Radar reflectivity in snowfall

Backscattering properties of dry snowflakes at different microwave frequencies are examined. It is shown that the Rayleigh approximation does not often provide the necessary accuracy for snowflake reflectivity calculations for radar wavelengths used in meteorology; however, another simple approximation, the Rayleigh-Gans approximation, can be safely used for such calculations. Reflectivity-snowfall rate relationships are derived for different snow densities and different radar frequencies. It is shown that dual-wavelength radar measurements can be used for estimating the effective sizes of snowflakes. Experimental data obtained during radar snowfall measurements in the WISP project of 1991 with the NOAA X- and Ka-band radars are found to be consistent with the described theoretical results     

Surface Position-Resolved Thermophysical Properties for Metallic Alloys

Thermophysical properties are collective measures of a material to transport dynamical quantities of physical nature on its surface or through the bulk. As such, the exact nature of couplings between particles in a many-body assembly of building block atoms or molecules sensitively determines their values. The couplings between nearest neighbors are the product of the local elemental composition and the material phase. In this study, thermal cycling of a four-element Wood’s alloy specimen brings out cadmium-rich patches to the top surface of the specimen. An assembly of such patches leads to depth-dependent deviations of elemental composition from that of the bulk. Surface-layer atoms are driven to form a high temperature laser-produced plasma (LPP), and time-resolved spectroscopy of their emissions show the variability of elemental composition over surface positions as well as over depth from the surface. These thermal history-driven composition anomalies contribute to significant variability in the measured values of spectral emissivity and thermal diffusivity.     

Thermal stability of indium-tin-oxide/n-GaAs Schottky diodes

The thermal degradation of ITO Schottky contacts on GaAs has been studied. The rectifying contacts show rapid degradation with heating and could have serious implications for optoelectronic devices that operate at elevated temperatures.<>     

Investigation of the Interaction of Sodium Chloride and Two Amino Sulfonic Acids,HEPES and MOPSO,by EMF Measurements

Ionic interactions in the two systems NaCl-HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid) and NaCl-MOPSO (3-(N-Morpholino)-2-hydroxypropanesulfonic acid) have been studied in terms of their mutual influence on the respective activity coefficients of each component. Activity coefficients for each component of the two systems and for corresponding buffers are calculated from emf measurements of solutions containing NaCl, the aminosulfonic acid, and its conjugate base in a NalSE/solution/AgCl-Ag cell at 5, 15, 25, and 37 °C.     

Compact equivalent circuit model of two‐layer spiral inductors

A compact lumped‐element equivalent circuit model of two‐layer integrated spiral inductors on silicon substrates is developed in this article. Based on this proposed model, excellent agreements are achieved between the measured and simulated S‐parameters for different inductors. Also, both self‐ and mutual inductances of two‐layer inductors are accurately extracted, and their overall performances are understood clearly. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 148–153, 2003.     

Human body detection in wet snowpack by an FM-CW radar

An FM-CW radar system was applied to detect a human body buried in a very wet snowpack. This radar uses the L-band microwave frequency with a maximum output power of 100 mW, and utilizes digital signal processing techniques. Field experiments were carried out to detect and map a human body embedded at a depth of 125 cm in a natural snowpack. The radar is shown to have a potential ability to detect avalanche victims, indicating that it may become a tool for snow rescuer operations     

Forced convection subcooled boiling of binary mixtures

A mode based on an additive mechanism of heat transfer is proposed for forced convection subcooled boiling of binary mixtures. The contributing modes of heat transfer are: (i) the heat transferred as latent heat by the rising bubbles, (ii) the heat transferred as the heat contained in the superheated thermal layer that is removed from the surface in the wake of the rising bubbles and (iii) the single phase forced convection heat transfer from the heating surface not influenced by the bubbles. Experimental data from the literature on binary systems show good agreement with the model, validating the postulated mechanism.