In the gneisses from the drillhole ZK2304 of the Donghai area, there have been preserved high- and ultrahigh-pressure metamorphic mineral assemblages, a series of complicated retrogressive textures and relevant metamo...In the gneisses from the drillhole ZK2304 of the Donghai area, there have been preserved high- and ultrahigh-pressure metamorphic mineral assemblages, a series of complicated retrogressive textures and relevant metamorphic reactions. In addition to garnet, jadeititic-clinopyroxene and rutile, other peak stage (M2) minerals in some gneisses include phengite, aragonite and coesite or quartz pseudomorphs after coesite. The typical peak-stage mineral assemblages in gneisses are characterized by garnet + jadeitic-clinopyroxene + rutile + coesite, garnet + jadeitic-clinopyroxene + phengite + rutile ± coesite and garnet + jadeitic-clinopyroxene + aragonite + rutile ± coesite. The grossular content (Gro) in garnet is high and may reach 50. 1 mol%. The SiO2 content of phengite ranges from 54.37% to 54.84% with 3.54-3.57 p.f.u. Quartz pseudomorphs after coesite occur as inclusions in garnet.The gneisses of the Donghai area have been subjected to multistage recrystallization and exhibit a closewise P-T evolutional path characterized by the near-isothermal decompression. The inclusion assemblage (Hb+Ep+Bi+Pl+Qz) within garnet and other minerals has recorded a pre-peak stage (Mi) epidote amphibole fades metamorphic event. High- and ultrahigh-pressure peak metamorphism (M2) took place at T=750-860℃ and P>2.7 GPa. The symplectitic assemblages after garnet, jadeitic-clinopyroxene and rutile imply a near-isothermal decompression metamorphism (M3, M4) during the rapid exhumation. Several lines of evidence of petrography and metamorphic reactions indicate that both gneisses and eclogites have experienced ultrahigh-pressure metamorphism in the Donghai area. This research may be of great significance for an in-depth study of the metamorphism and tectonic evolution in the Su-Lu ultrahigh-pressure metamorphic belt.展开更多
Comparison of regular(diurnal,seasonal and solar cycle)variations of high-latitude,mid-latitude and low-latitude ionospheric characteristics has been provided on basis of local empirical models of the peak electron de...Comparison of regular(diurnal,seasonal and solar cycle)variations of high-latitude,mid-latitude and low-latitude ionospheric characteristics has been provided on basis of local empirical models of the peak electron density and the peak height.The local empirical models were derived from the hand-scaled ionogram data recorded by DPS-4 digisondes located at Norilsk(69°N,88°E),Irkutsk(52°N,104°E)and Hainan(19°N,109°E)for a 6-year period from December,2002 to December,2008.The technique used to build the local empirical model is described.The primary focus is diurnal-seasonal behavior under low solar activity and its change with increasing solar activity.Both common and specific features of the high-latitude(Norilsk),mid-latitude(Irkutsk)and low-latitude(Hainan)regular variations were revealed using their local empirical models.展开更多
Gd2O3 thin films as high-κ gate dielectrics were deposited directly on Si(001) substrates by magnetron sputtering at a pressure of 1.3 Pa and different temperatures. X-ray diffraction results revealed that all the ...Gd2O3 thin films as high-κ gate dielectrics were deposited directly on Si(001) substrates by magnetron sputtering at a pressure of 1.3 Pa and different temperatures. X-ray diffraction results revealed that all the films grown from 450 to 570 ℃ were crystalline, and the Gd2O3 thin films consisted of a mixture of cubic and monoclinic phases. The growth temperature was a critical parameter for the phase constituents and their relative amount. Low temperature was favorable for the formation of cubic phase while higher temperature gave rise to more monoclinic phase. All the Gd2O3 thin films grown from different temperatures exhibited acceptable electrical properties, such as low leakage current density (JL) of 10-5 A/cm^2 at zero bias with capacitance equivalent SiO2 thickness in the range of 6-13 nm. Through the comparison between films grown at 450 and 570 ℃, the existence of monoclinic phase caused an increase in JL by nearly one order of magnitude and a reduction of effective dielectric constant from 17 to 9.展开更多
Objective: To investigate the effectiveness of a high-fidelity teaching simulation based on an NLN/Jeffries simulation in the nursing education theoretical framework and its influencing factors. Methods: A high-fide...Objective: To investigate the effectiveness of a high-fidelity teaching simulation based on an NLN/Jeffries simulation in the nursing education theoretical framework and its influencing factors. Methods: A high-fidelity teaching simulation on clinical nursing practices using intelligent human analogues was conducted with 200 students, and The Simulation Design Scale, and the Student Satisfaction and Self-Confidence in Learning Scale developed by the National League for Nursing were used to evaluate the training effectiveness and its influencing factors. Results: For the high-fidelity teaching simulation, students gave scores of 4.36± 0.54 points for satisfaction and 4.33 ± 0.46 points for Self-Confidence. The students highly rated the five dimensions of teaching design, i.e., teaching objectives/information, assistance/support for students, problem solving, guided feedback, and fidelity. The teaching design was closely correlated with the satisfaction of the high-fidelity teaching simulation and self-efficacy, and the dimensions of teaching objectives/informa- tion and assistance/support for students were particularly strong predictors of teaching effectiveness. Conclusions: A high-fidelity teaching simulation based on Jeffries' theoretical framework improved student satisfaction with the simulation and their Self-Confidence. In planning simulations, teachers should take into account five characteristics, i.e., teaching objectives/information on simulation education, assistance/support for students, problem solving, guided reflection, and fidelity, to achieve better teaching effectiveness.展开更多
The Roman high(RHA) and low-Avoidance (RLA) rats were selectively bred for rapid vs poor acquisition of two-way active avoidance behavior. These lines differ in numerous behavioral traits, with RLA rats being more fea...The Roman high(RHA) and low-Avoidance (RLA) rats were selectively bred for rapid vs poor acquisition of two-way active avoidance behavior. These lines differ in numerous behavioral traits, with RLA rats being more fearful/anxious than RHA rats, and the latter being novelty-seekers and showing larger intake of, and preference for, addictive substances including ethanol (ETH). Moreover, several differences in central dopaminergic, serotonergic, and GABAergic functions have been reported in these two lines. Since those neural systems are involved in the regulation of ETH consumption, it was considered of interest to investigate: 1) the differences in ETH intake and preference between RHA and RLA rats, 2) the effects of ETH on DA release in the shell of the nucleus accumbens (AcbSh) using brain microdialysis. ETH solutions of increasing concentrations (2% - 10%) were presented on alternate days in a free choice with water. To examine ETH intake and preference stability, animals were subsequently switched to daily presentations of 10% ETH for 10 consecutive days. RHA rats consumed significantly larger amounts of ETH and displayed higher ETH preference than did RLA rats throughout the acquisition and maintenance phases. Following chronic exposure to ETH the animals were habituated to a restricted access to ETH schedule (2% ETH, 2 h per day × 4 days) before surgical implantation of a dialysis probe in the AcbSh. Under these experimental conditions, voluntary ETH intake (2%, 1 h, p.o.) produced a significant increase in accumbal DA output in RHA rats but not in their RLA counterparts. Finally, the i.p. administration of ETH (0.25 g/kg) to na?ve Roman rats produced a significant increment in accumbal DA output only in RHA rats. These results indicate that the mesolimbic dopaminergic system of RHA rats is more responsive to the effects of ETH than that of RLA rats.展开更多
In order to improve the comprehensive utilization rate of highfines sand(HFS)produced by the mine,full solid waste shotcrete(HFS-BFRS)was prepared with HFS asfine aggregate in cooperation with basaltfiber(BF).The strengt...In order to improve the comprehensive utilization rate of highfines sand(HFS)produced by the mine,full solid waste shotcrete(HFS-BFRS)was prepared with HFS asfine aggregate in cooperation with basaltfiber(BF).The strength growth characteristics of HFS-BFRS were analyzed.And thefitting equation of compressive strength growth characteristics of HFS-BFRS under the synergistic effect of multiple factors was given.And based on the orthogonal experimental method,the effects on the compressive strength,splitting tensile strength andflex-ural strength of HFS-BFRS under the action of different levels of influencing factors were investigated.The effect of three factors on the mechanical properties of HFS-BFRS,3,and 28 d,respectively,was revealed by choosing the colloidal sand ratio(C/H),basaltfiber volume fraction(BF Vol)and naphthalene high-efficiency water reducing agent(FDN)as the design variables,combined with indoor tests and theoretical analysis.The results show that the sensitivity of the three factors on compressive strength andflexural strength is C/H>FDN>BF Vol,and split-ting tensile strength is BF Vol>FDN>C/H.Finally,thefitting ratio of HFS-BFRS was optimized by the factor index method,and the rationality was verified by thefield test.For thefluidity of HFS-BFRS,the slump can be improved by 139%under the action of 1.2%FDN,which guarantees the pump-ability of HFS-BFRS.展开更多
Shock effects of 93 Grove Mountains (GRV) ordinary chondrites were studied in this work, including fracture, various types of extinction, and recrystallization of silicates observed under optical microscopy. Shock-i...Shock effects of 93 Grove Mountains (GRV) ordinary chondrites were studied in this work, including fracture, various types of extinction, and recrystallization of silicates observed under optical microscopy. Shock-induced veins and pockets show various microtextures, decomposition and phase transformation of minerals. The confirmed high-pressure polymorphs of silicates are ringwoodite, majorite, pyroxene glass and maskelynite. Based on the shock effects and assemblages of high-pressure minerals, shock stages of all of 93 GRV ehondrites were classified. In comparison with literature, the Grove Mountains meteorites have a higher fraction (23 out of 93 ) of heavily shocked samples (S4--S5). Most of the heavily shocked meteorites are L group (22 out of 23), except for one H chondrite. The distinct shock metamorphism between H and. L groups may indicate different surface properties of their parent bodies. In addition, there is relationship between petrologic types and shock stages, with most heavily shocked samples observed in equilibrated ordinary chondrites ( especially Type 5 and 6).展开更多
High(or medium)-entropy alloys(H/MEAs)are complex concentrated solid solutions prone to develop the chemical short-range orders(CSROs),as an indispensable structural constituent to make H/MEAs essentially different fr...High(or medium)-entropy alloys(H/MEAs)are complex concentrated solid solutions prone to develop the chemical short-range orders(CSROs),as an indispensable structural constituent to make H/MEAs essentially different from the traditional alloys.The CSROs are predicted to play roles in dislocation behaviors and mechanical properties.So far,the image of CSROs is built up by the theoretical modeling and computational simulations in terms of the conventional concept,i.e.,the preference/avoidance of elemental species to satisfy the short-ranged ordering in the first and the next couple of nearest-neighbor atomic shells.In these simulated CSROs,however,the structural image is missing on the atomic scale,even though the lattice periodicity does not exist in the CSROs.Further,it is pending as to the issues if and what kind of CSRO may be formed in a specific H/MEA.All these are ascribed to the challenge of experimentally seeing the CSROs.Until recently,the breakthrough does not appear to convincingly identify the CSROs in the H/MEAs by using the state-of-the-art transmission electron microscope.To be specific,the electron diffractions provide solid evidence to doubtlessly ascertain CSROs.The structure motif of CSROs is then constructed,showing both the lattice structure and species ordering occupation,along with the stereoscopic topography of the CSRO.It is suggested that the CSROs,as the first landscape along the path of development of the local chemical ordering,offer one more route to substantially develop the ordered structure on the atomic scale in the H/MEAs,parallel to the existing grain-leveled microstructure.The findings of CSROs make a step forward to understand the CSROs-oriented relationship between the microstructure and mechanical properties.This review focuses on the recent progress mainly in the experimental aspects of the identification,structure motif,and mechanical stability in CSROs,along with the chemical medium-range orders as the growing CSROs。展开更多
A mathematical model and experimental analysis of the impact of oxide thickness on the ambipolar conduction in Schottky Barrier Carbon Nanotubes(CNTs)Field Effect Transistor(SB CNTFETs)is presented.Suppression of ambi...A mathematical model and experimental analysis of the impact of oxide thickness on the ambipolar conduction in Schottky Barrier Carbon Nanotubes(CNTs)Field Effect Transistor(SB CNTFETs)is presented.Suppression of ambipolar conduction in SB CNTFETs is imperative in order to establish them as the future of IC technology.The ambipolar nature of SB CNTFETs leads to a great amount of leakage current.Employing a gate oxide dielectric of thickness,tox^50 nm suppresses the ambipolar behavior.In an SB CNTFET,it is the electric field at the source/drain contacts that control the conductance and the band bending length at the contacts is defined by tox.Therefore,tox is the prime parameter that influences the width of the Schottky barrier and the current in the subthreshold region.Due to the wide SB,there is a loss in on-current due to tunneling,but the current due to thermionic emission is increased by employing a high-κdielectric such as Zirconium dioxide(ZrO2).This work proposes an approach to suppress ambipolar behavior in SB CNTFETs without decreasing the on current.The thickness and dielectric constant of the gate oxide are optimized using the particle swarm optimization(PSO)algorithm to achieve suppression of ambipolar conduction without any loss in on-current.The proposed SB CNTFET was modeled using Verilog-A.Experimental demonstration of the suppression of ambipolar property is also presented.Two SB CNTFETs are fabricated using high-κdielectric such as ZrO2 with different thickness.A device with thin(~5 nm)gate oxide and another device with thick(~50 nm)gate oxide were fabricated.From the experimental results,it is observed that the device with the thin gate oxide exhibited ambipolar characteristics and the device with the thick gate oxide did not exhibit ambipolar characteristics.The increase in thickness,tox,ensures suppression of ambipolar behavior.展开更多
YBa2Cu4O8/La2/3 Ca1/3 MnO3/YBa2Cu4O8 ( Y-124/LCMO/Y- 124) heterostructure was prepared by facing-target sputtering technique. The oscillatory superconducting transition temperature was observed when the thickness of...YBa2Cu4O8/La2/3 Ca1/3 MnO3/YBa2Cu4O8 ( Y-124/LCMO/Y- 124) heterostructure was prepared by facing-target sputtering technique. The oscillatory superconducting transition temperature was observed when the thickness of LCMO d L is larger than critical thickness d L^CR. The metal-insulator transition temperature can only be detected at d L 〉 d L^CR. The dependence on the spacer layer in LCMO/Y-124 systems suggests strongly the interplay of ferromagnetic and superconducting couplings.展开更多
Nowadays Chinese fashion & accessory business has possessed some new features similar to the information industry , and has a developing tendency of information -media - like. High - sensitive - level fashion mark...Nowadays Chinese fashion & accessory business has possessed some new features similar to the information industry , and has a developing tendency of information -media - like. High - sensitive - level fashion market is breeding, which results in the transformation of the fashion industrial structure. Designer brands work well in concert with this trend and two kinds of high - sensitive - level segments formed in Chinese fashion market.展开更多
Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si(001) imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompa...Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si(001) imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maximum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.展开更多
If one considers the number of language learners that are worldwide,the number of classroom-based language assessments(CBLAs)that are given each year,and the number of decisions that are made on the basis of these,it ...If one considers the number of language learners that are worldwide,the number of classroom-based language assessments(CBLAs)that are given each year,and the number of decisions that are made on the basis of these,it is obvious that in terms of sheer numbers,more students are affected by CBLAs per year than by those based on large-scale language assessments.Because of this,it is essential that classroom teachers have the knowledge,skills,and tools to enable them to develop and use CBLAs that they can justify to stakeholders,e.g.,students,parents,and school authorities.In this paper we describe the approach to CBLAs that we have developed.First,we discuss the role of assessment in teaching and learning,the kinds of decisions that classroom teachers need to make,and the different modes of CBLAs.We then describe the process of using CBLAs to help teachers make decisions that will have beneficial consequences.Next,we discuss fairness and accountability in assessment and the process of assessment justification,including an assessment use argument.Finally,we discuss the process of developing CBLAs,using an example of a classroom-based language assessment to illustrate this.展开更多
As an invisible“endocrine organ”,gut microbiota is widely involved in the regulation of nervous system,endocrine system,circulatory system,and digestive system.It is also closely related to host health and the occur...As an invisible“endocrine organ”,gut microbiota is widely involved in the regulation of nervous system,endocrine system,circulatory system,and digestive system.It is also closely related to host health and the occurrence of many chronic diseases.Relevant literature shows that high temperature,low temperature,and highaltitude hypoxia may have negative effects on commensal microorganisms.The stimulation of exercise may aggravate this reaction,which is related to the occurrence of exercise-induced fever and gastrointestinal and respiratory diseases.The intervention of probiotics can alleviate the above problems to a certain extent.Therefore,this paper takes exercise in a special environment as the starting point,deeply analyses the intervention effect and potential mechanism of probiotics,and provides the theoretical basis and reference for follow-up research and application of probiotics in sports science.展开更多
Bi_(2)SeO_(5)是一种具有优异电绝缘性能的范德华(vdW)层状介电材料,引起了极大关注.然而,目前关于Bi_(2)SeO_(5)的研究主要停留在实验层面,仍然缺乏对其原子级薄膜的介电性能的相关理论认识.本文通过第一性原理计算确定了Bi_(2)SeO_(5...Bi_(2)SeO_(5)是一种具有优异电绝缘性能的范德华(vdW)层状介电材料,引起了极大关注.然而,目前关于Bi_(2)SeO_(5)的研究主要停留在实验层面,仍然缺乏对其原子级薄膜的介电性能的相关理论认识.本文通过第一性原理计算确定了Bi_(2)SeO_(5)的介电性能,发现其块体、双层和单层均具有超高平均介电常数(εr>20).研究表明,单层Bi_(2)SeO_(5)与双层Bi_(2)O_(2)Se之间的导带和价带能量偏移量均大于1 eV,表明单层Bi_(2)SeO_(5)依然可作为原子薄Bi_(2)O_(2)Se的良好介电层.此外,不同于h-BN或其他2D vdW绝缘体,Bi_(2)SeO_(5)的εr由其离子部分主导,且随着厚度的减小几乎保持不变.计算发现,单层Bi_(2)SeO_(5)的等效氧化层厚度可薄至0.3 n m,且单层Bi_(2)SeO_(5)在拉伸或压缩应变达到6%时均能保持高介电常数,这极大地促进了它与各种二维半导体的集成.本工作证明单层Bi_(2)SeO_(5)可以作为高性能二维电子器件良好的封装和介电层.展开更多
Over the past several years,high-β_(N) experiments have been carried out on HL-2A.The high-β_(N) is realized using double transport barriers(DTBs)with hybrid scenarios.A stationary high-β_(N) (>2)scenario was ob...Over the past several years,high-β_(N) experiments have been carried out on HL-2A.The high-β_(N) is realized using double transport barriers(DTBs)with hybrid scenarios.A stationary high-β_(N) (>2)scenario was obtained by pure neutral-beam injection(NBI)heating.Transient high performance was also achieved,corresponding to β_(N)≥3,ne/ne_(G)∼0.6,H_(98)∼1.5,f_(bs)∼30%,q_(95)∼4.0,and𝐺∼0.4.The high-β_(N) scenario was successfully modeled using integrated simulation codes,that is,the one modeling framework for integrated tasks(OMFIT).In high-𝛽𝑁plasmas,magnetohydrodynamic(MHD)instabilities are abundant,including low-frequency global MHD oscilla-tion with n=1,high-frequency coherent mode(HCM)at the edge,and neoclassical tearing mode(NTM)and Alfvénic modes in the core.In some high-β_(N) discharges,it is observed that the NTMs with m/n=3/2 limit the growth of the plasma energy and decrease β_(N).The low-n global MHD oscillation is consistent with the coupling of destabilized internal(m/n=1/1)and external(m/n=3/1 or 4/1)modes,and plays a crucial role in triggering the onset of ELMs.Achieving high-β_(N) on HL-2A suggests that core-edge interplay is key to the plasma confinement enhancement mechanism.Experiments to enhance β_(N) will contribute to future plasma operation,such as international thermonuclear experimental reactor.展开更多
A series of high dielectric material Er2O3 thin films with different thicknesses were deposited on p-type Si(100)substrate by pulse laser deposition at different temperatures.Phase structures of the films were deter...A series of high dielectric material Er2O3 thin films with different thicknesses were deposited on p-type Si(100)substrate by pulse laser deposition at different temperatures.Phase structures of the films were determined by means of X-ray diffraction(XRD)and high resolution transmission electron microscopy(HRTEM).Leakage current density was measured with an HP4142B semiconductor parameter analyzer.The XRD and HRTEM results reveal that Er2O3 thin films deposited below 400°C are amorphous,while films deposited from 400 to 840°C are well crystallized with(111)-preferential crystallographic orientation.I-V curves show that,for ultrathin crystalline Er2O3 films,the leakage current density increases by almost one order of magnitude from 6.20×10^-5 to 6.56×10^-4 A/cm^2,when the film thickness decreases by only 1.9 nm from 5.7 to 3.8 nm.However the leakage current density of ultrathin amorphous Er2O3 films with a thickness of 3.8 nm is only 1.73×10^-5 A/cm^2.Finally,analysis of leakage current density showed that leakage of ultrathin Er2O3 films at high field is mainly caused by Fowler-Nordheim tunneling,and the large leakage of ultrathin crystalline Er2O3 films could arise from impurity defects at the grain boundary.展开更多
Monolayer molybdenum disulfide(MoS_(2))has emerged as one of the most promising channel materials for next-generation nanoelectronics and optoelectronics owing to its atomic thickness,dangling-bond-free flat surface,a...Monolayer molybdenum disulfide(MoS_(2))has emerged as one of the most promising channel materials for next-generation nanoelectronics and optoelectronics owing to its atomic thickness,dangling-bond-free flat surface,and high electrical quality.Currently,high-quality monolayer MoS_(2)wafers are primarily grown on sapphire substrates incompatible with conventional device fabrication,and thus transfer processes to a suitable substrate are typically required before the device can be processed.Here,we demonstrate the batch production of transfer-free MoS2 top-gate devices directly on sapphire growth substrates via step engineering.By introducing substrate steps on growth substrate sapphire,high-κdielectric layers with superior quality and uniform can be directly deposited on the epitaxially grown monolayer MoS_(2).For the substrate with a maximum step density of 100μm^(−1),the gate capacitance can reach~1.87μF∙cm^(−2),while the interface trap state density(Dit)can be as low as~7.6×10^(10)cm^(−2)∙eV^(−1).The direct deposition of high-quality dielectric layers on grown monolayer MoS2 enables the batch fabrication of top-gate devices devoid of transfer and thus excellent device yield of>96%,holding great promise for large-scale twodimensional(2D)integrated circuits.展开更多
In the mid 20th century, great efforts were made to investigate the formation process of high-latitude cold vortex, which is regarded as a major weather system in the atmospheric circulation. In the late 1970s, Chines...In the mid 20th century, great efforts were made to investigate the formation process of high-latitude cold vortex, which is regarded as a major weather system in the atmospheric circulation. In the late 1970s, Chinese researchers noticed that the Northeast China cold vortex (NECV) is an active and frequently occurring weather system over Northeast Asia, which is generated under specific conditions of topography and land-sea thermal contrast on the local and regional scales. Thereby, the NECV study was broadened to include synoptic situations, mesoscale and dynamic features, the heavy rain process, etc. Since the 21st century, in the context of the global warming, more attention has been paid to studies of the mechanisms that cause the NECV variations during spring and early summer as well as the climatic impacts of the NECV system. Note that the NECV activity, frequent or not, not only affects local temperature and precipitation anomalies, but also regulates the amount of precipitation over northern China, the Huai River basin, and the middle and lower reaches of Yangtze River. The NECV influence can even reach the Guangdon~ Guangxi region. However, compared to the achievements for the blocking system study, theoretical studies with regard to the NECV system are still insufficient. Research activities regarding the mechanisms for the NECV formation, particularly theoretical studies using linear or weak nonlinear methods need to be strengthened in the future. Meanwhile, great efforts should be made to deepen our understanding of the relations of the NECV system to the oceanic thermal forcing, the low-frequency atmospheric variations over mid-high latitudes, and the global warming.展开更多
With a continuously increasing population and better food consumption levels, im- proving the efficiency of arable land use and increasing its productivity have become funda- mental strategies to meet the growing food...With a continuously increasing population and better food consumption levels, im- proving the efficiency of arable land use and increasing its productivity have become funda- mental strategies to meet the growing food security needs in China. A spatial distribution map of medium- and low-yield cropland is necessary to implement plans for cropland improvement In this study, we developed a new method to identify high-, medium-, and low-yield cropland from Moderate Resolution Imaging Spectroradiometer (MODIS) data at a spatial resolution of 500 m. The method could be used to reflect the regional heterogeneity of cropland productiv- ity because the classification standard was based on the regionalization of cropping systems in China. The results showed that the proportion of high-, medium-, and low-yield cropland in China was 21%, 39%, and 40%, respectively. About 75% of the low-yield cropland was lo- cated in hilly and mountainous areas, and about 53% of the high-yield cropland was located in plain areas. The five provinces with the largest area of high-yield cropland were all located in the Huang-Huai-Hai region, and the area amounted to 42% of the national high-yield cropland area. Meanwhile, the proportion of high-yield cropland was lower than 15% in Hei- Iongjiang, Sichuan, and Inner Mongolia, which had the largest area allocated to cropland in China. If all the medium-yield cropland could be improved to the productive level of high-yield cropland and the low-yield cropland could be improved to the level of medium-yield cropland, the total productivity of the land would increase 19% and 24%, respectively.展开更多
文摘In the gneisses from the drillhole ZK2304 of the Donghai area, there have been preserved high- and ultrahigh-pressure metamorphic mineral assemblages, a series of complicated retrogressive textures and relevant metamorphic reactions. In addition to garnet, jadeititic-clinopyroxene and rutile, other peak stage (M2) minerals in some gneisses include phengite, aragonite and coesite or quartz pseudomorphs after coesite. The typical peak-stage mineral assemblages in gneisses are characterized by garnet + jadeitic-clinopyroxene + rutile + coesite, garnet + jadeitic-clinopyroxene + phengite + rutile ± coesite and garnet + jadeitic-clinopyroxene + aragonite + rutile ± coesite. The grossular content (Gro) in garnet is high and may reach 50. 1 mol%. The SiO2 content of phengite ranges from 54.37% to 54.84% with 3.54-3.57 p.f.u. Quartz pseudomorphs after coesite occur as inclusions in garnet.The gneisses of the Donghai area have been subjected to multistage recrystallization and exhibit a closewise P-T evolutional path characterized by the near-isothermal decompression. The inclusion assemblage (Hb+Ep+Bi+Pl+Qz) within garnet and other minerals has recorded a pre-peak stage (Mi) epidote amphibole fades metamorphic event. High- and ultrahigh-pressure peak metamorphism (M2) took place at T=750-860℃ and P>2.7 GPa. The symplectitic assemblages after garnet, jadeitic-clinopyroxene and rutile imply a near-isothermal decompression metamorphism (M3, M4) during the rapid exhumation. Several lines of evidence of petrography and metamorphic reactions indicate that both gneisses and eclogites have experienced ultrahigh-pressure metamorphism in the Donghai area. This research may be of great significance for an in-depth study of the metamorphism and tectonic evolution in the Su-Lu ultrahigh-pressure metamorphic belt.
基金Supported by Russian Foundation for Basic Research(13-05-91159-GFEN_a)Project 14.518.11.7065 and agreement N8388 of the Ministry of Education and Science of the Russian Federation+1 种基金the National Natural Science Foundation(41274146)the Specialized Research Fund for State Key Laboratory in China
文摘Comparison of regular(diurnal,seasonal and solar cycle)variations of high-latitude,mid-latitude and low-latitude ionospheric characteristics has been provided on basis of local empirical models of the peak electron density and the peak height.The local empirical models were derived from the hand-scaled ionogram data recorded by DPS-4 digisondes located at Norilsk(69°N,88°E),Irkutsk(52°N,104°E)and Hainan(19°N,109°E)for a 6-year period from December,2002 to December,2008.The technique used to build the local empirical model is described.The primary focus is diurnal-seasonal behavior under low solar activity and its change with increasing solar activity.Both common and specific features of the high-latitude(Norilsk),mid-latitude(Irkutsk)and low-latitude(Hainan)regular variations were revealed using their local empirical models.
基金General Research Institute for Nonferrous Metals Research Fund (82262)
文摘Gd2O3 thin films as high-κ gate dielectrics were deposited directly on Si(001) substrates by magnetron sputtering at a pressure of 1.3 Pa and different temperatures. X-ray diffraction results revealed that all the films grown from 450 to 570 ℃ were crystalline, and the Gd2O3 thin films consisted of a mixture of cubic and monoclinic phases. The growth temperature was a critical parameter for the phase constituents and their relative amount. Low temperature was favorable for the formation of cubic phase while higher temperature gave rise to more monoclinic phase. All the Gd2O3 thin films grown from different temperatures exhibited acceptable electrical properties, such as low leakage current density (JL) of 10-5 A/cm^2 at zero bias with capacitance equivalent SiO2 thickness in the range of 6-13 nm. Through the comparison between films grown at 450 and 570 ℃, the existence of monoclinic phase caused an increase in JL by nearly one order of magnitude and a reduction of effective dielectric constant from 17 to 9.
基金supported by Jiangsu Province Health Vocational and Technical Education Research Grants Program(No.201402)Jiangsu Province College“Qing Lan Project”[Su Teacher No.2014(23)]The Science and Technology Innovation Team Project of Suzhou Health College(No.szwzytd 201304)
文摘Objective: To investigate the effectiveness of a high-fidelity teaching simulation based on an NLN/Jeffries simulation in the nursing education theoretical framework and its influencing factors. Methods: A high-fidelity teaching simulation on clinical nursing practices using intelligent human analogues was conducted with 200 students, and The Simulation Design Scale, and the Student Satisfaction and Self-Confidence in Learning Scale developed by the National League for Nursing were used to evaluate the training effectiveness and its influencing factors. Results: For the high-fidelity teaching simulation, students gave scores of 4.36± 0.54 points for satisfaction and 4.33 ± 0.46 points for Self-Confidence. The students highly rated the five dimensions of teaching design, i.e., teaching objectives/information, assistance/support for students, problem solving, guided feedback, and fidelity. The teaching design was closely correlated with the satisfaction of the high-fidelity teaching simulation and self-efficacy, and the dimensions of teaching objectives/informa- tion and assistance/support for students were particularly strong predictors of teaching effectiveness. Conclusions: A high-fidelity teaching simulation based on Jeffries' theoretical framework improved student satisfaction with the simulation and their Self-Confidence. In planning simulations, teachers should take into account five characteristics, i.e., teaching objectives/information on simulation education, assistance/support for students, problem solving, guided reflection, and fidelity, to achieve better teaching effectiveness.
文摘The Roman high(RHA) and low-Avoidance (RLA) rats were selectively bred for rapid vs poor acquisition of two-way active avoidance behavior. These lines differ in numerous behavioral traits, with RLA rats being more fearful/anxious than RHA rats, and the latter being novelty-seekers and showing larger intake of, and preference for, addictive substances including ethanol (ETH). Moreover, several differences in central dopaminergic, serotonergic, and GABAergic functions have been reported in these two lines. Since those neural systems are involved in the regulation of ETH consumption, it was considered of interest to investigate: 1) the differences in ETH intake and preference between RHA and RLA rats, 2) the effects of ETH on DA release in the shell of the nucleus accumbens (AcbSh) using brain microdialysis. ETH solutions of increasing concentrations (2% - 10%) were presented on alternate days in a free choice with water. To examine ETH intake and preference stability, animals were subsequently switched to daily presentations of 10% ETH for 10 consecutive days. RHA rats consumed significantly larger amounts of ETH and displayed higher ETH preference than did RLA rats throughout the acquisition and maintenance phases. Following chronic exposure to ETH the animals were habituated to a restricted access to ETH schedule (2% ETH, 2 h per day × 4 days) before surgical implantation of a dialysis probe in the AcbSh. Under these experimental conditions, voluntary ETH intake (2%, 1 h, p.o.) produced a significant increase in accumbal DA output in RHA rats but not in their RLA counterparts. Finally, the i.p. administration of ETH (0.25 g/kg) to na?ve Roman rats produced a significant increment in accumbal DA output only in RHA rats. These results indicate that the mesolimbic dopaminergic system of RHA rats is more responsive to the effects of ETH than that of RLA rats.
基金This work was supported by the National Natural Science Foundation of China(51834001,52104129)a project supported by the China Postdoctoral Science Foundation(2020M672226,2022T150195)Key Laboratory of Mine Ecological Effects and Systematic Restoration,Ministry of Natural Resources,Open Fund(MEER-2022-09).
文摘In order to improve the comprehensive utilization rate of highfines sand(HFS)produced by the mine,full solid waste shotcrete(HFS-BFRS)was prepared with HFS asfine aggregate in cooperation with basaltfiber(BF).The strength growth characteristics of HFS-BFRS were analyzed.And thefitting equation of compressive strength growth characteristics of HFS-BFRS under the synergistic effect of multiple factors was given.And based on the orthogonal experimental method,the effects on the compressive strength,splitting tensile strength andflex-ural strength of HFS-BFRS under the action of different levels of influencing factors were investigated.The effect of three factors on the mechanical properties of HFS-BFRS,3,and 28 d,respectively,was revealed by choosing the colloidal sand ratio(C/H),basaltfiber volume fraction(BF Vol)and naphthalene high-efficiency water reducing agent(FDN)as the design variables,combined with indoor tests and theoretical analysis.The results show that the sensitivity of the three factors on compressive strength andflexural strength is C/H>FDN>BF Vol,and split-ting tensile strength is BF Vol>FDN>C/H.Finally,thefitting ratio of HFS-BFRS was optimized by the factor index method,and the rationality was verified by thefield test.For thefluidity of HFS-BFRS,the slump can be improved by 139%under the action of 1.2%FDN,which guarantees the pump-ability of HFS-BFRS.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(kzcx2-yw-110,KZCX2-YW-Q08)
文摘Shock effects of 93 Grove Mountains (GRV) ordinary chondrites were studied in this work, including fracture, various types of extinction, and recrystallization of silicates observed under optical microscopy. Shock-induced veins and pockets show various microtextures, decomposition and phase transformation of minerals. The confirmed high-pressure polymorphs of silicates are ringwoodite, majorite, pyroxene glass and maskelynite. Based on the shock effects and assemblages of high-pressure minerals, shock stages of all of 93 GRV ehondrites were classified. In comparison with literature, the Grove Mountains meteorites have a higher fraction (23 out of 93 ) of heavily shocked samples (S4--S5). Most of the heavily shocked meteorites are L group (22 out of 23), except for one H chondrite. The distinct shock metamorphism between H and. L groups may indicate different surface properties of their parent bodies. In addition, there is relationship between petrologic types and shock stages, with most heavily shocked samples observed in equilibrated ordinary chondrites ( especially Type 5 and 6).
基金supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(No.2019YFA0209902)the National Natural Science Foundation of China(Nos.11998102,11972350,and 11790293)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040503).
文摘High(or medium)-entropy alloys(H/MEAs)are complex concentrated solid solutions prone to develop the chemical short-range orders(CSROs),as an indispensable structural constituent to make H/MEAs essentially different from the traditional alloys.The CSROs are predicted to play roles in dislocation behaviors and mechanical properties.So far,the image of CSROs is built up by the theoretical modeling and computational simulations in terms of the conventional concept,i.e.,the preference/avoidance of elemental species to satisfy the short-ranged ordering in the first and the next couple of nearest-neighbor atomic shells.In these simulated CSROs,however,the structural image is missing on the atomic scale,even though the lattice periodicity does not exist in the CSROs.Further,it is pending as to the issues if and what kind of CSRO may be formed in a specific H/MEA.All these are ascribed to the challenge of experimentally seeing the CSROs.Until recently,the breakthrough does not appear to convincingly identify the CSROs in the H/MEAs by using the state-of-the-art transmission electron microscope.To be specific,the electron diffractions provide solid evidence to doubtlessly ascertain CSROs.The structure motif of CSROs is then constructed,showing both the lattice structure and species ordering occupation,along with the stereoscopic topography of the CSRO.It is suggested that the CSROs,as the first landscape along the path of development of the local chemical ordering,offer one more route to substantially develop the ordered structure on the atomic scale in the H/MEAs,parallel to the existing grain-leveled microstructure.The findings of CSROs make a step forward to understand the CSROs-oriented relationship between the microstructure and mechanical properties.This review focuses on the recent progress mainly in the experimental aspects of the identification,structure motif,and mechanical stability in CSROs,along with the chemical medium-range orders as the growing CSROs。
文摘A mathematical model and experimental analysis of the impact of oxide thickness on the ambipolar conduction in Schottky Barrier Carbon Nanotubes(CNTs)Field Effect Transistor(SB CNTFETs)is presented.Suppression of ambipolar conduction in SB CNTFETs is imperative in order to establish them as the future of IC technology.The ambipolar nature of SB CNTFETs leads to a great amount of leakage current.Employing a gate oxide dielectric of thickness,tox^50 nm suppresses the ambipolar behavior.In an SB CNTFET,it is the electric field at the source/drain contacts that control the conductance and the band bending length at the contacts is defined by tox.Therefore,tox is the prime parameter that influences the width of the Schottky barrier and the current in the subthreshold region.Due to the wide SB,there is a loss in on-current due to tunneling,but the current due to thermionic emission is increased by employing a high-κdielectric such as Zirconium dioxide(ZrO2).This work proposes an approach to suppress ambipolar behavior in SB CNTFETs without decreasing the on current.The thickness and dielectric constant of the gate oxide are optimized using the particle swarm optimization(PSO)algorithm to achieve suppression of ambipolar conduction without any loss in on-current.The proposed SB CNTFET was modeled using Verilog-A.Experimental demonstration of the suppression of ambipolar property is also presented.Two SB CNTFETs are fabricated using high-κdielectric such as ZrO2 with different thickness.A device with thin(~5 nm)gate oxide and another device with thick(~50 nm)gate oxide were fabricated.From the experimental results,it is observed that the device with the thin gate oxide exhibited ambipolar characteristics and the device with the thick gate oxide did not exhibit ambipolar characteristics.The increase in thickness,tox,ensures suppression of ambipolar behavior.
文摘YBa2Cu4O8/La2/3 Ca1/3 MnO3/YBa2Cu4O8 ( Y-124/LCMO/Y- 124) heterostructure was prepared by facing-target sputtering technique. The oscillatory superconducting transition temperature was observed when the thickness of LCMO d L is larger than critical thickness d L^CR. The metal-insulator transition temperature can only be detected at d L 〉 d L^CR. The dependence on the spacer layer in LCMO/Y-124 systems suggests strongly the interplay of ferromagnetic and superconducting couplings.
文摘Nowadays Chinese fashion & accessory business has possessed some new features similar to the information industry , and has a developing tendency of information -media - like. High - sensitive - level fashion market is breeding, which results in the transformation of the fashion industrial structure. Designer brands work well in concert with this trend and two kinds of high - sensitive - level segments formed in Chinese fashion market.
基金supported by the Special Project of Shanghai Nano Technology (0852nm02400 and 0752nm012)Shaoxing Science and Technology Commission (2007A21015)+3 种基金Shanghai Rising-Star Program (07QA14026)the National Natural Science Foundation of China (10804072)the Key Fundamental Project of Shanghai (08JC1410400)Shanghai Education Commission (07zz143)
文摘Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si(001) imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maximum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.
文摘If one considers the number of language learners that are worldwide,the number of classroom-based language assessments(CBLAs)that are given each year,and the number of decisions that are made on the basis of these,it is obvious that in terms of sheer numbers,more students are affected by CBLAs per year than by those based on large-scale language assessments.Because of this,it is essential that classroom teachers have the knowledge,skills,and tools to enable them to develop and use CBLAs that they can justify to stakeholders,e.g.,students,parents,and school authorities.In this paper we describe the approach to CBLAs that we have developed.First,we discuss the role of assessment in teaching and learning,the kinds of decisions that classroom teachers need to make,and the different modes of CBLAs.We then describe the process of using CBLAs to help teachers make decisions that will have beneficial consequences.Next,we discuss fairness and accountability in assessment and the process of assessment justification,including an assessment use argument.Finally,we discuss the process of developing CBLAs,using an example of a classroom-based language assessment to illustrate this.
基金National Natural Science Foundation of China(11775059)National Key Technology R&D Program of China(2019YFF0301600).
文摘As an invisible“endocrine organ”,gut microbiota is widely involved in the regulation of nervous system,endocrine system,circulatory system,and digestive system.It is also closely related to host health and the occurrence of many chronic diseases.Relevant literature shows that high temperature,low temperature,and highaltitude hypoxia may have negative effects on commensal microorganisms.The stimulation of exercise may aggravate this reaction,which is related to the occurrence of exercise-induced fever and gastrointestinal and respiratory diseases.The intervention of probiotics can alleviate the above problems to a certain extent.Therefore,this paper takes exercise in a special environment as the starting point,deeply analyses the intervention effect and potential mechanism of probiotics,and provides the theoretical basis and reference for follow-up research and application of probiotics in sports science.
基金supported by the National Natural Science Foundation of China (92064005, 12104072, and 12147102)Chongqing Research Program of Basic Research and Frontier Technology,China (cstc2021jcyj-msxm X0640)the Fundamental Research Funds for the Central Universities of China (2023CDJXY-048)。
文摘Bi_(2)SeO_(5)是一种具有优异电绝缘性能的范德华(vdW)层状介电材料,引起了极大关注.然而,目前关于Bi_(2)SeO_(5)的研究主要停留在实验层面,仍然缺乏对其原子级薄膜的介电性能的相关理论认识.本文通过第一性原理计算确定了Bi_(2)SeO_(5)的介电性能,发现其块体、双层和单层均具有超高平均介电常数(εr>20).研究表明,单层Bi_(2)SeO_(5)与双层Bi_(2)O_(2)Se之间的导带和价带能量偏移量均大于1 eV,表明单层Bi_(2)SeO_(5)依然可作为原子薄Bi_(2)O_(2)Se的良好介电层.此外,不同于h-BN或其他2D vdW绝缘体,Bi_(2)SeO_(5)的εr由其离子部分主导,且随着厚度的减小几乎保持不变.计算发现,单层Bi_(2)SeO_(5)的等效氧化层厚度可薄至0.3 n m,且单层Bi_(2)SeO_(5)在拉伸或压缩应变达到6%时均能保持高介电常数,这极大地促进了它与各种二维半导体的集成.本工作证明单层Bi_(2)SeO_(5)可以作为高性能二维电子器件良好的封装和介电层.
基金supported in part by the ITER-CN(Grants No.2017YFE0301202 and 2019YFE03020000)by National Natural Science Foundation of China(Grants No.12125502,11875021 and 11835010)by Sichuan Foundation(Grant No.2020JDJQ0070).
文摘Over the past several years,high-β_(N) experiments have been carried out on HL-2A.The high-β_(N) is realized using double transport barriers(DTBs)with hybrid scenarios.A stationary high-β_(N) (>2)scenario was obtained by pure neutral-beam injection(NBI)heating.Transient high performance was also achieved,corresponding to β_(N)≥3,ne/ne_(G)∼0.6,H_(98)∼1.5,f_(bs)∼30%,q_(95)∼4.0,and𝐺∼0.4.The high-β_(N) scenario was successfully modeled using integrated simulation codes,that is,the one modeling framework for integrated tasks(OMFIT).In high-𝛽𝑁plasmas,magnetohydrodynamic(MHD)instabilities are abundant,including low-frequency global MHD oscilla-tion with n=1,high-frequency coherent mode(HCM)at the edge,and neoclassical tearing mode(NTM)and Alfvénic modes in the core.In some high-β_(N) discharges,it is observed that the NTMs with m/n=3/2 limit the growth of the plasma energy and decrease β_(N).The low-n global MHD oscillation is consistent with the coupling of destabilized internal(m/n=1/1)and external(m/n=3/1 or 4/1)modes,and plays a crucial role in triggering the onset of ELMs.Achieving high-β_(N) on HL-2A suggests that core-edge interplay is key to the plasma confinement enhancement mechanism.Experiments to enhance β_(N) will contribute to future plasma operation,such as international thermonuclear experimental reactor.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(No.072C201301)the Graduate Student Innovation Program of the Chinese Academy of Sciences
文摘A series of high dielectric material Er2O3 thin films with different thicknesses were deposited on p-type Si(100)substrate by pulse laser deposition at different temperatures.Phase structures of the films were determined by means of X-ray diffraction(XRD)and high resolution transmission electron microscopy(HRTEM).Leakage current density was measured with an HP4142B semiconductor parameter analyzer.The XRD and HRTEM results reveal that Er2O3 thin films deposited below 400°C are amorphous,while films deposited from 400 to 840°C are well crystallized with(111)-preferential crystallographic orientation.I-V curves show that,for ultrathin crystalline Er2O3 films,the leakage current density increases by almost one order of magnitude from 6.20×10^-5 to 6.56×10^-4 A/cm^2,when the film thickness decreases by only 1.9 nm from 5.7 to 3.8 nm.However the leakage current density of ultrathin amorphous Er2O3 films with a thickness of 3.8 nm is only 1.73×10^-5 A/cm^2.Finally,analysis of leakage current density showed that leakage of ultrathin Er2O3 films at high field is mainly caused by Fowler-Nordheim tunneling,and the large leakage of ultrathin crystalline Er2O3 films could arise from impurity defects at the grain boundary.
基金supported by the National Key Research and Development Program of China(Nos.2021YFA1202900 and 2021YFA1400502)the Strategic Priority Research Program of Chinese Academy of Sciences(CAS)(No.XDB30000000)+1 种基金the National Natural Science Foundation of China(NSFC)(Nos.61888102,11834017,61734001,62122084,12274447,and 12074412)the Key-Area Research and Development Program of Guangdong Province(No.2020B0101340001).
文摘Monolayer molybdenum disulfide(MoS_(2))has emerged as one of the most promising channel materials for next-generation nanoelectronics and optoelectronics owing to its atomic thickness,dangling-bond-free flat surface,and high electrical quality.Currently,high-quality monolayer MoS_(2)wafers are primarily grown on sapphire substrates incompatible with conventional device fabrication,and thus transfer processes to a suitable substrate are typically required before the device can be processed.Here,we demonstrate the batch production of transfer-free MoS2 top-gate devices directly on sapphire growth substrates via step engineering.By introducing substrate steps on growth substrate sapphire,high-κdielectric layers with superior quality and uniform can be directly deposited on the epitaxially grown monolayer MoS_(2).For the substrate with a maximum step density of 100μm^(−1),the gate capacitance can reach~1.87μF∙cm^(−2),while the interface trap state density(Dit)can be as low as~7.6×10^(10)cm^(−2)∙eV^(−1).The direct deposition of high-quality dielectric layers on grown monolayer MoS2 enables the batch fabrication of top-gate devices devoid of transfer and thus excellent device yield of>96%,holding great promise for large-scale twodimensional(2D)integrated circuits.
基金Supported by the National Natural Science Foundation of China(41630424,41275096,41175083,41305059,and 41405094)China Meteorological Administration Special Public Welfare Research Fund(GYHY201106016 and GYHY201006020)
文摘In the mid 20th century, great efforts were made to investigate the formation process of high-latitude cold vortex, which is regarded as a major weather system in the atmospheric circulation. In the late 1970s, Chinese researchers noticed that the Northeast China cold vortex (NECV) is an active and frequently occurring weather system over Northeast Asia, which is generated under specific conditions of topography and land-sea thermal contrast on the local and regional scales. Thereby, the NECV study was broadened to include synoptic situations, mesoscale and dynamic features, the heavy rain process, etc. Since the 21st century, in the context of the global warming, more attention has been paid to studies of the mechanisms that cause the NECV variations during spring and early summer as well as the climatic impacts of the NECV system. Note that the NECV activity, frequent or not, not only affects local temperature and precipitation anomalies, but also regulates the amount of precipitation over northern China, the Huai River basin, and the middle and lower reaches of Yangtze River. The NECV influence can even reach the Guangdon~ Guangxi region. However, compared to the achievements for the blocking system study, theoretical studies with regard to the NECV system are still insufficient. Research activities regarding the mechanisms for the NECV formation, particularly theoretical studies using linear or weak nonlinear methods need to be strengthened in the future. Meanwhile, great efforts should be made to deepen our understanding of the relations of the NECV system to the oceanic thermal forcing, the low-frequency atmospheric variations over mid-high latitudes, and the global warming.
基金STS Project of CAS,No.KFJ-EW-STS-001National Natural Science Foundation of China,No.41430861
文摘With a continuously increasing population and better food consumption levels, im- proving the efficiency of arable land use and increasing its productivity have become funda- mental strategies to meet the growing food security needs in China. A spatial distribution map of medium- and low-yield cropland is necessary to implement plans for cropland improvement In this study, we developed a new method to identify high-, medium-, and low-yield cropland from Moderate Resolution Imaging Spectroradiometer (MODIS) data at a spatial resolution of 500 m. The method could be used to reflect the regional heterogeneity of cropland productiv- ity because the classification standard was based on the regionalization of cropping systems in China. The results showed that the proportion of high-, medium-, and low-yield cropland in China was 21%, 39%, and 40%, respectively. About 75% of the low-yield cropland was lo- cated in hilly and mountainous areas, and about 53% of the high-yield cropland was located in plain areas. The five provinces with the largest area of high-yield cropland were all located in the Huang-Huai-Hai region, and the area amounted to 42% of the national high-yield cropland area. Meanwhile, the proportion of high-yield cropland was lower than 15% in Hei- Iongjiang, Sichuan, and Inner Mongolia, which had the largest area allocated to cropland in China. If all the medium-yield cropland could be improved to the productive level of high-yield cropland and the low-yield cropland could be improved to the level of medium-yield cropland, the total productivity of the land would increase 19% and 24%, respectively.