bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein binding on thermally grown silicon dioxide
Authors: Lee Stephen C. , Keener Matthew T. , Tokachichu Dharma R. , Bhushan Bharat , Barnes Phillip D. , Cipriany Benjamin R. , Gao Min , Brillson Leonard J.
Published: October 2005

Proteins can confer functional properties to micro- or nanodevices or can passivate microdevice surfaces. We investigated the binding behavior, structure, and activity of a model protein (streptavidin) bound to thermally grown silicon dioxide, a substrate chosen for its prevalence in microfabricated devices. Multiple binding techniques (direct adsorption, substrate nanometer-scale patterning, and chemical conjugation) were investigated. Atomic force microscopy (AFM) images of surfaces prepared using these methods revealed differential morphological differences in proteins bound using each method. AFM adhesion measurements with protein-functionalized tips also showed a variation in adhesion strength between the techniques that was further supported by fluorescence imaging and biological assay. We show that nanometer-scale patterning and chemical conjugation both improve protein binding to the surface compared to direct adsorption. These techniques provide methods for directed attachment of proteins to biomedical devices.
Formation of vertical ridge structure in 660nm laser diodes for high power single mode operation
Authors: Cho Soohaeng , Lee Sangbum , Kang Joonseok , Ma Byungjin , Lee Changyun , Shin Youngchul , Kim Bumjoon , Kang Donghoon , Kim Youngmin , Park Yongjo
Published: October 2005

We report a method for formation of a ridge with almost vertical sidewalls in the fabrication of ridge stripe AlGaInP laser diode structures, which cannot be easily achieved when a conventional wet-etch process is used, for high power operation with a fundamental transverse mode. By depositing additional oxides protecting layers on the sidewalls after the dry-etch process, a wet-etch process, which is necessary to remove the plasma-induced damaged portion of the etched region, can be safely applied and the vertical ridge shape maintained. Using this method, the ideally rectangular ridges were obtained and the single mode operation of 660nm laser diode with up to 270mW output power was successfully achieved.
Fabrication of identical sub-100 nm closely spaced parallel lines using electron beam lithography
Authors: Chen Ke , Cybart Shane A. , Dynes R. C.
Published: October 2005

The electron proximity effect makes it difficult to fabricate uniform patterns at nanometer scale. A simple scheme to correct the effect is presented and applied to fabricate 100 parallel lines spaced at 250 and 500 nm on a photoresist mask using electron beam lithography. The width of each line is less than 100 nm and nearly identical. Two rectangles adjacent to the first and the last lines were exposed with a dosage below the threshold that the electron beam resist requires for development. The linewidths are more uniform with this proximity effect correction than without it. This technique has been used to fabricate ion-damaged high temperature superconducting Josephson junction arrays.
Electron beam lithography with negative Calixarene resists on dense materials: Taking advantage of proximity effects to increase pattern density
Authors: Bühlmann S. , Muralt P. , Kuenzi P.-A. , Staufer U.
Published: October 2005

A high-resolution negative Calixarene resist has been used to pattern 2-nm-thick TiO2 films on 50-nm-thick Pt layers by electron beam lithography, in order to carry out site controlled growth of Pb(Zr,Ti)O3 structures. Single dot structures have been written in a 60-nm-thick Calixarene layer at e-beam acceleration voltages of 10 kV (100 pA) and 20 kV (200 pA). The necessary dose for complete dot development ranged from 5 to 25mC∕cm2. Due to the high density Pt layer, the dot-size depended very much on the volume of backscattered electrons. The minimum dot size (70 nm) was found to lie in the range of the resist film thickness. Proximity effects have been studied. At smaller beam energies, a reversed proximity effect has been observed, in the sense that the dot size decreased due to proximity. An irradiation model is proposed based on exposure from bottom to top, and taking into account a competition between cross-linking and bond-scission.
X-ray reflectometry and x-ray fluorescence monitoring of the atomic layer deposition process for high-k gate dielectrics
Authors: Hung P. Y. , Gondran Carolyn , Ghatak-Roy Amiya , Terada Shinichi , Bunday Ben , Yeung Henry , Diebold Alain
Published: October 2005

This work introduces inline x-ray fluorescence (XRF) and x-ray reflectometry (XRR) metrology tools to aid the process development of atomic layer deposition on high-k dielectric films. In this approach, XRR monitors the deposition rate of the thickness and identifies the transition from the three-dimensional to the two-dimensional growth regime. XRF is used to monitor the atomic deposition rate. The interpretation of XRR result is verified with transmission electron microscopy (TEM) and Auger electron spectroscopy. Unlike the conventional approach using Rutherford backscattering to monitor deposition rate and TEM to monitor thickness, this proposed scheme is noninvasive and does not require any sample preparation. In addition, the inline approach prevents exposing the film to a nonproduction grade environment and avoids the potential growth of the high-k interface or degradation of the film during the measurement.
Simultaneous optical measurement of Ge content and carbon doping in strained epitaxial SiGe films
Authors: Morris S. , Le Cunff D. , Ristoiu D. , Vachellerie V. , Deleglise F. , Dutartre D.
Published: October 2005

We use an analytical technique, previously shown to be able to decouple germanium and boron contents, to measure simultaneously the germanium and carbon contents of a set of carbon-doped epitaxial SiGe films. The method is based on the use of “perturbation functions” to account empirically for the effects that the dopant has upon the fundamental dielectric functions of the undoped material. For a set of five wafers with nominally the same germanium fraction but varying carbon levels, the ability to match measurements by secondary ion mass spectrometry using a production-grade optical metrology tool was demonstrated. Not only could correct results be obtained for the carbon content, but the agreement of the measurement of germanium fraction was also significantly improved. The method holds great promise for improving run-to-run process control for advanced epitaxy processes.
Investigations on the mechanism of silicon etching with chlorine-trifluoride
Authors: Höchst Arnim , Fischer Frank , Kirbach Gunter , Urban Andrea , Becker Volker , Irmscher Mathias , Sailer Holger , Kern Dieter P.
Published: October 2005

We investigated chlorine trifluoride (ClF3) etching of silicon with a patterned oxide mask layer prepared by e-beam lithography. The mask apertures varied from 0.1μmto300μm. This enables to adjust the flow rate of ClF3 molecules into the etched cavity leading to a strong variation of the ClF3 abundance at the silicon surface. A crucial dependence of the etch rate on the aperture area was observed revealing a maximum of the etch rate for a specific ClF3 abundance. A physical description of the etch process is developed in order to distinguish between different mechanisms within the etching process. At low ClF3 abundance the etch rate is limited due to a lack of ClF3. For high abundance the etch rate is assumed to be hampered by a diffusion like transport of ClF3 molecules through a fluorosilyl layer formed on the silicon surface. It can be shown that the etch rate of silicon with ClF3 is not limited by the chemical reaction at high ClF3 abundance. Additionally, we observed a change in etching behavior from isotropic to anisotropic with a strong correlation to the etching regime.
120
-
nm
-T-shaped-Mo∕Pt∕Au-gate AlGaN∕GaN high electron mobility transistors
Authors: Yamashita Yoshimi , Endoh Akira , Ikeda Keiji , Hikosaka Kohki , Mimura Takashi , Higashiwaki Masataka , Matsui Toshiaki , Hiyamizu Satoshi
Published: October 2005

We fabricated 120-nm-T-shaped-Mo∕Pt∕Au-gate AlGaN∕GaN high electron mobility transistors (HEMTs) on sapphire substrates. The gate leakage current Igs of the Mo∕Pt∕Au-gate HEMT at a gate-source voltage Vgs of −5V was as much as five orders of magnitude lower than that of the Ni∕Pt∕Au-gate HEMT under the as-deposited condition. The off-state breakdown voltage, defined as the gate-source voltage when the gate-source current is −1mA∕mm, was about −60V for the Mo∕Pt∕Au-gate HEMT. These dc performances are comparable to those of the Ni∕Pt∕Au-gate HEMTs in which the Schottky contacts were improved with rapid thermal annealing at 500°C. The Mo∕Pt∕Au-gate HEMTs also exhibited good rf performance without RTA. The cutoff frequency fT was more than 50GHz and the maximum oscillation frequency fmax was about 100GHz.
Influence of oxide hard mask on profiles of sub-100 nm Si and SiGe gates
Authors: Shamiryan Denis , Paraschiv Vasile , Locorotondo Sabrina , Beckx Stephan , Boullart Werner , Vanhaelemeersch Serge
Published: October 2005

Oxide hard mask was found to have a profound effect on sub-100 nm Si and SiGe gates profiles. The gates patterned with hard mask only (photoresist is stripped after hard mask patterning) exhibit considerable profile distortion. It has been found that the distortion is caused by the ions deflection due to the charge accumulation on the hard mask. The distortion can be avoided by using either a thinner (15 nm–20 nm) hard mask (that accumulates less charges) or by increasing the ion energy, using higher (above 150 W) bias power (ions impinging the surface with higher speed are less likely to be deflected).
Spindt tip composed of carbon nanotubes
Authors: Moon Jong Hyun , Lim Sung Hoon , Yoon Hyun Sik , Park Kyu Chang , Kang Simon , Bae Craig , Kim Jung Jae , Jang Jin
Published: October 2005

We report the synthesis of a cone-shaped bundle composed of carbon nanotubes (CNTs) in the gate holes by a multi-step growing method: (1) growth of carbon nanotubes in the gate hole; (2) etching the grown CNTs by in situ plasma treatment; (3) regrowth of CNTs. The new CNT bundle in the gate holes exhibited a turn-on gate voltage of 23.5V, an anode current density of 0.034mA∕cm2 at the gate voltage of 30V, and a transconductance of 2.05×10−4S; these are about 50% enhancement compared to conventional CNTs. The field emitter array with the Spindt-type CNTs in the gate holes shows uniform light emission.
Electrical and optical characteristics of hydrogen-plasma treated ZnO nanoneedles
Authors: Yoo Jinkyoung , Park Won Il , Yi Gyu-Chul
Published: October 2005

We report on optical characteristics as well as electron emission of hydrogen-plasma treated ZnO nanoneedle arrays. The nanoneedle arrays were vertically grown on Si substrates using catalyst-free metalorganic chemical vapor deposition and subsequently treated by hydrogen plasma at room temperature. After hydrogen plasma treatment, the field emission characteristic curves of nanoneedle arrays exhibited significantly reduced turn-on field and increased emission current density, and the electrical conductivity was increased. In addition, low temperature photoluminesence (PL) measurements indicate that a neutral-donor bound exciton PL peak intensity was increased by the hydrogen- plasma treatment. These effects of the plasma treatment on the physical properties may be explained in terms of hydrogen doping effect.
Influence of the growth temperature on the atomic distribution of TEOS deposited SiO2 films
Authors: Vamvakas Vassilis Em. , Davazoglou Dimitris
Published: October 2005

Dispersion analysis was performed on low pressure chemically vapor deposited SiO2 films from tetraethylorthosilicate (TEOS) vapors at temperatures between 635 and 820°C. The transmission spectra were best reproduced using four Lorentzian oscillators within the range 900–1400cm−1 and two Lorentzian oscillators within the range 700–900cm−1. This is justified if one considers that two kinds of Si–O–Si bridges exist in films: those bearing characteristics similar to bulk fused silica (bulk-like bridges) and those located near the interfaces and grain boundaries (boundary-like bridges). The ratio of the populations of bulk to boundary-like bridges increases with deposition temperature from 1.2:1 at 635 to 2.1:1 at 820°C. Postdeposition annealing also causes an increase of bulk-like bridges at the of boundary-like ones. The distribution of the Si–O–Si angles in TEOS SiO2 films, related to the way atoms are arranged in them, is not a simple but it is a superposition of two Gaussians with different central values and full width at half maximum. The distance between the central angles of the two Gaussians was found to be between 7.7° for films deposited at 635°C and decreases to reach a value equal to 6.3° for those deposited at 820°C.
Surface-enhanced Raman spectroscopy of nanodiamond particles on silver
Authors: Perevedentseva E. , Karmenyan A. , Chung P.-H. , Cheng C.-L.
Published: October 2005

Surface-enhanced Raman scattering was applied to study the nanodiamond with particles’ sizes 100 and 5 nm, positioned on silver (Ag) substrate using high focused laser beam acceleration method. The nanodiamond particles suspended in distilled water were accelerated by a near infrared laser beam and attached to an Ag foil serving as the target. This allows the nanodiamond particles to be ordered, positioned, and to penetrate deep into Ag. The nanodiamond–Ag surface structure after nanoparticles∕laser beam treatment was analyzed using micro-Raman spectroscopy and scanning electron microscopy. Strong interaction between the nanodiamond and Ag surface can be achieved, which allows us to observe surface-enhanced Raman scattering (SERS). The most significant enhancement observed for carbon was trans-polyacetylene bands in addition to the D and G bands. The enhancement can achieve orders in magnitude both for 100 and 5 nm nanodiamonds. The selective enhancement of some composite band intensity, a characteristic feature of SERS referred to as the blinking effect, was also observed.
Presence of nanosize Au dots on the formation of ohmic contact for the Ni–Au base film to p-GaN
Authors: Yang Jiin-Long , Chen J. S. , Chang S. J.
Published: October 2005

The role of nanosize Au dots in the contact characteristic of Au∕Ni∕NiO stacked films to p-type GaN is studied. The nanosize Au dots were fabricated by heating a 1-nm-thick Au film at 150 °C in nitrogen ambient for 6 min. The NiO(2 nm), Ni(2 nm), and Au(2 nm) films were deposited sequentially on p-GaN, without or with the preformed Au dots. Without the nanosize Au dots, the Au∕Ni∕NiO∕p-GaN structure shows nonlinear current-voltage (I-V) curves, even after annealing at 400 °C. On the contrary, the Au∕Ni∕NiO∕dot-Au∕p-GaN structure exhibits linear I-V curves of ohmic behavior after annealing at 400 °C in oxygen ambient. The nanosize Au dots indirect contact with p-GaN imitate the microstructure of Au islands in the annealed Au–Ni system and they create a microstructure of the Au–NiO–GaN triple-phase junction. The mechanism for the formation of contact via annealing and the presence of triple-phase junction are discussed.
Nanopatterning of polyfluorene derivative using electron-beam lithography
Authors: Doi Yusuke , Saeki Akinori , Koizumi Yoshiko , Seki Shu , Okamoto Kazumasa , Kozawa Takahiro , Tagawa Seiichi
Published: October 2005

Direct nanopatterning of polyfluorene derivative is demonstrated using electron-beam lithography. Polyfluorene, which has attracted much attention because of its strong fluorescence and application in organic light emitters, is a negative (crosslinking) type material upon exposure to radiation, and requires a large amount of exposure dose ∼2300μC∕cm2 to be patterned in the present case. This extremely large dose would lead to radiation damage of the polymer. To address this issue, a polyfluorene derivative for acid-catalyzed chemical amplification was synthesized to realize nanopatterning of π-conjugated polymer without degrading its optical property. The synthesized polyfluorene derivative was investigated in terms of sensitivity, optical absorption, and spatial resolution. Sensitivity of 4μC∕cm2 was achieved, and lines of 70 nm width were fabricated after optimization of the process conditions.
Thermal stability of trimethylsilylated mesoporous silica thin films as the ultralow-k dielectric for copper interconnects
Authors: Chen J. Y. , Pan F. M. , Chang L. , Cho A. T. , Chao K. J.
Published: October 2005

Surfactant templated mesoporous silica thin films were prepared as the intermetal dielectric for ultralarge scaled integrated circuit application, and the thermal and chemical stability of the Cu∕nitridedTa∕mesoporous silica film stack on the Si wafer was studied. Trimethylsilylation of the mesoporous silica thin film by hexamethyldisilazane vapor treatment significantly improves hydrophobicity of the mesoporous dielectric, and a dielectric constant (k) smaller than 2 can be obtained for the thin film. According to Fourier transform infrared spectroscopy and thermal desorption spectroscopy, decomposition of trimethylsilyl groups on the pore surface becomes significant at temperatures larger than 400 °C. However, when the metallized film stack was annealed at temperatures higher than 400 °C, the film stack shows little delamination between layers and still retains smooth interfaces according to Auger electron spectroscopy and transmission electron microscopy analyses. Ta2C nanoparticles were found to exist at the Ta(N)∕mesoporous silica interface of the film stack annealed at 600 °C. Bias-temperature stress test of the metallized film stack shows little Cu diffusion into the mesoporous dielectric layer.
Effects of ambient gases on the direct growth of SiC nanowires by a simple heating method
Authors: Ryu Yonghwan , Yong Kijung
Published: October 2005

A large quantity of highly uniform SiC nanowires was directly synthesized from Si substrates using a thermal heating method. The atomic structure, morphology, and composition of the SiC nanowires were strongly dependent on the ambient gases (Ar,N2) used during nanowire growth. The nanowires grown in Ar were coated with amorphous carbon layers while the nanowires grown in N2 had no coating layers. Also, nitrogen and oxygen were incorporated only into SiC nanowires grown in N2. A proposed model for the role of ambient gases in the SiC nanowire growth is discussed.
Conformability and optical reflectance of Ti∕Au film sputtered on the Si vertical sidewalls
Authors: Jo Kyoung-Woo , Yun Sung-Sik , Punithavelan Nallamuthu , Ho Jeong Sung , kyu Lee Sun , Lee Jong-Hyun
Published: October 2005

A high quality reflective vertical surface is required for various optical micro electro mechanical system (MEMS) devices. In this paper, we discuss an extensive investigation of Ti∕Au sputtering, with respect to temperature, pressure, and electric power input, followed by rapid thermal annealing (RTA) to improve the adhesion and reflection characteristics of a vertical micromirror. The vertical surface was fabricated by means of the deep reactive ion etching (DRIE) process of a silicon-on-insulator (SOI) wafer, with an 80-μm-thick layer of Si. Then, 20-nm-thick Ti and 200-nm-thick Au films were deposited on the vertical surface as adhesion and reflective layers, respectively, using rf/dc magnetron sputtering. The Au films were deposited at room temperature (20°C) and annealed at 380°C for 30s in a RTA chamber. While taking into consideration the conformability and the reflectance of the Au vertical mirror, the process conditions were optimized at an argon pressure of 10mTorr and an electric power input of 300W. The best surface roughness obtained was 7nm (rms) for a useful upper sidewall with a reflectance of 97.5% in the IR (Infrared) range (1500nm–1600nm).
Simultaneous elastic and electromechanical imaging by scanning probe microscopy: Theory and applications to ferroelectric and biological materials
Authors: Shin J. , Rodriguez B. J. , Baddorf A. P. , Thundat T. , Karapetian E. , Kachanov M. , Gruverman A. , Kalinin S. V.
Published: October 2005

An approach for combined imaging of elastic and electromechanical properties of materials, referred to as piezoacoustic scanning probe microscopy (PA-SPM), is presented. Applicability of this technique for elastic and electromechanical imaging with nanoscale resolution in such dissimilar materials as ferroelectrics and biological tissues is demonstrated. The PA-SPM signal formation is analyzed based on the theory of nanoelectromechanics of piezoelectric indentation and signal sensitivity to materials properties and imaging conditions. It is shown that simultaneous measurements of local indentation stiffness and indentation piezocoefficient provide the most complete description of the local electroelastic properties for transversally isotropic materials, thus making piezoacoustic SPM a comprehensive imaging and analysis tool. The contrast formation mechanism in the low frequency regime is described in terms of tip-surface contact mechanics. Signal generation volumes for electromechanical and elastic signals are determined and relative sensitivity of piezoresponse force microscopy (PFM) and atomic force acoustic microscopy (AFAM) for topographic cross-talk is established.
Simple universal connections between energy velocities in anisotropic elastic media
Authors: Hayes M.
Published: October 2005

The propagation of linearly polarized plane harmonic waves in homogeneous anisotropic perfectly elastic media is considered. Three arbitrary coplanar directions of propagation are chosen. It is shown that there are connections between the energy velocities corresponding to the three waves which may propagate in each of these three directions. These connections are universal in the sense that they are independent of the elastic constants describing the material and are therefore valid, irrespective of the elastic symmetry of the material. These connections provide a useful check on measurements for the experimentalist.
Analysis of propagation of waves of acoustic frequencies in curved ducts
Authors: Rostafinski W.
Published: October 2005

The propagation of waves of acoustic frequencies in curved ducts of rectangular cross section is studied for the first four modes. The analysis makes use of Bessel functions of the order [n + 1/2] to construct curves of wavenumber in the duct versus imposed wavenumber and to determine the profile of vibrational velocities. A wide range of duct widths and unrestricted radii of curvature have been considered. The characteristics of motion in a bend are compared with propagation of waves in a straight duct, and important differences in the behavior of waves are noted.
Webster wave equation in two dimensions
Authors: Yeow K. W.
Published: October 2005

The Webster wave equation, describing the transmission of sound in one-dimensional variable-area acoustic horns, is extended to two dimensions, using the “fluid element” approach and the “plane-wave” assumption of Webster. The extended wave equation is applicable to any arbitrary, variable-area rotationally symmetric channels whose transverse dimension is much less than a wavelength, and describes the transmission of higher-order (m, 0) tangential modes. Two forms of the two-dimensional Webster wave equation are given, one for axisymmetric propagation in the radial direction, as for example in the diffuser section of a centrifugal compressor, and the other for propagation in the axial direction, as for example, in the intake annulus of an axial compressor. Both forms agree with known standard equations for special system geometries, and may be used to analyze the transmission of (m, 0) modes originating from rotor—stator interaction in those rotating blade turbomachine systems whose channel geometries much too complicated to be handled by usual “variables-separate” methods.
Scattering of sound from a random time-varying rough surface
Authors: Zipfel G. G.
Published: October 2005

The statistical moments of the acoustic field scattering from a random time-varying rough surface have been found in terms of a series expansion with a diagrammatic representation. The surface is assumed to be pressure-release with multivariate Gaussian statistics. The mean field and the field-correlation function are discussed in particular. Partial summation of the series for these field moments is carried out in terms of linear integral equations.
Analysis of the class-IV flextensional transducer by use of wave mechanics
Authors: Brigham Gerald A.
Published: October 2005

A model of the class-IV oval flextensional transducer is developed by using the differential equations for an oval ring to describe the radiating shells, longitudinal wave theory to describe the ceramic bar, and elliptical radiation functions to determine the acoustic pressure field. Comparisons between the model parameters and experimental data for deflection, resonance, and impedance are quite good over a decade bandwidth for the ceramic bar and for the bar with a single oval ring. The results of a comparison between the model and experimental results for the complete, air-filled transducer are quite satisfactory in bandwidth, resonance frquency, and source level.
Effects of horizontally varying internal wavefields on multipath interference for propagation through the deep sound channel
Authors: DeFerrari Harry A.
Published: October 2005

Fluctuations of CW signals transmitted through real ocean paths are characterized by smooth slow variations in phase and rapid noise-like variations in transmission loss. The variations are thought to be the results of internal waves, which perturb the sound-speed field and thereby produce time-varying multipath interference. This study is concerned with modeling the effects of large-scale horizontal and vertical perturbation of the sound-speed field on multipath interference of CW signals, for the particular case of long-range propagation through the deep sound channel. The vertical profile is approximated by two layers of linear sound-speed gradient and arbitrary horizontal variations are introduced by numerical methods. The influence of horizontal wavelength of idealized internal wavefields is studied by using model simulations of time-varying transmission. The travel times along the individual ray paths are shown to be influenced by fluctuations of the sound-speed field with horizontal scales which are (1) approximately equal to the cycle distance of the ray; or (2) greater than several cycle distances of the ray. Both scales of disturbance induce multipath interference but the latter also induces temporally correlated phase shift for all ray paths. The models are used to interpret results of fixed system measurements of CW transmission fluctuations over a 700-NM range. Model computations show that horizontally invariant internal waves cannot cause both the phase and transmission loss fluctuations which are consistent with experiments. When horizontal fluctuations are introduced, statistics of CW transmission fluctuations match experimental results.
Coherence function for cylindrically spreading waves in a random medium
Authors: Fitelson M. M.
Published: October 2005

The coherence function for a cylindrically spreading wave in a random medium is obtained as the exact solution of an equation derived from the wave equation when forward scattering is dominant. The region of validity for this equation is obtained under the assumption that the index of refraction is a Gaussian field. The coherence function for cylindrically spreading waves is compared with the corresponding solution for the plane-wave case. Both the cylindrical and plane-wave solutions are shown to have essentially the same range of validity.
Attenuation in randomly inhomogeneous sound channels
Authors: Mellen R. H. , Browning D. G. , Ross J. M.
Published: October 2005

Measurement of sound absorption in sea water by sound-channel experiments can be seriously affected by volume scattering. Ray diffusion caused by random inhomogeneities in sound speed leads to an additional component of attenuation independent of frequency. Order-of-magnitude estimates of diffusion loss, with the variance and scale size of perturbations determined from the sound-speed profiles, are in reasonable agreement for a broad range of experimental data.
Viscoelastic relaxation in a series of short-chain polydimethyl siloxanes
Authors: Barlow A. J. , Erginsav A.
Published: October 2005

The viscosity, shear modulus, and viscoelastic relaxational behavior of series of linear short-chain polydimethyl siloxane liquids have been determined. The five silicones studied are those with 5, 7, 9, 10, and 11 Si atoms per molecule. Measurements were made of the dynamic shear resistance at a frequency of 459 MHz and at temperatures down to −140°C. The relaxational behavior of the 5 and 7 Si atom liquid is found to be similar to that of a wide range of supercooled organic liquids. The relaxational curves for the 9, 10, and 11 Si atom siloxanes indicate a progressively broader relaxation region. This broadening is considered to be due to the onset of polymer mode behavior. There are differences between some previously reported results for a 10 Si atom liquid and those given here.
Effect of boundary conditions on the ultrasonic-beam characteristics of circular disks
Authors: Dekker Don L. , Piziali Robert L. , Dong Eugene
Published: October 2005

The ultrasonic-beam characteristics of piston (case 1) are first reviewed and then two radially symmetric velocity distributions—a simply supported disk Ussd [1 − (r/R)2] (case 2), and a clamped disk Ucd[1 − (r/R)2]2 (case 3)—are used to calculate the axial intensity and directivity of the resulting ultrasonic beam. The oscillations in axial intensity for both cases 2 and 3 are less than that for case 1. The axial intensities are compared both for equal maximum velocities and equal source strengths. According to the Fraunhofer equation, the diverging portion of the beam from a piston begins at approximately 1.6 R2/λ; not at the position of the last axial maximum, approximately R2/λ. The position of the last axial maximum lessens from R2/λ for case 1, to 3/4 R2/λ for case 2, and 9/16 R2/λ for case 3, Directivity calculations show that the conical half-angle for case 2 is 20% greater than for case 1, and for case 3, it is 60% greater than case 1. The first side lobes for cases 2 and 3 are 7 and 13 dB down, respectively, from the first side lobe of case 1. The second side lobes for cases 2 and 3 are 9 and 18 dB down, respectively, from the second side lobe of case 1.
Jet noise at schools near Los Angeles International Airport
Authors: Lane Samuel R. , Meecham William C.
Published: October 2005

In this study, indoor and outdoor measurements of jet aircraft noise were made at seven schools beneath the eastern approach paths to the Los Angeles International Airport. At five elementary schools, the jet noise in the schoolyards ranged from 96 to 118 dBC and constituted a high risk of hearing damage for the children. The frequency of jet aircraft overflights averages one per 2-min interval for a total of about 200 per school day (8:30 a.m.–3:30 p.m.). The corresponding jet-noise levels in the classrooms (80% of which are not air-conditioned or acoustically treated) ranged from 80 to 96 dBA and caused continual disruption of communication and the learning processes. An investigation of aircraft operation alternatives indicated that the noise could be reduced by 10 dB or more if engine power were properly managed when the aircraft approaches the school areas, or if the aircraft approached at higher altitudes and landed further to the west on the unused 6000-ft-long portion of the 12 000-ft-long runways.
Theoretical prediction of highway noise fluctuations
Authors: Marcus Allan H.
Published: October 2005

A theoretical model is developed to predict fluctuations in traffic noise due to statistical variation in properties of highway traffic, including differences in vehicle type, variations in individual vehicle emissions, clustering of vehicles by vehicle type, and variations in vehicle spacings within and between platoons. Traffic flow is described by a Markov renewal process (MRP), and the noise heard by an off-highway observer as a filtered MRP. Simple formulas for the arithmetic mean, variance, and covariance function of noise intensity are derived for the "shot noise" case (exponentially distributed spacings). A more complicated model with car and truck clustering is investigated numerically, based on traffic data given by Jewell for the southbound curb lane of U.S. 40 in Berkeley, California. Even with only a modest degree of truck clustering and variability in vehicle spacings and noise emission, the variation in noise level is much greater than usually predicted. The coefficient of variation of noise intensity is greater than unity at distances from the roadway less than 700 ft. Peak noise levels may thus be greatly underestimated (2 to 3 dB per highway lane) if these sources of variability are ignored.
Effect of rotating diffusers and sampling techniques on sound-pressure averaging in reverberation rooms
Authors: Tichy Jiri , Baade Peter K.
Published: October 2005

The paper summarizes different means and techniques for measuring sound-power and -pressure averaging in reverberation rooms. Stationary reflectors, properly located in the nearfield of the source and properly oriented with respect to the floor, can contribute considerably to the scattering of the energy radiated by the sound source. The final effect consists of reduction of the dependence of the radiated sound power on the source position. Rotating diffuser vanes are important for determining the sound power radiated at single frequencies. There are three effects: (i) The motion of the vane causes fluctuations of the sound pressure at each point of the chamber and, thus, reduces the dependence of the sound pressure on the microphone location. (ii) The motion of the vane causes a Doppler effect; an originally single-frequency tone becomes a frequency-modulated tone. Thus, a single line spectrum becomes a multiline spectrum, which reduces the spatial variations of the sound pressure and also increases the number of room modes excited. (iii) The radiation impedance of the source depends on the instantaneous position of the vane and, thus, its rotation provides averaging of the radiated power. When averaging the sound pressure, different sampling techniques can be used.
Sequential vs simultaneous two-channel signal detection: more evidence for a high-level interrupt theory
Authors: Gilliom J. D. , Sorkin R. D.
Published: October 2005

Performance was studied in a binaural two-channel sequential detection task under four stimulus conditions—frequency in each channel, either the same or different, and background noise in the earphones, either correlated or uncorrelated. For each stimulus condition, two procedural conditions were used—a fixed procedure, in which the order of presentation of observation intervals was fixed and known to the observer, and a random procedure, in which the order of presentation of observation intervals was a trial-by-trial random event. Two-channel performance was evaluated relative to performance in corresponding single-channel tasks. Overall, there was a decrement from single- to two-channel conditions; this decrement was symmetrical across channels and was not affected by knowledge of the order of observation intervals. The overall decrement increased when channel frequencies were the same, especially when the background noise was correlated. Performance, conditional upon contralateral events, was also determined, and the performance decrement in two-channel conditions was found to be primarily due to those trials on which there was a contralateral signal event. Associated with the larger performance decrements was a shift in the apparent criterion in the direction of “following” contralateral stimulus events. These results were compared to the results of earlier studies which employed monaural and binaural two-channel simultaneous detection paradigms as well as a monaural two-channel sequential detection paradigm. Possible hypotheses for the decrement in two-channel performance are discussed; one candidate is a processor model based upon an interrupt system and incorporating a noisy recognition process.
Loudness discomfort level under earphone and in the free field: the effects of calibration methods
Authors: Morgan Donald E. , Dirks Donald D.
Published: October 2005

Previous earphone LDL data from this laboratory were characterized by an intensity level increase in the low frequencies which we suggested resulted from the difference between the SPL measured in a standard coupler and that actually generated in the ear under a supra-aural earphone. The experiments reported herein were conducted to determine if the frequency effect could be explained adequately on the basis of differences between conventional and real-ear calibration methods and to extend the LDL measurement to free-field conditions. Determination of the SPL generated by an earphone and by a loudspeaker in the free field was accomplished with a probe tube at the entrance to the ear canal under earphone and free-field conditions and by conventional calibration methods. Psychophysical measurements of loudness discomfort (LDL) and loudness balance (ABLB) were conducted under earphone and in the free field. Corrections derived from differences between standard calibration procedures and probe tube measurements were applied to the psychophysical measurements. The corrected results lead to the following conclusions: (1) there is no intensity level increase in the low frequency LDL under earphone; (2) there are no differences between earphone and free field LDL and ABLB judgments. The relationships between these data and previously published MAP-MAF differences are discussed.
Effect of masker duration and masker level on forward and backward masking
Authors: Penner M. J.
Published: October 2005

Temporal masking of clicks by noise was investigated using forward and backward masking paradigms. The level and duration of the noise and temporal separation, Δt, between the click and noise were varied. There are three primary findings. First, for Δt less than 1 msec, as the noise level increased by 20 dB the click threshold increased by 20 dB. Between 1 and 10 msec the increase depended on Δt, so that the signal-to-noise ratio was not preserved. Second, the duration of the masker did not greatly affect the click threshold when Δt was brief (0.1 msec) or long (100 msec). For intermediate Δt's, the threshold increased by as much as 30 dB as the noise duration increased from 1 to 625 msec. Third and finally, for very brief Δt's, under some conditions, detectability actually improved as the click was moved closer to the noise. The theoretical implications of these results are discussed in terms of various theories of temporal integration.
Short-period infrasonic-noise spatial coherence
Authors: Flores José S. , Otero Alfredo H.
Published: October 2005

A new method for treating the problem of infrasonic-noise spatial coherence with relation to a noise-reducing array design is developed. The behavior of this coherence at Peñas, Bolivia (4000 m above sea level), is investigated. The optimum spacing between sampling inlets for that particular location seems to be approximately 12 m at this preliminary stage of the work. The noise recorded with a two-inlet noise-reducing array at a 12-m separation was 40% less than that using only one inlet.
Impulse response and radiation impedance of an annular piston
Authors: Stepanishen P. R.
Published: October 2005

An approach is presented to evaluate the impulse response of an annular piston, which is mounted in an infinite planar rigid baffle. Since the impulse response is defined to be the time-dependent force on the ring, which results from an impulsive velocity of the ring, the impulse response and radiation impedance of the ring are a Fourier transform pair. A closed-form expression for the impulse response of a ring of any size is developed from the well-known double surface integral representation of the radiation impedance. Various integral and asymptotic expressions for the radiation impedance of the ring are derived from the impulse response, and the results are shown to be in agreement with those of earlier investigators. Several numerical results are also presented to show the effect of changing the ring size on the impulse response, and on the radiation resistance and reactance of the ring.
Farfield viscous effects in nonlinear noise propagation
Authors: Harris Wesley L.
Published: October 2005

The method of parametric differentiation has been applied to predict the farfield noise propagation in both a lossless and a dissipative medium. The classical nonlinear acoustical problems of calculating the sound field of two rectilinear vortices rotating about an axis between them in a lossless medium and of calculating the sound field generated by a rotating cylinder in a viscous medium have been investigated. Solutions to these classical problems valid for asymptotically small Mach number have been extended to larger values of the Mach number parameter. It is shown that in the lossless medium, the governing equation transformed to parameter space reduces to a wave equation in the farfield. In the dissipative medium, the system of nonlinear partial differential equations transformed to parameter space reduces to a linear partial differential equation of the propagating type which contains a third-order derivative as well as the wave operator. Pressure distributions in the farfield are obtained in the lossless medium; the results appear reasonable physically and mathematically self-self-consistent. The method of parametric differentiation and Newton's method are compared.
Measurements of sonic-boom overpressures from Apollo space vehicles
Authors: Hilton David A. , Henderson Herbert R.
Published: October 2005

This paper presents representative results of sonic-boom overpressure data recorded during the launch and reentry of the Apollo 15 and 16 space vehicle systems. Comparisons are made between measured overpressures and those predicted using available theory. The measurements were obtained along the vehicle ground track at 68, 87, 92, 129, and 970 km downrange from the launch site during ascent, and at 9, 13, 55, 185, and 500 km from the splash-down point during reentry. Also included are tracings of the sonic-boom signatures along with a brief description of the launch and recovery test areas in which the measurements were obtained, the sonic-boom instrumentation deployment, flight profiles and operating conditions, and high-altitude weather information for the general measurement areas.
Damping of gas bubbles in water from desinent threshold for subharmonic-1/2
Authors: Ceschia M. , Iernetti G.
Published: October 2005

Threshold for subharmonic-1/2 emission has been measured in water saturated with different gases in a sound field of 0.7 MHz. Incipient threshold is determined by bubbles of radii smaller than that of resonance at subharmonic-1/2, the desinent threshold by bubbles resonant at this frequency. The latter can be correlated to the lowest sound pressure for subharmonic-1/2 emission and to the resonant-bubble damping constant. The experimental data are in good agreement with the predictions, for He, N2, air, O2, and Ar bubbles in water, but for H2 bubbles the threshold results are about three times the predicted values.
Some considerations in choosing an explosive source and processing filter for the measurement of transmission loss
Authors: Hanna J. S. , Parkins B. E.
Published: October 2005

Explosives are often used as a source of acoustic energy in transmission measurements in the ocean because of the broad-band spectra of underwater explosions and the wide range of levels that can be generated. At the same time, this broad-band spectrum can complicate a transmission loss measurement because the spectral character of the shock wave and subsequent bubble pulses of the shot can be very similar to the spectral character of the loss which is due to the multipath structure of the propagation. This complication can be avoided by the proper choice of the detonation depth and the charge weight. When these choices have been made, the properties of the analyzing filter of the data processing system must then be selected; this must be done with regard for the nature of that portion of the multipath structure to be resolved as well as the nature of the charge spectrum. This paper discusses the principles involved in making these choices and gives illustrations of both short- and long-range measurements.
Intermodal coupling coefficients for a fluid-loaded rectangular plate
Authors: Pope Larry D. , Leibowitz Ralph C.
Published: October 2005

The intermodal coupling coefficients are calculated for a thin, simply supported rectangular plate in an infinite rigid baffle. The coefficients describe the modal auto- and cross-resistive and reactive coupling induced by a dense fluid-filled half-space above the plate.
Long-range sound fluctuations with drifting hydrophones
Authors: Spindel R. C. , Porter R. P. , Jaffee R. J.
Published: October 2005

Phase fluctuations of underwater sound (406 Hz) transmitted between a fixed source and deep free-drifting hydrophones have been obtained for transmission ranges of 200 km. Phase variations due to hydrophone drift are removed by a bottom-moored, CW tracking system that corrects for motion-induced phase variations of 0.06 rad or larger. Most of the energy traveled along refracted paths, eliminating much of the phase fluctuation due to bottom and surface scatter. Residual surface scatter effects are removed by narrow-band filtering. Maximum observed phase fluctuations are 15 cycles over 3 h on the deepest hydrophones (1500 m). The mean-square phase spectrum has a slope of −2 for frequencies between 0.4 and 40 cycles/h. The shallow hydrophone (300 m) data contain half the phase fluctuation of the deep hydrophones. Depth dependence of the fluctuations is attributed to internal gravity waves.
Internal tidal influence on deep-ocean acoustic-ray propagation
Authors: Weinberg N. L. , Clark J. G. , Flanagan R. P.
Published: October 2005

Based upon previous studies of fixed-system acoustic-environmental relationships in the Straits of Florida, work on transmission fluctuations has been extended to the deep ocean. The model for the acoustic propagation study employs linear profiles for the sections at the surface and bottom, and hyperbolic cosines for the region about the minimum sound-velocity axis. Closed-form solutions are known for each profile segment, and combining these, the initial angles of all ray arrivals which reach a specified receiver from a given source are determined. By calculating travel time, spreading loss, and the boundary effects at the surface and bottom, the amplitude and phase (assuming CW transmission of a known frequency) of each arrival can be found. These arrivals, when summed as a function of time, yield the resultant acoustic time series for sound-speed profile variations derived from assumed amplitudes of internal tides of 2,4,7, and 10 m. These time series are compared with data. It is shown that the effect of surface tides on acoustic propagation in the deep ocean is minimal.
Impact on coaxial circular cylinders of two materials
Authors: O'Leary Patrick M. , Eringen A. Cemal
Published: October 2005

In this paper, the problem of an impulsive load on a bar, composed of two coaxial cylinders of different materials, is investigated. Double integral transforms are used to solve the equations of motion. The exact solution appears as a sum of Fourier integrals, whose integrands are all divided by the generalized version of the Pochammer-Chree frequency equation. Asymptotic values are obtained by using the saddle-point method of integration. The displacements and stress functions are plotted for various times at a point far away from the point of impact. These functions are also plotted across the bar to show the effect of the interface surface.