Surface roughness noise prediction for silent aircraft experimental design SAX-40

Surface roughness noise is a potentially important contributor to airframe noise. In this paper, noise assessment due to surface roughness is performed for a conceptual Silent Aircraft design SAX-40 by means of a prediction model developed in previous theoretical work and validated experimentally. Estimates of three idealized test cases show that surface roughness could produce a significant noise level above that due to the trailing edge at high frequencies. Roughness height and roughness density are the two most significant parameters influencing surface roughness noise, with roughness height having the dominant effect. The ratio of roughness height to boundary-layer thickness is the relevant non-dimensional parameter and this decreases in the streamwise direction. The candidate surface roughness is selected for SAX-40 to meet an aggressive noise target and keep surface roughness noise at a negligible level. Copyright © 2008 by Yu Liu and Ann P. Dowling.

The effect of an upstream turbine on a low-aspect ratio vane

The interaction between a high-pressure rotor and a downstream vane is dominated by vortex-blade interaction. Each rotor blade passing period two co-rotating vortex pairs, the tip-leakage and upper passage vortex and the lower passage and trailing shed vortex, impinge on, and are cut by, the vane leading edge. In addition to the streamwise vortex the tip-leakage flow also contains a large velocity deficit. This causes the interaction of the tip-leakage flow with a downstream vane to differ from typical vortex blade interaction. This paper investigates the effect these interaction mechanisms have on a downstream vane. The test geometry considered was a low aspect ratio second stage vane located within a S-shaped diffuser with large radius change mounted downstream of a shroudless high-pressure turbine stage. Experimental measurements were conducted at engine-representative Mach and Reynolds numbers, and data was acquired using a fast-response aerodynamic probe upstream and downstream of the vane. Time-resolved numerical simulations were undertaken with and without a rotor tip gap in order to investigate the relative magnitude of the interaction mechanisms. The presence of the upstream stage is shown to significantly change the structure of the secondary flow in the vane and to cause a small drop in its performance.

Laser micromachining of sputtered DLC films

DLC films with different thicknesses (from 100 nm to 1.9 μm) were deposited using sputtering of graphite target in pure argon atmosphere without substrate heating. Film microstructures (sp2/sp3 ratio) and mechanical properties (modulus, hardness, stress) were characterized as a function of film thickness. A thin layer of aluminum about 60 nm was deposited on the DLC film surface. Laser micromachining of Al/DLC layer was performed to form microcantilever structures, which were released using a reactive ion etching system with SF6 plasma. Due to the intrinsic stress in DLC films and bimorph Al/DLC structure, the microcantilevers bent up with different curvatures. For DLC film of 100 nm thick, the cantilever even formed microtubes. The relationship between the bimorph beam bending and DLC film properties (such as stress, modulus, etc.) were discussed in details. © 2005 Elsevier B.V. All rights reserved.

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.

RNAi, DRD1, and histone methylation actively target developmentally important Non-CG DNA methylation in Arabidopsis

Cytosine DNA methylation protects eukaryotic genomes by silencing transposons and harmful DNAs, but also regulates gene expression during normal development. Loss of CG methylation in the Arabidopsis thaliana met1 and ddm1 mutants causes varied and stochastic developmental defects that are often inherited independently of the original met1 or ddm1 mutation. Loss of non-CG methylation in plants with combined mutations in the DRM and CMT3 genes also causes a suite of developmental defects. We show here that the pleiotropic developmental defects of drm1 drm2 cmt3 triple mutant plants are fully recessive, and unlike phenotypes caused by met1 and ddm1, are not inherited independently of the drm and cmt3 mutations. Developmental phenotypes are also reversed when drm1 drm2 cmt3 plants are transformed with DRM2 or CMT3, implying that non-CG DNA methylation is efficiently re-established by sequence-specific signals. We provide evidence that these signals include RNA silencing though the 24-nucleotide short interfering RNA (siRNA) pathway as well as histone H3K9 methylation, both of which converge on the putative chromatin-remodeling protein DRD1. These signals act in at least three partially intersecting pathways that control the locus-specific patterning of non-CG methylation by the DRM2 and CMT3 methyltransferases. Our results suggest that non-CG DNA methylation that is inherited via a network of persistent targeting signals has been co-opted to regulate developmentally important genes. © 2006 Chan et al.

How to avoid the problems of target-setting

Purpose: Advocates and critics of target-setting in the workplace seem unable to reach beyond their own well-entrenched battle lines. While the advocates of goal-directed behaviour point to what they see as demonstrable advantages, the critics of target-setting highlight equally demonstrable disadvantages. Indeed, the academic literature on this topic is currently mired in controversy, with neither side seemingly capable of envisaging a better way forward. This paper seeks to break the current deadlock and move thinking forward in this important aspect of performance measurement and management by outlining a new, more fruitful approach, based on both theory and practical experience. Design/methodology/approach: The topic was approached in three phases: assembling and reading key academic and other literature on the subject of target-setting and goal-directed behaviour, with a view to understanding, in depth, the arguments advanced by the advocates and critics of target-setting; comparing these published arguments with one's own experiential findings, in order to bring the essence of disagreement into much sharper focus; and then bringing to bear the academic and practical experience to identify the essential elements of a new, more fruitful approach offering all the benefits of goal-directed behaviour with none of the typical disadvantages of target-setting. Findings: The research led to three key findings: the advocates of goal-directed behaviour and critics of target-setting each make valid points, as seen from their own current perspectives; the likelihood of these two communities, left to themselves, ever reaching a new synthesis, seems vanishingly small (with leading thinkers in the goal-directed behaviour community already acknowledging this); and, between the three authors, it was discovered that their unusual combination of academic study and practical experience enabled them to see things differently. Hence, they would like to share their new thinking more widely. Research limitations/implications: The authors fully accept that their paper is informed by extensive practical experience and, as yet, there have been no opportunities to test their findings, conclusions and recommendations through rigorous academic research. However, they hope that the paper will move thinking forward in this arena, thereby informing future academic research. Practical implications: The authors hope that the practical implications of the paper will be significant, as it outlines a novel way for organisations to capture the benefits of goal-directed behaviour with none of the disadvantages typically associated with target-setting. Social implications: Given that increased efficiency and effectiveness in the management of organisations would be good for society, the authors think the paper has interesting social implications. Originality/value: Leading thinkers in the field of goal-directed behaviour, such as Locke and Latham, and leading critics of target-setting, such as Ordóñez et al. continue to argue with one another - much like, at the turn of the nineteenth century, proponents of the "wave theory of light" and proponents of the "particle theory of light" were similarly at loggerheads. Just as this furious scientific debate was ultimately resolved by Taylor's experiment, showing that light could behave both as a particle and wave at the same time, the authors believe that the paper demonstrates that goal-directed behaviour and target-setting can successfully co-exist. © Emerald Group Publishing Limited.

Developing a technology intelligence strategy at kodak european research: Scan & target

OVERVIEW: Kodak European Research (KER) developed a strategy for technology intelligence based on a theoretical model developed by Kerr et al. (2006). KER scouts designed and implemented a four-step approach to identify relevant technologies and research centers across Europe, Africa and the Middle East. The approach provides clear guidance for integrating web searches, scouting trips, networking and interactions with intermediaries. KER's example illustrates how companies can organize themselves to look outside corporate boundaries in search of technologies relevant for their business. The approach may be useful to those in other companies who have been asked to start a technology intelligence activity. © 2010 Industrial Research Institute, Inc.