基于AD8349的无线直接变频发射机设计与实现

分析无线直接变频发射机中的边带和本振泄漏问题,导出调制信号和本振信号的幅度和相位不平衡度与该类发射机的边带和本振抑制能力之间的定量关系,并用MATLAB软件进行了仿真.最后,基于最新的AD8349型直接正交上变频器,介绍直接变频发射机优化设计的具体措施,并给出实验结果.     

微波相移法在线测量烟道飞灰含碳量

从电磁波传播的基本理论出发,分析了微波在含有石墨碳的灰分中的传播,推导了电磁波在含碳的灰分介质中的幅度衰减和相位变化关系,提出一种新的利用微波测量烟道灰分中碳含量的方法,按该方法设计制作了相应的实验装置并获得了与理论分析一致的实验结果.     

一种实用的电磁振动机调频调幅可控硅控制装置

本文介绍一种电磁推动机可控硅调频调幅控制装置的原理及设计思想,并附有原理总图。运用这种装置控制电振机,可使电振机工作在最佳状态,节约电能。同时能满足调频的需要.     

冀中地区文安斜坡带成藏特征研究

斜坡带的重新认识对油田的稳定发展越来越重要。通过对文安斜坡带生油洼槽的生油条件、油气运移聚集规律、成藏特征研究后认为：文安斜坡带具有充足的油源，是油气运移的必然指向，但其总体勘探开发程度相对较低，仍具有较大的滚动勘探开发潜力；同时，圈闭形成与油气大规模运移期具有良好的配置关系，具备形成大中型岩性油气藏的物质基础。及时总结文安斜坡的成藏条件、基本成藏规律以及勘探开发成效，对斜坡带的研究以及提高油田勘探开发综合效益，具有重要的指导和借鉴意义。     

REFLECTION AND TRANSMISSION OF WATER WAVES BY POROUS VERTICAL PLATES

The reflection and transmission of small amplitude surface waves by two verticalporous plates with spacing L fixed in the middle of an infinitely long channel of constant depthare studied.Analytical solutions in closed forms are obtained for the surface wave profiles.It isfound that,when the spacing L is a quarter-wavelength plus a multiple of the half-wavelength ofthe incident wave,not only the reflected wave amplitude but also the transmitted wave amplitudereduce to minima.On the other hand,when the spacing L is a multiple of the half-wavelengthof the incident wave,both the reflected wave amplitude and the transmitted wave amplitude havethe maximum values.For these two special cases,the energy dissipation caused by the twoporous plates and the water between them are also discussed.     

Useful Characteristics for Controlling the Cancellation Performance and Center Frequency of a Linearization Loop

The cancellation performance of a linearization loop is limited by the degree of an amplitude imbalance and a phase imbalance. A delay mismatch causes a phase variation as a function of frequency. Therefore, the cancellation performance and linearization bandwidth are limited by a delay mismatch. The expression for the effects of an amplitude imbalance, a phase imbalance, and a delay mismatch on the characteristics of a linearization loop is derived and analyzed. The simulation results are compared with the results obtained by means of using a commercial simulation tool and the exact agreement is reported. The derived equation could be used in designing a linearization loop and predicting the cancellation performance of the linearization loop usefully. Some useful characteristics, known from the simulation results obtained by using the derived equation, of a linearization loop for designing and implementing feedforward amplifiers are described in detail.     

Design of Amplitude and Phase Modulated Signals for Differential Space-Time Block Codes

A differential space-time block code (DSTBC) provides full diversity advantage and does not require any radio channel estimation in the receiver, which makes it an attractive alternative to the well-known coherent space-time block code (STBC). However the original design of DSTBC allows only pure phase shift keying (M-PSK) modulation scheme, which are not optimal for M > 4. In this paper a simultaneous amplitude and phase modulation scheme for DSTBC with 2 transmit and several receive antennas is introduced. The performance of the proposed scheme is investigated and compared with DSTBC techniques using pure M-PSK modulation. Alexandre Vanaev received B.Eng. degree in Electrical and Electronic engineering from the St. Petersburg State Polytechnic University, Russia in 1998, and M.Sc. degree in “Information and communication systems” from Technical University Hamburg-Harburg in 2002. He is currently pursuing his Ph.D. in the Technical University Hamburg-Harburg, Department of Telecommunications. His research interests include prospective OFDM-based wireless communication systems and MIMO technology. Prof. Hermann Rohling is with the Technical University Hamburg-Harburg, Germany where he has developed an international reputation for Mobile Communication (4G) and automotive radar systems. Previously Prof. Rohling was with the AEG Research Institute, Ulm as a researcher working in the area of digital signal processing for radar and communications applications. His research interests have includedWideband Mobile Communications especially based on Multicarrier Transmission Techniques (OFDM) for future broadband systems (4G), signal theory, digital radar signal processing, detection, estimation and differential GPS for high precision navigation. Prof. Rohling is a member of Informationstechnische Gesellschaft (ITG), German Institute of Navigation (DGON) and a Fellow of IEEE. He is a chairman of the September 2006 International OFDM Workshop (InOWo 2006) and the International Radar Symposium (IRS 2006) in Krakow, Poland. Prof. Rohling is theVice President of the Technical University Hamburg-Harburg.     

溶洞的浅层地震反射特征及工程应用

本文从地震波的动力学和运动学观点,分析了不同构造类型的溶洞在地震反射波法勘探中的动力学和运动学方面的特征。根据这些特征,地震反射波法探测溶洞具有可行性、直观性和高效性。这些特征为复杂的地质剖面解释提供可靠依据,为地震反射波法勘探溶洞奠定了基础,在实际工作中取得较好效果。     

装配式切刀的动态特性研究

加工中振动是影响切刀工作性能和工件质量的主要因素,通过分析建立了装配式车刀工艺系统的数学模型,为使问题求解方便,将模型转换为一阶微分方程组(代数方程),具体分析工艺系统元件振动的发生频率,以C6140车床装配式切刀工艺系统为例,进行了实验研究,绘制了幅频特性曲线,得出了切断刀产生振动的频率范围,便于生产实践中选择。     

Fatigue performance of 6261-T6 aluminium alloy – constant and variable amplitude loading of parent plate and welded specimens

The work reported in this paper is a summary of the results obtained from several projects run over a five year period. A number of thrusts were encompassed in the project scope, which was to examine the fatigue strength of extruded 6261-T6 I-beams with centrally located, welded cover plates under constant amplitude (CA) and variable (two-level repeated block) amplitude (VA) loading. The CA part of the work examined the effect of cover plate geometry, specimen size, thermal and vibratory stress relief, and differences in fabrication quality on fatigue performance. A number of cases were identified which gave rise to cross-overs in performance in moving from shorter to longer fatigue lives. The aim of the VA part of the work was to identify situations which might give rise to fatigue lives shorter than predicted by linear damage summation models, such as Miner's rule. Two such cases were identified: specimens which had been subjected to vibratory stress relief; and specimens in which weld ‘quality' (as assessed by profile, heat affected zone hardness, extent and microstructure) varied. Explanations for these observations are proposed and supported by interpretation of a two-level block of small fatigue crack growth.