Hydraulic fracturing is a commonly used stimulation technique for production optimization in various geological formations such as tight sandstone,shale,coal bed methane,and heat extraction in geothermal reservoirs.Br...Hydraulic fracturing is a commonly used stimulation technique for production optimization in various geological formations such as tight sandstone,shale,coal bed methane,and heat extraction in geothermal reservoirs.Breakdown pressure is a vital component in hydraulic fracture job design,which is affected by various parameters including rock strength and depth.Various methods including modelling and experimental approaches exist to quantify the breakdown pressure.There have been many strategies to reduce this pressure for efficient and economical hydraulic fracture jobs,especially when this pressure exceeds pump capacity.This study provides a detailed review of breakdown pressure in terms of fundamentals,influencing factors,and estimation approaches.In addition,different strategies are also presented to reduce the breakdown pressure along with cost analysis.Lastly,research gaps pertinent to this area are highlighted for emphasis in future research.Specifically,it has been found that high breakdown pressure is associated with challenges,but there are no comprehensive techniques and strategies to lower this pressure in formations with very high in situ stress profiles or complicated tectonic settings.Developing such methods is important to minimize operational failures,lower costs and reduce the environmental risks during reservoir exploitation.This study reviews the fundamentals,influencing factors,and estimation methods of breakdown pressure and provides a deep understanding of the strategies for its reduction.The study also presents the cost analyses,and highlights research gaps for future investigation.展开更多
By the random distribution of metals in a single phase,entropy engineering is applied to construct dense neighboring active centers with diverse electronic and geometric structures,realizing the continuous optimizatio...By the random distribution of metals in a single phase,entropy engineering is applied to construct dense neighboring active centers with diverse electronic and geometric structures,realizing the continuous optimization of multiple primary reactions for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).Many catalysts developed through entropy engineering have been built in nearly equimolar ratios to pursue high entropy,hindering the identification of the active sites and potentially diluting the concentration of real active sites while weakening their electronic interactions with reaction intermediates.Herein,this work proposes an entropy-engineering strategy in metal nanoparticle-embedded nitrogen carbon electrocatalysts,implemented by entropy-engineered Prussian blue analogs(PBA)as precursors to enhance the catalytic activity of primary Cu-Fe active sites.Through the introduction of the micro-strains driven by entropy engineering,density functional theory(DFT)calculations and geometric phase analysis(GPA)using Lorentz electron microscopy further elucidate the optimization of the adsorption/desorption of intermediates.Furthermore,the multi-dimensional morphology and the size diminishment of the nanocrystals serve to expand the electrochemical area,maximizing the catalytic activity for both ORR and OER.Notably,the Zn-air battery assembled with CuFeCoNiZn-NC operated for over 1300 h with negligible decay.This work presents a paradigm for the design of low-cost electrocatalysts with entropy engineering for multi-step reactions.展开更多
Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have be...Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four aspects.Firstly,the characteristics of several representative dual-pol radars are reviewed.Various approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological echoes.Using dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in China.The limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are summarized.The challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed.展开更多
MXenes are emerging transition metal carbides and nitrides-based 2D conductive materials.They have found wide applications in sensors due to their excellent valuable properties.This paper reviews the recent research s...MXenes are emerging transition metal carbides and nitrides-based 2D conductive materials.They have found wide applications in sensors due to their excellent valuable properties.This paper reviews the recent research status of MXene-based electrochemical(bio)sensors for detecting biomarkers,pesticides,and other aspects.The first part of this paper introduced the synthesis strategy and the effect of surface modification on various prop-erties of MXenes.The second part of this paper discussed the application of MXenes as electrode modifiers for detecting pesticides,environmental pollutants,and biomarkers such as glucose,hydrogen peroxide,etc.Hope this review will inspire more efforts toward research on MXene-based sensors to meet the growing requirements.展开更多
From July to September 2008, air samples were collected aboard the R/V XUE LONG icebreaker （Snow Dragon） as part of the 2008 Chinese National Arctic Research Expedition program. ∑20PCBs in the atmosphere ranged fro...From July to September 2008, air samples were collected aboard the R/V XUE LONG icebreaker （Snow Dragon） as part of the 2008 Chinese National Arctic Research Expedition program. ∑20PCBs in the atmosphere ranged from 6.20 to 365 pg.m^-3 with average concentration 117±107 pg.m^- 3. Congener profiles in all samples showed a prevalence of tri- and tetrachlorobiphenyls, dominated by PCB-18, PCB-28, PCB-44 and PCB-52. Along the cruise, the highest concentration was observed over the Sea of Japan and the lowest over the high-latitude Arctic Ocean. Air mass backward trajectories indicated that samples with relatively high levels of PCBs might have been influenced by atmospheric transport of these chemicals from primary and/ or secondary sources. PCB-18 displayed a significant correlation between vapor pressure and ambient temperature along the cruise, but there was no such correlation between gas-phase concentration and latitude. This suggests that atmospheric PCB-18 was related to volatilization from the earth surface during summer 2008, during which temperatures were relatively high. PCB-52 presented a significant correlation between gas-phase concentration and latitude, but no such correlation was found between vapor pressure and ambient temperature, indicating that atmospheric PCB-52 detected during the cruise might be attributed directly to atmospheric transport from source regions. In the Arctic, levels of PCB-52 in the floating sea ice region were higher than those measured in the open sea area and pack ice region. Intense ice retreat during summer 2008 might have enhanced the volatilization of previously accumulated PCBs from sea ice, especially those with heavier molecular weight and lower vapor pressure such as PCB-52.展开更多
The generation of runaway electrons(REs)is observed during the low-density helium ohmic plasma discharge in the Experimental Advanced Superconducting Tokamak(EAST).The growth rate of hard x-ray(HXR)is inversely propor...The generation of runaway electrons(REs)is observed during the low-density helium ohmic plasma discharge in the Experimental Advanced Superconducting Tokamak(EAST).The growth rate of hard x-ray(HXR)is inversely proportional to the line-average density.Besides,the RE generation in helium plasma is higher than that in deuterium plasma at the same density,which is obtained by comparing the growth rate of HXR with the same discharge conditions.The potential reason is the higher electron temperature of helium plasma in the same current and electron density plateau.Furthermore,two Alfvén eigenmodes driven by REs have been observed.The frequency evolution of the mode is not fully satisfied with the Alfvén scaling and when extension of the Alfvén frequency is towards 0,the high frequency branch is~50 kHz.The different spatial position of the two modes and the evolution of the helium concentration could be used to understand deviation between theoretical and experimental observation.展开更多
The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechan...The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated.Herein,under the same volume fraction and distribution conditions of graphene,molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field.Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison.The results show that the strengthening effect changes with varying the graphene sheet size.Besides the graphene dislocation blocking effect and the load-bearing effect,the deformation mechanisms change from stacking fault tetrahedron,dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size.The hardness of Cu/graphene composite,with the graphene sheet not completely covering the metal matrix,can even be higher than that of the fully covered composite.The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.展开更多
The eutectic point is a critical parameter in the phase diagrams of solid–liquid equilibrium. In this study, high-pressure differential thermal analysis(HPDTA) was utilized to measure the melting temperatures of Fe–...The eutectic point is a critical parameter in the phase diagrams of solid–liquid equilibrium. In this study, high-pressure differential thermal analysis(HPDTA) was utilized to measure the melting temperatures of Fe–C alloy(3.4–4.2 wt.% C)under 5 GPa and to plot the liquidus temperature curves spanning from hypoeutectic to hypereutectic compositions. Our results indicate that under 5 GPa, the carbon content at the eutectic point of the Fe–C alloy decreases to 3.6–3.7 wt.%C, representing a reduction of approximately 0.6 wt.% C compared to the atmospheric pressure value(4.3 wt.% C). Concurrently, the eutectic temperature rises to 1195℃, showing an elevation of 48℃relative to the atmospheric pressure condition(1147℃). Microstructural analysis, x-ray diffraction(XRD), and hardness tests further corroborate these findings, demonstrating that high pressure significantly suppresses the solubility of carbon in γ-Fe, resulting in a decrease in the eutectic carbon content. Additionally, the hardness of the Fe–C alloy under 5 GPa is increased by more than 50% compared to that of the same type of Fe–C alloy under atmospheric pressure. This study provides essential experimental data for constructing high-pressure Fe–C phase diagrams and offers valuable insights for the design of high-performance Fe-based materials under extreme conditions.展开更多
The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the...The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the grain boundaries were pinned by high-density nanosized Al_(3)(Yb,Zr)precipitates during extrusion deformation,consequently,the average grain size was significantly reduced from 232.7μm to 3.2μm.This grain refinement contributed substantially to the improvement in both strength and elongation.The ultimate tensile strength,yield strength,and elongation of the Yb/Zr modified alloy increased to 705.3 MPa,677.6 MPa,and 8.7%,respectively,representing enhancements of 16.2%,19.3%,and 112.2%compared to the unmodified alloy.Moreover,the distribution of MgZn_(2)phases along grain boundaries became more discontinuous in the Yb/Zr modified alloy,which effectively retarded the propagation of intergranular corrosion and improved the corrosion resistance.展开更多
Solid polymer electrolytes have garnered significant attention for lithium batteries because of their flexibility and safety.However,poor ionic conductivity,lithium dendrite formation,and high impedance hinder their p...Solid polymer electrolytes have garnered significant attention for lithium batteries because of their flexibility and safety.However,poor ionic conductivity,lithium dendrite formation,and high impedance hinder their practical application.In this study,a thin,flexible,3D hybrid solid electrolyte(3DHSE)is prepared by in situ thermal cross-linking polymerization with electrospun 3D nanowebs.The 3DHSE comprises Al-doped Li_(7)La_(3)Zr_(2)O_(12)(ALLZO)embedded in electrospun poly(vinylidene fluoride-cohexafluoropropylene)(PVDF-HFP)nonwoven 3D nanowebs and an in situ cross-linked polyethylene oxide(PEO)-based solid polymer electrolyte.The 3DHSE exhibits high tensile strength(6.55 MPa),a strain of 40.28%,enhanced ionic conductivity(7.86×10^(-4) S cm^(-1)),and a superior lithium-ion transference number(0.76)to that of the PVDF-HFP-based solid polymer electrolyte(PSPE).This enables highly stable lithium plating/stripping cycling for over 900 h at 25℃ with a current density of 0.2 mA cm^(-2).The LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NCM811)/3DHSE/Li cell has a higher capacity(140.56 mAh g^(-1) at 0.1 C)than the NCM811/PSPE/Li cell(124.88 mAh g^(-1) at 0.1 C)at 25℃.The 3DHSE enhances mechanical properties,stabilizes interfacial contact,improves ion transport,prevents NCM811 cracking,and significantly boosts cycling performance.This study highlights the potential of the 3DHSE as a candidate for advanced lithium polymer battery technology.展开更多
This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepa...This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepared by melt-spinning following vacuum arc-melting.For the as-prepared and annealed samples,the carbon existed in the La_(2)Fe_(2)Si_(2)C and NaZn_(13)-type La(Fe,Si)_(13)(denoted by 1:13)phases,respectively.During the annealing process,the C atoms inhibited the diffusion reaction and depressed the generation of 1:13 phase,reducing mass fraction of the 1:13 phase in annealed La_(1.2)Fe_(11.6)Si_(1.4)Cx compounds.The introduction of carbon resulted in lattice expansion and increased the Curie temperature(T_(C))from 192 K to 273 K with x=0.5.The first-order magnetic transition was gradually transformed into the second-order magnetic transition with increasing carbon content,which induced the significant reduction of thermal and magnetic hysteresis,as well as the maximum magnetic entropy change and adiabatic temperature change vary from 18.92 J/(kg·K)to 4.60 J/(kg·K)and from 4.9 K to 2.2 K under an applied field change of 0-2 T.The results demonstrate that interstitial carbon doping is an effective strategy to improve the magnetocaloric performance of La(Fe,Si)_(13)alloys.展开更多
Particle-to-particle dry graphene coatings on Ni-rich layered oxide materials are proposed for highenergy lithium-ion batteries(LIBs)to mitigate the inherent and engineering challenges related to the electrochemically...Particle-to-particle dry graphene coatings on Ni-rich layered oxide materials are proposed for highenergy lithium-ion batteries(LIBs)to mitigate the inherent and engineering challenges related to the electrochemically fragile surfaces,as well as limiting electrode thickness and density.Utilizing a shear stress-based coating process without supplementary solvent or heat treatment,graphene sheets derived from graphene powder are applied onto the surface of spherical LiNi_(0.89)Co_(0.055)Mn_(0.055)O_(2)(NCM)material.This process achieves a coating thickness equivalent to or fewer than 10 layers of graphene and exposes the basal plane.The graphene-coated material increases particle hardness and mitigates degradation caused by inter-particle pressure,enabling the formation of high-density electrodes without pulverization.In the absence of additional carbon-conducting agents for the high-density composite electrode with a density of 4.0 g cm^(-3),it significantly enhances rate capability,demonstrating more than 5 times improvement by achieving 149.4 mAh g^(-1)at 2 C compared to the bare sample(28.9 mAh g^(-1)).Furthermore,the dry graphene coating enables the high areal capacity of 6.98 mAh cm^(-2).By exposing the basal plane of the graphene coating,the process enhances chemical stability,effectively inhibiting side reactions at the interface and mitigating cycle degradation.展开更多
BACKGROUND Colorectal cancer(CRC)is the second leading cause of cancer-related deaths worldwide with an alarming rise in early-onset CRC(eoCRC)over the past several decades.Unlike late-onset CRC,the drivers behind eoC...BACKGROUND Colorectal cancer(CRC)is the second leading cause of cancer-related deaths worldwide with an alarming rise in early-onset CRC(eoCRC)over the past several decades.Unlike late-onset CRC,the drivers behind eoCRC remain less clear.While certain risk factors such as obesity and smoking have demonstrated a relatively strong association with eoCRC in the literature,some studies have challenged these associations,emphasizing the need for additional studies.METHODS This cross-sectional study used de-identified data from the National Health and Nutrition Examination Survey(1999-2023),including 30321 United States adults aged 18 to 49 years.Participants with missing key variables were excluded.Standardized protocols were used to collect demographic,lifestyle,anthropo-metric[body mass index(BMI),body roundness index(BRI),waist circumference(WC)],and self-reported CRC data.Logistic regression and propensity score matching assessed associations between obesity-related parameters and eoCRC.Statistical analyses were performed in R and Stata,with P<0.05 defined as significant.RESULTS Of 30321 participants,48 received a diagnosis of eoCRC.Patients with eoCRC were older(mean age 39.96 years vs 34.36 years;P<0.001)and had higher WC and BRI.None of the eoCRC patients were heavy drinkers(P=0.006).Unadjusted models demonstrated significant associations of eoCRC with BRI quartiles,as well as BMI-defined obesity,WC,and smoking.In unadjusted models,BRI remained the strongest independent predictor;those in the highest BRI quartiles had over 10-fold greater odds of eoCRC.In fully adjusted models,BRI remained significant,but BMI-and waist-based obesity were not.CONCLUSION BRI is a stronger predictor of eoCRC risk compared to other obesity indices and is a superior tool for identifying young individuals at higher risk of CRC.展开更多
Despite significant progress in the structure and properties of porous absorbing materials,major challenges remain due to complex preparation technology,high production costs,and poor corrosion resistance.In this stud...Despite significant progress in the structure and properties of porous absorbing materials,major challenges remain due to complex preparation technology,high production costs,and poor corrosion resistance.In this study,nanowires were used as the substrate,liquid nitrogen controls ice crystal growth orientation,and ammonia gas facilitates the generation of magnetic substances.The resulting pure magnetic porous foam(PMF)material exhibits enhanced performance in absorbing electromagnetic waves(EMWs)and improved corrosion resistance.The PMF's microstructure was analyzed for its dielectric and magnetic loss characteristics.The PMF combines a porous framework,nanoscale architecture,and exclusive magnetic components to create a lightweight foam absorbent material with enhanced magnetic dissipation capabilities.Among them,the Fe_(4)N PMF demonstrates an impressive minimum reflection loss(RLmin)value of−66.8 dB at a thickness of 1.09 mm,exhibits an effective absorption bandwidth of 4.00 GHz,and shows exceptional corrosion resistance with a self-corrosion potential of−0.65 V.Moreover,the effectiveness of the Fe_(4)N PMF in absorbing intelligent EMWs has been validated through radar cross-section(RCS)simulations.In summary,this study has developed electromagnetic wave-absorbing materials with slim profiles,lightweight properties,strong absorption capabilities,and excellent corrosion resistance.These characteristics make them highly promising for microwave absorption applications.展开更多
Mimicking the hierarchical structure of the skin is one of the most important strategies in skin tissue engineering.Monolayer wound dressings are usually not able to provide several functions at the same time and cann...Mimicking the hierarchical structure of the skin is one of the most important strategies in skin tissue engineering.Monolayer wound dressings are usually not able to provide several functions at the same time and cannot meet all clinical needs.In order to maximize therapeutic efficiency,herein,we fabricated a Tri-layer wound dressing,where the middle layer was fabricated via 3D-printing and composed of alginate,tragacanth and zinc oxide nanoparticles(ZnO NPs).Both upper and bottom layers were constructed using electrospinning technique;the upper layer was made of hydrophobic polycaprolactone to mimic epidermis,while the bottom layer consisted of Soluplus■ and insulin-like growth factor-1(IGF-1)to promote cell behavior.Swelling,water vapor permeability and tensile properties of the dressings were evaluated and the Tri-layer dressing exhibited impressive antibacterial activity and cell stimulation following by the release of ZnO NPs and IGF-1.Additionally,the Tri-layer dressing led to faster healing of full-thicknesswound in ratmodel compared to monolayer and Bilayer dressings.Overall,the evidence confirmed that the Trilayer wound dressing is extremely effective for full-thickness wound healing.展开更多
Perovskite/Silicon tandem solar cells have attracted increasing attention in photovoltaic fields.However,expensive electrode materials and complex manufacturing procedures of top semitransparent perovskite solar cells...Perovskite/Silicon tandem solar cells have attracted increasing attention in photovoltaic fields.However,expensive electrode materials and complex manufacturing procedures of top semitransparent perovskite solar cells(PSCs)and conventional bottom silicon(Si)solar cells are incompatible with economical pro-duction.Single-walled carbon nanotube(SWCNT)films have been regarded as promising transparent elec-trodes because of their hydrophobic nature,earth-abundant carbon sources,mechanical robustness,and good chemical stability.Herein,we report a new and simple four-terminal tandem device with the in-tegration of SWCNT-based semitransparent PSCs and SWCNT-Si heterojunction solar cells.The employed SWCNT film is composed of high-crystallinity and small-bundled nanotubes with excellent optical trans-mittance and electric conductivity.It was adopted as the top electrode to realize semitransparent PSCs,which deliver a power conversion efficiency(PCE)of 12.02%,and the value can be further enhanced to 17.2%by introducing Spiro-OMeTAD into the SWCNT network.Interestingly,this semitransparent PSC has a bifacial feature and exhibits a bifaciality factor value of 91.1%.Moreover,the SWCNT film was trans-ferred onto the surface of a Si wafer at room temperature to achieve the SWCNT-Si device with a PCE of 16.2%.Eventually,by integrating these two solar cells,a perovskite/SWCNT-Si tandem device with an efficiency of over 22%was obtained.展开更多
Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by dire...Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by direct Sb doping method.It can be found that doping Sb into Bi_(2)Te_(3) lattice array for Bi-site replacement facilitates the generation of Sb′Te anti-site defects.This anti-site defects can increase the hole concentration and optimize electrical transport properties of Bi_(2−x)Sb_(x)Te_(3) alloys.In addition,the point defects induced by mass and stress fluctuations and the Sb impurities produced during the sintering process can enhance the multi-scale phonon scattering and reduce the lattice thermal conductivity.As a result,the Bi_(0.47)Sb_(1.63)Te_(3) sample has a maximum thermoelectric figure of merit ZT of 1.04 at 350 K.It is worth noting that the bipolar effect of Bi_(2)Te_(3)-based alloys can be weakened with the increase of Sb content.The Bi_(0.44)Sb_(1.66)Te_(3) sample has a maximum average ZT value(0.93)in the temperature range of 300–500 K,indicating that direct doping of Sb can broaden the temperature range corresponding to the optimal ZT value.This work provides an idea for developing high-performance near room temperature thermoelectric materials with a wide temperature range.展开更多
One of the significant technological challenges in safeguarding electronic devices pertains to the modulation of electromagnetic(EM)wave jamming and the recycling of defensive shields.The synergistic effect of heterod...One of the significant technological challenges in safeguarding electronic devices pertains to the modulation of electromagnetic(EM)wave jamming and the recycling of defensive shields.The synergistic effect of heterodimensional materials can effectively enable the manipulation of EM waves by altering the nanostructure.Here we propose a novel approach for upcycling by-products of silver nanowires that can fabricate shape-tunable aerogels which enable the modulation of its interaction with microwaves by heterodimensional structure of byproducts.By-product heterodimensionality was used to design EM-wave-jamming-dissipation structures and therefore two typical tunable aerogel forms were studied.The first tunable form was aerogel film,which shielded EM interference(EMI shielding effectiveness(EMI SE)>89 dB)and the second tunable form was foam,which performed dual EM functions(SE>30 dB&reflective loss(RL)<-35 dB,effective absorption bandwidth(EAB)>6.7 GHz).We show that secondary recycled aerogels retain nearly all of their EM protection properties,making this type of closed-loop cycle an appealing option.Our findings pave the way for the development of adaptive EM functions with nanoscale regulation in a green and closed-loop cycle,and they shed light on the fundamental understanding of microwave interactions with heterodimensional structures.展开更多
Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in nort...Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in northern hardwood forests along an elevation gradient of decreasing temperature and increasing soil N availability to evaluate how this critical nutrient cycling process can be expected to respond to global and regional environmental changes.Foliar N resorption proficiency(NRP)increased significantly at lower elevations for both sugar maple and American beech,the dominant species in these forests.Foliar N resorption efficiency(NRE)also decreased with increasing elevation,but only in one year.Both species exhibited strong negative relationships between NRP and soil N availability.Thus,we anticipate that with climate warming and decreasing N inputs,northern hardwood forests can be expected to exhibit stronger N conservation via foliar resorption.Both species also exhibited strong correlations between resorption efficiency of N and C,but resorption of both elements was much greater for beech than sugar maple,suggesting contrasting mechanisms of nutrient conservation between these two widespread species.展开更多
文摘Hydraulic fracturing is a commonly used stimulation technique for production optimization in various geological formations such as tight sandstone,shale,coal bed methane,and heat extraction in geothermal reservoirs.Breakdown pressure is a vital component in hydraulic fracture job design,which is affected by various parameters including rock strength and depth.Various methods including modelling and experimental approaches exist to quantify the breakdown pressure.There have been many strategies to reduce this pressure for efficient and economical hydraulic fracture jobs,especially when this pressure exceeds pump capacity.This study provides a detailed review of breakdown pressure in terms of fundamentals,influencing factors,and estimation approaches.In addition,different strategies are also presented to reduce the breakdown pressure along with cost analysis.Lastly,research gaps pertinent to this area are highlighted for emphasis in future research.Specifically,it has been found that high breakdown pressure is associated with challenges,but there are no comprehensive techniques and strategies to lower this pressure in formations with very high in situ stress profiles or complicated tectonic settings.Developing such methods is important to minimize operational failures,lower costs and reduce the environmental risks during reservoir exploitation.This study reviews the fundamentals,influencing factors,and estimation methods of breakdown pressure and provides a deep understanding of the strategies for its reduction.The study also presents the cost analyses,and highlights research gaps for future investigation.
基金supported by the National Natural Science Foundation of China(52071083,52231007,12327804,52471224)Zhuhai Fudan Innovation Institute,and the Science and Technology Commission of Shanghai Municipality(23ZR1405000).
文摘By the random distribution of metals in a single phase,entropy engineering is applied to construct dense neighboring active centers with diverse electronic and geometric structures,realizing the continuous optimization of multiple primary reactions for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).Many catalysts developed through entropy engineering have been built in nearly equimolar ratios to pursue high entropy,hindering the identification of the active sites and potentially diluting the concentration of real active sites while weakening their electronic interactions with reaction intermediates.Herein,this work proposes an entropy-engineering strategy in metal nanoparticle-embedded nitrogen carbon electrocatalysts,implemented by entropy-engineered Prussian blue analogs(PBA)as precursors to enhance the catalytic activity of primary Cu-Fe active sites.Through the introduction of the micro-strains driven by entropy engineering,density functional theory(DFT)calculations and geometric phase analysis(GPA)using Lorentz electron microscopy further elucidate the optimization of the adsorption/desorption of intermediates.Furthermore,the multi-dimensional morphology and the size diminishment of the nanocrystals serve to expand the electrochemical area,maximizing the catalytic activity for both ORR and OER.Notably,the Zn-air battery assembled with CuFeCoNiZn-NC operated for over 1300 h with negligible decay.This work presents a paradigm for the design of low-cost electrocatalysts with entropy engineering for multi-step reactions.
基金primarily supported by the National Key Research and Development Program of China(Grant Nos.2017YFC1501703 and 2018YFC1506404)the National Natural Science Foundation of China(Grant Nos.41875053,41475015 and 41322032)+2 种基金the National Fundamental Research 973 Program of China(Grant Nos.2013CB430101 and2015CB452800)the Open Research Program of the State Key Laboratory of Severe Weatherthe Key Research Development Program of Jiangsu Science and Technology Department(Social Development Program,No.BE2016732)
文摘Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four aspects.Firstly,the characteristics of several representative dual-pol radars are reviewed.Various approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological echoes.Using dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in China.The limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are summarized.The challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed.
文摘MXenes are emerging transition metal carbides and nitrides-based 2D conductive materials.They have found wide applications in sensors due to their excellent valuable properties.This paper reviews the recent research status of MXene-based electrochemical(bio)sensors for detecting biomarkers,pesticides,and other aspects.The first part of this paper introduced the synthesis strategy and the effect of surface modification on various prop-erties of MXenes.The second part of this paper discussed the application of MXenes as electrode modifiers for detecting pesticides,environmental pollutants,and biomarkers such as glucose,hydrogen peroxide,etc.Hope this review will inspire more efforts toward research on MXene-based sensors to meet the growing requirements.
基金supported by grants from the National Natural Science Foundation of China (Grant nos. 41025020, 40776001, and 41203075)Chinese Academy of Sciences (Grant no. KZCX2-YWQN506)+2 种基金the Fundamental Research Funds for the Central Universitiesfunded by the Area of Excellence Scheme under the University Grants Committee of the Hong Kong Special Administrative Region, China (Grant no. Ao E/P-04/2004)a Hong Kong Research Grants Council (Grant no. City U 160610)
文摘From July to September 2008, air samples were collected aboard the R/V XUE LONG icebreaker （Snow Dragon） as part of the 2008 Chinese National Arctic Research Expedition program. ∑20PCBs in the atmosphere ranged from 6.20 to 365 pg.m^-3 with average concentration 117±107 pg.m^- 3. Congener profiles in all samples showed a prevalence of tri- and tetrachlorobiphenyls, dominated by PCB-18, PCB-28, PCB-44 and PCB-52. Along the cruise, the highest concentration was observed over the Sea of Japan and the lowest over the high-latitude Arctic Ocean. Air mass backward trajectories indicated that samples with relatively high levels of PCBs might have been influenced by atmospheric transport of these chemicals from primary and/ or secondary sources. PCB-18 displayed a significant correlation between vapor pressure and ambient temperature along the cruise, but there was no such correlation between gas-phase concentration and latitude. This suggests that atmospheric PCB-18 was related to volatilization from the earth surface during summer 2008, during which temperatures were relatively high. PCB-52 presented a significant correlation between gas-phase concentration and latitude, but no such correlation was found between vapor pressure and ambient temperature, indicating that atmospheric PCB-52 detected during the cruise might be attributed directly to atmospheric transport from source regions. In the Arctic, levels of PCB-52 in the floating sea ice region were higher than those measured in the open sea area and pack ice region. Intense ice retreat during summer 2008 might have enhanced the volatilization of previously accumulated PCBs from sea ice, especially those with heavier molecular weight and lower vapor pressure such as PCB-52.
基金Project supported by the National Key R&D Program of China(Grant Nos.2017YFE0301205 and 2022YFE03050003)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.Y2021116)+1 种基金the National Natural Science Foundation of China(Grant Nos.12005262,12105186,12175277,and 11975271)the Users of Excellence Program of Hefei Science Center CAS(Grant No.2021HSC-UE016).
文摘The generation of runaway electrons(REs)is observed during the low-density helium ohmic plasma discharge in the Experimental Advanced Superconducting Tokamak(EAST).The growth rate of hard x-ray(HXR)is inversely proportional to the line-average density.Besides,the RE generation in helium plasma is higher than that in deuterium plasma at the same density,which is obtained by comparing the growth rate of HXR with the same discharge conditions.The potential reason is the higher electron temperature of helium plasma in the same current and electron density plateau.Furthermore,two Alfvén eigenmodes driven by REs have been observed.The frequency evolution of the mode is not fully satisfied with the Alfvén scaling and when extension of the Alfvén frequency is towards 0,the high frequency branch is~50 kHz.The different spatial position of the two modes and the evolution of the helium concentration could be used to understand deviation between theoretical and experimental observation.
基金Foundation of Northwest Institute for Nonferrous Metal Research(ZZXJ2203)Capital Projects of Financial Department of Shaanxi Province(YK22C-12)+3 种基金Innovation Capability Support Plan in Shaanxi Province(2023KJXX-083)Key Research and Development Projects of Shaanxi Province(2024GXYBXM-351,2024GX-YBXM-356)National Natural Science Foundation of China(62204207,12204383)Xi'an Postdoctoral Innovation Base Funding Program。
文摘The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated.Herein,under the same volume fraction and distribution conditions of graphene,molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field.Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison.The results show that the strengthening effect changes with varying the graphene sheet size.Besides the graphene dislocation blocking effect and the load-bearing effect,the deformation mechanisms change from stacking fault tetrahedron,dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size.The hardness of Cu/graphene composite,with the graphene sheet not completely covering the metal matrix,can even be higher than that of the fully covered composite.The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2023YFA1406200)。
文摘The eutectic point is a critical parameter in the phase diagrams of solid–liquid equilibrium. In this study, high-pressure differential thermal analysis(HPDTA) was utilized to measure the melting temperatures of Fe–C alloy(3.4–4.2 wt.% C)under 5 GPa and to plot the liquidus temperature curves spanning from hypoeutectic to hypereutectic compositions. Our results indicate that under 5 GPa, the carbon content at the eutectic point of the Fe–C alloy decreases to 3.6–3.7 wt.%C, representing a reduction of approximately 0.6 wt.% C compared to the atmospheric pressure value(4.3 wt.% C). Concurrently, the eutectic temperature rises to 1195℃, showing an elevation of 48℃relative to the atmospheric pressure condition(1147℃). Microstructural analysis, x-ray diffraction(XRD), and hardness tests further corroborate these findings, demonstrating that high pressure significantly suppresses the solubility of carbon in γ-Fe, resulting in a decrease in the eutectic carbon content. Additionally, the hardness of the Fe–C alloy under 5 GPa is increased by more than 50% compared to that of the same type of Fe–C alloy under atmospheric pressure. This study provides essential experimental data for constructing high-pressure Fe–C phase diagrams and offers valuable insights for the design of high-performance Fe-based materials under extreme conditions.
基金Project(51501228)supported by the National Natural Science Foundation of ChinaProject(202109)supported by the Open Sharing Fund for the Large-scale Instruments and Equipments of Central South University,China。
文摘The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the grain boundaries were pinned by high-density nanosized Al_(3)(Yb,Zr)precipitates during extrusion deformation,consequently,the average grain size was significantly reduced from 232.7μm to 3.2μm.This grain refinement contributed substantially to the improvement in both strength and elongation.The ultimate tensile strength,yield strength,and elongation of the Yb/Zr modified alloy increased to 705.3 MPa,677.6 MPa,and 8.7%,respectively,representing enhancements of 16.2%,19.3%,and 112.2%compared to the unmodified alloy.Moreover,the distribution of MgZn_(2)phases along grain boundaries became more discontinuous in the Yb/Zr modified alloy,which effectively retarded the propagation of intergranular corrosion and improved the corrosion resistance.
基金supported by the National Research Foundation of Korea(NRF)(no.:NRF-2020M3H4A3081874)the National Research Council of Science&Technology(NST)grant by the Korea government(MSIT)(no.:GTL24011-000)the Korea Research Institute of Chemical Technology(KRICT),Republic of Korea(no.KS2422-20).
文摘Solid polymer electrolytes have garnered significant attention for lithium batteries because of their flexibility and safety.However,poor ionic conductivity,lithium dendrite formation,and high impedance hinder their practical application.In this study,a thin,flexible,3D hybrid solid electrolyte(3DHSE)is prepared by in situ thermal cross-linking polymerization with electrospun 3D nanowebs.The 3DHSE comprises Al-doped Li_(7)La_(3)Zr_(2)O_(12)(ALLZO)embedded in electrospun poly(vinylidene fluoride-cohexafluoropropylene)(PVDF-HFP)nonwoven 3D nanowebs and an in situ cross-linked polyethylene oxide(PEO)-based solid polymer electrolyte.The 3DHSE exhibits high tensile strength(6.55 MPa),a strain of 40.28%,enhanced ionic conductivity(7.86×10^(-4) S cm^(-1)),and a superior lithium-ion transference number(0.76)to that of the PVDF-HFP-based solid polymer electrolyte(PSPE).This enables highly stable lithium plating/stripping cycling for over 900 h at 25℃ with a current density of 0.2 mA cm^(-2).The LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NCM811)/3DHSE/Li cell has a higher capacity(140.56 mAh g^(-1) at 0.1 C)than the NCM811/PSPE/Li cell(124.88 mAh g^(-1) at 0.1 C)at 25℃.The 3DHSE enhances mechanical properties,stabilizes interfacial contact,improves ion transport,prevents NCM811 cracking,and significantly boosts cycling performance.This study highlights the potential of the 3DHSE as a candidate for advanced lithium polymer battery technology.
基金supported by the National Natural Science Foundation of China(Grant No.52272263)the University Synergy Innovation Program of Anhui Province,China(Grant No.GXXT-2022-008)+2 种基金the University Natural Science Research Project of Anhui Province,China(Grant No.2024AH050145)the Youth Foundation of Anhui University of Technology(Grant No.QZ202303)the National Innovation and Entrepreneurship Training Program for College Students(Grant No.202310360018).
文摘This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepared by melt-spinning following vacuum arc-melting.For the as-prepared and annealed samples,the carbon existed in the La_(2)Fe_(2)Si_(2)C and NaZn_(13)-type La(Fe,Si)_(13)(denoted by 1:13)phases,respectively.During the annealing process,the C atoms inhibited the diffusion reaction and depressed the generation of 1:13 phase,reducing mass fraction of the 1:13 phase in annealed La_(1.2)Fe_(11.6)Si_(1.4)Cx compounds.The introduction of carbon resulted in lattice expansion and increased the Curie temperature(T_(C))from 192 K to 273 K with x=0.5.The first-order magnetic transition was gradually transformed into the second-order magnetic transition with increasing carbon content,which induced the significant reduction of thermal and magnetic hysteresis,as well as the maximum magnetic entropy change and adiabatic temperature change vary from 18.92 J/(kg·K)to 4.60 J/(kg·K)and from 4.9 K to 2.2 K under an applied field change of 0-2 T.The results demonstrate that interstitial carbon doping is an effective strategy to improve the magnetocaloric performance of La(Fe,Si)_(13)alloys.
基金supported by the Hyundai NGV and Technology Innovation Program(20010900)funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea)+1 种基金the support by BK21 FOUR(Human Tech Materials-based Global Elite Cultivation Center for Student Success)funded by the Ministry of Education(MOE,Korea)supported by the Technology Innovation Program Development Program(Grant No.20017477)funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea)。
文摘Particle-to-particle dry graphene coatings on Ni-rich layered oxide materials are proposed for highenergy lithium-ion batteries(LIBs)to mitigate the inherent and engineering challenges related to the electrochemically fragile surfaces,as well as limiting electrode thickness and density.Utilizing a shear stress-based coating process without supplementary solvent or heat treatment,graphene sheets derived from graphene powder are applied onto the surface of spherical LiNi_(0.89)Co_(0.055)Mn_(0.055)O_(2)(NCM)material.This process achieves a coating thickness equivalent to or fewer than 10 layers of graphene and exposes the basal plane.The graphene-coated material increases particle hardness and mitigates degradation caused by inter-particle pressure,enabling the formation of high-density electrodes without pulverization.In the absence of additional carbon-conducting agents for the high-density composite electrode with a density of 4.0 g cm^(-3),it significantly enhances rate capability,demonstrating more than 5 times improvement by achieving 149.4 mAh g^(-1)at 2 C compared to the bare sample(28.9 mAh g^(-1)).Furthermore,the dry graphene coating enables the high areal capacity of 6.98 mAh cm^(-2).By exposing the basal plane of the graphene coating,the process enhances chemical stability,effectively inhibiting side reactions at the interface and mitigating cycle degradation.
文摘BACKGROUND Colorectal cancer(CRC)is the second leading cause of cancer-related deaths worldwide with an alarming rise in early-onset CRC(eoCRC)over the past several decades.Unlike late-onset CRC,the drivers behind eoCRC remain less clear.While certain risk factors such as obesity and smoking have demonstrated a relatively strong association with eoCRC in the literature,some studies have challenged these associations,emphasizing the need for additional studies.METHODS This cross-sectional study used de-identified data from the National Health and Nutrition Examination Survey(1999-2023),including 30321 United States adults aged 18 to 49 years.Participants with missing key variables were excluded.Standardized protocols were used to collect demographic,lifestyle,anthropo-metric[body mass index(BMI),body roundness index(BRI),waist circumference(WC)],and self-reported CRC data.Logistic regression and propensity score matching assessed associations between obesity-related parameters and eoCRC.Statistical analyses were performed in R and Stata,with P<0.05 defined as significant.RESULTS Of 30321 participants,48 received a diagnosis of eoCRC.Patients with eoCRC were older(mean age 39.96 years vs 34.36 years;P<0.001)and had higher WC and BRI.None of the eoCRC patients were heavy drinkers(P=0.006).Unadjusted models demonstrated significant associations of eoCRC with BRI quartiles,as well as BMI-defined obesity,WC,and smoking.In unadjusted models,BRI remained the strongest independent predictor;those in the highest BRI quartiles had over 10-fold greater odds of eoCRC.In fully adjusted models,BRI remained significant,but BMI-and waist-based obesity were not.CONCLUSION BRI is a stronger predictor of eoCRC risk compared to other obesity indices and is a superior tool for identifying young individuals at higher risk of CRC.
基金financially supported by the National Natural Science Foundation of China(No.52471212)the National Key Research and Development Program(No.2022YFE0109800).
文摘Despite significant progress in the structure and properties of porous absorbing materials,major challenges remain due to complex preparation technology,high production costs,and poor corrosion resistance.In this study,nanowires were used as the substrate,liquid nitrogen controls ice crystal growth orientation,and ammonia gas facilitates the generation of magnetic substances.The resulting pure magnetic porous foam(PMF)material exhibits enhanced performance in absorbing electromagnetic waves(EMWs)and improved corrosion resistance.The PMF's microstructure was analyzed for its dielectric and magnetic loss characteristics.The PMF combines a porous framework,nanoscale architecture,and exclusive magnetic components to create a lightweight foam absorbent material with enhanced magnetic dissipation capabilities.Among them,the Fe_(4)N PMF demonstrates an impressive minimum reflection loss(RLmin)value of−66.8 dB at a thickness of 1.09 mm,exhibits an effective absorption bandwidth of 4.00 GHz,and shows exceptional corrosion resistance with a self-corrosion potential of−0.65 V.Moreover,the effectiveness of the Fe_(4)N PMF in absorbing intelligent EMWs has been validated through radar cross-section(RCS)simulations.In summary,this study has developed electromagnetic wave-absorbing materials with slim profiles,lightweight properties,strong absorption capabilities,and excellent corrosion resistance.These characteristics make them highly promising for microwave absorption applications.
基金support of Isfahan University of Medical Sciences(Project code No.#1401262).
文摘Mimicking the hierarchical structure of the skin is one of the most important strategies in skin tissue engineering.Monolayer wound dressings are usually not able to provide several functions at the same time and cannot meet all clinical needs.In order to maximize therapeutic efficiency,herein,we fabricated a Tri-layer wound dressing,where the middle layer was fabricated via 3D-printing and composed of alginate,tragacanth and zinc oxide nanoparticles(ZnO NPs).Both upper and bottom layers were constructed using electrospinning technique;the upper layer was made of hydrophobic polycaprolactone to mimic epidermis,while the bottom layer consisted of Soluplus■ and insulin-like growth factor-1(IGF-1)to promote cell behavior.Swelling,water vapor permeability and tensile properties of the dressings were evaluated and the Tri-layer dressing exhibited impressive antibacterial activity and cell stimulation following by the release of ZnO NPs and IGF-1.Additionally,the Tri-layer dressing led to faster healing of full-thicknesswound in ratmodel compared to monolayer and Bilayer dressings.Overall,the evidence confirmed that the Trilayer wound dressing is extremely effective for full-thickness wound healing.
基金supported by the National Natu-ral Science Foundation of China(Nos.62304163 and 62374128)the Key Research and Development Program of Shaanxi Province(No.2024GX-YBXM-512)+6 种基金the Young Talent Fund of Xi’an As-sociation for Science and Technology(No.959202413054)the Qinchuangyuan Cited High-level Innovation and Entrepreneurship Talent Projects(No.QCYRCXM-2022-364)the Natural Science Ba-sic Research Program of Shaanxi(No.2023-JC-QN-0471)the Open Project of State Key Laboratory of Silicon and Advanced Semi-conductor Materials(No.SKL2023-03)the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology,No.2024-KF-12)the Xidian University Specially Funded Project for Interdisciplinary Explo-ration(Nos.TZJH2024066,TZJH2024052,and TZJH2024050)the Fundamental Research Funds for the Central Universities(No.ZYTS25157).
文摘Perovskite/Silicon tandem solar cells have attracted increasing attention in photovoltaic fields.However,expensive electrode materials and complex manufacturing procedures of top semitransparent perovskite solar cells(PSCs)and conventional bottom silicon(Si)solar cells are incompatible with economical pro-duction.Single-walled carbon nanotube(SWCNT)films have been regarded as promising transparent elec-trodes because of their hydrophobic nature,earth-abundant carbon sources,mechanical robustness,and good chemical stability.Herein,we report a new and simple four-terminal tandem device with the in-tegration of SWCNT-based semitransparent PSCs and SWCNT-Si heterojunction solar cells.The employed SWCNT film is composed of high-crystallinity and small-bundled nanotubes with excellent optical trans-mittance and electric conductivity.It was adopted as the top electrode to realize semitransparent PSCs,which deliver a power conversion efficiency(PCE)of 12.02%,and the value can be further enhanced to 17.2%by introducing Spiro-OMeTAD into the SWCNT network.Interestingly,this semitransparent PSC has a bifacial feature and exhibits a bifaciality factor value of 91.1%.Moreover,the SWCNT film was trans-ferred onto the surface of a Si wafer at room temperature to achieve the SWCNT-Si device with a PCE of 16.2%.Eventually,by integrating these two solar cells,a perovskite/SWCNT-Si tandem device with an efficiency of over 22%was obtained.
基金supported by the Anhui Province Natural Science Foundation for Excellent Youth Scholars(2208085Y17)the University Synergy Innovation Program of Anhui Province(GXXT-2022-008+1 种基金GXXT-2021-022)the Anhui Key Lab of Metal Material and Processing Open Project.
文摘Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by direct Sb doping method.It can be found that doping Sb into Bi_(2)Te_(3) lattice array for Bi-site replacement facilitates the generation of Sb′Te anti-site defects.This anti-site defects can increase the hole concentration and optimize electrical transport properties of Bi_(2−x)Sb_(x)Te_(3) alloys.In addition,the point defects induced by mass and stress fluctuations and the Sb impurities produced during the sintering process can enhance the multi-scale phonon scattering and reduce the lattice thermal conductivity.As a result,the Bi_(0.47)Sb_(1.63)Te_(3) sample has a maximum thermoelectric figure of merit ZT of 1.04 at 350 K.It is worth noting that the bipolar effect of Bi_(2)Te_(3)-based alloys can be weakened with the increase of Sb content.The Bi_(0.44)Sb_(1.66)Te_(3) sample has a maximum average ZT value(0.93)in the temperature range of 300–500 K,indicating that direct doping of Sb can broaden the temperature range corresponding to the optimal ZT value.This work provides an idea for developing high-performance near room temperature thermoelectric materials with a wide temperature range.
基金supported by the National Key Research and Development Program of China(Grant 2021YFA0715600,2021YFA0717700,2018YFB2202900)National Natural Science Foundation of China(52192610,62274127,62374128)+5 种基金the Fundamental Research Funds for the Central Universities,2023 Qinchuangyuan Construction Two Chain Integration Special Project(23LLRH0043)Key Research and Development Program of Shaanxi Province(Grant 2024GX-YBXM-512)Foundation of Zhejiang Provincial Key Lab of Solar Energy Utilization&Energy Saving Technology(ZJS-OP-2020-11)GuangDong Basic and Applied Basic Research Foundation(Grant 2022A1515111220)the fund of the state Key Laboratory of Solidification Processing in NPU(Grant No.SKLSP202317)Young Elite Scientists Sponsorship Program by CAST,Doctoral Student Special Plan.
文摘One of the significant technological challenges in safeguarding electronic devices pertains to the modulation of electromagnetic(EM)wave jamming and the recycling of defensive shields.The synergistic effect of heterodimensional materials can effectively enable the manipulation of EM waves by altering the nanostructure.Here we propose a novel approach for upcycling by-products of silver nanowires that can fabricate shape-tunable aerogels which enable the modulation of its interaction with microwaves by heterodimensional structure of byproducts.By-product heterodimensionality was used to design EM-wave-jamming-dissipation structures and therefore two typical tunable aerogel forms were studied.The first tunable form was aerogel film,which shielded EM interference(EMI shielding effectiveness(EMI SE)>89 dB)and the second tunable form was foam,which performed dual EM functions(SE>30 dB&reflective loss(RL)<-35 dB,effective absorption bandwidth(EAB)>6.7 GHz).We show that secondary recycled aerogels retain nearly all of their EM protection properties,making this type of closed-loop cycle an appealing option.Our findings pave the way for the development of adaptive EM functions with nanoscale regulation in a green and closed-loop cycle,and they shed light on the fundamental understanding of microwave interactions with heterodimensional structures.
基金National Science Foundation supported this research through the Long Term Ecological Research(LTER)Grant to Hubbard Brook(NSF DEB1114804,1637685,and 2224545)by the project grant(NSF DEB,2020397).
文摘Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in northern hardwood forests along an elevation gradient of decreasing temperature and increasing soil N availability to evaluate how this critical nutrient cycling process can be expected to respond to global and regional environmental changes.Foliar N resorption proficiency(NRP)increased significantly at lower elevations for both sugar maple and American beech,the dominant species in these forests.Foliar N resorption efficiency(NRE)also decreased with increasing elevation,but only in one year.Both species exhibited strong negative relationships between NRP and soil N availability.Thus,we anticipate that with climate warming and decreasing N inputs,northern hardwood forests can be expected to exhibit stronger N conservation via foliar resorption.Both species also exhibited strong correlations between resorption efficiency of N and C,but resorption of both elements was much greater for beech than sugar maple,suggesting contrasting mechanisms of nutrient conservation between these two widespread species.
