SUMMARYUnder the assumption of an immovable point source for the earthquake energy release, a mathematical model is developed to compute the components of the free field surface rotation consistent with assigned translational components.Experimental evidence on these quantities is offered by the strong-motion instrument arrays. However, lack of adequate identification of the different wave contributions prevents in general a direct measurement of rotational and torsional components, allowing only a qualitative assessment of just how large these components might be. The only exceptions are the records of SMART-1, which offer the entire information to derive rotations.The available data of strong-motion instrument arrays for this problem are summarized in Table 1. They are in qualitative agreement with the suggestions of the mathematical model.Earthquake response spectra for the rotational components are developed for a few selected cases, in particular a rotational spectrum consistent with the prescription of USNRC Regulatory Guide 1.60.The correlations between the translational and rotational components of the ground motion are also shown.
Proportional electroluminescence (EL) in noble gases is used in two-phase detectors for dark matter searches to record (in the gas phase) the ionization signal induced by particle scattering in the liquid phase. The “standard” EL mechanism is considered to be due to noble gas excimer emission in the vacuum ultraviolet (VUV). In addition, there are two alternative mechanisms, producing light in the visible and near infrared (NIR) ranges. The first is due to bremsstrahlung of electrons scattered on neutral atoms (“neutral bremsstrahlung”, NBrS). The second, responsible for electron avalanche scintillation in the NIR at higher electric fields, is due to transitions between excited atomic states. In this work, we have for the first time demonstrated two alternative techniques of the optical readout of two-phase argon detectors, in the visible and NIR range, using a silicon photomultiplier matrix and electroluminescence due to either neutral bremsstrahlung or avalanche scintillation. The amplitude yield and position resolution were measured for these readout techniques, which allowed to assess the detection threshold for electron and nuclear recoils in two-phase argon detectors for dark matter searches. To the best of our knowledge, this is the first practical application of the NBrS effect in detection science.
The effect of corrosion on bond strength of ribbed bars in reinforced concrete (RC) is studied by axisymmetric finite-element analysis, modelling different levels of confinement given by the transverse steel reinforcement. The importance of this parameter is highlighted by a summary of the experimental results in the literature. An approach is developed to model the corrosion product expansion causing concrete-cover cracking. The numerical analyses reproduce the experimental results of the bond tests performed in two different studies. A parametric study shows the effect of the varying transverse steel percentage on the residual bond strength, and the influence of different arrangements of confinement bars. These results lead to a discussion of the different findings of several experimental researches. The conclusions regard the main parameters to be included in a model to predict the bond strength of corroded bars. Some indications for the assessment of corroding structures are given.
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