Mass flow in a circumbinary disk with a gap around supermassive binary black holes

We study the interaction between supermassive binary black holes in an elliptical orbit and their surrounding disk with a gap. The gap in the disk is a low density region formed due to the tidal effects of the less massive black hole. The binary we have investigated has a sub-parsec separation and is coplanar with the disk. We find that the maximum variation of the surface density in the gap reaches 50% during an orbital period. However, in other regions of the disk, the density variation is much less than 1%. Furthermore, we calculate the corresponding variation of spectral energy distribution within a period, but little variation is found. The reason for these results is that the viscosity timescale of the disk at the binary radius is much longer than the orbital period of the binary.     

数据深度加权半参数估计法在方差分量估计中的应用研究

针对天地基联合测控中多源异质数据存在多耦合性系统模型误差和粗差的情况,提出了基于数据深度加权半参数估计的方差分量估计法.利用半参数估计法补偿不确定性模型误差,同时构建数据深度权抑制粗差的影响,使半参数估计不受粗差的影响,为方差分量估计提供合理的权矩阵,使得方差分量估计能对存在不确定性模型误差和粗差的结构定权.进行了天地基对空间目标的联合测控仿真试验.结果表明,改进的方差分量估计法能有效补偿不确定性模型误差并抑制粗差的影响,确定更加合理的权值.     

卫星钟差预报模型中周期项的选取方法及性能分析

针对卫星钟差预报(SCB)中周期项选取方法存在的问题,在分析卫星钟周期波动特性的基础上,给出了正确的周期项选取方法,并与现有方法进行了比较.利用IGS(International GNSS Service)的卫星钟差数据,比较分析了二次多项式加周期项模型与传统模型的预报精度.从理论上分析了周期项对传统模型的改善程度及适用条件.结果表明:按照提出方法得到的周期项更符合实际,将其应用于钟差预报时能获得更高的预报精度,大量仿真实验还表明卫星钟周期性波动相对较大时周期项对传统模型有明显改善.     

在近距双星系统中同步双星达到轨道圆形化时的轨道和自转演化的数值解和演化趋势

从非同步自转双星的轨道和自转的演化方程组推出同步双星的轨道和自转的演化方程组.用数值积分法给出演化方程组的数值解.计算同步自转双星EKCep达到轨道圆形化的时间和那时的轨道半长轴、轨道偏心率和主星自转角速度的演变数值.最后对轨道和自转的演化趋势做了推论.     

长期GPS精密星历分析与轨道参数的函数逼近

以力学模型为基础,只能分析GPS卫星在短时间内的变化规律,而利用IGS提供的精密星历可以分析卫星在长时间段内的变化规律。基于精密星历研究了计算GPS卫星轨道参数的方法,然后对轨道参数在长时间段内的变化情况进行了分析,给出了分析的主要结果,并提出用正弦函数对轨道参数进行逼近,以得到GPS轨道的解析模型。     

基于观测器的具外部扰动的离散时间系统的滑模控制

针对一类具有配外部扰动的多输入多输出(MIMO)离散时间系统(DTS),提出了改进的状态观测器的设计方案,使得该观测器不受外部扰动的影响。对外部扰动满足匹配条件的MIMO-DTS,提出了基于状态观测器和扰动估计器的滑模控制器设计方案,该设计方案不要求知道系统的状态和外部扰动的上界。提出的仿真例子说明了本文方法的可行性和有效性。     

第45个世界地球日活动主题确定

正2014年4月22日是第45个世界地球日,纪念活动主题确定为"珍惜地球资源转变发展方式——节约集约利用国土资源共同保护自然生态空间"。世界地球日主题宣传活动周于4月20日~4月26日举行。其间,国土资源部开通官方微信,发布国土资源公报,推介国土资源优秀科普图书,举办科普展览、专家主题论坛、在京高校大学生主题演讲比赛等活动。各国土资源科普基地会免费或优惠向全社会公众或青少年开放,国土资源部各重     

Track of Super Typhoon Haiyan Predicted by a Typhoon Model for the South China Sea

Super Typhoon Haiyan was the most notable typhoon in 2013. In this study, results from the operational prediction of Haiyan by a tropical regional typhoon model for the South China Sea are analyzed. It is shown that the model has successfully reproduced Haiyan’s rapid passage through the Philippines and its northward deflection after its second landfall in Vietnam. However, the predicted intensity of Haiyan is weaker than the observed. An analysis of higher-resolution model simulations indicates that the storm is characterized by an upper-level warm core during its mature stage and a deep layer of easterly flow. Sensitivity experiments are conducted to study the impact of certain physical processes such as the interaction between stratus and cumulus clouds on the improvement of the typhoon intensity forecast. It is found that appropriate boundary layer and cumulus convective parameterizations, and orographic gravity-wave parameterization, as well as improved initial conditions and increased horizontal grid resolution, all help to improve the intensity forecast of Haiyan.     

风云气象卫星数据处理算法的若干创新

This study introduces some innovations in the data processing algorithm for Chinese FY meteorological satellites. Issues about satellite image navigation, radiation calibration, and data assimilation are discussed.
A time series of the earth＇s disk center-line count provides information on the orientation of the satellite spin axis. With this information, the altitude parameters of the satellite and then the earth disk location in the south-north direction may be solved. In each spin cycle, the satellite views the sun and the earth. Given the satellite position and altitude, the angle （β） subtended at the satellite by the sun and the earth can be calculated and predicted. Thus, the earth＇s disk location in the east-west direction is fixed. Based on this principle, we derived an automatic image navigation algorithm for FY2 geosynchronous meteorological satellites with an accuracy approaching pixel level.
The FY2 meteorological satellite traveling in a geostationary orbit suffers a large amount of radiation from the sun. The radiation varies on both diurnal and annual scales, which causes radiation responses in the thermal infrared （IR） bands wherein the wavelengths greater than 3.5 μm vibrate periodically on scales of hours to years. These vibrations must be precisely calibrated. First, based on the accurate estimation of the radiant contribution from the front-optics, the variation characteristics of the calibration parameters are obtained on a temporal scale of hours from the space-borne inner-blackbody （IBB） measurement results. Second, the in-orbit measured radiation of the lunar surface is referenced and utilized to correct the sys- tematic bias of the IBB calibration from daily to annual scales. By using such algorithms, we achieved a calibration accuracy of the FY2 satellite＇s IR imagery of less than 1 K.
The on-orbit satellite instrument parameters play an important role in data quality; however, they may be mis-measured due to limitations in the measurement conditions or may be     

从气旋和反气旋谈正、负阻尼

在定常条件下,利用简化的大气运动控制方程,分析了气旋与反气旋的基本特征。在此基础上,利用常微分方程的定性分析与求解,获得了气旋和反气旋轨道的解析解。接合气旋与反气旋的基本特征,论证了正负阻尼在气旋和反气旋运动中具体体现,并从物理机理上说明产生气旋和反气旋运动中正负阻尼的差异在于水平辐合在低层的不同。