Physics & Mathematics

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Systematization of basic divergent integrals in perturbation theory and renormalization group functions
(Elsevier, 2009-02) Brito, L.C.T.; Fargnoli, H.G.; Scarpelli, A.P. Baêta; Sampaio, Marcos; Nemes, M.C.
We show that to n loop order the divergent content of a Feynman amplitude is spanned by a set of basic (logarithmically divergent) integrals I (i) log(λ2), i = 1, 2,...,n, λ being the renormalization group scale, which need not be evaluated. Only the coefficients of the basic divergent integrals are show to determine renormalization group functions. Relations between these coefficients of different loop orders are derived.
Uniqueness of moving boundary for a heat conduction problem with nonlinear interface conditions
(Elsevier, 2010-01) Wei, T.
In this paper, based on the maximum principle and the unique continuation theorem, we present a uniqueness result for a moving boundary of a heat problem in a multilayer medium with nonlinear interface conditions.
The Design of an Intelligent Security Access Control System Based on Fingerprint Sensor FPC1011C
(Scientific Research, 2010-07) Wang, Yan; Liu, Hongli; Feng, Jun
This paper deals with the design of an intelligent access control system based on the fingerprint sensor FPC-1011C. The design uses the S3C2410 and TMS320VC5510A as the system processor. A fingerprint acquisi-tion module and a wireless alarm module were designed by using the fingerprint sensor FPC1011C and GPRS module SIM100 respectively. The whole system was implemented wireless alarm through messages and GPRS-Internet in the GSM/GPRS web. In order to achieve the simple and high Real-time system, the μC-Linux system migration was also implemented
Two Simple Analog Multiplier Based Linear VCOs Using a Single Current Feedback Op-Amp
(Scientific research, 2010-07) Bhaskar, Data R.; Senani, Raj; Singh, Abdhesh K.; Gupta, Shanti S.
Two simple voltage-controlled-oscillators(VCO) with linear tuning laws employing only a single current feedback operational amplifier (CFOA) in conjunction with two analog multipliers(AM) have been highlighted. The workability of the presented VCOs has been demonstrated by experimental results based upon AD844 type CFOAs and AD534 type AMs
Definition of Increasing the Fibre Capturing Surface of Saw Teeth of Cotton Ginning Machine through Mathematic Modelling
(2011-06) Mamatovich, Azizov S.; Abdusamat, Karimov
Theoretical and the experimental researches executed in Uzbekistan and abroad explored some ways of a substantiation of a rational profile of a tooth of a saw and its fibre capturing ability. Despite that, untill now, optimum parameters of a saw gin which provides high quality ginning without harming the quality of cotton fibre have not been found. Considering the stated above in the given job the influence of the changed form of saw teeth on fibre-capturing area is examined. The analytical formulas for the additional area promoting to double the fibre capture quantity by saw teeth are received
A Mathematical Model for Magnetohydrodynamic Convection Flow in a Rotating Horizontal Channel with Inclined Magnetic Field, Magnetic Induction and Hall Current Effects
(2011-06) Ghosh, Swapan K.; Bég, Osman A.; Aziz, Abdul
Closed-form and asymptotic solutions are derived for the steady, fully-developed hydromagnetic free and forced convection flow in a rotating horizontal parallel-plate channel under the action of an inclined magnetic field and constant pressure gradient along the longitudinal axis of the channel. The magnetic field is strong enough to generate Hall current effects and the magnetic Reynolds number of sufficient magnitude that induced magnetic field effects are also present. Secondary flow is present owing to the Hall current effect. The channel plates are also taken to be electrically-conducting. The conservation equations are formulated in an (x, y, z) coordinate system and non-dimensionalized using appropriate transformations. The resulting non-dimensional coupled ordinary differential equations for primary and secondary velocity components and primary and secondary induced magnetic field components and transformed boundary conditions are shown to be controlled by the dimensionless pressure gradient parameter (px), Hartmann number (M 2 ), Grashof number (G), Hall current parameter (m), rotational parameter (K 2 ), magnetic field inclination (q), and the electrical conductance ratios of the upper (f1) and lower (f2) plates. Solutions are derived using the method of complex variables. Asymptotic solutions are also presented for very high rotation parameter and Hartmann number of order equal to unity, for which Ekman-Hartmann boundary layers are identified at the plates. A parametric study of the evolution of velocity and induced magnetic field distributions is undertaken. It is shown that generally increasing Hall current effect (m) serves to accentuate the secondary (cross) flow but oppose the primary flow. An increase in rotational parameter (K 2 ) is also found to counteract primary flow intensity. An elevation in the Grashof number i.e. free convection parameter (G) is shown to aid the secondary induced magnetic field component (Hz); however there is a decrease in magnitudes of the primary induced magnetic field component (Hx) with increasing Grashof number. Increasing inclination of the applied magnetic field (q, is also found to oppose the primary flow (u1) but conversely to strongly assist the secondary flow (w1). Both critical primary (Gcx) and secondary (Gcz) Grashof numbers are shown to be reduced with increasing inclination of the magnetic field (q), increasing Hall parameter (m) and rotational parameter (K 2 ). Applications of the study arise in rotating MHD induction power generators and also astrophysical flows
A Simplified Nonlinear Generalized Maxwell Model for Predicting the Time Dependent Behavior of Viscoelastic Materials
(2011-06) Monsia, Marc Delphin
In this paper, a simple nonlinear Maxwell model consisting of a nonlinear spring connected in series with a nonlinear dashpot obeying a power-law with constant material parameters, for representing successfully the time-dependent properties of a variety of viscoelastic materials, is proposed. Numerical examples are performed to illustrate the sensitivity of the model to material parameters
Modelling of Internal Stresses in Sheet Glass during the Cooling
(2011-06) Benbahouche, Saci; Roumili, Fouad; Sangleboeuf, Jean-Christophe
Internal stresses in glass are generated by interactions between thermal contraction, elasticity at low temperatures, viscoelastic flow at higher temperature, and temperature gradients caused by cooling. This work intends to work out calculation program for real temperature distribution and internals stress, and to study their behaviour during the quenching through a flat plate of soda-lime glass from different temperatures
Experimental Research on Damage Parameter of Concrete in Non-Uniform Stress Field
(2011-06) Deng, Aimin; Xu, Daoyuan
The damage variables of describing the material damage state should be chosen first when the research of concrete structures by use of theory of damage theory. The method of calculation of damage parameter by the measure of the change of the elastic modulus of concrete specimens is effectively. In this paper, the wedge splitting tests with double bearing of three groups of different initial crack lengths of concrete specimens were conducted, and the stress and the strain of the points with different distance from the initial crack tip measured and calculated, and the damage value with peak stress of the various points were calculated based on the stress-strain curves. From the results of the test, the damage parameter can be confirmed under the non-uniform stress field, and the initial crack length has some influence on the damage parameter, and the longer the initial crack length and the greater the damage parameter
Mathematical Modelling of Mass Transfer and Free Convection Current Effects on Unsteady Viscous Flow with Ramped Wall Temperature
(2011-08) Narahari, Marneni; Bég, Osman Anwar; Ghosh, Swapan Kumar
An exact analysis of the flow of an incompressible viscous fluid past an infinite vertical plate is conducted taking into account the presence of foreign mass or constant mass flux and ramped wall temperature. The dimensionless governing coupled linear partial differential equations are solved using the Laplace transform technique. Two different solutions for the fluid velocity are obtained–one valid for the fluids of Schmidt numbers different from unity, and the other for which the Schmidt number is unity. The effects of Prandtl number (Pr), Schmidt number (Sc), time (t) and mass to thermal buoyancy ratio parameter (N) for both aiding and opposing buoyancy effects on the velocity and skin-friction are studied. Also, the heat and mass transfer effects on the flow near a ramped temperature plate have been compared with the flow near a plate with constant temperature.
Acousto-Diffusive Waves in a Piezoelectric-Semiconductor-Piezoelectric Sandwich Structure
(2011-10) Sharma, Jagan Nath; Sharma, Kuldeep Kumar; Kumar, Ashwani
The propagation of acoustic waves in a homogeneous isotropic semiconducting layer sandwiched between two homogeneous transversely isotropic piezoelectric halfspaces has been investigated. The mathematical model of the problem is depicted by a set of partial differential equations of motion, Gauss equation in piezoelectric material and electron diffusion equation in semiconductor along with the boundary conditions to be satisfied at the piezoelectric-semiconductor interfaces. The secular equations describing the symmetric and asymmetric modes of wave propagation have been derived in compact form after obtaining the analytical expressions for various field quantities that govern the wave motion. The complex secular equation has been solved numerically using functional interaction method along with irreducible cardano method. The computer simulated results are obtained with the help of MATLAB software for 6mm cadmium selenide (CdSe) piezoelectric material and n-type silicon (Si) semiconductor in respect of dispersion curve, attenuation and specific loss factor of energy dissipation for symmetric (sym) and asymmetric (asym) modes of wave propagation. The study may find applications in non-destructive testing, resonators, waveguides etc
A Finite Element Approximation of the Stokes Equations
(2011-12) Alami, Samy; Elakkad, Abdeslam; El-Mekaoui, Jawad; Elkhalfi, Ahmed; El Hammoumi, Mohammed
In this work, a numerical solution of the incompressible Stokes equations is proposed. The method suggested is based on an algorithm of discretization by the unstable of Q1 – P0 velocity/pressure finite element approximation. It is shown that the inf-sup stability constant is O(h) in two dimensions and O( ) in three dimensions. The basic tool in the analysis is the method of modified equations which is applied to finite difference representations of the underlying finite element equations. In order to evaluate the performance of the method, the numerical results are compared with some previously published works or with others coming from commercial code like Adina system
Numerical Investigation of Flow Structure Interaction Coupling Effects in Hard Disk Drives
(2012-02) Yin-Kwee, Eddie; Teo, Qing R.; Liu, Ning Y.
This paper studies the flow structural interaction (FSI) within a hard disk drive (HDD) through the use of a novel coupling method. The interaction studied was the fluid induced vibration in the HDD. A two step coupling approach was used, where the fluid and structural components were solved sequentially. The result obtained was a ratio of 0.65 between the vibration amplitudes of a fixed head stack assembly (HSA) and a moving HSA. The ratio was next applied on a real 3.5 inch HDD, to allow the parameter to be further improved upon. A new benchmark index of 0.69 was developed from this. This parameter may allow future researchers to model the out of plane vibrations of a HSA easily, saving precious time. A 31% more accurate simulation of FSI within 3.5 inch HDD at 15000 rpm is achieved by the use of this new coupling method and benchmark index
A Fatigue Analysis of a Hydraulic Francis Turbine Runner
(2012-02) Flores, Miriam; Urquiza, Gustavo; Rodríguez, José María
In this work, the estimation of crack initiation life of a hydraulic Francis turbine runner is presented. The life prediction is based on the local strain approach to predict the initiation life. First, the analysis is carried out in air and in water condition and the runner’s natural frequencies were calculated using the finite element (FE) method. The analysis in air is compared with experimental analysis in order to have a representative model of real runner and subsequently the numerical analysis was perform in water. In the case of the runner immersed in water, the added mass effect due to the fluid structure interaction (FSI) is considered. Second, the static and dynamic stresses were calculated according to life estimation. For the calculation of static stresses, the pressure distribution of water and the centrifugal forces were applied to the runner. The dynamic stresses were estimated for interactions between the guide vane and the runner. Lastly, the estimation of the crack initiation life of the runner was obtained
The Mesoscopic Constitutive Equations for Polymeric Fluids and Some Examples of Viscometric Flows
(2012-02) Pyshnograi, Gregory; Joda, Hyder N. A.; Pyshnograi, Ivan
Constitutive equations for melts and concentrated solutions of linear polymers are derived as consequences of dynamics of a separate macromolecule. The model is investigated for viscometric flows. It was shown that the model gives a good description of non-linear effects of simple shear polymer flows: viscosity anomalies, first and second normal stresses, non-steady shear stresses
Modeling Evaporating Droplets in Complex Unsteady Flows
(Scientific Research, 2012-06) Ghosal, Sandip; Apte, Sourabh V.
In many applications, a moving fluid carries a suspension of droplets of a second phase which may change in size due to evaporation or condensation. Examples include liquid fuel drops in engines and raindrops or ice-crystals in a thunderstorm. If the number of such particles is very large, and, if further, the flow is inhomogeneous, unsteady or turbulent, it may be practically impossible to explicitly compute all of the fluid and particle degrees of freedom in a numerical simulation of the system. Under such circumstances Lagrangian Particle Tracking (LPT) of a small subset of the particles is used to reduce the computational effort. The purpose of this paper is to compare the LPT with an alternate method that is based on an approximate solution of the conservation equation of particle density in phase space by the method of moments (MOM). Closure is achieved by invoking the assumption that the droplet size distribution is locally lognormal. The resulting coupled transport equations for the local mean and variance of the particle size distribution are then solved in conjunction with the usual equations for the fluid and associated scalar fields. The formalism is applied to the test case of a uniform distribution of droplets placed in a non homogeneous temperature field and stirred with a decaying Taylor vortex. As a benchmark, we perform a direct numerical simulation (DNS) of high resolution that keeps track of all the particles together with the fluid flow.
Mazumder Effect of Liquid and Gas Velocities on Magnitude and Location of Maximum Erosion in U-Bend
(Scientific Research, 2012-06) Mazumder, Quamrul H.
Solid particle erosion is a micromechanical process that is influenced by flow geometry, material of the impacting surface, impact angle, particle size and shape, particle velocity, flow condition and fluid properties. Among the various factors, particle size and velocity have been considered to be the most important parameters that cause erosion. Particle size and velocity are influenced by surrounding flow velocities and carrying fluid properties. Higher erosion rates have been observed in gas-solid flow in geometries where the flow direction changes rapidly, such as elbows, tees, valves, etc, due to local turbulence and unsteady flow behaviors. This paper presents the results of a Computational fluid dynamic (CFD) simulation of dilute gas-solid flow through a U-Bend and the dynamics behavior of entrained solid particles in the flow. The effect of liquid and gas velocities on location of erosion were investigated for 50, 100, 150, 200, 250 and 300 microns sand particles. Three different fluid velocities of 15, 30.48 and 45 m/s were used in the CFD analysis. The magnitude and location of erosion presented in the paper can be used to determine the areas susceptible to maximum erosive wear in elbows and U-bends, along with corresponding rate of metal loss in these areas.
Some New Results on Prime Graphs
(Scientific Research, 2012-07) Vaidya, Samir K.; Prajapati, Udayan M.
We investigate prime labeling for some graphs resulted by identifying any two vertices of some graphs. We also introduce the concept of strongly prime graph and prove that the graphs Cn, Pn, and K1,n are strongly prime graphs. Moreover we prove that Wn is a strongly prime graph for every even integer n ≥ 4.
An Analytical Model of the Power Law Distributions in the Complex Network
(2012-08) Takagi, Kosuke
It is known that complex networks in nature exhibit some significant statistical features. We notice power law distributions which frequently emerge with respect to network structures of various quantities. One example is the scale-freeness which is described by the degree distribution in the power law shape. In this paper, within an analytical approach, we investigate the analytical conditions under which the distribution is reduced to the power law. We show that power law distributions are obtained without introducing conditions specific to each system or variable. Conversely, if we demand no special condition to a distribution, it is imposed to follow the power law. This result explains the universality and the ubiquitous presence of the power law distributions in complex networks
Computational Fluid Dynamics Analysis of Greenhouses with Artificial Heat Tube
(2012-08) Couto, Nuno; Rouboa, Abel; Monteiro, Eliseu; Viera, José
With the workmanship decrease in farms, the necessity to rationalize the use of other inputs and the development of technology has rapidly expanded the use of computer simulation in agricultural systems. One of the agricultural systems in which the modeling process of plant growth has been more engaged is the greenhouse production for horticultural crops. In Mediterranean climate, it is during the night that the energy losses are important and can be compensated with an artificial heat input. In this work an experiment was performed in a greenhouse in the north of Portugal. Temperature values in several points and air velocity in the aperture were measured during the night for three different cases: natural convective heating (case A); artificial heating tubes (AHT) (case B); AHT and natural ventilation (case C). A CFD simulation, carried out using FLOTRAN module of ANSYS, was also performed in two-dimensional configuration to obtain the indoor air temperature and velocity fields for the three cases. A very good agreement between experimental and numerical temperature values were verified, which allows to validate the adopted numerical procedure. In case A, the average temperature was 2.2˚C. An average increase of 6.7˚C and 3.5˚C on the air temperature was obtained for the case B and case C, respectively. These results clearly emphasis the influence of each thermal load on greenhouse indoor air properties

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