星蚀期北斗卫星轨道性能分析——SLR检核结果

星蚀期北斗卫星的轨道性能是北斗卫星导航系统性能分析的重要部分。了解北斗卫星导航系统星历中星蚀期轨道的精度,不仅可为系统服务性能评估提供支持,还有助于了解星蚀期精密定轨中相关模型可能存在的问题,进而为精密定轨函数模型改进提供参考。本文基于2014年1月至2015年7月的卫星激光测距资料,重点分析了星蚀期对北斗不同类型卫星轨道的影响,同时也对北斗广播星历和精密星历中整体轨道径向精度进行检核。结果表明：星蚀期内（尤其是偏航机动期间）,IGSO/MEO卫星的广播星历和精密星历轨道均存在明显的精度下降;广播星历轨道径向误差达1.5～2.0m,精密星历轨道径向误差超过10.0cm。但仅从轨道径向残差序列中难以发现星蚀期对GEO卫星轨道是否有显著影响。非星蚀期间,IGSO/MEO卫星和GEO卫星的广播星历轨道径向精度分别优于0.5 m和0.9 m。IGSO/MEO卫星的精密星历轨道径向精度优于10.0cm,GEO卫星的轨道径向精度约50.0cm,且存在40.0cm左右的系统性偏差。

轨道板性能在线监测系统

轨道服役性能参数是轨道结构状态的总体反映。当轨道出现病害或是潜在病害时,轨道服役性能参数势必会发生变化。自主研发出的1套轨道板性能在线监测系统,可实现在线采集轨道板温度并对其性能进行分析,已成功运用于华东地区某客运专线轨道性能的在线监测中。该系统主要由便携式前端采集硬件、后端处理分析中心及用户终端三部分构成,具有测试参数全面、高精度采集、远程传输等优势。

台车式擦窗机及其轨道抗震性能研究

运用非线性有限元之动力特性及动力响应分析方法,对传统设计的台车式擦窗机及轨道在地震工况下的抗震性能进行了核算和研究,指出了原有设计的不足,提出了提高台车式擦窗机及轨道抗震性能的措施,得出了有益的结论。

Damage characteristics of Cu−Cr−Zr alloy rail of electromagnetic railgun after simulated launch

The damage characteristics of different speed sections of Cu−Cr−Zr alloy rail after simulated launch were studied.The microstructure,morphologies and properties of samples were investigated by using XRD,XPS,EBSD,SEM,hardness test,electrochemical test and DSC techniques.It was found that deposition layers were formed on the surfaces of the simulated launch samples.The thickness and surface roughness of these deposition layers increased with increasing the heat effect,suggesting a launch speed dependent damage degree of the arc ablation.The hardness variation of samples is attributed to the effects of the deposition layer and deformation hardening.The surface deposition layer affects corrosion resistance and crystalline characteristics,leading to changes in subsequent service performances.Additionally,the surface texture and plastic deformation ability of the samples are related to the recrystallization degree and deformation grain amount.

蒸汽养护对混凝土CRTSⅢ型轨道板性能的影响分析

高速铁路的平顺性、安全性和可靠性很大程度上有赖于CRTSⅢ型轨道板的预制质量。本文针对混凝土CRTSⅢ型轨道板开展养护后性能研究,首先开展轨道板混凝土配比设计,然后采用实验研究了掺合料掺量、养护时间和养护参数对CRTSⅢ型轨道板性能的影响规律。研究结果表明,混凝土浇筑后的静停时间为4 h,升温阶段的升温速度不宜大于15℃/h,恒温阶段的蒸汽温度不宜超过45℃。综合考虑最佳养护工艺一般为蒸养15 h+水养3 d+自然喷淋养护至28 d。

A reconfigurable tracked mobile robot based on four-linkage mechanism

A novel reconfigurable tracked robot based on four-link mechanism was proposed and released for the complicated terrain environment. This robot was modularly designed and developed, which is composed of one suspension and one pair of symmetrical deployed reconfigurable track modules. This robot can implement multiple locomotion configurations by changing the track configuration, and the geometric theory analysis shows that the track length keeps constant during the process of track reconfiguration. Furthermore, a parameterized geometric model of the robot was established to analyze the kinematic performance of the robot while overcoming various obstacles. To investigate the feasibility and correctness of design theory and robot scheme, an example robot was designed to climb 45° slopes and 200 mm steps, and a group of design parameters of the robot were determined. Finally, A prototype of this robot was developed, and the test results show that the robot own powerful mobility and obstacle overcoming performance, for example, running across obstacle like mantis, extending to stride over entrenchment, standing up to elevate height, and going ahead after overturn.

Electron Flux Distributions in the Photodetachment of H_2^-in an Electric Field

The electron flux distributions in the photdetachment of a negative hydrogen molecular ion in an electric field have been studied by using the two-center model and the dosed orbit theory. An analytic formula is presented for the electron flux of H2 in the presence of an electric field. The results show that the interference between the two orbits passing through the given spatial point leads to the oscillation in the electron flux distribution. Besides, the interference between the two centers of the H2^- is also very important. The comparison between the electron flux of H2^- in electric field with the result of H^- shows that at the equilibrium distance of two centers in the H2^-, the interference of the two nuclei on the detached electron＇s flux distribution is very strong, while at larger distance of the two centers, the interference effect of the two centers is decreased.

Cooperative DVB-SH Satellite Broadcasting Systems with Rotated Signal Constellations

In this paper,we study the advantages of cooperation in broadcasting systems from a geosynchronous earth orbit(GEO)satellite to mobile terminals(MTs),achieved through a terrestrial complementary ground station(CGS) with fixed installment,which acts as a relay.Moreover and in the context of the digital video broadcasting-satellite-to-handheld(DVB-SH) standard,the performance improvements offered by the rotated constellations method are investigated,where prior transmission,a phase rotation of the transmitted symbols by a fixed angle is applied followed by a random component interleaver.Turbo codes with soft decision decoding and appropriate random channel interleavers are also considered.We present analytical expressions for the bit log-likelihood ratios(LLRs)that are needed for soft decision decoding at the MT turbo decoder,while the code combining technique is adapted to improve the end-to-end(E2E) performance.Then,we obtain through extensive computer simulations the average bit error probability(ABEP) of quadrature phase-shift keying(QPSK) signals received over pure land-mobile satellite(LMS)and pure CGS links for coding rates 1/3 and6/7.Moreover,the optimal rotation angles are obtained for both links.E2 E ABEP results are then presented assuming cooperation between GEO and CGS,while the power allocation issue is investigated under fixed total transmission power.Our performance evaluation results show that by using the constellation rotation technique,a performance gain can be achieved for high coding rates.

缬苯那嗪类似物P109人肝微粒体中代谢产物鉴定及酶表型研究

化合物P109是缬苯那嗪结构类似物,其在9位进行了环丙烷甲基取代,具有与缬苯那嗪相似的药物活性与药理作用机制。为研究P109在人肝微粒体孵育体系中的代谢产物,采用Waters Eclipse Plus-C18色谱柱(150 mm×2.1 mm×3.5μm)分离,以0.1%甲酸水(A)-0.1%甲酸乙腈(B)为流动相进行梯度洗脱,利用超高效液相色谱-高性能台式四极杆-轨道阱质谱(UHPLC-Q Exactive^(TM) Orbitrap MS)技术,在正离子模式下分析样品,筛选出9个化合物(包括P109及其8个代谢产物),并进行结构鉴定。结果表明,P109经人肝微粒体主要发生氧化、水解、脱环丙烷甲基的Ⅰ相代谢反应。代谢产物酶表型研究表明,P109的主要代谢酶亚型为CYP3A4和CYP2C8,次要代谢酶亚型为CYP2D6。本研究初步阐明了P109在人肝微粒体中的代谢规律及代谢产物酶表型,可为新药筛选、毒理学研究提供支持。

Temperature-induced deformation of CRTS II slab track and its effect on track dynamical properties

Two finite-element models of the CRTS II slab track are presented to simulate temperature-induced deformations of the concrete track slab with no deterioration or with a deteriorated cement asphalt mortar(CAM).One model,which considers the fully bonding interface between the slab and the CAM layer,could applied to a track that is in good condition;the other model uses cohesive zone elements to simulate the deteriorated CAM with some possible interfacial separation and slip.Utilizing both of the models,temperature-induced warp deformations of track under various temperature loads are investigated.The influence of temperature deformation on the dynamic properties of the track is analyzed based on the train-track coupled dynamics.Numerical results show that the deteriorated CAM layer can significantly increase temperature deformations of a CRTS II track slab,which would produce tiny rail irregularities.There are clear differences between the deformation shapes of the track slabs that have an inseparable mortar layer and those have a separable mortar layer.The track slab with a deteriorated mortar layer showed more open curl distortion than the track slab in good condition.The dynamical response index of the slab track is intensified to a certain level due to the temperature deformation;with an increase of the train speed,the track dynamical responses increased linearly.However,rail irregularities due to the temperature deformations are very tiny.Even if a track is exposed to extreme temperature loads and the mortar layer is deteriorated,temperature deformation can have a negligible effect on the track’s dynamical properties.

Properties of CaB_6 single crystals synthesized under high pressure and temperature

Pure CaB6single crystals are synthesized under high pressure (1 GPa) and temperature (1050°C). The temperature-dependenceof electric resistivity and Hall coefficient from 2 to 300 K shows that the CaB6single crystals are conductors withsemi-metallic behavior and electron carriers. Band structure calculations indicate that the conduction and valence bands meetat the X point at the Fermi level, which is consistent with the experimentally determined conducting behavior of CaB6singlecrystals. Calculations of state density suggest that the states at the Fermi level originate from the 2p orbital of the B atoms andthe 3d orbital of the Ca atom. Magnetization measurements show the paramagnetic nature of the CaB6. The micro-hardness ofCaB6is 24.39 GPa, and the Raman spectra of CaB6yield three sharp peaks at around 780.9, 1138.9, and 1282.1 cm 1for T2g,Eg, and A1g, respectively. The specific heat of the crystal is measured and found to be well described by the Debye and Einsteincombined model. The fitting results show Debye and Einstein temperatures are 1119 and 199 K, respectively.

Fuel-optimal trajectory design using solar electric propulsion under power constraints and performance degradation

The fuel-optimal transfer trajectories using solar electric propulsion are designed considering the power constraints and solar array performance degradation.Three different performance degradation models including linear,positive and negative exponential degradations are used in the analysis of three typical rendezvous missions including Apophis,Venus and Ceres,respectively.The optimal control problem is formulated using the calculus of variations and Pontryagin’s maximum principle,which leads to a bang-bang control that is solved by indirect method combined with a homotopic technique.In demonstrating the effects of the power constraints and solar array performance degradation on the power budget and fuel consumption,the time histories of the power profile and the fuel consumptions are compared for the three missions.This study indicates that it is necessary to consider the power constraints and solar array performance degradation for the SEP-based low-thrust trajectory design,espacially for long-duration outbound flights.

Crashworthiness of bamboo-inspired circular tubes used for the energy absorber of rail vehicles

A new type of thin-walled circular tubes(CTs),which is inspired by the bamboo with highly-efficient energy absorption(EA)capability,was proposed and designed for the potential application of the energy absorber of rail vehicles in this study.And then,the axial crushing behavior and crashworthiness of the bamboo-inspired bionic tube(BT)were experimentally and numerically investigated,compared with the single CT and foam-filled tube(FT).The typical crushing responses(e.g.,deformation mode,load-displacement response,energy absorption,and strain distribution)and quantitative crashworthiness indicators(EA,SEA,FP,Fm,and CFE)of these three types of CTs were presented and discussed.Effects of impact velocity and foam relative density on the crashworthiness of tested tubes were also explored.The experimental and simulation results show that the BT specimen exhibits the best capability of load-carrying,energy absorption,and crashworthiness among three types of tubes.Compared with the CT specimen,the EA value of BT specimens increased by 93.1%,while the corresponding Fm value raised from 74.2 kN to 143.4 kN.

Nature of the Ga-Ga bonding in Na_2[Arx~*GaGaArx~*](Arx~*=C_6H_3 -2,6-(C_6H_5)_2):Electron localization function analysis

The nature of the Ga-Ga bonding in Na2[Arx＊GaGaArx＊] （Arx＊ = C6H3-2,6-（C6Hs）2） has been investigated and compared with that of in Hz[Arx＊GaGaArx＊] using electron localization function （ELF） and orbital analysis. The calculation results show that in Na2[Arx＊GaGaArx＊], the Ga-Ga interaction is a non-classical triple bond, the heart of Na2[Arx＊GaGaArx＊] is the Ga2Na2 cluster rather than a simple Ga-Ga bond, and the contribution of the sodium atoms to the short Ga-Ga bond length is considerable. As the two sodium atoms are substituted by two hydrogen atoms, the Ga-Ga bond is replaced by two 3-center, 2-electron （3c-2e） Ga-H-Ga covalent bridged bonding.