A STUDY OF THE NITRIC ACID OXIDATION OF PETROLEUM ASPHALTENES.

Petroleum asphaltenes have been subjected to progressive oxidation using 70% nitric acid, and the reaction products monitored by elemental analysis. Gas chromatographic-mass spectroscopic (gc-IIs) analysis of products from exhaustive oxidation has also been carried out. The oxidation of asphaltenes rapidly produces both water-soluble and water-insoluble oxygen rich species, some of which can be attributed to products of an aromatic nitration reaction. Massive degradation, in the course of which material is steadily converted to water soluble products, continues with prolonged reaction time. The widespread formation of carboxylic acids accounts only in part for the large oxygen uptake, and the gc-ms evidence suggests that a number of other oxygenated structures, in which carbonyl and hydroxyl groups are likely to be most important, are formed as stable intermediates.     

Nanoantenna with Geometric Diode for Energy Harvesting

A graphene based geometrical diodes coupled with nanoantennas for infrared (IR) energy harvesting has been introduced. The geometrical diode is an electronic device in which the current flow through it is controlled by its geometry. The I–V characteristics of the graphene based geometrical diodes are calculated by the Monte Carlo simulation. Different shapes of graphene geometrical diodes, arrowhead, modified staircase, and quarter-elliptical geometries have been examined. The equivalent impedance, capacitance, and responsitivity of each geometric diode have been calculated. The radiation characteristics of nanoantenna designed at 20.5 THz have been investigated. The IR harvesting using nanoantenna coupled with the graphene geometric diode has been calculated and interpreted. Full-wave simulation for the nanoantenna coupled to the geometric diode has been introduced. The DC voltage collected by the nanoantenna and rectified using the geometrical diode has been calculated.     

Enhanced the optical,electrical, and shielding properties of some alkali-borate glasses doped with lanthanide cerium oxide,CeO2

Sodium borate glass doped with cerium oxide, 0–10 wt%, has been prepared based on the quenching method from the melting point. The XRD, DSC, FTIR, and UV–Vis are used to study the structure, thermal, optical properties and shielding attenuation of the studied materials. XRD analysis showed that the as-prepared samples are amorphous in nature. Increased CeO₂ content in the glassy matrix led to an increase in the glass stability, the dielectric constant value, as well as the optical transparency. The measured shielding parameters of the present study revealed that the glass system containing 10 wt% of CeO₂ exhibits the better photon shielding performance than the glass of 0 wt% CeO₂. Cerium-rich glass showed the highest resistance for both gamma-ray and the fast neutrons among all the present samples. The removal cross-sections varied from between 89?×?10^–3 cm^?1, for the cerium-free sample, and 97?×?10^–3 cm^?1 for cerium-rich sample. Such observation may nominated Ce-rich glass to be used in some shielding and attenuation applications, especially for gamma-ray and fast neutrons applications.

     

Limit laws for terminal nodes in random circuits with restricted fan-out: a family of graphs generalizing binary search trees

We introduce a family of graphs C(n,i,s,a) that generalizes the binary search tree. The graphs represent logic circuits with fan-in i, restricted fan-out s, and arising by n progressive additions of random gates to a starting circuit of a isolated nodes. We show via martingales that a suitably normalized version of the number of terminal nodes in binary circuits converges in distribution to a normal random variate.Received: 23 July 2003, Published online: 29 October 2004     

Random sprouts as internet models,and Pólya processes

The sprout, a tree growing in real time is introduced. The sprout is a generalization and an embedding in time of the standard recursive tree. The sprout is proposed as a model for the growth of the Internet. The tree size is analyzed via an associated two-color stochastic process (the sprout process), which is a special case of the Pólya process. Owing to its potential as a modeling tool, the more general Pólya process is analyzed on average. In addition to the usage of the Pólya process in evaluating sprouts, we also give a heuristic interpretation of the result for Pólya urns, which might be a first step toward understanding several nonclassic urn models, as those with nonconstant row sum and those with multiple eigenvalues.Received: 23 September 2002, Revised: 6 March 2004, Published online: 14 October 2004     

Distances in random digital search trees

Distances between nodes in random trees is a popular topic, and several classes of trees have recently been investigated. We look into this matter in digital search trees. By analytic techniques, such as the Mellin Transform and poissonization, we describe a program to determine the moments of these distances. The program is illustrated on the mean and variance. One encounters delayed Mellin transform equations, which we solve by inspection. In addition to various asymptotics, we give an exact expression for the mean and for the variance in the unbiased case. Interestingly, the unbiased case gives a bounded variance, whereas the biased case gives a variance growing with the number of keys. It is therefore possible in the biased case to show that an appropriately normalized version of the distance converges to a limit. The complexity of moment calculation increases substantially with each higher moment; it is prudent to seek a shortcut to the limit via a method that avoids the computation of all moments. Toward this end, we utilize the contraction method to show that in biased digital search trees the distribution of a suitably normalized version of the distances approaches a limit that is the fixed-point solution of a distributional equation (distances being measured in the Wasserstein metric space). An explicit solution to the fixed-point equation is readily demonstrated to be Gaussian.