bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the use of large scale windtunnel models
Authors: Giacchetto A. 
Published: February 2023

Abstract
The use of large scale windtunnel models offers considerable advantages to an experimenter1. the possibility of obtaining high Reynolds number, certainly significant and sometimes equal to that in flight, for moderate stagnation pressures2. an accurate representation of geometric elements, i.e. good form similitude (it is necessary to emphasise the importance of being very thorough in this area)3. large internal volumes which enable numerous transducers to be implanted, ambitious experimental devices and means of remote control of model motorisation4. test conditions remain those corresponding to industrial manufacturing methods and so avoid problems related to extreme miniaturisation.Additionally, there exist some test conditions for which scale reduction is limited or even impossible; for example, because of physical phenomena, limitation in industrial methods of miniaturisation, or quite simply because the subject is itself the flying object. These conditions are applicable to all tests whether industrial or research. They are especially true for industrial tests where these concern important decisions. They are also true for research tests whenever they need to be sufficiently close to flight reality. Wind-tunnels are always a means to reduce the costs and risks of aeronautical project developments. The risk taken in extrapolating from windtunnel tests to flight are lower when the test is more realistic and this gives a clear advantage to tests on large sized models.
Multidisciplinary optimisation of a supersonic transport using design of experiments theory and response surface modelling
Authors: Giunta A. A. , Balabanov V. , Haim D. , Grossman B. , Mason W. H. , Watson L. T. , Haftka R. T. 
Published: February 2023

AbstractThe presence of numerical noise in engineering design optimisation problems inhibits the use of many gradient-based optimisation methods. This numerical noise may result in the inaccurate calculation of gradients which in turn slows or prevents convergence during optimisation, or it may promote convergence to spurious local optima. The problems created by numerical noise are particularly acute in aircraft design applications where a single aerodynamic or structural analysis of a realistic aircraft configuration may require tens of CPU hours on a supercomputer. The computational expense of the analyses coupled with the convergence difficulties created by numerical noise are significant obstacles to performing aircraft multidisciplinary design optimisation. To address these issues, a procedure has been developed to create noise-free algebraic models of subsonic and supersonic aerodynamic performance quantities, for use in the optimisation of high-speed civil transport (HSCT) aircraft configurations. This procedure employs methods from statistical design of experiments theory and response surface modelling to create the noise-free algebraic models. Results from a sample HSCT design problem involving ten variables are presented to demonstrate the utility of this method.
Efficient and robust algorithms for trim and stability analysis of advanced rotorcraft simulations
Authors: McVicar J. S. G. , Bradley R. 
Published: February 2023

AbstractThis paper derives innovative techniques for use in the trimming and stability analysis of advanced rotorcraft simulations. It begins by exploiting the symmetry of the rotor to produce an efficient definition of periodic trim which is applicable to rotorcraft simulations. This definition is then expanded to produce a trimming algorithm which is capable of concurrently ascertaining the initial conditions and control inputs necessary to trim latest generation simulation models to a specified periodic trim state. The algorithm is based on a periodic shooting approach with Newton-Raphson iteration and exploits the symmetry of the rotor to minimise computational workload. The definition of periodic trim is then further developed to produce a technique by which the stability characteristics of rotorcraft can be ascertained from advanced simulation models. This technique is based on a Floquet approach and again exploits the symmetry of the rotor to reduce computational burden. The paper concludes by presenting results obtained when the stability characteristics of a tiltrotor simulation model are investigated.
The use of inverse simulation for preliminary assessment of helicopter handling qualities
Authors: Thomson D. G. , Bradley R. 
Published: February 2023

AbstractThis paper describes a method for using inverse simulation to obtain a preliminary assessment of helicopter handling qualities. Formal descriptions of standard manoeuvres, defined to establish the handling qualities of military helicopters, are used to drive an inverse simulation of a subject helicopter. The simulation generates the controls and states of the helicopter as it executes the manoeuvre and the results may be used to calculate values of quickness, a parameter defined to measure responsiveness. Initial results reveal that in the context of inverse simulation quickness is independent of vehicle configuration when, as specified in the requirements, the quickness is based on the helicopter's kinematic states. An alternative quickness parameter, associated with the control displacements required to fly the manoeuvre is shown to be capable of discriminating between the pilot workload involved in flying two different configurations through the same manoeuvre.
Recent experience in the prediction and assessment of windtunnel wall interference
Authors: Ashill P. R. , Jordan R. , Simmons M. J. 
Published: February 2023

AbstractRecent experience in the prediction and assessment of windtunnel wall interference is reviewed. Three areas of development are identified. The first deals with the influence of wall boundary layers on wall-induced velocities in solid-wall windtunnels; the second is concerned with preparations for determining wall interference in the European Transonic Windtunnel and the third relates to recent studies aimed at providing the basis for correcting data to free-air conditions.
V-22 flight test update
Authors: Dunford P. J. , Marr R. L. 
Published: February 2023

AbstractThe Bell-Boeing V-22 Osprey tiltrotor is a unique aircraft capable of landing vertically, flying at speeds in excess of 300 KTAS (knots, true air speed), with the added feature of folding the rotor and wing for deployment from ships for US Navy, Marines, and SOF operations. During the development of the V-22, including 1200 hours of flight testing, a number of significant technology and design development challenges were encountered and overcome. This paper presents an overview of many of these challenges. It also reviews the integrated approach to testing to be used in the next phase of the flight test programme, and describes the changes that have been implemented to improve flight test productivity.
Predicted performance characteristics of a
variable cycle turbofan
Authors: Ulizar I. , Pilidis P. 
Published: February 2023

AbstractThe selective bleed turbofan is a two shaft, three compressor, variable cycle aircraft engine. Its bypass ratio (BPR) can be modulated to suit the operating flight conditions. At subsonic flight speeds it operates as a medium bypass turbofan (low pressure mode or LPM). It becomes a low bypass turbofan (high pressure mode or HPM) when flying faster and is capable of supersonic cruise without reheat (RH).The aim of this paper is to describe the selection of the main engine design parameters in the HP mode and to outline the challenges to be met to enable the powerplant to operate in the other mode. The components have to perform satisfactorily over a wide range of varying conditions. The resulting demands are reflected in many ways, for example in the operating lines of the low pressure compressors and in the overall efficiency changes with increased bypass ratio. In the case of the present investigation the two bypass ratios selected are 0·3 for the high pressure mode and 0·7 for the low pressure mode. The latter was selected after an examination of a choice of bypass ratios ranging from 0·4 to 1·0. The change in variable stators required to achieve the LP mode cycle is indicated.The effect of changing bypass ratio on engine performance and handling is shown. The main conclusion is that the design of this engine seems to be feasible within current technological capabilities and further investigation is encouraged because it appears to yield significant benefits.
Repairing composite aircraft structures — RAF experience of peacetime and battle damage techniques
Authors: Chicken S. H. , Welburn S. , Reed S. 
Published: February 2023

AbstractThe RAF has been undertaking peacetime repairs on composite rotor blades, fibreglass radomes and panels on a variety of combat aircraft types for many years. However, the Service's main experience in the repair of aircraft structures manufactured from carbon fibre composite (CFC) material has been related to the Harrier II. In any future conflict involving air power, battle damaged aircraft, including the Harrier II, will have to be repaired rapidly to meet operational requirements. The repair techniques used may have to differ from those undertaken in peacetime but they must still aim to restore the full static strength of the aircraft within the time constraints imposed by the operational situation. Therefore, aircraft battle damage repair (ABDR) is a carefully planned alternative to conventional repair techniques. This paper describes the main CFC structures of the Harrier II and outlines the variety of RAF peace and wartime structural repair procedures applied to the aircraft. Examples are provided of various simple and complex repairs. Greater emphasis on adhesively bonded repairs is called for if Harrier II experience is to aid in the logistic support of Eurofighter 2000 (EF2000) in peace and war.
A problem of minimal induced resistance in unsteady motion
Authors: Losilevskii G. 
Published: February 2023

AbstractEnergy considerations are used to find the spanwise circulatory lift distribution yielding minimal induced resistance for a harmonically oscillating planar wing in a steady incompressible flow. Under the restriction that the time-averaged and oscillatory constituents of the wing's circulatory lift are known, the optimal distribution is such that its time-averaged constituent is elliptical, but the oscillatory one is generally not. The latter varies from elliptical to rectangular as the frequency of the oscillations increases. When the oscillatory part of the lift is not prescribed, present results infer that its reduction — as, for example, by an elastic twist — will typically reduce the drag, even if the twist yields a non-optimal (for that lift) lift distribution.
The reduction of numerical entropy generated by unsteady Shockwaves
Authors: Allen C. B. 
Published: February 2023

AbstractThe computation of slowly moving Shockwaves is considered. A numerical error is introduced into the solution during an explicit computation, which results in the generation of spurious entropy. The generation of this spurious entropy and its effect on the pressure wave in Euler flows is examined, in one dimension by considering a moving shock in a constant area duct, and in two dimensions by considering an unsteady aerofoil flow. An efficient temporal discretisation is presented, whose advantages over the explicit scheme are two-fold. First, the numerical entropy generation due to shock motion is eliminated, and second, the CPU requirements for a two-dimensional unsteady computation are reduced by a factor of five from that required for the explicit scheme, for no loss of accuracy.
Effect of sandpaper roughness and stream turbulence on the laminar layer and its transition
Authors: Gibbings J. C. , Al-Shukri S. M. 
Published: February 2023

AbstractThe work reported here was an experimental study of the combined influence of a sandpaper rough surface and a stream turbulence upon laminar and transitional boundary layers. Data correlations were obtained using the previously determined parameter of an equivalent Nikuradse size of roughness. These correlations are derived for the development of the laminar layer in thickness and profile shape factor, for the onset and the length of transition and for the distribution of intermittency through transition. Further fundamental differences in flow behaviour from those in a rough pipe have been found to add to those already reported.
A facility for simultaneous particle image velocimetry and high resolution unsteady pressure measurement
Authors: Hurst D. , Galbraith R. A. McD. , Coton F. N. , Grant I. 
Published: February 2023

AbstractThis paper describes a facility for the acquisition of simultaneous high quality particle image velocimetry (PIV) and unsteady surface pressures with high spatial and temporal resolution. The facility, developed through a long-standing collaboration between the Department of Aerospace Engineering at Glasgow University and the Fluid Loading and Instrumentation Centre at Heriot-Watt University, is currently being used in collaborative projects and has the potential to provide a level of detail previously unattainable for CFD validation.Results from both measurement techniques will be presented to demonstrate the range and potential of the two systems. In addition, the value of combining the two techniques will be demonstrated by results from a blade-vortex interaction experiment in which both methods were applied. Finally, future applications of the combined system will be discussed.
Vortical flow structures at a helicopter rotor model measured by LDV and PIV
Authors: Raffel M. , Seelhorstt U. , Willert C. 
Published: February 2023

AbstractFlowfield measurements of the blade tip vortices from a rotating helicopter rotor model were performed by three component laser-Doppler velocimetry (3D-LDV) and conventional (two component) particle image velocimetry (PIV). In general, the results are in good correspondence, but also illustrate the different properties of both techniques: LDV offers the capability of three-component measurements, whereas PIV captures the unsteadyness of the flowfield.
EPS Sensitivity and Mergers
Authors: Dasgupta Sudipto , Harford Jarrad , Ma Fangyuan 
Published: February 2023

AbstractAnnouncements of mergers very often discuss the immediate impact of the deal on the acquirer’s earnings per share (EPS). We argue that the focus on EPS reflects the difficulty of evaluating and communicating deal synergy in mergers and acquisitions (M&A) practice and provide supporting evidence. We show that the acquirer’s EPS focus affects how deals are structured, the premium that is paid, and the types of deals that are done. EPS-driven M&A decisions are also associated with costly distortions in the acquirer’s financial and investment policies.
Broad learning control of a two-link flexible manipulator with prescribed performance and actuator faults
Authors: Niu Wenkai , Kong Linghuan , Wu Yifan , Huang Haifeng , He Wei 
Published: February 2023

AbstractIn this paper, we present a broad learning control method for a two-link flexible manipulator with prescribed performance (PP) and actuator faults. The trajectory tracking errors are processed through two consecutive error transformations to achieve the constraints in terms of the overshoot, transient error, and steady-state error. And the barrier Lyapunov function is employed to implement constraints on the transition state variable. Then, the improved radial basis function neural networks combined with broad learning theory are constructed to approximate the unknown model dynamics of flexible robotic manipulator. The proposed fault-tolerant PP control cannot only ensure tracking errors converge into a small region near zero within the preset finite time but also address the problem caused by actuator faults. All the closed-loop error signals are uniformly ultimately bounded via the Lyapunov stability theory. Finally, the feasibility of the proposed control is verified by the simulation results.
Prolonged duration of post-traumatic amnesia: A sensitive classification for predicting cognitive outcomes in children recovering from traumatic brain injury
Authors: Segev Shira , Silberg Tamar , Bar Orly , Erez Neta , Ahonniska-Assa Jaana , Brezner Amichai , Landa Jana 
Published: February 2023

AbstractObjective:A paucity of data exists regarding the duration of post-traumatic amnesia (PTA) as a predictor of cognitive functioning among children after traumatic brain injury (TBI). The study aimed to assess the relationship between PTA duration and areas of neurocognitive function among the pediatric population in the sub-acute phase of recovery and rehabilitation.Methods:Data were collected from medical files on 103 children aged 5.5–16.5 hospitalized at a pediatric rehabilitation department with a diagnosis of moderate–severe TBI (msTBI) between the years 2004–2019. The Children Orientation and Amnesia Test was used to evaluate PTA duration. Measures of high-order cognitive abilities of attention and executive function were collected using the Test of Everyday Attention–Child version (TEA-Ch).Results:Three PTA duration groups were assembled out of a cluster analysis: “Long PTA” (M = 21 days), “Very Long PTA” (M = 47 days), and “Extremely Long PTA” (M = 94 days). Analyses revealed that the “Long PTA” group preformed significantly better than the “Very Long PTA” and “Extremely Long PTA” groups on all TEA-Ch measures, that is, Selective Attention, Attentional Control Switching, and Sustained Attention.Conclusions:This study is the first to demonstrate that PTA duration is a useful predictor of high-order cognitive functions among children with msTBI in the sub-acute phase of recovery and rehabilitation. The findings emphasize the importance of using a more sensitive classification of prolonged PTA durations to improve outcome prediction and allocation of resources to those who can benefit most after severe brain injuries.
Greater subjective cognitive decline severity is associated with worse memory performance and lower entorhinal cerebral blood flow in healthy older adults
Authors: Nakhla Marina Z. , Bangen Katherine J. , Schiehser Dawn M. , Roesch Scott , Zlatar Zvinka Z. 
Published: February 2023

AbstractObjective:Subjective cognitive decline (SCD) is a potential early risk marker for Alzheimer’s disease (AD), but its utility may vary across individuals. We investigated the relationship of SCD severity with memory function and cerebral blood flow (CBF) in areas of the middle temporal lobe (MTL) in a cognitively normal and overall healthy sample of older adults. Exploratory analyses examined if the association of SCD severity with memory and MTL CBF was different in those with lower and higher cardiovascular disease (CVD) risk status.Methods:Fifty-two community-dwelling older adults underwent magnetic resonance imaging, neuropsychological testing, and were administered the Everyday Cognition Scale (ECog) to measure SCD. Regression models investigated whether ECog scores were associated with memory performance and MTL CBF, followed by similar exploratory regressions stratified by CVD risk status (i.e., lower vs higher stroke risk).Results:Higher ECog scores were associated with lower objective memory performance and lower entorhinal cortex CBF after adjusting for demographics and mood. In exploratory stratified analyses, these associations remained significant in the higher stroke risk group only.Conclusions:Our preliminary findings suggest that SCD severity is associated with cognition and brain markers of preclinical AD in otherwise healthy older adults with overall low CVD burden and that this relationship may be stronger for individuals with higher stroke risk, although larger studies with more diverse samples are needed to confirm these findings. Our results shed light on individual characteristics that may increase the utility of SCD as an early risk marker of cognitive decline.
Disrupting future discounting: a commentary on an underutilised psychological approach for improving adherence to diet and physical activity interventions
Authors: Kakoschke Naomi , Cox David N , Ryan Jillian , Gwilt Ian , Davis Aaron , Jansons Paul , de Courten Barbora , Brinkworth Grant 
Published: February 2023

AbstractNon-communicable diseases (NCD) such as CVD and type 2 diabetes mellitus are major contributors to the burden of disease. NCD are largely driven by modifiable lifestyle factors including poor diet and insufficient physical activity, and consequently, prevention is a public health priority. Although diet and physical activity levels can be improved via lifestyle interventions, long-term adherence to such interventions remains low, which limits their effectiveness. Thus, it is critical to identify the underlying mechanisms that challenge uptake and adherence to such interventions. The current commentary discusses an important, but underexplored, psychological driver of poor adherence to lifestyle interventions, namely, future discounting, which describes the tendency to prefer smaller, short-term rewards over larger, long-term rewards. For example, in the nutrition domain, future discounting refers to valuing the immediate reward of excessive intake of energy-dense, nutrient-poor, discretionary foods high in salt, sugar, and saturated fat, and insufficient intake of low-energy, nutrient-dense, whole foods such as vegetables. Prominent theoretical models propose that excessive future discounting is a major contributor to the development of unhealthy lifestyle behaviours. Furthermore, a vast body of evidence suggests that future discounting plays a key role in risk of NCD. Thus, the evidence to date supports the idea that future discounting is an important multi-behaviour target for supporting lifestyle behaviour change; however, this approach has been largely neglected in preventive health efforts. Furthermore, this commentary discusses promising techniques (e.g. Episodic Future Thinking) for disrupting future discounting to promote improved adherence to lifestyle interventions aimed at reducing NCD risk.
Duration of the constitution-making process as an indicator of post-constitutional political uncertainty: The insurance theory revisited
Authors: Aydin-Cakir Aylin 
Published: February 2023

AbstractCriticizing the insurance theory, this article asserts that to measure post-constitutional political uncertainty, one should consider not only the power distribution among the ‘political’ actors but the power distribution among all actors involved in the constitution-making process, including the public and civil society. Comparing the constitution-making processes of the constitutions of Egypt (2012) and Tunisia (2014), this study presents the duration of the constitution-making process as an alternative measure of power distribution among all actors. The theoretical framework asserts that the long constitution-making process increases the possibility of deliberation at the public level. That will help to develop trust among polarized political actors and improve political actors’ perception of the public as a credible control and constraint mechanism. This will ensure that the incoming government will respect the newly established institutions and lead to the establishment of an independent and powerful judiciary. In the second part of the article, to test this argument, I use a large dataset that covers information on the content and design processes of 140 countries’ most recent constitutions adopted between 1945 and 2018. The empirical results indicate that as the duration of the constitution-making increases, the number of constitutional guarantees for judicial independence also increases.