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: Powder metallurgy (P/M) is the only economic way to
produce porous parts/products. P/M can produce near net shape parts
hence reduces wastage of raw material and energy, avoids various
machining operations. The most vital use of P/M is in production of
metallic filters and self lubricating bush bearings and siding surfaces.
The porosity of the part can be controlled by varying compaction
pressure, sintering temperature and composition of metal powder
mix. The present work is aimed for experimental analysis of friction
and wear properties of self lubricating copper and tin bush bearing.
Experimental results confirm that wear rate of sintered component
is lesser for components having 10% tin by weight percentage. Wear
rate increases for high tin percentage (experimented for 20% tin and
30% tin) at same sintering temperature. Experimental results also
confirms that wear rate of sintered component is also dependent on
sintering temperature, soaking period, composition of the preform,
compacting pressure, powder particle shape and size.
Interfacial friction between die and punch, between inter powder
particles, between die face and powder particle depends on
compaction pressure, powder particle size and shape, size and shape
of component which decides size & shape of die & punch, material of
die & punch and material of powder particles.
Abstract: The biosynthesis of nanoparticles by microorganisms,
on the contrary to chemical synthesis, is an environmentally-friendly
process which has low energy requirements. In this investigation, we
used the microorganism Geobacillus wiegelii, strain GWE1, an
aerobic thermophile belonging to genus Geobacillus, isolated from a
drying oven. This microorganism has the ability to reduce selenite
evidenced by the change of color from colorless to red in the culture.
Elemental analysis and composition of the particles were verified
using transmission electron microscopy and energy-dispersive X-ray
analysis. The nanoparticles have a defined spherical shape and a
selenium elemental state. Previous experiments showed that the
presence of the whole microorganism for the reduction of selenite
was not necessary. The results strongly suggested that an intracellular
NADPH/NADH-dependent reductase mediates selenium
nanoparticles synthesis under aerobic conditions. The enzyme was
purified and identified by mass spectroscopy MALDI-TOF TOF
technique. The enzyme is a 1-pyrroline-5-carboxylate dehydrogenase.
Histograms of nanoparticles sizes were obtained. Size distribution
ranged from 40-160 nm, where 70% of nanoparticles have less than
100 nm in size. Spectroscopic analysis showed that the nanoparticles
are composed of elemental selenium. To analyse the effect of pH in
size and morphology of nanoparticles, the synthesis of them was
carried out at different pHs (4.0, 5.0, 6.0, 7.0, 8.0). For
thermostability studies samples were incubated at different
temperatures (60, 80 and 100 ºC) for 1 h and 3 h. The size of all
nanoparticles was less than 100 nm at pH 4.0; over 50% of
nanoparticles have less than 100 nm at pH 5.0; at pH 6.0 and 8.0 over
90% of nanoparticles have less than 100 nm in size. At neutral pH
(7.0) nanoparticles reach a size around 120 nm and only 20% of them
were less than 100 nm. When looking at temperature effect,
nanoparticles did not show a significant difference in size when they
were incubated between 0 and 3 h at 60 ºC. Meanwhile at 80 °C the
nanoparticles suspension lost its homogeneity. A change in size was
observed from 0 h of incubation at 80ºC, observing a size range
between 40-160 nm, with 20% of them over 100 nm. Meanwhile
after 3 h of incubation at size range changed to 60-180 nm with 50%
of them over 100 nm. At 100 °C the nanoparticles aggregate forming
nanorod structures. In conclusion, these results indicate that is
possible to modulate size and shape of biologically synthesized
nanoparticles by modulating pH and temperature.
Abstract: In today’s world, the LED display has been used for
presenting visual information under various circumstances. Such
information is an important intermediary in the human information
processing. Researchers have been investigated diverse factors that
influence this process effectiveness. The letter size is undoubtedly
one major factor that has been tested and recommended by many
standards and guidelines. However, viewing information on the
display from direct perpendicular position is a typical assumption
whereas many actual events are required viewing from the angles.
This current research aims to study the effect of oblique viewing
angle and viewing distance on ability to recognize alphabet, number,
and English word. The total of ten participants was volunteered to our
3 x 4 x 4 within subject study. Independent variables include three
distance levels (2, 6, and 12 m), four oblique angles (0, 45, 60, 75
degree), and four target types (alphabet, number, short word, and
long word). Following the method of constant stimuli our study
suggests that the larger oblique angle, ranging from 0 to 75 degree
from the line of sight, results in significant higher legibility threshold
or larger font size required (p-value < 0.05). Viewing distance factor
also shows to have significant effect on the threshold (p-value
Abstract: In this paper, snow samples containing dust particles
from several sampling points around the city of Ostrava were
analyzed. The pH values of sampled snow were measured and solid
particles analyzed. Particle size, zeta potential and content of selected
heavy metals were determined in solid particles. The pH values of
most samples lay in the slightly acid region. Mean values of particle
size ranged from 290.5 to 620.5 nm. Zeta potential values varied
between -5 and -26.5 mV. The following heavy metal concentration
ranges were found: copper 0.08-0.75 mg/g, lead 0.05-0.9 mg/g,
manganese 0.45-5.9 mg/g and iron 25.7-280.46 mg/g. The highest
values of copper and lead were found in the vicinity of busy
crossroads, and on the contrary, the highest levels of manganese and
iron were detected close to a large steelworks. The proportion
between pH values, zeta potentials, particle sizes and heavy metal
contents was established. Zeta potential decreased with rising pH
values and, simultaneously, heavy metal content in solid particles
increased. At the same time, higher metal content corresponded to
lower particle size.
Abstract: Composite materials have important assets compared
to traditional materials. They bring many functional advantages:
lightness, mechanical resistance and chemical, etc. In the present
study we examine the effect of a circular central notch and a precrack
on the tensile fracture of two woven composite materials. The tensile
tests were applied to a standardized specimen, notched and a
precarcked (orientation of the crack 0°, 45° and 90°). These tensile
tests were elaborated according to an experimental planning design of
the type 23.31 requiring 24 experiments with three repetitions. By the
analysis of regression, we obtained a mathematical model describing
the maximum load according to the influential parameters (hole
diameter, precrack length, angle of a precrack orientation). The
specimens precracked at 90° have a better behavior than those having
a precrack at 45° and still better than those having of the precracks
oriented at 0°. In addition the maximum load is inversely
proportional to the notch size.
Abstract: The most important problem occurs on oil spills in sea
water is to reduce the oil spills size. This study deals with the
development of high pressurized nozzle using dispersion method for
oil leakage in offshore. 3D numerical simulation results were
obtained using ANSYS Fluent 13.0 code and correlate with the
experimental data for validation. This paper studies the contribution
of the process on flow speed and pressure of the flow from two
different geometrical designs of nozzles and to generate a spray
pattern suitable for dispersant application. Factor of size distribution
of droplets generated by the nozzle is calculated using pressures
ranging from 2 to 6 bars. Results obtain from both analyses shows a
significant spray pattern and flow distribution as well as distance.
Results also show a significant contribution on the effect of oil
leakage in terms of the diameter of the oil spills break up.
Abstract: This research studies the electroplating of zinc coating
in the zinc chloride bath mixed with supercritical CO2. The sodium
fluoride (NaF) was used as the bath additive to change the structure
and property of the coating, and therefore the roughness and corrosion
resistance of the zinc coating was investigated. The surface
characterization was performed using optical microscope (OM), X-ray
diffractometer (XRD), and α-step profilometer. Moreover, the
potentiodynamic polarization measurement in 3% NaCl solution was
employed in the corrosion resistance evaluation. Because of the
emulsification of the electrolyte mixed in Sc-CO2, the electroplated
zinc produced the coating with smoother surface, smaller grain, better
throwing power and higher corrosion resistance. The main role played
by the NaF was to reduce the coating’s roughness and grain size. In
other words, the CO2 mixed with the electrolyte under the supercritical
condition performed the similar function as brighter and leveler in zinc
electroplating to enhance the throwing power and corrosion resistance
of the coating.
Abstract: Generally, the traditional Shewhart p chart has been developed by for charting the binomial data. This chart has been developed using the normal approximation with condition as low defect level and the small to moderate sample size. In real applications, however, are away from these assumptions due to skewness in the exact distribution. In this paper, a modified Exponentially Weighted Moving Average (EWMA) control chat for detecting a change in binomial data by improving square root transformations, namely ISRT p EWMA control chart. The numerical results show that ISRT p EWMA chart is superior to ISRT p chart for small to moderate shifts, otherwise, the latter is better for large shifts.
Abstract: A bubbly flow in a vertical miniature tube is analyzed theoretically. The liquid and gas phase are co-current flowing upward. The gas phase is injected via a nozzle whose inner diameter is 0.11mm and it is placed on the axis of the tube. A force balance is applied on the bubble at its detachment. The set of governing equations are solved by use of Mathematica software. The bubble diameter and the bubble generation frequency are determined for various inlet phase velocities represented by the inlet mass quality. The results show different behavior of bubble growth and detachment depending on the tube size.
Abstract: Through the fast growing technologies, design of power factor correction (PFC) circuit is facing several challenges. In this paper, a two-phase interleaved boost converter with ripple steering technique is proposed. Among the various topologies, Interleaved Boost converter (IBC) is considered as superior due to enriched performance, lower ripple content, compact weight and size. A thorough investigation is presented here for the proposed topology. Simulation study for the IBC has been carried out using MATLAB/SIMULINK. Theoretical analysis and hardware prototype has been performed to validate the results.
Abstract: It is well-known as Fitts’ law that the time for a user to point a target on a GUI screen can be modeled as a linear function of “index of difficulty (ID).” In this paper, the authors investigate whether the traditional ID formulation is appropriate independently of device screen sizes. Result of our experiment reveals that the ID formulation may not consistently capture actual difficulty: users’ pointing performances are not consistent among pointing target variations of which index of difficulty are consistent. The term A/W may not be appropriate because the term causes the observed inconsistency. Based on this finding, the authors then evaluate the applicability of possible models other than Fitts’ one. Multiple regression models are found to be able to appropriately represent the effects of target design variations. The authors next make an attempt to improve the definition of ID in Fitts’ model. Our idea is to raise the size or the distance values depending on the screen size. The modified model is found to fit well to the users’ pointing data, which supports the idea.
Abstract: The two common approaches to Structural Equation Modeling (SEM) are the Covariance-Based SEM (CB-SEM) and Partial Least Squares SEM (PLS-SEM). There is much debate on the performance of CB-SEM and PLS-SEM for small sample size and when distributions are nonnormal. This study evaluates the performance of CB-SEM and PLS-SEM under normality and nonnormality conditions via a simulation. Monte Carlo Simulation in R programming language was employed to generate data based on the theoretical model with one endogenous and four exogenous variables. Each latent variable has three indicators. For normal distributions, CB-SEM estimates were found to be inaccurate for small sample size while PLS-SEM could produce the path estimates. Meanwhile, for a larger sample size, CB-SEM estimates have lower variability compared to PLS-SEM. Under nonnormality, CB-SEM path estimates were inaccurate for small sample size. However, CB-SEM estimates are more accurate than those of PLS-SEM for sample size of 50 and above. The PLS-SEM estimates are not accurate unless sample size is very large.
Abstract: Securing the data stored on E-passport is a very important issue. RSA encryption algorithm is suitable for such application with low data size. In this paper the design and implementation of 1024 bit-key RSA encryption and decryption module on an FPGA is presented. The module is verified through comparing the result with that obtained from MATLAB tools. The design runs at a frequency of 36.3 MHz on Virtex-5 Xilinx FPGA. The key size is designed to be 1024-bit to achieve high security for the passport information. The whole design is achieved through VHDL design entry which makes it a portable design and can be directed to any hardware platform.
Abstract: Pumping systems are an integral part of water desalination plants, their effective functioning is vital for the operation of a plant. In this research work, the reliability and availability of pressurized pumps in a reverse osmosis desalination plant are studied with the objective of finding configurations that provides optimal performance. Six configurations of a series system with different number of warm and cold standby components were examined. Closed form expressions for the mean time to failure (MTTF) and the long run availability are derived and compared under the assumption that the time between failures and repair times of the primary and standby components are exponentially distributed. Moreover, a cost/ benefit analysis is conducted in order to identify a configuration with the best performance and least cost. It is concluded that configurations with cold standby components are preferable especially when the pumps are of the size.
Abstract: Two types of crushing were applied to grains of red sorghum: manual crushing using a mortar and pestle of kitchen and mechanical crushing using a hammer mill. The flours obtained at the end of these various crushing were filtered and subdivided in different fractions according to the diameters of the mesh of the sieves (0.16mm; 0.25mm; 0.315mm; 0.4mm, and 0.63mm…). Some physical, chemical and nutritional traits of these flours were evaluated using Association of Official Analytical Chemists (AOAC). In vitro digestibility of these flours was also studied with freezing of flour 1% like substrate and α-amylase from B. licheniformis (E.C.3.2.1.1; Megazyme, Wicklow, Ireland). The results revealed that the batches of flours which have the finest diameters as 0.16mm; 0.25mm are the richest one in nutrients and are also the most digestible. Also mechanical crushing is the best mean to obtain significant amount of flours. In conclusion, the type of crushing and the size of the particles have an impact on the final concentration of some nutrients of the flours obtained. Indeed, the finest particles (0.16mm – 0.25mm 0.315mm) obtained after sifting of the flours are more nutritive and have a better digestibility than others size. So the finest particles could be advised for management of cereals namely the sorghum for the production of the infantile foods.
Abstract: The present work involves measurements to examine
the effects of initial conditions on aerodynamic and acoustic
characteristics of a Jet at M=0.8 by changing the orientation of sharp
edged orifice plate. A thick plate with chamfered orifice presented divergent and convergent openings when it was flipped over. The centerline velocity was found to decay more rapidly for divergent
orifice and that was consistent with the enhanced mass entrainment
suggesting quicker spread of the jet compared with that from the convergent orifice. The mixing layer region elucidated this effect of
initial conditions at an early stage – the growth was found to be comparatively more pronounced for the divergent orifice resulting in
reduced potential core size. The acoustic measurements, carried out in the near field noise region outside the jet within potential core
length, showed the jet from the divergent orifice to be less noisy. The frequency spectra of the noise signal exhibited that in the initial
region of comparatively thin mixing layer for the convergent orifice,
the peak registered a higher SPL and a higher frequency as well. The noise spectra and the mixing layer development suggested a direct correlation between the coherent structures developing in the initial
region of the jet and the noise captured in the surrounding near field.
Abstract: Many advanced Routing protocols for wireless sensor networks have been implemented for the effective routing of data. Energy awareness is an essential design issue and almost all of these routing protocols are considered as energy efficient and its ultimate objective is to maximize the whole network lifetime. However, the introductions of video and imaging sensors have posed additional challenges. Transmission of video and imaging data requires both energy and QoS aware routing in order to ensure efficient usage of the sensors and effective access to the gathered measurements. In this paper, the performance of the energy-aware QoS routing Protocol are analyzed in different performance metrics like average lifetime of a node, average delay per packet and network throughput. The parameters considered in this study are end-to-end delay, real time data generation/capture rates, packet drop probability and buffer size. The network throughput for realtime and non-realtime data was also has been analyzed. The simulation has been done in NS2 simulation environment and the simulation results were analyzed with respect to different metrics.
Abstract: The present study describes the biosynthesis of a milkclotting
protease by solid state fermentation (SSF) of a locally
isolated mould, Rhizopus stolonifer. The production medium was
prepared using wheat bran at 50% (w/v). The production conditions
are optimized by varying 7 parameters: carbon and nitrogen sources,
medium moisture, temperature, pH, fermentation time and
inoculum-s size. The maximum enzyme synthesis was measured after
96 h of incubation time at temperature of 28°C. The optimum pH
determined was 6 and the inoculum size was 3.106spores/ml. The
optimum initial moisture content is comprised between 50 to 70%.
The formation of milk clotting protease is enhanced when galactose
and peptone are used at 10% (w/v) and 1% (w/v) concentrations
respectively. The maximum production of milk clotting protease is
120 US/ml.
Abstract: Software development has experienced remarkable progress in the past decade. However, due to the rising complexity and magnitude of the project the development productivity has not been consistently improved. By analyzing the latest ISBSG data repository with 4106 projects, we discovered that software development productivity has actually undergone irregular variations between the years 1995 and 2005. Considering the factors significant to the productivity, we found its variations are primarily caused by the variations of average team size and the unbalanced uses of the less productive language 3GL.