MIL-100(V) derived porous vanadium oxide/carbon microspheres with oxygen defects and intercalated water molecules as high-performance cathode for aqueous zinc ion battery

The development of aqueous zinc ion battery cathode materials with high capacity and high magnification is still a challenge.Herein,porous vanadium oxide/carbon(p-VO_(x)@C,mainly VO_(2) with a small amount of V_(2)O_(3)) core/shell microspheres with oxygen vacancies are facilely fabricated by using a vanadium-based metal-organic framework(MIL-100(V)) as a sacrificial template.This unique structure can improve the conductivity of the VO_(x),accelerate electrolyte diffusion,and suppress structural collapse during circulation.Subsequently,H_(2)O molecules are introduced into the interlayer of VO_(x) through a highly efficient in-situ electrochemical activation process,facilitating the intercalation and diffusion of zinc ions.After the activation,an optimal sample exhibits a high specific capacity of 464.3 mA h g^(-1) at0.2 A g^(-1) and 395.2 mA h g^(-1) at 10 A g^(-1),indicating excellent rate performance.Moreover,the optimal sample maintains a capacity retention of about 89.3% after 2500 cycles at 10 A g^(-1).Density functional theory calculation demonstrates that the presence of oxygen vacancies and intercalated water molecules can significantly reduce the diffusion barrier for zinc ions.In addition,it is proved that the storage of zinc ions in the cathode is achieved by reversible intercalation/extraction during the charge and discharge process through various ex-situ analysis technologies.This work demonstrates that the p-VO_(x)@C has great potential for applications in aqueous ZIBs after electrochemical activation.

Kinetic-Thermodynamic Promotion Engineering toward High-Density Hierarchical and Zn-Doping Activity-Enhancing ZnNiO@CF for High-Capacity Desalination

Despite the promising potential of transition metal oxides(TMOs)as capacitive deionization(CDI)electrodes,the actual capacity of TMOs electrodes for sodium storage is significantly lower than the theoretical capacity,posing a major obstacle.Herein,we prepared the kinetically favorable Zn_(x)Ni_(1−x)O electrode in situ growth on carbon felt(Zn_(x)Ni_(1−x)O@CF)through constraining the rate of OH^(−)generation in the hydrothermal method.Zn_(x)Ni_(1−x)O@CF exhibited a high-density hierarchical nanosheet structure with three-dimensional open pores,benefitting the ion transport/electron transfer.And tuning the moderate amount of redox-inert Zn-doping can enhance surface electroactive sites,actual activity of redox-active Ni species,and lower adsorption energy,promoting the adsorption kinetic and thermodynamic of the Zn_(0.2)Ni_(0.8)O@CF.Benefitting from the kinetic-thermodynamic facilitation mechanism,Zn_(0.2)Ni_(0.8)O@CF achieved ultrahigh desalination capacity(128.9 mgNaCl g^(-1)),ultra-low energy consumption(0.164 kW h kgNaCl^(-1)),high salt removal rate(1.21 mgNaCl g^(-1) min^(-1)),and good cyclability.The thermodynamic facilitation and Na^(+)intercalation mechanism of Zn_(0.2)Ni_(0.8)O@CF are identified by the density functional theory calculations and electrochemical quartz crystal microbalance with dissipation monitoring,respectively.This research provides new insights into controlling electrochemically favorable morphology and demonstrates that Zn-doping,which is redox-inert,is essential for enhancing the electrochemical performance of CDI electrodes.

Negative magnetoresistance in the antiferromagnetic semimetal V_(1/3)TaS_(2)

Intercalated transition metal dichalcogenides(TMDCs)attract much attention due to their rich properties and potential applications.In this article,we grew successfully high-quality V_(1/3)TaS_(2) crystals by a vapor transport method.We measured the magnetization,longitudinal resistivityρxx(T,H),Hall resistivityρxy(T,H),as well as performed calculations of the electronic band structure.It was found that V_(1/3)TaS_(2) is an A-type antiferromagnet with the Neel temperature T_(N)=6.20 K,and exhibits a negative magnetoresistance(MR)near T_(N).Both band structure calculations and Hall resistivity measurements demonstrated it is a magnetic semimetal.

Changes in terrestrial surface dry and wet conditions on the Loess Plateau(China) during the last half century

This paper, using a revised Penman-Monteith model, computed the terrestrial surface humidity index of the Loess Plateau （China） based on climatic factors of monthly mean temperature, maximum temperature, minimum temperature, relative humidity, precipitation, wind speed and sunshine duration observed on the plateau from 1961 to 2008. The temporal-spatial distribution, anomaly distribution and sub-regional temporal variations of the terrestrial surface dry and wet conditions were analyzed as well. The results showed a decreasing trend in the annual average surface humidity from the southeast to the northwest in the research anna. Over the period of 1961-2008, an aridification tendency appeared sharply in the central interior region of the Loess Plateau, and less sharply in the middle part of the region. The border region showed the weakest tendency ol; aridification. It is clear that aridification diffused in all directions from the interior region. The spatial anomaly distribution of the terrestrial surface dry and wet conditions on the Loess Plateau can be divided into three key areas： the southern, western and eastern regions. The terrestrial annual humidity index displayed a significantly descending trend and showed remarkable abrupt changes from wet to dry in the years 1967, 1977 and 1979. In the above mentioned three key areas for dry and wet conditions, the terrestrial annual humidity index exhibited a fluctuation period of 3-4 years, while in the southern region, a fluctuation period of 7-8 years existed at the same time.

Armoring Black Phosphorus Anode with Stable Metal–Organic‑Framework Layer for Hybrid K‑Ion Capacitors

Potassium-ion capacitors(KICs)are promising for sustainable and eco-friendly energy storage technologies,yet their slow reaction kinetics and poor cyclability induced by large K-ion size are a major obstacle toward practical applications.Herein,by employing black phosphorus nanosheets(BPNSs)as a typical high-capacity anode material,we report that BPNS anodes armored with an ultrathin oriented-grown metal–organic-framework(MOF)interphase layer(BPNS@MOF)exhibit regulated potassium storage behavior for highperformance KICs.The MOF interphase layers as protective layer with ordered pores and high chemical/mechanical stability facilitate K ion diffusion and accommodate the volume change of electrode,beneficial for improved reaction kinetics and enhanced cyclability,as evidenced by substantial characterizations,kinetics analysis and DFT calculations.Consequently,the BPNS@MOF electrode as KIC anodes exhibits outstanding cycle performance outperforming most of the reported state-of-art KICs so far.

Large Magnetoresistance and Nontrivial Berry Phase in Nb_(3)Sb Crystals with A15 Structure

Compounds with the A15 structure have attracted extensive attention due to their superconductivity and nontrivial topological band structures.We have successfully grown Nb_(3)Sb single crystals with the A15 structure and systematically measured the longitudinal resistivity,Hall resistivity and quantum oscillations in magnetization.Similar to other topological trivial/nontrivial semimetals,Nb_(3)Sb exhibits large magnetoresistance(MR)at low temperatures(717%,2 K and 9 T),unsaturating quadratic field dependence of MR and up-turn behavior in ρ_(xx)(T)curves under magnetic field,which is considered to result from a perfect hole-electron compensation,as evidenced by the Hall resistivity measurements.The nonzero Berry phase obtained from the de-Hass van Alphen(dHvA)oscillations demonstrates that Nb_(3)Sb is topologically nontrivial.These results indicate that Nb_(3)Sb superconductor is also a semimetal with large MR and nontrivial Berry phase.This indicates that Nb_(3)Sb may be another platform to search for the Majorana zero-energy mode.

Magnetoresistance and Kondo Effect in Nodal-Line Semimetal VAs_(2)

We performed calculations of the electronic band structure and the Fermi surface,measured the longitudinal resistivity ρxx(T,H),Hall resistivity ρxy(T,H),and magnetic susceptibility as a function of temperature at various magnetic fields for VAs_(2) with a monoclinic crystal structure.The band structure calculations show that VAs_(2) is a nodal-line semimetal when spin-orbit coupling is ignored.The emergence of a minimum at around11 K in ρxx(T) measured at H=0 demonstrates that some additional magnetic impurities(V^(4+),S=1/2)exist in VAs_(2) single crystals,inducing Kondo scattering,evidenced by both the fitting of ρxx(T) data and the susceptibility measurements.It is found that a large positive magnetoresistance(MR) reaching 649% at 10 K and 9 T,its nearly quadratic field dependence,and a field-induced up-turn behavior of ρxx(T) also emerge in VAs_(2),although MR is not so large due to the existence of additional scattering compared with other topological nontrivial/trivial semimetals.The observed properties are attributed to a perfect charge-carrier compensation,which is evidenced by both the calculations relying on the Fermi surface and the Hall resistivity measurements.These results indicate that the compounds containing V(3d^(3)4s^(2)) element can be as a platform for studying the influence of magnetic impurities to the topological properties.

2022年长江流域重大干旱发展过程中西太平洋副热带高压的多维度异常特征

2022年长江流域发生了罕见的夏秋冬连旱.此次干旱是伏秋季降水异常偏少和气温异常偏高叠加形成的复合型干旱,与冬季干旱连在一起的超长事件;其中8月全流域的高温干旱异常特征最为显著.以往关于西太平洋副热带高压(简称西太副高)的异常变化对长江流域高温热浪和干旱的影响的相关研究主要侧重于纬向异常这种单一维度的异常,而较少关注其经向、厚度、面积、持续时间的多个维度异常;且单一维度的异常不足以刻画其作为主控环流因子对极端高温干旱事件的影响.为了揭示西太副高的多维度异常特征对此次长江流域重大干旱的影响,本文重点分析了干旱发展过程中西太副高的多个维度异常特征.结果表明,在整个干旱发展过程中,8月西太副高在500 hPa上纬向偏西异常最为显著,无明显的经向异常.覆盖长江流域的面积为历年同期最大.在垂直方向上自低层往高层不断西伸;400~200 h Pa上西太副高与南亚高压位置相互联通,以高压坝的形式覆盖长江流域,西太副高的厚度异常深厚.通过与历史同期8月不同程度干旱年份进行对比分析,结果发现,只有当西太副高的空间异常持续维持,才能造成流域严重的高温干旱.

西北地区气候暖湿化的研究进展与展望

西北地区地理位置特殊,气候变化独特,形成机理复杂,对社会和自然环境的影响突出.尤其,自21世纪初有研究提出西北气候从暖干向暖湿转型的科学认识后,其气候变化问题引起了社会各界的普遍关注,也兴起了对西北气候变化趋势、驱动机制及影响的广泛研究,多年来已积累了大量的研究成果.然而,由于以往不同研究所用资料的类型、序列长度和时空分辨率不同,所关注的时段和区域不同,认识问题的视角和维度不同,使得存在一些分歧认识或者相悖结论.鉴于此,本研究通过系统梳理西北地区气候变化研究的历史经纬,归纳已有的研究成果,综合考虑不同视角和维度,划分了西北地区增暖与干湿变化科学认识的6个阶段;概括了西北暖湿化的驱动机制;评估了暖湿化对生态、农业及水资源等的影响;预估了未来暖湿变化趋势及其存在的可能风险;提出未来研究需要从大气、水文及生态等多学科相互作用角度探讨气候暖湿化的驱动机制、暖湿化背景下极端天气气候事件的变化特征、地表水分循环对暖湿化的响应特征、暖湿化与水文和生态的耦合机制、暖湿化对水安全、生态安全及粮食安全带来的机遇和风险,以及“双碳”(碳达峰、碳中和)目标下西北地区未来气候变化趋势等重点科学问题上取得突破.

西北地区气候湿化趋势的新特征

21世纪初有研究提出西北气候暖湿化,但由于当时变湿时段短、变幅小,对此观点有不少存疑,并且对暖湿化的趋势发展、持续时间及影响程度等问题缺乏明确结论.本研究通过构建变湿综合指数,利用多元数据,系统分析了西北暖湿化的时空特征.研究表明,在百年尺度上,西北西部和东部温度均经历了20世纪40年代和60年代至今的两个增暖期,且当前的暖期更强;西部与东部的降水在很多时期呈跷跷板变化,但21世纪开始西部与东部同时进入增湿期.1961年以来西北西部基本为一致变湿趋势,1987年以来更为显著;而东部在1961~1997年呈干化趋势,1997年也转为湿化趋势.西部的温度、降水和干燥度变化一致性较好,大多时段以冷干和暖湿为主;而东部变化的一致性较差,21世纪之前很少出现暖湿时段,直至21世纪暖湿配置才较为频繁.西北地区温度呈现空间一致的增加特征,且变暖程度逐渐增强;降水则呈西增东减的空间变化,但西增东减的分界线近3个气候态时段以来持续东扩.西北地区降水、干燥度和变湿综合指数均表现为非线性增强,变湿的增强、东扩征兆显著,21世纪以来尤为突出.不过,当前气候暖湿化并没有改变基本的气候形态,但如果未来气候趋势持续当前的增强特征,对基本气候形态的改变并非没有可能.气候变湿的增强、东扩特征可能是21世纪以来西风环流和东亚夏季风环流协同增强作用的结果.

Climatic Warming and Humidification in the Arid Region of Northwest China: Multi-Scale Characteristics and Impacts on Ecological Vegetation

The climatic warming and humidification observed in the arid region of Northwest China(ARNC) and their impacts on the ecological environment have become an issue of concern. The associated multi-scale characteristics and environmental responses are currently poorly understood. Using data from satellite remote sensing, field observations, and the Coupled Model Intercomparison Project phase 6, this paper systematically analyzes the process and scale characteristics of the climatic warming and humidification in the ARNC and their impacts on ecological vegetation. The results show that not only have temperature and precipitation increased significantly in the ARNC over the past 60 years, but the increasing trend of precipitation is also obviously intensifying. The dryness index, which comprehensively considers the effects of precipitation and temperature, has clearly decreased, and the trend in humidification has increased. Spatially, the trend of temperature increase has occurred over the entire region, while 93.4% of the region has experienced an increase in precipitation, suggesting a spatially consistent climatic warming and humidification throughout the ARNC. Long-term trends and interannual changes in temperature and precipitation dominate the changes in climatic warming and humidification. Compared to interannual variations in temperature, the trend change of temperature contributes more to the overall temperature change. However, the contribution of interannual variations in precipitation is greater than that of the precipitation trend to the overall precipitation change. The current climatic warming and humidification generally promote the growth of ecological vegetation. Since the 1980 s,82.4% of the regional vegetation has thrived. The vegetation index has a significant positive correlation with precipitation and temperature. However, it responds more significantly to interannual precipitation variation, although the vegetation response varies significantly under different types of land use. The warming and humidification of the climate in the ARNC are probably related to intensifications of the westerly wind circulation and ascending air motions.They are expected to continue in the future, although the strength of the changes will probably be insufficient to significantly change the basic climate pattern in the ARNC. The results of this study provide helpful information for decision making related to China's "Belt and Road" development strategies.

Templated spherical coassembly strategy to fabricate MoS_(2)/C hollow spheres with physical/chemical polysulfides trapping for lithium-sulfur batteries

Rational design of advanced polar hosts with high sulfur loading,facilitated ionic/electronic transport and effectively suppressed shuttling effect has great potential for high performance lithium-sulfur batteries,yet it remains challenging.Here we propose a novel templated spherical coassembly strategy to fabricate the MoS_(2)/C hollow spheres as an efficient sulfur host material.The unique hollow structure provides enough interior space for accommodating a substantial amount of sulfur,and effectively suppresses the diffusion of dissolved polysulfides by both physical confinement and chemical adsorption.Moreover,the ionic transport as well as the ability to mitigate volume variation upon cycling is also improved,thereby maximizing the utilization of sulfur.Owing to these merits,when evaluated as a sulfur host for lithiumsulfur batteries,the MoS_(2)/C hollow spheres exhibit appealing electrochemical performance with an impressive specific capacity of 1082 mA hg^(-1)at 0.1 C,excellent rate capability and superior cycling stability with a low fading rate of 0.04%per cycle.

Large unsaturated positive and negative magnetoresistance in Weyl semimetal TaP

After successfully growing single-crystal Ta P, we measured its longitudinal resistivity(ρxx) and Hall resistivity(ρyx) at magnetic fields up to 9 T in the temperature range of 2-300 K. At 8 T, the magnetoresistance(MR) reached 3.28 × 105% at 2 K, 176%at 300 K. Neither value appeared saturated. We confirmed that Ta P is a hole-electron compensated semimetal with a low carrier concentration and high hole mobility of μh=3.71 × 10~5cm^2/V s, and found that a magnetic-field-induced metal-insulator transition occurs at room temperature. Remarkably, because a magnetic field(H) was applied in parallel to the electric field(E), a negative MR due to a chiral anomaly was observed and reached-3000% at 9 T without any sign of saturation, either, which is in contrast to other Weyl semimetals(WSMs). The analysis of the Shubnikov-de Haas(Sd H) oscillations superimposed on the MR revealed that a nontrivial Berry's phase with a strong offset of 0.3958, which is the characteristic feature of charge carriers enclosing a Weyl node. These results indicate that Ta P is a promising candidate not only for revealing fundamental physics of the WSM state but also for some novel applications.

Lean blowout characteristics of spray flame in a multi-swirl staged combustor under different fuel decreasing rates

Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative for safe operation.The objective of this work is to evaluate the effects of fuel decreasing rates and pressure drops of the injector on LBO performances in a multiswirl staged combustor equipped with an airblast injector.A set of hardware and control system was developed to realize a user-defined fuel supply law.High-speed imaging was applied to record complete LBO processes under the conditions of linear fuel reduction and stable airflow.Partical Image Velocimetry(PIV)and Planar Mie(PMie)scattering were used to acquire the flow fields and spray fields under non-reacting conditions.Experimental results have shown that LBO limits extend to leaner conditions as the pressure drop of the injector increases.With an increase of the fuel decreasing rate,the exhaust temperature before flame extinction increases,and the LBO Fuel-to-Air-Ratio(FAR)decreases.The time evolution of the integral CH*intensity conforms to a linear function during the LBO process.Proper Orthogonal Decomposition(POD)was used to analyze the dynamic characteristics of lean-burn flames.Under different fuel decreasing rates and pressure drops of the injector,flames close to LBO present similar modal spatial distributions,alternately appearing axial,radial,high-order axial,and high-order radial oscillations.

Bulk superconductivity in the Dirac semimetal TlSb

A feasible strategy for realizing the Majorana fermions is searching for a simple compound with both bulk superconductivity and Dirac surface states.In this paper,we perform calculations of electronic band structure,the Fermi surface,and the surface states,and measure the resistivity,magnetization,and specific heat of a TlSb compound with a CsCl-type structure.The band structure calculations show that TlSb is a Dirac semimetal when spin-orbit coupling is considered.TlSb is first determined to be a type-Ⅱsuperconductor with T_(c)=4.38 K,Hc1(0)=148 Oe,H_(c2)(0)=1.12 T,andκ_(GL)=10.6.We also confirm that TlSb is a moderately coupled s-wave superconductor.Although we cannot determine the band near the Fermi level EF that is responsible for superconductivity,its coexistence with topological surface states implies that the TlSb compound may be a simple material platform to realize the fault-tolerant quantum computations.

Metamagnetic transitions and anomalous magnetoresistance in EuAg4As2 crystals

In this work,we systematically studied the magnetic and transport properties of EuAg4As2 single crystals.It was found that the two antiferromagnetic transitions(TN1=10 K and TN2=15 K)were driven to lower temperatures by an applied magnetic field.Below TN1,two successive metamagnetic transitions were observed when a magnetic field was applied in the ab plane(H//abplane).For both H//ab and H//c,EuAg4As2 showed a positive,unexpectedly large magnetoresistance(up to 202%)in lower magnetic fields below TN1,and a large negative magnetoresistance(up to-78%)at high fields/intermediate temperatures,thus presenting potential applications in magnetic sensors.Finally,the magnetic phase diagrams of EuAg4As2 were constructed for both H//ab and H//c using the resistivity and magnetisation data.