1,721,096 research outputs found
Finite element analysis of dynamic response of wrinkling membranes
No full textA new iterative scheme for finite element analysis of wrinkling membranes, originally devised for static analysis, is extended for analyzing dynamic response of wrinkling membranes. The scheme is found to be successfully implemented with an explicit total Lagrangian finite element code based upon the central difference method. The finite element implementation of the scheme is straightforward, and only minor modifications are needed for existing membrane finite element codes. In light of application for contact-impact, discussed are a couple of existing contact algorithms which are well suited for treating contact-impact of wrinkling membranes with rigid bodies. The validity of the scheme is demonstrated via a numerical simulation of an inflating automotive airbag, made of orthotropic membranes, under impulse pressure loading. (C) 1999 Elsevier Science B.V. All rights reserved
Plasma-enhanced ALD of titanium-silicon-nitride using TiCl4, SiH4, and N-2/H-2/Ar plasma
No full textThin films of Ti-Si-N were deposited by plasma-enhanced atomic layer deposition (PEALD) using TiCl4, SiH4, and N-2 /H-2 /Ar radicals at 350degreesC. When the reactants were supplied in the sequence of TiCl4 pulse, SiH4 pulse, then N-2 /H-2 /Ar plasma, the thickness per cycle and Si content in Ti-Si-N thin film saturated at 0.73 Angstrom/cycle and 8.5 atom % (Cl less than or equal to 0.5 atom %), respectively. The thickness per cycle is different from that of metallorganic ALD (MOALD). Although X-ray diffraction did not detect the presence of silicon nitride, the silicon nitride phase was investigated by electron spectroscopy for chemical analysis. The addition of Si in Ti-Si-N thin films results in increased resistivity (approximately 500 muOmega cm) and improved Cu diffusion barrier properties due to the Si3N4 phase. (C) 2004 The Electrochemical Society.Korea Advanced Institute of Science and Technology assisted in meeting the publication costs of this article
GREEN-FUNCTION ANALYSIS OF THE ACOUSTIC FIELD IN A FINITE 3-PORT CIRCULAR CHAMBER
No full textThe velocity potential which expresses the acoustic fields in a three-port circular duct (one source port being located on the cylindrical wall. a second one being situated on the circular but flat surface at one end and the third passive port being the circular Bat surface at the other end. assumed to have frequency dependent generalized wall impedance), is obtained based on a Green function which satisfies the linear acoustic wave equation and homogeneous boundary conditions. The boundary conditions are assumed to be rigid except for the active source ports and the passive termination. The Green function is derived in terms of the frequency dependent orthogonal eigenfunctions which satisfy frequency dependent termination impedance boundary conditions. To illustrate the potential value of the solution, the modal density, acoustic potential energy distributions and the modal participations along the duct are examined for the open end and anechoic termination cases. The possibility of using the solution for the determination of the positions of detection and error microphones in an active noise control system is also discussed
Active intensity control for the reduction of radiated duct noise
No full textMean intensity based active control for the cancellation of radiated noise out of the duct exit is studied. The active intensity control strategy is derived based on the relation of the exterior sound field radiated out of the duct termination and the interior sound field of the duct. One of the characteristics of this control strategy is that the maximum possible control performance can be maintained regardless of the sensor location, compared with the conventional local pressure control methods at either interior downstream or exterior field positions. This is a simple consequence of the active intensity at the interior downstream being not space-dependent as long as it is plane wave. A time-domain adaptive filtering method for the active intensity control is also suggested and experimental results for an open ended duct based on the adaptive filtering method are presented. For the purpose of practical comparison, experimental results for conventional sound pressure control based on the well known filtered-x LMS algorithm are also presented. The experimental results show the potential of the active intensity control strategy for reducing the emitted noise out of the duct exit. (C) 1997 Academic Press Limited
Causally constrained active sound power control in an enclosed space
No full textIn this paper the causality problem is considered of an active sound power control system that attempts to reduce total acoustic potential energy in an enclosed space by total source power minimization. To find the causally constrained optima under the white random sound field, time domain analysis based on the classical Wiener filtering technique for the active sound power control system in the enclosed sound field is accomplished. For simplicity, a two-monopole source system surrounded by an arbitrary acoustic impedance condition at the enclosure boundary is considered, which turns out to be a multiple-error Wiener filtering problem that has six errors. Theoretical causal and non-causal optimal filters for the white random noise are derived, and their frequency characteristics are also analyzed by the spectral factorization theorem. Simple numerical simulation for a one-dimensional sound field considering plane waves is performed to compare the control performance of non-causal filtering with that of causal filtering. The simulation result shows an important characteristic of the causally constrained optimal filtering; the basic acoustic controllability determined by the wavelength and location of control source is still maintained, even if the control performances in the overall frequency range are degraded due to the lack of predictability of the primary random excitation signal. The simulation result also reveals that large portions of the control source power show negative power, which means that the control source behaves as an active sound power absorber. This result is different from the well-known property of an optimal control source to minimize the total source power output in the deterministic sound field where the primary excitation is harmonic; i.e., the control source neither radiates nor absorbs any net acoustic power under optimal conditions to minimize the total sound power of the sources. (C) 1997 Academic Press Limited
GREEN SOLUTION OF THE ACOUSTIC-WAVE EQUATION FOR A CIRCULAR EXPANSION CHAMBER WITH ARBITRARY LOCATIONS OF INLET, OUTLET PORT, AND TERMINATION IMPEDANCE
No full textThe acoustic characteristics of a circular expansion chamber whose inlet and outlet are situated on arbitrary locations of the chamber, i.e., the side wall or the face of the chamber, are analyzed based on the Green's function of a chamber with homogeneous boundary conditions. The Green's function is found by considering the boundary condition of the walls as rigid except at the location of the source, which is assumed to be a uniform volumetric acoustic source. The complete solution that determines the sound pressure distribution, intensity, and sound power pattern inside of the chamber are found. The solutions are compared with those based on the modal expansion techniques for the aforementioned cases. To verify the solutions, experiments were also performed, which determines the transmission loss of the expansion chamber. Side-inlet/side-outlet, face-inlet/side-outlet chambers were tested. A two-microphone method was used to accurately determine the transmission losses of the chambers. The Green's solutions are verified by comparison with the experimental results and the solutions based on the modal expansion techniques
FORMATION OF AN (ALPHA-PYRONE)FE(CO)3 COMPLEX IN THE REACTION OF A TERT-BUTYL-SUBSTITUTED (ALKYNYLCARBENE)IRON(0) COMPLEX WITH CYCLOHEXADIENE
No full text(Eta4-alpha-pyrone)Fe(CO)3 complexes (2) are formed in the reactions of [(3,3-dimethylbutynyl)ethozymeth-ylene]Fe(CO)4 (1a) with 1,3-cyclohexadiene, 1,3-cycloheptadiene, and cycloheptatriene under CO pressure. However, an (eta4-vinylketene)iron complex (3) is formed as the major product in the reaction of [((trimethylsilyl)-ethynyl)ethoxymethylene]Fe(CO)4 (1b) with cyclohexadiene.116sciescopu
PEALD of a ruthenium adhesion layer for copper interconnects
No full textRuthenium thin films were produced by plasma-enhanced atomic layer deposition (PEALD) using an alternating supply of bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)(2)] and NH3 plasma at a deposition temperature of 270 degreesC. The film thickness per cycle was self-limited at 0.038 nm/cycle, which was thinner than the thickness obtained from the conventional ALD using oxygen instead of NH3 plasma. The ruthenium thin film prepared with PEALD had a preferential orientation toward (002), and it was progressively promoted with NH3 plasma power. The PEALD of ruthenium shows a merit in controlling ultrathin film thickness with less than 2 nm more precisely and more easily than the conventional ALD, due to the reduced transient period at the initial film growth stage. Also, ruthenium thin film improved the interfacial adhesion of metallorganic chemical vapor deposited copper to diffusion barrier metals by forming Cu-Ru chemical bonds at the interface without degrading the film resistivity of copper. (C) 2004 The Electrochemical Society.This work was supported by the project of National Research Laboratory (NRL).
The Korea Advanced Institute of Science and Technology assisted in meeting the publication costs of this article
Effect of electron collisions on the plasma-sheath formation
No full textThe effects of electron collisions in the plasma-sheath are numerically investigated. We employ a one-dimensional electrostatic particle-in-cell code, with collisions incorporated using the Monte Carlo method. While it has been reported previously that the presheath potential drop increases with the ion collision frequency, the effects of electron collisions were not explored. The present study shows the inclusion of electron collisions reduces the potential drop, especially in the presheath region. The result is more or less the same when a weak magnetic field is imposed. We note that the reduced electron flux, caused by electron collisions, makes the presheath potential drop shallower as the required ion drift motions to balance the electron current are smaller. (C) 2003 Elsevier Science B.V. All rights reserved
CIGMA : aCtive Inventory service in Global e-MArket based on High Performance Catalog DB Caching
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