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1] In this study, ionospheric solar flare effects on the total electron content (TEC) and associated time rate of change (rTEC) derived from ground-based global positioning system (GPS) receivers in the midday region are examined. The occurrence times and locations of 11 solar flares are isolated from the 1-8 Å X-ray radiations of the geosynchronous operational environmental satellite (GOES) and the SOHO Extreme Ultraviolet Imaging Telescope (EIT) images, respectively, while the TEC and rTEC are obtained from the international GPS services (IGS). Results show that the maximum value of the TEC increase solely depends on the flare class, while the maximum value of the rTEC increase is related to not only the flare class but also the time rate of change in flare radiations. A statistical analysis further demonstrates that the two maximum values are inversely proportional to the cosine of the great circle angle between the center and flare locations on the solar disc.

Convective heat transfer and friction drag in a duct inserted with aluminum foams have been studied experimentally. The combined effects of foam porosity (ε=0.7, 0.8, and 0.95) and flow Reynolds number (1900⩽Re⩽7800) are examined. Frictional drags for flow across the aluminum foam are measured by pressure taps, while interstitial heat transfer coefficients in the aluminum foam are determined using a transient single-blow technique with a thermal non-equilibrium two-equation model. Solid material temperature distribution is further measured for double check of the heat transfer results. To understand the frictional drag mechanisms, smoke-wire flow visualization is conducted in the aluminum-foam ducts. Results show that both the friction factor and the volumetric heat transfer coefficient increase with decreasing the foam porosity at a fixed Reynolds number. In addition, the aluminum foam of ε=0.8 has the best thermal performance under the same pumping power constraint among the three aluminum foams investigated. Finally, empirical correlations for pore Nusselt number are developed in terms of pore Reynolds number under various foam porosities.

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