基于分布律规则的风向传感器故障检测算法

风向传感器采用的格雷码编码方式使得风向传感器故障具有一定的“隐蔽性”,而传统故障检测方法需要拆卸风向传感器破坏了气象观测资料的完整性.基于概率分布从数理统计角度建立了码盘式风向传感器的测量数学模型,并在此基础上提出了基于分布律规则的风向传感器故障检测算法,通过VB/SQL/MATLAB混合编程技术实现了图示化的风向传感器故障检测程序,最后进行了故障检测试验.试验结果表明：提出的基于分布律规则的风向传感器故障检测算法能够在不拆卸风向传感器的情况下准确发现和判断出风向传感器单一或组合式故障类型.     

COTREC方法在江西地区的应用和检验

基于江西及其周边地区的雷达组合反射率拼图,将二维Boussinesq(水平无辐散)质量连续方程约束至江西地区的TREC风场,得到改善后的TREC风场(COTREC风场),并基于COTREC风矢量开展了江西地区雷达回波的外推。个例分析表明,经过二维无辐散连续方程约束后,COTREC风中的噪声和不一致得到了显著的平滑,其风速水平梯度和风向切变都显著减小。基于COTREC风外推的雷达回波在形态上也得到了明显的改善,其外推回波中由风场的噪声或不一致引起的异常失真回波明显减少。为了进一步评估TREC和COTREC方法的外推表现,对2018年7月1—31日江西地区有明显降水的287个时次的雷达回波分别进行了1 h和2 h外推。结果表明:相对于TREC方法,COTREC方法在1 h和2 h的外推时间上均能改善外推回波的精度,其外推回波与实况的相关系数和TS评分均较TREC方法高。     

基于江西省雷达回波拼图的TREC方法应用及效果检验

基于江西省及周边16部新一代多普勒天气雷达拼图资料,利用交叉相关跟踪法(TREC)计算江西地区雷达回波的移动矢量(TREC风),并对求解的TREC风进行异常值更正和空洞补齐等质量控制,最后利用后向外推法对江西地区2017年6月29日09:54的雷达回波进行2 h内的外推。结果表明,TREC方法能较好地获得江西地区未来2 h内的雷达回波位置和空间结构,且在0—1 h的外推回波非常接近实况。通过对2018年6月1—9日201个天气过程0—2 h外推的TS评分统计表明,基于该方法外推的2 h内的雷达回波精度都较高(TS评分0.3),但TS评分随外推时间的增长而快速降低,当外推时间为30 min时TS评分高达0.61,外推时间增至60 min时TS评分降至0.48,外推时间延长至120 min时TS评分进一步减至0.31。     

南昌双偏振天气雷达地物杂波抑制效果分析

为评估南昌CINRAD/SAD双偏振天气雷达对地物杂波的抑制效果,使用2019年6—10月南昌单偏振雷达基数据和2022年同期南昌双偏振雷达基数据,对比分析了不同仰角和晴、雨条件下单、双偏振天气雷达反射率频率。结果表明：单、双偏振雷达在0.5°仰角因周边山区地形、建筑物遮挡的影响,在西北方向和东南方向存在明显的数据缺失。升级为双偏振雷达后,在各个仰角上周围反射率高频区的范围明显减小,雷达能有效消除雷达站点周边杂波的影响。晴天时,双偏振雷达对晴空杂波的过滤效果极佳;雨天时,双偏振雷达对南昌周边及梅岭山区的回波进行了弱化处理,可以有效减少地形回波、非气象回波的干扰。双偏振天气雷达产品差分相移率和相关系数能较清楚地辨别出虚假回波,可更好地用于确定降水粒子的信息。     

Cell contact-dependent lethal effect of the dinoflagellate Heterocapsa circularisquama on phytoplankton–phytoplankton interactions

We used bi-algal culture experiments to investigate and verify the roles of growth interaction between Heterocapsa circularisquama and Prorocentrum dentatum in monospecific bloom formation. Growth of H. circularisquama was slightly inhibited when inoculated at 10² cells mL^–1 along with P. dentatum at 10⁴ cells mL^–1. In other combinations of inoculation densities, P. dentatum density rapidly decreased to extremely low levels in the presence of H. circularisquama. We used a mathematical model to simulate growth and interactions of H. circularisquama and P. dentatum in bi-algal cultures. The model indicates that one species will always inhibit the growth of the other and that the relative initial cell densities of the species are critical in determining the outcome. When cultured together under conditions without cell contact, growth of H. circularisquama and P. dentatum was not inhibited. As with P. dentatum, the growth of Heterosigma akashiwo and Skeletonema costatum was inhibited in intact cell suspensions with H. circularisquama, but a nontoxic species, Heterocapsa triquetra, did not affect the growth of P. dentatum or the other species. Similarly, cell suspensions of H. circularisquama showed hemolytic activity toward rabbit erythrocytes, but those of H. triquetra did not. In addition, the cell-free supernatant of H. circularisquama cultures showed no significant hemolytic activity. These results suggest that H. circularisquama causes lethality in P. dentatum by direct cell contact in which live-cell-mediated hemolytic activity might be a contributing factor.     

MEMS加速度传感器在强震观测中的应用

提出基于MEMS加速度传感器的强震仪设计方案,并在强震观测中完成了地震加速度数据的采集、触发判断和存储.     

Evolution of wave shape over a low-crested structure

This paper investigates the evolution of wave shape over a low-crested structure (LCS) using a 2-D RANS-VOF model. The model predictions of surface elevation and wave skewness and asymmetry are in good agreement with the recent measurements collected in a small scale wave channel at the University of Cantabria (UCA). The empirical formulae relating wave skewness and asymmetry to local Ursell number by Peng et al. (2009) have been extended to include the effect of wave reflection and the ramp in front of LCS and a wider range of Ursell number in the present study. In the presence of LCS, wave skewness decreases slightly above the seaward slope, then increases rapidly up to a maximum value above the structure crest, and decreases drastically above the leeward slope. Wave asymmetry decreases sharply above the seaward slope to a negative minimum value at the structure crest, and then increases rapidly to a positive value above the leeward slope. Our bispectral analysis indicates that sum interactions increase skewness and decrease asymmetry while difference interactions have opposite effects and that the former dominate above the seaward slope and on the structure crest but the latter dominate above the leeward slope of LCS. The observed wave shape evolution over a LCS can be attributed to the changes in the interplay of sum and difference interactions. We found that incident wave height and wave period, relative structure freeboard, structure crest width and structure porosity are the controlling factors for wave shape evolution over LCS. This study provides new insights on the role of wave skewness and asymmetry in the breakwaters stability and sediment transport around the structure and on the beaches behind it.     

网络数据流分析方法

介绍网络数据流中最主要的数据流挖掘技术.     

Quantitative photogrammetric analysis of digital underwater videoimagery

This paper presents a photogrammetric model for digital underwater video imagery, which has been mostly applied to qualitative analysis in the marine environment. With this model, quantitative analysis of underwater images is possible, e.g., to locate positions, calculate sizes, and measure shapes of objects from image features. The underwater photogrammetric model is based on a three-dimensional optical ray tracing technique which rigorously models imaging systems with multilens configurations and multiple refractions. The calibration procedure with two independent phases has been proven to be efficient in simplifying the computation and improving the calibration accuracy. With the current imaging system configuration and photogrammetric model, an accuracy of 0.8 cm in lateral directions and 1.2 cm along the depth direction for objects located about 2-3 m from the camera system in the object space is attainable. A PC-based digital underwater photogrammetric prototype system has been developed to implement the underwater photogrammetric model     

浅谈地震剖面的假象识别

假象识别是正确解释地震剖面的前提,也是描述地震成像保真度(精准度)的主要标准之一.本文通过分析反射地震剖面实例,对几种常见的、易被误解的地震成像假象的特征进行了分类阐述,提出基于成因识别地震成像假象的思路.从地震剖面成像过程来看,假象的成因包括信号误判、成像畸变和波速模型误差这三个主要因素.许多不易被识别的假象起源于地震数据处理成像过程中对信号的误判,犹如“张冠李戴”;成像畸变假象的根源包括成像照明度、资料频宽和方法假设等方面的缺陷,造成抹痕等成像结果畸变假象;当地震波速度模型误差较大时,地震成像结果不仅会出现成像位置错误,还可能在波阻抗不连续点出现散射拖尾假象.因此,衡量地震成像精准度的标准应包括成像结果的分辨率、位置准确度和假象识别三个要素.这些要素相互影响,因此应该根据研究目标和实际情况,综合评判地震成像中假象的影响.