检索结果-内蒙古大学图书馆

An algorithm for selecting transducer element array positions

The Journal of the Acoustical Society of America 2005年第S1期79卷 S91-S91页

作者： King W. Wiemann W. Jack Hughes Graduate Program in Acoustics Applied Research Laboratory The Pennsylvania State University P.O. Box 30 State College PA 16804

A lumped‐parameter equivalent circuit of a tonpilz transducer is used to predict element amplitude and phase tolerance for different radiation loadings, based on in‐air measurements of the transducers. Relationships among the measurable parameters of a transducer and its performance characteristics have been explored. Preliminary estimates of acceptable tolerances for each circuit parameter have been established. A two‐part technique to determine the placement of transducer elements in an array which minimizes the impact of element tolerances on the directional beam pattern has been developed. This technique has been used to place, in an array, elements with tolerances of ± 9% in amplitude and ± 11° in phase. The resulting theoretical array response achieved sidelobe levels that were within 1 dB of the −40‐dB design. The first half of the technique selects four elements at a time from a larger selection pool, and places them in a manner that partially cancels their respective amplitude and phase variations. The second half of the technique uses a permutation search algorithm which rearranges the initial placement of elements in and out of the array looking for improvements in the array response.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Comparative measurements on viscoelastic materials used for vibration damping

引用

The Journal of the Acoustical Society of America 2005年第S1期74卷 S91-S91页

作者： Christian Pillot Geoffrey L. Wilson Institut National des Sciences Appliquées de Lyon 69621 Villeurbanne Cedex France Graduate Program in Acoustics The Pennsylvania State University University Park PA 16802 Applied Research Laboratory The Pennsylvania State University University Park PA 16802

In a previous paper at the 99th meeting of the Acoustical Society of America in Atlanta in 1980 a new viscoelastometer was described. This instrument enables the Young's modulus and loss factor to be easily obtained over a wide range of frequencies and temperatures. The prototype of this instrument is being used in a continuing project for the systematic evaluation of the properties of a wide variety of commercially available materials. The method will be. described and some examples given.

关键词：

来源：评论

学校读者我要写书评

暂无评论

A mathematical model for wave propagation in bilaminar composite plates

引用

The Journal of the Acoustical Society of America 2005年第S1期87卷 S164-S164页

作者： Si‐Hwan Yum Sabih I. Hayek Graduate Program in Acoustics 101 Applied Research Bldg. Penn State Univ. University Park PA 16802 Dept. of Eng. Mech. Sci. Penn State Univ. University Park PA 16802 Appl. Res. Lab. Penn State Univ. University Park PA 16802

Refined models for plate deformation allow for new types of thickness and extensional displacements not currently feasible in the classical or Timoshenko‐Mindlin plate theories. An infinite bilaminar composite plate is fabricated in such a way that the two plates, made of different isotropic, homogeneous materials, are perfectly bonded. A new mathematical model of the vibration of an infinite bilaminar composite plate has been obtained by using energy methods. The displacement field is based on symmetric and antisymmetric displacement functions in both the thickness stretch and the thickness shear of each layer. From this model, the Timoshenko‐Mindlin thick plate theory and the Bernoulli‐Euler classic plate theory for a single plate can be recovered as special limiting cases. For this model, a six‐branched frequency‐wavenumber spectrum of the composite layer is computed. This allows the introduction of suitable correction coefficients to correct the resulting frequency spectra so that they correspond to those of the exact elasticity theory.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Effect of a downstream ventilated gas cavity on the spectrum of turbulent boundary layer wall pressure fluctuations

Effect of a downstream ventilated gas cavity on the spectrum...

引用

2004 ASME International Mechanical Engineering Congress and Exposition, IMECE

作者： Young, Steven D. Brungart, Timothy A. Lauchle, Gerald C. Applied Research Laboratory Pennsylvania State University State College PA 16804 United States Graduate Program Acoustics and Applied Research Laboratory Pennsylvania State University State College PA 16804 United States

This paper theoretically and experimentally examines the effect of a downstream ventilated gas cavity on the spectrum of turbulent boundary layer wall pressure fluctuations. The theoretical model predicts that the ratio of the point spectrum of the turbulent boundary layer wall pressure fluctuations upstream of a ventilated gas cavity to the blocked point pressure spectrum decays rapidly to zero as the cavity origin is approached and undergoes oscillations in amplitude that relax to unity as the quantityωx/U c goes to infinity upstream of the cavity. Here ω is the radian frequency, x is the distance upstream from the cavity origin and U c is the convection velocity. A water tunnel experiment was performed to investigate the theoretical predictions. Dynamic wall pressure sensors were mounted flush to the surface of a flat plate at various distances upstream from a rearward facing step. Carbon dioxide gas was injected into the separated flow region downstream of the step to form a ventilated cavity. The water tunnel measurements were unable to verify the reduction in the amplitude of the turbulent boundary layer wall pressure fluctuations as the step and cavity were approached but did verify the fundamental oscillation predicted by the theoretical model and its relaxation to unity as ωx/Uc went to infinity upstream of the step and cavity. Copyright © 2004 by ASME.

关键词： Boundary layers

来源：评论

学校读者我要写书评

暂无评论

On the Relationship between Signal Bandwidth and Frequency Correlation for Surface Forward Scattered Signals

引用

AIP Conference Proceedings 2004年第1期728卷 204-213页

作者： Lee Culver David Bradley Applied Research Laboratory The Pennsylvania State University P.O. Box 30 State College PA 16804 Graduate Program in Acoustics The Pennsylvania State University P.O. Box 30 State College PA 16804

The relationship between the signal bandwidth and the correlation of a single surface reflected arrival with the transmitted signal has been investigated experimentally and compared with two theories. The dependence of correlation on signal bandwidth is termed frequency correlation. Decorrelation of surface scattered signals is a direct consequence of time spread. Thus the acoustic measurement utilized two pure tone signals, from which time spread has been estimated, and four broadband signals with different bandwidths, from which correlation with the transmitted signal has been calculated. A model developed by Dahl for the ocean surface bistatic scattering cross section was used to predict time spread, which agreed very well with the measured time spread. Next, scattering cross section prediction was employed in two theories that predict frequency correlation. The first, published by Reeves in 1974, compared well with the measurements for bandwidths up to 2 kHz, but under predicted correlation for signal bandwidth between 7 and 22 kHz. In the second, linear systems theory was used to develop a mathematical relationship between time spread and frequency correlation. Predictions made using the linear systems theory agree well with the measured values for signal bandwidths up to 22kHz. Further work is required to evaluate the linear systems theory under higher sea state conditions.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Acoustic radiation from separated boundary-layer flow over a rearward-facing step on a flat panel

Acoustic radiation from separated boundary-layer flow over a...

引用

2003 ASME International Mechanical Engineering Congress

作者： Kargus IV, Walter A. Lauchle, Gerald C. Johnson Electric Automotive 47660 Halyard Drive Plymouth MI 48170 United States Graduate Program in Acoustics Applied Research Laboratory Penn State University University Park PA 16802 United States

The acoustic radiation from a turbulent boundary layer that occurs downstream of a rearward facing step discontinuity and reattaches to a flat plate is considered experimentally. The step is exposed to a zero incidence, uniform subsonic flow. A quiet wall jet facility situated in an anechoic chamber is used for the studies. The "point" wall pressure spectra are measured by small, "pinhole" microphones located at various locations under the layer, including a point directly in the 90° corner of the step. The wall pressure fluctuations measured at the various locations are correlated with the signal detected by a far-field microphone. The measured cross-spectral densities are thus used to identify the relative contributions of the various flow regimes to the direct radiation. It is shown that the separation of the flow over the corner of the step is a dominant acoustic source, which is supported not only by the measured cross spectra, but also by the favorable comparison of the measured velocity power law to the theoretical value. Measurements made where the flow reattaches and at the turbulent boundary layer are less conclusive. This is because the pinhole tube attached to the microphone produced a sound due to a fluid-dynamic oscillation, which contaminated the measurement of the aeroacoustic sources.

关键词： Boundary layers

来源：评论

学校读者我要写书评

暂无评论

Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators

引用

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

关键词：

来源：评论

学校读者我要写书评

暂无评论

On the acoustic radiation from a loudspeaker's cabinet

AES: Journal of the Audio Engineering Society

引用

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

来源：评论

学校读者我要写书评

暂无评论

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

Noninvasive ultrasonic transdermal insulin delivery in rabbi...

引用

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

来源：评论

学校读者我要写书评

暂无评论

Benefits of rake and skew for turbulence ingestion noise

Benefits of rake and skew for turbulence ingestion noise

引用

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

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：