Bulk modulus cell

The bulk modulus cell consists of a hollow, cylindrical steel probe with a projecting stem (Figure 3.142). When exposed to a process pressure, the probe is compressed, and the probe tip is moved to the right. This stem motion is then converted into a pressure reading. The hysteresis and temperature sensitivity of this unit are similar to that of other elastic element pressure sensors. The main advantages of this sensor are its fast response and safety in effect, the unit is not subject to failure. The bulk modulus cell can detect pressures up to 15,000 bar (200,000 psig) with 1-2% full-span error. 

A guide to tire stabilities of inter-metallic compounds can be obtained from the semi-empirical model of Miedema et al. (loc. cit.), in which the heat of interaction between two elements is determined by a contribution arising from the difference in work functions, A0, of tire elements, which leads to an exothermic contribution, and tire difference in the electron concentration at tire periphery of the atoms, A w, which leads to an endothermic contribution. The latter term is referred to in metal physics as the concentration of electrons at the periphery of the Wigner-Seitz cell which contains the nucleus and elecUonic structure of each metal atom within the atomic volume in the metallic state. This term is also closely related to tire bulk modulus of each element. The work function difference is very similar to the electronegativity difference. The equation which is used in tire Miedema treatment to... 

The detailed first principles study of the three stable polymorphs has been performed recently using the LCAO technique The main drawback of that work is that no cell optimization was performed for anatase or brookite. The energy-volume curves that were used to calculate the bulk modulus, B, and its pressure derivative, B, have been produced by varying the volume with the c/a ratio and fractional atomic coor nates being fixed at experimental values which makes results unreliable. 

Amorphous HIPS resin pellets compact very little in the temperature range of 25 °C to about 75 °C, a temperature that is about 25 °C below Tg, as shown in Fig. 4.5. The HIPS resin compacts to a much higher degree for temperatures of 25 °C below Tg up to Tg. Like the LDPE resin, the bulk density at 25 °C and zero pressure was measured using the cell shown in Fig. 4.2 at 0.62 g/cmL At temperatures 25 °C below the Tg (100 °C), the bulk modulus of the resin is relatively high, and thus the pellets do not deform easily under pressure. At higher temperatures, how... 

The faces in low density LDPE foams are partly buckled or wrinkled, as a result of processing (a.l7). This affects both the bulk modulus and the Young s modulus. The foam bulk modulus Kp is predicted, using the Kelvin closed cell foam model, to be ... 

A Kelvin foam model with planar cell faces was used (a. 17) to predict the thermal expansion coefficient of LDPE foams as a function of density. The expansion of the heated gas is resisted by biaxial elastic stresses in the cell faces. However SEM shows that the cell faces are slightly wrinkled or buckled as a result of processing. This decreases the bulk modulus of the... 

Once the lattice parameters are measured at various pressures, the pressure dependence of the unit cell volume is fitted with an equation of state (EOS). The simplest, and most used, is the Mumaghan [9] EOS based on the assumption that the bulk modulus has a linear dependence with the pressure ... 

For the case where cr, = cTj = cTj which is known as hydrostatic stress (the situation when pressure is applied on a glass embedded in a material of low elastic constants - glass piece in steatite or in AgCl in a high pressure cell or simply embedded in a liquid) - then there are no shear strains. The hydrostatic stress is simply the pressure, P and the volumetric strain is Cm so that bulk modulus is also defined as... 

Using the Morse potential that was fit to the cohesive energy, lattice parameter and bulk modulus of Cu in problem 2 of chap. 4, compute the relaxation energy associated with a vacancy in Cu. In light of this relaxation energy, compute the relaxed vacancy formation energy in Cu and compare it to experimental values. How do the structure and energy of the vacancy depend upon the size of the computational cell ... 

The volume—pressure relationship for e-Fe has been determined up to 300 GPa at room temperature (Figure 3 Mao et al., 1990). Determining the temperature dependence of the bulk modulus of iron is crucial for accurate comparison between the density of iron and that of the iimer core. Several in situ X-ray diffraction studies in the diamond-anvil cell (Huangeta/., 1987 Dubrovinsky eta/., 1998, 2000) and in the multi-anvil apparatus (Funamori et al., 1996 Uchida et al., 2001) have provided limited data on the thermal expansion of e-Fe at high pressures. The data of Dubrovinsky et al. 

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