3D Simulations to investigate initial condition effects on the growth of Rayleigh–Taylor mixing

The effect of initial conditions on the growth rate of turbulent Rayleigh–Taylor (RT) mixing has been studied using carefully formulated numerical simulations. An implicit large-eddy simulation (ILES) that uses a finite-volume technique was employed to solve the three-dimensional incompressible Euler equations with numerical dissipation. The initial conditions were chosen to test the dependence of the RT growth parameters (α_b, α_s) on variations in (a) the spectral bandwidth, (b) the spectral shape, and (c) discrete banded spectra. Our findings support the notion that the overall growth of the RT mixing is strongly dependent on initial conditions. Variation in spectral shapes and bandwidths are found to have a complex effect of the late time development of the RT mixing layer, and raise the question of whether we can design RT transition and turbulence based on our choice of initial conditions. In addition, our results provide a useful database for the initialization and development of closures describing RT transition and turbulence.     

A MATHEMATICAL MODEL FOR MILD HYDROCRACKING:KINETICS AND PRODUCT YIELDS FROM A CRUDE OIL BLEND IN LIGHT GAS OIL OVER HYDROTREATING CATALYST.

Abstract

Mild hydrocracking of 30% crude oil (Indian Crude oil.North Gujarat base)solution in light gas oil is carried out over a commercial hydrotreating catalyst at a temperature range of 300–450°c and pressure of 6. 8–20.OMpa in laboratory reactor. About 30 to 60% of the long residue (365° c+ cut) in the solution is converted to light distillates.

A mathematical model has been developed to predict the yields of products.     

Characterization of tribocharging properties of powder paint

The charge-to-mass ratio (q/m) of individual particles plays a vital role in the powder coating process. Simultaneous measurements of particle size and electrostatic charge were performed on triboelectrically charged powder paint and other powders in the particle size range 1.0 to 65.0 μm in diameter. An electrical single particle aerodynamic relaxation time (ESPART) analyzer was used to measure electrostatic charge (q) and aerodynamic size (d_a) distributions on a single particle basis and in a noninvasive manner. The powders were triboelectrically charged against nonconducting surfaces. Experimental data show that (1) the magnitude of the charge increases linearly with the surface area of the particle and consequently, the charge-to-mass ratio of the particles decreases inversely with respect to d_a in the entire size range, and (2) twenty to sixty percent of the particles were charged with opposite polarity. The average charge attained by particles larger than 4.0 μm in diameter was less than the Gaussian limit of saturation charge. The charge-to-mass ratio of the bulk powder sample depends upon the range of particle size in the sample. The mass median aerodynamic diameter of the sample studied was 30.0 μm with the geometric standard deviation of 2.0     

Dose and dose-rate dependence of optically stimulated signals in quartz: theoretical simulations

In a recent paper Bailey proposed a general model to describe many optically stimulated luminescence (OSL) and thermoluminescence properties of natural quartz. This model consists of five electron trapping centres and four recombination centres: one of the recombination centres is assumed to be radiative and the remaining non-radiative. This paper investigates some additional aspects of the Bailey model. Firstly, the single-aliquot regenerative-dose (SAR) method has been simulated using the model. It is shown that the simulated natural dose (2 Gy) given to the 'sample' in the simulation can be estimated to within approximately 2% using the SAR method. Furthermore, sensitivity-corrected OSL growth curves have been calculated over a dose range of 0 to 2500 Gy. Using the model, it is also demonstrated that the shape of the sensitivity-corrected OSL growth curve is independent of dose rate, for dose rates of 0.001 Gy x s(-1) and 0.1 Gy x s(-1), over a dose range of 0-500 Gy.     

Constructivist Management of Knowledge,Communication and Enterprise Innovation: Lessons from Indian Experience

Prime movers of enterprise innovation are inside the organisation. The enterprise NIIT, studied in this paper, tells us how elicitation and recognition of knowledge and its contents set an enterprise on the move. Recognised knowledge is actionable. Each act of recognition is an addition to knowledge content, and such additions took place in NIIT through acts of communications and self-searching. These contents form a large collage that cannot be strewn into a single novelistic episode. Perspectives and context, motives and suggestions render to each member of the enterprise different disjoint appearances of knowledge. There are thus many knowledge systems and multiple narrations, each with small episode-like finality. Enterprise innovation is achieved not through any grand episodic integration of all knowledge contents, but by constructively eliciting further new contents of knowledge, and encouraging acts of communications and discourses on this new knowledge. Constructive management of knowledge and communication towards enterprise innovation has thus been defined. Through such constructive management, NIIT enabled itself innovationally and empowered its members in eliciting knowledge and acting communicatively. A critical feature of knowledge work is that it requires multidisciplinary expertise and mutual learning in order to achieve a complex synthesis of highly specialised state-of-the-art technologies and knowledge domains. A convivial work culture and a culture of communicative acts enable sharing of the non-informatised yet recognised contents of knowledge.     

Free Transverse and Lateral Vibration of Beams with Torsional Coupling

The free vibration of beams whose flexural motions in both principal planes are coupled with torsion is investigated by using the dynamic stiffness method. First, the governing differential equations of motion in free vibration are derived using Hamilton’s principle. The dynamic stiffness matrix is then developed from the solution of these differential equations when the oscillatory motion of the beam is harmonic. Finally, the resulting dynamic stiffness matrix is applied with particular reference to the Wittrick–Williams algorithm to carry out the free vibration analysis of a few illustrative examples. The numerical results are discussed and this is followed by some concluding remarks.     

Novel Low-Overhead Operand Isolation Techniques for Low-Power Datapath Synthesis

Power consumption in datapath modules due to redundant switching is an important design concern for high-performance applications. Operand isolation schemes that reduce this redundant switching incur considerable overhead in terms of delay, power, and area. This paper presents novel operand isolation techniques based on supply gating that reduce overheads associated with isolating circuitry. The proposed schemes also target leakage minimization and additional operand isolation at the internal logic of datapath to further reduce power consumption. We integrate the proposed techniques and power/delay models to develop a synthesis flow for low-power datapath synthesis. Simulation results show that the proposed operand isolation techniques achieve at least 40% reduction in power consumption compared to original circuit with minimal area overhead (5%) and delay penalty (0.15%)     

An Analytical 1-D Model for Ion Implantation of Any Species into Single-Crystal Silicon Based on Legendre Polynomials

A computationally-efficient 1-D analytical model for ion implantation of any species into single crystal silicon is presented. By interpolating between a few species, the model can predict as-implanted profiles for all the other species. The model uses Legendre polynomials as basis functions. The results of the model are in good agreement with UT-MARLOWE, which is a physically-based and experimentally verified Monte Carlo simulator.     

Analysis of gate-bias-induced heating effects in deep-submicron ESD protection designs

This paper presents a detailed investigation of the degradation of electrostatic discharge (ESD) strength with high gate bias for deep-submicron salicided ESD protection nMOS transistors, which has significant implications for protection designs where high gate coupling occurs under ESD stress. It has been shown that gate-bias-induced heating is the primary cause of early ESD failure and that this impact of gate bias depends on the finger width of the protection devices. In addition, it has been established that substrate biasing can effectively alleviate the adverse impact of the gate bias and can improve ESD strength despite the gate-coupling level. Improved understanding of ESD behavior for advanced devices under high gate-coupling conditions can extend design capabilities of protection structures.