Abstract: Today-s Voltage Regulator Modules (VRMs) face increasing design challenges as the number of transistors in microprocessors increases per Moore-s Law. These challenges have recently become even more demanding as microprocessors operate at sub voltage range at significantly high current. This paper presents a new multiphase topology with cell configuration for improved performance in low voltage and high current applications. A lab scale hardware prototype of the new topology was design and constructed. Laboratory tests were performed on the proposed converter and compared with a commercially available VRM. Results from the proposed topology exhibit improved performance compared to the commercially available counterpart.
Abstract: This paper presents a novel methodology for Maximum Power Point Tracking (MPPT) of a grid-connected 20 kW Photovoltaic (PV) system using neuro-fuzzy network. The proposed method predicts the reference PV voltage guarantying optimal power transfer between the PV generator and the main utility grid. The neuro-fuzzy network is composed of a fuzzy rule-based classifier and three Radial Basis Function Neural Networks (RBFNN). Inputs of the network (irradiance and temperature) are classified before they are fed into the appropriated RBFNN for either training or estimation process while the output is the reference voltage. The main advantage of the proposed methodology, comparing to a conventional single neural network-based approach, is the distinct generalization ability regarding to the nonlinear and dynamic behavior of a PV generator. In fact, the neuro-fuzzy network is a neural network based multi-model machine learning that defines a set of local models emulating the complex and non-linear behavior of a PV generator under a wide range of operating conditions. Simulation results under several rapid irradiance variations proved that the proposed MPPT method fulfilled the highest efficiency comparing to a conventional single neural network.
Abstract: The majority of existing predictors for time series are
model-dependent and therefore require some prior knowledge for the
identification of complex systems, usually involving system
identification, extensive training, or online adaptation in the case of
time-varying systems. Additionally, since a time series is usually
generated by complex processes such as the stock market or other
chaotic systems, identification, modeling or the online updating of
parameters can be problematic. In this paper a model-free predictor
(MFP) for a time series produced by an unknown nonlinear system or
process is derived using tracking theory. An identical derivation of the
MFP using the property of the Newton form of the interpolating
polynomial is also presented. The MFP is able to accurately predict
future values of a time series, is stable, has few tuning parameters and
is desirable for engineering applications due to its simplicity, fast
prediction speed and extremely low computational load. The
performance of the proposed MFP is demonstrated using the
prediction of the Dow Jones Industrial Average stock index.
Abstract: Nanomaterials have attracted considerable attention
during the last two decades, due to their unusual electrical, mechanical
and other physical properties as compared with their bulky
counterparts. The mechanical properties of nanostructured materials
show strong size dependency, which has been explained within the
framework of continuum mechanics by including the effects of surface
stress. The size-dependent deformations of two-dimensional
nanosized structures with surface effects are investigated in the paper
by the finite element method. Truss element is used to evaluate the
contribution of surface stress to the total potential energy and the
Gurtin and Murdoch surface stress model is implemented with
ANSYS through its user programmable features. The proposed
approach is used to investigate size-dependent stress concentration
around a nanosized circular hole and the size-dependent effective
moduli of nanoporous materials. Numerical results are compared with
available analytical results to validate the proposed modeling
approach.
Abstract: The main goal of this work is to propose a way for
combined use of two nontraditional algorithms by solving topological
problems on telecommunications concentrator networks. The
algorithms suggested are the Simulated Annealing algorithm and the
Genetic Algorithm. The Algorithm of Simulated Annealing unifies
the well known local search algorithms. In addition - Simulated
Annealing allows acceptation of moves in the search space witch lead
to decisions with higher cost in order to attempt to overcome any
local minima obtained. The Genetic Algorithm is a heuristic approach
witch is being used in wide areas of optimization works. In the last
years this approach is also widely implemented in
Telecommunications Networks Planning. In order to solve less or
more complex planning problem it is important to find the most
appropriate parameters for initializing the function of the algorithm.
Abstract: Nowadays, the rapid development of multimedia
and internet allows for wide distribution of digital media data.
It becomes much easier to edit, modify and duplicate digital
information Besides that, digital documents are also easy to
copy and distribute, therefore it will be faced by many
threatens. It-s a big security and privacy issue with the large
flood of information and the development of the digital
format, it become necessary to find appropriate protection
because of the significance, accuracy and sensitivity of the
information. Nowadays protection system classified with more
specific as hiding information, encryption information, and
combination between hiding and encryption to increase information
security, the strength of the information hiding science is due to the
non-existence of standard algorithms to be used in hiding secret
messages. Also there is randomness in hiding methods such as
combining several media (covers) with different methods to pass a
secret message. In addition, there are no formal methods to be
followed to discover the hidden data. For this reason, the task of this
research becomes difficult. In this paper, a new system of information
hiding is presented. The proposed system aim to hidden information
(data file) in any execution file (EXE) and to detect the hidden file
and we will see implementation of steganography system which
embeds information in an execution file. (EXE) files have been
investigated. The system tries to find a solution to the size of the
cover file and making it undetectable by anti-virus software. The
system includes two main functions; first is the hiding of the
information in a Portable Executable File (EXE), through the
execution of four process (specify the cover file, specify the
information file, encryption of the information, and hiding the
information) and the second function is the extraction of the hiding
information through three process (specify the steno file, extract the
information, and decryption of the information). The system has
achieved the main goals, such as make the relation of the size of the
cover file and the size of information independent and the result file
does not make any conflict with anti-virus software.
Abstract: The world is moving rapidly toward the deployment
of information and communication systems. Nowadays, computing
systems with their fast growth are found everywhere and one of the main challenges for these systems is increasing attacks and security threats against them. Thus, capturing, analyzing and verifying security requirements becomes a very important activity in
development process of computing systems, specially in developing
systems such as banking, military and e-business systems. For
developing every system, a process model which includes a process,
methods and tools is chosen. The Rational Unified Process (RUP) is
one of the most popular and complete process models which is used
by developers in recent years. This process model should be extended to be used in developing secure software systems. In this
paper, the Requirement Discipline of RUP is extended to improve RUP for developing secure software systems. These proposed extensions are adding and integrating a number of Activities, Roles,
and Artifacts to RUP in order to capture, document and model threats
and security requirements of system. These extensions introduce a
group of clear and stepwise activities to developers. By following these activities, developers assure that security requirements are
captured and modeled. These models are used in design, implementation and test activitie
Abstract: The need of high frame-rate imaging has been triggered by the new applications of ultrasound imaging to transient elastography and real-time 3D ultrasound. Using plane wave excitation (PWE) is one of the methods to achieve very high frame-rate imaging since an image can be formed with a single insonification. However, due to the lack of transmit focusing, the image quality with PWE is lower compared with those using conventional focused transmission. To solve this problem, we propose a filter-retrieved transmit focusing (FRF) technique combined with cross-correlation weighting (FRF+CC weighting) for high frame-rate imaging with PWE. A restrospective focusing filter is designed to simultaneously minimize the predefined sidelobe energy associated with single PWE and the filter energy related to the signal-to-noise-ratio (SNR). This filter attempts to maintain the mainlobe signals and to reduce the sidelobe ones, which gives similar mainlobe signals and different sidelobes between the original PWE and the FRF baseband data. Normalized cross-correlation coefficient at zero lag is calculated to quantify the degree of similarity at each imaging point and used as a weighting matrix to the FRF baseband data to further suppress sidelobes, thus improving the filter-retrieved focusing quality.
Abstract: This paper studies a vital issue in wireless
communications, which is the transmission of images over Wireless
Personal Area Networks (WPANs) through the Bluetooth network. It
presents a simple method to improve the efficiency of error control
code of old Bluetooth versions over mobile WPANs through
Interleaved Error Control Code (IECC) technique. The encoded
packets are interleaved by simple block interleaver. Also, the paper
presents a chaotic interleaving scheme as a tool against bursts of
errors which depends on the chaotic Baker map. Also, the paper
proposes using the chaotic interleaver instead of traditional block
interleaver with Forward Error Control (FEC) scheme. A comparison
study between the proposed and standard techniques for image
transmission over a correlated fading channel is presented.
Simulation results reveal the superiority of the proposed chaotic
interleaving scheme to other schemes. Also, the superiority of FEC
with proposed chaotic interleaver to the conventional interleavers
with enhancing the security level with chaotic interleaving packetby-
packet basis.
Abstract: In this paper, we proposed the effects of Mo thickness
on the properties of AZO/Mo/AZO multilayer thin films for
opto-electronics applications. The structural, optical and electrical
properties of AZO/Mo/AZO thin films were investigated.
Optimization of the thin films coatings resulted with low resistivity of
9.98 × 10-5 )-cm, mobility of 12.75 cm2/V-s, carrier concentration of
1.05 × 1022 cm-3, maximum transmittance of 79.13% over visible
spectrum of 380 – 780 nm and Haacke figure of merit (FOM) are 5.95
× 10-2 )-1 under Mo layer thickness of 15 nm. These results indicate an
alternative candidate for use as a transparent electrode in solar cells
and various displays applications.
Abstract: This research investigates the design of a low-cost 3D
spatial interaction approach using the Wii Remote for immersive
Head-Mounted Display (HMD) virtual reality. Current virtual reality
applications that incorporate the Wii Remote are either desktop
virtual reality applications or systems that use large screen displays.
However, the requirements for an HMD virtual reality system differ
from such systems. This is mainly because in HMD virtual reality,
the display screen does not remain at a fixed location. The user views
the virtual environment through display screens that are in front of
the user-s eyes and when the user moves his/her head, these screens
move as well. This means that the display has to be updated in realtime
based on where the user is currently looking. Normal usage of
the Wii Remote requires the controller to be pointed in a certain
direction, typically towards the display. This is too restrictive for
HMD virtual reality systems that ideally require the user to be able to
turn around in the virtual environment. Previous work proposed a
design to achieve this, however it suffered from a number of
drawbacks. The aim of this study is to look into a suitable method of
using the Wii Remote for 3D interaction in a space around the user
for HMD virtual reality. This paper presents an overview of issues
that had to be considered, the system design as well as experimental
results.
Abstract: Calcium is a vital second messenger used in signal transduction. Calcium controls secretion, cell movement, muscular contraction, cell differentiation, ciliary beating and so on. Two theories have been used to simplify the system of reaction-diffusion equations of calcium into a single equation. One is excess buffer approximation (EBA) which assumes that mobile buffer is present in excess and cannot be saturated. The other is rapid buffer approximation (RBA), which assumes that calcium binding to buffer is rapid compared to calcium diffusion rate. In the present work, attempt has been made to develop a model for calcium diffusion under excess buffer approximation in neuron cells. This model incorporates the effect of [Na+] influx on [Ca2+] diffusion,variable calcium and sodium sources, sodium-calcium exchange protein, Sarcolemmal Calcium ATPase pump, sodium and calcium channels. The proposed mathematical model leads to a system of partial differential equations which have been solved numerically using Forward Time Centered Space (FTCS) approach. The numerical results have been used to study the relationships among different types of parameters such as buffer concentration, association rate, calcium permeability.
Abstract: Use of fly ash as a supplementary cementing material
in large volumes can bring both technological and economic benefits
for concrete industry. In this investigation mix proportions for high
volume fly ash concrete were determined at cement replacement
levels of 50%, 55%, 60% and 65% with low calcium fly ash. Flexural
and compressive strengths of different mixes were measured at ages
of 7, 28 and 90 days. Flexural strength of composite section prepared
from pavement quality and lean high volume fly ash concrete was
determined at the age of 28 days. High volume fly ash concrete mixes
exhibited higher rate of strength gain and age factors than
corresponding reference concrete mixes. The optimum cement
replacement level for pavement quality concrete was found to be
60%. The consideration of bond between pavement quality and lean
of high volume fly ash concrete will be beneficial in design of rigid
pavements.
Abstract: Rooted in the study of social functioning of space in architecture, Space Syntax (SS) and the more recent Network Pattern (NP) researches demonstrate the 'spatial structures' of city, i.e. the hierarchical patterns of streets, junctions and alley ends. Applying SS and NP models, planners can conceptualize the real city-s patterns. Although, both models yield the optimal path of the city their underpinning displays of the city-s spatial configuration differ. The Axial Map analyzes the topological non-distance-based connectivity structure, whereas, the Central-Node Map and the Shortcut-Path Map, in contrast, analyze the metrical distance-based structures. This research contrasts and combines them to understand various forms of city-s structures. It concludes that, while they reveal different spatial structures, Space Syntax and Network Pattern urban models support each the other. Combining together they simulate the global access and the locally compact structures namely the central nodes and the shortcuts for the city.
Abstract: After reporting a literature review on Customer
Relationship Management (CRM) and knowledge management, some
important issued arise, in particular related to the lack of success of
CRM strategies implementation. The paper contributes to this
proposing an integrated model of CRM success taking into account
complementary factors such as organizational factors, technology,
knowledge management and customer orientation.
Abstract: This paper describes a new approach of classification
using genetic programming. The proposed technique consists of
genetically coevolving a population of non-linear transformations on
the input data to be classified, and map them to a new space with a
reduced dimension, in order to get a maximum inter-classes
discrimination. The classification of new samples is then performed
on the transformed data, and so become much easier. Contrary to the
existing GP-classification techniques, the proposed one use a
dynamic repartition of the transformed data in separated intervals, the
efficacy of a given intervals repartition is handled by the fitness
criterion, with a maximum classes discrimination. Experiments were
first performed using the Fisher-s Iris dataset, and then, the KDD-99
Cup dataset was used to study the intrusion detection and
classification problem. Obtained results demonstrate that the
proposed genetic approach outperform the existing GP-classification
methods [1],[2] and [3], and give a very accepted results compared to
other existing techniques proposed in [4],[5],[6],[7] and [8].
Abstract: Due to the legacy of apartheid segregation South Africa remains a divided society where most voters live in politically homogenous social environments. This paper argues that political discussion within one’s social context plays a primary role in shaping political attitudes and vote choice. Using data from the Comparative National Elections Project 2004 and 2009 South African post-election surveys, the paper explores the extent of social context partisan homogeneity in South Africa and finds that voters are not overly embedded in homogenous social contexts. It then demonstrates the consequences of partisan homogeneity on voting behavior. Homogenous social contexts tend to encourage stronger partisan loyalties and fewer defections in vote choice while voters in more heterogeneous contexts show less consistency in their attitudes and behaviour. Finally, the analysis shows how momentous sociopolitical events at the time of a particular election can change the social context, with important consequences for electoral outcomes.
Abstract: An on-line condition monitoring method for transmission line is proposed using electrical circuit theory and IT technology in this paper. It is reasonable that the circuit parameters such as resistance (R), inductance (L), conductance (g) and capacitance (C) of a transmission line expose the electrical conditions and physical state of the line. Those parameters can be calculated from the linear equation composed of voltages and currents measured by synchro-phasor measurement technique at both end of the line. A set of linear voltage drop equations containing four terminal constants (A, B ,C ,D ) are mathematical models of the transmission line circuits. At least two sets of those linear equations are established from different operation condition of the line, they may mathematically yield those circuit parameters of the line. The conditions of line connectivity including state of connecting parts or contacting parts of the switching device may be monitored by resistance variations during operation. The insulation conditions of the line can be monitored by conductance (g) and capacitance(C) measurements. Together with other condition monitoring devices such as partial discharge, sensors and visual sensing device etc.,they may give useful information to monitor out any incipient symptoms of faults. The prototype of hardware system has been developed and tested through laboratory level simulated transmission lines. The test has shown enough evident to put the proposed method to practical uses.
Abstract: Cyprus- offshore aquaculture industry has promising
prospects taking into account that Cyprus is an island. Its production
trend is increasing overtaking bigger countries such Greece and Italy.
However, current mooring systems seem to be under-performing
acting as obstacles for its future development. Furthermore, shallow
coastal waters scarcity due to competing industries dictates future
development to come by moving further from shore exposing fish
farms and subsequently mooring systems to harsher environmental
loadings. It is, therefore, of paramount importance to design mooring
systems based on engineering and scientific principles and leave
behind the present “trial and error" methods. This paper presents the
current state of Cyprus- offshore aquaculture industry and focuses of
its mooring designs by proposing a new methodology for designing
more reliable systems, hence ensuring its future.
Abstract: Most real world systems express themselves formally
as a set of nonlinear algebraic equations. As applications grow, the
size and complexity of these equations also increase. In this work, we
highlight the key concepts in using the homotopy analysis method
as a methodology used to construct efficient iteration formulas for
nonlinear equations solving. The proposed method is experimentally
characterized according to a set of determined parameters which
affect the systems. The experimental results show the potential and
limitations of the new method and imply directions for future work.