A survey of radio jets with Chandra and HST

Relativistic jets are a common property of radio-loud Active Galactic Nuclei (AGN). Understanding jet physical properties is an essential precursor to understanding the mechanisms of energy transport, and ultimately, how energy is extracted from the central black hole. In this paper, I highlight recent developments from Chandra and HST observations of kpc-scale jets in AGN, with particular emphasis on our survey of 17 radio jets in a sample of FRII radio galaxies. These observations show that (1) X-ray and optical emission is common from kpc-scale jets, (2) a large fraction of the bolometric luminosity is emitted at X-rays, and (3) in most sources, a candidate emission process for the X-rays is inverse Compton scattering of the Cosmic Microwave Background off the relativistic electrons in the jet. If the latter scenario holds, the implication is that jets are still relativistic on kpc scales.     

喷管扩张段烧蚀的“台阶效应”计算

当喉衬和扩张段内衬采用具有不同烧蚀率的材料时,常出现“台阶效应”.本文以气动热化学烧蚀机理为基楚,提出应用适当的对流换热和加剧的化学反应计算对台阶效应区进行修正的方法,使台阶效应区的烧蚀率预示更切合实际工况.     

Microstructure,porosity and mechanical properties of selective laser melted AlSi10Mg

Finite element modeling (FEM), microscopy, X-ray computed tomography (CT) and mechanical property tests were used to study the microstructure, porosity and mechanical properties of an AlSi10Mg alloy produced by selective laser melting (SLM). The simulation of the melt pool and thermal history under different energy densities produced an optimized result with an energy density of 44.5 J·mm⁻³. The high cooling rate during the SLM process significantly refined the previous α-Al dendrites. The growth direction of the network-like Al-Si eutectic structure at different orientations confirmed the anisotropic nature of the microstructure. Furthermore, the microhardness, tensile testing and fracture analysis results proved that there were no obvious distinctions in the strength between the transverse and longitudinal directions, and that the ductility was anisotropic, possibly due to the shape and distribution of the pores. The pores measured by X-ray CT at different energy densities confirmed that the sphericity of the pores was inversely related to pores volumes. With optimized processing conditions, the porosity of the selective laser melted sample decreased leading to the improved fabricated fuel system component via SLM.     

DME脉冲调制信号波形参数对空间频谱占用的影响分析

航空测距器DME的开发、调试和性能验证都要用到高斯双脉冲调制格式的DME信号。由于专用的DME信号模拟器技术复杂、价格昂贵,人们常用具有快沿双脉冲调制功能的模拟信号源替代。本文以航空测距器DME信号要求为依据,初步分析了这种替代可能存在的问题,并通过实验对不同边沿条件下高斯双脉冲、矩形双脉冲调制信号的功率频谱占用情况进行了验证。     

试飞员能力模型研究

在飞行器研制和人类飞行探索中,试飞员的能力至关重要。针对以往对试飞员能力的评价基本停留在"客观、正确、诚信、能力以及尊重他人"等主观、感性层面,分析了试飞员在飞行器研制试验与鉴定中的作用和任务,给出了试飞员能力模型和"百分制"对试飞员的计划、飞行、评价、报告和建议等基本能力的量化分配。将试飞员能力显性化,有利于试飞员能力的客观评价。     

ASTROSAT

The ASTROSAT satellite is an Indian National Space Observatory under development in India. Due for launch in 2010, ASTROSAT will carry a complement of five scientific instruments enabling simultaneous observations from the optical through to the hard X-ray energy band. This capability will enable broad-band spectroscopy and high time-resolution monitoring of both galactic and extra-galactic targets, such as X-ray binaries and AGN. One of the instruments is being built in collaboration with the Canadian Space Agency and another in collaboration with the University of Leicester. ASTROSAT also carries a scanning sky monitor to observe the variable X-ray sky. After an initial period of science verification and guaranteed time, a certain fraction of ASTROSAT observing time will also be made available to the community via a call for proposals. Here I summarise the instrument complement and principle scientific objectives of the mission.     

微分法在定位误差分析与计算中的应用

介绍了微分法分析计算定位误差的原理和适用范围,通过生产实例分析,证明了该方法在解决多误差因素定位误差分析与计算中的简便与快捷,从而有效简化了复杂定位方案定位误差的分析与计算,提高了夹具的设计效率。     

丁腈橡胶增韧环氧树脂基烧蚀防热材料性能

以丁腈橡胶(CTBN)为增韧剂对环氧树脂(F51)进行增韧改性,通过FTIR、TG以及力学性能测试研究了丁腈橡胶对环氧树脂固化反应、热稳定性能和力学性能的影响,并分析了其增韧机理;分别采用燃气流剪切烧蚀试验和电弧风动烧蚀实验考核了低密度烧蚀材料的烧蚀性能。结果表明:经CTBN改性后,两者的分子链产生了一定程度的交联;树脂基体的拉伸、弯曲性能有所下降,但韧性得到了增强;热稳定性大大提高,增韧后的F51树脂在800℃时的残重率由增韧前的23%提高到了54%;低密度烧蚀材料的抗剪切、抗剥蚀能力得到了增强,且碳层的尺寸稳定性也得到了改善,烧蚀性能提高。     

Application of small-size antennas for estimation of angles of arrival of HF signals scattered by ionospheric irregularities

A modification of the Doppler Interferometry Technique is suggested to enable estimating angles of arrival of comparatively broadband HF signals scattered by random irregularities of the ionospheric plasma with the use of small-size weakly directional antennas. The technique is based on the measurements of cross-spectra phases of the probe radiation recorded at least in three spatially separated points. The developed algorithm has been used to investigate the angular and frequency-time characteristics of HF signals propagating at frequencies above the maximum usable one (MUF) for the direct radio path Moscow-Kharkiv. The received signal spectra show presence of three families of spatial components attributed, respectively, to scattering by plasma irregularities near the middle point of the radio path, ground backscatter signals and scattering of the sounding signals by the intense plasma turbulence associated with auroral activations. It has been shown that the regions responsible for the formation of the third family components are located well inside the auroral oval. The drift velocity and direction of the auroral ionosphere plasma have been determined. The obtained estimates are consistent with the classical conception of the ionospheric plasma convection at high latitudes and do not contradict the results of investigations of the auroral ionosphere dynamics using the SuperDARN network.     

基于H∞方法的控制系统作动器最优控制仿真研究

在设计控制系统模型时,首先引入了有限差分法(FDM)离散化后的波动方程,然后基于H∞最优控制原理,检查闭环控制系统的稳定性和可探测性,对控制系统传感器和作动器的位置进行优化配置.通过计算闭环反馈系统的范数,最终得到了控制系统的最优控制算法.仿真结果表明,利用波动方程来优化控制系统传感器和作动器位置的算法是可行的,可广泛应用于飞控系统的设计中.