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Numerical Study of Multi-Factor Coupling Effects on Energy Conversion Performance of Nanofluidic Reverse Electrodialysis
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作者 Hao Li Cunlu Zhao +4 位作者 Jinhui Zhou Jun Zhang Hui Wang Yanmei Jiao Yugang Zhao 《Frontiers in Heat and Mass Transfer》 2025年第2期507-528,共22页
Based on the rapid advancements in nanomaterials and nanotechnology,the Nanofluidic Reverse Electrodialysis(NRED)has attracted significant attention as an innovative and promising energy conversion strategy for extrac... Based on the rapid advancements in nanomaterials and nanotechnology,the Nanofluidic Reverse Electrodialysis(NRED)has attracted significant attention as an innovative and promising energy conversion strategy for extracting sustainable and clean energy fromthe salinity gradient energy.However,the scarcity of research investigating the intricate multi-factor coupling effects on the energy conversion performance,especially the trade-offs between ion selectivity and mass transfer in nanochannels,of NRED poses a great challenge to achieving breakthroughs in energy conversion processes.This numerical study innovatively investigates the multi-factor coupling effect of three critical operational factors,including the nanochannel configuration,the temperature field,and the concentration difference,on the energy conversion processes of NRED.In this work,a dimensionless amplitude parameter s is introduced to emulate the randomly varied wall configuration of nanochannels that inherently occur in practical applications,thereby enhancing the realism and applicability of our analysis.Numerical results reveal that the application of a temperature gradient,which is oriented in opposition to the concentration gradient,enhances the ion transportation and selectivity simultaneously,leading to an enhancement in both output power and energy conversion efficiency.Additionally,the increased fluctuation of the nanochannel wall from s=0 to s=0.08 improves ion selectivity yet raises ion transport resistance,resulting in an enhancement in output power and energy conversion efficiency but a slight reduction in current.Furthermore,with increasing the concentration ratio cH/cL from 10 to 1000,either within a fixed temperature field or at a constant dimensionless amplitude,the maximumpower consistently attains its optimal value at a concentration ratio of 100 but the cation transfer number experiences amonotonic decrease across this entire range of concentration ratios.Finally,uponmodifying the operational parameters fromthe baseline condition of s=0,c_(H)/c_(L)=10,andΔT=0 K to the targetedconditionof s=0.08,c_(H)/c_(L)=50,andΔT=25 K,there is a concerted improvement observed in the open-circuit potential,short-circuit current,andmaximumpower,with respective increments of 8.86%,204.97%,and 232.01%,but a reduction in cation transfer number with a notable decrease of 15.37%. 展开更多
关键词 Salinity gradient energy nanofluidic reverse electrodialysis energy conversion nanochannel configuration multi-factor coupling effect
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Uneven frost heave deformation in water conveyance channels in cold-arid regions:Experimental evidence and thermo-hydromechanical coupling analysis
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作者 Zhaoxi Wang Chen Cao +5 位作者 Qingbo Yu Jiejie Shen Mengxia Han Weitong Xia Xun Sun Qing Wang 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第11期7107-7126,共20页
Uneven frost heave deformation can shorten the operational lifespan of foundation engineering.Clarifying the mechanisms of uneven frost heave facilitates the targeted mitigation of frost damage.This study focused on a... Uneven frost heave deformation can shorten the operational lifespan of foundation engineering.Clarifying the mechanisms of uneven frost heave facilitates the targeted mitigation of frost damage.This study focused on a water conveyance channel in Jilin Province,northern China,and found after monitoring that the frost heave at the channel bottom lining exceeded that at the crest by 44.5 mm,with the freezing temperature at the bottom being over 2℃lower than that at the crest.Soil columns with an initial gravimetric moisture content of 12%,16%,18%,and 20%were then prepared.The effects of temperature and moisture content on frost heave were analyzed under two freezing conditions(-5℃and-10℃)through unidirectional freezing tests.A coupled thermo-hydro-mechanical(THM)frost heave model,validated by the test results,was further established.In the soil with an initial moisture content of 20%,the formation of ice lenses associated with substantial water migration contributed to a large temperature gradient,which can jointly induce frost heave.Under the-10℃condition,the temperature gradient in the soil column with a 20%initial moisture content reached 0.84℃/cm,the total water migration reached 10.72%,and the frost heave deformation was 1.86 mm.The THM coupling results indicated that,under the interaction of a large temperature gradient and moisture accumulation,the volumetric ice content remained high in the bottom soil during freezing and peaked at 0.36.The frost damage to the bottom soil was severe,and the maximum deformation reached 57 mm. 展开更多
关键词 Frost heave Channel lining Initial moisture content Temperature gradient Unidirectional freezing test Water migration Multi-physics coupling simulation
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Rotating spin-1/2 Bose–Einstein condensates in a gradient magnetic field with spin–orbit coupling
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作者 Ji-Guo Wang Yue-Qing Li 《Communications in Theoretical Physics》 SCIE CAS CSCD 2020年第9期140-145,共6页
We study the ground-state phases of two-dimensional rotating spin-orbit coupled spin-1/2 Bose-Einstein condensates(BECs) in a gradient magnetic field. The competition between gradient magnetic field, spin-orbit coupli... We study the ground-state phases of two-dimensional rotating spin-orbit coupled spin-1/2 Bose-Einstein condensates(BECs) in a gradient magnetic field. The competition between gradient magnetic field, spin-orbit coupling and rotation leads to a variety of ground-state phase structures. In the weakly rotation regime, as the increase of gradient magnetic field strength, the BECs experiences a phase transition from the unstable phase to the single vortex-line phase. The unstable phase presents the vortex lines structures along the off-diagonal direction. With magnetic field gradient strength increasing, the number of vortex lines changes accordingly. As the magnetic field gradient strength increases further, the single vortex-line phase with a single vortex line along the diagonal direction is formed. The phase diagram shows that the boundary between the two phases is linear with the relative repulsion λ?≥?1 and is nonlinear with λ? 展开更多
关键词 Bose–Einstein condensate spin–orbit coupling gradient magnetic field
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Derivation of General Formula for Coupling Loss of Single-mode Fiber Collimators with Gradient-index Rod Lenses
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作者 XIE Hu, LUO Feng guang, CAO Ming cui, YUAN Jing, WAN Zhu jun (State Key Lab.of Laser Technol.,Huazhong University of Sci.& Technol.,Wuhan 430074,CHN) 《Semiconductor Photonics and Technology》 CAS 2003年第4期215-220,共6页
Gradient-index rod lens (GRIN-lens) whose pitch is ordinary value with bevel ferrule coupling system is analyzed, an equivalent method which can be used to analyze this system is put forward, and a general formula for... Gradient-index rod lens (GRIN-lens) whose pitch is ordinary value with bevel ferrule coupling system is analyzed, an equivalent method which can be used to analyze this system is put forward, and a general formula for determining the coupling loss with axes mismatch, radial mismatch, and angular mismatch is derived by use of the Gaussian field approximation and mode-field coupling theory. The experimental results are in good agreement with the theory prediction. It indicates that these formulas are suitable to analyze the gradient-index rod lens coupling system with pigtail fiber. 展开更多
关键词 gradient―index rod lens single―mode fiber coupling loss COLLIMATOR
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Beyond Classical Elasticity:A Review of Strain Gradient Theories,Emphasizing Computer Modeling,Physical Interpretations,and Multifunctional Applications
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作者 Shubham Desai Sai Sidhardh 《Computer Modeling in Engineering & Sciences》 2025年第8期1271-1334,共64页
The increasing integration of small-scale structures in engineering,particularly in Micro-Electro-Mechanical Systems(MEMS),necessitates advanced modeling approaches to accurately capture their complex mechanical behav... The increasing integration of small-scale structures in engineering,particularly in Micro-Electro-Mechanical Systems(MEMS),necessitates advanced modeling approaches to accurately capture their complex mechanical behavior.Classical continuum theories are inadequate at micro-and nanoscales,particularly concerning size effects,singularities,and phenomena like strain softening or phase transitions.This limitation follows from their lack of intrinsic length scale parameters,crucial for representingmicrostructural features.Theoretical and experimental findings emphasize the critical role of these parameters on small scales.This review thoroughly examines various strain gradient elasticity(SGE)theories commonly employed in literature to capture these size-dependent effects on the elastic response.Given the complexity arising from numerous SGE frameworks available in the literature,including first-and second-order gradient theories,we conduct a comprehensive and comparative analysis of common SGE models.This analysis highlights their unique physical interpretations and compares their effectiveness in modeling the size-dependent behavior of low-dimensional structures.A brief discussion on estimating additional material constants,such as intrinsic length scales,is also included to improve the practical relevance of SGE.Following this theoretical treatment,the review covers analytical and numerical methods for solving the associated higher-order governing differential equations.Finally,we present a detailed overview of strain gradient applications in multiscale andmultiphysics response of solids.Interesting research on exploring the relevance of SGE for reduced-order modeling of complex macrostructures,a universal multiphysics coupling in low-dimensional structures without being restricted to limited material symmetries(as in the case of microstructures),is also presented here for interested readers.Finally,we briefly discuss alternative nonlocal elasticity approaches(integral and integro-differential)for incorporating size effects,and conclude with some potential areas for future research on strain gradients.This review aims to provide a clear understanding of strain gradient theories and their broad applicability beyond classical elasticity. 展开更多
关键词 Strain gradient nonlocal elasticity size effects MICROSTRUCTURE multiphysics coupling
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Coupling Magneto-Electro-Elastic node-based smoothed radial point interpolation method for free vibration and transient analysis of Functionally Graded Magneto-Electro-Elastic structures 被引量:2
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作者 Liming ZHOU Shuhui REN +2 位作者 Bin NIE Guikai GUO Xiangyang CUI 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2020年第1期227-243,共17页
A Coupling Magneto-Electro-Elastic(MEE)Node-based Smoothed Radial Point Interpolation Method(CM-NS-RPIM)was proposed to solve the free vibration and transient responses of Functionally Graded Magneto-Electro-Elastic(F... A Coupling Magneto-Electro-Elastic(MEE)Node-based Smoothed Radial Point Interpolation Method(CM-NS-RPIM)was proposed to solve the free vibration and transient responses of Functionally Graded Magneto-Electro-Elastic(FGMEE)structures.By introducing the modified Newmark method,the displacement,electrical potential and magnetic potential of the structures under transient mechanical loading were obtained.Based on G space theory and the weakened weak(W2)formulation,the equations of the multi-physics coupling problems were derived.Using triangular background elements,the free vibration and transient responses of three numerical examples were studied.Results proved that CM-NS-RPIM performed better than the standard FEM by reducing the overly-stiff of structures.Moreover,CM-NS-RPIM could reduce the number of nodes while guaranteeing the accuracy.Besides,triangular elements could be generated automatically even for complex geometries.Therefore,the effectiveness and validity of CM-NS-RPIM were demonstrated,which were valuable for the design of intelligence devices,such as energy harvesters and sensors. 展开更多
关键词 coupling MAGNETO-ELECTRO-ELASTIC node-based smoothed radial point interpolation method Functionally Graded MAGNETO-ELECTRO-ELASTIC gradient smoothing technique Rayleigh damping Transient responses
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Ru thickness-dependent interlayer coupling and ultrahigh FMR frequency in FeCoB/Ru/FeCoB sandwich trilayers
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作者 Le Wang Zhao-Xuan Jing +1 位作者 Ao-Ran Zhou Shan-Dong Li 《Chinese Physics B》 SCIE EI CAS CSCD 2022年第8期552-560,共9页
The antiferromagnetic(AFM) interlayer coupling effective field in a ferromagnetic/non-magnetic/ferromagnetic(FM/NM/FM) sandwich structure, as a driving force, can dramatically enhance the ferromagnetic resonance(FMR) ... The antiferromagnetic(AFM) interlayer coupling effective field in a ferromagnetic/non-magnetic/ferromagnetic(FM/NM/FM) sandwich structure, as a driving force, can dramatically enhance the ferromagnetic resonance(FMR) frequency. Changing the non-magnetic spacer thickness is an effective way to control the interlayer coupling type and intensity, as well as the FMR frequency. In this study, Fe Co B/Ru/Fe Co B sandwich trilayers with Ru thickness(tRu) ranging from 1 A to 16 A are prepared by a compositional gradient sputtering(CGS) method. It is revealed that a stress-induced anisotropy is present in the Fe Co B films due to the B composition gradient in the samples. A tRu-dependent oscillation of interlayer coupling from FM to AFM with two periods is observed. An AFM coupling occurs in a range of 2 A ≤ tRu≤ 8 A and over 16 A, while an FM coupling is present in a range of tRu< 2 A and 9 A ≤ tRu≤ 14.5 A. It is interesting that an ultrahigh optical mode(OM) FMR frequency in excess of 20 GHz is obtained in the sample with tRu= 2.5 A under an AFM coupling. The dynamic coupling mechanism in trilayers is simulated, and the corresponding coupling types at different values of tRuare verified by Layadi’s rigid model. This study provides a controllable way to prepare and investigate the ultrahigh FMR films. 展开更多
关键词 interlayer exchange coupling optical mode resonance acoustic mode resonance component gradient sputtering
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The Optimal Precursors for ENSO Events Depicted Using the Gradientdefinition-based Method in an Intermediate Coupled Model
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作者 Bin MU Juhui REN +3 位作者 Shijin YUAN Rong-Hua ZHANG Lei CHEN Chuan GAO 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2019年第12期1381-1392,共12页
The predictability of El Ni-o-Southern Oscillation (ENSO) has been an important area of study for years. Searching for the optimal precursor (OPR) of ENSO occurrence is an effective way to understand its predictabilit... The predictability of El Ni-o-Southern Oscillation (ENSO) has been an important area of study for years. Searching for the optimal precursor (OPR) of ENSO occurrence is an effective way to understand its predictability. The CNOP (conditional nonlinear optimal perturbation), one of the most effective ways to depict the predictability of ENSO, is adopted to study the optimal sea surface temperature (SST) precursors (SST-OPRs) of ENSO in the IOCAS ICM (intermediate coupled model developed at the Institute of Oceanology, Chinese Academy of Sciences). To seek the SST-OPRs of ENSO in the ICM, non-ENSO events simulated by the ICM are chosen as the basic state. Then, the gradient-definition-based method (GD method) is employed to solve the CNOP for different initial months of the basic years to obtain the SSTOPRs. The experimental results show that the obtained SST-OPRs present a positive anomaly signal in the western-central equatorial Pacific, and obvious differences exist in the patterns between the different seasonal SST-OPRs along the equatorial western-central Pacific, showing seasonal dependence to some extent. Furthermore, the non-El Ni-o events can eventually evolve into El Ni-o events when the SST-OPRs are superimposed on the corresponding seasons;the peaks of the Ni-o3.4 index occur at the ends of the years, which is consistent with the evolution of the real El Ni-o. These results show that the GD method is an effective way to obtain SST-OPRs for ENSO events in the ICM. Moreover, the OPRs for ENSO depicted using the GD method provide useful information for finding the early signal of ENSO in the ICM. 展开更多
关键词 OPTIMAL precursor ENSO gradient-definition-based method conditional nonlinear OPTIMAL perturbation INTERMEDIATE coupled model
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渗流-应力耦合作用下砂岩蠕变特性与损伤特征研究
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作者 许江 崔梦芹 +3 位作者 彭守建 陈奕安 饶豪魁 曹琦 《矿业研究与开发》 北大核心 2025年第1期144-157,共14页
为降低渗透水压作用下蠕变对工程长期稳定性造成的不利影响,利用渗流-应力耦合伺服控制加载试验系统开展不同水力梯度下的蠕变试验,探究砂岩的流变特性和渗流特性;结合三维数字图像相关技术(3D-DIC),研究砂岩的微裂纹演化规律及变形局... 为降低渗透水压作用下蠕变对工程长期稳定性造成的不利影响,利用渗流-应力耦合伺服控制加载试验系统开展不同水力梯度下的蠕变试验,探究砂岩的流变特性和渗流特性;结合三维数字图像相关技术(3D-DIC),研究砂岩的微裂纹演化规律及变形局部化特征;同时基于CT扫描技术探究砂岩的裂纹损伤特征。结果表明:(1)水力梯度越大,蠕变变形量越大,微裂纹发育扩展速率更快,应变场云图变化越明显,相较于轴向应变场云图,径向应变场云图中更早出现较大应变点和应变局部化特征;(2)水力梯度越大,应变增量越大,应变变化速率越快,砂岩蠕变寿命越短,通过建立虚拟应变片,发现砂岩局部破坏带内外的应变变化不一致,表明砂岩蠕变变形过程中存在局部化特征;(3)低水力梯度下,孔裂隙更多被压密闭合,渗流通道减少,流量不断减小,高水力梯度下,损伤不断积累,渗流通道增多,流量出现增加现象;(4)通过CT扫描可知,3条主裂纹贯通整个试样,引导砂岩破坏,同时生成次生裂纹,促进裂纹扩展,靠近砂岩的加载端,施加的渗透水压更大,砂岩上部分衍生出的次生裂纹更多,形成复杂的裂纹网络结构。 展开更多
关键词 砂岩 渗流-应力耦合 蠕变 水力梯度 变形局部化 应变增量
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不同热载荷模型对等温反应器管板强度的影响
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作者 彭德其 党振 +1 位作者 张建平 谭卓伟 《北京化工大学学报(自然科学版)》 北大核心 2025年第2期99-109,共11页
为提高大型压力容器管板轻量化设计的安全性和经济性,通过数值模拟比较了温度载荷模型、对流载荷模型和流固耦合载荷模型对等温反应器管板温度场和应力场的影响,得到管板关键位置上的应力分布规律,并采用压力容器规范标准对各模型的等... 为提高大型压力容器管板轻量化设计的安全性和经济性,通过数值模拟比较了温度载荷模型、对流载荷模型和流固耦合载荷模型对等温反应器管板温度场和应力场的影响,得到管板关键位置上的应力分布规律,并采用压力容器规范标准对各模型的等效应力进行强度评估。结果表明:温度载荷模型的管板温度梯度最大,管板应力集中现象最突出,流固耦合载荷模型的管板温度梯度最小,管板应力集中现象有较大缓解;管板的局部薄膜应力和一次+二次应力均随管板温度梯度的增加而增大,温度载荷模型的这两种应力分别为36.49 MPa和155.73 MPa,对流载荷模型为31.40 MPa和132.74 MPa,流固耦合载荷模型为27.84 MPa和112.84 MPa。相较于其他两种热载荷模型,采用流固耦合载荷模型计算的管板各项应力更接近真实情况,通过该模型对大型压力容器管板进行优化设计的可靠度最高。 展开更多
关键词 管板 流固耦合 温度梯度 强度设计 数值模拟
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Directional growth behavior of a(Al) dendrites during concentration-gradientcontrolled solidification process in static magnetic field 被引量:2
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作者 李磊 徐博 +6 位作者 佟伟平 何立子 班春燕 张辉 左玉波 朱庆丰 崔建忠 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2015年第7期2438-2445,共8页
The large and small sized Cu(solid)/Al(liquid) couples were prepared to investigate the directional growth behavior of primary a(Al) phase during a concentration-gradient-controlled solidification process under ... The large and small sized Cu(solid)/Al(liquid) couples were prepared to investigate the directional growth behavior of primary a(Al) phase during a concentration-gradient-controlled solidification process under various static magnetic fields(SMFs).The results show that in the large couples,the α(Al) dendrites reveal a directional growth character whether without or with the SMF.However,the 12 T magnetic field induces regular growth,consistent deflection and the decrease of secondary arm spacing of the dendrites.In the small couples,the α(Al) dendrites still reveal a directional growth character to some extent with a SMF of ≤5 T.However,an 8.8 T SMF destroys the directional growth and induces severe random deflections of the dendrites.When the SMF increases to 12 T,the a(Al) dendrites become quite regular despite of the consistent deflection.The directional growth arises from the continuous long-range concentration gradient field built in the melt.The morphological modification is mainly related to the suppression of natural convections and the induction of thermoelectric magnetic convection by the SMF. 展开更多
关键词 α(Al) dendrite diffusion couple concentration gradient field static magnetic field directional growth thermoelectric magnetic convection
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交叉梯度约束的地震走时与重力联合反演方法研究
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作者 谭智 姜金钟 +1 位作者 石磊 李永华 《地震研究》 北大核心 2025年第4期550-560,共11页
不同地球物理数据参与的联合反演,可有效减少反演的多解性,为地球内部结构研究提供多参数约束。重力与地震联合反演的开展常基于速度-密度经验关系,但由于地下结构复杂,部分地区岩石物理关系难以准确确定。针对这一问题,提出了一种基于... 不同地球物理数据参与的联合反演,可有效减少反演的多解性,为地球内部结构研究提供多参数约束。重力与地震联合反演的开展常基于速度-密度经验关系,但由于地下结构复杂,部分地区岩石物理关系难以准确确定。针对这一问题,提出了一种基于交叉梯度约束的地震走时与重力联合反演方法。该方法将频率域重力反演和近震体波走时反演相结合,采用优化的顺序策略,实现了速度模型与密度模型的相似性耦合。理论模型和青藏高原东北缘实际观测数据试验都显示,联合反演有效提高了密度结构的垂向分辨率。重力数据的引入,更好地约束了地壳浅层(地下5 km以内)P波速度结构,明显改善了体波射线分布稀疏地区的横向分辨能力。 展开更多
关键词 重震联合反演 结构耦合 交叉梯度 顺序策略
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模式能量梯度上升的光束入腔指向方法
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作者 邢成文 徐天尧 +7 位作者 马超群 栾苏琪 李跃 孟范超 孟令强 吕刚 印雄飞 贾建军 《中国光学(中英文)》 北大核心 2025年第3期682-690,共9页
为了解决光束与法布里珀罗腔的入腔失调问题,本文基于谐振模式能量梯度上升自适应调整双反射镜步进,实现所需谐振模式的入腔光束指向。首先,利用双反射镜步进与入腔光束失调的关系,提出分离式入腔光束平移与角度调整方法。其次,利用Effi... 为了解决光束与法布里珀罗腔的入腔失调问题,本文基于谐振模式能量梯度上升自适应调整双反射镜步进,实现所需谐振模式的入腔光束指向。首先,利用双反射镜步进与入腔光束失调的关系,提出分离式入腔光束平移与角度调整方法。其次,利用EfficientNET神经网络对谐振模式图片进行分类,实现不同激光模式的图像识别。最后,利用腔后模式能量梯度调整双反射镜步进,低成本、高效率实现目标谐振模式的入腔耦合。本文的入腔光束指向调整方法为超稳激光器以及引力波探测中法布里珀罗腔的入腔耦合提供了新思路。 展开更多
关键词 入腔耦合 光束指向控制 法布里珀罗腔 双快速反射镜 梯度上升
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硅电极组分梯度设计抑制力-化学耦合劣化
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作者 谭博文 耿双龙 +1 位作者 张锴 郑百林 《无机材料学报》 北大核心 2025年第7期772-780,I0011-I0014,共13页
作为锂离子电池负极,硅材料具有高能量密度的优点,但其充放电循环中的体积效应会引发活性涂层的上下表面不稳定,且内部极化会诱导产生扩散应力,两者共同导致结构退化和容量衰减。受功能梯度材料启发,本研究提出了一种五层复合组分梯度... 作为锂离子电池负极,硅材料具有高能量密度的优点,但其充放电循环中的体积效应会引发活性涂层的上下表面不稳定,且内部极化会诱导产生扩散应力,两者共同导致结构退化和容量衰减。受功能梯度材料启发,本研究提出了一种五层复合组分梯度硅电极。通过实验与多尺度力-电-化学耦合仿真发现,本研究所设计的对称组分梯度硅电极和线性组分梯度硅电极在减缓力-化学耦合劣化方面效果显著,较传统的均匀电极表现出更好的循环和倍率性能。对称梯度电极锂离子电池在0.2C(1C=2.65 mA·cm^(-2))倍率下循环100次后,比容量剩余2065 mAh·g^(-1),容量保持率为81%,而均匀电极为51%。线性梯度电极在1C倍率下的平均放电容量则是均匀电极的1.5倍,且两类梯度电极循环前后的阻抗变化均小于均匀电极。上述组分梯度电极采用多层复合涂布工艺制备,无需材料改性便能提高电极的结构稳定性和电化学性能,为高性能锂离子电池的设计与制造提供了参考。 展开更多
关键词 锂离子电池 硅电极 功能梯度材料 多物理场耦合
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土地利用转型与乡村转型发展耦合关系研究——以江苏省县域为例 被引量:3
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作者 戈大专 王如敏 卢小雪 《资源科学》 北大核心 2025年第1期196-210,共15页
【目的】土地利用转型与乡村转型发展的耦合水平在不同社会经济发展阶段或区域表现出明显的梯度分异特征,理清二者耦合关系为推动乡村可持续振兴创造条件。【方法】本文以2000—2020年江苏省县域为例,解析其土地利用转型与乡村转型发展... 【目的】土地利用转型与乡村转型发展的耦合水平在不同社会经济发展阶段或区域表现出明显的梯度分异特征,理清二者耦合关系为推动乡村可持续振兴创造条件。【方法】本文以2000—2020年江苏省县域为例,解析其土地利用转型与乡村转型发展耦合关系的理论框架,应用耦合协调与VAR(Vector Autoregressive Model)模型探讨二者时空演变特征及相互作用机理。【结果】①研究期内,江苏省县域土地利用转型与乡村转型发展呈现由低速异质性向高速同质化转变的格局特征,表现为局部地区领先和梯度有序提升的宏观特征;②江苏省土地利用转型与乡村转型发展的耦合关系经历了从全省失调到部分低度耦合,再从低度耦合向中、高度耦合转变的两个阶段,呈现出逐年上升、不断向好的发展态势,在空间格局上总体表现出“南高北低”的梯度分异格局;③土地利用转型与乡村转型发展耦合关系复杂,后者是前者的原因与驱动力,前者为后者提供物质基础与空间支持,二者存在着明显的互促关系,乡村转型发展不仅受到自身影响还受到土地利用转型的冲击,并表现出较强的自我促进特征,土地利用转型对乡村发展产生一定的胁迫效应。【结论】土地利用转型与乡村转型发展的耦合关系决定了区域乡村转型的内在动力,调控二者关系为优化乡村空间治理体系和助推乡村可持续发展提供有效路径。 展开更多
关键词 土地利用转型 乡村转型发展 耦合关系 梯度分异 江苏省
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基于深度强化学习优化LQR的虚拟重联高速列车间隔控制方法
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作者 龚飞杰 上官伟 +2 位作者 宋鸿宇 敦旖晨 蔡伯根 《铁道学报》 北大核心 2025年第11期116-126,共11页
虚拟重联采用列车编队运行的方式,有效提升了运行效率,其中列车间隔控制问题是虚拟重联运行安全的重要保障。针对虚拟重联下列车的间隔控制问题,在构建的列车动力学模型和运行安全包络的基础上计算动态目标间隔,利用该动态间隔建立线性... 虚拟重联采用列车编队运行的方式,有效提升了运行效率,其中列车间隔控制问题是虚拟重联运行安全的重要保障。针对虚拟重联下列车的间隔控制问题,在构建的列车动力学模型和运行安全包络的基础上计算动态目标间隔,利用该动态间隔建立线性二次型调节器(LQR)列车间隔控制模型的状态方程,基于LQR的状态反馈控制律构建二次型优化模型,通过求解优化模型的Riccati方程得到控制量,并利用Lyapunov稳定性定理证明其闭环反馈控制的稳定性;进一步,为了解决因LQR控制器参数导致的间隔控制精度低问题,利用深度确定性策略梯度(DDPG)对LQR参数进行优化整定,搭建Actor-Critic优化控制参数网络,定义LQR参数为DDPG的动作,间隔控制误差为DDPG的状态,将间隔控制误差减小作为奖励增大的方向,通过迭代学习得到优化参数。使用武广高铁中的“咸宁北-赤壁北”区段的线路数据对所提方法进行仿真试验验证,并与模型预测控制(MPC)和滑模控制(SMC)进行对比。验证结果表明:LQR能够有效控制虚拟重联列车间隔运行,并在面对通信丢失的极端场景下仍然稳定控制间隔运行,在使用DDPG对LQR参数进行优化整定后,使得列车的间隔控制绝对误差下降了68.5%,且明显小于基于经验参数值的MPC、SMC、LQR,大幅度提升了列车间隔运行控制精度,进一步保障了列车运行安全并提升了运行效率。 展开更多
关键词 虚拟重联 间隔控制 深度确定性策略梯度 线性二次型调节器 控制参数优化
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城乡梯度视角下武汉市“三生”功能耦合协调时空演变及影响因素 被引量:2
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作者 孙远洋 张蕾 +1 位作者 何国钰 雷锡琼 《农业工程学报》 北大核心 2025年第8期261-271,共11页
探究快速城市化地区“三生”功能交互关系的城乡差异及其演化规律,对推进城乡融合背景下国土空间高质量发展具有重要意义。该研究采用断裂点法识别2000、2010和2020年武汉市“城区-城郊-乡村”区域的转换特征,并利用耦合协调度模型、基... 探究快速城市化地区“三生”功能交互关系的城乡差异及其演化规律,对推进城乡融合背景下国土空间高质量发展具有重要意义。该研究采用断裂点法识别2000、2010和2020年武汉市“城区-城郊-乡村”区域的转换特征,并利用耦合协调度模型、基尼系数和空间回归模型分析“三生”功能耦合协调度的城乡时空差异特征及其差异化的影响机制。结果表明:1)城区“生活-生态”功能、“生产-生态”功能和“三生”功能的失调现象均有所缓解,协调区域占比分别增加21.98%、13.16%和0.17%,而城郊和乡村区域“三生”功能间的协调程度减弱,协调区域占比分别减少14.32%和5.50%;2)乡村转城郊、非转换乡村、非转换城郊区域的“生产-生态”的协调区域占比分别平均减少22.03%、6.23%和7.26%,2000—2010年城郊转城区域的“生活-生态”功能的明显下降6.27%;3)坡度、土地垦殖率、森林覆盖率和建设用地密度对不同城乡梯度“三生”功能耦合协调度均具有显著的正向影响,而海拔、降水量、地均GDP和到市中心距离等因素的影响具有明显的城乡梯度差异。研究结果可为特大城市城乡融合发展和国土空间优化提供参考依据。 展开更多
关键词 城乡梯度 “三生”功能 耦合协调 影响因素 武汉市
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梯度孔隙阳极对固体氧化物燃料电池蠕变损伤影响
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作者 宋明 夏凡辰 +3 位作者 王炳英 张玉财 汪玉 吴琼 《硅酸盐学报》 北大核心 2025年第8期2219-2228,共10页
梯度孔隙阳极固体氧化物燃料电池(SOFC)的多物理场耦合行为对其长期高温服役性能具有重要影响。本工作构建了电化学-气体流动-物质传递-温度-固体力学耦合的多物理场模型,并结合蠕变延性耗竭理论开发了蠕变损伤计算方法,研究了不均匀温... 梯度孔隙阳极固体氧化物燃料电池(SOFC)的多物理场耦合行为对其长期高温服役性能具有重要影响。本工作构建了电化学-气体流动-物质传递-温度-固体力学耦合的多物理场模型,并结合蠕变延性耗竭理论开发了蠕变损伤计算方法,研究了不均匀温度场条件下一种梯度孔隙阳极的SOFC蠕变损伤演化与裂纹扩展机制。结果表明:均匀温度场假设低估了SOFC构件中的等效应力,并改变了应力分布特征;梯度孔隙阳极设计使SOFC上连接体在64 kh时首先达到临界损伤值,裂纹萌生于燃料出口40 mm肋外表面,呈表面裂纹形态,并在80 kh时裂纹长度扩展至32 mm。通过对不同阳极孔隙率设计的蠕变损伤分析表明,梯度孔隙阳极设计的SOFC相比阳极孔隙率分别为0.2、0.3和0.4的均匀孔隙阳极SOFC,其寿命分别提高了31.4%、26.4%和17.9%。研究结果揭示了此种梯度孔隙阳极在长期高温服役中的潜在优势,为SOFC的结构优化设计提供了理论依据。 展开更多
关键词 固体氧化物燃料电池 梯度孔隙阳极 多物理场耦合建模 延性耗竭理论 蠕变损伤
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基于偶应力弹性梯度理论的饱和孔隙介质中Rayleigh波的传播特性
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作者 李国强 郑佩 张克明 《应用数学和力学》 北大核心 2025年第10期1329-1341,共13页
基于偶应力弹性梯度理论,研究了饱和孔隙介质中Rayleigh波的传播特性.首先,基于偶应力理论建立了包含材料内禀长度的波动方程,并在频域内通过位移场的势函数分解,将两组耦合的波动方程解耦为4个标量的Helmholtz方程,分别控制P1波、P2波... 基于偶应力弹性梯度理论,研究了饱和孔隙介质中Rayleigh波的传播特性.首先,基于偶应力理论建立了包含材料内禀长度的波动方程,并在频域内通过位移场的势函数分解,将两组耦合的波动方程解耦为4个标量的Helmholtz方程,分别控制P1波、P2波、SV波和SH波的传播.进一步,针对Rayleigh波,通过求解Helmholtz方程的特征值问题,确定了势函数的具体形式.然后,通过引入边界条件,求解了Rayleigh波的传播特性.最后,通过数值算例,研究了材料内禀长度对Rayleigh波的传播特性的影响规律. 展开更多
关键词 孔隙介质 RAYLEIGH波 偶应力 弹性梯度理论 归一化位移
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