scholarly journals An Operational Approach to the Acoustic Analogy Equations

10.5772/20485 ◽  
2011 ◽  
Author(s):  
Dorel Homentcovschi ◽  
Ronald Miles
Keyword(s):  
Acoustic Analogy ◽  
Operational Approach

An Operational Approach to Record Linkage

1983 ◽  
Vol 22 (02) ◽  
pp. 77-82 ◽  
Author(s):  
M. P. Mi ◽  
J. T. Kagawa ◽  
M. E. Earle
Keyword(s):  
Decision Making ◽  
Record Linkage ◽  
Operational Approach ◽  
Resident Population ◽  
Rate Of Failure

An operational approach to computerized record linkage has been developed based on the concept of probability of chance match in two groups of records brought together for comparison. Tolerance levels can be readily derived from these records for decision-making in accepting or rejecting a linked pair. This approach is especially suitable for iteration when linked pairs are removed in successive cycles. An application of linkage for death clearance of the 1942 resident population of 437,967 registered in Hawaii during a 38-year period from 1942 to 1979 is presented. The reliability of linkage and rate of failure were analyzed.

Application of acoustic analogy to automotive engine-cooling fan noise prediction

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1095-1098 ◽  
Author(s):  
Jeonghan Lee ◽  
Kyungseok Cho ◽  
Soogab Lee
Keyword(s):  
Noise Prediction ◽  
Acoustic Analogy ◽  
Fan Noise ◽  
Automotive Engine ◽  
Engine Cooling ◽  
Cooling Fan

Private Equity and Value Creation in Frontier Markets: The Need for an Operational Approach

2014 ◽  
Author(s):  
Stephen J. Mezias ◽  
Afzal Amijee
Keyword(s):  
Value Creation ◽  
Private Equity ◽  
Operational Approach

The Operational Approach is as New as Nonteleological Definitions

1982 ◽  
Vol 87 (5) ◽  
pp. 1169-1173
Author(s):  
Michel Verdon
Keyword(s):  
Operational Approach

scholarly journals Remote whispering metamaterial for non-radiative transceiving of ultra-weak sound

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jin Zhang ◽  
Wei Rui ◽  
Chengrong Ma ◽  
Ying Cheng ◽  
Xiaojun Liu ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Detection Limit ◽  
Free Space ◽  
Signal To Noise Ratio ◽  
Resonance Energy Transfer ◽  
Information Leakage ◽  
Resonance Energy ◽  
Acoustic Analogy ◽  
Signal To Noise ◽  
Airborne Sound

AbstractTransceiving ultra-weak sound typically relies on signal pre-amplification at the transmitting end via active electro-acoustic devices, which inherently perturbs the environment in the form of noise that inevitably leads to information leakage. Here we demonstrate a passive remote-whispering metamaterial (RWM) enabling weak airborne sound at audible frequencies to reach unprecedented signal enhancement without altering the detected ambient soundscape, which is based on the extraordinary scattering properties of a metamaterial formed by a pair of self-resonating subwavelength Mie meta-cavities, constituting the acoustic analogy of Förster resonance energy transfer. We demonstrate efficient non-radiative sound transfer over distances hundreds times longer than the radius of the meta-cavities, which enables the RWM to recover weak sound signals completely overwhelmed by strong noise with enhanced signal-to-noise ratio from −3 dB below the detection limit of 0 dB in free space to 17.7 dB.

scholarly journals Fit-For-Purpose, Private-Sector Led Land Regularization and Financing of Informal Settlements in Brazil

Land ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 797
Author(s):  
Malcolm Childress ◽  
Selina Carter ◽  
Edgard Barki
Keyword(s):  
Private Sector ◽  
Business Model ◽  
Social Enterprise ◽  
Informal Settlement ◽  
Property Values ◽  
Informal Settlements ◽  
Private Land ◽  
Operational Approach ◽  
Municipal Governments ◽  
Fit For Purpose

This paper aims to analyze the financial and operational approach to land regularization and financing used in Brazil by an innovative private social enterprise in order to demonstrate that the approach widens the concept fit-for-purpose land regularization to include fit-for-purpose land financing, with relevance for wider efforts in informal settlement regularization and upgrading. In this approach, the enterprise acts as a coordinator and broker to organize the residents of informal settlements to regularize their settlements by negotiating buyouts of the underlying private owners at discounted values, handling titling and registration of the occupants, and coordinating with municipal governments to provide infrastructure. The analysis of parcel-level repayment and price data provides evidence of the sustainability of the business model and increase of property values of the regularized parcels. The results presented from the enterprise’s own repayment data demonstrate that under (non-pandemic) historical conditions residents are largely able to pay an affordable monthly payment over 7–10 years to the enterprise for the service to purchase the plots and maintain the enterprise. In operation since 2001, the enterprise has regularized over 20,000 parcels in more than 30 settlements, primarily in the cities of Sao Paolo and Curitiba in Brazil. The approach suggests that it could be widely replicable and add to the set of options for regularizing informal settlements, especially when purchase of private land is required.

scholarly journals Rotor Interaction Noise in Counter-Rotating Propfan Propulsion Systems

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Andreas Peters ◽  
Zoltán S. Spakovszky
Keyword(s):  
Polar Angle ◽  
Secondary Flows ◽  
Tip Vortex ◽  
System Level ◽  
Analysis Tool ◽  
Acoustic Analogy ◽  
Wake Interaction ◽  
Open Rotor ◽  
And Performance ◽  
The Individual

Due to their inherent noise challenge and potential for significant reductions in fuel burn, counter-rotating propfans (CRPs) are currently being investigated as potential alternatives to high-bypass turbofan engines. This paper introduces an integrated noise and performance assessment methodology for advanced propfan powered aircraft configurations. The approach is based on first principles and combines a coupled aircraft and propulsion system mission and performance analysis tool with 3D unsteady, full-wheel CRP computational fluid dynamics computations and aeroacoustic simulations. Special emphasis is put on computing CRP noise due to interaction tones. The method is capable of dealing with parametric studies and exploring noise reduction technologies. An aircraft performance, weight and balance, and mission analysis was first conducted on a candidate CRP powered aircraft configuration. Guided by data available in the literature, a detailed aerodynamic design of a pusher CRP was carried out. Full-wheel unsteady 3D Reynolds-averaged Navier-Stokes (RANS) simulations were then used to determine the time varying blade surface pressures and unsteady flow features necessary to define the acoustic source terms. A frequency domain approach based on Goldstein’s formulation of the acoustic analogy for moving media and Hanson’s single rotor noise method was extended to counter-rotating configurations. The far field noise predictions were compared to measured data of a similar CRP configuration and demonstrated good agreement between the computed and measured interaction tones. The underlying noise mechanisms have previously been described in literature but, to the authors’ knowledge, this is the first time that the individual contributions of front-rotor wake interaction, aft-rotor upstream influence, hub-endwall secondary flows, and front-rotor tip-vortices to interaction tone noise are dissected and quantified. Based on this investigation, the CRP was redesigned for reduced noise incorporating a clipped rear-rotor and increased rotor-rotor spacing to reduce upstream influence, tip-vortex, and wake interaction effects. Maintaining the thrust and propulsive efficiency at takeoff conditions, the noise was calculated for both designs. At the interaction tone frequencies, the redesigned CRP demonstrated an average reduction of 7.25 dB in mean sound pressure level computed over the forward and aft polar angle arcs. On the engine/aircraft system level, the redesigned CRP demonstrated a reduction of 9.2 dB in effective perceived noise (EPNdB) and 8.6 EPNdB at the Federal Aviation Regulations (FAR) 36 flyover and sideline observer locations, respectively. The results suggest that advanced open rotor designs can possibly meet Stage 4 noise requirements.

Operational Approach to Space and Time Measurements in Flat Space

1969 ◽  
Vol 37 (2) ◽  
pp. 178-189 ◽  
Author(s):  
James L. Anderson ◽  
Ronald Gautreau
Keyword(s):  
Flat Space ◽  
Operational Approach ◽  
Space And Time

Wake-Airfoil Interaction as Broadband Noise Source: A Large-Eddy Simulation Study

2005 ◽  
Vol 4 (1-2) ◽  
pp. 93-115 ◽  
Author(s):  
Jérôme Boudet ◽  
Nathalie Grosjean ◽  
Marc C. Jacob
Keyword(s):  
Large Eddy Simulation ◽  
Particle Image ◽  
Broadband Noise ◽  
Far Field ◽  
Acoustic Analogy ◽  
Eddy Simulation ◽  
Naca0012 Airfoil ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Proper Orthogonal

A large-eddy simulation is carried out on a rod-airfoil configuration and compared to an accompanying experiment as well as to a RANS computation. A NACA0012 airfoil (chord c = 0.1 m) is located one chord downstream of a circular rod (diameter d = c/10, Red = 48 000). The computed interaction of the resulting sub-critical vortex street with the airfoil is assessed using averaged quantities, aerodynamic spectra and proper orthogonal decomposition (POD) of the instantaneous flow fields. Snapshots of the flow field are compared to particle image velocimetry (PIV) data. The acoustic far field is predicted using the Ffowcs Williams & Hawkings acoustic analogy, and compared to the experimental far field spectra. The large-eddy simulation is shown to accurately represent the deterministic pattern of the vortex shedding that is described by POD modes 1 & 2 and the resulting tonal noise also compares favourably to measurements. Furthermore higher order POD modes that are found in the PIV data are well predicted by the computation. The broadband content of the aerodynamic and the acoustic fields is consequently well predicted over a large range of frequencies ([0 kHz; 10 kHz]).

A study of sound sources and unsteady surface pressure in an axial fan

2021 ◽  
pp. 2150267
Author(s):  
Bo Luo ◽  
Wuli Chu ◽  
Song Yan ◽  
Zhengjing Shen ◽  
Haoguang Zhang
Keyword(s):  
Leading Edge ◽  
Noise Spectrum ◽  
Industrial Applications ◽  
Acoustic Analogy ◽  
Dynamics Modeling ◽  
Axial Fan ◽  
Sound Sources ◽  
Recirculating Flow ◽  
Aerodynamic Interaction ◽  
Blade Tip

The noise emitted from an axial fan has become one of the primary concerns for many industrial applications. This paper presents the work to predict the noise generation and investigate sound sources in a low speed axial fan. Computational fluid dynamics modeling is conducted using Scale Adaptive Simulation for the unsteady flow field. The sound predictions by the acoustic analogy are in good agreement with the experimental data. The results from this study show that the aerodynamic interaction between the blades and outlet vanes has a major contribution to the radiated noise spectrum. Two types of sources of narrowband humps are identified in the axial fan. The first is found at the leading edge of the blade tip, which is related to the interaction of coherent flow structures in the blade tip region. The second is found in the vicinity of the blade hub, which can be attributed to the recirculating flow and hub vortex. The noise below the frequency of 1500 Hz is mainly due to the blade-outlet vane aerodynamic interaction, manifested as the tonal sound at BPF and its harmonics, whereas above 1500 Hz the broadband component of sound is mainly related to the turbulent boundary layers.

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