261 research outputs found

    An airfoil for general aviation applications

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    A new airfoil, the NLF(1)-0115, has been recently designed at the NASA Langley Research Center for use in general-aviation applications. During the development of this airfoil, special emphasis was placed on experiences and observations gleaned from other successful general-aviation airfoils. For example, the flight lift-coefficient range is the same as that of the turbulent-flow NACA 23015 airfoil. Also, although beneficial for reducing drag and having large amounts of lift, the NLF(1)-0115 avoids the use of aft loading which can lead to large stick forces if utilized on portions of the wing having ailerons. Furthermore, not using aft loading eliminates the concern that the high pitching-moment coefficient generated by such airfoils can result in large trim drags if cruise flaps are not employed. The NASA NLF(1)-0115 has a thickness of 15 percent. It is designed primarily for general-aviation aircraft with wing loadings of 718 to 958 N/sq m (15 to 20 lb/sq ft). Low profile drag as a result of laminar flow is obtained over the range from c sub l = 0.1 and R = 9x10(exp 6) (the cruise condition) to c sub l = 0.6 and R = 4 x 10(exp 6) (the climb condition). While this airfoil can be used with flaps, it is designed to achieve c(sub l, max) = 1.5 at R = 2.6 x 10(exp 6) without flaps. The zero-lift pitching moment is held at c sub m sub o = 0.055. The hinge moment for a .20c aileron is fixed at a value equal to that of the NACA 63 sub 2-215 airfoil, c sub h = 0.00216. The loss in c (sub l, max) due to leading edge roughness, rain, or insects at R = 2.6 x 10 (exp 6) is 11 percent as compared with 14 percent for the NACA 23015

    Heat transfer coefficient saturation in superconducting Nb tunnel junctions contacted to a NbTiN circuit and an Au energy relaxation layer

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    In this paper we present the experimental realization of a Nb tunnel junction connected to a high-gap superconducting NbTiN embedding circuit. We investigate relaxation of nonequilibrium quasiparticles in a small volume Au layer between the Nb tunnel junction and the NbTiN circuit. We find a saturation in the effective heat-transfer coefficient consistent with a simple theoretical model. This saturation is determined by the thickness of the Au layer. Our findings are important for the design of the ideal Au energy relaxation layer for practical SIS heterodyne mixers and we suggest two geometries, one, using a circular Au layer and, two, using a half-circular Au layer. Our work is concluded with an outlook of our future experiments.Comment: Applied Superconductivity Conference 201

    Development and Implementation Strategies for International ERP Software Projects

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    In this paper we address a question highly relevant for many companies developing and implementing ERP or other software internationally. These companies have to integrate subsidiaries all over the world by using standard business processes implemented within the software, while at the same time take care of country-specific and other local requirements. The paper presents a framework of three different strategies, evaluates these strategies, and reports case study results that allow the comparison of these strategies. It is shown, that these strategies are not only relevant for ERP projects, but also for other software projects, especially global e-commerce projects

    The Effects of the Critical Ice Accretion on Airfoil and Wing Performance

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    In support of the NASA Lewis Modern Airfoils Ice Accretion Test Program, the University of Illinois at Urbana-Champaign provided expertise in airfoil design and aerodynamic analysis to determine the aerodynamic effect of ice accretion on modern airfoil sections. The effort has concentrated on establishing a design/testing methodology for "hybrid airfoils" or "sub-scale airfoils," that is, airfoils having a full-scale leading edge together with a specially designed and foreshortened aft section. The basic approach of using a full-scale leading edge with a foreshortened aft section was considered to a limited extent over 40 years ago. However, it was believed that the range of application of the method had not been fully exploited. Thus a systematic study was being undertaken to investigate and explore the range of application of the method so as to determine its overall potential

    Experiments of Propeller-Induced Flow Effects on a Low-Reynolds-Number Wing

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    Novel findings are discussed in this paper that will be especially beneficial to designers and modelers of small-scale unmanned air vehicles and high-altitude long-endurance vehicles that both operate at low Reynolds numbers (Re = 50,000-300,000). Propeller-induced Oow effects in both tractor and pusher configurations on a recta ngular wing using the Wortmann FX 63-137 airfoil (a common low-Reynolds-number high-lift airfoil) are presented in this paper . Significant performance benefits can be found for a wing in the tractor configuration. Experiments, including trip tests and upper-surface oil Dow visualization, show and verify that the propeller slipstream induces early transition to turbulent Oow in the regions within the slipstrean1 and the premature fomiation of a separation bubble in the regions outside the slipstream. The result is a reduction of pressure drag and an increase in lift of the wing where lift-to-drag ratios arc as high as 10-12 (a maximum of\u27 70% increase in lift-to-drag ratio from a clean wing configuration) and are measured at both low and high angles of attack up to s tall (0-16 deg). Similar performance benefits are n ot observed in pusher configuration results where only increased local Oow velocity and varying inOow angle effects are apparent. Thus, contrary to the design rules for optimal performance of wings at high Reynolds number s, at low Reynolds numbers, a propeller in the tractor configuration exhibits significant performance improvements, especially in cruise configurations Oow angles of attack), as compared with a propeller in the pusher configuration or even a clean wing

    Correlating the ability of lignocellulosic polymers to constrain water with the potential to inhibit cellulose saccharification

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    BACKGROUND: Studies in bioconversions have continuously sought the development of processing strategies to overcome the “close physical association” between plant cell wall polymers thought to significantly contribute to biomass recalcitrance [Adv Space Res 18:251–265, 1996],[ Science 315:804–807, 2007]. To a lesser extent, studies have sought to understand biophysical factors responsible for the resistance of lignocelluloses to enzymatic degradation. Provided here are data supporting our hypothesis that the inhibitory potential of different cell wall polymers towards enzymatic cellulose hydrolysis is related to how much these polymers constrain the water surrounding them. We believe the entropy-reducing constraint imparted to polymer associated water plays a negative role by increasing the probability of detrimental interactions such as junction zone formation and the non-productive binding of enzymes. RESULTS: Selected commercial lignocellulose-derived polymers, including hemicelluloses, pectins, and lignin, showed varied potential to inhibit 24-h cellulose conversion by a mix of purified cellobiohydrolase I and ÎČ-glucosidase. At low dry matter loadings (0.5% w/w), insoluble hemicelluloses were most inhibitory (reducing conversion relative to cellulose-only controls by about 80%) followed by soluble xyloglucan and wheat arabinoxylan (reductions of about 70% and 55%, respectively), while the lignin and pectins tested were the least inhibitory (approximately 20% reduction). Low field nuclear magnetic resonance (LF-NMR) relaxometry used to observe water-related proton relaxation in saturated polymer suspensions (10% dry solids, w/w) showed spin-spin, T(2,) relaxation time curves generally approached zero faster for the most inhibitory polymer preparations. The manner of this decline varied between polymers, indicating different biophysical aspects may differentially contribute to overall water constraint in each case. To better compare the LF-NMR data to inhibitory potential, T(2) values from monocomponent exponential fits of relaxation curves were used as a measure of overall water constraint. These values generally correlated faster relaxation times (greater water constraint) with greater inhibition of the model cellulase system by the polymers. CONCLUSIONS: The presented correlation of cellulase inhibition and proton relaxation data provides support for our water constraint-biomass recalcitrance hypothesis. Deeper investigation into polymer-cellulose-cellulase interactions should help elucidate the types of interactions that may be propagating this correlation. If these observations can be verified to be more than correlative, the hypothesis and data presented suggest that a focus on water-polymer interactions and ways to alter them may help resolve key biological lignocellulose processing bottlenecks

    Slipstream Measurements of Small-Scale Propellers at Low Reynolds Numbers

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    The continuing growth in the use of small UAVs has required the need to more fully understand the propellers that power them. Part of this understanding is the behavior of the propeller slipstream. Using a 7-hole probe, the slipstreams of several small-scale propellers (diameters of 4.2, 5, and 9 in) were measured in both static (V∞ = 0) and advancing-flow (V∞ \u3e 0) conditions at several locations downstream. For static conditions, as the slipstream expanded downstream, the maximum values of the axial and swirl velocities decreased. The general shape of the static slipstream was also found to be nearly the same for the propellers even though their planforms were different. During advancing-flow conditions, a contraction in the slipstream occurred by 0.5 diameters behind the propeller. Beyond that location, the size of the slipstream was relatively constant up to 3 diameters downstream (furthest distance measured). For advancing-flow slipstreams, the shape of the axial velocity distribution was observed to be dependent on the planform shape of the propeller. The static slipstream of a propeller-wing configuration showed that the slipstream portions above and below the wing moved away from each other towards opposite wing tips. However, the maximum axial and swirl velocities in the propeller-wing slipstream did not diminish compared with the isolated propeller slipstream

    Transportation Barriers to Healthcare in Adults 65+ in the Greater Burlington Area

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    Introduction. Missed appointments often lead to poorer health care outcomes for patients and pose a major economic burden on medical centers. Transportation is an obstacle to accessing medical care for elderly patients in Vermont and results in delayed medical appointments. Methods. We surveyed senior citizens in Chittenden county to determine both the type of transportation barriers and medical care missed due to the lack of transpor- tation. An original survey assessing the impact of transportation to health care was distributed in person and through an online platform. Participants were asked to identify the following in the past year: how often transportation was an issue for healthcare, specific barriers to transportation, and which specific health care appointments were missed due to lack of transportation. Ninety-six surveys out of a total of 251 collected were included in the analysis. Respondents were grouped into either having high transportation barriers, n=43, (always, often, sometimes had issues in the past year), or low transportation barriers, n=53, (rarely had issues). Results. The high barriers group reported more missed appointments, with eye appointments being the most frequent, and depended more on other modes of trans- portation. The low barriers group was able to drive themselves to their appointments more often. Conclusion. The results suggest a trend between barriers to transportation and a lack of access to healthcare appointments. Although more than half of the survey respondents indicated that they do not currently experience transportation barriers, many expressed concern about the transportation difficulties they could encounter in the future.https://scholarworks.uvm.edu/comphp_gallery/1263/thumbnail.jp
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