APU故障智能诊断系统设计

针对高旋环境下测试困难、测量精度低这一问题,提出了一种能在高旋环境下实现轴向减速装置,以达到稳定的良好的测试环境。该装置通过驱动仓内大量程陀螺仪测得的转速反馈给控制系统,控制系统输出控制信号来控制伺服电机,同时电机捷联内筒仓,使其相对外部转动方向反向旋转,实现轴向减速。实验结果表明,该装置可在高旋弹药飞行过程中提供稳定测试环境,从而得到更精准的姿态解算结果,为高旋环境下的测试提供了新的思路,具有广阔的应用前景。     

Numerical and empirical modeling of peak deceleration and stress analysis of polyurethane elastomer under impact loading test

In this work, we present the modeling of the peak deceleration (PD) using data of the experimental drop test. Specimens with different thicknesses and areas tested in the drop test device which has adaptable height and weight. In the empirical modeling of the PD, the thickness, area, drop mass and drop height considered as separable functions. An analytical model and Neural Network (NN) was used as the empirical models. Further, the stress on the material was calculated using differential equations and the Finite Element Method (FEM). The Obtained PD from the experimental test, analytical and NN models was converted to the stress on the material using a derived differential equation. Finally, the best model for analyzing the PD and Stress on the material was presented.     

混凝土复合靶结构参数对侵彻过载的影响

混凝土复合靶基体靶板的层数和中间粘结层厚度是复合靶能否模拟单一靶的两个重要影响因 素, 利用AUTODYN2D仿真软件, 重点研究了这两个因素对弹体侵彻过载的影响. 首先通 过已有的实验和理论公式验证了初始仿真模型和材料参数的合理性. 在此基础上, 通过改变 基体靶板的层数和中间粘结层厚度建立了多组侵彻复合靶的仿真算例. 通过弹体侵彻速度、 过载曲线的对比, 结果表明: 全尺寸深侵彻过载实验中复合靶能够代替单一靶, 但复合靶中 间粘结层的厚度不要大于1/2弹头部长度; 当中间粘结层厚度超过弹头部长度1/2时, 弹体 侵彻复合靶过载与侵彻单一靶的偏离程度随基体靶板层数的增加而增大, 上述结论可为实验 中构建混凝土复合靶提供参考.     

弹体侵彻与贯穿有限厚度混凝土靶体的力学特性

为了便于研究弹体贯穿混凝土靶体的力学本质,首先假设钻地弹是刚性弹体。在水动力侵彻模型的基础上,认为在弹体的冲击下,靶体裂缝扩展到靶体背面时就开始不稳定增长。将此时刻作为贯穿的发生时刻,据此利用裂缝增长的耗能机制求得了发生贯穿时,裂缝距靶体背面的临界距离。在求解贯穿发生后的侵彻阻抗力时考虑了由于靶体背面贯穿块的运动而造成的弹体相对速度的降低。计算表明,弹体端部侵入靶体与贯穿发生后2阶段弹体的减加速度变化剧烈,而弹体端部完全进入靶体后至发生贯穿阶段,弹体的减加速度变化相对较小。将计算结果与前人实验做了对比,验证了结果的可信性。 更多还原     

Curvature Inspired Cosmological Scenario

Using modified gravity with non-linear terms of curvature, R ² and R ^(2+r) (with r being a positive real number and R being the scalar curvature), cosmological scenario, beginning at the Planck scale, is obtained. Here a unified picture of cosmology is obtained from f(R)-gravity. In this scenario, universe begins with power-law inflation followed by deceleration and acceleration in the late universe as well as possible collapse of the universe in future. It is different from f(R)-dark energy models with non-linear curvature terms assumed as dark energy. Here, dark energy terms are induced by linear as well as non-linear terms of curvature in Friedmann equation being derived from modified gravity. It is also interesting to see that, in this model, dark radiation and dark matter terms emerge spontaneously from the gravitational sector. It is found that dark energy, obtained here, behaves as quintessence in the early universe and phantom in the late universe. Moreover, analogous to brane-tension in brane-gravity inspired Friedmann equation, a tension term λ arises here being called as cosmic tension, It is found that, in the late universe, Friedmann equation (obtained here) contains a term −ρ ²/2λ (ρ being the phantom energy density) analogous to a similar term in Friedmann equation with loop quantum effects, if λ>0 and brane-gravity correction when λ<0.     

Future Destiny of Quintessential Universe and Constraint on Model from Deceleration Parameter

The evolution of the quintessence in various stages of the universe, i.e., the radiation-, matter-, and quintessence-dominated stages, is closely related with the tracking behavior and the deceleration parameter of the universe. We gave the explicit relation between the equation-of-state of the quintessence in the epoch of the matter-quintessence equality and the inverse power index of the quintessence potential, obtained the constraint on this potential parameter coming from the present deceleration parameter, i.e., a low inverse power index. We point out that the low inverse power-law potential with a single term cannot work for the tracking solution. In order to have both of the tracker and the suitable deceleration parameter it is necessary to introduce at least two terms in the quintessence potential. We give the future evolution of the quintessential universe.     

Cold Molecules: Preparation,Applications, and Challenges

Research with cold molecules has developed rapidly in recent years. There is now a variety of established methods for cooling molecules into the millikelvin range. Nevertheless, a focal point of current research is directed toward finding new ways to bring the temperature of molecules even closer to absolute zero. Samples of cold molecules offer not only important applications for high‐resolution spectroscopy, which benefit from the increased interaction time of slow molecules with electromagnetic radiation; they also promise access to an exotic regime of chemical reactivity, in which phenomena such as quantum tunneling and quantum resonances predominate. This review begins with an introduction to the methods by which cold molecules can be prepared, with special emphasis on Stark deceleration and traps. In addition to applications of cold molecules that have already been partially achieved, an important focus of the review concentrates on possible future applications, and both aspects are illustrated with selected examples.     

Equation of motion for a radiating charged particle in classical electrodynamics

We propose classical equations of motion for charged particles in an electromagnetic field. These are general formulas for the particle acceleration that take the radiation-induced deceleration into account and contain no second derivatives of the particle velocity. In several particular cases considered, the new equations yield results coinciding with those known in the literature and experimentally verified. We show that in the range of ultrahigh energies, classical electrodynamics does not lead to inherent inconsistencies and in principle allows particle motion with energies exceeding the Pomeranchuk limit.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 143, No. 1, pp. 112–130, April, 2005.     

The Hubble diagram of metal-rich QSOs and deceleration parameter q0

For 163 metal-rich Quasars, the m_v-logZ diagram shows a very close correlation. Using multiple regression analysis for these sources (N = 163), we obtained q₀,= 1.142 and correlation coefficient γ = 0.69. These results suggested that the Universe is closed and all metal-rich quasars are of a single category. On the other hand, the evolution is very small at Z⩽2 for metal-rich quasars.     

长杆高速侵彻的特征控制参量分析

针对理想长杆侵彻,通过对长杆侵彻Alekseevskii-Tate模型近似解进行分析,指出单一的无量纲速度衰减系数α（deceleration index）不足以完全表征长杆高速侵彻的准定常阶段。在此基础上,重新定义了2个无量纲特征参量:Johnson破坏数Φ_Jp和特征时间系数β,2个参量之间的关系为α=β/Φ_Jp。分析表明,Φ_Jp和β（或α和β）可实现对长杆高速侵彻准定常阶段的弹尾速度的完全表征;若再引入长杆弹相对临界速度v_c*,则可完全表征长杆侵彻的准定常阶段。此外,还证明了α能够判定侵彻过程偏离定常状态的程度,并指出通过确定Φ_Jp和β（或α和β）,可针对攻防需求对长杆弹侵彻设计进行指导。