bluuebunny/crossref_metadata_2025 huggingface dataset:
Rigorous coupled wave analysis of front-end-of-line wafer alignment marks
Authors: Yeo Swee Hock , Tan Chin Boon , Khoh Andrew
Published: January 2005

In photolithography, wafer alignment marks are used to align the current masking layer to the previous layer. Conventional marks are usually gratings with equal width of lines and spaces. In order to achieve more reliable alignment signal, higher order of the reflected beam is required to define the edges precisely. However, the strength of reflected beam for conventional marks decreases as the order number increases. In this article, enhanced order marks, which are able to give better diffraction efficiency at higher reflected order, are studied. A model based on rigorous coupled wave analysis is adopted and developed to analyze different types of step grating alignment marks. As the period-to-wavelength and depth-to-period ratios for alignment mark are acceptable, this model is adequate to generate reliable results. When small periodic gratings of 5.33, 3.20, and 2.29 μm are incorporated into 16 μm periodic marks, the reflected diffraction efficiency is enhanced at third, fifth, and seventh orders, respectively. Forbidden mark depth, which gives almost zero diffraction efficiency for higher reflected order, is also identified for both 633 and 532 nm alignment wavelength. The results also show that, irregardless of the type of marks and alignment wavelength, whenever the zeroth order reflected diffraction efficiency drops to minimum, it gives the strongest higher order reflected diffraction efficiency. When transverse magnetic polarization is considered, it is able to give higher reflected diffraction efficiency if compared to transverse electric polarization. The experimental results demonstrated that overlay as low as 10 nm can be achieved when fifth order enhanced mark was used for 90 nm and 0.11 μm technology node process.
Fabrication of natural diamond microlenses by plasma etching
Authors: Choi H. W. , Gu E. , Liu C. , Griffin C. , Girkin J. M. , Watson I. M. , Dawson M. D.
Published: January 2005

Advantageous properties including optical transparency, high thermal conductivity, and high carrier mobility make natural diamond an attractive choice for a range of optical and electrical devices. However, its hardness and chemical inertness provide a significant challenge for device processing. We demonstrate the ability to etch natural type IIa diamond using inductively coupled plasma etching with a significant etch rate of 228nm∕min. The etched surfaces were characterized by atomic force microscopy and found to have a root-mean-square roughness of below 3 nm. Using the photoresist reflow technique, refractive microlens arrays, with diameters ranging from 10 to 100 μm, were fabricated on the same diamond substrates. The lenses were characterized by confocal microscopy, which showed that their focal lengths, ranging from 5 to 500 μm, were in excellent agreement with the predicted values, demonstrating the high fidelity of the fabrication process.
Partial blanking of an electron beam using a quadrupole lens
Authors: Zhang Feng , Smith Henry I.
Published: January 2005

Inadequate pattern-placement accuracy is becoming a limiting factor for conventional scanning-electron-beam lithography (SEBL) in many applications, such as mask writing and fabrication of integrated optical devices. Spatial-phase-locked electron-beam lithography (SPLEBL) with continuous feedback promises sub-1-nm placement accuracy by monitoring and correcting the beam position in real-time during exposure [J. T. Hastings, F. Zhang, and H. I. Smith, J. Vac. Sci. Technol. B 21, 2650 (2003)]. Ideally, SPLEBL provides a continuous reference signal to infer and correct beam position. Hence, the beam current must be reduced by a factor of 10 or more when traversing areas that are not to be exposed. To accomplish this we have investigated a partial-beam-blanker which consists of a quadrupole lens and a current-limiting aperture. This design has several desirable features. First, it does not shift the center of mass of the beam, so that spurious deflection can be avoided. Second, the operating voltage of the device is very low, which makes it suitable for high modulation rate. Third, this device can be easily incorporated into existing SEBL system design. In this article, the theoretical background will be provided, and the effect of the quadrupole lens on the beam probe size evaluated.
Electron-beam-assisted etching of CrOx films by Cl2
Authors: Wang S. , Sun Y.-M. , White J. M. , Stivers A. , Liang T.
Published: January 2005

Based on analysis by in situ Auger electron spectroscopy, partially oxidized Cr films, 3–10nm thick, were etched by the combination of 2keV electrons and Cl2(g). The Cl2 gas pressure in the area irradiated by the e beam is critical and must be in the mTorr regime. For the flux (8mAcm−2) of electrons used, the etching rate saturated for estimated local Cl2 pressures above 2mTorr. The effects on etching of small amounts of Si are described.
Evaluation of lanthanum based gate dielectrics deposited by atomic layer deposition
Authors: Triyoso D. H. , Hegde R. I. , Grant J. M. , Schaeffer J. K. , Roan D. , White B. E. , Tobin P. J.
Published: January 2005

In this article, we evaluated physical and electrical characteristics of La-based gate dielectrics (La2O3 and LaAlxOy) deposited by atomic layer deposition (ALD). The precursors used for La2O3 and LaAlxOy are lanthanum tris[bis(trimethylsilyl)amide] La[N(SiMe3)2]3, trimethyl aluminum [Al(CH3)3], and water. Physical properties of these dielectric films were studied using ellipsometry, x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). To investigate electrical properties of these La-based dielectrics, metal oxide semiconductor capacitors (MOSCAPs) were fabricated using metal gates (Ta–Si–N, TiN and Pt). Linear growth rate characteristics were observed for ALD (La2O3 and LaAlxOy films deposited at temperatures of 225to275°C. XPS and XTEM analysis of La-based films grown on a chemical oxide starting surface revealed a rough La-based dielectric/Si interface and chemical interaction with the Si substrate. In general, adding Al into La2O3 improved electrical properties of the films. Devices with La based dielectric deposited on a ∼10Å Al2O3 underlayer had better capacitance-voltage characteristics compared to those deposited directly on a chemical oxide surface. Adding Al to the dielectric also resulted in lower leakage current and smaller hysteresis. For devices with Ta–Si–N gates, a significant decrease in maximum capacitances was observed after forming gas annealing, probably due to interaction between the gate electrode and the dielectric. XTEM images for these devices indicated an indistinct interface between the Ta–Si–N gate and the La-based dielectrics. The XTEM images also showed microcrystals in Ta–Si–N that may be formed in Si deficient regions of the metal gate. No interaction between TiN or Pt with La gate dielectrics was observed by XTEM up to 800°C annealing temperature. After 900°C annealing, some interaction between LaAlxOy and Pt gate was observed. Our results indicated that silicon substrate interactions may limit the utilization of ALD La based dielectrics in future complementary metal-oxide semiconductor processing.
Deposition control for reduction of 193nm photoresist degradation in dielectric etching
Authors: Negishi N. , Takesue H. , Sumiya M. , Yoshida T. , Momonoi Y. , Izawa M.
Published: January 2005

The 193nm photoresist (ArF resist) degradation mechanism in dielectric etching was investigated by using an ultra-high-frequency electron-cyclotron-resonance plasma. This investigation focused on via-hole etching. It was found that the bottom-antireflection coating (BARC) etching condition is a critical factor in the reduction of striation and pitting after via-hole etching. X-ray photoelectron spectroscopy and scanning electron spectroscopy studies revealed that argon-less and low-incident-ion-energy conditions in BARC etching can keep the resist surface smooth and maintain a carbon-rich micromask-less state because decomposition of the C–H or OC–O bonds is suppressed. As a result, resist damage after via-hole etching is reduced remarkably. Furthermore, in the via-hole etching, it was also found that the characteristics of the fluorocarbon polymer, i.e., deposition rate and flourine-to-carbon ratio of the fluorocarbon polymer, stacked on the resist surface during etching strongly affect the ArF resist degradation. Low-sticking-coefficient radicals such as CF2 and a low amount of deposition thickness are suitable for damage-less etching. In regard to the formation of striations at the pattern corner, the sputtering effect was taken into consideration. As a result, in the case of via-hole etching, line-edge-roughness in the trench pattern was improved by about 50%, and a striation-less and pitting-less hole etched profile was obtained by using either an argon-and-xenon (20%) mixture as a dilution gas or a fluorocarbon gas at low flow rate under low gas pressure.
High-current-density field emitters based on arrays of carbon nanotube bundles
Authors: Manohara Harish M. , Bronikowski Michael J. , Hoenk Michael , Hunt Brian D. , Siegel Peter H.
Published: January 2005

We have developed high-current density field emission sources using arrays of multiwalled carbon nanotube bundles. The field emission behavior of a variety of lithographically patterned array geometries was investigated and the arrays of 1-μm and 2-μm-diameter nanotube bundles spaced 5μm apart (edge-to-edge spacing) were identified as the most optimum combination, routinely producing 1.5–1.8A∕cm2 at low electric fields of approximately 4V∕μm, rising to >6A∕cm2 at 20V∕μm over a ∼100-μm-diameter area. We have found that the field emission performance depends strongly on the bundle diameter and interbundle spacing and such arrays perform significantly better in field emission than ordered arrays of isolated nanotubes or dense, continuous mats of nanotubes previously reported in literature.
Temperature dependent defect formation and charging in hafnium oxides and silicates
Authors: Lim D. , Haight R.
Published: January 2005

We studied the thermal stability of hafnium oxides and silicates with femtosecond pump/probe photoelectron spectroscopy, employed to monitor photovoltage shifts in the underlying Si substrate induced by the absorption of femtosecond pulses of 800 nm light. Annealing of hafnium oxides and silicates, deposited on thin SiON interlayer oxides grown on lightly doped Si (100) substrates, reveals an abrupt onset of charging at elevated temperatures. Core level photoemission and transmission electron microscopy were used to correlate the observed charge injection at elevated temperatures with structural and chemical changes in the SiON and HfO2 dielectric layers.
Characteristics of heavily doped p+∕n ultrashallow junction prepared by plasma doping and laser annealing
Authors: Baek Sungkweon , Heo Sungho , Choi Haejung , Hwang Hyunsang
Published: January 2005

High quality p+∕n ultrashallow junctions were fabricated by high dose plasma doping and two step annealing involving low-temperature furnace annealing and excimer laser annealing. Without a preamorphization process, laser annealing is effective in terms of activation and annealing. Meanwhile, the junction depth can be controlled by the low-temperature annealing process prior to the laser annealing. By combining low-temperature preannealing and laser annealing, ultrashallow (junction depth ∼22nm), low sheet resistance (∼275Ω∕sq.), and a defect-free p+∕n junction can be obtained without preamorphization.
Solvent-assisted polymer-bonding lithography
Authors: Luan Shifang , Xing Rubo , Wang Zhe , Yu Xinhong , Han Yanchun
Published: January 2005

Solvent-assisted polymer-bonding lithography based on surface adhesion to the transfer pattern between the polymer films is presented. Its primary feature is the application of solvent vapor to enhance the adhesion between the polymers on the elastomeric polydimethylsiloxane mold and the substrate. When the mold is lifted off, the pattern is transferred to the substrate, assuming that the work of adhesion of the polymer/mold and the polymer/substrate was permitted. Solvent-assisted polymer-bonding lithography can fabricate micrometer and submicron patterns between the same and different polymers on the planar and nonplanar substrates at low temperatures and pressures.
Electron-beam patterning with sub-2nm line edge roughness
Authors: Malac Marek , Egerton Ray , Freeman Mark , Lau June , Zhu Yimei , Wu Lijun
Published: January 2005

Negative tone patterns were created by polymer-contamination writing in a transmission electron microscope. Typical line edge roughness of the polymer lines was found to be below 1nm. The patterns were transferred to bismuth films using an anisotropic ion etch, resulting in final bismuth line edge roughness less than 2nm. This low roughness was achieved by growing the bismuth film such that the same crystallographic planes were exposed to the etching flux of ions.
Pulsed laser deposition of lanthanum monosulfide thin films on silicon substrates
Authors: Fairchild S. , Jones J. , Cahay M. , Garre K. , Draviam P. , Boolchand P. , Wu X. , Lockwood D. J.
Published: January 2005

Thin films of lanthanum monosulfide (LaS) have been successfully deposited on Si substrates by pulsed laser deposition. The values of deposition parameters (chamber pressure, substrate temperature, substrate-to-target separation, laser energy, repetition rate, and spot size on the target) leading to a successful growth of films in their cubic rocksalt structure are identified. The films are golden yellow in appearance with a mirror-like surface morphology and possess a sheet resistance around 0.1Ω∕square. X-ray diffraction analysis of thick films (several microns) leads to a lattice constant of 5.863(7)Å, which is close to the bulk LaS value. High-resolution transmission electron microscopy reveals the films to be comprised of nanocrystalline regions separated by amorphous ones. The root-mean-square variation of film surface roughness measured over a 1μm×1μm area is found to be 1.74nm by atomic force microscopy. These films have potential for semiconductor, vacuum microelectronics, and optoelectronics applications.
Characterization of subwavelength elastic cylinders with the decomposition of the time-reversal operator: Theory and experiment
Authors: Minonzio Jean-Gabriel , Prada Claire , Chambers David , Clorennec Dominique , Fink Mathias
Published: January 2005

The decomposition of the time-reversal operator provides information on the scattering medium. It has been shown [Chambers and Gautesen, J. Acoust. Soc. Am. 109, 2616–2624 (2001)] that a small spherical scatterer is in general associated with four eigenvalues and eigenvectors of the time-reversal operator. In this paper, the 2D problem of scattering by an elastic cylinder, imbedded in water, measured by a linear array of transducers is considered. In this case, the array response matrix has three nonzero singular values. Experimental results are obtained with linear arrays of transducers and for wires of different diameters smaller that the wavelength. It is shown how the singular value distribution and the singular vectors depend on the elastic velocities cL, cT, the density ρ of each wire, and on the density ρ0 and velocity c0 of the surrounding fluid. These results offer a new perspective towards solution of the inverse problem by determining more than scattering contrast using conventional array processing like that used in medical ultrasonic imaging.
Acoustical wave propagator for time-domain dynamic stress concentration in a plate with a sharp change of section
Authors: Peng S. Z. , Pan J.
Published: January 2005

The acoustical wave propagator technique is applied to study the time-domain dynamic stress concentration in a two-dimensional flexible plate with a sharp change of section. As a wave packet approaches the plate discontinuity where the sharp change of thickness is introduced, the spatial interference patterns in the displacement of the plate and internal stresses vary with time. The constructive interference of stresses is referred to as time-domain stress concentration. The superposition of wave fronts of incident and reflected wave packets is used to explain the spatial distribution of the interference patterns. The increase of dynamic stress near the vicinity of the discontinuity boundary of the plate is studied as a function of time and the thickness ratio of the plates.
Resonant properties of a nonlinear dissipative layer excited by a vibrating boundary: Q-factor and frequency response
Authors: Enflo B. O. , Hedberg C. M. , Rudenko O. V.
Published: January 2005

Simplified nonlinear evolution equations describing non-steady-state forced vibrations in an acoustic resonator having one closed end and the other end periodically oscillating are derived. An approach based on a nonlinear functional equation is used. The nonlinear Q-factor and the nonlinear frequency response of the resonator are calculated for steady-state oscillations of both inviscid and dissipative media. The general expression for the mean intensity of the acoustic wave in terms of the characteristic value of a Mathieu function is derived. The process of development of a standing wave is described analytically on the base of exact nonlinear solutions for different laws of periodic motion of the wall. For harmonic excitation the wave profiles are described by Mathieu functions, and their mean energy characteristics by the corresponding eigenvalues. The sawtooth-shaped motion of the boundary leads to a similar process of evolution of the profile, but the solution has a very simple form. Some possibilities to enhance the Q-factor of a nonlinear system by suppression of nonlinear energy losses are discussed.
The reflection of ultrasound from partially contacting rough surfaces
Authors: Thomas Ruth , Drinkwater Bruce W. , Liaptsis Dimosthenis
Published: January 2005

Ultrasound is commonly used to detect and size cracks in a range of engineering components. Modeling techniques are well established for smooth and open cracks. However, real cracks are often rough (relative to the ultrasonic wavelength) and closed due to compressive stress. This paper describes an investigation into the combined effects of crack face roughness and closure on ultrasonic detectability. A contact model has been used to estimate the size and shape of scatterers (voids) at the interface of these rough surfaces when loaded. The response of such interfaces to excitation with a longitudinal ultrasonic pulse over a wide range of frequencies has been investigated. The interaction of ultrasound with this scattering interface is predicted using a finite-element model and good agreement with experiments on rough surfaces is shown. Results are shown for arrays of equi-sized scatterers and a distribution of scatterer sizes. It is shown that the response at high frequencies is dependent on the size, shape, and distribution of the scatterers. It is also shown that the finite-element results depart from the mass–spring model predictions when the product of wave number and scatterer half-width is greater than 0.4.
The role of visual speech cues in reducing energetic and informational masking
Authors: Helfer Karen S. , Freyman Richard L.
Published: January 2005

Two experiments compared the effect of supplying visual speech information (e.g., lipreading cues) on the ability to hear one female talker’s voice in the presence of steady-state noise or a masking complex consisting of two other female voices. In the first experiment intelligibility of sentences was measured in the presence of the two types of maskers with and without perceived spatial separation of target and masker. The second study tested detection of sentences in the same experimental conditions. Results showed that visual cues provided more benefit for both recognition and detection of speech when the masker consisted of other voices (versus steady-state noise). Moreover, visual cues provided greater benefit when the target speech and masker were spatially coincident versus when they appeared to arise from different spatial locations. The data obtained here are consistent with the hypothesis that lipreading cues help to segregate a target voice from competing voices, in addition to the established benefit of supplementing masked phonetic information.
Krylov subspace iterative methods for boundary element method based near-field acoustic holography
Authors: Valdivia Nicolas , Williams Earl G.
Published: January 2005

The reconstruction of the acoustic field for general surfaces is obtained from the solution of a matrix system that results from a boundary integral equation discretized using boundary element methods. The solution to the resultant matrix system is obtained using iterative regularization methods that counteract the effect of noise on the measurements. These methods will not require the calculation of the singular value decomposition, which can be expensive when the matrix system is considerably large. Krylov subspace methods are iterative methods that have the phenomena known as “semi-convergence,” i.e., the optimal regularization solution is obtained after a few iterations. If the iteration is not stopped, the method converges to a solution that generally is totally corrupted by errors on the measurements. For these methods the number of iterations play the role of the regularization parameter. We will focus our attention to the study of the regularizing properties from the Krylov subspace methods like conjugate gradients, least squares QR and the recently proposed Hybrid method. A discussion and comparison of the available stopping rules will be included. A vibrating plate is considered as an example to validate our results.
Equations for finite-difference, time-domain simulation of sound propagation in moving inhomogeneous media and numerical implementation
Authors: Ostashev Vladimir E. , Wilson D. Keith , Liu Lanbo , Aldridge David F. , Symons Neill P. , Marlin David
Published: January 2005

Finite-difference, time-domain (FDTD) calculations are typically performed with partial differential equations that are first order in time. Equation sets appropriate for FDTD calculations in a moving inhomogeneous medium (with an emphasis on the atmosphere) are derived and discussed in this paper. Two candidate equation sets, both derived from linearized equations of fluid dynamics, are proposed. The first, which contains three coupled equations for the sound pressure, vector acoustic velocity, and acoustic density, is obtained without any approximations. The second, which contains two coupled equations for the sound pressure and vector acoustic velocity, is derived by ignoring terms proportional to the divergence of the medium velocity and the gradient of the ambient pressure. It is shown that the second set has the same or a wider range of applicability than equations for the sound pressure that have been previously used for analytical and numerical studies of sound propagation in a moving atmosphere. Practical FDTD implementation of the second set of equations is discussed. Results show good agreement with theoretical predictions of the sound pressure due to a point monochromatic source in a uniform, high Mach number flow and with Fast Field Program calculations of sound propagation in a stratified moving atmosphere.
Helmholtz resonator lined with absorbing material
Authors: Selamet A. , Xu M. B. , Lee I.-J. , Huff N. T.
Published: January 2005

A closed-form, two-dimensional analytical solution is developed to investigate the acoustic performance of a concentric circular Helmholtz resonator lined with fibrous material. The effect of density and the thickness of the fibrous material in the cavity is examined on the resonance frequency and the transmission loss. With the expressions for the eigenvalue and eigenfunction in the cavity, the transmission loss is obtained for a piston-driven model by applying a pressure/velocity matching technique. The results from the analytical methods are compared to the numerical predictions from a three-dimensional boundary element method and the experimental data obtained from an impedance tube setup. It is shown that the acoustic performance of a Helmholtz resonator may be modified considerably by the density and thickness of the fibrous material without changing the cavity dimensions.
A statistics-based pitch contour model for Mandarin speech
Authors: Chen Sin-Horng , Lai Wen-Hsing , Wang Yih-Ru
Published: January 2005

A statistics-based syllable pitch contour model for Mandarin speech is proposed. This approach takes the mean and the shape of a syllable log-pitch contour as two basic modeling units and considers several affecting factors that contribute to their variations. The affecting factors include the speaker, prosodic state (which essentially represents the high-level linguistic components of F0 and will be explained more clearly in Sec. I), tone, and initial and final syllable classes. The parameters of the two modeling units were automatically estimated using the expectation-maximization (EM) algorithm. Experimental results showed that the root mean squared errors (RMSEs) obtained in the closed and open tests in the reconstructed pitch period were 0.362 and 0.373 ms, respectively. This model provides a way to separate the effects of several major factors. All of the inferred values of the affecting factors were in close agreement with our prior linguistic knowledge. It also gives a quantitative and more complete description of the coarticulation effect of neighboring tones rather than conventional qualitative descriptions of the tone sandhi rules. In addition, the model can provide useful cues to determine the prosodic phrase boundaries, including those occurring at intersyllable locations, with or without punctuation marks.
On the choice of expansion functions in the Helmholtz equation least-squares method
Authors: Semenova Tatiana , Wu Sean F.
Published: January 2005

This paper examines the performance of Helmholtz equation least-squares (HELS) method in reconstructing acoustic radiation from an arbitrary source by using three different expansions, namely, localized spherical waves (LSW), distributed spherical waves (DSW), and distributed point sources (DPS), under the same set of measurements. The reconstructed acoustic pressures are validated against the benchmark data measured at the same locations as reconstruction points for frequencies up to 3275 Hz. Reconstruction is obtained by using Tikhonov regularization or its modification with the regularization parameter selected by error-free parameter-choice methods. The impact of the number of measurement points on the resultant reconstruction accuracy under different expansion functions is investigated. Results demonstrate that DSW leads to a better-conditioned transfer matrix, yields more accurate reconstruction than both LSW and DPS, and is not affected as much by the change in measurement points. Also, it is possible to obtain optimal locations of the auxiliary sources for DSW, LSW, and DPS by taking an independent layer of measurements. Use of these auxiliary sources and an optimal combination of regularization and error-free parameter choice methods can yield a satisfactory reconstruction of acoustic quantities on the source surfaces as well as in the field in the most cost-effective manner.
Effects on the glottal voice source of vocal loudness variation in untrained female and male voices
Authors: Sundberg Johan , Fahlstedt Ellinor , Morell Anja
Published: January 2005

Subglottal pressure is one of the main voice control factors, controlling vocal loudness. In this investigation the effects of subglottal pressure variation on the voice source in untrained female and male voices phonating at a low, a middle, and a high fundamental frequency are analyzed. The subjects produced a series of /pae/ syllables at varied degrees of vocal loudness, attempting to keep pitch constant. Subglottal pressure was estimated from the oral pressure during the /p/ occlusion. Ten subglottal pressure values, approximately equidistantly spaced within the pressure range used, were identified, and the voice source of the vowels following these pressure values was analyzed by inverse filtering the airflow signal as captured by a Rothenberg mask. The maximum flow declination rate (MFDR) was found to increase linearly with subglottal pressure, but a given subglottal pressure produced lower values for female than for male voices. The closed quotient increased quickly with subglottal pressure at low pressures and slowly at high pressures, such that the relationship can be approximated by a power function. For a given subglottal pressure value, female voices reached lower values of closed quotient than male voices.
High-intensity rocket noise: Nonlinear propagation, atmospheric absorption, and characterization
Authors: McInerny Sally Anne , Ölçmen Semih M.
Published: January 2005

Analyses of rocket noise data measured at far-field locations during the launch of a large rocket and a smaller rocket are presented. Weak shocks are present in all of the data sets. In order to characterize these shocks, those segments of the waveforms where the acoustic pressure is increasing are isolated and the rate of increase in pressure plotted versus magnitude of pressure rise. The plots follow a trend consistent with random noise at low values of pressure rise, then transition to the pressure-squared dependence expected for weak shocks at higher pressure rise values. Power spectral densities of the noise during the period of maximum overall sound-pressure levels display high- and low-frequency spectral slopes that are close to those predicted for shock-dominated noise. It is concluded that shocks must be included in propagation models if high frequency levels are to be estimated as a function of distance from the source. Initial shock thicknesses will have to be characterized experimentally and will require instrumentation with a bandwidth well in excess of 20 kHz. Reflection-free data are essential if meaningful assessments of the statistical properties of the noise are to be made.
A scale value for the balance inside a historical opera house
Authors: Prodi Nicola , Velecka Sylvia
Published: January 2005

In the framework of opera house acoustics, the term “balance” refers to the acoustical competition between the singer on the stage and the orchestra in the pit. The mechanism allowing the operatic singers to be heard over the orchestra has to do with their skill in enhancing the vocal emission by a peculiar use of the formant frequencies. This vital factor is sensed by the listeners and, apart from the obvious sound power ratio of the stage and the pit sources, is the main cue that helps to formulate a subjective impression of the balance. To achieve its objective qualification, two calibrated sound sources can be placed on the stage and in the pit, respectively, and their sound level difference is measured at the listeners’ seats. The scope of this work is to investigate the relationship between the subjective impression and the objective indicator of the balance and to develop a scale value for the parameter in the case of a historical opera house. For this scope a set of acoustical data from the Teatro Comunale in Ferrara will be used to create synthetic sound fields with controlled conditions of the balance between the stage and the pit. This methodology employs an anechoic piece for soprano (with piano accompaniment) and is implemented in a dead room equipped with an acoustical rendering system. The sound fields are used to investigate the appropriate balance values by means of listening tests. The results of the scaling exercise show that a suitable range of values can be extracted and that the sound from the stage and the pit is perceived as balanced when the loudness difference between the two is comprised within −2.0 dBA and +2.3 dBA.
Investigation of the phase velocities of guided acoustic waves in soft porous layers
Authors: Boeckx L. , Leclaire P. , Khurana P. , Glorieux C. , Lauriks W. , Allard J. F.
Published: January 2005

A new experimental method for measuring the phase velocities of guided acoustic waves in soft poroelastic or poroviscoelastic plates is proposed. The method is based on the generation of standing waves in the material and on the spatial Fourier transform of the displacement profile of the upper surface. The plate is glued on a rigid substrate so that it has a free upper surface and a nonmoving lower surface. The displacement is measured with a laser Doppler vibrometer along a line corresponding to the direction of propagation of plane surface waves. A continuous sine with varying frequencies was chosen as excitation signal to maximize the precision of the measurements. The spatial Fourier transform provides the wave numbers, and the phase velocities are obtained from the relationship between wave number and frequency. The phase velocities of several guided modes could be measured in a highly porous foam saturated by air. The modes were also studied theoretically and, from the theoretical results, the experimental results, and a fitting procedure, it was possible to determine the frequency behavior of the complex shear modulus and of the complex Poisson ratio from 200 Hz to 1.4 kHz, in a frequency range higher than the traditional methods.
Voice responses to changes in pitch of voice or tone auditory feedback
Authors: Sivasankar Mahalakshmi , Bauer Jay J. , Babu Tara , Larson Charles R.
Published: January 2005

The present study was undertaken to examine if a subject’s voice F0 responded not only to perturbations in pitch of voice feedback but also to changes in pitch of a side tone presented congruent with voice feedback. Small magnitude brief duration perturbations in pitch of voice or tone auditory feedback were randomly introduced during sustained vowel phonations. Results demonstrated a higher rate and larger magnitude of voice F0 responses to changes in pitch of the voice compared with a triangular-shaped tone (experiment 1) or a pure tone (experiment 2). However, response latencies did not differ across voice or tone conditions. Data suggest that subjects responded to the change in F0 rather than harmonic frequencies of auditory feedback because voice F0 response prevalence, magnitude, or latency did not statistically differ across triangular-shaped tone or pure-tone feedback. Results indicate the audio–vocal system is sensitive to the change in pitch of a variety of sounds, which may represent a flexible system capable of adapting to changes in the subject’s voice. However, lower prevalence and smaller responses to tone pitch-shifted signals suggest that the audio–vocal system may resist changes to the pitch of other environmental sounds when voice feedback is present.
Help! There are 60 screaming kids in my lab!—Outreach activities for 5th graders (L)
Authors: Darvennes Corinne M.
Published: January 2005

In this letter a day of hands-on activities for 60 5th graders is described in the Acoustics and Vibrations Laboratory at TTU. This includes the logistics of having 60 kids in the lab and keeping their attention, a description of each activity, and the equipment used. The purpose of this publication is to encourage my colleagues to reach out to the next generation of scientists and engineers, by showing them that a few well-targeted activities do not take a gargantuan effort but have a big impact.
Inverse method predicting spinning modes radiated by a ducted fan from free-field measurements
Authors: Lewy Serge
Published: January 2005

In the study the inverse problem of deducing the modal structure of the acoustic field generated by a ducted turbofan is addressed using conventional farfield directivity measurements. The final objective is to make input data available for predicting noise radiation in other configurations that would not have been tested. The present paper is devoted to the analytical part of that study. The proposed method is based on the equations governing ducted sound propagation and free-field radiation. It leads to fast computations checked on Rolls-Royce tests made in the framework of previous European projects. Results seem to be reliable although the system of equations to be solved is generally underdetermined (more propagating modes than acoustic measurements). A limited number of modes are thus selected according to any a priori knowledge of the sources. A first guess of the source amplitudes is obtained by adjusting the calculated maximum of radiation of each mode to the measured sound pressure level at the same angle. A least squares fitting gives the final solution. A simple correction can be made to take account of the mean flow velocity inside the nacelle which shifts the directivity patterns. It consists of modifying the actual frequency to keep the cut-off ratios unchanged.
Synthesis fidelity and time-varying spectral change in vowels
Authors: Assmann Peter F. , Katz William F.
Published: January 2005

Recent studies have shown that synthesized versions of American English vowels are less accurately identified when the natural time-varying spectral changes are eliminated by holding the formant frequencies constant over the duration of the vowel. A limitation of these experiments has been that vowels produced by formant synthesis are generally less accurately identified than the natural vowels after which they are modeled. To overcome this limitation, a high-quality speech analysis-synthesis system (STRAIGHT) was used to synthesize versions of 12 American English vowels spoken by adults and children. Vowels synthesized with STRAIGHT were identified as accurately as the natural versions, in contrast with previous results from our laboratory showing identification rates 9%–12% lower for the same vowels synthesized using the cascade formant model. Consistent with earlier studies, identification accuracy was not reduced when the fundamental frequency was held constant across the vowel. However, elimination of time-varying changes in the spectral envelope using STRAIGHT led to a greater reduction in accuracy (23%) than was previously found with cascade formant synthesis (11%). A statistical pattern recognition model, applied to acoustic measurements of the natural and synthesized vowels, predicted both the higher identification accuracy for vowels synthesized using STRAIGHT compared to formant synthesis, and the greater effects of holding the formant frequencies constant over time with STRAIGHT synthesis. Taken together, the experiment and modeling results suggest that formant estimation errors and incorrect rendering of spectral and temporal cues by cascade formant synthesis contribute to lower identification accuracy and underestimation of the role of time-varying spectral change in vowels.
THE BETHE–SOMMERFELD CONJECTURE FOR THE 3-DIMENSIONAL PERIODIC LANDAU OPERATOR
Authors: ELTON DANIEL M.
Published: January 2005

The 3-dimensional Schrödinger operator H corresponding to a uniform magnetic field and a periodic electric potential V is considered. Under the condition of magnetic flux rationality, and with a mild regularity assumption on V, it is shown that the number of gaps in the spectrum of H is finite.
A QUANTIZATION OF BOX-BALL SYSTEMS
Authors: INOUE R. , KUNIBA A. , OKADO M.
Published: January 2005

An L operator is presented related to an infinite dimensional limit of the fusion R matrices for [Formula: see text] and [Formula: see text]. It is factorized into the local propagation operators which quantize the deterministic dynamics of particles and antiparticles in the soliton cellular automata known as the box-ball systems and their generalizations. Some properties of the dynamical amplitudes are also investigated.
TRANSMISSION FAULT-TOLERANCE OF ITERATED LINE DIGRAPHS
Authors: RUAN LU , HAN SHITOU , LI DEYING , NGO HUNG Q. , HUANG SCOTT C.-H.
Published: January 2005

The main result of this paper states that, if every cyclic modification of a d-regular digraph has super line-connectivity d, then the line digraph also has super line-connectivity d. Since many well-known interconnection network topologies, such as the Kautz digraphs, the de Bruijn digraphs, etc., can be constructed by iterating the line digraph construction, our result leads to several known and new connectivity results for these topologies, as shown later in the paper.
CURRENT REVERSALS IN THE RESPONSE BEHAVIOR OF A BROWNIAN PARTICLE
Authors: EICHHORN RALF , CLEUREN BART
Published: January 2005

A model for a Brownian particle is introduced which shows multiple current reversals in response to an external static force, i.e. the average particle velocity reverses its direction several times upon continuously increasing or decreasing the external force. The model is studied analytically, and the physical mechanism behind the current reversals is discussed.
ON THE INFLUENCE OF SPACE-QUANTIZATION EFFECTS ON THE RF NOISE BEHAVIOUR OF DG MOSFETS
Authors: RENGEL RAUL , GONZALEZ TOMAS , MARTIN MARIA J.
Published: January 2005

We present a particle-based Monte Carlo investigation of the high frequency noise behavior of a double gate MOSFET. The effective potential approach has been considered for the description of vertical quantum confinement of carriers within the channel. The intrinsic noise sources and the main circuital noise parameters are studied, together with the static and dynamic parameters, thus allowing to provide a full comprehension of the inner physics of the device and elucidating the consequences of quantum mechanical space-quantization effects (like charge repulsion from the gate-oxide boundaries). Results show that neglecting quantum phenomena leads to an important overestimation of gate capacitance and device transconductance and an underestimation of the final influence of induced gate noise (via the normalized parameter R) on the circuital noise parameters at RF and microwave frequency ranges.
RATCHETS IN HOMOGENEOUS EXTENDED SYSTEMS: INTERNAL MODES AND THE ROLE OF NOISE
Authors: SÁNCHEZ ANGEL , MORALES-MOLINA LUIS , MERTENS FRANZ G. , QUINTERO NIURKA R. , BUCETA JAVIER , LINDENBERG KATJA
Published: January 2005

We revisit the issue of directed motion induced by zero average forces in extended systems driven by ac forces. It has been shown recently that a directed energy current appears if the ac external force, f(t), breaks the symmetry f(t)=-f(t+T/2), T being the period, if topological solitons (kinks) existed in the system. In this work, a collective coordinate approach allows us to identify the mechanism through which the width oscillation drives the kink and its relation with the mathematical symmetry conditions. Furthermore, our theory predicts, and numerical simulations confirm, that the direction of motion depends on the initial phase of the driving, while the system behaves in a ratchet-like fashion if averaging over initial conditions. Finally, the presence of noise overimposed to the ac driving does not destroy the directed motion; on the contrary, it gives rise to an activation process that increases the velocity of the motion. We conjecture that this could be a signature of resonant phenomena at larger noises.
INVESTIGATION OF CHAOTIC SWITCHING STRATEGIES IN PARRONDO'S GAMES
Authors: TANG TZE WEI , ALLISON ANDREW , ABBOTT DEREK
Published: January 2005

An analysis of Parrondo's games with different chaotic switching strategies is carried out. We generalize a fair way to compare between different switching strategies. The performance of Parrondo's games with chaotic switching strategies is compared to random and periodic switching strategies. The rate of winning of Parrondo's games with chaotic switching strategies depends on coefficient(s) defining the chaotic generator, initial conditions of the chaotic sequence and the proportion of Game A played. Maximum rate of winning can be obtained with all the above mentioned factors properly set, and this occurs when chaotic switching strategy approaches periodic-like behavior.
A NEW TECHNIQUE FOR EXTRACTING THE MOSFET THRESHOLD VOLTAGE USING NOISE MEASUREMENTS
Authors: GIUSI G. , DONATO N. , CIOFI C. , CRUPI F.
Published: January 2005

In this work we propose a new technique for the evaluation of the threshold voltage of MOS transistors based on the measurement of the channel thermal noise. Since this new method allows the evaluation of the threshold voltage without any current flowing through the channel, it inherently eliminates the limitations coming from the need of using too approximate models for the interpretation of current-voltage measurements in MOS devices. The results of actual measurements on p-channel MOSFETs are reported that confirm the validity and the significance of the proposed approach.
A NOTE ON THE PRECEDING PAPER BY PIOTROWSKI AND SLADKOWSKI AND THE RESPONSE OF ASTUMIAN
Authors: BEHRENDS EHRHARD
Published: January 2005

We point out that the analysis of Piotrowski and Sladkowski of the paradox described by Astumian has a flaw since they consider a different game.
RESPONSE TO KLAPPENECKER'S REMARK ON A NON-BREAKABLE DATA ENCRYPTION SCHEME BY KISH AND SETHURAMAN
Authors: KISH LASZLO B.
Published: January 2005

Some additional comments on Klappenecker's remarks are presented. In the original paper the possibility of man-in-the-middle attack was not considered. A simple method is shown which safely protects against this attack. Finally, a special case is shown where this encryption method is more advantageous than quantum encryption.
Differential role of nitric oxide in regional sympathetic responses to stimulation of NTS A2a adenosine receptors
Authors: Scislo Tadeusz J. , Tan Nobusuke , O'Leary Donal S.
Published: January 2005

Our previous studies showed that preganglionic adrenal (pre-ASNA), renal (RSNA), lumbar, and postganglionic adrenal sympathetic nerve activities (post-ASNA) are inhibited after stimulation of arterial baroreceptors, nucleus of the solitary tract (NTS), and glutamatergic and P2x receptors and are activated after stimulation of adenosine A1 receptors. However, stimulation of adenosine A2a receptors inhibited RSNA and post-ASNA, whereas it activated pre-ASNA. Because the effects evoked by NTS A2a receptors may be mediated via activation of nitric oxide (NO) mechanisms in NTS neurons, we tested the hypothesis that NO synthase (NOS) inhibitors would attenuate regional sympathetic responses to NTS A2a receptor stimulation, whereas NO donors would evoke contrasting responses from pre-ASNA versus RSNA and post-ASNA. Therefore, in chloralose/urethane-anesthetized rats, we compared hemodynamic and regional sympathetic responses to microinjections of selective A2a receptor agonist (CGS-21680, 20 pmol/50 nl) after pretreatment with NOS inhibitors Nω-nitro-l-arginine methyl ester (10 nmol/100 nl) and 1-[2-(trifluoromethyl)phenyl]imidazole (100 pmol/100 nl) versus pretreatment with vehicle (100 nl). In addition, responses to microinjections into the NTS of different NO donors [40 and 400 pmol/50 nl sodium nitroprusside (SNP); 0.5 and 5 nmol/50 nl 3,3-bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene (DETA NONOate, also known as NOC-18), and 2 nmol/50 nl 3-(2-hydroxy-2-nitroso-1-propylhydrazino)-1-propanamine (PAPA NONOate, also known as NOC-15)], the NO precursor l-arginine (10–50 nmol/50 nl), and sodium glutamate (500 pmol/50 nl) were evaluated. SNP, DETA NONOate, and PAPA NONOate activated pre-ASNA and inhibited RSNA and post-ASNA, whereas l-arginine and glutamate microinjected into the same site of the NTS inhibited all these sympathetic outputs. Decreases in heart rate and depressor or biphasic responses accompanied the neural responses. Pretreatment with NOS inhibitors reversed the normal depressor and sympathoinhibitory responses to stimulation of NTS A2a receptors into pressor and sympathoactivatory responses and attenuated the heart rate decreases; however, it did not change the increases in pre-ASNA. We conclude that NTS NO mechanisms differentially affect regional sympathetic outputs and differentially contribute to the pattern of regional sympathetic responses evoked by stimulation of NTS A2a receptors.