Abstract: The proper selection of the AC-side passive filter
interconnecting the voltage source converter to the power supply is
essential to obtain satisfactory performances of an active power filter
system. The use of the LCL-type filter has the advantage of
eliminating the high frequency switching harmonics in the current
injected into the power supply. This paper is mainly focused on
analyzing the influence of the interface filter parameters on the active
filtering performances. Some design aspects are pointed out. Thus,
the design of the AC interface filter starts from transfer functions by
imposing the filter performance which refers to the significant current
attenuation of the switching harmonics without affecting the
harmonics to be compensated. A Matlab/Simulink model of the entire
active filtering system including a concrete nonlinear load has been
developed to examine the system performances. It is shown that a
gamma LC filter could accomplish the attenuation requirement of the
current provided by converter. Moreover, the existence of an optimal
value of the grid-side inductance which minimizes the total harmonic
distortion factor of the power supply current is pointed out.
Nevertheless, a small converter-side inductance and a damping
resistance in series with the filter capacitance are absolutely needed
in order to keep the ripple and oscillations of the current at the
converter side within acceptable limits. The effect of change in the
LCL-filter parameters is evaluated. It is concluded that good active
filtering performances can be achieved with small values of the
capacitance and converter-side inductance.
Abstract: Artificial Intelligence (AI) methods are increasingly being used for problem solving. This paper concerns using AI-type learning machines for power quality problem, which is a problem of general interest to power system to provide quality power to all appliances. Electrical power of good quality is essential for proper operation of electronic equipments such as computers and PLCs. Malfunction of such equipment may lead to loss of production or disruption of critical services resulting in huge financial and other losses. It is therefore necessary that critical loads be supplied with electricity of acceptable quality. Recognition of the presence of any disturbance and classifying any existing disturbance into a particular type is the first step in combating the problem. In this work two classes of AI methods for Power quality data mining are studied: Artificial Neural Networks (ANNs) and Support Vector Machines (SVMs). We show that SVMs are superior to ANNs in two critical respects: SVMs train and run an order of magnitude faster; and SVMs give higher classification accuracy.
Abstract: The operational behavior of a six-phase squirrel cage
induction machine with faulted stator terminals is presented in this
paper. The study is carried out using the derived mathematical model
of the machine in the arbitrary reference frame. Tests are conducted
on a 1 kW experimental machine.
Steady-state and dynamic performance are analyzed for the
machine unloaded and loaded conditions. The results shows that with
one of the stator phases experiencing either an open- circuit or short
circuit fault the machine still produces starting torque, albeit the
running performance is significantly derated.
Abstract: The basis of this paper is the assumption, that graviton
is a measurable entity of molecular gravitational acceleration and this
is not a hypothetical entity. The adoption of this assumption as an
axiom is tantamount to fully opening the previously locked door to
the boundary theory between laminar and turbulent flows. It leads to
the theorem, that the division of flows of Newtonian (viscous) fluids
into laminar and turbulent is true only, if the fluid is influenced by a
powerful, external force field. The mathematical interpretation of this
theorem, presented in this paper shows, that the boundary between
laminar and turbulent flow can be determined theoretically. This is a
novelty, because thus far the said boundary was determined
empirically only and the reasons for its existence were unknown.
Abstract: In this paper, a tri–neuron network model with time
delay is investigated. By using the Bendixson-s criterion for high–
dimensional ordinary differential equations and global Hopf bifurcation
theory for functional differential equations, sufficient conditions
for existence of periodic solutions when the time delay is sufficiently
large are established.
Abstract: This paper studies the design of a simple constellation
precoding for a multiple-input multiple-output orthogonal frequency
division multiplexing (MIMO-OFDM) system over Rayleigh fading
channels where OFDM is used to keep the diversity replicas orthogonal
and reduce ISI effects. A multi-user environment with K synchronous
co-channel users is considered. The proposed scheme provides
a bandwidth efficient transmission for individual users by increasing
the system throughput. In comparison with the existing coded
MIMO-OFDM schemes, the precoding technique is designed under
the consideration of its low implementation complexity while providing
a comparable error performance to the existing schemes.
Analytic and simulation results have been presented to show the distinguished
error performance.
Abstract: The majority of today's IR systems base the IR task on two main processes: indexing and searching. There exists a special group of dynamic IR systems where both processes (indexing and searching) happen simultaneously; such a system discards obsolete information, simultaneously dealing with the insertion of new in¬formation, while still answering user queries. In these dynamic, time critical text document databases, it is often important to modify index structures quickly, as documents arrive. This paper presents a method for dynamization which may be used for this task. Experimental results show that the dynamization process is possible and that it guarantees the response time for the query operation and index actualization.
Abstract: This interdisciplinary study is an investigation to evaluate user-interfaces in business administration. The study is going to be implemented on two computerized business administration systems with two distinctive user-interfaces, so that differences between the two systems can be determined. Both systems, a commercial and a prototype developed for the purpose of this study, deal with ordering of supplies, tendering procedures, issuing purchase orders, controlling the movement of the stocks against their actual balances on the shelves and editing them on their tabulations. In the second suggested system, modern computer graphics and multimedia issues were taken into consideration to cover the drawbacks of the first system. To highlight differences between the two investigated systems regarding some chosen standard quality criteria, the study employs various statistical techniques and methods to evaluate the users- interaction with both systems. The study variables are divided into two divisions: independent representing the interfaces of the two systems, and dependent embracing efficiency, effectiveness, satisfaction, error rate etc.
Abstract: Understanding road features such as lanes, the color
of lanes, and sidewalks in a live video captured from a moving
vehicle is essential to build video-based navigation systems. In this
paper, we present a novel idea to understand the road features using
support vector machines. Various feature vectors including color
components of road markings and the difference between two
regions, i.e., chosen AOIs, and so on are fed into SVM, deciding
colors of lanes and sidewalks robustly. Experimental results are
provided to show the robustness of the proposed idea.
Abstract: In this work Membrane Distillation is applied to
concentrate orange Juice. Clarified orange juice (11o Brix) obtained
from fresh fruits and a sugar solution was subjected to membrane
distillation. The experiments were performed on a flat sheet module
using orange juice and sucrose solution as feeds. The concentration
of a sucrose solution, used as a model fruit juice and also orange
juice, was carried out in a direct contact membrane distillation using
hydrophobic PTFE membrane of pore size 0.2 μm and porosity 70%.
Surface modification of PTFE membrane has been carried out by
treating membrane with alcohol and water solution to make it
hydrophilic and then hydrophobicity was regained by drying. The
influences of the feed temperature, feed concentration, flow rate,
operating time on the permeate flux were studied for treated and non
treated membrane. In this work treated and non treated membrane
were compared in terms of water flux, Within the tested range, MD
with surface modified membrane the water flux has been
significantly improved by treating the membrane surface.
Abstract: Modernizing legacy applications is the key issue facing IT managers today because there's enormous pressure on organizations to change the way they run their business to meet the new requirements. The importance of software maintenance and reengineering is forever increasing. Understanding the architecture of existing legacy applications is the most critical issue for maintenance and reengineering. The artifacts recovery can be facilitated with different recovery approaches, methods and tools. The existing methods provide static and dynamic set of techniques for extracting architectural information, but are not suitable for all users in different domains. This paper presents a simple and lightweight pattern extraction technique to extract different artifacts from legacy systems using regular expression pattern specifications with multiple language support. We used our custom-built tool DRT to recover artifacts from existing system at different levels of abstractions. In order to evaluate our approach a case study is conducted.
Abstract: A nonlinear optimal controller with a fuzzy gain
scheduler has been designed and applied to a Line-Of-Sight (LOS)
stabilization system. Use of Linear Quadratic Regulator (LQR)
theory is an optimal and simple manner of solving many control
engineering problems. However, this method cannot be utilized
directly for multigimbal LOS systems since they are nonlinear in
nature. To adapt LQ controllers to nonlinear systems at least a
linearization of the model plant is required. When the linearized
model is only valid within the vicinity of an operating point a gain
scheduler is required. Therefore, a Takagi-Sugeno Fuzzy Inference
System gain scheduler has been implemented, which keeps the
asymptotic stability performance provided by the optimal feedback
gain approach. The simulation results illustrate that the proposed
controller is capable of overcoming disturbances and maintaining a
satisfactory tracking performance.
Abstract: A portable sensor for the analysis of phosphate in
aqueous samples has been developed. The sensor incorporates
microfluidic technology, colorimetric detection, and wireless
communications into a compact and rugged portable device. The
detection method used is the molybdenum yellow method, in which a
phosphate-containing sample is mixed with a reagent containing
ammonium metavanadate and ammonium molybdate in an acidic
medium. A yellow-coloured compound is generated and the
absorption of this compound is measured using a light emitting diode
(LED) light source and a photodiode detector. The absorption is
directly proportional to the phosphate concentration in the original
sample. In this paper we describe the application of this phosphate
sensor to the analysis of wastewater at a municipal wastewater
treatment plant in Co. Kildare, Ireland.
Abstract: Due to the high increase in and demand for a wide assortment of applications that require low-cost, high-efficiency, and compact systems, RF power amplifiers are considered the most critical design blocks and power consuming components in wireless communication, TV transmission, radar, and RF heating. Therefore, much research has been carried out in order to improve the performance of power amplifiers. Classes-A, B, C, D, E and F are the main techniques for realizing power amplifiers.
An implementation of high efficiency class-F power amplifier with Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) was realized in this paper. The simulation and optimization of the class-F power amplifier circuit model was undertaken using Agilent’s Advanced Design system (ADS). The circuit was designed using lumped elements.
Abstract: In this study, the sorption of Malachite green (MG) on Hydrilla verticillata biomass, a submerged aquatic plant, was investigated in a batch system. The effects of operating parameters such as temperature, adsorbent dosage, contact time, adsorbent size, and agitation speed on the sorption of Malachite green were analyzed using response surface methodology (RSM). The proposed quadratic model for central composite design (CCD) fitted very well to the experimental data that it could be used to navigate the design space according to ANOVA results. The optimum sorption conditions were determined as temperature - 43.5oC, adsorbent dosage - 0.26g, contact time - 200min, adsorbent size - 0.205mm (65mesh), and agitation speed - 230rpm. The Langmuir and Freundlich isotherm models were applied to the equilibrium data. The maximum monolayer coverage capacity of Hydrilla verticillata biomass for MG was found to be 91.97 mg/g at an initial pH 8.0 indicating that the optimum sorption initial pH. The external and intra particle diffusion models were also applied to sorption data of Hydrilla verticillata biomass with MG, and it was found that both the external diffusion as well as intra particle diffusion contributes to the actual sorption process. The pseudo-second order kinetic model described the MG sorption process with a good fitting.
Abstract: The aim of this study was to synthesize the single
walled carbon nanotubes (SWCNTs) and determine their hydrogen
storage capacities. SWCNTs were firstly synthesized by chemical
vapor deposition (CVD) of acetylene (C2H2) on a magnesium oxide
(MgO) powder impregnated with an iron nitrate (Fe(NO3)3·9H2O)
solution. The synthesis parameters were selected as: the synthesis
temperature of 800°C, the iron content in the precursor of 5% and the
synthesis time of 30 min. Purification process of SWCNTs was
fulfilled by microwave digestion at three different temperatures (120,
150 and 200 °C), three different acid concentrations (0.5, 1 and 1.5
M) and for three different time intervals (15, 30 and 60 min). Nitric
acid (HNO3) was used in the removal of the metal catalysts. The
hydrogen storage capacities of the purified materials were measured
using volumetric method at the liquid nitrogen temperature and gas
pressure up to 100 bar. The effects of the purification conditions such
as temperature, time and acid concentration on hydrogen adsorption
were investigated.
Abstract: This paper describes an experimental, theoretical
model and numerical study of concentrated vortex flow past a sphere
in a hydraulic check valve. The phenomenon of the rotation of the
ball around the axis of the device through which liquid flows has
been found. That is, due to the rotation of the sphere in the check
valve vibration is caused. We observe the rotation of the sphere
around the longitudinal axis of the check valve. This rotation is
induced by a vortex shedding from the sphere. We will discuss
computational simulation and experimental investigations of this
strong sphere rotation. The frequency of the sphere vibration and
interaction with the check valve wall has been measured as a function
of the wide range Reynolds Number. The validity of the
computational simulation and of the assumptions on which it is based
has been proved experimentally. This study demonstrates the
possibility to control the vibrations in a hydraulic system and proves
to be very effective suppression of the self-excited vibration.
Abstract: Helical milling operations are used to generate or
enlarge boreholes by means of a milling tool. The bore diameter can be
adjusted through the diameter of the helical path. The kinematics of
helical milling on a three axis machine tool is analysed firstly. The
relationships between processing parameters, cutting tool geometry
characters with machined hole feature are formulated. The feed motion
of the cutting tool has been decomposed to plane circular feed and
axial linear motion. In this paper, the time varying cutting forces acted
on the side cutting edges and end cutting edges of the flat end cylinder
miller is analysed using a discrete method separately. These two
components then are combined to produce the cutting force model
considering the complicated interaction between the cutters and
workpiece. The time varying cutting force model describes the
instantaneous cutting force during processing. This model could be
used to predict cutting force, calculate statics deflection of cutter and
workpiece, and also could be the foundation of dynamics model and
predicting chatter limitation of the helical milling operations.
Abstract: Based on a long-term vegetation index dataset of NDVI and meteorological data from 68 meteorological stations in the Qinghai-Tibet plateau and their relations with major climate factors were analyzed. The results show the following: 1) The linear trends of temperature in the Qinghai-Tibet plateau indicate that the temperature in the plateau generally increased, but it rose faster in the last 20 years. 2) The most significant NDVI increase occurred in the eastern and southern plateau. However, the western and northern plateau demonstrate a decreasing trend. 3) There is a significant positive linear correlation between NDVI and temperature and a negative correlation between NDVI and mean wind speed. However, no significant statistical relationship was found between NDVI and relative humidity, precipitation or sunshine duration.4) The changes in NDVI for the plateau are driven by temperature-precipitation, but for the desert and forest areas, the relation changes to precipitation-temperature-wind velocity and wind velocity-temperature-precipitation.
Abstract: A self-association model has been used to understand
the concentration dependence of free energy of mixing (GM), heat of
mixing (HM), entropy of mixing (SM), activity (a) and microscopic
structures, such as concentration fluctuation in long wavelength limit
(Scc(0)) and Warren-Cowley short range order parameter ( 1
α )for Cu-
Tl molten alloys at 1573K. A comparative study of surface tension of
the alloys in the liquid state at that temperature has also been carried
out theoretically as function of composition in the light of Butler-s
model, Prasad-s model and quasi-chemical approach. Most of the
computed thermodynamic properties have been found in agreement
with the experimental values. The analysis reveals that the Cu-Tl
molten alloys at 1573K represent a segregating system at all
concentrations with moderate interaction. Surface tensions computed
from different approaches have been found to be comparable to each
other showing increment with the composition of copper.