Depth Dependence Research Articles

TEMPORAL AND SPATIAL VARIATIONS IN TSUNAMI CODA ENERGY IN MEDIUM- TO LONG-TERM DECAY PROCESSES

Temporal and spatial variations in tsunami coda waves in medium- to long-term decay processes were investigated based on theoretical analysis and observations. In this paper, medium- and long-term were defined as approximately τ ≤ t ≤ 2τ and t ≥ 2τ, respectively, where t is elapsed time from the earthquake origin time, and τ is the coda energy e-folding decay time. In the medium- to long-term decay processes, the energy and amplitude of tsunami coda waves may become small so that the energy dissipation due to turbulent friction can be negligible compared to the directional spectrum of coda waves. It was found that the energy balance equation without dissipation for the directional spectrum, D(f,θ), should be approximately satisfied in a quasi-steady state, and the quantity CCgD(f,θ) should hold for any two points, where C and Cg are the wave phase speed and group velocity, respectively. The latter relationship indicates the inverse proportion of the tsunami coda energy to the water depth, and the similarity of the frequency spectrum of coda waves between any two points. The water depth dependency of tsunami coda was confirmed over a wide frequency range by using the 2011 Tohoku Earthquake Tsunami data. However, the tsunami coda energy with periods of 30–70 min did not follow the h-1 law, because continental seiche and edge waves were generated at Kochi, and the amplitude of tsunami coda waves at other stations did not show exponential decay in time. The estimated frequency spectra of coda waves at depths larger than 100 m were found to be inversely proportional to frequency squared, f2, for a wide frequency range. The f-2 law of frequency spectrum was theoretically derived by using linear shallow water equations with linear friction and dispersion terms. The effects of linear friction and dispersion on the frequency spectrum were deduced from the spectral solutions.

Investigation of local scour around two vertical piles by using numerical method

Local scour around two vertical piles is investigated numerically. A three-dimensional finite element solver is used to conduct the numerical study. The flow model is based on the three-dimensional Reynolds Averaged Navier-Stokes (RANS) equation by using the SST k-ω turbulence model closure. As for the scour model, both suspended load transport and bed load transport are considered. The numerical model is validated against (1) flow over smooth bed (2) local scour around one vertical pile by comparing with published data. In order to add weight of evidence on the effectiveness of present numerical model, two experimental tests are carried out. Present numerical model works well to predict the velocity and local scour around piles by comparing with published data and present experiment. Then the numerical model is used to study local scour around two vertical piles in tandem, side by side and staggered arrangements. The dependence of scour depth at the upstream side of the piles on gap ratio is discussed. Moreover, the time scale of scour under various gap ratios is investigated.

Cluster structure of superconducting phase and the nature of peaks in the doping dependences of the London penetration depth in iron pnictides

The mechanism of formation of dome-like phase diagrams and the features of magnetic field penetration in iron pnictides with hetero- and isovalent doping are considered within the framework of the previously proposed model, which assumes the local character of doping and the cluster structure of resulted superconducting phase. It is shown that the proposed model, despite its simplicity and neglect of the features of the electronic structure, makes it possible not only to accurately calculate the positions of superconducting domes on the phase diagrams of specific HTSC compounds, but also to explain the nature and position of sharp peaks in the London penetration depth depending on the doping level.

ИССЛЕДОВАНИЯ ИНКОРПОРИРОВАННОГО В ОРГАНИЗМ ЧЕЛОВЕКА РАДИОНУКЛИДА АМЕРИЦИЯ-241 С ПОМОЩЬЮ РАНЕВОГО ДЕТЕКТОРА

Purpose: to develop a method for experimental study of the distribution of radionuclide 241Am in human organs and tissues during wound admission to clarify the process of formation of doses of alpha radiation.
 Material and methods: in clinical practice of Burnazyan FMBC of the FMBA of Russia To improve the method of determination, an experiment was performed to determine the depth of radionuclide on pigskin with the location of 241Am point sources behind different thicknesses. 
 Results: the used methods of measurement, tested on pigskin, allowed to obtain the dependence of the localization depth of radionuclide 241Am on the measured on the surface of the tissue ratios of photons with different energies.
 Conclusion: Set the ratio of photons with different energies on the thickness of the barrier (depth), and proven methodology allow you to go directly to the planning of experimental studies on the barrier effect created in the bone material, and including a radionuclide, the formation of doses of alpha radiation on the bone marrow.

Microstructure-informed prediction and measurement of nanoindentation hardness of an Fe-9Cr alloy irradiated with Fe-ions of 1 and 5 MeV energy

Hardening of Fe-9%Cr alloys exposed to irradiation with Fe2+ ions of two different energies, 1 and 5 MeV, is investigated using nanoindentation. The limited penetration depth of the ions causes steep damage gradients in the near-surface volumes of the irradiated samples. This damage gives rise to graded microstructures resulting in depth-dependent irradiation hardening. Nanoindentation integrates the depth-dependent hardness over the indentation plastic zone. Our study combines quantitative analysis of the ion-irradiated microstructures with the determination of the full depth dependence of irradiation hardening. The microstructure-informed model incorporates direct experimental evidence revealed by a former investigation using cross-sectional scanning transmission electron microscopy. For both ion energies, the observed microstructures consist of dislocation loops with band-like distributions and are concluded to be the dominant source of the measured irradiation-induced hardening. The model predictions are found to be in reasonable agreement with the as-measured nanoindentation response. The comparison of hardening predictions with different kinds of superposition rules of hardening contributions suggests linear superposition as the most appropriate selection under the present conditions. The possible transferability of these results to neutron irradiation is also discussed.

Shear-driven Hall-magnetohydrodynamic dynamos

Nonlinear Hall-magnetohydrodynamic dynamos associated with coherent structures in subcritical shear flows are investigated by using unstable invariant solutions. The dynamo solution found has a relatively simple structure, but it captures the features of the typical nonlinear structures seen in simulations, such as current sheets. As is well known, the Hall effect destroys the symmetry of the magnetohydrodynamic equations and thus modifies the structure of the current sheet and mean field of the solution. Depending on the strength of the Hall effect, the generation of the magnetic field changes in a complex manner. However, a too strong Hall effect always acts to suppress the magnetic field generation. The hydrodynamic/magnetic Reynolds number dependence of the critical ion skin depth at which the dynamos start to feel the Hall effect is of interest from an astrophysical point of view. An important consequence of the matched asymptotic expansion analysis of the solution is that the higher the Reynolds number, the smaller the Hall current affects the flow. We also briefly discuss how the above results for a relatively simple shear flow can be extended to more general flows such as infinite homogeneous shear flows and boundary layer flows. The analysis of the latter flows suggests that interestingly a strong induction of the generated magnetic field might occur when there is a background shear layer.

TWO APPROACHES FOR DETERMINING AREAS OF PLASTIC DEFORMATION IN A HOMOGENEOUS BASE FOUNDATION

The paper presents comparison of results of calculations of position, sizes and shapes of plastic deformation areas carried out on the basis of use of Coulomb plasticity condition and solution of elastic-plastic problem and mixed problem of elasticity theory and ground plasticity theory which resulted, among other things, in graphs of dependence of depth of plastic zones development on value of intensity of external influence. Calculations have been executed at three values of coefficient of side pressure of ground about = 0.37; 0.54; 0.72 for uniform strip load (no die), and for absolutely rigid die under condition of full sticking and under condition of no friction on ground-stamp contact. As a result, it was found that the plastic regions corresponding to the "Coulomb" solution differ essentially from similar regions based on elastic-plastic (mixed) solutions. Their sizes, with the same intensity of loading, are larger, their rate of development into the deepening of the base is higher than that of the alternative ones, and when the load reaches the maximum permissible value, they merge under the punch and form a single sickle-shaped area. In the case of "Coulomb" plastic areas, their shape and rate of development into the foundation in the initial stages of loading are rather strongly dependent on the value of soil side pressure coefficient. In the case of "mixed" solution, the "velocity" of this process is practically independent of the value of coefficient o. If we use the condition of closing of plastic regions in the foundation under load as the criterion for determination of the maximum permissible value of intensity of external action, then in "Coulomb" regions this value will be substantially lower than in alternative ones for all considered values of the coefficient of lateral pressure of soil.

A Far-Field Ground-Motion Model for the North Australian Craton from Plate-Margin Earthquakes

ABSTRACT The Australian territory is just over 400 km from an active convergent plate margin with the collision of the Sunda–Banda Arc with the Precambrian and Palaeozoic Australian continental crust. Seismic energy from earthquakes in the northern Australian plate-margin region are channeled efficiently through the low-attenuation North Australian craton (NAC), with moderate-sized (Mw≥5.0) earthquakes in the Banda Sea commonly felt in northern Australia. A far-field ground-motion model (GMM) has been developed for use in seismic hazard studies for sites located within the NAC. The model is applicable for hypocentral distances of approximately 500–1500 km and magnitudes up to Mw 8.0. The GMM provides coefficients for peak ground acceleration, peak ground velocity, and 5%-damped pseudospectral acceleration at 20 oscillator periods from 0.1 to 10 s. A strong hypocentral depth dependence is observed in empirical data, with earthquakes occurring at depths of 100–200 km demonstrating larger amplitudes for short-period ground motions than events with shallower hypocenters. The depth dependence of ground motion diminishes with longer spectral periods, suggesting that the relatively larger ground motions for deeper earthquake hypocenters may be due to more compact ruptures producing higher stress drops at depth. Compared with the mean Next Generation Attenuation-East GMM developed for the central and eastern United States (which is applicable for a similar distance range), the NAC GMM demonstrates significantly higher short-period ground motion for Banda Sea events, transitioning to lower relative accelerations for longer period ground motions.

Groove Formation on Metal Substrates by Nanosecond Laser Removal of Melted Material

An effective strategy to produce grooves on carbon steel substrates by nanosecond laser radiation is proposed. The aim is to increase the productivity of grooves creation. In this study, two different modes of laser treatment are compared. The first mode focuses on the evaporation of material, while the second focuses on the formation of melted material and its removal by the action of pressure vapors produced by evaporated material. Within some ranges of processing parameters, the shape of the groove can be linearly controlled. The dependence of the groove depth also has a logarithmic nature when the number of passes is increased. Using the liquid phase mode in some ranges of parameters can reduce the amount of evaporated material in comparison with standard techniques in which the material is removed in the form of gas, and fine dust is emitted.

High dose 30 MeV 58Ni5+ ion irradiation causes microstructure evolution in nuclear graphite at 400 °C

A 30 MeV 58Ni5+ ion beam was used to irradiate fine-grained graphite grade IG110 and ultrafine-grained graphite grade G1 at 400 °C to study their microstructure evolution under irradiation. Taking advantage of the depth dependence of the damage rate and cumulative damage of ion irradiation, the microstructure change exploration of graphite with multiple damage levels within a single fluence specimen was achieved by characterizing the sample cross-section with HR-TEM and micro-Raman. The Raman 2D maps of the cross-sections of the graphite samples irradiated with various fluences and displacement damages up to ∼18 displacements per atom were analyzed. Evidenced by the saturation of the intensity ratio of graphite Raman D and G band (ID/IG), the irradiation damage and annealing equilibrium was observed. Moreover, ID/IG in combined with the full width at half maximum of the G band (FWHM (G)), shows an inverse evolution compared with the graphitization process, which is also supported by the HR-TEM observation. Demonstrated by the increasing rate of ID/IG with FWHM (G) and the saturation ID/IG, the microstructure changes of fine-grained graphite IG110 and ultrafine-grained graphite G1 was distinguished.

Mechanical behaviour of corroded strands under chloride attack: A new constitutive law

The paper presents an experimental and analytical study on the tensile behaviour of naturally corroded prestressing strands. A total of twenty-four strands were extracted from full-scale beams which were exposed during 10 years to chlorides from sea water. Firstly, a database has been created on the dependency of the maximum pit depth on the strand mass loss or on the section loss of the most corroded wire. Secondly, the morphology of corrosion pits and the maximum cross-sectional loss of each external wire have been measured. Finally, based on conducted tensile tests, a new constitutive law (CPS-model) is proposed to predict the mechanical behaviour of prestressing strands induced by pitting corrosion.

Evidence for stellar contamination in the transmission spectra of HAT-P-12b

Context. Transmission spectroscopy characterizes the wavelength dependence of transit depth, revealing atmospheric absorption features in planetary terminator regions. In this context, different optical transmission spectra of HAT-P-12b reported in previous studies exhibited discrepant atmospheric features (e.g., Rayleigh scattering and alkali absorption). Aims. We aim to understand the atmosphere of HAT-P-12b using two transit spectroscopic observations by the Gran Telescopio Canarias (GTC) and to search for evidence of stellar activity contaminating the transmission spectra, which might be the reason behind the discrepancies. Methods. We used Gaussian processes to account for systematic noise in the transit light curves and used nested sampling for Bayesian inferences. We performed joint atmospheric retrievals using the two transmission spectra obtained by GTC OSIRIS, as well as previously published results, coupled with stellar contamination corrections for different observations. Results. The retrieved atmospheric model exhibits no alkali absorption signatures, but shows tentative molecular absorption features including H2O, CH4, and NH3. The joint retrieval of the combined additional public data analysis retrieves similar results, but with a higher metallicity. Conclusions. Based on Bayesian model comparison, the discrepancies of the transmission spectra of HAT-P-12b can be explained by the effect of different levels of unocculted stellar spots and faculae. In addition, we did not find strong evidence for a cloudy or hazy atmosphere from the joint analysis, which is inconsistent with prior studies based on the observations of the Hubble Space Telescope.

Depth dependence of climatic controls on soil microbial community activity and composition

Subsoil microbiomes play important roles in soil carbon and nutrient cycling, yet our understanding of the controls on subsoil microbial communities is limited. Here, we investigated the direct (mean annual temperature and precipitation) and indirect (soil chemistry) effects of climate on microbiome composition and extracellular enzyme activity throughout the soil profile across two elevation-bioclimatic gradients in central California, USA. We found that microbiome composition changes and activity decreases with depth. Across these sites, the direct influence of climate on microbiome composition and activity was relatively lower at depth. Furthermore, we found that certain microbial taxa change in relative abundance over large temperature and precipitation gradients only in specific soil horizons, highlighting the depth dependence of the climatic controls on microbiome composition. Our finding that the direct impacts of climate are muted at depth suggests that deep soil microbiomes may lag in their acclimation to new temperatures with a changing climate.

Study of the RBE depth dependence of protons using a damage diagnostic algorithm and its application in proton therapy based on Monte Carlo simulation

The present study aimed to calculate the yields of DNA breaks and the variation of relative biological effectiveness (RBE) at different depths for protons using Geant4-DNA. For this purpose, an atomic model of DNA and a DNA damage classification matrix were used to calculate different DNA break yields for 62-MeV protons. As the reference radiation, the secondary electron spectrum produced by 60Co was evaluated. This helped to calculate the SSB and DSB yields. Moreover, RBE was found to be between 1.1 at the first point and 1.51 in the Bragg peak region. In this region, it was 37% greater than the 5-mm depth in the plateau region. Considering different threshold energies, the energy deposition at 10.79 eV had the most contribution to the total damage. As the results suggested, the depth dependence of RBE should be taken into account for proton therapy. It was also found that DNA break yields significantly depend on the threshold energy value.

Downhole Distributed Acoustic Sensing Provides Insights Into the Structure of Short‐Period Ocean‐Generated Seismic Wavefield

AbstractOcean‐generated seismic waves are omnipresent in passive seismic records around the world and present both a challenge for earthquake observations and an input signal for interferometric methods for characterization of the Earth's interior. Understanding of these waves requires the knowledge of the depth dependence of the oceanic noise at the transition into the continent. To this end, we examine 80 days of continuous acquisition with distributed acoustic sensor (DAS) system deployed in two deep boreholes near the south‐eastern coast of Australia. The iDASv3™ system deployed in a deep borehole at the CO2CRC Otway Project site provides sufficiently high sensitivity and low instrumentation noise for frequencies from 100 mHz to 20 Hz. Analysis of the seismograms and correlation with wave climate allows decomposing the DAS response into microseisms generated by swell from remote storms (0.15 Hz) and local winds (between 0.2 and 2 Hz), and strong body wave energy from large surf breaks at the coast (from 2 to 20 Hz). The depth dependence of the microseisms provides useful insights into the energy partition between the Rayleigh wave modes and may augment conventional kinematic analysis of the sparse surface seismological arrays. Overall, ocean‐generated signals at each channel along the borehole are strongly related to the wave climate, so that—with sufficient amount of training data—the passive seismic records on several downhole DAS sensors has a potential for high‐precision monitoring of formations surrounding the borehole as well as remote storms in the ocean.

Nonvolatile multilevel switching in artificial synaptic transistors based on epitaxial LiCoO2 thin films

In this study, we fabricate high-quality epitaxial ${\mathrm{Li}}_{1\text{--}x}\mathrm{Co}{\mathrm{O}}_{2}$ (LCO) thin films on $\mathrm{SrTi}{\mathrm{O}}_{3}$ substrates with different orientations and systematically investigate the change in the crystal orientation of thin-film grains by tuning the oxygen deposition pressure. Further tensile strain study reveals the depth dependence in these epitaxial LCO thin films. Further, synaptic transistors are fabricated based on these high-quality epitaxial LCO films, and long-duration nonvolatile potentiation and depression states are established. By reducing the thickness of the LCO channel, the signal-to-noise ratio of the nonvolatile switching is substantially improved. Changes in the potentiation and depression states are found to significantly depend on the lattice orientation of the LCO channel, suggesting that an anisotropic Li-ion diffusion rate in highly crystallized LCO films plays an important role in the device performance.

Imaging buried objects with the hard/soft x-ray photoemission electron microscope

We apply charged-particle simulation to determine the constraints imposed additionally on the photoemission electron microscope (PEEM) when x rays are applied to image buried objects. PEEM initiates its image acquisition by reading the electron-emission profile on the specimen surface, but the profile is not invariant if the electrons originate from a buried object. In this work, we show that, other than the anticipated intensity reduction, the electron-emission profile projected from a buried object displays a blurrier edge for a deeper burial, whereas the distribution of an emission angle becomes narrower for electrons carrying greater kinetic energy. The burial not only redefines the objects seen by PEEM but also introduces additional depth and energy dependence to the resulted images. We demonstrate that inserting a contrast aperture in the PEEM lens can improve the image quality and ease the burial dependence.

Are Deep Aquifers Really Confined? Insights From Deep Groundwater Tidal Responses in the North China Platform

AbstractMany deep aquifers overlain by barrier formations in the continental US are used as geological repositories for wastewaters coproduced from hydrocarbon exploration. This practice is to protect shallow groundwater following the US Environmental Protection Agency’s regulation. Implicit in such practice is the assumption that deep aquifers overlain by mudstones or shales are confined so that the injected fluids will not migrate upward to contaminate shallow groundwater. However, no systematic test of this hypothesis has been made. Here we invert the groundwater response to both the M2 and the O1 tides and to the barometric pressure across a large (2.046 × 106 km2) geologic regime, the North China Platform, to systematically evaluate the hydraulic parameters as functions of depth and time without a priori assumption. Our result, the first of such inversion, shows no depth dependence of aquifer confinement to a depth of 3,400 m and that deep confined aquifers overlain by barrier formations may become leaky after distant earthquakes. It suggests that monitoring of aquifer confinement may be needed to ensure if the targeted deep aquifer for wastewater injection is really confined. The results may be timely and of global significance because the practice of hydrofracking for natural gas and the deep injection for the disposal of the coproduced wastewaters in the US may soon be adopted by other countries, such as China.

INJECTION MODEL OF CEMENT MORTAR PENETRATION INTO CRACKED ROCKS BEHIND WALLING

The natural and technological factors influencing on the depth of injection cement mortars penetration into the cracked rocks and emptiness under the lining of mountain tunnels have been studied. There are the width of cracks in rocks and groundwater pressure in them, the dynamic viscosity of the solution, which is determined by the content of additives-superplasticizer and watercement ratio W/C, the magnitude and duration of pressure during the projection (crimping). Thesefacts were established after the analytical of literature sources and the analysis of features, design and a technical condition of real tunnel, geological structure of processing rocks under their lining. Based on the fundamental rheological equation - Newton's law in viscous flow models of dependences of depth of penetration on factors mentioned above are developed. Because of research of these models the sizes of technological factors, including dynamic viscosity of the mortar, providing the required penetration of cement mortars were received. To ensure the penetration of the solution to a depth of 10 m in cracks with a width of 10 mm, the dynamic viscosity should not exceed over 0.05 Pa·s, and in cracks of 1 mm – 0.01 Pa·s. To ensure the penetration of the solution to a depth of 2 m in cracks with a width of 1 mm, the dynamic viscosity should be in the range of 0.03–0.1 Pa·s, and in cracks of 0.1 mm – 0.0025–0, 01 Pa·s. Superplasticizers allows reducing the dynamic viscosity ofsolutions to such values and effectively increasing the depth of their penetration into cracks and, as a result increasing the water resistance and load-bearing capacity of the fractured rock. The technology of injecting cement mortars with superplasticizer additives has been improved and developed for: the reconstruction of underground structures and massive artificial structures; the designing of a spherical bearing between galvanized concrete without a bald spot and the exposedmetal beams. The technology is recommended to be used for waterproofing and increasing the bearing capacity of tunnel, piers, bridges, and for the device of a laying layer between а withoutballast reinforced concrete bridge plate and longitudinal beams of metal bridges.

Quantitative analysis of Cenozoic faults and fractures and their impact on groundwater flow in the bedrock aquifers of Ireland

Faults and fractures are a critical store and pathway for groundwater in Ireland’s limestone bedrock aquifers either directly as conductive structures or indirectly as the locus for the development of karst conduits. From the quantitative analysis of post-Devonian faults and fractures in a range of lithological sequences, this report describes the principal characteristics of Cenozoic strike-slip faults and joints, the youngest and the most intrinsically conductive fractures within Irish bedrock. Analysis of these structures in more than 120 outcrop, quarry, mine and cave locations in a range of bedrock types, provides a basis for: (1) definition of quantitative models for their depth dependency, lithological control, scaling systematics and links to preexisting structure, (2) conceptualisation of their impact on groundwater behaviour, and (3) estimation of groundwater flow parameters. The quantitative models provide constraints on fracture-controlled flow connectivity. Commonly observed decreases in sustainable flows and water strike interceptions with depth are attributed to increasing confinement and decreasing fracture connectivity and dissolution. Faults and joints have quite different end member geometries, with faults having strongly heterogeneous scale-independent properties and joints more often showing scale-dependent stratabound properties. The highest and most sustainable groundwater flows are usually associated with the complexity of structure of Cenozoic faults and of preexisting Carboniferous structures (on which conductive fracturing localises), enhanced by karstification and strongly jointed limestone bedrock particularly in the near-surface. Increased groundwater flow is promoted within bedded, rather than massive (i.e. unbedded), limestone sequences, characterised by bedding-parallel fractures and karst connecting otherwise subvertical fractures and subvertical wells.