Abstract: Laser engraving is a manufacturing method for those applications where previously Electrical Discharge Machining (EDM) was the only choice. Laser engraving technology removes material layer-by-layer and the thickness of layers is usually in the range of few microns. The aim of the present work is to investigate the influence of the process parameters on the surface quality when machined by laser engraving. The examined parameters were: the pulse frequency, the beam speed and the layer thickness. The surface quality was determined by the surface roughness for every set of parameters. Experimental results on Al7075 material showed that the surface roughness strictly depends on the process parameters used.
Abstract: High purity hydrogen and the valuable by-product of carbon nanotubes (CNTs) can be produced by the methane catalytic decomposition. The methane conversion and the performance of CNTs were determined by the choices of catalysts and the condition of decomposition reaction. In this paper, Ni/MgO and Ni/O-D (oxidized diamond) catalysts were prepared by wetness impregnation method. The effects of reaction temperature and space velocity of methane on the methane conversion were investigated in a fixed-bed. The surface area, structure and micrography were characterized with BET, XPS, SEM, EDS technology. The results showed that the conversion of methane was above 8% within 150 min (T=500) for 33Ni/O-D catalyst and higher than 25% within 120 min (T=650) for 41Ni/MgO catalyst. The initial conversion increased with the increasing temperature of the decomposition reaction, but their catalytic activities decreased rapidly while at too higher temperature. To decrease the space velocity of methane was propitious to promote the methane conversion, but not favor of the hydrogen yields. The appearance of carbon resulted from the methane decomposition lied on the support type and the condition of catalytic reaction. It presented as fiber shape on the surface of Ni/O-D at the relatively lower temperature such as 500 and 550, but as grain shape stacked on and overlayed on the surface of the metal nickel while at 650. The carbon fiber can form on the Ni/MgO surface at 650 and the diameter of the carbon fiber increased with the decreasing space velocity.
Abstract: A new mechanism responsible for structural life
consumption due to resonant fatigue in turbine blades, or vanes, is
presented and explained. A rotating blade or vane in a gas turbine can
change its contour due to erosion and/or material build up, in any of
these instances, the surface pressure distribution occurring on the
suction and pressure sides of blades-vanes can suffer substantial
modification of their pressure and temperatures envelopes and flow
characteristics. Meanwhile, the relative rotation between the blade
and duct vane while the pressurized gas flows and the consequent
wake crossings, will induce a fluctuating thrust force or lift that will
excite the blade.
An actual totally used up set of vane-blade components in a HP
turbine power stage in a gas turbine is analyzed. The blade suffered
some material erosion mostly at the trailing edge provoking a
peculiar surface pressure envelope which evolved as the relative
position between the vane and the blade passed in front of each other.
Interestingly preliminary modal analysis for this eroded blade
indicates several natural frequencies within the aeromechanic power
spectrum, moreover, the highest frequency component is 94% of one
natural frequency indicating near resonant condition.
Independently of other simultaneously occurring fatigue cycles
(such as thermal, centrifugal stresses).
Abstract: Linear Discrimination Analysis (LDA) is a linear
solution for classification of two classes. In this paper, we propose a
variant LDA method for multi-class problem which redefines the
between class and within class scatter matrices by incorporating a
weight function into each of them. The aim is to separate classes as
much as possible in a situation that one class is well separated from
other classes, incidentally, that class must have a little influence on
classification. It has been suggested to alleviate influence of classes
that are well separated by adding a weight into between class scatter
matrix and within class scatter matrix. To obtain a simple and
effective weight function, ordinary LDA between every two classes
has been used in order to find Fisher discrimination value and passed
it as an input into two weight functions and redefined between class
and within class scatter matrices. Experimental results showed that
our new LDA method improved classification rate, on glass, iris and
wine datasets, in comparison to different versions of LDA.
Abstract: Magnesium alloy has been widely investigated as
biodegradable cardiovascular stent and bone implant. Its application
for biodegradable esophageal stenting remains unexplored. This
paper reports the biodegradation behaviors of AZ31 magnesium alloy
in artificial saliva and various types of beverage in vitro. Results
show that the magnesium ion release rate of AZ31 in artificial saliva
for a stent (2cm diameter, 10cm length at 50% stent surface
coverage) is 43 times lower than the daily allowance of human body
magnesium intakes. The degradation rates of AZ31 in different
beverages could also be significantly different. These results suggest
that the esophagus in nature is a less aggressive chemical
environment for degradation of magnesium alloys. The significant
difference in degradation rates of AZ31 in different beverages opens
new opportunities for development of degradation controllable
esophageal stent through customizing ingested beverages.
Abstract: One year (November 2009-October 2010) sediment monitoring was used to evaluate pollution status, concentration and distribution of heavy metals (As, Cu, Cd, Cr, Hg, Ni, Pb and Zn) in West Port of Malaysia. Sediment sample were collected from nine stations every four months. Geo-accumulation factor and Pollution Load Index (PLI) were estimated to better understand the pollution level in study area. The heavy metal concentration (Mg/g dry weight) were ranged from 20.2 to 162 for As, 7.4 to 27.6 for Cu, 0.244 to 3.53 for Cd, 11.5 to 61.5 for Cr, 0.11 to 0.409 for Hg, 7.2 to 22.2 for Ni, 22.3 to 80 for Pb and 23 to 98.3 for Zn. In general, concentration some metals (As,Cd, Hg and Pb) was higher than background values that are considered as serious concern for aquatic life and the human health.
Abstract: A measurement system was successfully fabricated to
detect ion concentrations (hydrogen and chlorine) in this study.
PIC18F4520, the microcontroller was used as the control unit in the
measurement system. The measurement system was practically used
to sense the H+ and Cl- in different examples, and the pH and pCl
values were exhibited on real-time LCD display promptly. In the study,
the measurement method is used to judge whether the response voltage
is stable. The change quantity is smaller than 0.01%, that the present
response voltage compares with next response voltage for H+
measurement, and the above condition is established only 6 sec.
Besides, the change quantity is smaller than 0.01%, that the present
response voltage compares with next response voltage for Clmeasurement,
and the above condition is established only 5 sec.
Furthermore, the average error quantities would also be considered,
and they are 0.05 and 0.07 for measurements of pH and pCl values,
respectively.
Abstract: A mathematical model for determining the overall efficiency
of a multistage tractor gearbox including all gear, lubricant,
surface finish related parameters and operating conditions is
presented. Sliding friction, rolling friction and windage losses were
considered as the main sources of power loss in the gearing system. A
computer code in FORTRAN was developed to simulate the model.
Sliding friction contributes about 98% of the total power loss for
gear trains operating at relatively low speeds (less than 2000 rpm
input speed). Rolling frictional losses decrease with increased load
while windage losses are only significant for gears running at very
high speeds (greater than 3000 rpm). The results also showed that the
overall efficiency varies over the path of contact of the gear meshes
ranging between 94% to 99.5%.
Abstract: Due to the excess of a vehicle operation through its life, some elements may face failure and deteriorate with time. This leads us to carry out maintenance, repair, tune up or full overhaul. After a certain period, the vehicle elements deteriorations increase with time which causes a very high increase of doing the maintenance operations and their costs. However, the logic decision at this point is to replace the current vehicle by a new one with minimum failure and maximum income. The importance of studying vehicle replacement problems come from the increase of stopping days due to many deteriorations in the vehicle parts. These deteriorations increase year after year causing an increase of operating costs and decrease the vehicle income. Vehicle replacement aims to determine the optimum time to keep, maintain, overhaul, renew and replace vehicles. This leads to an improvement in vehicle income, total operating costs, maintenance cost, fuel and oil costs, ton-kilometers, vehicle and engine performance, vehicle noise, vibration, and pollution. The aim of this paper is to find the optimum replacement policies of Kuwait Passenger Transport Company (KPTCP) fleet of busses. The objective of these policies is to maximize the busses pure profits. The dynamic programming (D.P.) technique is used to generate the busses optimal replacement policies
Abstract: Gabor-based face representation has achieved enormous success in face recognition. This paper addresses a novel algorithm for face recognition using neural networks trained by Gabor features. The system is commenced on convolving a face image with a series of Gabor filter coefficients at different scales and orientations. Two novel contributions of this paper are: scaling of rms contrast and introduction of fuzzily skewed filter. The neural network employed for face recognition is based on the multilayer perceptron (MLP) architecture with backpropagation algorithm and incorporates the convolution filter response of Gabor jet. The effectiveness of the algorithm has been justified over a face database with images captured at different illumination conditions.
Abstract: Data mining techniques have been used in medical
research for many years and have been known to be effective. In order
to solve such problems as long-waiting time, congestion, and delayed
patient care, faced by emergency departments, this study concentrates
on building a hybrid methodology, combining data mining techniques
such as association rules and classification trees. The methodology is
applied to real-world emergency data collected from a hospital and is
evaluated by comparing with other techniques. The methodology is
expected to help physicians to make a faster and more accurate
classification of chest pain diseases.
Abstract: This paper is devoted to present and discuss a model that allows a local segmentation by using statistical information of a given image. It is based on Chan-Vese model, curve evolution, partial differential equations and binary level sets method. The proposed model uses the piecewise constant approximation of Chan-Vese model to compute Signed Pressure Force (SPF) function, this one attracts the curve to the true object(s)-s boundaries. The implemented model is used to extract weld defects from weld radiographic images in the aim to calculate the perimeter and surfaces of those weld defects; encouraged resultants are obtained on synthetic and real radiographic images.
Abstract: The Marangoni convective instability in a horizontal
fluid layer with the insoluble surfactant and nondeformable free
surface is investigated. The surface tension at the free surface is
linearly dependent on the temperature and concentration gradients.
At the bottom surface, the temperature conditions of uniform
temperature and uniform heat flux are considered. By linear stability
theory, the exact analytical solutions for the steady Marangoni
convection are derived and the marginal curves are plotted. The
effects of surfactant or elasticity number, Lewis number and Biot
number on the marginal Marangoni instability are assessed. The
surfactant concentration gradients and the heat transfer mechanism at
the free surface have stabilizing effects while the Lewis number
destabilizes fluid system. The fluid system with uniform temperature
condition at the bottom boundary is more stable than the fluid layer
that is subjected to uniform heat flux at the bottom boundary.
Abstract: Asphalt surfaces are exposed to various weather
conditions and dynamic loading caused by passing trucks and
vehicles. In such situations, asphalt cement shows so different
rheological-mechanical behavior. If asphalt cement isn-t compatible
enough, asphalt layer will be damaged immediately and expensive
repairing procedures should be performed then. To overcome this
problem, researchers study on mechanical improved asphalt cement.
In this study, bentonite was used in order to modify bitumen
characteristics and the modified bitumen's characteristics were
investigated by asphalt cement tests. Then, the optimal bitumen
content in various compounds was determined and asphalt samples
with different contents of additives were prepared and tested. Results
show using this kind of additive not only has caused improvement in
bitumen mechanical properties, but also improvement in Marshall
Parameters was achieved.
Abstract: This paper presents an authoring tool which makes a
user easily and intuitively design vibrotactile sensation. A mobile
hardware platform powered by ANDROID, a multi-purpose haptic
driver and a linear resonance actuator are used to implement the
system of the presented authoring tool. The tool allows users to easily
and simply create a vibrotactile sensation by drawing vibrotactile
images and to feel the sensation by rubbing drawn images on the touch
screen of a mobile device. The tool supports a graphical interface for
designing, editing and playing vibrotactile images as well as a
pre-defined file format for save and open.
Abstract: Classification of electroencephalogram (EEG) signals
extracted during mental tasks is a technique that is actively pursued
for Brain Computer Interfaces (BCI) designs. In this paper, we
compared the classification performances of univariateautoregressive
(AR) and multivariate autoregressive (MAR) models
for representing EEG signals that were extracted during different
mental tasks. Multilayer Perceptron (MLP) neural network (NN)
trained by the backpropagation (BP) algorithm was used to classify
these features into the different categories representing the mental
tasks. Classification performances were also compared across
different mental task combinations and 2 sets of hidden units (HU): 2
to 10 HU in steps of 2 and 20 to 100 HU in steps of 20. Five different
mental tasks from 4 subjects were used in the experimental study and
combinations of 2 different mental tasks were studied for each
subject. Three different feature extraction methods with 6th order
were used to extract features from these EEG signals: AR
coefficients computed with Burg-s algorithm (ARBG), AR
coefficients computed with stepwise least square algorithm (ARLS)
and MAR coefficients computed with stepwise least square
algorithm. The best results were obtained with 20 to 100 HU using
ARBG. It is concluded that i) it is important to choose the suitable
mental tasks for different individuals for a successful BCI design, ii)
higher HU are more suitable and iii) ARBG is the most suitable
feature extraction method.
Abstract: Importance of strategic planning is unquestionable. However, the practical implementation of a strategic plan faces too many obstacles. The aim of the article is explained the importance of strategic planning and to find how companies in Moravian-Silesian Region deal with strategic planning, and to introduce the model, which helps to set strategic goals in financial indicators area. This model should be part of the whole process of strategic planning and can be use to predict the future values of financial indicators of the company with regard to the factor, which influence these indicators.
Abstract: Organic farmers across Saskatchewan face soil
phosphorus (P) shortages. Due to the restriction on inputs in organic
systems, farmers rely on crop rotation and naturally-occurring
arbuscular mycorrhizal fungi (AMF) for plant P supply. Crop rotation
is important for disease, pest, and weed management. Crops that are
not colonized by AMF (non-mycorrhizal) can decrease colonization
of a following crop. An experiment was performed to quantify soil P
cycling in four cropping sequences under organic management and
determine if mustard (non-mycorrhizal) was delaying the
colonization of subsequent wheat. Soils from the four cropping
sequences were measured for inorganic soil P (Pi), AMF spore
density (SD), phospholipid fatty acid analysis (PLFA, for AMF
biomarker counts), and alkaline phosphatase activity (ALPase,
related to AMF metabolic activity). Plants were measured for AMF
colonization and P content and uptake of above-ground biomass. A
lack of difference in AMF activity indicated that mustard was not
depressing colonization. Instead, AMF colonization was largely
determined by crop type and crop rotation.
Abstract: A new hybrid method to realise high-precision
distortion determination for optical ultra-precision 3D measurement
systems based on stereo cameras using active light projection is
introduced. It consists of two phases: the basic distortion
determination and the refinement. The refinement phase of the
procedure uses a plane surface and projected fringe patterns as
calibration tools to determine simultaneously the distortion of both
cameras within an iterative procedure. The new technique may be
performed in the state of the device “ready for measurement" which
avoids errors by a later adjustment. A considerable reduction of
distortion errors is achieved and leads to considerable improvements
of the accuracy of 3D measurements, especially in the precise
measurement of smooth surfaces.
Abstract: This communication is intended to provide some issues for thought on the importance of implementation of Blended Learning in traditional universities, particularly in the Spanish university system. In this respect, we believe that virtual environments are likely to meet some of the needs raised by the Bologna agreement, trying to maintain the quality of teaching and at the same time taking advantage of the functionalities that virtual learning platforms offer. We are aware that an approach of learning from an open and constructivist nature in universities is a complex process that faces significant technological, administrative and human barriers. Therefore, in order to put plans in our universities, it is necessary to analyze the state of the art of some indicators relating to the use of ICT, with special attention to virtual teaching and learning, so that we can identify the main obstacles and design adaptive strategies for their full integration in the education system. Finally, we present major initiatives launched in the European and state framework for the effective implementation of new virtual environments in the area of higher education.