295 research outputs found

    Estimation of fan pressure ratio requirements and operating performance for the National Transonic Facility

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    The National Transonic Facility (NTF), a fan-driven, transonic, pressurized, cryogenic wind tunnel, will operate over the Mach number range of 0.10 to 1.20 with stagnation pressures varying from 1.00 to about 8.8 atm and stagnation temperatures varying from 77 to 340 K. The NTF is cooled to cryogenic temperatures by the injection of liquid nitrogen into the tunnel stream with gaseous nitrogen as the test gas. The NTF can also operate at ambient temperatures using a conventional chilled water heat exchanger with air on nitrogen as the test gas. The methods used in estimating the fan pressure ratio requirements are described. The estimated NTF operating envelopes at Mach numbers from 0.10 to 1.20 are presented

    Guide for users of the National Transonic Facility

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    The National Transonic Facility (NTF) is a fan-driven, closed-circuit, continuous flow, pressurized wind tunnel. The test section is 2.5 m x 2.5 m and 7.62 m long with a slotted-wall configuration. The NTF will have a Mach number range from 0.2 to 1.2, with Reynolds number up to 120 10 to the sixth power at Mach 1 (based on a reference length of 0.25 m). The pressure range for the facility will be from 1 to about 9 bars (1 ban = 100 kPa), and the temperature can be varied from 340 to 78 K. This report provides potential users of the NTF with the information required for preliminary planning to test programs and for preliminary layout of models and model supports which may be used in such programs

    Flow visualization study of close-coupled canard wing and strake wing configuration

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    The Langley 1/8-scale V/STOL model tunnel was used to qualitatively determine the flow fields associated with semi-span close coupled canard wing and strake wing models. Small helium filled bubbles were injected upstream of the models to make the flow visible. Photographs were taken over the angle-of-attack ranges of -10 deg to 40 deg

    Systematic review: efficacy and safety of medical marijuana in selected neurologic disorders: report of the Guideline Development Subcommittee of the American Academy of Neurology.

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    OBJECTIVE: To determine the efficacy of medical marijuana in several neurologic conditions. METHODS: We performed a systematic review of medical marijuana (1948-November 2013) to address treatment of symptoms of multiple sclerosis (MS), epilepsy, and movement disorders. We graded the studies according to the American Academy of Neurology classification scheme for therapeutic articles. RESULTS: Thirty-four studies met inclusion criteria; 8 were rated as Class I. CONCLUSIONS: The following were studied in patients with MS: (1) Spasticity: oral cannabis extract (OCE) is effective, and nabiximols and tetrahydrocannabinol (THC) are probably effective, for reducing patient-centered measures; it is possible both OCE and THC are effective for reducing both patient-centered and objective measures at 1 year. (2) Central pain or painful spasms (including spasticity-related pain, excluding neuropathic pain): OCE is effective; THC and nabiximols are probably effective. (3) Urinary dysfunction: nabiximols is probably effective for reducing bladder voids/day; THC and OCE are probably ineffective for reducing bladder complaints. (4) Tremor: THC and OCE are probably ineffective; nabiximols is possibly ineffective. (5) Other neurologic conditions: OCE is probably ineffective for treating levodopa-induced dyskinesias in patients with Parkinson disease. Oral cannabinoids are of unknown efficacy in non-chorea-related symptoms of Huntington disease, Tourette syndrome, cervical dystonia, and epilepsy. The risks and benefits of medical marijuana should be weighed carefully. Risk of serious adverse psychopathologic effects was nearly 1%. Comparative effectiveness of medical marijuana vs other therapies is unknown for these indications

    A MAC Layer Abstraction for Heterogeneous Carrier Grade Mesh Networks

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    [Poster] ICT-MobileSummit 2009, 10-12 June 2009, Santander, SpainProviding carrier grade services to a large number of mobile users is becoming an important challenge for wireless network operators. One promising solution for offering cost-efficient alternatives compared to classical cellular approaches is the use of wireless mesh networks along with the use of heterogeneous radio technologies. In this paper we propose a MAC abstraction layer to lessen the management burden of heterogeneous radio technologies. This abstraction layer is intended to hide the complexity and specifics of different wireless interfaces, this way supporting the use of a single set of routing and capacity handling mechanisms.European Community's Seventh Framework ProgramThe research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement No 214994.Publicad

    Practice Guideline: Cervical and Ocular Vestibular Evokedmyogenic Potential Testing: Report of the Guideline Development Dissemination and Implementation Subcommittee of the American Academy of Neurology

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    Objective: To systematically review the evidence and make recommendations with regard to diagnostic utility of cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP, respectively). Four questions were asked: Does cVEMP accurately identify superior canal dehiscence syndrome (SCDS)? Does oVEMP accurately identify SCDS? For suspected vestibular symptoms, does cVEMP/oVEMP accurately identify vestibular dysfunction related to the saccule/ utricle? For vestibular symptoms, does cVEMP/oVEMP accurately and substantively aid diagnosis of any specific vestibular disorder besides SCDS? Methods: The guideline panel identified and classified relevant published studies (January 1980- December 2016) according to the 2004 American Academy of Neurology process. Results and Recommendations: Level C positive: Clinicians may use cVEMP stimulus threshold values to distinguish SCDS from controls (2 Class III studies) (sensitivity 86%-91%, specificity 90%-96%). Corrected cVEMP amplitude may be used to distinguish SCDS from controls (2 Class III studies) (sensitivity 100%, specificity 93%). Clinicians may use oVEMP amplitude to distinguish SCDS from normal controls (3 Class III studies) (sensitivity 77%-100%, specificity 98%-100%). oVEMP threshold may be used to aid in distinguishing SCDS from controls (3 Class III studies) (sensitivity 70%-100%, specificity 77%-100%). Level U: Evidence is insufficient to determine whether cVEMP and oVEMP can accurately identify vestibular function specifically related to the saccule/utricle, or whether cVEMP or oVEMP is useful in diagnosing vestibular neuritis or M

    Pinch Resonances in a Radio Frequency Driven SQUID Ring-Resonator System

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    In this paper we present experimental data on the frequency domain response of a SQUID ring (a Josephson weak link enclosed by a thick superconducting ring) coupled to a radio frequency (rf) tank circuit resonator. We show that with the ring weakly hysteretic the resonance lineshape of this coupled system can display opposed fold bifurcations that appear to touch (pinch off). We demonstrate that for appropriate circuit parameters these pinch off lineshapes exist as solutions of the non-linear equations of motion for the system.Comment: 9 pages, 8 figures, Uploaded as implementing a policy of arXiving old paper

    Morphological and ecological convergence at the lower size limit for vertebrates highlighted by five new miniaturised microhylid frog species from three different Madagascan genera

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    Miniaturised frogs form a fascinating but poorly understood amphibian ecomorph and have been exceptionally prone to taxonomic underestimation. The subfamily Cophylinae (family Microhylidae), endemic to Madagascar, has a particularly large diversity of miniaturised species which have historically been attributed to the single genus Stumpffia largely based on their small size. Recent phylogenetic work has revealed that several independent lineages of cophyline microhylids evolved towards highly miniaturised body sizes, achieving adult snout- vent lengths under 16 mm. Here, we describe five new species belonging to three clades that independently miniaturised and that are all genetically highly divergent from their relatives: (i) a new genus (Mini gen.nov.) with three new species from southern Madagascar, (ii) one species of Rhombophryne, and (iii) one species of Anodonthyla. Mini mum sp. nov. from Manombo in eastern Madagascar is one of the smallest frogs in the world, reaching an adult body size of 9.7 mm in males and 11.3 mm in females. Mini scule sp.nov. from Sainte Luce in southeastern Madagascar is slightly larger and has maxillary teeth. Mini ature sp.nov. from Andohahela in southeast Madagascar is larger than its congeners but is similar in build. Rhombophryne proportionalis sp.nov. from Tsaratanana in northern Madagascar is unique among Madagascar's miniaturised frogs in being a proportional dwarf, exhibiting far less advanced signs of paedomorphism than other species of similar size. Anodonthyla eximia sp.nov. from Ranomafana in eastern Madagascar is distinctly smaller than any of its congeners and is secondarily terrestrial, providing evidence that miniaturisation and terrestriality may be evolutionarily linked. The evolution of body size in Madagascar's microhylids has been more dynamic than previously understood, and future studies will hopefully shed light on the interplay between ecology and evolution of these remarkably diverse frogs
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