BP网络实时图像自动选取算法研究

实时图像的自动选取是景像匹配自动化的关键技术.提出了一种基于神经网络的实时图像自动选取算法.仿真研究表明,引入Sobel算子的3层BP网络实时图像自动选取算法结构简单、训练时间短和分类准确性高,其并行处理能力能满足景像匹配技术的实时性要求.经最小二乘和Bayes精匹配算法检验,实时图经此网络选取、粗匹配和精匹配,可达到高于0.5像素的定位精度.     

月面表层无人采样控制技术

针对"嫦娥五号"月面表层无人采样任务过程中机械臂精确控制难度大、器地协同工作复杂导致常规遥操作工作模式难以在有限时间内完成任务的问题,提出了月面表层无人采样高效控制方法和新的工作模式.通过建立采样区量化评价指标体系实现采样点规划、采用预先规划方法进行任务规划和机械臂运动控制规划、在线学习机械臂末端精调路径与多视角融合图...     

基于最小二乘估计的雷达系统误差卫星标定方法

雷达系统误差标定对精密测量雷达系统精度具有重要作用.本文针对基于精轨卫星的雷达系统误差参数标定技术,建立误差参数解算数学模型,对关键算法的最小二乘估计进行分析推导,并对卫星标定技术实现进行了系统设计.采用本文算法,依据某雷达常规手段实测的系统误差参数项进行仿真及仿真结果分析.研究结果表明,基于最小二乘估计的方法在卫星标定技术中是可行的.     

巨蟹座

星座故事 传说宙斯的儿子赫拉克勒斯征服了狮子精后,就开始去征服水蛇怪许德拉.正当他与水蛇怪酣战时,天后赫拉派了一只巨大的螃蟹去帮助水蛇怪.这只大螃蟹用双螯紧紧夹住赫拉克勒斯的脚,这位英雄立刻用棒把这只螃蟹击得粉碎.后来,赫拉心疼巨蟹,把它升到天上成为巨蟹座.     

静止轨道卫星才300千克?

正地球静止轨道通信卫星自从发明以来,一直沿着越来越大、越来越重的道路前进。但是,并非所有客户都需要这么大的卫星。大卫星的投资大、保险贵、运营成本高,而且需要很多租户才能把成本收回来。因此,进入21世纪后,美国轨道科学·ATK公司和德国OHB公司都开发了比较小型的地球静止轨道(GEO)卫星平台,或者用于租户不算太多的市场,或者用来给大卫星提供补充。但是,这两家公司都不如一家新成立的企业胆子大。轨道科学·ATK公司和OHB公司的GEO卫星发射重     

航天人再获何梁何利奖

2011年11月8日,在北京举行的何梁何利基金2011年度颁奖大会上,中国航天科技集团公司九院主任设计师王巍荣获“2011年度何梁何利基金科学与技术进步奖”,成为继张贵田、孟执中、贺祖明三位专家之后,集团公司第4位获得该项荣誉的专家。     

8mm可调稳幅源

一、引言近年来,随着我国毫米波技术的迅速发展,需要建立毫米波计量标准。一个幅度稳定的信号源,无论是在建标工作中,还是在毫米波日常测试工作中,都是必不可少的。目前,我国的毫米波固态源大多是固定频率的,即使有频率可调的,频率稳定度和幅度稳定度也都较差,难以满足计量测试工作的要求。而速调管毫米波源,调节频率麻烦,体积大,价格贵,频率和幅度稳定度也不太理想。又由于一些国家在毫米波技术、设备方面对我国实行严格的禁运政策,即使能引进某些产品,也只能是小功率的源,且价格十分昂贵。这种小功率的源在大多数计量测试工作中都不能满足工作需要。为此,我们和中国科技大学协作研制了     

斜楔式扭转振动器原理研究

为了解决扭转振动攻丝系统体积大、成本高、使用寿命短等关键问题,使攻丝力矩明显减小的振动攻丝技术能够得到广泛应用,提出了一种结构紧凑、压力角小、具有对称结构、制造工艺简单的斜楔式扭转振动器的传动原理,导出了该振动器的输出运动方程所要满足的必要条件,并给出了输入输出构件凸轮廓线的一般方程.最后通过一个例子证实了方程的正确性.这种扭转振动器可以广泛地应用于振动攻丝、振动铰孔加工.     

一种航天器安装精测数据修正与处理方法CSCD

针对航天测绘等高性能遥感对精测数据的高要求,提出一种高精度精测数据修正与处理方法。分析发现单精度浮点数可给精测数据引入很大误差,为此一方面采用更高精度的双精度型浮点数减少存储截断误差,另方面设计了精测数据误差修正算法对原始数据误差进行修正;采用多叉树数据结构对精测数据与精测关系同时进行记录,并基于该数据结构提出了可进行多阶段精测数据复合分析、多设备间相对安装指向分析和设备安装精度分析等操作的统一处理方法;该方法已用于资源三号卫星等型号,实现了遥感卫星精测数据的高精度处理与一站式操作,规范了数据处理方法与流程。     

一种航天器安装精测数据修正与处理方法

针对航天测绘等高性能遥感对精测数据的高要求,提出一种高精度精测数据修正与处理方法。分析发现单精度浮点数可给精测数据引入很大误差,为此一方面采用更高精度的双精度型浮点数减少存储截断误差,另方面设计了精测数据误差修正算法对原始数据误差进行修正;采用多叉树数据结构对精测数据与精测关系同时进行记录,并基于该数据结构提出了可进行多阶段精测数据复合分析、多设备间相对安装指向分析和设备安装精度分析等操作的统一处理方法;该方法已用于资源三号卫星等型号,实现了遥感卫星精测数据的高精度处理与一站式操作,规范了数据处理方法与流程。     

Great solar bursts of October 19, 22 and 23, 1989

Itapetinga measurements at 48 GHz with the multibeam technique are used to determine the relative position of solar burst centroid of emission with high spatial accuracy and time resolution. For the Great Bursts of October 19,22, 1989, with a large production of relativistic particles, and October 23, it is suggested that, at 48 GHz, the bursts might have originated in more then one source in space and time. Additionally the October 19 and 22 Ground Level Events exhibited very unusual intensity-time profiles including double component structures for the onset phase. The Bern observatory spectral radio emission data show a strong spectral flattening typical for large source inhomogeneties. The interpretation for this is that large solar flares are a superposition of a few strong bursts (separated both in space and time) in the same flaring region.     

Detection of volcanic,CO2, and ENSO signals in surface air temperature

The Russian surface air temperature data set (Northern Hemisphere, gridded, monthly average, 1891–1981) is analyzed to separate signals from large volcanic eruptions, ENSO (El Niño/Southern Oscillation) events, and signals in conjunction with hemispheric temperature changes. Characteristic patterns of zonal average temperature as a function of month and latitude as well as monthly average maps are produced for each forcing. The largest response to volcanic forcing appears at a lag of 2 and 3 years following volcanic eruptions. The zonal average response shows cooling at all latitudes and months, except in the Arctic in summer. The largest cooling is in the high latitudes in the winter. This agrees very well with energy balance model calculations of the response pattern to large volcanic eruptions, and can be explained by sea ice/thermal inertia and, to a lesser extent, snow/albedo feedbacks. The spatial pattern shows large areas of cooling at all longitudes. In response to ENSO oscillations the largest response is synchronous or with the temperature lagging ENSO oscillations by 6 months. The zonal average response is virtually zero, but the spatial patterns show large variations of opposite sign at different longitudes. Patterns produced by weighting temperature anomalies with hemispheric mean temperature indicate patterns to be expected following a CO₂ warming.     

Turbulence,complexity, and solar flares

The issue of predicting solar flares is one of the most fundamental in physics, addressing issues of plasma physics, high-energy physics, and modelling of complex systems. It also poses societal consequences, with our ever-increasing need for accurate space weather forecasts. Solar flares arise naturally as a competition between an input (flux emergence and rearrangement) in the photosphere and an output (electrical current build up and resistive dissipation) in the corona. Although initially localised, this redistribution affects neighbouring regions and an avalanche occurs resulting in large scale eruptions of plasma, particles, and magnetic field. As flares are powered from the stressed field rooted in the photosphere, a study of the photospheric magnetic complexity can be used to both predict activity and understand the physics of the magnetic field. The magnetic energy spectrum and multifractal spectrum are highlighted as two possible approaches to this.     

Monitoring the changing aereal extent of irrigated lands of the gefara plain,libya

The inventory of large often non-homogeneous tracts of land by resource agencies has led to the development of estimation methods and sampling strategies that produce estimates of the aereal extent of various features from ‘limited’ observations of the universe of interest. Landsat data has furnished a tool that allows for potential improvement in estimates of resource parameters over extensive areas. This paper examines the methodology and results of a procedure which uses an economical sampling procedure allied with the large area covering qualities of the satellite imaging system to make improved estimates of irrigated land in a more timely, efficient and ‘accurate’ manner.     

Two-level optimization approach for Mars orbital long-duration,large non-coplanar rendezvous phasing maneuvers

A relative dynamics equation-set based on orbital element differences with J₂ effects is derived, based on which a two-level approach is proposed to optimize the Mars orbital rendezvous phasing with a large difference in the initial ascending node. The up-level problem uses the revolution deviation between the target spacecraft and the chaser as the design variable, and employs a linear search to find the optimum. The low-level problem uses the maneuver revolutions, locations, and impulses as the design variables, and is solved using a hybrid genetic algorithm combined with sequential quadratic programming. To improve the solution accuracy, an iteration method is developed to satisfy the terminal constraints of the absolute numerical integration trajectory. Test cases involving Mars sample return missions with large initial node differences are presented, which show that the relative dynamics, two-level optimization model, and hybrid optimization algorithm are efficient and robust. Compared with previously published results, the total velocity increment has been further reduced by utilizing this proposed approach. It is found that a five-impulse plan requires the least quantity of propellant, and a propellant-optimal minimum rendezvous duration exists for this long-duration, large non-coplanar rendezvous problem.     

The dynamic heliosphere,solar activity,and cosmic rays

This brief review addresses the relation between solar activity, cosmic ray variations and the dynamics of the heliosphere. The global features of the heliosphere influence what happens inside its boundaries on a variety of time-scales. Galactic and anomalous cosmic rays are the messengers that convey vital information on global heliospheric changes in the manner that they respond to these changes. By observing cosmic rays over a large range of energies at Earth, and with various space detectors, a better understanding is gained about space weather and climate. The causes of the cosmic ray variability are reviewed, with emphasis on the 11-year and 22-year cycles, step modulation, charge-sign dependent modulation and particle drifts. Advances in this field are selectively discussed in the context of what still are some of the important uncertainties and outstanding issues.     

Influence of a long duration exposure, 69 months, to the space flight factors in Artemia cysts, tobacco and rice seeds.

Three french laboratories have participated in the Free Flyer Biostack experiment. Artemia cysts, tobacco seeds and rice caryopsis and embryos were used. Biological objects in monolayers were dead. In opposite, a large fraction of samples used in bulk survived. A stimulatory effect occurred in the first steps of development in Artemia cysts. In fact, the larval survival was unchanged or slightly reduced. In tobacco a drastic decrease in germination and survival rate was observed. Space flight did not induce genetic changes. In rice, results depend on the variety which was investigated; the growth rate stimulation in flight samples is discussed with respect to controls.     

非晶态Co-T-Zr(T=Cr,Mo,V,W)合金作为磁强计磁芯材料的研究

以快淬法制备了非晶态Co_(90～x)T_xZr_(10)(T=Cr,Mo,V,W;x=0,4,6,8,10,12)合金系列样品,并对其一些热和磁性能进行了测试研究,探讨了它们在磁强计上应用的可能性。结果表明,随着样品中T元素含量的增加,样品的晶化温度和晶化激活能升高,饱和磁化强度和居里温度下降,交流磁导率变化不大。退火处理对交流磁导率和损耗有较大影响。以现有理论对实验结果进行了分析。非晶态Co_(78)Cr_(12)Zr_(10)合金适于用作磁强计探头的磁芯材料,尤其是它良好的高频性能使磁强计测量的交流磁场的截止频率大干20kHz。     

1988年12月16日同CME相协的微波Ⅳ型大爆发

1988年12月16日云南天文台PhoenixⅠ日冕射电频谱仪观测到一次同日冕物质抛射相伴随的微波Ⅳ型大爆发。从0826—0941UT;三个波段的主峰间出现了121min的长周期振荡。在第一主峰的6个次峰间出现了1.2min的短周期振荡。根据北京怀柔磁场图,计算了爆发源区的亮温度,电子幂律分布等物理参量。采用慢波模式计算的短周期振荡与观测结果相符。初步解释了这次微波Ⅳ型大爆发,CME及其它伴生现象。      

Uncertainties in gravity wave parameters,momentum fluxes,and flux divergences estimated from multi-layer measurements of mesospheric nightglow layers

Measurements of dynamic parameters of atmospheric gravity waves, mainly the vertical wavelength, the momentum flux and the momentum flux divergence, are affected by large uncertainties crudely documented in the scientific literature. By using methods of error analysis, we have quantified these uncertainties for frequently observed temporal and spatial wave scales. The results show uncertainties of ～10%, ～35%, and ～65%, at least, in the vertical wavelength, momentum flux, and flux divergence, respectively. The large uncertainties in the momentum flux and flux divergence are dominated by uncertainties in the Brunt-Väisälä frequency and in spatial separation of the nightglow layers, respectively. The measured uncertainties in fundamental wave parameters such as the wave amplitude, intrinsic period, horizontal wavelength, and wave orientation are ～10% or less and estimated directly from our nightglow image data set. Other key environmental quantities such as the scale height and the Brunt-Väisälä frequency, frequently considered as constants in gravity wave parameter estimations schemes, are actually quite variable, presenting uncertainties of ～4% and ～9%, respectively, according to the several solar activity and seasonal atmosphere scenarios from the NRLMSISE-00 model simulated here.