bluuebunny/crossref_metadata_2025 huggingface dataset:
Diagonal Quadratic Approximation for Parallelization of Analytical Target Cascading
Authors: Li Yanjing , Lu Zhaosong , Michalek Jeremy J.
Published: April 2008

Analytical target cascading (ATC) is an effective decomposition approach used for engineering design optimization problems that have hierarchical structures. With ATC, the overall system is split into subsystems, which are solved separately and coordinated via target/response consistency constraints. As parallel computing becomes more common, it is desirable to have separable subproblems in ATC so that each subproblem can be solved concurrently to increase computational throughput. In this paper, we first examine existing ATC methods, providing an alternative to existing nested coordination schemes by using the block coordinate descent method (BCD). Then we apply diagonal quadratic approximation (DQA) by linearizing the cross term of the augmented Lagrangian function to create separable subproblems. Local and global convergence proofs are described for this method. To further reduce overall computational cost, we introduce the truncated DQA (TDQA) method, which limits the number of inner loop iterations of DQA. These two new methods are empirically compared to existing methods using test problems from the literature. Results show that computational cost of nested loop methods is reduced by using BCD, and generally the computational cost of the truncated methods is superior to the nested loop methods with lower overall computational cost than the best previously reported results.
The Effect of Cementite Size and Morphology on the Abrasive Wear Behavior of UHC Steel
Authors: Ozdemir Niyazi , Sarsilmaz Furkan , Orhan Nuri
Published: April 2008

In this study, the abrasive wear behavior of a grain refined hypereutectoid carbon steel containing 1.2% C, 4% Al, 0.20% Mo, and 0.1% Ti was investigated experimentally. Thermal cycles were applied to all specimens about ten times to obtain a fine-grained structure and to gain more softness structures, such as spheroidized cementite for these steels. After every thermal cycle, the microstructures of specimens were examined by scanning electron microscopy to determine the transformation mechanism of structure. Microstructure analyses showed that size of cementite decreased as a function of heat treatment cycle. With the increase of heat treatment cycle, the grain size of cementite in all specimens started to decrease. As a consequence, these cementite islands transformed to spherical cementite having an average grain size of 5μm. In addition, the wear test results indicated a correspondence between wear rate and thermal cycling. However, the hardness values decreased with increasing heat treatment cycle.
A Markovian Finishing Process
Authors: Mohamed M. A. S.
Published: April 2008

Addressed is the mechanism of finishing processes for a workpiece surface using hard abrasive tools such as grinding, abrasive paper, and filing. The mechanism is intended to monitor the gradual changes of the workpiece surface state roughness as the tool is applied for several strokes. Based on a number of common features, the present study simulates each rubbing stroke as a Markov process, and each set of several strokes as a Markov chain. In the simulating model, the discrete probabilistic properties of a specific tool abrasive surface can be expressed in terms of a corresponding Markov matrix operator. Thus, the tool action after one rubbing stroke is obtained via a matrix mapping from a given state roughness to a subsequent state roughness of the workpiece surface. Although the suggested model is capable to handle a comprehensive finishing mechanism, the study focuses on the simple case of zero feeding using a hard abrasive tool, in which the Markov matrix shrinks to a special triangular form. Main findings show that major aspects of the tool surface are transferred to the stepwise roughness state of the workpiece immediately after the first stroke. In addition, regardless of the initial roughness state of the workpiece surface, whether with flat or randomly distributed heights, the ultimate state roughness is unique and definitely features the theoretical case of a plain flat surface. However, this theoretical case is infeasible since it can only be reached after infinite number of strokes.
Testing of a Noninvasive Probe for Measurement of Blood Perfusion
Authors: Robinson Paul S. , Scott Elaine P. , Diller Thomas E.
Published: April 2008

Parameter estimation techniques have been utilized in the development of a methodology to noninvasively measure blood perfusion using a new thermal surface probe. The core of this probe is comprised of a small, lightweight heat flux sensor that is placed in contact with tissue and provides time-resolved signals of heat flux and surface temperature while the probe is cooled by air jets. Parameter estimation techniques were developed that incorporate heat flux and temperature data with calculated data from a biothermal model of the tissue and probe. The technique simultaneously estimates blood perfusion and thermal contact resistance between the probe and tissue. Validation of this concept was carried out by experimentation with controlled flow through nonbiological porous media. Warm water was circulated through a fine pore sponge to provide a phantom model for blood perfusion through biological tissue. The parameter estimation technique was applied to measurements taken over a range of flow rates. Heat flux and temperature measurements and the resulting perfusion estimates correlated well with the experimentally imposed perfusion rate. This research helps establish the validity of using this method to develop a practical, noninvasive probe to clinically measure blood perfusion.
A Signal Grammar to Guide Functional Modeling of Electromechanical Products
Authors: Nagel Robert L. , Vucovich Jayson P. , Stone Robert B. , McAdams Daniel A.
Published: April 2008

In modern product design methodologies, designers are increasingly required to combine elements spanning multiple engineering domains, thus blurring the boundaries between engineering disciplines. Functional modeling with the Functional Basis provides the basic tools required to integrate system models at the conceptual level; however, there is a lack of unified rules to address the structure of functional models. This article covers the development of a signal grammar for functional modeling with a Functional Basis. At the conceptual level, signal flows represent the information vital to a proper system operation. Signal flows are explored through their Functional Basis lexicon and primary/carrier flow relationships. A grammar, consisting of morphology and syntax, is presented and applied to a set of electromechanical, component-based building block examples. To further demonstrate the application of signals in functional modeling, an electromechanical product is explored functionally with the application of the signal grammar.
Analysis of Rotational Precision for an Isosceles-Trapezoidal Flexural Pivot
Authors: Xu Pei , Jingjun Yu , Guanghua Zong , Shusheng Bi , Zhiwei Yu
Published: April 2008

An isosceles-trapezoidal flexural pivot can be of great use for practical designs, especially in the cases that a pure rotation about a virtual pivot is required. The analysis of rotational precision for such a structure is important for the mechanical design in precise-required applications. For this purpose, a rigid isosceles-trapezoidal linkage model is first proposed to provide an accurate analytical result for its notch-type flexural counterpart. The influence of dimensional parameters on the center shift is discussed. In order to disclose the equivalence between leaf-type flexure structure and its pseudo-rigid-body model, a transitional model is introduced, from which an equivalent pseudo-rigid-body model for leaf-type isosceles-trapezoidal flexure structure is then derived. The results of both simulation and experiment verify that the equivalent rigid model is also accurate enough in the case of a larger deflection.
A Class of Parallel Robots Practically Free of Parallel Singularities
Authors: Horin Patricia Ben , Shoham Moshe
Published: April 2008

This paper presents a class of 6-DOF three-legged parallel robots that are practically free of parallel singularities. The robots of this class have legs with a characteristic passive pair of prismatic and spherical joints, the first being directly attached to the platform. First, the direct kinematics of this class is solved, showing that for a certain arrangement there exists only one assembly mode. Then, the robot singularities are derived, showing that they practically do not exist in this structure. The advantages of this class of robots are hence simple direct kinematics and no need of singularity calculations.
Microrobot Design Using Fiber Reinforced Composites
Authors: Wood R. J. , Avadhanula S. , Sahai R. , Steltz E. , Fearing R. S.
Published: April 2008

Mobile microrobots with characteristic dimensions on the order of 1cm are difficult to design using either microelectromechanical systems technology or precision machining. This is due to the challenges associated with constructing the high strength links and high-speed, low-loss joints with micron scale features required for such systems. Here, we present an entirely new framework for creating microrobots, which makes novel use of composite materials. This framework includes a new fabrication process termed smart composite microstructures (SCM) for integrating rigid links and large angle flexure joints through a laser micromachining and lamination process. We also present solutions to actuation and integrated wiring issues at this scale using SCM. Along with simple design rules that are customized for this process, our new complete microrobotic framework is a cheaper, quicker, and altogether superior method for creating microrobots that we hope will become the paradigm for robots at this scale.
Singularity-Free Joint Actuation in Omnidirectional Mobile Platforms With Powered Offset Caster Wheels
Authors: Oetomo Denny , Ang Marcelo H.
Published: April 2008

This paper presents the analysis of singularity and motion capability of a mobile platform articulated by offset powered caster wheels. Specifically, it presents the analysis of the equations of motion resulting in the sufficient and necessary actuation condition to yield a workspace that is entirely free of singular configurations. This paper shows that powering both the steer and drive joints on two sets of offset caster wheels in a mobile platform guarantees a singularity-free condition throughout the entire workspace. Analysis and discussion on equations of motions that lead to this result are presented.
Measuring Luxation of Dental Implants In Vitro
Authors: Ilieş Horea T. , Flanagan Dennis , Raby Matthew , Stevenson Richard
Published: April 2008

Loading of dental implants immediately after placement is an important attribute for the patients receiving the implants, but may induce a failure in the osseointegration of the implant. Even though the loading required to induce such failures is currently unknown, it is estimated that the osseointegration may fail if an implant is luxated in bone by more than 50μm. Therefore, the ability to measure this loading can provide the practicing dentist with critical information in estimating the functional life of a newly placed implant. This paper discusses the design and fabrication of a cost-effective test setup for measuring the amount of horizontal force required to displace a nonosseointegrated implant, and presents the results of our pilot in vitro load measurements for dental implants mounted in a bovine mandible. Although the sample size of our measurements is not statistically significant, the initial data show that the amount of horizontal force required to displace a 4.3×13mm implant by 50μm is in the order of 150N, and therefore the implant may fail to osseointegrate for biting forces that are as low as 440N, which is about half of the typical biting force of an adult in the molar area. One implication of our study is that implants having smaller diameters may move and fail to osseointegrate for even lower biting forces. Furthermore, our work represents the first steps in developing appropriate metrics to correlate the measured biting force generated by a patient with his or her candidacy for immediate functional implant loading.
A Calibration Procedure for a Bone Loading System
Authors: García-Rodríguez Sylvana , Smith Everett L. , Ploeg Heidi-Lynn
Published: April 2008

Trabecular bone tissue is a three-dimensional structure that is difficult to duplicate with in vitro cell cultures or animal models. In an attempt to better understand the underlying mechanisms of tissue response to load, a system to load isolated bone preparations was developed. This ex vivo bone culture and loading system, given the name of ZETOS, compressively loads trabecular bone (10mm diameter, 5.0mm height) to evaluate its morphological and physiological responses while keeping cells viable. Compliance of the system may change with time, thus requiring recalibration. The purpose of this research was to develop and validate a recalibration protocol for the ZETOS system. Ten reference bodies (RBs) were designed and machined out of aluminum 7075-T6, with a structural rigidity range representative of trabecular bone (0.628–28.3N∕μm, or apparent elastic modulus of 40MPa–1.80GPa). Finite element analysis (FEA) was used to calculate the rigidity of each RB and was validated with physical testing in a universal testing machine. Results from FEA were then used to calibrate the system and relate force, piezoelectric actuator expansion, and specimen compressive deformation through a surface generated by spline interpolation, thus creating a calibration table. Calibration of ZETOS was verified by testing the RBs as well as three custom-made, metal springs and comparing measured rigidity to that calculated by FEA. Mean percent difference of FEA results with respect to those from physical testing was 3.28%. The mean percent difference of RB rigidity found with ZETOS with respect to rigidity found with FEA was 1.12% and for the metal springs, the mean percent difference was 1.74%. The calibration procedure for the ZETOS bone loading system has been successfully applied and verified. The use of RBs and FEA allows users to easily and periodically evaluate and recalibrate the system. Accuracy in studies of human bone mechanotransduction in a controlled environment can therefore be achieved. The recalibration procedure is relevant for other ZETOS users and may serve as the basis for calibration of other testing systems for small specimens of compliant materials.
Generation of Epicyclic Gear Trains of One Degree of Freedom
Authors: Rao Y. V. D. , Rao A. C.
Published: April 2008

New planetary gear trains (PGTs) are generated using graph theory. A geared kinematic chain is converted to a graph and a graph in turn is algebraically represented by a vertex-vertex adjacency matrix. Checking for isomorphism needs to be an integral part of the enumeration process of PGTs. Hamming matrix is written from the adjacency matrix, using a set of rules, which is adequate to detect isomorphism in PGTs. The present work presents the twin objectives of testing for isomorphism and compactness using the Hamming matrices and moment matrices.
Modified Disturbance Function Method for a 6-6 Gough–Stewart Parallel Manipulator to Traverse the Singularity Hypersurface
Authors: Wang Yu-Xin , Li Yu-Tong , Pan Shuang-Xia
Published: April 2008

Due to the motion uncertainty at the singular point, while the manipulator traverses the singularity hypersurface and moves from one singularity-free region to another, its motion is uncertain. To obtain a desired motion after it traverses the singularity hypersurface, the disturbance function approach was presented by the authors. Because the configuration transformation process takes place within the maximum loss control domain (MLCD), the motion uncertainty within the MLCD still exists. In order to eliminate this kind of motion uncertainty, a modified disturbance function method is presented in this paper. With the aid of the optimization method, the modified disturbance function is constructed through setting up the constraint equations to ensure each trace point locating beyond the MLCD corresponding to the perturbed singular point, and permitting some components of the configuration parameters with a little deviation. Under the action of the modified disturbances, the manipulator moves beyond the MLCD and traverses the singularity hypersurface with a controllable motion.
Optimal Kinematic Design and Application of a Redundantly Actuated 3DOF Planar Parallel Manipulator
Authors: Wu Jun , Wang Jinsong , Wang Liping
Published: April 2008

This paper addresses optimal kinematic design and application of a redundantly actuated parallel manipulator with 3DOFs. Based on the kinematic model, the Jacobian matrix is derived and then transferred to a uniform form such that the conditioning index has explicit physical meaning. Based on the task workspace, the width between two columns is determined. Then, a comprehensive performance index, which compromises the conflict between workspace utilization performance measure and conditioning index, is proposed for the optimum design. The parallel manipulator is incorporated into a 4DOF hybrid machine tool, which also includes a feed worktable. Furthermore, a 5DOF machine tool is created by combining the parallel manipulator with a 2DOF worktable to machine blades of gas turbines.
Spatiotemporal classification of vocal fold dynamics by a multimass model comprising time-dependent parameters
Authors: Wurzbacher Tobias , Döllinger Michael , Schwarz Raphael , Hoppe Ulrich , Eysholdt Ulrich , Lohscheller Jörg
Published: April 2008

A model-based approach is proposed to objectively measure and classify vocal fold vibrations by left–right asymmetries along the anterior–posterior direction, especially in the case of nonstationary phonation. For this purpose, vocal fold dynamics are recorded in real time with a digital high-speed camera during phonation of sustained vowels as well as pitch raises. The dynamics of a multimass model with time-dependent parameters are matched to vocal fold vibrations extracted at dorsal, medial, and ventral positions by an automatic optimization procedure. The block-based optimization accounts for nonstationary vibrations and compares the vocal fold and model dynamics by wavelet coefficients. The optimization is verified with synthetically generated data sets and is applied to 40 clinical high-speed recordings comprising normal and pathological voice subjects. The resulting model parameters allow an intuitive visual assessment of vocal fold instabilities within an asymmetry diagram and are applicable to an objective quantification of asymmetries.
Numerical simulation of a piano soundboard under downbearing
Authors: Mamou-Mani Adrien , Frelat Joël , Besnainou Charles
Published: April 2008

A finite element model of a piano soundboard is used to study the effect of the strings tension (downbearing) on its vibration, considering the ribs, the bridges and the crown. The downbearing is modeled with the prestress theory. Prestress calculation with linear and nonlinear models including geometric rigidity are compared in terms of the modal frequencies. The effects of the downbearing in modal frequencies and mobility are investigated and the importance of the crown on these results is evaluated. A simple phenomenological law is exhibited, which characterizes the evolution of eigenfrequencies with downbearing, including the initial crown.
Acoustic model for robustness analysis of optimal multipoint room equalization
Authors: Kim Lae-Hoon , Hasegawa-Johnson Mark , Lim Jun-Seok , Sung Koeng-Mo
Published: April 2008

In this paper, an acoustic model for the robustness analysis of optimal multipoint room equalization is proposed. The optimal multipoint equalization aims to have the optimal performance in a least-squares sense for all measured points. The model can be used for theoretical robustness estimation depending on the critical design parameters such as the number of measurement points, the distance between measurements, or the frequency before applying real equalization system. The analysis results show that it is important to set the appropriate number of measurement points and the distances between measurement points to ensure the enlarged equalization region at a specific frequency.
A model for sonar interrogation of complex bottom and surface targets in shallow-water waveguides
Authors: Giddings Thomas E. , Shirron Joseph J.
Published: April 2008

Many problems of current interest in underwater acoustics involve low-frequency broadband sonar interrogation of objects near the sea surface or sea floor of a shallow-water environment. When the target is situated near the upper or lower boundary of the water column the acoustic interactions with the target objects are complicated by interactions with the nearby free surface or fluid-sediment interface, respectively. A practical numerical method to address such situations is presented. The model provides high levels of accuracy with the flexibility to handle complex, three-dimensional targets in range-independent environments. The model is demonstrated using several bottom target scenarios, with and without locally undulating seabeds. The impact of interface and boundary interactions is considered with an eye toward using the sonar return signal as the basis for acoustic imaging or spectral classification.
Automated species recognition of antbirds in a Mexican rainforest using hidden Markov models
Authors: Trifa Vlad M. , Kirschel Alexander N. G. , Taylor Charles E. , Vallejo Edgar E.
Published: April 2008

Behavioral and ecological studies would benefit from the ability to automatically identify species from acoustic recordings. The work presented in this article explores the ability of hidden Markov models to distinguish songs from five species of antbirds that share the same territory in a rainforest environment in Mexico. When only clean recordings were used, species recognition was nearly perfect, 99.5%. With noisy recordings, performance was lower but generally exceeding 90%. Besides the quality of the recordings, performance has been found to be heavily influenced by a multitude of factors, such as the size of the training set, the feature extraction method used, and number of states in the Markov model. In general, training with noisier data also improved recognition in test recordings, because of an increased ability to generalize. Considerations for improving performance, including beamforming with sensor arrays and design of preprocessing methods particularly suited for bird songs, are discussed. Combining sensor network technology with effective event detection and species identification algorithms will enable observation of species interactions at a spatial and temporal resolution that is simply impossible with current tools. Analysis of animal behavior through real-time tracking of individuals and recording of large amounts of data with embedded devices in remote locations is thus a realistic goal.
Low-frequency and high-frequency distortion product otoacoustic emission suppression in humans
Authors: Gorga Michael P. , Neely Stephen T. , Dierking Darcia M. , Kopun Judy , Jolkowski Kristin , Groenenboom Kristin , Tan Hongyang , Stiegemann Bettina
Published: April 2008

Distortion product otoacoustic emission suppression (quantified as decrements) was measured for f2=500 and 4000Hz, for a range of primary levels (L2), suppressor frequencies (f3), and suppressor levels (L3) in 19 normal-hearing subjects. Slopes of decrement-versus-L3 functions were similar at both f2 frequencies, and decreased as f3 increased. Suppression tuning curves, constructed from decrement functions, were used to estimate (1) suppression for on- and low-frequency suppressors, (2) tip-to-tail differences, (3) QERB, and (4) best frequency. Compression, estimated from the slope of functions relating suppression “threshold” to L2 for off-frequency suppressors, was similar for 500 and 4000Hz. Tip-to-tail differences, QERB, and best frequency decreased as L2 increased for both frequencies. However, tip-to-tail difference (an estimate of cochlear-amplifier gain) was 20dB greater at 4000Hz, compared to 500Hz. QERB decreased to a greater extent with L2 when f2=4000Hz, but, on an octave scale, best frequency shifted more with level when f2=500Hz. These data indicate that, at both frequencies, cochlear processing is nonlinear. Response growth and compression are similar at the two frequencies, but gain is greater at 4000Hz and spread of excitation is greater at 500Hz.
Using blind source separation techniques to improve speech recognition in bilateral cochlear implant patients
Authors: Kokkinakis Kostas , Loizou Philipos C.
Published: April 2008

Bilateral cochlear implants seek to restore the advantages of binaural hearing by improving access to binaural cues. Bilateral implant users are currently fitted with two processors, one in each ear, operating independent of one another. In this work, a different approach to bilateral processing is explored based on blind source separation (BSS) by utilizing two implants driven by a single processor. Sentences corrupted by interfering speech or speech-shaped noise are presented to bilateral cochlear implant users at 0dB signal-to-noise ratio in order to evaluate the performance of the proposed BSS method. Subjects are tested in both anechoic and reverberant settings, wherein the target and masker signals are spatially separated. Results indicate substantial improvements in performance in both anechoic and reverberant settings over the subjects’ daily strategies for both masker conditions and at various locations of the masker. It is speculated that such improvements are due to the fact that the proposed BSS algorithm capitalizes on the variations of interaural level differences and interaural time delays present in the mixtures of the signals received by the two microphones, and exploits that information to spatially separate the target from the masker signals.
Perception of suprathreshold amplitude modulation and intensity increments: Weber’s law revisited
Authors: Wojtczak Magdalena , Viemeister Neal F.
Published: April 2008

The perceived strength of intensity fluctuations evoked by suprathreshold sinusoidal amplitude modulation (AM) and the perceived size of intensity increments were compared across levels of a wideband noise and a 1-kHz tone. For the 1-kHz tone, the comparisons were made in quiet and in a high-pass noise. The data indicate that suprathreshold modulation depths and intensity increments, perceived as equivalent across levels, follow a pattern resembling Weber’s law for noise and the “near miss” to Weber’s law for a tone. The effect of a high-pass noise was largely consistent with that observed for AM and increment detection. The data suggest that Weber’s law is not a direct consequence of the dependence of internal noise on stimulus level, as suggested by multiplicative internal noise models. Equal loudness ratios and equal loudness differences (computed using loudness for the stationary portions before and after the increment) accounted for the increment-matching data for noise and for the tone, respectively, but neither measure predicted the results for both types of stimuli. Predictions based on log-transformed excitation patterns and predictions using an equal number of intensity just-noticeable differences were in qualitative, but not quantitative, agreement with the data.
Expressions of dissipated powers and stored energies in poroelastic media modeled by {u,U} and {u,P} formulations
Authors: Dazel Olivier , Sgard Franck , Becot François-Xavier , Atalla Noureddine
Published: April 2008

This paper is devoted to the rigorous obtention of the energy balance in porous materials. The wave propagation in the porous media is described by Biot-Allard’s {u,U} and {u,P} formulations. The paper derives the expressions for stored kinetic and strain energies together with dissipated energies. It is shown that, in the case of mixed formulations, these expressions do not correspond to the real and imaginary parts of the variational formulations. A quantitative convergence analysis of finite element scheme is then undertaken with the help of these indicators. It is shown that the order of convergence of these indicators for linear finite-element is one and that they are then well fitted to check the validity of finite-element models.
Behavioral avoidance threshold level of a harbor porpoise (Phocoena phocoena) for a continuous 50kHz pure tone
Authors: Kastelein Ronald A. , Verboom Willem C. , Jennings Nancy , de Haan Dick
Published: April 2008

The use of ultrasonic sounds in alarms for gillnets may be advantageous, but the deterring effects of ultrasound on porpoises are not well understood. Therefore a harbor porpoise in a large floating pen was subjected to a continuous 50kHz pure tone with a source level of 122±3dB (re 1μPa, rms). When the test signal was switched on during test periods, the animal moved away from the sound source. Its respiration rate was similar to that during baseline periods, when the sound was switched off. The behavior of the porpoise was related to the sound pressure level distribution in the pen. The sound level at the animal’s average swimming location during the test periods was approximately 107±3dB (re 1μPa, rms). The avoidance threshold sound pressure level for a continuous 50kHz pure tone for this porpoise, in the context of this study, is estimated to be 108±3dB (re 1μPa, rms). This study demonstrates that porpoises may be deterred from an area by high frequency sounds that are not typically audible to fish and pinnipeds and would be less likely masked by ambient noise.
Low-frequency sound transmission through a gas–liquid interface
Authors: Godin Oleg A.
Published: April 2008

Typically, sound speed in gases is smaller and mass density is much smaller than in liquids, resulting in a very strong acoustic impedance contrast at a gas–liquid interface. Sound transmission through a boundary with a strong impedance contrast is normally very weak. This paper studies the power output of localized sound sources and acoustic power fluxes through a plane gas–liquid interface in a layered medium. It is shown that, for low-frequency sound, a phenomenon of anomalous transparency can occur where most of the acoustic power generated by a source in a liquid half-space can be radiated into a gas half-space. The main physical mechanism responsible for anomalous transparency is found to be an acoustic power transfer by inhomogeneous (evanescent) waves in the plane-wave decomposition of the acoustic field in the liquid. The effects of a liquid’s stratification and of guided sound propagation in the liquid on the anomalous transparency of the gas–liquid interface are considered. Geophysical and biological implications of anomalous transparency of water–air interface to infrasound are indicated.
A three-dimensional articulatory model of the velum and nasopharyngeal wall based on MRI and CT data
Authors: Serrurier Antoine , Badin Pierre
Published: April 2008

An original three-dimensional (3D) linear articulatory model of the velum and nasopharyngeal wall has been developed from magnetic resonance imaging (MRI) and computed tomography images of a French subject sustaining a set of 46 articulations, covering his articulatory repertoire. The velum and nasopharyngeal wall are represented by generic surface triangular meshes fitted to the 3D contours extracted from MRI for each articulation. Two degrees of freedom were uncovered by principal component analysis: first, VL accounts for 83% of the velum variance, corresponding to an oblique vertical movement seemingly related to the levator veli palatini muscle; second, VS explains another 6% of the velum variance, controlling a mostly horizontal movement possibly related to the sphincter action of the superior pharyngeal constrictor. The nasopharyngeal wall is also controlled by VL for 47% of its variance. Electromagnetic articulographic data recorded on the velum fitted these parameters exactly, and may serve to recover dynamic velum 3D shapes. The main oral and nasopharyngeal area functions controlled by the articulatory model, complemented by the area functions derived from the complex geometry of each nasal passage extracted from coronal MRIs, were fed to an acoustic model and gave promising results about the influence of velum movements on the spectral characteristics of nasals.
Binaural speech unmasking and localization in noise with bilateral cochlear implants using envelope and fine-timing based strategies
Authors: van Hoesel Richard , Böhm Melanie , Pesch Jörg , Vandali Andrew , Battmer Rolf D. , Lenarz Thomas
Published: April 2008

Four adult bilateral cochlear implant users, with good open-set sentence recognition, were tested with three different sound coding strategies for binaural speech unmasking and their ability to localize 100 and 500Hz click trains in noise. Two of the strategies tested were envelope-based strategies that are clinically widely used. The third was a research strategy that additionally preserved fine-timing cues at low frequencies. Speech reception thresholds were determined in diotic noise for diotic and interaurally time-delayed speech using direct audio input to a bilateral research processor. Localization in noise was assessed in the free field. Overall results, for both speech and localization tests, were similar with all three strategies. None provided a binaural speech unmasking advantage due to the application of 700μs interaural time delay to the speech signal, and localization results showed similar response patterns across strategies that were well accounted for by the use of broadband interaural level cues. The data from both experiments combined indicate that, in contrast to normal hearing, timing cues available from natural head-width delays do not offer binaural advantages with present methods of electrical stimulation, even when fine-timing cues are explicitly coded.
Adaptive wave field synthesis for broadband active sound field reproduction: Signal processing
Authors: Gauthier Philippe-Aubert , Berry Alain
Published: April 2008

Sound field reproduction is a physical approach to the reproduction of the natural spatial character of hearing. It is also useful in experimental acoustics and psychoacoustics. Wave field synthesis (WFS) is a known open-loop technology which assumes that the reproduction environment is anechoic. A real reflective reproduction space thus reduces the objective accuracy of WFS. Recently, adaptive wave field synthesis (AWFS) was defined as a combination of WFS and active compensation. AWFS is based on the minimization of reproduction errors and on the penalization of departure from the WFS solution. This paper focuses on signal processing for AWFS. A classical adaptive algorithm is modified for AWFS: filtered-reference least-mean-square. This modified algorithm and the classical equivalent leaky algorithm have similar convergence properties except that the WFS solution influences the adaptation rule of the modified algorithm. The paper also introduces signal processing for independent radiation mode control of AWFS on the basis of plant decoupling. Simulation results for AWFS are introduced for free-field and reflective spaces. The two algorithms effectively reproduce the sound field and compensate for the reproduction errors at the error sensors. The independent radiation mode control allows a more flexible tuning of the algorithm.
Angle-dependent ultrasonic detection and imaging of brachytherapy seeds using singular spectrum analysis
Authors: Mamou Jonathan , Ramachandran Sarayu , Feleppa Ernest J.
Published: April 2008

Transrectal-ultrasound-guided brachytherapy uses small titanium-shelled radioactive seeds to locally treat prostate cancer. During the implantation procedure, needles inserted transperitoneally cause gland movement resulting in seed misplacement and suboptimal dosimetry. In a previous study, an algorithm based on singular spectrum analysis (SSA) applied to envelope-detected ultrasound signals was proposed to determine seed locations [J. Mamou and E. J. Feleppa, J. Acoust. Soc. Am. 121, 1790–1801 (2007)]. Successful implementation of the SSA algorithm could allow correcting dosimetry errors during the implantation procedure. The algorithm demonstrated promise when the seed orientation was parallel to the needle and normal to the ultrasound beam. In this present study, the algorithm was tested when the seed orientation deviated up to 22° from normality. Experimental data from a seed in an ideal environment and in beef were collected with a single-element, spherically focused, 5MHz transducer. Simulations were designed and evaluated with the algorithm. Finally, objective quantitative scoring metrics were developed to evaluate the algorithm performance and for comparison with B-mode images. The results quantitatively established that the SSA algorithm always outperformed B-mode images and that seeds could be detected accurately up to a deviation of approximately 10°.
Adaptive wave field synthesis for active sound field reproduction: Experimental results
Authors: Gauthier Philippe-Aubert , Berry Alain
Published: April 2008

Sound field reproduction has applications in music reproduction, spatial audio, sound environment reproduction, and experimental acoustics. Sound field reproduction can be used to artificially reproduce the spatial character of natural hearing. The objective is then to reproduce a sound field in a real reproduction environment. Wave field synthesis (WFS) is a known open-loop technology which assumes that the reproduction environment is anechoic. The room response thus reduces the quality of the physical sound field reproduction by WFS. In recent research papers, adaptive wave field synthesis (AWFS) was defined as a potential solution to compensate for these quality reductions from which WFS objective performance suffers. In this paper, AWFS is experimentally investigated as an active sound field reproduction system with a limited number of reproduction error sensors to compensate for the response of the listening environment. Two digital signal processing algorithms for AWFS are used for comparison purposes, one of which is based on independent radiation mode control. AWFS performed propagating sound field reproduction better than WFS in three tested reproduction spaces (hemianechoic chamber, standard laboratory space, and reverberation chamber).
The low-frequency sound speed of fluid-like gas-bearing sediments
Authors: Wilson Preston S. , Reed Allen H. , Wood Warren T. , Roy Ronald A.
Published: April 2008

The low-frequency sound speed in a fluid-like kaolinite sediment containing air bubbles was measured using an acoustic resonator technique and found to be 114m∕s with negligible dispersion between 100 and 400Hz. The sediment’s void fraction and bubble size distribution was determined from volumetric images obtained from x-ray computed tomography scans. A simplified version of Wood’s effective medium model, which is dependent only upon the ambient pressure, the void fraction, the sediment’s bulk mass density, and the assumption that all the bubbles are smaller than resonance size at the highest frequency of interest, described the measured sound speed.
Segmentation of verb forms in preverbal infants
Authors: Marquis Alexandra , Shi Rushen
Published: April 2008

It has been observed that children’s early vocabulary is dominated by nouns, with verbs being much delayed. The current study investigated if this delay is related to infants’ failure to segment verb forms. Using a preferential looking procedure, French-learning preverbal infants were tested on novel verbs segmentation. Infants at the onset of vocabulary learning (11-month-olds) succeeded in segmenting the targets: they listened longer to test sentences containing previously familiarized verbs versus those containing nonfamiliarized verbs, suggesting that the delay in verb learning is not due to segmentation difficulty. Semantic and syntactic complexities of verbs could be among the underlying factors.
Rollover effect of signal level on vowel formant discrimination
Authors: Liu Chang
Published: April 2008

The goal of this study was to measure the ability of normal-hearing listeners to discriminate formant frequency for vowels in isolation and sentences at three signal levels. Results showed significant elevation in formant thresholds as formant frequency and linguistic context increased. The signal level indicated a rollover effect, especially for F2, in which formant thresholds at 85dB SPL were lower than thresholds at 70 or 100dB SPL in both isolated vowels and sentences. This rollover level effect could be due to reduced frequency selectivity and forward/backward masking in sentence at high signal levels for normal-hearing listeners.
Effect of spectral resolution on the intelligibility of ideal binary masked speech
Authors: Li Ning , Loizou Philipos C.
Published: April 2008

Most binary-mask studies assume a fine time–frequency representation of the signal that may not be available in some applications (e.g., cochlear implants). This study assesses the effect of spectral resolution on intelligibility of ideal-binary masked speech. In Experiment 1, speech corrupted in noise at −5to5dB signal-to-noise ratio (SNR) was filtered into 6–32 channels and synthesized using the ideal binary mask. Results with normal-hearing listeners indicated substantial improvements in intelligibility with 24–32 channels, particularly in −5dB SNR. Results from Experiment 2 indicated that having access to the ideal binary mask in the F1/F2 region is sufficient for good performance.
Incorporation of phonetic constraints in acoustic-to-articulatory inversion
Authors: Potard Blaise , Laprie Yves , Ouni Slim
Published: April 2008

This study investigates the use of constraints upon articulatory parameters in the context of acoustic-to-articulatory inversion. These speaker independent constraints, referred to as phonetic constraints, were derived from standard phonetic knowledge for French vowels and express authorized domains for one or several articulatory parameters. They were experimented on in an existing inversion framework that utilizes Maeda’s articulatory model and a hypercubic articulatory-acoustic table. Phonetic constraints give rise to a phonetic score rendering the phonetic consistency of vocal tract shapes recovered by inversion. Inversion has been applied to vowels articulated by a speaker whose corresponding x-ray images are also available. Constraints were evaluated by measuring the distance between vocal tract shapes recovered through inversion to real vocal tract shapes obtained from x-ray images, by investigating the spreading of inverse solutions in terms of place of articulation and constriction degree, and finally by studying the articulatory variability. Results show that these constraints capture interdependencies and synergies between speech articulators and favor vocal tract shapes close to those realized by the human speaker. In addition, this study also provides how acoustic-to-articulatory inversion can be used to explore acoustical and compensatory articulatory properties of an articulatory model.
Relationship between listening difficulty and acoustical objective measures in reverberant sound fields
Authors: Sato Hayato , Morimoto Masayuki , Sato Hiroshi , Wada Megumi
Published: April 2008

The previous work [Morimoto et al., J. Acoust. Soc. Am. 116, 1607–1613] showed that listening difficulty ratings can be used to evaluate speech transmission performance more exactly and sensitively than intelligibility. Meanwhile, speech transmission performance is usually evaluated using acoustical objective measures, which are directly associated with physical parameters of room acoustic design. However, the relationship between listening difficulty ratings and acoustical objective measures was not minutely investigated. In the present study, a total of 96 impulse responses were used to investigate the relationship between listening difficulty ratings and several objective measures in unidirectional sound fields. The result of the listening test showed that (1) the correlation between listening difficulty ratings and speech transmission index (STI) is the strongest of all tested objective measures, and (2) A-weighted D50, C50, and center time, which are obtained from the impulse responses passed through an A-weighted filter, also strongly correlate with listening difficulty ratings, and their correlations with listening difficulty ratings are not statistically different from the correlation between listening difficulty ratings and STI.
Lüke and power residue sequence diffusers
Authors: Dadiotis Konstantinos , Angus Jamie A. S. , Cox Trevor J.
Published: April 2008

Conventional Schroeder diffusers have been successfully used for many years. However, their frequency range is limited by the flat plate effect that occurs when all the wells radiate in phase. This occurs at harmonics of p times the design frequency f0, where p is the small prime that is used to generate the structure. A typical diffuser, using p=7 and f0=500Hz, has an upper frequency limit of only 3.5kHz. Achieving a first flat plate frequency above 20kHz requires a prime equal to at least 41 and results in diffusers that are too big to be practical in most applications. This paper suggests an alternative approach using number theoretic sequences that, although short in length, are based on large integers. Two new sequences, Type-II Lüke and power residue, have this desired characteristic. They are investigated using both simple models and the more exact boundary element method. The results show the flat plate effect is moved to much higher frequencies as expected. For Lüke sequences at certain frequencies, redirection rather than dispersion is achieved. Modulation techniques can be used to mitigate these problems. Power residue sequences perform the best, providing good diffusion and a flat plate frequency outside the audible range.
Dial A440 for absolute pitch: Absolute pitch memory by non-absolute pitch possessors
Authors: Smith Nicholas A. , Schmuckler Mark A.
Published: April 2008

Listeners without absolute (or “perfect”) pitch have difficulty identifying or producing isolated musical pitches from memory. Instead, they process the relative pattern of pitches, which remains invariant across pitch transposition. Musically untrained non-absolute pitch possessors demonstrated absolute pitch memory for the telephone dial tone, a stimulus that is always heard at the same absolute frequency. Listeners accurately classified pitch-shifted versions of the dial tone as “normal,” “higher than normal” or “lower than normal.” However, the role of relative pitch processing was also evident, in that listeners’ pitch judgments were also sensitive to the frequency range of stimuli.
Simultaneous estimation of attenuation and structure parameters of aggregated red blood cells from backscatter measurements
Authors: Franceschini Emilie , Yu François T. H. , Cloutier Guy
Published: April 2008

The analysis of the ultrasonic frequency-dependent backscatter coefficient of aggregating red blood cells reveals information about blood structural properties. The difficulty in applying this technique in vivo is due to the frequency-dependent attenuation caused by intervening tissue layers that distorts the spectral content of backscattering properties from blood microstructures. An optimization method is proposed to simultaneously estimate tissue attenuation and blood structure factor. With in vitro experiments, the method gave satisfactory estimates with relative errors below 22% for attenuations between 0.101 and 0.317dB∕cm∕MHz, signal-to-noise ratios>28dB and kR<2.7 (k being the wave number and R the aggregate radius).