TC11钛合金在疲劳－蠕变交互作用下的形变特征及位错结构

 研究了经常规,近β和β锻造工艺所获得的具有等轴、双态和网篮３种显微组织的ＴＣ１１钛合金在疲劳－蠕变交互作用下的形变特性及位错结构。发现不同显微组织或同一组织内部的初生α和条状α具有的层错能不同是形成不同位错亚结构的根本原因。     

活动网络计划约束的复杂性度量及其应用

根据反映活动网络计划约束特征的节点的紧前紧后活动数,提出了一个衡量活动网络计划约束的复杂系数──网络复杂性系数（ＣＮＣ）,并结合有资源约束的网络计划问题提出了一个衡量该类问题的复杂性系数──资源约束的网络复杂性系数（ＣＲＮＣ）,最后介绍了网络复杂性系数在随机活动网络发生器算法设计中的应用,给出了一个产生给定复杂系数的随机活动网络的随机活动网络发生器的设计算法。     

Ti—15—3合金时效性能研究

研究了不同炉号的Ｔｉ－１５－３（Ｔｉ－１５Ｖ－３Ｃｒ－３Ｓｎ－３Ａｌ）合金时效温度、时间以及Ａｌ当量与力学性能的关系。在５００～５４０℃范围内拉伸强度与时效温度呈线性关系,平均斜率为－３ＭＰａ／℃。得出了强度与Ａｌ当量的线性方程式,推算出最佳Ａｌ含量为３．１％～３．３％。采用统计方法研究了强度与塑性关系,并研究了冷加工对时效性能的影响。研究的达到１０８０ＭＰａ强度级别的５２０℃／１０ｈ／ＡＣ的时效制度具有满意的力学性能,并应用于制造飞机阻力伞梁。     

基于VHDL语言的扩频相关器设计与实现

介绍了扩频相关器在信号处理中对特定码字进行相关处理,完成信号的解扩或解码,恢复出传送的信息.扩频相关器采用数字处理方式,处理信号的形式比较灵活,可以对不同的码型、不同的码长进行相关处理,为位同步的提取带来了极大的方便.设计了包含相关器的整个直扩系统,并进行了仿真,验证了所设计的相关器的正确性.     

Si-Ti-C-O纤维的XPS研究

运用ＸＰＳ分析手段系统研究了Ｓｉ－Ｔｉ－Ｃ－Ｏ纤维的线成及其结构,并与ＳｉＣ纤维进行比较,讨论了引入Ｔｉ后纤维的组成与结构的变化及其性能的关系。     

Si3N4—SiC纤维先驱体——低分子量聚硅氮烷的合成与分析

以ＭｅＳｉＣｌ２（式中Ｍｅ代表ＣＨ３）或共混合物与ＮＨ３反应制得低分子量聚硅氮烷，该产物是制备Ｓｉ３Ｎ４－ＳｉＣ纤维先驱体的基本原料。研究了不同配比的Ｍｅ２ＳｉＣｌ２／ＭｅＳｉＨＣｌ２混合物氨解反应所需的时间，氨解产物的物理性能、分子量及其分布，着重要分析了氨解产物的结构。     

俯仰振荡翼型跨音速粘性绕流的数值计算

以ＬＵ－ＴＶＤ混合格式求解二维非定常湍流Ｎ－Ｓ方程,计算了绕１／４弦点振荡的翼型跨音速粘性绕流解,与实验结果吻合较好。通过取不同ＣＦＬ数计算表明：在能得到非定常稳态解的情况下,取小ＣＦＬ数更能真实地反映非定常时间历程,具有更高的可信度     

军用运输机发展浅析

首先介绍了军用运输机在现代战争中的作用和地位,阐述了当前军用运输机的发展现状,详细论述了Ｃ－１７、Ｃ－１３０Ｊ、Ａｎ－７０这三种当前最新型军用运输机的各项技术性能,对其各性能指标列表进行了对比,最后归纳总结出当前军用运输机的发展趋势,并对发展我国大型军用运输机提出了一些建议。     

基于神经网络的GAIN—SCHEDULED飞行控制器设计方法研究

采用神经网络设计ＧＡＩＮＳＣＨＥＤ－ＵＬＥＤ控制器，给出神经网络ＧＡＩＮ－ＳＣＨＥＤＵＬ－ＩＮＧ控制器的实现方法，这亲做可以简化控制器的ＳＣＨＥＤＵＬＩＮＧ参数，并且能够区分不同条件下的控制器结构。将其用于飞行控制器的设计，验证了所提方法的有效性。     

碳／碳复合材料表面沉积SiC的形态和成分

在ＰＡＮ碳布和沥青基体碳的Ｃ／Ｃ复合材料表面涂复了ＳｉＣ。用ＣＨ４和Ｎ,为载气的ＳｉＣｌ４作原料,用Ｈ２为稀释气,在两种气体混合比和三种温度下化学气相沉积ＳｉＣ涂层。分析表明,涂层的主要元素有Ｃ,Ｓｉ、Ｃｌ和微量Ｃａ。电镜观察表明,涂层中Ｃ原子含量为６２％时呈菜花状或云团状,而当Ｃ／Ｓｉ比接近于１时,表面呈菠萝状。     

Range Sidelobe Suppression for Barker Codes

The utility of Barker-type phase-reversal codes is extended by the use of sidelobe suppression techniques that can be easily implemented in digital form. It is shown that sidelobe suppression techniques can be found where the tapped delay line used to reduce the sidelobes has only a few distinct tap weights, in which case the complexity of the digital processor is greatly reduced. An example is given where the technique is applied to Barker codes with positive sidelobes, specifically, the 13-element Barker code. If higher pulse compression factors are desired than are obtainable with Barker codes, multistage Barker codes may be used. The sidelobes then may be suppressed for any one or all of the different coding stages.     

Effects of Random Implementation Errors in Matched Filters for Binary Phase Code Pulse Signals

The effects of implementation errors in tapped delay line filters on the peak-to-sidelobe ratio and the signal-to-noise ratio of binary PSK pulse compression codes are considered. As error model the delay elements and weighting factors of such filters are assumed to have an error distribution with known mean and variance.     

Design and analysis of new p(n,k) polyphase pulse compression codes

P(n,k) codes as a new class of polyphase pulse compression codes are introduced and analyzed in detail. The P(n,k) codes are conceptually derived by step approximation of the phase function of a nonlinear-frequency modulated (NLFM) Chirp signal with a favorable energy density spectrum. The significant advantages of P(n,k) codes over conventional polyphase codes are lower autocorrelation sidelobes and an improved tolerance of low Doppler shifts and precompression bandwidth limitations. The primary disadvantage of the P(n,k) codes over conventional codes is a loss in range resolution. The uniform P(n,k) codes are especially attractive for radars employing digital signal professing because their favorable correlation properties also remain when quantization effects are taken into account     

Quasi-Complementary Sequences

A method of constructing digital phase reversal codes which have few nonzero sidelobes and which are available in frequent lengths is given. This is particularly important in the area of longer codes. The codes are a form of combined sequence and, hence, have the desirable property of bandwidth reduction for the outer code. However, only two member codes are required. A major usage of these codes may be in addressing.     

线性分组码限距离译码器的性能分析

为了提高自动重传请求(ARQ)系统的通过率,在混合ARQ系统中,使用限距离译码器改善系统的性能。在限距离译码时,线性分组码纠正重量t的错误图样。纯纠错译码器和纯检错译码器都是限距离译码器的特例。本文首先介绍了Krautchouk多项式的几个重要性质,然后,用线性分组码及其对偶码的重量分布,分别导出了两种形式的错误译码概率的简化计算公式。由于生成函数方法的使用,成功地得到了重复码、汉明码和扩展汉明码的错误译码概率的解析公式,最后,讨论了Golay码和某些本原BCH码错误译码概率的计算方法。     

General forms and properties of zero cross-correlation radarwaveforms

General forms for both the complementary and noncomplementary zero cross-correlation waveform sets are developed. Various properties of these codes and their relationship to zero sidelobe periodic codes are stated and proved. Some radar applications and practical considerations of using these codes are briefly discussed     

互补编码导航信号的一种设计方法

本文叙述了互补编码导航信号的一种设计方法。证明了按此法构成的编码可保证时分多台导航系统在信号搜索过程中能自动识别主、副台,在信号跟踪过程中能抑制多次反射天波对地波的干扰。并给出了编码实例。     

GF(q)域上的低密度校验(LDPC)码的译码及其在深空通信中的应用

低密度校验码是一类能有效逼近香农限的好码,而高进制的LDPC码具有比二进制LDPC码更好的性能,但其译码复杂度太高不利于工程应用。本文提出了一种基于协同优化算法的低复杂度的高进制LDPC码的译码算法,并讨论了其在深空通信中的应用。     

Effects of Doppler Mismatch on Combined Barker Codes

The output response of a matched filter for several cases of combined Barker codes is computed for various amounts of Doppler mismatch. It is shown that combined Barker codes, like conventional Barker codes, are extremely sensitive to Doppler shift.     

Ambiguity properties of quadratic congruential coding

The ambiguity characteristics of multiple access frequency hop codes based on standard quadratic congruences are investigated in the light of results obtained for codes based on Costas arrays and extended quadratic congruences. While the autoambiguity properties are found to be very similar to those of Costa codes, i.e. nearly ideal, the cross-ambiguity properties of quadratic congruential codes are much better. These results are valid across the whole class of code sets considered, but they are obtained at some expense in the pulse compression characteristics of the codes. A uniform upper bound is placed on the entire cross-ambiguity function surface, and bounds are placed on the amplitude of spurious peaks in the autoambiguity function. These bounds depend on the time-bandwidth product and code length exclusively and lead naturally to a discussion of the design tradeoffs for these two parameters. Examples of typical autoambiguity and cross-ambiguity functions are given to illustrate the performance of quadratic congruential coding with respect to Costas coding