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Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators

The Journal of the Acoustical Society of America 2003年第5期113卷 2379-2381页

作者： G. W. Swift Steven L. Garrett Graduate Program in Acoustics and Applied Research Laboratory The Pennsylvania State University P.O. Box 30 State College Pennsylvania 16804-0030

G. W. Swift, Steven L. Garrett; Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators , The Journal of the Acoustical Society of America, V

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On the acoustic radiation from a loudspeaker's cabinet

AES: Journal of the Audio Engineering Society

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AES: Journal of the Audio Engineering Society 2003年第4期51卷 234-243页

作者： Bastyr, Kevin J. Capone, Dean E. Graduate Program in Acoustics Pennsylvania State University State College PA 16804 United States Applied Research Laboratory Pennsylvania State University State College PA 16804 United States

A scanning laser Doppler vibrometer and a computational boundary-element model are used to study the acoustic radiation from loudspeaker cabinets. In contrast to the research findings of Skrodzka, loudspeaker cabinets are shown to contribute significantly to the total radiated pressure at their lower resonance frequencies. This occurs because, despite a cabinet's relatively small surface velocity, its radiation efficiency is many times greater than that of the drivers. The radiation from two different versions of NHT's model 2.9 loudspeaker is investigated. The first is a standard production 2.9, the second a 2.9 without the standard internal bracing. A comparison of their performance yields insight into the effects of wall bracing location: suffer cabinets with lower amplitude wall vibrations do not always radiate less sound.

关键词： Acoustic waves

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Benefits of rake and skew for turbulence ingestion noise

Benefits of rake and skew for turbulence ingestion noise

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2003 ASME International Mechanical Engineering Congress

作者： Gavin, Joseph R. Jonson, Michael L. Lysak, Peter D. Lauchle, Gerald C. General Dynamics Electric Boat Corp. 75 Eastern Point Rd Groton CT 06340 United States Pennsylvania State University Applied Research Laboratory P.O. Box 30 State College PA 16804 United States Graduate Program in Acoustics ARL Pennsylvania State University University Park PA 16802 United States

Turbulent flow through a fan or pump produces a broadband spectrum of unsteady lifting forces on the blades. These forces cause undesirable blade stresses, blade vibration and sound. Jonson (1994) has shown that broadband improvements can be obtained by adding rake and skew to the stacking line of rotor blade sections. This paper adds understanding to those experimental results, and shows that benefits can be reliably predicted using analytical methods.

关键词： Acoustic noise

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Noninvasive ultrasonic transdermal insulin delivery in rabbits using the light weight cymbal array

Noninvasive ultrasonic transdermal insulin delivery in rabbi...

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2003 IEEE Ultrasonics Symposium - Proceedings

作者： Lee, Seungjun Snyder, Benjamin Meyer, Richard J. Nayak, Vivekanand Markley, Douglas Newnham, Robert E. Smith, Nadine Barrie Bioengineering Department Pennsylvania State University University Park PA 16802 United States Material Research Laboratory Pennsylvania State University University Park PA 16802 United States Applied Research Laboratory Pennsylvania State University University Park PA 16802 United States Electrical Engineering Pennsylvania State University University Park PA 16802 United States Graduate Program in Acoustics Pennsylvania State University University Park PA 16802 United States

The low profile Cymbal array for enhanced insulin transport through in vivo animal skin using rabbits was discussed. Through the use of the cymbal array, the US-insulin experimental group showed a blood glucose level decrease of -208.1 ± 29 mg/dL within 90 minutes. The small increase in blood glucose was attributable to the low skin permeability of insulin. It was shown that the US alone did not alter the blood glucose level of the rabbit.

关键词： Ultrasonic applications

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Noninvasive ultrasonic transdermal insulin delivery in rabbits using the light weight cymbal array

Noninvasive ultrasonic transdermal insulin delivery in rabbi...

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IEEE Symposium (IUS) Ultrasonics

作者： S. Lee B. Snyder R.J. Meyer V. Nayak D. Markley R.E. Newnham N.B. Smith Bioengineering Department The Pennsylvania State University University Park PA U.S.A. Material Research Laboratory The Pennsylvania State University University Park PA U.S.A. Applied Research laboratory The Pennsylvania State University University Park PA U.S.A. Electrical Engineering The Pennsylvania State University University Park PA U.S.A. Graduate Program in Acoustics The Pennsylvania State University University Park PA U.S.A.

The purpose of this study was to demonstrate US transdermal delivery of insulin in vivo using rabbits with a novel, low profile two-by-two US array based on the cymbal transducer. As a practical device, the cymbal array (f=20 kHz) was 37/spl times/37/spl times/7 mm/sup 3/ in size and weighed less than 22g. With a similar intensity (I/sub sptp/=100 mW/cm/sup 2/, 20% duty cycle), our goal was to determine if the same effect could be achieved with rabbits. Fourteen New Zealand White rabbit (2.7-3.4 kg) experiments were performed in three groups: two controls and one US with insulin exposure. The first group (control 1) had insulin placed in the reservoir with no US while the second group (control 2) had saline in the reservoir with US operating at I/sub sptp/=100 mW/cm/sup 2/ for 60 minutes. The third group (US-Insulin) was subjected to insulin with US exposure for 60 minutes (I/sub sptp/=100 mW/cm/sup 2/). At the commencement of the experiment, 0.3 mL of blood was collected from the ear vein to determine the blood glucose level (mg/dL) using a blood glucose monitoring system. The insulin reservoir was removed with the array after the US was turned off at 60 minutes exposure. For both control 1 and 2, the blood glucose level showed an increase at 15 and 30 minutes and remained at approximately +50 mg/dL. For the US-Insulin group, the glucose level was found to decrease -132.6/spl plusmn/35.7 mg/dL in 60 minutes. After the US and insulin were removed, the blood glucose level of US-Insulin group continued to decrease to -208.1/spl plusmn/29 mg/dL. These results indicate the feasibility of using a low cost, light weight Cymbal array for enhanced transdermal insulin delivery using US.

关键词： Insulin Rabbits Optical arrays Blood Sugar Reservoirs Ultrasonic transducer arrays In vivo Ultrasonic transducers Ear

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Processing of forward scattered acoustic fields with intensity sensors

Processing of forward scattered acoustic fields with intensi...

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Ocean's 2002 Conference and Exhibition

作者： Rapids, Brian R. Lauchle, Gerald C. Pennsylvania State University Applied Research Laboratory Graduate Program in Acoustics P.O. Box 30 State College PA 16804 United States Pennsylvania State University Graduate Program in Acoustics Applied Research Laboratory University Park PA 16802 United States

In bistatic scattering geometries, the detection of a signal scattered in the forward direction by a stationary object can be difficult because the incident and scattered waves combine into a simultaneous mixture. Reverberation can complicate the measurements even further. At opposite ends of the forward scattering phenomenon are the Rayleigh scattering region, where the scattered wave is masked by the incident wave;and the geometrical optics region, where the two wavefields interfere to form an acoustic shadow. Pressure sensors can only provide an estimate of the magnitude of the intensity associated with an equivalent plane wave field, while true intensity sensors measure simultaneously the acoustic pressure and particle velocity components (or a related quantity such as acceleration, displacement, or pressure gradient) at a single "point" in space. The coherent measurement of both acoustic field parameters provides not only the magnitude of acoustic intensity but the phase between acoustic pressure and velocity. It is hypothesized that processing methods could be developed which exploit the relationship between these types of coherent measurements in order to extract information regarding the presence and nature of an object residing on or very close to the bistatic baseline. In this paper, this hypothesis is explored computationally using a rigid prolate spheroid as a canonical scattering body.

关键词： Acoustic wave scattering

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Acoustic qualities of ship wakes

Acoustic qualities of ship wakes

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作者： Bradley, D.L. Culver, R.L. Di, X. Bjørnø, L. Applied Research Laboratory Graduate Program in Acoustics Pennsylvania State University P.O. Box 30 State College PA 16804 United States

The major influence on sound propagation and attenuation in surface ship wakes arises from the presence of bubbles. The aim of the research behind this paper is to obtain a better understanding of the propagation conditions for sound in surface ship wakes in order to be able to produce realistic sound propagation models for predicting acoustic qualities of wakes. A high resolution, multi-beam sonar, looking upward at a wake produced by a passing surface ship, has provided data characterizing the wake structure in the along-wake, the cross-wake and the depth directions. A simple wake model has been developed from historical data, and this model has been used with a 2D PE code to calculate the loss of acoustic energy in the wake. Understanding the complexity of the wake bubble structure, and its effect on acoustic propagation, remains a challenging research goal.

关键词： Underwater acoustics

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Flow-induced noise on underwater pressure-vector acoustic sensors

Flow-induced noise on underwater pressure-vector acoustic se...

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Ocean's 2002 Conference and Exhibition

作者： Lauchle, Gerald C. Wang, Jack Howe, Michael S. Pennsylvania State University Graduate Program in Acoustics Applied Research Laboratory University Park PA 16802 United States Trane Company Acoustics and Mechanics Technology 3600 Pammel Creek Road LaCrosse WI 54601 United States Boston University College of Engineering 110 Cummington Street Boston MA 02215 United States

Flow-induced self noise on moored and drifting hydrophones arise when the sensors are subjected to oceanic currents such as those due to wave motion and changing tides. Flow-induced self noise on underwater acoustic particle velocity (or acceleration) sensors, and on intensity probes that measure particle velocity and pressure simultaneously is the subject of this paper. The sensors considered are configured as neutrally-buoyant spheres that encase an accelerometer or geophone. These velocity sensors are very sensitive to the turbulent fluctuations in the free stream, or those, which are generated by the flow over the sensor body itself. The flow-induced self noise is thus determined by the level of unsteady force created by the turbulence and unsteady flow. Experiments are conducted by towing a spherical velocity sensor from 0.5 to 2.0 knots in a quiet basin of water that is 9 m long. A model is developed for the flow-induced unsteady drag and side force of the sphere. This is based on integrating the local wall pressure fluctuations over the surface of the sphere. Wind tunnel experiments are performed to obtain the necessary statistics of these pressure fluctuations. The semi-empirical model is then validated using the towed sensor unsteady velocity spectra, which are easily converted to unsteady drag or side force spectra by Newton's Second Law. Predictions of the flow noise response of neutrally-buoyant spherical velocity sensors of various sizes are then performed. It is concluded that at the same flow velocity, a large inertial sensor is less responsive than a small one to the turbulent flow over its surface and in the near wake.

关键词： Sensors

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Development of a high frequency underwater acoustic intensity probe

Development of a high frequency underwater acoustic intensit...

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Ocean's 2002 Conference and Exhibition

作者： McConnell, James A. Weber, Thomas C. Lauchle, Gerald C. Gabrielson, Thomas B. Acoustech Corporation P.O. Box 139 State College PA 16804 United States Pennsylvania State University Graduate Program in Acoustics Applied Research Laboratory University Park PA 16802 United States Pennsylvania State University Applied Research Laboratory P. O. Box 30 State College PA 16804 United States

The development of an underwater acoustic intensity probe for high frequency applications (e.g., f ∼ 10 kHz) is presented. The probe measures the acoustic pressure along with two orthogonal components of the particle acceleration;hence, the probe relies on inertial sensing as opposed to a gradient technique. The acoustic pressure is measured with a ring hydrophone that is capped at both ends. The accelerometers are positioned within the internal cavity created by the hydrophone and are oriented to measure sound in the horizontal plane. The probe is negatively buoyant, contains a viscoelastic suspension system, and is positioned within a free-flooding stainless steel cage that contains extensional damping treatments and exhibits a low scattering cross-section. Negative buoyancy results from making the probe small so that it does not scatter the acoustic field over the frequency range of interest nor exhibit any in-band structural modes. The consequence of this action translates into an in-water acceleration sensitivity that is reduced by a factor of two relative to the intrinsic value. The hydrophone has an omni-directional beam pattern and the accelerometers have dipole directivity. Lumped parameter circuit models will be presented along with performance data.

关键词： Underwater acoustics

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Utilization of the high-frequency piezoelectric ceramic hollow spheres for exposimetry and tissue ablation

Utilization of the high-frequency piezoelectric ceramic holl...

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2002 IEEE Ultrasonics Symposium

作者： Al-Bataineh, Osama M. Meyer Jr., Richard J. Newnham, Robert E. Smith, Nadine Barrie Bioengineering Department The Pennsylvania State University University Park PA 16802 United States Applied Research Laboratory The Pennsylvania State University University Park PA 16802 United States Materials Research Institute The Pennsylvania State University University Park PA 16802 United States Graduate Program in Acoustics The Pennsylvania State University University Park PA 16802 United States

Miniature, high-frequency piezoelectric cermic hollow spheres were evaluated for potential use as hydrophones for exposimetry of high intensity ultrasound fields and as minimally invasive ablation devices. As a minimally invasive interstitial ablation device, several in vitro experiments were conducted using two different size spheres. The results demonstrated an increased necrosed tissue volume for increasing exposure time.

关键词： Ultrasonic transducers

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