GNSS接收机DCB短期时变特征分析和估计方法

提出一种使用非差非组合精密单点定位(PPP)估计和分析接收机DCB短时时变特征的方法。首先利用非差非组合PPP得到包含接收机DCB的重构电离层参数估值;然后通过IGS电离层GIMs格网模型内插剥离各历元站星斜向电离层距离延迟;最后通过最小二乘约束得到各历元接收机DCB解。由于格网本身精度(2~8 TECU)和插值精度限制,解算出来的接收机DCB并不能真实反映其短期时变特征。为此,提出利用站间单差或者历元间差分的方法还原其真实的变化态势。实验结果表明,所提出的方法能够正确估计接收机DCB,并能真实还原其短期时变特征,具有良好的适用性。     

Building a model-based personalised recommendation approach for tourist attractions from geotagged social media data

When travelling, people are accustomed to taking and uploading photos on social media websites, which has led to the accumulation of huge numbers of geotagged photos. Combined with multisource information (e.g. weather, transportation, or textual information), these geotagged photos could help us in constructing user preference profiles at a high level of detail. Therefore, using these geotagged photos, we built a personalised recommendation system to provide attraction recommendations that match a user's preferences. Specifically, we retrieved a geotagged photo collection from the public API for Flickr (Flickr.com) and fetched a large amount of other contextual information to rebuild a user's travel history. We then created a model-based recommendation method with a two-stage architecture that consists of candidate generation (the matching process) and candidate ranking. In the matching process, we used a support vector machine model that was modified for multiclass classification to generate the candidate list. In addition, we used a gradient boosting regression tree to score each candidate and rerank the list. Finally, we evaluated our recommendation results with respect to accuracy and ranking ability. Compared with widely used memory-based methods, our proposed method performs significantly better in the cold-start situation and when mining ‘long-tail’ data.     

Three-dimensional numerical simulation of geothermal field in space-wavenumber domain

Large-scale,fine,and efficient numerical simulation of a geothermal field plays an important role in geothermal energy development.Confronted with the problem o...     

1951—2018年衢州市椪柑采摘期连阴雨天气变化特征

基于1951—2018年衢州市椪柑采摘期降水量、雨日、日照时数、相对湿度等逐日气象资料,应用统计分析和小波分析方法,分析椪柑采摘期连阴雨天气变化特征及其大气环流背景.结果表明:1951—2018年衢州椪柑采摘期连阴雨日数、次数和强度呈略微增加趋势、滑动3d无雨次数呈减少趋势;滑动3d无雨次数存在明显的5a、7a和15a...     

基于加权破产博弈模型的跨境流域水资源分配研究

基于公平合理利用视角,将多准则决策模型与破产理论相结合探讨跨境水资源分配问题.通过梳理国际水法,设计了跨境流域水资源公平合理分配的指标体系,采用投影法解决这一多准则决策问题,并依此加权调整流域国用水需求.在加权调整用水需求和考虑议价能力的基础上,基于破产博弈模型探讨跨境流域水资源分配问题,以提高分配方案的公平合理性和可...     

Ecopath with Ecosim在水生生态系统研究中的应用

地球上的水体为人类提供着无法计量的生态系统服务和相应的生态价值。然而,水生生态系统一直承受着巨大的捕捞和环境压力。为更好地分析人类以及自然扰动对水生生态系统的影响,并建立科学合理的管理机制,许多研究种群结构和动态的模型软件以     

Wavelet analysis and nonparametric test for climate change in Tarim River Basin of Xinjiang during 1959–2006

Using wavelet analysis, regression analysis and the Mann-Kendall test, this paper analyzed time-series (1959–2006) weather data from 23 meteorological stations in an attempt to characterize the climate change in the Tarim River Basin of Xinjiang Uygur Autonomous Region, China. Major findings are as follows: 1) In the 48-year study period, average annual temperature, annual precipitation and average annual relative humidity all presented nonlinear trends. 2) At the 16-year time scale, all three climate indices unanimously showed a rather flat before 1964 and a detectable pickup thereafter. At the 8-year time scale, an S-shaped nonlinear and uprising trend was revealed with slight fluctuations in the entire process for all three indices. Incidentally, they all showed similar pattern of a slight increase before 1980 and a noticeable up-swing afterwards. The 4-year time scale provided a highly fluctuating pattern of periodical oscillations and spiral increases. 3) Average annual relative humidity presented a negative correlation with average annual temperature and a positive correlation with annual precipitation at each time scale, which revealed a close dynamic relationship among them at the confidence level of 0.001. 4) The Mann-Kendall test at the 0.05 confidence level demonstrated that the climate warming trend, as represented by the rising average annual temperature, was remarkable, but the climate wetting trend, as indicated by the rising annual precipitation and average annual relative humidity, was not obvious.     

Fuzzy comprehensive evaluation model for water resources carrying capacity in Tarim River Basin, Xinjiang, China

This paper explores the method of comprehensive evaluation of water resources carrying capacity and sets up an evaluation model applying the fuzzy comprehensive evaluation method. Based on the data of nature, society, economics and water resources of the Tarim River Basin in 2002, we evaluated the water resources carrying capacity of the basin by means of the model. The results show that the comprehensive grades are 0.438 and 0.454 for Aksu and Kashi prefectures respectively, where the current water resources exploitation and utilization has reached a relative high degree and there is only a very limited water carrying capacity, 0.620 for Kizilsu Kirgiz Autonomous Prefecture, where water resources carrying capacity is much higher, and in between for Hotan Prefecture and Bayingolin Mongolian Autonomous Prefecture. As a whole, the comprehensive grade of the Tarim River Basin is 0.508 and the current water resources exploitation and utilization has reached a relative high degree. Thus, we suggest that the integrated management of the water resources in the basin should be strengthened in order to utilize water resources scientifically and sustainably.     

Karyotype analysis of four nemertean species

We performed a karyotype analysis on four species from Phylum Nemertea using regenerating somatic cells. Two palaeonemertean species, Cephalothrix hongkongiensis and Cephalothrix sp., had the same chromosome number (2n=28), but different karyotypes (16 m+10 sm+2 st, NF=54 and 22 m+4 sm+2 st, NF=54, respectively). The karyotypes of the two heteronemerteans, Notospermus geniculatus and Ramphogordius sanguineus were 2n=38, 30 m+6 sm+2 sm/st (NF=76/74) and 2n=56, 48 m+4 sm+4 sm/st (NF=112/108), respectively.