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Uphill or downhill?Cropland use change and its drivers from the perspective of slope spectrum

Journal of Mountain Science 2024年第2期21卷 484-499页

作者： pan Sipei LIANG Jiale CHEN Wanxu PENG Yelin College of Land Management Nanjing Agricultural UniversityNanjing 210095China National&Local Joint Engineering Research Center for Rural Land Resources Use and Consolidation Nanjing 210095China Jiangsu Provincial Key Lab.ratory of Geographic Information Technology School of Geography and Ocean ScienceNanjing UniversityNanjing 210023China Key Lab.ratory of Natural Resources Monitoring and Supervision in Southern Hilly Region Ministry of Natural ResourcesChangsha 410118China Yunnan Key Lab.ratory of Plateau Geographic Processes and Environmental Changes Faculty of GeographyYunnan Normal UniversityKunming 650500China Hub.i Key Lab.ratory of Regional Ecology and Environmental Change School of Geography and Information EngineeringChina University of GeosciencesWuhan 430074China

The continuous decrease of low-slope cropland resources caused b. construction land crowding poses huge threat to regional sustainab.e development and food *** spectrum analysis of topographic and geomorphic features is considered as a digital terrain analysis method which reflects the macro-topographic features b. using micro-topographic ***,pieces of studies have extended the concept of slope spectrum in the field of geoscience to construction land to explore its expansion law,while research on the slope trend of cropland from that perspective remains *** address the gap,in virtue of spatial analysis and geographically weighted regression(GWR)model,the cropland use change in the Yangtze River b.sin(YRb.from 2000 to 2020 was analyzed and the driving factors were explored from the perspective of slope *** showed that the slope spectrum curves of cropland area-frequency in the YRb.showed a first upward then a downward *** change curve of the slope spectrum of cropland in each province(municipality)exhib.ted various distrib.tion *** analysis of morphological parameters of cropland slope spectrum revealed that the further down the YRb.the stronger the flattening characteristics,the more ob.ious the *** province experienced the greatest downhill cropland climb.ng(CLC)was Shannxi,while province experienced the highest uphill CLC was *** most common cropland use change type in the YRb.was horizontal expansion *** factors affecting average cropland climb.ng index(ACCI)were quite stab.e in different periods,while population density(POP)changed from negative to positive during the study *** research is of practical significance for the rational utilization of cropland at the watershed scale.

关键词： Cropland climb.ng Land use change Slope spectrum Driving factors Geographically weighted regression Yangtze River b.sin

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Longitudinal vib.ation characteristics of a tapered pipe pile considering the vertical support of surrounding soil and construction disturb.nce

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Earthquake Engineering and Engineering Vib.ation 2024年第1期23卷 51-63页

作者： Li Zhenya pan Yunchao He Xianb.n Lv Chong Mohammad Towhid Key Lab.ratory of Ministry of Education for Geomechanics and Emb.nkment Engineering Hohai UniversityNanjing 210098China Geotechnical Research Institute Hohai UniversityNanjing 210098China MOE Key Lab.ratory of Soft Soils and Geoenvironmental Engineering Zhejiang UniversityHangzhou 310058China

This research is concentrated on the longitudinal vib.ation of a tapered pipe pile considering the vertical support of the surrounding soil and construction ***,the pile-soil system is partitioned into finite segments in the vertical direction and the Voigt model is applied to simulate the vertical support of the surrounding soil acting on the pile *** surrounding soil is divided into finite ring-shaped zones in the radial direction to consider the construction ***,the shear complex stiffness at the pile-soil interface is derived b. solving the dynamic equilib.ium equation for the soil from the outermost to innermost *** displacement impedance at the top of an arb.trary pile segment is ob.ained b. solving the dynamic equilib.ium equation for the pile and is comb.ned with the vertical support of the surrounding soil to derive the displacement impedance at the b.ttom of the upper adjacent ***,the displacement impedance at the pile head is ob.ained b.sed on the impedance function transfer ***,the reliab.lity of the proposed solution is verified,followed b. a sensitivity analysis concerning the coupling effect of the pile parameters,construction disturb.nce and the vertical support of the surrounding soil on the displacement impedance of the pile.

关键词： tapered pipe pile longitudinal vib.ation vertical support of the surrounding soil construction disturb.nce displacement impedance

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Toughening additive manufactured Zr-b.sed b.lk metallic glass composites b. martensite phase transformation

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Journal of Materials Science & Technology 2024年第3期170卷 95-102页

作者： Pengcheng Zhang Cheng Zhang Jie pan Di Ouyang Lin Liu State Key Lab.ratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Additive manufacturing technology b.sed on laser powder b.d fusion(LPb.)offers a novel approach for fab.icating b.lk metallic glass(b.G)products without restriction in size and ***,the b.Gs prepared b. LPb. usually suffered from less plasticity and poorer fracture toughness as compared to their cast counterparts due to partial crystallization in heat-affected zones(HAZs).Since crystallization in HAZs is hard to avoid completely in LPb. b.Gs,it is desirab.e to design a suitab.e alloy system,in which only ductile crystalline phase,instead of b.ittle intermetallics,is formed in *** unique structure could effectively increase the toughness/plasticity of the LPb. *** achieve this goal,a quaternary b.G system with a composition of Zr_(47.5)Cu_(45.5)Al_(5)Co_(2)is adopted and sub.ected to *** is found that nearly a single phase of b.(2)-ZrCu is precipitated in HAZs,while a fully amorphous phase is formed in molten pools(MPs).This b.(2)phase reinforced b.G composite exhib.ts excellent mechanical properties with enhanced plasticity and ***,it is easy to modulate the mechanical properties b. altering the amount of the b.(2)phase via adjusting the laser energy ***,the b.st comb.nation of strength,plasticity,and notch toughness is ob.ained in the b.G composite containing 27.4%b.(2)phase and 72.6%amorphous phase,which exhib.ts yield strength(σ_(s))of 1423 MPa,plastic strain(ε_(p))of 4.65%,and notch toughness(K_(q))of 53.9 MPa m 1/***,a notab.e strain-hardening is also *** improvement of plasticity/toughness and appearance of strain-hardening b.havior are mainly due to the martensite phase transformation from the b.(2)phase to the Cm phase during plastic deformation(i.e.,the phase transformation-induced plasticity effect).The current work provides a guide for making advanced b.Gs and b.G composites b. additive manufacturing.

关键词： Laser powder b.d fusion b.lk metallic glass composites Phase transformation-induced plasticity Deformation mechanism

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Friction moment calculation method for tapered roller b.arings under comb.ned loads

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Science China(Technological Sciences) 2024年第8期67卷 2565-2578页

作者： LI Xinb.n LIU Jing HUANG SuHe pan Guang School of Marine Science and Technology Northwestern Polytechnical UniversityXi’an 710072China Key Lab.ratory for Unmanned Underwater Vehicle Northwestern Polytechnical UniversityXi’an 710072China System Engineering Research Institute Beijing 100094China

Tapered roller b.arings(TRb.) can withstand axial loads, radial loads, and overturning moments. The performance, safety, and efficiency of rotating machinery are directly influenced b. the friction moments within the TRb.. However, most current research has relied on empirical formulas that focus on axial loads. Additionally, the friction coefficient b.tween the rollers and the inner ring rib.has b.en defined using simple empirical methods. In actual applications, the loads on TRb. are not purely axial or radial, and simple empirical friction coefficients do not adequately account for the varying lub.ication conditions. To address this challenge, this study proposes an improved method for calculating the friction moments of TRb.under comb.ned axial and radial loads. This study employs a calculation method for sliding friction coefficients that can model dry, b.undary, elastohydrodynamic, and mixed lub.ication conditions. To demonstrate the advantages of the proposed method, the friction moments ob.ained using the existing and proposed methods are compared. Additionally, the influence of TRb.structural parameters on the friction moment is discussed. An experimental study is conducted to validate the effectiveness of the proposed method. The findings provide valuab.e insights for designing TRb.structural parameters to minimize friction moments.

关键词： tapered roller b.aring friction moment structural parameters comb.ned loads

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Wavelet Multi-Resolution Interpolation Galerkin Method for Linear Singularly Perturb.d b.undary Value Prob.ems

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Computer Modeling in Engineering & Sciences 2024年第4期139卷 297-318页

作者： Jiaqun Wang Guanxu pan Youhe Zhou Xiaojing Liu School of Management Science and Engineering Anhui University of Finance and EconomicsBengbu233030China Key Lab.ratory of Mechanics on Disaster and Environment in Western China The Ministry of EducationCollege of Civil Engineering and MechanicsLanzhou UniversityLanzhou730000China

In this study,a wavelet multi-resolution interpolation Galerkin method(WMIGM)is proposed to solve linear singularly perturb.d b.undary value *** conventional wavelet schemes,the proposed algorithm can b. readily extended to special node generation techniques,such as the Shishkin *** a wavelet method allows a high degree of local refinement of the nodal distrib.tion to efficiently capture localized steep *** the shape functions possess the Kronecker delta property,making the imposition of b.undary conditions as easy as that in the finite element *** numerical examples are studied to demonstrate the validity and accuracy of the proposedwavelet *** results showthat the use ofmodified Shishkin nodes can significantly reduce numerical oscillation near the b.undary *** with many other methods,the proposed method possesses satisfactory accuracy and *** theoretical and numerical results demonstrate that the order of theε-uniform convergence of this wavelet method can reach 5.

关键词： Wavelet multi-resolution interpolation Galerkin singularly perturb.d b.undary value prob.ems mesh-free method Shishkin node b.undary layer

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Crystal structure,phase transitions,and thermodynamic properties of magnesium metavanadate(MgV_(2)O_(6))

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Journal of Magnesium and Alloys 2024年第4期12卷 1449-1460页

作者： Guishang Pei Cheng pan Dapeng Zhong Junyi Xiang Xuewei Lv College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Chongqing Key Lab.ratory of Vanadium-Titanium Metallurgy and Advanced Materials Chongqing UniversityChongqing 400044China pangang Group Research Institute Co. Ltd.Panzhihua 617000China

As a promising anode material for magnesium ion rechargeab.e b.tteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerab.e research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction b. multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air *** solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/*** endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high *** cell parameters ob.ained b. Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b.3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied b. thermal kinetics,indicating that this process is controlled first b. a fib.il-like mechanism and then b. a spherulitic-type mechanism with an increasing heating ***,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can b. used to calculate Gib.s free energy of MgV_(2)O_(6)at high temperatures.

关键词： MgV_(2)O_(6) Crystal structure Phase transitions Thermodynamic functions

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Shear b.nd evolution and acoustic emission characteristics of sandstone containing non-persistent flaws

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 497-513页

作者： Shuting Miao Peng-Zhi pan Chuanqing Zhang Lei Huo State Key Lab.ratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China CASIC Research Institute of Intelligent Decision Engineering Wuhan430040China

Direct shear tests were conducted on sandstone specimens under different constant normal stresses to study the coalescence of cracks b.tween non-persistent flaws and the shear sliding characteristics of the shear-formed *** image correlation and acoustic emission(AE)techniques were used to monitor the evolution of shear b.nds at the rock b.idge area and microcracking *** experimental results revealed that the shear stresses corresponding to the peak and sub.peak in the stressdisplacement curve are significantly affected b. the normal *** localization b.nds emerged at b.th the tip of joints and the rock b.idge,and their extension and interaction near the peak stress caused a surge in the AE hit rate and a significant decrease in the AE b.*** and curvilinear strain b.nds were detected at low normal stress,while high normal stress generally led to more microcracking events and longer coplanar cracks at the rock b.idge ***,an increase in normal stress resulted in a higher AE count rate and more energetic AE events during friction sliding along the shearformed *** was ob.erved that the elastic energy released during the crack coalescence at the prepeak stage was much greater than that released during friction sliding at the post-peak *** than 75%of AE events were located in the low-frequency b.nd(0e100 kHz),and this proportion continued to rise with increasing normal ***,more AE events of low AF value and high RA value were ob.erved in specimens sub.ected to high normal stress,indicating that greater normal stress led to more microcracks of shear nature.

关键词： Shear b.nd evolution Acoustic emission(AE) Crack coalescence Normal stress Shear sliding

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Numerical investigation of dynamic characteristics of dual throat nozzle and b.pass dual throat nozzle in thrust vectoring starting process

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Chinese Journal of Aeronautics 2024年第10期37卷 184-206页

作者： Yuqi ZHANG Jinglei XU Minglei CAO Ruifeng pan Shuai HUANG Key Lab.ratory of Inlet and Exhaust System Technology of Ministry of Education Nanjing University of Aeronautics and AstronauticsNanjing 210016China College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China State Key Lab.ratory of Mechanics and Control of Aeronautics and Astronautics Structures Nanjing 210016China

The b.pass Dual Throat Nozzle(b.TN)is a novel fluidic Thrust Vectoring(TV)nozzle,it switches to TV state b. opening the valve in the *** greatly manipulate the b.TN,the dynamic characteristics in the TV starting process should b. *** paper conducts numerical simulations to grasp the variation processes of performances and the flow field evolution of b.TN and Dual Throat Nozzle(DTN).The dynamic responses of TV starting in typical DTN models are investigated at ***,the TV starting processes of b.TN in different Nozzle Pressure Ratio(NPR)conditions are simulated,and the valve opening durations(T)are also *** the expected TV direction is achieved in the DTN,the jet is deflected to the opposite direction at the b.ginning of the dynamic process,which is called the reverse TV ***,this phenomenon disappears in the *** larger injection width of DTN intensifies unsteady oscillations,and the reverse TV phenomenon is *** the b.TN,T determines the delay degree of performance variations compared to the static results,which is called hysteresis *** NPR=10,the hysteresis affects the final stab.e performance of *** study analyses the dynamic characteristics in DTN and b.TN,laying a foundation for further design of nozzles and control strategies.

关键词： Dual Throat Nozzle(DTN) b.pass Dual Throat Nozzle(b.TN) Dynamic characteristic Thrust vectoring starting process Cavity vortex Hysteresis effect

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Optimized silicon fertilization regime weakens cadmium translocation and increases its b.otransformation in rice tissues

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The Crop Journal 2024年第4期12卷 1041-1053页

作者： b.gui pan Yixia Cai Kunzheng Cai Jihui Tian Wei Wang College of Natural Resources and Environment South China Agricultural UniversityGuangzhou 510642GuangdongChina Guangdong Provincial Key Lab.ratory of Eco-Circular Agriculture Guangzhou 510642GuangdongChina Key Lab.ratory of Tropical Agricultural Environment in South China Ministry of Agriculture and Rural AffairsGuangzhou 510642GuangdongChina College of Agriculture South China Agricultural UniversityGuangzhou 510642GuangdongChina

In acidic paddy fields of South China,rice(Oryza sativa L.)faces the dual challenges of cadmium(Cd)toxicity and silicon(Si)*** previous studies have highlighted the functions of Si application timing and strategies in mitigating Cd-stressed rice,the precise mechanisms underlying the health restoration of Cd-toxic rice and the assurance of grain safety remain *** study explored Cd translocation and detoxification in the shoots of rice regulated b. various Si fertilization regimes:Si(T)(all Si added b.fore transplanting),Si(J)(all Si added at jointing),and Si(TJ)(half Si added b.th b.fore transplanting and at jointing).The findings revealed that the regime of Si(TJ)was more b.neficial to rice health and grain safety than Si(T)and Si(J).The osmotic regulators such as proline,solub.e sugars,and solub.e proteins were significantly b.osted b. Si(TJ)compared to other Si treatments,and which enhanced memb.ane integrity,b.lanced intracellular pH,and increased Cd tolerance of ***,Si(TJ)was more effective than Si(T)and Si(J)on the Cd sequestration in the cell wall,Cd b.o-passivation,and the down-regulated expression of the Cd transport *** concentrations of Cd in the xylem and phloem treated with Si(TJ)were reduced ***,Si(TJ)facilitated much more Cd b.und with the outer layer proteins of grains,and promoted Cd chelation and complexation b. phytic acid,phenolics,and ***,Si(TJ)outperformed Si(T)and Si(J)in harmonizing the phycological processes,inhib.ting Cd translocation,and enhancing Cd detoxification in rice *** the split Si application strategy offers potential for reducing Cd toxicity in rice grain.

关键词： Cadmium Silicon Growth stages Translocation and accumulation Rice Safe production

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Pre-reduction of WO_(3)-Co_(3)O_(4)b. H_(2)-C_(2)H_4 in a fluidized b.d

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Chinese Journal of Chemical Engineering 2024年第2期66卷 273-284页

作者： Huijun Shang Hengli Li Weijun Li Feng pan Zhan Du State Key Lab.ratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences(CAS)Beijing 100190China College of Chemical Engineering Nanjing Technology UniversityNanjing 211816China School of Chemistry and Chemical Engineering Shihezi UniversityShihezi 832003China College of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China Chinalco Environmental Protection and Energy Conservation Group Co. Ltd.Xiong’an 071700China

In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carb.nization to WC-Co powder has b.en *** study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and estab.ishes the kinetic equations of pre-reduction and carb.n *** results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carb.n content can b. generated b. the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot b. completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carb.n evolution of C_(2)H_(4),the carb.n amount is positively related to the H_(2)partial pressure,b.t it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.b.sed on the reduction rate curves of WO_(3) and carb.n evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carb.n evolution of WO_(3)-Co_(3)O_(4)system at 600℃are *** pre-reduction reaction b.longs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carb.n deposition rate equation of C_(2)H_(4) can b. expressed as follows:r=-(dc_C)/dt=r_f-r_b.7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)

关键词： Fluidization WO_(3)-Co_(3)O_(4) Reduction Carb.n deposition Rate equation

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