Abstract: The contra-rotating axial machine is a promising solution for several applications, where high pressure and efficiencies are needed. Also, they allow reducing the speed of rotation, the radial spacing and a better flexibility of use. However, this requires a better understanding of their operation, including the influence of second rotor on the overall aerodynamic performances. This work consisted of both experimental and numerical studies to characterize this counter-rotating fan, especially the analysis of the effects of the blades stagger angle and the inter-distance between the rotors. The experimental study served to validate the computational fluid dynamics model (CFD) used in the simulations. The numerical study permitted to cover a wider range of parameter and deeper investigation on flow structures details, including the effects of blade stagger angle and inter-distance, associated with the interaction between the rotors. As a result, there is a clear improvement in aerodynamic performance compared with a conventional machine.
Abstract: Adopting inappropriate body posture during addiction can cause muscular and skeletal deformities. This study is aimed at investigating the effects of a program of the selected corrective exercises on the kyphosis of addicted male patients. Materials and methods: This was a quasi-experimental study. This study has been carried out using the semi-experimental method. The subjects of the present study included 104 addicted men between 25 to 45 years of age. In 2014, these men were referred to one of the NA (Narcotic Anonymous) centres in Kashan in 2015. A total of 24 people suffering from drug withdrawal, who had abnormal kyphosis, were purposefully selected as a sample. The sample was randomly divided into two groups, experimental and control; each group consisted of 12 people. The experimental group participated in a training program for 12 weeks consisting of three 60 minute sessions per week. That includes strengthening, stretching and PNF exercises (deep stretching of the muscle). The control group did no exercise or corrective activity. The Kolmogorov-Smirnov test was used to assess normal distribution of data; and a paired t-test and covariance analysis test were used to assess the effectiveness of the exercises, with a significance level of P≤0.05 by using SPSS18. The results showed that three months of the selected corrective exercises had a significant effect (P≤ 0.005) on the correction of the kyphosis of the addicted male patients after three months of rehabilitation (drug withdrawal) in the experimental group, while there was no significant difference recorded in the control group (P≥0.05). The results show that exercise and corrective activities can be used as non-invasive and non-pharmacological methods to rehabilitate kyphosis abnormalities after drug withdrawal and treatment for addiction.
Abstract: The aim of the current work was to employ the finite
element method to model a slab, with a small hole across its width,
undergoing plastic plane strain deformation. The computational
model had, however, to be validated by comparing its results with
those obtained experimentally. Since they were in good agreement,
the finite element method can therefore be considered a reliable tool
that can help gain better understanding of the mechanism of ductile
failure in structural members having stress raisers. The finite element
software used was ANSYS, and the PLANE183 element was utilized.
It is a higher order 2-D, 8-node or 6-node element with quadratic
displacement behavior. A bilinear stress-strain relationship was used
to define the material properties, with constants similar to those of the
material used in the experimental study. The model was run for
several tensile loads in order to observe the progression of the plastic
deformation region, and the stress concentration factor was
determined in each case. The experimental study involved employing the visioplasticity
technique, where a circular mesh (each circle was 0.5 mm in
diameter, with 0.05 mm line thickness) was initially printed on the
side of an aluminum slab having a small hole across its width.
Tensile loading was then applied to produce a small increment of
plastic deformation. Circles in the plastic region became ellipses,
where the directions of the principal strains and stresses coincided
with the major and minor axes of the ellipses. Next, we were able to
determine the directions of the maximum and minimum shear
stresses at the center of each ellipse, and the slip-line field was then
constructed. We were then able to determine the stress at any point in
the plastic deformation zone, and hence the stress concentration
factor. The experimental results were found to be in good agreement
with the analytical ones.
Abstract: Collection of storm water runoff and forcing it into the
groundwater is the need of the hour to sustain the ground water table.
However, the runoff entraps various types of sediments and other
floating objects whose removal are essential to avoid pollution of
ground water and blocking of pores of aquifer. However, it requires
regular cleaning and maintenance due to problem of clogging. To
evaluate the performance of filter system consisting of coarse sand
(CS), gravel (G) and pebble (P) layers, a laboratory experiment was
conducted in a rectangular column. The effect of variable thickness
of CS, G and P layers of the filtration unit of the recharge shaft on the
recharge rate and the sediment concentration of effluent water were
evaluated.
Medium sand (MS) of three particle sizes, viz. 0.150–0.300 mm
(T1), 0.300–0.425 mm (T2) and 0.425–0.600 mm of thickness 25 cm,
30 cm and 35 cm respectively in the top layer of the filter system and
having seven influent sediment concentrations of 250–3,000 mg/l
were used for experimental study. The performance was evaluated in
terms of recharge rates and clogging time. The results indicated that
100 % suspended solids were entrapped in the upper 10 cm layer of
MS, the recharge rates declined sharply for influent concentrations of
more than 1,000 mg/l. All treatments with higher thickness of MS
media indicated recharge rate slightly more than that of all treatment
with lower thickness of MS media respectively. The performance of
storm water infiltration systems was highly dependent on the
formation of a clogging layer at the filter. An empirical relationship
has been derived between recharge rates, inflow sediment load, size
of MS and thickness of MS with using MLR.
Abstract: This paper presents reliability indices evaluation of the
rotor core magnetization of the induction motor operated as a self
excited induction generator by using probability distribution approach
and Monte Carlo simulation. Parallel capacitors with calculated
minimum capacitive value across the terminals of the induction motor
operated as a SEIG with unregulated shaft speed have been connected
during the experimental study. A three phase, 4 poles, 50Hz, 5.5 hp,
12.3A, 230V induction motor coupled with DC Shunt Motor was
tested in the electrical machine laboratory with variable reactive loads.
Based on this experimental study, it is possible to choose a reliable
induction machines operated as a SEIG for unregulated renewable
energy application in remote area or where grid is not available.
Failure density function, cumulative failure distribution function,
survivor function, hazard model, probability of success and
probability of failure for reliability evaluation of the three phase
induction motor operating as a SEIG have been presented graphically
in this paper.
Abstract: Bio-electrical responses obtained from freshwater
sediments by employing microbial fuel cell (MFC) technology were
investigated in this experimental study. During the electricity
generation, organic matter in the sediment was microbially oxidized
under anaerobic conditions with an electrode serving as a terminal
electron acceptor. It was found that the sediment organic matter
(SOM) associated with electrochemically-active electrodes became
more humified, aromatic, and polydispersed, and had a higher average
molecular weight, together with the decrease in the quantity of SOM.
The alteration of characteristics of the SOM was analogous to that
commonly observed in the early stage of SOM diagenetic process (i.e.,
humification). These findings including an elevation of the sediment
redox potential present a possibility of the MFC technology as a new
soil/sediment remediation technique based on its potential benefits:
non-destructive electricity generation and bioremediation.
Abstract: Green Roofs offers numerous advantages, including lowering ambient temperature, which is of increasing interest due to global warming concerns. However, there are technical problems pertaining to waterproofing to be resolved. Currently, the only recognized green roof waterproofing test is the German standard FLL. This paper examines the potential of replicating the test in tropical climate and reducing the test duration by using pre-grown plants. A three year old sample and a new setup were used for this experimental study. The new setup was prepared with close reference to the FLL standards and was compared against the three year old sample. Results showed that the waterproofing membrane was damaged by plant roots in both setups. Joints integrity was also challenged.
Abstract: The possibility of intrinsic electromagnetic fields
within living cells and their resonant self-interaction and interaction
with ambient electromagnetic fields is suggested on the basis of a
theoretical and experimental study. It is reported that intrinsic
electromagnetic fields are produced in the form of radio-frequency
and infra-red photons within atoms (which may be coupled or
uncoupled) in cellular structures, such as the cell cytoskeleton and
plasma membrane. A model is presented for the interaction of these
photons among themselves or with atoms under a dipole-dipole
coupling, induced by single-photon or two-photon processes. This
resonance is manifested by conspicuous field amplification and it is
argued that it is possible for these resonant photons to undergo
tunnelling in the form of evanescent waves to a short range (of a few
nanometers to micrometres). This effect, suggested as a resonant
photon tunnelling mechanism in this report, may enable these fields
to act as intracellular signal communication devices and as bridges
between macromolecules or cellular structures in the cell
cytoskeleton, organelles or membrane. A brief overview of an
experimental technique and a review of some preliminary results are
presented, in the detection of these fields produced in living cell
membranes under physiological conditions.
Abstract: Today air-core coils (ACC) are a viable alternative to
ferrite-core coils in a range of applications due to their low induction
effect. An analytical study was carried out and the results were used as
a guide to understand the relationship between the magnet-coil
distance and the resulting attractive magnetic force. Four different
ACC models were fabricated for experimental study. The variation in
the models included the dimensions, the number of coil turns and the
current supply to the coil. Comparison between the analytical and
experimental results for all the models shows an average discrepancy
of less than 10%. An optimized ACC design was selected for the
scanner which can provide maximum magnetic force.
Abstract: Cognitive models allow predicting some aspects of utility
and usability of human machine interfaces (HMI), and simulating
the interaction with these interfaces. The action of predicting is based
on a task analysis, which investigates what a user is required to do
in terms of actions and cognitive processes to achieve a task. Task
analysis facilitates the understanding of the system-s functionalities.
Cognitive models are part of the analytical approaches, that do not
associate the users during the development process of the interface.
This article presents a study about the evaluation of a human
machine interaction with a contextual assistant-s interface using ACTR
and GOMS cognitive models. The present work shows how these
techniques may be applied in the evaluation of HMI, design and
research by emphasizing firstly the task analysis and secondly the
time execution of the task. In order to validate and support our
results, an experimental study of user performance is conducted at
the DOMUS laboratory, during the interaction with the contextual
assistant-s interface. The results of our models show that the GOMS
and ACT-R models give good and excellent predictions respectively
of users performance at the task level, as well as the object level.
Therefore, the simulated results are very close to the results obtained
in the experimental study.
Abstract: The present work presents the extraction of copper(II)
from sulphuric acid solutions with Sodium diethyldithiocarbamate
(SDDT), and six different organic diluents: Dichloromethane,
Chloroform, Carbon tetrachloride, Toluene, xylene and Cyclohexane,
were tested. The pair SDDT/Chloroform showed to be the most
selective in removing the copper cations, and hence was considered
throughout the experimental study.
The effects of operating parameters such as the initial concentration
of the extracting agent, the agitation time, the agitation speed and the
acid concentration were considered.
For an initial concentration of Cu (II) of 63 ppm in a 0.5 M sulphuric
acid solution, both with a mass of the extracting agent of 20 mg, an
extraction percentage of about 97.8 % and a distribution coefficient
of 44.42 were obtained, respectively, confirming the performance
of the SDDT-Chloroform pair.
Abstract: This paper in essence presents comparative
experimental data on the mechanical performance of steel and
synthetic fibre-reinforced concrete under compression, tensile split
and flexure. URW1050 steel fibre and HPP45 synthetic fibre, both
with the same concrete design mix, have been used to make cube
specimens for a compression test, cylinders for a tensile split test and
beam specimens for a flexural test. The experimental data
demonstrated steel fibre reinforced concrete to be stronger in flexure
at early stages, whilst both fibre reinforced concrete types displayed
comparatively the same performance in compression, tensile splitting
and 28-day flexural strength. In terms of post-crack controlHPP45
was preferable.
Abstract: Experimental study on the influence of fibre content
on crack behaviour and propagation in synthetic-fibre reinforced
beams has been reported in this paper. The tensile behaviour of
metallic fibre concrete is evaluated in terms of residual flexural
tensile strength values determined from the load-crack mouth
opening displacement curve or load-deflection curve obtained by
applying a centre-point load on a simply supported notched prism.
The results achieved demonstrate that an increase in fibre content has
an almost negligible effect on compressive and tensile splitting
properties, causes a marginal increment in flexural tensile strength
and increasesthe Re3 value.
Abstract: Two-dimensional finite element model was created in this work to investigate the stresses distribution within rock-like samples with offset open non-persistent joints under biaxial loading. The results of this study have explained the fracture mechanisms observed in tests on rock-like material with open non-persistent offset joints [1]. Finite element code SAP2000 was used to study the stresses distribution within the specimens. Four-nodded isoperimetric plain strain element with two degree of freedom per node, and the three-nodded constant strain triangular element with two degree of freedom per node were used in the present study.The results of the present study explained the formation of wing cracks at the tip of the joints for low confining stress as well as the formation of wing cracks at the middle of the joint for the higher confining stress. High shear stresses found in the numerical study at the tip of the joints explained the formation of secondary cracks at the tip of the joints in the experimental study. The study results coincide with the experimental observations which showed that for bridge inclination of 0o, the coalescence occurred due to shear failure and for bridge inclination of 90o the coalescence occurred due to tensile failure while for the other bridge inclinations coalescence occurred due to mixed tensile and shear failure.