bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration Delocalization of Nearly Periodic Structures Using Coupled Piezoelectric Networks
Authors: Tang J. , Wang K. W.
Published: January 2003

It is known that, when the mechanical coupling between the substructures is weak, small imperfections in a periodic structure can induce vibration localization. This phenomenon could lead to large vibration in certain regions of the structure and could be very harmful to the system. In this study, it is shown that the proposed coupled piezoelectric circuits can greatly relieve or even eliminate such localization problems. Part of the structural vibration energy will be transferred into electrical energy through the piezoelectric materials, and the newly created electro-mechanical wave/energy channel will sustain the energy propagation throughout the structure. The effectiveness and robustness of the coupled piezoelectric circuits on reducing vibration localization is demonstrated through analysis. Design guidelines are also established via approximation techniques and parametric studies.
A Moving-Load Model for Disc-Brake Stability Analysis
Authors: Ouyang H. , Mottershead J. E. , Li W.
Published: January 2003

There are many elasto-mechanical systems that involve two components in moving contact where large-amplitude vibration and noise can be excited. This paper models the vibration and dynamic instability of a car disc brake as a moving load problem in which one component (the disc) is amenable to analytical treatment while the other component (the pads, calliper and mounting) has to be dealt with by the finite element method. A method is presented for solving the dynamic instability of the car disc brake as a nonlinear eigenvalue problem. The same approach can tackle other moving load problems.
Feature Variation and its Impact on Structural Acoustic Response Predictions
Authors: Cunefare Kenneth A.
Published: January 2003

This paper presents a screening technique to assess the impact on model fidelity introduced by variations in the properties or positions of features in harmonically forced fluid-loaded structural acoustic models. The perspective taken is one of knowledge of a reference state, with a desire to determine the impact on the total radiated acoustic power due to perturbations in the reference state. Such perturbations change the predicted resonance frequencies of a structure under consideration, and hence, change the predicted response amplitudes. The method uses a single degree of freedom response model in the local region of each fluid-loaded resonance, coupled with eigenvalue sensitivities or variations, to estimate the perturbation impact. The perturbation is scaled by the degree to which each given mode participates in the response quantity of interest. The SDOF model yields results that indicate that proportional bandwidth analysis will be less sensitive to perturbation than constant bandwidth analysis. This is demonstrated through comparison of a constant bandwidth analysis and a 1/3 octave analysis applied to the same system. Elements of the analysis method are not necessarily restricted to model perturbations nor acoustic power, rather they may be used to assess the perturbation of any quadratic response quantity of interest due to changes in resonance frequency.
Improvement of Nonlinear Single Resonant Mode Method
Authors: Nobari A. S. , Shahramyar M.
Published: January 2003

Presently, the Nonlinear Single Resonant Mode (NLSRM) method is the most efficient method for extending standard linear modal analysis concept to nonlinear systems. In this method, it is assumed that the mode of vibration in the resonant condition is close to the nonlinear normal mode and only one mode has nonlinear behavior. Therefore, predicting which one of the modes will exhibit nonlinear behavior is very important especially for a large system. The main object of this paper is twofold: (1) to improve the NLSRM method, (2) to use the sensitivity analysis for the prediction of nonlinear mode. The results are compared to the results of harmonic balance (HB) and time domain (TD) methods. It is shown that there is a very good agreement between HB and TD results with those of improved NLSRM methods and also the methodology for prediction of nonlinear mode is well suited.
Broadband Spatially Feedforward Active Noise Control Algorithms Using a Comb Filter
Authors: Bai Mingsian R. , Lai Jienwen
Published: January 2003

A controller composed of a nonrecursive filter and a recursive filter is used to approximate the ideal controller for a spatially feedforward duct ANC problem. The nonrecursive part represents the dynamics of the transducer, whereas the recursive part is in the form of a comb filter. The parameters of the comb filter are obtained from the impulse response of the controller by using the least-square method. The comb filter is then cascaded with the nonrecursive part implemented as either a fixed filter or an adaptive filter. In the latter approach, two types of LMS-based algorithms are used. The proposed algorithms are implemented on the platform of a digital signal processor. Experimental results showed that the approximated controller attained 17 dB maximal attenuation in the frequency band 200∼600Hz.
Feature Based Macroplanning Including Fixturing
Authors: Sundararajan V. , Wright Paul K.
Published: January 2003

Macroplanning is concerned with deciding on setups and sequences of operations by taking into account interactions between features and issues of fixturing. The algorithms presented in this paper use a set of features arranged in a graph-like data structure to determine the fixture configurations and setups. Operation sequences for the features and tool-paths are determined by separate modules working in conjunction with the macroplanner. Examples are presented to demonstrate the capability of the algorithms implemented in an integrated CAD/ CAM system called CyberCut.
Automatic CAD Model Reconstruction from Multiple Point Clouds for Reverse Engineering
Authors: Huang Jianbing , Menq Chia-Hsiang
Published: January 2003

In this paper, a systematic scheme is proposed and novel technologies are developed to automatically reconstruct a CAD model from a set of point clouds scanned from the boundary surface of an existing object. The proposed scheme is composed of three major steps. In the first step, multiple input point clouds are incrementally integrated into a watertight triangle mesh to recover the object shape. In the second step, mesh segmentation is applied to the triangle mesh to extract individual geometric feature surfaces. Finally, the manifold topology describing the connectivity information between different geometric surfaces is automatically extracted and the mathematical description of each geometric feature is computed. The computed topology and geometry information represented in ACIS modeling kernel form a CAD model that may be used for various downstream applications. Compared with prior work, the proposed approach has the unique advantage that the processes of recognizing geometric features and of reconstructing CAD models are fully automated. Integrated with state of the art scanning devices, the developed model reconstruction method can be used to support reverse engineering of high precision mechanical components. It has potential applications to many engineering problems with a major impact on rapid design and prototyping, shape analysis, and virtual reality.
Texture development of CeO2 thin films deposited by ion beam assisted deposition
Authors: Wang J. , Fromknecht R. , Linker G.
Published: January 2003

CeO 2 thin films were prepared on amorphous quartz glass substrates by the ion beam assisted deposition (IBAD) technique at room temperature. In order to control both the in-plane and out-of-plane texture of the films, a special geometrical arrangement of the ion sources, the target, and the substrate was used. A new concept, considering the role of reflected particles from the target, which we call self-IBAD, was introduced. The structural properties of the CeO2 films were investigated by x-ray diffraction. Good biaxially textured films were obtained with out-of-plane mosaic spreads of 3.0° and in-plane alignment of 10.8°.
Tribological properties of nitrogen-containing amorphous carbon film produced by dc plasma chemical vapor deposition
Authors: Zhang Wei , Wazumi Koichiro , Tanaka Akihiro , Koga Yoshinori
Published: January 2003

The nitrogen-contained amorphous carbon (a-C:N) films were deposited in a dc plasma chemical vapor deposition system with different substrate bias voltages. The structural, mechanical, and tribological properties of the a-C:N films were investigated. The influence of the bias voltage on the tribological behaviors of the a-C:N films was evaluated under various environments (dry air, O2, N2, and vacuum) using a ball-on-disk friction tester. It showed that the sp3 C and hydrogen concentration of the a-C:N films decreases with increasing the bias voltage. However, the nitrogen concentration increases with increasing the bias voltage. As a result, the hardness and internal stress decrease and the critical load for fracturing increases as the substrate bias increases. For the tribological properties of the a-C:N films, the friction coefficient of the films slightly decreases in the environments of N2, O2, or dry air, but increases slightly in the vacuum environment by increasing the bias voltage. It indicates that the incorporated nitrogen in the a-C:N films would decrease the friction coefficient of the films in N2 or O2 environments, but slightly increases the friction coefficient of the films in a vacuum. The excellent wear resistance of the a-C:N films, in the level of 10−9–10−8 mm3/Nm, can be observed in N2, vacuum, and dry air environments. In addition, the effect of the bias voltage on the wear rate of the a-C:N films becomes less obvious by nitrogen incorporation. So, we suggest the incorporated nitrogen, which bonded to carbon and restrained the increase of the fraction of sp2 C–C, would restrain the wear of the a-C:N films in different environments, especially in dry air.
Ionization-assisted deposition of strontium electron injection layer for organic light emitting diode
Authors: Tanaka Kuniaki , Usui Hiroaki
Published: January 2003

Strontium (Sr) thin films were prepared by the ionization-assisted deposition (IAD) method for the electron injection layer between tris(8-hydroxyquinolino)aluminum (Alq3) electron transport layer and Al cathode of the organic light emitting diode (LED). The Sr films, around 10 nm in thickness, deposited by IAD were effective in improving the device characteristics such as the luminescence efficiency and, especially, the device lifetime. The best LED characteristics were obtained at the ion acceleration voltage Va of around 800 V. It was found that the deposition condition influences the morphological and chemical properties of the film. The IAD Sr had smaller interdiffusion into Alq3 compared to the standard evaporated one. The film deposited by IAD at higher Va was metallic, and had a densely packed uniform microstructure, while the ones deposited at low Va or by standard evaporation assumed oxide nature, having considerable amount of voids. It is expected that the IAD can optimize the LED characteristics through the control of Sr film properties.
Fundamental beam studies of radical enhanced atomic layer deposition of TiN
Authors: Greer Frank , Fraser D. , Coburn J. W. , Graves David B.
Published: January 2003

TiN films were deposited using radical enhanced atomic layer deposition (REALD) in an ultrahigh vacuum beam system. The REALD cycle used for the film deposition consisted of separate, sequential exposures of TiCl4, deuterium atoms, and nitrogen atoms. By using this three step deposition process with independently controlled beams of TiCl4 molecules, deuterium radicals, and nitrogen radicals, it was possible to monitor each step in the REALD cycle, measuring the sticking and reaction probabilities of each of these species on silicon as a function of surface temperature using a quartz crystal microbalance. Results from the ex situ XPS analysis of the deposited films are promising and suggest that deuterium radicals can abstract Cl from TiClx surface species for substrate temperatures as low as 300 K. The films display low residual chlorine content (<0.3%) when the D atom exposure is sufficiently large. The results from the third stage in the REALD TiN process are consistent with the addition of approximately stoichiometric amounts of nitrogen. However, the data suggest that during the first few REALD cycles, the nitrogen diffuses into and reacts with the underlying silicon substrate.
Critical Mg doping on the blue-light emission in p-type GaN thin films grown by metal–organic chemical-vapor deposition
Authors: Kim Keunjoo , Harrison Joseph G.
Published: January 2003

The photoluminescence and photocurrent from p-type GaN films were investigated at temperatures of 30 and 297 K for various Mg-doping concentrations. At a low Mg-doping level, there exists a photoluminescence center of the donor and acceptor pair transition at the 3.28 eV band. This center correlates with the defects for a shallow donor of the VGa and for an acceptor of MgGa. The acceptor level shows a binding energy of 0.2–0.25 eV, which was observed by measuring the photocurrent signal at a photon energy of 3.02–3.31 eV. At a high Mg-doping level, we found a photoluminescence center of a deep donor and acceptor pair transition of the 2.76 eV blue band. This center is attributed to the defect structures of MgGa –VN for the deep donor and MgGa for the acceptor. For low-doped samples, thermal annealing provides an additional photocurrent signal for unoccupied deep acceptor levels of 0.87–1.35 eV above the valence band, indicating p-type activation.
Soft x-ray photoemission studies of Hf oxidation
Authors: Suzer S. , Sayan S. , Banaszak Holl M. M. , Garfunkel E. , Hussain Z. , Hamdan N. M.
Published: January 2003

Soft x-ray photoemission spectroscopy has been applied to determine the binding energy shifts and the valance band offset of HfO2 grown on Hf metal. Charging of oxide films upon x-ray exposure is found to be very severe and special care is taken to eliminate it. Photoemission results show the presence of metallic Hf (from the substrate) with a 4f7/2 binding energy of 14.22 eV, fully oxidized Hf (from HfO2) with a 4f7/2 binding energy of 18.16 eV, and at least one clearly defined suboxide peak. The position of the valence band of HfO2 with respect to the Hf(metal) Fermi level is 4.23 eV.
Thermal desorption study of selected austenitic stainless steels
Authors: Bacher J.-P. , Benvenuti C. , Chiggiato P. , Reinert M.-P. , Sgobba S. , Brass A.-M.
Published: January 2003

Residual hydrogen in stainless steel results in a steady outgassing from vacuum chamber walls, hindering the achievement of ultrahigh vacuum conditions. The total content, the binding states, and the diffusivity of residual hydrogen in austenitic stainless steels, which together define the room temperature hydrogen outgassing rate, have been investigated by thermal desorption spectroscopy (TDS). Seven different steel types have been studied by means of two different TDS systems. The study has been extended to include the effects of various postproduction treatments, aimed at reducing the hydrogen content and/or outgassing, namely vacuum firing and baking both in air and under vacuum. A large variety of hydrogen desorption peaks have been observed, which have been attributed to diffusible hydrogen, hydrogen trapping in the surface oxides or in lattice defects induced by precipitates, and steel recrystallization. The hydrogen depletion effectiveness of vacuum baking at different temperatures has been quantified, and the consequences of air baking have been clarified, leading to practical guidelines for technological applications.
Plasma and process characterization of high power magnetron physical vapor deposition with integrated plasma equipment—feature profile model
Authors: Zhang Da , Stout Phillip J. , Ventzek Peter L. G.
Published: January 2003

High power magnetron physical vapor deposition (HPM-PVD) has recently emerged for metal deposition into deep submicron features in state of the art integrated circuit fabrication. However, the plasma characteristics and process mechanism are not well known. An integrated plasma equipment-feature profile modeling infrastructure has therefore been developed for HPM-PVD deposition, and it has been applied to simulating copper seed deposition with an Ar background gas for damascene metalization. The equipment scale model is based on the hybrid plasma equipment model [M. Grapperhaus et al., J. Appl. Phys. 83, 35 (1998); J. Lu and M. J. Kushner, ibid., 89, 878 (2001)], which couples a three-dimensional Monte Carlo sputtering module within a two-dimensional fluid model. The plasma kinetics of thermalized, athermal, and ionized metals and the contributions of these species in feature deposition are resolved. A Monte Carlo technique is used to derive the angular distribution of athermal metals. Simulations show that in typical HPM-PVD processing, Ar+ is the dominant ionized species driving sputtering. Athermal metal neutrals are the dominant deposition precursors due to the operation at high target power and low pressure. The angular distribution of athermals is off axis and more focused than thermal neutrals. The athermal characteristics favor sufficient and uniform deposition on the sidewall of the feature, which is the critical area in small feature filling. In addition, athermals lead to a thick bottom coverage. An appreciable fraction (∼10%) of the metals incident to the wafer are ionized. The ionized metals also contribute to bottom deposition in the absence of sputtering. We have studied the impact of process and equipment parameters on HPM-PVD. Simulations show that target power impacts both plasma ionization and target sputtering. The Ar+ ion density increases nearly linearly with target power, different from the behavior of typical ionized PVD processing. The total metal flux to the wafer increases with target power due to enhanced target sputtering. However, the ionization fraction of the total flux decreases due in part to the increased diffusion loss of charged species. Wafer bias power controls ion energy, and it has a negligible impact on plasma ionization and deposition flux composition. Feature simulations show the redistribution of deposited metals within a feature when wafer resputtering is promoted at sufficient bias power. Target-wafer spacing (TWS) impacts the total ionization and metal flux to the wafer. The Ar+ density and deposition rate decrease with increasing TWS due to increased surface loss. Simulations suggest that reducing the TWS results in more efficient usage of target source.
Plasma display panel vacuum in-line sealing technology by using a bubble-reduced frit
Authors: Kwon Sang Jik , Yang Hwi Chan , Whang Ki-Woong
Published: January 2003

Improper base vacuum level in any vacuum microelectronic device, such as a plasma display panel (PDP), will damage the overall performance of the device due to impurities such as H2, O2, CO, CO2, and N2. In conventional tubulation packaging technology, the obtainable base vacuum level before plasma gas filling will be very poor because of the pumping conductance limitation for such a large panel size with a small gap of 150 μm, especially due to the barrier ribs inside the PDP panel. The time required to reach any reasonable level will be too long. In this study, we performed the sealing of the two glass plates composing the PDP panel, a plasma gas filling into the panel and a hole-off (named instead of a conventional “tip-off”) process, all in a vacuum chamber, called as “vacuum in-line sealing.” Several factors related with the heating process of a frit glass were investigated. A prepared frit glass was successfully applied for the vacuum in-line sealing approach without suffering bubbles. We successfully have fabricated an operable PDP panel with a 2 in. diagonal size by using the fully vacuum in-line sealing technology for the first time in the world. The sealing temperature of the two plates was around 330 °C which corresponded to a temperature about 120 °C lower than that used in a conventional air environment. The base vacuum level inside the panel before gas filling was about 5×10−6 Torr at the time of sealing. The total elapsed time for the sealing processes was less than 6 h, including the gas fill and the hole-off processes.
Effect of changing the electrode gap on the spatial and electrical properties of O2/CF4 plasmas
Authors: Steffens Kristen L. , Sobolewski Mark A.
Published: January 2003

Planar laser-induced fluorescence (PLIF) measurements were made to determine two-dimensional spatial maps of CF2 density as a chemical marker of plasma uniformity in 9% O2/91% CF4 chamber-cleaning plasmas. Broadband optical emission and discharge current and voltage measurements were also made and compared to the PLIF results. Measurements were made in a capacitively coupled Gaseous Electronics Conference Reference Cell as pressure was varied from 13 (100 mTorr) to 133 Pa (1000 mTorr) and electrode gap was varied from 2.25 to 0.5 cm. Smaller gaps resulted in increased radial uniformity and extended the pressure range over which CF2 density and electrical properties remain insensitive to pressure. These effects are explained by a decrease in the bulk plasma resistance at narrower electrode gaps, which changes the path that rf current takes through the discharge, thus affecting where electron heating and CF2 production occur. These results provide insight into the optimization of chamber-cleaning processes and reactors as well as provide necessary data for validation of plasma simulations.
Supersonic jet epitaxy of gallium nitride using triethylgallium and ammonia
Authors: McGinnis Arthur J. , Thomson Darren , Banks Andrew , Preble Edward , Davis Robert F. , Lamb H. Henry
Published: January 2003

Gallium nitride (GaN) films were grown on GaN(0001)/AlN/6H–SiC composite substrates at 700–780 °C by supersonic jet epitaxy using triethylgallium (TEG) and NH3. TEG was seeded in He and N2 supersonic free jets to obtain kinetic energies of ∼2.1 and ∼0.5 eV, respectively, and NH3 was supplied from a variable leak valve. Higher TEG beam intensities (by about a factor of 5) were obtained by seeding in He. In situ reflection high-energy electron diffraction indicated a transition from three-dimensional to two-dimensional (2D) growth between 730 and 750 °C for films grown using TEG seeded in He and a constant NH3/TEG flux ratio. Ex situ atomic force microscopy of films grown at 730 and 750 °C revealed smooth surfaces comprised of quasi-2D islands with irregular perimeters. Cross-sectional transmission electron microscopy evidenced that the film grown at 750 °C was homoepitaxial α-GaN with a high density of planar lattice defects. Secondary ion mass spectrometry detected high residual carbon concentrations in the films. The GaN growth rate at 750 °C was found to depend on TEG flux and NH3 pressure in a manner consistent with Langmuir–Hinshelwood kinetics. Films grown under NH3-rich conditions were faceted and microscopically rough, whereas nonfaceted, basal-plane growth was observed under Ga-rich conditions. The first-order dependence of growth rate on TEG flux under NH3-rich conditions was used to estimate Ga incorporation efficiencies for high- and low-energy TEG beams. The Ga incorporation efficiency is lower for high-energy TEG beams, consistent with a decrease in the sticking coefficient for dissociative chemisorption.
Highly sensitive plasma absorption probe for measuring low-density high-pressure plasmas
Authors: Nakamura K. , Ohata M. , Sugai H.
Published: January 2003

This article reports a new type of sensitive plasma absorption probe (PAP), which is characterized with a thin wire antenna directly exposed to plasma. In the sensitive PAP, the power reflection coefficient resonantly decreases at a certain frequency due to absorption of a surface wave, which is excited along a sheath formed around the antenna. The electron density is derived from the measured absorption frequency in comparison to a wave dispersion relation: the dispersion is calculated under assumptions that the sheath width is twice the Debye length and that wavelength is twice the antenna length. This sensitive PAP also enables measurements of very low electron densities (∼108 cm−3) and very high pressures (∼10 Torr), in comparison to a conventional standard PAP. In addition, both electron temperature and electron density can be measured using a pair of sensitive PAPs of different antenna radii.
Discrete-time modeling of woodwind instrument bores using wave variables
Authors: van Walstijn Maarten , Campbell Murray
Published: January 2003

A method for simulation of acoustical bores, useful in the context of sound synthesis by physical modeling of woodwind instruments, is presented. As with previously developed methods, such as digital waveguide modeling (DWM) [Smith, Comput. Music J. 16, 74–91 (1992)] and the multi convolution algorithm (MCA) [Martı́nez et al., J. Acoust. Soc. Am. 84, 1620–1627 (1988)], the approach is based on a one-dimensional model of wave propagation in the bore. Both the DWM method and the MCA explicitly compute the transmission and reflection of wave variables that represent actual traveling pressure waves. The method presented in this report, the wave digital modeling (WDM) method, avoids the typical limitations associated with these methods by using a more general definition of the wave variables. An efficient and spatially modular discrete-time model is constructed from the digital representations of elemental bore units such as cylindrical sections, conical sections, and toneholes. Frequency-dependent phenomena, such as boundary losses, are approximated with digital filters. The stability of a simulation of a complete acoustic bore is investigated empirically. Results of the simulation of a full clarinet show that a very good concordance with classic transmission-line theory is obtained.
Scattering from a single bubble near a roughened air–water interface: Laboratory measurements and modeling
Authors: Dahl Peter H. , Kapodistrias George
Published: January 2003

The problem of scattering from a single bubble located close to a slightly roughened, air–water interface is studied both theoretically and experimentally. Two well-controlled laboratory experiments were performed to investigate the effects of surface roughness on the scattering response of the bubble. In the first experiment, a bubble of radius 1200 μm was placed on a fine thread at a variable distance, d, from the mean-still-water level of the surface, which was roughened using a wind source. In the second experiment, a bubble of radius 800 μm was utilized, while the water surface was roughened using a plunger wave-making source. The waveheights and important characteristic length scales associated with each experiment were quantified using digital photography. The wind source produced waveheights that were represented by a Gaussian distribution, while the plunger source produced waveheights that were represented by a bimodal distribution. To model the acoustic measurements, an expression describing the four scattering paths, from source to bubble to receiver, was used. A random phase shift due to the surface roughness was added to the paths that interacted with the surface, and expectations of this phase shift were computed based on the analytical representations for the waveheight distribution. The data show good agreement with the simulations and the sensitivity of scattering from a subsurface bubble to small changes in waveheight is illustrated. The experiments highlight important parametric dependencies, which are summarized here, and the relation between monostatic and bistatic scattering is also discussed.
Effect of current stimulus on in vivo cochlear mechanics
Authors: Parthasarathi Anand A. , Grosh Karl , Zheng Jiefu , Nuttall Alfred L.
Published: January 2003

In this paper, the influence of direct current stimulation on the acoustic impulse response of the basilar membrane (BM) is studied. A positive current applied in the scala vestibuli relative to a ground electrode in the scala tympani is found to enhance gain and increase the best frequency at a given location on the BM. An opposite effect is found for a negative current. Also, the amplitude of low-frequency cochlear microphonic at high sound levels is found to change with the concurrent application of direct current stimulus. BM vibrations in response to pure tone acoustic excitation are found to possess harmonics whose levels relative to the fundamental increase with the application of positive current and decrease with the application of negative current. A model for outer hair cell activity that couples changes in length and stiffness to transmembrane potential is used to interpret the results of these experiments and others in the literature. The importance of the in vivo mechanical and electrical loading is emphasized. Simulation results show the somewhat paradoxical finding that for outer hair cells under tension, hyperpolarization causes shortening of the cell length due to the dominance of voltage dependent stiffness changes.
Acoustic scattering by a cylindrical shell with symmetric line constraints in the heavy fluid-loading limit
Authors: Skelton E. A.
Published: January 2003

A cylindrical shell, modelled using Donnell–Mushtari thin shell theory, is reinforced by two internal rigid plates attached to the shell along lines parallel to the shell axis. A circumferential mode expansion is used to obtain numerical results for the scattered sound field due to the presence of the reaction forces along the attachment lines. In the heavy fluid-loading limit, which is appropriate for low and mid-frequency ranges for practical underwater structures, asymptotic analysis is presented which allows the peak frequencies in the scattered field due to the reaction forces to be expressed (to leading order) in terms of the geometry and the shell and fluid parameters. These predictions agree well with results obtained by numerically evaluating the infinite sums needed to calculate the reaction forces and hence the scattered field.
Virtual error sensing for active noise control in a one-dimensional waveguide:  Performance prediction versus measurement (L)
Authors: Munn Jacqueline M. , Cazzolato Ben S. , Kestell Colin D. , Hansen Colin H.
Published: January 2003

Virtual error sensing is a novel active noise control technique, which is designed to produce a zone of attenuation remote from the physical error sensors. In this letter virtual sensing is investigated for tonal noise (both on and off resonance) in a long narrow duct. The performance of the virtual error sensors using real-time control is compared to the performance determined from an analytical model and the performance determined through the postprocessing of experimental data. Two examples of control using postprocessed experimental transfer function data are presented; the first relied on transfer functions measured using broadband noise and the second relied on transfer functions measured at discrete frequencies. The results highlight the significant errors encountered as a result of using broadband transfer functions in lightly damped enclosures.
Leaky helical flexural wave backscattering contributions from tilted water-filled cylindrical shells
Authors: Blonigen Florian J. , Marston Philip L.
Published: January 2003

Helical flexural waves on a bluntly truncated tilted water-filled cylindrical steel shell in water are found to give large contributions to the backscattering above the coincidence frequency. The presence of the water inside the shell increases the damping of the leaky wave when short tone bursts are used. The magnitude of the scattering is found by modifying a ray analysis developed for empty shells. When longer bursts are used, some of the internally radiated energy (corresponding to the case of one internal chord) is superposed on the ordinary helical ray backscattering. This occurs as a consequence of the internal excitation of helical rays.
Echolocation in the Risso’s dolphin, Grampus griseus
Authors: Philips Jennifer D. , Nachtigall Paul E. , Au Whitlow W. L. , Pawloski Jeffrey L. , Roitblat Herbert L.
Published: January 2003

The Risso’s dolphin (Grampus griseus) is an exclusively cephalopod-consuming delphinid with a distinctive vertical indentation along its forehead. To investigate whether or not the species echolocates, a female Risso’s dolphin was trained to discriminate an aluminum cylinder from a nylon sphere (experiment 1) or an aluminum sphere (experiment 2) while wearing eyecups and free swimming in an open-water pen in Kaneohe Bay, Hawaii. The dolphin completed the task with little difficulty despite being blindfolded. Clicks emitted by the dolphin were acquired at average amplitudes of 192.6 dB re 1 μPa, with estimated sources levels up to 216 dB re 1 μPa-1 m. Clicks were acquired with peak frequencies as high as 104.7 kHz (Mfp=47.9 kHz), center frequencies as high as 85.7 kHz (Mf0=56.5 kHz), 3-dB bandwidths up to 94.1 kHz (MBW=39.7 kHz), and root-mean-square bandwidths up to 32.8 kHz (MRMS=23.3 kHz). Click durations were between 40 and 70 μs. The data establish that the Risso’s dolphin echolocates, and that, aside from slightly lower amplitudes and frequencies, the clicks emitted by the dolphin were similar to those emitted by other echolocating odontocetes. The particular acoustic and behavioral findings in the study are discussed with respect to the possible direction of the sonar transmission beam of the species.
Suppression of large intraluminal bubble expansion in shock wave lithotripsy without compromising stone comminution: Refinement of reflector geometry
Authors: Zhou Yufeng , Zhong Pei
Published: January 2003

Using the Hamilton model [Hamilton, J. Acoust. Soc. Am. 93, 1256–1266 (1993)], the effects of reflector geometry on the pulse profile and sequence of the shock waves produced by the original and upgraded reflector of an HM-3 lithotripter were evaluated qualitatively. Guided by this analysis, we have refined the geometry of the upgraded reflector to enhance its suppressive effect on intraluminal bubble expansion without compromising stone comminution in shock wave lithotripsy. Using the original HM-3 reflector at 20 kV, rupture of a standard vessel phantom made of cellulose hollow fiber (i.d.=0.2 mm), in which degassed water seeded with ultrasound contrast agents was circulated, was produced at the lithotripter focus after about 30 shocks. In contrast, using the upgraded reflector at 24 kV no rupture of the vessel phantom could be produced within a 20-mm diameter around the lithotripter focus even after 200 shocks. On the other hand, stone comminution was comparable between the two reflector configurations, although slightly larger fragments were produced by the upgraded reflector. After 2000 shocks, stone comminution efficiency produced by the original HM-3 reflector at 20 kV is 97.15±1.92% (mean±SD), compared to 90.35±1.96% produced by the upgraded reflector at 24 kV (p<0.02). All together, it was found that the upgraded reflector could significantly reduce the propensity for vessel rupture in shock wave lithotripsy while maintaining satisfactory stone comminution.
Application of an acoustic noise removal method to aircraft-based atmospheric temperature measurements
Authors: Hugo Ronald J. , Nowlin Scott R. , Hahn Ila L. , Eaton Frank D. , McCrae Kim A.
Published: January 2003

An acoustic noise removal method is used to reject engine acoustical disturbances from aircraft-based atmospheric temperature measurements. Removal of engine noise from atmospheric temperature measurements allows a larger wave number range to be fit while quantifying the magnitude of atmospheric temperature turbulence. The larger wave number range was found to result in a more statistically certain spectral slope estimate, with up to a 50% reduction in the standard deviation of measured spectral slopes. The noise removal technique was found to break down under conditions of weak atmospheric temperature turbulence where the engine acoustical disturbance can be several orders of magnitude larger than atmospheric temperature turbulence.
Effect of amplitude modulation coherence for masked speech signals filtered into narrow bands
Authors: Buss Emily , Wall Joseph W. , Grose John H.
Published: January 2003

Introduction of masker amplitude modulation (AM) can improve signal detection in a number of paradigms. In some cases this advantage depends on the coherence of modulation across a relatively wide frequency range. In the experiments described below, observers were asked to identify masked spondee words produced by a single male talker. The target spondees and masking noise were filtered into nine narrow bands, and the coherence of AM of either the speech signal or noise masker was manipulated. Inherent modulation of the masker bands was manipulated via assignment of real and imaginary values to the associated components of each band in the frequency domain, and AM of speech bands was achieved via multiplication with envelopes extracted from these maskers. Responses were based on two alternatives, four alternatives, or open response sets. The effect of masker AM coherence was highly dependent upon the size of the response set: coherent AM was associated with better thresholds in a two-alternative response set, but poorer thresholds in an open response set. Results with AM speech did not depend critically upon the across-frequency temporal synchrony of AM imposed on the speech material.
Compensation for source nonstationarity in multireference, scan-based near-field acoustical holography
Authors: Kwon Hyu-Sang , Kim Yong-Joe , Bolton J. Stuart
Published: January 2003

Multireference, scan-based near-field acoustical holography is a useful measurement tool that can be applied when an insufficient number of microphones is available to make measurements on a complete hologram surface simultaneously. The scan-based procedure can be used to construct a complete hologram by joining together subholograms captured using a relatively small, roving scan array and a fixed reference array. For the procedure to be successful, the source levels must remain stationary for the time taken to record the complete hologram; that is unlikely to be the case in practice, however. Usually, the reference signal levels measured during each scan differ from each other with the result that spatial noise is added to the hologram. A procedure to suppress the effects of source level, and hence reference level, variations is proposed here. The procedure is based on a formulation that explicitly features the acoustical transfer functions between the sources and both the reference and scanning, field microphones. When it is assumed that source level changes do not affect the sources’ directivity, a nonstationarity compensation procedure can be derived that is based on measured transfer functions between the reference and field microphones. It has been verified both experimentally and in numerical simulations that the proposed procedure can help suppress spatially distributed noise caused by the type of source level nonstationarity that is characteristic of realistic sources.
Identification of B- and T-Cell Epitopes of BB, a Carrier Protein Derived from the G Protein ofStreptococcusStrain G148
Authors: Goetsch Liliane , Haeuw Jean Francois , Champion Thierry , Lacheny Christine , N’Guyen Thien , Beck Alain , Corvaia Nathalie
Published: January 2003

Most conventional vaccines consist of killed organisms or purified antigenic proteins. Such molecules are generally poorly immunogenic and need to be coupled to carrier proteins. We have identified a new carrier molecule, BB, derived from the G protein ofStreptococcusstrain G148. We show that BB is able to induce strong antibody responses when conjugated to peptides or polysaccharides. In order to localize T and B cell epitopes in BB and match them with the albumin-binding region of the molecule, we immunized mice with BB, performed B and T pepscan analyses, and compared the results with pepscan done with sera and cells from humans. Our results indicate that BB has two distinct T helper epitopes, seven linear B-cell epitopes, and one conformational B-cell epitope in BALB/c mice. Four linear B-cell epitopes were identified from human sera, three of which overlapped mouse B-cell epitopes. Finally, three human T-cell epitopes were detected on the BB protein. One of these T-cell epitopes is common to BALB/c mice and humans and was localized in the region that contains the albumin-binding site. These data are of interest for the optimization of new carrier molecules derived from BB.
Use of Vesicular Stomatitis Virus Pseudotypes Bearing Hantaan or Seoul Virus Envelope Proteins in a Rapid and Safe Neutralization Test
Authors: Ogino Michiko , Ebihara Hideki , Lee Byoung-Hee , Araki Koichi , Lundkvist Åke , Kawaoka Yoshihiro , Yoshimatsu Kumiko , Arikawa Jiro
Published: January 2003

A vesicular stomatitis virus (VSV) pseudotype bearing hantavirus envelope glycoproteins was produced and used in a neutralization test as a substitute for native hantavirus. The recombinant VSV, in which the enveloped protein gene (G) was replaced by the green fluorescent protein gene and complemented with G protein expressed in
trans
(VSVΔG*G), was kindly provided by M. A. Whitt. 293T cells were transfected with plasmids for the expression of envelope glycoproteins (G1 and G2) of HTNV or SEOV and were then infected with VSVΔG*G. Pseudotype VSV with the Hantaan (VSVΔG*-HTN) or Seoul (VSVΔG*-SEO) envelope glycoproteins were harvested from the culture supernatant. The number of infectious units (IU) of the pseudotype VSVs ranged from 10
5
to 10
6
/ml. The infectivity of VSVΔG*-HTN and VSVΔG*-SEO was neutralized with monoclonal antibodies, immune rabbit sera, and sera from patients with hemorrhagic fever with renal syndrome, and the neutralizing titers were similar to those obtained with native hantaviruses. These results show that VSVΔG*-HTN and -SEO can be used as a rapid, specific, and safe neutralization test for detecting hantavirus-neutralizing antibodies as an effective substitute for the use of native hantaviruses. Furthermore, the IU of VSVΔG*-HTN and -SEO did not decrease by more than 10-fold when stored at 4°C for up to 30 days. The stability of the pseudotype viruses allows distribution of the material to remote areas by using conventional cooling boxes for use as a diagnostic reagent.
Infection Exclusion of the Rickettsial PathogenAnaplasma marginalein the Tick VectorDermacentor variabilis
Authors: de la Fuente José , Blouin Edmour F. , Kocan Katherine M.
Published: January 2003

Anaplasma marginaleis a tick-borne, rickettsial cattle pathogen that is endemic in several areas of the United States. Recent studies (J. de la Fuente, J. C. Garcia-Garcia, E. F. Blouin, J. T. Saliki, and K. M. Kocan, Clin. Diagn. Lab. Immunol. 9:658-668, 2002) demonstrated that infection of cultured tick cells and bovine erythrocytes with one genotype ofA. marginaleexcluded infection with other genotypes, a phenomenon referred to as infection exclusion. The present study was undertaken to confirm the phenomenon of infection exclusion ofA. marginalegenotypes in a tick vector,Dermacentor variabilis. Only one genotype ofA. marginale(Virginia isolate) was detected by PCR in ticks that fed first on a calf infected with a Virginia isolate and second on a calf infected with an Oklahoma isolate. These studies demonstrate that infection exclusion ofA. marginalegenotypes also occurs in naturally infected ticks, as well as in cattle and cultured tick cells, and results in establishment of only one genotype per tick.
Detection of Low-Avidity Immunoglobulin G in Oral Fluid Samples: New Approach for Rubella Diagnosis and Surveillance
Authors: Akingbade D. , Cohen B. J. , Brown D. W. G.
Published: January 2003

Low-avidity rubella immunoglobulin G (IgG) was detected in oral fluid samples from 30 of 32 rubella IgM-positive patients (sensitivity, 94%) and from 4 of 34 IgM-negative patients (specificity, 88%). Measuring IgG avidity in oral fluid samples could improve the reliability of rubella surveillance when the incidence of the disease and the positive predictive value of IgM tests are low.
Competitive Enzyme-Linked Immunosorbent Assay Based on a Rhoptry-Associated Protein 1 Epitope Specifically Identifies
Babesia bovis
-Infected Cattle
Authors: Goff Will L. , McElwain Terry F. , Suarez Carlos E. , Johnson Wendell C. , Brown Wendy C. , Norimine Junzo , Knowles Donald P.
Published: January 2003

The competitive enzyme-linked immunosorbent assay (cELISA) format has proven to be an accurate, reliable, easily standardized, and high-throughput method for detecting hemoparasite infections. In the present study, a species-specific, broadly conserved, and tandemly repeated B-cell epitope within the C terminus of the rhoptry-associated protein 1 of the hemoparasite
Babesia bovis
was cloned and expressed as a histidine-tagged thioredoxin fusion peptide and used as antigen in a cELISA. The assay was optimized with defined negative and positive bovine sera, where positive sera inhibited the binding of the epitope-specific monoclonal antibody BABB75A4. The cELISA accurately differentiated animals with
B. bovis
-specific antibodies from uninfected animals and from animals with antibodies against other tick-borne hemoparasites (98.7% specificity). In addition,
B. bovis
-specific sera from Australia, Argentina, Bolivia, Puerto Rico, and Morocco inhibited the binding of BABB75A4, confirming conservation of the epitope. The assay first detected experimentally infected animals between 13 and 17 days postinfection, and with sera from naturally infected carrier cattle, was comparable to indirect immunofluorescence (98.3% concordance). The assay appears to have the characteristics necessary for an epidemiologic and disease surveillance tool.
Alterations in T-Cell Receptor Vβ Repertoire of CD4 and CD8 T Lymphocytes in Human Immunodeficiency Virus-Infected Children
Authors: Kharbanda Monica , McCloskey Thomas W. , Pahwa Rajendra , Sun Mei , Pahwa Savita
Published: January 2003

Perturbations in the T-cell receptor (TCR) Vβ repertoire were assessed in the CD4 and CD8 T lymphocytes of human immunodeficiency virus (HIV)-infected children who were receiving therapy during the chronic phase of infection by flow cytometry (FC) and PCR analysis. By FC, representation of 21 TCR Vβ subfamilies was assessed for an increased or decreased percentage in CD4 and CD8 T cells, and by PCR, 22 TCR Vβ subfamilies of CD4 and CD8 T cells were analyzed by CDR3 spectratyping for perturbations and reduction in the number of peaks, loss of Gaussian distribution, or clonal dominance. The majority of the TCR Vβ subfamilies were examined by both methods and assessed for deviation from the norm by comparison with cord blood samples. The CD8-T-lymphocyte population exhibited more perturbations than the CD4 subset, and clonal dominance was present exclusively in CD8 T cells. Of the 55 total CD8-TCR Vβ families classified with clonal dominance by CDR3 spectratyping, only 18 of these exhibited increased expression by FC. Patients with high numbers of CD8-TCR Vβ families with decreased percentages had reduced percentages of total CD4 T cells. Increases in the number of CD4-TCR Vβ families with increased percentages showed a positive correlation with skewing. Overall, changes from normal were often discordant between the two methods. This study suggests that the assessment of HIV-induced alterations in TCR Vβ families at cellular and molecular levels yields different information and that our understanding of the immune response to HIV is still evolving.