Computationally efficient models for quantization effects in MOSelectron and hole accumulation layers

In this paper, models appropriate for device simulators are developed which account for the quantum mechanical nature of accumulated regions. Accumulation layer quantization is important in deep submicron (⩽0.25 μm) MOS devices in the overlapped source/drain extension regions, in accumulation mode SOI devices, and in buried-channel PMOS structures. Computationally efficient models suitable for routine device simulation are presented that predict the reduction of the accumulated net electron (hole) sheet charge when quantization of the electron (hole) accumulation region is accounted for. The results of comparisons with self-consistent simulations support the validity of these models. In addition, simulation results will be shown which illustrate that when inversion layer quantum mechanical effects are modeled, it is also necessary to account for accumulation layer quantum mechanical effects in order to obtain more physically accurate as well as numerically stable solutions     

Abnormal grain growth in a medium-carbon microalloyed steel

An experimental study on the grain growth of a medium-carbon V-Ti microalloyed steel with two levels of AIN has been carried out. A system to study grain-size distributions in order to detect the abnormal grain growth has been proposed. Log-normal distributions were verified and then properties of normal distributions were applied to distinguish normal and abnormal grains. The benefits of working with the relative difference (RD) of grain size in order to compare the grain-growth behaviour have been discussed. It was experimentally concluded that abnormal growth appears when RD is larger than 2.5. From the results a map of abnormal grain growth against time and temperature could be plotted. It was concluded that abnormal grain growth is due to the AIN dissolution when the above maps are correlated with the theoretical volume fraction of precipitates. The importance and effect of heating rate have also been shown: high heating rates can produce abnormal growth at higher temperatures than those of the equilibrium dissolution.     

Analysis of sectoral energy and exergy use of Saudi Arabia

This paper presents the analysis of sectoral energy and exergy utilization of Saudi Arabia by considering the energy and exergy flows for the 12 years between 1990 and 2001. Sectoral energy and exergy efficiencies are obtained for the subsectors and the devices used in each sector. Energy and exergy flow diagrams for Saudi Arabia are also presented, respectively, to illustrate the situation on how energy and exergy efficiencies vary in each sector. The residential sector appears to be the most energy efficient sector, and the industrial sector to be the most exergy efficient. It is believed that the current methodology is useful for analyzing sectoral energy and exergy utilization, which will help Saudi Arabia with energy savings through energy efficiency and/or energy conservation measures. It is also be helpful to establish standards to facilitate application in various sectors and processes for a sustainable energy planning. Copyright © 2004 John Wiley & Sons, Ltd.     

Fractionation and analysis of fluorescent products of lipid peroxidation

The fluorescence excitation spectrum of model conjugated Schiff base compounds that arise from the reaction of malonaldehyde with amino acids was shown to contain a maximum at 260–280 nm in addition to the previously observed maximum at 350–390 nm. Excitation at either maximum results in emission at a single maximum at 440–480 nm. The excitation and emission maxima of the model fluorescent compounds, together with the characteristic reductions in fluorescence intensity caused by alkaline pH or heavy metal coordination, provide criteria with which to examine lipid peroxidation products for the presence of the conjugated Schiff base fluorophore. Silicic acid column chromatography and silica gel thin layer chromatography were employed to fractionate the fluorescent products of model lipid peroxidation systems and of rat testicular lipid soluble extracts. These products contained large families of compounds whose fluorescence characteristics were the same as those of the Schiff base floorophores. The fractionation methods used enabled more thorough fluorescence characterization of many of the products of lipid peroxidation, but the fluores-cence criteria available do not provide definitive proof of structure.     

Comparative analysis of mass transfer at vibrating electrodes

The application of oscillatory flows to electrochemical processes was found to increase the rate of mass transfer and improve the quality of deposit. Various mechanisms to which this phenomenon is attributable are discussed and expressions for the average rate of mass transfer, resulting thereof, are derived. Comparison with experimental data indicates that the stretched-film concept, although an oversimplification of the physical situation, is most successful in correlating the data.Nomenclature A Amplitude of oscillatory motion (cm) - c Concentration of the diffusing species (g mol cm^–3) - D Diffusivity (cm² s^–1) - F Frequency of oscillation (Hz) - k Instantaneous mass transfer coefficient (cm s^–1) - ¯k _vib Time-average vibratory mass transfer coefficient (cm s^–1) - L Length of active area (cm) - S Velocity gradient at solid-liquid interface (cm s^–1 cm^–1) - u Oscillatory velocity of fluid layers adjacent to the electrode (cm s^–1) - _u Rel Relative velocity between the electrode and the bulk of the fluid (cm s^–1) - v Relative velocity between the electrode and the fluid layers adjacent to it (cm s^–1) - W Width of active area (cm) - x Distance along the surface of the electrode (cm) - z Distance perpendicular to the surface of the electrode (cm) - Dimensionless distance=z(S/9Dx)^1/3 - Dimensionless distance=z ²/2 - Kinematic viscosity of the electroyte (cm² s^–1) - Angular frequency=2F     

Degradation of cyanobacteria toxin by advanced oxidation processes

Advanced oxidation processes (AOPs) using O(3), H(2)O(2), O(3)/H(2)O(2), O(3)/Fe(II), and Fenton treatment were investigated for the degradation of aqueous solutions of cyanobacteria. The effects of concentration of reactants, temperature, and pH on toxins degradation were monitored and the reaction kinetics was assessed. O(3) alone or combined with either H(2)O(2) or Fe(II) were efficient treatment for toxins elimination. A higher toxin oxidation tendency was observed with Fenton reaction; total toxins degradation (MC-LR and MC-RR) was achieved in only 60s. The ozonation treatment was successfully described by second-order kinetics model, with a first-order with respect to the concentration of either ozone or toxin. At 20 degrees C, with initial concentration of MC-LR of 1mg/L, the overall second-order reaction rate constant ranged from 6.79 x 10(4) to 3.49 x 10(3)M(-1)s(-1) as the solution pH increased from 2 to 11. The reaction kinetics of the other AOPs (O(3)/H(2)O(2), O(3)/Fe(II), and Fenton), were fitted to pseudo first-order kinetics. A rapid reaction was observed to took place at higher initial concentrations of O(3), H(2)O(2) and Fe(II), and higher temperatures. At pH 3, initial concentration of toxin of 1mg/L, the pseudo first-order rate constant, achieved by Fenton process, was in order of 8.76+/-0.7s(-1).