Environmental change within the Balkan region during the past ca. 50 ka recorded in the sediments from lakes Prespa and Ohrid

Lakes Prespa and Ohrid, in the Balkan region, are considered to be amongst the oldest lakes in Europe. Both lakes are hydraulically connected via karst aquifers. From Lake Ohrid, several sediment cores up to 15 m long have been studied over the last few years. Here, we document the first long sediment record from nearby Lake Prespa to clarify the influence of Lake Prespa on Lake Ohrid and the environmental history of the region. Radiocarbon dating and dated tephra layers provide robust age control and indicate that the 10.5 m long sediment record from Lake Prespa reaches back to 48 ka. Glacial sedimentation is characterized by low organic matter content and absence of carbonates in the sediments, which indicate oligotrophic conditions in both lakes. Holocene sedimentation is characterized by particularly high carbonate content in Lake Ohrid and by particularly high organic matter content in Lake Prespa, which indicates a shift towards more mesotrophic conditions in the latter. Long-term environmental change and short-term events, such as related to the Heinrich events during the Pleistocene or the 8.2 ka cooling event during the Holocene, are well recorded in both lakes, but are only evident in certain proxies. The comparison of the sediment cores from both lakes indicates that environmental change affects particularly the trophic state of Lake Prespa due to its lower volume and water depth

Model predictive Direct Flux Vector Control of multi three-phase induction motor drives

A model predictive control scheme for multiphase induction machines, configured as multi three-phase structures, is proposed in this paper. The predictive algorithm uses a Direct Flux Vector Control scheme based on a multi three-phase approach, where each three-phase winding set is independently controlled. In this way, the fault tolerant behavior of the drive system is improved. The proposed solution has been tested with a multi-modular power converter feeding a six-phase asymmetrical induction machine (10kW, 6000 rpm). Complete details about the predictive control scheme and adopted flux observer are included. The experimental validation in both generation and motoring mode is reported, including post open-winding fault operations. The experimental results demonstrate the feasibility of the proposed drive solution

Geometric Deep Learning: a Temperature Based Analysis of Graph Neural Networks

We examine a Geometric Deep Learning model as a thermodynamic system treating the weights as non-quantum and non-relativistic particles. We employ the notion of temperature previously defined in [7] and study it in the various layers for GCN and GAT models. Potential future applications of our findings are discussed.Comment: Published on Proceedings of GSI 202

Environmental change within the Balkan region during the past ca. 50 ka recorded in the sediments from lakes Prespa and Ohrid

Lakes Prespa and Ohrid, in the Balkan region, are considered to be amongst the oldest lakes in Europe. Both lakes are hydraulically connected via karst aquifers. From Lake Ohrid, several sediment cores up to 15 m long have been studied over the last few years. Here, we document the first long sediment record from nearby Lake Prespa to clarify the influence of Lake Prespa on Lake Ohrid and the environmental history of the region. Radiocarbon dating and dated tephra layers provide robust age control and indicate that the 10.5 m long sediment record from Lake Prespa reaches back to 48 ka. Glacial sedimentation is characterized by low organic matter content and absence of carbonates in the sediments, which indicate oligotrophic conditions in both lakes. Holocene sedimentation is characterized by particularly high carbonate content in Lake Ohrid and by particularly high organic matter content in Lake Prespa, which indicates a shift towards more mesotrophic conditions in the latter. Long-term environmental change and short-term events, such as related to the Heinrich events during the Pleistocene or the 8.2 ka cooling event during the Holocene, are well recorded in both lakes, but are only evident in certain proxies. The comparison of the sediment cores from both lakes indicates that environmental change affects particularly the trophic state of Lake Prespa due to its lower volume and water depth

Comment on: ‘‘The dark nature of Somma-Vesuvius volcano:Evidence from the 3.5 ka BP Avellino eruption’’ by Milia A.Raspini A., Torrente M.M.,

We present here some criticism to the scientific content of the paper of Milia et al. [2007. The dark nature of Somma-Vesuvius volcano: evidence from the 3.5 ka B.P. Avellino eruption. Quaternary International, 173–174, 57–66] published in Quaternary International. Milia et al. (2007) interpreted seismic lines in the Gulf of Naples (southern Italy), and inferred the presence of deposits from a large debris avalanche which occurred just before the Avellino eruption of Somma-Vesuvius volcano. The authors supported their seismic profile interpretation with on-land stratigraphies and logs. However, we present here different on-land data that demonstrate the inconsistency of the occurrence of any debris avalanche before or after the Avellino eruption, and we provide also an alternative interpretation for the observed seismic facies offshore of Somma-Vesuvius

Output feedback control of flow separation over an aerofoil using plasma actuators

We address the problem of controlling the unsteady flow separation over an aerofoil, using plasma actuators. Despite the complexity of the dynamics of interest, we show how the problem of controlling flow separation can be formulated as a simple set-point tracking problem, so that a simple control strategy may be used. A robust output feedback control is designed, on the basis of a low-order, linear, dynamical model approximating the incompressible Navier-Stokes equations, obtained from the snapshots of 2D laminar finite element simulations at Re=1,000. Fast flow reattachment is achieved, along with both stabilisation and increase/reduction of the lift/drag, respectively. Accurate 2D finite element simulations of the full-order nonlinear equations illustrate the effectiveness of the proposed approach: good dynamic performances are obtained, as both the Reynolds number and the angle of attack are varied. The chosen output can be experimentally measured by appropriate sensors and, despite its simplicity, the proposed set-point tracking controller is sufficient to suppress the laminar separation bubble; moreover, its extension to 3D turbulent configurations is straightforward, thus illustrating the effectiveness of the designed control algorithm in more practical conditions, which are far from the design envelope

Volcaniclastic debris flow occurrences in the Campania region (southern Italy) and their relation to Holocene - late Pleistocene pyroclastic fall deposits: implications for large scale hazard mapping

The Campania Region (Southern Italy) is characterized by the frequent occurrence of volcaniclastic debris flows that produce damage to property and loss of life (more than 170 deaths between 1996 and 1999). Historical investigation allowed the identification of more than 500 events during the last four centuries; in particular, more than half of these occurred in the last 100 years, causing hundreds of deaths. The aim of this paper is to identify debris flow proneness and to quantify hazard. To this end, we compared several elements such as the thickness distribution of pyroclastic fall deposits from the last 18 ka of the Vesuvius and Phlegrean Fields volcanoes, the slopes of relieves, and the historical record of volcaniclastic debris flows from AD 1500 to the present. Results show that flow occurrence is not only a function of the cumulative thickness of past pyroclastic fall deposits but also depends on the age of emplacement. Deposits younger than 10 ka (Holocene eruptions) apparently increase the risk of debris flows, while those older than 10 ka (Late Pleistocene eruptions) seem to play a less prominent role. This is probably in relation to different climatic conditions, and therefore different rates of erosion of pyroclastic falls between the Holocene and the Late Pleistocene. Based on the above considerations, we compiled a large-scale debris flow hazard map of the study area in which five main hazard zones are identified: very low, low, moderate, high and very high

Tephrostratigraphy and tephrochronology of lakes Ohrid and Prespa, Balkans

Four cores from Balkans lakes Ohrid and Prespa were studied for recognition of tephra layers and cryptotephras, and the results presented along with the review of data from other two already published cores from Lake Ohrid. The six cores provide a previously unrealised tephrostratigraphic framework of the two lakes, and supply the first detailed tephrochronologic profile (composite) for the Balkans, which spans from the end of the Middle Pleistocene to the end of the Ancient Age (AD 472). A total of 12 tephra layers and cryptotephras were recognised in the cores. One is of Middle Pleistocene age (131 ky) and correlated to the marine tephra layer P-11 from Pantelleria Island. Eight volcanic layers are Upper Pleistocene in age, and encompass the period between ca. 107 ky and ca. 31 ky. This interval contains some of the main regional volcanic markers of the Central Mediterranean area, including X-6, X-5, Y-5 and Y-3 tephra layers. The other layers of this interval have been related to the marine tephra layers C20, Y-6 and C10, while one was for the first time recognised in distal areas and correlated to the Taurano eruption of probable Vesuvian origin. Three cryptotephras were of Holocene age. Two of which have been correlated to Mercato and AD 472 eruptions of Somma-Vesuvius, while the third has been correlated to the FL eruption from Mount Etna. These recognitions provide a link of the Ohrid and Prespa lacustrine successions to other archives of the Central Mediterranean area, like South Adriatic, Ionian, and South Tyrrhenian Seas, lakes of Southern Italy (Lago Grande di Monticchio, Pantano di San Gregorio Magno and Lago di Pergusa) and Balkans (Lake Shkodra)

GIS-assisted modelling for debris flow hazard assessment based on the events of May 1998 in the area of Sarno, Southern Italy. II: Velocity and Dynamic Pressure

The velocity and dynamic pressure of debris flows are critical determinants of the impact of these natural phenomena on infrastructure. Therefore, the prediction of these parameters is critical for hazard assessment and vulnerability analysis. We present here an approach to predict the velocity of debris flows on the basis of the energy line concept. First, we obtained empirically and field-based estimates of debris flow peak discharge, mean velocity at peak discharge and velocity, at channel bends and within the fans of ten of the debris flow events that occurred in May 1998 in the area of Sarno, Southern Italy. We used this data to calibrate regression models that enable the prediction of velocity as a function of the vertical distance between the energy line and the surface. Despite the complexity in morphology and behaviour of these flows, the statistical fits were good and the debris flow velocities can be predicted with an associated uncertainty of less than 30% and less than 3 m s-1. We wrote code in Visual Basic for Applications (VBA) that runs within ArcGIS® to implement the results of these calibrations and enable the automatic production of velocity and dynamic pressure maps. The collected data and resulting empirical models constitute a realistic basis for more complex numerical modelling. In addition, the GIS implementation constitutes a useful decision-support tool for real-time hazard mitigation. Copyright © 2008 John Wiley & Sons, Ltd