platinum extraction from different secondary sources has been experimentally tested by many researchers. in this article, dissolution of platinum in aqua-regia solution from two types of spent catalysts (reforming and nitric acid production) was kinetically studied. a variety of kinetic models for heterogeneous solid-liquid reactions, including homogeneous diffusion model, shrinking core model,...

Highly optimized tolerance is a model of optimization in engineered systems, which gives rise to power-law distributions of failure events in such systems. The archetypal example is the highly optimized forest fire model. Here we give an analytic solution for this model which explains the origin of the power laws. We also generalize the model to incorporate risk aversion, which results in trunc...

A modified Rigrod theory that uses a nonhomogeneous gain saturation law is used to model outcoupled, total, and intracavity power from a high-gain and a low-gain cw HF chemical laser with good accuracy. The homogeneous gain saturation law is found to have significant limitations when used to model total power data over a wide range of threshold gain values. The use of a nonhomogeneous gain satu...

We fit the surface-brightness profiles of 21 elliptical galaxies using both the Sérsic function and a new empirical model which combines an inner power law with an outer Sérsic function. The profiles are combinations of deconvolved HST profiles from the literature and ellipse fits to the full WFPC2 mosaic images, and thus span a radial range from ∼ 0. ′′02 to ∼ twice the half-light radius. We a...

[1] A series of hypervelocity impact experiments were conducted at NASA Ames Vertical Range, using spherical copper projectiles and polycrystalline dolomite targets. The intensities of atomic lines and molecular bands in the first 2 microseconds after each impact were measured using a high-speed spectrometer system and assessed as functions of impact velocity (2–5.5 km/s) at a fixed impact angl...

The effect of oleic acid (5 and 10% v/v) and xanthan gum (0.5 and 1% wt) on  partitioning and retention of ethyl acetate and diacetyl from two matrices with a different composition was investigated by applying static head space gas chromatography. Two matrices with different composition have been developed: one containing carbohydrates (xanthan gum) and in the second one, called co...

The morphology of glacial valley can be described in terms of power law or quadratic equations fitted to valley cross-profiles. These two models are used to study the cross-profiles of 86 valley cross-profiles in the Zardkuh Mountain in order to understand the evolutional patterns of valleys. Assessment of using the power law function indicates that b values for both valley sides range from 1.0...