基于选权拟合法的电离层电子密度层析重构

附加约束的电离层层析算法是解决电离层电子密度反演中不适定问题的主要方法,为避免此类方法中约束权阵的选取不当对电子密度分布重构产生的不良影响,本文将选权拟合法应用到电离层层析成像技术中.该方法特别设计了依据电子密度空间分布特性构造参数权矩阵的方案.新方法有明确的物理意义,挖掘了隐含的信息量,为解决电离层电子密度反演中由于观测数据的不足等因素引起的不适定问题提供了一种新途径,可以得到符合客观实际的结果.数值模拟实验和实测数据的反演结果证实了该算法有效性、可靠性和优越性.     

波前构建法中网格点相对定位及属性计算研究

针对波前构建法射线追踪中非规则的波前四边形网格与规则的矩形网格节点之间的相对定位问题,采用矢量叉积判断方法从四个方面较详细的讨论了规则的矩形网格节点与非规则的波前四边形的相对位置关系,并针对四种不同的位置关系采用不同的插值算法进行其属性的转换计算,误差分析及计算实例表明本文所采用的网格定位方法以及属性转换的插值算法从理论到实际应用都是正确的、切实可行的.     

2009年7月22日日全食引起的电离层扰动及其对定位的影响

2009年7月22日发生在亚太地区的日全食,从北半球中纬地区一直延伸到南半球中纬地区.这次日食期间发生的磁暴和日食时间同步,使得电离层变化较为复杂.为了分析日食期间电离层扰动及其对定位的影响,所采用的GPS数据来源于日全食带内的重庆CORS网(4个站)、武汉CORS网(8个站)数据、IGS站WUHN、SHAO的数据,以及日偏食区域内不同纬度处的若干IGS站.通过比较日食前后连续三天的各个地方TEC变化,以及利用高采样率的CORS网数据研究日食期间TEC的瞬时变化,根据位置和时间的不同,各地日食期间TEC下降约(1~4)TECU.但是,磁暴期间TEC的响应整体表现为正相暴,偏离值达50%以上,且和日食食甚后的TEC变化相重合.同时,求解了日食期间伪距单点定位的实时精度和CORS网内中短基线的实时精度,伪距单点定位的平面精度变化不显著,高程精度下降达数十米,日食初期CORS网中基线的平面精度仍在厘米级内,高程精度仍在分米级内,但是,日食后期发生的磁暴导致基线的平面精度下降到分米级,高程精度下降到米级.     

Regeneration and utilization of nutrients during collapse of a Mesodinium rubrum red tide and its influence on phytoplankton species composition

High-biomass red tides occur frequently in some semi-enclosed bays of Hong Kong where ambient nutrients are not high enough to support such a high phytoplankton biomass. These high-biomass red tides release massive inorganic nutrients into local waters during their collapse. We hypothesized that the massive inorganic nutrients released from the collapse of red tides would fuel growth of other phytoplankton species. This could influence phytoplankton species composition. We tested the hypothesis using a red tide event caused by Mesodinium rubrum(M. rubrum) in a semi-enclosed bay, Port Shelter. The red tide patch had a cell density as high as 5.0×10~5 cells L~(-1), and high chlorophyll a(63.71 μg L~(-1)). Ambient inorganic nutrients(nitrate:NO_3~-, ammonium: NH_4~+, phosphate: PO_4~(3-), silicate: SiO_4~(3-)) were low both in the red tide patch and the non-red-tide patch(clear waters outside the red tide patch). Nutrient addition experiments were conducted by adding all the inorganic nutrients to water samples from the two patches followed by incubation for 9 days. The results showed that the addition of inorganic nutrients did not sustain high M. rubrum cell density, which collapsed after day 1, and did not drive M. rubrum in the non-red-tide patch sample to the same high-cell density in the red tide patch sample. This confirmed that nutrients were not the driving factor for the formation of this red tide event, or for its collapse. The death of M. rubrum after day 1 released high concentrations of NO_3~-,PO_4~(3-), SiO_4~(3-), NH_4~+, and urea. Bacterial abundance and heterotrophic activity increased, reaching the highest on day 3 or 4, and decreased as cell density of M. rubrum declined. The released nutrients stimulated growth of diatoms, such as Chaetoceros affinis var. circinalis, Thalassiothrix frauenfeldii, and Nitzschia sp., particularly with additions of SiO_4~(3-) treatments, and other species. These results demonstrated that initiation of M. rubrum red tides in the bay was not directly driven by nutrients.However, the massive inorganic nutrients released from the collapse of the red tide could induce a second bloom in low-ambient nutrient water, influencing phytoplankton species composition.     

基于双差定位方法的内蒙古中西部地区地震精确定位

针对测震台网定位存在偏差的问题,采用双差定位方法,对2008—2019年9月内蒙古测震台网及周边台站记录的内蒙古中西部地区4410个地震事件进行重新定位.研究表明,利用双差定位方法重新定位后地震分布更集中,更符合内蒙古中西部地区的地质构造特征,定位精度显著提高.     

基于单站多系统的GNSS硬件延迟估算方法及其应用

随着全球导航卫星系统（Global Navigation Satellite Systems,GNSS）的不断发展,中国地区单个GNSS接收站在一个时刻可以接收到超过30颗GNSS卫星的信号,这为单站GNSS硬件延迟估算方法的研究提供了有利条件.本文首先通过GNSS硬件实验,分析了不同温度条件下GNSS系统硬件延迟的变化特征,研究结果显示：当温度快速变化时,硬件延迟变化比较剧烈,变化幅度可达12.53 TECU（1 TECU=10 ¹⁶el·m^-2）;在恒温条件或室温条件下,硬件延迟变化比较缓慢,变化幅度在1.00 TECU左右.在GNSS系统硬件延迟实验的基础上,充分利用单站多星观测的特点,提出了一种基于单站多系统的GNSS硬件延迟的估算方法——单站三角分解与差分消元法,并将该方法应用于河北保定站2015-2017年GNSS系统硬件延迟的求解中.通过对估算的GNSS系统硬件延迟进行分析显示：单站三角分解与差分消元法具有计算速度快、独立性好的特点;在北斗系统上硬件延迟的求解效果优于GPS、GLONASS系统,硬件延迟求解的结果整体上比利用欧洲定轨中心全球电离层地图校正的结果大2.50~3.00TECU左右;同时,该方法在消除GNSS系统硬件延迟后,获得的垂直总电子含量（Total Electron Content,TEC）能较好地反映电离层TEC的周日变化、日出增强、半年变化、年变化和春秋分不对称性等特征.

     

Variation of particulate organic carbon and its relationship with bio-optical properties during a phytoplankton bloom in the Pearl River estuary

In this study, variations in the particulate organic carbon (POC) were monitored during a phytoplankton bloom event, and the corresponding changes in bio-optical properties were tracked at one station (114.29°E, 22.06°N) located in the Pearl River estuary. A greater than 10-fold increase in POC (112.29-1173.36 mg m⁻³) was observed during the bloom, with the chlorophyll a concentration (Chl-a) varying from 0.984 to 25.941 mg m⁻³. A power law function is used to describe the relationship between POC and Chl-a, and the POC:Chl-a ratio tends to change inversely with Chl-a. Phytoplankton carbon concentration is indirectly estimated using the conceptual model proposed by Sathyendranath et al. (2009), and this carbon is found to contribute 47.21% (±10.65%) to total POC. The estimated carbon-to-chlorophyll ratio of phytoplankton in diatom-dominated waters is found to be comparable with results reported in the literature. Empirical algorithms for determining the concentrations of Chl-a and POC were developed based on the relationships of these variables with the blue-to-green reflectance ratio. With these bio-optical models, the levels of particulate organic carbon and Chl-a could be predicted from the radiometric data measured by a marine optical buoy, which showed much more detailed information about the variability in biogeochemical parameters during this bloom event.     

饱和南京细砂永久应变势模型的试验研究

土单元永久应变势的预测模型是土动力学的重要研究内容之一。现有的土单元永久应变势模型没有反映振动孔压增长的影响,难以合理解释地震动作用引起的饱和砂土地基永久变形一般是由土层软化或再固结变形所致的机理。基于饱和南京细砂永久变形动三轴试验结果的有效应力状态分析,研究了试样的永久变形与振动孔压增长的关系,建立了一个能反映振动孔压增长影响的土单元永久应变势模型,给出了土单元永久应变势的数学表达式,分析了土单元永久应变势模型参数的影响因素。初步的验证性试验表明:模型预测与试验测得的试样永久应变势与振动孔压增长曲线比较接近,说明该模型具有一定的合理性。     

利用地磁脉动预报地球同步轨道相对论电子通量的方法研究

本文利用低纬地磁台站的Pi1、Pi2地磁脉动（Pi1-2）资料和地球同步轨道的Pc5地磁脉动资料,对2004年1月到2006年12月38个磁暴事件的地磁脉动参数进行了统计分析.在此基础上,考虑相对论电子的局部加速机制,并加入损失机制,建立了一个初步的磁暴期间地球同步轨道相对论电子通量对数值的预报模型.利用该模型,我们对上述38个磁暴事件进行预报试验,最优化结果是：相对论电子通量对数值的预测值和观测值之间的线性相关系数为0.82,预报效率为0.67.这说明该模式具有较好的预报效果,也表明利用地磁脉动参数进行相对论电子通量预报是可行的.     

A feature weighting and selection method for improving the homogeneity of regions in regionalization of watersheds

The method used for feature selection or feature weighting in regionalization of watersheds may affect the results of regionalization methods considerably. It can play a key role in forming hydrologically homogeneous regions for regional flood frequency analysis. In this study, a method based on exploring the nearest and farthest neighbours of data points is introduced for identifying salient features for regionalization of watersheds. The method includes options to relate watershed features to flood data records in order to increase the homogeneity of the regions. The nearest and farthest neighbours are identified based on the criteria such as the mutual information criterion and Spearman's rank correlation coefficient. Then, the watershed features more able to explain the relationships between the nearest and farthest neighbours are identified as salient features to form homogeneous features for regional flood frequency analysis. The results show that the optimum option of the proposed method improves the performances of the hard and fuzzy clustering algorithms in more than half of the cases based on the cluster validity indices. Furthermore, the results reveal that the optimum option can increase the number of the homogeneous regions formed by clustering algorithms to a great extent. By using the optimum option with 5 nearest and 5 farthest neighbours, longitude, drainage area, and run‐off coefficient are identified as the salient features to regionalize Sefidrud basin. The results show that the proposed method can be considered as an efficient method to form homogeneous regions for regional flood frequency analysis.     

AVO属性分析方法的改进及其在煤系地层中的应用

在进行AVO属性分析时,直接应用梯度和截距属性做交会图,往往无法将异常与背景趋势有效的分离开.特别在煤系发育的地层中,由于其顶、底界面通常为良好的波阻抗界面,会形成较强的反射波,从而掩盖周围地层的异常信息.基于以上原因,煤系地层中异常信息的分类提取,尤其是煤层气的识别方法一直备受关注.本文对一项AVO截距斜率交会图技术进行了改进,并深入分析了此方法在煤系地层中的应用.最终本文给出了所选区块不同类型异常的分类方法,并进行了实际验证,结果表明该方法用于异常反演有很好的效果.     

On the prediction of relativistic electron fluence based on its relationship with geomagnetic activity over a solar cycle

A study has been carried out to determine the relationship between high energy relativistic (>2 MeV) electron fluence and auroral zone geomagnetic activity for a solar cycle. Data for 1987–1997, spanning Solar Cycle 22, were used in the study. The relativistic electron fluence data were based on fluxes observed by the GOES geosynchronous satellites. The geomagnetic data were the DRX indices derived from a Canadian magnetic observatory located in the auroral zone at Fort Churchill, near the footprint of field lines passing through geostationary satellites. This work, based on data from a solar cycle, confirms earlier findings using limited data from segments of a solar cycle of enhancement in fluence 2–3 days after increases in geomagnetic activity, and shows the cycle dependence of fluence with respect to geomagnetic activity. This study underlines the influence of recurrent coronal holes on fluence level as well as the possible role of Pc5 magnetic pulsations as an electron acceleration mechanism, and highlights the predictability of fluence from ground geomagnetic data. A fluence prediction algorithm can now solely be based on derived expressions relating fluence and DRX. Thus, a simple fluence prediction scheme can easily be implemented to provide a 2–3 day advance warning of space weather conditions hazardous to geosynchronous satellites, since during days of high fluence, the likelihood of internal charging in a satellite is high, with possible discharges that could result in satellite operational anomalies. For verification purpose, daily values of fluence for 1997–2000 and for January 1994 were postcast using the derived expressions. The postcast values were validated, and the results give credence to the fluence prediction scheme.     

Development of a fluorescent antibody method for the detection of Enterococcus faecium and its potential for coastal aquatic environment monitoring

A direct, microscopic fluorescent antibody method was developed to detect the occurrence of Enterococcus faecium in coastal aquatic environments and was compared with the conventional membrane filtering method. The "in situ" application of the antibody-based protocol in the analysis of water samples collected from coastal polyhaline habitats demonstrated good sensitivity and ease of implementation. Data obtained with the microscopic technique were in agreement with those obtained from culture counts. The fluorescent antibody method proved to be a rapid and reliable technique for the detection of E. faecium. The advantages and limitations intrinsic to the method are discussed, highlighting the potential of this new technique for monitoring coastal aquatic environments.     

An improvement on the method of the pattern recognition ICHAM and its application

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过套管地层电阻率曲线环境影响校正方法研究

过套管电阻率测井是在金属套管井中测量地层电阻率的一种电法测井技术,其测量结果受套管、层厚/围岩、水泥环等井眼环境因素的影响,所以在进行过套管电阻率测井资料解释时必须进行测井环境影响因素校正.本文在论述过套管电阻率测井原理的基础上,针对大庆油田引进的俄罗斯过套管电阻率测井仪器ECOS,分别考察了层厚/围岩、水泥环对测量结果的响应规律,利用正演模拟方法研制完成了层厚/围岩影响校正图版以及水泥环影响校正图版.在计算机上实现了层厚/围岩、水泥环影响校正的算法,并利用模型算例和测井实例验证了本文方法的合理性.该方法能够减少水泥环的影响,提高层厚小于1.0 m薄层电阻率的测量精度,为过套管电阻率测井资料正确解释提供了保障.     

Type-specific and indicator taxa of phytoplankton as a quality criterion for assessing the ecological status of Finnish boreal lakes

Key issues in the implementation of the Water Framework Directive are classification of lakes using biological quality parameters and type-specific reference conditions. This work is one of three studies considering different metrics of phytoplankton in the classification of ecological status. Phytoplankton was studied in a total of 55 Finnish boreal lakes, including 32 reference lakes. We tested the suitability of taxonomic composition and abundance of phytoplankton groups for biological classification. We also preliminarily determined the type-specific taxa for the studied lakes. The type-specific taxa for reference conditions are coincidently the indicator species/taxa for high ecological status. Interestingly, some taxa type-specific for impacted oligo-humic lakes proved to be the type-specific taxa for humic reference lakes. The pressure of human impact was observed not only as increase of biomass but also as changes in the species composition. The phytoplankton composition indicated the ecological status of impacted lakes moderately well. There was some variation in the indications given by different algal groups, probably due to the preliminary class boundaries used. However, the preliminary combination of indicative parameters to estimate the ecological status of the studied impacted lakes was in general in accordance with earlier classification of water quality in Finnish lakes.