There have been different views on the origins of gas reservoirs of Ordovician Majiagou Fm in the Ordos Basin,but none of them supports the opinion that there are scale source rocks(TOC>0.5%)in the Majiagou Fm.In t...There have been different views on the origins of gas reservoirs of Ordovician Majiagou Fm in the Ordos Basin,but none of them supports the opinion that there are scale source rocks(TOC>0.5%)in the Majiagou Fm.In this paper,a series of analysis was made on cores and cutting samples taken from recent newly-drilled wells in the Ordovician reservoirs in the centraleeastern areas of the Ordos Basin.Accordingly,the organic abundance features of different types of source rocks in the Majiagou Fm were presented,and for the first time,it was discovered and verified that there are effective scale source rocks with high organic abundance.Based on these analysis and studies,the following results were achieved.First,the effective source rocks of Majiagou Fm are composed of thinethick layered dark dolomite-bearing mudstones,dolomitic mudstones and argillaceous dolomites,and their enrichment and distribution are obviously controlled by sedimentary facies.During the sedimentation of Majiagou Fm,the effective scale source rocks developed better at the regressive stage than at the transgressive stage.The effective source rocks are primarily distributed in the upper part of Ma 5 Member(especially concentrated in the third and fourth sub-members)and secondly in Ma 3 Member,Ma 1 Member and the middleelower part of Ma 5 Member.Second,the effective source rocks are areally distributed in a dual-girdle form around the Mizhi Salt Depression,and those in the secondary depressions are mediumethick layered,with a large total thickness and high organic abundance.Third,the effective source rocks in the center of Mizhi Depression and the secondary uplifts are thin-layered,with a small total thickness and low organic abundance.And fourth,the organic abundance of the effective source rocks varies from 0.30% to 8.45%.Phytoplankton and Acritarchs are the main parent materials of hydrocarbon,and organic matters are of sapropel or sapropel prone type.To sum up,the Ordovician effective source rocks in the Ordos Basin are generally at an over-mature stage and they contribute greatly to the natural gas in the Majiagou Fm.In these effective source rocks,dry gas is mainly generated at a high rate.展开更多
The topographic factor(LS factor),derived from the multiplication of the slope length(L)and slope steepness(S)factors,is a vital parameter in soil erosion models.Generated from the digital elevation model(DEM),the LS ...The topographic factor(LS factor),derived from the multiplication of the slope length(L)and slope steepness(S)factors,is a vital parameter in soil erosion models.Generated from the digital elevation model(DEM),the LS factor always varies with the changing DEM resolution,i.e.,the LS factor scale effect.Previous studies have found the phenomenon of the LS factor scale effect,but the underlying causes of this phenomenon has not been well explored.Therefore,how the DEM resolution affects the LS factor and how the scale effect of the L and S factors influence the LS factor scale effect remains unclear.To address these problems,we collected 20 watersheds from the Guangdong Province with different topographic reliefs,and compared the corresponding L,S and LS factors at 10-m and 30-m resolution DEMs.Our results indicate that the S factor,heavily influenced by slope underestimation in coarse-resolution DEMs,makes a difference in the LS factor scale effect.In addition,the LS factor scale effect becomes less significant with increasing reliefs,suggesting the possibility of using 30-m DEM for LS calculation in rugged terrains.Our findings on the underlying mechanisms of the LS factor scale effect help to identify the uncertainty in the LS factor estimation,thereby enhancing the accuracy of soil erosion assessment,particularly in regions with different topographic characteristics and contribute to more effective soil conservation strategies and decision-making.展开更多
Scale effects and evaluation models are crucial to the accuracy of landscape ecological risk evaluation.However,most studies conduct these evaluations at a single scale or with a single model,ignoring potential scale ...Scale effects and evaluation models are crucial to the accuracy of landscape ecological risk evaluation.However,most studies conduct these evaluations at a single scale or with a single model,ignoring potential scale effects and changes in landscape patterns.To address this,we took the Leshan City in Sichuan Province of China as a study case.We determined that the optimal spatial granularity for the study area is 150 m by analyzing the sensitivities of eight landscape pattern indices such as landscape fragmentation,landscape spreading,and Shannon's diversity at different spatial granularities,and employing the inflection point identification method.Building on this,we constructed a landscape pattern index model(ERI model)and a landscape pattern index model coupled with the ecological process of soil erosion(SI-ERI model)by incorporating the natural geographic factors of the study area.We used the ERI and SI-ERI models to evaluate the landscape ecological risk of Leshan City across multiple scales,including ecological,administrative,and sample scales.After conducting overlay and spatial autocorrelation analyses of the multi-scale evaluation results,we determined that the administrative scale is optimal for evaluating landscape ecological risk in the study area.At this scale,we verified the accuracy and reliability of the two models'evaluation results against the actual ecological environment in typical areas within the study area.The findings indicated that the SI-ERI model provided more precise and accurate spatial characterization,effectively reflecting the actual landscape ecological risk of Leshan City.According to the SI-ERI model's evaluation results at the administrative scale,Leshan City's overall risk level is relatively low,with good ecological environmental quality.Low-risk areas constitute 56.16%and medium-low-risk areas make up 23.81%,aligning closely with the city's actual situation.This study thus offers a scientific basis and theoretical reference for managing ecological risks and planning urban development in Leshan City.展开更多
Joint surface roughness is comprised of two components:large-scale(waviness,first-order)and smallscale(unevenness,second-order).To investigate the scale effect of two-order roughness,a surface area method is used to s...Joint surface roughness is comprised of two components:large-scale(waviness,first-order)and smallscale(unevenness,second-order).To investigate the scale effect of two-order roughness,a surface area method is used to separate the waviness and unevenness from the whole joint surface of each size.The results show that as the joint size increases,the first-order roughness exhibits a decrease,whereas the second-order roughness remains constant.This indicates that the roughness scale effect is primarily attributed to the waviness.Then,the influence of two-order roughness on the scale effect of joint shear strength is examined through a series of laboratory tests.The test results reveal a negative scale effect on the peak friction angle,which exhibits a strong correlation with the first-order roughness.The decrease in the peak friction angle with normal stress can be attributed primarily to the degradation of second-order roughness,which shows a negative exponential trend.Finally,an empirical model for estimating the peak friction angle of rock joints at different scales is proposed based on two-order roughness.The prediction accuracy of this model is validated by comparing the existing criteria.展开更多
Research on scale effects on flows over weirs has been conducted on a limited basis, primarily focusing on flows upstream of a single-type weir, such as ogee, broad-crested, and sharp-crested (linear and non-linear) w...Research on scale effects on flows over weirs has been conducted on a limited basis, primarily focusing on flows upstream of a single-type weir, such as ogee, broad-crested, and sharp-crested (linear and non-linear) weirs. However, the scale effects downstream of these single-type weirs have not been thoroughly investigated. This study examined the scale effects on flows over a combined weir system consisting of an ogee weir and a sharp-crested weir, both upstream and downstream, utilizing physical modeling at a 1:33.33 scale based on Froude similarity and three-dimensional (3D) computational fluid dynamics (CFD) modeling. The sharp-crested weir in this study was represented by two sluice gates that remain closed and submerged during flood events. The experimental data confirmed that the equivalent discharge coefficients of the combined weir system behaved similarly to those of a sharp-crested weir across various H/P (where H is the total head, and P is the weir height) values. However, scale effects on the discharge rating curve due to surface tension and viscosity could only be minimized when H/P > 0.4, Re > 26 959, and We > 240 (where Re and We are the Reynolds and Weber numbers, respectively), provided that the water depth exceeded 0.042 m above the crest. Additionally, Re greater than 4 × 104 was necessary to minimize scale effects caused by viscosity in flows in the spillway channel and stilling basin (with baffle blocks). The limiting criteria aligned closely with existing literature. This study offers valuable insights for practical applications in hydraulic engineering in the future.展开更多
The application of ecosystem services(ES)theories in land consolidation is a confusing issue that has long plagued scholars and government officials.As the upgraded version of traditional land consolidation,comprehens...The application of ecosystem services(ES)theories in land consolidation is a confusing issue that has long plagued scholars and government officials.As the upgraded version of traditional land consolidation,comprehensive land consolidation(CLC)emphasizes ecological benefits,but it does not achieve the expected effect during the pilot phase.This study first proposed a theoretical analysis framework based on ES knowledge to answer the three key questions of why,where,and how to implement CLC better.Taking mountainous counties as the study area,we found that ES trade-offs/synergies,bundles,and drivers were significantly affected by scale effects.ES knowledge can play a crucial role in designing multi-scale CLC strategies regarding the objective,zoning,intensity,and mode.Specifically,mitigating the significant trade-offs between recreational opportunities,food production,and other ES is the top priority of CLC.Land consolidation zoning based on the ES bundles analysis is more rational and can provide the scientific premise for designing locally adapted CLC measures.Land consolidation can be classified into high-intensity direct intervention and low-intensity indirect intervention modes,based on the major drivers of ES.These findings help narrow the gap between ES and CLC practices.展开更多
The scale effect on shear strength of rock joints is well-documented.However,whether scale effects are negative,positive,or even exist or not is still controversial.Joint roughness significantly influences the shear s...The scale effect on shear strength of rock joints is well-documented.However,whether scale effects are negative,positive,or even exist or not is still controversial.Joint roughness significantly influences the shear strength of rock joints.Compared to the shear tests,using the joint roughness coefficient(JRC)and its roughness parameters offers a more convenient method for describing the scale effect on shear strength.However,it is crucial to understand that the scale effect mechanisms of JRC are distinct from those of shear strength.Therefore,this paper aims to clarify these distinct mechanisms.By digitally extracting roughness parameters from granite samples,it is found that the scale effect of roughness parameters mainly comes from the sampling methods and the geometric characteristics of parameters.Furthermore,a full data sampling method considering heterogeneity is proposed to obtain more representative roughness parameters.To reveal the scale effect mechanisms of shear strength,Gaussian filtering is firstly used to separate the waviness and unevenness components of roughness,facilitating a deeper understanding of the geometric characteristics of roughness.It is suggested that the wavelength of the waviness component can reflect the scale effect on shear strength.Secondly,numerical simulations of ideal artificial joint models are conducted to validate that the wavelength of the waviness component serves as the dividing point between positive and negative scale effects.The mechanical mechanisms of positive and negative scale effects are also interpreted.Finally,these mechanisms successfully elucidate the occurrence patterns of the scale effect on natural joint profiles.展开更多
The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engin...The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engineering projects.During the collection process of JRC samples,the redundancy or insufficiency of representative rock joint surface topography(RJST) information in serial length JRC samples is the essential reason that affects the reliability of the scale effect results.Therefore,this paper proposes an adaptive sampling method,in which we use the entropy consistency measure Q(a) to evaluate the consistency of the joint morphology information contained in adjacent JRC samples.Then the sampling interval is automatically adjusted according to the threshold Q(at) of the entropy consistency measure to ensure that the degree of change of RJST information between JRC samples is the same,and ultimately makes the representative RJST information in the collected JRC samples more balanced.The application results of actual cases show that the proposed method can obtain the scale effect in the JRC efficiently and reliably.展开更多
Geological strength index(GSI)has been widely used as an input parameter in predicting the strength and deformation properties of rock masses.This study derived a series of equations to satisfy the original GSI lines ...Geological strength index(GSI)has been widely used as an input parameter in predicting the strength and deformation properties of rock masses.This study derived a series of equations to satisfy the original GSI lines on the basic GSI chart.Two axes ranging from 0 to 100 were employed for surface conditions of the discontinuities and the structure of rock mass,which are independent of the input parameters.The derived equations can analyze GSI values ranging from 0 to 100 within±5%error.The engineering dimensions(EDs)such as the slope height,tunnel width,and foundation width were used together with representative elementary volume(REV)in jointed rock mass to define scale factor(sf)from 0.2 to 1 in evaluating the rock mass structure including joint pattern.The transformation of GSI into a scaledependent parameter based on engineering scale addresses a crucial requirement in various engineering applications.The improvements proposed in this study were applied to a real slope which was close to the time of failure.The results of stability assessments show that the new proposals have sufficient capability to define rock mass quality considering EDs.展开更多
In this study,the thermodynamic behaviors of the intrinsic frequency and buckling temperature of rectangular plates of functionally graded materials(FGMs)are explored based on the modified couple stress theory(MCST)an...In this study,the thermodynamic behaviors of the intrinsic frequency and buckling temperature of rectangular plates of functionally graded materials(FGMs)are explored based on the modified couple stress theory(MCST)and the novel dual powerlaw scale distribution theory.The effects of linear,homogeneous,and non-homogeneous temperature fields on the frequency and buckling temperature of FGM microplates are evaluated in detail.The results show that the porosity greatly affects the mechanical properties of FGM plates,reducing their frequency and flexural temperature compared with non-porous plates.Different temperature profiles alter plate frequencies and buckling temperatures.The presence and pattern of scale effect parameters are also shown to be crucial for the mechanical response of FGM plates.The present research aims to provide precise guidelines for the micro-electro-mechanical system(MEMS)fabrication by elucidating the complex interplay between thermal,material,and structural factors that affect the performance of FGM plates in advanced applications.展开更多
For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out s...For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out scale model test to establish a distortion model similar to the real ship structure under combined load. A similarity criterion for ship distortion model under the combined action of bending moment and surface pressure was proposed, and the scale effect for the criterion was verified by a se ries of numerical analysis and model tests. The results show that the similarity criterion for ship distor tion model under combined loads has a certain scale effect. For the model tests of ship cabin struc tures, it is suggested that the scale range between the plate thickness scale and the main dimension scale should be controlled within 2:1, which can be used as a reference for distortion model design and ultimate strength test of large-scale ship structures.展开更多
Landscape fragmentation is generally viewed as an indicator of environmental stresses or risks,but the fragmentation intensity assessment also depends on the scale of data and the definition of spatial unit.This study...Landscape fragmentation is generally viewed as an indicator of environmental stresses or risks,but the fragmentation intensity assessment also depends on the scale of data and the definition of spatial unit.This study aimed to explore the scale-dependence of forest fragmentation intensity along a moisture gradient in Yinshan Mountain of North China,and to estimate environmental sensitivity of forest fragmentation in this semi-arid landscape.We developed an automatic classification algorithm using simple linear iterative clustering(SLIC)and Gaussian mixture model(GMM),and extracted tree canopy patches from Google Earth images(GEI),with an accuracy of 89.2%in the study area.Then we convert the tree canopy patches to forest category according to definition of forest that tree density greater than 10%,and compared it with forest categories from global land use datasets,FROM-GLC10 and GlobeLand30,with spatial resolutions of 10 m and 30 m,respectively.We found that the FROM-GLC10 and GlobeLand30 datasets underestimated the forest area in Yinshan Mountain by 16.88%and 21.06%,respectively;and the ratio of open forest(OF,10%<tree coverage<40%)to closed forest(CF,tree coverage>40%)areas in the underestimated part was 2:1.The underestimations concentrated in warmer and drier areas occupied mostly by large coverage of OFs with severely fragmented canopies.Fragmentation intensity of canopies positively correlated with spring temperature while negatively correlated with summer precipitation and terrain slope.When summer precipitation was less than 300 mm or spring temperature higher than 4℃,canopy fragmentation intensity rose drastically,while the forest area percentage kept stable.Our study suggested that the spatial configuration,e.g.,sparseness,is more sensitive to drought stress than area percentage.This highlights the importance of data resolution and proper fragmentation measurements for forest patterns and environmental interpretation,which is the base of reliable ecosystem predictions with regard to the future climate scenarios.展开更多
Based on the newest understandings of geological assessment and new progresses in engineering technologies in the development of shale gas rich in the southern Sichuan Basin,this paper analyzed the shale gas enrichmen...Based on the newest understandings of geological assessment and new progresses in engineering technologies in the development of shale gas rich in the southern Sichuan Basin,this paper analyzed the shale gas enrichment laws and the key factors of its commercial production,discussed the scale and efficient development modes,and clarified the further developing orientation.The following findings were concluded.(1)The Lower Silurian Longmaxi shale is the sweetest spot in this study area with a low density and a high uranium/thorium(U/Th)ratio,TOC content,quartz content,and free gas content.Besides,its distribution laws are mainly controlled by the sedimentary facies of deep water shelf.(2)The overpressured zones away from the ancient(present)erosion zones and large faults,mainly controlled by multi-stage tectonic evolution,belong to the most favorable sweet spots not only because there are well-developed organic matters and pores but the produced gas there is mainly of secondary cracking retention oil.(3)Layout,drilling,completion(fracturing)and management of wells will be essential to achieve high productions in the shale gas production.(4)The existing main technologies have helped achieve efficient development of quality shale gas resources underground less than 3500 m in such national shale gas demonstration zones as ChangningeWeiyuan,Zhaotong,etc.Also,there shows a good potential of shale gas resources in those shallower strata and the strata with the burial depth of 3500-4000 m.In conclusion,with the help of continuous progress in technologies,an annual shale gas production rate of 40 billion cubic meters will be possibly achieved in this study area.展开更多
The detection of hypersonic targets usually confronts range migration(RM)issue before coherent integration(CI).The traditional methods aiming at correcting RM to obtain CI mainly considers the narrow-band radar condit...The detection of hypersonic targets usually confronts range migration(RM)issue before coherent integration(CI).The traditional methods aiming at correcting RM to obtain CI mainly considers the narrow-band radar condition.However,with the increasing requirement of far-range detection,the time bandwidth product,which is corresponding to radar’s mean power,should be promoted in actual application.Thus,the echo signal generates the scale effect(SE)at large time bandwidth product situation,influencing the intra and inter pulse integration performance.To eliminate SE and correct RM,this paper proposes an effective algorithm,i.e.,scaled location rotation transform(ScLRT).The ScLRT can remove SE to obtain the matching pulse compression(PC)as well as correct RM to complete CI via the location rotation transform,being implemented by seeking the actual rotation angle.Compared to the traditional coherent detection algorithms,Sc LRT can address the SE problem to achieve better detection/estimation capabilities.At last,this paper gives several simulations to assess the viability of ScLRT.展开更多
Many existing efforts have taken advantage of large-scale spatial-temporal data to partition cities via constructed human interaction networks.However,few studies focus on communities emerging between adjacent cities ...Many existing efforts have taken advantage of large-scale spatial-temporal data to partition cities via constructed human interaction networks.However,few studies focus on communities emerging between adjacent cities in big urban agglomerations,which we call“cross-city”communities.In this study,we introduce a novel framework to detect cross-city communities in urban agglomerations under different scales leveraging a large number of fine-grained mobile signaling data aiming to break the original administrative boundaries.Taking the Pearl River Delta(PRD)urban agglomeration in China as study area,we investigate the existence of potential communities at three scales,i.e.city-group level,city level and sub-city level.The partition results are expected to benefit transportation planning,urban zoning and administrative boundary re-delineation.The results from our study highlight the necessity of considering cross-city communities and their scale effects when examining urban spatial interactions.展开更多
To analyze the effect of single grain deformation behaviors on microforming process, a crystal plasticity model was developed considering grains at free surface layer as single grains. Based on the rate-dependent crys...To analyze the effect of single grain deformation behaviors on microforming process, a crystal plasticity model was developed considering grains at free surface layer as single grains. Based on the rate-dependent crystal plasticity theory, the analysis of the scale effect mechanism on upsetting deformation of micro rods was performed with respect to specimen dimension, original grain orientation and its distribution. The results show that flow stress decreases significantly with the scaling down of the specimen. The distribution of the grain orientation has an evident effect on flow stress of the micro specimen, and the effect becomes smaller with the progress of plastic deformation. For the anisotropy of single grains, inhomogeneous deformation occurs at the surface layer, which leads to the increase of surface roughness, especially for small specimens. The effect of grain anisotropy on the surface topography can be decreased by the transition grains. The simulation results are validated by upsetting deformation experiments. This indicates that the developed model is suitable for the analysis of microforming processes with characteristics, such as scale dependency, scatter of flow stress and inhomogeneous deformation.展开更多
Regarding the scale effects on propeller＇s noncavitation hydrodynamics and hydroacoustics, three similar 7bladed highly-skewed propellers in the wake flow are addressed with diameters of 250, 500 and 1 000 mm, respec...Regarding the scale effects on propeller＇s noncavitation hydrodynamics and hydroacoustics, three similar 7bladed highly-skewed propellers in the wake flow are addressed with diameters of 250, 500 and 1 000 mm, respectively. The discrete line-spectrum noise and its standardized spectrum level scaling law, together with the total sound pressure level are analyzed. The non-cavitation noise predictions are completed by both the frequency domain method and the time domain method. As a fluctuated noise source, the time-dependent fluctuated pressure and normal velocity distribution on propeller blades are obtained by the unsteady Reynolds-averaged Navier-Stokes （ URANS ） simulation. Results show that the pressure coefficient distribution of three propellers on the 0.7R section is nearly superposed under the same advance ratio. The periodic thrust fluctuation of three propellers can exactly reflect the tonal components of the axial passing frequency （APF） and the blade passing frequency （BPF）, and the fluctuation enhancement from the small to the middle propeller at the BPF is greater than that from the middle to the big one. By the two noise prediction methods, the increment of the total sound pressure level from the small to the big propeller differs by 2.49 dB. Following the standardized scaling law, the spectrum curves of the middle and big propellers are nearly the same while significantly differing from the small one. The increment of both the line-spectrum level and the total sound pressure increases with the increase in diameter. It is suggested that the model scale of the propeller should be as large as possible in engineering to reduce the prediction error of the empirical scalin~ law and weaken the scale effects.展开更多
The complex topography of natural bedrock shorelines on islands necessitates detailed model testing to thoroughly inves-tigate wave overtopping mechanisms and their variation patterns.This understanding is vital for o...The complex topography of natural bedrock shorelines on islands necessitates detailed model testing to thoroughly inves-tigate wave overtopping mechanisms and their variation patterns.This understanding is vital for optimizing the elevation of coastal structures to meet the design requirements for wave overtopping and to ensure safety and efficacy.This paper investigates a nuclear power plant project on an island in Zhejiang Province,China.This study employs small-scale overall model tests and large-scale lo-cal model tests to examine the complex dynamics of wave interaction with the island’s shoreline.It analyzes the influences of wave parameters,shoreline geometry,and underwater topography on wave overtopping behavior.Comparisons between physical model re-sults and empirical formulae reveal substantial discrepancies in overtopping rates across different model scales.The results stress the remarkable effect of accurate underwater topography representation on wave overtopping predictions and emphasize the need for pre-cise topographic modeling.The results also show that overtopping discharges for complex terrains deviate considerably from values determined using traditional empirical formulas for breakwater overtopping.This outcome indicates that conventional methods may insufficiently address the complexities of natural coastal features.To guarantee reliable predictions of overtopping volumes at specif-ic elevations along complex coastlines,this study advocates employing physical modeling across numerous scales while accounting for detailed terrain and hydrodynamic characteristics.展开更多
In this paper,a fractional-order kinematic model is utilized to capture the size-dependent static bending and free vibration responses of piezoelectric nanobeams.The general nonlocal strains in the Euler-Bernoulli pie...In this paper,a fractional-order kinematic model is utilized to capture the size-dependent static bending and free vibration responses of piezoelectric nanobeams.The general nonlocal strains in the Euler-Bernoulli piezoelectric beam are defined by a frame-invariant and dimensionally consistent Riesz-Caputo fractional-order derivatives.The strain energy,the work done by external loads,and the kinetic energy based on the fractional-order kinematic model are derived and expressed in explicit forms.The boundary conditions for the nonlocal Euler-Bernoulli beam are derived through variational principles.Furthermore,a finite element model for the fractional-order system is developed in order to obtain the numerical solutions to the integro-differential equations.The effects of the fractional order and the vibration order on the static bending and vibration responses of the Euler-Bernoulli piezoelectric beams are investigated numerically.The results from the present model are validated against the existing results in the literature,and it is demonstrated that they are theoretically consistent.Although this fractional finite element method(FEM)is presented in the context of a one-dimensional(1D)beam,it can be extended to higher dimensional fractional-order boundary value problems.展开更多
Global forest cover is undergoing significant transformations due to anthropogenic activities and natural disturbances,profoundly impacting hydrological processes.However,the inherent spatial heterogeneity within wate...Global forest cover is undergoing significant transformations due to anthropogenic activities and natural disturbances,profoundly impacting hydrological processes.However,the inherent spatial heterogeneity within watersheds leads to varied hydrological responses across spatiotemporal scales,challenging comprehensive assessment of logging impacts at the watershed scale.Here,we developed multiple forest logging scenarios using the soil and water assessment tool(SWAT)model for the Le'an River watershed,a 5,837 km2 subtropical watershed in China,to quantify the hydrological effects of forest logging across different spatiotemporal scales.Our results demonstrate that increasing forest logging ratios from 1.54% to 9.25% consistently enhanced ecohydrological sensitivity.However,sensitivity varied across spatiotemporal scales,with the rainy season(15.30%-15.81%)showing higher sensitivity than annual(11.56%-12.07%)and dry season(3.38%-5.57%)periods.Additionally,the ecohydrological sensitivity of logging varied significantly across the watershed,with midstream areas exhibiting the highest sensitivity(13.13%-13.25%),followed by downstream(11.87%-11.98%)and upstream regions(9.96%-10.05%).Furthermore,the whole watershed exhibited greater hydrological resilience to logging compared to upstream areas,with attenuated runoff changes due to scale effects.Scale effects were more pronounced during dry seasons((-8.13 to -42.13)×10^(4) m^(3)·month^(-1))than in the rainy season((-11.11 to -26.65)×10^(4) m^(3)·month^(-1)).These findings advance understanding of logging impacts on hydrology across different spatiotemporal scales in subtropical regions,providing valuable insights for forest management under increasing anthropogenic activities and climate change.展开更多
基金Project supported by the S&T Project of PetroChina Exploration&Production Company“Evaluation on Ordovician source rocks in the Ordos Basin”(No.:2012-011)“Characteristics and comprehensive evaluation of Ordovician gas sources and optimization of favorable zones in the Ordos Basin”(No.:2014-008).
文摘There have been different views on the origins of gas reservoirs of Ordovician Majiagou Fm in the Ordos Basin,but none of them supports the opinion that there are scale source rocks(TOC>0.5%)in the Majiagou Fm.In this paper,a series of analysis was made on cores and cutting samples taken from recent newly-drilled wells in the Ordovician reservoirs in the centraleeastern areas of the Ordos Basin.Accordingly,the organic abundance features of different types of source rocks in the Majiagou Fm were presented,and for the first time,it was discovered and verified that there are effective scale source rocks with high organic abundance.Based on these analysis and studies,the following results were achieved.First,the effective source rocks of Majiagou Fm are composed of thinethick layered dark dolomite-bearing mudstones,dolomitic mudstones and argillaceous dolomites,and their enrichment and distribution are obviously controlled by sedimentary facies.During the sedimentation of Majiagou Fm,the effective scale source rocks developed better at the regressive stage than at the transgressive stage.The effective source rocks are primarily distributed in the upper part of Ma 5 Member(especially concentrated in the third and fourth sub-members)and secondly in Ma 3 Member,Ma 1 Member and the middleelower part of Ma 5 Member.Second,the effective source rocks are areally distributed in a dual-girdle form around the Mizhi Salt Depression,and those in the secondary depressions are mediumethick layered,with a large total thickness and high organic abundance.Third,the effective source rocks in the center of Mizhi Depression and the secondary uplifts are thin-layered,with a small total thickness and low organic abundance.And fourth,the organic abundance of the effective source rocks varies from 0.30% to 8.45%.Phytoplankton and Acritarchs are the main parent materials of hydrocarbon,and organic matters are of sapropel or sapropel prone type.To sum up,the Ordovician effective source rocks in the Ordos Basin are generally at an over-mature stage and they contribute greatly to the natural gas in the Majiagou Fm.In these effective source rocks,dry gas is mainly generated at a high rate.
基金funded by the Guangdong Major Project of Basic and Applied Basic Research(2021B0301030007)the Supplemental Funds for Major Scientific Research Projects of Beijing Normal University,Zhuhai(ZHPT2023013)+1 种基金the National Natural Science Foundation of China(42301387)the Science and Technology Program of Guangdong(No.2024B1212070012)。
文摘The topographic factor(LS factor),derived from the multiplication of the slope length(L)and slope steepness(S)factors,is a vital parameter in soil erosion models.Generated from the digital elevation model(DEM),the LS factor always varies with the changing DEM resolution,i.e.,the LS factor scale effect.Previous studies have found the phenomenon of the LS factor scale effect,but the underlying causes of this phenomenon has not been well explored.Therefore,how the DEM resolution affects the LS factor and how the scale effect of the L and S factors influence the LS factor scale effect remains unclear.To address these problems,we collected 20 watersheds from the Guangdong Province with different topographic reliefs,and compared the corresponding L,S and LS factors at 10-m and 30-m resolution DEMs.Our results indicate that the S factor,heavily influenced by slope underestimation in coarse-resolution DEMs,makes a difference in the LS factor scale effect.In addition,the LS factor scale effect becomes less significant with increasing reliefs,suggesting the possibility of using 30-m DEM for LS calculation in rugged terrains.Our findings on the underlying mechanisms of the LS factor scale effect help to identify the uncertainty in the LS factor estimation,thereby enhancing the accuracy of soil erosion assessment,particularly in regions with different topographic characteristics and contribute to more effective soil conservation strategies and decision-making.
基金supported by grants from the Ministry of Science and Technology of the People’s Republic of China(Grant Nos.2019YFC1803500,2019YFC1803504)the Key R&D Projects of Sichuan Provincial Science and Technology Department(Grant Nos.2018SZ0298,2023YFS0390)+1 种基金the Bureau of Science and Technology Aba Qiang Tibetan Autonomous Prefecture(Grant Nos.R22YYJSYJ0004,R23YYJSYJ0010)Southwest University of Science and Technology Doctoral Program(23zx7175)。
文摘Scale effects and evaluation models are crucial to the accuracy of landscape ecological risk evaluation.However,most studies conduct these evaluations at a single scale or with a single model,ignoring potential scale effects and changes in landscape patterns.To address this,we took the Leshan City in Sichuan Province of China as a study case.We determined that the optimal spatial granularity for the study area is 150 m by analyzing the sensitivities of eight landscape pattern indices such as landscape fragmentation,landscape spreading,and Shannon's diversity at different spatial granularities,and employing the inflection point identification method.Building on this,we constructed a landscape pattern index model(ERI model)and a landscape pattern index model coupled with the ecological process of soil erosion(SI-ERI model)by incorporating the natural geographic factors of the study area.We used the ERI and SI-ERI models to evaluate the landscape ecological risk of Leshan City across multiple scales,including ecological,administrative,and sample scales.After conducting overlay and spatial autocorrelation analyses of the multi-scale evaluation results,we determined that the administrative scale is optimal for evaluating landscape ecological risk in the study area.At this scale,we verified the accuracy and reliability of the two models'evaluation results against the actual ecological environment in typical areas within the study area.The findings indicated that the SI-ERI model provided more precise and accurate spatial characterization,effectively reflecting the actual landscape ecological risk of Leshan City.According to the SI-ERI model's evaluation results at the administrative scale,Leshan City's overall risk level is relatively low,with good ecological environmental quality.Low-risk areas constitute 56.16%and medium-low-risk areas make up 23.81%,aligning closely with the city's actual situation.This study thus offers a scientific basis and theoretical reference for managing ecological risks and planning urban development in Leshan City.
基金supported by the National Natural Science Foundation of China(Grant Nos.42272333 and 42377154)the Ningbo Natural Science Foundation(Grant No.2023J085).
文摘Joint surface roughness is comprised of two components:large-scale(waviness,first-order)and smallscale(unevenness,second-order).To investigate the scale effect of two-order roughness,a surface area method is used to separate the waviness and unevenness from the whole joint surface of each size.The results show that as the joint size increases,the first-order roughness exhibits a decrease,whereas the second-order roughness remains constant.This indicates that the roughness scale effect is primarily attributed to the waviness.Then,the influence of two-order roughness on the scale effect of joint shear strength is examined through a series of laboratory tests.The test results reveal a negative scale effect on the peak friction angle,which exhibits a strong correlation with the first-order roughness.The decrease in the peak friction angle with normal stress can be attributed primarily to the degradation of second-order roughness,which shows a negative exponential trend.Finally,an empirical model for estimating the peak friction angle of rock joints at different scales is proposed based on two-order roughness.The prediction accuracy of this model is validated by comparing the existing criteria.
基金supported by the Ministry of Public Works and Housing of Indonesia and Parahyangan Catholic University(Grant No.II/PD/2023-07/02-SJ).
文摘Research on scale effects on flows over weirs has been conducted on a limited basis, primarily focusing on flows upstream of a single-type weir, such as ogee, broad-crested, and sharp-crested (linear and non-linear) weirs. However, the scale effects downstream of these single-type weirs have not been thoroughly investigated. This study examined the scale effects on flows over a combined weir system consisting of an ogee weir and a sharp-crested weir, both upstream and downstream, utilizing physical modeling at a 1:33.33 scale based on Froude similarity and three-dimensional (3D) computational fluid dynamics (CFD) modeling. The sharp-crested weir in this study was represented by two sluice gates that remain closed and submerged during flood events. The experimental data confirmed that the equivalent discharge coefficients of the combined weir system behaved similarly to those of a sharp-crested weir across various H/P (where H is the total head, and P is the weir height) values. However, scale effects on the discharge rating curve due to surface tension and viscosity could only be minimized when H/P > 0.4, Re > 26 959, and We > 240 (where Re and We are the Reynolds and Weber numbers, respectively), provided that the water depth exceeded 0.042 m above the crest. Additionally, Re greater than 4 × 104 was necessary to minimize scale effects caused by viscosity in flows in the spillway channel and stilling basin (with baffle blocks). The limiting criteria aligned closely with existing literature. This study offers valuable insights for practical applications in hydraulic engineering in the future.
基金National Natural Science Foundation of China,No.42171255,No.41971216。
文摘The application of ecosystem services(ES)theories in land consolidation is a confusing issue that has long plagued scholars and government officials.As the upgraded version of traditional land consolidation,comprehensive land consolidation(CLC)emphasizes ecological benefits,but it does not achieve the expected effect during the pilot phase.This study first proposed a theoretical analysis framework based on ES knowledge to answer the three key questions of why,where,and how to implement CLC better.Taking mountainous counties as the study area,we found that ES trade-offs/synergies,bundles,and drivers were significantly affected by scale effects.ES knowledge can play a crucial role in designing multi-scale CLC strategies regarding the objective,zoning,intensity,and mode.Specifically,mitigating the significant trade-offs between recreational opportunities,food production,and other ES is the top priority of CLC.Land consolidation zoning based on the ES bundles analysis is more rational and can provide the scientific premise for designing locally adapted CLC measures.Land consolidation can be classified into high-intensity direct intervention and low-intensity indirect intervention modes,based on the major drivers of ES.These findings help narrow the gap between ES and CLC practices.
基金funded by the National Natural Science Foundation Projects(Grant Nos.41772287 and 42277132)the Key R&D Project of Zhejiang Province(Grant No.2021C03159).
文摘The scale effect on shear strength of rock joints is well-documented.However,whether scale effects are negative,positive,or even exist or not is still controversial.Joint roughness significantly influences the shear strength of rock joints.Compared to the shear tests,using the joint roughness coefficient(JRC)and its roughness parameters offers a more convenient method for describing the scale effect on shear strength.However,it is crucial to understand that the scale effect mechanisms of JRC are distinct from those of shear strength.Therefore,this paper aims to clarify these distinct mechanisms.By digitally extracting roughness parameters from granite samples,it is found that the scale effect of roughness parameters mainly comes from the sampling methods and the geometric characteristics of parameters.Furthermore,a full data sampling method considering heterogeneity is proposed to obtain more representative roughness parameters.To reveal the scale effect mechanisms of shear strength,Gaussian filtering is firstly used to separate the waviness and unevenness components of roughness,facilitating a deeper understanding of the geometric characteristics of roughness.It is suggested that the wavelength of the waviness component can reflect the scale effect on shear strength.Secondly,numerical simulations of ideal artificial joint models are conducted to validate that the wavelength of the waviness component serves as the dividing point between positive and negative scale effects.The mechanical mechanisms of positive and negative scale effects are also interpreted.Finally,these mechanisms successfully elucidate the occurrence patterns of the scale effect on natural joint profiles.
基金supported by the National Natural Science Foundation of China(No.42207175)。
文摘The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engineering projects.During the collection process of JRC samples,the redundancy or insufficiency of representative rock joint surface topography(RJST) information in serial length JRC samples is the essential reason that affects the reliability of the scale effect results.Therefore,this paper proposes an adaptive sampling method,in which we use the entropy consistency measure Q(a) to evaluate the consistency of the joint morphology information contained in adjacent JRC samples.Then the sampling interval is automatically adjusted according to the threshold Q(at) of the entropy consistency measure to ensure that the degree of change of RJST information between JRC samples is the same,and ultimately makes the representative RJST information in the collected JRC samples more balanced.The application results of actual cases show that the proposed method can obtain the scale effect in the JRC efficiently and reliably.
文摘Geological strength index(GSI)has been widely used as an input parameter in predicting the strength and deformation properties of rock masses.This study derived a series of equations to satisfy the original GSI lines on the basic GSI chart.Two axes ranging from 0 to 100 were employed for surface conditions of the discontinuities and the structure of rock mass,which are independent of the input parameters.The derived equations can analyze GSI values ranging from 0 to 100 within±5%error.The engineering dimensions(EDs)such as the slope height,tunnel width,and foundation width were used together with representative elementary volume(REV)in jointed rock mass to define scale factor(sf)from 0.2 to 1 in evaluating the rock mass structure including joint pattern.The transformation of GSI into a scaledependent parameter based on engineering scale addresses a crucial requirement in various engineering applications.The improvements proposed in this study were applied to a real slope which was close to the time of failure.The results of stability assessments show that the new proposals have sufficient capability to define rock mass quality considering EDs.
基金Project supported by the National Key Research and Development Program of China(No.2022YFB3207100)Hubei Provincial Strategic Scientist Training Plan(No.2022EJD009)the Fundamental Research Funds for the Central Universities of China(No.2042023kf1041)。
文摘In this study,the thermodynamic behaviors of the intrinsic frequency and buckling temperature of rectangular plates of functionally graded materials(FGMs)are explored based on the modified couple stress theory(MCST)and the novel dual powerlaw scale distribution theory.The effects of linear,homogeneous,and non-homogeneous temperature fields on the frequency and buckling temperature of FGM microplates are evaluated in detail.The results show that the porosity greatly affects the mechanical properties of FGM plates,reducing their frequency and flexural temperature compared with non-porous plates.Different temperature profiles alter plate frequencies and buckling temperatures.The presence and pattern of scale effect parameters are also shown to be crucial for the mechanical response of FGM plates.The present research aims to provide precise guidelines for the micro-electro-mechanical system(MEMS)fabrication by elucidating the complex interplay between thermal,material,and structural factors that affect the performance of FGM plates in advanced applications.
文摘For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out scale model test to establish a distortion model similar to the real ship structure under combined load. A similarity criterion for ship distortion model under the combined action of bending moment and surface pressure was proposed, and the scale effect for the criterion was verified by a se ries of numerical analysis and model tests. The results show that the similarity criterion for ship distor tion model under combined loads has a certain scale effect. For the model tests of ship cabin struc tures, it is suggested that the scale range between the plate thickness scale and the main dimension scale should be controlled within 2:1, which can be used as a reference for distortion model design and ultimate strength test of large-scale ship structures.
基金the Natural Science Foundation of China(Grant No.41790425).
文摘Landscape fragmentation is generally viewed as an indicator of environmental stresses or risks,but the fragmentation intensity assessment also depends on the scale of data and the definition of spatial unit.This study aimed to explore the scale-dependence of forest fragmentation intensity along a moisture gradient in Yinshan Mountain of North China,and to estimate environmental sensitivity of forest fragmentation in this semi-arid landscape.We developed an automatic classification algorithm using simple linear iterative clustering(SLIC)and Gaussian mixture model(GMM),and extracted tree canopy patches from Google Earth images(GEI),with an accuracy of 89.2%in the study area.Then we convert the tree canopy patches to forest category according to definition of forest that tree density greater than 10%,and compared it with forest categories from global land use datasets,FROM-GLC10 and GlobeLand30,with spatial resolutions of 10 m and 30 m,respectively.We found that the FROM-GLC10 and GlobeLand30 datasets underestimated the forest area in Yinshan Mountain by 16.88%and 21.06%,respectively;and the ratio of open forest(OF,10%<tree coverage<40%)to closed forest(CF,tree coverage>40%)areas in the underestimated part was 2:1.The underestimations concentrated in warmer and drier areas occupied mostly by large coverage of OFs with severely fragmented canopies.Fragmentation intensity of canopies positively correlated with spring temperature while negatively correlated with summer precipitation and terrain slope.When summer precipitation was less than 300 mm or spring temperature higher than 4℃,canopy fragmentation intensity rose drastically,while the forest area percentage kept stable.Our study suggested that the spatial configuration,e.g.,sparseness,is more sensitive to drought stress than area percentage.This highlights the importance of data resolution and proper fragmentation measurements for forest patterns and environmental interpretation,which is the base of reliable ecosystem predictions with regard to the future climate scenarios.
基金Project supported by China Academy of Engineering Strategic Consulting Key Research Project“Study on Effective Development Path of China’s Shale Gas Scale”(No.:2018-XZ-032)National Major Science and Technology Project“Large Oil and Gas Field and CBM Development-Changning-Weiyuan Shale Gas Development of Demonstration Project”(No.:2016ZX05062-002)PetroChina Major Project“Research and Application of Key Technologies for Producing 30 Billion Cm of Natural Gas in Southwest Oil and Gas Fields”(No.:2016E-0611).
文摘Based on the newest understandings of geological assessment and new progresses in engineering technologies in the development of shale gas rich in the southern Sichuan Basin,this paper analyzed the shale gas enrichment laws and the key factors of its commercial production,discussed the scale and efficient development modes,and clarified the further developing orientation.The following findings were concluded.(1)The Lower Silurian Longmaxi shale is the sweetest spot in this study area with a low density and a high uranium/thorium(U/Th)ratio,TOC content,quartz content,and free gas content.Besides,its distribution laws are mainly controlled by the sedimentary facies of deep water shelf.(2)The overpressured zones away from the ancient(present)erosion zones and large faults,mainly controlled by multi-stage tectonic evolution,belong to the most favorable sweet spots not only because there are well-developed organic matters and pores but the produced gas there is mainly of secondary cracking retention oil.(3)Layout,drilling,completion(fracturing)and management of wells will be essential to achieve high productions in the shale gas production.(4)The existing main technologies have helped achieve efficient development of quality shale gas resources underground less than 3500 m in such national shale gas demonstration zones as ChangningeWeiyuan,Zhaotong,etc.Also,there shows a good potential of shale gas resources in those shallower strata and the strata with the burial depth of 3500-4000 m.In conclusion,with the help of continuous progress in technologies,an annual shale gas production rate of 40 billion cubic meters will be possibly achieved in this study area.
基金supported by the National Natural Science Foundation of China(62101099)the Chinese Postdoctoral Science Foundation(2021M690558,2022T150100,2018M633352,2019T120825)+3 种基金the Young Elite Scientist Sponsorship Program(YESS20200082)the Aeronautical Science Foundation of China(2022Z017080001)the Open Foundation of Science and Technology on Electronic Information Control Laboratorythe Natural Science Foundation of Sichuan Province(2023NSFSC1386)。
文摘The detection of hypersonic targets usually confronts range migration(RM)issue before coherent integration(CI).The traditional methods aiming at correcting RM to obtain CI mainly considers the narrow-band radar condition.However,with the increasing requirement of far-range detection,the time bandwidth product,which is corresponding to radar’s mean power,should be promoted in actual application.Thus,the echo signal generates the scale effect(SE)at large time bandwidth product situation,influencing the intra and inter pulse integration performance.To eliminate SE and correct RM,this paper proposes an effective algorithm,i.e.,scaled location rotation transform(ScLRT).The ScLRT can remove SE to obtain the matching pulse compression(PC)as well as correct RM to complete CI via the location rotation transform,being implemented by seeking the actual rotation angle.Compared to the traditional coherent detection algorithms,Sc LRT can address the SE problem to achieve better detection/estimation capabilities.At last,this paper gives several simulations to assess the viability of ScLRT.
基金supported in part by the Guangxi science and technology program(GuiKe 2021AB30019)Sichuan Science and Technology Program(2022YFN0031,2023YFN0022,and 2023YFS0381)+2 种基金Hubei key R&D plan(2022BAA048)Zhuhai industry university research cooperation project of China(ZH22017001210098PWC)Shanxi Science and Technology Program(202201150401020).
文摘Many existing efforts have taken advantage of large-scale spatial-temporal data to partition cities via constructed human interaction networks.However,few studies focus on communities emerging between adjacent cities in big urban agglomerations,which we call“cross-city”communities.In this study,we introduce a novel framework to detect cross-city communities in urban agglomerations under different scales leveraging a large number of fine-grained mobile signaling data aiming to break the original administrative boundaries.Taking the Pearl River Delta(PRD)urban agglomeration in China as study area,we investigate the existence of potential communities at three scales,i.e.city-group level,city level and sub-city level.The partition results are expected to benefit transportation planning,urban zoning and administrative boundary re-delineation.The results from our study highlight the necessity of considering cross-city communities and their scale effects when examining urban spatial interactions.
基金Project (50835002) supported by the National Natural Science Foundation of ChinaProject (QC08C55) supported by the Natural Science Foundation of Heilongjiang Province, China Project (200802131031) supported by the PhD. Programs Foundation of Ministry of Education of China for Young Scholars
文摘To analyze the effect of single grain deformation behaviors on microforming process, a crystal plasticity model was developed considering grains at free surface layer as single grains. Based on the rate-dependent crystal plasticity theory, the analysis of the scale effect mechanism on upsetting deformation of micro rods was performed with respect to specimen dimension, original grain orientation and its distribution. The results show that flow stress decreases significantly with the scaling down of the specimen. The distribution of the grain orientation has an evident effect on flow stress of the micro specimen, and the effect becomes smaller with the progress of plastic deformation. For the anisotropy of single grains, inhomogeneous deformation occurs at the surface layer, which leads to the increase of surface roughness, especially for small specimens. The effect of grain anisotropy on the surface topography can be decreased by the transition grains. The simulation results are validated by upsetting deformation experiments. This indicates that the developed model is suitable for the analysis of microforming processes with characteristics, such as scale dependency, scatter of flow stress and inhomogeneous deformation.
基金The National Natural Science Foundation of China(No.51009144)
文摘Regarding the scale effects on propeller＇s noncavitation hydrodynamics and hydroacoustics, three similar 7bladed highly-skewed propellers in the wake flow are addressed with diameters of 250, 500 and 1 000 mm, respectively. The discrete line-spectrum noise and its standardized spectrum level scaling law, together with the total sound pressure level are analyzed. The non-cavitation noise predictions are completed by both the frequency domain method and the time domain method. As a fluctuated noise source, the time-dependent fluctuated pressure and normal velocity distribution on propeller blades are obtained by the unsteady Reynolds-averaged Navier-Stokes （ URANS ） simulation. Results show that the pressure coefficient distribution of three propellers on the 0.7R section is nearly superposed under the same advance ratio. The periodic thrust fluctuation of three propellers can exactly reflect the tonal components of the axial passing frequency （APF） and the blade passing frequency （BPF）, and the fluctuation enhancement from the small to the middle propeller at the BPF is greater than that from the middle to the big one. By the two noise prediction methods, the increment of the total sound pressure level from the small to the big propeller differs by 2.49 dB. Following the standardized scaling law, the spectrum curves of the middle and big propellers are nearly the same while significantly differing from the small one. The increment of both the line-spectrum level and the total sound pressure increases with the increase in diameter. It is suggested that the model scale of the propeller should be as large as possible in engineering to reduce the prediction error of the empirical scalin~ law and weaken the scale effects.
基金funded by the National Natural Science Foundation of China(Nos.52039005,52371258,52071031)the Tianjin Science and Technology Plan Project(No.22PTZWHZ00060)the Subtopic of National Key Research and Development Program Projects(No.2022YFB2602301).
文摘The complex topography of natural bedrock shorelines on islands necessitates detailed model testing to thoroughly inves-tigate wave overtopping mechanisms and their variation patterns.This understanding is vital for optimizing the elevation of coastal structures to meet the design requirements for wave overtopping and to ensure safety and efficacy.This paper investigates a nuclear power plant project on an island in Zhejiang Province,China.This study employs small-scale overall model tests and large-scale lo-cal model tests to examine the complex dynamics of wave interaction with the island’s shoreline.It analyzes the influences of wave parameters,shoreline geometry,and underwater topography on wave overtopping behavior.Comparisons between physical model re-sults and empirical formulae reveal substantial discrepancies in overtopping rates across different model scales.The results stress the remarkable effect of accurate underwater topography representation on wave overtopping predictions and emphasize the need for pre-cise topographic modeling.The results also show that overtopping discharges for complex terrains deviate considerably from values determined using traditional empirical formulas for breakwater overtopping.This outcome indicates that conventional methods may insufficiently address the complexities of natural coastal features.To guarantee reliable predictions of overtopping volumes at specif-ic elevations along complex coastlines,this study advocates employing physical modeling across numerous scales while accounting for detailed terrain and hydrodynamic characteristics.
基金Project supported by the National Natural Science Foundation of China(No.12172169)。
文摘In this paper,a fractional-order kinematic model is utilized to capture the size-dependent static bending and free vibration responses of piezoelectric nanobeams.The general nonlocal strains in the Euler-Bernoulli piezoelectric beam are defined by a frame-invariant and dimensionally consistent Riesz-Caputo fractional-order derivatives.The strain energy,the work done by external loads,and the kinetic energy based on the fractional-order kinematic model are derived and expressed in explicit forms.The boundary conditions for the nonlocal Euler-Bernoulli beam are derived through variational principles.Furthermore,a finite element model for the fractional-order system is developed in order to obtain the numerical solutions to the integro-differential equations.The effects of the fractional order and the vibration order on the static bending and vibration responses of the Euler-Bernoulli piezoelectric beams are investigated numerically.The results from the present model are validated against the existing results in the literature,and it is demonstrated that they are theoretically consistent.Although this fractional finite element method(FEM)is presented in the context of a one-dimensional(1D)beam,it can be extended to higher dimensional fractional-order boundary value problems.
基金supported by the National Natural Science Foundation of China(No.31660234).
文摘Global forest cover is undergoing significant transformations due to anthropogenic activities and natural disturbances,profoundly impacting hydrological processes.However,the inherent spatial heterogeneity within watersheds leads to varied hydrological responses across spatiotemporal scales,challenging comprehensive assessment of logging impacts at the watershed scale.Here,we developed multiple forest logging scenarios using the soil and water assessment tool(SWAT)model for the Le'an River watershed,a 5,837 km2 subtropical watershed in China,to quantify the hydrological effects of forest logging across different spatiotemporal scales.Our results demonstrate that increasing forest logging ratios from 1.54% to 9.25% consistently enhanced ecohydrological sensitivity.However,sensitivity varied across spatiotemporal scales,with the rainy season(15.30%-15.81%)showing higher sensitivity than annual(11.56%-12.07%)and dry season(3.38%-5.57%)periods.Additionally,the ecohydrological sensitivity of logging varied significantly across the watershed,with midstream areas exhibiting the highest sensitivity(13.13%-13.25%),followed by downstream(11.87%-11.98%)and upstream regions(9.96%-10.05%).Furthermore,the whole watershed exhibited greater hydrological resilience to logging compared to upstream areas,with attenuated runoff changes due to scale effects.Scale effects were more pronounced during dry seasons((-8.13 to -42.13)×10^(4) m^(3)·month^(-1))than in the rainy season((-11.11 to -26.65)×10^(4) m^(3)·month^(-1)).These findings advance understanding of logging impacts on hydrology across different spatiotemporal scales in subtropical regions,providing valuable insights for forest management under increasing anthropogenic activities and climate change.
