two equation turbulence closure model for wall bounded and free shear flows the model can be used for both wall bounded and free shear flows using one set of model constants

nonparametric quantile estimations for dynamic smooth coefficient models in this article quantile regression methods are suggested for a class of smooth coefficient time series models we use both local polynomial and local constant fitting schemes to estimate the smooth coefficients in a quantile framework we establish the asymptotic properties of both the local polynomial and local constant estimators for mixing time series also a bandwidth selector based on the nonparametric version of the akaike information criterion is suggested together with a consistent estimate of the asymptotic covariance matrix furthermore the asymptotic behaviors of the estimators at boundaries are examined a comparison of the local polynomial quantile estimator with the local constant estimator is presented a simulation study is carried out to illustrate the performance of estimates an empirical application of the model to real data further demonstrates the potential of the proposed modeling procedures

an improved k ω φ α turbulence model applied to near wall separated and impinging jet flows and heat transfer abstract a turbulence model based on elliptic blending concept referred to as improved k model compared against the original k model developed previously is developed and verified this model consists of four governing equations among them the k and equations are based on the wilcox s k model with some modifications and improvements according to the original k model and the and equations are extracted from the original k model directly without any change the improved k model is applied to near wall separated and impinging jet flows and convective heat transfer i e the 2d fully developed channel flow the 2d backward facing step flow the 2d impinging jet flow and the convective heat transfer in the 2d fully developed channel flow and the 2d impinging jet flow the computational results are compared with available dns and experimental data and also to those computed using the original k model and the popular menter s sst k model it is shown that the improved k model has better numerical stability higher computational efficiency and more concise form than the original k model in addition compared with the original k model the improved k model can yield similar velocity profiles in the fully developed channel flow and step flow and friction and pressure coefficients in the step flow and very close temperature profiles in the fully developed channel flow moreover it shows significant improvements on the predictions for the fluid flow and heat transfer in the impinging jet flow as a whole the improved k model predicts better results than both of the original k model and the sst k model

positive solutions for a schrodinger poisson system involving concave convex nonlinearities abstract in this paper we study the critical growth schrodinger poisson system with a concave term and establish the existence of multiple positive solutions via using the variational method

on the distribution of a studentized quantile la variance asymptotique du quantile d echantillon depend de la valeur de la densite de population et du quantile de la population on considere l estimateur de siddiqui bloch gastwinth

schrodinger poisson equations without ambrosetti rabinowitz condition abstract we prove the existence of ground state solutions for a stationary schrodinger poisson equation in r 3 the proof is based on the mountain pass theorem and it does not require the ambrosetti rabinowitz condition

positive solutions for some non autonomous schrodinger poisson systems abstract in this paper we study the schrodinger poisson system sp u u k x x u a x u p 1 u x r 3 k x u 2 x r 3 with p 3 5 assuming that a r 3 r and k r 3 r are nonnegative functions such that lim x a x a 0 lim x k x 0 and satisfying suitable assumptions but not requiring any symmetry property on them we prove the existence of positive solutions

improving the predictive capability of turbulence models using evidence theory when turbulence models are used in the simulation of a flow for which experimental results do not exist there is as yet no reliable procedure for choosing a model or for quantifying the uncertainty of the results the present study develops an approach based on evidence theory for the resolution of these issues the results of turbulence model validations and of predictions of those models are fused to determine the intervals in which a flow quantity is likely to fall and a measure of confidence for each interval the approach is tested in a subsonic flow around the rae 2822 airfoil nomenclature ij ij ij ab c matrix elements c airfoil chord k turbulent kinetic energy m basic probability assignment m mach number p proposition probability s proposition support u mean velocity e u experimental mean velocity or error boundaries if an experimental error range is available m

markov chain marginal bootstrap markov chain marginal bootstrap mcmb is a new method for constructing confidence intervals or regions for maximum likelihood estimators of certain parametric models and for a wide class of m estimators of linear regression the mcmb method distinguishes itself from the usual bootstrap methods in two important aspects it involves solving only one dimensional equations for parameters of any dimension and produces a markov chain rather than a conditionally independent sequence it is designed to alleviate computational burdens often associated with bootstrap in high dimensional problems the validity of mcmb is established through asymptotic analyses and illustrated with empirical and simulation studies for linear regression and generalized linear models

computation of compression ramp flow with a cross diffusion modified k epsilon model we propose a new k e model with a cross diffusion term that can be used to analyze turbulent nonequilibrium flows

a resampling method based on pivotal estimating functions summary suppose that under a semiparametric model setting one is interested in drawing inferences about a finite dimensi onal parameter vector based on an estimating function generally a consistent point estimator j for 0 the true value for j can be easily obtained by finding a root of the corresponding estimating equation to estimate the variance of ft however may involve complicated and subjective nonparametric functional estimates in this paper a general and simple resampling method for inferences about js0 based on pivotal estimating functions is proposed the new procedure is illustrated with the quantile and rank regression models for both cases our proposal can be easily and efficiently implemented with existing statistical software

adaptive l estimation for linear models asymptotically efficient adaptive estimators for the slope parameters of the linear regression model are constructed based upon the regression quantile statistics suggested by koenker and bassett the estimators are natural analogues of the adaptive l estimators of location of sacks but employ kernel density type estimators of the optimal l estimator weight function

regression rank scores and regression quantiles we show that regression quantiles which could be computed as solutions of a linear programming problem and the solutions of the corresponding dual problem which we call the regression rank scores generalize the duality of order statistics and of ranks from the location to the linear model noting this fact we study the regression quantile and regression rank score processes in the heteroscedastic linear regression model obtaining some new estimators and interesting comparisons with existing estimators

positive solutions for a schrodinger poisson system with singularity and critical exponent abstract we study multiplicity of positive solutions for a class of schrodinger poisson system with singularity and critical exponent and obtain two positive solutions via the variational and perturbation methods

existence of infinitely many large solutions for the nonlinear schrodinger maxwell equations abstract in this paper we study the nonlinear stationary schrodinger maxwell equations u v x u u f x u in r 3 u 2 in r 3 using the variant fountain theorem introduced by zou w zou variant fountain theorems and their applications manuscripta math 104 2001 343 358 under certain assumptions on v and f we get infinitely many large solutions for

a direct approach to inference in nonparametric and semiparametric quantile models we construct a generic confidence interval for a conditional quantile via the direct approach it avoids estimating the conditional density function of the dependent variable given the covariate and is asymptotically valid for any conditional quantile any conditional quantile estimator and any data structure provided that certain weak convergence of the conditional quantile process holds for the original quantile estimator we also construct a generic confidence band for the conditional quantile function across a range of covariate values by using yang stute estimator and two semiparametric quantile functions we demonstrate the flexibility and simplicity of the direct approach the advantages of our new confidence intervals are borne out in a simulation study

infinitely many positive solutions for a schrodinger poisson system abstract we are interested in the existence of infinitely many positive solutions of the schrodinger poisson system u u v x u u p 1 u x r 3 v x u 2 x r 3 where v x is a positive bounded function 1 p 5 and v r r x has the following decay property v r a r m o 1 r m with a 0 m 3 2 0 the solutions obtained are non radial

conservation errors and convergence characteristics of iterative space marching algorithms the new iterative space marching algorithms for numerical solution of the parabolized navier stokes equations are critically examined it is shown by analysis and numerical examples that employing parabolized flux difference splitting in the marching direction can lead to serious conservation errors even though a finite volume formulation is employed schemes employing parabolized flux vector splitting in the marching direction are shown to be conservative the structure of the iterative algorithm is examined to determine what factors play important roles in the convergence of the local iteration

implicit solution method for incompressible navier stokes equations including two layer k tau turbulence model the two dimensional incompressible navier stokes equations including a low reynolds number two layer k turbulence model are solved by an implicit time stepping routine using the method of artificial compressibility the two layer model uses a transport equation for the turbulent kinetic energy k and a new algebraic relationship for the turbulent time scale near the wall but reverts to the two equation k turbulence model in the bulk of the flow away from the wall the algebraic relationship for the turbulent time scale and the eddy viscosity damping function f are validated by direct numerical simulation data and asymptotic analysis of near wall turbulence a fifth order upwind biased differencing scheme is used to discretize the convective and pressure terms and second order central differences are employed for other spatial derivatives the nonlinear equations are solved using the preconditioned generalized minimal residual technique in conjunction with numerical linearization a ld 1 u factorization of the approximate jacobian matrix is used as preconditioning matrix

infinitely many solutions for a class of sublinear schrodinger maxwell equations abstract in this paper we study the existence of infinitely many solutions for a class of sublinear schrodinger maxwell equations the proof is based on the variant fountain theorem established by zou recent results from the literature are extended

high energy solutions for the superlinear schrodinger maxwell equations abstract in this paper we study the existence of infinitely many large energy solutions for the superlinear schrodinger maxwell equations u v x u u f x u in r 3 u 2 in r 3 via the fountain theorem in critical point theory

on ground state solutions for the schrodinger poisson equations with critical growth abstract in this paper we study the existence of ground state solutions for the following schrodinger poisson equation u v x u u u q 1 u u 4 u in r 3 u 2 in r 3 where is a positive parameter under some certain assumptions on v we prove that for every 0 and q 2 5 such a class of schrodinger poisson equation with critical growth has at least a positive ground state solution via variational methods some recent results from the literature are extended

estimating conditional proportion curves by regression residuals researchers often derive a categorical outcome from an observed continuous measurement y for example human obesity status can be defined by the body mass index they proceed to estimate the conditional proportion curve p x p y c x x versus the covariate x by regular categorical data analysis in doing so they fail to fully use the rich information in the original continuous measurement researchers also face additional difficulties caused by the uncertainty of the cutoff c x which defines the categories for example some cutoff may cause artificial discontinuity or non smoothness in the conditional proportion curve p x we propose a fully nonparametric empirical estimator using the standardized regression residuals from the general location scale model y m x v x e for the original continuous measurement we prove the consistency of the proposed estimator in regular settings the proposed estimator has several attractive features it readily provides estimates for alternative cutoff values and easily accommodates the discontinuity in p x caused by special cutoff numerical examples demonstrate that our method has better performance in mean squared error than some alternative approaches we also discuss a design adjusted version of the proposed estimators to accommodate survey designs the proposed methods are applied to data on obesity measurements among female hispanic americans this new approach can be applied to other epidemiological and socio economic research that needs to define population categories from underlying continuous measurements copyright 2010 john wiley sons ltd

quantile regression inference with adaptive control of size abstractregression quantiles have asymptotic variances that depend on the conditional densities of the response variable given regressors this article develops a new estimate of the asymptotic var

direct use of regression quantiles to construct confidence sets in linear models direct use of the empirical quantile function provides a standard distribution free approach to constructing confidence intervals and confidence bands for population quantiles we apply this method to construct confidence intervals and confidence bands for regression quantiles and to construct prediction intervals based on sample regression quantiles comparison of the direct method with the studentization and the bootstrap methods are discussed simulation results show that the direct method has the advantage of robustness against departure from the normality assumption of the error terms

staggered finite volume scheme for solving cascade flow with a k omega turbulence model a k turbulence model by wilcox is applied to cascade flow calculations a staggered finite volume scheme is proposed to solve the compressible reynolds averaged navier stokes equations and the k equations are solved on staggered control volumes with k and defined at the cell vertices of the original grid by use of this combination of the cell centered and cell vertex schemes the method maintains a small stencil for all diffusion terms and closely couples the navier stokes and k equations

wall normal free reynolds stress model for rotating flows applied to turbomachinery a recently developed near wall wall normal free reynolds stress model is extended and applied to the computation of transonic three dimensional e ows in turbomachinery rotors with tip clearance the reynolds stress model used is completely independent of the distance from the wall and of the normal to the wall direction this is achieved by using a pseudonormal direction dee ned by the gradients of turbulence length scale and anisotropy tensor invariants in the pressure strain echo terms the effects of rotation are included through theexact coriolis termsin the reynolds stress transport equations and through the isotropization of absolute e ow production model used for the rapid pressure strain terms the model is initially validated by comparison with measurements in rotating fully developed plane channel e ows computational results obtained with the proposed reynolds stress model are compared with measurements and with k computations for various operating points of the nasa 37 rotor using a 3 10 6 multiblock computational grid with 41 radial stations within the tip clearance gap the proposed model substantially improves the agreement with measurements compared to existing algebraic and two equation models

existence and nonexistence of positive solutions for a static schrodinger poisson slater equation abstract in this paper we study the following type of the schrodinger poisson slater equation with critical growth u u 2 1 4 x u u p 1 u u 4 u in r 3 where 0 and p 11 7 5 for the case of p 2 5 we develop a novel perturbation approach together with the well known mountion pass theorem to prove the existence of positive ground states for the case of p 2 we obtain the nonexistence of nontrivial solutions by restricting the range of and also study the existence of positive solutions by the constrained minimization method for the case of p 11 7 2 we use a truncation technique developed by brezis and oswald 9 together with a measure representation concentration compactness principle due to lions 27 to prove the existence of radial symmetrical positive solutions for 0 with some 0 the above results nontrivially extend some theorems on the subcritical case obtained by ianni and ruiz 18 to the critical case

multiple positive solutions for a schrodinger newton system with sign changing potential abstract in this paper we study the schrodinger newton systems with sign changing potential in a bounded domain by using the variational method and analytic techniques the existence and multiplicity of positive solutions are established

coverage probabilities of bootstrap confidence intervals for quantiles an asymptotic expansion of length 2 is established for the coverage probabilities of confidence intervals for the underlying q quantile which are derived by bootstrapping the sample q quantile the corresponding level error turns out to be of order o n 1 2 which is unexpectedly low a confidence interval of even more practical use is derived by using backward critical points the resulting confidence interval is of the same length as the one derived by ordinary bootstrap but it is distribution free and has higher coverage probability

quantile regression for dynamic panel data with fixed effects abstract this paper studies a quantile regression dynamic panel model with fixed effects panel data fixed effects estimators are typically biased in the presence of lagged dependent variables as regressors to reduce the dynamic bias we suggest the use of the instrumental variables quantile regression method of chernozhukov and hansen 2006 along with lagged regressors as instruments in addition we describe how to employ the estimated models for prediction monte carlo simulations show evidence that the instrumental variables approach sharply reduces the dynamic bias and the empirical levels for prediction intervals are very close to nominal levels finally we illustrate the procedures with an application to forecasting output growth rates for 18 oecd countries

critical evaluation of two equation models for near wall turbulence abstract a variety of two equation turbulence models including several versions of the k epsilon model as well as the k omega model are analyzed critically for near wall turbulent flows from a theoretical and computational standpoint it is shown that the k epsilon model has two major problems associated with it the lack of natural boundary conditions for the dissipation rate and the appearance of higher order correlations in the balance of terms for the dissipation rate at the wall in so far as the former problem is concerned either physically inconsistent boundary conditions have been used or the boundary conditions for the dissipation rate have been tied to higher order derivatives of the turbulent kinetic energy which leads to numerical stiffness the k omega model can alleviate these problems since the asymptotic behavior of w is known in more detail and since its near wall balance involves only exact viscous terms however the modeled form of the omega equation that is used in the literature is incomplete an exact viscous term is missing which causes the model to behave in an asymptotically inconsistent manner by including this viscous term and by introducing new wall damping functions with improved asymptotic behavior a new k tau model where tau 1 omega is turbulent time scale is developed it is demonstrated that this new model is computationally robust and yields improved predictions for turbulent boundary layers jhd