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A novel approach to the dynamic response analysis of Euler-Bernoulli beams resting on a Winkler soil model and subjected to impact loads
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作者 Adolfo Foriero Filippo Santucci de Magistris Giovanni Fabbrocino 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2024年第2期389-401,共13页
This work presents a novel approach to the dynamic response analysis of a Euler-Bernoulli beam resting on a Winkler soil model and subjected to an impact loading.The approach considers that damping has much less impor... This work presents a novel approach to the dynamic response analysis of a Euler-Bernoulli beam resting on a Winkler soil model and subjected to an impact loading.The approach considers that damping has much less importance in controlling the maximum response to impulsive loadings because the maximum response is reached in a very short time,before the damping forces can dissipate a significant portion of the energy input into the system.The development of two sine series solutions,relating to different types of impulsive loadings,one involving a single concentrated force and the other a distributed line load,are presented.This study revealed that when a simply supported Euler-Bernoulli beam,resting on a Winkler soil model,is subject to an impact load,the resulting vertical displacements,bending moments and shear forces produced along the span of the beam are considerably affected.In particular,the quantification of this effect is best observed,relative to the corresponding static solution,via an amplification factor.The computed impact amplification factors,for the sub-grade moduli used in this study,were in magnitude greater than 2,thus confirming the multiple-degree-of-freedom nature of the problem. 展开更多
关键词 beam-Winkler-soil model sub-grade moduli impact load impact distributed line load dynamic solution impact amplification factor
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Dynamic model and driving strategy of corporate social responsibility
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作者 WANG Mao-xiang 《Ecological Economy》 2023年第2期192-200,共9页
Corporate social responsibility is the inevitable requirement for the survival and development of enterprises in modern society,as well as the basic guarantee for the sustainable development of economy and society.In ... Corporate social responsibility is the inevitable requirement for the survival and development of enterprises in modern society,as well as the basic guarantee for the sustainable development of economy and society.In order to analyze the driving factors of corporate social responsibility from both internal and external aspects,the dynamic model of corporate social responsibility was constructed,and the driving strategies of corporate social responsibility were also suggested.The driving factors of corporate social responsibility include not only the external constraints of policies,regulations and stakeholders,but also the internal requirements of the sustainable development of enterprises.Only when the external driving force is transformed into the spontaneous and conscious responsibility behavior of the enterprise,can the enterprise achieve its due effect.Moreover,in order to better fulfill the social responsibility,enterprise should build a management system of social responsibility,enhance the awareness of social responsibility,and promote the effective implementation of social responsibility projects.The relevant department should strengthen the all-round supervision of corporate social responsibility,and further improve the policies,laws and regulations related to social responsibility.Enterprises should strengthen communication with stakeholders,actively disclose social responsibility information,and constantly improve social responsibility behavior.By implementing social responsibility,enterprise can improve its business environment,enhance corporate brand image and core competitiveness,and promote the sustainable development of economy and society. 展开更多
关键词 corporate social responsibility dynamic factors driving model driving strategy
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Dynamic Factor Method of Computing Dynamic Mathematical Model for System Simulation
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作者 老大中 吴娟 +1 位作者 杨策 蒋滋康 《Journal of Beijing Institute of Technology》 EI CAS 2003年第2期143-148,共6页
The computational methods of a typical dynamic mathematical model that can describe the differential element and the inertial element for the system simulation are researched. The stability of numerical solutions of t... The computational methods of a typical dynamic mathematical model that can describe the differential element and the inertial element for the system simulation are researched. The stability of numerical solutions of the dynamic mathematical model is researched. By means of theoretical analysis, the error formulas, the error sign criteria and the error relationship criterion of the implicit Euler method and the trapezoidal method are given, the dynamic factor affecting the computational accuracy has been found, the formula and the methods of computing the dynamic factor are given. The computational accuracy of the dynamic mathematical model like this can be improved by use of the dynamic factor. 展开更多
关键词 system simulation dynamic mathematical model computational method dynamic factor ERROR
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Analytical Solution for Model-Based Dynamic Power Factor Measurement in AC Resistance Spot Welding
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作者 贡亮 刘成良 《Journal of Shanghai Jiaotong university(Science)》 EI 2007年第3期333-340,共8页
On the basis of welding transformer circuit model, a new measuring method was proposed. This method measures the peak angle of the welding current, and then calculates the dynamic power factor in each half-wave. An ar... On the basis of welding transformer circuit model, a new measuring method was proposed. This method measures the peak angle of the welding current, and then calculates the dynamic power factor in each half-wave. An artificial neural network is trained and used to generate simulation data for the analytical solution, i.e. a high-order binary polynomial, which can be easily adopted to calculate the power factor online. The tailored sensing and computing system ensures that the method possesses a real-time computational capacity and satisfying accuracy. A DSP-based resistance spot welding monitoring system was developed to perform ANN computation. The experimental results suggest that this measuring method is feasible. 展开更多
关键词 电阻焊 动能因子 模型 表面组件
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Numerical study on dynamic properties of rubberised concrete with different rubber contents
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作者 Lei Pan Hong Hao +1 位作者 Jian Cui Thong M.Pham 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2023年第6期228-240,共13页
As a green environmentally-friendly material,rubberised concrete(Ru C),which has the characteristics of low elastic modulus,large deformation capacity,high damping,good energy dissipation and good crack resistance,has... As a green environmentally-friendly material,rubberised concrete(Ru C),which has the characteristics of low elastic modulus,large deformation capacity,high damping,good energy dissipation and good crack resistance,has attracted extensive attention and research in the civil engineering discipline.However,most of existing studies are based on experimental tests on Ru C material properties,and there has been no numerical study based on meso-scale modelling of Ru C yet.To more comprehensively investigate the Ru C dynamic material properties without conducting intensive experimental tests,this study developed a high-fidelity meso-scale model considering coarse and fine aggregates and rubber crumbs to numerically investigate the mechanical properties of rubberised concrete under different strain rates.The meso-scale model was verified against both quasi-static compressive testing data and Split Hopkinson Pressure Bar(SHPB)dynamic testing data.Using the verified numerical model,the dynamic properties of rubberised concrete with various rubber content(0%-30%)under different strain rates were studied.The numerical results show that the developed meso-scale model can use to predict the static and dynamic properties of rubberised concrete with high accuracy.The dynamic compressive strength of the rubberised concrete increases with the increment of the strain rate,and the strain rate sensitivity increases with the rubber content ranging from 0 to 30%.Based on intensive numerical simulation data,empirical DIFs is used as a function of strain rate and rubber content to predict the dynamic strength of rubberised concrete. 展开更多
关键词 Rubberised concrete Meso-scale model Numerical simulation Strain rate effect dynamic increase factor
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Dynamic change of agricultural energy efficiency and its influencing factors in China
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作者 Haipeng Li Li Luo +1 位作者 Xiong Zhang Junbiao Zhang 《Chinese Journal of Population,Resources and Environment》 2021年第4期311-320,共10页
In order to practice the concept of‘lucid waters and lush mountains are invaluable assets’and promote the green development of agriculture,it is necessary to improve the efficiency of agricultural energy utilization... In order to practice the concept of‘lucid waters and lush mountains are invaluable assets’and promote the green development of agriculture,it is necessary to improve the efficiency of agricultural energy utilization.Based on the panel data of 28 provinces from 1995 to 2018,this paper calculated China’s agricultural energy input from two categories of direct energy and indirect energy,and used EBM(Epsilon-based Measure)mixed distance function model to measure the energy efficiency of agriculture in China.The nuclear density function and spatial autocorrelation were used to analyze the dynamic evolution of agricultural energy efficiency,and the dynamic panel model was used to analyze the influencing factors of agricultural energy efficiency.The results showed that:①From 1995 to 2018,the total agricultural energy input had increased year by year in China,with an average annual growth rate of 2%.Energy input structure changed from indirect energy-based to direct energy-based.Agricultural energy efficiency showed an evolutionary trend of‘rising-stagnating-rising rapidly’in China.The agricultural energy efficiency was generally low in China,and there was a large space for improvement in agricultural energy efficiency.②From 1995 to 2018,the average annual growth rate of agricultural energy efficiency in the eastern,central and western regions was 2.7%,1.9%and 1.4%respectively.In 2018,the agricultural energy efficiency in the eastern,central and western regions was 0.81,0.71 and 0.59 respectively.The gap between regions was expanding rapidly,and the agricultural energy efficiency in the central and western regions needed to be improved.③From 1995 to 2018,the agricultural energy efficiency of each province was polarized and the absolute gap was widened.There was obvious improvement in agricultural energy efficiency in Guangdong,Shandong,Jiangxi,Jiangsu,Liaoning and Tianjin,while the agricultural energy efficiency of Xinjiang,Guizhou,Zhejiang,Shanghai,and Inner Mongolia deteriorated.④From 1995 to 2018,there was no global spatial correlation of China’s agricultural energy efficiency.However,local‘high-high’concentration gradually appeared in the eastern region since 2010.⑤The first lag of energy efficiency had a significant positive impact on agricultural energy efficiency,and agricultural energy efficiency improvement had a time lag.The level of human capital,per capita net income of farmers and the level of urbanizaton had a significant positive impact on agricultural energy efficiency.The disaster rate,the level of development of secondary and tertiary industries,and the level of opening up had a significant negative impact on agricultural energy efficiency.In the implementation of the strategy of rural revitalization,we should focus on the central and western regions,take the cultivation of professional farmers as the key,focus on improving agricultural production conditions,enhance the level of cooperation between regions,exert the leading role of the secondary and tertiary industries,and enhance the ability of agricultural disaster prevention and mitigation. 展开更多
关键词 EBM model dynamic panel model Agricultural energy efficiency dynamic change Influencing factor
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Mathematical model of dynamic imbibition in nanoporous reservoirs
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作者 TIAN Weibing WU Keliu +3 位作者 CHEN Zhangxing LEI Zhengdong GAO Yanling LI Jing 《Petroleum Exploration and Development》 CSCD 2022年第1期170-178,共9页
The oil-water imbibition equation in the nano-scale pores considering the dynamic contact angle effect, nanoconfinement effect, inertia effect, and inlet end effect was established, and the relation between the fricti... The oil-water imbibition equation in the nano-scale pores considering the dynamic contact angle effect, nanoconfinement effect, inertia effect, and inlet end effect was established, and the relation between the friction coefficient of solid-oil-water three-phase contact line and the fluid viscosity in the interface zone was derived. In combination with the capillary bundle model and the lognormal distribution theory, the imbibition model of tight core was obtained and key parameters affecting imbibition dynamics were analyzed. The study shows that in the process of nanopore imbibition, the dynamic contact angle effect has the most significant impact on the imbibition, followed by nanoconfinement effect(multilayer sticking effect and slippage effect), and the inertia effect and inlet end effect have the least impact;in the initial stage of imbibition, the effect of inertial force decreases, and the effect of contact line friction increases, so the dynamic contact angle gradually increases from the initial equilibrium contact angle to the maximum and then remains basically stable;in the later stage of imbibition,the effect of contact line friction decreases, and the contact angle gradually decreases from the maximum dynamic contact angle and approaches the initial equilibrium contact angle;as the pore radius decreases, the dynamic contact angle effect increases in the initial stage of imbibition and decreases in the later stage of imbibition;as the oil-water interfacial tension increases, the imbibition power increases, and the dynamic contact angle effect increases;there is a critical value for the influence of interfacial tension on the imbibition dynamics. In improving oil recovery by imbibition in tight oil reservoir, interfacial tension too low cannot achieve good imbibition effect, and the best interfacial tension needs to be obtained through optimization. 展开更多
关键词 tight reservoir NANOPORE CAPILLARY imbibition model imbibition dynamics influencing factors
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Spatiotemporal Dynamics of Green Total-factor Water-use Efficiency and Its Influencing Factors in China
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作者 MA Dalai ZHANG Fengtai +3 位作者 GAO Lei YANG Guangming YANG Qing AN Youzhi 《Chinese Geographical Science》 SCIE CSCD 2021年第5期795-814,共20页
In this study,we developed an evaluation index system for green total-factor water-use efficiency(GTFWUE)which reflected both economic and green efficiencies of water resource utilization.Then we measured the GTFWUE o... In this study,we developed an evaluation index system for green total-factor water-use efficiency(GTFWUE)which reflected both economic and green efficiencies of water resource utilization.Then we measured the GTFWUE of 30 provinces/municipalities/autonomous regions(hereafter provinces)in China(not including Tibet,Hong Kong,Macao,Taiwan as no data)from 2000 to 2018 using a minimum distance to the strong frontier model that contained an undesirable output.We further analyzed the regional differences and spatial correlations of GTFWUE using these values based on Global and Local Moran’s I statistics,and empirically determined the factors affecting GTFWUE using a spatial econometric model.The evaluation results revealed that the GTFWUE differed substantially between the regions.The provinces with high and low GTFWUE values were located in the coastal and inland areas of China,respectively.The eastern region had a significantly higher GTFWUE than the central and western regions.The GTFWUEs for all three regions(eastern,central,and western regions)decreased slowly from 2000 to 2011(except 2005),remained stable from 2012 to 2016,and rapidly increased in 2017 before decreasing again in 2018.We found significant spatial correlations between the provincial GTFWUEs.The GTFWUE for most provinces belonged to the high-high or low-low cluster region,revealing a significant spatial clustering effect of provincial GTFWUEs.We also found that China’s GTFWUE was highly promoted by economic growth,population size,opening-up level,and urbanization level,and was evidently hindered by water endowment,technological progress,and government influence.However,the water-use structure had little impact on GTFWUE.This study fully demonstrated that the water use mode would be improved,and water resources needed to be used more efficiently and green in China.Moreover,based on the findings of this study,several policy recommendations were proposed from the aspects of cross-regional cooperation,economy,society,and institution. 展开更多
关键词 green total-factor water-use efficiency(GTFWUE) spatiotemporal dynamics water scarcity influencing factors spatial econometric model
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Capital mobility in Latin American and Caribbean countries: new evidence from dynamic common correlated effects panel data modeling
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作者 Vasudeva N.R.Murthy Natalya Ketenci 《Financial Innovation》 2020年第1期895-911,共17页
This study investigates the degree of capital mobility in a panel of 16 Latin American and 4 Caribbean countries during 1960 to 2017 against the backdrop of the Feldstein-Horioka hypothesis by applying recent panel da... This study investigates the degree of capital mobility in a panel of 16 Latin American and 4 Caribbean countries during 1960 to 2017 against the backdrop of the Feldstein-Horioka hypothesis by applying recent panel data techniques.This is the first study on capital mobility in Latin American and Caribbean countries to employ the recently developed panel data procedure of the dynamic common correlated effects modeling technique of Chudik and Pesaran(J Econ 188:393–420,2015)and the error-correction testing of Gengenbach,Urbain,and Westerlund(Panel error correction testing with global stochastic trends,2008,J Appl Econ 31:982–1004,2016).These approaches address the serious panel data econometric issues of crosssection dependence,slope heterogeneity,nonstationarity,and endogeneity in a multifactor error-structure framework.The empirical findings of this study reveal a low average(mean)savings–retention coefficient for the panel as a whole and for most individual countries,as well as indicating a cointegration relationship between saving and investment ratios.The results indicate that there is a relatively high degree of capital mobility in the Latin American and Caribbean countries in the short run,while the long-run solvency condition is maintained,which is due to reduced frictions in goods and services markets causing increase competition.Increased capital mobility in these countries can promote economic growth and hasten the process of globalization by creating a conducive economic environment for FDI in these countries. 展开更多
关键词 dynamic common correlated effects Panel-error correction modeling Cross-sectional dependence Unobserved common factors Slope heterogeneity Capital mobility
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Simulation Analysis of Macroeconomic Policy Orientations' Effects on the Industrial Economy——Based on Dynamic CGE Model
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作者 原磊 王秀丽 《China Economist》 2014年第2期100-112,共13页
There are three different orientations of the macroeconomic policies,namely,factor-expansion,prudent-continuation and structural-adjustment.The paper uses the dynamic CGE model to simulate the effects of the three dif... There are three different orientations of the macroeconomic policies,namely,factor-expansion,prudent-continuation and structural-adjustment.The paper uses the dynamic CGE model to simulate the effects of the three different orientations on the economy,and arrives at the following conclusions:while the factor-expansion policies can lead to growth of economic output,they also result in the further imbalance in the industrial structure and the "crowding-out effect" on the private investment.In addition,such growth is unsustainable in the long run;the growth of the industrial economy will decline rapidly to a lower level after reaching a certain high level.The prudent-continuation policies refer to the continuation of the current policies that sustain the current trends of the industrial economy,and such policies reduce the growth of the industrial economy to a lower level in the long run.The structural-adjustment policies reduce the economic output at the current stage;however,it can bring a gradual improvement of industrial structure and a balance of the supply and demand.In the long run,the optimized structure will improve the total factor productivity(TFP) and the production-possibility frontier,and thereby realize a longterm steady and rapid growth of the industrial economy.Four policy recommendations are proposed based on the simulation of the models,including taking the structural adjustment as the fundamental orientation of macroeconomic policies,lowering the "floor level" of economic growth with macro regulation,giving play to the fundamental role of market mechanism in structural adjustment and increasing the role of TFP in the growth of the industrial economy. 展开更多
关键词 宏观经济政策 工业经济 CGE模型 取向 仿真 分析基 全要素生产率 结构调整
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Experimental Study on Free Spanning Submarine Pipeline Under Dynamic Excitation 被引量:9
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作者 李昕 刘亚坤 +2 位作者 周晶 马恒春 朱彤 《China Ocean Engineering》 SCIE EI 2002年第4期537-548,共12页
Seismic load has a significant effect on the response of a free spanning submarine pipeline when the pipeline is constructed in a seismically active region. The model experiment is performed on an underwater shaking t... Seismic load has a significant effect on the response of a free spanning submarine pipeline when the pipeline is constructed in a seismically active region. The model experiment is performed on an underwater shaking table to simulate the response of submarine pipelines under dynamic input. In consideration of the effects of the terrestrial and submarine pipeline, water depth, support condition, distance from seabed, empty and full pipeline, and span on dynamic response, 120 groups of experiments are conducted. Affecting factors are analyzed and conclusions are drawn for reference. For the control of dynamic response, the span of a submarine pipeline is by far more important than the other factors. Meanwhile, the rosponse difference between a submarine pipeline under sine excitation and that under random excitation exists in experiments. 展开更多
关键词 free spanning submarine pipeline underwater shaking table model experiment dynamic response factor analysis
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Multistable Spatiotemporal Dynamics in the Driven Frenkel-Kontorova Lattice 被引量:1
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作者 ZHENG Zhi-Gang 《Communications in Theoretical Physics》 SCIE CAS CSCD 2001年第7期37-43,共7页
Spatiotemporal dynamics of the damped dc-driven Frenkel-Kontorova lattice is studied. Multistable topologies are shown. Intermittency of the dynamical contraction factor is found, and this behavior is a consequence of... Spatiotemporal dynamics of the damped dc-driven Frenkel-Kontorova lattice is studied. Multistable topologies are shown. Intermittency of the dynamical contraction factor is found, and this behavior is a consequence of the collisions of kinks and antikinks. Fast kinks and antikinks are unstable. The transition from the localized kink to the whirling mode is found to be a temporal bifurcation cascade of generations of kink-antikink pairs and the collision-induced avalanche dynamics. Noise-induced topology transition is observed and discussed. 展开更多
关键词 Frenkel-Kontorova model kink-antikink pair dynamicAL CONTRACTION factor
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Dynamic behaviors of pretensioned cable AERORail structure
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作者 李方元 吴培峰 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第6期2267-2276,共10页
The AERORail, a new aerial transport platform, was chosen as the object of this work. Following a review of the literature on static behaviors, model tests on the basic dynamic mechanical characteristics were conducte... The AERORail, a new aerial transport platform, was chosen as the object of this work. Following a review of the literature on static behaviors, model tests on the basic dynamic mechanical characteristics were conducted. A series of 90 tests were completed with different factors, including tension force, vehicle load and vehicle speed. With regard to the proper tension and vehicle load, at a certain speed range, the tension increments of the rail's cable were proved relatively small. It can be assumed that the change of tension is small and can be reasonably ignored when the tension of an entire span is under a dynamic load. When the tension reaches a certain range, the calculation of the cable track structure using classical cable theory is acceptable. The tests prove that the average maximum dynamic amplification factor of the deflection is small, generally no more than 1.2. However, when the vehicle speed reaches a certain value, the amplified factor will reach 2.0. If the moving loads increase, the dynamic amplification factor of dynamic deflection will also increase. The tension will change the rigidity of the structure and the vibration frequency; furthermore, the resonance speed will change at a certain tension. The vibration is noticeable when vehicles pass through at the resonance speed, and this negative impact on driving comfort requires the right velocity to avoid the resonance. The results demonstrate that more design details are required for the AERORail structure. 展开更多
关键词 预应力索结构 动态特性 动力放大系数 车辆速度 动态力学特性 模型试验 车辆负载 振动频率
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胶东型金矿
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作者 杨立强 邓军 +5 位作者 张良 杨伟 谢东 汪龙 邱昆峰 李大鹏 《岩石学报》 SCIE EI CAS CSCD 北大核心 2024年第6期1691-1711,共21页
胶东是全球唯一已知赋存于前寒武纪变质地体中的晚中生代巨型金矿省,其成矿系统独具特色,具体表现为:(1)位于陆内复合构造域,经历了多期重大构造-热事件,大规模金成矿作用受控于120±2Ma古太平洋板块俯冲方向变化及其诱发的软流圈... 胶东是全球唯一已知赋存于前寒武纪变质地体中的晚中生代巨型金矿省,其成矿系统独具特色,具体表现为:(1)位于陆内复合构造域,经历了多期重大构造-热事件,大规模金成矿作用受控于120±2Ma古太平洋板块俯冲方向变化及其诱发的软流圈上涌、岩石圈改造和伸展-挤压变形交替及控矿断裂剪压-剪张转换;(2)多重控矿构造和多样赋矿建造联合控制了不同规模和类型金矿的发育,形成了三山岛、焦家、招平、栖霞、郭即和牟乳六条NE向金矿带和三山岛-栖霞EW向富金廊带,导致了金矿化类型(焦家式/破碎带蚀变岩型、玲珑式/石英脉型、蓬家夼式/蚀变砾岩±角砾岩型、辽上式/黄铁矿-碳酸盐脉型)及其地质-地球化学特征的多样性;(3)主要矿化元素Au、Ag、Cu、Pb和Zn均达到工业利用要求,并有多种共/伴生关键金属超常富集;(4)不同金矿带中硫化物Pb同位素组成与探明金资源储量及到郯庐断裂带的距离线性相关,反映距离幔源流体主通道越近、金属硫化物中放射性成因Pb含量和幔源组分占比越多、金成矿强度越大;(5)区域总体相对均一的Δ199 Hg(平均~0.012‰)及Δ199 Hg/Δ201 Hg与金品位呈线性负相关,表明成矿物质来源于富集岩石圈地幔、且地幔被俯冲洋壳及其上覆沉积物交代的程度控制了金品位的高低;(6)区域恒定的Δ33 S同位素组成(~0‰)排除了巨量金源自太古宙变质基底及其重熔花岗岩的可能,重的δ34 S(平均9.0±3.7‰)来源于俯冲的古太平洋板片及其上覆沉积物的脱挥发份;不同金矿带Δ33 S/δ34 S与探明金资源储量及其到郯庐断裂带距离线性相关,反映成矿期地壳伸展程度控制了金成矿强度;(7)区域He-Ar和H-O同位素组成显示壳幔混合特征,焦家式金矿的成矿流体组成更靠近地幔、玲珑式金矿位于地幔与地壳过渡带;三山岛、焦家和招平金矿带的成矿流体相对接近幔源流体,而郭即金矿带具有相对开放的构造环境;不同金矿带氢-氧同位素组成和探明金资源储量正相关,可能表征了从西到东成矿流体通量和流体-岩石反应强度逐渐降低。基于对上述特征的总结,提出了胶东型金矿的成因模式,明确了其成矿地球动力学背景和深部驱动、巨量金属和流体及络合物来源、输运通道和方式、源→汇过程和机制、成矿后变化和保存等成矿系统形成的关键因素,确立了“拆离断裂系与基底活化带及幔源流体通道复合控矿”的勘查思路和“四步式”的勘查模型。综上,胶东金矿不同尺度的鉴别特征及其形成的关键因素明显不同于全球已知的其他金矿类型,难以被已有成矿模式所涵盖,属于一种新的金矿类型——胶东型,其成因模式对华北、华南、西伯利亚、西澳伊尔岗、北美怀俄明和南美圭亚那等陆内金矿床具有普适性;系列找矿突破则验证了该成因模式与勘查模型的合理性和适用性。因此,本文认为胶东型金矿是全球研究热点和重要的金矿勘查方向,而该地区找矿的主攻目标是资源量大且品位和产状稳定的破碎带蚀变岩型金矿。 展开更多
关键词 矿床地质-地球化学特征 成矿系统 时-空结构 成矿动力学 控矿因素 成因及勘查模型 胶东型金矿
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环境规制与中国经济绿色增长研究——基于省级面板数据的经验分析
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作者 许先普 袁翠 《衡水学院学报》 2024年第4期34-39,104,共7页
选取2003—2019年中国30个省份的面板数据,基于DEA-Malmquist指数模型测算绿色全要素生产率并分析其时空演变特征。运用动态面板模型和系统广义矩法检验环境规制对中国绿色全要素生产率的影响。研究表明:总体上,环境规制与绿色全要素生... 选取2003—2019年中国30个省份的面板数据,基于DEA-Malmquist指数模型测算绿色全要素生产率并分析其时空演变特征。运用动态面板模型和系统广义矩法检验环境规制对中国绿色全要素生产率的影响。研究表明:总体上,环境规制与绿色全要素生产率符合U型关系;分区域来看,东部地区的环境规制与绿色全要素生产率的关系为U型,中部和西部地区为倒U型;从作用机制来看,技术创新在环境规制对绿色全要素生产率的影响过程中发挥正向中介效应。因此,政府应采取分阶段制定环境政策,尽早跨越“波特拐点”;实行差异化规制手段,统筹区域协调发展;加强技术创新,实现绿色经济高质量发展等措施。 展开更多
关键词 绿色全要素生产率 环境规制 动态面板模型 系统广义矩
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服务业进出口、OFDI和全要素生产率的动态关系研究——基于VAR模型的实证分析
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作者 甘志霞 李松洁 《技术与创新管理》 2024年第1期87-93,共7页
研究服务业贸易、投资与服务业之间的影响关系,对提升我国服务行业国际竞争力、促进其高质量发展具有重要意义。论文使用我国2000—2021年数据,构建VAR模型对服务业进出口、服务业对外直接投资(OFDI)和全要素生产率的动态交互关系进行... 研究服务业贸易、投资与服务业之间的影响关系,对提升我国服务行业国际竞争力、促进其高质量发展具有重要意义。论文使用我国2000—2021年数据,构建VAR模型对服务业进出口、服务业对外直接投资(OFDI)和全要素生产率的动态交互关系进行实证分析。研究结果显示,服务业进出口对服务业对外直接投资具有正相关关系,且长期支持效果明显;服务业进出口对OFDI、全要素生产率提升具有促进作用;在短期内,全要素生产率与OFDI之间存在双向促进作用,从长期来看则存在一定负向影响。基于实证研究结论,文中提出制定政策鼓励服务企业参与国际化竞争、发挥服务业进出口对OFDI的促进效应、提升服务企业自主创新能力等相关对策建议。 展开更多
关键词 服务业进出口 服务业对外直接投资 全要素生产率 VAR模型 动态互动关系 逆向技术溢出效应
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脑卒中住院患者性别、年龄及时空分布特征:基于宁夏地区19万例患者数据 被引量:1
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作者 赵媛 刘尚红 +6 位作者 张延芳 马立旭 李红 李小花 田园 郭忠琴 梁沛枫 《中国全科医学》 北大核心 2024年第8期915-920,共6页
背景脑卒中是血液无法流入大脑而导致脑组织受损的一种急性脑血管疾病,其致残率、致死率以及复发率较高,宁夏地区相关研究多为脑卒中临床相关分析,缺乏对近年宁夏地区脑卒中住院情况的变化趋势分析。目的分析宁夏地区脑卒中住院患者疾... 背景脑卒中是血液无法流入大脑而导致脑组织受损的一种急性脑血管疾病,其致残率、致死率以及复发率较高,宁夏地区相关研究多为脑卒中临床相关分析,缺乏对近年宁夏地区脑卒中住院情况的变化趋势分析。目的分析宁夏地区脑卒中住院患者疾病流行特征及分布情况,为制定脑卒中综合防治措施提供依据。方法收集宁夏地区共55家中医及西医医院的病案首页数据,筛选出2013—2019年出院且主要诊断为脑卒中[国际疾病分类(ICD)-10编码为I60~I63]的数据进行分析。应用SPSS 24.0软件采用χ^(2)检验对性别及年龄进行差异性分析,应用地理信息系统采用全局空间自相关分析方法对宁夏地区2013—2019年脑卒中住院率数据的分布进行分析。结果最终纳入190634例脑卒中患者数据。2013—2019年宁夏地区脑卒中住院率呈逐年上升趋势(住院率分别为24.302/10000、30.045/10000、34.949/10000、39.397/10000、44.049/10000、47.617/10000、52.944/10000,χ_(趋势)^(2)=5.982,P=0.014),且在每年的寒冷季节住院率较高,每年3月份有1个明显的高峰,之后稍有下降。2013—2019年宁夏地区脑卒中住院患者中,缺血性脑卒中167194例,出血性脑卒中23440例;缺血性脑卒中和出血性脑卒中患者不同性别、年龄比较,差异有统计学意义(χ^(2)=473.533、7518.543,P<0.05);且从数据上看,缺血性脑卒中和出血性脑卒中男性、≥60岁住院患者所占比例均超过50%。全局空间自相关分析结果显示,2013年、2018年和2019年脑卒中住院率存在空间聚集性(P<0.05)。空间分布图显示,宁夏地区住院的脑卒中患者主要集中在宁夏中北部。结论2013—2019年宁夏地区脑卒中患者住院率表现为不断上升且存在不同程度的聚集性,住院率较高的地区集中在宁夏中北部。 展开更多
关键词 脑卒中 住院病人 性别因素 年龄因素 动态队列 空间自相关 模型 统计学 宁夏
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磁致伸缩执行器数学建模与仿真分析
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作者 李贵飞 李跃松 +1 位作者 库祥臣 张贻哲 《计算机仿真》 2024年第1期328-332,394,共6页
针对设计的磁致伸缩执行器的输出特性及其内部复杂物理现象,基于电磁学理论、Jiles-Atherton模型、能量守恒理论、结构动力学理论提出了更为准确的执行器动力学行为描述模型并分析。上述模型考虑输入电流、磁导率、动态损耗、电磁力等... 针对设计的磁致伸缩执行器的输出特性及其内部复杂物理现象,基于电磁学理论、Jiles-Atherton模型、能量守恒理论、结构动力学理论提出了更为准确的执行器动力学行为描述模型并分析。上述模型考虑输入电流、磁导率、动态损耗、电磁力等多种因素间的关系及其对输出特性的影响,以Jiles-Atherton模型定义磁致伸缩材料并通过maxwell软件对以磁致伸缩材料为核心的执行器进行有限元仿真分析,将仿真结果与数学解析模型结合并加以修正,得到更加准确的系统动力学模型。最终在MATLAB/Simulink中搭建系统动力学模型仿真分析发现,由电磁场所产生的交变电磁力导致磁致伸缩棒预压力偏置现象对执行器输出性能较大,而电流、动态损耗及磁导率通过影响磁场进而影响执行器输出。 展开更多
关键词 磁致伸缩执行器 有限元仿真 系统动力学模型 输出影响因素
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Nelson-Siegel模型中的时变载荷因子及其对提高经济形势预测的重要作用
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作者 张靖泽 沈根祥 《统计研究》 北大核心 2024年第2期77-86,共10页
现有文献中Nelson-Siegel模型大多将载荷因子λ提前固定为常数或作为待估静态参数,较少考虑载荷因子λ的时变化。本文基于得分驱动时变参数建模方法,在状态空间模型框架内考虑时变载荷因子λ,构建GAS-λ-DNS模型,并提取相应时变载荷因... 现有文献中Nelson-Siegel模型大多将载荷因子λ提前固定为常数或作为待估静态参数,较少考虑载荷因子λ的时变化。本文基于得分驱动时变参数建模方法,在状态空间模型框架内考虑时变载荷因子λ,构建GAS-λ-DNS模型,并提取相应时变载荷因子。结果显示,时变载荷因子λ_(t)呈现出极强的波动性,同时与经济周期密切相关;将时变载荷因子λ_(t)应用于预测工业产出增速,发现载荷因子相比于传统宏观预测因子具有额外增量信息,引入λ_(t)可以显著提高模型预测精度。本文结论对Nelson-Siegel利率期限结构建模和宏观经济预测因子选取具有参考价值。 展开更多
关键词 动态Nelson-Siegel模型 GAS模型 时变载荷因子 宏观经济预测
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循环荷载作用下土工格栅加筋黄土动力特性研究
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作者 唐富春 张吾渝 +1 位作者 唐鑫 刘成奎 《水利水电技术(中英文)》 北大核心 2024年第3期148-161,共14页
【目的】由于黄土所具有的结构疏松、抗剪性低,以及对水、力及震动都十分敏感等工程特性,故探究采用双向土工格栅对西宁地区黄土加筋前后土体动力性能的改善效果。【方法】采用GDS双向动三轴测试系统开展不同加筋层间距、不同围压、不... 【目的】由于黄土所具有的结构疏松、抗剪性低,以及对水、力及震动都十分敏感等工程特性,故探究采用双向土工格栅对西宁地区黄土加筋前后土体动力性能的改善效果。【方法】采用GDS双向动三轴测试系统开展不同加筋层间距、不同围压、不同动应力幅值工况条件下加筋黄土的动三轴试验,分析循环荷载作用下加筋层间距对黄土动强度、动剪切模量、阻尼比等动力响应特性的影响,探讨分析加筋黄土动力响应特性的演化规律。【结果】结果显示:黄土动应变随着动应力的增大而增大,骨干曲线呈现应变强化型,并且骨干曲线随加筋层间距的减小逐渐由曲线型过渡为直线型;随着加筋层间距的减小,黄土强度随之增大,随着围压和加筋层间距的增加,黄土幅值剪应力明显增大,动剪应变减小,阻尼比明显减小。【结论】结果表明:围压和加筋层间距对加筋黄土的动力特性具有显著的增强作用,且存在一个最优加筋层间距。研究成果可为西宁地区加筋黄土道路设计提供参考依据。 展开更多
关键词 土工格栅 动三轴模型试验 加筋间距 动力特性 循环荷载 变形 影响因素
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