用相关系数法匹配色谱图形鉴别海面溢油源

用皮尔逊相关系数法匹配色谱图形,根据溢油与可疑油的相似性鉴别溢油源。通过风化实验,研究出六个受风化影响很小的油色谱峰作为信息点,用K-最邻近分类法鉴别非常相似的油品。     

Ocean wave forecasting using recurrent neural networks

The tremendous increase in offshore operational activities demands improved wave forecasting techniques. With the knowledge of accurate wave conditions, it is possible to carry out the marine activities such as offshore drilling, naval operations, merchant vessel routing, nearshore construction, etc. more efficiently and safely. This paper describes an artificial neural network, namely recurrent neural network with rprop update algorithm and is applied for wave forecasting. Measured ocean waves off Marmugao, west coast of India are used for this study. Here, the recurrent neural network of 3, 6 and 12 hourly wave forecasting yields the correlation coefficients of 0.95, 0.90 and 0.87, respectively. This shows that the wave forecasting using recurrent neural network yields better results than the previous neural network application.     

多组多滞后区间中立型非线性时变控制系统的鲁棒镇定

采用无滞后控制系统与滞后控制系统的等价性方法，研究了多组多滞后区间系数中立型非线性时变控制系统的鲁棒镇定问题，给出了区间长度及时滞的估计范围，进而得到了系统渐近稳定的判定条件。此判据包涵了有关文献的结果，结论更具有一般性。     

GNSS三频周跳探测与修复算法

针对使用组合观测值探测周跳存在不敏感周跳且难以修复的问题,研究了三频周跳探测与修复的几何原理,从几何角度研究了多个相位无几何组合(GF)探测周跳的异同,以及加入MW组合后的效果,并搜索了相应的不敏感周跳。提出了以对应的横截面积最小为原则选取组合量的方法。经北斗三频实测数据验证,GF组合的数量以两个为宜,加入MW组合后不敏感周跳进一步减少,优化选取的两个GF组合和MW组合联合探测周跳仅存在一个不敏感周跳,且探测到的周跳均能正确修复。     

基于CloudSat/CALIPSO资料的我国北方2个区域云垂直分布差异研究

选用2008年1月—2014年10月的Cloud Sat/CALIPSO卫星资料,对中国北方两个4°×4°区域云垂直结构及其微物理参量进行了对比研究,区域1(114~118°E,37.5~41.5°N)和区域2(110°E~114°E,37.5~41.5°N)纬度相同经度不同。结果表明:1)区域1(E1)和区域2(E2)暖云层、混合云层和冷云层的云出现概率(Cloud Occurrence Probability,COP)差别较大。E1暖云层COP春季最大,E2则在夏、秋季达到较大值;E1混合层COP最大值出现在冬季,E2则出现在春季;2个区域冷云层COP均在春季达到最大。2)2个区域的COP高值区厚度有明显的季节性差异,E1的COP高值主要出现在夏、冬季,E2则主要出现在春、夏季。E1秋、冬季云体雷达回波最大值强于E2,但春、夏季弱于区域1。3)E2在春、秋季的液水含量、冰水含量、云滴有效半径均高于E1。     

Unusual comets (?) as observed from the Hubble Space Telescope

In separate projects, the Hubble Space Telescope has been used to assess the nature of 3 unusual objects: Chiron, Pholus and P/Shoemaker-Levy 9. This paper will compare these objects and discuss how the unique capabilities of the HST may be used to address the issue of cometary activity in each. Chiron, which has exhibited obvious cometary characteristics for several years, might have a bound dust coma that is unresolvable from the ground. In an attempt to directly observe this bound coma, we have obtained a series of images of Chiron with the HST Planetary Camera. Inner coma structure out to 0.2 has been detected. From these observations we infer a low bulk nucleus density for Chiron. Both HST and ground-based images of 5145 Pholus have been obtained to search for evidence of activity. The ground-based data give the most sensitive limits; however, it is shown that the WFPC-2 on HST can give limits 2–3 orders of magnitude more sensitive than conventional ground-based limits. Finally, as part of a collaborative effort, we have been obtaining HST observations of SL9 in order to determine the fragment sizes and to assess their nature (i.e., cometary vs. asteroid). Both ground-based observations from the UH 2.2m telescope on Mauna Kea and HST observations show that the near-nucleus dust is redder than the sun. While FOS spectra did not detect OH emission, the WFPC-2 HST data show that the inner coma remained very circular from July 1993 up until 2 weeks prior to impact, implying continued production of dust.     

黄河下游及河口区表层沉积物中U,Ra,Th,40K和137Cs的测定

本文从地球化学和环境保护的角度,用8180—4Kγ谱仪直接测定方法确定了天然放射性元素U,Ra,Th,~(40)K,及人工核素~(137)Cs的含量,讨论了它们的分布特点及其影响因素,指出了河口区与下游段元素变化的差异及其制约条件。     

A framework for identifying activity groups from individual space-time profiles

ABSTRACT

Datasets collecting the ever-changing position of moving individuals are usually big and possess high spatial and temporal resolution to reveal activity patterns of individuals in greater detail. Information about human mobility, such as ‘when, where and why people travel’, is contained in these datasets and is necessary for urban planning and public policy making. Nevertheless, how to segregate the users into groups with different movement and behaviours and generalise the patterns of groups are still challenging. To address this, this article develops a theoretical framework for uncovering space-time activity patterns from individual’s movement trajectory data and segregating users into subgroups according to these patterns. In this framework, individuals’ activities are modelled as their visits to spatio-temporal region of interests (ST-ROIs) by incorporating both the time and places the activities take place. An individual’s behaviour is defined as his/her profile of time allocation on the ST-ROIs she/he visited. A hierarchical approach is adopted to segregate individuals into subgroups based upon the similarity of these individuals’ profiles. The proposed framework is tested in the analysis of the behaviours of London foot patrol police officers based on their GPS trajectories provided by the Metropolitan Police.     

A Simple Limit Equilibrium Approach for Calculation of Ultimate Bearing Capacity of Shallow Foundations on Two-Layered Granular Soils

The bearing capacity of shallow foundations in a non-homogeneous soil profile has been a challenging task in geotechnical engineering. In this paper, a limit equilibrium method is used for calculating bearing capacity factors of shallow foundations constructed on a two-layered granular soil profile. The main objective has been to determine the ultimate bearing capacity computed from equivalent bearing capacity factors N_q and N_γ and comparing that with numerical analysis using finite element methods. It will be shown that the data obtained form the developed method are well comparable with those obtained from FE approach, specially when the difference between shear strength parameters of layers is low which is a practical case for sedimentary soil profiles and also for artificially compacted soils. A computer program has been developed to investigate the influence of various parameters on bearing capacity factors.