Analysis of a variational Bayesian adaptive cubature Kalman filter tracking loop for high dynamic conditions

GPS Solutions - Under high dynamic conditions, a robust tracking loop is essential for accuracy positioning with the global position system. In previous studies, the extended Kalman filter...     

旋翼无人机单目视觉障碍物径向光流检测法

针对旋翼无人机在室外复杂环境下传统金字塔LK光流法检测障碍物准确性不高,适应性差的问题,提出了一种基于径向光流的单目视觉自主实时障碍物检测方法。该方法通过融合金字塔LK光流与切向光流求解径向光流,并基于径向光流设计了一种新的障碍物判定策略检测障碍物。试验表明,与传统金字塔LK光流法相比,在不增加算法复杂度的情况下,该方法具有更高的准确性和更强的适应性,可满足工程实践中无人机自主避障要求。     

中国极地考察站广域网通信建设与服务现状及展望

通过中国极地考察"十五"能力南极两站卫星通信网络系统项目的建设,我国南极考察站的广域网通信能力和站区网络通信能力已经有了很大提高。系统阐述南极两站的广域网通信现状,内容包括南极两站卫星通信链路的建设情况、考察站计算机网络系统建设情况以及该系统所提供的服务情况,涉及卫星通信、局域网以及VOIP等技术;对未来几年极地考察通信中可能会采用的通信技术建设提出建议。     

失地民众的征地拆迁满意度研究——以湖北咸宁市嘉通高速公路征地拆迁为例

结合国内征地拆迁的现状和特点,构建失地民众征地拆迁满意度模型,利用湖北省嘉通高速公路沿线村落的调查数据,采用基于PLS法的结构方程模型对征地拆迁民众满意度进行了实证分析。研究表明:失地民众对征地拆迁满意度不高,主要与民众对补偿款的满意程度、就业扶持力度以及信息是否公开透明等影响因素有关,此外,民众除了重视物质方面的补偿,还同等看重信息透明度、政策公平度等“无形”补偿。根据研究结果,建议政府与开发商合作提高就业扶持力度,利用新媒体平台拓展信息覆盖程度,完善纠纷解决机制。     

Simulation on phosphorus release characteristics of Poyang Lake sediments under variable water levels and velocities

Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake varied. Water level dropped, the velocity decreased and water exchange time lengthened, which changed the release of phosphorous from sediments. In order to investigate how the hydrodynamic factors influence the release of phosphorous from sediments, we used a two-way annular flume device to simulate the release characteristics of phosphorous from sediments under variable water levels and velocities. We found that both water level rising and velocity increasing could enhance the disturbance intensity to sediments, which caused the increase of suspended solids (SS) concentration, total phosphorus (TP) concentration in the overlying water, and the ability that phosphorus released to overlying water from sediments enhanced as well: when overlying water velocity maintained 0.3 m/s, SS concentration increased to 4035.85 mg/L at the water level 25 cm which was about 25 times compared to the minimum value and TP concentration in the overlying water also reached the maximum value at the water level 25 cm which was 1.2 times that of the value at 10 cm; when water level maintained 15 cm, SS concentration increased to 4363.35 mg/L at the velocity of 0.5 m/s which was about 28 times compared to the value of 0 m/s, and TP concentration in the overlying water increased from 0.11 mg/L to 0.44 mg/L. When the water level maintained 15 cm, the phosphorous release rate reached the maximum value of 4.86 mg/(md) at 0.4 m/s. The concentration of total dissolved phosphorous (TDP) and soluble reactive phosphate (SRP) both in overlying water and sediment-water interface were negatively correlated with pH. Using the parabolic equation, the optimum water level at a velocity of 0.3 m/s was calculated to be 0.57 cm, and the optimum velocity at water level of 15 cm was found to be 0.2 m/s.     

Climate change and glacier area variations in China during the past half century

Glacier variations in the Tibetan Plateau and surrounding mountain ranges in China affect the livelihood of over one billion people who depend on water from the Yellow, Yangtze, Brahmaputra, Ganges and Indus rivers originating in these areas. Based on the results of the present study and published literature, we found that the glaciers shrank 15.7% in area from 1963 to 2010 with an annual area change of -0.33%. The shrinkage generally decreased from peripheral mountain ranges to the interior of Tibet.The linear trends of annual air temperature and precipitation at 147 stations were 0.36°C(10a)~(-1) and 8.96 mm(10a)~(-1) respectively from 1961 to 2010. The shrinkage of glaciers was well correlated with the rising temperature and the spatial patterns of the shrinkage were influenced by other factors superimposed on the rising temperature such as glacier size, type, elevation, debris cover and precipitation.     

Ground-Based Radar Reflectivity Mosaic of Mei-yu Precipitation Systems over the Yangtze River–Huaihe River Basins

The 3D radar reflectivity produced by a mosaic software system, with measurements from 29 operational weather radars in the Yangtze River–Huaihe River Basins(YRHRB) during the mei-yu season of 2007, is compared to coincident TRMM PR observations in order to evaluate the value of the ground-based radar reflectivity mosaic in characterizing the 3D structures of mei-yu precipitation. Results show reasonable agreement in the composite radar reflectivity between the two datasets,with a correlation coefficient of 0.8 and a mean bias of -1 dB. The radar mosaic data at constant altitudes are reasonably consistent with the TRMM PR observations in the height range of 2–5 km, revealing essentially the same spatial distribution of radar echo and nearly identical histograms of reflectivity. However, at altitudes above 5 km, the mosaic data overestimate reflectivity and have slower decreasing rates with height compared to the TRMM PR observations. The areas of convective and stratiform precipitation, based on the mosaic reflectivity distribution at 3-km altitude, are highly correlated with the corresponding regions in the TRMM products, with correlation coefficients of 0.92 and 0.97 and mean relative differences of -7.9% and -2.5%, respectively. Finally, the usefulness of the mosaic reflectivity at 3-km altitude at 6-min intervals is illustrated using a mesoscale convective system that occurred over the YRHRB.     

Petrology and Geochemistry of the Banded Iron Formation of the Kuluketage Block,Xinjiang, NW China: Implication for BIF Depositional Setting

The Kuluketage block, located in the northeast Tarim craton, is one of the largest Precambrian blocks in the Xinjiang province. Recently, many banded iron formation (BIF)‐type (Superior‐type) deposits have been discovered in the western part of the Kuluketage block. These deposits occurred in the Paleoproterozoic Shayiti Formation, Xingditage Group, which has a nearly E–W distribution in the southern Xinger and Xingdi faults. Tremolite biotite schist and quartzite are the main wall rocks. The geochemical characteristics of schist indicate that the BIFs occurred in a passive continental margin environment. The LA–ICP–MS zircon ²⁰⁶Pb/²³⁸U ages of BIF and late syenite are 1945 ± 10 Ma(MSWD = 0.77) (weighted average age) and 1974 ± 27 Ma(MSWD = 1.05) (upper intercept age), respectively, indicating that the BIFs occurred in the Paleoproterozoic. In addition, the approximately 1.9 Ga magmatic and metamorphic events are consistent with the global‐scale 2.1–1.8 Ga collisional orogen events which are associated with the assembly of the Columbia supercontinent. The geochemical characteristics show that magnetite and quartz are dominant components (total content, 91.65–98.22 wt.%), and the Zr(Nb) and TiO₂, Zr(Nb) and Al₂O₃ and Zr and Y/Ho display strongly positive correlations, illustrating the addition of crustal materials into the chemical precipitate of the original BIFs. The higher Zr, Nb and Al₂O₃ contents and a lower Y/Ho ratio of the Kuluketage BIFs indicate a higher terrigenous detrital component contaminant compared to BIFs of North China Craton (NCC). The rare earth and yttrium (REY) distribution patterns show a slight LREE enrichment and weak Eu positive anomaly features, indicating that the source of Fe and Si of the Kuluketage BIFs is mainly from the contribution of low‐temperature hydrothermal alteration of the oceanic crust. In addition, along with the decreasing BIF depositional age, the declining of Eu anomaly values reflects the increasing importance of low‐temperature hydrothermal solutions relative to high‐temperature hydrothermal solutions. Moreover, no Ce anomalies in studied BIFs, NCC and Xinyu BIFs are attributed to relative reducing environmental condition when the original BIFs precipitated.