Pulse, read width

The TestLab data should be analyzed for period, pulse full width at half maximum, peak power, and total energy release. To facilitate this analysis, the data will be transferred to the laboratory web page (your instructor can also transfer the files to a disk which you provide) in a form to be read into a spreadsheet, i.e. a. wks file. Each pulse will be denoted by the number of the pulse on that day and the date. Thus a file 3921.wks is the third pulse... 

The sequence begins with a 90° pulse of width T90 and a rotating-frame phase direction assumed along the x axis. The rotating-frame Hamiltonian during this RF pulse is defined by H o=- hyBiIxy where Bi is the amplitude of the rotating flux density component of the RF field. The reduced density operator immediately after this pulse reads... 

Analogous to the principal concept of multiplex CARS microspectroscopy (cf. Sect. 6.3.5), in multiplex SRS detection a pair of a broad-bandwidth pulse, eg., white-light femtosecond pulse, and a narrow-bandwidth picosecond pulse that determine the spectral width of the SRS spectrum and its inherent spectral resolution, respectively, is used to simultaneously excite multiple Raman resonances in the sample. Due to SRS, modulations appear in the spectrum of the transmitted broad-bandwidth pulse, which are read out using a photodiode array detector. Unlike SRS imaging, it is difficult to integrate phase-sensitive lock-in detection with a multiplex detector in order to directly retrieve the Raman spectrum from these modulations. Instead, two consecutive spectra, i.e., one with the narrow-bandwidth picosecond beam present and one with that beam blocked, are recorded. Their ratio allows the computation of the linear Raman spectrum that can readily be interpreted in a quantitative manner [49]. Unlike the spectral analysis of a multiplex CARS spectrum, no retrieval of hidden phase information is required to obtain the spontaneous Raman response in multiplex SRS microspectroscopy. 

The MR effect is a change of electrical resistivity of a metal or alloy when it is in a magnetic field. This change in resistivity due to the magnetic field can be used to sense magnetic field (data) in the magnetic medium. An MR read head is schematically shown in Fig. 43. It can be seen that the MR sensor is placed between two shields in order to reduce the pulse width of the MR sensor. The most... 

Inhomogeneity in the applied rf field means not all nuclei within the sample volume experience the desired pulse flip angle (Fig. 9.1b), notably those at the sample periphery. This is similar in effect to the (localised) poor calibration of pulse widths and references to rf (or Bi) inhomogeneity below could equally read pulse width miscalibration . Modifications that make sequences... 

The microcontroller reads and interprets the signals from the sensor element and reports to the climate control system using a PWM pulse-width modulation signal. This signal communicates the level of pollution to the climate control, which in response initiates the actuation of the fresh-air inlet. The use of a microcontroller enables us to enhance the performance of the climate control system by programming it to behave in accordance with the wishes of the customer. The software determines, for example, the total fresh air inlet closed versus open time, the structure of the PWM signal output, sensor behavior at start up, and many more variables. 

The 3842/43/44/45 series of pulse width modulators are possibly the most popular controllers for off-line applications for several years now. Originally from Unitrode (now Texas Instruments, TI ), I can find clones from at least 12 more semiconductor companies on the web (see if you can better the count). The list may in fact be quite endless. Their quality is however often questionable, though I do admit that their Application Information seems all rather well written (hmmm, but did I read that somewhere else ). 

In recording the FID, the pulse width and read pulse (90°) must be set properly to assure highest possible sensitivity. Then the pulse delay time must be determined. It is normally set at 5x the longest T. Next the spectral width (SW) is set. In C NMR, the chemical shift range is 250 ppm, so at 50 MHz, the resonances will lie within 12,500 Hz which is the required SW. The number of data points (DP) must be 2" (from the FT algorithm) For NMR, 16K or 32K are usually considered sufficiently high. The digital resolution (DR) is calculated ... 

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