Abstract: Nanofibers are effective materials which have
frequently been investigated to produce high quality air filters. As an
environmental approach our aim is to achieve nanofibers by melting.
In spun-bond systems extruder, spin-pump, nozzle package and
attenuator are used. Molten polymer which flows from extruder is
made steady by spin-pump. Regular melt passes through nozzle holes
and forms fibers under high pressure. The fibers pulled from nozzle
are shrunk to micron size by an attenuator; after solidification, they
are collected on a conveyor. In this research different designs of
attenuator system have been studied; and also CFD analysis has been
done on these different designs. Afterwards, one of these designs
tested and finally some optimizations have been done to reduce
pressure loss and increase air velocity.
Abstract: Fluid viscous damping systems are well suited for
many air vehicles subjected to shock and vibration. These damping
system work with the principle of viscous fluid throttling through the
orifice to create huge pressure difference between compression and
rebound chamber and obtain the required damping force. One
application of such systems is its use in aircraft door system to
counteract the door’s velocity and safely stop it. In exigency
situations like crash or emergency landing where the door doesn’t
open easily, possibly due to unusually tilting of fuselage or some
obstacles or intrusion of debris obstruction to move the parts of the
door, such system can be combined with other systems to provide
needed force to forcefully open the door and also securely stop it
simultaneously within the required time i.e. less than 8 seconds. In
the present study, a hydraulic system called snubber along with other
systems like actuator, gas bottle assembly which together known as
emergency power assist system (EPAS) is designed, built and
experimentally studied to check the magnitude of angular velocity,
damping force and time required to effectively open the door.
Whenever needed, the gas pressure from the bottle is released to
actuate the actuator and at the same time pull the snubber’s piston to
operate the emergency opening of the door. Such EPAS installed in
the suspension arm of the aircraft door is studied explicitly changing
parameters like orifice size, oil level, oil viscosity and bypass valve
gap and its spring of the snubber at varying temperature to generate
the optimum design case. Comparative analysis of the EPAS at
several cases is done and conclusions are made. It is found that
during emergency condition, the system opening time and angular
velocity, when snubber with 0.3mm piston and shaft orifice and
bypass valve gap of 0.5 mm with its original spring is used, shows
significant improvement over the old ones.
Abstract: Using cold EGR method with variable venturi and
turbocharger has a very significant effect on reduction of NOX and
grime simultaneously. EGR cooler is one of the most important parts
in the cold EGR circuit. In this paper optimum design of cooler for
working in different percentages of EGR and for determining
optimum temperature of exhausted gases, growth of efficiency,
reduction of weight, dimension, expenditures, sediment and also
optimum performance by using gasoil which has significant amounts
of brimstone are investigated and optimized.
Abstract: In this paper, the optimum design for renewable energy system powered an aquaculture pond was determined. Hybrid Optimization Model for Electric Renewable (HOMER) software program, which is developed by U.S National Renewable Energy Laboratory (NREL), is used for analyzing the feasibility of the stand alone and hybrid system in this study. HOMER program determines whether renewable energy resources satisfy hourly electric demand or not. The program calculates energy balance for every 8760 hours in a year to simulate operation of the system. This optimization compares the demand for the electrical energy for each hour of the year with the energy supplied by the system for that hour and calculates the relevant energy flow for each component in the model. The essential principle is to minimize the total system cost while HOMER ensures control of the system. Moreover the feasibility analysis of the energy system is also studied. Wind speed, solar irradiance, interest rate and capacity shortage are the parameters which are taken into consideration. The simulation results indicate that the hybrid system is the best choice in this study, yielding lower net present cost. Thus, it provides higher system performance than PV or wind stand alone systems.
Abstract: This paper describes the design optimization of ferrocement-laminated plate made up of reinforcing steel wire mesh(es) and cement mortar. For the improvement of the designing process, the plate is modeled as a multi-layer medium, dividing the ferrocement plate into layers of mortar and ferrocement. The mortar layers are assumed to be isotropic in nature and the ferrocement layers are assumed to be orthotropic. The ferrocement layers are little stiffer, but much more costlier, than the mortar layers due the presence of steel wire mesh. The optimization is performed for minimum weight design of the laminate using a genetic algorithm. The optimum designs are discussed for different plate configurations and loadings, and it is compared with the worst designs obtained at the final generation. The paper provides a procedure for the designers in decision-making process.
Abstract: Finned-tube heat exchangers are predominantly used in space conditioning systems, as well as other applications requiring heat exchange between two fluids. The design of finned-tube heat exchangers requires the selection of over a dozen design parameters by the designer such as tube pitch, tube diameter, tube thickness, etc… Finned-tube heat exchangers are common devices; however, their performance characteristics are complicated. In this paper numerical studies have been carried out to analyze the performances of finned tube heat exchanger (without fins considered for experimental purpose) by predicting the characteristics of temperature difference and pressure drop. In this study, a design considering 5 design variables and also maximizing the temperature difference and pressure drop was suggested by applying DOE. During this process, L18 orthogonal array was adopted. Parametric analytical studies have been carried out using ANOVA to determine the relative importance of each variable with respect to the temperature difference and the pressure drop. Following the results, the final design was suggested by predicting the optimum design therefore confirming the optimized condition.
Abstract: Development in construction industry is leading to involve complexities in engineering systems; whereas it also required to its sustainability towards social, environmental, and economical aspects. Experts with requisite background and expertise are involved in order to integrate knowledge in achieving whole criteria through design process. Collaborative design is needed in order to attain optimum design through shared solution and goal from experts. This study is conducted to explore issues and approaches development of collaborative design research in construction and its influence to sustainability of the development. Literature review method is used in order to conceptually figure future research direction of collaborative design research. This research is a part of beginning process in doctoral research program, and will be used to support dissertation’s conceptual definition.
Abstract: Determination of attentional status is important because working performance and an unexpected accident is highly related with the attention. The autonomic nervous and the central nervous systems can reflect the changes in person’s attentional status. Reduced number of suitable pysiological parameters among autonomic and central nervous systems related signal parameters will be critical in optimum design of attentional devices. In this paper, we analyze the EEG (Electroencephalography) and HRV (Heart Rate Variability) signals to demonstrate the effective relation with brain signal and cardiovascular signal during event-related attention, which will be later used in selecting the minimum set of attentional parameters. Time and frequency domain parameters from HRV signal and frequency domain parameters from EEG signal are used as input to the optimum feature parameters selector.
Abstract: In this paper the principle, basic torque theory and design optimisation of a six-phase reluctance dc machine are considered. A trapezoidal phase current waveform for the machine drive is proposed and evaluated to minimise ripple torque. Low cost normal laminated salient-pole rotors with and without slits and chamfered poles are investigated. The six-phase machine is optimised in multi-dimensions by linking the finite-element analysis method directly with an optimisation algorithm; the objective function is to maximise the torque per copper losses of the machine. The armature reaction effect is investigated in detail and found to be severe. The measured and calculated torque performances of a 35 kW optimum designed six-phase reluctance dc machine drive are presented.
Abstract: A new design approach for three-stage operational
amplifiers (op-amps) is proposed. It allows to actually implement a
symmetrical push-pull class-AB amplifier output stage for wellestablished
three-stage amplifiers using a feedforward
transconductance stage. Compared with the conventional design
practice, the proposed approach leads to a significant
improvement of the symmetry between the positive and the
negative op-amp step response, resulting in similar values of the
positive/negative settling time. The new approach proves to be very
useful in order to fully exploit the potentiality allowed by the op-amp
in terms of speed performances. Design examples in a commercial
0.35-μm CMOS prove the effectiveness of theproposed strategy.
Abstract: The effect of autofrettage process in strain hardened
thick-walled pressure vessels has been investigated theoretically by
finite element modeling. Equivalent von Mises stress is used as yield
criterion to evaluate the optimum autofrettage pressure and the
optimum radius of elastic-plastic junction. It has been observed that
the optimum autofrettage pressure increases along with the working
pressure. For two different working pressures, the effect of the ratio
of outer to inner radius (b/a=k) value on the optimum autofrettage
pressure is also noticed. The Optimum autofrettage pressure solely
depends on K value rather than on the inner or outer radius.
Furthermore, percentage reduction of von Mises stresses is compared
for different working pressures and different k values. Maximum von
Mises stress developed at different autofrettage pressure is equated
for elastic perfectly plastic and elastic-plastic material with different
slope of strain hardening segment. Cylinder material having higher
slope of strain hardening segment provides better benedictions in the
autofrettage process.
Abstract: In the present work, the performance of the particle
swarm optimization and the genetic algorithm compared as a typical
geometry design problem. The design maximizes the heat transfer
rate from a given fin volume. The analysis presumes that a linear
temperature distribution along the fin. The fin profile generated using
the B-spline curves and controlled by the change of control point
coordinates. An inverse method applied to find the appropriate fin
geometry yield the linear temperature distribution along the fin
corresponds to optimum design. The numbers of the populations, the
count of iterations and time to convergence measure efficiency.
Results show that the particle swarm optimization is most efficient
for geometry optimization.
Abstract: This paper studies the optimum design for reducing
optical loss of an 8x8 mechanical type optical switch due to the
temperature change. The 8x8 optical switch is composed of a base, 8
input fibers, 8 output fibers, 3 fixed mirrors and 17 movable mirrors.
First, an innovative switch configuration is proposed with
thermal-compensated design. Most mechanical type optical switches
have a disadvantage that their precision and accuracy are influenced
by the ambient temperature. Therefore, the thermal-compensated
design is to deal with this situation by using materials with different
thermal expansion coefficients (α). Second, a parametric modeling
program is developed to generate solid models for finite element
analysis, and the thermal and structural behaviors of the switch are
analyzed. Finally, an integrated optimum design program, combining
Autodesk Inventor Professional software, finite element analysis
software, and genetic algorithms, is developed for improving the
thermal behaviors that the optical loss of the switch is reduced. By
changing design parameters of the switch in the integrated design
program, the final optimum design that satisfies the design constraints
and specifications can be found.
Abstract: In this study the integration of an absorption heat
pump (AHP) with the concentration section of an industrial pulp and
paper process is investigated using pinch technology. The optimum
design of the proposed water-lithium bromide AHP is then achieved
by minimizing the total annual cost. A comprehensive optimization is
carried out by relaxation of all stream pressure drops as well as heat
exchanger areas involving in AHP structure. It is shown that by
applying genetic algorithm optimizer, the total annual cost of the
proposed AHP is decreased by 18% compared to one resulted from
simulation.
Abstract: An accurate optimal design of laminated composite
structures may present considerable difficulties due to the complexity
and multi-modality of the functional design space. The Big Bang
– Big Crunch (BB-BC) optimization method is a relatively new
technique and has already proved to be a valuable tool for structural
optimization. In the present study the exceptional efficiency of the
method is demonstrated by an example of the lay-up optimization
of multilayered anisotropic cylinders based on a three-dimensional
elasticity solution. It is shown that, due to its simplicity and speed,
the BB-BC is much more efficient for this class of problems when
compared to the genetic algorithms.
Abstract: In this paper, an automatic control system design
based on Integral Squared Error (ISE) parameter optimization
technique has been implemented on longitudinal flight dynamics of
an UAV. It has been aimed to minimize the error function between
the reference signal and the output of the plant. In the following
parts, objective function has been defined with respect to error
dynamics. An unconstrained optimization problem has been solved
analytically by using necessary and sufficient conditions of
optimality, optimum PID parameters have been obtained and
implemented in control system dynamics.
Abstract: Optimal design of structure has a main role in reduction of material usage which leads to deduction in the final cost of construction projects. Evolutionary approaches are found to be more successful techniques for solving size and shape structural optimization problem since it uses a stochastic random search instead of a gradient search. By reviewing the recent literature works the problem found was the optimization of weight. A new meta-heuristic algorithm called as Cuckoo Search (CS) Algorithm has used for the optimization of the total weight of the truss structures. This paper has used set of 10 bars and 25 bars trusses for the testing purpose. The main objective of this work is to reduce the number of iterations, weight and the total time consumption. In order to demonstrate the effectiveness of the present method, minimum weight design of truss structures is performed and the results of the CS are compared with other algorithms.
Abstract: This Paper presents a particle swarm optimization (PSO) method for determining the optimal proportional-integral-derivative (PID) controller parameters, for speed control of a linear brushless DC motor. The proposed approach has superior features, including easy implementation, stable convergence characteristic and good computational efficiency. The brushless DC motor is modelled in Simulink and the PSO algorithm is implemented in MATLAB. Comparing with Genetic Algorithm (GA) and Linear quadratic regulator (LQR) method, the proposed method was more efficient in improving the step response characteristics such as, reducing the steady-states error; rise time, settling time and maximum overshoot in speed control of a linear brushless DC motor.
Abstract: The purpose of this paper is applied Taguchi method on the optimization for PEMFC performance, and a representative Computational Fluid Dynamics (CFD) model is selectively performed for statistical analysis. The studied factors in this paper are pressure of fuel cell, operating temperature, the relative humidity of anode and cathode, porosity of gas diffusion electrode (GDE) and conductivity of GDE. The optimal combination for maximum power density is gained by using a three-level statistical method. The results confirmed that the robustness of the optimum design parameters influencing the performance of fuel cell are founded by pressure of fuel cell, 3atm; operating temperature, 353K; the relative humidity of anode, 50%; conductivity of GDE, 1000 S/m, but the relative humidity of cathode and porosity of GDE are pooled as error due to a small sum of squares. The present simulation results give designers the ideas ratify the effectiveness of the proposed robust design methodology for the performance of fuel cell.
Abstract: The launching nose plays an important role in the
incremental launching construction. The parameters of the launching
nose essentially affect the internal forces of the girder during the
construction. The appropriate parameters can decrease the internal
forces in the girder and save the material and reduce the cost. The
simplified structural model, which is made with displacement method
according to the characteristic of incremental launching construction
and the variation rule of the internal forces, calculates and analyzes the
effect of the length, the rigidity and weight of launch nose on the
internal forces of girder during the incremental launching
construction. The method, which can calculate the launching nose
parameters for the optimum incremental launching construction, is
achieved. This method is simple, reliable and easy for practical use.