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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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      <title>Propagation Attenuation of Plane Waves in Single-Phased Soil by Periodic Pile Barriers</title>
      <link>https://trid.trb.org/View/1505448</link>
      <description><![CDATA[Pile barriers have been broadly used to decrease the effect of ground vibration generated by machines or traffic. In recent years, the periodic theory of solid-state physics was introduced to study the reduction characteristics of periodic pile barriers. In the present paper, a finite-element method based on a partial differential equation (PDE) is introduced to study the propagation and attenuation of plane waves in single-phased soil by pile barriers. In this method, single-phased soil and pile barriers are considered as a periodic system, and the attenuation zones (AZs) of this periodic system are further calculated based on the plane-strain assumption. The influences of soil types and pile configurations on the AZs are comprehensively considered. To verify the existence of AZs using the periodic pile barriers, both two-dimensional and three-dimensional finite periodic pile barrier models were built, and the vibration reduction was analyzed in the frequency domain. After that, based on a practical ambient vibration wave, a periodic pile barrier system was designed, and the isolation effectiveness was verified by numerical simulations in the time domain. The present investigation provides a new method for designing pile barriers to block midfrequency vibration in single-phased soil.]]></description>
      <pubDate>Tue, 29 May 2018 16:04:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/1505448</guid>
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    <item>
      <title>Damage Localization in Offshore Structures using Shaped Inputs</title>
      <link>https://trid.trb.org/View/1482810</link>
      <description><![CDATA[Input shaping is an active control procedure by which vibrations in a structural subdomain are suppressed. Recently, a scheme based on shaped inputs has been proposed for damage localization purposes; cast on the premise that the vibration signature of a structural domain in a damaged phase will be identical to the signature of the healthy, reference counterpart if, for the same loading conditions, the subdomain containing damage is inactive in terms of vibrations. The idea is, thus, to apply controllable inputs that are shaped such that particular vibration quantities (depending on the type of damage one seeks to localize) are suppressed in one subdomain at the time, hereby resulting in damage being localized when the vibration signature induced by the shaped inputs in the damaged phase corresponds to that obtained in the reference phase. The present paper treats an application study that illustrates the damage localization scheme in simulations on a finite element model of an offshore jacket structure exposed to stochastic plane wave fields generated from a directional wave spectrum, and with fluid-structure interaction considered in terms of the Morison equation. In both structural phases, that is, the reference and the damaged one with a single mass perturbation, four inputs to be shaped are applied, and the resulting displacements are extracted from a single spatial location within the model. It is contended that the damage is localized when suppressing displacements (and their time-derivatives) near or, ideally, directly at its location.]]></description>
      <pubDate>Thu, 30 Nov 2017 09:53:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/1482810</guid>
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    <item>
      <title>Improvements of the Beamforming Technique in Pininfarina Full Scale Wind Tunnel by using a 3D Scanning System</title>
      <link>https://trid.trb.org/View/1429663</link>
      <description><![CDATA[Acoustic comfort is a key selling point leading vehicle manufacturers to invest money and resources in research activity. As a consequence the localization of internal and external noise sources of the vehicle is becoming more and more important.         The “Beamforming” technique is a well-known method, based on an array of microphones, suitable to identify the external noise sources of a road vehicle. This technique is able to localize the noise sources by estimating the amplitudes of plane, or spherical, waves incident toward the array. For many different reasons, such as the unknown position in the space of the noise sources, the processing time, the algorithm simplicity and so on, the investigation is generally made only on a virtual plane (planar Beamforming) and not in the full three-dimensional space. As a consequence the results accuracy, especially in terms of Sound Pressure Level (SPL) is not entirely satisfactory.         Based on these considerations, Pininfarina started a research program to improve the “Beamforming” technique by surveying the three-dimensional geometry of the full scale vehicle placed in the wind tunnel test section. This approach allows for a direct investigation of the noise sources on the 3D model, improving the source detection.         The details of the 3D scanning system are described together with its application. Moreover, are presented three experiments that show, with respect to the Planar “Beamforming” (PBF) technique, the improvements of the SPL values of the noise sources detected focusing the microphones array on the surveyed 3D geometry.       ]]></description>
      <pubDate>Wed, 29 Nov 2017 14:56:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/1429663</guid>
    </item>
    <item>
      <title>The Proper Use of Plane Wave Models for Muffler Design</title>
      <link>https://trid.trb.org/View/1433548</link>
      <description><![CDATA[In many industries, muffler and silencer design is primarily accomplished via trial and error. Prototypes are developed and tested, or numerical simulation (finite or boundary element analysis) is used to assess the performance. While these approaches reliably determine the transmission loss, designers often do not understand why their changes improve or degrade the muffler performance. Analyses are time consuming and models cannot be changed without some effort. The intent of the current work is to demonstrate how plane wave muffler models can be used in industry. It is first demonstrated that plane wave models can reliably determine the transmission loss for complicated mufflers below the cutoff frequency. Some tips for developing dependable plane wave models are summarized. Moreover, it is shown that plane wave models used correctly help designers develop intuition and a better understanding of the effect of their design changes.       ]]></description>
      <pubDate>Tue, 27 Jun 2017 16:10:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/1433548</guid>
    </item>
    <item>
      <title>Physics-based computational methods for aero-acoustics</title>
      <link>https://trid.trb.org/View/1424838</link>
      <description><![CDATA[This paper provides a review of several physics-based methods developed for predicting sound propagation in flows. The basic principle of physics-based methods is to incorporate some known properties of the underlying physics into the numerical model. For instance, instead of using standard polynomials or Chebyshev polynomials to interpolate the solution, physics-based methods generally use canonical solutions such as Green’s functions or plane waves to construct a local description of the solution. The methods described in this paper include the Green’s function discretisation, the partition of unity finite element method and the wave-based discontinuous Galerkin method. The principles of these methods are described and their performance and shortcomings are discussed. A key issue that emerges in several of these methods is that the canonical solutions are only valid for uniform coefficients, while the methods are intended to be used with strongly inhomogeneous propagation media.]]></description>
      <pubDate>Mon, 31 Oct 2016 11:42:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/1424838</guid>
    </item>
    <item>
      <title>ANTIPLANE DIFFRACTION FROM CANYON ABOVE SUBSURFACE UNLINED TUNNEL</title>
      <link>https://trid.trb.org/View/504008</link>
      <description><![CDATA[The two-dimensional scattering and diffraction of plane shear horizontal waves by a surface semicircular canyon on top of an underground circular unlined tunnel (cavity) in a homogeneous elastic half-space has been analyzed.  Using an exact analytic series solution of the problem for a general angle of wave incidence, the ground motions of the half-space surface on and near the canyon and that of the underground cavity were evaluated.  These surface motions depend on the following parameters:  the angle of incidence of the plane shear horizontal waves, the dimensionless frequency or wave number, the ratio of the radius of the surface canyon to that of the underground cavity, and the ratio of the depth of the cavity to its radius. The paper also provides the methodology for further studies involving other surface and subsurface topographies, such as that of a rigid foundation above rigid subway infrastructures and the case of multiple foundations above the subway.]]></description>
      <pubDate>Fri, 25 Jun 1999 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/504008</guid>
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    <item>
      <title>FORCES INTERACTING BETWEEN TRACKS AND GROUND AND SLIPPAGE OF TRACKED VEHICLES</title>
      <link>https://trid.trb.org/View/374922</link>
      <description><![CDATA[The calculation of the dynamic behavior of tracked vehicles and their power units requires knowledge of all forces interacting between tracks and ground.  These forces have in the past been determined with the help of a mathematical model based on a plane motion of tracks without consideration of slippage.  The present study expands on the ground model to take innto consideration all possible gradients and waved surfaces as well as slippage. Slippage due to elastic deformation of the track is neglected. Study of equilibrium forces with help of numerical iteration makes it possible to determine the arrangement of forces interacting between tracks and ground at any given instant in the vehicle's motion.  Surplus forces accelerate the tracks and hull longitudinally, laterally and around the vertical axis.  The integration of the accelerations produce the speed of the hull, the speed of the tracks and the slippage. Simplifications produce handy equations for determining slippage and tracks forces. Results of measurements on a model vehicle substantiate the method developed here for calculating track slippage and arrangement of forces.]]></description>
      <pubDate>Wed, 02 Jun 1993 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/374922</guid>
    </item>
    <item>
      <title>APPLICATIONS OF DIFFRACTION THEORY TO AEROACOUSTICS</title>
      <link>https://trid.trb.org/View/83179</link>
      <description><![CDATA[A review is given of the fundamentals of diffraction theory and the application of the theory to several problems of aircraft noise generation, propagation, and measurement. The general acoustic diffraction problem is defined and the governing equations set down. Diffraction phenomena are illustrated using the classical problem of the diffraction of a plane wave by a half-plane. Infinite series and geometric acoustic methods for solving diffraction problems are described. Four applications of diffraction theory are discussed: the selection of an appropriate shape for a microphone, the use of aircraft wings to shield the community from engine noise, the reflection of engine noise from an aircraft fuselage and the radiation of trailing edge noise.]]></description>
      <pubDate>Tue, 31 Jul 1979 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/83179</guid>
    </item>
    <item>
      <title>ANALYTICAL STUDIES OF SOME ACOUSTIC PROBLEMS OF JET ENGINES</title>
      <link>https://trid.trb.org/View/49057</link>
      <description><![CDATA[The propagation and generation of acoustic waves in a choked nozzle is considered where pressure and entropy fluctuations caused by gas stream non-uniformities like 'hot spots,' are incident on the nozzle entrance. A novel noise-generation mechanism is found which produces acoustic waves of strength proportional to the entrance entropy fluctuation and local gradient of the mean flow velocity. A transformation is introduced which relates the solutions of problems involving the propagation of acoustic waves in a moving medium to the solutions of associated problems in a stationary medium. The method is described by discussing the Sommerfeld problem for a half plane in a subsonic flow. For supersonic case, all the diffraction problems are related to a single reference problem. A decomposition of the pressure field in a 'geometrical optics' field and a diffracted field is given, showing some remarkable similarities to the subsonic solution. The radiation of acoustic modes from a duct immersed in a subsonically moving medium is treated by a similar transformation. The presence of the uniform flow has roughly the same effect as, an increase in frequency of the incident wave, at constant mode number. The effect of acoustical lining on the radiation pattern is examined, and side radiation is shown to be greatly reduced for the lower order modes.]]></description>
      <pubDate>Thu, 22 Jun 1978 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/49057</guid>
    </item>
    <item>
      <title>A RESEARCH PROGRAM TO REDUCE INTERIOR NOISE IN GENERAL AVIATION AIRPLANES. DESIGN OF AN ACOUSTIC PANEL TEST FACILITY</title>
      <link>https://trid.trb.org/View/69480</link>
      <description><![CDATA[The design, construction, and costs of a test facility for determining the sound transmission loss characteristics of various panels and panel treatments are described. The pressurization system and electronic equipment used in experimental testing are discussed as well as the reliability of the facility and the data gathered. Tests results are compared to pertinent acoustical theories for panel behavior and minor anomalies in the data are examined. A method for predicting panel behavior in the stiffness region is also presented.]]></description>
      <pubDate>Tue, 14 Mar 1978 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/69480</guid>
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