Hydrogen internal friction

It should be noted that low-temperature dynamical processes were also observed for hydrogen trapped by some substitutional impurities (Ti, Zr) in niobium using the internal friction [119, 120] and heat capacity [121] measurements. In particular, the heat capacity of a NbTio os ahoy doped with H(D) shows considerable hydrogen- or deuterium-induced contributions between 0.05 and 2 K [121]. However, the available experimental information is not sufficient to elucidate the microscopic picture of hydrogen motion in these systems. The same also refers to the low-temperature dynamical processes ofhydrogen in b.c.cVandTa [106, 107,122]. 

B. S. Berry and W. C. Pritchet, Hydrogen-Related Internal Friction Peaks in Metallic Glasses, Scripta Metall. 15 637 (1981). 

O. Yoshinari, M. Koiwa, A. Inoue and T. Masumoto, Hydrogen Related Internal Friction Peaks in Amorphous and Crystallized Pd-Cu-Si Alloys, Acta Metall. 31 2063 (1983). 

R. Cantelli, F. M. Mazzolai and M. Nuovo, Internal Friction due to Long-Range Diffusion of Hydrogen in Niobium (Gorsky Effect), Phys. Stat. Sol. 34 597 (1969). 

The selectivity of the TBR can be increased for this type of reaction if a shell catalyst is used. The use of shell catalysts leads to reduction in catalyst load, which then becomes comparable to that of a MR. The higher productivity of the TBR is reached at the cost of relatively high pressure drop, up to 5 bar per reactor unit, which limits the size of the reactor. A TBR is characterized by much higher frictional pressure drop, which is negligible in an MR and is balanced by hydrostatic pressure with zero net pressure drop. This creates a unique possibility of operation with an internal hydrogen, pumpless recirculation. 

Next, Fig. 5 shows a typical center of mass trajectory for the case of a full chaotic internal phase space. The eyecatching new feature is that the motion is no more restricted to some bounded volume of phase space. The trajectory of the CM motion of the hydrogen atom in the plane perpendicular to the magnetic field now closely resembles the random motion of a Brownian particle. In fact, the underlying equation of motion at Eq. (35) for the CM motion is a Langevin-type equation without friction. The corresponding stochastic Lan-gevin force is replaced by our intrinsic chaotic force — e B x r). A main characteristic of random Brownian motion is the diffusion law, i.e. the linear dependence of the travelled mean-square distance on time. We have plotted in Fig. 6 for our case of a chaotic force for 500 CM trajectories the mean-square distance as a function of time. Within statistical accuracy the plot shows a linear dependence. The mean square distance

of the CM after time t, therefore, obeys the diffusion equation... 

In MMA and MA no such hydrogen bonds are operative. The distinct difference in the pre-exponential for bulk polymerization of these two monomers (see entries 4 and 7 in Table 1), however also originates from effects on internal rotational mobihty. The lower value of A(fep MMA) is due to enhanced intramolecular friction induced by the a-methyl groups on the polymer backbone. 

The purpose of this chapter is to present the experimental results for the full-scale LAD outflow tests in liquid hydrogen. Test conditions were taken over a wide range of liquid temperatures (20.3-24.2 K), tank pressures (100-350 kPa), and outflow rates (0.010-0.055 kg/s) thermally and operationally representative of an in-space propellant transfer from a depot storage tank or to a smaller scale in-space engine. Horizontal LAD tests were conducted to measure independently the frictional and dynamic losses down the channel. Flow-through-screen tests were performed to measure independently the dominate pressure loss in LEO, the FTS resistance. Meanwhile, 1-g inverted vertical LAD outflow tests were conducted to obtain performance data for two full-scale 325 x 2300 LAD channels. One of the channels had a perforated plate and a custom-built internal thermodynamic vent system to enhance performance. Model predictions from Chapter 3 are compared to each set of experimental data. 

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