Robust vector quantization for wireless channels

This study focuses on two issues: parametric modeling of the channel and index assignment of codevectors, to design a vector quantizer that achieves high robustness against channel errors. We first formulate the design of a robust zero-redundancy vector quantizer as a combinatorial optimization problem leading to a genetic search for a minimum-distortion index assignment. The performance is further enhanced by the use of the Fritchman (1967) channel model that more closely characterizes the statistical dependencies between error sequences. This study also presents an index assignment algorithm based on the Fritchman model with parameter values estimated using a real-coded genetic algorithm. Simulation results indicate that the global explorative properties of genetic algorithms make them very effective in estimating Fritchman model parameters, and use of this model can match index assignment to expected channel conditions     

也谈替代定理

对文献[1]中的结论提出了质疑，补充了教材中替代定理的应用条件，从而完善了替代定理。     

Discrete diffraction of light in optically induced bulk and planar photonic superlattices in photorefractive lithium niobate

Experimental multielement planar and channel waveguide structures induced by coherent radiation in bulk samples of photorefractive lithium niobate and planar waveguides on their basis including those formed in a projection scheme with scaling of image dimensions are described. The possibility of linear and nonlinear light localization in optically-induced bulk and planar one-dimensional photorefractive photonic superlattices is demonstrated. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 57–62, September, 2008.     

Tone interference immunity in a Fourier transform data transmissionsystem

An algorithm that can minimize the effects of a tone interference in a Fourier transform data transmission (FTDT) system is derived. The algorithm works well even in the presence of additive white Gaussian noise. The error performance of the FTDT system with this tone removal method is discussed. A simulation study shows that this algorithm limits the system error performance deterioration due to a large tone interference to about 0.3 dB. The implementation of this algorithm requires three complex words at the transmitter transform input to be filled with zeros. The observed values at the corresponding location at the receiver transform output are used to evaluate the characteristics of the interfering tone. The effects of the tone interference can then be eliminated     

Design of Modified Short Backfire Antennas for Millimeter-Waves Wireless LAN Applications

A set of novel modified short backfire antennas are proposed and designed for the application of millimeter-wave wireless LAN systems, by using the FDTD method. By changing the geometrical parameters and feeding structure, the short backfire antennas can generate different kinds of radiation patterns, including narrow pattern, fan-like pattern and conical patterns. Antenna parameters such as reflection bandwidth, input impedance, and far field radiation pattern are presented for each kind of antennas. The proposed different kinds of antennas are suitable for various purposes of wireless LAN applications.     

确定信号情况下矢量水听器检测及估计性能研究

在某些场合,例如水下定位、编码通信,信号具有确知脉冲信号特性,声源相对于接收器的方位,可以采用矢量水听器处理来获得。对于确知脉冲信号,本文证明了在各向同性噪声场下,参考声压和振速的相关处理器的方向是声源方位的最大似然方位估计,以及方位估计的克拉美-罗界CRB(Cramer-Rao Bound)。给出了计算机的仿真结果。     

开态热载流子应力下的n-MOSFETs的氧化层厚度效应

在最大衬底电流条件下(Vg=Vd/2),研究了不同氧化层厚度的表面沟道n-MOSFETs在热载流子应力下的退化.结果表明, Hu的寿命预测模型的两个关键参数m与n氧化层厚度有着密切关系.此外,和有着线性关系,尽管不同的氧化层厚度会引起不同的模型参数,但是如果对于不同厚度的氧化层,采用不同的m与n,Hu的模型仍然成立.在这个结果的基础上,Hu的寿命预测模型能用于更薄的氧化层.     

Synthesis and self‐assembly of poly(styrene)‐b‐poly(N‐vinylpyrrolidone) amphiphilic diblock copolymers made via a combined ATRP and MADIX approach

Amphiphilic diblock copolymers of polystyrene (PS) and poly(N‐vinylpyrrolidone) (PNVP) were prepared by a combination of ATRP and MADIX. Well‐defined PS with bromine end group was synthesized by ATRP in bulk at 110 °C using (1‐bromoethyl) benzene as an initiator. The Br‐ end group was then converted to xanthate as verified by ¹H NMR spectroscopy, elemental analysis, and UV‐spectroscopy. PS‐b‐PNVP copolymers were produced by MADIX of NVP in bulk at 60 °C using PS‐xanthate as a macro‐chain transfer agent and the kinetics of polymerization were investigated. The structures of PS‐b‐PNVP were characterized using GPC and ¹H NMR. Amphiphilic PS‐b‐PNVP could form spherical micelles with PS cores and PNVP shells in aqueous solution as confirmed by ¹H NMR and laser light scattering (LLS). The values of critical micelle concentration of PS‐b‐PNVP and the average aggregation number of PS‐b‐PNVP in the micelles were measured using pyrene as a probe and static LLS, respectively. The aggregation number increases concomitantly with temperature (10–50 °C), but the hydrodynamic radius of the micelles remains almost constant over the same temperature range, which may indicate shell dehydration at a higher temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5604–5615, 2008