Positive $P_N$ Closures

نویسندگان
چکیده

برای دانلود باید عضویت طلایی داشته باشید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Positive PN Closures

We introduce a modification to the standard spherical harmonic closure used with linear kinetic equations of particle transport. While the standard closure is known to produce negative particle concentrations, the modification corrects this defect by requiring that the ansatz used to the close the equations is itself a non-negative function. We impose this requirement via explicit constraints i...

متن کامل

Positive Filtered PN Moment Closures for Linear Kinetic Equations

Abstract. We propose a positive-preserving moment closure for linear kinetic transport equations based on a filtered spherical harmonic (FPN ) expansion in the angular variable. The recently proposed FPN moment equations are known to suffer from the occurrence of (unphysical) negative particle concentrations. The origin of this problem is that the FPN approximation is not always positive at the...

متن کامل

Positive Polynomials and Sequential Closures of Quadratic Modules

Let S = {x ∈ Rn | f1(x) ≥ 0, . . . , fs(x) ≥ 0} be a basic closed semi-algebraic set in Rn and let PO(f1, . . . , fs) be the corresponding preordering in R[X1, . . . , Xn]. We examine for which polynomials f there exist identities f + εq ∈ PO(f1, . . . , fs) for all ε > 0. These are precisely the elements of the sequential closure of PO(f1, . . . , fs) with respect to the finest locally convex ...

متن کامل

Positive solutions for nonlinear systems of third-order generalized sturm-liouville boundary value problems with $(p_1,p_2,ldots,p_n)$-laplacian

In this work, byemploying the Leggett-Williams fixed point theorem, we study theexistence of at least three positive solutions of boundary valueproblems for system of third-order ordinary differential equationswith $(p_1,p_2,ldots,p_n)$-Laplacianbegin{eqnarray*}left { begin{array}{ll} (phi_{p_i}(u_i''(t)))'  +  a_i(t) f_i(t,u_1(t), u_2(t), ldots, u_n(t)) =0 hspace{1cm} 0  leq t leq 1, alpha_i u...

متن کامل

Collapsing Closures

A description in the Jacobs and Langen domain is a set of sharing groups where each sharing group is a set of program variables. The presence of a sharing group in a description indicates that all the variables in the group can be bound to terms that contain a common variable. The expressiveness of the domain, alas, is compromised by its intractability. Not only are descriptions potentially exp...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

ژورنال

عنوان ژورنال: SIAM Journal on Scientific Computing

سال: 2010

ISSN: 1064-8275,1095-7197

DOI: 10.1137/090764918