Pulsed measuring principle

There are a number of NMR methods available for evaluation of self-diffusion coefficients, all of which use the same basic measurement principle [60]. Namely, they are all based on the application of the spin-echo technique under conditions of either a static or a pulsed magnetic field gradient. Essentially, a spin-echo pulse sequence is applied to a nucleus in the ion of interest while at the same time a constant or pulsed field gradient is applied to the nucleus. The spin echo of this nucleus is then measured and its attenuation due to the diffusion of the nucleus in the field gradient is used to determine its self-diffusion coefficient. The self-diffusion coefficient data for a variety of ionic liquids are given in Table 3.6-6. 

The basic measurement principle of an X-ray device is counting. We open a beam shutter, count discrete pulses, and close the shutter again. The shutter is mimicked by electronics which opens a gate to a counter for a certain period of time. After the... 

While in the case of the kinetic theory of gases w/ith VISCOVAC the counting of particles directly represents the measuring principle (transferring the particle pulses to the rotating ball, w/hich is thus slowed dovm). With... 

This is a simplified description of the measurement principle. For a complete description and for limitations of the method at very high pulse intensities, see 51). 

Figure 5.4, one can easily understand why the interfacial electron transfer should take place in the 10-100 fsec range because this ET process should be faster than the photo-luminescence of the dye molecules and energy transfer between the molecules. Recently Zimmermann et al. [58] have employed the 20 fsec laser pulses to study the ET dynamics in the DTB-Pe/TiC>2 system and for comparison, they have also studied the excited-state dynamics of free perylene in toluene solution. Limited by the 20 fsec pulse-duration, from the uncertainty principle, they can only observe the vibrational coherences (i.e., vibrational wave packets) of low-frequency modes (see Figure 5.5). Six significant modes, 275, 360, 420, 460, 500 and 625 cm-1, have been resolved from the Fourier transform spectra of ultrashort pulse measurements. The Fourier transform spectrum has also been compared with the Raman spectrum. A good agreement can be seen (Figure 5.5). For detail of the analysis of the quantum beat, refer to Figures 5.5-5.7 of Zimmermann et al. s paper [58], These modes should play an important role not only in ET dynamics or excited-state dynamics, but also in absorption spectra. Therefore, the steady state absorption spectra of DTB-Pe, both in...

Fig. 2. (a) The free induction decay, G(t) for 19F in a single crystal of CaFi for B0 along [1,0,0]. The experimental points are given by circles and crosses from the CW and pulse measurements, respectively, and the theoretical curve is that of Eq. (14), corresponding to an exponential decay multiplied by a sine function. Note that F(t) is equivalent to G(t) in the present notation. Reproduced with permission from A. Abragam, The Principles of Nuclear Magnetism, p. 121, Oxford University Press, London, 1961. (b) The lineshape in the frequency domain corresponding to the Fourier transform of the theoretical curve. 

In a pulsed-mode NMR experiment, which is performed at both constant magnetic field and constant rf frequency, rf radiation is supplied by a brief but powerful computer-controlled pulse of rf current through the transmitter coil. This monochromatic (single-frequency) pulse, centered at the operating frequency v0, is characterized by a power (measured in watts and controlling the magnitude of B,) and a pulse width (tp), the duration of the pulse measured in microseconds. However, as a direct consequence of the uncertainty principle [Eq. (1.6)], this brief pulse acts as if it covers a range... 

In this study the following TLS equipment models of different manufacturers have been employed based on different measurement principles Trimble GX3D Scanner [9], based on the principle of measurement by pulses or flight time Leica HDS 6200 [10], based on the principle of measurement of phase difference, and Scan Station CIO [11], based on the principle of measurement by pulses or flight time. The technical specifications of laser scanners used in this research are shown in Table 1. 

The Coulter counter is a resistive pulse technique of particle sizing invented in 1953. The measurement principle is as follows. A particle passes through a pore and displaces conducting fluid in that pore (Fig. 2). The resistance of a pore Rp increases by SRp when a particle enters since the particle displaces cmiducting fluid. Assuming that the current density is uniform across the... 

Heat-Transfer-Detection-Based Flow Sensors These thermal-anemometer-based flow sensors can sense very low flows in microchannels. The measurement principle is based on the thermal time of flight. The length of the heating pulse and the time of flight used in the measurement are measured in milliseconds. An example of the structure of a flow sensor is shown in Fig. 5 [1]. The structure consists of a heater in the middle, with an upstream and a downstream temperature sensor integrated into the wall of the channel. When there is no flow in the channel, heat diffuses into the two temperature sensor regions and no differential temperature is detected. An increase in the flow rate in the channel favors convection of heated fluid in the direction of the flow, and the differential temperature detected by the sensors increases. 

The flow measurement principle for the time-of-flight sensor is illustrated in Fig. 4. In this method, the time taken for a heat pulse to pass over a known distance is recorded. The heat pulse generated by an electrical pulse applied to the heater microfilm travels due to the fluid flow and is detected by a sensor microfilm [8, 10]. The time between the heat pulse generation and its detection can then be used for flow estimation (Fig. 4b). 

In a pulsed measurement, a general relationship exists between the depth of an optical-absorbing feature and the time required for heat conduction to the surface. This principle is illustrated in Figure 2 for the case of pulsed excitation, with the temperature measured at the rear surface of a sample composed of three different absorbing layers. 

The Coulter counter is a resistive pulse technique of particle sizing invented in 1953. The measurement principle is... 

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