Структурная характеризация короткопериодной сверхрешетки на основе гетероструктуры CdF-=SUB=-2-=/SUB=-/CaF-=SUB=-2-=/SUB=-/Si(111) методами просвечивающей электронной микроскопии и рентгеновской дифрактометрии

A detailed study of the structure of a short-period superlattice based on alternating layers of cadmium and calcium fluorides, grown by molecular beam epitaxy on a Si (111) substrate, by transmission electron microscopy and X-ray diffractometry, has been carried out. It was found that the superlattice is in a pseudomorphic state, and a lateral inhomogeneity with a fragment size of 10 - 40 nm was found. The reason for the broadening of the main and satellite peaks of the SL on the (111) diffraction curve has been clarified.

Reconciling phase velocities from ambient noise and earthquake-generated surface waves by accounting for arrival-angle effects

<p>The shear-wave velocities structure at depth can be unraveled from ambient noise (AN) as well as from earthquake-generated (EQ) surface waves. While the first approach mostly provides information at crustal scale, earthquake-based surface waves sense deeper structures due to their lower frequency content. However, for periods between 20 and 40 s, where the two methods often overlap, a number of studies have shown that phase velocities from EQ surface waves are systematically higher (~1%) than those retrieved from AN. The reason for such systematic bias is still debated; finite-frequency effects, overtone contamination, and off-path propagation of surface waves due to structural inhomogeneities have all been invoked as possible explanations of the discrepancy in question.</p><p>We explore the validity of the latter hypothesis, by correcting Rayleigh-wave phase velocities for the effect of off-path arrivals at two stations. The deviation from the theoretical path is estimated by evaluating the resemblance of the vertical with the π/2-shifted radial component of the recorded seismograms. We developed a two-station algorithm implementing such a correction and tested it on a dataset of seismograms collected from more than 350 stations recording 443 earthquake events from 2005 to 2019. We demonstrate that by compensating for the arrival-angle effects, the discrepancy between the two methods is significantly reduced. This result suggests that the off-path propagation between epicenters and receivers due to lateral inhomogeneity in the Earth's structure explains most of the discrepancy between AN and EQ phase velocities previously reported in the literature. Such improvement in determining Rayleigh phase velocities will lead to more reliable seismic tomographies and enhanced interpretations of seismic anomalies in terms of thermo-chemical characteristics.</p>

Experimental study of mechanoelectric transformations in low saturated rocks

The results of study of the electrical response of dry and slightly saturated with salted water (NaCl) or kerosene cores of Berea sandstone to acoustic effect in the frequency range of 0.5–10 kHz are presented herein. A strong lateral inhomogeneity by saturation was created during the experiments. The electrical response is sensitive to the addition of all types of fluid in the rock samples. At the same time, the reaction to the addition of highly concentrated salt solution in the samples is weak, while the reaction to the addition of weak concentrated salt solution and kerosene is strong. A high correlation is observed between the shape of the electrical response spectra of dry and damped cores, up to 0.9. For kerosene, the shape of the spectrum varies greatly, the rank correlation coefficient of the shape of the spectra is 0.3. The fact of a significant increase in electrical response on addition of non-polar fluid (kerosene) to the core is beyond the theoretical framework and may be associated with the creation of strong lateral petrophysical heterogeneity by saturation. The strong sensitivity of the amplitude of the electroseismic response of rocks to very weak but non-homogeneous saturation is interesting for the development of remote methods for determination of the type of fluid saturation of rocks, when searching for minerals and for the development of the methods for prediction of geophysical catastrophes.

Analysis of Stress Inhomogeneous Coefficient of a Continuous Rigid Frame Bridge during Construction Stage

The box section which can meet the requirements of wider deck is widely used in the construction of continuous rigid frame bridge. However, the shearing force lag is very obvious, which causes the inhomogeneous distribution of stress in the cross section, and it may threaten the safety of the bridge structure when it is serious. Taking a continuous rigid frame bridge located in Yunnan, China as an example, this paper establishes the finite element calculation model of the bridge to analyze the stress inhomogeneity in the construction stage. The results show that the shear lag coefficient of the section is constantly changing during the dynamic process of construction, with the increase of the length of the cantilever, the shear lag coefficient gradually converges to 1; prestress is the most important factor that causes the lateral inhomogeneity of the positive stress.

Geophysical investigation and its geological interpretation in the frame of an intergrated survey prior to a dam construction in Plati River Valley, Rethymno, Greece.

A geophysical survey using electrical resistivity tomography (ERT) method(25 ERT profiles of 240m total length and 2 ERT profiles of 1000m total length) in the area of Plati River valley gave valuable information regarding the stratigraphy, related to loose sediments, various faces of flysch and limestone, the tectonic status and the detection of areas of thick and extensive sheared siltstone, that geoelectrically is similar to clay,material useful for the core of the future dam. Both branches of river and valley and in greater detail the area near the position of the dam have detected showing the underground in a 2D and 3D manner. The thickness of neogene andflysch exceeds 40m. Alternations of siltstones-sandstones are met in flysch and in places cohesive sandstones are also met without continuation in an extended area. The siltstonelayers due to their shear character present clayey characteristics in respect of their resistivities. In general zones of limestone uplift have not been detected, which may create problems of leakages apart of the dam area where lateral inhomogeneity between flysch and limestone has been detected (probable fault). The various limestone bodies met in flysch or neogene do not have continuation in depth and they are isolated.