钛合金表面抗激光涂层损伤特性及热效应影响研究

实验研究了钛合金和高反射型陶瓷涂层材料抗连续型激光烧蚀的损伤及温度分布特性，并从热效应影响角度对比分析了二者在抗激光损伤效果方面的差异性。研究结果表明：相比于钛合金，高反射型陶瓷涂层材料能有效增强钛合金基底抗激光损伤的能力；在同等激光功率密度辐照下，陶瓷涂层材料能有效提升钛合金基底耐受激光辐照的时间长度。实验结果表明该陶瓷涂层材料的激光损伤阈值比钛合金高约5.8倍。实验发现陶瓷涂层温升速率高于钛合金，但由于陶瓷材料具有较高的反射特性，以及良好的热吸收和热传导特性，因此能使由激光辐照产生的热量在其表面较快地扩散，而降低向基底方向传导的程度，最终提升陶瓷涂层的抗激光损伤阈值。     

Orbit-attitude-vibration coupled dynamics of tethered solar power satellite

A new orbit-attitude-vibration coupled dynamic model of the tethered solar power satellite (Tethered SPS) is established based on absolute nodal coordinate formulation. The Hamilton’s equation of the system is derived by introducing generalized momentum through Legendre transformation. The correctness of the proposed model is verified by an example. The dynamic characteristics of the Tethered SPS are studied using the symplectic Runge-Kutta method. Simulation results show that the orbital radius and the total energy of the system are well preserved. The attitude of the system is unstable when the mass of the bus system is small. However, the attitude stability is dependent on some other parameters of the system, which requires further studies. It is also found that the average tether force/deformation can be roughly estimated by simplifying the solar panel as a particle. The proposed model can be used to study the orbit-attitude-vibration coupled dynamics and control problems.     

Effect of matching between the magnetic field and channel length on the performance of low sputtering Hall thrusters

Discharge characteristics of a non-wall-loss Hall thruster were studied under different channel lengths using a design based on pushing a magnetic field through a double permanent magnet ring. The effect of different magnetic field intensities and channel lengths on ionization, efficiency, and plume divergence angle were studied. The experimental results show that propellant utilization is improved for optimal matching between the magnetic field and channel length. While matching the magnetic field and channel length, the ionization position of the neutral gas changes. The ion flow is effectively controlled, allowing the thrust force, specific impulse, and efficiency to be improved. Our study shows that the channel length is an important design parameter to consider for improving the performance of non-wall-loss Hall thrusters.     

太阳能飞机循环飞行的高度剖面能量策略

为满足设定的太阳能飞机多日连续飞行条件，依据飞行过程中当前时刻的飞行高度、光伏输出功率、动力电池组余量等系统状态参数，研究如何分配动力电池组充放电和电推进系统输入等功率。所用策略立足于实时功率平衡，充分利用正午前后的光伏峰值功率用于飞机爬升及充电，在午后下滑过程中利用全部光伏输出，以最大化利用光伏资源；在光伏有效输出不足时则以一定的维持功率下滑，使能量的综合损失最小。方法能够提高以预定夜间飞行高度连续多日续航的成功率，提升飞行高度、纬度、季节范围或搭载能力，或者拓展这几种飞行条件的组合域，优化太阳能飞机的适用性。     

Orbital stability close to asteroid 624 Hektor using the polyhedral model

We investigate the orbital stability close to the unique L4-point Jupiter binary Trojan asteroid 624 Hektor. The gravitational potential of 624 Hektor is calculated using the polyhedron model with observational data of 2038 faces and 1021 vertexes. Previous studies have presented three different density values for 624 Hektor. The equilibrium points in the gravitational potential of 624 Hektor with different density values have been studied in detail. There are five equilibrium points in the gravitational potential of 624 Hektor no matter the density value. The positions, Jacobian, eigenvalues, topological cases, stability, as well as the Hessian matrix of the equilibrium points are investigated. For the three different density values the number, topological cases, and the stability of the equilibrium points with different density values are the same. However, the positions of the equilibrium points vary with the density value of the asteroid 624 Hektor. The outer equilibrium points move away from the asteroid’s mass center when the density increases, and the inner equilibrium point moves close to the asteroid’s mass center when the density increases. There exist unstable periodic orbits near the surface of 624 Hektor. We calculated an orbit near the primary’s equatorial plane of this binary Trojan asteroid; the results indicate that the orbit remains stable after 28.8375?d.     

年薪制与国有企业经营者激励机制的研究

中国加入WTO后 ,市场化改革将逐步深入 ,完善国有企业经营者激励机制显得尤为紧迫。目前国有企业普遍推行的年薪制在实施方案上存在明显缺陷 ,必须加以改进和完善 ,而整个企业体制改革的不到位 ,也制约着经营者激励机制的形成 ,因此要尽快突破体制上存在的主要障碍。     

FET振荡器注入锁相伏特拉级数分析

应用伏特拉级数法分析了电容耦合ＦＥＴ振荡系统在外加信号下的注入锁定现象，推导出输出信号和注入锁定带宽表达式。与一般非线性系统分析方法相比，伏特拉级数法在建立好系统模型后只需进行代数运算，从而避开了求解非线性，非齐次高阶微分方程的复杂过程。     

Parametric Rao Test for Multichannel Adaptive Signal Detection

The parametric Rao test for a multichannel adaptive signal detection problem is derived by modeling the disturbance signal as a multichannel autoregressive (AR) process. Interestingly, the parametric Rao test takes a form identical to that of the recently introduced parametric adaptive matched filter (PAMF) detector for space-time adaptive processing (STAP) in airborne surveillance radar systems and other similar applications. The equivalence offers new insights into the performance and implementation of the PAMF detector. Specifically, the Rao/PAMF detector is asymptotically (for large samples) a parametric generalized likelihood ratio test (GLRT), due to an asymptotic equivalence between the Rao test and the GLRT. The asymptotic distribution of the Rao test statistic is obtained in closed form, which follows an exponential distribution under the null hypothesis H ₀ and, respectively, a noncentral Chi-squared distribution with two degrees of freedom under the alternative hypothesis H ₁. The noncentrality parameter of the noncentral Chi-squared distribution is determined by the output signal-to-interference-plus-noise ratio (SINR) of a temporal whitening filter. Since the asymptotic distribution under H ₀ is independent of the unknown parameters, the Rao/PAMF asymptotically achieves constant false alarm rate (CFAR). Numerical results show that these results are accurate in predicting the performance of the parametric Rao/PAMF detector even with moderate data support.     

40Gb/s系统技术解决方案探讨

40Gh／8系统的应用面临光信号的色散、衰减、交换、编码等方面技术的挑战。利用固定补偿模块或源色散补偿技术可以实现光的精确色散及补偿。赖曼式放大器对40Gh／s系统的光传输提供了有力的技术支持，利用赖曼放大器以及全光交换机或光电光交换机则可以实现光信号的有效放大和高性能交换，而带外FEC技术和相应的编码技术可以进一步提高系统的容错能力及传输速率。