12,732 research outputs found
Computation of turbulent boundary layers on curved surfaces, 1 June 1975 - 31 January 1976
An accurate method was developed for predicting effects of streamline curvature and coordinate system rotation on turbulent boundary layers. A new two-equation model of turbulence was developed which serves as the basis of the study. In developing the new model, physical reasoning is combined with singular perturbation methods to develop a rational, physically-based set of equations which are, on the one hand, as accurate as mixing-length theory for equilibrium boundary layers and, on the other hand, suitable for computing effects of curvature and rotation. The equations are solved numerically for several boundary layer flows over plane and curved surfaces. For incompressible boundary layers, results of the computations are generally within 10% of corresponding experimental data. Somewhat larger discrepancies are noted for compressible applications
A PROTOCOL OR A SET OF STANDARDS TO GUIDE AGRICULTURAL ECONOMICS RESEARCH
This article examines some difficult decisions that agricultural economists must confront in doing research. Over many years, rules and standards have developed in agricultural economics that guide researchers, providing an underlying framework for research methods. This article deals with applying these seldom discussed guidelines to specific research situations confronted by agricultural economists. With this article, we hope to stimulate a dialogue among agricultural economists about the need for additional, appropriate methodological guidelines in agricultural economics research.Research and Development/Tech Change/Emerging Technologies,
An integrated study of earth resources in the State of California based on Skylab and supporting aircraft data
There are no author-identified significant results in this report
Family Law and Gay and Lesbian Family Issues in the Twentieth Century
Over these thirty years, lesbians and gay men have increasingly challenged conventional definitions of marriage and the family. In this brief article, we tell the story of gay people and family law in the United States across this period. We divide our discussion into two sections: issues regarding the recognition of the same-sex couple relationship and issues regarding gay men and lesbians as parents. These issues overlap, of course, but since family law discussions commonly treat adult-adult issues of all sorts separately from parent-child issues, we believe it convenient and helpful to do so as well
Connected and disconnected quark contributions to hadron spin
By introducing an external spin operator to the fermion action, the quark
spin fractions of hadrons are determined from the linear response of the hadron
energies using the Feynman-Hellmann (FH) theorem. At our SU(3)-flavour
symmetric point, we find that the connected quark spin fractions are
universally in the range 55-70\% for vector mesons and octet and decuplet
baryons. There is an indication that the amount of spin suppression is quite
sensitive to the strength of SU(3) breaking. We also present first preliminary
results applying the FH technique to calculations of quark-line disconnected
contributions to hadronic matrix elements of axial and tensor operators. At the
SU(3)-flavour symmetric point we find a small negative contribution to the
nucleon spin from disconnected quark diagrams, while the corresponding tensor
matrix elements are consistent with zero.Comment: 7 pages, 5 figures, 32nd International Symposium on Lattice Field
Theor
Einstein Cluster Alignments Revisited
We have examined whether the major axes of rich galaxy clusters tend to point
toward their nearest neighboring cluster. We have used the data of Ulmer,
McMillan, and Kowalski, who used position angles based on X-ray morphology. We
also studied a subset of this sample with updated positions and distances from
the MX Northern Abell Cluster Survey (for rich clusters () with well
known redshifts). A Kolmogorov-Smirnov (KS) test showed no significant signal
for nonrandom angles on any scale Mpc. However, refining the
null hypothesis with the Wilcoxon rank-sum test, we found a high confidence
signal for alignment. Confidence levels increase to a high of 99.997% as only
near neighbors which are very close are considered. We conclude there is a
strong alignment signal in the data, consistent with gravitational instability
acting on Gaussian perturbations.Comment: Minor revisions. To be published in Ap
Applications of the Feynman-Hellmann theorem in hadron structure
The Feynman-Hellmann (FH) relation offers an alternative way of accessing
hadronic matrix elements through artificial modifications to the QCD
Lagrangian. In particular, a FH-motivated method provides a new approach to
calculations of disconnected contributions to matrix elements and high-momentum
nucleon and pion form factors. Here we present results for the total nucleon
axial charge, including a statistically significant non-negative total
disconnected quark contribution of around at an unphysically heavy pion
mass. Extending the FH relation to finite-momentum transfers, we also present
calculations of the pion and nucleon electromagnetic form factors up to
momentum transfers of around 7-8 GeV. Results for the nucleon are not able
to confirm the existence of a sign change for the ratio , but
suggest that future calculations at lighter pion masses will provide
fascinating insight into this behaviour at large momentum transfers
Principles of Record of Performance in Beef Cattle
This publication provides a summary of the basic principles that should be considered in Record of Performance Programs with beef cattle. These principles are based on the results of research being conducted under Regional Project NC-1 as interpreted by the research personnel who participate in this effort
Disconnected contributions to the spin of the nucleon
The spin decomposition of the proton is a long-standing topic of much
interest in hadronic physics. Lattice QCD has had much success in calculating
the connected contributions to the quark spin. However, complete calculations,
which necessarily involve gluonic and strange-quark contributions, still
present some challenges. These "disconnected" contributions typically involve
small signals hidden against large statistical backgrounds and rely on
computationally intensive stochastic techniques. In this work we demonstrate
how a Feynman-Hellmann approach may be used to calculate such quantities, by
measuring shifts in the proton energy arising from artificial modifications to
the QCD action. We find a statistically significant non-zero result for the
disconnected quark spin contribution to the proton of about -5% at a pion mass
of 470 MeV
- …