bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical Modification of Vegetable Oils for Lubricant Basestocks
Authors: Erhan S. Z. , Adhvaryu A. , Liu Z.
Published: February 2009

Use of vegetable oil based lubricants will reduce petroleum imports and have a favorable environmental impact. The vegetable oils are derived from a renewable sources, biodegradable, non-toxic, possess high flash points and have low volatility. Inadequate oxidative stability and poor low-temperature properties of vegetable oils limit their utilization as lubricants. In this study, we report the development of chemical modification methods to improve these functional properties. The resultant vegetable oil derivatives having diester substitution at the sites of unsaturation shows comparable properties to mineral base fluids.
Lubricating Oil Tribology of a Biodiesel-Fuelled Compression Ignition Engine
Authors: Agarwal Avinash Kumar
Published: February 2009

Biodiesel is an alternative fuel derived from vegetable oils by modifying their molecular structure through transesterification process. Linseed oil methyl ester (LOME) was prepared using methanol in the presence of potassium hydroxide as catalyst. Use of linseed oil methyl ester in compression ignition engines was found to develop a very compatible engine-fuel system with lower emission characteristics. Two identical engines were subjected to long-term endurance tests, fuelled by optimum biodiesel blend (20% LOME) and diesel oil respectively. Various tribological studies on lubricating oil samples drawn at regular intervals for both engines were conducted in order to correlate the comparative performance of the two fuels and the effect of fuel chemistry on lubricating oil performance and life. A number of tests were conducted in order to evaluate comparative performance of the two fuels such as density measurement, viscosity measurements, flash point determination, moisture content determination, pentane and benzene insolubles, thin layer chromatography, differential scanning calorimetry etc. All these tests were used for indirect interpretation of comparative performance of these fuels. Biodiesel fuels performance is found to be superior to that of diesel oil and the lubricating oil life is found to have increased, while operating the engine on this fuel.   NOTE: This paper was presented at the ASME 2003 Internal Combustion Engine Division Spring Technical Conference but was printed in the ASME 2003 Internal Combustion Engine and Rail Transportation Divisions Fall Technical Conference proceedings, pages 427–441. It should appear under the Lubrication and Friction heading.
Survey of Gas Engine Performance and Future Trends
Authors: Callahan Timothy J.
Published: February 2009

Worldwide, reciprocating engines play a major role in power generation. Many of the reciprocating engines are diesel engines used as stand-by generators, but increasingly, natural gas engines are providing distributed base load generation and finding service in combined heat and power applications. The economics of power generation continues to place a premium on engine efficiency while environmental regulators continue to legislate lower and lower exhaust emission levels, specifically NOx emissions. NOx emissions and efficiency tend to be proportional, so while not mutually exclusive, low NOx and high efficiency are difficult to obtain simultaneously. In spite of the NOx-efficiency relationship, natural gas engines are more efficient with lower emissions today than in the past and the trend toward higher efficiency will continue in the future. This paper surveys current natural gas engine performance and emissions and projects future engine performance. This paper also introduces the ARES and ARICE programs for developing revolutionary technology for high efficiency and low emissions.
Open Chamber Spark Ignited Combustion System Development for High Power Density and Low Emissions
Authors: Ludu Andrei , Baufeld Torsten , Philipp Harald , Gru¨nig Carolus
Published: February 2009

High power density and thermal efficiency combined with very low NOx exhaust emissions are main challenges in today’s gas engine development programmes. Until recently open chamber combustion systems using traditional spark ignition were considered to be limited by knock and misfire in their potential to achieve the above mentioned goals. The main task of the work reported here was to achieve a stable, knock-free combustion using a knock-prone gas fuel of 70 methane number for a specific power density of 25 kW/L at 250 mg/m3N NOx emission according to the TA Luft. The combustion system development was carried out on a single cylinder engine (SCE), thus, a special aspect of the work was to ensure transferability of the single cylinder engine combustion system development results to the targeted V12 multi-cylinder engine. Prior to engine testing, intensive simulation work was undertaken to specify the most promising engine hardware configurations. The main emphasis was on the 3D CFD analysis of the in-cylinder charge motion and its interaction with carefully chosen combustion chamber geometry variants. The ultimate scope was to generate high local turbulence levels during combustion, enabling a short combustion duration with low variation coefficients. The experimental phase included engine tests for several combustion relevant parameters and the detailed combustion analysis with respect to flame propagation and knock centre location using the optical combustion diagnosis system AVL VISIOLUTION. This paper describes the overall work procedure as well as the analytical and experimental methods and tools employed in the combustion system development programme. It also gives information on engine test results, the value and contribution of combustion visualisation, as well as on the engine performance which could be finally reached.
Gas Dynamic Design Analyses of Charging Zone for Reverse-Flow Pressure Wave Superchargers
Authors: Akbari Pezhman , Mu¨ller Norbert
Published: February 2009

The paper is focused on a comprehensive and systematic gas dynamic analysis of the high-pressure phase (charging zone) of pressure wave superchargers. The procedure is documented for a four-port reverse flow (RF) wave rotor, the typical configuration for engine wave superchargers, also named Comprex. A one-dimensional analytical gas dynamic model is employed to calculate flow characteristics inside the channels. Existing normal shock wave equations along with isentropic relations for expansion waves are used for calculations. Useful design parameters such as cycle timing and port widths are determined by formulating traveling times of the waves inside the channels. The gas dynamic study of the internal wave process demonstrates its fundamental dependence on the externally imposed compression ratio of the pressure wave supercharger.
GDI Engine Exhaust Aftertreatment System Analysis and Oxygen Sensor Based Identification, Modeling and Control of Lean NOx Trap
Authors: Ye Zhengmao
Published: February 2009

This paper presents a thorough analysis of the exhaust gas aftertreatment systems of Gasoline Direct Injection (GDI) engines. The mechanism of the exhaust gas aftertreatment systems is investigated using chemical thermodynamics. The physical models of three-way-catalyst (TWC) and lean NOx trap (LNT) are presented. The objective is to propose an alternative approach for the identification of A/F ratio and oxygen concentration in the exhaust systems to substitute the costly oxygen sensors. A simple control scheme is included within the model identification and prediction results are compared with the testing data from the universal exhaust gas oxygen (UEGO) sensor and from the heated exhaust gas oxygen (HEGO) sensor. The oxygen storage effect has an essential impact on the LNT storage and purge operations, which will also affect the overall fuel economy of GDI engine systems. Its influence on the fuel economy has been estimated by numerical simulations, which is correspondent to the extra percentage of fuel consumption.
Design Studies for Twist-Coupled Wind Turbine Blades
Authors: Locke James , Valencia Ulyses , Ishikawa Kosuke
Published: February 2009

This study presents results obtained for three designs of the Northern Power Systems (NPS) 9.2-meter version of the ERS-100 wind turbine rotor blade. The ERS-100 wind turbine rotor blade was designed and developed by TPI composites. The baseline design uses e-glass unidirectional fibers in combination with ±45-degree and random mat layers for the skin and spar cap. This project involves developing structural finite element models of the baseline design and carbon hybrid designs with twist-bend coupling. All designs were evaluated for a unit load condition and two extreme wind conditions. The unit load condition was used to evaluate the static deflection, twist and twist-coupling parameter. Maximum deflections and strains were determined for the extreme wind conditions. Buckling eigenvalues were determined for a tip load condition. The results indicate that carbon fibers can be used to produce twist-coupled designs with comparable deflections, strains and buckling loads.
Blade-Wake Interaction Noise for Turbines With Downwind Rotors
Authors: McNerney G. M. , van Dam C. P. , Yen-Nakafuji D. T.
Published: February 2009

The interaction between the rotor and the tower wake is an important source of noise for wind turbines with downwind rotors. These noise levels may significantly impact the immediate environment. During rotation the rotor blades encounter periodic changes in flow conditions as a result of the tower presence. Typically turbine towers have a circular or modified circular cross section which significantly modifies the flow in the vicinity of the tower. Upstream, the tower causes the flow to decelerate and, hence, causes a rise in pressure. Because of its bluff shape, the flow separates prematurely from the tower and this tends to create a wide, unsteady, vortical wake. The wake characteristics are dependent on the cross-sectional shape of the tower, its surface properties, the Reynolds number (based on tower diameter and wind velocity) of the flow, and the turbulence level of the incoming flow. The wake modifies the dynamic pressure and the local flow incidence angle as seen by the blades and, hence, modifies the aerodynamic loading of the blade during blade passage. The resulting n per revolution fluctuation in the blade loading (where n is the number of blades) is the source of low frequency but potentially high amplitude sound levels. The WTC Proof of Concept 250 kW (POC) wind turbine has been observed by field personnel to produce low frequency emissions at the National Wind Technology Center (NWTC) site during specific atmospheric conditions. Consequently, WTC is conducting a three-phase program to characterize the low frequency emissions of its two-bladed wind turbines and to develop noise mitigation techniques if needed. This paper summarizes the first phase of this program including recent low-frequency noise measurements conducted on the WTC POC250 kW wind turbine, the wake characteristics of circular towers as they pertain to the blade-wake interaction problem, and techniques to attenuate the sound pressure levels caused by the blade-wake interaction.
Aerodynamic Characteristics of the LS(1)-0417MOD Airfoil Model
Authors: Janiszewska Jolanta M. , Gregorek Gerald , Lee John
Published: February 2009

The LS(1)-0417MOD airfoil model was tested in The Ohio State University’s 3×5 wind tunnel both clean and with the application of leading edge grit roughness and with vortex generators. The tests were conducted in both two-dimensional and three-dimensional model configurations and for steady state and unsteady flow conditions. Pressure data were obtained from six spanwise stations. The results showed that the application of the grit roughness reduces the maximum lift coefficients in all configurations. Unsteady maximum lift coefficients were always higher than those for steady state and had, generally, large hysteresis loops. In the case of the unsteady flow however, the hysteresis loops were smaller for the three dimensional (wing) flows. The smallest hysteresis loops were found at the tip spanwise station. The application of the vortex generators at certain chordwise locations reduced the hysteresis loops and increased the maximum lift coefficient, especially in the three dimensional configuration.
The Edge Singularity of an Actuator Disc With a Constant Normal Load
Authors: van Kuik Gijs A. M.
Published: February 2009

All rotor and propeller design methods using momentum theory are based on the concept of the actuator disc, formulated by Froude. In this concept, the rotor load is represented by a uniform pressure jump. This pressure jump generates infinite pressure gradients at the edge of the disc, leading to a velocity singularity. The subject of this paper is the characterization of this velocity singularity assuming inviscid flow. The edge singularity is also the singular leading edge of the vortex sheet emanating from the edge. The singularity is determined as a simple bound vortex of order O(1), carrying an edge force Fedge = −ρ Vedge × Γ. The order of Fedge equals the order of Vedge. This order is determined by a radial momentum analysis. The classical momentum theory for actuators with a constant, normal load Δp appears to be inconsistent: the axial balance provides a value for the velocity at the actuator, with which the radial balance cannot be satisfied. The only way to obtain consistency is to allow the radial component of Fedge to enter the radial balance. The analysis does not resolve on the axial component of Fedge. A quantitative analysis by a full flow field calculation has to assess the value of Fedge for the various actuator disc flow states. Two other solutions for the edge singularity have been published. It is shown that both solutions do not comply with the governing boundary conditions.
Probabilistic Methods for Predicting Wind Turbine Design Loads
Authors: Moriarty Patrick J. , Holley William E. , Butterfield Sandy
Published: February 2009

Further study of probabilistic methods for predicting extreme wind turbine loading was performed on two large-scale wind turbine models with stall and pitch regulation. Long-term exceedance probability distributions were calculated using maxima extracted from time series simulations of in-plane and out-of-plane blade loads. It was discovered that using a threshold on the selection of maxima increased the accuracy of the fitted distribution in following the trends of the largest extreme values for a given wind condition. The optimal threshold value for in-plane and out-of-plane blade loads was found to be the mean value plus 1.4 times the standard deviation of the original time series for the quantity of interest. When fitting a distribution to a given data set, the higher-order moments were found to have the greatest amount of uncertainty and also the largest influence on the extrapolated long-term load’s. This uncertainty was reduced by using large data sets, smoothing of the moments between wind conditions and parametrically modeling moments of the distribution. A deterministic turbulence model using the 90th percentile level of the conditional turbulence distribution given mean wind speed was used to greatly simplify the calculation of the long-term probability distribution. Predicted extreme loads using this simplified distribution were equal to or more conservative than the loads predicted by the full integration method.
Probabilistic Analysis of List Data for the Estimation of Extreme Design Loads for Wind Turbine Components
Authors: Pandey M. D. , Sutherland H. J.
Published: February 2009

Robust estimation of wind turbine design loads for service lifetimes of 30 to 50 years that are based on field measurements of a few days is a challenging problem. Estimating the long-term load distribution involves the integration of conditional distributions of extreme loads over the mean wind speed and turbulence intensity distributions. However, the accuracy of the statistical extrapolation is fairly sensitive to both model and sampling errors. Using measured inflow and structural data from the LIST program, this paper presents a comparative assessment of extreme loads using three distributions: namely, the Gumbel, Weibull and Generalized Extreme Value distributions. The paper uses L-moments, in place of traditional product moments, to reduce the sampling error. The paper discusses the application of extreme value theory and highlights its practical limitations. The proposed technique has the potential of improving estimates of the design loads for wind turbines.
Dissociation between distortion-product and click-evoked otoacoustic emissions in sheep (Ovis aries)
Authors: McFadden Dennis , Pasanen Edward G. , Valero Michelle D. , Roberts Eila K. , Lee Theresa M.
Published: February 2009

Distortion-product otoacoustic emissions (DPOAEs) were weak or absent in about one-third of sheep (Ovis aries) of both sexes tested for otoacoustic emissions (OAEs) even though their click-evoked OAEs (CEOAEs) seemingly were typical of other sheep of the same sex. Various pieces of evidence suggest that the absence of measurable DPOAEs was unlikely to be attributable to anesthetic effects, a poorly located probe tip, a pressure differential between middle and outer ears, season of the year, body position during testing, temperature effects, or previous medical history. Sheep apparently can exhibit a marked dissociation between DPOAEs and CEOAEs. In those sheep having measurable DPOAEs, the DPOAEs were stronger in males than in females, which is the opposite direction of effect from the CEOAEs measured in these same sheep and in humans. In female sheep exposed to higher-than-normal levels of androgens during gestation, the measurable DPOAEs were stronger than in untreated females. Although this also was the opposite direction of effect from expected, it still was a shift in the male direction, in accord with past findings about the masculinizing effects of androgens on OAEs. In sheep, androgen exposure appears to have different effects on the mechanisms underlying DPOAEs from those underlying CEOAEs.
Clear speech production of Korean stops: Changing phonetic targets and enhancement strategies
Authors: Kang Kyoung-Ho , Guion Susan G.
Published: February 2009

The proposal that phonological contrast is enhanced through greater approximation of phonetic targets was investigated by comparing clear speech to conversational and citation-form speech produced by Korean speakers. The stop system of Korean is undergoing a sound change in which younger speakers produce the aspirated-lenis stop contrast differently from previous generations. Older speakers differentiate this contrast primarily with the acoustic correlate of voice onset time (VOT) and secondarily with F0. Younger speakers are merging VOT values for this contrast. As a result, the primary acoustic correlate is now F0 for younger speakers. These production differences likely indicate that younger speakers have developed different phonetic targets for stop production. These different phonetic targets were predicted to result in different enhancement patterns in clear speech: Younger speakers were predicted to enhance F0 differences, whereas older speakers were predicted to enhance VOT differences in clear speech. Results indicated that the older group solely used VOT to enhance the contrast in clear speech, whereas the younger group primarily used F0 but also demonstrated small VOT enhancement. These results indicate that clear speech enhancement strategies reflect phonetic targets. Older and younger speakers have different F0 and VOT targets and these different targets conditioned different enhancement strategies.
Angle-dependent ultrasonic detection and imaging of two types of brachytherapy seeds using singular spectrum analysis
Authors: Mamou Jonathan , Ramachandran Sarayu , Feleppa Ernest J.
Published: February 2009

Brachytherapy to treat prostate cancer uses transrectal ultrasound to guide implantation of titanium-shelled radioactive seeds. Transperitoneal implantation allows errors in placement that cause suboptimal dosimetry. Conventional ultrasound cannot reliably image implanted seeds; therefore, seed misplacements cannot be corrected in the operating room. Previously, an algorithm based on singular spectrum analysis was shown to image palladium seeds better than B-mode ultrasound could. The algorithm is now applied to imaging an iodine seed in gel and in beef tissue as a function of seed angle relative to the incident ultrasound. Results indicate that both seed types are imaged reliably by the algorithm.
The structure of raylike arrivals in a shallow-water waveguide
Authors: Roux Philippe , Cornuelle Bruce D. , Kuperman W. A. , Hodgkiss W. S.
Published: February 2009

Acoustic remote sensing of the oceans requires a detailed understanding of the acoustic forward problem. The results of a shallow-water transmission experiment between a vertical array of sources and a vertical array of receivers are reported. The source array is used to provide additional degrees of freedom to isolate and track raylike arrivals by beamforming over both source and receiver arrays. The coordinated source-receiver array processing procedure is presented and its effectiveness in an example of tracking raylike arrivals in a fluctuating ocean environment is shown. Many of these arrivals can be tracked over an hour or more and show slowly varying amplitude and phase. The use of a double-beamforming algorithm lays the foundation for shallow-water acoustic remote sensing using travel time and source and receive angles of selected eigenrays.
Recognition of spectrally degraded phonemes by younger, middle-aged, and older normal-hearing listeners
Authors: Schvartz Kara C. , Chatterjee Monita , Gordon-Salant Sandra
Published: February 2009

The effects of spectral degradation on vowel and consonant recognition abilities were measured in young, middle-aged, and older normal-hearing (NH) listeners. Noise-band vocoding techniques were used to manipulate the number of spectral channels and frequency-to-place alignment, thereby simulating cochlear implant (CI) processing. A brief cognitive test battery was also administered. The performance of younger NH listeners exceeded that of the middle-aged and older listeners, when stimuli were severely distorted (spectrally shifted); the older listeners performed only slightly worse than the middle-aged listeners. Significant intragroup variability was present in the middle-aged and older groups. A hierarchical multiple-regression analysis including data from all three age groups suggested that age was the primary factor related to shifted vowel recognition performance, but verbal memory abilities also contributed significantly to performance. A second regression analysis (within the middle-aged and older groups alone) revealed that verbal memory and speed of processing abilities were better predictors of performance than age alone. The overall results from the current investigation suggested that both chronological age and cognitive capacities contributed to the ability to recognize spectrally degraded phonemes. Such findings have important implications for the counseling and rehabilitation of adult CI recipients.
The contribution of obstruent consonants and acoustic landmarks to speech recognition in noise
Authors: Li Ning , Loizou Philipos C.
Published: February 2009

The obstruent consonants (e.g., stops) are more susceptible to noise than vowels, raising the question whether the degradation of speech intelligibility in noise can be attributed, at least partially, to the loss of information carried by obstruent consonants. Experiment 1 assesses the contribution of obstruent consonants to speech recognition in noise by presenting sentences containing clean obstruent consonants but noise-corrupted voiced sounds (e.g., vowels). Results indicated substantial (threefold) improvement in speech recognition, particularly at low signal-to-noise ratio levels (−5dB). Experiment 2 assessed the importance of providing partial information, within a frequency region, of the obstruent-consonant spectra while leaving the remaining spectral region unaltered (i.e., noise corrupted). Access to the low-frequency (0–1000Hz) region of the clean obstruent-consonant spectra was found to be sufficient to realize significant improvements in performance and that was attributed to improvement in transmission of voicing information. The outcomes from the two experiments suggest that much of the improvement in performance must be due to the enhanced access to acoustic landmarks, evident in spectral discontinuities signaling the onsets of obstruent consonants. These landmarks, often blurred in noisy conditions, are critically important for understanding speech in noise for better determination of the syllable structure and word boundaries.
Analysis and prediction of acoustic speech features from mel-frequency cepstral coefficients in distributed speech recognition architectures
Authors: Darch Jonathan , Milner Ben , Vaseghi Saeed
Published: February 2009

The aim of this work is to develop methods that enable acoustic speech features to be predicted from mel-frequency cepstral coefficient (MFCC) vectors as may be encountered in distributed speech recognition architectures. The work begins with a detailed analysis of the multiple correlation between acoustic speech features and MFCC vectors. This confirms the existence of correlation, which is found to be higher when measured within specific phonemes rather than globally across all speech sounds. The correlation analysis leads to the development of a statistical method of predicting acoustic speech features from MFCC vectors that utilizes a network of hidden Markov models (HMMs) to localize prediction to specific phonemes. Within each HMM, the joint density of acoustic features and MFCC vectors is modeled and used to make a maximum a posteriori prediction. Experimental results are presented across a range of conditions, such as with speaker-dependent, gender-dependent, and gender-independent constraints, and these show that acoustic speech features can be predicted from MFCC vectors with good accuracy. A comparison is also made against an alternative scheme that substitutes the higher-order MFCCs with acoustic features for transmission. This delivers accurate acoustic features but at the expense of a significant reduction in speech recognition accuracy.
Shear elasticity estimation from surface wave: The time reversal approach
Authors: Brum J. , Catheline S. , Benech N. , Negreira C.
Published: February 2009

In this work the shear elasticity of soft solids is measured from the surface wave speed estimation. An external source creates mechanical waves which are detected using acoustic sensors. The surface wave speed estimation is extracted from the complex reverberated elastic field through a time-reversal analysis. Measurements in a hard and a soft gelatin-based phantom are validated by independent transient elastography estimations. In contrast with other elasticity assessment methods, one advantage of the present approach is its low sound technology cost. Experiments performed in cheese and soft phantoms allows one to envision applications in the food industry and medicine.
A new method to generate an almost-diagonal matrix in the boundary integral equation formulation
Authors: Chandrasekhar B. , Rao Sadasiva M.
Published: February 2009

In this work, a new numerical procedure is developed to generate an almost-diagonal matrix for the solution of boundary integral equation formulation dealing with acoustic scattering problems. The major drawback of the traditional boundary integral equation procedure resulting in a dense system matrix is eliminated in this new procedure by grouping the basis functions into a cluster. The geometry of the structure is modeled by planar triangles and the basis functions are defined on the nodes. By doing so, one can get a benefit of a smaller size matrix to begin with. Furthermore, by grouping these node-based basis functions into a cluster, an almost-diagonal matrix is generated. Thus, the solution procedure developed in this work may be utilized for very large scattering problems since the required computer resources are very low. The solution procedure developed in this work is validated for the scattering cross section of the simple shapes with the closed form solutions wherever available and with the other numerical solution procedures.
Time-series analysis for online recognition and localization of sick pig (Sus scrofa) cough sounds
Authors: Exadaktylos Vasileios , Silva Mitchell , Ferrari Sara , Guarino Marcella , Taylor C. James , Aerts Jean-Marie , Berckmans Daniel
Published: February 2009

This paper considers the online localization of sick animals in pig houses. It presents an automated online recognition and localization procedure for sick pig cough sounds. The instantaneous energy of the signal is initially used to detect and extract individual sounds from a continuous recording and their duration is used as a preclassifier. Autoregression (AR) analysis is then employed to calculate an estimate of the sound signal, and the parameters of the estimated signal are subsequently evaluated to identify the sick cough sounds. It is shown that the distribution of just three AR parameters provides an adequate classifier for sick pig coughs. A localization technique based on the time difference of arrival is evaluated on field data and is shown that it is of acceptable accuracy for this particular application. The algorithm is applied on continuous recordings from a pig house to evaluate its effectiveness. The correct identification ratio ranged from 73% (27% false positive identifications) to 93% (7% false positive identifications) depending on the position of the microphone that was used for the recording. Although the false negative identifications are about 50% it is shown that this accuracy can be enough for the purpose of this tool. Finally, it is suggested that the presented application can be used to online monitor the welfare in a pig house, and provide early diagnosis of a cough hazard and faster treatment of sick animals.
Listening to every other word: Examining the strength of linkage variables in forming streams of speech
Authors: Kidd Gerald , Best Virginia , Mason Christine R.
Published: February 2009

In a variation on a procedure originally developed by Broadbent [(1952). “Failures of attention in selective listening,” J. Exp. Psychol. 44, 428–433] listeners were presented with two sentences spoken in a sequential, interleaved-word format. Sentence one (target) comprised the odd-numbered words in the sequence and sentence two (masker) comprised the even-numbered words in the sequence. The task was to report the words in sentence one. The goal was to determine the effectiveness of cues linking the words of the target (or masker) over time. Three such “linkage variables” were examined: (1) fixed talker, (2) fixed perceived interaural location, and (3) correct syntactic structure. All of the linkage variables provided a significant advantage when applied to the target compared to the baseline condition in which the linkage variables were randomized. However, these linkage variables were not effective when applied to the masker. Word position effects were found such that performance in the baseline condition declined, and the advantages of the linkage variables increased, for the words near the end of the sentence. Overall, this approach appears to be useful for examining interference in speech recognition that has little or no peripheral component. The results suggest that variables that link target words together improve their resiliency to interference and/or their recall.
The relationship between native allophonic experience with vowel duration and perception of the English tense/lax vowel contrast by Spanish and Russian listeners
Authors: Kondaurova Maria V. , Francis Alexander L.
Published: February 2009

Two studies explored the role of native language use of an acoustic cue, vowel duration, in both native and non-native contexts in order to test the hypothesis that non-native listeners’ reliance on vowel duration instead of vowel quality to distinguish the English tense/lax vowel contrast could be explained by the role of duration as a cue in native phonological contrasts. In the first experiment, native Russian, Spanish, and American English listeners identified stimuli from a beat/bit continuum varying in nine perceptually equal spectral and duration steps. English listeners relied predominantly on spectrum, but showed some reliance on duration. Russian and Spanish speakers relied entirely on duration. In the second experiment, three tests examined listeners’ use of vowel duration in native contrasts. Duration was equally important for the perception of lexical stress for all three groups. However, English listeners relied more on duration as a cue to postvocalic consonant voicing than did native Spanish or Russian listeners, and Spanish listeners relied on duration more than did Russian listeners. Results suggest that, although allophonic experience may contribute to cross-language perceptual patterns, other factors such as the application of statistical learning mechanisms and the influence of language-independent psychoacoustic proclivities cannot be ruled out.
A cocktail party with a cortical twist: How cortical mechanisms contribute to sound segregation
Authors: Elhilali Mounya , Shamma Shihab A.
Published: February 2009

Sound systems and speech technologies can benefit greatly from a deeper understanding of how the auditory system, and particularly the auditory cortex, is able to parse complex acoustic scenes into meaningful auditory objects and streams under adverse conditions. In the current work, a biologically plausible model of this process is presented, where the role of cortical mechanisms in organizing complex auditory scenes is explored. The model consists of two stages: (i) a feature analysis stage that maps the acoustic input into a multidimensional cortical representation and (ii) an integrative stage that recursively builds up expectations of how streams evolve over time and reconciles its predictions with the incoming sensory input by sorting it into different clusters. This approach yields a robust computational scheme for speaker separation under conditions of speech or music interference. The model can also emulate the archetypal streaming percepts of tonal stimuli that have long been tested in human subjects. The implications of this model are discussed with respect to the physiological correlates of streaming in the cortex as well as the role of attention and other top-down influences in guiding sound organization.
Analysis of frequency dependence of ultrasonic backscatter coefficient in cancellous bone
Authors: Ta Dean , Wang Weiqi , Huang Kai , Wang Yuanyuan , Le Lawrence H.
Published: February 2009

The ultrasonic scattering mechanism in cancellous bone is investigated theoretically and a model describing the frequency dependence of ultrasonic scattering from cancellous bone is presented. The ultrasonic backscatter coefficient (BSC) of bovine tibiae, human calcanei in vitro and in vivo, were measured and discussed. The data of BSC were also fitted by polynomial. The results demonstrate that BSC is a nonlinear function of frequency and increases with frequency. A good agreement was obtained between BSC values from theory and experiment. Also, the high correlation coefficient between BSC and bone mineral density was obtained, r=0.85±0.07 (mean±SD) (n=15, p<0.001). Based on the values of BSC, the status of cancellous bone and the degree of osteoporotic fracture risk may be assessed.
Simulations of photoacoustic wave propagation using a finite-difference time-domain method with Berenger’s perfectly matched layers
Authors: Sheu Yae-Lin , Li Pai-Chi
Published: February 2009

This study developed a numerical solution of the general photoacoustic generation equations involving the heat conduction theory and the state, continuity, and Navier–Stokes equations in 2.5D axisymmetric cylindrical coordinates using a finite-difference time-domain scheme. The numerical techniques included staggered grids and Berenger’s perfectly matched layers (PMLs), and linear-perturbation analytical solutions were used to validate the simulation results. The numerical results at different detection angles and durations of laser pulses agreed with the theoretical estimates to within an error of 2% in the absolute differences. It was also demonstrated that the simulator can be used to develop advanced photoacoustic imaging methods. The performance of Berenger’s PMLs was also assessed by comparisons with the traditional first-order Mur’s boundary condition. At the edges of the simulation domain, a ten-layer PML medium with polynomial attenuation coefficient grading from 0 to 5×106 m3/kg s was designed to reduce the reflection to as low as −60 and −32 dB in the axial and radial directions, respectively. The reflections at the axial and radial boundaries were 32 and 7 dB lower, respectively, for the ten-layer PML absorbing layer than for the first-order Mur’s boundary condition.
Sonar signal processing using probabilistic signal and ocean environmental models
Authors: Culver R. Lee , Camin H. John
Published: February 2009

Acoustic signals propagating through the ocean are refracted, scattered, and attenuated by the ocean volume and boundaries. Many aspects of how the ocean affects acoustic propagation are understood, such that the characteristics of a received signal can often be predicted with some degree of certainty. However, acoustic ocean parameters vary with time and location in a manner that is not, and cannot be, precisely known; some uncertainty will always remain. For this reason, the characteristics of the received signal can never be precisely predicted and must be described in probabilistic terms. A signal processing structure recently developed relies on knowledge of the ocean environment to predict the statistical characteristics of the received signal, and incorporates this description into the processor in order to detect and classify targets. Acoustic measurements at 250 Hz from the 1996 Strait of Gibraltar Acoustic Monitoring Experiment are used to illustrate how the processor utilizes environmental data to classify source depth and to underscore the importance of environmental model fidelity and completeness.
Variations of road traffic noise in residential areas
Authors: Makarewicz Rufin , Żółtowski Maciej
Published: February 2009

The ability to predict road noise in urban area is important. The community noise equivalent level (Lden) varies from day to day (weekdays, weekends, holidays, etc.). There is a need to compromise between the accuracy in the determination of Lden and limited resources of input data, the measuring equipment, and time. The problem can be managed using the method proposed in this study. It requires only one short-term measurement of the time-average sound level, LAeq,T.
Numerical investigation of out-of-plane sound propagation in a shallow water experiment
Authors: Sturm Frédéric , Ivansson Sven , Jiang Yong-Min , Chapman N. Ross
Published: February 2009

In an experiment in the Florida Straits, broadband pulses were transmitted over a range of 10km and received by a vertical hydrophone array. For pulses with center frequency below 400Hz, the received signal consisted of a dominant arrival followed by a secondary one delayed by about 0.4s. A hypothesis that the secondary arrival was caused by 3D out-of-plane propagation is investigated here numerically with a 3D parabolic equation model (3DWAPE) and a 3D ray model (MOC3D). Both models clearly predict a secondary arrival caused by 3D horizontal refraction from the sloping bottom in the shoreward direction.
Platelets Kill Intraerythrocytic Malarial Parasites and Mediate Survival to Infection
Authors: McMorran Brendan J. , Marshall Vikki M. , de Graaf Carolyn , Drysdale Karen E. , Shabbar Meriam , Smyth Gordon K. , Corbin Jason E. , Alexander Warren S. , Foote Simon J.
Published: February 2009

Platelets play a critical role in the pathogenesis of malarial infections by encouraging the sequestration of infected red blood cells within the cerebral vasculature. But platelets also have well-established roles in innate protection against microbial infections. We found that purified human platelets killed
Plasmodium falciparum
parasites cultured in red blood cells. Inhibition of platelet function by aspirin and other platelet inhibitors abrogated the lethal effect human platelets exert on
P. falciparum
parasites. Likewise, platelet-deficient and aspirin-treated mice were more susceptible to death during erythrocytic infection with
Plasmodium chabaudi
. Both mouse and human platelets bind malarial-infected red cells and kill the parasite within. These results indicate a protective function for platelets in the early stages of erythrocytic infection distinct from their role in cerebral malaria.
The Overwhelming Evidence
Authors: Pigliucci Massimo
Published: February 2009

Why Evolution Is True
.
By Jerry A. Coyne
. Viking, New York, 2009. 304 pp. $27.95, C$31. ISBN 9780670020539. Oxford University Press, Oxford. 329 pp. £14.99. ISBN 9780199230846.
Evolution of the
Drosophila
Nuclear Pore Complex Results in Multiple Hybrid Incompatibilities
Authors: Tang Shanwu , Presgraves Daven C.
Published: February 2009

Speciation often involves the evolution of incompatible gene interactions that cause sterility or lethality in hybrids between populations. These so-called hybrid incompatibilities occur between two or more functionally divergent loci. We show that the
nucleoporin 160kDa
(
Nup160
) gene of the fruitfly
Drosophila simulans
is incompatible with one or more factors on the
D. melanogaster
X chromosome, causing hybrid lethality.
Nup160
encodes a nuclear pore complex protein and shows evidence of adaptive evolution. Furthermore, the protein encoded by
Nup160
directly interacts with that of another hybrid lethality gene,
Nup96
, indicating that at least two lethal hybrid incompatibility genes have evolved as byproducts of divergent coevolution among interacting components of the
Drosophila
nuclear pore complex.
Blue or Red? Exploring the Effect of Color on Cognitive Task Performances
Authors: Mehta Ravi , Zhu Rui (Juliet)
Published: February 2009

Existing research reports inconsistent findings with regard to the effect of color on cognitive task performances. Some research suggests that blue or green leads to better performances than red; other studies record the opposite. Current work reconciles this discrepancy. We demonstrate that red (versus blue) color induces primarily an avoidance (versus approach) motivation (study 1,
n
= 69) and that red enhances performance on a detail-oriented task, whereas blue enhances performance on a creative task (studies 2 and 3,
n
= 208 and 118). Further, we replicate these results in the domains of product design (study 4,
n
= 42) and persuasive message evaluation (study 5,
n
= 161) and show that these effects occur outside of individuals' consciousness (study 6,
n
= 68). We also provide process evidence suggesting that the activation of alternative motivations mediates the effect of color on cognitive task performances.
Treatment of Fungal Bioaerosols by a High-Temperature, Short-Time Process in a Continuous-Flow System
Authors: Jung Jae Hee , Lee Jung Eun , Lee Chang Ho , Kim Sang Soo , Lee Byung Uk
Published: February 2009

Airborne fungi, termed fungal bioaerosols, have received attention due to the association with public health problems and the effects on living organisms in nature. There are growing concerns that fungal bioaerosols are relevant to the occurrence of allergies, opportunistic diseases in hospitals, and outbreaks of plant diseases. The search for ways of preventing and curing the harmful effects of fungal bioaerosols has created a high demand for the study and development of an efficient method of controlling bioaerosols. However, almost all modern microbiological studies and theories have focused on microorganisms in liquid and solid phases. We investigated the thermal heating effects on fungal bioaerosols in a continuous-flow environment. Although the thermal heating process has long been a traditional method of controlling microorganisms, the effect of a continuous high-temperature, short-time (HTST) process on airborne microorganisms has not been quantitatively investigated in terms of various aerosol properties. Our experimental results show that the geometric mean diameter of the tested fungal bioaerosols decreased when they were exposed to increases in the surrounding temperature. The HTST process produced a significant decline in the (1→3)-β-
d
-glucan concentration of fungal bioaerosols. More than 99% of the
Aspergillus versicolor
and
Cladosporium cladosporioides
bioaerosols lost their culturability in about 0.2 s when the surrounding temperature exceeded 350°C and 400°C, respectively. The instantaneous exposure to high temperature significantly changed the surface morphology of the fungal bioaerosols.
Establishment of an Analytical System for the Human Fecal Microbiota, Based on Reverse Transcription-Quantitative PCR Targeting of Multicopy rRNA Molecules
Authors: Matsuda Kazunori , Tsuji Hirokazu , Asahara Takashi , Matsumoto Kazumasa , Takada Toshihiko , Nomoto Koji
Published: February 2009

An analytical system based on rRNA-targeted reverse transcription-quantitative PCR (RT-qPCR) was established for the precise evaluation of human intestinal microbiota. Group- and species-specific primer sets for
Clostridium perfringens
,
Lactobacillus
spp. (six subgroups and three species),
Enterococcus
spp., and
Staphylococcus
spp. targeting 16S rRNA gene sequences were newly developed for the quantitative analysis of such subdominant populations in human intestines. They were used together with previously reported group-specific primer sets for
Enterobacteriaceae
,
Pseudomonas
spp., and six predominant bacterial groups (the
Clostridium coccoides
group, the
Clostridium leptum
subgroup, the
Bacteroides fragilis
group,
Bifidobacterium
spp., the
Atopobium
cluster, and
Prevotella
spp.) for the examination of fecal samples from 40 healthy adults by RT-qPCR with lower detection limits of 10
2
to 10
4
cells per g of feces. The RT-qPCR method gave data equivalent to those yielded by qPCR for predominant populations of more than 10
8
cells per g of feces and could quantify bacterial populations that were not detectable (
Staphylococcus
and
Pseudomonas
) or those only detected at lower incidences (
Prevotella
,
C. perfringens
,
Lactobacillus
, and
Enterococcus
) by qPCR or the culture method. The RT-qPCR analysis of
Lactobacillus
spp. at the subgroup level revealed that a subject has a mean of 4.6 subgroups, with an average count of log
10
(6.3 ± 1.5) cells per g of feces. These results suggest that RT-qPCR is effective for the accurate enumeration of human intestinal microbiota, especially the entire analysis of both predominant and subdominant populations.