LRS Bianchi-I anisotropic cosmological model with dominance of dark energy     

Anil Kumar Yadav  Bijan Saha 《Astrophysics and Space Science》2012,337(2):759-765

The present study deals with spatially homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type I cosmological model with dominance of dark energy. To get the deterministic model of Universe, we assume that the shear scalar (σ) in the model is proportional to expansion scalar (θ). This condition leads to A=B ⁿ , where A, B are metric potential and n is positive constant. It has been found that the anisotropic distribution of dark energy leads to the present accelerated expansion of Universe. The physical behavior of the Universe has been discussed in detail.  相似文献   

Interacting Scalar And Spinor Fields In Bianchi Type I Universe Filled With Magneto-Fluid     

Bijan?SahaEmail author 《Astrophysics and Space Science》2005,299(2):149-158

Self-consistent system of spinor, scalar and BI gravitational fields in presence of magneto-fluid and Λ term is considered. Assuming that the expansion of the BI universe is proportional to the σ₁ component of the shear tensor, exact solutions for the metric functions, as well as for scalar and spinor fields are obtained. For a non-positive Λ, the initially anisotropic space–time becomes isotropic one in the process of expansion; whereas for Λ > 0, an oscillatory mode of expansion of the BI model occurs. PACS numbers: 03.65.Pm and 04.20.Ha  相似文献   

Inelastic earthquake spectra     

F. E. Elghadamsi  B. Mohraz 《地震工程与结构动力学》1987,15(1):91-104

This paper presents a procedure for computing inelastic design spectra in terms of yield displacement. The procedure results in substantial computational savings as compared to the current procedures for computing the inelastic spectra in terms of displacement ductility. The proposed method is used to obtain inelastic design spectra for alluvium and rock. The results for alluvium are compared to those from the Newmark and Hall,¹⁰ Riddell and Newmark¹² and Lai and Biggs⁴ studies. The findings indicate that for given ductility and frequency one may de-amplify the elastic response or reduce the elastic forces more for a structure on rock than for a structure on alluvium. A technique is presented so that the inelastic design spectrum can be scaled to any desired yield displacement and acceleration. An example is presented to illustrate how the proposed inelastic spectra can be used to compute the required ductility for a given system.  相似文献   

Westerly jet stream and past millennium climate change in Arid Central Asia simulated by COSMO-CLM model     

Bijan Fallah  Sahar Sodoudi  Ulrich Cubasch 《Theoretical and Applied Climatology》2016,124(3-4):1079-1088

This study tackles one of the most debated questions around the evolution of Central Asian climate: the “Puzzle” of moisture changes in Arid Central Asia (ACA) throughout the past millennium. A state-of-the-art Regional Climate Model (RCM) is subsequently employed to investigate four different 31-year time slices of extreme dry and wet spells, chosen according to changes in the driving data, in order to analyse the spatio-temporal evolution of the moisture variability in two different climatological epochs: Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). There is a clear regime behavior and bimodality in the westerly Jet phase space throughout the past millennium in ACA. The results indicate that the regime changes during LIA show a moist ACA and a dry East China. During the MCA, the Kazakhstan region shows a stronger response to the westerly jet equatorward shift than during the LIA. The out-of-phase pattern of moisture changes between India and ACA exists during both the LIA and the MCA. However, the pattern is more pronounced during the LIA.  相似文献   

Shake table tests on a mass eccentric model with base isolation   总被引：1，自引：0，他引：1  

Bijan Samali  Yi Min Wu  Jianchun Li 《地震工程与结构动力学》2003,32(9):1353-1372

A mass eccentric structure is usually more seismically vulnerable than its concentric counterpart because of the coupled torsional–translational response of such structures. In this work, dynamic characteristics and response of a five‐storey benchmark model with moderate mass eccentricity were investigated using a shake table, simulating four different ground motions. The effectiveness of laminated rubber bearings (LRB) and lead‐core rubber bearings (LCRB) in protecting eccentric structures was examined and evaluated in relation to translational and torsional responses of the benchmark model. It was observed that both translational and torsional responses were significantly reduced with the addition of either a LRB or LCRB isolated system regardless of the nature of ground motion input. The LRB were identified to be more effective than LCRB in reducing model relative displacements, the relative torsional angle as well as accelerations, and therefore provided a better protection of the superstructure and its contents. On the other hand, LCRB rendered a smaller torsional angle and absolute displacement of the base isolation system, hence a more stable structural system. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Effect of a Non‐Ionic Surfactant on Xylene Removal in a Scoria‐Compost‐Based Biofilter          下载免费PDF全文

Mohammad Mehdi Amin  Amir Rahimi  Bijan Bina  Fazel Mohammadi Moghadam  Heshmatollah Nourmoradi  Mohsen Heidari 《洁净——土壤、空气、水》2016,44(12):1759-1765

  相似文献   

The role of viscoelastic damping on retrofitting seismic performance of asymmetric reinforced concrete structures     

Alam  Zeshan  Zhang  Chunwei  Samali  Bijan 《地震工程与工程振动(英文版)》2020,19(1):223-237

The primary purpose of this research is to improve the seismic response of a complex asymmetric tall structure using viscoelastic(VE) dampers. Asymmetric structures have detrimental effects on the seismic performance because such structures create abrupt changes in the stiffness or strength that may lead to undesirable stress concentrations at weak locations. Structural control devices are one of the effective ways to reduce seismic impacts, particularly in asymmetric structures. For passive vibration control of structures, VE dampers are considered among the most preferred devices for energy dissipation. Therefore, in this research, VE dampers are implemented at strategic locations in a realistic case study structure to increase the level of distributed damping without occupying significant architectural space and reducing earthquake vibrations in terms of story displacements(drifts) and other design forces. It has been concluded that the seismic response of the considered structure retrofitted with supplemental VE dampers corresponded well in controlling the displacement demands. Moreover, it has been demonstrated that seismic response in terms of interstory drifts was effectively mitigated with supplemental damping when added up to a certain level. Exceeding the supplemental damping from this level did not contribute to additional mitigation of the seismic response of the considered structure. In addition, it was found that the supplemental damping increased the total acceleration of the considered structure at all floor levels, which indicates that for irregular tall structures of this type, VE dampers were only a good retrofitting measure for earthquake induced interstory deformations and their use may not be suitable for acceleration sensitive structures. Overall, the research findings demonstrate how seismic hazards to these types of structures can be reduced by introducing additional damping into the structure.  相似文献   

A coupled model analyses on the interaction between oceanic eddies and tropical cyclones over the Bay of Bengal     

Anandh  Thanka Swamy  Das  Bijan Kumar  Kuttippurath  J.  Chakraborty  Arun 《Ocean Dynamics》2020,70(3):327-337

Ocean Dynamics - The Bay of Bengal (BOB) region of Indian Ocean is affected by numerous tropical cyclones during pre- and post-monsoon seasons when various eddies are generated in the central and...  相似文献   

An integrated indicator framework for spatial assessment of industrial and social vulnerability to indirect disaster losses   总被引：2，自引：0，他引：2  

Bijan Khazai  Mirjam Merz  Carola Schulz  Dietmar Borst 《Natural Hazards》2013,67(2):145-167

The focus of this study is on multi-dimensional vulnerability of regions to indirect disaster losses. An integrated indicator framework has been developed which captures the multi-layered vulnerability drivers in industrial production systems and also accounts for the social fragilities and coping capacities in communities. By combining industrial vulnerability and social vulnerability spatially, and proposing a methodology to account between their interactions, the total vulnerability to indirect risks of regions is revealed. The outcome of the framework is a ranking of industrial sectors and geographic areas according to their vulnerability against indirect losses. It answers the question which of the two affected regions is in a better position to cope with indirect consequences in a disaster. Indicators provide a flexible framework for the comparison and integration of different data types and allow the combination of social as well as economic aspects. Decision-Making Trial and Evaluation Laboratory (DEMATEL) methodology was applied to analyze direct and indirect dependencies within the selected social and industrial vulnerability indicators. The hierarchical indicator system has been implemented in a software system based on multi-criteria decision theory (MCDA) with an interactive interface to take into account a broader range of expert judgement. The methodology was applied in a case study in the state of Baden-Wuerttemberg in Germany for 16 different industrial sectors. The approach helps to identify particular vulnerable processes and points out where mitigation measures could be implemented most effectively.  相似文献   

Water and wastewater treatment from BTEX by carbon nanotubes and Nano-Fe     

Bijan Bina  Mohammad Mehdi Amin  Alimorad Rashidi  Hamidreza Pourzamani 《Water Resources》2014,41(6):719-727

The removal of benzene, toluene, ethylbenzene, and xylene (BTEX) from aqueous solution by multi- and single-walled carbon nanotubes (MWCNTs and SWCNTs), hybrid carbon nanotubes (HCNTs) and nano-Fe was evaluated for a nanomaterials dose of 1 g/L and a BTEX concentration of 10 mg/L and pH 7. The equilibrium amount (q _e ) (mg/g) removed by SWCNTs (B: 9.98, T: 9.96, E: 9.97, and X: 9.97 mg/g) was higher than for MWCNTs, HCNTs and nano-Fe in a c ₀ of 10 mg/L and for a contact time of 10 min. The q _e of total BTEX removed via SWCNTs was 39.89 mg/g. The order of uptake for SWCNTs is X > T = E > B, which is related to the increasing water solubility and the decreasing molecular weight of the compounds. The SWCNTs performed better for BTEX sorption than the MWCNTs, HCNTs and nano-Fe. The results of desorption study show that BTEX adsorbed on SWCNTs can easily be desorbed at 105 ± 2°C. It was concluded that recycling CNTs using heat improved the performance of the CNTs. For the first time, better adsorption performance was observed for recycled CNTs than for raw CNTs. SWCNTs are efficient BTEX adsorbents that could be used for cleaning up environmental pollution.  相似文献