bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion Characterization of Iron-Based High-Performance Amorphous-Metal Thermal-Spray Coatings
Authors: Farmer J. C. , Haslam J. J. , Day S. D. , Branagan D. J. , Blue C. A. , Rivard J. D. K. , Aprigliano L. F. , Yang N. , Perepezko J. H. , Beardsley M. B.
Published: August 2008

New corrosion-resistant, iron-based amorphous metals have been identified from published data or developed through combinatorial synthesis, and tested to determine their relative corrosion resistance. Many of these materials can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS # N06022) in some very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. One of these compositions, SAM1651, is discussed in detail to illustrate the promise of this general class of materials.
Justification for Elevated Hydrogen Limits in Risk-Based Radioactive Waste Packages
Authors: Wagner Russell
Published: August 2008

The U.S. Nuclear Regulatory Commission (NRC) has provided set guidance that hydrogen concentrations in radioactive material packages be limited to 5 vol% unless the package is designed to withstand a bounding hydrogen deflagration or detonation. The NRC guidance further specifies that the expected shipping time for a package be limited to one-half the time to reach 5 vol% hydrogen. This guidance has presented logistical problems for transport of retrieved legacy waste packages on the Department of Energy (DOE) Hanford Site that frequently contain greater than 5 vol% hydrogen due to their age and the lack of venting requirements at the time they were generated. Such packages do not meet the performance-based criteria for Type B packaging, and are considered risk-based packages. Duratek Technical Services (Duratek) has researched the true risk of hydrogen deflagration and detonation with closed packages, and has developed technical justification for elevated concentration limits of up to 15 vol% hydrogen in risk-based packages when transport is limited to the confines of the Hanford Site. Duratek has presented elevated hydrogen limit justification to the DOE Richland Operations Office and is awaiting approval for incorporation into the Hanford Site Transportation Safety Document. This paper details the technical justification methodology for the elevated hydrogen limits.
A Markov Chain Model for Fatigue Crack Growth, Inspection and Repair: The Relationship Between Probability of Detection, Reliability and the Number of Repairs in Fleets of Railroad Tank Cars
Authors: Riddell William T. , Lynch James
Published: August 2008

A Markov chain model to simulate the process of fatigue crack growth, non-destructive inspection and repair in a fleet of railroad tank cars is developed and presented. Crack growth is modeled to reproduce crack shapes that were observed during destructive tear-down tests at the end of life for several tank cars. The Markov chain model is further extended to include non-destructive inspections using POD curves that were established during baseline tests of several methods used in the railroad tank car industry. Next, the model is used to predict the effect of various non-destructive inspection techniques on fatigue-related reliability of the fleet, as well as the number of repairs that are required as a result of the inspections.
Water Flow Analysis in a One Eyed Annulus Cavity Subjected to a Perpendicular Flow
Authors: Boissiere Xavier , Laine Christian
Published: August 2008

For safety and economic reasons, one of the greatest concerns in modern nuclear power stations is to increase the service life of the steam generator. Enormous work has been undertaken to obtain better knowledge of the mechanical and thermal loads, which are generally overestimated to ensure maximum safety. One of the technical problems is that the reactor is fed with relatively cold (40 °C) water into the hot steam generator. The connection zone, i.e. where the cold water pipe is connected to the steam generator, is protected by an annular cavity inside the feed water nozzle to reduce thermal stresses. We have to identify the thermo-hydraulic behaviour in that zone in order to get more accurate thermal information for the boundary condition in the thermo-mechanical calculations for this connection. No database is available for this configuration model, so we need to qualify the flow before using CFD modeling. Therefore a specific experimental testing bench along with numerical modeling has been developed. The first requirement is that the flow in the annular cavity is representative of the actual one. For this purpose, we used Reynolds and Strouhal similitudes to set up the flow in the model. Attention has been focused on the understanding of the flow in the annular cavity. PIV measurements enable us to have a good understanding of the flow structure. We also present and discuss the results in terms of velocity profiles. The main result is that the flow is unsteady in the cavity and depends on the length and thickness of the annular cavity. Experimental results give us data to validate our numerical approach, which is used to test several configurations.
Simulation of Wave Interaction With Arbitrarily Oriented Defects in Thin Sections Using Spectral Element Method
Authors: Baskaran G. , Lakshmana Rao C. , Balasubramaniam Krishnan
Published: August 2008

Numerical simulation of wave propagation and its interaction with defects in a long range (1 m) thin sections (10 mm) using the regular finite element method is very costly, since it requires very fine meshes to accurately capture response signals. Spectral element method (SEM) is a numerical technique that solves the dynamic problem in frequency domain. SEM has been applied for detection of vertical and horizontal defects. This paper discusses application of SEM to any arbitrarily orientated crack in long range pressure vessels. The simulation of applications of Lamb wave for detection and sizing using TOFD technique is demonstrated. The advantage of the current formulation is quick detection of defects in thin bodies of any orientation using Lamb waves and sizing the same using TOFD techniques are illustrated.
Risk-Based Inspection (RBI) of Steam Systems
Authors: Antaki George A. , Monahon Thomas M. , Cansler Ralph W.
Published: August 2008

This paper describes the implementation of a risk-based inspection program for process and utility steam lines in a large chemical process facility. The paper addresses the development of an RBI matrix, the likelihood attributes, the consequence scores, and the overall risk in terms of personnel safety and costs. The likelihood of failure considers prior experience, degradation mechanisms, novelty of process, abnormal loads and age. The consequence of failure considers public health and safety, worker health and safety, environmental impact, operations impact, and recovery costs. Once assigned a likelihood and consequence score, systems are plotted on the RBI matrix to develop inspection priorities. The RBI ranking determines which systems will be inspected (high risk) and those that need not be inspected (low risk). The risk ranking is followed by inspection planning which includes selection of the inspection technique and inspection locations, together with the development of pre-inspection acceptance criteria.
Incorporating Neural Network Material Models Within Finite Element Analysis for Rheological Behavior Prediction
Authors: Kessler B. Scott , El-Gizawy A. Sherif , Smith Douglas E.
Published: August 2008

The accuracy of a finite element model for design and analysis of a metal forging operation is limited by the incorporated material model’s ability to predict deformation behavior over a wide range of operating conditions. Current rheological models prove deficient in several respects due to the difficulty in establishing complicated relations between many parameters. More recently, artificial neural networks (ANN) have been suggested as an effective means to overcome these difficulties. To this end, a robust ANN with the ability to determine flow stresses based on strain, strain rate, and temperature is developed and linked with finite element code. Comparisons of this novel method with conventional means are carried out to demonstrate the advantages of this approach.
An Evaluation of the Integrity of the Reactor Vessel Support System for a Postulated Reactor Vessel Closure Head Drop Accident of KSNP+
Authors: Byun Young Jin , Sung Ki Kwang , Lee Dae Hee , Choi Taek Sang
Published: August 2008

The integrity of the RV support system of the Korean Standard Nuclear Plant Plus (KSNP+) is investigated for a postulated RV closure head drop accident. This was considered due to the adoption of the IHA (Integrated Head Assembly) in KSNP+ reactor design, which causes the increase of the weight of the RV closure head assembly. The head drop accident could be anticipated during the RV head handling process. The drop event may cause an impact load on the RV and support system. Three different scenarios and three different analysis models were considered and developed for the head drop analysis. The entire reactor vessel and support system are modeled by using lumped masses and beam elements. The nonlinear elasto-plastic dynamic analyses were performed using a commercial code to evaluate the time-dependent behavior of the support columns. The analysis results show that the local plastic deformation occurs in the columns, but the plastic deformation in overall cross section does not occur. As a result, the RV support system would remain intact, and continue to support the reactor vessel in such an accident.
Dynamics of Submerged Expandable Tubes in Borehole Wells
Authors: Karrech Ali , Seibi Abdennour , Pervez Tasneem , Sab Karam
Published: August 2008

Solid Expandable Tubular Technology (SETT) is a new development in the petroleum industry. It consists in accomplishing hydraulic expansion of a submerged tube by propelling a mandrel through it using a differential pressure. The progress of the mandrel deforms the tube beyond its elastic limit. Towards the end of the expansion process, the mandrel pops out of the tube resulting in displacement, stress and pressure waves. A mathematical model is developed to describe the dynamics of the tube-fluid system due to the pop-out phenomenon. The model takes into consideration the effects of the coupling between fluids and structure as well as the inherent system damping on the response. Through a specific field case, the model provides an analytical solution describing the wave propagating in the tube-fluid system and identifies the potential failure locations.
Reactor Pressure Vessel Modification Approaches
Authors: Payne Ronald J. , Levesque Stephen
Published: August 2008

Stress corrosion cracking of Alloy 600 has lead to the modification and replacement of many nuclear power plant components. Among these components are the Bottom Mounted Nozzles (BMN) of the Reactor Pressure Vessel (RPV). Modifications of these components have been performed on an emergent basis. Since that time, Framatome ANP has developed state-of-the-art modification methods for the repair of BMNs using the Electrical Power Research Institute (EPRI) managed Materials Reliability Program (MRP) attributes for an ideal repair as a basis for evaluation of modification concepts. These attributes were used to evaluate the optimal modification concepts and develop processes and tooling to support future modification activity. This paper details the BMN configurations, modification evaluation criteria, several modification concepts, and the development of the tooling to support the optimal modification scenarios.
Non Destructive Testing of Welds: Applications to Pressure Equipment Standards
Authors: Tchilian Jean-Michel , Zeelenberg Erik , Baylac Guy
Published: August 2008

This paper presents the correlation established between the product/component standards and the standards for the non destructive examination of welds.
Utilizing Normalized Correlation to Extract Meaningful Data From Noisy NDE Signals
Authors: Shukert Douglas S.
Published: August 2008

Remote Induced Current Potential Drop (RICPD) is a nondestructive inspection method for finding cracks within stainless steel pipes. One problem with RICPD inspection is that the RICPD signal is very weak and is therefore, susceptible to being overshadowed by noise. Especially when trying to detect shallow cracks, the RICPD signal-to-noise ratio can be quite small, making signals from cracks indistinguishable from random signal noise. By using a mathematical filtering technique known as “normalized correlation” RICPD signals can be processed to extract meaningful data from noisy signals. Normalized correlation uses the signal waveform from a known crack as a model and compares that model waveform to every point of the RICPD test signal. All points that produce a match to the model are suspected cracks. Since normalized correlation does not depend on the magnitude of the signal or on the signal-to-noise ratio, even small cracks that produce nearly imperceptible signals can be detected. To successfully apply the normalized correlation algorithm, all that is needed is a model of the signal waveform from a known crack. The normalized correlation filtering technique has been successfully applied to 40mm thick blocks of stainless steel in the laboratory to detect underside man-made slits as shallow as 10mm.
Determining Effective Thickness of Cylinders in Pressure Equipment With Significant Thickness Variations for Fitness for Service Assessments
Authors: Rodery Clay D.
Published: August 2008

In many in-service issues involving pressure equipment, it is often the case that the thickness of a cylinder reveals significant variations in thickness around its cross section. This variation could represent loss of thickness due to corrosion or erosion, or could involve additions of thickness from repair activities. A common issue deals with determining the overall affect of such variations on the integrity of the vessel. This paper describes a spreadsheet tool employing common geometric properties such that these thickness variations may be simply reduced to an effective thickness of the cylinder cross section. This effective thickness may then be used for purposes of conducting fitness for service assessments, or to assist in the planning of repairs. The use of this tool is illustrated with two case studies.
Technical Basis for Revised Flaw Acceptance Criteria Under IWB-3610 of ASME Section XI
Authors: Cipolla Russell C. , Wichman Keith R.
Published: August 2008

This paper describes the change from the KIa to KIc in performing flaw evaluation for Class 1 ferritic steel components according to IWB-3610 and Appendix A of the ASME Boiler and Pressure Vessel Code, Section XI. The primary reason for making this change is to reduce the excess conservatism in the current flaw evaluation acceptance criteria. The Appendix A calculation methods can be used in accepting flaws detected as part of the plant inservice inspection program. The KIa and KIc reference curves represent two lower bound fracture toughness curves available in ASME Section XI. The KIa reference curve is a lower bound on all static, dynamic and arrest fracture toughness, whereas the KIc reference curve is a lower bound on static fracture toughness only. A similar change has already been implemented in the calculation of the heatup and cooldown pressure-temperature (P-T) limit curves, which are also based on fracture mechanics analysis. The P-T limits are developed according to Appendix G of Section XI, which employ similar methods to those of Appendix A. A key input parameter to the P-T calculations is the lower bound fracture toughness curve, KIc (prior to change in Appendix G, the lower bound curve KIR was used, which was equivalent to KIa). Based on the work described in this technical basis paper, Section XI recently approved the change from KIa to KIc in IWB-3610. In addition, changes to the use of KIc for fracture initiation, changes were also made to IWB-3613, which provides acceptance criteria for flanges and other shell regions near structural discontinuities. These changes clarified the scope of the article as to what discontinuities are covered and a redefinition for the minimum temperature from RTNDT + 60°F (RTNDT + 33°C) to just RTNDT. These changes are also discussed in this paper. The changes will appear in the 2005 addenda to the 2004 Code Edition for Section XI.
Fatigue Assessment of a Weld Joint of a Pressure Vessel
Authors: Kalnins Arturs , Bergsten Vic , Rana Mahendra
Published: August 2008

A full-penetration weld on both sides between a shell and a flat head is evaluated for fatigue strength by four methods, two based on structural stress and two on notch stress. Internal pressure is cycled with constant amplitude. The allowable cycles are calculated by each method. The number of cycles for the same geometry and loading varies widely, ranging from 4,835 to 137,000.
Numerical Analyses of Locomotive Impacts on a Spent Fuel Truck Cask and Trailer
Authors: Ammerman Doug , Stevens Dave , Barsotti Matt
Published: August 2008

During the transportation of spent nuclear fuel by truck, the possibility exists that a train could run into the spent fuel cask at a grade crossing. Sandia National Laboratories has conducted a numerical study to assess the possibility of cask breach or material release in the event of a high-speed, broadside locomotive collision. A numerical approach has the advantage over conducting a physical test as was done in the 1970s [1] in that varying parameters can be examined. For example, one of the criticisms of the 1970s test was the height of the cask. In the test, the centerline of the cask was above the main frame-rails of the locomotive. In this study the position of the cask with respect to the locomotive was varied. The response of the cask and trailer in different collision scenarios was modeled numerically with LS-DYNA [2]. The simulations were performed as a collaborative endeavor between Sandia National Laboratories (SNL), Applied Research Associates, Inc. (ARA) and Foster-Miller, Inc (FMI). ARA developed the GA-4 Spent Fuel Cask and Cask Transporter models described in this report. These models were then combined with two existing FMI heavy freight locomotive finite element models to create the overall simulation scenarios. The modeling effort, results, and conclusions are presented in this paper.
Neutron Source Strength Estimates From (α, n) Reactions in Binary Mixtures of Actinide Particles and Light Element Particles
Authors: Boles Jason L. , Hafner Ronald S. , Fischer Larry E.
Published: August 2008

This paper describes an example of a model used to estimate the neutron source term from (α, n) reactions from a mixture of PuO2 and BeO particles. The (α, n) reaction occurs when an α-particle, emitted by an actinide isotope such as 239Pu, collides with, and is absorbed by, the nucleus of a light element such as beryllium. Neutrons are produced through the reaction 24α+49Be→612C+01n.(1) This reaction is commonly abbreviated as 9Be(α, n)12C, or just Be(α, n).
The Long-Term Performance of Concrete in Nuclear Applications
Authors: Fillmore Denzel L. , Winston Philip L. , Morton Sheryl L. , Hoffman Cecelia R. , Van Ausdeln Leo A. , Saegusa Toshiari , Shirai Koji , Hattori Takatoshi , Sasahara Akihiro
Published: August 2008

The Idaho National Laboratory investigated long-term concrete performance for nuclear applications. Scientists searched the open literature for information on the effects of heat and radiation. They also examined the concrete shield of the Pacific Sierra Nuclear Ventilated Storage Cask (VSC-17) for concrete deterioration and loss of shielding. The literature search revealed that low doses, <109 n/cm2 or <1011 Rad gamma, of radiation over periods less than 50 years do not appear to significantly affect concrete. Exposure over 100 years was not studied. The effects of higher doses of radiation are not as clear. Generally, the threshold of degradation is 95°C, and degradation increases with increasing temperature and time. In 15 years of VSC-17 use, there is no apparent effect from environment, radiation, or temperature that has adversely affected the shielding or structural functions, although there has been some minor cracking of the concrete.
Cost and Fatigue Life Comparison of Vessels Meeting the Rules of ASME Section VIII Division 1 and 2 Code and En 13445 Standard
Authors: Pastor Thomas P.
Published: August 2008

Several identical vessels were designed using the applicable rules of ASME Section VIII, Division 1, Division 2 Code and EN 13445 Standard. Cost estimates were obtained on these vessels. Fatigue life assessment was also conducted on two vessels using the rules of ASME Section VIII, Division 2 and EN 13445. The results of this study are presented.
Piping Fluid Transients Made Simple: Part II — Application of the SSFFC Methods
Authors: Ibrahim Zakaria N.
Published: August 2008

Piping systems transporting fluid between plant components are subjected to a variety of anticipated and/or postulated flow changes that disturb their steady state operations. These changes cause the fluid flow to accelerate and/or decelerate. However, consideration of fluid elasticity transforms these disturbances into weak and/or strong propagating sound waves, depending upon the abruptness level of the fluid state change. This generates dynamic forces on the pipe segments of the piping system. A simple concept for understanding the piping fluid transient phenomenon from its physical perspective is presented. The piping system consists of several pipe segments, each segment having a constant cross-sectional flow area. The pipe segment is further divided into a consecutive series of zones. Each zone comprises two or three sub-zones of quasi steady state flow. The sub-zones are separated by interface fronts into which the jump in fluid pressure and velocity occurs across them. These fronts propagate and clash with each other to create the next temporal set of sub-zones quasi steady state flow. This method is denoted in this paper as steady state flow fronts clashing ‘SSFFC’. Clashing between the incident, transmitted and/or reflected wave fronts within the zone are introduced. As a follow-up to the first part of this two-part publication, this paper demonstrates two sample applications of SSFFC method utilizing the proposed wave front bookkeeping technique.
Fatigue Performance of Laser Peened Materials
Authors: Hill Michael R. , Pistochini Theresa E. , DeWald Adrian T.
Published: August 2008

Laser peening is an emerging technology for the surface treatment of metallic materials that is capable of enhancing resistance to fatigue failure. This paper describes some recent results from joint research programs conducted to generate data on residual stress and fatigue performance of laser peened materials. Specifically, we present data for residual stress imparted by laser peening and fatigue life improvement of laser peened coupons relative to as-machined coupons. These data are presented for a range of high-strength materials employed in aircraft and other demanding applications: BSTOA Ti-6A14V titanium alloy, 300M steel, MP35N Ni-Co-Cr-Mo alloy, and 7050-T7451 aluminum alloy. For each material, residual stress distributions were measured for treatment with different laser peening parameter sets. For particular laser peening parameter sets, stress versus life data were generated for as-machined and laser peened fatigue coupons, which quantifies fatigue life improvement attained by laser peening over a range of applied loads.
Utilizing Direct Tension Squirter Indicators in Industrial Applications
Authors: Frisard Ron
Published: August 2008

In the world of critical bolting applications there is a need for achieving correct gasket loads. The new technology of Direct Tension Squirter Washers is designed to show visual indication when 60% of yield for a B7 bolt has been reached. Torque wrench inconsistencies have caused many gasket failures. There are many times the incorrect gasket load has been applied to bolted joints resulting in joint failure. The root cause of these failures range from bad calculation of friction for anti seize to damaged threads. DTSW ensures the bolts have reached the correct bolting load resulting in a properly loaded gasket that will not be doomed for failure. This paper will review the DTSW Technology and how it can be applied in Industry applications. It will discuss the inaccuracy of torque wrench technology in today’s industrial bolting environment. The paper will also highlight show the DTSW technology ease of use compared to typical Indicator washers that require feeler gauges.
Recent Advances in Efficient and Robust Two-Way Coupling Between FEA and CFD
Authors: Raw Michael J.
Published: August 2008

The established FEA and CFD codes ANSYS and CFX have been coupled to support transient and strongly coupled interaction between structures and fluids analyses. The presentation will outline the technical approaches used for the communications technology, data interpolation, non-linear convergence of the implicit condition, and the mesh morphing problem. For the communications a TCP/IP socket communication system has been used that is very efficient and very portable, including within parallelized simulations. The data interpolation issue is addressed to ensure full conservation of forces and energy flow. For stability under highly interacting or non-linear conditions, the fully coupled implicit problem must be solved, or converged, at each time step. The algorithm that manages this iteration and data exchange is explained. Finally, some of the approaches used to smoothly morph the moving mesh are detailed. These capabilities are all supported in the ANSYS 10.0 software release (summer 2005).
Noise reduction in tunnels by hard rough surfaces
Authors: Law Ming Kan , Li Kai Ming , Leung Chun Wah
Published: August 2008

This paper examines the feasibility of using two-dimensional hard rough surfaces to reduce noise levels in traffic tunnels with perfectly reflecting boundaries. First, the Twersky boss model is used to estimate the acoustic impedance of a hard rough surface. Second, an image source model is then used to compute the propagation of sound in a long rectangular enclosure with finite impedance. The total sound fields are calculated by summing the contributions from all image sources coherently. Two model tunnels are built to validate the proposed model experimentally. Finally, a case study for a realistic geometrical configuration is presented to explore the use of hard rough surfaces for reducing traffic noise in a tunnel which is constructed with hard boundaries.
Sources of variability in distortion product otoacoustic emissions
Authors: Garner Cassie A. , Neely Stephen T. , Gorga Michael P.
Published: August 2008

The goal of this study was to determine the extent to which the variability seen in distortion product otoacoustic emissions (DPOAEs), among ears with normal hearing, could be accounted for. Several factors were selected for investigation, including behavioral threshold, differences in middle-ear transmission characteristics either in the forward or the reverse direction, and differences in contributions from the distortion and reflection sources. These variables were assessed after optimizing stimulus parameters for individual ears at each frequency. A multiple-linear regression was performed to identify whether the selected variables, either individually or in combination, explained significant portions of variability in DPOAE responses. Behavioral threshold at the f2 frequency and behavioral threshold squared at that same frequency explained the largest amount of variability in DPOAE level, compared to the other variables. The combined model explained a small, but significant, amount of variance in DPOAE level at five frequencies. A large amount of residual variability remained, even at frequencies where the model accounted for significant amounts of variance.
Directionality and maneuvering effects on a surface ship underwater acoustic signature
Authors: Trevorrow Mark V. , Vasiliev Boris , Vagle Svein
Published: August 2008

This work examines underwater source spectra of a small (560tons, 40m length), single-screw oceanographic vessel, focusing on directionality and effects of maneuvers. The measurements utilized a set of four, self-contained buoys with GPS positioning, each recording two calibrated hydrophones with effective acoustic bandwidth from 150Hzto5kHz. In straight, constant-speed runs at speeds up to 6.2ms−1, the ship source spectra showed spectral levels in reasonable agreement with reference spectra. The broadband source level was observed to increase as approximately speed to the fourth power over the range of 2.6–6.1ms−1, partially biased at low speeds by nonpropulsion machinery signals. Source directionality patterns were extracted from variations in source spectra while the ship transited past the buoy field. The observed spectral source levels exhibited a broadside maximum, with bow and stern aspect reduced by approximately 12–9dB, respectively, independent of frequency. An empirical model is proposed assuming that spectral source levels exhibit simultaneous variations in aspect angle, speed, and turn rate. After correction for source directionality and speed during turning maneuvers, an excess of up to 18dB in one-third octave source levels was observed.
Characterization of an elastic target in a shallow water waveguide by decomposition of the time-reversal operator
Authors: Philippe Franck D. , Prada Claire , de Rosny Julien , Clorennec Dominique , Minonzio Jean-Gabriel , Fink Mathias
Published: August 2008

This paper reports the results of an investigation into extracting of the backscattered frequency signature of a target in a waveguide. Retrieving the target signature is difficult because it is blurred by waveguide reflections and modal interference. It is shown that the decomposition of the time-reversal operator method provides a solution to this problem. Using a modal theory, this paper shows that the first singular value associated with a target is proportional to the backscattering form function. It is linked to the waveguide geometry through a factor that weakly depends on frequency as long as the target is far from the boundaries. Using the same approach, the second singular value is shown to be proportional to the second derivative of the angular form function which is a relevant parameter for target identification. Within this framework the coupling between two targets is considered. Small scale experimental studies are performed in the 3.5MHz frequency range for 3mm spheres in a 28mm deep and 570mm long waveguide and confirm the theoretical results.
Segregation of unvoiced speech from nonspeech interference
Authors: Hu Guoning , Wang DeLiang
Published: August 2008

Monaural speech segregation has proven to be extremely challenging. While efforts in computational auditory scene analysis have led to considerable progress in voiced speech segregation, little attention has been given to unvoiced speech, which lacks harmonic structure and has weaker energy, hence more susceptible to interference. This study proposes a new approach to the problem of segregating unvoiced speech from nonspeech interference. The study first addresses the question of how much speech is unvoiced. The segregation process occurs in two stages: Segmentation and grouping. In segmentation, the proposed model decomposes an input mixture into contiguous time-frequency segments by a multiscale analysis of event onsets and offsets. Grouping of unvoiced segments is based on Bayesian classification of acoustic-phonetic features. The proposed model for unvoiced speech segregation joins an existing model for voiced speech segregation to produce an overall system that can deal with both voiced and unvoiced speech. Systematic evaluation shows that the proposed system extracts a majority of unvoiced speech without including much interference, and it performs substantially better than spectral subtraction.
Statistics of instabilities in a state space model of the human cochlea
Authors: Ku Emery M. , Elliott Stephen J. , Lineton Ben
Published: August 2008

A state space model of the human cochlea is used to test Zweig and Shera’s [(1995) “The origin of periodicity in the spectrum of evoked otoacoustic emissions,” J. Acoust. Soc. Am. 98(4), 2018–2047] multiple-reflection theory of spontaneous otoacoustic emission (SOAE) generation. The state space formulation is especially well suited to this task as the unstable frequencies of an active model can be rapidly and unambiguously determined. The cochlear model includes a human middle ear boundary and matches human enhancement, tuning, and traveling wave characteristics. Linear instabilities can arise across a wide bandwidth of frequencies in the model when the smooth spatial variation of basilar membrane impedance is perturbed, though it is believed that only unstable frequencies near the middle ear’s range of greatest transmissibility are detected as SOAEs in the ear canal. The salient features of Zweig and Shera’s theory are observed in this active model given several classes of perturbations in the distribution of feedback gain along the cochlea. Spatially random gain variations are used to approximate what may exist in human cochleae. The statistics of the unstable frequencies for random, spatially dense variations in gain are presented; the average spacings of adjacent unstable frequencies agree with the preferred minimum distance observed in human SOAE data.
Spectral integration of speech bands in normal-hearing and hearing-impaired listeners
Authors: Hall Joseph W. , Buss Emily , Grose John H.
Published: August 2008

This investigation examined whether listeners with mild–moderate sensorineural hearing impairment have a deficit in the ability to integrate synchronous spectral information in the perception of speech. In stage 1, the bandwidth of filtered speech centered either on 500 or 2500Hz was varied adaptively to determine the width required for approximately 15%–25% correct recognition. In stage 2, these criterion bandwidths were presented simultaneously and percent correct performance was determined in fixed block trials. Experiment 1 tested normal-hearing listeners in quiet and in masking noise. The main findings were (1) there was no correlation between the criterion bandwidths at 500 and 2500Hz; (2) listeners achieved a high percent correct in stage 2 (approximately 80%); and (3) performance in quiet and noise was similar. Experiment 2 tested listeners with mild–moderate sensorineural hearing impairment. The main findings were (1) the impaired listeners showed high variability in stage 1, with some listeners requiring narrower and others requiring wider bandwidths than normal, and (2) hearing-impaired listeners achieved percent correct performance in stage 2 that was comparable to normal. The results indicate that listeners with mild–moderate sensorineural hearing loss do not have an essential deficit in the ability to integrate across-frequency speech information.
Reliability of estimating the room volume from a single room impulse response
Authors: Kuster Martin
Published: August 2008

The methods investigated for the room volume estimation are based on geometrical acoustics, eigenmode, and diffuse field models and no data other than the room impulse response are available. The measurements include several receiver positions in a total of 12 rooms of vastly different sizes and acoustic characteristics. The limitations in identifying the pivotal specular reflections of the geometrical acoustics model in measured room impulse responses are examined both theoretically and experimentally. The eigenmode method uses the theoretical expression for the Schroeder frequency and the difficulty of accurately estimating this frequency from the varying statistics of the room transfer function is highlighted. Reliable results are only obtained with the diffuse field model and a part of the observed variance in the experimental results is explained by theoretical expressions for the standard deviation of the reverberant sound pressure and the reverberation time. The limitations due to source and receiver directivity are discussed and a simple volume estimation method based on an approximate relationship with the reverberation time is also presented.
Bottom-up approach for microstructure optimization of sound absorbing materials
Authors: Perrot Camille , Chevillotte Fabien , Panneton Raymond
Published: August 2008

Results from a numerical study examining micro-/macrorelations linking local geometry parameters to sound absorption properties are presented. For a hexagonal structure of solid fibers, the porosity ϕ, the thermal characteristic length Λ′, the static viscous permeability k0, the tortuosity α∞, the viscous characteristic length Λ, and the sound absorption coefficient are computed. Numerical solutions of the steady Stokes and electrical equations are employed to provide k0, α∞, and Λ. Hybrid estimates based on direct numerical evaluation of ϕ, Λ′, k0, α∞, Λ, and the analytical model derived by Johnson, Allard, and Champoux are used to relate varying (i) throat size, (ii) pore size, and (iii) fibers’ cross-section shapes to the sound absorption spectrum. The result of this paper tends to demonstrate the important effect of throat size in the sound absorption level, cell size in the sound absorption frequency selectivity, and fibers’ cross-section shape in the porous material weight reduction. In a hexagonal porous structure with solid fibers, the sound absorption level will tend to be maximized with a 48±10μm throat size corresponding to an intermediate resistivity, a 13±8μm fiber radius associated with relatively small interfiber distances, and convex triangular cross-section shape fibers allowing weight reduction.
Experimental investigation of the influence of a posterior gap on glottal flow and sound
Authors: Park Jong Beom , Mongeau Luc
Published: August 2008

The influence of a posterior gap on the airflow through the human glottis was investigated using a driven synthetic model. Instantaneous orifice discharge coefficient of a glottal shaped orifice was obtained from the time-varying orifice area and the velocity distribution of the pulsated jet measured on the axial plane using a single hot-wire probe. Instantaneous orifice discharge coefficient values were found to undergo a cyclic hysteresis loop when plotted versus Reynolds number and time, indicating a pressure head increase and a net energy transfer from the air flow to the orifice wall. The net energy transferred was estimated to be around 10% of the value presumably required to achieve self-sustained oscillation. The radiated sound pressure was measured to characterize the influence of the minimum flow through the posterior gap on the broadband component of the radiated sound. The presence of a posterior gap was found to significantly increase the broadband sound level produced over the frequency range in which human hearing is most sensitive.
Time reversal of flexural waves in a beam at audible frequency
Authors: Francoeur Dany , Berry Alain
Published: August 2008

There has been very limited work on the application of time Reversal to the propagation of audible frequency waves in mechanical structures. The present work concentrates on the application of time reversal to the focusing of audible range, flexural waves in an infinite beam, and to the detection of local heterogeneity in such a beam. Practical applications of time reversal of flexural waves in structures include vibration energy focusing, detection of vibratory or acoustic sources, and detection of defects in mechanical structures. An analytical model of flexural wave propagation in the beam as well as sensing and emission using piezoelectric transducers is presented. Time reversal experiments are conducted and compared to the model results in either a homogeneous beam or a beam with point mass heterogeneities. In the various situations tested, it is shown that time reversal effectively compensates the spreading in time of the impulse due to the dispersive propagation of flexural waves. One interesting aspect of this property is the generation of large amplitude impulsive responses in the beam using remote actuators. Finally, the “Décomposition de l’Opérateur de Retournement Temporel” approach is examined to detect and localize point mass scatterers in the beam.
Sound-wave coherence in atmospheric turbulence with intrinsic and global intermittency
Authors: Wilson D. Keith , Ostashev Vladimir E. , Goedecke George H.
Published: August 2008

The coherence function of sound waves propagating through an intermittently turbulent atmosphere is calculated theoretically. Intermittency mechanisms due to both the turbulent energy cascade (intrinsic intermittency) and spatially uneven production (global intermittency) are modeled using ensembles of quasiwavelets (QWs), which are analogous to turbulent eddies. The intrinsic intermittency is associated with decreasing spatial density (packing fraction) of the QWs with decreasing size. Global intermittency is introduced by allowing the local strength of the turbulence, as manifested by the amplitudes of the QWs, to vary in space according to superimposed Markov processes. The resulting turbulence spectrum is then used to evaluate the coherence function of a plane sound wave undergoing line-of-sight propagation. Predictions are made by a general simulation method and by an analytical derivation valid in the limit of Gaussian fluctuations in signal phase. It is shown that the average coherence function increases as a result of both intrinsic and global intermittency. When global intermittency is very strong, signal phase fluctuations become highly non-Gaussian and the average coherence is dominated by episodes with weak turbulence.
Prediction of the acoustic form function by neural network techniques for immersed tubes
Authors: Dariouchy A. , Aassif E. , Maze G. , Décultot D. , Moudden A.
Published: August 2008

A new approach is used to predict the acoustic form function (FF) for an infinite length cylindrical shell excited perpendicularly to its axis using the artificial neural network (ANN) techniques. The Wigner–Ville distribution is used like a comparison tool between the FF calculated by the analytical method and that predicted by the ANN techniques for a stainless steel tube. During the development of the network, several configurations are evaluated for various radius ratios b∕a (a: outer radius: b: inner radius of the tube). The optimal model is a network with one hidden layer. It is able to predict the FF with a mean relative error about 1.61% for the cases studied in this paper.
Nondestructive characterization of musical pillars of Mahamandapam of Vitthala Temple at Hampi, India
Authors: Kumar Anish , Jayakumar T. , Rao C. Babu , Sharma Govind K. , Rajkumar K. V. , Raj Baldev , Arundhati P.
Published: August 2008

This paper presents the first scientific investigation on the musical pillars of the Vitthala Temple at Hampi, India. The solid stone columns in these pillars produce audible sound, when struck with a finger. Systematic investigations on the acoustic characteristics of the musical pillars of mahamandapam (great stage) of the Vitthala Temple have been carried out. The 11 most popular pillars that produce sounds of specific musical instruments are considered for the investigations. The sound produced from these 11 most popular musical pillars was recorded systematically and different nondestructive testing techniques such as low frequency ultrasonic testing, impact echo testing, and in situ metallography were employed on the musical columns of these pillars. The peak frequencies in the amplitude spectrum of the sound produced from various columns in these pillars are correlated with the dimensional measurements and ultrasonic velocity determined using impact echo technique. The peak frequencies obtained experimentally have been found to have excellent correlation with the calculated flexural frequencies based on the dimensional measurements and ultrasonic velocities of the columns.
Consonant identification in noise by native and non-native listeners: Effects of local context
Authors: Cutler Anne , Garcia Lecumberri Maria Luisa , Cooke Martin
Published: August 2008

Speech recognition in noise is harder in second (L2) than first languages (L1). This could be because noise disrupts speech processing more in L2 than L1, or because L1 listeners recover better though disruption is equivalent. Two similar prior studies produced discrepant results: Equivalent noise effects for L1 and L2 (Dutch) listeners, versus larger effects for L2 (Spanish) than L1. To explain this, the latter experiment was presented to listeners from the former population. Larger noise effects on consonant identification emerged for L2 (Dutch) than L1 listeners, suggesting that task factors rather than L2 population differences underlie the results discrepancy.
Application of Hamiltonian of ray motion to room acoustics
Authors: Koyanagi Sin’ichiro , Nakano Takeru , Kawabe Tetsuji
Published: August 2008

Based on a standard Hamiltonian of acoustic ray, it is shown that a ray motion in a finite region can be treated as a particle motion inside a potential well. The boundary reflections of ray can be described by introducing a so-called confining potential to confine a ray motion in a closed domain. It is shown that the square well potential model for the ray motion can reproduce the reverberation time in a two-dimensional room with irregular walls which is consistent with the Norris–Eyring law. It is also shown that the sound reverberation relates the ray chaos of the billiards in polygons with smooth convex walls.
A simple-shear rheometer for linear viscoelastic characterization of vocal fold tissues at phonatory frequencies
Authors: Chan Roger W. , Rodriguez Maritza L.
Published: August 2008

Previous studies reporting the linear viscoelastic shear properties of the human vocal fold cover or mucosa have been based on torsional rheometry, with measurements limited to low audio frequencies, up to around 80Hz. This paper describes the design and validation of a custom-built, controlled-strain, linear, simple-shear rheometer system capable of direct empirical measurements of viscoelastic shear properties at phonatory frequencies. A tissue specimen was subjected to simple shear between two parallel, rigid acrylic plates, with a linear motor creating a translational sinusoidal displacement of the specimen via the upper plate, and the lower plate transmitting the harmonic shear force resulting from the viscoelastic response of the specimen. The displacement of the specimen was measured by a linear variable differential transformer whereas the shear force was detected by a piezoelectric transducer. The frequency response characteristics of these system components were assessed by vibration experiments with accelerometers. Measurements of the viscoelastic shear moduli (G′ and G″) of a standard ANSI S2.21 polyurethane material and those of human vocal fold cover specimens were made, along with estimation of the system signal and noise levels. Preliminary results showed that the rheometer can provide valid and reliable rheometric data of vocal fold lamina propria specimens at frequencies of up to around 250Hz, well into the phonatory range.
Quantifying the through-thickness asymmetry of sound absorbing porous materials
Authors: Salissou Y. , Panneton R.
Published: August 2008

A method to quantify the through-thickness asymmetry of a sound absorbing porous material is proposed and discussed. Its calculation only requires impedance tube measurements of the acoustical surface impedance performed on both sides of the tested material. The method may be used for quality control or to assess the level of asymmetry of the material in terms of its acoustic properties. As a first validation, a two-layered porous system seen as an equivalent asymmetrical single porous layer with a sudden change in its physical properties is studied. From this study, a criterion of asymmetry is suggested and experimentally tested.