Long-Term Stability of Baseline Impact Scores in High School Football Players across Age Groups

In recent decades, the increased awareness of the prevalence of concussions has resulted in significant advancements in concussion assessment and treatment, including annual or bi-annual pre-season computerized baseline assessments. However, limited research has focused on the differences in stability of baseline neurocognitive performance among different age groups in adolescence. The main purpose of the present study was to explore the long-term stability of ImPACT baseline assessments across one-year intervals in multiple age groups within a sample of high school football players. Subjects who completed two baseline assessments between the ages of 14 and 17 who had completed two baselines one year apart were selected from a de-identified archival database. Subjects were separated into three groups based on age at first baseline (i.e., 14, 15, and 16). Results indicate differences in baseline performance stability between age groups, with younger athletes demonstrating improvements in performance consistent with ongoing cognitive development and older athletes demonstrating more stability in performance. Importantly, the Reaction Time composite score remained stable among all groups. Results also provide evidence for wide ranging Reliable Change Indices across all age groups, which can make it difficult to interpret meaningful change after injury for those whose baseline was completed one year ago. These findings indicate younger athletes (i.e., 14- and 15-year-olds) should ideally complete baselines prior to each athletic season (e.g., fall, winter, spring), whereas older athletes (e.g., 16-year-olds) should complete baselines annually. The use of more frequent baselines aims to increase clinicians’ ability to detect clinically meaningful change following concussion, which in turn would lead to increased accuracy in return-to-play decision making. However, it is also important to recognize potential pitfalls of increased baseline testing (e.g., practice effects, lack of available resources), which are discussed. When recent baselines are not available, these results indicate the Reaction Time composite may serve as an important indicator of departure from baseline given its demonstrated stability across groups. In addition to clinical implications, the present results are consistent with Luria’s theory of cognitive development which indicates some cognitive skills continue to develop throughout adolescence along with corresponding cortical areas. Lastly, these results provide some information regarding the cognitive development of high school football players within the context of repeated exposure to sub-concussive impacts, though such conclusions are limited be the absence of a control group

Application of Importance Sampling for Point Source Analysis with the IceCube Neutrino Observatory

The IceCube Neutrino Observatory observes astrophysical neutrinos produced by the most energetic processes in the Universe. To date, the exact sources of these neutrinos, particles with no electric charge and almost negligible mass, are still a mystery. In an attempt to identify the sources of the highest energy neutrinos, the IceCube Collaboration uses likelihood analysis to search for clustering of neutrino events in the sky. An important part of this analysis is knowing how often neutrinos randomly cluster on the sky to replicate what an astrophysical neutrino source would look like. However, numerous simulations are required to properly understand this, and hence so are excessive computational resources. In this thesis, importance sampling is used to force rare clusters of neutrinos to occur on simulated skies. Two methods of importance sampling have been created to force these clusters to occur, a Gaussian weighting method and a binomial weighting method. Once these events are clustered, an appropriate weight can be applied to the sky the cluster is created on, and a likelihood analysis can be performed. We demonstrate how these methods can be used to identify the frequency at which rare clusterings of neutrinos occur, without the requirement of exhaustive computational time. We find that these rare clusters can be forced to occur on a sky with importance sampling, as can appropriate weights indicating the frequency the cluster would appear at a fixed point in space. However, further investigation is required to understand how to correctly apply sampling weights to the results when we perform the likelihood analysis over a full sky. The result of using importance sampling to identify rare clusters of neutrinos is used to investigate the effectiveness of a new test statistic for hypothesis testing in point source analysis. The most powerful test statistic for this analysis is the maximum likelihood, ℒ.̂ This is obtained by maximising a likelihood function relative to the maximum number of signal events, ̂, from some position on the sky. We construct a new statistic using a combination of the ℒ̂ and ̂ values, which has been suggested to be a more powerful test statistic than ℒ̂on its own. Using distributions obtained with importance sampling, we find that there is no evidence to indicate that a test statistic constructed using ℒ̂and ̂ is more powerful than ℒ̂on its own. Furthermore, we find that it simply replicates the results of ℒ̂by itself, due to the strong correlation between the ℒ̂and ̂ combinations in the null and alternate hypotheses tested.Thesis (MPhil) -- University of Adelaide, School of Physical Sciences, 202

Landing Gear Noise Prediction and Analysis for Tube-and-Wing and Hybrid-Wing-Body Aircraft

Improvements and extensions to landing gear noise prediction methods are developed. New features include installation effects such as reflection from the aircraft, gear truck angle effect, local flow calculation at the landing gear locations, gear size effect, and directivity for various gear designs. These new features have not only significantly improved the accuracy and robustness of the prediction tools, but also have enabled applications to unconventional aircraft designs and installations. Systematic validations of the improved prediction capability are then presented, including parametric validations in functional trends as well as validations in absolute amplitudes, covering a wide variety of landing gear designs, sizes, and testing conditions. The new method is then applied to selected concept aircraft configurations in the portfolio of the NASA Environmentally Responsible Aviation Project envisioned for the timeframe of 2025. The landing gear noise levels are on the order of 2 to 4 dB higher than previously reported predictions due to increased fidelity in accounting for installation effects and gear design details. With the new method, it is now possible to reveal and assess the unique noise characteristics of landing gear systems for each type of aircraft. To address the inevitable uncertainties in predictions of landing gear noise models for future aircraft, an uncertainty analysis is given, using the method of Monte Carlo simulation. The standard deviation of the uncertainty in predicting the absolute level of landing gear noise is quantified and determined to be 1.4 EPNL dB

Modeling and Prediction of Krueger Device Noise

This paper presents the development of a noise prediction model for aircraft Krueger flap devices that are considered as alternatives to leading edge slotted slats. The prediction model decomposes the total Krueger noise into four components, generated by the unsteady flows, respectively, in the cove under the pressure side surface of the Krueger, in the gap between the Krueger trailing edge and the main wing, around the brackets supporting the Krueger device, and around the cavity on the lower side of the main wing. For each noise component, the modeling follows a physics-based approach that aims at capturing the dominant noise-generating features in the flow and developing correlations between the noise and the flow parameters that control the noise generation processes. The far field noise is modeled using each of the four noise component's respective spectral functions, far field directivities, Mach number dependencies, component amplitudes, and other parametric trends. Preliminary validations are carried out by using small scale experimental data, and two applications are discussed; one for conventional aircraft and the other for advanced configurations. The former focuses on the parametric trends of Krueger noise on design parameters, while the latter reveals its importance in relation to other airframe noise components

Progress of Aircraft System Noise Assessment with Uncertainty Quantification for the Environmentally Responsible Aviation Project

Aircraft system noise predictions have been performed for NASA modeled hybrid wing body aircraft advanced concepts with 2025 entry-into-service technology assumptions. The system noise predictions developed over a period from 2009 to 2016 as a result of improved modeling of the aircraft concepts, design changes, technology development, flight path modeling, and the use of extensive integrated system level experimental data. In addition, the system noise prediction models and process have been improved in many ways. An additional process is developed here for quantifying the uncertainty with a 95% confidence level. This uncertainty applies only to the aircraft system noise prediction process. For three points in time during this period, the vehicle designs, technologies, and noise prediction process are documented. For each of the three predictions, and with the information available at each of those points in time, the uncertainty is quantified using the direct Monte Carlo method with 10,000 simulations. For the prediction of cumulative noise of an advanced aircraft at the conceptual level of design, the total uncertainty band has been reduced from 12.2 to 9.6 EPNL dB. A value of 3.6 EPNL dB is proposed as the lower limit of uncertainty possible for the cumulative system noise prediction of an advanced aircraft concept

On Noise Assessment for Blended Wing Body Aircraft

A system noise study is presented for the blended-wing-body (BWB) aircraft configured with advanced technologies that are projected to be available in the 2025 timeframe of the NASA N+2 definition. This system noise assessment shows that the noise levels of the baseline configuration, measured by the cumulative Effective Perceived Noise Level (EPNL), have a large margin of 34 dB to the aircraft noise regulation of Stage 4. This confirms the acoustic benefits of the BWB shielding of engine noise, as well as other projected noise reduction technologies, but the noise margins are less than previously published assessments and are short of meeting the NASA N+2 noise goal. In establishing the relevance of the acoustic assessment framework, the design of the BWB configuration, the technical approach of the noise analysis, the databases and prediction tools used in the assessment are first described and discussed. The predicted noise levels and the component decomposition are then analyzed to identify the ranking order of importance of various noise components, revealing the prominence of airframe noise, which holds up the levels at all three noise certification locations and renders engine noise reduction technologies less effective. When projected airframe component noise reduction is added to the HWB configuration, it is shown that the cumulative noise margin to Stage 4 can reach 41.6 dB, nearly at the NASA goal. These results are compared with a previous NASA assessment with a different study framework. The approaches that yield projections of such low noise levels are discussed including aggressive assumptions on future technologies, assumptions on flight profile management, engine installation, and component noise reduction technologies. It is shown that reliable predictions of component noise also play an important role in the system noise assessment. The comparisons and discussions illustrate the importance of practical feasibilities and constraints in aircraft system noise studies, which include aerodynamic performance, propulsion efficiency, flight profile limitation and many other factors. For a future aircraft concept to achieve the NASA N+2 noise goal it will require a range of fully successful noise reduction technology developments

Measurement of the Noise Resulting from the Interaction of Turbulence with a Lifting Surface

An experimental study of the noise resulting from the interaction of an airfoil with incident turbulence is presented. The test models include NACA0015 airfoils of different chord lengths, a flat plate with a sharp leading edge, and an airfoil of same section as a reference Fowler flap. The airfoils are immersed in nearly isotropic turbulence. Two approaches for performing the noise measurements are used and compared. The effects that turbulence intensity and scales, airfoil geometry, velocity and angle of attack have on the incident turbulence interaction noise are examined. Detailed directivity measurements are presented. It is found that noise spectral levels beyond the peak frequency decrease more with decreasing airfoil leading edge sharpness, and that spectral peak level (at 0 deg. angle of attack) appears to be mostly controlled by the airfoil fs thickness and chord. Increase in turbulence scale and intensity are observed to lead to a uniform increase of the noise spectral levels with an LI(sup 2) dependence (where L is the turbulence longitudinal integral scale and I is the turbulence intensity). Noise levels are found to scale with the 6th power of velocity and the 2nd power of the airfoil chord. Sensitivity to changes in angle of attack appears to have a turbulence longitudinal integral scale to chord (C) ratio dependence, with large effects on noise for L/C greater than or equal to 1 and decreased effects as L/C becomes smaller than 1. For all L/C values, the directivity pattern of the noise resulting from the incident turbulence is seen to remain symmetric with respect to the direction of the mean flow until stall, at which point, the directivity becomes symmetric with respect to the airfoil chord. It is also observed that sensitivity to angle of attack changes is more pronounced on the model suction side than on the model pressure side, and in the higher frequency range of the spectra for the largest airfoils tested (L/C less than 0.24)

Deciphering tectonic controls on fluvial sedimentation within the Barmer Basin, India: The lower cretaceous Ghaggar-Hakra formation

The Cretaceous of NW India is poorly known from sparse outcrops in Rajasthan and Gujarat. Here, we describe the stratigraphy and sedimentology of outcrops of the Ghaggar-Hakra Formation of probable Lower Cretaceous age from the Sarnoo Hills, eastern Barmer Basin, Rajasthan and correlate them with equivalent sediments in core from the subsurface of the Barmer Basin. At outcrop the Ghaggar-Hakra Formation contains three fluvial sandstone sequences of varying depositional type and geometry interbedded with associated floodplain deposits. At the base of the exposure the Darjaniyon-ki Dhani Sandstone is composed of compositionally mature, granule-grade quartzitic conglomerates that form braid bars. The deposits represent a poorly-developed braided system. Subsequently, the Sarnoo Sandstone constitutes medium- to very coarse-grained, cross-bedded sandstones, that fine upwards into fine-grained rippled and laminated sandstones, forming in-channel bars and point bars, implying the development of a meandering system. Lastly, capping the exposed sequence, the Nosar Member is composed of very coarse- to medium-grained, planar and trough cross-bedded quartz-arenites. These deposits represent in-channel dunes that display evidence of braiding, indicating the establishment of a well-developed braided system. The intervening mudrocks are characteristic of floodplain deposits, which are mottled, with vertical fractures, soil slickenlines and a pedogenic nature.Within the core the sequence differs from outcrop as there are two separate environments a braided system with associated floodplain deposits and a lacustrine system. The braided river comprises of very coarse- to fine-grained cross-bedded and rippled sandstones. The associated floodplain deposits are mottled, rooted, fractured and have rizoliths within. The detrital composition of the braidplain sandstones does not vary greatly from the outcrop as the minerals are quartz, lithics, heavy minerals and clays. However, the authigenic minerals do vary, as in the subsurface we see kaolinite clays, quartz overgrowths, siderite, pyrite and chlorite cements, whereas at the surface there are quartz overgrowths, calcite, dolomite and haematite cements with kaolinite clays. It is likely that the braided river in core is the same sequence as seen at outcrop. We interpret the successions here into a single fluvial system that has been affected by regional tectonics from the separation of Madagascar (Aptian) from the Indian continent and the continent drifting northwards. This heavily influenced the localised tectonics, which alludes to why there is a significant change in fluvial style from the Sarnoo Sandstone (meandering) to the Nosar Member (braided)

Potential for Landing Gear Noise Reduction on Advanced Aircraft Configurations

The potential of significantly reducing aircraft landing gear noise is explored for aircraft configurations with engines installed above the wings or the fuselage. An innovative concept is studied that does not alter the main gear assembly itself but does shorten the main strut and integrates the gear in pods whose interior surfaces are treated with acoustic liner. The concept is meant to achieve maximum noise reduction so that main landing gears can be eliminated as a major source of airframe noise. By applying this concept to an aircraft configuration with 2025 entry-into-service technology levels, it is shown that compared to noise levels of current technology, the main gear noise can be reduced by 10 EPNL dB, bringing the main gear noise close to a floor established by other components such as the nose gear. The assessment of the noise reduction potential accounts for design features for the advanced aircraft configuration and includes the effects of local flow velocity in and around the pods, gear noise reflection from the airframe, and reflection and attenuation from acoustic liner treatment on pod surfaces and doors. A technical roadmap for maturing this concept is discussed, and the possible drag increase at cruise due to the addition of the pods is identified as a challenge, which needs to be quantified and minimized possibly with the combination of detailed design and application of drag reduction technologies

ANOPP Landing Gear Noise Prediction Comparisons to Model-scale Data

The NASA Aircraft NOise Prediction Program (ANOPP) includes two methods for computing the noise from landing gear: the "Fink" method and the "Guo" method. Both methods have been predominately validated and used to predict full-scale landing gear noise. The two methods are compared, and their ability to predict the noise for model-scale landing gear is investigated. Predictions are made using both the Fink and Guo methods and compared to measured acoustic data obtained for a high-fidelity, 6.3%-scale, Boeing 777 main landing gear. A process is developed by which full-scale predictions can be scaled to compare with model-scale data. The measurements were obtained in the NASA Langley Quiet Flow Facility for a range of Mach numbers at a large number of observer polar (flyover) and azimuthal (sideline) observer angles. Spectra and contours of the measured sound pressure levels as a function of polar and azimuthal angle characterize the directivity of landing gear noise. Comparisons of predicted noise spectra and contours from each ANOPP method are made. Both methods predict comparable amplitudes and trends for the flyover locations, but deviate at the sideline locations. Neither method fully captures the measured noise directivity. The availability of these measured data provides the opportunity to further understand and advance noise prediction capabilities, particularly for noise directivity