Abstract: The use of information and communication
technologies such as computers, mobile phones and the Internet is
becoming prevalent in today’s world; and it is facilitating access to a
vast amount of data, services and applications for the improvement of
people’s lives. However, this prevalence of ICTs is hampered by the
problem of low income levels in developing countries to the point
where people cannot timeously replace or repair their ICT devices
when damaged or lost; and this problem serves as a motivation for
this study whose aim is to examine the perceptions of teachers on the
reliability of cellphones when used for teaching and learning
purposes. The research objectives unfolding this aim are of two
types: Objectives on the selection and design of theories and models,
and objectives on the empirical testing of these theories and models.
The first type of objectives is achieved using content analysis in an
extensive literature survey: and the second type of objectives is
achieved through a survey of high school teachers from the ILembe
and UMgungundlovu districts in the KwaZulu-Natal province of
South Africa. Data collected from this questionnaire based survey is
analysed in SPSS using descriptive statistics and Pearson correlations
after checking the reliability and validity of the questionnaires. The
main hypothesis driving this study is that there is a relationship
between the demographics and the attribution identity of teachers on
one hand, and their perceptions on the reliability of cellphones on the
other hand, as suggested by existing literature; except that attribution
identities are considered in this study under three angles: intention,
knowledge and ability, and action. The results of this study confirm
that the perceptions of teachers on the reliability of cellphones for
teaching and learning are affected by the school location of these
teachers, and by their perceptions on learners’ cellphones usage
intentions and actual use.
Abstract: Present study is aimed on the cutting process of circular
cross-section rods where the fracture is used to separate one rod
into two pieces. Incorporating the phenomenological ductile fracture
model into the explicit formulation of finite element method, the
process can be analyzed without the necessity of realizing too many
real experiments which could be expensive in case of repetitive
testing in different conditions. In the present paper, the steel AISI
1045 was examined and the tensile tests of smooth and notched
cylindrical bars were conducted together with biaxial testing of the
notched tube specimens to calibrate material constants of selected
phenomenological ductile fracture models. These were implemented
into the Abaqus/Explicit through user subroutine VUMAT and used
for cutting process simulation. As the calibration process is based
on variables which cannot be obtained directly from experiments,
numerical simulations of fracture tests are inevitable part of the
calibration. Finally, experiments regarding the cutting process were
carried out and predictive capability of selected fracture models is
discussed. Concluding remarks then make the summary of gained
experience both with the calibration and application of particular
ductile fracture criteria.
Abstract: Drying behavior of blanched sweet potato in a cabinet
dryer using different five air temperatures (40-80°C) and ten sweet
potato varieties sliced to 5mm thickness were investigated. The
drying data were fitted to eight models. The Modified Henderson and
Pabis model gave the best fit to the experimental moisture ratio data
obtained during the drying of all the varieties while Newton (Lewis)
and Wang and Singh models gave the least fit. The values of Deff
obtained for Bophelo variety (1.27 x 10-9 to 1.77 x 10-9 m2/s) was
the least while that of S191 (1.93 x 10-9 to 2.47 x 10-9 m2/s) was the
highest which indicates that moisture diffusivity in sweet potato is
affected by the genetic factor. Activation energy values ranged from
0.27-6.54 kJ/mol. The lower activation energy indicates that drying
of sweet potato slices requires less energy and is hence a cost and
energy saving method. The drying behavior of blanched sweet potato
was investigated in a cabinet dryer. Drying time decreased
considerably with increase in hot air temperature. Out of the eight
models fitted, the Modified Henderson and Pabis model gave the best
fit to the experimental moisture ratio data on all the varieties while
Newton, Wang and Singh models gave the least. The lower activation
energy (0.27 - 6.54 kJ/mol) obtained indicates that drying of sweet
potato slices requires less energy and is hence a cost and energy
saving method.
Abstract: This paper considers the characterization of a complex
electromagnetic environment due to multiple sources of
electromagnetic radiation as a five-dimensional surface which can be
described by a set of several surface sections including: instant EM
field intensity distribution maps at a given frequency and altitude,
instantaneous spectrum at a given location in space and the time
evolution of the electromagnetic field spectrum at a given point in
space. This characterization if done over time can enable the
exposure levels of Radio Frequency Radiation at every point in the
analysis area to be determined and results interpreted based on
comparison of the determined RFR exposure level with the safe
guidelines for general public exposure given by recognized body
such as the International commission on non-ionizing radiation
protection (ICNIRP), Institute of Electrical and Electronic Engineers
(IEEE), the National Radiation Protection Authority (NRPA).
Abstract: This paper presents a regression model with
autocorrelated errors in which the inputs are social moods obtained by
analyzing the adjectives in Twitter posts using a document topic
model, where document topics are extracted using LDA. The
regression model predicts Dow Jones Industrial Average (DJIA) more
precisely than autoregressive moving-average models.
Abstract: Turbulent flow in complex geometries receives considerable attention due to its importance in many engineering applications. It has been the subject of interest for many researchers. Some of these interests include the design of storm water channels. The design of these channels requires testing through physical models. The main practical limitation of physical models is the so called “scale effect”, that is, the fact that in many cases only primary physical mechanisms can be correctly represented, while secondary mechanisms are often distorted. These observations form the basis of our study, which centered on problems associated with the design of storm water channels near the Dead Sea, in Israel. To help reach a final design decision we used different physical models. Our research showed good coincidence with the results of laboratory tests and theoretical calculations, and allowed us to study different effects of fluid flow in an open channel. We determined that problems of this nature cannot be solved only by means of theoretical calculation and computer simulation. This study demonstrates the use of physical models to help resolve very complicated problems of fluid flow through baffles and similar structures. The study applies these models and observations to different construction and multiphase water flows, among them, those that include sand and stone particles, a significant attempt to bring to the testing laboratory a closer association with reality.
Abstract: Vertical slotted walls can be used as permeable
breakwaters to provide economical and environmental protection
from undesirable waves and currents inside the port. The permeable
breakwaters are partially protection and have been suggested to
overcome the environmental disadvantages of fully protection
breakwaters. For regular waves a semi-analytical model is based on
an eigenfunction expansion method and utilizes a boundary condition
at the surface of each wall are developed to detect the energy
dissipation through the slots. Extensive laboratory tests are carried
out to validate the semi-analytic models. The structure of the physical
model contains two walls and it consists of impermeable upper and
lower part, where the draft is based a decimal multiple of the total
depth. The middle part is permeable with a porosity of 50%. The
second barrier is located at a distant of 0.5, 1, 1.5 and 2 times of the
water depth from the first one. A comparison of the theoretical results
with previous studies and experimental measurements of the present
study show a good agreement and that, the semi-analytical model is
able to adequately reproduce most the important features of the
experiment.
Abstract: In this paper, we present a neural-network (NN) based
approach to represent a nonlinear Tagagi-Sugeno (T-S) system. A
linear differential inclusion (LDI) state-space representation is utilized
to deal with the NN models. Taking advantage of the LDI
representation, the stability conditions and controller design are
derived for a class of nonlinear structural systems. Moreover, the
concept of utilizing the Parallel Particle Swarm Optimization (PPSO)
algorithm to solve the common P matrix under the stability criteria is
given in this paper.
Abstract: The aim of this research is to evaluate the effectiveness of software quality assurance approaches of Sri Lankan offshore software development organizations, and to propose a framework which could be used across all offshore software development organizations.
An empirical study was conducted using derived framework from popular software quality evaluation models. The research instrument employed was a questionnaire survey among thirty seven Sri Lankan registered offshore software development organizations.
The findings demonstrate a positive view of Effectiveness of Software Quality Assurance – the stronger predictors of Stability, Installability, Correctness, Testability and Changeability. The present study’s recommendations indicate a need for much emphasis on software quality assurance for the Sri Lankan offshore software development organizations.
Abstract: A brief review of the empirical studies on the methodology of the stock market decision support would indicate that they are at a threshold of validating the accuracy of the traditional and the fuzzy, artificial neural network and the decision trees. Many researchers have been attempting to compare these models using various data sets worldwide. However, the research community is on the way to the conclusive confidence in the emerged models. This paper attempts to use the automotive sector stock prices from National Stock Exchange (NSE), India and analyze them for the intra-sectorial support for stock market decisions. The study identifies the significant variables and their lags which affect the price of the stocks using OLS analysis and decision tree classifiers.
Abstract: This paper presents a nonparametric method to obtain the hazard rate “Bathtub curve” for power system components. The model is a mixture of the three known phases of a component life, the decreasing failure rate (DFR), the constant failure rate (CFR) and the increasing failure rate (IFR) represented by three parametric Weibull models. The parameters are obtained from a simultaneous fitting process of the model to the Kernel nonparametric hazard rate curve. From the Weibull parameters and failure rate curves the useful lifetime and the characteristic lifetime were defined. To demonstrate the model the historic time-to-failure of distribution transformers were used as an example. The resulted “Bathtub curve” shows the failure rate for the equipment lifetime which can be applied in economic and replacement decision models.
Abstract: This paper presents a complete dynamic modeling
of a membrane distillation process. The model contains two
consistent dynamic models. A 2D advection-diffusion equation
for modeling the whole process and a modified heat equation
for modeling the membrane itself. The complete model describes
the temperature diffusion phenomenon across the feed, membrane,
permeate containers and boundary layers of the membrane. It gives
an online and complete temperature profile for each point in the
domain. It explains heat conduction and convection mechanisms that
take place inside the process in terms of mathematical parameters, and
justify process behavior during transient and steady state phases. The
process is monitored for any sudden change in the performance at any
instance of time. In addition, it assists maintaining production rates
as desired, and gives recommendations during membrane fabrication
stages. System performance and parameters can be optimized
and controlled using this complete dynamic model. Evolution of
membrane boundary temperature with time, vapor mass transfer along
the process, and temperature difference between membrane boundary
layers are depicted and included. Simulations were performed over
the complete model with real membrane specifications. The plots
show consistency between 2D advection-diffusion model and the
expected behavior of the systems as well as literature. Evolution
of heat inside the membrane starting from transient response till
reaching steady state response for fixed and varying times is
illustrated.
Abstract: Information technology has made a pivotal progress across disparate disciplines, one of which is AEC (Architecture, Engineering and Construction) industry. CAD is a form of computer-aided building modulation that architects, engineers and contractors use to create and view two- and three-dimensional models. The AEC industry also uses building information modeling (BIM), a newer computerized modeling system that can create four-dimensional models; this software can greatly increase productivity in the AEC industry. BIM models generate open source IFC (Industry Foundation Classes) files which aim for interoperability for exchanging information throughout the project lifecycle among various disciplines. The methods developed in previous studies require either an IFC schema or MVD and software applications, such as an IFC model server or a Building Information Modeling (BIM) authoring tool, to extract a partial or complete IFC instance model. This paper proposes an efficient algorithm for extracting a partial and total model from an Industry Foundation Classes (IFC) instance model without an IFC schema or a complete IFC model view definition (MVD).
Abstract: The objective of this paper is finding the way of economic restructuring - that is, change in the shares of sectoral gross outputs - resulting in the maximum possible increase in the gross domestic product (GDP) combined with decreases in energy consumption and CO2 emissions. It uses an input-output model for the GDP and factorial models for the energy consumption and CO2 emissions to determine the projection of the gradient of GDP, and the antigradients of the energy consumption and CO2 emissions, respectively, on a subspace formed by the structure-related variables. Since the gradient (antigradient) provides a direction of the steepest increase (decrease) of the objective function, and their projections retain this property for the functions' limitation to the subspace, each of the three directional vectors solves a particular problem of optimal structural change. In the next step, a type of factor analysis is applied to find a convex combination of the projected gradient and antigradients having maximal possible positive correlation with each of the three. This convex combination provides the desired direction of the structural change. The national economy of the United States is used as an example of applications.
Abstract: This paper presents a Gaussian process model-based
short-term electric load forecasting. The Gaussian process model is
a nonparametric model and the output of the model has Gaussian
distribution with mean and variance. The multiple Gaussian process
models as every hour ahead predictors are used to forecast future
electric load demands up to 24 hours ahead in accordance with the
direct forecasting approach. The separable least-squares approach that
combines the linear least-squares method and genetic algorithm is
applied to train these Gaussian process models. Simulation results
are shown to demonstrate the effectiveness of the proposed electric
load forecasting.
Abstract: In this paper, we forecast the volatility of Baht/USDs using Markov Regime Switching GARCH (MRS-GARCH) models. These models allow volatility to have different dynamics according to unobserved regime variables. The main purpose of this paper is to find out whether MRS-GARCH models are an improvement on the GARCH type models in terms of modeling and forecasting Baht/USD volatility. The MRS-GARCH is the best performance model for Baht/USD volatility in short term but the GARCH model is best perform for long term.
Abstract: Flows developed between two parallel disks have
many engineering applications. Two types of non-swirling flows can
be generated in such a domain. One is purely source flow in disc type
domain (outward flow). Other is purely sink flow in disc type domain
(inward flow). This situation often appears in some turbo machinery
components such as air bearings, heat exchanger, radial diffuser,
vortex gyroscope, disc valves, and viscosity meters. The main goal of
this paper is to show the mesh convergence, because mesh
convergence saves time, and economical to run and increase the
efficiency of modeling for both sink and source flow. Then flow field
is resolved using a very fine mesh near-wall, using enhanced wall
treatment. After that we are going to compare this flow using
standard k-epsilon, RNG k-epsilon turbulence models. Lastly
compare some experimental data with numerical solution for sink
flow. The good agreement of numerical solution with the
experimental works validates the current modeling.
Abstract: In this paper, five ontologies are described, which include the event concepts. The paper provides an overview and comparison of existing event models. The main criteria for comparison are that there should be possibilities to model events with stretch in the time and location and participation of objects; however, there are other factors that should be taken into account as well. The paper also shows an example of using ontologies in complex event processing.
Abstract: The numerical simulation of electromagnetic interactions is still a challenging problem, especially in problems that result in fully three dimensional mathematical models.
The goal of this work is to use mathematical modeling to characterize the reliability and capacity of eddy current technique to detect and characterize defects embedded in aeronautical in-service pieces.
The finite element method is used for describing the eddy current technique in a mathematical model by the prediction of the eddy current interaction with defects. However, this model is an approximation of the full Maxwell equations.
In this study, the analysis of the problem is based on a three dimensional finite element model that computes directly the electromagnetic field distortions due to defects.
Abstract: We consider the biggest challenge in speech recognition – noise reduction. Traditionally detected transient noise pulses are removed with the corrupted speech using pulse models. In this paper we propose to cope with the problem directly in Dynamic Time Warping domain. Bidirectional Dynamic Time Warping algorithm for the recognition of isolated words impacted by transient noise pulses is proposed. It uses simple transient noise pulse detector, employs bidirectional computation of dynamic time warping and directly manipulates with warping results. Experimental investigation with several alternative solutions confirms effectiveness of the proposed algorithm in the reduction of impact of noise on recognition process – 3.9% increase of the noisy speech recognition is achieved.