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991.
Guijiang Zhou Cheuk‐Lam Ho Wai‐Yeung Wong Qi Wang Dongge Ma Lixiang Wang Zhenyang Lin Todd B. Marder Andrew Beeby 《Advanced functional materials》2008,18(3):499-511
A new and synthetically versatile strategy has been developed for the phosphorescence color tuning of cyclometalated iridium phosphors by simple tailoring of the phenyl ring of ppy (Hppy = 2‐phenylpyridine) with various main‐group moieties in [Ir(ppy‐X)2(acac)] (X = B(Mes)2, SiPh3, GePh3, NPh2, POPh2, OPh, SPh, SO2Ph). This can be achieved by shifting the charge‐transfer character from the pyridyl groups in some traditional iridium ppy‐type complexes to the electron‐withdrawing main‐group moieties and these assignments were supported by theoretical calculations. This new color tuning strategy in IrIII‐based triplet emitters using electron‐withdrawing main‐group moieties provides access to IrIII phosphors with improved electron injection/electron transporting features essential for highly efficient, color‐switchable organic light‐emitting diodes (OLEDs). The present work furnished OLED colors spanning from bluish‐green to red (505–609 nm) with high electroluminescence efficiencies which have great potential for application in multicolor displays. The maximum external quantum efficiency of 9.4%, luminance efficiency of 10.3 cd A−1 and power efficiency of 5.0 lm W−1 for the red OLED (X = B(Mes)2), 11.1%, 35.0 cd A−1, and 26.8 lm W−1 for the bluish‐green device (X = OPh), 10.3%, 36.9 cd A−1, and 28.6 lm W−1 for the bright green device (X = NPh2) as well as 10.7%, 35.1 cd A−1, and 23.1 lm W−1 for the yellow‐emitting device (X = SO2Ph) can be obtained. 相似文献
992.
993.
994.
Wing-Kai Hon Tak-Wah Lam Kunihiko Sadakane Wing-Kin Sung Siu-Ming Yiu 《Algorithmica》2007,48(1):23-36
With the first human DNA being decoded into a sequence of about 2.8 billion characters, much biological research has been
centered on analyzing this sequence. Theoretically speaking, it is now feasible to accommodate an index for human DNA in the
main memory so that any pattern can be located efficiently. This is due to the recent breakthrough on compressed suffix arrays,
which reduces the space requirement from O(n log n) bits to O(n) bits. However, constructing compressed suffix arrays is still
not an easy task because we still have to compute suffix arrays first and need a working memory of O(n log n) bits (i.e.,
more than 13 gigabytes for human DNA). This paper initiates the study of constructing compressed suffix arrays directly from
the text. The main contribution is a construction algorithm that uses only O(n) bits of working memory, and the time complexity
is O(n log n). Our construction algorithm is also time and space efficient for texts with large alphabets such as Chinese
or Japanese. Precisely, when the alphabet size is |Σ|, the working space is O(n log |Σ|) bits, and the time complexity remains
O(n log n), which is independent of |Σ|. 相似文献
995.
996.
Ka-Veng Yuen Yuanfeng Shi James L. Beck Heung-Fai Lam 《Structural and Multidisciplinary Optimization》2007,34(5):431-443
Magnetorheological (MR) damper is one of the most promising semi-active control devices for mitigating seismic response, and
so, it has received significant attention in recent years. Because of the inherent nonlinear nature of MR damper devices,
one challenge to effectively utilize this technology is the development of an appropriate control algorithm. A semi-active
control methodology is presented to control structural systems using MR dampers that addresses structural modeling uncertainties.
Based on the same idea as the clipped-optimal linear controller, the proposed semi-active control law uses a robust reliability-based
active linear control methodology to calculate the reference control forces that the MR dampers attempt to produce approximately.
These reference control forces can be calculated using incomplete response measurements at the current and/or previous time
steps without any state estimation. The main purpose of the proposed approach is to achieve a more robust performance for
uncertain structural systems subjected to uncertain strong-motion excitation. The performance of the proposed approach is
demonstrated through a simulated example of a ten-story building with MR dampers installed.
Y. Shi formerly from the Department of Civil and Environmental Engineering, University of Macau, Macau SAR, China. 相似文献
997.
Benson S. Y. Lam Hong Yan 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2007,11(4):341-348
A measurement of cluster quality is often needed for DNA microarray data analysis. In this paper, we introduce a new cluster validity index, which measures geometrical features of the data. The essential concept of this index is to evaluate the ratio between the squared total length of the data eigen-axes with respect to the between-cluster separation. We show that this cluster validity index works well for data that contain clusters closely distributed or with different sizes. We verify the method using three simulated data sets, two real world data sets and two microarray data sets. The experiment results show that the proposed index is superior to five other cluster validity indices, including partition coefficients (PC), General silhouette index (GS), Dunn’s index (DI), CH Index and I-Index. Also, we have given a theorem to show for what situations the proposed index works well. 相似文献
998.
Wai-San Chan Edmund Y. Lam Michael K. Ng Giuseppe Y. Mak 《Multidimensional Systems and Signal Processing》2007,18(2-3):83-101
From consumer electronics to biomedical applications, device miniaturization has shown to be highly desirable. This often
includes reducing the size of some optical systems. However, diffraction effects impose a constraint on image quality when
we simply scale down the imaging parameters. Over the past few years, compound-eye imaging system has emerged as a promising
architecture in the development of compact visual systems. Because multiple low-resolution (LR) sub-images are captured, post-processing
algorithms for the reconstruction of a high-resolution (HR) final image from the LR images play a critical role in affecting
the image quality. In this paper, we describe and investigate the performance of a compound-eye system recently reported in
the literature. We discuss both the physical construction and the mathematical model of the imaging components, followed by
an application of our super-resolution algorithm in reconstructing the image. We then explore several variations of the imaging
system, such as the incorporation of a phase mask in extending the depth of field, which are not possible with a traditional
camera. Simulations with a versatile virtual camera system that we have built verify the feasibility of these additions, and
we also report the tolerance of the compound-eye system to variations in physical parameters, such as optical aberrations,
that are inevitable in actual systems. 相似文献
999.
New bounded real lemmas for linear systems with parameter uncertainties belonging to a convex bounded-polyhedral domain are
established in this paper. Both continuous- and discrete-time uncertain systems are investigated. The derived conditions are
expressed in terms of a set of linear matrix inequalities defined at the vertices of the uncertainty polytope. Numerical comparisons
with those appearing recently in the literature show that the proposed conditions provide less conservative results. 相似文献
1000.
The evaluation of the functional reliability of different designs is a common task and times to failure can be compared using the likelihood ratio test. In the microelectronics industry, as in many others, the high cost of testing places severe restrictions on the sample size. Moreover, the products in these tests are often new and do not have previous reliability histories. These factors make the selection of the Type I and Type II errors in comparison tests very difficult. This paper presents the Monte Carlo simulation results of Type II errors for the likelihood ratio test of comparison as a function of the Type I error and the (small) sample size. Our conclusions are summarized as follows: (1) the common microelectronics industry standard sample size of 32 is often insufficient to reach satisfactory conclusions; (2) small sample tests should only be used for prescreening for significant differences; and (3) when only small samples are available, the Type I and the Type II errors must be selected carefully to prevent misleading conclusions. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献