利用人工神经网络建立我国南海地区电离层模式

为了解决我国南海地区短波无线电通信信道的选择问题,本文建立了该区域一种新的电离层模式．模式中使用了人工神经网络技术,神经网络选用了５个预报变量,并用南海地区的６个电离层站的观测资料训练网络．结果表明：这个模式能够反映我国低纬电离层随太阳活动水平、经纬度和时间的变化,它适用于我国南海和东南海地区高频通信的频率预报．     

海南省地震短波无线通讯网XD-D2B型单边带15瓦电台的使用与维护

海南省地震局各地震台,各市县地震局（办）绝大部分都使用ＸＤ－Ｄ２Ｂ型单边带１５Ｗ电台,成为全局使用和维护均居首位的短波无线通讯设备。１电台使用中的故障我局短波无线通讯网使用的天线大多是４４ｍ双极天线,架设中出现以下问题。①天线没有拉开。如文昌市地震台...     

华北联网中心的短波天线：华北地区遥测地震台网联网论文续五

对华北联网中心北京中心短波天线的设计，功能，安装方案作了较为详细的介绍。     

从重复重力测量资料中提取河西—祁连地区的地震特征的研究

利用富里叶分析法分离出了河西—祁连地区重力变化的长波项和短波项，并结合该区的几次地震进行了分析研究，得到以下初步认识：１．长波项图象特征表明，地震前地壳深处物质的迁移性运动是地震活动的背景性因素；短波图象则是地震发生前的异常表现。２．无论是长波项，还是短波项，在地震前其图象都有高梯度带，但其物理意义不同：长波图象的高梯度带是由于地壳深部的结构不同，使物质迁移受到一定程度的阻档所致；短波图象的高梯度带则是未来地震的危险地带。３．河西—祁连地区的垂直力源的局部性和短暂性的根源在于形成力源的地壳深部物质迁移的局部性和短暂性。     

地下钻杆透层天线

对于有耗分层媒质中的垂直透层天线，建立了Ｈａｌｌｅｎ积分方程分析法的一般理论以及求取地面电场和电压的计算方法．作为应用实例，给出了地下３层媒质中钻杆天线上的电流积分方程，并对典型的地质参数进行了数值计算．所得结果和结论，与已知的理论结果和实验规律吻合。     

辽宁区域地震短波通信传播特性和频率选择探讨

辽宁区域地震短波通信网对电磁波在无线通信中的传播特性及频率选择等问题，没有进行深入的理论研究和探讨。笔者将通信工作的实践经验升至理论的高度，研究探讨辽宁区域地震短波通信传播特性和频率选择办法，达到在短波数据通信中，选择最佳频率，增加沟通率的目的     

短波信道与其链路穿过的电离层相关性分析

电离层的状态及其变化在短波通信、天波超视距雷达和短波广播等依赖天波技术的系统应用中有重要意义.以前很少看到关于短波信道与其链路穿过电离层的状态及其变化的同步观测及其相关性定量描述.本文利用2011年7月21-27日厦门—武汉链路短波信道观测数据和2011年12月10-16日西安武汉—莆田链路短波信道观测数据,以及厦门、武汉、西安电离层垂直观测数据,对西安—武汉—莆田链路短波信道、厦门—武汉链路短波信道及其链路穿过的电离层特征参量相关性进行了分析研究,结果如下:(1)西安—莆田链路短波信道的最大可用频率(MUF)与该链路的中点(武汉)电离层F层临界频率(foF2)的相关系数最大,为0.974;(2)西安—莆田链路MUF与链路端点(西安)电离层foF2的相关系数稍小些,西安武汉链路MUF与链路两端(武汉、西安)电离层foF2的相关系数也稍小些,但都接近于0.930;(3)西安—莆田链路MUF与厦门(距离莆田约为140 km)电离层foF2也比较小,为0.912;(4)西安一武汉链路MUF与厦门(距离武汉约770 km)电离层foF2的相关系数更小一些,为0.877;(5)根据厦门电离层垂测仪的观测,去除掉与电离层Es相关的数据后,厦门一武汉短波信道MUF与厦门电离层foF2的相关系数为0.557;不去除时,其相关系数几乎为零.这些结果对于提高短波信道预测能力和短波信道信息在依赖天波技术系统中应用水平有重要帮助.     

一个分层水库温跃层的模拟与验证

以西安金盆水库为例,建立了分层水库水温结构的数值模拟方法,并以实测数据进行模型验证.运用Fluent软件数值研究了不同短波辐射强度及短波辐射衰减系数条件下温跃层的形成过程与特性.水库水面总传热量在春、夏季为正值,在秋、冬季为负值,长波辐射是水面总传热量的主要影响因素,短波辐射则是温跃层形成的主要影响因素.随短波辐射衰减系数的降低,温跃层厚度增加,温跃层内温度梯度减小,短波辐射衰减系数值与实测的藻类浓度存在良好的正相关性.水库具有极限短波辐射强度,温跃层内温差随水面短波辐射强度的增加呈现先增加后减小的变化趋势;但水面短波辐射强度过高时,难以达到热平衡而形成稳定的温跃层.     

高增益复合天线在超长站距遥测地震台网中的应用

自行研制的复合阵列天线具有增高,方向性图尖锐,抗干扰能力强的特点。天线系统应用于超长距离的信号转输取得了很好的效果。乌鲁木齐遥测地震台网使用自行研制的天线系统用２．５～３．５Ｗ发射功率发射。该天线可接收新疆乌鲁木齐台网长站距,超长站距（２８０ｋｍ）２２３～２３５ＭＨｚ频段的地震信号。信号场强贮备满足规范要求,不低于３０ｄｂ从而保证了超长站距无线遥测地震信号的接收质量。     

井间电磁探测接收的理论考察和实验研究

井间电磁测井技术测量井间地层电磁波传播特性,通过正反演获得井间电阻率分布信息,由此揭示地层油气水的分布信息.井间电磁接收是井间电磁测井技术中一项重要内容,是开展井间电磁成像测井系统研制中必须攻克的难题之一.本文通过对比磁反馈与无磁反馈两种天线接收幅度与相位特性,发现磁反馈接收天线频带平稳无相位跳变点,相比无反馈天线具有明显优势.在磁反馈天线的基础上,本文分析不同天线磁芯、不同天线缠绕方式对天线幅频特性的响应,发现这些参数均对天线幅频特性有不同影响,为天线设计与研制提供参考设计参数.在接收天线研究的基础上,采用噪声匹配放大、1/f滤波、工频压制、数字锁相放大、相敏检波等软硬件处理技术,进一步降低噪声,提高接收精度和灵敏度.为有效开展井间同步发射与接收采集,采用高精度时间同步技术,提高同步与电磁波相位提取的精度.针对接收线路与系统中存在的误差,采用两距离井间电磁刻度方法进行压制.井间电磁接收样机研制完成后,分别在现场进行井下噪声测试、非金属套管井间、金属套管井间等系列井间电磁接收测量实验,研究与实验结果表明:本文所研究的井间电磁接收技术可实现500 m以上大井距和双层金属套管井间测量．     

无人机地震灾情监测系统在四川高原山区的应用研究

无人机地震灾情监测系统主要由无人机飞行平台、飞行控制系统、遥感系统、软件系统和无线电遥控系统等几部分组成,具有运行成本低、执行任务灵活性高等特点,是快速获取震后灾情信息的重要手段。结合四川高原山区的自然地理和气象条件,对无人机地震灾情监测系统在四川高原山区的应用进行了研究。该系统在高原山区的应用将在提升地震灾情现场勘查能力,迅速获取灾情信息,增加救灾工作的时效性,及为后期科学考察提供辅助信息等方面提供重要的技术支撑。     

Reconnaissance of an oil spill

When oil is spilled in the sea at a temperature near its pour point, it can become invisible to aerial reconnaissance through being fragmented by wave action. The lumps formed drift in the wind at a velocity less than 2–4% of the wind speed and the velocity of oil lenses.     

超宽带天线矩形口径辐射特性研究

本文利用惠更斯等效原理,从时域和频域两方面研究了超宽带天线矩形口径的瞬态辐射特性,以及能量传播特性的解析解.最后利用二维模拟论证了激励脉冲在自由空间的传播特性与天线口径几何尺寸、形状和主辐射面、辐射波形之间的关系,得出轴线上的辐射波形与口径形状无关,与口径面积大小成正比的模拟结论,为设计超宽带天线口径和为进一步设计超宽带电磁辐射提供了理论依据.     

Application of aerial photography to the study of small scale upper ocean phenomena

The industrial waste dumped 180 n. miles south of Galveston was monitored in July 1977 by water sampling, hydrographic measurements, acoustic tracking on board two vessels, and by aerial photography. The plume of the waste diffused vertically and horizontally. Photodensitometry of aerial photos of the plume showed lateral dispersion of the plume in agreement with two other methods: acoustic tracking of the waste suspensoid and transmissometer sampling. In addition, the method showed small scale features like the lateral and longitudinal variations in the photodensity, indicating the waste concentration. This waste concentration showed periodic changes in its axial distance, with the spectral peak at about 160 m wave length. It shows a sharp increase at the windward edge of the plume as do the acoustic records. This phenomenon is explained in terms of the shearing current near the surface together with vertical diffusion. The periodic change along the axis is explained in terms of the Langmuir circulation and in terms of internal ship waves.     

Beach erosion and recovery during consecutive storms at a steep‐sloping,meso‐tidal beach

This study analyses beach morphological change during six consecutive storms acting on the meso‐tidal Faro Beach (south Portugal) between 15 December 2009 and 7 January 2010. Morphological change of the sub‐aerial beach profile was monitored through frequent topographic surveys across 11 transects. Measurements of the surf/swash zone dimensions, nearshore bar dynamics, and wave run‐up were extracted from time averaged and timestack coastal images, and wave and tidal data were obtained from offshore stations. All the information combined suggests that during consecutive storm events, the antecedent morphological state can initially be the dominant controlling factor of beach response; while the hydrodynamic forcing, and especially the tide and surge levels, become more important during the later stages of a storm period. The dataset also reveals the dynamic nature of steep‐sloping beaches, since sub‐aerial beach volume reductions up to 30 m³/m were followed by intertidal area recovery (–2 < z < 3 m) with rates reaching ~10 m³/m. However, the observed cumulative dune erosion and profile pivoting imply that storms, even of regular intensity, can have a dramatic impact when they occur in groups. Nearshore bars seemed to respond to temporal scales more related to storm sequences than to individual events. The formation of a prominent crescentic offshore bar at ~200 m from the shoreline appeared to reverse the previous offshore migration trend of the inner bar, which was gradually shifted close to the seaward swash zone boundary. The partially understood nearshore bar processes appeared to be critical for storm wave attenuation in the surf zone; and were considered mainly responsible for the poor interpretation of the observed beach behaviour on the grounds of standard, non‐dimensional, morphological parameters. Copyright © 2011 John Wiley & Sons, Ltd.     

The role of beach morphology on coastal cliff erosion under extreme waves

Erosion of hard‐rock coastal cliffs is understood to be caused by a combination of both marine and sub‐aerial processes. Beach morphology, tidal elevation and significant wave heights, especially under extreme storm conditions, can lead to variability in wave energy flux to the cliff‐toe. Wave and water level measurements in the nearshore under energetic conditions are difficult to obtain and in situ observations are rare. Here we use monthly cliff‐face volume changes detected using terrestrial laser scanning alongside beach morphological changes and modelled nearshore hydrodynamics to examine how exposed cliffs respond to changes in extreme wave conditions and beach morphology. The measurements cover the North Atlantic storms of 2013 to 2014 and consider two exposed stretches of coastline (Porthleven and Godrevy, UK) with contrasting beach morphology fronting the cliffs; a flat dissipative sandy beach at Godrevy and a steep reflective gravel beach at Porthleven. Beach slope and the elevation of the beach–cliff junction were found to influence the frequency of cliff inundation and the power of wave–cliff impacts. Numerical modelling (XBeach‐G) showed that under highly energetic wave conditions, i.e. those that occurred in the North Atlantic during winter 2013–2014, with H_s = 5.5 m (dissipative site) and 8 m (reflective site), the combination of greater wave height and steeper beach at the reflective site led to amplified wave run‐up, subjecting these cliffs to waves over four times as powerful as those impacting the cliffs at the dissipative site (39 kWm^‐1 compared with 9 kWm^‐1). This study highlighted the sensitivity of cliff erosion to extreme wave conditions, where the majority (over 90% of the annual value) of cliff‐face erosion ensued during the winter. The significance of these short‐term erosion rates in the context of long‐term retreat illustrates the importance of incorporating short‐term beach and wave dynamics into geomorphological studies of coastal cliff change. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

单幅高空间分辨率卫星图像提取建筑物三维信息的方法研究

随着防震减灾事业的发展,对基础地理信息的要求日渐提高,利用卫星遥感影像快速补充与更新已有数据成为获取地理信息的主要方法。文中论述了太阳空间位置、卫星空间位置与建筑物空间位置对平面影像上阴影形状的约束,探讨了垂直于建筑物主方向的阴影平均宽度的统计算法和提取建筑物边界的点生长算法,给出了计算建筑物高度的数学公式,并研究出1种基于单幅高空间分辨率遥感图像数据的建筑物边界及高度快速自动生成技术。以上海市宝山区为试验区,得到了该区建筑物位置、面积和高度信息,经实地验证其试验结果可满足相应种类的灾情评估基础信息的要求     

Aerial photosieving of exposed gravel bars for the rapid calibration of airborne grain size maps

In recent years, fluvial remote sensing has seen considerable progress in terms of methods capable of system scale characterisation of river catchments. One key development is automated grain size mapping. It has been shown that high resolution aerial photography can be used to automatically produce grain size maps over entire rivers. However, current aerial grain size mapping procedures all require field calibration data. The collection of such data can be costly and problematic in the case of remote areas. This paper presents a method developed to remove the need for field based calibration data. Called ‘aerial photosieving’, this method consists of using the same very high resolution aerial imagery intended for grain size map production to visually measure particle sizes on‐screen in order to provide calibration data. The paper presents a rigorous comparison of field‐based photosieving calibration data and aerial photosieving calibration data. Statistical tests are used to demonstrate that aerial photosieving gives similar results when compared with field‐based data with only a slight systematic overprediction. The new aerial photosieving method therefore simplifies the overall procedure required for the production of grain size maps and thus improves the cost‐effectiveness and potential availability of this new fluvial remote sensing technology. Copyright © 2010 John Wiley &Sons, Ltd.     

Impact of three-dimensional attitude variations of an unmanned aerial vehicle magnetometry system on magnetic data quality

Optically pumped vapour magnetometers have an orientation dependency in measuring the scalar component of the ambient magnetic field which leads to challenges for integration with mobile platforms. Quantifying the three-dimensional attitude variations (yaw, pitch and roll) of an optically pumped vapour magnetometer, while in-flight and suspended underneath a rotary unmanned aerial vehicle, aids in the successful development of reliable, high-resolution unmanned aerial vehicle magnetometry surveys. This study investigates the in-flight three-dimensional attitude characteristics of a GEM Systems Inc. GSMP-35U potassium vapour magnetometer suspended 3 m underneath a Dà-Jiāng Innovations S900 multi-rotor unmanned aerial vehicle. A series of unmanned aerial vehicle-borne attitude surveys quantified the three-dimensional attitude variations that a simulated magnetometer payload experienced while freely (or semi-rigidly) suspended underneath the unmanned aerial vehicle in fair weather. Analysis of the compiled yaw, pitch and roll data resulted in the design of a specialized semi-rigid magnetometer mount, implemented to limit magnetometer rotation about the yaw axis. A subsequent unmanned aerial vehicle-borne magnetic survey applying this specialized mount resulted in more than 99% of gathered GSMP-35U magnetic data being within industry standards. Overall, this study validates that maintaining magnetometer attitude variations within quantified limits (±5° yaw, ±10° pitch and roll) during flight can yield reliable, continuous and high-resolution unmanned aerial vehicle-borne magnetic measurements.     

Aerial magnetic mapping with an unmanned aerial vehicle and a fluxgate magnetometer: a new method for rapid mapping and upscaling from the field to regional scale

Magnetic measurements with an unmanned aerial vehicle are ideal for filling the gap between ground and airborne magnetic surveying. However, to obtain accurate aeromagnetic data, the compensation of magnetic effects of the unmanned aerial vehicle is a challenge. Typically, scalar magnetometers are towed several metres under the unmanned aerial vehicle to minimize its magnetic field. In this study, a fluxgate three-component magnetometer is attached 42 cm in front of the unmanned aerial vehicle at the tip of a composite pipe. Using a scalar calibration, the sensor can be calibrated, and the permanent and induced magnetic fields of the unmanned aerial vehicle can be compensated. The contributions of the magnetic measurements at different altitudes to the unmanned aerial vehicle results were tested over an area of 1 km² in the Northern Vosges Mountains. The area is located in a hamlet surrounded by a forest where few geological outcrops are observed. Three magnetic surveys of the same area are obtained at different altitudes: 100, 30 and 1 m above the ground. The unmanned aerial vehicle magnetic data are compared with a helicopter aeromagnetic survey at 300 m above the ground and a ground magnetic survey using upward continuations of the maps to compare the results. The magnetic maps (300, 100, 30 and 1 m above the ground) show very different magnetic anomaly patterns (e.g. amplitude, shape, wavelength and orientation). The magnetic data at different altitudes improve the understanding of the geology from the local to more general scales.