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This paper uses an incremental mode-superposition procedure to compute the inelastic dynamic response of multi-degree-of-freedom systems. A damping matrix proportional to the instantaneous properties is used throughout the analysis. The non-linear response of several shear type plane and space frames with elastic-plastic and bilinear column properties subjected to ground excitation was computed by both the incremental mode-superposition and the direct integration of the coupled equations of motion. When all modes are considered, the responses computed by the incremental mode-superposition are identical to those from the direct integration. Fewer modes can also be used to compute the response with reasonable accuracy by performing the modal truncation for each time increment. The study shows that incorporating instantaneous damping in non-linear dynamic analysis is relatively simple and requires less computational time than the direct integration. 相似文献
3.
Bijan Modak 《Journal of Astrophysics and Astronomy》1984,5(3):317-322
The paper presents some spherically symmetric cosmological Solutions in which the velocity field is shear-free but there is
a flux of energy. The solutions are believed to be new and the previous known solutions of this class due to Bergmann and
Maiti may be obtained as special cases of our metrics. 相似文献
4.
In the Izeh section (Zagros Basin, SW Iran), about two third of the planktonic foraminiferal species, representing less than 20% of the individuals, present in the Maastrichtian polytaxic assemblages, became suddenly extinct at the K/Pg boundary. This mass species extinction testifies end-Cretaceous catastrophic bioevent. The Cretaceous species remain became apparently extinct gradually during the earliest Danian. In fact the unkeeled globotruncanids (Globotruncanella and Rugoglobigerina) as well as the small heterohelicids (Heterohelix and Pseudoguembelina) were also affected by extinction and they were reworked in the basal Danian. Except guembelitriids which persisted longer time. The sudden species extinctions were selective, eliminating geographically restricted large, complex, and deeper dwelling forms (i.e., globotruncanids and large heterohelicids). Contrary, few cosmopolitan small, simple surface-subsurface dwellers (i.e., guembelitriids among small heterohelicids and hedbergellids) crossed the K/Pg boundary and survived the catastrophic event. This selective bioevent is related to the end-Cretaceous bolide and produced ejecta impact inducing major environmental changes as decrease in temperature, collapse of nutriment, and flow breakdown in the water mass stratification. Our geochemical results (δ13C negative shift, δ 18O positive shift, and trace elements anomalies) are consistent with the cooling due to the collision winter triggering collapse of nutriment. Especially the δ 18O values across the upper Maastrichtian and the K-Pg transition in Izeh section although they are lower; they report similar fluctuations to those in El Kef section. Thus these lower values may be indicative of somewhat warmer water at the sea floor. Besides, like as elsewhere, in Izeh, this Cretaceous end catastrophic bioevent is followed by a delayed gradual recovery. Thus, immediately after the K/Pg boundary was created a nearly empty niche in which persisted few Cretaceous survivors with dwarf individuals. These survivors despite they suffered very stressful environmental conditions, they constituted the root stock of globigerinids from which the Cenozoic planktonic foraminiferal species evolved and developed carnivorous food diet. 相似文献
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SWAT model application and prediction uncertainty analysis in the Lake Tana Basin,Ethiopia 总被引:4,自引:0,他引:4
Lake Tana Basin is of significant importance to Ethiopia concerning water resources aspects and the ecological balance of the area. Many years of mismanagement, wetland losses due to urban encroachment and population growth, and droughts are causing its rapid deterioration. The main objective of this study was to assess the performance and applicability of the soil water assessment tool (SWAT) model for prediction of streamflow in the Lake Tana Basin, so that the influence of topography, land use, soil and climatic condition on the hydrology of Lake Tana Basin can be well examined. The physically based SWAT model was calibrated and validated for four tributaries of Lake Tana. Sequential uncertainty fitting (SUFI‐2), parameter solution (ParaSol) and generalized likelihood uncertainty estimation (GLUE) calibration and uncertainty analysis methods were compared and used for the set‐up of the SWAT model. The model evaluation statistics for streamflows prediction shows that there is a good agreement between the measured and simulated flows that was verified by coefficients of determination and Nash Sutcliffe efficiency greater than 0·5. The hydrological water balance analysis of the basin indicated that baseflow is an important component of the total discharge within the study area that contributes more than the surface runoff. More than 60% of losses in the watershed are through evapotranspiration. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
7.
Abbas Abbaszadeh Shahri Bijan Esfandiyari Roshanak Rajablou 《Arabian Journal of Geosciences》2012,5(4):555-564
During the earthquakes, a number of earth dams have had severe damages or suffered major displacements as a result of liquefaction, thus modeling by computer codes can provide a reliable tool to predict the response of the dam foundation against earthquakes. These modeling can be used in the design of new dams or safety assessments of existing ones. In this paper, on the basis of the field and laboratory tests and by combination of several software packages a seismic geotechnical-based analysis procedure is proposed and verified by comparison with computer model tests and field and laboratory experiences. Verification or validation of the analyses relies to the ability of the applied computer codes. By using the Silakhor earthquake (2006, M s 6.1) as a basis in order to check the efficiency of the proposed framework, the procedure is applied to the Korzan earth dam of Iran which is located in Hamedan Province to analyze and estimate the liquefaction and safety factor. Design and development of a computer code by the authors which was named as the ??Abbas Converter?? with graphical user interface which operates as logic connecter function that can compute and model the soil profiles is the critical point of this study. The results confirmed and proved the ability of the generated computer code on the evaluation of soil behavior during earthquake excitations. Also, this code was able to facilitate this study better than previous ones have, taking over the encountered problem. 相似文献
8.
Peyman Afzal Hamid Harati Younes Fadakar Alghalandis Amir Bijan Yasrebi 《Chemie der Erde / Geochemistry》2013
The aim of this study is to identify geochemical anomalies using power spectrum–area (S–A) method based on the grade values of Cu, Mo and Au in 2709 soil samples collected from Kahang porphyry-type Cu deposit, Central Iran. S–A log–log plots indicated that there are three stages of Cu, Mo and Au enrichment. The third enrichment was considered as the main stage for the presence of Cu, Mo and Au at the concentrations above 416 ppm, 23 ppm and 71 ppb, respectively. Elemental anomalies are positively associated with monzo–granite–diorite and breccias units which are in the central and western parts of the deposit. The anomalies are located within the potassic, phyllic and argillic alteration types and also there is the positive correlation between the anomalies and nearing faults in the studied area. The results obtained via fractal model were interpreted accordingly to incorporate the information for the mineralized areas including detailed geological map, structural analysis and alterations. The results show that S–A multifractal modeling is applicable for anomalies delineation based on soil data. 相似文献
9.
10.
Bijan Saha 《Astrophysics and Space Science》2007,312(1-2):3-11
We consider a system of nonlinear spinor and a Bianchi type I gravitational fields in presence of viscous fluid. The nonlinear
term in the spinor field Lagrangian is chosen to be λ
F, with λ being a self-coupling constant and F being a function of the invariants I an J constructed from bilinear spinor forms S and P. Self-consistent solutions to the spinor and BI gravitational field equations are obtained in terms of τ, where τ is the volume scale of BI universe. System of equations for τ and ε, where ε is the energy of the viscous fluid, is deduced. This system is solved numerically for some special cases.
相似文献