Abstract: This study investigates how AlGaAs/GaAs thin film
solar cells perform under varying global solar spectrum due to the
changes of environmental parameters such as the air mass and the
atmospheric turbidity. The solar irradiance striking the solar cell is
simulated using the spectral irradiance model SMARTS2 (Simple
Model of the Atmospheric Radiative Transfer of Sunshine) for clear
skies on the site of Setif (Algeria). The results show a reduction in the
short circuit current due to increasing atmospheric turbidity, it is
63.09% under global radiation. However increasing air mass leads to
a reduction in the short circuit current of 81.73%. The efficiency
decreases with increasing atmospheric turbidity and air mass.
Abstract: Near infrared (NIR) spectroscopy has always been of
great interest in the food and agriculture industries. The development
of prediction models has facilitated the estimation process in recent
years. In this study, 110 crude palm oil (CPO) samples were used to
build a free fatty acid (FFA) prediction model. 60% of the collected
data were used for training purposes and the remaining 40% used for
testing. The visible peaks on the NIR spectrum were at 1725 nm and
1760 nm, indicating the existence of the first overtone of C-H bands.
Principal component regression (PCR) was applied to the data in
order to build this mathematical prediction model. The optimal
number of principal components was 10. The results showed
R2=0.7147 for the training set and R2=0.6404 for the testing set.
Abstract: The levels of maximum power density of GSM
signals in the cities of Lagos, Ibadan and Abuja were studied.
Measurements were made with a calibrated hand held spectrum
analyzer 200m away from 271 base stations, at 1.2m to the ground
level. The maximum GSM 900 signal power density was
139.63μW/m2 in Lagos, 162.49μW/m2 in Ibadan and 5411.26μW/m2
in Abuja. Also, the maximum GSM 1800 signal power density was
296.82μW/m2 in Lagos, 116.82μW/m2 in Ibadan and 1263.00μW/m2
in Abuja. The level of power density of GSM 900 and GSM 1800
signals in the cities of Lagos, Ibadan and Abuja are far less than the
recommended value of 4.5W/m2 for GSM 900 and 9.0 W/m2 for
GSM 1800 by the ICNRP guideline. It can be concluded that
exposure to GSM signals in these cities cannot contribute to the
health detriments caused by thermal effects of radiofrequency
radiation.
Abstract: A key issue in seismic risk analysis within the context
of Performance-Based Earthquake Engineering is the evaluation of
the expected seismic damage of structures under a specific
earthquake ground motion. The assessment of the seismic
performance strongly depends on the choice of the seismic Intensity
Measure (IM), which quantifies the characteristics of a ground
motion that are important to the nonlinear structural response. Several
conventional IMs of ground motion have been used to estimate their
damage potential to structures. Yet, none of them has been proved to
be able to predict adequately the seismic damage. Therefore,
alternative, scalar intensity measures, which take into account not
only ground motion characteristics but also structural information
have been proposed. Some of these IMs are based on integration of
spectral values over a range of periods, in an attempt to account for
the information that the shape of the acceleration, velocity or
displacement spectrum provides. The adequacy of a number of these
IMs in predicting the structural damage of 3D R/C buildings is
investigated in the present paper. The investigated IMs, some of
which are structure specific and some are non structure-specific, are
defined via integration of spectral values. To achieve this purpose
three symmetric in plan R/C buildings are studied. The buildings are
subjected to 59 bidirectional earthquake ground motions. The two
horizontal accelerograms of each ground motion are applied along
the structural axes. The response is determined by nonlinear time
history analysis. The structural damage is expressed in terms of the
maximum interstory drift as well as the overall structural damage
index. The values of the aforementioned seismic damage measures
are correlated with seven scalar ground motion IMs. The comparative
assessment of the results revealed that the structure-specific IMs
present higher correlation with the seismic damage of the three
buildings. However, the adequacy of the IMs for estimation of the
structural damage depends on the response parameter adopted.
Furthermore, it was confirmed that the widely used spectral
acceleration at the fundamental period of the structure is a good
indicator of the expected earthquake damage level.
Abstract: Food contamination occurs during post process
handling. This leads to spoilage and growth of pathogenic
microorganisms in the food, thereby reducing its shelf life or
spreading of food borne diseases. Several methods are tried and one
of which is use of antimicrobial packaging. Here, papain, a protease
enzyme, is covalently immobilized with the help of glutarldehyde on
polyurethane and used as a food wrap to protect food from microbial
contamination. Covalent immobilization of papain was achieved at a
pH of 7.4; temperature of 4°C; glutaraldehyde concentration of 0.5%;
incubation time of 24h; and 50mg of papain. The formation of -C=Nobserved
in the Fourier transform infrared spectrum confirmed the
immobilization of the enzyme on the polymer. Immobilized enzyme
retained higher activity than the native free enzyme. The modified
polyurethane showed better reduction of Staphylococcus aureus
biofilm than bare polymer film (eight folds reduction in live colonies,
two times reduction in protein and 6 times reduction in
carbohydrates). The efficacy of this was studied by wrapping it over
S. aureus contaminated cottage cheese (paneer) and cheese and
stored at a temperature of 4°C for 7days. The modified film reduced
the bacterial contamination by eight folds when compared to the bare
film. FTIR also indicated reduction in lipids, sugars and proteins in
the biofilm.
Abstract: This work presents a Computational Fluid Dynamics
(CFD) simulation of a butterfly valve used to control the flow of
combustible gas mixture in an industrial process setting.The work
uses CFD simulation to analyze the flow characteristics in the
vicinity of the valve, including the pressure distributions and
Frequency spectrum of the pressure pulsations downstream the valves
and the vortex shedding allow predicting the torque fluctuations
acting on the valve shaft and the possibility of generating mechanical
vibration and resonance.These fluctuations are due to aerodynamic
torque resulting from fluid turbulence and vortex shedding in the
valve vicinity.
The valve analyzed is located in a pipeline between two opposing
90o elbows, which exposes the valve and the surrounding structure to
the turbulence generated upstream and downstream the elbows at
either end of the pipe.CFD simulations show that the best location for
the valve from a vibration point of view is in the middle of the pipe
joining the elbows.
Abstract: Multispectral screening systems are becoming more
popular because of their very interesting properties and applications.
One of the most significant applications of multispectral screening
systems is prevention of terrorist attacks. There are many kinds of
threats and many methods of detection. Visual detection of objects
hidden under clothing of a person is one of the most challenging
problems of threats detection. There are various solutions of the
problem; however, the most effective utilize multispectral
surveillance imagers. The development of imaging devices and
exploration of new spectral bands is a chance to introduce new
equipment for assuring public safety. We investigate the possibility
of long lasting detection of potentially dangerous objects covered
with various types of clothing. In the article we present the results of
comparative studies of passive imaging in three spectrums – visible,
infrared and terahertz.
Abstract: This paper considers the characterization of a complex
electromagnetic environment due to multiple sources of
electromagnetic radiation as a five-dimensional surface which can be
described by a set of several surface sections including: instant EM
field intensity distribution maps at a given frequency and altitude,
instantaneous spectrum at a given location in space and the time
evolution of the electromagnetic field spectrum at a given point in
space. This characterization if done over time can enable the
exposure levels of Radio Frequency Radiation at every point in the
analysis area to be determined and results interpreted based on
comparison of the determined RFR exposure level with the safe
guidelines for general public exposure given by recognized body
such as the International commission on non-ionizing radiation
protection (ICNIRP), Institute of Electrical and Electronic Engineers
(IEEE), the National Radiation Protection Authority (NRPA).
Abstract: This paper presents a 4-DOF nonlinear model of a
cracked de Laval rotor-stator system derived based on Energy
Principles. The model has been used to simulate coupled torsionallateral
response of the faulty system with multiple parametric
excitations; rotor-stator-rub, a breathing transverse crack, eccentric
mass and an axial force. Nonlinearity of a “breathing” crack is
incorporated in the model using a simple hinge mechanism suitable
for a shallow crack. Response of the system while passing via its
critical speed with intermittent rotor-stator rub is analyzed. Effects of
eccentricity with phase and acceleration are investigated. Features of
crack, rub and eccentricity in vibration response are explored for
condition monitoring. The presence of a crack and rub are observable
in the power spectrum despite excitations by an axial force and rotor
unbalance. Obtained results are consistent with existing literature and
could be adopted into rotor condition monitoring strategies.
Abstract: The detection of environmental gases, 12CO2, 13CO2,
and CH4, using near-infrared semiconductor lasers with a short
laser path length is studied by means of wavelength-modulation
spectroscopy. The developed system is compact and has high
sensitivity enough to detect the absorption peaks of isotopic 13CO2
of a 3-% CO2 gas at 2 μm with a path length of 2.4 m, where
its peak size is two orders of magnitude smaller than that of the
ordinary 12CO2 peaks. In addition, the detection of 12CO2 peaks of
a 385-ppm (0.0385-%) CO2 gas in the air is made at 2 μm with a
path length of 1.4 m. Furthermore, in pursuing the detection of an
ancient environmental CH4 gas confined to a bubble in ice at the
polar regions, measurements of the absorption spectrum for a trace
gas of CH4 in a small area are attempted. For a 100-% CH4 gas
trapped in a ∼ 1 mm3 glass container, the absorption peaks of CH4
are obtained at 1.65 μm with a path length of 3 mm, and also the
gas pressure is extrapolated from the measured data.
Abstract: Spectrum sensing is the main feature of cognitive
radio technology. Spectrum sensing gives an idea of detecting the
presence of the primary users in a licensed spectrum. In this paper we
compare the theoretical results of detection probability of different
fading environments like Rayleigh, Rician, Nakagami-m fading
channels with the simulation results using energy detection based
spectrum sensing. The numerical results are plotted as Pf Vs Pd for
different SNR values, fading parameters. It is observed that
Nakagami fading channel performance is better than other fading
channels by using energy detection in spectrum sensing. A MATLAB
simulation test bench has been implemented to know the performance
of energy detection in different fading channel environment.
Abstract: The article presents the concept of an electromagnetic
circuit generator with permanent magnets mounted on the surface
rotor core designed for single phase work. Computation field-circuit
model was shown. The spectrum of time course of voltages in the
idle work was presented. The cross section with graphically
presentation of magnetic induction in particular parts of
electromagnetic circuits was presented. Distribution of magnetic
induction at the rated load point for each phase was shown. The time
course of voltages and currents for each phases for rated power were
displayed. An analysis of laboratory results and measurement of load
characteristics of the generator was discussed. The work deals with
three electromagnetic circuits of generators with permanent magnet
where output voltage characteristics versus rated power were
expressed.
Abstract: Cognitive Radio is a turning out technology that
empowers viable usage of the spectrum. Energy Detector-based
Sensing is the most broadly utilized spectrum sensing strategy.
Besides, it's a lot of generic as receivers doesn't would like any
information on the primary user's signals, channel data, of even the
sort of modulation. This paper puts forth the execution of energy
detection sensing for AM (Amplitude Modulated) signal at 710 KHz,
FM (Frequency Modulated) signal at 103.45 MHz (local station
frequency), Wi-Fi signal at 2.4 GHz and WiMAX signals at 6 GHz.
The OFDM/OFDMA based WiMAX physical layer with
convolutional channel coding is actualized utilizing USRP N210
(Universal Software Radio Peripheral) and GNU Radio based
Software Defined Radio (SDR). Test outcomes demonstrated the
BER (Bit Error Rate) augmentation with channel noise and BER
execution is dissected for different Eb/N0 (the energy per bit to noise
power spectral density ratio) values.
Abstract: This paper addresses the reduction of peak to average
power ratio (PAPR) for the OFDM in Mobile-WiMAX physical layer
(PHY) standard. In the process, the best achievable PAPR of 0 dB is
found for the OFDM spectrum using phase modulation technique
which avoids the nonlinear distortion. The performance of the
WiMAX PHY standard is handled by the software defined radio
(SDR) prototype in which GNU Radio and USRP N210 employed as
software and hardware platforms respectively. It is also found that
BER performance is shown for different coding and different
modulation schemes. To empathize wireless propagation in specific
environments, a sliding correlator wireless channel sounding system
is designed by using SDR testbed.
Abstract: The most important part of modern lean low NOx combustors is a premixer where swirlers are often used for intensification of mixing processes and further formation of required flow pattern in combustor liner. Swirling flow leads to formation of complex eddy structures causing flow perturbations. It is able to cause combustion instability. Therefore, at design phase, it is necessary to pay great attention to aerodynamics of premixers. Analysis based on unsteady CFD modeling of swirling flow in production combustor swirler showed presence of large number of different eddy structures that can be conditionally divided into three types relative to its location of origin and a propagation path. Further, features of each eddy type were subsequently defined. Comparison of calculated and experimental pressure fluctuations spectrums verified correctness of computations.
Abstract: The growth of wireless devices affects the availability
of limited frequencies or spectrum bands as it has been known that
spectrum bands are a natural resource that cannot be added.
Meanwhile, the licensed frequencies are idle most of the time.
Cognitive radio is one of the solutions to solve those problems.
Cognitive radio is a promising technology that allows the unlicensed
users known as secondary users (SUs) to access licensed bands
without making interference to licensed users or primary users (PUs).
As cloud computing has become popular in recent years, cognitive
radio networks (CRNs) can be integrated with cloud platform. One of
the important issues in CRNs is security. It becomes a problem since
CRNs use radio frequencies as a medium for transmitting and CRNs
share the same issues with wireless communication systems. Another
critical issue in CRNs is performance. Security has adverse effect to
performance and there are trade-offs between them. The goal of this
paper is to investigate the performance related to security trade-off in
CRNs with supporting cloud platforms. Furthermore, Queuing
Network Models with preemptive resume and preemptive repeat
identical priority are applied in this project to measure the impact of
security to performance in CRNs with or without cloud platform. The
generalized exponential (GE) type distribution is used to reflect the
bursty inter-arrival and service times at the servers. The results show
that the best performance is obtained when security is disabled and
cloud platform is enabled.
Abstract: We have studied a method to widen the spectrum
of optical pulses that pass through an InGaAsP waveguide for
application to broadband optical communication. In particular, we
have investigated the competitive effect between spectral broadening
arising from nonlinear refraction (optical Kerr effect) and shrinking
due to two photon absorption in the InGaAsP waveguide with
χ(3) nonlinearity. The shrunk spectrum recovers broadening by
the enhancement effect of the nonlinear refractive index near the
bandgap of InGaAsP with a bandgap wavelength of 1490 nm. The
broadened spectral width at around 1525 nm (196.7 THz) becomes
10.7 times wider than that at around 1560 nm (192.3 THz) without
the enhancement effect, where amplified optical pulses with a pulse
width of ∼ 2 ps and a peak power of 10 W propagate through a
1-cm-long InGaAsP waveguide with a cross-section of 4 (μm)2.
Abstract: A simple multi-wavelength passively Q-switched
Erbium-doped fiber laser (EDFL) is demonstrated using low cost
multi-walled carbon nanotubes (MWCNTs) based saturable absorber
(SA), which is prepared using polyvinyl alcohol (PVA) as a host
polymer. The multi-wavelength operation is achieved based on
nonlinear polarization rotation (NPR) effect by incorporating 50 m
long photonic crystal fiber (PCF) in the ring cavity. The EDFL
produces a stable multi-wavelength comb spectrum for more than 14
lines with a fixed spacing of 0.48 nm. The laser also demonstrates a
stable pulse train with the repetition rate increases from 14.9 kHz to
25.4 kHz as the pump power increases from the threshold power of
69.0 mW to the maximum pump power of 133.8 mW. The minimum
pulse width of 4.4 μs was obtained at the maximum pump power of
133.8 mW while the highest energy of 0.74 nJ was obtained at pump
power of 69.0 mW.
Abstract: Fluid rheology may have essential impact on sound propagation in a liquid-filled pipe, especially, in a low frequency range. Rheological parameters of liquid are temperature-sensitive, which ultimately results in a temperature dependence of the wave speed and attenuation in the waveguide. The study is devoted to modeling of this effect at sound propagation in an elastic pipe with polymeric liquid, described by generalized Maxwell model with non-zero high-frequency viscosity. It is assumed that relaxation spectrum is distributed according to the Spriggs law; temperature impact on the liquid rheology is described on the basis of the temperature-superposition principle and activation theory. The dispersion equation for the waveguide, considered as a thin-walled tube with polymeric solution, is obtained within a quasi-one-dimensional formulation. Results of the study illustrate the influence of temperature on sound propagation in the system.
Abstract: The effect of tillage technology of maize on intensity of weed infestation and weed species composition was observed at experimental field. Maize is grown consecutively since 2001. The experimental site is situated at an altitude of 230 m above sea level in the Czech Republic. Variants of tillage technology are CT: plowing – conventional tillage 0.22 m, MT: loosening – disc tillage on the depth of 0.1 – 0.12 m, NT: direct sowing – without tillage. The evaluation of weed infestation was carried out by numerical method in years 2012 and 2013. Within the monitoring were found 20 various species of weeds. Conventional tillage (CT) primarily supports the occurrence of perennial weeds (Cirsium arvense, Convolvulus arvensis). Late spring species (Chenopodium album, Echinochloa crus-galli) were more frequently noticed on variants of loosening (MT) and direct sowing (NT). Different tillage causes a significant change of weed species spectrum in maize.