Abstract: As per the statistical data, the Doubly-fed Induction
Generator (DFIG) based wind turbine with variable speed and
variable pitch control is the most common wind turbine in the
growing wind market. This machine is usually used on the grid
connected wind energy conversion system to satisfy grid code
requirements such as grid stability, Fault Ride Through (FRT), power
quality improvement, grid synchronization and power control etc.
Though the requirements are not fulfilled directly by the machine, the
control strategy is used in both the stator as well as rotor side along
with power electronic converters to fulfil the requirements stated
above. To satisfy the grid code requirements of wind turbine, usually
grid side converter is playing a major role. So in order to improve the
operation capacity of wind turbine under critical situation, the
intensive study of both machine side converter control and grid side
converter control is necessary In this paper DFIG is modeled using
power components as variables and the performance of the DFIG
system is analysed under grid voltage fluctuations. The voltage
fluctuations are made by lowering and raising the voltage values in
the utility grid intentionally for the purpose of simulation keeping in
view of different grid disturbances.
Abstract: Nowadays, energy dissipation devices are commonly
used in structures. High rate of energy absorption during earthquakes
is the benefit of using such devices, which results in damage
reduction of structural elements, specifically columns. The hysteretic
damping capacity of energy dissipation devices is the key point that it
may adversely make analysis and design process complicated. This
effect may be generally represented by Equivalent Viscous Damping
(EVD). The equivalent viscous damping might be obtained from the
expected hysteretic behavior regarding to the design or maximum
considered displacement of a structure. In this paper, the hysteretic
damping coefficient of a steel Moment Resisting Frame (MRF),
which its performance is enhanced by a Buckling Restrained Brace
(BRB) system has been evaluated. Having foresight of damping
fraction between BRB and MRF is inevitable for seismic design
procedures like Direct Displacement-Based Design (DDBD) method.
This paper presents an approach to calculate the damping fraction for
such systems by carrying out the dynamic nonlinear time history
analysis (NTHA) under harmonic loading, which is tuned to the
natural system frequency. Two MRF structures, one equipped with
BRB and the other without BRB are simultaneously studied.
Extensive analysis shows that proportion of each system damping
fraction may be calculated by its shear story portion. In this way,
contribution of each BRB in the floors and their general contribution
in the structural performance may be clearly recognized, in advance.
Abstract: In recent decades, probabilistic constrained optimal
control problems have attracted much attention in many research
fields. Although probabilistic constraints are generally intractable
in an optimization problem, several tractable methods haven been
proposed to handle probabilistic constraints. In most methods,
probabilistic constraints are reduced to deterministic constraints
that are tractable in an optimization problem. However, there is a
gap between the transformed deterministic constraints in case of
known and unknown probability distribution. This paper examines
the conservativeness of probabilistic constrained optimization method
for unknown probability distribution. The objective of this paper is
to provide a quantitative assessment of the conservatism for tractable
constraints in probabilistic constrained optimization with unknown
probability distribution.
Abstract: The present study is a functional analysis of the
relationship between castes which indicates the dynamics of the caste
structure in the rural setting. The researcher has tried to show both
the cooperation and competition on important ceremonial and social
occasions. The real India exists in the villages, so we need to know
about their solidarity and also what the village life is and has been
shaping into. We need to emphasize a microcosmic study of Indian
rural life. Furthermore, caste integration is an acute problem country
faces today. To resolve this we are required to know the dynamics of
behavior of the people of different castes and for the study of the
caste dynamics a study of caste relations are needed. The present
study is an attempt in this direction.
Abstract: This study examined the mental health and behavioral
problems in early adolescence with the instrument of Achenbach
System of Empirically Based Assessment (ASEBA). The purpose of
the study was stratified sampling method was used to collect data
from 1975 participants. Multiple regression models and hierarchical
regression models were applied to examine the relations between the
background variables and internalizing problems, and the ones
between students’ performance and internalizing problems. The
results indicated that several background variables as predictors could
significantly predict the anxious/depressed problem; reading and
social study scores could significantly predict the anxious/depressed
problem. However the class as a hierarchical macro factor did not
indicate the significant effect. In brief, the majority of these models
represented that the background variables, behaviors and academic
performance were significantly related to the anxious/depressed
problem.
Abstract: Ecological systems are exposed and are influenced by
various natural and anthropogenic disturbances. They produce
various effects and states seeking response symmetry to a state of
global phase coherence or stability and balance of their food webs.
This research project addresses the development of a computational
methodology for modeling plankton food webs. The use of
algorithms to establish connections, the generation of representative
fuzzy multigraphs and application of technical analysis of complex
networks provide a set of tools for defining, analyzing and evaluating
community structure of coastal aquatic ecosystems, beyond the
estimate of possible external impacts to the networks. Thus, this
study aims to develop computational systems and data models to
assess how these ecological networks are structurally and
functionally organized, to analyze the types and degree of
compartmentalization and synchronization between oscillatory and
interconnected elements network and the influence of disturbances on
the overall pattern of rhythmicity of the system.
Abstract: Communicating users' needs, goals and problems help
designers and developers overcome challenges faced by end users.
Personas are used to represent end users’ needs. In our research,
creating personas allowed the following questions to be answered:
Who are the potential user groups? What do they want to achieve by
using the service? What are the problems that users face? What
should the service provide to them? To develop realistic personas, we
conducted a focus group discussion with undergraduate and graduate
students and also interviewed a university librarian. The personas
were created to help evaluating the Institutional Repository that is
based on the DSpace system. The profiles helped to communicate
users' needs, abilities, tasks, and problems, and the task scenarios
used in the heuristic evaluation were based on these personas. Four
personas resulted of a focus group discussion with undergraduate and
graduate students and from interviewing a university librarian. We
then used these personas to create focused task-scenarios for a
heuristic evaluation on the system interface to ensure that it met
users' needs, goals, problems and desires. In this paper, we present
the process that we used to create the personas that led to devise the
task scenarios used in the heuristic evaluation as a follow up study of
the DSpace university repository.
Abstract: Fiber Reinforced Polymer (FRP) is a composite material with exceptional properties that are capable to replace conventional steel reinforcement in reinforced and pre-stressed concrete structures. However, the main obstacle for their wide use in pre-stressed concrete application is the anchorage system. Due to the weakness of FRP in the transverse direction, the pre-stressing capacity of FRP bars are limited. This paper investigates the modification of the conventional wedge anchorage system to be used for stressing of FRP bars in pre-stressed applications. Epoxy adhesive material with glass FRP (GFRP) bars and conventional steel wedge were used in this paper. The GFRP bars are encased with epoxy at the anchor zone and the wedge system was used in pull-out test. The results showed a loading capacity of 47.6 kN which is 69% of the bar ultimate capacity. Additionally, nylon wedge was made with the same dimensions of the steel wedge and tested for GFRP bars without epoxy layer. The nylon wedge showed a loading capacity of 19.7 kN which is only 28.5% of the ultimate bar capacity.
Abstract: This study was carried out for an underground subway station at Seoul Metro, Korea. The optimal set-points of the ventilation control system are determined every 3 hours, then, the ventilation controller adjusts the ventilation fan speed according to the optimal set-point changes. Compared to manual ventilation system which is operated irrespective of the OAQ, the IDP-based ventilation control system saves 3.7% of the energy consumption. Compared to the fixed set-point controller which is operated irrespective of the IAQ diurnal variation, the IDP-based controller shows better performance with a 2% decrease in energy consumption, maintaining the comfortable IAQ range inside the station.
Abstract: This study aimed to explore the practical experience
of child welfare caseworkers and professionalism in child case
management in Malaysia. This paper discussed the specific social
work practice competency and the challenges faced by child
caseworkers in the fieldwork. This research was qualitative with
grounded theory approach. Four sessions of focused group discussion
(FGD) were conducted involving a total of 27 caseworkers (child
protector and probation officers) in the Klang Valley. The study
found that the four basic principles of knowledge in child case
management namely: 1. knowledge in child case management; 2.
professional values of caseworkers towards children; 3. skills in
managing cases; and 4. culturally competent practice in child case
management. In addition, major challenges faced by the child case
manager are the capacity and commitment of the family in children’s
rehabilitation program, the credibility of caseworkers are being
challenged, and the challenges of support system from intra and interagency.
This study is important for policy makers to take into account
the capacity and the needs of the child’s caseworker in accordance
with the national social work competency framework. It is expected
that case management services for children will improve
systematically in line with national standards.
Abstract: Passive control methods can be utilized to build
earthquake resistant structures, and also to strengthen the vulnerable
ones. In this paper, we studied the effect of this system in increasing
the ductility and energy dissipation and also modeled the behavior of
this type of eccentric bracing, and compared the hysteresis diagram
of the modeled samples with the laboratory samples. We studied
several samples of frames with vertical shear-links in order to assess
the behavior of this type of eccentric bracing. Each of these samples
was modeled in finite element software ANSYS 9.0, and was
analyzed under the static cyclic loading. It was found that vertical
shear-links have a more stable hysteresis loops. Another analysis
showed that using honeycomb beams as the horizontal beam along
with steel reinforcement has no negative effect on the hysteresis
behavior of the sample.
Abstract: This paper describes the collection and analysis of
data obtained from face-to-face interviews conducted in selected
Libyan industrial companies. The objectives of the interviews are to
enhance understanding, and generate explanations of current issues in
culture and quality management systems in Libyan companies. The
method used in analyzing the questions, as well as the main finding
of each question are explained. The interviews probed areas identify
national and organizational culture, quality management systems,
current methods, effects, barriers and other factors affecting the
success of quality management implementation. Eleven questions are
prepared and been discussed with the interviewees.
Abstract: This paper introduces a method to optimal design of a
hybrid Wind/Photovoltaic/Fuel cell generation system for a typical
domestic load that is not located near the electricity grid. In this
configuration the combination of a battery, an electrolyser, and a
hydrogen storage tank are used as the energy storage system. The aim
of this design is minimization of overall cost of generation scheme
over 20 years of operation. The Matlab/Simulink is applied for
choosing the appropriate structure and the optimization of system
sizing. A teaching learning based optimization is used to optimize the
cost function. An overall power management strategy is designed for
the proposed system to manage power flows among the different
energy sources and the storage unit in the system. The results have
been analyzed in terms of technical and economic. The simulation
results indicate that the proposed hybrid system would be a feasible
solution for stand-alone applications at remote locations.
Abstract: Investigating the dynamic responses of high rise
structures under the effect of siesmic ground motion is extremely
important for the proper analysis and design of multitoried structures.
Since the presence of infilled walls strongly influences the behaviour
of frame systems in multistoried buildings, there is an increased need
for developing guidelines for the analysis and design of infilled
frames under the effect of dynamic loads for safe and proper design
of buildings. In this manuscript, we evaluate the natural frequencies
and natural periods of single bay single storey frames considering the
effect of infill walls by using the Eigen value analysis and validating
with SAP 2000 (free vibration analysis). Various parameters obtained
from the diagonal strut model followed for the free vibration analysis
is then compared with the Finite Element model, where infill is
modeled as shell elements (four noded). We also evaluated the effect
of various parameters on the natural periods of vibration obtained by
free vibration analysis in SAP 2000 comparing them with those
obtained by the empirical expressions presented in I.S. 1893(Part I)-
2002.
Abstract: The primary objective of this work was to study the
effect of resin chemistry, pH and molarity of binding and elution
buffer on aggregate removal using Cation Exchange Chromatography
and find the optimum conditions which can give efficient aggregate
removal with minimum loss of yield. Four different resins were used
for carrying out the experiments: Fractogel EMD SO3
-(S), Fractogel EMD COO-(M), Capto SP ImpRes and S Ceramic HyperD. Runs
were carried out on the AKTA Avant system. Design of Experiments
(DOE) was used for analysis using the JMP software. The
dependence of the yield obtained using different resins on the
operating conditions was studied. Success has been achieved in
obtaining yield greater than 90% using Capto SP ImpRes and
Fractogel EMD COO-(M) resins. It has also been found that a change
in the operating conditions generally has different effects on the
yields obtained using different resins.
Abstract: The access to relevant information that is adapted to
user’s needs, preferences and environment is a challenge in many
applications running. That causes an appearance of context-aware
systems. To facilitate the development of this class of applications, it
is necessary that these applications share a common context
metamodel. In this article, we will present our context metamodel
that is defined using the OMG Meta Object facility (MOF).This
metamodel is based on the analysis and synthesis of context concepts
proposed in literature.
Abstract: Traditional mechanical control systems in thrust
vectoring are efficient in rocket thrust guidance but their costs
and their weights are excessive. The fluidic injection in the nozzle
divergent constitutes an alternative procedure to achieve the goal. In
this paper, we present a 3D analytical model for fluidic injection
in a supersonic nozzle integrating an orifice. The fluidic vectoring
uses a sonic secondary injection in the divergent. As a result, the
flow and interaction between the main and secondary jet has built in
order to express the pressure fields from which the forces and thrust
vectoring are deduced. Under various separation criteria, the present
analytical model results are compared with the existing numerical
and experimental data from the literature.
Abstract: The goal of the modern education system is to prepare
students to be able to adapt to ever-changing life situations. They
must be able to acquire required knowledge independently; apply
such knowledge in practice to solve various problems by using
modern technologies; think critically and creatively; competently use
information; be communicative, work in a team; and develop their
own moral values, intellect and cultural awareness. As a result, the
status of education significantly increases; new requirements to its
quality have been formed. In recent years the competency-based
approach in education has become of significant interest. This
approach is a strengthening of applied and practical characteristics of
a school education and leads to the forming of the key students’
competencies which define their success in future life. In this article,
the authors’ attention focuses on a range of key competencies,
educational, informational and communicative and on the possibility
to develop such competencies via STEM education. This research
shows the change in students’ attitude towards scientific disciplines
such as mathematics, general science, technology and engineering as
a result of STEM education. Two staged analyzed questionnaires
completed by students of forms II to IV in the republic of Trinidad
and Tobago allowed the authors to categorize students between two
levels that represent students’ attitude to various disciplines. The
significance of differences between selected levels was confirmed
with the use of Pearson’s chi-squared test. In summary, the analysis
of obtained data makes it possible to conclude that STEM education
has a great potential for development of core students’ competencies
and encourage the development of positive student attitude towards
the above mentioned above scientific disciplines.
Abstract: Electrohydraulic servo system have been used in
industry in a wide number of applications. Its dynamics are highly
nonlinear and also have large extent of model uncertainties and
external disturbances. In this paper, a robust back-stepping control
(RBSC) scheme is proposed to overcome the problem of disturbances
and system uncertainties effectively and to improve the tracking
performance of EHS systems. In order to implement the proposed
control scheme, the system uncertainties in EHS systems are
considered as total leakage coefficient and effective oil volume. In
addition, in order to obtain the virtual controls for stabilizing system,
the update rule for the system uncertainty term is induced by
the Lyapunov control function (LCF). To verify the performance and
robustness of the proposed control system, computer simulation of
the proposed control system using Matlab/Simulink Software
is executed. From the computer simulation, it was found that the
RBSC system produces the desired tracking performance and has
robustness to the disturbances and system uncertainties of EHS
systems.
Abstract: The teaching of computer programming for beginners
has been generally considered as a difficult and challenging task.
Several methodologies and research tools have been developed,
however, the difficulty of teaching still remains. Our work integrates
the state of the art in teaching programming with game software and
further provides metrics for the evaluation of student performance in
a collaborative activity of playing games. This paper aims to present a
multi-agent system architecture to be incorporated to the educational
collaborative game software for teaching programming that monitors,
evaluates and encourages collaboration by the participants. A
literature review has been made on the concepts of Collaborative
Learning, Multi-agents systems, collaborative games and techniques
to teach programming using these concepts simultaneously.