Abstract: In the present study, the properties of Al-Al2O3
nanocomposite hollow sphere structures were investigated. For this
reason, the Al-based nanocomposite hollow spheres with different
amounts of nano-alumina reinforcement (0-10wt %) and different
ratio of thickness to diameter (t/D: 0.06-0.3) were prepared via a
powder metallurgy method. Then, the effect of mentioned parameters
was studied on physical and quasi static mechanical properties of
their related prepared structures (open/closed cell) such as density,
hardness, strength, and energy absorption. It was found that, as the
t/D ratio increases the relative density, compressive strength and
energy absorption increase. The highest values of strength and energy
absorption were obtained from the specimen with 5 wt. % of
nanoparticle reinforcement, t/D of 0.3 (t=1 mm, D=400μm) as 22.88
MPa and 13.24 MJ/m3, respectively. The moderate specific strength
of prepared composites in the present study showed the good
consistency with the properties of others low carbon steel composite
with similar structure.
Abstract: In this paper, the exergy analysis of vapor absorption
refrigeration system using LiBr-H2O as working fluid is carried out
with the modified Gouy-Stodola approach rather than the classical
Gouy-Stodola equation and effect of varying input parameters is also
studied on the performance of the system. As the modified approach
uses the concept of effective temperature, the mathematical
expressions for effective temperature have been formulated and
calculated for each component of the system. Various constraints and
equations are used to develop program in EES to solve these
equations. The main aim of this analysis is to determine the
performance of the system and the components having major
irreversible loss. Results show that exergy destruction rate is
considerable in absorber and generator followed by evaporator and
condenser. There is an increase in exergy destruction in generator,
absorber and condenser and decrease in the evaporator by the
modified approach as compared to the conventional approach. The
value of exergy determined by the modified Gouy-Stodola equation
deviates maximum i.e. 26% in the generator as compared to the
exergy calculated by the classical Gouy-Stodola method.
Abstract: In the present work, fly ash geopolymer based
composites including polyester (PES) waste were studied. Specimens
of three compositions were prepared: (a) fly ash geopolymer with 5%
PES waste; (b) fly ash geopolymer mortar with 5% PES waste; (c) fly
ash geopolymer mortar with 6.25% PES waste. Compressive and
bending strength measurements, water absorption test and
determination of thermal conductivity coefficient were performed.
The results showed that the addition of sand in a mixture of
geopolymer with 5% PES content led to higher compressive strength,
while it increased water absorption and reduced thermal conductivity
coefficient. The increase of PES addition in geopolymer mortars
resulted in a more dense structure, indicated by the increase of
strength and thermal conductivity and the decrease of water
absorption.
Abstract: In this research (using induction furnace process)
nodular iron with three different percentages of copper (residual,
0.5% and 1,2%) was obtained. Chemical analysis was performed by
mass spectrometry and microstructures were characterized by Optical
Microscopy (ASTM E3) and Scanning Electron Microscopy (SEM).
The study of mechanical behavior was carried out in a mechanical
test machine (ASTM E8) and a Pin on disk tribometer (ASTM G99)
was used to assess wear resistance. It is observed that the dissolution
of copper in crystal lattice increases the pearlite structure improving
the wear and hardness behavior, but producing a contrary effect on
the energy absorption.
Abstract: In this paper, extract of papaya leaves are used as a
natural dye and combined by variations of solvent concentration
applied on DSSC (Dye-Sensitized Solar Cell). Indonesian geographic
located on the equator line occasions the magnitude of the potential
to develop organic solar cells made from extracts of chlorophyll as a
substitute for inorganic materials or synthetic dye on DSSC material.
Dye serves as absorbing photons which are then converted into
electrical energy. A conductive coated glass layer called TCO
(Transparent Conductive Oxide) is used as a substrate of electrode.
TiO2 nanoparticles as binding dye molecules, redox couple iodide/
tri-iodide as the electrolyte and carbon as the counter electrode in the
DSSC are used. TiO2 nanoparticles, organic dyes, electrolytes, and
counter electrode are arranged and combined with the layered
structure of the photo-catalyst absorption layer. Dye absorption
measurements using a spectrophotometer at 400-800 nm light
spectrum produces a total amount of chlorophyll 80.076 mg/l. The
test cell at 7 watt LED light with 5000 lux luminescence was
obtained Voc and Isc of 235.5 mV and 14 μA, respectively.
Abstract: This paper presents nonlinear pulse propagation characteristics for different input optical pulse shapes with various input pulse energy levels in semiconductor optical amplifiers. For simulation of nonlinear pulse propagation, finite-difference beam propagation method is used to solve the nonlinear Schrödinger equation. In this equation, gain spectrum dynamics, gain saturation are taken into account which depends on carrier depletion, carrier heating, spectral-hole burning, group velocity dispersion, self-phase modulation and two photon absorption. From this analysis, we obtained the output waveforms and spectra for different input pulse shapes as well as for different input energies. It shows clearly that the peak position of the output waveforms are shifted toward the leading edge which due to the gain saturation of the SOA for higher input pulse energies. We also analyzed and compared the normalized difference of full-width at half maximum for different input pulse shapes in the SOA.
Abstract: The purpose of this study is to compare Self
Compacting Concrete (SCC) and Conventional Concrete (CC) in
terms of their capillary water absorption. During the comparison of
SCC and CC, the effects of two different factors were also
investigated: concrete strength class and curing condition. In the
study, both SCC and CC were produced in three different concrete
classes (C25, C50 and C70) and the other parameter (i.e. curing
condition) was determined as two levels: moisture and air curing. It
was observed that, for both curing environments and all strength
classes of concrete, SCCs had lower capillary water absorption values
than that of CCs. It was also detected that, for both SCC and CC,
capillary water absorption values of samples kept in moisture curing
were significantly lower than that of samples stored in air curing.
Additionally, it was determined that capillary water absorption values
for both SCC and CC decrease with increasing strength class of
concrete for both curing environments.
Abstract: This work is focused on the study of valuation of
recycled concrete aggregates, by measuring certain properties of
concrete in the fresh and hardened state. In this study, rheological
tests and physic-mechanical characterization on concretes and
mortars were conducted with recycled concrete whose geometric
properties were identified aggregates. Mortars were elaborated with
recycled fine aggregate (0/5mm) and concretes were manufactured
using recycled coarse aggregates (5/12.5 mm and 12.5/20 mm). First,
a study of the mortars was conducted to determine the effectiveness
of polycarboxylate superplasticizer on the workability of these and
their action deflocculating of the recycled sand. The rheological
behavior of mortars based on fine aggregate recycled was
characterized. The results confirm that the mortars composed of
different fractions of recycled sand (0 /5) have a better mechanical
properties (compressive and flexural strength) compared to normal
mortar. Also, the mechanical strengths of concretes made with
recycled aggregates (5/12.5 mm and 12.5/20 mm), are comparable to
those of conventional concrete with conventional aggregates,
provided that the implementation can be improved by the addition of
a superplasticizer.
Abstract: Metallic foams have good potential for lightweight
structures for impact and blast mitigation. Therefore it is important to
find out the optimized foam structure (i.e. cell size, shape, relative
density, and distribution) to maximise energy absorption. In this
paper, quasistatic compression and microstructural characterization
of closed-cell aluminium foams of different pore size and cell
distributions have been carried out. We present results for two
different aluminium metal foams of density 0.49-0.51 g/cc and 0.31-
0.34 g/cc respectively that have been tested in quasi-static
compression. The influence of cell geometry and cell topology on
quasistatic compression behaviour has been investigated using optical
microscope and computed tomography (micro-CT) analysis. It is
shown that the deformation is not uniform in the structure and
collapse begins at the weakest point.
Abstract: The Proton Exchange Membranes (PEM) are largely studied because they operate at low temperatures and they are suitable for mobile applications. However, there are some deficiencies in their operation, mainly those that use ethanol as a hydrogen source, that require a certain attention. Therefore, this research aimed to develop Nafion® composite membranes, mixing clay minerals, kaolin and halloysite to the polymer matrix in order to improve the ethanol molecule retentions and, at the same time, to keep the system’s protonic conductivity. The modified Nafion/Kaolin, Nafion/Halloysite composite membranes were prepared in weight proportion of 0.5, 1.0 and 1.5. The membranes obtained were characterized as to their ethanol permeability, protonic conductivity and water absorption. The composite morphology and structure are characterized by SEM and EDX and the thermal behavior is determined by TGA and DSC. The analysis of the results shows ethanol permeability reduction from 48% to 63%. However, the protonic conductivity results are lower in relation to pure Nafion®. As to the thermal behavior, the Nafion® composite membranes were stable up to a temperature of 325ºC.
Abstract: Group contribution methods such as the UNIFAC are
very useful to researchers and engineers involved in synthesis,
feasibility studies, design and optimization of separation processes.
They can be applied successfully to predict phase equilibrium and
excess properties in the development of chemical and separation
processes. The main focus of this work was to investigate the
possibility of absorbing selected volatile organic compounds (VOCs)
into polydimethylsiloxane (PDMS) using three selected UNIFAC
group contribution methods. Absorption followed by subsequent
stripping is the predominant available abatement technology of
VOCs from flue gases prior to their release into the atmosphere. The
original, modified and effective UNIFAC models were used in this
work. The thirteen selected VOCs that have been considered in this
research are: pentane, hexane, heptanes, trimethylamine, toluene,
xylene, cyclohexane, butyl acetate, diethyl acetate, chloroform,
acetone, ethyl methyl ketone and isobutyl methyl ketone. The
computation was done for solute VOC concentration of 8.55x10-8
which is well in the infinite dilution region. The results obtained in
this study compare very well with those published in literature
obtained through both measurements and predictions. The phase
equilibrium obtained in this study show that PDMS is a good
absorbent for the removal of VOCs from contaminated air streams
through physical absorption.
Abstract: Photo-BJMOSFET (Bipolar Junction Metal-Oxide-
Semiconductor Field Effect Transistor) fabricated on SOI film was proposed. ITO film is adopted in the device as gate electrode to reduce
light absorption. Depletion region but not inversion region is formed
in film by applying gate voltage (but low reverse voltage) to achieve
high photo-to-dark-current ratio. Comparisons of photoelectriccharacteristics
executed among VGK=0V, 0.3V, 0.6V, 0.9V and 1.0V
(reverse voltage VAK is equal to 1.0V for total area of 10×10μm2). The
results indicate that the greatest improvement in photo-to-dark-current
ratio is achieved up to 2.38 at VGK=0.6V. In addition,
photo-BJMOSFET is compatible with CMOS integration due to big
input resistance
Abstract: Service life of existing reinforced concrete (RC)
structures in coastal towns of Sabah has been affected very much.
Concrete crack, spalling of concrete cover and reinforcement rusting
of RC buildings are seen even within 5 years of construction in
Sabah. Hence, in this study a new mix design of concrete grout was
developed using locally available materials and investigated under
two curing conditions and workability, compressive strength,
Accelerated Mortar Bar Test (AMBT), water absorption, volume of
permeable voids (VPV), Sorptivity and 90-days salt ponding test
were conducted. The compressive strength of concrete grout at the
age 90 days was found to be 44.49 N/mm2 under water curing. It was
observed that the percentage of mortar bar length change was below
1% for developed concrete grout. The water absorption of the
concrete grout was in between the range of 0.88 % to 3.60 % under
two different curing up to the age 90 days. It was also observed that
the VPV of concrete was in the range of 0 % to 9.75 and 2.44% to
13.05% under water curing and site curing respectively. It was found
that the Sorptivity of the concrete grout under water curing at the age
of 28 days is 0.211mm/√min and at the age 90 day are 0.067
mm/√min. The chloride content decreased greatly, 90% after a depth
of 15 mm. It was noticed that the site cured samples showed higher
chloride contents near surface compared to water cured samples.
This investigation suggested that the developed mix design of
concrete grout using locally available construction materials can be
used for crack repairing of existing RC structures in Sabah.
Abstract: Many commercial processes are available for the
removal of H2S from gaseous streams. The desulfurization of gas
streams using aqueous ferric sulfate solution as washing liquor is
studied. Apart from sulfur, only H2O is generated in the process, and
consequently, no waste treatment facilities are required. A distinct
advantage of the process is that the reaction of H2S with is so rapid
and complete that there remains no danger of discharging toxic waste
gas. In this study, the reactive absorption of hydrogen sulfide into
aqueous ferric sulfate solution has been studied and design
calculations for equipments have been done and effective operation
parameters on this process considered. Results show that high
temperature and low pressure are suitable for absorption reaction.
Variation of hydrogen sulfide concentration and Fe3+ concentration
with time in absorption reaction shown that the reaction of ferric
sulfate and hydrogen sulfide is first order with respect to the both
reactant. At low Fe2(SO4)3 concentration the absorption rate of H2S
increase with increasing the Fe2(SO4)3 concentration. At higher
concentration a decrease in the absorption rate was found. At higher
concentration of Fe2(SO4)3, the ionic strength and viscosity of
solution increase remarkably resulting in a decrease of solubility,
diffusivity and hence absorption rate.
Abstract: This research aimed to modify pineapple leaf paper
(PALP) for using as wet media in the evaporation cooling system by
improving wet mechanical property (tensile strength) without
compromising water absorption property. Polyamideamineepichorohydrin
resin (PAE) and carboxymethylcellulose (CMC)
were used to strengthen the paper, and the PAE and CMC ratio of
80:20 showed the optimum wet and dry tensile index values, which
were higher than those of the commercial cooling pad (CCP).
Compared with CCP, PALP itself and all the PAE/CMC modified
PALP possessed better water absorption. The PAE/CMC modified
PALP had potential to become a new type of wet media.
Abstract: We propose photo-BJMOSFET (Bipolar Junction Metal-Oxide-Semiconductor Field Effect Transistor) fabricated on SOI film. ITO film is adopted in the device as gate electrode to reduce light absorption. I-V characteristics of photo-BJMOSFET obtained in dark (dark current) and under 570nm illumination (photo current) are studied furthermore to achieve high photo-to-dark-current contrast ratio. Two variables in the calculation were the channel length and the thickness of the film which were set equal to six different values, i.e., L=2, 4, 6, 8, 10, and 12μm and three different values, i.e., dsi =100, 200 and 300nm, respectively. The results indicate that the greatest photo-to-dark-current contrast ratio is achieved with L=10μm and dsi=200 nm at VGK=0.6V.
Abstract: This study addresses the effect of impurities on the
crystallization of Na2CO3 produced within a strategy for capturing
CO2 from flue gases by alkaline absorption. A novel technology -
membrane assisted crystallization - is proposed for Na2CO3
crystallization from mother liquors containing impurities. High purity
of Na2CO3•10H2O crystals was obtained without impacting the
performance of the mass transfer of water vapor through membranes
during crystallization.
Abstract: The breakdown strength characteristic of Low Density
Polyethylene films (LDPE) under DC voltage application and the
effect of water absorption have been studied. Mainly, our experiment
was investigated under two conditions; dry and heavy water
absorption. Under DC ramp voltage, the result found that the
breakdown strength under heavy water absorption has a lower value
than dry condition. In order to clarify the effect, the temperature rise of
film was observed using non contact thermograph until the occurrence
of the electrical breakdown and the conduction current of the sample
was also measured in correlation with the thermograph measurement.
From the observations, it was shown that under the heavy water
absorption, the hot spot in the samples appeared at lower voltage. At
the same voltage the temperature of the hot spot and conduction
current was higher than that under the dry condition. The measurement
result has a good correlation between the existence of a critical field
for conduction current and thermograph observation. In case of the
heavy water absorption, the occurrence of the threshold field was
earlier than the dry condition as result lead to higher of conduction
current and the temperature rise appears after threshold field was
significantly increased in increasing of field. The higher temperature
rise was caused by the higher current conduction as the result the
insulation leads to breakdown to the lower field application.
Abstract: This paper concerns about the experimental and
numerical investigations of energy absorption and axial tearing
behaviour of aluminium 6060 circular thin walled tubes under static
axial compression. The tubes are received in T66 heat treatment
condition with fixed outer diameter of 42mm, thickness of 1.5mm
and length of 120mm. The primary variables are the conical die
angles (15°, 20° and 25°). Numerical simulations are carried on
ANSYS/LS-DYNA software tool, for investigating the effect of
friction between the tube and the die.
Abstract: Brick is one of the most common masonry units used as building material. Due to the demand, different types of waste have been investigated to be incorporated into the bricks. Many types of sludge have been incorporated in fired clay brick for example marble sludge, stone sludge, water sludge, sewage sludge, and ceramic sludge. The utilization of these waste materials in fired clay bricks usually has positive effects on the properties such as lightweight bricks with improved shrinkage, porosity, and strength. This paper reviews on utilization of different types of sludge wastes into fired clay bricks. Previous investigations have demonstrated positive effects on the physical and mechanical properties as well as less impact towards the environment. Thus, the utilizations of sludge waste could produce a good quality of brick and could be one of alternative disposal methods for the sludge wastes.