期刊文献+
共找到41,462篇文章
< 1 2 250 >
每页显示 20 50 100
Scale-dependent behavior of microstructure characteristics of laser powder bed fused TiB_(2)/AlSi10Mg composite
1
作者 Zhe Feng Geng Wang +13 位作者 Yongxia Wang Mingji Dang Wei Fan Hua Tan Zhiwei Hao Siyu Zhang Yuguang Chen Yijie Peng Tianchi Zhang Shuoqing Shi Xufei Lu Fengying Zhang Xin Lin Weidong Huang 《Journal of Materials Science & Technology》 2025年第9期158-172,共15页
The pre-alloyed TiB_(2)/AlSi10Mg composite,a new high-strength aluminum alloy developed for laser pow-der bed fusion(LPBF)technology,offers promising applications in lightweight and multi-scaled structures.However,the... The pre-alloyed TiB_(2)/AlSi10Mg composite,a new high-strength aluminum alloy developed for laser pow-der bed fusion(LPBF)technology,offers promising applications in lightweight and multi-scaled structures.However,thermal behavior during LPBF is markedly scale-dependent,leading to microstructural varia-tions that significantly affect the load-bearing capacity of multi-scaled structures.Therefore,this study systematically investigates the scale-dependent behavior of microstructure characteristics of this com-posite.Utilizing a hatching scanning strategy,it was found that the marginal zones of samples are pre-dominantly composed of coarse Al cell and Al grain structures,contrasting with the fine microstructures in the central zones.With increasing structure scale,cell and grain structures in both the marginal and central zones become more refined,with cell sizes reducing by 49%-72%(∼3.02μm→0.86-1.55μm).Particularly,the minimum-scaled structures also feature broken eutectic Si particles and nanopores.The essence is primarily due to the low heat dissipation with higher peak temperature and longer duration time at high temperatures in both the small-scale structures and marginal zones.Additionally,smaller structures correlate with reduced microhardness and tensile strength,accompanied by the“softening”of the marginal zones.The strength of the minimum-scaled structure is only half that of the standard sample.Our findings suggest a scale threshold of 2.0 mm for researching scale effect.Encouragingly,in-corporating additional contour scanning significantly counteracts the adverse influence of the scale effect.Owing to the combined influence of extended inter-layer time and laser remelting,all samples demon-strate a distinctly refined microstructure.This results in consistently high levels of microhardness and strength,with the“hardening”of the marginal zones.Eventually,the relationship between mechanical properties and microstructure sizes is established.This study provides valuable insights into the innova-tive designs and engineering applications of multi-scaled structures in LPBF using various materials. 展开更多
关键词 scale-dependent behavior Microstructure characteristics Scanning strategy Laser powder bed fusion
原文传递
Predicting suitability of different scale-dependent dispersivities for reactive solute transport through stratified porous media 被引量:2
2
作者 Deepak Swami Abhimanyu Sharma +1 位作者 Pramod Kumar Sharma Dericks P.Shukla 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2016年第6期921-927,共7页
In this paper,the behavior of breakthrough curves(BTCs) for reactive solute transport through stratified porous media is investigated.A physical laboratory model for layered porous media was constructed,in which thin ... In this paper,the behavior of breakthrough curves(BTCs) for reactive solute transport through stratified porous media is investigated.A physical laboratory model for layered porous media was constructed,in which thin layer of gravel was sandwiched in between two thick layers of natural soil.Gravel layer and natural soil layers were hydraulically connected as single porous continuum.A constant source of tracer was connected through gravel layer and elucidated at different sampling points in the direction of flow.Flexible multiprocess non-equilibrium(MPNE) transport equation with scale-dependent dispersivity function was used to simulate experimental BTCs of reactive solute transport through layered porous media.The values of equilibrium sorption coefficient and other input parameters were obtained experimentally.The simulation of BTC was performed using MPNE model with scale-dependent dispersivity.The simulation of different scale-dependent dispersivities was then compared and it was found that for field scale of estimation of dispersivity,asymptotic and exponential dispersivity functions performed better.In continuation to the comparison of simulated BTCs obtained using different models,spatial moment analysis of each aforesaid scale-dependent dispersivity model was also done.Spatial moment analysis provides the information related to mean solute mass,rate of mass travel,and mean plume dispersion.Linear and constant dispersivities showed higher variance as compared to asymptotic and exponential dispersion functions.This supports the field applicability of asymptotic and exponential dispersivity functions.The BTCs were also found to elucidate a nonzero concentration with time,which was clearly affected by physical non-equilibrium.In natural condition,such information is required in effective aquifer remediation process. 展开更多
关键词 Multiprocess non-equilibrium(MPNE) scale-dependent dispersivity Stratified porous media Spatial moment
在线阅读 下载PDF
Hominin and human dispersals in palaeolithic East Asia
3
作者 Robin DENNELL 《人类学学报》 北大核心 2025年第1期132-164,共33页
Dispersals,colonisation,immigration and population assimilation or replacement are fundamental themes in the Palaeolithic record of East Asia.Some of these issues can be studied within a biogeographic framework that e... Dispersals,colonisation,immigration and population assimilation or replacement are fundamental themes in the Palaeolithic record of East Asia.Some of these issues can be studied within a biogeographic framework that explains why and how the distribution of hominin species changed over time and space in response to climatic and environmental change.Because hominins(and especially humans)can change their behaviour through technical,social and cognitive developments,biogeographic models also have to incorporate this factor when investigating dispersals.This is particularly important with the dispersals in East Asia by Homo sapiens into rainforests,across open sea to off-shore islands,to the Arctic and the highest parts of the Tibetan Plateau.This paper suggests how hominin and human dispersals in East Asia might be investigated by using a biogeographic framework that can incorporate changes in hominin adaptability and behaviour. 展开更多
关键词 HOMININ HUMAN dispersal East Asia biogeographic
原文传递
Flatness detection method of splicing detector based on channel spectral dispersion
4
作者 ZHAO Hong-chao ZHANG Xiao-qian AN Qi-chang 《中国光学(中英文)》 北大核心 2025年第4期889-898,共10页
For segmented detectors,surface flatness is critical as it directly influences both energy resolution and image clarity.Additionally,the limited adjustment range of the segmented detectors necessitates precise benchma... For segmented detectors,surface flatness is critical as it directly influences both energy resolution and image clarity.Additionally,the limited adjustment range of the segmented detectors necessitates precise benchmark construction.This paper proposes an architecture for detecting detector flatness based on channel spectral dispersion.By measuring the dispersion fringes for coplanar adjustment,the final adjustment residual is improved to better than 300 nm.This result validates the feasibility of the proposed technology and provides significant technical support for the development of next-generation large-aperture sky survey equipment. 展开更多
关键词 large aperture telescope segmented detector surface wavefront detection channel spectral dispersion
在线阅读 下载PDF
Natal and breeding dispersal patterns in a patchy population of the western yellow wagtail
5
作者 Dmitry Shitikov Nikita Grachev +4 位作者 Viktoria Grudinskaya Alexander Grabovsky Stanislav Samsonov Alexey Korolev Tatiana Makarova 《Current Zoology》 2025年第4期535-543,共9页
Dispersal is an important life history trait with signifcant consequences for spatially structured populations,as the exchange of individuals between habitat patches is crucial for maintaining metapopulation connectiv... Dispersal is an important life history trait with signifcant consequences for spatially structured populations,as the exchange of individuals between habitat patches is crucial for maintaining metapopulation connectivity.In this study,we used a long-term data set(2005–2023)to describe dispersal patterns in a patchy population of the Western Yellow Wagtail Motacilla fava within a large(approximately 1,300 km2)study area in the boreal zone of European Russia.We quantifed dispersal distances for birds that dispersed outside their natal or breeding habitat patches and applied a multistate capture–recapture approach to estimate natal and breeding dispersal probabilities.Of 395 adult wagtails and 1,610 nestlings ringed,3%of birds ringed as adults and 3%of birds ringed as nestlings were resighted outside their natal or breeding patches.The probability of natal dispersal(0.29±0.05)was signifcantly higher than the probability of breeding dispersal(0.05±0.01).The median natal dispersal distances(2.8 km for males,3.9 km for females)were the same as the median breeding dispersal distances(2.7 km for males,3.9 km for females).We did not fnd a signifcant effect of the fedging date on either the natal dispersal distance or the natal dispersal probability.Similarly,we did not fnd a signifcant effect of the previous reproductive success on either the breeding dispersal distance or the breeding dispersal probability.Our results indicate that strong breeding site fdelity and short-distance natal dispersal are the dominant dispersal strategies in a patchy population of the western yellow wagtail. 展开更多
关键词 breeding dispersal dispersal probability natal dispersal patchy population western yellow wagtail
原文传递
Search for Dispersed Repeats in Oryza sativa Genome Using Iterative Procedure Method
6
作者 Valentina RUDENKO Eugene KOROTKOV 《Rice science》 2025年第4期472-474,共3页
In this study,we searched for dispersed repeats(DRs)in the rice(Oryza sativa)genome using the iterative procedure(IP)method.The results revealed that the O.sativa genome contained 79 DR families,comprising 992739 DNA ... In this study,we searched for dispersed repeats(DRs)in the rice(Oryza sativa)genome using the iterative procedure(IP)method.The results revealed that the O.sativa genome contained 79 DR families,comprising 992739 DNA repeats,of which 496762 and 495977 were identified on the forward and reverse DNA strands,respectively.The detected DRs were,on average,374 bp in length and occupied 66.4%of the O.sativa genome.Totally 61%of DRs,identified by the IP method,overlapped with previously annotated dispersed repeats(ADRs)detected using the Extensive De Novo TE Annotator(EDTA)pipeline. 展开更多
关键词 Oryza sativa genome dna repeatsof iterative procedure annotated dispersed repeats dispersed repeats drs de novo TE annotator dispersed repeats
在线阅读 下载PDF
Positive role of regulator in desulfurization of chalcopyrite in seawater based on chelation and dispersion
7
作者 SONG Ning-bo YIN Wan-zhong +1 位作者 GONG Xiu-feng YAO Jin 《Journal of Central South University》 2025年第5期1791-1801,共11页
The chemical composition of seawater affects the desulfurization of chalcopyrite in flotation.In this study,desulfurization experiments of chalcopyrite were conducted in both deionized(DI)water and seawater.The result... The chemical composition of seawater affects the desulfurization of chalcopyrite in flotation.In this study,desulfurization experiments of chalcopyrite were conducted in both deionized(DI)water and seawater.The results showed that,the copper grade of the concentrate obtained from seawater flotation decreased to 24.30%,compared to 24.60%in DI water.Concurrently,the recovery of chalcopyrite decreased from 51.39%to 38.67%,while the selectivity index(SI)also had a reduction from 2.006 to 1.798.The incorporation of ethylene diamine tetraacetic acid(EDTA),sodium silicate(SS),and sodium hexametaphosphate(SHMP)yielded an enhancement in the SI value,elevating it from 1.798 to 1.897,2.250 and 2.153,separately.It is particularly noteworthy that an excess of EDTA resulted in a SI value of merely 1.831.The mechanism of action was elucidated through analysis of surface charge measurements,X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FT-IR),extended Derjaguin-Landau Verwey-Overbeek(E-DLVO)theory,and density functional theory(DFT)calculations. 展开更多
关键词 CHALCOPYRITE DESULFURIZATION CHELATION dispersION E-DLVO theory
在线阅读 下载PDF
Inverse design of broadband and dispersion-flattened highly GeO2-doped optical fibers based on neural networks and particle swarm algorithm
8
作者 LI Runrui WANG Chuncan 《Optoelectronics Letters》 2025年第6期328-335,共8页
Reverse design of highly GeO2-doped silica optical fibers with broadband and flat dispersion profiles is proposed using a neural network(NN) combined with a particle swarm optimization(PSO) algorithm.Firstly,the NN mo... Reverse design of highly GeO2-doped silica optical fibers with broadband and flat dispersion profiles is proposed using a neural network(NN) combined with a particle swarm optimization(PSO) algorithm.Firstly,the NN model designed to predict optical fiber dispersion is trained with an appropriate choice of hyperparameters,achieving a root mean square error(RMSE) of 9.47×10-7on the test dataset,with a determination coefficient(R2) of 0.999.Secondly,the NN is combined with the PSO algorithm for the inverse design of dispersion-flattened optical fibers.To expand the search space and avoid particles becoming trapped in local optimal solutions,the PSO algorithm incorporates adaptive inertia weight updating and a simulated annealing algorithm.Finally,by using a suitable fitness function,the designed fibers exhibit flat group velocity dispersion(GVD) profiles at 1 400—2 400 nm,where the GVD fluctuations and minimum absolute GVD values are below 18 ps·nm-1·km-1and 7 ps·nm-1·km-1,respectively. 展开更多
关键词 neural network predict optical fiber dispersion inverse design neural network nn dispersion flattening inverse desig BROADBAND particle swarm optimization pso
原文传递
Strain-manipulated dispersion characteristics of magnonic crystals with Dzyaloshinskii–Moriya interaction and applications on spin-wave devices
9
作者 Chuhan Zhou Xiaotian Jiao +3 位作者 Jiaxi Xu Zhaonian Jin Lin Chen Zhikuo Tao 《Chinese Physics B》 2025年第2期431-436,共6页
Dispersion characteristics of magnonic crystals have attracted considerable attention because of the potential applications for spin-wave devices.In this work,we investigated the strain-manipulated dispersion characte... Dispersion characteristics of magnonic crystals have attracted considerable attention because of the potential applications for spin-wave devices.In this work,we investigated the strain-manipulated dispersion characteristics of magnonic crystals with Dzyaloshinskii–Moriya interaction(DMI)and discussed the potential applications in spin-wave devices.Here,the ground states and stabilities of the magnonic crystals were investigated.Then,the strain-manipulated dispersion characteristics of the magnonic crystals based on domains and skyrmions were studied.The simulation results indicated that,the applied strain could manipulate the band widths and the positions of the allowed frequency bands.Finally,the realization of magnonic crystal heterojunctions and potential applications in spin-wave devices,such as filters,diodes,and transistors based on strain-manipulated magnonic crystals were proposed.Our research provides a theoretical foundation for designing tunable spin-wave devices based on strain-manipulated magnonic crystals with DMI. 展开更多
关键词 magnonic crystal spin wave dispersion relation SKYRMION DOMAIN
原文传递
Genistein solid dispersion:preparation,physical-chemical characters and anti-oxidant properties
10
作者 Xiaofei Liu Yang Liu +1 位作者 Hongyue Wang Xiangrong Zhang 《Journal of Polyphenols》 2025年第3期112-126,共15页
The aim of this study was to enhance the applicability of genistein(GEN)and investigate genistein solid dispersion(GEN-SD).The optimal process parameters were determined as follows:anhydrous ethanol volume ratio of 4:... The aim of this study was to enhance the applicability of genistein(GEN)and investigate genistein solid dispersion(GEN-SD).The optimal process parameters were determined as follows:anhydrous ethanol volume ratio of 4:1,ultrasonication time of 30 min,rotary evaporation temperature of 50°C,and a drug-to-carrier mass ratio of 1:7.The results of the dissolution and solubility experiments showed that the dissolution rate and solubility of the optimized solid dispersion were significantly improved compared to pure GEN.Comprehensive characterization of the GEN-SD using X-ray diffraction,differential scanning calorimetry,scanning electron microscopy,and Fourier transform infrared spectroscopy clarified variations in crystalline form,thermal properties,and microscopic morphology.Antioxidant experiments showed that GEN-SD exhibited antioxidant activity and could effectively scavenge various free radicals.Stability studies demonstrated that GEN-SD was stable at a high temperature of 60℃and a light intensity of 4500 lx. 展开更多
关键词 GENISTEIN Solid dispersion Polyvinylpyrrolidone K30 ANTIOXIDANT
暂未订购
Spatial,social,and environmental factors infuencing nataldispersal in the colonial griffon vulture
11
作者 Felix Martinez Martina Carrete Guillermo Blanco 《Current Zoology》 2025年第2期170-183,共14页
Natal dispersal is a critical trait for individual ftness and the viability,structure,and genetic identity of populations.However,there is a pronounced information gap for large and long-lived species due to the diffc... Natal dispersal is a critical trait for individual ftness and the viability,structure,and genetic identity of populations.However,there is a pronounced information gap for large and long-lived species due to the diffculty of monitoring individuals at appropriate spatio-temporal scales.Here we study how individual traits and social and environmental characteristics infuence natal dispersal decisions of griffon vultures(Gypsfulvus)using long-term(30 years)monitoring of a large number of individuals marked as nestlings in Spain.Our results show a strong philopatryin both sexes,with some individuals recruiting as breeders on the same cliffs,and even the same nests,where they were born.This philopatrictendency was modulated by the effect of conspecifc density on individual parameters and emphasized the importance of conspecifc attraction and changes in food availability that may have infuenced the increment in colony size and the colonization of new areas.Although furtherresearch is needed considering smaller colonies and more isolated population nuclei,our results highlight the importance of long-term studieson long-lived species to understand the factors that determine their population dynamics and their relationship with anthropogenic activities,whose effects should be predicted and managed using conservation criteria. 展开更多
关键词 Gyps fulvus mad-cow crisis natal dispersal PHILOPATRY recruitment VULTURES
原文传递
Seed dispersal by deception:A game between mimetic seeds and their bird dispersers
12
作者 Min-Fei Jin Xiang-Hai Cai Gao Chen 《Plant Diversity》 2025年第2期169-177,共9页
Mimetic seeds attract birds to disperse seeds mainly by mimicking fleshy fruits or arillate seeds,however,they provide little nutritive reward for bird dispersers.The key characteristics of mimetic seeds are conspicuo... Mimetic seeds attract birds to disperse seeds mainly by mimicking fleshy fruits or arillate seeds,however,they provide little nutritive reward for bird dispersers.The key characteristics of mimetic seeds are conspicuous seed color,hard seed coat,certain toxic secondary metabolites,and perhaps smooth waxy layer.In this review,we discuss the global distribution of mimetic seeds,the interaction of mimetic seeds with bird dispersers,and secondary metabolites that underlie key characteristics of mimetic seeds.Mimetic-seed species mainly occur in the tropics,with large numbers distributed along coastal areas.The interaction between mimetic-seed species and bird dispersers can be antagonistic,mutualistic,or both.These interactions are generally established by conspicuous visual cues and hard tactile cues from mimetic seeds.The formation and variation of key characteristics of mimetic seeds may contribute to the metabolism of several kind of secondary compounds.Here,we also discuss mimetic-seed dispersal in the context of an evolutionary game,and propose several aspects of mimetic-seed dispersal that remain unstudied.While this review is based on preliminary findings and does not account for other potential influencing factors such as climate,it is expected to contribute to an improved understanding of mimetic-seed dispersal. 展开更多
关键词 Mimetic seeds Frugivorous birds Seed dispersal DECEPTION Secondary metabolites Evolutionary game
在线阅读 下载PDF
Numerical analysis of dispersion,attenuation,and seismic effects in a porous rock saturated with three-phase immiscible fluids
13
作者 Xin Luo Xue-Hua Chen +2 位作者 Tong Li Gui-Rong Luo Peng Wang 《Petroleum Science》 2025年第7期2828-2850,共23页
Multiphase flow in porous rock is of great importance in the application of many industrial processes,including reservoir delineation,enhanced oil recovery,and CO_(2) sequestration.However,previous research typically ... Multiphase flow in porous rock is of great importance in the application of many industrial processes,including reservoir delineation,enhanced oil recovery,and CO_(2) sequestration.However,previous research typically investigated the dispersive behaviors when rock saturated with single or two-phase fluids and conducted limited studies on three-phase immiscible fluids.This study investigated the seismic dispersion,attenuation,and reflection features of seismic waves in three-phase immiscible fluidsaturated porous rocks.First,we proposed the calculation formulas of effective fluid modulus and effective fluid viscosity of multiphase immiscible fluids by taking into account the capillary pressure,reservoir wettability,and relative permeability simultaneously.Then,we analysed the frequencydependent behaviors of three-phase immiscible fluid-saturated porous rock under different fluid proportion cases using the Chapman multi-scale model.Next,the seismic responses are analysed using a four-layer model.The results indicate that the relative permeability,capillary pressure parameter,and fluid proportions are all significantly affect dispersion and attenuation.Comparative analyses demonstrate that dispersion and attenuation can be observed within the frequency range of seismic exploration for a lower capillary parameter a3 and higher oil content.Seismic responses reveal that the reflection features,such as travel time,seismic amplitude,and waveform of the bottom reflections of saturated rock and their underlying reflections are significantly dependent on fluid proportions and capillary parameters.For validation,the numerical results are further verified using the log data and real seismic data.This numerical analysis helps to further understand the wave propagation characteristics for a porous rock saturated with multiphase immiscible fluids. 展开更多
关键词 Multiphase immiscible fluids dispersION ATTENUATION Relative permeability Capillary parameter Seismic responses
原文传递
Stability Analysis of an Epidemic Predator-Prey Model with Prey Dispersal and Holling Type-Ⅱ Functional Response
14
作者 Lingshu WANG Mei ZHANG Ya-nan ZHANG 《Journal of Mathematical Research with Applications》 2025年第2期179-194,共16页
This paper examines an epidemic predator-prey model with prey dispersal and Holling type-II functional response. In this model, it is assumed that the predator population suffers a transmissible disease. By analyzing ... This paper examines an epidemic predator-prey model with prey dispersal and Holling type-II functional response. In this model, it is assumed that the predator population suffers a transmissible disease. By analyzing the corresponding characteristic equations, the local stability of each of feasible equilibria and the existence of Hopf bifurcations at the coexistence equilibrium is addressed. Using Lyapunov functionals and LaSalle's invariance principle, we obtained the sufficient conditions for the global stability of the trivial equilibrium, the predator-extinction equilibrium, the disease-free equilibrium and the coexistence equilibrium, respectively. The paper also includes numerical simulations to illustrate the analytical results. 展开更多
关键词 predator-prey model dispersal Holling type-II functional response Hopf bifurcation stability
原文传递
Climatic niche divergence and long-distance dispersal contributed to the pantropical intercontinental disjunctions of a liana lineage(Uncaria,Rubiaceae)
15
作者 Xian-Han Huang Jing-Yi Peng +11 位作者 Nan Lin Jian Liu Jun-Tong Chen Qun Liu Xin-Jian Zhang Quan-Sheng Fu Peng-Rui Luo Zhi-Yu Wang Shiou Yih Lee Qiang Zhou Hang Sun Tao Deng 《Plant Diversity》 2025年第5期772-783,共12页
The formation of pantropical intercontinental disjunction(PID)in plants has generally been attributed to vicariance,boreotropical migration,and long-distance dispersal.However,this pattern has primarily been examined ... The formation of pantropical intercontinental disjunction(PID)in plants has generally been attributed to vicariance,boreotropical migration,and long-distance dispersal.However,this pattern has primarily been examined in herbs,shrubs,and trees,and less commonly studied in interlayer plant taxa.Here we examined evolutionary processes that resulted in the PID of a pantropical woody liana,Uncaria(Rubiaceae).We first constructed a comprehensive phylogeny by employing 73 plastid protein-coding sequences from 29 accessions of Uncaria(including 16 newly sequenced)from different continents.We then inferred divergence time,history and ecological niche evolution of this genus.Our results showed that Uncaria consisted of four well-supported clades that belonged to two geographically distinct lineages:the Asia-Oceania lineage and the Afro-Neotropical lineage.Biogeographic reconstruction showed this genus likely originated in Asia during the early Miocene(ca.19.03 Ma)and the Middle Miocene Climatic Optimum may have triggered the early diversification of Uncaria.Due to its recent origin and small seeds with long wings,wind or water-mediated long-distance dispersal may have contributed to the distribution of Uncaria in tropical Oceania(via stepping-stone dispersal)and tropical Africa and America(by transoceanic dispersal).Our findings also indicate that diversification of Uncaria was primarily driven by ecological niche divergence,particularly climatic factors.Our study emphasizes the dual role of climatic niche divergence and long-distance dispersal in shaping the PID of Uncaria,providing references for many other extant lineages with similar distributions. 展开更多
关键词 Niche evolution Long-distance dispersal Pantropical intercontinental disjunction Miocene Woody lianas Uncaria
在线阅读 下载PDF
Modification of dispersive soil by physical adsorption method using activated carbon
16
作者 Henghui Fan Guanzhou Ren +5 位作者 Dongyang Yan Peng Ju Tao Wu Yuan Gao Zhen Zhu Gaowen Zhao 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第2期1213-1226,共14页
This study addresses the challenges posed by dispersive soil in various engineering fields,including hydraulic and agricultural engineering,by exploring the effects of physical adsorption on soil modification.The prim... This study addresses the challenges posed by dispersive soil in various engineering fields,including hydraulic and agricultural engineering,by exploring the effects of physical adsorption on soil modification.The primary objective is to identify an environmentally friendly stabilizer that can alleviate cracking and erosion resulting from soil dispersivity.Activated carbon(AC),known for its porous nature,was examined for its potential to enhance soil strength and erosion resistance.The charge neutralization process was evaluated by monitoring pH and conductivity,in addition to a comprehensive analysis of microscopic and mineral properties.The results show that high sodium levels or low clay contents result in the dispersive nature of soil in water.However,the incorporation of AC can transform such soil into a non-dispersive state.Moreover,both soil strength and erosion resistance exhibited enhancements with increasing AC content and curing duration.The incorporation of AC resulted in a maximum 5.6-fold increase in unconfined compressive strength and a 1.8-fold increase in tensile strength for dispersive soil.Notably,a significant correlation was observed during the curing phase among soil dispersivity,mechanical properties,and pH values.Microscopic analyses revealed that the porous structure of AC facilitated a filling effect and enhanced adsorption capacity,which contributed to improved soil characteristics and reduced dispersivity.The release of hydrogen ions and the formation of aggregates promote water stability.Validation tests conducted on dispersive soil from northern Shaanxi demonstrated the efficacy of physical adsorption using AC as a viable method for modifying dispersive soil in the water conservancy hub. 展开更多
关键词 dispersive soil Physical adsorption Activated carbon(AC) Improved behavior MECHANISM
在线阅读 下载PDF
Effects of multi-scale wave-induced fluid flow on seismic dispersion,attenuation and frequency-dependent anisotropy in periodic-layered porous-cracked media
17
作者 Zhao-Yun Zong Yan-Wen Feng +1 位作者 Fu-Bin Chen Guang-Zhi Zhang 《Petroleum Science》 2025年第2期684-696,共13页
The wave-induced fluid flow(WIFF) occurring in the ubiquitous layered porous media(e.g.,shales)usually causes the appreciable seismic energy dissipation,which further leads to the frequency dependence of wave velocity... The wave-induced fluid flow(WIFF) occurring in the ubiquitous layered porous media(e.g.,shales)usually causes the appreciable seismic energy dissipation,which further leads to the frequency dependence of wave velocity(i.e.,dispersion) and elastic anisotropy parameters.The relevant knowledge is of great importance for geofluid discrimination and hydrocarbon exploration in the porous shale reservoirs.We derive the wave equations for a periodic layered transversely isotropy medium with a vertical axis of symmetry(VTI) concurrently with the annular cracks(PLPC medium) based on the periodic-layered model and anisotropic Biot's theory,which simultaneously incorporate the effects of microscopic squirt fluid flow,mesoscopic interlayer fluid flow and macroscopic global fluid flow.Notably,the microscopic squirt shorten fluid flow emerges between the annular-shaped cracks and stiff pores,which generates one attenuation peak.Specifically,we first establish the stress-strain relationship and pore fluid pressure in a PLPC medium,and then use them to derive the wave equations by means of the Newton's second law.The plane analysis is implemented on the wave equations to yield the analytic solutions for phase velocities and attenuation factors of four waves,namely,fast P-wave,slow P-wave,SV-wave and SH-wave,and the anisotropy parameters can be therefore computed.Simulation results show that P-wave velocity have three attenuation peaks throughout the full frequency band,which respectively correspond to the influences of interlayer flow,the squirt flow and the Biot flow.Through the results of seismic velocity dispersion and attenuation at different incident angles,we find that the WIFF mechanism also has a significant impact on the dispersion characteristics of elastic anisotropy parameters within the low-mid frequency band.Moreover,it is shown that several poroelastic parameters,such as layer thickness ratio,crack aspect ratio and crack density have notable influence on seismic dispersion and attenuation.We compare the proposed modeled velocities with that given by the existing theory to confirm its validity.Our formulas and result can provide a better understanding of wave propagation in PLPC medium by considering the unified impacts of micro-,meso-and macro-scale WIFF mechanisms,which potentially lays a theoretical basis of rock physics for seismic interpretation. 展开更多
关键词 Wave-induced fluid flow Multi-scale wave equations ANISOTROPY dispersion and attenuation
原文传递
Vertical exchange versus horizontal dispersal in structuring local planktonic and sedimentary bacterial communities in polluted lotic ecosystems
18
作者 Wei Zhang Wei Xiong +3 位作者 Min Wang Dongliang Zhao Xiaoyu Guo Aibin Zhan 《Journal of Environmental Sciences》 2025年第10期859-870,共12页
Elucidating the mechanisms underlying community assembly remains a central question in community ecology,especially in aquatic ecosystems disrupted by human activities.Understanding the causes and consequences of comm... Elucidating the mechanisms underlying community assembly remains a central question in community ecology,especially in aquatic ecosystems disrupted by human activities.Understanding the causes and consequences of community responses to changing environment is essential for revealing the ecological effects of anthropogenic disturbances and proposing practical strategies for ecological restoration.While stochastic dispersal and species sorting are known to influence local biological communities,most studies have focused on horizontal dispersal,often neglecting the vertical exchange of organisms between planktonic and sedimentary communities when studying stochastic dispersal.We used a highly disturbed urban river in Beijing as a model system to investigate the relative roles of stochastic dispersal versus species sorting driven by local pollution,as well as two components of stochastic dispersal,vertical exchange and horizontal dispersal,in structuring local bacterial communities.Our integrated analyses of planktonic and sedimentary bacterial communities revealed that,despite different spatial patterns along the river,both types of bacterial communities were primarily shaped by stochastic dispersal processes rather than species sorting influenced by the environmental gradient.Notably,in addition to the effect of horizontal dispersal along the river,the vertical exchange between planktonic and sedimentary bacterial communities significantly contributed to the formation of local communities.These findings suggest that both vertical exchange and horizontal dispersal should be considered when assessing the role of stochastic dispersal in shaping local community structure in microbial communities. 展开更多
关键词 Water pollution Vertical dispersal Species sorting Bacterial communities River management Urban ecosystem
原文传递
The effect of dispersal on a predator-prey model with Holling type-Ⅱ functional response
19
作者 WANG Ling-shu ZHANG Mei +1 位作者 ZHANG Ya-nan WANG Yan 《Applied Mathematics(A Journal of Chinese Universities)》 2025年第3期602-616,共15页
A predator-prey model with prey dispersal and Holling type-Ⅱ functional response is investigated.In this model,the time delay due to the gestation of the predator and stagestructure for the predator are considered.By... A predator-prey model with prey dispersal and Holling type-Ⅱ functional response is investigated.In this model,the time delay due to the gestation of the predator and stagestructure for the predator are considered.By analyzing the corresponding characteristic equations,the local stability of each of the nonnegative equilibria is discussed.The existence of Hopf bifurcations at the positive equilibrium is established.By using Lyapunov functionals and LaSalle’s invariance principle,sufficient conditions are obtained for the global stability of the positive equilibrium,the nonnegative boundary equilibrium and the trivial equilibrium of the model,respectively.Numerical simulations are carried out to illustrate the main results. 展开更多
关键词 predator-prey model dispersal Holling type-Ⅱfunctional response time delay STAGE-STRUCTURE STABILITY
在线阅读 下载PDF
Adaptive Dispersion Estimation for Linearized Electronic Dispersion Compensation in IM-DD Systems
20
作者 Huo Jiahao Tao Jianlong +3 位作者 Zhang Xiaoying Zhu Jin Qin Peng Wei Huangfu 《China Communications》 2025年第4期55-64,共10页
An adaptive dispersion estimation(ADE)is proposed to compensate dispersion and estimate the transfer function of the fiber channel with GerchbergSaxton(G-S)algorithm,using the stochastic gradient descent(SGD)method in... An adaptive dispersion estimation(ADE)is proposed to compensate dispersion and estimate the transfer function of the fiber channel with GerchbergSaxton(G-S)algorithm,using the stochastic gradient descent(SGD)method in the intensity-modulation and direct-detection(IM-DD)system,improving the tolerance of the algorithm to chromatic dispersion(CD).In order to address the divergence arising from the perturbation in the amplitude of the received signal caused by the filtering effect of the non-ideal channels,a channel-compensation equalizer(CCE)derived from the back-to-back(BTB)scenario is employed at the transmitter to make the amplitude of the received signal depicting the CD effect more accurately.The simulation results demonstrate the essentiality of CCE for the convergence and performance improvement of the G-S algorithm.Results show that it supports 112Gb/s four-level pulse amplitude modulation(PAM4)over 100 km standard single-mode fiber(SSMF)transmission under the 7%forward error correction(FEC)threshold of 3.8E-3.Besides,ADE improves the tolerance to wavelength drift from about 4 nm to 42 nm,and there is a better tolerance for fiber distance perturbation,indicating the G-S algorithm and its derived algorithms with the ADE scheme exhibit superior robustness to the perturbation in the system. 展开更多
关键词 chromatic dispersion digital signal process intensity modulation and direct detection
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部