一种基于Agent位置透明及消息缓冲体的消息传递机制

针对移动 Agent的可靠消息传递问题 ,提出 1种基于 Agent位置透明及消息缓冲体的消息传递机制 ,并从 Agent命名、Agent服务注册和消息缓冲几个方面 ,给出消息传递机制的具体实现算法。与现有通信机制相比 ,较好解决了 Agent在移动前后及移动过程中的消息传递问题。     

移动Agent结构化安全机制的研究

分析了移动 Agent的安全问题和现有的 Agent安全保护技术 ,从重构移动 Agent的结构入手 ,提出了将 Agent的安全机制从功能体中分离出来独立实现 ,从而构建 1种新的移动 Agent的结构化安全机制的方法 ,并对此进行了阐述     

一种基于拍卖理论的移动Agent资源分配模型

描述了 1种以区间值为价格的移动 Agent资源底价密封拍卖模型 ,并赋予资源所有者参与价格制定的权利     

一种基于伽利略搜救系统的联合定位算法

分析了伽利略搜救系统的地面站定位模型。提出了一种适用于该系统的,在存在多余观测的情况下,基于信号的时间延迟和多普勒频率测量值加权后,共同参与平差计算的联合定位算法模型及其误差分布模型。仿真结果表明,与单纯使用一种观测值的定位算法相比,该算法可以提高定位精度,是一种适合伽利略搜救地面站使用的定位算法。     

基于MPI+OpenMP的水声传播并行预报方法

基于SMP集群,利用MPI+OpenMP混合并行编程方法,设计和开发了水声传播产品多级混合并行预报算法,该算法结合SMP集群的体系架构特点,通过节点内共享内存,节点间消息传递的方式,充分发挥两种模式各自的优势,克服MPI模式进程间通信时间长、OpenMP模式扩展性差的缺点,并对程序进行了优化处理,实现了水声传播产品的快速高效预报。测试结果表明,该方法可充分发挥两种并行编程模式的优点,有效提高水声传播产品预报程序的并行效率和扩展性,大幅降低预报时间。     

胶州湾不同季节浮游动物昼夜垂直移动规律初步研究

在胶州湾内设置连续站(36°5'54″N,120°15'20″E),分别于2006-2007年分春季、夏季、秋季、冬季四季进行垂直分段拖网,研究了胶州湾浮游动物垂直移动的规律。结果显示,浮游动物在不同季节显示不同的垂直迁移行为。同时,对该海域出现的优势种类的垂直移动规律进行了研究并分类,发现不同物种同一季节迁移方式不同,对于同一种类,在不同季节也表现出不同的迁移规律。因此,浮游动物垂直迁移规律不是一成不变的,由外界环境因子和内在因素共同作用决定。不同季节影响浮游动物垂直迁移的关键因子不同,其中春季、夏季、秋季三季主要影响因子是光照,冬季除了光照,还有温度、盐度和浮游植物密度。总体与温度和浮游植物密度正相关,与盐度负相关。对于不同种类,影响其垂直迁移的主要因子也不尽相同。     

一种改进的水下声学定位算法

通过分析讨论泰勒级数展开法和Chan算法的优缺点,提出了一种先由Chan算法解算求得初始参考值,再由泰勒级数展开法在该初始值处展开进行迭代求解的协同定位算法。通过实验,将本方法与传统定位算法(泰勒法)、Chan算法进行对比。结果表明,该方法无需额外提供初始值,解算出较好的结果的同时且能保持良好的时间效率。通过此方法,在实际生产作业中可节约定位时间,改善定位精度。     

墨西哥湾海洋环境对蓝蟹(Callinectes sapidus)幼体分布和扩散的影响

本文以蓝蟹为例,研究海洋环境对甲壳动物幼体迁移规律和机制的影响。利用不规则三角形网格和有限体积模型(finite-volume coastal ocean model, FVCOM)耦合kinesis模型的方法,分析研究了墨西哥湾物理环境对蓝蟹(Callinectessapidus)幼体的分布和扩散途径的影响。蓝蟹在每年的四、五月份海水落潮期间产卵,通过跟踪算法从产卵区域沿着墨西哥湾海域进行模拟,获得了80天内蓝蟹幼体的粒子移动轨迹,记录并分析了幼体经过海域的盐度值。研究结果证明了该方法可有效模拟蓝蟹幼体在特定海域的迁移规律和扩散机制,进一步研究可为了解海洋物理环境对蓝蟹和其他渔业资源的影响提供借鉴。     

无线传感器网络中一种增强DV-Hop算法

无线传感器网络中的DV-Hop算法是1种无需测距的节点定位算法。经仿真观察,该算法存在类似“块效应“的定位误差。文中作者提出1种增强DV-Hop算法,通过锚节点的定位结果,对未知节点的定位结果进行修正。经仿真验证,增强算法可以有效解决“块效应“,提高算法的定位精度与鲁棒性。     

基于相关性分析的水下定位异常数据校正及丢失数据修补方法

超短基线是实现水下拖体设备精确导航定位的必备设备,是目前我国在国际海底区域进行资源深入调查研究的重要装备。受水声信号传播损失、多径效应和其它设备噪声等因素的影响,超短基线水下定位数据存在诸多异常点,已严重影响水下定位数据的可信度和使用。针对该问题,本文提出并实现了一种基于相关性分析的剔除随机异常点和回归填充改正算法,并采用国际海底区域实测水下定位数据对算法可靠性进行了验证,同时采用模拟仿真方法对小时间尺度的定位数据进行了预测对比,取得较好效果。结果表明,该算法快捷、有效,有望在后续国际海底区域调查中推广应用,为国际海底资源调查水下装备的准确定位提供直接服务。     

基于北斗卫星的海洋测量数据传输系统

针对目前我国海洋测量船上测量数据无法实时传输的现状,采用我国自主研发的北斗卫星导航系统为无线信道单元,结合数据压缩及长报文通信协议等技术,设计了基于北斗卫星的海洋测量数据传输系统,解决了海洋测量船上测量数据实时传输的问题。     

海洋观测通信组网安全及其硬件加速研究

从我国海洋信息观测需求入手,分析海上临时无线组网安全通信基本需要,提出一种基于AES和RSA算法与消息认证码(MAC)组合的一次性双向口令认证协议,并对RSA算法硬件加速评估,优化算法设计,减少资源消耗,解决海上信息采集临时组网通信安全问题。     

基于辛几何算法的高斯束叠前深度偏移

辛几何算法是专门针对动力学过程设计的算法,以提高动力学问题求解的精度与效率。高斯束偏移过程中的运动学与动力学射线追踪,从物理上讲是一个动力学过程,可以利用辛几何算法对其进行优化。本文将基于辛几何算法的运动学射线追踪引入高斯束叠前深度偏移中,并在推导了动力学射线追踪方程组的辛差分格式基础上,实现了基于辛几何算法的高斯束叠前深度偏移。模型实验表明,基于辛几何算法的运动学射线追踪,其效率与精度相比常规算法都具有一定优势,而基于辛几何算法的高斯束叠前深度偏移方法能够对复杂构造模型精确成像。     

空间互相关方法在分析海底沙波迁移规律中的应用

海底沙波具有显著的活动性并能够对海底工程设施造成潜在威胁,因此对海底沙波活动性的评估一直以来受到广泛关注。目前大多数研究者仍利用平面剖面对比来分析海底沙波的迁移特征。然而,该方法难以全面高效地获取海底沙波二维平面迁移矢量。本文基于2007年和2009年的高分辨率多波束测深数据,详细阐述了空间互相关方法在分析北部湾东南海域海底沙波迁移规律中的应用过程。利用实测数据进行对比分析,获得了研究区海底沙波的活动特征,并进一步讨论了空间互相关算法中不同参数的选取对结果的影响。结果显示,利用空间互相关分析方法能够有效获取海底沙波二维迁移矢量,获得的海底沙波迁移速率和迁移方向与前人研究成果吻合,表明了该方法的可行性和可靠性。但在对实际DTM数据进行空间互相关分析时,需根据海底沙波形态、数据质量等因素选取合适的参数及矢量获取方法。本研究实验了一种确定海底沙波迁移规律的新方法,该方法将有效提升获得海底地形变化规律的效率和准确度,可获得更加精细的海底地形动力过程。     

便携式天文定向系统及其精度分析

天文定向是以观测天体来确定地面目标方位角的高精度自主定向方法。但是,传统的天文定向设备繁重,无法满足机动应用。针对这一问题,利用电子经纬仪和内置GPS OEM板的掌上电脑,建立了新型便携式天文定向系统,提出了将时角法模型推广到太阳和任意恒星定向的新思路。测试结果表明该系统精度高、速度快,能满足快速机动定向的需求。     

An Ecological-Physical Coupled Model with Ontogenetic Vertical Migration of Zooplankton in the Northwestern Pacific

A vertical one-dimensional ecosystem model with vertical migration of zooplankton was constructed and applied to Station A-7 off Sanriku district of Japan in the northwest Pacific Ocean. The model consists of an eight-compartment ecosystem model coupled with a physical model of the oceanic mixed layer. The transition of phytoplankton species responsible for the spring bloom is well reproduced by this model with vertical migration of zooplankton but is not simulated by the model without vertical migration. This new model also simulates an observed inter-annual variability of the spring bloom, with the timing and intensity of the simulated bloom in a given year depending upon the strength of mixing during the preceding winter. This revised version was published online in August 2006 with corrections to the Cover Date.     

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin,Malawi Rift (EARS)

The Cenozoic East African Rift System (EARS) is an exceptional example of active continental extension, providing opportunities for furthering our understanding of hydrocarbon plays within rifts. It is divided into structurally distinct western and eastern branches. The western branch comprises deep rift basins separated by transfer zones, commonly localised onto pre-existing structures, offering good regional scale hydrocarbon traps. At a basin-scale, local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution. Here, we consider the evolution of the Central basin of the Malawi Rift, in particular the influence of pre-existing structural fabrics.Integrating basin-scale multichannel 2D, and high resolution seismic datasets we constrain the border, Mlowe-Nkhata, fault system (MNF) to the west of the basin and smaller Mbamba fault (MF) to the east and document their evolution. Intra basin structures define a series of horsts, which initiated as convergent transfers, along the basin axis. The horsts are offset along a NE–SW striking transfer fault parallel to and along strike of the onshore Karoo (Permo-Triassic) Ruhuhu graben. Discrete pre-existing structures probably determined its location and, oriented obliquely to the extension orientation it accommodated predominantly strike-slip deformation, with more slowly accrued dip-slip.To the north of this transfer fault, the overall basin architecture is asymmetric, thickening to the west throughout; while to the south, an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western MNF. The presence of the axial horst increasingly focussed sediment supply to the west. As the transfer fault increased its displacement, so this axial supply was interrupted, effectively starving the south-east while ponding sediments between the western horst margin and the transfer fault. This asymmetric bathymetry and partitioned sedimentation continues to the present-day, overprinting the early basin symmetry and configuration. Sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small (10–100 m) scale. The observed influence of basin-scale transfer faults on sediment dispersal and fault compartmentalization due to pre-existing structures oblique to the extension orientation is relevant to analogous exploration settings.     

Simulation of Random Waves and Associated Laminar Bottom Shear Stresses

This work presents a new approach for simulating the random waves in viscous fluids and the associated bottom shear stresses. By generating the incident random waves in a numerical wave flume and solving the unsteady two-dimensional Navier-Stokes equations and the fully nonlinear free surface boundaiy conditions for the fluid flows in the flume, the viscous flows and laminar bottom shear stresses induced by random waves axe determined. The deterministic spectral amplitude method implemented by use of the fast Fourier transform algorithm was adopted to generate the incident random waves. The accuracy of the numerical scheme is confirmed by comparing the predicted wave spectrum with the target spectrum and by comparing the nanlerical transfer function between the shear stress and the surface elevation with the theoretical transfer function. The maximum bottom shear stress caused by random waves, computed by this wave model, is compared with that obtained by Myrhaug＇ s model （1995）. The transfer function method is also employed to determine the maximum shear stress, and is proved accurate.     

Design and implementation of time efficient trajectories for autonomous underwater vehicles

This paper discusses control strategies adapted for practical implementation and efficient motion of autonomous underwater vehicles (AUVs). For AUVs we would like efficiency in both the measured time and the energy consumption, the mission dictating the weight to put on each of these cost. As a first approach to this problem, we focus in this paper on time minimization. Based on the structure of the time optimal trajectories and of the pure motions, we develop an algorithm to design time efficient trajectories corresponding to piecewise constant thrust arcs with few actuator switchings. We do that by solving a new optimization problem where the unknowns are the time period between two actuator switchings as well as the values of the constant thrust arcs. We apply a direct method to compute the solutions numerically. With our algorithm, we gain considerable computational time. Moreover, with as few as three actuator switchings, the duration of our trajectories is within 10% of the optimal trajectories. Since our control strategies have a simple structure they can be implemented on a test-bed vehicle. For the experiments displayed in this paper we use a spherical underwater vehicle which exhibits with almost no preference of direction or orientation for movement; this gives us a very controllable and versatile vehicle.