Abstract: A single-phase closed thermosyphon has been
fabricated and experimented to utilize solar energy for water heating.
The working fluid of the closed thermosyphon is heated at the flatplate
collector and the hot water goes to the water tank due to density
gradient caused by temperature differences. This experimental work
was done using insulated water tank and insulated connecting pipe
between the tank and the flat-plate collector. From the collected data,
performance parameters such as instantaneous collector efficiency
and heat removal factor are calculated. In this study, the effects of
glazing were also observed. The water temperature rise and the
maximum instantaneous efficiency obtained from this experiment
with glazing using insulated water tank and insulated connecting pipe
are 17°C in a period of 5 hours and 60% respectively. Whereas the
water temperature rise and the maximum instantaneous efficiency
obtained from this experiment with glazing using non-insulated water
tank and non-insulated connecting pipe are 14°C in a period of 5
hours and 39% respectively.
Abstract: The psychological impact of peer influence on its
individual group members, can make them resist HIV/AIDS
counselling and testing. This study investigated the correlate of peer
influence and resistance to HIV/AIDS counselling and testing among
students in tertiary institutions in Kano state, Nigeria. To achieve
this, three null hypotheses were postulated and tested. Cross-
Sectional Survey Design was employed in which 1512 sample was
selected from a student population of 104,841.Simple Random
Sampling was used in the selection. A self-developed 20-item scale
called Peer Influence and Psychological Resistance Inventory
(PIPRI) was used for data collection. Pearson Product Moment
Correlation (PPMCC) via test-retest method was applied to estimate a
reliability coefficient of 0.86 for the scale. Data obtained was
analyzed using t-test and PPMCC at 0.05 level of confidence. Results
reveal 26.3% (397) of the respondents being influenced by their peer
group, while 39.8% showed resistance. Also, the t-tests and PPMCC
statistics were greater than their respective critical values. This shows
that there was a significant gender difference in peer influence and a
difference between peer influence and resistance to HIV/AIDS
counselling and testing. However, a positive relationship between
peer influence and resistance to HIV/AIDS counselling and testing
was shown. A major recommendation offered suggests the use of
reinforcement and social support for positive attitudes and
maintenance of safe behaviour among students who patronize
HIV/AIDS counselling.
Abstract: In this paper, the effect of admixtures on the tensional
strength of concrete in Urmia-lake water have been investigated. We
made different types of concretes with the ratio of w/c and replaced
different percentages of micro-silica, air-entraining, super plasticizer,
corrosion-inhibiting, and caulk with two types of cement I and II as
well as investigating in both ordinary water and Urmia-lake water.
The tensional strength was investigated on these samples.
Abstract: Cement-based grouts has been used successfully to
repair cracks in many concrete structures such as bridges, tunnels,
buildings and to consolidate soils or rock foundations. In the present
study the rheological characterization of cement grout with
water/binder ratio (W/B) is fixed at 0.5. The effect of the replacement
of cement by bentonite (2 to 10% wt) in presence of superplasticizer
(0.5% wt) was investigated. Several rheological tests were carried out
by using controlled-stress rheometer equipped with vane geometry in
temperature of 20°C. To highlight the influence of bentonite and
superplasticizer on the rheological behavior of grout cement, various
flow tests in a range of shear rate from 0 to 200 s-1 were observed.
Cement grout showed a non-Newtonian viscosity behavior at all
concentrations of bentonite. Three parameter model Herschel-
Bulkley was chosen for fitting of experimental data. Based on the
values of correlation coefficients of the estimated parameters, The
Herschel-Bulkley law model well described the rheological behavior
of the grouts. Test results showed that the dosage of bentonite
increases the viscosity and yield stress of the system and introduces
more thixotropy. While the addition of both bentonite and
superplasticizer with cement grout improve significantly the fluidity
and reduced the yield stress due to the action of dispersion of SP.
Abstract: Since the emergence of e-Commerce, the world of
business has witnessed a radical shift in the way business activities
are conducted. However, the emergence of m-Commerce has further
pushed the boundaries of virtual commerce revolution. As a result,
there seems to be a growing blur in the distinction between e-
Commerce and m-Commerce. In addition, existing definitions for
both forms of commerce highlight characteristics (e.g. type of device
and activity conducted) that may be applicable to both concepts. The
aim of this paper is to identify the characteristics that help define and
delineate between e- and m- Commerce. The paper concludes that
characteristics of mobility, ubiquity and immediacy provide a clearer
and simpler template to distinguish between e-Commerce and m-
Commerce.
Abstract: In this paper family of multilevel inverter topology
with reduced number of power switches is presented. The proposed
inverter can generate both even and odd level. The proposed topology
is suitable for symmetric structure. The proposed symmetric inverter
results in reduction of power switches, power diode and gate driver
circuits and also it may further minimize the installation area and
cost. To prove the superiority of proposed topology is compared with
conventional topologies. The performance of this symmetric
multilevel inverter has been tested by computer based simulation and
prototype based experimental setup for nine-level inverter is
developed and results are verified.
Abstract: The cooling channels of injection mould play a crucial
role in determining the productivity of moulding process and the
product quality. It’s not a simple task to design high quality cooling
channels. In this paper, an intelligent cooling channels design system
including automatic layout of cooling channels, interference checking
and assembly of accessories is studied. Automatic layout of cooling
channels using genetic algorithm is analyzed. Through integrating
experience criteria of designing cooling channels, considering the
factors such as the mould temperature and interference checking, the
automatic layout of cooling channels is implemented. The method of
checking interference based on distance constraint algorithm and the
function of automatic and continuous assembly of accessories are
developed and integrated into the system. Case studies demonstrate the
feasibility and practicality of the intelligent design system.
Abstract: Fritillaria oranensis (Liliaceae) was described in 1874
by pomel from Algeria. Plant samples have been collected from the
mount of Tessala (Sidi-Bel-Abbes). The morphological features of
various organs of the plant are described in detail. In the
morphological part of the study, features of various organs of the
plants such as stem and leaf were determined and illustrated.
Ecological studies provide information about the physical and
chemical structure of soil types in Tessala Mountain. The aim of this
original investigation is to put forth ecological and anatomical
features of these species for the first time, but at the same time given
detailed account of the morphological characteristics of the stem and
leaf of Fritillaria oranensis.
Abstract: Recently, an increasing number of researchers have
been focusing on working out realistic solutions to sustainability
problems. As sustainability issues gain higher importance for
organisations, the management of such decisions becomes critical.
Knowledge representation is a fundamental issue of complex
knowledge based systems. Many types of sustainability problems
would benefit from models based on experts’ knowledge. Cognitive
maps have been used for analyzing and aiding decision making. A
cognitive map can be made of almost any system or problem. A
fuzzy cognitive map (FCM) can successfully represent knowledge
and human experience, introducing concepts to represent the essential
elements and the cause and effect relationships among the concepts to
model the behaviour of any system. Integrated waste management
systems (IWMS) are complex systems that can be decomposed to
non-related and related subsystems and elements, where many factors
have to be taken into consideration that may be complementary,
contradictory, and competitive; these factors influence each other and
determine the overall decision process of the system. The goal of the
present paper is to construct an efficient IWMS which considers
various factors. The authors’ intention is to propose an expert based
system design approach for implementing expert decision support in
the area of IWMSs and introduces an appropriate methodology for
the development and analysis of group FCM. A framework for such a
methodology consisting of the development and application phases is
presented.
Abstract: A noble low NOx combustion technology, based on
partial oxidation combustion concept in a fuel rich combustion zone, is
successfully applied in this research. The burner is designed such that
a portion of fuel is heated and pre-vaporized in the furnace then
injected into a fuel rich combustion zone so that a partial oxidation
reaction occurs. The effects of equivalence ratio, thermal load, and
fuel distribution ratio on the emissions of NOx and CO are
experimentally investigated. This newly developed combustion
technology showed very low NOx emission level, about 12 ppm, when
light oil is used as a fuel.
Abstract: In the present work, hydrogen gas sensor of modest
sensitivity utilizing functionalized multiwalled carbon nanotubes
partially decorated with tin oxide nanoparticles (F-MWCNTs/SnO2)
has been fabricated. This sensing material was characterized by
scanning electron microscopy (SEM). In addition, a remarkable
finding was that the F-MWCNTs/SnO2 sensor shows good sensitivity
as compared to F-MWCNTs for low concentration (0.05-1% by
volume) of H2 gas. The fabricated sensors show complete resistance
recovery and good repeatability when exposed to H2 gas at the room
temperature conditions.
Abstract: In this paper two approaches to joint signal detection,
time of arrival (ToA) and angle of arrival (AoA) estimation in
multi-element antenna array are investigated. Two scenarios were
considered: first one, when the waveform of the useful signal
is known a priori and, second one, when the waveform of the
desired signal is unknown. For first scenario, the antenna array
signal processing based on multi-element matched filtering (MF)
with the following non-coherent detection scheme and maximum
likelihood (ML) parameter estimation blocks is exploited. For second
scenario, the signal processing based on the antenna array elements
covariance matrix estimation with the following eigenvector analysis
and ML parameter estimation blocks is applied. The performance
characteristics of both signal processing schemes are thoroughly
investigated and compared for different useful signals and noise
parameters.
Abstract: A novel simulation method to determine the
displacements of machine tools due to thermal factors is presented.
The specific characteristic of this method is the employment of
original CAD data from the design process chain, which is
interpreted by an algorithm in terms of geometry-based allocation of
convection and radiation parameters. Furthermore analogous models
relating to the thermal behaviour of machine elements are
automatically implemented, which were gained by extensive
experimental testing with thermography imaging. With this a
transient simulation of the thermal field and in series of the
displacement of the machine tool is possible simultaneously during
the design phase. This method was implemented and is already used
industrially in the design of machining centres in order to improve
the quality of herewith manufactured workpieces.
Abstract: Mech-Degla, Degla-Beida and Frezza are the date
(Phoenix dactylifera L.) common varieties with a more or less good
availability and feeble trade value. Some morphologic and
physicochemical factors were determined. Results show that the
whole date weight is significantly different (P= 95%) concerning
Mech-Degla and Degla-Beida which are more commercialized than
Frezza whereas the pulp mass proportion in relation to whole fruits is
highest for Frezza (88.28%). Moreover, there is a large variability
concerning the weights and densities of constitutive tissues in each
variety. The white tissue is dominant in Mech-Degla in opposite to
the two other varieties. The variance analyze showed that the
difference in weights between brown and white tissues is significant
(P = 95%) for all studied varieties. Some other morphologic and
chemical proprieties of the whole pulps and their two constitutive
parts (brown or pigmented and white) are also investigated. The
predominance of phenolics in Mech-Degla (4.01g/100g, w.b) and
Frezza (4.96 g/100g, w.b) pulps brown part is the main result
revealed in this study.
Abstract: Nonstandard tests are necessary for analyses and
verification of new developed structural and technological solutions
with application of composite materials. One of the most critical
primary structural parts of a typical aerospace structure is T-joint.
This structural element is loaded mainly in shear, bending, peel and
tension. The paper is focused on the shear loading simulations. The
aim of the work is to obtain a representative uniform distribution of
shear loads along T-joint during the mechanical testing. A new
design of T-joint test procedure, numerical simulation and
optimization of representative boundary conditions are presented.
The different conditions and inaccuracies both in simulations and
experiments are discussed. The influence of different parameters on
stress and strain distributions is demonstrated on T-joint made of
CFRP (carbon fibre reinforced plastic). A special test rig designed by
VZLU (Aerospace Research and Test Establishment) for T-shear test
procedure is presented.
Abstract: In this paper the effect of wall waviness of side walls
in a two-dimensional wavy enclosure is numerically investigated.
Two vertical wavy walls and straight top wall are kept isothermal and
the bottom wall temperature is higher and spatially varying with
cosinusoidal temperature distribution. A computational code based on
Finite-volume approach is used to solve governing equations and
SIMPLE method is used for pressure velocity coupling. Test is
performed for several different numbers of undulations. The Prandtl
number was kept constant and the Ra number denotes that the flow is
laminar. Temperature and velocity fields are determined. Therefore,
according to the obtained results a correlation is proposed for average
Nusselt number as a function of number of side wall waves. The
results indicate that the Nusselt number is highly affected by number
of waves and increasing it decreases the wavy walls Nusselt number;
although the Nusselt number is not highly affected by surface
waviness when the number of undulations is below one.
Abstract: This paper presents a 4-DOF nonlinear model of a
cracked de Laval rotor-stator system derived based on Energy
Principles. The model has been used to simulate coupled torsionallateral
response of the faulty system with multiple parametric
excitations; rotor-stator-rub, a breathing transverse crack, eccentric
mass and an axial force. Nonlinearity of a “breathing” crack is
incorporated in the model using a simple hinge mechanism suitable
for a shallow crack. Response of the system while passing via its
critical speed with intermittent rotor-stator rub is analyzed. Effects of
eccentricity with phase and acceleration are investigated. Features of
crack, rub and eccentricity in vibration response are explored for
condition monitoring. The presence of a crack and rub are observable
in the power spectrum despite excitations by an axial force and rotor
unbalance. Obtained results are consistent with existing literature and
could be adopted into rotor condition monitoring strategies.
Abstract: Urban greenery remains the bastion of urban
landscape and a key to sustainable development due to its integral
connections to the general health and wellbeing of urban residents.
However, in an era of rapid urbanisation, recent studies indicate that
urban greenery, especially ecologically sensitive areas, in many
African cities is becoming increasingly depleted. Given the scale and
rate of natural and anthropogenic change, effective management of
urban greenery as the ultimate goal of restoring depleting urban
landscapes is urgent. This review advocates for an urban resilience
model to managing urban greenery.
Abstract: Different strategies and tools are available at the oil
and gas industry for detecting and analyzing tension and possible
fractures in borehole walls. Most of these techniques are based on
manual observation of the captured borehole images. While this
strategy may be possible and convenient with small images and few
data, it may become difficult and suitable to errors when big
databases of images must be treated. While the patterns may differ
among the image area, depending on many characteristics (drilling
strategy, rock components, rock strength, etc.). In this work we
propose the inclusion of data-mining classification strategies in order
to create a knowledge database of the segmented curves. These
classifiers allow that, after some time using and manually pointing
parts of borehole images that correspond to tension regions and
breakout areas, the system will indicate and suggest automatically
new candidate regions, with higher accuracy. We suggest the use of
different classifiers methods, in order to achieve different knowledge
dataset configurations.
Abstract: This paper is concerning the issues of behaviour of
lightweight expanded clay aggregates concrete exposed to high
temperature. Lightweight aggregates from expanded clay are
produced by firing of row material up to temperature 1050°C.
Lightweight aggregates have suitable properties in terms of volume
stability, when exposed to temperatures up to 1050°C, which could
indicate their suitability for construction applications with higher risk
of fire. The test samples were exposed to heat by using the standard
temperature-time curve ISO 834. Negative changes in resulting
mechanical properties, such as compressive strength, tensile strength,
and flexural strength were evaluated. Also visual evaluation of the
specimen was performed. On specimen exposed to excessive heat, an
explosive spalling could be observed, due to evaporation of
considerable amount of unbounded water from the inner structure of
the concrete.