Dynamic deviation reduction‐based concurrent dual‐band digital predistortion

This article introduces the concurrent dual‐band digital predistortion (DPD) architecture with only one upconvertion unit, which is suitable for the linearization of wideband power amplifiers (PAs) excited by concurrent dual‐band signals. By extending the conventional dynamic deviation reduction (DDR) model to the concurrent dual‐band mode, we propose two DDR‐based concurrent dual‐band models, the dual‐band DDR (DB‐DDR) model and the simplified dual‐band DDR (SDB‐DDR) model. The performance of these two models is experimentally assessed with two types of wideband PAs (a GaN Class F PA and a GaN Doherty PA) driven by the concurrent dual‐band signal, and compared with the prior two‐dimensional digital predistortion (2D‐DPD) model and the two‐dimensional modified memory polynomial (2D‐MMP) model. The results prove the good DPD performance and low computational complexity of the proposed models. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:401–411, 2014.     

代数约简的条件信息熵表示及其高效约简算法

给出如何保持正区域不变的语义分析,提出一种修正条件信息熵计算公式,证明保持修正条件信息熵不变与保持正区域不变相互等价。在此基础上,给出代数约简概念的修正条件信息熵表示。给出反例说明修正条件信息熵不具有单调性,导致没法给出自底向上的启发式约简算法,证明了代数协调集中不可删除属性的不可逆性质,提出一种自顶向下直接删除属性的高效约简算法。它从所有条件属性集出发,逐步删除不必要的属性,只需遍历各属性一次,即可保证得到原始决策表的一个代数约简。数值算例和实验验证了该算法的正确性和高效性。     

Chemical Reaction Engineering and Research and development of gas solid systems

A general procedure is proposed for innovative research and development of gas-solid reactor systems, with a brief explanation of the significance of each step in the procedureBased upon the contacting mode between gas and solid phases, as well as the ways of supplying thermal energy to the reacting regions, various types of gas-solid reactor systems are classified by using tables of so called “matrix” form, for thermal cracking and gasification of heavy oils, gasification of coal, gasification of solid waste, calcination of limestone, clinkering of cement and reduction of iron ore.The importance of fundamental concepts is emphasized for successful research and development by presenting several examples; namely, calcination of limestone, thermal cracking of heavy oils and gasification of solid waste materials.In connection with the direction in which fundamental research should be oriented, four primary ways of thinking are proposed, which can be applied to obtain innovative ideas for further research and development in this field.One example of the author's practical experience was selected to show the role of the fundamental research in the course of large scale development. Finally the author outlines the role of chemical reaction engineering to innovate the novel gas-solid reactor systems which may be inevitable for simultaneous solution of the three big E's; namely, Energy, Environment and Economy.     

Silica to Silicon: Key Carbothermic Reactions and Kinetics

The primary carbothermic reactions for the reduction of silica to produce silicon were defined and the reaction kinetics were determined. Most possible reactions between silicon oxide and carbon or carbon compounds were studied by a series of thermogravimetric analyses at temperatures up to 2000°C. Four key sequential reactions occur with SiC and SiO as intermediate reactants; two reactions involve SiO₂ and two involve SiO. Reaction rate versus temperature, activation energy, and preexponential factors were determined for each of six reactions involving SiO₂ or SiO. These kinetic studies show that SiO, when combined with either carbon or Sic, reacts in the gaseous state, and the sublimation of SiO is not the rate-limiting reaction for forming silicon.     

Comments on the characterisation of oxidation catalysts using TPR/TPO

Temperature programmed reduction (TPR) and oxidation (TPO) are used extensively in catalyst characterisation. In this paper, we examine the use of TPR/TPO cycles for the characterisation of a range of molybdates and single oxides. In particular we observe that the first cycle differs from that of subsequent analyses, even when the maximum temperature is limited to that used in the catalytic reaction. The effect is independent of heating rates and cooling atmospheres and has been demonstrated using different bed configurations. This observation has significance when these oxides are used in periodic flow reactors that involve many cyclical reduction/oxidation.     

A minimum variance distortionless response filter based on the bifrequency spectrum for single-channel noise reduction

This paper deals with the problem of single-channel noise reduction in the short-time Fourier transform (STFT) domain. Many algorithms have been developed to solve this important problem, most of which generally assume that the STFT coefficients in different frequency bands are uncorrelated, so the noise reduction is achieved by applying a gain function to the STFT of the noisy speech in each frequency band. However, this assumption is not accurate and the STFT coefficients of speech signals between neighboring frequency bands are correlated in practice due to the use of small lengths of the fast Fourier transform (FFT) and overlap add/save techniques in implementation. This paper formulates the noise reduction problem by taking into account the interband correlation using the so-called bifrequency spectrum. Based on this formulation, a single-channel minimum variance distortionless response (MVDR) filter is derived, which is shown to be able to significantly improve the signal-to-noise ratio (SNR) and meanwhile maintain the desired speech not much distorted. Simulations are presented to justify the claimed merits of the developed MVDR filter.     

基于组合方法的人脸识别算法研究

该文试探一种加权融合流形学习的方法进行人脸识别,该算法通过Haar小波和局部线性嵌入（LLE）加权融合的方式来进行人脸识别。首先通过Haar小波变换对人脸图像进行一级分解,得到四个子图;然后利用LLE算法对四个子图降维处理,并加权融合;最后利用支持向量机（SVM）进行分类判决。通过在ORL库中进行实验,结果表明,该文提出的Haar＋LLE识别效率比单独使用主成分分析（PCA）和LLE更高效。     

削弱或抑制抗氧剂、光稳定剂作用的有关因素

介绍了削弱或抑制抗氧剂、光稳定剂作用的常见因素及实例，分析了防老化塑料制品发生提前老化现象的可能性和原因。     

交通运输业节能减排国际管理手段及启示

交通运输业的能源消费在许多国家中都占有较高比例,经济发展较快的国家更是如此。介绍了能源消费大国英国、美国、欧盟以及日本交通运输业节能减排采取的主要管理手段,包括健全的法律体系、节能技术创新、有效的税费政策等。借鉴其先进经验,为我国交通运输业节能减排管理工作提供启示。