Abstract: This paper presents a model for the evaluation of
energy performance and aerodynamic forces acting on a three-bladed
small vertical axis Darrieus wind turbine depending on blade chord
curvature with respect to rotor axis.
The adopted survey methodology is based on an analytical code
coupled to a solid modeling software, capable of generating the
desired blade geometry depending on the blade design geometric
parameters, which is linked to a finite volume CFD code for the
calculation of rotor performance.
After describing and validating the model with experimental data,
the results of numerical simulations are proposed on the bases of two
different blade profile architectures, which are respectively
characterized by a straight chord and by a curved one, having a chord
radius equal to rotor external circumference. A CFD campaign of
analysis is completed for three blade-candidate airfoil sections, that is
the recently-developed DU 06-W-200 cambered blade profile, a
classical symmetrical NACA 0021 and its derived cambered airfoil,
characterized by a curved chord, having a chord radius equal to rotor
external circumference.
The effects of blade chord curvature on angle of attack, blade
tangential and normal forces are first investigated and then the
overall rotor torque and power are analyzed as a function of blade
azimuthal position, achieving a numerical quantification of the
influence of blade camber on overall rotor performance.
Abstract: Electrical distribution systems are incurring large losses as the loads are wide spread, inadequate reactive power compensation facilities and their improper control. A comprehensive static VAR compensator consisting of capacitor bank in five binary sequential steps in conjunction with a thyristor controlled reactor of smallest step size is employed in the investigative work. The work deals with the performance evaluation through analytical studies and practical implementation on an existing system. A fast acting error adaptive controller is developed suitable both for contactor and thyristor switched capacitors. The switching operations achieved are transient free, practically no need to provide inrush current limiting reactors, TCR size minimum providing small percentages of nontriplen harmonics, facilitates stepless variation of reactive power depending on load requirement so as maintain power factor near unity always. It is elegant, closed loop microcontroller system having the features of self regulation in adaptive mode for automatic adjustment. It is successfully tested on a distribution transformer of three phase 50 Hz, Dy11, 11KV/440V, 125 KVA capacity and the functional feasibility and technical soundness are established. The controller developed is new, adaptable to both LT & HT systems and practically established to be giving reliable performance.
Abstract: The problem of robust disturbance rejection (RDR) using a proportional state feedback controller is studied for the case of Left Invertible MIMO generalized state space linear systems with nonlinear uncertain structure. Sufficient conditions for the problem to have a solution are established. The set of all proportional feedback controllers solving the problem subject to these conditions is analytically determined.
Abstract: The theoretical prediction of the acoustical
polarization effects in the heterogeneous composites, made of thick
elastic solids with thin nematic films, is presented. The numericalanalytical
solution to the problem of the different wave propagation
exhibits some new physical effects in the low frequency domain: the
appearance of the critical frequency and the existence of the narrow
transition zone where the wave rapidly changes its speed. The
associated wave attenuation is highly perturbed in this zone. We also
show the possible appearance of the critical frequencies where the
attenuation changes the sign. The numerical results of parametrical
analysis are presented and discussed.
Abstract: If an unsteady heat transfer or heat impulse happens in
part of the cryogenic pipeline system of large space environment
simulation equipment while running in vacuum environment, it will
lead to abnormal flow of the cryogenic fluid in the pipeline. When the
situation gets worse, the cryogenic fluid in the pipeline will have phase
change and a gas block which results in the malfunction of the
cryogenic pipeline system. Referring to the structural parameter of a
typical cryogenic pipeline system and the basic equation, an analytical
model and a calculation model for cryogenic pipeline system can be
built. The various factors which influence the thermal resistance of a
cryogenic pipeline system can be analyzed and calculated by using the
qualitative analysis relation deduced for thermal resistance of pipeline.
The research conclusion could provide theoretical support for the
design and operation of a cryogenic pipeline system
Abstract: This work is focused on the steady boundary layer flow
near the forward stagnation point of plane and axisymmetric bodies
towards a stretching sheet. The no slip condition on the solid
boundary is replaced by the partial slip condition. The analytical
solutions for the velocity distributions are obtained for the various
values of the ratio of free stream velocity and stretching velocity, slip
parameter, the suction and injection velocity parameter, magnetic
parameter and dimensionality index parameter in the series forms with
the help of homotopy analysis method (HAM). Convergence of the
series is explicitly discussed. Results show that the flow and the skin
friction coefficient depend heavily on the velocity slip factor. In
addition, the effects of all the parameters mentioned above were more
pronounced for plane flows than for axisymmetric flows.
Abstract: The quantitative determination of several trace
elements (Cr, As, Se, Cd, Hg, Pb) existing as inorganic impurities in
some oriental herb-products such as Lingzhi Mushroom capsules,
Philamin powder, etc using ICP-MS has been studied. Various
instrumental parameters such as power, gas flow rate, sample depth, as
well as the concentration of nitric acid and thick background due to
high concentration of possible interferences on the determination of
these above-mentioned elements was investigated and the optimum
working conditions of the sample measurement on ICP-MS
(Agilent-7500a) were reported. Appropriate isotope internal standards
were also used to improve the accuracy of mercury determination.
Optimal parameters for sampling digestion were also investigated. The
recovery of analytical procedure was examined by using a Certified
Reference Material (IAEA-CRM 359). The recommended procedure
was then applied for the quantitative determination of Cr, As, Se, Cd,
Hg, Pb in Lingzhi Mushroom capsule, and Philamine powder samples.
The reproducibility of sample measurement (average value between
94 and 102%) and the uncertainty of analytical data (less than 20%)
are acceptable.
Abstract: This paper presents an investigation into the design of a flight control system, using a robust sliding mode control structure, designed using the exact feedback linearization procedure of the dynamic of a small-size autonomous helicopter in hover. The robustness of the controller in the context of stabilization and trajectory tracking with respect to small body forces and air resistance on the main and tail rotor, is analytically proved using Lyapunov approach. Some simulation results are presented to illustrate the performance and robustness of such controller in the presence of small body forces and air resistance.
Abstract: Observations show that power plant efficiency
decreases in hot summer days. Water droplet injection in air
condensers is suggested in order to decrease the inlet air temperature.
Nozzle arrangement, injected water flow rate and droplets diameter
effects on evaporation rate and the resulting air temperature are
investigated using numerical simulation. Decreasing the diameter of
injected droplets and increasing the number of injecting nozzles,
decreases the outlet air temperature. Also a more uniform air
temperature can be obtained using more injecting nozzles. Numerical
results are in good agreement with analytical results.
Abstract: Analytical procedure was carried out in this paper to
calculate the ultimate load capacity of reinforced concrete corbels
strengthened or repaired externally with CFRP sheets. Strut and tie
method and shear friction method proposed earlier for analyzing
reinforced concrete corbels were modified to incorporate the effect of
external CFRP sheets bonded to the corbel. The points of weakness
of any method that lead to an inaccuracy, especially when
overestimating test results were checked and discussed. Comparison
of prediction with the test data indicates that the ratio of test /
calculated ultimate load is 0.82 and 1.17 using strut and tie method
and shear friction method, respectively. If the limits of maximum
shear stress is followed, the calculated ultimate load capacity using
shear friction method was found to underestimates test data
considerably.
Abstract: Incompressible Navier-Stokes equations are reviewed
in this work. Three-dimensional Navier-Stokes equations are solved
analytically. The Mathematical derivation shows that the solutions
for the zero and constant pressure gradients are similar. Descriptions
of the proposed formulation and validation against two laminar
experiments and three different turbulent flow cases are reported in
this paper. Even though, the analytical solution is derived for nonreacting
flows, it could reproduce trends for cases including
combustion.
Abstract: This paper presents a conceptual model of agreement
options for negotiation support in multi-person decision on
optimizing high-rise building columns. The decision is complicated
since many parties involved in choosing a single alternative from a
set of solutions. There are different concern caused by differing
preferences, experiences, and background. Such building columns as
alternatives are referred to as agreement options which are
determined by identifying the possible decision maker group,
followed by determining the optimal solution for each group. The
group in this paper is based on three-decision makers preferences that
are designer, programmer, and construction manager. Decision
techniques applied to determine the relative value of the alternative
solutions for performing the function. Analytical Hierarchy Process
(AHP) was applied for decision process and game theory based agent
system for coalition formation. An n-person cooperative game is
represented by the set of all players. The proposed coalition
formation model enables each agent to select individually its allies or
coalition. It further emphasizes the importance of performance
evaluation in the design process and value-based decision.
Abstract: In this paper, an analytical approach for free vibration
analysis of rectangular and circular membranes is presented. The
method is based on wave approach. From wave standpoint vibration
propagate, reflect and transmit in a structure. Firstly, the propagation
and reflection matrices for rectangular and circular membranes are
derived. Then, these matrices are combined to provide a concise and
systematic approach to free vibration analysis of membranes.
Subsequently, the eigenvalue problem for free vibration of membrane
is formulated and the equation of membrane natural frequencies is
constructed. Finally, the effectiveness of the approach is shown by
comparison of the results with existing classical solution.
Abstract: In this paper, for the first time, a two-dimensional
(2D) analytical drain current model for sub-100 nm multi-layered
gate material engineered trapezoidal recessed channel (MLGMETRC)
MOSFET: a novel design is presented and investigated using
ATLAS and DEVEDIT device simulators, to mitigate the large gate
leakages and increased standby power consumption that arise due to
continued scaling of SiO2-based gate dielectrics. The twodimensional
(2D) analytical model based on solution of Poisson-s
equation in cylindrical coordinates, utilizing the cylindrical
approximation, has been developed which evaluate the surface
potential, electric field, drain current, switching metric: ION/IOFF
ratio and transconductance for the proposed design. A good
agreement between the model predictions and device simulation
results is obtained, verifying the accuracy of the proposed analytical
model.
Abstract: In this paper, we have applied the homotopy perturbation
method (HPM) for obtaining the analytical solution of unsteady
flow of gas through a porous medium and we have also compared the
findings of this research with some other analytical results. Results
showed a very good agreement between results of HPM and the
numerical solutions of the problem rather than other analytical solutions
which have previously been applied. The results of homotopy
perturbation method are of high accuracy and the method is very
effective and succinct.
Abstract: A study of electromagnetic flow meter is presented in the paper. Comparison has been made between the analytical and the numerical results by the use of FEM numerical analysis (Quick Field 5.6) for determining polarization voltage through the circle cross section of the polarization transducer. Exciting and geometrical parameters increasing its effectiveness has been examined. The aim is to obtain maximal output signal. The investigations include different variants of the magnetic flux density distribution around the tube: homogeneous field of magnitude Bm, linear distribution with maximal value Bm and trapezium distribution conserving the same exciting magnetic energy as the homogeneous field.
Abstract: This study deals with the phenomena of reflection and transmission (refraction) of qSV-waves, for an incident of quasi transverse vertically waves, at a plane interface of two semi-infinite piezoelectric elastic media under the influence of the initial stresses. The relations governing the reflection and transmission coefficients of these reflected waves for various suitable boundary conditions are derived. We have shown analytically that reflection and transmission coefficients of (qP) and (qSV) waves depend upon the angle of incidence, the parameters of electric potential, the material constants of the medium as will as the initial stresses presented in the media. The numerical calculations of the reflection and transmission amplitude ratios for different values of initial stresses have been carried out by computer for different materials as examples and the results are given in the form of graphs. Finally, some of particular cases are considered.
Abstract: Global competitiveness has recently become the
biggest concern of both manufacturing and service companies.
Electronic commerce, as a key technology enables the firms to reach
all the potential consumers from all over the world. In this study, we
have presented commonly used electronic payment systems, and then
we have shown the evaluation of these systems in respect to different
criteria. The payment systems which are included in this research are
the credit card, the virtual credit card, the electronic money, the
mobile payment, the credit transfer and the debit instruments. We
have realized a systematic comparison of these systems in respect to
three main criteria: Technical, economical and social. We have
conducted a fuzzy multi-criteria decision making procedure to deal
with the multi-attribute nature of the problem. The subjectiveness
and imprecision of the evaluation process are modeled using
triangular fuzzy numbers.
Abstract: This paper deals with analysis of flexural stiffness,
indentation and their energies in three point loading of sandwich
beams with composite faces from Eglass/epoxy and cores from
Polyurethane or PVC. Energy is consumed in three stages of
indentation in laminated beam, indentation of sandwich beam and
bending of sandwich beam. Theory of elasticity is chosen to present
equations for indentation of laminated beam, then these equations
have been corrected to offer better results. An analytical model has
been used assuming an elastic-perfectly plastic compressive behavior
of the foam core. Classical theory of beam is used to describe three
point bending. Finite element (FE) analysis of static indentation
sandwich beams is performed using the FE code ABAQUS. The
foam core is modeled using the crushable foam material model and
response of the foam core is experimentally characterized in uniaxial
compression.
Three point bending and indentation have been done
experimentally in two cases of low velocity and higher velocity
(quasi-impact) of loading. Results can describe response of beam in
terms of core and faces thicknesses, core material, indentor diameter,
energy absorbed, and length of plastic area in the testing. The
experimental results are in good agreement with the analytical and
FE analyses. These results can be used as an introduction for impact
loading and energy absorbing of sandwich structures.
Abstract: In this paper optical code-division multiple-access (OCDMA) packet network is considered, which offers inherent security in the access networks. Two types of random access protocols are proposed for packet transmission. In protocol 1, all distinct codes and in protocol 2, distinct codes as well as shifted versions of all these codes are used. O-CDMA network performance using optical orthogonal codes (OOCs) 1-D and two-dimensional (2-D) wavelength/time single-pulse-per-row (W/T SPR) codes are analyzed. The main advantage of using 2-D codes instead of onedimensional (1-D) codes is to reduce the errors due to multiple access interference among different users. In this paper, correlation receiver is considered in the analysis. Using analytical model, we compute and compare packet-success probability for 1-D and 2-D codes in an O-CDMA network and the analysis shows improved performance with 2-D codes as compared to 1-D codes.