A class of vector‐valued dilation‐and‐modulation frames on the half real line

Vector‐valued frames were first introduced under the name of superframes by Balan in the context of signal multiplexing and by Han and Larson from the mathematical aspect. Since then, the wavelet and Gabor frames in have interested many mathematicians. The space models vector‐valued causal signal spaces because of the time variable being nonnegative. But it admits no nontrivial shift‐invariant system and thus no wavelet or Gabor frame since is not a group by addition (not as ). Observing that is a group by multiplication, we, in this paper, introduce a class of multiplication‐based dilation‐and‐modulation ( ) systems, and investigate the theory of frames in . Since is not closed under the Fourier transform, the Fourier transform does not fit . We introduce the notion of Θ_a transform in , and using Θ_a‐transform matrix method, we characterize frames, Riesz bases, and dual frames in and obtain an explicit expression of duals for an arbitrary given frame. An example theorem is also presented.     

中高频SPWM 变频器的设计与控制

介绍一种以80C196MC单片机为核心的中高频变频调速装置.经长期使用,系统运行可靠,可满足中高速变频调速的要求.     

ADSL系统中帧同步的解决方案

介绍了ＡＤＳＬ（非对称数字用户环路）的基本原理，并提出了一种ＡＤＳＬ系统中帧（符号）同步的简单解决方法及其计算机模拟结果。     

Amplitude modulation of a low-coherence source, applications to distance and dynamic displacement sensing

The possibilities of the radio-frequency amplitude modulation of a low-coherence source for distance and displacement measurements are discussed. This intensity-based method, used within a Michelson interferometer, is a novel alternative to perform dynamic deformation measurements. The theoretical background is presented, together with the experimental verification of the principle. Besides, the results of the first quasi-dynamic tests are shown and the perspectives of the technique discussed. This method is specially useful for the dynamic monitoring of civil structures, where large measurements bases are needed. Furthermore, the application of the amplitude modulation for distance measurements is demonstrated experimentally.     

Assessment of amplitude modulation in environmental noise measurements

This paper introduces a method to assess the parameters of amplitude modulation as applicable to environmental noise monitoring tasks. It is based on the analysis of time histories of sound pressure levels correlated with a reference cosine signal. The method brings accurate results in situations where the time history does not exhibit a clear modulation pattern or the signal-to-noise ratio is poor. These features make the suggested technique attractive for practical implementation.     

单片机控制语音合成电话自动应答

用单片机对电话进行监测和对语音合成芯片进行管理，实现电话自动应答，电话记录以及放音。     

High-frequency characterization of an optical phase modulator with phase modulation-to-intensity modulation conversion in dispersive fibers

We propose a new method for characterizing optical phase modulators based on phase modulation-to-intensity modulation (PM-to-IM) conversion in dispersive fibers.The fiber dispersion spectrally alters the relative phasing of the phase-modulated signal and leads to the PM-to-IM conversion,which is extended to measure the modulation efficiency of optical phase modulators.In the demonstration,the frequency-dependent modulation index and half-wave voltage are experimentally measured for a commercial phase modulator.Compared with conventional methods,the proposed method works without the restriction of small-signal operations,and allows swept-frequency measurement with high resolution and accuracy by using a vector network analyzer.     

J‐compensated PGSE: an improved NMR diffusion experiment with fewer phase distortions

Peak distortion caused by homonuclear ¹H J‐coupling is a major problem in many spin‐echo‐based experiments such as pulsed gradient spin‐echo (PGSE) experiments. Although peak phase distortions can be lessened by the incorporation of anti‐phase purging sequences, the sensitivity is substantially decreased. Techniques for lessening the effect of homonuclear J‐coupling evolution in spin‐echo‐based experiments have been investigated. Two potentially useful candidates include a J‐compensated inversion sequence that is efficient over a wide range of J‐coupling values and a pulse sequence that refocuses homonuclear J‐evolution during the spin‐echo. The latter was found to work superbly on samples containing two spin (AX or AB) systems and still provided significant advantage over the standard method on samples containing more complicated spin systems. Implementation of this J‐refocusing technique into a PGSE‐type experiment (J‐PGSE) leads to dramatic improvement of spectra and easier data analysis. The J‐PGSE sequence should find applications in many diffusion studies where the PGSE‐type method is required and should be a viable alternative to PGSTE especially in dilute samples due to its enhanced sensitivity. Copyright © 2009 John Wiley & Sons, Ltd.     

热成象系统的动态调制传递函数

研究了热成象系统相对目标作简谐运动方式下系统的动态调制传递函数，导出了热成象系统的动态调制传递函数ＭＤ（ｆ，ｖ），用解析方法描述了热成象系统的动态调制传递函数。     

伪随机信号调幅中频电子治疗仪的研究

阐明了如何解当今中频电子治疗仪在临床应用中存在的主极问题；研制出解决治疗阈值与疼痛阈值分离、有效地克服机体适应性、增强机体物理功能的新型电子医疗设备－ＳＴＭ－Ⅱ型中频电子治疗仪，在大量的临床应用中取得了满意的效果。