Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
A Numerical Study of Chamber Size and Boundary Eects on CPT Tip Resistance in NC Sand
2911
EN
M.M.
Ahmadi
Department of Civil Engineering,Sharif University of Technology
P.K.
Robertson
Department of Civil and Environmental Engineering,University of Alberta
Journal Article
2009
05
20
A numerical modeling procedure was used to quantify calibration chamber size and boundary
eects for cone penetration testing in sand. In the numerical analyses, chamber diameter
and boundary conditions were varied to investigate the eects of chamber size and boundary
conditions on cone tip resistance. These analyses show that, for loose sand, a chamber-tocone
diameter ratio of 33 is sucient for the boundaries to have no in
uence on the cone tip
measurements. However, for very dense sand, the numerical analyses show that the chamberto-
cone diameter ratio should be more than 100 to ensure that boundaries have no in
uence
on cone tip measurements. Numerical analysis indicates that, not only the sand relative density
but its stress state is also a signicant factor in in
uencing the chamber size eects. The
results of the numerical analyses were compared to existing empirically based relationships.
Suggestions are provided to reduce the eects of chamber size and boundaries on cone tip
resistance measurements in sand.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Generation of Orthoimage from High-Resolution DEM and High-Resolution Image
2912
EN
M.
Saati
Department of Geomatics Engineering,University of Tehran
J.
Amini
Department of Geomatics Engineering,University of Tehran
Journal Article
2009
05
25
Generating an orthoimage from high-resolution satellite images is an important undertaking for
various remote sensing and photogrammetric applications. In this paper, a method is proposed
that uses Articial Neural Networks (ANN) to generate orthoimage Ikonos Geo images. For
orthoimage generation, a Digital Elevation Model (DEM) with a cell size of 4 m and RMS error
of 0.24 m is constructed with neural networks, based on a Quad Tree (QT) structure. In order
to determine object-to-image relationships, rational function models, polynomials and neural
networks with back propagation learning algorithms were used. Ground Control Points (GCPs)
and check points were taken from topographic maps of 1:2000, with a contour interval of 2.5 m,
to evaluate the accuracy of DEM and object-to-image transformations. The method described
in this paper is tested with an Ikonos Geo image from a region of Bilesavar, Iran.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Some New Robust Pseudo Forward and Rotation Gaits for the Snakeboard
2913
EN
M.
Mahzoon
Department of Mechanical Engineering,Shiraz University
A.
Asnafi
Department of Mechanical Engineering,Yasouj University
Journal Article
2009
05
25
The goal of this paper is to introduce some new robust gaits of the snakeboard. This is achieved
by dening two parameters; the ratios of the frequencies and amplitudes of the snakeboard's
sinusoidal shape variable dynamics, and properly adjusting their variations. The gaits are
produced via stable and/or moving limit cycles. The highly symmetric patterns generated by
these gaits, besides their inherent beauty and coherency, exemplify the rich information content
of the underlying nonlinear system.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
An Inverse Problem Method for Gas Temperature Estimation in Partially Filled Rotating Cylinders
2914
EN
M.M.
Heydari
Department of Mechanical Engineering,Sharif University of Technology
B.
Farhanieh
Department of Mechanical Engineering,Sharif University of Technology
Journal Article
2009
05
25
The objective of this article is to study gas temperature estimation in a partially lled rotating
cylinder. From the measured temperatures on the shell, an inverse analysis is presented for
estimating the gas temperature in an arbitrary cross-section of the aforementioned system. A
nite-volume method is employed to solve the direct problem. By minimizing the objective
function, a hybrid eective algorithm, which contains a local optimization algorithm, is adopted
to estimate the unknown parameter. The measured data are simulated by adding random errors to
the exact solution. The eects of measurement errors on the accuracy of the inverse analysis are
investigated. Two optimization algorithms are used in determination of the gas temperature. The
conjugate gradient method is found to be better than the Levenberg-Marquardt method, since
the former produces more accurate results for the same measurement errors. A good agreement
between the exact value and the estimated result has been observed for both algorithms.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Characteristic Variables and Entrainment in 3-D Density Currents
2915
EN
B.
Firoozabadi
Department of Mechanical Engineering,Sharif University of Technology
Journal Article
2009
05
25
A CFD code has been developed to describe the salt solution density current, which propagates
three-dimensionally in deep ambient water. The height and width of the dense layer are two
dominated length scales in a 3-D structure of the density current. In experimental eorts, it
is common to measure the height and width of this current via its brightness. Although there
are analytical relations to calculate the current height in a two-dimensional
ow, these relations
cannot be used to identify the width and height of a 3-D density current, due to the existence
of two unknown parameters. In the present model, the height and width of the dense layer
are obtained by using the boundary layer concept. Also, a comparison is made between depth
averaged and characteristic variables. Then, the computed velocity and concentration proles
are compared with the experimental data and the results show good agreement between them. In
this work, the entrainment coecient was also calculated using depth-averaged parameters and
compared with the experimental data. The result has the same trend as the Ellison and Turner
experiments. Present results show that the boundary layer concept can be useful in identifying
the height and width of a 3-D density current.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Three-Dimensional Data Transfer Operators in Plasticity Using SPR Technique with C0, C1 and C2 Continuity
2916
EN
S.A.
Gharehbaghi
Department of Civil Engineering,University of Tehran
A.R.
Khoei
Department of Civil Engineering,Sharif University of Technology
Journal Article
2009
05
26
In this paper, the data transfer operators are developed in three-dimensional elasto-plasticity
using the Superconvergent Patch Recovery (SPR) method. The transfer operators are dened
for mapping of the state and internal variables between dierent meshes. The internal variables
are transferred from Gauss points of old mesh to the nodal points. The variables are then
transferred from the nodal points of old mesh to the nodal points of new mesh. Finally, the values
are computed at the Gauss points of new mesh using their values at the nodal points. Aspects
of the transfer operators are presented in a three-dimensional superconvergent path recovery
technique, based on C0, C1 and C2 continuity. Finally, the eciency of the computational
algorithms is demonstrated using a circular tube subjected to internal pressure.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Uniform Fractional Part: A Simple Fast Method for Generating Continuous Random Variates
2917
EN
H.
Mahlooji
Department of Industrial Engineering,Sharif University of Technology
A.
Eshragh Jahromi
Department of Industrial Engineering,Sharif University of Technology
Journal Article
2009
05
26
A known theorem in probability is adopted and through a probabilistic approach, it is generalized
to develop a method for generating random deviates from the distribution of any continuous
random variable. This method, which may be considered as an approximate version of the
Inverse Transform algorithm, takes two random numbers to generate a random deviate, while
maintaining all the other advantages of the Inverse Transform method, such as the possibility of
generating ordered as well as correlated deviates and being applicable to all density functions,
regardless of their parameter values.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Applying Circular Coloring to Open Shop Scheduling
2918
EN
M.
Modarres
Department of Industrial Engineering,Sharif University of Technology
M.
Ghandehari
Department of Industrial Engineering,Sharif University of Technology
Journal Article
2009
05
26
IN this paper, a new approach to formulate a class of scheduling problems is introduced, which
can be applied to many other discrete problems with complicated structures. The concept
of graph circular coloring is applied to develop a model for the special case of an open shop
scheduling problem. In this problem, there are some independent jobs to be processed in a
shop with dedicated renewable resources. Each job consists of several tasks with no precedence
restriction. Each task is processed without preemption. The processing time of the tasks is given.
Processing each task requires using some multiple specied types of resource, while no more than
one task can use each resource, simultaneously. Some tasks can be shared by more than one job
and the process may be repeated more than once. The objective is to develop a schedule which
yields the minimal makespan length of all jobs, as well as the number of cycles. The model is rst
developed for cases when the processing time of each task is one unit and, then, it is generalized
by relaxing this restriction. In both cases, a circular coloring formulation is shown in comparison
with traditional formulation (single process execution) results in an improved makespan and also
the required information regarding the optimum number of cycles to repeat the process.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Source Parameters of the March 31st, 2006, Dorud Earthquake in Iran
2919
EN
M.
Mostafazadeh
-------,IIEES
Journal Article
2009
05
26
The occurrence of the western Iran earthquake of 31 March 2006 provided an important
opportunity to study the source properties of earthquakes in this region. Although moderate
in size (ML = 6:1, IIEES), this earthquake was the largest to have occurred in the region since
the deployment of the Global Digital Seismograph Network. The far-eld data determination of
body wave (P) spectra, interpreted in terms of the circular seismic source model, are used to
estimate the parameters seismic moment (MO), corner frequency (f0) , source radius (r) and
stress drop (). P waves recorded at teleseismic distances can be obtained from stations of
this network that are
at to displacement, in a frequency range of 0.19 to 0.32 Hz. The average
seismic moment (MO = 14:92 1019 N-M) and source radius (r = 9281 m) were calculated
from the long period spectral levels, which were corrected for the radiation pattern of a double
couple point source. In addition, the stress drops ( = 87106 N/m2) of this event have been
calculated by using an average seismic moment and source radius. Additional errors in the stress
drop determination are produced by uncertainty in the seismic moment. Scatter in the seismic
moment values is caused by such factors as site condition and errors in the radiation pattern.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Numerical Modeling of Hydraulic Fracturing in Oil Sands
2920
EN
A.
Pak
Department of Civil Engineering,Sharif University of Technology
D.H.
Chan
School of Civil and Environmental Engineering,University of Alberta
Journal Article
2009
05
26
Hydraulic fracturing is a widely used and ecient technique for enhancing oil extraction from
heavy oil sands deposits. Application of this technique has been extended from cemented rocks
to uncemented materials, such as oil sands. Models, which have originally been developed
for analyzing hydraulic fracturing in rocks, are in general not satisfactory for oil sands. This
is due to a high leak-o in oil sands, which causes the mechanism of hydraulic fracturing to
be dierent from that for rocks. A thermal hydro-mechanical fracture nite element model is
developed, which is able to simulate hydraulic fracturing under isothermal and non-isothermal
conditions. Plane strain or axisymmetric hydraulic fracture problems can be simulated by this
model and various boundary conditions, such as specied pore pressure/
uid
ux, specied
temperature/heat
ux, and specied loads/traction, can be modeled. The developed model has
been veried by comparing its results to existing analytical and numerical solutions for thermoelastic
consolidation problems. The model has been used to simulate a laboratory experiment
of hydraulic fracture propagation in oil sands. The results from the numerical model are in
agreement with experimental observations. The numerical model and laboratory experiments
both indicate that, for uncemented porous materials, such as sands (as opposed to rocks), a
single planar fracture is unlikely to occur and a system of multiple fractures or a fracture zone
consisting of interconnected tiny cracks should be expected.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Time-Domain Analysis of Sandwich Shells with Passive Constrained Viscoelastic Layers
2921
EN
M.
Salehi
Department of Mechanical Engineering,Amirkabir University of Technology
F.
Bakhtiari-Nejad
Department of Mechanical Engineering,Amirkabir University of Technology
A.
Besharati
-------,Iran Aerospace Industries Organization
Journal Article
2009
05
26
Damping eects on THE vibration behavior of a sandwich cylindrical shell with a passive
constrained viscoelastic layer are investigated in the time-domain. Equations of motion in terms
of transverse modal coordinates in the frequency-domain are obtained by means of an energy
method and the Lagrange equation, and they are solved by the assumed-mode method. The
viscoelastic behavior is represented by the frequency complex modulus model. The equations of
motion are transferred from the frequency-domain to the time-domain by the Inverse Fast Fourier
Transform, (IFFT). Thickness eects of constrained and viscoelastic layers are investigated by a
transient external load response and evaluation of the damping factor and settling time.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Application of a Kinematics-Driven Approach in Human Spine Biomechanics During an Isometric Lift
2922
EN
M.
Parnianpour
Department of Mechanical Engineering,Sharif University of Technology
A.
Shirazi-Adl
Department of Mechanical Engineering,Ă‰cole Polytechnique
Journal Article
2009
05
26
Eective prevention and treatment management of spinal disorders can only be based on accurate
estimation of muscle forces and spinal loads during various activities such as lifting. The
infeasibility of experimental methods to measure muscle and spinal loads has prompted the use of
biomechanical modeling techniques. A major shortcoming in many previous and current models
is the consideration of equilibrium conditions only at a single cross section, rather than along
the entire length of the spine, when attempting to compute muscle forces and spinal loads. The
assumption of extensor global muscles with straight rather than curved paths and of the spinal
segments as joints with no translational degrees-of-freedom, are additional issues that need to be
critically evaluated when simulating lifting tasks. The kinematics-driven approach, which satises
equilibrium conditions in all spinal directions and levels and yields spinal postures compatible with
external loads, muscle forces and nonlinear passive properties, while also taking into account the
wrapping of trunk muscles, is employed. Results demonstrate that, regardless of the method
used (optimization or EMG-assisted), single-level free body diagram models yield estimations
that grossly violate equilibrium at other levels. The computed results are also markedly leveldependent.
The crucial eects of the proper consideration of global muscles with curved paths
and of spinal segments with translational degrees-of-freedom when attempting to estimate muscle
forces and spinal loads in isometric lifting tasks are also demonstrated.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
Impact of Table Size on the Performance of Thermo-Plastic Roong Systems Under Wind Uplift Pressures
2923
EN
S.M.
Zahrai
Department of Civil Engineering,University of Tehran
Journal Article
2009
05
26
Roong systems have always been vulnerable to strong wind uplift pressures. Wind forces have
dynamic eects on structures, as they change in time and space. Therefore, a dynamic means of
evaluating roong systems is necessary in order to identify the component of the system having
the least resistance to wind uplift forces. Although researchers worldwide have conducted tests
on roong structures, they have all used various table sizes, as there is still no standard chamber
size for experimental purposes. This paper aims to study the impact of table size on roong
system performance. To achieve this objective, extensive analytical work has been conducted
to investigate the performance of roong systems subjected to wind pressure. Analytical results
compared well with those obtained from experimental work, validating the numerical modeling.
This paper presents some of these result comparisons. It was found that an increase in table
width beyond a certain level, about 3 m for cases considered here, did not signicantly change
the results, while the rate of fastener load change might be high for a smaller table width. This
specic limit depends on the roong system conguration. Furthermore, a larger membrane
width (fastener row spacing) would increase the width of the ideal table. Ideal table sizes were
also suggested for various congurations having a TPO (Thermo-Plastic Olens) membrane and
correction factors were eventually developed for dierent table sizes.
Sharif University of Technology
Scientia Iranica
1026-3098
15
5
2008
10
01
A Fuzzy Intelligent Information Agent Architecture for Supply Chains
2924
EN
M.H.
Fazel Zarandi
Department of Industrial Engineering,Amirkabir University of Technology
S.M.
Moattar Hoseini
Department of Industrial Engineering,Amirkabir University of Technology
Journal Article
2009
05
26
Through the emergence of information and communication technologies and customer-oriented
approaches in business and industry, for achieving competitive advantages and in order to remain
at the top in every business, more
exible and responsive supply chain systems are required.
The next generation of supply chain systems must be agile, adaptive, cooperative, integrated
and
exible. Agent-based supply chain management is an approach that addresses the next
generation of supply chain system features. This paper focuses on the role of an information
agent in agent-based supply chain management within an uncertain environment. For this
purpose, a proper modular architecture for the information agent, based on fuzzy theory, is
proposed. Here, the knowledge-based module in the architecture is fuzzy rules. The system is
used for updating forecasted values and implementing customer commitment in a proper manner.
Finally, the proposed architecture is tested and veried and the results of the developed approach
are discussed.