591 research outputs found
Navigation/traffic control satellite mission study. Volume 1 - Summary
System of satellites, ground stations, and hardware of various user craft for transoceanic traffic contro
Air traffic control surveillance accuracy and update rate study
The results of an air traffic control surveillance accuracy and update rate study are presented. The objective of the study was to establish quantitative relationships between the surveillance accuracies, update rates, and the communication load associated with the tactical control of aircraft for conflict resolution. The relationships are established for typical types of aircraft, phases of flight, and types of airspace. Specific cases are analyzed to determine the surveillance accuracies and update rates required to prevent two aircraft from approaching each other too closely
The applications of satellites to communications, navigation and surveillance for aircraft operating over the contiguous United States. Volume 1 - Technical report
Satellite applications to aircraft communications, navigation, and surveillance over US including synthesized satellite network and aircraft equipment for air traffic contro
Navigation/traffic control satellite mission study. Volume 2 - Systems analyses
Systems analysis of spacecraft network for transoceanic traffic contro
Navigation/traffic control satellite mission study. Volume 3 - System concepts
Satellite network for air traffic control, solar flare warning, and collision avoidanc
Certainty ranges facilitated explicit and transparent judgments regarding evidence credibility
Objectives: The Grading of Recommendations Assessment, Development and Evaluation approach to rating certainty of evidence includes five domains of reasons for rating down certainty. Only one of these, precision, is easily amenable through the confidence interval to quantitation. The other four (risk of bias, inconsistency, indirectness, and publication bias) are not. Nevertheless, conceptually, one could consider a quantified "certainty range" within which the true effect lies. The certainty range would be at least as wide as the confidence interval and would expand with each additional reason for uncertainty. Study Design and Setting: We have applied this concept to rating the certainty of evidence in the baseline risk of venous thromboembolism (VTE) and bleeding in patients undergoing urological surgery. We considered rating up moderate or low quality evidence when the net benefit of VTE prophylaxis was unequivocally positive, that is, when the smallest plausible value of VTE reduction was greater than the largest plausible value of increased bleeding. To establish whether the net benefit was unequivocally positive, we expanded the range of plausible values by 20% for each of the four nonquantitative domains in which there were serious limitations. Results: We present how we applied these methods to examples of open radical cystectomy and laparoscopic partial nephrectomy. In high-VTE risk laparoscopic partial nephrectomy patients and high-and medium-VTE risk open radical cystectomy patients, results proved robust to expanded certainty intervals, justifying rating up quality of evidence. In low -risk patients, the results were not robust, and rating up was therefore not appropriate. Conclusion: This work represents the first empirical application in a decision -making context of the previously suggested concept of certainty ranges and should stimulate further exploration of the associated theoretical and practical issues. (C) 2018 Elsevier Inc. All rights reserved.Peer reviewe
Formalism for dilepton production via virtual photon bremsstrahlung in hadronic reactions
We derive a set of new formulas for various distributions in dilepton
production via virtual photon bremsstrahlung from pseudoscalar mesons and
unpolarized spin-one-half fermions. These formulas correspond to the leading
and sub-leading terms in the Low-Burnett-Kroll expansion for real photon
bremsstrahlung. The relation of our leading-term formulas to previous works is
also shown. Existing formulas are examined in the light of Lorentz covariance
and gauge invariance. Numerical comparison is made in a simple example, where
an "exact" formula and real photon data exist. The results reveal large
discrepancies among different bremsstrahlung formulas. Of all the leading-term
bremsstrahlung formulas, the one derived in this work agrees best with the
exact formula. The issues of M_T-scaling and event generators are also
addressed.Comment: 37 pages, RevTeX, epsf.sty, 10 embedded figure
Parton distribution functions from nonlocal light-cone operators with definite twist
We introduce the chiral-even and chiral-odd quark distributions as forward
matrix elements of related bilocal quark operators with well-defined
(geometric) twist. Thereby, we achieve a Lorentz invariant classification of
these distributions which differ from the conventional ones by explicitly
taking into account the necessary trace terms. The relations between both kinds
of distribution functions are given and the mismatch between their different
definition of twist is discussed. Wandzura-Wilczek--like relations between the
conventional distributions (based on dynamical twist) are derived by means of
geometric twist distribution functions.Comment: 17 pages, REVTEX, Extended version, The Introduction has been
rewritten, Setion V "Wandzura-Wilczek--like relations" and App. B are added;
Sign errors are correcte
Pion and Rho Structure Functions from Lattice QCD
We calculate the lower moments of the deep-inelastic structure functions of
the pion and the rho meson on the lattice. Of particular interest to us are the
spin-dependent structure functions of the rho. The calculations are done with
Wilson fermions and for three values of the quark mass, so that we can perform
an extrapolation to the chiral limit.Comment: 30pp, LaTeX2e with 15 eps figures using epsfig. Postscript file also
available from ftp://ftp.th.physik.uni-frankfurt.de/pub/cbest/pionrho.ps or
http://www.th.physik.uni-frankfurt.de/~cbest/pionrho.p
He Structure and Mechanisms of He Backward Elastic Scattering
The mechanism of He backward elastic scattering is studied.
It is found that the triangle diagrams with the subprocesses He,
He and He, where and
denote the singlet deuteron and diproton pair in the state,
respectively, dominate in the cross section at 0.3-0.8 GeV, and their
contribution is comparable with that for a sequential transfer of a pair
at 1-1.5 GeV.
The contribution of the , estimated on the basis of the spectator
mechanism of the He reaction, increases the HeHe cross section by one order of magnitude as compared to the
contribution of the deuteron alone.
Effects of the initial and final states interaction are taken into account.Comment: 17 pages, Latex, 4 postscript figures, expanded version, accepted by
Physical Review
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