Design of efficient base isolation for hammers and presses     

Abdul Ghafar Chehab  M. Hesham El Naggar   《Soil Dynamics and Earthquake Engineering》2003,23(2):127-141

Foundations supporting hammers and presses have to withstand powerful short-period impact loads. When designing these foundations, their vibration amplitudes and the forces transmitted to the supporting piles or soil medium must be reduced to meet serviceability and stability requirements. Mounting systems are often used to achieve this goal. The objectives of this paper are to investigate the efficiency of mounting systems for different foundation configurations and to provide practical guidance for their design. A comprehensive parametric study was conducted and the results were used to establish a set of charts for the design of efficient mounting systems.  相似文献   

A quantitative study of the energy release in the aftershocks of the Bhuj earthquake, 2001, India, using Lg phase     

G. Jayachandran  M.M. Abdul RazakA.G.V. Prasad  E. Unnikrishnan 《Physics of the Earth and Planetary Interiors》2003,138(2):131-145

The devastating earthquake on 26 January 2001 at Bhuj, India, resulted in large-scale death and destruction of properties of several million US dollars. The moment magnitude of the earthquake was 7.7 and its maximum focal intensity exceeded X in MM scale. The rate of aftershocks of this earthquake, recorded at Gauribidanur seismic array station (GBA), shows a monotonic decay with time superposed with oscillations. For the Indian continent the Lg phase is a prominent arrival at regional distances. The estimate of Lg amplitude is obtained by optimally fitting the Lg wave train to a exponential decay curve. The logarithm of these amplitudes and logarithm of root mean square (rms) value of actual amplitudes of the Lg are calibrated with USGS m_b to create a local m_bLg magnitude scale. The energy released from these aftershocks is calculated from the rms value of Lg phase. The plot of cumulative energy release with time follows the power law of the form t^p, superposed with oscillations. The exponent of the power law, p, is estimated both by a time-window scanning method and by an interpolation method. The value of p is 0.434 for time-window scanning method and 0.432 for the interpolation method. The predominant periods found in the oscillatory part of the cumulative energy, obtained by differencing the observed from the power law fit, are 10.6, 7.9, 5.4, 4.6 and 3.5 h for time-window scanning method. The corresponding periods for interpolation method are 13.4, 11.5, 7.4, 4.2, 3.5, 2.6 and 2.4 h.  相似文献   

Role of the Kazerun fault system in active deformation of the Zagros fold-and-thrust belt (Iran)     

Christine Authemayou  Olivier Bellier  Dominique Chardon  Zaman Malekzade  Mohammad Abassi 《Comptes Rendus Geoscience》2005,337(5):539-545

Field structural and SPOT image analyses document the kinematic framework enhancing transfer of strike-slip partitioned motion from along the backstop to the interior of the Zagros fold-and-thrust belt in a context of plate convergence slight obliquity. Transfer occurs by slip on the north-trending right-lateral Kazerun Fault System (KFS) that connects to the Main Recent Fault, a major northwest-trending dextral fault partitioning oblique convergence at the rear of the belt. The KFS formed by three fault zones ended by bent orogen-parallel thrusts allows slip from along the Main Recent Fault to become distributed by transfer to longitudinal thrusts and folds. To cite this article: C. Authemayou et al., C. R. Geoscience 337 (2005).  相似文献   

Transient seepage analysis in zoned anisotropic soils based on the scaled boundary finite‐element method          下载免费PDF全文

Mohammad Hossein Bazyar  Abbas Talebi 《国际地质力学数值与分析法杂志》2015,39(1):1-22

The scaled boundary finite‐element method, a semi‐analytical computational scheme primarily developed for dynamic stiffness of unbounded domains, is applied to the analysis of unsteady seepage flow problems. This method is based on the finite‐element technology and gains the advantages of the boundary element method as well. Only boundary of the domain is discretized, no fundamental solution is required and singularity problems can be modeled rigorously. Anisotropic and non‐homogeneous materials satisfying similarity are modeled with no additional efforts. In this study, firstly, formulation of the method for the transient seepage flow problems is derived followed by its solution procedures. The accuracy, simplicity and applicability of the method are demonstrated via four numerical examples of transient seepage flow – three of them are available in the literature. Homogenous, non‐homogenous, isotropic and anisotropic material properties are considered to show the versatility of the technique. Excellent agreement with the finite‐element method is observed. The method out‐performs the finite‐element method in modeling singularity points. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Estimation of daily stream water temperatures with a Bayesian regression approach          下载免费PDF全文

Mohammad M. Sohrabi  Rohan Benjankar  Daniele Tonina  Seth J. Wenger  Daniel J. Isaak 《水文研究》2017,31(9):1719-1733

Stream water temperature plays a significant role in aquatic ecosystems where it controls many important biological and physical processes. Reliable estimates of water temperature at the daily time step are critical in managing water resources. We developed a parsimonious piecewise Bayesian model for estimating daily stream water temperatures that account for temporal autocorrelation and both linear and nonlinear relationships with air temperature and discharge. The model was tested at 8 climatically different basins of the USA and at 34 sites within the mountainous Boise River Basin (Idaho, USA). The results show that the proposed model is robust with an average root mean square error of 1.25 °C and Nash–Sutcliffe coefficient of 0.92 over a 2‐year period. Our approach can be used to predict historic daily stream water temperatures in any location using observed daily stream temperature and regional air temperature data.  相似文献   

Integration of aquifer geology,groundwater flow and arsenic distribution in deltaic aquifers – A unifying concept          下载免费PDF全文

Mohammad A. Hoque  William G. Burgess  Kazi M. Ahmed 《水文研究》2017,31(11):2095-2109

Groundwater arsenic (As) presents a public health risk of great magnitude in densely populated Asian delta regions, most acutely in the Bengal Basin (West Bengal, India and Bangladesh). Research has focused on the sources, mobilisation, and heterogeneity of groundwater As, but a consistent explanation of As distribution from local to basin scale remains elusive. We show for the Bengal Aquifer System that the numerous, discontinuous silt‐clay layers together with surface topography impose a hierarchical pattern of groundwater flow, which constrains As penetration into the aquifer and controls its redistribution towards discharge zones, where it is re‐sequestered to solid phases. This is particularly so for the discrete periods of As release to groundwater in the shallow subsurface associated with sea level high‐stand conditions of Quaternary inter‐glacial periods. We propose a hypothesis concerning groundwater flow ( S ilt‐clay layers I mpose H ierarchical groundwater flow patterns constraining A rsenic progression [SIHA]), which links consensus views on the As source and history of sedimentation in the basin to the variety of spatial and depth distributions of groundwater As reported in the literature. SIHA reconciles apparent inconsistencies between independent, in some cases contrasting, field observations. We infer that lithological and topographic controls on groundwater flow, inherent to SIHA, apply more generally to deltaic aquifers elsewhere. The analysis suggests that groundwater As may persist in the aquifers of Asian deltas over thousands of years, but in certain regions, particularly at deeper levels, As will not exceed low background concentrations unless groundwater flow systems are short‐circuited by excessive pumping.  相似文献   

Introducing a new conceptual instantaneous unit hydrograph model based on a hydraulic approach     

Setareh Khaleghi  Mohammad Parvin Nia 《水文科学杂志》2013,58(13-14):1967-1975

ABSTRACT

A novel approach is introduced for simulation of instantaneous unit hydrographs (IUHs). The model consists of a series of linear reservoirs that are connected to each other, and is referred to as the inter-connected linear reservoir model (ICLRM). By assuming the flow between two reservoirs is a linear function of the difference between the water levels in the reservoirs, a system of first-order linear differential equations is obtained as the ICLRM governing equation. By solving the equations, the discharge from the last reservoir is considered as an IUH. A small-scale laboratory device was constructed for the simulation of IUHs using the model. By studying four hydrographs extracted from the literature, and simulating them using both the ICLRM and the Nash model, it is concluded that the ICLRM can predict these hydrographs more accurately than the Nash model. Due to the simplicity of the construction and operation of the ICLRM and, more importantly, its visual aspect, the ICLRM may be considered as an effective educational tool for studying IUHs.  相似文献   

The influence of physical and biological processes on the ichthyoplankton communities in the Gulf of Sirte (Southern Mediterranean Sea)          下载免费PDF全文

Angela Cuttitta  Sergio Bonomo  Salem Zgozi  Angelo Bonanno  Bernardo Patti  Enza Maria Quinci  Marco Torri  Mohamed Hamza  Abdul Fatah  Daw Haddoud  Akram El Turki  Abdul Bari Ramadan  Simona Genovese  Salvatore Mazzola 《Marine Ecology》2016,37(4):831-844

This paper reports on the first study on the ichthyoplankton community structure in the Gulf of Sirte and its spatial distribution in relation to environmental conditions and zooplankton abundance. The results make an important contribution to the future management of fisheries in this unexplored, but much exploited, area. Biological samples were collected in July 2008 using a Bongo40 net. In total, 1914 larvae were found and 1652 of these were identified. In particular, bathypelagic taxa were the most abundant, followed by demersal, mesopelagic, pelagic and epipelagic taxa. The ichthyoplankton community had a patchwork distribution influenced by oligotrophic conditions, the bottom depth and oceanographical features. The results suggest that environmental forcings were able to transport the ichthyoplankton to productive areas. Indeed, maximum fish egg densities were found in coastal stations in correspondence with the Atlantic Tunisian Current inflow, whereas larvae were mainly concentrated in the east side of the Gulf, probably as a result of advection by the anticyclonic circulation. Additionally, the distribution patterns of the total larvae density and the different assemblages were well matched with the abundance of the zooplankton, probably determining final larval survival, growth and recruitment.  相似文献   

Steady critical discharge rates from vertical and horizontal wells in fresh–saline aquifers with sharp interfaces     

Raziyeh Hendizadeh  Mazda Kompanizare  Mohammad R. Hashemi  G. Reza Rakhshandehroo 《Hydrogeology Journal》2016,24(4):865-876

In this study, the critical (or maximum) discharge rates before saline water enters a well were determined for vertical and horizontal wells in a freshwater aquifer which is separated from a static saline aquifer by a sharp interface. Flow around the well was solved by integration of a point sink solution along the well axis, and both the critical discharge rate and critical interface rise were determined through a comparison of the heads and vertical gradients at the saline–fresh water interface. The rates were determined for vertical and horizontal wells with various lengths and depths for different aquifer salinities. Results were generalized by drawing dimensionless type curves. The results showed that the dimensionless total critical discharge rates are higher for the longer horizontal wells and longer vertical wells with a certain bottom depth, and they almost linearly decrease with well depth at rates of 0.7–0.9. For the dimensionless well length of 0.2, the dimensionless total discharge rate of a horizontal well is about 0.1 more than that of a vertical well with the same length and well-top depth. Also, the critical discharge rates per unit length of well are inversely proportional to well length and remarkably higher for shallower wells. Additionally, the critical pumping rate is proportional to the salinity difference of the aquifers. These results were confirmed by comparison to existing solutions for vertical wells with dimensionless lengths of 0.2, 0.5 and 0.6, and for critical interface rises in the range of 0.75–0.9.  相似文献   

Tectonic evolution of the La González pull-apart basin in the Mérida Andes: combination of geological data and satellite radar interferometry (InSAR)     

Hamid Reza Javadi  Maryam Dehghani  Mohammad Foroutan  Amir Naeimi  Mahasa Roustaei  Abdollah Saidi  Josef Angel Urbina 《International Journal of Earth Sciences》2016,105(5):1603-1620

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