Spinning rates

Figure 3 shows a composite result from several simulations and considers the relationship between disk temperature and spin rate for a helium carrier in a fixed reactor geometry (fo/f[Pg.338]

Figure 2. Radial-axial velocity field and temperature contours for a rotating-disk reactor at an operating condition where a buoyancy-driven recirculation vortex has developed. The disk temperature is HOOK, the Reynolds number is 1000, Gr/Re / = 6.2, fo/f = 1.28, and L/f = 2.16. The disk radius is 4.9 cm, the spin rate is 495 rpm. The maximum axial velocity is 55.3 cm/sec. The gas is helium.

Figure 3. Relationship of susceptor temperature to spin rate that is required to operate a particular reactor geometry in the one-dimensional regime.

Gr/v Re = 9.6) without causing recirculation, and thus nonuniform surface flux. Since the disk temperature is fixed in this simulation, a smaller value of the mixed-convection parameter corresponds to a larger value of the disk spin rate. 

The other boundary conditions are relatively simple. The temperature and species composition far from the disk (the reactor inlet) are specified. The radial and circumferential velocities are zero far from the disk a boundary condition is not required for the axial velocity at large x. The radial velocity on the disk is zero, the circumferential velocity is determined from the spinning rate W = Q, and the disk temperature is specified. 

Figure 6. Species profiles in a rotating disk CVD reactor. Inlet gas is 0.1 percent silane in a carrier of 99.9 percent helium. The disk temperature is 1000 K and the spin rate is 1000 rpm.

Fig. 47 Carbon-13 solid state NMR spectrum of camphor (50.309 MHz, cross-polarization contact time 5 ms, spin rate 1650 Hz)...

Fig. 48a,b Carbon-13 spectra of a bisphosphonate (structure given) in solution (a, in CDC13) and in the solid state (b, CP/MAS, spinning rate 12 kHz)... 

Fig. 49 Phosphorus-31 CP/MAS spectra of polycrystalline triphenylphosphine (powder) at the given spinning rates...

Fig. 50 Phosphorus-31 CP/MAS spectrum of the nickel complex shown, which is immobilized on silica gel, recorded at a spinning rate of 4 kHz (lower spectrum) and HRMAS spectrum of an acetone suspension, recorded at a spinning rate of 2 kHz (upper spectrum)...

Oil/water interfacial tensions were measured for a number of heavy crude oils at temperatures up to 200°C using the spinning drop technique. The influences of spinning rate, surfactant type and concentration, NaCI and CaCI2 concentrations, and temperature were studied. The heavy oil type and pH (in the presence of surfactant) had little effect on interfacial tensions. Instead, interfacial tensions depended strongly on the surfactant type, temperature, and NaCI and CaCL concentrations. Low interfacial tensions (<0.1 mN/m) were difficult to achieve at elevated temperatures. 

The 0.4 cm i.d. capillary tubes were used instead of the recommended 0.2 cm i.d. 1 28 1 in order to facilitate the addition of highly viscous oils. Figure 2 shows the effect of spinning rate on the interfacial tension of an n-butanol/deionized water system us i ng two tube s izes. The dashed Ii ne represents the best fit for 15 data points measured using a 0.2 cm i.d. tube, where the mean interfacial tension is 1.76 mN/m (standard deviation of 0.02) with a range of 1.73 to 1.80 mN/m for speeds ranging from... 

Figure 2 Effect of spinning rate on the interfacial tension of r -butanol/water system at 30°C.

Figure 3 Effect of spinning rate on the interfacial tension of Clearwater bitumen/D20, and Sun Tech IV (5 g/L) and NaCI (10 g/L) system at 75°C.

The basic components of the solid state spectrometer are the same as the solution-phase instrument data system, pulse programmer, observe and decoupler transmitters, magnetic system, and probes. In addition, high-power amplifiers are required for the two transmitters and a pneumatic spinning unit to achieve the necessary spin rates for MAS. Normally, the observe transmitter for 13C work requires broadband amplification of approximately 400 W of power for a 5.87-T, 250-MHz instrument. The amplifier should have triggering capabilities so that only the radiofrequency (rf) pulse is amplified. This will minimize noise contributions to the measured spectrum. So that the Hartmann-Hahn condition may be achieved, the decoupler amplifier must produce an rf signal at one-fourth the power level of the observe channel for carbon work. 

In order to achieve higher spin rates, it is paramount to recognize possible imbalances to prevent machine misalignment that would result in mechanical stress on the bearings as well as unnecessary noise development. The first step to avoid imbalance is a gentle run-up for a few seconds at the beginning, as shown in the upper panel of Fig. 3.4. Here the spin speed is continually raised in discrete and slow steps so that the laundry is distributed evenly around the drum. 

SWEEP OFFSET (Hz) SPECTRUM AMPLITUDE INTEGRAL AMPLITUDE SPINNING RATE (RPS) ... 

There are a lot of other things in a typical NMR. There are spinning sidebands, small duplicates of stronger peaks, evenly spaced from the parent peak. They fall at multiples of the spin rate, here about 30 Hz. Spin the sample tube faster and these sidebands move farther away slow the tube and they must get closer. 

In practice, the spinning rate of the sample about the magic angle needs to be fast relative to the observed static line width of the sample. So, for example, if the observed anisotropic line width is 20 kHz, then the sample must spin at faster than 20 kHz, or 20,000 revolutions per... 

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