Theoretical Study of Natural Convection Flows in Closed-End Cylindrical Vessels Final Report

Analytical solutions of natural convection flows in closed-end cylindrical vessels to obtain exact temperature and velocity distributions in laminar flow region under steady state conditio

Subsonic flow and supersonic cross-flow near the center portion of a wing Final technical report

Analysis of supersonic conical flow and solutions for subsonic region on compression side of delta win

Correlated Spectral and Temporal Variability in the High-Energy Emission from Blazars

Blazar flare data show energy-dependent lags and correlated variability between optical/X-ray and GeV-TeV energies, and follow characteristic trajectories when plotted in the spectral-index/flux plane. This behavior is qualitatively explained if nonthermal electrons are injected over a finite time interval in the comoving plasma frame and cool by radiative processes. Numerical results are presented which show the importance of the effects of synchrotron self-Compton cooling and plasmoid deceleration. The use of INTEGRAL to advance our understanding of these systems is discussed.Comment: 8 pages, 5 figures, uses epsf.sty, rotate.sty Invited paper in "The Extreme Universe," 3rd INTEGRAL Workshop, 14-18 September 1998, Taorimina, Ital

On Error Torques of Squeeze-film Cylindrical Journal Bearings

Error torques of squeeze film cylindrical journal bearing

Atmospheric teleconnection mechanisms of extratropical North Atlantic SST influence on Sahel rainfall

Extratropical North Atlantic cooling has been tied to droughts over the Sahel in both paleoclimate observations and modeling studies. This study, which uses an atmospheric general circulation model (GCM) coupled to a slab ocean model that simulates this connection, explores the hypothesis that the extratropical North Atlantic cooling causes the Sahel droughts via an atmospheric teleconnection mediated by tropospheric cooling. The drying is also produced in a regional climate model simulation of the Sahel when reductions in air temperature (and associated geopotential height and humidity changes) from the GCM simulation are imposed as the lateral boundary conditions. This latter simulation explicitly demonstrates the central role of tropospheric cooling in mediating the atmospheric teleconnection from extratropical North Atlantic cooling. Diagnostic analyses are applied to the GCM simulation to infer teleconnection mechanisms. An analysis of top of atmosphere radiative flux changes diagnosed with a radiative kernel technique shows that extratropical North Atlantic cooling is augmented by a positive low cloud feedback and advected downstream, cooling Europe and North Africa. The cooling over North Africa is further amplified by a reduced greenhouse effect from decreased atmospheric specific humidity. A moisture budget analysis shows that the direct moisture effect and monsoon weakening, both tied to the ambient cooling and resulting circulation changes, and feedbacks by vertical circulation and evaporation augment the rainfall reduction. Cooling over the Tropical North Atlantic in response to the prescribed extratropical cooling also augments the Sahel drying. Taken together, they suggest a thermodynamic pathway for the teleconnection. The teleconnection may also be applicable to understanding the North Atlantic influence on Sahel rainfall over the twentieth century

Development and performance of IR detectors in the 1.5 to 2.4 micrometer region that operate at 240 K

High performance 1.5 to 2.4 micrometers (Hg,Cd)Te photodetectors for operating at 240 K or above are discussed. The detailed characterization of the detector with respect to detector temperature and background flux led to a development of an empirical model for minority carrier trapping. The concept of detective time constant is presented and successfully demonstrated by the four detectors delivered on this contract. An alternative approach is presented with the use of photovoltaic (Hg,Cd)Te detectors

Flavor SU(3) analysis of charmless B->PP decays

We perform a global fits to charmless $B \to PP$ decays which independently constrain the $(\bar\rho,\bar\eta)$ vertex of the unitarity triangle. The fitted amplitudes and phase are used to predict the branching ratios and CP asymmetries of all decay modes, including those of the $B_s$ system. Different schemes of SU(3) breaking in decay amplitude sizes are analyzed. The possibility of having a new physics contribution to $K \pi$ decays is also discussed.Comment: 3 pages, 2 figs. Talk given at EPS-HEP07 To appear in the proceedings, Reference adde