The assembly of the volant bird body plan from the ancestral bulky dinosaurian condition is an enduring topic of evolutionary biology.The body plan of volant birds demonstrates a pronounced decrease in body size and p...The assembly of the volant bird body plan from the ancestral bulky dinosaurian condition is an enduring topic of evolutionary biology.The body plan of volant birds demonstrates a pronounced decrease in body size and proportionate elongation of the forelimbs.Given the scaling relationship between limb and body size,changes to the former were likely clouded by changes to the entire body size.展开更多
Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.He...Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.Here,we present new geochemical data which provides insight to the sedimentary environment of aeolian sands in the Dinggye region,southern Tibet.We sampled aeolian dune sands in a variety of settings,and determined grain size and concentration of major oxides and trace elements in the fine and coarse fractions.Results show that aeolian sediments are dominated by fine and medium sands,with a single-peaked frequency curve and a 3-stage probability cumulative curve.The fine and coarse fractions exhibit considerable heterogeneity in elemental concentrations and ratios and upper continental crust-normalized(UCC)distribution.The geochemical evidence indicates that wind dynamic sorting is responsible for the differentiation between fine and coarse fractions in different types of aeolian sand,rather than sediment provenance.Additionally,fine-fraction sediments are well dispersed and can be differentiated from the coarse fraction,suggesting that they contain more environmental information.Multidimensional scale(MDS)and principal component analysis(PCA)of commonly used tracer elements show that flood plain sediments are the sand source for mobile dunes and nebkhas,and lakeshore sediments are the sand source for climbing sand sheets.展开更多
A stochastic local limited one-dimensional rice-pile model is numerically investigated. The distributions for avalanche sizes have a clear power-law behavior and it displays a simple finite size scaling. We obtain the...A stochastic local limited one-dimensional rice-pile model is numerically investigated. The distributions for avalanche sizes have a clear power-law behavior and it displays a simple finite size scaling. We obtain the avalanche exponents Ts= 1.54±0.10,βs = 2.17±0.10 and TT = 1.80±0.10, βT =1.46 ± 0.10. This self-organized critical model belongs to the same universality class with the Oslo rice-pile model studied by K. Christensen et al. [Phys. Rev. Lett. 77 （1996） 107], a rice-pile model studied by L.A.N. Amaral et al. [Phys. Rev. E 54 （1996） 4512], and a simple deterministic self-organized critical model studied by M.S. Vieira [Phys. Rev. E 61 （2000） 6056].展开更多
Aims The present study aims(i)to examine if recently reported interspecific shoot-level biomass allocational trade-offs,i.e.isometric trade-offs between leaf mass(LM)and stem mass(SM)and between leaf size and leaf num...Aims The present study aims(i)to examine if recently reported interspecific shoot-level biomass allocational trade-offs,i.e.isometric trade-offs between leaf mass(LM)and stem mass(SM)and between leaf size and leaf number,hold intraspecifically and(ii)to explore whether those scaling relationships are independent of shoot type(i.e.long vs.short shoots).Methods In order to address our questions,we used Fagus sylvatica saplings growing under a broad light range that were sampled in theWestern Carpathians Mountains(Slovakia).Important Findings We found that:(i)intraspecific shoot-level biomass allocational trade-offs differ from those reported interspecifically and that(ii)long and short shoots differ in biomass allocation scaling coefficients.Allometric relationships with slopes statistically smaller than 1.0 or higher than -1.0,were found between SM and LM and between mean leafing intensity and individual leaf mass,respectively,in long shoots.In contrast,isometric scaling was found in short shoots.This suggests that leaf mass in short shoots is unaffected by shoot stem mass,in contrast to long shoots.Short shoots also had a larger fraction of biomass allocated to leaves.Beech shoots,as has been observed in other shoot dimorphic species,are specialized,with short shoots specializing in carbon gain and long shoots in space acquisition.A greater shift in LM than in SM among species during speciation shifting from allometric intraspecific relationships to an isometric interspecific scaling relationship between those traits could explain the discrepancies between the outputs of the present intraspecific study and others similar studies.This study draws attention to the importance of considering shoot types in future studies dealing with allocation rules in species with dimorphic shoots.展开更多
In this paper,a scaling law relating the mesh size to the Reynolds number was proposed to ensure consistent results for large eddy simulation(LES)as the Reynolds number was varied.The grid size scaling law was develop...In this paper,a scaling law relating the mesh size to the Reynolds number was proposed to ensure consistent results for large eddy simulation(LES)as the Reynolds number was varied.The grid size scaling law was developed by analyzing the lengthscale of the turbulent motion by using DNS data from the literature.The wall-resolving LES was then applied to a plane channel flow to validate the scaling law.The scaling law was tested at different Reynolds numbers(Ret=395,590 and 1000),and showed good results compared to direct numerical simulation(DNS)in terms of mean flow and various turbulent statistics.The velocity spectra analysis shows the evidence of the Kolmogorov–5/3 inertial subrange and verifies that the current LES can resolve the bulk of the turbulent kinetic energy by satisfying the grid scaling law.Meanwhile,the near-wall turbulent flow structures can also be well captured.Reasonably accurate predictions can thus be obtained for flows at even higher Reynolds numbers with significantly lower computational costs compared to DNS by applying the mesh scaling law.展开更多
For some models of relevance in the social sciences we review some exam-ples in which system size plays an important role in the final outcome of the dynamics.We discuss the conditions under which changes of behavior ...For some models of relevance in the social sciences we review some exam-ples in which system size plays an important role in the final outcome of the dynamics.We discuss the conditions under which changes of behavior can appear only when the number of agents in the model takes a finite value.Those changes of behavior can be related to the apparent phase transitions that appear in some physical models.We show examples in the Galam's model of opinion transmission and the Axelrod's model of culture formation stressing the role that the network of interactions has on the main results of both models.Finally,we present the phenomenon of system-size stochastic resonance by which a forcing signal(identified as an advertising agent)is optimally amplified by a population of the right(intermediate)size.Our work stresses the role that the system size has in the dynamics of social systems and the inappropriateness of taking the thermodynamic limit for these systems.展开更多
A one-dimensional sand-pile model (Manna model), which has a stochastic redistribution process, is studied both in discrete and continuous manners. The system evolves into a critical state after a transient period. A ...A one-dimensional sand-pile model (Manna model), which has a stochastic redistribution process, is studied both in discrete and continuous manners. The system evolves into a critical state after a transient period. A detailed analysis of the probability distribution of the avalanche size and duration is numerically investigated. Interestingly,contrary to the deterministic one-dimensional sand-pile model, where multifractal analysis works well, the analysis based on simple finite-size scaling is suited to fitting the data on the distribution of the avalanche size and duration. The exponents characterizing these probability distributions are measured. Scaling relations of these scaling exponents and their universality class are discussed.展开更多
文摘The assembly of the volant bird body plan from the ancestral bulky dinosaurian condition is an enduring topic of evolutionary biology.The body plan of volant birds demonstrates a pronounced decrease in body size and proportionate elongation of the forelimbs.Given the scaling relationship between limb and body size,changes to the former were likely clouded by changes to the entire body size.
基金supported by the National Natural Science Foundation of China(Project No.41807448)。
文摘Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.Here,we present new geochemical data which provides insight to the sedimentary environment of aeolian sands in the Dinggye region,southern Tibet.We sampled aeolian dune sands in a variety of settings,and determined grain size and concentration of major oxides and trace elements in the fine and coarse fractions.Results show that aeolian sediments are dominated by fine and medium sands,with a single-peaked frequency curve and a 3-stage probability cumulative curve.The fine and coarse fractions exhibit considerable heterogeneity in elemental concentrations and ratios and upper continental crust-normalized(UCC)distribution.The geochemical evidence indicates that wind dynamic sorting is responsible for the differentiation between fine and coarse fractions in different types of aeolian sand,rather than sediment provenance.Additionally,fine-fraction sediments are well dispersed and can be differentiated from the coarse fraction,suggesting that they contain more environmental information.Multidimensional scale(MDS)and principal component analysis(PCA)of commonly used tracer elements show that flood plain sediments are the sand source for mobile dunes and nebkhas,and lakeshore sediments are the sand source for climbing sand sheets.
基金supported by the Science Foundation of Henan University of Science and Technology under Grant Nos.05-032 and 2006QN033
文摘A stochastic local limited one-dimensional rice-pile model is numerically investigated. The distributions for avalanche sizes have a clear power-law behavior and it displays a simple finite size scaling. We obtain the avalanche exponents Ts= 1.54±0.10,βs = 2.17±0.10 and TT = 1.80±0.10, βT =1.46 ± 0.10. This self-organized critical model belongs to the same universality class with the Oslo rice-pile model studied by K. Christensen et al. [Phys. Rev. Lett. 77 （1996） 107], a rice-pile model studied by L.A.N. Amaral et al. [Phys. Rev. E 54 （1996） 4512], and a simple deterministic self-organized critical model studied by M.S. Vieira [Phys. Rev. E 61 （2000） 6056].
基金B.J.was funded by grants of Slovak Scientific Grant Agency(VEGA)No.2/0055/10,2/0034/10R.M.by the Spanish MICINN(grants AGL2010-10935-E,CGL2011-28778,and‘Ramon y Cajal’contract)the Madrid Regional Government(grant URJC-CM-2010-CET-5412).
文摘Aims The present study aims(i)to examine if recently reported interspecific shoot-level biomass allocational trade-offs,i.e.isometric trade-offs between leaf mass(LM)and stem mass(SM)and between leaf size and leaf number,hold intraspecifically and(ii)to explore whether those scaling relationships are independent of shoot type(i.e.long vs.short shoots).Methods In order to address our questions,we used Fagus sylvatica saplings growing under a broad light range that were sampled in theWestern Carpathians Mountains(Slovakia).Important Findings We found that:(i)intraspecific shoot-level biomass allocational trade-offs differ from those reported interspecifically and that(ii)long and short shoots differ in biomass allocation scaling coefficients.Allometric relationships with slopes statistically smaller than 1.0 or higher than -1.0,were found between SM and LM and between mean leafing intensity and individual leaf mass,respectively,in long shoots.In contrast,isometric scaling was found in short shoots.This suggests that leaf mass in short shoots is unaffected by shoot stem mass,in contrast to long shoots.Short shoots also had a larger fraction of biomass allocated to leaves.Beech shoots,as has been observed in other shoot dimorphic species,are specialized,with short shoots specializing in carbon gain and long shoots in space acquisition.A greater shift in LM than in SM among species during speciation shifting from allometric intraspecific relationships to an isometric interspecific scaling relationship between those traits could explain the discrepancies between the outputs of the present intraspecific study and others similar studies.This study draws attention to the importance of considering shoot types in future studies dealing with allocation rules in species with dimorphic shoots.
文摘In this paper,a scaling law relating the mesh size to the Reynolds number was proposed to ensure consistent results for large eddy simulation(LES)as the Reynolds number was varied.The grid size scaling law was developed by analyzing the lengthscale of the turbulent motion by using DNS data from the literature.The wall-resolving LES was then applied to a plane channel flow to validate the scaling law.The scaling law was tested at different Reynolds numbers(Ret=395,590 and 1000),and showed good results compared to direct numerical simulation(DNS)in terms of mean flow and various turbulent statistics.The velocity spectra analysis shows the evidence of the Kolmogorov–5/3 inertial subrange and verifies that the current LES can resolve the bulk of the turbulent kinetic energy by satisfying the grid scaling law.Meanwhile,the near-wall turbulent flow structures can also be well captured.Reasonably accurate predictions can thus be obtained for flows at even higher Reynolds numbers with significantly lower computational costs compared to DNS by applying the mesh scaling law.
基金support from MCyT(Spain)and FEDER(EU)through projects FIS2004-5073 and FIS2004-953.
文摘For some models of relevance in the social sciences we review some exam-ples in which system size plays an important role in the final outcome of the dynamics.We discuss the conditions under which changes of behavior can appear only when the number of agents in the model takes a finite value.Those changes of behavior can be related to the apparent phase transitions that appear in some physical models.We show examples in the Galam's model of opinion transmission and the Axelrod's model of culture formation stressing the role that the network of interactions has on the main results of both models.Finally,we present the phenomenon of system-size stochastic resonance by which a forcing signal(identified as an advertising agent)is optimally amplified by a population of the right(intermediate)size.Our work stresses the role that the system size has in the dynamics of social systems and the inappropriateness of taking the thermodynamic limit for these systems.
文摘A one-dimensional sand-pile model (Manna model), which has a stochastic redistribution process, is studied both in discrete and continuous manners. The system evolves into a critical state after a transient period. A detailed analysis of the probability distribution of the avalanche size and duration is numerically investigated. Interestingly,contrary to the deterministic one-dimensional sand-pile model, where multifractal analysis works well, the analysis based on simple finite-size scaling is suited to fitting the data on the distribution of the avalanche size and duration. The exponents characterizing these probability distributions are measured. Scaling relations of these scaling exponents and their universality class are discussed.
