Estimation of quality of service parameters for OFDM–TDMA networks using Markov chains and service curve

This paper presents a model based on Queueing Theory for Orthogonal Frequency‐Division Multiplexing–Time‐Division Multiple Access (OFDM–TDMA) networks. This network model requires a Markovian model to the traffic processes. Thus, we present a Markov Modulated Fluid Model (MMFM) with autocorrelation function fitting for the network traffic, in order to evaluate the performance of the transmission link in OFDM–TDMA systems. That is, we deduce equations for estimating QoS parameters of OFDM–TDMA systems. The obtained results confirm that the proposed network model is efficient in describing the OFDM based link performance. A novel equation is also introduced for estimating the buffer overflow probability in OFDM–TDMA systems using a proposed network service curve. The computational effort is reduced compared to the Queueing Theory based method of overflow probability estimation. Besides, the results show that the estimates are very close to those obtained by simulations.     

有机半导体ADN的DFT理论计算研究

采用密度泛函理论( DFT)方法对9,10-二(2-萘基)蒽(ADN)进行了B3LYP/6-31G水平上的分子结构优化、红外光谱、Raman光谱、紫外-可见光谱、分子前线轨道、Mulliken电荷等理论计算.研究结果表明:理论计算结果与实验数据吻合得较好,对IR、THz、UV-Vis吸收光谱和Raman散射光谱中的特征峰进行了归属,发现ADN在0.1～10 THz波谱范围内有5个明显的吸收峰,分别位于1.08、2.52、4.44、5.64及6.60 THz,其中5.64 THz的吸收是最强的,它是由萘环面外弯曲及蒽环面内摇摆振动产生的.ADN在紫外光波段有三个吸收峰,分别对应于386.34、352.98及352.50 nm,其中386.34 nm的紫外吸收峰最强.ADN理论计算能隙值为3.516 eV,比实验值3.2 eV略高.ADN的Mulliken电荷计算表明,所有H原子的Mulliken电荷皆为正电荷,C原子Mulliken电荷与其具体的化学环境相关.     

基于DS理论的混合式时空域信息融合模型

利用信息融合技术进行目标识别,已经成为模式识别领域的重要研究方向。而利用DS理论进行时空域信息融合是信息融合领域的一个研究热点。信息融合技术既包括了在空间域上对多个证据的融合,也包括了在时间域上对不同时刻的同一证据源提供的证据的融合。本文首先介绍递归集中式,递归分布无反馈式和递归分布有反馈式三种典型时空信息融合模型,通过对各模型进行的理论分析和算例仿真,得出一个与前人不同的观点;然后以空间目标融合识别为背景,提出一种有效的混合式时空信息融合模型。在保证识别率的前提下,该模型能节约系统资源,降低运算量。仿真实验验证了该模型的有效性。      

Effects of ground plane dimensions on patterns radiated by slot antennas

Using a hybrid MoM-UTD formulation, this paper investigates the effects of ground-plane dimensions on the radiation fields of a slot antenna. It is shown that the radiated field strength of a slot cut in a finite ground plane is generally higher than that of a similar slot in a ground plane of infinite extent. Indeed, computational results reveal that the E-plane radiated field strength of a slot is about 3 dB higher when the ratio of the ground plane width to slot length is an even integer; and 1 dB higher when the ratio is an odd integer. In the case of the H-plane, the field strengths radiated by a slot in both infinite and finite sized ground planes are virtually identical, suggesting, therefore, that in this case, the contribution of the edge diffraction is insignificant. Results also indicate that a ground plane thickness of less than 20 mm has negligible effects on the radiation fields, as the strength of coupled fields, which is a manifestation of the effect of the finite thickness of the ground plane, is very small. As a validation, patterns computed compare favourably with experimental data available in the literature.     

Determinants of the intention to use Buy-Online,Pickup In-Store (BOPS): The moderating effects of situational factors and product type

Despite the wider introduction of the buy online and pick up in-store (BOPS) service by retailers, research on BOPS is still sparse, especially those from the consumer perspective. This paper employs the scenario-based factorial survey method to investigate how the perceived characteristics of innovation and the perceived risk of online shopping influence the consumers’ intention to use BOPS while also considering the moderating effects of situational factors (location convenience) and product type (involvement). Our findings indicated that the consumer perceptions of relative advantage, complexity, compatibility, and risks involved in online shopping are important antecedents to intention to use BOPS, and that these relationships were significantly moderated by locational convenience and product involvement. The implications of the findings and suggestions for future research are discussed in detail.     

Electron mobility in n-doped zinc sulphide

A study of the mobility of n-doped wurtzite and zincblende ZnS is reported. We have determined nonequilibrium thermodynamic state of the ZnS—driven far away from equilibrium by a strong electric field—in the steady state. The dependence of the mobility (which depends on the nonequilibrium thermodynamic state of the sample) on the electric field strength is derived, which decreases with the strength of electric field. We analyzed the contributions to the mobility arising out of the different channels of electron scattering, namely, the polar optic, deformation, interactions with the phonons, and with ionized impurities. The case of n-ZnS WZ and ZB have been analyzed: as expected the main contribution comes from the polar-optic interactions in this strong-polar semiconductor. The other interactions are in decreasing order, the deformation acoustic and the one due to impurities.     

网络技术下概念整合理论对语篇连贯意义的建构

随着认知语言学的发展,它的研究范围已渐渐向语篇分析扩展。文章探讨认知语言学的概念整合理论,重点考察其中的多域复合网络对语篇连贯的强大建构能力,在超文本网络技术飞速发展的今天,研究如何在网络技术的支持下,发挥网络资源优势,以完善从认知角度对语篇连贯的建构。     

信息产业化时代欧元区成员国财政政策协调的博弈模型

随着全球经济一体化和信息化水平越来越高,世界经济的发展越来越清楚地呈现出五种趋势全球化、区域化、信息化、自由化与市场化。在实现了货币一体化后,欧元区域内出现了统一的货币政策和各国独立的财政政策的不对称结构,对于这种问题,全球经济学家把研究焦点集中在如何协调欧元区各国的财政政策。本文运用博弈论的分析方法,通过建立博弈模型,对在统一的货币政策下,各欧元区成员国可能做出的财政政策选择进行分析,得出在这种制度设计下欧元区各国难以做到财政政策相互协调的结论。同时,从结论中得出相关的政策建议以及对我国更好促进区域经济平衡发展的启示。     

GTD model-based time-shift invariant target identification using matching pursuits and likelihood ratio tests

In order to improve the identification capability of ultra wide-band radar, this paper introduces a step-variant multiresolution approach for the time-shift parameter estimation. Subsequently, combining with the approach, a Geometrical Theory of Diffraction （GTD） model-based time-shift Invariant method to target identification using Matching Pursuits and Likelihood Ratio Test （IMPLRT） is developed. Simulation results using measured scattering signatures of two targets in an ultra wide-band chamber are presented contrasting the performance of the IMPLRT to the Wang＇s MPLRT technique.     

超声波清洗技术倍受瞩目

本文介绍了超声波清洗的工艺，并对超声波清洗技术的应用作了介绍，指出了超声波清洗技术的几点主要优势。