Phase assignment for synthesis of low-power domino circuits

High performance circuit techniques such as domino logic have migrated from the microprocessor world into more mainstream ASIC designs but domino logic comes at a heavy cost in terms of total power dissipation. A set of results related to automated phase assignment for the synthesis of low-power domino circuits is presented: (1) it is demonstrated that the choice of phase assignment at the primary outputs of a circuit can significantly impact lower dissipation in the domino block, and (2) a method to determine a phase assignment that minimises power consumption in the final circuit implementation is proposed. Preliminary experimental results on a mixture of public domain benchmarks and real industry circuits show potential power savings as high as 34% over the minimum area realisation of the logic. Furthermore, the low-power synthesised circuits still meet timing constraints     

Performance analysis of the segment npn anode LIGBT

The performance of a high-voltage lateral insulated gate bipolar transistor (LIGBTs) with segmented n+p/n anode fabricated in junction isolation technology is experimentally investigated at both room and elevated temperatures. Detailed two dimensional numerical modeling of a vertical representation of the structure shows that significant electron current passes through the n/sup +/p/n segment of the anode region during the on-state and when devices are subjected to clamped inductive switching. It is shown that the magnitude of electron current can be controlled by modifying the p-base charge which enables enhancement of the turn-off loss/forward voltage drop tradeoff in comparison to conventional LIGBTs.     

Innovation in power semiconductor industry: past and future

Power microelectronics plays an important role in many of the consumer and industrial applications today. With increase in demand for energy savings and efficient systems, the requirements for rapid advancement in MOS controlled power semiconductor device concepts and technologies are becoming more crucial than ever before. This puts a considerable pressure on industries to be innovative and competitive at the device, technology, manufacturing, and marketing levels. Today manufacturing companies are faced with intensifying competition and a turbulent economic environment. To some extent technology is seen as a means by which firms can strive to adapt to the requirements of this difficult and uncertain environment. On the other hand, rapid rates of technological change and associated shorter product cycles are themselves part of the difficulty, as is the increased blurring of long-established industrial boundaries (Kodama's, 1985) process of "technological fusion". The growing complexity and increased pace of industrial technological change especially in power microelectronics are forcing firms to forge new alliances and to seek greater flexibility and efficiency in responding to market changes. The aim of this paper is to explore these aspects.     

Doppler estimation using a coherent ultrawide-band random noiseradar

The University of Nebraska has developed an ultrawide-band (UWB) coherent random noise radar operating over the 1-2 GHz frequency range. The system achieves phase coherence by using heterodyne correlation of the received signal with a time-delayed frequency-shifted replica of the transmit waveform. Knowledge of the phase of the received signal and its time dependence due to target motion permits the extraction of the mean Doppler frequency from which the target speed can be inferred. Theoretical analysis, simulation studies, and laboratory measurements using a microwave delay line showed that it was possible to estimate the Doppler frequency from targets with linear as well as rotational motion. Field measurements using a photonic delay line demonstrated the success of this technique at a range of about 200 m at target speeds of up to 9 m/s. Analysis shows that the accuracy with which the Doppler frequency can be estimated depends not only on the phase performance of various components within the system, but also upon the random nature and bandwidth (BW) of the transmit waveform, and the characteristics of unsteady target motion     

Volatile aroma compounds of raw and roasted palm kernel

The volatile aroma compounds of raw and roasted palm kernel, isolated by hydrodistillation, were analysed by g.l.c. and g.c.-m.s. A number of compounds have been identified for the first time in this commodity. It was found that δ-lactones and ethyl esters were predominant in the flavour profile. In roasted palm kernels, flavour analysis showed the presence of a number of pyrazines formed during heating. Most of the lactones and esters identified in raw palm kernel were present in the roasted samples also. The flavour concentrate included a number of fatty acids in both the raw and roasted samples, in small amounts.     

Fluorine in Drug Design: A Case Study with Fluoroanisoles

Anisole and fluoroanisoles display distinct conformational preferences, as evident from a survey of their crystal structures. In addition to altering the free ligand conformation, various degrees of fluorination have a strong impact on physicochemical and pharmacokinetic properties. Analysis of anisole and fluoroanisole matched molecular pairs in the Pfizer corporate database reveals interesting trends: 1) PhOCF₃ increases log D by ～1 log unit over PhOCH₃ compounds; 2) PhOCF₃ shows lower passive permeability despite its higher lipophilicity; and 3) PhOCF₃ does not appreciably improve metabolic stability over PhOCH₃. Emerging from the investigation, difluoroanisole (PhOCF₂H) strikes a better balance of properties with noticeable advantages of log D and transcellular permeability over PhOCF₃. Synthetic assessment illustrates that the routes to access difluoroanisoles are often more straightforward than those for trifluoroanisoles. Whereas replacing PhOCH₃ with PhOCF₃ is a common tactic to optimize ADME properties, our analysis suggests PhOCF₂H may be a more attractive alternative, and greater exploitation of this motif is recommended.     

Response of alkali activated fly ash mortars to microwave curing

Volumetric heating provided by microwave curing results in faster property development as compared to conventional heat curing that relies on heat conduction from the skin to the core. This paper discusses the compressive strength and microstructure development of microwave cured NaOH activated fly ash mortars, and relates them to the microwave energy absorption by the material which is a function of its dielectric properties. Microwave curing parameters are chosen so as to eliminate the effects of thermal runaway. Strengths that are comparable to or greater than those of mortars heat cured for 48 h at 75 °C are obtained in less than 120 min of microwave curing. The rate of energy absorption by the mortars is found to be relatively constant for a considerable fraction of the microwave curing duration, attributable to the compensation for the drop in dielectric loss factor as a result of moisture loss by the increase in internal electric field. Compressive strength is shown to be related to the microwave energy absorbed by the specimens, especially during the time when free water is present in the system.     

Analysis of pulsatile flow and its role on particle removal from surfaces

The use of pulsatile flow for energy efficient particle removal from surfaces is evaluated through modeling calculations. The governing equation for pulsatile flow in a channel between parallel plates with an oscillatory pressure input is solved and wall shear stress, identified as a measure for particle removal, calculated for fixed power input. It is observed that as the frequency of oscillation is increased the average wall shear stress with an oscillatory pressure input is higher than the corresponding steady state value only above a critical frequency. Similar results are obtained for pulsatile flow in a pipe. Explanation for this observation is presented based on how velocity profile changes as a function of frequency and consequently its effect on wall shear stress versus power dissipated. Based on these observations we propose that there is a critical frequency above which an oscillatory pressure input will be energy efficient for particle removal.     

Using Stochastic Differential Equation for Verification of Noise in Analog/RF Circuits

Today’s analog/RF design and verification face significant challenges due to circuit complexity, process variations and short market windows. In particular, the influence of technology parameters on circuits, and the issues related to noise modeling and verification still remain a priority for many applications. Noise could be due to unwanted interaction between the circuit elements or it could be inherited from the circuit elements. In addition, manufacturing disparity influence the characteristic behavior of the manufactured circuits. In this paper, we propose a methodology for modeling and verification of analog/RF designs in the presence of noise and process variations. Our approach is based on modeling the designs using stochastic differential equations (SDE) that will allow us to incorporate the statistical nature of noise. We also integrate the device variation due to 0.18μ m fabrication process in an SDE based simulation framework for monitoring properties of interest in order to quickly detect errors. Our approach is illustrated on nonlinear Tunnel-Diode and a Colpitts oscillator circuits.