Analysis of multistage amplifiers with hybrid cascode feedforward compensation using a modified model for load impedance

Hybrid cascode feedforward compensation (HCFC) is an effective technique to stabilize nano-scale three-stage amplifiers driving ultra-large load capacitors. It divides the compensation capacitance and shares it between two high-speed local feedback loops embedded within the amplifier core. In this article, a systematic approach to analyze the transfer function and to evaluate the pole expressions of nano-scale HCFC amplifiers is presented. For the first time, the equivalent output impedance is successfully modeled to approximate the complicated transfer function of the HCFC amplifier without the need for lengthy pencil-and-paper calculations. An HCFC amplifier is designed and simulated in 90-nm CMOS technology, to verify the effectiveness of the new analytic approach. The simulated transfer function of the amplifier is almost identical to a calculated transfer function derived based on the new model.     

Mining and fusion of petroleum data with fuzzy logic and neural network agents

Analyzing data from well logs and seismic is often a complex and laborious process because a physical relationship cannot be established to show how the data are correlated. In this study, we will develop the next generation of “intelligent” software that will identify the nonlinear relationship and mapping between well logs/rock properties and seismic information and extract rock properties, relevant reservoir information and rules (knowledge) from these databases. The software will use fuzzy logic techniques because the data and our requirements are imperfect. In addition, it will use neural network techniques, since the functional structure of the data is unknown. In particular, the software will be used to group data into important data sets; extract and classify dominant and interesting patterns that exist between these data sets; discover secondary, tertiary and higher-order data patterns; and discover expected and unexpected structural relationships between data sets.     

Hybrid cascode compensation with feedforward stage for high-speed area-efficient three-stage CMOS amplifiers

Hybrid cascode feedforward compensation (HCFC) is proposed for low-power area-efficient three stage amplifiers driving large capacitive loads. With no overhead in power or area, the total compensation capacitor is divided and shared between two internal high-speed loops instead of solely one loop as is common in prior art. Detailed analysis of HCFC shows significant improvement in terms of stability and bandwidth. This is verified for a 1.2-V amplifier driving a 500-pF capacitive load in 90-nm CMOS technology, where HCFC reduces the total capacitor size and improves the gain-bandwidth by at least 30 and 40 %, respectively, compared to the prevailing schemes.     

Determining the occurrence time of different stages of asphaltene aggregation using molecular dynamics simulations

This work presents a framework for future studies to better understand the appropriate time to include chemical inhibitors at different stages of asphaltene aggregation in the oil. For this purpose, molecular dynamics (MD) simulations were performed to study the aggregation of asphaltene molecules in heptane, in terms of strength, dynamics, and the occurrence time of each stage of aggregation from single molecules to a large flocculate. Results indicate that the nucleation of nanoaggregates begins prior to 10?ns, clusters start forming at 98?ns, and flocculation happens after 120?ns. It was also observed that the final flocculate had a globular shape.     

Hybrid cascode feedforward compensation for nano-scale low-power ultra-area-efficient three-stage amplifiers

A modified frequency compensation technique is proposed for low-power area-efficient three-stage amplifiers driving medium to large capacitive loads. Coined hybrid cascode feedforward compensation (HCFC), the total compensation capacitor is divided and shared between two internal high-speed feedback loops instead of only one loop as is common in prior art. Detailed analysis of this technique shows significant improvement in terms of bandwidth and stability. This is verified for a 1.2-V amplifier driving a 500-pF capacitive load in 90-nm CMOS technology, where HCFC reduces the total capacitor size and improves the gain-bandwidth by at least 30% and 40% respectively, compared to the prevailing schemes.     

Past, present and future intelligent reservoir characterization trends

As we approach the next millennium, and as our problems become too complex to rely only on one discipline to solve them more effectively, multi-disciplinary approaches in the petroleum industry become more of a necessity than professional curiosity. We will be forced to bring down the walls we have built around classical disciplines such as petroleum engineering, geology, geophysics and geochemistry, or at the very least, make them more permeable. Our data, methodologies and approaches to tackle problems will have to cut across various disciplines. As a result, today's “integration”, which is based on integration of results, will have to give way to a new form of integration, that is, integration of disciplines. In addition, to solve our complex problem, one needs to go beyond standard techniques and silicon hardware. The model needs to use several emerging methodologies and soft computing techniques: Expert Systems, Artificial Intelligence, Neural Network, Fuzzy Logic (GL), Genetic Algorithm (GA), Probabilistic Reasoning (PR), and Parallel Processing techniques. Soft computing differs from conventional (hard) computing in that, unlike hard computing, it is tolerant of imprecision, uncertainty, and partial truth. Soft Computing is also tractable, robust, efficient and inexpensive. In this paper, we reveal (explore) the role of Soft Computing techniques in intelligent reservoir characterization and exploration.     

Effects of dry ice on gas permeability of nano-silver-impregnated Populus nigra and Fagus orientalis

Effects of dry-ice treatment (frozen CO(2) at -78.5°C) on gas permeability of untreated and nano-silver-impregnated poplar and beech specimens were studied here on the basis of their biological structure and woody mass as well as their vessel element types. A 200?ppm aqueous dispersion of silver nano-particles was used for impregnation; the size range of silver nano-particles was 20-80?nm. Dry-ice treatment increased gas permeability by 87 and 45% in poplar and beech, respectively. Nano-silver impregnation also increased gas permeability by 190 and 89% in poplar and beech, respectively. Dry-ice treatment on nano-silver-impregnated specimens increased gas permeability even more (31% increase in poplar but only 0.96% in beech). It may be concluded that dry-ice treatment on solid woods may be used as a practical method to increase permeability in species that because of their biological structures are impermeable; since this method alters the biological structure slightly and consequently decreases mechanical strength of solid woods insignificantly, it may substitute methods such as incising to increase permeability.     

Design of low-power single-stage operational amplifiers based on an optimized settling model

Settling behavior of operational amplifiers (opamps) is important in many analog signal-processing applications. In this paper, the analysis of single-stage opamps based on settling time has been performed. A simple yet accurate model for the settling response of first-order opamps that modifies conventional models is proposed to revise the equations. The presented approach leads to a new simple settling-based design methodology for single-stage operational amplifiers. Circuit-level simulations demonstrate the effectiveness of the procedure.     

Mass transport around two spheres at low Reynolds numbers

A relaxation technique has been used to solve the conservation of species equation to obtain mass-transfer rates around two equally sized spheres placed parallel to their line of centers in Stokes' flow. Four different sphere spacings were studied in the Peclét number range of 0–50. It was found that the overall Sherwood number for either sphere was always less than that of a single isolated sphere, and at low Peclét numbers, overall Sherwood numbers of less than 2 were obtained.     

Three‐stage nested‐Miller‐compensated operational amplifiers: Analysis,design, and optimization based on settling time

In analog signal‐processing applications, settling performance of the employed operational amplifiers (opamps) is usually of great matter. Under low‐voltage environment of modern technologies where only a few transistors are allowed to be stacked, three‐stage amplifiers are gaining more interest. Unfortunately, design and optimization of three‐stage opamps based on settling time still suffer from lack of a comprehensive analysis of the settling behavior and closed‐form relations between settling time/error and other parameters. In this paper, a thorough analysis of the settling response of three‐stage nested‐Miller‐compensated opamps, including linear and non‐linear sections, is presented. This analysis leads to a design methodology which determines the circuit requirements for desired settling time/error. Based on settling time, it allows optimizations in power consumption and area. Copyright © 2010 John Wiley & Sons, Ltd.