Abstract: This work studies the effect of thickness on structural
and electrical properties of CuAlS2 thin films grown by two stage
vacuum thermal evaporation technique. CuAlS2 thin films of
thicknesses 50nm, 100nm and 200nm were deposited on suitably
cleaned corning 7059 glass substrate at room temperature (RT). In
the first stage Cu-Al precursors were grown at room temperature by
thermal evaporation and in the second stage Cu-Al precursors were
converted to CuAlS2 thin films by sulfurisation under sulfur
atmosphere at the temperature of 673K. The structural properties of
the films were examined by X-ray diffraction (XRD) technique while
electrical properties of the specimens were studied using four point
probe method. The XRD studies revealed that the films are of
crystalline in nature having tetragonal structure. The variations of the
micro-structural parameters, such as crystallite size (D), dislocation
density ( ), and micro-strain ( ), with film thickness were
investigated. The results showed that the crystallite sizes increase as
the thickness of the film increases. The dislocation density and
micro-strain decreases as the thickness increases. The resistivity ( )
of CuAlS2 film is found to decrease with increase in film thickness,
which is related to the increase of carrier concentration with film
thickness. Thus thicker films exhibit the lowest resistivity and high
carrier concentration, implying these are the most conductive films.
Low electrical resistivity and high carrier concentration are widely
used as the essential components in various optoelectronic devices
such as light-emitting diode and photovoltaic cells.
Abstract: In this paper, we present an analytical method for
analysis of nano-scale spherical shell subjected to thermo-mechanical
shocks based on nonlocal elasticity theory. Thermo-mechanical
properties of nano shpere is assumed to be temperature dependent.
Governing partial differential equation of motion is solved
analytically by using Laplace transform for time domain and power
series for spacial domain. The results in Laplace domain is
transferred to time domain by employing the fast inverse Laplace
transform (FLIT) method. Accuracy of present approach is assessed
by comparing the the numerical results with the results of published
work in literature. Furtheremore, the effects of non-local parameter
and wall thickness on the dynamic characteristics of the nano-sphere
are studied.
Abstract: Cavities are frequently found beneath conduits on pile
foundations in old embankments. Cavity reduces seepage length
significantly and consequently causes piping failure of embankments.
Case studies of embankment failures indicate that the relative
settlement between ground and pile supported-concrete conduit was
the main reason of the cavity. In this paper, an attempt to simulate the
cavity-induced piping failure mechanism was made using finite
element numerical method. Piping potential is examined by carrying
out parametric study for influencing factors such as cavity length,
water level, and flow conditions. The concentration of hydraulic
gradient adjacent to cavity was found. It is found that the hydraulic
gradient close to the cavity exceeds considerably the critical hydraulic
gradient causing piping. Piping failure potential due to the existence of
cavity is evaluated and contour map for the potential risk of an
embankment for piping failure is proposed.
Abstract: Effect of Zn addition on the microstructure and
mechanical properties of Mg-Zn alloys with Zn contents from 6 to 10
weight percent was investigated in this study. Through calculation of
phase equilibria of Mg-Zn alloys, carried out by using FactSage® and
FTLite database, solution treatment temperature was decided as
temperatures from 300 to 400oC, where supersaturated solid solution
can be obtained. Solid solution treatment of Mg-Zn alloys was
successfully conducted at 380oC and supersaturated microstructure
with all beta phase resolved into matrix was obtained. After solution
treatment, hot rolling was successfully conducted by reduction of
60%. Compression and tension tests were carried out at room
temperature on the samples as-cast, solution treated, hot-rolled and
recrystallized after rolling. After solid solution treatment, each alloy
was annealed at temperatures of 180 and 200oC for time intervals from
1 min to 48 hrs and hardness of each condition was measured by
micro-Vickers method. Peak aging conditions were deduced as at the
temperature of 200oC for 10 hrs. By addition of Zn by 10 weight
percent, hardness and strength were enhanced.
Abstract: Strategic investment decisions are characterized by
high innovation potential and long-term effects on the
competitiveness of enterprises. Due to the uncertainty and risks
involved in this complex decision making process, the need arises for
well-structured support activities. A method that considers cost and
the long-term added value is the cost-benefit effectiveness estimation.
One of those methods is the “profitability estimation focused on
benefits – PEFB”-method developed at the Institute of Management
Cybernetics at RWTH Aachen University. The method copes with
the challenges associated with strategic investment decisions by
integrating long-term non-monetary aspects whilst also mapping the
chronological sequence of an investment within the organization’s
target system. Thus, this method is characterized as a holistic
approach for the evaluation of costs and benefits of an investment.
This participation-oriented method was applied to business
environments in many workshops. The results of the workshops are a
library of more than 96 cost aspects, as well as 122 benefit aspects.
These aspects are preprocessed and comparatively analyzed with
regards to their alignment to a series of risk levels. For the first time,
an accumulation and a distribution of cost and benefit aspects
regarding their impact and probability of occurrence are given. The
results give evidence that the PEFB-method combines precise
measures of financial accounting with the incorporation of benefits.
Finally, the results constitute the basics for using information
technology and data science for decision support when applying
within the PEFB-method.
Abstract: The power buck converter is the most widely used
DC/DC converter topology. They have a very large application area
such as DC motor drives, photovoltaic power system which require
fast transient responses and high efficiency over a wide range of load
current. This work proposes, the modelling of DC/DC power buck
converter using state-space averaging method and the current-mode
control using a proportional-integral controller. The efficiency of the
proposed model and control loop are evaluated with operating point
changes. The simulation results proved the effectiveness of the linear
model of DC/DC power buck converter.
Abstract: In this paper, it is aimed to improve autonomous flight
performance of a load-carrying (payload: 3 kg and total: 6kg)
unmanned aerial vehicle (UAV) through active wing and horizontal
tail active morphing and also integrated autopilot system parameters
(i.e. P, I, D gains) and UAV parameters (i.e. extension ratios of wing
and horizontal tail during flight) design. For this purpose, a loadcarrying
UAV (i.e. ZANKA-II) is manufactured in Erciyes
University, College of Aviation, Model Aircraft Laboratory is
benefited. Optimum values of UAV parameters and autopilot
parameters are obtained using a stochastic optimization method.
Using this approach autonomous flight performance of UAV is
substantially improved and also in some adverse weather conditions
an opportunity for safe flight is satisfied. Active morphing and
integrated design approach gives confidence, high performance and
easy-utility request of UAV users.
Abstract: The rising demand for format-flexible packaging
machines is caused by current market changes. Increasing the formatflexibility
is a new goal for the packaging machine manufacturers’
product development process. There are no methodical or designorientated
tools for a comprehensive consideration of this target. This
paper defines the term format-flexibility in the context of packaging
machines and shows the state-of-the-art for improving the
changeover of production machines. The requirements for a new
approach and the concept itself will be introduced, and the method
elements will be explained. Finally, the use of the concept and the
result of the development of a format-flexible packaging machine
will be shown.
Abstract: The very well-known stacked sets of numbers referred
to as Pascal’s triangle present the coefficients of the binomial
expansion of the form (x+y)n. This paper presents an approach (the
Staircase Horizontal Vertical, SHV-method) to the generalization of
planar Pascal’s triangle for polynomial expansion of the form
(x+y+z+w+r+⋯)n. The presented generalization of Pascal’s triangle
is different from other generalizations of Pascal’s triangles given in
the literature. The coefficients of the generalized Pascal’s triangles,
presented in this work, are generated by inspection, using embedded
Pascal’s triangles. The coefficients of I-variables expansion are
generated by horizontally laying out the Pascal’s elements of (I-1)
variables expansion, in a staircase manner, and multiplying them with
the relevant columns of vertically laid out classical Pascal’s elements,
hence avoiding factorial calculations for generating the coefficients
of the polynomial expansion. Furthermore, the classical Pascal’s
triangle has some pattern built into it regarding its odd and even
numbers. Such pattern is known as the Sierpinski’s triangle. In this
study, a presentation of Sierpinski-like patterns of the generalized
Pascal’s triangles is given. Applications related to those coefficients
of the binomial expansion (Pascal’s triangle), or polynomial
expansion (generalized Pascal’s triangles) can be in areas of
combinatorics, and probabilities.
Abstract: Many embankment dams have suffered failures during
earthquakes due to the increase of pore water pressure under seismic
loading. After analyzing of the behavior of embankment dams under
severe earthquakes, major advances have been attained in the
understanding of the seismic action on dams. The present study concerns numerical analysis of the seismic
response of earth dams. The procedure uses a nonlinear stress-strain
relation incorporated into the code FLAC2D based on the finite
difference method. This analysis provides the variation of the pore
water pressure and horizontal displacement.
Abstract: This paper describes a simple way to control the speed
of PMBLDC motor using Fuzzy logic control method. In the
conventional PI controller the performance of the motor system is
simulated and the speed is regulated by using PI controller. These
methods used to improve the performance of PMSM drives, but in
some cases at different operating conditions when the dynamics of
the system also vary over time and it can change the reference speed,
parameter variations and the load disturbance. The simulation is
powered with the MATLAB program to get a reliable and flexible
simulation. In order to highlight the effectiveness of the speed control
method the FLC method is used. The proposed method targeted in
achieving the improved dynamic performance and avoids the
variations of the motor drive. This drive has high accuracy, robust
operation from near zero to high speed. The effectiveness and
flexibility of the individual techniques of the speed control method
will be thoroughly discussed for merits and demerits and finally
verified through simulation and experimental results for comparative
analysis.
Abstract: For several hundred years, the design of railway tracks
has practically remained unchanged. Traditionally, rail tracks are
placed on a ballast layer due to several reasons, including economy,
rapid drainage, and high load bearing capacity. The primary function
of ballast is to distributing dynamic track loads to sub-ballast and
subgrade layers, while also providing lateral resistance and allowing
for rapid drainage. Upon repeated trainloads, the ballast becomes
fouled due to ballast degradation and the intrusion of fines which
adversely affects the strength and deformation behaviour of ballast.
This paper presents the use of three-dimensional discrete element
method (DEM) in studying the shear behaviour of the fouled ballast
subjected to direct shear loading. Irregularly shaped particles of
ballast were modelled by grouping many spherical balls together in
appropriate sizes to simulate representative ballast aggregates. Fouled
ballast was modelled by injecting a specified number of miniature
spherical particles into the void spaces. The DEM simulation
highlights that the peak shear stress of the ballast assembly decreases
and the dilation of fouled ballast increases with an increase level of
fouling. Additionally, the distributions of contact force chain and
particle displacement vectors were captured during shearing progress,
explaining the formation of shear band and the evolutions of
volumetric change of fouled ballast.
Abstract: Microstructure and mechanical properties of AZ91D
Mg alloys for nonflammable use, containing Ca and Y, were
investigated in this study. Solid solution treatment of AZ91D Mg alloy
with Ca and Y was successfully conducted at 420oC and
supersaturated microstructure with almost all beta phases resolved into
matrix was obtained. After solid solution treatment, the alloy was
annealed at temperatures of 180 and 200oC for time intervals from 1
min to 48 hrs and hardness of each condition was measured by
micro-Vickers method. Peak aging conditions were deduced from the
results as at the temperature of 200oC for 10 hrs. Hot rolling was also
carried out at 400oC by the reduction ratio of 0.6 through 5 passes
followed by recrystallization treatment. Tensile and compressive
properties were measured at room temperature on the specimens of
each process, i.e. as-cast, solution treatment, hot rolling, and
recrystallization.
Abstract: Although Mobile Wireless Sensor Networks (MWSNs),
which consist of mobile sensor nodes (MSNs), can cover a wide range
of observation region by using a small number of sensor nodes, they
need to construct a network to collect the sensing data on the base
station by moving the MSNs. As an effective method, the network
construction method based on Virtual Rails (VRs), which is referred
to as VR method, has been proposed. In this paper, we propose two
types of effective techniques for the VR method. They can prolong
the operation time of the network, which is limited by the battery
capabilities of MSNs and the energy consumption of MSNs. The
first technique, an effective arrangement of VRs, almost equalizes
the number of MSNs belonging to each VR. The second technique,
an adaptive movement method of MSNs, takes into account the
residual energy of battery. In the simulation, we demonstrate that each
technique can improve the network lifetime and the combination of
both techniques is the most effective.
Abstract: Scripts are one of the basic text resources to understand
broadcasting contents. Topic modeling is the method to get the
summary of the broadcasting contents from its scripts. Generally,
scripts represent contents descriptively with directions and speeches,
and provide scene segments that can be seen as semantic units.
Therefore, a script can be topic modeled by treating a scene segment
as a document. Because scene segments consist of speeches mainly,
however, relatively small co-occurrences among words in the scene
segments are observed. This causes inevitably the bad quality of
topics by statistical learning method. To tackle this problem, we
propose a method to improve topic quality with additional word
co-occurrence information obtained using scene similarities. The
main idea of improving topic quality is that the information that
two or more texts are topically related can be useful to learn high
quality of topics. In addition, more accurate topical representations
lead to get information more accurate whether two texts are related
or not. In this paper, we regard two scene segments are related
if their topical similarity is high enough. We also consider that
words are co-occurred if they are in topically related scene segments
together. By iteratively inferring topics and determining semantically
neighborhood scene segments, we draw a topic space represents
broadcasting contents well. In the experiments, we showed the
proposed method generates a higher quality of topics from Korean
drama scripts than the baselines.
Abstract: This research work is an experimental study, through
development of an adhesive from Prosopis africana endosperm. The
prosopis seed for this work were obtained from Enugu State in the
South East part of Nigeria. The seeds were prepared by separating the
endosperm from the seed coat and cotyledon. Three methods were
used to separate them, which are acidic method, roasting method and
boiling method. 20g of seed were treated with different
concentrations (25, 40, 55, 70, and 85% w/w) at 100°C and constant
time (30 minutes), under continuous stirring with magnetic stirrer.
Also 20g of seed were treated with sulphuric acid of concentrations
40% w/w at 100°C with different time (10, 15, 20, 25, 30 minutes),
under continuous stirring with magnetic stirrer. Finally, 20g of seed
were treated with sulphuric acid of concentrations 40% w/w at
different temperature (20°C, 40°C, 60°C, 80°C, and 100°C) with
constant time (30 minutes), under continuous stirring with magnetic
stirrer. The whole endosperm extracted was adhesive. The physical
properties of the adhesive were determined (appearance, odour, taste,
solubility, pH, size, and binding strength). The percentage of the
adhesive yield makes the commercialization of the seed in Nigeria
possible and profitable. The very high viscosity attained at low
concentrations makes prosopis adhesive an excellent thickener in the
food industry.
Abstract: Rapid developments in technology in the present age
have made it necessary for communities to follow technological
developments and adapt themselves to these developments. One of
the fields that are most rapidly affected by these developments is
undoubtedly education. Determination of the attitudes of preservice
teachers, who live in an age of technology and get ready to raise
future individuals, is of paramount importance both educationally and
professionally. The purpose of this study was to analyze attitudes of
preservice teachers towards technology and some variables that
predict these attitudes (gender, daily duration of internet use, and the
number of technical devices owned). 329 preservice teachers
attending the education faculty of a large university in central Turkey
participated, on a volunteer basis, in this study, where relational
survey model was used as the research method. Research findings
reveal that preservice teachers’ attitudes towards technology are
positive and at the same time, the attitudes of male preservice
teachers towards technology are more positive than their female
counterparts. As a result of the stepwise multiple regression analysis
where factors predicting preservice teachers’ attitudes towards
technology, it was found that duration of daily internet use was the
strongest predictor of attitudes towards technology.
Abstract: Fresh concrete has one of dynamic properties known
as slump. Slump of concrete is design to compatible with placing
method. Due to hydration reaction of cement, the slump of concrete
is loss through time. Therefore, delayed concrete probably get reject
because slump is unacceptable. In order to recover the slump of
delayed concrete the second dose of superplasticizer (naphthalene
based type F) is added into the system, the slump recovery can be
done as long as the concrete is not setting. By adding superplasticizer
as solution for recover unusable slump loss concrete may affects
other concrete properties. Therefore, this paper was observed setting
times and compressive strength of concrete after being re-dose with
chemical admixture type F (superplasticizer, naphthalene based) for
slump recovery. The concrete used in this study was fly ash concrete
with fly ash replacement of 0%, 30% and 50% respectively. Concrete
mix designed for test specimen was prepared with paste content (ratio
of volume of cement to volume of void in the aggregate) of 1.2 and
1.3, water-to-binder ratio (w/b) range of 0.3 to 0.58, initial dose of
superplasticizer (SP) range from 0.5 to 1.6%. The setting times of
concrete were tested both before and after re-dosed with different
amount of second dose and time of dosing. The research was
concluded that addition of second dose of superplasticizer would
increase both initial and final setting times accordingly to dosage of
addition. As for fly ash concrete, the prolongation effect was higher
as the replacement of fly ash increase. The prolongation effect can
reach up to maximum about 4 hours. In case of compressive strength,
the re-dosed concrete has strength fluctuation within acceptable range
of ±10%.
Abstract: Cadmium oxide (CdO) nanoparticles have been
prepared by chemical coprecipitation method. The synthesized
nanoparticles were characterized by X-ray diffraction analysis
(XRD), scanning electron microscopy (SEM), transmission electron
microscopy (TEM), UV analysis, and dielectric studies. The
crystalline nature and particle size of the CdO nanoparticles were
characterized by Powder X-ray diffraction analysis (XRD). The
morphology of prepared CdO nanoparticles was studied by scanning
electron microscopy. The particle size was studied using the
transmission electron microscopy (TEM).The optical properties were
obtained from UV-Vis absorption spectrum. The dielectric properties
of CdO nanoparticles were studied in the frequency range of 50 Hz–5
MHz at different temperatures. The frequency dependence of the
dielectric constant and dielectric loss is found to decrease with an
increase in the frequency at different temperatures. The ac
conductivity of CdO nanoparticle has been studied.
Abstract: The quality of concrete is usually defined by compressive strength, but flexural strength is the most important characteristic of concrete in a pavement which control the mix design of concrete instead of compressive strength. Therefore, the aggregates which are selected for the pavements are affected by higher flexural strength. Roller Compacting Concrete Pavement (RCCP) is not a new construction method. The other characteristic of this method is no bleeding and less shrinkage due to the lower amount of water. For this purpose, a roller is needed for placing and compacting. The surface of RCCP is not smooth; therefore, the most common use of this pavement is in an industrial zone with slower traffic speed which requires durable and tough pavement. For preparing a smoother surface, it can be achieved by asphalt paver. RCCP decrease the finishing cost because there are no bars, formwork, and the lesser labor need for placing the concrete. In this paper, different aspect of RCCP such as mix design, flexural, compressive strength and focus on the different part of RCCP on detail have been investigated.