ACES Publication Search
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ACES Journal February 2013ACES
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ACES Journal Paper | |
Year: 2013      Volume: 28      Number: 2 | |
Click here to download PDF File Size: 6948 KB |
ACES Journal November 2017 Full | |
ACES Journal Paper | |
Year: 2017      Volume: 32      Number: 11 | |
Click here to download PDF File Size: 12999 KB | |
ACES |
ACES Journal June 2013 Full IssueACES
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ACES Journal Paper | |
Year: 2013      Volume: 28      Number: 6 | |
Click here to download PDF File Size: 6230 KB |
ACES June 2011 Full JournalACES
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ACES Journal Paper | |
Year: 2011      Volume: 26      Number: 6 | |
Click here to download PDF File Size: 10506 KB |
ACES Journal September 2012ACES
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ACES Journal Paper | |
Year: 2012      Volume: 27      Number: 9 | |
Click here to download PDF File Size: 10714 KB |
Numerical Solution of Electromagnetic Integral Equations by the Meshfree Collocation MethodB. Honarbakhsh, A. Tavakoli
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ACES Journal Paper | |
Year: 2012      Volume: 27      Number: 9 | |
Click here to download PDF File Size: 1208 KB | |
This paper presents guidelines for
mesh free numerical solution of electromagnetic
integral equations. Both static and dynamic
problems are considered, including the EFIE and
the MPIE for dynamic case. Different choices of
the kind of meshfree method, shape functions and
their parameters are studied and proper choices are
suggested by logical deduction, experience or
previous reports. The final configuration is applied
to classical problems in one and two dimensions
such as electric charge (density) and electric
current (density) distributions over a line and flat
plates, respectively. The method is validated by
convergence analysis and is compared with MoM.
In addition, suggestions are made for bypassing
numerical integrations that make the construction
of the coefficient matrix integration free. |
Polarimetric Scattering from a 3-D Rectangular Crack in a PEC Covered by a Dielectric LayerM. Bozorgi, A. Tavakoli
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ACES Journal Paper | |
Year: 2011      Volume: 26      Number: 6 | |
Click here to download PDF File Size: 1808 KB | |
A novel direct approach for calculation
of the polarimetric scattering fields from a narrow
3-D rectangular crack in an infinite ground plane
underneath a dielectric layer is presented. Since
the electromagnetic fields are directly calculated
and thus the approach in inversible, this technique
is suitable for microwave NDT applications
where cracks of narrow width, arbitrary length
and depth under a dielectric layer are frequently
encountered. A set of coupled field integral
equations (FIE) with logarithmic and
hypersingular kernels are derived and then
descritized by a collocation method based on
Chebyshev polynomials. The results of this direct
approach are in good agreement with noninversible
full numerical FEM and MoM results. |
ACES Journal July 2012ACES
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ACES Journal Paper | |
Year: 2012      Volume: 27      Number: 7 | |
Click here to download PDF File Size: 5271 KB |
Analysis of Thin Microstrip Antennas by Meshless MethodsB. Honarbakhsh, A. Tavakoli
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ACES Journal Paper | |
Year: 2012      Volume: 27      Number: 12 | |
Click here to download PDF File Size: 490 KB | |
In this paper, different meshless
methods are applied to the analysis of microstrip
antennas with thin substrate. Comparison is made
between the performance of the methods with
respect to convergence, CPU time and condition
number of final coefficient matrix. The exact
modal solution and method of moments are used
for validation. The input impedance results of all
methods are in agreement with each other. |
ACES Journal December 2012ACES
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ACES Journal Paper | |
Year: 2012      Volume: 27      Number: 12 | |
Click here to download PDF File Size: 5520 KB |
The Meshless Local Boundary Equation MethodB. Honarbakhsh, A. Tavakoli
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ACES Journal Paper | |
Year: 2012      Volume: 27      Number: 7 | |
Click here to download PDF File Size: 734 KB | |
A method similar to the local boundary
integral equation method that preserves its
properties and is free from singular integrals is
proposed. The approach is based on selection of
the weighting functions from a homogeneous
solution of the problem rather than the
fundamental solution. Many examples of 2D
Laplace and Helmholtz equations and 3D vector
wave equation are presented for verification. The
method shows optimistic performance over piecewise
smooth boundaries. Radial basis functions of
thin plate spline type are used for meshless
discretization. The dependable performance of the
proposed method provides a hopeful applicability
to numerical solutions of partial differential
equations. |
ACES Journal January 2014 Full IssueACES
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ACES Journal Paper | |
Year: 2014      Volume: 29      Number: 1 | |
Click here to download PDF File Size: 15617 KB | |
ACES |
Application of an IE-Based Domain Decomposition Method for Analysis of Planar Microstrip Array Structures: Meshless ApproachB. Honarbakhsh, A. Tavakoli
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ACES Journal Paper | |
Year: 2015      Volume: 30      Number: 8 | |
Click here to download PDF File Size: 1069 KB | |
In this paper, application of an integral
equation based domain decomposition method (DDM),
developed for numerical solution of one-dimensional
Fredholm integral equations of the second kind, is
extended to electric field and mixed potential integral
equations in two dimensions. Even though the original
DDM was developed based on the Nyström method,
results of the present work shows that meshfree approach
can also be utilized. The extended DDM is employed for
efficient meshfree analysis of planar microstrip array
structures in the sense of reduced-size shape function and
stiffness matrices. Results are validated by method of
moments. |
Reduction of Mutual coupling in Microstrip Array Antenna using Polygonal Defected Ground StructureA. Farahbakhsh, G. Moradi, S. Mohanna
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ACES Journal Paper | |
Year: 2011      Volume: 26      Number: 4 | |
Click here to download PDF File Size: 877 KB | |
The surface wave propagation is a
significant problem in microstrip array antennas.
Several methods have been reported to suppress
the propagation of surface wave such as defected
ground structure (DGS). The main problem in
DGS is to determine the shape of ground slot. In
this paper, a new method is proposed in which the
slot is assumed to be a polygon and its shape is
obtained by enhanced genetic algorithm (GA) and
ant colony optimization (ACO) to have an array
antenna with good gain and the least amount of
return loss and mutual coupling. |
Ultra Low RCS Measurement Using Doppler Frequency ShiftE. S. Kashani, Y. Norouzi, A. Tavakoli, P. Dehkhoda
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ACES Journal Paper | |
Year: 2014      Volume: 29      Number: 1 | |
Click here to download PDF File Size: 1618 KB | |
A new clutter removal method is
proposed for ultra-low RCS measurement in
anechoic chamber. In the proposed method, the
target is moved along the line of sight of the radar
in a sinusoidal manner. This movement generates
some Doppler frequency shift. At the receiver, a
filter matched to this Doppler shifter signal is
implemented digitally. While the matched filter
removes clutter signal largely it preserves the
echo from the moving target. As it is shown
through analytic estimation as well as
simulations, the method can attenuate the clutter
and noise level far beyond previously suggested
methods. It also removes some of the difficulties
in higher frequencies that exist in previous
methods.
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A Comparative Study of Opposition-Based Differential Evolution and Meta-Particle Swarm Optimization on Reconstruction of Three Dimensional Conducting ScatterersM. Maddahali, A. Tavakoli, M. Dehmollaian
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ACES Journal Paper | |
Year: 2017      Volume: 32      Number: 9 | |
Click here to download PDF File Size: 1676 KB | |
In this paper, opposition-based differential
evolution and Meta-particle swarm optimization is
applied to reconstruct three dimensional conducting
scatterers. Rational Bezier surfaces are utilized to
model the shape of the scatterers. The mathematical
representation of this surfaces are expanded in terms of
Bernstein polynomials. The unknown coefficients of
these polynomials depend on a few control points in
space. An optimization method is used to find the
location of the control points such that a specific
measure of the difference between radar cross section
(RCS) of the reconstructed and the original target is
minimized. Physical optics (PO) approximation is used
to find the RCS of a reconstructed scatterer in each
iteration of the proposed algorithm. Simulation results
show that these algorithms are very stable in the
presence of noise. |
ACES Journal November 2016 FullACES
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ACES Journal Paper | |
Year: 2016      Volume: 31      Number: 11 | |
Click here to download PDF File Size: 10847 KB | |
ACES |
ACES April 2011 Full JournalACES
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ACES Journal Paper | |
Year: 2011      Volume: 26      Number: 4 | |
Click here to download PDF File Size: 13224 KB |
A Three-Conductor Transmission Line Model for MOS TransistorsF. Daneshmandian, A. Abdipour, R. Mirzavand
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ACES Journal Paper | |
Year: 2015      Volume: 30      Number: 6 | |
Click here to download PDF File Size: 763 KB | |
An accurate high frequency small signal
model for MOS transistors is presented. In the proposed
model, by considering the layout of the MOS transistor,
it is considered as a three-conductor transmission line.
Then, a set of current-voltage equations are derived for
the structure using the transmission line theory. These
coupled equations are solved by the Finite-Difference
Time-Domain (FDTD) technique in a marching-in-time
process. To verify the model, the scattering parameters
of a 0.13 m transistor are extracted from the time
domain results over the 1–100 GHz frequency band and
compared with the results obtained from the available
models and commercial simulator. The suggested
model can be useful in design of various types of high
frequency integrated circuits. |
Analytical Solution of Scattering by a 2D Dielectric Filled Crack in a Ground Plane Coated by a Dielectric Layer: TM CaseB. Ghalamkari, A Tavakoli, M. Dehmollaian
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ACES Journal Paper | |
Year: 2013      Volume: 28      Number: 6 | |
Click here to download PDF File Size: 600 KB | |
In this paper, KP method is applied to
study the scattering of a 2D loaded crack on a
ground plane, coated by a dielectric layer for TM
case. For simplicity, the geometry is divided into
three regions, whose fields are expressed in terms
of Bessel eigen functions. The governing
equations involve several infinite summations with
infinite number of unknown coefficients. By the
use of Weber-Schafheitlin discontinuous integrals,
these infinite summations could efficiently be
truncated with high numerical accuracy. Boundary
conditions are applied to determine unknown
coefficients. We employ finite element method
(FEM) and convergence analysis to confirm our
results. Finally, the influence of coating dielectric
layer and filling material is investigated on the
scattered field. |
Analytical Solution of Scattering by a 2D Dielectric Filled Crack in a Ground Plane Coated by a Dielectric Layer: TE CaseB. Ghalamkari, A. Tavakoli, M. Dehmollaian
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ACES Journal Paper | |
Year: 2012      Volume: 27      Number: 11 | |
Click here to download PDF File Size: 810 KB | |
Analytical solution of scattering by a
2D loaded crack on a ground plane, coated by a
dielectric layer for TE case is studied theoretically
using Kobayashi and Nomura's (Kobayashi
Potential) method. The geometry is divided into
three regions whose fields are expressed in terms
of Bessel eigenfunctions. The problem is reduced
to a system of equations involving truncated
summations with an infinite number of unknowns.
Excitation coefficients are determined by applying
the boundary conditions. By applying Weber-
Schafheitlin discontinuous integrals, the infinite
summations could efficiently be truncated with
high numerical accuracy. For validation, in
addition to convergence analysis, near-field
magnetic current densities on the crack and the
radar cross section (RCS) results are compared
with those of Finite Element Method (FEM).
Having the analytical method, the influence of the
filling and the dielectric layer is investigated. |
Efficient Electromagnetic Scattering Analysis of Open-ended Circular Cavities with Modal MoM MethodA. Aghabarati, P. Dehkhoda, A. Tavakoli
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ACES Journal Paper | |
Year: 2016      Volume: 31      Number: 11 | |
Click here to download PDF File Size: 2341 KB | |
An efficient and accurate technique is introduced to calculate the scattered electromagnetic (EM) fields from an open-ended circular cavity (OECC). In this paper, it is assumed that the OECC is perforated in an infinite perfect electric conductor (IPEC). Then, the scattered fields are calculated using modal Method of Moments. The complexity and computational cost of the encountered quadruple integrals are addressed in detail. Here, the singularities are extracted and resolved. Next, the scattered far field of a circular PEC plate of the same size is calculated by physical optics approximation. The final OECC scattered field is the sum of these two solutions. A very good agreement is observed between the results of this method and full wave numerical simulations and measurements. The proposed approach is highly efficient and accurate over a wide range of frequencies and incidence angles, making it appealing for analysis of large frequency dispersive structures. |
Forward Scattering from a Three Dimensional Layered Media with Rough Interfaces and Buried Object(s) by FDTDS. H. Mirjahanmardi, P. Dehkhoda, A. Tavakoli
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ACES Journal Paper | |
Year: 2017      Volume: 32      Number: 11 | |
Click here to download PDF File Size: 2578 KB | |
In this paper, the finite difference time
domain (FDTD) method is implemented to analyze
the scattered field from a three dimensional structure
including two-layer rough interfaces with or without
buried object(s). The effects of different parameters such
as rough interface correlation length as well as its root
mean square (rms) height, the moisture content of the
soil, also the buried object position and size on the
scattered field are studied. Simulations show that by
increasing the soil moisture, the level of scattering from
the structure (without the buried object) is increased. In
addition, it is shown that the same amount of moisture
change, but in different percentage level, shows
completely different effect on the scattering level.
Furthermore, it is observed that changing the correlation
length in the small perturbation range does not have a
significant effect on the scattering coefficients. Moreover,
images from the buried objects are obtained to show
the visualization of object observation with different
materials in a background. The solution has been validated
by the finite integration based commercial software,
CST. |
Shape Reconstruction of Three Dimensional Conducting Objects Using Opposition-Based Differential EvolutionM. Maddahali, A. Tavakoli, M. Dehmollaian
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ACES Journal Paper | |
Year: 2017      Volume: 32      Number: 1 | |
Click here to download PDF File Size: 1694 KB | |
In this paper, shape reconstruction of three
dimensional conducting objects using radar cross
section (RCS) of the scatterer and opposition-based
differential evolution is investigated. The shape of the
scatterer is modeled with nonuniform rational B-spline
(NURBS) surfaces composed of more than one Bezier
patches. NURBS are piecewise polynomial with
unknown coefficients that are determined in the
procedure of shape reconstruction. Opposition-based
differential evolution (ODE) is then employed as an
optimization tool to find the unknown coefficients.
Physical optics approximation is used to predict RCS of
the large conducting scatterer in various directions and
at multiple frequencies. The effect of noise is also
considered in the inverse process. |
Eccentricity Compensation in Switched Reluctance Machines via Controlling Winding Turns/Stator Current: Theory, Modeling, and Electromagnetic AnalysisE. Afjei, M. R. Tavakoli, H. Torkaman
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ACES Journal Paper | |
Year: 2013      Volume: 28      Number: 2 | |
Click here to download PDF File Size: 970 KB | |
In this paper, a new eccentricity
compensation method for Switched Reluctance
Machines (SRMs) is presented. In this regard, the
dependency of radial force (RF) on variation of
number of turns for stator coils and fault level is
demonstrated analytically and principle of the new
compensation strategy is introduced as well. This
strategy is implemented on an SRM utilizing
Finite Element Method (FEM) under different
fault conditions. This approach is accomplished
through switching among the various
arrangements in the number of turns for the coils
on the stator poles; hence, unbalanced magnetic
force (UMF) is controlled without additional
auxiliary coils. Simultaneously, regulating the
stator currents guarantees the motor torque is not
diminished. This comprehensive approach is
suitable for different types and structures of SRMs
and will compensate or control eccentricities in a
wide range of eccentricity faults namely 10%-70%
while motor performance is not impaired. |
Scattering by a 2D Crack: The Meshfree Collocation ApproachB. Honarbakhsh, A. Tavakoli
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ACES Journal Paper | |
Year: 2012      Volume: 27      Number: 3 | |
Click here to download PDF File Size: 787 KB | |
In this paper, the meshfree collocation
method is applied to the problem of EM scattering
by a 2D crack in a PEC plane. The hybrid PDE-IE
formulation is the mathematical statement of the
problem. Consequently, the geometry and the
filling material of the cavity is arbitrary.
Validations are based on convergence analysis,
modal solution and measurement results.
Furthermore, elliminating numerical integrations
has lead to a fast, accurate, and general meshfree
solution. |
A Closed-Form Spatial Green’s Function for the Thick Microstrip Substrate: The Meshless Interpolation ApproachB. Honarbakhsh, A. Tavakoli
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ACES Journal Paper | |
Year: 2013      Volume: 28      Number: 2 | |
Click here to download PDF File Size: 430 KB | |
n this paper the Green’s functions
(GFs) of a thick microstrip in the spatial-domain is
computed based on expanding the corresponding
spectral-domain functions over inverse quadric
(IQ) radial basis functions (RBFs). The scattered
data interpolation ability of RBFs is exploited for
efficient sampling of the Sommerfeld integration
path (SIP), passing from close vicinity of
singularities in the complex k? plane. By this, the
information content of spectral-domain GFs is
preserved, which makes it possible to compute the
far-fields accurately. Thus, the method can be
applied to the analysis of electrically large
structures near layered media. The proposed
method is direct with only one approximation
level. |
Analysis of Thick Microstrip Antennas by the Meshfree Collocation MethodB. Honarbakhsh, A. Tavakoli
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ACES Journal Paper | |
Year: 2013      Volume: 28      Number: 2 | |
Click here to download PDF File Size: 816 KB | |
A meshless integration free approach is
applied to numerical solution of the mixed
potential integral equation (MPIE) governing
various microstrip resonators/antennas. The idea
behind the discrete complex image method
(DCIM) is exploited to provide closed form
expressions for all of the integrals, leading to an
efficient spectral-domain meshless integral
equation (IE) solver. The proposed meshfree
method (MFM) is compared with low order
method of moments (MoM) from the aspects of
memory usage and simulation time, which shows
superior performance of the MFM. |
Design and Electromagnetic Analysis of a New Rotary-Linear Switched Reluctance Motor in Static ModeM. M. Nezamabadi, E. Afjei, H. Torkaman
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ACES Journal Paper | |
Year: 2016      Volume: 31      Number: 2 | |
Click here to download PDF File Size: 1165 KB | |
A newly designed rotary-linear switched
reluctance (RLSRM) motor is presented and
electromagnetically analyzed in this paper. The motor
has an integrated structure and can control both linear
and rotary motions. It is mainly designed to control the
engagement of a rotating gear. For this purpose a twosection
motor comprised of a rotary and a linear SRM is
designed. In the middle part of the motor assembly, a
three-phase rotary SRM with 6 stator and 4 rotor poles
creates rotary motion. The linear section which is a
transverse flux two-phase SRM is composed of two parts
placing at each side of the rotary section. The cylindrical
translators inside the linear stator poles provide short
magnetic flux paths which reduce the core losses and
increase the force per volume. The motor parameters
derived from the motor design procedure are evaluated
using 3-dimensional finite element analysis (3DFEA).
The motor performance indices such as flux linkages,
flux density, mutual flux, static torque and force for
various loads are obtained and assessed for rotary and
linear motions. Finally, a comparative study is performed
and 3DFEA results are compared with two different
RLSRM structures. The comparison shows that the
proposed structure has the highest force per motor
volume. |
ACES Journal November 2016 Front/Back MatterACES
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ACES Journal Paper | |
Year: 2016      Volume: 31      Number: 11 | |
Click here to download PDF File Size: 97 KB | |
ACES |
Real-Coded Genetic Algorithm with Differential Evolution Operator for Terahertz Quasi-Optical Power Divider/Combiner DesignF. Zhang, K. Song, Y. Fan
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ACES Journal Paper | |
Year: 2017      Volume: 32      Number: 10 | |
Click here to download PDF File Size: 1630 KB | |
This paper describes a modified real-coded
genetic algorithm with a differential evolution operator
(RGA-DE) for a shaped reflector of terahertz (THz)
quasi-optical power divider/combiner. The real-coded
genetic algorithm (RGA) is more convenient to define
the reflector surfaces as compared to other coding
methods. Interpolation method is applied to smooth
the sophisticated surfaces. A better searching ability is
obtained in a small number of individuals by using the
differential evolution operator instead of the conventional
crossover operator. So a bionics algorithm combining
real-coded genetic algorithm and differential evolution
(DE) algorithm has been presented to design the THz
quasi-optical multiple-way holographic power-combining
circuits. The RGA-DE has been utilized to optimize the
coupling coefficient kappa of the field distribution to get
close to 1. Two real-world examples operating at 380 GHz
and 450 GHz respectively are described. The computed
results are verified by using the commercial software
FEKO Suite. |
ACES Journal October 2017 Full | |
ACES Journal Paper | |
Year: 2017      Volume: 32      Number: 10 | |
Click here to download PDF File Size: 12783 KB | |
ACES |
ACES Journal November 2017 Front/Back Matter | |
ACES Journal Paper | |
Year: 2017      Volume: 32      Number: 11 | |
Click here to download PDF File Size: 188 KB | |
ACES |
An Interpolation Scheme for Green’s Function and its Application in Method of MomentY. Xu, H. Yang, X. Liu, R. Shen
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ACES Journal Paper | |
Year: 2018      Volume: 33      Number: 7 | |
Click here to download PDF File Size: 2044 KB | |
An interpolation scheme is put forward to
accelerate the calculation of free space Green’s function.
Through theoretical analysis, a universal rule on how to
build value lists for the phase item of Green’s function
is discussed. And this rule can guarantee accuracy of
the interpolation scheme. Accuracy and efficiency of
the scheme are verified in the calculation of impedance
matrix for method of moment. Besides, this scheme can
also be applied to other applications which contain the
calculation of Green’s functions and is especially useful
for the analysis of large scale problems. Moreover, this
scheme can be combined with other existing improved
approaches of method of moment. |
ACES Journal January 2017 FullACES
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ACES Journal Paper | |
Year: 2017      Volume: 32      Number: 1 | |
Click here to download PDF File Size: 12449 KB | |
ACES |