Seasonal and bathymetric variations of epiphytic macroflora on Posidonia oceanica (L.) Delile leaves in the National Marine Park of Zakynthos (Greece)     

Anastasia Tsirika  Georgios Skoufas  & Savvas Haritonidis 《Marine Ecology》2007,28(S1):146-153

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Ground Response to Tunnel Re-profiling Under Heavily Squeezing Conditions     

Apostolos Vrakas  Georgios Anagnostou 《Rock Mechanics and Rock Engineering》2016,49(7):2753-2762

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Testing optically stimulated luminescence dating on sand-sized quartz of deltaic deposits from the Sperchios delta plain,central Greece   总被引：1，自引：1，他引：0  

Evangelos Tsakalos  Elias Dimitriou  Maria Kazantzaki  Christos Anagnostou  John Christodoulakis  Eleni Filippaki 《古地理学报》2018,(2)

This study reports on the first investigation into the potential of luminescence dating to establish a chronological framework for the depositional sequences of the Sperchios delta plain, central Greece. A series of three borehole cores(20 m deep) and two shallow cores(4 m deep), from across the delta plain, were extracted, and samples were collected for luminescence dating. The luminescence ages of sand-sized quartz grains were obtained from small aliquots of quartz, using the Single-Aliquot Regenerative-dose(SAR) protocol.The equivalent dose determination included a series of tests and the selection of the Minimum Age Model(MAM) as the most appropriate statistical model. This made it possible to confirm the applicability of quartz Optically Stimulated Luminescence(OSL) dating to establish absolute chronology for deltaic sediments from the Sperchios delta plain.Testing age results of the five cores showed that the deltaic sediments were deposited during the Holocene.A relatively rapid deposition is implied for the top ~14 m possibly as a result of the deceleration in the rate of the sea-level rise and the transition to terrestrial conditions, while on the deeper parts, the reduced sedimentation rate may indicate a lagoonal or coastal environment.  相似文献   

A model for swelling rock in tunnelling     

G. Anagnostou 《Rock Mechanics and Rock Engineering》1993,26(4):307-331

Summary In this paper, the phenomenon of swelling in tunnelling will be treated as a hydraulic-mechanical coupled process. This approach allows one to model the observed floor heaves realistically, i. e. without the prediction inevitable in the previous models of movements at the tunnel crown and walls. Furthermore, the development of heave and pressure over the course of time can be studied. The absence of deformations above the floor level is here interpreted as a consequence of the hydraulic boundary conditions. Besides the importance of seepage flow, the influence of rock strength is illustrated. Swelling rock is considered as an elastoplastic material. This allows one to predict the often large haaves of a tunnel floor as observed in situ. According to the numerical results, the area of practically relevant swelling strains extends as far as the plastic zone.  相似文献   

Continuous,Direct Gas-Geochemical Monitoring in Hydrothermal Vents: Installation and Long-Term Operation on Nisyros Island (Greece)     

Manfred Teschner  Eckhard Faber  Jürgen Poggenburg  Georgios E. Vougioukalakis  Georgios Hatziyannis 《Pure and Applied Geophysics》2007,164(12):2549-2571

In this paper the installation and long-term operation of a system for continuous monitoring of fumarolic gases is described. Several physicochemical and gas-geochemical parameters such as the concentration of CO₂, H₂S and CO in the fumarolic emissions, as well as the temperatures of the hydrothermal steam and soil in close vicinity of the fumarole and steam pressure are measured in short-time intervals (typically 15 seconds). Data are logged on-site and in parallel transferred to a remote station by digital telemetry. Specially developed software enables the real-time observation of the local conditions in the crater and full bidirectional control of the monitoring system. Fluctuations in the monitored parameters are also reported. From the data presented it can be concluded that environmental conditions (direction and strength of wind, precipitation) will interact with some of the parameters monitored. These influences can only be revealed by continuously operated monitoring systems.  相似文献   

Comparison of Deep Underwater Measurements and Radar Observations of Rainfall     

Amitai  E. Nystuen  J.A. Anagnostou  E.N. Anagnostou  M.N. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(3):406-410

Deep-water acoustical measurements of rainfall are compared to high-resolution ground radar observations for the first time. The measurements of underwater ambient sound were made from a subsurface mooring near Methoni, Greece, in 2004. The acoustical measurements were at 60-, 200-, 1000-, and 2000-m depths. Simultaneous ground-based polarimetric -band radar observations were made over the acoustic mooring. Comparisons show acoustic detection of rain events and storm structure that are in agreement with the radar observations. Results from a comparison between the underwater sound pressure level at different depths and the observed radar reflectivities are presented.  相似文献   

Comparison of Raindrop Size Distribution Estimates From X-Band and S-Band Polarimetric Observations     

Anagnostou  M.N. Anagnostou  E.N. Vivekanandan  J. Ogden  F.L. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(4):601-605

This letter evaluates the consistency of rainfall drop size distribution (DSD) parameters that were estimated from attenuation-corrected X-band dual-polarization (XPOL) radar measurements with estimates from a colocated S-band dual-polarization radar (S-Pol). The DSD retrieval technique uses reflectivity and differential reflectivity, and a constrained relationship to estimate the three parameters of a ldquonormalizedrdquo gamma distribution model. The more definitive S-Pol DSD parameter estimates are used as a reference to assess the performance of the corresponding XPOL estimates for different rain-path attenuation values. Results show that XPOL attenuation-corrected profiles can provide rainfall DSD estimations that are consistent to an S-band dual-polarization radar, even in cases of moderate to high rain-path attenuation.  相似文献   

Sources of Inaccuracy in Boron Isotope Measurement Using LA-MC-ICP-MS     

Jan Fietzke  Eleni Anagnostou 《Geostandards and Geoanalytical Research》2023,47(3):481-492

Laser ablation multi-collector-inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) has become a valuable tool for the in situ measurement of the boron isotope composition of geological samples at high (tens to hundreds of μm) spatial resolution. That said, this application suffers from significant analytical challenges. We focus in this study on the underlying processes of two of the main causes for inaccuracies using this technique. We provide empirical evidence that not only Ca ions (Sadekov et al. 2019, Standish et al. 2019, Evans et al. 2021) but also Ar ions, that are reflected within the flight tube of the mass spectrometer, are the source for previously reported issues with spectral baselines. We also address the impact of plasma conditions on the instrumental mass fractionation as a source for matrix- and mass-load-related analytical biases. Comparing experimental data with the results of a dedicated release and diffusion model (RDM) we estimate that a close to complete (~ 97%) release of boron from the sample aerosol is needed to allow for consistently accurate LA boron isotope measurement results without the need for corrections.  相似文献   

Impact of sub-grid variability of precipitation and canopy water storage on hydrological processes in a coupled land–atmosphere model     

Dagang Wang  Guiling Wang  Emmanouil N. Anagnostou 《Climate Dynamics》2009,32(5):649-662

The impact of sub-grid variability of precipitation and canopy water storage is investigated by applying a new canopy interception scheme into the Community Atmosphere Model version 3 (CAM3) coupled with the Community Land Model version 3 (CLM3). Including such sub-grid variability alters the partitioning of net radiation between sensible heat flux and latent heat flux on land surface, which leads to changes in precipitation through various pathways/mechanisms. The areas with most substantial changes are Amazonia and Central Africa where convective rain is dominant and vegetation is very dense. In these areas, precipitation during December–January–February is increased by up to 2 mm/day. This increase is due to the enhanced large-scale circulation and atmospheric instability caused by including the sub-grid variability. Cloud feedback plays an important role in modifying the large-scale circulation and atmospheric instability. Turning off cloud feedback mitigates the changes in surface convergence and boundary layer height caused by inclusion of sub-grid variability of precipitation and water storage canopy, which moderate the effect on precipitation.  相似文献   

Development and validation of a novel-based combination operational air quality forecasting system in Greece   总被引：1，自引：1，他引：0  

Stamatis Zoras  Vasilios Evagelopoulos  Ioannis Pytharoulis  Georgios Kallos 《Meteorology and Atmospheric Physics》2010,106(3-4):127-133

In the present work, a model combination is developed in order to provide the public, in north-western Greece, with the next day air quality forecast. Generally, the development and deployment of a real-time numerical air quality prediction system is technically challenging while even more in complex terrain. The Air Pollution Model (TAPM) (http://www.cmar.csiro.au/research/tapm) is a hydrostatic prognostic mesoscale model. It has been calibrated for the area in recent studies and used in air quality assessments. In 2007, TAPM has started operating in a real-time operational mode for the prediction of next day’s weather forecast, particulate matter (PM₁₀ with an aerodynamic diameter <10 μm) daily average concentration and Air Pollution Indexes. The model setup is a link up between TAPM and SKIRON modeling system (http://forecast.uoa.gr).  相似文献