Computer-aided liner optimization for broadband noise

In this article the attenuation of broadband noise in an acoustically-lined circular-section duct is investigated. The aim is to predict how an axially segmented liner influences the attenuation of broadband noise in an aero-engine intake. The sound field is modelled using a multi-modal representation, assuming an ensemble of uncorrelated modes over a wide range of frequencies. An optimization procedure based on a Response Surface Model is used to investigate the optimum uniform and axially-segmented acoustic liner that maximizes the attenuation of broadband noise. An approximate calculation of the Perceived Noise level (PNL) is used for the objective function. In this article the benefit of using an axially segmented liner instead of a uniform liner to attenuate broadband noise is demonstrated

Tradeoffs in jet inlet design: a historical perspective

The design of the inlet(s) is one of the most demanding tasks of the development process of any gas turbine-powered aircraft. This is mainly due to the multi-objective and multidisciplinary nature of the exercise. The solution is generally a compromise between a number of conflicting goals and these conflicts are the subject of the present paper. We look into how these design tradeoffs have been reflected in the actual inlet designs over the years and how the emphasis has shifted from one driver to another. We also review some of the relevant developments of the jet age in aerodynamics and design and manufacturing technology and we examine how they have influenced and informed inlet design decision

Response surface method optimization of uniform and axially segmented duct acoustic liners

An extensive duct acoustics propagation study is presented that has been conducted to assess the design of a liner for an aeroengine inlet duct. The aim is to predict how different liner configurations, at various flight conditions affect the attenuation of sound in an inlet. Two different noise source models are used: single mode and multimode. These represent the two principal fan noise sources: tonal and broadband noise. The two noise source models are then combined to predict the overall attenuation. An optimization procedure based on a response surface model is presented, to investigate a uniform and an axially segmented acoustic liner. The objective function used in the optimization is based on an approximate calculation of the perceived noise level. The aim is to utilize and axially segmented liner to increase, compared to a uniform liner, the overall sound attenuation that is predicted. The main feature that emerges is that it is possible to increase the attenuation with an axially segmented liner only when a limited number of propagating modes are present

Liner optimization using a hybrid finite element method

This paper makes use of a novel finite element method for aeroacoustics analysis to examine and optimise the design of liners for aeroengine inlets. The finite element approximation used is very efficient since it allows the treatment of non-axisymmetric nacelles by combining a standard biquadratic approximation in the axial and radial directions, with a spectral representation in the circumferential direction. Results from the code are used in a multi-fidelity optimization approach which is based on response surface and formal design of experiment methods. The design optimization also makes use of Grid computing technology to allow efficient use of computational resources and effective management of the analysis results. The use of these various techniques in combination allows for significant improvements to liner designs with realistic geometries at modest computational cost

CSF angiogenin levels in amyotrophic lateral Sclerosis-Frontotemporal dementia spectrum

Objective: Angiogenin (ANG) is a pro-angiogenic and neurotrophic factor with an important role in stress-induced injury, by promoting neovascularization and neuronal survival. Identification of loss-of-function mutations and evidence of beneficial effect of ANG administration in transgenic SOD1G93A mice have linked ANG to the pathogenesis of Amyotrophic Lateral Sclerosis (ALS), stimulating interest in considering circulating ANG levels as an ALS disease biomarker although robust evidence is still lacking. Aim of our study was to assess differences of ANG levels in the cerebrospinal fluid (CSF) of a large cohort of patients with ALS and frontotemporal dementia (FTD) compared to controls and to explore correlations between ANG content and disease-related clinical variables. Methods: ANG levels were measured in CSF samples using a commercially available ELISA kit in 88 patients affected with ALS and/or FTD and 46 unrelated individuals (control group). Results: ANG levels didn\u2019t differ significantly between cases and controls. Patients with FTD or ALS-FTD showed significantly increased CSF concentration of ANG compared to ALS patients without dementia and controls in a multivariate regression model (p < 0.001). No correlations were found in ALS/FTD patients between ANG levels and clinical parameters, including age, presence of C9orf72 repeat expansion, body mass index (BMI). Conclusions: our findings highlight a role of ANG as CSF biomarker useful to identify ALS patients with concurrent FTD and suggest that it should be further explored as potential biomarker for FTD

An eye-tracker controlled cognitive battery: overcoming verbal-motor limitations in ALS

We assessed language, attention, executive, and social cognition abilities in a sample of patients with Amyotrophic Lateral Sclerosis (ALS) by means of a recently developed cognitive battery based on oculomotor control with eye-tracking (ET) technology. Twenty-one ALS patients and 21 age- and education-matched healthy subjects underwent the ET-based cognitive assessment, together with the standard cognitive screening tools [Frontal Assessment Battery (FAB); Montreal Cognitive Assessment (MoCA); and Digit Sequencing Task]. Psychological measures of anxiety (State-Trait Anxiety Inventory-Y) and depression (Beck Depression Inventory) were also collected, and an ET usability questionnaire was administered. For patients, clinical and respiratory examinations were also performed, together with behavioural assessment (Frontal Behavioural Inventory). The developed battery discriminated among patients and controls with regard to measures of verbal fluency, frontal abilities, and social cognition. Measures of diagnostic utility confirmed a higher diagnostic accuracy of such ET-based tests with respect to FAB; similar diagnostic accuracy emerged when comparing them to the other standard cognitive tools (MoCA, WM). Usability ratings about the ET tests were comparable among the two groups. The ET-based neuropsychological battery demonstrated good levels of diagnostic accuracy and usability in a clinical population of non-demented ALS patients, compared to matched healthy controls. Future studies will be aimed at further investigate validity and usability components by recruiting larger sample of patients, both in moderate-to-severe stages of the disease and affected by more severe cognitive impairment

An eye-tracking controlled neuropsychological battery for cognitive assessment in neurological diseases

Traditional cognitive assessment in neurological conditions involving physical disability is often prevented by the presence of verbal–motor impairment; to date, an extensive motor–verbal-free neuropsychological battery is not available for such purposes. We adapted a set of neuropsychological tests, assessing language, attentional abilities, executive functions and social cognition, for eye-tracking (ET) control, and explored its feasibility in a sample of healthy participants. Thirty healthy subjects performed a neuropsychological assessment, using an ET-based neuropsychological battery, together with standard “paper and pencil” cognitive measures for frontal (Frontal Assessment Battery—FAB) and working memory abilities (Digit Sequencing Task) and for global cognitive efficiency (Montreal Cognitive Assessment—MoCA). Psychological measures of anxiety (State-Trait Anxiety Inventory-Y—STAI-Y) and depression (Beck Depression Inventory—BDI) were also collected, and a usability questionnaire was administered. Significant correlations were observed between the “paper and pencil” screening of working memory abilities and the ET-based neuropsychological measures. The ET-based battery also correlated with the MoCA, while poor correlations were observed with the FAB. Usability aspects were found to be influenced by both working memory abilities and psychological components. The ET-based neuropsychological battery developed could provide an extensive assessment of cognitive functions, allowing participants to perform tasks independently from the integrity of motor or verbal channels. Further studies will be aimed at investigating validity and usability components in neurological populations with motor–verbal impairments