我国水声换能器技术研究进展与发展机遇

概要评述我国水声换能器技术方面近20年的研究进展,包括应用新型功能材料、提出新的设计概念及新结构、改进工艺技术等。重点从低频换能器、高频宽带换能器、深水换能器、矢量水听器等4个技术方向进行介绍,最后对水声换能器技术领域未来所面临的挑战和发展机遇谈些认识。     

不同意义下的震源深度

通过对1993年6月发生在环太平洋地震带上几个5．7级以上地震的分析，利用震中初始确定（PDE）资料及全球数字地震台网（GDSN）宽频带资料，对震源深度进行了初步讨论。     

单侧破裂震源的破裂特征分析

利用GDSN的宽频带波形资料,通过由子事件迭加进行的波形模拟,根据台站视震源时间函数和子事件视时间差,对单侧破裂震源的破裂特征进行了分析。     

Appreciating the Contribution of Broadband ICT With Rural and Remote Communities: Stepping Stones Toward an Alternative Paradigm

This article challenges conventional policy development and evaluation approaches that emphasize the instrumental side of technology. There is a growing gap between conventional planning and evaluation approaches for rural broadband ICTs that seek to demonstrate a direct link between investments and results on the one hand, and on the other, with evidence that the contribution of ICTs to rural economic, social and cultural wellbeing is increasingly difficult to demonstrate beyond short-term measurable indicators. The article proposes an alternative paradigm based on sociotechnical systems, stakeholder engagement, an acknowledgment of the multiple dimensions at play, and the growing evidence of unpredictability of ICTs. The article emphasizes a perspective based on “contribution,” not attribution; policymaking that is both adaptive and inclusive of multiple perspectives; methodological testing of emerging evaluation methodologies; and projects as learning experiments. This alternative theoretical and policymaking paradigm is encapsulated in a metaphor based on the management of natural resources where stakeholders track their own indicators of impact by reading how the system responds to a project intervention.     

Geographic dimensions of broadband data uncertainty

Abstract

This article reviews sources of uncertainty in broadband provision data from Federal Communications Commission’s Form 477 database, which is the largest publicly available broadband database for the United States. This uncertainty analysis reveals that reporting thresholds result in understating of broadband in rural areas serviced by smaller providers in the 1999–2004 ZIP code area dataset. In this same time series, the routine used to aggregate data to larger spatial units (i.e., counties) produces variations in the amount of autocorrelation detected by diagnostic spatial statistics. The amount of autocorrelation in the data also varies with the strategy implemented for interpolating suppressed data. This investigation also highlights the value of a spatial approach to visualizing and analyzing the impact of uncertainty on broadband availability.     

自适应粒子群算法在微波电路中应用

常规粒子群算法(SPSO)在优化过程中易陷入局部最优,本文分析了常规粒子群算法陷入局部最优的原因,提出采用一种自适应粒子群算法(APSO)避免陷入局部最优,改善算法的收敛性和精度。最后用自适应粒子群算法设计宽带阶梯阻抗变换器,结果表明,与常规粒子群算法相比,自适应粒子群算法全局速度快、成功率和精度也有显著提高。     

基于QoS的宽带移动通信系统接入控制的研究

提出了一种能在承载多媒体业务的移动通信网络中提供较高服务质量保证的接入控制方法 .该方法将接入控制与带宽预留相结合 ,保证传输业务服务质量的要求 .仿真结果表明 ,与两种传统的接入控制算法相比 ,本文所提出的算法能够使强行中止概率降低 .该算法能用于未来多媒体通信系统中     

FH/DS系统抗干扰性能分析

直序列扩频与跳频扩频在实际中最常用的两种扩频信号。文章介绍了基于跳频（FH）信号通信系统抗干扰的基本原理。借助MATLAB仿真软件,采用MFSK调制方式,在宽带干扰、不同比例的部分频带干扰条件下,对不同跳频速率的系统性能进行仿真。通过分析仿真结果,较好的说明了跳频信号通信系统的优点,最后给出了提高跳频系统抗干扰能力的相应措施。     

有线电视宽带接入网技术的应用

随着互联网技术的日益成熟,通过网络传送的高清晰度的音频、视频、图像等多媒体数据正在不断吞噬着有限的信道带宽,因此,有线电视宽带接入网技术无疑已经成为了当今的热点。面对竞争日益加大的市场环境,有线电视已经无路可退,必须有效加强有线电视宽带接入网技术的应用,只有这样,才能够实现有线电视的可持续性发展。本文就有线电视宽带接入网技术的应用进行了深入的探讨,提出了自己的建议和看法,具有一定的参考价值。     

宽带印刷天线与双极化微带及波导缝隙天线阵

In order to meet the urgent needs in wireless communications, microwave image synthetic aperture radars （SAR）, and electronic warfare systems, this dissertation studies several types of broadband dual-polarized planar antenna elements and arrays, and proposes a few of novel designs with experimental verification. The main accomplishments reported in the dissertation are as follows.