Guilin University of Technology,Guilin(541004),China.
文摘The NaNbO_(3) antiferroelectrics have been considered as a potential candidate for dielectric capacitorsapplications. However, the high-electric-field-unstable antiferroelectric phase resulted in low energystorage density and efficiency. Herein, good energy storage properties were realized in (1-x)NaNbO_(3)- xNaTaO_(3) ceramics, by building a new phase boundary. As a result, a high recoverable energy density(Wrec) of 2.2 J/cm3 and efficiency (h) of 80.1% were achieved in 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic at300 kV/cm. The excellent energy storage performance originates from an antiferroelectric-paraelectricphase boundary with simultaneously high polarization and low hysteresis, by tailoring the ratio ofantiferroelectric and paraelectric phases. Moreover, the 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic also exhibitedgood temperature and frequency stability, together with excellent charge-discharge performance. Theresults pave a good way of designing new NaNbO_(3)-based antiferroelectrics with good energy storageperformance.
基金supported by the National Nature Science Foundation of China(Grant No.51902167)Zhejiang Province Nature Science Foundation of China(Grant No.LY21E020002)+1 种基金Ningbo Nature Science Foundation of China(Grant No.2019A610001)Key Laboratory of Engineering Dielectrics and Its Application(Harbin University of Science and Technology),Ministry of Education.
文摘Inspired by increasing demand of advanced pulsed power capacitors,the development of lead-free dielectric ceramic capacitors with high energy storage density and temperature-insensitive performance are extremely crucial.Herein,the lead-free relaxor ferroelectric ceramics based on(1-x)(Na_(0.5)Bi_(0.5))0.6Sr_(0.4)TiO_(3-x)Sr_(0.7)La_(0.2)ZrO_(3)[abbreviated as(1-x)NBST-xSLZ]are prepared by the solid-state reaction route.The large recoverable energy density(Wrec)of 3.45 J/cm^(3)and efficiency(h)of 90.1%are simultaneously realized in 0.86NBST-0.14SLZ ceramic due to increased breakdown strength.Furthermore,both the Wrec and h of 0.86NBST-0.14SLZ ceramic display superior of thermal stability(20e180C),frequency stability(1e1000 Hz),and cycle stability(10^(4))within a satisfactory range of variation.In addition,the 0.86NBST-0.14SLZ ceramic can also achieve a large current density(CD)of 625 A/cm^(2),an ultrahigh power density(PD)of 50 MW/cm^(3)and a fast discharge rate(t0.90)of 160.8 ns at 160 kV/cm.These results demonstrate that the 0.86NBST-0.14SLZ ceramic could be a highly competitive and ecofriendly relaxor ferroelectric material for next-generation pulsed power capacitors.
基金supported by Ministero de Ciencia y Tecnología under Grant No. AYA 2007-67287
文摘We introduce a technique for increasing density in optical data storage systems. This technique is based on the use of a superresolving filter at the pupil of a confocal readout system. The main characteristic of this confocal readout system is that the light beam traverses twice through the pupil filter. We describe how to analyze the system performance for general filters, but we focus the study on filters with no focus displacement. Although the storage density attainable depends on the filter characteristics, we show that the storage density can be easily duplicated.
文摘The Ba_(0.3)Sr_(0.6)Ca_(0.1)TiO_(3)(BSCT)powder was prepared through the solid-state reaction.And then preparing ceramic samples with quantitative doped-Bi_(2)O_(3)·3TiO_(2) and diferent doped-MgO.X-ray diffractometer(XRD)and scanning electron microscopy(SEM)were used to investigate the phase compositions,distribution and morphology of the ceramic samples.SM-11J49 capacitance measurement instrument and CS2674A pressure tester were used to measure the dieletric properties of the samples.The results show that the compactness and the dielectric constant of the ceramics increases first and then decreases when the doped MgO content was changed from 1.5 to 4.5 wt.%.The trend of breakdown strength is characterized by M-shaped pattern with the increase of doped-MgO content.Calculation results demonstrate that when the doped-MgO content is 2.0%,the samples have the highest energy storage density.
基金Author SA gratefully acknowledges the financial support pro-vided by the CSIR-EMRII(Ref.No.0194/NS)SERB,Department of Science and Technology(CRG/2020/001509)India to carry out this work.Author KB acknowledges DST-INSPIRE,India(Fellowship Code No.IF160462)for financial assistance.
文摘In this work,the dependency of the polarization(P)-electric field(E)loop area A of lead free ferro-electrics Na_(0.5)Bi_(0.5)TiO_(3)(NBT), K_(0.5)Bi_(0.5)TiO_(3)(KBT),and Na_(0.25)K_(0.25)Bi_(0.5)TiO_(3)(NKBT)on the amplitude(E0)of the electric field is studied.Based on the nature of the hysteresis loop with increasing E0,the lnA versus lnE0 graph is divided into three stages and the scaling exponents of each stage are estimated.In the third stage,NBT,KBT,and NKBT show different shapes of P-E loops(square,slanted and pinched,respectively).Although,almost similar slopes in the third stage are obtained from the lnA versus lnE0 graphs of KBT and NKBT,the formation of pinched P-E loop of NKBT is discussed based on the current-time curve under a complete cycle of the applied electric field.The shape of the P-E loop also affects the recoverable energy storage density(Wrec)of the material.Similar to the scaling of A,the variation of lnWrec with lnE0 of NBT,KBT and NKBT are examined.Interestingly,three stages are only noticed in the lnWrec-lnE0 curve of pinched P-E loop(NKBT),whereas lnWrec linearly increases with lnE0 for square and slanted P-E loop.Such type of behavior of Wrec of NKBT is explained based on the reversible domain switching mechanism of the pinched P-E loop.
基金supported by the National Natural Science Foundation of China(No.52203011).
文摘Dielectric films are critical components in the fabrication of capacitors. However, their reliance on petroleum-derived polymers presents significant environmental challenges. To address this issue, we report on a high-performance biomass-based dielectric material derived from vanillin(VA), a renewable aromatic aldehyde. Vanillin was first esterified to synthesize vanillin methacrylate(VMA), which was then copolymerized with methyl methacrylate(MMA) via free-radical polymerization to yield P(VMA-MMA). By crosslinking the aldehyde groups in VMA with the amine groups in the polyether amine D400(PEA), we fabricated a series of P(VMA-MMA)@PEA dielectric films with precisely tunable crosslinking densities. The unique molecular structure of vanillin, featuring both a benzene ring and an ester group, facilitates strong δ-π interactions and dipolar polarization, synergistically enhancing energy storage density while minimizing dielectric loss. At an optimal P(VMA-MMA) ratio of 1:10and 80% theoretical crosslinking degree, the dielectric constant reaches 3.4 at 10^(-3 )Hz, while the breakdown strength reaches 670.2 MV/m. Furthermore, the film exhibits an energy storage density of 7.1 J/cm3at 500 MV/m while maintaining a charge-discharge efficiency exceeding 90%.This study demonstrates a green and reliable strategy for designing biomass-based dielectric materials and opens new avenues for the development of eco-friendly energy-storage technologies.
基金the Natural Science Foundation of China(No.51462028)Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(NJYT-17-A10,NJYT-17-B09)。
文摘Conventionally,interface effects between polymers and fillers are essential for determining the breakdown strength and energy storage density of polymer-based dielectric composites.In this study,we found that interface effects between different fillers have similar behavior.BN and Ba TiO3 fiber composite fillers with three different interface bonding strengths were successfully achieved by controlling composite processes(BT-fiber/BN<BT-fiber@BN<BT-fiber&BN),and introduced into a polyimide(PI)matrix to form composite films.Considerably enhanced breakdown strength and energy storage density were obtained in BT-fiber&BN/PI composites owing to strong interface bonding,compared to other two composite fillers,which are well supported by the data from the finite element simulation.Specifically,PI composites with only 3 wt%BT-fiber&BN possess an optimized energy storage density of approximately 4.25 J/cm^(3)at 4343 k V/cm.These results provide an effective way for adjusting and improving the energy storage properties of polymer-based composites.
基金funded by National Natural Science Foundation of China(No.U20A20308,52177017 and 51977050)Heilongjiang Province Natural Science Foundation of China(No.ZD2020E009)+3 种基金China Postdoctoral Science Foundation(No.2020T130156)Heilongjiang Postdoctoral Financial Assistance(No.LBHZ18098)Fundamental Research Foundation for Universities of Heilongjiang Province(No.2019-KYYWF-0207 and 2018-KYYWF-1624)University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province(No.UNPYSCT-2020177)
文摘Optimizing the high-temperature energy storage characteristics of energy storage dielectrics is of great significance for the development of pulsed power devices and power control systems.Selecting a polymer with a higher glass transition temperature(T_(g))as the matrix is one of the effective ways to increase the upper limit of the polymer operating temperature.However,current high-T_(g)polymers have limitations,and it is difficult to meet the demand for high-temperature energy storage dielectrics with only one polymer.For example,polyetherimide has high-energy storage efficiency,but low breakdown strength at high temperatures.Polyimide has high corona resistance,but low high-temperature energy storage efficiency.In this work,combining the advantages of two polymer,a novel high-T_(g)polymer fiber-reinforced microstructure is designed.Polyimide is designed as extremely fine fibers distributed in the composite dielectric,which will facilitate the reduction of high-temperature conductivity loss for polyimide.At the same time,due to the high-temperature resistance and corona resistance of polyimide,the high-temperature breakdown strength of the composite dielectric is enhanced.After the polyimide content with the best high-temperature energy storage characteristics is determined,molecular semiconductors(ITIC)are blended into the polyimide fibers to further improve the high-temperature efficiency.Ultimately,excellent high-temperature energy storage properties are obtained.The 0.25 vol%ITIC-polyimide/polyetherimide composite exhibits high-energy density and high discharge efficiency at 150℃(2.9 J cm^(-3),90%)and 180℃(2.16 J cm^(-3),90%).This work provides a scalable design idea for high-performance all-organic high-temperature energy storage dielectrics.
基金Funded by the National Key R&D Program of China(No.2018YFB1501002)。
文摘SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum and kaolin as the raw materials,Co_(2)O_(3)as the additive via pressureless graphite-buried sintering method in this study.Influences of Co_(2)O_(3)on the microstructure and properties of SiC composite ceramics for solar absorber and storage integration were studied.The results indicate that sample D2(5wt%Co_(2)O_(3))sintered at 1480℃exhibits optimal performances for 119.91 MPa bending strength,93%solar absorption,981.5 kJ/kg(25-800℃)thermal storage density.The weight gain ratio is 12.58 mg/cm2after 100 h oxidation at 1000℃.The Co_(2)O_(3)can decrease the liquid phase formation temperature and reduce the viscosity of liquid phase during sintering.The liquid with low viscosity not only promotes the elimination of pores to achieve densification,but also increases bending strength,solar absorption,thermal storage density and oxidation resistance.A dense SiO_(2) layer was formed on the surface of SiC after 100 h oxidation at 1000℃,which protects the sample from further oxidation.However,excessive Co_(2)O_(3)will make the microstructure loose,which is disadvantageous to the performances of samples.
基金financially supported by the National Natural Science Foundation of China (No.51477012)Beijing Nova Program (No.xx2016046)。
文摘Dielectric and energy storage properties of PbOSrO-Na_(2)O-Nb_(2)O_(5)-SiO_(2)(PSNNS) thin films with annealing temperature from 700 to 850 ℃ were investigated by measuring their capacitance-electric filed curve and hysteresis loops.The results show that the highest dielectric constant and energy density are 81.2 and 17.0 J·cm^(-3),respectively,which is obtained in the sample with annealing temperature of 800 ℃.Annealed from 700 to800 ℃,the dielectric constant and energy storage performance of PSNNS films are continuously improved.However,with annealing temperature up to 850 ℃,their dielectric constant decreases,which might be related with the removal of interfacial defects as a function of annealing temperature.Defect is one of the causes of space charge phenomenon,resulting in the increase in dielectric constant.Moreover,the micro structure analysis by X-ray diffraction(XRD) and transmission electron microscope(TEM) indicates that the change of crystallization phase and interfacial polarization takes responsibility to the results.
基金Under the auspices of Excellent Young Scholars of Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences(No.DLSYQ13004)Chinese Academy of Sciences/State Administration of Foreign Experts Affairs International Partnership Program for Creative Research Teams(No.KZZD-EW-TZ-07-09)
文摘Rapid urbanization has led to dramatic changes in urban forest structures and functions, and consequently affects carbon(C) storage in cities. In this study, field surveys were combined with high resolution images to investigate the variability of C storage of urban forests in Changchun, Northeast China. The main objectives of this study were to quantify the C storage of urban forests in Changchun City, Northeast China and understand the effects of forest type and urbanization on C storage of urban forests. The results showed that the mean C density and the total C storage of urban forests in Changchun were 4.41 kg/m2 and 4.74 × 108 kg, respectively. There were significant differences in C density among urban forest types. Landscape and relaxation forest(LF) had the highest C density with 5.41 kg/m2, while production and management forest(PF) had the lowest C density with 1.46 kg/m2. These differences demonstrate that urban forest type is an important factor needed to be considered when the C storage is accurately estimated. Further findings revealed significant differences in different gradients of urbanization, and the mean C density decreased from the first ring(6.99 kg/m2) to the fourth ring(2.87 kg/m2). The total C storage increased from the first ring to the third ring. These results indicate that C storage by urban forests will be significantly changed during the process of urbanization. The results can provide insights for decision-makers and urban planners to better understand the effects of forest type and urbanization on C storage of urban forests in Changchun, and make better management plans for urban forests.
基金financially supported by the National Key Research and Development Program of China(2022YFB4002103)the National Natural Science Foundation of China(22279107)。
文摘Extensive usage of highly conductive carbon materials with large specific surface area(e.g.,carbon nanotubes,CNTs)in lithium ion batteries(LIBs),especially as current collector of anodes,suffers from low initial coulombic efficiency(ICE),large interfacial resistance,and severe embrittlement,as the large specific surface area often results in severe interfacial decomposition of the electrolyte and the formation of thick and fluffy solid electrolyte interphase(SEI)during cycling of LIBs.Herein,we demonstrate that when the CNT-based current collector and Na foil(which are being stacked intimately upon each other)are being placed in Na+-based organic electrolyte,local redox reaction between the Na foil and the electrolyte would occur spontaneously,generating a thin and homogeneous NaF-based passivating layer on the CNTs.More importantly,we found that owing to the weak solvation behaviors of Na+in the organic electrolyte,the resulting passivation layer,which is rich in NaF,is thin and dense;when used as the anode current collector in LIBs,the pre-existing passivating layer can function effectively in isolating the anode from the solvated Li+,thus suppressing the formation of bulky SEI and the destructive intercalation of solvated Li+.The relevant half-cell(graphite as anode)exhibits a high ICE of 92.1%;the relevant pouch cell with thus passivated CNT film as current collectors for both electrodes(LiCoO_(2)as cathode,graphite as anode)displays a high energy density of 255 Wh kg^(-1),spelling an increase of 50%compared with that using the conventional metal current collectors.
基金The work was supported by the National Natural Science Foundation of China(Grant Number:41463005)Key research and development program of Jiangxi province(Grant Number:20181ACG70021).
文摘Temperate and high-latitude forests are carbon sinks and play pivotal roles in offsetting greenhouse gas emissions of CO2.However,uncertainty still exists for subtropical forests,especially in monsoon-prevalent eastern Asia.Earlier studies have depended on remote sensing,ecosystem modeling,carbon fluxes,or single period forest surveys to estimate carbon sequestration capacities,and the results vary significantly.This study was designed to utilize multi-period forest survey data to explore spatial-dynamics of biomass storage in subtropical forests of China.Jiangxi province,a region with over 60%subtropical forest cover,was selected as the case study site and is located in central east China.Based on forest inventory data 1984-2013,and the stock-difference and biomass expansion factor methods,the carbon storage and density,of arboreal forests,economic forests,bamboo forests,woodlands and shrubberies were estimated.The results show that carbon storage increased from 159.1 Tg C in 1988 to 276.1 TgC in 2013,making up 3.1-3.8%of carbon stored throughout China.Among the four types of forests,the amount of carbon stored was as follows:arboreal forest>economic forest>bamboo forest>woodland and shrubbery.Arboreal forests accounted for 64.0-79.4%of the total.Forest carbon density increased from 21.2 Mg C ha-1 in 1984 to26.2 Mg C ha-1 in 2013,equal to 61.2-70.2%of the average carbon density of China’s forests in the same period.Forest carbon storage in Jiangxi will reach 355.5 Tg C and 535.8 Tg C in 2020 and 2030,respectively,and forest carbon density is predicted to be 31.9 Mg C ha-1and 46.4 Mg C ha-1,respectively.As one of the few studies using multi-period data tracking biomass dynamics in Jiangxi province,the findings of this study may be used as a reference for other research.Using Jiangxi as a case study underlies the fact that subtropical forests in China have great carbon sequestration potential and have fundamental significance to offset global environmental change effects.
基金financial support from the National Key Laboratory of Transient Physics,Nanjing University of Science and Technology(Grant No.6142604230101)Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant Nos.KYCX20_0321 and KYCX20_0322).
文摘Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on compact and portable pulsed power supplies,the National Key Laboratory of Transient Physics(NKLTP)recently developed a pulsed power supply consisting of a set of compact pulse-forming units(PFU),each with a capacitor energy storage of 220 kJ.This integrated PPS comes with a complete system configuration,a miniature compact structure,a high rate of repetition,and high power,with energy storage density exceeding 1.2 MJ/m^(3).This paper describes the device-level design of the unit,the system layout,the control system,the thermal management system,and the experimental results of the pulsed power supply.The experimental results verified the good reliability of the PPS at high repetition rates with each unit module delivering an output current of more than 100 kA.Additionally,flexible current pulse shapes can be formed by setting the charging voltage and the trigger sequence of the PFUs.The pulse forming network(PFN)developed from these PFUs was successfully applied to electromagnetic launch.
基金financially supported by the National Natural Science Foundation of China (22378424,22127812)the Science Foundation of China University of Petroleum Beijing,China (2462023BJRC017)。
文摘CO_(2) hydrate-based sequestration in submarine sediments shows great potential for carbon emission reduction.Considering the proportional relationship of CO_(2) and water for hydrates formation,their existing ratio largely determines the CO_(2) sequestration density and phase state.Here,this work focuses on determining the optimal ratio of CO_(2) to seawater in sediments simulated with 20-40 mesh(0.42-0.85 mm) quartz sand,in order to maximize CO_(2) hydrate conversion in sediments.The results show that the conversion rate of CO_(2) hydrate increases with the initial water saturation,reaching 15.3%at 80% initial water saturation.The optimal CO_(2) hydrate formation occurs at 30% initial water saturation,with the corresponding CO_(2) storage density in hydrate form of 33.09 kg·m^(-3) and the hydrate saturation of 22.3%.However,CO_(2) hydrate conversion rate is <10%,which implies that most CO2 still exists in liquid state,despite the presence of free water.The total CO_(2) sequestration density is negatively correlated with the initial water saturation,and at 10% initial water saturation,398.73 kg·m^(-3) of CO_(2) is sequestered,of which only 18.02 kg·m^(-3) is hydrated.Additionally,the lower initial water saturation corresponds to the shorter time to achieve t_(90) of CO_(2) consumption,and the water conversion rate to hydrate reaches 90% at 10% initial water saturation.In summary,adjusting the volume ratio of liquid CO_(2) to seawater can effectively increase the sequestration amount of CO_(2) hydrates,but methods to increase CO_(2) conversion to hydrate still need to be established.
