一种改进的FAMAC协议的仿真与性能分析

介绍了一种多信道接入协议MC，提出了一种基于虚拟载波监听的改进方案，利用OPNET软件对其性能进行了分析，仿真结果表明改进的FAMAC协议与原FAMAC协议相比，在含有隐藏终端和暴露终端的复杂网络拓扑条件下能够显著地节约信道资源，而协议的性能却没有明显的下降。     

蓝芽技术及在船舶操纵系统中船应用模型

系统介绍了现代无线蓝芽技术，分析了蓝芽系统的组成及协议体系，并提出蓝芽技术在船舶操纵系统中的应用模型。     

实时视频网络多路传输的研究与开发

介绍了数码监控系统中基于Internet的多路视频实时传输的原理和方法。采用TCP/IP协议，通过Winsock及多线程编程，实现了基于Internet的多路视频的实时网络传输，介绍了一种能对网络的视频流量进行自适应控制的算法，对数码监控系统的远程监控部分起到了至关重要的作用。     

基于iCAN协议和PC104的测控系统设计方案

CAN总线是被广泛应用的现场总线之一.介绍了CAN总线的发展和应用,分析了CAN总线多种应用层协议并存的问题.详细介绍了一种由我国自主开发的CAN总线应用协议--iCAN协议,同时分析了PC104的主要特点.通过采用研华生产的PCI04,设计了一个基于iCAN协议的测控系统.     

通用自动识别系统的SOTDMA通信模型初探

以未来船舶通信导航系统中(AIS)采用的SOTDMA数字通信技术为基础，介绍了SOTDMA时隙预约算法和帧结构图谱，简化了SOTDMA数据链系统协议，提出了PC机运行环境下的时隙预约仿真模型。     

新型多跳自组织航运通信系统

提出构建一种基于Ad hoc网络的新型多跳自组织航运通信系统,给出其节点模型、网络模型和协议栈模型,并对其业务模式、协议栈、信道编码、接入协议、分群管理、路由算法、安全控制、网络管理与集成等系统实现问题进行综合论述。     

基于CANopen协议的直线电机监控主站的设计与实现

CAN总线由于实时性强、传输距离较远、抗电磁干扰能力强、成本低等优点,广泛应用于工业自动化、汽车、船舶等领域。本文将CANopen协议应用于基于电磁弹射技术的直线电机监控系统,分析CANopen协议的对象词典和报文格式,详细介绍了基于CANopen协议的直线电机监控主站的实现方案,实验表明基于CANopen协议的监控主站能很好地满足控制系统的需求。     

基于DSP的嵌入式协议栈的研究和实现

通过分析以DSP为处理器的嵌入式系统中协议栈的应用,给出基于DSP的嵌入式TCP/IP协议栈的实现方案,设计嵌入式通信协议模型、总体结构和各个协议工作的主要流程,在DSP上对TCP/IP协议栈进行了设计,实现ARP,IP,ICMP,UDP协议.     

基于STEP标准的船舶工程数据共享研究

本文介绍了在船舶设计和船舶工程研究等多个应用系统中,基于STEP标准的集成产品数据共享环境的基本结构。集成产品信息模型是集成产品数据共享环境的模型,其中目前有的信息模型STEP标准还不能支持,如：CFD,需要从几个相关的应用协议和集成资源扩展而来。本文最后从共享产品数据库的建立和访问两方面概要阐述了信息共享的实现。     

基于STEP标准的船舶工程数据共享的研究

本文介绍了在船舶设计和船舶工程研究等多个应用系统中,基于STEP标准的集成产品数据共享环境的基本结构.集成产品信息模型是集成产品数据共享环境的模型,其中目前有的信息模型STEP标准还不能支持,比如:CFD,需要从几个相关的应用协议和集成资源扩展而来.文章最后从共享产品数据库的建立和访问两方面概要阐述了信息共享的实现.     

基于网络准入控制系统的SSLVPN平台设计与实现

随着网络技术的不断发展,终端用户远程安全接入需求也日益增长,为了满足用户的相关互联网应用需求,SSL VPN技术应运而生.SSLVPN提供了远程用户访问敏感公司数据最简单最安全的解决技术,远程用户通过SSLVPN创建的加密隧道,安全高效的接入公司办公网络.基于网络准入控制的SSLVPN平台为远程用户提供了可实现的应用平台.     

网络安全协议比较研究

网络安全协议是以密码学为基础的协议,在网络环境中提供各种各样的安全服务,在网络安全中占据重要的位置。文章介绍了四种常用网络安全协议（包括SSH协议、SSL协议、SET协议和IPSec协议）的组成、服务、安全体系结构、加密方式和易遭受的攻击等,并从四个方面分析比较了它们的特点,对于促进网络安全协议机制的研究和开发具有一定的现实意义。     

自升式抛石整平平台船的设计与应用

针对长江口深水航道治理工程恶劣的作业环境,将海上施工平台的概念引用到水下抛石整平施工工艺中,研究的主要内容包括设备的施工作业方式、平台的结构、平台自浮的拖航稳定性、平台支腿靴板对基础的压力、平台升降装置、抛石整平机构及作业时的稳定性等,阐述了平台船的特点和先进性,以及在今后大型水工工程中的应用前景。     

多因素数学模型在温州瓯江口浅滩围涂工程研究中的应用

建立了波浪、潮流、盐度、悬沙、底床冲淤等多种因素数学模型,在模型验证的基础上,对瓯江口温州浅滩围涂工程海区的波浪场、潮流场、盐度场、悬沙场、底床冲淤场进行了数值模拟研究,对温州浅滩围涂工程对瓯江泄洪、瓯江南北口分流比、乐清湾养殖业、瓯江口港口航道及状元岙深水区、南口口外滩地的影响进行了分析论证。分析研究结果表明,温州浅滩围涂工程是可行的。     

High-resolution surveys of the biogeochemistry of the New England shelfbreak front during Summer, 2002

We present the observations from a pair of field experiments at the New England shelfbreak front in June and August of 2002, each consisting of 14 cross-frontal surveys using the Lamont Pumping SeaSoar. Measurements of the front's physical, chemical, and bio-optical characteristics were made at high spatial and temporal resolution. The front, based on water-column hydrographic distributions, was found within a few km of the 200 m isobath during both cruises. We present here composite sections, based on averages of individual sections shifted in space to a common frontal location, of the cross-frontal distributions of these properties as a measure of the mean state of the front in both June and August. The observations show the familiar temperature, salinity, and density distributions of the summertime front, dominated by surface thermal heating. Nutrient and bio-optical distributions show the combined effects of water-mass exchange and biological processes. T, S, silicate, and phosphate distributions are suggestive of cross-frontal exchange of slope- and shelf waters, although transport mechanisms and pathways are not apparent. These properties, along with nitrate and optical measures of the suspended particle distributions, show vertical displacements of isopleths as the front is approached: property contours slope upwards toward the front from the shoreward side, and downwards toward the front from the seaward side. Again, actual water-movement pathways are not constrained by these suggestive patterns. Bio-optical distributions show elevated indicators of photosynthetic efficiency both seaward and shoreward of the front, but the front itself is a minimum in biomass. Accumulation of photosynthetic biomass appears to be controlled primarily by nitrate scarcity in waters within and above the pycnocline. At the base of the pycnocline, light limitation appears to be the controlling factor, although the base of the euphotic zone is deeper than the biomass maxima and the base of the pycnocline. Mechanisms explaining this phenomenon are unclear, but tenuous evidence suggests low stratification at the depth of the 1% light level may not allow phytoplankton to optimize for the low-light, high-nutrient conditions at depth. Cross-frontal differences in nutrient and bio-optical parameters, particularly in August, suggest distinct phytoplankton assemblages, and the presence of calcite-forming or nitrogen fixing groups to the community structure, especially in very shallow waters across the front and in pycnocline waters seaward of the front.     

Matching biological traits to environmental conditions in marine benthic ecosystems

The effects of variability in environmental conditions on species composition in benthic ecosystems are well established, but relatively little is known about how environmental variability relates to ecosystem functioning. Benthic invertebrate assemblages are heavily involved in the maintenance of ecological processes and investigation of the biological characteristics (traits) expressed in these assemblages can provide information about some aspects of functioning. The aim of this study was to establish and explore relationships between environmental variability and biological traits expressed in megafauna assemblages in two UK regions. Patterns of trait composition were matched to environmental conditions and subsets of variables best describing these patterns determined. The nature of the relationships were subsequently examined at two separate scales, both between and within the regions studied. Over the whole area, some traits related to size, longevity, reproduction, mobility, flexibility, feeding method, sociability and living habit were negatively correlated with salinity, sea surface temperature, annual temperature range and the level of fishing effort, and positively associated with fish taxon richness and shell content of the substratum. Between the two regions, reductions in temperature range and shell content were associated with infrequent relative occurrences of short-lived, moderately mobile, flexible, solitary, opportunistic, permanent-burrow dwelling fauna and those exhibiting reproductive strategies based on benthic development. Relationships between some traits and environmental conditions diverged within the two regions, with increases in fishing effort and shell content of the substratum being associated with low frequencies of occurrence of moderately mobile and moderately to highly flexible fauna within one region, but high frequencies in the other. These changes in trait composition have implications for ecosystem processes, with, for example, reductions in permanent-burrow dwellers within one of the regions potentially compromising the ability of the assemblages to process and store chemicals and waste products. However, the connections between environmental conditions and trait composition are complex and incorporate many factors. Experimental investigations will be necessary to determine the extent and consequences of these important relationships.     

Disused shrimp ponds: Options for redevelopment of mangroves

Associated with the rapid increase in the production of cultured marine shrimp has been large‐scale conversion of mangroves to shrimp ponds. Production in many regions has proved to be unsustainable, largely due to inappropriate construction methods, poor environmental conditions, overstocking, and disease. A number of shrimp ponds consequently are unproductive and lie idle. Accurate assessments of pond disuse are difficult to obtain; however, unofficial estimates have suggested that as many as 70% of ponds may be disused after a period in production. Pond construction, shrimp culture, and pond disuse lead to alterations to the physical and chemical properties of soil, hydrological conditions, and the flora and fauna composition of the pond area. The case for restoration, or rehabilitation to a sustainable use, is strong. Consideration must be given to the causes of production failure, the environmental conditions remaining following disuse, the needs and preferences of pond owners and coastal managers, and technical constraints.     

Regulation and Approval of Drugs and Pesticides Used in Canadian Salmon Culture

When Canadian salmon farmers find the health of their stock is compromised by infection or disease, the use of drugs or pesticides can be required. In Canada, there is a very limited range of these chemicals legally available to farmers and veterinarians. The formal approval and registration process for these chemotherapeutants is complicated. It involves the overlap of a variety of government departments, depending on the method of application of the therapeutic compound. These formal channels, through which chemotherapeutic products, specifically drugs and pesticides, are licensed for use, are both lengthy and costly to navigate. Often, these costs exceed any potential returns from the sale of the products (OCAD, 2001; Harper, 2002). Consequently, unapproved drugs, which would not normally be available for use, are obtained through alternative channels, which may pose a number of environmental, human, and animal safety concerns. This article seeks to provide a better understanding of the approval process and regulations governing drugs and pesticides and how they are made available for use in Canadian salmon culture.     

基于ARM的嵌入式通讯平台设计

文章介绍了以NXP的ARM7 TDMI内核控制器为核心的嵌入式通讯平台的设计,包括CAN、工业以太网、USB、RS232、RS485、UART、无线等目前流行的各种通讯方式的设计以及液晶显示、触摸屏、按键的硬件设计,给出了比较完整的方案设计和硬件连接,同时对于所采用的操作系统进行了简单介绍。