We have studied the ultrafast optical response of native-oxide terminated Si~001! with pump-probe reflectivity using 800 nm, 28 fs pulses at an excitation density of (5.560.3)310 cm. Time-dependent reflectivity changes comprise third-order-response coherent-transient variations arising from anisotropic state filling and linear-response variations arising from excited free carriers, state fillin...

The surface velocity of a rapidly moving ice stream has been determined to high accuracy and spatial density with the use of sequential satellite imagery. Variations of ice velocity are spatially related to surface undulations, and transverse velocity variations of up to 30 percent occur. Such large variations negate the concept of plug flow and call into question earlier mass-balance calculati...

various sources of geodetic, geological and geophysical information can improve our understanding about the crustal density. in this paper we propose a methodology for determination of crustal density based on terrestrial gravity observations, geopotential models, digital terrain models (dtm), geological maps and cross-sections, deep geophysical profiles, and geoid models. the method can be alg...

fundamental understanding of the goaf gas distribution in a gassy coal mine is necessary for developing effective goaf gas drainage strategies in the longwall coal mine. the goaf gas was subjected to the surface and body forces that were classified depending upon whether they acted on the surface area or the volume of the gas element. of these forces, the body forces were more predominant in di...

â â  a great portion of precipitation in the south western iran falls in the snow formation. surface runoff produced from melting snow has an important role in the recharging ground water, surface and subsurface flows. rapid snowmelt can even cause flooding . since the snowmelt cannot be easily detected from optical satellite images, snow cover area (sca) is derived as an important hydrological...

Al2O3 films were prepared using electron beam evaporation at room temperature. The samples were irradiated with oxygen plasma under different energy. The variations in average surface defect density and root mean square (RMS) surface roughness were characterized using an optical microscope and an atomic force microscope. Surface average defect density increased after plasma treatment. The RMS s...

as a first step towards mechanization related to any product, including date fruit, it is necessary to have comprehensive information about the product. physical and mechanical properties are needed for the design of post harvest machinery and equipment. the objective of this study was to determine and compare some physical properties such as dimension, mass and volume, particulate density, pit...