The damping properties of the foam-filled shaft of primary feathers of the pigeon Columba livia

The avian feather combines mechanical properties of robustness and flexibility while maintaining a low weight. Under periodic and random dynamic loading, the feathers sustain bending forces and vibrations during flight. Excessive vibrations can increase noise, energy consumption, and negatively impact flight stability. However, damping can alter the system response, and result in increased stability and reduced noise. Although the structure of feathers has already been studied, little is known about their damping properties. In particular, the link between the structure of shafts and their damping is unknown. This study aims at understanding the structure-damping relationship of the shafts. For this purpose, laser Doppler vibrometry (LDV) was used to measure the damping properties of the feather shaft in three segments selected from the base, middle, and tip. A combination of scanning electron microscopy (SEM) and micro-computed tomography (µCT) was used to investigate the gradient microstructure of the shaft. The results showed the presence of two fundamental vibration modes, when mechanically excited in the horizontal and vertical directions. It was also found that the base and middle parts of the shaft have higher damping ratios than the tip, which could be attributed to their larger foam cells, higher foam/cortex ratio, and higher percentage of foam. This study provides the first indication of graded damping properties in feathers.

Adaptive Unsaturated Bistable Stochastic Resonance Multi-Frequency Signals Detection Based on Preprocessing

Stochastic resonance (SR) has been widely used for extracting single-frequency weak periodic signals. For multi-frequency weak signals, empirical mode decomposition (EMD) can adaptively decompose the complex signal, but this method also suffers from mode mixing, which affects the accuracy of detection. SR can convert part of the noise energy into signal energy, which compensates for the defects of EMD. According to the advantages of SR and EMD, we constructed a multi-frequency signals detection method using adaptive unsaturated bistable SR based on EMD (EMD-AUBSR). In this study, we avoid the inherent saturation of SR by reconstructing the potential function and improve the multi-frequency signals detection ability by adding the preprocessing element. For strong background noise, the experimental results show that this proposed can effectively detect multi-frequency weak signals and decrease signal aliasing, whereas EMD alone cannot.

Identification of the Major Noise Energy Sources in Rail Vehicles Moving at a Speed of 200 km/h

In this work, the problematic identification of the main sources of noise occurring from the exploitation of railway vehicles moving at a speed of 200 km/h were analyzed. Within the conducted experimental research, the testing fields were appointed, measurement apparatus selected, and a methodology for conducting measurements was defined, including the assessment of noise on a curve and straight track for electric multiple units of the so-called Pendolino, an Alstom type ETR610 series ED25 train. The measurements were made using a microphone camera Bionic S-112 at a distance of 22 m from the track axis. As a result of the conducted experimental research, it was indicated that the noise resulting from vibrations arising at the wheel-rail contact (rolling noise) was the dominant source of sound.

Energy conservation potential in highway illumination system: A Techno-Enviro-Economic study on retrofitting HPS with LED luminaires

Adequate and appropriate illumination across the highway isessential for safety. High-pressure sodium luminaires (HPS) are usually standard throughout Pakistan. However, with the advancements in illumination technologies and growing trend of energy efficiency, retrofitting of conventional HPS luminaires with light-emitting diode luminaires (LEDs) is becoming popular. Low energy consumption, high color rendering index (CRI), longer life span, and variety in correlated color temperature (CCT) make LED luminaires ideal for replacing inefficient HPS lights. The retrofitting of HPS with LED illumination system comes with a capital cost, and its feasibility depends on the energy conservation potential. This study presents a case of 4,014 HPS luminaires installed across an 85 km long highway in second highly populated city of Pakistan. A targeted energy audit of HPS illumination system was conducted and compared with the proposed LED system of equivalent illumination quality. The results indicate that by retrofitting the HPS luminaires, the energy consumption can be reduced by 60% and with 83.3% reduction in the apparent power. Furthermore, the proposed LED illumination system will significantly improve the power quality, light noise, energy losses, carbon footprint, and operational cost.

Impact of Artificial Noise on Security Capability of Energy Harvesting Overlay Networks

Artificial noise, energy harvesting, and overlay communications can assure design metrics of modern wireless networks such as data security, energy efficiency, and spectrum utilization efficiency. This paper studies impact of artificial noise on security capability of energy harvesting overlay networks in which the cognitive transmitter capable of self-powering its operation by harvesting radio frequency energy and self-securing its communications against eavesdroppers by generating artificial noise amplifies and forwards the signal of the primary transmitter as well as transmits its individual signal concurrently. To quantify this impact, the current paper firstly suggests accurate expressions of crucial security performance indicators. Then, computer simulations are supplied to corroborate these expressions. Finally, numerous results are demonstrated to expose insights into this impact from which optimum specifications are determined. Notably, primary/cognitive communications can be secured at distinct degrees by flexibly controlling multiple specifications of the suggested system model.

Spatial autocorrelation method for reliable measurements of two-station dispersion curves in heterogeneous ambient noise wavefields

Summary The microtremor survey method (MSM) is used to estimate S-wave velocity profiles from microtremors or ambient noise. Although array-based MSM analyses are usually used for shallow exploration purposes because of their robustness, the extraction of numerous phase velocity dispersion curves by two-station microtremor analysis is attractive because those dispersion curves can be used to construct high-resolution phase velocity maps by solving a least-squares problem. However, in exploration studies (>1 Hz), the reliability of two-station microtremor analysis can be affected by short data acquisition times and heterogeneous noise distributions mainly caused by anthropogenic noises. In this study, we propose a new approach to estimate surface-wave dispersion curves between station pairs considering a heterogeneous ambient noise distribution based on the spatial autocorrelation method. We first estimated azimuthal variations of noise energy from the complex coherencies between all station pairs in a receiver array, and then estimated dispersion curves between station pairs. Our field example demonstrates that modelling the azimuthal noise energy distribution allows us to use not only the real parts of complex coherencies, but also the imaginary parts, which are usually neglected when assuming a homogeneous noise field. The simultaneous use of the real and imaginary parts of complex coherencies improves the reliability and continuity of phase velocity estimations between station pairs. Because the stability of phase velocity estimations depends on the azimuths between station pairs, we carefully selected between-station azimuths that produce stable phase velocities. Selected phase velocities at 8 Hz can be used to construct high-resolution phase velocity maps with least-squares inversion. Because our approach does not require a regular receiver interval for two-station analysis, it allows for more flexible seismic array geometries. This is particularly important for MSM analyses in urban areas, where limited space is available to install seismic stations. We conclude that our proposed approach is effective in reconstructing high-resolution shallow structures in heterogeneous ambient noise fields.

PECULIARITIES OF NON-AUDITORY EFFECTS OF NOISE DEPENDING ON THE DOSE AND PROCESSED AMOUNT OF ACOUSTIC INFORMATION

Most of non-auditory effects cannot be explained as a simple consequence of noise energy influence. The level of arousal also depends on predictability of acoustic signals (level of entropy). The present article aims to analyse the contribution of noise dose and the level of entropy in non-auditory effects. 117 metallurgists and 15 healthy non-adapted to noise men were exposed to 4 different combinations of noise dose and entropy (during 8 hour working shift and 1 hour in a soundproof room correspondingly). Experiment was 2x2 factorial design. Functional state of cardiovascular and central nervous system was evaluated before and after exposure. The chosen noise characteristics account for up to 80% of the dispersion of nonspecific effects. The largest number of significant differences were between the groups, where the controlled factors were either at the lower or the upper level of variation. Noise dose and entropy contribute to such non-specific reactions as systolic/diastolic blood pressure, Stress Index, Kerdo index, duration of RR intervals, visual/hearing motion time delay. The cardiovascular system is the most sensitive to the variation of the entropy of the acoustic field.

Algorithm for Reducing Truck Noise on Via Baltica Transport Corridors in Lithuania

The section of Via Baltica going through the territory of the Republic of Lithuania is the most traffic intensive land logistics corridor in the country. The annual transportation volume has been increasing on this road; thus, the reduction of pollution caused by vehicles has become important. If gas emissions are regulated, and carriers have to pay pollution taxes, this does not apply to noise levels. The article presents the traffic intensity in this logistics corridor, measurements of the noise level at the characteristic points, its relation to the number of vehicles passing through it and an expert evaluation of proposed methods for noise energy reduction. Environmental noise is an unwanted or harmful sound that propagates in terms of both duration and geographical coverage. Noise is associated with many human activities, but road, rail and air traffic noises have the greatest impact. Due to irrationally arranged transport network, the transit flow of freight transport crosses residential areas of the city, places of rest and recreation of the population, causing high noise levels in adjacent areas. This is the biggest problem for the urban environment. Environmental noise affects many Europeans and is therefore considered by society to be one of the biggest environmental problems. This article presents an assessment of a new traffic noise algorithm. The presented expert survey on noise energy reduction allows choosing the most appropriate method for reducing noise energy in Via Baltica transport logistics corridor. Based on the expert survey, a hierarchical table for noise energy reduction was compiled. It will allow assessing the validity of individual noise energy reduction solutions. It has become relevant for improving infrastructure of other transport corridors and choosing the most appropriate solutions to reduce vehicle noise pollution. A further application of this model can be focused on economic evaluation, forecasting of expected benefits and so on.