The ITU and national regulatory authorities in the era of liberalization

As one of the most important organizations regulating telecommunications, the International Telecommunication Union (ITU) has a strong influence on the activities of National Regulatory Authorities (NRA)s. With the trend towards liberalization well underway, it is vital to study the relationships between the ITU and NRAs in this new era. This article examines the ITU's various functions and shows how they are vital to NRAs. It demonstrates that, notwithstanding the entry of the World Trade Organization into the telecommunications field, the ITU still has a role to play and that better cooperation between it and NRAs will lead to the healthy development of telecommunications.     

歼击机总体设计相关参数的模糊综合评判

 用模糊数学的方法，建立能够综合表达歼击机近距格斗机动性能的相关参数表达式。该参数可作为飞机总体设计阶段的设计目标，还可作为综合衡量歼击机机动性能的指标。     

单片微机8031构成的智能化频率计

详细介绍了应用8031单片机控制测频的工作原理及硬软件设计,对关键电路ICM7226B作了较详细的介绍。     

重复热处理工艺对30CrMnSiA钢疲劳性能的影响

本文介绍了30CrMnSiA钢的九种不同的重复热处理工艺，结果显示B种热处理工艺能使30CrMnsiA钢具有最佳的抗疲劳性能并证明不同的重复热处理状态对钢的疲劳性能有影响。     

轰六丁飞机超低空突防飞行性能分析

首先简要分析了低空和超低空突防飞行在战术上的优越性。并根据国内外有关的飞行实践，结合轰六丁飞机的实际飞行，从理论上较详细地分析了轰六丁飞机低空和超低空飞行的有关问题，如飞行速度和高度的选择、机动飞行的特点以及地面任务的保障等。最后，为保证飞行安全，充分发挥轰六丁飞机低空和超低空突防的作战能力提出了一些建议。     

飞行中飞机加油门后的动态特点分析

主要对飞机单纯加油门后的运动规律做了定量的理论计算，对定长周期运动进行了一定物分析，得出了飞机在小速度时加油后有三种可能的状态，即收敛、发散和中立稳定。并指出飞机加油门后的增速状态是暂时的，一般民政部下增速之后，是一个高度与速度相互转化的振荡过程。同时还指出低空小速度时，在加油门后暂时的增速过程中靠拉杆争取高度是不安全的。     

不连续增强镁基复合材料的制备与应用

综述了不连续增强镁基复合材料的制备工艺及特点，介绍了其应用情况，展望了其发展前景。     

部分喷嘴关闭对预旋供气系统参数均匀性影响的计算

为了研究部分喷嘴关闭对预旋供气系统的供气流量和供气温度及其均匀性的影响,采用稳态的固定转子相位法对180°旋转盘腔进行了数值模拟,并通过改变转子相位的稳态计算来近似模拟瞬态问题的时空变化特性。结果表明:在设计点工况(系统压比为1.32,旋转马赫数为0.678)下,喷嘴流通面积关闭14.3%时,引气总流量和供气总流量分别下降10.9%和9.9%。单个供气孔流量的波动幅度由1.1%增大为5.4%。供气的相对总温降低1 K左右,波动幅度由约0.5 K增大为1.5 K。     

适用于深空探测器的时间线转移路标启发式规划方法

针对深空探测器各子系统状态并行及约束耦合的特点,设计了最大转移代价计算方法,并在此基础上提出了时间线路标提取方法。然后,针对路标集合重复计算耗时长的问题,提出了路标增量式搜索算法实现路标集合动态快速更新,并进一步结合最大目标节点筛选策略提出了时间线转移路标启发式规划方法。仿真结果表明,时间线转移路标启发式规划方法能够有效减少冗余规划步数,提高规划求解效率。     

Numerical analysis on noise of rotor with unconventional blade tips based on CFD/Kirchhoff method

A solver is developed aiming at efficiently predicting rotor noise in hover and forward flight. In this solver, the nonlinear near-field solutions are calculated by a hybrid approach which includes the Navier-Stokes and Euler equations based on a moving-embedded grid system and adaptive grid methodology. A combination of the third-order upwind scheme and flux-difference splitting scheme, instead of the second-order center-difference scheme which may cause larger wake dissipation, has been employed in the present computational fluid dynamics (CFD) method. The sound pressure data in the near field can be calculated directly by solving the Navier-Stokes equations, and the sound propagation can be predicted by the Kirchhoff method. A harmonic expansion approach is presented for rotor far-field noise prediction, which gives an analytical expression for the integral function in the Kirchhoff formula. As a result, the interpolation process is simplified and the efficiency and accuracy of the interpolation are improved. Then, the high-speed impulsive (HIS) noise of a helicopter rotor at different tip Mach numbers and on different observers is calculated and analyzed in hover and forward flight, which shows a highly directional characteristic of the rotor HIS noise with a maximum value in the rotor plane, and the HSI noise weakens rapidly with the increasing of the directivity angle. In order to investigate the effects of the rotor blade-tip shape on its aeroacoustic characteristics, four kinds of blade tips are designed and their noise characteristics have been simulated. At last, a new unconventional CLOR-II blade tip has been designed, and the noise characteristics of the presented CLOR-II model rotor have been simulated and measured compared to the reference rotors with a rectangular or swept-back platform blade tip. The results demonstrate that the unconventional CLOR-II blade tip can significantly reduce the HSI noise of a rotor.