
Archive issue  vol.5 No.4
1.
FINITE ELEMENT ANALYSIS OF THE HEMODYNAMICS
IN THE HUMAN CAROTID ARTERY BIFURCATION
A. POSTELNICU
Transilvania University of Brasov,
Department of Fluid Mechanics,
Brasow, 2200, ROMANIA
D. MINEA
Transilvania University of Brasov,
Department of Neurology,
Brasov, 2200, ROMANIA
The present paper brings new lights on blood flow patterns in rigid artery bifurcation models, differing in angle of bifurcation. Using the ANSYS 5.4/FLOTRAN package, a numerical analysis in two dimensions was performed, under physiologically relevant flow conditions. For two bifurcation models, one with large angle the other with a small one, the distributions of velocities, shearstress and pressure in the domain of carotid artery bifurcation have been obtained. It is argued and proved that the vascular geometry at the bifurcation level represents a risk factor in atherogenesis, the relevant factors for this process being the flow separation, reversal flow regions and wall shear stress.

Key words: 
finite element simulation, blood flow, bifurcation, atherosclerosis. 
TOP OF PAGE 
2.
NONLINEAR BEHAVIOUR OF PITCHED ROOF STEEL FRAMES
SUBJECTED TO SEQUENTIAL LOADS
B.H.M. CHAN, S.L. CHAN and S.S. LAW
Dept of Civil and Structural Engineering
The Hong Kong Polytechnic University
HONG KONG, P.R. CHINA
This paper investigates the importance of sequential loads on the ultimate behaviour of pitched roof steel frames. In most previous studies related to inelastic or advanced analysis, loads are assumed to apply proportionally, which contrasts to the more realistic cases of invariant gravitational loads and varying lateral loads due to wind and seismic forces. Based on the previous work on the inelastic and large deflection analysis, the tangent modulus method is coded in a computer program. Numerical examples are given to demonstrate the discrepancy between these two approaches and to indicate the potential danger of using the oversimplified proportional load assumption in design and analysis of semirigid pitched roof steel frames.

Key words: 
secondorder analysis, sequential load, proportional load, pitched roof steel frame, semirigid frame. 
TOP OF PAGE 
3.
FUZZY LOGIC SYSTEM FOR SUPERFICIAL DEFECTS
CLASSIFICATION IN METAL PATCHES
V. NIOLA
Mechanic Department for Energetic, University of Naples,
Facolta di Ingegneria DIME, Universita di Napoli,
via Claudio 21 cap. 80125, Napoli, ITALIA
email: vniola@cds.unina.it
M. LONGOBARDI
GEPIN Engineering S.p.A. , Centro Direzionale
di Napoli  Isola E3  80100 Napoli, ITALIA
email: marco.longobardi@gepinengineering.it
The system achieved is an integration of the identification system, we planned and carried out, as we previously described (Niola et al., 1999). From the depth map onwards, that is the output of the identification system, the classification system, operating on the single lines of the map, reconstructs through interpolation the level lines of the image, which are to be fitted to Fuzzy set; in order to do this, a mixed neurofuzzy technique is adopted.
The so achieved input Fuzzy sets, level lines that have been modelled, are compared to the output Fuzzy sets, which reproduce a parameterisation of the defect according to its depth, by means of inference rules planned on purpose.
The final result will give a quantification of the defect found, besides pointing out the area in which it has been noticed.

Key words: 
fuzzy set, membership functions, level lines, superficial defects, adaptive neuralfuzzy, modelling, classification. 
TOP OF PAGE 
4.
THEORETICAL ANALYSIS OF THE HYDRODYNAMIC
CHARACTERISTICS OF ELECTRORHEOLOGICAL FLUID IN
A PARALLEL DUCT FLOW
K. SHIMADA
Akita Prefectural University
Faculty of System Science and Technology
Department of Machine Intelligence and System Engineering
844 AzaEbinokuchi, Tsuchiya, Honjoh, Akita, 0150055, JAPAN
email: shimada@akitapu.ac.jp
H. NISHIDA
Toyama Polytechnic College
12891 Kawabuchi, Uozu, Toyama, 9370856, JAPAN
H. YAMAGUCHI
Doshisya University, Department of Mechanical Engineering
Kyotanabe, Kyoto, 6300321, JAPAN
Theoretical analysis was conducted of the hydrodynamic characteristics of the twodimensional flow of electrorheological fluid between parallel plates by using the mechanical dynamic model proposed herein. The model includes the Voigt model and a slider. It can present four types of relations between shear stress and shear rate. The theoretical results were compared with the experimental data. The theoretical analysis explains the experimental results qualitatively. The qualitative tendency is the same for the four types of relations between shear rate and shear stress. Based on the theoretical results, velocity distribution of flow in four types of relations is not influenced by shear stress and shear rate. This finding differs from that for rotational flow around a rotating disk. The pressure difference depends on apparent viscosity. The local Reynolds number depends on the local velocity at a low given flow velocity and on the local kinematic viscosity at a high given flow velocity.

Key words: 
fluid dynamics, internal flow, viscoelastic fluid, electrorheological fluid, pressure difference, twodimensional flow, mechanical dynamic model, viscosity, Reynolds number, electric field. 
TOP OF PAGE 
5.
TWOSTAGE ATOMIZATION MODEL FOR LIQUID JET
DISINTEGRATION IN GAS ATOMIZERS
Y.M. SHTEMLER, M.P. LEVITSKY and I.R. SHREIBER
Institute for Industrial Mathematics
4/24 Hanachtom Str., BeerSheva 84249, ISRAEL
S.P. LEVITSKY
School of Engineering
71 Bazel Str., BeerSheva 84100, ISRAEL
Y. BERKOVICH
Israel Electric Corporation
POB 10, Haifa 31000, ISRAEL
Atomization of a liquid jet in a convergentdivergent gas nozzle is studied both theoretically and experimentally. The jet enters the nozzle through a central tube and is primarily disintegrated in the vicinity of the tube exit. An integral model allows cumbersome calculations to be avoided. The model uses idealized schemes for the coarsely and finely dispersed mixture after primary and secondary atomization, respectively. Comparison of theoretical results with experimental data demonstrates the applicability of the model for prediction of the atomizer's geometry and operating conditions necessary for producing the finest possible mixture.

Key words: 
modeling, liquid disintegration, atomization shock. 
TOP OF PAGE 
6.
VIBRATION OF ANNULAR ELLIPTIC ORTHOTROPIC PLATES USING
TWO DIMENSIONAL ORTHOGONAL POLYNOMIALS
S. CHAKRAVERTY
Central Building Research Institute, Roorkee University
Roorkee, 247667, U.P., INDIA
R.B. BHAT
Department of Mechanical Engineering, Concordia University
Maisonneuve Boulevard West, Montréal
Québec H3G 1M8, CANADA
I. STIHARU
Department of Mechanical Engineering, Concordia University
1455 De Maisonneuve Boulevard West, Montréal
Québec H3G 1M8, CANADA
The free vibration natural frequencies of specially orthotropic annular elliptic and circular plates are analyzed by the RayleighRitz method, using twodimensional boundary characteristic orthogonal polynomials generated following a recurrence scheme as assumed shape functions. The first eight natural frequencies are reported here for various values of aspect ratios of the outer and inner ellipse. Results are given for various boundary conditions at the inner and outer edges of the annular plate. The influence of the material property as it changes from isotropic to orthotropic on the natural frequencies is presented graphically. When the inner hole of the annular plate becomes zero i.e. for rectangular orthotropic full circular and elliptic plates, the results are compared with those that are available in the existing literature, and are found to be in good agreement. Presented results may be used as bench marks for validating those obtained by approximate methods such as the finite element method.

Key words: 
vibration of orthotropic elliptic plates, orthogonal twodimensional polynomials, polynomials generation recurrence scheme, boundary conditions of plate, annular elliptic plates. 
TOP OF PAGE 
7.
STOCHASTIC FINITE ELEMENT METHOD FOR SENSITIVITY
ANALYSIS OF STRUCTURES
B. BHATTACHARYYA
Department of Applied Mechanics, Bengal Engineering College
Howrah  711 103, INDIA
S. CHAKRABORTY
Department of Civil Engineering, Bengal Engineering College
Howrah  711 103, INDIA
The conventional sensitivity analysis of structures is based on the assumption of complete certainty of design parameters. However, occurrence of uncertainty is unavoidable in structures. In the present work, an attempt has been made to study the response sensitivity, considering the effect of uncertainty in structural design parameters. The random parameters are modeled as Gaussian stochastic process and simulated through covariance matrix decomposition. The advantages of Neumann expansion technique has been utilized in deriving the finite element solution of the response sensitivity within the framework of Monte Carlo simulation. Numerical examples are presented to explain the accuracy and efficacy of Neumann expansion method over direct simulation the process.

Key words: 
sensitivity, uncertain parameter, stochastic finite element, Monte Carlo simulation, Neumann expansion. 
TOP OF PAGE 
8.
ON COUPLESTRESS FLUID HEATED FROM BELOW IN POROUS
MEDIUM IN THE PRESENCE OF ROTATION
R.C. SHARMA
Himachal Pradesh University
Department of Mathematics
Summer Hill, Shimla  171 005, INDIA
SUNIL
Regional Engineering College
Department of Applied Sciences
Hamirpur, (H.P.)  177 005, INDIA
M. PAL
Government Degree College
Department of Mathematics
Palampur, (H.P.)  176 061, INDIA
A layer of a couplestress fluid heated from below in a porous medium is considered to include the effect of uniform rotation. For the case of stationary convection, the couple stress may hasten the onset of convection in the presence of rotation while in the absence of rotation, it always postpones the onset of convection. For the case of stationary convection, rotation postpones the onset of convection. Graphs have been plotted by giving numerical values to the parameters, to depict the stability characteristics. Rotation is found to introduce oscillatory modes in the system, which were nonexistent in its absence. A sufficient condition for the nonexistence of overstability is obtained.

Key words: 
couplestress fluid heated from below, porous medium, rotation. 
TOP OF PAGE 
9.
ON THE PLANE STEADY FLOWS OF A VISCOUS INCOMPRESSIBLE
FLUID OF FINITE ELECTRICAL CONDUCTIVITY IN THE PRESENCE OF
A MAGNETIC FIELD
R.K. NAEEM and S.M. SHAD AHSAN
University of Karachi, Department of Mathematics
Karachi75270, PAKISTAN
Basic equations describing the motion of a viscous incompressible fluid of finite electrical conductivity in the presence of a magnetic field (1) for constant vorticity flows are recast in a new form. It is indicated that the other flow variables can be expressed either in terms of the magnetic flux function 'fi' or the stream function 'psi' where these functions satisfy a partial differential equation whose every solution, including Naeem (1996), is a solution to the basic flow equations and (2) for variable vorticity flows an unknown function f(r) is introduced in the basic flow equations. The solutions are determined and one solution admits, as a particular case, Naeem's solution by appropriately choosing the arbitrary constants therein. Some applications of the solutions to physically possible situations are also presented.

Key words: 
plane steady flows, viscous incompressible fluid, magnetic field, MFD flows, electrically conducting viscous fluid. 
TOP OF PAGE 
10.
RADIATIVE EFFECTS IN NONDARCY AXISYMMETRIC FREE CONVECTION IN A POROUS MEDIUM
M.A. ELHAKIEM
South Valley University
Faculty of Science, Mathematics Department
Aswan, EGYPT
R.S.R. GORLA
Cleveland State University
Mechanical Engineering Department
Cleveland, Ohio 44115, U.S.A.
An analysis is presented for the effect of radiation on nonDarcy axisymmetric free convection in a saturated porous medium. Similarity solutions are obtained for two cases: variable surface temperature condition and uniform surface heat flux condition. Discussion is provided for the effects of radiation, nonDarcy parameter and lateral surface mass flux parameter on heat transfer. The rate of heat transfer in the nonDarcy case is less than in the corresponding Darcy case.

Key words: 
radiation, porous media, nonDarcy model and free convection. 
TOP OF PAGE 
11.
VISCOUSINVISCID INTERACTIONS FOR SURFACECOOLED AXISYMMETRIC BOUNDARYLAYER FLOWS
J.W. ELLIOTT and M.E. STRANGE
Department of Mathematics,
University of Hull, Hull HU6 7RX. U.K.
A theoretical, high Reynolds number, investigation into the combined influence of surface cooling and curvature on the stability and transition properties of a compressible axisymmetric boundarylayer is presented. Here we consider the boundarylayer flow along a semiinfinite circular cylinder where the temperature of the cylinder surface is kept significantly below the freestream temperature and the cylinder radius is comparable with the boundarylayer thickness. Here we concentrate on linear, viscousinviscid interactive TollmienSchlichting modes, rather than the inviscid, inflectional kind.

Key words: 
surface cooling, axisymmetric flow, boundary layer. 
TOP OF PAGE 
12.
MACROSCOPIC DESCRIPTION OF THE NONLINEAR
ELECTROMECHANICAL COUPLING IN FERROELECTRICS
U. BÖHLE, M. KAMLAH, D. MUNZ and C. TSAKMAKIS
Forschungszentrum Karlsruhe GmbH, Institut für Materialforschung II
Postfach 3640, D76021 Karlsruhe, GERMANY
Our objective is the construction of a phenomenological ferroelectricity model for general electromechanical loading histories, which is simple enough to be implemented in an FEcode with reasonable expenditure. In this paper, we motivate and verify the onedimensional formulation of such a model. This is done by introducing remanent polarization and remanent strain as internal variables besides stress, strain, electric field and polarization. Polarization induced anisotropy is taken into account to the extent deemed necessary. For the sake of simplicity, no rate effects are included. By bilinear approximation the following characteristic phenomena of macroscopic ferroelectricity are represented: dielectric hysteresis, polarization induced piezoelectricity, butterfly hysteresis, ferroelastic hysteresis, mechanical depolarization, field dependent coercitive stress.

Key words: 
piezoceramics, ferroelectricity, phenomenological modeling, finite element implementation. 
TOP OF PAGE 

