Abstract: This research describes a voltammetric approach to determine amounts of vitamin C (Ascorbic acid) in orange juice sample, using three screen printed electrode. The anodic currents of vitamin C were proportional to vitamin C concentration in the range of 0 – 10.0 mM with the limit of detection of 1.36 mM. The method was successfully employed with 2 µL of the working solution dropped on the electrode surface. The proposed method was applied for the analysis of vitamin C in packed orange juice without sample purification or complexion of sample preparation step.
Abstract: The shortage of the automotive market in relation
to options for sources of high power car audio systems, led to
development of this work. Thus, we developed a source with stabilized
voltage with 4320 W effective power. Designed to the voltage of
14.4 V and a choice of two currents: 30 A load option in battery
banks and 300 A at full load. This source can also be considered as
a source of general use dedicated commercial with a simple control
circuit in analog form based on discrete components. The assembly of
power circuit uses a methodology for higher power than the initially
stipulated.
Abstract: Power quality in terms of power factor, THD and precisely regulated output voltage are the major key factors for efficient operation of power electronic converters. This paper presents an easy and effective active wave shaping control scheme for the pulsed input current drawn by the uncontrolled diode bridge rectifier thereby achieving power factor nearer to unity and also satisfying the THD specifications. It also regulates the output DC-bus voltage. CCM boost power factor correction with constant frequency operation features smaller inductor current ripple resulting in low RMS currents on inductor and switch thus leading to low electromagnetic interference. The objective of this work is to develop an active PFC control circuit using CCM boost converter implementing variable duty cycle control. The proposed scheme eliminates inductor current sensing requirements yet offering good performance and satisfactory results for maintaining the power quality. Simulation results have been presented which covers load changes also.
Abstract: Rogowski coils are increasingly used for measurement
of AC and transient electric currents. Mostly used Rogowski coils
now are with circular or rectangular cores. In order to increase the
sensitivity of the measurement of Rogowski coil and perform smooth
wire winding, this paper studies the effect of increasing the mutual
inductance in order to increase the coil sensitivity by presenting the
calculation and simulation of a Rogowski coil with equilateral
hexagonal shaped core and comparing the resulted mutual inductance
with commonly used core shapes.
Abstract: Cavitation is one of the most well-known process faults that may occur in different industrial equipment especially centrifugal pumps. Cavitation also may happen in water pumps and turbines. Sometimes cavitation has been severe enough to wear holes in the impeller and damage the vanes to such a degree that the impeller becomes very ineffective. More commonly, the pump efficiency will decrease significantly during cavitation and continue to decrease as damage to the impeller increases. Typically, when cavitation occurs, an audible sound similar to ‘marbles’ or ‘crackling’ is reported to be emitted from the pump. In this paper, the most effective monitoring items and techniques in detecting cavitation discussed in details. Besides, some successful solutions for solving this problem for sea water vertical Centrifugal lift Pump discussed through a case history related to Iran oil industry. Furthermore, balance line modification, strainer choking and random resonance in sea water pumps discussed. In addition, a new Method for diagnosing mechanical conditions of sea water vertical Centrifugal lift Pumps introduced. This method involves disaggregating bus current by device into disaggregated currents having correspondences with operating currents in response to measured bus current. Moreover, some new patents and innovations in mechanical sea water pumping and cooling systems discussed in this paper.
Abstract: This paper presents an idea for analog current comparison which compares input signal and reference currents with high speed and accuracy. Proposed circuit utilizes amplification properties of common gate configuration, where voltage variations of input current are amplified and a compared output voltage is developed. Cascaded inverter stages are used to generate final CMOS compatible output voltage. Power consumption of circuit can be controlled by the applied gate bias voltage. The comparator is designed and studied at 180nm CMOS process technology for a supply voltage of 3V.
Abstract: We study a Dirichlet boundary value problem for Lane-Emden equation involving two fractional orders. Lane-Emden equation has been widely used to describe a variety of phenomena in physics and astrophysics, including aspects of stellar structure, the thermal history of a spherical cloud of gas, isothermal gas spheres,and thermionic currents. However, ordinary Lane-Emden equation does not provide the correct description of the dynamics for systems in complex media. In order to overcome this problem and describe dynamical processes in a fractalmedium, numerous generalizations of Lane-Emden equation have been proposed. One such generalization replaces the ordinary derivative by a fractional derivative in the Lane-Emden equation. This gives rise to the fractional Lane-Emden equation with a single index. Recently, a new type of Lane-Emden equation with two different fractional orders has been introduced which provides a more flexible model for fractal processes as compared with the usual one characterized by a single index. The contraction mapping principle and Krasnoselskiis fixed point theorem are applied to prove the existence of solutions of the problem in a Banach space. Ulam-Hyers stability for iterative Cauchy fractional differential equation is defined and studied.
Abstract: This paper presents a new compact analytical model of
the gate leakage current in high-k based nano scale MOSFET by
assuming a two-step inelastic trap-assisted tunneling (ITAT) process
as the conduction mechanism. This model is based on an inelastic
trap-assisted tunneling (ITAT) mechanism combined with a semiempirical
gate leakage current formulation in the BSIM 4 model. The
gate tunneling currents have been calculated as a function of gate
voltage for different gate dielectrics structures such as HfO2, Al2O3
and Si3N4 with EOT (equivalent oxide thickness) of 1.0 nm. The
proposed model is compared and contrasted with santaurus
simulation results to verify the accuracy of the model and excellent
agreement is found between the analytical and simulated data. It is
observed that proposed analytical model is suitable for different highk
gate dielectrics simply by adjusting two fitting parameters. It was
also shown that gate leakages reduced with the introduction of high-k
gate dielectric in place of SiO2.
Abstract: Heterogeneous repolarization causes dispersion of the T-wave and has been linked to arrhythmogenesis. Such heterogeneities appear due to differential expression of ionic currents in different regions of the heart, both in healthy and diseased animals and humans. Mice are important animals for the study of heart diseases because of the ability to create transgenic animals. We used our previously reported model of mouse ventricular myocytes to develop 2D mouse ventricular tissue model consisting of 14,000 cells (apical or septal ventricular myocytes) and to study the stability of action potential propagation and Ca2+ dynamics. The 2D tissue model was implemented as a FORTRAN program code for highperformance multiprocessor computers that runs on 36 processors. Our tissue model is able to simulate heterogeneities not only in action potential repolarization, but also heterogeneities in intracellular Ca2+ transients. The multicellular model reproduced experimentally observed velocities of action potential propagation and demonstrated the importance of incorporation of realistic Ca2+ dynamics for action potential propagation. The simulations show that relatively sharp gradients of repolarization are predicted to exist in 2D mouse tissue models, and they are primarily determined by the cellular properties of ventricular myocytes. Abrupt local gradients of channel expression can cause alternans at longer pacing basic cycle lengths than gradual changes, and development of alternans depends on the site of stimulation.
Abstract: This paper presents the development of a wavelet
based algorithm, for distinguishing between magnetizing inrush
currents and power system fault currents, which is quite adequate,
reliable, fast and computationally efficient tool. The proposed
technique consists of a preprocessing unit based on discrete wavelet
transform (DWT) in combination with an artificial neural network
(ANN) for detecting and classifying fault currents. The DWT acts as
an extractor of distinctive features in the input signals at the relay
location. This information is then fed into an ANN for classifying
fault and magnetizing inrush conditions. A 220/55/55 V, 50Hz
laboratory transformer connected to a 380 V power system were
simulated using ATP-EMTP. The DWT was implemented by using
Matlab and Coiflet mother wavelet was used to analyze primary
currents and generate training data. The simulated results presented
clearly show that the proposed technique can accurately discriminate
between magnetizing inrush and fault currents in transformer
protection.
Abstract: The morphological short-term evolution of Ponta do Tubarão Island (PTI) was investigated through high accurate surveys based on post-processed kinematic (PPK) relative positioning on Global Navigation Satellite Systems (GNSS). PTI is part of a barrier island system on a high energy northeast Brazilian coastal environment and also an area of high environmental sensitivity. Surveys were carried out quarterly over a two years period from May 2010 to May 2012. This paper assesses statically the performance of digital elevation models (DEM) derived from different interpolation methods to represent morphologic features and to quantify volumetric changes and TIN models shown the best results to that purposes. The MDE allowed quantifying surfaces and volumes in detail as well as identifying the most vulnerable segments of the PTI to erosion and/or accumulation of sediments and relate the alterations to climate conditions. The coastal setting and geometry of PTI protects a significant mangrove ecosystem and some oil and gas facilities installed in the vicinities from damaging effects of strong oceanwaves and currents. Thus, the maintenance of PTI is extremely required but the prediction of its longevity is uncertain because results indicate an irregularity of sedimentary balance and a substantial decline in sediment supply to this coastal area.
Abstract: Recently, permeable breakwaters have been suggested to overcome the disadvantages of fully protection breakwaters. These protection structures have minor impacts on the coastal environment and neighboring beaches where they provide a more economical protection from waves and currents. For regular waves, a numerical model is used (FLOW-3D, VOF) to investigate the hydraulic performance of a permeable breakwater. The model of permeable breakwater consists of a pair of identical vertical slotted walls with an impermeable upper and lower part, where the draft is a decimal multiple of the total depth. The middle part is permeable with a porosity of 50%. The second barrier is located at distant of 0.5 and 1.5 of the water depth from the first one. The numerical model is validated by comparisons with previous laboratory data and semi-analytical results of the same model. A good agreement between the numerical results and both laboratory data and semi-analytical results has been shown and the results indicate the applicability of the numerical model to reproduce most of the important features of the interaction. Through the numerical investigation, the friction factor of the model is carefully discussed.
Abstract: Statistical analysis of electrophysiological recordings
obtained under, e.g. tactile, stimulation frequently suggests participation
in the network dynamics of experimentally unobserved “hidden"
neurons. Such interneurons making synapses to experimentally
recorded neurons may strongly alter their dynamical responses to
the stimuli. We propose a mathematical method that formalizes this
possibility and provides an algorithm for inferring on the presence
and dynamics of hidden neurons based on fitting of the experimental
data to spike trains generated by the network model. The model
makes use of Integrate and Fire neurons “chemically" coupled
through exponentially decaying synaptic currents. We test the method
on simulated data and also provide an example of its application to
the experimental recording from the Dorsal Column Nuclei neurons
of the rat under tactile stimulation of a hind limb.
Abstract: In this paper, we analyze the rotor eddy currents losses provoqued by the stator slot harmonics developed in the permanent magnets or pole pieces of synchronous machines. An analytical approach is presented to evaluate the effect of slot ripples on rotor field and losses calculation. This analysis is then tested on a model by 2D/3D finite element (FE) calculation. The results show a good agreement on loss calculations when skin effect is negligible and the magnet is considered.
Abstract: Both prognostic and diagnostic modes of a 3D baroclinic
model in hydrodynamic and sediment transport models of
the Princeton Ocean Model (POM) were conducted to separate
prognose and diagnose effects of different hydrodynamic factors on
transport of suspended sediment discharged from the rivers to the
Gulf of Thailand (GoT). Both transport modes of suspended sediment
distribution in the GoT were numerically simulated. It could be
concluded that the suspended sediment discharged from the rivers
around the GoT. Most of sediments in estuaries and coastal areas are
deposited outside the GoT under the condition of wind-driven current,
and very small amount of the sediments of them are transported
faraway. On the basis of wind forcing, sediments from the lower
GoT to the upper GoT are mainly transported south-northwestward
and also continuously moved north-southwestward. An obvious 3D
characteristic of suspended sediment transport is produced in the
wind-driven current residual circulation condition. In this study, the
transport patterns at the third layer are generally consistent with
the typhoon-induced strong currents in two case studies of Typhoon
Linda 1997. The case studies presented the prognostic and diagnostic
modes during 00UTC28OCT1997 to 12UTC06NOV1997 in a short
period with the current condition for pre-operation of the suspended
sediment transport model in estuaries and coastal areas.
Abstract: A numerical investigation has carried out to understand the melting characteristics of phase change material (PCM) in a fin type latent heat storage with the addition of embedded aluminum spiral fillers. It is known that melting performance of PCM can be significantly improved by increasing the number of embedded metallic fins in the latent heat storage system but to certain values where only lead to small improvement in heat transfer rate. Hence, adding aluminum spiral fillers within the fin gap can be an option to improve heat transfer internally. This paper presents extensive computational visualizations on the PCM melting patterns of the proposed fin-spiral fillers configuration. The aim of this investigation is to understand the PCM-s melting behaviors by observing the natural convection currents movement and melting fronts formation. Fluent 6.3 simulation software was utilized in producing twodimensional visualizations of melting fractions, temperature distributions and flow fields to illustrate the melting process internally. The results show that adding aluminum spiral fillers in Fin type latent heat storage can promoted small but more active natural convection currents and improve melting of PCM.
Abstract: One of the efficient factors in comprehensive
development of an area is to provide water sources and on the other
hand the appropriate management of them. Population growth and
nourishment security for such a population necessitate the
achievement of constant development besides the reforming of
traditional management in order to increase the profit of sources; In
this case, the constant exploitation of sources for the next generations
will be considered in this program. The achievement of this
development without the consideration and possibility of water
development will be too difficult. Zayanderood basin with 41500
areas in square kilometers contains 7 sub-basins and 20 units of
hydrologic. In this basin area, from the entire environment
descending, just a small part will enter into the river currents and the
rest will be out of efficient usage by various ways. The most
important surface current of this basin is Zayanderood River with
403 kilometers length which is originated from east slopes of Zagros
mount and after draining of this basin area it will enter into
Gaavkhooni pond. The existence of various sources and
consumptions of water in Zayanderood basin, water transfer of the
other basin areas into this basin, of course the contradiction between
the upper and lower beneficiaries, the existence of worthwhile
natural ecosystems such as Gaavkhooni swamp in this basin area and
finally, the drought condition and lack of water in this area all
necessitate the existence of comprehensive management of water
sources in this central basin area of Iran as this method is a kind of
management which considers the development and the management
of water sources as an equilibrant way to increase the economical
and social benefits. In this study, it is tried to survey the network of
surface water sources of basin in upper and lower sections; at the
most, according to the difficulties and deficiencies of an efficient
management of water sources in this basin area, besides the
difficulties of water draining and the destructive phenomenon of
flood-water, the appropriate guidelines according to the region
conditions are presented in order to prevent the deviation of water in
upper sections and development of regions in lower sections of
Zayanderood dam.
Abstract: Transient eddy current problem is solved in the
present paper by the method of the Laplace transform for the case of
a double conductor line located parallel to a conducting half-space.
The Fourier sine and cosine integral transforms are used in order to
find the Laplace transform of the solution. The inverse Laplace
transform of the solution is found in closed form. The integrated
electromotive force per unit length of the double conductor line is
calculated in the form of an improper integral.
Abstract: In this paper a novel, simple and reliable digital firing
scheme has been implemented for speed control of three-phase
induction motor using ac voltage controller. The system consists of
three-phase supply connected to the three-phase induction motor via
three triacs and its control circuit. The ac voltage controller has three
modes of operation depending on the shape of supply current. The
performance of the induction motor differs in each mode where the
speed is directly proportional with firing angle in two modes and
inversely in the third one. So, the control system has to detect the
current mode of operation to choose the correct firing angle of triacs.
Three sensors are used to feed the line currents to control system to
detect the mode of operation. The control strategy is implemented
using a low cost Xilinx Spartan-3E field programmable gate array
(FPGA) device. Three PI-controllers are designed on FPGA to
control the system in the three-modes. Simulation of the system is
carried out using PSIM computer program. The simulation results
show stable operation for different loading conditions especially in
mode 2/3. The simulation results have been compared with the
experimental results from laboratory prototype.
Abstract: In this paper, an approach for finding optimized
layouts for connecting PV units delivering maximum array output
power is suggested. The approach is based on considering the
different varying parameters of PV units that might be extracted from
a general two-diode model. These are mainly, solar irradiation,
reverse saturation currents, ideality factors, series and shunt
resistances in addition to operating temperature. The approach has
been tested on 19 possible 2×3 configurations and allowed to
determine the optimized configurations as well as examine the effects
of the different units- parameters on the maximum output power.
Thus, using this approach, standard arrays with n×m units can be
configured for maximum generated power and allows designing PV
based systems having reduced surfaces to fit specific required power,
as it is the case for solar cars and other mobile systems.