Abstract: Feature selection plays an important role in applications with high dimensional data. The assessment of the stability of feature selection/ranking algorithms becomes an important issue when the dataset is small and the aim is to gain insight into the underlying process by analyzing the most relevant features. In this work, we propose a graphical approach that enables to analyze the similarity between feature ranking techniques as well as their individual stability. Moreover, it works with whatever stability metric (Canberra distance, Spearman's rank correlation coefficient, Kuncheva's stability index,...). We illustrate this visualization technique evaluating the stability of several feature selection techniques on a spectral binary dataset. Experimental results with a neural-based classifier show that stability and ranking quality may not be linked together and both issues have to be studied jointly in order to offer answers to the domain experts.
Abstract: This paper presents PSS (Power system stabilizer) design based on optimal fuzzy PID (OFPID). OFPID based PSS design is considered for single-machine power systems. The main motivation for this design is to stabilize or to control low-frequency oscillation on power systems. Firstly, describing the linear PID control then to combine this PID control with fuzzy logic control mechanism. Finally, Fuzzy PID parameters (Kp. Kd, KI, Kupd, Kui) are tuned by Genetic Algorthm (GA) to reach optimal global stability. The effectiveness of the proposed PSS in increasing the damping of system electromechanical oscillation is demonstrated in a one-machine-infinite-bus system
Abstract: In this paper, the problem of stability criteria of neural networks (NNs) with two-additive time-varying delay compenents is investigated. The relationship between the time-varying delay and its lower and upper bounds is taken into account when estimating the upper bound of the derivative of Lyapunov functional. As a result, some improved delay stability criteria for NNs with two-additive time-varying delay components are proposed. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.
Abstract: The hard clam (meretrix lusoria) cultivated industry
has been developed vigorously for recent years in Taiwan, and
seawater quality determines the cultivated environment. The pH
concentration variation affects survival rate of meretrix lusoria
immediately. In order to monitor seawater quality, solid-state sensing
electrode of ruthenium-doped titanium dioxide (TiO2:Ru) is developed
to measure hydrogen ion concentration in different cultivated
solutions. Because the TiO2:Ru sensing electrode has high chemical
stability and superior sensing characteristics, thus it is applied as a pH
sensor. Response voltages of TiO2:Ru sensing electrode are readout by
instrument amplifier in different sample solutions. Mean sensitivity
and linearity of TiO2:Ru sensing electrode are 55.20 mV/pH and 0.999
from pH1 to pH13, respectively. We expect that the TiO2:Ru sensing
electrode can be applied to real environment measurement, therefore
we collect two sample solutions by different meretrix lusoria
cultivated ponds in the Yunlin, Taiwan. The two sample solutions are
both measured for 200 seconds after calibration of standard pH buffer
solutions (pH7, pH8 and pH 9). Mean response voltages of sample 1
and sample 2 are -178.758 mV (Standard deviation=0.427 mV) and
-180.206 mV (Standard deviation =0.399 mV), respectively. Response
voltages of the two sample solutions are between pH 8 and pH 9 which
conform to weak alkali range and suitable meretrix lusoria growth. For
long-term monitoring, drift of cultivated solutions (sample 1 and
sample 2) are 1.16 mV/hour and 1.03 mV/hour, respectively.
Abstract: Using electrical machine in conventional vehicles, also called hybrid vehicles, has become a promising control scheme that enables some manners for fuel economy and driver assist for better stability. In this paper, vehicle stability control, fuel economy and Driving/Regeneration braking for a 4WD hybrid vehicle is investigated by using an electrical machine on each non-driven wheels. In front wheels driven vehicles, fuel economy and regenerative braking can be obtained by summing torques applied on rear wheels. On the other hand, unequal torques applied to rear wheels provides enhanced safety and path correction in steering. In this paper, a model with fourteen degrees of freedom is considered for vehicle body, tires and, suspension systems. Thereafter, powertrain subsystems are modeled. Considering an electrical machine on each rear wheel, a fuzzy controller is designed for each driving, braking, and stability conditions. Another fuzzy controller recognizes the vehicle requirements between the driving/regeneration and stability modes. Intelligent vehicle control to multi objective operation and forward simulation are the paper advantages. For reaching to these aims, power management control and yaw moment control will be done by three fuzzy controllers. Also, the above mentioned goals are weighted by another fuzzy sub-controller base on vehicle dynamic. Finally, Simulations performed in MATLAB/SIMULINK environment show that the proposed structure can enhance the vehicle performance in different modes effectively.
Abstract: Chatter vibration has been a troublesome problem
for a machine tool toward the high precision and high speed machining.
Essentially, the machining performance is determined by the dynamic
characteristics of the machine tool structure and dynamics of cutting
process, which can further be identified in terms of the stability lobe
diagram. Therefore, realization on the machine tool dynamic behavior
can help to enhance the cutting stability. To assess the dynamic
characteristics and machining stability of a vertical milling system
under the influence of a linear guide, this study developed a finite
element model integrated the modeling of linear components with the
implementation of contact stiffness at the rolling interface. Both the
finite element simulations and experimental measurements reveal that
the linear guide with different preload greatly affects the vibration
behavior and milling stability of the vertical column spindle head
system, which also clearly indicate that the predictions of the
machining stability agree well with the cutting tests. It is believed that
the proposed model can be successfully applied to evaluate the
dynamics performance of machine tool systems of various
configurations.
Abstract: The authors present an algorithm for order reduction of linear time invariant dynamic systems using the combined advantages of the eigen spectrum analysis and the error minimization by particle swarm optimization technique. Pole centroid and system stiffness of both original and reduced order systems remain same in this method to determine the poles, whereas zeros are synthesized by minimizing the integral square error in between the transient responses of original and reduced order models using particle swarm optimization technique, pertaining to a unit step input. It is shown that the algorithm has several advantages, e.g. the reduced order models retain the steady-state value and stability of the original system. The algorithm is illustrated with the help of two numerical examples and the results are compared with the other existing techniques.
Abstract: In this paper, application of Sliding Mode Control (SMC) technique for an Active Magnetic Bearing (AMB) system with varying rotor speed is considered. The gyroscopic effect and mass imbalance inherited in the system is proportional to rotor speed in which this nonlinearity effect causes high system instability as the rotor speed increases. Transformation of the AMB dynamic model into regular system shows that these gyroscopic effect and imbalance lie in the mismatched part of the system. A H2-based sliding surface is designed which bound the mismatched parts. The solution of the surface parameter is obtained using Linear Matrix Inequality (LMI). The performance of the controller applied to the AMB model is demonstrated through simulation works under various system conditions.
Abstract: A compact tunable 10 W picosecond source based on
Yb-doped fiber amplification of gain switch laser diode has been
demonstrated. A gain switch semiconductor laser diode was used as
the seed source, and a multi-stage single mode Yb-doped fiber
preamplifier was combined with two large mode area double-clad
Yb-doped fiber main amplifiers to construct the amplification system.
The tunable pulses with high stability and excellent beam quality
(M2
Abstract: This paper studies the problem of exponential
stability of perturbed discrete linear systems with periodic
coefficients. Assuming that the unperturbed system is exponentially
stable we obtain conditions on the perturbations under which the
perturbed system is exponentially stable.
Abstract: The very nonlinear nature of the generator and system
behaviour following a severe disturbance precludes the use of
classical linear control technique. In this paper, a new approach of
nonlinear control is proposed for transient and steady state stability
analysis of a synchronous generator. The control law of the generator
excitation is derived from the basis of Lyapunov stability criterion.
The overall stability of the system is shown using Lyapunov
technique. The application of the proposed controller to simulated
generator excitation control under a large sudden fault and wide
range of operating conditions demonstrates that the new control
strategy is superior to conventional automatic voltage regulator
(AVR), and show very promising results.
Abstract: Innovations and innovative activity get the increasing
value for successful financial and economic activity of the countries
and regions. The level of innovative sphere development determines
place of a country or a region in world economy and forms a basis of
steady economic growth. This article is devoted to different aspects
of organization of the national economic safety in the conditions of
innovative development, its problems, risks and threats. Economy
can be considered as aspiring for transition to innovative way only
with finding of economic safety: financial independence, power
stability and technological progress. There are statistical indicators,
defining the level of economic security and factors, threatening
economic safety of the state. The research is based on the analysis of
factors and indicators in conditions of innovative development. The
paper is illustrated by the examples of possible estimated system of
the economic safety level.
Abstract: Homogeneous composites of alumina and zirconia
with a small amount of MgO (99%) were obtained for ZTA ceramic containing 0.05 wt% MgO in
1500 °C.
Abstract: Use of microemulsion in enhanced oil recovery has become more attractive in recent years because of its high level of extraction efficiency. Experimental investigations have been made on characterization of microemulsions of oil-brinesurfactant/ cosurfactant system for its use in enhanced oil recovery (EOR). Sodium dodecyl sulfate, propan-1-ol and heptane were selected as surfactant, cosurfactant and oil respectively for preparation of microemulsion. The effects of salinity on the relative phase volumes and solubilization parameters have also been studied. As salinity changes from low to high value, phase transition takes place from Winsor I to Winsor II via Winsor III. Suitable microemulsion composition has been selected based on its stability and ability to reduce interfacial tension. A series of flooding experiments have been performed using the selected microemulsion. The flooding experiments were performed in a core flooding apparatus using uniform sand pack. The core holder was tightly packed with uniform sands (60-100 mesh) and saturated with brines of different salinities. It was flooded with the brine at 25 psig and the absolute permeability was calculated from the flow rate of the through sand pack. The sand pack was then flooded with the crude oil at 800 psig to irreducible water saturation. The initial water saturation was determined on the basis of mass balance. Waterflooding was conducted by placing the coreholder horizontally at a constant injection pressure at 200 pisg. After water flooding, when water-cut reached above 95%, around 0.5 pore volume (PV) of the above microemulsion slug was injected followed by chasing water. The experiments were repeated using different composition of microemulsion slug. The additional recoveries were calculated by material balance. Encouraging results with additional recovery more than 20% of original oil in place above the conventional water flooding have been observed.
Abstract: Temperature, humidity and precipitation in an area,
are parameters proved influential in the climate of that area, and one
should recognize them so that he can determine the climate of that
area. Climate changes are of primary importance in climatology, and
in recent years, have been of great concern to researchers and even
politicians and organizations, for they can play an important role in
social, political and economic activities. Even though the real cause
of climate changes or their stability is not yet fully recognized, they
are a matter of concern to researchers and their importance for
countries has prompted them to investigate climate changes in
different levels, especially in regional, national and continental level.
This issue has less been investigated in our country. However, in
recent years, there have been some researches and conferences on
climate changes. This study is also in line with such researches and
tries to investigate and analyze the trends of climate changes
(temperature and precipitation) in Sefid-roud (the name of a river)
basin. Three parameters of mean annual precipitation, temperature,
and maximum and minimum temperatures in 36 synoptic and
climatology stations in a statistical period of 49 years (1956-2005) in
the stations of Sefid-roud basin were analyzed by Mann-Kendall test.
The results obtained by data analysis show that climate changes are
short term and have a trend. The analysis of mean temperature
revealed that changes have a significantly rising trend, besides the
precipitation has a significantly falling trend.
Abstract: DC-DC converters are widely used in regulated switched mode power supplies and in DC motor drive applications. There are several sources of unwanted nonlinearity in practical power converters. In addition, their operation is characterized by switching that gives birth to a variety of nonlinear dynamics. DC-DC buck and boost converters controlled by pulse-width modulation (PWM) have been simulated. The voltage waveforms and attractors obtained from the circuit simulation have been studied. With the onset of instability, the phenomenon of subharmonic oscillations, quasi-periodicity, bifurcations, and chaos have been observed. This paper is mainly motivated by potential contributions of chaos theory in the design, analysis and control of power converters, in particular and power electronics circuits, in general.
Abstract: This paper presents an adaptive nonlinear position
controller with velocity constraint, capable of combining the
input-output linearization technique and Lyapunov stability theory.
Based on the Lyapunov stability theory, the adaptation law of the
proposed controller is derived along with the verification of the overall
system-s stability. Computer simulation results demonstrate that the
proposed controller is robust and it can ensure transient stability of
BLDCM, under the occurrence of a large sudden fault.
Abstract: In this paper, a new model order reduction
phenomenon is introduced at the design stage of linear phase digital
IIR filter. The complexity of a system can be reduced by adopting the
model order reduction method in their design. In this paper a mixed
method of model order reduction is proposed for linear IIR filter. The
proposed method employs the advantages of factor division technique
to derive the reduced order denominator polynomial and the reduced
order numerator is obtained based on the resultant denominator
polynomial. The order reduction technique is used to reduce the delay
units at the design stage of IIR filter. The validity of the proposed
method is illustrated with design example in frequency domain and
stability is also examined with help of nyquist plot.
Abstract: Acoustic function plays an important role in
aerodynamic mechanical engineering. It can classify the kind of
air-vehicle such as subsonic or supersonic. Acoustic velocity
relates with velocity and Mach number. Mach number relates
again acoustic stability or instability condition. Mach number
plays an important role in growth or decay in energy system.
Acoustic is a function of temperature and temperature is directly
proportional to pressure. If we control the pressure, we can control
acoustic function. To get pressure stability condition, we apply
Navier-Stokes equations.
Abstract: Most of the drugs used for pharmaceutical purposes
are poorly water-soluble drugs. About 40% of all newly discovered
drugs are lipophilic and the numbers of lipophilic drugs seem to
increase more and more. Drug delivery systems such as
nanoparticles, micelles or liposomes are applied to improve their
solubility and thus their bioavailability. Besides various techniques of
solubilization, oil-in-water emulsions are often used to incorporate
lipophilic drugs into the oil phase. To stabilize emulsions surface
active substances (surfactants) are generally used. An alternative
method to avoid the application of surfactants was of great interest.
One possibility is to develop O/W-emulsion without any addition of
surface active agents or the so called “surfactant-free emulsion or
SFE”. The aim of this study was to develop and characterize SFE as a
drug carrier by varying the production conditions. Lidocaine base
was used as a model drug. The injection method was developed.
Effects of ultrasound as well as of temperature on the properties of
the emulsion were studied. Particle sizes and release were
determined. The long-term stability up to 30 days was performed.
The results showed that the surfactant-free O/W emulsions with
pharmaceutical oil as drug carrier can be produced.