Summary of forward velocity effects on fan noise

Available experimental data comparing the in-flight and static behavior of fan noise are reviewed. These results are then compared with recent data obtained for a fan stage tested with forward velocity in a low speed wind tunnel. Tentative conclusions are presented about the significance and nature of the changes in noise observed when a forward velocity is imposed. Finally, the implications of the emerging picture of in-flight fan source noise for suppressor design are discussed

Effects of forward velocity and acoustic treatment on inlet fan noise

Flyover and static noise data from several engines are presented that show inlet fan noise measured in flight can be lower than that projected from static tests for some engines. The differences between flight and static measurements appear greatest when the fan fundamental tone due to rotor-stator interaction or to the rotor alone field is below cutoff. Data from engine and fan tests involving inlet treatment on the walls only are presented that show the attenuation from this treatment is substantially larger than expected from previous theories or flow duct experience. Data showing noise shielding effects due to the location of the engine on the airplane are also presented. These observations suggest that multiringed inlets may not be necessary to achieve the desired noise reduction in many applications

Acoustic performance of inlet multiple-pure-tone suppressors installed on NASA quiet engine C

The length of multiple-pure-tone (MPT) treatment required to reasonably suppress the MPT's produced by a supersonic tip speed fan was defined. Other suppression, broadband, and blade passing frequency, which might be accomplished were also determined. The experimental results are presented in terms of both far-field and duct acoustic data

System Architecture Virtual Integration: A Case Study

International audienceAerospace industry is experiencing exponential growth in the size and complexity of onboard software. It is also seeing a significant increase in errors and rework of that software. All of those factors contribute to greater cost; the current development process is reaching the limit of affordability of building safe aircraft. An international consortium of aerospace companies with government participation has initiated the System Architecture Virtual Integration (SAVI) program, whose goal is to achieve an affordable solution through a paradigm shift of―integrate then build. A key concept of this paradigm shift is an architecture- centric approach to analysis of virtually integrated system models with respect to multiple operational quality attributes such as performance, safety, and reliability. By doing so early and throughout the life cycle at different levels of fidelity, system-level faults are discovered earlier in the life cycle—reducing risk, cost, and development time. The first phase of this program demonstrated the feasibility of this new development process through a proof of concept demonstration and a return on investment analysis, which are the topics of this paper

Dynamic capabilities in the upstream oil and gas sector: Managing next generation competition

AbstractThe Dynamic Capabilities Framework, originally developed to enhance understanding of strategic agility in high-tech firms operating in high-velocity markets, is shown to be relevant for the Upstream Oil and Gas sector, in the context of five industry game-changers. Here operational and general managers with key strategic decision-making responsibilities significant challenges created by increased demand for energy resources, new technologies that have opened unconventional plays, increased competition, shrinking global geoscience and engineering talent pools, and the reality and perception of environmental risks. The Dynamic Capabilities Framework is distinguished from other “textbook” strategic methodologies and is applied to today’s upstream strategic context and inflection point. Dynamic capabilities join with strategy to empower an organization’s ability to integrate, build and reconfigure internal and external competencies to address rapidly changing markets. Dynamic capabilities differ from ordinary capabilities in that they orchestrate clusters of ordinary capabilities, best practices and competencies to gain competitive and performance advantages – capturing opportunities and managing strategic risks. Three dynamic capabilities are described that have particular importance for upstream oil and gas companies in the new business environment: (1) ambidexterity across mature and emerging domains; (2) the ability to manage the upstream business ecosystem; and (3) the ability to manage Health, Safety, Security and Environmental (HSSE) considerations in the multinational corporation and throughout the business ecosystem

Crystal Structure of a Ube2S-Ubiquitin Conjugate

Protein ubiquitination occurs through the sequential formation and reorganization of specific protein-protein interfaces. Ubiquitin-conjugating (E2) enzymes, such as Ube2S, catalyze the formation of an isopeptide linkage between the C-terminus of a “donor” ubiquitin and a primary amino group of an “acceptor” ubiquitin molecule. This reaction involves an intermediate, in which the C-terminus of the donor ubiquitin is thioester-bound to the active site cysteine of the E2 and a functionally important interface is formed between the two proteins. A docked model of a Ube2S-donor ubiquitin complex was generated previously, based on chemical shift mapping by NMR, and predicted contacts were validated in functional studies. We now present the crystal structure of a covalent Ube2S-ubiquitin complex. The structure contains an interface between Ube2S and ubiquitin in trans that resembles the earlier model in general terms, but differs in detail. The crystallographic interface is more hydrophobic than the earlier model and is stable in molecular dynamics (MD) simulations. Remarkably, the docked Ube2S-donor complex converges readily to the configuration seen in the crystal structure in 3 out of 8 MD trajectories. Since the crystallographic interface is fully consistent with mutational effects, this indicates that the structure provides an energetically favorable representation of the functionally critical Ube2S-donor interface

Contribution of Matrix Metalloproteinase-9 to Cerebral Edema and Functional Outcome following Experimental Subarachnoid Hemorrhage

Background: Cerebral edema is an important risk factor for death and poor outcome following subarachnoid hemorrhage (SAH). However, underlying mechanisms are still poorly understood. Matrix metalloproteinase (MMP)-9 is held responsible for the degradation of microvascular basal lamina proteins leading to blood-brain barrier dysfunction and, thus, formation of vasogenic cerebral edema. The current study was conducted to clarify the role of MMP-9 for the development of cerebral edema and for functional outcome after SAH. Methods: SAH was induced in FVB/N wild-type (WT) or MMP-9 knockout (MMP-9(-/-)) mice by endovascular puncture. Intracranial pressure (ICP), regional cerebral blood flow (rCBF), and mean arterial blood pressure (MABP) were continuously monitored up to 30 min after SAH. Mortality was quantified for 7 days after SAH. In an additional series neurological function and body weight were assessed for 3 days after SAH. Subsequently, ICP and brain water content were quantified. Results: Acute ICP, rCBF, and MABP did not differ between WT and MMP-9(-/-) mice, while 7 days' mortality was lower in MMP-9(-/-) mice (p = 0.03; 20 vs. 60%). MMP-9(-/-) mice also exhibited better neurological recovery, less brain edema formation, and lower chronic ICP. Conclusions: The results of the current study suggest that MMP-9 contributes to the development of early brain damage after SAH by promoting cerebral edema formation. Hence, MMP-9 may represent a novel molecular target for the treatment of SAH. Copyright (C) 2011 S. Karger AG, Base