3,352 research outputs found
SEA analysis in the cabin of a regional turboprop with metamaterial lining panels
The main goal of this paper is to evaluate the comfort, and hence the interior sound pressure
levels, in the cabin of a regional turboprop with metamaterial lining panels under Turbulent
Boundary Layer flow over the fuselage during cruise flight conditions. In the preliminary
work phase, the design of metamaterial and a numerical analysis at component level were
performed. Then, the CAD model of the fuselage was created representing the typical features
and dimensions of an airplane for regional flights and a Statistical Energy Analysis (SEA) model
was built by using Va One software. An investigation on the influence of designed metamaterial
on the soundproofing of the cabin was presented. Results reveal a reduction in Sound Pressure
Level (SPL) of almost 5 dB with respect to classical materials, in overall the frequency range
and for all the cavities analyzed, in the configuration with metamaterial applied as core of the
sandwich lining panels
Seismic Waveguide of Metamaterials
We have developed a new method of an earthquake-resistant design to support
conventional aseismic designs using acoustic metamaterials. We suggest a simple
and practical method to reduce the amplitude of a seismic wave exponentially.
Our device is an attenuator of a seismic wave. Constructing a cylindrical
shell-type waveguide that creates a stop-band for the seismic wave, we convert
the wave into an evanescent wave for some frequency range without touching the
building we want to protect.Comment: 4 pages, 4 figure
Experimental investigation of the influence of the turbulent boundary layer on the pressure distribution over a rigid two dimensional wavy wall
Influence of turbulent boundary layer on pressure distribution over rigid two dimensional wavy wal
Book Reviews
HANDBOOK OF LEGAL MEDICINE. By Alan R. Moritz and C. Joseph Stetler.
THE (SOVIET) SOCIALIST THEORY OF INTERNATIONAL LAW. By Bernard A. Ramundo with the assistance of Armins Rusis.
LAW, LIBERTY AND MORALITY. By H. L. A. Hart
The influence of baffle fairings on the acoustic performance of rectangular splitter silencers
A numerical model based on the finite element method is developed for a finite length, HVAC splitter silencer. The model includes an arbitrary number of bulk-reacting splitters separated from the airway by a thin perforated metal sheet and accommodates higher order modes in the incident sound field. Each perforated sheet is joined to rigid, impervious, metallic fairing situated at either end of a splitter. The transmission loss for the silencer is quantified by application of the point collocation technique, and predictions are compared to experimental measurements reported in the literature. The splitter fairing is shown to significantly affect silencer performance, especially when higher order incident modes are present. It is concluded that laboratory measurements, and theoretical predictions, that are based on a predominantly plane wave sound source are unlikely to reflect accurately the true performance of an HVAC silencer in a real ducting system
Influence of the COVID-19 Pandemic on mood and training in Australian community tennis players
The COVID-19 outbreak has led to the implementation of strict restrictions in Australia, which have severely impacted sporting activities. Tennis is played by 6.2% of the population within the Oceania region, and is a valuable sport for maintaining social, mental, and physical health. Current literature indicates the COVID-19 pandemic has negatively affected the mental health of Australian residents. The aim of this study was to investigate changes in training and match play due to the outbreak, and its effects on emotional well-being of Australian senior tennis players. Additionally, explore any differences between middle aged (41-60 years) and senior (61 years and over) Australian tennis players. An online survey was used to assess training and match play habits, as well as ascertain the emotional well-being of tennis players. The survey was active from 24th April 2020 until 6th June 2020. Participants were adult (41+ years) tennis players from Australia. Wilcoxon signed rank tests were performed to check for differences in training hours and tennis matches played. Mann-Whitney tests were used to assess the difference in Brief Emotional Experience Scale (BEES) scores, employment status as well as the training hours and tennis matches played between the two age groups. A Kendall\u27s Tau B correlation test was performed to assess the associations of training, match play and demographic characteristics with BEES scores. Kruskal-Wallis tests assessed differences in BEES scores between participants of differing match play formats, tennis experience and cessation of tennis training time periods. There were 245 respondents who met our inclusion criteria. Tennis training hours along with the tennis matches played significantly decreased during COVID-19 compared to pre-COVID-19, 85.09 and 88.48%, respectively. No significant ( \u3e 0.05) differences were observed between age groups for any of the training modality hours, nor was there any significant difference in number of tennis matches played. The participants average BEES score was 0.99 ± 1.27, indicating that respondents had a positive emotional well-being during the COVID-19 pandemic. The emotional well-being of the senior group was significantly ( = 0.002) higher than the middle aged group. Together, our results show that training and tennis match play decreased during the COVID-19 pandemic, however the emotional well-being of senior tennis players in Australia appeared to not be negatively affected
Prediction of sound absorption based on specific airflow resistance and air permeability of textiles
Late Triassic to Jurassic Magmatic and Tectonic Evolution of the Intermontane Terranes in Yukon, Northern Canadian Cordillera: Transition From Arc to Syn-Collisional Magmatism and Post-Collisional Lithospheric Delamination
End-on arc collision and onset of the northern Cordilleran orogen is recorded in Late Triassic to Jurassic plutons in the Intermontane terranes of Yukon, and in development of the synorogenic Whitehorse trough (WT). A synthesis of the extensive data set for these plutons supports interpretation of the magmatic and tectonic evolution of the northern Intermontane terranes. Late Triassic juvenile plutons that locally intrude the Yukon-Tanana terrane represent the northern extension of arc magmatism within Stikinia. Early Jurassic plutons that intrude Stikinia and Yukon-Tanana terranes were emplaced during crustal thickening (200–195 Ma) and subsequent exhumation (190–178 Ma). The syn-collisional magmatism migrated to the south and shows increasing crustal contributions with time. This style of magmatism in Yukon contrasts with coeval, juvenile arc magmatism in British Columbia (Hazelton Group), that records southward arc migration in the Early Jurassic. Exhumation and subsidence of the WT in the north were probably linked to the retreating Hazelton arc by a sinistral transform. East of WT, Early Jurassic plutons intruded into Yukon-Tanana record continued arc magmatism in Quesnellia. Middle Jurassic plutons were intruded after final enclosure of the Cache Creek terrane and imbrication of the Intermontane terranes. The post-collisional plutons have juvenile isotopic compositions that, together with stratigraphic evidence of surface uplift, are interpreted to record asthenospheric upwelling and lithospheric delamination. A revised tectonic model proposes that entrapment of the Cache Creek terrane was the result of Hazelton slab rollback and development of a sinistral transform fault system linked to the collision zone to the north
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