Abstract: Three sulphonic acid-doped polyanilines were
synthesized through chemical oxidation at low temperature (0-5 oC)
and potential of these polymers as sensing agent for O2 gas detection
in terms of fluorescence quenching was studied. Sulphuric acid,
dodecylbenzene sulphonic acid (DBSA) and camphor sulphonic acid
(CSA) were used as doping agents. All polymers obtained were dark
green powder. Polymers obtained were characterized by Fourier
transform infrared spectroscopy, ultraviolet-visible absorption
spectroscopy, thermogravimetry analysis, elemental analysis,
differential scanning calorimeter and gel permeation
chromatography. Characterizations carried out showed that polymers
were successfully synthesized with mass recovery for sulphuric aciddoped
polyaniline (SPAN), DBSA-doped polyaniline (DBSA-doped
PANI) and CSA-doped polyaniline (CSA-doped PANI) of 71.40%,
75.00% and 39.96%, respectively. Doping level of SPAN, DBSAdoped
PANI and CSA-doped PANI were 32.86%, 33.13% and
53.96%, respectively as determined based on elemental analysis.
Sensing test was carried out on polymer sample in the form of
solution and film by using fluorescence spectrophotometer. Samples
of polymer solution and polymer film showed positive response
towards O2 exposure. All polymer solutions and films were fully
regenerated by using N2 gas within 1 hour period. Photostability
study showed that all samples of polymer solutions and films were
stable towards light when continuously exposed to xenon lamp for 9
hours. The relative standard deviation (RSD) values for SPAN
solution, DBSA-doped PANI solution and CSA-doped PANI
solution for repeatability were 0.23%, 0.64% and 0.76%,
respectively. Meanwhile RSD values for reproducibility were 2.36%,
6.98% and 1.27%, respectively. Results for SPAN film, DBSAdoped
PANI film and CSA-doped PANI film showed the same
pattern with RSD values for repeatability of 0.52%, 4.05% and
0.90%, respectively. Meanwhile RSD values for reproducibility were
2.91%, 10.05% and 7.42%, respectively. The study on effect of the
flow rate on response time was carried out using 3 different rates
which were 0.25 mL/s, 1.00 mL/s and 2.00 mL/s. Results obtained
showed that the higher the flow rate, the shorter the response time.
Abstract: For smaller mechatronic device, especially for micro
Electronic system, a micro machining is a must. However, most
investigations on vibration of a mill have been limited to the
traditional type mill. In this article, vibration and dynamic
characteristics of a micro mill were investigated in this study. The
trend towards higher precision manufacturing technology requires
producing miniaturized components. To improve micro-milled
product quality, obtain a higher production rate and avoid milling
breakage, the dynamic characteristics of micro milling must be
studied. A stepped pre-twisted mill is used to simulate the micro mill.
The finite element analysis is employed in this work. The flute length
and diameter effects of the micro mill are considered. It is clear that
the effects of micro mill shape parameters on vibration in a micro mill
are significant.
Abstract: The quantitative determination of several trace
elements (Cr, As, Se, Cd, Hg, Pb) existing as inorganic impurities in
some oriental herb-products such as Lingzhi Mushroom capsules,
Philamin powder, etc using ICP-MS has been studied. Various
instrumental parameters such as power, gas flow rate, sample depth, as
well as the concentration of nitric acid and thick background due to
high concentration of possible interferences on the determination of
these above-mentioned elements was investigated and the optimum
working conditions of the sample measurement on ICP-MS
(Agilent-7500a) were reported. Appropriate isotope internal standards
were also used to improve the accuracy of mercury determination.
Optimal parameters for sampling digestion were also investigated. The
recovery of analytical procedure was examined by using a Certified
Reference Material (IAEA-CRM 359). The recommended procedure
was then applied for the quantitative determination of Cr, As, Se, Cd,
Hg, Pb in Lingzhi Mushroom capsule, and Philamine powder samples.
The reproducibility of sample measurement (average value between
94 and 102%) and the uncertainty of analytical data (less than 20%)
are acceptable.
Abstract: A four element prototype phased array surface probe
has been designed and constructed to improve clinical human
prostate spectroscopic data. The probe consists of two pairs of
adjacent rectangular coils with an optimum overlap to reduce the
mutual inductance. The two pairs are positioned on the anterior and
the posterior pelvic region and two couples of varactors at the input
of each coil undertake the procedures of tuning and matching. The
probe switches off and on automatically during the consecutive
phases of the MR experiment with the use of an analog switch that is
triggered by a microcontroller. Experimental tests that were carried
out resulted in high levels of tuning accuracy. Also, the switching
mechanism functions properly for various applied loads and pulse
sequence characteristics, producing only 10 μs of latency.
Abstract: This study examined the role of driving experience in hazard perception and categorization using traffic scene pictures. Specifically, young-inexperienced, moderately experienced and very experienced (taxi) drivers observed traffic scene pictures while connected to an eye tracking system and were asked to rate the level of hazardousness of each picture and to mention the three most prominent hazards in it. Target pictures included nine, nearly identical, pairs of pictures where one picture in each pair included an actual hazard as an additional element. Altogether, 22 areas of interest (AOIs) were predefined and included 13 potential hazards and 9 actual hazards. Data analysis included both verbal reports and eye scanning patterns of these AOIs. Generally, both experienced and taxi drivers noted a relatively larger number of potential hazards than young inexperienced drivers Thus, by relating to less salient potential hazards, experienced drivers have demonstrated a better situation model of the traffic environment.
Abstract: Historic religious buildings located in seismic areas
have developed different failure mechanisms. Simulation of failure
modes is done with computer programs through a nonlinear dynamic
analysis or simplified using the method of failure blocks. Currently
there are simulation methodologies of failure modes based on the
failure rigid blocks method only for Roman Catholic churches type.
Due to differences of shape in plan, elevation and construction
systems between Orthodox churches and Catholic churches, for the
first time there were initiated researches in the development of this
simulation methodology for Orthodox churches. In this article are
presented the first results from the researches. The theoretical results
were compared with real failure modes recorded at an Orthodox
church from Banat region, severely damaged by earthquakes in
1991. Simulated seismic response, using a computer program based
on finite element method was confirmed by cracks after earthquakes.
The consolidation of the church was made according to these
theoretical results, realizing a rigid floor connecting all the failure
blocks.
Abstract: In this paper, an automated algorithm to estimate and remove the continuous baseline from measured spectra containing both continuous and discontinuous bands is proposed. The algorithm uses previous information contained in a Continuous Database Spectra (CDBS) to obtain a linear basis, with minimum number of sampled vectors, capable of representing a continuous baseline. The proposed algorithm was tested by using a CDBS of flame spectra where Principal Components Analysis and Non-negative Matrix Factorization were used to obtain linear bases. Thus, the radical emissions of natural gas, oil and bio-oil flames spectra at different combustion conditions were obtained. In order to validate the performance in the baseline estimation process, the Goodness-of-fit Coefficient and the Root Mean-squared Error quality metrics were evaluated between the estimated and the real spectra in absence of discontinuous emission. The achieved results make the proposed method a key element in the development of automatic monitoring processes strategies involving discontinuous spectral bands.
Abstract: Recently, Thai education system is engaged in serious and promising reforms. One of the crucial elements in most of these educational reforms is the teacher professional development. Teachers today are under growing pressure to perform. However, most new teachers are not adequately prepared to meet the expectation. Consequently, this paper seeks to investigate the opinion of mentor teachers and university supervisors about professional development in the aspect of learning management skill of the preservice teachers in Rajabhat Universities, then compare the opinion between the mentor teachers and university supervisors about professional development in the aspect of learning management skill of the pre-service teachers. The study involved a cohort of 40 university supervisors and 77 mentor teachers. The research concludes by showing that mentor teachers viewed pre-service teacher as a professional teacher with an effective learning management skill. However, in the perspective of the university supervisor, pre-service teachers still have inadequate learning management skill.
Abstract: The aim of the current study is to develop a numerical
tool that is capable of achieving an optimum shape and design of
hyperbolic cooling towers based on coupling a non-linear finite
element model developed in-house and a genetic algorithm
optimization technique. The objective function is set to be the
minimum weight of the tower. The geometric modeling of the tower
is represented by means of B-spline curves. The finite element
method is applied to model the elastic buckling behaviour of a tower
subjected to wind pressure and dead load. The study is divided into
two main parts. The first part investigates the optimum shape of the
tower corresponding to minimum weight assuming constant
thickness. The study is extended in the second part by introducing the
shell thickness as one of the design variables in order to achieve an
optimum shape and design. Design, functionality and practicality
constraints are applied.
Abstract: The stone is a constituent part of the geological
structure of the Territory, introducing himself as a subject that has always interconnected human and environment in the development of a discourse of meanings and symbols that reflect elements realized in
different cultures and experiences.
This action meant that the first settlements and their areas of influence gained importance in the field of humanization and spatial
organization of the territory, not only for the appropriation that its
inhabitants did, but mainly because the community regardless of their
economic or social condition, used it as living space and cultural integration.
These factors become decisive in the characterization of the
landscape area in the northwest of Portugal, because the stone is a
material that appears not only in the natural landscape, but is also a strong element in humanized landscape, becoming this relation the
main characterization of the study area.
Abstract: This paper studies mixed-mode fracture mechanics in
rock based on experimental and numerical analyses. Experiments
were performed on sharp-cracked specimens using the modified
Arcan specimen test loading device. The modified Arcan specimen
test was, in association with a special loading device, an appropriate
apparatus for experimental mixed-mode fracture analysis. By
varying the loading angle from 0° to 90°, pure mode-I, pure mode-II
and a wide range of mixed-mode data were obtained experimentally.
Using the finite element results, correction factors applied to the
rectangular fracture specimen. By employing experimentally
measured critical loads and the aid of the finite element method,
mixed-mode fracture toughness for the limestone under consideration
determined.
Abstract: The mechanical behavior of porous media is governed by the interaction between its solid skeleton and the fluid existing inside its pores. The interaction occurs through the interface of gains and fluid. The traditional analysis methods of porous media, based on the effective stress and Darcy's law, are unable to account for these interactions. For an accurate analysis, the porous media is represented in a fluid-filled porous solid on the basis of the Biot theory of wave propagation in poroelastic media. In Biot formulation, the equations of motion of the soil mixture are coupled with the global mass balance equations to describe the realistic behavior of porous media. Because of irregular geometry, the domain is generally treated as an assemblage of fmite elements. In this investigation, the numerical formulation for the field equations governing the dynamic response of fluid-saturated porous media is analyzed and employed for the study of transient wave motion. A finite element model is developed and implemented into a computer code called DYNAPM for dynamic analysis of porous media. The weighted residual method with 8-node elements is used for developing of a finite element model and the analysis is carried out in the time domain considering the dynamic excitation and gravity loading. Newmark time integration scheme is developed to solve the time-discretized equations which are an unconditionally stable implicit method Finally, some numerical examples are presented to show the accuracy and capability of developed model for a wide variety of behaviors of porous media.
Abstract: Mapping between local and global coordinates is an
important issue in finite element method, as all calculations are
performed in local coordinates. The concern arises when subparametric
are used, in which the shape functions of the field variable
and the geometry of the element are not the same. This is particularly
the case for C* elements in which the extra degrees of freedoms
added to the nodes make the elements sub-parametric. In the present
work, transformation matrix for C1* (an 8-noded hexahedron
element with 12 degrees of freedom at each node) is obtained using
equivalent C0 elements (with the same number of degrees of
freedom). The convergence rate of 8-noded C1* element is nearly
equal to its equivalent C0 element, while it consumes less CPU time
with respect to the C0 element. The existence of derivative degrees
of freedom at the nodes of C1* element along with excellent
convergence makes it superior compared with it equivalent C0
element.
Abstract: This paper seeks to explore the actual classroom
setting, to examine its role for students- learning, and attitude in the
class. It presents a theoretical approach of the classroom as system to
be explored and examines the concrete reality of Greek secondary
education students, under the light of the above approach. Based on
the findings of a quantitative and qualitative research, authors
propose a rather ontological approach of the classroom and underline
what the key-elements for such approach should be. The paper
explores extensively the theoretical dimensions for the change of
paradigm required and addresses the new issues to be considered.
Abstract: This paper describes a three-dimensional thermal
model of the current path included in the low voltage power circuit
breakers. The model can be used to analyse the thermal behaviour of
the current path during both steady-state and transient conditions.
The current path lengthwise temperature distribution and timecurrent
characteristic of the terminal connections of the power circuit
breaker have been obtained. The influence of the electric current and
voltage drop on main electric contact of the circuit breaker has been
investigated. To validate the three-dimensional thermal model, some
experimental tests have been done. There is a good correlation
between experimental and simulation results.
Abstract: One of Effective parameters on the performance of linear induction motors is number of poles which must be selected and optimized to increase power efficiency and motor performance significantly. In this paper a double-sided linear induction motor with different poles number by using MAXWELL3D software is designed and with finite element method is analyzed electromagnetically. Then for dynamic simulation, linear motor by using MATLAB software is simulated. The results show that by adding poles number, system time response is increased and motor after more time reaches to steady state. Also propulsion force of motor is increased.
Abstract: Programmable logic controllers are the main controllers in the today's industries; they are used for several applications in industrial control systems and there are lots of examples exist from the PLC applications in industries especially in big companies and plants such as refineries, power plants, petrochemical companies, steel companies, and food and production companies. In the PLCs there are some functions in the function library in software that can be used in PLC programs as basic program elements. The aim of this project are introducing and implementing a new function block of a neural network to the function library of PLC. This block can be applied for some control applications or nonlinear functions calculations after it has been trained for these applications. The implemented neural network is a Perceptron neural network with three layers, three input nodes and one output node. The block can be used in manual or automatic mode. In this paper the structure of the implemented function block, the parameters and the training method of the network are presented by considering the especial method of PLC programming and its complexities. Finally the application of the new block is compared with a classic simulated block and the results are presented.
Abstract: The presence of a vertical fatigue crack in the web of
a plate girder subjected to pure bending influences the bending
moment capacity of the girder. The growth of the crack may lead to
premature elastic failure due to flange local yielding, flange local
buckling, or web local buckling. Approximate expressions for the
bending moment capacities corresponding to these failure modes
were formulated. Finite element analyses were then used to validate
the expressions. The expressions were employed to assess the effects
of crack length on the capacity. Neglecting brittle fracture, tension
buckling, and ductile failure modes, it was found that typical girders
are governed by the capacity associated with flange local yielding as
influenced by the crack. Concluding, a possible use of the capacity
expressions in girder design was demonstrated.
Abstract: The effects of dynamic subgrid scale (SGS) models are
investigated in variational multiscale (VMS) LES simulations of bluff
body flows. The spatial discretization is based on a mixed finite
element/finite volume formulation on unstructured grids. In the VMS
approach used in this work, the separation between the largest and the
smallest resolved scales is obtained through a variational projection
operator and a finite volume cell agglomeration. The dynamic version
of Smagorinsky and WALE SGS models are used to account for
the effects of the unresolved scales. In the VMS approach, these
effects are only modeled in the smallest resolved scales. The dynamic
VMS-LES approach is applied to the simulation of the flow around a
circular cylinder at Reynolds numbers 3900 and 20000 and to the flow
around a square cylinder at Reynolds numbers 22000 and 175000. It
is observed as in previous studies that the dynamic SGS procedure
has a smaller impact on the results within the VMS approach than in
LES. But improvements are demonstrated for important feature like
recirculating part of the flow. The global prediction is improved for
a small computational extra cost.
Abstract: Mercury is a natural occurring element and present in
various concentrations in the environment. Due to its toxic effects, it
is desirable to research mercury sensitive materials to adsorb
mercury. This paper describes the preparation of Au nanoparticles for
mercury adsorption by using a microwave (MW)-polyol method in
the presence of three different Sodium Chloride (NaCl)
concentrations (10, 20 and 30 mM). Mixtures of spherical, triangular,
octahedral, decahedral particles and 1-D product were obtained using
this rapid method. Sizes and shapes was found strongly depend on the
concentrations of NaCl. Without NaCl concentration, spherical,
triangular plates, octahedral, decahedral nanoparticles and 1D
product were produced. At the lower NaCl concentration (10 mM),
spherical, octahedral and decahedral nanoparticles were present,
while spherical and decahedral nanoparticles were preferentially form
by using 20 mM of NaCl concentration. Spherical, triangular plates,
octahedral and decahedral nanoparticles were obtained at the highest
NaCl concentration (30 mM). The amount of mercury adsorbed using
20 ppm mercury solution is the highest (67.5 %) for NaCl
concentration of 30 mM. The high yield of polygonal particles will
increase the mercury adsorption. In addition, the adsorption of
mercury is also due to the sizes of the particles. The sizes of particles
become smaller with increasing NaCl concentrations (size ranges, 5-
16 nm) than those synthesized without addition of NaCl (size ranges
11-32 nm). It is concluded that NaCl concentrations affects the
formation of sizes and shapes of Au nanoparticles thus affects the
mercury adsorption.