地震应急卫星通信网路由异常分析

地震应急卫星通信网一直存在路由异常的问题,时常造成卫星站点通信不畅。通过对网络拓扑结构进行分析,总结造成路由异常的原因。通过列举实例,提出以通过设置静态路由的方式,来解决目前网络中存在的路由异常问题。     

OSPF在地震应急卫星通信网中的应用研究

在地震灾害发生后,地震应急卫星通信网为地震救援提供高效可靠的音视频以及数据传输信道。由于地震灾害的突发性和不可预见性,地震应急卫星通信网在满足业务传输需求的同时需要实现灵活组网。OSPF(Open Shortest Path First,优先开放最短路由协议)较小的网络开销以及兼具灵活的组网方式,对于带宽资源有限的卫星通信系统来说无疑是相当具有优势的。本文着重研究了OSPF在地震应急卫星通信网中的具体应用。     

面向多源数据融合的移动GIS的设计与实现

对Android嵌入式操作平台的移动GIS进行了探索;研究了系统架构设计和关键技术,包括地理空间表达的矢量数据结构和栅格数据结构,适合嵌入式系统特点的三维景观电子地图的渲染和显示;通过获得HTTP网络服务,实现与服务器端的数据通信,并将系统应用于校园移动拼车服务平台。     

中国未来地球计划的协同推广机制建设初探

本文在回顾科学成果传播方式与模式的基础上,以科学成果集成、网络传播和公众科学素养提升为出发点分析了当前科学传播面临的挑战与时代需求。基于对未来地球计划科学组织模式的解读,分析了未来地球计划成果传播模式的特点,并从科学研究、社会认知和科学决策层面探讨了科学成果推广和普及机制。有针对性地提出了充分引入利益相关者参与、推进创新科学成果推广机制与平台建设等科学传播相关政策建议。     

Precoding Based Channel Prediction for Underwater Acoustic OFDM

The life duration of underwater cooperative network has been the hot topic in recent years. And the problem of node energy consuming is the key technology to maintain the energy balance among all nodes. To ensure energy efficiency of some special nodes and obtain a longer lifetime of the underwater cooperative network, this paper focuses on adopting precoding strategy to preprocess the signal at the transmitter and simplify the receiver structure. Meanwhile, it takes into account the presence of Doppler shifts and long feedback transmission delay in an underwater acoustic communication system. Precoding technique is applied based on channel prediction to realize energy saving and improve system performance. Different precoding methods are compared. Simulated results and experimental results show that the proposed scheme has a better performance, and it can provide a simple receiver and realize energy saving for some special nodes in a cooperative communication.     

The communicative competence of Chinese seafarers and their employability in the international maritime labour market

In the past two decades, the seafarer workforce in China has been growing at a much faster pace than that of the Chinese merchant fleet, resulting in an oversupply of seafarers in the domestic market. As one of the major seafarer suppliers in the world, China still faces great challenges to assign Chinese seafarers to the international maritime labour market. Although literature claims that a lack of English communication ability of Chinese seafarers is one of the main barriers for them to compete with seafarers of other nationalities for job opportunities, there is little empirical research to substantiate such claim. To fill this gap, this paper aims to investigate: 1) employers’ views on the current level of Chinese seafarers’ communicative competence; and 2) to what extent their communicative competence correlates with their employability in the international maritime labour market. To achieve the research objectives, a questionnaire survey relating to factors affecting the employability of Chinese seafarers on foreign ships was conducted. Interviews were carried out with employers who had been recruiting seafarers in China. The findings show that English communicative competence is among the top determinants for seafarers to be employed on foreign ships. Most employers believe that there has been a declining trend in the communicative competence of Chinese seafarers over the last decade. Employers interviewed agree that a high priority should be placed on the improvement of quality of maritime English teachers.     

云南省地震应急短波通信系统建设及应用

介绍了云南省地震应急短波通信系统的建设情况、实际工作频率的选择依据,并以景谷6.6级地震为例详细说明了该系统的应用模式。地震应急短波通信系统经历了多次地震应急的考验,在震区通信中断时确实能够提供最后的通信保障,达到了预期的设计目标。     

地震应急卫星站点常见问题与故障处理

对地震应急卫星通信系统的站点进行了简要介绍,根据日常卫星运行维护工作中的经验,总结了省地震局卫星站点容易出现的故障,提出了通过设备指示灯快速识别设备故障的方法,并对可能出现的常见故障提出了解决方案,对省地震局应急通信现场工程师有一定的参考和实用价值。     

超短波和微波通信在地震应急中的应用

破坏性地震发生后,运营商公共网络通信（SDH/MSTP光纤、DDN、GPRS、CMDA、WCDMA、LTE等）由于光缆中断、基站拥塞等原因已经无法正常使用,卫星通信链路会因用户激增而造成堵塞。宁夏地震局立足于本省地理优势,探索建立一张不依赖于运营商的独立运营的无线应急通信网,以采用超短波、微波通信作为信息传递的主干线路,旨在解决破坏性地震后的网络通信与数据传输问题,为抗震救灾提供基础通信保障。     

Application of satellite communication to hydrographic data processing

The Hydrographic Department and the Information Systems Department at the Naval Oceanographic Office (NAVOCEANO) successfully transmitted coastal area sounding and position data collected by USNS John McDonnell, a recently built survey vessel, from the Gulf of Mexico to NAVOCEANO at Stennis Space Center, Mississippi.

Two external modems were used to modulate and demodulate the data that were received from a MICROVAX 3400 aboard USNS McDonnell and sent to the Intergraph Interactive Workstation at NAVOCEANO via the MARISTAT communication satellite. The Kermit file transfer protocol was used to bridge the different operating environments between input/output (I/O) devices and central processors.

Office processors were able to evaluate the data prior to the departure of the survey platform from the area. From this data, smooth sheets‐were produced. Equipment upgrades and more efficient use of satellite availability within the entire INMARSAT system should allow near‐real‐time editing and validation of field hydro‐graphic data.