Current outlook: sustained growth, sustained inflation

A report on the May 4, 1990 meeting of the Fourth District Economists' Roundtable, at which participants predicted a stronger long-term growth rate for the national economy through 1991 and an inflation rate of about 4 percent.Economic conditions - United States

Sustained arc ignition system

Circuitry for maintaining an arc or spark across a spark gap for a desired length of time is disclosed. A high voltage, direct current source is connected in series with a secondary winding of a high voltage, stepup transformer or coil and a spark gap such as a spark plug for example. The high voltage source may be on continuously or may be turned on and off by a control circuit such as a solid state switch which is, in turn, responsive to a timing device such as a set of ignition contact points or a magnetic pulse generator operating in synchronism with a spark ignition engine. The timing device also provides signals to a current switching circuit which interrupts, current flow through a primary winding of the high voltage coil at the prescribed time that a spark is desired at the spark gap

Effect of sustained attention on Early Start Denver Model outcomes

Introduction: There is very little research on the use of sustained attention as an outcome predictor for the Early Start Denver Model (ESDM). We hypothesized that a child’s level of sustained attention prior to therapy will correlate with positive ESDM outcomes. Methods: 10 pre-preschool age children with a diagnosis of autism spectrum disorder received one year of ESDM therapy. A novel coding scheme was developed to evaluate each child’s pre-treatment level of sustained attention. Mullen Scales of Early Learning were evaluated prior to and after one year of ESDM. Pre-treatment levels of sustained attention were compared to pre-and post-treatment Mullen scores. Sustained attention was evaluated as an outcome predictor for ESDM. Results: Preliminary results identified a positive correlation between the duration of an episode of sustained attention and the pre- and post-treatment Mullen scores. A positive correlation was also identified between the functional use of an object during an episode of sustained attention and the pre- and post-treatment Mullen scores. Conclusion: Preliminary results support the hypothesis that a child’s level of sustained attention prior to therapy will correlate with positive ESDM outcomes. More participants are required to confirm the significance of the preliminary results

Alternatives for sustained disaster risk reduction

The daily media is filled with images of catastrophic events which seem increasingly frequent and violent In parallel there are a large range of scientific studies debates in the policy arena, and a growing number of international institutions focused on disaster reduction. But a paradox remains that despite advances in technology, disasters continue to increase, affecting many individuals in rich as well as poor countries

Combustion instability sustained by unsteady vortex combustion

The determination of an internal feedback mechanism which leads to combustion instability inside a small scale laboratory combustor is presented in this paper. During combustion instability, the experimental findings show that a large vortical structure is formed at an acoustic resonant mode of the system. The subsequent unsteady burning, within the vortex as it is convected downstream, feeds energy into the acoustic field and sustains the large resonant oscillations. These vortices are formed when the acoustic velocity fluctuation at the flameholder is a large fraction of the mean flow velocity. The propagation of these vortices is not a strong function of the mean flow speed and appears to be dependent upon the frequency of the instability. Continued existence of large vortical structures which characterize unstable operation depends upon the fuel-air ratio, system acoustics, and fuel type

Synchronization properties of self-sustained mechanical oscillators

We study, both analytically and numerically, the dynamics of mechanical oscillators kept in motion by a feedback force, which is generated electronically from a signal produced by the oscillators themselves. This kind of self-sustained systems may become standard in the design of frequency-control devices at microscopic scales. Our analysis is thus focused on their synchronization properties under the action of external forces, and on the joint dynamics of two to many coupled oscillators. Existence and stability of synchronized motion are assessed in terms of the mechanical properties of individual oscillators --namely, their natural frequencies and damping coefficients-- and synchronization frequencies are determined. Similarities and differences with synchronization phenomena in other coupled oscillating systems are emphasized.Comment: To appear in Phys. Rev.