日本遥感卫星JERS—1地面轨径的确定

叙述日本ＪＥＲＳ—１卫星地面轨径的确定，并根据地面参考系建立起来的栅格推导出卫星ＳＡＲ景象的实际位置．

普速铁路挖掘机配合小半径曲线换轨的应用

本文采用比较分析的研究方法,通过挖掘机(150)和快速换轨车(HGCZ-2000)小半径曲线换轨时的对比,总结挖掘机和快速换轨车换轨的优缺点,确定挖掘机在小半径曲线换轨的可行性,同时对挖掘机换轨流程进行简述。

小半径曲线防磨护轨有限元分析及改进设计

根据小半径曲线防磨护轨的结构特点 ,采用三维块单元建立有限元分析模型 ,并对原始设计进行分析计算 ,结果为应力集中较大。在对应力及变形分析基础上提出了结构的改进设计方案。通过有限元分析计算表明 ,改进后的设计方案应力分布趋于均匀 ,并有可靠的机械强度。

75kg·m^(-1)钢轨用轨撑设计与铺装试验

针对重载铁路小半径曲线和长大坡道线路的轨距、线型难于保持,外轨侧磨严重,养护维修工程量大的情况,研制了普通型和减振型2种形式的75 kg.m-1钢轨用轨撑。在大秦线的轨道动力特性试验和现场试铺表明:与既有Ⅱ型弹条扣件相比,安装2种轨撑后测试断面的轨头横向静刚均有大幅增大,其中,外轨轨头的横向静刚度增大40%～54%,内轨轨头的横向静刚度增大9%～113%;轨撑提高了钢轨的横向抗力和抗倾覆的能力,提高了行车安全性;钢轨横移和钢轨侧磨明显减小,轨距和轨向保持良好,减小了日常养护维修工程量。减振型轨撑的减振效果更好。

城市轻轨施工难点剖析及对策

文章以长期在大连市轻轨施工中遇到的重点、难点为实例,重点阐述了整体道床施工、无缝线路哈克紧固件冻结接头、轨道后固定技术、小半径曲线轨道施工等新技术、新工艺难点及解决方法,以供同类工程借鉴。

Geosat卫星定轨中的大气阻力摄动

在利用卫星测高资料定轨的过程中，大气阻力摄动的影响较大。本文在比较几种常用大气密度模型误差对定轨影响的基础上，将密度改正公式引入到Geosat卫星的精密定轨中。结果显示，该公式可以有效地提高卫星的径向定轨精度。

基于网格法的NURBS自由曲线速度场规划

针对轮廓运动系统存在的轨径缩减现象及非均匀有理B样条(NURBS)轨迹曲率变化的不规则等问题,提出一种速度规划方法。根据NURBS轨迹的特点,难以利用一般几何方法构建其速度场,基于方向场理论,以划分网格点的方式构建速度场,将双轴位置协调控制转化为各单轴速度控制,消除轨径缩减现象。将速度场所编码的轨迹与指令轨迹之间的轮廓误差进行仿真与实验对比计算,结果表明,所提出的构建任意轨迹速度场方案是可行的,能够将双轴协调控制完全简化为各单轴速度控制,提高了轮廓精确度。

Dynamic load sharing characteristics and sun gear radial orbits of double-row planetary gear train

A new non-linear bending-torsional coupled model for double-row planetary gear set was proposed, and planet's eccentricity error, static transmission error, and time-varying meshing stiffness were taken into consideration. The solution of differential governing equation of motion is determined by applying the Fourier series method. The behaviors of dynamic load sharing characteristics affected by the system parameters including gear eccentricities error, ring gear's supporting stiffness, planet's bearing stiffness, torsional stiffness of first stage carrier and input rotation rate were investigated qualitatively and systematically, and sun gear radial orbits at first and second stage were explored as well. Some theoretical results are summarized as guidelines for further research and design of double-row planetary gear train at last.

GF-3 data real-time processing method based on multi-satellite distributed data processing system

Due to the limited scenes that synthetic aperture radar(SAR)satellites can detect,the full-track utilization rate is not high.Because of the computing and storage limitation of one satellite,it is difficult to process large amounts of data of spaceborne synthetic aperture radars.It is proposed to use a new method of networked satellite data processing for improving the efficiency of data processing.A multi-satellite distributed SAR real-time processing method based on Chirp Scaling(CS)imaging algorithm is studied in this paper,and a distributed data processing system is built with field programmable gate array(FPGA)chips as the kernel.Different from the traditional CS algorithm processing,the system divides data processing into three stages.The computing tasks are reasonably allocated to different data processing units(i.e.,satellites)in each stage.The method effectively saves computing and storage resources of satellites,improves the utilization rate of a single satellite,and shortens the data processing time.Gaofen-3(GF-3)satellite SAR raw data is processed by the system,with the performance of the method verified.

新钢铁水运输线路升级改造实践

随着新钢三期工程项目的相继投产,产能不断释放,铁水运输量也迅速增加,铁水运输车辆轴重也随之不断增大,铁水运输线路出现了钢轨磨耗加剧,轨枕被压溃、失效,路基翻浆冒泥严重及道口安全风险增大等各种问题。为此,采取换填法对路基进行改造,优化混凝土枕道岔施工工艺,改造小半径曲线轨撑型减磨防脱护轨砼枕,实施钢轨—混凝土整体道口板技术,解决了铁水"一罐制"运输组织模式带来的种种问题,保障了铁水运输的安全。

Modeling of Track Formation in Semiconductors Irradiated with Swift Heavy Ions

The interaction of the heavy charged particles, of energy higher than a few MeV/amu with semiconductor single crystals can lead to the structural modification of their physical properties and participate at the creation of the defects which are called latent tracks. Several models were tested for explaining the track formation in semiconductors irradiated with swift heavy ions, one of them is the thermal spike model. This work shows that the experimental data obtained in semiconductors, in our case in InP irradiated with swift heavy ions can be described on the basis of the thermal spike model. The experimental results obtained on InP have allowed the parameters of this model to be understood. The only free parameter is the electron-phonon coupling constant g which is unknown in InP This model allows the evolution of track radii to be found as a function of electronic stopping power （dE/dx）e for different beam energies. For InP a good agreement is observed between calculated track radii and experimental ones on one hand, and on the other hand between calculated and experimental threshold value of electronic stopping power. This allows determining the electron-phonon coupling value for InP to be equal 0.9 × 10%11 Wcm-3K-land the （dE/dx）e threshold for latent track formation in InP equal 27 ＋ 3 keV/nm for ion energies ranging from 0.4-10 MeV/amu.

Two-sided Long Baseline Radargrammetry from Ascending Descending Orbits with Application to Mapping Post-seismic Topography in the West Sichuan Foreland Basin

One-sided ascending or descending Synthetic Aperture Radar（SAR） stereoradargrammetry has limited accuracy of topographic mapping due to the short spatial baseline（-100 km） and small intersection angle. In order to improve the performance and reliability of generating digital elevation model（DEM） from spaceborne SAR radargrammetry, an exploration of two-sided stereoradargrammetry from the combination of ascending and descending orbits with geometric configuration of long spatial baseline（-1000 km） was conducted in this study. The slant-range geometry between SAR sensors to the earth surface and the Doppler positioning equations were employed to establish the stereoscopic intersection model. The measurement uncertainty of two-sided radargrammetric elevation was estimated on the basis of radar parallax of homogeneous points between input SAR images. Two stereo-pairs of ALOS/PALSAR（Advanced Land Observing Satellite/Phased Array type L-band Synthetic Aperture Radar） acquisitions with the orbital separation almost 1080 km over the west Sichuan foreland basin with rolling topography in southwestern China were employed in the study to obtain the up-to-date terrain data after the 2008 Wenchuan earthquake that hit this area. Thequantitative accuracy assessment of two-sided radargrammetric DEM was performed with reference to field GPS observations. The experimental results show that the elevation accuracy reaches 5.5 m without ground control points（GCPs） used, and the accuracy is further improved to 1.5 m with only one GPS GCP used as the least constraint. The theoretical analysis and testing results demonstrate that the twosided long baseline SAR radargrammetry from the ascending and descending orbits can be a very promising technical alternative for large-area and high accuracy topographic mapping.

CRESDA Successfully Processed the First Track Data of GF-3

The first images obtained from Gaofen-3（GF-3）,China’s first C-band high-resolution Synthetic Aperture Radar（SAR）satellite with a resolution of one meter in spatial diameter were published on August 25.This satellite undertakes an important task with its all-day,all-weather observation capability as part of the China High-resolution Earth Observation System（CHEOS）.With 12 imaging modes,

Tensor force effect on proton shell structure in neutron-rich Ca isotopes

In the framework of the Skyrme-Hartree-Fock approach with 36 sets of the TI J parameterizations,the tensor force effect on the evolution of the single-proton states in the calcium isotopes is systematically investigated.It is shown that the single-proton states with higher angular momenta are influenced significantly by the tensor force and the trend in the evolution of somesingle-particle energy differences with the mass number of the isotopes depends sensitively on a parameter βT associated with the intensity of the tensor force.To understand this phenomenon,we analyze the spin-orbit potentials and the radial wave functions of relevant single-proton orbits in detail.In addition,it is found that some TI J interactions could cause the 2s1/21d3/2 energy level inversion in 48Ca.

Vibration characteristics of bogie hunting motion based on root loci curves

Vibration behaviors of bogie hunting motion contain key information that dominates the dynamic performance of rail vehicles,in which the eigenvalue of each mode reflects the damping ratio and the natural frequency.This paper focuses on the root loci curves of bogie hunting motion,starting from a rigid bogie,then to a bogie with flexible primary suspension.With regard to the rigid bogie,analytical formulas for the eigenvalues,the critical speed as well as the corresponding hunting frequency are derived and verified.While for the flexible bogie,the root loci curves are calculated numerically.The study shows that both free rigid bogie and free wheelset are dynamically unstable at any speed.The critical speed increases with diminished wheel-rail conicity,track gauge,and wheelset and bogie inertia,and with increased wheelbase and wheel radius.The dominating factors such as the stiffness of the primary suspension and the wheel-rail conicity should be optimized for a practical design.The influences of the damping coefficients and the variations of creep coefficients are negligible.The motor suspension affects the root loci curves and the critical speed significantly.Both inappropriate motor suspension design and rigidly suspended motor reduce the critical speed.The increase of critical speed by a motor suspension can only be achieved when the lower natural frequency of the motor-bogie frame-wheelsets system coincides with or is close to the hunting frequency.Special care should be taken for the design of motor suspension,the first is to avoid the decreased damping ratio in a certain speed range below the critical speed and the second is that the variations of parameters should not induce the rapid reduction of the critical speed.The main feature of the present study is that the root loci curves,which are derived as analytical formulas or calculated numerically,are used to study the vibrational behaviors of bogie hunting motion.Both the influencing laws of the dominating parameters and the principles regarding the motor suspension are significant for the stability design of modem railway vehicles which may use innovative structures/materials as well as modem control and monitoring technologies.

Satellite-station time synchronization information based real-time orbit error monitoring and correction of navigation satellite in Beidou System

Satellite-station two-way time comparison is a typical design in Beidou System(BDS)which is significantly different from other satellite navigation systems.As a type of two-way time comparison method,BDS time synchronization is hardly influenced by satellite orbit error,atmosphere delay,tracking station coordinate error and measurement model error.Meanwhile,single-way time comparison can be realized through the method of Multi-satellite Precision Orbit Determination(MPOD)with pseudo-range and carrier phase of monitor receiver.It is proved in the constellation of 3GEO/2IGSO that the radial orbit error can be reflected in the difference between two-way time comparison and single-way time comparison,and that may lead to a substitute for orbit evaluation by SLR.In this article,the relation between orbit error and difference of two-way and single-way time comparison is illustrated based on the whole constellation of BDS.Considering the all-weather and real-time operation mode of two-way time comparison,the orbit error could be quantifiably monitored in a real-time mode through comparing two-way and single-way time synchronization.In addition,the orbit error can be predicted and corrected in a short time based on its periodic characteristic.It is described in the experiments of GEO and IGSO that the prediction accuracy of space signal can be obviously improved when the prediction orbit error is sent to the users through navigation message,and then the UERE including terminal error can be reduced from 0.1 m to 0.4 m while the average accuracy can be improved more than 27%.Though it is still hard to make accuracy improvement for Precision Orbit Determination(POD)and orbit prediction because of the confined tracking net and the difficulties in dynamic model optimization,in this paper,a practical method for orbit accuracy improvement is proposed based on two-way time comparison which can result in the reflection of orbit error.

Separating impacts of vegetation change and climate variability on streamflow using hydrological models together with vegetation data

Vegetation information is seldom considered in lumped conceptual rainfall-runoff models.This paper uses two modified rainfall-runoff models,the Xinanjiang-ET and SIMHYD-ET models in which vegetation leaf area index is incorporated,to investigate impacts of vegetation change and climate variability on streamflow in a Southern Australian catchment,the Crawford River experimental catchment,where Tasmanian blue gum plantations were introduced gradually from 1998 till 2005.The Xinanjiang-ET and SIMHYD-ET models incorporate remotely-sensed leaf area index(LAI) data obtained from the Advanced Very High Resolution Radiometer(AVHRR) on board NOAA polar orbiting satellites.Compared to the original versions,the Xinanjiang-ET and SIMHYD-ET models show marginal improvements in runoff simulations in the pre-plantation period(1882-1997).The calibrated Xinanjaing-ET and SIMHYD-ET models are then used to simulate plantation impact on streamflow in the post-plantation period.The total change in streamflow between the pre-plantation and post-plantation periods is 32.4 mm/a.The modelling results from the two models show that plantation reduces streamflow by 20.5 mm/a,and climate variability reduces streamflow by 11.9 mm/a.These results suggest that increase in plantations can reduce streamflow substantially,even more than climate variability.

Feasibility study of inclined geosynchronous SAR focusing using Beidou IGSO signals

Dear editor,Geosynchronous synthetic aperture radar(GEO SAR)[1,2]has an inclined geosynchronous orbit of around 36000 km,which leads to its short revisit time of around 24 hours and a wide coverage of up to approximately one third of the Earth surface.Its long integration time guarantees the fine resolution.Thus,GEO SAR owns the promising capability of providing images with the high resolution,

Numerical investigation on wheel-turnout rail dynamic interaction excited by wheel diameter difference in high-speed railway

The wheel-rail relationship in turnout is more complicated than that in ordinary track. Profile wear and machining errors of the wheelset cause deviations Of the rolling radius on different wheels. Therefore, wheelsets move to the direction of smaller diameter wheels in search of a new stable state and to change the condition before entering the turnout. Thc main aim of the present work is to examine the wheel-turnout rail dynamic interaction combined with the static contact behaviour. Calculations are performed on a high-speed vehicle CRH2 and the No. 12 turnout of the passenger dedicated line. The wheel-turnout contac! geometric relationship and normal contact behaviour under wheel diameter difference are assessed by the trace principle and finite element method. A high-speed vehicle-turnout coupling dynamic model is established based on SIMPACK software to analyse the wheel-rail dynamic interaction, riding comfort, and wear. Both the wheel diameter amplitudes and distribution patterns are accounted for. The simulation shows that wheel diameter difference can greatly disturb the positions＇ variation of wheel-rail contact points and affect the normal contact behaviour on switch rails by changing the load transition position. The effect of wheel diameter diffierence on wheel-turnout rail dynamic interaction can be divided into three according to its amplitude： when the wheel diameter difference is within 0-1.5 mm, the wheel flange comes into contact with the switch rail in advance, causing a rapidly increased lateral wheel-rail force; when it is within 1.5 2.5 mm, trains are subject to instability under equivalent in-phase wheel diameter difference; when it is larger than 2.5 mm, the continuous flange-switch rail contact helps strengthen the vehicle stability, but increases the wheel-rail wear. It is recommended to control the wheel diameter difference to within 2.5 mm but limit it to 2 mm if it is distributed in-phase.

SAR motion compensation based on the correction of residual attitude errors

As residual attitude errors are likely to affect the synthetic aperture radar (SAR) imaging, this paper presents a SAR motioncompensation algorithm based on the correction of residual attitude errors. The existing methods all use the antenna stableplatform to correct the attitude errors, and then compensate the trajectory deviations in the following imaging process. Besidescompensating the trajectory deviations, the modified method of this paper also considers the influence of residual attitude er-rors on the SAR imaging, and can compensate both the trajectory deviations and the residual attitude errors. Compared withthe existing methods, the modified method in this paper can more precisely compensate the imperfect motion on the SAR im-aging, especially good for the SAR system with a small platform, near operating distance and a narrow antenna beam. Such asystem causes severe residual attitude errors and needs to consider the influence of antenna beam pointing errors on the imag-ing. The validity of the modified method presented by this paper is demonstrated by the result of the experiment.