This study numerically examines the heat and mass transfer characteristics of two ternary nanofluids via converging and diverg-ing channels.Furthermore,the study aims to assess two ternary nanofluids combinations to d...This study numerically examines the heat and mass transfer characteristics of two ternary nanofluids via converging and diverg-ing channels.Furthermore,the study aims to assess two ternary nanofluids combinations to determine which configuration can provide better heat and mass transfer and lower entropy production,while ensuring cost efficiency.This work bridges the gap be-tween academic research and industrial feasibility by incorporating cost analysis,entropy generation,and thermal efficiency.To compare the velocity,temperature,and concentration profiles,we examine two ternary nanofluids,i.e.,TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O and TiO_(2)+SiO_(2)+Cu/H_(2)O,while considering the shape of nanoparticles.The velocity slip and Soret/Dufour effects are taken into consideration.Furthermore,regression analysis for Nusselt and Sherwood numbers of the model is carried out.The Runge-Kutta fourth-order method with shooting technique is employed to acquire the numerical solution of the governed system of ordinary differential equations.The flow pattern attributes of ternary nanofluids are meticulously examined and simulated with the fluc-tuation of flow-dominating parameters.Additionally,the influence of these parameters is demonstrated in the flow,temperature,and concentration fields.For variation in Eckert and Dufour numbers,TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O has a higher temperature than TiO_(2)+SiO_(2)+Cu/H_(2)O.The results obtained indicate that the ternary nanofluid TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O has a higher heat transfer rate,lesser entropy generation,greater mass transfer rate,and lower cost than that of TiO_(2)+SiO_(2)+Cu/H_(2)O ternary nanofluid.展开更多
In this paper, we have investigated two observed situations in a multi-lane road. The first one concerns a fast merging vehicle. The second situation is related to the case of a fast vehicle leaving the fastest lane b...In this paper, we have investigated two observed situations in a multi-lane road. The first one concerns a fast merging vehicle. The second situation is related to the case of a fast vehicle leaving the fastest lane back into the slowest lane and targeting a specific way out. We are interested in the relaxation time T, i.e., which is the time that the merging （diverging） vehicle spends before reaching the desired lane. Using analytical treatment and numerical simulations for the NaSch model, we have found two states, namely, the free state in which the merging （diverging） vehicle reaches the desired lane, and the trapped state in which T diverges. We have established phase diagrams for several values of the braking probability. In the second situation, we have shown that diverging from the fast lane targeting a specific way out is not a simple task. Even if the diverging vehicle is in the free phase, two different states can be distinguished. One is the critical state, in which the diverging car can probably reach the desired way out. The other is the safe state, in which the diverging car can surely reach the desired way out. In order to be in the safe state, we have found that the driver of the diverging car must know the critical distance （below which the way out will be out of his reach） in each lane. Furthermore, this critical distance depends on the density of cars, and it follows an exponential law.展开更多
Since the first Diverging Diamond Interchange (DDI) implementation in 2009, most of the performance studies developed for this type of interchange have been based on simulations and historical crash data, with a small...Since the first Diverging Diamond Interchange (DDI) implementation in 2009, most of the performance studies developed for this type of interchange have been based on simulations and historical crash data, with a small numbe<span style="font-family:Verdana;">r of studies using Automated Traffic Signal Performance Measures (ATS</span><span style="font-family:Verdana;">PM). Simulation models require considerable effort to collect volumes and to model actual controller operations. Safety studies based on historical crashes usually require from 3 to 5 years of data collection. ATSPMs rely on sensing equipment. This study describes the use of connected vehicle trajectory data to analyze the performance of a DDI located in the metropolitan area of Fort Wayne, IN. An extension of the Purdue Probe Diagram (PPD) is proposed to assess the levels of delay, progression, and saturation. Further, an additional PPD variation is presented that provides a convenient visualization to qualitatively understand progression patterns and to evaluate queue length for spillback in the critical interior crossover. Over 7000 trajectories and 130,000 GPS points were analyzed between the 7</span><sup><span style="font-family:Verdana;">th</span></sup><span style="font-family:Verdana;"> and the 11</span><sup><span style="font-family:Verdana;">th</span></sup><span style="font-family:Verdana;"> of June 2021 from 5:00 AM to 10:00 PM to estimate the DDI’s arrivals on green, level of service, split failures, and downstream blockage. Although this technique was demonstrated for weekdays, the ubiquity of connected vehicle data makes it very ea</span><span style="font-family:Verdana;">sy to adapt these techniques to analysis during special events, winter sto</span><span style="font-family:Verdana;">rms, and weekends. Furthermore, the methodologies presented in this paper can be applied by any agency wanting to assess the performance of any DDI in their jurisdiction.</span>展开更多
The flow in a finite diverging channel opening into a large space and resembling the experimental prototype of Putkaradze and Vorobieff (2006) was numerically investigated. The effects of the Reynolds number,initial c...The flow in a finite diverging channel opening into a large space and resembling the experimental prototype of Putkaradze and Vorobieff (2006) was numerically investigated. The effects of the Reynolds number,initial condition,intersection angle,length of the wedge edges,and the outer boundary condition were examined. The numerical results showed that the flow in the wedge undergoes a change from symmetrical flow to unsymmetrical flow with a weak backflow,then a vortical (circulation) flow and finally an unsteady jet flow as the Reynolds number is increased for an intersection angle of 32° and a wedge edge of length 30 times the width of the inlet slit. For the unsteady flow,the jet attached to one side of the wedge constantly loses stability and rolls up into a mushroom-shaped vortex-pair near the outlet of the wedge. As the intersection angle is increased to 50°,a stable jet flow is observed as a new regime between the vortex and unsteady regimes. Both the intersection angle and the wedge length have negative effects on the stability of the flow,although the effect of the wedge length on the critical Reynolds number for the symmetry-breaking instability is not pronounced. The outer boundary condition was found not to affect the flow patterns inside the wedge significantly. At a certain Re regime above the onset of symmetry-breaking instability,the flows evolve into steady state very slowly except for the initial stage in the case of decreasing flow flux. Two different solutions can be observed within the normal observation time for the experiment,providing a possible explanation for the hysteresis phenomenon in the experiment.展开更多
The mixing degree upstream of the diverging area is one of the important factors influencing the pollutant allocation characteristics of braided rivers,but the effect remains unclear at present.In this paper,physical ...The mixing degree upstream of the diverging area is one of the important factors influencing the pollutant allocation characteristics of braided rivers,but the effect remains unclear at present.In this paper,physical model tests were designed to study the effect on the pollutant flux ratio with six branching forms and a series of longitudinal discharge distances.The results indicated that the mixing degree upstream of the diverging area,which is closely related to the longitudinal discharge distance,notably affected the pollutant flux ratio.The lower the mixing degree,the larger was the deviation of the pollutant flux ratio from the discharge ratio.Moreover,a linear relationship was attained between the dimensionless mixing degree and the dimensionless deviation of the pollutant flux ratio from the discharge ratio.Consideration of different branching angles or different water layers or different branches did not affect this trend.The experimental results further demonstrated that the intercept and slope of the aforementioned linear relationship depended on the branching angle and exhibited an opposite monotonicity with a symmetric branch angle as the dividing point.These results help towards a better understanding of the mechanism of the factors influencing pollutant transport in complicated braided rivers,and provide a new approach to predicting the pollutant flux ratio of braided rivers.展开更多
The flow visualization work with the aid of PIV and Piezometer deals with flip-flop flow around diamond-shaped cylinder bundle revised with concavities on both bundle walls. It is disclosed that 1) the concavity const...The flow visualization work with the aid of PIV and Piezometer deals with flip-flop flow around diamond-shaped cylinder bundle revised with concavities on both bundle walls. It is disclosed that 1) the concavity constructed on both side-walls of a diamond cylinder induces a substantial change in the flow patterns in the exit jet-stream field and jet- stream dispersion, 2) pressure characteristics are quantitatively measured in a diverging-flow region in diamond cylinder bundles with concavityand in its downstream region, and 3) flip-flop flow occurs in the flow passages and its occurrence condition is obtained.展开更多
This study aims to develop a reliable safety evaluation model for diverging vehicles and investigates the impact of the surrounding traffic environment on freeway diverging risks.High-resolution trajectory data from t...This study aims to develop a reliable safety evaluation model for diverging vehicles and investigates the impact of the surrounding traffic environment on freeway diverging risks.High-resolution trajectory data from three sites in the Netherlands(Delft,Ter-Heide and Zonzeel)were employed for the risk analysis.Linear regression(LR),support vector machine(SVM),random forest(RF),extreme randomize trees(ET),adaptive boosting(Adaboost),extreme gradient boosting(XGboost)and multilayer perceptron(MLP),were developed for safety evaluation.The result showed that MLP outperforms the other models for diverging risk prediction over all the indicators,conflict thresholds and locations.Pairwise matrix,shapely addictive explanation(SHAP),and LR algorithms were further adopted to interpret the influence of the surrounding environment.It indicates that an increase in traffic density,subject vehicle(SV)lateral speed,the distance of SV from ramp nose and SV length would increase the diverging risk.At the same time,an increase in leading vehicle speed and space headway would decrease diverging risk.Finally,spatial analysis was also conducted to explore the stability of identified traffic features regarding the impact on the diverging risk across the sites.展开更多
The smooth integration of counting and absolute deviation （SICA） penalized variable selection procedure for high-dimensional linear regression models is proposed by Lv and Fan （2009）. In this article, we extend th...The smooth integration of counting and absolute deviation （SICA） penalized variable selection procedure for high-dimensional linear regression models is proposed by Lv and Fan （2009）. In this article, we extend their idea to Cox＇s proportional hazards （PH） model by using a penalized log partial likelihood with the SICA penalty. The number of the regression coefficients is allowed to grow with the sample size. Based on an approximation to the inverse of the Hessian matrix, the proposed method can be easily carried out with the smoothing quasi-Newton （SQN） algorithm. Under appropriate sparsity conditions, we show that the resulting estimator of the regression coefficients possesses the oracle property. We perform an extensive simulation study to compare our approach with other methods and illustrate it on a well known PBC data for predicting survival from risk factors.展开更多
For analyzing correlated binary data with high-dimensional covariates,we,in this paper,propose a two-stage shrinkage approach.First,we construct a weighted least-squares(WLS) type function using a special weighting sc...For analyzing correlated binary data with high-dimensional covariates,we,in this paper,propose a two-stage shrinkage approach.First,we construct a weighted least-squares(WLS) type function using a special weighting scheme on the non-conservative vector field of the generalized estimating equations(GEE) model.Second,we define a penalized WLS in the spirit of the adaptive LASSO for simultaneous variable selection and parameter estimation.The proposed procedure enjoys the oracle properties in high-dimensional framework where the number of parameters grows to infinity with the number of clusters.Moreover,we prove the consistency of the sandwich formula of the covariance matrix even when the working correlation matrix is misspecified.For the selection of tuning parameter,we develop a consistent penalized quadratic form(PQF) function criterion.The performance of the proposed method is assessed through a comparison with the existing methods and through an application to a crossover trial in a pain relief study.展开更多
Studies from behavioral economics show that the subjective prospect value of money has diminishing sensitivity to losses/gains,represented by an S-shape,and this has been applied in representing the subjective prospec...Studies from behavioral economics show that the subjective prospect value of money has diminishing sensitivity to losses/gains,represented by an S-shape,and this has been applied in representing the subjective prospect value of time in many transportation studies such as travel behavior modeling and network equilibrium.In this study,we demonstrate that the prospect value of time has an increasing sensitivity to losses/gains and can be represented by anϨ-shape,which contrasts that of money.We further explain the rationality of this surprising finding based on psychological and behavioral theories and discuss extensive practical implications.The correlations between sensitivities to gains and losses in terms of magnitude are revealed as well to shed light on potential underlying correlated behavioral principles.Substantial loss-aversion features are observed in the empirical analysis,supporting endowment effects.Implications of the findings on decision-making and other areas that utilize time as a key indicator have been discussed.The findings may revolutionize many research areas that utilize time as a key indicator such as transportation engineering.展开更多
In this paper, for the generalized linear models （GLMs） with diverging number of covariates, the asymptotic properties of maximum quasi-likelihood estimators （MQLEs） under some regular conditions are developed. Th...In this paper, for the generalized linear models （GLMs） with diverging number of covariates, the asymptotic properties of maximum quasi-likelihood estimators （MQLEs） under some regular conditions are developed. The existence, weak convergence and the rate of convergence and asymptotic normality of linear combination of MQLEs and asymptotic distribution of single linear hypothesis teststatistics are presented. The results are illustrated by Monte-Carlo simulations.展开更多
Large dimensional predictors are often introduced in regressions to attenuate the possible modeling bias. We consider the stable direction recovery in single-index models in which we solely assume the response Y is in...Large dimensional predictors are often introduced in regressions to attenuate the possible modeling bias. We consider the stable direction recovery in single-index models in which we solely assume the response Y is independent of the diverging dimensional predictors X when βτ 0 X is given, where β 0 is a p n × 1 vector, and p n →∞ as the sample size n →∞. We first explore sufficient conditions under which the least squares estimation β n0 recovers the direction β 0 consistently even when p n = o(√ n). To enhance the model interpretability by excluding irrelevant predictors in regressions, we suggest an e1-regularization algorithm with a quadratic constraint on magnitude of least squares residuals to search for a sparse estimation of β 0 . Not only can the solution β n of e1-regularization recover β 0 consistently, it also produces sufficiently sparse estimators which enable us to select "important" predictors to facilitate the model interpretation while maintaining the prediction accuracy. Further analysis by simulations and an application to the car price data suggest that our proposed estimation procedures have good finite-sample performance and are computationally efficient.展开更多
In many applications,covariates can be naturally grouped.For example,for gene expression data analysis,genes belonging to the same pathway might be viewed as a group.This paper studies variable selection problem for c...In many applications,covariates can be naturally grouped.For example,for gene expression data analysis,genes belonging to the same pathway might be viewed as a group.This paper studies variable selection problem for censored survival data in the additive hazards model when covariates are grouped.A hierarchical regularization method is proposed to simultaneously estimate parameters and select important variables at both the group level and the within-group level.For the situations in which the number of parameters tends to∞as the sample size increases,we establish an oracle property and asymptotic normality property of the proposed estimators.Numerical results indicate that the hierarchically penalized method performs better than some existing methods such as lasso,smoothly clipped absolute deviation(SCAD)and adaptive lasso.展开更多
This paper considers partially linear additive models with the number of parameters diverging when some linear cons train ts on the parame trie par t are available.This paper proposes a constrained profile least-squar...This paper considers partially linear additive models with the number of parameters diverging when some linear cons train ts on the parame trie par t are available.This paper proposes a constrained profile least-squares estimation for the parametrie components with the nonparametric functions being estimated by basis function approximations.The consistency and asymptotic normality of the restricted estimator are given under some certain conditions.The authors construct a profile likelihood ratio test statistic to test the validity of the linear constraints on the parametrie components,and demonstrate that it follows asymptotically chi-squared distribution under the null and alternative hypo theses.The finite sample performance of the proposed method is illus trated by simulation studies and a data analysis.展开更多
While interval-valued picture fuzzy sets(IvPFSs)provide a powerful tool for modeling uncertainty and ambiguity in various fields,existing divergence measures for IvPFSs remain limited and often produce counterintuitiv...While interval-valued picture fuzzy sets(IvPFSs)provide a powerful tool for modeling uncertainty and ambiguity in various fields,existing divergence measures for IvPFSs remain limited and often produce counterintuitive results.To address these shortcomings,this paper introduces two novel divergencemeasures for IvPFSs,inspired by the Jensen-Shannon divergence.The fundamental properties of the proposed measures-non-degeneracy,symmetry,triangular inequality,and boundedness-are rigorously proven.Comparative analyses with existing measures are conducted through specific cases and numerical examples,clearly demonstrating the advantages of our approach.Furthermore,we apply the new divergence measures to develop an enhanced interval-valued picture fuzzy TOPSIS method for risk assessment in construction projects,showing the practical applicability and effectiveness of our contributions.展开更多
Adaptation to different environments can lead to local adaptations that facilitate morphological divergence between closely related taxa,potentially leading to speciation.Quantifying habitat variation can thus provide...Adaptation to different environments can lead to local adaptations that facilitate morphological divergence between closely related taxa,potentially leading to speciation.Quantifying habitat variation can thus provide valuable insights into evolutionary processes.Arboreal dwarf chameleons of the genus Bradypodion exhibit 3 distinct ecomorphological forms:forest,shrub,and“little brown chameleons”(LBCs).It is assumed these ecomorphs are the result of convergence among species that are in similar habitats regardless of ancestry,or in some cases,morphological conservatism and retention of an ancestral form that is adapted to a shared habitat type.If so,then the habitat of different ecomorphs would differ in vegetation structure.Our results show that vegetation structure in fynbos/grassy habitats is characterized by significantly narrower perches than shrubby habitats,but both have a largely vertical perch orientation.In contrast,forests have significantly fewer vertical perches than fynbos/grassy habitats with significantly thicker diameter perches.Accordingly,LBC and shrub species used more vertically oriented perches than forest species,suggesting that perch use corresponds with the most widely available perch angles.Although LBC chameleons used the smallest diameter perches,when corrected for body size,there was no difference in perch diameter among ecomorphs.These results suggest that the body size of LBC chameleons is constrained by the prevalence of small-diameter perches in their habitat.Species in habitats with wider perches attain larger body size.These findings support the notion that variation in perch structure is critical for phenotypic convergence that has resulted in the 3 Bradypodion ecomorphs.展开更多
Pollination niches,which encompass the factors influencing pollen exchange among angiosperms,are fundamental to understanding reproductive success and the intricate eco-evolutionary dynamics of plants.In this study,we...Pollination niches,which encompass the factors influencing pollen exchange among angiosperms,are fundamental to understanding reproductive success and the intricate eco-evolutionary dynamics of plants.In this study,we investigated pollination niche shift among four sympatric Eriosyce cacti with restricted distributions in the South American Mediterranean region.Utilizing a comprehensive approachdincluding pollination niche analysis,pollinator color perception studies,reproductive output assessments,molecular phylogenetics,gene flow analyses,and species distribution modelingdwe revealed a significant pollination niche displacement in E.chilensis and its variety,E.chilensis var.albidiflora.These taxa transitioned from a hummingbird-pollinated system prevalent in the Eriosyce sect.Neoporteria,characteristic of their sister species E.litoralis,to a bee-pollination strategy akin to that of the co-occurring species E.mutabilis.This shift highlights a simultaneous convergence of E.chilensis toward E.mutabilis and divergence from E.litoralis in pollination strategies,providing adaptive advantages by reducing pollen limitation and enhancing seed production.The morphological and flowering phenological similarities between E.chilensis and E.mutabilis suggest the evolution of a shared advertising display,potentially indicative of floral mimicry,wherein both species benefit from attracting shared bee pollinators.Genomic analyses reveal distinct pollinator-driven selection pressures,with E.chilensis/E.albidiflora exhibiting traits that promote reproductive isolation from E.litoralis,supporting a scenario of rapid speciation occurring within the past half of million years in the absence of geographic barriers.These findings underscore the pivotal role of pollinator interactions in shaping angiosperm speciation and biodiversity,highlighting their dynamic influence on ecological and evolutionary processes.展开更多
基金supported by DST-FIST(Government of India)(Grant No.SR/FIST/MS-1/2017/13)and Seed Money Project(Grant No.DoRDC/733).
文摘This study numerically examines the heat and mass transfer characteristics of two ternary nanofluids via converging and diverg-ing channels.Furthermore,the study aims to assess two ternary nanofluids combinations to determine which configuration can provide better heat and mass transfer and lower entropy production,while ensuring cost efficiency.This work bridges the gap be-tween academic research and industrial feasibility by incorporating cost analysis,entropy generation,and thermal efficiency.To compare the velocity,temperature,and concentration profiles,we examine two ternary nanofluids,i.e.,TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O and TiO_(2)+SiO_(2)+Cu/H_(2)O,while considering the shape of nanoparticles.The velocity slip and Soret/Dufour effects are taken into consideration.Furthermore,regression analysis for Nusselt and Sherwood numbers of the model is carried out.The Runge-Kutta fourth-order method with shooting technique is employed to acquire the numerical solution of the governed system of ordinary differential equations.The flow pattern attributes of ternary nanofluids are meticulously examined and simulated with the fluc-tuation of flow-dominating parameters.Additionally,the influence of these parameters is demonstrated in the flow,temperature,and concentration fields.For variation in Eckert and Dufour numbers,TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O has a higher temperature than TiO_(2)+SiO_(2)+Cu/H_(2)O.The results obtained indicate that the ternary nanofluid TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O has a higher heat transfer rate,lesser entropy generation,greater mass transfer rate,and lower cost than that of TiO_(2)+SiO_(2)+Cu/H_(2)O ternary nanofluid.
文摘In this paper, we have investigated two observed situations in a multi-lane road. The first one concerns a fast merging vehicle. The second situation is related to the case of a fast vehicle leaving the fastest lane back into the slowest lane and targeting a specific way out. We are interested in the relaxation time T, i.e., which is the time that the merging （diverging） vehicle spends before reaching the desired lane. Using analytical treatment and numerical simulations for the NaSch model, we have found two states, namely, the free state in which the merging （diverging） vehicle reaches the desired lane, and the trapped state in which T diverges. We have established phase diagrams for several values of the braking probability. In the second situation, we have shown that diverging from the fast lane targeting a specific way out is not a simple task. Even if the diverging vehicle is in the free phase, two different states can be distinguished. One is the critical state, in which the diverging car can probably reach the desired way out. The other is the safe state, in which the diverging car can surely reach the desired way out. In order to be in the safe state, we have found that the driver of the diverging car must know the critical distance （below which the way out will be out of his reach） in each lane. Furthermore, this critical distance depends on the density of cars, and it follows an exponential law.
文摘Since the first Diverging Diamond Interchange (DDI) implementation in 2009, most of the performance studies developed for this type of interchange have been based on simulations and historical crash data, with a small numbe<span style="font-family:Verdana;">r of studies using Automated Traffic Signal Performance Measures (ATS</span><span style="font-family:Verdana;">PM). Simulation models require considerable effort to collect volumes and to model actual controller operations. Safety studies based on historical crashes usually require from 3 to 5 years of data collection. ATSPMs rely on sensing equipment. This study describes the use of connected vehicle trajectory data to analyze the performance of a DDI located in the metropolitan area of Fort Wayne, IN. An extension of the Purdue Probe Diagram (PPD) is proposed to assess the levels of delay, progression, and saturation. Further, an additional PPD variation is presented that provides a convenient visualization to qualitatively understand progression patterns and to evaluate queue length for spillback in the critical interior crossover. Over 7000 trajectories and 130,000 GPS points were analyzed between the 7</span><sup><span style="font-family:Verdana;">th</span></sup><span style="font-family:Verdana;"> and the 11</span><sup><span style="font-family:Verdana;">th</span></sup><span style="font-family:Verdana;"> of June 2021 from 5:00 AM to 10:00 PM to estimate the DDI’s arrivals on green, level of service, split failures, and downstream blockage. Although this technique was demonstrated for weekdays, the ubiquity of connected vehicle data makes it very ea</span><span style="font-family:Verdana;">sy to adapt these techniques to analysis during special events, winter sto</span><span style="font-family:Verdana;">rms, and weekends. Furthermore, the methodologies presented in this paper can be applied by any agency wanting to assess the performance of any DDI in their jurisdiction.</span>
基金supported by the National Basic Research Program (973) of China (No. 2006CB705400)the National Natural Science Foundation of China (Nos. 10602051 and 50735004)
文摘The flow in a finite diverging channel opening into a large space and resembling the experimental prototype of Putkaradze and Vorobieff (2006) was numerically investigated. The effects of the Reynolds number,initial condition,intersection angle,length of the wedge edges,and the outer boundary condition were examined. The numerical results showed that the flow in the wedge undergoes a change from symmetrical flow to unsymmetrical flow with a weak backflow,then a vortical (circulation) flow and finally an unsteady jet flow as the Reynolds number is increased for an intersection angle of 32° and a wedge edge of length 30 times the width of the inlet slit. For the unsteady flow,the jet attached to one side of the wedge constantly loses stability and rolls up into a mushroom-shaped vortex-pair near the outlet of the wedge. As the intersection angle is increased to 50°,a stable jet flow is observed as a new regime between the vortex and unsteady regimes. Both the intersection angle and the wedge length have negative effects on the stability of the flow,although the effect of the wedge length on the critical Reynolds number for the symmetry-breaking instability is not pronounced. The outer boundary condition was found not to affect the flow patterns inside the wedge significantly. At a certain Re regime above the onset of symmetry-breaking instability,the flows evolve into steady state very slowly except for the initial stage in the case of decreasing flow flux. Two different solutions can be observed within the normal observation time for the experiment,providing a possible explanation for the hysteresis phenomenon in the experiment.
基金supported by the National Natural Science Foundation of China(No.51879176)the Jiangxi Provincial Water Conservancy Science and Technology Project(No.202022YBKT09),China。
文摘The mixing degree upstream of the diverging area is one of the important factors influencing the pollutant allocation characteristics of braided rivers,but the effect remains unclear at present.In this paper,physical model tests were designed to study the effect on the pollutant flux ratio with six branching forms and a series of longitudinal discharge distances.The results indicated that the mixing degree upstream of the diverging area,which is closely related to the longitudinal discharge distance,notably affected the pollutant flux ratio.The lower the mixing degree,the larger was the deviation of the pollutant flux ratio from the discharge ratio.Moreover,a linear relationship was attained between the dimensionless mixing degree and the dimensionless deviation of the pollutant flux ratio from the discharge ratio.Consideration of different branching angles or different water layers or different branches did not affect this trend.The experimental results further demonstrated that the intercept and slope of the aforementioned linear relationship depended on the branching angle and exhibited an opposite monotonicity with a symmetric branch angle as the dividing point.These results help towards a better understanding of the mechanism of the factors influencing pollutant transport in complicated braided rivers,and provide a new approach to predicting the pollutant flux ratio of braided rivers.
文摘The flow visualization work with the aid of PIV and Piezometer deals with flip-flop flow around diamond-shaped cylinder bundle revised with concavities on both bundle walls. It is disclosed that 1) the concavity constructed on both side-walls of a diamond cylinder induces a substantial change in the flow patterns in the exit jet-stream field and jet- stream dispersion, 2) pressure characteristics are quantitatively measured in a diverging-flow region in diamond cylinder bundles with concavityand in its downstream region, and 3) flip-flop flow occurs in the flow passages and its occurrence condition is obtained.
基金This research was sponsored by the National Natural Science Foundation of China(Grant No.71901223)Natural Science Foundation of Hunan Province(Grant No.2021JJ40746).
文摘This study aims to develop a reliable safety evaluation model for diverging vehicles and investigates the impact of the surrounding traffic environment on freeway diverging risks.High-resolution trajectory data from three sites in the Netherlands(Delft,Ter-Heide and Zonzeel)were employed for the risk analysis.Linear regression(LR),support vector machine(SVM),random forest(RF),extreme randomize trees(ET),adaptive boosting(Adaboost),extreme gradient boosting(XGboost)and multilayer perceptron(MLP),were developed for safety evaluation.The result showed that MLP outperforms the other models for diverging risk prediction over all the indicators,conflict thresholds and locations.Pairwise matrix,shapely addictive explanation(SHAP),and LR algorithms were further adopted to interpret the influence of the surrounding environment.It indicates that an increase in traffic density,subject vehicle(SV)lateral speed,the distance of SV from ramp nose and SV length would increase the diverging risk.At the same time,an increase in leading vehicle speed and space headway would decrease diverging risk.Finally,spatial analysis was also conducted to explore the stability of identified traffic features regarding the impact on the diverging risk across the sites.
基金Supported by the National Natural Science Foundation of China(No.11171263)
文摘The smooth integration of counting and absolute deviation （SICA） penalized variable selection procedure for high-dimensional linear regression models is proposed by Lv and Fan （2009）. In this article, we extend their idea to Cox＇s proportional hazards （PH） model by using a penalized log partial likelihood with the SICA penalty. The number of the regression coefficients is allowed to grow with the sample size. Based on an approximation to the inverse of the Hessian matrix, the proposed method can be easily carried out with the smoothing quasi-Newton （SQN） algorithm. Under appropriate sparsity conditions, we show that the resulting estimator of the regression coefficients possesses the oracle property. We perform an extensive simulation study to compare our approach with other methods and illustrate it on a well known PBC data for predicting survival from risk factors.
基金supported by National Natural Science Foundation of China(Grant No.11201306)the Innovation Program of Shanghai Municipal Education Commission(Grant No.13YZ065)+2 种基金the Fundamental Research Project of Shanghai Normal University(Grant No.SK201207)the scholarship under the State Scholarship Fund by the China Scholarship Council in 2011the Research Grant Council of Hong Kong, Hong Kong,China(Grant No.#HKBU2028/10P)
文摘For analyzing correlated binary data with high-dimensional covariates,we,in this paper,propose a two-stage shrinkage approach.First,we construct a weighted least-squares(WLS) type function using a special weighting scheme on the non-conservative vector field of the generalized estimating equations(GEE) model.Second,we define a penalized WLS in the spirit of the adaptive LASSO for simultaneous variable selection and parameter estimation.The proposed procedure enjoys the oracle properties in high-dimensional framework where the number of parameters grows to infinity with the number of clusters.Moreover,we prove the consistency of the sandwich formula of the covariance matrix even when the working correlation matrix is misspecified.For the selection of tuning parameter,we develop a consistent penalized quadratic form(PQF) function criterion.The performance of the proposed method is assessed through a comparison with the existing methods and through an application to a crossover trial in a pain relief study.
文摘Studies from behavioral economics show that the subjective prospect value of money has diminishing sensitivity to losses/gains,represented by an S-shape,and this has been applied in representing the subjective prospect value of time in many transportation studies such as travel behavior modeling and network equilibrium.In this study,we demonstrate that the prospect value of time has an increasing sensitivity to losses/gains and can be represented by anϨ-shape,which contrasts that of money.We further explain the rationality of this surprising finding based on psychological and behavioral theories and discuss extensive practical implications.The correlations between sensitivities to gains and losses in terms of magnitude are revealed as well to shed light on potential underlying correlated behavioral principles.Substantial loss-aversion features are observed in the empirical analysis,supporting endowment effects.Implications of the findings on decision-making and other areas that utilize time as a key indicator have been discussed.The findings may revolutionize many research areas that utilize time as a key indicator such as transportation engineering.
基金supported by Major Programm of Natural Science Foundation of China under Grant No.71690242the Natural Science Foundation of China under Grant No.11471252the National Social Science Fund of China under Grant No.18BTJ040
文摘In this paper, for the generalized linear models （GLMs） with diverging number of covariates, the asymptotic properties of maximum quasi-likelihood estimators （MQLEs） under some regular conditions are developed. The existence, weak convergence and the rate of convergence and asymptotic normality of linear combination of MQLEs and asymptotic distribution of single linear hypothesis teststatistics are presented. The results are illustrated by Monte-Carlo simulations.
基金supported by National Natural Science Foundation of China (Grant No. 10701035)Chen Guang Project of Shanghai Education Development Foundation (Grant No. 2007CG33)+1 种基金supported by Research Grants Council of Hong KongFaculty Research Grant from Hong Kong Baptist University
文摘Large dimensional predictors are often introduced in regressions to attenuate the possible modeling bias. We consider the stable direction recovery in single-index models in which we solely assume the response Y is independent of the diverging dimensional predictors X when βτ 0 X is given, where β 0 is a p n × 1 vector, and p n →∞ as the sample size n →∞. We first explore sufficient conditions under which the least squares estimation β n0 recovers the direction β 0 consistently even when p n = o(√ n). To enhance the model interpretability by excluding irrelevant predictors in regressions, we suggest an e1-regularization algorithm with a quadratic constraint on magnitude of least squares residuals to search for a sparse estimation of β 0 . Not only can the solution β n of e1-regularization recover β 0 consistently, it also produces sufficiently sparse estimators which enable us to select "important" predictors to facilitate the model interpretation while maintaining the prediction accuracy. Further analysis by simulations and an application to the car price data suggest that our proposed estimation procedures have good finite-sample performance and are computationally efficient.
基金supported by National Natural Science Foundation of China(Grant Nos.11171112,11101114 and 11201190)National Statistical Science Research Major Program of China(Grant No.2011LZ051)
文摘In many applications,covariates can be naturally grouped.For example,for gene expression data analysis,genes belonging to the same pathway might be viewed as a group.This paper studies variable selection problem for censored survival data in the additive hazards model when covariates are grouped.A hierarchical regularization method is proposed to simultaneously estimate parameters and select important variables at both the group level and the within-group level.For the situations in which the number of parameters tends to∞as the sample size increases,we establish an oracle property and asymptotic normality property of the proposed estimators.Numerical results indicate that the hierarchically penalized method performs better than some existing methods such as lasso,smoothly clipped absolute deviation(SCAD)and adaptive lasso.
基金supported by the National Natural Science Foundation of China under Grant No.11771250the Natural Science Foundation of Shandong Province under Grant No.ZR2019MA002the Program for Scientific Research Innovation of Graduate Dissertation under Grant No.LWCXB201803
文摘This paper considers partially linear additive models with the number of parameters diverging when some linear cons train ts on the parame trie par t are available.This paper proposes a constrained profile least-squares estimation for the parametrie components with the nonparametric functions being estimated by basis function approximations.The consistency and asymptotic normality of the restricted estimator are given under some certain conditions.The authors construct a profile likelihood ratio test statistic to test the validity of the linear constraints on the parametrie components,and demonstrate that it follows asymptotically chi-squared distribution under the null and alternative hypo theses.The finite sample performance of the proposed method is illus trated by simulation studies and a data analysis.
基金the Deanship of Research and Graduate Studies at King Khalid University for funding this work through Small Research Project under grant number RGP1/141/46.
文摘While interval-valued picture fuzzy sets(IvPFSs)provide a powerful tool for modeling uncertainty and ambiguity in various fields,existing divergence measures for IvPFSs remain limited and often produce counterintuitive results.To address these shortcomings,this paper introduces two novel divergencemeasures for IvPFSs,inspired by the Jensen-Shannon divergence.The fundamental properties of the proposed measures-non-degeneracy,symmetry,triangular inequality,and boundedness-are rigorously proven.Comparative analyses with existing measures are conducted through specific cases and numerical examples,clearly demonstrating the advantages of our approach.Furthermore,we apply the new divergence measures to develop an enhanced interval-valued picture fuzzy TOPSIS method for risk assessment in construction projects,showing the practical applicability and effectiveness of our contributions.
基金funded by the National Research Foundation of South Africa,Dimensions of Biodiversity Program(Grant no.136381).
文摘Adaptation to different environments can lead to local adaptations that facilitate morphological divergence between closely related taxa,potentially leading to speciation.Quantifying habitat variation can thus provide valuable insights into evolutionary processes.Arboreal dwarf chameleons of the genus Bradypodion exhibit 3 distinct ecomorphological forms:forest,shrub,and“little brown chameleons”(LBCs).It is assumed these ecomorphs are the result of convergence among species that are in similar habitats regardless of ancestry,or in some cases,morphological conservatism and retention of an ancestral form that is adapted to a shared habitat type.If so,then the habitat of different ecomorphs would differ in vegetation structure.Our results show that vegetation structure in fynbos/grassy habitats is characterized by significantly narrower perches than shrubby habitats,but both have a largely vertical perch orientation.In contrast,forests have significantly fewer vertical perches than fynbos/grassy habitats with significantly thicker diameter perches.Accordingly,LBC and shrub species used more vertically oriented perches than forest species,suggesting that perch use corresponds with the most widely available perch angles.Although LBC chameleons used the smallest diameter perches,when corrected for body size,there was no difference in perch diameter among ecomorphs.These results suggest that the body size of LBC chameleons is constrained by the prevalence of small-diameter perches in their habitat.Species in habitats with wider perches attain larger body size.These findings support the notion that variation in perch structure is critical for phenotypic convergence that has resulted in the 3 Bradypodion ecomorphs.
基金supported by the Fondo Nacional de Desarrollo Científico y Tecnologico[1160583 and 1211441 to P.C.G.,1240877 to G.O.C.]the Comision Nacional de Investigacion Científica y Tecnologica PIA[REDII 170031 to P.C.G., G.O.C.]+3 种基金ANID PIA/BASAL[FB210006]to the Instituto de Ecología y Biodiversidad(IEB)ANID PIA/BASAL[PFB210018]to the Cape Horn International Center(CHIC)A.V.M.acknowledges the support of ANID/BASAL FB210006 by the Institute of EcologyBiodiversity(IEB)with counterpart contributions from the Anglo-American Foundation.B.M.M.is grateful to the ANID Scholarship 20210673.
文摘Pollination niches,which encompass the factors influencing pollen exchange among angiosperms,are fundamental to understanding reproductive success and the intricate eco-evolutionary dynamics of plants.In this study,we investigated pollination niche shift among four sympatric Eriosyce cacti with restricted distributions in the South American Mediterranean region.Utilizing a comprehensive approachdincluding pollination niche analysis,pollinator color perception studies,reproductive output assessments,molecular phylogenetics,gene flow analyses,and species distribution modelingdwe revealed a significant pollination niche displacement in E.chilensis and its variety,E.chilensis var.albidiflora.These taxa transitioned from a hummingbird-pollinated system prevalent in the Eriosyce sect.Neoporteria,characteristic of their sister species E.litoralis,to a bee-pollination strategy akin to that of the co-occurring species E.mutabilis.This shift highlights a simultaneous convergence of E.chilensis toward E.mutabilis and divergence from E.litoralis in pollination strategies,providing adaptive advantages by reducing pollen limitation and enhancing seed production.The morphological and flowering phenological similarities between E.chilensis and E.mutabilis suggest the evolution of a shared advertising display,potentially indicative of floral mimicry,wherein both species benefit from attracting shared bee pollinators.Genomic analyses reveal distinct pollinator-driven selection pressures,with E.chilensis/E.albidiflora exhibiting traits that promote reproductive isolation from E.litoralis,supporting a scenario of rapid speciation occurring within the past half of million years in the absence of geographic barriers.These findings underscore the pivotal role of pollinator interactions in shaping angiosperm speciation and biodiversity,highlighting their dynamic influence on ecological and evolutionary processes.
