Analysis of the conditions for the worst case switching activity in integrated circuits

Relentless advances in IC technologies have fueled steady increases on fabricated component density and working frequencies. As feature sizes decrease to nanometer scales, an increase in switching activity per unit of area and time is observed. When extreme switching activity occurs in a small region of an integrated circuit, malfunctions may be triggered that compromise behavior. This can be either a consequence of a decrease in bias levels in the power grid caused by IR-Drop, or due to unexpected glitching on gates’ outputs caused by ground bounce. For proper circuit verification, both conditions have to be accurately estimated and accounted for. Achieving this in an accurate manner for a large circuit is a very challenging problem. In this paper we propose and compare methods for the identification of the conditions leading to extreme situations of switching activity in integrated circuits. Our approach is based on both spatial and time partitioning which are used to address the accuracy and computational requirements. We propose a method for determining the exact conditions for worst case switching activity in a small circuit area during a short time interval. We then show how this method can be combined with partitioning to allow for accurate full circuit verification.     

Optimization of the culture medium composition using response surface methodology for new recombinant cyprosin B production in bioreactor for cheese production

The optimization of culture medium composition was carried out for improvement the recombinant cyprosin B production, an enzyme with high milk-clotting activity. Response surface methodology (RSM) was applied to evaluate the effect of variables namely glucose, yeast extract (YE) and bactopeptone present in the culture medium, used for recombinant cyprosin B production by transformed Saccharomyces cerevisiae BJ1991 strain in shake-flask and bioreactor culture conditions. The central composite experimental design (CCD) was adopted to derive a statistical model for optimizing the composition of the fermentation medium. The optimal concentration estimated for each variable related to a theoretical maximum of cyprosin B activity (488 U mL⁻¹) was 30 g L⁻¹ glucose, 15 g L⁻¹ YE and 27 g L⁻¹ bactopeptone. The optimized medium composition, based on empirical model, led to a cyprosin B activity of 519 U mL⁻¹, which corresponds to an increase of 46%. The fermentation using optimized culture medium in a 5-L bioreactor allowed a significant increase in biomass (82%) and recombinant cyprosin B production (139%). The improvement in the recombinant cyprosin B production after optimization process can be considered adequate for large-scale applications, and the clotting activity of cyprosin B account for their use in industrial cheese making.     

A CFD approach to the atmospheric dispersion of radionuclides in the vicinity of NPPs

Most studies of atmospheric dispersion of radionuclides released from Nuclear Power Plants (NPPs) are based on Gaussian plume models or on the use of a convection–diffusion equation. Such methods, which do not involve solving the flow problem, are useful in the atmospheric mesoscale, of the order of 2–2000 km from the NPP. However, they do not account for the turbulence generated by the interaction of the wind with obstacles and with the released material stream, which are the dominant factors in the local scale, of the order of 0–2 km from the source of emission. Here, the authors advocate the use of computational fluid dynamics (CFD) to study the dispersion problem. The physical model comprises the Navier–Stokes equations, a convection–diffusion energy equation, and transport equations for the radionuclides. The paper details the stabilized finite element formulation used, stressing its connection with the variational multiscale/large eddy simulation approach. Adaptive techniques combining error estimation and remeshing are also employed. The method is implemented on a Beowulf parallel computing system using domain decomposition and the message passing interface (MPI). Controlled emissions from a chimney and release from severe accidents have been simulated, showing the importance of the local phenomena on the dispersion problem.     

Vibrations of axially moving flexible beams made of functionally graded materials

Problems related to the vibrations of axially moving flexible beams made of functionally graded materials are addressed. The problem of an axially moving beam may be interpreted as a telescopic system in which the mass is not constant, the mechanism of elastic deformation is transverse bending. A thin-walled beam with annular cross-section is analyzed, in which a continuously graded variation in the composition of ceramic and metal phases across the wall thickness with a simple power law is considered. In this paper a finite element scheme is employed to obtain numerical approximations to the variational equation of the problem. Normally, finite element approaches use fixed-size elements, however, for this kind of problems the increase of the number of elements, step by step as the mass enters, is a cumbersome task. For this reason an approach based on a beam-element of variable domain is adopted. The length of the element is a prescribed function of time. Results highlighting the effects of the beam flexibility, tip mass and material constituents on the dynamics of the axially moving beams are presented and the corresponding conclusions are given.     

Impact of avoidance angle mitigation techniques on the interference produced by non‐GSO systems in a multiple non‐GSO interference environment

This paper adresses the impact of avoidance angle mitigation techniques on the interference produced by non‐GSO systems in a multiple non‐GSO interference environment. It considers a situation involving a victim LEO system and two other non‐GSO interfering systems (one MEO and another LEO) that mitigate around (and only around) the victim LEO system. Interference statistics are obtained using the so called Analytical Method for non‐GSO interference computations. The methodology described, including the interference model adopted, and the type of result obtained in Section 3, that shows the variation of the percentage of the total time allowance used by the interference as a function of the Earth station‐based and the satellite‐based avoidance angles, are very helpful in the process of selecting adequate values for these angles. The burden imposed on the mitigating systems by the use of avoidance angle strategies was evaluated through its impact on the coverage capability of the mitigating systems. Copyright © 2003 John Wiley & Sons, Ltd.     

Vascular anatomy at the ureteropelvic junction

In roosters, fertility peaks to 96% at 32 weeks, shortly after sexual maturation, and then declines rapidly to 68% at 70 weeks and to less than 10% at 110 weeks, as a result of intratesticular retention of spermatozoa. The reduction in fertility is associated with functional structural changes of the interstitial tissue, reflected in decreased plasma androgen levels from 2.7 ng/ml at 32 weeks to less than 0.5 ng/ml at 110 weeks. In high fertility roosters, the interstitial tissue is tightly packed with Leydig cells, which contain relatively large amounts of rough endoplasmic reticulum and lipid droplets, both related to androgen synthesis. In the old rooster, which has a low fertility, the interstitial tissue contains only occasional Leydig cells within an enlarged intercellular space. These Leydig cells contain small amounts of endoplasmic reticulum, mainly rough, and there are low plasma androgen levels. It is concluded that differentiation of roosters' interstitial tissue is reflected by plasma levels of androgen. This, in turn, is related to the mechanism of spermatozoa release from Sertoli cells and, consequently, with the level of fertility.     

Volatile components of mangaba fruit (Hancornia speciosa Gomes) at three stages of maturity

The effect of stage of maturity on the volatile components of mangaba fruit (Hancornia speciosa Gomes) growing at Sergipe State, Brazil, was investigated at three different stages. The volatile profile obtained by hydrodistillation, using a Clevenger-type apparatus, was analysed by GC–FID and GC–MS. It was possible to identify 33 compounds in the immature fruits, such as 1-octen-3-ol (2.8%), (Z)-linalool oxide (9.1%), (E)-linalool oxide (6.3%), linalool (16.1%), 2-phenylethanol (4.5%), α-terpineol (5.5%), geraniol (3.1%), hexadecanal (2.5%) and octadecanol (2.7%); 34 compounds in the fruits at the intermediate stage, such as ethyl propanoate (4.1%), n-propyl acetate (11.1%), 3-methyl-3-buten-1-ol (6.8%), 2-methyl propyl acetate (2.5%), furfural (18.6%), (Z)-3-hexenol (3.2%), 1-hexanol (2.4%), 3-methyl-3-buten-1-yl acetate (5.4%), (Z)-3-hexen-1-yl acetate (2.9%), n-hexyl acetate (3.3%), (Z)-linalool oxide (3.9%), (E)-linalool oxide (2.4%), linalool (3.8%), 2-phenylethanol (2.8%) and α-terpineol (2.5%); and 32 components in the mature fruits, such as 3-hydroxy-2-butanone (9.1%), 2,4,5-trimethyl-1,3-dioxolane (6.8%), 3-methyl-3-buten-1-ol (12.1%), 3-methyl-1-butanol (5.2%), furfural (8.3%), 3-methyl-1-butanyl acetate (8.8%) and 3-methyl-3-buten-1-yl acetate (28.2%).     

Expression of ion channels during differentiation of a human skeletal muscle cell line

An immortal, cloned cell line (RCMH), obtained from human skeletal muscle was established in our laboratory and shown to express muscle specific proteins. We measured ligand binding to ion channels, ion currents using whole cell patch clamp and intracellular calcium both in cells grown in complete media and in cells grown for 4-40 days in media supplemented with hormones and nutrients (differentiating media). Markers for differentiated muscle, such as the muscle isoform of creatine kinase and the cytoskeletal proteins alpha-actinin, alpha-sarcomeric actin, myosin and titin were present in early stages. Receptors for gamma toxin from Tityus serrulatus scorpion venom, a specific modulator for voltage dependent sodium channels, were present (0.9-1.0 pmol mg-1 protein) during stage 1 (0-6 days in culture with differentiating media) and increased by 50% in stage 3 (more than 10 days in differentiating media). High and low affinity dihydropyridine receptors present in stage 1 convert into a single type of high affinity receptors in stage 3. Both intracellular calcium release and InsP3 receptors were evident in stage 1 but ryanodine receptors were expressed only in stage 3. RCMH cells showed no voltage sensitive currents in stage 1. Between 7 and 10 days in differentiating media (stage 2), an outward potassium current was observed. Small inward currents appeared only in stage 3; we identified both tetrodotoxin sensitive and tetrodotoxin resistant sodium currents as well as calcium currents. This pattern is consistent with the expression of voltage dependent calcium release before appearance of both the action potential and ryanodine receptors.     

A new algorithm for the robust optimization of rotor-bearing systems

This article presents a new algorithm for the robust optimization of rotor-bearing systems. The goal of the optimization problem is to find the values of a set of parameters for which the natural frequencies of the system are as far away as possible from the rotational speeds of the machine. To accomplish this, the penalization proposed by Ritto, Lopez, Sampaio, and Souza de Cursi in 2011 is employed. Since the rotor-bearing system is subject to uncertainties, such a penalization is modelled as a random variable. The robust optimization is performed by minimizing the expected value and variance of the penalization, resulting in a multi-objective optimization problem (MOP). The objective function of this MOP is known to be non-convex and it is shown that its resulting Pareto front (PF) is also non-convex. Thus, a new algorithm is proposed for solving the MOP: the normal boundary intersection (NBI) is employed to discretize the PF handling its non-convexity, and a global optimization algorithm based on a restart procedure and local searches are employed to minimize the NBI subproblems tackling the non-convexity of the objective function. A numerical analysis section shows the advantage of using the proposed algorithm over the weighted-sum (WS) and NSGA-II approaches. In comparison with the WS, the proposed approach obtains a much more even and useful set of Pareto points. Compared with the NSGA-II approach, the proposed algorithm provides a better approximation of the PF requiring much lower computational cost.     

The use of fibrous ion exchangers in gold hydrometallurgy

This article examines a family of ion-exchange fibers, FIBAN, containing primary and secondary amine groups. These ion exchangers have a fiber diameter of 20–40 Μm, high osmotic and mechanic stability, a high rate of adsorption and regeneration, and excellent dynamic characteristics as filtering media. Inparticular, this article discusses the use of FIBAN fibrous ion exchangers in the recovery of gold cyanide andbase-metal cyanides (copper and mercury) from mineral-leaching solutions. The influence of polymer structure and water content on their extraction ability is described, along with key parameters of gold hydrometallurgy such as extraction efficiency, selectivity, pH dependence, gold cyanide loading, kinetics, and stripping.