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191.
H. M. Abdel Magid R. E. A. Sabrah R. K. Rabi A. R. H. El Nadi S. I. Abdel Aal 《Journal of Arid Environments》1993,25(4)
Addition and incorporation of organic fertilizers is known to improve the properties of agricultural soils. Therefore, during 22 weeks of field incubation we studied the biodegradation (measured by static absorption of CO2) of two organic manures viz. municipal refuse and chicken manure incorporated into sandy soils, under sprinker irrigation, at the rates of 0, 16·5, 33·0, 49·5 and 66·0, and 0, 4·1, 8·25, 16·5, and 33·0 tonnes/ha, respectively.The results obtained indicated that the cumulative amount of CO2 respired was linearly correlated with the rate of organic material applied (p < 0.001). Statistical analysis of the data obtained showed that both the intercept (rate of decomposition) and the slope (rate of reaction with time) increased with increasing rate of application of organic manure. The magnitude of increment was highest at the application rates of 33·0 and 8·25 tonnes/ha for municipal refuse and chicken manure, respectively. The rate of increment, generally, declined thereafter thus indicating that these two rates are the optimum levels of incorporation of the appropriate organic manures under the conditions of this study.The maximum organic-carbon mineralized, accounting for 10·5 and approximately 50%, was obtained at the optimum rates for municipal refuse and chicken manure, respectively. Both simple and multiple regression equations describing the relationship between soil temperature and soil-moisture content each separately and in combination, as independent variables, and the cumulative rate of CO2 production were computed. A substantially strong relationship with soil temperature but inconsistent and contradicting results with soil moisture were obtained. Inclusion of soil temperature and moisture in a single model as an independent variable in relation to cumulative CO2 as a dependent variable improved the soil moisture-CO2 production relationship. 相似文献
192.
M. El Sawwaf 《Geotechnical and Geological Engineering》2010,28(4):311-323
The paper presents the results of laboratory model tests and theoretical analysis on the behavior of a strip footing supported
on sheet pile wall-stabilized sandy slope and loaded vertically to failure. The parameters varied in the study include the
height, stiffness and location of the sheet pile wall, the location of the footing relative to the slope crest and the relative
density of sand. Two-dimensional plane strain finite element analyses was used to analyze a prototype strip footing on sandy
slope with same conditions. The results indicate that the inclusion of sheet pile wall has significant effect in improving
the response of the strip footing and the slope itself. The theoretical results confirm the experimental results of the model
footing tests and show reasonable agreement. Based on the numerical and experimental results, critical values of the sheet
pile wall parameters for maximum stabilizing effect are established. 相似文献
193.
Influence of liquid bridges on the mechanical behaviour of polydisperse granular materials 总被引:1,自引:0,他引:1
We investigate a polydisperse granular material in which the particle interactions are governed by a capillary force law. The cohesion force for a grain‐pair with unequal diameters is expressed as an explicit function of the inter‐particle distance and the volume of the liquid bridge. This analytical relation is validated by experiments on a reference material. Then, it is completed by a rupture criterion and cast in the form of a force law that accounts for solid contact, capillary force and rupture characteristics of a grain‐pair. Finally, in order to evaluate the influence of capillary cohesion on the macroscopic behaviour, radial and axial compression tests on cylindrical assemblies of wet particles are simulated using a 3D distinct element method. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
194.
Mahmoud M. El Banna 《Environmental Geology》2006,49(5):645-652
Bathymetry of the seafloor in the area in front of Ras El Bar coast, the characters of the seafloor sediments and the effects
of protective structures on seafloor bathymetry were examined. Seafloor depths in front of Ras El Bar seawall ranged between
2 and 4 m. These depths, coupled with wave climate, result in waves breaking directly onto the wall and exerting high, dynamic
pressures on the area at the structure’s toe. The sandy seafloor in front of the wall has been scoured. Sea water has undermined
the wall causing removal of sediment, destabilization of its slope and the whole face of the wall has slipped. Toe protection
in the form of a rocky apron is required to prevent such damage. West of the seawall, the constructed breakwater system has
affected the bathymetry of the seafloor in the area. Shoaling and submerged spits have been formed in the shadow of each breakwater
unit. The gaps between the breakwater units have attained deep depths and steep slopes. Scours and steep slopes adjacent to
the head of the breakwater units have been recorded. Seaward of the breakwater system, deeper depths and gentle slopes characterize
the seafloor. Offshore–onshore current and sediment movements toward the northeast is inferred from the configuration of the
bottom contour lines. 相似文献
195.
Reliability‐based control algorithms for nonlinear hysteretic systems based on enhanced stochastic averaging of energy envelope 下载免费PDF全文
Current reliability‐based control techniques have been successfully applied to linear systems; however, incorporation of stochastic nonlinear behavior of systems in such control designs remains a challenge. This paper presents two reliability‐based control algorithms that minimize failure probabilities of nonlinear hysteretic systems subjected to stochastic excitations. The proposed methods include constrained reliability‐based control (CRC) and unconstrained reliability‐based control (URC) algorithms. Accurate probabilistic estimates of nonlinear system responses to stochastic excitations are derived analytically using enhanced stochastic averaging of energy envelope proposed previously by the authors. Convolving these demand estimates with capacity models yields the reliability of nonlinear systems in the control design process. The CRC design employs the first‐level and second‐level optimizations sequentially where the first‐level optimization solves the Hamilton–Jacobi–Bellman equation and the second‐level optimization searches for optimal objective function parameters to minimize the probability of failure. In the URC design, a single optimization minimizes the probability of failure by directly searching for the optimal control gain. Application of the proposed control algorithms to a building on nonlinear foundation has shown noticeable improvements in system performance under various stochastic excitations. The URC design appears to be the most optimal method as it reduced the probability of slight damage to 8.7%, compared with 11.6% and 19.2% for the case of CRC and a stochastic linear quadratic regulator, respectively. Under the Kobe ground motion, the normalized peak drift displacement with respect to stochastic linear quadratic regulator is reduced to 0.78 and 0.81 for the URC and CRC cases, respectively, at comparable control force levels. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
196.
B. K. Maheshwari K. Z. Truman M. H. El Naggar P. L. Gould 《Soil Dynamics and Earthquake Engineering》2004,24(4):343-356
A three-dimensional method of analysis is presented for the seismic response of structures constructed on pile foundations. An analysis is formulated in the time domain and the effects of material nonlinearity of soil on the seismic response are investigated. A subsystem model consisting of a structure subsystem and a pile-foundation subsystem is used. Seismic response of the system is found using a successive-coupling incremental solution scheme. Both subsystems are assumed to be coupled at each time step. Material nonlinearity is accounted for by incorporating an advanced plasticity-based soil model, HiSS, in the finite element formulation. Both single piles and pile groups are considered and the effects of kinematic and inertial interaction on seismic response are investigated while considering harmonic and transient excitations. It is seen that nonlinearity significantly affects seismic response of pile foundations as well as that of structures. Effects of nonlinearity on response are dependent on the frequency of excitation with nonlinearity causing an increase in response at low frequencies of excitation. 相似文献
197.
In the field of galaxies images, the relative coordinate positions of each star with respect to all the other stars are adapted. Therefore the membership of star cluster will be adapted by two basic criterions, one for geometric membership and other for physical (photometric) membership. So in this paper, we presented a new method for the determination of open cluster membership based on K-means clustering algorithm. This algorithm allows us to efficiently discriminate the cluster membership from the field stars. To validate the method we applied it on NGC 188 and NGC 2266, membership stars in these clusters have been obtained. The color-magnitude diagram of the membership stars is significantly clearer and shows a well-defined main sequence and a red giant branch in NGC 188, which allows us to better constrain the cluster members and estimate their physical parameters. The membership probabilities have been calculated and compared to those obtained by the other methods. The results show that the K-means clustering algorithm can effectively select probable member stars in space without any assumption about the spatial distribution of stars in cluster or field. The similarity of our results is in a good agreement with results derived by previous works. 相似文献
198.
A. El Mandour F. El Yaouti Y. Fakir Y. Zarhloule J. Benavente 《Environmental Geology》2008,54(3):491-503
The Bou-Areg plain in the Mediterranean coast at the North-eastern of Morocco is characterized by a semi-arid climate. The
aquifer consists of two sedimentary formations of Plio-quaternary age: the upper formation of fine silts and the lower one
of coarse silts with sand and gravels. The aquifer is underlain by marly bedrock of Miocene age that dips toward the coastal
lagoon of Bou-Areg. The hydrodynamic characteristics vary between 10−4 and 10−3 m/s; and transmissivities range between 10−4 and 10−1 m2/s. The general direction of flow is SW to NE, toward the lagoon. The aquifer is crossed by the river Selouane, which also
ends in the lagoon. The groundwater is characterized by a high salinity that can reach 7.5 g/l. The highest values are observed
in the upstream and in the downstream sectors of the aquifer. The temporal evolution of the physico-chemical parameters depends
on the climatic conditions and piezometric variations. The analysis of the spatio-temporal distribution of the physico-chemical
parameters suggests different sources of groundwater salinization: the seawater intrusion, the influence of marly gypsum-bearing
terrains, and the influence of anthropogenic products as the agricultural fertilizers, which cause great nitrate concentrations
that vary between 80 and 140 mg/l. 相似文献
199.
Neoproterozoic granites of Sharm El-Sheikh area,Egypt: mineralogical and thermobarometric variations
Mohamed?F.?GhoneimEmail author Mohamed?Th.?S.?Heikal Bothina?T.?El?Dosuky Tamer?S.?Abu-Alam Mahmoud?I.?Sherif 《Arabian Journal of Geosciences》2015,8(1):125-141
Calc-alkaline and alkaline intrusions of the late Neoproterozic form essential part of the Arabian–Nubian Shield. They were formed during the collision between East- and West-Gondwana. Sharm El-Sheikh area, Sinai, includes wide compositional array of these intrusions that can be considered as a case study. Variations in both tectonic and thermobarometric condition for granitic intrusions are studied. Four mappable granitic types are recognized namely monzogranite, syenogranite, alkali feldspar granites, and riebeckite-bearing granites. The monzogranite and the syenogranite of the study area are mostly I-type, whereas the alkali feldspar granite and the riebeckite-bearing granite belong to A-type granitoid. The calc-alkaline intrusions were formed in compressional setting due to decompressional melting of mafic lower crust. Partial melting and anatexing of crustal rocks are suggested to explain the protolith of the alkaline intrusions. The transition from the calc-alkaline magma to the alkaline one occurred as a result of the tectonic transition from compression regime to tectonic relaxation (extension setting) during the last stage of the Pan-African Orogeny. The amphiboles of the studied granites are classified as calcic- and alkali-amphiboles. The calcic-amphiboles are ferro-edenite while the alkali-amphiboles are typically riebeckite. Both amphibole types are of magmatic nature. Coexisting amphiboles and plagioclases are used to estimate the physicochemical parameters of magma crystallization. The syenogranite underwent temperature and pressure of formation range of 520–730 °C, <3 kbar. The alkali feldspar granite records 450–830 °C, <4 kbar, while the riebeckite-bearing granite records the lowest temperature condition among all varieties and estimate formation at 350–650 °C, <4 kbar. 相似文献
200.
Matyasovszky István Makra László Tusnády Gábor Csépe Zoltán Nyúl László G. Chapman Daniel S. Sümeghy Zoltán Szűcs Gábor Páldy Anna Magyar Donát Mányoki Gergely Erostyák János Bodnár Károly Bergmann Karl-Christian Deák Áron József Thibaudon Michel Albertini Roberto Bonini Maira Šikoparija Branko Radišić Predrag Gehrig Regula Rybníček Ondřej Severova Elena Rodinkova Victoria Prikhodko Alexander Maleeva Anna Stjepanović Barbara Ianovici Nicoleta Berger Uwe Seliger Andreja Kofol Weryszko-Chmielewska Elżbieta Šaulienė Ingrida Shalaboda Valentina Yankova Raina Peternel Renata Ščevková Jana Bullock James M. 《Theoretical and Applied Climatology》2018,133(1-2):277-295
Theoretical and Applied Climatology - The drivers of spatial variation in ragweed pollen concentrations, contributing to severe allergic rhinitis and asthma, are poorly quantified. We analysed the... 相似文献