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Usual Assumption (usual + assumption)

Distribution by Scientific Domains

Engineering	33%
Chemistry	33%

Selected Abstracts

Power-delay optimization of D-latch/MUX source coupled logic gates

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 1 2005
M. Alioto
In this paper a design strategy for MUX, XOR and D-latch source coupled logic (SCL) gates is proposed. To this end, an analytical model of the delay and the noise margin as a function of the transistors' aspect ratio and bias current is first introduced. Successively, analytical equations of the transistors' aspect ratio to meet a given noise margin specification are derived as a function of the bias current, and are then used along with the delay model to express the delay as an explicit function of the bias current and noise margin. The simplified delay expression explicitly relates speed performance to power dissipation and the noise margin, thereby providing the designer with the required understanding of the trade-offs involved in the design. Therefore, the criteria proposed allow the designer to consciously manage the power-delay trade-off. The delay dependence on the logic swing is also investigated with results showing that this delay is not necessarily reduced by reducing the logic swing, in contrast with the usual assumption. Since the results obtained are valid for all SCL gates and are independent of the CMOS process used, the guidelines provided afford a deeper understanding of SCL gates from a design point of view. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Regional Labour Market Adjustment: Are Positive and Negative Shocks Different?

LABOUR, Issue 2 2002
Sari Pekkala
This paper analyses regional labour market adjustment in the Finnish provinces during 1971,96. It investigates the interrelations of employment, unemployment and labour force participation to examine how a change in labour demand is adjusted to. The study questions the usual assumption that positive and negative shocks evoke similar adjustment processes. Instead, we test for the possibility that the effects of positive and negative shocks are asymmetric. The analysis reveals that there is little asymmetry in the adjustment to region-specific labour demand shocks, but adjustment to total (region-specific plus common component) shocks displays more asymmetry. The region-specific component of a labour demand shock has short-lived effects on unemployment and participation, and its effect on employment is very small but permanent [persistent?]. Initially, most of the fall in employment is absorbed by the unemployment and participation rate, but after a few years migration plays a larger role in the adjustment process. [source]

Schallfeldsimulation mit Spiegelquellen , Eine Planungshilfe für reflexionsarme Räume

BAUPHYSIK, Issue 4 2009
Xueqin Zha Prof.
Schall; Berechnungsverfahren; sound protection and acoustics; calculation methods Abstract Konventionelle Auslegungen von akustischen Freifeldräumen nach ISO 3745 sind häufig mit Risiken behaftet, weil die übliche Annahme eines Absorptionsgrades bei senkrechtem Schalleinfall von 99 % herkömmlicher faseriger oder poröser Auskleidungen von Fall zu Fall weder notwendig noch ausreichend sein kann. Es wird ein Simulationsprogramm vorgestellt, das mit der phasenrichtigen Überlagerung der Schallwellen einer realen Punkt- und einer Serie von Spiegelquellen arbeitet, welche die unvollständig absorbierenden Begrenzungsflächen des Raumes ersetzen. Damit werden verschiedene Einflüsse aufgezeigt, die die Freifeldeigenschaften ebenso stark beeinflussen können wie der Absorptionsgrad der Auskleidung. So lässt sich bereits in einem frühen Planungsstadium mehr Sicherheit über die Qualität eines Akustik-Prüfstandes zur Bestimmung von Schallleistung, Spektrum und Richtcharakteristik technischer Schallquellen gewinnen. Sound field simulation by image sources , A design tool for anechoic rooms. Conventional designs of anechoic rooms according to ISO 3745 often bear risks since the usual assumption of an absorption coefficient at normal incidence of 99 % of traditional fibrous or porous claddings may be not necessary in one case but insufficient in another. A simulation program is presented which is based on the wave interferences of the sound from a real point source and a number of image sources which replace imperfectly absorbing bounding surfaces. Its application demonstrates various effects which can influence the free-field characteristics to the same extent as the absorption of the cladding. By this one may gain more confidence , at an early stage of the planning process , in the quality of an acoustic test facility for the determination of sound power, spectrum and directivity of technical sound sources. [source]

Optimal observability of sustained stochastic competitive inhibition oscillations at organellar volumes

FEBS JOURNAL, Issue 1 2006
Kevin L. Davis
When molecules are present in small numbers, such as is frequently the case in cells, the usual assumptions leading to differential rate equations are invalid and it is necessary to use a stochastic description which takes into account the randomness of reactive encounters in solution. We display a very simple biochemical model, ordinary competitive inhibition with substrate inflow, which is only capable of damped oscillations in the deterministic mass-action rate equation limit, but which displays sustained oscillations in stochastic simulations. We define an observability parameter, which is essentially just the ratio of the amplitude of the oscillations to the mean value of the concentration. A maximum in the observability is seen as the volume is varied, a phenomenon we name system-size observability resonance by analogy with other types of stochastic resonance. For the parameters of this study, the maximum in the observability occurs at volumes similar to those of bacterial cells or of eukaryotic organelles. [source]

Excess thermodynamic properties in liquid binary mixtures

JOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2008
F. Aliotta
Abstract Excess volumes and adiabatic compressibility have been measured in several binary liquid mixtures to answer the question whether structural information can be gained through the analysis of the concentration dependence of the excess quantities. The obtained results are compared with independent indications from Raman spectroscopy, which is able to probe directly the occurrence and the nature of effective intermolecular interactions. Some doubts have arisen against the usual approach adopted for estimating the excess quantities and about the adequacy of the usual assumptions for the reference ideal behaviours. In particular, it is shown how excess compressibility can result just from statistical effects also in absence of any excess volume contribution. The leading idea is supported by the comparison of the experimental data with the results from a naive model for binary mixtures of hard spheres. The model turns out to be able to produce a very wide spectrum of structural and thermodynamic behaviours depending on the values of its parameters and on the nature (additive or non-additive) of the hard-sphere potential. A discussion is proposed on the re-evaluation of excess thermodynamic data and on their ability in providing direct information on intermolecular interactions. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Dynamic policies for uncertain time-critical tasking problems

NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 2 2008
Kevin D. Glazebrook
Abstract A recent paper by Gaver et al. 6 argued the importance of studying service control problems in which the usual assumptions (i) that tasks will wait indefinitely for service and (ii) that successful service completions can be observed instantaneously are relaxed. Military and other applications were cited. They proposed a model in which arriving tasks are available for service for a period whose duration is unknown to the system's controller. The allocation of a large amount of processing to a task may make more likely its own successful completion but may also result in the loss of many unserved tasks from the system. Gaver et al. 6 called for the design of dynamic policies for the allocation of service which maximizes the rate of successful task completions achieved, or which come close to doing so. This is the theme of the paper. We utilize dynamic programming policy improvement approaches to design heuristic dynamic policies for service allocation which may be easily computed. In all cases studied, these policies achieve throughputs close to optimal. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008 [source]