一种时频混叠的欠定混合通信信号盲分离算法

针对衰减-延迟欠定混合通信信号的盲分离问题,提出了一种基于子空间最小距离的源信号估计算法,通过计算观测信号到混合矩阵列矢量张成子空间的距离,估计任意时频点同时存在的源信号数目以及当前源信号对应的混合矩阵列矢量,把欠定混合问题转化为超定问题,然后通过计算Moore-Penrose逆矩阵求解源信号,理论分析和仿真结果验证了算法的有效性。     

汉乐府名篇教学探析

乐府是汉代文学的重要部分，对五言诗歌的成熟起了极为重要的作用。在古代文学的教学过程中，将汉乐府和先秦时期的诗经、楚辞进行比较，从思想内容、叙事艺术、人物形象等方面解读汉乐府中的名篇，可以让学生更好地理解掌握汉代文学的特点。     

A Good Ally - Norway and International Statebuilding in Afghanistan, 2001-2014

The article examines the findings of the Commission of Inquiry established by the Norwegian government in 2014 to evaluate all aspects of Norway’s civilian and military contribution to the international operation in Afghanistan from 2001 to 2014. Concerned with the wider implications of the Commission’s findings, it focuses on two issues in particular: (1) Norway’s relations with the US, a close and long-standing strategic ally whose resources, capabilities and dominance of decision-making dwarfed that of all other coalition partners in Afghanistan; and (2) Norway’s record in the province of Faryab, where, from 2005 to 2012, a Norwegian-led Provincial Reconstruction Team was charged with bringing security, good governance and development to the province. How Norway prioritised and managed relations with the US highlights and helps to problematise the challenges – political, practical and moral – facing small and medium-sized powers operating in a coalition alongside the US. Norwegian efforts in Faryab are revealing of the dilemmas and contradictions that plagued and, ultimately, fatally undermined the international intervention as a whole. As such, Norway’s experience provides a microcosm through which the inherent limitations of the attempt to transfer the structures of modern statehood and Western democracy to Afghanistan can be better understood.     

Fabrication of AA7005/TiB2-B4C surface composite by friction stir processing: Evaluation of ballistic behaviour

The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB₂ and B₄C ceramic reinforcement particles. Surface composites with different weight fractions of TiB₂ and B₄C particles were processed by friction stir processing. Micro-hardness and depth of penetration tests were carried out to evaluate the ballistic properties of the surface composites. The surface hardness of the composite was found to be nearly 70 HV higher than base alloy. The depth of penetration of the steel projectile was 20–26 mm in the composites as compared to 37 mm in the base alloy. Ballistic mass efficiency factor of the surface composite was found to be 1.6 times higher than base alloy. This is mainly attributed to the dispersion strengthening from the reinforcement particles.     

Determination of burn‐in parameters and residual life for highly reliable products

Today, many products are designed and manufactured to function for a long period of time before they fail. Determining product reliability is a great challenge to manufacturers of highly reliable products with only a relatively short period of time available for internal life testing. In particular, it may be difficult to determine optimal burn‐in parameters and characterize the residual life distribution. A promising alternative is to use data on a quality characteristic (QC) whose degradation over time can be related to product failure. Typically, product failure corresponds to the first passage time of the degradation path beyond a critical value. If degradation paths can be modeled properly, one can predict failure time and determine the life distribution without actually observing failures. In this paper, we first use a Wiener process to describe the continuous degradation path of the quality characteristic of the product. A Wiener process allows nonconstant variance and nonzero correlation among data collected at different time points. We propose a decision rule for classifying a unit as normal or weak, and give an economic model for determining the optimal termination time and other parameters of a burn‐in test. Next, we propose a method for assessing the product's lifetime distribution of the passed units. The proposed methodologies are all based only on the product's initial observed degradation data. Finally, an example of an electronic product, namely contact image scanner (CIS), is used to illustrate the proposed procedure. © 2002 Wiley Periodicals, Inc. Naval Research Logistics, 2003     

伟大的旗帜深刻的意蕴

党的十七大鲜明确立了中国特色社会主义旗帜的指导地位。中国特色社会主义旗帜,是马克思主义真理观和价值观相统一的旗帜;其精神实质,是坚持科学社会主义基本原则与根据我国实际和时代特征赋予其鲜明中国特色的有机统一;其实践形态,是中国特色社会主义道路;其理论形态,是中国特色社会主义理论体系。高举中国特色社会主义伟大旗帜,就需要倍加珍惜、长期坚持和不断发展这条道路和理论体系。     

A general model of heterogeneous system lifetimes and conditions for system burn‐in

Burn‐in is a technique to enhance reliability by eliminating weak items from a population of items having heterogeneous lifetimes. System burn‐in can improve system reliability, but the conditions for system burn‐in to be performed after component burn‐in remain a little understood mathematical challenge. To derive such conditions, we first introduce a general model of heterogeneous system lifetimes, in which the component burn‐in information and assembly problems are related to the prediction of system burn‐in. Many existing system burn‐in models become special cases and two important results are identified. First, heterogeneous system lifetimes can be understood naturally as a consequence of heterogeneous component lifetimes and heterogeneous assembly quality. Second, system burn‐in is effective if assembly quality variation in the components and connections which are arranged in series is greater than a threshold, where the threshold depends on the system structure and component failure rates. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 364–380, 2003.     

坦克装甲车辆火控技术的现状及发展

对坦克火控系统的技术现状和发展前景进行了较为详尽的论述,并指出了当前国内火控发展中面临的主要技术难题及解决办法.     

风场的科学计算可视化在导弹射击中的应用

在导弹射击时,消除风会对导弹飞行造成不利的影响,因此基于可视化分析的研究模型、流程等,利用科学计算方法直观分析优点对风的大小和方向进行分析,并采用开放图形接口对实验风场数据进行了三维图形绘制以提高导弹打击目标的精度,对实际中导弹的风场阻力研究有一定的指导意义.     

切向空气气流对激光辐照碳纤维复合材料的影响

实验研究了靶材表面存在和不存在切向空气气流时,975nm连续激光对碳纤维增强树脂基复合材料的辐照效应,发现切向气流的加载有利于激光对碳纤维复合材料的破坏.从理论上对激光辐照下碳纤维复合材料的破坏机理进行了初步分析,基于碳的氧化特性和氧化反应机理,推导了碳纤维的氧化速率方程.采用改进的光滑粒子方法,对激光辐照下复合材料树...