Abstract: Green house effect has becomes a serious concern in
many countries due to the increase consumption of the fossil fuel.
There have been many studies to find an alternative power source.
Wind energy found to be one of the most useful solutions to help in
overcoming the air pollution and global. There is no agreed solution
to conversion of wind energy to electrical energy. In this paper, the
advantages of using a Switched Reluctance Generator (SRG) for
wind energy applications. The theoretical study of the self excitation
of a SRG and the determination of the variable parameters in a SRG
design are discussed. The design parameters for the maximum power
output of the SRG are computed using Matlab simulation. The
designs of the circuit to control the variable parameters in a SRG to
provide the maximum power output are also discussed.
Abstract: Bicycle configuration is not as large as those of motorcycles or automobiles, while it indeed composes a complicated dynamic system. People-s requirements on comfortability, controllability and safety grow higher as the research and development technologies improve. The shock absorber affects the vehicle suspension performances enormously. The absorber takes the vibration energy and releases it at a suitable time, keeping the wheel under a proper contact condition with road surface, maintaining the vehicle chassis stability. Suspension design for mountain bicycles is more difficult than that of city bikes since it encounters dynamic variations on road and loading conditions. Riders need a stiff damper as they exert to tread on the pedals when climbing, while a soft damper when they descend downhill. Various switchable shock absorbers are proposed in markets, however riders have to manually switch them among soft, hard and lock positions. This study proposes a novel design of the bicycle shock absorber, which provides automatic smooth tuning of the damping coefficient, from a predetermined lower bound to theoretically unlimited. An automatic quick releasing valve is involved in this design so that it can release the peak pressure when the suspension fork runs into a square-wave type obstacle and prevent the chassis from damage, avoiding the rider skeleton from injury. This design achieves the automatic tuning process by innovative plunger valve and fluidic passage arrangements without any electronic devices. Theoretical modelling of the damper and spring are established in this study. Design parameters of the valves and fluidic passages are determined. Relations between design parameters and shock absorber performances are discussed in this paper. The analytical results give directions to the shock absorber manufacture.
Abstract: An experimental and numerical study has been conducted to clarify heat transfer characteristics and effectiveness of a cross-flow heat exchanger employing staggered wing-shaped tubes at different angels of attack. The water-side Rew and the air-side Rea were at 5 x 102 and at from 1.8 x 103 to 9.7 x 103, respectively. The tubes arrangements were employed with various angles of attack θ1,2,3 from 0° to 330° at the considered Rea range. Correlation of Nu, St, as well as the heat transfer per unit pumping power (ε) in terms of Rea, design parameters for the studied bundle were presented. The temperature fields around the staggered wing-shaped tubes bundle were predicted by using commercial CFD FLUENT 6.3.26 software package. Results indicated that the heat transfer was increased by increasing the angle of attack from 0° to 45°, while the opposite was true for angles of attack from 135° to 180°. The best thermal performance and hence η of studied bundle was occurred at the lowest Rea and/or zero angle of attack. Comparisons between the experimental and numerical results of the present study and those, previously, obtained for similar available studies showed good agreements.
Abstract: Complex engineering design problems consist of
numerous factors of varying criticalities. Considering fundamental features of design and inferior details alike will result in an extensive
waste of time and effort. Design parameters should be introduced gradually as appropriate based on their significance relevant to the
problem context. This motivates the representation of design parameters at multiple levels of an abstraction hierarchy. However, developing abstraction hierarchies is an area that is not well
understood. Our research proposes a novel hierarchical abstraction methodology to plan effective engineering designs and processes. It
provides a theoretically sound foundation to represent, abstract and stratify engineering design parameters and tasks according to causality and criticality. The methodology creates abstraction
hierarchies in a recursive and bottom-up approach that guarantees no
backtracking across any of the abstraction levels. The methodology consists of three main phases, representation, abstraction, and layering to multiple hierarchical levels. The effectiveness of the
developed methodology is demonstrated by a design problem.
Abstract: The tree structured approach of non-uniform filterbank
(NUFB) is normally used in perfect reconstruction (PR). The PR is
not always feasible due to certain limitations, i.e, constraints in
selecting design parameters, design complexity and some times
output is severely affected by aliasing error if necessary and
sufficient conditions of PR is not satisfied perfectly. Therefore, there
has been generalized interest of researchers to go for near perfect
reconstruction (NPR). In this proposed work, an optimized tree
structure technique is used for the design of NPR non-uniform
filterbank. Window functions of Blackman family are used to design
the prototype FIR filter. A single variable linear optimization is used
to minimize the amplitude distortion. The main feature of the
proposed design is its simplicity with linear phase property.
Abstract: This paper investigates the development of weld zone
in Resistance Spot Welding (RSW) which focuses on weld nugget and Heat Affected Zone (HAZ). The effects of four factors namely
weld current, weld time, electrode force and hold time were studied using a general 24 factorial design augmented by five centre points. The results of the analysis showed that all selected factors except
hold time exhibit significant effect on weld nugget radius and HAZ size. Optimization of the welding parameters (weld current, weld
time and electrode force) to normalize weld nugget and to minimize
HAZ size was then conducted using Central Composite Design (CCD) in Response Surface Methodology (RSM) and the optimum
parameters were determined. A regression model for radius of weld nugget and HAZ size was developed and its adequacy was evaluated.
The experimental results obtained under optimum operating conditions were then compared with the predicted values and were
found to agree satisfactorily with each other
Abstract: Automated material handling is given prime
importance in the semi automated and automated facilities since it
provides solution to the gigantic problems related to inventory and
also support the latest philosophies like just in time production JIT
and lean production. Automated storage and retrieval system is an
antidote (if designed properly) to the facility sufferings like getting
the right material , materials getting perished, long cycle times or
many other similar kind of problems. A working model of automated
storage and retrieval system (AS/RS) is designed and developed
under the design parameters specified by Material Handling Industry
of America (MHIA). Later on analysis was carried out to calculate
the throughput and size of the machine. The possible implementation
of this technology in local scenario is also discussed in this paper.
Abstract: In this paper, an attempt has been made to obtain nonsensitive
solutions in the multi-objective optimization of a
photovoltaic/thermal (PV/T) air collector. The selected objective
functions are overall energy efficiency and exergy efficiency.
Improved thermal, electrical and exergy models are used to calculate
the thermal and electrical parameters, overall energy efficiency,
exergy components and exergy efficiency of a typical PV/T air
collector. A computer simulation program is also developed. The
results of numerical simulation are in good agreement with the
experimental measurements noted in the previous literature. Finally,
multi-objective optimization has been carried out under given
climatic, operating and design parameters. The optimized ranges of
inlet air velocity, duct depth and the objective functions in optimal
Pareto front have been obtained. Furthermore, non-sensitive solutions
from energy or exergy point of view in the results of multi-objective
optimization have been shown.
Abstract: This paper details few mechanical modeling and
design issues of RF MEMS switches. We concentrate on an
electrostatically actuated broad side series switch; surface
micromachined with a crab leg membrane. The same results are
extended to any complex structure. With available experimental data
and fabrication results, we present the variation in dynamic
performance and compliance of the switch with reference to few
design issues, which we find are critical in deciding the dynamic
behavior of the switch, without compromise on the RF
characteristics. The optimization of pull in voltage, transient time and
resonant frequency with regard to these critical design parameters are
also presented.
Abstract: In this study, a longitudinal joint connection was
proposed for the short-span slab-type modular bridges with rapid
construction. The slab-type modular bridge consists of a number of
precast slab modules and has the joint connection between the
modules in the longitudinal direction of the bridge. A finite element
based parameter analysis was conducted to design the shape and the
dimensions of the longitudinal joint connection. Numbers of shear
keys within the joint, height and depth of the shear key, tooth angle,
and the spacing were considered as the design parameters. Using the
local cracking load at the corner of the shear key and the
cross-sectional area of the joint, an efficiency factor was proposed to
evaluate the effectiveness of the longitudinal joint connection. The
dimensions of shear key were determined by comparing the cracking
loads and the efficiency factors obtained from the finite element
analysis.
Abstract: An interesting method to produce calcium carbonate is based in a gas-liquid reaction between carbon dioxide and aqueous solutions of calcium hydroxide. The design parameters for gas-liquid phase are flow regime, individual mass transfer, gas-liquid specific interfacial area. Most studies on gas-liquid phase were devoted to the experimental determination of some of these parameters, and more specifically, of the mass transfer coefficient, kLa which depends fundamentally on the superficial gas velocity and on the physical properties of absorption phase. The principle investigation was directed to study the effect of the vibration on the mass transfer coefficient kLa in gas-liquid phase during absorption of CO2 in the in aqueous solution of calcium hydroxide. The vibration with a higher frequency increase the mass transfer coefficient kLa, but vibration with lower frequency didn-t improve it, the mass transfer coefficient kLa increase with increase the superficial gas velocity.