bluuebunny/crossref_metadata_2025 huggingface dataset:
Transverse vibration of prestressed beams: An experimental technique for the determination of dynamic viscoelastic material properties of tissue mimicking materials
Authors: Yazicioglu Yigit , Martin Bryn A. , Navarro-Castillo Karen , Kutluay Umit , Royston Thomas J.
Published: May 2008

An experimental dynamic material property identification technique is presented that is based on the theoretical formulations of a vibrating prestressed beam. The technique determines the viscoelastic material properties of tissue mimicking materials that govern their dynamic behavior. Results are presented for silicone-based materials (Sylgard 184, Dow Corning, Midland, MI) that are formed in the lab using a range of mixing ratios and cast in the form of a thick string held between fixed supports under tensile pre-stress. The specimens are excited through the transverse harmonic displacement of the boundary. Transverse vibration at an arbitrary location is measured and compared with theory to identify material viscoelastic moduli valid up to at least several hundred Hertz. The presented technique can aid in providing accurate viscoelastic parameter values for phantoms that are used in the development of a range of medical diagnostic techniques that attempt to identify pathology or tissue differentiation via changes in mechanical stiffness and viscosity.
Acoustical requirements of classrooms and new concepts of teaching
Authors: Eggenschwiler Kurt , Cslovejcsek Markus
Published: May 2008

In recent years acoustic requirements for classrooms were published in various guidelines. Of course it is important that the present knowledge will be implemented, but how should this be done? And what is the correspondence of acoustic requirements and new concepts of learning? These questions are the basis of a cooperation of the Laboratory of Acoustics at Empa, Dübendorf and the School of Teacher Education, Aarau in Switzerland. The cooperation itself is one possibility to transfer knowledge. In addition it was planned but not yet realized to develop concepts of knowledge transfer by student work (diploma thesis). Classroom acoustics were discussed in seminars and there were completed some diploma theses. One project dealt with the acoustic problems of a new teaching concept. Part of the concept is that teaching of four groups of pupils takes place in three classrooms and in the corridor. The doors of the classrooms remain open and at the same time pupils work individually, in groups, and a small group is instructed by a teacher. There were found suggestions for improving the acoustics, but for different reason the realization was not possible.
Beam-forming and dispersion measurements at the edge of a pine forest
Authors: White Michael J. , Swearingen Michelle E.
Published: May 2008

Beam-forming analyses were performed on four-microphone linear arrays placed just within the interior of a pine forest to separate signal arrivals by direction from an impulsive sound source in an open field. The arrays were deployed in three configurations: transverse, longitudinal, and vertical. The arrays spacings were organized in a pattern that provides six baselines with four microphones. Longitudinal and transverse configurations show arrivals scattered from trunks, and the vertical configurations indicate some refraction and scattering by the canopy. Signal dispersion curves developed using the four-microphone arrays had greater variation in trace velocity at higher frequencies in each configuration.
Use of the transmission line matrix method for the sound propagation modeling in urban area
Authors: Guillaume Gwenaël , Picaut Judicaël , Dutilleux Guillaume
Published: May 2008

This paper deals with the sound propagation modeling in urban area. This problematic requires to take into account many phenomena that can have a substantial impact as well in semienclosed spaces as on long-range outdoor sound propagation, such as reflections and absorption on the frontages and on the ground, atmospheric attenuation, sound velocity variations related with wind and temperature vertical gradients, atmospheric turbulences. The numerical method used is the TLM (transmission line modeling), which has been originated in electromagnetism and adapted for acoustics applications. It consists in a physical rendering of the waves propagation based on the Huygens' principle. It is established on a spatiotemporal discretization of the domain using an iterative temporal process for sound pressure propagation, instead of the resolution of mathematical equations. The TLM model has then been developed in two and three dimensions allowing to combine all the phenomena affecting the sound propagation in urban area. Numerical simulations are given for canyon streets.
Predictions of sound pressure levels in streets using a diffusion model: numerical validations and experimental comparisons
Authors: Billon Alexis , Picaut Judicaël
Published: May 2008

Predictions of sound propagation in urban areas have attracted a considerable over the years. If the sound energy is assimilated to particles with a constant energy, their movement can be described by a transport equation. In canyon streets, this transport equation can be reduced to a diffusion equation whose expression is more simple. In this presentation, sound absorption at the boundaries (buildings facades and ground), as well as atmospheric sound attenuation are introduced. The problem is then solved numerically using a finite elements method for the configuration of a canyon street. A systematic validation of the obtained model is carried out in terms of sound pressure level by comparison to numerical simulations taken from the literature. Comparisons with experimental data are then conducted. Finally, applications in more complex configurations are presented.
Numerical prediction of the effect of traffic lights on the vehicle noise at urban street intersections
Authors: Parrondo Jorge , Zurita Ruben , Corrales Jose A. , Fernandez Joaquin
Published: May 2008

Intersections of urban streets are particularly noisy locations due to the addition of the noise from vehicles at different streets, a long period of noise emission from queuing vehicles with traffic lights in red and the noise from accelerating vehicles. Besides, the traffic lights impose a modulation in the passage of the vehicles, so that the subsequent noise variability along time contributes to increase the annoyance degree. This paper presents a code especially developed to simulate both the spatial and temporal distribution of the sound pressure levels induced by the vehicle traffic in street intersections. The algorithm combines a traffic model with vehicles in dynamic motion through the domain with a model for sound propagation, based on the method of virtual images in which the determination of the location of the successive image sources was reduced to a reference horizontal plane. Sound emission from each vehicle was established according to the Harmonoise guidelines. After verifying the code predictions by comparison with measurements at several street intersections, the method was applied systematically to investigate the effect of varying the regulation parameters of the traffic lights on the Leq and L10 distributions for some particular cases.
An integrated multimodal acoustic particle manipulator and optical evanescent field waveguide
Authors: Glynne-Jones Peter , Hill Martyn , Townsend Rosemary J. , Harris Nicholas R. , Wilkinson James S. , Zhang Fan , Melvin Tracy
Published: May 2008

A new acoustic/optical/microfluidic system is presented for the manipulation of bead-tagged DNA molecules. Acoustic radiation forces are used to manipulate microspheres into and away from the evanescent field of a laser coupled waveguide that is integrated into the reflector of the acoustic chamber. With suitable fluorophores the presence of the target DNA can be detected with a fluorescence microscope enabling large populations of beads to be examined simultaneously. The integrated waveguide and multimodal acoustic chamber are presented here, with results showing that the microspheres can be successfully detected as they are brought into the evanescent field using a quarter-wave acoustic configuration. It is also shown that by measuring the time of flight of a microsphere between the half- and quarter-wave nodal planes the bead size can be determined, providing a means of multiplexing the detection (detecting a range of different target DNA sequences).
Effect of intense neutron dose radiation on piezoceramics
Authors: Augereau Franck P. , Ferrandis Jean-Yves , Villard Jean-François , Fourmentel Damien , Dierckx Mark , Wagemans Jan
Published: May 2008

Four grades of commercial PZT materials have been exposed to nuclear radiation during five months in an irradiation channel of the BR1 research reactor at SCK̇CEN (Belgium). This experimental study was performed in the framework of the Joint Instrumentation Laboratory with the CEA French Commission of Atomic Energy to validate these materials for future applications in severe conditions such as online measurements in irradiation experiments performed in research reactors. For this purpose, thin piezoelectric discs were irradiated while a remote network analyser continuously monitored the frequency response of their electrical impedance. The total neutron dose has reached a level of 1.5.1017 neutrons/cm2. Positive and negative shifts of the peak resonance frequency have been recorded but in any case with a variation lower than 1%. On the other hand, the amplitude of the electrical impedance at resonance frequency has largely decreased with even a reduction by factor two or three for some piezoelectric cells. Transitory effects have also been detected for these two parameters as function of the reactor activity. Additional thermal and gamma radiation effect have been investigated. Similarly, some piezoelectric cells glued on glass delay line have been tested with satisfactory results to these stresses.
An automated 3 dimensional scanning system for validation of acoustical simulation results
Authors: Simonaho Simo-Pekka
Published: May 2008

To validate acoustical simulation results, a great number of measurement points are needed especially in 3 dimensional cases. These measurements can be extremely laborious when done manually. Also, the spatial information of the measurement points has to be accurate. In this work, an automated 3-D scanning system with high spatial resolution for validation of acoustical simulation results is introduced. The system consists of a multi channel data acquisition hardware, a microphone array and a 3-D scanning system. The movement of the microphone array is controlled by the data acquisition hardware. The performance of the automated 3-D scanning system is demonstrated and the experimentally measured pressure fields are compared to simulation results.
Phoneme confusions as a function of noise, spectral resolution and L2 experience
Authors: Shannon Robert , Padilla Monica
Published: May 2008

Consonant and vowel confusion matrices were measured from normal hearing listeners with varying degrees of experience in English. There were five listeners each in the following categories: native English speakers, and Spanish speakers who were immersed in English at the ages of 0-5 years, 5-10 years, 10-18 years, and over 18 years. 12 vowels (hVd) or 18 consonants (vCv) were presented and responses were collected in a confusion matrix. Spectral resolution was varied by using a noise-band vocoder with 2, 4, 6, 8, and 16 channels, as well as unprocessed speech. All stimuli were presented in speech shaped noise at SNR levels of -5 dB to +15 dB in 5 dB steps as well as in quiet. Noise and spectral resolution had a similar effect on voicing, manner and place of articulation, and also had similar effects as a function of L2 experience. For native speakers of Spanish the duration of L2 experience had the largest effect on voicing cues, less effect on manner cues, and almost no effect on place cues.
Amplitude modulation of noise cues voicing distinction in fricatives
Authors: Pincas Jonathan , Jackson Philip J.
Published: May 2008

The aperiodic noise source in fricatives is characteristically amplitude modulated by voicing. Previous psychoacoustic studies have established that observed levels of AM in voiced fricatives are detectable, and its inclusion in synthesis has improved speech quality. Phonological voicing in fricatives can be cued by a number of factors: the voicing fundamental, duration of any devoicing, duration of frication, and formant transitions. However, the possible contribution of AM has not been investigated. In a cue trading experiment, subjects distinguished between the nonsense words “ahser” and “ahzer.” The voicing boundary was measured along a formant-transition duration continuum, as a function of AM depth, voicing amplitude and masking of the voicing component by low-frequency noise. The presence of AM increased voiced responses by approximately 30%. The ability of AM to cue voicing was strongest at greater modulation depths and when voicing was unavailable as a cue, as might occur in telecommunication systems or noisy environments. Further work would examine other fricatives and phonetic contexts, as well as interaction with other cues.
Statistical conversion of speech parameter trajectory for mapping between features of different modalities
Authors: Toda Tomoki
Published: May 2008

A state-of-the-art speech parameter conversion technique and its application to a mapping between features of different modalities are reviewed. Many statistical approaches to the parameter conversion have been studied particularly for voice conversion in speech synthesis research. A typical method conducts the parameter conversion frame by frame based on the minimum mean square error using a Gaussian mixture model of the joint probability density of input and output parameters [Y. Stylianou et al., IEEE Trans. SAP, 6(2), 131-142 (1998)]. Although this method is reasonably effective, the deterioration of the conversion accuracy is caused by essential problems of the frame-based conversion process. Recently a conversion method based on the maximum likelihood estimation of a parameter trajectory has been proposed [T. Toda et al., IEEE Trans. ASLP, 15(8), 2222-2235 (2007)]. This method realizes the appropriate converted parameter sequence by (1) using not only static but also dynamic feature statistics and (2) considering a global variance feature of the converted parameters. It has been reported that this method is effective in several applications such as a spectral determination from articulatory movements, an acoustic-to-articulatory inversion mapping, and a conversion of body-transmitted speech into air-transmitted speech.
Audiovisual automatic speech recognition: Progress and challenges
Authors: Potamianos Gerasimos
Published: May 2008

The paper overviews recent progress and challenges in a number of audiovisual speech processing technologies with main emphasis on the problem of automatic speech recognition. It is well known that visual channel information can improve automatic speech processing for human-computer interaction. To automatically process and incorporate such information into automatic systems, a number of steps are required that are surprisingly similar accross speech technologies. Crucial above all is the issue of feature representation of visual speech and its robust extraction. In addition, appropriate integration of the audio and visual representations is required, in order to ensure improved performance of the bimodal systems over audio-only baselines. These topics are discussed in detail in the talk, with main emphasis on their application to the speech recognition problem in the challenging environments of automobiles and smart rooms.
Analysis and synthesis of nonverbal facial motion
Authors: Beskow Jonas , Granström Björn
Published: May 2008

Until recently, most efforts in audio-visual speech synthesis have been concerned with verbal content. However, in human-human communication it is obvious that nonverbal signals plays an important role, such as when expressing emotions and attitudes. Interaction is also often regulated using facial cues, for example gaze, head and eyebrow movements. Some of these cues have a direct coupling to the speech signal, while other occur during both while speaking and listening. When applying interactive talking agents in man-machine systems, nonverbal signals may be very important in easing the flow of communication. In a series of experiments we have been exploring the function of nonverbal facial motion. These studies include an experiment on the interaction between expressive speech and prominence, as well as an attempt to synthesize emotions and attitudes in a talking head, using 3D motion capture data. Further we will report on a real-time experiment with human-human avatar-mediated conversation, where the subjects' turn-taking behavior is affected by facial motion in the avatars.
Multiple forward scattering through an ocean waveguide with 3D random inhomogeneities
Authors: Makris Nicholas , Ratilal Purnima , Chen Tianrun
Published: May 2008

Analytic expressions have been derived for the mean and spatial covariance of the acoustic field multiply forward scattered though a stratified ocean waveguide containing 3D random surface or volume inhomogeneities [Ratilal and Makris, J. Acoust. Soc. Am. 118, 3532-3559 (2005)]. These expressions are further used to derive the temporal coherence of an acoustic signal propagated through 3D random inhomogeneities. Field moments are given in terms of moments of the scatter function density of the 3D random inhomogeneities, which enables straightforward application to a broad range of 3D scatterers. Here we give examples of the attenuation, dispersion and loss of temporal coherence expected after multiple forward scattering through (1) random internal waves in both continental shelf and deep ocean environments, (2) fish schools, and (3) random wind-generated bubbles in continental shelf and surf-zone area. We show that 3D scattering effects become important when the Fresnel width exceeds the cross-range coherence scale of the inhomogeneities, and can lead to substantial power loss.
Using parallel programming and a three-dimensional visualization cave to map the acoustic energy distribution from a seismic array in the ocean
Authors: Sidorovskaia Natalia , Tashmukhambetov Arslan , Ioup George E. , Ioup Juliette W.
Published: May 2008

Modeling and visualization of the dynamic acoustic field during a seismic exploration survey represent a computational challenge due to broadband, directional nature of the acoustic signal radiated by a seismic array. Standard acoustic propagation models (RAM and SWAMP) are upgraded for parallel processing and tested in the LONI (the Louisiana Optical Network Initiative) environment, using the Louisiana fiber optics grid computing network to model the three-dimensional time-varying acoustic field in the ocean during a seismic exploration survey. The generated volume of data is transferred and visualized in the advanced immersive visualization environment, supported by Louisiana Immersive Technology Enterprise (LITE) facilities. The proposed technology is one of the first steps in developing real-time monitoring of the acoustic energy distribution in a large oceanic volume. This can be beneficial for environmental impact assessment and regulation and for seismic survey design. [Research supported in part by the Joint Industry Project through OGP and by ITI of University of Louisiana at Lafayette.]
Acoustic mode beam effects of nonlinear internal gravity waves in shallow water
Authors: Duda Timothy , Lin Ying-Tsong , Lynch James F.
Published: May 2008

Ducting of sound between short-wavelength nonlinear internal gravity waves in coastal environments has been demonstrated by substantial evidence. The ducting takes a unique form for each of the acoustic normal modes. Some consequences of this are examined here using three-dimensional parabolic equation modeling and theory. For a pair of waves having a broadband 200-Hz source placed between (i.e., in the duct), strong interference patterns within the duct are developed for each mode after a few kilometers. Some of the energy escapes at high angle with respect to the duct direction. Termination of the internal wave duct, an observed feature, results in beams of energy unique to each mode to radiate outward. Specific cases having water depths of order 80 m and propagation distances of 20 to 30 km are examined. Situations where one or more modes are completely absent at selected positions are compared with similar events observed in the field.
Measurement and modeling of targets deployed on and within sand sediments
Authors: Williams Kevin L. , Thorsos Eric , Kargl Steven , Lopes Joseph , Lim Raymond , Dowdy Carrie
Published: May 2008

Acoustic signatures of elastic targets located near sediment interfaces include effects due to energy interacting with the sediment. Therefore, modeling target response also requires models of scattering from, penetration into and propagation within ocean sediments. We first describe at-sea and test pond measurements carried out on “proud” (target resting on the sediment) and buried targets at frequencies in the range of 2 to 50 kHz. The results from some of these measurements are then compared to models incorporating various levels of sophistication relative to both the target and the sediment physics. The modeling hierarchy includes the following: (1) simple sonar equation estimates that treat the target physics via a frequency dependent target strength and use formally averaged results for sediment scattering, (2) realization level modeling that allows calculation of sediment and target scattering for individual pings with sufficient fidelity to carry out synthetic aperture processing (for a proud target only its geometrical scattering is considered while the elastic response can be included for a buried target), (3) T-matrix and finite element modeling in which the target elastic response is included but sediment scattering is treated using formal averages and/or flat surface approximations. [Work supported by the Office of Naval Research and the Strategic Environmental Research and Development Program, USA.]
Target detection of man made objects in side scan sonar images - segmentation based false alarm reduction -
Authors: Neumann Max , Knauer Christian , Nolte Bodo , Brecht Dieter , Jans Wolfgang , Ebert Alfons
Published: May 2008

This paper presents a fast and robust algorithm for significantly reducing the number of false detections caused by screening algorithms for side scan sonar (SSS) images. The presented algorithm consists of two processing steps. First, an iterative segmentation process is carried out for seperating the image into shadow and background. This segmentation is based on an energy function which combines the local neighborhood segment information and the amplitude of a pixel. By minimizing this function, a clear shadow, the most significant target characteristic, will be extracted. Second, based on the region of interest (ROI) and the shadow contour, a robust classification approach is applied, utilizing the area of the shadow, the first two statistical moments of the pixel amplitude and the existence of parallel lines (Hough transformation). This algorithm was tested using a data set with approx. 2400 ROIs containing about 200 targets and 270 targetlike stones or sandrippel. This data set was gathered during five different measurement campaigns in the Baltic Sea and the Mediterranean Sea using three different SSS systems Benthos C3D, Klein2000 and Marine Sonics). These data were collected by FWG and WTD71 as well as by Atlas Electronik with the SeaOtter MK1 AUV.
MCM sensor requirements: performance measures
Authors: Dugelay Samantha
Published: May 2008

This paper presents a comparison of two measures of performance suitable to characterise operational performance of mine hunting sonars in various environmental conditions. The first measure is a direct adaptation of information theory and bounds the capability of a sonar to distinguish between objects, i.e., a classification capability. The bounds take into account the amount of distinguishable pixels between objects and the statistical information content of each pixel. Successfully applied in Radar, this approach has also demonstrated the performance of synthetic aperture sonar at NURC using a Rayleigh distribution for statistical pixel distribution. The measure is now being further developed to include high resolution distributions such as K-law which readily appear in high resolution images. The second measure, Johnson's criteria aims to provide guidance on resolution required for operator detection, classification and identification. This measure originally derived from experiments on night vision images is now being modified to simultaneously incorporate target highlight and shadow information in varying environmental conditions. Finally, the predictions of these measures will in the future be compared to each other and to current system performances.
Multiple-sensor fusion approach to seabed classification
Authors: Zerr Benoit , Kerneis David , Solaiman Basel
Published: May 2008

Seabed classification is key issue for civilian and military underwater applications, from offshore exploitation to mine counter measure. Most of the existing automated classification techniques relies on the analysis of the data provided by a single sensor, supposed to unambiguously separate the different classes of seabed. In this paper we present a different approach which considers that, even if a sensor cannot tell the differences between two classes, classification will improve by considering that the seabed belongs to one of these two classes, and, further, that the analysis of the data from another sensor can resolve the ambiguity. For each sensor, the classification is achieved in a conventional way by feature extraction and supervised classification. The fusion of the results implements the theory of evidence through Dempster-Shafer method. After a description of the method, the paper discusses the experimental results from the fusion of information delivered by three sensors: an imaging sidescan sonar, a vertical echo sounder and an interferometric bathymetric sonar. The major part of the experimental data has been acquired by towed or hull mounted sensors. As these sensors are a subset of the payloads operated simultaneously by the new DGA-SHOM DAURADE AUV, preliminary seabed classification results in covert REA missions will also be presented and discussed.
The research on measuring the coefficient of sound absorption in turbid seawater
Authors: Li Qi , Liu Yongwei
Published: May 2008

When naval mine-hunting sonars and side-scan surveying sonars operating at 20∼60 kHz are working in shallow coastal waters, the visco-thermal absorption of sound by suspended mud in the water may greatly decrease their detection properties. This kind of water is also characterized as turbid seawater. However, the research on measuring the coefficient of sound absorption in turbid seawater has little been done. The main difference between turbid seawater and clear seawater is that there are mud particles suspending in turbid seawater. It is also the main reason why sound absorption in turbid seawater is greater than that in clear seawater. In the paper, the coefficient of sound absorption at 20̃60 kHz in turbid seawater has been measured by the reverberation technique. Results demonstrate that if the concentration of the mud is bellow 0.11 kg/m3, the mud in turbid seawater doesn't cause additional absorption. When the concentration of the mud is between 0.14 and 0.49 kg/m3, the coefficient of sound absorption in turbid seawater is as twice at least as that in clear seawater.
Growth and wood quality of young loblolly pine trees in relation to stand density and climatic factors
Authors: Cregg B. M. , Dougherty P. M. , Hennessey T. C.
Published: May 2008

A 10-year-old stand of loblolly pine (Pinustaeda L.) in southeastern Oklahoma was thinned to three target basal-area levels: 5.8, 11.5, and 23 m2•ha−1 (control). Specific gravity, latewood percentage, date of transition from earlywood to latewood, growth, and climate variables were measured for 2 years after thinning. Variation in the measured wood properties was more influenced by climatic variation than by the thinning treatments. Diameter growth and per-tree basal-area growth were significantly greater on the thinned treatments both years after thinning. However, stand basal-area growth was greatest on the unthinned treatment. Basal-area growth rates were significantly related to stand basal area, tree size, soil water potential, and air temperature. Early in the summer, growth was positively related to mean daily temperature, while later in the summer, growth was negatively related to mean daily temperature, reflecting the influence of high-temperature stress on growth. A year with high summer rainfall (1984) resulted in wood with a higher percentage of latewood and higher specific gravity than wood produced in a year with low summer rainfall (1985). The date of latewood initiation was significantly related to tree size, soil moisture, and evaporative demand. The date of transition from earlywood to latewood occurred 10–14 days sooner on the unthinned plots in both years. However, annual ring latewood percentage and specific gravity were not significantly affected by thinning. Increased late-season growth rates compensated for the later transition date on the thinned treatments, resulting in no net change in ring latewood percentage due to thinning. The results indicate that individual tree basal-area growth can be increased by thinning without reducing wood density.
Understory plant community classifications as predictors of forest site quality for lodgepole pine and white spruce in west-central Alberta
Authors: La Roi George H. , Strong Wayne L , Pluth Donald J.
Published: May 2008

Understory vegetation of 103 lodgepole pine (Pinuscontorta Loudon var. latifolia Engelm.) and white spruce (Piceaglauca (Moench) Voss) stands, 70–150 years old, in a 16 000 km2 region of west-central Alberta was classified by 14 methods using species cover or log2 cover classes. Six classifications, including five selected by dendrogram and ordination elucidation of understory community types (UCTs), were evaluated by analysis of variance to identify UCTs with significantly different site indices of pine and spruce. Each classification consists of three to five UCTs, referable to two forest types, both levels distinguished by differences in constancy and cover of understory species. Significant differences (P < 0.05) in pine site index at 70 years occur between UCTs belonging to the same and different forest types, using divisive two-way indicator species analysis (TSL) and agglomerative furthest neighbour (FNL) and minimum variance (MVL) cluster analysis classifications, all based on log2 cover classes. Comparable differences between UCTs for spruce occur within one forest type, using FNL, MVL, and minimum variance cluster analysis based on raw percent cover (MVR). Ordination of stands based on understory species cover reveals that spatially segregated UCTs usually have significantly different site indices. If a single classification method is desired for both lodgepole pine and white spruce, MVL appears most suitable for predicting site indices in the region.
Asymmetric, two-sided competition in even-aged monocultures of red pine
Authors: Brand David G. , Magnussen Steen
Published: May 2008

A framework for analysis of even-aged plant monocultures was developed and used to examine hypotheses on the process of competition, using data obtained from three independently established red pine (Pinusresinosa Ait.) stand-density experiments. Growth rate and relative production rate (a measure of tree vigour) were computed for the individual trees in stands of differing density at points in time when these stands had the same mean stem volume. Competition is shown to be both asymmetric (small trees lose vigour more rapidly than large trees as density increases) and two-sided (not only do larger trees affect smaller trees, but to some degree small trees also cause growth reduction in larger neighbours). Increasing density results in increased size inequality as smaller trees lose vigour and become suppressed. The asymmetric, two-sided competition process in red pine stands is considered ecologically inherent for a species adapted to existence in even-aged monocultures.
Influence of stand density on log quality of lodgepole pine
Authors: Ballard Louis A. , Long James N.
Published: May 2008

We examined the relationship between stand density and stem quality characteristics for lodgepole pine (Pinuscontorta). The influence of initial stand density on end of rotation log quality was inferred by analyzing data from unmanaged, rotation-age stands. Quality characteristics examined included first log branch diameters, taper, wood density, and the proportion of sapwood. After differences in diameter at breast height were accounted for, only branch size was strongly influenced by stand density. A strong negative exponential relationship was found between the mean of the five largest branches per first log and number of trees per hectare.
Rate of increase of black-stain root disease in Douglas-fir plantations in Oregon and Washington
Authors: Hansen Everett M. , Goheen Donald J.
Published: May 2008

Spread of black-stain root disease, caused by Verticicladiellawageneri Kendrick, was monitored for 10 years in 27 infection centers in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) plantations in western Oregon and Washington. The number of trees killed by black stain increased 4.4 times over the 10-year interval. Mortality increased 3.1 times in the first 5-year interval but only 1.4 times in the second 5 years. Infection centers expanded at an average radial rate of 0.9 m/year in the first 5 years and 0.4 m/year in the second, but only 31% of crop trees were killed within infection centers. The rate of disease increase within established infection centers decreased with stand age.
Longevity and duration of radial growth in Douglas-fir branches
Authors: Kershaw Jr. John A. , Maguire Douglas A. , Hann David W.
Published: May 2008

Duration of branch radial growth and longevity were summarized for 2153 branches immediately below the current live crown of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees in southwestern Oregon. Branch longevity averaged 24 years with a range of 4 to 72 years. The number of years without perceptible (13 × hand lens) annual branch radial growth averaged 8 years with a range of 0 to 49 years. Expressed as a percentage of branch longevity, the period lacking perceptible radial growth ranged from 0 to 93% with an average of 34%. As would be expected, greater longevity implied survival deeper into the crown; average percentage of longevity without radial growth also decreased with increasing depth into crown. The implications of branch growth patterns to stem growth and wood quality are discussed.
Effect of ozone and aluminum on pitch pine (Pinusrigida) seedlings: growth and nutrient relations
Authors: Schier George A. , McQuattie Carolyn J. , Jensen Keith F.
Published: May 2008

Newly germimated pitch pine (Pinusrigida Mill.) seedlings inoculated with a mycorrhizal fungus (Pisolithustinctorius (Pers.) Coker & Couch) were grown for 13 weeks in sand irrigated with nutrient solution (pH 4.0) containing 0, 12.5, 25, 50, or 100 mg/L of aluminum (Al) in growth chambers fumigated with 0, 50, 100, or 200 ppb ozone. Increasing the concentration of ozone or Al caused increasing reductions in needle length, seedling height, and biomass of needles, stems, and roots. Significant ozone × Al interactions indicated that ozone and Al were interacting synergistically in reducing growth. Effect of treatments on the root/shoot ratio demonstrated that shoot growth was more sensitive to Al than root growth, whereas root growth was more sensitive to ozone. The concentration of most mineral elements (P, K, Ca, Mg, Mn, Cu, Zn) in needles was reduced by ozone or Al. Iron was the only element that increased with increasing concentrations of ozone or Al.
Estimation of leaf weight of standing trees of Eucalyptusregnans
Authors: West P. W. , Wells K. F.
Published: May 2008

A model was developed to estimate total leaf dry weight of individual standing trees of Eucalyptusregnans F. Muell. in even-aged, monoculture stands aged 8–20 years. Tree biomass data were collected for a sample of 42 trees from four plots at three sites in Victoria and Tasmania. One plot had been heavily thinned 10 years prior to sampling. The model was based on the pipe model theory, L(x) = as(x)p(x), where L(x) is leaf dry weight above some height (x), s(x) and p(x) are, respectively, stem sapwood area and permeability at x, and a is a parameter. Permeability is known to vary with site and tree conditions, and an empirical model was developed that replaced ap(x) in the pipe model theory with a function in terms of tree age, diameter at breast height over bark, and distance along the stem from the tip of the tree. The resulting model to predict leaf weight appeared to be unbiased across sites, among trees within sites, and with respect to thinning treatment. It was found that given a prediction from the model of total leaf dry weight of one tree, it could be assumed with 95% confidence that the true value of leaf weight fell within an interval bounded by values of −60 to +76% of the estimate. When the model was used to predict stand leaf weight by summing estimates from many individual trees, the interval was bounded by minimum values of −3 to +19% of the stand estimate. These errors of estimate were probably conservative. It appeared that errors of similar magnitude may apply to other published models of this type.
Effect of seed provenance and fungal species on bead formation in roots of Piceamariana seedlings
Authors: Thomson J. , Matthes-Sears U. , Peterson R. L.
Published: May 2008

The effects of both seed source and fungal species on the formation of beads in roots of Piceamariana (Mill.) B.S.P. were examined. Seed was collected from two sites near Chapleau, Ontario. One provenance was an upland site with sandy soil, the second a lowland site with peaty soil. Seedlings were grown under aseptic conditions in test tubes and inoculated with either Laccariabicolor (Maire), Laccarialaccata (Scop, ex Fr.), Laccariaproximo (Boud.) Pat., or agar plugs. Each constriction or striation on the root was counted as a single bead. These constricted regions were associated with the accumulation of a darkly stained substance and the absence of a Hartig net. Bead formation on first order lateral roots from each treatment was assessed and the data were analyzed for significance with a two-way factorial ANOVA. There was a significant interaction between seed source and fungal species on the numbers of beads formed. Bead formation was significantly more common on the lowland seed source in the L. laccata treatment only. L. laccata inoculation resulted in the greatest number of beads on first order lateral roots followed by control and L. proximo treatments. Colonization of seedlings with L. bicolor resulted in the formation of significantly fewer beads than in the control or any other treatment.
Time- and pH-dependent leaching of ions from deciduous and coniferous foliage
Authors: Puckett L. J.
Published: May 2008

Leaching of ions from foliage of black gum (Nyssasylvatica Marsh.), chestnut oak (Quercusprinus L.), and white pine (Pinusstrobus L.) in response to increasing exposure time to and concentration of H+ was examined in a laboratory study. Ten individual leaves and needle bundles were exposed to H+ solutions at pH 3.0, 4.0, and 5.6 for periods of 5, 50, 500, and 1000 min. Increases in the removal of Ca2+ and Mg2+ from all species tested were strongly related to increases in experiment duration and H+ concentration, confirming the role of ion exchange in the removal of these ions from the forest canopy. Removal of Na+ and K+ did not appear to be strongly influenced by ion exchange. Positive relations between SO42− and H+ (and presumably Cl−) for the deciduous species suggest that anion exchange may be involved in the removal process. Given the relatively small number of anion exchange sites on cuticles, and because SO42− is the primary anion in both rain and throughfall, anion exchange is not likely to contribute significant amounts of anions under natural conditions. It is difficult to extrapolate results from an experiment of this type to what might be expected under natural conditions. However, the response of whole leaves and needles fits that expected based on the ion selectivity of the cuticle as a carboxylic acid ion-exchange medium and holds promise for understanding the processes involved in ion leaching from forest canopies.
Determination of the origin of Widdringtonianodiflora on Zomba Mountain in Malawi by the aid of allozymes
Authors: Kananji Bakali
Published: May 2008

Five enzymes (α-esterase, β-esterase, glutamic-oxaloacetic transaminase, malate dehydrogenase, and 6-phosphogluconic dehydrogenase) were scored in diploid tissue for 14 loci to determine the probable origin of the seed used to establish the plantation of Widdringtonianodiflora (L.) Powrie on Zomba Mountain, Malawi. Samples were drawn from the Zomba plantation and from Chambe and Thuchila natural forests on Mulanje Mountain. There were departures from Hardy–Weinberg expectations at most loci, which is a result of a deficiency in heterozygotes. Both the unweighted pair group method and single linkage clustering using genetic distances showed that the Zomba Mountain plantation seed source is more closely related to the Chambe population than to the Thuchila population.
Water in the Solar System
Authors: Encrenaz Thérèse
Published: May 2008

Water is ubiquitous in the Universe, and also in the Solar System. By setting the snow line at its condensation level in the protosolar disk, water was responsible for separating the planets into the terrestrial and the giant ones. Water ice is a major constituent of the comets and the small bodies of the outer Solar System, and water vapor is found in the giant planets, both in their interiors and in the stratospheres. Water is a trace element in the atmospheres of Venus and Mars today. It is very abundant on Earth, mostly in liquid form, but it was probably also abundant in the primitive atmospheres of Venus and Mars. Water is found in different states on the three planets, as vapor on Venus and ice (or permafrost) on Mars. Most likely, this difference has played a major role in the diverging destinies of the three planets.
Theory of Metal/Dielectric Interfaces -Breakdown of Schottky Barrier Limits-
Authors: Shiraishi Kenji , Nakayama Takashi , Nakaoka Takashi , Ohta Akio , Miyazaki Seiichi
Published: May 2008

Recent development of VLSI technique requires wide variety of controlled interfaces especially in high-k metal gate technologies. As for metal/dielectric interfaces, they have been intensively studied, and a lot of knowledge and concepts have been proposed so far. In this paper, we point out the breakdown of the two Schottky barrier limits of Bardeen and Schottky limits which has been believed for a long time as the intrinsic limit of Schottky barrier heights, by considering the characteristics of metal density of states and the atomistic structures of metal/insulator interfaces. Moreover, we have experimentally confirmed that Fermi level of Au (typical high work function metal) further lowers, when Au is in contact with HfO2, by photoemission measurements, indicating the breakdown of the Schottky limit.
Application of Synchrotron X-ray Diffraction Methods to Gate Stacks of Advanced MOS Devices
Authors: Shimura Takayoshi , Inoue T. , Okamoto Y. , Hosoi Takuji , Ogura Atsushi , Sakata O. , Kimura S. , Edo H. , Iida S. , Watanabe H.
Published: May 2008

We demonstrate two topics of the application of synchrotron X-ray diffraction methods to thin films used in gate stack structures. One is related to the structural change in the interfacial SiO2 layer between the high-k dielectric layer and the Si substrate. It is shown that O2 molecules dissociate into O atoms during diffusion through the HfO2 layer and these O atoms destroy the ordered SiO2 in the interfacial layer. The other is the characterization of strained Si wafers using a synchrotron X-ray microbeam diffraction and topography. The nonuniformity in micro- and centimeter scales is shown for the SiGe layer of the strained Si wafers.
An Overview of Recent Advances in Metrology Development for Nanoelectronics at the National Institute of Standards and Technology (NIST)
Authors: Obeng Y. , Knight Stephen , Martinez de Pinillos J
Published: May 2008

Nanoelectronics require the introduction of several new uncharacterized material(s) combinations and new processing techniques. The critical metrology and characterization needs of the nanoelectronics industry are being addressed with a broad range of development programs at the National Institute of Standards and Technology (NIST). In this paper, we provide an overview of the recent advances in nanoelectronics enabling metrology developments at NIST. We will discuss a broad range of new techniques, equipment and infrastructure that are being developed to enable atomic and nano-scale measurements. Examples include, but are not limited to: high resolution, low noise techniques and infrastructure for nanoscale chemical analysis; metrology for characterizing device and material intrinsic reliability; electrical, optical and physical characterization of novel materials; and monitoring of processes.
Combinatorial Methodology for the Exploration of Metal Gate Electrodes on HfO2 for the Advanced Gate Stack
Authors: Chang Kao-Shuo , Green Martin , Suehle John S. , Hattrick-Simpers Jason , Takeuchi Ichiro , Ohmori Kenji , Chikyow T. , De Gendt Stefan , Majhi Prashant
Published: May 2008

Combinatorial methodology offers an efficient platform to accelerate the exploration of new materials. We demonstrate the effectiveness of this technique on the study of new metal gates for the advanced gate stack. We report two examples, Ni-Ti-Pt ternary composition spreads, and Ta1-xAlxNy binary composition spreads, using a combinatorial sputtering tool. For the Ni-Ti-Pt library, wavelength dispersive spectroscopy (WDS), and scanning x-ray microdiffraction spectroscopy were used to determine compositions, and structures, respectively. Scanning Kelvin probe microscopy (SKPM) was used to measure work functions (Φm) directly. Our results show Φm variation is consistent with the variation for the corresponding bulk values. For the Ta1-xAlxNy metal gate electrodes, the extracted equivalent oxide thickness (EOT) map suggests thermal stability of the stack, and flat-band voltage shift (ΔVfb) varied systematically as per our expectation.
Ion Implantation: A Method of Producing Low-k Silicon Oxide-based Materials
Authors: Leoni Elisa , De Sousa Meneses Domingos , Ntsoenzok Esidor , Canino Mariaconcetta , Regula Gabrielle
Published: May 2008

The reduction of the dielectric constant of the inter-metal dielectric is a key task for realizing high performances IC devices. In this work ion implantation is proposed as a novel method to reduce the dielectric properties of SiO2. Thermally grown SiO2 on silicon was implanted by Xe at 300 keV and a fluence of 5×1016 at/cm2. The dielectric constant of the obtained structure, measured by means of the C-V method and Infrared measurements, was shown to strongly decrease. From the IR reflection spectra, a hypothesis of the implantation defects involved in lowering the ionic contribution to the dielectric constant will be proposed.