Ocean-bottom seismic observatories

Observations of seismic motion and other geophysical parameters on the ocean bottom over extended periods of time and over a wide range of frequencies (periods) provide information on the suitability of the ocean bottom as a site for the detection of seismic events. Instrument systems consisting of long- and short-period seismographs, long- and short-period pressure sensors, a temperature sensor, and a water-current sensor were operated on the ocean bottom. Experience and calculation indicate that these systems can be well coupled to the sediment surface, mechanically stable, and relatively insensitive to water currents. Local and distant earthquakes, tides, microseisms (3-8 seconds period), long-period (2-6 minutes period) pressure disturbances, and temperature fluctuations have been well recorded from the ocean bottom at depths greater than 2000 fm. Instrument systems were implanted at two locations: south of Bermuda (2400 fm depth, seismic measurements only) and west of San Francisco (2200 fm depth). Data were telemetered acoustically to a ship (Bermuda) and via deep-sea cable to a shore station (California). Results to date indicate that the ocean bottom can be a favorable location for the detection of seismic events.     

条纹管激光成像雷达在近程海面监测应用分析

近程海面监测通常要在低照度条件下,获得高清晰、高分辨目标图像,以提高监测效能。与传统被动红外成像监测相比,激光成像雷达是一种主动成像技术,能获取目标强度像和距离像（统称为四维像）,具有较高的目标探测与目标识别概率。分析了美国条纹管激光成像雷达的发展现状及具有的技术优势,阐述了条纹管激光成像雷达采用的闪光式体制、一次成像、高速获取目标数据的原理。指出条纹管激光成像雷达既适用于近程海面监测,也可与现有监测手段,如被动红外、微波雷达等复合使用,提高监测效率。     

侧视雷达与激光雷达的发展及应用

雷达作为观测地球的重要手段正在高速发展,由最初的真实天线侧视雷达发展为合成孔径雷达,进而发展能探测地面多层垂直目标的激光雷达,其地面精度范围在1 m以内,每平方千米可获得135 000个数据点,这将促使人们对地球系统有更为深刻的了解。除阐述各类雷达的发展状况外,还对其在地球科学特别是地质学、水资源以及土壤植被、海底水深等方面的应用现状作了讨论。     

TCP over optical burst-switched networks with controlled burst retransmission

For optical burst-switched (OBS) networks in which TCP is implemented at a higher layer, the loss of bursts can lead to serious degradation of TCP performance. Due to the bufferless nature of OBS, random burst losses may occur, even at low traffic loads. Consequently, these random burst losses may be mistakenly interpreted by the TCP layer as congestion in the network. The TCP sender will then trigger congestion control mechanisms, thereby reducing TCP throughput unnecessarily. In this paper, we introduce a controlled retransmission scheme in which the bursts lost due to contention in the OBS network are retransmitted at the OBS layer. The OBS retransmission scheme can reduce the burst loss probability in the OBS core network. Also, the OBS retransmission scheme can reduce the probability that the TCP layer falsely detects congestion, thereby improving the TCP throughput. We develop an analytical model for evaluating the burst loss probability in an OBS network that uses a retransmission scheme, and we also analyze TCP throughput when the OBS layer implements burst retransmission. We develop a simulation model to validate the analytical results. Simulation and analytical results show that an OBS layer with controlled burst retransmission provides up to two to three orders of magnitude improvement in TCP throughput over an OBS layer without burst retransmission. This significant improvement is primarily because the TCP layer triggers fewer time-outs when the OBS retransmission scheme is used.     

An accurate model for evaluating blocking probabilities in multi-class OBS systems

This letter presents an analytical model that can be used to evaluate the blocking probability of each service class in a multi-class optical burst-switching network. The model allows, for the first time, the evaluation of blocking probabilities in optical burst switching (OBS) systems with arbitrary burst-length distributions and arbitrary offsets. This includes OBS systems in which the mean burst length of each class is different. Such systems do not follow the conservation law and cannot, therefore, be analyzed using previously published OBS models. For an OBS system with two classes, an offered load of 10/sup -3/, and a 1:5 ratio of high-priority to low-priority traffic, we show that our model accurately predicts the blocking probability for each class, whereas predictions from previously published models that assume conservation disagree with the simulation results by as much as 75%.     

Edge node buffer usage in optical burst switching networks

Optical Burst Switching (OBS) combines the benefits of Optical Packet Switching and Optical Circuit Switching technologies to provide an efficient, yet cost effective, method for data transmission in an all-optical, bufferless, core network. While most studies on OBS has concentrated on the core OBS network, we contribute new studies for the buffer requirement of an OBS edge node. The buffer usage for OBS systems only arises in the edge nodes since they contain an array of assemblers which combines electronic data with a common destination into an OBS burst stream for transmission in an all-optical bufferless core network. Specifically, we present two analytical results for buffer usage in an OBS edge node: one for Poisson traffic and the other for self-similar traffic input. The results show that the aggregated traffic from many assemblers inherits the characteristics of the source input traffic. This means that the output traffic approaches Poisson if the input traffic is Poisson, and the output traffic remains self-similar if the input is self-similar. These results lead to the following important design issues when dimensioning buffer requirements in an OBS edge node: if the traffic input is Poisson, the M/G/m model is the model to use for obtaining the upper bound on buffer usage in an OBS edge node; and for the case of self-similar traffic, Brichet’s method can be used to provide the upper and lower bound.     

基于GMPLS的OBS网络技术

GMPLS(通用多协议标签交换)是MPLS技术向光网络发展的产物。描述GMPLS和MPLS控制平台的区别,介绍引用GMPLS协议作为控制平面的OBS网络。提出的网络结构是在OBS的突发控制包中用通用标签代替源节点和目的节点地址,并使用GMPLS协议栈对路由协议、信令功能以及链路管理协议进行增强和扩展以便更好地支持OBS网络。     

高分辨率卫星海洋背景成像仿真方法

海洋背景的仿真是海面目标场景仿真的关键环节,是海洋目标-背景耦合作用模拟的重要基础,决定了仿真图像中目标与背景差异特征的正确性和真实性。高分辨率遥感成像下,海面细节特征突显,以往视海表为均匀辐射面的处理方法给高分辨率海洋场景仿真造成较大误差。重点研究了海面三维形态、多组分分布与海水方向反射特性的耦合作用和辐射模型,提出了海面高分辨率遥感成像仿真方法。通过频谱分析的方法构建海面三维模型,根据海面组分分布的不同及不同位置海面法向的不同,修正了低分辨率下的海洋BRDF模型,使其满足高分辨率卫星图像的仿真应用,计算出不同组分的海面的方向反射数据,并将其与海面三维模型关联,构建了亚米级海面三维辐射模型,通过光线追踪方法建立海面零视距辐射场,并经过大气影响和传感器效应,模拟不同海况条件下卫星遥感图像。结果表明:将ZY3-02卫星实测海面图像与相同成像条件下的仿真图像对比,图像均值的误差为3.7%,标准差误差为9.9%,可以较真实地模拟高分辨率卫星成像下的海洋背景。     

A partial-success-rate-based resource reservation scheme for slotted OBS networks

Optical burst switching (OBS) is a promising technology for next-generation optical networks. Slotted OBS is an improved version of OBS to reduce burst loss rate, in which wavelength channels are divided into time slots. Slotted OBS has an implicit and under-used property that resources for two bursts with the same source and the same destination are interchangeable. The property further means that resource for a long-distance burst can be partially used by a short-distance burst. In this paper, we utilize the property to design a resource reservation scheme for slotted OBS networks. The scheme reserves a batch of slots every time; the specific number of slots is calculated according to number of arrived bursts and partial success rate (a newly introduced conception in this paper) at each node. Simulation results show that the proposed scheme can get lower burst loss rate, comparing with the well-performing two-way signaling scheme.     

一种用于可控震源数据采集的接力式网络结构

将以太网技术应用于可控震源地震数据采集系统,以解决可控震源地震数据采集中的数据传输瓶颈,并针对可控震源地震数据采集系统的特点,提出了一种接力式的网络拓扑结构,给出了基于该拓扑结构的网络协议设计要点,着重讨论了其中IP的动态分配和路由表的建立方法.     

数码相机在自动气象站中的应用

通常传统自动气象站只能采集常规的气象数据,如：温度、湿度、风力等,而无法采集自动气象站当地的高分辨率图像信息,通过对奥林巴斯数码相机进行研究,采用奥林巴斯提供的CAMEDIA SDK 3.3开发套件,设计了一套基于高分辨数码相机的自动气象站图像采集和传输系统。系统通过自动站的高分辨率数码相机远程采集图像,并通过网络传输到数据中心,实现了自动气象站对当地图像信息的采集与传输。着重介绍分析了数码相机在系统中的应用,并实现了图像数据的自动采集功能。 更多还原     

Migration Strategies Toward All Optical Metropolitan Access Rings

Nowadays, network operators are steadily deploying optical circuit switching (OCS) equipment in their metropolitan networks in order to cope with traffic increase and, most importantly, in order to reduce capital expenditures and operational expenditures of existing active technologies. On the other hand, optical burst switching (OBS) technology is expected to become mature in the medium term, and it may be used as an alternative to current OCS networks due to its potential advantages in terms of bandwidth allocation granularity. While OBS is being extensively studied in the literature, little attention has been paid in conducting a comparative analysis of OBS versus OCS, especially concerning cost analysis. In this paper, we provide a comparative analysis of OBS versus OCS as an evolutionary technology for all-optical rings in the metropolitan-access network. This paper is specifically targeted toward optimizing the number of optoelectronic receivers and wavelengths with real traffic matrices from the metropolitan rings in Madrid, Spain. Such matrices also include traffic projections of foreseeable broadband services, which are based on a market analysis from the largest operator in Spain. Our findings show that OCS might be more efficient than OBS in the metro-access segment, which is characterized by a highly centralized traffic pattern. However, the more distributed the traffic is, the more efficient the OBS is as well. Consequently, OBS might be better suited to metro-core networks, which show a more distributed and dynamic traffic pattern.     

Fair Bandwidth Allocation in Optical Burst Switching Networks

Optical burst switching (OBS) is a promising switching technology for next-generation Internet backbone networks. One of the design challenges is how to provide fair bandwidth allocation in OBS networks; the schemes proposed for general store-and-forward IP switching networks can not be used because of the non-buffering and un-fully utilized bandwidth characteristics of OBS networks. We propose a rate fairness preemption (RFP) scheme to achieve approximately weighted max-min fair bandwidth allocation in OBS networks. We present an analysis of the burst loss probability in RFP-based OBS networks. The analysis and simulation results show that the RFP scheme provides fair bandwidth allocation in OBS networks.      

OBSns:一种OBS通用仿真平台的设计

光突发交换(OBS)是当前全光交换网络技术的研究热点之一,而仿真是OBS研究的一种重要手段。为了给研究者提供方便,同时实现各种研究结果的对比,开发了一种通用的OBS网络仿真平台--OBSns。OBSns以网络仿真工具NS-2为基础,对突发数据传输采用虚拟化的方法,实现了OBS网络的关键元素如突发组装、突发控制分组生成和传输、突发调度等等。同时OBSns是开放的,其各个元素都可以替换,从而为新算法和协议的研究提供了便利。     

基于信息自由度采样的信号重构方法研究进展

有限的采样能力和高分辨的重构需求是现代信号处理中最基本的矛盾.不完全采样(或观测),高分辨重构信号,是信号处理、通信、应用数学等领域的期待解决的问题之一.本文通过回顾现有的不完全采样、高分辨率重构方法的研究成果,提炼出一个基于信息自由度采样的信号优化重构方法的框架.在此框架中有三个核心方面,信息自由度决定采样率,采样方法确定约束条件,信号特征指导目标函数的建立.本文着重综述采样重构方法有效性的分析手段,评论其优缺点.最后,我们展望基于信息自由度采样的信号重构问题的研究前景,并展示我们的新探索与新成果.     

微型光谱仪的CCD 数据采集系统设计

微型光谱仪是近年来光谱仪发展的主要方向。针对微型光谱仪数据采集系统的设计需求,应用TCD1304DG 线阵CCD 完成了以FPGA(EP4CE15)为控制核心的高分辨率数据采集系统设计,系统使用了集成Programmable Gain Amplifier(PGA)、16 位模数转换功能的Analog Front End(AFE)芯片,开发了USB2.0 高速数据传输电路并完成了光谱采集上位机软件的设计,实现了对光谱数据的实时处理。小型集成的电路设计方案满足了光谱仪对小型化、便携使用的特点和要求。     

High-resolution ocean color remote sensing of benthic habitats: a case study at the Roatan island, Honduras

Natural resource managers clamor for detailed reef habitat maps for monitoring smaller scale disturbances in reef communities. Coastal ocean color remote sensing techniques permit benthic habitats to be explored with higher resolution than ever before. The objective of this research was to develop an accurate benthic habitat map for an area off the northwest coast of Roatan Island, Honduras, using high-resolution multispectral IKONOS data. Atmospheric (Rayleigh and aerosol path radiance) and water column corrections (water depth and water column attenuation) were applied to the imagery, making it a robust method for mapping benthic habitats. Water depth for each pixel was calculated based on a site-specific polynomial model. A mechanistic radiative transfer approach was developed that removed the confound effect of the water column (absorption and scattering) from the imagery to retrieve an estimate of the bottom reflectance (albedo). Albedos were /spl les/ 12% for seagrass benthos, 12% to 24% for coral areas, and /spl ges/ 24% for sand-dominated areas. The retrieved bottom albedos were then used to classify the benthos, generating a detailed map of benthic habitats, followed by accuracy assessment.     

Optimized Combination of Converter Pools and FDL Buffers for Contention Resolution in Optical Burst Switching

Optical burst switching (OBS) has attracted interest as a transport network architecture for the future optical Internet. As OBS relies on statistical multiplexing efficient contention resolution is a key issue in order to achieve a low burst loss probability. First, this paper discusses options and key design parameters for contention resolution in OBS. Then, it evaluates the performance of OBS nodes which employ shared wavelength converter pools and simple fiber delay line (FDL) buffers. Finally, optimized strategies for the order of probing a wavelength converter pool and an FDL buffer for contention resolution are presented and compared. It is shown that these strategies can be used to optimize performance for a given, for example, minimal cost, dimensioning of the wavelength converter pool and the FDL buffer.     

基于GL0816传感器的高速线阵CMOS相机系统设计

为了满足印刷等高端工业检测中物体快速运动,需要大幅面、高行频、高分辨率图像采集等要求,研发了一款微米级高分辨率、高速线阵工业相机。首先,介绍了高行频、高分辨率国产CMOS图像传感器GL0816的功能与特点。然后,基于该芯片设计了一套高速大幅面高分辨率线阵工业相机系统,该系统采用FPGA作为整个系统的控制核心,以DDR3LSDRAM作为图像缓存器,以GigE vision2.0协议为输出标准,以SFP+作为高速图像输出接口。最后,搭建相机系统测试环境,对所设计的相机进行系统测试。结果表明:该相机系统行分辨率为8 192,可连续采集2 000行作为一帧图像输出,行频为50kHz,动态范围为57.32dB,信噪比为40.95dB,具有实时图像采集功能。该相机系统具有大幅面、高帧频、高分辨率、高信噪比、宽动态范围等优点,适用于印刷检测行业快速运动目标捕获成像及图像实时显示。