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71.
In this paper, the Einstein field equations have been solved for a cloud of string with heat flux in Bianchi type III space-time. The physical and geometrical properties of the model have been examined. 相似文献
72.
The volcanosedimentary units of Late Mesozoic-Tertiary age that outcrop in the Southeast Anatolian orogenic belt are commonly
referred to as the Maden complex. There is a long-lasting controversy over its definition, age, stratigraphic and structural
position, and the origin, and thus, the orogenic evolution. To solve this problem, large strips across the Southeast Anatolian
orogenic belt have been studied extensively, and different rock groups which were regarded previously as the Maden unit have
been differentiated. Their major characteristics and differences have been identified. The Maden unit sensu stricto is here
redefined as a volcanosedimentary succession of Middle Eocene age representing a short-lived back-arc basin which reached
the stage of an embryonic ocean. Presently, the Maden group occurs mainly within the lower nappe stack of the nappe zone of
the Southeast Anatolian orogen. It rests stratigraphically on an amalgamated nappe package consisting of the different metamorphic
tectonic units and, in turn, is overlain tectonically by the upper nappe units. 相似文献
73.
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75.
This study defines the Mio-Pliocene to present-day stress regime acting at the northeastern corner of the eastern Mediterranean region along the Karasu Valley (i.e., the Amanos Range), taking in the Antakya, Osmaniye and Kahramanmaras provinces. The inversion slip vectors measured on fault planes and chronologies between striations indicate that the stress regime varied from transpressional initially to transtensional, having consistent NW- and NE-trending σHmax (σ1) and σHmin (σ3) axes, respectively; there are significantly different mean stress-ratio (Rm) values however. The older mean stress state is characterized by N151±11°E-trending σ1 and N59±12°E-trending σ3 axes, and by a mean arithmetic Rm value of 0.76, indicating that the regional stress regime is transpressional. The younger stress regime is characterized by N154±8°E-trending σ1 and N243±8°E-trending σ3 axes, and by a mean arithmetic Rm value of 0.17, indicating a transtensional character for this regional stress regime. The low R values of the stress deviators related to the recent stress state reflect normal-component slips. The earthquake focal mechanism inversions confirm that the younger stress regime continues into the Recent. The inversion identifies a transtensional stress regime representing strike-slip and an extensional stress state with a consistent NE-trending σHmin (σ3) axis. These stress states are characterized by N66°E and N249°E-trending σ3 axes, respectively. Both significant regional stress regimes induce left-lateral displacement along the southern part of the East Anatolian Fault (EAF, or Amanos Fault). The temporal change, probably in Quaternary time, within the regional stress regime—from transpression to transtension—resulted from the coeval influences of subduction processes in the west–southwest (i.e., along the Cyprus arc), continental collision in the east, and westward escape of the Anatolian block. 相似文献
76.
The interaction between normal or reverse fault ruptures and shallow foundations resting on a homogeneous undrained soil layer is investigated. After performing a thorough set of non‐linear finite element simulations, three simple kinematic mechanisms are proposed to predict the conditions for the fault rupture to be diverted by the foundation. The results obtained by both numerical and analytical approaches are in good agreement, and support the adequacy of the proposed mechanisms. A relationship is established for assessing the minimum foundation bearing load needed for diversion of the fault rupture trace, either normal or reverse. This relationship is proved to be independent of the fault type and dip angle, so that it can be applied easily for engineering applications, even in the absence of specific tectonic information. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
77.
Observing permanent seals with different physical and mechanical characteristics under various conditions in the field is almost impossible. In conjunction with the development of high-speed computer algorithms, numerical simulation has become one of the major means to study the dynamics of such problems. Therefore, this study covers only the numerical approach to analyze the stability of underground seals. In this regard, the purpose of this study is to provide an insight to the design of underground seals by numerically analyzing their behaviors under different static and dynamic explosion overpressures using a geo-technical commercial software FLAC3D. For this purpose, a series of numerical models were constructed for a typical seal in an underground gallery with different properties such as seal thickness, seal dimensions, gallery geometry, and strength of the seal material to investigate the stability of seals exposed to various static and dynamic explosion overpressures. A total of 896 numerical analyses (512 static and 384 dynamic) were performed and evaluated. Regarding the gallery geometry, it was found that seals constructed in trapeze-shaped galleries are more stable than those constructed in horseshoe-shaped galleries having the same dimensions. Moreover, the results showed that the seal stability increases with the increasing seal thickness rather than the strength of the seal material. The statistical analyses suggest that there is a very strong exponential relationship between the seal thickness and the maximum displacement measured at the midpoints of the outer surfaces of the seals. The coefficients of determination values obtained are in the range of 0.92–0.93 and 0.92–0.95 for static and dynamic analyses, respectively. We proposed formulas which use the longer dimension of the seal (W max ), maximum allowable displacement on the seal (D max ), explosion overpressure applied onto the seal (P exp ), and compressive strength of the seal material (σ c and σ cd for static and dynamic conditions, respectively) to predict the minimum required seal thickness (T s ) for static and dynamic conditions. The proposed formulas enable calculating the necessary seal thickness easily if the explosion overpressure (or hydrostatic pressure) is known or approximated. 相似文献
78.
Marian Marschalko David Krčmář Isik Yilmaz Renáta Fľaková Zlatica Ženišová 《Environmental Earth Sciences》2018,77(3):95
The aim of the study is to evaluate the warming effect (thermal contamination) of city centres with high building density. This phenomenon has a number of scientific and practical implications. The case study was conducted in Bratislava (Slovakia), in the geological environment of alluvial gravels of the Danube River, where a permanent warming of the subsurface in the city centre is experienced, which is mainly affected by high building density and underground utilities. Thanks to this thermal contamination, the heat pumps efficiency is greater in winter, while in summer, their effectiveness is lower. Economically, this negative phenomenon in the case of heat pumps has a positive effect, since it increases energy efficiency during the heating period. This phenomenon is not universal and depends on the specific boundary conditions of the geological settings and hydrogeological conditions. 相似文献
79.
Geotechnical and Geological Engineering - The development of infiltration techniques has facilitated the estimation of soils hydraulic properties. Among these, the simplified Beerkan infiltration... 相似文献
80.
Collapse of zooplankton stocks during Liriope tetraphylla (Hydromedusa) blooms and dense mucilaginous aggregations in a thermohaline stratified basin 下载免费PDF全文
Izzet Noyan Yilmaz 《Marine Ecology》2015,36(3):595-610
A growing number of studies report an increase in jellyfish populations worldwide that may have consequences for marine planktonic food web dynamics. The principal objective of this study was to understand the changes in a zooplankton community during blooms of Liriope tetraphylla and subsequent mucilage events in the Sea of Marmara, a small highly stratified transitional basin between the Black and Aegean Seas. Liriope blooms observed in 2006 and 2007 reached a maximum abundance of 2978 ind.·m?3, following the species' first observation in 2005. Jellyfish species are known to play a key guild role by restructuring plankton communities and in the Sea of Marmara Liriope caused a temporal regime shift from a crustacean‐ to a jellyfish‐controlled system. A rapid decline in abundance of most important zooplankton species followed the Liriope increase, together with a drastic shift in community structure. The dominant summer–autumn species Penilia avirostris (Cladocera) vanished in the autumn of 2006 and was diminished ~30‐fold in 2007 when compared with years without Liriope. The decline in zooplankton and the devastating effects of mucilage on pelagic ecosystem and socio‐economics through restricting commercial fisheries implied sensitivity of the already perturbed Marmara ecosystem to changes in predator densities and environmental stability. 相似文献