877 resultados para Back-EMF
Resumo:
Over the last 5–10 years, marine spatial planning (MSP) has emerged as a new management regime for national and international waters and has already attracted a substantial body of multi-disciplinary research on its goals and policy processes. This paper argues that this literature has generally lacked deeper reflexive engagement with the emerging system of governance for our seas that has meant that many of MSP’s core concepts, assumptions and institutional arrangements have not been subject rigorous intellectual debate. In an attempt to initiate such an approach, this article explores the relationship between MSP and its land-based cousin, terrestrial spatial planning (TSP). While it is recognized that there are inherent limitations to a comparison of these two systems, it is argued that the tradition of social science debate over the purpose and processes of TSP can be used as a useful stimulus for a more rigorous reflection of such issues as they relate to MSP. The article therefore explores some of the parallels between MSP and TSP and then discusses some of the key intellectual traditions that have shaped TSP and the implications these may have for future marine planning practice. The article concludes with a number of potentially useful new avenues that may form the basis of a critical research agenda for MSP.
Resumo:
Off-design performance is of key importance now in the design of automotive turbocharger turbines. Due to automotive drive cycles, a turbine that can extract more energy at high pressure ratios and lower rotational speeds is desirable. Typically a radial turbine provides peak efficiency at U/C values of 0.7, but at high pressure ratios and low rotational speeds, the U/C value will be low and the rotor will experience high values of positive incidence at the inlet. The positive incidence causes high blade loading resulting in additional tip leakage flow in the rotor as well as flow separation on the suction surface of the blade. An experimental assessment has been performed on a scaled automotive VGS (variable geometry system). Three different stator vane positions have been analyzed: minimum, 25%, and maximum flow position. The first tests were to establish whether positioning the endwall clearance on the hub or shroud side of the stator vanes produced a different impact on turbine efficiency. Following this, a back swept rotor was tested to establish the potential gains to be achieved during off-design operation. A single passage CFD model of the test rig was developed and used to provide information on the flow features affecting performance in both the stator vanes and turbine. It was seen that off-design performance was improved by implementing clearance on the hub side of the stator vanes rather than on the shroud side. Through CFD analysis and tests, it was seen that two leakage vortices form, one at the leading edge and one after the spindle of the stator vane. The vortices affect the flow angle at the inlet to the rotor, in the hub region. The flow angle is shifted to more negative values of incidence, which is beneficial at the off-design conditions but detrimental at the design point. The back swept rotor was tested with the hub side stator vane clearance configuration. The efficiency and MFR were increased at the minimum and 25% stator vane position. At the design point, the efficiency and MFR were decreased. The CFD investigation showed that the incidence angle was improved at the off-design conditions for the back swept rotor. This reduction in the positive incidence angle, along with the improvement caused by the stator vane tip leakage flow, reduced flow separation on the suction surface of the rotor. At the design point, both the tip leakage flow of the stator vanes and the back swept blade angle caused flow separation on the pressure surface of the rotor. This resulted in additional blockage at the throat of the rotor reducing MFR and efficiency.
Resumo:
Power back-off performances of the modified power-combining Class-E amplifier under different amplitudemodulation schemes such as envelope elimination and restoration (EER) and envelope tracking (ET) are experimentally assessed in this paper. The modified output load network adopting three-harmonic terminations technique eliminates the need for additional lossy filtering section in the transmitter chain. Small dc-feed inductances rather than massive RF chokes as in the classic Class-E amplifier are used so as to increase the modulation bandwidth and therefore improve the linearity of the EER transmitter. High efficiency over a wide dynamic range using amplitude modulation through drain-voltage control (EER) was achieved and this agrees well with the Class-E theoretical prediction. When the PA was used within the ET scheme, an increase of average drain efficiency of as high as 40% with respect to the CW excitation was obtained for a multi-carrier input signal with 12dB peak-to-average power ratio. © 2011 Institut fur Mikrowellen.
Resumo:
OBJECTIVES: To evaluate the feasibility of an RCT of a pedometer-driven walking program and education/advice to remain active compared with education/advice only for treatment of chronic low back pain (CLBP). METHODS: Fifty-seven participants with CLBP recruited from primary care were randomly allocated to either: (1) education/advice (E, n=17) or (2) education/advice plus an 8-week pedometer-driven walking program (EWP, n=40). Step targets, actual daily step counts, and adverse events were recorded in a walking diary over the 8 weeks of intervention for the EWP group only. All other outcomes (eg, functional disability using the Oswestry Disability Questionnaire (ODQ), pain scores, physical activity (PA) measurement etc.) were recorded at baseline, week 9 (immediately post-intervention), and 6 months in both groups. RESULTS: The recruitment rate was 22% and the dropout rate was lower than anticipated (13% to 18% at 6 mo). Adherence with the EWP was high, 93% (n=37/40) walked for =6 weeks, and increased their steps/day [mean absolute increase in steps/d, 2776, 95% confidence interval (CI), 1996-3557] by 59% (95% CI, 40.73%-76.25%) from baseline. Mean percentage adherence with weekly step targets was 70% (95% CI, 62%-77%). Eight (20%) minor-related adverse events were observed in 13% (5/40) of the participants. The EWP group participants demonstrated an 8.2% point improvement [95% CI, -13 to -3.4] on the ODQ at 6 months compared with 1.6% points [95% CI, -9.3 to 6.1) for the E group (between group d=0.44). There was also a larger mean improvement in pain (d=0.4) and a larger increase in PA (d=0.59) at 6 months in EWP. DISCUSSION: This preliminary study demonstrated that a main RCT is feasible. EWP was safe and produced a real increase in walking; CLBP function and pain improved, and participants perceived a greater improvement in their PA levels. These improvements require confirmation in a fully powered RCT.
Resumo:
Objective: To determine the feasibility of a randomized controlled trial investigating the effectiveness of physiotherapy for sleep disturbance in chronic low back pain (CLBP) (=12wks). Design: Randomized controlled trial with evaluations at baseline, 3 months, and 6 months. Setting: Outpatient physiotherapy department in an academic teaching hospital. Participants: Participants with CLBP were randomly assigned to a walking program (n=20; mean age ± SD, 46.4±13.8y), supervised exercise class (n=20; mean age ± SD, 41.3±11.9y), or usual physiotherapy (n=20; mean age ± SD, 47.1±14.3y). The 3-month evaluation was completed by 44 participants (73%), and 42 (70%) participants completed the 6-month evaluation. Interventions: Participants received a physiotherapy-delivered 8-week walking program, an 8-week group supervised exercise class (1 class/wk), or 1-to-1 usual physiotherapy (advice, manual therapy, and exercise). Main Outcome Measures: Sleep was assessed by the self-reported Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), Pittsburgh Sleep Diary, and objective actigraphy. Results: Groups were comparable at baseline. Most (95%, n=57) of the participants had sleep disturbance. The acceptability of actigraphy was excellent at baseline (58 of 60 participants), but dropped at 3 months (26 of 44 participants). There were improvements on the PSQI and ISI in all groups at 3 and 6 months, with predominantly medium effect sizes (Cohen d=0.2-0.5). Conclusions: The high prevalence of sleep disturbance indicated the feasibility of good recruitment in future trials. The PSQI would be a suitable screening tool and outcome measure alongside an objective nonobtrusive sleep outcome measure. The effectiveness of physiotherapy for sleep disturbance in CLBP warrants investigation in a fully powered randomized controlled trial. © 2013 American Congress of Rehabilitation Medicine.
Resumo:
In 2014 it will be 40 years since Luce Irigaray’s (second) doctoral thesis Speculum de l'autre femme was first published. That book, widely recognized as the most important text in feminist philosophy, was to introduce Irigaray’s critique of western philosophy and psychoanalysis and her ethics of sexual difference for which she was to become so well known. Irigaray, well into her eighties now, has published continuously since Speculum, despite her exclusion from French academic life after her expulsion in 1974 from the Université de Paris VIII Vincennes. That her latest book In the Beginning, She Was, released on the eve of Speculum’s anniversary, is perhaps the most personally revelatory of her works and revisits many of the same themes and issues that concerned her in Speculum cannot be coincidental. In this critical notice we examine Irigaray’s latest offering arguing that her contribution is twofold as she combines with new clarity her longstanding critique of phallocratic culture and her transformative vision of humanity as a culture of sexuate difference. There are a number of important themes addressed in the six chapters of the book, but for the purposes of this discussion our analysis will focus mostly on elaborating her critique of Western culture, on the usefulness of her work for rethinking masculine subject formation and on the figure of Antigone, as a feminine subject on her own terms, as a way of imagining a possible relation between two subjects within a culture of sexuate difference. We argue that this book continues to illustrate Irigaray’s importance as one of the most radical and prophetic philosophers of our time.
Resumo:
The Fonualei Spreading Center affords an excellent opportunity to evaluate geochemical changes with increasing depth to the slab in the Lau back-arc basin. We present H2O and CO2 concentrations and Sr, Nd, Pb, Hf and U-Th-Ra isotope data for selected glasses as well as new Hf isotope data from boninites and seamounts to the north of the Tonga arc. The Pb and Hf isotope data are used to show that mantle flow is oriented to the southwest and that the tear in the northern end of the slab may not extend east as far as the boninite locality. Along the Fonualei Spreading Center, key geochemical parameters change smoothly with increasing distance from the arc front and increasing slab surface temperatures. The latter may range from 720 to 866 degrees C, based on decreasing H2O/Ce ratios. Consistent with experimental data, the geochemical trends are interpreted to reflect changes in the amount and composition of wet pelite melts or super-critical fluids and aqueous fluids derived from the slab. With one exception, all of the lavas preserve both U-238 excesses and Ra-226 excesses. We suggest that lavas from the Fonualei Spreading Center and Valu Fa Ridge are dominated by fluid-fluxed melting whereas those from the East and Central Lau Spreading Centers, where slab surface temperatures exceed similar to 850-900 degrees C, are largely derived through decompression. A similar observation is found for the Manus and East Scotia back-arc basins and may reflect the expiry of a key phase such as lawsonite in the subducted basaltic crust.