Volume 1, No. 11 (2005)
Articles
APPLICATION THE STOCHASTIC INTEGRAL IN BROWNIAN MOTION
BURCĂ GENOVEVA, SPĂTARU CĂTĂLINA
In this paper we present the stochastic d’Itô integral with respect to a Brownian motion. It is part of wider stochastic integral theory with respect to a continuous semi-martingale; hence we define the class of random functions which are going to be integrated. The whole presentation is based on probability filtering space
MODELING A COMPRESSION VALVE GEOMETRY OF A MONO-TUBESHOCK ABSORBER FOR A CONSTANT DAMPING FORCE
DUMA VIRGIL-FLORIN*, PERNEVAN MARIA**, BARGLAZAN MIRCEA***, PERNEVAN IOAN**
The purpose of this paper is to ascertain the variation of the compression valve interstice geometry versus the damper velocity, for a mono-tube shock absorber, in order to achieve the damping with a constant force.
THEORETICAL AND EXPERIMENTAL RESEARCH REGARDING MALFUNCTIONING DETECTION FROM HYDRAULIC SYSTEMS
PRODAN DAN, IACOB ROBERT
In this paper is presented a method to track the malfunctioning from hydraulic systems. This method aloud the identification of causes, even apparatus with malfunctions, not being needed to dismantle the system.The method of detection the inappropriate function of installation is based on establishing the temperatures from the whole system.
STUDY ABOUT THE DAMPING OFTHE PRESSURE WAVES
TOPLICEANU LILIANA
The study presents the numerical integration of the hyperbolic system of partial differential equations that define the pressure wave propagation into an infinite pipeline, corresponding to the barotropic fluid, in specific boundary conditions for the case of sonic transmission of energy by vibrations. It is used a systematization of Jukowski’s theories, elements of Riemann and G. Constantinescu studies for the pressure wave propagation.
LINEAR REGULATOR FOR THE ELECTRIC MOTOR OF AN AIR COMPRESSOR FOR MAINTAINING A CONSTANT PRESSURE INSIDE THE VESSEL
VRINCEANU GRETA, COBREA CODRIN
Because the electric motor of the compressor is a variable speed motor, it is necessary to attach a linear regulator in order to maintain a constant pressure inside the compressor’s vessel. The paper present the circuit lay-out of a linear regulator used to maintain a constant pressure inside the compressor’s vessel.
ELECTRONIC DEVICE FOR OVERLOAD PROTECTION OF THE ROTARY DRUM AGGREGATES
VRINCEANU GRETA, COBREA CODRIN
In case of a sudden shutdown and for a long time of the rotary drum, the superior part of the shell is cooling down faster then the inferior part which is in contact with the processed material. To avoid the sudden shutdown because of an eventually overload, the rotary drum is equipped with a power supply supervisory.The paper describes such an electronic device.
A METHOD FOR THE SOLUTION OF HEAT TRANSFER PROBLEMS WITH A CHANGE OF PHASE
CĂLIMAN RADU, OLARU IONEL
A method of broad applicability is presented which can be used to obtain solutions to problems involving a phase change. The solution in one of the phases is specified as a known single-phase solution; an inverse analysis then determines the solution for the other phase. Two problems are studied: The first yields the similarity solution for the planar geometry and the second gives the exact solution to a more general problem. Convergence is shown and error bounds are given. The method can accommodate convection, heat generation, variable properties, non planar, and multidimensional systems.
A THEORY OF ROTATING CONDENSATION
CĂLIMAN RADU, OLARU IONEL
An analysis is made for film condensation on a rotating disk situated in a large body of pure saturated vapor. The centrifugal field associated with the rotation sweeps the condensate outward along the disk surface, and gravity forces need not be involved.The problem is formulated as an exact solution of the complete Navier-Stokes and energy equations.
PRACTICAL INTEREST OF ROTATING CONDENSATION
OLARU IONEL, CĂLIMAN RADU
The problem of rotating condensation is formulated as an exact solution of the complete Navier-Stokes and energy equations. Numerical solutions are obtained for Prandtl numbers between 0.003 and 100 and for cpΔT/hfg in the range 0.0001 to 1.0.
ELASTIC-PLASTIC STATE AT ROTATIVE DISKS IN THERMAL REGIMEPART I – ANALYTIC CALCULUS RELATIONS (THE UTILIZATION OF APOLYNOMINAL FOR THE RELATION BETWEEN σe AND εe)
RADU GHEORGHE, COMĂNESCU IOANA
In order to determine the state of stress and deformation due to the temperature, one has to study,as exactly as possible, the temperature’s propagation mode. There are many practical situations when insome bodies’ material exist self-balanced stresses, even in the absence of any load. These are residualstresses. Their magnitude and their distribution depend on the material, on the technological workingprocess, on the machine parts’ size. The residual stresses appear mainly because of the local deformationsin the elastic-plastic field, because of some structural transformation or because of some thermo-elastic-plastic deformations. The paper presents some aspects regarding the residual stresses due to the heattreatment and to the shallow working.
ELASTIC-PLASTIC STATE AT ROTATIVE DISKS IN THERMAL REGIMEPART II – THE DETERMINATION OF RESIDUAL STRESSES DUE TO THETEMPERATURE
RADU GHEORGHE, COMĂNESCU IOANA
In order to determine the stress and deformation state of some structures one must know the residual stresses due to the temperature. One considers the situations when the stresses reach the limits imposed by von Mises criterion; plastic deformations will appear; these have as effect a redistribution of residual stresses. In order to determine the residual stresses, theoretical studies and experimental research, based on the section method, have been done. One has studied the hot laminated structures. Following the ununiform cooling, residual thermal-elastic-plastic stresses appear in the material. The performed determinations based on the section method lead to high precision determination of the residual stresses field. The established theoretical equations were also verified.