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Sample records for sound radiation characteristics

  1. Sound radiation and transmission characteristics of finite composite panels

    NASA Astrophysics Data System (ADS)

    Patil, Avinash R.

    2000-10-01

    Laminated composite and sandwich composite panels are used widely in aircraft and space structures. Corrugated panels or bead-stiffened panels are used in building structures and automobiles. In these applications, the sound transmission through such panels is an important factor in their design. Their sound radiation characteristics are also important. These panels have been analyzed earlier mostly by assuming them to be of infinite size. But in real applications, only finite panels were used. The finite size of a panel affects its sound radiation below the critical frequency and consequently it also affects the resonant sound transmission through the panel. In the present work, such panels are analyzed considering their finite size. The analysis presented in this thesis is restricted to laminated composite panels, which have no coupling between bending and twisting. Corrugated panels with corrugations in only one direction were analyzed in this work. Sandwich composite panels, which have a symmetric configuration, were analyzed as well. Statistical Energy Analysis (SEA) was used for this purpose. The dispersion relations for laminated composite, sandwich composite and corrugated panels were studied. The phenomenon known as 'critical frequency band' was explained. Wavenumber diagrams were plotted for various frequencies. The mode count was obtained for the panels. A frequency averaged radiation efficiency was obtained from first principles. These results were used to calculate various SEA parameters. The transmission loss of the panels was predicted by using SEA and it is compared with the experimental results obtained by other researchers. The parametric analysis and optimization of a sandwich composite panel was carried out here. The analysis in this thesis is useful in the design of panels used for various engineering applications.

  2. Radiative characteristics for atmospheric models from lidar sounding and AERONET

    NASA Astrophysics Data System (ADS)

    Sapunov, Maxim; Kuznetsov, Anatoly; Efremenko, Dmitry; Bochalov, Valentin; Melnikova, Irina; Samulenkov, Dimity; Vasilyev, Alexander; Poberovsky, Anatoly; Frantsuzova, Inna

    2016-04-01

    observations and used for radiation calculation. Radiative divergence, transmitted and reflected irradiance and heating rate are calculated. These radiative characteristics are important for cloud and precipitation prognosis. Acknowledgments: The authors are grateful for the support of work: Agreement No. 14.574.21.0088 from the 16.07.2014 (topic: Conducting applied research on the development of an automated information system for monitoring and forecasting the balance for urban storm water drainage systems") in the framework of realization of the Federal target program "Research and development on priority directions of development of scientific-technological complex of Russia for 2014 - 2020" (a Unique identifier for applied scientific research (project) RFMEFI57414X0088) The work was performed using equipment of the Resource Centers "Observatory of environmental safety" and "Geomodel", Research Park of St. Petersburg State University

  3. Radiation characteristics of multiple and single sound hole vihuelas and a classical guitar.

    PubMed

    Bader, Rolf

    2012-01-01

    Two recently built vihuelas, quasi-replicas of the Spanish Renaissance guitar, one with a small body and one sound hole and one with a large body with five sound holes, together with a classical guitar are investigated. Frequency dependent radiation strengths are measured using a 128 microphone array, back-propagating the frequency dependent sound field upon the body surface. All three instruments have a strong sound hole radiation within the low frequency range. Here the five tone holes vihuela has a much wider frequency region of strong sound hole radiation up to about 500 Hz, whereas the single hole instruments only have strong sound hole radiations up to about 300 Hz due to the enlarged radiation area of the sound holes. The strong broadband radiation of the five sound hole vihuela up to about 500 Hz is also caused by the sound hole phases, showing very consistent in-phase relations up to this frequency range. Also the radiation strength of the sound holes placed nearer to the center of the sound box are much stronger than those near the ribs, pointing to a strong position dependency of sound hole to radiation strength. The Helmholtz resonance frequency of the five sound hole vihuela is influenced by this difference in radiation strength but not by the rosettas, which only have a slight effect on the Helmholtz frequency.

  4. Vibration analysis and sound field characteristics of a tubular ultrasonic radiator.

    PubMed

    Liang, Zhaofeng; Zhou, Guangping; Zhang, Yihui; Li, Zhengzhong; Lin, Shuyu

    2006-12-01

    A sort of tubular ultrasonic radiator used in ultrasonic liquid processing is studied. The frequency equation of the tubular radiator is derived, and its radiated sound field in cylindrical reactor is calculated using finite element method and recorded by means of aluminum foil erosion. The results indicate that sound field of tubular ultrasonic radiator in cylindrical reactor appears standing waves along both its radial direction and axial direction, and amplitudes of standing waves decrease gradually along its radial direction, and the numbers of standing waves along its axial direction are equal to the axial wave numbers of tubular radiator. The experimental results are in good agreement with calculated results.

  5. Analysis of propagation characteristics of flexural wave in honeycomb sandwich panel and design of loudspeaker for radiating inclined sound

    NASA Astrophysics Data System (ADS)

    Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi

    2015-07-01

    A loudspeaker for an auditory guiding system is proposed. This loudspeaker utilizes inclined sound transformed from a flexural wave in a honeycomb sandwich panel. We focused on the fact that the inclined sound propagates extensively with uniform level and direction. Furthermore, sound can be generated without group delay dispersion because the phase velocity of the flexural wave in the sandwich panel becomes constant with increasing frequency. These characteristics can be useful for an auditory guiding system in public spaces since voice-guiding navigation indicates the right direction regardless of position on a pathway. To design the proposed loudspeaker, the behavior of the sandwich panel is predicted using a theoretical equation in which the honeycomb core is assumed as an orthotropic continuum. We calculated the phase velocity dispersion of the flexural wave in the sandwich panel and compared the results obtained using the equation with those of a simulation based on the finite element method and an experiment in order to confirm the applicability of the theoretical equation. It was confirmed that the phase velocities obtained using the theoretical equation and by the simulation were in good agreement with that obtained experimentally. The obtained results suggest that the behavior of the sandwich panel can be predicted using the parameters of the panel. In addition, we designed an optimized honeycomb sandwich panel for radiating inclined sound by calculating the phase velocity characteristics of various panels that have different parameters of core height and cell size using the theoretical equation. Sound radiation from the optimized panel was simulated and compared with that of a homogeneous plate. It was clear that the variance of the radiation angle with varying frequency of the optimized panel was smaller than that of the homogeneous plate. This characteristic of sound radiation with a uniform angle is useful for indicating the destination direction. On

  6. Sound radiation around a flying fly.

    PubMed

    Sueur, Jérôme; Tuck, Elizabeth J; Robert, Daniel

    2005-07-01

    Many insects produce sounds during flight. These acoustic emissions result from the oscillation of the wings in air. To date, most studies have measured the frequency characteristics of flight sounds, leaving other acoustic characteristics--and their possible biological functions--unexplored. Here, using close-range acoustic recording, we describe both the directional radiation pattern and the detailed frequency composition of the sound produced by a tethered flying (Lucilia sericata). The flapping wings produce a sound wave consisting of a series of harmonics, the first harmonic occurring around 190 Hz. In the horizontal plane of the fly, the first harmonic shows a dipolelike amplitude distribution whereas the second harmonic shows a monopolelike radiation pattern. The first frequency component is dominant in front of the fly while the second harmonic is dominant at the sides. Sound with a broad frequency content, typical of that produced by wind, is also recorded at the back of the fly. This sound qualifies as pseudo-sound and results from the vortices generated during wing kinematics. Frequency and amplitude features may be used by flies in different behavioral contexts such as sexual communication, competitive communication, or navigation within the environment.

  7. Sound radiation from railway sleepers

    NASA Astrophysics Data System (ADS)

    Zhang, Xianying; Thompson, David J.; Squicciarini, Giacomo

    2016-05-01

    The sleepers supporting the rails of a railway track are an important source of noise at low frequencies. The sound radiation from the sleepers has been calculated using a three-dimensional boundary element model including the effect of both reflective and partially absorptive ground. When the sleeper flexibility and support stiffness are taken into account, it is found that the radiation ratio of the sleeper can be approximated by that of a rigid half-sleeper. When multiple sleepers are excited through the rail, their sound radiation is increased. This effect has been calculated for cases where the sleeper is embedded in a rigid or partially absorptive ground. It is shown that it is sufficient to consider only three sleepers in determining their radiation ratio when installed in track. At low frequencies the vibration of the track is localised to the three sleepers nearest the excitation point whereas at higher frequencies the distance between the sleepers is large enough for them to be treated independently. Consequently the sound radiation increases by up to 5 dB below 100 Hz compared with the result for a single sleeper whereas above 300 Hz the result can be approximated by that for a single sleeper. Measurements on a 1/5 scale model railway track are used to verify the numerical predictions with good agreement being found for all configurations.

  8. Sound radiation and transmission loss characteristics of a honeycomb sandwich panel with composite facings: Effect of inherent material damping

    NASA Astrophysics Data System (ADS)

    Arunkumar, M. P.; Jagadeesh, M.; Pitchaimani, Jeyaraj; Gangadharan, K. V.; Babu, M. C. Lenin

    2016-11-01

    This paper presents the results of numerical studies carried out on vibro-acoustic and sound transmission loss behaviour of aluminium honeycomb core sandwich panel with fibre reinforced plastic (FRP) facings. Layered structural shell element with equivalent orthotropic elastic properties of core and orthotropic properties of FRP facing layer is used to predict the free and forced vibration characteristics. Followed by this, acoustic response and transmission loss characteristics are obtained using Rayleigh integral. Vibration and acoustic characteristics of FRP sandwich panels are compared with aluminium sandwich panels. The result reveals that FRP panel has better vibro-acoustic and transmission loss characteristics due to high stiffness and inherent material damping associated with them. Resonant amplitudes of the response are fully controlled by modal damping factors calculated based on modal strain energy. It is also demonstrated that FRP panel can be used to replace the aluminium panel without losing acoustic comfort with nearly 40 percent weight reduction.

  9. Noise characteristics of jet flap type exhaust flows. [effects of Mach number, slot nozzle aspect ratio, and flap length on radiated sound power

    NASA Technical Reports Server (NTRS)

    Schrecker, G. O.; Maus, J. R.

    1974-01-01

    An experimental investigation of the aerodynamic noise and flow field characteristics of internal-flow jet-augmented flap configurations (abbreviated by the term jet flap throughout the study) is presented. The first part is a parametric study of the influence of the Mach number (subsonic range only), the slot nozzle aspect ratio and the flap length on the overall radiated sound power and the spectral composition of the jet noise, as measured in a reverberation chamber. In the second part, mean and fluctuating velocity profiles, spectra of the fluctuating velocity and space correlograms were measured in the flow field of jet flaps by means of hot-wire anemometry. Using an expression derived by Lilley, an attempt was made to estimate the overall sound power radiated by the free mixing region that originates at the orifice of the slot nozzle (primary mixing region) relative to the overall sound power generated by the free mixing region that originates at the trailing edge of the flap (secondary mixing region). It is concluded that at least as much noise is generated in the secondary mixing region as in the primary mixing region. Furthermore, the noise generation of the primary mixing region appears to be unaffected by the presence of a flap.

  10. Structure-borne sound: Structural vibrations and sound radiation at audio frequencies /2nd revised and enlarged edition/

    NASA Astrophysics Data System (ADS)

    Cremer, Lothar; Heckl, Manfred

    The fundamental principles of sound production and propagation in and from structures are examined analytically in an introductory textbook, and their design implications are considered. Chapters are devoted to the definition, measurement, and generation of structure-borne sound; wave types and characteristics; damping; impedances; attenuation; and sound radiation from structures. Diagrams, drawings, graphs, and tables of numerical data are provided.

  11. Sound radiation from a flanged inclined duct.

    PubMed

    McAlpine, Alan; Daymond-King, Alex P; Kempton, Andrew J

    2012-12-01

    A simple method to calculate sound radiation from a flanged inclined duct is presented. An inclined annular duct is terminated by a rigid vertical plane. The duct termination is representative of a scarfed exit. The concept of a scarfed duct has been examined in turbofan aero-engines as a means to, potentially, shield a portion of the radiated sound from being transmitted directly to the ground. The sound field inside the annular duct is expressed in terms of spinning modes. Exterior to the duct, the radiated sound field owing to each mode can be expressed in terms of its directivity pattern, which is found by evaluating an appropriate form of Rayleigh's integral. The asymmetry is shown to affect the amplitude of the principal lobe of the directivity pattern, and to alter the proportion of the sound power radiated up or down. The methodology detailed in this article provides a simple engineering approach to investigate the sound radiation for a three-dimensional problem.

  12. Bilateral sound propagation characteristics in electronic TMJ sound recording.

    PubMed

    Yang, K P; Koh, K H; Williams, W J; Widmalm, S E; Djurdjanovic, D

    1999-01-01

    Temporomandibular Joint (TMJ) sounds, clicking and crepitation, are important signs of possible TM disorder or dysfunction (TMD). The sound are usually recorded and observed by stethoscope auscultation or palpation. Sound from one TMJ may propagate through head tissues and be recorded on the contra lateral side misleading the examiner to classify both joints as non-silent. Errors in localization of sound source may lead to an erroneous diagnosis. Widmalm et al. (1997) suggested a mathematical model for estimation of the sound propagation characteristics through the head tissues. A modified model applying the auto-spectral density and cross-spectral density of the signal was used to estimate the bilateral sound propagation characteristics of temporomandibular joint sounds from two subjects. The result indicates that the head tissues act as a bandpass filter causing strong attenuation in some frequency areas with little attenuation in others. The phase response of the transfer function provides a good mean to estimate the latency in time between sounds.

  13. Radiated BPF sound measurement of centrifugal compressor

    NASA Astrophysics Data System (ADS)

    Ohuchida, S.; Tanaka, K.

    2013-12-01

    A technique to measure radiated BPF sound from an automotive turbocharger compressor impeller is proposed in this paper. Where there are high-level background noises in the measurement environment, it is difficult to discriminate the target component from the background. Since the effort of measuring BPF sound was taken in a room with such condition in this study, no discrete BPF peak was initially found on the sound spectrum. Taking its directionality into consideration, a microphone covered with a parabolic cone was selected and using this technique, the discrete peak of BPF was clearly observed. Since the level of measured sound was amplified due to the area-integration effect, correction was needed to obtain the real level. To do so, sound measurements with and without a parabolic cone were conducted for the fixed source and their level differences were used as correction factors. Consideration is given to the sound propagation mechanism utilizing measured BPF as well as the result of a simple model experiment. The present method is generally applicable to sound measurements conducted with a high level of background noise.

  14. Relationship between sound radiation from sound-induced and force-excited vibration: Analysis using an infinite elastic plate model.

    PubMed

    Yairi, Motoki; Sakagami, Kimihiro; Nishibara, Kosuke; Okuzono, Takeshi

    2016-07-01

    Although sound radiation from sound-induced vibration and from force-excited vibration of solid structures are similar phenomena in terms of radiating from vibrating structures, the general relationship between them has not been explicitly studied to date. In particular, airborne sound transmission through walls and sound radiation from structurally vibrating surfaces in buildings are treated as different issues in architectural acoustics. In this paper, a fundamental relationship is elucidated through the use of a simple model. The transmission coefficient for random-incidence sound and the radiated sound power under point force excitation of an infinite elastic plate are both analyzed. Exact and approximate solutions are derived for the two problems, and the relationship between them is theoretically discussed. A conversion function that relates the transmission coefficient and radiated sound power is obtained in a simple closed form through the approximate solutions. The exact solutions are also related by the same conversion function. It is composed of the specific impedance and the wavenumber, and is independent of any elastic plate parameters. The sound radiation due to random-incidence sound and point force excitation are similar phenomena, and the only difference is the gradient of those characteristics with respect to the frequency.

  15. Theoretical Modelling of Sound Radiation from Plate

    NASA Astrophysics Data System (ADS)

    Zaman, I.; Rozlan, S. A. M.; Yusoff, A.; Madlan, M. A.; Chan, S. W.

    2017-01-01

    Recently the development of aerospace, automotive and building industries demands the use of lightweight materials such as thin plates. However, the plates can possibly add to significant vibration and sound radiation, which eventually lead to increased noise in the community. So, in this study, the fundamental concept of sound pressure radiated from a simply-supported thin plate (SSP) was analyzed using the derivation of mathematical equations and numerical simulation of ANSYS®. The solution to mathematical equations of sound radiated from a SSP was visualized using MATLAB®. The responses of sound pressure level were measured at far field as well as near field in the frequency range of 0-200 Hz. Result shows that there are four resonance frequencies; 12 Hz, 60 Hz, 106 Hz and 158 Hz were identified which represented by the total number of the peaks in the frequency response function graph. The outcome also indicates that the mathematical derivation correlated well with the simulation model of ANSYS® in which the error found is less than 10%. It can be concluded that the obtained model is reliable and can be applied for further analysis such as to reduce noise emitted from a vibrating thin plate.

  16. Radiation of sound from unflanged cylindrical ducts

    NASA Technical Reports Server (NTRS)

    Hartharan, S. L.; Bayliss, A.

    1983-01-01

    Calculations of sound radiated from unflanged cylindrical ducts are presented. The numerical simulation models the problem of an aero-engine inlet. The time dependent linearized Euler equations are solved from a state of rest until a harmonic solution is attained. A fourth order accurate finite difference scheme is used and solutions are obtained from a fully vectorized Cyber-203 computer program. Cases of both plane waves and spin modes are treated. Spin modes model the sound generated by a turbofan engine. Boundary conditions for both plane waves and spin modes are treated. Solutions obtained are compared with experiments conducted at NASA Langley Research Center.

  17. Acoustic wavepackets and sound radiation by jets

    NASA Astrophysics Data System (ADS)

    Sasidharan Nair, Unnikrishnan; Gaitonde, Datta

    2016-11-01

    The three-dimensional spatio-temporal evolution of the acoustic mode in a supersonic jet is analyzed using Doak's Momentum Potential Theory on an LES database. The acoustic mode exhibits a well-defined wavepacket nature in the core and convects at sonic speed. Its spatial coherence is significantly higher than the hydrodynamic component, resulting in an efficient sound radiation mechanism dominated by the axisymmetric and the first helical modes. Enthalpy transport by the acoustic mode yields insight into the sound energy flux emitted by the jet. Intrusion and ejection of coherent vortices into the core and ambient outer fluid respectively are found to be major intermittent sources of acoustic radiation. The scalar potential which defines the acoustic mode is found to satisfy the homogenous wave propagation equation in the nearfield which makes it a suitable variable to predict farfield radiation. The propagated acoustic field closely resembles the corresponding nearfield LES result. The acoustic mode thus provides a physically consistent wavepacket model to predict sound radiation from jets. Ongoing efforts on subsonic jets will discern the influence, if any, of the Mach number on the model.

  18. Robust Feedback Control of Flow Induced Structural Radiation of Sound

    NASA Technical Reports Server (NTRS)

    Heatwole, Craig M.; Bernhard, Robert J.; Franchek, Matthew A.

    1997-01-01

    A significant component of the interior noise of aircraft and automobiles is a result of turbulent boundary layer excitation of the vehicular structure. In this work, active robust feedback control of the noise due to this non-predictable excitation is investigated. Both an analytical model and experimental investigations are used to determine the characteristics of the flow induced structural sound radiation problem. The problem is shown to be broadband in nature with large system uncertainties associated with the various operating conditions. Furthermore the delay associated with sound propagation is shown to restrict the use of microphone feedback. The state of the art control methodologies, IL synthesis and adaptive feedback control, are evaluated and shown to have limited success for solving this problem. A robust frequency domain controller design methodology is developed for the problem of sound radiated from turbulent flow driven plates. The control design methodology uses frequency domain sequential loop shaping techniques. System uncertainty, sound pressure level reduction performance, and actuator constraints are included in the design process. Using this design method, phase lag was added using non-minimum phase zeros such that the beneficial plant dynamics could be used. This general control approach has application to lightly damped vibration and sound radiation problems where there are high bandwidth control objectives requiring a low controller DC gain and controller order.

  19. Sound radiation from a subsonic rotor subjected to turbulence

    NASA Technical Reports Server (NTRS)

    Sevik, M.

    1974-01-01

    The broadband sound radiated by a subsonic rotor subjected to turbulence in the approach stream has been analyzed. The power spectral density of the sound intensity has been found to depend on a characteristic time scale-namely, the integral scale of the turbulence divided by the axial flow velocity-as well as several length-scale ratios. These consist of the ratio of the integral scale to the acoustic wavelength, rotor radius, and blade chord. Due to the simplified model chosen, only a limited number of cascade parameters appear. Limited comparisons with experimental data indicate good agreement with predicted values.

  20. Sound Radiation from a Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Laufer, J.

    1961-01-01

    If the restriction of incompressibility in the turbulence problem is relaxed, the phenomenon of energy radiation in the form of sound from the turbulent zone arises. In order to calculate this radiated energy, it is shown that new statistical quantities, such as time-space correlation tensors, have to be known within the turbulent zone in addition to the conventional quantities. For the particular case of the turbulent boundary layer, indications are that the intensity of radiation becomes significant only in supersonic flows. Under these conditions, the recent work of Phillips is examined together with some experimental findings of the author. It is shown that the qualitative features of the radiation field (intensity, directionality) as predicted by the theory are consistent with the measurements; however, even for the highest Mach number flow, some of the assumptions of the asymptotic theory are not yet satisfied in the experiments. Finally, the question of turbulence damping due to radiation is discussed, with the result that in the Mach number range covered by the experiments, the energy lost from the boundary layer due to radiation is a small percentage of the work done by the wall shearing stresses.

  1. Sound Radiation from a Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Laufer, J.

    1961-01-01

    If the restriction of incompressibility in the turbulence problem is relaxed, the phenomenon of energy radiation in the form of sound from the turbulent zone arises. In order to calculate this radiated energy, it is shown that new statistical quantities, such as time-space correlation tensors, have to be known within the turbulent zone in addition to the conventional quantities. For the particular case of the turbulent boundary layer, indications are that the intensity of radiation becomes significant only in supersonic flows. Under these conditions, the recent work of Phillips is examined together with some experimental findings of the author. It is shown that the qualitative features of the radiation field (intensity, directionality) as predicted by the theory are consistent with the measurements; however, even for the highest Mach number flow, some of the assumptions of the asymptotic theory are not yet satisfied in the experiments. Finally, the question of turbulence damping due to radiation is discussed, with the result that in the Mach number range covered by the experiments, the energy lost from the boundary layer due to radiation is a small percentage of the work done by the wall shearing stresses.

  2. Characteristics of the audio sound generated by ultrasound imaging systems.

    PubMed

    Fatemi, Mostafa; Alizad, Azra; Greenleaf, James F

    2005-03-01

    Medical ultrasound scanners use high-energy pulses to probe the human body. The radiation force resulting from the impact of such pulses on an object can vibrate the object, producing a localized high-intensity sound in the audible range. Here, a theoretical model for the audio sound generated by ultrasound scanners is presented. This model describes the temporal and spectral characteristics of the sound. It has been shown that the sound has rich frequency components at the pulse repetition frequency and its harmonics. Experiments have been conducted in a water tank to measure the sound generated by a clinical ultrasound scanner in various operational modes. Results are in general agreement with the theory. It is shown that a typical ultrasound scanner with a typical spatial-peak pulse-average intensity value at 2 MHz may generate a localized sound-pressure level close to 100 dB relative to 20 microPa in the audible (< 20 kHz) range under laboratory conditions. These findings suggest that fetuses may become exposed to a high-intensity audio sound during maternal ultrasound examinations. Therefore, contrary to common beliefs, ultrasound may not be considered a passive tool in fetal imaging.

  3. Characteristics of the audio sound generated by ultrasound imaging systems

    NASA Astrophysics Data System (ADS)

    Fatemi, Mostafa; Alizad, Azra; Greenleaf, James F.

    2005-03-01

    Medical ultrasound scanners use high-energy pulses to probe the human body. The radiation force resulting from the impact of such pulses on an object can vibrate the object, producing a localized high-intensity sound in the audible range. Here, a theoretical model for the audio sound generated by ultrasound scanners is presented. This model describes the temporal and spectral characteristics of the sound. It has been shown that the sound has rich frequency components at the pulse repetition frequency and its harmonics. Experiments have been conducted in a water tank to measure the sound generated by a clinical ultrasound scanner in various operational modes. Results are in general agreement with the theory. It is shown that a typical ultrasound scanner with a typical spatial-peak pulse-average intensity value at 2 MHz may generate a localized sound-pressure level close to 100 dB relative to 20 μPa in the audible (<20 kHz) range under laboratory conditions. These findings suggest that fetuses may become exposed to a high-intensity audio sound during maternal ultrasound examinations. Therefore, contrary to common beliefs, ultrasound may not be considered a passive tool in fetal imaging..

  4. The prediction and measurement of sound radiated by structures

    NASA Technical Reports Server (NTRS)

    Lyon, R. H.; Brito, J. D.

    1976-01-01

    Theories regarding the radiation of sound are reviewed and the implementation in strategies for explaining or measuring the sound produced by practical strucutres are discussed. Particular attention is given to those aspects that relate to the determination of the relative amounts of sound generated by various parts of a machine or structure, which can be very useful information for noise reduction efforts.

  5. Effects of symmetrical foundation on sound radiation from a submarine hull structure.

    PubMed

    Li, Chenyang; Su, Jinpeng; Wang, Jian; Hua, Hongxing

    2015-11-01

    The effects of a passive noise control method for suppressing sound radiation from a submarine hull structure are investigated. The control method is realized by symmetrizing the foundation about the horizontal plane. The coupled finite element method and boundary element method are adopted to compute the acoustic characteristics of the submerged hull. From the numerical results, the symmetrical foundation has advantages in sound radiation reduction when the hull is subjected to the axial load, but has little influences in the vertical and transverse load cases. Using the modal decomposition technique, the contributions of each individual mode to the sound radiation are analyzed to reveal the mechanism of the control method.

  6. Effect of wheel load on wheel vibration and sound radiation

    NASA Astrophysics Data System (ADS)

    Han, Jian; Wang, Ruiqian; Wang, Di; Guan, Qinghua; Zhang, Yumei; Xiao, Xinbiao; Jin, Xuesong

    2015-01-01

    The current researches of wheel vibration and sound radiation mainly focus on the low noise damped wheel. Compared with the traditional research, the relationship between the sound and wheel/rail contact is difficulty and worth studying. However, there are few studies on the effect of wheel load on wheel vibration and sound radiation. In this paper, laboratory test carried out in a semi-anechoic room investigates the effect of wheel load on wheel natural frequencies, damping ratios, wheel vibration and its sound radiation. The laboratory test results show that the vibration of the wheel and total sound radiation decrease significantly with the increase of the wheel load from 0 t to 1 t. The sound energy level of the wheel decreases by 3.7 dB. When the wheel load exceeds 1 t, the attenuation trend of the vibration and sound radiation of the wheel becomes slow. And the increase of the wheel load causes the growth of the wheel natural frequencies and the mode damping ratios. Based on the finite element method (FEM) and boundary element method (BEM), a rolling noise prediction model is developed to calculate the influence of wheel load on the wheel vibration and sound radiation. In the calculation, the used wheel/rail excitation is the measured wheel/rail roughness. The calculated results show that the sound power level of the wheel decreases by about 0.4 dB when the wheel load increases by 0.5 t. The sound radiation of the wheel decreases slowly with wheel load increase, and this conclusion is verified by the field test. This research systematically studies the effect of wheel load on wheel vibration and sound radiation, gives the relationship between the sound and wheel/rail contact and analyzes the reasons, therefore, it provides a reference for further research.

  7. Sound attenuation characteristics of cellular metamaterials

    NASA Astrophysics Data System (ADS)

    Varanasi, Satya Surya Srinivas

    could be mitigated by the addition of appropriate treatments such as a lightweight grid that modified the incident sound field to be normally directed. Although the performance of the metamaterial-based barrier solutions was better compared to the conventional ones, the performance can be poor at the system eigenfrequencies. The possibility of shifting energy from the deficit bands to other regions where the barriers are more efficient was numerically explored for embodiments of segmented cellular materials having non-linear stiffness characteristics. The acoustical behavior of such materials was probed through representative two-dimensional models of a segmented plate with a contact interface. Super-harmonic response peaks were observed for pure harmonic excitations, the strength of which were found to strongly depend on the degree of non-linearity or bilinear stiffness ratio. The closer an excitation frequency was to the characteristic eigenfrequencies of the structure, the stronger was the super-harmonic response, which supported the idea of transferring energy from problematic frequency bands to higher frequencies. Finally, the possibility of a spatial-shift of energy from longitudinal to lateral direction was explored with the idea of eliminating the design constraints associated with conventional absorbing materials, and with the hope of realizing a compact sound absorber. The embodiment was a two-phase chiral composite made using a Topologically Interlocked Material (TIM) with its unit cell being a tetrahedron consisting of two helicoid dissections. A comparative study was conducted with standard microstructures inspired by the Voigt and Reuss models. The twist mode of the chiral composites was found to be excited by an incident sound field normal to the plane of the TIM assembly. Although this behavior is not unique to a chiral microstructure, many other microstructures do not exhibit this behavior. The excitation of the twist mode by the incident sound field

  8. Sound radiation from a water-filled pipe, radiation into light fluid.

    PubMed

    Liu, Bilong; Pan, Jie; Li, Xiaodong; Tian, Jing

    2002-12-01

    This paper is concerned with the sound radiation from a water-filled exhaust pipe. The pipe opening and a plate attached to it form a vibrating surface for this radiation. Fluid-structural coupling between the pipe and enclosed fluid is included in the system modeling, but light fluid assumption is used for sound radiation into the space above the vibrating surface. In this paper, a numerical study on the n = 0 mode in the pipe shows that the wave types associated with this mode have different characteristics in two regions of the nondimensional frequency omega. In the first region of 0sound radiation from the pipe opening and the attached plate. This paper also demonstrates the effect of these waves and their coupling in the water-filled pipe and across the plate and pipe boundary on the radiated sound pressure. Experimental results obtained in a semi-anechoic room are used to partially validate the theoretical and numerical predictions.

  9. On the sound radiation of a rolling tyre

    NASA Astrophysics Data System (ADS)

    Kropp, Wolfgang; Sabiniarz, Patrick; Brick, Haike; Beckenbauer, Thomas

    2012-04-01

    The sound radiation from rolling tyres is still not very well understood. Although details such as horn effect or directivity during rolling have been investigated, it is not clear which vibrational modes of the tyre structure are responsible for the radiated sound power. In this work an advanced tyre model based on Wave Guide Finite Elements is used in connection with a contact model validated in previous work. With these tools the tyre vibrations during rolling on an ISO surface are simulated. Starting from the calculated contact forces in time the amplitudes of the modes excited during rolling are determined as function of frequency. A boundary element model also validated in previous work is applied to predict the sound pressure level on a reference surface around a tyre placed on rigid ground as function of the modal composition of the tyre vibrations. Taking into account different modes when calculating the vibrational field as input into the boundary element calculations, it is possible to identify individual modes or groups of modes of special relevance for the radiated sound power. The results show that mainly low-order modes with relative low amplitudes but high radiation efficiency in the frequency range around 1 kHz are responsible for the radiated sound power at these frequencies, while those modes which are most strongly excited in that frequency range during rolling are irrelevant for the radiated sound power. This fact is very essential when focusing on the design of quieter tyres.

  10. Visualization of relation between sound symbolic word and perceptual characteristics of environmental sounds

    NASA Astrophysics Data System (ADS)

    Kwon, J.; Sakamoto, M.

    2017-01-01

    Humans interact with environmental sounds by easily and quickly identifying external and natural sounds in daily life. Interestingly, we verbalize the perceived auditory information from environmental sound. Onomatopoeia, i.e. sound symbolic word, indicates the linguistic form deeply related to environmental sound. The objective of this study is to visualize the relationship between perceptual properties of onomatopoeia and affective characteristics ("pleasant - unpleasant") perceived from the environmental sound. We have mapped the correlation between perceptual properties by phonemes of onomatopoeia and "pleasant/unpleasant" evaluations of environmental sound. The results showed that many onomatopoeias are related to various perceptual and affective scales. We suggest the importance of relation between the perceptual characteristics in auditory sensation and the phonological properties of sound symbolic words.

  11. Underwater Sound Radiation from Large Raindrops

    DTIC Science & Technology

    1991-09-01

    the predicted sound spectrum for an assumed reasonable drop size distribution. Also, the total rainfall rate and drop size distribution has been... predicted sound spectrum for an assumed reasonable drop size distribution. Also, the total rainfall rate and drop size distribution has been calculated from...have been only marginally successful (Scrimger,et al., 1989; Tan, 1990). N120 tipotlons and N \\ earthqukes 0 turbulent \\ .,Shipping 60o Iu~,I~ii r

  12. A model problem for sound radiation by an installed jet

    NASA Astrophysics Data System (ADS)

    Nogueira, Petrônio A. S.; Cavalieri, André V. G.; Jordan, Peter

    2017-03-01

    A model for sound generation by a jet in the vicinity of a flat plate, mimicking an exhaust jet installed near an aircraft wing, is presented. An earlier model (Cavalieri et al. J. Sound Vib. 333 (2014) 6516-6531) is further simplified by considering that the sound source is an axially-extended, cylindrical wavepacket concentrated on the jet lipline, and that this source is scattered by the trailing edge of a semi-infinite flat plate; the model is shown to match earlier results and considerably simplifies the analysis. It is used to evaluate how the parameters of the problem influence sound radiation by subsonic jets. We show that the axisymmetric mode of the source is the most acoustically efficient, similarly to what is seen for free jets; but unlike the latter problem, the sound scattered by the trailing edge is only weakly dependent on the details of the wavepacket envelope and on the two-point coherence of the source, the wavepacket phase speed being the salient feature for installed jet noise. We then use the model to evaluate how geometrical parameters of jet-plate configurations modify the radiated sound. The acoustic radiation is particularly sensitive to the jet-plate distance due to the exponential radial decay of near-field disturbances; the relative axial position of jet and trailing edge is shown to play a comparably minor role. Finally, changes in the angle of attack of the plate and in the sweep angle of the trailing edge considerably modify the radiated sound, leading to significant reductions of the acoustic intensity in some directions. The various properties of installed jet noise are further explored by appealing to the wavenumber transform of the tailored Green's function used to compute the scattered field; insight is thus provided on how jet-wing configurations might be designed so as to reduce installation noise.

  13. Perceiving and Reenacting Spatiotemporal Characteristics of Walking Sounds

    ERIC Educational Resources Information Center

    Young, William; Rodger, Matthew; Craig, Cathy M.

    2013-01-01

    Many studies have examined the processes involved in recognizing types of human action through sound, but little is known about whether the physical characteristics of an action (such as kinetic and kinematic parameters) can be perceived and imitated from sound. Twelve young healthy adults listened to recordings of footsteps on a gravel path taken…

  14. Perceiving and Reenacting Spatiotemporal Characteristics of Walking Sounds

    ERIC Educational Resources Information Center

    Young, William; Rodger, Matthew; Craig, Cathy M.

    2013-01-01

    Many studies have examined the processes involved in recognizing types of human action through sound, but little is known about whether the physical characteristics of an action (such as kinetic and kinematic parameters) can be perceived and imitated from sound. Twelve young healthy adults listened to recordings of footsteps on a gravel path taken…

  15. Some characteristics of the concert harp's acoustic radiation.

    PubMed

    Le Carrou, Jean-Loic; Leclere, Quentin; Gautier, Francois

    2010-05-01

    The way a musical instrument radiates plays an important part in determining the instrument's sound quality. For the concert harp, the soundboard has to radiate the string's vibration over a range of 7 octaves. Despite the effort of instrument makers, this radiation is not uniform throughout this range. In a recent paper, Waltham and Kotlicki [J. Acoust. Soc. Am. 124, 1774-1780 (2008)] proposed an interesting approach for the study of the string-to-string variance based on the relationship between the string attachment position and the operating deflection shapes of the soundboard. Although the soundboard vibrational characteristics determine a large part of the instrument's radiation, it is also important to study directly its radiation to conclude on the origins of the string-to-string variation in the sound production. This is done by computing the equivalent acoustical sources on the soundboard from the far field sound radiation measured around the harp, using the acoustic imaging technique inverse frequency response function. Results show that the radiated sound depends on the correlation between these sources, and the played string's frequency and location. These equivalent sources thus determine the magnitude and directivity of each string's partial in the far field, which have consequences on the spectral balance of the perceived sound for each string.

  16. Sound radiation from randomly vibrating beams of finite circular cross section

    NASA Technical Reports Server (NTRS)

    Sutterlin, M. W.; Pierce, A. D.

    1976-01-01

    The radiation of sound from vibrating cylindrical beams is analyzed based on the frequency of the beam vibrations and the physical characteristics of the beam and its surroundings. A statistical analysis of random beam vibrations allows this result to be independent of the boundary conditions at the ends of the beam. The acoustic power radiated by the beam can be determined from a knowledge of the frequency band vibration data without a knowledge of the individual modal vibration amplitudes. A practical example of the usefulness of this technique is provided by the application of the theoretical calculations to the prediction of the octave band acoustic power output of the picking sticks of an automatic textile loom. Calculations are made of the expected octave band sound pressure levels based on measured acceleration data. These theoretical levels are subsequently compared with actual sound pressure level measurements of loom noise.

  17. Control of sound radiating from an orthotropic plate

    NASA Astrophysics Data System (ADS)

    Meirovich, L.; Thangjitham, S.

    1992-10-01

    This paper is concerned with the problem of actively suppressing the acoustic radiation pressure generated by an orthotropic plate vibrating in air. The approach is to control the vibration of the modes of the plate most responsible for acoustic radiation pressure. This is accomplished by relating the far-field radiation pressure to the state of the plate. The control of the far-field radiation pressure is carried out by means of actuators placed on the elastic plate. A numerical example demonstrates the application of active control to suppress the far-field sound radiating from a simply-supported rectangular thin orthotropic plate subjected to a harmonic disturbance. The influence on the control of effectiveness of various design parameters, such as the number of controlled modes, the choice of controlled modes, and the number of actuators, is investigated.

  18. An experimental investigation of sound radiation from a duct with a circumferentially varying liner

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.; Silcox, R. J.

    1983-01-01

    The radiation of sound from an asymmetrically lined duct is experimentally studied for various hard-walled standing mode sources. Measurements were made of the directivity of the radiated field and amplitude reflection coefficients in the hard-walled source section. These measurements are compared with baseline hardwall and uniformly lined duct data. The dependence of these characteristics on mode number and angular location of the source is investigated. A comparison between previous theoretical calculations and the experimentally measured results is made and in general good agreement is obtained. For the several cases presented an asymmetry in the liner impedance distribution was found to produce related asymmetries in the radiated acoustic field.

  19. Sound radiation quantities arising from a resilient circular radiator.

    PubMed

    Aarts, Ronald M; Janssen, Augustus J E M

    2009-10-01

    Power series expansions in ka are derived for the pressure at the edge of a radiator, the reaction force on the radiator, and the total radiated power arising from a harmonically excited, resilient, flat, circular radiator of radius a in an infinite baffle. The velocity profiles on the radiator are either Stenzel functions (1-(sigma/a)2)n, with sigma the radial coordinate on the radiator, or linear combinations of Zernike functions Pn(2(sigma/a)2-1), with Pn the Legendre polynomial of degree n. Both sets of functions give rise, via King's integral for the pressure, to integrals for the quantities of interest involving the product of two Bessel functions. These integrals have a power series expansion and allow an expression in terms of Bessel functions of the first kind and Struve functions. Consequently, many of the results in [M. Greenspan, J. Acoust. Soc. Am. 65, 608-621 (1979)] are generalized and treated in a unified manner. A foreseen application is for loudspeakers. The relation between the radiated power in the near-field on one hand and in the far field on the other is highlighted.

  20. Estimating sound power radiated from rectangular baffled panels using a radiation factor.

    PubMed

    Palumbo, Dan

    2009-10-01

    A method is introduced which is shown to predict radiated sound power from rectangular baffled panels. The method employs a filtered wavenumber transform to extract the power in the supersonic wavenumbers on the panel and a radiation factor to scale the supersonic power to match the actual radiated sound power. Although empirically derived, the radiation factor is shown to be related to the radiation efficiency of an infinite panel. The radiation factor is simple, depending only on the ratio of the wavenumbers of the panel to the radiation medium, and the method is straightforward to use, requiring only the panel normal velocities. The computation is efficient, as much as two orders of magnitude faster than a Rayleigh integration, thus providing a means of combining sound power predictions with finite element optimizations. A formula is derived which predicts the lowest frequency for which the method is valid as a function of the bin width of the wavenumber transform. The radiation factor method is shown to produce radiated sound power estimates which favorably compare to estimates derived from intensity measurements of physical test specimens and to Rayleigh integral estimates computed using both simulated and measured velocities.

  1. Sound radiation due to boundary layer transition

    NASA Technical Reports Server (NTRS)

    Wang, Meng

    1993-01-01

    This report describes progress made to date towards calculations of noise produced by the laminar-turbulence transition process in a low Mach number boundary layer formed on a rigid wall. The primary objectives of the study are to elucidate the physical mechanisms by which acoustic waves are generated, to clarify the roles of the fluctuating Reynolds stress and the viscous stress in the presence of a solid surface, and to determine the relative efficiency as a noise source of the various transition stages. In particular, we will examine the acoustic characteristics and directivity associated with three-dimensional instability waves, the detached high-shear layer, and turbulent spots following a laminar breakdown. Additionally, attention will be paid to the unsteady surface pressures during the transition, which provide a source of flow noise as well as a forcing function for wall vibration in both aeronautical and marine applications.

  2. Decentralized Control of Sound Radiation Using Iterative Loop Recovery

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Cabell, Randolph H.; Fuller, Chris R.

    2009-01-01

    A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units.

  3. Decentralized control of sound radiation using iterative loop recovery.

    PubMed

    Schiller, Noah H; Cabell, Randolph H; Fuller, Chris R

    2010-10-01

    A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units.

  4. Passively minimizing structural sound radiation using shunted piezoelectric materials

    NASA Astrophysics Data System (ADS)

    Bulent Ozer, M.; Royston, Thomas J.

    2003-10-01

    Two methods are presented to determine optimal inductance and resistance values of the shunt circuit across a piezoceramic material, which is bonded to a simply supported plate in order to minimize sound radiation from the plate. The first method (DH) makes use of den Hartog's damped vibration absorber principle. The second method (SM) uses the Sherman Morrison matrix inversion theorem. The effectiveness of each method is compared with regard to minimizing total acoustic sound-power radiation and acoustic pressure at a point. Optimization algorithms and case studies are presented using a linearized model for the piezoceramic and using a nonlinear model for the piezoceramic that accounts for the inherent dielectric hysteresis. Case studies demonstrate that the second method (SM) results in superior performance, under both linear and nonlinear system assumptions. Studies also illustrate that, if the nonlinearity in the system is significant, it must be incorporated in the optimization process.

  5. Potential theoretic methods for far field sound radiation calculations

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.; Stenger, Edward J.; Scott, J. R.

    1995-01-01

    In the area of computational acoustics, procedures which accurately predict the far-field sound radiation are much sought after. A systematic development of such procedures are found in a sequence of papers by Atassi. The method presented here is an alternate approach to predicting far field sound based on simple layer potential theoretic methods. The main advantages of this method are: it requires only a simple free space Green's function, it can accommodate arbitrary shapes of Kirchoff surfaces, and is readily extendable to three-dimensional problems. Moreover, the procedure presented here, though tested for unsteady lifting airfoil problems, can easily be adapted to other areas of interest, such as jet noise radiation problems. Results are presented for lifting airfoil problems and comparisons are made with the results reported by Atassi. Direct comparisons are also made for the flat plate case.

  6. Influence of inhomogeneous damping distribution on sound radiation properties of complex vibration modes in rectangular plates

    NASA Astrophysics Data System (ADS)

    Unruh, Oliver

    2016-09-01

    In order to reduce noise emitted by vibrating structures additional damping treatments such as constraint layer damping or embedded elastomer layers can be used. To save weight and cost, the additional damping is often placed at some critical locations of the structure, what leads to spatially inhomogeneous distribution of damping. This inhomogeneous distribution of structural damping leads to an occurrence of complex vibration modes, which are no longer dominated by pure standing waves, but by a superposition of travelling and standing waves. The existence of complex vibration modes raises the question about their influence on sound radiation. Previous studies on the sound radiation of complex modes of rectangular plates reveal, that, depending on the direction of travelling waves, the radiation efficiency of structural modes can slightly decrease or significantly increase. These observations have been made using a rectangular plate with a simple inhomogeneous damping configuration which includes a single plate boundary with a higher structural damping ratio. In order to answer the question about the influence of other possible damping configurations on the sound radiation properties, this paper addresses the self- and mutual-radiation efficiencies of the resulting complex vibration modes. Numerical simulations are used for the calculation of complex structural modes of different inhomogeneous damping configurations with varying geometrical form and symmetry. The evaluation of self- and mutual-radiation efficiencies reveals that primarily the symmetry properties of the inhomogeneous damping distribution affect the sound radiation characteristics. Especially the asymmetric distributions of inhomogeneous damping show a high influence on the investigated acoustic metrics. The presented study also reveals that the acoustic cross-coupling between structural modes, which is described by the mutual-radiation efficiencies, generally increases with the presence of

  7. Normal mode sound field of a directional radiator

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Zhu, B.

    1987-12-01

    In this paper, the sound field of a general type of directional radiator in a stratified medium is treated, and the concept of directivity is applied to calculation of the normal modes. The result shows that the normal mode field of a directional radiator can be obtained by supplementing the normal mode expression of an omnidirectional point source with the directional excitation function, which is dependent on the position and directivity of the radiator. In addition, the normal mode fields of radiators with vertical-symmetrical, vertical-antisymmetrical, single-sided and sharp directivities are calculated, respectively. For a vertical line array in a homogeneous water layer, if the source distribution is proportional to the eigenfunction of some normal mode, the zeros of the directional excitation function correspond precisely to the directions of the eigenrays of other normal modes.

  8. Frequency-independent radiation modes of interior sound radiation: An analytical study

    NASA Astrophysics Data System (ADS)

    Hesse, C.; Vivar Perez, J. M.; Sinapius, M.

    2017-03-01

    Global active control methods of sound radiation into acoustic cavities necessitate the formulation of the interior sound field in terms of the surrounding structural velocity. This paper proposes an efficient approach to do this by presenting an analytical method to describe the radiation modes of interior sound radiation. The method requires no knowledge of the structural modal properties, which are often difficult to obtain in control applications. The procedure is exemplified for two generic systems of fluid-structure interaction, namely a rectangular plate coupled to a cuboid cavity and a hollow cylinder with the fluid in its enclosed cavity. The radiation modes are described as a subset of the acoustic eigenvectors on the structural-acoustic interface. For the two studied systems, they are therefore independent of frequency.

  9. Frequency-independent radiation modes of interior sound radiation: Experimental study and global active control

    NASA Astrophysics Data System (ADS)

    Hesse, C.; Papantoni, V.; Algermissen, S.; Monner, H. P.

    2017-08-01

    Active control of structural sound radiation is a promising technique to overcome the poor passive acoustic isolation performance of lightweight structures in the low-frequency region. Active structural acoustic control commonly aims at the suppression of the far-field radiated sound power. This paper is concerned with the active control of sound radiation into acoustic enclosures. Experimental results of a coupled rectangular plate-fluid system under stochastic excitation are presented. The amplitudes of the frequency-independent interior radiation modes are determined in real-time using a set of structural vibration sensors, for the purpose of estimating their contribution to the acoustic potential energy in the enclosure. This approach is validated by acoustic measurements inside the cavity. Utilizing a feedback control approach, a broadband reduction of the global acoustic response inside the enclosure is achieved.

  10. Perceiving and reenacting spatiotemporal characteristics of walking sounds.

    PubMed

    Young, William; Rodger, Matthew; Craig, Cathy M

    2013-04-01

    Many studies have examined the processes involved in recognizing types of human action through sound, but little is known about whether the physical characteristics of an action (such as kinetic and kinematic parameters) can be perceived and imitated from sound. Twelve young healthy adults listened to recordings of footsteps on a gravel path taken from walks of different stride lengths (SL) and cadences. In 1 protocol, participants performed a real-time reenactment of the walking action depicted in a sound sample. Second, participants listened to 2 different sound samples and discriminated differences in SL. In a 2nd experiment, these procedures were repeated using synthesized sounds derived from the kinetic interactions between the foot and walking surface. A 3rd experiment examined the influence of altered cadence on participants' ability to discriminate changes in SL. Participants significantly adapted their own SL and cadence according to those depicted in both real and synthesized sounds (p < .01). However, although participants accurately discriminated between large changes in SL, these perceptions were heavily influenced by temporal factors, that is, when cadence changed between samples. These findings show that spatial attributes of action sounds can be both mimicked and discriminated, even when only basic kinetic interactions present within the action are specified.

  11. Underwater sound radiation patterns of contemporary merchant ships

    NASA Astrophysics Data System (ADS)

    Gassmann, M.; Wiggins, S. M.; Hildebrand, J. A.

    2016-12-01

    Merchant ships radiate underwater sound as an unintended by-product of their operation and as consequence contribute significantly to low-frequency, man-made noise in the ocean. Current measurement standards for the description of underwater sound from ships (ISO 17208-1:2016 and ANSI S12.64-2009) require nominal hydrophone depths of 15°, 30° and 45° at the starboard and portside of the test vessel.To opportunistically study the underwater sound of contemporary merchant ships that were tracked by the Automatic Identification System (AIS), an array of seven high-frequency acoustic recording packages (HARPs) with a sampling frequency of 200 kHz was deployed in the Santa Barbara Channel in the primary outgoing shipping lane for the port of Los Angeles and Long Beach. The vertical and horizontal aperture of the array allowed for starboard and portside measurements at all standard-required nominal hydrophone depths in addition to measurements taken at the keel aspect. Based on these measurements, frequency-dependent radiation patterns of contemporary merchant ships were estimated and used to evaluate current standards for computing ship source levels.

  12. Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

    NASA Astrophysics Data System (ADS)

    Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi

    2016-01-01

    A method of suppressing sound radiation to the far field of a near-field acoustic communication system using an evanescent sound field is proposed. The amplitude of the evanescent sound field generated from an infinite vibrating plate attenuates exponentially with increasing a distance from the surface of the vibrating plate. However, a discontinuity of the sound field exists at the edge of the finite vibrating plate in practice, which broadens the wavenumber spectrum. A sound wave radiates over the evanescent sound field because of broadening of the wavenumber spectrum. Therefore, we calculated the optimum distribution of the particle velocity on the vibrating plate to reduce the broadening of the wavenumber spectrum. We focused on a window function that is utilized in the field of signal analysis for reducing the broadening of the frequency spectrum. The optimization calculation is necessary for the design of window function suitable for suppressing sound radiation and securing a spatial area for data communication. In addition, a wide frequency bandwidth is required to increase the data transmission speed. Therefore, we investigated a suitable method for calculating the sound pressure level at the far field to confirm the variation of the distribution of sound pressure level determined on the basis of the window shape and frequency. The distribution of the sound pressure level at a finite distance was in good agreement with that obtained at an infinite far field under the condition generating the evanescent sound field. Consequently, the window function was optimized by the method used to calculate the distribution of the sound pressure level at an infinite far field using the wavenumber spectrum on the vibrating plate. According to the result of comparing the distributions of the sound pressure level in the cases with and without the window function, it was confirmed that the area whose sound pressure level was reduced from the maximum level to -50 dB was

  13. Method for measuring violin sound radiation based on bowed glissandi and its application to sound synthesis.

    PubMed

    Perez Carrillo, Alfonso; Bonada, Jordi; Patynen, Jukka; Valimaki, Vesa

    2011-08-01

    This work presents a method for measuring and computing violin-body directional frequency responses, which are used for violin sound synthesis. The approach is based on a frame-weighted deconvolution of excitation and response signals. The excitation, consisting of bowed glissandi, is measured with piezoelectric transducers built into the bridge. Radiation responses are recorded in an anechoic chamber with multiple microphones placed at different angles around the violin. The proposed deconvolution algorithm computes impulse responses that, when convolved with any source signal (captured with the same transducer), produce a highly realistic violin sound very similar to that of a microphone recording. The use of motion sensors allows for tracking violin movements. Combining this information with the directional responses and using a dynamic convolution algorithm, helps to improve the listening experience by incorporating the violinist motion effect in stereo.

  14. Breathing and Snoring Sound Characteristics during Sleep in Adults

    PubMed Central

    Levartovsky, Asaf; Dafna, Eliran; Zigel, Yaniv; Tarasiuk, Ariel

    2016-01-01

    Study Objectives: Sound level meter is the gold standard approach for snoring evaluation. Using this approach, it was established that snoring intensity (in dB) is higher for men and is associated with increased apnea-hypopnea index (AHI). In this study, we performed a systematic analysis of breathing and snoring sound characteristics using an algorithm designed to detect and analyze breathing and snoring sounds. The effect of sex, sleep stages, and AHI on snoring characteristics was explored. Methods: We consecutively recruited 121 subjects referred for diagnosis of obstructive sleep apnea. A whole night audio signal was recorded using noncontact ambient microphone during polysomnography. A large number (> 290,000) of breathing and snoring (> 50 dB) events were analyzed. Breathing sound events were detected using a signal-processing algorithm that discriminates between breathing and nonbreathing (noise events) sounds. Results: Snoring index (events/h, SI) was 23% higher for men (p = 0.04), and in both sexes SI gradually declined by 50% across sleep time (p < 0.01) independent of AHI. SI was higher in slow wave sleep (p < 0.03) compared to S2 and rapid eye movement sleep; men have higher SI in all sleep stages than women (p < 0.05). Snoring intensity was similar in both genders in all sleep stages and independent of AHI. For both sexes, no correlation was found between AHI and snoring intensity (r = 0.1, p = 0.291). Conclusions: This audio analysis approach enables systematic detection and analysis of breathing and snoring sounds from a full night recording. Snoring intensity is similar in both sexes and was not affected by AHI. Citation: Levartovsky A, Dafna E, Zigel Y, Tarasiuk A. Breathing and snoring sound characteristics during sleep in adults. J Clin Sleep Med 2016;12(3):375–384. PMID:26518701

  15. Directivity pattern of the sound radiated from axisymmetric stepped plates.

    PubMed

    He, Xiping; Yan, Xiuli; Li, Na

    2016-08-01

    For the purpose of optimal design and efficient utilization of the kind of stepped plate radiator in air, in this contribution, an approach for calculation of the directivity pattern of the sound radiated from a stepped plate in flexural vibration with a free edge is developed based on Kirchhoff-Love hypothesis and Rayleigh integral principle. Experimental tests of directivity pattern for a fabricated flat plate and two fabricated plates with one and two step radiators were carried out. It shows that the configuration of the measured directivity patterns by the proposed analytic approach is similar to those of the calculated approach. Comparison of the agreement between the calculated directivity pattern of a stepped plate and its corresponding theoretical piston show that the former radiator is equivalent to the latter, and the diffraction field generated by the unbaffled upper surface may be small. It also shows that the directivity pattern of a stepped radiator is independent of the metallic material but dependent on the thickness of base plate and resonant frequency. The thicker the thickness of base plate, the more directive the radiation is. The proposed analytic approach in this work may be adopted for any other plates with multi-steps.

  16. Sound quality prediction for engine-radiated noise

    NASA Astrophysics Data System (ADS)

    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.

  17. Far-field sound radiation of a submerged cylindrical shell at finite depth from the free surface.

    PubMed

    Li, T Y; Miao, Y Y; Ye, W B; Zhu, X; Zhu, X M

    2014-09-01

    The far-field sound radiation behavior of a circular cylindrical shell submerged at finite depth from the free surface is studied. Based on the Flügge shell theory and the Helmholtz equation, the structure-acoustic coupling equation is established. An image method is applied so that the sound boundary condition of the free surface can be satisfied. Analytical expression of the far-field sound pressure is obtained using the stationary phase method and the Graf's addition theorem. In order to evaluate the effect of the submerged depth on sound radiation, the results of the submerged cylindrical shell at finite depth from the free surface are compared with those of the submerged cylindrical shell in the infinite fluid. The characteristics of the far-field sound pressure with the change of the depth are investigated. It is found that the submerged depth has a significant influence on the far-field sound pressure radiated from the submerged cylindrical shell due to the free surface effects. The work provides more understanding on the sound radiation properties of the submerged circular cylindrical shell without assuming infinite fluid field, which was commonly used in previous studies.

  18. Acoustical Characteristics of Mastication Sounds: Application of Speech Analysis Techniques

    NASA Astrophysics Data System (ADS)

    Brochetti, Denise

    Food scientists have used acoustical methods to study characteristics of mastication sounds in relation to food texture. However, a model for analysis of the sounds has not been identified, and reliability of the methods has not been reported. Therefore, speech analysis techniques were applied to mastication sounds, and variation in measures of the sounds was examined. To meet these objectives, two experiments were conducted. In the first experiment, a digital sound spectrograph generated waveforms and wideband spectrograms of sounds by 3 adult subjects (1 male, 2 females) for initial chews of food samples differing in hardness and fracturability. Acoustical characteristics were described and compared. For all sounds, formants appeared in the spectrograms, and energy occurred across a 0 to 8000-Hz range of frequencies. Bursts characterized waveforms for peanut, almond, raw carrot, ginger snap, and hard candy. Duration and amplitude of the sounds varied with the subjects. In the second experiment, the spectrograph was used to measure the duration, amplitude, and formants of sounds for the initial 2 chews of cylindrical food samples (raw carrot, teething toast) differing in diameter (1.27, 1.90, 2.54 cm). Six adult subjects (3 males, 3 females) having normal occlusions and temporomandibular joints chewed the samples between the molar teeth and with the mouth open. Ten repetitions per subject were examined for each food sample. Analysis of estimates of variation indicated an inconsistent intrasubject variation in the acoustical measures. Food type and sample diameter also affected the estimates, indicating the variable nature of mastication. Generally, intrasubject variation was greater than intersubject variation. Analysis of ranks of the data indicated that the effect of sample diameter on the acoustical measures was inconsistent and depended on the subject and type of food. If inferences are to be made concerning food texture from acoustical measures of mastication

  19. Analysis of the radiated information in spinning sound fields.

    PubMed

    Carley, Michael

    2010-10-01

    The information content of a spinning sound field is analyzed using a combination of exact and asymptotic results, in order to set limits on how accurately source identification can be carried out. Using a transformation of the circular source to an exactly equivalent set of line source modes, given by Chebyshev polynomials, it is found that the line source modes of order greater than the source wavenumber generate exponentially small fields. Asymptotic analysis shows that the remaining, lower order, modes radiate efficiently only into a region around the source plane, with this region shrinking as the mode order is increased. The results explain the ill-conditioning of source identification methods; the successful use of low order models in active noise control; and the low radiation efficiency of subsonic jets.

  20. Sound insulation characteristics of finite length orthotropic shells

    NASA Astrophysics Data System (ADS)

    Chonan, S.; Koriyama, H.

    1988-11-01

    An analysis is presented of the acoustic characteristics of orthotropic cylindrical shells excited by axisymmetric plane sound waves traveling within the shells. The shell is exposed in a free field in the range of length, and is otherwise covered with an infinite rigid baffle. The problem is studied on the basis of a thick shell theory in which account is taken of the effects of shear deformation and rotatory inertia. The air outside the shell is described by the Helmholtz linear acoustic equation. The sound transmission loss through the shell wall is obtained and calculated for various values of the physical parameters involved.

  1. Prediction of sound radiation from different practical jet engine inlets

    NASA Technical Reports Server (NTRS)

    Meyer, W. L.; Zinn, B. T.

    1982-01-01

    Computer codes which were based upon a special integral representation of the external solutions of the Helmholtz equation were upgraded so that they would yield accurate results for the acoustic radiation patterns in the field surrounding an axisymmetric body for nondimensional wave numbers, based on duct radius, of up to twenty. The accuracy of these computer programs was checked by the use of the point source method for the generation of exact solutions and then by comparison with the results of other experimental and theoretical studies. These computer codes were used in a parametric study of the dependence of the radiated sound field on input modal distribution, wave number, and inlet lip shape. The results of this study show that: (1) as the wave number (i.e., cut off ratio) is increased for a given input modal distribution that the acoustic radiation peak moves towards the inlet centerline and becomes more compact (i.e., narrows); (2) as the input mode number is increased for a given cut off ratio the acoustic radiation peak moves away from the inlet centerline and becomes more compact.

  2. Large-eddy simulation of circular cylinder flow at subcritical Reynolds number: Turbulent wake and sound radiation

    NASA Astrophysics Data System (ADS)

    Guo, Li; Zhang, Xing; He, Guowei

    2016-02-01

    The flows past a circular cylinder at Reynolds number 3900 are simulated using large-eddy simulation (LES) and the far-field sound is calculated from the LES results. A low dissipation energy-conserving finite volume scheme is used to discretize the incompressible Navier-Stokes equations. The dynamic global coefficient version of the Vreman's subgrid scale (SGS) model is used to compute the sub-grid stresses. Curle's integral of Lighthill's acoustic analogy is used to extract the sound radiated from the cylinder. The profiles of mean velocity and turbulent fluctuations obtained are consistent with the previous experimental and computational results. The sound radiation at far field exhibits the characteristic of a dipole and directivity. The sound spectra display the -5/3 power law. It is shown that Vreman's SGS model in company with dynamic procedure is suitable for LES of turbulence generated noise.

  3. Structural topology optimization on sound radiation at resonance frequencies in thermal environments

    NASA Astrophysics Data System (ADS)

    Yang, XiongWei; Li, YueMing

    2015-03-01

    Thermal and acoustic environments pose severe challenges to the structural design of hypersonic vehicles. One of them is to find optimal design that exhibits ideal acoustic characteristics in a frequency band, which is discussed in this paper through topology optimization aiming at resonance sound radiation in thermal environments. The sound radiation at resonance frequencies is the main component of response, minimization on which is likely to provide a satisfactory design. A bi-material plate subjected to uniform temperature rise and excited by harmonic loading is studied here. Thermal stress is first evaluated and considered as pre stress in the following dynamic analysis; radiated sound power is then calculated through Rayleigh integral. Sensitivity analysis is carried out through adjoint method considering the complicated relationship between stress-induced geometric stiffness and design variables. As the resonance frequency is constantly changing during the optimization, its sensitivity should be considered. It is also noticed that mode switching may occur, so mode tracking technique is employed in this work. Some numerical examples are finally discussed.

  4. The use of an active controlled enclosure to attenuate sound radiation from a heavy radiator

    NASA Astrophysics Data System (ADS)

    Sun, Yao; Yang, Tiejun; Zhu, Minggang; Pan, Jie

    2017-03-01

    Active structural acoustical control usually experiences difficulty in the control of heavy sources or sources where direct applications of control forces are not practical. To overcome this difficulty, an active controlled enclosure, which forms a cavity with both flexible and open boundary, is employed. This configuration permits indirect implementation of active control in which the control inputs can be applied to subsidiary structures other than the sources. To determine the control effectiveness of the configuration, the vibro-acoustic behavior of the system, which consists of a top plate with an open, a sound cavity and a source panel, is investigated in this paper. A complete mathematical model of the system is formulated involving modified Fourier series formulations and the governing equations are solved using the Rayleigh-Ritz method. The coupling mechanisms of a partly opened cavity and a plate are analysed in terms of modal responses and directivity patterns. Furthermore, to attenuate sound power radiated from both the top panel and the open, two strategies are studied: minimizing the total radiated power and the cancellation of volume velocity. Moreover, three control configurations are compared, using a point force on the control panel (structural control), using a sound source in the cavity (acoustical control) and applying hybrid structural-acoustical control. In addition, the effects of boundary condition of the control panel on the sound radiation and control performance are discussed.

  5. Sound Radiated by a Wave-Like Structure in a Compressible Jet

    NASA Technical Reports Server (NTRS)

    Golubev, V. V.; Prieto, A. F.; Mankbadi, R. R.; Dahl, M. D.; Hixon, R.

    2003-01-01

    This paper extends the analysis of acoustic radiation from the source model representing spatially-growing instability waves in a round jet at high speeds. Compared to previous work, a modified approach to the sound source modeling is examined that employs a set of solutions to linearized Euler equations. The sound radiation is then calculated using an integral surface method.

  6. Further insight into the sound-producing mechanism of clownfishes: what structure is involved in sound radiation?

    PubMed

    Colleye, Orphal; Nakamura, Masaru; Frédérich, Bruno; Parmentier, Eric

    2012-07-01

    It was recently demonstrated that clownfishes produce aggressive sounds by snapping their jaw teeth. To date, only the onset of the sound has been studied, which raises the question, what structure is involved in sound radiation? Here, a combination of different approaches has been used to determine the anatomical structure(s) responsible for the size-related variations observed in sound duration and frequency. Filling the swimbladder with physiological liquid specifically modified size-related acoustic features by inducing a significant decrease in pulse duration of approximately 3 ms and a significant increase in dominant frequency of approximately 105 Hz. However, testing the acoustics of the swimbladder by striking it with a piezoelectric impact hammer showed that this structure is a highly damped sound source prevented from prolonged vibrations. In contrast, the resonant properties of the rib cage seems to account for the size-related variations observed in acoustic features. For an equivalent strike on the rib cage, the duration and dominant frequency of induced sounds changed with fish size: sound duration and dominant frequency were positively and negatively correlated with fish size, respectively. Such relationships between sonic features and fish size are consistent with those observed in natural sounds emitted by fish. Therefore, the swimbladder itself does not act as a resonator; its wall just seems to be driven by the oscillations of the rib cage. This set of observations suggests the need for reassessment of the acoustic role of swimbladders in various fish species.

  7. Active control of sound radiation from a vibrating rectangular panel by sound sources and vibration inputs - An experimental comparison

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.; Hansen, C. H.; Snyder, S. D.

    1991-01-01

    Active control of sound radiation from a rectangular panel by two different methods has been experimentally studied and compared. In the first method a single control force applied directly to the structure is used with a single error microphone located in the radiated acoustic field. Global attenuation of radiated sound was observed to occur by two main mechanisms. For 'on-resonance' excitation, the control force had the effect of increasing the total panel input impedance presented to the nosie source, thus reducing all radiated sound. For 'off-resonance' excitation, the control force tends not significantly to modify the panel total response amplitude but rather to restructure the relative phases of the modes leading to a more complex vibration pattern and a decrease in radiation efficiency. For acoustic control, the second method, the number of acoustic sources required for global reduction was seen to increase with panel modal order. The mechanism in this case was that the acoustic sources tended to create an inverse pressure distribution at the panel surface and thus 'unload' the panel by reducing the panel radiation impedance. In general, control by structural inputs appears more effective than control by acoustic sources for structurally radiated noise.

  8. Laboratory ultrasonic generator. [characteristics of ultrasonic sound generator for experimental and industrial applications

    NASA Technical Reports Server (NTRS)

    Tudose, C.; Dobrescu, F.

    1974-01-01

    The characteristics of an ultrasonic generator with magnetostrictive amplifiers are described. The generator was designed to supply an output power of about 400 watts at a consumption of about 1 kilowatt. The generator produces sound waves in the frequency range of 18 to 30 KHz. The circuit design is described and examples of the construction are illustrated. The generator is used to study different industrial processes such as the effect of ultrasonic radiation of the emulsification of liquids, the dispersion of solids, and ultrasonic filtration.

  9. Laboratory ultrasonic generator. [characteristics of ultrasonic sound generator for experimental and industrial applications

    NASA Technical Reports Server (NTRS)

    Tudose, C.; Dobrescu, F.

    1974-01-01

    The characteristics of an ultrasonic generator with magnetostrictive amplifiers are described. The generator was designed to supply an output power of about 400 watts at a consumption of about 1 kilowatt. The generator produces sound waves in the frequency range of 18 to 30 KHz. The circuit design is described and examples of the construction are illustrated. The generator is used to study different industrial processes such as the effect of ultrasonic radiation of the emulsification of liquids, the dispersion of solids, and ultrasonic filtration.

  10. Prediction of sound radiated from different practical jet engine inlets

    NASA Technical Reports Server (NTRS)

    Zinn, B. T.; Meyer, W. L.

    1980-01-01

    Existing computer codes for calculating the far field radiation patterns surrounding various practical jet engine inlet configurations under different excitation conditions were upgraded. The computer codes were refined and expanded so that they are now more efficient computationally by a factor of about three and they are now capable of producing accurate results up to nondimensional wave numbers of twenty. Computer programs were also developed to help generate accurate geometrical representations of the inlets to be investigated. This data is required as input for the computer programs which calculate the sound fields. This new geometry generating computer program considerably reduces the time required to generate the input data which was one of the most time consuming steps in the process. The results of sample runs using the NASA-Lewis QCSEE inlet are presented and comparison of run times and accuracy are made between the old and upgraded computer codes. The overall accuracy of the computations is determined by comparison of the results of the computations with simple source solutions.

  11. Some sound transmission loss characteristics of typical general aviation structural materials

    NASA Technical Reports Server (NTRS)

    Roskam, J.; Van Dam, C.; Grosveld, F.; Durenberger, D.

    1978-01-01

    Experimentally measured sound transmission loss characteristics of flat aluminum panels with and without damping and stiffness treatment are presented and discussed. The effect of pressurization on sound transmission loss of flat aluminum panels is shown to be significant.

  12. Supersonic intensity and non-negative intensity for prediction of radiated sound.

    PubMed

    Liu, Daipei; Peters, Herwig; Marburg, Steffen; Kessissoglou, Nicole

    2016-05-01

    Two numerical methods to identify the surface areas of a vibrating structure that radiate sound are presented. The supersonic intensity identifies only the supersonic wave components of the sound field contributing to far-field radiated sound. The supersonic intensity is calculated using a two-dimensional convolution between a spatial radiation filter and the sound field. To compute the spatial radiation filter, the shortest surface distance between two points on the structure is calculated using the geodesic distance method. The non-negative intensity is based on acoustic radiation modes and identifies the radiated sound power from a vibrating structure. Numerical models of a baffled plate, a cylinder and an engine crankcase are presented. The supersonic intensity is shown to be difficult to implement at low frequencies due to the size of the spatial radiation filter and accuracy of the surface distances. A cut-off coefficient associated with the acoustic wavenumber of the spatial radiation filter is used to reduce the aperture error. A comparison of the two intensity-based techniques both in terms of a sound power ratio and the modal assurance criterion is introduced to identify the optimal values of the cut-off coefficients that result in better convergence between the intensity techniques.

  13. Sound power radiation from a vibrating structure in terms of structure-dependent radiation modes

    NASA Astrophysics Data System (ADS)

    Ji, Lin; Bolton, J. Stuart

    2015-01-01

    As a good supplement of conventional acoustic radiation modes (a-modes), a set of so-called "structure-dependent radiation modes" (s-modes) is introduced to describe the sound power radiation from a vibrating structure. Differing from a-modes, s-modes are determined by not only the acoustic resistance matrix of the structure but also the frequency-independent normal modes of the structure. Such a new definition has the following main advantages over the conventional one: (1) it can reflect directly the influences of dynamic properties (e.g., boundary conditions) of the structures on its sound power radiation; (2) the number of s-modes generated is generally less than that of a-modes since the former depends on the number of structural modes involved in the vibration while the latter depends on the number of segmented elemental radiators of the structure, and consequently, the demand for large data storage can be greatly alleviated, especially for large structures and/or higher frequency vibrations; (3) the set of s-modes possesses a better convergence than that of a-modes because the higher ordered s-modes can decay more rapidly than the same ordered a-modes. Two baffled, finite, models, i.e., a simple beam and a thin plate, are employed to investigate numerically the acoustic properties of s-modes, and then compared with those of a-modes. It has been shown that the two sets of radiation modes share a very similar frequency-dependent behavior in that the radiation efficiency falls off very rapidly with increasing mode order at low frequency range (typically with kl<1). Meanwhile, the number of s-modes required to describe the total sound power radiation is found to be the same as that of a-modes. Consequently, an appropriate truncation of a-modes can be achieved by using the number of vibrational modes involved. Nevertheless, the odd-ordered (even-ordered) s-modes are found only associated with the odd-numbered (even-ordered) structural modes. In case of only few

  14. Relating the radiated piano sound field to the vibrational modes of the soundboard

    NASA Astrophysics Data System (ADS)

    Hansen, Uwe J.; Bork, Ingolf; Rossing, Thomas D.

    2003-10-01

    The sound field near a piano sound board is determined by moving a microphone over a grid of points above and below the sound board as well as in a plane in front of the piano using the experimental techniques of modal analysis with soundboard excitation at a bridge point by a swept sine signal. Since the standard modal analysis signal processing technique relies on tracking phase relations between excitation and response, it is possible to relate the sound field in terms of the vibrating structure which radiated it. Animations of sound board motion and sound field pressure variations are shown for the lowest four modes. It is noted that in all modes the locations of maximal excursion correlate with the sound pressure maxima or minima, respectively.

  15. Wave field synthesis of moving virtual sound sources with complex radiation properties.

    PubMed

    Ahrens, Jens; Spors, Sascha

    2011-11-01

    An approach to the synthesis of moving virtual sound sources with complex radiation properties in wave field synthesis is presented. The approach exploits the fact that any stationary sound source of finite spatial extent radiates spherical waves at sufficient distance. The angular dependency of the radiation properties of the source under consideration is reflected by the amplitude and phase distribution on the spherical wave fronts. The sound field emitted by a uniformly moving monopole source is derived and the far-field radiation properties of the complex virtual source under consideration are incorporated in order to derive a closed-form expression for the loudspeaker driving signal. The results are illustrated via numerical simulations of the synthesis of the sound field of a sample moving complex virtual source.

  16. Response characteristics of a viscoelastic gel under the co-action of sound waves and an electric field

    NASA Astrophysics Data System (ADS)

    Tang, Hong; Zhao, Xiaopeng; Wang, Baoxiang; Zhao, Yan

    2006-02-01

    We design a flexible sound tunable sandwiched panel structure, which is composed of a nanoelectrorheological gel layer and two conductive rubber sheets, and experimentally investigate the tunable behaviors of the sound transmitted through the panel. For the frequency range of 380-500 Hz the transmitted sound pressure level (SPL) decreases with the electric field strength Ee, while at about 550-650 Hz the SPL increases with Ee. Within 500-550 Hz a hump appears and the hump apex shifts in the high frequency direction with increase of Ee. Besides this, the phase angle of the transmitted sound wave changes with Ee within these frequency ranges. The weight fraction of particles in the electrorheological gels also influences these observed tunable characteristics. The theoretical calculation based on a vibration-radiation model agrees with the experimental results, qualitatively. It is revealed that the electric field induced viscoelasticity change in the electrorheological gel and hence the vibration-radiation variation on the sandwiched panel is the origin of the phenomenon. The flexible composite electrorheological panel could be used in sound sensitive artificial skins or sound tunable actuators and has potential for use in robots and intelligent structures and systems.

  17. Airborne sound transmission loss characteristics of woodframe construction

    Treesearch

    Fred F. Rudder

    1985-01-01

    This report summarizes the available data on the airborne sound transmission loss properties of wood-frame construction and evaluates the methods for predicting the airborne sound transmission loss. The first part of the report comprises a summary of sound transmission loss data for wood-frame interior walls and floor-ceiling construction. Data bases describing the...

  18. Sound absorption characteristics of tree bark and forest floor

    Treesearch

    G. Reethof; O. H. McDaniel; G. M. Heisler

    1977-01-01

    Results of basic research on absorption of sound by tree bark and forest floors are presented. Amount of sound absorption by tree bark was determined by laboratory experiments with bark samples in a standing-wave tube. A modified portable standing-wave tube was used to measure absorption of sound by forest floors with different moisture contents, with and without leaf...

  19. Minimisation of the sound power radiated by a submarine through optimisation of its resonance changer

    NASA Astrophysics Data System (ADS)

    Merz, Sascha; Kessissoglou, Nicole; Kinns, Roger; Marburg, Steffen

    2010-04-01

    An important cause of sound radiation from a submarine in the low frequency range is fluctuating forces at the propeller. The forces are transmitted to the hull via the shaft and the fluid. Sound radiation occurs due to hull and propeller vibrations as well as dipole sound radiation caused by the operation of the propeller in a non-uniform wake. In order to minimise sound radiation caused by propeller forces, a hydraulic vibration attenuation device known as a resonance changer can be implemented in the propeller/shafting system. In this work, cost functions that represent the overall radiated sound power are investigated, where the virtual stiffness, damping and mass of the resonance changer were chosen as design parameters. The minima of the cost functions are found by applying gradient based optimisation techniques. The finite element and boundary element methods are used to model the structure and the fluid, respectively. The adjoint operator is employed to calculate the sensitivity of the cost function to the design parameters. The influence of sound radiation due to propeller vibration on the optimisation of the resonance changer as well as the influence of the reduction in amplitude for higher harmonics of the blade-passing frequency on the control performance is investigated.

  20. Effects of seawater temperature on sound characteristics in Ophidion rochei (Ophidiidae).

    PubMed

    Kéver, L; Boyle, K S; Parmentier, E

    2015-08-01

    Although the sound production mechanisms of male and female Ophidion rochei (Ophidiidae) differ significantly, temperature affects them in the same manner. In both sexes, temperature correlated negatively with pulse period and positively with sound frequencies but had no, or weak effects on other sound characteristics.

  1. Vibrational mode and sound radiation of electrostatic speakers using circular and annular diaphragms

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Hsi; Chiang, Hsin-Yuan

    2016-06-01

    This study modeled two diaphragms comprising a pair of indium tin oxide (ITO) transparent plates sandwiching a vibrating diaphragm to create circular (30 mm radius) and annular (30 mm outer and 3 mm inner radius) push-pull electrostatic speakers. We then measured the displacement amplitudes and mode shapes produced by the devices. Vibration characteristics were used to predict sound pressure levels (SPLs) using the lumped parameter method (LPM) and distributed parameter method (DPM). The two measurement results obtained using a laser system were compared to the SPLs obtained using traditional acoustic measurement (AM) from 20 Hz to 20 kHz in order to verify our predictions. When using LPM and DPM, the SPL prediction results in the first three symmetric modes were in good agreement with the AM results. Under the assumption of linear operations, the DPM and amplitude-fluctuation electronic speckle pattern interferometry (ESPI) techniques proved effective in determining the visualization of mode shape (0,1)-(0,3). The use of ITO plates is a practical technique for the prediction of SPL, as well as measurement of mode shapes. The four evaluation methods, i.e. LPM, DPM, ESPI and AM, present a high degree of consistency with regard to vibrational mode and sound radiation characteristics.

  2. Distress sounds of thorny catfishes emitted underwater and in air: characteristics and potential significance.

    PubMed

    Knight, Lisa; Ladich, Friedrich

    2014-11-15

    Thorny catfishes produce stridulation (SR) sounds using their pectoral fins and drumming (DR) sounds via a swimbladder mechanism in distress situations when hand held in water and in air. It has been argued that SR and DR sounds are aimed at different receivers (predators) in different media. The aim of this study was to analyse and compare sounds emitted in both air and water in order to test different hypotheses on the functional significance of distress sounds. Five representatives of the family Doradidae were investigated. Fish were hand held and sounds emitted in air and underwater were recorded (number of sounds, sound duration, dominant and fundamental frequency, sound pressure level and peak-to-peak amplitudes). All species produced SR sounds in both media, but DR sounds could not be recorded in air for two species. Differences in sound characteristics between media were small and mainly limited to spectral differences in SR. The number of sounds emitted decreased over time, whereas the duration of SR sounds increased. The dominant frequency of SR and the fundamental frequency of DR decreased and sound pressure level of SR increased with body size across species. The hypothesis that catfish produce more SR sounds in air and more DR sounds in water as a result of different predation pressure (birds versus fish) could not be confirmed. It is assumed that SR sounds serve as distress sounds in both media, whereas DR sounds might primarily be used as intraspecific communication signals in water in species possessing both mechanisms. © 2014. Published by The Company of Biologists Ltd.

  3. Measurement and characterisation of radiated underwater sound from a 3.6 MW monopile wind turbine.

    PubMed

    Pangerc, Tanja; Theobald, Peter D; Wang, Lian S; Robinson, Stephen P; Lepper, Paul A

    2016-10-01

    This paper describes underwater sound pressure measurements obtained in close proximity (∼50 m) to two individual wind turbines, over a 21-day period, capturing the full range of turbine operating conditions. The sound radiated into the water was characterised by a number of tonal components, which are thought to primarily originate from the gearbox for the bandwidth measured. The main signal associated with the turbine operation had a mean-square sound pressure spectral density level which peaked at 126 dB re 1 μPa(2) Hz(-1) at 162 Hz. Other tonal components were also present, notably at frequencies between about 20 and 330 Hz, albeit at lower amplitudes. The measured sound characteristics, both in terms of frequency and amplitude, were shown to vary with wind speed. The sound pressure level increased with wind speed up to an average value of 128 dB re 1 μPa at a wind speed of about 10 ms(-1), and then showed a general decrease. Overall, differences in the mean-square sound pressure spectral density level of over 20 dB were observed across the operational envelope of the turbine.

  4. Structure of supersonic jet flow and its radiated sound

    NASA Technical Reports Server (NTRS)

    Mankbadi, Reda R.; Hayer, M. Ehtesham; Povinelli, Louis A.

    1994-01-01

    The present paper explores the use of large-eddy simulations as a tool for predicting noise from first principles. A high-order numerical scheme is used to perform large-eddy simulations of a supersonic jet flow with emphasis on capturing the time-dependent flow structure representating the sound source. The wavelike nature of this structure under random inflow disturbances is demonstrated. This wavelike structure is then enhanced by taking the inflow disturbances to be purely harmonic. Application of Lighthill's theory to calculate the far-field noise, with the sound source obtained from the calculated time-dependent near field, is demonstrated. Alternative approaches to coupling the near-field sound source to the far-field sound are discussed.

  5. Some characteristics and effects of natural radiation.

    PubMed

    Mc Laughlin, J P

    2015-11-01

    Since life first appeared on the Earth, it has, in all its subsequent evolved forms including human, been exposed to natural radiation in the environment both from terrestrial and extra-terrestrial sources. Being an environmental mutagen, ionising natural radiation may have played a role of some significance in the evolution of early life forms on Earth. It has been estimated by United Nations Scientific Committee on the Effects of Atomic Radiation that at the present time, exposure to natural radiation globally results in an annual average individual effective dose of about 2.4 mSv. This represents about 80 % of the total dose from all sources. The three most important components of natural radiation exposure are cosmic radiation, terrestrial radioactivity and indoor radon. Each of these components exhibits both geographical and temporal variabilities with indoor radon exposure being the most variable and also the largest contributor to dose for most people. In this account, an overview is given of the characteristics of the main components of the natural radiation environment and some of their effects on humans. In the case of cosmic radiation, these range from radiation doses to aircrew and astronauts to the controversial topic of its possible effect on climate change. In the case of terrestrial natural radiation, accounts are given of a number of human exposure scenarios. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  6. Acoustic characteristics of vowel sounds in patients with Parkinson disease.

    PubMed

    Bang, Young-Im; Min, Kyunghoon; Sohn, Young H; Cho, Sung-Rae

    2013-01-01

    The purpose of this study was to define the acoustic voice and speech characteristics of patients with Parkinson disease (PD). Seven female patients with PD and seven female healthy controls participated in this study. Each subject was instructed to vocalize extended corner vowels (/a/, /e/, /i/, /u/) three times for at least 5 seconds at a comfortable voice loudness and tone. The voice was analyzed using the Praat program. As a result, female patients with PD showed a significant increase in jitter and noise-to-harmonics ratio (NHR). In addition, F1 and F2 among the PD patients demonstrated asymmetric centralization of unrounded vowels (/a/, /e/, /i/) in high/low/front/back positions of the tongue, consequently leading to a significant decrease in vowel space area, compared to healthy controls. This study showed the acoustic characteristics of vowel sounds not only by laryngeal variables such as abnormal jitter and NHR, but also by articulatory variables such as asymmetric centralization and reduced vowel space area in female patients with PD. Therefore, it is important to use these objective and sensitive variables to evaluate the status or severity of hypokinetic dysarthria in patients with PD.

  7. Effect of a fluid layer on the sound radiation of a plate and its active control

    NASA Astrophysics Data System (ADS)

    Sun, Yao; Pan, Jie; Yang, Tiejun

    2015-11-01

    In this paper, a baffled plate facing a layer of fluid is used to investigate the effects of the radiating environment on the plate's sound radiation and its active control. By varying the thickness of the fluid layer, different radiation environments are presented to the plate, resulting in a variation in the efficiencies and shapes of the radiation modes of the plate. As the design of feed-forward control of the radiated sound power and of feedback control of the vibration velocity or volume velocity is limited by the properties of the secondary control path (an open-loop frequency response function), the performance of the control system may be deteriorated if a controller optimally designed for one radiation environment is used for a different environment. The effects of radiation environment on the properties of the secondary control path and performance of active control are investigated.

  8. Sound radiation from a fluid-loaded infinite plate with a patch.

    PubMed

    Zhang, Yanni; Pan, Jie

    2013-01-01

    This paper focuses on the solution to the vibro-acoustic response of a line-driven fluid-loaded plate with an elastic patch acting as a distributed inhomogeneity. The patch affects the plate's sound radiation by adding extra loading to the driving force and by scattering structural waves. When the driving force is located beneath the patch, the extra loading reduces the plate's supersonic velocity response and sound radiation. At some frequencies, however, the constructive superposition of scattered structural waves and near-field waves by the driving force outweighs the effect of patch loading and results in an increased sound radiation power. When the patch is located away from the driving force, wave scattering phenomena dominates the plate vibration and subsequent sound radiation. By examining the effect of the length and location of the patch on the sound power, it is possible to relate the changes in the sound power to the changes in supersonic velocity spectrum and velocity distribution contributed by the trapped modes in the patched area and interference between the scattered waves by the patch and the near- and far-field structural waves directly generated by the driving force.

  9. Acoustic radiation torque on an irregularly shaped scatterer in an arbitrary sound field.

    PubMed

    Fan, Zongwei; Mei, Deqing; Yang, Keji; Chen, Zichen

    2008-11-01

    To eliminate the limitation of the conventional acoustic radiation torque theory, which is only applicable to a disklike scatterer in a plane sound field, a new theory is established to calculate the radiation torque on any irregularly shaped scatterer in any arbitrary sound field. First, with the aid of the conservation law of angular momentum, the acoustic radiation torque is expressed as the angular momentum flux through a spherical surface with the center at the scatterer's centroid. Second, the velocity potential of the scattered field is derived, taking into account the influences of the translational and rotational movements of the scatterer induced by the first order stress of the incident sound field. Finally, a general calculating formula of the acoustic radiation torque is achieved. For a disklike scatterer in a plane sound filed, results from the above formula are well identical with those conventional formulas. By studying the case of a semicircular cylinder scatterer in a standing-wave sound field, it is found that for an irregularly shaped scatterer its rotation velocity is normally nonzero and the radiation torque changes with the spatial attitude.

  10. Biological effect of audible sound control on mung bean (Vigna radiate) sprout.

    PubMed

    Cai, W; He, H; Zhu, S; Wang, N

    2014-01-01

    Audible sound (20-20000 Hz) widely exists in natural world. However, the interaction between audible sound and the growth of plants is usually neglected in biophysics research. Not much effort has been put forth in studying the relation of plant and audible sound. In this work, the effect of audible sound on germination and growth of mung bean (Vigna radiate) was studied under laboratory condition. Audible sound ranging 1000-1500 Hz, 1500-2000 Hz, and 2000-2500 Hz and intensities [80 dB (A), 90 dB (A), 100 dB (A)] were used to stimulate mung bean for 72 hours. The growth of mung bean was evaluated in terms of mean germination time, total length, and total fresh weight. Experimental results indicated that the sound wave can reduce the germination period of mung bean and the mung bean under treatments of sound with intensity around 90 dB and frequency around 2000 Hz and significant increase in growth. Audible sound treatment can promote the growth of mung bean differently for distinct frequency and intensity. The study provides us with a way to understand the effects and rules of sound field on plant growth and a new way to improve the production of mung bean.

  11. Biological Effect of Audible Sound Control on Mung Bean (Vigna radiate) Sprout

    PubMed Central

    Cai, W.; He, H.; Zhu, S.; Wang, N.

    2014-01-01

    Audible sound (20–20000 Hz) widely exists in natural world. However, the interaction between audible sound and the growth of plants is usually neglected in biophysics research. Not much effort has been put forth in studying the relation of plant and audible sound. In this work, the effect of audible sound on germination and growth of mung bean (Vigna radiate) was studied under laboratory condition. Audible sound ranging 1000–1500 Hz, 1500–2000 Hz, and 2000–2500 Hz and intensities [80 dB (A), 90 dB (A), 100 dB (A)] were used to stimulate mung bean for 72 hours. The growth of mung bean was evaluated in terms of mean germination time, total length, and total fresh weight. Experimental results indicated that the sound wave can reduce the germination period of mung bean and the mung bean under treatments of sound with intensity around 90 dB and frequency around 2000 Hz and significant increase in growth. Audible sound treatment can promote the growth of mung bean differently for distinct frequency and intensity. The study provides us with a way to understand the effects and rules of sound field on plant growth and a new way to improve the production of mung bean. PMID:25170517

  12. Spectral Characteristics of Wake Vortex Sound During Roll-Up

    NASA Technical Reports Server (NTRS)

    Booth, Earl R., Jr. (Technical Monitor); Zhang, Yan; Wang, Frank Y.; Hardin, Jay C.

    2003-01-01

    This report presents an analysis of the sound spectra generated by a trailing aircraft vortex during its rolling-up process. The study demonstrates that a rolling-up vortex could produce low frequency (less than 100 Hz) sound with very high intensity (60 dB above threshold of human hearing) at a distance of 200 ft from the vortex core. The spectrum then drops o rapidly thereafter. A rigorous analytical approach has been adopted in this report to derive the spectrum of vortex sound. First, the sound pressure was solved from an alternative treatment of the Lighthill s acoustic analogy approach [1]. After the application of Green s function for free space, a tensor analysis was applied to permit the removal of the source term singularity of the wave equation in the far field. Consequently, the sound pressure is expressed in terms of the retarded time that indicates the time history and spacial distribution of the sound source. The Fourier transformation is then applied to the sound pressure to compute its spectrum. As a result, the Fourier transformation greatly simplifies the expression of the vortex sound pressure involving the retarded time, so that the numerical computation is applicable with ease for axisymmetric line vortices during the rolling-up process. The vortex model assumes that the vortex circulation is proportional to the time and the core radius is a constant. In addition, the velocity profile is assumed to be self-similar along the aircraft flight path, so that a benchmark vortex velocity profile can be devised to obtain a closed form solution, which is then used to validate the numerical calculations for other more realistic vortex profiles for which no closed form solutions are available. The study suggests that acoustic sensors operating at low frequency band could be profitably deployed for detecting the vortex sound during the rolling-up process.

  13. The structure of supersonic jet flow and its radiated sound

    NASA Technical Reports Server (NTRS)

    Mankbadi, Reda R.; Hayder, M. E.; Povinelli, Louis A.

    1993-01-01

    Large-eddy simulation of a supersonic jet is presented with emphasis on capturing the unsteady features of the flow pertinent to sound emission. A high-accuracy numerical scheme is used to solve the filtered, unsteady, compressible Navier-Stokes equations while modelling the subgrid-scale turbulence. For random inflow disturbance, the wave-like feature of the large-scale structure is demonstrated. The large-scale structure was then enhanced by imposing harmonic disturbances to the inflow. The limitation of using the full Navier-Stokes equation to calculate the far-field sound is discussed. Application of Lighthill's acoustic analogy is given with the objective of highlighting the difficulties that arise from the non-compactness of the source term.

  14. REM-RED Cosmic Radiation Monitoring Experiment On-Board the REXUS-17 Sounding Rocket

    NASA Astrophysics Data System (ADS)

    Zabori, B.; Gerecs, A.; Hurtonyne Gyovai, A.; Benyei, D.; Naczi, F.; Hurtony, T.

    2015-09-01

    The cosmic radiation field is not well known up to the altitude of the lower orbiting spacecrafts. There are several ways to measure the cosmic radiation in this altitude; however it is not easy to apply them to a sounding rocket. The easiest way is to use Geiger-Muller (GM) counters to quantify the radiation level. The REMRED rocket experiment performed measurements with active radiation instruments (GM counters) in order to quantify the cosmic radiation field from the Earth's surface up to the maximum altitude of the REXUS rocket (about 90 km). The flight of the REM-RED experiment was carried out on the 1 7th of March 201 5 from the ESRANGE Space Center on-board the REXUS-17 student mission sounding rocket.

  15. Active control of low-frequency sound radiation by cylindrical shell with piezoelectric stack force actuators

    NASA Astrophysics Data System (ADS)

    Cao, Yin; Sun, Hongling; An, Fengyan; Li, Xiaodong

    2012-05-01

    A novel active control method of sound radiation from a cylindrical shell under axial excitations is proposed and theoretically analyzed. This control method is based on a pair of piezoelectric stack force actuators which are installed on the shell and parallel to the axial direction. The actuators are driven in phase and generate the same forces to control the vibration and the sound radiation of the cylindrical shell. The model considered is a fluid-loaded finite stiffened cylindrical shell with rigid end-caps and only low-frequency axial vibration modes are involved. Numerical simulations are performed to explore the required control forces and the optimal mounting positions of actuators under different cost functions. The results show that the proposed force actuators can reduce the radiated sound pressure of low-frequency axial modes in all directions.

  16. A theoretical approach to sound propagation and radiation for ducts with suppressors

    NASA Technical Reports Server (NTRS)

    Rice, E. J.; Sawdy, D. T.

    1981-01-01

    The several phenomena involved in theoretical prediction of the far-field sound radiation attenuation from an acoustically lined duct were studied. These include absorption by the suppressor, termination reflections, and far-field radiation. Extensive parametric studies show that the suppressor absorption performance can be correlated with mode cut-off ratio or angle of propagation. The other phenomena can be shown to depend explicitly upon mode cut-off ratio. A complete system can thus be generated which can be used to evaluate aircraft sound suppressors and which can be related to the sound source through the cut-off ratio-acoustic power distribution. Although the method is most fully developed for inlet suppressors, several aft radiated noise phenomena are also discussed. This simplified suppressor design and evaluation method is summarized, the recent improvements in the technique are presented, and areas where further refinement is necessary are discussed. Noise suppressor data from engine experiments are compared with the theoretical calculations.

  17. Active/Passive Control of Sound Radiation from Panels using Constrained Layer Damping

    NASA Technical Reports Server (NTRS)

    Gibbs, Gary P.; Cabell, Randolph H.

    2003-01-01

    A hybrid passive/active noise control system utilizing constrained layer damping and model predictive feedback control is presented. This system is used to control the sound radiation of panels due to broadband disturbances. To facilitate the hybrid system design, a methodology for placement of constrained layer damping which targets selected modes based on their relative radiated sound power is developed. The placement methodology is utilized to determine two constrained layer damping configurations for experimental evaluation of a hybrid system. The first configuration targets the (4,1) panel mode which is not controllable by the piezoelectric control actuator, and the (2,3) and (5,2) panel modes. The second configuration targets the (1,1) and (3,1) modes. The experimental results demonstrate the improved reduction of radiated sound power using the hybrid passive/active control system as compared to the active control system alone.

  18. Decentralized harmonic control of sound radiation and transmission by a plate using a virtual impedance approach.

    PubMed

    Quaegebeur, Nicolas; Micheau, Philippe; Berry, Alain

    2009-05-01

    The problem under study in this article is the active control of sound transmission and radiation of a panel under a periodic excitation. The control strategy investigated uses independent control loops between an individual polyvinylidene fluoride (PVDF) sensor and an individual lead zirconate titanate (PZT) actuator. The specific approach employed here uses the concept of virtual impedance. The aim is to determine for each frequency the optimal impedance between each PVDF sensor and the corresponding PZT actuator in order to reduce the sound power radiated by the plate. Theoretical predictions are compared to measurements of the sound radiated and transmission loss of a panel mounted with eight PZT-PVDF units. Reductions of up to 20 dB of the acoustic power can be achieved around mechanical resonances of the system, while the control strategy has little effect for off-resonance excitations.

  19. Adjoint-based minimization of the sound radiated by a Mach 1.3 turbulent jet

    NASA Astrophysics Data System (ADS)

    Kim, Jeonglae; Bodony, Daniel; Freund, Jonathan

    2010-11-01

    A control optimization using the adjoint of the perturbed and linearized Navier--Stokes equations is applied to a simulation of a Mach 1.3 turbulent jet to reduce its radiated sound. The solution of the adjoint system provides gradient information for a minimization algorithm to circumvent the flow complexity and reduce the sound directly. Comparisons between the loud and the perturbed-but-quiet versions of the same jet are examined to identify sound mechanisms. The overall algorithm is designed such that the control can be optimized with degrees of freedom comparable to that of the numerical discretization or with constraints on its spatial or temporal profiles to reflect hardware limitations. The large-eddy simulation of the uncontrolled, baseline jet is carried out in curvilinear coordinates using a non-dissipative high-order finite-difference. The far-field sound is computed using a Ffowcs Williams and Hawkings surface. Turbulence and far-field sound statistics agree with experimental data. An unconstrained optimal control reduces the sound cost functional by 17%. The far-field sound is reduced at all angles with a maximum reduction of 2.7dB in the peak radiation direction. Constraining the control in actuator-like zones shows a similar result. Optimizations are ongoing.

  20. Outgoing long-wave radiation computed from HIRS2/MSU soundings. [High InfraRed Spectrometer/Microwave Sounding Unit

    SciTech Connect

    Wu, M.C.; Susskind, J. )

    1990-05-20

    Fields of outgoing long-wave radiation (OLR) have been computed using geophysical parameters retrieved from analysis of HIRS2/MSU sounding data as input to a modified version of the Wu-Kaplan radiation code used in the Goddard Laboratory for Atmospheres fourth-order general circulation model. Monthly mean results for 1979 agree with monthly mean OLR fields measured by the Nimbus 7 Earth radiation budget (ERB) broadband narrow field of view instrument within standard deviations of 6.3 W/m{sup 2} but with a global mean bias of 8.0 W/m{sup 2}. Results are shown for July 1979. The areas of disagreement between high-resolution infrared radiation sounder OLR and ERB OLR are small but spatially coherent with patterns which may be related to sampling differences. The difference patterns are much less extensive than those between OLR derived from advanced very high resolution radiometer 11-{mu}m observations and ERB OLR. The ability to compute OLR from geophysical parameters is complementary to direct measurement of OLR because it enables one to attribute changes in OLR in space and time to changes in other geophysical parameters. In addition, it allows one to compute fields not directly measurable from satellite, such as the difference of the upward long-wave flux between the surface and the top of the atmosphere and the long-wave cloud radiative forcing.

  1. Measurement of the energy characteristics of a sound field in an interferometer

    NASA Astrophysics Data System (ADS)

    Ivannikov, A. N.; Rozhin, F. V.; Tonakanov, O. S.

    1983-02-01

    The basic relationships characterizing sound-field parameters in an interferometer are presented. A description is given of an experimental setup and method for determining the characteristics of a reflecting surface on the basis of measurements of power flux density. It is suggested that this approach may offer a new source of information about the acoustic properties of sound-absorbing materials.

  2. Active control of sound transmission/radiation from elastic plates by vibration inputs. I - Analysis

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.

    1990-01-01

    Active control of sound radiation from vibrating plates by oscillating forces applied directly to the structure is analytically studied. The model consists of a plane acoustic wave incident on a clamped elastic circular thin plate. Control is achieved by point forces, and quadratic optimization is used to calculate the optimal control gains necessary to minimize a cost function proportional to the radiated acoustic power (the transmitted field). The results show that global attenuation of broadband radiated sound levels for low to mid-range frequencies can be achieved with one or two control forces, irrespective of whether the system is on or off resonance. The efficiency of the control strategy is demonstrated to be related to the nature of the coupling between the plate modes of response and the radiated field.

  3. Energy density of standing sound waves at the radiation-dominated phase of the universe expansion (hydrodynamic derivation)

    NASA Astrophysics Data System (ADS)

    Inogamov, N. A.; Sunyaev, R. A.

    2015-12-01

    In the early Universe up to hydrogen recombination in the Universe, the radiation pressure was much greater than the pressure of baryons and electrons. Moreover, the energy density of cosmic microwave background (CMB) photons was greater than or close to the energy density contained in the rest mass of baryonic matter, i.e., the primordial plasma was a radiated-dominated one and the adiabatic index was close to 4/3. The small density perturbations from which the observed galaxies have grown grew as long as the characteristic perturbation scales exceeded the horizon of the Universe сt at that time. On smaller scales, the density perturbations were standing sound waves. Radiative viscosity and heat conduction must have led to the damping of sound waves on very small scales. After the discovery of the cosmic microwave background, J. Silk calculated the scales of this damping, which is now called Silk damping, knowing the CMBtemperature and assuming the density of baryons and electrons. Observations with the South Pole Telescope, the Atacama Cosmology Telescope, and the Planck satellite have revealed the predicted damping of acoustic peaks in the CMB power spectrum and confirmed one important prediction of the theory. In 1970, R.A. Sunyaev and Ya.B. Zeldovich showed that such energy release in the early Universe should lead to characteristic deviations of the CMB spectrum from the Planck one. The development of the technology of cryogenic detectors of submillimeter and millimeter wavelength radiation has made it possible to measure the CMB spectral distortions at 10-8 of its total intensity (PIXIE). This has sharply increased the interest of theoretical cosmologists in the problem of energy release when smallscale sound waves are damped. We have derived a relativistic formula for the energy of a standing sound wave in a photon-baryon-electron plasma from simple hydrodynamic and thermodynamic relations. This formula is applicable for an arbitrary relation between the

  4. Measurements of sound radiation from cavities at subsonic speeds

    NASA Technical Reports Server (NTRS)

    Yu, Y. H.

    1976-01-01

    To better understand the physical mechanisms responsible for noise generated by flow over cavities with a range of dimensions common to commercial aircraft, a series of measurements of farfield sound pressure level, fluctuating surface pressure, and drag coefficient was made. An examination of the resultant data shows that two theoretical models are needed for this range of dimensions. The shallow cavity (width-to-depth ratio larger than 1.0) can be approximated by a dipole located near the downstream edge of the cavity and the deep cavity (ratio less than 1.0) can be approximated by a dipole located near the downstream edge with the superimposed effects of the upstream edge of the cavity.

  5. The radiation of a sound pulse from a jet nozzle

    NASA Astrophysics Data System (ADS)

    Bloy, A. W.

    1985-03-01

    A high-amplitude sound pulse was produced in a jet pipe by injecting helium over a period of a few milliseconds. The test configuration allowed the incident and reflected waves to be isolated so that the pressure measurements in the jet pipe and in the far field could be directly compared. These measurements were made for jet Mach numbers in the range 0 less than or equal to M less than or equal to 0.7 and are compared with the low-frequency solutions of Cargill (1982). There is good agreement between experiment and theory, particularly at the lower jet Mach numbers, although the pulse amplitudes used in the experiments produce significant nonlinear effects when there is no mean flow.

  6. Time domain BEM for sound radiation of tires

    NASA Astrophysics Data System (ADS)

    Banz, Lothar; Gimperlein, Heiko; Nezhi, Zouhair; Stephan, Ernst P.

    2016-07-01

    This work investigates a time domain boundary element method for the acoustic wave equation in an exterior domain in the half-space mathbb {R}^3_+. The Neumann problem is formulated as a boundary integral equation of the second kind, and the convergence and stability of conforming Galerkin approximations is studied in the complex geometry of a car or truck tire above a street. After a validation experiment, numerical results are presented in time or frequency domain for realistic benchmarks in traffic noise: the sound emission of vibrating tires, noise amplification in the horn-like geometry between the tire and the road, as well as the Doppler effect of a moving tire. The results are compared with calculations in frequency domain.

  7. Active control of sound transmission/radiation from elastic plates by vibration inputs. II - Experiments

    NASA Technical Reports Server (NTRS)

    Metcalf, V. L.; Fuller, C. R.; Silcox, R. J.; Brown, D. E.

    1992-01-01

    Actively controlled harmonic force inputs were applied experimentally to reduce the sound transmitted through an elastic circular plate. The control implementation used a time domain least mean square adaptive algorithm with two error sensors. The control forces were applied directly to the plate by point force vibration inputs, while the error information and performance were measured in the radiated acoustic field by microphones. Test cases were also performed in which the error sensors were accelerometers mounted on the plate. When accelerometers were used as error sensors, the controller performance was degraded; leading to the conclusion that minimizing plate motion does not necessarily lead to an associated decrease in radiated sound levels. In contrast, the results show excellent attenuation of the transmitted sound field when microphone error sensors were used. This result was consistent over a range of frequencies. In addition, the experimental results are compared to previously derived analytical results and the effect of using a point or global minimization scheme is discussed.

  8. Active control of sound transmission/radiation from elastic plates by vibration inputs. II - Experiments

    NASA Technical Reports Server (NTRS)

    Metcalf, V. L.; Fuller, C. R.; Silcox, R. J.; Brown, D. E.

    1992-01-01

    Actively controlled harmonic force inputs were applied experimentally to reduce the sound transmitted through an elastic circular plate. The control implementation used a time domain least mean square adaptive algorithm with two error sensors. The control forces were applied directly to the plate by point force vibration inputs, while the error information and performance were measured in the radiated acoustic field by microphones. Test cases were also performed in which the error sensors were accelerometers mounted on the plate. When accelerometers were used as error sensors, the controller performance was degraded; leading to the conclusion that minimizing plate motion does not necessarily lead to an associated decrease in radiated sound levels. In contrast, the results show excellent attenuation of the transmitted sound field when microphone error sensors were used. This result was consistent over a range of frequencies. In addition, the experimental results are compared to previously derived analytical results and the effect of using a point or global minimization scheme is discussed.

  9. Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation

    SciTech Connect

    Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.

    1993-01-01

    Changes in the composition of trace gases in the earth`s atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth`s climate that may be caused by radiatively active gases introduced into the earth`s atmosphere by man`s activities. Radiatively active trace gases produce temperature changes in the earth`s atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.

  10. Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation

    SciTech Connect

    Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.

    1993-01-01

    Changes in the composition of trace gases in the earth's atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth's climate that may be caused by radiatively active gases introduced into the earth's atmosphere by man's activities. Radiatively active trace gases produce temperature changes in the earth's atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.

  11. Identification of impact force acting on composite laminated plates using the radiated sound measured with microphones

    NASA Astrophysics Data System (ADS)

    Atobe, Satoshi; Nonami, Shunsuke; Hu, Ning; Fukunaga, Hisao

    2017-09-01

    Foreign object impact events are serious threats to composite laminates because impact damage leads to significant degradation of the mechanical properties of the structure. Identification of the location and force history of the impact that was applied to the structure can provide useful information for assessing the structural integrity. This study proposes a method for identifying impact forces acting on CFRP (carbon fiber reinforced plastic) laminated plates on the basis of the sound radiated from the impacted structure. Identification of the impact location and force history is performed using the sound pressure measured with microphones. To devise a method for identifying the impact location from the difference in the arrival times of the sound wave detected with the microphones, the propagation path of the sound wave from the impacted point to the sensor is examined. For the identification of the force history, an experimentally constructed transfer matrix is employed to relate the force history to the corresponding sound pressure. To verify the validity of the proposed method, impact tests are conducted by using a CFRP cross-ply laminate as the specimen, and an impulse hammer as the impactor. The experimental results confirm the validity of the present method for identifying the impact location from the arrival time of the sound wave detected with the microphones. Moreover, the results of force history identification show the feasibility of identifying the force history accurately from the measured sound pressure using the experimental transfer matrix.

  12. Measurement and analysis of radiated sound from a low speed fan with a large tip gap.

    PubMed

    Bilka, M J; Anthoine, J; Schram, C

    2014-05-01

    The wake flow field and radiated sound from a low speed axial fan is studied experimentally. The fan geometry uses controlled diffusion blades and is designed with a low aspect ratio (0.9). The fan is installed with a large tip gap, approximately 10% of the blade span. The radiated sound field is analyzed using a known trailing edge noise formulation. First, the model is compared to an experiment of a single airfoil in a wind tunnel to assess the predictive capabilities. Second, measurements of the fan are made at two different blade loading conditions. Hot wire measurements are made in the near wake of the fan to assess the extent of the tip leakage flow for each condition. The radiated sound fields are compared with the trailing edge noise theory. Use is made of the wake measurements as an input to a surface pressure model. When the fan is operated with the optimal blade loading, the influence of the tip leakage flow is found to be of secondary acoustic impact. When the fan is operated at a high loading condition for the blades, a more significant leakage flow develops and is found to be responsible for the dominant radiated sound.

  13. Active Control of Turbulent Boundary Layer Induced Sound Radiation from Multiple Aircraft Panels

    NASA Technical Reports Server (NTRS)

    Gibbs, Gary P.; Cabell, Randolph H.

    2002-01-01

    The objective of this work is to experimentally investigate active structural acoustic control of turbulent boundary layer (TBL) induced sound radiation from multiple panels on an aircraft sidewall. One possible approach for controlling sound radiation from multiple panels is a multi-input/multi-output scheme which considers dynamic coupling between the panels. Unfortunately, this is difficult for more than a few panels, and is impractical for a typical aircraft which contains several hundred such panels. An alternative is to implement a large number of independent control systems. Results from the current work demonstrate the feasibility of reducing broadband radiation from multiple panels utilizing a single-input/single-output (SISO) controller per bay, and is the first known demonstration of active control of TBL induced sound radiation on more than two bays simultaneously. The paper compares sound reduction for fully coupled control of six panels versus independent control on each panel. An online adaptive control scheme for independent control is also demonstrated. This scheme will adjust for slow time varying dynamic systems such as fuselage response changes due to aircraft pressurization, etc.

  14. RADIATION CHARACTERISTICS OF A GENERALIZED PHASED ARRAY

    NASA Technical Reports Server (NTRS)

    Acosta, R. J.

    1994-01-01

    The phased array has become a key component in the design of advanced antenna systems. This computer program was developed to examine the radiation characteristics of a generalized phased array antenna. Using a very efficient numerical technique, this program calculates the array's radiated power and its directivity. The results can be used to determine the radiation pattern of a generalized phased array at near- or far-field observation points. This program is a key research tool at the NASA Lewis Research Center for analyzing advanced space communication antenna systems. Results from this program compare favorably with experimental Lewis results for arrays of 2x2 and 3x3 elements. Given the array geometry and element characteristics, generalized phased array attributes can be broken into two areas: 1) the power radiated and its directivity at any given point, and 2) the co- and cross-polarization field components. This program allows arbitrarily located source elements with an analytically described cosine pattern. The formulation is based on a Romberg integration scheme and takes into account arbitrary element polarization, E and H plane element patterns, and mutual coupling. The input consists of the array geometry; phase, amplitude, linear and circular polarization of each source element; and the cosine functions of the element pattern. The output is a series of observation angles with their associated field magnitude and polarizations. Total radiated power and peak directivity are also calculated. This program is written in FORTRAN IV for batch execution and has been implemented on an IBM 370 computer operating under TSS with a central memory requirement of approximately 22K of 8 bit bytes. The IBM Scientific Subroutine Package (SSP) is required to run the program. This program was developed in 1986.

  15. Avoiding antiperspirants during breast radiation therapy: Myth or sound advice?

    PubMed

    Baumann, Brian C; Zeng, Chuan; Freedman, Gary M; Verginadis, Ioannis I; MacArthur, Kelly M; Lin, Lilie L; Vachani, Carolyn; Koumenis, Constantinos; Solberg, Timothy D; Metz, James M

    2017-08-01

    Breast cancer patients are typically advised to avoid antiperspirants for fear of increasing radiation dermatitis in the axilla. We hypothesized that antiperspirants would have minimal effect on skin dose. We found no difference in surface dose±antiperspirants using 6MV photons at gantry angles of 0°/30°/60°/90° regardless of aluminum concentration. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. LQR-based optimization of multiple tuned resonators for plate sound radiation reduction

    NASA Astrophysics Data System (ADS)

    Michielsen, J.; Arteaga, I. Lopez; Nijmeijer, H.

    2016-02-01

    A linear quadratic regulator based optimization problem is formulated in order to minimize the broad-band low-frequency domain vibration and acoustic response of a baffled simply supported plate by means of multiple optimally tuned mass-spring-damper systems. To this end, we propose a robust method to obtain a (stable) state-space model describing the far-field radiated sound power, also known as the radiation filter. The Kirchhoff plate equation, which describes the plate vibrations, is discretized based on the Rayleigh-Ritz method. The resulting state-space models of the plate and the mass-springdamper systems are coupled to the radiation filter. Finally, the optimal spring stiffness and damping values of each mass-spring-damper system are successfully obtained by minimizing the kinetic energy or the far-field radiated sound power of the plate for low computational cost. In general, the results indicate that tuned mass-spring-damper systems have great potential to reduce the broadband low frequency vibration and acoustic response of vibro-acoustic systems. From the results, it can be concluded that there are fundamental differences between the optimal TMD systems if one minimizes the kinetic energy or the far-field radiated sound power.

  17. Airborne Sound Transmission Loss Characteristics of Wood-Frame Construction.

    DTIC Science & Technology

    1985-03-01

    frame" wood, constructionacoustic sound with Measurements ............................. 26 transmission loss; .theory: walls: floor-ceiling.- W ...wood- D I st ribut Ion/ frame construction. Gen. Tech. Rep. FPL-43. Madison, W : U.S. Department .. . . ... . of Agriculture, Forest Service, Forest...Insulation Class (tIC) ratings refer to impact noise insulation of ’. floor-ceiling assemblies and are not considered in this report. 2 %I , W - % % X X Xe

  18. Sound

    NASA Astrophysics Data System (ADS)

    Capstick, J. W.

    2013-01-01

    1. The nature of sound; 2. Elasticity and vibrations; 3. Transverse waves; 4. Longitudinal waves; 5. Velocity of longitudinal waves; 6. Reflection and refraction. Doppler's principle; 7. Interference. Beats. Combination tones; 8. Resonance and forced vibrations; 9. Quality of musical notes; 10. Organ pipes; 11. Rods. Plates. Bells; 12. Acoustical measurements; 13. The phonograph, microphone and telephone; 14. Consonance; 15. Definition of intervals. Scales. Temperament; 16. Musical instruments; 17. Application of acoustical principles to military purposes; Questions; Answers to questions; Index.

  19. Prediction of sound radiation from different practical jet engine inlets

    NASA Technical Reports Server (NTRS)

    Zinn, B. T.; Meyer, W. L.

    1981-01-01

    Computer codes, capable of producing accurate results for nondimensional wave numbers (based on duct radius) of up to 20, were developed and used to generate results for various other inlet configurations. Both reflection coefficients and radiation patterns were calculated by the integral solution procedure for the following five inlet configurations: the NASA Langley Bellmouth, the NASA Lewis JT-15D-1 ground test nacelle, and three hyperbolic inlets of 50, 70, and 90 degrees. Results obtained are compared with results from other experimental and theoretical studies.

  20. Characteristics of Dry Chin-Tuck Swallowing Vibrations and Sounds

    PubMed Central

    Dudik, Joshua M; Jestrović, Iva; Luan, Bo; Coyle, James L.; Sejdić, Ervin

    2015-01-01

    Objective The effects of the chin-tuck maneuver, a technique commonly employed to compensate for dysphagia, on cervical auscultation are not fully understood. Characterizing a technique that is known to affect swallowing function is an important step on the way to developing a new instrumentation-based swallowing screening tool. Methods In this study, we recorded data from 55 adult participants who each completed five saliva swallows in a chin-tuck position. The resulting data was processed using previously designed filtering and segmentation algorithms. We then calculated 9 time, frequency, and time-frequency domain features for each independent signal. Results We found that multiple frequency and time domain features varied significantly between male and female subjects as well as between swallowing sounds and vibrations. However, our analysis showed that participant age did not play a significant role on the values of the extracted features. Finally, we found that various frequency features corresponding to swallowing vibrations did demonstrate statistically significant variation between the neutral and chin-tuck positions but sounds showed no changes between these two positions. Conclusion The chin-tuck maneuver affects many facets of swallowing vibrations and sounds and its effects can be monitored via cervical auscultation. Significance These results suggest that a subject’s swallowing technique does need to be accounted for when monitoring their performance with cervical auscultation based instrumentation. PMID:25974926

  1. Control of broadband radiated sound with adaptive structures

    NASA Astrophysics Data System (ADS)

    Smith, J. P.; Fuller, Chris R.; Burdisso, Ricardo A.

    1993-09-01

    Active structural acoustic control using adaptive structures has been demonstrated for harmonic disturbances. This paper presents an extension of this work to the attenuation of acoustic radiation from structures subject to broadband disturbances. An adaptive, multi-input multi-output (MIMO), feedforward broadband acoustic control system has been developed based on the least mean squares (LMS) algorithm. The compensators are adaptive finite impulse response (FIR) filters. The control inputs are implemented with piezoelectric ceramic actuators. Both far-field microphones and polyvinylidene fluoride (PVDF) structural sensors designed to observe the efficient acoustic radiating modes are used as error sensors. The disturbance is band-limited zero mean white noise and is implemented with a point force shaker. In the control of harmonically excited systems, satisfactory attenuation is possible with a single-input single-output (SISO) controller. In contrast, for systems excited with broadband disturbances, a MIMO controller is necessary for significant acoustic attenuation. Experimental results for the control of a simply supported plate are presented.

  2. Control of sound radiation with active/adaptive structures

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.; Rogers, C. A.; Robertshaw, H. H.

    1992-01-01

    Recent research is discussed in the area of active structural acoustic control with active/adaptive structures. Progress in the areas of structural acoustics, actuators, sensors, and control approaches is presented. Considerable effort has been given to the interaction of these areas with each other due to the coupled nature of the problem. A discussion is presented on actuators bonded to or embedded in the structure itself. The actuators discussed are piezoceramic actuators and shape memory alloy actuators. The sensors discussed are optical fiber sensors, Nitinol fiber sensors, piezoceramics, and polyvinylidene fluoride sensors. The active control techniques considered are state feedback control techniques and least mean square adaptive algorithms. Results presented show that significant progress has been made towards controlling structurally radiated noise by active/adaptive means applied directly to the structure.

  3. Control of sound radiation with active/adaptive structures

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.; Rogers, C. A.; Robertshaw, H. H.

    1992-01-01

    Recent research is discussed in the area of active structural acoustic control with active/adaptive structures. Progress in the areas of structural acoustics, actuators, sensors, and control approaches is presented. Considerable effort has been given to the interaction of these areas with each other due to the coupled nature of the problem. A discussion is presented on actuators bonded to or embedded in the structure itself. The actuators discussed are piezoceramic actuators and shape memory alloy actuators. The sensors discussed are optical fiber sensors, Nitinol fiber sensors, piezoceramics, and polyvinylidene fluoride sensors. The active control techniques considered are state feedback control techniques and least mean square adaptive algorithms. Results presented show that significant progress has been made towards controlling structurally radiated noise by active/adaptive means applied directly to the structure.

  4. Sound Radiated from a Cylindrical Duct with Keller's Geometrical Theory

    NASA Astrophysics Data System (ADS)

    HOCTER, S. T.

    2000-04-01

    An exact solution to the problem of radiation from a cylindrical duct has been available using the Wiener-Hopf technique for many years, and a number of approximate methods can also be considered. When parameter spaces involving high frequency are required, it is possible to use ray-theory-based techniques to solve the problem. Keller proposed such a method, introducing a geometrical theory of diffraction (GTD) which extended the concept of geometrical optics to account for diffracted rays. When a ray propagates inside the duct, it will reflect off the duct rim creating a Keller cone of singly diffracted rays, allowing formulae to be obtained for the singly diffracted field using Keller's GTD. Expressions for the singly diffracted field are presented, and then compared with the exact solution for a range of parameters. The choice of parameters is governed by a set of mode angles which are used in describing geometrically how a ray propagates through the duct and out into free space.

  5. Statistical characteristics of ionospheric variability using oblique sounding data

    NASA Astrophysics Data System (ADS)

    Kurkin, Vladimir; Polekh, Nelya; Ivanova, Vera; Dumbrava, Zinaida; Podelsky, Igor

    Using data from oblique sounding obtained over two paths Magadan-Irkutsk and Khabarovsk-Irkutsk in the 2006-2011 the statistical parameters of ionospheric variability are studied during equinox and the winter solstice. It was shown that the probability of maximum observed frequency registration with average standard deviations from the median in the range 5-10% in winter is 0.43, in spring and autumn - 0.64 over Magadan-Irkutsk path. In winter during daytime standard deviation does not exceed 10%, and at night it reaches 20% or more. During the equinox the daytime standard deviation increases to 12%, and at night it does not exceed 16%. This may be due to changes in lighting conditions at the midpoint of the path (58.2(°) N, 124.2(°) E). As far Khabarovsk-Irkutsk path standard deviations from their median less than the ones obtained for Magadan-Irkutsk path. The estimations are consistent with previously obtained results deduced from the vertical sounding data. The study was done under RF President Grant of Public Support for RF Leading Scientific Schools (NSh-2942.2014.5) and RFBR Grant No 14-05-00259.

  6. Research on characteristics of radiated noise of large cargo ship in shallow water

    NASA Astrophysics Data System (ADS)

    Liu, Yongdong; Zhang, Liang

    2017-01-01

    With the rapid development of the shipping industry, the number of the world's ship is gradually increasing. The characteristics of the radiated noise of the ship are also of concern. Since the noise source characteristics of multichannel interference, the surface wave and the sea temperature microstructure and other reasons, the sound signal received in the time-frequency domain has varying characteristics. The signal of the radiated noise of the large cargo ship JOCHOH from horizontal hydrophone array in some shallow water of China is processed and analyzed in the summer of 2015, and the results show that a large cargo ship JOCHOH has a number of noise sources in the direction of the ship's bow and stern lines, such as host, auxiliary and propellers. The radiating sound waves generated by these sources do not meet the spherical wave law at lower frequency in the ocean, and its radiated noise has inherent spatial distribution, the variation characteristics of the radiated noise the large cargo ship in time and frequency domain are given. The research method and results are of particular importance.

  7. Neural Modulation Tuning Characteristics Scale to Efficiently Encode Natural Sound Statistics

    PubMed Central

    Rodríguez, Francisco A.; Chen, Chen; Read, Heather L.; Escabí, Monty A.

    2012-01-01

    The efficient-coding hypothesis asserts that neural and perceptual sensitivity evolved to faithfully represent biologically relevant sensory signals. Here we characterized the spectrotemporal modulation statistics of several natural sound ensembles and examined how neurons encode these statistics in the central nucleus of the inferior colliculus (CNIC) of cats. We report that modulation-tuning in the CNIC is matched to equalize the modulation power of natural sounds. Specifically, natural sounds exhibited a tradeoff between spectral and temporal modulations, which manifests as 1/f modulation power spectrum (MPS). Neural tuning was highly overlapped with the natural sound MPS and neurons approximated proportional resolution filters where modulation bandwidths scaled with characteristic modulation frequencies, a behavior previously described in human psychoacoustics. We demonstrate that this neural scaling opposes the 1/f scaling of natural sounds and enhances the natural sound representation by equalizing their MPS. Modulation tuning in the CNIC may thus have evolved to represent natural sound modulations in a manner consistent with efficiency principles and the resulting characteristics likely underlie perceptual resolution. PMID:21106835

  8. Effects of forward velocity on sound radiation from convecting monopole and dipole sources in jet flow. [subsonic aircraft model

    NASA Technical Reports Server (NTRS)

    Dash, R.

    1979-01-01

    A theoretical model is presented of the effects of forward velocity of an aircraft at arbitrary subsonic speed on sound radiated from convecting monopole and dipole sources embedded in the jet flow. It is found that with increasing forward velocity there is a steadily increasing amplification (over the static case) of the sound radiated into the forward arc and a large reduction of the sound which is radiated into the rearward arc. The same trend is also shown to result when there is a reduction in the exhaust velocity, with, however, a further rise in amplification in the forward quadrant and a drop in attenuation in the aft quadrant.

  9. Active control of sound radiated by a submarine in bending vibration

    NASA Astrophysics Data System (ADS)

    Caresta, Mauro

    2011-02-01

    This paper theoretically investigates the use of inertial actuators to reduce the sound radiated by a submarine hull in bending vibration under harmonic excitation from the propeller. The radial forces from the propeller are tonal at the blade passing frequency and are transmitted to the hull through the stern end cone. The hull is modelled as a fluid loaded cylindrical shell with ring stiffeners and two equally spaced bulkheads. The cylinder is closed by end-plates and conical end caps. The actuators are arranged in circumferential arrays and attached to the prow end cone. Both Active Vibration Control and Active Structural Acoustic Control are analysed. The inertial actuators can provide control forces with a magnitude large enough to reduce the sound radiated by the vibrations of the hull in some frequency ranges.

  10. Acoustic characteristics improvement of PZT ceramic sounder for sound source of artificial larynx

    NASA Astrophysics Data System (ADS)

    Ooe, Katsutoshi; Kanetake, Ryota; Tanaka, Akimitsu

    2006-01-01

    For utterance handicapped persons, various speech production substitutes which aim to reconstruct speech functions have been developed and used practically. But conventional speech production substitutes have various problems, therefore perfect speech production substitutes expect to be developed. We focused to PZT ceramics sounder as a sound source of an electric drive artificial larynx. We first produced the artificial larynx which uses PZT ceramic sounder, and then evaluated its performance. The voice of the power spectrum of the artificial larynx user is similar to that of the speaking person's voice. The vocalized sound of the artificial larynx user shows good characteristics at formant frequency which is important for vowel discrimination. The feature of our artificial larynx is its own structure, and the typical structure means that the sound source and the implant are separated. This structure gives high biocompatibility in our artificial larynx. In this report, the acoustic characteristics improvement of the sound source is described. The characteristics improvement is achieved by optimization of the electric control and its structure. Until now, we have researched about the enzyme immobilization method onto gold or platinum substrate using biomoleculer immobilization technology. By biomoleculer immobilization onto the sound source surface, it is thought that the biocompatibility of it improves. In the future, we aim at the realization of implantable sound source which applied biomoleculer immobilization technology.

  11. Forced response sound radiation from acoustically or mechanically excited small plates

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    1992-01-01

    Sound radiation from an acoustically excited, clamped aluminum plate is measured and expressed in terms of noise reduction to take into account the incident acoustic excitation field. Its mode shapes and modal frequencies are measured and show good agreement with the predictions from a finite element MSC/NASTRAN model. Noise reduction is measured at 15 points behind the plate and demonstrate good agreement with predictions employing the SYSNOISE numerical analysis system for acoustic-structure interaction.

  12. A statistical theory of sound radiation from a two-dimensional lined duct

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.; Watson, W. R.

    1979-01-01

    A statistical theory coupled with a finite element theory is employed for investigation of sound radiation from a two-dimensional lined duct. The analysis does not utilize duct modes, and can be applied to a non-uniform duct with variable wall liner properties. Numerical results are presented for various shapes of the incident wave. The results are in good agreement with the Wiener-Hopf calculation for cases where the latter can be made.

  13. Forced response sound radiation from acoustically or mechanically excited small plates

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    1992-01-01

    Sound radiation from an acoustically excited, clamped aluminum plate is measured and expressed in terms of noise reduction to take into account the incident acoustic excitation field. Its mode shapes and modal frequencies are measured and show good agreement with the predictions from a finite element MSC/NASTRAN model. Noise reduction is measured at 15 points behind the plate and demonstrate good agreement with predictions employing the SYSNOISE numerical analysis system for acoustic-structure interaction.

  14. Rigorous solutions for sound radiation from circular ducts with hyperbolic horns or infinite plane baffle

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.

    1980-01-01

    A rigorous treatment is presented of sound radiation from circular ducts with either a hyperbolic horn or an infinite plane baffle. In the analysis hyperboloidal wave functions are used, which are defined here, for the first time, as a class of eigensolutions of the wave equation for oblate spheroidal co-ordinates. The numerical results include the complex conversion (or reflection) coefficients and the radiation directivity for various incident wave modes, spinning modes as well as axisymmetric modes. The solutions are valid for the whole frequency range including frequencies above and below the cut-off frequencies of the duct modes involved.

  15. Radiation calculations on the base of atmospheric models from lidar sounding

    NASA Astrophysics Data System (ADS)

    Melnikova, Irina; Samulenkov, Dmitry; Sapunov, Maxim; Vasilyev, Alexander; Kuznetsov, Anatoly; Frolkis, Victor

    2017-02-01

    The results of lidar sounding in the Resource Center "Observatory of Environmental Safety" of the St. Petersburg University, Research Park, have been obtained in the center of St. Petersburg. Observations are accomplished during 12 hours on 5 March 2015, from 11 am till 11 pm. Four time periods are considered. Results of AERONET observations and retrieval at 4 stations around St. Petersburg region are considered in addition. Optical models of the atmosphere in day and night time are constructed from the lidar and AERONET observations and used for radiation calculation. The radiative divergence, transmitted and reflected irradiance and heating rate are calculated.

  16. Outgoing long-wave radiation computed from HIRS2/MSU soundings

    NASA Astrophysics Data System (ADS)

    Wu, Man-Li C.; Susskind, J.

    1990-05-01

    Fields of outgoing long-wave radiation (OLR) have been computed using geophysical parameters retrieved from analysis of HIRS2/MSU sounding data as input to a modified version of the Wu-Kaplan radiation code used in the Goddard Laboratory for Atmospheres fourth-order general circulation model. Monthly mean results for 1979 agree with monthly mean OLR fields measured by the Nimbus 7 earth radiation budget (ERB) broadband narrow field of view instrument within standard deviations of 6.3 W/sq m but with a global mean bias of 8.0 W/sq m. Results are shown for July 1979. The areas of disagreement between high-resolution infrared radiation sounder OLR and ERB OLR are small but spatially coherent with patterns which may be related to sampling differences. The difference patterns are much less extensive than those between OLR derived from advanced very high resolution radiometer 11-micron observations and ERB OLR.

  17. FEA-based methods for optimising structure-borne sound radiation

    NASA Astrophysics Data System (ADS)

    Klaerner, Matthias; Wuehrl, Mario; Kroll, Lothar; Marburg, Steffen

    2017-05-01

    Lightweight components are typically stiff and thin-walled and thus tend to have significant sound radiation. Moreover using fibre reinforced plastics offers a wide range of adjusting the material properties such as stiffness and even damping by manipulating layup, fibre and matrix material or fibre volume content. With numerous free parameters within the composites, there is a need of efficient simulation methods in design and optimisation. In contrast, acoustic measures require complex multi-physical models with fluid-structure interaction and are commonly not implemented in standard FEA software. Different approaches based on the surface velocity of the component fill the gap. Namely, there is the equivalent radiated power, assuming a unit radiation efficiency all over the surface and neglecting local effects as an upper bound of structure-borne noise. In addition, the volume velocity provides good results for the lower frequency range with the frequency-dependent radiation efficiency as well as the lumped parameter model predictions being exact for dipole modes, too. Last, the kinetic energy is implicitly given in steady state FEA solutions and thus provides information about the dynamic behaviour without any additional efforts. Possibilities and limits of estimating the radiated sound power by these methods will be shown by numerical studies on a composite component. Moreover, the total power as an integral over frequency is used to demonstrate the feasibility and accuracy of such optimisation objectives.

  18. Underwater sound radiation from an elastically coated plate with a discontinuity introduced by a signal conditioning plate.

    PubMed

    Zhang, Yanni; Pan, Jie

    2013-01-01

    Underwater structural sound radiation and reflection can be reduced by adding an elastic coating to a structure. To increase the signal-to-noise ratio of a detecting hydrophone placed in front of the coating, a signal conditioning plate (SCP) of finite size placed between the coating and the hydrophone is proposed to increase the local reflection of incoming sound. This paper studies the effects of a SCP as a distributed discontinuity on the general properties of the sound radiation of a coated plate. The discontinuity introduced by the SCP changes the vibration and radiated sound power of the coated plate by scattering and reflecting structural waves in the coating. The trapped modal response of the structural waves is also observed and found to be responsible for the increase of sound and vibration of the plate at the corresponding resonance frequencies.

  19. A theoretical approach to sound propagation and radiation for ducts with suppressors

    NASA Technical Reports Server (NTRS)

    Rice, E. J.; Sawdy, D. T.

    1981-01-01

    The several phenomena involved in theoretical prediction of the far-field sound radiation attenuation from an acoustically lined duct have been studied. These include absorption by the suppressor, termination reflection, and far-field radiation. Extensive parameteric studies have shown that the suppressor absorption performance can be correlated with mode cut-off ratio or angle of propagation. The other phenomena can be shown to depend explicitly upon mode cut-off ratio. A complete system can thus be generated which can be used to evaluate aircraft sound suppressors and which can be related to the sound source through the cut-off ratio-acoustic power distribution. Although the method is most fully developed for inlet suppressors, several aft radiated noise phenomena will also be discussed. This paper summarized this simplified suppressor design and evaluation method, presents the recent improvements in the technique and discusses areas where further refinement is necessary. Noise suppressor data from engine experiments are compared with the theoretical calculations.

  20. Observable Characteristics of Solar Radiation (revised Tables)

    NASA Astrophysics Data System (ADS)

    Makarova, E. A.; Kharitonov, A. V.; Kaznachevskaja, T. V.; Roshchina, E. M.; Sarychev, A. P.

    The following characteristics of solar radiation in the spectral range from X-rays at 0.1 nm to the millimeter radio waves are given: spectral flux distributions in energy units at the 1 AU distance from the Sun, spectral radiance of the center of the solar disk, mean spectral radiance of the solar disk, limb darkening and blanketing coefficients. The most recent data have been taken into account. In comparison with our monograph (Makarova et al. 1991), the data are given with smaller wavelength steps and averaging bins. Since the fluxes in the far ultraviolet and X-ray ranges depend on the activity level, in the wavelengths <120 nm we present the data for the minimum and maximum of solar activity.

  1. Vibration characteristics of bone conducted sound in vitro.

    PubMed

    Stenfelt, S; Håkansson, B; Tjellström, A

    2000-01-01

    A dry skull added with damping material was used to investigate the vibratory pattern of bone conducted sound. Three orthogonal vibration responses of the cochleae were measured, by means of miniature accelerometers, in the frequency range 0.1-10 kHz. The exciter was attached to the temporal, parietal, and frontal bones, one at the time. In the transmission response to the ipsilateral cochlea, a profound low frequency antiresonance (attenuation) was found, verified psycho-acoustically, and shown to yield a distinct lateralization effect. It was also shown that, for the ipsilateral side, the direction of excitation coincides with that of maximum response. At the contralateral cochlea, no such dominating response direction was found for frequencies above the first skull resonance. An overall higher response level was achieved, for the total energy transmission in general and specifically for the direction of excitation, at the ipsilateral cochlea when the transducer was attached to the excitation point closest to the cochlea. The transranial attenuation was found to be frequency dependent, with values from -5 to 10 dB for the energy transmission and -30 to 40 dB for measurements in a single direction, with a tendency toward higher attenuation at the higher frequencies.

  2. Measurement of Acoustic Intensity Distribution and Radiation Power of Flat-Plate Phased-Array Sound Source

    NASA Astrophysics Data System (ADS)

    Yokoyama, Tomoki; Takahashi, Kumiko; Seki, Daizaburou; Hasegawa, Akio

    2002-05-01

    The acoustic intensity distribution and radiation power of a flat-plate phased-array sound source consisting of Tonpilz-type transducers were measured. This study shows that the active acoustic intensity is skewed in the direction of wave propagation. In addition, it clarifies that if the measurement is carried out in the immediate vicinity of the sound source, the reactive acoustic intensity distribution is effective for identifying the positions of the individual sound source elements. Experimental values of active radiation power agree well with theoretical values. Conversely, experimental values of reactive radiation power do not agree with theoretical values; it is clear that they fluctuate significantly with distance from the radiating surface. The reason for this is explained in the case of a point sound source.

  3. An analytical model for the underwater sound pressure waveforms radiated when an offshore pile is driven.

    PubMed

    Hall, Marshall V

    2015-08-01

    An analytical model has been developed for the pile vibration and consequent sound pressure and particle velocity radiated underwater when an offshore cylindrical pile is struck by a drop hammer. The model, which is based on the coupled equations of motion for axial and radial vibration of a thin cylindrical shell, yields frequency-dependent phase velocity and attenuation of these vibrations. The amplitude of the pulse of axial and radial displacement that travels down a pile following an axial impact is described in terms of the hammer properties. Solutions are obtained for the radiated sound pressure and particle velocity, using Junger and Feit's Transform Formulation of the Pressure Field of Cylindrical Radiators [(Acoustical Society of America, New York, 1993), p. 216]. The model is applied to published data on radiated noise from offshore driving of a steel pile. The modeled pressure waveforms at 12-m horizontal range and at 9 hydrophone depths correlate significantly with the measured waveforms. The modeled pressures of the initial positive peaks (appropriately low-pass filtered) agree with data to within 1 dB. The initial negative peaks however exceed the data by up to 7 dB, and as hydrophone depth increases, the model negative peaks have a maximum at 7 m, whereas the data have a maximum at 9 m.

  4. Ship classification using nonlinear features of radiated sound: an approach based on empirical mode decomposition.

    PubMed

    Bao, Fei; Li, Chen; Wang, Xinlong; Wang, Qingfu; Du, Shuanping

    2010-07-01

    Classification for ship-radiated underwater sound is one of the most important and challenging subjects in underwater acoustical signal processing. An approach to ship classification is proposed in this work based on analysis of ship-radiated acoustical noise in subspaces of intrinsic mode functions attained via the ensemble empirical mode decomposition. It is shown that detection and acquisition of stable and reliable nonlinear features become practically feasible by nonlinear analysis of the time series of individual decomposed components, each of which is simple enough and well represents an oscillatory mode of ship dynamics. Surrogate and nonlinear predictability analysis are conducted to probe and measure the nonlinearity and regularity. The results of both methods, which verify each other, substantiate that ship-radiated noises contain components with deterministic nonlinear features well serving for efficient classification of ships. The approach perhaps opens an alternative avenue in the direction toward object classification and identification. It may also import a new view of signals as complex as ship-radiated sound.

  5. Measurement of energetic radiation caused by thunderstorm activities by a sounding balloon and ground observation

    NASA Astrophysics Data System (ADS)

    Torii, T.

    2015-12-01

    Energetic radiation caused by thunderstorm activity is observed at various places, such as the ground, high mountain areas, and artificial satellites. In order to investigate the radiation source and its energy distribution, we measured energetic radiation by a sounding balloon, and the ground observation. On the measurement inside/above the thundercloud, we conducted a sounding observation using a radiosonde mounted two GM tubes (for gamma-rays, and for beta/gamma-rays), in addition to meteorological instruments. The balloon passed through a region of strong echoes in a thundercloud shown by radar image, at which time an increase in counting rate of the GM tube about 2 orders of magnitude occurred at the altitude from 5 km to 7.5 km. Furthermore, the counting rate of two GM tubes indicated the tendency different depending on movement of a balloon. This result suggests that the ratio for the gamma-rays (energetic photons) of the beta-rays (energetic electrons) varies according to the place in the thundercloud. Furthermore, we carried out a ground observation of the energetic gamma rays during winter thunderstorm at a coastal area facing the Sea of Japan. Two types of the energetic radiation have been observed at this time. We report the outline of these measurements and analysis in the session of the AGU meeting.

  6. On the Sound Field of a Rotating Propeller

    NASA Technical Reports Server (NTRS)

    Gutin, L.

    1948-01-01

    The sound field of a rotating propeller is teated theoretically on the basis of aerodynamic principles. For the lower harmonics, the directional characteristics and the radiated sound energy are determined and are in conformity with existing experimental results.

  7. Spherical harmonic analysis of the sound radiation from omnidirectional loudspeaker arrays

    NASA Astrophysics Data System (ADS)

    Pasqual, A. M.

    2014-09-01

    Omnidirectional sound sources are widely used in room acoustics. These devices are made up of loudspeakers mounted on a spherical or polyhedral cabinet, where the dodecahedral shape prevails. Although such electroacoustic sources have been made readily available to acousticians by many manufacturers, an in-depth investigation of their vibroacoustic behavior has not been provided yet. In order to fulfill this lack, this paper presents a theoretical study of the sound radiation from omnidirectional loudspeaker arrays, which is carried out by using a mathematical model based on the spherical harmonic analysis. Eight different loudspeaker arrangements on the sphere are considered: the well-known five Platonic solid layouts and three extremal system layouts. The latter possess useful properties for spherical loudspeaker arrays used as directivity controlled sound sources, so that these layouts are included here in order to investigate whether or not they could be of interest as omnidirectional sources as well. It is shown through a comparative analysis that the dodecahedral array leads to the lowest error in producing an omnidirectional sound field and to the highest acoustic power, which corroborates the prevalence of such a layout. In addition, if a source with less than 12 loudspeakers is required, it is shown that tetrahedra or hexahedra can be used alternatively, whereas the extremal system layouts are not interesting choices for omnidirectional loudspeaker arrays.

  8. Characterization of Sound Radiation by Unresolved Scales of Motion in Computational Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert; Zhou, Ye

    1999-01-01

    Evaluation of the sound sources in a high Reynolds number turbulent flow requires time-accurate resolution of an extremely large number of scales of motion. Direct numerical simulations will therefore remain infeasible for the forseeable future: although current large eddy simulation methods can resolve the largest scales of motion accurately the, they must leave some scales of motion unresolved. A priori studies show that acoustic power can be underestimated significantly if the contribution of these unresolved scales is simply neglected. In this paper, the problem of evaluating the sound radiation properties of the unresolved, subgrid-scale motions is approached in the spirit of the simplest subgrid stress models: the unresolved velocity field is treated as isotropic turbulence with statistical descriptors, evaluated from the resolved field. The theory of isotropic turbulence is applied to derive formulas for the total power and the power spectral density of the sound radiated by a filtered velocity field. These quantities are compared with the corresponding quantities for the unfiltered field for a range of filter widths and Reynolds numbers.

  9. Decentralized Control of Sound Radiation from an Aircraft-Style Panel Using Iterative Loop Recovery

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Cabell, Randolph H.; Fuller, Chris R.

    2008-01-01

    A decentralized LQG-based control strategy is designed to reduce low-frequency sound transmission through periodically stiffened panels. While modern control strategies have been used to reduce sound radiation from relatively simple structural acoustic systems, significant implementation issues have to be addressed before these control strategies can be extended to large systems such as the fuselage of an aircraft. For instance, centralized approaches typically require a high level of connectivity and are computationally intensive, while decentralized strategies face stability problems caused by the unmodeled interaction between neighboring control units. Since accurate uncertainty bounds are not known a priori, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is validated using real-time control experiments performed on a built-up aluminum test structure representative of the fuselage of an aircraft. Experiments demonstrate that the iterative approach is capable of achieving 12 dB peak reductions and a 3.6 dB integrated reduction in radiated sound power from the stiffened panel.

  10. Direct and inverse problems in radiation of sound from discrete random sources on two coaxial rings

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    1979-01-01

    An analytical model consisting of two ring sources of sound is developed to study the direct radiation in terms of correlation, coherence, and phase and also to aid in solving the inverse-radiation problem of determining the noise source in terms of farfield measurements. The rings consist of discrete sources which are either monopoles or quadrupoles with Gaussian autocorrelations. Only adjacent sources, both within and between the rings, are correlated. Results show that from the farfield information one can determine when the sources are compact or noncompact with respect to the acoustic wavelength and distinguish between the types of sources. In addition, from the inverse-radiation approach one can recover the center of mass, the location and separation distance of the ring, and the respective diameters.

  11. Sound radiation from an infinite elastic cylinder with dual-wave propagation-intensity distributions

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.

    1988-01-01

    The radiation of sound from an elastic cylindrical shell filled with fluid and supporting multiwave propagation is studied analytically. Combinations of supersonic and subsonic shell waves are considered. The radiated field is mapped by using acoustic intensity vectors evaluated at various locations. Both time averaged and instantaneous intensity are investigated. The acoustic intensity is seen to vary markedly with axial distance down the cylinder. The effect is shown to be associated with cross terms in the intensity relations, and its magnitude and location to depend upon the relative phase and amplitudes of individual waves. Subsonic shell waves are demonstrated to interact strongly with supersonic shell waves to cause a large modification in the radiated intensity distributions near the shell surface.

  12. Direct and inverse problems in radiation of sound from discrete random sources on two coaxial rings

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    1979-01-01

    An analytical model consisting of two ring sources of sound is developed to study the direct radiation in terms of correlation, coherence, and phase and also to aid in solving the inverse-radiation problem of determining the noise source in terms of farfield measurements. The rings consist of discrete sources which are either monopoles or quadrupoles with Gaussian autocorrelations. Only adjacent sources, both within and between the rings, are correlated. Results show that from the farfield information one can determine when the sources are compact or noncompact with respect to the acoustic wavelength and distinguish between the types of sources. In addition, from the inverse-radiation approach one can recover the center of mass, the location and separation distance of the ring, and the respective diameters.

  13. Radiation of Sound Waves Via Soliton Excitation of the Angarmonic Chain of Atoms in a Dislocation Core

    NASA Astrophysics Data System (ADS)

    Gestrin, S. G.; Shchukina, E. V.

    2016-07-01

    It is demonstrated that propagation of the soliton described by the Boussinesq equation along a linear defect of the crystal structure leads to radiation of sound waves (analog of the Vavilov-Cherenkov effect). Radiation that has a continuous spectrum diverges conically from the dislocation line, and the apex angle of the cone is determined by the ratio of the sound speed in the crystal to the soliton speed. With increasing soliton speed, the maximum of the spectral flux density of sound energy is displaced toward higher frequencies. An analytical expression for energy losses is derived.

  14. A statistical theory for sound radiation and reflection from a duct

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.

    1979-01-01

    A new analytical method is introduced for the study of the sound radiation and reflection from the open end of a duct. The sound is thought of as an aggregation of the quasiparticles-phonons. The motion of the latter is described in terms of the statistical distribution, which is derived from the classical wave theory. The results are in good agreement with the solutions obtained using the Wiener-Hopf technique when the latter is applicable, but the new method is simple and provides straightforward physical interpretation of the problem. Furthermore, it is applicable to a problem involving a duct in which modes are difficult to determine or cannot be defined at all, whereas the Wiener-Hopf technique is not.

  15. Some factors influencing radiation of sound from flow interaction with edges of finite surfaces

    NASA Technical Reports Server (NTRS)

    Hayden, R. E.; Fox, H. L.; Chanaud, R. C.

    1976-01-01

    Edges of surfaces which are exposed to unsteady flow cause both strictly acoustic effects and hydrodynamic effects, in the form of generation of new hydrodynamic sources in the immediate vicinity of the edge. An analytical model is presented which develops the explicit sound-generation role of the velocity and Mach number of the eddy convection past the edge, and the importance of relative scale lengths of the turbulence, as well as the relative intensity of pressure fluctuations. The Mach number (velocity) effects show that the important paramater is the convection Mach number of the eddies. The effects of turbulence scale lengths, isotropy, and spatial density (separation) are shown to be important in determining the level and spectrum of edge sound radiated for the edge dipole mechanism. Experimental data is presented which provides support for the dipole edge noise model in terms of Mach number (velocity) scaling, parametric dependence on flow field parameter, directivity, and edge diffraction effects.

  16. Simulations of cloud-radiation interaction with imposed largescale dynamics from the DYNAMO northern sounding array

    NASA Astrophysics Data System (ADS)

    Wang, S.; Sobel, A. H.; Fridlind, A. M.

    2014-12-01

    The recently accomplished CINDY/DYNAMO project observed three MJO events in the equatorial Indian Ocean from October to December 2011. Analysis of the moist static energy budget by Sobel et al. (2014) indicates that the moist static energy anomalies in these events grew and were sustained to a significant extent by radiative feedbacks. We present here a study of radiative fluxes and clouds in a set of cloud-resolving simulations of the same DYNAMO MJO events. The simulations are driven by the large scale forcing dataset from the DYNAMO northern sounding array, and carried out in doubly-periodic domains using the WRF model. Simulated cloud properties and radiative fluxes are compared to the observed reflectivity from the SPolka radar and observed radiative fluxes from the CERES and VISST datasets. To accommodate the uncertainty in cloud microphysics, we have tested a number of single-moment (SM) and double-moment (DM) microphysical schemes in the WRF model. We find that in general the SM schemes tend to underestimate radiative flux anomalies in the active phase of the MJOs, while the DM schemes perform better but can instead overestimate radiative fluxes. All the microphysics schemes tested exhibit bias in the shape of the histograms of radiative fluxes and radar reflectivity. Analysis of CRM-simulated radar reflectivity indicates that this microphysics-related radiative flux uncertainty is closely related to how much stratiform clouds the CRM can simulate. SM schemes underestimate stratiform clouds by a factor of 2, while DM schemes simulate much more stratiform cloud, closer to observation, but shows a peak in the histogram at 15-20 dBz that is absent in observations. The double-moment Morrison scheme appears to give the best results in TOA fluxes associated with the MJO convective anomalies despite biases in the histograms of cloud and radiative fluxes.

  17. Psychometric Characteristics of Single-Word Tests of Children's Speech Sound Production

    ERIC Educational Resources Information Center

    Flipsen, Peter, Jr.; Ogiela, Diane A.

    2015-01-01

    Purpose: Our understanding of test construction has improved since the now-classic review by McCauley and Swisher (1984) . The current review article examines the psychometric characteristics of current single-word tests of speech sound production in an attempt to determine whether our tests have improved since then. It also provides a resource…

  18. Psychometric Characteristics of Single-Word Tests of Children's Speech Sound Production

    ERIC Educational Resources Information Center

    Flipsen, Peter, Jr.; Ogiela, Diane A.

    2015-01-01

    Purpose: Our understanding of test construction has improved since the now-classic review by McCauley and Swisher (1984) . The current review article examines the psychometric characteristics of current single-word tests of speech sound production in an attempt to determine whether our tests have improved since then. It also provides a resource…

  19. Sound radiation of a railway rail in close proximity to the ground

    NASA Astrophysics Data System (ADS)

    Zhang, Xianying; Squicciarini, Giacomo; Thompson, David J.

    2016-02-01

    The sound radiation of a railway in close to proximity to a ground (both rigid and absorptive) is predicted by the boundary element method (BEM) in two dimensions (2D). Results are given in terms of the radiation ratio for both vertical and lateral motion of the rail, when the effects of the acoustic boundary conditions due to the sleepers and ballast are taken into account in the numerical models. Allowance is made for the effect of wave propagation along the rail by applying a correction in the 2D modelling. It is shown that the 2D correction is necessary at low frequency, for both vertical and lateral motion of an unsupported rail, especially in the vicinity of the corresponding critical frequency. However, this correction is not applicable for a supported rail; for vertical motion no correction is needed to the 2D result while for lateral motion the corresponding correction would depend on the pad stiffness. Finally, the corresponding numerical predictions of the sound radiation from a rail are verified by comparison with experimental results obtained using a 1/5 scale rail model in different configurations.

  20. Prediction of low frequency and impulsive sound radiation from horizontal axis wind turbines

    NASA Technical Reports Server (NTRS)

    Martinez, R.; Widnall, S. E.; Harris, W. L.

    1981-01-01

    Theoretical models to predict the radiation of low frequency and impulsive sound from horizontal axis wind turbines due to three sources: (1) steady blade loads; (2) unsteady blade loads due to operation in a ground shear; (3) unsteady loads felt by the blades as they cross the tower wake. These models are then used to predict the acoustic output of MOD-1, the large wind turbine operated near Boone, N.C. Predicted acoustic time signals are compared to those actually measured near MOD-1 and good agreement is obtained.

  1. Interaction Metrics for Feedback Control of Sound Radiation from Stiffened Panels

    NASA Technical Reports Server (NTRS)

    Cabell, Randolph H.; Cox, David E.; Gibbs, Gary P.

    2003-01-01

    Interaction metrics developed for the process control industry are used to evaluate decentralized control of sound radiation from bays on an aircraft fuselage. The metrics are applied to experimentally measured frequency response data from a model of an aircraft fuselage. The purpose is to understand how coupling between multiple bays of the fuselage can destabilize or limit the performance of a decentralized active noise control system. The metrics quantitatively verify observations from a previous experiment, in which decentralized controllers performed worse than centralized controllers. The metrics do not appear to be useful for explaining control spillover which was observed in a previous experiment.

  2. Patterns of sound radiation behind pointlike charged obstacles in plasma flows.

    PubMed

    Guio, P; Miloch, W J; Pécseli, H L; Trulsen, J

    2008-07-01

    The electrostatic potential and plasma density variations around a pointlike charged object in a plasma flow are studied. These objects can represent small charged dust particles, for instance. The radiation patterns can be interpreted as the result of sound waves being radiated by the obstacle. Two limits are considered: one where the electron-ion temperature ratio is large, Te>Ti , and one where Te/Ti approximately 1 . The former limit can be described by a simple model based on geometrical optics, while the latter requires a kinetic model in order to account for the effects of ion Landau damping. The results are illustrated by numerical simulation using a particle-in-cell code, where the electrons are treated as an isothermal massless fluid, giving a nonlinear Poisson equation. The analytical results are in good agreement with the numerical simulations.

  3. Sound Radiation from a Supersonic Jet Passing Through a Partially Open Exhaust Duct

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2011-01-01

    The radiation of sound from a perfectly expanded Mach 2.5 cold supersonic jet of 25.4 mm exit diameter flowing through a partially open rigid-walled duct with an upstream i-deflector has been studied experimentally. In the experiments, the nozzle is mounted vertically, with the nozzle exit plane at a height of 73 jet diameters above ground level. Relative to the nozzle exit plane (NEP), the location of the duct inlet is varied at 10, 5, and -1 jet diameters. Far-field sound pressure levels were obtained at 54 jet diameters above ground with the aid of acoustic sensors equally spaced around a circular arc of radius equal to 80 jet diameters from the jet axis. Data on the jet acoustic field for the partially open duct were obtained and compared with those with a free jet and with a closed duct. The results suggest that for the partially open duct the overall sound pressure level (OASPL) decreases as the distance between the NEP and the duct inlet plane decreases, while the opposite trend is observed for the closed duct. It is also concluded that the observed peak frequency in the partially open duct increases above the free jet value as the angle from the duct axis is increased, and as the duct inlet plane becomes closer to the NEP.

  4. Sound propagation in and radiation from acoustically lined flow ducts: A comparison of experiment and theory

    NASA Technical Reports Server (NTRS)

    Plumblee, H. E., Jr.; Dean, P. D.; Wynne, G. A.; Burrin, R. H.

    1973-01-01

    The results of an experimental and theoretical study of many of the fundamental details of sound propagation in hard wall and soft wall annular flow ducts are reported. The theory of sound propagation along such ducts and the theory for determining the complex radiation impedance of higher order modes of an annulus are outlined, and methods for generating acoustic duct modes are developed. The results of a detailed measurement program on propagation in rigid wall annular ducts with and without airflow through the duct are presented. Techniques are described for measuring cut-on frequencies, modal phase speed, and radial and annular mode shapes. The effects of flow velocity on cut-on frequencies and phase speed are measured. Comparisons are made with theoretical predictions for all of the effects studies. The two microphone method of impedance is used to measure the effects of flow on acoustic liners. A numerical study of sound propagation in annular ducts with one or both walls acoustically lined is presented.

  5. The radiation of sound from a propeller at angle of attack

    NASA Technical Reports Server (NTRS)

    Mani, Ramani

    1990-01-01

    The mechanism by which the noise generated at the blade passing frequency by a propeller is altered when the propeller axis is at an angle of attack to the freestream is examined. The measured noise field is distinctly non axially symmetric under such conditions with far field sound pressure levels both diminished and increased relative to the axially symmetric values produced with the propeller at zero angle of attack. Attempts have been made to explain this non axially symmetric sound field based on the unsteady (once per rev) loading experienced by the propeller blades when the propeller axis is at non zero angle of attack. A calculation based on this notion appears to greatly underestimate the measured azimuthal asymmetry of noise for high tip speed, highly loaded propellers. A new mechanism is proposed; namely, that at angle of attack, there is a non axially symmetric modulation of the radiative efficiency of the steady loading and thickness noise which is the primary cause of the non axially symmetric sound field at angle of attack for high tip speed, heavily loaded propellers with a large number of blades. A calculation of this effect to first order in the crossflow Mach number (component of freestream Mach number normal to the propeller axis) is carried out and shows much better agreement with measured noise data on the angle of attack effect.

  6. Sound transmission loss characteristics of sandwich panels with a truss lattice core.

    PubMed

    Ehsan Moosavimehr, S; Srikantha Phani, A

    2017-04-01

    Sandwich panels are extensively used in constructional, naval, and aerospace structures due to the high stiffness and strength-to-weight ratios. In contrast, the sound transmission properties are adversely influenced by the low effective mass. Phase velocity matching of structural waves propagating within the panel and the incident pressure waves from the fluid medium leads to coincidence effects resulting in reduced impedance and high sound transmission. Truss-like lattice cores with porous microarchitecture and reduced inter panel connectivity offer the potential to satisfy the conflicting structural and vibroacoustic response requirements. This study combines Bloch-wave analysis and the finite element method to understand wave propagation and hence sound transmission in sandwich panels with a truss lattice core. Three dimensional coupled fluid-structure finite element simulations are conducted to compare the performance of a representative set of lattice core topologies. Potential advantages of sandwich structures with a lattice core are identified. The significance of partial band gaps is evident in the sound transmission loss characteristics of the panels studied. This work demonstrates that, even without optimization, significant enhancements in sound transmission loss performance can be achieved in truss lattice core sandwich panels compared to a traditional sandwich panel employing a honeycomb core under constant mass constraint.

  7. Effects of changing in the neck circumference during sleep on snoring sound characteristics.

    PubMed

    Saha, Shumit; Taheri, Mahsa; Mossuavi, Zahra; Yadollahi, Azadeh

    2015-01-01

    Rostral fluid shift during sleep from the lower body part into the neck can increase neck circumference (NC) and narrow the upper airway. Such narrowing in the upper airway may increase turbulence of airflow passing through the upper airway; thus, induce snoring. The objective of this study was to investigate the effects of changes in NC during sleep on snoring sound characteristics. Fifteen non-obese men slept supine, and their sleep was monitored by a regular polysomnography. Snoring sounds were recorded with a microphone attached to the neck. NC was measured before and after sleep with a measuring tape. Snoring sounds' average power was calculated in different frequency ranges of 100 - 4000 Hz, 100 - 150 Hz, 150 - 450 Hz, 450 - 600 Hz, 600 - 1200 Hz, 1200 - 1800 Hz, 1800 - 2500 Hz and 2500 - 4000 Hz. Statistical analysis showed that increases in NC after sleep were strongly correlated with higher average power of the snoring sounds in the frequency ranges of 100-4000 Hz (r=0.74, P=0.004), 100-150 Hz (r=0.70, P=0.008), 150-450 Hz (r=0.73, P=0.005), and 450 - 600 Hz (r= 0.65, P=0.025). These results encourage the use of snoring sound analysis for monitoring the effects of fluid accumulation in the neck in relation to sleep apnea.

  8. Acoustical characteristics of water sounds for soundscape enhancement in urban open spaces.

    PubMed

    Jeon, Jin Yong; Lee, Pyoung Jik; You, Jin; Kang, Jian

    2012-03-01

    The goal of the present study is to characterize water sounds that can be used in urban open spaces to mask road traffic noise. Sounds and visual images of a number of water features located in urban open places were obtained and subsequently analyzed in terms of psychoacoustical metrics and acoustical measures. Laboratory experiments were then conducted to investigate which water sound is appropriate for masking urban noise. The experiments consisted of two sessions: (1) Audio-only condition and (2) combined audio-visual condition. Subjective responses to stimuli were rated through the use of preference scores and 15 adjectives. The results of the experiments revealed that preference scores for the urban soundscape were affected by the acoustical characteristics of water sounds and visual images of water features; Sharpness that was used to explain the spectral envelopes of water sounds was proved to be a dominant factor for urban soundscape perception; and preferences regarding the urban soundscape were significantly related to adjectives describing "freshness" and "calmness."

  9. [High-speed target recognition positioning system based on multi-spectral radiation characteristics].

    PubMed

    Li, Jian-Min; Wang, Gao

    2014-11-01

    In order to achieve quick recognition and positioning of the high-speed target, using multi-spectral radiation combined with acoustic positioning technology, in the passive state, the blast wave spectral characteristics and acoustic characteristics of the measured target were rapidly obtained, thus analysis was performed to determine the type, location and other important parameters. Multi-spectral radiation detection target recognition formula was deduced. The accuracy of the optical path length and the logical integration time was calculated by shock acoustic positioning method. Experiments used 5.56 mm NATO bullets, 7.62 mm 56-rifle bullets, 12.7 mm 54 type machine-gun bullets as a target identified projectile. Interference fringes were collected by the static Fourier transform interferometer system and ICX387AL type CCD, and the peak of sound pressure was collected using 2209 pulse sound pressure meter made by B & K Company from Denmark Experimental results show that for the 5.56 mm NATO bullets, the three characteristic wavelengths position amplitudes are close to each other, with the maximum amplitude at 966 nm; For the 7.62 mm 56-rifle bullets, 935 nm is the maximum amplitude position, while for 966 and 997 nm position the magnitudes are sunukar; For 12.7 mm 54 type machine-gun bullets, the three wavelengths show a ladder-like distribution. With the increase in the detection distance spectral radiation energy decreased. Meanwhile, with the decrease in the total radiation spectrum, the spectrum of target was affected strongly by background noise, and the SNR of system was decreased. But the spectral characteristics of different target still exist, the target species can be identified by the system with the ratio algorithm of characteristic peaks. Through spectral calibration and characteristic wavelengths extraction, the target can successfully identify the type of projectile and target position, and it meets the design requirements.

  10. Double panel with skyhook active damping control units for control of sound radiation.

    PubMed

    Gardonio, Paolo; Alujević, Neven

    2010-09-01

    This paper presents an experimental study on decentralized velocity feedback control on a double panel consisting of an external aluminum panel and a honeycomb trim panel. The decentralized feedback loops are formed by a 3x3 array of coil-magnet electrodynamic actuators that react off the trim panel and a lightweight stiff frame structure located in the air gap between the two panels. Microelectromechanical systems (MEMS) accelerometers are located on the opposite side of the trim panel in correspondence to the electrodynamic actuators. The grid structure is designed to provide an inertial reference to the actuators. In this way the velocity feedback control loops produce skyhook active damping on the double panel, which minimizes the vibrational response and sound radiation of the trim panel at low audio frequencies. Two configurations are considered where the grid structure is either weakly coupled or strongly coupled to the external panel. Both stability and control performance of the two configurations are analyzed experimentally. The study shows that the control configuration with the weakly coupled grid structure enables the implementation of larger stable feedback control gains, which lead to reductions of the sound radiated by the trim panel between 10 and 30 dB for the first seven resonance peaks.

  11. Modelling and feedback control of sound radiation from a vibrating panel

    NASA Astrophysics Data System (ADS)

    1999-06-01

    This paper considers the feedback control of sound radiation from a panel. Modelling is first used to design the sensors and actuators which are most effective in terms of both their acoustic and control performance. Controlling the volume velocity of a panel to reduce its sound radiation has previously been shown to be an effective strategy when the disturbance is tonal and, in this paper, the technique is extended to broadband disturbances. The use of various structural actuators and sensors is compared for their performance and practicality in active structural acoustic control (ASAC) applications. The best combination of transducers is then used to design an experimental rig. Measured frequency response functions are found to compare well with those obtained in simulations. Feedback control of the volume velocity of the panel is then investigated. It is shown that, to increase the performance of a feedback control system, the plant frequency response should be as close to minimum phase as possible, which can be achieved by changing the positions of secondary actuators on the plate. Internal model control (IMC) is then reviewed and an IMC feedback controller implemented in real time on the plate. The attenuation obtained is compared with the attenuation obtained from simulations. Limitations in the current experimental system are also discussed.

  12. Gamma radiation characteristics of plutonium dioxide fuel

    NASA Technical Reports Server (NTRS)

    Gingo, P. J.

    1969-01-01

    Investigation of plutonium dioxide as an isotopic fuel for Radioisotope Thermoelectric Generators yielded the isotopic composition of production-grade plutonium dioxide fuel, sources of gamma radiation produced by plutonium isotopes, and the gamma flux at the surface.

  13. Numerical simulation of turbulence transition and sound radiation for flow through a rigid glottal model.

    PubMed

    Suh, Jungsoo; Frankel, Steven H

    2007-06-01

    Large eddy simulation (LES)-based computational aeroacoustics techniques were applied to a static model of the human glottis, idealized here as a planar channel with an orifice, to study flow-acoustic interactions related to speech. Rigid models of both converging and diverging glottal passages, each featuring a 20 deg included angle and a minimal glottal diameter of 0.04 cm, with an imposed transglottal pressure of 15 cm H2O, were studied. The Favre-filtered compressible Navier-Stokes equations were integrated for this low-Mach-number flow using an additive semi-implicit Runge-Kutta method and a high-order compact finite-difference scheme with characteristic-based nonreflecting boundary conditions and a multiblock approach. Flow asymmetries related to the Coanda effect and transition to turbulence, as well as the far-field sound, were captured. Acoustic-analogy-based far-field sound predictions were compared with direct simulations and showed that dipole sources, arising from unsteady flow forces exerted on the glottal walls, are primarily responsible for the tonal sound observed in the divergent glottis case.

  14. Predicting Radiation Characteristics from Antenna Physical Dimensions

    DTIC Science & Technology

    1992-12-10

    EIRP ..... effective isotropic radiated power (Watts) Ama .. ..... maximum theoretical effective area (square meters) Imax ..... maximum theoretical...4.7a)271- ý- (jPR) 2 ÷(JOR) 3_1 Eo=- Id---! 32sin (e) 1 1 + ) 2 + R 3 je-j (4 .7b)4n (jPRa) (j OR) (jm DR HR=H =E,4O (4.7c) At far-field distances...directivity EIRP.....effective isotropic radiated power (Watts) A,. ..... maximum theoretical effective area (square meters) Imax ..... maximum

  15. Active sound radiation control of a thick piezolaminated smart rectangular plate

    NASA Astrophysics Data System (ADS)

    Hasheminejad, Seyyed M.; Keshavarzpour, Hemad

    2013-09-01

    A spatial state-space formulation based on the linear three-dimensional piezoelasticity theory in conjunction with the classical Rayleigh integral acoustic radiation model is employed to obtain a semi-analytic solution for the coupled vibroacoustic response of a simply supported, arbitrarily thick, piezolaminated rectangular plate, set in an infinite rigid baffle. The smart structure is composed of an orthotropic supporting core layer integrated with matched volume velocity spatially distributed piezoelectric sensor and uniform force actuator layers. To assist controller design, a frequency-domain subspace-based identification technique is applied to estimate the coupled fluid-structure dynamics of the system. A standard linear quadratic Gaussian (LQG) optimal controller is subsequently synthesized and simulated based on the identified model and the optimal control input voltage for minimizing the estimated net volume velocity (total radiated power) of the panel is calculated in both frequency and time domains. Numerical simulations demonstrate the effectiveness of the adopted volumetric sensing/actuation technique in conjunction with the optimal control strategy for suppressing the predicted sound radiation response of a three-layered (NaNb5O15/Al/PZT4) sandwich panel in both frequency and time domains. The trade-off between dynamic performance and control effort penalty is examined for two different types of loading (i.e., impulsive and broadband random disturbances). Validity of the results is demonstrated by comparison with a commercial finite element package, as well as with the data available in the literature.

  16. Neutron Radiation Induced Degradation of Diode Characteristics

    DTIC Science & Technology

    1992-12-01

    de fluance utilis6 dans ce travail (diode du type 3). La plupart des r~sultats anterieurs sur les, diodes A jonction p-n correspondent aux rdsultats...termes des thories pour une jonction p-n et pour les effects de radiations sur semiconducteurs. II est prddit qu’une diode du type 3 pourrait &tre

  17. Broadband, wide-area active control of sound radiated from vibrating structures using local surface-mounted radiation suppression devices

    NASA Astrophysics Data System (ADS)

    Mason, V. Bradford; Naghshineh, Koorosh; Toth, G. K.

    A new active noise-control device, which offers a practical solution for complex noise problems, has been developed and experimentally evaluated. Noise reduction is achieved by distributing an array of control devices over the surface of the radiating structure (e.g., aircraft fuselage interior). Each device consists of a motion sensor, a control circuit, and a loudspeaker. The control circuits are independent and can be manufactured inexpensively from analog components. The loudspeaker is driven such that it reduces the volume velocity of the radiating structure within its close proximity. Experimental verification of this concept was performed using a uniformly vibrating circular plate with a single device. The controller transfer function was derived and implemented in an analog circuit. Broadband (50-500 Hz) sound reductions in the range of 10-20 dB were achieved over a wide spatial area, including the immediate vicinity of the device. The controller was found to be stable and robust. Since this device in its final implementation may be mounted behind the aircraft trim panels, it was covered by a large, flexible panel. The performance was measured and found to be excellent.

  18. Acoustic characteristics of voluntary expiratory sounds after swallow for detecting dysphagia.

    PubMed

    Yamashita, M; Yokoyama, K; Takei, Y; Furuya, N; Nakamichi, Y; Ihara, Y; Takahashi, K; Groher, M E

    2014-09-01

    This research was designed to investigate the acoustic characteristics of voluntary expiratory sounds after swallow for detecting dysphagia. Forty-nine patients with complaints of swallow difficulty received a videofluorographic (VF) examination. They were divided into three groups: nine who did not have any apparent disease (Group N), 22 patients with head and neck cancer (Group H&N) and 18 patients with other diseases including cerebrovascular disease (Group OD). After liquid barium swallows, they exhaled voluntarily without voicing. Videofluorographic findings were classified into four groups: normal (Normal), acceptable swallow (Acceptable), swallow with residue (Resid) and swallows with penetration or aspiration (Pen/Asp). The duration of expiratory sounds was measured on the time waveform. Frequency characteristics of expiratory sounds were obtained using one-third octave band analysis ranging from 62·5 to 2000·0 Hz of central frequency. The averaged level of the 1000·0-Hz band was chosen as the reference band level (RB level). The revised averaged level of each band was obtained by subtracting the RB level from the averaged level of each band. Zero decibel of the revised magnitude of the 125·0-Hz band was set as the critical value to differentiate dysphagia (Resid or Pen/Asp) from no dysphagia (Normal or Acceptable). Comparison of this assessment with VF findings showed a significant percentage agreement (85·4%). These results suggest that frequency characteristics of post-swallow expiratory sounds can differentiate dysphagia from no dysphagia among multiple dysphagic patient groups. © 2014 John Wiley & Sons Ltd.

  19. On analytic design of loudspeaker arrays with uniform radiation characteristics

    PubMed

    Aarts; Janssen

    2000-01-01

    Some notes on analytical derived loudspeaker arrays with uniform radiation characteristics are presented. The array coefficients are derived via analytical means and compared with so-called maximal flat sequences known from telecommunications and information theory. It appears that the newly derived array, i.e., the quadratic phase array, has a higher efficiency than the Bessel array and a flatter response than the Barker array. The method discussed admits generalization to the design of arrays with desired nonuniform radiating characteristics.

  20. Determining radiated sound power of building structures by means of laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Roozen, N. B.; Labelle, L.; Rychtáriková, M.; Glorieux, C.

    2015-06-01

    This paper introduces a methodology that makes use of laser Doppler vibrometry to assess the acoustic insulation performance of a building element. The sound power radiated by the surface of the element is numerically determined from the vibrational pattern, offering an alternative for classical microphone measurements. Compared to the latter the proposed analysis is not sensitive to room acoustical effects. This allows the proposed methodology to be used at low frequencies, where the standardized microphone based approach suffers from a high uncertainty due to a low acoustic modal density. Standardized measurements as well as laser Doppler vibrometry measurements and computations have been performed on two test panels, a light-weight wall and a gypsum block wall and are compared and discussed in this paper. The proposed methodology offers an adequate solution for the assessment of the acoustic insulation of building elements at low frequencies. This is crucial in the framework of recent proposals of acoustic standards for measurement approaches and single number sound insulation performance ratings to take into account frequencies down to 50 Hz.

  1. Effects of wall admittance changes on duct transmission and radiation of sound.

    NASA Technical Reports Server (NTRS)

    Lansing, D. L.; Zorumski, W. E.

    1973-01-01

    This paper is concerned with the effect of changes in duct wall acoustic properties on the transmission of sound through ducts. Two special problems are considered. The first problem is that of a rectangular infinite-length duct with airflow and a single change in duct wall acoustic admittance. The second problem is that of an axisymmetric field in a finite circular duct without airflow and with an arbitrary number of duct wall acoustic admittance changes. Results for the first problem show the effect of wall admittance change and flow on the acoustic power transmission within the duct. Results for the second problem show the interactive effects of multiple duct liner sections on power radiated from a finite duct.

  2. Radiative characteristics of the Chelyabinsk superbolide

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Masahisa

    2015-12-01

    On Feb. 15, 2013, a meteoroid with a size of about 19 m plunged into the terrestrial atmosphere at 19 km s-1 and burst at an altitude of about 30 km over the city of Chelyabinsk, Russia. Here we present light curves for the bolide in the red, green, and blue color bands, derived from an analysis of a video that was recorded by a dashboard camera and released on the Internet. Our results demonstrate that the bolide was blue-green in color, which is inconsistent with the Planck spectrum before the meteoroid began to fragment. Fragmentation triggered a flare-up of the bolide and 90% of its radiation energy at optical wavelengths was released within a period of about 2 s after that. During the same period, the brightness ratios among the three bands became consistent with 4000 K blackbody radiation. Based on the peak luminosity, a surface area of several square kilometers would be required for a 4000 K blackbody. It is considered that the radiation source of the bolide was an elongated cloud of vapor and debris produced through severe fragmentation of the meteoroid.

  3. The structural characteristics of radiation oncology in Japan in 2003

    SciTech Connect

    Shibuya, Hitoshi . E-mail: shibuya.mrad@tmd.ac.jp; Tsujii, Hirohiko

    2005-08-01

    Purpose: To ascertain the basic structural characteristics of radiation oncology facilities in Japan, we conducted a national survey on their status in 2003. The aims of the survey included the following: present status of radiation treatment facilities, equipment, personnel, patient loads, and other factors. Methods and Materials: A mail survey verified each potential facility delivering megavoltage radiation therapy and collected data on treatment devices, other equipment, personnel, new patients, and so on. Responses were obtained from 100% of potential facilities. Results: A total of 726 facilities delivered radiation therapy, with 859 megavoltage devices, 203 RALS (remote after-loading system) and other radioactive sources, with 941 FTE (full-time employee) radiation oncologists including 369 FTE Japanese Society of Therapeutic Radiation Oncology-certified radiation oncologists, 1555 FTE radiation therapists, and 70 FTE physicists in 2003. Megavoltage devices included two heavy ion units and four proton units. In total, there were 149,793 new patients and 146,351 (98%) by external irradiation; 4379 (3%) were treated by brachytherapy with or without external irradiation. Eighty-six percent of the facilities had treatment-planning computers, but 4% had no treatment-planning capability. Six percent (44 facilities) of all facilities used hyperthermia, 12% (85 facilities) intraoperative radiation therapy, and 2% (12 facilities) intensity-modulated radiation therapy. Conclusion: Facilities surveys continue to provide a source of census data on radiation oncology in Japan, allowing comparisons among facility groups and over time.

  4. An experimental evaluation of the application of the Kirchhoff formulation for sound radiation from an oscillating airfoil

    NASA Technical Reports Server (NTRS)

    Brooks, T. F.

    1977-01-01

    The Kirchhoff integral formulation is evaluated for its effectiveness in quantitatively predicting the sound radiated from an oscillating airfoil whose chord length is comparable with the acoustic wavelength. A rigid airfoil section was oscillated at samll amplitude in a medium at rest to produce the sound field. Simultaneous amplitude and phase measurements were made of surface pressure and surface velocity distributions and the acoustic free field. Measured surface pressure and motion are used in applying the theory, and airfoil thickness and contour are taken into account. The result was that the theory overpredicted the sound pressure level by 2 to 5, depending on direction. Differences are also noted in the sound field phase behavior.

  5. Near-field sound radiation of fan tones from an installed turbofan aero-engine.

    PubMed

    McAlpine, Alan; Gaffney, James; Kingan, Michael J

    2015-09-01

    The development of a distributed source model to predict fan tone noise levels of an installed turbofan aero-engine is reported. The key objective is to examine a canonical problem: how to predict the pressure field due to a distributed source located near an infinite, rigid cylinder. This canonical problem is a simple representation of an installed turbofan, where the distributed source is based on the pressure pattern generated by a spinning duct mode, and the rigid cylinder represents an aircraft fuselage. The radiation of fan tones can be modelled in terms of spinning modes. In this analysis, based on duct modes, theoretical expressions for the near-field acoustic pressures on the cylinder, or at the same locations without the cylinder, have been formulated. Simulations of the near-field acoustic pressures are compared against measurements obtained from a fan rig test. Also, the installation effect is quantified by calculating the difference in the sound pressure levels with and without the adjacent cylindrical fuselage. Results are shown for the blade passing frequency fan tone radiated at a supersonic fan operating condition.

  6. Synchronized vortex shedding and sound radiation from two side-by-side rectangular cylinders of different cross-sectional aspect ratios

    SciTech Connect

    Octavianty, Ressa Asai, Masahito

    2015-10-15

    Synchronized vortex shedding from two side-by-side cylinders and the associated sound radiation were examined experimentally at Reynolds numbers of the order of 10{sup 4} in low-Mach-number flows. In addition to a pair of square cylinders, a pair of rectangular cylinders, one with a square cross section (d × d) and the other with a rectangular cross section (d × c) having a cross-sectional aspect ratio (c/d) of 1.2–1.5, was considered. The center-to-center distance between the two cylinders L/d was 3.6, 4.5, and 6.0; these settings were within the non-biased flow regime for side-by-side square cylinders. In case of a square cylinder pair, anti-phase synchronized vortex shedding occurring for L/d = 3.6 and 4.5 generated a quadrupole-like sound source which radiated in-phase, planar-symmetric sound in the far field. Synchronized vortex shedding from the two rectangular cylinders with different c/d also occurred with almost the same frequency as the characteristic frequency of the square-cylinder wake in the case of the small center-to-center distance, L/d = 3.6, for all the cylinder pairs examined. The synchronized sound field was anti-phase and asymmetric in amplitude, unlike the case of a square cylinder pair. For larger spacing L/d = 4.5, synchronized vortex shedding and anti-phase sound still occurred, but only for close cross-sectional aspect ratios (c/d = 1.0 and 1.2), and highly modulated sound was radiated with two different frequencies due to non-synchronized vortex shedding from the two cylinders for larger differences in c/d. It was also found that when synchronized vortex shedding occurred, near-wake velocity fluctuations exhibited high spanwise-coherency, with a very sharp spectral peak compared with the single-cylinder case.

  7. Sound radiation from annular ducts/nozzles using modal decomposition of in-duct acoustic power

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.

    1983-01-01

    Using a refined acoustic impulse technique, an experimental program was carried out to determine the proper procedure for measuring the acoustic power for both incident and reflected sound fields for annular ducts with and without nozzles at various flow conditions. Several radial and azimuthal pressure measurements were made, and using these complex pressure data, the modal content of the pressure field was determined. A mathematical approach for the modal decomposition of annular duct acoustic power was developed. The acoustic power due to each individual mode and also their total sum were derived. The acoustic characteristics of annular duct-nozzle systems were studied at various flow conditions. The results derived from the experiments include the termination reflection coefficient, the normalized transmission coefficients, the power transfer functions and the power imbalance.

  8. The effects of ballast on the sound radiation from railway track

    NASA Astrophysics Data System (ADS)

    Zhang, Xianying; Thompson, David; Jeong, Hongseok; Squicciarini, Giacomo

    2017-07-01

    In a conventional railway track, the rails are laid on sleepers, usually made of concrete, which are supported by a layer of coarse stones known as ballast. This paper focuses on quantifying the influence that the ballast has on the noise produced by the vibration of the track, particularly on the rail and sleeper radiation ratios. A one-fifth scale model of a railway track has been used to conduct acoustic and vibration measurements. This includes reduced-scale ballast that has been produced with stone sizes in the correct proportions. Two different scaling factors (1:√5 and 1:5) have been adopted for the stone sizes in an attempt to reproduce approximately the acoustic properties of full-scale ballast. It is shown that, although a scale factor of 1:√5 gives a better scaling of the acoustic properties, the stones scaled at 1:5 also give acceptable results. The flow resistivity and porosity of this ballast sample have been measured. These have been used in a local reaction model based on the Johnson-Allard formulation to predict the ballast absorption, showing good agreement with measurements of the absorption coefficient. The effects of the presence of the ballast on the noise radiation from a reduced-scale steel rail and concrete sleeper have been investigated experimentally with the ballast located on a rigid foundation. Comparisons are made with the corresponding numerical predictions obtained by using the boundary element method, in which the ballast is represented by a surface impedance. Additionally the finite element method has been used in which the porous medium is considered as an equivalent fluid. From these results it is shown that the extended reaction model gives better agreement with the measurements. Finally, the effects of the ballast vibration on the sleeper radiation have also been investigated for a case of three sleepers embedded in ballast. The ballast vibration is shown to increase the sound radiation by between 1 and 4.5 dB for

  9. Propagation and radiation of sound from flanged circular ducts with circumferentially varying wall admittances. I Semi-infinite ducts. II - Finite ducts with sources

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.

    1984-01-01

    Sound propagation in infinite, semiinfinite, and finite circular ducts with circumferentially varying wall admittances is investigated analytically. The infinite case is considered, and an example demonstrates the effects of wall-admittance distribution on dispersion characteristics and mode shapes. An exact solution is obtained for the semiinfinite case, a circular duct with a flanged opening: sidelobe suppression and circumferential-mode energy scattering leading to radiated-field asymmetry are found. A finite duct system with specified hard-walled pressure sources is examined in detail, evaluating reflection coefficients, transmission losses, and radiated-field directivity. Graphs and diagrams are provided, and the implications of the results obtained for the design of aircraft-turbofan inlet liners are discussed.

  10. Propagation and radiation of sound from flanged circular ducts with circumferentially varying wall admittances. I Semi-infinite ducts. II - Finite ducts with sources

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.

    1984-01-01

    Sound propagation in infinite, semiinfinite, and finite circular ducts with circumferentially varying wall admittances is investigated analytically. The infinite case is considered, and an example demonstrates the effects of wall-admittance distribution on dispersion characteristics and mode shapes. An exact solution is obtained for the semiinfinite case, a circular duct with a flanged opening: sidelobe suppression and circumferential-mode energy scattering leading to radiated-field asymmetry are found. A finite duct system with specified hard-walled pressure sources is examined in detail, evaluating reflection coefficients, transmission losses, and radiated-field directivity. Graphs and diagrams are provided, and the implications of the results obtained for the design of aircraft-turbofan inlet liners are discussed.

  11. Sound radiation from a resilient spherical cap on a rigid sphere.

    PubMed

    Aarts, Ronald M; Janssen, Augustus J E M

    2010-04-01

    It has been argued that the sound radiation of a loudspeaker is modeled realistically by assuming the loudspeaker cabinet to be a rigid sphere with a resilient spherical cap. Series expansions, valid in the whole space outside the sphere, for the pressure due to a harmonically excited cap with an axially symmetric velocity distribution are presented. The velocity profile is expanded in functions orthogonal on the cap, rather than on the whole sphere. As a result, only a few expansion coefficients are sufficient to accurately describe the velocity profile. An adaptation of the standard solution of the Helmholtz equation to this particular parametrization is required. This is achieved by using recent results on argument scaling of orthogonal (Zernike) polynomials. The approach is illustrated by calculating the pressure due to certain velocity profiles that vanish at the rim of the cap to a desired degree. The associated inverse problem, in which the velocity profile is estimated from pressure measurements around the sphere, is also feasible as the number of expansion coefficients to be estimated is limited. This is demonstrated with a simulation.

  12. Effect of a serrated trailing edge on sound radiation from nearby quadrupoles.

    PubMed

    Karimi, Mahmoud; Croaker, Paul; Kinns, Roger; Kessissoglou, Nicole

    2017-05-01

    A periodic boundary element technique is implemented to study the noise reduction capability of a plate with a serrated trailing edge under quadrupole excitation. It is assumed for this purpose that the quadrupole source tensor is independent of the trailing edge configuration and that the effect of the trailing edge shape is to modify sound radiation from prescribed boundary layer sources. The flat plate is modelled as a continuous structure with a finite repetition of small spanwise segments. The matrix equation formulated by the periodic boundary element method for this 3D acoustic scattering problem is represented as a block Toeplitz matrix. The discrete Fourier transform is employed in an iterative algorithm to solve the block Toeplitz system. The noise reduction mechanism for a serrated trailing edge in the near field is investigated by comparing contour plots obtained from each component of the quadrupole for unserrated and serrated trailing edge plate models. The noise reduction due to the serrated trailing edge is also examined as a function of the source location.

  13. Radiative amplification of sound waves in the winds of O and B stars

    NASA Technical Reports Server (NTRS)

    Macgregor, K. B.; Hartmann, L.; Raymond, J. C.

    1979-01-01

    The velocity perturbation associated with an outwardly propagating sound wave in a radiation-driven stellar wind gives rise to a periodic Doppler shifting of absorption lines formed in the flow. A linearized theory applicable to optically thin waves is used to show that the resulting fluctuation in the absorption-line force can cause the wave amplitude to grow. Detailed calculations of the acceleration due to a large number of lines indicate that significant amplification can occur throughout the high-velocity portion of winds in which the dominant force-producing lines have appreciable optical depths. In the particular case of the wind of Zeta Pup (O4f), it is found that the e-folding distance for wave growth is considerably shorter than the scale lengths over which the physical properties of the flow vary. A qualitative estimate of the rate at which mechanical energy due to nonlinear waves can be dissipated suggests that this mechanism may be important in heating the supersonic portion of winds of early-type stars.

  14. Subjective Reaction to Structurally Radiated Sound from Underground Railways: Field Results

    NASA Astrophysics Data System (ADS)

    Vadillo, E. G.; Herreros, J.; Walker, J. G.

    1996-05-01

    Structurally radiated noise from underground railways is becoming a major problem for railways administrations, due to the increase in the number of tunnels in urban areas, and to the increase in train speeds, wheelset tonnage and operation frequency. As a result, the number of complaints from residents living above railway tunnels is also increasing. Several control measures have been proposed in the past 15 years, both for the track design and for the vehicle design. Nevertheless, these measures are expensive, and not always effective. While several standards have been proposed for vibration limits in the type of problem, there are few standards to define acceptable levels for this type of structure-borne sound. This paper presents field results obtained during 1994 and 1995 in the vicinity of underground railways, where measurements of vibration and low-frequency noise were obtained during train pass-bys. These results, together with measurements of environment noise due to other sources, are considered together with the responses to a questionnaire completed by the people by the people affected. This paper complements laboratory work carried out at the ISVR [1].

  15. Evaluation of acoustic characteristics of snoring sounds obtained during drug-induced sleep endoscopy.

    PubMed

    Herzog, Michael; Plößl, Sebastian; Glien, Alexander; Herzog, Beatrice; Rohrmeier, Christian; Kühnel, Thomas; Plontke, Stefan; Kellner, Patrick

    2015-09-01

    Snoring sounds are discussed to contain acoustic information about their geneses. Nocturnal snoring can easily be recorded acoustically but it is difficult to visually verify its genesis. Contrary, snoring patterns induced by drug-induced sleep endoscopy (DISE) can be visually differentiated. The aim of the study was to classify patterns of obstructions and vibration during DISE and to evaluate acoustic characteristics between these different patterns of snoring. DISE was performed in 41 male patients with sleep-disordered breathing. The recorded video sequences (n = 108) were classified visually at a mute mode in different patterns of snoring (velar, velar obstructive, tonsillar, post-apnoeic). The sound tracks of these subgroups were analysed and compared with regard to the parameters sound pressure level, loudness, sharpness, roughness, fluctuations strength and centre frequency. Obstructive snoring patterns revealed a higher loudness than non-obstructive patterns (>25 sone). Velar snoring showed more roughness (>150 cAsper) than tonsillar and post-apnoeic snoring and revealed the lowest centre frequency (<3000 Hz) of all patterns. Tonsillar snoring presented the highest sharpness (>1.6 acum) whereas post-apnoeic snoring revealed the largest fluctuation strength (>50 cVacil). Different snoring patterns induced by DISE can be classified visually, and an approach to differentiate them acoustically by means of psychoacoustic analyses is demonstrated. On the basis of these results, nocturnal snoring might also be differentiated by psychoacoustic algorithms which could be implemented in acoustic polygraphic screening devices in the future.

  16. [Characteristics of infrared radiation of meridians and acupoints].

    PubMed

    Zheng, Juan-Juan; Shen, Xue-Yong; Zhao, Yi

    2010-10-01

    Infrared radiation temperature and characteristics of infrared spectrum of meridians and acupoints are summarized in this article. The infrared radiant track along the running course of meridians might be a ubiquitous phenomenon of the vital activity. The high temperature bands below the meridian lines at the cuticular layer are often taken as the manifestation of the tract. It could be induced by various stimulations on acupoints with warm-needling as the best causative method. High temperature and low resistance are considered as 2 features of the acupoint zone. The adenosine-triphosphate energy metabolism of the acupoint zone is higher than the non-point zone, which indicates that essential physiological and pathological information are carried by infrared radiation temperature of acupoint and infrared spectrum of acupoint. However, it is realized that study on characteristics of infrared radiation only is far from enough to reveal the essence of meridians and acupoints. And much still remains to be done in strengthening basic studies of characteristics of infrared radiation, structure pattern of meridians and acupoints as well as volt-ampere characteristics.

  17. Vortex sound radiation in a flow duct with a dipole source and a flexible wall of finite length.

    PubMed

    Chiang, Y K; Choy, Y S; Tang, S K

    2017-03-01

    The noise attenuation of fan-ducted noise at low blade-passage frequency remains a challenge. The present study investigates the noise reduction mechanism of a tensioned membrane housing device that directly controls the sound radiation from the doublet which is enclosed in an infinitely long duct with a point vortex. The time dependent sound radiation mechanism and the vibro-acoustics coupling mechanism of the systems are studied by adopting the potential theory and matched asymptotic expansion technique. The silencing performance of such a passive approach depends on the amplitude and phase of the sound field created by the doublet and the acoustic pressure induced by the membrane oscillation in order to achieve sound cancellation. Results show that the response of membrane vibration is strongly associated with the flow field induced by the grazing uniform flow and also the fluid loading generated by the inviscid vortex. The geometrical property of the cavity and the mechanical properties of the flexible membranes play important roles in controlling the performance of the proposed device.

  18. Decentralized Control of Sound Radiation using a High-Authority/Low-Authority Control Strategy with Anisotropic Actuators

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Cabell, Randolph H.; Fuller, Chris R.

    2008-01-01

    This paper describes a combined control strategy designed to reduce sound radiation from stiffened aircraft-style panels. The control architecture uses robust active damping in addition to high-authority linear quadratic Gaussian (LQG) control. Active damping is achieved using direct velocity feedback with triangularly shaped anisotropic actuators and point velocity sensors. While active damping is simple and robust, stability is guaranteed at the expense of performance. Therefore the approach is often referred to as low-authority control. In contrast, LQG control strategies can achieve substantial reductions in sound radiation. Unfortunately, the unmodeled interaction between neighboring control units can destabilize decentralized control systems. Numerical simulations show that combining active damping and decentralized LQG control can be beneficial. In particular, augmenting the in-bandwidth damping supplements the performance of the LQG control strategy and reduces the destabilizing interaction between neighboring control units.

  19. Measurement of acoustic characteristics of Japanese Buddhist temples in relation to sound source location and direction.

    PubMed

    Soeta, Yoshiharu; Shimokura, Ryota; Kim, Yong Hee; Ohsawa, Tomohiro; Ito, Ken

    2013-05-01

    Although temples are important buildings in the Buddhist community, the acoustic quality has not been examined in detail. Buddhist monks change the location and direction according to the ceremony, and associated acoustical changes have not yet been examined scientifically. To discuss the desired acoustics of temples, it is necessary to know the acoustic characteristics appropriate for each phase of a ceremony. In this study, acoustic measurements were taken at various source locations and directions in Japanese temples. A directional loudspeaker was used as the source to provide vocal acoustic fields, and impulse responses were measured and analyzed. The speech transmission index was higher and the interaural cross-correlation coefficient was lower for the sound source directed toward the side wall than that directed toward the altar. This suggests that the change in direction improves speech intelligibility, and the asymmetric property of direct sound and complex reflections from the altar and side wall increases the apparent source width. The large and coupled-like structure of the altar of a Buddhist temple may have reinforced the reverberation components and the table in the altar, which is called the "syumidan," may have decreased binaural coherence.

  20. Impact of the chosen turbulent flow empirical model on the prediction of sound radiation and vibration by aircraft panels

    NASA Astrophysics Data System (ADS)

    Rocha, Joana

    2016-07-01

    A precise definition of the turbulent boundary layer excitation is required to accurately predict the sound radiation and surface vibration levels, produced by an aircraft panel excited turbulent flow during flight. Hence, any existing inaccuracy on turbulent boundary layer excitation models leads to an inaccurate prediction of the panel response. A number of empirical models have been developed over the years to provide the turbulent boundary layer wall pressure spectral density. However, different empirical models provide dissimilar predictions for the wall pressure spectral density. The objective of the present study is to investigate and quantify the impact of the chosen empirical model on the predicted radiated sound power, and on the predicted panel surface acceleration levels. This study provides a novel approach and a detailed analysis on the use of different turbulent boundary layer wall pressure empirical models, and impact on mathematical predictions. Closed-form mathematical relationships are developed, and recommendations are provided for the level of deviation and uncertainty associated to different models, in relation to a baseline model, both for panel surface acceleration and radiated sound power.

  1. Sound absorption of tropical woods and their radiation-induced composites

    NASA Astrophysics Data System (ADS)

    Chia, L. H. L.; Teoh, S. H.; Tharmaratnam, K.; Tan, L. C.

    This is a preliminary study on the sound absorption properties of two tropical hardwoods, Light Red Meranti and Ramin, and their wood-polymer composites. Sound absorption is measured using a standing wave apparatus. The samples are of one thickness (7mm) and cut longitudinally. Wood-polymer composites are made by impregnating the samples with methyl methacrylate which is polymerized in situ through γ-irradiation. Both woods and their composites are better sound absorbers at higher sound frequencies. With partial impregnation, the absorption coefficients are improved upon particularly in the region between 1-3 kHz.

  2. Low-flow characteristics of streams in the Puget Sound region, Washington

    USGS Publications Warehouse

    Hidaka, F.T.

    1973-01-01

    Periods of low streamflow are usually the most critical factor in relation to most water uses. The purpose of this report is to present data on low-flow characteristics of streams in the Puget Sound region, Washington, and to briefly explain some of the factors that influence low flow in the various basins. Presented are data on low-flow frequencies of streams in the Puget Sound region, as gathered at 150 gaging stations. Four indexes were computed from the flow-flow-frequency curves and were used as a basis to compare the low-flow characteristics of the streams. The indexes are the (1) low-flow-yield index, expressed in unit runoff per square mile; (2) base-flow index, or the ratio of the median 7-day low flow to the average discharge; (3) slope index, or slope of annual 7-day low-flow-frequency curve; and (4) spacing index, or spread between the 7-day and 183-day low-flow-frequency curves. The indexes showed a wide variation between streams due to the complex interrelation between climate, topography, and geology. The largest low-flow-yield indexes determined--greater than 1.5 cfs (cubic feet per second) per square mile--were for streams that head at high altitudes in the Cascade and Olympic Mountains and have their sources at glaciers. The smallest low-flow-yield indexes--less than 0.5 cfs per square mile--were for the small streams that drain the lowlands adjacent to Puget Sound. Indexes between the two extremes were for nonglacial streams that head at fairly high altitudes in areas of abundant precipitation. The base-flow index has variations that can be attributed to a basin's hydrogeology, with very little influence from climate. The largest base-flow indexes were obtained for streams draining permeable unconsolidated glacial and alluvial sediments in parts of the lowlands adjacent to Puget Sound. Large volume of ground water in these materials sustain flows during late summer. The smallest indexes were computed for streams draining areas underlain by

  3. Sounds from an oil production island in the Beaufort Sea in summer: characteristics and contribution of vessels.

    PubMed

    Blackwell, Susanna B; Greene, Charles R

    2006-01-01

    The objective of this study was to determine the levels, characteristics, and range dependence of underwater and in-air sounds produced during the open-water seasons of 2000-2003 by the Northstar oil development, located in nearshore waters of the Alaskan Beaufort Sea. Specifically, sounds originating at the island itself (from construction, drilling, and oil production activities) were compared with sounds produced by vessels performing island support. Sounds were obtained with boat-based recordings (at distances up to 37 km from Northstar), a cabled hydrophone (distance approximately 450 m), and with autonomous seafloor recorders (distance approximately 22 km). Vessels (crew boat, tugs, self-propelled barges) were the main contributors to the underwater sound field and were often detectable underwater as much as approximately 30 km offshore. Without vessels, broadband island sounds reached background values at 2-4 km. Island sound levels showed more variation (lower min, higher max) during construction than during drilling and production. In-air broadband measurements were not affected by the presence of vessels and reached background values 1-4 km from Northstar. However, one airborne tone (81 Hz) believed to originate at Northstar was still detectable in the spectrum 37 km away.

  4. 47 CFR 73.160 - Vertical plane radiation characteristics, f(θ).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Vertical plane radiation characteristics, f(Î... SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(θ). (a) The vertical plane radiation characteristics show the relative field being radiated at a...

  5. 47 CFR 73.160 - Vertical plane radiation characteristics, f(θ).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Vertical plane radiation characteristics, f(Î... SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(θ). (a) The vertical plane radiation characteristics show the relative field being radiated at a...

  6. 47 CFR 73.160 - Vertical plane radiation characteristics, f(θ).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Vertical plane radiation characteristics, f(Î... SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(θ). (a) The vertical plane radiation characteristics show the relative field being radiated at a...

  7. 47 CFR 73.160 - Vertical plane radiation characteristics, f(θ).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Vertical plane radiation characteristics, f(Î... SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(θ). (a) The vertical plane radiation characteristics show the relative field being radiated at a...

  8. 47 CFR 73.160 - Vertical plane radiation characteristics, f(θ).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Vertical plane radiation characteristics, f(Î... SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.160 Vertical plane radiation characteristics, f(θ). (a) The vertical plane radiation characteristics show the relative field being radiated at a...

  9. The Imagery of Sound

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Automated Analysis Corporation's COMET is a suite of acoustic analysis software for advanced noise prediction. It analyzes the origin, radiation, and scattering of noise, and supplies information on how to achieve noise reduction and improve sound characteristics. COMET's Structural Acoustic Foam Engineering (SAFE) module extends the sound field analysis capability of foam and other materials. SAFE shows how noise travels while airborne, how it travels within a structure, and how these media interact to affect other aspects of the transmission of noise. The COMET software reduces design time and expense while optimizing a final product's acoustical performance. COMET was developed through SBIR funding and Langley Research Center for Automated Analysis Corporation.

  10. Development of the numerical method for calculating sound radiation from a rotating dipole source in an opened thin duct

    NASA Astrophysics Data System (ADS)

    Choi, Han-Lim; Lee, Duck Joo

    2006-08-01

    Sound radiation from a rotating dipole source in an opened thin duct is analyzed using the thin-body boundary element method in the frequency domain. The difficulty in describing the rotating source in the frequency domain is overcome by introducing a fixed Kirchhoff surface around the rotating source. Acoustic pressures generated from a rotating dipole source, a rotating point force, on the Kirchhoff surface are calculated using Lowson's equation. Normal derivatives on the Kirchhoff surface of acoustic pressures in the Helmholtz integral equation are derived analytically in this paper. Radiated acoustic pressure from the Kirchhoff source and that of the rotating original source in a free field are compared. Effects of the number of elements on the Kirchhoff surface are verified. The analytic solution for a dipole source in a duct is compared with the one obtained by the current Kirchhoff-Helmholtz thin-body boundary element method (K-H TBEM). Sound radiation from a ducted rotating force is calculated using K-H TBEM for selected rotating speeds. It is shown that wave propagation is strongly dependent on the cutoff frequency of the duct. Radiated acoustic pressure can be increased or decreased according to the relation between the cutoff frequency of the duct and the rotating frequency of the source.

  11. Radiative Characteristics of On-Chip Terahertz Undulatory Structures

    SciTech Connect

    Spencer, J

    2004-06-09

    Work on compact, variable, efficient, and high brightness radiation sources is extended by calculating the radiated power and angular distributions for characteristic configurations and drive sources. On the assumption that the transport physics with Maxwell's Equations are valid but modified by the material properties, a number of analogs are suggested between free and bound electron sources of radiation. Characteristics of representative 1-to-n port examples are discussed in terms of a few basic shape parameters and the wavelength. Conditions for coherence and interference are discussed and demonstrated for the latter. Figures-of-merit are defined in terms of brightness, efficiencies or effective impedances such as the radiation coupling impedance Z{sub rc}. Both time and frequency domain techniques are used and checked against other calculations and measurements where available. Finally, we discuss some further possibilities together with various impediments to realizing these kinds of devices such as the Terahertz (THz) modulation problem as well as nonlinear methods for their optimization. To our knowledge, there have been no implementations of such possibilities.

  12. Analysis of the surface load and radiated sound of a vibrating airfoil with application to the experiment of Brooks

    NASA Technical Reports Server (NTRS)

    Yates, J. E.

    1984-01-01

    A method is developed for calculating the surface load and radiated sound from a vibrating surface in a compressible viscous fluid. The method is applied to a thin two-dimensional elliptic cross-section. For large values of the viscous diffusion parameter, the surface load tends to an elliptic distribution in agreement with the results of inviscid theory when edge pressure continuity is enforced. For thin surfaces, the surface load is insensitive to variations in the thickness ratio. A three-dimensional spectral technique is developed to calculate the inviscid surface load and radiated sound from a thin vibrating airfoil. The inviscid theory predicts the correct form of the far field sound pressure and its phase. The actual levels are somewhat sensitive to the choice of theoretical spanwise surface pressure mode but are in better agreement with the experiment than the surface pressure. The comparison of theoretical and experimental surface pressure indicates that the viscous theory, used to validate the inviscid theory, is either inadequate or there is a source of experimental error.

  13. Simulations of cloud-radiation interaction using large-scale forcing derived from the CINDY/DYNAMO northern sounding array

    SciTech Connect

    Wang, Shuguang; Sobel, Adam H.; Fridlind, Ann; Feng, Zhe; Comstock, Jennifer M.; Minnis, Patrick; Nordeen, Michele L.

    2015-09-25

    The recently completed CINDY/DYNAMO field campaign observed two Madden-Julian oscillation (MJO) events in the equatorial Indian Ocean from October to December 2011. Prior work has indicated that the moist static energy anomalies in these events grew and were sustained to a significant extent by radiative feedbacks. We present here a study of radiative fluxes and clouds in a set of cloud-resolving simulations of these MJO events. The simulations are driven by the large scale forcing dataset derived from the DYNAMO northern sounding array observations, and carried out in a doubly-periodic domain using the Weather Research and Forecasting (WRF) model. simulated cloud properties and radiative fluxes are compared to those derived from the S-Polka radar and satellite observations. Furthermore, to accommodate the uncertainty in simulated cloud microphysics, a number of single moment (1M) and double moment (2M) microphysical schemes in the WRF model are tested.

  14. Simulations of cloud-radiation interaction using large-scale forcing derived from the CINDY/DYNAMO northern sounding array

    DOE PAGES

    Wang, Shuguang; Sobel, Adam H.; Fridlind, Ann; ...

    2015-09-25

    The recently completed CINDY/DYNAMO field campaign observed two Madden-Julian oscillation (MJO) events in the equatorial Indian Ocean from October to December 2011. Prior work has indicated that the moist static energy anomalies in these events grew and were sustained to a significant extent by radiative feedbacks. We present here a study of radiative fluxes and clouds in a set of cloud-resolving simulations of these MJO events. The simulations are driven by the large scale forcing dataset derived from the DYNAMO northern sounding array observations, and carried out in a doubly-periodic domain using the Weather Research and Forecasting (WRF) model. simulatedmore » cloud properties and radiative fluxes are compared to those derived from the S-Polka radar and satellite observations. Furthermore, to accommodate the uncertainty in simulated cloud microphysics, a number of single moment (1M) and double moment (2M) microphysical schemes in the WRF model are tested.« less

  15. Effects of head geometry simplifications on acoustic radiation of vowel sounds based on time-domain finite-element simulations.

    PubMed

    Arnela, Marc; Guasch, Oriol; Alías, Francesc

    2013-10-01

    One of the key effects to model in voice production is that of acoustic radiation of sound waves emanating from the mouth. The use of three-dimensional numerical simulations allows to naturally account for it, as well as to consider all geometrical head details, by extending the computational domain out of the vocal tract. Despite this advantage, many approximations to the head geometry are often performed for simplicity and impedance load models are still used as well to reduce the computational cost. In this work, the impact of some of these simplifications on radiation effects is examined for vowel production in the frequency range 0-10 kHz, by means of comparison with radiation from a realistic head. As a result, recommendations are given on their validity depending on whether high frequency energy (above 5 kHz) should be taken into account or not.

  16. A RADIATION TRANSFER SOLVER FOR ATHENA USING SHORT CHARACTERISTICS

    SciTech Connect

    Davis, Shane W.; Stone, James M.; Jiang Yanfei

    2012-03-01

    We describe the implementation of a module for the Athena magnetohydrodynamics (MHD) code that solves the time-independent, multi-frequency radiative transfer (RT) equation on multidimensional Cartesian simulation domains, including scattering and non-local thermodynamic equilibrium (LTE) effects. The module is based on well known and well tested algorithms developed for modeling stellar atmospheres, including the method of short characteristics to solve the RT equation, accelerated Lambda iteration to handle scattering and non-LTE effects, and parallelization via domain decomposition. The module serves several purposes: it can be used to generate spectra and images, to compute a variable Eddington tensor (VET) for full radiation MHD simulations, and to calculate the heating and cooling source terms in the MHD equations in flows where radiation pressure is small compared with gas pressure. For the latter case, the module is combined with the standard MHD integrators using operator splitting: we describe this approach in detail, including a new constraint on the time step for stability due to radiation diffusion modes. Implementation of the VET method for radiation pressure dominated flows is described in a companion paper. We present results from a suite of test problems for both the RT solver itself and for dynamical problems that include radiative heating and cooling. These tests demonstrate that the radiative transfer solution is accurate and confirm that the operator split method is stable, convergent, and efficient for problems of interest. We demonstrate there is no need to adopt ad hoc assumptions of questionable accuracy to solve RT problems in concert with MHD: the computational cost for our general-purpose module for simple (e.g., LTE gray) problems can be comparable to or less than a single time step of Athena's MHD integrators, and only few times more expensive than that for more general (non-LTE) problems.

  17. A Radiation Transfer Solver for Athena Using Short Characteristics

    NASA Astrophysics Data System (ADS)

    Davis, Shane W.; Stone, James M.; Jiang, Yan-Fei

    2012-03-01

    We describe the implementation of a module for the Athena magnetohydrodynamics (MHD) code that solves the time-independent, multi-frequency radiative transfer (RT) equation on multidimensional Cartesian simulation domains, including scattering and non-local thermodynamic equilibrium (LTE) effects. The module is based on well known and well tested algorithms developed for modeling stellar atmospheres, including the method of short characteristics to solve the RT equation, accelerated Lambda iteration to handle scattering and non-LTE effects, and parallelization via domain decomposition. The module serves several purposes: it can be used to generate spectra and images, to compute a variable Eddington tensor (VET) for full radiation MHD simulations, and to calculate the heating and cooling source terms in the MHD equations in flows where radiation pressure is small compared with gas pressure. For the latter case, the module is combined with the standard MHD integrators using operator splitting: we describe this approach in detail, including a new constraint on the time step for stability due to radiation diffusion modes. Implementation of the VET method for radiation pressure dominated flows is described in a companion paper. We present results from a suite of test problems for both the RT solver itself and for dynamical problems that include radiative heating and cooling. These tests demonstrate that the radiative transfer solution is accurate and confirm that the operator split method is stable, convergent, and efficient for problems of interest. We demonstrate there is no need to adopt ad hoc assumptions of questionable accuracy to solve RT problems in concert with MHD: the computational cost for our general-purpose module for simple (e.g., LTE gray) problems can be comparable to or less than a single time step of Athena's MHD integrators, and only few times more expensive than that for more general (non-LTE) problems.

  18. Wind Effect on the Characteristics of Radio Wave Scattering for the Two-Position Radio Acoustic Sounding

    NASA Astrophysics Data System (ADS)

    Bryukhovetski, A. S.; Vichkan', A. V.

    2017-06-01

    Purpose: Radio wave scattering by a sound pulse in the atmosphere when wind is present is investigated theoretically. Design/methodology/approach: The asymptotic of the scattered field in the Fresnel diffraction approximation is analyzed with Gaussian directional patterns of radiating systems. Findings: It is shown that for small angles of backscattering the field is concentrated in a bounded area moving under the exposure of transverse wind velocity. Conclusions: Explanation of the focusing effects dependence on wind velocity is suggested.

  19. Prediction of radiation ratio and sound transmission of complex extruded panel using wavenumber domain Unite element and boundary element methods

    NASA Astrophysics Data System (ADS)

    Kim, H.; Ryue, J.; Thompson, D. J.; Müller, A. D.

    2016-09-01

    Recently, complex shaped aluminium panels have been adopted in many structures to make them lighter and stronger. The vibro-acoustic behaviour of these complex panels has been of interest for many years but conventional finite element and boundary element methods are not efficient to predict their performance at higher frequencies. Where the cross-sectional properties of the panels are constant in one direction, wavenumber domain numerical analysis can be applied and this becomes more suitable for panels with complex cross-sectional geometries. In this paper, a coupled wavenumber domain finite element and boundary element method is applied to predict the sound radiation from and sound transmission through a double-layered aluminium extruded panel, having a typical shape used in railway carriages. The predicted results are compared with measured ones carried out on a finite length panel and good agreement is found.

  20. Simulations of Cloud-Radiation Interaction Using Large-Scale Forcing Derived from the CINDY/DYNAMO Northern Sounding Array

    NASA Technical Reports Server (NTRS)

    Wang, Shuguang; Sobel, Adam H.; Fridlind, Ann; Feng, Zhe; Comstock, Jennifer M.; Minnis, Patrick; Nordeen, Michele L.

    2015-01-01

    The recently completed CINDY/DYNAMO field campaign observed two Madden-Julian oscillation (MJO) events in the equatorial Indian Ocean from October to December 2011. Prior work has indicated that the moist static energy anomalies in these events grew and were sustained to a significant extent by radiative feedbacks. We present here a study of radiative fluxes and clouds in a set of cloud-resolving simulations of these MJO events. The simulations are driven by the large-scale forcing data set derived from the DYNAMO northern sounding array observations, and carried out in a doubly periodic domain using the Weather Research and Forecasting (WRF) model. Simulated cloud properties and radiative fluxes are compared to those derived from the S-PolKa radar and satellite observations. To accommodate the uncertainty in simulated cloud microphysics, a number of single-moment (1M) and double-moment (2M) microphysical schemes in the WRF model are tested. The 1M schemes tend to underestimate radiative flux anomalies in the active phases of the MJO events, while the 2M schemes perform better, but can overestimate radiative flux anomalies. All the tested microphysics schemes exhibit biases in the shapes of the histograms of radiative fluxes and radar reflectivity. Histograms of radiative fluxes and brightness temperature indicate that radiative biases are not evenly distributed; the most significant bias occurs in rainy areas with OLR less than 150 W/ cu sq in the 2M schemes. Analysis of simulated radar reflectivities indicates that this radiative flux uncertainty is closely related to the simulated stratiform cloud coverage. Single-moment schemes underestimate stratiform cloudiness by a factor of 2, whereas 2M schemes simulate much more stratiform cloud.

  1. Investigation on the effect of MR elastomer based adaptive vibration absorbers on the radiated sound from circular elastic plates

    NASA Astrophysics Data System (ADS)

    Hemmatian, M.; Sedaghati, R.

    2016-04-01

    This study aims to investigate the effect of using magnetorheological elastomer (MRE)-based adaptive tuned vibration absorbers (ATVA) on the sound transmission in an elastic plate. Sound transmission loss (STL) of an elastic circular thin plate is analytically studied. The plate is excited by a plane acoustic wave as an incident sound and the displacement of the plate is calculated using corresponding mode shapes of the system for clamped boundary condition. Rayleigh integral approach is used to express the transmitted sound pressure in terms of the plate's displacement modal amplitude. In order to increase sound transmission loss of the plate, the MRE-based ATVA is considered. The basic idea is to be able to change the stiffness of the ATVA by varying magnetic field in order to reduce the transmitted acoustic energy of the host structure in a wide frequency range. Here, a MRE-based ATVA under the shear mode consisting of an oscillator mass, magnetic conductor, coils and MRE is investigated. In order to predict the viscoelastic characteristics of the field-dependent MRE based on the applied magnetic field, the double pole model is used. Finally, MRE-based ATVAs are integrated with the plate to absorb the plate energy with the aim of decreasing the transmitted sound power. Results show that plate with integrated MRE-based ATVAs suppresses the axisymmetric vibration of the plate and thus considerably improves the STL. Parametric studies on the influence of the position of MRE-based ATVAs and the effects of applied current on their performance are also presented.

  2. Research on Radiation Characteristic of Plasma Antenna through FDTD Method

    PubMed Central

    Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

    2014-01-01

    The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic. PMID:25114961

  3. Research on radiation characteristic of plasma antenna through FDTD method.

    PubMed

    Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

    2014-01-01

    The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic.

  4. Polarization characteristics of radiation in both 'light' and conventional undulators

    NASA Astrophysics Data System (ADS)

    Potylitsyn, A. P.; Kolchuzhkin, A. M.; Strokov, S. A.

    2017-07-01

    As a rule, an intensity spectrum of undulator radiation (UR) is calculated by using the classical approach, even for electron energy higher than 10 GeV. Such a spectrum is determined by an electron trajectory in an undulator while neglecting radiation loss. Using Planck's law, the UR photon spectrum can be calculated from the obtained intensity spectrum, for both linear and nonlinear regimes. The electron radiation process in a field of strong electromagnetic waves is considered within the quantum electrodynamics framework, using the Compton scattering process or radiation in a 'light' undulator. A comparison was made of the results from using these two approaches, for UR spectra generated by 250-GeV electrons in an undulator with a 11.5-mm period; this comparison shows that they coincide with high accuracy. The characteristics of the collimated UR beam (i.e. spectrum and circular polarization) were simulated while taking into account the discrete process of photon emission along an electron trajectory in both undulator types. Both spectral photon distributions and polarization dependence on photon energy are 'smoothed', in comparison to that expected for a long undulator-the latter of which considers the ILC positron source (ILC Technical Design Report).

  5. Results from cascade thrust reverser noise and suppression experiments. [sound power level directivity and spectral characteristics

    NASA Technical Reports Server (NTRS)

    Gutierrez, O. A.; Stone, J. R.; Friedman, R.

    1974-01-01

    Results from experimental work on model scale cascade reversers with cold airflow are presented. Sound power level directivity and spectral characteristics for cascade reversers are reported. Effect of cascade exit area ratio, vane profile shape, and emission arc are discussed. Model equivalent diameters varied from 3 to 5 inches, pressure ratios range from 1.15 to 3.0. Depending on the reverser type, acoustic power was proportional to the 4 1/2 to 6th power of ideal jet velocity. Reverser noise peaked at higher frequency and was more omnidirectional than nozzle-alone jet noise. Appreciable reduction in sideline noise was obtained from plane shields. Airfoil-vaned cascades were the most aerodynamically efficient and least noisy reversers. Scaling of cascade reverser data to example aircraft engines showed all cascades above the 95 PNdB sideline goal from STOL aircraft. However, the airfoil-vaned reverser has a good potential for meeting this goal for high-bypass (low pressure ratio) exhausts.

  6. Deep ocean sound speed characteristics passively derived from the ambient acoustic noise field

    NASA Astrophysics Data System (ADS)

    Evers, L. G.; Wapenaar, K.; Heaney, K. D.; Snellen, M.

    2017-02-01

    The propagation of acoustic waves in the ocean strongly depends on the temperature. Low frequency acoustic waves can penetrate the ocean down to depths where few in-situ measurements are available. It is therefore attractive to obtain a measure of the deep ocean temperature from acoustic waves. The latter is especially true if the ambient acoustic noise field can be used instead of deterministic transient signals. In this study the acoustic velocity, and hence the temperature, is derived in an interferometric approach from hydrophone array recordings. The arrays were separated by over 125 km, near Ascension Island in the Atlantic Ocean, at a depth of 850m. Furthermore, the dispersive characteristics of the deep ocean sound channel are resolved based on the retrieved lag times for different modes. In addition, it is shown how the resolution of the interferometric approach can be increased by cross correlating array beams rather than recordings from single-sensor pairs. The observed acoustic lag times between the arrays corresponds well to modeled values, based on full-wave modeling through best-known oceanic models.

  7. Wideband characterization of the complex wave number and characteristic impedance of sound absorbers.

    PubMed

    Salissou, Yacoubou; Panneton, Raymond

    2010-11-01

    Several methods for measuring the complex wave number and the characteristic impedance of sound absorbers have been proposed in the literature. These methods can be classified into single frequency and wideband methods. In this paper, the main existing methods are revisited and discussed. An alternative method which is not well known or discussed in the literature while exhibiting great potential is also discussed. This method is essentially an improvement of the wideband method described by Iwase et al., rewritten so that the setup is more ISO 10534-2 standard-compliant. Glass wool, melamine foam and acoustical/thermal insulator wool are used to compare the main existing wideband non-iterative methods with this alternative method. It is found that, in the middle and high frequency ranges the alternative method yields results that are comparable in accuracy to the classical two-cavity method and the four-microphone transfer-matrix method. However, in the low frequency range, the alternative method appears to be more accurate than the other methods, especially when measuring the complex wave number.

  8. Seeing with sound? exploring different characteristics of a visual-to-auditory sensory substitution device.

    PubMed

    Brown, David; Macpherson, Tom; Ward, Jamie

    2011-01-01

    Sensory substitution devices convert live visual images into auditory signals, for example with a web camera (to record the images), a computer (to perform the conversion) and headphones (to listen to the sounds). In a series of three experiments, the performance of one such device ('The vOICe') was assessed under various conditions on blindfolded sighted participants. The main task that we used involved identifying and locating objects placed on a table by holding a webcam (like a flashlight) or wearing it on the head (like a miner's light). Identifying objects on a table was easier with a hand-held device, but locating the objects was easier with a head-mounted device. Brightness converted into loudness was less effective than the reverse contrast (dark being loud), suggesting that performance under these conditions (natural indoor lighting, novice users) is related more to the properties of the auditory signal (ie the amount of noise in it) than the cross-modal association between loudness and brightness. Individual differences in musical memory (detecting pitch changes in two sequences of notes) was related to the time taken to identify or recognise objects, but individual differences in self-reported vividness of visual imagery did not reliably predict performance across the experiments. In general, the results suggest that the auditory characteristics of the device may be more important for initial learning than visual associations.

  9. Characteristics of distal radius speed of sound data in Chinese mainland men and women.

    PubMed

    Huang, Ligang; Pan, Jiafei; Jin, Hongting; Xiao, Luwei; Tao, Jing; Tong, Peijian

    2015-01-01

    Quantitative ultrasound (QUS) assessment of bone health status, as a reliable method, is rapidly gaining popularity. Speed of sound (SOS) is one parameter of skeletal status provided by QUS assessment. The objective of the present study was first to determine the normative distal radius SOS data on healthy Chinese mainland men and women and second to investigate the effects of sex, age, and body size on this parameter. A study cohort consisting of 19,980 healthy Chinese women and 8722 men aged 20-89 yr participated in this investigation. They answered a detailed questionnaire on their healthy condition, and their anthropometric measurements were taken. Their distal radius SOS values were evaluated using the Sunlight ultrasound systems. The distal radius SOS values exhibited a characteristic rise-then-fall pattern with increasing age in both sexes. The peak SOS value occurred at the age of 40-49 both in males and females. Age-related differences were both pronounced among males and females. Pearson correlation and regression analysis showed that age was a major determinant of SOS in both sexes. In females, SOS values had a much stronger correlation with age than male subjects. Body weight was also correlated with SOS but not as well as age. The SOS values of distal radius at present study may be used as normal reference data for Chinese mainland population and will be useful for comparing the results of individual studies and determining diagnostic criteria of osteoporosis by QUS.

  10. Deep ocean sound speed characteristics passively derived from the ambient acoustic noise field

    NASA Astrophysics Data System (ADS)

    Evers, L. G.; Wapenaar, K.; Heaney, K. D.; Snellen, M.

    2017-07-01

    The propagation of acoustic waves in the ocean strongly depends on the temperature. Low-frequency acoustic waves can penetrate the ocean down to depths where few in situ measurements are available. It is therefore attractive to obtain a measure of the deep ocean temperature from acoustic waves. The latter is especially true if the ambient acoustic noise field can be used instead of deterministic transient signals. In this study the acoustic velocity, and hence the temperature, is derived in an interferometric approach from hydrophone array recordings. The arrays were separated by over 125 km, near Ascension Island in the Atlantic Ocean, at a depth of 850 m. Furthermore, the dispersive characteristics of the deep ocean sound channel are resolved based on the retrieved lag times for different modes. In addition, it is shown how the resolution of the interferometric approach can be increased by cross correlating array beams rather than recordings from single-sensor pairs. The observed acoustic lag times between the arrays corresponds well to modelled values, based on full-wave modelling through best-known oceanic models.

  11. Characteristics of the earth radiation budget experiment solar monitors

    NASA Technical Reports Server (NTRS)

    Lee, Robert B., III; Barkstrom, Bruce R.; Cess, Robert D.

    1987-01-01

    The earth radiation budget experiment solar monitors, active cavity pyrheliometers, have been developed to measure every two weeks the total optical solar irradiance from the earth radiation budget satellite (ERBS) and the National Oceanic and Atmospheric Administration NOAA-9 spacecraft platforms. In the unfiltered 0.2-50-micron wavelength broadband region, the monitors were used to obtain 1365 W/sq m as the mean value for the solar irradiance, with measurement precisions and accuracies approaching 0.1 and 0.2 percent, respectively. The design and characteristics of the solar monitors are presented along with the data reduction model. For the October 1984 through July 1985 period, the resulting ERBS and NOAA-9 solar irradiance values are intercompared.

  12. Gravitational Radiation Characteristics of Nonspinning Black-Hole Binaries

    NASA Technical Reports Server (NTRS)

    Kelly, B. J.; Baker, J. G.; Boggs, W. D.; Centrella, J. M.; vanMeter, J. R.; McWilliams, S. T.

    2008-01-01

    We present a detailed descriptive analysis of the gravitational radiation from binary mergers of non-spinning black holes, based on numerical relativity simulations of systems varying from equal-mass to a 6:1 mass ratio. Our analysis covers amplitude and phase characteristics of the radiation, suggesting a unified picture of the waveforms' dominant features in terms of an implicit rotating source, applying uniformly to the full wavetrain, from inspiral through ringdown. We construct a model of the late-stage frequency evolution that fits the l = m modes, and identify late-time relationships between waveform frequency and amplitude. These relationships allow us to construct a predictive model for the late-time waveforms, an alternative to the common practice of modelling by a sum of quasinormal mode overtones. We demonstrate an application of this in a new effective-one-body-based analytic waveform model.

  13. Gravitational Radiation Characteristics of Nonspinning Black-Hole Binaries

    NASA Technical Reports Server (NTRS)

    Kelly, Barnard

    2008-01-01

    "We present a detailed descriptive analysis of the gravitational radiation from binary mergers of non-spinning black holes, based on numerical relativity simulations of systems varying from equal-mass to a 6:1 mass ratio. Our analysis covers amplitude and phase characteristics of the radiation, suggesting a unified picture of the waveforms' dominant features in terms of an implicit rotating source. applying uniformly to the full wavetrain, from inspiral through ringdown. We construct a model of the late-stage frequency evolution that fits the $\\ell = m$ modes, and identify late-time relationships between waveform frequency and amplitude. These relationships allow us to construct a predictive model for the late-time waveforms, an alternative to the common practice of modelling by a sum of quasinormal mode overtones. We demonstrate an application of this in a new effective-one-body-based analytic waveform model."

  14. Characteristics of the earth radiation budget experiment solar monitors.

    PubMed

    Lee Iii, R B; Barkstrom, B R; Cess, R D

    1987-08-01

    The earth radiation budget experiment solar monitors, active cavity pyrheliometers, have been developed to measure every two weeks the total optical solar irradiance from the earth radiation budget satellite (ERBS) and the National Oceanic and Atmospheric Administration NOAA-9 spacecraft platforms. In the unfiltered 0.2-50-microm wavelength broadband region, the monitors were used to obtain 1365 W/m(2) as the mean value for the solar irradiance with measurement precisions and accuracies approaching 0.1 and 0.2%, respectively. The design and characteristics of the solar monitors are presented along with the data reduction model. For the Oct. 1984 through July 1985 period, the resulting ERBS and NOAA-9 solar irradiance values are intercompared.

  15. Response Characteristics and Experimental Study of Underground Magnetic Resonance Sounding Using a Small-Coil Sensor.

    PubMed

    Qin, Shengwu; Ma, Zhongjun; Jiang, Chuandong; Lin, Jun; Xue, Yiguo; Shang, Xinlei; Li, Zhiqiang

    2017-09-15

    Due to its unique sensitivity to hydrogen protons, magnetic resonance sounding (MRS) is the only geophysical method that directly detects water and can provide nondestructive information on subsurface aquifer properties. The relationship between the surface MRS signal and the location and characteristics of aquifers using large-coil (typically 50-150 m) sensors has been discussed based on forward modelling and experiments. However, few researchers have studied underground MRS using a small-coil sensor. In this paper, a parametric study and a large-scale physical model test were conducted to shed light on the critical response characteristics of underground MRS using a small-coil sensor. The effects of the size and number of turns of the transmitter coil and receiver coil, the geomagnetic declination, the geomagnetic inclination, and the position, thickness, and water content of a water-bearing structure on the performance of the underground MRS were studied based on numerical simulations. Furthermore, we derived the kernel function and underground MRS signal curves for a water-bearing structure model based on the simulations. Finally, a large-scale physical model test on underground MRS using a small-coil sensor was performed using a physical test system for geological prediction of tunnels at Shandong University. The results show that the inversion results of the physical model test were in good agreement with the physical prototype results. Using both numerical modeling and physical model tests, this study showed that underground MRS using a small-coil sensor can be used to predict water-bearing structures in underground engineering.

  16. Experimental verification of low-frequency, highly-directive sound radiation in ambient air by amplitude-modulated, high-intensity ultrasonic waves

    NASA Astrophysics Data System (ADS)

    Lierke, E. G.

    2000-07-01

    A 21 kHz standing-wave amplifier at the focus of a 36 cm diameter parabolic mirror (ka=70) is used for highly directive radiation of low frequency sine waves, voice signals and even music (of poor quality). The low frequency waves are amplitude-modulated onto the ultrasonic carrier wave and radiated into a solid angle of ±1° (-3 dB). Low frequency sound waves with frequencies between 50 Hz and 3 kHz are radiated over a distance of more than 20 m. The achievable audio sound pressure levels decrease with approximately 20 dB per distance doubling and reached about 30 dB at 20 m distance. The discussion of the measurements is based on Blackstock's weak shock theory [5] and on the nonsaturated radiation pressure at saturated sound pressure levels.

  17. Characteristics of surface sound pressure and absorption of a finite impedance strip for a grazing incident plane wave.

    PubMed

    Sum, K S; Pan, J

    2007-07-01

    Distributions of sound pressure and intensity on the surface of a flat impedance strip flush-mounted on a rigid baffle are studied for a grazing incident plane wave. The distributions are obtained by superimposing the unperturbed wave (the specularly reflected wave as if the strip is rigid plus the incident wave) with the radiated wave from the surface vibration of the strip excited by the unperturbed pressure. The radiated pressure interferes with the unperturbed pressure and distorts the propagating plane wave. When the plane wave propagates in the baffle-strip-baffle direction, it encounters discontinuities in acoustical impedance at the baffle-strip and strip-baffle interfaces. The radiated pressure is highest around the baffle-strip interface, but decreases toward the strip-baffle interface where the plane wave distortion reduces accordingly. As the unperturbed and radiated waves have different magnitudes and superimpose out of phase, the surface pressure and intensity increase across the strip in the plane wave propagation direction. Therefore, the surface absorption of the strip is nonzero and nonuniform. This paper provides an understanding of the surface pressure and intensity behaviors of a finite impedance strip for a grazing incident plane wave, and of how the distributed intensity determines the sound absorption coefficient of the strip.

  18. Heart sounds as a result of acoustic dipole radiation of heart valves

    NASA Astrophysics Data System (ADS)

    Kasoev, S. G.

    2005-11-01

    Heart sounds are associated with impulses of force acting on heart valves at the moment they close under the action of blood-pressure difference. A unified model for all the valves represents this impulse as an acoustic dipole. The near pressure field of this dipole creates a distribution of the normal velocity on the breast surface with features typical of auscultation practice: a pronounced localization of heart sound audibility areas, an individual area for each of the valves, and a noncoincidence of these areas with the projections of the valves onto the breast surface. In the framework of the dipole theory, the optimum size of the stethoscope’s bell is found and the spectrum of the heart sounds is estimated. The estimates are compared with the measured spectrum.

  19. Broad band sound from wind turbine generators

    NASA Technical Reports Server (NTRS)

    Hubbard, H. H.; Shepherd, K. P.; Grosveld, F. W.

    1981-01-01

    Brief descriptions are given of the various types of large wind turbines and their sound characteristics. Candidate sources of broadband sound are identified and are rank ordered for a large upwind configuration wind turbine generator for which data are available. The rotor is noted to be the main source of broadband sound which arises from inflow turbulence and from the interactions of the turbulent boundary layer on the blade with its trailing edge. Sound is radiated about equally in all directions but the refraction effects of the wind produce an elongated contour pattern in the downwind direction.

  20. Sound Absorbers

    NASA Astrophysics Data System (ADS)

    Fuchs, H. V.; Möser, M.

    Sound absorption indicates the transformation of sound energy into heat. It is, for instance, employed to design the acoustics in rooms. The noise emitted by machinery and plants shall be reduced before arriving at a workplace; auditoria such as lecture rooms or concert halls require a certain reverberation time. Such design goals are realised by installing absorbing components at the walls with well-defined absorption characteristics, which are adjusted for corresponding demands. Sound absorbers also play an important role in acoustic capsules, ducts and screens to avoid sound immission from noise intensive environments into the neighbourhood.

  1. Atmospheric sound propagation

    NASA Technical Reports Server (NTRS)

    Cook, R. K.

    1969-01-01

    The propagation of sound waves at infrasonic frequencies (oscillation periods 1.0 - 1000 seconds) in the atmosphere is being studied by a network of seven stations separated geographically by distances of the order of thousands of kilometers. The stations measure the following characteristics of infrasonic waves: (1) the amplitude and waveform of the incident sound pressure, (2) the direction of propagation of the wave, (3) the horizontal phase velocity, and (4) the distribution of sound wave energy at various frequencies of oscillation. Some infrasonic sources which were identified and studied include the aurora borealis, tornadoes, volcanos, gravity waves on the oceans, earthquakes, and atmospheric instability waves caused by winds at the tropopause. Waves of unknown origin seem to radiate from several geographical locations, including one in the Argentine.

  2. Characteristics of gunshot sound displays by North Atlantic right whales in the Bay of Fundy.

    PubMed

    Parks, Susan E; Hotchkin, Cara F; Cortopassi, Kathryn A; Clark, Christopher W

    2012-04-01

    North Atlantic right whales (Eubalaena glacialis) produce a loud, broadband signal referred to as the gunshot sound. These distinctive sounds may be suitable for passive acoustic monitoring and detection of right whales; however, little is known about the prevalence of these sounds in important right whale habitats, such as the Bay of Fundy. This study investigates the timing and distribution of gunshot sound production on the summer feeding grounds using an array of five marine acoustic recording units deployed in the Bay of Fundy, Canada in mid-summer 2004 and 2005. Gunshot sounds were common, detected on 37 of 38 recording days. Stereotyped gunshot bouts averaged 1.5 h, with some bouts exceeding 7 h in duration with up to seven individuals producing gunshots at any one time. Bouts were more commonly detected in the late afternoon and evening than during the morning hours. Locations of gunshots in bouts indicated that whales producing the sounds were either stationary or showed directional travel, suggesting gunshots have different communication functions depending on behavioral context. These results indicate that gunshots are a common right whale sound produced during the summer months and are an important component in the acoustic communication system of this endangered species.

  3. Wind tunnel blockage tests at Mach 5 of vacuum duct models for two sound radiation shields

    NASA Technical Reports Server (NTRS)

    Beckwith, I. E.; Harvey, W. D.

    1975-01-01

    Two sound shield models with dummy vacuum exhaust ducts were tested in a Mach 5 pilot quiet tunnel. The first model simulates a new sound shield of 3 in. (7.62 cm) inside diameter and the second model is a shield of 4 in. (10.16 cm) inside diameter. The dummy vacuum exhaust ducts were attached to the external housing of the models. The flow in the first model, which had a by pass mass flow ratio of about 0.6, could not be started except at the two highest test Reynolds numbers where only the central core flow region was started. The flow in the second model with a mass ratio of approximately 0.3 was fully started except at the lowest unit Reynolds number where some unsteadiness and partial flow separation at the wall was observed. Since the external housing and dummy vacuum ducts were the same for both models, these results indicate that the ratio of by pass mass flow to total mass flow for a wind tunnel sound shield of this particular design must be less than about 0.3. Hence, a lower limit is imposed on the inlet diameter of the sound shield in relation to the exit diameter of the wind tunnel nozzle. This lower limit on the inlet diameter may possibly be reduced by improvements in streamlining of the external housing and ducts, by reductions in blockage area, or by the use of external ducting shrouds.

  4. Method for generating realistic sound stimuli with given characteristics by controlled combination of audio recordings.

    PubMed

    Accolti, Ernesto; Miyara, Federico

    2015-01-01

    Audio recordings are often used to improve ecological validity of stimuli for laboratory research on effects of noise. In this paper a method is proposed for composing realistic environmental sound stimuli with (1) specified overall spectrum and (2) specified statistical distribution of sound event durations and semantic categories. The combination is addressed as a mixed integer linear programming problem. Objective measurements, for eight stimuli and a moderate-size database, validate the method. The mean error in octave bands exposure level is 2.6 dB and the statistical distribution of sound event durations and semantic categories is perfectly matched.

  5. Gamma radiation influence on technological characteristics of wheat flour

    NASA Astrophysics Data System (ADS)

    Teixeira, Christian A. H. M.; Inamura, Patricia Y.; Uehara, Vanessa B.; Mastro, Nelida L. d.

    2012-08-01

    This study aimed at determining the influence of gamma radiation on technological characteristics of wheat (Triticum sativum) flour and physical properties of pan breads made with this flour. The bread formulation included wheat flour, water, milk, salt, sugar, yeast and butter. The α-amylase activity of wheat flour irradiated with 1, 3 and 9 kGy in a Gammacell 220 (AECL), one day, five days and one month after irradiation was evaluated. Deformation force, height and weight of breads prepared with the irradiated flour were also determined. The enzymatic activity increased—reduction of falling number time—as radiation dose increased, their values being 397 s (0 kGy), 388 s (1 kGy), 343 s (3 kGy) and 293 s (9 kGy) respectively, remaining almost constant over the period of one month. Pan breads prepared with irradiated wheat flour showed increased weight. Texture analysis showed that bread made of irradiated flour presented an increase in maximum deformation force. The results indicate that wheat flour ionizing radiation processing may confer increased enzymatic activity on bread making and depending on the irradiation dose, an increase in weight, height and deformation force parameters of pan breads made of it.

  6. Radiated Sound of a High-Speed Water-Jet-Propelled Transportation Vessel.

    PubMed

    Rudd, Alexis B; Richlen, Michael F; Stimpert, Alison K; Au, Whitlow W L

    2016-01-01

    The radiated noise from a high-speed water-jet-propelled catamaran was measured for catamaran speeds of 12, 24, and 37 kn. The radiated noise increased with catamaran speed, although the shape of the noise spectrum was similar for all speeds and measuring hydrophone depth. The spectra peaked at ~200 Hz and dropped off continuously at higher frequencies. The radiated noise was 10-20 dB lower than noise from propeller-driven ships at comparable speeds. The combination of low radiated noise and high speed could be a factor in the detection and avoidance of water-jet-propelled ships by baleen whales.

  7. Characteristics of Cloud Radiation Forcing over East China.

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Chyung; Gong, Wei; Kau, Wen-Shung; Chen, Cheng-Ta; Hsu, Huang-Hsiung; Tu, Chia-Hsiu

    2004-02-01

    Observations indicate that the East Asian summer monsoon (EASM) exhibits distinctive characteristics of large cloud amounts with associated heavy and persistent rainfall, although short breaks for clear sky usually occur. Consequently, the effects of cloud radiation interactions can play an important role in the general circulation of the atmosphere and, thus, the evolution of the EASM. In this note, as a first step toward studying the topic, the 5-yr (January 1985 December 1989) Earth Radiation Budget Experiment (ERBE) dataset is used to show the spatial and temporal patterns of both shortwave (SW) and longwave (LW) cloud radiative forcing (CRF) at the top of the atmosphere over east China, and to compare the observed features with Atmospheric Model Intercomparison Project-II (AMIP-II) simulations with the University at Albany, State University of New York (SUNYA) Community Climate Model 3 (CCM3) and the ECHAM4 general circulation models.The observations indicate that the net CRF provides a cooling effect to the atmosphere surface climate system, dominated by the SW CRF cooling (albedo effect) with partial compensation from the LW CRF warming (greenhouse effect). The SW CRF shows a strong seasonal cycle, and its peak magnitude is particularly large, 110 W m-2, for south China and the Yangtze Huai River valley (YHRV) during May and June, while the LW CRF is about 50 W m-2 for the same months with a weak dependence on the latitudes and seasons. These characteristics are in sharp contrast to the Northern Hemispheric zonal means of the same latitude bands and seasons, thus implying a unique role for cloud radiation interaction in east China. Both model simulations show similar observed characteristics, although biases exist. For example, in May, the ECHAM4 underestimates the SW CRF while the SUNYA CCM3 simulates a significantly larger value, both attributed to the respective biases in the simulated total cloud cover. Model-to-observation comparisons of the association

  8. Frequency characteristics of the action of powerful radio-frequency radiation on the ionospheric F layer

    SciTech Connect

    Erukhimov, L.M.; Ivanov, V.A.; Mityakov, N.A.; Uryadov, V.P.; Frolov, V.A.; Shumaev, V.V.

    1988-03-01

    The results of an investigation of the effect of artificial ionospheric nonuniformities on the characteristics of LFM signals with vertical and oblique sounding of the ionosphere are presented. A classification of the effects observed on ionograms from vertical and oblique-sounding LFM ionosonde, owing to the effect of artificial nonuniformities of different scale, is given. It was found that powerful beams of radio waves have a characteristic effect on the ionospheric plasma under conditions when moving ionospheric disturbances appear.

  9. Development of a GPU-based high-performance radiative transfer model for the Infrared Atmospheric Sounding Interferometer (IASI)

    SciTech Connect

    Huang Bormin; Mielikainen, Jarno; Oh, Hyunjong; Allen Huang, Hung-Lung

    2011-03-20

    Satellite-observed radiance is a nonlinear functional of surface properties and atmospheric temperature and absorbing gas profiles as described by the radiative transfer equation (RTE). In the era of hyperspectral sounders with thousands of high-resolution channels, the computation of the radiative transfer model becomes more time-consuming. The radiative transfer model performance in operational numerical weather prediction systems still limits the number of channels we can use in hyperspectral sounders to only a few hundreds. To take the full advantage of such high-resolution infrared observations, a computationally efficient radiative transfer model is needed to facilitate satellite data assimilation. In recent years the programmable commodity graphics processing unit (GPU) has evolved into a highly parallel, multi-threaded, many-core processor with tremendous computational speed and very high memory bandwidth. The radiative transfer model is very suitable for the GPU implementation to take advantage of the hardware's efficiency and parallelism where radiances of many channels can be calculated in parallel in GPUs. In this paper, we develop a GPU-based high-performance radiative transfer model for the Infrared Atmospheric Sounding Interferometer (IASI) launched in 2006 onboard the first European meteorological polar-orbiting satellites, METOP-A. Each IASI spectrum has 8461 spectral channels. The IASI radiative transfer model consists of three modules. The first module for computing the regression predictors takes less than 0.004% of CPU time, while the second module for transmittance computation and the third module for radiance computation take approximately 92.5% and 7.5%, respectively. Our GPU-based IASI radiative transfer model is developed to run on a low-cost personal supercomputer with four GPUs with total 960 compute cores, delivering near 4 TFlops theoretical peak performance. By massively parallelizing the second and third modules, we reached 364x

  10. Growth and physiological characteristics of E. coli in response to the exposure of sound field.

    PubMed

    Gu, Shao-Bin; Yang, Bin; Wu, Ying; Li, Shi-Chang; Liu, Wen; Duan, Xiao-Fei; Li, Meng-Wei

    2013-09-15

    It is undeniable that environmental sonic vibration can affect our emotions and mood, but so far the study of physical stimuli provoked by audible wave on single cells has been rarely concerned. To investigate the response of E. coli to audible wave exposure, the growth status and alterations in antioxidant enzyme activity were studied in liquid culture. The data showed that the growth of E. coli was promoted in the treatments of different frequencies sound wave. The most significant effect on growth promotion appeared when sound wave was maintained at 100 dB and 5000 Hz. Simultaneously, sonic vibration evoked significantly increases the level of total protein content contents. And the changes of activities of Super Oxide Dismutase (SOD) and catalase (CAT) were observed obviously. The results suggested that the growth promotion effect of audible sound may be non-linear and shows obvious frequency and intensity peculiarities. Moreover, the increase in activity of antioxidant enzymes implied that a number of active oxygen species generated in bacterial cell under the exposure of audible sound. We speculate that the audible sound may cause a secondary oxidative stress. Further studies are needed to elucidate the mechanisms of active oxygen species generation induced by audible sound.

  11. Are occlusal characteristics, headache, parafunctional habits and clicking sounds associated with the signs and symptoms of temporomandibular disorder in adolescents?

    PubMed

    Lauriti, Leandro; Motta, Lara Jansiski; Silva, Paula Fernanda da Costa; Leal de Godoy, Camila Haddad; Alfaya, Thays Almeida; Fernandes, Kristianne Porta Santos; Mesquita-Ferrari, Raquel Agnelli; Bussadori, Sandra Kalil

    2013-10-01

    [Purpose] To assess the association between the oclusal characteristics, headache, parafunctional habits and clicking sounds and signs/symptoms of TMD in adolescents. [Subjects] Adolescents between 14 and 18 years of age. [Methods] The participants were evaluated using the Helkimo Index and a clinical examination to track clicking sounds, parafunctional habits and other signs/symptoms of temporomandibular disorder (TMD). Subjects were classified according to the presence or absence of headache, type of occlusion, facial pattern and type of bite. In statistical analyse we used the chi-square test and Fisher's exact test, with a level of significance of 5%. [Results] The sample was made up of 81 adolescents with a mean age of 15.64 years; 51.9% were male. The prevalence of signals/symptoms of TMD was 74.1%, predominantly affecting females. Signals/symptoms of TMD were significantly associated with clicking sounds, headache and nail biting. No associations were found between signals/symptoms of TMD and angle classification, type of bite and facial pattern. [Conclusion] Headache is one of the most closely associated symptoms of TMD. Clicking sounds were found in the majority of cases. Therefore, the sum of two or more factors may be necessary for the onset and perpetuation of TMD.

  12. Estimation of Electron Density profile Using the Propagation Characteristics of Radio Waves by S-520-29 Sounding Rocket

    NASA Astrophysics Data System (ADS)

    Itaya, K.; Ishisaka, K.; Ashihara, Y.; Abe, T.; Kumamoto, A.; Kurihara, J.

    2015-12-01

    S-520-29 sounding rocket experiment was carried out at Uchinoura Space Center (USC) at 19:10 JST on 17 August, 2014. The purpose of this sounding rocket experiments is observation of sporadic E layer that appears in the lower ionosphere at near 100km. Three methods were used in order to observe the sporadic E layer. The first method is an optical method that observe the light of metal ion emitted by the resonance scattering in sporadic E layer using the imager. The second method is observation of characteristic of radio wave propagation that the LF/MF band radio waves transmitted from the ground. The third method is measuring the electron density in the vicinity of sounding rocket using the fast Langmuir probe and the impedance probe. We analyze the propagation characteristics of radio wave in sporadic E layer appeared from the results of the second method observation. This rocket was equipped with LF/MF band radio receiver for observe the LF/MF band radio waves in rocket flight. Antenna of LF/MF band radio receiver is composed of three axis loop antenna. LF/MF band radio receiver receives three radio waves of 873kHz (JOGB), 666kHz (JOBK), 60kHz (JJY) from the ground. 873kHz and 60kHz radio waves are transmitting from north side, and 666kHz radio waves are transmitting from the east side to the trajectory of the rocket. In the sounding rocket experiment, LF/MF band radio receiver was working properly. We have completed the observation of radio wave intensity. We analyze the observation results using a Doppler shift calculations by frequency analysis. Radio waves received by the sounding rocket include the influences of Doppler shift by polarization and the direction of rocket spin and the magnetic field of the Earth. So received radio waves that are separate into characteristics waves using frequency analysis. Then we calculate the Doppler shift from the separated data. As a result, 873kHz, 666kHz radio waves are reflected by the ionosphere. 60kHz wave was able to

  13. Dependence of sound characteristics on the bowing position in a violin

    NASA Astrophysics Data System (ADS)

    Roh, YuJi; Kim, Young H.

    2014-12-01

    A quantitative analysis of violin sounds produced for different bowing positions over the full length of a violin string has been carried out. An automated bowing machine was employed in order to keep the bowing parameters constant. A 3-dimensional profile of the frequency spectrum was introduced in order to characterize the violin's sound. We found that the fundamental frequency did not change for different bowing positions, whereas the frequencies of the higher harmonics were different. Bowing the string at 30 mm from the bridge produced musical sounds. The middle of the string was confirmed to be a dead zone, as reported in previous works. In addition, the quarter position was also found to be a dead zone. Bowing the string 90 mm from the bridge dominantly produces a fundamental frequency of 864 Hz and its harmonics.

  14. Validation of the radiation pattern of the VHF MST radar MAARSY by scattering off a sounding rocket's payload

    NASA Astrophysics Data System (ADS)

    Renkwitz, T.; Schult, C.; Latteck, R.; Stober, G.

    2015-11-01

    The Middle Atmosphere Alomar Radar System (MAARSY) is a monostatic radar with an active phased array antenna designed for studies of phenomena in the mesosphere and lower thermosphere. Its design, in particular the flexible beam forming and steering capability, makes it a powerful instrument to perform observations with high angular and temporal resolution. For the configuration and analysis of experiments carried out with the radar it is essential to have knowledge of the actual radiation pattern. Therefore, during the time since the radar was put into operation various active and passive experiments have been performed to gain knowledge of the radiation pattern. With these experiments the beam pointing accuracy, the beam width and phase distribution of the antenna array were investigated. Here, the use of a sounding rocket and its payload as a radar target is described which was launched in the proximity of the radar. The analysis of these observations allows the detailed investigation of the two-way radiation pattern for different antenna array sizes and beam pointing positions.

  15. Emitted radiation characteristics of plutonium dioxide radioisotope thermoelectric generators

    NASA Technical Reports Server (NTRS)

    Gingo, P. J.; Steyn, J. J.

    1971-01-01

    The nuclear and emitted radiation characteristics of the radioisotope elements and impurities in commercial grade plutonium dioxide are presented in detail. The development of the methods of analysis are presented. Radioisotope thermoelectric generators (RTG) of 1575, 3468 and 5679 thermal watts are characterized with respect to neutron and gamma photon source strength as well as spatial and number flux distribution. The results are presented as a function of detector position and light element contamination concentration for fuel age ranging from 'fresh' to 18 years. The data may be used to obtain results for given O-18 and Pu-236 concentrations. The neutron and gamma photon flux and dose calculations compare favorably with reported experimental values for SNAP-27.

  16. Beamed microwave power transmitting and receiving subsystems radiation characteristics

    NASA Technical Reports Server (NTRS)

    Dickinson, R. M.

    1980-01-01

    Measured characteristics of the spectrum of typical converters and the distribution of radiated Radio Frequency (RF) energy from the terminals (transmitting antenna and rectenna) of a beamed microwave power subsystem are presented for small transmitting and receiving S-band (2.45 GHz) subarrays. Noise and harmonic levels of tube and solid-state RF power amplifiers are shown. The RF patterns and envelope of a 64 element slotted waveguide antenna are given for the fundamental frequency and harmonics through the fifth. Reflected fundamental and harmonic patterns through the fourth for a 42 element rectenna subarray are presented for various dc load and illumination conditions. Bandwidth measurements for the waveguide antenna and rectenna are shown.

  17. End-to-end calculation of the radiation characteristics of VVER-1000 spent fuel assemblies

    SciTech Connect

    Linge, I. I.; Mitenkova, E. F. Novikov, N. V.

    2012-12-15

    The results of end-to-end calculation of the radiation characteristics of VVER-1000 spent nuclear fuel are presented. Details of formation of neutron and gamma-radiation sources are analyzed. Distributed sources of different types of radiation are considered. A comparative analysis of calculated radiation characteristics is performed with the use of nuclear data from different ENDF/B and EAF files and ANSI/ANS and ICRP standards.

  18. Experiments on the low frequency barrier characteristics of cellular metamaterial panels in a diffuse sound field.

    PubMed

    Varanasi, Srinivas; Bolton, J Stuart; Siegmund, Thomas

    2017-01-01

    The metamaterial under investigation here consists of a periodic arrangement of unit plates in a grid-like frame such that there is a contrast in the local areal mass between cell interior and cell wall. In the low frequency range and under normal incidence this metamaterial panel exhibits a sound transmission loss significantly larger than the transmission loss of an unstructured panel with the same homogeneous mass per unit area. However, when the incident sound field is diffuse, the relative advantage of the metamaterial barrier is reduced or eliminated. A sequence of experiments is documented to demonstrate that the relative advantage of the metamaterial barrier can be realized even in a diffuse sound field by creating a hybrid barrier system which embeds the metamaterial layer between a normalizing waveguide layer on the incident side and an absorbing layer on the transmitted side. The sound normalizing waveguide layer is a lattice structure, and the absorbing layer is high performance glass fiber mat. By using measurements of the transmission loss of a 1.2 m square panel system the role of each of these components is demonstrated.

  19. Do Irrelevant Sounds Impair the Maintenance of All Characteristics of Speech in Memory?

    ERIC Educational Resources Information Center

    Gabriel, D.; Gaudrain, E.; Lebrun-Guillaud, G.; Sheppard, F.; Tomescu, I. M.; Schnider, A.

    2012-01-01

    Several studies have shown that maintaining in memory some attributes of speech, such as the content or pitch of an interlocutor's message, is markedly reduced in the presence of background sounds made of spectrotemporal variations. However, experimental paradigms showing this interference have only focused on one attribute of speech at a time,…

  20. Do Irrelevant Sounds Impair the Maintenance of All Characteristics of Speech in Memory?

    ERIC Educational Resources Information Center

    Gabriel, D.; Gaudrain, E.; Lebrun-Guillaud, G.; Sheppard, F.; Tomescu, I. M.; Schnider, A.

    2012-01-01

    Several studies have shown that maintaining in memory some attributes of speech, such as the content or pitch of an interlocutor's message, is markedly reduced in the presence of background sounds made of spectrotemporal variations. However, experimental paradigms showing this interference have only focused on one attribute of speech at a time,…

  1. Thermally annealed silicon nitride films: Electrical characteristics and radiation effects

    SciTech Connect

    Stein, H.J.

    1985-03-15

    Electrical characteristics, including retention under /sup 60/Co ..gamma..-ray irradiation of MNOS (metal-nitride-oxide-semiconductor) structures with LPCVD (low-pressure chemical-vapor-deposited) silicon nitride have been investigated. Capacitance-voltage techniques were used to measure injected, retained, and equilibrium charge. Current-voltage techniques were used to measure voltage and temperature dependence of charge transport. Measurements were made on MNOS with the following nitride annealing histories: (1) as-deposited at 750 /sup 0/C, (2) 950 /sup 0/C in N/sub 2/, and (3) 950 /sup 0/C in N/sub 2/ followed by 900 /sup 0/C in H/sub 2/. Internal IR reflection techniques were used to measure chemically bonded hydrogen in the nitride films. Annealing at 950 /sup 0/C in N/sub 2/ (1) decreased the concentration of hydrogen, (2), decreased equilibrium positive charge, and (3) increased low- and high-field transport. Partial restoration of the as-deposited characteristics was achieved by subsequent annealing in H/sub 2/ at 900 /sup 0/C. Charge loss (retention) under /sup 60/Co ..gamma..-ray irradiation is essentially independent of high-temperature annealing whereas degradation is observed for net negative charge retention measured in the absence of ionizing radiation. Effects of annealing on MNOS structures and models to explain the results are discussed.

  2. Thermally annealed silicon nitride films: Electrical characteristics and radiation effects

    NASA Astrophysics Data System (ADS)

    Stein, Herman J.

    1985-03-01

    Electrical characteristics, including retention under 60Co γ-ray irradiation of MNOS (metal-nitride-oxide-semiconductor) structures with LPCVD (low-pressure chemical-vapor-deposited) silicon nitride have been investigated. Capacitance-voltage techniques were used to measure injected, retained, and equilibrium charge. Current-voltage techniques were used to measure voltage and temperature dependence of charge transport. Measurements were made on MNOS with the following nitride annealing histories: (1) as-deposited at 750 °C, (2) 950 °C in N2, and (3) 950 °C in N2 followed by 900 °C in H2. Internal IR reflection techniques were used to measure chemically bonded hydrogen in the nitride films. Annealing at 950 °C in N2 (1) decreased the concentration of hydrogen, (2), decreased equilibrium positive charge, and (3) increased low- and high-field transport. Partial restoration of the as-deposited characteristics was achieved by subsequent annealing in H2 at 900 °C. Charge loss (retention) under 60Co γ-ray irradiation is essentially independent of high-temperature annealing whereas degradation is observed for net negative charge retention measured in the absence of ionizing radiation. Effects of annealing on MNOS structures and models to explain the results are discussed.

  3. Sexual dimorphism of sonic apparatus and extreme intersexual variation of sounds in Ophidion rochei (Ophidiidae): first evidence of a tight relationship between morphology and sound characteristics in Ophidiidae

    PubMed Central

    2012-01-01

    Background Many Ophidiidae are active in dark environments and display complex sonic apparatus morphologies. However, sound recordings are scarce and little is known about acoustic communication in this family. This paper focuses on Ophidion rochei which is known to display an important sexual dimorphism in swimbladder and anterior skeleton. The aims of this study were to compare the sound producing morphology, and the resulting sounds in juveniles, females and males of O. rochei. Results Males, females, and juveniles possessed different morphotypes. Females and juveniles contrasted with males because they possessed dramatic differences in morphology of their sonic muscles, swimbladder, supraoccipital crest, and first vertebrae and associated ribs. Further, they lacked the ‘rocker bone’ typically found in males. Sounds from each morphotype were highly divergent. Males generally produced non harmonic, multiple-pulsed sounds that lasted for several seconds (3.5 ± 1.3 s) with a pulse period of ca. 100 ms. Juvenile and female sounds were recorded for the first time in ophidiids. Female sounds were harmonic, had shorter pulse period (±3.7 ms), and never exceeded a few dozen milliseconds (18 ± 11 ms). Moreover, unlike male sounds, female sounds did not have alternating long and short pulse periods. Juvenile sounds were weaker but appear to be similar to female sounds. Conclusions Although it is not possible to distinguish externally male from female in O. rochei, they show a sonic apparatus and sounds that are dramatically different. This difference is likely due to their nocturnal habits that may have favored the evolution of internal secondary sexual characters that help to distinguish males from females and that could facilitate mate choice by females. Moreover, the comparison of different morphotypes in this study shows that these morphological differences result from a peramorphosis that takes place during the development of the gonads. PMID:23217241

  4. TEMPORAL AND SPATIAL VARIATION IN SOLAR RADIATION AND PHOTO-ENHANCED TOXICITY RISKS OF SPILLED OIL IN PRINCE WILLIAM SOUND, ALASKA

    EPA Science Inventory

    Solar irradiance (W/m2) and downwelling diffuse attenuation coefficients (Kd; m-1) were determined in several locations in Prince William Sound, Alaska, USA, between April 2003 and December 2005 to assess temporal and spatial variation in solar radiation and the risks of photoenh...

  5. TEMPORAL AND SPATIAL VARIATION IN SOLAR RADIATION AND PHOTO-ENHANCED TOXICITY RISKS OF SPILLED OIL IN PRINCE WILLIAM SOUND, ALASKA

    EPA Science Inventory

    Solar irradiance (W/m2) and downwelling diffuse attenuation coefficients (Kd; m-1) were determined in several locations in Prince William Sound, Alaska, USA, between April 2003 and December 2005 to assess temporal and spatial variation in solar radiation and the risks of photoenh...

  6. Sound Velocity and Bottom Characteristics for LRAPP Atlantic Areas I, II, and III

    DTIC Science & Technology

    1971-06-01

    sound channel is present only east of about 200 W longitude between Cape Finisterre and the Canary Island.; (see 6 UNCLASSIFIED UNCLASSIFIED SFigure 11...Canary I and Iberian Basins, upper axial depths range from appruximately 300 meters near Cape Finisterre to greater than 900 meters north of the...except over the Mid-Atlantic Ridge and in the Labrador Basin. In the Canary and Iberian Basins, upper axial depths range from less than 300 meters off Cape

  7. Direct Computation of Sound Radiation by Jet Flow Using Large-scale Equations

    NASA Technical Reports Server (NTRS)

    Mankbadi, R. R.; Shih, S. H.; Hixon, D. R.; Povinelli, L. A.

    1995-01-01

    Jet noise is directly predicted using large-scale equations. The computational domain is extended in order to directly capture the radiated field. As in conventional large-eddy-simulations, the effect of the unresolved scales on the resolved ones is accounted for. Special attention is given to boundary treatment to avoid spurious modes that can render the computed fluctuations totally unacceptable. Results are presented for a supersonic jet at Mach number 2.1.

  8. The radiation of sound by the instability waves of a compressible plane turbulent shear layer

    NASA Technical Reports Server (NTRS)

    Tam, C. K. W.; Morris, P. J.

    1980-01-01

    The problem of acoustic radiation generated by instability waves of a compressible plane turbulent shear layer is solved. The solution provided is valid up to the acoustic far-field region. It represents a significant improvement over the solution obtained by classical hydrodynamic-stability theory which is essentially a local solution with the acoustic radiation suppressed. The basic instability-wave solution which is valid in the shear layer and the near-field region is constructed in terms of an asymptotic expansion using the method of multiple scales. This solution accounts for the effects of the slightly divergent mean flow. It is shown that the multiple-scales asymptotic expansion is not uniformly valid far from the shear layer. Continuation of this solution into the entire upper half-plane is described. The extended solution enables the near- and far-field pressure fluctuations associated with the instability wave to be determined. Numerical results show that the directivity pattern of acoustic radiation into the stationary medium peaks at 20 degrees to the axis of the shear layer in the downstream direction for supersonic flows. This agrees qualitatively with the observed noise-directivity patterns of supersonic jets.

  9. Influence of the facial ruff on the sound-receiving characteristics of the barn owl's ears.

    PubMed

    von Campenhausen, Mark; Wagner, Hermann

    2006-10-01

    The barn owl, a nocturnal predator, derives its German name ("Schleiereule", direct English translation "veil owl") from the conspicuous ruff that covers the ear openings and gives the head a face-like appearance. The ruff is a specialization for the perception of sound. The densely-ramified reflector feathers forming the border of the ruff direct sound to the ear-openings. We studied the influence of the ruff on the behaviorally relevant sound-localization parameters interaural time difference (ITD) and interaural level difference (ILD). The directionality of the ear was much greater when the ruff was intact than when the reflector feathers were removed. With ruff intact, the distribution of ILDs was oblique and the maximum ITD occurred around 110 degrees of azimuth. When all head feathers were removed, the steepest ILD gradient was much closer to the horizontal axis and ITD was maximal at 90 degrees . Many effects were frequency specific. Thus, the ruff reflects some properties of the human pinna. However, by shifting the point where ITD becomes maximal beyond 90 degrees , the ruff also introduces a break of the front-back symmetry of ITD.

  10. Low-frequency sound exposure causes reversible long-term changes of cochlear transfer characteristics.

    PubMed

    Drexl, Markus; Otto, Larissa; Wiegrebe, Lutz; Marquardt, Torsten; Gürkov, Robert; Krause, Eike

    2016-02-01

    Intense, low-frequency sound presented to the mammalian cochlea induces temporary changes of cochlear sensitivity, for which the term 'Bounce' phenomenon has been coined. Typical manifestations are slow oscillations of hearing thresholds or the level of otoacoustic emissions. It has been suggested that these alterations are caused by changes of the mechano-electrical transducer transfer function of outer hair cells (OHCs). Shape estimates of this transfer function can be derived from low-frequency-biased distortion product otoacoustic emissions (DPOAE). Here, we tracked the transfer function estimates before and after triggering a cochlear Bounce. Specifically, cubic DPOAEs, modulated by a low-frequency biasing tone, were followed over time before and after induction of the cochlear Bounce. Most subjects showed slow, biphasic changes of the transfer function estimates after low-frequency sound exposure relative to the preceding control period. Our data show that the operating point changes biphasically on the transfer function with an initial shift away from the inflection point followed by a shift towards the inflection point before returning to baseline values. Changes in transfer function and operating point lasted for about 180 s. Our results are consistent with the hypothesis that intense, low-frequency sound disturbs regulatory mechanisms in OHCs. The homeostatic readjustment of these mechanisms after low-frequency offset is reflected in slow oscillations of the estimated transfer functions.

  11. Performance characteristics of the electrochemical concentration cell ozonesonde. [in atmospheric sounding

    NASA Technical Reports Server (NTRS)

    Torres, A. L.; Bandy, A. R.

    1978-01-01

    A large number of electrochemical concentration cell (ECC) ozonesondes were calibrated in relation to a UV photometric absorption ozone instrument prior to using the ozonesondes in atmospheric soundings. The two methods of measuring ozone were in reasonable agreement on the average, but there was considerable variation from one ozonesonde to another. Averaging the individual linear regressions gives an ECC ozone concentration equal to 0 + or - 8 nbar plus (0.96 + or - 0.10) times the concentration determined with the UV instrument, where uncertainties represent 90% confidence limits. Applying individual calibration corrections to atmospheric sounding data reduced the mean difference between Dobson spectrophotometric measurements of total ozone overburdens and corresponding values obtained from ozonesonde data from -8.5 + or - 8.2 to -1.4 + or - 7.3% for a series of measurements carried out in 1977. Corresponding uncorrected and corrected differences averaged 3.2 + or - 9.7 and 1.9 + or - 10.6%, respectively, for soundings carried out in 1976.

  12. Broadband Sound Pressure Field Characteristics of Marine Seismic Sources Used by R/V Polarstern

    NASA Astrophysics Data System (ADS)

    Breitzke, M.; Boebel, O.; El Naggar, S.; Jokat, W.; Kuhn, G.; Niessen, F.; Schenke, H.; Werner, B.; Diebold, J.

    2006-05-01

    Single airguns and airgun arrays of different size and volume are used as sound sources for scientific marine seismic reflection and refraction surveys conducted by R/V Polarstern in the Arctic and Antarctic Ocean. To ensure that these research activities do not affect marine wildlife and particularly marine mammals in the Antarctic Treaty Area south of 60°S knowledge of the sound pressure field of the seismic sources is essential. Therefore, a broadband marine seismic source characterization study was conducted at the Heggernes Acoustic Range in the Herdlefjord, Norway in October 2003. The objectives were (1) to determine the spatial distribution of the sound pressure levels emitted by Polarstern's seismic sources, (2) to compute the source levels assuming a spherical amplitude decay, (3) to determine mitigation radii, within which at least some species of marine mammals might possibly experience behavioral or physiological disturbance due to the received sound pressure levels. The thresholds currently in use to determine mitigation radii are 160 dBRMS re 1 μPa for potential behavioral disturbance and 180 dBRMS re 1 μPa for potential physiological and hearing effects like temporary threshold shifts. To determine the spatial distribution of the sound pressure levels each airgun (array) was shot along a line of 2- 3 km length running between 2 hydrophone chains with receivers in 35, 100, 198 and 267 m depth. A GI-Gun (2.4 l), a G-Gun (8.5 l) and a Bolt PAR CT800 (32.8 l) were deployed as single sources, and 3 GI-Guns (7.4 l), 3 G-Guns (25.6 l) and 8 VLF-Guns (24 l) as arrays. The measurements are complemented by a modeling approach for an 8 G-Gun (68.2 l) and 8 G-Gun+1 Bolt PAR CT800 array (100.1 l). The data analysis includes a determination of peak-peak, zero-peak and RMS-amplitudes, sound exposure levels and amplitude spectra as function of source-receiver distance. The amplitude vs distance graphs, analyzed for the 4 hydrophone depths, show the typical

  13. Hybrid Active/Passive Control of Sound Radiation from Panels with Constrained Layer Damping and Model Predictive Feedback Control

    NASA Technical Reports Server (NTRS)

    Cabell, Randolph H.; Gibbs, Gary P.

    2000-01-01

    There has been considerable interest over the past several years in applying feedback control methods to problems of structural acoustics. One problem of particular interest is the control of sound radiation from aircraft panels excited on one side by a turbulent boundary layer (TBL). TBL excitation appears as many uncorrelated sources acting on the panel, which makes it difficult to find a single reference signal that is coherent with the excitation. Feedback methods have no need for a reference signal, and are thus suited to this problem. Some important considerations for the structural acoustics problem include the fact that the required controller bandwidth can easily extend to several hundred Hertz, so a digital controller would have to operate at a few kilohertz. In addition, aircraft panel structures have a reasonably high modal density over this frequency range. A model based controller must therefore handle the modally dense system, or have some way to reduce the bandwidth of the problem. Further complicating the problem is the fact that the stiffness and dynamic properties of an aircraft panel can vary considerably during flight due to altitude changes resulting in significant resonant frequency shifts. These considerations make the tradeoff between robustness to changes in the system being controlled and controller performance especially important. Recent papers concerning the design and implementation of robust controllers for structural acoustic problems highlight the need to consider both performance and robustness when designing the controller. While robust control methods such as H1 can be used to balance performance and robustness, their implementation is not easy and requires assumptions about the types of uncertainties in the plant being controlled. Achieving a useful controller design may require many tradeoff studies of different types of parametric uncertainties in the system. Another approach to achieving robustness to plant changes is to

  14. Radiation Effects on Flow Characteristics in Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Brewster, M. Q.; Gross, Klaus W.

    1989-01-01

    A JANNAF sponsored workshop was held to discuss the importance and role of radiative heat transfer in rocket combustion chambers. The potential impact of radiative transfer on hardware design, reliability, and performance was discussed. The current state of radiative transfer prediction capability in CFD modeling was reviewed and concluded to be substantially lacking in both the physical models used and the radiative property data available. There is a clear need to begin to establish a data base for making radiation calculations in rocket combustion chambers. A natural starting point for this effort would be the NASA thermochemical equilibrium code (CEC).

  15. Modern new nuclear fuel characteristics and radiation protection aspects.

    PubMed

    Terry, Ian R

    2005-01-01

    The glut of fissile material from reprocessing plants and from the conclusion of the cold war has provided the opportunity to design new fuel types to beneficially dispose of such stocks by generating useful power. Thus, in addition to the normal reactor core complement of enriched uranium fuel assemblies, two other types are available on the world market. These are the ERU (enriched recycled uranium) and the MOX (mixed oxide) fuel assemblies. Framatome ANP produces ERU fuel assemblies by taking feed material from reprocessing facilities and blending this with highly enriched uranium from other sources. MOX fuel assemblies contain plutonium isotopes, thus exploiting the higher neutron yield of the plutonium fission process. This paper describes and evaluates the gamma, spontaneous and alpha reaction neutron source terms of these non-irradiated fuel assembly types by defining their nuclear characteristics. The dose rates which arise from these terms are provided along with an overview of radiation protection aspects for consideration in transporting and delivering such fuel assemblies to power generating utilities.

  16. Vibration and sound radiation of an electrostatic speaker based on circular diaphragm.

    PubMed

    Chiang, Hsin-Yuan; Huang, Yu-Hsi

    2015-04-01

    This study investigated the lumped parameter method (LPM) and distributed parameter method (DPM) in the measurement of vibration and prediction of sound pressure levels (SPLs) produced by an electrostatic speaker with circular diaphragm. An electrostatic speaker with push-pull configuration was achieved by suspending the circular diaphragm (60 mm diameter) between two transparent conductive plates. The transparent plates included a two-dimensional array of holes to enable the visualization of vibrations and avoid acoustic distortion. LPM was used to measure the displacement amplitude at the center of the diaphragm using a scanning vibrometer with the aim of predicting symmetric modes using Helmholtz equations and SPLs using Rayleigh integral equations. DPM was used to measure the amplitude of displacement across the entire surface of the speaker and predict SPL curves. LPM results show that the prediction of SPL associated with the first three symmetric resonant modes is in good agreement with the results of DPM and acoustic measurement. Below the breakup frequency of 375 Hz, the SPL predicted by LPM and DPM are identical with the results of acoustic measurement. This study provides a rapid, accurate method with which to measure the SPL associated with the first three symmetric modes using semi-analytic LPM.

  17. Hydrologic and salinity characteristics of Currituck Sound and selected tributaries in North Carolina and Virginia, 1998-99

    USGS Publications Warehouse

    Caldwell, William Scott

    2001-01-01

    Data collected at three sites in Currituck Sound and three tributary sites between March 1, 1998, and February 28, 1999, were used to describe hydrologic and salinity characteristics of Currituck Sound. Water levels and salinity were measured at West Neck Creek at Pungo and at Albemarle and Chesapeake Canal near Princess Anne in Virginia, and at Coinjock, Bell Island, Poplar Branch, and Point Harbor in North Carolina. Flow velocity also was measured at the West Neck Creek and Coinjock sites. The maximum water-level range during the study period was observed near the lower midpoint of Currituck Sound at Poplar Branch. Generally, water levels at all sites were highest during March and April, and lowest during November and December. Winds from the south typically produced higher water levels in Currituck Sound, whereas winds from the north typically produced lower water levels. Although wind over Currituck Sound is associated with fluctuations in water level within the sound, other mechanisms, such as the effects of wind on Albemarle Sound and on other water bodies south of Currituck Sound, likely affect low-frequency water-level variations in Currituck Sound. Flow in West Neck Creek ranged from 313 cubic feet per second to the south to -227 cubic feet per second to the north (negative indicates flow to the north). Flow at the Coinjock site ranged from 15,300 cubic feet per second to the south to -11,700 cubic feet per second to the north. Flow was to the south 68 percent of the time at the West Neck Creek site and 44 percent of the time at the Coinjock site. Daily flow volumes were calculated as the sum of the instantaneous flow volumes. The West Neck Creek site had a cumulative flow volume to the south of 7.69 x 108 cubic feet for the period March 1, 1998, to February 28, 1999; the Coinjock site had a cumulative flow volume to the north of -1.33 x 1010 cubic feet for the same study period. Wind direction and speed influence flow at the West Neck Creek and Coinjock

  18. Possibility to sound the atmospheric ozone by a radiosonde equipped with two temperature sensors, sensitive and non-sensitive to the long wave radiation

    NASA Technical Reports Server (NTRS)

    Kitaoka, T.; Sumi, T.

    1994-01-01

    The sensitiveness of white coated thermistor sensors and non-sensitiveness of the gold coated over white thermistor sensors (which have been manufactured by a vacuum evaporation process) to long wave radiation were ascertained by some simple experiments in-room and also by analyses of some results of experimental soundings. From results of analyses on the temperature discrepancies caused by long wave radiation, the possibility to sound the atmospheric ozone partial pressure by a radiosonde equipped with two kinds of sensors, sensitive and non-sensitive to the long wave radiation was suggested, and the test results of the newly developed software for the deduction of ozone partial pressure in upper layers was also shown. However, it was found that the following is the necessary condition to realize the purpose. The sounding should be made by a radiosonde equipped with three sensors, instead of two, one being non-sensitive to the long wave radiation perfectly, and the other two also non-sensitive partially to the downward one, with two different angles of exposure upward. It is essential for the realization of the purpose to get two different values of temperature discrepancies simultaneously observed by the three sensors mentioned above and to avoid the troublesome effects of the upward long wave radiation.

  19. Active Control of Radiated Sound With Integrated Piezoelectric Composite Structures. Volume 2 Appendices (Concl.)

    DTIC Science & Technology

    2007-11-02

    were calculated u.mg their perimnental dat and Leo.realt=a calculations for bimorph actuators from the sme pi=oe!-ec’ic ceramics having the e dimensons...piezoelectric actuators to replace shak- rs obser toe sme ers and realize a more compact or "smart" structure. 3 radiate to the far field. One of the...Wk) (8) 9(k)=(ifrI(k) ifr 2(k) A ifrk(k)) (9) The cost function is constructed as the mean square error signal, i.e. = E[e2(k)] (10) Substituting

  20. Active Control of Radiated Sound with Integrated Piezoelectric Composite Structures. Volume 3: Appendices (Concl.)

    DTIC Science & Technology

    1998-11-06

    L. I. Nass, Encyclopedia ofPVC (2nd Edition V. 1, V. 2 dnd V. 3), M. Dekker, Inc., New York, 1986. [8] B . J . Lazan , Damping of Materials and Members...Piezoelectric, Double-Amplifier Active- Skin, Part I. Analytical," B . D. Johnson and C. R. Fuller, submitted to J . Acoust. Soc. of Amer.(1998) 27. "Broadband...Control of Plate Radiation Using a Piezoelectric, Double-Amplifier Active- Skin, Part tI. Experimental," B . D. Johnson and C. R. Fuller, submitted to J

  1. Wood for sound.

    PubMed

    Wegst, Ulrike G K

    2006-10-01

    The unique mechanical and acoustical properties of wood and its aesthetic appeal still make it the material of choice for musical instruments and the interior of concert halls. Worldwide, several hundred wood species are available for making wind, string, or percussion instruments. Over generations, first by trial and error and more recently by scientific approach, the most appropriate species were found for each instrument and application. Using material property charts on which acoustic properties such as the speed of sound, the characteristic impedance, the sound radiation coefficient, and the loss coefficient are plotted against one another for woods. We analyze and explain why spruce is the preferred choice for soundboards, why tropical species are favored for xylophone bars and woodwind instruments, why violinists still prefer pernambuco over other species as a bow material, and why hornbeam and birch are used in piano actions.

  2. Sound Radiation from Ducted Fans Using Computational Aeroacoustics on Parallel Computers.

    NASA Astrophysics Data System (ADS)

    Ozyoruk, Yusuf

    1995-01-01

    As a component of a more advanced, new generation fan noise prediction technology, a computational aeroacoustics algorithm has been developed using an entirely new approach. Unlike previous approaches, the current method accounts for the nonuniform background flow and aerodynamic-acoustic coupling issues by solving the 3-D, time-dependent, full nonlinear Euler equations (although the developed computer program is a Navier-Stokes solver). The equations are solved on a 3-D body fitted curvilinear coordinate system using temporally and spatially 4th-order accurate finite difference, Runge -Kutta time integration. The time-accurate flow field is determined only in a relatively small physical domain using nonreflecting boundary conditions on its outer boundaries. A moving surface Kirchhoff method using the formulation of Farassat and Myers has been developed and coupled to the flow solver for far-field noise predictions. The acoustic field is obtained by subtracting the mean field from the total field. To establish the mean flow field, steady state solutions are required and Jameson's full approximation storage multigrid method has been extended to make use of the current high resolution algorithm for obtaining such solutions fast. Formulations in cylindrical coordinates together with cell-centered finite differencing are used to effectively treat the grid singularity along the centerline. Well designed grids aid this treatment. A 3-D grid generator has been developed using the conformal mappings of Ives and Menor to provide the hybrid radiation code with capabilities for very rapid and good quality mesh generation. The hybrid radiation code has been written in CM-Fortran, which is essentially High Performance Fortran. Some novel optimization procedures have been developed and implemented in the code, which runs efficiently on the CM-200 and CM-5 parallel computers. The code has been tested solving a large variety of problems, ranging from an oscillating piston problem

  3. An initial study of voice characteristics of children using two different sound coding strategies in comparison to normal hearing children.

    PubMed

    Coelho, Ana Cristina; Brasolotto, Alcione Ghedini; Bevilacqua, Maria Cecília

    2015-06-01

    To compare some perceptual and acoustic characteristics of the voices of children who use the advanced combination encoder (ACE) or fine structure processing (FSP) speech coding strategies, and to investigate whether these characteristics differ from children with normal hearing. Acoustic analysis of the sustained vowel /a/ was performed using the multi-dimensional voice program (MDVP). Analyses of sequential and spontaneous speech were performed using the real time pitch. Perceptual analyses of these samples were performed using visual-analogic scales of pre-selected parameters. Seventy-six children from three years to five years and 11 months of age participated. Twenty-eight were users of ACE, 23 were users of FSP, and 25 were children with normal hearing. Although both groups with CI presented with some deviated vocal features, the users of ACE presented with voice quality more like children with normal hearing than the users of FSP. Sound processing of ACE appeared to provide better conditions for auditory monitoring of the voice, and consequently, for better control of the voice production. However, these findings need to be further investigated due to the lack of comparative studies published to understand exactly which attributes of sound processing are responsible for differences in performance.

  4. Sound radiation from a high speed axial flow fan due to the inlet turbulence quadrupole interaction

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Rosenbaum, B. M.; Albers, L. U.

    1974-01-01

    A formula is obtained for the total acoustic power spectra radiated out the front of the fan as a function of frequency. The formula involves the design parameters of the fan as well as the statistical properties of the incident turbulence. Numerical results are calculated for values of the parameters in the range of interest for quiet fans tested at the Lewis Research Center. As in the dipole analysis, when the turbulence correlation lengths become equal to the interblade spacing, the predicted spectra exhibit peaks around the blade passing frequency and its harmonics. There has recently been considerable conjecture about whether the stretching of turbulent eddies as they enter a stationary fan could result in the inlet turbulence being the dominant source of pure tones from nontranslating fans. The results of the current analysis show that, unless the turbulent eddies become quite elongated, this noise source contributes predominantly to the broadband spectrum.

  5. Acoustic radiation force in tissue-like solids due to modulated sound field

    NASA Astrophysics Data System (ADS)

    Dontsov, Egor V.; Guzina, Bojan B.

    2012-10-01

    The focus of this study is the sustained body force (the so-called acoustic radiation force) in homogeneous tissue-like solids generated by an elevated-intensity, focused ultrasound field (Mach number=O(10-3)) in situations when the latter is modulated by a low-frequency signal. This intermediate-asymptotics problem, which bears relevance to a number of emerging biomedical applications, is characterized by a number of small (but non-vanishing) parameters including the Mach number, the ratio between the modulation and ultrasound frequency, the ratio of the shear to bulk modulus, and the dimensionless attenuation coefficient. On approximating the response of soft tissues as that of a nonlinear viscoelastic solid with heat conduction, the featured second-order problem is tackled via a scaling paradigm wherein the transverse coordinates are scaled by the width of the focal region, while the axial and temporal coordinate are each split into a "fast" and "slow" component with the twin aim of: (i) canceling the linear terms from the field equations governing the propagation of elevated-intensity ultrasound, and (ii) accounting for the effect of ultrasound modulation. In the context of the focused ultrasound analyses, the key feature of the proposed study revolves around the dual-time-scale treatment of the temporal variable, which allows one to parse out the contribution of ultrasound and its modulation in the nonlinear solution. In this way the acoustic radiation force (ARF), giving rise to the mean tissue motion, is exacted by computing the "fast" time average of the germane field equations. A comparison with the existing theory reveals a number of key features that are brought to light by the new formulation, including the contributions to the ARF of ultrasound modulation and thermal expansion, as well as the precise role of constitutive nonlinearities in generating the sustained body force in tissue-like solids by a focused ultrasound beam.

  6. Postnatal development of sound pressure transformations by the head and pinnae of the cat: Monaural characteristics

    PubMed Central

    Tollin, Daniel J.; Koka, Kanthaiah

    2009-01-01

    Although there have been many anatomical, physiological, and psychophysical studies of auditory development in cat, there have been no comparable studies of the development of the sound pressured transformations by the cat head and pinnae. Because the physical dimensions of the head and pinnae determine the spectral and temporal transformations of sound, as head and pinnae size increase during development, the magnitude and frequency ranges of these transformations are hypothesized to systematically change. This hypothesis was tested by measuring directional transfer functions (DTFs), the directional components of head-related transfer functions, and the linear dimensions of the head and pinnae in cats from the onset of hearing (∼1.5 weeks) through adulthood. Head and pinnae dimensions increased by factors of ∼2 and ∼2.5, respectively, reaching adult values by ∼23 and ∼16 weeks, respectively. The development of the spectral notch cues to source location, the spatial- and frequency-dependent distributions of DTF amplitude gain (acoustic directionality), maximum gain, and the acoustic axis, and the resonance frequency and associated gain of the ear canal and concha were systematically related to the dimensions of the head and pinnae. These monaural acoustical properties of the head and pinnae in the cat are mature by 16 weeks. PMID:19206874

  7. Postnatal development of sound pressure transformations by the head and pinnae of the cat: monaural characteristics.

    PubMed

    Tollin, Daniel J; Koka, Kanthaiah

    2009-02-01

    Although there have been many anatomical, physiological, and psychophysical studies of auditory development in cat, there have been no comparable studies of the development of the sound pressured transformations by the cat head and pinnae. Because the physical dimensions of the head and pinnae determine the spectral and temporal transformations of sound, as head and pinnae size increase during development, the magnitude and frequency ranges of these transformations are hypothesized to systematically change. This hypothesis was tested by measuring directional transfer functions (DTFs), the directional components of head-related transfer functions, and the linear dimensions of the head and pinnae in cats from the onset of hearing ( approximately 1.5 weeks) through adulthood. Head and pinnae dimensions increased by factors of approximately 2 and approximately 2.5, respectively, reaching adult values by approximately 23 and approximately 16 weeks, respectively. The development of the spectral notch cues to source location, the spatial- and frequency-dependent distributions of DTF amplitude gain (acoustic directionality), maximum gain, and the acoustic axis, and the resonance frequency and associated gain of the ear canal and concha were systematically related to the dimensions of the head and pinnae. These monaural acoustical properties of the head and pinnae in the cat are mature by 16 weeks.

  8. Characteristics of detectors for prevention of nuclear radiation terrorism

    NASA Astrophysics Data System (ADS)

    Kolesnikov, S. V.; Ryabeva, E. V.; Samosadny, V. T.

    2017-01-01

    There is description of one type of detectors in use for the task of nuclear terrorism cases prevention to determine the direction to the radioactive source and geometrical structure of radiation field. This type is a modular detector with anisotropic sensitivity. The principle of work of a modular detecting device is the simultaneous operation of several detecting modules with anisotropic sensitivity to gamma radiation.

  9. An improved fast radiative transfer model for special sensor microwave imager/sounder upper atmosphere sounding channels

    NASA Astrophysics Data System (ADS)

    Han, Yong; van Delst, Paul; Weng, Fuzhong

    2010-08-01

    Special sensor microwave imager/sounder (SSMIS) on board the U. S. Defense Meteorology Satellite Program satellites includes six upper atmosphere sounding (UAS) channels for probing air temperature in the upper stratosphere and mesosphere. Three of the UAS channels 19-21 are sensitive to the Doppler frequency shift due to Earth's rotation. The sensitivity to the frequency shift in large degree depends on the O2 Zeeman splitting effect, which is a function of the Earth's magnetic field strength and the angle between the Earth's magnetic field and propagation direction of the electromagnetic wave. Since the brightness temperatures can change up to 2 K as a result of the Doppler shift, the fast radiative transfer model developed earlier for the SSMIS UAS channels has recently been improved to take the Doppler shift into account. In the fast model, an averaged transmittance within the channel frequency passbands is parameterized and trained with a line-by-line radiative transfer model that accurately computes the monochromatic transmittances at fine frequency steps within each passband. The model is evaluated by comparing it with the line-by-line model in an independent experiment. The root mean square differences between the two models are 0.21, 0.39, 0.34, and 0.19 K for channels 19-22, respectively. Using the model, the sensitivities of the radiances to the Doppler shift are analyzed through simulations. A theoretical explanation is given for the dependence of the sensitivities on the Zeeman splitting effect. Results from the analysis are then compared to the observations and a good agreement is achieved.

  10. Design and characteristics of a WEP test in a sounding-rocket payload

    NASA Astrophysics Data System (ADS)

    Reasenberg, Robert D.; Patla, Biju R.; Phillips, James D.; Thapa, Rajesh

    2012-09-01

    We describe SR-POEM, a Galilean test of the weak equivalence principle that is to be conducted during the free fall portion of the flight of a sounding rocket payload. This test of a single pair of substances will have a measurement uncertainty of σ(η) < 2×10-17 after averaging the results of eight separate drops, each of 120 s duration. The entire payload is inverted between successive drops to cancel potential sources of systematic error. The weak equivalence principle measurement is made with a set of four of the SAO laser gauges, which have achieved an Allan deviation of 0.04 pm for an averaging time of 30 s. We discuss aspects of the current design with an emphasis on those that bear on the accuracy of the determination of η. The discovery of a violation(η ≠ 0) would have profound implications for physics, astrophysics and cosmology.

  11. Near- to far-field characteristics of acoustic radiation through plug flow jets.

    PubMed

    Gabard, G

    2008-11-01

    This paper reports a theoretical study of the radiation of sound through jet exhausts. It focuses on the transition from near field to far field by considering the features of the near-field solution and how these features translate to the far field. The main focus of this work is the importance in some cases of lateral waves radiating from the jet. While the presence of lateral waves has long been recognized, there has been no systematic investigation of the practical consequences of these waves in the prediction of sound propagation through round jets. The physical mechanisms involved in the generation of these waves are presented as well as the conditions under which they become significant. Another issue is the possibility of "channeled waves" inside the jet associated with strong sound radiation in the forward arc. This paper also discusses the validity of the far-field approximation when lateral waves are present. It is shown that the standard far-field approximation can be improved by adding correction terms that account for the presence of the lateral waves and channeled waves. The challenge posed to computational aeroacoustics by these near-field effects is also discussed.

  12. Studies of atmosphere radio-sounding for monitoring of radiation environments around nuclear power plants

    NASA Astrophysics Data System (ADS)

    Boyarchuk, Kirill; Karelin, Alexander; Tumanov, Mikhail

    2014-05-01

    The nuclear power plants practically do not discharge to the atmosphere any products causing significant radioactive contaminations. However, during the years of the nuclear power industry, some large accidents occurred at the nuclear objects, and that caused enormous environmental contamination. Among the most significant accidents are: thermal explosion of a reservoir with high-level wastes at the Mayak enterprise in the South Ural region, near the town of Kyshtym, in the end of September 1957; accident at the nuclear power plant in Windscale, UK, in October 1957; accident at the Three-Mile Island, USA, in 1979; accident at the Chernobyl power plant in April 1986. In March of 2011, a large earthquake and the following tsunami caused the largest nuclear catastrophe of XXI century, the accident at the Fucushima-1 power plant. The last accident highlighted the need to review seriously the safety issues at the active power plants and to develop the new effective methods for remote detection and control over radioactive environmental contamination and over general geophysical situation in the areas. The main influence of the fission products on the environment is its ionisation, and therefore various detectable biological and physical processes that are caused by ions. Presence of an ionisation source within the area under study may cause significant changes of absolute humidity and, that is especially important, changes of the chemical potential of atmosphere vapours indicating presence of charged condensation centres. These effects may cause anomalies in the IR radiation emitted from the Earth surface and jumps in the chemical potentials of water vapours that may be observed by means of the satellite remote sensing by specialized equipment (works by Dimitar Ouzounov, Sergey Pulinets, e.a.). In the current study, the theoretical description is presented from positions of the molecular-kinetic condensation theory that shows significant changes of the absolute and

  13. Efficient approximation of the Struve functions Hn occurring in the calculation of sound radiation quantities.

    PubMed

    Aarts, Ronald M; Janssen, Augustus J E M

    2016-12-01

    The Struve functions Hn(z), n=0, 1, ...  are approximated in a simple, accurate form that is valid for all z≥0. The authors previously treated the case n = 1 that arises in impedance calculations for the rigid-piston circular radiator mounted in an infinite planar baffle [Aarts and Janssen, J. Acoust. Soc. Am. 113, 2635-2637 (2003)]. The more general Struve functions occur when other acoustical quantities and/or non-rigid pistons are considered. The key step in the paper just cited is to express H1(z) as (2/π)-J0(z)+(2/π) I(z), where J0 is the Bessel function of order zero and the first kind and I(z) is the Fourier cosine transform of [(1-t)/(1+t)](1/2), 0≤t≤1. The square-root function is optimally approximated by a linear function ĉt+d̂, 0≤t≤1, and the resulting approximated Fourier integral is readily computed explicitly in terms of sin z/z and (1-cos z)/z(2). The same approach has been used by Maurel, Pagneux, Barra, and Lund [Phys. Rev. B 75, 224112 (2007)] to approximate H0(z) for all z≥0. In the present paper, the square-root function is optimally approximated by a piecewise linear function consisting of two linear functions supported by [0,t̂0] and [t̂0,1] with t̂0 the optimal take-over point. It is shown that the optimal two-piece linear function is actually continuous at the take-over point, causing a reduction of the additional complexity in the resulting approximations of H0 and H1. Furthermore, this allows analytic computation of the optimal two-piece linear function. By using the two-piece instead of the one-piece linear approximation, the root mean square approximation error is reduced by roughly a factor of 3 while the maximum approximation error is reduced by a factor of 4.5 for H0 and of 2.6 for H1. Recursion relations satisfied by Struve functions, initialized with the approximations of H0 and H1, yield approximations for higher order Struve functions.

  14. Characteristics of bottom dissolved oxygen in Long Island Sound, New York

    NASA Astrophysics Data System (ADS)

    Lee, Younjoo J.; Lwiza, Kamazima M. M.

    2008-01-01

    The variability of bottom dissolved oxygen (DO) in Long Island Sound, New York, is examined using water quality monitoring data collected by the Connecticut Department of Environmental Protection from 1995 to 2004. Self-organizing map analysis indicates that hypoxia always occurs in the Narrows during summer and less frequently in the Western and the Central Basins. The primary factor controlling the bottom DO, changes spatially and temporally. For non-summer seasons, the levels of bottom DO are strongly associated with water temperature, which means DO availability is primarily driven by solubility. During summer, stratification intensifies under weak wind conditions and bottom DO starts to decrease and deviate from the saturation level except for stations in the Eastern Basin. For the westernmost and shallow (<15 m) stations, bottom DO is correlated with the density stratification (represented by difference between surface and bottom density). In contrast, at deep stations (>20 m), the relationship between oxygen depletion and stratification is not significant. For stations located west of the Central Basin, bottom DO continues to decrease during summer until it reaches its minimum when bottom temperature is around 19-20 °C. In most cases the recovery to saturation levels at the beginning of fall is fast, but not necessarily associated with increased wind mixing. Therefore, we propose that the DO recovery may be a manifestation of either the reduced microbial activity combined with the depletion of organic matter or horizontal exchange. Hypoxic volume is weakly correlated to the summer wind speed, spring total nitrogen, spring chlorophyll a, and maximum river discharge. When all variables are combined in a multiple regression, the coefficient of determination ( r2) is 0.92. Surprisingly, the weakest variable is the total nitrogen, because when it is excluded the coefficient r2 only drops to 0.84. Spring bloom seems to be an important source of organic carbon

  15. Modeling and analyzing characteristics of self-infrared radiation on airplane-skin

    NASA Astrophysics Data System (ADS)

    Li, Zhaozhao; Wu, Wenyuan; Wu, Chengguo; Yang, Yuntao; Huang, Yanhua; Sunxiaobo, Zhuan

    2016-01-01

    The characteristic of the self-infrared radiation of airplane-skin is very important for the stealth performance of airplane. Based on the theory of the airplane-skin temperature field, the distribution of the atmospheric temperature field and the principle of the black-body radiation function the self-infrared radiation model was established. In specified flight conditions, the influence of the atmospheric temperature, the speed of flight, the emissivity and the sight angle detection on the self-infrared radiation of the airplane skin were analyzed. Through the simulation of infrared radiation, some results under different flight states are obtained. The simulation results show that skin infrared radiation energy mainly concentrate on the far infrared wavebands, and various factors have different effects on the infrared radiation of skin. This conclusion can help reduce the infrared radiation and improve the stealth performance of airplane in the engineering design and the selection of flight conditions.

  16. Measurement of the sound transmission characteristics of normal neck tissue using a reflectionless uniform tube.

    PubMed

    Wu, Liang; Xiao, Ke; Dong, Jiaqi; Wang, Supin; Wan, Mingxi

    2014-07-01

    Understanding the sound transmission of the neck tissue is necessary and important in areas such as vocal function evaluation and electrolarynx improvement. In this paper, a simple method using a reflectionless tube was proposed to measure the neck frequency response function (NFRF) of ten normal subjects (five males and five females) during Mandarin vowel production. The NFRFs across different subjects producing different vowels were measured at different neck positions and compared to confirm the effectiveness of the method, and determine the NFRF variations in normal subjects. The results showed that the proposed method offered an easy and effective way to obtain an accurate NFRF. For normal subjects, the neck tissue can be treated as a low-pass filter, with a maximum gain at 310 Hz and a roll-off at a slope of -8.4 dB/octave, flattening out above 2000 Hz. The measurement position on the neck did not influence the shape of the NFRF, but did change the overall gains of the NFRF. In addition, there was a significant gender difference in NFRFs at the low frequencies. Finally, some potential applications of this method and the results are suggested.

  17. Evaluation of thermo-radiation characteristics of IR windows in hypersonic vehicles

    NASA Astrophysics Data System (ADS)

    Wang, Yahui; Wang, Qiang; Zhang, Bochuan; Liang, Bo; Xu, Li; Yun, Hongquan

    2015-04-01

    When hypersonic vehicles have high-hypersonic flights in the atmosphere, high-temperature IR windows become the main factor of complicated aero-thermo-radiation effects, which would reduce the performance of IR detection systems, or even make these systems fail. By analyzing thermal radiation transfer in IR windows, an experimental platform is established to measure thermo-radiation characteristics of IR window materials. And a method is proposed to evaluate thermo-radiation characteristics of IR windows with uneven temperature distribution. Take a MWIR detection system of a hypersonic vehicle as an example, thermo-radiation characteristics of a sapphire IR window is evaluated. The results indicate that, thermo-radiation characteristics of the sapphire IR window material in 3.7μm-4.8μm have an approximate cubic relationship with temperature at 100°C~350°C. With the rise of temperature, the transmittance of the sapphire material decrease, while the window self-radiation increase. As the sapphire IR window is exposed in high-temperature and high-speed airflow, the transmittance drops 4%, still bigger than 95%, self-radiation enhance about 9 times, while temperature of the window rises rapidly. Self-radiation can drive detector into saturation easily, of which the influence on the MWIR detection system is bigger than that of transmittance.

  18. Contributions to the study of ultrasonic machining. [characteristics of ultrasonic sound generators for industrial applications

    NASA Technical Reports Server (NTRS)

    Savii, G.; Iclanzan, T.

    1974-01-01

    Problems in the industrial application of ultrasounds are discussed. Starting from the industrial characteristics of ultrasonic working, especially of hard and fragile materials that are difficult to work by means of conventional methods, the characteristics of the feed system, the circulation system of the abrasive suspension, and the ultra-acoustic unit of machines for ultrasonic working are described. Experiments on the behavior of different types of ultra-acoustic unit design and on the optimal operating conditions connected with the manner of execution, fixation, and excitation conditions are analyzed.

  19. Contributions to the study of ultrasonic machining. [characteristics of ultrasonic sound generators for industrial applications

    NASA Technical Reports Server (NTRS)

    Savii, G.; Iclanzan, T.

    1974-01-01

    Problems in the industrial application of ultrasounds are discussed. Starting from the industrial characteristics of ultrasonic working, especially of hard and fragile materials that are difficult to work by means of conventional methods, the characteristics of the feed system, the circulation system of the abrasive suspension, and the ultra-acoustic unit of machines for ultrasonic working are described. Experiments on the behavior of different types of ultra-acoustic unit design and on the optimal operating conditions connected with the manner of execution, fixation, and excitation conditions are analyzed.

  20. Characteristic, parametric, and diffracted transition X-ray radiation for observation of accelerated particle beam profile

    NASA Astrophysics Data System (ADS)

    Chaikovska, I.; Chehab, R.; Artru, X.; Shchagin, A. V.

    2017-07-01

    The applicability of X-ray radiation for the observation of accelerated particle beam profiles is studied. Three types of quasi-monochromatic X-ray radiation excited by the particles in crystals are considered: characteristic X-ray radiation, parametric X-ray radiation, diffracted transition X-ray radiation. Radiation is collected at the right angle to the particle beam direction. It is show that the most intensive differential yield of X-ray radiation from Si crystal can be provided by characteristic radiation at incident electron energies up to tens MeV, by parametric radiation at incident electron energies from tens to hundreds MeV, by diffracted transition X-ray radiation at GeV and multi-GeV electron energies. Therefore these kinds of radiation are proposed for application to beam profile observation in the corresponding energy ranges of incident electrons. Some elements of X-ray optics for observation of the beam profile are discussed. The application of the DTR as a source of powerful tunable monochromatic linearly polarized X-ray beam excited by a multi-GeV electron beam on the crystal surface is proposed.

  1. Polarimeter measures sea state characteristics using emitted infrared radiation

    NASA Technical Reports Server (NTRS)

    Egan, W. G.; Hilgeman, T.

    1977-01-01

    An infrared polarimeter, capable of operating between 1 and 12 micrometers wavelength has been used to measure the polarization of emitted radiation from the sea. The observed polarization at 10.6 micrometers from a smooth sea was found to be positive, indicating the dominance of reflected infrared sky radiation over the emitted. With the appearance of waves, the percent polarization increased, as expected, for a zenith angle well above the Brewster angle for water. This is qualitatively in accordance with a model presented to explain the behavior. Initial analyses indicate that the polarized components of the sea's emitted and reflected radiation are affected by type and direction of waves, angle of viewing, and foam. The effects of variations in these parameters require further delineation. The infrared polarimetric technique appears to be a novel new passive method for remote monitoring of waves.

  2. Radiative Characteristics of On-Chip Terahertz (THz) Structures

    SciTech Connect

    Hussein, Yasser A.; Spencer, James E.; /SLAC

    2005-06-07

    Previously, we explored possibilities for producing narrow-band THz radiation using either free or bound electrons (solid state) in micro-undulatory configurations [1] because integrated circuit technology appeared well matched to this region extending from about 300 GHz to 30 THz. This range [2]-[3] has largely been neglected until recently because it runs from the limit of WR-3 waveguide around 300 GHz up to CO{sub 2} lasers where the laser regime becomes dominant. There are mainly two approaches for generating THz radiation, i.e. through free or bound electron (BE) implementations. In this paper, emphasis is on producing this radiation using bound electrons via IC technology but in close analogy to free electron lasers (FELs) that are comparatively immense, expensive, need high power and have low efficiencies [4].

  3. A characteristic scale in radiation fields of fractal clouds

    SciTech Connect

    Wiscombe, W.; Cahalan, R.; Davis, A.; Marshak, A.

    1996-04-01

    The wavenumber spectrum of Landsat imagery for marine stratocumulus cloud shows a scale break when plotted on a double log plot. We offer an explanation of this scale break in terms of smoothing by horizontal radiative fluxes, which is parameterized and incorporated into an improved pixel approximation. We compute the radiation fields emerging from cloud models with horizontally variable optical depth fractal models. We use comparative spectral and multifractal analysis to qualify the validity of the independent pixel approximation at the largest scales and demonstrate it`s shortcomings on the smallest scales.

  4. Characteristics of Smith-Purcell radiation in millimeter wavelength region

    NASA Astrophysics Data System (ADS)

    Naumenko, G. A.; Potylitsyn, A. P.; Karataev, P.; Bleko, V.; Sukhikh, L. G.; Shevelev, M. V.; Popov, Yu

    2016-07-01

    Investigations of the Smith-Purcell radiation (SPR) were began with non-relativistic electron beams with some unexpected experimental results. Further the experimental investigations were performed with relativistic electron beams for application to beam diagnostics. Large discrepancy between different theoretical models significantly increases the role of experimental studies of this phenomenon. In this report we present some problems and features of experimental investigations of SPR in millimeter wavelength region. The problems of prewave zone and coherent effects are considered. The shadowing effect, focusing of radiation using a parabolic SPR target and effect of inclination of target strips were investigated with moderately relativistic electron beam.

  5. Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A2, S/N 108, 08

    NASA Technical Reports Server (NTRS)

    Valdez, A.

    2000-01-01

    This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A2, S/N 108, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

  6. Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 108 2

    NASA Technical Reports Server (NTRS)

    Valdez, A.

    2000-01-01

    This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1 SIN 108, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

  7. Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 109

    NASA Technical Reports Server (NTRS)

    Valdez, A.

    2000-01-01

    This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 109, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

  8. Effect of high-power laser radiation on characteristics of thin silicon nitride films

    SciTech Connect

    Roizin, Y.O.; Khuan, K.S.

    1986-09-01

    High-power laser radiation is used in microelectronic technology for purposes such as annealing radiation defects in MOS structures after ion implantation. This paper considers accumulated changes in electrical characteristics of metal-nitride-oxide-semiconductor (MNOS) structures under the action of neodymium laser pulses with an energy density below the visible damage threshold. The experimental results obtained are interpreted.

  9. Some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening

    NASA Technical Reports Server (NTRS)

    Bahadur, H.; Parshad, R.

    1983-01-01

    The paper reports some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening. The present results show how the frequency shift in quartz crystals can be influenced by heat processing prior to irradiation and how this procedure can lead to radiation hardening for obtaining precise frequencies and time intervals from quartz oscillators in space.

  10. Quality Characteristics of Dried Bananas Produced with Infrared Radiation Technology

    USDA-ARS?s Scientific Manuscript database

    Browning of fruits during drying is a major quality concern. The enzyme polyphenol oxidase has been found to be the main cause of browning in bananas. Infrared radiation (IR) drying could be used to minimize enzymatic browning hence eliminating the need for pre-treatments. This study was to inves...

  11. Retention characteristics of SNOS nonvolatile devices in a radiation environment

    SciTech Connect

    McWhorter, P.J.; Miller, S.L.; Dellin, T.A.; Axness, C.A.

    1987-12-01

    A quantitative model is developed that can accurately predict the threshold voltage shift, and hence data loss, in SNOS nonvolatile memory transistors over a wide range of dose rates. The model accounts for both the time dependent and radiation induced mechanisms leading to data loss. Experimental measurements are made to verify the validity and accuracy of the model under a variety of irradiation conditions.

  12. Study on the electromagnetic radiation characteristics of discharging excimer laser system

    NASA Astrophysics Data System (ADS)

    Zhao, Duliang; Liang, Xu; Fang, Xiaodong; Wang, Qingsheng

    2016-10-01

    Excimer laser in condition of high voltage, large current and fast discharge will produce strong electromagnetic pulse radiation and electromagnetic interference on the around electrical equipment. The research on characteristics and distribution of excimer laser electromagnetic radiation could provide important basis for electromagnetic shielding and suppressing electromagnetic interference, and further improving the electromagnetic compatibility of system. Firstly, electromagnetic radiation source is analyzed according to the working principle of excimer laser. The key test points of the electromagnetic radiation, hydrogen thyratron, main discharge circuit and laser outlet, are determined by the mechanical structure and the theory of electromagnetic radiation. Secondly, characteristics of electromagnetic field were tested using a near field probe on the key positions of the vertical direction at 20, 50, and 80 cm, respectively. The main radiation frequencies and the radiation field characteristics in the near field are obtained. The experimental results show that the main radiation frequencies distribute in 47, 65, and 130 MHz for electric field and the main radiation frequencies distribute in 34, 100, and 165 MHz for magnetic field. The intensity of electromagnetic field decreases rapidly with the increase of test distance. The higher the frequency increases, the faster the amplitude attenuate. Finally, several electromagnetic interference suppression measurement methods are proposed from the perspective of electromagnetic compatibility according to the test results.

  13. Computation of the radiation characteristics of a generalized phased array

    NASA Technical Reports Server (NTRS)

    Acosta, R. J.

    1986-01-01

    With the advent of monolithic microwave integrated circuit (MMIC) technology, the phased array has become a key component in the design of advanced antenna systems. Array-fed antennas are used extensively in today's multiple beam satellite antennas. A computer program based on a very efficient numerical technique for calculating the radiated power (Romberg integration), directivity, and radiation pattern of a phased array is described. The formulation developed is very general, and takes into account arbitrary element polarization, E- and H-plane element pattern, element location, and complex element excitation. For comparison purposes sample cases have been presented. Excellent agreement has been obtained for all cases. Also included are a user guide and a copy of the computer program.

  14. Characteristics of infrared photodetectors produced by radiation doping.

    NASA Technical Reports Server (NTRS)

    Gross, C.; Mattauch, R. J.; Viola, T. J., Jr.

    1973-01-01

    High-energy electrons (approximately 7 MeV) were used to radiation-dope extrinsic silicon. Both n- and p-type silicon photodetectors were fabricated using this doping technique. The 500 K blackbody responsivity, spectral response, and peak detectivity were determined for these devices. The peak detectivity values measured were 4.8 Gm Hz to the 1/2 power per W at 2.15 microns for 0.1-ohm-cm n-type devices and 3.7 Gm Hz to the 1/2 power per W at 40 microns for 10-ohm-cm p-type detectors. A comparison of the thermally generated background majority carrier concentration for radiation-doped and conventional impurity-doped detectors is made.

  15. Acoustic fatigue and sound transmission characteristics of a ram composite panel design

    NASA Technical Reports Server (NTRS)

    Cockburn, J. A.; Chang, K. Y.; Kao, G. C.

    1972-01-01

    An experimental study to determine the acoustic fatigue characteristics of a flat multi-layered structural panel is described. The test panel represented a proposed design for the outer skin of a research application module to be housed within the space shuttle orbiter vehicle. The test specimen was mounted in one wall of the Wyle 100,000 cu ft reverberation room and exposed to a broadband acoustic environment having an overall level of 145 db. The test panel was exposed to nine separate applications of the acoustic environment, each application consisting of 250 seconds duration. Upon completion of the ninth test run, the specimen was exposed to a simulated micrometeoroid impact near the panel center. One additional test run of 250 seconds duration was then performed to complete the overall simulation of 50 flight missions. The experimental results show that no significant fatigue damage occurred until the test specimen was exposed to a simulated micrometeoroid impact. The intermediate foam layer forming the core of the test specimen suffered considerable damage due to this impact, causing a marked variation in the dynamic characteristics of the overall test panel. During the final application of the acoustic environment, the strain and acceleration response spectra showed considerable variation from those spectra obtained prior to impact of the panel. Fatigue damage from acoustic loading however, was limited to partial de-bonding around the edges of the composite panel.

  16. A study on characteristics of EM radiation from stripline structure

    NASA Astrophysics Data System (ADS)

    Kayano, Yoshiki; Inoue, Hiroshi

    2011-10-01

    In recent years, effective methods for predicting and suppressing electromagnetic interference over a broad band are required. In this paper, we focus on the prediction of electromagnetic (EM) radiation from a stripline structure with a ground thin wire by an equivalent circuit model. First, frequency responses of common-mode (CM) current on the printed circuit board and EM radiation are studied with finite difference time domain modeling. Secondly, an equivalent circuit model for predicting CM current is proposed. The equivalent circuit model for prediction is based on the concepts of CM antenna impedance, distributed constant circuit, and electric coupling between the power plane and the thin ground wire. Good agreement between the predicted and full-wave analysis results indicates the validity of the proposed equivalent circuit model. The frequency response of EM radiation from the stripline structure can be identified using our proposed model. In addition, the equivalent circuit model provides enough flexibility for different geometric parameters and can be used to develop physical insights and design guidelines.

  17. Evaluation of Auditory Characteristics of Communications and Hearing Protection Systems (C&HPSs) Part 1 - Sound Attenuation to Low-Intensity Sounds

    DTIC Science & Technology

    2010-01-01

    reports and focuses on the sound attenuation obtained from three commercially available C&HPSs: Sennheiser SLC-110, Nacre QuietPro, and Silynx...QuietOps. Real-ear attenuation at threshold values were obtained for 12 listeners with each of the three systems. The results showed that the Nacre ...3  2.3.2  Nacre AS – QuietPro ...........................................................................................4  2.3.3  Silynx

  18. Radiation characteristics of electromagnetic eigenmodes at the corrugated interface of a left-handed material.

    PubMed

    Cuevas, Mauro; Depine, Ricardo A

    2009-08-28

    We study the radiation characteristics of electromagnetic surface waves at a periodically corrugated interface between a conventional and a negatively refracting (or left-handed) material. In this case, and contrary to the surface plasmon polariton in a metallic grating, surface plasmon polaritons may radiate on both sides of the rough interface along which they propagate. We find novel radiation regimes which provide an indirect demonstration of other unusual phenomena characteristic of electromagnetic wave propagation in left-handed materials, such as negative refraction or backward wave propagation.

  19. Characteristics of dual element ultrasonic transducers in the long pulse radiation mode

    NASA Astrophysics Data System (ADS)

    Kazakov, V. V.; Sanin, A. G.

    2017-01-01

    The frequency and transfer characteristics of dual element ultrasonic transducers are theoretically and experimentally investigated in the long pulse radiation mode for the case where one of the piezoelectric elements is connected to a control circuit in the form of an inductance coil or a resistor. For the controlled damper and controlled layer cases, the characteristic features of radiation as functions of the control circuit parameters are determined, as well as the conditions for an increase in ultrasonic wave radiation power. With certain conditions being satisfied, we demonstrate the possibility of amplitude modulation of the emitted ultrasonic wave by periodic switching of control circuit elements.

  20. Virtual Reality of Sound Generated from Vibrating Structures

    NASA Astrophysics Data System (ADS)

    KIM, S. J.; SONG, J. Y.

    2002-11-01

    The advancement of virtual reality (VR) technology in cyberspace is amazing, but its development is mainly concentrated on the visual part. In this paper, the development of VR technology to produce sound based on the exact physics is studied. Our main concern is on the sound generated from vibrating structures. This may be useful, for example, in apprehending sound field characteristics of an aircraft cabin in design stage. To calculate sound pressure from curved surface of a structure, a new integration scheme is developed in boundary element method. Several example problems are solved to confirm our integration scheme. The pressure distributions on a uniformly driven sphere and cylinders are computed and compared with analytic solutions, and radiation efficiency of a vibrating plate under one-dimensional flow is also calculated. Also, to realize sound through computer simulation, two concepts, "structure-oriented analysis" and "human-oriented analysis", are proposed. Using these concepts, virtual sound field of an aircraft cabin is created.

  1. Recognition of composition and of microphysical characteristics of aerosol clouds in multifrequency sounding

    NASA Astrophysics Data System (ADS)

    Bravy, Boris G.; Vasiliev, German K.; Agroskin, Vladimir Y.

    2002-02-01

    The recognition of composition and of microphysical characteristics of aerosol impurities is one of the most urgent tasks in monitoring of atmosphere. Some approaches to its solution are considered in the work. At first stage we were limited to five substances: fine-dispersion water and dust as background aerosol components of atmosphere; coarse- dispersion tributilamin, turbine oil and petroleum as possible impurities. Tributilamin was chosen as spectral analog of V gases. The modeling of input spectra and the recognition were carried out on 12 discrete lines in 2.9 - 4 micrometers spectral rage. As is well known, in this range the considered impurities have the pronounced spectral dependences of aerosol backscattering, the so-called spectral resonances. Spectra of aerosol backscattering for these substances were calculated with Mie theory. We applied evolutionary algorithm (genetic algorithm) and also more traditional optimization methods, namely gradient descent method, for recognition procedure. The comparative analysis of the mentioned methods was done; the concrete results of recognition and the dependence of recognition efficiency on the number of wavelength channels and on the accuracy of spectrum recording are given.

  2. Simulations of the loading and radiated sound of airfoils and wings in unsteady flow using computational aeroacoustics and parallel computers

    NASA Astrophysics Data System (ADS)

    Lockard, David Patrick

    This thesis makes contributions towards the use of computational aeroacoustics (CAA) as a tool for noise analysis. CAA uses numerical methods to simulate acoustic phenomena. CAA algorithms have been shown to reproduce wave propagation much better than traditional computational fluid dynamics (CFD) methods. In the current approach, a finite-difference, time-domain algorithm is used to simulate unsteady, compressible flows. Dispersion-relation-preserving methodology is used to extend the range of frequencies that can be represented properly by the scheme. Since CAA algorithms are relatively inefficient at obtaining a steady-state solution, multigrid methods are applied to accelerate the convergence. All of the calculations are performed on parallel computers. Excellent speedup ratios are obtained for the explicit, time-stepping algorithm used in this research. A common problem in the area of broadband noise is the prediction of the acoustic field generated by a vortical gust impinging on a solid body. The problem is modeled initially in two-dimensions by a flat plate experiencing a uniform mean flow with a sinusoidal, vertical velocity perturbation. Good agreement is obtained with results from semi-analytic methods for several gust frequencies. Then, a cascade of plates is used to simulate a turbomachinery blade row. A new approach is used to impose the vortical disturbance inside the computational domain rather than imposing it at the computational boundary. The influence of the mean flow on the radiated noise is examined by considering NACA0012 and RAE2822 airfoils. After a steady-state is obtained from the multigrid method, the un-steady simulation is used to model the vortical gust's interaction with the airfoil. The mean loading on the airfoil is shown to have a significant effect on the directivity of the sound with the strongest influence observed for high frequencies. Camber is shown to have a similar effect as the angle of attack. A three-dimensional problem

  3. HIRS-AMTS satellite sounding system test - Theoretical and empirical vertical resolving power. [High resolution Infrared Radiation Sounder - Advanced Moisture and Temperature Sounder

    NASA Technical Reports Server (NTRS)

    Thompson, O. E.

    1982-01-01

    The present investigation is concerned with the vertical resolving power of satellite-borne temperature sounding instruments. Information is presented on the capabilities of the High Resolution Infrared Radiation Sounder (HIRS) and a proposed sounding instrument called the Advanced Moisture and Temperature Sounder (AMTS). Two quite different methods for assessing the vertical resolving power of satellite sounders are discussed. The first is the theoretical method of Conrath (1972) which was patterned after the work of Backus and Gilbert (1968) The Backus-Gilbert-Conrath (BGC) approach includes a formalism for deriving a retrieval algorithm for optimizing the vertical resolving power. However, a retrieval algorithm constructed in the BGC optimal fashion is not necessarily optimal as far as actual temperature retrievals are concerned. Thus, an independent criterion for vertical resolving power is discussed. The criterion is based on actual retrievals of signal structure in the temperature field.

  4. Measuring space radiation impact on the characteristics of optical glasses; measurement results and recommendations from testing a selected set of materials

    NASA Astrophysics Data System (ADS)

    Fruit, Michel; Gusarov, Andrei I.; Doyle, Dominic B.

    2002-09-01

    Radiation sensitivity of glass is a general concern for the designer of Space optical instruments. ASTRIUM, in cooperation with SCK-CEN, has conducted a study (under ESA sponsorship) to define the approach for the gathering of a comprehensive database to quantify these effects through the use of linear sensitivity coefficients (called "Dose Coefficients"). These "Dose coefficients" cover not only transmittance but also other characteristics such as refractive index. After having recalled the basics of the proposed approach, results of the first irradiation tests which have been run on a selected set of classical glasses nd their Radiation hardened Cerium doped analogs (including BK7, K5, LaK9 and other Schott glasses) will be discussed. PRotons and gamma radiation have been performed with the aim to demonstrate equivalence, thus allowing to further considering only gamma radiation for an extensive testing of available glasses. Relaxation impacts on some months period have been tentatively analyzed. All these measurements have been processed and the modeling approach of the radiations impacts has been derived, as shown in the publication from A. Gusarov at this conference. This will constitute the grounds for the building of a comprehensive "Dose Coefficients" data base, as expressed in the publication from D. Doyle also at this conference. From this, recommendations for a sound characterization of radiation impacts on refractive optical materials have been established and are the subject of this publication.

  5. Radiation characteristics and turbulence-radiation interactions in sooting turbulent jet flames

    NASA Astrophysics Data System (ADS)

    HASH(0x3416010), R. S.; HASH(0x33f0c38), M. F.; Haworth, D. C.

    2010-03-01

    A comprehensive modeling strategy including detailed chemistry, soot and radiation models coupled with state-of-the-art closures for turbulence-chemistry interactions and turbulence-radiation interactions is applied to various luminous turbulent jet flames. Six turbulent jet flames are simulated with Reynolds numbers varying from 6700 to 15,000, two fuel types (pure ethylene, 90% methane-10% ethylene blend) and different oxygen concentrations in the oxidizer stream (from 21% O2 to 55% O2). All simulations are carried out with a single set of physical and numerical parameters (model constants). A Lagrangian particle Monte Carlo method is used to solve a modeled joint probability density function (PDF) transport equation, which allows accurate closure for turbulence-chemistry interactions including nonlinear soot subprocesses. Radiation is calculated using a particle-based photon Monte Carlo method that is coupled with the PDF method to accurately account for both emission and absorption turbulence-radiation interactions (TRI). Line-by-line databases are used for accurate spectral radiative properties of CO2 and H2O; soot radiative properties also are modeled as nongray. For the flames that have been investigated, soot emission can be almost 45% of the total emission, even when the peak soot volume fraction is of the order of a few parts-per-million (ppm) and up to 99% of soot emission can escape the domain without re-absorption. Turbulence-radiation interactions have a strong effect on the net radiative heat loss from these sooting flames. For a given temperature, species and soot distribution, TRI increases emission from the flames by 30-60%, and the net heat loss from the flame increases by 45-90% when accounting for TRI. This is higher than the corresponding increase in radiative heat loss due to TRI in nonsooting flames. Absorption TRI was found to be negligible in these laboratory-scale sooting flames with soot levels on the order of a few ppm, but may be

  6. SU-E-T-159: Characteristics of Fiber-Optic Radiation Sensor for Proton Therapeutic Beam

    SciTech Connect

    Son, J; Kim, M; Hwang, U; Park, J; Lim, Y; Lee, S; Shin, D; Park, S; Yoon, M

    2015-06-15

    Purpose: A fiber-optic radiation sensor using Cerenkov radiation has been widely studied for use as a dosimeter for proton therapeutic beam. Although the fiber-optic radiation sensor has already been investigated for proton therapeutic, it has been examined relatively little work for clinical therapeutic proton beams. In this study, we evaluated characteristics of a fiber-optic radiation sensor for clinical therapeutic proton beams. We experimentally evaluated dose-rate dependence, dose response and energy dependence for the proton beam. Methods: A fiber-optic radiation sensor was placed in a water phantom. Beams with energies of low, middle and high were used in the passively-scattered proton therapeutic beam at the National Cancer Center in Korea. The sensor consists of two plastic optical fibers (POF). A reference POF and 2 cm longer POF were used to utilize the subtraction method for having sensitive volume. Each POF is optically coupled to the Multi-Anode Photo Multiplier Tube (MAPMT) and the MAPMT signals are processed using National Instruments Data Acquisition System (NI-DAQ). We were investigated dosimetric properties including dose-rate dependence, dose response and energy dependence. Results: We have successfully evaluated characteristics of a fiber optic radiation sensor using Cerenkov radiation. The fiber-optic radiation sensor showed the dose response linearity and low energy dependence. In addition, as the dose-rate was increased, Cerenkov radiation increased linearly. Conclusion: We evaluated the basic characteristics of the fiber optic radiation sensor, the dosimetry tool, to raise the quality of proton therapy. Based on the research, we developed a real time dosimetry system of the optic fiber to confirm the real time beam position and energy for therapeutic proton pencil beam.

  7. Helicopter flight noise tests about the influence of rotor-rotational and forward speed changes on the characteristics of the immitted sound

    NASA Astrophysics Data System (ADS)

    Heller, H. H.; Splettstoesser, W.

    1983-04-01

    The noise characteristics of three modern medium-weight twin-turbo engine helicopters were determined using flight tests which collected straight-level overflight noise data. The data were analyzed spectrally and in terms of several commonly applied noise-metrics, such as the maximum. A-weighted Sound Pressure Level L sub A and the maximum Overall Sound Pressure Level OASPL. The results indicate the decisive effect of the advancing blade tip Mach-number on the emitted sound, which shows the growing influence of high-speed impulsive noise components on the noise signature at blade Mach-numbers beyond approximately 0.8. It is found that both the maximum tone-corrected and the Effective Perceived Noise Level observed on the ground for a helicopter in horizontal overflight depend strongly on the forward flight and the main rotor rotational speed.

  8. Parametric study of flame radiation characteristics of a tubular-can combustor

    NASA Technical Reports Server (NTRS)

    Humenik, F. M.; Claus, R. W.; Neely, G. M.

    1983-01-01

    A series of combustor tests were conducted with a tubular-can combustor to study flame radiation characteristics and effects with parametric variations in combustor operating conditions. Two alternate combustor assemblies using a different fuel nozzle were compared. Spectral and total radiation detectors were positioned at three stations along the length of the combustor can. Data were obtained for a range of pressures from 0.34 to 2.07 MPa (50 to 300 psia), inlet temperatures from 533 to 700K (500 to 800 F), for Jet A (13.9 deg hydrogen) and ERBS (12.9% hydrogen) fuels, and with fuel-air ratios nominally from 0.008 to 0.021. Spectral radiation data, total radiant heat flux data, and liner temperature data are presented to illustrate the flame radiation characteristics and effects in the primary, secondary, and tertiary combustion zones.

  9. Spectral characteristics of VUV radiation emitted by a laser plume

    SciTech Connect

    Khater, Mohamed A.

    2013-12-16

    We study some experimental parameters and conditions of laser-generated plasma plumes using time-integrated, spatially resolved emission spectroscopy in the VUV range. The influences of the laser focusing lens type, laser wavelength, as well as laser pulse energy on the emission characteristics of the laser plasmas are investigated. The aim of the work is to improve the detection capability of the laser-induced plasma spectroscopy (LIPS) technique. The results obtained demonstrate a set of optimum conditions for maximum spectral line intensities and signal-to-background ratios of laser-produced plasmas in the VUV regime.

  10. Distributed Seismic Moment Fault Model, Spectral Characteristics and Radiation Patterns

    NASA Astrophysics Data System (ADS)

    Shani-Kadmiel, Shahar; Tsesarsky, Michael; Gvirtzman, Zohar

    2014-05-01

    We implement a Distributed Seismic Moment (DSM) fault model, a physics-based representation of an earthquake source based on a skewed-Gaussian slip distribution over an elliptical rupture patch, for the purpose of forward modeling of seismic-wave propagation in 3-D heterogeneous medium. The elliptical rupture patch is described by 13 parameters: location (3), dimensions of the patch (2), patch orientation (1), focal mechanism (3), nucleation point (2), peak slip (1), rupture velocity (1). A node based second order finite difference approach is used to solve the seismic-wave equations in displacement formulation (WPP, Nilsson et al., 2007). Results of our DSM fault model are compared with three commonly used fault models: Point Source Model (PSM), Haskell's fault Model (HM), and HM with Radial (HMR) rupture propagation. Spectral features of the waveforms and radiation patterns from these four models are investigated. The DSM fault model best incorporates the simplicity and symmetry of the PSM with the directivity effects of the HMR while satisfying the physical requirements, i.e., smooth transition from peak slip at the nucleation point to zero at the rupture patch border. The implementation of the DSM in seismic-wave propagation forward models comes at negligible computational cost. Reference: Nilsson, S., Petersson, N. A., Sjogreen, B., and Kreiss, H.-O. (2007). Stable Difference Approximations for the Elastic Wave Equation in Second Order Formulation. SIAM Journal on Numerical Analysis, 45(5), 1902-1936.

  11. Effects of finite ground plane on the radiation characteristics of a circular patch antenna

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Arun K.

    1990-02-01

    An analytical technique to determine the effects of finite ground plane on the radiation characteristics of a microstrip antenna is presented. The induced currents on the ground plane and on the upper surface of the patch are determined from the discontinuity of the near field produced by the equivalent magnetic current source on the physical aperture of the patch. The radiated fields contributed by the induced current on the ground plane and the equivalent sources on the physical aperture yield the radiation pattern of the antenna. Radiation patterns of the circular patch with finite ground plane size are computed and compared with the experimental data, and the agreement is found to be good. The radiation pattern, directive gain, and input impedance are found to vary widely with the ground plane size.

  12. Characteristics of Quantum Radiation of Slowly Varying Nonstationary Kerr-Newman Black Holes

    NASA Astrophysics Data System (ADS)

    Hua, Jia-Chen; Huang, Yong-Chang

    Quantum radiative characteristics of slowly varying nonstationary Kerr-Newman black holes are investigated by using the method of generalized tortoise coordinate transformation. It is shown that the temperature and the shape of the event horizon of this kind of black holes depend on the time and the angle. Further, we reveal a previously ignored relationship between thermal radiation and nonthermal radiation, which is that the chemical potential in the thermal radiation spectrum is equal to the highest energy of the negative energy state of particles in nonthermal radiation for slowly varying nonstationary Kerr-Newman black holes. Also, we show that the deduced general results can be degenerated to the known conclusion of stationary Kerr-Newman black holes.

  13. The influence of a pressure wavepacket's characteristics on its acoustic radiation.

    PubMed

    Serré, R; Robinet, J-C; Margnat, F

    2015-06-01

    Noise generation by flows is modeled using a pressure wavepacket to excite the acoustic medium via a boundary condition of the homogeneous wave equation. The pressure wavepacket is a generic representation of the flow unsteadiness, and is characterized by a space envelope of pseudo-Gaussian shape and by a subsonic phase velocity. The space modulation yields energy in the supersonic range of the wavenumber spectrum, which is directly responsible for sound radiation and directivity. The influence of the envelope's shape on the noise emission is studied analytically and numerically, using an acoustic efficiency defined as the ratio of the acoustic power generated by the wavepacket to that involved in the modeled flow. The methodology is also extended to the case of acoustic propagation in a uniformly moving medium, broadening possibilities toward practical flows where organized structures play a major role, such as co-flow around cruising jet, cavity, and turbulent boundary layer flows. The results of the acoustic efficiency show significant sound pressure levels, especially for asymmetric wavepackets radiating in a moving medium.

  14. Estimation of radiation characteristics of circular microstrip antenna in weakly ionized plasma medium

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Kumar, Manoj; Kumar, Pramod

    2010-02-01

    The paper deals with the analysis of circular microstrip antenna in weakly ionized plasma medium using the concept of vector magnetic potential, the expression for electric field and magnetic field has been obtained. Attempt has also been made to obtain the radiation resistance, trans-conductance and power radiated from the antenna. Particular emphasis has been given to estimate the effects of weakly ionized plasma medium on the directivity of antenna. It has been found that radiation characteristics and directivity of antenna affected sincerely by the weakly ionized plasma medium.

  15. On microscopic theory of radiative nuclear reaction characteristics

    NASA Astrophysics Data System (ADS)

    Kamerdzhiev, S. P.; Achakovskiy, O. I.; Avdeenkov, A. V.; Goriely, S.

    2016-07-01

    A survey of some results in the modern microscopic theory of properties of nuclear reactions with gamma rays is given. First of all, we discuss the impact of Phonon Coupling (PC) on the Photon Strength Function (PSF) because it represents the most natural physical source of additional strength found for Sn isotopes in recent experiments that could not be explained within the standard HFB + QRPA approach. The self-consistent version of the Extended Theory of Finite Fermi Systems in the Quasiparticle Time Blocking Approximation is applied. It uses the HFB mean field and includes both the QRPA and PC effects on the basis of the SLy4 Skyrme force. With our microscopic E1 PSFs, the following properties have been calculated for many stable and unstable even-even semi-magic Sn and Ni isotopes as well as for double-magic 132Sn and 208Pb using the reaction codes EMPIRE and TALYS with several Nuclear Level Density (NLD) models: (1) the neutron capture cross sections; (2) the corresponding neutron capture gamma spectra; (3) the average radiative widths of neutron resonances. In all the properties considered, the PC contribution turned out to be significant, as compared with the standard QRPA one, and necessary to explain the available experimental data. The results with the phenomenological so-called generalized superfluid NLD model turned out to be worse, on the whole, than those obtained with the microscopic HFB + combinatorial NLD model. The very topical question about the M1 resonance contribution to PSFs is also discussed. Finally, we also discuss the modern microscopic NLD models based on the self-consistent HFB method and show their relevance to explain the experimental data as compared with the phenomenological models. The use of these self-consistent microscopic approaches is of particular relevance for nuclear astrophysics, but also for the study of double-magic nuclei.

  16. On microscopic theory of radiative nuclear reaction characteristics

    SciTech Connect

    Kamerdzhiev, S. P.; Achakovskiy, O. I. Avdeenkov, A. V.; Goriely, S.

    2016-07-15

    A survey of some results in the modern microscopic theory of properties of nuclear reactions with gamma rays is given. First of all, we discuss the impact of Phonon Coupling (PC) on the Photon Strength Function (PSF) because it represents the most natural physical source of additional strength found for Sn isotopes in recent experiments that could not be explained within the standard HFB + QRPA approach. The self-consistent version of the Extended Theory of Finite Fermi Systems in the Quasiparticle Time Blocking Approximation is applied. It uses the HFB mean field and includes both the QRPA and PC effects on the basis of the SLy4 Skyrme force. With our microscopic E1 PSFs, the following properties have been calculated for many stable and unstable even–even semi-magic Sn and Ni isotopes as well as for double-magic {sup 132}Sn and {sup 208}Pb using the reaction codes EMPIRE and TALYS with several Nuclear Level Density (NLD) models: (1) the neutron capture cross sections; (2) the corresponding neutron capture gamma spectra; (3) the average radiative widths of neutron resonances. In all the properties considered, the PC contribution turned out to be significant, as compared with the standard QRPA one, and necessary to explain the available experimental data. The results with the phenomenological so-called generalized superfluid NLD model turned out to be worse, on the whole, than those obtained with the microscopic HFB + combinatorial NLD model. The very topical question about the M1 resonance contribution to PSFs is also discussed.Finally, we also discuss the modern microscopic NLD models based on the self-consistent HFB method and show their relevance to explain the experimental data as compared with the phenomenological models. The use of these self-consistent microscopic approaches is of particular relevance for nuclear astrophysics, but also for the study of double-magic nuclei.

  17. Characteristics of surface solar radiation in Sino-Singapore Eco-city

    NASA Astrophysics Data System (ADS)

    Hou, M.; Huang, H.; Shen, Y. F.; Yao, W.; Wang, G. S.; Bu, Q. J.; Shan, X. L.; Chang, C. H.

    2017-01-01

    Using solar observation and meteorological data of the Sino-Singapore Tianjin Eco-city from August 14th 2014 to August 12th 2015, characteristics of solar radiation of the eco-city and characteristics of solar radiation on a tilted surface under different weather conditions were analyzed and assessed. And the accuracy and error sources of isotropic and anisotropic calculation model for solar radiation on a tilted surface were studied. The results show that observed radiation on a horizontal and tilted surface is quite different at monthly, seasonal and annual time scales, so the estimated photovoltaic power generation based on the solar radiation on a horizontal surface is not accurate. Diurnal cycle of solar radiation is affected by different weather conditions and the power stations need to adjust generation strategies according to weather conditions. Accuracy of the two kinds of tilted radiation calculation models is similar and the overall calculation effect is reasonable. The uncertainty of the direct portion segment calculation function is the main cause of calculated errors.

  18. SYNCHROTRON RADIATION, FREE ELECTRON LASER, APPLICATION OF NUCLEAR TECHNOLOGY, ETC.: Study on the characteristics of linac based THz light source

    NASA Astrophysics Data System (ADS)

    Zhu, Xiong-Wei; Wang, Shu-Hong; Chen, Sen-Yu

    2009-10-01

    There are many methods based on linac for THz radiation production. As one of the options for the Beijing Advanced Light, an ERL test facility is proposed for THz radiation. In this test facility, there are 4 kinds of methods to produce THz radiation: coherent synchrotron radiation (CSR), synchrotron radiation (SR), low gain FEL oscillator, and high gain SASE FEL. In this paper, we study the characteristics of the 4 kinds of THz light sources.

  19. Research on infrared radiation characteristics of Pyromark1200 high-temperature coating

    NASA Astrophysics Data System (ADS)

    Song, Xuyao; Huan, Kewei; Dong, Wei; Wang, Jinghui; Zang, Yanzhe; Shi, Xiaoguang

    2014-11-01

    Pyromark 1200 (Tempil Co, USA), which is a type of high-temperature high-emissivity coating, is silicon-based with good thermal radiation performance. Its stably working condition is at the temperature range 589~922 K thus a wide range of applications in industrial, scientific research, aviation, aerospace and other fields. Infrared emissivity is one of the most important factors in infrared radiation characteristics. Data on infrared spectral emissivity of Pyromark 1200 is in shortage, as well as the reports on its infrared radiation characteristics affected by its spray painting process, microstructure and thermal process. The results of this research show that: (1) The coating film critical thickness on the metal base is 10μm according to comparison among different types of spray painting process, coating film thickness, microstructure, which would influence the infrared radiation characteristics of Pyromark 1200 coating. The infrared spectral emissivity will attenuate when the coating film thickness is lower or much higher than that. (2) Through measurements, the normal infrared radiation characteristics is analyzed within the range at the temperature range 573~873 K under normal atmospheric conditions, and the total infrared spectral emissivity of Pyromark 1200 coating is higher than 0.93 in the 3~14 μm wavelength range. (3) The result of 72-hour aging test at the temperature 673 K which studied the effect of thermal processes on the infrared radiation characteristics of the coating shows that the infrared spectral emissivity variation range is approximately 0.01 indicating that Pyromark 1200 coating is with good stability. Compared with Nextel Velvet Coating (N-V-C) which is widely used in optics field, Pyromark 1200 high-temperature coating has a higher applicable temperature and is more suitable for spraying on the material surface which is in long-term operation under high temperature work conditions and requires high infrared spectral emissivity.

  20. Relationship between in situ sound velocity and granular characteristics of seafloor sediments in the Qingdao offshore region

    NASA Astrophysics Data System (ADS)

    Zhang, Yanxin; Guo, Changsheng; Wang, Jingqiang; Hou, Zhengyu; Chen, Wenjing

    2017-05-01

    The sound velocity of seafloor sediments from shallow seas can provide important information for harbor design, and ocean and seacoast engineering projects. In this study, in situ measurements were used to obtain accurate sediment sound velocities at 45 stations offshore of Qingdao. The relationships between the sound velocity and granular properties of the seafloor sediments were analyzed. Sound velocity showed an increase with the sand content, sand-clay ratio, and sorting coefficient; and a nonlinear decreasing trend with increasing mean grain size and clay content. We plotted a sound velocity distribution map, which shows that the sound velocity was closely related to the geological environment. Previous empirical equations suggested by Hamilton, Anderson, and Liu were used to calculate the velocity with grain size. A comparison between the measured and calculated velocities indicates that the empirical equations have territorial limitations, and extensive data are essential to establish global empirical equations. Future work includes the calibration of the laboratory acoustic measurements with an in situ technique.

  1. Nonlinear acoustics in cicada mating calls enhance sound propagation.

    PubMed

    Hughes, Derke R; Nuttall, Albert H; Katz, Richard A; Carter, G Clifford

    2009-02-01

    An analysis of cicada mating calls, measured in field experiments, indicates that the very high levels of acoustic energy radiated by this relatively small insect are mainly attributed to the nonlinear characteristics of the signal. The cicada emits one of the loudest sounds in all of the insect population with a sound production system occupying a physical space typically less than 3 cc. The sounds made by tymbals are amplified by the hollow abdomen, functioning as a tuned resonator, but models of the signal based solely on linear techniques do not fully account for a sound radiation capability that is so disproportionate to the insect's size. The nonlinear behavior of the cicada signal is demonstrated by combining the mutual information and surrogate data techniques; the results obtained indicate decorrelation when the phase-randomized and non-phase-randomized data separate. The Volterra expansion technique is used to fit the nonlinearity in the insect's call. The second-order Volterra estimate provides further evidence that the cicada mating calls are dominated by nonlinear characteristics and also suggests that the medium contributes to the cicada's efficient sound propagation. Application of the same principles has the potential to improve radiated sound levels for sonar applications.

  2. Fundamental plasma emission involving ion sound waves

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1987-01-01

    The theory for fundamental plasma emission by the three-wave processes L + or - S to T (where L, S and T denote Langmuir, ion sound and transverse waves, respectively) is developed. Kinematic constraints on the characteristics and growth lengths of waves participating in the wave processes are identified. In addition the rates, path-integrated wave temperatures, and limits on the brightness temperature of the radiation are derived.

  3. Fundamental plasma emission involving ion sound waves

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1987-01-01

    The theory for fundamental plasma emission by the three-wave processes L + or - S to T (where L, S and T denote Langmuir, ion sound and transverse waves, respectively) is developed. Kinematic constraints on the characteristics and growth lengths of waves participating in the wave processes are identified. In addition the rates, path-integrated wave temperatures, and limits on the brightness temperature of the radiation are derived.

  4. Evaluation of moving-coil loudspeaker and passive radiator parameters using normal-incidence sound transmission measurements: theoretical developments.

    PubMed

    Leishman, Timothy W; Anderson, Brian E

    2013-07-01

    The parameters of moving-coil loudspeaker drivers are typically determined using direct electrical excitation and measurement. However, as electro-mechano-acoustical devices, their parameters should also follow from suitable mechanical or acoustical evaluations. This paper presents the theory of an acoustical method of excitation and measurement using normal-incidence sound transmission through a baffled driver as a plane-wave tube partition. Analogous circuits enable key parameters to be extracted from measurement results in terms of open and closed-circuit driver conditions. Associated tools are presented that facilitate adjacent field decompositions and derivations of sound transmission coefficients (in terms of driver parameters) directly from the circuits. The paper also clarifies the impact of nonanechoic receiving tube terminations and the specific benefits of downstream field decompositions.

  5. Radiation characteristics and generation of higher-order modes of circular microstrip antennas

    NASA Astrophysics Data System (ADS)

    Kumar, G.; Shafai, L.

    1984-08-01

    The characteristics of higher-order modes of circular microstrip antennas, such as radiation pattern, directivity, bandwidth, efficiency, and location of the feedpoint to match a 50 ohm line, are studied, and the effects of varying the substrate parameters are investigated. A multifeed technique to generate any particular mode is also presented.

  6. Moisture removal characteristics of thin layer rough rice under sequenced infrared radiation heating and cooling

    USDA-ARS?s Scientific Manuscript database

    Rice drying with infrared (IR) radiation has been investigated during recent years and showed promising potential with improved quality and energy efficiency. The objective of this study was to further investigate the moisture removal characteristics of thin layer rough rice heated by IR and cooled ...

  7. Drying characteristics and quality of rough rice under infrared radiation heating

    USDA-ARS?s Scientific Manuscript database

    Infrared (IR) radiation heating could provide high heating rate and rapid moisture removal for rough rice drying. The objective of this research was to investigate the effect of the drying bed thickness on drying characteristics and quality of rough rice subjected to IR heating. Samples of freshly ...

  8. Study on electromagnetic radiation and mechanical characteristics of coal during an SHPB test

    NASA Astrophysics Data System (ADS)

    Chengwu, Li; Qifei, Wang; Pingyang, Lyu

    2016-06-01

    Dynamic loads provided by a Split Hopkinson pressure bar are applied in the impact failure experiment on coal with an impact velocity of 4.174-17.652 m s-1. The mechanical property characteristics of coal and an electromagnetic radiation signal can be detected and measured during the experiment. The variation of coal stress, strain, incident energy, dissipated energy and other mechanical parameters are analyzed by the unidimensional stress wave theory. It suggests that with an increase of the impact velocity, the mechanical parameters and electromagnetic radiation increased significantly and the dissipated energy of the coal sample has a high discrete growing trend during the failure process of coal impact. Combined with the received energy of the electromagnetic radiation signal, the relationship between these mechanical parameters and electromagnetic radiation during the failure process of coal burst could be analyzed by the grey correlation model. The results show that the descending order of the gray correlation degree between the mechanical characteristics and electromagnetic radiation energy are impact velocity, maximum stress, the average stress, incident energy, the average strain, maximum strain, the average strain rate and dissipation energy. Due to the correlation degree, the impact velocity and incident energy are relatively large, and the main factor affecting the electromagnetic radiation energy of coal is the energy magnitude. While the relationship between extreme stress and the radiation energy change trend is closed, the stress state of coal has a greater impact on electromagnetic radiation than the strain and destruction which can deepen the research of the coal-rock dynamic disaster electromagnetic monitoring technique.

  9. Studying characteristics of a fine layered structure of the lower troposphere on the basis of acoustic pulse sounding

    NASA Astrophysics Data System (ADS)

    Chunchuzov, I. P.; Perepelkin, V. G.; Popov, O. E.; Kulichkov, S. N.; Vardanyan, A. A.; Ayvazyan, G. Y.; Khachikyan, Kh. Z.

    2017-05-01

    Results of acoustic sounding of the lower troposphere with the aid of detonation generators of acoustic pulses are given. This sounding method is based on a partial reflection of acoustic pulses with shock fronts from vertical wind-velocity and temperature gradients continuously varying with height in the troposphere and on the penetration of reflected signals into the region of acoustic shadow. Experiments on tropospheric sounding were carried out on the ground of the Barva Innovation Scientific and Technical Center (Talin, Armenia) in September 2015. In these experiments, an antihail acoustic system was first used as a generator of acoustic pulses. Experimental results have been compared with data obtained earlier in similar experiments carried out in the vicinity of Zvenigorod with the use of a special detonation generator of acoustic pulses. Due to the high resolution (in height) of the sounding method, which reaches 1 m in the stably stratified lower troposphere within a height range of 250-600 m, the vertical profiles of layered effective sound speed inhomogeneities with vertical scales from a few to a few tens of meters have been retrieved. The influence of these fluctuations on the form and amplitude of acoustic signals at a long distance from their pulsed source has been studied.

  10. [Spectral characteristics of vowel-like sounds in children of the first year of life and speech development].

    PubMed

    Andreeva, N G; Samokishchuk, A P; Kulikov, G A

    2003-11-01

    To study the continuity in speech development, an investigation of vowel-like sounds recorded in the course of longitudinal research of speech formation was carried out in 12 infants beginning with the first month up to 12 months of their life. It was revealed that features ensuring separation of vowel-like sounds are specific by their amplitude relation and frequency location of the most expressed spectral maxima, including the maxima corresponding to the fundamental frequency. As fundamental frequency increased, the vowel-like sounds [a], [u], [i] began to exhibit specific changes of the amplitude ratios of the spectral maxima. It was established that peculiarities of frequency positions of spectral maxima and relations of their amplitudes may be the very features on the bases of which children compare their own vowel-like sounds to the vowels of the adults in sound imitation. These findings and literature data corroborated the opinion of continuity in speech development, beginning with the early preverbal vocalizations.

  11. A new concept in underwater high fidelity low frequency sound generation

    NASA Astrophysics Data System (ADS)

    Fonseca, Paulo J.; Alves, J. Maia

    2012-05-01

    This article reports on a new type of system for high fidelity underwater sound generation (patent pending PT105474). The system includes an underwater sound actuator and the corresponding electronic driver. The sound is generated by a rigid plate that is actuated (both for positioning/dumping and excitation) using purely electromagnetic forces, thus, avoiding the use of any elastic membrane. Since there is no compressible air inside the device, which is flooded by water, the operation of this device is independent from depth, broadening its applications to any water pressure. Characterization of the frequency response, the radiation characteristics, and the dynamic range of this new device for underwater sound generation is presented.

  12. A new concept in underwater high fidelity low frequency sound generation.

    PubMed

    Fonseca, Paulo J; Alves, J Maia

    2012-05-01

    This article reports on a new type of system for high fidelity underwater sound generation (patent pending PT105474). The system includes an underwater sound actuator and the corresponding electronic driver. The sound is generated by a rigid plate that is actuated (both for positioning/dumping and excitation) using purely electromagnetic forces, thus, avoiding the use of any elastic membrane. Since there is no compressible air inside the device, which is flooded by water, the operation of this device is independent from depth, broadening its applications to any water pressure. Characterization of the frequency response, the radiation characteristics, and the dynamic range of this new device for underwater sound generation is presented.

  13. Mesenchymal Stem Cells Retain Their Defining Stem Cell Characteristics After Exposure to Ionizing Radiation

    SciTech Connect

    Nicolay, Nils H.; Sommer, Eva; Lopez, Ramon; Wirkner, Ute; Trinh, Thuy; Sisombath, Sonevisay; Debus, Jürgen; Ho, Anthony D.; Saffrich, Rainer; Huber, Peter E.

    2013-12-01

    Purpose: Mesenchymal stem cells (MSCs) have the ability to migrate to lesion sites and undergo differentiation into functional tissues. Although this function may be important for tissue regeneration after radiation therapy, the influence of ionizing radiation (IR) on cellular survival and the functional aspects of differentiation and stem cell characteristics of MSCs have remained largely unknown. Methods and Materials: Radiation sensitivity of human primary MSCs from healthy volunteers and primary human fibroblast cells was examined, and cellular morphology, cell cycle effects, apoptosis, and differentiation potential after exposure to IR were assessed. Stem cell gene expression patterns after exposure to IR were studied using gene arrays. Results: MSCs were not more radiosensitive than human primary fibroblasts, whereas there were considerable differences regarding radiation sensitivity within individual MSCs. Cellular morphology, cytoskeletal architecture, and cell motility were not markedly altered by IR. Even after high radiation doses up to 10 Gy, MSCs maintained their differentiation potential. Compared to primary fibroblast cells, MSCs did not show an increase in irradiation-induced apoptosis. Gene expression analyses revealed an upregulation of various genes involved in DNA damage response and DNA repair, but expression of established MSC surface markers appeared only marginally influenced by IR. Conclusions: These data suggest that human MSCs are not more radiosensitive than differentiated primary fibroblasts. In addition, upon photon irradiation, MSCs were able to retain their defining stem cell characteristics both on a functional level and regarding stem cell marker expression.

  14. Radiative characteristics of Clouds embedded in and occurring beneath Smoke analyzed using airborne multiangular measurements

    NASA Astrophysics Data System (ADS)

    Gautam, R.; Gatebe, C. K.; Varnai, T.; Singh, M.; Poudyal, R.

    2016-12-01

    Clouds in the presence of absorbing aerosols results in their apparent darkening, observed at the Top of Atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the warming/darkening effect and potential impacts on regional climate via semidirect and thermodynamic pathways, above-cloud aerosols have been characterized in recent satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, retrievals of aerosol and cloud properties are affected by large uncertainties when they co-occur. In this study, we present radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer (CAR), collected during the ARCTAS and SAFARI campaigns in Canada and southern Africa, respectively. Scattered cumulus clouds embedded in dense smoke over land (Canada) as well as smoke aerosols above marine stratocumulus clouds (southeast Atlantic) show characteristic spectral gradient across the UV-visible-NIR spectrum using CAR data. In general, clouds in the presence of smoke are impacted by absorbing aerosol-induced darkening at the shorter wavelengths (e.g. UV and blue bands), as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. The circular and spiral flights not only allowed the complete characterization of the angular distribution of smoke-cloud radiative interactions, but also provided the vertical distribution of smoke and clouds. Overall, the observational-based smoke-cloud radiative interactions were found to be physically consistent with theoretical 1D and 3D radiation calculations. These airborne observations are also complemented by satellite data from MODIS reflectances and CERES shortwave fluxes, providing a synergistic radiative impact assessment of clouds in the presence of smoke. http://car.gsfc.nasa.gov/

  15. The Use of Compressive Sensing to Reconstruct Radiation Characteristics of Wide-Band Antennas from Sparse Measurements

    DTIC Science & Technology

    2015-06-01

    Wide- Band Antennas from Sparse Measurements by Patrick Debroux and Berenice Verdin Approved for public release...Army Research Laboratory The Use of Compressive Sensing to Reconstruct Radiation Characteristics of Wide- Band Antennas from Sparse Measurements ...Compressive Sensing to Reconstruct Radiation Characteristics of Wide-Band Antennas from Sparse Measurements 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  16. Sound Symbolism.

    ERIC Educational Resources Information Center

    Hinton, Leanne, Ed.; And Others

    Sound symbolism is the study of the relationship between the sound of an utterance and its meaning. In this interdisciplinary collection of new studies, 24 leading scholars discuss the role of sound symbolism in a theory of language. Contributions and authors include the following: "Sound-Symbolic Processes" (Leanne Hinton, Johanna…

  17. Sound Symbolism.

    ERIC Educational Resources Information Center

    Hinton, Leanne, Ed.; And Others

    Sound symbolism is the study of the relationship between the sound of an utterance and its meaning. In this interdisciplinary collection of new studies, 24 leading scholars discuss the role of sound symbolism in a theory of language. Contributions and authors include the following: "Sound-Symbolic Processes" (Leanne Hinton, Johanna…

  18. CONTROL OF LASER RADIATION PARAMETERS: Tunable acousto-optic filters with the multiple interaction of light and sound

    NASA Astrophysics Data System (ADS)

    Voloshinov, V. B.; Magdich, L. N.; Knyazev, G. A.

    2005-11-01

    Optical multipass schemes of the interaction of light and sound, which are promising for filtration of optical beams based on tunable acousto-optic filters, are studied. The features of operation of acousto-optic filters in the rejection and transmission regimes are considered. It is proved theoretically and confirmed experimentally that the use of multiple interaction improves the spectral and energy parameters of acousto-optic devices. The collinear and transverse geometry of acousto-optic interaction in cells based on a paratellurite crystal is studied in the double-pass, three-pass, and multipass diffraction regimes.

  19. Predicting the Underwater Sound of Moderate and Heavy Rainfall from Laboratory Measurements of Radiation from Single Large Raindrops

    DTIC Science & Technology

    1992-03-01

    AD-A252 748 NAVAL POSTGRADUATE SCHOOL Monterey, Calfornia DTIC7,cR ft 𔃺’J% LECTE ~?CRPI3 ~UL 131992D THESIS PREDICTING THE UNDERWATER SOUND OF...Space Center, Mississippi. xvi I. INTRODUCTION Precipitation is an important factor in air/ocean climate modeling and weather forecasting. However...increases from 0.6 m/s to 3.3 m/s, the spectral peak near 15 kHz becomes less pronounced. The reason for the observed change is that, as wind speed

  20. Linearly Tapered Slot Antenna Radiation Characteristics at Millimeter-Wave Frequencies

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1998-01-01

    An endfire travelling wave antenna, such as, a linearly tapered slot antenna (LTSA) is a viable alternative to a patch antenna at millimeter-wave frequencies because of its simple design and ease of fabrication. This paper presents the radiation characteristics of LTSA at higher millimeter-wave frequencies. The measured radiation patterns are observed to be well behaved and symmetric with the main beam in the endfire direction. The measured gain is about 10 dB. The LTSAs have potential wireless applications at 50 GHz, 77 GHz, and 94 GHz.

  1. Thermal radiation characteristics of silicon inverse opal in mid infrared range

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Xie, Kai

    2015-03-01

    A binary solvent with large density was used as dispersant for silica spheres, in which silica spheres with large diameter can suspend steadily and disperse very well. With this suspension, fine opals with 2100 nm SiO2 mono-disperse spheres were successfully prepared by solvent evaporation method. Low pressure vapor deposition method was then used to fill the voids of the silica opals with Si, and silicon inverse opal with photonic band gaps in mid infrared region was obtained. The infrared radiation characteristic of resulted sample was examined. It is shown that silicon inverse opal structure is effective in suppressing silicon thermal radiation in the photonic band gap spectral region.

  2. Radiation hydrodynamics using characteristics on adaptive decomposed domains for massively parallel star formation simulations

    NASA Astrophysics Data System (ADS)

    Buntemeyer, Lars; Banerjee, Robi; Peters, Thomas; Klassen, Mikhail; Pudritz, Ralph E.

    2016-02-01

    We present an algorithm for solving the radiative transfer problem on massively parallel computers using adaptive mesh refinement and domain decomposition. The solver is based on the method of characteristics which requires an adaptive raytracer that integrates the equation of radiative transfer. The radiation field is split into local and global components which are handled separately to overcome the non-locality problem. The solver is implemented in the framework of the magneto-hydrodynamics code FLASH and is coupled by an operator splitting step. The goal is the study of radiation in the context of star formation simulations with a focus on early disc formation and evolution. This requires a proper treatment of radiation physics that covers both the optically thin as well as the optically thick regimes and the transition region in particular. We successfully show the accuracy and feasibility of our method in a series of standard radiative transfer problems and two 3D collapse simulations resembling the early stages of protostar and disc formation.

  3. Preliteracy Speech Sound Production Skill and Linguistic Characteristics of Grade 3 Spellings: A Study Using the Templin Archive

    ERIC Educational Resources Information Center

    Overby, Megan S.; Masterson, Julie J.; Preston, Jonathan L.

    2015-01-01

    Purpose: This archival investigation examined the relationship between preliteracy speech sound production skill (SSPS) and spelling in Grade 3 using a dataset in which children's receptive vocabulary was generally within normal limits, speech therapy was not provided until Grade 2, and phonological awareness instruction was discouraged at the…

  4. Preliteracy Speech Sound Production Skill and Linguistic Characteristics of Grade 3 Spellings: A Study Using the Templin Archive

    ERIC Educational Resources Information Center

    Overby, Megan S.; Masterson, Julie J.; Preston, Jonathan L.

    2015-01-01

    Purpose: This archival investigation examined the relationship between preliteracy speech sound production skill (SSPS) and spelling in Grade 3 using a dataset in which children's receptive vocabulary was generally within normal limits, speech therapy was not provided until Grade 2, and phonological awareness instruction was discouraged at the…

  5. Blending vocal music with a given sound field due to the characteristics of the running autocorrelation function of singing voices

    NASA Astrophysics Data System (ADS)

    Kato, Kosuke; Fujii, Kenji; Kawai, Keiji; Ando, Yoichi; Yano, Takashi

    2004-05-01

    This is a study to meet music and the opera house acoustics. It is said that singers adjust their interpretation style according to the acoustical condition of the sound field in a room. However, this mechanism of blending of musical performance with the sound field is unknown. In order to obtain a method of performance blending of opera house acoustics, we attempted to develop evaluation criteria for a singing voice in terms of the minimum value of the effective duration of the running autocorrelation function (r-ACF), (te)min, of sound source signals. This temporal factor has shown to have close correlation with the subjective response of both listeners and performers to sound fields [Y. Ando, Architectural Acoustics (AIP Press/Springer-Verlag, New York, 1998)]. As example for the control of (te)min due to performing style, effects of singing style, kind of vowel, relative pitch, vibrato extent, and intonation on the values of (te)min are demonstrated. In addition, the fine structure of the r-ACF is discussed with regard to the identification of vowels of singing voice. a)Now at 1-10-27 Yamanokami, Kumamoto, Japan.

  6. Effect of temporary open-air markets on the sound environment and acoustic perception based on the crowd density characteristics.

    PubMed

    Meng, Qi; Sun, Yang; Kang, Jian

    2017-12-01

    The sound environment and acoustic perception of open-air markets, which are very common in high-density urban open spaces, play important roles in terms of the urban soundscape. Based on objective and subjective measurements of a typical temporary open-air market in Harbin city, China, the effects of the temporary open-air market on the sound environment and acoustic perception were studied, considering different crowd densities. It was observed that a temporary open-air market without zoning increases the sound pressure level and subjective loudness by 2.4dBA and 0.21dBA, respectively, compared to the absence of a temporary market. Different from the sound pressure level and subjective loudness, the relationship between crowd density and the perceived acoustic comfort is parabolic. Regarding the effect of a temporary open-air market with different zones on the sound environment and acoustic perception, when the crowd densities were the same, subjective loudness in the fruit and vegetable sales area was always higher than in the food sales area and the clothing sales area. In terms of acoustic comfort, with an increase in crowd density, acoustic comfort in the fruit and vegetable sales area decreased, and acoustic comfort in the food sales area and the clothing sales area exhibited a parabolic change trend of increase followed by decrease. Overall, acoustic comfort can be effectively improved by better planning temporary open-air markets in high-density urban open spaces. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. GPS Sounding Rocket Developments

    NASA Technical Reports Server (NTRS)

    Bull, Barton

    1999-01-01

    Sounding rockets are suborbital launch vehicles capable of carrying scientific payloads several hundred miles in altitude. These missions return a variety of scientific data including; chemical makeup and physical processes taking place in the atmosphere, natural radiation surrounding the Earth, data on the Sun, stars, galaxies and many other phenomena. In addition, sounding rockets provide a reasonably economical means of conducting engineering tests for instruments and devices used on satellites and other spacecraft prior to their use in more expensive activities. This paper addresses the NASA Wallops Island history of GPS Sounding Rocket experience since 1994 and the development of highly accurate and useful system.

  8. GPS Sounding Rocket Developments

    NASA Technical Reports Server (NTRS)

    Bull, Barton

    1999-01-01

    Sounding rockets are suborbital launch vehicles capable of carrying scientific payloads several hundred miles in altitude. These missions return a variety of scientific data including; chemical makeup and physical processes taking place in the atmosphere, natural radiation surrounding the Earth, data on the Sun, stars, galaxies and many other phenomena. In addition, sounding rockets provide a reasonably economical means of conducting engineering tests for instruments and devices used on satellites and other spacecraft prior to their use in more expensive activities. This paper addresses the NASA Wallops Island history of GPS Sounding Rocket experience since 1994 and the development of highly accurate and useful system.

  9. Long-term radiation effects on GaAs solar cell characteristics

    NASA Technical Reports Server (NTRS)

    Heinbockel, J. H.; Doviak, M. J.

    1978-01-01

    This report investigates preliminary design considerations which should be considered for a space experiment involving Gallium Arsenide (GaAs) solar cells. The electron radiation effects on GaAs solar cells were conducted in a laboratory environment, and a statistical analysis of the data is presented. In order to augment the limited laboratory data, a theoretical investigation of the effect of radiation on GaAs solar cells is also developed. The results of this study are empirical prediction equations which can be used to estimate the actual damage of electrical characteristics in a space environment. The experimental and theoretical studies also indicate how GaAs solar cell parameters should be designed in order to withstand the effects of electron radiation damage.

  10. Near Field Radiation Characteristics of Implantable Square Spiral Chip Inductor Antennas for Bio-Sensors

    NASA Technical Reports Server (NTRS)

    Nessel, James A.; Simons, Rainee N.; Miranda, Felix A.

    2007-01-01

    The near field radiation characteristics of implantable Square Spiral Chip Inductor Antennas (SSCIA) for Bio-Sensors have been measured. Our results indicate that the measured near field relative signal strength of these antennas agrees with simulated results and confirm that in the near field region the radiation field is fairly uniform in all directions. The effects of parameters such as ground-plane, number of turns and microstrip-gap width on the performance of the SSCIA are presented. Furthermore, the SSCIA antenna with serrated ground plane produce a broad radiation pattern, with a relative signal strength detectable at distances within the range of operation of hand-held devices for self-diagnosis.

  11. Regional atmospheric visibility characteristics and its effect on radiation in China

    NASA Astrophysics Data System (ADS)

    Chen, S. C.; Hao, T. Y.; Shi, J.; Shan, X. L.

    2017-01-01

    Spatial and temporal characteristics of atmospheric visibility in China were investigated by using monitored meteorological data. The results show that The atmospheric lowest visibility (<10km) occurrence frequency in China can be observed in the east of Sichuan, Chongqing, and the east of Guizhou. The visibility in most regions of China exhibits a decreasing trend from 1980 to 2010. It is also found that fog is major weather phenomenon affecting visibility in China. The second is precipitation except the Northwest and Inner Mongolia, where sand and dust is the major weather phenomenon affecting visibility. Our results also identify the total radiation under the condition of low visibility is less than that under the condition of normal, meanwhile, the atmospheric scattered radiation increase. Net radiation in the condition of low visibility is less than that in the normal condition in most cases over China.

  12. Calculating the radiation characteristics of accelerated electrons in laser-plasma interactions

    SciTech Connect

    Li, X. F.; Yu, Q.; Qu, J. F.; Kong, Q.; Gu, Y. J.; Ma, Y. Y.; Kawata, S.

    2016-03-15

    In this paper, we studied the characteristics of radiation emitted by electrons accelerated in a laser–plasma interaction by using the Lienard–Wiechert field. In the interaction of a laser pulse with a underdense plasma, electrons are accelerated by two mechanisms: direct laser acceleration (DLA) and laser wakefield acceleration (LWFA). At the beginning of the process, the DLA electrons emit most of the radiation, and the DLA electrons emit a much higher peak photon energy than the LWFA electrons. As the laser–plasma interaction progresses, the LWFA electrons become the major radiation emitter; however, even at this stage, the contribution from DLA electrons is significant, especially to the peak photon energy.

  13. Detailed Characteristics of Radiation Belt Electrons Revealed by CSSWE/REPTile Measurements

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Li, X.; Schiller, Q.; Gerhardt, D. T.; Millan, R. M.

    2016-12-01

    The outer radiation belt electrons are highly dynamic. We study the detailed characteristics of the relativistic electrons in the outer belt using measurements from the Colorado Student Space Weather Experiment (CSSWE) mission, a low Earth orbit Cubesat, which transverses the radiation belt four times in one orbit ( 1.5 hr) and has the advantage of measuring the dynamic activities of the electrons including their rapid precipitations. Among the features of the relativistic electrons, we show the measured electron distribution as a function of geomagnetic activities and local magnetic field strength. Moreover, a specific precipitation band, which happened on 19 Jan 2013, is investigated based on the conjunctive measurement of CSSWE and the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL). In this precipitation band event, the net loss of the 0.58 1.63 MeV electrons (L=3.5 6) is estimated to account for 6.84% of the total electron content.

  14. Primary Breast Cancer Tumor and Patient Characteristics as Predictors of Adjuvant Radiation Therapy.

    PubMed

    VanderBeek, Laura; Francescutti, Valerie; Farrokhyar, Forough; Lovrics, Peter; Strang, Barbara; Kahnamoui, Kamyar

    2017-01-01

    Adjuvant radiation therapy reduces the risk of local recurrence of breast cancer. Our study identifies patient and tumor characteristics that guide the use of adjuvant radiation therapy and evaluates our adherence to recommended guidelines. A retrospective review was undertaken of 1,667 stage I-III breast cancer patients treated at a regional cancer center from 2004 to 2007. Univariate analysis was used to select factors for entry into a multivariate stepwise logistic regression model. Descriptive statistics was used to compare use of radiation therapy of 382 stage I-III breast cancer patients diagnosed in 2013 to those from 2004 to 2007. The primary indicators for any radiation therapy (n = 935) were breast conserving surgery (OR 79.5, 95% CI [47.6-132.9]), four to nine positive lymph nodes (71.9, [17.0-304.7]), and greater than nine positive lymph nodes (60.5, [7.9-460.8]). In post-mastectomy patients (n = 408), the indicators for radiation therapy were four to nine positive lymph nodes (29.4, [12.9-67.4]) and greater than nine positive lymph nodes (108.3, [14.5-807.5]). In breast conserving surgery patients (n = 1,081) 96.1% were offered radiation therapy. Patients offered local-regional radiation therapy were more likely to have any positive nodes (ORs 4.3-91.0), have had a mastectomy (4.3, [2.2-8.4]), and had larger tumors (1.6, [1.3-2.0]). Local-regional radiation therapy was recommended less frequently in node positive patients in 2004-2007 (35.0%) compared to in 2013 (70.5%) [p < 0.001]. Patients who had a breast conserving surgery or had four or more positive lymph nodes were more likely to receive radiation therapy. Patients with any positive lymph nodes, larger tumors, or who had a mastectomy were more likely to receive local-regional radiation therapy. Our institution was more likely to offer local-regional radiation therapy in node positive breast cancer in 2013 compare to 2004-2007. © 2016 Wiley Periodicals, Inc.

  15. Radiation and scattering characteristics of microstrip antennas on normally biased ferrite substrates

    NASA Astrophysics Data System (ADS)

    Pozar, David M.

    1992-09-01

    Radiation and scattering characteristics of microstrip antennas and arrays printed on ferrite substrates with a normal magnetic bias field are described. The extra degree of freedom offered by the biased ferrite can be used to obtain a number of novel characteristics, including switchable and tunable circularly polarized radiation from a microstrip antenna having a single feed point, dynamic wide-angle impedance matching for phased arrays of microstrip antennas, and a switchable radar cross section (RCS) reduction technique for microstrip antennas. Results are obtained from full-wave moment method solutions for single microstrip antennas and infinite arrays of microstrip antennas. A cavity model solution for a circular patch antenna on a biased ferrite substrate is also presented, to aid in understanding the operation of these antennas.

  16. Spectral characteristics of blood irradiated in vivo by therapeutic doses of ultraviolet radiation

    NASA Astrophysics Data System (ADS)

    Zalesskaya, G. A.; Ulashchik, V. S.; Kalosha, I. I.

    2009-10-01

    The influence of therapeutic doses of UV radiation (λ = 254 nm) on spectral characteristics of blood irradiated in vivo has been studied. A comparative analysis of the electronic and IR absorption spectra of blood and its components before and after irradiation, as well as of the gas composition and concentration of blood hemoglobins, revealed that phototransformations of hemoglobins are primary mechanisms of photoreactions in blood UV irradiated in vivo.

  17. Utilization of the integral equation method for determining the characteristic radiation features of antennas

    NASA Astrophysics Data System (ADS)

    Zink, M.

    The integral equation method in the form of the electric field integral equation for wire grid models provides the current distribution on the surface of structures under study. Characteristic parameters such as the input impedance and the radiation diagram are obtained in this fashion. These parameters are determined for a dipole in free space, a monopole over a circular ground plane, and a torus antenna. Good results are obtained for the far field and the variables related to it.

  18. Characteristics and development of the coherent synchrotron radiation sources for THz spectroscopy

    NASA Astrophysics Data System (ADS)

    Barros, J.; Evain, C.; Roussel, E.; Manceron, L.; Brubach, J.-B.; Tordeux, M.-A.; Couprie, M.-E.; Bielawski, S.; Szwaj, C.; Labat, M.; Roy, P.

    2015-09-01

    We report on the characteristics of coherent synchrotron radiation (CSR) as a source for spectroscopy. The optimization of the source and the resulting figures of merits in terms of flux, signal to noise, spatial distribution and spectral and temporal distribution are presented together with a spectroscopic application. The emission of THz during the slicing operation is also described. The conclusion opens up perspectives made possible by the availability of this intense and stable THz source.

  19. Surface accuracy and radiation pattern characteristics of mesh deployable refector antennas

    NASA Astrophysics Data System (ADS)

    Ueno, Miyoshi; Ebisui, Takashi; Okamato, Teruki; Orikasa, Teruaki; Sugimoto, Toshio; Iso, Akio

    To facilitate the growth of mobile satellite communications, both an increase in the Equivalent Isotropically Radiated Power (EIRP) of satellites and improved frequency reuse are required to achiveve compact size, low cost terminal usage, and high channel capacity. High gain and low sidelobe antenna technology are very important for high EIRP and frequency reuse, respectively. These requirements are expected to be met by using a large deployable mesh reflector antenna, which is the key technology for future multibeam moble communications systems. In this paper, surface accruracy and related electrical characteristics are studied using a TETRUS-(Tetra Trigonal Prism Truss) type deployable mesh reflector antenna. Surface accuracy and related electrical characteristics of reflector antennas becaue any distortion of the ideal paraboloidal configuration causes antenna patterns to deteriorate, thereby reducing reflector aperture efficiency and increasing sidelobe and grating lobe levels. The sidelobe and grating lobe characteristics are especially important in frequency reuse. First, we show the problem with the radiation pattern characteristics of TETUS antenna. We then propose a new antenna configuration called the 'HYBRID TETRUS' that improves these characteristics. The mechanical performances of two partial deployable models are also described. Mechanical testing results reveal agreement between the calculated and measured values and high rigidities.

  20. Radiative Characteristics of Pulsed Power Driven Stainless Steel Nested Wire Arrays

    NASA Astrophysics Data System (ADS)

    Davis, J.; Clark, R. W.; Thornhill, J. W.; Apruzese, J. P.; Velikovich, A.; Deeney, C.; Coverdale, C.; Lepell, D.

    2001-10-01

    The radiative characteristics of nested arrays of stainless steel wires are investigated with the aid of numerical simulations and compared with experimental results measured on the Z facility. The wire load contains a cocktail of 5 elements: Fe, Ni, Cr, Mg, and Si. This multimaterial load is ideal for benchmarking the simulation. The modeling and numerical simulations were done with a 1-D radiation MHD model self-consistently driven by an equivalent Z circuit model. The ionization dynamic model is represented by a collisional radiative model where the opacity for the lines and continuum is self-consistently calculated online and transported through the plasma. The collision between inner and outer arrays is treated classically allowing for differences in gap to wire diameter spacing. Results are presented for the L- and K-shell radiation yields and emission spectra as a function of photon energy from 0.01 to 10 keV. Numerical simulations and comparisons are also made between the TCREfootnote J. Thornhill, J. Apruzese, J. Davis, R. Clark, et. al., Phys. Plasmas \\underbar 8, 3480 (2001). and probability of escape radiation transport models.

  1. Preliteracy Speech Sound Production Skill and Linguistic Characteristics of Grade 3 Spellings: A Study Using the Templin Archive.

    PubMed

    Overby, Megan S; Masterson, Julie J; Preston, Jonathan L

    2015-12-01

    This archival investigation examined the relationship between preliteracy speech sound production skill (SSPS) and spelling in Grade 3 using a dataset in which children's receptive vocabulary was generally within normal limits, speech therapy was not provided until Grade 2, and phonological awareness instruction was discouraged at the time data were collected. Participants (N = 250), selected from the Templin Archive (Templin, 2004), varied on prekindergarten SSPS. Participants' real word spellings in Grade 3 were evaluated using a metric of linguistic knowledge, the Computerized Spelling Sensitivity System (Masterson & Apel, 2013). Relationships between kindergarten speech error types and later spellings also were explored. Prekindergarten children in the lowest SPSS (7th percentile) scored poorest among articulatory subgroups on both individual spelling elements (phonetic elements, junctures, and affixes) and acceptable spelling (using relatively more omissions and illegal spelling patterns). Within the 7th percentile subgroup, there were no statistical spelling differences between those with mostly atypical speech sound errors and those with mostly typical speech sound errors. Findings were consistent with predictions from dual route models of spelling that SSPS is one of many variables associated with spelling skill and that children with impaired SSPS are at risk for spelling difficulty.

  2. Characteristics of sound propagation in shallow water over an elastic seabed with a thin cap-rock layer.

    PubMed

    Duncan, Alec J; Gavrilov, Alexander N; McCauley, Robert D; Parnum, Iain M; Collis, Jon M

    2013-07-01

    Measurements of low-frequency sound propagation over the areas of the Australian continental shelf, where the bottom sediments consist primarily of calcarenite, have revealed that acoustic transmission losses are generally much higher than those observed over other continental shelves and remain relatively low only in a few narrow frequency bands. This paper considers this phenomenon and provides a physical interpretation in terms of normal modes in shallow water over a layered elastic seabed with a shear wave speed comparable to but lower than the water-column sound speed. A theoretical analysis and numerical modeling show that, in such environments, low attenuation of underwater sound is expected only in narrow frequency bands just above the modal critical frequencies which in turn are governed primarily by the water depth and compressional wave speed in the seabed. In addition, the effect of a thin layer of harder cap-rock overlaying less consolidated sediments is considered. Low-frequency transmission loss data collected from an offshore seismic survey in Bass Strait on the southern Australian continental shelf are analyzed and shown to be in broad agreement with the numerical predictions based on the theoretical analysis and modeling using an elastic parabolic equation solution for range-dependent bathymetry.

  3. Preliteracy Speech Sound Production Skill and Linguistic Characteristics of Grade 3 Spellings: A Study Using the Templin Archive

    PubMed Central

    Masterson, Julie J.; Preston, Jonathan L.

    2015-01-01

    Purpose This archival investigation examined the relationship between preliteracy speech sound production skill (SSPS) and spelling in Grade 3 using a dataset in which children's receptive vocabulary was generally within normal limits, speech therapy was not provided until Grade 2, and phonological awareness instruction was discouraged at the time data were collected. Method Participants (N = 250), selected from the Templin Archive (Templin, 2004), varied on prekindergarten SSPS. Participants' real word spellings in Grade 3 were evaluated using a metric of linguistic knowledge, the Computerized Spelling Sensitivity System (Masterson & Apel, 2013). Relationships between kindergarten speech error types and later spellings also were explored. Results Prekindergarten children in the lowest SPSS (7th percentile) scored poorest among articulatory subgroups on both individual spelling elements (phonetic elements, junctures, and affixes) and acceptable spelling (using relatively more omissions and illegal spelling patterns). Within the 7th percentile subgroup, there were no statistical spelling differences between those with mostly atypical speech sound errors and those with mostly typical speech sound errors. Conclusions Findings were consistent with predictions from dual route models of spelling that SSPS is one of many variables associated with spelling skill and that children with impaired SSPS are at risk for spelling difficulty. PMID:26380965

  4. A perspective on 30 years of progress in ambient noise: Source mechanisms and the characteristics of the sound field

    NASA Astrophysics Data System (ADS)

    Cato, Douglas H.

    2012-11-01

    The last 30 years has seen substantial progress in ocean ambient noise research, particularly in understanding the mechanisms of sound generation by the sources of ambient noise, the way in which the noise field is affected by sound propagation, and improvements in quantifying the relationship between noise and environmental parameters. This has led to significant improvements in noise prediction. Activity was probably strongest in the 1980s and 1990s, as evident, for example, in the Sea Surface Sound conferences and their published proceedings (four over 10 years). Although much of the application has been to sonar, there has also been interest in using ambient noise to measure properties of the environment and in its significance to marine life. There have been significant changes in the ambient noise itself over the last 30 years. The contribution from human activities appears to have increased, particularly that due to increases in shipping numbers. Biological noise has also increased with the significant increases in populations of some whale species following the cessation of broad scale whaling in the 1960s and early 1970s. Concern about the effects of noise on marine animals as well as the way they exploit the noise has led to renewed interest in ambient noise.

  5. Effect of dietary calcium and phosphorus level sequences on performance, structural soundness and bone characteristics of growing-finishing swine.

    PubMed

    Cera, K R; Mahan, D C

    1988-07-01

    The effects of feeding various dietary Ca:P level sequences on gain and feed efficiency, leg structural soundness and bone indices of growing-finishing swine were evaluated as an incomplete 3 X 3 factorial arrangement of treatments in a split-plot design. A total of 664 pigs were fed one of three total dietary Ca:P levels (.52:.40, .65:.50, .80:.60%) from 19-kg to 56-kg body weights followed by one of three Ca:P levels (.45:.32, .52:.40, .65:.50%) to market weight. The .80:.60% and .65:.50% Ca:P mineral sequence was not evaluated. Diets were formulated to 14.5% crude protein using a corn-soybean meal mixture with proportions of dicalcium phosphate and limestone altered to attain the desired dietary Ca:P levels. Maximum gains occurred at the .65:.50% and .52:.40% Ca:P level during the grower (P less than .01) and finisher (P less than .01) periods, respectively. No grower X finisher phase pig gain or feed intake interaction resulted, providing evidence of no carry-over response on these measurements from the grower to the finisher period. Serum P concentration increased and plateaued at the same dietary Ca:P level, as did rate of gain at both 56-kg and 95-kg body weights. Leg soundness subjectively evaluated at 56-kg and 95-kg body weights revealed no effect of dietary Ca:P level on soundness scores at 56 kg, but at 95-kg body weight, the interaction between grower and finisher diets was significant. Percentage bone ash of the humerus, shaft thickness and bending moment of the femur increased as dietary Ca:P level increased at both 56-kg and 95-kg body weights.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Abdominal sounds

    MedlinePlus

    ... may be a sign of early bowel obstruction. Causes Most of the sounds you hear in your stomach and intestines are ... a list of more serious conditions that can cause abnormal bowel sounds. Hyperactive, hypoactive, or missing bowel sounds may be ...

  7. Spectral Cauchy characteristic extraction of strain, news and gravitational radiation flux

    NASA Astrophysics Data System (ADS)

    Handmer, Casey J.; Szilágyi, Béla; Winicour, Jeffrey

    2016-11-01

    We present a new approach for the Cauchy-characteristic extraction (CCE) of gravitational radiation strain, news function, and the flux of the energy-momentum, supermomentum and angular momentum associated with the Bondi-Metzner-Sachs asymptotic symmetries. In CCE, a characteristic evolution code takes numerical data on an inner worldtube supplied by a Cauchy evolution code, and propagates it outwards to obtain the space-time metric in a neighborhood of null infinity. The metric is first determined in a scrambled form in terms of coordinates determined by the Cauchy formalism. In prior treatments, the waveform is first extracted from this metric and then transformed into an asymptotic inertial coordinate system. This procedure provides the physically proper description of the waveform and the radiated energy but it does not generalize to determine the flux of angular momentum or supermomentum. Here we formulate and implement a new approach which transforms the full metric into an asymptotic inertial frame and provides a uniform treatment of all the radiation fluxes associated with the asymptotic symmetries. Computations are performed and calibrated using the spectral Einstein code.

  8. Radiometric sounding system

    SciTech Connect

    Whiteman, C.D.; Anderson, G.A.; Alzheimer, J.M.; Shaw, W.J.

    1995-04-01

    Vertical profiles of solar and terrestrial radiative fluxes are key research needs for global climate change research. These fluxes are expected to change as radiatively active trace gases are emitted to the earth`s atmosphere as a consequence of energy production and industrial and other human activities. Models suggest that changes in the concentration of such gases will lead to radiative flux divergences that will produce global warming of the earth`s atmosphere. Direct measurements of the vertical variation of solar and terrestrial radiative fluxes that lead to these flux divergences have been largely unavailable because of the expense of making such measurements from airplanes. These measurements are needed to improve existing atmospheric radiative transfer models, especially under the cloudy conditions where the models have not been adequately tested. A tethered-balloon-borne Radiometric Sounding System has been developed at Pacific Northwest Laboratory to provide an inexpensive means of making routine vertical soundings of radiative fluxes in the earth`s atmospheric boundary layer to altitudes up to 1500 m above ground level. Such vertical soundings would supplement measurements being made from aircraft and towers. The key technical challenge in the design of the Radiometric Sounding System is to develop a means of keeping the radiometers horizontal while the balloon ascends and descends in a turbulent atmospheric environment. This problem has been addressed by stabilizing a triangular radiometer-carrying platform that is carried on the tetherline of a balloon sounding system. The platform, carried 30 m or more below the balloon to reduce the balloon`s effect on the radiometric measurements, is leveled by two automatic control loops that activate motors, gears and pulleys when the platform is off-level. The sensitivity of the automatic control loops to oscillatory motions of various frequencies and amplitudes can be adjusted using filters.

  9. Tethered balloon-based soundings of ozone, aerosols, and solar radiation near Mexico City during MIRAGE-MEX

    NASA Astrophysics Data System (ADS)

    Greenberg, J. P.; Guenther, A. B.; Turnipseed, A.

    A tethered balloon sampling system was used to measure vertical profiles of ozone, particles, and solar radiation in the atmospheric boundary layer on the northern edge of Mexico City, in March 2006 as part of the Megacity Impact on Regional and Global Environment-Mexico experiment. Several commercial sensors, designed for surface applications, were deployed on a tethered balloon platform. Profiles indicate that for these 3 scalars the boundary layer (surface up to 700 m) was well mixed in the period 10:00-16:00 LST. Good agreement was observed for median surface and balloon ozone and particle number concentrations. For most profiles, the surface deposition of ozone was not significant compared to median profile concentrations. Particle number concentration (0.3, 0.5, 1.0 and 5.0 μm) also showed little variation with attitude. Radiatprofiles showed a monotonic increase in diffuse radiation from the maximum altitude of profiles to the surface. Consequently, it was inferred that surface measurements of these likely were representative of lower boundary layer values during this time period.

  10. Optical and thermodynamic properties of MgO from radiative shock temperature and sound speed measurements on samples preheated to 2300 K

    NASA Astrophysics Data System (ADS)

    Fatýanov, O. V.; Asimow, P. D.

    2013-12-01

    Thermodynamic properties of MgO, one of the major end-members of deep planetary interiors, play a significant role in the processes inside the Earth's lower mantle. Of particular importance in geophysics and geochemistry is the MgO melting behavior at high pressure. Despite considerable theoretical and experimental efforts over decades, it remains essentially unknown. The melting temperature predictions for MgO at 135 GPa, the Earth's core-mantle boundary pressure, range from 5 to 9 kK. In a continuous effort to resolve this inconsistency and to probe the P-T region previously unexplored, we developed a technique for radiative shock temperature measurements in single-crystal MgO preheated to 2300 K. Large ventilated Mo capsules were employed to hold ~20 mm long MgO crystals with controlled longitudinal thermal gradients. These hot targets were impacted by 0.8 mm thick Ta flyers launched at 6.5 to 7.5 km/s on the Caltech two-stage light-gas gun. Six spectral radiance histories from MgO shock front were recorded in every shot with 3 ns time resolution over 440-750 nm or 500-830 nm spectral range. The majority of our experiments showed smooth pressure dependence of MgO shock temperature and sound speed consistent with the solid phase at 197-243 GPa. Although most observed temperatures are ~700 K lower and sound speeds ~1 km/s higher than the model predictions, the pressure slopes for both parameters are in close agreement with those calculated for the solid phase. Unconfirmed data from a single experiment at 239 GPa and 8.3 kK showed correlated temperature and sound speed anomalies (both values lower than expected) that may be explained by partial melting. Our past and recent data on shock-compressed preheated MgO suggest its melting curve above 200 GPa is higher than the extrapolation of the experiments of Zerr & Boehler or the theoretical calculation by Strachan et. al. These results, features of shock experiments with 2300 K pre-heat temperatures, data analysis

  11. Statistical comparison between Hysplit sounding and lidar observation of planetary boundary layer characteristics over New York City

    NASA Astrophysics Data System (ADS)

    Gan, Chuen Meei; Wu, Yonghua; Gross, Barry; Moshary, Fred

    2010-04-01

    The need to characterize in a robust way Planetary Boundary Layer (PBL) heights is crucial as in air quality forecast and transport models. In particular, incorrect determination of PBL heights can severely distort the surface air quality predictions such as PM2.5. Local properties and morphological features can influence PBL dynamics through local circulation phenomena such as the sea-breeze development as well as influences from the Urban Heat Island Canopy resulting in multiple layers that need to be resolved. In this paper, based on a combination of wavelet and image processing methods, we develop methods to quantify multilayer PBL's and assess their dynamics with meteorological measurements including temperature, wind and humidity profiles. In particular, meteorologically based PBL heights based on both the Potential Temperature Gradient and Richardson Number are compared against both lidar and ceilometer measurements. It is shown that in general, the Potential Temperature Gradient method is better correlated to the PBL dynamics. Meanwhile, the Hysplit model provides sounding data which can be used for comparison between actual sounding and lidar measurements. On the other hand, when strong atmospheric instability is present or layering develops, the comparison between different methods can provide information about the PBL internal structure. Further comparisons with air quality models such as MM5 are also made and illustrate the difficulty in these models properly predicting the PBL dynamics seen in urban areas.

  12. Radiative Characteristics of Clouds Embedded in Smoke Derived from Airborne Multiangular Measurements

    NASA Technical Reports Server (NTRS)

    Gautam, Ritesh; Gatebe, Charles K.; Singh, Manoj; Varnai, Tamas; Poudyal, Rajesh

    2016-01-01

    Clouds in the presence of absorbing aerosols result in their apparent darkening, observed at the top of atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the large radiative effect and potential impacts on regional climate, above-cloud aerosols have recently been characterized in multiple satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, recent literature indicates large uncertainties in satellite retrievals of above-cloud aerosol optical depth (AOD) and single scattering albedo (SSA), which are among the most important parameters in the assessment of associated radiative effects. In this study, we analyze radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer, collected during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites campaign in Canada during the 2008 summer season. We found a strong positive reflectance (R) gradient in the UV-visible (VIS)-near infrared (NIR) spectrum for clouds embedded in dense smoke, as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. Several cases of clouds embedded in thick smoke were found, when the aircraft made circular/spiral measurements, which not only allowed the complete characterization of angular distribution of smoke scattering but also provided the vertical distribution of smoke and clouds (within 0.5-5 km). Specifically, the largest darkening by smoke was found in the UV/VIS, with R(sub 0.34 microns) reducing to 0.2 (or 20%), in contrast to 0.8 at NIR wavelengths (e.g., 1.27 microns). The observed darkening is associated with large AODs (0.5-3.0) and moderately low SSA (0.85-0.93 at 0.53 microns), resulting in a significantly large instantaneous aerosol forcing efficiency of 254 +/- 47 W/sq m/t. Our

  13. Radiative characteristics of clouds embedded in smoke derived from airborne multiangular measurements

    NASA Astrophysics Data System (ADS)

    Gautam, Ritesh; Gatebe, Charles K.; Singh, Manoj K.; Várnai, Tamás.; Poudyal, Rajesh

    2016-08-01

    Clouds in the presence of absorbing aerosols result in their apparent darkening, observed at the top of atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the large radiative effect and potential impacts on regional climate, above-cloud aerosols have recently been characterized in multiple satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, recent literature indicates large uncertainties in satellite retrievals of above-cloud aerosol optical depth (AOD) and single scattering albedo (SSA), which are among the most important parameters in the assessment of associated radiative effects. In this study, we analyze radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer, collected during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites campaign in Canada during the 2008 summer season. We found a strong positive reflectance (R) gradient in the UV-visible (VIS)-near infrared (NIR) spectrum for clouds embedded in dense smoke, as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. Several cases of clouds embedded in thick smoke were found, when the aircraft made circular/spiral measurements, which not only allowed the complete characterization of angular distribution of smoke scattering but also provided the vertical distribution of smoke and clouds (within 0.5-5 km). Specifically, the largest darkening by smoke was found in the UV/VIS, with R0.34μm reducing to 0.2 (or 20%), in contrast to 0.8 at NIR wavelengths (e.g., 1.27 µm). The observed darkening is associated with large AODs (0.5-3.0) and moderately low SSA (0.85-0.93 at 0.53 µm), resulting in a significantly large instantaneous aerosol forcing efficiency of 254 ± 47 W m-2 τ-1. Our observations of smoke

  14. Radiative Characteristics of Clouds Embedded in Smoke Derived from Airborne Multiangular Measurements

    NASA Technical Reports Server (NTRS)

    Gautam, Ritesh; Gatebe, Charles K.; Singh, Manoj; Varnai, Tamas; Poudyal, Rajesh

    2016-01-01

    Clouds in the presence of absorbing aerosols result in their apparent darkening, observed at the top of atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the large radiative effect and potential impacts on regional climate, above-cloud aerosols have recently been characterized in multiple satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, recent literature indicates large uncertainties in satellite retrievals of above-cloud aerosol optical depth (AOD) and single scattering albedo (SSA), which are among the most important parameters in the assessment of associated radiative effects. In this study, we analyze radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer, collected during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites campaign in Canada during the 2008 summer season. We found a strong positive reflectance (R) gradient in the UV-visible (VIS)-near infrared (NIR) spectrum for clouds embedded in dense smoke, as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. Several cases of clouds embedded in thick smoke were found, when the aircraft made circular/spiral measurements, which not only allowed the complete characterization of angular distribution of smoke scattering but also provided the vertical distribution of smoke and clouds (within 0.5-5 km). Specifically, the largest darkening by smoke was found in the UV/VIS, with R(sub 0.34 microns) reducing to 0.2 (or 20%), in contrast to 0.8 at NIR wavelengths (e.g., 1.27 microns). The observed darkening is associated with large AODs (0.5-3.0) and moderately low SSA (0.85-0.93 at 0.53 microns), resulting in a significantly large instantaneous aerosol forcing efficiency of 254 +/- 47 W/sq m/t. Our

  15. Photoacoustic Sounds from Meteors

    NASA Astrophysics Data System (ADS)

    Spalding, Richard; Tencer, John; Sweatt, William; Conley, Benjamin; Hogan, Roy; Boslough, Mark; Gonzales, Gigi; Spurný, Pavel

    2017-02-01

    Concurrent sound associated with very bright meteors manifests as popping, hissing, and faint rustling sounds occurring simultaneously with the arrival of light from meteors. Numerous instances have been documented with -11 to -13 brightness. These sounds cannot be attributed to direct acoustic propagation from the upper atmosphere for which travel time would be several minutes. Concurrent sounds must be associated with some form of electromagnetic energy generated by the meteor, propagated to the vicinity of the observer, and transduced into acoustic waves. Previously, energy propagated from meteors was assumed to be RF emissions. This has not been well validated experimentally. Herein we describe experimental results and numerical models in support of photoacoustic coupling as the mechanism. Recent photometric measurements of fireballs reveal strong millisecond flares and significant brightness oscillations at frequencies ≥40 Hz. Strongly modulated light at these frequencies with sufficient intensity can create concurrent sounds through radiative heating of common dielectric materials like hair, clothing, and leaves. This heating produces small pressure oscillations in the air contacting the absorbers. Calculations show that -12 brightness meteors can generate audible sound at ~25 dB SPL. The photoacoustic hypothesis provides an alternative explanation for this longstanding mystery about generation of concurrent sounds by fireballs.

  16. Photoacoustic Sounds from Meteors

    PubMed Central

    Spalding, Richard; Tencer, John; Sweatt, William; Conley, Benjamin; Hogan, Roy; Boslough, Mark; Gonzales, GiGi; Spurný, Pavel

    2017-01-01

    Concurrent sound associated with very bright meteors manifests as popping, hissing, and faint rustling sounds occurring simultaneously with the arrival of light from meteors. Numerous instances have been documented with −11 to −13 brightness. These sounds cannot be attributed to direct acoustic propagation from the upper atmosphere for which travel time would be several minutes. Concurrent sounds must be associated with some form of electromagnetic energy generated by the meteor, propagated to the vicinity of the observer, and transduced into acoustic waves. Previously, energy propagated from meteors was assumed to be RF emissions. This has not been well validated experimentally. Herein we describe experimental results and numerical models in support of photoacoustic coupling as the mechanism. Recent photometric measurements of fireballs reveal strong millisecond flares and significant brightness oscillations at frequencies ≥40 Hz. Strongly modulated light at these frequencies with sufficient intensity can create concurrent sounds through radiative heating of common dielectric materials like hair, clothing, and leaves. This heating produces small pressure oscillations in the air contacting the absorbers. Calculations show that −12 brightness meteors can generate audible sound at ~25 dB SPL. The photoacoustic hypothesis provides an alternative explanation for this longstanding mystery about generation of concurrent sounds by fireballs. PMID:28145486

  17. Photoacoustic sounds from meteors

    DOE PAGES

    Spalding, Richard; Tencer, John; Sweatt, William; ...

    2017-02-01

    Concurrent sound associated with very bright meteors manifests as popping, hissing, and faint rustling sounds occurring simultaneously with the arrival of light from meteors. Numerous instances have been documented with –11 to –13 brightness. These sounds cannot be attributed to direct acoustic propagation from the upper atmosphere for which travel time would be several minutes. Concurrent sounds must be associated with some form of electromagnetic energy generated by the meteor, propagated to the vicinity of the observer, and transduced into acoustic waves. Previously, energy propagated from meteors was assumed to be RF emissions. This has not been well validated experimentally.more » Herein we describe experimental results and numerical models in support of photoacoustic coupling as the mechanism. Recent photometric measurements of fireballs reveal strong millisecond flares and significant brightness oscillations at frequencies ≥40 Hz. Strongly modulated light at these frequencies with sufficient intensity can create concurrent sounds through radiative heating of common dielectric materials like hair, clothing, and leaves. This heating produces small pressure oscillations in the air contacting the absorbers. Calculations show that –12 brightness meteors can generate audible sound at ~25 dB SPL. As a result, the photoacoustic hypothesis provides an alternative explanation for this longstanding mystery about generation of concurrent sounds by fireballs.« less

  18. Study on MMW radiation characteristics and imaging of aquatic plants for environmental application

    NASA Astrophysics Data System (ADS)

    Zhou, Luyan; Zhang, Guangfeng; Liu, Jing

    2017-02-01

    Working all-day and all-weather, the passive millimeter wave radiometer is widely used in remote sensing, guidance and other fields. In order to solve the increasingly serious problem of water pollution, especially the pollution caused by the rapidly breed of the aquatic plants, a simple and effective method to monitor the water environment is proposed. Aquatic plants can be distinguished through millimeter wave system, as they have high bright temperature compared to Water. The 8mm radiometer is used to measure the radiation characteristics of aquatic plants and image. The simulation results and radiation imaging experiments prove the feasibility and effectively of monitoring aquatic plants by millimeter wave radiometer. This study will contribute to monitoring the aquatic plants growth and decreasing the pollution.

  19. Dispersion characteristics of planar grating with arbitrary grooves for terahertz Smith-Purcell radiation

    SciTech Connect

    Cao, Miaomiao Li, Ke; Liu, Wenxin Wang, Yong

    2015-03-15

    In this paper, a novel method of getting the dispersion relations in planar grating with arbitrary grooves for terahertz Smith-Purcell radiation is investigated analytically. The continuous profile of the groove is approximately replaced by a series of rectangular steps. By making use of field matches method and the continuity of transverse admittance, the universal dispersion equation for grating with arbitrarily shaped grooves is derived. By solving the dispersion equation in presence of electron beam, the growth rate is obtained directly and the dependence on beam parameters is analyzed. Comparisons of the dispersion characteristics among some special groove shapes have been made by numerical calculation. The results show that the rectangular-step approximation method provides a novel approach to obtain the universal dispersion relation for grating with arbitrary grooves for Smith-Purcell radiation.

  20. A comparison of the radiation tolerance characteristics of multijunction solar cells with series and voltage-matched configurations

    NASA Technical Reports Server (NTRS)

    Gee, J. M.; Curtis, H. B.

    1988-01-01

    The effect of series and voltage-matched configurations on the performance of multijunction solar cells in a radiation environment was investigated. It was found that the configuration of the multijunction solar cell can have a significant impact on its radiation tolerence characteristics.

  1. Radiation characteristics of input power from surface wave sustained plasma antenna

    NASA Astrophysics Data System (ADS)

    Naito, T.; Yamaura, S.; Fukuma, Y.; Sakai, O.

    2016-09-01

    This paper reports radiation characteristics of input power from a surface wave sustained plasma antenna investigated theoretically and experimentally, especially focusing on the power consumption balance between the plasma generation and the radiation. The plasma antenna is a dielectric tube filled with argon and small amount of mercury, and the structure is a basic quarter wavelength monopole antenna at 2.45 GHz. Microwave power at 2.45 GHz is supplied to the plasma antenna. The input power is partially consumed to sustain the plasma, and the remaining part is radiated as a signal. The relationship between the antenna gain and the input power is obtained by an analytical derivation and numerical simulations. As a result, the antenna gain is kept at low values, and most of the input power is consumed to increase the plasma volume until the tube is filled with the plasma whose electron density is higher than the critical electron density required for sustaining the surface wave. On the other hand, the input power is consumed to increase the electron density after the tube is fully filled with the plasma, and the antenna gain increases with increasing the electron density. The dependence of the antenna gain on the electron density is the same as that of a plasma antenna sustained by a DC glow discharge. These results are confirmed by experimental results of the antenna gain and radiation patterns. The antenna gain of the plasma is a few dB smaller than that of the identical metal antenna. The antenna gain of the plasma antenna is sufficient for the wireless communication, although it is difficult to substitute the plasma antenna for metal antennas completely. The plasma antenna is suitable for applications having high affinity with the plasma characteristics such as low interference and dynamic controllability.

  2. Radiation characteristics of input power from surface wave sustained plasma antenna

    SciTech Connect

    Naito, T.; Yamaura, S.; Fukuma, Y.; Sakai, O.

    2016-09-15

    This paper reports radiation characteristics of input power from a surface wave sustained plasma antenna investigated theoretically and experimentally, especially focusing on the power consumption balance between the plasma generation and the radiation. The plasma antenna is a dielectric tube filled with argon and small amount of mercury, and the structure is a basic quarter wavelength monopole antenna at 2.45 GHz. Microwave power at 2.45 GHz is supplied to the plasma antenna. The input power is partially consumed to sustain the plasma, and the remaining part is radiated as a signal. The relationship between the antenna gain and the input power is obtained by an analytical derivation and numerical simulations. As a result, the antenna gain is kept at low values, and most of the input power is consumed to increase the plasma volume until the tube is filled with the plasma whose electron density is higher than the critical electron density required for sustaining the surface wave. On the other hand, the input power is consumed to increase the electron density after the tube is fully filled with the plasma, and the antenna gain increases with increasing the electron density. The dependence of the antenna gain on the electron density is the same as that of a plasma antenna sustained by a DC glow discharge. These results are confirmed by experimental results of the antenna gain and radiation patterns. The antenna gain of the plasma is a few dB smaller than that of the identical metal antenna. The antenna gain of the plasma antenna is sufficient for the wireless communication, although it is difficult to substitute the plasma antenna for metal antennas completely. The plasma antenna is suitable for applications having high affinity with the plasma characteristics such as low interference and dynamic controllability.

  3. Vibro-acoustic analysis procedures for the evaluation of the sound insulation characteristics of agricultural machinery cabins

    NASA Astrophysics Data System (ADS)

    Desmet, W.; Pluymers, B.; Sas, P.

    2003-09-01

    Over the last few years, customer demands regarding acoustic performance, along with the tightening of legal regulations on noise emission levels and human exposure to noise, have made the noise and vibration properties into important design criteria for agricultural machinery cabins. In this framework, both experimental analysis procedures for prototype testing as well as reliable numerical prediction tools for early design assessment are compulsory for an efficient optimization of the cabin noise and vibration comfort. This paper discusses several numerical approaches, which are based on the finite element and boundary element method, in terms of their practical use for airborne sound insulation predictions. To illustrate the efficiency and reliability of the various vibro-acoustic analysis procedures, the numerical procedures are applied for the case of a harvester driver's cabin and validated with experimental results.

  4. Characteristic measurements of silicon dioxide aerogel plasmas generated in a Planckian radiation environment

    SciTech Connect

    Dong Quanli; Wang Shoujun; Li Yutong; Zhang Yi; Zhao Jing; Wei Huigang; Shi Jianrong; Zhao Gang; Zhang Jiyan; Gu Yuqiu; Ding Yongkun; Wen Tianshu; Zhang Wenhai; Hu Xin; Liu Shenye; Zhang Lin; Tang Yongjian; Zhang Baohan; Zheng Zhijian; Nishimura, Hiroaki

    2010-01-15

    The temporally and spatially resolved characteristics of silicon dioxide aerogel plasmas were studied using x-ray spectroscopy. The plasma was generated in the near-Planckian radiation environment within gold hohlraum targets irradiated by laser pulses with a total energy of 2.4 kJ in 1 ns. The contributions of silicon ions at different charge states to the specific components of the measured absorption spectra were also investigated. It was found that each main feature in the absorption spectra of the measured silicon dioxide aerogel plasmas was contributed by two neighboring silicon ionic species.

  5. The Measurement of Spectral Characteristics and Composition of Radiation in Atlas with MEDIPIX2-USB Devices

    NASA Astrophysics Data System (ADS)

    Campbell, M.; Doležal, Z.; Greiffenberg, D.; Heijne, E.; Holy, T.; Idárraga, J.; Jakůbek, J.; Král, V.; Králík, M.; Lebel, C.; Leroy, C.; Llopart, X.; Lord, G.; Maneuski, D.; Ouellette, O.; Sochor, V.; Pospíšil, S.; Suk, M.; Tlustos, L.; Vykydal, Z.; Wilhelm, I.

    2008-06-01

    A network of devices to perform real-time measurements of the spectral characteristics and composition of radiation in the ATLAS detector and cavern during its operation is being built. This system of detectors will be a stand alone system fully capable of delivering real-time images of fluxes and spectral composition of different particle species including slow and fast neutrons. The devices are based on MEDIPIX2 pixel silicon detectors that will be operated via active USB cables and USB-Ethernet extenders through an Ethernet network by a PC located in the USA15 ATLAS control room. The installation of 14 devices inside ATLAS (detector and cavern) is in progress.

  6. Optimisation of frequency-modulated characteristics of output radiation in a lidar with Raman amplification

    SciTech Connect

    Grigorievsky, V I; Tezadov, Ya A

    2016-03-31

    The reported study is aimed at increasing the power in the transmission path of a lidar with Raman amplification for longpath sensing of methane by optimising the frequency-modulated characteristics of the output radiation. The pump current of the used distributed-feedback master laser was modulated by a linearfrequency signal with simultaneous application of a non-synchronous high-frequency signal. For such a modulation regime, the Raman amplifier provided the mean output power of 2.5 W at a wavelength of 1650 nm. The spectral broadening did not significantly decrease the lidar sensitivity at long paths. (lidars)

  7. Modeling the effects of wind tunnel wall absorption on the acoustic radiation characteristics of propellers

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Eversman, W.

    1986-01-01

    Finite element theory is used to calculate the acoustic field of a propeller in a soft walled circular wind tunnel and to compare the radiation patterns to the same propeller in free space. Parametric solutions are present for a 'Gutin' propeller for a variety of flow Mach numbers, admittance values at the wall, microphone position locations, and propeller to duct radius ratios. Wind tunnel boundary layer is not included in this analysis. For wall admittance nearly equal to the characteristic value of free space, the free field and ducted propeller models agree in pressure level and directionality. In addition, the need for experimentally mapping the acoustic field is discussed.

  8. Modeling the effects of wind tunnel wall absorption on the acoustic radiation characteristics of propellers

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Eversman, W.

    1986-01-01

    Finite element theory is used to calculate the acoustic field of a propeller in a soft walled circular wind tunnel and to compare the radiation patterns to the same propeller in free space. Parametric solutions are present for a "Gutin" propeller for a variety of flow Mach numbers, admittance values at the wall, microphone position locations, and propeller to duct radius ratios. Wind tunnel boundary layer is not included in this analysis. For wall admittance nearly equal to the characteristic value of free space, the free field and ducted propeller models agree in pressure level and directionality. In addition, the need for experimentally mapping the acoustic field is discussed.

  9. Conceptualisation of the characteristics of advanced practitioners in the medical radiation professions

    SciTech Connect

    Smith, Tony; Harris, Jillian; Woznitza, Nick; Maresse, Sharon; Sale, Charlotte

    2015-09-15

    Professions grapple with defining advanced practice and the characteristics of advanced practitioners. In nursing and allied health, advanced practice has been defined as ‘a state of professional maturity in which the individual demonstrates a level of integrated knowledge, skill and competence that challenges the accepted boundaries of practice and pioneers new developments in health care’. Evolution of advanced practice in Australia has been slower than in the United Kingdom, mainly due to differences in demography, the health system and industrial relations. This article describes a conceptual model of advanced practitioner characteristics in the medical radiation professions, taking into account experiences in other countries and professions. Using the CanMEDS framework, the model includes foundation characteristics of communication, collaboration and professionalism, which are fundamental to advanced clinical practice. Gateway characteristics are: clinical expertise, with high level competency in a particular area of clinical practice; scholarship and teaching, including a masters qualification and knowledge dissemination through educating others; and evidence-based practice, with judgements made on the basis of research findings, including research by the advanced practitioner. The pinnacle of advanced practice is clinical leadership, where the practitioner has a central role in the health care team, with the capacity to influence decision making and advocate for others, including patients. The proposed conceptual model is robust yet adaptable in defining generic characteristics of advanced practitioners, no matter their clinical specialty. The advanced practice roles that evolve to meet future health service demand must focus on the needs of patients, local populations and communities.

  10. Gravitational radiation by point particle eccentric binary systems in the linearised characteristic formulation of general relativity

    NASA Astrophysics Data System (ADS)

    Cedeño Montaña, C. E.; de Araujo, J. C. N.

    2016-04-01

    We study a binary system composed of point particles of unequal masses in eccentric orbits in the linear regime of the characteristic formulation of general relativity, generalising a previous study found in the literature in which a system of equal masses in circular orbits is considered. We also show that the boundary conditions on the time-like world tubes generated by the orbits of the particles can be extended beyond circular orbits. Concerning the power lost by the emission of gravitational waves, it is directly obtained from the Bondi's News function. It is worth stressing that our results are completely consistent, because we obtain the same result for the power derived by Peters and Mathews, in a different approach, in their seminal paper of 1963. In addition, the present study constitutes a powerful tool to construct extraction schemes in the characteristic formalism to obtain the gravitational radiation produced by binary systems during the inspiralling phase.

  11. Patterning Characteristics of a Chemically-Amplified Negative Resist in Synchrotron Radiation Lithography

    NASA Astrophysics Data System (ADS)

    Deguchi, Kimiyoshi; Miyoshi, Kazunori; Ishii, Tetsuyoshi; Matsuda, Tadahito

    1992-09-01

    To explore the applicability of synchrotron radiation X-ray lithography for fabricating sub-quartermicron devices, we investigate the patterning characteristics of the chemically-amplified negative resist SAL601-ER7. Since these characteristics depend strongly on the conditions of the chemical amplification process, the effects of post-exposure baking and developing conditions on sensitivity and resolution are examined. The resolution-limiting factors are investigated, revealing that pattern collapse during the development process and fog caused by Fresnel diffraction, photo-electron scattering, and acid diffusion in the resist determine the resolution and the maximum aspect ratio of the lines and spaces pattern. Using the model of a swaying beam supported at one end, it is shown that pattern collapse depends on the resist pattern’s flexural stiffness. Patterning stability, which depends on the delay time between exposure and baking, is also discussed.

  12. An analysis of the radiation field characteristics for extremity dose assessment during maintenance periods at nuclear power plants in Korea.

    PubMed

    Kim, Hee Geun; Kong, Tae Young

    2012-12-01

    Workers who maintain the water chambers of steam generators during maintenance periods in nuclear power plants (NPPs) have a higher likelihood of high radiation exposure, even if they are exposed for a short period of time. In particular, it is expected that the hands of workers would receive the highest radiation exposure as a consequence of hand contact with radioactive materials. In this study, a characteristic analysis of inhomogeneous radiation fields for contact operations was conducted using thermoluminescent dosemeters for the whole body and extremities during maintenance periods at Korean NPPs. It was observed that inhomogeneous radiation fields for contact operations at NPPs were dominated by high-energy photons.

  13. Gazetteer of hydrologic characteristics of streams in Massachusetts; Taunton and Ten Mile River basins and coastal river basins of Mount Hope Bay, Narragansett Bay, and Rhode Island Sound

    USGS Publications Warehouse

    Wandle, S.W.; Keezer, G.R.

    1984-01-01

    The study area includes streams draining the Taunton River (562 square miles), the Tenmile River (53.1 square miles), and the minor streams flowing into Mount Hope Bay, Narragansett Bay, and Rhode Island Sound in southern Massachusetts, and adjacent areas of Rhode Island. Drainage areas, using the latest available 1:24 ,000 scale topographic maps, were computed for the first time for streams draining more than 3 square miles and were re-computed for data-collection sites. Streamflow characteristics, at 10 gaging stations were calculated using a new data base with daily flow records through 1981. These characteristics include annual and monthly flow statistics, duration of daily flow values, and the annual 7-day mean low flow at the 2-year and 10-year recurrence intervals. Seven-day low-flow statistics are presented for 44 partial-record sites and the procedures used to determine the hydrologic characteristics of a basin are summarized. Basin characteristics representing 14 commonly used indices to estimate various streamflows are presented for selected gaged streams. This gazetteer will aid in the planning and managing of water-resources related activities, and will provide a common data base for governmental agencies and the engineering and planning communities. (USGS)

  14. The Characteristics and Radiative Impacts of Cirrus observed by Cloud Radar during EPIC2001

    NASA Astrophysics Data System (ADS)

    Zuidema, P.; Matrosov, S.; Fairall, C.; Uttal, T.; Shupe, M.

    2002-12-01

    Cirrus unobscured by lower cloud occurred almost 10% of the time during the first leg of EPIC, and up to 35% on selected days. This presentation investigates the applicability of the Matrosov et al. (2002) technique for estimating cirrus ice water contents, particle sizes, volume extinction coefficients and optical depths. The technique is attractive because its reliance on radar measurements alone increases its applicability above dual-instrument techniques. For example, the method can be applied to situations where high cloud is associated with lower precipitation, a common situation during the first leg of EPIC. The vertical component of the Doppler velocity (Vz) measurements are used to infer particle size. Errors occur in the inference of Vz from the Doppler velocity through the contribution of the (imperfectly-known) horizontal winds, and the impact of the ship movement upon the radar beam orientation. This study investigates the applicability of the retrieval method to the EPIC data and quantifies the associated errors. Results are judged through comparisons of radiative flux calculations (for the unobscured cirrus) to the shipboard broadband solar flux measurements. These radiative heating rate and cloud forcing calculations reveal the impact of the cirrus on the earth's radiation budget. Comparisons are made between the microphysical characteristics of the unobscured cirrus, and the cirrus associated with the presence of lower precipitation.

  15. Radiation characteristics and implosion dynamics of Z-pinch dynamic hohlraums performed on PTS facility

    NASA Astrophysics Data System (ADS)

    Huang, Xian Bin; Ren, Xiao Dong; Dan, Jia Kun; Wang, Kun Lun; Xu, Qiang; Zhou, Shao Tong; Zhang, Si Qun; Cai, Hong Chun; Li, Jing; Wei, Bing; Ji, Ce; Feng, Shu Ping; Wang, Meng; Xie, Wei Ping; Deng, Jian Jun

    2017-09-01

    The preliminary experimental results of Z-pinch dynamic hohlraums conducted on the Primary Test Stand (PTS) facility are presented herein. Six different types of dynamic hohlraums were used in order to study the influence of load parameters on radiation characteristics and implosion dynamics, including dynamic hohlraums driven by single and nested arrays with different array parameters and different foams. The PTS facility can deliver a current of 6-8 MA in the peak current and 60-70 ns in the 10%-90% rising time to dynamic hohlraum loads. A set of diagnostics monitor the implosion dynamics of plasmas, the evolution of shock waves in the foam and the axial/radial X-ray radiation, giving the key parameters characterizing the features of dynamic hohlraums, such as the trajectory and related velocity of shock waves, radiation temperature, and so on. The experimental results presented here put our future study on Z-pinch dynamic hohlraums on the PTS facility on a firm basis.

  16. High-frequency electric field and radiation characteristics of cellular microtubule network.

    PubMed

    Havelka, D; Cifra, M; Kučera, O; Pokorný, J; Vrba, J

    2011-10-07

    Microtubules are important structures in the cytoskeleton, which organizes the cell. Since microtubules are electrically polar, certain microtubule normal vibration modes efficiently generate oscillating electric field. This oscillating field may be important for the intracellular organization and intercellular interaction. There are experiments which indicate electrodynamic activity of variety of cells in the frequency region from kHz to GHz, expecting the microtubules to be the source of this activity. In this paper, results from the calculation of intensity of electric field and of radiated electromagnetic power from the whole cellular microtubule network are presented. The subunits of microtubule (tubulin heterodimers) are approximated by elementary electric dipoles. Mechanical oscillation of microtubule is represented by the spatial function which modulates the dipole moment of subunits. The field around oscillating microtubules is calculated as a vector superposition of contributions from all modulated elementary electric dipoles which comprise the cellular microtubule network. The electromagnetic radiation and field characteristics of the whole cellular microtubule network have not been theoretically analyzed before. For the perspective experimental studies, the results indicate that macroscopic detection system (antenna) is not suitable for measurement of cellular electrodynamic activity in the radiofrequency region since the radiation rate from single cells is very low (lower than 10⁻²⁰ W). Low noise nanoscopic detection methods with high spatial resolution which enable measurement in the cell vicinity are desirable in order to measure cellular electrodynamic activity reliably. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. A study of the characteristics of radiation contaminants within a clinically useful photon beam.

    PubMed

    Krithivas, G; Rao, S N

    1985-01-01

    Contaminant radiation within a therapeutic beam has been studied for accelerator-produced 24-MV x rays by a direct measurement utilizing independent jaws. A carefully positioned diode was exposed to secondary radiation for various collimator settings that project field sizes between [10 X (0 + 5)] and [26 X (0 + 13)] cm at a source-to-axis distance of 1 m. [The notation [L X (W1 + W2)] means the projected field area due to lower (L) and upper (W1, W2) jaws.] Measurements were taken by placing polystyrene sheets with density thicknesses ranging from 0.21 to 4.53 g cm-2 in front of the detector. The data strongly demonstrate that with increasing field size, the ratio of the dose due to electrons to that due to photons increases rapidly. The characteristic feature of the electron depth dose curves may be linked to the observed shift in the depth of dose maximum (dmax) with field size. Data taken with a magnetic field of 0.15 T permit analysis of photons and electrons with regard to their intensity, energy, and behavior in a phantom. From an analysis of 12.5 X 12.5 cm data, various radiation components have been studied and are correlated with the observed contaminants.

  18. Acoustic characteristics of biosonar sounds of free-ranging botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the Negro River, Amazon, Brazil.

    PubMed

    Yamamoto, Yukiko; Akamatsu, Tomonari; da Silva, Vera M F; Yoshida, Yayoi; Kohshima, Shiro

    2015-08-01

    Odontoceti emit broadband high-frequency clicks on echolocation for orientation or prey detection. In the Amazon Basin, two odontoceti species, boto (Amazon River dolphin, Inia geoffrensis) and tucuxi (Sotalia fluviatilis), live sympatrically. The acoustic characteristics of the echolocation clicks of free-ranging botos and tucuxis were measured with a hydrophone array consisting of a full-band and an acoustic event recorder (A-tag). The clicks of the two species were short-duration broadband signals. The apparent source level was 201 dB 1 μPa peak-to-peak at 1 m in the botos and 181 dB 1 μPa peak-to-peak at 1 m in the tucuxis, and the centroid frequency was 82.3 kHz in the botos and 93.1 kHz in the tucuxis. The high apparent source level and low centroid frequency are possibly due to the difference in body size or sound production organs, especially the nasal structure, the sound source of clicks in odontoceti.

  19. Meteor fireball sounds identified

    NASA Technical Reports Server (NTRS)

    Keay, Colin

    1992-01-01

    Sounds heard simultaneously with the flight of large meteor fireballs are electrical in origin. Confirmation that Extra/Very Low Frequency (ELF/VLF) electromagnetic radiation is produced by the fireball was obtained by Japanese researchers. Although the generation mechanism is not fully understood, studies of the Meteorite Observation and Recovery Project (MORP) and other fireball data indicate that interaction with the atmosphere is definitely responsible and the cut-off magnitude of -9 found for sustained electrophonic sounds is supported by theory. Brief bursts of ELF/VLF radiation may accompany flares or explosions of smaller fireballs, producing transient sounds near favorably placed observers. Laboratory studies show that mundane physical objects can respond to electrical excitation and produce audible sounds. Reports of electrophonic sounds should no longer be discarded. A catalog of over 300 reports relating to electrophonic phenomena associated with meteor fireballs, aurorae, and lightning was assembled. Many other reports have been cataloged in Russian. These may assist the full solution of the similar long-standing and contentious mystery of audible auroral displays.

  20. Sound radiation from single and annular stream nozzles, with modal decomposition of in-duct acoustic power

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.

    1987-01-01

    An experimental program was carried out to study the acoustic characteristics of single and annular stream duct-nozzle systems at various flow conditions by using a refined acoustic impulse technique. In this technique, signal synthesis and signal averaging processes are incorporated to generate a desired impulsive signal from acoustic driver(s) and to eliminate background noise (flow noise) from in-duct and far field signals, respectively. The contribution of higher order modes to incident reflected and transmitted acoustic powers is accounted for by using a modal decomposition process. The annular stream terminations were tested statically at various annular stream flow velocities with no inner stream flow. The results derived from the experiments include in-duct acoustic powers, termination reflection coefficients, transmission coefficients, far field power, and acoustic dissipation.

  1. Sound radiation from single and annular stream nozzles, with modal decomposition of in-duct acoustic power

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.

    1987-01-01

    An experimental program was carried out to study the acoustic characteristics of single and annular stream duct-nozzle systems at various flow conditions by using a refined acoustic impulse technique. In this technique, signal synthesis and signal averaging processes are incorporated to generate a desired impulsive signal from acoustic driver(s) and to eliminate background noise (flow noise) from in-duct and far field signals, respectively. The contribution of higher order modes to incident reflected and transmitted acoustic powers is accounted for by using a modal decomposition process. The annular stream terminations were tested statically at various annular stream flow velocities with no inner stream flow. The results derived from the experiments include in-duct acoustic powers, termination reflection coefficients, transmission coefficients, far field power, and acoustic dissipation.

  2. Categorizing Sounds

    DTIC Science & Technology

    1988-09-30

    Classification) CatemorizinR Sounds 12. PERSONAL AUTHOR(S) Dr. Gremory R. Lockhead 13a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Year, Month,Day) S...variability in judgments of univariate sounds depends on what stimuli occurred recently (sequence effects), what stimuli might occur (set and range effects...CLASSIFICATION OF TH IS PAGE UNCLASSIFIED CATEGORIZING SOUNDS =- Gregory R. Lockhead Department of Psychology 3 Duke University -4 Durham, North Carolina 27706

  3. A method for characterizing aerodynamic sound sources in turbomachines

    NASA Astrophysics Data System (ADS)

    Mongeau, L.; Thompson, D. E.; Mclaughlin, D. K.

    1995-03-01

    A method based on Weidemann's acoustic similarity laws [1] was used to investigate the aerodynamic sound generated by a partially ducted centrifugal pump rotor. The primary objective of the method was to determine the spectral characteristics of the sound source by isolating the effects of acoustic phenomena such as duct resonances or sound reflections. Pump-radiated sound pressure spectra were measured for different impeller rotational speeds, keeping the operating condition constant. The spectra, assumed to be expressed as the product of a source spectral distribution function and an acoustic frequency response function, were then decomposed into a product form following a computer-implemented algorithm. The method was successful in accurately determining the spectral distribution of the broadband aerodynamic noise generating mechanisms involved and that of the acoustic frequency response of the system. The absolute levels of the source function and the acoustic function were established by assuming that, over a limited low frequency range, the average gain of the frequency response function is unity so that comparisons between different pump operating conditions could be made. The source spectral distribution was found to be independent of the microphone location and the acoustic loading. When applicable, this method therefore allows the characterization of aerodynamic sound sources by measuring ordinary sound pressure spectra, at any one point around the source, without having to isolate the source from the system. The source characterization method was instrumental in the study of sound generation by rotating stall presented in a previous publication [2].

  4. Effect of radiation light characteristics on surface hardness of paint-on resin for shade modification.

    PubMed

    Arikawa, Hiroyuki; Kanie, Takahito; Fujii, Koichi; Ban, Seiji

    2005-12-01

    The purpose of this study was to investigate the effect of radiation light characteristics--of different types of clinical light-curing unit--on polymerization efficiency, as determined by the surface hardness of light-cured paint-on resins. Four shades of paint-on resin for shade modification of restorative resins were used. Materials were cured using one laboratory and three clinical light-curing units with different light sources, namely tungsten-halogen, LED, plasma arc, and xenon flash lamps. Knoop hardness measurements were taken at both the top and bottom surfaces of the specimens to assess the mechanical properties and degree of polymerization. Both LED and plasma arc light units caused significantly poorer surface hardness than the halogen and laboratory xenon lights. In addition, the transparent shade was more sensitive to surface hardness than other chromatic shades. Our results indicated that the polymerization efficiency of paint-on resin was significantly influenced by the radiation light characteristics of clinical light-curing units.

  5. Observational characteristics of cloud radiative effects over three arid regions in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Li, Jiandong; Wang, Tianhe; Habib, Ammara

    2017-08-01

    Cloud-radiation processes play an important role in regional energy budgets and surface temperature changes over arid regions. Cloud radiative effects (CREs) are used to quantitatively measure the aforementioned climatic role. This study investigates the characteristics of CREs and their temporal variations over three arid regions in central Asia (CA), East Asia (EA), and North America (NA), based on recent satellite datasets. Our results show that the annual mean shortwave (SW) and net CREs (SWCRE and NCRE) over the three arid regions are weaker than those in the same latitudinal zone of the Northern Hemisphere. In most cold months (November-March), the longwave (LW) CRE is stronger than the SWCRE over the three arid regions, leading to a positive NCRE and radiative warming in the regional atmosphere-land surface system. The cold-season mean NCRE at the top of the atmosphere (TOA) averaged over EA is 4.1 W m-2, with a positive NCRE from November to March, and the intensity and duration of the positive NCRE is larger than that over CA and NA. The CREs over the arid regions of EA exhibit remarkable annual cycles due to the influence of the monsoon in the south. The TOA LWCRE over arid regions is closely related to the high-cloud fraction, and the SWCRE relates well to the total cloud fraction. In addition, the relationship between the SWCRE and the low-cloud fraction is good over NA because of the considerable occurrence of low cloud. Further results show that the interannual variation of TOA CREs is small over the arid regions of CA and EA, but their surface LWCREs show certain decreasing trends that correspond well to their decreasing total cloud fraction. It is suggested that combined studies of more observational cloud properties and meteorological elements are needed for indepth understanding of cloud-radiation processes over arid regions of the Northern Hemisphere.

  6. Interpolated Sounding and Gridded Sounding Value-Added Products

    SciTech Connect

    M. P. Jensen; Toto, T.

    2016-03-01

    Standard Atmospheric Radiation Measurement (ARM) Climate Research Facility sounding files provide atmospheric state data in one dimension of increasing time and height per sonde launch. Many applications require a quick estimate of the atmospheric state at higher time resolution. The INTERPOLATEDSONDE (i.e., Interpolated Sounding) Value-Added Product (VAP) transforms sounding data into continuous daily files on a fixed time-height grid, at 1-minute time resolution, on 332 levels, from the surface up to a limit of approximately 40 km. The grid extends that high so the full height of soundings can be captured; however, most soundings terminate at an altitude between 25 and 30 km, above which no data is provided. Between soundings, the VAP linearly interpolates atmospheric state variables in time for each height level. In addition, INTERPOLATEDSONDE provides relative humidity scaled to microwave radiometer (MWR) observations.

  7. Main Characteristics of the VLF Magnetic Field Waves Recorded by the Search Coil Magnetometer Experiment Onboard the CUSP Sounding Rocket

    NASA Astrophysics Data System (ADS)

    Pinçon, J.; Krasnoselskikh, V.; de Feraudy, H.; Rezeau, L.; Robert, P.; Pfaff, R. F.

    2003-12-01

    The CUSP rocket is a NASA Black Brant X sounding rocket dedicated to the exploration of the electrodynamic coupling, pulsations, and acceleration processes in the dayside cusp and the boundary layer interface. The launch occured on December 14, 2002, from Ny Åleysund, Spitzbergen (79° N) during Bz negative conditions. We present the magnetic field waves measurement collected in the frequency range [10 Hz - 10 kHz] by the three axis Search Coil Magnetometer (SCM) experiment onboard CUSP. The observations reveal the presence of intense field fluctuations corresponding to ELF hiss which is only seen on closed field lines and hence can be used to define the magnetic boundary of the cusp. Several data analysis techniques were applied to the 3 components of the magnetic field fluctuations associated with the ELF hiss to obtain information regarding the wave polarization and the wave vector directions. The magnetic field wave data are compared with simultaneous observations of electric field wave data to further enhance our understanding of these wave phenomena. The main results coming from this detailed study are presented and discussed.

  8. The effect of oblique angle of sound incidence, realistic edge conditions, curvature and in-plane panel stresses on the noise reduction characteristics of general aviation type panels

    NASA Technical Reports Server (NTRS)

    Grosveld, F.; Lameris, J.; Dunn, D.

    1979-01-01

    Experiments and a theoretical analysis were conducted to predict the noise reduction of inclined and curved panels. These predictions are compared to the experimental results with reasonable agreement between theory and experiment for panels under an oblique angle of sound incidence. Theoretical as well as experimental results indicate a big increase in noise reduction when a flat test panel is curved. Further curving the panel slightly decreases the noise reduction. Riveted flat panels are shown to give a higher noise reduction in the stiffness-controlled frequency region, while bonded panels are superior in this region when the test panel is curved. Experimentally measured noise reduction characteristics of flat aluminum panels with uniaxial in-plane stresses are presented and discussed. These test results indicate an important improvement in the noise reduction of these panels in the frequency range below the fundamental panel/cavity frequency.

  9. Measuring the characteristics of backscattering of sound on a rough surface in the near-field zone of a phased array

    NASA Astrophysics Data System (ADS)

    Salin, M. B.; Potapov, O. A.; Salin, B. M.; Chashchin, A. S.

    2016-01-01

    The paper presents the results of an experiment on measuring the characteristics of backscattering of sound waves by a rough surface. Measurements were conducted in the near zone of a vertical array, which made it possible with a high degree of accuracy to control the propagation conditions and the angles of incidence of an acoustic wave onto the surface. Tonal signals were emitted in a constant mode at frequencies of 0.5-3.5 kHz. The Doppler spectrum of the scattered signal was analyzed in detail, the spectral component corresponding to Bragg scattering was isolated, and the width of this component was determined. The possibilities of calculating the scattered field using two forms of the sea state spectrum are studied and compared: the two-dimensional spatiotemporal sea state spectrum, which was measured optically, and the conventional one-dimensional time spectrum, measured with a single surveying mark.

  10. Real-ear acoustical characteristics of impulse sound generated by golf drivers and the estimated risk to hearing: a cross-sectional study.

    PubMed

    Zhao, Fei; Bardsley, Barry

    2014-01-21

    This study investigated real-ear acoustical characteristics in terms of the sound pressure levels (SPLs) and frequency responses in situ generated from golf club drivers at impact with a golf ball. The risk of hearing loss caused by hitting a basket of golf balls using various drivers was then estimated. Cross-sectional study. The three driver clubs were chosen on the basis of reflection of the commonality and modern technology of the clubs. The participants were asked to choose the clubs in a random order and hit six two-piece range golf balls with each club. The experiment was carried out at a golf driving range in South Wales, UK. 19 male amateur golfers volunteered to take part in the study, with an age range of 19-54 years. The frequency responses and peak SPLs in situ of the transient sound generated from the club at impact were recorded bilaterally and simultaneously using the GN Otometric Freefit wireless real-ear measurement system. A swing speed radar system was also used to investigate the relationship between noise level and swing speed. Different clubs generated significantly different real-ear acoustical characteristics in terms of SPL and frequency responses. However, they did not differ significantly between the ears. No significant correlation was found between the swing speed and noise intensity. On the basis of the SPLs measured in the present study, the percentage of daily noise exposure for hitting a basket of golf balls using the drivers described above was less than 2%. The immediate danger of noise-induced hearing loss for amateur golfers is quite unlikely. However, it may be dangerous to hearing if the noise level generated by the golf clubs exceeded 116 dBA.

  11. Real-ear acoustical characteristics of impulse sound generated by golf drivers and the estimated risk to hearing: a cross-sectional study

    PubMed Central

    Zhao, Fei; Bardsley, Barry

    2014-01-01

    Objectives This study investigated real-ear acoustical characteristics in terms of the sound pressure levels (SPLs) and frequency responses in situ generated from golf club drivers at impact with a golf ball. The risk of hearing loss caused by hitting a basket of golf balls using various drivers was then estimated. Design Cross-sectional study. Setting The three driver clubs were chosen on the basis of reflection of the commonality and modern technology of the clubs. The participants were asked to choose the clubs in a random order and hit six two-piece range golf balls with each club. The experiment was carried out at a golf driving range in South Wales, UK. Participants 19 male amateur golfers volunteered to take part in the study, with an age range of 19–54 years. Outcome measures The frequency responses and peak SPLs in situ of the transient sound generated from the club at impact were recorded bilaterally and simultaneously using the GN Otometric Freefit wireless real-ear measurement system. A swing speed radar system was also used to investigate the relationship between noise level and swing speed. Results Different clubs generated significantly different real-ear acoustical characteristics in terms of SPL and frequency responses. However, they did not differ significantly between the ears. No significant correlation was found between the swing speed and noise intensity. On the basis of the SPLs measured in the present study, the percentage of daily noise exposure for hitting a basket of golf balls using the drivers described above was less than 2%. Conclusions The immediate danger of noise-induced hearing loss for amateur golfers is quite unlikely. However, it may be dangerous to hearing if the noise level generated by the golf clubs exceeded 116 dBA. PMID:24448845

  12. The separation of radiating and non-radiating near-field pressure fluctuations in supersonic jets

    NASA Astrophysics Data System (ADS)

    Du, Yongle; Morris, Philip J.

    2015-10-01

    Conventional analysis infers the jet noise source characteristics from either the turbulent fluctuations in the mixing layer, the near-field pressure fluctuations, or the far-field radiated sound. It is generally accepted that the first two techniques include both the radiating and non-radiating noise sources while the last senses only the radiated sound. Understanding of the characteristics of the non-radiating and radiating fluctuations helps to shed light on the noise source mechanisms. For this purpose, a quantitative analysis is introduced in this study to separate the radiating from the non-radiating near-field fluctuations. The analysis uses a high-fidelity unsteady jet flow and noise simulation for an internally mixed dual-stream nozzle. Based on the predicted far-field acoustic pressure on a virtual microphone array, a simple beamforming method is used to derive the equivalent wavepacket-like noise sources on a conical surface outside the jet mixing layer. These radiating noise sources are compared with the total near-field pressure fluctuations to examine their different characteristics. Wavepacket-like noise sources are filtered with the POD (Proper Orthogonal Decomposition) at discrete frequencies. Although the two equivalent noise sources show different amplitude distributions and phase velocities, they agree favorably with the Mach wave radiation theory as well as with the near-field turbulence. Both reproduce well the noise radiation pattern in terms of the phase, wavelength, radiation direction and noise levels when inserted into the wave equation.

  13. Experimental investigation on Performance and Emission Characteristics of J20, P20, N20 Biodiesel blends and Sound Characteristics of P20 Biodiesel blend Used in Single Cylinder Diesel Engine

    NASA Astrophysics Data System (ADS)

    rajasekar, R.; karthik, N.; Xavier, Goldwin

    2017-05-01

    Present work provides the effect of biodiesel blends and Sound Characteristics of P20 Biodiesel blend compared with Performance and emission Characteristics of diesel. Methods and analysis biodiesel blends was prepared by the Transesterification Process. Experiments were conducted in single cylinder constant speed direct injection diesel engine for various test fuels. Research is mainly focused on pongamia oil. It was observed that a 20% Pongamia oil blends and its properties were similar to diesel. The results showed that 20% Pongamia oil blends gave better performance, less in noise and emission compared with ester of Jatropha and neem oil blends. Hence Pongamia blends can be used in existing diesel engine without compromising the engine performance.

  14. Conceptualisation of the characteristics of advanced practitioners in the medical radiation professions

    PubMed Central

    Smith, Tony; Harris, Jillian; Woznitza, Nick; Maresse, Sharon; Sale, Charlotte

    2015-01-01

    Professions grapple with defining advanced practice and the characteristics of advanced practitioners. In nursing and allied health, advanced practice has been defined as ‘a state of professional maturity in which the individual demonstrates a level of integrated knowledge, skill and competence that challenges the accepted boundaries of practice and pioneers new developments in health care’. Evolution of advanced practice in Australia has been slower than in the United Kingdom, mainly due to differences in demography, the health system and industrial relations. This article describes a conceptual model of advanced practitioner characteristics in the medical radiation professions, taking into account experiences in other countries and professions. Using the CanMEDS framework, the model includes foundation characteristics of communication, collaboration and professionalism, which are fundamental to advanced clinical practice. Gateway characteristics are: clinical expertise, with high level competency in a particular area of clinical practice; scholarship and teaching, including a masters qualification and knowledge dissemination through educating others; and evidence-based practice, with judgements made on the basis of research findings, including research by the advanced practitioner. The pinnacle of advanced practice is clinical leadership, where the practitioner has a central role in the health care team, with the capacity to influence decision making and advocate for others, including patients. The proposed conceptual model is robust yet adaptable in defining generic characteristics of advanced practitioners, no matter their clinical specialty. The advanced practice roles that evolve to meet future health service demand must focus on the needs of patients, local populations and communities. PMID:26451243

  15. [Research on Spectrum Radiation Characteristics of a New Type Infrared/ Ultraviolet Dual Color Decoy].

    PubMed

    Chen, Chun-sheng; Dai, Meng-yan; Liu, Hai-feng; Xie, Chang-you; Zhang, Tong; Fang, Guo-feng

    2015-07-01

    The advantage of traditional MTV infrared decoys which are mainly consist of magnesium, Teflon and VITON is that it emits high radiant energy, so it is an effective countermeasure to traditional seekers which seek the target by heat source. The spectral radiant intensity which generated from high temperature combustion of MTV infrared decoys in near infrared region and ultraviolet band is very high, and that in Mid-IR region is relative lower, however the radiant intensity of real jet fighter in ultraviolet band is low and the infrared radiant intensity ratio of Mid-IR to near IR band is greater than 1. Thus, the traditional MTV infrared decoys are hardly able to counter the seekers equipped with dual color combined guidance system. Based on the spectral matching principle, we designed and prepared a new infrared/ultraviolet dual color decoy which is mainly consist of oxidant (wt% 45-75), fuel (wt% 10-25), energetic binder (wt% 25-50) and additives. We conducted theoretical calculations on combustion products of the reagent combinations using CEA (Chemic equilibrium & Application) software and initially determined the content of each component of the decoy formulation on the basis of the calculations results, then investigated the infrared radiation characteristics of decoys employing SR5000 spectrum radiometer and remote sensing interferometer spectrometer Tensor37 and analyzed the possible reasons for test results difference of the two systems separately from the test principle and calculation method, the testing environment, stability of testing results and other aspects. We studied the ultraviolet radiation characteristics of decoys using S2000 fiber optical spectrometer and the test results were consistent with the fighter ultraviolet radiant intensity which gained from theoretical calculation. We researched on the temperature characteristics of decoys by Imager IR 8325 mid-infrared thermal imager and it turned out that the dual color decoy is similar to the

  16. Spatiotemporal multifractal characteristics of electromagnetic radiation in response to deep coal rock bursts

    NASA Astrophysics Data System (ADS)

    Hu, S.; Wang, E.; Liu, X.

    2014-08-01

    Dynamic collapses of deeply mined coal rocks are severe threats to miners; in order to predict collapses more accurately using electromagnetic radiation (EMR), we investigate the spatiotemporal multifractal characteristics and formation mechanism of EMR induced by underground coal mining. Coal rock in the burst-prone zone often exchanges materials (gas, water and coal) and energy with its environment and gradually transitions from its original stable equilibrium structure to a nonequilibrium dissipative structure with implicit spatiotemporal complexity or multifractal structures, resulting in temporal variation in multifractal EMR. The inherent law of EMR time series during damage evolution was analyzed by using time-varying multifractal theory. Results show that the time-varying multifractal characteristics of EMR are determined by damage evolution processes. Moreover, the dissipated energy caused by the damage evolutions, such as crack propagation, fractal sliding and shearing, can be regarded as the fingerprint of various EMR micro-mechanics. The dynamic spatiotemporal multifractal spectrum of EMR considers both spatial (multiple fractures) and temporal (dynamic evolution) characteristics of coal rocks and records the dynamic evolution processes of rock bursts. Thus, it can be used to evaluate the coal deformation and fracture process. The study is of significance for us to understand the EMR mechanism in detail and to increase the accuracy of the EMR method in forecasting dynamic disasters.

  17. Time-Varying Multifractal Characteristics and Formation Mechanism of Loaded Coal Electromagnetic Radiation

    NASA Astrophysics Data System (ADS)

    Hu, Shaobin; Wang, Enyuan; Li, Zhonghui; Shen, Rongxi; Liu, Jie

    2014-09-01

    Dynamic collapses of deeply mined coal rocks are severe threats to miners. To predict the collapses more accurately using electromagnetic radiation (EMR), we investigate the time-varying multifractal characteristics and formation mechanism of EMR induced by underground coal mining. A series of uniaxial compression and multi-stage loading experiments with coal samples of different mechanical properties were carried out. The EMR signals during their damage evolution were monitored in real-time; the inherent law of EMR time series was analyzed by fractal theory. The results show that the time-varying multifractal characteristics of EMR are determined by damage evolutions process, the dissipated energy caused by damage evolutions such as crack propagation, fractal sliding and shearing can be regard as the fingerprint of various EMR micro-mechanics. Based on the Irreversible thermodynamics and damage mechanics, we introduced the damage internal variable, constructed the dissipative potential function and established the coupled model of the EMR and the dissipative energy, which revealed the nature of dynamic nonlinear characteristics of EMR. Dynamic multifractal spectrum is the objective response of EMR signals, thus it can be used to evaluate the coal deformation and fracture process.

  18. Spatiotemporal multifractal characteristics of electromagnetic radiation in response to deep coal rock bursts

    NASA Astrophysics Data System (ADS)

    Shaobin, H.; Enyuan, W.; Xiaofei, L.

    2014-04-01

    Dynamic collapses of deeply mined coal rocks are severe threats to miners, in order to predict the collapses more accurately using electromagnetic radiation (EMR), we investigate the spatiotemporal multifractal characteristics and formation mechanism of EMR induced by underground coal mining. Coal rock in the burst-prone zone often exchanges materials and energy with its environment and gradually transits from its original stable equilibrium structure to a non-equilibrium dissipative structure with implicit spatiotemporal complexity or multifractal structures, resulting in temporal variation in multifractal EMR. The inherent law of EMR time series during damage evolution was analyzed by using time-varying multifractal theory. Results show that the time-varying multifractal characteristics of EMR are determined by damage evolutions process, the dissipated energy caused by damage evolutions such as crack propagation, fractal sliding and shearing can be regarded as the fingerprint of various EMR micro-mechanics. Dynamic spatiotemporal multifractal spectrum of EMR considers both spatial (multiple fractures) and temporal (dynamic evolution) characteristics of coal rocks, and records the dynamic evolution processes of rock bursts. Thus, it can be used to evaluate the coal deformation and fracture process. The study is of significance for us to in-depth understand EMR mechanism and to increase the accuracy of applying the EMR method to forecast dynamic disasters.

  19. Physical and Radiative Characteristics and Long Term Variability of the Okhotsk Sea Ice Cover

    NASA Technical Reports Server (NTRS)

    Nishio, Fumihiko; Comiso, Josefino C.; Gersten, Robert; Nakayama, Masashige; Ukita, Jinro; Gasiewski, Al; Stanko, Boba; Naoki, Kazuhiro

    2007-01-01

    Much of what we know about the large scale characteristics of the Okhotsk Sea ice cover comes from ice concentration maps derived from passive microwave data. To understand what these satellite data represents in a highly divergent and rapidly changing environment like the Okhotsk Sea, we analyzed concurrent satellite, aircraft, and ship data and characterized the sea ice cover at different scales from meters to tens of kilometers. Through comparative analysis of surface features using co-registered data from visible, infrared and microwave channels we evaluated how the general radiative and physical characteristics of the ice cover changes as well as quantify the distribution of different ice types in the region. Ice concentration maps from AMSR-E using the standard sets of channels, and also only the 89 GHz channel for optimal resolution, are compared with aircraft and high resolution visible data and while the standard set provides consistent results, the 89 GHz provides the means to observe mesoscale patterns and some unique features of the ice cover. Analysis of MODIS data reveals that thick ice types represents about 37% of the ice cover indicating that young and new ice represent a large fraction of the lice cover that averages about 90% ice concentration, according to passive microwave data. A rapid decline of -9% and -12 % per decade is observed suggesting warming signals but further studies are required because of aforementioned characteristics and because the length of the ice season is decreasing by only 2 to 4 days per decade.

  20. Radiative characteristics of the Canadian Climate Centre second-generation general circulation model

    SciTech Connect

    Barker, H.W. ); Li, Zhanqing ); Blanchet, J.P. )

    1994-07-01

    Several observational datasets were used to assess the quality of the radiative characteristics of the Canadian Climate Centre (CCC) second-generation GCM. The GCM data were obtained from the Atmospheric Model Intercomparison Project (AMIP) simulation. Data corresponding to the period January 1985 through December 1988 wee examined since this period of the AMIP simulation overlaps with the Earth Radiation Budget Experiment (ERBE) and the International Satellite Cloud Climatology Project (ISCCP) datasets. Attention was given to mean January and July conditions. Optical properties of surfaces, clear skies, and cloudy skies were examined. Ocean albedos are too high in the Tropics and too low in the polar regions relative to surface observations and theoretical estimates. Compared to a satellite-derived dataset, however, they are slightly underestimated. Throughout much of the Sahara and Saudi Deserts surface albedos are too low, while for much of Western Australia they are too high. Excessive amounts of snow in Southeast Asia seem to have been sustained by a localized snow albedo feedback related to inappropriate snow albedo specification and a weak masking effect by vegetation. Neglect of freshwater lakes in the Canadian Shield leads to negative and positive albedo anomalies in winter and summer, respectively. Like many GCMs, the CCC model has too little atmospheric H[sub 2]O vapor. This results in too much outgoing longwave radiation from clear skies, especially in the Tropics. Neglect of all trace gases except for CO[sub 2] and weak H[sub 2]O vapor absorption this bias. 55 refs., 13 figs., 4 tabs.

  1. Review on the characteristics of radiation detectors for dosimetry and imaging

    NASA Astrophysics Data System (ADS)

    Seco, Joao; Clasie, Ben; Partridge, Mike

    2014-10-01

    The enormous advances in the understanding of human anatomy, physiology and pathology in recent decades have led to ever-improving methods of disease prevention, diagnosis and treatment. Many of these achievements have been enabled, at least in part, by advances in ionizing radiation detectors. Radiology has been transformed by the implementation of multi-slice CT and digital x-ray imaging systems, with silver halide films now largely obsolete for many applications. Nuclear medicine has benefited from more sensitive, faster and higher-resolution detectors delivering ever-higher SPECT and PET image quality. PET/MR systems have been enabled by the development of gamma ray detectors that can operate in high magnetic fields. These huge advances in imaging have enabled equally impressive steps forward in radiotherapy delivery accuracy, with 4DCT, PET and MRI routinely used in treatment planning and online image guidance provided by cone-beam CT. The challenge of ensuring safe, accurate and precise delivery of highly complex radiation fields has also both driven and benefited from advances in radiation detectors. Detector systems have been developed for the measurement of electron, intensity-modulated and modulated arc x-ray, proton and ion beams, and around brachytherapy sources based on a very wide range of technologies. The types of measurement performed are equally wide, encompassing commissioning and quality assurance, reference dosimetry, in vivo dosimetry and personal and environmental monitoring. In this article, we briefly introduce the general physical characteristics and properties that are commonly used to describe the behaviour and performance of both discrete and imaging detectors. The physical principles of operation of calorimeters; ionization and charge detectors; semiconductor, luminescent, scintillating and chemical detectors; and radiochromic and radiographic films are then reviewed and their principle applications discussed. Finally, a general

  2. Electric discharge in the water: physics of formation and radiative characteristics.

    NASA Astrophysics Data System (ADS)

    Anpilov, Andrei; Barkhudarov, Eduard; Kozlov, Yurii; Kossyi, Igor; Silakov, Valerii; Temchin, Savelii

    2004-09-01

    ELECTRIC DISCHARGE IN THE WATER: PHYSICS OF FORMATION AND RADIATIVE CHARACTERISTICS 2.10. Lighting plasmas. 2.26. Other plasma topics. A.M.Anpilov, E.M.Barkhudarov, Yu.N.Kozlov, I.A.Kossyi, V.P.Silakov and S.M.Temchin Two types of electric discharge in the water have been investigated: discharge between two electrodes and multielectrode gliding surface discharge. Results are presented from experimental studies of the prebreakdown phase of an electric discharge between the point (anode) and plane (cathode) electrodes immersed in the water with different initial conductivity. When a high-voltage pulse is applied, the induced conductivity is detected in the discharge gap. Its value is one order of magnitude higher than the initial one. It is shown that the induced conductivity increases almost linearly with initial conductivity. The induced conductivity correlates with the UV emission from the cathode surface. A qualitative analysis of the experimental results is performed. Investigations of a spectrum of radiation of discharge in water have been carried out. On the base of broadening and shifting of atomic hydrogen and oxygen lines electron density in a prebreakdown as well as breakdown stages has been determined. Results are presented from investigations of multispark electric discharge in water excited along multielectrode metal-dielectric systems with gas supply into the interelectrode gaps. The intensity distribution of discharge radiation in the region covering the biologically active soft UV (190 £l£430 nm) has been determined and the absolute number of quanta in this wavelength interval has been measured. The potentiality of the gliding surface discharge in water for its disinfection is analysed.

  3. Luminescence, radiative recombination, and current voltage characteristics in sensitized TiO2 solar cells

    NASA Astrophysics Data System (ADS)

    Smestad, Greg P.

    1992-12-01

    A connection is made between the luminescence or radiative recombination in an absorber material and the current voltage characteristics of a quantum converter of light. A relationship between luminescence and voltage is derived, using detailed balance and the chemical potential of the excitation, which is similar to that obtained using the techniques of Shockley and Queisser or R. T. Ross. This model relates the absorptivity and photoluminescence efficiency of the light absorber to the I V curve. In this way both thermodynamic properties, or voltage, and the kinetics, or charge transfer and current, can be combined in order to optimize materials and configurations. The model is applied to dye sensitized Ti02 solar cells, and compared with preliminary experimental data for Ru based charge transfer dyes and inorganic compounds. The luminescence model is found to be applicable to dye sensitized converters, as well as to standard silicon solar cells, light detectors, and LEDs.

  4. Radiative Characteristics of the Pulse-Periodic Discharge Plasma Initiated by Runaway Electrons

    NASA Astrophysics Data System (ADS)

    Lomaev, M. I.; Beloplotov, D. V.; Tarasenko, V. F.; Sorokin, D. A.

    2016-07-01

    Results of experimental investigations of amplitude-temporal and spectral characteristics of radiation of a pulse-periodic discharge plasma initiated in nitrogen by runaway electrons are presented. The discharge was initiated by high-voltage nanosecond voltage pulses with repetition frequency of 60 Hz in a sharply inhomogeneous electric field in a gap between the conic potential cathode and the planar grounded aluminum anode. It is established that intensive lines of Al I atoms and Al II atomic ions, lines of N I atoms and N II ions, bands of the first (1+) and second positive (2+) nitrogen systems, as well as bands of cyanogen CN are observed in the emission spectrum of the discharge plasma under the given excitation conditions.

  5. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spectral and temporal characteristics of a laser plasma

    NASA Astrophysics Data System (ADS)

    Lipchak, A. I.; Solomonov, V. I.; Tel'nov, V. A.; Osipov, V. V.

    1995-04-01

    An experimental investigation was made of the spectral and temporal characteristics of a laser plasma formed by the interaction of a CO2 laser pulse with a target in atmospheric air. The results obtained indicate that the main role in the process of filling the excited states in a laser plasma is played by a recombination cascade and that both atoms and molecules of the atmospheric gases are excited. The result also show that a laser plasma can be used in spectroscopic analysis of multicomponent samples. The solution of the thermophysical problem of heating of a target by laser radiation supports the existing ideas on the process of formation of a plasma near the target surface in air.

  6. The influence of the resonance effects on the radiative characteristics of helium plasma

    NASA Astrophysics Data System (ADS)

    Koryukina, E. V.; Koryukin, V. I.

    2017-05-01

    In the present work, the influence of an alternating circularly polarized electric field on the energy spectrum of the He atom is studied. The calculations are performed by the method of the energy matrix diagonalization of an atom in the electric field. This method has allowed us to study the behaviour of the helium energy spectrum from the same numerical procedure under resonant and non-resonant excitations by the electric field. Based on the calculation results, we have found that the resonance effects take place not only in the vicinity of resonance, but they influence the shift directions of the Stark states even under non-resonant excitation. Additionally, we have established that the helium energy spectrum behaves consistently in the electric field. The results obtained have allowed us to clarify mechanisms of the influence of the resonance effects on the radiative characteristics of helium plasma.

  7. Study of the dosimetric characteristics of cosmic radiation at civil aviation altitudes.

    PubMed

    Ferrari, A; Pellicioni, M; Rancati, T

    2002-01-01

    The dependence of the doses on solar activity for intermediate levels of the solar modulation parameter has been studied by means of simulations carried out by the Monte Carlo transport code FLUKA. The vertical cut-off rigidities investigated lie between 0.4 and 6.1 GV. The calculated results show that the linear dependence proposed in a previous work, for the effective dose rate as a function of the solar modulation parameter, can be considered as an acceptable approximation. In addition, some dosimetric characteristics of cosmic radiation and some properties of the dosemeters in use for monitoring in the cosmic ray environment have been analysed with a view to simplifying measurements. The depth-dose curves in the ICRU sphere and the response of a tissue-equivalent ionisation chamber have been determined by the FLUKA code for a number of cosmic ray spectra On the basis of the calculated results, it is concluded that a value of the depth. d, which would make the ambient dose equivalent a conservative predictor of the effective dose, cannot be specified for cosmic radiation. However, the operational quantity can be useful in order to verify the predictions of Monte Carlo calculations. It is demonstrated that a crude approximation of the ambient dose equivalent could be obtained by multiplying by 2 the absorbed dose measured by a tissue-equivalent ionisation chamber with wall thickness of 10 mm.

  8. Experimental Investigation of Heat Transfer Characteristics of Automobile Radiator using TiO2-Nanofluid Coolant

    NASA Astrophysics Data System (ADS)

    Salamon, V.; Senthil kumar, D.; Thirumalini, S.

    2017-08-01

    The use of nanoparticle dispersed coolants in automobile radiators improves the heat transfer rate and facilitates overall reduction in size of the radiators. In this study, the heat transfer characteristics of water/propylene glycol based TiO2 nanofluid was analyzed experimentally and compared with pure water and water/propylene glycol mixture. Two different concentrations of nanofluids were prepared by adding 0.1 vol. % and 0.3 vol. % of TiO2 nanoparticles into water/propylene glycol mixture (70:30). The experiments were conducted by varying the coolant flow rate between 3 to 6 lit/min for various coolant temperatures (50°C, 60°C, 70°C, and 80°C) to understand the effect of coolant flow rate on heat transfer. The results showed that the Nusselt number of the nanofluid coolant increases with increase in flow rate. At low inlet coolant temperature the water/propylene glycol mixture showed higher heat transfer rate when compared with nanofluid coolant. However at higher operating temperature and higher coolant flow rate, 0.3 vol. % of TiO2 nanofluid enhances the heat transfer rate by 8.5% when compared to base fluids.

  9. Comparison of experimentally and theoretically determined radiation characteristics of photosynthetic microorganisms

    NASA Astrophysics Data System (ADS)

    Kandilian, Razmig; Pruvost, Jérémy; Artu, Arnaud; Lemasson, Camille; Legrand, Jack; Pilon, Laurent

    2016-05-01

    This paper aims to experimentally and directly validate a recent theoretical method for predicting the radiation characteristics of photosynthetic microorganisms. Such predictions would facilitate light transfer analysis in photobioreactors (PBRs) to control their operation and to maximize their production of biofuel and other high-value products. The state of the art experimental method can be applied to microorganisms of any shape and inherently accounts for their non-spherical and heterogeneous nature. On the other hand, the theoretical method treats the microorganisms as polydisperse homogeneous spheres with some effective optical properties. The absorption index is expressed as the weighted sum of the pigment mass absorption cross-sections and the refractive index is estimated based on the subtractive Kramers-Kronig relationship given an anchor refractive index and wavelength. Here, particular attention was paid to green microalgae Chlamydomonas reinhardtii grown under nitrogen-replete and nitrogen-limited conditions and to Chlorella vulgaris grown under nitrogen-replete conditions. First, relatively good agreement was found between the two methods for determining the mass absorption and scattering cross-sections and the asymmetry factor of both nitrogen-replete and nitrogen-limited C. reinhardtii with the proper anchor point. However, the homogeneous sphere approximation significantly overestimated the absorption cross-section of C. vulgaris cells. The latter were instead modeled as polydisperse coated spheres consisting of an absorbing core containing pigments and a non-absorbing but strongly refracting wall made of sporopollenin. The coated sphere approximation gave good predictions of the experimentally measured integral radiation characteristics of C. vulgaris. In both cases, the homogeneous and coated sphere approximations predicted resonance in the scattering phase function that were not observed experimentally. However, these approximations were

  10. Circuital characteristics and radiation properties of an UWB electric-magnetic planar antenna for Ku-band applications

    NASA Astrophysics Data System (ADS)

    Haider, N.; Caratelli, D.; Yarovoy, A. G.

    2013-01-01

    A planar, directive antenna with large fractional bandwidth is introduced in this paper. A detailed discussion on the proposed antenna topology and its architecture is reported. The proposed element is a combination of a patch and a loop radiator. A proper combination of the electric field radiator (patch) with a magnetic field radiator (loop around the patch) is exploited for expanding the operational bandwidth. A parametric study is presented to investigate the effect of the antenna geometrical parameters on its performance. A general and computationally efficient procedure for extracting the antenna equivalent circuit is described and used to achieve a meaningful circuit theory-based insight into the characteristics of the radiating structure. The theoretical and experimental results are compared, and it is demonstrated that the element features over 100% fractional bandwidth, good impedance matching, and unidirectional and stable radiation patterns.

  11. Static and Dynamic Characteristic Models of Global Solar Radiation Fluctuation in the Scope of Load Frequency Control

    NASA Astrophysics Data System (ADS)

    Akatsuka, Motoki; Hara, Ryoichi; Kita, Hiroyuki; Takitani, Katsuyuki; Saito, Masami

    Penetration of photovoltaic generation (PV) system into the power system may give some negative impacts to stable operations of power system; for example, to the frequency control. Therefore, investigation on the short-term fluctuation of PV generation is important as a precaution against further PV penetration. Since the PV generation is almost proportional to the incident solar radiation, this paper develops static and dynamic characteristic models for short-term fluctuation in the global solar radiation. The static characteristic model is a set of standard deviations which have been statistically estimated based on the past observed data. The dynamic characteristic model is autoregressive models which are designed for the actually observed time sequential short-term fluctuation data. In both models, the clearness index is used to eliminate seasonal variation of solar radiation.

  12. GPS Sounding Rocket Developments

    NASA Technical Reports Server (NTRS)

    Bull, Barton

    1999-01-01

    Sounding rockets are suborbital launch vehicles capable of carrying scientific payloads several hundred miles in altitude. These missions return a variety of scientific data including; chemical makeup and physical processes taking place In the atmosphere, natural radiation surrounding the Earth, data on the Sun, stars, galaxies and many other phenomena. In addition, sounding rockets provide a reasonably economical means of conducting engineering tests for instruments and devices used on satellites and other spacecraft prior to their use in more expensive activities. The NASA Sounding Rocket Program is managed by personnel from Goddard Space Flight Center Wallops Flight Facility (GSFC/WFF) in Virginia. Typically around thirty of these rockets are launched each year, either from established ranges at Wallops Island, Virginia, Poker Flat Research Range, Alaska; White Sands Missile Range, New Mexico or from Canada, Norway and Sweden. Many times launches are conducted from temporary launch ranges in remote parts of the world requi6ng considerable expense to transport and operate tracking radars. An inverse differential GPS system has been developed for Sounding Rocket. This paper addresses the NASA Wallops Island history of GPS Sounding Rocket experience since 1994 and the development of a high accurate and useful system.

  13. GPS Sounding Rocket Developments

    NASA Technical Reports Server (NTRS)

    Bull, Barton

    1999-01-01

    Sounding rockets are suborbital launch vehicles capable of carrying scientific payloads several hundred miles in altitude. These missions return a variety of scientific data including; chemical makeup and physical processes taking place In the atmosphere, natural radiation surrounding the Earth, data on the Sun, stars, galaxies and many other phenomena. In addition, sounding rockets provide a reasonably economical means of conducting engineering tests for instruments and devices used on satellites and other spacecraft prior to their use in more expensive activities. The NASA Sounding Rocket Program is managed by personnel from Goddard Space Flight Center Wallops Flight Facility (GSFC/WFF) in Virginia. Typically around thirty of these rockets are launched each year, either from established ranges at Wallops Island, Virginia, Poker Flat Research Range, Alaska; White Sands Missile Range, New Mexico or from Canada, Norway and Sweden. Many times launches are conducted from temporary launch ranges in remote parts of the world requi6ng considerable expense to transport and operate tracking radars. An inverse differential GPS system has been developed for Sounding Rocket. This paper addresses the NASA Wallops Island history of GPS Sounding Rocket experience since 1994 and the development of a high accurate and useful system.

  14. Sound Advice.

    ERIC Educational Resources Information Center

    Popke, Michael

    2000-01-01

    Discusses the planning and decision-making process in acquiring sound equipment for sports stadiums that will help make the experience of fans more pleasurable. The bidding process and use of consultants is explored. (GR)

  15. Sound Advice.

    ERIC Educational Resources Information Center

    Popke, Michael

    2000-01-01

    Discusses the planning and decision-making process in acquiring sound equipment for sports stadiums that will help make the experience of fans more pleasurable. The bidding process and use of consultants is explored. (GR)

  16. Sound Radiation from an Enclosure

    DTIC Science & Technology

    2002-09-05

    enclosure and tested hanging from a " bungee cord" to simulate free boundary conditions. Figure 9 shows views of the experimental mesh with 64...square difference between the analytical function and the experimental data) and jump to the correct value for the minimum knowing the derivatives of...the analytical function with respect to the parameters. For a linear optimization problem, this technique yields the minimum in a single jump . For a

  17. Solar ultraviolet radiation: properties, characteristics and amounts observed in Brazil and South America*

    PubMed Central

    Corrêa, Marcelo de Paula

    2015-01-01

    The beneficial and harmful effects of human exposure to solar ultraviolet radiation (UV-R) are topics that arouse great interest not only among physicians and scientists, but also the general public and the media. Currently, discussions on vitamin D synthesis (beneficial effect) are confronted with the high and growing number of new cases of non-melanoma skin cancer and other diseases of the skin and eyes (harmful effect) diagnosed each year in Brazil. However, the lack of scientific knowledge on the UV-R in Brazil and South America leads to adoption of protective measures based on studies conducted in Europe and USA, where the amounts of UV-R available at surface and the sun-exposure habits and characteristics of the population are significantly different from those observed in Brazil. In order to circumvent this problem, the Brazilian Society of Dermatology recently published the Brazilian Consensus of Photoprotection based on recent studies performed locally. The main goal of this article is to provide detailed educational information on the main properties and characteristics of UV-R and UV index in a simple language. It also provides: a) a summary of UV-R measurements recently performed in Brazil; b) a comparison with those performed in Europe; and, c) an evaluation to further clarify the assessment of potential harm and health effects owing to chronic exposures. PMID:26131858

  18. Dose verification in intensity modulation radiation therapy: a fractal dimension characteristics study.

    PubMed

    Wu, Jia-Ming; Kuo, Chung-Ming; Chen, Ching-Jiang

    2013-01-01

    This study describes how to identify the coincidence of desired planning isodose curves with film experimental results by using a mathematical fractal dimension characteristic method to avoid the errors caused by visual inspection in the intensity modulation radiation therapy (IMRT). The isodose curves of the films delivered by linear accelerator according to Plato treatment planning system were acquired using Osiris software to aim directly at a single interested dose curve for fractal characteristic analysis. The results were compared with the corresponding planning desired isodose curves for fractal dimension analysis in order to determine the acceptable confidence level between the planning and the measurement. The film measured isodose curves and computer planning curves were deemed identical in dose distribution if their fractal dimensions are within some criteria which suggested that the fractal dimension is a unique fingerprint of a curve in checking the planning and film measurement results. The dose measured results of the film were presumed to be the same if their fractal dimension was within 1%. This quantitative rather than qualitative comparison done by fractal dimension numerical analysis helps to decrease the quality assurance errors in IMRT dosimetry verification.

  19. Turbid media optical properties derived from the characteristics of propagating laser radiation beams

    NASA Astrophysics Data System (ADS)

    Gurdev, Ljuan; Dreischuh, Tanja; Vankov, Orlin; Bliznakova, Irina; Avramov, Lachezar; Stoyanov, Dimitar

    2014-06-01

    The possibility is studied to develop a straightforward analytical approach to the determination of the optical properties of liquid turbid media having forward-peaked scattering indicatrices. The approach is based on investigating the in-depth behavior of the radius and the axial intensity of a laser radiation beam propagating through the turbid medium. Based on the small-angle approximation, the detected forward-propagating light power spatial distribution, at relatively small or large optical depths along the beam axis, is obtained asymptotically in analytical form allowing one to derive relatively simple expressions of the extinction, reduced-scattering and absorption coefficients and the anisotropy factor of the medium through the characteristics of the propagating light beam. Preliminary experiments have also been performed, using Intralipid dilutions of different relatively low concentrations and measuring the cross-sectional radial distribution of the detected light power at different depths along the beam axis. The corresponding on-axis detected light power profiles have been measured independently as well. The experimental results are consistent with the analytical expressions obtained that allow one to estimate the optical coefficients and the anisotropy factor of the investigated media on the basis of the measured beam characteristics. The values obtained are near those predicted by other researchers.

  20. Solar ultraviolet radiation: properties, characteristics and amounts observed in Brazil and South America.

    PubMed

    Corrêa, Marcelo de Paula

    2015-01-01

    The beneficial and harmful effects of human exposure to solar ultraviolet radiation (UV-R) are topics that arouse great interest not only among physicians and scientists, but also the general public and the media. Currently, discussions on vitamin D synthesis (beneficial effect) are confronted with the high and growing number of new cases of non-melanoma skin cancer and other diseases of the skin and eyes (harmful effect) diagnosed each year in Brazil. However, the lack of scientific knowledge on the UV-R in Brazil and South America leads to adoption of protective measures based on studies conducted in Europe and USA, where the amounts of UV-R available at surface and the sun-exposure habits and characteristics of the population are significantly different from those observed in Brazil. In order to circumvent this problem, the Brazilian Society of Dermatology recently published the Brazilian Consensus of Photoprotection based on recent studies performed locally. The main goal of this article is to provide detailed educational information on the main properties and characteristics of UV-R and UV index in a simple language. It also provides: a) a summary of UV-R measurements recently performed in Brazil; b) a comparison with those performed in Europe; and, c) an evaluation to further clarify the assessment of potential harm and health effects owing to chronic exposures.

  1. Physical and Radiative Characteristic and Long-term Variability of the Okhotsk Sea Ice Cover

    NASA Technical Reports Server (NTRS)

    Nishio, Fumihiko; Comiso, Josefino C.; Gersten, Robert; Nakayama, Masashige; Ukita, Jinro; Gasiewski, Al; Stanko, Boba; Naoki, Kazuhiro

    2008-01-01

    Much of what we know about the large scale characteristics of the Okhotsk Sea ice cover has been provided by ice concentration maps derived from passive microwave data. To understand what satellite data represent in a highly divergent and rapidly changing environment like the Okhotsk Sea, we take advantage of concurrent satellite, aircraft, and ship data acquired on 7 February and characterized the sea ice cover at different scales from meters to hundreds of kilometers. Through comparative analysis of surface features using co-registered data from visible, infrared and microwave channels we evaluated the general radiative and physical characteristics of the ice cover as well as quantify the distribution of different ice types in the region. Ice concentration maps from AMSR-E using the standard sets of channels, and also only the 89 GHz channel for optimal resolution, are compared with aircraft and high resolution visible data and while the standard set provides consistent results, the 89 GHz provides the means to observe mesoscale patterns and some unique features of the ice cover. Analysis of MODIS data reveals that thick ice types represents about 37% of the ice cover indicating that young and new ice types represent a large fraction of the ice cover that averages about 90% ice concentration according to passive microwave data. These results are used to interpret historical data that indicate that the Okhotsk Sea ice extent and area are declining at a rapid rate of about -9% and -12 % per decade, respectively.

  2. Exploring Sound with Insects

    ERIC Educational Resources Information Center

    Robertson, Laura; Meyer, John R.

    2010-01-01

    Differences in insect morphology and movement during singing provide a fascinating opportunity for students to investigate insects while learning about the characteristics of sound. In the activities described here, students use a free online computer software program to explore the songs of the major singing insects and experiment with making…

  3. Exploring Sound with Insects

    ERIC Educational Resources Information Center

    Robertson, Laura; Meyer, John R.

    2010-01-01

    Differences in insect morphology and movement during singing provide a fascinating opportunity for students to investigate insects while learning about the characteristics of sound. In the activities described here, students use a free online computer software program to explore the songs of the major singing insects and experiment with making…

  4. Determining optical and radiation characteristics of cathode ray tubes' glass to be reused as radiation shielding glass

    NASA Astrophysics Data System (ADS)

    Zughbi, A.; Kharita, M. H.; Shehada, A. M.

    2017-07-01

    A new method of recycling glass of Cathode Ray Tubes (CRTs) has been presented in this paper. The glass from CRTs suggested being used as raw materials for the production of radiation shielding glass. Cathode ray tubes glass contains considerable amounts of environmentally hazardous toxic wastes, namely heavy metal oxides such as lead oxide (PbO). This method makes CRTs glass a favorable choice to be used as raw material for Radiation Shielding Glass and concrete. The heavy metal oxides increase its density, which make this type of glass nearly equivalent to commercially available shielding glass. CRTs glass have been characterized to determine heavy oxides content, density, refractive index, and radiation shielding properties for different Gamma-Ray energies. Empirical methods have been used by using the Gamma-Ray source cobalt-60 and computational method by using the code XCOM. Measured and calculated values were in a good compatibility. The effects of irradiation by gamma rays of cobalt-60 on the optical transparency for each part of the CRTs glass have been studied. The Results had shown that some parts of CRTs glass have more resistant to Gamma radiation than others. The study had shown that the glass of cathode ray tubes could be recycled to be used as radiation shielding glass. This proposed use of CRT glass is only limited to the available quantity of CRT world-wide.

  5. Radiative characteristics of aerosol during extreme fire event over Siberia in summer 2012

    NASA Astrophysics Data System (ADS)

    Zhuravleva, Tatiana B.; Kabanov, Dmitriy M.; Nasrtdinov, Ilmir M.; Russkova, Tatiana V.; Sakerin, Sergey M.; Smirnov, Alexander; Holben, Brent N.

    2017-01-01

    Microphysical and optical properties of aerosol were studied during a mega-fire event in summer 2012 over Siberia using ground-based measurements of spectral solar radiation at the AERONET site in Tomsk and satellite observations. The data were analysed using multi-year (2003-2013) measurements of aerosol characteristics under background conditions and for less intense fires, differing in burning biomass type, stage of fire, remoteness from observation site, etc. (ordinary smoke). In June-August 2012, the average aerosol optical depth (AOD, 500 nm) had been 0.95 ± 0.86, about a factor of 6 larger than background values (0.16 ± 0.08), and a factor of 2.5 larger than in ordinary smoke. The AOD values were extremely high on 24-28 July and reached 3-5. A comparison with satellite observations showed that ground-based measurements in the region of Tomsk not only reflect the local AOD features, but are also characteristic for the territory of Western Siberia as a whole. Single scattering albedo (SSA, 440 nm) in this period ranged from 0.91 to 0.99 with an average of ˜ 0.96 in the entire wavelength range of 440-1020 nm. The increase in absorptance of aerosol particles (SSA(440 nm) = 0.92) and decrease in SSA with wavelength observed in ordinary smoke agree with the data from multi-year observations in analogous situations in the boreal zone of USA and Canada. Volume aerosol size distribution in extreme and ordinary smoke had a bimodal character with significant prevalence of fine-mode particles, but in summer 2012 the mean median radius and the width of the fine-mode distribution somewhat increased. In contrast to data from multi-year observations, in summer 2012 an increase in the volume concentration and median radius of the coarse mode was observed with growing AOD. The calculations of the average radiative effects of smoke and background aerosol are presented. Compared to background conditions and ordinary smoke, under the extreme smoke conditions the

  6. [Post-radiation effect on the interhemispheric asymmetry in EEG and thermography characteristics].

    PubMed

    Zhavoronkova, L A; Gabova, A V; Kuznetsova, G D; Sel'skiĭ, A G; Pasechnik, V I; Kholodova, N B; Ianovich, A V

    2003-01-01

    Complex analysis of EEG and thermographic parameters carried out in 10 healthy subjects and 34 patients, Chernobyl clean-up participants revealed a correlation between EEG and brain temperature changes in the baseline state and during mental arithmetic. During cognitive activity the maximal increase in the average EEG coherence and temperature shifts in healthy subjects were observed in the left frontotemporal and right parietotemporal areas. In patients changes in both parameters under study were most pronounced, the interhemispheric relations were impaired. The visual analysis revealed "flat" and "hypersynchronous" EEG types in patients. The dominant pathologic activity in the betal range indicative of mediobasal and oral brainstem lesions was characteristic of the flat EEG. This type of activity was observed in 60% of patients. In these cases, a general decrease in EEG coherence and temperature was most pronounced in the left hemisphere. The hypersynchronou EEG type (40% patients) was characterized by paroxysmal activity in the theta and alpha ranges suggesting diencephalic brain lesions. In these cases, EEG coherence and temperature were more variable; changes in the right hemisphere were significant, be it increase or decrease. Our complex approach to investigation of brain activity in different aspects seems to be promising in estimation of the brain functional state both in healthy persons and patients in remote terms after exposure to radiation. The specific hemispheric temperature changes revealed in Chernobyl patients especially during cognitive activity can be the sequels of postradiation disorders of vascular neuro-circulation. The EEG findings suggest subcortical disorders at different levels (diencephalic or brainstem) and functional failure of the right or left hemispheres in remote terms after exposure to radiation.

  7. Sound Guard

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Lubrication technology originally developed for a series of NASA satellites has produced a commercial product for protecting the sound fidelity of phonograph records. Called Sound Guard, the preservative is a spray-on fluid that deposits a microscopically thin protective coating which reduces friction and prevents the hard diamond stylus from wearing away the softer vinyl material of the disc. It is marketed by the Consumer Products Division of Ball Corporation, Muncie, Indiana. The lubricant technology on which Sound Guard is based originated with NASA's Orbiting Solar Observatory (OSO), an Earth-orbiting satellite designed and built by Ball Brothers Research Corporation, Boulder, Colorado, also a division of Ball Corporation. Ball Brothers engineers found a problem early in the OSO program: known lubricants were unsuitable for use on satellite moving parts that would be exposed to the vacuum of space for several months. So the company conducted research on the properties of materials needed for long life in space and developed new lubricants. They worked successfully on seven OSO flights and attracted considerable attention among other aerospace contractors. Ball Brothers now supplies its "Vac Kote" lubricants and coatings to both aerospace and non-aerospace industries and the company has produced several hundred variations of the original technology. Ball Corporation expanded its product line to include consumer products, of which Sound Guard is one of the most recent. In addition to protecting record grooves, Sound Guard's anti-static quality also retards particle accumulation on the stylus. During comparison study by a leading U.S. electronic laboratory, a record not treated by Sound Guard had to be cleaned after 50 plays and the stylus had collected a considerable number of small vinyl particles. The Sound Guard-treated disc was still clean after 100 plays, as was its stylus.

  8. Assessment of and a Solution to the Intensity Diffusion Error Intrinsic in Short-Characteristic Radiative Transfer

    NASA Astrophysics Data System (ADS)

    Peck, Courtney; Rast, Mark; Criscuoli, Serena

    2017-08-01

    Short characteristic radiative transfer coupled with 3D MHD simulations are routinely used to compare simulations with observations of the solar atmosphere. While it has been known that the method of short characteristics radiative transfer results in intensity diffusion, it has been routinely employed to solve radiative transfer due to its computational expediency. In this talk, we discuss the effect of spatial smearing due to short characteristics radiative transfer under both linear and high-order interpolation. We then demonstrate that linear interpolation results in an effective spatial smearing related to the number of grid heights above the τ = 1 surface and conserves intensity. Additionally, we show that the use of high-order strict monotonic interpolation reduces the amount of smearing, but at the expense of error in the integrated emergent intensity. Finally, we demonstrate that these issues can be easily avoided at no added computational expense by interpolating the atmosphere onto a ray-directed grid and computing the radiative transfer for vertical rays through the grid.

  9. Large Eddy Simulation of Sound Generation by Turbulent Reacting and Nonreacting Shear Flows

    NASA Astrophysics Data System (ADS)

    Najafi-Yazdi, Alireza

    appears to be associated with the transverse vibration of the shear-layer interface within the ambient quiescent flow, and has dipolar characteristics. This mechanism is believed to be responsible for sound radiation along the sideline directions. Jet noise suppression through the use of microjets was studied. The microjet injection induced secondary instabilities in the shear layer which triggered the transition to turbulence, and suppressed laminar vortex pairing. This in turn resulted in a reduction of OASPL at almost all observer locations. In all cases, the bandpass filtering of the nearfield flow and the associated sound provides revealing details of the sound radiation process. The results suggest that circumferential modes are significant and need to be included in future wavepacket models for jet noise prediction. Numerical simulations of sound radiation from nonpremixed flames were also performed. The simulations featured the solution of the fully compressible Navier-Stokes equations. Therefore, sound generation and radiation were directly captured in the simulations. A thickened flamelet model was proposed for nonpremixed flames. The model yields artificially thickened flames which can be better resolved on the computational grid, while retaining the physically currect values of the total heat released into the flow. Combustion noise has monopolar characteristics for low frequencies. For high frequencies, the sound field is no longer omni-directional. Major sources of sound appear to be located in the jet shear layer within one potential core length from the jet nozzle.

  10. Spectral and amplitude-time characteristics of radiation of plasma of a repetitively pulsed discharge initiated by runaway electrons

    NASA Astrophysics Data System (ADS)

    Lomaev, M. I.; Beloplotov, D. V.; Sorokin, D. A.; Tarasenko, V. F.

    2016-02-01

    Spectral and amplitude-time characteristics of radiation of plasma of a repetitively pulsed discharge initiated by runaway electrons were studied experimentally in nitrogen. Intense emission lines of copper atoms, nitrogen atoms, and ions, as well as the first and the second positive systems of nitrogen, NO, and CN, were observed in the regime of repetitively pulsed excitation.

  11. Effect of Berry Size and Sodium Hydroxide Pretreatment on the Drying Characteristics of Blueberries under Infrared Radiation Heating

    USDA-ARS?s Scientific Manuscript database

    This research studied the effect on the drying characteristics of blueberries under infrared radiation (IR) heating of berry size and dipping pretreatment in hot sodium hydroxide (NaOH) solution. Changes in the microstructure and diffusion coefficient of the berries after the NaOH pretreatment were...

  12. Polarization and spectral characteristics of the two-photon luminescence from colloidal gold nanoparticles excited by tunable laser radiation

    SciTech Connect

    Yashunin, D. A. Korytin, A. I.; Stepanov, A. N.

    2015-12-15

    We have experimentally studied two-photon luminescence from a colloidal solution of spherical gold nanoparticles by tuning the wavelength of the exciting radiation. The measured polarization and spectral characteristics of the two-photon luminescence signal show that the observed nonlinear optical response is determined by the dimers present in the solution with a concentration of a few percent of total nanoparticle number.

  13. Radiation

    NASA Image and Video Library

    Outside the protective cocoon of Earth's atmosphere, the universe is full of harmful radiation. Astronauts who live and work in space are exposed not only to ultraviolet rays but also to space radi...

  14. Interpolated Sounding and Gridded Sounding Value-Added Products

    SciTech Connect

    Toto, T.; Jensen, M.

    2016-03-01

    Standard Atmospheric Radiation Measurement (ARM) Climate Research Facility sounding files provide atmospheric state data in one dimension of increasing time and height per sonde launch. Many applications require a quick estimate of the atmospheric state at higher time resolution. The INTERPOLATEDSONDE (i.e., Interpolated Sounding) Value-Added Product (VAP) transforms sounding data into continuous daily files on a fixed time-height grid, at 1-minute time resolution, on 332 levels, from the surface up to a limit of approximately 40 km. The grid extends that high so the full height of soundings can be captured; however, most soundings terminate at an altitude between 25 and 30 km, above which no data is provided. Between soundings, the VAP linearly interpolates atmospheric state variables in time for each height level. In addition, INTERPOLATEDSONDE provides relative humidity scaled to microwave radiometer (MWR) observations.The INTERPOLATEDSONDE VAP, a continuous time-height grid of relative humidity-corrected sounding data, is intended to provide input to higher-order products, such as the Merged Soundings (MERGESONDE; Troyan 2012) VAP, which extends INTERPOLATEDSONDE by incorporating model data. The INTERPOLATEDSONDE VAP also is used to correct gaseous attenuation of radar reflectivity in products such as the KAZRCOR VAP.

  15. Characteristic 8 keV X rays possess radiobiological properties of higher-LET radiation.

    PubMed

    Shridhar, Ravi; Estabrook, William; Yudelev, Mark; Rakowski, Joseph; Burmeister, Jay; Wilson, George D; Joiner, Michael C

    2010-03-01

    Electronic brachytherapy systems are being developed that can deliver X rays of varying energy depending on the material of a secondary target. A copper target produces characteristic 8 keV X rays. Our aim was to determine whether 8 keV X rays might deliver greater biological effectiveness than megavoltage photons. Cells of the U251 human glioma cell line were used to compare the biological effects of 8 keV X rays and (60)Co gamma rays in terms of relative biological effectiveness (RBE), oxygen enhancement ratio (OER), and DNA damage. The RBE at 50% and 10% survival was 2.6 and 1.9, respectively. At 50% survival, the OER for cells treated with 8 keV X rays was 1.6 compared with 3.0 for (60)Co gamma rays. The numbers of H2AX foci per Gy after treatment with 8 keV X rays and (60)Co gamma rays were similar; however, the size of the foci generated at 8 keV was significantly larger, possibly indicating more complex DNA damage. The mean area of H2AX foci generated by 8 keV X rays was 0.785 microm(2) (95% CI: 0.756-0.814) compared with 0.491 microm(2) (95% CI: 0.462-0.520) for (60)Co gamma rays (P < 0.0001). Characteristic 8 keV X rays produce two to three times the biological effectiveness of megavoltage photons, with a radiobiological profile similar to higher-LET radiations.

  16. Underwater Sound Propagation from Marine Pile Driving.

    PubMed

    Reyff, James A

    2016-01-01

    Pile driving occurs in a variety of nearshore environments that typically have very shallow-water depths. The propagation of pile-driving sound in water is complex, where sound is directly radiated from the pile as well as through the ground substrate. Piles driven in the ground near water bodies can produce considerable underwater sound energy. This paper presents examples of sound propagation through shallow-water environments. Some of these examples illustrate the substantial variation in sound amplitude over time that can be critical to understand when computing an acoustic-based safety zone for aquatic species.

  17. Effect of Index of Refraction on Radiation Characteristics in a Heated Absorbing, Emitting, and Scattering Layer

    NASA Technical Reports Server (NTRS)

    Siegel, R.; Spuckler, C. M.

    1992-01-01

    The effect of the index of refraction on the temperature distribution and radiative heat flux in semitransparent materials, such as some ceramics, is investigated analytically. In the case considered here, a plane layer of a ceramic material is subjected to external radiative heating incident on each of its surfaces; the material emits, absorbs, and isotropically scatters radiation. It is shown that, for radiative equilibrium in a gray layer with diffuse interfaces, the temperature distribution and radiative heat flux for any index of refraction can be obtained in a simple manner from the results for an index of refraction of unity.

  18. Effect of Index of Refraction on Radiation Characteristics in a Heated Absorbing, Emitting, and Scattering Layer

    NASA Technical Reports Server (NTRS)

    Siegel, R.; Spuckler, C. M.

    1992-01-01

    The effect of the index of refraction on the temperature distribution and radiative heat flux in semitransparent materials, such as some ceramics, is investigated analytically. In the case considered here, a plane layer of a ceramic material is subjected to external radiative heating incident on each of its surfaces; the material emits, absorbs, and isotropically scatters radiation. It is shown that, for radiative equilibrium in a gray layer with diffuse interfaces, the temperature distribution and radiative heat flux for any index of refraction can be obtained in a simple manner from the results for an index of refraction of unity.

  19. Geophysical Sounding

    NASA Astrophysics Data System (ADS)

    Blake, E.

    1998-01-01

    Of the many geophysical remote-sensing techniques available today, a few are suitable for the water ice-rich, layered material expected at the north martian ice cap. Radio echo sounding has been used for several decades to determine ice thickness and internal structure. Selection of operating frequency is a tradeoff between signal attenuation (which typically increases with frequency and ice temperature) and resolution (which is proportional to wavelength). Antenna configuration and size will be additional considerations for a mission to Mars. Several configurations for ice-penetrating radar systems are discussed: these include orbiter-borne sounders, sounding antennas trailed by balloons and penetrators, and lander-borne systems. Lander-borne systems could include short-wave systems capable of resolving fine structure and layering in the upper meters beneath the lander. Spread-spectrum and deconvolution techniques can be used to increase the depth capability of a radar system. If soundings over several locations are available (e.g., with balloons, rovers, or panning short-wave systems), then it will be easier to resolve internal layering, variations in basal reflection coefficient (from which material properties may be inferred), and the geometry of nonhorizontal features. Sonic sounding has a long history in oil and gas exploration. It is, however, unlikely that large explosive charges, or even swept-frequency techniques such as Vibroseis, would be suitable for a Polar lander -- these systems are capable of penetrating several kilometers of material at frequencies of 10-200 Hz, but the energy required to generate the sound waves is large and potentially destructive. The use of audio-frequency and ultrasonic sound generated by piezoelectric crystals is discussed as a possible method to explore layering and fine features in the upper meters of the ice cap. Appropriate choice of transducer(s) will permit operation over a range of fixed or modulated frequencies

  20. Infrared radiation and stealth characteristics prediction for supersonic aircraft with uncertainty

    NASA Astrophysics Data System (ADS)

    Pan, Xiaoying; Wang, Xiaojun; Wang, Ruixing; Wang, Lei

    2015-11-01

    The infrared radiation (IR) intensity is generally used to embody the stealth characteristics of a supersonic aircraft, which directly affects its survivability in warfare. Under such circumstances, the research on IR signature as an important branch of stealth technology is significant to overcome this threat for survivability enhancement. Considering the existence of uncertainties in material and environment, the IR intensity is indeed a range rather than a specific value. In this paper, subjected to the properties of the IR, an analytic process containing the uncertainty propagation and the reliability evaluation is investigated when taking into account that the temperature of object, the atmospheric transmittance and the spectral emissivity of materials are all regarded as uncertain parameters. For one thing, the vertex method is used to analyze and estimate the dispersion of IR intensity; for another, the safety assessment of the stealth performance for aircraft is conducted by non-probabilistic reliability analysis. For the purpose of the comparison and verification, the Monte Carlo simulation is discussed as well. The validity, usage, and efficiency of the developed methodology are demonstrated by two application examples eventually.

  1. Characteristics of the propagation of radioactive pollutants near a radiation-hazardous object

    SciTech Connect

    Romanov, V.I.

    1995-09-01

    It is well known that the radiation effect of nuclear enterprises on the environment is due mainly to gas-aerosol emissions which emanate from the object in the form of a jet flow. A characteristic feature of the propagation of radioactive impurities near such structures is that they depend on the local thermal and wind conditions at the location of the source of contamination. Transferring directly the results of laboratory investigations of the propagation and diffusion of fluxes to objects in the environment and neglecting the peculiarities of the wind and thermal interference with the underlying surface and other buildings can lead to incorrect conclusions. In this paper, we examine two examples: (1) emissions through the plant stack or other ventilation system openings, and (2) leakage of radioactive pollutants into the reactor building and from there to the atmosphere. A mathematical description on each example is provided, and data on the Archimedes number for a convective jet is given as a function of the deflecting wind velocity.

  2. Characteristics of the earth's radiation budget derived from the first year of data from the Earth Radiation Budget Experiment

    NASA Technical Reports Server (NTRS)

    Gibson, G. G.; Denn, F. M.; Young, D. F.; Harrison, E. F.; Minnis, P.; Barkstrom, B. R.

    1990-01-01

    The first year of broadband Earth Radiation Budget Experiment (ERBE) data is analyzed for top-of-the-atmosphere regional variations of outgoing longwave (LW) flux and planetary albedo for total scene as well as clear-sky conditions. The annual variation of radiative parameters is examined for February 1985 through January 1986 for selected regions, latitude zones, and the entire globe. Results show significant seasonal variations for both LW fluxes and albedo. A broad longwave flux maximum (with a relative minimum corresponding to the intertropical convergence zone in the middle) covers the tropics and the subtropics with its center moving about 20 deg in latitude between seasonal extremes. Minimum albedo (about 20 percent) occurs within 15 deg of the equator. In the tropics and midlatitudes, there is a tendency toward higher albedos during the summer. Larger albedos at the higher latitudes are caused by solar zenith angle effects and by increased snow and ice cover. Net warming occurs between 35 deg N and 35 deg S latitude near the equinoxes and in a 90-deg-wide latitude band at the solstices centered around 35 deg latitude in the summer hemisphere. This energy surplus at lower latitudes coupled with an energy deficit in the poleward regions is the primary driver of atmospheric circulations. For the year, the global net radiation is nearly in balance.

  3. Characteristics of the earth's radiation budget derived from the first year of data from the Earth Radiation Budget Experiment

    NASA Technical Reports Server (NTRS)

    Gibson, G. G.; Denn, F. M.; Young, D. F.; Harrison, E. F.; Minnis, P.; Barkstrom, B. R.

    1990-01-01

    The first year of broadband Earth Radiation Budget Experiment (ERBE) data is analyzed for top-of-the-atmosphere regional variations of outgoing longwave (LW) flux and planetary albedo for total scene as well as clear-sky conditions. The annual variation of radiative parameters is examined for February 1985 through January 1986 for selected regions, latitude zones, and the entire globe. Results show significant seasonal variations for both LW fluxes and albedo. A broad longwave flux maximum (with a relative minimum corresponding to the intertropical convergence zone in the middle) covers the tropics and the subtropics with its center moving about 20 deg in latitude between seasonal extremes. Minimum albedo (about 20 percent) occurs within 15 deg of the equator. In the tropics and midlatitudes, there is a tendency toward higher albedos during the summer. Larger albedos at the higher latitudes are caused by solar zenith angle effects and by increased snow and ice cover. Net warming occurs between 35 deg N and 35 deg S latitude near the equinoxes and in a 90-deg-wide latitude band at the solstices centered around 35 deg latitude in the summer hemisphere. This energy surplus at lower latitudes coupled with an energy deficit in the poleward regions is the primary driver of atmospheric circulations. For the year, the global net radiation is nearly in balance.

  4. Numerical study of radiation effect on the municipal solid waste combustion characteristics inside an incinerator

    SciTech Connect

    Wang, Jingfu Xue, Yanqing; Zhang, Xinxin; Shu, Xinran

    2015-10-15

    Highlights: • A 3-D model for the MSW incinerator with preheated air was developed. • Gas radiative properties were obtained from a statistical narrow-band model. • Non-gray body radiation model can provide more accurate simulation results. - Abstract: Due to its advantages of high degree volume reduction, relatively stable residue, and energy reclamation, incineration becomes one of the best choices for Municipal Solid Waste (MSW) disposal. However, detailed measurements of temperature and gas species inside a furnace are difficulty by conventional experimental techniques. Therefore, numerical simulation of MSW incineration in the packed bed and gas flow field was applied. In this work, a three dimensional (3-D) model of incinerator system, including flow, heat transfer, detailed chemical mechanisms, and non-gray gas models, was developed. Radiation from the furnace wall and the flame formed above the bed is of importance for drying and igniting the waste. The preheated air with high temperature is used for the MSW combustion. Under the conditions of high temperature and high pressure, MSW combustion produces a variety of radiating gases. The wavelength-depend radiative properties of flame adopted in non-gray radiation model were obtained from a statistical narrow-band model. The influence of radiative heat transfer on temperature, flow field is researched by adiabatic model (without considering radiation), gray radiation model, and non-gray radiation model. The simulation results show that taking into account the non-gray radiation is essential.

  5. [Effect of enhanced UV-B radiation on photosynthetic structure and photosynthetic characteristics of Mentha piperita].

    PubMed

    Wu, Nengbiao; Ma, Hongqun; Hu, Litao; Hong, Hong; Sun, Jinchun; Zhang, Yanghuan; Dai, Dalin

    2009-12-01

    To reveal the effects of UV-B radiation on the growth of medical plant Mentha piperita, simulate an enhanced UV-B radiation and evaluate intensity of radiation on the photosynthesis of M. piperita. Three different levels of UV-B radiation were set in the experiment which included: natural light control (0 W x m(-2)), light UV-B radiation stress (0.15 W x m(-2)) and heavy UV-B radiation stress (0.35 W x m(-2)). The chloroplast ultrastructure, photosynthesis indexes and chlorophyll fluorescence parameters of the M. piperita were observed under the three treatments. Although the chloroplast ultrastructure was destroyed to some degree under the light UV-B radiation stress, F(v)/(F)m, F(v)/F(o), qP, phiPS II and ETR could resume to the comparative level of natural light control. At the same time, qN increased firstly and decreased thereafter. But under the high strength UV-B radiation stress, the photosynthetic structures were badly destroyed, which could not recover through protecting mechanism by itself. It was showed that M. piperita was able to protect photosynthetic structures by increasing respiration and dissipation when photosynthetic capacity reduced under light UV-B radiation stress. It is demonstrated that M. piperita has high adaptation to light UV-B radiation stress, which is kind of promising medical plant for area with higher UV-B radiation.

  6. Characteristic of the radiation field in low Earth orbit and in deep space.

    PubMed

    Reitz, Guenther

    2008-01-01

    The radiation exposure in space by cosmic radiation can be reduced through careful mission planning and constructive measures as example the provision of a radiation shelter, but it cannot be completely avoided. The reason for that are the extreme high energies of particles in this field and the herewith connected high penetration depth in matter. For missions outside the magnetosphere ionizing radiation is recognized as the key factor through its impact on crew health and performance. In absence of sporadic solar particle events the radiation exposure in Low Earth orbit (LEO) inside Spacecraft is determined by the galactic cosmic radiation (protons and heavier ions) and by the protons inside the South Atlantic Anomaly (SAA), an area where the radiation belt comes closer to the earth surface due to a displacement of the magnetic dipole axes from the Earth's center. In addition there is an albedo source of neutrons produced as interaction products of the primary galactic particles with the atoms of the earth atmosphere. Outside the spacecraft the dose is dominated by the electrons of the horns of the radiation belt located at about 60" latitude in Polar Regions. The radiation field has spatial and temporal variations in dependence of the Earth magnetic field and the solar cycle. The complexity of the radiation field inside a spacecraft is further increased through the interaction of the high energy components with the spacecraft shielding material and with the body of the astronauts. In interplanetary missions the radiation belt will be crossed in a couple of minutes and therefore its contribution to their radiation exposure is quite small, but subsequently the protection by the Earth magnetic field is lost, leaving only shielding measures as exposure reduction means. The report intends to describe the radiation field in space, the interaction of the particles with the magnetic field and shielding material and give some numbers on the radiation exposure in low earth

  7. Effects of variability in land surface characteristics on the summer radiation budget across desert-oasis region in Northwestern China

    NASA Astrophysics Data System (ADS)

    Zhang, Yongyong; Zhao, Wenzhi

    2015-02-01

    The oasis area in the middle reaches of the Heihe River has changed since a water diversion scheme was implemented in 2000. The resultant variation land surface characteristics affects radiation budget during the oasisification process. The aim of this study was to investigate the variation in radiation budget within land surfaces during the oasisification process, through spatial instead of time-successional sequence method. Radiant data in the oasis fringe (maize field) and the desert-oasis ecotone was observed during the summer of 2009. The results showed that solar radiation (SR) in the oasis fringe was identical to that of the desert-oasis ecotone on selected clear, cloudy, and rainy days. Surface reflective radiation (SRR) and surface effective radiation (SER) both decreased from clear day to cloudy day and were lowest on the rainy day. The diurnal variation in radiation budget for cloudy and rainy days did not follow the same cycle as on clear day. The albedo values in the oasis fringe and the desert-oasis ecotone were 0.18 and 0.26, respectively. The diurnal variation in albedo tended toward a "U-shaped" curve on clear day. When the solar elevation angle was greater than 40°; the albedo was symmetrical in the a.m. and p.m. time frames. The radiation budget changed within land surfaces during the oasisification process. In summer, the albedo decreased, as did SER, with the transition from desert to oasis interior; whereas the surface-absorbed radiation (SAR) and net radiation (NR) both increased. More than half of the absorbed net energy in the desert was released in longwave form. The absorbed energy in the oasis was conserved to ensure stable light and heat resources utilization for agricultural production.

  8. Sound Solutions

    ERIC Educational Resources Information Center

    Starkman, Neal

    2007-01-01

    Poor classroom acoustics are impairing students' hearing and their ability to learn. However, technology has come up with a solution: tools that focus voices in a way that minimizes intrusive ambient noise and gets to the intended receiver--not merely amplifying the sound, but also clarifying and directing it. One provider of classroom audio…

  9. Sound Solutions

    ERIC Educational Resources Information Center

    Starkman, Neal

    2007-01-01

    Poor classroom acoustics are impairing students' hearing and their ability to learn. However, technology has come up with a solution: tools that focus voices in a way that minimizes intrusive ambient noise and gets to the intended receiver--not merely amplifying the sound, but also clarifying and directing it. One provider of classroom audio…

  10. Sound and computer information presentation

    SciTech Connect

    Bly, S

    1982-03-01

    This thesis examines the use of sound to present data. Computer graphics currently offers a vast array of techniques for communicating data to analysts. Graphics is limited, however, by the number of dimensions that can be perceived at one time, by the types of data that lend themselves to visual representation, and by the necessary eye focus on the output. Sound offers an enhancement and an alternative to graphic tools. Multivariate, logarithmic, and time-varying data provide examples for aural representation. For each of these three types of data, the thesis suggests a method of encoding the information into sound and presents various applications. Data values were mapped to sound characteristics such as pitch and volume so that information was presented as sets or sequences of notes. In all cases, the resulting sounds conveyed information in a manner consistent with prior knowledge of the data. Experiments showed that sound does convey information accurately and that sound can enhance graphic presentations. Subjects were tested on their ability to distinguish between two sources of test items. In the first phase of the experiments, subjects discriminated between two 6-dimensional data sets represented in sound. In the second phase of the experiment, 75 subjects were selected and assigned to one of three groups. The first group of 25 heard test items, the second group saw test items, and the third group both heard and saw the test items. The average percentage correct was 64.5% for the sound-only group, 62% for the graphics-only group, and 69% for the sound and graphics group. In the third phase, additional experiments focused on the mapping between data values and sound characteristics and on the training methods.

  11. Differences in published characteristics of GLE60 and their consequences on computed radiation dose rates along selected flight paths

    NASA Astrophysics Data System (ADS)

    Bütikofer, R.; Flückiger, E. O.

    2013-02-01

    The radiation dose rates at flight altitudes can increase by orders of magnitude for a short time during energetic solar cosmic ray events, so called ground level enhancements (GLEs). Especially at high latitudes and flight altitudes, solar energetic particles superposed on galactic cosmic rays may cause radiation that exceeds the maximum allowed dosage limit for the general public. Therefore the determination of the radiation dose rate during GLEs should be as reliable as possible. Radiation dose rates along flight paths are typically determined by computer models that are based on cosmic ray flux and anisotropy parameters derived from neutron monitor and/or satellite measurements. The characteristics of the GLE on 15 April 2001 (GLE60) were determined and published by various authors. In this work we compare these results and investigate the consequences on the computed radiation dose rates along selected flight paths. In addition, we compare the computed radiation dose rates with measurements that were made during GLE60 on board two transatlantic flights.

  12. Comparative Characteristics Of Coherent And Incoherent Radiation In The Photography Of Ulcer

    NASA Astrophysics Data System (ADS)

    Novikov, V. F.; Paramonov, L. V.

    1985-01-01

    The efficiency of He-Ne laser radiation and incoherent radiation by red light sources with different spectral bandwidths is compared for the endoscopic phototherapy of gastric and duodenal ulcers. Coherent and incoherent radiation is determined to result in the same theraputic effect when doing the treatment of ulcer deseases. The methods of ulcer treatment is suggested with a conventional fibrogastroscope fitted with red glass filter.

  13. A review on photoneutrons characteristics in radiation therapy with high-energy photon beams.

    PubMed

    Naseri, Alireza; Mesbahi, Asghar

    2010-09-22

    In radiation therapy with high-energy photon beams (E > 10 MeV) neutrons are generated mainly in linacs head thorough (γ,n) interactions of photons with nuclei of high atomic number materials that constitute the linac head and the beam collimation system. These neutrons affect the shielding requirements in radiation therapy rooms and also increase the out-of-field radiation dose of patients undergoing radiation therapy with high-energy photon beams. In the current review, the authors describe the factors influencing the neutron production for different medical linacs based on the performed measurements and Monte Carlo studies in the literature.

  14. Numerical study of radiation effect on the municipal solid waste combustion characteristics inside an incinerator.

    PubMed

    Wang, Jingfu; Xue, Yanqing; Zhang, Xinxin; Shu, Xinran

    2015-10-01

    Due to its advantages of high degree volume reduction, relatively stable residue, and energy reclamation, incineration becomes one of the best choices for Municipal Solid Waste (MSW) disposal. However, detailed measurements of temperature and gas species inside a furnace are difficulty by conventional experimental techniques. Therefore, numerical simulation of MSW incineration in the packed bed and gas flow field was applied. In this work, a three dimensional (3-D) model of incinerator system, including flow, heat transfer, detailed chemical mechanisms, and non-gray gas models, was developed. Radiation from the furnace wall and the flame formed above the bed is of importance for drying and igniting the waste. The preheated air with high temperature is used for the MSW combustion. Under the conditions of high temperature and high pressure, MSW combustion produces a variety of radiating gases. The wavelength-depend radiative properties of flame adopted in non-gray radiation model were obtained from a statistical narrow-band model. The influence of radiative heat transfer on temperature, flow field is researched by adiabatic model (without considering radiation), gray radiation model, and non-gray radiation model. The simulation results show that taking into account the non-gray radiation is essential. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. A review on photoneutrons characteristics in radiation therapy with high-energy photon beams

    PubMed Central

    Naseri, Alireza; Mesbahi, Asghar

    2010-01-01

    In radiation therapy with high-energy photon beams (E > 10 MeV) neutrons are generated mainly in linacs head thorough (γ,n) interactions of photons with nuclei of high atomic number materials that constitute the linac head and the beam collimation system. These neutrons affect the shielding requirements in radiation therapy rooms and also increase the out-of-field radiation dose of patients undergoing radiation therapy with high-energy photon beams. In the current review, the authors describe the factors influencing the neutron production for different medical linacs based on the performed measurements and Monte Carlo studies in the literature. PMID:24376940

  16. Short sound decay of ancient Chinese music bells

    NASA Astrophysics Data System (ADS)

    Pan, Jie; Li, Xiaodong; Tian, Jing; Lin, Tanran

    2002-12-01

    Ancient Chinese music bells, which have oval-like cross sections, possess the unique feature of a short sound-decay time that is especially suitable for music with fast tempo. Although recorded in the literature nearly 1000 years ago, this feature has never been truly understood. Recent damping measurement of oval pipes with different axial ratios suggested a challenging task for acousticians as the increase of the modal damping with the pipe's axial ratio is significant only when the pipe response is measured in air but not in vacuum. In this paper, the decrease of sound-decay time of oval pipes with the increased cross-section ovality is investigated. This is the first time that such short sound-decay feature is explained in terms of the rich sound radiation characteristics of the symmetric modes of music bells and the oval pipes. Finite element and boundary element methods are employed to explain how axial ratio significantly affects the normal velocity distribution, radiation efficiency, and directivity of acoustic modes.

  17. Radiation characteristics and effective optical properties of dumbbell-shaped cyanobacterium Synechocystis sp.

    NASA Astrophysics Data System (ADS)

    Heng, Ri-Liang; Pilon, Laurent

    2016-05-01

    This study presents experimental measurements of the radiation characteristics of unicellular freshwater cyanobacterium Synechocystis sp. during their exponential growth in F medium. Their scattering phase function at 633 nm average spectral absorption and scattering cross-sections between 400 and 750 nm were measured. In addition, an inverse method was used for retrieving the spectral effective complex index of refraction of overlapping or touching bispheres and quadspheres from their absorption and scattering cross-sections. The inverse method combines a genetic algorithm and a forward model based on Lorenz-Mie theory, treating bispheres and quadspheres as projected area and volume-equivalent coated spheres. The inverse method was successfully validated with numerically predicted average absorption and scattering cross-sections of suspensions consisting of bispheres and quadspheres, with realistic size distributions, using the T-matrix method. It was able to retrieve the monomers' complex index of refraction with size parameter up to 11, relative refraction index less than 1.3, and absorption index less than 0.1. Then, the inverse method was applied to retrieve the effective spectral complex index of refraction of Synechocystis sp. approximated as randomly oriented aggregates consisting of two overlapping homogeneous spheres. Both the measured absorption cross-section and the retrieved absorption index featured peaks at 435 and 676 nm corresponding to chlorophyll a, a peak at 625 nm corresponding to phycocyanin, and a shoulder around 485 nm corresponding to carotenoids. These results can be used to optimize and control light transfer in photobioreactors. The inverse method and the equivalent coated sphere model could be applied to other optically soft particles of similar morphologies.

  18. Radiation Characteristics of Reflectarray Antennas: Methodology and Applications to Dual Configurations

    NASA Technical Reports Server (NTRS)

    Khayatian, Behrouz; Rahmat-Samii, Yahya; Huang, John

    2006-01-01

    Reflectarrays combines key features of large reflectors and phased array elements to generate a collimated beam as required in high gain antennas. In reflectarrays, a large flat reflecting surface with many resonant patch elements is illuminated by a feed (or by a feed/subreflector in dual reflector configuration). In many space applications, reflectarrays applications can be advantageous because their large surface can be folded or rolled as a part of spacecraft payload before being deployed. Consequently, a reflectarray can significantly reduce both volume and mass requirements in space deployment. To optimize reflectarray antenna performance, a phase correction mechanism must be applied to its individual array elements some of which are well documented in the literatures. In this study, we attempt to extend analytical techniques in reflector analysis to reflectarrays by introducing a number of approaches to estimate the reflectarray antenna performance independent of its phase compensation mechanism. In one approach, a Physical Optics (PO) current will be assigned to the surface of individual reflectarray elements upon which a phase correction will be applied. In the second approach, a transmit/receive (TX/RX) radiation characteristics will be assigned to individual reflectarray elements from which coupling coefficients will be calculated and assigned as the excitation coefficient of individual elements. PO approach is modeled in the UCLA reflector code while coupling (TX/RX) method is implemented in both UCLA code as well as TICRA (GRASP) software. Results are presented for single and dual configurations with the main reflector as a reflectarray. The approach described is used to design a 3-m Cassegrain offset-fed configuration for dual X/Ka-bands application.

  19. PREFACE: Aerodynamic sound Aerodynamic sound

    NASA Astrophysics Data System (ADS)

    Akishita, Sadao

    2010-02-01

    The modern theory of aerodynamic sound originates from Lighthill's two papers in 1952 and 1954, as is well known. I have heard that Lighthill was motivated in writing the papers by the jet-noise emitted by the newly commercialized jet-engined airplanes at that time. The technology of aerodynamic sound is destined for environmental problems. Therefore the theory should always be applied to newly emerged public nuisances. This issue of Fluid Dynamics Research (FDR) reflects problems of environmental sound in present Japanese technology. The Japanese community studying aerodynamic sound has held an annual symposium since 29 years ago when the late Professor S Kotake and Professor S Kaji of Teikyo University organized the symposium. Most of the Japanese authors in this issue are members of the annual symposium. I should note the contribution of the two professors cited above in establishing the Japanese community of aerodynamic sound research. It is my pleasure to present the publication in this issue of ten papers discussed at the annual symposium. I would like to express many thanks to the Editorial Board of FDR for giving us the chance to contribute these papers. We have a review paper by T Suzuki on the study of jet noise, which continues to be important nowadays, and is expected to reform the theoretical model of generating mechanisms. Professor M S Howe and R S McGowan contribute an analytical paper, a valuable study in today's fluid dynamics research. They apply hydrodynamics to solve the compressible flow generated in the vocal cords of the human body. Experimental study continues to be the main methodology in aerodynamic sound, and it is expected to explore new horizons. H Fujita's study on the Aeolian tone provides a new viewpoint on major, longstanding sound problems. The paper by M Nishimura and T Goto on textile fabrics describes new technology for the effective reduction of bluff-body noise. The paper by T Sueki et al also reports new technology for the

  20. Sound Speed and Attenuation in Multiphase Media

    DTIC Science & Technology

    2012-03-15

    factor for bottom loss models. Originally this research concerned the description of the low frequency, LF, radiation and scattering of sound from...observations. The quandary was: why do investigators find exponents n between 1.6 and 1.87 less than 2? Numerical studies have shown obvious factors ...Nantucket Sound Experiment sound transmission experiment [17] where roughness and internal waves are not a factor required a power exponent of n = 1.87