Welding, brazing, and soldering handbook

Handbook gives information on the selection and application of welding, brazing, and soldering techniques for joining various metals. Summary descriptions of processes, criteria for process selection, and advantages of different methods are given

Full-scale aircraft simulation with cryogenic tunnels and status of the National Transonic Facility

The effect of thermal and caloric imperfections in cryogenic nitrogen on boundary layers was determined to indicate that in order to simulate nonadiabatic laminar or turbulent boundary layers in a cryogenic nitrogen wind tunnel, the flight enthalpy ratio, rather than the temperature ratio, should be reproduced. The absence of significant real gas effects on both viscous and inviscid flows makes it unlikely that there will be large real gas effects on the cryogenic tunnel simulation of shock boundary layer interactions or other complex flow conditions encountered in flight. Condensation effects were studied to determine the minimum usable temperature and indicated that under most circumstances free stream Mach number rather than maximum local Mach number determines the onset of condensation effects

The cryogenic wind tunnel concept for high Reynolds number testing

Theoretical considerations indicate that cooling the wind-tunnel test gas to cryogenic temperatures will provide a large increase in Reynolds number with no increase in dynamic pressure while reducing the tunnel drive-power requirements. Studies were made to determine the expected variations of Reynolds number and other parameters over wide ranges of Mach number, pressure, and temperature, with due regard to avoiding liquefaction. Practical operational procedures were developed in a low-speed cryogenic tunnel. Aerodynamic experiments in the facility demonstrated the theoretically predicted variations in Reynolds number and drive power. The continuous-flow-fan-driven tunnel is shown to be particularly well suited to take full advantage of operating at cryogenic temperatures

Snowmass 2001: Jet Energy Flow Project

Conventional cone jet algorithms arose from heuristic considerations of LO hard scattering coupled to independent showering. These algorithms implicitly assume that the final states of individual events can be mapped onto a unique set of jets that are in turn associated with a unique set of underlying hard scattering partons. Thus each final state hadron is assigned to a unique underlying parton. The Jet Energy Flow (JEF) analysis described here does not make such assumptions. The final states of individual events are instead described in terms of flow distributions of hadronic energy. Quantities of physical interest are constructed from the energy flow distribution summed over all events. The resulting analysis is less sensitive to higher order perturbative corrections and the impact of showering and hadronization than the standard cone algorithms.Comment: REVTeX4, 13 pages, 6 figures; Contribution to the P5 Working Group on QCD and Strong Interactions at Snowmass 200

Traveling wave solutions in the Burridge-Knopoff model

The slider-block Burridge-Knopoff model with the Coulomb friction law is studied as an excitable medium. It is shown that in the continuum limit the system admits solutions in the form of the self-sustained shock waves traveling with constant speed which depends only on the amount of the accumulated stress in front of the wave. For a wide class of initial conditions the behavior of the system is determined by these shock waves and the dynamics of the system can be expressed in terms of their motion. The solutions in the form of the periodic wave trains and sources of counter-propagating waves are analyzed. It is argued that depending on the initial conditions the system will either tend to synchronize or exhibit chaotic spatiotemporal behavior.Comment: 12 pages (ReVTeX), 7 figures (Postscript) to be published in Phys. Rev.

Next-to-Next-to-Leading Order Higgs Production at Hadron Colliders

The Higgs boson production cross section at pp and p\bar{p} colliders is calculated in QCD at next-to-next-to-leading order (NNLO). We find that the perturbative expansion of the production cross section is well behaved and that scale dependence is reduced relative to the NLO result. These findings give us confidence in the reliability of the prediction. We also report an error in the NNLO correction to Drell-Yan production.Comment: 5 pages, 4 figures, minor change

Can Low-Severity Fire Reverse Compositional Change in Montane Forests of the Sierra Nevada, California, USA?

Throughout the Sierra Nevada, nearly a century of fire suppression has altered the tree species composition, forest structure, and fire regimes that were previously characteristic of montane forests. Species composition is fundamentally important because species differ in their tolerances to fire and environmental stressors, and these differences dictate future forest structure and influence fire regime attributes. In some lower montane stands, shade-tolerant, fire-sensitive species have driven a threefold increase in tree density that may intensify the risk of high-severity fire. In upper montane forests, which were historically characterized by longer fire return intervals, the effects of fire exclusion are both less apparent and less studied. Although land managers have been reintroducing fire to lower and upper montane forests for \u3e4 decades, the potentially restorative effects of these actions on species composition remain largely unassessed. We used tree diameter and species data from 51 recently burned and 46 unburned plots located throughout lower and upper montane forests in Yosemite National Park and Sequoia & Kings Canyon National Parks to examine the effects of low-to moderate-severity (hereafter, lower-severity)fire on the demography of seven prevalent tree species. The density of Abies concolor concolor 30–45 cm dbh, A. magnifica Calocedrus decurrens concolor but not for C. decurrens, and (2) variability in tree density among plots that burned at lower severity exceeded the range of tree densities reported in historical data sets. High proportions of shade-tolerant species in some postfire stands may increase the prevalence of shade-tolerant species in the future, a potential concern for managers who seek to minimize ladder fuels and promote forest structure that is less prone to high-severity fire

Applications of QCD

Talk given at XIXth International Symposium on Lepton and Photon Interactions at High Energies (LP 99), Stanford, California, 9-14 August 1999.Comment: latex, 26 page

GSFC Heliophysics Science Division FY2010 Annual Report

This report is intended to record and communicate to our colleagues, stakeholders, and the public at large about heliophysics scientific and flight program achievements and milestones for 2010, for which NASA Goddard Space Flight Center's Heliophysics Science Division (HSD) made important contributions. HSD comprises approximately 323 scientists, technologists, and administrative personnel dedicated to the goal of advancing our knowledge and understanding of the Sun and the wide variety of domains that its variability influences. Our activities include: Leading science investigations involving flight hardware, theory, and data analysis and modeling that will answer the strategic questions posed in the Heliophysics Roadmap; Leading the development of new solar and space physics mission concepts and support their implementation as Project Scientists; Providing access to measurements from the Heliophysics Great Observatory through our Science Information Systems; and Communicating science results to the public and inspiring the next generation of scientists and explorers

Single-Inclusive Jet Production in Polarized pp Collisions at O(alpha_s^3)

We present a next-to-leading order QCD calculation for single-inclusive high-p_T jet production in longitudinally polarized pp collisions within the ``small-cone'' approximation. The fully analytical expressions obtained for the underlying partonic hard-scattering cross sections greatly facilitate the analysis of upcoming BNL-RHIC data on the double-spin asymmetry A_{LL}^{jet} for this process in terms of the unknown polarization of gluons in the nucleon. We simultaneously rederive the corresponding QCD corrections to unpolarized scattering and confirm the results existing in the literature. We also numerically compare to results obtained with Monte-Carlo methods and assess the range of validity of the ``small-cone'' approximation for the kinematics relevant at BNL-RHIC.Comment: 23 pages, 8 eps-figure