基于GNSS方位辅助惯性导航系统的水下地形精密测量技术

多波束测深技术是目前水下地形测量的主要技术手段,测量平台的瞬时姿态及方位是影响多波束测深系统最终成果准确度的重要因素。GNSS方位辅助惯性导航系统,作为目前应用较为广泛的方位、姿态、及位置综合测量系统,不仅能够提供高精度位置信息,同时也能提供测量平台的瞬时姿态及方位数据,而且因为具有GNSS方位辅助测量,使得最终方位测量结果比传统方位测量精度大大提高,这对于多波束最终测量成果精度提高具有重要意义。文中从GNSS方位辅助惯性导航系统原理及技术优势出发,结合Trimble RTX后处理技术,从姿态测量、方位测量及辅助高程测量方面分析了在多波束水下地形测量中的应用,并以实际测量成果来展现其在水下地形精密测量技术方面的优势,结果显示,定位精度可以达到优于2 cm级别,方位精度可以优于0.01°(依赖于双GNSS天线之间的基线长度),该技术对水下地形测量准确度提升作用显著。     

火星资源赋存状况及其原位利用技术研究进展与展望

太空资源的勘探及利用是深空探测的重要目的之一。火星是人类最容易到达和资源利用最为迫切的行星,对火星资源进行勘查和原位利用是未来火星载人探测及基地建设需要解决的重要问题。本文对火星大气资源、水资源、土壤与岩石矿物资源、风能与太阳能资源等可利用资源的类型及赋存状况进行了分析,制作了火星资源的全球分布图,并从资源分布的角度提出了未来火星资源探测及火星基地建设的首选区域。同时,本文也总结了火星原位资源利用技术的研究进展及问题,认为未来需要从以下几个方面开展进一步研究：加强火星资源的针对性勘查与评估;开发新的资源利用模式与技术;建立资源利用成本的综合评估模型;完善资源开发与利用相关的法律法规。     

“Trends” and variations of global oceanic evaporation data sets from remote sensing

The variability in global oceanic evaporation data sets was examined for the period 1988-2000. These data sets are satellite estimates based on bulk aerodynamic formulations and include the NASA/Goddard Space Flight Center Satellite-based Surface Turbulent Flux version 2 （ GSSTF2）, the Japanese-ocean flux using remote sensing observations （J-OFURO）, and the Hamburg Ocean-Atmosphere Parameters and Fluxes from Satellite version 2 （HOAPS2）. The National Center for Environmental Prediction （NCEP） reanalysis is also included for comparison. An increase in global average surface latent heat flux （SLHF） can be observed in all the data sets. Empirical mode decomposition （EMD） shows long-term increases that started around 1990 for all remote sensing data sets. The effect of Mt. Pinatubo eruption in 1991 is clearly evident in HOAPS2 but is independent of the longterm increase. Linear regression analyses show increases of 9.4%, 13.0%, 7. 3%, and 3.9% for GSSTF2, J-OFURO, HOAPS2 and NCEP, for the periods of the data sets. Empirical orthogonal function （EOF） analyses show that the pattern of the first EOF of all data sets is consistent with a decadal variation associated with the enhancement of the tropical Hadley circulation, which is supported by other satellite observations. The second EOF of all four data sets is an ENSO mode, and the correlations between their time series and an SO1 are 0.74, 0.71,0.59, and 0.61 for GSSTF2, J-OFURO, HOAPS2, and NCEP in that order. When the Hadley modes are removed from the remote sensing data, the residue global increases are reduced to 2.2% , 7. 3%, and 〈 1% for GSSTF2, J-OFURO and HOAPS, respectively. If the ENSO mode is used as a calibration standard for the data sets, the Hadley mode is at least comparable to, if not larger than, the ENSO mode during our study period.     

A numerical scheme for morphological bed level calculations

The typical equation for bed level change in sediment transport in river, estuary and near shore systems is based on conservation of sediment mass. It is generally a nonlinear conservation equation for bed level. The physics here are similar to shallow water wave equations and gas dynamics equation which will develop shock waves in many circumstances. Many state-of-art morphological models use classical lower order Lax–Wendroff or modified Lax–Wendroff schemes for morphology which are not very stable for long time sediment transport processes simulation. Filtering or artificial diffusion are often added to achieve stability. In this paper, several shock capturing schemes are discussed for simulating bed level change with different accuracy and stability behaviors. The conclusion is in favor of a fifth order Euler-WENO scheme which is introduced to sediment transport simulations here over other schemes. The Euler-WENO scheme is shown to have significant advantages over schemes with artificial viscosity and filtering processes, hence is highly recommended especially for phase-resolving sediment transport models.     

The impact of scour processes on a smothered reef system in the Irish Sea

The Irish Sea, like many marine areas, is threatened by anthropogenic activities. In particular the Pisces Reef system, a series of smothered rocky reefs are subject to fishing pressures as a result of their position within a Nephrops norvegicus fishery. In an area of sediment deposition and retention the reefs modify the environment by increasing the energy of near-bottom currents which results in localised scouring. This is the first study to attempt to characterise and investigate the ecological functioning of the Pisces Reef system. A multidisciplinary approach was essential for accurate investigation of the area. To facilitate more effective management of the benthic habitats of the Reef system, this study integrates acoustic, seismic, grab sampling and video ground-truthing methods for benthic habitat discrimination. Orientation of the scour hollows also suggest that seabed features could be used to infer dominant flow regimes such as the Irish Sea Gyre. The data revealed significant geology–benthos relationships. A unique biotope was described for the reef habitat and it was demonstrated that scouring may influence community composition through disturbance mechanisms. This study provides preliminary information required for management of a unique habitat within a uniform region.     

基于非线性动力学模型的旅游生态容量分析

近年来,大量增加的游客给景区的旅游生态容量带来了较大的压力,矛盾日渐突出。为了实现景区的环境保护与可持续发展,研究游客活动量与景区旅游生态容量之间的关系是十分必要的。本文从非线性动力学观点出发,构建二者非线性动力学模型,并进行平衡态分析。研究结果表明:(1)系统要达到可持续发展,必须建立在景区环境的自我更新能力及人工恢复程度之和大于外界污染水平,且游客的增长率必须保持在较低水平的基础上;(2)景区旅游生态容量的承载力是有限的,所能容纳的游客也是有限的,超过一定的限度就会引起生态系统失衡。采取严格控制游客量,加强对景区内外环境的保护和改善、提升游客素养等措施,对于系统的协调发展至关重要。     

南极长城站海雾特征分析

本文根据对海雾气象要素场、大气层结和天气形势的分析及其持续时间和季节、年际变化的统计分析,结合个例,讨论了南极长城站海雾的特征和形成机制。认为长城站海雾大多为平流冷却雾,高频率的偏北风和南大洋极锋附近显著的经向海温梯度是长城站多海雾的根本原因;夏半年海雾要多于冬半年,海雾的年际分布差异明显;海雾可出现于0-17m/s的各级风力中,3-11m/s偏北风最有利于海雾的维持;气温为-2-4℃、气-海温差为0-2℃时最易出现海雾;海雾的发生一般伴有稳定的大气层结;"东高西低"是长城站海雾的主要天气形势;海雾的持续时间取决于高压在南极半岛维持时间的长短,平均有10个小时。     

浅层气藏流体相控属性参数建模及应用

对钻井资料较少的莺歌海盆地某气田采用流体相控属性建模,利用叠前纵横波速度比反演预测储层含气性和储层测井综合解释成果,用随机模拟方法建立储层的流体相模型;用流体相模型进行间接相控,建立了用波阻抗约束的随机模拟孔隙度模型,解决了浅层气藏由于受含气效应影响导致模拟的气层孔隙度偏高而难以正确反映储层物性分布的问题。在此基础上求得连通因子平面分布,勾出孔隙度分隔带,解释了研究区压力和气体类型分区特征。     

基于遗传—神经网络方法的广西台风灾害评估模型研究

选取1981—2018年影响广西且灾情记录比较完整的86个台风样本,基于台风灾害伤亡人数、直接经济损失划分灾情等级,选取致灾因子,利用遗传算法与神经网络相结合的方法建立广西台风灾害评估模型.结果表明:选取的台风灾害致灾因子与台风灾情等级之间具有显著的相关性,构建的遗传—神经网络集合预报模型对台风灾情预估效果较好,训练样...