General Rotorcraft Aeromechanical Stability Program (GRASP): Theory manual

Science.gov (United States)

Hodges, Dewey H.; Hopkins, A. Stewart; Kunz, Donald L.; Hinnant, Howard E.

1990-01-01

The general rotorcraft aeromechanical stability program (GRASP) was developed to calculate aeroelastic stability for rotorcraft in hovering flight, vertical flight, and ground contact conditions. GRASP is described in terms of its capabilities and its philosophy of modeling. The equations of motion that govern the physical system are described, as well as the analytical approximations used to derive them. The equations include the kinematical equation, the element equations, and the constraint equations. In addition, the solution procedures used by GRASP are described. GRASP is capable of treating the nonlinear static and linearized dynamic behavior of structures represented by arbitrary collections of rigid-body and beam elements. These elements may be connected in an arbitrary fashion, and are permitted to have large relative motions. The main limitation of this analysis is that periodic coefficient effects are not treated, restricting rotorcraft flight conditions to hover, axial flight, and ground contact. Instead of following the methods employed in other rotorcraft programs. GRASP is designed to be a hybrid of the finite-element method and the multibody methods used in spacecraft analysis. GRASP differs from traditional finite-element programs by allowing multiple levels of substructure in which the substructures can move and/or rotate relative to others with no small-angle approximations. This capability facilitates the modeling of rotorcraft structures, including the rotating/nonrotating interface and the details of the blade/root kinematics for various types. GRASP differs from traditional multibody programs by considering aeroelastic effects, including inflow dynamics (simple unsteady aerodynamics) and nonlinear aerodynamic coefficients.

NDARC NASA Design and Analysis of Rotorcraft. Appendix 6; Input

Science.gov (United States)

Johnson, Wayne

2017-01-01

The NASA Design and Analysis of Rotorcraft (NDARC) software is an aircraft system analysis tool that supports both conceptual design efforts and technology impact assessments. The principal tasks are to design (or size) a rotorcraft to meet specified requirements, including vertical takeoff and landing (VTOL) operation, and then analyze the performance of the aircraft for a set of conditions. For broad and lasting utility, it is important that the code have the capability to model general rotorcraft configurations, and estimate the performance and weights of advanced rotor concepts. The architecture of the NDARC code accommodates configuration flexibility, a hierarchy of models, and ultimately multidisciplinary design, analysis, and optimization. Initially the software is implemented with low-fidelity models, typically appropriate for the conceptual design environment. An NDARC job consists of one or more cases, each case optionally performing design and analysis tasks. The design task involves sizing the rotorcraft to satisfy specified design conditions and missions. The analysis tasks can include off-design mission performance calculation, flight performance calculation for point operating conditions, and generation of subsystem or component performance maps. For analysis tasks, the aircraft description can come from the sizing task, from a previous case or a previous NDARC job, or be independently generated (typically the description of an existing aircraft). The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and propulsion. For each component, attributes such as performance, drag, and weight can be calculated; and the aircraft attributes are obtained from the sum of the component attributes. Description and analysis of conventional rotorcraft configurations is facilitated, while retaining the capability to model novel and advanced concepts. Specific rotorcraft configurations considered are single-main-rotor and tail

NDARC NASA Design and Analysis of Rotorcraft - Input, Appendix 2

Science.gov (United States)

Johnson, Wayne

2016-01-01

The NASA Design and Analysis of Rotorcraft (NDARC) software is an aircraft system analysis tool that supports both conceptual design efforts and technology impact assessments. The principal tasks are to design (or size) a rotorcraft to meet specified requirements, including vertical takeoff and landing (VTOL) operation, and then analyze the performance of the aircraft for a set of conditions. For broad and lasting utility, it is important that the code have the capability to model general rotorcraft configurations, and estimate the performance and weights of advanced rotor concepts. The architecture of the NDARC code accommodates configuration exibility, a hierarchy of models, and ultimately multidisciplinary design, analysis, and optimization. Initially the software is implemented with low-fidelity models, typically appropriate for the conceptual design environment. An NDARC job consists of one or more cases, each case optionally performing design and analysis tasks. The design task involves sizing the rotorcraft to satisfy specified design conditions and missions. The analysis tasks can include off-design mission performance calculation, flight performance calculation for point operating conditions, and generation of subsystem or component performance maps. For analysis tasks, the aircraft description can come from the sizing task, from a previous case or a previous NDARC job, or be independently generated (typically the description of an existing aircraft). The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and propulsion. For each component, attributes such as performance, drag, and weight can be calculated; and the aircraft attributes are obtained from the sum of the component attributes. Description and analysis of conventional rotorcraft configurations is facilitated, while retaining the capability to model novel and advanced concepts. Specific rotorcraft configurations considered are single-main-rotor and tail

NDARC NASA Design and Analysis of Rotorcraft. Appendix 5; Theory

Science.gov (United States)

Johnson, Wayne

2017-01-01

The NASA Design and Analysis of Rotorcraft (NDARC) software is an aircraft system analysis tool that supports both conceptual design efforts and technology impact assessments. The principal tasks are to design (or size) a rotorcraft to meet specified requirements, including vertical takeoff and landing (VTOL) operation, and then analyze the performance of the aircraft for a set of conditions. For broad and lasting utility, it is important that the code have the capability to model general rotorcraft configurations, and estimate the performance and weights of advanced rotor concepts. The architecture of the NDARC code accommodates configuration flexibility, a hierarchy of models, and ultimately multidisciplinary design, analysis, and optimization. Initially the software is implemented with low-fidelity models, typically appropriate for the conceptual design environment. An NDARC job consists of one or more cases, each case optionally performing design and analysis tasks. The design task involves sizing the rotorcraft to satisfy specified design conditions and missions. The analysis tasks can include off-design mission performance calculation, flight performance calculation for point operating conditions, and generation of subsystem or component performance maps. For analysis tasks, the aircraft description can come from the sizing task, from a previous case or a previous NDARC job, or be independently generated (typically the description of an existing aircraft). The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and propulsion. For each component, attributes such as performance, drag, and weight can be calculated; and the aircraft attributes are obtained from the sum of the component attributes. Description and analysis of conventional rotorcraft configurations is facilitated, while retaining the capability to model novel and advanced concepts. Specific rotorcraft configurations considered are single-main-rotor and tail

NDARC NASA Design and Analysis of Rotorcraft Theory Appendix 1

Science.gov (United States)

Johnson, Wayne

2016-01-01

The NASA Design and Analysis of Rotorcraft (NDARC) software is an aircraft system analysis tool that supports both conceptual design efforts and technology impact assessments. The principal tasks are to design (or size) a rotorcraft to meet specified requirements, including vertical takeoff and landing (VTOL) operation, and then analyze the performance of the aircraft for a set of conditions. For broad and lasting utility, it is important that the code have the capability to model general rotorcraft configurations, and estimate the performance and weights of advanced rotor concepts. The architecture of the NDARC code accommodates configuration flexibility, a hierarchy of models, and ultimately multidisciplinary design, analysis, and optimization. Initially the software is implemented with low-fidelity models, typically appropriate for the conceptual design environment. An NDARC job consists of one or more cases, each case optionally performing design and analysis tasks. The design task involves sizing the rotorcraft to satisfy specified design conditions and missions. The analysis tasks can include off-design mission performance calculation, flight performance calculation for point operating conditions, and generation of subsystem or component performance maps. For analysis tasks, the aircraft description can come from the sizing task, from a previous case or a previous NDARC job, or be independently generated (typically the description of an existing aircraft). The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and propulsion. For each component, attributes such as performance, drag, and weight can be calculated; and the aircraft attributes are obtained from the sum of the component attributes. Description and analysis of conventional rotorcraft configurations is facilitated, while retaining the capability to model novel and advanced concepts. Specific rotorcraft configurations considered are single-main-rotor and tail

NDARC: NASA Design and Analysis of Rotorcraft. Appendix 3; Theory

Science.gov (United States)

Johnson, Wayne

2016-01-01

The NASA Design and Analysis of Rotorcraft (NDARC) software is an aircraft system analysis tool that supports both conceptual design efforts and technology impact assessments. The principal tasks are to design (or size) a rotorcraft to meet speci?ed requirements, including vertical takeoff and landing (VTOL) operation, and then analyze the performance of the aircraft for a set of conditions. For broad and lasting utility, it is important that the code have the capability to model general rotorcraft con?gurations, and estimate the performance and weights of advanced rotor concepts. The architecture of the NDARC code accommodates con?guration ?exibility, a hierarchy of models, and ultimately multidisciplinary design, analysis, and optimization. Initially the software is implemented with low-?delity models, typically appropriate for the conceptual design environment. An NDARC job consists of one or more cases, each case optionally performing design and analysis tasks. The design task involves sizing the rotorcraft to satisfy speci?ed design conditions and missions. The analysis tasks can include off-design mission performance calculation, ?ight performance calculation for point operating conditions, and generation of subsystem or component performance maps. For analysis tasks, the aircraft description can come from the sizing task, from a previous case or a previous NDARC job, or be independently generated (typically the description of an existing aircraft). The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and propulsion. For each component, attributes such as performance, drag, and weight can be calculated; and the aircraft attributes are obtained from the sum of the component attributes. Description and analysis of conventional rotorcraft con?gurations is facilitated, while retaining the capability to model novel and advanced concepts. Speci?c rotorcraft con?gurations considered are single-main-rotor and tail-rotor helicopter

Hybrid Finite Element Developments for Rotorcraft Interior Noise Computations within a Multidisciplinary Design Environment, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — One of the main attributes contributing to the civil competitiveness of rotorcraft, is the continuously increasing expectations for passenger comfort which is...

Design of Quiet Rotorcraft Approach Trajectories: Verification Phase

Science.gov (United States)

Padula, Sharon L.

2010-01-01

Flight testing that is planned for October 2010 will provide an opportunity to evaluate rotorcraft trajectory optimization techniques. The flight test will involve a fully instrumented MD-902 helicopter, which will be flown over an array of microphones. In this work, the helicopter approach trajectory is optimized via a multiobjective genetic algorithm to improve community noise, passenger comfort, and pilot acceptance. Previously developed optimization strategies are modified to accommodate new helicopter data and to increase pilot acceptance. This paper describes the MD-902 trajectory optimization plus general optimization strategies and modifications that are needed to reduce the uncertainty in noise predictions. The constraints that are imposed by the flight test conditions and characteristics of the MD-902 helicopter limit the testing possibilities. However, the insights that will be gained through this research will prove highly valuable.

14 CFR 21.5 - Airplane or Rotorcraft Flight Manual.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Airplane or Rotorcraft Flight Manual. 21.5... CERTIFICATION PROCEDURES FOR PRODUCTS AND PARTS General § 21.5 Airplane or Rotorcraft Flight Manual. (a) With each airplane or rotorcraft that was not type certificated with an Airplane or Rotorcraft Flight Manual...

NDARC-NASA Design and Analysis of Rotorcraft Theoretical Basis and Architecture

Science.gov (United States)

Johnson, Wayne

2010-01-01

The theoretical basis and architecture of the conceptual design tool NDARC (NASA Design and Analysis of Rotorcraft) are described. The principal tasks of NDARC are to design (or size) a rotorcraft to satisfy specified design conditions and missions, and then analyze the performance of the aircraft for a set of off-design missions and point operating conditions. The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and propulsion. For each component, attributes such as performance, drag, and weight can be calculated. The aircraft attributes are obtained from the sum of the component attributes. NDARC provides a capability to model general rotorcraft configurations, and estimate the performance and attributes of advanced rotor concepts. The software has been implemented with low-fidelity models, typical of the conceptual design environment. Incorporation of higher-fidelity models will be possible, as the architecture of the code accommodates configuration flexibility, a hierarchy of models, and ultimately multidisciplinary design, analysis and optimization.

Helicopter Rotor Noise Prediction: Background, Current Status, and Future Direction

Science.gov (United States)

Brentner, Kenneth S.

1997-01-01

Helicopter noise prediction is increasingly important. The purpose of this viewgraph presentation is to: 1) Put into perspective the recent progress; 2) Outline current prediction capabilities; 3) Forecast direction of future prediction research; 4) Identify rotorcraft noise prediction needs. The presentation includes an historical perspective, a description of governing equations, and the current status of source noise prediction.

Multidisciplinary Conceptual Design for Reduced-Emission Rotorcraft

Science.gov (United States)

Silva, Christopher; Johnson, Wayne; Solis, Eduardo

2018-01-01

Python-based wrappers for OpenMDAO are used to integrate disparate software for practical conceptual design of rotorcraft. The suite of tools which are connected thus far include aircraft sizing, comprehensive analysis, and parametric geometry. The tools are exercised to design aircraft with aggressive goals for emission reductions relative to fielded state-of-the-art rotorcraft. Several advanced reduced-emission rotorcraft are designed and analyzed, demonstrating the flexibility of the tools to consider a wide variety of potentially transformative vertical flight vehicles. To explore scale effects, aircraft have been sized for 5, 24, or 76 passengers in their design missions. Aircraft types evaluated include tiltrotor, single-main-rotor, coaxial, and side-by-side helicopters. Energy and drive systems modeled include Lithium-ion battery, hydrogen fuel cell, turboelectric hybrid, and turboshaft drive systems. Observations include the complex nature of the trade space for this simple problem, with many potential aircraft design and operational solutions for achieving significant emission reductions. Also interesting is that achieving greatly reduced emissions may not require exotic component technologies, but may be achieved with a dedicated design objective of reducing emissions.

BVI induced vibration and noise alleviation by active and passive approaches

Science.gov (United States)

Liu, Li

This dissertation describes the development of a comprehensive aeroelastic/aeroacoustic simulation capability for the modeling of vibration and noise in rotorcraft induced by blade-vortex interaction (BVI). Subsequently this capability is applied to study vibration and noise reduction, using active and passive control approaches. The active approach employed is the actively controlled partial span trailing edge flaps (ACF), implemented in single and dual, servo and plain flap configurations. The passive approach is based on varying the sweep and anhedral on the tip of the rotor. Two different modern helicopters are chosen as the baseline for the implementation of ACF approach, one resembling a four-bladed MBB BO-105 hingeless rotor and the other similar to a five-bladed MD-900 bearingless rotor. The structural model is based on a finite element approach capable of simulating composite helicopter blades with swept tips, and representing multiple load paths at the blade root which is a characteristic of bearingless rotors. An unsteady compressible aerodynamic model based on a rational function approximation (RFA) approach is combined with a free wake analysis which has been enhanced by improving the wake analysis resolution and modeling a dual vortex structure. These enhancements are important for capturing BVI effects. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades has been developed, which is required by the acoustic analysis. A modified version of helicopter noise code WOPWOP with provisions for blade flexibility has been combined with the aeroelastic analysis to predict the BVI noise. Several variants of the higher harmonic control (HHC) algorithm have been applied for the active noise control, as well as the simultaneous vibration and noise control. Active control of BVI noise is accomplished using feedback from an onboard microphone. The simulation has been extensively validated against experimental data and

Application of Machine Learning to Rotorcraft Health Monitoring

Science.gov (United States)

Cody, Tyler; Dempsey, Paula J.

2017-01-01

Machine learning is a powerful tool for data exploration and model building with large data sets. This project aimed to use machine learning techniques to explore the inherent structure of data from rotorcraft gear tests, relationships between features and damage states, and to build a system for predicting gear health for future rotorcraft transmission applications. Classical machine learning techniques are difficult, if not irresponsible to apply to time series data because many make the assumption of independence between samples. To overcome this, Hidden Markov Models were used to create a binary classifier for identifying scuffing transitions and Recurrent Neural Networks were used to leverage long distance relationships in predicting discrete damage states. When combined in a workflow, where the binary classifier acted as a filter for the fatigue monitor, the system was able to demonstrate accuracy in damage state prediction and scuffing identification. The time dependent nature of the data restricted data exploration to collecting and analyzing data from the model selection process. The limited amount of available data was unable to give useful information, and the division of training and testing sets tended to heavily influence the scores of the models across combinations of features and hyper-parameters. This work built a framework for tracking scuffing and fatigue on streaming data and demonstrates that machine learning has much to offer rotorcraft health monitoring by using Bayesian learning and deep learning methods to capture the time dependent nature of the data. Suggested future work is to implement the framework developed in this project using a larger variety of data sets to test the generalization capabilities of the models and allow for data exploration.

Aeromechanics and man-machine integration technology opportunities for rotorcraft of the 1990s and beyond

Science.gov (United States)

Kerr, Andrew W.

1989-01-01

Programs related to rotorcraft aeromechanics and man-machine integration are discussed which will support advanced army rotorcraft design. In aeromechanics, recent advances in computational fluid dynamics will be used to characterize the complex unsteady flowfields of rotorcraft, and a second-generation comprehensive helicopter analysis system will be used along with models of aerodynamics, engines, and control systems to study the structural dynamics of rotor/body configurations. The man-machine integration program includes the development of advanced cockpit design technology and the evaluation of cockpit and mission equipment concepts in a real-time full-combat environment.

Rotorcraft system identification techniques for handling qualities and stability and control evaluation

Science.gov (United States)

Hall, W. E., Jr.; Gupta, N. K.; Hansen, R. S.

1978-01-01

An integrated approach to rotorcraft system identification is described. This approach consists of sequential application of (1) data filtering to estimate states of the system and sensor errors, (2) model structure estimation to isolate significant model effects, and (3) parameter identification to quantify the coefficient of the model. An input design algorithm is described which can be used to design control inputs which maximize parameter estimation accuracy. Details of each aspect of the rotorcraft identification approach are given. Examples of both simulated and actual flight data processing are given to illustrate each phase of processing. The procedure is shown to provide means of calibrating sensor errors in flight data, quantifying high order state variable models from the flight data, and consequently computing related stability and control design models.

A History of Rotorcraft Comprehensive Analyses

Science.gov (United States)

Johnson, Wayne

2013-01-01

A history of the development of rotorcraft comprehensive analyses is presented. Comprehensive analyses are digital computer programs that calculate the aeromechanical behavior of the rotor and aircraft, bringing together the most advanced models of the geometry, structure, dynamics, and aerodynamics available in rotary wing technology. The development of the major codes of the last five decades from industry, government, and universities is described. A number of common themes observed in this history are discussed.

14 CFR 29.519 - Hull type rotorcraft: Water-based and amphibian.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Hull type rotorcraft: Water-based and... § 29.519 Hull type rotorcraft: Water-based and amphibian. (a) General. For hull type rotorcraft, the... along and among the hull and auxiliary floats, if used, in a rational and conservative manner, assuming...

Helical Face Gear Development Under the Enhanced Rotorcraft Drive System Program

Science.gov (United States)

Heath, Gregory F.; Slaughter, Stephen C.; Fisher, David J.; Lewicki, David G.; Fetty, Jason

2011-01-01

U.S. Army goals for the Enhanced Rotorcraft Drive System Program are to achieve a 40 percent increase in horsepower to weight ratio, a 15 dB reduction in drive system generated noise, 30 percent reduction in drive system operating, support, and acquisition cost, and 75 percent automatic detection of critical mechanical component failures. Boeing s technology transition goals are that the operational endurance level of the helical face gearing and related split-torque designs be validated to a TRL 6, and that analytical and manufacturing tools be validated. Helical face gear technology is being developed in this project to augment, and transition into, a Boeing AH-64 Block III split-torque face gear main transmission stage, to yield increased power density and reduced noise. To date, helical face gear grinding development on Northstar s new face gear grinding machine and pattern-development tests at the NASA Glenn/U.S. Army Research Laboratory have been completed and are described.

Computer vision techniques for rotorcraft low altitude flight

Science.gov (United States)

Sridhar, Banavar

1990-01-01

Rotorcraft operating in high-threat environments fly close to the earth's surface to utilize surrounding terrain, vegetation, or manmade objects to minimize the risk of being detected by an enemy. Increasing levels of concealment are achieved by adopting different tactics during low-altitude flight. Rotorcraft employ three tactics during low-altitude flight: low-level, contour, and nap-of-the-earth (NOE). The key feature distinguishing the NOE mode from the other two modes is that the whole rotorcraft, including the main rotor, is below tree-top whenever possible. This leads to the use of lateral maneuvers for avoiding obstacles, which in fact constitutes the means for concealment. The piloting of the rotorcraft is at best a very demanding task and the pilot will need help from onboard automation tools in order to devote more time to mission-related activities. The development of an automation tool which has the potential to detect obstacles in the rotorcraft flight path, warn the crew, and interact with the guidance system to avoid detected obstacles, presents challenging problems. Research is described which applies techniques from computer vision to automation of rotorcraft navigtion. The effort emphasizes the development of a methodology for detecting the ranges to obstacles in the region of interest based on the maximum utilization of passive sensors. The range map derived from the obstacle-detection approach can be used as obstacle data for the obstacle avoidance in an automatic guidance system and as advisory display to the pilot. The lack of suitable flight imagery data presents a problem in the verification of concepts for obstacle detection. This problem is being addressed by the development of an adequate flight database and by preprocessing of currently available flight imagery. The presentation concludes with some comments on future work and how research in this area relates to the guidance of other autonomous vehicles.

New Concepts and Perspectives on Micro-Rotorcraft and Small Autonomous Rotary-Wing Vehicles

Science.gov (United States)

Young, Larry A.; Aiken, E. W.; Johnson, J. L.; Demblewski, R.; Andrews, J.; Aiken, Irwin W. (Technical Monitor)

2001-01-01

A key part of the strategic vision for rotorcraft research as identified by senior technologists within the Army/NASA Rotorcraft Division at NASA Ames Research Center is the development and use of small autonomous rotorcraft. Small autonomous rotorcraft are defined for the purposes of this paper to be a class of vehicles that range in size from rotary-wing micro air vehicles (MAVs) to larger, more conventionally sized, rotorcraft uninhabited aerial vehicles (UAVs) - i.e. vehicle gross weights ranging from hundreds of grams to thousands of kilograms. The development of small autonomous rotorcraft represents both a technology challenge and a potential new vehicle class that will have substantial societal impact for: national security, personal transport, planetary science, and public service.

Gear noise, vibration, and diagnostic studies at NASA Lewis Research Center

Science.gov (United States)

Zakrajsek, J. J.; Oswald, F. B.; Townsend, D. P.; Coy, J. J.

1990-01-01

The NASA Lewis Research Center and the U.S. Army Aviation Systems Command are involved in a joint research program to advance the technology of rotorcraft transmissions. This program consists of analytical as well as experimental efforts to achieve the overall goals of reducing weight, noise, and vibration, while increasing life and reliability. Recent analytical activities are highlighted in the areas of gear noise, vibration, and diagnostics performed in-house and through NASA and U.S. Army sponsored grants and contracts. These activities include studies of gear tooth profiles to reduce transmission error and vibration as well as gear housing and rotordynamic modeling to reduce structural vibration and transmission and noise radiation, and basic research into current gear failure diagnostic methodologies. Results of these activities are presented along with an overview of near-term research plans in the gear noise, vibration, and diagnostics area.

The Effects of Ambient Conditions on Helicopter Harmonic Noise Radiation: Theory and Experiment

Science.gov (United States)

Greenwood, Eric; Sim, Ben W.; Boyd, D. Douglas, Jr.

2016-01-01

The effects of ambient atmospheric conditions, air temperature and density, on rotor harmonic noise radiation are characterized using theoretical models and experimental measurements of helicopter noise collected at three different test sites at elevations ranging from sea level to 7000 ft above sea level. Significant changes in the thickness, loading, and blade-vortex interaction noise levels and radiation directions are observed across the different test sites for an AS350 helicopter flying at the same indicated airspeed and gross weight. However, the radiated noise is shown to scale with ambient pressure when the flight condition of the helicopter is defined in nondimensional terms. Although the effective tip Mach number is identified as the primary governing parameter for thickness noise, the nondimensional weight coefficient also impacts lower harmonic loading noise levels, which contribute strongly to low frequency harmonic noise radiation both in and out of the plane of the horizon. Strategies for maintaining the same nondimensional rotor operating condition under different ambient conditions are developed using an analytical model of single main rotor helicopter trim and confirmed using a CAMRAD II model of the AS350 helicopter. The ability of the Fundamental Rotorcraft Acoustics Modeling from Experiments (FRAME) technique to generalize noise measurements made under one set of ambient conditions to make accurate noise predictions under other ambient conditions is also validated.

Measurement of Rotorcraft Blade Deformation Using Projection Moiré Interferometry

Directory of Open Access Journals (Sweden)

Gary A. Fleming

2000-01-01

Full Text Available Projection Moiré Interferometry (PMI has been used to obtain near instantaneous, quantitative blade deformation measurements of a generic rotorcraft model at several test conditions. These laser-based measurements provide quantitative, whole field, dynamic blade deformation profiles conditionally sampled as a function of rotor azimuth. The instantaneous nature of the measurements permits computation of the mean and unsteady blade deformation, blade bending, and twist. The PMI method is presented, and the image processing steps required to obtain quantitative deformation profiles from PMI interferograms are described. Experimental results are provided which show blade bending, twist, and unsteady motion. This initial proof-of-concept test has demonstrated the capability of PMI to acquire accurate, full field rotorcraft blade deformation data.

Model Following and High Order Augmentation for Rotorcraft Control, Applied via Partial Authority

Science.gov (United States)

Spires, James Michael

This dissertation consists of two main studies, a few small studies, and design documentation, all aimed at improving rotorcraft control by employing multi-input multi-output (MIMO) command-modelfollowing control as a baseline, together with a selectable (and de-selectable) MIMO high order compensator that augments the baseline. Two methods of MIMO command-model-following control design are compared for rotorcraft flight control. The first, Explicit Model Following (EMF), employs SISO inverse plants with a dynamic decoupling matrix, which is a purely feed-forward approach to inverting the plant. The second is Dynamic Inversion (DI), which involves both feed-forward and feedback path elements to invert the plant. The EMF design is purely linear, while the DI design has some nonlinear elements in vertical rate control. For each of these methods, an architecture is presented that provides angular rate model-following with selectable vertical rate model-following. Implementation challenges of both EMF and DI are covered, and methods of dealing with them are presented. These two MIMO model-following approaches are evaluated regarding (1) fidelity to the command model, and (2) turbulence rejection. Both are found to provide good tracking of commands and reduction of cross coupling. Next, an architecture and design methodology for high order compensator (HOC) augmentation of a baseline controller for rotorcraft is presented. With this architecture, the HOC compensator is selectable and can easily be authority-limited, which might ease certification. Also, the plant for this augmentative MIMO compensator design is a stabilized helicopter system, so good flight test data could be safely gathered for more accurate plant identification. The design methodology is carried out twice on an example helicopter model, once with turbulence rejection as the objective, and once with the additional objective of closely following pilot commands. The turbulence rejection HOC is feedback

Practices to identify and preclude adverse Aircraft-and-Rotorcraft-Pilot Couplings - A design perspective

Science.gov (United States)

Pavel, Marilena D.; Masarati, Pierangelo; Gennaretti, Massimo; Jump, Michael; Zaichik, Larisa; Dang-Vu, Binh; Lu, Linghai; Yilmaz, Deniz; Quaranta, Giuseppe; Ionita, Achim; Serafini, Jacopo

2015-07-01

Understanding, predicting and supressing the inadvertent aircraft oscillations caused by Aircraft/Rotorcraft Pilot Couplings (A/RPC) is a challenging problem for designers. These are potential instabilities that arise from the effort of controlling aircraft with high response actuation systems. The present paper reviews, updates and discusses desirable practices to be used during the design process for unmasking A/RPC phenomena. These practices are stemming from the European Commission project ARISTOTEL Aircraft and Rotorcraft Pilot Couplings - Tools and Techniques for Alleviation and Detection (2010-2013) and are mainly related to aerodynamic and structural modelling of the aircraft/rotorcraft, pilot modelling and A/RPC prediction criteria. The paper proposes new methodologies for precluding adverse A/RPCs events taking into account the aeroelasticity of the structure and pilot biodynamic interaction. It is demonstrated that high-frequency accelerations due to structural elasticity cause negative effects on pilot control, since they lead to involuntary body and limb-manipulator system displacements and interfere with pilot's deliberate control activity (biodynamic interaction) and, finally, worsen handling quality ratings.

Assessment of High Temperature Superconducting (HTS) electric motors for rotorcraft propulsion

Science.gov (United States)

Doernbach, Jay

1990-01-01

The successful development of high temperature superconductors (HTS) could have a major impact on future aeronautical propulsion and aeronautical flight vehicle systems. Applications of high temperature superconductors have been envisioned for several classes of aeronautical systems, including subsonic and supersonic transports, hypersonic aircraft, V/STOL aircraft, rotorcraft and solar powered aircraft. The potential of HTS electric motors and generators for providing primary shaft power for rotorcraft propulsion is examined. Three different sized production helicopters were investigated; namely, the Bell Jet Ranger, the Sikorsky Black Hawk and the Sikorsky Super Stallion. These rotorcraft have nominal horsepower ratings of 500, 3600, and 13400 respectively. Preliminary results indicated that an all-electric HTS drive system produces an improvement in rotorcraft Takeoff Gross Weight (TOGW) for those rotorcraft with power ratings above 2000 horsepower. The predicted TOGW improvements are up to 9 percent for the medium-sized Sikorsky Black Hawk and up to 20 percent for the large-sized Sikorsky Super Stallion. The small-sized Bell Jet Ranger, however, experienced a penalty in TOGW with the all-electric HTS drive system.

Road traffic noise: self-reported noise annoyance versus GIS modelled road traffic noise exposure.

Science.gov (United States)

Birk, Matthias; Ivina, Olga; von Klot, Stephanie; Babisch, Wolfgang; Heinrich, Joachim

2011-11-01

self-reported road traffic noise annoyance is commonly used in epidemiological studies for assessment of potential health effects. Alternatively, some studies have used geographic information system (GIS) modelled exposure to road traffic noise as an objective parameter. The aim of this study was to analyse the association between noise exposure due to neighbouring road traffic and the noise annoyance of adults, taking other determinants into consideration. parents of 951 Munich children from the two German birth cohorts GINIplus and LISAplus reported their annoyance due to road traffic noise at home. GIS modelled road traffic noise exposure (L(den), maximum within a 50 m buffer) from the noise map of the city of Munich was available for all families. GIS-based calculated distance to the closest major road (≥10,000 vehicles per day) and questionnaire based-information about family income, parental education and the type of the street of residence were explored for their potential influence. An ordered logit regression model was applied. The noise levels (L(den)) and the reported noise annoyance were compared with an established exposure-response function. the correlation between noise annoyance and noise exposure (L(den)) was fair (Spearman correlation r(s) = 0.37). The distance to a major road and the type of street were strong predictors for the noise annoyance. The annoyance modelled by the established exposure-response function and that estimated by the ordered logit model were moderately associated (Pearson's correlation r(p) = 0.50). road traffic noise annoyance was associated with GIS modelled neighbouring road traffic noise exposure (L(den)). The distance to a major road and the type of street were additional explanatory factors of the noise annoyance appraisal.

Integration of Environment Sensing and Control Functions for Robust Rotorcraft UAV (RUAV) Guidance

Science.gov (United States)

Dadkhah Tehrani, Navid

Unmanned Air Vehicles (UAVs) have started supplanting manned aircraft in a broad range of tasks. Vehicles such as miniature rotorcrafts with broad maneuvering range and small size can enter remote locations that are hard to reach using other air and ground vehicles. Developing a guidance system which enables a Rotorcraft UAV (RUAV) to perform such tasks involves combing key elements from robotics motion planning, control system design, trajectory optimization as well as dynamics modeling. The focus of this thesis is to integrate a guidance system for a small-scale rotorcraft to enable a high level of performance and situational awareness. We cover large aspects of the system integration including modeling, control system design, environment sensing as well as motion planning in the presence of uncertainty. The system integration in this thesis is performed around a Blade-CX2 miniature coaxial helicopter. The first part of the thesis focuses on the development of the parameterized model for the Blade-CX2 helicopter with an emphasis on the coaxial rotor configuration. The model explicitly accounts for the dynamics of lower rotor and uses an implicit lumped parameter model for the upper rotor and stabilizer-bar. The parameterized model was identified using frequency domain system identification. In the second part of the thesis, we use the identified model to design a control law for the Blade-CX2 helicopter. The control augmentation for the Blade-CX2 helicopter was based on a nested attitude-velocity loop control architecture and was designed following classical loop-shaping and dynamic inversion techniques. A path following layer wrapped around the velocity control system enables the rotorcraft to follow reference trajectories specified by a sequence of waypoints and velocity vectors. Such reference paths are common in autonomous guidance systems. Finally, the third part of the thesis addresses the problem of autonomous navigation through a partially known or

The New Evolution for SIA Rotorcraft UAV Project

Directory of Open Access Journals (Sweden)

Juntong Qi

2010-01-01

Full Text Available This paper describes recent research on the design, implement, and testing of a new small-scaled rotorcraft Unmanned Aerial Vehicle (RUAV system—ServoHeli-40. A turbine-powered UAV weighted less than 15 kg was designed, and its major components were tested at the Shenyang Institute of Automation, Chinese Academy of Sciences in Shenyang, China. The aircraft was designed to reach a top speed of more than 20 mps, flying a distance of more than 10 kilometers, and it is going to be used as a test-bed for experimentally evaluating advanced control methodologies dedicated on improving the maneuverability, reliability, as well as autonomy of RUAV. Sensors and controller are all onboard. The full system has been tested successfully in the autonomous mode using the multichannel active modeling controller. The results show that in a real windy environment the rotorcraft UAV can follow the trajectory which was assigned by the ground control station exactly, and the new control method is obviously more effective than the one in the past year's research.

Mechanisms and actuators for rotorcraft blade morphing

Science.gov (United States)

Vocke, Robert D., III

The idea of improved fight performance through changes in the control surfaces dates back to the advent of aviation with the Wright brothers' pioneering work on "wing warping," but it was not until the recent progress in material and actuator development that such control surfaces seemed practical for modern aircraft. This has opened the door to a new class of aircraft that have the ability to change shape or morph, which are being investigated due to the potential to have a single platform serve multiple mission objectives, as well as improve performance characteristics. While the majority of existing research for morphing aircraft has focused on fixedwing aircraft, rotary-wing aircraft have begun to receive more attention. The purpose of this body of work is to investigate the current state of morphing actuation technology for rotorcraft and improve upon it. Specifically, this work looks at two types of morphing: Pneumatic Artificial Muscle (PAM) actuated trailing edge flaps and conformal variable diameter morphing. First, active camber changes through the use of PAM powered trailing edge flaps were investigated due to the potential for reductions in power requirements and vibration/noise levels. A PAM based antagonistic actuation system was developed utilizing a novel combination of mechanism geometry and PAM bias contraction optimization to overcome the natural extension stiffening characteristics of PAMs. In open-loop bench-top testing against a "worst-case" constant torsional loading, the system demonstrated actuation authority suitable for both primary control and vibration/noise reduction. Additionally, closed-loop test data indicated that the system was capable of tracking complex waveforms consistent with those needed for rotorcraft control. This system demonstrated performance on-par with the state of the art pneumatic trailing edge flap actuators, yet with a much smaller footprint and impact on the rotor-blade. The second morphing system developed in

A robust direct-integration method for rotorcraft maneuver and periodic response

Science.gov (United States)

Panda, Brahmananda

1992-01-01

The Newmark-Beta method and the Newton-Raphson iteration scheme are combined to develop a direct-integration method for evaluating the maneuver and periodic-response expressions for rotorcraft. The method requires the generation of Jacobians and includes higher derivatives in the formulation of the geometric stiffness matrix to enhance the convergence of the system. The method leads to effective convergence with nonlinear structural dynamics and aerodynamic terms. Singularities in the matrices can be addressed with the method as they arise from a Lagrange multiplier approach for coupling equations with nonlinear constraints. The method is also shown to be general enough to handle singularities from quasisteady control-system models. The method is shown to be more general and robust than the similar 2GCHAS method for analyzing rotorcraft dynamics.

77 FR 50576 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures; OMB Approval of...

Science.gov (United States)

2012-08-22

... Composite Rotorcraft Structures; OMB Approval of Information Collection AGENCY: Federal Aviation... Rotorcraft Structures,'' which was published on December 1, 2011. DATES: The rule published on December 1... and Fatigue Evaluation of Composite Rotorcraft Structures,'' published in the Federal Register (76 FR...

Inexpensive Reliable Oil-Debris Optical Sensor for Rotorcraft Health Monitoring, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Rotorcrafts form a unique subset of air vehicles in that a rotorcraft's propulsion system is used not only for propulsion, but it also serves as the primary source...

Multi-model Simulation for Optimal Control of Aeroacoustics.

Energy Technology Data Exchange (ETDEWEB)

Collis, Samuel Scott; Chen, Guoquan

2005-05-01

Flow-generated noise, especially rotorcraft noise has been a serious concern for bothcommercial and military applications. A particular important noise source for rotor-craft is Blade-Vortex-Interaction (BVI)noise, a high amplitude, impulsive sound thatoften dominates other rotorcraft noise sources. Usually BVI noise is caused by theunsteady flow changes around various rotor blades due to interactions with vorticespreviously shed by the blades. A promising approach for reducing the BVI noise isto use on-blade controls, such as suction/blowing, micro-flaps/jets, and smart struc-tures. Because the design and implementation of such experiments to evaluate suchsystems are very expensive, efficient computational tools coupled with optimal con-trol systems are required to explore the relevant physics and evaluate the feasibilityof using various micro-fluidic devices before committing to hardware.In this thesis the research is to formulate and implement efficient computationaltools for the development and study of optimal control and design strategies for com-plex flow and acoustic systems with emphasis on rotorcraft applications, especiallyBVI noise control problem. The main purpose of aeroacoustic computations is todetermine the sound intensity and directivity far away from the noise source. How-ever, the computational cost of using a high-fidelity flow-physics model across thefull domain is usually prohibitive and itmight also be less accurate because of thenumerical diffusion and other problems. Taking advantage of the multi-physics andmulti-scale structure of this aeroacoustic problem, we develop a multi-model, multi-domain (near-field/far-field) method based on a discontinuous Galerkin discretiza-tion. In this approach the coupling of multi-domains and multi-models is achievedby weakly enforcing continuity of normal fluxes across a coupling surface. For ourinterested aeroacoustics control problem, the adjoint equations that determine thesensitivity of the cost

Environmental noise and noise modelling-some aspects in Malaysian development

International Nuclear Information System (INIS)

Leong, Mohd Salman; Mohd Shafiek bin Hj Yaacob

1994-01-01

Environmental noise is of growing concern in Malaysia with the increasing awareness of the need for an environmental quality consistent with improved quality of life. While noise is one of the several elements in an Environmental Impact Assessment report, the degree of emphasis in the assessment is not as thorough as other aspects in the EIA study. The measurements, prediction (if at all any), and evaluation tended to be superficial. The paper presents a summary of correct noise descriptors and annoyance assessment parameters appropriate for the evaluation of environmental noise. The paper further highlights current inadequacies in the Environmental Quality Act for noise pollution, and annoyance assessment. Some examples of local noise pollution are presented. A discussion on environmental noise modelling is presented. Examples illustrating environmental noise modelling for a mining operation and a power station are given. It is the authors' recommendation that environmental noise modelling be made mandatory in all EIA studies such that a more definitive assessment could be realised

Rotorcraft pursuit-evasion in nap-of-the-earth flight

Science.gov (United States)

Menon, P. K. A.; Cheng, V. H. L.; Kim, E.

1990-01-01

Two approaches for studying the pursuit-evasion problem between rotorcraft executing nap-of-the-earth flight are presented. The first of these employs a constant speed kinematic helicopter model, while the second approach uses a three degree of freedom point-mass model. The candidate solutions to the first differential game are generated by integrating the state-costate equations backward in time. The second problem employs feedback linearization to obtain guidance laws in nonlinear feedback form. Both approaches explicitly use the terrain profile data. Sample extremals are presented.

Sensitivity Analysis of Multidisciplinary Rotorcraft Simulations

Science.gov (United States)

Wang, Li; Diskin, Boris; Biedron, Robert T.; Nielsen, Eric J.; Bauchau, Olivier A.

2017-01-01

A multidisciplinary sensitivity analysis of rotorcraft simulations involving tightly coupled high-fidelity computational fluid dynamics and comprehensive analysis solvers is presented and evaluated. An unstructured sensitivity-enabled Navier-Stokes solver, FUN3D, and a nonlinear flexible multibody dynamics solver, DYMORE, are coupled to predict the aerodynamic loads and structural responses of helicopter rotor blades. A discretely-consistent adjoint-based sensitivity analysis available in FUN3D provides sensitivities arising from unsteady turbulent flows and unstructured dynamic overset meshes, while a complex-variable approach is used to compute DYMORE structural sensitivities with respect to aerodynamic loads. The multidisciplinary sensitivity analysis is conducted through integrating the sensitivity components from each discipline of the coupled system. Numerical results verify accuracy of the FUN3D/DYMORE system by conducting simulations for a benchmark rotorcraft test model and comparing solutions with established analyses and experimental data. Complex-variable implementation of sensitivity analysis of DYMORE and the coupled FUN3D/DYMORE system is verified by comparing with real-valued analysis and sensitivities. Correctness of adjoint formulations for FUN3D/DYMORE interfaces is verified by comparing adjoint-based and complex-variable sensitivities. Finally, sensitivities of the lift and drag functions obtained by complex-variable FUN3D/DYMORE simulations are compared with sensitivities computed by the multidisciplinary sensitivity analysis, which couples adjoint-based flow and grid sensitivities of FUN3D and FUN3D/DYMORE interfaces with complex-variable sensitivities of DYMORE structural responses.

Experimental Investigation of Rotorcraft Outwash in Ground Effect

Science.gov (United States)

Tanner, Philip E.; Overmeyer, Austin D.; Jenkins, Luther N.; Yao, Chung-Sheng; Bartram, Scott M.

2015-01-01

The wake characteristics of a rotorcraft are affected by the proximity of a rotor to the ground surface, especially during hover. Ground effect is encountered when the rotor disk is within a distance of a few rotor radii above the ground surface and results in an increase in thrust for a given power relative to that same power condition with the rotor out of ground effect. Although this phenomenon has been highly documented and observed since the beginning of the helicopter age, there is still a relatively little amount of flow-field data existing to help understand its features. Joint Army and NASA testing was conducted at NASA Langley Research Center using a powered rotorcraft model in hover at various rotor heights and thrust conditions in order to contribute to the complete outwash data set. The measured data included outwash velocities and directions, rotor loads, fuselage loads, and ground pressures. The researchers observed a linear relationship between rotor height and percent download on the fuselage, peak mean outwash velocities occurring at radial stations between 1.7 and 1.8 r/R regardless of rotor height, and the measurement azimuthal dependence of the outwash profile for a model incorporating a fuselage. Comparisons to phase-locked PIV data showed similar contours but a more contracted wake boundary for the PIV data. This paper describes the test setup and presents some of the averaged results.

Rotorcraft Low Altitude CNS (Communications, Navigation and Surveillance) Benefit/Cost Analysis, Rotorcraft Operations Data

Science.gov (United States)

1989-09-01

inventory of rotorcraft activity by mission and location. 17. Key Words 18. Distribution Statement Helicopter Helicopter Missions This document is available...helicopter is used to transport skiers /hikers to remote, normally inaccessible places. This mission is performed in rural or wilderness areas at altitudes...their applicability to the CNS benefit/cost analysis. Because of the uncertainty in the knowledge of the characteristics of both current and future

Miniature Rotorcraft Flight Control Stabilization System

Science.gov (United States)

2008-05-30

forgetting factor g = Magnitude of earth’s gravity Bgv , = gravity vector expressed in the body and inertial frames Igv intlon, intlat = lateral and...algorithm and QUEST on an example small rotorcraft a set of data was generated as shown in Fig. 1. Using the known Euler angles, Igv , and measurement data

Model of aircraft noise adaptation

Science.gov (United States)

Dempsey, T. K.; Coates, G. D.; Cawthorn, J. M.

1977-01-01

Development of an aircraft noise adaptation model, which would account for much of the variability in the responses of subjects participating in human response to noise experiments, was studied. A description of the model development is presented. The principal concept of the model, was the determination of an aircraft adaptation level which represents an annoyance calibration for each individual. Results showed a direct correlation between noise level of the stimuli and annoyance reactions. Attitude-personality variables were found to account for varying annoyance judgements.

Comprehensive Modeling and Analysis of Rotorcraft Variable Speed Propulsion System With Coupled Engine/Transmission/Rotor Dynamics

Science.gov (United States)

DeSmidt, Hans A.; Smith, Edward C.; Bill, Robert C.; Wang, Kon-Well

2013-01-01

This project develops comprehensive modeling and simulation tools for analysis of variable rotor speed helicopter propulsion system dynamics. The Comprehensive Variable-Speed Rotorcraft Propulsion Modeling (CVSRPM) tool developed in this research is used to investigate coupled rotor/engine/fuel control/gearbox/shaft/clutch/flight control system dynamic interactions for several variable rotor speed mission scenarios. In this investigation, a prototypical two-speed Dual-Clutch Transmission (DCT) is proposed and designed to achieve 50 percent rotor speed variation. The comprehensive modeling tool developed in this study is utilized to analyze the two-speed shift response of both a conventional single rotor helicopter and a tiltrotor drive system. In the tiltrotor system, both a Parallel Shift Control (PSC) strategy and a Sequential Shift Control (SSC) strategy for constant and variable forward speed mission profiles are analyzed. Under the PSC strategy, selecting clutch shift-rate results in a design tradeoff between transient engine surge margins and clutch frictional power dissipation. In the case of SSC, clutch power dissipation is drastically reduced in exchange for the necessity to disengage one engine at a time which requires a multi-DCT drive system topology. In addition to comprehensive simulations, several sections are dedicated to detailed analysis of driveline subsystem components under variable speed operation. In particular an aeroelastic simulation of a stiff in-plane rotor using nonlinear quasi-steady blade element theory was conducted to investigate variable speed rotor dynamics. It was found that 2/rev and 4/rev flap and lag vibrations were significant during resonance crossings with 4/rev lagwise loads being directly transferred into drive-system torque disturbances. To capture the clutch engagement dynamics, a nonlinear stick-slip clutch torque model is developed. Also, a transient gas-turbine engine model based on first principles mean

Enhanced Core Noise Modeling for Turbofan Engines

Science.gov (United States)

Stone, James R.; Krejsa, Eugene A.; Clark, Bruce J.

2011-01-01

This report describes work performed by MTC Technologies (MTCT) for NASA Glenn Research Center (GRC) under Contract NAS3-00178, Task Order No. 15. MTCT previously developed a first-generation empirical model that correlates the core/combustion noise of four GE engines, the CF6, CF34, CFM56, and GE90 for General Electric (GE) under Contract No. 200-1X-14W53048, in support of GRC Contract NAS3-01135. MTCT has demonstrated in earlier noise modeling efforts that the improvement of predictive modeling is greatly enhanced by an iterative approach, so in support of NASA's Quiet Aircraft Technology Project, GRC sponsored this effort to improve the model. Since the noise data available for correlation are total engine noise spectra, it is total engine noise that must be predicted. Since the scope of this effort was not sufficient to explore fan and turbine noise, the most meaningful comparisons must be restricted to frequencies below the blade passage frequency. Below the blade passage frequency and at relatively high power settings jet noise is expected to be the dominant source, and comparisons are shown that demonstrate the accuracy of the jet noise model recently developed by MTCT for NASA under Contract NAS3-00178, Task Order No. 10. At lower power settings the core noise became most apparent, and these data corrected for the contribution of jet noise were then used to establish the characteristics of core noise. There is clearly more than one spectral range where core noise is evident, so the spectral approach developed by von Glahn and Krejsa in 1982 wherein four spectral regions overlap, was used in the GE effort. Further analysis indicates that the two higher frequency components, which are often somewhat masked by turbomachinery noise, can be treated as one component, and it is on that basis that the current model is formulated. The frequency scaling relationships are improved and are now based on combustor and core nozzle geometries. In conjunction with the Task

Underwater noise modelling for environmental impact assessment

Energy Technology Data Exchange (ETDEWEB)

Farcas, Adrian [Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT (United Kingdom); Thompson, Paul M. [Lighthouse Field Station, Institute of Biological and Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL (United Kingdom); Merchant, Nathan D., E-mail: nathan.merchant@cefas.co.uk [Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT (United Kingdom)

2016-02-15

Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

Underwater noise modelling for environmental impact assessment

International Nuclear Information System (INIS)

Farcas, Adrian; Thompson, Paul M.; Merchant, Nathan D.

2016-01-01

Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

A Higher Harmonic Optimal Controller to Optimise Rotorcraft Aeromechanical Behaviour

Science.gov (United States)

Leyland, Jane Anne

1996-01-01

Three methods to optimize rotorcraft aeromechanical behavior for those cases where the rotorcraft plant can be adequately represented by a linear model system matrix were identified and implemented in a stand-alone code. These methods determine the optimal control vector which minimizes the vibration metric subject to constraints at discrete time points, and differ from the commonly used non-optimal constraint penalty methods such as those employed by conventional controllers in that the constraints are handled as actual constraints to an optimization problem rather than as just additional terms in the performance index. The first method is to use a Non-linear Programming algorithm to solve the problem directly. The second method is to solve the full set of non-linear equations which define the necessary conditions for optimality. The third method is to solve each of the possible reduced sets of equations defining the necessary conditions for optimality when the constraints are pre-selected to be either active or inactive, and then to simply select the best solution. The effects of maneuvers and aeroelasticity on the systems matrix are modelled by using a pseudo-random pseudo-row-dependency scheme to define the systems matrix. Cases run to date indicate that the first method of solution is reliable, robust, and easiest to use, and that it was superior to the conventional controllers which were considered.

Modeling aircraft noise induced sleep disturbance

Science.gov (United States)

McGuire, Sarah M.

One of the primary impacts of aircraft noise on a community is its disruption of sleep. Aircraft noise increases the time to fall asleep, the number of awakenings, and decreases the amount of rapid eye movement and slow wave sleep. Understanding these changes in sleep may be important as they could increase the risk for developing next-day effects such as sleepiness and reduced performance and long-term health effects such as cardiovascular disease. There are models that have been developed to predict the effect of aircraft noise on sleep. However, most of these models only predict the percentage of the population that is awakened. Markov and nonlinear dynamic models have been developed to predict an individual's sleep structure during the night. However, both of these models have limitations. The Markov model only accounts for whether an aircraft event occurred not the noise level or other sound characteristics of the event that may affect the degree of disturbance. The nonlinear dynamic models were developed to describe normal sleep regulation and do not have a noise effects component. In addition, the nonlinear dynamic models have slow dynamics which make it difficult to predict short duration awakenings which occur both spontaneously and as a result of nighttime noise exposure. The purpose of this research was to examine these sleep structure models to determine how they could be altered to predict the effect of aircraft noise on sleep. Different approaches for adding a noise level dependence to the Markov Model was explored and the modified model was validated by comparing predictions to behavioral awakening data. In order to determine how to add faster dynamics to the nonlinear dynamic sleep models it was necessary to have a more detailed sleep stage classification than was available from visual scoring of sleep data. An automatic sleep stage classification algorithm was developed which extracts different features of polysomnography data including the

Overview of en route noise prediction using a integrated noise model

Science.gov (United States)

2010-04-20

En route aircraft noise is often ignored in aircraft noise modeling because large amounts of noise attenuation due to long propagation distances between the aircraft and the receivers on the ground, reduced power in cruise flight compared to takeoff ...

77 FR 4890 - Damage Tolerance and Fatigue Evaluation for Composite Rotorcraft Structures, and Damage Tolerance...

Science.gov (United States)

2012-02-01

...-AJ52, 2120-AJ51 Damage Tolerance and Fatigue Evaluation for Composite Rotorcraft Structures, and Damage Tolerance and Fatigue Evaluation for Metallic Structures; Correction AGENCY: Federal Aviation Administration... Tolerance and Fatigue Evaluation for Composite Rotorcraft Structures'' (76 FR 74655), published December 1...

Modeling and Prediction of Krueger Device Noise

Science.gov (United States)

Guo, Yueping; Burley, Casey L.; Thomas, Russell H.

2016-01-01

This paper presents the development of a noise prediction model for aircraft Krueger flap devices that are considered as alternatives to leading edge slotted slats. The prediction model decomposes the total Krueger noise into four components, generated by the unsteady flows, respectively, in the cove under the pressure side surface of the Krueger, in the gap between the Krueger trailing edge and the main wing, around the brackets supporting the Krueger device, and around the cavity on the lower side of the main wing. For each noise component, the modeling follows a physics-based approach that aims at capturing the dominant noise-generating features in the flow and developing correlations between the noise and the flow parameters that control the noise generation processes. The far field noise is modeled using each of the four noise component's respective spectral functions, far field directivities, Mach number dependencies, component amplitudes, and other parametric trends. Preliminary validations are carried out by using small scale experimental data, and two applications are discussed; one for conventional aircraft and the other for advanced configurations. The former focuses on the parametric trends of Krueger noise on design parameters, while the latter reveals its importance in relation to other airframe noise components.

In-flight performance optimization for rotorcraft with redundant controls

Science.gov (United States)

Ozdemir, Gurbuz Taha

A conventional helicopter has limits on performance at high speeds because of the limitations of main rotor, such as compressibility issues on advancing side or stall issues on retreating side. Auxiliary lift and thrust components have been suggested to improve performance of the helicopter substantially by reducing the loading on the main rotor. Such a configuration is called the compound rotorcraft. Rotor speed can also be varied to improve helicopter performance. In addition to improved performance, compound rotorcraft and variable RPM can provide a much larger degree of control redundancy. This additional redundancy gives the opportunity to further enhance performance and handling qualities. A flight control system is designed to perform in-flight optimization of redundant control effectors on a compound rotorcraft in order to minimize power required and extend range. This "Fly to Optimal" (FTO) control law is tested in simulation using the GENHEL model. A model of the UH-60, a compound version of the UH-60A with lifting wing and vectored thrust ducted propeller (VTDP), and a generic compound version of the UH-60A with lifting wing and propeller were developed and tested in simulation. A model following dynamic inversion controller is implemented for inner loop control of roll, pitch, yaw, heave, and rotor RPM. An outer loop controller regulates airspeed and flight path during optimization. A Golden Section search method was used to find optimal rotor RPM on a conventional helicopter, where the single redundant control effector is rotor RPM. The FTO builds off of the Adaptive Performance Optimization (APO) method of Gilyard by performing low frequency sweeps on a redundant control for a fixed wing aircraft. A method based on the APO method was used to optimize trim on a compound rotorcraft with several redundant control effectors. The controller can be used to optimize rotor RPM and compound control effectors through flight test or simulations in order to

Contributions to the Characterization and Mitigation of Rotorcraft Brownout

Science.gov (United States)

Tritschler, John Kirwin

Rotorcraft brownout, the condition in which the flow field of a rotorcraft mobilizes sediment from the ground to generate a cloud that obscures the pilot's field of view, continues to be a significant hazard to civil and military rotorcraft operations. This dissertation presents methodologies for: (i) the systematic mitigation of rotorcraft brownout through operational and design strategies and (ii) the quantitative characterization of the visual degradation caused by a brownout cloud. In Part I of the dissertation, brownout mitigation strategies are developed through simulation-based brownout studies that are mathematically formulated within a numerical optimization framework. Two optimization studies are presented. The first study involves the determination of approach-to-landing maneuvers that result in reduced brownout severity. The second study presents a potential methodology for the design of helicopter rotors with improved brownout characteristics. The results of both studies indicate that the fundamental mechanisms underlying brownout mitigation are aerodynamic in nature, and the evolution of a ground vortex ahead of the rotor disk is seen to be a key element in the development of a brownout cloud. In Part II of the dissertation, brownout cloud characterizations are based upon the Modulation Transfer Function (MTF), a metric commonly used in the optics community for the characterization of imaging systems. The use of the MTF in experimentation is examined first, and the application of MTF calculation and interpretation methods to actual flight test data is described. The potential for predicting the MTF from numerical simulations is examined second, and an initial methodology is presented for the prediction of the MTF of a brownout cloud. Results from the experimental and analytical studies rigorously quantify the intuitively-known facts that the visual degradation caused by brownout is a space and time-dependent phenomenon, and that high spatial frequency

Analysis of a Shock-Associated Noise Prediction Model Using Measured Jet Far-Field Noise Data

Science.gov (United States)

Dahl, Milo D.; Sharpe, Jacob A.

2014-01-01

A code for predicting supersonic jet broadband shock-associated noise was assessed using a database containing noise measurements of a jet issuing from a convergent nozzle. The jet was operated at 24 conditions covering six fully expanded Mach numbers with four total temperature ratios. To enable comparisons of the predicted shock-associated noise component spectra with data, the measured total jet noise spectra were separated into mixing noise and shock-associated noise component spectra. Comparisons between predicted and measured shock-associated noise component spectra were used to identify deficiencies in the prediction model. Proposed revisions to the model, based on a study of the overall sound pressure levels for the shock-associated noise component of the measured data, a sensitivity analysis of the model parameters with emphasis on the definition of the convection velocity parameter, and a least-squares fit of the predicted to the measured shock-associated noise component spectra, resulted in a new definition for the source strength spectrum in the model. An error analysis showed that the average error in the predicted spectra was reduced by as much as 3.5 dB for the revised model relative to the average error for the original model.

Aero-acoustic noise of wind turbines. Noise prediction models

Energy Technology Data Exchange (ETDEWEB)

Maribo Pedersen, B. [ed.

1997-12-31

Semi-empirical and CAA (Computational AeroAcoustics) noise prediction techniques are the subject of this expert meeting. The meeting presents and discusses models and methods. The meeting may provide answers to the following questions: What Noise sources are the most important? How are the sources best modeled? What needs to be done to do better predictions? Does it boil down to correct prediction of the unsteady aerodynamics around the rotor? Or is the difficult part to convert the aerodynamics into acoustics? (LN)

Improvement of airfoil trailing edge bluntness noise model

Directory of Open Access Journals (Sweden)

Wei Jun Zhu

2016-02-01

Full Text Available In this article, airfoil trailing edge bluntness noise is investigated using both computational aero-acoustic and semi-empirical approach. For engineering purposes, one of the most commonly used prediction tools for trailing edge noise are based on semi-empirical approaches, for example, the Brooks, Pope, and Marcolini airfoil noise prediction model developed by Brooks, Pope, and Marcolini (NASA Reference Publication 1218, 1989. It was found in previous study that the Brooks, Pope, and Marcolini model tends to over-predict noise at high frequencies. Furthermore, it was observed that this was caused by a lack in the model to predict accurately noise from blunt trailing edges. For more physical understanding of bluntness noise generation, in this study, we also use an advanced in-house developed high-order computational aero-acoustic technique to investigate the details associated with trailing edge bluntness noise. The results from the numerical model form the basis for an improved Brooks, Pope, and Marcolini trailing edge bluntness noise model.

Adaptive Rotorcraft Condition and Usage Tracking System (ARCUTS), Phase I

Data.gov (United States)

National Aeronautics and Space Administration — International Electronic Machines (IEM), a leader in the development of innovative sensor solutions for transportation systems, will develop the Adaptive Rotorcraft...

A Noise Robust Statistical Texture Model

DEFF Research Database (Denmark)

Hilger, Klaus Baggesen; Stegmann, Mikkel Bille; Larsen, Rasmus

2002-01-01

Appearance Models segmentation framework. This is accomplished by augmenting the model with an estimate of the covariance of the noise present in the training data. This results in a more compact model maximising the signal-to-noise ratio, thus favouring subspaces rich on signal, but low on noise......This paper presents a novel approach to the problem of obtaining a low dimensional representation of texture (pixel intensity) variation present in a training set after alignment using a Generalised Procrustes analysis.We extend the conventional analysis of training textures in the Active...

Computational Wind Tunnel: A Design Tool for Rotorcraft, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — During initial design studies, parametric variation of vehicle geometry is routine. In addition, rotorcraft engineers traditionally use the wind tunnel to evaluate...

Computational Wind Tunnel: A Design Tool for Rotorcraft, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Rotorcraft engineers traditionally use the wind tunnel to evaluate and finalize designs. Insufficient correlation between wind tunnel results and flight tests, have...

Structures technology for a new generation of rotorcraft

Science.gov (United States)

Bartlett, Felton D., Jr.

1989-01-01

This paper presents an overview of structures research at the U. S. Army Aerostructures Directorate. The objectives of this research are to investigate, explore, and demonstrate emerging technologies that will provide lighter, safer, more survivable, and more cost-effective structures for rotorcraft in the 1990s and beyond. The emphasis of today's R&D is to contribute proven structures technology to the U. S. rotorcraft industry and Army aviation that directly impacts tomorrow's fleet readiness and mission capabilities. The primary contributor toward meeting these challenges is the development of high-strength and durable composites to minimize structural weight while maximizing cost effectiveness. Special aviation issues such as delamination of dynamic components, impact damage to thin skins, crashworthiness, and affordable manufacturing need to be resolved before the full potential of composites technology can be realized. To that end, this paper highlights research into composites structural integrity, crashworthiness, and materials applications which addresses these issues.

A simplified analog for a rotorcraft-in-ground-effect flow using a forced impinging jet

Science.gov (United States)

Geiser, Jayson; Kiger, Ken

2010-11-01

The phenomenon of rotorcraft brown-out is defined as the intense suspension and re-ingestion of sand during the take-off and landing of a rotor-lifted aircraft. To mitigate the problem of rotorcraft brown-out, the non-equilibrium sediment suspension process that occurs within a typical rotorcraft wake must be understood. We attempt to understand the most basic aspects of this complex flow through the use of an axisymmetric forced impinging jet. While this flow neglects the swirl component associated with a rotorcraft, it does reproduce the typical coherent vortex structures, and permits their repeatable generation within an axisymmetric mean stagnation flow. The goal of the current work is to determine the forcing conditions that produce isolated, but intense and repeatable structures that can be followed through their interaction with the wall boundary. Stereo PIV imaging is applied to detail the breakdown of a vortex ring in the wall jet zone. The secondary vortex generation and decay are observed experimentally with 3-D vector fields, and their results are interpreted with respect to their significance in the context of sediment mobilization.

Rotorcraft research in India: recent developments

OpenAIRE

Ganguli, Ranjan

2010-01-01

Purpose - The purpose of this paper is to discuss published research in rotorcraft which has taken place in India during the last ten years The helicopter research is divided into the following parts health monitoring smart rotor design optimization control helicopter rotor dynamics active control of structural response (ACSR) and helicopter design and development Aspects of health monitoring and smart rotor are discussed in detail Further work needed and areas for international collaboration...

78 FR 12254 - Interest in Restructure of Rotorcraft Airworthiness Standards

Science.gov (United States)

2013-02-22

...: FAA, Rotorcraft Directorate, Regulations and Policy Group (Attn: John Vanhoudt, ASW-111), 2601 Meacham... standards and safety levels, or whether the existing standards philosophy based on weight (currently 7,000...

Embedded Data Acquisition Tools for Rotorcraft Diagnostic Sensors

Science.gov (United States)

Wagoner, Robert

2014-01-01

Rotorcraft drive trains must withstand enormous pressure while operating continuously in extreme temperature and vibration environments. Captive components, such as planetary and spiral bevel gears, see enormous strain but are not accessible to fixed instrumentation, such as a piezoelectric transducer. Thus, it is difficult to directly monitor components that are most susceptible to damage. This innovation is a self-contained data processing unit within a specialized fixture that installs directly inside the rotating pinion gear in the gearbox. From this location, it detects and transmits high-resolution prognostic data to a fixed transceiver. The sensor is based on microelectromechanical systems (MEMS) technology and uses innovative circuit designs to capture high-bandwidth data and transmit it wirelessly from inside an operational helicopter transmission. With Ridgetop's advanced MEMS-based sensor, researchers have, for the first time, been able to extract high-resolution acoustic signatures wirelessly from sensors within the transmission that would otherwise be muffled by background gear noises. Ridgetop's innovative instrument will help researchers perform dynamic analysis of gear interaction and develop improved designs for gear components. In addition, data from this instrument can be used to validate new algorithms that detect and predict faults based on external acoustic signatures, for prognostic purposes. The result of this work will be an improvement in safety, performance, and cost for future generations of rotating components.

An aircraft noise pollution model for trajectory optimization

Science.gov (United States)

Barkana, A.; Cook, G.

1976-01-01

A mathematical model describing the generation of aircraft noise is developed with the ultimate purpose of reducing noise (noise-optimizing landing trajectories) in terminal areas. While the model is for a specific aircraft (Boeing 737), the methodology would be applicable to a wide variety of aircraft. The model is used to obtain a footprint on the ground inside of which the noise level is at or above 70 dB.

Analysis of modeling aircraft noise with the Nord2000 noise model

Science.gov (United States)

2012-10-31

This report provides comparisons between AEDT/INM and the Nord 2000 Noise Models for the following parameters: ground type, simple terrain (downward slope, upward slope, hill), temperature and humidity, temperature gradients (positive and negative), ...

A robust rotorcraft flight control system design methodology utilizing quantitative feedback theory

Science.gov (United States)

Gorder, Peter James

1993-01-01

Rotorcraft flight control systems present design challenges which often exceed those associated with fixed-wing aircraft. First, large variations in the response characteristics of the rotorcraft result from the wide range of airspeeds of typical operation (hover to over 100 kts). Second, the assumption of vehicle rigidity often employed in the design of fixed-wing flight control systems is rarely justified in rotorcraft where rotor degrees of freedom can have a significant impact on the system performance and stability. This research was intended to develop a methodology for the design of robust rotorcraft flight control systems. Quantitative Feedback Theory (QFT) was chosen as the basis for the investigation. Quantitative Feedback Theory is a technique which accounts for variability in the dynamic response of the controlled element in the design robust control systems. It was developed to address a Multiple-Input Single-Output (MISO) design problem, and utilizes two degrees of freedom to satisfy the design criteria. Two techniques were examined for extending the QFT MISO technique to the design of a Multiple-Input-Multiple-Output (MIMO) flight control system (FCS) for a UH-60 Black Hawk Helicopter. In the first, a set of MISO systems, mathematically equivalent to the MIMO system, was determined. QFT was applied to each member of the set simultaneously. In the second, the same set of equivalent MISO systems were analyzed sequentially, with closed loop response information from each loop utilized in subsequent MISO designs. The results of each technique were compared, and the advantages of the second, termed Sequential Loop Closure, were clearly evident.

Catastrophe Insurance Modeled by Shot-Noise Processes

Directory of Open Access Journals (Sweden)

Thorsten Schmidt

2014-02-01

Full Text Available Shot-noise processes generalize compound Poisson processes in the following way: a jump (the shot is followed by a decline (noise. This constitutes a useful model for insurance claims in many circumstances; claims due to natural disasters or self-exciting processes exhibit similar features. We give a general account of shot-noise processes with time-inhomogeneous drivers inspired by recent results in credit risk. Moreover, we derive a number of useful results for modeling and pricing with shot-noise processes. Besides this, we obtain some highly tractable examples and constitute a useful modeling tool for dynamic claims processes. The results can in particular be used for pricing Catastrophe Bonds (CAT bonds, a traded risk-linked security. Additionally, current results regarding the estimation of shot-noise processes are reviewed.

Analytical expressions for transition edge sensor excess noise models

International Nuclear Information System (INIS)

Brandt, Daniel; Fraser, George W.

2010-01-01

Transition edge sensors (TESs) are high-sensitivity thermometers used in cryogenic microcalorimeters which exploit the steep gradient in resistivity with temperature during the superconducting phase transition. Practical TES devices tend to exhibit a white noise of uncertain origin, arising inside the device. We discuss two candidate models for this excess noise, phase slip shot noise (PSSN) and percolation noise. We extend the existing PSSN model to include a magnetic field dependence and derive a basic analytical model for percolation noise. We compare the predicted functional forms of the noise current vs. resistivity curves of both models with experimental data and provide a set of equations for both models to facilitate future experimental efforts to clearly identify the source of excess noise.

Modeling Of Construction Noise For Environmental Impact Assessment

Directory of Open Access Journals (Sweden)

Mohamed F. Hamoda

2008-06-01

Full Text Available This study measured the noise levels generated at different construction sites in reference to the stage of construction and the equipment used, and examined the methods to predict such noise in order to assess the environmental impact of noise. It included 33 construction sites in Kuwait and used artificial neural networks (ANNs for the prediction of noise. A back-propagation neural network (BPNN model was compared with a general regression neural network (GRNN model. The results obtained indicated that the mean equivalent noise level was 78.7 dBA which exceeds the threshold limit. The GRNN model was superior to the BPNN model in its accuracy of predicting construction noise due to its ability to train quickly on sparse data sets. Over 93% of the predictions were within 5% of the observed values. The mean absolute error between the predicted and observed data was only 2 dBA. The ANN modeling proved to be a useful technique for noise predictions required in the assessment of environmental impact of construction activities.

Evaluation of internal noise methods for Hotelling observer models

International Nuclear Information System (INIS)

Zhang Yani; Pham, Binh T.; Eckstein, Miguel P.

2007-01-01

The inclusion of internal noise in model observers is a common method to allow for quantitative comparisons between human and model observer performance in visual detection tasks. In this article, we studied two different strategies for inserting internal noise into Hotelling model observers. In the first strategy, internal noise was added to the output of individual channels: (a) Independent nonuniform channel noise, (b) independent uniform channel noise. In the second strategy, internal noise was added to the decision variable arising from the combination of channel responses. The standard deviation of the zero mean internal noise was either constant or proportional to: (a) the decision variable's standard deviation due to the external noise, (b) the decision variable's variance caused by the external noise, (c) the decision variable magnitude on a trial to trial basis. We tested three model observers: square window Hotelling observer (HO), channelized Hotelling observer (CHO), and Laguerre-Gauss Hotelling observer (LGHO) using a four alternative forced choice (4AFC) signal known exactly but variable task with a simulated signal embedded in real x-ray coronary angiogram backgrounds. The results showed that the internal noise method that led to the best prediction of human performance differed across the studied model observers. The CHO model best predicted human observer performance with the channel internal noise. The HO and LGHO best predicted human observer performance with the decision variable internal noise. The present results might guide researchers with the choice of methods to include internal noise into Hotelling model observers when evaluating and optimizing medical image quality

Enhanced Fan Noise Modeling for Turbofan Engines

Science.gov (United States)

Krejsa, Eugene A.; Stone, James R.

2014-01-01

This report describes work by consultants to Diversitech Inc. for the NASA Glenn Research Center (GRC) to revise the fan noise prediction procedure based on fan noise data obtained in the 9- by 15 Foot Low-Speed Wind Tunnel at GRC. The purpose of this task is to begin development of an enhanced, analytical, more physics-based, fan noise prediction method applicable to commercial turbofan propulsion systems. The method is to be suitable for programming into a computational model for eventual incorporation into NASA's current aircraft system noise prediction computer codes. The scope of this task is in alignment with the mission of the Propulsion 21 research effort conducted by the coalition of NASA, state government, industry, and academia to develop aeropropulsion technologies. A model for fan noise prediction was developed based on measured noise levels for the R4 rotor with several outlet guide vane variations and three fan exhaust areas. The model predicts the complete fan noise spectrum, including broadband noise, tones, and for supersonic tip speeds, combination tones. Both spectra and directivity are predicted. Good agreement with data was achieved for all fan geometries. Comparisons with data from a second fan, the ADP fan, also showed good agreement.

Optimal Height Calculation and Modelling of Noise Barrier

Directory of Open Access Journals (Sweden)

Raimondas Grubliauskas

2011-04-01

Full Text Available Transport is one of the main sources of noise having a particularly strong negative impact on the environment. In the city, one of the best methods to reduce the spread of noise in residential areas is a noise barrier. The article presents noise reduction barrier adaptation with empirical formulas calculating and modelling noise distribution. The simulation of noise dispersion has been performed applying the CadnaA program that allows modelling the noise levels of various developments under changing conditions. Calculation and simulation is obtained by assessing the level of noise reduction using the same variables. The investigation results are presented as noise distribution isolines. The selection of a different height of noise barriers are the results calculated at the heights of 1, 4 and 15 meters. The level of noise reduction at the maximum overlap of data, calculation and simulation has reached about 10%.Article in Lithuanian

Research Plans for Improving Understanding of Effects of Very Low-Frequency Noise of Heavy Lift Rotorcraft

Science.gov (United States)

Fidell, Sanford; Horonieff, Richard D.; Schmitz, Fredric H.

2010-01-01

This report reviews the English-language technical literature on infrasonic and low-frequency noise effects; identifies the most salient effects of noise produced by a future large civil tiltrotor aircraft on crew, passengers, and communities near landing areas; and recommends research needed to improve understanding of the effects of such noise on passengers, crew, and residents of areas near landing pads.

Free Flight Rotorcraft Flight Test Vehicle Technology Development

Science.gov (United States)

Hodges, W. Todd; Walker, Gregory W.

1994-01-01

A rotary wing, unmanned air vehicle (UAV) is being developed as a research tool at the NASA Langley Research Center by the U.S. Army and NASA. This development program is intended to provide the rotorcraft research community an intermediate step between rotorcraft wind tunnel testing and full scale manned flight testing. The technologies under development for this vehicle are: adaptive electronic flight control systems incorporating artificial intelligence (AI) techniques, small-light weight sophisticated sensors, advanced telepresence-telerobotics systems and rotary wing UAV operational procedures. This paper briefly describes the system's requirements and the techniques used to integrate the various technologies to meet these requirements. The paper also discusses the status of the development effort. In addition to the original aeromechanics research mission, the technology development effort has generated a great deal of interest in the UAV community for related spin-off applications, as briefly described at the end of the paper. In some cases the technologies under development in the free flight program are critical to the ability to perform some applications.

Applications of artificial intelligence to rotorcraft

Science.gov (United States)

Abbott, Kathy H.

1987-01-01

The application of AI technology may have significant potential payoff for rotorcraft. In the near term, the status of the technology will limit its applicability to decision aids rather than total automation. The specific application areas are categorized into onboard and nonflight aids. The onboard applications include: fault monitoring, diagnosis, and reconfiguration; mission and tactics planning; situation assessment; navigation aids, especially in nap-of-the-earth flight; and adaptive man-machine interfaces. The nonflight applications include training and maintenance diagnostics.

Vibration Noise Modeling for Measurement While Drilling System Based on FOGs

Directory of Open Access Journals (Sweden)

Chunxi Zhang

2017-10-01

Full Text Available Aiming to improve survey accuracy of Measurement While Drilling (MWD based on Fiber Optic Gyroscopes (FOGs in the long period, the external aiding sources are fused into the inertial navigation by the Kalman filter (KF method. The KF method needs to model the inertial sensors’ noise as the system noise model. The system noise is modeled as white Gaussian noise conventionally. However, because of the vibration while drilling, the noise in gyros isn’t white Gaussian noise any more. Moreover, an incorrect noise model will degrade the accuracy of KF. This paper developed a new approach for noise modeling on the basis of dynamic Allan variance (DAVAR. In contrast to conventional white noise models, the new noise model contains both the white noise and the color noise. With this new noise model, the KF for the MWD was designed. Finally, two vibration experiments have been performed. Experimental results showed that the proposed vibration noise modeling approach significantly improved the estimated accuracies of the inertial sensor drifts. Compared the navigation results based on different noise model, with the DAVAR noise model, the position error and the toolface angle error are reduced more than 90%. The velocity error is reduced more than 65%. The azimuth error is reduced more than 50%.

Vibration Noise Modeling for Measurement While Drilling System Based on FOGs.

Science.gov (United States)

Zhang, Chunxi; Wang, Lu; Gao, Shuang; Lin, Tie; Li, Xianmu

2017-10-17

Aiming to improve survey accuracy of Measurement While Drilling (MWD) based on Fiber Optic Gyroscopes (FOGs) in the long period, the external aiding sources are fused into the inertial navigation by the Kalman filter (KF) method. The KF method needs to model the inertial sensors' noise as the system noise model. The system noise is modeled as white Gaussian noise conventionally. However, because of the vibration while drilling, the noise in gyros isn't white Gaussian noise any more. Moreover, an incorrect noise model will degrade the accuracy of KF. This paper developed a new approach for noise modeling on the basis of dynamic Allan variance (DAVAR). In contrast to conventional white noise models, the new noise model contains both the white noise and the color noise. With this new noise model, the KF for the MWD was designed. Finally, two vibration experiments have been performed. Experimental results showed that the proposed vibration noise modeling approach significantly improved the estimated accuracies of the inertial sensor drifts. Compared the navigation results based on different noise model, with the DAVAR noise model, the position error and the toolface angle error are reduced more than 90%. The velocity error is reduced more than 65%. The azimuth error is reduced more than 50%.

Model/data comparison of typhoon-generated noise

International Nuclear Information System (INIS)

Wang Jing-Yan; Li Feng-Hua

2016-01-01

Ocean noise recorded during a typhoon can be used to monitor the typhoon and investigate the mechanism of the wind-generated noise. An analytical expression for the typhoon-generated noise intensity is derived as a function of wind speed. A “bi-peak” structure was observed in an experiment during which typhoon-generated noise was recorded. Wind speed dependence and frequency dependence were also observed in the frequency range of 100 Hz–1000 Hz. The model/data comparison shows that results of the present model of 500 Hz and 1000 Hz are in reasonable agreement with the experimental data, and the typhoon-generated noise intensity has a dependence on frequency and a power-law dependence on wind speed. (special topic)

Modeling road-tyre noise

OpenAIRE

Martins, Mário M. Abreu; Santos, Luís Picado; Freitas, Elisabete F.

2008-01-01

The growing awareness by the broader public of the consequences to health and wellbeing due to road noise has led to a growing number of legal requirements being produced to deal with this matter, both in the design of new or assessment of existing infrastructure. In this article the purpose is to make an up-to-date review of existing studies being carried out to deliver models for predicting noise produced from tyre-road contact, taking account of different methodological appr...

Towards More Efficient Comprehensive Rotor Noise Simulation, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Rotorcraft design and optimization currently still rely largely on simplified (low-fidelity) models, such as rotor disk or wake models to reduce the turn-around time...

Applicability of models to estimate traffic noise for urban roads.

Science.gov (United States)

Melo, Ricardo A; Pimentel, Roberto L; Lacerda, Diego M; Silva, Wekisley M

2015-01-01

Traffic noise is a highly relevant environmental impact in cities. Models to estimate traffic noise, in turn, can be useful tools to guide mitigation measures. In this paper, the applicability of models to estimate noise levels produced by a continuous flow of vehicles on urban roads is investigated. The aim is to identify which models are more appropriate to estimate traffic noise in urban areas since several models available were conceived to estimate noise from highway traffic. First, measurements of traffic noise, vehicle count and speed were carried out in five arterial urban roads of a brazilian city. Together with geometric measurements of width of lanes and distance from noise meter to lanes, these data were input in several models to estimate traffic noise. The predicted noise levels were then compared to the respective measured counterparts for each road investigated. In addition, a chart showing mean differences in noise between estimations and measurements is presented, to evaluate the overall performance of the models. Measured Leq values varied from 69 to 79 dB(A) for traffic flows varying from 1618 to 5220 vehicles/h. Mean noise level differences between estimations and measurements for all urban roads investigated ranged from -3.5 to 5.5 dB(A). According to the results, deficiencies of some models are discussed while other models are identified as applicable to noise estimations on urban roads in a condition of continuous flow. Key issues to apply such models to urban roads are highlighted.

Advances in automated noise data acquisition and noise source modeling for power reactors

International Nuclear Information System (INIS)

Clapp, N.E. Jr.; Kryter, R.C.; Sweeney, F.J.; Renier, J.A.

1981-01-01

A newly expanded program, directed toward achieving a better appreciation of both the strengths and limitations of on-line, noise-based, long-term surveillance programs for nuclear reactors, is described. Initial results in the complementary experimental (acquisition and automated screening of noise signatures) and theoretical (stochastic modeling of likely noise sources) areas of investigation are given

Noise in restaurants: levels and mathematical model.

Science.gov (United States)

To, Wai Ming; Chung, Andy

2014-01-01

Noise affects the dining atmosphere and is an occupational hazard to restaurant service employees worldwide. This paper examines the levels of noise in dining areas during peak hours in different types of restaurants in Hong Kong SAR, China. A mathematical model that describes the noise level in a restaurant is presented. The 1-h equivalent continuous noise level (L(eq,1-h)) was measured using a Type-1 precision integral sound level meter while the occupancy density, the floor area of the dining area, and the ceiling height of each of the surveyed restaurants were recorded. It was found that the measured noise levels using Leq,1-h ranged from 67.6 to 79.3 dBA in Chinese restaurants, from 69.1 to 79.1 dBA in fast food restaurants, and from 66.7 to 82.6 dBA in Western restaurants. Results of the analysis of variance show that there were no significant differences between means of the measured noise levels among different types of restaurants. A stepwise multiple regression analysis was employed to determine the relationships between geometrical and operational parameters and the measured noise levels. Results of the regression analysis show that the measured noise levels depended on the levels of occupancy density only. By reconciling the measured noise levels and the mathematical model, it was found that people in restaurants increased their voice levels when the occupancy density increased. Nevertheless, the maximum measured hourly noise level indicated that the noise exposure experienced by restaurant service employees was below the regulated daily noise exposure value level of 85 dBA.

Noise in restaurants: Levels and mathematical model

Directory of Open Access Journals (Sweden)

Wai Ming To

2014-01-01

Full Text Available Noise affects the dining atmosphere and is an occupational hazard to restaurant service employees worldwide. This paper examines the levels of noise in dining areas during peak hours in different types of restaurants in Hong Kong SAR, China. A mathematical model that describes the noise level in a restaurant is presented. The 1-h equivalent continuous noise level (Leq,1-h was measured using a Type-1 precision integral sound level meter while the occupancy density, the floor area of the dining area, and the ceiling height of each of the surveyed restaurants were recorded. It was found that the measured noise levels using Leq,1-h ranged from 67.6 to 79.3 dBA in Chinese restaurants, from 69.1 to 79.1 dBA in fast food restaurants, and from 66.7 to 82.6 dBA in Western restaurants. Results of the analysis of variance show that there were no significant differences between means of the measured noise levels among different types of restaurants. A stepwise multiple regression analysis was employed to determine the relationships between geometrical and operational parameters and the measured noise levels. Results of the regression analysis show that the measured noise levels depended on the levels of occupancy density only. By reconciling the measured noise levels and the mathematical model, it was found that people in restaurants increased their voice levels when the occupancy density increased. Nevertheless, the maximum measured hourly noise level indicated that the noise exposure experienced by restaurant service employees was below the regulated daily noise exposure value level of 85 dBA.

Improvement of airfoil trailing edge bluntness noise model

DEFF Research Database (Denmark)

Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

2016-01-01

In this article, airfoil trailing edge bluntness noise is investigated using both computational aero-acoustic and semi-empirical approach. For engineering purposes, one of the most commonly used prediction tools for trailing edge noise are based on semi-empirical approaches, for example, the Brooks......, Pope, and Marcolini airfoil noise prediction model developed by Brooks, Pope, and Marcolini (NASA Reference Publication 1218, 1989). It was found in previous study that the Brooks, Pope, and Marcolini model tends to over-predict noise at high frequencies. Furthermore, it was observed...

Film grain noise modeling in advanced video coding

Science.gov (United States)

Oh, Byung Tae; Kuo, C.-C. Jay; Sun, Shijun; Lei, Shawmin

2007-01-01

A new technique for film grain noise extraction, modeling and synthesis is proposed and applied to the coding of high definition video in this work. The film grain noise is viewed as a part of artistic presentation by people in the movie industry. On one hand, since the film grain noise can boost the natural appearance of pictures in high definition video, it should be preserved in high-fidelity video processing systems. On the other hand, video coding with film grain noise is expensive. It is desirable to extract film grain noise from the input video as a pre-processing step at the encoder and re-synthesize the film grain noise and add it back to the decoded video as a post-processing step at the decoder. Under this framework, the coding gain of the denoised video is higher while the quality of the final reconstructed video can still be well preserved. Following this idea, we present a method to remove film grain noise from image/video without distorting its original content. Besides, we describe a parametric model containing a small set of parameters to represent the extracted film grain noise. The proposed model generates the film grain noise that is close to the real one in terms of power spectral density and cross-channel spectral correlation. Experimental results are shown to demonstrate the efficiency of the proposed scheme.

Dichotomous noise models of gene switches

Energy Technology Data Exchange (ETDEWEB)

Potoyan, Davit A., E-mail: potoyan@rice.edu; Wolynes, Peter G., E-mail: pwolynes@rice.edu [Department of Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005 (United States)

2015-11-21

Molecular noise in gene regulatory networks has two intrinsic components, one part being due to fluctuations caused by the birth and death of protein or mRNA molecules which are often present in small numbers and the other part arising from gene state switching, a single molecule event. Stochastic dynamics of gene regulatory circuits appears to be largely responsible for bifurcations into a set of multi-attractor states that encode different cell phenotypes. The interplay of dichotomous single molecule gene noise with the nonlinear architecture of genetic networks generates rich and complex phenomena. In this paper, we elaborate on an approximate framework that leads to simple hybrid multi-scale schemes well suited for the quantitative exploration of the steady state properties of large-scale cellular genetic circuits. Through a path sum based analysis of trajectory statistics, we elucidate the connection of these hybrid schemes to the underlying master equation and provide a rigorous justification for using dichotomous noise based models to study genetic networks. Numerical simulations of circuit models reveal that the contribution of the genetic noise of single molecule origin to the total noise is significant for a wide range of kinetic regimes.

Urban Noise Modelling in Boka Kotorska Bay

Directory of Open Access Journals (Sweden)

Aleksandar Nikolić

2014-04-01

Full Text Available Traffic is the most significant noise source in urban areas. The village of Kamenari in Boka Kotorska Bay is a site where, in a relatively small area, road traffic and sea (ferry traffic take place at the same time. Due to the specificity of the location, i.e. very rare synergy of sound effects of road and sea traffic in the urban area, as well as the expressed need for assessment of noise level in a simple and quick way, a research was conducted, using empirical methods and statistical analysis methods, which led to the creation of acoustic model for the assessment of equivalent noise level (Leq. The developed model for noise assessment in the Village of Kamenari in Boka Kotorska Bay quite realistically provides data on possible noise levels at the observed site, with very little deviations in relation to empirically obtained values.

Modeling environmental noise exceedances using non-homogeneous Poisson processes.

Science.gov (United States)

Guarnaccia, Claudio; Quartieri, Joseph; Barrios, Juan M; Rodrigues, Eliane R

2014-10-01

In this work a non-homogeneous Poisson model is considered to study noise exposure. The Poisson process, counting the number of times that a sound level surpasses a threshold, is used to estimate the probability that a population is exposed to high levels of noise a certain number of times in a given time interval. The rate function of the Poisson process is assumed to be of a Weibull type. The presented model is applied to community noise data from Messina, Sicily (Italy). Four sets of data are used to estimate the parameters involved in the model. After the estimation and tuning are made, a way of estimating the probability that an environmental noise threshold is exceeded a certain number of times in a given time interval is presented. This estimation can be very useful in the study of noise exposure of a population and also to predict, given the current behavior of the data, the probability of occurrence of high levels of noise in the near future. One of the most important features of the model is that it implicitly takes into account different noise sources, which need to be treated separately when using usual models.

Low dose CT simulation using experimental noise model

Energy Technology Data Exchange (ETDEWEB)

Nakanishi, Satori; Zamyatin, Alexander A. [Toshiba Medical Systems Corporation, Tochigi, Otawarashi (Japan); Silver, Michael D. [Toshiba Medical Research Institute, Vernon Hills, IL (United States)

2011-07-01

We suggest a method to obtain system noise model experimentally without relying on assumptions on statistical distribution of the noise; also, knowledge of DAS gain and electronic noise level are not required. Evaluation with ultra-low dose CT data (5 mAs) shows good match between simulated and real data noise. (orig.)

Trailing edge noise model applied to wind turbine airfoils

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F.

2008-01-15

The aim of this work is firstly to provide a quick introduction to the theory of noise generation that are relevant to wind turbine technology with focus on trailing edge noise. Secondly, the socalled TNO trailing edge noise model developed by Parchen [1] is described in more details. The model is tested and validated by comparing with other results from the literature. Finally, this model is used in the optimization process of two reference airfoils in order to reduce their noise signature: the RISOE-B1-18 and the S809 airfoils. (au)

Model tracking dual stochastic controller design under irregular internal noises

International Nuclear Information System (INIS)

Lee, Jong Bok; Heo, Hoon; Cho, Yun Hyun; Ji, Tae Young

2006-01-01

Although many methods about the control of irregular external noise have been introduced and implemented, it is still necessary to design a controller that will be more effective and efficient methods to exclude for various noises. Accumulation of errors due to model tracking, internal noises (thermal noise, shot noise and l/f noise) that come from elements such as resistor, diode and transistor etc. in the circuit system and numerical errors due to digital process often destabilize the system and reduce the system performance. New stochastic controller is adopted to remove those noises using conventional controller simultaneously. Design method of a model tracking dual controller is proposed to improve the stability of system while removing external and internal noises. In the study, design process of the model tracking dual stochastic controller is introduced that improves system performance and guarantees robustness under irregular internal noises which can be created internally. The model tracking dual stochastic controller utilizing F-P-K stochastic control technique developed earlier is implemented to reveal its performance via simulation

Modeling Noise Sources and Propagation in External Gear Pumps

Directory of Open Access Journals (Sweden)

Sangbeom Woo

2017-07-01

Full Text Available As a key component in power transfer, positive displacement machines often represent the major source of noise in hydraulic systems. Thus, investigation into the sources of noise and discovering strategies to reduce noise is a key part of improving the performance of current hydraulic systems, as well as applying fluid power systems to a wider range of applications. The present work aims at developing modeling techniques on the topic of noise generation caused by external gear pumps for high pressure applications, which can be useful and effective in investigating the interaction between noise sources and radiated noise and establishing the design guide for a quiet pump. In particular, this study classifies the internal noise sources into four types of effective load functions and, in the proposed model, these load functions are applied to the corresponding areas of the pump case in a realistic way. Vibration and sound radiation can then be predicted using a combined finite element and boundary element vibro-acoustic model. The radiated sound power and sound pressure for the different operating conditions are presented as the main outcomes of the acoustic model. The noise prediction was validated through comparison with the experimentally measured sound power levels.

Realistic camera noise modeling with application to improved HDR synthesis

Science.gov (United States)

Goossens, Bart; Luong, Hiêp; Aelterman, Jan; Pižurica, Aleksandra; Philips, Wilfried

2012-12-01

Due to the ongoing miniaturization of digital camera sensors and the steady increase of the "number of megapixels", individual sensor elements of the camera become more sensitive to noise, even deteriorating the final image quality. To go around this problem, sophisticated processing algorithms in the devices, can help to maximally exploit the knowledge on the sensor characteristics (e.g., in terms of noise), and offer a better image reconstruction. Although a lot of research focuses on rather simplistic noise models, such as stationary additive white Gaussian noise, only limited attention has gone to more realistic digital camera noise models. In this article, we first present a digital camera noise model that takes several processing steps in the camera into account, such as sensor signal amplification, clipping, post-processing,.. We then apply this noise model to the reconstruction problem of high dynamic range (HDR) images from a small set of low dynamic range (LDR) exposures of a static scene. In literature, HDR reconstruction is mostly performed by computing a weighted average, in which the weights are directly related to the observer pixel intensities of the LDR image. In this work, we derive a Bayesian probabilistic formulation of a weighting function that is near-optimal in the MSE sense (or SNR sense) of the reconstructed HDR image, by assuming exponentially distributed irradiance values. We define the weighting function as the probability that the observed pixel intensity is approximately unbiased. The weighting function can be directly computed based on the noise model parameters, which gives rise to different symmetric and asymmetric shapes when electronic noise or photon noise is dominant. We also explain how to deal with the case that some of the noise model parameters are unknown and explain how the camera response function can be estimated using the presented noise model. Finally, experimental results are provided to support our findings.

Validation of an Aero-Acoustic Wind Turbine Noise Model Using Advanced Noise Source Measurements of a 500kW Turbine

DEFF Research Database (Denmark)

Bertagnolio, Franck; Aagaard Madsen, Helge; Fischer, Andreas

2016-01-01

rotor noise model is presented. It includes the main sources of aeroacoustic noise from wind turbines: turbulent inflow, trailing edge and stall noise. The noise measured by one microphone located directly downstream of the wind turbine is compared to the model predictions at the microphone location....... A good qualitative agreement is found. When wind speed increases, the rotor noise model shows that at high frequencies the stall noise becomes dominant. It also shows that turbulent inflow noise is dominant at low frequencies for all wind speeds and that trailing edge noise is dominant at low wind speeds...

Coherence method of identifying signal noise model

International Nuclear Information System (INIS)

Vavrin, J.

1981-01-01

The noise analysis method is discussed in identifying perturbance models and their parameters by a stochastic analysis of the noise model of variables measured on a reactor. The analysis of correlations is made in the frequency region using coherence analysis methods. In identifying an actual specific perturbance, its model should be determined and recognized in a compound model of the perturbance system using the results of observation. The determination of the optimum estimate of the perturbance system model is based on estimates of related spectral densities which are determined from the spectral density matrix of the measured variables. Partial and multiple coherence, partial transfers, the power spectral densities of the input and output variables of the noise model are determined from the related spectral densities. The possibilities of applying the coherence identification methods were tested on a simple case of a simulated stochastic system. Good agreement was found of the initial analytic frequency filters and the transfers identified. (B.S.)

White Gaussian Noise - Models for Engineers

Science.gov (United States)

Jondral, Friedrich K.

2018-04-01

This paper assembles some information about white Gaussian noise (WGN) and its applications. It starts from a description of thermal noise, i. e. the irregular motion of free charge carriers in electronic devices. In a second step, mathematical models of WGN processes and their most important parameters, especially autocorrelation functions and power spectrum densities, are introduced. In order to proceed from mathematical models to simulations, we discuss the generation of normally distributed random numbers. The signal-to-noise ratio as the most important quality measure used in communications, control or measurement technology is accurately introduced. As a practical application of WGN, the transmission of quadrature amplitude modulated (QAM) signals over additive WGN channels together with the optimum maximum likelihood (ML) detector is considered in a demonstrative and intuitive way.

Stochastic resonance in a piecewise nonlinear model driven by multiplicative non-Gaussian noise and additive white noise

Science.gov (United States)

Guo, Yongfeng; Shen, Yajun; Tan, Jianguo

2016-09-01

The phenomenon of stochastic resonance (SR) in a piecewise nonlinear model driven by a periodic signal and correlated noises for the cases of a multiplicative non-Gaussian noise and an additive Gaussian white noise is investigated. Applying the path integral approach, the unified colored noise approximation and the two-state model theory, the analytical expression of the signal-to-noise ratio (SNR) is derived. It is found that conventional stochastic resonance exists in this system. From numerical computations we obtain that: (i) As a function of the non-Gaussian noise intensity, the SNR is increased when the non-Gaussian noise deviation parameter q is increased. (ii) As a function of the Gaussian noise intensity, the SNR is decreased when q is increased. This demonstrates that the effect of the non-Gaussian noise on SNR is different from that of the Gaussian noise in this system. Moreover, we further discuss the effect of the correlation time of the non-Gaussian noise, cross-correlation strength, the amplitude and frequency of the periodic signal on SR.

Background noise model development for seismic stations of KMA

Science.gov (United States)

Jeon, Youngsoo

2010-05-01

The background noise recorded at seismometer is exist at any seismic signal due to the natural phenomena of the medium which the signal passed through. Reducing the seismic noise is very important to improve the data quality in seismic studies. But, the most important aspect of reducing seismic noise is to find the appropriate place before installing the seismometer. For this reason, NIMR(National Institution of Meteorological Researches) starts to develop a model of standard background noise for the broadband seismic stations of the KMA(Korea Meteorological Administration) using a continuous data set obtained from 13 broadband stations during the period of 2007 and 2008. We also developed the model using short period seismic data from 10 stations at the year of 2009. The method of Mcmara and Buland(2004) is applied to analyse background noise of Korean Peninsula. The fact that borehole seismometer records show low noise level at frequency range greater than 1 Hz compared with that of records at the surface indicate that the cultural noise of inland Korean Peninsula should be considered to process the seismic data set. Reducing Double Frequency peak also should be regarded because the Korean Peninsula surrounded by the seas from eastern, western and southern part. The development of KMA background model shows that the Peterson model(1993) is not applicable to fit the background noise signal generated from Korean Peninsula.

Dynamical reduction models with general gaussian noises

International Nuclear Information System (INIS)

Bassi, Angelo; Ghirardi, GianCarlo

2002-02-01

We consider the effect of replacing in stochastic differential equations leading to the dynamical collapse of the statevector, white noise stochastic processes with non white ones. We prove that such a modification can be consistently performed without altering the most interesting features of the previous models. One of the reasons to discuss this matter derives from the desire of being allowed to deal with physical stochastic fields, such as the gravitational one, which cannot give rise to white noises. From our point of view the most relevant motivation for the approach we propose here derives from the fact that in relativistic models the occurrence of white noises is the main responsible for the appearance of untractable divergences. Therefore, one can hope that resorting to non white noises one can overcome such a difficulty. We investigate stochastic equations with non white noises, we discuss their reduction properties and their physical implications. Our analysis has a precise interest not only for the above mentioned subject but also for the general study of dissipative systems and decoherence. (author)

Dynamical reduction models with general Gaussian noises

International Nuclear Information System (INIS)

Bassi, Angelo; Ghirardi, GianCarlo

2002-01-01

We consider the effect of replacing in stochastic differential equations leading to the dynamical collapse of the state vector, white-noise stochastic processes with nonwhite ones. We prove that such a modification can be consistently performed without altering the most interesting features of the previous models. One of the reasons to discuss this matter derives from the desire of being allowed to deal with physical stochastic fields, such as the gravitational one, which cannot give rise to white noises. From our point of view, the most relevant motivation for the approach we propose here derives from the fact that in relativistic models intractable divergences appear as a consequence of the white nature of the noises. Therefore, one can hope that resorting to nonwhite noises, one can overcome such a difficulty. We investigate stochastic equations with nonwhite noises, we discuss their reduction properties and their physical implications. Our analysis has a precise interest not only for the above-mentioned subject but also for the general study of dissipative systems and decoherence

Collapse models with non-white noises

International Nuclear Information System (INIS)

Adler, Stephen L; Bassi, Angelo

2007-01-01

We set up a general formalism for models of spontaneous wavefunction collapse with dynamics represented by a stochastic differential equation driven by general Gaussian noises, not necessarily white in time. In particular, we show that the non-Schroedinger terms of the equation induce the collapse of the wavefunction to one of the common eigenstates of the collapsing operators, and that the collapse occurs with the correct quantum probabilities. We also develop a perturbation expansion of the solution of the equation with respect to the parameter which sets the strength of the collapse process; such an approximation allows one to compute the leading-order terms for the deviations of the predictions of collapse models with respect to those of standard quantum mechanics. This analysis shows that to leading order, the 'imaginary noise' trick can be used for non-white Gaussian noise

Design and Performance Optimizations of Advanced Erosion-Resistant Low Conductivity Thermal Barrier Coatings for Rotorcraft Engines

Science.gov (United States)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2012-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future rotorcraft engine higher fuel efficiency and lower emission goals. For thermal barrier coatings designed for rotorcraft turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability, because the rotorcraft are often operated in the most severe sand erosive environments. Advanced low thermal conductivity and erosion-resistant thermal barrier coatings are being developed, with the current emphasis being placed on thermal barrier coating toughness improvements using multicomponent alloying and processing optimization approaches. The performance of the advanced thermal barrier coatings has been evaluated in a high temperature erosion burner rig and a laser heat-flux rig to simulate engine erosion and thermal gradient environments. The results have shown that the coating composition and architecture optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic oxidation durability

Model-based temperature noise monitoring methods for LMFBR core anomaly detection

International Nuclear Information System (INIS)

Tamaoki, Tetsuo; Sonoda, Yukio; Sato, Masuo; Takahashi, Ryoichi.

1994-01-01

Temperature noise, measured by thermocouples mounted at each core fuel subassembly, is considered to be the most useful signal for detecting and locating local cooling anomalies in an LMFBR core. However, the core outlet temperature noise contains background noise due to fluctuations in the operating parameters including reactor power. It is therefore necessary to reduce this background noise for highly sensitive anomaly detection by subtracting predictable components from the measured signal. In the present study, both a physical model and an autoregressive model were applied to noise data measured in the experimental fast reactor JOYO. The results indicate that the autoregressive model has a higher precision than the physical model in background noise prediction. Based on these results, an 'autoregressive model modification method' is proposed, in which a temporary autoregressive model is generated by interpolation or extrapolation of reference models identified under a small number of different operating conditions. The generated autoregressive model has shown sufficient precision over a wide range of reactor power in applications to artificial noise data produced by an LMFBR noise simulator even when the coolant flow rate was changed to keep a constant power-to-flow ratio. (author)

Jet Noise Modeling for Supersonic Business Jet Application

Science.gov (United States)

Stone, James R.; Krejsa, Eugene A.; Clark, Bruce J.

2004-01-01

This document describes the development of an improved predictive model for coannular jet noise, including noise suppression modifications applicable to small supersonic-cruise aircraft such as the Supersonic Business Jet (SBJ), for NASA Langley Research Center (LaRC). For such aircraft a wide range of propulsion and integration options are under consideration. Thus there is a need for very versatile design tools, including a noise prediction model. The approach used is similar to that used with great success by the Modern Technologies Corporation (MTC) in developing a noise prediction model for two-dimensional mixer ejector (2DME) nozzles under the High Speed Research Program and in developing a more recent model for coannular nozzles over a wide range of conditions. If highly suppressed configurations are ultimately required, the 2DME model is expected to provide reasonable prediction for these smaller scales, although this has not been demonstrated. It is considered likely that more modest suppression approaches, such as dual stream nozzles featuring chevron or chute suppressors, perhaps in conjunction with inverted velocity profiles (IVP), will be sufficient for the SBJ.

Fractional Gaussian noise: Prior specification and model comparison

KAUST Repository

Sørbye, Sigrunn Holbek

2017-07-07

Fractional Gaussian noise (fGn) is a stationary stochastic process used to model antipersistent or persistent dependency structures in observed time series. Properties of the autocovariance function of fGn are characterised by the Hurst exponent (H), which, in Bayesian contexts, typically has been assigned a uniform prior on the unit interval. This paper argues why a uniform prior is unreasonable and introduces the use of a penalised complexity (PC) prior for H. The PC prior is computed to penalise divergence from the special case of white noise and is invariant to reparameterisations. An immediate advantage is that the exact same prior can be used for the autocorrelation coefficient ϕ(symbol) of a first-order autoregressive process AR(1), as this model also reflects a flexible version of white noise. Within the general setting of latent Gaussian models, this allows us to compare an fGn model component with AR(1) using Bayes factors, avoiding the confounding effects of prior choices for the two hyperparameters H and ϕ(symbol). Among others, this is useful in climate regression models where inference for underlying linear or smooth trends depends heavily on the assumed noise model.

Fractional Gaussian noise: Prior specification and model comparison

KAUST Repository

Sø rbye, Sigrunn Holbek; Rue, Haavard

2017-01-01

Fractional Gaussian noise (fGn) is a stationary stochastic process used to model antipersistent or persistent dependency structures in observed time series. Properties of the autocovariance function of fGn are characterised by the Hurst exponent (H), which, in Bayesian contexts, typically has been assigned a uniform prior on the unit interval. This paper argues why a uniform prior is unreasonable and introduces the use of a penalised complexity (PC) prior for H. The PC prior is computed to penalise divergence from the special case of white noise and is invariant to reparameterisations. An immediate advantage is that the exact same prior can be used for the autocorrelation coefficient ϕ(symbol) of a first-order autoregressive process AR(1), as this model also reflects a flexible version of white noise. Within the general setting of latent Gaussian models, this allows us to compare an fGn model component with AR(1) using Bayes factors, avoiding the confounding effects of prior choices for the two hyperparameters H and ϕ(symbol). Among others, this is useful in climate regression models where inference for underlying linear or smooth trends depends heavily on the assumed noise model.

Cross-band noise model refinement for transform domain Wyner–Ziv video coding

DEFF Research Database (Denmark)

Huang, Xin; Forchhammer, Søren

2012-01-01

TDWZ video coding trails that of conventional video coding solutions, mainly due to the quality of side information, inaccurate noise modeling and loss in the final coding step. The major goal of this paper is to enhance the accuracy of the noise modeling, which is one of the most important aspects...... influencing the coding performance of DVC. A TDWZ video decoder with a novel cross-band based adaptive noise model is proposed, and a noise residue refinement scheme is introduced to successively update the estimated noise residue for noise modeling after each bit-plane. Experimental results show...... that the proposed noise model and noise residue refinement scheme can improve the rate-distortion (RD) performance of TDWZ video coding significantly. The quality of the side information modeling is also evaluated by a measure of the ideal code length....

Cost Analysis for Large Civil Transport Rotorcraft

Science.gov (United States)

Coy, John J.

2006-01-01

This paper presents cost analysis of purchase price and DOC+I (direct operating cost plus interest) that supports NASA s study of three advanced rotorcraft concepts that could enter commercial transport service within 10 to 15 years. The components of DOC+I are maintenance, flight crew, fuel, depreciation, insurance, and finance. The cost analysis aims at VTOL (vertical takeoff and landing) and CTOL (conventional takeoff and landing) aircraft suitable for regional transport service. The resulting spreadsheet-implemented cost models are semi-empirical and based on Department of Transportation and Army data from actual operations of such aircraft. This paper describes a rationale for selecting cost tech factors without which VTOL is more costly than CTOL by a factor of 10 for maintenance cost and a factor of two for purchase price. The three VTOL designs selected for cost comparisons meet the mission requirement to fly 1,200 nautical miles at 350 knots and 30,000 ft carrying 120 passengers. The lowest cost VTOL design is a large civil tilt rotor (LCTR) aircraft. With cost tech factors applied, the LCTR is reasonably competitive with the Boeing 737-700 when operated in economy regional service following the business model of the selected baseline operation, that of Southwest Airlines.

Improved Denoising via Poisson Mixture Modeling of Image Sensor Noise.

Science.gov (United States)

Zhang, Jiachao; Hirakawa, Keigo

2017-04-01

This paper describes a study aimed at comparing the real image sensor noise distribution to the models of noise often assumed in image denoising designs. A quantile analysis in pixel, wavelet transform, and variance stabilization domains reveal that the tails of Poisson, signal-dependent Gaussian, and Poisson-Gaussian models are too short to capture real sensor noise behavior. A new Poisson mixture noise model is proposed to correct the mismatch of tail behavior. Based on the fact that noise model mismatch results in image denoising that undersmoothes real sensor data, we propose a mixture of Poisson denoising method to remove the denoising artifacts without affecting image details, such as edge and textures. Experiments with real sensor data verify that denoising for real image sensor data is indeed improved by this new technique.

Percolation model of excess electrical noise in transition-edge sensors

International Nuclear Information System (INIS)

Lindeman, M.A.; Anderson, M.B.; Bandler, S.R.; Bilgri, N.; Chervenak, J.; Gwynne Crowder, S.; Fallows, S.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.; Kilbourne, C.A.; Lai, T.; Man, J.; McCammon, D.; Nelms, K.L.; Porter, F.S.; Rocks, L.E.; Saab, T.; Sadleir, J.; Vidugiris, G.

2006-01-01

We present a geometrical model to describe excess electrical noise in transition-edge sensors (TESs). In this model, a network of fluctuating resistors represents the complex dynamics inside a TES. The fluctuations can cause several resistors in series to become superconducting. Such events short out part of the TES and generate noise because much of the current percolates through low resistance paths. The model predicts that excess white noise increases with decreasing TES bias resistance (R/R N ) and that perpendicular zebra stripes reduce noise and alpha of the TES by reducing percolation

75 FR 793 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures

Science.gov (United States)

2010-01-06

... metal structures are different. Composites are complex materials that have unique advantages in fatigue... stiffness, dynamic behavior, loads, and functional performance of composite structures. In the existing rule... and Fatigue Evaluation of Composite Rotorcraft Structures AGENCY: Federal Aviation Administration (FAA...

Effects of random noise in a dynamical model of love

Energy Technology Data Exchange (ETDEWEB)

Xu Yong, E-mail: hsux3@nwpu.edu.cn [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China); Gu Rencai; Zhang Huiqing [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China)

2011-07-15

Highlights: > We model the complexity and unpredictability of psychology as Gaussian white noise. > The stochastic system of love is considered including bifurcation and chaos. > We show that noise can both suppress and induce chaos in dynamical models of love. - Abstract: This paper aims to investigate the stochastic model of love and the effects of random noise. We first revisit the deterministic model of love and some basic properties are presented such as: symmetry, dissipation, fixed points (equilibrium), chaotic behaviors and chaotic attractors. Then we construct a stochastic love-triangle model with parametric random excitation due to the complexity and unpredictability of the psychological system, where the randomness is modeled as the standard Gaussian noise. Stochastic dynamics under different three cases of 'Romeo's romantic style', are examined and two kinds of bifurcations versus the noise intensity parameter are observed by the criteria of changes of top Lyapunov exponent and shape of stationary probability density function (PDF) respectively. The phase portraits and time history are carried out to verify the proposed results, and the good agreement can be found. And also the dual roles of the random noise, namely suppressing and inducing chaos are revealed.

Effects of random noise in a dynamical model of love

International Nuclear Information System (INIS)

Xu Yong; Gu Rencai; Zhang Huiqing

2011-01-01

Highlights: → We model the complexity and unpredictability of psychology as Gaussian white noise. → The stochastic system of love is considered including bifurcation and chaos. → We show that noise can both suppress and induce chaos in dynamical models of love. - Abstract: This paper aims to investigate the stochastic model of love and the effects of random noise. We first revisit the deterministic model of love and some basic properties are presented such as: symmetry, dissipation, fixed points (equilibrium), chaotic behaviors and chaotic attractors. Then we construct a stochastic love-triangle model with parametric random excitation due to the complexity and unpredictability of the psychological system, where the randomness is modeled as the standard Gaussian noise. Stochastic dynamics under different three cases of 'Romeo's romantic style', are examined and two kinds of bifurcations versus the noise intensity parameter are observed by the criteria of changes of top Lyapunov exponent and shape of stationary probability density function (PDF) respectively. The phase portraits and time history are carried out to verify the proposed results, and the good agreement can be found. And also the dual roles of the random noise, namely suppressing and inducing chaos are revealed.

Study on Noise Prediction Model and Control Schemes for Substation

Science.gov (United States)

Gao, Yang; Liu, Songtao

2014-01-01

With the government's emphasis on environmental issues of power transmission and transformation project, noise pollution has become a prominent problem now. The noise from the working transformer, reactor, and other electrical equipment in the substation will bring negative effect to the ambient environment. This paper focuses on using acoustic software for the simulation and calculation method to control substation noise. According to the characteristics of the substation noise and the techniques of noise reduction, a substation's acoustic field model was established with the SoundPLAN software to predict the scope of substation noise. On this basis, 4 reasonable noise control schemes were advanced to provide some helpful references for noise control during the new substation's design and construction process. And the feasibility and application effect of these control schemes can be verified by using the method of simulation modeling. The simulation results show that the substation always has the problem of excessive noise at boundary under the conventional measures. The excess noise can be efficiently reduced by taking the corresponding noise reduction methods. PMID:24672356

STAMINA - Model description. Standard Model Instrumentation for Noise Assessments

NARCIS (Netherlands)

Schreurs EM; Jabben J; Verheijen ENG; CMM; mev

2010-01-01

Deze rapportage beschrijft het STAMINA-model, dat staat voor Standard Model Instrumentation for Noise Assessments en door het RIVM is ontwikkeld. Het instituut gebruikt dit standaardmodel om omgevingsgeluid in Nederland in kaart te brengen. Het model is gebaseerd op de Standaard Karteringsmethode

Parameter Estimation for Traffic Noise Models Using a Harmony Search Algorithm

Directory of Open Access Journals (Sweden)

Deok-Soon An

2013-01-01

Full Text Available A technique has been developed for predicting road traffic noise for environmental assessment, taking into account traffic volume as well as road surface conditions. The ASJ model (ASJ Prediction Model for Road Traffic Noise, 1999, which is based on the sound power level of the noise emitted by the interaction between the road surface and tires, employs regression models for two road surface types: dense-graded asphalt (DGA and permeable asphalt (PA. However, these models are not applicable to other types of road surfaces. Accordingly, this paper introduces a parameter estimation procedure for ASJ-based noise prediction models, utilizing a harmony search (HS algorithm. Traffic noise measurement data for four different vehicle types were used in the algorithm to determine the regression parameters for several road surface types. The parameters of the traffic noise prediction models were evaluated using another measurement set, and good agreement was observed between the predicted and measured sound power levels.

Rotorcraft On-Blade Pressure and Strain Measurements Using Wireless Optical Sensor System, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Experimental measurements of rotor blades are important for understanding the aerodynamics and dynamics of a rotorcraft. This understanding can help in solving...

Evaluating Performances of Traffic Noise Models | Oyedepo ...

African Journals Online (AJOL)

Traffic noise in decibel dB(A) were measured at six locations using 407780A Integrating Sound Level Meter, while spot speed and traffic volume were collected with cine-camera. The predicted sound exposure level (SEL) was evaluated using Burgess, British and FWHA model. The average noise level obtained are 77.64 ...

Analytical high frequency GaN HEMT model for noise simulations

Science.gov (United States)

Eshetu Muhea, Wondwosen; Mulugeta Yigletu, Fetene; Lazaro, Antonio; Iñiguez, Benjamin

2017-12-01

A compact high frequency model for AlGaN/GaN HEMT device valid for noise simulations is presented in this paper. The model is developed based on active transmission line approach and linear two port noise theory that makes it applicable for quasi static as well as non-quasi static device operation. The effects of channel length modulation and velocity saturation are discussed. Moreover, the effect of the gate leakage current on the noise performance of the device is investigated. It is shown that there is an apparent increase in noise generated in the device due to the gate current related shot noise. The common noise figures of merit for HFET are calculated and verified with experimental data.

A shock absorber model for structure-borne noise analyses

Science.gov (United States)

Benaziz, Marouane; Nacivet, Samuel; Thouverez, Fabrice

2015-08-01

Shock absorbers are often responsible for undesirable structure-borne noise in cars. The early numerical prediction of this noise in the automobile development process can save time and money and yet remains a challenge for industry. In this paper, a new approach to predicting shock absorber structure-borne noise is proposed; it consists in modelling the shock absorber and including the main nonlinear phenomena responsible for discontinuities in the response. The model set forth herein features: compressible fluid behaviour, nonlinear flow rate-pressure relations, valve mechanical equations and rubber mounts. The piston, base valve and complete shock absorber model are compared with experimental results. Sensitivity of the shock absorber response is evaluated and the most important parameters are classified. The response envelope is also computed. This shock absorber model is able to accurately reproduce local nonlinear phenomena and improves our state of knowledge on potential noise sources within the shock absorber.

Simulation to Support Local Search in Trajectory Optimization Planning

Science.gov (United States)

Morris, Robert A.; Venable, K. Brent; Lindsey, James

2012-01-01

NASA and the international community are investing in the development of a commercial transportation infrastructure that includes the increased use of rotorcraft, specifically helicopters and civil tilt rotors. However, there is significant concern over the impact of noise on the communities surrounding the transportation facilities. One way to address the rotorcraft noise problem is by exploiting powerful search techniques coming from artificial intelligence coupled with simulation and field tests to design low-noise flight profiles which can be tested in simulation or through field tests. This paper investigates the use of simulation based on predictive physical models to facilitate the search for low-noise trajectories using a class of automated search algorithms called local search. A novel feature of this approach is the ability to incorporate constraints directly into the problem formulation that addresses passenger safety and comfort.

Smart Rotorcraft Field Assistants for Terrestrial and Planetary Science

Science.gov (United States)

Young, Larry A.; Aiken, Edwin W.; Briggs, Geoffrey A.

2004-01-01

Field science in extreme terrestrial environments is often difficult and sometimes dangerous. Field seasons are also often short in duration. Robotic field assistants, particularly small highly mobile rotary-wing platforms, have the potential to significantly augment a field season's scientific return on investment for geology and astrobiology researchers by providing an entirely new suite of sophisticated field tools. Robotic rotorcraft and other vertical lift planetary aerial vehicle also hold promise for supporting planetary science missions.

Numerical modeling of wind turbine aerodynamic noise in the time domain.

Science.gov (United States)

Lee, Seunghoon; Lee, Seungmin; Lee, Soogab

2013-02-01

Aerodynamic noise from a wind turbine is numerically modeled in the time domain. An analytic trailing edge noise model is used to determine the unsteady pressure on the blade surface. The far-field noise due to the unsteady pressure is calculated using the acoustic analogy theory. By using a strip theory approach, the two-dimensional noise model is applied to rotating wind turbine blades. The numerical results indicate that, although the operating and atmospheric conditions are identical, the acoustical characteristics of wind turbine noise can be quite different with respect to the distance and direction from the wind turbine.

Development of autonomous magnetometer rotorcraft for wide area assessment

Energy Technology Data Exchange (ETDEWEB)

Roelof Versteeg; Matt Anderson; Les Beard; Eric Corban; Darryl Curley; Jeff Gamey; Ross Johnson; Dwight Junkin; Mark McKay; Jared Salzmann; Mikhail Tchernychev; Suraj Unnikrishnan; Scott Vinson

2010-04-01

dynamic acquisition, i.e. survey mission inflight reprioritization). We describe and report on a one year effort with as primary goal to provide a recommendation to SERDP for a path forward in the implementation of one or more autonomous unmanned magnetometer rotorcraft platforms. This recommendation (which is provided in chapter 6) is based on the following three elements a) An assessment on the applicability of autonomous rotorcraft magnetometer systems to the current DoD site inventory, and an initial assessment of which type(s) of autonomous unmanned magnetometer rotorcraft platforms (in terms of performance characteristics such as payload, altitude, obstacle avoidance, production rate and flight time) would be most relevant to this inventory (chapter 3); b) An evaluation of the feasibility of assembling such platforms from commercial components (unmanned rotorcraft, control systems and sensors – both magnetometer sensors and supporting sensors). This evaluation included several highly successful field tests (chapter 4 and 5); c) A recommendation of the path forward, which includes a detailed outline of the efforts required in the design, assembly and testing of different modular platforms (chapter 6)

Joint models for noise annoyance and willingness to pay for road noise reduction

DEFF Research Database (Denmark)

Fosgerau, Mogens; Bue Bjørner, Thomas

2006-01-01

Recent contingent valuation (CV) studies of the willingness to pay (WTP) for road noise reduction have used stated annoyance as an independent variable. We argue that this may be inappropriate due to potential endogeneity bias. Instead, an alternative model is proposed that treats both WTP...... and annoyance as endogenous variables in a simultaneous equation model as a combination of a linear regression with an ordered probit with correlated error terms and possibly common parameters. Thus, information on stated annoyance is utilised to estimate WTP with increased efficiency. Application of the model...... to a dataset from Copenhagen indicates a potential for improving the precision of the estimate of WTP for noise reduction with CV data....

Adaptive Active Noise Suppression Using Multiple Model Switching Strategy

Directory of Open Access Journals (Sweden)

Quanzhen Huang

2017-01-01

Full Text Available Active noise suppression for applications where the system response varies with time is a difficult problem. The computation burden for the existing control algorithms with online identification is heavy and easy to cause control system instability. A new active noise control algorithm is proposed in this paper by employing multiple model switching strategy for secondary path varying. The computation is significantly reduced. Firstly, a noise control system modeling method is proposed for duct-like applications. Then a multiple model adaptive control algorithm is proposed with a new multiple model switching strategy based on filter-u least mean square (FULMS algorithm. Finally, the proposed algorithm was implemented on Texas Instruments digital signal processor (DSP TMS320F28335 and real time experiments were done to test the proposed algorithm and FULMS algorithm with online identification. Experimental verification tests show that the proposed algorithm is effective with good noise suppression performance.

A trade-off analysis design tool. Aircraft interior noise-motion/passenger satisfaction model

Science.gov (United States)

Jacobson, I. D.

1977-01-01

A design tool was developed to enhance aircraft passenger satisfaction. The effect of aircraft interior motion and noise on passenger comfort and satisfaction was modelled. Effects of individual aircraft noise sources were accounted for, and the impact of noise on passenger activities and noise levels to safeguard passenger hearing were investigated. The motion noise effect models provide a means for tradeoff analyses between noise and motion variables, and also provide a framework for optimizing noise reduction among noise sources. Data for the models were collected onboard commercial aircraft flights and specially scheduled tests.

Handling Qualities of Large Rotorcraft in Hover and Low Speed

Science.gov (United States)

2015-03-01

shaft axes can themselves be a function of the nacelle angle. Following the rules of calculus of variations, the variation for the -force from Eq. (7...their preference. Main inceptor forces, in terms of gradients , breakouts, damping, and friction are provided by a hydraulic McFadden variable force...during training and formal evaluation. 29 Table 8. Inceptor force-displacement characteristics. Cockpit Control Rotorcraft Configuration Gradient

Effect of noise on defect chaos in a reaction-diffusion model.

Science.gov (United States)

Wang, Hongli; Ouyang, Qi

2005-06-01

The influence of noise on defect chaos due to breakup of spiral waves through Doppler and Eckhaus instabilities is investigated numerically with a modified Fitzhugh-Nagumo model. By numerical simulations we show that the noise can drastically enhance the creation and annihilation rates of topological defects. The noise-free probability distribution function for defects in this model is found not to fit with the previously reported squared-Poisson distribution. Under the influence of noise, the distributions are flattened, and can fit with the squared-Poisson or the modified-Poisson distribution. The defect lifetime and diffusive property of defects under the influence of noise are also checked in this model.

A critical review of principal traffic noise models: Strategies and implications

Energy Technology Data Exchange (ETDEWEB)

Garg, Naveen, E-mail: ngarg@mail.nplindia.ernet.in [Apex Level Standards and Industrial Metrology Division, CSIR-National Physical Laboratory, New Delhi 110012 (India); Department of Mechanical, Production and Industrial Engineering, Delhi Technological University, Delhi 110042 (India); Maji, Sagar [Department of Mechanical, Production and Industrial Engineering, Delhi Technological University, Delhi 110042 (India)

2014-04-01

The paper presents an exhaustive comparison of principal traffic noise models adopted in recent years in developed nations. The comparison is drawn on the basis of technical attributes including source modelling and sound propagation algorithms. Although the characterization of source in terms of rolling and propulsion noise in conjunction with advanced numerical methods for sound propagation has significantly reduced the uncertainty in traffic noise predictions, the approach followed is quite complex and requires specialized mathematical skills for predictions which is sometimes quite cumbersome for town planners. Also, it is sometimes difficult to follow the best approach when a variety of solutions have been proposed. This paper critically reviews all these aspects pertaining to the recent models developed and adapted in some countries and also discusses the strategies followed and implications of these models. - Highlights: • Principal traffic noise models developed are reviewed. • Sound propagation algorithms used in traffic noise models are compared. • Implications of models are discussed.

Application of autoregressive moving average model in reactor noise analysis

International Nuclear Information System (INIS)

Tran Dinh Tri

1993-01-01

The application of an autoregressive (AR) model to estimating noise measurements has achieved many successes in reactor noise analysis in the last ten years. The physical processes that take place in the nuclear reactor, however, are described by an autoregressive moving average (ARMA) model rather than by an AR model. Consequently more correct results could be obtained by applying the ARMA model instead of the AR model to reactor noise analysis. In this paper the system of the generalised Yule-Walker equations is derived from the equation of an ARMA model, then a method for its solution is given. Numerical results show the applications of the method proposed. (author)

Noise Residual Learning for Noise Modeling in Distributed Video Coding

DEFF Research Database (Denmark)

Luong, Huynh Van; Forchhammer, Søren

2012-01-01

Distributed video coding (DVC) is a coding paradigm which exploits the source statistics at the decoder side to reduce the complexity at the encoder. The noise model is one of the inherently difficult challenges in DVC. This paper considers Transform Domain Wyner-Ziv (TDWZ) coding and proposes...

Colored noise and memory effects on formal spiking neuron models

Science.gov (United States)

da Silva, L. A.; Vilela, R. D.

2015-06-01

Simplified neuronal models capture the essence of the electrical activity of a generic neuron, besides being more interesting from the computational point of view when compared to higher-dimensional models such as the Hodgkin-Huxley one. In this work, we propose a generalized resonate-and-fire model described by a generalized Langevin equation that takes into account memory effects and colored noise. We perform a comprehensive numerical analysis to study the dynamics and the point process statistics of the proposed model, highlighting interesting new features such as (i) nonmonotonic behavior (emergence of peak structures, enhanced by the choice of colored noise characteristic time scale) of the coefficient of variation (CV) as a function of memory characteristic time scale, (ii) colored noise-induced shift in the CV, and (iii) emergence and suppression of multimodality in the interspike interval (ISI) distribution due to memory-induced subthreshold oscillations. Moreover, in the noise-induced spike regime, we study how memory and colored noise affect the coherence resonance (CR) phenomenon. We found that for sufficiently long memory, not only is CR suppressed but also the minimum of the CV-versus-noise intensity curve that characterizes the presence of CR may be replaced by a maximum. The aforementioned features allow to interpret the interplay between memory and colored noise as an effective control mechanism to neuronal variability. Since both variability and nontrivial temporal patterns in the ISI distribution are ubiquitous in biological cells, we hope the present model can be useful in modeling real aspects of neurons.

Computer model for noise in the dc Squid

International Nuclear Information System (INIS)

Tesche, C.D.; Clarke, J.

1976-08-01

A computer model for the dc SQUID is described which predicts signal and noise as a function of various SQUID parameters. Differential equations for the voltage across the SQUID including the Johnson noise in the shunted junctions are integrated stepwise in time

Optical linear algebra processors - Noise and error-source modeling

Science.gov (United States)

Casasent, D.; Ghosh, A.

1985-01-01

The modeling of system and component noise and error sources in optical linear algebra processors (OLAPs) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.

Optical linear algebra processors: noise and error-source modeling.

Science.gov (United States)

Casasent, D; Ghosh, A

1985-06-01

The modeling of system and component noise and error sources in optical linear algebra processors (OLAP's) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.

A high and low noise model for strong motion accelerometers

Science.gov (United States)

Clinton, J. F.; Cauzzi, C.; Olivieri, M.

2010-12-01

We present reference noise models for high-quality strong motion accelerometer installations. We use continuous accelerometer data acquired by the Swiss Seismological Service (SED) since 2006 and other international high-quality accelerometer network data to derive very broadband (50Hz-100s) high and low noise models. The proposed noise models are compared to the Peterson (1993) low and high noise models designed for broadband seismometers; the datalogger self-noise; background noise levels at existing Swiss strong motion stations; and typical earthquake signals recorded in Switzerland and worldwide. The standard strong motion station operated by the SED consists of a Kinemetrics Episensor (2g clip level; flat acceleration response from 200 Hz to DC; insulated sensor / datalogger systems placed in vault quality sites. At all frequencies, there is at least one order of magnitude between the ALNM and the AHNM; at high frequencies (> 1Hz) this extends to 2 orders of magnitude. This study provides remarkable confirmation of the capability of modern strong motion accelerometers to record low-amplitude ground motions with seismic observation quality. In particular, an accelerometric station operating at the ALNM is capable of recording the full spectrum of near source earthquakes, out to 100 km, down to M2. Of particular interest for the SED, this study provides acceptable noise limits for candidate sites for the on-going Strong Motion Network modernisation.

Computer model for estimating electric utility environmental noise

International Nuclear Information System (INIS)

Teplitzky, A.M.; Hahn, K.J.

1991-01-01

This paper reports on a computer code for estimating environmental noise emissions from the operation and the construction of electric power plants that was developed based on algorithms. The computer code (Model) is used to predict octave band sound power levels for power plant operation and construction activities on the basis of the equipment operating characteristics and calculates off-site sound levels for each noise source and for an entire plant. Estimated noise levels are presented either as A-weighted sound level contours around the power plant or as octave band levels at user defined receptor locations. Calculated sound levels can be compared with user designated noise criteria, and the program can assist the user in analyzing alternative noise control strategies

Comparison of Langevin and Markov channel noise models for neuronal signal generation.

Science.gov (United States)

Sengupta, B; Laughlin, S B; Niven, J E

2010-01-01

The stochastic opening and closing of voltage-gated ion channels produce noise in neurons. The effect of this noise on the neuronal performance has been modeled using either an approximate or Langevin model based on stochastic differential equations or an exact model based on a Markov process model of channel gating. Yet whether the Langevin model accurately reproduces the channel noise produced by the Markov model remains unclear. Here we present a comparison between Langevin and Markov models of channel noise in neurons using single compartment Hodgkin-Huxley models containing either Na+ and K+, or only K+ voltage-gated ion channels. The performance of the Langevin and Markov models was quantified over a range of stimulus statistics, membrane areas, and channel numbers. We find that in comparison to the Markov model, the Langevin model underestimates the noise contributed by voltage-gated ion channels, overestimating information rates for both spiking and nonspiking membranes. Even with increasing numbers of channels, the difference between the two models persists. This suggests that the Langevin model may not be suitable for accurately simulating channel noise in neurons, even in simulations with large numbers of ion channels.

Nuclear spin noise in the central spin model

Science.gov (United States)

Fröhling, Nina; Anders, Frithjof B.; Glazov, Mikhail

2018-05-01

We study theoretically the fluctuations of the nuclear spins in quantum dots employing the central spin model which accounts for the hyperfine interaction of the nuclei with the electron spin. These fluctuations are calculated both with an analytical approach using homogeneous hyperfine couplings (box model) and with a numerical simulation using a distribution of hyperfine coupling constants. The approaches are in good agreement. The box model serves as a benchmark with low computational cost that explains the basic features of the nuclear spin noise well. We also demonstrate that the nuclear spin noise spectra comprise a two-peak structure centered at the nuclear Zeeman frequency in high magnetic fields with the shape of the spectrum controlled by the distribution of the hyperfine constants. This allows for direct access to this distribution function through nuclear spin noise spectroscopy.

An aerodynamic noise propagation model for wind turbines

DEFF Research Database (Denmark)

Zhu, Wei Jun; Sørensen, Jens Nørkær; Shen, Wen Zhong

2005-01-01

A model based on 2-D sound ray theory for aerodynamic noise propagation from wind turbine rotating blades is introduced. The model includes attenuation factors from geometric spreading, sound directivity of source, air absorption, ground deflection and reflection, as well as effects from temperat......A model based on 2-D sound ray theory for aerodynamic noise propagation from wind turbine rotating blades is introduced. The model includes attenuation factors from geometric spreading, sound directivity of source, air absorption, ground deflection and reflection, as well as effects from...... temperature and airflow. At a given receiver point, the sound pressure is corrected by taking into account these propagation effects. As an overall assumption, the noise field generated by the wind turbine is simplified as a point source placed at the hub height of the wind turbine. This assumtion...... is reasonable, for the receiver is located in the far field, at distances from the wind turbine that are much longer than the diameter of the rotor....

Noise Controlled Synchronization in Potassium Coupled Neural Models

DEFF Research Database (Denmark)

Postnov, D. E.; Ryazanova, L. S.; Zhirin, R. A.

2007-01-01

The paper applies biologically plausible models to investigate how noise input to small ensembles of neurons, coupled via the extracellular potassium concentration, can influence their firing patterns. Using the noise intensity and the volume of the extracellular space as control parameters, we......-temporal oscillations in neuronal ensembles....

Modeling the characteristics of wheel/rail rolling noise

Science.gov (United States)

Lui, Wai Keung; Li, Kai Ming; Frommer, Glenn H.

2005-04-01

To study the sound radiation characteristics of a passing train, four sets of noise measurements for different train operational conditions have been conducted at three different sites, including ballast tracks at grade and railway on a concrete viaduct. The time histories computed by the horizontal radiation models were compared with the measured noise profiles. The measured sound exposure levels are used to deduce the vertical directivity pattern for different railway systems. It is found that the vertical directivity of different railway systems shows a rather similar pattern. The vertical directivity of train noise is shown to increase up to about 30× before reducing to a minimum at 90×. A multipole expansion model is proposed to account for the vertical radiation directivity of the train noise. An empirical formula, which has been derived, compares well with the experimental data. The empirical model is found to be applicable to different train/rail systems at train speeds ranging up to 120 km/h in this study. [Work supported by MTR Corporation Ltd., Innovation Technology Commission of the HKSAR Government and The Hong Kong Polytechnic University.

The Effects of Degraded Visual Cueing and Divided Attention on Obstruction Avoidance in Rotorcraft

National Research Council Canada - National Science Library

Hoh, Roger

1990-01-01

.... in such flight conditions, the pilot workload was very high, just for aircraft control. This left the pilot very little excess workload capacity to maintain awareness of the rotorcraft position and rates with respect to obstructions...

Properties of autoregressive model in reactor noise analysis, 1

International Nuclear Information System (INIS)

Yamada, Sumasu; Kishida, Kuniharu; Bekki, Keisuke.

1987-01-01

Under appropriate conditions, stochastic processes are described by the ARMA model, however, the AR model is popularly used in reactor noise analysis. Hence, the properties of AR model as an approximate representation of the ARMA model should be made clear. Here, convergence of AR-parameters and PSD of AR model were studied through numerical analysis on specific examples such as the neutron noise in subcritical reactors, and it was found that : (1) The convergence of AR-parameters and AR model PSD is governed by the ''zero nearest to the unit circle in the complex plane'' (μ -1 ,|μ| M . (3) The AR model of the neutron noise of subcritical reactors needs a large model order because of an ARMA-zero very close to unity corresponding to the decay constant of the 6-th group of delayed neutron precursors. (4) In applying AR model for system identification, much attention has to be paid to a priori unknown error as an approximate representation of the ARMA model in addition to the statistical errors. (author)

Noise and dose modeling for pediatric CT optimization: preliminary results

International Nuclear Information System (INIS)

Miller Clemente, Rafael A.; Perez Diaz, Marlen; Mora Reyes, Yudel; Rodriguez Garlobo, Maikel; Castillo Salazar, Rafael

2008-01-01

Full text: A Multiple Linear Regression Model was developed to predict noise and dose in computed tomography pediatric imaging for head and abdominal examinations. Relative values of Noise and Volumetric Computed Tomography Dose Index was used to estimate de model respectively. 54 images of physical phantoms were performed. Independent variables considered included: phantom diameter, tube current and kilovolts, x ray beam collimation, reconstruction diameter and equipment's post processing filters. Predicted values show good agreement with measurements, which were better in noise model (R 2 adjusted =0.953) than the dose model (R 2 adjusted =0.744). Tube current, object diameter, beam collimation and reconstruction filter were identified as the most influencing factors in models. (author)

14 CFR 61.161 - Aeronautical experience: Rotorcraft category and helicopter class rating.

Science.gov (United States)

2010-01-01

... category and helicopter class rating. 61.161 Section 61.161 Aeronautics and Space FEDERAL AVIATION... helicopter class rating. (a) A person who is applying for an airline transport pilot certificate with a rotorcraft category and helicopter class rating, must have at least 1,200 hours of total time as a pilot that...

Engineering science research issues in high power density transmission dynamics for aerospace applications. [rotorcraft geared rotors

Science.gov (United States)

Singh, Rajendra; Houser, Donald R.

1993-01-01

This paper discusses analytical and experimental approaches that will be needed to understand dynamic, vibro-acoustic and design characteristics of high power density rotorcraft transmissions. Complexities associated with mathematical modeling of such systems will be discussed. An overview of research work planned during the next several years will be presented, with emphasis on engineering science issues such as gear contact mechanics, multi-mesh drive dynamics, parameter uncertainties, vibration transmission through bearings, and vibro-acoustic characteristics of geared rotor systems and housing-mount structures. A few examples of work in progress are cited.

An experimental evaluation of a new approach to aircraft noise modelling

NARCIS (Netherlands)

Roo, F. de; Salomons, E.M.

2008-01-01

Common engineering models for aircraft noise, such as INM, yield noise levels by interpolation of Noise Power Distance (NPD) tables. In the European project Imagine (2004 - 2006), a different approach was proposed: the source is characterized by an emission spectrum and the received noise spectrum

Source modelling of train noise - Literature review and some initial measurements

Energy Technology Data Exchange (ETDEWEB)

Zhang Xuetao; Jonasson, Hans; Holmberg, Kjell

2000-07-01

A literature review of source modelling of railway noise is reported. Measurements on a special test rig at Surahammar and on the new railway line between Arlanda and Stockholm City are reported and analyzed. In the analysis the train is modelled as a number of point sources with or without directivity and each source is combined with analytical sound propagation theory to predict the sound propagation pattern best fitting the measured data. Wheel/rail rolling noise is considered to be the most important noise source. The rolling noise can be modelled as an array of moving point sources, which have a dipole-like horizontal directivity and some kind of vertical directivity. In general it is necessary to distribute the point sources on several heights. Based on our model analysis the source heights for the rolling noise should be below the wheel axles and the most important height is about a quarter of wheel diameter above the railheads. When train speeds are greater than 250 km/h aerodynamic noise will become important and even dominant. It may be important for low frequency components only if the train speed is less than 220 km/h. Little data are available for these cases. It is believed that aerodynamic noise has dipole-like directivity. Its spectrum depends on many factors: speed, railway system, type of train, bogies, wheels, pantograph, presence of barriers and even weather conditions. Other sources such as fans, engine, transmission and carriage bodies are at most second order noise sources, but for trains with a diesel locomotive engine the engine noise will be dominant if train speeds are less than about 100 km/h. The Nord 2000 comprehensive model for sound propagation outdoors, together with the source model that is based on the understandings above, can suitably handle the problems of railway noise propagation in one-third octave bands although there are still problems left to be solved.

Statistics of a neuron model driven by asymmetric colored noise.

Science.gov (United States)

Müller-Hansen, Finn; Droste, Felix; Lindner, Benjamin

2015-02-01

Irregular firing of neurons can be modeled as a stochastic process. Here we study the perfect integrate-and-fire neuron driven by dichotomous noise, a Markovian process that jumps between two states (i.e., possesses a non-Gaussian statistics) and exhibits nonvanishing temporal correlations (i.e., represents a colored noise). Specifically, we consider asymmetric dichotomous noise with two different transition rates. Using a first-passage-time formulation, we derive exact expressions for the probability density and the serial correlation coefficient of the interspike interval (time interval between two subsequent neural action potentials) and the power spectrum of the spike train. Furthermore, we extend the model by including additional Gaussian white noise, and we give approximations for the interspike interval (ISI) statistics in this case. Numerical simulations are used to validate the exact analytical results for pure dichotomous noise, and to test the approximations of the ISI statistics when Gaussian white noise is included. The results may help to understand how correlations and asymmetry of noise and signals in nerve cells shape neuronal firing statistics.

Noise-Induced Transition in a Voltage-Controlled Oscillator Neuron Model

International Nuclear Information System (INIS)

Xie Huizhang; Liu Xuemei; Li Zhibing; Ai Baoquan; Liu Lianggang

2008-01-01

In the presence of Gaussian white noise, we study the properties of voltage-controlled oscillator neuron model and discuss the effects of the additive and multiplicative noise. It is found that the additive noise can accelerate and counterwork the firing of neuron, which depends on the value of central frequency of neuron itself, while multiplicative noise can induce the continuous change or mutation of membrane potential

Preventing Noise-Induced Extinction in Discrete Population Models

Directory of Open Access Journals (Sweden)

Irina Bashkirtseva

2017-01-01

Full Text Available A problem of the analysis and prevention of noise-induced extinction in nonlinear population models is considered. For the solution of this problem, we suggest a general approach based on the stochastic sensitivity analysis. To prevent the noise-induced extinction, we construct feedback regulators which provide a low stochastic sensitivity and keep the system close to the safe equilibrium regime. For the demonstration of this approach, we apply our mathematical technique to the conceptual but quite representative Ricker-type models. A variant of the Ricker model with delay is studied along with the classic widely used one-dimensional system.

Numerically modeling Brownian thermal noise in amorphous and crystalline thin coatings

Science.gov (United States)

Lovelace, Geoffrey; Demos, Nicholas; Khan, Haroon

2018-01-01

Thermal noise is expected to be one of the noise sources limiting the astrophysical reach of Advanced LIGO (once commissioning is complete) and third-generation detectors. Adopting crystalline materials for thin, reflecting mirror coatings, rather than the amorphous coatings used in current-generation detectors, could potentially reduce thermal noise. Understanding and reducing thermal noise requires accurate theoretical models, but modeling thermal noise analytically is especially challenging with crystalline materials. Thermal noise models typically rely on the fluctuation-dissipation theorem, which relates the power spectral density of the thermal noise to an auxiliary elastic problem. In this paper, we present results from a new, open-source tool that numerically solves the auxiliary elastic problem to compute the Brownian thermal noise for both amorphous and crystalline coatings. We employ the open-source deal.ii and PETSc frameworks to solve the auxiliary elastic problem using a finite-element method, adaptive mesh refinement, and parallel processing that enables us to use high resolutions capable of resolving the thin reflective coating. We verify numerical convergence, and by running on up to hundreds of compute cores, we resolve the coating elastic energy in the auxiliary problem to approximately 0.1%. We compare with approximate analytic solutions for amorphous materials, and we verify that our solutions scale as expected with changing beam size, mirror dimensions, and coating thickness. Finally, we model the crystalline coating thermal noise in an experiment reported by Cole et al (2013 Nat. Photon. 7 644–50), comparing our results to a simpler numerical calculation that treats the coating as an ‘effectively amorphous’ material. We find that treating the coating as a cubic crystal instead of as an effectively amorphous material increases the thermal noise by about 3%. Our results are a step toward better understanding and reducing thermal noise to

System Identification and Verification of Rotorcraft UAVs

Science.gov (United States)

Carlton, Zachary M.

The task of a controls engineer is to design and implement control logic. To complete this task, it helps tremendously to have an accurate model of the system to be controlled. Obtaining a very accurate system model is not a trivial one, as much time and money is usually associated with the development of such a model. A typical physics based approach can require hundreds of hours of flight time. In an iterative process the model is tuned in such a way that it accurately models the physical system's response. This process becomes even more complicated for unstable and highly non-linear systems such as the dynamics of rotorcraft. An alternate approach to solving this problem is to extract an accurate model by analyzing the frequency response of the system. This process involves recording the system's responses for a frequency range of input excitations. From this data, an accurate system model can then be deduced. Furthermore, it has been shown that with use of the software package CIFER® (Comprehensive Identification from FrEquency Responses), this process can both greatly reduce the cost of modeling a dynamic system and produce very accurate results. The topic of this thesis is to apply CIFER® to a quadcopter to extract a system model for the flight condition of hover. The quadcopter itself is comprised of off-the-shelf components with a Pixhack flight controller board running open source Ardupilot controller logic. In this thesis, both the closed and open loop systems are identified. The model is next compared to dissimilar flight data and verified in the time domain. Additionally, the ESC (Electronic Speed Controller) motor/rotor subsystem, which is comprised of all the vehicle's actuators, is also identified. This process required the development of a test bench environment, which included a GUI (Graphical User Interface), data pre and post processing, as well as the augmentation of the flight controller source code. This augmentation of code allowed for

Improved virtual channel noise model for transform domain Wyner-Ziv video coding

DEFF Research Database (Denmark)

Huang, Xin; Forchhammer, Søren

2009-01-01

Distributed video coding (DVC) has been proposed as a new video coding paradigm to deal with lossy source coding using side information to exploit the statistics at the decoder to reduce computational demands at the encoder. A virtual channel noise model is utilized at the decoder to estimate...... the noise distribution between the side information frame and the original frame. This is one of the most important aspects influencing the coding performance of DVC. Noise models with different granularity have been proposed. In this paper, an improved noise model for transform domain Wyner-Ziv video...... coding is proposed, which utilizes cross-band correlation to estimate the Laplacian parameters more accurately. Experimental results show that the proposed noise model can improve the rate-distortion (RD) performance....

Four-jet impingement: Noise characteristics and simplified acoustic model

International Nuclear Information System (INIS)

Brehm, C.; Housman, J.A.; Kiris, C.C.; Barad, M.F.; Hutcheson, F.V.

2017-01-01

Highlights: • Large eddy simulation of unique four jet impingement configuration. • Characterization of flow features using POD, FFT, and wavelet decomposition. • Noise source identification utilizing causality method. • Development of simplified acoustic model utilizing equivalent source method. • Comparison with experimental data from BENS experiment. - Abstract: The noise generation mechanisms for four directly impinging supersonic jets are investigated employing implicit large eddy simulations with a higher-order weighted essentially non-oscillatory scheme. Although these types of impinging jet configurations have been used in many experiments, a detailed investigation of the noise generation mechanisms has not been conducted before. The flow field is highly complex and contains a wide range of temporal and spatial scales relevant for noise generation. Proper orthogonal decomposition is utilized to characterize the unsteady nature of the flow field involving unsteady shock oscillations, large coherent turbulent flow structures, and the sporadic appearance of vortical flow structures in the center of the four-jet impingement region. The causality method based on Lighthills acoustic analogy is applied to link fluctuations of flow quantities inside the source region to the acoustic pressure in the far field. It will be demonstrated that the entropy fluctuation term plays a vital role in the noise generation process. Consequently, the understanding of the noise generation mechanisms is employed to develop a simplified acoustic model of the four-jet impingement device by utilizing the equivalent source method. Finally, three linear acoustic four-jet impingement models of the four-jet impingement device are used as broadband noise sources inside an engine nacelle and the acoustic scattering results are validated against far-field acoustic experimental data.

Modeling and Eigenfrequency Analysis of Sound-Structure Interaction in a Rectangular Enclosure with Finite Element Method

Directory of Open Access Journals (Sweden)

Samira Mohamady

2009-01-01

Full Text Available Vibration of structures due to external sound is one of the main causes of interior noise in cavities like automobile, aircraft, and rotorcraft, which disturb the comfort of passengers. Accurate modelling of such phenomena is required in eigenfrequency analysis and in designing an active noise control system to reduce the interior noise. In this paper, the effect of periodic noise travelling into a rectangular enclosure is investigated with finite element method (FEM using COMSOL Multiphysics software. The periodic acoustic wave is generated by a point source outside the enclosure and propagated through the enclosure wall and excites an aluminium flexible panel clamped onto the enclosure. The behaviour of the transmission of sound into the cavity is investigated by computing the modal characteristics and the natural frequencies of the cavity. The simulation results are compared with previous analytical and experimental works for validation and an acceptable match between them were obtained.

Noise-and delay-induced phase transitions of the dimer–monomer surface reaction model

International Nuclear Information System (INIS)

Zeng Chunhua; Wang Hua

2012-01-01

Highlights: ► We study the dimer–monomer surface reaction model. ► We show that noise induces first-order irreversible phase transition (IPT). ► Combination of noise and time-delayed feedback induce first- and second-order IPT. ► First- and second-order IPT is viewed as noise-and delay-induced phase transitions. - Abstract: The effects of noise and time-delayed feedback in the dimer–monomer (DM) surface reaction model are investigated. Applying small delay approximation, we construct a stochastic delayed differential equation and its Fokker–Planck equation to describe the state evolution of the DM reaction model. We show that the noise can only induce first-order irreversible phase transition (IPT) characteristic of the DM model, however the combination of the noise and time-delayed feedback can simultaneously induce first- and second-order IPT characteristics of the DM model. Therefore, it is shown that the well-known first- and second-order IPT characteristics of the DM model may be viewed as noise-and delay-induced phase transitions.

Nonlinear GARCH model and 1 / f noise

Science.gov (United States)

Kononovicius, A.; Ruseckas, J.

2015-06-01

Auto-regressive conditionally heteroskedastic (ARCH) family models are still used, by practitioners in business and economic policy making, as a conditional volatility forecasting models. Furthermore ARCH models still are attracting an interest of the researchers. In this contribution we consider the well known GARCH(1,1) process and its nonlinear modifications, reminiscent of NGARCH model. We investigate the possibility to reproduce power law statistics, probability density function and power spectral density, using ARCH family models. For this purpose we derive stochastic differential equations from the GARCH processes in consideration. We find the obtained equations to be similar to a general class of stochastic differential equations known to reproduce power law statistics. We show that linear GARCH(1,1) process has power law distribution, but its power spectral density is Brownian noise-like. However, the nonlinear modifications exhibit both power law distribution and power spectral density of the 1 /fβ form, including 1 / f noise.

Low-Altitude Operation of Unmanned Rotorcraft

Science.gov (United States)

Scherer, Sebastian

Currently deployed unmanned rotorcraft rely on preplanned missions or teleoperation and do not actively incorporate information about obstacles, landing sites, wind, position uncertainty, and other aerial vehicles during online motion planning. Prior work has successfully addressed some tasks such as obstacle avoidance at slow speeds, or landing at known to be good locations. However, to enable autonomous missions in cluttered environments, the vehicle has to react quickly to previously unknown obstacles, respond to changing environmental conditions, and find unknown landing sites. We consider the problem of enabling autonomous operation at low-altitude with contributions to four problems. First we address the problem of fast obstacle avoidance for a small aerial vehicle and present results from over a 1000 rims at speeds up to 10 m/s. Fast response is achieved through a reactive algorithm whose response is learned based on observing a pilot. Second, we show an algorithm to update the obstacle cost expansion for path planning quickly and demonstrate it on a micro aerial vehicle, and an autonomous helicopter avoiding obstacles. Next, we examine the mission of finding a place to land near a ground goal. Good landing sites need to be detected and found and the final touch down goal is unknown. To detect the landing sites we convey a model based algorithm for landing sites that incorporates many helicopter relevant constraints such as landing sites, approach, abort, and ground paths in 3D range data. The landing site evaluation algorithm uses a patch-based coarse evaluation for slope and roughness, and a fine evaluation that fits a 3D model of the helicopter and landing gear to calculate a goodness measure. The data are evaluated in real-time to enable the helicopter to decide on a place to land. We show results from urban, vegetated, and desert environments, and demonstrate the first autonomous helicopter that selects its own landing sites. We present a generalized

Adaptive Noise Model for Transform Domain Wyner-Ziv Video using Clustering of DCT Blocks

DEFF Research Database (Denmark)

Luong, Huynh Van; Huang, Xin; Forchhammer, Søren

2011-01-01

The noise model is one of the most important aspects influencing the coding performance of Distributed Video Coding. This paper proposes a novel noise model for Transform Domain Wyner-Ziv (TDWZ) video coding by using clustering of DCT blocks. The clustering algorithm takes advantage of the residual...... modelling. Furthermore, the proposed cluster level noise model is adaptively combined with a coefficient level noise model in this paper to robustly improve coding performance of TDWZ video codec up to 1.24 dB (by Bjøntegaard metric) compared to the DISCOVER TDWZ video codec....... information of all frequency bands, iteratively classifies blocks into different categories and estimates the noise parameter in each category. The experimental results show that the coding performance of the proposed cluster level noise model is competitive with state-ofthe- art coefficient level noise...

Examination of the low frequency limit for helicopter noise data in the Federal Aviation Administration's Aviation Environmental Design Tool and Integrated Noise Model

Science.gov (United States)

2010-04-19

The Federal Aviation Administration (FAA) aircraft noise modeling tools Aviation Environmental Design Tool (AEDTc) and Integrated Noise Model (INM) do not currently consider noise below 50 Hz in their computations. This paper describes a preliminary ...

Spring-block Model for Barkhausen Noise

International Nuclear Information System (INIS)

Kovacs, K.; Brechet, Y.; Neda, Z.

2005-01-01

A simple mechanical spring-block model is used for studying Barkhausen noise (BN). The model incorporates the generally accepted physics of domain wall movement and pinning. Computer simulations on this model reproduces the main features of the hysteresis loop and Barkhausen jumps. The statistics of the obtained Barkhausen jumps follows several scaling laws, in qualitative agreement with experimental results. The model consists of a one-dimensional frictional spring-block system. The blocks model the Bloch-walls that separate inversely oriented magnetic domains, and springs correspond to the magnetized regions. Three types of realistic forces are modelled with this system: 1. the force resulting from the magnetic energy of the neighboring domains in external magnetic field (modelled by forces having alternating orientations and acting directly on the blocks); 2. the force resulting from the magnetic self-energy of each domain (modelled by the elastic forces of the springs); 3. the pinning forces acting on the domain walls (modelled by position dependent static friction acting on blocks). The dynamics of the system is governed by searching for equilibrium: one particular domain wall can jump to the next pinning center if the resultant of forces 1. and 2. is greater then the pinning force. The external magnetic field is successively increased (or decreased) and the system is relaxed to mechanical equilibrium. During the simulations we are monitoring the variation of the magnetization focusing on the shape of the hysteresis loop, power spectrum, jump size (avalanche size) distribution, signal duration distribution, signal area distribution. The simulated shape of the hysteresis loops fulfills all the requirements for real magnetization phenomena. The power spectrum indicates different behavior in the low (1/f noise) and high (white noise) frequency region. All the relevant distribution functions show scaling behavior over several decades of magnitude with a naturally

Engineering modeling of traffic noise in shielded areas in cities.

Science.gov (United States)

Salomons, Erik M; Polinder, Henk; Lohman, Walter J A; Zhou, Han; Borst, Hieronymous C; Miedema, Henk M E

2009-11-01

A computational study of road traffic noise in cities is presented. Based on numerical boundary-element calculations of canyon-to-canyon propagation, an efficient engineering algorithm is developed to calculate the effect of multiple reflections in street canyons. The algorithm is supported by a room-acoustical analysis of the reverberant sound fields in the source and receiver canyons. Using the algorithm, a simple model for traffic noise in cities is developed. Noise maps and exposure distributions of the city of Amsterdam are calculated with the model, and for comparison also with an engineering model that is currently used for traffic noise impact assessments in cities. Considerable differences between the two model predictions are found for shielded buildings with day-evening-night levels of 40-60 dB at the facades. Further, an analysis is presented of level differences between the most and the least exposed facades of buildings. Large level differences are found for buildings directly exposed to traffic noise from nearby roads. It is shown that by a redistribution of traffic flow around these buildings, one can achieve low sound levels at quiet sides and a corresponding reduction in the percentage of highly annoyed inhabitants from typically 23% to 18%.

Model for Estimating Noise-Induced Hearing Loss Associated With Occupational Noise Exposure in a Specified US Navy Population

National Research Council Canada - National Science Library

Tufts, Jennifer; Weathersby, Paul K; Marshall, Lynne; Sachs, Felix

2007-01-01

This report details the initial steps in the development of a method for modeling the noise-induced hearing loss accrued by a population of Sailors exposed to high-level steady-state occupational noise...

A model for measurement of noise in CCD digital-video cameras

International Nuclear Information System (INIS)

Irie, K; Woodhead, I M; McKinnon, A E; Unsworth, K

2008-01-01

This study presents a comprehensive measurement of CCD digital-video camera noise. Knowledge of noise detail within images or video streams allows for the development of more sophisticated algorithms for separating true image content from the noise generated in an image sensor. The robustness and performance of an image-processing algorithm is fundamentally limited by sensor noise. The individual noise sources present in CCD sensors are well understood, but there has been little literature on the development of a complete noise model for CCD digital-video cameras, incorporating the effects of quantization and demosaicing

Noise stabilization effects in models of interdisciplinary physics

International Nuclear Information System (INIS)

Spagnolo, B; Augello, G; Caldara, P; Fiasconaro, A; La Cognata, A; Pizzolato, N; Valenti, D; Dubkov, A A; Pankratov, A L

2009-01-01

Metastability is a generic feature of many nonlinear systems, and the problem of the lifetime of metastable states involves fundamental aspects of nonequilibrium statistical mechanics. The investigation of noise-induced phenomena in far from equilibrium systems is one of the approaches used to understand the behaviour of physical and biological complex systems. The enhancement of the lifetime of metastable states through the noise enhanced stability effect and the role played by the resonant activation phenomenon will be discussed in models of interdisciplinary physics: (i) polymer translocation dynamics; (ii) transient regime of FitzHugh-Nagumo model; (iii) market stability in a nonlinear Heston model; (iv) dynamics of Josephson junctions; (v) metastability in a quantum bitable system.

Operational modeling of dose and noise for computed tomography in a pediatric hospital

International Nuclear Information System (INIS)

Miller Clemente, Rafael A.; Perez Diaz, Marlen; Mora Reyes, Yudel; Rodriguez Garlobo, Maikel; Castillo Salazar, Rafael

2008-01-01

Noise becomes a critical factor in Computed Tomography (CT) because most detailed applications on soft tissue show a low contrast nature. Noise establishes an inferior limit to the contrast detectable by the observer. Various pixel noise models had been devised taking into account operational parameters on Single and Multi Detector Slice CT. The aim of this work was to obtain a predictive operational model for image noise addressed to pediatric protocols, taking into account scanning factors with a Single Slice CT unit dedicated to pediatric applications. A multiple linear regression model is proposed to predict noise in images of uniform phantoms equivalent to head and abdomen. A model for reported volumetric Computed Tomography Dose Index (CTDI VOL ) was obtained too for tradeoffs analysis approaching optimization purposes in pediatric applications. Eight independent variables were considered: phantom diameter, reconstruction mode, tube current, tube kVp, collimation, Field of View (FOV), reconstruction filter, and post processing filter. Results show good agreement with measurements, with adjusted coefficients of multiple determination of 0.936 and 0.744 for noise and CTDI VOL models respectively. Tube current, object diameter, collimation and reconstruction filters were the most influencing variables. The model application contributes to identify each factor's influence enhancing the operational possibilities approaching optimization of noise and dose tradeoffs. Acceptable noise levels and optimization strategies can be devised from models obtained towards lower tube current values combined with greater slice thickness and kVp taking into account the doses to pediatric patients. (author)

Theoretical Modeling of Intensity Noise in InGaN Semiconductor Lasers

Directory of Open Access Journals (Sweden)

Moustafa Ahmed

2014-01-01

Full Text Available This paper introduces modeling and simulation of the noise properties of the blue-violet InGaN laser diodes. The noise is described in terms of the spectral properties of the relative intensity noise (RIN. We examine the validity of the present noise modeling by comparing the simulated results with the experimental measurements available in literature. We also compare the obtained noise results with those of AlGaAs lasers. Also, we examine the influence of gain suppression on the quantum RIN. In addition, we examine the changes in the RIN level when describing the gain suppression by the case of inhomogeneous spectral broadening. The results show that RIN of the InGaN laser is nearly 9 dB higher than that of the AlGaAs laser.

New Hybrid Variational Recovery Model for Blurred Images with Multiplicative Noise

DEFF Research Database (Denmark)

Dong, Yiqiu; Zeng, Tieyong

2013-01-01

A new hybrid variational model for recovering blurred images in the presence of multiplicative noise is proposed. Inspired by previous work on multiplicative noise removal, an I-divergence technique is used to build a strictly convex model under a condition that ensures the uniqueness...

A Convex Variational Model for Restoring Blurred Images with Multiplicative Noise

DEFF Research Database (Denmark)

Dong, Yiqiu; Tieyong Zeng

2013-01-01

In this paper, a new variational model for restoring blurred images with multiplicative noise is proposed. Based on the statistical property of the noise, a quadratic penalty function technique is utilized in order to obtain a strictly convex model under a mild condition, which guarantees...

Modelling of Substrate Noise and Mitigation Schemes for UWB Systems

DEFF Research Database (Denmark)

Shen, Ming; Mikkelsen, Jan H.; Larsen, Torben

2012-01-01

tuned elements in the signal paths. However, for UWB designs this is not a viable option and other means are therefore required. Moreover, owing to the ultra-wideband nature and low power spectral density of the signal, UWB mixed-signal integrated circuits are more sensitive to substrate noise compared...... with narrow-band circuits. This chapter presents a study on the modeling and mitigation of substrate noise in mixed-signal integrated circuits (ICs), focusing on UWB system/circuit designs. Experimental impact evaluation of substrate noise on UWB circuits is presented. It shows how a wide-band circuit can......The last chapter of this first part of the book, chapter seven, is devoted to Modeling of Substrate Noise and Mitigation Schemes for Ultrawideband (UWB) systems, and is written by Ming Shen, Jan H. Mikkelsen, and Torben Larsen from Aalborg University, Denmark. In highly integrated mixed...

Vision based techniques for rotorcraft low altitude flight

Science.gov (United States)

Sridhar, Banavar; Suorsa, Ray; Smith, Philip

1991-01-01

An overview of research in obstacle detection at NASA Ames Research Center is presented. The research applies techniques from computer vision to automation of rotorcraft navigation. The development of a methodology for detecting the range to obstacles based on the maximum utilization of passive sensors is emphasized. The development of a flight and image data base for verification of vision-based algorithms, and a passive ranging methodology tailored to the needs of helicopter flight are discussed. Preliminary results indicate that it is possible to obtain adequate range estimates except at regions close to the FOE. Closer to the FOE, the error in range increases since the magnitude of the disparity gets smaller, resulting in a low SNR.

Noise propagation in resolution modeled PET imaging and its impact on detectability

International Nuclear Information System (INIS)

Rahmim, Arman; Tang, Jing

2013-01-01

Positron emission tomography imaging is affected by a number of resolution degrading phenomena, including positron range, photon non-collinearity and inter-crystal blurring. An approach to this issue is to model some or all of these effects within the image reconstruction task, referred to as resolution modeling (RM). This approach is commonly observed to yield images of higher resolution and subsequently contrast, and can be thought of as improving the modulation transfer function. Nonetheless, RM can substantially alter the noise distribution. In this work, we utilize noise propagation models in order to accurately characterize the noise texture of reconstructed images in the presence of RM. Furthermore we consider the task of lesion or defect detection, which is highly determined by the noise distribution as quantified using the noise power spectrum. Ultimately, we use this framework to demonstrate why conventional trade-off analyses (e.g. contrast versus noise, using simplistic noise metrics) do not provide a complete picture of the impact of RM and that improved performance of RM according to such analyses does not necessarily translate to the superiority of RM in detection task performance. (paper)

MOSFET LF noise under Large Signal Excitation: Measurement, Modelling and Application

NARCIS (Netherlands)

van der Wel, A.P.

2005-01-01

Regarding LF noise in MOSFETs, it is noted that the MOSFET is a surface channel device. Both n and p-channel devices exhibit similar low frequency (LF) noise behaviour that can be explained by a carrier number fluctuation model (section 3.5). LF noise in MOSFETs is predominantly caused by Random

Persistence and extinction for stochastic logistic model with Levy noise and impulsive perturbation

OpenAIRE

Chun Lu; Qiang Ma; Xiaohua Ding

2015-01-01

This article investigates a stochastic logistic model with Levy noise and impulsive perturbation. In the model, the impulsive perturbation and Levy noise are taken into account simultaneously. This model is new and more feasible and more accordance with the actual. The definition of solution to a stochastic differential equation with Levy noise and impulsive perturbation is established. Based on this definition, we show that our model has a unique global positive solut...

Nonlinear interaction model of subsonic jet noise.

Science.gov (United States)

Sandham, Neil D; Salgado, Adriana M

2008-08-13

Noise generation in a subsonic round jet is studied by a simplified model, in which nonlinear interactions of spatially evolving instability modes lead to the radiation of sound. The spatial mode evolution is computed using linear parabolized stability equations. Nonlinear interactions are found on a mode-by-mode basis and the sound radiation characteristics are determined by solution of the Lilley-Goldstein equation. Since mode interactions are computed explicitly, it is possible to find their relative importance for sound radiation. The method is applied to a single stream jet for which experimental data are available. The model gives Strouhal numbers of 0.45 for the most amplified waves in the jet and 0.19 for the dominant sound radiation. While in near field axisymmetric and the first azimuthal modes are both important, far-field sound is predominantly axisymmetric. These results are in close correspondence with experiment, suggesting that the simplified model is capturing at least some of the important mechanisms of subsonic jet noise.

Rotorcraft Use in Disaster Relief and Mass Casualty Incidents - Case Studies

Science.gov (United States)

1990-06-01

Disaster Relief and Mass 6. Performing Organization Code C asuallty Incidents- C ase Studies 8._P rfo minOr ani ati nR porNo 7. Author (s) 8...disaster planning process; and 3) produce a color video tape promoting the need for and the use of rotorcraft and heliports in disaster relief. 17...disaster prepaLedness ageicies for use in the integration of local helicopter assets into the disaster planning process; and 3) produce a color video tape

The Role of Flow Diagnostic Techniques in Fan and Open Rotor Noise Modeling

Science.gov (United States)

Envia, Edmane

2016-01-01

A principal source of turbomachinery noise is the interaction of the rotating and stationary blade rows with the perturbations in the airstream through the engine. As such, a lot of research has been devoted to the study of the turbomachinery noise generation mechanisms. This is particularly true of fan and open rotors, both of which are the major contributors to the overall noise output of modern aircraft engines. Much of the research in fan and open rotor noise has been focused on developing theoretical models for predicting their noise characteristics. These models, which run the gamut from the semi-empirical to fully computational ones, are, in one form or another, informed by the description of the unsteady flow-field in which the propulsors (i.e., the fan and open rotors) operate. Not surprisingly, the fidelity of the theoretical models is dependent, to a large extent, on capturing the nuances of the unsteady flowfield that have a direct role in the noise generation process. As such, flow diagnostic techniques have proven to be indispensible in identifying the shortcoming of theoretical models and in helping to improve them. This presentation will provide a few examples of the role of flow diagnostic techniques in assessing the fidelity and robustness of the fan and open rotor noise prediction models.

The influence of noise on nonlinear time series detection based on Volterra-Wiener-Korenberg model

Energy Technology Data Exchange (ETDEWEB)

Lei Min [State Key Laboratory of Vibration, Shock and Noise, Shanghai Jiao Tong University, Shanghai 200030 (China)], E-mail: leimin@sjtu.edu.cn; Meng Guang [State Key Laboratory of Vibration, Shock and Noise, Shanghai Jiao Tong University, Shanghai 200030 (China)

2008-04-15

This paper studies the influence of noises on Volterra-Wiener-Korenberg (VWK) nonlinear test model. Our numerical results reveal that different types of noises lead to different behavior of VWK model detection. For dynamic noise, it is difficult to distinguish chaos from nonchaotic but nonlinear determinism. For time series, measure noise has no impact on chaos determinism detection. This paper also discusses various behavior of VWK model detection with surrogate data for different noises.

Non-white noise in fMRI: Does modelling have an impact?

DEFF Research Database (Denmark)

Lund, Torben Ellegaard; Madsen, Kristoffer Hougaard; Sidaros, Karam

2006-01-01

are typically modelled as an autoregressive (AR) process. In this paper, we propose an alternative approach: Nuisance Variable Regression (NVR). By inclusion of confounding effects in a general linear model (GLM), we first confirm that the spatial distribution of the various fMRI noise sources is similar......The sources of non-white noise in Blood Oxygenation Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) are many. Familiar sources include low-frequency drift due to hardware imperfections, oscillatory noise due to respiration and cardiac pulsation and residual movement artefacts...

On low-frequency errors of uniformly modulated filtered white-noise models for ground motions

Science.gov (United States)

Safak, Erdal; Boore, David M.

1988-01-01

Low-frequency errors of a commonly used non-stationary stochastic model (uniformly modulated filtered white-noise model) for earthquake ground motions are investigated. It is shown both analytically and by numerical simulation that uniformly modulated filter white-noise-type models systematically overestimate the spectral response for periods longer than the effective duration of the earthquake, because of the built-in low-frequency errors in the model. The errors, which are significant for low-magnitude short-duration earthquakes, can be eliminated by using the filtered shot-noise-type models (i. e. white noise, modulated by the envelope first, and then filtered).

International scale implementation of the CNOSSOS-EU road traffic noise prediction model for epidemiological studies

International Nuclear Information System (INIS)

Morley, D.W.; Hoogh, K. de; Fecht, D.; Fabbri, F.; Bell, M.; Goodman, P.S.; Elliott, P.; Hodgson, S.; Hansell, A.L.; Gulliver, J.

2015-01-01

The EU-FP7-funded BioSHaRE project is using individual-level data pooled from several national cohort studies in Europe to investigate the relationship of road traffic noise and health. The detailed input data (land cover and traffic characteristics) required for noise exposure modelling are not always available over whole countries while data that are comparable in spatial resolution between different countries is needed for harmonised exposure assessment. Here, we assess the feasibility using the CNOSSOS-EU road traffic noise prediction model with coarser input data in terms of model performance. Starting with a model using the highest resolution datasets, we progressively introduced lower resolution data over five further model runs and compared noise level estimates to measurements. We conclude that a low resolution noise model should provide adequate performance for exposure ranking (Spearman's rank = 0.75; p < 0.001), but with relatively large errors in predicted noise levels (RMSE = 4.46 dB(A)). - Highlights: • The first implementation of CNOSSOS-EU for national scale noise exposure assessment. • Road traffic noise model performance with varying resolution of inputs is assessed. • Model performance is good with low resolution inputs (r_s = 0.75). • This model will be applied in epidemiological studies of European cohorts. - The CNOSSOS-EU road traffic noise model estimates can be used for international scale exposure assessment when parameterised with freely available low resolution covering a large geographic area.

Noise in Genetic Toggle Switch Models

Directory of Open Access Journals (Sweden)

Andrecut M.

2006-06-01

Full Text Available In this paper we study the intrinsic noise effect on the switching behavior of a simple genetic circuit corresponding to the genetic toggle switch model. The numerical results obtained from a noisy mean-field model are compared to those obtained from the stochastic Gillespie simulation of the corresponding system of chemical reactions. Our results show that by using a two step reaction approach for modeling the transcription and translation processes one can make the system to lock in one of the steady states for exponentially long times.

Physical model study of neutron noise induced by vibration of reactor internals

International Nuclear Information System (INIS)

Liu Jinhui; Gu Fangyu

1999-01-01

The author presents a physical model of neutron noise induced by reactor internals vibration in frequency domain. Based on system control theory, the reactor dynamic equations are coupled with random vibration equation, and non-linear terms are also taken into accounted while treating the random vibration. Experiments carried out on a zero-power reactor show that the model can be used to describe dynamic character of neutron noise induced by internals' vibration. The model establishes a method to help to determine internals'vibration features, and to diagnosis anomalies through neutron noise

Consistent modelling of wind turbine noise propagation from source to receiver.

Science.gov (United States)

Barlas, Emre; Zhu, Wei Jun; Shen, Wen Zhong; Dag, Kaya O; Moriarty, Patrick

2017-11-01

The unsteady nature of wind turbine noise is a major reason for annoyance. The variation of far-field sound pressure levels is not only caused by the continuous change in wind turbine noise source levels but also by the unsteady flow field and the ground characteristics between the turbine and receiver. To take these phenomena into account, a consistent numerical technique that models the sound propagation from the source to receiver is developed. Large eddy simulation with an actuator line technique is employed for the flow modelling and the corresponding flow fields are used to simulate sound generation and propagation. The local blade relative velocity, angle of attack, and turbulence characteristics are input to the sound generation model. Time-dependent blade locations and the velocity between the noise source and receiver are considered within a quasi-3D propagation model. Long-range noise propagation of a 5 MW wind turbine is investigated. Sound pressure level time series evaluated at the source time are studied for varying wind speeds, surface roughness, and ground impedances within a 2000 m radius from the turbine.

Development of in-vehicle noise prediction models for Mumbai Metropolitan Region, India

Directory of Open Access Journals (Sweden)

Vishal Konbattulwar

2016-08-01

Full Text Available Traffic noise is one of the major sources of noise pollution in metropolitan regions causing various health hazards (e.g., long-term sleep disturbance, increase in blood pressure, physical tension, etc.. In this research, noise prediction models, which can measure the noise level experienced by the commuters while driving or traveling by motorized vehicles in the Mumbai Metropolitan Region, India, were developed. These models were developed by conducting a comprehensive study of various factors (e.g., vehicle speed, traffic volume and road characteristics, etc. affecting the levels of concentration of noise. A widespread data collection was done by conducting road trips of total length of 403.80 km via different modes of transport, such as air-conditioned (A/C car, non A/C car, bus and intermediate public transport (i.e., traditional 3-wheeler autos. Multiple regression analyses were performed to develop a functional relation between equivalent noise levels experienced by passengers while traveling (which was considered as a dependent variable and explanatory variables such as traffic characteristics, vehicle class, vehicle speed, various other location characteristics, etc. Noise levels are generally higher in the vicinity of intersections and signalized junctions. Independent data sets (for each mode of transport were used to validate the developed models. It was noted that maximum differences between observed and estimated values from the model were within the range of ±7.8% of the observed value.

A combined aeroelastic-aeroacoustic model for wind turbine noise: Verification and analysis of field measurements

DEFF Research Database (Denmark)

Bertagnolio, Franck; Aagaard Madsen, Helge; Fischer, Andreas

2017-01-01

In this paper, semi-empirical engineering models for the three main wind turbine aerodynamic noise sources, namely, turbulent inflow, trailing edge and stall noise, are introduced. They are implemented into the in-house aeroelastic code HAWC2 commonly used for wind turbine load calculations...... and design. The results of the combined aeroelastic and aeroacoustic model are compared with field noise measurements of a 500kW wind turbine. Model and experimental data are in fairly good agreement in terms of noise levels and directivity. The combined model allows separating the various noise sources...... and highlights a number of mechanisms that are difficult to differentiate when only the overall noise from a wind turbine is measured....

Concepts for Multi-Speed Rotorcraft Drive System - Status of Design and Testing at NASA GRC

Science.gov (United States)

Stevens, Mark A.; Lewicki, David G.; Handschuh, Robert F.

2015-01-01

In several studies and on-going developments for advanced rotorcraft, the need for variable/multi-speed capable rotors has been raised. Speed changes of up to 50 percent have been proposed for future rotorcraft to improve vehicle performance. A rotor speed change during operation not only requires a rotor that can perform effectively over the operating speed/load range, but also requires a propulsion system possessing these same capabilities. A study was completed investigating possible drive system arrangements that can accommodate up to a 50 percent speed change. Key drivers were identified from which simplicity and weight were judged as central. This paper presents the current status of two gear train concepts coupled with the first of two clutch types developed and tested thus far with focus on design lessons learned and areas requiring development. Also, a third concept is presented, a dual input planetary differential as leveraged from a simple planetary with fixed carrier.

Stochastic bifurcation in a model of love with colored noise

Science.gov (United States)

Yue, Xiaokui; Dai, Honghua; Yuan, Jianping

2015-07-01

In this paper, we wish to examine the stochastic bifurcation induced by multiplicative Gaussian colored noise in a dynamical model of love where the random factor is used to describe the complexity and unpredictability of psychological systems. First, the dynamics in deterministic love-triangle model are considered briefly including equilibrium points and their stability, chaotic behaviors and chaotic attractors. Then, the influences of Gaussian colored noise with different parameters are explored such as the phase plots, top Lyapunov exponents, stationary probability density function (PDF) and stochastic bifurcation. The stochastic P-bifurcation through a qualitative change of the stationary PDF will be observed and bifurcation diagram on parameter plane of correlation time and noise intensity is presented to find the bifurcation behaviors in detail. Finally, the top Lyapunov exponent is computed to determine the D-bifurcation when the noise intensity achieves to a critical value. By comparison, we find there is no connection between two kinds of stochastic bifurcation.

Road traffic noise prediction model for heterogeneous traffic based on ASJ-RTN Model 2008 with consideration of horn

Science.gov (United States)

Hustim, M.; Arifin, Z.; Aly, S. H.; Ramli, M. I.; Zakaria, R.; Liputo, A.

2018-04-01

This research aimed to predict the noise produced by the traffic in the road network in Makassar City using ASJ-RTN Model 2008 by calculating the horn sound. Observations were taken at 37 survey points on road side. The observations were conducted at 06.00 - 18.00 and 06.00 - 21.00 which research objects were motorcycle (MC), light vehicle (LV) and heavy vehicle (HV). The observed data were traffic volume, vehicle speed, number of horn and traffic noise using Sound Level Meter Tenmars TM-103. The research result indicates that prediction noise model by calculating the horn sound produces the average noise level value of 78.5 dB having the Pearson’s correlation and RMSE of 0.95 and 0.87. Therefore, ASJ-RTN Model 2008 prediction model by calculating the horn sound is said to be sufficiently good for predicting noise level.

Noise barriers and the harmonoise sound propagation model

NARCIS (Netherlands)

Salomons, E.M.; Maercke, D. van; Randrianoelina, A.

2009-01-01

The Harmonoise sound propagation model ('the Harmonoise engineering model') was developed in the European project Harmonoise (2001-2004) for road and rail traffic noise. In 2008, CSTB Grenoble and TNO Delft have prepared a detailed description of the various steps involved in a calculation with the

The Impact of Noise Models on Capacity Performance of Distribution Broadband over Power Lines Networks

Directory of Open Access Journals (Sweden)

Athanasios G. Lazaropoulos

2016-01-01

Full Text Available This paper considers broadband potential of distribution Broadband over Power Lines (BPL networks when different well-known noise models of the BPL literature are applied. The contribution of this paper is twofold. First, the seven most representative and used noise models of the BPL literature are synopsized in this paper. With reference to this set, the broadband performance of a great number of distribution BPL topologies either Overhead (OV or Underground (UN, either Medium-Voltage (MV or Low-Voltage (LV, is investigated in terms of suitable capacity metrics. Second, based on the proposed capacity metrics, a comparative capacity analysis is performed among various well-validated noise models. Through the careful study of its results, it is demonstrated that during capacity computations of distribution BPL networks, the flat Additive White Gaussian Noise (FL noise model can be comfortably assumed as an efficient noise model either in 3–30 MHz or in 3–88 MHz frequency range since its capacity differences with the other well-proven noise models are negligible.

Moment stability for a predator–prey model with parametric dichotomous noises

International Nuclear Information System (INIS)

Jin Yan-Fei

2015-01-01

In this paper, we investigate the solution moment stability for a Harrison-type predator–prey model with parametric dichotomous noises. Using the Shapiro–Loginov formula, the equations for the first-order and second-order moments are obtained and the corresponding stable conditions are given. It is found that the solution moment stability depends on the noise intensity and correlation time of noise. The first-order and second-order moments become unstable with the decrease of correlation time. That is, the dichotomous noise can improve the solution moment stability with respect to Gaussian white noise. Finally, some numerical results are presented to verify the theoretical analyses. (paper)

Predictive modelling of noise level generated during sawing of rocks

Indian Academy of Sciences (India)

This paper presents an experimental and statistical study on noise level generated during of rock sawing by circular diamond sawblades. Influence of the operating variables and rock properties on the noise level are investigated and analysed. Statistical analyses are then employed and models are built for the prediction of ...

Noise level in neonatal incubators: A comparative study of three models.

Science.gov (United States)

Fernández Zacarías, F; Beira Jiménez, J L; Bustillo Velázquez-Gaztelu, P J; Hernández Molina, R; Lubián López, Simón

2018-04-01

Preterm infants usually have to spend a long time in an incubator, excessive noise in which can have adverse physiological and psychological effects on neonates. In fact, incubator noise levels typically range from 45 to 70 dB but differences in this respect depend largely on the noise measuring method used. The primary aim of this work was to assess the extent to which noise in an incubator comes from its own fan and how efficiently the incubator can isolate external noise. Three different incubator models were characterized for acoustic performance by measuring their internal noise levels in an anechoic chamber, and also for noise isolation efficiency by using a pink noise source in combination with an internal and an external microphone that were connected to an SVAN958 noise analyzer. The incubators studied produced continuous equivalent noise levels of 53.5-58 dB and reduced external noise by 5.2-10.4 dB. A preterm infant in an incubator is exposed to noise levels clearly exceeding international recommendations even though such levels usually comply with the limit set in the standard IEC60601-2-19: 2009 (60 dBA) under normal conditions of use. Copyright © 2018. Published by Elsevier B.V.

Aerodynamics of Rotorcraft (L’Aerodynamique des Aeronefs a Voilure Tournante)

Science.gov (United States)

1990-11-01

appreciate wether or not the airfoil drag was liable to differ significantly from the 2-D value imposed In the CAMRAD calculation. Rotor blade boundary layer...0079, 1986 24. P.G. Wilby, M.J. Riley, Judith Miller, "Some unsteady effects on helicopter rotors." 7th European Rotorcraft and Powered Lift Forum...1981 W b 9-20 25. H.J. Riley, Judith Miller, "Pressure distributions on a helicopter swept tip from flight tests and from calculations", Paper No 9, 9th

Total Variation Based Parameter-Free Model for Impulse Noise Removal

DEFF Research Database (Denmark)

Sciacchitano, Federica; Dong, Yiqiu; Andersen, Martin Skovgaard

2017-01-01

We propose a new two-phase method for reconstruction of blurred images corrupted by impulse noise. In the first phase, we use a noise detector to identify the pixels that are contaminated by noise, and then, in the second phase, we reconstruct the noisy pixels by solving an equality constrained...... total variation minimization problem that preserves the exact values of the noise-free pixels. For images that are only corrupted by impulse noise (i. e., not blurred) we apply the semismooth Newton's method to a reduced problem, and if the images are also blurred, we solve the equality constrained...... reconstruction problem using a first-order primal-dual algorithm. The proposed model improves the computational efficiency (in the denoising case) and has the advantage of being regularization parameter-free. Our numerical results suggest that the method is competitive in terms of its restoration capabilities...

Development of Seasonal ARIMA Models for Traffic Noise Forecasting

Directory of Open Access Journals (Sweden)

Guarnaccia Claudio

2017-01-01

Full Text Available In this paper, a time series analysis approach is adopted to monitor and predict a traffic noise levels dataset, measured in a site of Messina, Italy. In general, acoustical noise shows a high prediction complexity, since its slope is strongly related to the variability of the sources and to intrinsic randomness. In the analysed site the predominant source is road traffic, that has a periodic and non-stationary behaviour. The study of the time evolution of this hazardous agent is very useful to assess the impact to human health and activities. The time series models adopted in this paper are of the stochastic seasonal ARIMA class; these types of model are based on the strong periodicity registered in the acoustical equivalent levels. The observed periodicity is related to the highly variability of urban traffic in the different days of the week. Three different seasonal ARIMA models are proposed and calibrated on a rich dataset of 800 sound level measurements. The predictive capabilities of these techniques are encouraging. The implemented models show a good forecasting performances in terms of low residuals, i.e. difference between observed and estimated noise values. The residuals are analysed by means of statistical indexes, plots and tests.

Evaluation of Gear Condition Indicator Performance on Rotorcraft Fleet

Science.gov (United States)

Antolick, Lance J.; Branning, Jeremy S.; Wade, Daniel R.; Dempsey, Paula J.

2010-01-01

The U.S. Army is currently expanding its fleet of Health Usage Monitoring Systems (HUMS) equipped aircraft at significant rates, to now include over 1,000 rotorcraft. Two different on-board HUMS, the Honeywell Modern Signal Processing Unit (MSPU) and the Goodrich Integrated Vehicle Health Management System (IVHMS), are collecting vibration health data on aircraft that include the Apache, Blackhawk, Chinook, and Kiowa Warrior. The objective of this paper is to recommend the most effective gear condition indicators for fleet use based on both a theoretical foundation and field data. Gear diagnostics with better performance will be recommended based on both a theoretical foundation and results of in-fleet use. In order to evaluate the gear condition indicator performance on rotorcraft fleets, results of more than five years of health monitoring for gear faults in the entire HUMS equipped Army helicopter fleet will be presented. More than ten examples of gear faults indicated by the gear CI have been compiled and each reviewed for accuracy. False alarms indications will also be discussed. Performance data from test rigs and seeded fault tests will also be presented. The results of the fleet analysis will be discussed, and a performance metric assigned to each of the competing algorithms. Gear fault diagnostic algorithms that are compliant with ADS-79A will be recommended for future use and development. The performance of gear algorithms used in the commercial units and the effectiveness of the gear CI as a fault identifier will be assessed using the criteria outlined in the standards in ADS-79A-HDBK, an Army handbook that outlines the conversion from Reliability Centered Maintenance to the On-Condition status of Condition Based Maintenance.

Weberized Mumford-Shah Model with Bose-Einstein Photon Noise

International Nuclear Information System (INIS)

Shen Jianhong; Jung, Yoon-Mo

2006-01-01

Human vision works equally well in a large dynamic range of light intensities, from only a few photons to typical midday sunlight. Contributing to such remarkable flexibility is a famous law in perceptual (both visual and aural) psychology and psychophysics known as Weber's Law. The current paper develops a new segmentation model based on the integration of Weber's Law and the celebrated Mumford-Shah segmentation model (Comm. Pure Appl. Math., vol. 42, pp. 577-685, 1989). Explained in detail are issues concerning why the classical Mumford-Shah model lacks light adaptivity, and why its 'weberized' version can more faithfully reflect human vision's superior segmentation capability in a variety of illuminance conditions from dawn to dusk. It is also argued that the popular Gaussian noise model is physically inappropriate for the weberization procedure. As a result, the intrinsic thermal noise of photon ensembles is introduced based on Bose and Einstein's distributions in quantum statistics, which turns out to be compatible with weberization both analytically and computationally. The current paper focuses on both the theory and computation of the weberized Mumford-Shah model with Bose-Einstein noise. In particular, Ambrosio-Tortorelli's Γ-convergence approximation theory is adapted (Boll. Un. Mat. Ital. B, vol. 6, pp. 105-123, 1992), and stable numerical algorithms are developed for the associated pair ofnonlinear Euler-Lagrange PDEs

Noise and Synchronization Analysis of the Cold-Receptor Neuronal Network Model

Directory of Open Access Journals (Sweden)

Ying Du

2014-01-01

Full Text Available This paper analyzes the dynamics of the cold receptor neural network model. First, it examines noise effects on neuronal stimulus in the model. From ISI plots, it is shown that there are considerable differences between purely deterministic simulations and noisy ones. The ISI-distance is used to measure the noise effects on spike trains quantitatively. It is found that spike trains observed in neural models can be more strongly affected by noise for different temperatures in some aspects; meanwhile, spike train has greater variability with the noise intensity increasing. The synchronization of neuronal network with different connectivity patterns is also studied. It is shown that chaotic and high period patterns are more difficult to get complete synchronization than the situation in single spike and low period patterns. The neuronal network will exhibit various patterns of firing synchronization by varying some key parameters such as the coupling strength. Different types of firing synchronization are diagnosed by a correlation coefficient and the ISI-distance method. The simulations show that the synchronization status of neurons is related to the network connectivity patterns.

Moment stability for a predator-prey model with parametric dichotomous noises

Science.gov (United States)

Jin, Yan-Fei

2015-06-01

In this paper, we investigate the solution moment stability for a Harrison-type predator-prey model with parametric dichotomous noises. Using the Shapiro-Loginov formula, the equations for the first-order and second-order moments are obtained and the corresponding stable conditions are given. It is found that the solution moment stability depends on the noise intensity and correlation time of noise. The first-order and second-order moments become unstable with the decrease of correlation time. That is, the dichotomous noise can improve the solution moment stability with respect to Gaussian white noise. Finally, some numerical results are presented to verify the theoretical analyses. Project supported by the National Natural Science Foundation of China (Grant No. 11272051).

Evaluation of substitution monopole models for tire noise sound synthesis

Science.gov (United States)

Berckmans, D.; Kindt, P.; Sas, P.; Desmet, W.

2010-01-01

Due to the considerable efforts in engine noise reduction, tire noise has become one of the major sources of passenger car noise nowadays and the demand for accurate prediction models is high. A rolling tire is therefore experimentally characterized by means of the substitution monopole technique, suiting a general sound synthesis approach with a focus on perceived sound quality. The running tire is substituted by a monopole distribution covering the static tire. All monopoles have mutual phase relationships and a well-defined volume velocity distribution which is derived by means of the airborne source quantification technique; i.e. by combining static transfer function measurements with operating indicator pressure measurements close to the rolling tire. Models with varying numbers/locations of monopoles are discussed and the application of different regularization techniques is evaluated.

A Stochastic Approach to Noise Modeling for Barometric Altimeters

Directory of Open Access Journals (Sweden)

Angelo Maria Sabatini

2013-11-01

Full Text Available The question whether barometric altimeters can be applied to accurately track human motions is still debated, since their measurement performance are rather poor due to either coarse resolution or drifting behavior problems. As a step toward accurate short-time tracking of changes in height (up to few minutes, we develop a stochastic model that attempts to capture some statistical properties of the barometric altimeter noise. The barometric altimeter noise is decomposed in three components with different physical origin and properties: a deterministic time-varying mean, mainly correlated with global environment changes, and a first-order Gauss-Markov (GM random process, mainly accounting for short-term, local environment changes, the effects of which are prominent, respectively, for long-time and short-time motion tracking; an uncorrelated random process, mainly due to wideband electronic noise, including quantization noise. Autoregressive-moving average (ARMA system identification techniques are used to capture the correlation structure of the piecewise stationary GM component, and to estimate its standard deviation, together with the standard deviation of the uncorrelated component. M-point moving average filters used alone or in combination with whitening filters learnt from ARMA model parameters are further tested in few dynamic motion experiments and discussed for their capability of short-time tracking small-amplitude, low-frequency motions.

Computer Modelling of Functional Aspects of Noise in Endogenously Oscillating Neurons

Science.gov (United States)

Huber, M. T.; Dewald, M.; Voigt, K.; Braun, H. A.; Moss, F.

1998-03-01

Membrane potential oscillations are a widespread feature of neuronal activity. When such oscillations operate close to the spike-triggering threshold, noise can become an essential property of spike-generation. According to that, we developed a minimal Hodgkin-Huxley-type computer model which includes a noise term. This model accounts for experimental data from quite different cells ranging from mammalian cortical neurons to fish electroreceptors. With slight modifications of the parameters, the model's behavior can be tuned to bursting activity, which additionally allows it to mimick temperature encoding in peripheral cold receptors including transitions to apparently chaotic dynamics as indicated by methods for the detection of unstable periodic orbits. Under all conditions, cooperative effects between noise and nonlinear dynamics can be shown which, beyond stochastic resonance, might be of functional significance for stimulus encoding and neuromodulation.

Information contraction and extraction by multivariate autoregressive (MAR) modelling. Pt. 2. Dominant noise sources in BWRS

International Nuclear Information System (INIS)

Morishima, N.

1996-01-01

The multivariate autoregressive (MAR) modeling of a vector noise process is discussed in terms of the estimation of dominant noise sources in BWRs. The discussion is based on a physical approach: a transfer function model on BWR core dynamics is utilized in developing a noise model; a set of input-output relations between three system variables and twelve different noise sources is obtained. By the least-square fitting of a theoretical PSD on neutron noise to an experimental one, four kinds of dominant noise sources are selected. It is shown that some of dominant noise sources consist of two or more different noise sources and have the spectral properties of being coloured and correlated with each other. By diagonalizing the PSD matrix for dominant noise sources, we may obtain an MAR expression for a vector noise process as a response to the diagonal elements(i.e. residual noises) being white and mutually-independent. (Author)

V/STOL Rotary Propulsor Noise Prediction Model Update and Evaluation.

Science.gov (United States)

1979-12-01

Noise as Observed on and Jacques the Bertin Aerotrain July 1976 JSV 54(2) 3) Hoch, Berthelot Use of the Bertin Aerotrain for the Investigation July 1976...Atencio G.E. X376-B Jots 2 Drevet, et al Aerotrain - G.E. J85 9 Jaeck Wind Tunnel - G.E. J85 Nozzles 13 Pacbian, et al Wind Tunnel Model Jet 23 Brooks...Calculat6d Full-Scale Jet Noise Data Base Item 2. - This paper presents measurements made of the noise from a J85 engine installed on the Aerotrain . Data

Large rotorcraft transmission technology development program

Science.gov (United States)

Mack, J. C.

1983-01-01

Testing of a U.S. Army XCH-62 HLH aft rotor transmission under NASA Contract NAS 3-22143 was successfully completed. This test establishes the feasibility of large, high power rotorcraft transmissions as well as demonstrating the resolution of deficiencies identified during the HLH advanced technology programs and reported by USAAMRDLTR-77-38. Over 100 hours of testing was conducted. At the 100% design power rating of 10,620 horsepower, the power transferred through a single spiral bevel gear mesh is more than twice that of current helicopter bevel gearing. In the original design of these gears, industry-wide design methods were employed and failures were experienced which identified problem areas unique to gear size. To remedy this technology shortfall, a program was developed to predict gear stresses using finite element analysis for complete and accurate representation of the gear tooth and supporting structure. To validate the finite element methodology gear strain data from the existing U.S. Army HLH aft transmission was acquired, and existing data from smaller gears were made available.

Modeling speech intelligibility based on the signal-to-noise envelope power ratio

DEFF Research Database (Denmark)

Jørgensen, Søren

of modulation frequency selectivity in the auditory processing of sound with a decision metric for intelligibility that is based on the signal-to-noise envelope power ratio (SNRenv). The proposed speech-based envelope power spectrum model (sEPSM) is demonstrated to account for the effects of stationary...... through three commercially available mobile phones. The model successfully accounts for the performance across the phones in conditions with a stationary speech-shaped background noise, whereas deviations were observed in conditions with “Traffic” and “Pub” noise. Overall, the results of this thesis...

Extracting the noise spectral densities parameters of JFET transistor by modeling a nuclear electronics channel response

International Nuclear Information System (INIS)

Assaf, J.

2009-07-01

Mathematical model for the RMS noise of JFET transistor has been realized. Fitting the model according to the experimental results gives the noise spectral densities values. Best fitting was for the model of three noise sources and real preamplifier transfer function. After gamma irradiation, an additional and important noise sources appeared and two point defects are estimated through the fitting process. (author)

Effects of noise on a computational model for disease states of mood disorders

Science.gov (United States)

Tobias Huber, Martin; Krieg, Jürgen-Christian; Braun, Hans Albert; Moss, Frank

2000-03-01

Nonlinear dynamics are currently proposed to explain the progressive course of recurrent mood disorders starting with isolated episodes and ending with accelerated irregular (``chaotic") mood fluctuations. Such a low-dimensional disease model is attractive because of its principal accordance with biological disease models, i.e. the kindling and biological rhythms model. However, most natural systems are nonlinear and noisy and several studies in the neuro- and physical sciences have demonstrated interesting cooperative behaviors arising from interacting random and deterministic dynamics. Here, we consider the effects of noise on a recent neurodynamical model for the timecourse of affective disorders (Huber et al.: Biological Psychiatry 1999;46:256-262). We describe noise effects on temporal patterns and mean episode frequencies of various in computo disease states. Our simulations demonstrate that noise can cause unstructured randomness or can maximize periodic order. The frequency of episode occurence can increase with noise but it can also remain unaffected or even can decrease. We show further that noise can make visible bifurcations before they would normally occur under deterministic conditions and we quantify this behavior with a recently developed statistical method. All these effects depend critically on both, the dynamic state and the noise intensity. Implications for neurobiology and course of mood disorders are discussed.

An approximate fractional Gaussian noise model with computational cost

KAUST Repository

Sø rbye, Sigrunn H.; Myrvoll-Nilsen, Eirik; Rue, Haavard

2017-01-01

Fractional Gaussian noise (fGn) is a stationary time series model with long memory properties applied in various fields like econometrics, hydrology and climatology. The computational cost in fitting an fGn model of length $n$ using a likelihood

Noise Localization Method for Model Tests in a Large Cavitation Tunnel Using a Hydrophone Array

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Cheolsoo Park

2016-02-01

Full Text Available Model tests are performed in order to predict the noise level of a full ship and to control its noise signature. Localizing noise sources in the model test is therefore an important research subject along with measuring noise levels. In this paper, a noise localization method using a hydrophone array in a large cavitation tunnel is presented. The 45-channel hydrophone array was designed using a global optimization technique for noise measurement. A set of noise experiments was performed in the KRISO (Korea Research Institute of Ships & Ocean Engineering large cavitation tunnel using scaled models, including a ship with a single propeller, a ship with twin propellers and an underwater vehicle. The incoherent broadband processors defined based on the Bartlett and the minimum variance (MV processors were applied to the measured data. The results of data analysis and localization are presented in the paper. Finally, it is shown that the mechanical noise, as well as the propeller noise can be successfully localized using the proposed localization method.

Approximations to camera sensor noise

Science.gov (United States)

Jin, Xiaodan; Hirakawa, Keigo

2013-02-01

Noise is present in all image sensor data. Poisson distribution is said to model the stochastic nature of the photon arrival process, while it is common to approximate readout/thermal noise by additive white Gaussian noise (AWGN). Other sources of signal-dependent noise such as Fano and quantization also contribute to the overall noise profile. Question remains, however, about how best to model the combined sensor noise. Though additive Gaussian noise with signal-dependent noise variance (SD-AWGN) and Poisson corruption are two widely used models to approximate the actual sensor noise distribution, the justification given to these types of models are based on limited evidence. The goal of this paper is to provide a more comprehensive characterization of random noise. We concluded by presenting concrete evidence that Poisson model is a better approximation to real camera model than SD-AWGN. We suggest further modification to Poisson that may improve the noise model.

Noise variation by compressive stress on the model core of power transformers

Energy Technology Data Exchange (ETDEWEB)

Mizokami, Masato, E-mail: mizokami.g76.masato@jp.nssmc.com; Kurosaki, Yousuke

2015-05-01

The reduction of audible noise generated by cores for power transformers has been required due to environmental concern. It is known that compressive stress in the rolling direction of electrical steel affects magnetostriction and it can result in an increase in noise level. In this research, the effect of compressive stress to noise was investigated on a 3-phase 3-limb model core. Compressive stress was applied in the rolling direction of the limbs from the outside of the core. It increased the sound pressure levels and the slope of the rise was about 2 dBA/MPa. Magnetostriction on single sheet samples was also measured under compressive stress and the harmonic components of the magnetostriction were compared with those of noise. It revealed that the variation in magnetostriction with compressive stress did not entirely correspond to that in noise. In one of the experiments, localized bending happened on one limb during compressing the core. While deformation of the core had not been intended, the noise was measured. The deformation increased the noise by more than 10 dBA and it occurred on most of the harmonic components. - Highlights: • Audible noise was measured on a model core to which compressive stress was applied. • The stress in the rolling direction of the steel causes a rise in noise level. • The slope of the rise in sound pressure level up to 2.5 MPa is about 2 dBA/MPa. • Variation in magnetostriction by stress does not entirely agree with that in noise. • Bend arisen in the core causes an extreme increase in noise.

Noise variation by compressive stress on the model core of power transformers

International Nuclear Information System (INIS)

Mizokami, Masato; Kurosaki, Yousuke

2015-01-01

The reduction of audible noise generated by cores for power transformers has been required due to environmental concern. It is known that compressive stress in the rolling direction of electrical steel affects magnetostriction and it can result in an increase in noise level. In this research, the effect of compressive stress to noise was investigated on a 3-phase 3-limb model core. Compressive stress was applied in the rolling direction of the limbs from the outside of the core. It increased the sound pressure levels and the slope of the rise was about 2 dBA/MPa. Magnetostriction on single sheet samples was also measured under compressive stress and the harmonic components of the magnetostriction were compared with those of noise. It revealed that the variation in magnetostriction with compressive stress did not entirely correspond to that in noise. In one of the experiments, localized bending happened on one limb during compressing the core. While deformation of the core had not been intended, the noise was measured. The deformation increased the noise by more than 10 dBA and it occurred on most of the harmonic components. - Highlights: • Audible noise was measured on a model core to which compressive stress was applied. • The stress in the rolling direction of the steel causes a rise in noise level. • The slope of the rise in sound pressure level up to 2.5 MPa is about 2 dBA/MPa. • Variation in magnetostriction by stress does not entirely agree with that in noise. • Bend arisen in the core causes an extreme increase in noise

Compact modelling of InAlN/GaN HEMT for low noise applications

International Nuclear Information System (INIS)

Sakalas, P; Šimukovič, A; Matulionis, A; Piotrowicz, S; Jardel, O; Delage, S L; Mukherjee, A

2014-01-01

This paper presents results of high-frequency noise modelling of InAlN/GaN high electron mobility transistors (HEMTs) with different formulations of the minimum noise figure NF min . Current–voltage characteristics and s-parameters of 0.15 μm gate length and 2 × 75 μm gate width InAlN/GaN HEMTs were measured at room temperature in a wide frequency range (300 MHz to 50 GHz) and bias range (V GS from −4.8 to 1 V and V DS from 0 to 21 V). Both the EEHEMT1 and Angelov GaN compact models yielded excellent agreement for transfer and output characteristics, transconductance g m , and f T , f max. High-frequency noise parameters NF min , R n , Γ OPT of InAlN/GaN HEMT were measured in 8–50 GHz frequency band. Noise formulation within the EEHEMT1 model underestimates the measured NF min and R n . The well known three-parameter PRC noise model is in a better agreement with the measured data but neglects the shot noise resulting from the gate leakage. The inductive degenerated source matching method and EEHEMT1 were used to design a single stage LNA operated at 8 GHz frequency. A 10 dB gain with an input reflection of −12 dB with a 2.5 dB of noise factor were obtained at 8 GHz. (paper)

Predicting the Inflow Distortion Tone Noise of the NASA Glenn Advanced Noise Control Fan with a Combined Quadrupole-Dipole Model

Science.gov (United States)

Koch, L. Danielle

2012-01-01

A combined quadrupole-dipole model of fan inflow distortion tone noise has been extended to calculate tone sound power levels generated by obstructions arranged in circumferentially asymmetric locations upstream of a rotor. Trends in calculated sound power level agreed well with measurements from tests conducted in 2007 in the NASA Glenn Advanced Noise Control Fan. Calculated values of sound power levels radiated upstream were demonstrated to be sensitive to the accuracy of the modeled wakes from the cylindrical rods that were placed upstream of the fan to distort the inflow. Results indicate a continued need to obtain accurate aerodynamic predictions and measurements at the fan inlet plane as engineers work towards developing fan inflow distortion tone noise prediction tools.

Persistence and extinction for stochastic logistic model with Levy noise and impulsive perturbation

Directory of Open Access Journals (Sweden)

Chun Lu

2015-09-01

Full Text Available This article investigates a stochastic logistic model with Levy noise and impulsive perturbation. In the model, the impulsive perturbation and Levy noise are taken into account simultaneously. This model is new and more feasible and more accordance with the actual. The definition of solution to a stochastic differential equation with Levy noise and impulsive perturbation is established. Based on this definition, we show that our model has a unique global positive solution and obtains its explicit expression. Sufficient conditions for extinction are established as well as nonpersistence in the mean, weak persistence and stochastic permanence. The threshold between weak persistence and extinction is obtained.

ARMA modelling of neutron stochastic processes with large measurement noise

International Nuclear Information System (INIS)

Zavaljevski, N.; Kostic, Lj.; Pesic, M.

1994-01-01

An autoregressive moving average (ARMA) model of the neutron fluctuations with large measurement noise is derived from langevin stochastic equations and validated using time series data obtained during prompt neutron decay constant measurements at the zero power reactor RB in Vinca. Model parameters are estimated using the maximum likelihood (ML) off-line algorithm and an adaptive pole estimation algorithm based on the recursive prediction error method (RPE). The results show that subcriticality can be determined from real data with high measurement noise using much shorter statistical sample than in standard methods. (author)

A high-resolution ambient seismic noise model for Europe

Science.gov (United States)

Kraft, Toni

2014-05-01

measurement precision (i.e. earthquake location), while considering this extremely complex boundary condition. To solve this problem I have developed a high-resolution ambient seismic noise model for Europe. The model is based on land-use data derived from satellite imagery by the EU-project CORINE in a resolution of 100x100m. The the CORINE data consists of several land-use classes, which, besides others, contain: industrial areas, mines, urban fabric, agricultural areas, permanent corps, forests and open spaces. Additionally, open GIS data for highways, and major and minor roads and railway lines were included from the OpenStreetMap project (www.openstreetmap.org). This data was divided into three classes that represent good, intermediate and bad ambient conditions of the corresponding land-use class based on expert judgment. To account for noise propagation away from its source a smoothing operator was applied to individual land-use noise-fields. Finally, the noise-fields were stacked to obtain an European map of ambient noise conditions. A calibration of this map with data of existing seismic stations Europe allowed me to estimate the expected noise level in actual ground motion units for the three ambient noise condition classes of the map. The result is a high-resolution ambient seismic noise map, that allows the network designer to make educated predictions on the expected noise level for arbitrary location in Europe. The ambient noise model was successfully tested in several network optimization projects in Switzerland and surrounding countries and will hopefully be a valuable contribution to improving the data quality of microseismic monitoring networks in Europe.

Modeling vehicle interior noise exposure dose on freeways: Considering weaving segment designs and engine operation.

Science.gov (United States)

Li, Qing; Qiao, Fengxiang; Yu, Lei; Shi, Junqing

2017-07-05

Vehicle interior noise functions at the dominant frequencies of 500 Hz below and around 800 Hz, which fall into the bands that may impair hearing. Recent studies demonstrated that freeway commuters are chronically exposed to vehicle interior noise, bearing the risk of hearing impairment. The interior noise evaluation process is mostly conducted in a laboratory environment. The test results and the developed noise models may underestimate or ignore the noise effects from dynamic traffic and road conditions and configuration. However, the interior noise is highly associated with vehicle maneuvering. The vehicle maneuvering on a freeway weaving segment is more complex because of its nature of conflicting areas. This research is intended to explore the risk of the interior noise exposure on freeway weaving segments for freeway commuters and to improve the interior noise estimation by constructing a decision tree learning-based noise exposure dose (NED) model, considering weaving segment designs and engine operation. On-road driving tests were conducted on 12 subjects on State Highway 288 in Houston, Texas. On-board Diagnosis (OBD) II, a smartphone-based roughness app, and a digital sound meter were used to collect vehicle maneuvering and engine information, International Roughness Index, and interior noise levels, respectively. Eleven variables were obtainable from the driving tests, including the length and type of a weaving segment, serving as predictors. The importance of the predictors was estimated by their out-of-bag-permuted predictor delta errors. The hazardous exposure level of the interior noise on weaving segments was quantified to hazard quotient, NED, and daily noise exposure level, respectively. Results showed that the risk of hearing impairment on freeway is acceptable; the interior noise level is the most sensitive to the pavement roughness and is subject to freeway configuration and traffic conditions. The constructed NED model shows high predictive

Helicopter model rotor-blade vortex interaction impulsive noise: Scalability and parametric variations

Science.gov (United States)

Splettstoesser, W. R.; Schultz, K. J.; Boxwell, D. A.; Schmitz, F. H.

1984-01-01

Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale remarkable well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224 to 0.270), the scaling deteriorates, suggesting that the model scale rotor is not adequately simulating the full scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters - tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient - are highly sensitive to BVI noise radiation.

75 FR 50688 - Special Conditions: Erickson Air-Crane Incorporated S-64E and S-64F Rotorcraft

Science.gov (United States)

2010-08-17

... rotorcraft load combination classes for the special condition requirements concerning placards. (d) Modifying... of weight, altitude, and temperature for which takeoff and landing data are scheduled. The flight... determined at each weight, altitude, and temperature for which certification is sought with one engine...

Modeling and Compensating Temperature-Dependent Non-Uniformity Noise in IR Microbolometer Cameras

Directory of Open Access Journals (Sweden)

Alejandro Wolf

2016-07-01

Full Text Available Images rendered by uncooled microbolometer-based infrared (IR cameras are severely degraded by the spatial non-uniformity (NU noise. The NU noise imposes a fixed-pattern over the true images, and the intensity of the pattern changes with time due to the temperature instability of such cameras. In this paper, we present a novel model and a compensation algorithm for the spatial NU noise and its temperature-dependent variations. The model separates the NU noise into two components: a constant term, which corresponds to a set of NU parameters determining the spatial structure of the noise, and a dynamic term, which scales linearly with the fluctuations of the temperature surrounding the array of microbolometers. We use a black-body radiator and samples of the temperature surrounding the IR array to offline characterize both the constant and the temperature-dependent NU noise parameters. Next, the temperature-dependent variations are estimated online using both a spatially uniform Hammerstein-Wiener estimator and a pixelwise least mean squares (LMS estimator. We compensate for the NU noise in IR images from two long-wave IR cameras. Results show an excellent NU correction performance and a root mean square error of less than 0.25 ∘ C, when the array’s temperature varies by approximately 15 ∘ C.

An analytical model for studying noise effects in PWR type reactors

International Nuclear Information System (INIS)

Meyer, K.

1975-10-01

An analytical model based on the one-group diffusion method is described. It has been used for calculating the axial dependence of the spectral density of the ionization chamber noise supposing a site-independent stationary neutron flux distribution. Coolant inlet temperature fluctuations are considered as noise sources. (author)

Edgeworth Expansion Based Model for the Convolutional Noise pdf

Directory of Open Access Journals (Sweden)

Yonatan Rivlin

2014-01-01

Full Text Available Recently, the Edgeworth expansion up to order 4 was used to represent the convolutional noise probability density function (pdf in the conditional expectation calculations where the source pdf was modeled with the maximum entropy density approximation technique. However, the applied Lagrange multipliers were not the appropriate ones for the chosen model for the convolutional noise pdf. In this paper we use the Edgeworth expansion up to order 4 and up to order 6 to model the convolutional noise pdf. We derive the appropriate Lagrange multipliers, thus obtaining new closed-form approximated expressions for the conditional expectation and mean square error (MSE as a byproduct. Simulation results indicate hardly any equalization improvement with Edgeworth expansion up to order 4 when using optimal Lagrange multipliers over a nonoptimal set. In addition, there is no justification for using the Edgeworth expansion up to order 6 over the Edgeworth expansion up to order 4 for the 16QAM and easy channel case. However, Edgeworth expansion up to order 6 leads to improved equalization performance compared to the Edgeworth expansion up to order 4 for the 16QAM and hard channel case as well as for the case where the 64QAM is sent via an easy channel.

Computer vision techniques for rotorcraft low-altitude flight

Science.gov (United States)

Sridhar, Banavar; Cheng, Victor H. L.

1988-01-01

A description is given of research that applies techniques from computer vision to automation of rotorcraft navigation. The effort emphasizes the development of a methodology for detecting the ranges to obstacles in the region of interest based on the maximum utilization of passive sensors. The range map derived from the obstacle detection approach can be used as obstacle data for the obstacle avoidance in an automataic guidance system and as advisory display to the pilot. The lack of suitable flight imagery data, however, presents a problem in the verification of concepts for obstacle detection. This problem is being addressed by the development of an adequate flight database and by preprocessing of currently available flight imagery. Some comments are made on future work and how research in this area relates to the guidance of other autonomous vehicles.

Development of a noise prediction model based on advanced fuzzy approaches in typical industrial workrooms.

Science.gov (United States)

Aliabadi, Mohsen; Golmohammadi, Rostam; Khotanlou, Hassan; Mansoorizadeh, Muharram; Salarpour, Amir

2014-01-01

Noise prediction is considered to be the best method for evaluating cost-preventative noise controls in industrial workrooms. One of the most important issues is the development of accurate models for analysis of the complex relationships among acoustic features affecting noise level in workrooms. In this study, advanced fuzzy approaches were employed to develop relatively accurate models for predicting noise in noisy industrial workrooms. The data were collected from 60 industrial embroidery workrooms in the Khorasan Province, East of Iran. The main acoustic and embroidery process features that influence the noise were used to develop prediction models using MATLAB software. Multiple regression technique was also employed and its results were compared with those of fuzzy approaches. Prediction errors of all prediction models based on fuzzy approaches were within the acceptable level (lower than one dB). However, Neuro-fuzzy model (RMSE=0.53dB and R2=0.88) could slightly improve the accuracy of noise prediction compared with generate fuzzy model. Moreover, fuzzy approaches provided more accurate predictions than did regression technique. The developed models based on fuzzy approaches as useful prediction tools give professionals the opportunity to have an optimum decision about the effectiveness of acoustic treatment scenarios in embroidery workrooms.

Circuit Models and Experimental Noise Measurements of Micropipette Amplifiers for Extracellular Neural Recordings from Live Animals

Directory of Open Access Journals (Sweden)

Chang Hao Chen

2014-01-01

Full Text Available Glass micropipettes are widely used to record neural activity from single neurons or clusters of neurons extracellularly in live animals. However, to date, there has been no comprehensive study of noise in extracellular recordings with glass micropipettes. The purpose of this work was to assess various noise sources that affect extracellular recordings and to create model systems in which novel micropipette neural amplifier designs can be tested. An equivalent circuit of the glass micropipette and the noise model of this circuit, which accurately describe the various noise sources involved in extracellular recordings, have been developed. Measurement schemes using dead brain tissue as well as extracellular recordings from neurons in the inferior colliculus, an auditory brain nucleus of an anesthetized gerbil, were used to characterize noise performance and amplification efficacy of the proposed micropipette neural amplifier. According to our model, the major noise sources which influence the signal to noise ratio are the intrinsic noise of the neural amplifier and the thermal noise from distributed pipette resistance. These two types of noise were calculated and measured and were shown to be the dominating sources of background noise for in vivo experiments.

Theory of fluctuations and parametric noise in a point nuclear reactor model

International Nuclear Information System (INIS)

Rodriguez, M.A.; San Miguel, M.; Sancho, J.M.

1984-01-01

We present a joint description of internal fluctuations and parametric noise in a point nuclear reactor model in which delayed neutrons and a detector are considered. We obtain kinetic equations for the first moments and define effective kinetic parameters which take into account the effect of parametric Gaussian white noise. We comment on the validity of Langevin approximations for this problem. We propose a general method to deal with weak but otherwise arbitrary non-white parametric noise. Exact kinetic equations are derived for Gaussian non-white noise. (author)

Robustness of digitally modulated signal features against variation in HF noise model

Directory of Open Access Journals (Sweden)

Shoaib Mobien

2011-01-01

Full Text Available Abstract High frequency (HF band has both military and civilian uses. It can be used either as a primary or backup communication link. Automatic modulation classification (AMC is of an utmost importance in this band for the purpose of communications monitoring; e.g., signal intelligence and spectrum management. A widely used method for AMC is based on pattern recognition (PR. Such a method has two main steps: feature extraction and classification. The first step is generally performed in the presence of channel noise. Recent studies show that HF noise could be modeled by Gaussian or bi-kappa distributions, depending on day-time. Therefore, it is anticipated that change in noise model will have impact on features extraction stage. In this article, we investigate the robustness of well known digitally modulated signal features against variation in HF noise. Specifically, we consider temporal time domain (TTD features, higher order cumulants (HOC, and wavelet based features. In addition, we propose new features extracted from the constellation diagram and evaluate their robustness against the change in noise model. This study is targeting 2PSK, 4PSK, 8PSK, 16QAM, 32QAM, and 64QAM modulations, as they are commonly used in HF communications.

Controlling Decoherence in Superconducting Qubits: Phenomenological Model and Microscopic Origin of 1/f Noise

Science.gov (United States)

2011-04-28

quasiparticle poisoning which include a completely novel physical origin of these noises. We also proposed a model for excess low frequency flux noise which...and quasiparticle poisoning which include a completely novel physical origin of these noises. We also proposed a model for excess low frequency flux...metallic nanomechanical resonators, Phys. Rev. B 81, 184112 (2010). 3) L. Faoro, A. Kitaev and L. B. Ioffe, Quasiparticle poisoning and Josephson current

Noise in strong laser-atom interactions: Phase telegraph noise

International Nuclear Information System (INIS)

Eberly, J.H.; Wodkiewicz, K.; Shore, B.W.

1984-01-01

We discuss strong laser-atom interactions that are subjected to jump-type (random telegraph) random-phase noise. Physically, the jumps may arise from laser fluctuations, from collisions of various kinds, or from other external forces. Our discussion is carried out in two stages. First, direct and partially heuristic calculations determine the laser spectrum and also give a third-order differential equation for the average inversion of a two-level atom on resonance. At this stage a number of general features of the interaction are able to be studied easily. The optical analog of motional narrowing, for example, is clearly predicted. Second, we show that the theory of generalized Poisson processes allows laser-atom interactions in the presence of random telegraph noise of all kinds (not only phase noise) to be treated systematically, by means of a master equation first used in the context of quantum optics by Burshtein. We use the Burshtein equation to obtain an exact expression for the two-level atom's steady-state resonance fluorescence spectrum, when the exciting laser exhibits phase telegraph noise. Some comparisons are made with results obtained from other noise models. Detailed treatments of the effects ofmly jumps, or as a model of finite laser bandwidth effects, in which the laser frequency exhibits random jumps. We show that these two types of frequency noise can be distinguished in light-scattering spectra. We also discuss examples which demonstrate both temporal and spectral motional narrowing, nonexponential correlations, and non-Lorentzian spectra. Its exact solubility in finite terms makes the frequency-telegraph noise model an attractive alternative to the white-noise Ornstein-Uhlenbeck frequency noise model which has been previously applied to laser-atom interactions

Poisson-Gaussian Noise Reduction Using the Hidden Markov Model in Contourlet Domain for Fluorescence Microscopy Images

Science.gov (United States)

Yang, Sejung; Lee, Byung-Uk

2015-01-01

In certain image acquisitions processes, like in fluorescence microscopy or astronomy, only a limited number of photons can be collected due to various physical constraints. The resulting images suffer from signal dependent noise, which can be modeled as a Poisson distribution, and a low signal-to-noise ratio. However, the majority of research on noise reduction algorithms focuses on signal independent Gaussian noise. In this paper, we model noise as a combination of Poisson and Gaussian probability distributions to construct a more accurate model and adopt the contourlet transform which provides a sparse representation of the directional components in images. We also apply hidden Markov models with a framework that neatly describes the spatial and interscale dependencies which are the properties of transformation coefficients of natural images. In this paper, an effective denoising algorithm for Poisson-Gaussian noise is proposed using the contourlet transform, hidden Markov models and noise estimation in the transform domain. We supplement the algorithm by cycle spinning and Wiener filtering for further improvements. We finally show experimental results with simulations and fluorescence microscopy images which demonstrate the improved performance of the proposed approach. PMID:26352138

White Noise Assumptions Revisited : Regression Models and Statistical Designs for Simulation Practice

NARCIS (Netherlands)

Kleijnen, J.P.C.

2006-01-01

Classic linear regression models and their concomitant statistical designs assume a univariate response and white noise.By definition, white noise is normally, independently, and identically distributed with zero mean.This survey tries to answer the following questions: (i) How realistic are these

Stochastic resonance in a gain-noise model of a single-mode laser driven by pump noise and quantum noise with cross-correlation between real and imaginary parts under direct signal modulation

Institute of Scientific and Technical Information of China (English)

Chen Li-Mei; Cao Li; Wu Da-Jin

2007-01-01

Stochastic resonance (SR) is studied in a gain-noise model of a single-mode laser driven by a coloured pump noise and a quantum noise with cross-correlation between real and imaginary parts under a direct signal modulation. By using a linear approximation method, we find that the SR appears during the variation of signal-to-noise ratio (SNR)separately with the pump noise self-correlation time τ, the noise correlation coefficient between the real part and the imaginary part of the quantum noise λq, the attenuation coefficient γ and the deterministic steady-state intensity I0.In addition, it is found that the SR can be characterized not only by the dependence of SNR on the noise variables of τand λq, but also by the dependence of SNR on the laser system variables of γ and I0. Thus our investigation extends the characteristic quantity of SR proposed before.

Auto Regressive Moving Average (ARMA) Modeling Method for Gyro Random Noise Using a Robust Kalman Filter

Science.gov (United States)

Huang, Lei

2015-01-01

To solve the problem in which the conventional ARMA modeling methods for gyro random noise require a large number of samples and converge slowly, an ARMA modeling method using a robust Kalman filtering is developed. The ARMA model parameters are employed as state arguments. Unknown time-varying estimators of observation noise are used to achieve the estimated mean and variance of the observation noise. Using the robust Kalman filtering, the ARMA model parameters are estimated accurately. The developed ARMA modeling method has the advantages of a rapid convergence and high accuracy. Thus, the required sample size is reduced. It can be applied to modeling applications for gyro random noise in which a fast and accurate ARMA modeling method is required. PMID:26437409

Observations and modeling of seismic background noise

Science.gov (United States)

Peterson, Jon R.

1993-01-01

The preparation of this report had two purposes. One was to present a catalog of seismic background noise spectra obtained from a worldwide network of seismograph stations. The other purpose was to refine and document models of seismic background noise that have been in use for several years. The second objective was, in fact, the principal reason that this study was initiated and influenced the procedures used in collecting and processing the data.With a single exception, all of the data used in this study were extracted from the digital data archive at the U.S. Geological Survey's Albuquerque Seismological Laboratory (ASL). This archive dates from 1972 when ASL first began deploying digital seismograph systems and collecting and distributing digital data under the sponsorship of the Defense Advanced Research Projects Agency (DARPA). There have been many changes and additions to the global seismograph networks during the past twenty years, but perhaps none as significant as the current deployment of very broadband seismographs by the U.S. Geological Survey (USGS) and the University of California San Diego (UCSD) under the scientific direction of the IRIS consortium. The new data acquisition systems have extended the bandwidth and resolution of seismic recording, and they utilize high-density recording media that permit the continuous recording of broadband data. The data improvements and continuous recording greatly benefit and simplify surveys of seismic background noise.Although there are many other sources of digital data, the ASL archive data were used almost exclusively because of accessibility and because the data systems and their calibration are well documented for the most part. Fortunately, the ASL archive contains high-quality data from other stations in addition to those deployed by the USGS. Included are data from UCSD IRIS/IDA stations, the Regional Seismic Test Network (RSTN) deployed by Sandia National Laboratories (SNL), and the TERRAscope network

Thirty years of progress in applications and modeling of ocean ambient noise

Science.gov (United States)

Siderius, Martin; Buckingham, Michael J.

2012-11-01

Ambient noise in the ocean is a stochastic process, which traditionally was considered to be a nuisance, since it reduced the detectability of sonar signals of interest. However, over the last thirty years, it has come to be recognized that the ambient noise itself contains useful information about the ocean and ocean processes. To extract the information, various inversion procedures have been developed, based upon which a number of practical applications of the ambient noise have evolved. Since naturally generated ambient noise is always present in the ocean, it has the advantage of being non-invasive and non-damaging to marine life, including marine mammals. In this article, a summary of the commonly encountered ambient noise models is offered, along with the associated inversion procedures, and some of the more recent applications of the ambient noise are highlighted.

Noise Simulations of the High-Lift Common Research Model

Science.gov (United States)

Lockard, David P.; Choudhari, Meelan M.; Vatsa, Veer N.; O'Connell, Matthew D.; Duda, Benjamin; Fares, Ehab

2017-01-01

The PowerFLOW(TradeMark) code has been used to perform numerical simulations of the high-lift version of the Common Research Model (HL-CRM) that will be used for experimental testing of airframe noise. Time-averaged surface pressure results from PowerFLOW(TradeMark) are found to be in reasonable agreement with those from steady-state computations using FUN3D. Surface pressure fluctuations are highest around the slat break and nacelle/pylon region, and synthetic array beamforming results also indicate that this region is the dominant noise source on the model. The gap between the slat and pylon on the HL-CRM is not realistic for modern aircraft, and most nacelles include a chine that is absent in the baseline model. To account for those effects, additional simulations were completed with a chine and with the slat extended into the pylon. The case with the chine was nearly identical to the baseline, and the slat extension resulted in higher surface pressure fluctuations but slightly reduced radiated noise. The full-span slat geometry without the nacelle/pylon was also simulated and found to be around 10 dB quieter than the baseline over almost the entire frequency range. The current simulations are still considered preliminary as changes in the radiated acoustics are still being observed with grid refinement, and additional simulations with finer grids are planned.

Aerodynamic Measurements of a Gulfstream Aircraft Model With and Without Noise Reduction Concepts

Science.gov (United States)

Neuhart, Dan H.; Hannon, Judith A.; Khorrami, Mehdi R.

2014-01-01

Steady and unsteady aerodynamic measurements of a high-fidelity, semi-span 18% scale Gulfstream aircraft model are presented. The aerodynamic data were collected concurrently with acoustic measurements as part of a larger aeroacoustic study targeting airframe noise associated with main landing gear/flap components, gear-flap interaction noise, and the viability of related noise mitigation technologies. The aeroacoustic tests were conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Wind Tunnel with the facility in the acoustically treated open-wall (jet) mode. Most of the measurements were obtained with the model in landing configuration with the flap deflected at 39º and the main landing gear on and off. Data were acquired at Mach numbers of 0.16, 0.20, and 0.24. Global forces (lift and drag) and extensive steady and unsteady surface pressure measurements were obtained. Comparison of the present results with those acquired during a previous test shows a significant reduction in the lift experienced by the model. The underlying cause was traced to the likely presence of a much thicker boundary layer on the tunnel floor, which was acoustically treated for the present test. The steady and unsteady pressure fields on the flap, particularly in the regions of predominant noise sources such as the inboard and outboard tips, remained unaffected. It is shown that the changes in lift and drag coefficients for model configurations fitted with gear/flap noise abatement technologies fall within the repeatability of the baseline configuration. Therefore, the noise abatement technologies evaluated in this experiment have no detrimental impact on the aerodynamic performance of the aircraft model.

Modelling and mitigation of wheel squeal noise amplitude

Science.gov (United States)

Meehan, Paul A.; Liu, Xiaogang

2018-01-01

The prediction of vibration amplitude and sound pressure level of wheel squeal noise is investigated using a concise mathematical model that is verified with measurements from both a rolling contact two disk test rig and a field case study. The model is used to perform an energy-based analysis to determine a closed form solution to the steady state limit cycle amplitude of creep and vibration oscillations during squealing. The analytical solution compares well with a numerical solution using an experimentally tuned creep curve with full nonlinear shape. The predicted squeal sound level trend also compares well with that recorded at various crabbing velocities (proportional to angle of attack) for the test rig at different rolling speeds. In addition, further verification is performed against many field recordings of wheel squeal on a sharp curve of 300 m. A comparison with a simplified modified result from Rudd [1] is also provided and highlights the accuracy and advantages of the present efficient model. The analytical solution provides insight into why the sound pressure level of squeal noise increases with crabbing velocity (or angle of attack) as well as how the amplitude is affected by the critical squeal parameters including a detailed investigation of modal damping. Finally, the efficient model is used to perform a parametric investigation into means of achieving a 6 dB decrease in squeal noise. The results highlight the primary importance of crabbing velocity (and angle of attack) as well as the creep curve parameters that may be controlled using third body control (ie friction modifiers). The results concur with experimental and field observations and provide important theoretical insight into the useful mechanisms of mitigating wheel squeal and quantifying their relative merits.

Swept-sine noise-induced damage as a hearing loss model for preclinical assays

Directory of Open Access Journals (Sweden)

Lorena eSanz

2015-02-01

Full Text Available Mouse models are key tools for studying cochlear alterations in noise-induced hearing loss and for evaluating new therapies. Stimuli used to induce deafness in mice are usually white and octave band noises that include very low frequencies, considering the large mouse auditory range. We designed different sound stimuli, enriched in frequencies up to 20 kHz (violet noises to examine their impact on hearing thresholds and cochlear cytoarchitecture after short exposure. In addition, we developed a cytocochleogram to quantitatively assess the ensuing structural degeneration and its functional correlation. Finally, we used this mouse model and cochleogram procedure to evaluate the potential therapeutic effect of transforming growth factor β1 inhibitors P17 and P144 on noise-induced hearing loss. CBA mice were exposed to violet swept-sine noise with different frequency ranges (2-20 or 9-13 kHz and levels (105 or 120 dB SPL for 30 minutes. Mice were evaluated by auditory brainstem response and otoacoustic emission tests prior to and 2, 14 and 28 days after noise exposure. Cochlear pathology was assessed with gross histology; hair cell number was estimated by a stereological counting method. Our results indicate that functional and morphological changes induced by violet swept-sine noise depend on the sound level and frequency composition. Partial hearing recovery followed the exposure to 105 dB SPL, whereas permanent cochlear damage resulted from the exposure to 120 dB SPL. Exposure to 9-13 kHz noise caused an auditory threshold shift in those frequencies that correlated with hair cell loss in the corresponding areas of the cochlea that were spotted on the cytocochleogram. In summary, we present mouse models of noise-induced hearing loss, which depending on the sound properties of the noise, cause different degrees of cochlear damage, and could therefore be used to study molecules which are potential players in hearing loss protection and repair.

Retrospective Correction of Physiological Noise in DTI Using an Extended Tensor Model and Peripheral Measurements

Science.gov (United States)

Mohammadi, Siawoosh; Hutton, Chloe; Nagy, Zoltan; Josephs, Oliver; Weiskopf, Nikolaus

2013-01-01

Diffusion tensor imaging is widely used in research and clinical applications, but this modality is highly sensitive to artefacts. We developed an easy-to-implement extension of the original diffusion tensor model to account for physiological noise in diffusion tensor imaging using measures of peripheral physiology (pulse and respiration), the so-called extended tensor model. Within the framework of the extended tensor model two types of regressors, which respectively modeled small (linear) and strong (nonlinear) variations in the diffusion signal, were derived from peripheral measures. We tested the performance of four extended tensor models with different physiological noise regressors on nongated and gated diffusion tensor imaging data, and compared it to an established data-driven robust fitting method. In the brainstem and cerebellum the extended tensor models reduced the noise in the tensor-fit by up to 23% in accordance with previous studies on physiological noise. The extended tensor model addresses both large-amplitude outliers and small-amplitude signal-changes. The framework of the extended tensor model also facilitates further investigation into physiological noise in diffusion tensor imaging. The proposed extended tensor model can be readily combined with other artefact correction methods such as robust fitting and eddy current correction. PMID:22936599

ARMA modeling of stochastic processes in nuclear reactor with significant detection noise

International Nuclear Information System (INIS)

Zavaljevski, N.

1992-01-01

The theoretical basis of ARMA modelling of stochastic processes in nuclear reactor was presented in a previous paper, neglecting observational noise. The identification of real reactor data indicated that in some experiments the detection noise is significant. Thus a more rigorous theoretical modelling of stochastic processes in nuclear reactor is performed. Starting from the fundamental stochastic differential equations of the Langevin type for the interaction of the detector with neutron field, a new theoretical ARMA model is developed. preliminary identification results confirm the theoretical expectations. (author)

Electrocardiogram (ECG Signal Modeling and Noise Reduction Using Hopfield Neural Networks

Directory of Open Access Journals (Sweden)

F. Bagheri

2013-02-01

Full Text Available The Electrocardiogram (ECG signal is one of the diagnosing approaches to detect heart disease. In this study the Hopfield Neural Network (HNN is applied and proposed for ECG signal modeling and noise reduction. The Hopfield Neural Network (HNN is a recurrent neural network that stores the information in a dynamic stable pattern. This algorithm retrieves a pattern stored in memory in response to the presentation of an incomplete or noisy version of that pattern. Computer simulation results show that this method can successfully model the ECG signal and remove high-frequency noise.

Assessment of physiological noise modelling methods for functional imaging of the spinal cord.

Science.gov (United States)

Kong, Yazhuo; Jenkinson, Mark; Andersson, Jesper; Tracey, Irene; Brooks, Jonathan C W

2012-04-02

The spinal cord is the main pathway for information between the central and the peripheral nervous systems. Non-invasive functional MRI offers the possibility of studying spinal cord function and central sensitisation processes. However, imaging neural activity in the spinal cord is more difficult than in the brain. A significant challenge when dealing with such data is the influence of physiological noise (primarily cardiac and respiratory), and currently there is no standard approach to account for these effects. We have previously studied the various sources of physiological noise for spinal cord fMRI at 1.5T and proposed a physiological noise model (PNM) (Brooks et al., 2008). An alternative de-noising strategy, selective averaging filter (SAF), was proposed by Deckers et al. (2006). In this study we reviewed and implemented published physiological noise correction methods at higher field (3T) and aimed to find the optimal models for gradient-echo-based BOLD acquisitions. Two general techniques were compared: physiological noise model (PNM) and selective averaging filter (SAF), along with regressors designed to account for specific signal compartments and physiological processes: cerebrospinal fluid (CSF), motion correction (MC) parameters, heart rate (HR), respiration volume per time (RVT), and the associated cardiac and respiratory response functions. Functional responses were recorded from the cervical spinal cord of 18 healthy subjects in response to noxious thermal and non-noxious punctate stimulation. The various combinations of models and regressors were compared in three ways: the model fit residuals, regression model F-tests and the number of activated voxels. The PNM was found to outperform SAF in all three tests. Furthermore, inclusion of the CSF regressor was crucial as it explained a significant amount of signal variance in the cord and increased the number of active cord voxels. Whilst HR, RVT and MC explained additional signal (noise) variance

An adaptive grid to improve the efficiency and accuracy of modelling underwater noise from shipping

Science.gov (United States)

Trigg, Leah; Chen, Feng; Shapiro, Georgy; Ingram, Simon; Embling, Clare

2017-04-01

Underwater noise from shipping is becoming a significant concern and has been listed as a pollutant under Descriptor 11 of the Marine Strategy Framework Directive. Underwater noise models are an essential tool to assess and predict noise levels for regulatory procedures such as environmental impact assessments and ship noise monitoring. There are generally two approaches to noise modelling. The first is based on simplified energy flux models, assuming either spherical or cylindrical propagation of sound energy. These models are very quick but they ignore important water column and seabed properties, and produce significant errors in the areas subject to temperature stratification (Shapiro et al., 2014). The second type of model (e.g. ray-tracing and parabolic equation) is based on an advanced physical representation of sound propagation. However, these acoustic propagation models are computationally expensive to execute. Shipping noise modelling requires spatial discretization in order to group noise sources together using a grid. A uniform grid size is often selected to achieve either the greatest efficiency (i.e. speed of computations) or the greatest accuracy. In contrast, this work aims to produce efficient and accurate noise level predictions by presenting an adaptive grid where cell size varies with distance from the receiver. The spatial range over which a certain cell size is suitable was determined by calculating the distance from the receiver at which propagation loss becomes uniform across a grid cell. The computational efficiency and accuracy of the resulting adaptive grid was tested by comparing it to uniform 1 km and 5 km grids. These represent an accurate and computationally efficient grid respectively. For a case study of the Celtic Sea, an application of the adaptive grid over an area of 160×160 km reduced the number of model executions required from 25600 for a 1 km grid to 5356 in December and to between 5056 and 13132 in August, which

A rod-airfoil experiment as a benchmark for broadband noise modeling

Energy Technology Data Exchange (ETDEWEB)

Jacob, M.C. [Ecole Centrale de Lyon, Laboratoire de Mecanique des Fluides et d' Acoustique, Ecully Cedex (France); Universite Claude Bernard/Lyon I, Villeurbanne Cedex (France); Boudet, J.; Michard, M. [Ecole Centrale de Lyon, Laboratoire de Mecanique des Fluides et d' Acoustique, Ecully Cedex (France); Casalino, D. [Ecole Centrale de Lyon, Laboratoire de Mecanique des Fluides et d' Acoustique, Ecully Cedex (France); Fluorem SAS, Ecully Cedex (France)

2005-07-01

A low Mach number rod-airfoil experiment is shown to be a good benchmark for numerical and theoretical broadband noise modeling. The benchmarking approach is applied to a sound computation from a 2D unsteady-Reynolds-averaged Navier-Stokes (U-RANS) flow field, where 3D effects are partially compensated for by a spanwise statistical model and by a 3D large eddy simulation. The experiment was conducted in the large anechoic wind tunnel of the Ecole Centrale de Lyon. Measurements taken included particle image velocity (PIV) around the airfoil, single hot wire, wall pressure coherence, and far field pressure. These measurements highlight the strong 3D effects responsible for spectral broadening around the rod vortex shedding frequency in the subcritical regime, and the dominance of the noise generated around the airfoil leading edge. The benchmarking approach is illustrated by two examples: the validation of a stochastical noise generation model applied to a 2D U-RANS computation; the assessment of a 3D LES computation using a new subgrid scale (SGS) model coupled to an advanced-time Ffowcs-Williams and Hawkings sound computation. (orig.)

Field-Deployable Acoustic Digital Systems for Noise Measurement

Science.gov (United States)

Shams, Qamar A.; Wright, Kenneth D.; Lunsford, Charles B.; Smith, Charlie D.

2000-01-01

Langley Research Center (LaRC) has for years been a leader in field acoustic array measurement technique. Two field-deployable digital measurement systems have been developed to support acoustic research programs at LaRC. For several years, LaRC has used the Digital Acoustic Measurement System (DAMS) for measuring the acoustic noise levels from rotorcraft and tiltrotor aircraft. Recently, a second system called Remote Acquisition and Storage System (RASS) was developed and deployed for the first time in the field along with DAMS system for the Community Noise Flight Test using the NASA LaRC-757 aircraft during April, 2000. The test was performed at Airborne Airport in Wilmington, OH to validate predicted noise reduction benefits from alternative operational procedures. The test matrix was composed of various combinations of altitude, cutback power, and aircraft weight. The DAMS digitizes the acoustic inputs at the microphone site and can be located up to 2000 feet from the van which houses the acquisition, storage and analysis equipment. Digitized data from up to 10 microphones is recorded on a Jaz disk and is analyzed post-test by microcomputer system. The RASS digitizes and stores acoustic inputs at the microphone site that can be located up to three miles from the base station and can compose a 3 mile by 3 mile array of microphones. 16-bit digitized data from the microphones is stored on removable Jaz disk and is transferred through a high speed array to a very large high speed permanent storage device. Up to 30 microphones can be utilized in the array. System control and monitoring is accomplished via Radio Frequency (RF) link. This paper will present a detailed description of both systems, along with acoustic data analysis from both systems.

Methodology for experimental validation of a CFD model for predicting noise generation in centrifugal compressors

International Nuclear Information System (INIS)

Broatch, A.; Galindo, J.; Navarro, R.; García-Tíscar, J.

2014-01-01

Highlights: • A DES of a turbocharger compressor working at peak pressure point is performed. • In-duct pressure signals are measured in a steady flow rig with 3-sensor arrays. • Pressure spectra comparison is performed as a validation for the numerical model. • A suitable comparison methodology is developed, relying on pressure decomposition. • Whoosh noise at outlet duct is detected in experimental and numerical spectra. - Abstract: Centrifugal compressors working in the surge side of the map generate a broadband noise in the range of 1–3 kHz, named as whoosh noise. This noise is perceived at strongly downsized engines operating at particular conditions (full load, tip-in and tip-out maneuvers). A 3-dimensional CFD model of a centrifugal compressor is built to analyze fluid phenomena related to whoosh noise. A detached eddy simulation is performed with the compressor operating at the peak pressure point of 160 krpm. A steady flow rig mounted on an anechoic chamber is used to obtain experimental measurements as a means of validation for the numerical model. In-duct pressure signals are obtained in addition to standard averaged global variables. The numerical simulation provides global variables showing excellent agreement with experimental measurements. Pressure spectra comparison is performed to assess noise prediction capability of numerical model. The influence of the type and position of the virtual pressure probes is evaluated. Pressure decomposition is required by the simulations to obtain meaningful spectra. Different techniques for obtaining pressure components are analyzed. At the simulated conditions, a broadband noise in 1–3 kHz frequency band is detected in the experimental measurements. This whoosh noise is also captured by the numerical model

White noise theory of robust nonlinear filtering with correlated state and observation noises

NARCIS (Netherlands)

Bagchi, Arunabha; Karandikar, Rajeeva

1992-01-01

In the direct white noise theory of nonlinear filtering, the state process is still modeled as a Markov process satisfying an Ito stochastic differential equation, while a finitely additive white noise is used to model the observation noise. In the present work, this asymmetry is removed by modeling

White noise theory of robust nonlinear filtering with correlated state and observation noises

NARCIS (Netherlands)

Bagchi, Arunabha; Karandikar, Rajeeva

1994-01-01

In the existing `direct¿ white noise theory of nonlinear filtering, the state process is still modelled as a Markov process satisfying an Itô stochastic differential equation, while a `finitely additive¿ white noise is used to model the observation noise. We remove this asymmetry by modelling the

Understanding jet noise.

Science.gov (United States)

Karabasov, S A

2010-08-13

Jets are one of the most fascinating topics in fluid mechanics. For aeronautics, turbulent jet-noise modelling is particularly challenging, not only because of the poor understanding of high Reynolds number turbulence, but also because of the extremely low acoustic efficiency of high-speed jets. Turbulent jet-noise models starting from the classical Lighthill acoustic analogy to state-of-the art models were considered. No attempt was made to present any complete overview of jet-noise theories. Instead, the aim was to emphasize the importance of sound generation and mean-flow propagation effects, as well as their interference, for the understanding and prediction of jet noise.

Predetermining acceptable noise limits of EXAFS spectra in the limit of stochastic noise

International Nuclear Information System (INIS)

Hu, Yung-Jin; Booth, Corwin H

2009-01-01

The effect of stochastic noise on Extended X-ray Absorption Fine Structure (EXAFS) data measurement, analysis, and fitting is discussed. Stochastic noise reduces the ability to uniquely fit a calculated model to measured EXAFS data. Such noise can be reduced by common methods that increase the signal-to-noise ratio; however, these methods are not always practical. Therefore, predetermined, quantitative knowledge of the level of acceptable stochastic noise when fitting for a particular model system is essential in maximizing the chances of a successful EXAFS experiment and minimizing wasted beamtime. This paper outlines a method to estimate, through simulation, the acceptable level of stochastic noise in EXAFS spectra that still allows a successful test of a proposed model compound.

An instantaneous spatiotemporal model to predict a bicyclist's Black Carbon exposure based on mobile noise measurements

Science.gov (United States)

Dekoninck, Luc; Botteldooren, Dick; Int Panis, Luc

2013-11-01

Several studies have shown that a significant amount of daily air pollution exposure, in particular Black Carbon (BC), is inhaled during trips. Assessing this contribution to exposure remains difficult because on the one hand local air pollution maps lack spatio-temporal resolution, at the other hand direct measurement of particulate matter concentration remains expensive. This paper proposes to use in-traffic noise measurements in combination with geographical and meteorological information for predicting BC exposure during commuting trips. Mobile noise measurements are cheaper and easier to perform than mobile air pollution measurements and can easily be used in participatory sensing campaigns. The uniqueness of the proposed model lies in the choice of noise indicators that goes beyond the traditional overall A-weighted noise level used in previous work. Noise and BC exposures are both related to the traffic intensity but also to traffic speed and traffic dynamics. Inspired by theoretical knowledge on the emission of noise and BC, the low frequency engine related noise and the difference between high frequency and low frequency noise that indicates the traffic speed, are introduced in the model. In addition, it is shown that splitting BC in a local and a background component significantly improves the model. The coefficients of the proposed model are extracted from 200 commuter bicycle trips. The predicted average exposure over a single trip correlates with measurements with a Pearson coefficient of 0.78 using only four parameters: the low frequency noise level, wind speed, the difference between high and low frequency noise and a street canyon index expressing local air pollution dispersion properties.

Displacement-noise-free gravitational-wave detection with a single Fabry-Perot cavity: A toy model

International Nuclear Information System (INIS)

Tarabrin, Sergey P.; Vyatchanin, Sergey P.

2008-01-01

We propose a detuned Fabry-Perot cavity, pumped through both the mirrors, as a toy model of the gravitational-wave (GW) detector partially free from displacement noise of the test masses. It is demonstrated that the noise of cavity mirrors can be eliminated, but the one of lasers and detectors cannot. The isolation of the GW signal from displacement noise of the mirrors is achieved in a proper linear combination of the cavity output signals. The construction of such a linear combination is possible due to the difference between the reflected and transmitted output signals of detuned cavity. We demonstrate that in low-frequency region the obtained displacement-noise-free response signal is much stronger than the f gw 3 -limited sensitivity of displacement-noise-free interferometers recently proposed by S. Kawamura and Y. Chen. However, the loss of the resonant gain in the noise cancelation procedure results is the sensitivity limitation of our toy model by displacement noise of lasers and detectors

Evaluation of model-based versus non-parametric monaural noise-reduction approaches for hearing aids.

Science.gov (United States)

Harlander, Niklas; Rosenkranz, Tobias; Hohmann, Volker

2012-08-01

Single channel noise reduction has been well investigated and seems to have reached its limits in terms of speech intelligibility improvement, however, the quality of such schemes can still be advanced. This study tests to what extent novel model-based processing schemes might improve performance in particular for non-stationary noise conditions. Two prototype model-based algorithms, a speech-model-based, and a auditory-model-based algorithm were compared to a state-of-the-art non-parametric minimum statistics algorithm. A speech intelligibility test, preference rating, and listening effort scaling were performed. Additionally, three objective quality measures for the signal, background, and overall distortions were applied. For a better comparison of all algorithms, particular attention was given to the usage of the similar Wiener-based gain rule. The perceptual investigation was performed with fourteen hearing-impaired subjects. The results revealed that the non-parametric algorithm and the auditory model-based algorithm did not affect speech intelligibility, whereas the speech-model-based algorithm slightly decreased intelligibility. In terms of subjective quality, both model-based algorithms perform better than the unprocessed condition and the reference in particular for highly non-stationary noise environments. Data support the hypothesis that model-based algorithms are promising for improving performance in non-stationary noise conditions.

Definition of 1992 Technology Aircraft Noise Levels and the Methodology for Assessing Airplane Noise Impact of Component Noise Reduction Concepts

Science.gov (United States)

Kumasaka, Henry A.; Martinez, Michael M.; Weir, Donald S.

1996-01-01

This report describes the methodology for assessing the impact of component noise reduction on total airplane system noise. The methodology is intended to be applied to the results of individual study elements of the NASA-Advanced Subsonic Technology (AST) Noise Reduction Program, which will address the development of noise reduction concepts for specific components. Program progress will be assessed in terms of noise reduction achieved, relative to baseline levels representative of 1992 technology airplane/engine design and performance. In this report, the 1992 technology reference levels are defined for assessment models based on four airplane sizes - an average business jet and three commercial transports: a small twin, a medium sized twin, and a large quad. Study results indicate that component changes defined as program final goals for nacelle treatment and engine/airframe source noise reduction would achieve from 6-7 EPNdB reduction of total airplane noise at FAR 36 Stage 3 noise certification conditions for all of the airplane noise assessment models.

Listen to the noise: noise is beneficial for cognitive performance in ADHD.

Science.gov (United States)

Söderlund, Göran; Sikström, Sverker; Smart, Andrew

2007-08-01

Noise is typically conceived of as being detrimental to cognitive performance. However, given the mechanism of stochastic resonance, a certain amount of noise can benefit performance. We investigate cognitive performance in noisy environments in relation to a neurocomputational model of attention deficit hyperactivity disorder (ADHD) and dopamine. The Moderate Brain Arousal model (MBA; Sikström & Söderlund, 2007) suggests that dopamine levels modulate how much noise is required for optimal cognitive performance. We experimentally examine how ADHD and control children respond to different encoding conditions, providing different levels of environmental stimulation. Participants carried out self-performed mini tasks (SPT), as a high memory performance task, and a verbal task (VT), as a low memory task. These tasks were performed in the presence, or absence, of auditory white noise. Noise exerted a positive effect on cognitive performance for the ADHD group and deteriorated performance for the control group, indicating that ADHD subjects need more noise than controls for optimal cognitive performance. The positive effect of white noise is explained by the phenomenon of stochastic resonance (SR), i.e., the phenomenon that moderate noise facilitates cognitive performance. The MBA model suggests that noise in the environment, introduces internal noise into the neural system through the perceptual system. This noise induces SR in the neurotransmitter systems and makes this noise beneficial for cognitive performance. In particular, the peak of the SR curve depends on the dopamine level, so that participants with low dopamine levels (ADHD) require more noise for optimal cognitive performance compared to controls.

Numerical modelling of the pump-to-signal relative intensity noise ...

Indian Academy of Sciences (India)

An accurate numerical model to investigate the pump-to-signal relative intensity noise (RIN) transfer in two-pump fibre optical parametric amplifiers (2-P FOPAs) for low modulation frequencies is presented. Compared to other models in the field, this model takes into account the fibre loss, pump depletion as well as the gain ...

Multivariate Product-Shot-noise Cox Point Process Models

DEFF Research Database (Denmark)

Jalilian, Abdollah; Guan, Yongtao; Mateu, Jorge

We introduce a new multivariate product-shot-noise Cox process which is useful for model- ing multi-species spatial point patterns with clustering intra-specific interactions and neutral, negative or positive inter-specific interactions. The auto and cross pair correlation functions of the process...... can be obtained in closed analytical forms and approximate simulation of the process is straightforward. We use the proposed process to model interactions within and among five tree species in the Barro Colorado Island plot....

On estimation of the noise variance in high-dimensional linear models

OpenAIRE

Golubev, Yuri; Krymova, Ekaterina

2017-01-01

We consider the problem of recovering the unknown noise variance in the linear regression model. To estimate the nuisance (a vector of regression coefficients) we use a family of spectral regularisers of the maximum likelihood estimator. The noise estimation is based on the adaptive normalisation of the squared error. We derive the upper bound for the concentration of the proposed method around the ideal estimator (the case of zero nuisance).

Analytical prediction of the interior noise for cylindrical models of aircraft fuselages for prescribed exterior noise fields. Phase 2: Models for sidewall trim, stiffened structures and cabin acoustics with floor partition

Science.gov (United States)

Pope, L. D.; Wilby, E. G.

1982-01-01

An airplane interior noise prediction model is developed to determine the important parameters associated with sound transmission into the interiors of airplanes, and to identify apropriate noise control methods. Models for stiffened structures, and cabin acoustics with floor partition are developed. Validation studies are undertaken using three test articles: a ring stringer stiffened cylinder, an unstiffened cylinder with floor partition, and ring stringer stiffened cylinder with floor partition and sidewall trim. The noise reductions of the three test articles are computed using the heoretical models and compared to measured values. A statistical analysis of the comparison data indicates that there is no bias in the predictions although a substantial random error exists so that a discrepancy of more than five or six dB can be expected for about one out of three predictions.

Boundary layer measurements of the NACA0015 and implications for noise modeling

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F.

2011-01-15

A NACA0015 airfoil section instrumented with an array of high frequency microphones flush-mounted beneath its surface was measured in the wind tunnel at LM Wind Power in Lunderskov. Various inflow speeds and angles of attack were investigated. In addition, a hot-wire device system was used to measure the velocity profiles and turbulence characteristics in the boundary layer near the trailing edge of the airfoil. The measured boundary layer data are presented in this report and compared with CFD results. A relative good agreement is observed, though a few discrepancies also appear. Comparisons of surface pressure fluctuations spectra are used to analyze and improve trailing edge noise modeling by the so-called TNO model. Finally, a pair of hot-wires were placed on each side of the trailing edge in order to measure the radiated trailing edge noise. However, there is no strong evidence that such noise could be measured in the higher frequency range. Nevertheless, low-frequency noise could be measured and related to the presence of the airfoil but its origin is unclear. (Author)

Urban traffic noise assessment by combining measurement and model results

NARCIS (Netherlands)

Eerden, F.J.M. van der; Graafland, F.; Wessels, P.W.; Basten, T.G.H.

2013-01-01

A model based monitoring system is applied on a local scale in an urban area to obtain a better understanding of the traffic noise situation. The system consists of a scalable sensor network and an engineering model. A better understanding is needed to take appropriate and cost efficient measures,

The Analysis of Low Noise Protection Barriers Influence on Tram Traffic Noise Levels

Directory of Open Access Journals (Sweden)

Ahac Maja

2013-07-01

Full Text Available The paper describes the analysis of tram traffic noise situation in residential areas in the vicinity of Drzic Avenue, one of the major routes between the northern and southern part of the Croatian capital city Zagreb, and the effect of low barriers placed by the tracks on tram noise mitigation. In order to evaluate the effect of planned protection measure, noise models were produced and verified with short-term field measurements. Calculations were conducted by means of noise prediction software, using European interim noise prediction method and 3D model of analyzed area. Finally, the results of noise calculations for existing tram traffic situation and planned measure of protection are presented on noise maps.

Sensitivity analysis of the noise-induced oscillatory multistability in Higgins model of glycolysis

Science.gov (United States)

Ryashko, Lev

2018-03-01

A phenomenon of the noise-induced oscillatory multistability in glycolysis is studied. As a basic deterministic skeleton, we consider the two-dimensional Higgins model. The noise-induced generation of mixed-mode stochastic oscillations is studied in various parametric zones. Probabilistic mechanisms of the stochastic excitability of equilibria and noise-induced splitting of randomly forced cycles are analysed by the stochastic sensitivity function technique. A parametric zone of supersensitive Canard-type cycles is localized and studied in detail. It is shown that the generation of mixed-mode stochastic oscillations is accompanied by the noise-induced transitions from order to chaos.

An efficient model for background noise mapping

NARCIS (Netherlands)

Wei, W.; Renterghem, T. van; Botteldooren, D.; Hornikx, M.; Forssén, J.; Salomons, E.; Ögren, M.

2012-01-01

It has been shown that inhabitants of dwellings exposed to high noise levels benefit from having access to a quiet side. Therefore the European Environmental Noise Directive allows member states to include the presence of a quiet side in their reports. However, current practice applications of noise

A new approach to modelling radiation noise in CCD's

International Nuclear Information System (INIS)

Chugg, A.; Hopkinson, G.

1998-01-01

The energy depositions reported by Monte Carlo electron-photon irradiation transport codes are subject to a random error due to the finite number of particle histories used to generate the results. These statistical variations, normally a nuisance, may also be identified with the real radiation noise effects experienced by CCD pixels in persistent radiation environments. This paper explores the practicability of such radiation noise modelling by applying the ACCEPT code from the ITS suite to the case of a shielded CCD exposed to an electron flux. The results are compared with those obtained in a subsequent electron irradiation of the CCD by a Van de Graaff accelerator

A comparative study of time series modeling methods for reactor noise analysis

International Nuclear Information System (INIS)

Kitamura, Masaharu; Shigeno, Kei; Sugiyama, Kazusuke

1978-01-01

Two modeling algorithms were developed to study at-power reactor noise as a multi-input, multi-output process. A class of linear, discrete time description named autoregressive-moving average model was used as a compact mathematical expression of the objective process. One of the model estimation (modeling) algorithms is based on the theory of Kalman filtering, and the other on a conjugate gradient method. By introducing some modifications in the formulation of the problem, realization of the practically usable algorithms was made feasible. Through the testing with several simulation models, reliability and effectiveness of these algorithms were confirmed. By applying these algorithms to experimental data obtained from a nuclear power plant, interesting knowledge about the at-power reactor noise was found out. (author)

Modeling of Temperature-Dependent Noise in Silicon Nanowire FETs including Self-Heating Effects

Directory of Open Access Journals (Sweden)

P. Anandan

2014-01-01

Full Text Available Silicon nanowires are leading the CMOS era towards the downsizing limit and its nature will be effectively suppress the short channel effects. Accurate modeling of thermal noise in nanowires is crucial for RF applications of nano-CMOS emerging technologies. In this work, a perfect temperature-dependent model for silicon nanowires including the self-heating effects has been derived and its effects on device parameters have been observed. The power spectral density as a function of thermal resistance shows significant improvement as the channel length decreases. The effects of thermal noise including self-heating of the device are explored. Moreover, significant reduction in noise with respect to channel thermal resistance, gate length, and biasing is analyzed.

Noise analysis of genome-scale protein synthesis using a discrete computational model of translation

Energy Technology Data Exchange (ETDEWEB)

Racle, Julien; Hatzimanikatis, Vassily, E-mail: vassily.hatzimanikatis@epfl.ch [Laboratory of Computational Systems Biotechnology, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Swiss Institute of Bioinformatics (SIB), CH-1015 Lausanne (Switzerland); Stefaniuk, Adam Jan [Laboratory of Computational Systems Biotechnology, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

2015-07-28

Noise in genetic networks has been the subject of extensive experimental and computational studies. However, very few of these studies have considered noise properties using mechanistic models that account for the discrete movement of ribosomes and RNA polymerases along their corresponding templates (messenger RNA (mRNA) and DNA). The large size of these systems, which scales with the number of genes, mRNA copies, codons per mRNA, and ribosomes, is responsible for some of the challenges. Additionally, one should be able to describe the dynamics of ribosome exchange between the free ribosome pool and those bound to mRNAs, as well as how mRNA species compete for ribosomes. We developed an efficient algorithm for stochastic simulations that addresses these issues and used it to study the contribution and trade-offs of noise to translation properties (rates, time delays, and rate-limiting steps). The algorithm scales linearly with the number of mRNA copies, which allowed us to study the importance of genome-scale competition between mRNAs for the same ribosomes. We determined that noise is minimized under conditions maximizing the specific synthesis rate. Moreover, sensitivity analysis of the stochastic system revealed the importance of the elongation rate in the resultant noise, whereas the translation initiation rate constant was more closely related to the average protein synthesis rate. We observed significant differences between our results and the noise properties of the most commonly used translation models. Overall, our studies demonstrate that the use of full mechanistic models is essential for the study of noise in translation and transcription.

Deterministic decomposition and seasonal ARIMA time series models applied to airport noise forecasting

Science.gov (United States)

Guarnaccia, Claudio; Quartieri, Joseph; Tepedino, Carmine

2017-06-01

One of the most hazardous physical polluting agents, considering their effects on human health, is acoustical noise. Airports are a strong source of acoustical noise, due to the airplanes turbines, to the aero-dynamical noise of transits, to the acceleration or the breaking during the take-off and landing phases of aircrafts, to the road traffic around the airport, etc.. The monitoring and the prediction of the acoustical level emitted by airports can be very useful to assess the impact on human health and activities. In the airports noise scenario, thanks to flights scheduling, the predominant sources may have a periodic behaviour. Thus, a Time Series Analysis approach can be adopted, considering that a general trend and a seasonal behaviour can be highlighted and used to build a predictive model. In this paper, two different approaches are adopted, thus two predictive models are constructed and tested. The first model is based on deterministic decomposition and is built composing the trend, that is the long term behaviour, the seasonality, that is the periodic component, and the random variations. The second model is based on seasonal autoregressive moving average, and it belongs to the stochastic class of models. The two different models are fitted on an acoustical level dataset collected close to the Nice (France) international airport. Results will be encouraging and will show good prediction performances of both the adopted strategies. A residual analysis is performed, in order to quantify the forecasting error features.

Partial and Total Annoyance Due to Road Traffic Noise Combined with Aircraft or Railway Noise: Structural Equation Analysis

OpenAIRE

Gille, Laure-Anne; Marquis-Favre, Catherine; Lam, Kin-Che

2017-01-01

Structural equation modeling was used to analyze partial and total in situ annoyance in combined transportation noise situations. A psychophysical total annoyance model and a perceptual total annoyance model were proposed. Results show a high contribution of Noise exposure and Noise sensitivity to Noise annoyance, as well as a causal relationship between noise annoyance and lower Dwelling satisfaction. Moreover, the Visibility of noise source may increase noise annoyance, even when the visibl...

Acoustic fMRI noise : Linear time-invariant system model

NARCIS (Netherlands)

Sierra, Carlos V. Rizzo; Versluis, Maarten J.; Hoogduin, Johannes M.; Duifhuis, Hendrikus (Diek)

Functional magnetic resonance imaging (fMRI) enables sites of brain activation to be localized in human subjects. For auditory system studies, however, the acoustic noise generated by the scanner tends to interfere with the assessments of this activation. Understanding and modeling fMRI acoustic

An Investigation of Rotorcraft Stability-Phase Margin Requirements in Hover

Science.gov (United States)

Blanken, Chris L.; Lusardi, Jeff A.; Ivler, Christina M.; Tischler, Mark B.; Hoefinger, Marc T.; Decker, William A.; Malpica, Carlos A.; Berger, Tom; Tucker, George E.

2009-01-01

A cooperative study was performed to investigate the handling quality effects from reduced flight control system stability margins, and the trade-offs with higher disturbance rejection bandwidth (DRB). The piloted simulation study, perform on the NASA-Ames Vertical Motion Simulator, included three classes of rotorcraft in four configurations: a utility-class helicopter; a medium-lift helicopter evaluated with and without an external slung load; and a large (heavy-lift) civil tiltrotor aircraft. This large aircraft also allowed an initial assessment of ADS-33 handling quality requirements for an aircraft of this size. Ten experimental test pilots representing the U.S. Army, Marine Corps, NASA, rotorcraft industry, and the German Aerospace Center (DLR), evaluated the four aircraft configurations, for a range of flight control stability-margins and turbulence levels, while primarily performing the ADS-33 Hover and Lateral Reposition MTEs. Pilot comments and aircraft-task performance data were analyzed. The preliminary stability margin results suggest higher DRB and less phase margin cases are preferred as the aircraft increases in size. Extra care will need to be taken to assess the influence of variability when nominal flight control gains start with reduced margins. Phase margins as low as 20-23 degrees resulted in low disturbance-response damping ratios, objectionable oscillations, PIO tendencies, and a perception of an incipient handling qualities cliff. Pilot comments on the disturbance response of the aircraft correlated well to the DRB guidelines provided in the ADS-33 Test Guide. The A D-3S3 mid-term response-to-control damping ratio metrics can be measured and applied to the disturbance-response damping ratio. An initial assessment of LCTR yaw bandwidth shows the current Level 1 boundary needs to be relaxed to help account for a large pilot off-set from the c.g. Future efforts should continue to investigate the applicability/refinement of the current ADS-33

Evaluation and Modelling of Traffic Noise on the Asian Highway in Golestan National Park, Iran

Directory of Open Access Journals (Sweden)

Gharibi Shiva

2016-01-01

Full Text Available The increasing number of vehicles on Iran’s highways and major roads has led to an increase in noise levels. As a result, traffic is now considered a main source of noise pollution. This paper reports on the modelling of traffic noise levels in Golestan National Park, Golestan using vehicle data and other environmental features. For the evaluation of noise and the recording of independent environmental variables, Sampling stations were selected using a systematic-random method at 76 points at various distances and between 0-250 meters from the road. At each sampling point, traffic flow (number and speed of vehicles, number of horn beeps was measured for 15 minutes from 8 am to 8 pm. Simultaneously other environmental variables were assessed, including the geometry of the road surface and location conditions .The best multivariable regression based on the correlation coefficient (R and the coefficient of determination (R2 was achieved. The R-square (73% and the adjusted R-square (68% of the regression equation were 73% and 68% respectively. The results of modelling show that the most important variables affecting noise pollution are distance from the road, roughness coefficient, speed of medium-weight vehicles, relative humidity, and height and number of light vehicles. There is a negative correlation with distance from the road and noise pollution.The accuracy of the model was found to be about ±5 dB. Therefore, the model is suggested for the prediction of traffic noise on the Asian Highway in Golestan National Park.

Indirect Combustion Noise: Noise Generation by Accelerated Vorticity in a Nozzle Flow

Directory of Open Access Journals (Sweden)

Nancy Kings

2010-09-01

Full Text Available The noise generation by accelerated vorticity waves in a nozzle flow was investigated in a model experiment. This noise generation mechanism belongs, besides entropy noise, to the indirect combustion noise phenomena. Vorticity as well as entropy fluctuations, originating from the highly turbulent combustion zone, are convected with the flow and produce noise during their acceleration in the outlet nozzle of the combustion chamber. In the model experiment, noise generation of accelerated vorticity fluctuations was achieved. The vorticity fluctuations in the tube flow were produced by injecting temporally additional air into the mean flow. As the next step, a parametric study was conducted to determine the major dependencies of the so called vortex noise. A quadratic dependency of the vortex noise on the injected air amount was found. In order to visualise and classify the artificially generated vorticity structures, planar velocity measurements have been conducted applying Particle Image Velocimetry (PIV.

Active Vibration Control for Helicopter Interior Noise Reduction Using Power Minimization

Science.gov (United States)

Mendoza, J.; Chevva, K.; Sun, F.; Blanc, A.; Kim, S. B.

2014-01-01

This report describes work performed by United Technologies Research Center (UTRC) for NASA Langley Research Center (LaRC) under Contract NNL11AA06C. The objective of this program is to develop technology to reduce helicopter interior noise resulting from multiple gear meshing frequencies. A novel active vibration control approach called Minimum Actuation Power (MAP) is developed. MAP is an optimal control strategy that minimizes the total input power into a structure by monitoring and varying the input power of controlling sources. MAP control was implemented without explicit knowledge of the phasing and magnitude of the excitation sources by driving the real part of the input power from the controlling sources to zero. It is shown that this occurs when the total mechanical input power from the excitation and controlling sources is a minimum. MAP theory is developed for multiple excitation sources with arbitrary relative phasing for single or multiple discrete frequencies and controlled by a single or multiple controlling sources. Simulations and experimental results demonstrate the feasibility of MAP for structural vibration reduction of a realistic rotorcraft interior structure. MAP control resulted in significant average global vibration reduction of a single frequency and multiple frequency excitations with one controlling actuator. Simulations also demonstrate the potential effectiveness of the observed vibration reductions on interior radiated noise.

Development of a wind farm noise propagation prediction model - project progress to date

International Nuclear Information System (INIS)

Robinson, P.; Bullmore, A.; Bass, J.; Sloth, E.

1998-01-01

This paper describes a twelve month measurement campaign which is part of a European project (CEC Project JOR3-CT95-0051) with the aim to substantially reduce the uncertainties involved in predicting environmentally radiated noise levels from wind farms (1). This will be achieved by comparing noise levels measure at varying distances from single and multiple sources over differing complexities of terrain with those predicted using a number of currently adopted sound propagation models. Specific objectives within the project are to: establish the important parameters controlling the propagation of wind farm noise to the far field; develop a planning tool for predicting wind farm noise emission levels under practically encountered conditions; place confidence limits on the upper and lower bounds of the noise levels predicted, thus enabling developers to quantify the risk whether noise emission from wind farms will cause nuisance to nearby residents. (Author)

Literature review of models on tire-pavement interaction noise

Science.gov (United States)

Li, Tan; Burdisso, Ricardo; Sandu, Corina

2018-04-01

Tire-pavement interaction noise (TPIN) becomes dominant at speeds above 40 km/h for passenger vehicles and 70 km/h for trucks. Several models have been developed to describe and predict the TPIN. However, these models do not fully reveal the physical mechanisms or predict TPIN accurately. It is well known that all the models have both strengths and weaknesses, and different models fit different investigation purposes or conditions. The numerous papers that present these models are widely scattered among thousands of journals, and it is difficult to get the complete picture of the status of research in this area. This review article aims at presenting the history and current state of TPIN models systematically, making it easier to identify and distribute the key knowledge and opinions, and providing insight into the future research trend in this field. In this work, over 2000 references related to TPIN were collected, and 74 models were reviewed from nearly 200 selected references; these were categorized into deterministic models (37), statistical models (18), and hybrid models (19). The sections explaining the models are self-contained with key principles, equations, and illustrations included. The deterministic models were divided into three sub-categories: conventional physics models, finite element and boundary element models, and computational fluid dynamics models; the statistical models were divided into three sub-categories: traditional regression models, principal component analysis models, and fuzzy curve-fitting models; the hybrid models were divided into three sub-categories: tire-pavement interface models, mechanism separation models, and noise propagation models. At the end of each category of models, a summary table is presented to compare these models with the key information extracted. Readers may refer to these tables to find models of their interest. The strengths and weaknesses of the models in different categories were then analyzed. Finally

Receiver design for SPAD-based VLC systems under Poisson-Gaussian mixed noise model.

Science.gov (United States)

Mao, Tianqi; Wang, Zhaocheng; Wang, Qi

2017-01-23

Single-photon avalanche diode (SPAD) is a promising photosensor because of its high sensitivity to optical signals in weak illuminance environment. Recently, it has drawn much attention from researchers in visible light communications (VLC). However, existing literature only deals with the simplified channel model, which only considers the effects of Poisson noise introduced by SPAD, but neglects other noise sources. Specifically, when an analog SPAD detector is applied, there exists Gaussian thermal noise generated by the transimpedance amplifier (TIA) and the digital-to-analog converter (D/A). Therefore, in this paper, we propose an SPAD-based VLC system with pulse-amplitude-modulation (PAM) under Poisson-Gaussian mixed noise model, where Gaussian-distributed thermal noise at the receiver is also investigated. The closed-form conditional likelihood of received signals is derived using the Laplace transform and the saddle-point approximation method, and the corresponding quasi-maximum-likelihood (quasi-ML) detector is proposed. Furthermore, the Poisson-Gaussian-distributed signals are converted to Gaussian variables with the aid of the generalized Anscombe transform (GAT), leading to an equivalent additive white Gaussian noise (AWGN) channel, and a hard-decision-based detector is invoked. Simulation results demonstrate that, the proposed GAT-based detector can reduce the computational complexity with marginal performance loss compared with the proposed quasi-ML detector, and both detectors are capable of accurately demodulating the SPAD-based PAM signals.

Comparison of the iPCoD and DEPONS models for modelling population consequences of noise on harbour porpoises

DEFF Research Database (Denmark)

Nabe-Nielsen, Jacob; Harwood, John

Two different frameworks have been developed to assess the potential effects of noise associated with offshore renewable energy developments on harbour porpoise populations: The Interim Population Consequences of Disturbance (iPCoD) and Disturbance Effects of Noise on the Harbour Porpoise...... Population in the North Sea (DEPONS). Although both models simulate population dynamics based on the birth and survival rates of individual animals, they model survival in a different way. iPCoD uses average survival rates derived from data from North Sea animals. In the DEPONS model, survival emerges from...

Airport acoustics: Aircraft noise distribution and modelling of some ...

African Journals Online (AJOL)

Airport acoustics: Aircraft noise distribution and modelling of some aircraft parameters. MU Onuu, EO Obisung. Abstract. No Abstract. Nigerian Journal of Physics Vol. 17 (Supplement) 2005: pp. 177-186. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

Measurement, characterization, and modeling of noise in staring infrared focal plane arrays

International Nuclear Information System (INIS)

Scribner, D.A.; Kruer, M.R.; Gridley, C.J.; Sarkady, K.

1987-01-01

An account is given of selected methods for the measurement and characterization of spatial and temporal noise in staring focal plane arrays (FPAs), in order to demonstrate how these results can be used in simulations and analytic models to predict the performance of selected staring sensors. Attention is given to MIR FPAs applicable to the detection and tracking of point sources, and to the ways in which these spatial and temporal noise measurements can be incorporated into simulations and sensors having staring FPAs. Methods for predicting the performance of selected staring sensor systems are derivable from spatial and temporal noise values. 13 references

A unified flight control methodology for a compound rotorcraft in fundamental and aerobatic maneuvering flight

Science.gov (United States)

Thorsen, Adam

regime. An energy management system was developed in order to manage performance limits (namely power required) to promote carefree maneuvering and alleviate pilot workload. This system features limits on pilot commands and has additional logic for preserving control margins and limiting maximum speed in a dive. Nonlinear dynamic inversion (NLDI) is the framework of the unified controller, which incorporates primary and redundant controls. The inner loop of the NLDI controller regulates bank angle, pitch attitude, and yaw rate, while the outer loop command structure is varied (three modes). One version uses an outer loop that commands velocities in the longitudinal and vertical axes (velocity mode), another commands longitudinal acceleration and vertical speed (acceleration mode), and the third commands longitudinal acceleration and transitions from velocity to acceleration command in the vertical axis (aerobatic mode). The flight envelope is discretized into low, cruise, and high speed flight regimes. The unified outer loop primary control effectors for the longitudinal and vertical axes (collective pitch, pitch attitude, and propeller pitch) vary depending on flight regime. A weighted pseudoinverse is used to phase either the collective or propeller pitch in/out of a redundant control role. The controllers were evaluated in Penn State's Rotorcraft Flight Simulator retaining the cyclic stick for vertical and lateral axis control along with pedal inceptors for yaw axis control. A throttle inceptor was used in place of the pilot's traditional left hand inceptor for longitudinal axis control. Ultimately, a simple rigid body model of the aircraft was sufficient enough to design a controller with favorable performance and stability characteristics. This unified flight control system promoted a low enough pilot workload so that an untrained pilot (the author) was able to pilot maneuvers of varying complexity with ease. The framework of this unified system is generalized

Integration and comparison of assessment and modeling of road traffic noise in Baripada town, India

Energy Technology Data Exchange (ETDEWEB)

Kumar Swain, Bijay [Department of Environmental Science, Utkal University, Bhubaneswar-751004, Odisha (India); Goswami, Shreerup [Department of Geology, Ravenshaw University, Cuttack-753003, Odisha (India)

2013-07-01

The road traffic is the predominant source of noise pollution in urban areas. Despite enactment of legislations and despite effort from Government level to abate vehicle noise, the noise exposure of people of India due to road traffic has hardly changed, but has increased day by day due to growth of vehicular population. Thus, an attempt had been made to assess the noise level in 12 different squares (major intersection points) of Baripada town during four different specified times (7-10 a.m., 11 a.m.-2 p.m., 3-6 p.m., 7-10 p.m.). The equivalent noise levels of all the 12 squares were found to be much beyond the permissible limit (70 dB during day time). Noise descriptors such as L10, L50, L90, Leq, TNI (Traffic Noise Index), NPL (Noise Pollution Level) and NC (Noise climate) were assessed to reveal the extent of noise pollution due to heavy traffic in this town. It is pertinent to mention here that even the minimum Leq and NPL values were more than 70.9 dB and 88.4 dB, respectively. Chi-square (X2) test was also computed for investigated squares at different times to infer the level of significance. The test depicts that the noise levels of different squares do not differ significantly at the peak hour. The prediction model was used in the present study to predict equivalent noise levels. Comparison of predicted equivalent noise level with that of the actual measured data demonstrated that the model used for the prediction has the ability to calibrate the multi-component traffic noise and yield reliable results close to that by direct measurement. Episodic and impulsive noise levels by the air-horn of motor vehicles in Baripada were also appraised and were more than the permissible limit. Though, the dimension of the traffic generated noise pollution in Baripada was not so alarming like other towns of India, a preliminary public health survey has also been carried out.

Quantifying the Effects of Noise on Diffuse Interface Models: Cahn-Hilliard-Cook equations

Science.gov (United States)

Pfeifer, Spencer; Ganapathysubramanian, Baskar

2015-03-01

We present an investigation into the dynamics of phase separation through numerical simulations of the Cahn-Hilliard-Cook (CHC) equation. This model is an extension of the well-known Cahn- Hilliard equation, perturbed by an additive white noise. Studies have shown that random fluctuations are critical for proper resolution of physical phenomena. This is especially true for phase critical systems. We explore the transient behavior of the solution space for varying levels of noise. This is enabled by our massively scalable finite element-based numerical framework. We briefly examine the interplay between noise level and discretization (spatial and temporal) in obtaining statistically consistent solutions. We show that the added noise accelerates progress towards phase separation, but retards dynamics throughout subsequent coarsening. We identify a scaling exponent relating morphology metrics with the level of noise. We observe a very clear scaling effect of finite domain size, which is observed to be offset by increasing levels of noise. Domain scaling reveals a clear microstructural asymmetry at various stages of the evolution for lower noise levels. In contrast, higher noise levels tend to produce more uniform morphologies.

Pressure-Sensitive Paints Advance Rotorcraft Design Testing

Science.gov (United States)

2013-01-01

The rotors of certain helicopters can spin at speeds as high as 500 revolutions per minute. As the blades slice through the air, they flex, moving into the wind and back out, experiencing pressure changes on the order of thousands of times a second and even higher. All of this makes acquiring a true understanding of rotorcraft aerodynamics a difficult task. A traditional means of acquiring aerodynamic data is to conduct wind tunnel tests using a vehicle model outfitted with pressure taps and other sensors. These sensors add significant costs to wind tunnel testing while only providing measurements at discrete locations on the model's surface. In addition, standard sensor solutions do not work for pulling data from a rotor in motion. "Typical static pressure instrumentation can't handle that," explains Neal Watkins, electronics engineer in Langley Research Center s Advanced Sensing and Optical Measurement Branch. "There are dynamic pressure taps, but your costs go up by a factor of five to ten if you use those. In addition, recovery of the pressure tap readings is accomplished through slip rings, which allow only a limited amount of sensors and can require significant maintenance throughout a typical rotor test." One alternative to sensor-based wind tunnel testing is pressure sensitive paint (PSP). A coating of a specialized paint containing luminescent material is applied to the model. When exposed to an LED or laser light source, the material glows. The glowing material tends to be reactive to oxygen, explains Watkins, which causes the glow to diminish. The more oxygen that is present (or the more air present, since oxygen exists in a fixed proportion in air), the less the painted surface glows. Imaged with a camera, the areas experiencing greater air pressure show up darker than areas of less pressure. "The paint allows for a global pressure map as opposed to specific points," says Watkins. With PSP, each pixel recorded by the camera becomes an optical pressure

Signal and noise modeling in confocal laser scanning fluorescence microscopy.

Science.gov (United States)

Herberich, Gerlind; Windoffer, Reinhard; Leube, Rudolf E; Aach, Til

2012-01-01

Fluorescence confocal laser scanning microscopy (CLSM) has revolutionized imaging of subcellular structures in biomedical research by enabling the acquisition of 3D time-series of fluorescently-tagged proteins in living cells, hence forming the basis for an automated quantification of their morphological and dynamic characteristics. Due to the inherently weak fluorescence, CLSM images exhibit a low SNR. We present a novel model for the transfer of signal and noise in CLSM that is both theoretically sound as well as corroborated by a rigorous analysis of the pixel intensity statistics via measurement of the 3D noise power spectra, signal-dependence and distribution. Our model provides a better fit to the data than previously proposed models. Further, it forms the basis for (i) the simulation of the CLSM imaging process indispensable for the quantitative evaluation of CLSM image analysis algorithms, (ii) the application of Poisson denoising algorithms and (iii) the reconstruction of the fluorescence signal.

Experimental validation of the twins prediction program for rolling noise. Pt.1: description of the model and method

NARCIS (Netherlands)

Thompson, D.J.; Hemsworth, B.; Vincent, N.

1996-01-01

The C163 Expert Committee of the European Rail Research Institute (ERRI) concerned with Railway Noise, has been developing theoretical models for the generation of wheel/rail rolling noise. These models have been brought together into a software package, called TWINS ("Track-Wheel Interaction Noise

Modeling temperature noise in a fast-reactor pile

International Nuclear Information System (INIS)

Kebadze, B.V.; Pykhtina, T.V.; Tarasko, M.Z.

1987-01-01

To observe partial overlapping of the heat carrier cross section in piles, leading to local temperature rise or boiling of the sodium, provision is made for individual monitoring of the fuel assemblies with respect to the output temperature. Since the deviation of the mean flow rate through the pile and the output temperature is slight with this anomaly, the temperature fluctuations may provide a more informative index. The change in noise characteristics with partial overlapping of the cross sections occurs because of strong distortion of the temperature profile in the overlap region. The turbulent flow in the upper part of the pile transforms this nonuniformity into temperature pulsations which may be recorded by a sensor at the pile output. In this paper the characteristics of temperature noise are studied for various pile conditions and sensor locations by statistical modeling

A minimal model of burst-noise induced bistability.

Directory of Open Access Journals (Sweden)

Johannes Falk

Full Text Available We investigate the influence of intrinsic noise on stable states of a one-dimensional dynamical system that shows in its deterministic version a saddle-node bifurcation between monostable and bistable behaviour. The system is a modified version of the Schlögl model, which is a chemical reaction system with only one type of molecule. The strength of the intrinsic noise is varied without changing the deterministic description by introducing bursts in the autocatalytic production step. We study the transitions between monostable and bistable behavior in this system by evaluating the number of maxima of the stationary probability distribution. We find that changing the size of bursts can destroy and even induce saddle-node bifurcations. This means that a bursty production of molecules can qualitatively change the dynamics of a chemical reaction system even when the deterministic description remains unchanged.

Results from an acoustic modelling study of seismic airgun survey noise in Queen Charlotte Basin

Energy Technology Data Exchange (ETDEWEB)

MacGillivray, A.O.; Chapman, N.R. [Victoria Univ., BC (Canada). School of Earth and Ocean Sciences

2005-12-07

An acoustic modelling study was conducted to examine seismic survey noise propagation in the Queen Charlotte Basin (QCB) and better understand the physical aspects of sound transmission. The study results are intended to help determine the potential physiological and behavioural effects of airgun noise on marine mammals and fish. The scope of the study included a numerical simulation of underwater sound transmission in QCB in areas where oil and gas exploration activities may be conducted; a forecast of received noise levels by combining acoustic transmission loss computations with acoustic source levels representative of seismic exploration activity and, the use of received forecasts to estimate zones of impact for marine mammals. The critical environmental parameters in the QCB are the bathymetry of the ocean, the sound speed profile in the water and the geoacoustic profile of the seabed. The RAM acoustic propagation model developed by the United States Naval Research Laboratory was used to compute acoustic transmission loss in the QCB. The source level and directionality of the seismic array was determined by a full-waveform array source signature model. This modelling study of noise propagation from seismic surveys revealed several key findings. Among them, it showed that received noise levels in the water are affected by the source location, array orientation and the shape of the sound speed profile with respect to water depth. It also showed that noise levels are lowest in shallow bathymetry. 30 refs., 5 tabs., 13 figs.

Land Use Regression Modeling of Outdoor Noise Exposure in Informal Settlements in Western Cape, South Africa.

Science.gov (United States)

Sieber, Chloé; Ragettli, Martina S; Brink, Mark; Toyib, Olaniyan; Baatjies, Roslyn; Saucy, Apolline; Probst-Hensch, Nicole; Dalvie, Mohamed Aqiel; Röösli, Martin

2017-10-20

In low- and middle-income countries, noise exposure and its negative health effects have been little explored. The present study aimed to assess the noise exposure situation in adults living in informal settings in the Western Cape Province, South Africa. We conducted continuous one-week outdoor noise measurements at 134 homes in four different areas. These data were used to develop a land use regression (LUR) model to predict A-weighted day-evening-night equivalent sound levels (L den ) from geographic information system (GIS) variables. Mean noise exposure during day (6:00-18:00) was 60.0 A-weighted decibels (dB(A)) (interquartile range 56.9-62.9 dB(A)), during night (22:00-6:00) 52.9 dB(A) (49.3-55.8 dB(A)) and average L den was 63.0 dB(A) (60.1-66.5 dB(A)). Main predictors of the LUR model were related to road traffic and household density. Model performance was low (adjusted R 2 = 0.130) suggesting that other influences than those represented in the geographic predictors are relevant for noise exposure. This is one of the few studies on the noise exposure situation in low- and middle-income countries. It demonstrates that noise exposure levels are high in these settings.

Nonlinear modeling, strength-based design, and testing of flexible piezoelectric energy harvesters under large dynamic loads for rotorcraft applications

Science.gov (United States)

Leadenham, Stephen; Erturk, Alper

2014-04-01

There has been growing interest in enabling wireless health and usage monitoring for rotorcraft applications, such as helicopter rotor systems. Large dynamic loads and acceleration fluctuations available in these environments make the implementation of vibration-based piezoelectric energy harvesters a very promising choice. However, such extreme loads transmitted to the harvester can also be detrimental to piezoelectric laminates and overall system reliability. Particularly flexible resonant cantilever configurations tuned to match the dominant excitation frequency can be subject to very large deformations and failure of brittle piezoelectric laminates due to excessive bending stresses at the root of the harvester. Design of resonant piezoelectric energy harvesters for use in these environments require nonlinear electroelastic dynamic modeling and strength-based analysis to maximize the power output while ensuring that the harvester is still functional. This paper presents a mathematical framework to design and analyze the dynamics of nonlinear flexible piezoelectric energy harvesters under large base acceleration levels. A strength-based limit is imposed to design the piezoelectric energy harvester with a proof mass while accounting for material, geometric, and dissipative nonlinearities, with a focus on two demonstrative case studies having the same linear fundamental resonance frequency but different overhang length and proof mass values. Experiments are conducted at different excitation levels for validation of the nonlinear design approach proposed in this work. The case studies in this work reveal that harvesters exhibiting similar behavior and power generation performance at low excitation levels (e.g. less than 0.1g) can have totally different strength-imposed performance limitations under high excitations (e.g. above 1g). Nonlinear modeling and strength-based design is necessary for such excitation levels especially when using resonant cantilevers with no

Stochastic resonance and noise delayed extinction in a model of two competing species

Science.gov (United States)

Valenti, D.; Fiasconaro, A.; Spagnolo, B.

2004-01-01

We study the role of the noise in the dynamics of two competing species. We consider generalized Lotka-Volterra equations in the presence of a multiplicative noise, which models the interaction between the species and the environment. The interaction parameter between the species is a random process which obeys a stochastic differential equation with a generalized bistable potential in the presence of a periodic driving term, which accounts for the environment temperature variation. We find noise-induced periodic oscillations of the species concentrations and stochastic resonance phenomenon. We find also a nonmonotonic behavior of the mean extinction time of one of the two competing species as a function of the additive noise intensity.

Identification of multivariate models for noise analysis of nuclear plant

International Nuclear Information System (INIS)

Zwingelstein, G.C.; Upadhyaya, B.R.

1979-01-01

During the normal operation of a pressurized water reactor, neutron noise analysis with multivariate autoregressive procedures in a valuable diagnostic tool to extract dynamic characteristics for incipient failure detection. The first part of the paper will describe in details the equations for estimating the multivariate autoregressive model matrices and the structure of various matrices. The matrices are estimated by solving a set of matrix operations, called Yule-Walker equations. The selection of optimal model order will also be discussed. Once the optimal parameter set is obtained, simple and fast calculations are used to determine the auto power spectral density, cross spectra, coherence function, phase. In addition the spectra may be decomposed into components being contributed from different noise sources. An application using neutron flux data collected on a nuclear plant will illustrate the efficiency of the method

Range and Endurance Tradeoffs on Personal Rotorcraft Design

Science.gov (United States)

Snyder, Christopher A.

2016-01-01

Rotorcraft design has always been a challenging tradeoff among overall size, capabilities, complexity, and other factors based on available technology and customer requirements. Advancements in propulsion, energy systems and other technologies have enabled new vehicles and missions; complementary advances in analysis methods and tools enable exploration of these enhanced vehicles and the evolving mission design space. A system study was performed to better understand the interdependency between vehicle design and propulsion system capabilities versus hover / loiter requirements and range capability. Three representative vertical lift vehicles were developed to explore the tradeoff in capability between hover efficiency versus range and endurance capability. The vehicles were a single-main rotor helicopter, a tilt rotor, and a vertical take-off and landing (VTOL) aircraft. Vehicle capability was limited to two or three people (including pilot or crew) and maximum range within one hour of flight (100-200 miles, depending on vehicle). Two types of propulsion and energy storage systems were used in this study. First was traditional hydrocarbon-fueled cycles (such as Otto, diesel or gas turbine cycles). Second was an all-electric system using electric motors, power management and distribution, assuming batteries for energy storage, with the possibility of hydrocarbon-fueled range extenders. The high power requirements for hover significantly reduced mission radius capability. Loiter was less power intensive, resulting in about 1/2 the equivalent mission radius penalty. With so many design variables, the VTOL aircraft has the potential to perform well for a variety of missions. This vehicle is a good candidate for additional study; component model development is also required to adequately assess performance over the design space of interest.

Finite frequency current noise in the Holstein model

Science.gov (United States)

Stadler, P.; Rastelli, G.; Belzig, W.

2018-05-01

We investigate the effects of local vibrational excitations in the nonsymmetrized current noise S (ω ) of a nanojunction. For this purpose, we analyze a simple model—the Holstein model—in which the junction is described by a single electronic level that is coupled to two metallic leads and to a single vibrational mode. Using the Keldysh Green's function technique, we calculate the nonsymmetrized current noise to the leading order in the charge-vibration interaction. For the noise associated to the latter, we identify distinct terms corresponding to the mean-field noise and the vertex correction. The mean-field result can be further divided into an elastic correction to the noise and in an inelastic correction, the second one being related to energy exchange with the vibration. To illustrate the general behavior of the noise induced by the charge-vibration interaction, we consider two limit cases. In the first case, we assume a strong coupling of the dot to the leads with an energy-independent transmission, whereas in the second case we assume a weak tunneling coupling between the dot and the leads such that the transport occurs through a sharp resonant level. We find that the noise associated to the vibration-charge interaction shows a complex pattern as a function of the frequency ω and of the transmission function or of the dot's energy level. Several transitions from enhancement to suppression of the noise occurs in different regions, which are determined, in particular, by the vibrational frequency. Remarkably, in the regime of an energy-independent transmission, the zero-order elastic noise vanishes at perfect transmission and at positive frequency, whereas the noise related to the charge-vibration interaction remains finite, enabling the analysis of the pure vibrational-induced current noise.

NB-PLC channel modelling with cyclostationary noise addition & OFDM implementation for smart grid

Science.gov (United States)

Thomas, Togis; Gupta, K. K.

2016-03-01

Power line communication (PLC) technology can be a viable solution for the future ubiquitous networks because it provides a cheaper alternative to other wired technology currently being used for communication. In smart grid Power Line Communication (PLC) is used to support communication with low rate on low voltage (LV) distribution network. In this paper, we propose the channel modelling of narrowband (NB) PLC in the frequency range 5 KHz to 500 KHz by using ABCD parameter with cyclostationary noise addition. Behaviour of the channel was studied by the addition of 11KV/230V transformer, by varying load location and load. Bit error rate (BER) Vs signal to noise ratio SNR) was plotted for the proposed model by employing OFDM. Our simulation results based on the proposed channel model show an acceptable performance in terms of bit error rate versus signal to noise ratio, which enables communication required for smart grid applications.

Interior noise analysis of a construction equipment cabin based on airborne and structure-borne noise predictions

Energy Technology Data Exchange (ETDEWEB)

Kim, Sung Hee; Hong, Suk Yoon [Seoul National University, Seoul (Korea, Republic of); Song, Jee Hun [Chonnam National University, Gwangju (Korea, Republic of); Joo, Won Ho [Hyundai Heavy Industries Co. Ltd, Ulsan (Korea, Republic of)

2012-04-15

Noise from construction equipment affects not only surrounding residents, but also the operators of the machines. Noise that affects drivers must be evaluated during the preliminary design stage. This paper suggests an interior noise analysis procedure for construction equipment cabins. The analysis procedure, which can be used in the preliminary design stage, was investigated for airborne and structure borne noise. The total interior noise of a cabin was predicted from the airborne noise analysis and structure-borne noise analysis. The analysis procedure consists of four steps: modeling, vibration analysis, acoustic analysis and total interior noise analysis. A mesh model of a cabin for numerical analysis was made at the modeling step. At the vibration analysis step, the mesh model was verified and modal analysis and frequency response analysis are performed. At the acoustic analysis step, the vibration results from the vibration analysis step were used as initial values for radiated noise analysis and noise reduction analysis. Finally, the total cabin interior noise was predicted using the acoustic results from the acoustic analysis step. Each step was applied to a cabin of a middle-sized excavator and verified by comparison with measured data. The cabin interior noise of a middle-sized wheel loader and a large-sized forklift were predicted using the analysis procedure of the four steps and were compared with measured data. The interior noise analysis procedure of construction equipment cabins is expected to be used during the preliminary design stage.

Interior noise analysis of a construction equipment cabin based on airborne and structure-borne noise predictions

International Nuclear Information System (INIS)

Kim, Sung Hee; Hong, Suk Yoon; Song, Jee Hun; Joo, Won Ho

2012-01-01

Noise from construction equipment affects not only surrounding residents, but also the operators of the machines. Noise that affects drivers must be evaluated during the preliminary design stage. This paper suggests an interior noise analysis procedure for construction equipment cabins. The analysis procedure, which can be used in the preliminary design stage, was investigated for airborne and structure borne noise. The total interior noise of a cabin was predicted from the airborne noise analysis and structure-borne noise analysis. The analysis procedure consists of four steps: modeling, vibration analysis, acoustic analysis and total interior noise analysis. A mesh model of a cabin for numerical analysis was made at the modeling step. At the vibration analysis step, the mesh model was verified and modal analysis and frequency response analysis are performed. At the acoustic analysis step, the vibration results from the vibration analysis step were used as initial values for radiated noise analysis and noise reduction analysis. Finally, the total cabin interior noise was predicted using the acoustic results from the acoustic analysis step. Each step was applied to a cabin of a middle-sized excavator and verified by comparison with measured data. The cabin interior noise of a middle-sized wheel loader and a large-sized forklift were predicted using the analysis procedure of the four steps and were compared with measured data. The interior noise analysis procedure of construction equipment cabins is expected to be used during the preliminary design stage

Noise can speed convergence in Markov chains.

Science.gov (United States)

Franzke, Brandon; Kosko, Bart

2011-10-01

A new theorem shows that noise can speed convergence to equilibrium in discrete finite-state Markov chains. The noise applies to the state density and helps the Markov chain explore improbable regions of the state space. The theorem ensures that a stochastic-resonance noise benefit exists for states that obey a vector-norm inequality. Such noise leads to faster convergence because the noise reduces the norm components. A corollary shows that a noise benefit still occurs if the system states obey an alternate norm inequality. This leads to a noise-benefit algorithm that requires knowledge of the steady state. An alternative blind algorithm uses only past state information to achieve a weaker noise benefit. Simulations illustrate the predicted noise benefits in three well-known Markov models. The first model is a two-parameter Ehrenfest diffusion model that shows how noise benefits can occur in the class of birth-death processes. The second model is a Wright-Fisher model of genotype drift in population genetics. The third model is a chemical reaction network of zeolite crystallization. A fourth simulation shows a convergence rate increase of 64% for states that satisfy the theorem and an increase of 53% for states that satisfy the corollary. A final simulation shows that even suboptimal noise can speed convergence if the noise applies over successive time cycles. Noise benefits tend to be sharpest in Markov models that do not converge quickly and that do not have strong absorbing states.

Modeling signal-to-noise ratio of otoacoustic emissions in workers exposed to different industrial noise levels

Directory of Open Access Journals (Sweden)

Parvin Nassiri

2016-01-01

Full Text Available Introduction: Noise is considered as the most common cause of harmful physical effects in the workplace. A sound that is generated from within the inner ear is known as an otoacoustic emission (OAE. Distortion-product otoacoustic emissions (DPOAEs assess evoked emission and hearing capacity. The aim of this study was to assess the signal-to-noise ratio in different frequencies and at different times of the shift work in workers exposed to various levels of noise. It was also aimed to provide a statistical model for signal-to-noise ratio (SNR of OAEs in different frequencies based on the two variables of sound pressure level (SPL and exposure time. Materials and Methods: This case–control study was conducted on 45 workers during autumn 2014. The workers were divided into three groups based on the level of noise exposure. The SNR was measured in frequencies of 1000, 2000, 3000, 4000, and 6000 Hz in both ears, and in three different time intervals during the shift work. According to the inclusion criterion, SNR of 6 dB or greater was included in the study. The analysis was performed using repeated measurements of analysis of variance, spearman correlation coefficient, and paired samples t-test. Results: The results showed that there was no statistically significant difference between the three exposed groups in terms of the mean values of SNR (P > 0.05. Only in signal pressure levels of 88 dBA with an interval time of 10:30–11:00 AM, there was a statistically significant difference between the right and left ears with the mean SNR values of 3000 frequency (P = 0.038. The SPL had a significant effect on the SNR in both the right and left ears (P = 0.023, P = 0.041. The effect of the duration of measurement on the SNR was statistically significant in both the right and left ears (P = 0.027, P < 0.001. Conclusion: The findings of this study demonstrated that after noise exposure during the shift, SNR of OAEs reduced from the

Land Use Regression Modeling of Outdoor Noise Exposure in Informal Settlements in Western Cape, South Africa

Science.gov (United States)

Sieber, Chloé; Ragettli, Martina S.; Toyib, Olaniyan; Baatjies, Roslyn; Saucy, Apolline; Probst-Hensch, Nicole; Dalvie, Mohamed Aqiel; Röösli, Martin

2017-01-01

In low- and middle-income countries, noise exposure and its negative health effects have been little explored. The present study aimed to assess the noise exposure situation in adults living in informal settings in the Western Cape Province, South Africa. We conducted continuous one-week outdoor noise measurements at 134 homes in four different areas. These data were used to develop a land use regression (LUR) model to predict A-weighted day-evening-night equivalent sound levels (Lden) from geographic information system (GIS) variables. Mean noise exposure during day (6:00–18:00) was 60.0 A-weighted decibels (dB(A)) (interquartile range 56.9–62.9 dB(A)), during night (22:00–6:00) 52.9 dB(A) (49.3–55.8 dB(A)) and average Lden was 63.0 dB(A) (60.1–66.5 dB(A)). Main predictors of the LUR model were related to road traffic and household density. Model performance was low (adjusted R2 = 0.130) suggesting that other influences than those represented in the geographic predictors are relevant for noise exposure. This is one of the few studies on the noise exposure situation in low- and middle-income countries. It demonstrates that noise exposure levels are high in these settings. PMID:29053590

Performance of FHWA model for predicting traffic noise: a case study of metropolitan city, Lucknow (India

Directory of Open Access Journals (Sweden)

J. B. Srivastava

2009-09-01

Full Text Available Industrial and transport activities are the two major sources of noise pollution in any metropolitan city. Lucknow city, the capital of the largest populated state Uttar Pradesh in India has an area of 310 sq. km and is rapidly growing as a commercial, industrial and trading centre of northern India. The population of Lucknow city as per census 2001 is 22.45 Lacs. It is expected that by the year 2021 it will make 45 Lacs. The total vehicle population in Lucknow city on 31 March 2008, was nearly 1 million with almost 80% two wheelers, 12% cars, 1.36% three wheelers, 0.45% buses etc. A study was carried out to assess the existing status of noise levels and its impacts on the environment with a possibility of further expansion of the city. Ambient noise levels were measured at different locations selected on the basis of land use such as silence, heavy traffic and residential and commercial zones. It was found that noise levels at all selected locations were much higher (75–90 dB than the prescribed limits. The observed traffic volume and data on road geometry were used to predict noise levels using Federal Highway Administration Agency (FHWA model and the calculated noise levels were compared with the observed levels for checking the suitability of this model for predicting the future levels. It was established that the results obtained by FHWA model were very close to the observed noise levels and that the model was suitable to be used for other similar metropolitan cities in India.

The Realistic Versus the Spherical Head Model in EEG Dipole Source Analysis in the Presence of Noise

National Research Council Canada - National Science Library

Vanrumste, Bart

2001-01-01

.... For 27 electrodes, an EEG epoch of one time sample and spatially white Gaussian noise we found that the importance of the realistic head model over the spherical head model reduces by increasing the noise level.

Acoustic noise improves motor learning in spontaneously hypertensive rats, a rat model of attention deficit hyperactivity disorder.

Science.gov (United States)

Söderlund, Göran B W; Eckernäs, Daniel; Holmblad, Olof; Bergquist, Filip

2015-03-01

The spontaneously hypertensive (SH) rat model of ADHD displays impaired motor learning. We used this characteristic to study if the recently described acoustic noise benefit in learning in children with ADHD is also observed in the SH rat model. SH rats and a Wistar control strain were trained in skilled reach and rotarod running under either ambient noise or in 75 dBA white noise. In other animals the effect of methylphenidate (MPH) on motor learning was assessed with the same paradigms. To determine if acoustic noise influenced spontaneous motor activity, the effect of acoustic noise was also determined in the open field activity paradigm. We confirm impaired motor learning in the SH rat compared to Wistar SCA controls. Acoustic noise restored motor learning in SH rats learning the Montoya reach test and the rotarod test, but had no influence on learning in Wistar rats. Noise had no effect on open field activity in SH rats, but increased corner time in Wistar. MPH completely restored rotarod learning and performance but did not improve skilled reach in the SH rat. It is suggested that the acoustic noise benefit previously reported in children with ADHD is shared by the SH rat model of ADHD, and the effect is in the same range as that of stimulant treatment. Acoustic noise may be useful as a non-pharmacological alternative to stimulant medication in the treatment of ADHD. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Cascaded analysis of signal and noise propagation through a heterogeneous breast model

International Nuclear Information System (INIS)

Mainprize, James G.; Yaffe, Martin J.

2010-01-01

Purpose: The detectability of lesions in radiographic images can be impaired by patterns caused by the surrounding anatomic structures. The presence of such patterns is often referred to as anatomic noise. Others have previously extended signal and noise propagation theory to include variable background structure as an additional noise term and used in simulations for analysis by human and ideal observers. Here, the analytic forms of the signal and noise transfer are derived to obtain an exact expression for any input random distribution and the ''power law'' filter used to generate the texture of the tissue distribution. Methods: A cascaded analysis of propagation through a heterogeneous model is derived for x-ray projection through simulated heterogeneous backgrounds. This is achieved by considering transmission through the breast as a correlated amplification point process. The analytic forms of the cascaded analysis were compared to monoenergetic Monte Carlo simulations of x-ray propagation through power law structured backgrounds. Results: As expected, it was found that although the quantum noise power component scales linearly with the x-ray signal, the anatomic noise will scale with the square of the x-ray signal. There was a good agreement between results obtained using analytic expressions for the noise power and those from Monte Carlo simulations for different background textures, random input functions, and x-ray fluence. Conclusions: Analytic equations for the signal and noise properties of heterogeneous backgrounds were derived. These may be used in direct analysis or as a tool to validate simulations in evaluating detectability.

Cognitive-Motivational Determinants of Residents' Civic Engagement and Health (Inequities) in the Context of Noise Action Planning: A Conceptual Model.

Science.gov (United States)

Riedel, Natalie; van Kamp, Irene; Köckler, Heike; Scheiner, Joachim; Loerbroks, Adrian; Claßen, Thomas; Bolte, Gabriele

2017-05-30

The Environmental Noise Directive expects residents to be actively involved in localising and selecting noise abatement interventions during the noise action planning process. Its intervention impact is meant to be homogeneous across population groups. Against the background of social heterogeneity and environmental disparities, however, the impact of noise action planning on exposure to traffic-related noise and its health effects is unlikely to follow homogenous distributions. Until now, there has been no study evaluating the impact of noise action measures on the social distribution of traffic-related noise exposure and health outcomes. We develop a conceptual (logic) model on cognitive-motivational determinants of residents' civic engagement and health (inequities) by integrating arguments from the Model on household's Vulnerability to the local Environment, the learned helplessness model in environmental psychology, the Cognitive Activation Theory of Stress, and the reserve capacity model. Specifically, we derive four hypothetical patterns of cognitive-motivational determinants yielding different levels of sustained physiological activation and expectancies of civic engagement. These patterns may help us understand why health inequities arise in the context of noise action planning and learn how to transform noise action planning into an instrument conducive to health equity. While building on existing frameworks, our conceptual model will be tested empirically in the next stage of our research process.

Modeling the Unites States government's economic cost of noise-induced hearing loss for a military population.

Science.gov (United States)

Tufts, Jennifer B; Weathersby, Paul K; Rodriguez, Francisco A

2010-05-01

The purpose of this paper is to demonstrate the feasibility and utility of developing economic cost models for noise-induced hearing loss (NIHL). First, we outline an economic model of NIHL for a population of US Navy sailors with an "industrial"-type noise exposure. Next, we describe the effect on NIHL-related cost of varying the two central model inputs--the noise-exposure level and the duration of exposure. Such an analysis can help prioritize promising areas, to which limited resources to reduce NIHL-related costs should be devoted. NIHL-related costs borne by the US government were computed on a yearly basis using a finite element approach that took into account varying levels of susceptibility to NIHL. Predicted hearing thresholds for the population were computed with ANSI S3.44-1996 and then used as the basis for the calculation of NIHL-related costs. Annual and cumulative costs were tracked. Noise-exposure level and duration were systematically varied to determine their effects on the expected lifetime NIHL-related cost of a specific US Navy sailor population. Our nominal noise-exposure case [93 dB(A) for six years] yielded a total expected lifetime cost of US $13,472 per sailor, with plausible lower and upper bounds of US $2,500 and US $26,000. Starting with the nominal case, a decrease of 50% in exposure level or duration would yield cost savings of approximately 23% and 19%, respectively. We concluded that a reduction in noise level would be more somewhat more cost-effective than the same percentage reduction in years of exposure. Our economic cost model can be used to estimate the changes in NIHL-related costs that would result from changes in noise-exposure level and/or duration for a single military population. Although the model is limited at present, suggestions are provided for adapting it to civilian populations.

Light aircraft sound transmission studies - Noise reduction model

Science.gov (United States)

Atwal, Mahabir S.; Heitman, Karen E.; Crocker, Malcolm J.

1987-01-01

Experimental tests conducted on the fuselage of a single-engine Piper Cherokee light aircraft suggest that the cabin interior noise can be reduced by increasing the transmission loss of the dominant sound transmission paths and/or by increasing the cabin interior sound absorption. The validity of using a simple room equation model to predict the cabin interior sound-pressure level for different fuselage and exterior sound field conditions is also presented. The room equation model is based on the sound power flow balance for the cabin space and utilizes the measured transmitted sound intensity data. The room equation model predictions were considered good enough to be used for preliminary acoustical design studies.

Effects of Perfectly Correlated and Anti-Correlated Noise in a Logistic Growth Model

International Nuclear Information System (INIS)

Zhang Li; Cao Li

2011-01-01

The logistic growth model with correlated additive and multiplicative Gaussian white noise is used to analyze tumor cell population. The effects of perfectly correlated and anti-correlated noise on the stationary properties of tumor cell population are studied. As in both cases the diffusion coefficient has zero point in real number field, some special features of the system are arisen. It is found that in both cases, the increase of the multiplicative noise intensity cause tumor cell extinction. In the perfectly anti-correlated case, the stationary probability distribution as a function of tumor cell population exhibit two extrema. (general)

The effects of noise on binocular rivalry waves: a stochastic neural field model

International Nuclear Information System (INIS)

Webber, Matthew A; Bressloff, Paul C

2013-01-01

We analyze the effects of extrinsic noise on traveling waves of visual perception in a competitive neural field model of binocular rivalry. The model consists of two one-dimensional excitatory neural fields, whose activity variables represent the responses to left-eye and right-eye stimuli, respectively. The two networks mutually inhibit each other, and slow adaptation is incorporated into the model by taking the network connections to exhibit synaptic depression. We first show how, in the absence of any noise, the system supports a propagating composite wave consisting of an invading activity front in one network co-moving with a retreating front in the other network. Using a separation of time scales and perturbation methods previously developed for stochastic reaction–diffusion equations, we then show how extrinsic noise in the activity variables leads to a diffusive-like displacement (wandering) of the composite wave from its uniformly translating position at long time scales, and fluctuations in the wave profile around its instantaneous position at short time scales. We use our analysis to calculate the first-passage-time distribution for a stochastic rivalry wave to travel a fixed distance, which we find to be given by an inverse Gaussian. Finally, we investigate the effects of noise in the depression variables, which under an adiabatic approximation lead to quenched disorder in the neural fields during propagation of a wave. (paper)

Image simulation and a model of noise power spectra across a range of mammographic beam qualities

Energy Technology Data Exchange (ETDEWEB)

Mackenzie, Alistair, E-mail: alistairmackenzie@nhs.net; Dance, David R.; Young, Kenneth C. [National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford GU2 7XX, United Kingdom and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Diaz, Oliver [Centre for Vision, Speech and Signal Processing, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom and Computer Vision and Robotics Research Institute, University of Girona, Girona 17071 (Spain)

2014-12-15

Purpose: The aim of this work is to create a model to predict the noise power spectra (NPS) for a range of mammographic radiographic factors. The noise model was necessary to degrade images acquired on one system to match the image quality of different systems for a range of beam qualities. Methods: Five detectors and x-ray systems [Hologic Selenia (ASEh), Carestream computed radiography CR900 (CRc), GE Essential (CSI), Carestream NIP (NIPc), and Siemens Inspiration (ASEs)] were characterized for this study. The signal transfer property was measured as the pixel value against absorbed energy per unit area (E) at a reference beam quality of 28 kV, Mo/Mo or 29 kV, W/Rh with 45 mm polymethyl methacrylate (PMMA) at the tube head. The contributions of the three noise sources (electronic, quantum, and structure) to the NPS were calculated by fitting a quadratic at each spatial frequency of the NPS against E. A quantum noise correction factor which was dependent on beam quality was quantified using a set of images acquired over a range of radiographic factors with different thicknesses of PMMA. The noise model was tested for images acquired at 26 kV, Mo/Mo with 20 mm PMMA and 34 kV, Mo/Rh with 70 mm PMMA for three detectors (ASEh, CRc, and CSI) over a range of exposures. The NPS were modeled with and without the noise correction factor and compared with the measured NPS. A previous method for adapting an image to appear as if acquired on a different system was modified to allow the reference beam quality to be different from the beam quality of the image. The method was validated by adapting the ASEh flat field images with two thicknesses of PMMA (20 and 70 mm) to appear with the imaging characteristics of the CSI and CRc systems. Results: The quantum noise correction factor rises with higher beam qualities, except for CR systems at high spatial frequencies, where a flat response was found against mean photon energy. This is due to the dominance of secondary quantum noise

Effect of Correlated Noises in a Genetic Model

International Nuclear Information System (INIS)

Li, Zhang; Li, Cao

2010-01-01

The Stratonovich stochastic differential equation is used to analyze genotype selection in the presence of correlated Gaussian white noises. We study the steady state properties of the genotype selection and discuss the effects of the correlated noises. It is found that the degree of correlation of the noises can be used to select one type of genes from another type of mixing genes. The strong selection of genes caused by a large value of multiplicative noise intensity can be weakened by the intensive negative correlation. (general)

Nonlinear unitary quantum collapse model with self-generated noise

Science.gov (United States)

Geszti, Tamás

2018-04-01

Collapse models including some external noise of unknown origin are routinely used to describe phenomena on the quantum-classical border; in particular, quantum measurement. Although containing nonlinear dynamics and thereby exposed to the possibility of superluminal signaling in individual events, such models are widely accepted on the basis of fully reproducing the non-signaling statistical predictions of quantum mechanics. Here we present a deterministic nonlinear model without any external noise, in which randomness—instead of being universally present—emerges in the measurement process, from deterministic irregular dynamics of the detectors. The treatment is based on a minimally nonlinear von Neumann equation for a Stern–Gerlach or Bell-type measuring setup, containing coordinate and momentum operators in a self-adjoint skew-symmetric, split scalar product structure over the configuration space. The microscopic states of the detectors act as a nonlocal set of hidden parameters, controlling individual outcomes. The model is shown to display pumping of weights between setup-defined basis states, with a single winner randomly selected and the rest collapsing to zero. Environmental decoherence has no role in the scenario. Through stochastic modelling, based on Pearle’s ‘gambler’s ruin’ scheme, outcome probabilities are shown to obey Born’s rule under a no-drift or ‘fair-game’ condition. This fully reproduces quantum statistical predictions, implying that the proposed non-linear deterministic model satisfies the non-signaling requirement. Our treatment is still vulnerable to hidden signaling in individual events, which remains to be handled by future research.

Noise Gating Solar Images

Science.gov (United States)

DeForest, Craig; Seaton, Daniel B.; Darnell, John A.

2017-08-01

I present and demonstrate a new, general purpose post-processing technique, "3D noise gating", that can reduce image noise by an order of magnitude or more without effective loss of spatial or temporal resolution in typical solar applications.Nearly all scientific images are, ultimately, limited by noise. Noise can be direct Poisson "shot noise" from photon counting effects, or introduced by other means such as detector read noise. Noise is typically represented as a random variable (perhaps with location- or image-dependent characteristics) that is sampled once per pixel or once per resolution element of an image sequence. Noise limits many aspects of image analysis, including photometry, spatiotemporal resolution, feature identification, morphology extraction, and background modeling and separation.Identifying and separating noise from image signal is difficult. The common practice of blurring in space and/or time works because most image "signal" is concentrated in the low Fourier components of an image, while noise is evenly distributed. Blurring in space and/or time attenuates the high spatial and temporal frequencies, reducing noise at the expense of also attenuating image detail. Noise-gating exploits the same property -- "coherence" -- that we use to identify features in images, to separate image features from noise.Processing image sequences through 3-D noise gating results in spectacular (more than 10x) improvements in signal-to-noise ratio, while not blurring bright, resolved features in either space or time. This improves most types of image analysis, including feature identification, time sequence extraction, absolute and relative photometry (including differential emission measure analysis), feature tracking, computer vision, correlation tracking, background modeling, cross-scale analysis, visual display/presentation, and image compression.I will introduce noise gating, describe the method, and show examples from several instruments (including SDO

Investigation of hydraulic transmission noise sources

Science.gov (United States)

Klop, Richard J.

Advanced hydrostatic transmissions and hydraulic hybrids show potential in new market segments such as commercial vehicles and passenger cars. Such new applications regard low noise generation as a high priority, thus, demanding new quiet hydrostatic transmission designs. In this thesis, the aim is to investigate noise sources of hydrostatic transmissions to discover strategies for designing compact and quiet solutions. A model has been developed to capture the interaction of a pump and motor working in a hydrostatic transmission and to predict overall noise sources. This model allows a designer to compare noise sources for various configurations and to design compact and inherently quiet solutions. The model describes dynamics of the system by coupling lumped parameter pump and motor models with a one-dimensional unsteady compressible transmission line model. The model has been verified with dynamic pressure measurements in the line over a wide operating range for several system structures. Simulation studies were performed illustrating sensitivities of several design variables and the potential of the model to design transmissions with minimal noise sources. A semi-anechoic chamber has been designed and constructed suitable for sound intensity measurements that can be used to derive sound power. Measurements proved the potential to reduce audible noise by predicting and reducing both noise sources. Sound power measurements were conducted on a series hybrid transmission test bench to validate the model and compare predicted noise sources with sound power.

Recursive Subspace Identification of AUV Dynamic Model under General Noise Assumption

Directory of Open Access Journals (Sweden)

Zheping Yan

2014-01-01

Full Text Available A recursive subspace identification algorithm for autonomous underwater vehicles (AUVs is proposed in this paper. Due to the advantages at handling nonlinearities and couplings, the AUV model investigated here is for the first time constructed as a Hammerstein model with nonlinear feedback in the linear part. To better take the environment and sensor noises into consideration, the identification problem is concerned as an errors-in-variables (EIV one which means that the identification procedure is under general noise assumption. In order to make the algorithm recursively, propagator method (PM based subspace approach is extended into EIV framework to form the recursive identification method called PM-EIV algorithm. With several identification experiments carried out by the AUV simulation platform, the proposed algorithm demonstrates its effectiveness and feasibility.

A Survey of Modelling and Identification of Quadrotor Robot

Directory of Open Access Journals (Sweden)

Xiaodong Zhang

2014-01-01

Full Text Available A quadrotor is a rotorcraft capable of hover, forward flight, and VTOL and is emerging as a fundamental research and application platform at present with flexibility, adaptability, and ease of construction. Since a quadrotor is basically considered an unstable system with the characteristics of dynamics such as being intensively nonlinear, multivariable, strongly coupled, and underactuated, a precise and practical model is critical to control the vehicle which seems to be simple to operate. As a rotorcraft, the dynamics of a quadrotor is mainly dominated by the complicated aerodynamic effects of the rotors. This paper gives a tutorial of the platform configuration, methodology of modeling, comprehensive nonlinear model, the aerodynamic effects, and model identification for a quadrotor.

The Signal Importance of Noise

Science.gov (United States)

Macy, Michael; Tsvetkova, Milena

2015-01-01

Noise is widely regarded as a residual category--the unexplained variance in a linear model or the random disturbance of a predictable pattern. Accordingly, formal models often impose the simplifying assumption that the world is noise-free and social dynamics are deterministic. Where noise is assigned causal importance, it is often assumed to be a…

Noise source analysis of nuclear ship Mutsu plant using multivariate autoregressive model

International Nuclear Information System (INIS)

Hayashi, K.; Shimazaki, J.; Shinohara, Y.

1996-01-01

The present study is concerned with the noise sources in N.S. Mutsu reactor plant. The noise experiments on the Mutsu plant were performed in order to investigate the plant dynamics and the effect of sea condition and and ship motion on the plant. The reactor noise signals as well as the ship motion signals were analyzed by a multivariable autoregressive (MAR) modeling method to clarify the noise sources in the reactor plant. It was confirmed from the analysis results that most of the plant variables were affected mainly by a horizontal component of the ship motion, that is the sway, through vibrations of the plant structures. Furthermore, the effect of ship motion on the reactor power was evaluated through the analysis of wave components extracted by a geometrical transform method. It was concluded that the amplitude of the reactor power oscillation was about 0.15% in normal sea condition, which was small enough for safe operation of the reactor plant. (authors)

Noise-shaping all-digital phase-locked loops modeling, simulation, analysis and design

CERN Document Server

Brandonisio, Francesco

2014-01-01

This book presents a novel approach to the analysis and design of all-digital phase-locked loops (ADPLLs), technology widely used in wireless communication devices. The authors provide an overview of ADPLL architectures, time-to-digital converters (TDCs) and noise shaping. Realistic examples illustrate how to analyze and simulate phase noise in the presence of sigma-delta modulation and time-to-digital conversion. Readers will gain a deep understanding of ADPLLs and the central role played by noise-shaping. A range of ADPLL and TDC architectures are presented in unified manner. Analytical and simulation tools are discussed in detail. Matlab code is included that can be reused to design, simulate and analyze the ADPLL architectures that are presented in the book.   • Discusses in detail a wide range of all-digital phase-locked loops architectures; • Presents a unified framework in which to model time-to-digital converters for ADPLLs; • Explains a procedure to predict and simulate phase noise in oscil...

Sound quality prediction for engine-radiated noise

Science.gov (United States)

Liu, Hai; Zhang, Junhong; Guo, Peng; Bi, Fengrong; Yu, Hanzhengnan; Ni, Guangjian

2015-05-01

Diesel engine-radiated noise quality prediction is an important topic because engine noise has a significant impact on the overall vehicle noise. Sound quality prediction is based on subjective and objective evaluation of engine noise. The integrated satisfaction index (ISI) is proposed as a criterion for differentiate noise quality in the subjective evaluation, and five psychoacoustic parameters are selected for characterizing and analyzing the noise quality of the diesel engine objectively. The combination of support vector machines (SVM) and genetic algorithm (GA) is proposed in order to establish a model for predicting the diesel engine-radiated noise quality for all operation conditions. The performance of the GA-SVM model is compared with the BP neural network model, and the results show that the mean relative error of the GA-SVM model is smaller than the BP neural network model. The importance rank of the sound quality metrics to the ISI is indicated by the non-parametric correlation analysis. This study suggests that the GA-SVM model is very useful for accurately predicting the diesel engine-radiated noise quality.

Cognitive-Motivational Determinants of Residents’ Civic Engagement and Health (Inequities in the Context of Noise Action Planning: A Conceptual Model

Directory of Open Access Journals (Sweden)

Natalie Riedel

2017-05-01

Full Text Available The Environmental Noise Directive expects residents to be actively involved in localising and selecting noise abatement interventions during the noise action planning process. Its intervention impact is meant to be homogeneous across population groups. Against the background of social heterogeneity and environmental disparities, however, the impact of noise action planning on exposure to traffic-related noise and its health effects is unlikely to follow homogenous distributions. Until now, there has been no study evaluating the impact of noise action measures on the social distribution of traffic-related noise exposure and health outcomes. We develop a conceptual (logic model on cognitive-motivational determinants of residents’ civic engagement and health (inequities by integrating arguments from the Model on household’s Vulnerability to the local Environment, the learned helplessness model in environmental psychology, the Cognitive Activation Theory of Stress, and the reserve capacity model. Specifically, we derive four hypothetical patterns of cognitive-motivational determinants yielding different levels of sustained physiological activation and expectancies of civic engagement. These patterns may help us understand why health inequities arise in the context of noise action planning and learn how to transform noise action planning into an instrument conducive to health equity. While building on existing frameworks, our conceptual model will be tested empirically in the next stage of our research process.

Characterization of Flap Edge Noise Radiation from a High-Fidelity Airframe Model

Science.gov (United States)

Humphreys, William M., Jr.; Khorrami, Mehdi R.; Lockard, David P.; Neuhart, Dan H.; Bahr, Christopher J.

2015-01-01

The results of an experimental study of the noise generated by a baseline high-fidelity airframe model are presented. The test campaign was conducted in the open-jet test section of the NASA Langley 14- by 22-foot Subsonic Tunnel on an 18%-scale, semi-span Gulfstream airframe model incorporating a trailing edge flap and main landing gear. Unsteady surface pressure measurements were obtained from a series of sensors positioned along the two flap edges, and far field acoustic measurements were obtained using a 97-microphone phased array that viewed the pressure side of the airframe. The DAMAS array deconvolution method was employed to determine the locations and strengths of relevant noise sources in the vicinity of the flap edges and the landing gear. A Coherent Output Power (COP) spectral method was used to couple the unsteady surface pressures measured along the flap edges with the phased array output. The results indicate that outboard flap edge noise is dominated by the flap bulb seal cavity with very strong COP coherence over an approximate model-scale frequency range of 1 to 5 kHz observed between the array output and those unsteady pressure sensors nearest the aft end of the cavity. An examination of experimental COP spectra for the inboard flap proved inconclusive, most likely due to a combination of coherence loss caused by decorrelation of acoustic waves propagating through the thick wind tunnel shear layer and contamination of the spectra by tunnel background noise at lower frequencies. Directivity measurements obtained from integration of DAMAS pressure-squared values over defined geometric zones around the model show that the baseline flap and landing gear are only moderately directional as a function of polar emission angle.

Impulsive Noise Characterization in Narrowband Power Line Communication

Directory of Open Access Journals (Sweden)

Li Bai

2018-04-01

Full Text Available Currently, narrowband Power line communication (PLC is considered an attractive communication system in smart grid environments for applications such as advanced metering infrastructure (AMI. In this paper, we will present a comprehensive comparison and analysis in time and frequency domain of noise measured in China and Italy. In addition, impulsive noise in these two countries are mainly analyzed and modeled using two probability based models, Middleton Class A (MCA model and α stable distribution model. The results prove that noise measured in China is rich in impulsive noise, and can be modeled well by α stable distribution model, while noise measured in Italy has less impulsive noise, and can be better modeled by the MCA model.

Enhancement of epidemic spread by noise and stochastic resonance in spatial network models with viral dynamics.

Science.gov (United States)

Tuckwell, H C; Toubiana, L; Vibert, J F

2000-05-01

We extend a previous dynamical viral network model to include stochastic effects. The dynamical equations for the viral and immune effector densities within a host population of size n are bilinear, and the noise is white, additive, and Gaussian. The individuals are connected with an n x n transmission matrix, with terms which decay exponentially with distance. In a single individual, for the range of noise parameters considered, it is found that increasing the amplitude of the noise tends to decrease the maximum mean virion level, and slightly accelerate its attainment. Two different spatial dynamical models are employed to ascertain the effects of environmental stochasticity on viral spread. In the first model transmission is unrestricted and there is no threshold within individuals. This model has the advantage that it can be analyzed using a Fokker-Planck approach. The noise is found both to synchronize and uniformize the trajectories of the viral levels across the population of infected individuals, and thus to promote the epidemic spread of the virus. Quantitative measures of the speed of spread and overall amplitude of the epidemic are obtained as functions of the noise and virulence parameters. The mean amplitude increases steadily without threshold effects for a fixed value of the virulence as the noise amplitude sigma is increased, and there is no evidence of a stochastic resonance. However, the speed of transmission, both with respect to its mean and variance, undergoes rapid increases as sigma changes by relatively small amounts. In the second, more realistic, model, there is a threshold for infection and an upper limit to the transmission rate. There may be no spread of infection at all in the absence of noise. With increasing noise level and a low threshold, the mean maximum virion level grows quickly and shows a broad-based stochastic resonance effect. When the threshold within individuals is increased, the mean population virion level increases only

Tunable Interior Rotorcraft Noise Control, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — CRG has recently developed a new class of shape memory polymers (SMP) that are electrically activated, as opposed to the more mature thermally activated SMPs....

A numerical model for ocean ultra-low frequency noise: wave-generated acoustic-gravity and Rayleigh modes.

Science.gov (United States)

Ardhuin, Fabrice; Lavanant, Thibaut; Obrebski, Mathias; Marié, Louis; Royer, Jean-Yves; d'Eu, Jean-François; Howe, Bruce M; Lukas, Roger; Aucan, Jerome

2013-10-01

The generation of ultra-low frequency acoustic noise (0.1 to 1 Hz) by the nonlinear interaction of ocean surface gravity waves is well established. More controversial are the quantitative theories that attempt to predict the recorded noise levels and their variability. Here a single theoretical framework is used to predict the noise level associated with propagating pseudo-Rayleigh modes and evanescent acoustic-gravity modes. The latter are dominant only within 200 m from the sea surface, in shallow or deep water. At depths larger than 500 m, the comparison of a numerical noise model with hydrophone records from two open-ocean sites near Hawaii and the Kerguelen islands reveal: (a) Deep ocean acoustic noise at frequencies 0.1 to 1 Hz is consistent with the Rayleigh wave theory, in which the presence of the ocean bottom amplifies the noise by 10 to 20 dB; (b) in agreement with previous results, the local maxima in the noise spectrum support the theoretical prediction for the vertical structure of acoustic modes; and (c) noise level and variability are well predicted for frequencies up to 0.4 Hz. Above 0.6 Hz, the model results are less accurate, probably due to the poor estimation of the directional properties of wind-waves with frequencies higher than 0.3 Hz.

Robustness of SOC Estimation Algorithms for EV Lithium-Ion Batteries against Modeling Errors and Measurement Noise

Directory of Open Access Journals (Sweden)

Xue Li

2015-01-01

Full Text Available State of charge (SOC is one of the most important parameters in battery management system (BMS. There are numerous algorithms for SOC estimation, mostly of model-based observer/filter types such as Kalman filters, closed-loop observers, and robust observers. Modeling errors and measurement noises have critical impact on accuracy of SOC estimation in these algorithms. This paper is a comparative study of robustness of SOC estimation algorithms against modeling errors and measurement noises. By using a typical battery platform for vehicle applications with sensor noise and battery aging characterization, three popular and representative SOC estimation methods (extended Kalman filter, PI-controlled observer, and H∞ observer are compared on such robustness. The simulation and experimental results demonstrate that deterioration of SOC estimation accuracy under modeling errors resulted from aging and larger measurement noise, which is quantitatively characterized. The findings of this paper provide useful information on the following aspects: (1 how SOC estimation accuracy depends on modeling reliability and voltage measurement accuracy; (2 pros and cons of typical SOC estimators in their robustness and reliability; (3 guidelines for requirements on battery system identification and sensor selections.

Maximum Correntropy Criterion Kalman Filter for α-Jerk Tracking Model with Non-Gaussian Noise

Directory of Open Access Journals (Sweden)

Bowen Hou

2017-11-01

Full Text Available As one of the most critical issues for target track, α -jerk model is an effective maneuver target track model. Non-Gaussian noises always exist in the track process, which usually lead to inconsistency and divergence of the track filter. A novel Kalman filter is derived and applied on α -jerk tracking model to handle non-Gaussian noise. The weighted least square solution is presented and the standard Kalman filter is deduced firstly. A novel Kalman filter with the weighted least square based on the maximum correntropy criterion is deduced. The robustness of the maximum correntropy criterion is also analyzed with the influence function and compared with the Huber-based filter, and, moreover, the kernel size of Gaussian kernel plays an important role in the filter algorithm. A new adaptive kernel method is proposed in this paper to adjust the parameter in real time. Finally, simulation results indicate the validity and the efficiency of the proposed filter. The comparison study shows that the proposed filter can significantly reduce the noise influence for α -jerk model.

In Vitro Studies and Preliminary Mathematical Model for Jet Fuel and Noise Induced Auditory Impairment

Science.gov (United States)

2015-06-01

of JP-8 and a Fischer- Tropsch synthetic jet fuel following subacute inhalation exposure in rats. Toxicol Sci 116(1): 239-248. Gallinat, J...AFRL-RH-WP-TR-2015-0084 IN VITRO STUDIES AND PRELIMINARY MATHEMATICAL MODEL FOR JET FUEL AND NOISE INDUCED AUDITORY IMPAIRMENT...April 2014 – September 2014 4. TITLE AND SUBTITLE In Vitro Studies and Preliminary Mathematical Model for Jet Fuel and Noise Induced Auditory

Report on inter-noise 99; Inter-noise 99 sanka hokok

Energy Technology Data Exchange (ETDEWEB)

Koike, H. [Japan Automobile Research Institute Inc., Tsukuba (Japan)

2000-04-01

Inter-Noise (International Congress on Noise Control Engineering) is a society on noise/vibration and the control technology. Inter-Noise 99 was held on December 6, 7 and 8, 1999, at Fort Lauderdale, Florida, the U.S. The theme was Noise Control in the New Millennium. The number of the participants registered was 555 (151 from the U.S., 89 from Japan, 248 from European countries, and 69 from Asian/other countries). Dr. Harold Marshall gave a keynote lecture titled Noise Control by Design in the 21st Century - An Architectural Acoustic Perspective. From a standpoint of architectural acoustics, he stated the perspective, subjects, and course of the technical development pertaining to technologies needed in the 21st century. The papers read are mostly from the following fields: measuring technology, military exercise noise, modeling, forecast and simulation, aerodynamic/underwater sound, etc. In the session on the tire noise where the author read a paper, 14 papers were read. The number of the papers read was more than that in 1998, probably influenced by the tire noise regulation in Europe and Japan. (translated by NEDO)

Noise from offshore wind turbines

Energy Technology Data Exchange (ETDEWEB)

Soendergaard, B.; Plovsing, B.

2005-07-01

Noise assessment of wind turbines through calculations is based on sound power levels measured according to e.g. IEC 61400-11. With larger wind turbines and distances some of the calculation models give erroneous results. Noise propagation over water is different from propagation over land. For that reason it is important be able to make valid noise assessments for offshore wind farms. A suggestion for an offshore measurement method is described and a survey of models for noise propagation offshore has been made. (au)

Railroad Noise: Economic Valuation and Policy

NARCIS (Netherlands)

Brons, M.R.E.; Nijkamp, P.; Pels, E.; Rietveld, P.

2003-01-01

In developed countries noise annoyance is an important source of environmental concern. Research on noise annoyance caused by railroad traffic is relatively underdeveloped. Here, a causal chain model is presented in which railroad traffic density, noise emission, noise immission and noise annoyance

Spatiotemporal noise covariance estimation from limited empirical magnetoencephalographic data

International Nuclear Information System (INIS)

Jun, Sung C; Plis, Sergey M; Ranken, Doug M; Schmidt, David M

2006-01-01

The performance of parametric magnetoencephalography (MEG) and electroencephalography (EEG) source localization approaches can be degraded by the use of poor background noise covariance estimates. In general, estimation of the noise covariance for spatiotemporal analysis is difficult mainly due to the limited noise information available. Furthermore, its estimation requires a large amount of storage and a one-time but very large (and sometimes intractable) calculation or its inverse. To overcome these difficulties, noise covariance models consisting of one pair or a sum of multi-pairs of Kronecker products of spatial covariance and temporal covariance have been proposed. However, these approaches cannot be applied when the noise information is very limited, i.e., the amount of noise information is less than the degrees of freedom of the noise covariance models. A common example of this is when only averaged noise data are available for a limited prestimulus region (typically at most a few hundred milliseconds duration). For such cases, a diagonal spatiotemporal noise covariance model consisting of sensor variances with no spatial or temporal correlation has been the common choice for spatiotemporal analysis. In this work, we propose a different noise covariance model which consists of diagonal spatial noise covariance and Toeplitz temporal noise covariance. It can easily be estimated from limited noise information, and no time-consuming optimization and data-processing are required. Thus, it can be used as an alternative choice when one-pair or multi-pair noise covariance models cannot be estimated due to lack of noise information. To verify its capability we used Bayesian inference dipole analysis and a number of simulated and empirical datasets. We compared this covariance model with other existing covariance models such as conventional diagonal covariance, one-pair and multi-pair noise covariance models, when noise information is sufficient to estimate them. We

Dynamical response of the Ising model to the time dependent magnetic field with white noise

Science.gov (United States)

Akıncı, Ümit

2018-03-01

The effect of the white noise in time dependent magnetic field on the dynamic behavior of the Ising model has been investigated within the effective field theory based on Glauber type of stochastic process. Discrete white noise has been chosen from both Gaussian and uniform probability distributions. Detailed investigation on probability distribution of dynamical order parameter results that, both type of noise distributions yield the same probability distribution related to the dynamical order parameter, namely Gaussian probability distribution. The variation of the parameters that describe the probability distribution of dynamical order parameter (mean value and standard deviation) with temperature and strength of the noise have been inspected. Also, it has been shown that, rising strength of the noise can induce dynamical phase transition in the system.

Modeling of pH Dependent Electrochemical Noise in Ion Sensitive Field Effect Transistors ISFET

Directory of Open Access Journals (Sweden)

M. P. Das

2013-02-01

Full Text Available pH ISFETs are very important sensor for in vivo continuous monitoring application of physiological and environmental system. The accuracy of Ion Sensitive Field Effect Transistor (ISFET output measurement is greatly affected by the presences of noise, drift and slow response of the device. Although the noise analysis of ISFET so far performed in different literature relates only to sources originated from Field Effect Transistor (FET structure which are almost constant for a particular device, the pH dependent electrochemical noise has not been substantially explored and analyzed. In this paper we have investigated the low frequency pH dependent electrochemical noise that originates from the ionic conductance of the electrode-electrolyte-Field Effect Transistor structure of the device and that the noise depends on the concentration of the electrolyte and 1/f in nature. The statistical and frequency analysis of this electrochemical noise of a commercial ISFET sensor, under room temperature has been performed for six different pH values ranging from pH2 to pH9.2. We have also proposed a concentration dependent a/f & b/f2 model of the noise with different values of the coefficients a, b.

Helicopter noise in hover: Computational modelling and experimental validation

Science.gov (United States)

Kopiev, V. F.; Zaytsev, M. Yu.; Vorontsov, V. I.; Karabasov, S. A.; Anikin, V. A.

2017-11-01

The aeroacoustic characteristics of a helicopter rotor are calculated by a new method, to assess its applicability in assessing rotor performance in hovering. Direct solution of the Euler equations in a noninertial coordinate system is used to calculate the near-field flow around the spinning rotor. The far-field noise field is calculated by the Ffowcs Williams-Hawkings (FW-H) method using permeable control surfaces that include the blade. For a multiblade rotor, the signal obtained is duplicated and shifted in phase for each successive blade. By that means, the spectral characteristics of the far-field noise may be obtained. To determine the integral aerodynamic characteristics of the rotor, software is written to calculate the thrust and torque characteristics from the near-field flow solution. The results of numerical simulation are compared with experimental acoustic and aerodynamic data for a large-scale model of a helicopter main rotor in an open test facility. Two- and four-blade configurations of the rotor are considered, in different hover conditions. The proposed method satisfactorily predicts the aerodynamic characteristics of the blades in such conditions and gives good estimates for the first harmonics of the noise. That permits the practical use of the proposed method, not only for hovering but also for forward flight.

Low frequency noise from wind turbines mechanisms of generation and its modelling

DEFF Research Database (Denmark)

Aagaard Madsen, Helge

2010-01-01

competitive designs compared with the upwind threebladed rotor. The simulation package comprises an aeroelastic time simulation code HAWC2 and an acoustic low frequency noise (LFN) prediction model. Computed time traces of rotor thrust and rotor torque from the aeroelastic model are input to the acoustic...

Consistent modelling of wind turbine noise propagation from source to receiver

DEFF Research Database (Denmark)

Barlas, Emre; Zhu, Wei Jun; Shen, Wen Zhong

2017-01-01

The unsteady nature of wind turbine noise is a major reason for annoyance. The variation of far-field sound pressure levels is not only caused by the continuous change in wind turbine noise source levels but also by the unsteady flow field and the ground characteristics between the turbine...... propagation of a 5 MW wind turbine is investigated. Sound pressure level time series evaluated at the source time are studied for varying wind speeds, surface roughness, and ground impedances within a 2000 m radius from the turbine....... and receiver. To take these phenomena into account, a consistent numerical technique that models the sound propagation from the source to receiver is developed. Large eddy simulation with an actuator line technique is employed for the flow modelling and the corresponding flow fields are used to simulate sound...

The effects of noise on binocular rivalry waves: a stochastic neural field model

KAUST Repository

Webber, Matthew A

2013-03-12

We analyze the effects of extrinsic noise on traveling waves of visual perception in a competitive neural field model of binocular rivalry. The model consists of two one-dimensional excitatory neural fields, whose activity variables represent the responses to left-eye and right-eye stimuli, respectively. The two networks mutually inhibit each other, and slow adaptation is incorporated into the model by taking the network connections to exhibit synaptic depression. We first show how, in the absence of any noise, the system supports a propagating composite wave consisting of an invading activity front in one network co-moving with a retreating front in the other network. Using a separation of time scales and perturbation methods previously developed for stochastic reaction-diffusion equations, we then show how extrinsic noise in the activity variables leads to a diffusive-like displacement (wandering) of the composite wave from its uniformly translating position at long time scales, and fluctuations in the wave profile around its instantaneous position at short time scales. We use our analysis to calculate the first-passage-time distribution for a stochastic rivalry wave to travel a fixed distance, which we find to be given by an inverse Gaussian. Finally, we investigate the effects of noise in the depression variables, which under an adiabatic approximation lead to quenched disorder in the neural fields during propagation of a wave. © 2013 IOP Publishing Ltd and SISSA Medialab srl.

NDARC NASA Design and Analysis of Rotorcraft - Input, Appendix 4

Science.gov (United States)

Johnson, Wayne

2016-01-01

The NDARC code performs design and analysis tasks. The design task involves sizing the rotorcraft to satisfy specified design conditions and missions. The analysis tasks can include off-design mission performance analysis, flight performance calculation for point operating conditions, and generation of subsystem or component performance maps. The principal tasks (sizing, mission analysis, flight performance analysis) are shown in the figure as boxes with heavy borders. Heavy arrows show control of subordinate tasks. The aircraft description consists of all the information, input and derived, that denes the aircraft. The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and propulsion. This information can be the result of the sizing task; can come entirely from input, for a fixed model; or can come from the sizing task in a previous case or previous job. The aircraft description information is available to all tasks and all solutions. The sizing task determines the dimensions, power, and weight of a rotorcraft that can perform a specified set of design conditions and missions. The aircraft size is characterized by parameters such as design gross weight, weight empty, rotor radius, and engine power available. The relations between dimensions, power, and weight generally require an iterative solution. From the design flight conditions and missions, the task can determine the total engine power or the rotor radius (or both power and radius can be fixed), as well as the design gross weight, maximum takeoff weight, drive system torque limit, and fuel tank capacity. For each propulsion group, the engine power or the rotor radius can be sized. Missions are defined for the sizing task, and for the mission performance analysis. A mission consists of a number of mission segments, for which time, distance, and fuel burn are evaluated. For the sizing task, certain missions are designated to be used for design gross weight calculations; for

Proceedings of the 2009 spring noise conference : noise awareness : supporting sound partnerships

International Nuclear Information System (INIS)

2009-01-01

This conference provided a forum for industry, government, public, academics and acoustical professionals to discuss innovations in environmental and occupational noise identification, measurement, regulation and control. In addition to raising awareness about expanding noise issues, the conference objectives were to promote responsible industrial development and to identify strategies for reducing workplace noise exposure. The papers focused on research, developments and case studies and highlighted current issues and advancements in technology and software. Speakers from around the world discussed topics ranging from occupational noise issues to low frequency. The 8 sessions were entitled: (1) plenary session, (2) architecture, community planning and public health: effects of noise and noise control, (3) modeling, measurement and technology; (4) noise awareness and education: public, occupational and industrial, (5) regulations and economics: bylaws, legislation and the economics of noise control; (6) student papers, (7) vibration, industrial noise, transportation noise and occupational noise control, and (8) lunch speakers. The conference featured 46 presentations, of which 19 have been catalogued separately for inclusion in this database. refs., tabs., figs.

Coupling of an aeroacoustic model and a parabolic equation code for long range wind turbine noise propagation

Science.gov (United States)

Cotté, B.

2018-05-01

This study proposes to couple a source model based on Amiet's theory and a parabolic equation code in order to model wind turbine noise emission and propagation in an inhomogeneous atmosphere. Two broadband noise generation mechanisms are considered, namely trailing edge noise and turbulent inflow noise. The effects of wind shear and atmospheric turbulence are taken into account using the Monin-Obukhov similarity theory. The coupling approach, based on the backpropagation method to preserve the directivity of the aeroacoustic sources, is validated by comparison with an analytical solution for the propagation over a finite impedance ground in a homogeneous atmosphere. The influence of refraction effects is then analyzed for different directions of propagation. The spectrum modification related to the ground effect and the presence of a shadow zone for upwind receivers are emphasized. The validity of the point source approximation that is often used in wind turbine noise propagation models is finally assessed. This approximation exaggerates the interference dips in the spectra, and is not able to correctly predict the amplitude modulation.

On the prediction of impact noise, V: The noise from drop hammers

Science.gov (United States)

Richards, E. J.; Carr, I.; Westcott, M.

1983-06-01

In earlier papers in this series, the concepts of "acceleration" and "ringing" noise have been studied in relation to impact machines, and values of radiation efficiency have been obtained for the various types of structural components. In the work reported in this paper the predicted and measured noise radiation from a drop hammer, both in full-scale and in {1}/{3}- scale model form, were examined. It is found that overall noise levels ( Leq per event) can be predicted from vibration measurements to within ± 1·5 dB, and to within ±2·5 dB in one-third octave bands. In turn this has permitted noise reduction techniques to be examined by studies of local component vibration levels rather than overall noise, a method which provides considerable enlightenment at the design stage. It is shown that on one particular drop hammer, the noise energy is shared surprisingly uniformly over four or five sources, and that when these have been reduced, the overall noise reduction is severely limited by the "acceleration" noise from the "tup" or "hammer" itself. As this is difficult to eliminate without a basic change in forging technology, it follows that "tup" enclosure or modification of the sharpness of the final "hard" impact are the only means available for any serious noise reduction. Also indicated is the reliability of using model techniques, suitably scaled in frequency and impulse magnitude, in developing machinery with impact characteristics.

Enhancement of information transmission with stochastic resonance in hippocampal CA1 neuron models: effects of noise input location.

Science.gov (United States)

Kawaguchi, Minato; Mino, Hiroyuki; Durand, Dominique M

2007-01-01

Stochastic resonance (SR) has been shown to enhance the signal to noise ratio or detection of signals in neurons. It is not yet clear how this effect of SR on the signal to noise ratio affects signal processing in neural networks. In this paper, we investigate the effects of the location of background noise input on information transmission in a hippocampal CA1 neuron model. In the computer simulation, random sub-threshold spike trains (signal) generated by a filtered homogeneous Poisson process were presented repeatedly to the middle point of the main apical branch, while the homogeneous Poisson shot noise (background noise) was applied to a location of the dendrite in the hippocampal CA1 model consisting of the soma with a sodium, a calcium, and five potassium channels. The location of the background noise input was varied along the dendrites to investigate the effects of background noise input location on information transmission. The computer simulation results show that the information rate reached a maximum value for an optimal amplitude of the background noise amplitude. It is also shown that this optimal amplitude of the background noise is independent of the distance between the soma and the noise input location. The results also show that the location of the background noise input does not significantly affect the maximum values of the information rates generated by stochastic resonance.

A gate current 1/f noise model for GaN/AlGaN HEMTs

International Nuclear Information System (INIS)

Liu Yu'an; Zhuang Yiqi

2014-01-01

This work presents a theoretical and experimental study on the gate current 1/f noise in AlGaN/GaN HEMTs. Based on the carrier number fluctuation in the two-dimensional electron gas channel of AlGaN/GaN HEMTs, a gate current 1/f noise model containing a trap-assisted tunneling current and a space charge limited current is built. The simulation results are in good agreement with the experiment. Experiments show that, if V g < V x (critical gate voltage of dielectric relaxation), gate current 1/f noise comes from the superimposition of trap-assisted tunneling RTS (random telegraph noise), while V g > V x , gate current 1/f noise comes from not only the trap-assisted tunneling RTS, but also the space charge limited current RTS. This indicates that the gate current 1/f noise of the GaN-based HEMTs device is sensitive to the interaction of defects and the piezoelectric relaxation. It provides a useful characterization tool for deeper information about the defects and their evolution in AlGaN/GaN HEMTs. (semiconductor devices)

Modeling speed and width parameters of vehicle tires for prediction of the reduction in vehicle noise pollution

Directory of Open Access Journals (Sweden)

Amir Esmael Forouhid

2016-06-01

Full Text Available Introduction: Safe driving requires the ability of the driver to receive the messages and complying with them. The most significant consequences of noise pollution are on the human auditory system. Disorders in the auditory system can have harmful side effects for human health. By reducing this kind of pollution in large cities, the quality of life, which is one of the biggest goals of the governments, can be considerably increased. Hence, in the present research, some parameters of vehicle tires were examined as a source of noise pollution, and the results can be taken into consideration in noise pollution reduction. Material and Method: Several vehicles with different tire width were selected for measuring sound level. The sound levels were measured for moving vehicles with the use of the Statistical Pass By Method (SPB, ISO 11819-1. Following sound level measurements for moving vehicles and by considering tire width, mathematical model of noise level was predicted on the basis of the obtained information and by usage of SPSS program and considering vehicle tire parameters. Result: The result of this study showed that the vehicle speed and tire width can affect different sound levels emitted by moving tire on road surface. The average speed of vehicles can play an important role in the noise pollution. By increasing speed, rotation of the the tires on the asphalt is increased, as it is a known factors for noise pollution. Moreover, changing the speed of vehicles is accompanied with abnormal sounds of vehicle engine. According to regression model analysis, the obtained value of R2 for the model is 0.8367 which represents the coefficient of determination. Conclusion: The results suggest the main role of the vehicle speed and tire width in increasing the noise reaches to the drivers and consequent noise pollution, which demonstrates the necessity for noise control measures. According to the obtained model, it is understood that changes in noise

Modeling random telegraph signal noise in CMOS image sensor under low light based on binomial distribution

International Nuclear Information System (INIS)

Zhang Yu; Wang Guangyi; Lu Xinmiao; Hu Yongcai; Xu Jiangtao

2016-01-01

The random telegraph signal noise in the pixel source follower MOSFET is the principle component of the noise in the CMOS image sensor under low light. In this paper, the physical and statistical model of the random telegraph signal noise in the pixel source follower based on the binomial distribution is set up. The number of electrons captured or released by the oxide traps in the unit time is described as the random variables which obey the binomial distribution. As a result, the output states and the corresponding probabilities of the first and the second samples of the correlated double sampling circuit are acquired. The standard deviation of the output states after the correlated double sampling circuit can be obtained accordingly. In the simulation section, one hundred thousand samples of the source follower MOSFET have been simulated, and the simulation results show that the proposed model has the similar statistical characteristics with the existing models under the effect of the channel length and the density of the oxide trap. Moreover, the noise histogram of the proposed model has been evaluated at different environmental temperatures. (paper)

Modelling noise in second generation sequencing forensic genetics STR data using a one-inflated (zero-truncated) negative binomial model

DEFF Research Database (Denmark)

Vilsen, Søren B.; Tvedebrink, Torben; Mogensen, Helle Smidt

2015-01-01

We present a model fitting the distribution of non-systematic errors in STR second generation sequencing, SGS, analysis. The model fits the distribution of non-systematic errors, i.e. the noise, using a one-inflated, zero-truncated, negative binomial model. The model is a two component model...

Structured spatio-temporal shot-noise Cox point process models, with a view to modelling forest fires

DEFF Research Database (Denmark)

Møller, Jesper; Diaz-Avalos, Carlos

Spatio-temporal Cox point process models with a multiplicative structure for the driving random intensity, incorporating covariate information into temporal and spatial components, and with a residual term modelled by a shot-noise process, are considered. Such models are flexible and tractable fo...... dataset consisting of 2796 days and 5834 spatial locations of fires. The model is compared with a spatio-temporal log-Gaussian Cox point process model, and likelihood-based methods are discussed to some extent....

Structured Spatio-temporal shot-noise Cox point process models, with a view to modelling forest fires

DEFF Research Database (Denmark)

Møller, Jesper; Diaz-Avalos, Carlos

2010-01-01

Spatio-temporal Cox point process models with a multiplicative structure for the driving random intensity, incorporating covariate information into temporal and spatial components, and with a residual term modelled by a shot-noise process, are considered. Such models are flexible and tractable fo...... data set consisting of 2796 days and 5834 spatial locations of fires. The model is compared with a spatio-temporal log-Gaussian Cox point process model, and likelihood-based methods are discussed to some extent....

An Application of the Coherent Noise Model for the Prediction of Aftershock Magnitude Time Series

Directory of Open Access Journals (Sweden)

Stavros-Richard G. Christopoulos

2017-01-01

Full Text Available Recently, the study of the coherent noise model has led to a simple (binary prediction algorithm for the forthcoming earthquake magnitude in aftershock sequences. This algorithm is based on the concept of natural time and exploits the complexity exhibited by the coherent noise model. Here, using the relocated catalogue from Southern California Seismic Network for 1981 to June 2011, we evaluate the application of this algorithm for the aftershocks of strong earthquakes of magnitude M≥6. The study is also extended by using the Global Centroid Moment Tensor Project catalogue to the case of the six strongest earthquakes in the Earth during the last almost forty years. The predictor time series exhibits the ubiquitous 1/f noise behavior.

The signal-to-noise analysis of the Little-Hopfield model revisited

International Nuclear Information System (INIS)

Bolle, D; Blanco, J Busquets; Verbeiren, T

2004-01-01

Using the generating functional analysis an exact recursion relation is derived for the time evolution of the effective local field of the fully connected Little-Hopfield model. It is shown that, by leaving out the feedback correlations arising from earlier times in this effective dynamics, one precisely finds the recursion relations usually employed in the signal-to-noise approach. The consequences of this approximation as well as the physics behind it are discussed. In particular, it is pointed out why it is hard to notice the effects, especially for model parameters corresponding to retrieval. Numerical simulations confirm these findings. The signal-to-noise analysis is then extended to include all correlations, making it a full theory for dynamics at the level of the generating functional analysis. The results are applied to the frequently employed extremely diluted (a)symmetric architectures and to sequence processing networks

Selection of a Suitable Wall Pressure Spectrum Model for Estimating Flow-Induced Noise in Sonar Applications

Directory of Open Access Journals (Sweden)

V. Bhujanga Rao

1995-01-01

Full Text Available Flow-induced structural noise of a sonar dome in which the sonar transducer is housed, constitutes a major source of self-noise above a certain speed of the vessel. Excitation of the sonar dome structure by random pressure fluctuations in turbulent boundary layer flow leads to acoustic radiation into the interior of the dome. This acoustic radiation is termed flow-induced structural noise. Such noise contributes significantly to sonar self-noise of submerged vessels cruising at high speed and plays an important role in surface ships, torpedos, and towed sonars as well. Various turbulent boundary layer wall pressure models published were analyzed and the most suitable analytical model for the sonar dome application selected while taking into account high frequency, fluid loading, low wave number contribution, and pressure gradient effects. These investigations included type of coupling that exists between turbulent boundary layer pressure fluctuations and dome wall structure of a typical sonar dome. Comparison of theoretical data with measured data onboard a ship are also reported.

Median Filter Noise Reduction of Image and Backpropagation Neural Network Model for Cervical Cancer Classification

Science.gov (United States)

Wutsqa, D. U.; Marwah, M.

2017-06-01

In this paper, we consider spatial operation median filter to reduce the noise in the cervical images yielded by colposcopy tool. The backpropagation neural network (BPNN) model is applied to the colposcopy images to classify cervical cancer. The classification process requires an image extraction by using a gray level co-occurrence matrix (GLCM) method to obtain image features that are used as inputs of BPNN model. The advantage of noise reduction is evaluated by comparing the performances of BPNN models with and without spatial operation median filter. The experimental result shows that the spatial operation median filter can improve the accuracy of the BPNN model for cervical cancer classification.

Modelling noise propagation using Grid Resources. Progress within GDI-Grid

Science.gov (United States)

Kiehle, Christian; Mayer, Christian; Padberg, Alexander; Stapelfeld, Hartmut

2010-05-01

Modelling noise propagation using Grid Resources. Progress within GDI-Grid. GDI-Grid (english: SDI-Grid) is a research project funded by the German Ministry for Science and Education (BMBF). It aims at bridging the gaps between OGC Web Services (OWS) and Grid infrastructures and identifying the potential of utilizing the superior storage capacities and computational power of grid infrastructures for geospatial applications while keeping the well-known service interfaces specified by the OGC. The project considers all major OGC webservice interfaces for Web Mapping (WMS), Feature access (Web Feature Service), Coverage access (Web Coverage Service) and processing (Web Processing Service). The major challenge within GDI-Grid is the harmonization of diverging standards as defined by standardization bodies for Grid computing and spatial information exchange. The project started in 2007 and will continue until June 2010. The concept for the gridification of OWS developed by lat/lon GmbH and the Department of Geography of the University of Bonn is applied to three real-world scenarios in order to check its practicability: a flood simulation, a scenario for emergency routing and a noise propagation simulation. The latter scenario is addressed by the Stapelfeldt Ingenieurgesellschaft mbH located in Dortmund adapting their LimA software to utilize grid resources. Noise mapping of e.g. traffic noise in urban agglomerates and along major trunk roads is a reoccurring demand of the EU Noise Directive. Input data requires road net and traffic, terrain, buildings and noise protection screens as well as population distribution. Noise impact levels are generally calculated in 10 m grid and along relevant building facades. For each receiver position sources within a typical range of 2000 m are split down into small segments, depending on local geometry. For each of the segments propagation analysis includes diffraction effects caused by all obstacles on the path of sound propagation

A Vision-Based Method for Autonomous Landing of a Rotor-Craft Unmanned Aerial Vehicle

Directory of Open Access Journals (Sweden)

Z. Yuan

2006-01-01

Full Text Available This article introduces a real-time vision-based method for guided autonomous landing of a rotor-craft unmanned aerial vehicle. In the process of designing the pattern of landing target, we have fully considered how to make this easier for simplified identification and calibration. A linear algorithm was also applied using a three-dimensional structure estimation in real time. In addition, multiple-view vision technology is utilized to calibrate intrinsic parameters of camera online, so calibration prior to flight is unnecessary and the focus of camera can be changed freely in flight, thus upgrading the flexibility and practicality of the method.

A methodology for noise prediction of turbofan engines.

OpenAIRE

Gustavo Di Fiore dos Santos

2006-01-01

A computional model is developed for prediction of noise emission from na existing or new turbofan engine. This model allows the simulation of noise generation from high bypass ratio turbofan engines, appropriate for use with computational programs for gas turbine performance developed at ITA. Analytical and empirical methods are used for spectrum shape, spectrum level, overall noise and free-field directivity noise. The most significant noise sources in turbofan engines are modeled: fan, com...