Multi-frequency wavefield modeling of acoustic VTI wave equation using physics informed neural networks

Incorporating anisotropy is crucial for accurately modeling seismic wave propagation. However, numerical solutions are susceptible to dispersion artifacts, and they often require considerable computational resources. Moreover, their accuracy is dependent on the size of discretization, which is a function of the operating frequency. Physics informed neural networks (PINNs) have demonstrated the potential to tackle long-standing challenges in seismic modeling and inversion, addressing the associated computational bottleneck and numerical dispersion artifacts. Despite progress, PINNs exhibit spectral bias, resulting in a stronger capability to learn low-frequency features over high-frequency ones. This paper proposes the use of a simple fully-connected PINN model, and evaluates its potential to interpolate and extrapolate scattered wavefields that correspond to the acoustic VTI wave equation across multiple frequencies. The issue of spectral bias is tackled by incorporating the Kronecker neural network architecture with composite activation function formed using the inverse tangent (atan), exponential linear unit (elu), locally adaptive sine (l-sin), and locally adaptive cosine (l-cos) activation functions. This allows the construction of an effectively wider neural network with a minimal increase in the number of trainable parameters. The proposed scheme keeps the network size fixed for multiple frequencies and does not require repeated training at each frequency. Numerical results demonstrate the efficacy of the proposed approach in fast and accurate, anisotropic multi-frequency wavefield modeling

Geophysical prospecting in the Krousovitis dam (N. Greece) by seismic and resistivity methods

Abstract: The use of two geophysical methods in the investigation of the geological setting in the area of a dam foundation is presented in this study. The seismic method was used in order to map the structure of the upper layers near the riverbed. VES and resistivity tomographs were also carried out. The depth to the basement was estimated by interpreting the VES curves. Interpretation of the topographic images, along with the inferred models from the seismic data, revealed the thickness of the colluvial deposits

Subsurface Geological Characterization of the Late Neogene-Quaternary Argive Basin, Peloponnese, Greece Using Transient Electromagnetic Data and Vintage Stratigraphic Logs

The onshore and offshore clastic deposits of the Argive Basin and the Argolic Gulf, respectively, in Peloponnese, Greece, form a Late Neogene-Quaternary half-graben that connects with the Aegean Sea. The onshore Late Neogene-Quaternary sequence, comprised of chaotically intercalated cohesive and granular clastic deposits, is in angular unconformity with bedrock comprised of Triassic-Upper Cretaceous strongly-weathered, highly-fractured karstic limestones thrusted against Paleogene flysch deposits. While the surface geology of the Argive Basin is well-known, the subsurface geology remains both poorly mapped and understood. We utilized transient electromagnetic (TEM) soundings coupled with 185 vintage stratigraphic logs, current surface geology knowledge, and insights from available geophysical surveys to characterize the subsurface conditions of this sedimentary basin. We estimated the thickness of the young deposits (the depth to bedrock) and detected potential subsurface tectonic structures. The TEM-FAST 48HPC data acquisition system with integrated inversion and visualization software package was used with a single-loop dimension of 50 m x 50 m to collect a total of 329 TEM soundings at 151 stations scattered throughout the basin. The TEM station spacing varied from 200 to 750 m allowing the mapping of 80 km(2). The total depth of investigation with the inverted TEM data and the lithology logs was 130 m and 183 m, respectively. The joint interpretation produced several quasi-two-dimensional electrical resistivity profiles that traverse the sedimentary basin in various azimuths and depth slices of average electrical resistivity covering the basin. The depth slices and the vintage stratigraphic logs revealed an uneven bedrock topography overlain by an irregularly thick (over 180 m) Late Neogene-Quaternary heterolithic sediment cover

Sjuksköterskors och undersköterskors uppfattningar om omvårdnadens innehåll och arbete : En intervjustudie

Bakgrund: Omvårdnad är ett ord som kan ha flera olika betydelser, det kan vara ett verb som något man utövar eller en synonym med kunskap som något som erhålls. Syfte: Syftet med studien var att beskriva vad sjuksköterskor och undersköterskor ansåg inbegripas av begreppet omvårdnad och “god omvårdnad” samt vad för arbetsuppgifter de olika yrkeskategorierna utförde inom ramen för omvårdnad. Metod:Individuella intervjuer av tre sjuksköterskor och fyra undersköterskor. Innehållet analyserades med hjälp av kvalitativ innehållsanalys. Fem teman och 21 kategorier framkom. Resultat: Respondenterna uttryckte att den basala omvårdnaden hade en central roll inom begreppet omvårdnad. Vid diskussion om vad god omvårdnad innebar framhävde de flesta att ett gott bemötande var avgörande, att utföra arbetsuppgifter med omtanke och respekt. Att bedriva personcentrerad vård ansågs även ge god omvårdnad. Förutom basal omvårdnad och bemötande framkom det att medicinsk teknik var en stor del av arbetet inom omvårdnaden och att samarbete var en viktig del. Det rådde få meningsskiljaktigheter angående sjuksköterskans respektive undersköterskans arbetsuppgifter. Slutsats: Sjuksköterskorna och undersköterskorna som intervjuats har till stor del en samlad bild utav vad begreppet omvårdnad innebär. Det fokuserades mest på basal omvårdnad och gott bemötande vilket båda är två viktiga och centrala delar inom omvårdnaden. Att det inte fanns många meningsskiljaktigheter mellan undersköterskorna och sjuksköterskan kan ses som ett resultat av en tydlig arbetsfördelning. Background: Nursing is a word that can have several meanings, it can be a verb or be synonymous with knowledge. Aim: The aim with this study was to describe what registered nurses (RN) and certified nursing assistant (CNA) perceived by the expressions nursing  and “qualitative nursing ” and what tasks at work these two different professions performed within the limits of nursing. Method: Qualitative interview study with individual interviews with three RN's and four CNA's. The content was analyzed through qualitative content analysis. Five themes and 21 categories arose. Results: The respondents expressed that the basal nursing care had a central role within the concept; nursing. At discussions about what good nursing meant, it was brought forth that a good interaction was decisive, to perform work related tasks with consideration and respect. To exercise person centered care was also considered to be good nursing. Besides basal nursing care and interactions it became apparent that medical technique is a big part of the job within nursing and that cooperation is an important part as well. There were few differences in opinions concerning RN respectively CNA job tasks. Conclusion: RN's and CNA's that were interviewed have the same general idea about what the concept nursing implies. It mainly focused on basal nursing care and good interactions, which were both considered as important parts within nursing. It can be seen that the lack of differences in opinion between CNA's and RN's is brought forth by a clear division of work between the two