Velocity-time profile

Within a narrow pressure range, P, the behavior of the interface velocity-time profiles changes from either a zero slope or continuous negative slope to a break in the slope (eg, at 155 kb in Fig 26a and 134 I40kb in Fig 26b)... 

To analyze the recorded spectra, the spectrometer needs to be calibrated. The three main calibration parameters are the velocity scale, the center point of the spectrum and the nonlinearity of the velocity/time profile of the oscillation compared to a standard reference. The calibration is performed using a spectrum recorded from an a-iron foil at room temperature using the well defined line positions of the sextet from a-iron, which occur at 5.312mms , 3.076mms , and 0.840mms The center of this a-iron spectrum at room temperature is taken as the reference point (0.0 nun s ) for isomer shift values of sample spectra. The typical Mossbauer spectrum of the 14.4 keV transition of Fe in natural iron (Fig. 4.10) represents a simple example of pure nuclear Zeeman effect. Because of the cubic symmetry of the iron lattice, there is no quadrupole shift of the nuclear energy levels. The relative intensities of the six magnetic dipole transitions are... 

Figure 5.2 Experimental velocity-time profile of surface of 0.6295 cm thick Aluminum plate in contact with detonated slab of 5.08 cm thick Composition B. The calculated profile treating the metal as a fluid is also shown.

Along with, and closely connected to, the developments in precise impact techniques is the development of methods to carry out time-resolved materials response measurements of stress or particle velocity wave profiles. With time resolutions approaching 1 ns, these devices have enabled study of mechanical responses not possible in the early period of the 1960s. The improved time-resolutions have resulted from direct measurement of stress or particle velocity, rather than from improved accuracy and resolution in measurement of position and time. In a continuation of this trend, capabilities are being developed to provide direct measurements of the rate-of-change of stress. With the ability to measure such a derivative function, detailed study of new phenomena and improved resolution and accuracy in descriptions of known rate-dependent phenomena seem possible. 

Typical stress-time profiles for the various materials (28.5-at. % Ni, fee and bcc) and various stress regions are shown in Fig. 5.12. The leading part of the profile results from the transition from elastic to plastic deformation. The extraordinarily sharp rise in stress for the second wave in Fig. 5.12(a) and the faster arrival time compared with that in Fig. 5.12(b) is that expected if the input stress is above the transition, whereas the slower rise in Fig. 5.12(b) is that expected if the stress input to the sample is below the transition. The profile in Fig. 5.12(c) for the bcc alloy was obtained for an input particle velocity approximately equal to that in Fig. 5.12(a) for the fee alloy. The bcc alloy shows a poorly defined precursor region, but, in any event, much faster arrival times are observed for all stress amplitudes, as is indicative of lower compressibility. 

Aleksandrov et al (Ref 19) used an electromagnetic technique to get particle velocity (y) vs time profiles. They conclude that the breaks observed in such profiles coincide with the Chapman-Jouguet point, ie, the time of the break corresponds to the chem reaction time in a detonation. The reaction zone width, a, is then a = r (D — u)... 

The main characteristics of the green mixture used to control the CS process include mean reactant particle sizes, size distribution of the reactant particles reactant stoichiometry, j, initial density, po size of the sample, D initial temperature, Tq dilution, b, that is, fraction of the inert diluent in the initial mixture and reactant or inert gas pressure, p. In general, the combustion front propagation velocity, U, and the temperature-time profile of the synthesis process, T(t), depend on all of these parameters. The most commonly used characteristic of the temperature history is the maximum combustion temperature, T -In the case of negligible heat losses and complete conversion of reactants, this temperature equals the thermodynamically determined adiabatic temperature (see also Section V,A). However, heat losses can be significant and the reaction may be incomplete. In these cases, the maximum combustion temperature also depends on the experimental parameters noted earlier. 

The positions of the detonation fronts as functions of time are shown in Fig. 17 with the upper and lower lines corresponding to orientations 01 and 02, respectively. After about 5 ps the lines become parallel, indicating that the two detonation fronts have essentially the same velocity. This conclusion was verified by least-squares fits to the wavefront versus time profiles between 5 ps and 12.6 ps. The fits yielded detonation velocities... 

Menzel et al [98] found core peaking for all the gas fluxes they studied in their investigation, and the time averaged radially varying velocity component profiles have a maximum at the core of the column as shown in Fig 8.4. The column used had a diameter of 0.6 (m), and a height of 5.44 (m). The system considered was air-water. The water was operated in batch mode. The velocity measurements were performed with a hotfllm anemometer. 

VRI velocity time integral of aortic flow profile (mm)... 

F. 5.12 Non-dimensional circulation time profile across the upper half of aqueous plug of different lengths at constant mixture velocity (u ix = 0.01 m s ) in the 1 mm ID channel. TBP/ [C4mim][NTf2] (30 %, v/v) as carrier fluid... 

For the design (Sauter diameter, droplet velocity, pressure profile, residence time distribution, flooding load, etc.) see [6.71, 6.73-6.75]. Extractor selection and operating parameters have to be determined exper-... 

Flow of a falling film [6]. The velocity (length/time) profile of a fluid in an inclined flat surface can be expressed as... 

Before each shake, air-hammer tests were conducted to evaluate the new (modified) shear wave velocity (Vs) profile of the soil deposit. The Vs profiles were estimated based on the travel times of the waves, between accelerometers that are placed at known distances apart. These distances did not change significantly after each shake, as the recorded soil settlements were small due to the high relative density of the soil deposit. The travel times were estimated in a simplified way from the arrivals of the waves, produced by air-hammer. To make sure that the arrival times were adequately recorded, the DasyLab software was used as the acquisitirm system for the air-hammer array of accelerometers, allowing for a sampling frequency equal to 50 kHz. 

When an optical pulse with the spectral amplitude distribution E o)) propagates through a medium with refractive index n o)), its time profile will change because the group velocity... 

The laser interferometry technique is widely used for the study of the detonation wave time profile and structure due to its exceptionally good time resolution. The laser interferometry operating principle is based on the Doppler effect. The technique records the position and time dependence of the interferometric fields obtained due to the Doppler shift in wavelength of the reflected laser beam, resulting from the thin metal shim motion. The metal shim, 15-25 pm thick, is placed between the explosive charge and windows that are made of an inert optically transparent material, such as water, lithium fluoride, or polymethylmethacrylate. On the basis of the velocity of the explosive/metal shim interface as a function of time, it is possible to calculate the values of detonation parameters of the explosive (Gimenez et al., 1985, 1989 Hemsing, 1985 Leeetal., 1985). 

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