Thrust modulation methods for a subsonic V/STOL aircraft

Low speed wind tunnel tests were conducted to assess four methods for attaining thrust modulation for V/STOL aircraft. The four methods were: (1) fan speed change, (2) fan nozzle exit area change, (3) variable pitch rotor (VPR) fan, and (4) variable inlet guide vanes (VIGV). The interrelationships between inlet and thrust modulation system were also investigated using a double slotted inlet and thick lip inlet. Results can be summarized as: (1) the VPR and VIGV systems were the most promising, (2) changes in blade angle to obtain changes in fan thrust have significant implications for the inlet, and (3) both systems attained required level of thrust with acceptable levels of fan blade stress

Aerodynamic performance of a fan stage utilizing Variable Inlet Guide Vanes (VIGVs) for thrust modulation

An experimental research program was conducted in the Lewis Research Center's 9x15-foot (2.74x4.57 m) low speed wind tunnel to evaluate the aerodynamic performance of an inlet and fan system with variable inlet guide vanes (VIGVs) for use on a subsonic V/STOL aircraft. At high VIGV blade angles (lower weight flow and thrust levels), the fan stage was stalled over a major portion of its radius. In spite of the stall, fan blade stresses only exceeded the limits at the most extreme flow conditions. It was found that inlet flow separation does not necessarily lead to poor inlet performance or adverse fan operating conditions. Generally speaking, separated inlet flow did not adversely affect the fan blade stress levels. There were some cases, however, at high VIGV angles and high inlet angles-of-attack where excessive blade stress levels were encountered. An evaluation term made up of the product of the distortion parameter, K alpha, the weight flow and the fan pressure ratio minus one, was found to correlate quite well with the observed blade stress results

Effect of variable inlet guide vanes on the operating characteristics of a tilt nacelle inlet/powered fan model

The effects of a variable inlet guide vane (VIGV) assembly on the operating characteristics of a V/STOL inlet and on the performance of a 20-in. (0.508-m) diameter fan engine were investigated. The data indicate that the VIGVs are effective thrust modulators over a wide range of free-stream velocities, nacelle angles of attack, and fan speeds. The thrust modulation ranges, including choking limits, fan stall limits, and inlet separation boundaries are presented. The presence of the VIGV assembly causes significant losses in inlet angle-of-attack capability and generally increases the blade stress levels at all limit conditions except at high angle of attack and high free-stream velocity. Reducing the fan nozzle exit area limited the positive VIGV actuation range and consequently decreased the range of thrust modulation at all limit conditions except at both high free-stream velocity and high angle of attack conditions

Magnitude of nonlinearities in collisionless magnetoplasma waves

Perturbation technique used for approximate solutions to nonlinear hydromagnetic equations of cold collisionless plasm

Transonic off-design drag and performance of an axisymmetric inlet with 40 percent internal contraction on design

An experimental investigation determined the drag and pressure performance of an axisymmetric supersonic inlet when operated in the transonic speed range. The inlet configuration was derived from a Mach 2.5 mixed compression inlet design with assumed variable geometry. At typical engine airflows the drag coefficient varied from 0.057 to 0.192 when the Mach number changed from 0.80 to 1.27. The presence of a wing simulator resulted in a sizable increase in total drag at Mach 1.2. This interference drag, which is roughly a 0.1 increase in drag coefficient, originates equally from an increase in both additive and cowl pressure drag

Wind tunnel tests of a zero length, slotted-lip engine air inlet for a fixed nacelle V/STOL aircraft

Zero length, slotted lip inlet performance and associated fan blade stresses were determined during model tests using a 20 inch diameter fan simulator in the NASA-LeRC 9 by 15 foot low speed wind tunnel. The model configuration variables consisted of inlet contraction ratio, slot width, circumferential extent of slot fillers, and length of a constant area section between the inlet throat and fan face. The inlet performance was dependent on slot gap width and relatively independent of inlet throat/fan face spacer length and slot flow blockage created by 90 degree slot fillers. Optimum performance was obtained at a slot gap width of 0.36 inch. The zero length, slotted lip inlet satisfied all critical low speed inlet operating requirements for fixed horizontal nacelles subsonic V/STOL aircraft

Transonic off-design drag and performance of three mixed-compression axisymmetric inlets

An experimental investigation was conducted to determine the off-design drag and pressure performance of three axisymmetric supersonic inlets in the transonic speed range. For typical engine airflows at Mach 0.8 the drag coefficient varied from 0.045 to 0.09; at Mach 1.2 the largest drag coefficient measured was 0.25. Below Mach 0.9 a lower drag resulted when all or at least part of the excess weight flow was spilled over the cowl rather than through the bypass doors; above Mach 1.1 the lowest drag was obtained by bypassing excess flow

High-Kinetic Inductance Additive Manufactured Superconducting Microwave Cavity

Investigations into the microwave surface impedance of superconducting resonators have led to the development of single photon counters that rely on kinetic inductance for their operation. While concurrent progress in additive manufacturing, `3D printing', opens up a previously inaccessible design space for waveguide resonators. In this manuscript, we present results from the first synthesis of these two technologies in a titanium, aluminum, vanadium (Ti-6Al-4V) superconducting radio frequency resonator which exploits a design unattainable through conventional fabrication means. We find that Ti-6Al-4V has two distinct superconducting transition temperatures observable in heat capacity measurements. The higher transition temperature is in agreement with DC resistance measurements. While the lower transition temperature, not previously known in literature, is consistent with the observed temperature dependence of the superconducting microwave surface impedance. From the surface reactance, we extract a London penetration depth of $8\pm3{\mu}$m - roughly an order of magnitude larger than other titanium alloys and several orders of magnitude larger than other conventional elemental superconductors. This large London penetration depth suggests that Ti-6Al-4V may be a suitable material for high kinetic inductance applications such as single photon counting or parametric amplification used in quantum computing.Comment: 4 pages, 4 figure

ValiDichro: a website for validating and quality control of protein circular dichroism spectra

Circular dichroism (CD) spectroscopy is widely used in structural biology as a technique for examining the structure, folding and conformational changes of proteins. A new server, ValiDichro, has been developed for checking the quality and validity of CD spectral data and metadata, both as an aid to data collection and processing and as a validation procedure for spectra to be included in publications. ValiDichro currently includes 25 tests for data completeness, consistency and quality. For each test that is done, not only is a validation report produced, but the user is also provided with suggestions for correcting or improving the data. The ValiDichro server is freely available at http://valispec.cryst.bbk.ac.uk/circularDichroism/ValiDichro/upload.html

Mechanisms linking intimate partner violence and prevention of mother-to-child transmission of HIV: A qualitative study in South Africa.

: Prevention of mother-to-child transmission (PMTCT) can virtually eliminate HIV infection among infants, yet up to one-third of women miss PMTCT steps. Little is known about how partner dynamics such as intimate partner violence (IPV) influence pregnant and postpartum women's adherence to PMTCT. We conducted 32 qualitative interviews with HIV-positive pregnant and postpartum women in Johannesburg who experienced IPV. Trained researchers conducted in-depth interviews over the period of May 2014-Nov 2015 using narrative and social constructionist approaches. Interviews were transcribed verbatim and analyzed thematically and inductively using Dedoose qualitative software. Twenty-six women experienced recent IPV and one-third had poor adherence to PMTCT. Women's experience of partner violence influenced PMTCT behaviors through four pathways. First, fear of partner disclosure led some women to hide their HIV status to avoid a violent reaction. Despite strategic non-disclosure, several maintained good adherence by hiding medication or moving out from their partner's home. Second, IPV caused feelings of depression and anxiety that led to intentionally or accidentally missing medication. Five women stopped treatment altogether, in a type of passive suicidality, hoping to end the distress of IPV. Third, men's controlling behaviors reduced access to friends and family, limiting social support needed for good adherence. Fourth, in a protective pathway, women reported good adherence partly due to their mothering role. The identity around motherhood was used as a coping technique, reminding women that their infant's wellbeing depended on their own health. PMTCT is essential to prevent vertical HIV transmission, but women living with IPV face multiple pathways to non-adherence. Addressing IPV in antenatal care can support the health of women and infants and may enhance PMTCT coverage.<br/