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261.
A semiblind method is proposed for simultaneously estimating the carrier frequency offsets (CFOs) and channels of an uplink multiuser multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system. By incorporating the CFOs into the transmitted symbols and channels, the MIMO-OFDM with CFO is remodeled into an MIMO-OFDM without CFO. The known blind method for channel estimation (Zeng and Ng in 2004) (Y. H. Zeng and T. S. Ng, ldquoA semi-blind channel estimation method for multi-user multi-antenna OFDM systems,rdquo IEEE Trans. Signal Process., vol. 52, no. 5, pp. 1419-1429, May 2004.) is then directly used for the remodeled system to obtain the shaped channels with an ambiguity matrix. A pilot OFDM block for each user is then exploited to resolve the CFOs and the ambiguity matrix. Two dedicated pilot designs, periodical and consecutive pilots, are discussed. Based on each pilot design and the estimated shaped channels, two methods are proposed to estimate the CFOs. As a result, based on the second-order statistics (SOS) of the received signal and one pilot OFDM block, the CFOs and channels are found simultaneously. Finally, a fast equalization method is given to recover the signals corrupted by the CFOs. 相似文献
262.
Withayachumnankul W. Png G.M. Xiaoxia Yin Atakaramians S. Jones I. Hungyen Lin Seam Yu Ung Balakrishnan J. Ng B.W.-H. Ferguson B. Mickan S.P. Fischer B.M. Abbott D. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2007,95(8):1528-1558
T-ray wavelengths are long enough to pass through dry, nonpolar objects opaque at visible wavelengths, but short enough to be manipulated by optical components to form an image. Sensing in this band potentially provides advantages in a number of areas of interest to security and defense such as screening of personnel for hidden objects and the retection of chemical and biological agents. Several private companies are developing smaller, reliable cheaper systems allowing for commercialization and this motivates us to review a number of promising applications within this paper. While there are a number of challenges to be overcome there is little doubt that T-ray technology will play a significant role in the near future for advancement of security, public health, and defense. 相似文献
263.
Mok K.R.C. Colombeau B.. Benistant F.. Teo R.S. Yeong S.H. Yang B.. Jaraiz M.. Chu S.-F.S. 《Electron Devices, IEEE Transactions on》2007,54(9):2155-2163
In this paper, accurate and advanced CMOS process and device simulations based on atomistic kinetic Monte Carlo (kMC) process simulator are presented. First, the methodology used to predict continuum 2-D/3-D doping profiles from 3-D atomistic distribution that can be directly transferred from process to device simulator is described. Calibration of damage evolution, dopant diffusion and clustering, interaction with interfaces, and the impact of impurities, which are crucial for accurate simulations, will be presented and discussed. Subsequently, comparison with a wide range of electrical-device characteristics showed that experimental results were remarkably well reproduced by the simulations. Finally, we shall demonstrate that device optimization can be achieved based on kMC process simulations, even for novel coimplant processes. This paves the way for the use of kMC in the design of devices and the optimization of device performance in technology computer-aided design for manufacturing. 相似文献
264.
Andy C. Yau N. K. Bose Michael K. Ng 《Multidimensional Systems and Signal Processing》2007,18(2-3):173-188
In this paper, we study the problem of reconstruction of a high-resolution (HR) image from several blurred low-resolution
(LR) image frames in medium field. The image frames consist of blurred, decimated, and noisy versions of a HR image. The HR
image is modeled as a Markov random field (MRF), and a maximum a posteriori (MAP) estimation technique is used for the restoration.
We show that with the periodic boundary condition, a HR image can be restored efficiently by using fast Fourier transforms.
We also apply the preconditioned conjugate gradient method to restore HR images in the aperiodic boundary condition. Computer
simulations are given to illustrate the effectiveness of the proposed approach.
This research was conducted with support from the Army Research Office Grant DAAD 19-03-1-0261 and the National Science Foundation
Grant CCF-0429481.
Research supported in part by RGC Grant Nos. 7130/02P, 7046/03P, 7035/04P and 7035/04P and FRG/04-05/II-51. 相似文献
265.
J. Zhong G. Saraf H. Chen Y. Lu Hock M. Ng T. Siegrist A. Parekh D. Lee E. A. Armour 《Journal of Electronic Materials》2007,36(6):654-658
ZnO nanotips are grown on epitaxial GaN/c-sapphire templates by metalorganic chemical vapor deposition. X-ray diffraction
(XRD) studies indicate that the epitaxial relationship between ZnO nanotips and the GaN layer is (0002)ZnO||(0002)GaN and
(101̄0)ZnO||(101̄0)GaN. Temperature-dependent photoluminescence (PL) spectra have been measured. Sharp free exciton and donor-bound
exciton peaks are observed at 4.4 K with photon energies of 3.380 eV, 3.369 eV, and 3.364 eV, confirming high optical quality
of ZnO nanotips. Free exciton emission dominates at temperatures above 50 K. The thermal dissociation of these bound excitons
forms free excitons and neutral donors. The thermal activation energies of the bound excitons at 3.369 eV and 3.364 eV are
11 meV and 16 meV, respectively. Temperature-dependent free A exciton peak emission is fitted to the Varshni’s equation to
study the variation of energy bandgap versus temperature. 相似文献
266.
This paper presents a robust actuator fault reconstruction scheme for linear uncertain systems using sliding mode observers. In existing work, fault reconstruction via sliding mode observers is limited to either linear certain systems subject to unknown inputs, relative degree one systems or a specific class of relative degree two systems. This paper presents a new method that is applicable to a wider class of systems with relative degree higher than one, and can also be used for systems with more unknown inputs than outputs. The method uses two sliding mode observers in cascade. Signals from the first observer are processed and used to drive the second observer. Overall, this results in actuator fault reconstruction being feasible for a wider class of systems than using existing methods. A simulation example verifies the claims made in this paper. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
267.
A. Castel S. J. Foster T. Ng J. G. Sanjayan R. I. Gilbert 《Materials and Structures》2016,49(5):1619-1628
The main purpose of this research is to study the time dependent behaviour of a geopolymer concrete. The geopolymer binder is composed of 85.2 % of low calcium fly ash and only 14.8 % of ground granulated blast furnace slag. Both drying shrinkage and creep are studied. In addition, different curing conditions at elevated temperature were used. All experimental results were compared to predictions made using the Eurocode 2. The curing regime plays an important role in the magnitude and development of both creep and drying shrinkage of class F fly ash based geopolymer concrete. A minimum of 3 days at 40 °C or 1 day at 80 °C is required to obtain final drying shrinkage strains similar to or less than those adopted by Eurocode 2 for ordinary Portland cement (OPC) concrete. Creep strains were similar or less than those predicted by Eurocode 2 for OPC concrete when the geopolymer concrete was cured for 3 days at 40 °C. After 7 days at 80 °C, creep strains became negligible. 相似文献
268.
Silole‐Based Red Fluorescent Organic Dots for Bright Two‐Photon Fluorescence In vitro Cell and In vivo Blood Vessel Imaging 下载免费PDF全文
Bin Chen Guangxue Feng Bairong He Chiching Goh Shidang Xu Gabriel Ramos‐Ortiz Laura Aparicio‐Ixta Jian Zhou Laiguan Ng Zujin Zhao Bin Liu Ben Zhong Tang 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(6):782-792
Robust luminescent dyes with efficient two‐photon fluorescence are highly desirable for biological imaging applications, but those suitable for organic dots fabrication are still rare because of aggregation‐caused quenching. In this work, a red fluorescent silole, 2,5‐bis[5‐(dimesitylboranyl)thiophen‐2‐yl]‐1‐methyl‐1,3,4‐triphenylsilole ((MesB)2DTTPS), is synthesized and characterized. (MesB)2DTTPS exhibits enhanced fluorescence efficiency in nanoaggregates, indicative of aggregation‐enhanced emission (AEE). The organic dots fabricated by encapsulating (MesB)2DTTPS within lipid‐PEG show red fluorescence peaking at 598 nm and a high fluorescence quantum yield of 32%. Upon excitation at 820 nm, the dots show a large two‐photon absorption cross section of 3.43 × 105 GM, which yields a two‐photon action cross section of 1.09 × 105 GM. These (MesB)2DTTPS dots show good biocompatibility and are successfully applied to one‐photon and two‐photon fluorescence imaging of MCF‐7 cells and two‐photon in vivo visualization of the blood vascular of mouse muscle in a high‐contrast and noninvasive manner. Moreover, the 3D blood vasculature located at the mouse ear skin with a depth of over 100 μm can also be visualized clearly, providing the spatiotemporal information about the whole blood vascular network. 相似文献
269.
Chiung Ching Ho Hu Ng Wooi-Haw Tan Kok-Why Ng Hau-Lee Tong Timothy Tzen-Vun Yap Pei-Fen Chong C. Eswaran Junaidi Abdullah 《Pattern recognition letters》2013
This paper describes the baseline corpus of a new multimodal biometric database, the MMU GASPFA (Gait–Speech–Face) database. The corpus in GASPFA is acquired using commercial off the shelf (COTS) equipment including digital video cameras, digital voice recorder, digital camera, Kinect camera and accelerometer equipped smart phones. The corpus consists of frontal face images from the digital camera, speech utterances recorded using the digital voice recorder, gait videos with their associated data recorded using both the digital video cameras and Kinect camera simultaneously as well as accelerometer readings from the smart phones. A total of 82 participants had their biometric data recorded. MMU GASPFA is able to support both multimodal biometric authentication as well as gait action recognition. This paper describes the acquisition setup and protocols used in MMU GASPFA, as well as the content of the corpus. Baseline results from a subset of the participants are presented for validation purposes. 相似文献
270.
This study investigates the moderating effect of culture and the mediating effect of trust in a social network community on the relationship between social interactions and purchase intention. Trust transference theory, social interactions, and Hofstede's cultural dimensions are considered. The findings from the research support the moderating effect of culture and the mediating role of trust in a social network community on the relationship between social interactions (in terms of closeness and familiarity) and intention to purchase in social commerce environments. In addition, the mediating effect of trust in a social network community is conditional on culture. The findings also suggest that trust in a social network community may be attributed to the closeness and familiarity developed among its members resulting from social interactions. The results presented herein are in line with the trust transference theory. The empirical study results also suggest that social commerce market penetration in East Asia may have relatively fewer barriers to overcome and be more likely to succeed than in the Latin America region. 相似文献