Evaluation of the thermal conductivity of sandstone solid skeleton using the concept of equivalent microstructure     

Łydżba  Dariusz  Różański  Adrian  Sevostianov  Igor  Stefaniuk  Damian 《Acta Geotechnica》2022,17(11):5059-5072

Acta Geotechnica - We evaluate thermal conductivity of the skeleton of porous sandstone from the measurements of the effective thermal conductivities of dry and saturated specimens provided by...  相似文献   

Evidence of a phase shift to Epizoanthus gabrieli Carlgreen, 1951 (Order Zoanthidea) and loss of coral cover on reefs in the Southwest Atlantic          下载免费PDF全文

Igor C. S. Cruz  Ruy K. P. de Kikuchi  Leila L. Longo  Joel C. Creed 《Marine Ecology》2015,36(3):318-325

There is at present a ‘coral reef crisis’; one of the more drastic consequences of this is a phase shift, in which reef‐building corals are replaced by non‐reef building benthos such as macroalgae and soft corals. Previous studies have principally focused on the shift to macroalgae. Our goal was to investigate whether the dominance of the zoanthid Epizoanthus gabrieli on some reefs of Todos os Santos Bay, Brazil, represented a non‐algal phase shift. In 2003, we identified a high cover of this species on two reefs (52% and 70%), but only in 2007 was it possible to confirm a reduction in coral cover. This dominance has persisted for over 9 years, characterizing a true phase shift. This loss of coral cover may be a result of anthropogenic disturbances within the bay; however, given the large number of human impacts, further studies are needed to identify specific causes of this shift. Although there are some reports of phase shift involving species pertaining to the Class Anthozoa, this is the first report of this phenomenon involving the order Zoanthidea.  相似文献   

Evolution of dwarf early-type galaxies – I. Spatially resolved stellar populations and internal kinematics of Virgo cluster dE/dS0 galaxies     

Igor V. Chilingarian 《Monthly notices of the Royal Astronomical Society》2009,394(3):1229-1248

Understanding the origin and evolution of dwarf early-type galaxies remains an important open issue in modern astrophysics. Internal kinematics of a galaxy contains signatures of violent phenomena which may have occurred, e.g. mergers or tidal interactions, while stellar population keeps a fossil record of the star formation history; therefore studying connection between them becomes crucial for understanding galaxy evolution. Here, in the first paper of the series, we present the data on spatially resolved stellar populations and internal kinematics for a large sample of dwarf elliptical (dE) and lenticular (dS0) galaxies in the Virgo cluster. We obtained radial velocities, velocity dispersions, stellar ages and metallicities out to 1–2 half-light radii by reanalysing already published long-slit and integral-field spectroscopic data sets using the nbursts full spectral fitting technique. Surprisingly, bright representatives of the dE/dS0 class (   M_B =−18.0  to −16.0 mag) look very similar to intermediate-mass and giant lenticulars and ellipticals: (1) their nuclear regions often harbour young metal-rich stellar populations always associated with the drops in the velocity dispersion profiles; (2) metallicity gradients in the main discs/spheroids vary significantly from nearly flat profiles to −0.9 dex   r ⁻¹_e  , i.e. somewhat three times steeper than for typical bulges; (3) kinematically decoupled cores were discovered in four galaxies, including two with very little, if any, large-scale rotation. These results suggest similarities in the evolutionary paths of dwarf and giant early-type galaxies and call for reconsidering the role of major mergers in the dE/dS0 evolution.  相似文献   

The Virtual Solar Observatory—A Resource for International Heliophysics Research     

Frank Hill  Piet Martens  Keji Yoshimura  Joseph Gurman  Joseph Hourclé  George Dimitoglou  Igor Suárez-Solá  Steve Wampler  Kevin Reardon  Alisdair Davey  Richard S. Bogart  Karen Q. Tian 《Earth, Moon, and Planets》2009,104(1-4):315-330

The Virtual Solar Observatory (VSO) has been developed to allow researchers, educators, and the general public to access data and images from the major sources of on-line solar data. The VSO substantially reduces the effort required to locate disparate data sets, and removes the need for the user to locate the data and learn multiple interfaces. The VSO provides a single interface to about 60 geographically distributed data sets including space- and ground-based sources. These data sets incorporate several physical variables including magnetic field, intensity, Doppler velocity, etc., and all wavelengths from X-ray to radio. All layers of the sun, from the interior to the corona, are included. In this paper we describe the system and present the interface that the user will encounter. We also discuss future enhancements planned for the system.  相似文献   

Water losses risk assessment: an example from Carpathian karst   总被引：1，自引：1，他引：0  

Sasa Milanovic  Zoran Stevanovic  Igor Jemcov 《Environmental Earth Sciences》2010,60(4):817-827

The multipurpose dam and reservoir “Bogovina” in the Crni Timok valley is one of several projects that have been initiated to improve water availability in Serbia. The site and height of the dam were initially proposed without consideration of risk factors such as water leakage or stability of the banks. Later, complex hydrogeological and speleological surveys and tests identified the potential of significant water losses from the reservoir area connected mainly to the karstic aquifer, and the nearby Bogovina cave system. The analyses show that once the reservoir is filled up, groundwater flow currently oriented towards the future reservoir would saturate the upper part of the karstified rocks, reactivate currently unsaturated pathways and form a reverse discharge outside of the reservoir area. In response to these findings, the dam design and technical details have been adapted accordingly: the dam height has been reduced by 9 m, and it is proposed that grouting and consolidation work be conducted both at the foundation of the dam and extensively on the embankments. It was concluded that although the proposed remedial measures cannot guarantee reservoir tightness, they can reduce the risk of large-scale leaking.  相似文献   

North Atlantic warming: patterns of long-term trend and multidecadal variability   总被引：1，自引：1，他引：0  

Igor V. Polyakov  Vladimir A. Alexeev  Uma S. Bhatt  Evgenia I. Polyakova  Xiangdong Zhang 《Climate Dynamics》2010,34(2-3):439-457

Climate fluctuations in the North Atlantic Ocean have wide-spread implications for Europe, Africa, and the Americas. This study assesses the relative contribution of the long-term trend and variability of North Atlantic warming using EOF analysis of deep-ocean and near-surface observations. Our analysis demonstrates that the recent warming over the North Atlantic is linked to both long-term (including anthropogenic and natural) climate change and multidecadal variability (MDV, ~50–80 years). Our results suggest a general warming trend of 0.031 ± 0.006°C/decade in the upper 2,000 m North Atlantic over the last 80 years of the twentieth century, although during this time there are periods in which short-term trends were strongly amplified by MDV. For example, MDV accounts for ~60% of North Atlantic warming since 1970. The single-sign basin-scale pattern of MDV with prolonged periods of warming (cooling) in the upper ocean layer and opposite tendency in the lower layer is evident from observations. This pattern is associated with a slowdown (enhancement) of the North Atlantic thermohaline overturning circulation during negative (positive) MDV phases. In contrast, the long-term trend exhibits warming in tropical and mid-latitude North Atlantic and a pattern of cooling in regions associated with major northward heat transports, consistent with a slowdown of the North Atlantic circulation as evident from observations and confirmed by selected modeling results. This localized cooling has been masked in recent decades by warming during the positive phase of MDV. Finally, since the North Atlantic Ocean plays a crucial role in establishing and regulating the global thermohaline circulation, the multidecadal fluctuations discussed here should be considered when assessing long-term climate change and variability, both in the North Atlantic and at global scales.  相似文献   

Erratum to “Mineral waters in Slovakia — Evaluation of chemical composition stability using both historical records and the most recent data” [J. Geochem. Explor. 107 (2010) 382–390]     

Dušan Bodiš  Jozef Kordik  Igor Slaninka  Peter Malík  Pavel Liščák  Daniel Panák  Jarmila Božíková  Daniel Marcin 《Journal of Geochemical Exploration》2011,108(3):233

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Current countermeasure of beach erosion control and its application in Taiwan     

Ray-Yeng Yang  Ying-Chih Wu  Hwung-Hweng Hwung  Jiing-Yih Liou  Igor V. Shugan 《Ocean & Coastal Management》2010,53(9):552-561

The shoreline of Taiwan is approximately 1100 km long, composed of sandy beach, rocky coast, and reef coast. Almost half of the shoreline has been protected by seawalls, which play an important role for coastal protection and prevent people and infrastructure from coastal hazard. Besides, offshore breakwaters and groynes are also built in the serious erosion coastal shores. All these hard engineering structures made our coastal land safety to some extent at last fifty years. However, until now, the hard engineering structures applied for shore protection do not always work well on all the coasts around Taiwan. Some coastal areas still get eroded seriously with structures being damaged. Furthermore in the recent years, people gradually value the shore protection from different viewpoints, like environment, recreation, and ecology. The objectives of the shore protection are diversified by these new demands.Therefore, the purpose of this study is to evaluate the strategy on how to conjoint soft solutions into the current hard engineering structures for beach erosion control throughout Taiwan coast. Meanwhile, this paper will also introduce environmentally, user-oriented, and technically sound creditable protection works to meet the new trends of shore protection. For application purpose, two local sites in the southwestern Taiwan coast are selected for field experimental study to integrate the proposed soft solution with hard shore protection system at present. Furthermore for coastal management purpose, this paper also collects and analyzes hydro-morphodynamic data around Taiwan in order to identify beach erosion mechanism. Lastly, the results are presented by database and geographic information system.  相似文献   

Investigation of non-linear site amplification at two downhole strong ground motion arrays in Taiwan     

Kuo-Liang Wen  Igor A. Beresnev  Yeong Tein Yeh 《地震工程与结构动力学》1995,24(3):313-324

Non-linear seismic response of soil is studied by comparing the spectral ratios of surface to downhole horizontal accelerations on weak and strong motion. Data from two boreholes are analysed. One is drilled in the alluvial deposits in the south–west quadrant of the SMART 1 array. The second one penetrates Pleistocene terrace deposits in the northern part of the SMART2 array. Observed weak and strong motion spectral ratios are compared with the theoretical ones predicted by the geotechnical soil model which postulates a hysteretic constitutive law. A significant non-linear response is found at the first site for the events with surface peak acceleration exceeding roughly 0–15g. Deamplification of the strong motion occurred in the frequency range from approximately 1 to 10 Hz. The maximum observed difference between the average weak and strong motion amplification functions of an 11 m-thick near-surface stratum is a factor of 2–3. Nonlinear response characteristics are in qualitative agreement with the model. An additional corollary is that the amplification function calculated from the shear wave coda is equivalent to the average amplification calculated over the ensemble of small earthquakes. No statistically significant non-linear response is detected on the second array, that is tentatively accounted for by the stiffer soil conditions and weaker accelerations achieved at the SMART2 site. The results indicate that the non-linear amplification can be detectable at certain soil conditions above a threshold acceleration level.  相似文献   

Feldspar-bearing lherzolite xenoliths in alkali basalts from Hamar-Daban,southern Baikal region,Russia   总被引：4，自引：0，他引：4  

D. A. Ionov  Suzanne Y. O'Reilly  Igor V. Ashchepkov 《Contributions to Mineralogy and Petrology》1995,122(1-2):174-190

 Lherzolite xenoliths in Miocene to Pleistocene basalts from five sites in the Hamar-Daban range in southern Siberia provide sampling of the mantle close to the axis of the Baikal rift. These anhydrous spinel lherzolites commonly have foliated fabrics and spongy rims around clinopyroxene, and many contain accessory feldspar. The feldspar occurs in reaction zones adjacent to spinel and orthopyroxene (where it appears to have been formed by the reaction: spl+opx+cpx+fluid →fs+ol) and less commonly as thin, irregular veins. The feldspars have variable compositions but are generally alkali-rich; their K₂O content ranges from 0.3 to 11.2% and is much higher than in plagioclase from orogenic lherzolites (usually <0.1% K₂O). The temperature range for the Hamar-Daban xenolith suite (950–1010° C) is more restricted than for spinel peridotite xenoliths from other occurrences in the Baikal area. The feldspar-bearing lherzolites yield equilibration temperatures similar to or slightly lower than feldspar-free ones. The majority of the Hamar-Daban lherzolites are fertile and clinopyroxene-rich, as for most other occurrences in the Baikal region. Trace element compositions of selected xenoliths and their clinopyroxenes were determined by ICP-MS, INAA and proton microprobe. Feldspar-bearing xenoliths are enriched in alkalies indicating that feldspar formation is associated with addition of material and is not simply due to isochemical phase changes. Most xenoliths and their clinopyroxenes studied are depleted in light REE and have contents of Sr, Zr and Y common for fertile or moderately depleted mantle peridotites. Few are moderately enriched in LREE, Sr, Th and U. Sr-Nd isotope compositions of clinopyroxenes indicate long-term depletion in incompatible elements similar to unmetasomatised xenoliths from other occurrences south and east of Lake Baikal. The formation of feldspar and of spongy aggregates after clinopyroxene, and the enrichment in alkalies appear to be recent phenomena related to infiltration of an alkali-rich, H₂O-poor fluid into spinel peridotites. Received: 20 March 1995 / Accepted: 26 June 1995  相似文献