Abstract: The demand of high quality services has fueled
dimensional research and development in wireless communications
and networking. As a result, different wireless technologies like
Wireless LAN, CDMA, GSM, UMTS, MANET, Bluetooth and
satellite networks etc. have emerged in the last two decades. Future
networks capable of carrying multimedia traffic need IP convergence,
portability, seamless roaming and scalability among the existing
networking technologies without changing the core part of the
existing communications networks. To fulfill these goals, the present
networking systems are required to work in cooperation to ensure
technological independence, seamless roaming, high security and
authentication, guaranteed Quality of Services (QoS). In this paper, a
conceptual framework for a cooperative network (CN) is proposed
for integration of heterogeneous existing networks to meet out the
requirements of the next generation wireless networks.
Abstract: Carbon nanotube is one of the most attractive materials
for the potential applications of nanotechnology due to its excellent
mechanical, thermal, electrical and optical properties. In this paper we
report a supercapacitor made of nickel foil electrodes, coated with
multiwall carbon nanotubes (MWCNTs) thin film using
electrophoretic deposition (EPD) method. Chemical vapor deposition
method was used for the growth of MWCNTs and ethanol was used as
a hydrocarbon source. High graphitic multiwall carbon nanotube was
found at 750oC analyzing by Raman spectroscopy. We observed the
electrochemical performance of supercapacitor by cyclic
voltammetry. The electrodes of supercapacitor fabricated from
MWCNTs exhibit considerably small equivalent series resistance
(ESR), and a high specific power density. Electrophoretic deposition
is an easy method in fabricating MWCNT electrodes for high
performance supercapacitor.
Abstract: Brown seaweeds are abundant in Portuguese coastline
and represent an almost unexploited marine economic resource. One
of the most common species, easily available for harvesting in the
northwest coast, is Saccorhiza polyschides grows in the lowest shore
and costal rocky reefs. It is almost exclusively used by local farmers
as natural fertilizer, but contains a substantial amount of valuable
compounds, particularly alginates, natural biopolymers of high
interest for many industrial applications.
Alginates are natural polysaccharides present in cell walls of
brown seaweed, highly biocompatible, with particular properties that
make them of high interest for the food, biotechnology, cosmetics
and pharmaceutical industries. Conventional extraction processes are
based on thermal treatment. They are lengthy and consume high
amounts of energy and solvents. In recent years, microwave-assisted
extraction (MAE) has shown enormous potential to overcome major
drawbacks that outcome from conventional plant material extraction
(thermal and/or solvent based) techniques, being also successfully
applied to the extraction of agar, fucoidans and alginates. In the
present study, acid pretreatment of brown seaweed Saccorhiza
polyschides for subsequent microwave-assisted extraction (MAE) of
alginate was optimized. Seaweeds were collected in Northwest
Portuguese coastal waters of the Atlantic Ocean between May and
August, 2014. Experimental design was used to assess the effect of
temperature and acid pretreatment time in alginate extraction.
Response surface methodology allowed the determination of the
optimum MAE conditions: 40 mL of HCl 0.1 M per g of dried
seaweed with constant stirring at 20ºC during 14h. Optimal acid
pretreatment conditions have enhanced significantly MAE of
alginates from Saccorhiza polyschides, thus contributing for the
development of a viable, more environmental friendly alternative to
conventional processes.
Abstract: In this study, epoxy composite specimens reinforced
with multi-walled carbon nanotube filler were fabricated using shear
mixer and ultra-sonication processor. The mechanical and thermal
properties of the fabricated specimens were measured and evaluated.
From the electron microscope images and the results from the
measurements of tensile strengths, the specimens having 0.6 wt%
nanotube content show better dispersion and higher strength than those
of the other specimens. The Young’s moduli of the specimens
increased as the contents of the nanotube filler in the matrix were
increased. The specimen having a 0.6 wt% nanotube filler content
showed higher thermal conductivity than that of the other specimens.
While, in the measurement of thermal expansion, specimens having
0.4 and 0.6 wt% filler contents showed a lower value of thermal
expansion than that of the other specimens. On the basis of the
measured and evaluated properties of the composites, we believe that
the simple and time-saving fabrication process used in this study was
sufficient to obtain improved properties of the specimens.
Abstract: Nanocrystalline powders of the lead-free piezoelectric
material, tantalum-substituted potassium sodium niobate
(K0.5Na0.5)(Nb0.9Ta0.1)O3 (KNNT), were produced using a Retsch
PM100 planetary ball mill by setting the milling time to 15h, 20h,
25h, 30h, 35h and 40h, at a fixed speed of 250rpm. The average
particle size of the milled powders was found to decrease from 12nm
to 3nm as the milling time increases from 15h to 25h, which is in
agreement with the existing theoretical model. An anomalous
increase to 98nm and then a drop to 3nm in the particle size were
observed as the milling time further increases to 30h and 40h
respectively. Various sizes of these starting KNNT powders were
used to investigate the effect of milling time on the microstructure,
dielectric properties, phase transitions and piezoelectric properties of
the resulting KNNT ceramics. The particle size of starting KNNT
was somewhat proportional to the grain size. As the milling time
increases from 15h to 25h, the resulting ceramics exhibit
enhancement in the values of relative density from 94.8% to 95.8%,
room temperature dielectric constant (εRT) from 878 to 1213, and
piezoelectric charge coefficient (d33) from 108pC/N to 128pC/N. For
this range of ceramic samples, grain size refinement suppresses the
maximum dielectric constant (εmax), shifts the Curie temperature (Tc)
to a lower temperature and the orthorhombic-tetragonal phase
transition (Tot) to a higher temperature. Further increase of milling
time from 25h to 40h produces a gradual degradation in the values of
relative density, εRT, and d33 of the resulting ceramics.
Abstract: PVC foam-fly ash composites (PVC-FA) are
characterized for their structural, morphological, mechanical and
thermal properties. The tensile strength of the composites increased
modestly with higher fly ash loading, while there was a significant
increase in the elastic modulus for the same composites. On the other
hand, a decrease in elongation at UTS was observed upon increasing
fly ash content due to increased rigidity of the composites. Similarly,
the flexural modulus increased as the fly ash loading increased,
where the composites containing 25 phr fly ash showed the highest
flexural strength. Thermal properties of PVC-fly ash composites were
determined by Thermo Gravimetric Analysis (TGA). The
microstructural properties were studied by Scanning Electron
Microscopy (SEM). SEM results confirm that fly ash particles were
mechanically interlocked in PVC matrix with good interfacial
interaction with the matrix. Particle agglomeration and debonding
was observed in samples containing higher amounts of fly ash.
Abstract: Two types of glass fibers having different lengths
(1/16" and 1/32") were added into rigid PVC foams to enhance the
dimensional stability of extruded rigid Polyvinyl Chloride (PVC)
foam at different concentrations (0-20 phr) using a single screw
profile extruder. PVC foam-glass fiber composites (PVC-GF) were
characterized for their dimensional stability, structural, thermal, and
mechanical properties. Experimental results show that the
dimensional stability, heat resistance, and storage modulus were
enhanced without compromising the tensile and flexural strengths of
the composites. Overall, foam composites which were prepared with
longer glass fibers exhibit better mechanical and thermal properties
than those prepared with shorter glass fibers due to higher
interlocking between the fibers and the foam cells, which result in
better load distribution in the matrix.
Abstract: Recommendation systems are widely used in
e-commerce applications. The engine of a current recommendation
system recommends items to a particular user based on user
preferences and previous high ratings. Various recommendation
schemes such as collaborative filtering and content-based approaches
are used to build a recommendation system. Most of current
recommendation systems were developed to fit a certain domain such
as books, articles, and movies. We propose1 a hybrid framework
recommendation system to be applied on two dimensional spaces
(User × Item) with a large number of Users and a small number
of Items. Moreover, our proposed framework makes use of both
favorite and non-favorite items of a particular user. The proposed
framework is built upon the integration of association rules mining
and the content-based approach. The results of experiments show
that our proposed framework can provide accurate recommendations
to users.
Abstract: Due to the importance of ports to trade and economic
development of the regions in which they are inserted, in recent
decades the number of studies devoted to this subject has increased.
Part of these studies considers the ports as business agglomerations
and focuses on port governance. This is an important approach since
the port performance is the result of activities performed by actors
belonging to the port-logistics chain, which need to be properly
coordinated. This coordination takes place through a port governance
model. Given this context, this study aims to analyze the governance
model of the port of Santos from the perspective of port customers.
To do this, a closed-ended questionnaire based on a conceptual model
that considers the key dimensions associated with port governance
was applied to the international freight forwarders that operate in the
port. The results show the applicability of the considered model and
highlight improvement opportunities to be implemented at the port of
Santos.
Abstract: Aerated concrete is a load bearing construction
material, which has high heat insulation parameters. Walls can be
erected from aerated concrete masonry constructions and in perfect
circumstances additional heat insulation is not required. The most
common problem in aerated concrete heat insulation properties is the
humidity distribution throughout the cross section of the masonry
elements as well as proper and conducted drying process of the
aerated concrete construction because only dry aerated concrete
masonry constructions can reach high heat insulation parameters.
In order to monitor drying process of the masonry and detect
humidity distribution throughout the cross section of aerated concrete
masonry construction application of electrical impedance
spectrometry is applied. Further test results and methodology of this
non-destructive testing method is described in this paper.
Abstract: We report on the use of strong external optical
feedback to enhance the modulation response of semiconductor lasers
over a frequency passband around modulation frequencies higher
than 60 GHz. We show that this modulation enhancement is a type of
photon-photon resonance (PPR) of oscillating modes in the external
cavity formed between the laser and the external reflector. The study
is based on a time-delay rate equation model that takes into account
both the strong feedback and multiple reflections in the external
cavity. We examine the harmonic and intermodulation distortions
associated with single and two-tone modulations in the mm-wave
band of the resonant modulation. We show that compared with
solitary lasers modulated around the carrier-photon resonance
frequency, the present mm-wave modulated signal has lower
distortions.
Abstract: We model and simulate the combined effect of fiber
dispersion and frequency chirp of a directly modulated high-speed
laser diode on the figures of merit of a non-amplified 40-Gbps optical
fiber link. We consider both the return to zero (RZ) and non-return to
zero (NRZ) patterns of the pseudorandom modulation bits. The
performance of the fiber communication system is assessed by the
fiber-length limitation due to the fiber dispersion. We study the
influence of replacing standard single-mode fibers by non-zero
dispersion-shifted fibers on the maximum fiber length and evaluate
the associated power penalty. We introduce new dispersion
tolerances for 1-dB power penalty of the RZ and NRZ 40-Gbps
optical fiber links.
Abstract: Animal fats (camel, sheep, goat, rabbit and chicken)
and vegetable oils (corn, sunflower, palm oil and olive oil) were
substituted with different proportions (1, 5, 10 and 20%) of lard.
Fatty acid composition in TG and 2-MG were determined using
lipase hydrolysis and gas chromatography before and after
adulteration. Results indicated that, genuine lard had a high
proportion (60.97%) of the total palmitic acid at 2-MG. However, it
was 8.70%, 16.40%, 11.38%, 10.57%, 29.97 and 8.97% for camel,
beef, sheep, goat, rabbit and chicken, respectively. It could be noticed
also the position-2-MG is mostly occupied by unsaturated fatty acids
among all tested fats except lard. Vegetable oils (corn, sunflower,
palm oil and olive oil) revealed that the levels of palmitic acid
esterifies at 2-MG position was 6.84, 1.43, 9.86 and 1.70%,
respectively. It could be observed also the studied oils had a higher
level of unsaturated fatty acids in the same position, compared with
animal fats under investigation. Moreover, palmitic acid esterifies at
2-MG and PAEF increased gradually as the substituted levels
increased among all tested fat and oil samples. Statistical analysis
showed that the PAEF correlated well with lard level. The detection
of lard in some commercial processed foods (5 French fries, 4 Butter
fats, 5 processed meat and 6 candy samples) was carried out. Results
revealed that 2 samples of French fries and 4 samples of processed
meat contained lard due to their higher PAEF, while butter fat and
candy were free of lard.
Abstract: Today’s modern interconnected power system is
highly complex in nature. In this, one of the most important
requirements during the operation of the electric power system is the
reliability and security. Power and frequency oscillation damping
mechanism improve the reliability. Because of power system
stabilizer (PSS) low speed response against of major fault such as
three phase short circuit, FACTs devise that can control the network
condition in very fast time, are becoming popular. But FACTs
capability can be seen in a major fault present when nonlinear models
of FACTs devise and power system equipment are applied. To realize
this aim, the model of multi-machine power system with FACTs
controller is developed in MATLAB/SIMULINK using Sim Power
System (SPS) blockiest. Among the FACTs device, Static
synchronous series compensator (SSSC) due to high speed changes
its reactance characteristic inductive to capacitive, is effective power
flow controller. Tuning process of controller parameter can be
performed using different method. But Genetic Algorithm (GA)
ability tends to use it in controller parameter tuning process. In this
paper firstly POD controller is used to power oscillation damping.
But in this station, frequency oscillation dos not has proper damping
situation. So FOD controller that is tuned using GA is using that
cause to damp out frequency oscillation properly and power
oscillation damping has suitable situation.
Abstract: This paper proposes a backward/forward sweep
method to analyze the power flow in radial distribution systems. The
distribution system has radial structure and high R/X ratios. So the
newton-raphson and fast decoupled methods are failed with
distribution system. The proposed method presents a load flow study
using backward/forward sweep method, which is one of the most
effective methods for the load-flow analysis of the radial distribution
system. By using this method, power losses for each bus branch and
voltage magnitudes for each bus node are determined. This method
has been tested on IEEE 33-bus radial distribution system and
effective results are obtained using MATLAB.
Abstract: Learner motivation is considered to be an important
component for the Blended e-Learning (BL) Method. BL is an
effective learning method in multiple domains, which opens several
opportunities for its participants to engage in the learning
environment. This research explores the learners’ perspective of BL
according to the Self-Determination Theory (SDT). It identifies the
opportunities and challenges for using the BL in Logistics Education
(LE) in Egyptian Higher Education (HE). SDT is approached from
different perspectives within the relationship between Intrinsic
Motivation (IM), Extrinsic Motivation (EM) and Amotivation (AM).
A self-administered face-to-face questionnaire was used to collect
data from learners who were geographically widely spread around
three colleges of International Transport and Logistics (CILTs) at the
Arab Academy for Science, Technology and Maritime Transport
(AAST&MT) in Egypt. Six hundred and sixteen undergraduates
responded to a questionnaire survey. Respondents were drawn from
three branches in Greater Cairo, Alexandria, and Port Said. The data
analysis used was SPSS 22 and AMOS 18.
Abstract: The financial crises caused a collapse in prices of
most asset classes, raising the attention on alternative investments
such as sukuk, a smaller, fast growing but often misunderstood
market. We study diversification benefits of sukuk, their correlation
with other asset classes and the effects of their inclusion in
investment portfolios of institutional and retail investors, through a
comprehensive comparison of their risk/return profiles during and
after the financial crisis.
We find a beneficial performance adjusted for the specific
volatility together with a lower correlation especially during the
financial crisis. The distribution of sukuk returns is positively skewed
and leptokurtic, with a risk/return profile similarly to high yield
bonds. Overall, our results suggest that sukuk present diversification
opportunities, a significant volatility-adjusted performance and lower
correlations especially during the financial crisis.
Our findings are relevant for a number of institutional investors.
Long term investors, such as life insurers would benefit from sukuk’s
protective features during financial crisis yet keeping return and
growth opportunities, whereas banks would gain due to their role of
placers, advisors, market makers or underwriters.
Abstract: Regardless of the manufacturing process used,
subtractive or additive, material, purpose and application, produced
components are conventionally solid mass with more or less complex
shape depending on the production technology selected. Aspects
such as reducing the weight of components, associated with the low
volume of material required and the almost non-existent material
waste, speed and flexibility of production and, primarily, a high
mechanical strength combined with high structural performance, are
competitive advantages in any industrial sector, from automotive,
molds, aviation, aerospace, construction, pharmaceuticals, medicine
and more recently in human tissue engineering. Such features,
properties and functionalities are attained in metal components
produced using the additive technique of Rapid Prototyping from
metal powders commonly known as Selective Laser Melting (SLM),
with optimized internal topologies and varying densities. In order to
produce components with high strength and high structural and
functional performance, regardless of the type of application, three
different internal topologies were developed and analyzed using
numerical computational tools. The developed topologies were
numerically submitted to mechanical compression and four point
bending testing. Finite Element Analysis results demonstrate how
different internal topologies can contribute to improve mechanical
properties, even with a high degree of porosity relatively to fully
dense components. Results are very promising not only from the
point of view of mechanical resistance, but especially through the
achievement of considerable variation in density without loss of
structural and functional high performance.
Abstract: In this paper, the formulation of a new group explicit
method with a fourth order accuracy is described in solving the two
dimensional Helmholtz equation. The formulation is based on the
nine-point fourth order compact finite difference approximation
formula. The complexity analysis of the developed scheme is also
presented. Several numerical experiments were conducted to test the
feasibility of the developed scheme. Comparisons with other existing
schemes will be reported and discussed. Preliminary results indicate
that this method is a viable alternative high accuracy solver to the
Helmholtz equation.
Abstract: Underwater acoustic network is one of the rapidly
growing areas of research and finds different applications for
monitoring and collecting various data for environmental studies. The
communication among dynamic nodes and high error probability in
an acoustic medium forced to maximize energy consumption in
Underwater Sensor Networks (USN) than in traditional sensor
networks. Developing energy-efficient routing protocol is the
fundamental and a curb challenge because all the sensor nodes are
powered by batteries, and they cannot be easily replaced in UWSNs.
This paper surveys the various recent routing techniques that mainly
focus on energy efficiency.