Abstract: By the application of an improved back-propagation
neural network (BPNN), a model of current densities for a solid oxide
fuel cell (SOFC) with 10 layers is established in this study. To build
the learning data of BPNN, Taguchi orthogonal array is applied to
arrange the conditions of operating parameters, which totally 7 factors
act as the inputs of BPNN. Also, the average current densities
achieved by numerical method acts as the outputs of BPNN.
Comparing with the direct solution, the learning errors for all learning
data are smaller than 0.117%, and the predicting errors for 27
forecasting cases are less than 0.231%. The results show that the
presented model effectively builds a mathematical algorithm to predict
performance of a SOFC stack immediately in real time.
Also, the calculating algorithms are applied to proceed with the
optimization of the average current density for a SOFC stack. The
operating performance window of a SOFC stack is found to be
between 41137.11 and 53907.89. Furthermore, an inverse predicting
model of operating parameters of a SOFC stack is developed here by
the calculating algorithms of the improved BPNN, which is proved to
effectively predict operating parameters to achieve a desired
performance output of a SOFC stack.
Abstract: The effect of time-periodic oscillations of the Rayleigh- Benard system on the heat transport in dielectric liquids is investigated by weakly nonlinear analysis. We focus on stationary convection using the slow time scale and arrive at the real Ginzburg- Landau equation. Classical fourth order Runge-kutta method is used to solve the Ginzburg-Landau equation which gives the amplitude of convection and this helps in quantifying the heat transfer in dielectric liquids in terms of the Nusselt number. The effect of electrical Rayleigh number and the amplitude of modulation on heat transport is studied.
Abstract: Building Sector is the major electricity consumer and
it is costly to building owners. Therefore the application of thermal
energy storage (TES) has gained attractive to reduce energy cost.
Many attractive tariff packages are being offered by the electricity
provider to promote TES. The tariff packages offered higher cost of
electricity during peak period and lower cost of electricity during off
peak period. This paper presented the return of initial investment by
implementing a centralized air-conditioning plant integrated with
thermal energy storage with partially operation strategies. Building
load profile will be calculated hourly according to building
specification and building usage trend. TES operation conditions will
be designed according to building load demand profile, storage
capacity, tariff packages and peak/off peak period. The Payback
Period analysis method was used to evaluate economic analysis. The
investment is considered a good investment where by the initial cost
is recovered less than ten than seven years.
Abstract: The main goal of the study is to analyze all relevant
properties of the electro hydraulic systems and based on that to make
a proper choice of the control strategy that may be used for the
control of the servomechanism system. A combination of electronic
and hydraulic systems is widely used since it combines the
advantages of both. Hydraulic systems are widely spread because of
their properties as accuracy, flexibility, high horsepower-to-weight
ratio, fast starting, stopping and reversal with smoothness and
precision, and simplicity of operations. On the other hand, the
modern control of hydraulic systems is based on control of the circuit
fed to the inductive solenoid that controls the position of the
hydraulic valve. Since this circuit may be easily handled by PWM
(Pulse Width Modulation) signal with a proper frequency, the
combination of electrical and hydraulic systems became very fruitful
and usable in specific areas as airplane and military industry.
The study shows and discusses the experimental results obtained
by the control strategy (classical feedback (PID) & neural network)
using MATLAB and SIMULINK [1]. Finally, the special attention
was paid to the possibility of neuro-controller design and its
application to control of electro-hydraulic systems and to make
comparative with classical control.
Abstract: This study was designed to formulate,
pharmaceutically evaluate a topical skin-care cream (w/o emulsion)
of Aloe Vera versus its vehicle (Base) as control and determine their
effects on Stratum Corneum (SC) water content and Transepidermal
water loss (TEWL). Base containing no extract and a Formulation
containing 3% concentrated extract of Aloe Vera was developed by
entrapping in the inner aqueous phase of w/o emulsion (cream).
Lemon oil was incorporated to improve the odor. Both the Base and
Formulation were stored at 8°C ±0.1°C (in refrigerator), 25°C±0.1°C,
40°C±0.1°C and 40°C± 0.1°C with 75% RH (in incubator) for a
period of 4 weeks to predict their stability. The evaluation parameters
consisted of color, smell, type of emulsion, phase separation,
electrical conductivity, centrifugation, liquefaction and pH. Both the
Base and Formulation were applied to the cheeks of 21 healthy
human volunteers for a period of 8 weeks Stratum corneum (SC)
water content and Transepidermal water loss (TEWL) were
monitored every week to measure any effect produced by these
topical creams. The expected organoleptic stability of creams was
achieved from 4 weeks in-vitro study period. Odor was disappeared
with the passage of time due to volatilization of lemon oil. Both the
Base and Formulation produced significant (p≤0.05) changes in
TEWL with respect to time. SC water content was significantly
(p≤0.05) increased by the Formulation while the Base has
insignificant (p 0.05) effects on SC water content. The newly
formulated cream of Aloe Vera, applied is suitable for improvement
and quantitative monitoring of skin hydration level (SC water
content/ moisturizing effects) and reducing TEWL in people with dry
skin.
Abstract: Nanostructured materials have attracted many
researchers due to their outstanding mechanical and physical
properties. For example, carbon nanotubes (CNTs) or carbon
nanofibres (CNFs) are considered to be attractive reinforcement
materials for light weight and high strength metal matrix composites.
These composites are being projected for use in structural
applications for their high specific strength as well as functional
materials for their exciting thermal and electrical characteristics. The
critical issues of CNT-reinforced MMCs include processing
techniques, nanotube dispersion, interface, strengthening mechanisms
and mechanical properties. One of the major obstacles to the effective
use of carbon nanotubes as reinforcements in metal matrix
composites is their agglomeration and poor distribution/dispersion
within the metallic matrix. In order to tap into the advantages of the
properties of CNTs (or CNFs) in composites, the high dispersion of
CNTs (or CNFs) and strong interfacial bonding are the key issues
which are still challenging. Processing techniques used for synthesis
of the composites have been studied with an objective to achieve
homogeneous distribution of carbon nanotubes in the matrix.
Modified mechanical alloying (ball milling) techniques have emerged
as promising routes for the fabrication of carbon nanotube (CNT)
reinforced metal matrix composites. In order to obtain a
homogeneous product, good control of the milling process, in
particular control of the ball movement, is essential. The control of
the ball motion during the milling leads to a reduction in grinding
energy and a more homogeneous product. Also, the critical inner
diameter of the milling container at a particular rotational speed can
be calculated. In the present work, we use conventional and modified
mechanical alloying to generate a homogenous distribution of 2 wt.
% CNT within Al powders. 99% purity Aluminium powder (Acros,
200mesh) was used along with two different types of multiwall
carbon nanotube (MWCNTs) having different aspect ratios to
produce Al-CNT composites. The composite powders were processed
into bulk material by compaction, and sintering using a cylindrical
compaction and tube furnace. Field Emission Scanning electron
microscopy (FESEM), X-Ray diffraction (XRD), Raman
spectroscopy and Vickers macro hardness tester were used to
evaluate CNT dispersion, powder morphology, CNT damage, phase
analysis, mechanical properties and crystal size determination.
Despite the success of ball milling in dispersing CNTs in Al powder,
it is often accompanied with considerable strain hardening of the Al
powder, which may have implications on the final properties of the
composite. The results show that particle size and morphology vary
with milling time. Also, by using the mixing process and sonication
before mechanical alloying and modified ball mill, dispersion of the
CNTs in Al matrix improves.
Abstract: Leading topic of this article is description of Lorentz
forces in the container with cuboid and cylindrical shape. Inside of
the container is an electrically conductive melt. This melt is driven by
rotating magnetic field. Input data for comparing Lorentz forces in
the container with cuboid shape were obtained from the computing
program NS-FEM3D, which uses DDS method of computing. Values
of Lorentz forces for container with cylindrical shape were obtained
from inferred analytical formula.
Abstract: The great majority of the electric installations belong
to the first and second category. In order to ensure a high level of
reliability of their electric system feeder, two power supply sources
are envisaged, one principal, the other of reserve, generally a cold
reserve (electric diesel group).
The principal source being under operation, its control can be ideal
and sure, however for the reserve source being in stop, a preventive
maintenance-s which proceeds on time intervals (periodicity) and
for well defined lengths of time are envisaged, so that this source will
always available in case of the principal source failure.
The choice of the periodicity of preventive maintenance of the
source of reserve influences directly the reliability of the electric
feeder system. On the basis of the semi-markovians processes, the
influence of the periodicity of the preventive maintenance of the
source of reserve is studied and is given the optimal periodicity.
Abstract: An array of piezoelectric micro actuators can be used
for radiation of an ultrasonic carrier signal modulated in amplitude
with an acoustic signal, which yields audio frequency applications as
the air acts as a self-demodulating medium. This application is
known as the parametric array. We propose a parametric array with
array elements based on existing piezoelectric micro ultrasonic
transducer (pMUT) design techniques. In order to reach enough
acoustic output power at a desired operating frequency, a proper ratio
between number of array elements and array size needs to be used,
with an array total area of the order of one cm square. The
transducers presented are characterized via impedance, admittance,
noise figure, transducer gain and frequency responses.
Abstract: We have modeled the effect of a graded band gap
window on the performance of a single junction AlxGa1-xAs/GaAs
solar cell. First, we study the electrical characteristics of a single
junction AlxGa1-xAs/GaAs solar cell, by employing an optimized
structure for this solar cell, we show that grading the band gap of the
window can increase the conversion efficiency of the solar cell by
about 1.5%, and can also improve the quantum efficiency of the solar
cell especially at shorter wavelengths.
Abstract: A network of coupled stochastic oscillators is
proposed for modeling of a cluster of entangled qubits that is
exploited as a computation resource in one-way quantum
computation schemes. A qubit model has been designed as a
stochastic oscillator formed by a pair of coupled limit cycle
oscillators with chaotically modulated limit cycle radii and
frequencies. The qubit simulates the behavior of electric field of
polarized light beam and adequately imitates the states of two-level
quantum system. A cluster of entangled qubits can be associated
with a beam of polarized light, light polarization degree being
directly related to cluster entanglement degree. Oscillatory network,
imitating qubit cluster, is designed, and system of equations for
network dynamics has been written. The constructions of one-qubit
gates are suggested. Changing of cluster entanglement degree caused
by measurements can be exactly calculated.
Abstract: The electrical substation components are often subject to degradation due to over-voltage or over-current, caused by a short circuit or a lightning. A particular interest is given to the circuit breaker, regarding the importance of its function and its dangerous failure. This component degrades gradually due to the use, and it is also subject to the shock process resulted from the stress of isolating the fault when a short circuit occurs in the system. In this paper, based on failure mechanisms developments, the wear out of the circuit breaker contacts is modeled. The aim of this work is to evaluate its reliability and consequently its residual lifetime. The shock process is based on two random variables such as: the arrival of shocks and their magnitudes. The arrival of shocks was modeled using homogeneous Poisson process (HPP). By simulation, the dates of short-circuit arrivals were generated accompanied with their magnitudes. The same principle of simulation is applied to the amount of cumulative wear out contacts. The objective reached is to find the formulation of the wear function depending on the number of solicitations of the circuit breaker.
Abstract: Two completely different approaches for a Gigabit
Ethernet compliant stream transmission over 50m of 1mm PMMA SI-POF have been experimentally demonstrated and are compared in this paper. The first solution is based on a commercial RC-LED
transmission and a careful optimization of the physical layer architecture, realized during the POF-PLUS EU Project. The second solution exploits the performance of an edge-emitting laser at the
transmitter side in order to avoid any sort of electrical equalization at the receiver side.
Abstract: Effect of temperature and light was investigated on a
thin film of organic semiconductor formyl-TIPPCu(II) deposited on a
glass substrate with preliminary evaporated gold electrodes. The
electrical capacitance and resistance of the fabricated device were
evaluated under the effect of temperature and light. The relative
capacitance of the fabricated sensor increased by 4.3 times by rising
temperature from 27 to 1870C, while under illumination up to 25000
lx, the capacitance of the Au/formyl-TIPPCu(II)/Au photo capacitive
sensor increased continuously by 13.2 times as compared to dark
conditions.
Abstract: In this paper, an artificial neural network simulator is
employed to carry out diagnosis and prognosis on electric motor as
rotating machinery based on predictive maintenance. Vibration data
of the primary failed motor including unbalance, misalignment and
bearing fault were collected for training the neural network. Neural
network training was performed for a variety of inputs and the motor
condition was used as the expert training information. The main
purpose of applying the neural network as an expert system was to
detect the type of failure and applying preventive maintenance. The
advantage of this study is for machinery Industries by providing
appropriate maintenance that has an essential activity to keep the
production process going at all processes in the machinery industry.
Proper maintenance is pivotal in order to prevent the possible failures
in operating system and increase the availability and effectiveness of
a system by analyzing vibration monitoring and developing expert
system.
Abstract: This paper presents a microstrip meandered open
circuited stub with bandstop characteristic. The proposed structure is
designed on a high frequency laminate with dielectric constant of 4.0
and board thickness of 0.508 millimeters. The scattering parameters
and electromagnetic field distributions at various frequencies are
investigated by modeling the structure with three dimensional
electromagnetic simulation tool. In order to describe the resonant
and bandstop characteristic of the meandered open circuited stub, a
Smith chart as well as electric field at various frequencies and phases
is illustrated accordingly. The structure can be an alternative method
in suppressing the harmonic response of a bandpass filter.
Abstract: The development of the power electronics has allowed
increasing the precision and reliability of the electrical devices, thanks
to the adjustable inverters, as the Pulse Wide Modulation (PWM)
applied to the three level inverters, which is the object of this study.
The authors treat the relation between the law order adopted for a
given system and the oscillations of the electrical and mechanical
parameters of which the tolerance depends on the process with which
they are integrated (paper factory, lifting of the heavy loads,
etc.).Thus, the best choice of the regulation indexes allows us to
achieve stability and safety training without investment (management
of existing equipment). The optimal behavior of any electric device
can be achieved by the minimization of the stored electrical and
mechanical energy.
Abstract: Technology of thin film deposition is of interest in
many engineering fields, from electronic manufacturing to corrosion
protective coating. A typical deposition process, like that developed
at the University of Eindhoven, considers the deposition of a thin,
amorphous film of C:H or of Si:H on the substrate, using the
Expanding Thermal arc Plasma technique. In this paper a computing
procedure is proposed to simulate the flow field in a deposition
chamber similar to that at the University of Eindhoven and a
sensitivity analysis is carried out in terms of: precursor mass flow
rate, electrical power, supplied to the torch and fluid-dynamic
characteristics of the plasma jet, using different nozzles. To this
purpose a deposition chamber similar in shape, dimensions and
operating parameters to the above mentioned chamber is considered.
Furthermore, a method is proposed for a very preliminary evaluation
of the film thickness distribution on the substrate. The computing
procedure relies on two codes working in tandem; the output from
the first code is the input to the second one. The first code simulates
the flow field in the torch, where Argon is ionized according to the
Saha-s equation, and in the nozzle. The second code simulates the
flow field in the chamber. Due to high rarefaction level, this is a
(commercial) Direct Simulation Monte Carlo code. Gas is a mixture
of 21 chemical species and 24 chemical reactions from Argon plasma
and Acetylene are implemented in both codes. The effects of the
above mentioned operating parameters are evaluated and discussed
by 2-D maps and profiles of some important thermo-fluid-dynamic
parameters, as per Mach number, velocity and temperature. Intensity,
position and extension of the shock wave are evaluated and the
influence of the above mentioned test conditions on the film
thickness and uniformity of distribution are also evaluated.
Abstract: ZnO nanocrystals with mean diameter size 14 nm
have been prepared by precipitation method, and examined as
photocatalyst for the UV-induced degradation of insecticide diazinon
as deputy of organic pollutant in aqueous solution. The effects of
various parameters, such as illumination time, the amount of
photocatalyst, initial pH values and initial concentration of
insecticide on the photocatalytic degradation diazinon were
investigated to find desired conditions. In this case, the desired
parameters were also tested for the treatment of real water containing
the insecticide. Photodegradation efficiency of diazinon was
compared between commercial and prepared ZnO nanocrystals. The
results indicated that UV/ZnO process applying prepared
nanocrystalline ZnO offered electrical energy efficiency and
quantum yield better than commercial ZnO. The present study, on the
base of Langmuir-Hinshelwood mechanism, illustrated a pseudo
first-order kinetic model with rate constant of surface reaction equal
to 0.209 mg l-1 min-1 and adsorption equilibrium constant of 0.124 l
mg-1.
Abstract: Under the limitation of investment budget, a utility
company is required to maximize the utilization of their existing
assets during their life cycle satisfying both engineering and financial
requirements. However, utility does not have knowledge about the
status of each asset in the portfolio neither in terms of technical nor
financial values. This paper presents a knowledge based model for
the utility companies in order to make an optimal decision on power
transformer with their utilization. CommonKADS methodology, a
structured development for knowledge and expertise representation,
is utilized for designing and developing knowledge based model. A
case study of One MVA power transformer of Nepal Electricity
Authority is presented. The results show that the reusable knowledge
can be categorized, modeled and utilized within the utility company
using the proposed methodologies. Moreover, the results depict that
utility company can achieve both engineering and financial benefits
from its utilization.