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Performance evaluation of mobile ad hoc networks in the presence of energy-based selfishness
, Article 2006 3rd International Conference on Broadband Communications, Networks and Systems, BROADNETS 2006, San Jose, CA, 1 October 2006 through 5 October 2006 ; 2006 ; 1424404258 (ISBN); 9781424404254 (ISBN) ; Movaghar, A ; Sharif University of Technology
2006
Abstract
Cooperation of nodes for routing and packet forwarding is inevitable in a mobile ad hoc network. Selfishness in such networks is a significant challenge and can cause network performance to noticeably degrade. In this paper, we propose some new selfishness models elicited from psychological behavior of human beings. We also evaluate performance of MANET in the presence of different percentages of selfish nodes that act based on our selfishness models. Results show that energy-based selfishness is a serious problem that could affect performance depends on mobility of nodes, density of network, and time of simulation. This kind of selfishness needs a comprehensive mechanism to cope with and we...
Flow field around side-by-side piers with and without a scour hole
, Article European Journal of Mechanics, B/Fluids ; Volume 36 , 2012 , Pages 152-166 ; 09977546 (ISSN) ; Aslani Kordkandi, A ; Sharif University of Technology
2012
Abstract
The present study provides the experimental results of the flow pattern around two-circular piers positioned in side-by-side arrangement. The experiments were performed for two bed configurations (with and without a scour hole). Velocities were measured by an Acoustic Doppler Velocimeter (ADV). Flat bed and scour hole were frozen by synthetic glue to facilitate the performance of the experiments. The contours and distributions of the time-averaged velocity components, turbulence intensities, turbulence kinetic energy, and Reynolds stresses at different horizontal and vertical planes are presented. Streamlines and velocity vectors obtained from time-averaged velocity fields are used to show...
Flow field around single and tandem piers
, Article Flow, Turbulence and Combustion ; Volume 90, Issue 3 , April , 2013 , Pages 471-490 ; 13866184 (ISSN) ; Aslani-Kordkandi, A ; Sharif University of Technology
2013
Abstract
The present study provides a comparison between the flow pattern around two circular piers in tandem and a single pier set up on a moderately rough flat bed in a laboratory flume. Velocities are measured by an Acoustic Doppler Velocimeter (ADV). The contours of the time-averaged velocity components, Reynolds shear stresses, turbulence intensities and turbulence kinetic energy at different planes are presented. Streamlines and vectors are used to study the flow features. The analysis of power spectra around the piers is also presented. The results show that the presence of downstream pier changes the flow structure to a great extent, particularly in the near-wake region. Within the gap...
A higher-order Boussinesq-type model with moving bottom boundary: Applications to submarine landslide tsunami waves
, Article International Journal for Numerical Methods in Fluids ; Volume 53, Issue 6 , 2007 , Pages 1019-1048 ; 02712091 (ISSN) ; Najafi Jilani, A ; Sharif University of Technology
2007
Abstract
A two-dimensional depth-integrated numerical model is developed using a fourth-order Boussinesq approximation for an arbitrary time-variable bottom boundary and is applied for submarine-landslide-generated waves. The mathematical formulation of model is an extension of (4,4) Padé approximant for moving bottom boundary. The mathematical formulations are derived based on a higher-order perturbation analysis using the expanded form of velocity components. A sixth-order multi-step finite difference method is applied for spatial discretization and a sixth-order Runge-Kutta method is applied for temporal discretization of the higher-order depth-integrated governing equations and boundary...
A higher-order two-dimensional Boussinesq wave model
, Article Journal of Coastal Research ; Issue SPEC. ISSUE 50 , 2007 , Pages 1183-1187 ; 07490208 (ISSN) ; Najafi Jilani, A ; Sharif University of Technology
2007
Abstract
A two-dimensional Boussinesq-type model is presented accurate to O(μ)6 , μ = h0/l0, in dispersion and all consequential order for non-linearity with arbitrary bottom boundary, where h0 is the water depth and l0 is the characteristic wave length. The mathematical formulation is an extension of (4,4) the Padé approximant to include varying bottom boundary in two horizontal dimensions. A higher order perturbation method is used for mathematical derivation of the presented model. A two horizontal dimension numerical model is developed based on derived equations using the Finite Difference Method in higher-order scheme for time and space. The numerical wave model is verified successfully in...
Impulsive waves caused by subaerial landslides
, Article Environmental Fluid Mechanics ; Volume 8, Issue 3 , 2008 , Pages 263-280 ; 15677419 (ISSN) ; Nik Khah, A ; Sharif University of Technology
2008
Abstract
This paper presents the experimental results of impulsive waves caused by subaerial landslides. A wide range of effective parameters are considered and studied by performing 120 laboratory tests. Considered slide masses are both rigid and deformable. The effects of bed slope angle, water depth, slide impact velocity, geometry, shape and deformation on impulse wave characteristics have been inspected. The impulse wave features such as amplitude, period and also energy conversation are studied. The effects of slide Froude number and deformation on energy conversation from slide into wave are also investigated. Based on laboratory measured data an empirical equation for impulse wave amplitude...
Laboratory investigations on impulsive waves caused by underwater landslide
, Article Coastal Engineering ; Volume 55, Issue 12 , December , 2008 , Pages 989-1004 ; 03783839 (ISSN) ; Najafi Jilani, A ; Sharif University of Technology
2008
Abstract
Laboratory investigations have been performed on the submarine landslide generated waves by performing 120 laboratory tests. Both rigid and deforming-slide masses are considered. The effects of bed slope angle, initial submergence, slide geometry, shape and deformation on impulse wave characteristics have been inspected. Impulse wave amplitude, period, energy and nonlinearity are studied in this work. The effects of bed slope angle on energy conversion from slide into wave are also investigated. Laboratory-based prediction equations are presented for impulse wave amplitude and period in near and far-field and are successfully verified using the available data in previous laboratory and...
Error analysis of finite difference methods for two-dimensional advection-dispersion-reaction equation
, Article Advances in Water Resources ; Volume 28, Issue 8 , 2005 , Pages 793-806 ; 03091708 (ISSN) ; Hosseini, S. A ; Sharif University of Technology
2005
Abstract
In this paper, the numerical errors associated with the finite difference solutions of two-dimensional advection-dispersion equation with linear sorption are obtained from a Taylor analysis and are removed from numerical solution. The error expressions are based on a general form of the corresponding difference equation. The variation of these numerical truncation errors is presented as a function of Peclet and Courant numbers in X and Y direction, a Sink/Source dimensionless number and new form of Peclet and Courant numbers in X-Y plane. It is shown that the Crank-Nicolson method is the most accurate scheme based on the truncation error analysis. The effects of these truncation errors on...
Numerical errors of explicit finite difference approximation for two-dimensional solute transport equation with linear sorption
, Article Environmental Modelling and Software ; Volume 20, Issue 7 , 2005 , Pages 817-826 ; 13648152 (ISSN) ; Hosseini, S. A ; Sharif University of Technology
2005
Abstract
The numerical errors associated with explicit upstream finite difference solutions of two-dimensional advection - Dispersion equation with linear sorption are formulated from a Taylor analysis. The error expressions are based on a general form of the corresponding difference equation. The numerical truncation errors are defined using Peclet and Courant numbers in the X and Y direction, a sink/source dimensionless number and new Peclet and Courant numbers in the XY plane. The effects of these truncation errors on the explicit solution of a two-dimensional advection-dispersion equation with a first-order reaction or degradation are demonstrated by comparison with an analytical solution in...
Experimental investigation of clear-water local scour of compound piers
, Article Journal of Hydraulic Engineering ; Volume 136, Issue 6 , June , 2010 , Pages 343-351 ; 07339429 (ISSN) ; Baratian Ghorghi, Z ; Beheshti, A. A ; Sharif University of Technology
2010
Abstract
Local scour around complex piers under steady clear-water condition was studied experimentally for a variety of configuration, including different sizes and shapes of complex piers. A total of 70 experiments were carried out. Three sets of experiments were performed over the entire range of possible pile cap elevations for complex piers with different geometrical characteristics. The collected data are used to quantify the pile cap elevations that maximize or minimize the local scour depth. Some of the available methodologies to estimate the maximum local scour depth around such complex piers are evaluated. The predictions of the scour depths improved by using the revised methods of...
Scour hole depth prediction around pile groups: review, comparison of existing methods, and proposition of a new approach
, Article Natural Hazards ; Volume 88, Issue 2 , 2017 , Pages 977-1001 ; 0921030X (ISSN) ; Beheshti, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
2017
Abstract
A dataset of 365 laboratory tests for scour hole depth (SHD) around pile groups (PGs) under unidirectional aligned flow is compiled, and the performances of the existing equations are comparatively evaluated on the dataset using several statistical indices. A formulation based on a correction of HEC-18 equation provides the best estimate with a correlation factor of 0.58. The test durations of the considered data ranged between 4 and 389 h. A time factor (Kt) is proposed to take into account the temporal variation of the SHD around different PGs. Among the datasets, 51 long-duration experiments are scrutinized to show the temporal variation of scour depth toward equilibrium state. The time...
Sensitivity analysis of coherent ultrashort light pulse CDMA communication system with respect to dispersion
, Article Optical Transmission, Switching, and Subsystems V, Wuhan, 2 November 2007 through 5 November 2007 ; Volume 6783 , 2007 ; 0277786X (ISSN); 9780819469465 (ISBN) ; Jamshidi, K ; Salehi, J. A ; Sharif University of Technology
2007
Abstract
In this paper, we analyze the sensitivity degradation of a system due to various orders of chromatic dispersion. To do this, the power penalty of the uncoded and encoded pulse of a coherent ultrashort light pulse Code Division Multiple Access (CDMA) communication system due to various orders of chromatic dispersions are analyzed. Analysis of uncoded pulse shows that the power penalty is unacceptably high when second order dispersion is not compensated. However we can obtain acceptable level of power penalties while compensating second and third order dispersion. Also, due to the high order of dispersion, the power of encoded pulse decreases as it propagates through the fiber which leads to a...
Estimation of current-induced pile groups scour using a rule-based method
, Article Journal of Hydroinformatics ; Volume 15, Issue 2 , September , 2013 , Pages 516-528 ; 14647141 (ISSN) ; Etemad-Shahidi, A ; Ataie-Ashtiani, B ; Sharif University of Technology
2013
Abstract
Scour phenomenon around piles could endanger the stability of the structures placed on them. Therefore, an accurate estimation of the scour depth around piles is very important for engineers. Due to the complexity of the interaction between the current, seabed and pile group; prediction of the scour depth is a difficult task and the available empirical formulas have limited accuracy. Recently, soft computing methods such as artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) have been used for the prediction of the scour depth. However, these methods do not give enough insight into the generated models and are not as easy to use as the empirical formulas. In...
A combined analytical modeling machine learning approach for performance prediction of MapReduce jobs in cloud environment
, Article 18th International Symposium on Symbolic and Numeric Algorithms for Scientific Computing, SYNASC 2016, 24 September 2016 through 27 September 2016 ; 2017 , Pages 431-439 ; 9781509057078 (ISBN) ; Gianniti, E ; Ardagna, D ; Movaghar, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Nowadays MapReduce and its open source implementation, Apache Hadoop, are the most widespread solutions for handling massive dataset on clusters of commodity hardware. At the expense of a somewhat reduced performance in comparison to HPC technologies, the MapReduce framework provides fault tolerance and automatic parallelization without any efforts by developers. Since in many cases Hadoop is adopted to support business critical activities, it is often important to predict with fair confidence the execution time of submitted jobs, for instance when SLAs are established with end-users. In this work, we propose and validate a hybrid approach exploiting both queuing networks and support vector...
Synchronous measurements of the velocity and concentration in low density turbidity currents using an Acoustic Doppler Velocimeter
, Article Flow Measurement and Instrumentation ; Volume 17, Issue 1 , 2006 , Pages 59-68 ; 09555986 (ISSN) ; Shamsai, A ; Ataie Ashtiani, B ; Sharif University of Technology
2006
Abstract
Low density turbidity currents have been investigated in a laboratory flume. An Acoustic Doppler Velocimeter (ADV) was used to measure the velocity. The dimensionless velocity profiles were compared with previous studies to check the accuracy of acoustic measuring techniques for turbidity currents. Successful use of the ADV to measure the current velocity has led to interest in the technique of using acoustic sensors to estimate concentrations. Acoustic backscattering analyses are used for estimating the sediment concentration in turbidity currents. With this approach, concentration measurements can be reasonably well represented by a similarity profile. Using this technique, an accurate...
Improvement of soil moisture and groundwater level estimations using a scale-consistent river parameterization for the coupled ParFlow-CLM hydrological model: A case study of the Upper Rhine Basin
, Article Journal of Hydrology ; Volume 610 , 2022 ; 00221694 (ISSN) ; Fahs, M ; Bitar, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Accurate implementation of river interactions with subsurface water is critical in large-scale hydrologic models with a constant horizontal grid resolution when models apply kinematic wave approximation for both hillslope and river channel flow. The size of rivers can vary greatly in the model domain, and the implemented grid resolution is too coarse to accurately account for river interactions. Consequently, the flow velocity is underestimated when the width of the rivers is much narrower than the selected grid size. This leads to inaccuracy and uncertainties in calculations of water quantities. In addition, the rate of exfiltration and infiltration between the river and the subsurface may...
Effects of heterogeneities on capillary pressure-saturation-relative permeability relationships
, Article Journal of Contaminant Hydrology ; Volume 56, Issue 3-4 , 2002 , Pages 175-192 ; 01697722 (ISSN) ; Majid Hassanizadeh, S ; Celia, M. A ; Sharif University of Technology
2002
Abstract
In theories of multiphase flow through porous media, capillary pressure-saturation and relative permeability-saturation curves are assumed to be intrinsic properties of the medium. Moreover, relative permeability is assumed to be a scalar property. However, numerous theoretical and experimental works have shown that these basic assumptions may not be valid. For example, relative permeability is known to be affected by the flow velocity (or pressure gradient) at which the measurements are carried out. In this article, it is suggested that the nonuniqueness of capillary pressure-relative permeability-saturation relationships is due to the presence of microheterogeneities within a laboratory...
Tidal effects on groundwater dynamics in unconfined aquifers
, Article Hydrological Processes ; Volume 15, Issue 4 , 2001 , Pages 655-669 ; 08856087 (ISSN) ; Volker, R. E ; Lockington, D. A ; Sharif University of Technology
2001
Abstract
The variation of seawater level resulting from tidal fluctuations is usually neglected in regional groundwater flow studies. Although the tidal oscillation is damped near the shoreline, there is a quasi-steady-state rise in the mean water-table position, which may have an influence on regional groundwater flow. In this paper the effects of tidal fluctuations on groundwater hydraulics are investigated using a variably saturated numerical model that includes the effects of a realistic mild beach slope, seepage face and the unsaturated zone. In particular the impact of these factors on the velocity field in the aquifer is assessed. Simulations show that the tidal fluctuation has substantial...
Declaration of Conflicts of Interest in Networking Era: Raising the Bar
, Article Science and Engineering Ethics ; 2015 , Pages 1-3 ; 13533452 (ISSN) ; Sharif University of Technology
Springer Netherlands
2015
Preface: Thematic issue “Landslide-generated tsunamis waves”
, Article Landslides ; 2016 , Pages 1- ; 1612510X (ISSN) ; Sharif University of Technology
Springer Verlag
2016