Abstract: We present a novel construction of 16-QAM codewords of length n = 2k . The number of constructed codewords is 162×[4k-1×k-k+1] . When these constructed codewords are utilized as a code in OFDM systems, their peak-to-mean envelope power ratios (PMEPR) are bounded above by 3.6 . The principle of our scheme is illustrated with a four subcarrier example.
Abstract: In this paper, an analytical approach is used to study the coupled lateral-torsional vibrations of laminated composite beam. It is known that in such structures due to the fibers orientation in various layers, any lateral displacement will produce a twisting moment. This phenomenon is modeled by the bending-twisting material coupling rigidity and its main feature is the coupling of lateral and torsional vibrations. In addition to the material coupling, the effects of shear deformation and rotary inertia are taken into account in the definition of the potential and kinetic energies. Then, the governing differential equations are derived using the Hamilton-s principle and the mathematical model matches the Timoshenko beam model when neglecting the effect of bending-twisting rigidity. The equations of motion which form a system of three coupled PDEs are solved analytically to study the free vibrations of the beam in lateral and rotational modes due to the bending, as well as the torsional mode caused by twisting. The analytic solution is carried out in three steps: 1) assuming synchronous motion for the kinematic variables which are the lateral, rotational and torsional displacements, 2) solving the ensuing eigenvalue problem which contains three coupled second order ODEs and 3) imposing different boundary conditions related to combinations of simply, clamped and free end conditions. The resulting natural frequencies and mode shapes are compared with similar results in the literature and good agreement is achieved.
Abstract: To understand working features of a micro combustor,
a computer code has been developed to study combustion of
hydrogen–air mixture in a series of chambers with same shape aspect
ratio but various dimensions from millimeter to micrometer level.
The prepared algorithm and the computer code are capable of
modeling mixture effects in different fluid flows including chemical
reactions, viscous and mass diffusion effects. The effect of various
heat transfer conditions at chamber wall, e.g. adiabatic wall, with
heat loss and heat conduction within the wall, on the combustion is
analyzed. These thermal conditions have strong effects on the
combustion especially when the chamber dimension goes smaller and
the ratio of surface area to volume becomes larger.
Both factors, such as larger heat loss through the chamber wall
and smaller chamber dimension size, may lead to the thermal
quenching of micro-scale combustion. Through such systematic
numerical analysis, a proper operation space for the micro-combustor
is suggested, which may be used as the guideline for microcombustor
design. In addition, the results reported in this paper
illustrate that the numerical simulation can be one of the most
powerful and beneficial tools for the micro-combustor design,
optimization and performance analysis.
Abstract: Reinforced concrete crash barriers used in road traffic
must meet a number of criteria. Crash barriers are laid lengthwise,
one behind another, and joined using specially designed steel locks.
While developing BSV reinforced concrete crash barriers (type
ŽPSV), experiments and calculations aimed to optimize the shape of
a newly designed lock and the reinforcement quantity and
distribution in a crash barrier were carried out. The tension carrying
capacity of two parallelly joined locks was solved experimentally.
Based on the performed experiments, adjustments of nonlinear
properties of steel were performed in the calculations. The obtained
results served as a basis to optimize the lock design using a
computational model that takes into account the plastic behaviour of
steel and the influence of the surrounding concrete [6]. The response
to the vehicle impact has been analyzed using a specially elaborated
complex computational model, comprising both the nonlinear model
of the damping wall or crash barrier and the detailed model of the
vehicle [7].
Abstract: This paper deals with the evaluation of flow properties
of polymeric matrix with natural animal fillers. Technical university
of Liberec cooperates on the long-term development of “green
materials“ that should replace conventionally used materials
(especially in automotive industry). Natural fibres (of animal and
plant origin) from all over the world are collected and adapted
(drying, cutting etc.) for extrusion processing. Inside the extruder
these natural additives are blended with polymeric (synthetic and
biodegradable - PLA) matrix and created compound is subsequently
cut for pellets in the wet way. These green materials with unique
recipes are then studied and their mechanical, physical and
processing properties are determined. The main goal of this research
is to develop new ecological materials very similar to unfilled
polymers. In this article the rheological behaviour of chosen natural
animal fibres is introduced considering their shape and surface that
were observed with use of SEM microscopy.
Abstract: Through a proper analysis of residual strain and stress
distributions obtained at the surface of high speed milled specimens
of AA 6082–T6 aluminium alloy, the performance of an improved
indentation method is evaluated. This method integrates a special
device of indentation to a universal measuring machine. The
mentioned device allows introducing elongated indents allowing to
diminish the absolute error of measurement. It must be noted that the
present method offers the great advantage of avoiding both the
specific equipment and highly qualified personnel, and their inherent
high costs. In this work, the cutting tool geometry and high speed
parameters are selected to introduce reduced plastic damage.
Through the variation of the depth of cut, the stability of the shapes
adopted by the residual strain and stress distributions is evaluated.
The results show that the strain and stress distributions remain
unchanged, compressive and small. Moreover, these distributions
reveal a similar asymmetry when the gradients corresponding to
conventional and climb cutting zones are compared.
Abstract: This research aimed to study on the potential of
recycling organic waste in Suan Sunandha Rajabhat University as
compost. In doing so, the composition of solid waste generated in the
campus was investigated while physical and chemical properties of
organic waste were analyzed in order to evaluate the portion of waste
suitable for recycling as compost. As a result of the study, it was
found that (1) the amount of organic waste was averaged at 299.8
kg/day in which mixed food wastes had the highest amount of 191.9
kg/day followed by mixed leave & yard wastes and mixed fruit &
vegetable wastes at the amount of 66.3 and 41.6 kg/day respectively;
(2) physical and chemical properties of organic waste in terms of
moisture content was between 69.54 to 78.15%, major elements for
plant as N, P and K were 0.14 to 0.17%, 0.46 to 0.52% and 0.16 to
0.18% respectively, and carbon/nitrogen ratio (C/N) was about 15:1
to 17.5:1; (3) recycling organic waste as compost was designed by
aerobic decomposition using mixed food wastes : mixed leave & yard
wastes : mixed fruit & vegetable wastes at the portion of 3:2:1 by
weight in accordance with the potential of their amounts and their
physical and chemical properties.
Abstract: This paper deals with the problem of thermal and
mechanical shocks, which rising during operation, mostly at
interrupted cut. Here will be solved their impact on the cutting edge
tool life, the impact of coating technology on resistance to shocks
and experimental determination of tool life in heating flame.
Resistance of removable cutting edges against thermal and
mechanical shock is an important indicator of quality as well as its
abrasion resistance. Breach of the edge or its crumble may occur due
to cyclic loading. We can observe it not only during the interrupted
cutting (milling, turning areas abandoned hole or slot), but also in
continuous cutting. This is due to the volatility of cutting force on
cutting. Frequency of the volatility in this case depends on the type
of rising chips (chip size element). For difficult-to-machine materials
such as austenitic steel particularly happened at higher cutting speeds
for the localization of plastic deformation in the shear plane and for
the inception of separate elements substantially continuous chips.
This leads to variations of cutting forces substantially greater than for
other types of steel.
Abstract: The fractal-shaped orifices are assumed to have a
significant effect on the pressure drop downstream pipe flow due to
their edge self-similarity shape which enhances the mixing
properties. Here, we investigate the pressure drop after these fractals
using a digital micro-manometer at different stations downstream a
turbulent flow pipe then a direct comparison has been made with the
pressure drop measured from regular orifices with the same flow
area. Our results showed that the fractal-shaped orifices have a
significant effect on the pressure drop downstream the flow. Also
the pressure drop measured across the fractal-shaped orifices is
noticed to be lower that that from ordinary orifices of the same flow
areas. This result could be important in designing piping systems
from point of view of losses consideration with the same flow
control area. This is promising to use the fractal-shaped orifices as
flowmeters as they can sense the pressure drop across them
accurately with minimum losses than the regular ones.
Abstract: This paper introduces a framework that aims to
support the design and development of mobile services. The
traditional innovation process and its supporting instruments in form
of creativity tools, acceptance research and user-generated content
analysis are screened for potentials for improvement. The result is a
reshaped innovation process where acceptance research and usergenerated
content analysis are fully integrated within a creativity
tool. Advantages of this method are the enhancement of design
relevant information for developers and designers and the possibility
to forecast market success.
Abstract: This paper deals with the status of solid waste pollution in touristic spots of North coastal Andhra Pradesh. Case studies of Eco tourism, cultural tourism and pilgrim tourism are elaborately discussed and the study is based on both primary and secondary data. Data collection includes field collection of solid waste, semi structured interviews and observation of tourists. Results indicate generation of 72% Non biodegradable material in Eco touristic places like RK beach Visakhapatnam, Araku Valley. Pydithalli Jathra is a famous cultural touristic attraction and more than one lakh people converge here. The solid waste at this spot includes 20% coconut shells, 50% plastic bottles and covers, 20% Banana peelings and remaining are food materials. Radhasapthami is the most important festival celebrated at famous sun temple Arasavalli of Srikakulam. Here solid waste includes 50% water bottles, plastic covers, 10% papers, 10% hair, 30% left out food material and Banana peelings.
Abstract: Packing problems arise in a wide variety of application
areas. The basic problem is that of determining an efficient arrangement
of different objects in a region without any overlap and
with minimal wasted gap between shapes. This paper presents a
novel population based approach for optimizing arrangement of irregular
shapes. In this approach, each shape is coded as an agent and
the agents' reproductions and grouping policies results in arrangements
of the objects in positions with least wasted area between
them. The approach is implemented in an application for cutting
sheets and test results on several problems from literature are presented.
Abstract: Fuel cell is an emerging technology in the field
of renewable energy sources which has the capacity to replace
conventional energy generation sources. Fuel cell utilizes hydrogen
energy to produce electricity. The electricity generated by the fuel
cell can’t be directly used for a specific application as it needs
proper power conditioning. Moreover, the output power fluctuates
with different operating conditions. To get a stable output power
at an economic rate, power conditioning circuit is essential for fuel
cell. This paper implements a two-staged power conditioning unit for
fuel cell based distributed generation using hysteresis current control
technique.
Abstract: An accurate procedure to determine free vibrations of
beams and plates is presented.
The natural frequencies are exact solutions of governing vibration
equations witch load to a nonlinear homogeny system.
The bilinear and linear structures considered simulate a bridge.
The dynamic behavior of this one is analyzed by using the theory of
the orthotropic plate simply supported on two sides and free on the
two others. The plate can be excited by a convoy of constant or
harmonic loads. The determination of the dynamic response of the
structures considered requires knowledge of the free frequencies and
the shape modes of vibrations. Our work is in this context. Indeed,
we are interested to develop a self-consistent calculation of the Eigen
frequencies.
The formulation is based on the determination of the solution of
the differential equations of vibrations. The boundary conditions
corresponding to the shape modes permit to lead to a homogeneous
system. Determination of the noncommonplace solutions of this
system led to a nonlinear problem in Eigen frequencies.
We thus, develop a computer code for the determination of the
eigenvalues. It is based on a method of bisection with interpolation
whose precision reaches 10 -12. Moreover, to determine the
corresponding modes, the calculation algorithm that we develop uses
the method of Gauss with a partial optimization of the "pivots"
combined with an inverse power procedure. The Eigen frequencies
of a plate simply supported along two opposite sides while
considering the two other free sides are thus analyzed. The results
could be generalized with the case of a beam by regarding it as a
plate with low width.
We give, in this paper, some examples of treated cases. The
comparison with results presented in the literature is completely
satisfactory.
Abstract: An ordered porous antimony-doped tin oxide (ATO) film was successfully prepared using a simple coating process with colloidal templates. The facile production was effective when a combination of 16-nm ATO (as a model of an inorganic nanoparticle) and polystyrene (PS) spheres (as a model of the template) weresimply coated to produce a composite ATO/PS film. Heat treatment was then used to remove the PS and produce the porous film. The porous film with a spherical pore shape and a highly ordered porous structure could be obtained. A potential way for the control of pore size could be also achieved by changing initial template size. The theoretical explanation and mechanism of porous formation were also added, which would be important for the scaling-up prediction and estimation.
Abstract: A manufacturing feature can be defined simply as a
geometric shape and its manufacturing information to create the shape.
In a feature-based process planning system, feature library plays an
important role in the extraction of manufacturing features with their
proper manufacturing information. However, to manage the
manufacturing information flexibly, it is important to build a feature
library that is easy to modify. In this paper, a Wiki-based feature
library is proposed.
Abstract: This study investigated the effect of cross sectional
geometry on sediment transport rate. The processes of sediment
transport are generally associated to environmental management,
such as pollution caused by the forming of suspended sediment in the
channel network of a watershed and preserving physical habitats and
native vegetations, and engineering applications, such as the
influence of sediment transport on hydraulic structures and flood
control design. Many equations have been proposed for computing
the sediment transport, the influence of many variables on sediment
transport has been understood; however, the effect of other variables
still requires further research. For open channel flow, sediment
transport capacity is recognized to be a function of friction slope,
flow velocity, grain size, grain roughness and form roughness, the
hydraulic radius of the bed section and the type and quantity of
vegetation cover. The effect of cross sectional geometry of the
channel on sediment transport is one of the variables that need
additional investigation. The width-depth ratio (W/d) is a
comparative indicator of the channel shape. The width is the total
distance across the channel and the depth is the mean depth of the
channel. The mean depth is best calculated as total cross-sectional
area divided by the top width. Channels with high W/d ratios tend to
be shallow and wide, while channels with low (W/d) ratios tend to be
narrow and deep. In this study, the effects of the width-depth ratio on
sediment transport was demonstrated theoretically by inserting the
shape factor in sediment continuity equation and analytically by
utilizing the field data sets for Yalobusha River. It was found by
utilizing the two approaches as a width-depth ratio increases the
sediment transport decreases.
Abstract: Among many different methods that are used for
optimizing different engineering problems mathematical (numerical)
optimization techniques are very important because they can easily
be used and are consistent with most of engineering problems. Many
studies and researches are done on stability analysis of three
dimensional (3D) slopes and the relating probable slip surfaces and
determination of factors of safety, but in most of them force
equilibrium equations, as in simplified 2D methods, are considered
only in two directions. In other words for decreasing mathematical
calculations and also for simplifying purposes the force equilibrium
equation in 3rd direction is omitted. This point is considered in just a
few numbers of previous studies and most of them have only given a
factor of safety and they haven-t made enough effort to find the most
probable slip surface. In this study shapes of the slip surfaces are
modeled, and safety factors are calculated considering the force
equilibrium equations in all three directions, and also the moment
equilibrium equation is satisfied in the slip direction, and using
nonlinear programming techniques the shape of the most probable
slip surface is determined. The model which is used in this study is a
3D model that is composed of three upper surfaces which can cover
all defined and probable slip surfaces. In this research the meshing
process is done in a way that all elements are prismatic with
quadrilateral cross sections, and the safety factor is defined on this
quadrilateral surface in the base of the element which is a part of the
whole slip surface. The method that is used in this study to find the
most probable slip surface is the non-linear programming method in
which the objective function that must get optimized is the factor of
safety that is a function of the soil properties and the coordinates of
the nodes on the probable slip surface. The main reason for using
non-linear programming method in this research is its quick
convergence to the desired responses. The final results show a good
compatibility with the previously used classical and 2D methods and
also show a reasonable convergence speed.
Abstract: Aircraft propulsion systems often use Y-shaped
subsonic diffusing ducts as twin air-intakes to supply the ambient air
into the engine compressor for thrust generation. Due to space
constraint, the diffusers need to be curved, which causes severe flow
non-uniformity at the engine face. The present study attempt to
control flow in a mild-curved Y-duct diffuser using trapezoidalshaped
vortex generators (VG) attached on either both the sidewalls
or top and bottom walls of the diffuser at the inflexion plane. A
commercial computational fluid dynamics (CFD) code is modified
and is used to simulate the effects of SVG in flow of a Y-duct
diffuser. A few experiments are conducted for CFD code validation,
while the rest are done computationally. The best combination of Yduct
diffuser is found with VG-2 arranged in co-rotating sequence
and attached to both the sidewalls, which ensures highest static
pressure recovery, lowest total pressure loss, minimum flow
distortion and less flow separation in Y-duct diffuser. The decrease in
VG height while attached to top and bottom walls further improves
axial flow uniformity at the diffuser outlet by a great margin as
compared to the bare duct.
Abstract: Numerical design optimization is a powerful tool that
can be used by engineers during any stage of the design process.
There are many different applications for structural optimization. A
specific application that will be discussed in the following paper is
experimental data matching. Data obtained through tests on a physical
structure will be matched with data from a numerical model of that
same structure. The data of interest will be the dynamic characteristics
of an antenna structure focusing on the mode shapes and modal
frequencies. The structure used was a scaled and simplified model of
the Karoo Array Telescope-7 (KAT-7) antenna structure.
This kind of data matching is a complex and difficult task. This
paper discusses how optimization can assist an engineer during the
process of correlating a finite element model with vibration test data.