一种航母电磁飞机弹射系统研究

电磁发射技术一直是世界发达国家竞相发展的高新技术，是对传统发射技术的重大突破。电磁发射应用新的能源对物体驱动，从理论分析，其动能不受传统发射方式的能量限制，因而可以对大型物体以更高速度进行弹射。本文以直流直线电动机为驱动装置组成的航母电磁飞机弹射系统方案进行分析、计算，并通过原理试验验证了该方案的可行性。     

汽车电源系统电压波动抑制脉宽调制法

设计一种适用于现代燃油汽车的发电机电压控制器,实现了发电机电压的良好控制,并且减少了电压的波动,采用脉宽调制的方法控制发电机励磁系统,利用功率MOS管实现对励磁线圈电流的控制,利用PID算法进行脉宽的调节,最后通过试验验证了对发电机电压的良好控制。     

玄武岩纤维布加固连续梁弯矩重分布特征分析

对4根玄武岩纤维布加固的混凝土 T 形截面连续梁和1根对比梁进行抗弯试验,分析了试验梁的破坏模式和各控制截面的弯矩调幅系数.试验结果表明：加固梁跨中截面纵筋屈服前,加固梁和对比梁各控制截面荷载-挠度曲线基本重合;跨中截面纵筋屈服后,加固梁发生了明显的弯矩重分布,跨中截面弯矩调幅系数为0.09~0.22,中支座截面弯矩调幅系数为0.15~0.38;1~3层纤维布加固梁荷载-挠度曲线具有屈服平台,表现出明显的延性破坏特征.     

地铁屏蔽门门机驱动系统设计

门机驱动系统是地铁屏蔽门控制系统的重要组成部分.本驱动系统运用STM32F103RC处理器对无刷直流电机进行三闭环控制,实现了对屏蔽门的滑动门控制.对系统的设计原理、重要部分软件、硬件进行了描述.最后,通过对门机驱动系统进行测试和分析,确认该系统满足设计和实际使用要求.     

一种无线多跳网络业务性能跨层优化方法

为满足无线Mesh网络和Ad Hoc网络业务不同性能的要求,提出了一种跨层优化算法,给出了保证业务平均误包率的自适应调制编码的实现方法,并结合信道、冲突、缓冲区和业务要求等分析了业务性能.在此基础上,提出了调节误包率、优化业务吞吐率,并通过加权以满足业务不同吞吐率和延迟要求的优化算法,优化综合了物理层、MAC层、链路层和业务要求的影响.为验证算法的正确性,进行了仿真分析.结果表明,在给定的参数下,与未优化相比,丢包率约减小35.3%,延迟约降低65.6%.     

Gas turbulence modulation model for gas-solid flows in two-fluid approach

Turbulence enhancement by particle wake effect is studied by numerical simulation of gas turbulent flows passing over particle under various particle sizes, inlet gas velocities, gas viscosity, gas density and the distance of particles. By performing dimension analysis and using the form of gas-particle interaction source term for reference, a new semi-empirical turbulence enhancement model by the particle-wake effect is proposed. The turbulence model is then incorporated into second-order moment model for simulating gas-particle flows in a horizontal channel with different wall roughness and a sudden-expansion chamber. The results show that this model is with higher calculating accuracy than another two turbulence models in comparison with the experimental results.     

数字谷值电流控制开关DC-DC变换器

为了获得开关DC-DC变换器的最优数字谷值电流(DVC)控制技术,研究了电感电流连续模式下DVC控制开关DC-DC变换器的工作原理,对比分析了采用前缘、后缘、三角前缘和三角后缘4种涮制方式的DVC的占空比算法,并分析了各种算法的稳定性.在此基础上,对DVC控制开关DC-DC变换器的时域特性进行了仿真和试验研究,结果表明,采用后缘调制的DVC控制开关DC-DC变换器具有最优的负载瞬态特性,超调电压为62 mV,响应时间为1.118 ms.     

Simple closed-loop method to compensate interference asymmetry in time-division duplex MIMO-OFDM systems

In wireless communications systems with time-division duplex (TDD) deployment, channel reciprocity and symmetric interference between transmitter and receiver sides are two widely-adopted assumptions for the design of optimal adaptation transmission mode. However, in practice, there is an undesirable but non-negligible effect, namely the asymmetric interference, that makes the assumptions no longer valid. In this paper, a simple closed-loop feedback method of compensating interference asymmetry in TDD multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system is proposed. The system makes the estimated interference at transmit-side be able to track the instantaneous receive-side interference dynamically. The proposed method maintains constant frame error rate (FER) by adopting adaptive modulation coding (AMC) and power loading. The final simulations have verified the effectiveness of the new method.     

基于FPGA的数字相位调制系统的设计与实现

对2DPSK及QDPSK数字调制信号进行了分析,采用FPGA在QuartusⅡ环境下,利用VHDL语言及图形输入方式对调制系统进行了设计,用Ahera公司的芯片EP1 C3T144C-8为核心器件组建的系统进行了功能测试,得到了满意的验证波形．     

Experimental investigation of characteristics of pressure modulation in a fuel injection system

A piezoelectric atomization device achieves fuel pressure modulation through vibration of a piezoelectric pressure modulator. As a consequence, the fast alternating and slow moving streams collide with each other and further break up the fuel drop. In this paper, an experimental investigation was carried out to study the fluid dynamic characteristics of the spray atomization process of automotive port fuel injectors with a piezoelectric pressure modulator. The investigation mainly focuses on: (a) the coupling characteristics between the piezoelectric stack and the hydraulic as well as the transfer characteristics of pressure modulation from the piezoelectric modulator to the point above the orifice; (b) the time history of the pressure dynamic response at the point above the orifice under a typical modulation frequency, which reflects the variation of pressure modulation while the fuel injector is working; and (c) the time-variation characteristics related to mechanical structure and fluid dynamics. The experimental results expose some important dynamic characteristics of pressure modulation, which will be very significant and lead us to greatly improve the fuel injection system, optimize the control parameters and implement spray atomization with a high quality performance in the near future.