541 research outputs found
The Author Fluency Task (AFT) as a measure of print exposure for Korean L1 speakers
No full textThe Author Recognition Test (ART) is a proxy measure of quantifying reading experience through estimates of print exposure. The test is simple and quick—participants are given a list of author and non-author names and are instructed to check the names they recognize as authors. However, the ART’s reliability in assessing L2 speakers’ print exposure is of concern. To address this problem, the Author Fluency Task (AFT) has been suggested as an alternative. In the AFT, participants are given 3 minutes to list as many authors as possible, and are assessed based on the number of valid authors provided. In a previous study, the AFT was evaluated in comparison to the ART as a predictor of vocabulary knowledge, in the context of L1 and L2. L1 English speakers (n=60) and L1 French/L2 English speakers (n=60) completed the AFT, ART, and Lexical Test for Advanced Learners of English (LexTALE). Vocabulary was assessed using tests of connectives and collocations knowledge. Results showed that both the AFT and the ART were significant predictors of vocabulary scores, but models for L1 and L2 participants revealed that the preferred predictor in L2 was the AFT. Furthermore, when controlling for English proficiency (LexTALE), only AFT predicted additional variance in L2. These findings suggest that semantic fluency for author names reflects more intentional reading experience compared to the general cultural knowledge indexed by ART, which may be sufficient for assessing L1 speakers. The current study is a replication of the previous study with a different cohort—L1 Korean / L2 English speakers (n=60). Participants will complete the same battery of tasks with the Korean versions of the LexTALE and the ART in place of the French versions. We test whether L1 Korean / L2 English reading experience (as assessed by AFT and ART) is associated with individual differences in knowledge of English connectives and collocations, even when accounting for word recognition in both languages. Analogous findings to the previous study will provide supporting evidence that the AFT is more effective than the ART at gauging print exposure in L2 speakers, even in more distant populations
Aerodynamic flight control to provide flight control augmentation for aft cg future launch vehicles
No full textThis document reports on the past six years of the extensive and comprehensive flight mechanics — stability and control, special research project conducted at the NASA Marshall Space Flight Center where the author was the designated Principal Investigator and only investigator. The author has proposed, designed, wind-tunnel tested, and analyzed the static and dynamic stability and control characteristics of both forward and aft located, all-movable, blunt-trailing-edge, flight control augmentors (FCA\u27s) for futm-e aft-cg large Saturn-class launch vehicles (LV\u27s) that would not be controllable with engine gimbaling alone. To the author\u27s knowledge, all-movable FCA\u27s have never been used on a large Saturn-class LV. A review of our national heritage of LV\u27s that have used aerodynamic surfaces (V-2, Pershing, Redstone, Saturn I, Saturn IB, Saturn V, X-15) and current usage of these surfaces by other nations has been conducted. Stability derivatives and control derivatives have been calculated from both wind tunnel test programs data and the U.S. Air Force DATCOM computer code. The enhanced static and dynamic flight stability of the aft-cg experimental LV, when treated with the author-designed FCA\u27s, has been assessed and quantified using static margin and short-period damping as criteria. The increased control effectiveness of the blunt-trailing-edge FCA design was found to provide the maximum flight control augmentation. A titanium matrix composite was selected as the FCA material and a design review was held at the manufacturer, Textron Specialty Materials Company. The change in aeroelastic effects of the aft-cg LV were considered. From the NASTRAN generated modal data, significant mode shapes and response spectra have been analyzed and presented for both the original and aft-cg experimental LV
Conservation and Ecotourism in Brazil and Mexico: The Development Impact
No full textConservation projects alter local productive modes and have an impact on livelihoods. For example, sea turtle conservation projects affect fishing communities through hunting restrictions. It is not painless for communities to improve fishing technology in order to prevent the accidental capture of sea turtles. The inability to adapt to environmental requirements forces fishermen to abandon traditional livelihoods. A combination of environmental conservation and ecotourism development can provide the solution. (...)Conservation and Ecotourism in Brazil and Mexico: The Development Impact
Flow over partially liquid filled cavity
No full textExperiments have been carried out to investigate the effect of liquid cavity filling on the behavior of the gas flow over a flat plate cavity. PIV measurements in the gas phase reveal that cavity filling can affect vortex shedding in the cavity mouth. Shear layer vortices can break-up into smaller vortices, thereby losing their periodic interaction with the aft wall and, hence, their sound producing potential. Expected is that this is one of the mechanisms causing sound mitigation in corrugated pipes with liquid addition, observed in literature
An “Author Fluency Task”: Semantic fluency as predictor of L2 vocabulary knowledge
No full textReading experience provides critical input for language learning. This is typically quantified via estimates of print exposure, such as the Author Recognition Test (ART), although it may be unreliable in L2. This study introduces the Author Fluency Task (AFT) as an alternative measure, comparing with ART for assessing knowledge of English discourse connectives and collocations among 60 bilingual French/English speakers, and a comparison sample of 60 L1 English speakers. Participants completed AFT, ART, and LexTALE in both languages. Analysis of L2 measures showed AFT more accurately predicted L2 vocabulary knowledge than ART, even when controlling for proficiency (LexTALE). Conversely, ART was more effective for L1 speakers, showing a striking dissociation between the measures across language groups. Additionally, data showed limited contributions from L1 proficiency and print exposure on L2 vocabulary. These findings recommend AFT as a valuable tool for quantifying the role of L2 print exposure for language learning
An “Author Fluency Task”: Semantic fluency as predictor of L2 vocabulary knowledge
No full textReading experience provides critical input for language learning. This is typically quantified via estimates of print exposure, such as the Author Recognition Test (ART), although it may be unreliable in L2. This study introduces the Author Fluency Task (AFT) as an alternative measure, comparing with ART for assessing knowledge of English discourse connectives and collocations among 60 bilingual French/English speakers, and a comparison sample of 60 L1 English speakers. Participants completed AFT, ART, and LexTALE in both languages. Analysis of L2 measures showed AFT more accurately predicted L2 vocabulary knowledge than ART, even when controlling for proficiency (LexTALE). Conversely, ART was more effective for L1 speakers, showing a striking dissociation between the measures between language groups. Additionally, data showed a limited role for L1 proficiency and print exposure on advanced L2 vocabulary acquisition. These findings recommend AFT as a valuable tool for quantifying L2 print exposure's role in language learning
Fore and Aft Channel Reconstruction in the TerraSAR-X Dual Receive Antenna Mode
No full textThe TerraSAR-X satellite is a high resolution synthetic aperture radar (SAR) system launched in June 2007 which provides the option to split the antenna in along-track direction and sample two physical channels separately. Modern SARs are equipped with active phased array antennas and multiple channels. In order to keep costs low TerraSAR-X uses the redundant receiver unit for the second channel such that fore and aft channel signals are combined by a hybrid coupler to form sum and difference channel data. The dual receive antenna mode can either be used to acquire along-track interferometric data or to acquire signals with different polarizations at the same time (Quad pol). Fore and aft channel reconstruction is necessary if ground moving target indication algorithms such as the displaced phase center antenna technique or along-track interferometry shall be applied, and in order to separate the horizontally and vertically polarized received signal components. The proposed approach uses internal calibration pulses from different calibration beams in order to estimate and compensate the hardware impact. The theoretical framework together with the results from the experimental data evaluation for the fore and aft channel reconstruction of the TerraSAR-X dual receive antenna mode are presented. The impact of the receive hardware transformation matrix estimation accuracy on errors in the reconstructed fore and aft channel image data is studied, and
first examples on the ground moving target indication capability of the TerraSAR-X dual receive antenna mode are given
Aerodynamic Loads on an Aft-Mounted Propeller Induced by the Wing Wake
No full textThis paper presents an experimental and numerical study of the aerodynamic in-plane and out-of-plane loads of a propeller which are induced by the wake of an upstream wing impinging on the lower half of the propeller disk. A propeller was installed behind a wing model in a low-speed wind-tunnel and measurements were taken with an external balance and a rotating shaft balance to determine the aerodynamic characteristics of the wing and propeller. The installation of the wing shows negligible changes in propeller thrust coefficient at low advance ratios, while at medium thrust conditions (C T ≈ 0.3), the wing shows a small increase in propeller thrust in the order of 1%. The installation of the propeller aft of the wing shows a change on propeller efficiency ranging from ∆η p =–0.01 to +0.04. The location of the wake impingement at the propeller plane is shown to play an important factor for the time averaged and unsteady propeller loads. The radial location where the largest change in load occurs due to wake impingement, coincides with the location of highest propeller loading. A simplified and computationally efficient method is presented for estimation of these unsteady propeller loads in non-uniform inflow. The method shows good agreement for the integral unsteady blade thrust and integral propeller for different wake impingement locations. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Flight Performance and Propulsio
Aerodynamic Performance of an Aircraft with Aft-Fuselage Boundary Layer Ingestion Propulsion
No full textView Video Presentation: https://doi-org.tudelft.idm.oclc.org/10.2514/6.2021-2467.vidBoundary Layer Ingestion (BLI) is a technology that promises fuel consumption benefits for future civil aircraft. However, it introduces detrimental aerodynamic interactions between the propulsor and the airframe. In particular, the inflow to the BLI propulsor is affected by the flow around the airframe elements. The non-uniform inflow can influence the fan aerodynamic, aeroacoustic and aeroelastic performance. As a consequence, the fan design needs to tolerate the inlet distortions in all the flight phases. This paper discusses an experimental study of the aerodynamic performance of an aircraft with a BLI propulsor integrated at the aft-fuselage section, representative of a Propulsive Fuselage Concept (PFC) aircraft. Aerodynamic load measurements show that the BLI propulsor affects the longitudinal and lateral-directional equilibrium of the aircraft in off-cruise conditions. Flow measurements at the BLI propulsor inlet indicate that the fuselage boundary layer induces the strongest total pressure distortion. However, particularly at a non-zero sideslip angle, the vertical tail plane strongly affects the inflow to the BLI propulsor, introducing non-symmetric total pressure and velocity distortions. The analysis of the momentum and power fluxes in the flowfield show that around 20% of the total aircraft drag is produced in the fuselage boundary layer, while around 5% of the total aircraft drag power is dissipated in the fuselage wake. Furthermore, the BLI propulsor substantially reduces the axial kinetic energy flux in the fuselage boundary layer (the so-called ``wake-filling'' effect), suggesting an increased propulsive efficiency.Flight Performance and PropulsionFlow Physics and Technolog
Frequency domain modeling of nonlinear end stop behavior in Tuned Mass Damper systems under single- and multi-harmonic excitations
No full textNonsmooth dynamics of a Tuned Mass Damper system with lateral stops are studied using an alternating frequency/time harmonic balancing (AFT-HB) method. To this end, an extremely stiff end stop nonlinearity is considered. The application range of AFT-HB is investigated by including up to 250 harmonics in the external force, as well as in the motion description. Numerical simulations are performed by making use of a Newmark time integration algorithm for numerical verification of the results. The results for single harmonic excitations are further verified with an existing pseudo-arclength path-following tool. Two excitation scenarios are considered: single harmonic- and a wide-spectrum excitation with uniform distribution and random phase correlation between the harmonics. The AFT-HB algorithm is found to accurately reproduce the time integration results, for all considered cases. Finally, insights are gained into the differences between the system responses to single- and multi-harmonic excitations.Accepted Author ManuscriptDynamics of Micro and Nano System
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