Abstract: In this paper, according to the classical algorithm
LSQR for solving the least-squares problem, an iterative method is
proposed for least-squares solution of constrained matrix equation. By
using the Kronecker product, the matrix-form LSQR is presented to
obtain the like-minimum norm and minimum norm solutions in a
constrained matrix set for the symmetric arrowhead matrices. Finally,
numerical examples are also given to investigate the performance.
Abstract: Prior literature in the field of adaptive and
personalized learning sequence in e-learning have proposed and
implemented various mechanisms to improve the learning process
such as individualization and personalization, but complex to
implement due to expensive algorithmic programming and need of
extensive and prior data. The main objective of personalizing
learning sequence is to maximize learning by dynamically selecting
the closest teaching operation in order to achieve the learning
competency of learner. In this paper, a revolutionary technique has
been proposed and tested to perform individualization and
personalization using modified reversed roulette wheel selection
algorithm that runs at O(n). The technique is simpler to implement
and is algorithmically less expensive compared to other revolutionary
algorithms since it collects the dynamic real time performance matrix
such as examinations, reviews, and study to form the RWSA single
numerical fitness value. Results show that the implemented system is
capable of recommending new learning sequences that lessens time
of study based on student's prior knowledge and real performance
matrix.
Abstract: Geopolymer composites reinforced with flax fabrics
and nanoclay are fabricated and studied for physical and mechanical
properties using X-Ray Diffraction (XRD), Fourier Transform
Infrared Spectroscopy (FTIR), and Scanning Electron Microscope
(SEM). Nanoclay platelets at a weight of 1.0%, 2.0%, and 3.0% were
added to geopolymer pastes. Nanoclay at 2.0 wt.% was found to
improve density and decrease porosity while improving flexural
strength and post-peak toughness. A microstructural analysis
indicated that nanoclay behaves as filler and as an activator
supporting geopolymeric reaction while producing a higher content
geopolymer gel improving the microstructure of binders. The process
enhances adhesion between the geopolymer matrix and flax fibres.
Abstract: In this paper, for an arbitrary multiplicative functional
f from the set of all upper triangular fuzzy matrices to the fuzzy
algebra, we prove that there exist a multiplicative functional F and a
functional G from the fuzzy algebra to the fuzzy algebra such that the
image of an upper triangular fuzzy matrix under f can be represented
as the product of all the images of its main diagonal elements under
F and other elements under G.
Abstract: In this paper, we propose the variational EM inference
algorithm for the multi-class Gaussian process classification model
that can be used in the field of human behavior recognition. This
algorithm can drive simultaneously both a posterior distribution of a
latent function and estimators of hyper-parameters in a Gaussian
process classification model with multiclass. Our algorithm is based
on the Laplace approximation (LA) technique and variational EM
framework. This is performed in two steps: called expectation and
maximization steps. First, in the expectation step, using the Bayesian
formula and LA technique, we derive approximately the posterior
distribution of the latent function indicating the possibility that each
observation belongs to a certain class in the Gaussian process
classification model. Second, in the maximization step, using a derived
posterior distribution of latent function, we compute the maximum
likelihood estimator for hyper-parameters of a covariance matrix
necessary to define prior distribution for latent function. These two
steps iteratively repeat until a convergence condition satisfies.
Moreover, we apply the proposed algorithm with human action
classification problem using a public database, namely, the KTH
human action data set. Experimental results reveal that the proposed
algorithm shows good performance on this data set.
Abstract: In this article was evaluated the protective effect of
the alternative concrete obtained from the binary mixture of fly ash,
and iron and steel slag. After mixing the cement with aggregates,
structural steel was inserted in the matrix cementitious. The study
was conducted comparatively with specimens exposed to natural
conditions free of chloride ion. The chloride ion effect on the
specimens accelerated under controlled conditions (3.5% NaCl and
25°C temperature). The impedance data were acquired in a range of 1
mHz to 100 kHz.
Abstract: The laser-ultrasonic method is realized for
quantifying the influence of porosity on the local Young’s
modulus of isotropic composite materials. The method is based on
a laser thermooptical method of ultrasound generation combined
with measurement of the phase velocity of longitudinal and shear
acoustic waves in samples. The main advantage of this method
compared with traditional ultrasonic research methods is the
efficient generation of short and powerful probing acoustic pulses
required for reliable testing of ultrasound absorbing and
scattering heterogeneous materials. Using as an example samples
of a metal matrix composite with reinforcing microparticles of
silicon carbide in various concentrations, it is shown that to
provide an effective increase in Young’s modulus with increasing
concentration of microparticles, the porosity of the final sample
should not exceed 2%.
Abstract: Polycyclic Aromatic Hydrocarbons (PAHs) are
formed mainly because of incomplete combustion of organic
materials during industrial, domestic activities or natural occurrence.
Their toxicity and contamination of terrestrial and aquatic ecosystem
have been established. However, with limited validity index, previous
research has focused on PAHs isomer pair ratios of variable
physicochemical properties in source identification. The objective of
this investigation was to determine the empirical validity of Pearson
Correlation Coefficient (PCC) and Cluster Analysis (CA) in PAHs
source identification along soil samples of different land uses.
Therefore, 16 PAHs grouped, as Endocrine Disruption Substances
(EDSs) were determined in 10 sample stations in top and sub soils
seasonally. PAHs was determined the use of Varian 300 gas
chromatograph interfaced with flame ionization detector. Instruments
and reagents used are of standard and chromatographic grades
respectively. PCC and CA results showed that the classification of
PAHs along pyrolitic and petrogenic organics used in source
signature is about the predominance PAHs in environmental matrix.
Therefore, the distribution of PAHs in the studied stations revealed
the presence of trace quantities of the vast majority of the sixteen
PAHs, which may ultimately inhabit the actual source signature
authentication. Therefore, factors to be considered when evaluating
possible sources of PAHs could be; type and extent of bacterial
metabolism, transformation products/substrates, and environmental
factors such as salinity, pH, oxygen concentration, nutrients, light
intensity, temperature, co-substrates, and environmental medium are
hereby recommended as factors to be considered when evaluating
possible sources of PAHs.
Abstract: In present study, a large deposit of oolitic iron ore of
Late Carboniferous-Permotriassic-Lower Jurassic age was discovered
in Wadi Halfa and Argein areas, North Sudan. It seems that the iron
ore mineralization exists in the west and east bank of the River Nile
of the study area that are found on the Egyptian-Sudanese border.
The Carboniferous-Lower Jurassic age strata were covered by 67
sections and each section has been examined and carefully described.
The iron-ore in Wadi Halfa occurs as oolitic ironstone and contained
two horizons: (A) horizon and (B) horizon. Only horizon (A) was
observed in southern Argein area. The texture of the ore is variable
depending on the volume of the component. In thin sections, the
average of the ooids was ranged between 90%-80%. The matrix
varies between 10%-20% by volume and detritus quartz in other
component my reach up to 30% by volume in sandy massive ore.
Ooids size ranges from 0.2mm-1.00 mm on average in very coarse
ooids may attend up to 1 mm in size. The matrix around the ooids is
dominated by iron hydroxide, carbonate, fine, and amorphous silica.
The probable ore reserve estimate of 1.234 billion at a head grade of
41.29% Fe for the Wadi Halfa Oolitic Ironstone Formation. The iron
ore shows higher content of phosphorus ranges from 6.15% to 0.16%,
with mean 1.45%. The new technology Hatch–Ironstone Chloride
Segregation (HICS) can be used to produce commercial-quality of
iron and reduce phosphorus and silica to acceptable levels for steel
industry. The presence of infrastructures in addition to the presence
of massive quantities of iron ore would make exploitation
economically.
Abstract: To study the dynamic mechanics response of asphalt
pavement under the temperature load and vehicle loading, asphalt
pavement was regarded as multilayered elastic half-space system, and
theory analysis was conducted by regarding dynamic modulus of
asphalt mixture as the parameter. Firstly, based on the dynamic
modulus test of asphalt mixture, function relationship between the
dynamic modulus of representative asphalt mixture and temperature
was obtained. In addition, the analytical solution for thermal stress in
single layer was derived by using Laplace integral transformation and
Hankel integral transformation respectively by using thermal
equations of equilibrium. The analytical solution of calculation model
of thermal stress in asphalt pavement was derived by transfer matrix
of thermal stress in multilayer elastic system. Finally, the variation of
thermal stress in pavement structure was analyzed. The result shows
that there is obvious difference between the thermal stress based on
dynamic modulus and the solution based on static modulus. So the
dynamic change of parameter in asphalt mixture should be taken into
consideration when theoretical analysis is taken out.
Abstract: Polylactic acid (PLA) is the most commercially
available bio-based and biodegradable plastic at present. PLA has
been used in plastic related industries including single-used
containers, disposable and environmentally friendly packaging owing
to its renewability, compostability, biodegradability, and safety.
Although PLA demonstrates reasonably good optical, physical,
mechanical and barrier properties comparable to the existing
petroleum-based plastics, its brittleness and mold shrinkage as well as
its price are the points to be concerned for the production of rigid and
semi-rigid packaging. Blending PLA with other bio-based polymers
including thermoplastic starch (TPS) is an alternative not only to
achieve a complete bio-based plastic, but also to reduce the
brittleness, shrinkage during molding and production cost of the
PLA-based products. TPS is a material produced mainly from starch
which is cheap, renewable, biodegradable, compostable, and nontoxic.
It is commonly prepared by a plasticization of starch under
applying heat and shear force. Although glycerol has been reported as
one of the most plasticizers used for preparing TPS, its migration
caused the surface stickiness of the TPS products. In some cases,
mixed plasticizers or natural fibers have been applied to impede the
retrogradation of starch or reduce the migration of glycerol. The
introduction of fibers into TPS-based materials could reinforce the
polymer matrix as well. Therefore, the objective of the present
research is to study the effect of starch type (i.e. native starch and
phosphate starch), plasticizer type (i.e. glycerol and xylitol with a
weight ratio of glycerol to xylitol of 100:0, 75:25, 50:50, 25:75 and
0:100) and fiber content (i.e. in the range of 1-25 %wt) on properties
of PLA/TPS blend and composite. PLA/TPS blends and composites
were prepared using a twin-screw extruder and then converted into
dumbbell-shaped specimens using an injection molding machine. The
PLA/TPS blends prepared by using phosphate starch showed higher
tensile strength and stiffness than the blends prepared by using native
one. In contrast, the blends from native starch exhibited higher
extensibility and heat distortion temperature (HDT) than those from
the modified starch. Increasing xylitol content resulted in enhanced
tensile strength, stiffness and water resistance, but decreased
extensibility and HDT of the PLA/TPS blend. Tensile properties and
hydrophobicity of the blend could be improved by incorporating
silane treated-jute fibers.
Abstract: Carbon Fiber Reinforced Plastics (CFRPs) are widely
used for advanced applications, in particular in aerospace, automotive
and wind energy industries. Once cured to near net shape, CFRP
parts need several finishing operations such as trimming, milling or
drilling in order to accommodate fastening hardware and meeting the
final dimensions. The present research aims to study the effect of the
cutting temperature in trimming on the mechanical strength of high
performance CFRP laminates used for aeronautics applications. The
cutting temperature is of great importance when dealing with
trimming of CFRP. Temperatures higher than the glass-transition
temperature (Tg) of the resin matrix are highly undesirable: they
cause degradation of the matrix in the trimmed edges area, which can
severely affect the mechanical performance of the entire component.
In this study, a 9.50mm diameter CVD diamond coated carbide tool
with six flutes was used to trim 24-plies CFRP laminates. A
300m/min cutting speed and 1140mm/min feed rate were used in the
experiments. The tool was heated prior to trimming using a
blowtorch, for temperatures ranging from 20°C to 300°C. The
temperature at the cutting edge was measured using embedded KType
thermocouples. Samples trimmed for different cutting
temperatures, below and above Tg, were mechanically tested using
three-points bending short-beam loading configurations. New cutting
tools as well as worn cutting tools were utilized for the experiments.
The experiments with the new tools could not prove any correlation
between the length of cut, the cutting temperature and the mechanical
performance. Thus mechanical strength was constant, regardless of
the cutting temperature. However, for worn tools, producing a cutting
temperature rising up to 450°C, thermal damage of the resin was
observed. The mechanical tests showed a reduced mean resistance in
short beam configuration, while the resistance in three point bending
decreases with increase of the cutting temperature.
Abstract: In this study, we examine some spectral properties
of non-selfadjoint matrix-valued difference equations consisting of
a polynomial-type Jost solution. The aim of this study is to
investigate the eigenvalues and spectral singularities of the difference
operator L which is expressed by the above-mentioned difference
equation. Firstly, thanks to the representation of polynomial type Jost
solution of this equation, we obtain asymptotics and some analytical
properties. Then, using the uniqueness theorems of analytic functions,
we guarantee that the operator L has a finite number of eigenvalues
and spectral singularities.
Abstract: In the present study we have investigated axial
buckling characteristics of nanocomposite beams reinforced by
single-walled carbon nanotubes (SWCNTs). Various types of beam
theories including Euler-Bernoulli beam theory, Timoshenko beam
theory and Reddy beam theory were used to analyze the buckling
behavior of carbon nanotube-reinforced composite beams.
Generalized differential quadrature (GDQ) method was utilized to
discretize the governing differential equations along with four
commonly used boundary conditions. The material properties of the
nanocomposite beams were obtained using molecular dynamic (MD)
simulation corresponding to both short-(10,10) SWCNT and long-
(10,10) SWCNT composites which were embedded by amorphous
polyethylene matrix. Then the results obtained directly from MD
simulations were matched with those calculated by the mixture rule
to extract appropriate values of carbon nanotube efficiency
parameters accounting for the scale-dependent material properties.
The selected numerical results were presented to indicate the
influences of nanotube volume fractions and end supports on the
critical axial buckling loads of nanocomposite beams relevant to
long- and short-nanotube composites.
Abstract: This paper studies a mathematical model based on the
integral equations for dynamic analyzes numerical investigations of a
non-uniform or multi-material composite beam. The beam is
subjected to a sub-tangential follower force and elastic foundation.
The boundary conditions are represented by generalized
parameterized fixations by the linear and rotary springs. A
mathematical formula based on Euler-Bernoulli beam theory is
presented for beams with variable cross-sections. The non-uniform
section introduces non-uniformity in the rigidity and inertia of beams
and consequently, more complicated equilibrium who governs the
equation. Using the boundary element method and radial basis
functions, the equation of motion is reduced to an algebro-differential
system related to internal and boundary unknowns. A generalized
formula for the deflection, the slope, the moment and the shear force
are presented. The free vibration of non-uniform loaded beams is
formulated in a compact matrix form and all needed matrices are
explicitly given. The dynamic stability analysis of slender beam is
illustrated numerically based on the coalescence criterion. A realistic
case related to an industrial chimney is investigated.
Abstract: Carbon nanotubes (CNTs) are known for having high elastic properties with high surface area that promote them as good candidates for reinforcing polymeric matrices. In composite materials, CNTs lack chemical bonding with the surrounding matrix which decreases the possibility of better stress transfer between the components. In this work, a chemical treatment for activating the surface of the multi-wall carbon nanotubes (MWCNT) was applied and the effect of this functionalization on the elastic properties of the epoxy nanocomposites was studied. Functional amino-groups were added to the surface of the CNTs and it was evaluated to be about 34% of the total weight of the CNTs. Elastic modulus was found to increase by about 40% of the neat epoxy resin at CNTs’ weight fraction of 0.5%. The elastic modulus was found to decrease after reaching a certain concentration of CNTs which was found to be 1% wt. The scanning electron microscopic pictures showed the effect of the CNTs on the crack propagation through the sample by forming stress concentrated spots at the nanocomposite samples.
Abstract: The McEliece cryptosystem is an asymmetric type of
cryptography based on error correction code. The classical McEliece
used irreducible binary Goppa code which considered unbreakable
until now especially with parameter [1024, 524, and 101], but it is
suffering from large public key matrix which leads to be difficult to
be used practically. In this work Irreducible and Separable Goppa
codes have been introduced. The Irreducible and Separable Goppa
codes used are with flexible parameters and dynamic error vectors. A
Comparison between Separable and Irreducible Goppa code in
McEliece Cryptosystem has been done. For encryption stage, to get
better result for comparison, two types of testing have been chosen;
in the first one the random message is constant while the parameters
of Goppa code have been changed. But for the second test, the
parameters of Goppa code are constant (m=8 and t=10) while the
random message have been changed. The results show that the time
needed to calculate parity check matrix in separable are higher than
the one for irreducible McEliece cryptosystem, which is considered
expected results due to calculate extra parity check matrix in
decryption process for g2(z) in separable type, and the time needed to
execute error locator in decryption stage in separable type is better
than the time needed to calculate it in irreducible type. The proposed
implementation has been done by Visual studio C#.
Abstract: The shielding ability of a shielding cavity with an
aperture will be greatly degraded at resonance frequencies, and the
resonance modes and frequencies are affected by aperture resonances
and aperture-cavity coupling, which are closely related with aperture
sizes. The equivalent circuit method and numerical method of
Transmission Line Matrix (TLM) are used to analyze the effects of
aperture resonances and aperture-cavity coupling on the
electromagnetic resonances of a cavity with an aperture in this paper.
Both analytical and numerical results show that the resonance modes
of a shielding cavity with an aperture consist of cavity resonance
modes and aperture resonance modes, and the resonance frequencies
will shift with the change of the aperture sizes because of the aperture
resonances and aperture-cavity coupling. Variation rules of
electromagnetic resonances with aperture sizes for a cavity with an
aperture are given, which will be useful for design of shielding
cavities.
Abstract: This paper reports the viability of developing Zn-27Al
alloy matrix hybrid composites reinforced with alumina, graphite and
fly ash (solid waste bye product of coal in thermal power plants).
This research work was aimed at developing low cost-high
performance Zn-27Al matrix composite with low density. Alumina
particulates (Al2O3), graphite added with 0, 2, 3, 4 and 5 wt% fly ash
were utilized to prepare 10wt% reinforcing phase with Zn-27Al alloy
as matrix using two-step stir casting method. Density measurement,
estimated percentage porosity, tensile testing, micro hardness
measurement and optical microscopy were used to assess the
performance of the composites produced. The results show that the
hardness, ultimate tensile strength, and percent elongation of the
hybrid composites decrease with increase in fly ash content. The
maximum decrease in hardness and ultimate tensile strength of
13.72% and 15.25% respectively were observed for composite grade
containing 5wt% fly ash. The percentage elongation of composite
sample without fly ash is 8.9% which is comparable with that of the
sample containing 2wt% fly ash with percentage elongation of 8.8%.
The fracture toughness of the fly ash containing composites was
however superior to those of composites without fly ash with 5wt%
fly ash containing composite exhibiting the highest fracture
toughness. The results show that fly ash can be utilized as
complementary reinforcement in ZA-27 alloy matrix composite to
reduce cost.
Abstract: Structural failure is caused mainly by damage that
often occurs on structures. Many researchers focus on to obtain very
efficient tools to detect the damage in structures in the early state. In
the past decades, a subject that has received considerable attention in
literature is the damage detection as determined by variations in the
dynamic characteristics or response of structures. The study presents
a new damage identification technique. The technique detects the
damage location for the incomplete structure system using output
data only. The method indicates the damage based on the free
vibration test data by using ‘Two Points Condensation (TPC)
technique’. This method creates a set of matrices by reducing the
structural system to two degrees of freedom systems. The current
stiffness matrices obtain from optimization the equation of motion
using the measured test data. The current stiffness matrices compare
with original (undamaged) stiffness matrices. The large percentage
changes in matrices’ coefficients lead to the location of the damage. TPC technique is applied to the experimental data of a simply
supported steel beam model structure after inducing thickness change
in one element, where two cases consider. The method detects the
damage and determines its location accurately in both cases. In
addition, the results illustrate these changes in stiffness matrix can be
a useful tool for continuous monitoring of structural safety using
ambient vibration data. Furthermore, its efficiency proves that this
technique can be used also for big structures.