Unsteady ejectors: The effect of driver jet mark-space ratio

mark Unsteady ejectors can be driven by a wide range of driver jets. These vary from pulse detonation engines, which typically have a long gap between each slug of fluid exiting the detonation tube (mark-space ratios in the range 0.1-0.2) to the exit of a pulsejet where the mean mass flow rate leads to a much shorter gap between slugs (mark-space ratios in the range 2-3). The aim of this paper is to investigate the effect of mark-space ratio on the thrust augmentation of an unsteady ejector. Experimental testing was undertaken using a driver jet with a sinusoidal exit velocity profile. The mean value, amplitude and frequency of the velocity profile could be changed allowing the length to diameter ratio of the fluid slugs L/D and the mark-space ratio (the ratio of slug length to the spacing between slugs) L/S to be varied. The setup allowed L/S of the jet to vary from 0.8 to 2.3, while the L/D ratio of the slugs could take any values between 3.5 and 7.5. This paper shows that as the mark-space ratio of the driver jet is increased the thrust augmentation drops. Across the range of mark-space ratios tested, there is shown to be a drop in thrust augmentation of 0.1. The physical cause of this reduction in thrust augmentation is shown to be a decrease in the percentage time over which the ejector entrains ambient fluid. This is the direct result ofthe space between consecutive slugs in the driver jet decreasing. The one dimensional model reported in Heffer et al. [1] is extended to include the effect of varying L/S and is shown to accurately capture the experimentally measured behavior ofthe ejector. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

Active glass-polymer superlattice structure for photonic integration.

We propose an all-laser processing approach allowing controlled growth of organic-inorganic superlattice structures of rare-earth ion doped tellurium-oxide-based glass and optically transparent polydimethyl siloxane (PDMS) polymer; the purpose of which is to illustrate the structural and thermal compatibility of chemically dissimilar materials at the nanometer scale. Superlattice films with interlayer thicknesses as low as 2 nm were grown using pulsed laser deposition (PLD) at low temperatures (100 °C). Planar waveguides were successfully patterned by femtosecond-laser micro-machining for light propagation and efficient Er(3+)-ion amplified spontaneous emission (ASE). The proposed approach to achieve polymer-glass integration will allow the fabrication of efficient and durable polymer optical amplifiers and lossless photonic devices. The all-laser processing approach, discussed further in this paper, permits the growth of films of a multitude of chemically complex and dissimilar materials for a range of optical, thermal, mechanical and biological functions, which otherwise are impossible to integrate via conventional materials processing techniques.

Dasher

Dasher is an information-efficient text-entry interface, which can be driven by natural continuous pointing gestures or by pressing buttons. Dasher is a competitive text-entry system wherever a full-size keyboard cannot be used - for example, when operating a computer one-handed, by joystick, touchscreen, trackball, or mouse; when operating a computer with zero hands (i.e., by head-mouse or by eyetracker); on a palmtop computer; on a wearable computer. The gazetracking version of Dasher allows an experienced user to write text as fast as normal handwriting - 29 words per minute; using a mouse, experienced users can write at 39 words per minute. Dasher can be used to write efficiently in any language. Dasher is free software (distributed under the GPL) and is available for many computer platforms, including linux, windows, and android.

Getting to zero: evidence-based healthcare risk management is key.

In this article we call for a new approach to patient safety improvement, one based on the emerging field of evidence-based healthcare risk management (EBHRM). We explore EBHRM in the broader context of the evidence-based healthcare movement, assess the benefits and challenges that might arise in adopting an evidence-based approach, and make recommendations for meeting those challenges and realizing the benefits of a more scientific approach.