Psychoacoustic Test to Determine Sound Quality Metric Indicators of Rotorcraft Noise Annoyance

Noise certification metrics such as Effective Perceived Noise Level and Sound Exposure Level are used to ensure that helicopters meet regulations, but these metrics may not be good indicators of annoyance since noise complaints against helicopters persist. Sound quality (SQ) metrics, specifically fluctuation strength, tonality, impulsiveness, roughness, and sharpness, are explored to determine their relationship with annoyance. A psychoacoustic test was conducted at the NASA Langley Research Center Exterior Effects Room to assess annoyance to helicopter-like sounds over a range of SQ metric values. The amplitude, phase, and frequency of the AS350 helicopter main and tail rotor blade passage signal harmonics were manipulated to produce 105 unique helicopter-like sounds with prescribed values of SQ metrics. All sounds were set to roughly the same loudness level. These sounds were played to 40 subjects who rated each sound for annoyance. Analyses given in this paper point to which SQ metrics are important to the helicopter noise annoyance response

Peak Sidelobe Level Distribution Computation for Ad Hoc Arrays using Extreme Value Theory

Extreme Value Theory (EVT) is used to analyze the peak sidelobe level distribution for array element positions with arbitrary probability distributions. Computations are discussed in the context of linear antenna arrays using electromagnetic energy. The results also apply to planar arrays of random elements that can be transformed into linear arrays.Engineering and Applied Science

A Recording-Based Method for Auralization of Rotorcraft Flyover Noise

Rotorcraft noise is an active field of study as the sound produced by these vehicles is often found to be annoying. A means to auralize rotorcraft flyover noise is sought to help understand the factors leading to annoyance. Previous work by the authors focused on auralization of rotorcraft fly-in noise, in which a simplification was made that enabled the source noise synthesis to be based on a single emission angle. Here, the goal is to auralize a complete flyover event, so the source noise synthesis must be capable of traversing a range of emission angles. The synthesis uses a source noise definition process that yields periodic and aperiodic (modulation) components at a set of discrete emission angles. In this work, only the periodic components are used for the source noise synthesis for the flyover; the inclusion of modulation components is the subject of ongoing research. Propagation of the synthesized source noise to a ground observer is performed using the NASA Auralization Framework. The method is demonstrated using ground recordings from a flight test of the AS350 helicopter for the source noise definition

Emerging trends in cooling technologies for photovoltaic systems

Photovoltaic systems (PV), particularly solar photovoltaics, are gaining popularity as renewable energy sources. The rapid deployment of PV systems has attracted substantial investments, with around 170 billion dollars projected by 2025. However, challenges like dust accumulation, solar radiation, and temperature rise hinder PV efficiency. Elevated temperatures, exceeding standard levels, notably decrease voltage output and overall electricity generation efficiency. This review provides a comprehensive overview of recent cooling techniques adopted to enhance solar PV performance. Beginning with an introduction to global warming's impact and renewable energy's significance, the article explores cooling methodologies for solar PVs. These encompass Absorption & adsorption-based, PV/T hybrid, Microtechnology-based, and Water and air-based cooling systems. The review concludes this section with a detailed table comparing cooling technologies' performance, benefits, and challenges. The review then delves into four primary cooling techniques: Active cooling, Passive cooling, Nanofluid-based cooling, and Thermoelectric cooling. Passive cooling, which effectively reduces PV system temperature without external energy sources, is highlighted. Modalities of Passive cooling methods, such as Radiative cooling, Evaporative cooling, Liquid immersions, and Material coatings, are elaborated. Concluding, the article addresses challenges, opportunities, and future prospects related to diverse cooling techniques' utilisation, aiming to elevate solar PV system efficiency

Tin oxide for optoelectronic, photovoltaic and energy storage devices: a review

Tin dioxide (SnO2), the most stable oxide of tin, is a metal oxide semiconductor that finds its use in a number of applications due to its interesting energy band gap that is easily tunable by doping with foreign elements or by nanostructured design such as thin film, nanowire or nanoparticle formation, etc., and its excellent thermal, mechanical and chemical stability. In particular, its earth abundance and non-toxicity make it very attractive for use in a number of technologies for sustainable development such as energy harvesting and storage. This article attempts to review the state of the art of synthesis and properties of SnO2, focusing primarily on its application as a transparent conductive oxide (TCO) in various optoelectronic devices and second in energy harvesting and energy storage devices where it finds its use as an electron transport layer (ETL) and an electrode material, respectively. In doing so, we discuss how tin oxide meets the requirements for the above applications, the challenges associated with these applications, and how its performance can be further improved by adopting various strategies such as doping with foreign metals, functionalization with plasma, etc. The article begins with a review on the various experimental approaches to doping of SnO2 with foreign elements for its enhanced performance as a TCO as well as related computational studies. Herein, we also compare the TCO performance of doped tin oxide as a function of dopants such as fluorine (F), antimony (Sb), tantalum (Ta), tungsten (W), molybdenum (Mo), phosphorus (P), and gallium (Ga). We also discuss the properties of multilayer SnO2/metal/SnO2 structures with respect to TCO performance. Next, we review the status of tin oxide as a TCO and an ETL in devices such as organic light emitting diodes (OLEDs), organic photovoltaics (OPV), and perovskite solar cells (including plasma treatment approaches) followed by its use in building integrated photovoltaic (BIPV) applications. Next, we review the impact of SnO2, mainly as an electrode material on energy storage devices starting from the most popular lithium (Li)-ion batteries to Li–sulfur batteries and finally to the rapidly emerging technology of supercapacitors. Finally, we also compare the performance of doped SnO2 with gallium (Ga) doped zinc oxide (ZnO), the main sustainable alternative to SnO2 as a TCO and summarize the impact of SnO2 on circular economies and discuss the main conclusions and future perspectives. It is expected that the review will serve as an authoritative reference for researchers and policy makers interested in finding out how SnO2 can contribute to the circular economy of some of the most desired sustainable and clean energy technologies including the detailed experimental methods of synthesis and strategies for performance enhancement

A perception-driven autonomous urban vehicle

This paper describes the architecture and implementation of an autonomous passenger vehicle designed to navigate using locally perceived information in preference to potentially inaccurate or incomplete map data. The vehicle architecture was designed to handle the original DARPA Urban Challenge requirements of perceiving and navigating a road network with segments defined by sparse waypoints. The vehicle implementation includes many heterogeneous sensors with significant communications and computation bandwidth to capture and process high-resolution, high-rate sensor data. The output of the comprehensive environmental sensing subsystem is fed into a kino-dynamic motion planning algorithm to generate all vehicleFigure 1: Talos in action at the National Qualifying Event. motion. The requirements of driving in lanes, three-point turns, parking, and maneuvering through obstacle fields are all generated with a unified planner. A key aspect of the planner is its use of closed-loop simulation in a Rapidly-exploring Randomized Trees (RRT) algorithm, which can randomly explore the space while efficiently generating smooth trajectories in a dynamic and uncertain environment