滑窗式谱减法在航空降噪中的应用

航空噪声的存在严重影响了机务人员和地勤人员的通信及健康,降低噪声是解决这一问题的有效途径。文章提出了一种新的改进谱减法,根据采集的真实航空噪声数据,将传统谱减法和改进的谱减法结果进行了比、较,计算结果表明,改进形式的谱减法可以有效降低航空噪声,提高语音的可懂度和信噪比。     

Observations of the local interstellar medium with the Extreme Ultraviolet Explorer

Because of the strong absorption of extreme ultraviolet radiation by hydrogen and helium, almost every observation with the Extreme Ultraviolet Explorer (EUVE) satellite is affected by the diffuse clouds of neutral gas in the local interstellar medium (LISM). This paper reviews some of the highlights of the EUVE results on the distribution and physical state of the LISM and the implications of these results with respect to the interface of the LISM and the heliosphere. The distribution of sources found with the EUVE all-sky surveys shows an enhancement in absorption toward the galactic center. Individual spectra toward nearby continuum sources provide evidence of a greater ionization of helium than hydrogen in the Local Cloud with an mean ratio of H I/He I of 14.7. The spectral distribution of the EUV stellar radiation field has been measured, which provides a lower limit to local H II and He II densities, but this radiation field alone cannot explain the local helium ionization. A combination of EUVE measurements of H I, He I, and He II columns plus the measurement of the local He I density with interplanetary probes can place constraints on the local values of the H I density outside the heliosphere to lie between 0.15 and 0.34 cm^–3 while the H II density ranges between 0.0 and 0.14 cm^–3. The thermal pressure (P/k = nT) of the Local Cloud is derived to be between 1700 and 2300 cm^–3 K, a factor of 2 to 3 above previous estimates.     

Local clouds: Distribution, density and kinematics through ground-based and HST spectroscopy

The distribution, kinematics and physical properties of the interstellar matter surrounding the Sun can be inferred from ground-based and UV spectroscopic observations. On a 200 pc scale the local interstellar matter appears inhomogeneous and asymmetric. Although it generally flows towards the lower density region, it is composed of numerous small components a few parsecs in size with slightly different velocities. On a smaller scale the extent and the nature of the Local Cloud which flows over the Sun are discussed based on HST-GHRS observations of nearby stars.     

关键参数对二冲程煤油发动机爆震的影响

针对二冲程汽油发动机改用航空煤油后的爆震抑制和性能恢复进行了研究,利用GT-Power软件建立发动机的一维仿真模型并对煤油发动机的爆震进行了预测和优化。仿真结果表明:推迟点火时刻、远低于和远大于理论空燃比的混合气对爆震都有一定的抑制作用,试验结果验证了仿真结果的正确性。提出并采用协同推迟点火和增加喷油的控制策略进行试验研究。试验结果表明:在低转速大负荷工况下,爆震可被有效抑制,节气门全开时功率恢复在90%以上。发动机转速为5 500 r/min时,功率恢复能达到原机的95.7%。      

特种通用飞机改装流程及探讨

通过了解特种通用飞机改装流程及适航审批各阶段应开展的工作,对特种通用飞机改装过程中的注意事项进行了探讨,并给出了其适航审批过程中的合理化建议。     

小样本条件下航空武器打击精度评价算法

针对现有航空武器打击精度评价算法评价范围比较狭小,评价结果比较粗糙的问题,利用数理统计的理论和方法对航空武器打击精度的评价算法进行了深入研究,提出可变双临界值评价算法.对于给定的精度要求,通过调整可靠度,利用随之而变的上临界值与下临界值两个指标对航空武器打击精度进行准确客观的评价.理论分析和实例计算表明算法是有效可行的.     

军机维修一线体系管理的研究与设计

应用WSR系统工程方法．对军机维修系统进行分析和识别，构建了军机维修保障系统的管理控制模型．在此基础上，研究、设计并在军机维修一线实践了这一体系管理思想方法。     

环境友好型航空润滑油添加剂的研究现状及发展趋势

论述了对环境友好型航空润滑油的生态评价以及研究环境友好型航空润滑油添加剂的重要性。综述并分析摩擦改进剂、极压抗磨剂等可改善摩擦学性能的环境友好型航空润滑油添加剂的研究现状及研究内容,总结了环境友好型航空润滑油添加剂的主要发展方向。     

二维系统一般模型的正实控制

本文研究的是二维系统一般模型的正实控制。本文的目的是针对该模型,设计一个状态反馈控制器,使得闭环系统是稳定的并且闭环传递函数是延展严格正实的,所得到的解是通过线性矩阵不等式给出,通过解决该线性矩阵不等式可获得期待的状态反馈控制器。最后,我们提供了一个数值算例来验证提到方法的有效性。     

国内外航空乘务员招聘比较与探讨

从国内外航空公司乘务员的招聘过程中,比较各公司对乘务员要求和待遇上的差异,分析这些差异在实际工作中的表现和产生的效果。提醒国内航空公司更多的切实的关注乘务员的综合素质和真正的价值。