Volume LVIII Number 2/2006

 Fixed Point Theorems for Weak (o)-Contractive Multivalued Mappings
 Alexandru Petcu 
  pg. 1-8 
 In this paper are given fixed point theorems for a class of multivalued mappings called weak (o)-contractive in ordered vector spaces, respectively ordered topological vector spaces, which generalize known results.
 On the Definition of Multidimensional Generalized Riemann Integral
 Mihai Pascu 
  pg. 9-16 
 The paper wishes to investigate the possibilities of defining the multidimensional generalized Riemann integral. We propose a definition which covers the cases of unbounded domain and unbounded function at the same time. The equivalence between generalized integrability and the absolute integrability of functions depending on more than one variable is proved.
 The Approximate Calculation of Definite Simple and Multiple Integrals
 Tănase Dinu 
  pg. 17-24 
 This paper presents the logical schemata and the programs in turbo-pascal for the approximate calculation methods of the simple definite integral [2], of the double definite integral [3], and of the triple definite integral [4]. At the end there are analized the calculation errors corresponding to these methods that use the polynomials of interpolation to five nodes.
 On Viscous Dissipation in Newtonian Fluid Flow through an Annular Cross Section Tube
 Tudor Boacǎ 
  pg. 25-30 
 This paper considers the problem of viscous dissipation in the flow of Newtonian fluid through a tube of annular cross section, with Dirichlet boundary conditions. The solution of the problem is obtained by a series expansion about the complete eigenfunctions system of a Sturm-Liouville problem. Eigenfunctions and eigenvalues of this Sturm-Liouville problem are obtained by Galerkin’s method.
 The Statistical Estimation of the Indicators
 Ionuţ - Radu Bontaş, Alexandra Odăgescu 
  pg. 31-38 
 Under the conditions where the machines and the modern installations are working, a great importance is given to the ensurance of a most efficient and complete usage of the work means on the entire service period. Therefore, if through the quality of the products we understand the rate or the level through which these correspond to the productive or individual consumption needs, then the reliability means beside these, the usage of these on the projected parameters, the safe and the continuous exploitation, in well determined conditions, over a given period of time. This paper presents estimation types, functions and statistical hypotesis regarding the random variables.
 Characterization of Mean Residual Life for Uniform and Exponential Distributions
 Dan Isbăşoiu, Ilie Ristea, Ileana Dumitru 
  pg. 39-42 
 In this material, starting from relationships between failure rate, mean residual life and cumulative density function, we obtain a simple expression for mean residual life for each classical continuous distribution function. In this case we analyse cases of uniform and exponential distributions.
 Non-Archimedian Fields. Topological Properties of Zp, Qp (p-adics Numbers)
 Mureşan Alexe Călin 
  pg. 43-48 
 The present work tries to offer a new approach to some non-Archimedian norms and to some unusual properties determined by these. Then, as an example, p-adic numbers Qp and some topological properties will be illustrated. The present article will present as an example some abstract notions with p-adic numbers extended to Qp during the translation from non- Archimedian norms to the Qp norm.
 P-laplacien à Poids Indéfini
 Petre Sorin Iliaş 
  pg. 49-56 
 Dans cet article on démontre l’existence des solutions du problème Dirichlet -Δpu=λV(x)|u|p-2 u + f(x,u) en Ω, où le poids V est une fonction s-integrable Lebesgue sur Ω , f:Ωxℜ → ℜ est une fonction Carathéodory qui satisfait une condition de croissance et le paramètre réel λ<λ1, λ1 étant la première valeur propre positive du p-laplacien à poids indéfini. Par une formule équivalente, les solutions du problème Dirichlet sont les points critiques d’une fonctionnelle de classe C1 définie sur un espace Banach. On emploie, comme instrument de travail, une méthode variationnelle par laquelle on déduit leur existence et, automatiquement, l’existence des solutions du problème.
 Cohen-Macaulay Graphs
 Alin Ştefan 
  pg. 57-60 
 In this article the author present two methods meant to construct Cohen-Macaulay graphs and some interesting examples and properties. This paper also presents an important property of Cohen-Macalay ring to have Cohen-Macaulay fiber.
 Multi-dimensional Access and Storage Methods for Multimedia Data
 Monica Vlădoiu, Cătălina Negoiţă 
  pg. 61-66 
 Most multimedia data have to be seen from multiple points of view – for instance, the three coordinates x, y, z, and the time component. These n-dimensional data require special access and indexing techniques. It is obvious that multi-attribute searches can be performed, but the need for performance call for multidimensional indexes such as: k-d trees, multi-dimensional tries structures, grid files, point quad trees, MX quad trees, R trees, multi-key hash tables and iverted indices. Stored object clustering is another way of improving retrieval performance.
 Aspects Regarding the Evaluation of a Software for Students Online Assessment
 Iuliana Dobre 
  pg. 67-72 
 The advantages offered by the online technologies are various and more and more appreciated by both educators and scholars of all levels. Today, the online technologies are giving the educators involved in higher education the opportunity to reach a superior level compared to the traditional class from the overall educational process effectiveness point of view. This paper presents several aspects related to the evaluation of an educational software used for student performances assessment. Therefore, educators teach and students learn but the results are a common responsibility which shall be shared by both parties involved in the educational process.
 Querying and Information Retrieval in Multimedia Databases
 Cătălina Negoiţă, Monica Vlădoiu 
  pg. 73-78 
 Multimedia database management systems can be seen as storage and retrieval systems, in which large volumes of media objects are created, indexed, modified, searched and retrieved. There are two types of retrievals: navigation through database to locate the desired data and database querying that finds the desired data associatively, attribute-based, or content-based. Query processing in multimedia databases has the following stages: query specification and refining, query processing (compiling, optimizing, and executing), generation of relevancy ranked results, and relevance feedback. In content-based retrieval systems, the collections of multimedia objects are stored as digitized representations. The queries are characterized by fuzziness and ambiguity. Therefore, the user will not get from the beginning what s/he wants. Metrics (precision, recall) and indexation and content-based retrieval techniques can help, but the user is the one who will have the last word in appreciation of a query results.
 The Calculation of the Integrals using the Sample Mean Method
 Mădălina Cărbureanu 
  pg. 79-86 
 An interesting random number application is offered by the calculation of the definite integrals with the sample mean Monte Carlo method. What recommends the use of the sample mean method in the solving process of definite integrals are the advantages offered by this. One of the most important advantages is the quick way to obtain values which approximate the solution of the integral in question, from the best, with a minimum calculation effort. This method can be successfully applied even for difficult definite integrals.
 Results on the Magnetization of Ferromagnetic Substances Dependent on Temperature
 Grigore Ruxanda, Zoltan Borsos, Mihai Hotinceanu 
  pg. 87-92 
 This paper presents the study of the magnetization for the ferromagnetic substances depending on temperature. The Stoletov curves were obtained through three types of ferromagnetic materials, pointing out the modifications depending on temperature. The revealing of these variations can represent an experimental background for new theoretical models or, for the confirmation of theoretical models already proposed.
 Evaluation of the Effective Viscosity for Oil-Gas Mixture
 Zoltan Borsos, Anca Baciu 
  pg. 93-98 
 In this paper we propose a reformulation of the conventional theory in which the concept of the relative permeability of the porous media is replaced with the more familiar concept of an effective phase viscosity. In this theory the bubbles move with the oil as they evolve. The resulting systems of equations, using the PVT data, can be reduced to a coupled pair of nonlinear for the dispersed gas fraction and pressure difference, obtaining a second order evolution equation for the pressure difference. This system of equations can also be derived from the usual theory of two-phase flow.
 Pellicles and Films Making from Polymer Solution
 Georgeta Nan 
  pg. 99-102 
 In this paper there are presented some methods for making pellicles and films from a solution of polymer, films used for different experiments in polymer physics. The main methods used for this purpose are: a) spin-coating, b) self-inducing of making the structure, c) dip-coating d) the Ink-Jet deposition and e) the deposition on cylindrical surfaces.
 The X-Ray Fluorescence
 Mihaela Stancu, Zoltan Borsos, Grigore Ruxanda 
  pg. 103-110 
 The fluorescence of X-rays is a non-destructive method used for the qualitative and quantitative elementary composition determination of the sample with different number of elements. The main advantage of the analysis of the fluorescence radiation from the X-rays area consists in the simplicity of this spectrum. The vacantioning of the deep electronic levels of the atoms is followed by the appearance of the phenomenon of X-ray fluorescence. These phenomena depend on the mechanism where the electronic vacancies are created in the deep electronic levels of the atoms, depending on the atomic number of element Z. This method can be used without restrictions to the dosage for all elements from the periodic table with Z>12.
 Visualization Techniques of the Material Fault Shape
 Liana Şandru 
  pg. 111-116 
 The methods of emphasizing the material non-homogeneities of the material analyzed up to now, give directives about their occurring, without being able to provide clear information regarding their feature. Further a detection method is presented, called tomography taking, through which the fault geometry is emphasized.