-A joint probability density is derived for wavelengths and wave heights.It is asymmetric anddepends only on the spectral bandwidthεdefined by Cartwright and Longuet-Higgins(1956).After that atheoretical probability ...-A joint probability density is derived for wavelengths and wave heights.It is asymmetric anddepends only on the spectral bandwidthεdefined by Cartwright and Longuet-Higgins(1956).After that atheoretical probability density for wave steepness is obtained.It tends to Rayleigh distribution asε→0.Acomparison between theorethal steepness distribution and laboratory experiment result shows good agree-ment.展开更多
Human activities to improve the quality of life have accelerated the natural rate of soil erosion.In turn,these natural disasters have taken a great impact on humans.Human activities,particularly the conversion of veg...Human activities to improve the quality of life have accelerated the natural rate of soil erosion.In turn,these natural disasters have taken a great impact on humans.Human activities,particularly the conversion of vegetated land into agricultural land and built-up area,stand out as primary contributors to soil erosion.The present study investigated the risk of soil erosion in the Irga watershed located on the eastern fringe of the Chota Nagpur Plateau in Jharkhand,India,which is dominated by sandy loam and sandy clay loam soil with low soil organic carbon(SOC)content.The study used the Revised Universal Soil Loss Equation(RUSLE)and Geographical Information System(GIS)technique to determine the rate of soil erosion.The five parameters(rainfall-runoff erosivity(R)factor,soil erodibility(K)factor,slope length and steepness(LS)factor,cover-management(C)factor,and support practice(P)factor)of the RUSLE were applied to present a more accurate distribution characteristic of soil erosion in the Irga watershed.The result shows that the R factor is positively correlated with rainfall and follows the same distribution pattern as the rainfall.The K factor values in the northern part of the study area are relatively low,while they are relatively high in the southern part.The mean value of the LS factor is 2.74,which is low due to the flat terrain of the Irga watershed.There is a negative linear correlation between Normalized Difference Vegetation Index(NDVI)and the C factor,and the high values of the C factor are observed in places with low NDVI.The mean value of the P factor is 0.210,with a range from 0.000 to 1.000.After calculating all parameters,we obtained the average soil erosion rate of 1.43 t/(hm^(2)•a),with the highest rate reaching as high as 32.71 t/(hm^(2)•a).Therefore,the study area faces a low risk of soil erosion.However,preventative measures are essential to avoid future damage to productive and constructive activities caused by soil erosion.This study also identifies the spatial distribution of soil erosion rate,which will help policy-makers to implement targeted soil erosion control measures.展开更多
The frequent occurrence of extreme weather events has rendered numerous landslides to a global natural disaster issue.It is crucial to rapidly and accurately determine the boundaries of landslides for geohazards evalu...The frequent occurrence of extreme weather events has rendered numerous landslides to a global natural disaster issue.It is crucial to rapidly and accurately determine the boundaries of landslides for geohazards evaluation and emergency response.Therefore,the Skip Connection DeepLab neural network(SCDnn),a deep learning model based on 770 optical remote sensing images of landslide,is proposed to improve the accuracy of landslide boundary detection.The SCDnn model is optimized for the over-segmentation issue which occurs in conventional deep learning models when there is a significant degree of similarity between topographical geomorphic features.SCDnn exhibits notable improvements in landslide feature extraction and semantic segmentation by combining an enhanced Atrous Spatial Pyramid Convolutional Block(ASPC)with a coding structure that reduces model complexity.The experimental results demonstrate that SCDnn can identify landslide boundaries in 119 images with MIoU values between 0.8and 0.9;while 52 images with MIoU values exceeding 0.9,which exceeds the identification accuracy of existing techniques.This work can offer a novel technique for the automatic extensive identification of landslide boundaries in remote sensing images in addition to establishing the groundwork for future inve stigations and applications in related domains.展开更多
Catastrophic geological disasters frequently occur on slopes with obliquely inclined bedding structures(also referred to as obliquely inclined bedding slopes),where the apparent dip sliding is not readily visible.This...Catastrophic geological disasters frequently occur on slopes with obliquely inclined bedding structures(also referred to as obliquely inclined bedding slopes),where the apparent dip sliding is not readily visible.This phenomenon has become a focal point in landslide research.Yet,there is a lack of studies on the failure modes and mechanisms of hidden,steep obliquely inclined bedding slopes.This study investigated the Shanyang landslide in Shaanxi Province,China.Using field investigations,laboratory tests of geotechnical parameters,and the 3DEC software,this study developed a numerical model of the landslide to analyze the failure process of such slopes.The findings indicate that the Shanyang landslide primarily crept along a weak interlayer under the action of gravity.The landslide,initially following a dip angle with the support of a stable inclined rock mass,shifted direction under the influence of argillization in the weak interlayer,moving towards the apparent dip angle.The slide resistance effect of the karstic dissolution zone was increasingly significant during this process,with lateral friction being the primary resistance force.A reduction in the lateral friction due to karstic dissolution made the apparent dip sliding characteristics of the Shanyang landslide more pronounced.Notably,deformations such as bending and uplift at the slope’s foot suggest that the main slide resistance shifts from lateral friction within the karstic dissolution zone to the slope foot’s resistance force,leading to the eventual buckling failure of the landslide.This study unveils a novel failure mode of apparent dip creep-buckling in the Shanyang landslide,highlighting the critical role of lateral friction from the karstic dissolution zone in its failure mechanism.These insights offer a valuable reference for mitigating risks and preventing disasters related to obliquely inclined bedding landslides.展开更多
Background:The grazing behaviour of herbivores and their grazing personalities might in part be determined genetically,but there are few studies in beef cattle illustrating this.In this study,we investigated for first...Background:The grazing behaviour of herbivores and their grazing personalities might in part be determined genetically,but there are few studies in beef cattle illustrating this.In this study,we investigated for first time the genetic variation within a candidate‘grazing gene',the glutamate metabotropic receptor 5 gene(GRM5),and tested associations between variation in that gene and variation in grazing personality behaviours(GP-behaviours)displayed by free-ranging cows during winter grazing in the steep and rugged rangelands of New Zealand.Mature beef cows(n=303,from 3 to 10 years of age)were tracked with global positioning system(GPS)and,with 5-minutes(min)relocation frequency,various GP-behaviours were calculated.These included horizontal and vertical distances travelled,mean elevation,elevation range,elevation gain,slope,home range and movement tortuosity,variously calculated using daily relocation trajectories with repeated measurements(i.e.,7 to 24 days(d))and satellite-derived digital elevation models(DEM).The different GP-behaviours were fitted into mixed models to ascertain their associations with variant sequences and genotypes of GRM5.Results:We discovered three GRM5 variants(A,B and C)and identified the six possible genotypes in the cattle studied.The mixed models revealed that A was significantly associated with elevation range,home range and movement tortuosity.Similarly,GRM5 genotypes were associated(P<0.05)to home range and movement tortuosity,while trends suggesting association(P<0.1)were also revealed for elevation range and horizontal distance travelled.Most GP-behaviour models were improved by correcting for cow age-class as a fixed factor.The analysis of GP-behaviours averaged per cow age-class suggests that grazing personality is fully established as beef cows reached 4 years of age.Home range and movement tortuosity were not only associated with GRM5 variation,but also negatively correlated with each other(r=-0.27,P<0.001).Conclusions:There seems to be a genetically determined trade-off between home range and movement tortuosity that may be useful in beef cattle breeding programmes aiming to improve the grazing distribution and utilisation of steep and rugged rangelands.展开更多
Grass recovery is often implemented in the loess area of China to control erosion.However,the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear.Taking the typical...Grass recovery is often implemented in the loess area of China to control erosion.However,the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear.Taking the typical forage species(Coreopsis)in semiarid areas as subject,this study quantified the effects of canopies and roots on controlling slope runoff and erosion.A series of field experiments were conducted in a loess hilly region of China.Field plots(5 m length,2 m width,25°slope gradient)constructed with three ground covers(bare soil;Coreopsis with intact grass;only roots of Coreopsis),were applied with simultaneous simulated rainfall(60mm h^(-1))and upslope inflow(10,30,50,70,90L min^(-1)).The results showed that compared with bare soil,intact grass significantly reduced runoff and soil loss rates by 16.6% and 62.4% on average,and decreased soil erodibility parameter by 66.3%.As inflow rate increased,the reductions in runoff and soil loss rates increased from 2.93 to 14.00 L min^(-1)and 35.11 to 121.96 g m^(-2)min^(-1),respectively.Canopies relatively contributed 66.7% to lowering flow velocity,turbulence,weakening erosive force and increasing hydraulic resistance.Roots played a predominant role in reducing soil loss and enhancing soil antierodibility,with relative contributions of 78.8% and 73.8%.Furthermore,the maximum erosion depth reduced by Coreopsis was at the upper slope section which was previously eroded the most.These results demonstrated the efficiency of Coreopsis cover in controlling runoff and erosion on steep loess slopes,especially under large inflow rates and at upper slope sections.We suggest protecting Coreopsis with intact grass at upper slope sections,while the aboveground grass biomass can be used for grazing or harvesting at middle and lower slope sections,with roots reserved.展开更多
We study the ground states of attractive binary Bose-Einstein condensates with N particles,which are trapped in the steep potential wellsλV(x)inℝ2.We show that there exists a positive number N*such that if N>N*,th...We study the ground states of attractive binary Bose-Einstein condensates with N particles,which are trapped in the steep potential wellsλV(x)inℝ2.We show that there exists a positive number N*such that if N>N*,the system admits no ground state for anyλ>0.Moreover,there exist two positive numbers,M*andλ*(N),such that if N<M*,then for anyλ>λ*(N),the system admits at least one ground state.Asλ→∞,for any fixed N<M*,we give a detailed description for the limit behavior of both positive and semi-trivial ground states.展开更多
Numerical simulation tools based on potential-flow theory and/or Morison’s equation are widely used for predicting the hydrodynamic responses of floating offshore wind platforms.In general,these simplified approaches...Numerical simulation tools based on potential-flow theory and/or Morison’s equation are widely used for predicting the hydrodynamic responses of floating offshore wind platforms.In general,these simplified approaches are used for the analysis under operational conditions,albeit with a carefully selected approach to account for viscous effects.Nevertheless,due to the limit hydrodynamic modelling to linear and weakly nonlinear models,these approaches severely underpredict the low-frequency nonlinear wave loads and dynamic responses of a semisubmersible.They may not capture important nonlinearities in severe sea states.For the prediction of wave-induced motions and loads on a semisubmersible,this work systematically compares a fully nonlinear viscous-flow solver and a hybrid model combining the potential-flow theory with Morison-drag loads in steep waves.Results show that when nonlinear phenomena are not dominant,the results obtained by the hybrid model and the high-fidelity method show reasonable agreement,while larger discrepancies occur for highly nonlinear regular waves.Specifically,regular waves with various steepness over different frequencies are focused in the present study,which supplements the understanding in applicability of these two groups of method.展开更多
In this paper,we consider the nonlinear Kirchhoff type equation with a steep potential well−(a+b∫_(R)^(3)|∇u|^(2 )dx)Δu+λV(x)u=f(u)in R^(3),where a,b>0 are constants,λ is a positive parameter,V∈C(R3,R)is a ste...In this paper,we consider the nonlinear Kirchhoff type equation with a steep potential well−(a+b∫_(R)^(3)|∇u|^(2 )dx)Δu+λV(x)u=f(u)in R^(3),where a,b>0 are constants,λ is a positive parameter,V∈C(R3,R)is a steep potential well and the nonlinearity f∈C(R,R)satisfies certain assumptions.By applying a signchanging Nehari manifold combined with the method of constructing a sign-changing(PS)C sequence,we obtain the existence of ground state sign-changing solutions with precisely two nodal domains when λ is large enough,and find that its energy is strictly larger than twice that of the ground state solutions.In addition,we also prove the concentration of ground state sign-changing solutions.展开更多
Buyuan River, the largest tributary within the Chinese Lancang-Mekong River region downstream of the Jinghong Dam, plays a crucial role in river function and ecosystem service of the Lancang-Mekong River. The geomorph...Buyuan River, the largest tributary within the Chinese Lancang-Mekong River region downstream of the Jinghong Dam, plays a crucial role in river function and ecosystem service of the Lancang-Mekong River. The geomorphic evolution of a basin exerts a key control on riverine sediment input and transport. In this study, the geomorphic characteristics of Buyuan Basin are analyzed using morphological parameters, hydrodynamic parameters and the stream power river incision model. The results show that: 1) The slight north-south difference of channel density is most likely due to lithology and independent of tectonic activity and climate. 2) The weak tectonic activity and the low hypsometric integral(HI) value suggest that the macroscopic landform condition limits erosion and sediment production. 3) The logarithmic longitudinal profile of the main channel defends that the upstream sediments generated by erosion are easily deposited in the downstream channel, rather than being transported directly into the Lancang-Mekong River. 4) Approximately 74% of the reaches have annual average stream power less than 500 W·m^(-1). The narrow variation ranges of stream power in 50% of the river channel indicate relatively stable hydrodynamic environment. 5) Stream erosion and tectonic activity make the longitudinal profiles of the main channel and most tributary channels unstable. The wide range(between 22.01 and 45.58 with θ=0.43) of steepness index(k_(sn)) of longitudinal profiles implies differential uplift in the basin.展开更多
Based on phase focusing theory, focusing waves with different spectral types and breaking severities were generated in a wave flume. The time series of surface elevation fluctuation along the flume were obtained by ut...Based on phase focusing theory, focusing waves with different spectral types and breaking severities were generated in a wave flume. The time series of surface elevation fluctuation along the flume were obtained by utilizing 22 wave probes mounted along the mid-stream of the flume. Based on the wave spectrum obtained using fast Fourier transform(FFT), the instability characteristics of the energy spectrum were reported in this paper. By analyzing the variation of total spectral energy, the total spectral energy after wave breaking was found to clearly decrease, and the loss value and ratio gradually increased and tended to stabilize with the enhancement of breaking severity for different spectral types. When wave breaking occurred, the energy loss was primarily in a high-frequency range of f/fp>1.0, and energy gain was primarily in a low-frequency range of f/fp<1.0. As the breaking severity increased, the energy gain-loss ratio decreased gradually, which demonstrates that the energy was mostly dissipated. For plunging waves, the energy gain-loss ratio reached 24% for the constant wave steepness(CWS) spectrum, and was slightly larger at approximately 30% for the constant wave amplitude(CWA) spectrum, and was the largest at approximately 42% for the Pierson-Moskowitz(PM) spectrum.展开更多
Understanding the evolution of the fluvial geomorphology in an orogenic belt provides valuable insight into the relationship between upper crustal deformation and surface processes.The upper Lancang-Mekong River is in...Understanding the evolution of the fluvial geomorphology in an orogenic belt provides valuable insight into the relationship between upper crustal deformation and surface processes.The upper Lancang-Mekong River is in an area experiencing both uplift and erosion.The related processes provide a steady sediment supply to the lower reaches of the river and play an important role in the regional environmental changes.The Xiaohei(Weiyuan)River Basin is an important sub-basin in this area,which is characterized by large-scale topographic fluctuations,active tectonics and erosion,and anthropogenic activities.These different factors introduce numerous complexities to the local surface processes.In this study,we investigate and quantify the controls of geomorphic evolution of the Xiaohei River Basin.We located and mapped the main knick-zones within the channels and examined the main genetic factors,such as faults and stratigraphic differences.The results show that the areas with the lowest uplift rates are characterized by a low steepness index and are located in the southeastern part of the basin.The stream power of the mainstream increases downstream,with an average value of^122 W/m.The erosional activity of the various stream channels is intense.Overall,the basin tends to expansion,with only local instances of inward contraction.Our analysis confirms that a number of the geomorphic evolutionary characteristics of the Xiaohei River Basin are transient.In addition,the future potential for the increasing the number of dams and the hydropower development in the basin may weaken the expansion trend of the basin over a long period of time.展开更多
In this paper,the influence of heave and pitch motions on green water impact on the deck is numerically investigated.The vessel motions are determined using a potential theory based method and provided as input to fin...In this paper,the influence of heave and pitch motions on green water impact on the deck is numerically investigated.The vessel motions are determined using a potential theory based method and provided as input to finite volume based CFD computations of green water phenomenon.A dynamic mesh approach is adopted to determine instantaneous body positioning in the fluid domain.Detailed validation studies with published experimental results for 2D and 3D fixed vessel cases are initially performed to validate the present numerical approach before studying the moving vessel problem.The results show that inclusion of heave and pitch motion changes the disturbed wave field near the bow which influences the free surface as well as the impact loading due to green water.The effect of wave steepness on green water impact is also investigated and it is seen that the present numerical method is capable of capturing green water load.It is observed that the effects of vessel motions on green water load are not negligible and one should consider this effect too.The incorporation of vessel motions in the vertical plane affects the green water loading on the deck.展开更多
Sediment sampling and longitudinal river-bottom surveys were conducted along the thalweg on the Tanana River near the city of Nenana, Alaska, USA, to provide basic information for the engineering design requirements o...Sediment sampling and longitudinal river-bottom surveys were conducted along the thalweg on the Tanana River near the city of Nenana, Alaska, USA, to provide basic information for the engineering design requirements of hydrokinetic devices to be deployed in the area. The study reach was located at approximately 64°33'50'N and 149°04'W. The Tanana is a large glacier-fed river, with open-water flow conditions from May to October. The river presents a single channel in the study area. Granulometric analyses of sediment moving near the riverbed reveals the coexistence of three distinctive types of sediment along the study reach: 1) nearly uniform fine sand;2) bimodal distributions containing fine sand and medium gravel;and 3) medium gravel. Preliminary relationships between sediment loads and discharge were developed. Dunes with small superimposed dunes were found along the reach. The basic geometric parameters (i.e., wavelength and height) of dunes were measured, and steepness was calculated. In general, dune wavelength increased with increasing discharge. Dune wavelengths ranged from 41 to 67 m, while small-dune wavelengths ranged from 13 to 16 m. Steepness increased slightly with increasing discharge.展开更多
Some new results of the modeling of mean free surface of waves or wave set-up are presented. The stream function wave theory is applied to incident short waves. The limiting wave steepness is adopted as the wave break...Some new results of the modeling of mean free surface of waves or wave set-up are presented. The stream function wave theory is applied to incident short waves. The limiting wave steepness is adopted as the wave breaker index in the calculation of wave breaking dissipation. The model is based on Roelvink (1993), but the numerical techniques used in the solution are based on the Weighted-Average Flux (WAF) method (Watson et al., 1992), with Time-Operator-Splitting (TOS) used for the treatment of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modeling wave set-up. The short wave (or incident primary wave) energy equation issolved by use of a traditional Lax-Wendroff technique. The present model is found to be satisfactory compared with the measurements conducted by Stive (1983).展开更多
Through numerical modeling, a kind of simplified calculating method for standing wave pressure on vertical face breakwater have been put forward. Not only the formulas proposed in this paper are simple in form and ver...Through numerical modeling, a kind of simplified calculating method for standing wave pressure on vertical face breakwater have been put forward. Not only the formulas proposed in this paper are simple in form and very easy in use, but also they possess continuity on the full range of standing wave. And more, the precision requiremennts of calculation can be satisfied to a certain extent in engineering practice.展开更多
Based on the analysis and comparison of wave breaker indices defined by geometric, kinetic as well as dynamic stabilities and verified by observation, the value a, which is equal to H / Lthkd by Miche’s result and ma...Based on the analysis and comparison of wave breaker indices defined by geometric, kinetic as well as dynamic stabilities and verified by observation, the value a, which is equal to H / Lthkd by Miche’s result and may be modified by Goda’s results, is' suggested as the wave breaking criteria. The applicable values of a for pure waves or wave-current co-existing field are given in this paper. They are smaller than Miche’s result (0.142), and they have been verified by model tests.展开更多
Landslides are common hazards in orogenic belt areas.However,it is difficult to quantitatively express the driving effects of tectonic uplift and stream erosion on the occurrence of landslides on large spatial scales ...Landslides are common hazards in orogenic belt areas.However,it is difficult to quantitatively express the driving effects of tectonic uplift and stream erosion on the occurrence of landslides on large spatial scales by conducting field investigations.In this study,we analyzed a relatively large region that extends over the Yangbi River basin on the upper Lancang-Mekong in China.A series of quantitative indices,including kernel density of the landslide(KDL),hypsometric integral(HI),steepness index(ksn),stream power(?),and stream power gradient(ω)were used to explore the promoting effects of tectonic uplift and stream action intensity on landslides by mapping geomorphic dynamic parameters combined with actual landslide data.The analysis showed that the HI value in the highest landslide risk area was approximately 0.47,and that the KDL in the region can be expressed as a function of steepness or stream power gradient of the channel network,namely,KDL=0.0127 Ln ksn-0.0167(R2=0.72,P<0.001)and KDL=0.0219 Lnω-0.0558(R2=0.21,P<0.02).Therefore,the lower reach of the Yangbi River basin,with higher steepness and stream power gradient,usually has a high uplifting rate and stream incision that drives landslides and causes the entire river network system to be in a stage of longterm active erosion.Furthermore,the results suggest that sediments were being rapidly discharged from the steep tributary channels to the mainstream.This practical situation highlights that the downstream area of the river basin is a high-risk area for landslide hazards,especially in association with heavy rainfall and earthquakes.展开更多
基金National Natural Foundation of China.(No.49676277)
文摘-A joint probability density is derived for wavelengths and wave heights.It is asymmetric anddepends only on the spectral bandwidthεdefined by Cartwright and Longuet-Higgins(1956).After that atheoretical probability density for wave steepness is obtained.It tends to Rayleigh distribution asε→0.Acomparison between theorethal steepness distribution and laboratory experiment result shows good agree-ment.
基金the financial support received from the University Grants Commission (UGC) in the form of a Junior Research Fellowship (JRF)。
文摘Human activities to improve the quality of life have accelerated the natural rate of soil erosion.In turn,these natural disasters have taken a great impact on humans.Human activities,particularly the conversion of vegetated land into agricultural land and built-up area,stand out as primary contributors to soil erosion.The present study investigated the risk of soil erosion in the Irga watershed located on the eastern fringe of the Chota Nagpur Plateau in Jharkhand,India,which is dominated by sandy loam and sandy clay loam soil with low soil organic carbon(SOC)content.The study used the Revised Universal Soil Loss Equation(RUSLE)and Geographical Information System(GIS)technique to determine the rate of soil erosion.The five parameters(rainfall-runoff erosivity(R)factor,soil erodibility(K)factor,slope length and steepness(LS)factor,cover-management(C)factor,and support practice(P)factor)of the RUSLE were applied to present a more accurate distribution characteristic of soil erosion in the Irga watershed.The result shows that the R factor is positively correlated with rainfall and follows the same distribution pattern as the rainfall.The K factor values in the northern part of the study area are relatively low,while they are relatively high in the southern part.The mean value of the LS factor is 2.74,which is low due to the flat terrain of the Irga watershed.There is a negative linear correlation between Normalized Difference Vegetation Index(NDVI)and the C factor,and the high values of the C factor are observed in places with low NDVI.The mean value of the P factor is 0.210,with a range from 0.000 to 1.000.After calculating all parameters,we obtained the average soil erosion rate of 1.43 t/(hm^(2)•a),with the highest rate reaching as high as 32.71 t/(hm^(2)•a).Therefore,the study area faces a low risk of soil erosion.However,preventative measures are essential to avoid future damage to productive and constructive activities caused by soil erosion.This study also identifies the spatial distribution of soil erosion rate,which will help policy-makers to implement targeted soil erosion control measures.
基金supported by the National Natural Science Foundation of China(Grant Nos.42090054,41931295)the Natural Science Foundation of Hubei Province of China(2022CFA002)。
文摘The frequent occurrence of extreme weather events has rendered numerous landslides to a global natural disaster issue.It is crucial to rapidly and accurately determine the boundaries of landslides for geohazards evaluation and emergency response.Therefore,the Skip Connection DeepLab neural network(SCDnn),a deep learning model based on 770 optical remote sensing images of landslide,is proposed to improve the accuracy of landslide boundary detection.The SCDnn model is optimized for the over-segmentation issue which occurs in conventional deep learning models when there is a significant degree of similarity between topographical geomorphic features.SCDnn exhibits notable improvements in landslide feature extraction and semantic segmentation by combining an enhanced Atrous Spatial Pyramid Convolutional Block(ASPC)with a coding structure that reduces model complexity.The experimental results demonstrate that SCDnn can identify landslide boundaries in 119 images with MIoU values between 0.8and 0.9;while 52 images with MIoU values exceeding 0.9,which exceeds the identification accuracy of existing techniques.This work can offer a novel technique for the automatic extensive identification of landslide boundaries in remote sensing images in addition to establishing the groundwork for future inve stigations and applications in related domains.
基金jointly supported by the projects of the China Geological Survey(DD20230092,DD20201119)。
文摘Catastrophic geological disasters frequently occur on slopes with obliquely inclined bedding structures(also referred to as obliquely inclined bedding slopes),where the apparent dip sliding is not readily visible.This phenomenon has become a focal point in landslide research.Yet,there is a lack of studies on the failure modes and mechanisms of hidden,steep obliquely inclined bedding slopes.This study investigated the Shanyang landslide in Shaanxi Province,China.Using field investigations,laboratory tests of geotechnical parameters,and the 3DEC software,this study developed a numerical model of the landslide to analyze the failure process of such slopes.The findings indicate that the Shanyang landslide primarily crept along a weak interlayer under the action of gravity.The landslide,initially following a dip angle with the support of a stable inclined rock mass,shifted direction under the influence of argillization in the weak interlayer,moving towards the apparent dip angle.The slide resistance effect of the karstic dissolution zone was increasingly significant during this process,with lateral friction being the primary resistance force.A reduction in the lateral friction due to karstic dissolution made the apparent dip sliding characteristics of the Shanyang landslide more pronounced.Notably,deformations such as bending and uplift at the slope’s foot suggest that the main slide resistance shifts from lateral friction within the karstic dissolution zone to the slope foot’s resistance force,leading to the eventual buckling failure of the landslide.This study unveils a novel failure mode of apparent dip creep-buckling in the Shanyang landslide,highlighting the critical role of lateral friction from the karstic dissolution zone in its failure mechanism.These insights offer a valuable reference for mitigating risks and preventing disasters related to obliquely inclined bedding landslides.
基金CAMG was funded with a Lincoln University Ph D scholarship(Lincoln University Centennial Trust,New Zealand)with research funding from the New Zealand Hereford Association(NZHA)the Hellaby Grasslands Trust。
文摘Background:The grazing behaviour of herbivores and their grazing personalities might in part be determined genetically,but there are few studies in beef cattle illustrating this.In this study,we investigated for first time the genetic variation within a candidate‘grazing gene',the glutamate metabotropic receptor 5 gene(GRM5),and tested associations between variation in that gene and variation in grazing personality behaviours(GP-behaviours)displayed by free-ranging cows during winter grazing in the steep and rugged rangelands of New Zealand.Mature beef cows(n=303,from 3 to 10 years of age)were tracked with global positioning system(GPS)and,with 5-minutes(min)relocation frequency,various GP-behaviours were calculated.These included horizontal and vertical distances travelled,mean elevation,elevation range,elevation gain,slope,home range and movement tortuosity,variously calculated using daily relocation trajectories with repeated measurements(i.e.,7 to 24 days(d))and satellite-derived digital elevation models(DEM).The different GP-behaviours were fitted into mixed models to ascertain their associations with variant sequences and genotypes of GRM5.Results:We discovered three GRM5 variants(A,B and C)and identified the six possible genotypes in the cattle studied.The mixed models revealed that A was significantly associated with elevation range,home range and movement tortuosity.Similarly,GRM5 genotypes were associated(P<0.05)to home range and movement tortuosity,while trends suggesting association(P<0.1)were also revealed for elevation range and horizontal distance travelled.Most GP-behaviour models were improved by correcting for cow age-class as a fixed factor.The analysis of GP-behaviours averaged per cow age-class suggests that grazing personality is fully established as beef cows reached 4 years of age.Home range and movement tortuosity were not only associated with GRM5 variation,but also negatively correlated with each other(r=-0.27,P<0.001).Conclusions:There seems to be a genetically determined trade-off between home range and movement tortuosity that may be useful in beef cattle breeding programmes aiming to improve the grazing distribution and utilisation of steep and rugged rangelands.
基金supported by the National Natural Science Foundation of China(41907061)the Natural Science Foundation of Hubei province,China(2021CFB550)the joint fund for regional innovation and development of NSFC(U21A2039)。
文摘Grass recovery is often implemented in the loess area of China to control erosion.However,the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear.Taking the typical forage species(Coreopsis)in semiarid areas as subject,this study quantified the effects of canopies and roots on controlling slope runoff and erosion.A series of field experiments were conducted in a loess hilly region of China.Field plots(5 m length,2 m width,25°slope gradient)constructed with three ground covers(bare soil;Coreopsis with intact grass;only roots of Coreopsis),were applied with simultaneous simulated rainfall(60mm h^(-1))and upslope inflow(10,30,50,70,90L min^(-1)).The results showed that compared with bare soil,intact grass significantly reduced runoff and soil loss rates by 16.6% and 62.4% on average,and decreased soil erodibility parameter by 66.3%.As inflow rate increased,the reductions in runoff and soil loss rates increased from 2.93 to 14.00 L min^(-1)and 35.11 to 121.96 g m^(-2)min^(-1),respectively.Canopies relatively contributed 66.7% to lowering flow velocity,turbulence,weakening erosive force and increasing hydraulic resistance.Roots played a predominant role in reducing soil loss and enhancing soil antierodibility,with relative contributions of 78.8% and 73.8%.Furthermore,the maximum erosion depth reduced by Coreopsis was at the upper slope section which was previously eroded the most.These results demonstrated the efficiency of Coreopsis cover in controlling runoff and erosion on steep loess slopes,especially under large inflow rates and at upper slope sections.We suggest protecting Coreopsis with intact grass at upper slope sections,while the aboveground grass biomass can be used for grazing or harvesting at middle and lower slope sections,with roots reserved.
基金supported by NSFC(12075102 and 11971212)the Fundamental Research Funds for the Central Universities(lzujbky-2020-pd01)。
文摘We study the ground states of attractive binary Bose-Einstein condensates with N particles,which are trapped in the steep potential wellsλV(x)inℝ2.We show that there exists a positive number N*such that if N>N*,the system admits no ground state for anyλ>0.Moreover,there exist two positive numbers,M*andλ*(N),such that if N<M*,then for anyλ>λ*(N),the system admits at least one ground state.Asλ→∞,for any fixed N<M*,we give a detailed description for the limit behavior of both positive and semi-trivial ground states.
文摘Numerical simulation tools based on potential-flow theory and/or Morison’s equation are widely used for predicting the hydrodynamic responses of floating offshore wind platforms.In general,these simplified approaches are used for the analysis under operational conditions,albeit with a carefully selected approach to account for viscous effects.Nevertheless,due to the limit hydrodynamic modelling to linear and weakly nonlinear models,these approaches severely underpredict the low-frequency nonlinear wave loads and dynamic responses of a semisubmersible.They may not capture important nonlinearities in severe sea states.For the prediction of wave-induced motions and loads on a semisubmersible,this work systematically compares a fully nonlinear viscous-flow solver and a hybrid model combining the potential-flow theory with Morison-drag loads in steep waves.Results show that when nonlinear phenomena are not dominant,the results obtained by the hybrid model and the high-fidelity method show reasonable agreement,while larger discrepancies occur for highly nonlinear regular waves.Specifically,regular waves with various steepness over different frequencies are focused in the present study,which supplements the understanding in applicability of these two groups of method.
基金the National Natural Science Foundation of China (11971393)。
文摘In this paper,we consider the nonlinear Kirchhoff type equation with a steep potential well−(a+b∫_(R)^(3)|∇u|^(2 )dx)Δu+λV(x)u=f(u)in R^(3),where a,b>0 are constants,λ is a positive parameter,V∈C(R3,R)is a steep potential well and the nonlinearity f∈C(R,R)satisfies certain assumptions.By applying a signchanging Nehari manifold combined with the method of constructing a sign-changing(PS)C sequence,we obtain the existence of ground state sign-changing solutions with precisely two nodal domains when λ is large enough,and find that its energy is strictly larger than twice that of the ground state solutions.In addition,we also prove the concentration of ground state sign-changing solutions.
基金financially supported by the National Key Research and Development Program of China (2016YFA0601601)the National Science and Technology Support Program (2013BAB06B03)+2 种基金the National Natural Science Foundation of China (41472155)Candidates of the Young and MiddleAged Academic Leaders of Yunnan Province (2014HB005)Program for Excellent Young Talents of Yunnan University
文摘Buyuan River, the largest tributary within the Chinese Lancang-Mekong River region downstream of the Jinghong Dam, plays a crucial role in river function and ecosystem service of the Lancang-Mekong River. The geomorphic evolution of a basin exerts a key control on riverine sediment input and transport. In this study, the geomorphic characteristics of Buyuan Basin are analyzed using morphological parameters, hydrodynamic parameters and the stream power river incision model. The results show that: 1) The slight north-south difference of channel density is most likely due to lithology and independent of tectonic activity and climate. 2) The weak tectonic activity and the low hypsometric integral(HI) value suggest that the macroscopic landform condition limits erosion and sediment production. 3) The logarithmic longitudinal profile of the main channel defends that the upstream sediments generated by erosion are easily deposited in the downstream channel, rather than being transported directly into the Lancang-Mekong River. 4) Approximately 74% of the reaches have annual average stream power less than 500 W·m^(-1). The narrow variation ranges of stream power in 50% of the river channel indicate relatively stable hydrodynamic environment. 5) Stream erosion and tectonic activity make the longitudinal profiles of the main channel and most tributary channels unstable. The wide range(between 22.01 and 45.58 with θ=0.43) of steepness index(k_(sn)) of longitudinal profiles implies differential uplift in the basin.
基金financially supported by the State Key Research and Development Program of China(Grant No.2016YFC1401405)the National Natural Science Foundation of China(Grant Nos.51779038 and 51279028)
文摘Based on phase focusing theory, focusing waves with different spectral types and breaking severities were generated in a wave flume. The time series of surface elevation fluctuation along the flume were obtained by utilizing 22 wave probes mounted along the mid-stream of the flume. Based on the wave spectrum obtained using fast Fourier transform(FFT), the instability characteristics of the energy spectrum were reported in this paper. By analyzing the variation of total spectral energy, the total spectral energy after wave breaking was found to clearly decrease, and the loss value and ratio gradually increased and tended to stabilize with the enhancement of breaking severity for different spectral types. When wave breaking occurred, the energy loss was primarily in a high-frequency range of f/fp>1.0, and energy gain was primarily in a low-frequency range of f/fp<1.0. As the breaking severity increased, the energy gain-loss ratio decreased gradually, which demonstrates that the energy was mostly dissipated. For plunging waves, the energy gain-loss ratio reached 24% for the constant wave steepness(CWS) spectrum, and was slightly larger at approximately 30% for the constant wave amplitude(CWA) spectrum, and was the largest at approximately 42% for the Pierson-Moskowitz(PM) spectrum.
基金financially supported by the National Key Research and Development Program of China(No.2016YFA0601601)the National Science and Technology Support Program(No2013BAB06B03)the China Postdoctoral Science Foundation(No.2019M653506)
文摘Understanding the evolution of the fluvial geomorphology in an orogenic belt provides valuable insight into the relationship between upper crustal deformation and surface processes.The upper Lancang-Mekong River is in an area experiencing both uplift and erosion.The related processes provide a steady sediment supply to the lower reaches of the river and play an important role in the regional environmental changes.The Xiaohei(Weiyuan)River Basin is an important sub-basin in this area,which is characterized by large-scale topographic fluctuations,active tectonics and erosion,and anthropogenic activities.These different factors introduce numerous complexities to the local surface processes.In this study,we investigate and quantify the controls of geomorphic evolution of the Xiaohei River Basin.We located and mapped the main knick-zones within the channels and examined the main genetic factors,such as faults and stratigraphic differences.The results show that the areas with the lowest uplift rates are characterized by a low steepness index and are located in the southeastern part of the basin.The stream power of the mainstream increases downstream,with an average value of^122 W/m.The erosional activity of the various stream channels is intense.Overall,the basin tends to expansion,with only local instances of inward contraction.Our analysis confirms that a number of the geomorphic evolutionary characteristics of the Xiaohei River Basin are transient.In addition,the future potential for the increasing the number of dams and the hydropower development in the basin may weaken the expansion trend of the basin over a long period of time.
文摘In this paper,the influence of heave and pitch motions on green water impact on the deck is numerically investigated.The vessel motions are determined using a potential theory based method and provided as input to finite volume based CFD computations of green water phenomenon.A dynamic mesh approach is adopted to determine instantaneous body positioning in the fluid domain.Detailed validation studies with published experimental results for 2D and 3D fixed vessel cases are initially performed to validate the present numerical approach before studying the moving vessel problem.The results show that inclusion of heave and pitch motion changes the disturbed wave field near the bow which influences the free surface as well as the impact loading due to green water.The effect of wave steepness on green water impact is also investigated and it is seen that the present numerical method is capable of capturing green water load.It is observed that the effects of vessel motions on green water load are not negligible and one should consider this effect too.The incorporation of vessel motions in the vertical plane affects the green water loading on the deck.
文摘Sediment sampling and longitudinal river-bottom surveys were conducted along the thalweg on the Tanana River near the city of Nenana, Alaska, USA, to provide basic information for the engineering design requirements of hydrokinetic devices to be deployed in the area. The study reach was located at approximately 64°33'50'N and 149°04'W. The Tanana is a large glacier-fed river, with open-water flow conditions from May to October. The river presents a single channel in the study area. Granulometric analyses of sediment moving near the riverbed reveals the coexistence of three distinctive types of sediment along the study reach: 1) nearly uniform fine sand;2) bimodal distributions containing fine sand and medium gravel;and 3) medium gravel. Preliminary relationships between sediment loads and discharge were developed. Dunes with small superimposed dunes were found along the reach. The basic geometric parameters (i.e., wavelength and height) of dunes were measured, and steepness was calculated. In general, dune wavelength increased with increasing discharge. Dune wavelengths ranged from 41 to 67 m, while small-dune wavelengths ranged from 13 to 16 m. Steepness increased slightly with increasing discharge.
基金This project was supported by the Fok Ying Tung Education Foundation(Grant No.81068)and the China-Australia Institutional Links Project.
文摘Some new results of the modeling of mean free surface of waves or wave set-up are presented. The stream function wave theory is applied to incident short waves. The limiting wave steepness is adopted as the wave breaker index in the calculation of wave breaking dissipation. The model is based on Roelvink (1993), but the numerical techniques used in the solution are based on the Weighted-Average Flux (WAF) method (Watson et al., 1992), with Time-Operator-Splitting (TOS) used for the treatment of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modeling wave set-up. The short wave (or incident primary wave) energy equation issolved by use of a traditional Lax-Wendroff technique. The present model is found to be satisfactory compared with the measurements conducted by Stive (1983).
文摘Through numerical modeling, a kind of simplified calculating method for standing wave pressure on vertical face breakwater have been put forward. Not only the formulas proposed in this paper are simple in form and very easy in use, but also they possess continuity on the full range of standing wave. And more, the precision requiremennts of calculation can be satisfied to a certain extent in engineering practice.
基金This project is financially supported by the Natural Science Foundation of China
文摘Based on the analysis and comparison of wave breaker indices defined by geometric, kinetic as well as dynamic stabilities and verified by observation, the value a, which is equal to H / Lthkd by Miche’s result and may be modified by Goda’s results, is' suggested as the wave breaking criteria. The applicable values of a for pure waves or wave-current co-existing field are given in this paper. They are smaller than Miche’s result (0.142), and they have been verified by model tests.
基金financially supported by the National Key Research and Development Program of China(2018YFC1505002)National Natural Science Foundation of China(41672359,42107218,41807299)+2 种基金China Three Gorges Corporation(YMJ(XLD)(19)110)China Geology Survey Project(DD20190717)Natural Science Foundation of Hebei Province(D2019205090)。
文摘Landslides are common hazards in orogenic belt areas.However,it is difficult to quantitatively express the driving effects of tectonic uplift and stream erosion on the occurrence of landslides on large spatial scales by conducting field investigations.In this study,we analyzed a relatively large region that extends over the Yangbi River basin on the upper Lancang-Mekong in China.A series of quantitative indices,including kernel density of the landslide(KDL),hypsometric integral(HI),steepness index(ksn),stream power(?),and stream power gradient(ω)were used to explore the promoting effects of tectonic uplift and stream action intensity on landslides by mapping geomorphic dynamic parameters combined with actual landslide data.The analysis showed that the HI value in the highest landslide risk area was approximately 0.47,and that the KDL in the region can be expressed as a function of steepness or stream power gradient of the channel network,namely,KDL=0.0127 Ln ksn-0.0167(R2=0.72,P<0.001)and KDL=0.0219 Lnω-0.0558(R2=0.21,P<0.02).Therefore,the lower reach of the Yangbi River basin,with higher steepness and stream power gradient,usually has a high uplifting rate and stream incision that drives landslides and causes the entire river network system to be in a stage of longterm active erosion.Furthermore,the results suggest that sediments were being rapidly discharged from the steep tributary channels to the mainstream.This practical situation highlights that the downstream area of the river basin is a high-risk area for landslide hazards,especially in association with heavy rainfall and earthquakes.
