天基激光清除空间碎片任务分析

从天基激光技术参数和空间碎片清除需求两方面对天基激光碎片清除任务展开研究。基于激光支持爆轰波的传播机理,分析激光烧蚀推力的变化规律,揭示了短脉宽激光适用于碎片清除任务的原理,推导建立了激光烧蚀碎片的推力模型。对影响推力的典型激光参数进行研究,比较归纳了激光功率密度和光斑直径的通用求解模型,构建了最佳耦合条件下碎片速度增量与冲量耦合系数、脉冲个数之间的数学模型。从碎片尺寸和轨道区域两方面分析了将太阳同步轨道1~10 cm碎片作为清除对象的必要性,基于清除任务的合理性提出天基激光和碎片在“偶遇”条件下的作用模式,给出了清除距离和清除时间窗口。运用轨道动力学知识建立了基于近地点高度增量的天基激光碎片清除效果评估模型,案例分析表明了天基激光清除碎片的可行性。研究成果可为相关技术研究和任务设计提供参考。     

Advanced continuous phase modulation for high mobility communications

This paper focuses on the design of continuous phase-modulated systems and simplified receiver for high- mobility wireless communications. A class of spectrally efficient coded modulation systems is proposed and ana- lyzed in terms of Euclidean distance and spectral effi- ciency. Moreover, the simplified detector based on mismatched receiver is designed to reduce the detection complexity exponentially for partial response systems. To deal with the fast time-varying channels without channel state information, a class of noncoherent detection algo- rithms for continuous phase modulation systems is devel- oped to offer near-coherent performance. The proposed system is assessed over both the additive white Gaussian noise and fast-fading channels. Numerical and simulated results show that the proposed system offers not only high spectral efficiency but also near-optimum performance over fast time-varying scenarios.     

用于无线数字传输的双相编码调制

阐述了可变相移键控(VPSK)和甚小频移键控(VMSK)基带数字调制技术编解码原理，给出了双相码基带信号频谱的一般数学表达式和计算机仿真得出的频谱图.对VPSK和VMSK信号的频谱 利用率作出初步估计，并提出了基于FPGA的编解码器实现方案.     

脉搏波的复杂网络分析

脉搏波是人体重要的生理信号之一,从新的角度探索脉搏波的分析手段是脉搏波研究的一个重要方向.在分析现有脉搏波时域、频域分析方法的基础上,将复杂网络的分析方法引入脉搏波的分析之中,以拓展脉搏波的研究维度.分析了时间序列的网络化方法的现状,选择使用基于水平可见性(horizontal visibility graphs,HVG)的网络化方法对脉搏波进行网络化分析.获得使用脉搏波构建的网络的特性参数,确定了脉搏波网络的无标度特性,并从生理状态的角度进行了解释,为脉搏波的研究提供了一种新的手段.     

S变换在地震时频分析中的对比研究

介绍了S变换基本原理的基础上,通过设计实验数据,对比Fourier变换、短时窗傅立叶变换和S变换的时频分析特点,最后对地震数据分别应用S变换和Gabor变换,认为S变换具有自身独特的优点,更适合于地震资料的时频分析。     

多波束系统波束宽度对水深点不确定度影响分析

为了揭示多波束测深系统波束宽度对水深点垂直不确定度和水平不确定度的影响,采用理论分析和实验验证的方法,证明了波束宽度对不确定度的作用随波束倾斜角度的增加而增大;给出了波束宽度导致的垂直和水平误差计算模型,提出了波束宽度效应改正模型。该成果为准确计算水深点不确定度提供了理论依据。     

Effects of sample width on flame spread over horizontal charring solid surfaces on a plateau

Experiments were conducted on the Tibetan Plateau to investigate the effects of sample width (W) on flame spread over horizontal charring solid surfaces. The results show that the rate of spread is influenced by the combined effects of convection heat transfer and flame radiation. Moreover, two different regimes depending on sample width were found in flame spread behavior. The rate of spread decreased with width in the convective regime (W≤3 cm) but increased in the radiative regime (W>3 cm). Similar results were observed in comparative experiments conducted on a plain in Hefei, with the rate of spread reaching its minimum value at W=4 cm rather than 3 cm.     

普适单体偏振高维量子态幺正操作的光学实现

如何有效地实现高维量子态的制备和操控是量子信息科学研究的一个热点,我们在光学领域,基于线性光学技术和交叉相位调制技术,利用偏振高维量子态与单光子空间高维量子态的纠缠操作,实现这两类高维量子态之间的相互转换.由此,利用单光子空间高维量子态幺正操作的易实现性,可以间接实现偏振高维量子态的幺正操作.这一实现模式超越以往只适用于三维量子态操作的限制,适用于任意维度的单体高维量子态操作,可为高维量子态的深入研究提供一定的便利.     

Modulation of optical absorption edge in TiO2/SiO2 mesoporous composites

TiO-2/SiO-2 mesoporous composite was synthesized by soaking_hydrolyzing method and its structure was characterized. The relationship between the shift of absorption edge and the amount of TiO-2 nanoparticles within the mesopores of SiO-2 as well as the annealing temperature was investigated. The results indicate that the extent of the blue shift of absorption edge increases with the decreasing amount of nanoparticles and decreases wtih the increasing annealing temperature.     

天然锡中子反应数据的评价和理论计算

对天然锡中子反应的实验数据进行评价，并用光学模型（ＯＰＭ）、带宽度涨落修正的豪泽－费许巴哈理论（ＷＨＦ）以及平衡前发射的蒸发模型（ＰＥＭ），计算了入射能量为１～２０ＭｅＶ的中子与锡核相互作用的反应数据．计算结果与评价实验值符合较好．