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111.
C.J. Wu 《Applied Acoustics》2002,63(10):1143-1154
This work formulates the double-layer structural-acoustic coupling problem for cylindrical shell by using a combination of the wave-number domain approach (WDA) and the boundary integral equation (BIE). Expressions for the spectral radial velocity of the outer surface of a finite fluid-filled/submerged (FFS) cylindrical thin shell are formulated by means of the transfer matrix equation in wave-number domain. It is shown that the spectral variables on the inner surface of the shell are related to those on the outer surface of the shell. The far field sound radiation from this kind of shell is numerically evaluated for various fluid cases. An experimental verification is performed, and a good correlation between the theoretical results and the experimental results shows that the theoretical study work in this paper is correct. 相似文献
112.
Multiuser detection for DS-CDMA UWB in the home environment 总被引:20,自引:0,他引:20
We demonstrate the effectiveness of multiuser detection for an ultra-wideband (UWB) pulse based direct sequence spread spectrum system using code division multiple access. Extensive simulations were run using channel soundings of the 2-8 GHz band collected in a residential setting and characterized by a high level of multipath fragmentation. We show that the adaptive minimum mean square error (MMSE) multiuser detection (MUD) receivers are able to gather multipath energy and reject intersymbol and interchip interference for these channels to a much greater extent than RAKE receivers with 4 and 8 arms. We also demonstrate the adaptive MMSE is able to reject a narrowband IEEE 802.11a OFDM interferer, even for signal-to-interference ratio as severe as -30 dB. We show the adaptive MMSE exhibits only a 6 dB penalty relative to the single user case for the heavy multi-access interference (number of asynchronous users equal to spreading code length). The practical RAKE receivers were incapable of effectively rejecting either the strong narrowband interference or the heavily loaded wideband interference. Even more moderate levels of interference caused significant degradation in the performance of the practical RAKE receivers. 相似文献
113.
114.
Zhang Li Chun Jin Hai Yan Ye Hong Fei Gao Yu Zhi Ning Bao Jun Mo Bang Xian 《Electron Devices, IEEE Transactions on》2002,49(6):1075-1076
A polysilicon emitter RCA transistor (an ultra-thin interfacial oxide layer exists between polysilicon and silicon emitter) is presented which can operate at 77 K for the first time. An ultra-thin (1.5 nm) interfacial oxide layer is grown deliberately between polysilicon and silicon emitter using RCA oxidation and excellent device stability is obtained after rapid thermal annealing (RTA) treatment in nitrogen atmosphere. The RCA transistor exhibits good electrical performance at very low temperature for an emitter area of 3 × 8 μm2. The maximum toggle frequency of a 1:2 static divider is 1.2 GHz and 732 MHz at 300 K and 77 K, respectively 相似文献
115.
A thermodynamic modeling of GaN was carried out to describe the thermodynamic behavior of native defects, dopants, and carriers
(free electrons and holes) in GaN semiconductors. The compound energy model (CEM) was used. An unintentionally doped GaN was
taken as an example. Oxygen was introduced into the model as the unintentionally doped impurity, according to the practical
experimental phenomena. The energies of component compounds in the model were defined based on the results of the ab initio
calculations and adjusted to fit experimental data. The thermodynamic properties of the defects and the oxygen doped were
calculated to show the facility of the model. 相似文献
116.
Oliveira M. Dart-Mao Cheung C. Al-Zayed A. Chio I.-F.F. Swisher R.R. Lecuyer F. DeLisio M.P. 《Antennas and Propagation, IEEE Transactions on》2002,50(5):698-702
Grid-mixer arrays can achieve high linearity and dynamic range through quasi-optical power combining. We present a 100-element single-ended diode grid mixer operating at 2.45 GHz. Each element incorporates two diodes in series. We measure an input third-order intercept of 11 W (40.5 dBm), and output third-order intercept of 3.4 W (35.4 dBm), and an associated conversion loss of 5.1 dB. The power-handling capability of the array is 100 times larger than that of a microstrip mixer using a single element. The local oscillator (LO) drive requirement for the entire array is 1.4 W (31.6 dBm). The angular dependence of the array's IF power is also presented and is in agreement with theory 相似文献
117.
I. J. Lozada J. C. Osorio D. V. Griffiths M. Cerrolaza 《Numerical Methods for Partial Differential Equations》2006,22(2):296-316
The semi‐analytical integration of an 8‐node plane strain finite element stiffness matrix is presented in this work. The element is assumed to be super‐parametric, having straight sides. Before carrying out the integration, the integral expressions are classified into several groups, thus avoiding duplication of calculations. Symbolic manipulation and integration is used to obtain the basic formulae to evaluate the stiffness matrix. Then, the resulting expressions are postprocessed, optimized, and simplified in order to reduce the computation time. Maple symbolic‐manipulation software was used to generate the closed expressions and to develop the corresponding Fortran code. Comparisons between semi‐analytical integration and numerical integration were made. It was demonstrated that semi‐analytical integration required less CPU time than conventional numerical integration (using Gaussian‐Legendre quadrature) to obtain the stiffness matrix. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006 相似文献
118.
Medard M. Lumetta S. Liuyang Li 《Selected Areas in Communications, IEEE Journal on》2002,20(4):822-833
We describe an architecture for an optical local area network (LAN) or metropolitan area network (MAN) access. The architecture allows for bandwidth sharing within a wavelength and is robust to both link and node failures. The architecture can be utilized with an arbitrary, link-redundant mesh network (node-redundancy is necessary only to handle all node failures), and assumes neither the use of a star topology nor the ability to embed such a topology within the physical mesh. Reservation of, bandwidth is performed in a centralized fashion at a (replicated) head end node, simplifying the implementation of complex sharing policies relative to implementation on a distributed set of routers. Unlike a router, however, the head end does not take any action on individual packets and, in particular, does not buffer packets. The architecture thus avoids the difficulties of processing packets in the optical domain while allowing for packetized shared access of wavelengths. We describe the route construction scheme and prove its ability to recover from single link and single node failures, outline a flexible medium access protocol and discuss the implications for implementing specific policies, and propose a simple implementation of the recovery protocol in terms of state machines for per-link devices 相似文献
119.
Intelligent Monitoring for Adaptation in Grid Applications 总被引:1,自引:0,他引:1
Reed D.A. Mendes C.L. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2005,93(2):426-435
Grid applications access distributed, and often shared, resources. One consequence of this resource sharing is that measured application performance can vary widely and in unexpected ways. Determining the causes of poor performance, due to either anomalous application behavior or contention for shared resource use, and adapting to changing circumstances are critical to creation of robust Grid applications. Performance contracts and real-time adaptive control are two mechanisms to realize soft performance guarantees in Grid environments. Performance contracts formalize the relationship between application performance needs and resource capabilities. During execution, contract monitors use performance data to verify that expectations are met. When the contracted specifications are not satisfied, the system can choose to either adapt the application to available resources or reschedule the application on a new set of resources that can satisfy the original contract specifications. We describe an infrastructure for Grid application contract development and monitoring. This infrastructure, based on the Autopilot toolkit, provides flexible and scalable tools to assess both application and system behavior. 相似文献
120.
A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity. 相似文献