Partial separation of variables and reexpansion of cylindrical and plane waves are used to find the solution describing the uniform motion of a load along a thin circular cylindrical shell in an elastic half-space with the free surface parallel to the axis of the shell. This is a model problem for studying the dynamics of tunnels and shallow-buried pipelines under transport loads. Dispersion curves for the cases of sliding and tight contact between the shell and the half-space are plotted and analyzed. The effect of the shell parameters on the stress-strain state of the half-space is examined Introduction. The mathematical simulation of the dynamic behavior of tunnels and pipelines subject to transport loads leads to boundary-value problems for an elastic medium with cylindrical cavities reinforced with elastic single-and many-layer shells. The effect of the daylight surface is usually neglected for deep underground structures (their depth of burial is more than five typical transverse dimensions). The bibliography of such models can be found in [5]. Pozhuev [7] was the first to find the solution for an axisymmetric normal load moving with a constant subsonic velocity over a thin-walled cylindrical shell in an elastic medium. Similar studies for a two-layer shell were conducted in [1,3]. It was shown that there are critical velocities exceeding which causes free undamped vibrations in tunnels [3,5].For shallow underground structures (depth of burial is less than five typical transverse dimensions), the effect of the daylight surface should be taken into account. The motion of a subsonic periodic load along a nonreinforced cylindrical cavity in an elastic half-space was studied in [2,5], where incomplete separation of variables and reexpansion of cylindrical and plane waves were used to obtain the exact analytic solutions of the relevant boundary-value problems. However, finding such solutions for models of shallow lined tunnels is still a challenge. Note that a few publications address dynamic problems for a prestressed elastic layered half-space under a moving load [9, 10] and for shells under a nonstationary load [11, 12, etc.].We will find the solution describing the uniform motion of a load along a thin circular cylindrical shell in an elastic half-space with the free surface parallel to the shell axis. In finding the analytic solution, we will plot and analyze dispersion curves for the cases of sliding and tight contacts between the shell and the half-space. The influence of shell parameters on the stress-strain state (SSS) of the half-space will be examined.1. Formulation and the Solution of a Periodic Problem. Consider a thin infinitely long cylindrical shell with mid-surface radius R and thickness h 0 in an elastic, homogeneous, isotropic half-space with Lamé parameters l, m and density r. We choose a Cartesian coordinate system with the Z-axis aligned with the axis of the cavity parallel to the load-free flat boundary of the half-space and the X-axis perpendicular to this boundary: x £ h, where h is the...

Die Diaryljodosyltrifluoracetate (I) gehen unter der Einwirkung von SF4 in Methylenchlorid bei ‐10 bis 0°C in die Difluoride (II) (Ausbeute 78 bzw. 65%) über.

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Ein 45stündiges Erhitzen der Furandicarbonsäure (I) mit SF4 im Autoklaven auf 185°C liefert ein Gemisch der Trifluormethylverbindungen (II) und (III); analog erhält man aus der Dicarbonsäure (V) ein Gemisch der Fluorierungsprodukte (VI)‐(VIII), aus der Dicarbonsäure (IX) schon bei 1 15°C (in Gegenwart von HF) ein Gemisch der Fluorierungsprodukte (X) und (XI).

The work presents analysis of the correlation existing between the spectrometric performance of commercially produced hemispherical detectors of volume 500 mm 3 and the quality of starting CdZnTe material. More then 100 detectors made from CdZnTe crystals grown by eV Products, Saint-Gobain and Yinnel Tech. were studied. For the incoming inspection of the material an infrared (IR) transmission microscope was used. The presence of structural defects such as grain boundaries, twins, inclusions and cavities was checked and their shapes, sizes and spatial distributions were examined; the values of electron mobility-lifetime product (µτ) e were measured. The hemispherical detectors were made by a technology elaborated at the RITEC. Spectrometric performance of the detectors was verified by measuring the energy resolution and the peak-to-Compton ratio at the 662 keV line. It was found that all tested detectors had numerous structure defects, whose shapes, sizes, numbers and spatial distributions varied from sample to sample. Were found that hemispherical detectors made from samples containing inclusions of irregular shape had a poor spectrometric performance, while the detectors from samples containing large inclusions (>50 µm) of regular shape (triangular, hexagonal) as a rule performed well. It was also found that a highly non-uniform spatial distribution of structural defects usually leads to a poor spectrometric performance.