Abstract: In many practical situations, bubbles are dispersed in a
liquid phase. Understanding these complex bubbly flows is therefore
a key issue for applications such as shell and tube heat exchangers,
mineral flotation and oxidation in water treatment. Although a large
body of work exists for bubbles rising in an unbounded medium,
that of bubbles rising in constricted geometries has received less
attention. The particular case of a bubble sliding underneath an
inclined surface is common to two-phase flow systems. The current
study intends to expand this knowledge by performing experiments
to quantify the streamwise flow structures associated with a single
sliding air bubble under an inclined surface in quiescent water. This
is achieved by means of two-dimensional, two-component particle
image velocimetry (PIV), performed with a continuous wave laser
and high-speed camera. PIV vorticity fields obtained in a plane
perpendicular to the sliding surface show that there is significant bulk
fluid motion away from the surface. The associated momentum of the
bubble means that this wake motion persists for a significant time
before viscous dissipation. The magnitude and direction of the flow
structures in the streamwise measurement plane are found to depend
on the point on its path through which the bubble enters the plane.
This entry point, represented by a phase angle, affects the nature and
strength of the vortical structures. This study reconstructs the vorticity
field in the wake of the bubble, converting the field at different
instances in time to slices of a large-scale wake structure. This is, in
essence, Taylor’s ”frozen turbulence” hypothesis. Applying this to the
vorticity fields provides a pseudo three-dimensional representation
from 2-D data, allowing for a more intuitive understanding of the
bubble wake. This study provides insights into the complex dynamics
of a situation common to many engineering applications, particularly
shell and tube heat exchangers in the nucleate boiling regime.
Abstract: Measurement of the ultrasonic pulse velocity (UPV) is an important tool in diagnostic examination of concrete. In this method piezoelectric transducers are normally held in direct contact with the concrete surface. The current study aims to test the hypothesis that a preferential coupling effect might exist i.e. that the speed of sound measured depends on the couplant used. In this study, different coupling media of varying acoustic impedance were placed between the transducers and concrete samples made with constant aggregate content but with different compressive strengths. The preliminary results show that using coupling materials (both solid and a range of liquid substances) has an effect on the pulse velocity measured in a given concrete. The effect varies depending on the material used. The UPV measurements with solid coupling were higher than these from the liquid coupling at all strength levels. The tests using couplants generally recorded lower UPV values than the conventional test, except when carbon fiber composite was used, which retuned higher values. Analysis of variances (ANOVA) was performed to confirm that there are statistically significant differences between the measurements recorded using a conventional system and a coupled system.
Abstract: Sisal leaves were subjected to enzymatic retting
method to extract the sisal fibre. A portion of the fibre was pretreated
with alkali (NaOH), and further treated with benzoyl chloride
and silane treatment reagents. Both the treated and untreated Sisal
fibre composites were used to fabricate the composite by hand lay-up
technique using unsaturated polyester resin. Tensile, flexural, water
absorption, density, thickness swelling and chemical resistant tests
were conducted and evaluated on the composites. Results obtained
for all the parameters showed an increase in the treated fibre
compared to untreated fibre. FT-IR spectra results ascertained the
inclusion of benzoyl and silane groups on the fibre surface. Scanning
electron microscopy (SEM) result obtained showed variation in the
morphology of the treated and untreated fibre. Chemical modification
was found to improve adhesion of the fibre to the matrix, as well as
physico-mechanical properties of the composites.
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: This paper presents the results of a study on the
influence of varying percentages of rock bridges along a basal surface
defining a biplanar failure mode. A pseudo-coupled-hydromechanical
brittle fracture analysis is adopted using the state-of-the-art code
Slope Model. Model results show that rock bridge failure is strongly
influenced by the incorporation of groundwater pressures. The
models show that groundwater pressure can promote total failure of a
5% rock bridge along the basal surface. Once the percentage of the
rock bridges increases to 10 and 15%, although, the rock bridges are
broken, full interconnection of the surface defining the basal surface
of the biplanar mode does not occur. Increased damage is caused
when the rock bridge is located at the daylighting end of the basal
surface in proximity to the blast damage zone. As expected, some
cracking damage is experienced in the blast damage zone, where
properties representing a good quality controlled damage blast
technique were assumed. Model results indicate the potential increase
of permeability towards the blast damage zone.
Abstract: Rotary entrainment is a phenomenon in which the
interface of two immiscible fluids are subjected to external flux by
means of rotation. Present work reports the experimental study on
rotary motion of a horizontal cylinder between the interface of air and
water to observe the penetration of gas inside the liquid. Experiments
have been performed to establish entrainment of air mass in water
alongside the cylindrical surface. The movement of tracer and seeded
particles has been tracked to calculate the speed and path of the
entrained air inside water. Simplified particle image velocimetry
technique has been used to trace the movement of particles/tracers at
the moment they are injected inside the entrainment zone and
suspended beads have been used to replicate the particle movement
with respect to time in order to determine the flow dynamics of the
fluid along the cylinder. Present paper establishes a thorough experimental analysis of the
rotary entrainment phenomenon between air and water keeping in
interest the extent to which we can intermix the two and also to study
its entrainment trajectories.
Abstract: The research on thermoelectric has been a blooming field of research for the latest decade, owing to large amount of heat source available to be harvested, being eco-friendly and static in operation. This paper provides the performance of thermoelectric generator (TEG) with bulk material of bismuth telluride, Bi2Te3. Later, the performance of the TEGs is evaluated by considering attaching the TEGs on a plastic (polyethylene sheet) in contrast to the common method of attaching the TEGs on the metal surface.
Abstract: Background: Maintaining the correct body balance is
essential in the prevention of falls in the elderly, which is especially
important for women because of postmenopausal osteoporosis and
the serious consequences of falls. One of the exercise methods which
is very popular among adults, and which may affect body balance in
the positive way is the Pilates method. The aim of the study was to
evaluate the effect of regular Pilates exercises on the ability to
maintain body balance in static conditions in adult healthy women.
Material and methods: The study group consisted of 20 healthy
women attending Pilates twice a week for at least 1 year. The control
group consisted of 20 healthy women physically inactive. Women in
the age range from 35 to 50 years old without pain in musculoskeletal
system or other pain were only qualified to the groups. Body balance
was assessed using MatScan VersaTek platform with Sway Analysis
Module based on Matscan Clinical 6.7 software (Tekscan Inc.,
U.S.A). The balance was evaluated under the following conditions:
standing on both feet with eyes open, standing on both feet with eyes
closed, one-leg standing (separately on the right and left foot) with
eyes open. Each test lasted 30 seconds. The following parameters
were calculated: estimated size of the ellipse of 95% confidence, the
distance covered by the Center of Gravity (COG), the size of the
maximum shift in the sagittal and frontal planes and load distribution
between the left and right foot, as well as between rear- and forefoot.
Results: It was found that there is significant difference between the
groups in favor of the study group in the size of the confidence
ellipse and maximum shifts of COG in the sagittal plane during
standing on both feet, both with the eyes open and closed (p
Abstract: Foundation differential settlement and supported
structure tilting are an occasionally occurred engineering problem.
This may be caused by overloading, changes in ground soil properties
or unsupported nearby excavations. Engineering thinking points
directly toward the logic solution for such problem by uplifting the
settled side. This can be achieved with deep foundation elements
such as micro-piles and macro-piles™, jacked piers, and helical piers,
jet grouted mortar columns, compaction grout columns, cement
grouting or with chemical grouting, or traditional pit underpinning
with concrete and mortar. Although, some of these techniques offer
economic, fast and low noise solutions, many of them are quite the
contrary. For tilted structures, with the limited inclination, it may be much
easier to cause a balancing settlement on the less-settlement side
which shall be done carefully in a proper rate. This principal has been
applied in Leaning Tower of Pisa stabilization with soil extraction
from the ground surface. In this research, the authors attempt to
introduce a new solution with a different point of view. So, the
micro-tunneling technique is presented in here as an intended ground
deformation cause. In general, micro-tunneling is expected to induce
limited ground deformations. Thus, the researchers propose to apply
the technique to form small size ground unsupported holes to produce
the target deformations. This shall be done in four phases: 1.
Application of one or more micro-tunnels, regarding the existing
differential settlement value, under the raised side of the tilted
structure. 2. For each individual tunnel, the lining shall be pulled out
from both sides (from jacking and receiving shafts) in the slow rate.
3. If required, according to calculations and site records, an additional
surface load can be applied on the raised foundation side. 4. Finally, a
strengthening soil grouting shall be applied for stabilization after
adjustment. A finite element based numerical model is presented to simulate
the proposed construction phases for different tunneling positions and
tunnels group. For each case, the surface settlements are calculated
and induced plasticity points are checked. These results show the
impact of the suggested procedure on the tilted structure and its
feasibility. Comparing results also show the importance of the
position selection and tunnels group gradual effect. Thus, a new
engineering solution is presented to one of the structural and
geotechnical engineering challenges.
Abstract: Excessive fretting wear at the taper-trunnion junction
(trunnionosis) apparently contributes to the high failure rates of hip
implants. Implant wear and corrosion lead to the release of metal
particulate debris and subsequent release of metal ions at the tapertrunnion
surface. This results in a type of metal poisoning referred to
as metallosis. The consequences of metal poisoning include;
osteolysis (bone loss), osteoarthritis (pain), aseptic loosening of the
prosthesis and revision surgery. Follow up after revision surgery,
metal debris particles are commonly found in numerous locations. Background: A stable connection between the femoral ball head
(taper) and stem (trunnion) is necessary to prevent relative motions
and corrosion at the taper junction. Hence, the importance of
component assembly cannot be over-emphasized. Therefore, the aim
of this study is to determine the influence of head-stem junction
assembly by press fitting and the subsequent
disengagement/disassembly on the connection strength between the
taper ball head and stem. Methods: CoCr femoral heads were assembled with High stainless
hydrogen steel stem (trunnion) by Push-in i.e. press fit; and
disengaged by pull-out test. The strength and stability of the two
connections were evaluated by measuring the head pull-out forces
according to ISO 7206-10 standards. Findings: The head-stem junction strength linearly increases with
assembly forces.
Abstract: The study conducted a simulation of the effect of sea
water to the bonding capacity of GFRP sheet on the concrete beams
using a simulation tank. Fiber reinforced polymer (FRP) has been
developed and applied in many fields civil engineering structures on
the new structures and also for strengthening of the deteriorated
structures. The FRP has advantages such as its corrosion resistance as
well as high tensile strength to weight ratio. Compared to the other
FRP materials, Glass composed FRP (GFRP) is relatively cheaper.
GFRP sheet is applied externally by bonding it on the concrete surface.
The studies regarding the application of GFRP sheet have been
conducted such as strengthening system, bonding behavior of GFRP
sheet including the application as reinforcement in new structures. For
application to the structures with direct contact to sea environment, a
study regarding the effect of sea water to the bonding capacity of
GFRP sheet is important to be clarified. To achieve the objective of the
study, a series of concrete beams strengthened with GFRP sheet on
extreme tension surface were prepared. The beams then were stored on
the sea water tank for six months. Results indicated the bonding
capacity decreased after six month exposed to the sea water.
Abstract: The aim of the performed work is to establish the 2D
and 3D model of direct unsteady task of sample heat treatment by
moving source employing computer model on the basis of finite
element method. Complex boundary condition on heat loaded sample
surface is the essential feature of the task. Computer model describes
heat treatment of the sample during heat source movement over the
sample surface. It is started from 2D task of sample cross section as a
basic model. Possibilities of extension from 2D to 3D task are
discussed. The effect of the addition of third model dimension on
temperature distribution in the sample is showed. Comparison of
various model parameters on the sample temperatures is observed.
Influence of heat source motion on the depth of material heat
treatment is shown for several velocities of the movement. Presented
computer model is prepared for the utilization in laser treatment of
machine parts.
Abstract: This paper discusses micrometeorological aspects of the urban climate in three cities in Western São Paulo State: Presidente Prudente, Assis and Iepê. Particular attention is paid to the method used to estimate the components of the energy balance at the surface. Estimates of convective fluxes showed that the Bowen ratio was an indicator of the local climate and that its magnitude varied between 0.3 and 0.7. Maximum values for the Bowen ratio occurred earlier in Iepê (11:00 am) than in Presidente Prudente (4:00 pm). The results indicate that the Bowen ratio is modulated by the radiation balance at the surface and by different clusters of vegetation.
Abstract: MHD chemically reacting viscous fluid flow towards
a vertical surface with slip and convective boundary conditions has
been conducted. The temperature and the chemical species
concentration of the surface and the velocity of the external flow are
assumed to vary linearly with the distance from the vertical surface.
The governing differential equations are modeled and transformed
into systems of ordinary differential equations, which are then solved
numerically by a shooting method. The effects of various parameters
on the heat and mass transfer characteristics are discussed. Graphical
results are presented for the velocity, temperature, and concentration
profiles whilst the skin-friction coefficient and the rate of heat and
mass transfers near the surface are presented in tables and discussed.
The results revealed that increasing the strength of the magnetic field
increases the skin-friction coefficient and the rate of heat and mass
transfers toward the surface. The velocity profiles are increased
towards the surface due to the presence of the Lorenz force, which
attracts the fluid particles near the surface. The rate of chemical
reaction is seen to decrease the concentration boundary layer near the
surface due to the destructive chemical reaction occurring near the
surface.
Abstract: Erosion and abrasion are wear mechanisms reducing
the lifetime of machine elements like valves, pump and pipe systems.
Both wear mechanisms are acting at the same time, causing a
“Synergy” effect, which leads to a rapid damage of the surface.
Different parameters are effective on erosive abrasive wear rate. In
this study effect of particle impact angle on wear rate and wear
mechanism of ductile and brittle materials was investigated. A new
slurry pot was designed for experimental investigation. As abrasive
particle, silica sand was used. Particle size was ranking between 200-
500 μm. All tests were carried out in a sand-water mixture of 20%
concentration for four hours. Impact velocities of the particles were
4.76 m/s. As ductile material steel St 37 with Vickers Hardness
Number (VHN) of 245 and quenched St 37 with 510 VHN was used
as brittle material. After wear tests, morphology of the eroded
surfaces were investigated for better understanding of the wear
mechanisms acting at different impact angles by using Scanning
Electron Microscope. The results indicated that wear rate of ductile
material was higher than brittle material. Maximum wear rate was
observed by ductile material at a particle impact angle of 300 and
decreased further by an increase in attack angle. Maximum wear rate
by brittle materials was by impact angle of 450 and decreased further
up to 900. Ploughing was the dominant wear mechanism by ductile
material. Microcracks on the surface were detected by ductile
materials, which are nucleation centers for crater formation. Number
of craters decreased and depth of craters increased by ductile
materials by attack angle higher than 300. Deformation wear
mechanism was observed by brittle materials. Number and depth of
pits decreased by brittle materials by impact angles higher than 450.
At the end it is concluded that wear rate could not be directly related
to impact angle of particles due to the different reaction of ductile and
brittle materials.
Abstract: A solution methodology without using integral
transformation is proposed to develop analytical solutions for
transient heat conduction in nonuniform hollow cylinders with
time-dependent boundary condition at the outer surface. It is shown
that if the thermal conductivity and the specific heat of the medium
are in arbitrary polynomial function forms, the closed solutions of the
system can be developed. The influence of physical properties on the
temperature distribution of the system is studied. A numerical
example is given to illustrate the efficiency and the accuracy of the
solution methodology.
Abstract: In this study, to clarify the effectiveness of an
aluminum/chromium/tungsten-based-coated tool for cutting sintered
steel, tool wear was experimentally investigated. The sintered steel
was turned with the (Al60,Cr25,W15)N-, (Al60,Cr25,W15)(C,N)- and
(Al64,Cr28,W8)(C,N)-coated cemented carbide tools according to the
physical vapor deposition (PVD) method. Moreover, the tool wear of
the aluminum/chromium/tungsten-based-coated item was compared
with that of the (Al,Cr)N coated tool. Furthermore, to clarify the tool
wear mechanism of the aluminum/chromium/tungsten-coating film for
cutting sintered steel, Scanning Electron Microscope observation and
Energy Dispersive x-ray Spectroscopy mapping analysis were
conducted on the abraded surface. The following results were
obtained: (1) The wear progress of the (Al64,Cr28,W8)(C,N)-coated
tool was the slowest among that of the five coated tools. (2) Adding
carbon (C) to the aluminum/chromium/tungsten-based-coating film
was effective for improving the wear-resistance. (3) The main wear
mechanism of the (Al60,Cr25,W15)N-, the (Al60,Cr25,W15)(C,N)-
and the (Al64,Cr28,W8)(C,N)-coating films was abrasive wear.
Abstract: In this work new macroporous Ni electrodes modified
with Au nanoparticles for hydrogen production have been developed.
The supporting macroporous Ni electrodes have been obtained by
means of the electrodeposition at high current densities. Then, the Au
nanoparticles were synthesized and added to the electrode surface.
The electrocatalytic behaviour of the developed electrocatalysts was
studied by means of pseudo-steady-state polarization curves,
electrochemical impedance spectroscopy (EIS) and hydrogen
discharge curves. The size of the Au synthetized nanoparticles shows
a monomodal distribution, with a very sharp band between 10 and 50
nm. The characteristic parameters d10, d50 and d90 were 14, 20 and
31 nm respectively. From Tafel polarization data has been concluded
that the Au nanoparticles improve the catalytic activity of the
developed electrodes towards the HER respect to the macroporous Ni
electrodes. EIS permits to obtain the electrochemically active area by
means of the roughness factor value. All the developed electrodes
show roughness factor values in the same order of magnitude. From
the activation energy results it can be concluded that the Au
nanoparticles improve the intrinsic catalytic activity of the
macroporous Ni electrodes.
Abstract: Background in music analysis: Traditionally, when we
think about a composer’s sketches, the chances are that we are
thinking in terms of the working out of detail, rather than the
evolution of an overall concept. Since music is a “time art,” it follows
that questions of a form cannot be entirely detached from
considerations of time. One could say that composers tend to regard
time either as a place gradually and partially intuitively filled, or they
can look for a specific strategy to occupy it. It seems that the one
thing that sheds light on Stockhausen’s compositional thinking is his
frequent use of “form schemas,” that is often a single-page
representation of the entire structure of a piece.
Background in music technology: Sonic Visualiser is a program
used to study a musical recording. It is an open source application for
viewing, analyzing, and annotating music audio files. It contains a
number of visualisation tools, which are designed with useful default
parameters for musical analysis. Additionally, the Vamp plugin
format of SV supports to provide analysis such as for example
structural segmentation.
Aims: The aim of paper is to show how SV may be used to obtain
a better understanding of the specific musical work, and how the
compositional strategy does impact on musical structures and musical
surfaces. It is known that “traditional” music analytic methods don’t
allow indicating interrelationships between musical surface (which is
perceived) and underlying musical/acoustical structure.
Main Contribution: Stockhausen had dealt with the most diverse
musical problems by the most varied methods. A characteristic which
he had never ceased to be placed at the center of his thought and
works, it was the quest for a new balance founded upon an acute
connection between speculation and intuition. In the case with
Mikrophonie I (1964) for tam-tam and 6 players Stockhausen makes
a distinction between the “connection scheme,” which indicates the
ground rules underlying all versions, and the form scheme, which is
associated with a particular version. The preface to the published
score includes both the connection scheme, and a single instance of a
“form scheme,” which is what one can hear on the CD recording. In
the current study, the insight into the compositional strategy chosen
by Stockhausen was been compared with auditory image, that is, with
the perceived musical surface. Stockhausen’s musical work is
analyzed both in terms of melodic/voice and timbre evolution.
Implications: The current study shows how musical structures
have determined of musical surface. The general assumption is this,
that while listening to music we can extract basic kinds of musical
information from musical surfaces. It is shown that interactive
strategies of musical structure analysis can offer a very fruitful way
of looking directly into certain structural features of music.
Abstract: Steady three-dimensional and two free surface waves
generated by moving bodies are presented, the flow problem to be
simulated is rich in complexity and poses many modeling challenges
because of the existence of breaking waves around the ship hull, and
because of the interaction of the two-phase flow with the turbulent
boundary layer. The results of several simulations are reported. The
first study was performed for NACA0012 of hydrofoil with different
meshes, this section is analyzed at h/c= 1, 0345 for 2D. In the second
simulation a mathematically defined Wigley hull form is used to
investigate the application of a commercial CFD code in prediction of
the total resistance and its components from tangential and normal
forces on the hull wetted surface. The computed resistance and wave
profiles are used to estimate the coefficient of the total resistance for
Wigley hull advancing in calm water under steady conditions. The
commercial CFD software FLUENT version 12 is used for the
computations in the present study. The calculated grid is established
using the code computer GAMBIT 2.3.26. The shear stress k-ωSST
model is used for turbulence modeling and the volume of fluid
technique is employed to simulate the free-surface motion. The
second order upwind scheme is used for discretizing the convection
terms in the momentum transport equations, the Modified HRIC
scheme for VOF discretization. The results obtained compare well
with the experimental data.