Double-curved shells

Double-curved shells can take the form of special domes, be saddle shaped, or use hyperbolic shapes, as featured in architectural design textbooks. These shapes can be made similar in modular forms molded with RP, thereby providing an efficient structural shape with a higher buckling resistance than special shapes of comparative curvature and thickness. Structural benefits are derived from using RP-faced sandwich designs in different shapes. 

This work provides accurate potential energy curves as well as coupling matrix elements for the B2+/H and B4+/ He systems. From the molecular point of view, it appears important to involve all levels correlated to the entry channels in the collision dynamics and, in particular, to take into account rotational effects, which might be quite important. The results concerning the double electron capture process in the (B4+ + He) collision point out the limitations ofthe potential approach model, especially to account for open shell levels, for which more elaborate calculations are necessary. 

Some partial photoionization cross sections, derived in this way for neon, are shown in Fig. 2.11 as a function of photon energy. The uppermost curve is the total absorption cross section. At the onset of the ionization thresholds for the ejection of Is, 2s and 2p electrons this quantity shows the corresponding absorption edges (see the discussion related to equ. (2.11)). The partition of the total cross section into partial contributions cr(i) clearly demonstrates that the dominant features are due to main photoionization processes described by the partial cross sections satellite transitions from multiple photoionization processes are also present. If these are related to a K-shell ionization process, they are called in Fig. 2.11 multiple KL where the symbol KLX indicates that one electron from the K-shell and X electrons from the L-shell have been released by the photon interaction. Similarly, multiple I/ stands for processes where X electrons from the L-shell are ejected. Furthermore, these two groups of multiple processes are classified with respect to ionization accompanied by excitation, (e, n), or double ionization, ( ,e). If one compares in Fig. 2.11 the magnitude of the partial cross sections for 2p, 2s and Is photoionization at 1253.6 eV photon energy (Mg Ka radiation) and takes into account the different... 

In a double logarithmic plot of P(q) vs. q, the asymptotic slope at high q of the upper envelope of the scattering curve depends on the ratio of the wall membrane thickness to the outer diameter, e.g -2 for an infinitely thin shell from Eq. (2) and -4 for a solid sphere from Eq. (3). By fitting an experimental scattering curve to the theoretical functional form of Eq. (I). two parameters. 

The systematics of the double-ionisation thresholds turn out to be very important in determining the properties of doubly-excited spectra. These are most prominent for elements lying close to local minima, which is why alkaline-earth elements play a special role (see chapter 7). Another important issue is the existence of crossing points between the curves for double ionisation and for ionisation from an inner shell. This is further discussed in section 7.14. 

An instance of this type is found in the spectrum of Li I, as shown in fig. 4.4 note in particular how the df/dE curve for Li is distorted from the expected shape by the minimum below threshold, so that the curve rises rather than falls towards the threshold. The effect is not a perturbation alkali spectra have double excitations and inner-shell spectra very far in energy from the optical spectrum, so there are no intruders in this range. 

Strutinsky developed an extension of the liquid drop model which satisfactorily explains the fission isomers and asymmetric fission. For such short half-lives the barrier must be only 2-3 MeV. Noting the manner in which the shell model levels vary with deformation ( 11.5, the "Nilsson levels"), Strutinsky added shell corrections to the basic liquid-drop model and obtained the "double-well" potential energy curve in Figure 14.14b. In the first well the nucleus is a spheroid with the major axis about 25 % larger than the minor. In the second well, the deformation is much larger, the axis ratio being about 1.8. A nucleus in the second well is metastable (i.e. in isomeric state) as it is unstable to y-decay to the first well or to fission. Fission from the second well is hindered by a 2 - 3 MeV barrier, while from the first well the barrier is 5 - 6 MeV, accounting for the difference in half-lives. 

The single-well curve in Figure 14.14a predicts symmetric fission whereas the double-well curve (Fig. 14.14b) leads to the correct prediction of asymmetric fission and a thin neck. Incorporation of shell effects in the fission model also leads to the prediction that the half-lives of very heavy nuclides (Z 106) must be longer than the simple liquid-drop model would indicate. This has led to a search for "super heavy" elements with Z = 110-118. 

Vesicular LC phases are a new kind of LC phase with cellular structure that is formed by the spatial organization of cylindrical, spherical, or polyhedral aggregates of curved single layers, bilayers, or double layers. These phases have been considered as complicated columnar and cubic mesophases with core-shell morphology [192]. Till now only few vesicular mesophase are reported for thermotropic mesogens [193-196]. 

Introduction Anions have a strong tendency to adsorb specifically at metal surfaces, for example, to estabKsh a direct bond with the electrode by partial loss of their hydration shell. As a consequence of the contact with the electrode, the ionic character of the anions is markedly reduced, resulting in a higher surface concentration than in case of nonspecific adsorption. This effect was first observed in double-layer studies on mercury [229, 230] and later confirmed and studied in detail on single-crystal solid electrodes [231-234]. Specifically adsorbed anions can form various types of ordered structures, either more open (cf. sulfate on Au(hld) [235, 236]) or close-packed as reported for halides on different solid electrodes [21]. Cyclic current-potential curves often reveal sharp current peaks, indicative of phase transitions within the anionic adlayers and hence of the existence of ordered phases [21, 237]. Thermodynamic data of specific anion adsorption was obtained in surface tension studies (on mercury only [229,238-240]), capacitance measurements [231-233], cyclic voltammetry, and chronocoulometry [234]. As an... 

For heat-exchange surface areas of less than 200 ft and as low as 2 ft, double-pipe heat exchangers are often selected over shell-and-tube heat exchangers. The area. A, is usually based on the outside surface area of the inner pipe. The cost correlation here is based on the average of several of the references in Table 16.19. The base cost curve in Figure 16.11 fora... 

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