Abstract: Activated carbon is an amorphous carbon chain which
has extremely extended surface area. High surface area of activated
carbon is due to the porous structure. Activated carbon, using a
variety of materials such as coal and cellulosic materials; can be
obtained by both physical and chemical methods. The prepared
activated carbon can be used for decolorize, deodorize and also can
be used for removal of organic and non-organic pollution. In this
study, pomegranate peel was subjected to 800W microwave power
for 1 to 4 minutes. Also fresh pomegranate peel was used for the
reference material. Then ZnCl2 was used for the chemical activation
purpose. After the activation process, activated pomegranate peels
were used for the adsorption of Zn metal (40 ppm) in the waste water.
As a result of the adsorption experiments, removal of heavy metals
ranged from 89% to 85%.
Abstract: Activated carbons (M4P0, M4P2, and M5P2) used in
this research were produced from palm shell and polyetherether
ketone (PEEK) via carbonization, impregnation and microwave
activation. The adsorption/desorption process was carried out using
static volumetric adsorption. Regeneration is important in the overall
economy of the process and waste minimization. This work focuses
on the thermal regeneration of the CO2 exhausted microwave
activated carbons. The regeneration strategy adopted was thermal
with nitrogen purge desorption with N2 feed flow rate of 20 ml/min
for 1 h at atmospheric pressure followed by drying at 150oC.Seven
successive adsorption/regeneration processes were carried out on the
material. It was found that after seven adsorption regeneration cycles;
the regeneration efficiency (RE) for CO2 activated carbon from palm
shell only (M4P0) was more than 90% while that of hybrid palm
shell-PEEK (M4P2, M5P2) was above 95%. The cyclic adsorption
and regeneration shows the stability of the adsorbent materials.
Abstract: The characteristics of temperature distribution and
electric field in a natural rubber glove (NRG) using microwave
energy during microwave heating process are investigated
numerically and experimentally. A three-dimensional model of NRG
and microwave oven are considered in this work. The influences of
position, heating time and rotation angle of NRG on temperature
distribution and electric field are presented in details. The coupled
equations of electromagnetic wave propagation and heat transfer are
solved using the finite element method (FEM). The numerical model
is validated with an experimental study at a frequency of 2.45 GHz.
The results show that the numerical results closely match the
experimental results. Furthermore, it is found that the temperature
distribution and electric field increases with increasing heating time.
The hot spot zone appears in NRG at the tip of middle finger while
the maximum temperature occurs in case of rotation angle of NRG =
60 degree. This investigation provides the essential aspects for a
fundamental understanding of heat transport of NRG using
microwave energy in industry.
Abstract: This paper presents two types of microstrip bandpass
filter (BPF) at microwave frequencies. The first one is a tunable BPF
using planar patch resonators based on a varactor diode. The filter is
formed by a triple mode circular patch resonator with two pairs of
slots, in which the varactor diodes are connected. Indeed, this filter is
initially centered at 2.4 GHz; the center frequency of the tunable
patch filter could be tuned up to 1.8 GHz simultaneously with the
bandwidth, reaching high tuning ranges. Lossless simulations were
compared to those considering the substrate dielectric, conductor
losses and the equivalent electrical circuit model of the tuning
element in order to assess their effects. Within these variations,
simulation results showed insertion loss better than 2 dB and return
loss better than 10 dB over the passband. The second structure is a
BPF for ultra-wideband (UWB) applications based on multiple-mode
resonator (MMR) and rectangular-shaped defected ground structure
(DGS). This filter, which is compact size of 25.2 x 3.8 mm2, provides
in the pass band an insertion loss of 0.57 dB and a return loss greater
than 12 dB. The proposed filters presents good performances and the
simulation results are in satisfactory agreement with the
experimentation ones reported elsewhere.
Abstract: In recent years, the hair building fiber has become
popular, in other words, it is an effective method which helps people
who suffer hair loss or sparse hair since the hair building fiber is
capable to create a natural look of simulated hair rapidly. In the
markets, there are a lot of hair fiber brands that have been designed to
formulate an intense bond with hair strands and make the hair appear
more voluminous instantly. However, those products have their own
set of properties. Thus, in this report, some measurement techniques
are proposed to identify those products. Up to five different brands of
hair fiber are tested. The electrostatic and dielectric properties of the
hair fibers are macroscopically tested using design DC and high
frequency microwave techniques. Besides, the hair fibers are
microscopically analysis by magnifying the structures of the fiber
using scanning electron microscope (SEM). From the SEM photos,
the comparison of the uniformly shaped and broken rate of the hair
fibers in the different bulk samples can be observed respectively.
Abstract: Composite material based on Fe3Si micro-particles
and Mn-Zn nano-ferrite was prepared using powder metallurgy
technology. The sol-gel followed by autocombustion process was
used for synthesis of Mn0.8Zn0.2Fe2O4 ferrite. 3 wt.% of mechanically
milled ferrite was mixed with Fe3Si powder alloy. Mixed micro-nano
powder system was homogenized by the Resonant Acoustic Mixing
using ResodynLabRAM Mixer. This non-invasive homogenization
technique was used to preserve spherical morphology of Fe3Si
powder particles. Uniaxial cold pressing in the closed die at pressure
600 MPa was applied to obtain a compact sample. Microwave
sintering of green compact was realized at 800°C, 20 minutes, in air.
Density of the powders and composite was measured by
Hepycnometry. Impulse excitation method was used to measure
elastic properties of sintered composite. Mechanical properties were
evaluated by measurement of transverse rupture strength (TRS) and
Vickers hardness (HV). Resistivity was measured by 4 point probe
method. Ferrite phase distribution in volume of the composite was
documented by metallographic analysis.
It has been found that nano-ferrite particle distributed among
micro- particles of Fe3Si powder alloy led to high relative density
(~93%) and suitable mechanical properties (TRS >100 MPa, HV
~1GPa, E-modulus ~140 GPa) of the composite. High electric
resistivity (R~6.7 ohm.cm) of prepared composite indicate their
potential application as soft magnetic material at medium and high
frequencies.
Abstract: A compact UWB planar antenna fed with a
microstrip-line is proposed. The new design consist of a rectangular
patch with symmetric l-shaped slots and fed by 50 Ω microstrip
transmission line and a reduced ground-plane which have a periodic
slots with an overall size of 47 mm x 20 mm. It is intended to be used
in wireless applications that cover the ultra-wideband (UWB)
frequency band. A wider impedance bandwidth of around 116.5%
(1.875 – 7.115 GHz) with stable radiation pattern is achieved. The
proposed antenna has excellent characteristics, low profile and costeffective
compared to existing UWB antennas. The UWB antenna is
designed and analyzed using CST Microwave Studio in transient
mode to verify antenna parameters improvements.
Abstract: The dielectric properties and ionic conductivity of
novel "ceramic state" polymer electrolytes for high capacity lithium
battery are characterized by Radio frequency and Microwave
methods in two broad frequency ranges from 50 Hz to 20 KHz and 4
GHz to 40 GHz. This innovative solid polymer electrolyte which is
highly ionic conductive (10-3 S/cm at room temperature) from -40oC
to +150oC can be used in any battery application. Such polymer
exhibits properties more like a ceramic rather than polymer. The
various applied measurement methods produced accurate dielectric
results for comprehensive analysis of electrochemical properties and
ion transportation mechanism of this newly invented polymer
electrolyte. Two techniques and instruments employing air gap
measurement by Capacitance Bridge and in-waveguide measurement
by vector network analyzer are applied to measure the complex
dielectric spectra. The complex dielectric spectra are used to
determine the complex alternating current electrical conductivity and
thus the ionic conductivity.
Abstract: This paper presents a novel fractal antenna structure
proposed for UWB (Ultra – Wideband) applications. The frequency
band 3.1-10.6GHz released by FCC (Federal Communication
Commission) as the commercial operation of UWB has been chosen
as frequency range for this antenna based on coplanar waveguide
(CPW) feed and circular shapes fulfilled according to fractal
geometry. The proposed antenna is validated and designed by using
an FR4 substrate with overall area of 34x43 mm2. The simulated
results performed by CST-Microwave Studio and compared by ADS
(Advanced Design System) show good matching input impedance
with return loss less than -10dB between 2.9 GHz and 11 GHz.
Abstract: This paper presents analysis and design of a wideband
Wilkinson power divider for wireless applications. The design is
accomplished by transforming the lengths and impedances of the
quarter wavelength sections of the conventional Wilkinson power
divider into U-shaped sections. The designed power divider is
simulated by using ADS Agilent technologies and CST microwave
studio software. It is shown that the proposed power divider has
simple topology and good performances in terms of insertion loss,
port matching and isolation at all operating frequencies (1.8 GHz,
2.45 GHz and 3.55 GHz).
Abstract: This paper presents a new structure of microstrip band
pass filter (BPF) based on coupled stepped impedance resonators.
Each filter consists of two coupled stepped impedance resonators
connected to microstrip feed lines. The coupled junction is utilized to
connect the two BPFs to the antenna. This two band pass filters are
designed and simulated to operate for the digital communication
system (DCS) and Industrial Scientific and Medical (ISM) bands at
1.8 GHz and 2.45 GHz respectively. The proposed circuit presents
good performances with an insertion loss lower than 2.3 dB and
isolation between the two channels greater than 21 dB. The prototype
of the optimized diplexer have been investigated numerically by
using ADS Agilent and verified with CST microwave software.
Abstract: In this paper a new design of a broadband microwave
power limiter is presented and validated into simulation by using
ADS software (Advanced Design System) from Agilent technologies.
The final circuit is built on microstrip lines by using identical Zero
Bias Schottky diodes. The power limiter is designed by Associating 3
stages Schottky diodes. The obtained simulation results permit to
validate this circuit with a threshold input power level of 0 dBm until
a maximum input power of 30 dBm.
Abstract: This paper presents a novel design of a microstrip
fractal antenna based on the use of Sierpinski triangle shape, it’s
designed and simulated by using FR4 substrate in the operating
frequency bands (GPS, WiMAX), the design is a fractal antenna with
a modified ground structure. The proposed antenna is simulated and
validated by using CST Microwave Studio Software, the simulated
results presents good performances in term of radiation pattern and
matching input impedance.
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: Nitrogen-doped graphene quantum dots (N-GQDs)
were fabricated by microwave-assisted hydrothermal technique. The
optical properties of the N-GQDs were studied. The luminescence of
the N-GQDs can be tuned by varying the excitation wavelength.
Furthermore, two-photon luminescence of the N-GQDs excited by
near-infrared laser can be obtained. It is shown that N-doping play a
key role on two-photon luminescence. The N-GQDs are expected to
find application in biological applications including bioimaging and
sensing.
Abstract: This paper presents the electromagnetic interference
(EMI) shielding effectiveness of rice husk and carbon nanotubes
(RHCNTs) composites in the X-band region (8.2-12.4 GHz). The
difference weight ratio of carbon nanotubes (CNTs) were mix with
the rice husk. The rectangular waveguide technique was used to
measure the complex permittivity of the RHCNTs composites
materials. The complex permittivity is represented in terms of both
the real and imaginary parts of permittivity in X-band frequency. The
conductivity of RHCNTs shows increasing when the ratio of CNTs
mixture increases. The composites materials were simulated using
Computer Simulation Technology (CST) Microwave Studio
simulation software. The shielding effectiveness of RHCNTs and
pure rice husk was compared. The highest EMI SE of 30 dB is
obtained for RHCNTs composites of 10 wt % CNTs with 10mm
thickness.
Abstract: Microwave dielectric ceramic materials of
(Mg1-xNix)2(Ti0.95Sn0.05)O4 for x = 0.01, 0.03, 0.05, 0.07 and 0.09 were
prepared and sintered at 1250–1400 ºC. The microstructure and
microwave dielectric properties of the ceramic materials were
examined and measured. The observations shows that the content of
Ni2+ ions has little effect on the crystal structure, dielectric constant,
temperature coefficient of resonant frequency (τf) and sintering
temperatures of the ceramics. However, the quality values (Q×f) are
greatly improved due to the addition of Ni2+ ions. The present study
showed that the ceramic material prepared for x = 0.05 and sintered at
1325ºC had the best Q×f value of 392,000 GHz, about 23%
improvement compared with that of Mg2(Ti0.95Sn0.05)O4.
Abstract: This paper presents breast cancer detection by
observing the specific absorption rate (SAR) intensity for
identification tumor location, the tumor is identified in coordinates
(x,y,z) system. We examined the frequency between 4-8 GHz to look
for the most appropriate frequency. Results are simulated in
frequency 4-8 GHz, the model overview include normal breast with
50 mm radian, 5 mm diameter of tumor, and ultra wideband (UWB)
bowtie antenna. The models are created and simulated in CST
Microwave Studio. For this simulation, we changed antenna to 5
location around the breast, the tumor can be detected when an
antenna is close to the tumor location, which the coordinate of
maximum SAR is approximated the tumor location. For reliable, we
experiment by random tumor location to 3 position in the same size
of tumor and simulation the result again by varying the antenna
position in 5 position again, and it also detectable the tumor position
from the antenna that nearby tumor position by maximum value of
SAR, which it can be detected the tumor with precision in all
frequency between 4-8 GHz.
Abstract: The aim of the current research was to determine
quality parameters changes of dried venison during storage. Protein,
fat and moisture content dynamics as well microbiological quality
was analyzed. For the experiments the meat (0.02×4.00×7.00 cm)
pieces were marinated in “teriyaki sauce” marinade (composition:
teriyaki sauce, sweet and sour sauce, taco sauce, soy sauce, American
BBQ sauce hickory, sesame oil, garlic, garlic salt, tabasco red pepper
sauce) at 4±2°C temperature for 48±1h. Sodium monophosphate
(E339) was also added in part of marinade to improve the meat
textural properties. After marinating, meat samples were dried in
microwave-vacuum drier MUSSON–1, packaged in vacuum pouches
made from polymer film (PA/PE) with barrier properties and storage
for 4 months at 18±1°C temperature in dark place. Dried venison
samples were analyzed after 0, 35, 91 and 112 days of storage.
During the storage total plate counts of dried venison samples
significantly (p
Abstract: In this research, it is aimed not only microwave synthesis of magnesium borates but also evaluation of magnesium wastes. Synthesis process can be described with the reaction of Mg wastes and boric acid using microwave energy. X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) were applied to synthesized minerals. According to XRD results, magnesium borate hydrate mixtures were obtained as mcallisterite (pdf# = 01-070-1902, Mg2(B6O7(OH)6)2.9(H2O)) at higher crystallinity properties was achieved at the mole ratio raw material 1:1. Also, other kinds of magnesium borate hydrates were obtained at lower crystallinity such as admontite (pdf # = 01-076-0540, MgO(B2O3)3.7(H2O)), inderite (pdf # = 01-072-2308, 2MgO.3B2O3.15(H2O)) and magnesium borate hydrates (pdf # = 01-076-0539, MgO(B2O3)3.6(H2O)). FT-IR spectrums indicated that minor changes were seen at the band values of characteristic stretching in each experiment. At the end of experiments it is seen that using microwave energy may contribute positive effects to design of synthesis process such as reducing reaction time and products at higher crystallinity.