Underwater Acoustic Communication Based on Pattern Time Delay Shift Coding Scheme   总被引：1，自引：0，他引：1  

殷敬伟  惠俊英惠娟姚直象  王逸林 《中国海洋工程》2006,20(3):499-508

1 .Introduction Underwater acoustic (UWA) communicationis a fast developingfield,and its applicationis notlimitedto military affairs ,but is also extendinginto commercial fields .Catipovic (1990) ,Stojanovic(1996) and Kilfoyle and Baggeroer (2000) pointed…  相似文献   

高速水声通信中正交频分复用技术试验研究   总被引：1，自引：0，他引：1  

王明华  桑恩方  乔钢 《海洋工程》2006,24(4):100-104115

设计了基于正交频分复用的高速水声通信系统,并进行了湖上和海上试验研究。湖试中,在6 000 m距离下,传输速率达到7.6 kbps,误码率低于10-4;海试中,在12 km距离下,传输速率达到8.3 kbps,误码率低于10-3。试验结果表明,正交频分复用技术可以较好地克服码间干扰,有效地利用水声信道带宽,达到高速水声通信的目的。  相似文献   

GPS接收机与PC机间串口通信的实现   总被引：8，自引：1，他引：8  

公丕波  郝金明  朱伟刚 《海洋测绘》2005,25(3):35-37,41

简要介绍了当前流行的几种串口通信程序开发模式以及GPS接收机广泛采用的NMEA0183通信协议，设计了串口通信类CSerialPortGPS，该类能够实现GPS接收机与Pc机问的串口通信，并且能够对遵循NMEA0183协议的GPS数据进行数据校验和数据提取，并成功地将该类应用到了车载定位导航系统的开发中。  相似文献   

向环境监测系统推荐SDI-12通讯标准   总被引：1，自引：0，他引：1  

廉双喜 《海洋技术学报》2001,20(2):58-64

本文推荐 的SDI－12通讯标准是近五年来欧美国家在环境监测中广泛使用的一种串行数据通讯接口协议，在该协议支持下，只要通过一根三芯电缆，即可把一台数据采记录器与多台现场多要素检测仪联系起来，且具有远距离传送，全天候防护和节省经费的优点。  相似文献   

水声通信中基于小波变换的图像编码研究   总被引：2，自引：0，他引：2  

黄海云  朱维庆  朱敏 《海洋技术学报》2005,24(4):36-40,49

提出了一种高误比特率传输条件下的图像编码方法，它适用于水声信道的图像传输。针对水下图像的特点，选取合适的小波基和变换参数对图像进行离散小波变换；依据小波系数的能量分布特性，对不同的子带采用不同的量化和定长编码，编码率为0．8比特／像素。水声通信试验表明，在传输误比特率达到10^-2时，仍能得到可接受的图像质量。  相似文献   

Generating the evidence for marine fisheries policy and management     

John Holmes  John Lock 《Marine Policy》2010

The uptake of research in marine fisheries management and policy making depends on how effectively fisheries managers, researchers and scientific advisers communicate the needs for evidence, and the results and policy implications of research. The MariFish network of the major European funders of marine fisheries has therefore undertaken a study of current practices relating to communication of research needs and results, identifying strengths and weaknesses, and consequently how two-way communications, and hence the effectiveness of generating evidence for marine fisheries policy making and management, can be improved. Conclusions and recommendations for ‘good practice’ include the importance of building good relationships and trust between researchers and fisheries managers, the need for fisheries ministries to have sufficient inhouse scientific capacity to act as ‘intelligent customers’, and the key role of interpreters of research whose skills and career paths need to be carefully developed.  相似文献   

A goodness of fit measure related to r2 for model performance assessment     

William Earl Bardsley 《水文研究》2013,27(19):2851-2856

Checking the predictive worth of an environmental model inevitably includes a goodness of fit metric to quantify the degree of matching to recorded data, thereby giving a measure of model performance. Considerable analysis and discussion have taken place over fit indices in hydrology, but a neglected aspect is the degree of communicability to other disciplines. It is suggested that a fit index is best communicated to colleagues via reference to models giving unbiased predictions, because unbiased environmental models are a desirable goal across disciplines. That is, broad recognition of a fit index is aided if it simplifies in the unbiased case to a familiar and logical expression. This does not hold for the Nash–Sutcliffe Efficiency E which reduces to the somewhat awkward unbiased expression E = 2 – 1/r², where r² is the coefficient of determination. A new goodness of fit index V is proposed for model validation as V = r²/(2‐E), which simplifies to the easily communicated V = r⁴ in the unbiased case. The index is defined over the range 0 ≤ V ≤ 1, and it happens that V < E for larger values of E. Some synthetic and recorded data sets are used to illustrate characteristics of V in comparison to E. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Hilbert变换及其应用     

黄长蓉 《成都信息工程学院学报》1999,(3)

Ｈｉｌｂｅｒｔ变换是一个重要的变换，它在通信系统和数字信号处理系统中是非常有用的。现就Ｈｉｌｂｅｒｔ变换的应用进行了较详细的讨论。  相似文献   

基于位置服务的空间信息传输模型     

高博  万方杰  宋国民  奚玲 《测绘学院学报》2009,(1)

手机的基于位置的服务(LBS,Location Based Service)系统发展迅速,已经成为G IS应用的一个重要组成部分。LBS用户所处的环境以及对空间信息的使用方式均与传统的地图有了较大的差别,因此现有的地图传输理论已不能完全适应LBS系统的工作模式。在分析LBS系统特点的基础上,介绍了传统的Kolacny地图传输模型应用的局限性,提出了基于位置服务系统中的空间信息传输模型,这种模型具有对用户要求低、传输效率高以及表现形式多样化等特点。  相似文献   

Modeling and visualizing semantic and spatio-temporal evolution of topics in interpersonal communication on Twitter     

Caglar Koylu 《International journal of geographical information science》2019,33(4):805-832

Interpersonal communication on online social networks has a significant impact on the society by not only diffusing information, but also forming social ties, norms, and behaviors. Knowing how the conversational discourse semantically and geographically vary over time can help uncover the changing dynamics of interpersonal ties and the digital traces of social events. This article introduces a framework for modeling and visualizing the semantic and spatio-temporal evolution of topics in a spatially embedded and time-stamped interpersonal communication network. The framework consists of (1) a topic modeling workflow for modeling topics and extracting the evolution of conversational discourse; (2) a geo-social network modeling and smoothing approach to projecting connection characteristics and semantics of communication onto geographic space and time; (3) a web-based geovisual analytics environment for exploring semantic and spatio-temporal evolution of topics in a spatially embedded and time-stamped interpersonal communication network. To demonstrate, geo-located and reciprocal user mention and reply tweets over the course of the 2016 primary and presidential elections in the United States from 1 August 2015 to 15 November 2016 were analyzed. The large portion of the topics extracted from mention tweets were related to daily life routines, human activities, and interests such as school, work, sports, dating, wearing, birthday celebration, music, food, and live-tweeting. Specific focus on the analysis of political conversations revealed that the content of conversational discourse was split between civil rights and election-related discussions of the political campaigns and candidates. These political topics exhibited major shifts in terms of content and the popularity in reaction to primaries, debates, and events throughout the study period. While civil rights discussions were more dominant and in higher intensity across the nation and throughout the whole time period, election-specific conversations resulted in temporally varying local hotspots that correlated with locations of primaries and events.  相似文献