Abstract: There is a growing interest in the use of ultrasonic speckle tracking for biomedical image formation of tissue deformation. Speckle tracking is angle independent and has an ability to differentiate soft tissue into benign and malignant regions. In this paper a simulation model for dynamic ultrasound scatterer is presented. The model composes Field-II ultrasonic scatterers and FEM (ANSYS-11) nodes as a regional tissue deformation. A performance evaluation is presented on axial displacement and strain fields estimation of a uniformly elastic model, using speckle tracking based 1D cross-correlation of optimally segmented pre and post-deformation frames. Optimum correlation window length is investigated in terms of highest signal-to-noise ratio (SNR) for a selected region of interest of a smoothed displacement field. Finally, gradient based strain field of both smoothed and non-smoothed displacement fields are compared. Simulation results from the model are shown to compare favorably with FEM results.
Abstract: The curvature space-time by the presence of material, this deformation must present a pattern of deformation, not random. Space is uniform, elastic and any modification that occurs in one part, causes a change in another.
This deformation exists, must be a constant value and is independent of the observer, and relates the amount of matter, the force caused by the curvature of space and surface space. This unit of space is defined in this study as PIL and represents a constant area of space, deformable in the direction and sense of the center of mass of the body. The PIL is curved and connected to the center of mass of the Earth, to get to that point, through all matter, thus forming part of any place between particles at atomic and subatomic levels. At these levels the space between each particle is flat, unlike the macro where the space curves.
Abstract: In the present study, the problem of geometrically nonlinear free vibrations of functionally graded circular plates (FGCP) resting on Pasternak elastic foundation with immovable ends was studied. The material properties of the functionally graded composites examined were assumed to be graded in the thickness direction and estimated through the rule of mixture. The theoretical model is based on the classical Plate theory and the Von Kármán geometrical nonlinearity assumptions. Hamilton’s principle is applied and a multimode approach is derived to calculate the fundamental nonlinear frequency parameters, which are found to be in a good agreement with the published results dealing with the problem of functionally graded plates. On the other hand, the influence of the foundation parameters on the nonlinear frequency to the linear frequency ratio of the FGCP has been studied. The effect of the linear and shearing foundations is to decrease the frequency ratio, where it increases with the effect of the nonlinear foundation stiffness.
Abstract: According to synthetic plastics obtained from petroleum cause some environmental problems. Therefore, degradable plastics become widely used and studied for replacing the synthetic plastic waste. A biopolymer of poly hydroxybutyrate-co-hydroxyvalerate (PHBV) is subgroups of a main kind of polyhydroxyalkanoates (PHAs). Naturally, PHBV is hard, brittle and low flexible while natural rubber (NR) is high elastic latex. Then, they are blended and the biodegradation of the blended PHBV and NR films were examined in soil environment. The results showed that the degradation occurs predominantly in the bulk of the samples. The order of biodegradability was shown as follows: PHBV> PHBV/NR> NR. After biodegradation, the blended films were characterized by appearance analysis such as Scanning Electron Microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). It was found that the biodegradation mainly occurred at the polymer surface.
Abstract: In this study, artificial limestone brick samples are produced by using wood sawdust wastes (WSW) having different grades of sizes and limestone powder waste (LPW). The thermo-elastic properties of produced brick samples in various WSW amounts are investigated. At 30% WSW replacement with LPW in the brick sample the thermal conductivity value is effectively reduced and the reduction in the thermal conductivity value of brick sample at 30% WSW replacement with LPW is about 38.9% as compared with control sample. The energy conservation in buildings by using LPW and WSW in masonry brick material production having low thermal conductivity reduces energy requirements. A strong relationship is also found among the thermal conductivity, unit weight and ultrasonic pulse velocity values of brick samples produced. It shows a potential to be used for walls, wooden board substitute, alternative to the concrete blocks, ceiling panels, sound barrier panels, absorption materials etc.
Abstract: It can be determined in preference between
representative mechanical and mathematical model of elasticcreeping
deformation of transversally isotropic array with doubly
periodic system of tilted slots, and offer of the finite elements
calculation scheme, and inspection of the states of two diagonal
arbitrary profile cavities of deep inception, and in setting up the tense
and dislocation fields distribution nature in computing processes.
Abstract: This paper presents a new compact analytical model of
the gate leakage current in high-k based nano scale MOSFET by
assuming a two-step inelastic trap-assisted tunneling (ITAT) process
as the conduction mechanism. This model is based on an inelastic
trap-assisted tunneling (ITAT) mechanism combined with a semiempirical
gate leakage current formulation in the BSIM 4 model. The
gate tunneling currents have been calculated as a function of gate
voltage for different gate dielectrics structures such as HfO2, Al2O3
and Si3N4 with EOT (equivalent oxide thickness) of 1.0 nm. The
proposed model is compared and contrasted with santaurus
simulation results to verify the accuracy of the model and excellent
agreement is found between the analytical and simulated data. It is
observed that proposed analytical model is suitable for different highk
gate dielectrics simply by adjusting two fitting parameters. It was
also shown that gate leakages reduced with the introduction of high-k
gate dielectric in place of SiO2.
Abstract: We propose a phenomenological model for the
process of polymer desorption. In so doing, we omit the usual
theoretical approach of incorporating a fictitious viscoelastic
stress term into the flux equation. As a result, we obtain a
model that captures the essence of the phenomenon of trapping
skinning, while preserving the integrity of the experimentally
verified Fickian law for diffusion. An appropriate asymptotic
analysis is carried out, and a parameter is introduced to represent
the speed of the desorption front. Numerical simulations are
performed to illustrate the desorption dynamics of the model.
Recommendations are made for future modifications of the
model, and provisions are made for the inclusion of experimentally
determined frontal speeds.
Abstract: Superelastic Shape Memory Alloy (SMA) is accepted
when it used as connection in steel structures. The seismic behaviour
of steel frames with SMA is being assessed in this study. Three eightstorey
steel frames with different SMA systems are suggested, the
first one of which is braced with diagonal bracing system, the second
one is braced with nee bracing system while the last one is which the
SMA is used as connection at the plastic hinge regions of beams.
Nonlinear time history analyses of steel frames with SMA subjected
to two different ground motion records have been performed using
Seismostruct software. To evaluate the efficiency of suggested
systems, the dynamic responses of the frames were compared. From
the comparison results, it can be concluded that using SMA element
is an effective way to improve the dynamic response of structures
subjected to earthquake excitations. Implementing the SMA braces
can lead to a reduction in residual roof displacement. The shape
memory alloy is effective in reducing the maximum displacement at
the frame top and it provides a large elastic deformation range. SMA
connections are very effective in dissipating energy and reducing the
total input energy of the whole frame under severe seismic ground
motion. Using of the SMA connection system is more effective in
controlling the reaction forces at the base frame than other bracing
systems. Using SMA as bracing is more effective in reducing the
displacements. The efficiency of SMA is dependant on the input
wave motions and the construction system as well.
Abstract: The aim of this research was to calculate the
mechanical properties of Pd3Rh and PdRh3 ordered alloys. The
molecular dynamics (MD) simulation technique was used to obtain
temperature dependence of the energy, the Yong modulus, the shear
modulus, the bulk modulus, Poisson-s ratio and the elastic stiffness
constants at the isobaric-isothermal (NPT) ensemble in the range of
100-325 K. The interatomic potential energy and force on atoms were
calculated by Quantum Sutton-Chen (Q-SC) many body potential.
Our MD simulation results show the effect of temperature on the
cohesive energy and mechanical properties of Pd3Rh as well as
PdRh3 alloys. Our computed results show good agreement with the
experimental results where they have been available.
Abstract: The orthogonal processes to shape the triangle steel plate into a equilateral vertical steel are examined by an incremental elasto-plastic finite-element method based on an updated Lagrangian formulation. The highly non-linear problems due to the geometric changes, the inelastic constitutive behavior and the boundary conditions varied with deformation are taken into account in an incremental manner. On the contact boundary, a modified Coulomb friction mode is specially considered. A weighting factor r-minimum is employed to limit the step size of loading increment to linear relation. In particular, selective reduced integration was adopted to formulate the stiffness matrix. The simulated geometries of verticality could clearly demonstrate the vertical processes until unloading. A series of experiments and simulations were performed to validate the formulation in the theory, leading to the development of the computer codes. The whole deformation history and the distribution of stress, strain and thickness during the forming process were obtained by carefully considering the moving boundary condition in the finite-element method. Therefore, this modeling can be used for judging whether a equilateral vertical steel can be shaped successfully. The present work may be expected to improve the understanding of the formation of the equilateral vertical steel.
Abstract: Contact stress is an important problem in industry.
This is a problem that in the first attention may be don-t appears, but
disregard of these stresses cause a lot of damages in machines. These
stresses occur at locations such as gear teeth, bearings, cams and
between a locomotive wheel and the railroad rail. These stresses
cause failure by excessive elastic deformation, yielding and fracture.
In this paper we intend show the effective parameters in contact
stress and ponder effect of curvature. In this paper we study contact
stresses on the surface of gear teeth and compare these stresses for
four popular profiles of gear teeth (involute, cycloid, epicycloids, and
hypocycloid). We study this problem with mathematical and finite
element methods and compare these two methods on different profile
surfaces.
Abstract: The problem of N cracks interaction in an isotropic
elastic solid is decomposed into a subproblem of a homogeneous solid
without crack and N subproblems with each having a single crack
subjected to unknown tractions on the two crack faces. The unknown
tractions, namely pseudo tractions on each crack are expanded into
polynomials with unknown coefficients, which have to be determined
by the consistency condition, i.e. by the equivalence of the original
multiple cracks interaction problem and the superposition of the N+1
subproblems. In this paper, Kachanov-s approach of average tractions
is extended into the method of moments to approximately impose the
consistence condition. Hence Kachanov-s method can be viewed as
the zero-order method of moments. Numerical results of the stress
intensity factors are presented for interactions of two collinear cracks,
three collinear cracks, two parallel cracks, and three parallel cracks.
As the order of moment increases, the accuracy of the method of
moments improves.
Abstract: Behavior of dams against the seismic loads has been
studied by many researchers. Most of them proposed new numerical
methods to investigate the dam safety. In this paper, to study the
effect of nonlinear parameters of concrete in gravity dams, a twodimensional
approach was used including the finite element method,
staggered method and smeared crack approach. Effective parameters
in the models are physical properties of concrete such as modulus of
elasticity, tensile strength and specific fracture energy. Two different
models were used in foundation (mass-less and massed) in order to
determine the seismic response of concrete gravity dams. Results
show that when the nonlinear analysis includes the dam- foundation
interaction, the foundation-s mass, flexibility and radiation damping
are important in gravity dam-s response.
Abstract: A novel biomass composite inspired from wood porous
structure was manufactured by impregnating vinyl monomer into
wood cellular structure under vacuum conditions, and initiating the
monomer for in situ polymerization through a thermal treatment. The
vacuum condition was studied, and the mechanical properties of the
composite were also tested. SEM observation shows that polymer
generated in the wood porous structure, and strongly interacted with
wood matrix; and the polymer content increased with vacuum value
increasing. FTIR indicates that polymer grafted onto wood matrix,
resulting chemical complex between them. The rate of monomer
loading increased with increasing vacuum value and time, accordance
with rate of polymer loading. The compression strength and modulus
of elasticity linearly increased with the increasing rate of polymer
loading. Results indicate that the novel biomass composite possesses
good mechanical properties capable of applying in the fields of
construction, traffic and so forth.
Abstract: According to Rostler method (ASTM D 2006), saturates content of bitumen is determined based on its reactivity to sulphuric acid. While Corbett method (ASTM D 4124) based on its polarity level. This paper presents results from the study on the effect of saturates content determined by two different fractionation methods on the rheological and aging characteristics of bitumen. The result indicated that the increment of saturates content tended to reduce all the rheological characteristics concerned. Bitumen became less elastic, less viscous, and less resistant to plastic deformation, but became more resistant to fatigue cracking. After short and long term aging process, the treatment effect coefficients of saturates decreased, saturates became thicker due to aging process. This study concludes that saturates is not really stable or reactive in aging process. Therefore, the reactivity of saturates should be considered in bitumen aging index
Abstract: Magnesium wastes are produced by many industrial activities. This waste problem is becoming a future problem for the world. Magnesium borates have many advantages such as; high corrosion resistance, heat resistance, high coefficient of elasticity and can also be used in the production of material against radiation. Addition, magnesium borates have great potential in sectors
including ceramic and detergents industry and superconducting materials.
In this study, using the starting materials of waste magnesium and H3BO3 the hydrothermal method was applied at a moderate
temperature of 70oC. Several mole ratios of waste magnesium to H3BO3 are selected as; 1:2, 1:4, 1:6, 1:8, 1:10. Reaction time was determined as 1 hour. After the synthesis, X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques are applied to products. As a result the forms of mcallisterite “Mg2(B6O7(OH)6)2.9(H2O)”, admontite “MgO(B2O3)3.7(H2O)” and magnesium boron hydrate (MgO(B2O3)3.6(H2O)” are obtained.
Abstract: In this study, an analysis has been performed for
conjugate heat and mass transfer of a steady laminar boundary-layer
mixed convection of magnetic hydrodynamic (MHD) flow with
radiation effect of second grade subject to suction past a stretching
sheet. Parameters E Nr, Gr, Gc, Ec and Sc represent the dominance of
the viscoelastic fluid heat and mass transfer effect which have
presented in governing equations, respectively. The similar
transformation and the finite-difference method have been used to
analyze the present problem. The conjugate heat and mass transfer
results show that the non-Newtonian viscoelastic fluid has a better heat
transfer effect than the Newtonian fluid. The free convection with a
larger r G or c G has a good heat transfer effect better than a smaller
r G or c G , and the radiative convection has a good heat transfer
effect better than non-radiative convection.
Abstract: This paper describes the use of artificial neural
networks (ANN) for predicting non-linear layer moduli of flexible
airfield pavements subjected to new generation aircraft (NGA)
loading, based on the deflection profiles obtained from Heavy
Weight Deflectometer (HWD) test data. The HWD test is one of the
most widely used tests for routinely assessing the structural integrity
of airport pavements in a non-destructive manner. The elastic moduli
of the individual pavement layers backcalculated from the HWD
deflection profiles are effective indicators of layer condition and are
used for estimating the pavement remaining life. HWD tests were
periodically conducted at the Federal Aviation Administration-s
(FAA-s) National Airport Pavement Test Facility (NAPTF) to
monitor the effect of Boeing 777 (B777) and Beoing 747 (B747) test
gear trafficking on the structural condition of flexible pavement
sections. In this study, a multi-layer, feed-forward network which
uses an error-backpropagation algorithm was trained to approximate
the HWD backcalculation function. The synthetic database generated
using an advanced non-linear pavement finite-element program was
used to train the ANN to overcome the limitations associated with
conventional pavement moduli backcalculation. The changes in
ANN-based backcalculated pavement moduli with trafficking were
used to compare the relative severity effects of the aircraft landing
gears on the NAPTF test pavements.
Abstract: Excessive ductility demand on shorter piers is a
common problem for irregular bridges subjected to strong ground
motion. Various techniques have been developed to reduce the
likelihood of collapse of bridge due to failure of shorter piers. This
paper presents the new approach to improve the seismic behavior of
such bridges using Nitinol shape memory alloys (SMAs).
Superelastic SMAs have the ability to remain elastic under very large
deformation due to martensitic transformation. This unique property
leads to enhanced performance of controlled bridge compared with
the performance of the reference bridge. To evaluate the effectiveness
of the devices, nonlinear time history analysis is performed on a RC
single column bent highway bridge using a suite of representative
ground motions. The results show that this method is very effective in
limiting the ductility demand of shorter pier.