Abstract: In this study, thermal fatigue properties of 400 series
ferritic stainless steels have been evaluated in the temperature ranges
of 200-800oC and 200-900oC. Systematic methods for control of
temperatures within the predetermined range and measurement of load
applied to specimens as a function of temperature during thermal
cycles have been established. Thermal fatigue tests were conducted
under fully constrained condition, where both ends of specimens were
completely fixed. It has been revealed that load relaxation behavior at
the temperatures of thermal cycle was closely related with the thermal
fatigue property. Thermal fatigue resistance of 430J1L stainless steel
is found to be superior to the other steels.
Abstract: The irradiation of polymeric materials has received
much attention because it can produce diverse changes in chemical
structure and physical properties. Thus, studying the chemical and
structural changes of polymers is important in practice to achieve
optimal conditions for the modification of polymers. The effect of
gamma irradiation on the crystalline structure of poly(vinylidene
fluoride) (PVDF) has been investigated using differential scanning
calorimetry (DSC) and X-ray diffraction techniques (XRD). Gamma
irradiation was carried out in atmosphere air with doses between 100
kGy at 3,000 kGy with a Co-60 source. In the melting thermogram of
the samples irradiated can be seen a bimodal melting endotherm is
detected with two melting temperature. The lower melting
temperature is attributed to melting of crystals originally present and
the higher melting peak due to melting of crystals reorganized upon
heat treatment. These results are consistent with those obtained by
XRD technique showing increasing crystallinity with increasing
irradiation dose, although the melting latent heat is decreasing.
Abstract: The combination of multi–walled carbon nanotubes
(MWCNTs) with polymers offers an attractive route to reinforce the
macromolecular compounds as well as the introduction of new
properties based on morphological modifications or electronic
interactions between the two constituents. As they are only a few
nanometers in dimension, it offers ultra-large interfacial area per
volume between the nano-element and polymer matrix. Nevertheless,
the use of MWCNTs as a rough material in different applications has
been largely limited by their poor processability, insolubility, and
infusibility. Studies concerning the nanofiller reinforced polymer
composites are justified in an attempt to overcome these limitations.
This work presents one preliminary study of MWCNTs dispersion
into the PVDF homopolymer. For preparation, the composite
components were diluted in n,n-dimethylacetamide (DMAc) with
mechanical agitation assistance. After complete dilution, followed by
slow evaporation of the solvent at 60°C, the samples were dried.
Films of about 80 μm were obtained. FTIR and UV-Vis
spectroscopic techniques were used to characterize the
nanocomposites. The appearance of absorption bands in the FTIR
spectra of nanofilled samples, when compared to the spectrum of
pristine PVDF samples, are discussed and compared with the UV-Vis
measurements.
Abstract: This paper investigates the effects of breaks in bonds,
breaks in the earthing system and breaks in earth wire on the rise of
the earth potential (EPR) in a substation and at the transmission tower
bases using various models of an L6 tower. Different approaches
were adopted to examine the integrity of the earthing system and the
terminal towers. These effects were investigated to see the associated
difference in the EPR magnitudes with respect to a healthy system at
various locations. Comparisons of the computed EPR magnitudes
were then made between the healthy and unhealthy system to detect
any difference. The studies were conducted at power frequency for a
uniform soil with different soil resistivities. It was found that full
breaks in the double bond of the terminal towers increase the EPR
significantly at the fault location, while they reduce EPR at the
terminal tower bases. A fault on the isolated section of the grid can
result in EPR values up to 8 times of those on a healthy system at
higher soil resistivities, provided that the extended earthing system
stays connected to the grid.
Abstract: This paper analyzes the institutionalization of social
protest in Spain. In the current crisis Podemos party seems to
represent the political positions of the most affected citizens by the
economic situation. It studies using quantitative techniques (statistical
bivariate analysis), focusing on the exploitation of several bases of
statistics data from the Center for Sociological and Research of
Spanish Government, 15M movement characterization to its
institutionalization in the Podemos party. Making a comparison
between the participant's profile by the 15M and the social bases of
Podemos votes. Data on the transformation of the socio-demographic
profile of the fans, connoisseurs and 15M participants and voters are
given.
Abstract: Interaction between mixing and crystallization is often
ignored despite the fact that it affects almost every aspect of the
operation including nucleation, growth, and maintenance of the
crystal slurry. This is especially pronounced in multiple impeller
systems where flow complexity is increased. By choosing proper
mixing parameters, what closely depends on the knowledge of the
hydrodynamics in a mixing vessel, the process of batch cooling
crystallization may considerably be improved. The values that render
useful information when making this choice are mixing time and
power consumption. The predominant motivation for this work was
to investigate the extent to which radial dual impeller configuration
influences mixing time, power consumption and consequently the
values of metastable zone width and nucleation rate. In this research,
crystallization of borax was conducted in a 15 dm3 baffled batch
cooling crystallizer with an aspect ratio (H/T) of 1.3. Mixing was
performed using two straight blade turbines (4-SBT) mounted on the
same shaft that generated radial fluid flow. Experiments were
conducted at different values of N/NJS ratio (impeller speed/
minimum impeller speed for complete suspension), D/T ratio
(impeller diameter/crystallizer diameter), c/D ratio (lower impeller
off-bottom clearance/impeller diameter), and s/D ratio (spacing
between impellers/impeller diameter). Mother liquor was saturated at
30°C and was cooled at the rate of 6°C/h. Its concentration was
monitored in line by Na-ion selective electrode. From the values of
supersaturation that was monitored continuously over process time, it
was possible to determine the metastable zone width and
subsequently the nucleation rate using the Mersmann’s nucleation
criterion. For all applied dual impeller configurations, the mixing
time was determined by potentiometric method using a pulse
technique, while the power consumption was determined using a
torque meter produced by Himmelstein & Co. Results obtained in
this investigation show that dual impeller configuration significantly
influences the values of mixing time, power consumption as well as
the metastable zone width and nucleation rate. A special attention
should be addressed to the impeller spacing considering the flow
interaction that could be more or less pronounced depending on the
spacing value.
Abstract: Asphalt pavement itself is a mixture made up of mainly aggregates, binders, and fillers that acts as a composition used for pavement construction. An experimental program was setup to determine the fatigue performance test of Asphalt with three different grades of conventional binders. Asphalt specimen has achieved the maximum optimum bulk density and air voids with a consistent bulk density of 2.3 t/m3, with an air void of 5% ± 0.5, before loading into the Asphalt Mixture Performance Tested (AMPT) for fatigue test. The number of cycles is defined as the point where phase angle drops, which is caused by the formation of cracks due to the increasing micro cracks when asphalt is undergoing repeated cycles of loading. Thus, the data collected are analyzed using the drop of phase angle as failure criteria. Based in the data analyzed, it is evident that the fatigue life of asphalt lies on the grade of binder. The result obtained shows that all specimens do experience a drop in phase angle due to macro cracks in the asphalt specimen.
Abstract: High double excitation of two-electron atoms has been
investigated using hyperpherical coordinates within a modified
adiabatic expansion technique. This modification creates a novel
fictitious force leading to a spontaneous exchange symmetry breaking
at high double excitation. The Pauli principle must therefore be
regarded as approximation valid only at low excitation energy.
Threshold electron scattering from high Rydberg states shows an
unexpected time reversal symmetry breaking. At threshold for double
escape we discover a broad (few eV) Cooper pair.
Abstract: Reinforced cement concrete is getting extensively used
for construction of different type of structures for the last one century.
During this period, we have constructed many structures like
buildings, bridges, industrial structures, pavement, water tanks etc.
using this construction material. These structures have been created
with huge investment of resources. It is essential to maintain those
structures in functional condition. Since deterioration in RCC
Structures is a common and natural phenomenon it is required to have
a detailed plan, methodology for structural repair and rehabilitation
shall be in place for dealing such issues. It is important to know exact
reason of distress, type of distress and correct method of repair
concrete structures. The different methods of repair are described in
paper according to distress category which can be refereed for repair.
Major finding of the study is that to protect our structure we need to
have maintenance frequency and correct material to be chosen for
repair. Also workmanship during repair needs to be taken utmost care
for quality repair.
Abstract: Ultrasonic metal welding has been the subject of ongoing research and development, most recently concentrating on metal joining in miniature devices, for example to allow solder-free wire bonding. As well as at the small scale, there are also opportunities to research the joining of thicker sheet metals and to widen the range of similar and dissimilar materials that can be successfully joined using this technology. This study presents the design, characterisation and test of a lateral-drive ultrasonic metal spot welding device. The ultrasonic metal spot welding horn is modelled using finite element analysis (FEA) and its vibration behaviour is characterised experimentally to ensure ultrasonic energy is delivered effectively to the weld coupon. The welding stack and fixtures are then designed and mounted on a test machine to allow a series of experiments to be conducted for various welding and ultrasonic parameters. Weld strength is subsequently analysed using tensile-shear tests. The results show how the weld strength is particularly sensitive to the combination of clamping force and ultrasonic vibration amplitude of the welding tip, but there are optimal combinations of these and also limits that must be clearly identified.
Abstract: Centrifugal-casting machine is used in manufacturing
special machine components like multi-layer journal bearing used in
all internal combustion engine, steam, gas turbine and air craft turboengine
where isotropic properties and high precisions are desired.
Moreover, this machine can be used in manufacturing thin wall hightech
machine components like cylinder liners and piston rings of IC
engine and other machine parts like sleeves, and bushes. Heavy-duty
machine component like railway wheel can also be prepared by
centrifugal casting. A lot of technological developments are required
in casting process for production of good casted machine body and
machine parts. Usually defects like blowholes, surface roughness,
chilled surface etc. are found in sand casted machine parts. But these
can be removed by centrifugal casting machine using rotating
metallic die. Moreover, die rotation, its temperature control, and good
pouring practice can contribute to the quality of casting because of
the fact that the soundness of a casting in large part depends upon
how the metal enters into the mold or dies and solidifies. Poor
pouring practice leads to variety of casting defects such as
temperature loss, low quality casting, excessive turbulence, over
pouring etc. Besides these, handling of molten metal is very
unsecured and dangerous for the workers. In order to get rid of all
these problems, the need of an automatic pouring device arises. In
this research work, a robot assisted pouring device and a centrifugal
casting machine are designed, developed constructed and tested
experimentally which are found to work satisfactorily. The robot
assisted pouring device is further modified and developed for using it
in actual metal casting process. Lot of settings and tests are required
to control the system and ultimately it can be used in automation of
centrifugal casting machine to produce high-tech machine parts with
desired precision.
Abstract: The objective of this research is to develop a general technique so that one may predict the dynamic behaviour of a three-dimensional scale crane model subjected to time-dependent moving point forces by means of conventional finite element computer packages. To this end, the whole scale crane model is divided into two parts: the stationary framework and the moving substructure. In such a case, the dynamic responses of a scale crane model can be predicted from the forced vibration responses of the stationary framework due to actions of the four time-dependent moving point forces induced by the moving substructure. Since the magnitudes and positions of the moving point forces are dependent on the relative positions between the trolley, moving substructure and the stationary framework, it can be found from the numerical results that the time histories for the moving speeds of the moving substructure and the trolley are the key factors affecting the dynamic responses of the scale crane model.
Abstract: The boundary layer separation and new active flow control of a NACA 0025 airfoil were studied experimentally. This new flow control is sometimes known as a co-flow jet (cfj) airfoil. This paper presents the fluctuating velocity in a wall jet over the co-flow jet airfoil subjected to an adverse pressure gradient and a curved surface. In these results, the fluctuating velocity at the inner part increasing by increased the angle of attack up to 12o and this has due to the jet energized, while the angle of attack 20o has different. The airfoil cord based Reynolds number has 105.
Abstract: A composite material with carbon fiber and polymer
matrix has been used as adherent for manufacturing adhesive joints.
In order to evaluate different fiber orientations on joint performance,
the adherents with the 0°, ±15°, ±30°, ±45° fiber orientations were
used in the single lap joint configuration. The joints with an overlap
length of 25 mm were prepared according to the ASTM 1002
specifications and subjected to tensile loadings. The structural
adhesive used was a two-part epoxy to be cured at 70°C for an hour.
First, mechanical behaviors of the adherents were measured using
three point bending test. In the test, considerations were given to
stress to failure and elastic modulus. The results were compared with
theoretical ones using rule of mixture. Then, the joints were
manufactured in a specially prepared jig, after a proper surface
preparation. Experimental results showed that the fiber orientations
of the adherents affected the joint performance considerably; the
joints with ±45° adherents experienced the worst shear strength, half
of those with 0° adherents, and in general, there was a great
relationship between the fiber orientations and failure mechanisms.
Delamination problems were observed for many joints, which were
thought to be due to peel effects at the ends of the overlap. It was
proved that the surface preparation applied to the adherent surface
was adequate. For further explanation of the results, a numerical
work should be carried out using a possible non-linear analysis.
Abstract: This paper investigates the application of metallic
coatings on high fiber volume fraction carbon/epoxy polymer matrix
composites. For the grip of the metallic layer, a method of modifying
the surface of the composite by introducing a mixture of copper and
steel powder (filler powders) which can reduce the impact of thermal
spray particles. The powder was introduced to the surface at the time
of the forming. Arc spray was used to project the zinc coating layer.
The substrate was grit blasted to avoid poor adherence. The porosity, microstructure, and morphology of layers are
characterized by optical microscopy, SEM and image analysis. The
samples were studied also in terms of hardness and erosion resistance.
This investigation did not reveal any visible evidence damage to the
substrates. The hardness of zinc layer was about 25.94 MPa and the
porosity was around (∼6.70%). The erosion test showed that the zinc
coating improves the resistance to erosion. Based on the results
obtained, we can conclude that thermal spraying allows the production
of protective coating on PMC. Zinc coating has been identified as a
compatible material with the substrate. The filler powders layer
protects the substrate from the impact of hot particles and allows
avoiding the rupture of brittle carbon fibers.
Abstract: The recent instability in economy was found to be
influencing the situation in Malaysia whether directly or indirectly.
Taking that into consideration, the government needs to find the best
approach to balance its citizen’s socio-economic strata level urgently.
Through education platform is among the efforts planned and acted
upon for the purpose of balancing the effects of the influence,
through the exposure of social entrepreneurial activity towards youth
especially those in higher institution level. Armed with knowledge
and skills that they gained, with the support by entrepreneurial
culture and environment while in campus; indirectly, the students will
lean more on making social entrepreneurship as a career option when
they graduate. Following the issues of marketability and workability
of current graduates that are becoming dire, research involving how
far the willingness of student to create social innovation that
contribute to the society without focusing solely on personal gain is
relevant enough to be conducted. With that, this research is
conducted with the purpose of identifying the level of entrepreneurial
intention and social entrepreneurship among higher institution
students in Malaysia. Stratified random sampling involves 355
undergraduate students from five public universities had been made
as research respondents and data were collected through surveys. The
data was then analyzed descriptively using min score and standard
deviation. The study found that the entrepreneurial intention of higher
education students are on moderate level, however it is the contrary
for social entrepreneurship activities, where it was shown on a high
level. This means that while the students only have moderate level of
willingness to be a social entrepreneur, they are very committed to
created social innovation through the social entrepreneurship
activities conducted. The implication from this study can be
contributed towards the higher institution authorities in prediction the
tendency of student in becoming social entrepreneurs. Thus, the
opportunities and facilities for realizing the courses related to social
entrepreneurship must be created expansively so that the vision of
creating as many social entrepreneurs as possible can be achieved.
Abstract: A university-wide survey to obtain baseline data
regarding the perceptions of key terms related to e-learning and
distance learning among students, faculty and staff was conducted to
help achieve the goals of Princess Nourah bint Abdulrahman
University’s and the Kingdom of Saudi Arabia’s National Center for
e-learning and Distance Learning. This paper comprises a relevant
literature review, the survey methodology, preliminary data analysis,
discussion, and recommendations for further research. The major
findings indicate a deep and wide differentiation of understanding
among users of critical key terms.
Abstract: The UK has had its fair share of the shale gas
revolutionary waves blowing across the global oil and gas industry at
present. Although, its exploitation is widely agreed to have been
delayed, shale gas was looked upon favorably by the UK Parliament
when they recognized it as genuine energy source and granted
licenses to industry to search and extract the resource. This, although
a significant progress by industry, there yet remains another test the
UK fracking resource must pass in order to render shale gas
extraction feasible – it must be economically extractible and
sustainably so. Developing unconventional resources is much more
expensive and risky, and for shale gas wells, producing in
commercial volumes is conditional upon drilling horizontal wells and
hydraulic fracturing, techniques which increase CAPEX. Meanwhile,
investment in shale gas development projects is sensitive to gas price
and technical and geological risks. Using a Two-Factor Model, the
economics of the Bowland shale wells were analyzed and the
operational conditions under which fracking is profitable in the UK
was characterized. We find that there is a great degree of flexibility
about Opex spending; hence Opex does not pose much threat to the
fracking industry in the UK. However, we discover Bowland shale
gas wells fail to add value at gas price of $8/ Mmbtu. A minimum gas
price of $12/Mmbtu at Opex of no more than $2/ Mcf and no more
than $14.95M Capex are required to create value within the present
petroleum tax regime, in the UK fracking industry.
Abstract: Growth and remodeling of biological structures have
gained lots of attention over the past decades. Determining the
response of living tissues to mechanical loads is necessary for a wide
range of developing fields such as prosthetics design or computerassisted
surgical interventions. It is a well-known fact that biological
structures are never stress-free, even when externally unloaded. The
exact origin of these residual stresses is not clear, but theoretically,
growth is one of the main sources. Extracting body organ’s shapes
from medical imaging does not produce any information regarding
the existing residual stresses in that organ. The simplest cause of such
stresses is gravity since an organ grows under its influence from
birth. Ignoring such residual stresses might cause erroneous results in
numerical simulations. Accounting for residual stresses due to tissue
growth can improve the accuracy of mechanical analysis results. This
paper presents an original computational framework based on gradual
growth to determine the residual stresses due to growth. To illustrate
the method, we apply it to a finite element model of a healthy human
face reconstructed from medical images. The distribution of residual
stress in facial tissues is computed, which can overcome the effect of
gravity and maintain tissues firmness. Our assumption is that tissue
wrinkles caused by aging could be a consequence of decreasing
residual stress and thus not counteracting gravity. Taking into
account these stresses seems therefore extremely important in
maxillofacial surgery. It would indeed help surgeons to estimate
tissues changes after surgery.
Abstract: This paper investigates the thermo-electric effects
around the crack and notch tips under the electric current load. The
research methods include the finite element analysis and thermal
imaging experiment. The finite element solutions show that the electric
current density field concentrates at the crack tip. Due to the Joule
heating, this electric concentration causes the hot spot at the tip zone.
From numerical and experimental results, this hot spot is identified.
The temperature of the hot spot is affected by the electric load,
operation time and geometry of the sample.