bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure Dynamics of One Oil-Fired Drum Type Natural Circulation Steam Generating Unit
Authors: Debeljkovic D. Lj. , Sicovic A.
Published: September 2008

A mathematical model for a water level and pressure dynamics in the drum–riser–downcomer loop of natural circulation drum–type boiler is presented. The 11 [MW] oil-fired steam generation unit with natural circulation is considered. The model is based on the basis of fundamental conservation laws of mass, momentum and energy, together with very well known constitutive equations. The dynamic behaviour of each section is described in the mathematical terms and in the form of lumped parameter systems equations. The equations are linearized and manipulated into the state space form suitable for PC computer. Simulation results are shown compared with those in the literature in which an empirical model for two phase dynamics are employed. The presented model shows a reasonable prediction of water level and pressure dynamics for sudden changes in steam demand and other disturbances.
Simulation of Strongly Heated Internal Gas Flows Using a Near-Wall Two-Equation Heat Flux Model
Authors: Richards Adam H. , Spall Robert E.
Published: September 2008

A two-equation k-ω model is used to model a strongly heated, low-Mach number gas flowing upward in a vertical tube. Heating causes significant property variation and thickening of the viscous sublayer, consequently a fully developed flow does not evolve. Two-equation turbulence models generally perform poorly under such conditions. Consequently, in the present work, a near-wall two-equation heat transfer model is utilized in conjunction with the k-ω model to improve heat transfer predictions.
RELAP5-3D Analysis of Pressure Perturbation at the Peach Bottom BWR During Low-Flow Stability Tests
Authors: Lombardi Costa Antonella , Petruzzi Alessandro , D’Auria Francesco
Published: September 2008

Experimental and theoretical studies about the BWR (Boiling Water Reactor) stability have been performed to design a stable core configuration. BWR instabilities can be caused by interdependencies between thermal-hydraulic and reactivity feedback parameters such as the void-coefficient, for example, during a pressure perturbation event. In the present work, the pressure perturbation is considered in order to study in detail this type of transient. To simulate this event, including the strong feedback effects between core neutronic and reactor thermal-hydraulics, and to verify core behavior and evaluate parameters related to safety, RELAP5-3D code has been used in the analyses. The simulation was performed making use of Peach Bottom-2 BWR data to predict the dynamics of a real reactor during this type of event. Stability tests were conducted in the Peach Bottom 2 BWR, in 1977, and were done along the low-flow end of the rated power-flow line, and along the power-flow line corresponding to minimum recirculation pump speed. The calculated results are herein compared against the available experimental data.
Fuel Damage Reduction by Installation of Particle Traps in the Feedwater Lines
Authors: Henriksson Mats , Westin Johan , Lindqvist Hans , Lundstro¨m Anders , Alavyoon Farid , Kaipainen Tapio
Published: September 2008

Fuel damages are commonly caused by grinding of the cladding due to debris entering the reactor pressure vessel. In order to reduce the probability for fuel damages so-called particle traps have been developed and are currently in operation in two Swedish nuclear power plants. The particle traps are of type axial centrifugal separators, and are characterized by a robust design, high separation rate and low pressure drop (typically less than 1 bar). Special care has been taken in the design of the flow straightener, which efficiently eliminates the swirl in the flow. The model tests show that the Swirl number downstream of the particle trap is typically the same order of magnitude or less than that downstream of a pipe bend. The particles are separated from the main flow and collected in a separate chamber, which is emptied only during the outages. Traps have been developed for both upward or downward flow direction, with feedwater flows from 300 to 900 kg/s. The present paper describes the development work, which is primarily based on full-scale model tests supported by CFD-calculations. Some operating experiences from plants in which particle traps currently are in use are also reported.
Example for the Structural Integrity Evaluation of Thermal Mixing Tee Junction Designed with Sleeves to Protect the Pressure Retaining Wall for Thermal Striping Effects up to 250K
Authors: Schippers Marco , Mu¨ller Senem-Ertem , Hinderks Michael , Probert Thomas
Published: September 2008

The purpose of this paper is to present the structural integrity evaluation on thermal mixing T-junctions designed with thermal sleeves. The specific plant conditions and layout in the LWR piping of the main feed water system, the residual heat removal system and the emergency core cooling system for the BWR OKG2 are characterized by large temperature differences up to 250K and more than 1000 specified cycles within 40 years lifetime. Beside the investigations of low cycle fatigue evaluations are made for the high cyclic thermal fatigue and flow induced vibration. The evaluation method use computational fluid dynamic analysis (CFD) for indicating severe loads for the several plant conditions. Pre-evaluations using the steady Reynolds-Averaged Navier-Stokes model (RANS) are made to indicate the load cases with potential of large temperature fluctuation and their location. Large Eddy Simulations (LES) are prepared at the smaller region of interest for determination of high cyclic thermal loading at the inner surface of the sleeve and the shielding effect for the pressure retaining wall. Results from the CFD analysis are furthermore used for evaluation of the phenomenon of flow induced vibration. The structural and fatigue evaluation based on the design-by-analysis method using finite element models with linear and non linear elastic-plastic material behavior to ascertain the Ke-factor and their local effects on plasticity at cyclic computation. Discussed are the results with respect to the used method for the load determination, used boundary condition, simplification and the performed structural evaluation. The results will reflect among others to developed or established guidelines on thermal striping effects.
Dispersion Modeling of Beryllium Airborne Particulate Released During the Demolition of Contaminated Building
Authors: Ghenai C. , Nagaboina A. , Lagos L.
Published: September 2008

During the demolition of contaminated building, the Beryllium on the surface of the building can be released to the atmosphere. Workers on the site and also off site public can be exposed to the Beryllium airborne particulate that can cause health problems. The objective of this study is to assess the impacts of beryllium airborne particulate released during the demolition of building on workers and off site public. For the source inventory, data from building 333 at DOE Hanford site are used as an example to estimate the total amount of Beryllium on the surface of this building. Samples from the interior surfaces were collected in previous. The surface contaminations were measured and the contamination levels ranging from 1 to 11 μg/100 cm2 were found in this building. The fraction of Beryllium released to the atmosphere during the demolition process was estimated. The amount of Beryllium released from the demolition process are transported and dispersed in the air. The short term Industrial Source Complex (ISC3) model was used to predict the ambient Beryllium concentrations. The receptors are located at downwind distances between 52 m and 2000 m from the center of emission source for every 10-degree flow vector around the emission source (thirty six receptors for each downwind distance). The results presented in this paper show the total 24-hours averaged total airborne air concentration and the 8-hours averages Beryllium air concentration at each of the receptor location. A comparison between the maximum predicted concentration of Beryllium and the compliance benchmark for the site workers (0.2 μg/m3 over 8-hours time averaged) and off site public (0.01 μg/m3) was performed. The risk assessment analysis will help the decision makers to assess the risks from exposure to Beryllium during the demolition of buildings.
INPRO Assessment of an INS in the Area of Safety of Fuel Cycle Installations
Authors: Raj B. , Busurin Y. , Depisch F.
Published: September 2008

INPRO has defined requirements organized in a hierarchy of Basic Principles, User Requirements and Criteria (consisting of an indicator and an acceptance limit) to be met by innovative nuclear reactor systems (INS) in six areas, namely: economics, safety, waste management, environment, proliferation resistance, and infrastructure. If an INS meets all requirements in all areas it represents a sustainable system for the supply of energy, capable of making a significant contribution to meeting the energy needs of the 21st century. Draft manuals have been developed, for each INPRO area, to provide guidance for performing an assessment of whether an INS meets the INPRO requirements in a given area. The manuals set out the information that needs to be assembled to perform an assessment and provide guidance on selecting the acceptance limits and, for a given INS, for determining the value of the indicators for comparison with the associated acceptance limits. Each manual also includes an example of a specific assessment to illustrate the guidance. This paper discusses the manual for performing an INPRO assessment in the area of safety of fuel cycle installations. The example, chosen solely for the purpose of illustrating the INPRO methodology, describes an assessment of an MOX fuel fabrication plant based on sol-gel technology and illustrates an assessment performed for an INS at an early stage of development. The safety issues and the assessment steps are presented in detail in the paper.
DESAE (Dynamic Energy System- Atomic Energy): Integrated Computer Model for Perfoming Global Analysis in INPRO Assessment Studies
Authors: Tsibulskiy V. , Subbotin S. , Khoroshev M. , Depisch F.
Published: September 2008

The Agency’s International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO) was established to help to ensure that nuclear energy is available to contribute, in a sustainable manner, to the energy needs in the 21st century. In 2005, its membership continued to grow, with Ukraine and United States of America becoming additional members, and total INPRO membership now stands at 24.
A New Waveform Signal Processing Method Based on Adaptive Clustering-Genetic Algorithms
Authors: Shaaban Noha , Masuda Fukuzo , Morota Hidetsugu
Published: September 2008

We present a fast digital signal processing method for numerical analysis of individual pulses from CdZnTe compound semiconductor detectors. Using Maxi-Mini Distance Algorithm and Genetic Algorithms based discrimination technique. A parametric approach has been used for classifying the discriminated waveforms into a set of clusters each has a similar signal shape with a corresponding pulse height spectrum. A corrected total pulse height spectrum was obtained by applying a normalization factor for the full energy peak for each cluster with a highly improvements in the energy spectrum characteristics. This method applied successfully for both simulated and real measured data, it can be applied to any detector suffers from signal shape variation.
On the Modeling of Local Neutronically-Coupled Flow-Induced Oscillations in Advanced Boiling Water Reactors
Authors: Aniel-Buchheit Sylvie , Podowski Michael Z.
Published: September 2008

The purpose of this paper is to discuss the development in progress of a complete space- and time-dependent model of the coupled neutron kinetic and reactor thermal-hydraulics. The neutron kinetics model is based on two-group diffusion equations with Doppler and void reactivity feedback effects. This model is coupled with the model of two-phase flow and heat transfer in parallel coolant channels. The modeling concepts considered for this purpose include one-dimensional drift flux and two-fluid models, as well a CFD model implemented in the NPHASE advanced computational multiphase fluid dynamics (CMFD) computer code. Two methods of solution for the overall model are proposed. One is based on direct numerical integration of the spatially-discretized governing equations. The other approach is based on a quasi-analytical modal approach to the neutronics model, in which a complete set of eigenvectors is found for step-wise temporal changes of the cross-sections of core materials (fuel and coolant/moderator). The issues investigated in the paper include details of model formulation, as well as the results of calculations for neutronically-coupled density-wave oscillations.
Automatic recognition of harmonic bird sounds using a frequency track extraction algorithm
Authors: Heller Jason R. , Pinezich John D.
Published: September 2008

This paper demonstrates automatic recognition of vocalizations of four common bird species (herring gull [Larus argentatus], blue jay [Cyanocitta cristata], Canada goose [Branta canadensis], and American crow [Corvus brachyrhynchos]) using an algorithm that extracts frequency track sets using track properties of importance and harmonic correlation. The main result is that a complex harmonic vocalization is rendered into a set of related tracks that is easily applied to statistical models of the actual bird vocalizations. For each vocalization type, a statistical model of the vocalization was created by transforming the training set frequency tracks into feature vectors. The extraction algorithm extracts sets of frequency tracks from test recordings that closely approximate harmonic sounds in the file being processed. Each extracted set in its final form is then compared with the statistical models generated during the training phase using Mahalanobis distance functions. If it matches one of the models closely, the recognizer declares the set an occurrence of the corresponding vocalization. The method was evaluated against a test set containing vocalizations of both the 4 target species and 16 additional species as well as background noise containing planes, cars, and various natural sounds.
Ultrasonic velocity dispersion in bovine cortical bone: An experimental study
Authors: Haïat Guillaume , Sasso Magali , Naili Salah , Matsukawa Mami
Published: September 2008

Cortical bone quality is determinant in bone fragility and its ultrasonic evaluation has become possible in clinical practice. However, the interaction between a broadband ultrasonic pulse and this complex multiscale medium remains poorly understood. The frequency dependence of phase velocity, which may impact clinical measurements, has been sparsely investigated. Our objective is to evaluate the determinants of the frequency dependence of phase velocity in bovine femoral cortical bone samples using an in vitro ultrasonic transmission device. The apparent phase velocity varies quasilinearly on a 1MHz restricted bandwidth around 4MHz. After compensating for diffraction effects, significant differences in velocity dispersion are obtained according to the anatomical location. The microstructure of each sample is determined using an optical microscope, which allows assessing the dependence of dispersion on the type of bone microstructure. Mostly positive but also negative values of dispersion are measured. Negative dispersion is mainly obtained in samples constituted of mixed microstructure, which may be explained by phase cancellation effects due to the presence of different microstructures within the same sample. Dispersion is shown to be related to broadband ultrasonic attenuation values, especially in the radial direction. Results are compared with the local Kramers–Kronig relationships.
A sawtooth waveform inspired pitch estimator for speech and music
Authors: Camacho Arturo , Harris John G.
Published: September 2008

A sawtooth waveform inspired pitch estimator (SWIPE) has been developed for speech and music. SWIPE estimates the pitch as the fundamental frequency of the sawtooth waveform whose spectrum best matches the spectrum of the input signal. The comparison of the spectra is done by computing a normalized inner product between the spectrum of the signal and a modified cosine. The size of the analysis window is chosen appropriately to make the width of the main lobes of the spectrum match the width of the positive lobes of the cosine. SWIPE′, a variation of SWIPE, utilizes only the first and prime harmonics of the signal, which significantly reduces subharmonic errors commonly found in other pitch estimation algorithms. The authors’ tests indicate that SWIPE and SWIPE′ performed better on two spoken speech and one disordered voice database and one musical instrument database consisting of single notes performed at a variety of pitches.
Modeling the sound levels produced by bubble release of individual herring
Authors: Hahn Thomas R. , Thomas Gary
Published: September 2008

Herring (Clupea pallasii and C. harengus) are known to release gas from their swim bladder to assist a number of complex behaviors, such as buoyancy adjustments and predator avoidance. The noise associated with the release has recently been reported in the literature and related to oscillating bubbles. Average source levels (SLs) of 73dB with regard to μPa rms reference 1m have been reported for bubbles produced by herring in the laboratory. A model is provided for predicting the SL in terms of the gas flow rate from the swim bladder into the bubbles. Based on these laboratory conditions, an inversion yields a rate of 0.9 (0.3–3.2)ml∕min. Furthermore, the model predicts an acoustic SL of 89 (79–99)dB with regard to μPa rms reference 1m for pulses emitted by herring in a natural shallow water environment at unknown distance corresponding to a flow rate of 2.5ml∕min. An analysis of published acoustic data suggests that herring is capable of controlling the gas flow and the corresponding acoustic levels over a wide range according to different behavioral needs. The proposed model allows an extrapolation of the laboratory results to situations that are relevant for bubble release of herring schools in the ocean.
Nonuniform speaker normalization using affine transformation
Authors: Bharath Kumar S. V. , Umesh S.
Published: September 2008

In this paper, a well-motivated nonuniform speaker normalization model that affinely relates the formant frequencies of speakers enunciating the same sound is proposed. Using the proposed affine model, the corresponding universal-warping function that is required for normalization is shown to have the same parametric form as the mel scale formula. The parameters of this universal-warping function are estimated from the vowel formant data and are shown to be close to the commonly used formula for the mel scale. This shows an interesting connection between nonuniform speaker normalization and the psychoacoustics based mel scale. In addition, the affine model fits the vowel formant data better than commonly used ad hoc normalization models. This work is motivated by a desire to improve the performance of speaker-independent speech recognition systems, where speaker normalization is conventionally done by assuming a linear-scaling relationship between spectra of speakers. The proposed affine relation is extended to describe the relationship between spectra of speakers enunciating the same sound. On a telephone-based connected digit recognition task, the proposed model provides improved recognition performance over the linear-scaling model.
On the acoustics of ancient Greek and Roman theaters
Authors: Farnetani Andrea , Prodi Nicola , Pompoli Roberto
Published: September 2008

The interplay of architecture and acoustics is remarkable in ancient Greek and Roman theaters. Frequently they are nowadays lively performance spaces and the knowledge of the sound field inside them is still an issue of relevant importance. Even if the transition from Greek to Roman theaters can be described with a great architectural detail, a comprehensive and objective approach to the two types of spaces from the acoustical point of view is available at present only as a computer model study [P. Chourmouziadou and J. Kang, “Acoustic evolution of ancient Greek and Roman theaters,” Appl. Acoust. 69, re (2007)]. This work addresses the same topic from the experimental point of view, and its aim is to provide a basis to the acoustical evolution from Greek to Roman theater design. First, by means of in situ and scale model measurements, the most important features of the sound field in ancient theaters are clarified and discussed. Then it has been possible to match quantitatively the role of some remarkable architectural design variables with acoustics, and it is seen how this criterion can be used effectively to define different groups of ancient theaters. Finally some more specific wave phenomena are addressed and discussed.
Correlation analysis of three-dimensional strain imaging using ultrasound two-dimensional array transducers
Authors: Rao Min , Varghese Tomy
Published: September 2008

Two-dimensional (2D) transducer arrays represent a promising solution for implementing real time three-dimensional (3D) ultrasound elastography. 2D arrays enable electronic steering and focusing of ultrasound beams throughout a 3D volume along with improved slice thickness performance when compared to one-dimensional (1D) transducer arrays. Therefore, signal decorrelation caused by tissue motion in the elevational (out-of-plane) direction needs to be considered. In this paper, a closed form expression is derived for the correlation coefficient between pre- and postdeformation ultrasonic radio frequency signals. Signal decorrelation due to 3D motion of scatterers within the ultrasonic beam has been considered. Computer simulations are performed to corroborate the theoretical results. Strain images of a spherical inclusion phantom generated using 1D and 2D array transducers are obtained using a frequency domain simulation model. Quantitative image quality parameters, such as the signal-to-noise and contrast-to-noise ratios obtained using 1D, 2D, and 3D motion tracking algorithms, are compared to evaluate the performance with the 3D strain imaging system. The effect of the aperture size for 2D arrays and other factors that affect signal decorrelation are also discussed.
Structural-acoustic modeling of automotive vehicles in presence of uncertainties and experimental identification and validation
Authors: Durand Jean-François , Soize Christian , Gagliardini Laurent
Published: September 2008

The design of cars is mainly based on the use of computational models to analyze structural vibrations and internal acoustic levels. Considering the very high complexity of such structural-acoustic systems, and in order to improve the robustness of such computational structural-acoustic models, both model uncertainties and data uncertainties must be taken into account. In this context, a probabilistic approach of uncertainties is implemented in an adapted computational structural-acoustic model. The two main problems are the experimental identification of the parameters controlling the uncertainty levels and the experimental validation. Relevant experiments have especially been developed for this research in order to constitute an experimental database devoted to structural vibrations and internal acoustic pressures. This database is used to perform the experimental identification of the probability model parameters and to validate the stochastic computational model.
Whistle sequences in wild killer whales (Orcinus orca)
Authors: Riesch Rüdiger , Ford John K. B. , Thomsen Frank
Published: September 2008

Combining different stereotyped vocal signals into specific sequences increases the range of information that can be transferred between individuals. The temporal emission pattern and the behavioral context of vocal sequences have been described in detail for a variety of birds and mammals. Yet, in cetaceans, the study of vocal sequences is just in its infancy. Here, we provide a detailed analysis of sequences of stereotyped whistles in killer whales off Vancouver Island, British Columbia. A total of 1140 whistle transitions in 192 whistle sequences recorded from resident killer whales were analyzed using common spectrographic analysis techniques. In addition to the stereotyped whistles described by Riesch et al., [(2006). “Stability and group specificity of stereotyped whistles in resident killer whales, Orcinus orca, off British Columbia,” Anim. Behav. 71, 79–91.] We found a new and rare stereotyped whistle (W7) as well as two whistle elements, which are closely linked to whistle sequences: (1) stammers and (2) bridge elements. Furthermore, the frequency of occurrence of 12 different stereotyped whistle types within the sequences was not randomly distributed and the transition patterns between whistles were also nonrandom. Finally, whistle sequences were closely tied to close-range behavioral interactions (in particular among males). Hence, we conclude that whistle sequences in wild killer whales are complex signal series and propose that they are most likely emitted by single individuals.
Effects of spectral modulation filtering on vowel identification
Authors: Liu Chang , Eddins David A.
Published: September 2008

The goal of this study was to measure the effects of global spectral manipulations on vowel identification by progressively high-pass filtering vowel stimuli in the spectral modulation domain. Twelve American-English vowels, naturally spoken by a female talker, were subjected to varied degrees of high-pass filtering in the spectral modulation domain, with cutoff frequencies of 0.0, 0.5, 1.0, 1.5, and 2.0cycles/octave. Identification performance for vowels presented at 70dB sound pressure level with and without spectral modulation filtering was measured for five normal-hearing listeners. Results indicated that vowel identification performance was progressively degraded as the spectral modulation cutoff frequency increased. Degradation of vowel identification was greater for back vowels than for front or central vowels. Detailed acoustic analyses indicated that spectral modulation filtering resulted in a more crowded vowel space (F1×F2), reduced spectral contrast, and reduced spectral tilt relative to the original unfiltered vowels. Changes in the global spectral features produced by spectral modulation filtering were associated with substantial reduction in vowel identification. The results indicated that the spectral cues critical for vowel identification were represented by spectral modulation frequencies below 2cycles/octave. These results are considered in terms of the interactions among spectral shape perception, spectral smearing, and speech perception.
Radiation force in nonlinear, focused beams
Authors: Ostrovsky L. A.
Published: September 2008

The effect of cumulative nonlinear distortions in a focused ultrasonic wave on the dissipative radiation force (RF) is analyzed using a simplified analytical model separating the stages of geometrical focusing and the subsequent diffraction in the focal area. It is shown that in the absence of shocks, nonlinear steepening can significantly amplify the RF as compared with a harmonic wave. Two different types of dissipation, one corresponding to a classical viscous fluid and another typical of many biological tissues, are considered.
Finite-difference time-domain synthesis of infrasound propagation through an absorbing atmosphere
Authors: de Groot–Hedlin C.
Published: September 2008

Equations applicable to finite-difference time-domain (FDTD) computation of infrasound propagation through an absorbing atmosphere are derived and examined in this paper. It is shown that over altitudes up to 160km, and at frequencies relevant to global infrasound propagation, i.e., 0.02–5Hz, the acoustic absorption in dB/m varies approximately as the square of the propagation frequency plus a small constant term. A second-order differential equation is presented for an atmosphere modeled as a compressible Newtonian fluid with low shear viscosity, acted on by a small external damping force. It is shown that the solution to this equation represents pressure fluctuations with the attenuation indicated above. Increased dispersion is predicted at altitudes over 100km at infrasound frequencies. The governing propagation equation is separated into two partial differential equations that are first order in time for FDTD implementation. A numerical analysis of errors inherent to this FDTD method shows that the attenuation term imposes additional stability constraints on the FDTD algorithm. Comparison of FDTD results for models with and without attenuation shows that the predicted transmission losses for the attenuating media agree with those computed from synthesized waveforms.
Modal processing for acoustic communications in shallow water experiment
Authors: Morozov Andrey K. , Preisig James C. , Papp Joseph
Published: September 2008

Acoustical array data from the Shallow Water Acoustics experiment was processed to show the feasibility of broadband mode decomposition as a preprocessing method to reduce the effective channel delay spread and concentrate received signal energy in a small number of independent channels. The data were collected by a vertical array designed at the Woods Hole Oceanographic Institution. Phase-shift Keying (PSK) m-sequence modulated signals with different carrier frequencies were transmitted at a distance 19.2km from the array. Even during a strong internal waves activity a low bit error rate was achieved.
Geoacoustic inversion using combustive sound source signals
Authors: Potty Gopu R. , Miller James H. , Wilson Preston S. , Lynch James F. , Newhall Arthur
Published: September 2008

Combustive sound source (CSS) data collected on single hydrophone receiving units, in water depths ranging from 65to110m, during the Shallow Water 2006 experiment clearly show modal dispersion effects and are suitable for modal geoacoustic inversions. CSS shots were set off at 26m depth in 100m of water. The inversions performed are based on an iterative scheme using dispersion-based short time Fourier transform in which each time-frequency tiling is adaptively rotated in the time-frequency plane, depending on the local wave dispersion. Results of the inversions are found to compare favorably to local core data.
Analysis of wind-driven ambient noise in a shallow water environment with a sandy seabed
Authors: Knobles D. P. , Joshi S. M. , Gaul R. D. , Graber H. C. , Williams N. J.
Published: September 2008

On the New Jersey continental shelf ambient sound levels were recorded during tropical storm Ernesto that produced wind speeds up to 40knots in early September 2006. The seabed at the position of the acoustic measurements can be approximately described as coarse sand. Differences between the ambient noise levels for the New Jersey shelf measurements and deep water reference measurements are modeled using both normal mode and ray methods. The analysis is consistent with a nonlinear frequency dependent seabed attenuation for the New Jersey site.
Seabed acoustics of a sand ridge on the New Jersey continental shelf
Authors: Knobles D. P. , Wilson P. S. , Goff J. A. , Cho S. E.
Published: September 2008

Acoustic measurements were made on a sand ridge on the New Jersey continental shelf. Data collected on two L arrays separated by 20km from a single multi-frequency tow suggest small horizontal environmental variability. Values for the sound speed structure of the seabed are extracted by first applying a geo-acoustic inversion method to broadband and narrowband acoustic data from short-range sources. Then, a parabolic equation algorithm is used to properly include the bathymetry and sub-bottom layering. Finally, the frequency dependence of the seabed attenuation is inferred by optimizing the model fit to long-range transmission loss data in the 50–3000Hz band.
In situ measurements of velocity dispersion and attenuation in New Jersey Shelf sediments
Authors: Turgut Altan , Yamamoto Tokuo
Published: September 2008

The existence of acoustic velocity dispersion and frequency dependence of attenuation in marine sediments is investigated using in situ measurements from a wideband acoustic probe system during the Shallow Water 2006 experiment. Direct-path pulse propagation measurements show evidence of velocity dispersion within the 10–80kHz frequency band at two silty-sand sites on the New Jersey Shelf. The measured attenuation in dB/m shows linear frequency dependency within the 10–80kHz frequency band. The measured velocity dispersion and attenuation curves are in good agreement with those predicted by an extended Biot theory [Yamamoto and Turgut, J. Acoust. Soc. Am. 83, 1744–1751 (1988)] for sediments with a distribution of pore sizes.
Mid-frequency acoustic propagation in shallow water on the New Jersey shelf: Mean intensity
Authors: Tang Dajun , Henyey Frank S. , Wang Zhongkang , Williams Kevin L. , Rouseff Daniel , Dahl Peter H. , Quijano Jorge , Choi Jee Woong
Published: September 2008

Mid-frequency (1–10kHz) sound propagation was measured at ranges 1–9km in shallow water in order to investigate intensity statistics. Warm water near the bottom results in a sound speed minimum. Environmental measurements include sediment sound speed and water sound speed and density from a towed conductivity-temperature-depth chain. Ambient internal waves contribute to acoustic fluctuations. A simple model involving modes with random phases predicts the mean transmission loss to within a few dB. Quantitative ray theory fails due to near axial focusing. Fluctuations of the intensity field are dominated by water column variability.
Observation of sound focusing and defocusing due to propagating nonlinear internal waves
Authors: Luo J. , Badiey M. , Karjadi E. A. , Katsnelson B. , Tskhoidze A. , Lynch J. F. , Moum J. N.
Published: September 2008

Fluctuations of the low frequency sound field in the presence of an internal solitary wave packet during the Shallow Water ’06 experiment are analyzed. Acoustic, environmental, and on-board ship radar image data were collected simultaneously before, during, and after a strong internal solitary wave packet passed through the acoustic track. Preliminary analysis of the acoustic wave temporal intensity fluctuations agrees with previously observed phenomena and the existing theory of the horizontal refraction mechanism, which causes focusing and defocusing when the acoustic track is nearly parallel to the front of the internal waves [J. Acoust. Soc. Am., 122(2), pp. 747–760 (2007)].
Short range travel time geoacoustic inversion with vertical line array
Authors: Jiang Yong-Min , Chapman N. Ross , Gerstoft Peter
Published: September 2008

This paper presents travel time geoacoustic inversion of broadband data collected on a vertical line array at short range of 230m during the Shallow Water 2006 experiments. A ray-tracing method combined with a hybrid optimization algorithm that utilizes differential evolution and downhill simplex was used for the inversion of sediment properties. The ocean sound speed profile and geometric parameters were inverted prior to the sea bottom properties to account for the temporally variable ocean environment. The sediment sound speed and thickness estimates are consistent with in situ measurements and matched-field inversion results of longer-range data from the experiment.
Field measurements and modeling of attenuation from near-surface bubbles for frequencies 1–20kHz
Authors: Dahl Peter H. , Choi Jee Woong , Williams Neil J. , Graber Hans C.
Published: September 2008

Measurements of excess attenuation from near-surface bubbles from the Shallow Water '06 experiment are reported. These are transmission measurements made over the frequency range 1–20kHz, and they demonstrate a frequency, grazing angle, and wind speed dependence in attenuation. Data modeling points to bubble void fractions of order 10−6 in effect for wind speeds 10–13m∕s. Simultaneous measures of wind speed made within 1.5 and 11km of the open water experimental location differed by 2m∕s in their respective 30min average; this has cautionary implications for empirical models for bubble attenuation that are a strong function of wind speed.
Mid-frequency acoustic propagation in shallow water on the New Jersey shelf. II. Intensity fluctuation
Authors: Tang Dajun , Henyey Frank S. , Wang Zhongkang , Williams Kevin L. , Rouseff Daniel , Dahl Peter H. , Quijano Jorge , Choi Jee Woong
Published: September 2008

The scintillation index and the intensity cumulative distribution function of mid-frequency (2–10kHz) sound propagation are presented at ranges of 1–9 km in a shallow water channel. The fluctuations are due to water column sound speed variability. It is found that intensity is only correlated over a narrow frequency band (50–200 Hz) and the bandwidth is independent of center frequency and range. Furthermore, the intensity probability distribution peaks at zero for all frequencies, and follows an exponential distribution at small values.
Aspects of Electronic Structure Instability in Search for New Superconductors: Superconducting Boride at Liquid Nitrogen Temperature?
Authors: Baňacký Pavol
Published: September 2008

It has been shown that electron-phonon coupling in superconductors induces temperature-dependent electronic structure instability which is related to fluctuation of analytic critical point of some bands across the Fermi level. The band fluctuation results in a considerable reduction of chemical potential and to breakdown of the adiabatic Born-Oppenheimer approximation. At critical temperature Tc, superconducting system undergoes transition from the adiabatic electronic ground state into the antiadiabatic state at broken symmetry, which is stabilized due to the effect of nuclear dynamics. This effect is absent in non-superconducting compounds. In a good agreement with the experimental Tc of superconducting state transition, the critical temperature of the adiabatic ↔ antiadiabatic state transition has been calculated for three different superconductors. Two hypothetical compounds, LiB and ZnB2, are predicted to be potential superconductors with Tc about 17 and 77.5 K, respectively.
Aluminum Siting in the ZSM-22 and Theta-1 Zeolites Revisited: A QM/MM Study
Authors: Sklenak Stepan , Dědeček Jiří , Li Chengbin , Gao Fei , Jansang Bavornpon , Boekfa Bundet , Wichterlová Blanka , Sauer Joachim
Published: September 2008

The Al siting in the silicon rich ZSM-22 and Theta-1 zeolites of the TON structure was investigated analyzing already published 27Al 3Q MAS NMR experimental data using QM/MM calculations. The results of our computations show that Al atoms can be located in 6 framework T positions because the two eightfold sites (T1 and T2) split into four fourfold T sites after an Al/Si substitution. The observed resonance at 55.5 ppm corresponds to the T4 site which is predominantly occupied by Al. This site is not located on the surface of the TON ten-membered ring channel and thus the protonic sites related with the majority of Al atoms in the TON structure exhibit a significantly limited reaction space. The 27Al NMR signals centered at 57.6 and 58.7 ppm correspond to either the T2 and T3 sites, respectively, or only to T2. The T2 and T3 sites accommodate some 40% and up to 10%, respectively, of Al while the T1 site is unoccupied by Al. Isotropic shifts of 61.1 and 61.6 ppm were calculated for Al atoms located in the T1-1 and T1-2 sites, respectively. The effect of a silanol "nest" as a next-next-nearest neighbor on the 27Al isotropic chemical shift of Al located in the T4 site is calculated to be less than 1 ppm.
Psoas and quadratus lumborum muscle asymmetry among elite Australian Football League players
Authors: Hides J , Fan T , Stanton W , Stanton P , McMahon K , Wilson S
Published: September 2008

Objective

In this study, asymmetry relative to the preferred kicking leg was determined if it exists for the psoas and quadratus lumborum muscles among elite Australian Football League (AFL) players.

Design

AFL players were assessed at three time points from 2005 to 2007 (start of preseason, end of season and end of preseason training). MRI was used to determine the cross-sectional areas (CSAs) of the psoas and quadratus lumborum muscles at the L4–L5 vertebral level (psoas) and the L3–L4 vertebral level (quadratus lumborum).

Setting

MRI was performed in a hospital setting.

Participants

54 professional AFL players were eligible to participate in this study. The number of subjects at each of the three time points was 36 for time 1 (T1 Nov 2005), 31 for time 2 (T2 Aug 2006) and 43 for time 3 (T3 Feb Mar 2007).

Risk factors

The repeated measures factor in the analyses was “asymmetry”, defined as “ipsilateral” or “contralateral” to preferred kicking leg. Number of injuries (coded as 0, 1, 2 or more) was also included as a risk factor.

Main outcome measurements

The dependent variables were the CSAs of the psoas and quadratus lumborum muscles.

Results

At all three time points, the CSA of the psoas muscle was significantly greater ipsilateral to the kicking leg, while the CSA of the quadratus lumborum muscle was significantly greater on the side contralateral to the kicking leg. Asymmetry in muscle size was not related to number of injuries.

Conclusions

Asymmetry of the psoas and the quadratus lumborum muscles exists in elite AFL players.
Molecular phylogeny of the North American eurybioid asters (Asteraceae, Astereae) based on the nuclear ribosomal internal and external transcribed spacersThis paper is one of a selection of papers published in the Special Issue on Systematics Research.
Authors: Selliah Sugirthini , Brouillet Luc
Published: September 2008

The eurybioid asters Oreostemma , Herrickia , Eurybia , and Triniteurybia form a complex that is part of the North American clade of tribe Astereae. They comprise 31 species of perennial herbs that are widely distributed on the continent. Previous analyses had shown poor resolution among the four genera and among the species, particularly within Eurybia (23 spp.), which includes diploids and polyploids. We investigated phylogenetic relationships within the group using the nuclear ribosomal ITS and ETS regions, in separate and combined parsimony and Bayesian analyses. We detected incongruence between the ITS and ETS regions when polyploids were included, and so only diploids were considered in the combined analyses. Eurybia pygmaea (Lindl.) G.L. Nesom is confirmed as a member of Symphyotrichum ; Eurybia is monophyletic once this species is re-classified. The eurybioids form a paraphyletic grade with Oreostemma, sister to the remaining taxa, followed in succession by Herrickia , Eurybia , and Triniteurybia , and with the latter genus sister to subtribe Machaerantherinae. Thus the xeric Machaerantherinae (x = 6, 5, 4) is nested within the grade of mesic eurybioids (x = 9). Although largely grouping together, the polyploid taxa of Eurybia apparently do not constitute a clade and their relationships to the diploid taxa and to each other could not be assessed further. Among the diploids, two clades emerge: one including the western Eurybia integrifolia (Nutt.) G.L. Nesom and Eurybia sibirica (L.) G.L. Nesom, and the southeastern Eurybia eryngiifolia (Torr. & A. Gray) G.L. Nesom; and a second including the western Eurybia radulina (A. Gray) G.L. Nesom, the eastern cordate-leaved (sect. Eurybia) and the narrow-leaved, mostly coastal plain species of Eurybia. Our analyses, therefore, do not support the current classifications of Eurybia.
Black-fruited hawthorns of western North America — one or more agamic complexes?This paper is one of a selection of papers published in the Special Issue on Systematics Research.This paper is dedicated to the memory of the University of Idaho botanist who got us thinking about the complexities of Northwest hawthorns: the late Steven J. Brunsfeld.
Authors: Dickinson Timothy A. , Lo Eugenia Y.Y. , Talent Nadia , Love Rhoda M.
Published: September 2008

Black-fruited hawthorns in North America comprise two taxonomic groups within the genus Crataegus , section Brevispinae and section Douglasianae. The first of these has recently been shown to be monospecific, consisting of the blueberry haw, Crataegus brachyacantha Sarg. & Engelm., of Louisiana and Texas. Crataegus section Douglasianae, however, comprises several taxa in a single clade that is not closely related to section Brevispinae, and that is now one of the best-studied groups of hawthorns at least in North America. Most taxa in the group are found in, or west of, the Rocky Mountains. They include diploids, triploids, and tetraploids that can be ascribed to four or more species that differ in distribution and ecology, thorn morphology, leaf shape, and floral architecture. Diploids are self-incompatible, whereas polyploidy is associated with pseudogamous, gametophytic apomixis and self compatibility. Molecular data suggest that polyploids have arisen repeatedly, both within and from crosses between ploidy levels. We suggest that Crataegus section Douglasianae represents at least two agamic complexes that may serve as models for understanding the biology of, the relationships within, and the appropriate taxonomic treatment of other such groups that may make up much of the rest of the genus.
Systematics of three North American polyploid arctic alkali grasses (Puccinellia, Poaceae): morphology, ploidy, and AFLP markersThis paper is one of a selection of papers published in the Special Issue on Systematics Research.
Authors: Consaul Laurie L. , Gillespie Lynn J. , Waterway Marcia J.
Published: September 2008

We used flow cytometry, amplified fragment length polymorphisms (AFLP), and macromorphology from field and common garden specimens to delimit and identify parental taxa of three polyploid species of Puccinellia from the North American Arctic. Tetraploid Puccinellia bruggemannii T.J. Sørensen, hexaploid Puccinellia angustata (R. Br.) E.L. Rand & Redfield, and octoploid Puccinellia andersonii Swallen were generally separable based on ploidy and AFLP pattern, and showed allopolyploid origin. All three shared AFLP bands with at least two diploids and with Puccinellia phryganodes (Trin.) Scribn. & Merr., shown here to have both triploid and tetraploid populations in Canada. Approximately 10% of hexaploid individuals had AFLP patterns that were intermediate between P. angustata and P. bruggemannii, or P. angustata and P. andersonii, and occupied corresponding intermediate positions in morphological ordinations. Geographic distributions provide better support for introgression than for multiple polyploid events to account for these intermediate patterns. In common garden experiments, half of the characters had significantly different values between field and common garden specimens, but these plastic characters varied depending on the species pair analyzed and between experiments. Moreover, several characters were significantly different among species, but these characters were also different in each of the two experiments. Given this variation, we pooled the field and common garden data to determine important key characters by discriminant analysis of species pairs.