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881.
一种用于实时视频处理的高速二维DCT的电路设计和实现 总被引:2,自引:0,他引:2
绝大多数的国际图像和视频压缩标准都采用DCT(离散余弦变换)进行传输编码。本文介绍了一种基于矩阵分解算法的高速实时二维DCT处理器。为了满足视频处理的实时性,整个电路设计中广泛采用了流水线技术,文中详细介绍了二维DCT处理器的电路结构,最后给出了它的FPGA实现。 相似文献
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Conventional batch mode analysis of dissolved sulfide by cathodic stripping voltammetry (CSV) is known to suffer from loss of sulfide in the cell to the waste mercury pool, compromising quantification of sulfide. Here we report a simple alternative approach to batch-mode differential pulse CSV (DPCSV). A fresh aliquot of sample is used for each voltammetric scan to minimize loss of sulfide through reaction with the mercury by limiting the time for sulfide-mercury contact, which is found to be more important in suppressing the sulfide signal than the amount of free mercury in the cell. Our improved batch-mode method exhibited a limit of detection of 1.3 nM, a relative standard deviation of 2.5% in NaOH supporting electrolyte and a linear response to as high a concentration as 1600 nM in a supporting electrolyte composed of Na2CO3/NaHCO3 (pH 8.3) mixed with an equal volume of oxic groundwater. A relative standard deviation of 4.5% was obtained for a groundwater sample in Na2CO3/NaHCO3 (pH 8.3) supporting electrolyte. These values are comparable to previously published results. Compared to other sensitive sulfide analytical techniques such as gas chromatography or high performance liquid chromatography (HPLC), DPCSV is preferred for sulfide analysis in the field due to its simple and portable instrumentation, lack of complex sample preparation, and short analysis time. The method was applied on site to analyze Fe-rich, reducing groundwater samples collected at a landfill site in Winthrop, Maine. Sulfide concentrations ranged from undetectable (<4 nM) to 7340 nM, generally increasing as the oxidation/reduction potential (ORP) of the water became more negative. We also demonstrate, for the first time, that the onset of sulfate reduction as indicated by the presence of small amounts of sulfide (tens to hundreds of nM) occurs in groundwater systems when the ORP value reaches −130 mV. 相似文献
887.
N. Farzinnejad A.A. Miran Beigi L. Fotouhi K. Torkestani H.A. Ghadirian 《Journal of Electroanalytical Chemistry》2005,580(2):245-254
Electroreduction of 4-amino-6-methyl-3-thio-1,2,4-triazine-5-one (I), 6-methyl-3-thio-1,2,4-triazine-5-one (II), and 2,4-dimethoxy-6-methyl-1,3,5-triazine (III) in dimethylformamide was investigated. Electrochemical techniques including differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry, and coulometry were employed to study the mechanism of the electrode process. From the analysis of the voltammetric and spectroscopic experiments a mechanism was proposed for the electroreduction of thio-triazine and triazine compounds. Compounds I and II having thiol groups exhibited similar redox behavior. Both compounds displayed two cathodic peaks, whereas the third compound (III), with no thiol group, showed only one cathodic peak in the same potential range as the second peak of compounds I and II.The results of this study show that in the former wave, the one electron reduction of thiol led to a dimer (disulfide) species and in the latter, the triazine ring was reduced in a two-electron process. The effects of various physical and electrochemical parameters were studied and the electrochemical behavior of the monomers was reported as a function of these parameters. A completely irreversible behavior was observed from cyclic voltammograms obtained under different conditions. Furthermore, in this study some numerical constants, such as diffusion constant, transfer coefficient, and rate constant of coupled chemical reaction were determined. 相似文献
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唐益民 《电气电子教学学报》2003,25(4):55-58,63
直流脉宽调制伺服系统以其可控性好、调速范围宽、功率因数高等一系列优点被越来越多的应用于工业控制、机器人、军工、航空航天等领域,并引起业内学者的广泛的重视。但是目前许多国内大专院校相关课程缺少直流脉宽调制伺服系统的实验器材。本文基于此背景,研制了一种直流PWM伺服系统驱动器实验平台。它具备常规单极性、受限单极性以及双极性三种工作模式。试用结果表明该系统具有显示度强、可靠性高、接口灵活的优点,适合于实验使用。 相似文献
890.
Gordon G. Brown 《Journal of Molecular Spectroscopy》2006,238(2):200-212
The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is presented. A new CP-FTMW spectrometer capable of measuring the entire 7.5-18.5 GHz spectrum with a single polarizing pulse is described briefly. The CP-FTMW spectrometer takes advantage of recent advances in digital electronics by utilizing a 4.2 GS/s arbitrary waveform generator as a frequency source and a 12 GHz digital oscilloscope to digitize the down converted molecular free induction decay (FID). Signal averaging in the time domain is used to increase the signal-to-noise ratio. The rotational constants of three unique conformers of epifluorohydrin were measured, as well as the rotational constants of the three unique 13C isotopomers and the 18O isotopomer (in natural abundance) of the most stable conformer. The rotational constants of the two less stable conformers differ significantly from those previously reported [F.G. Fujiwara, J.L. Painter, H. Kim, J. Mol. Struct. 41 (1977) 169-175]. Ab initio calculations were performed for all three conformations and are compared to experimental values. 相似文献