Print Edition: ISSN 1584 - 2851
Online Edition: ISSN 1843 - 4401

Carpathian J. Math. is a category A journal in the CNCSIS classification

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Contents (PDF)
Vol. 20 (2004), No. 2,
Professor Ion Păvăloiu at his 65th Birthday
Author: Costica Mustăța
No. of downloads: 175 Full access PDF |
Improving the Round Trip Time Estimation in Internet Routers
Author: Darius Bufnea / Adrian Sterca / Claudiu COBÂRZAN / FLORIAN BOIAN
Abstract: We review in this paper the concept of TCP-friendliness and we debate one of its weaknesses. Unfortunately, this weakness reduces the practical applicability of the TCP- friendliness equation. For a very high percent of the Internet flows, the TCP-friendliness test may have wrong results. We suggest in this paper a router algorithm that improves the efficiency of the TCP-friendliness equation for some UDP flows. This algorithm uses the additional information retrieved by the router from competing TCP flows in order to obtain a better approximation for the round trip time as used in the TCP-friendliness test.
No. of downloads: 250 Full access PDF |
Generalized Inverses of Means
Author: Iulia Costin
No. of downloads: 259 Full access PDF |
Link-Cell Method for Evolutionary Multi-Modal Optimization Application in Dynamic Evolutionary Clustering
Author: Dan Dumitrescu / Ferenc Jarai-Szabo / Karoly Simon
Abstract: Evolutionary algorithms can be successfully used for solving multi-modal opti- mization problems. Inspired from Computational Physics a Link-Cell-based method is proposed in order to obtain improved evolutionary multi-modal optimization models. Recently a new evo- lutionary search and multi-modal optimization metaheuristics - called Genetic Chromodynamics (GC) - has been proposed and used to derive new evolutionary algorithms. Based on the GC metaheuristics a new dynamic evolutionary clustering technique has been developed. The pro- posed Link-Cell technique is combined with GC. In this way a new evolutionary multi-modal optimization model is obtained. This model is applied to GC-based dynamic clustering method (GCDC) and a new Link-Cell-based GCDC algorithm is developed. Some numerical experiments are described.
No. of downloads: 244 Full access PDF |
Localization of solutions for a problem arising in the theory of adiabatic tubular chemical reactors
Author: Andrei Horvat-Marc / Cristina Țicală
No. of downloads: 214 Full access PDF |
About the Dirichlet and Neumann boundary value problems expressed by means of monogenous quaternions
Author: Lidia Elena Kozma
Abstract: Using the solution of Dirichlet’s plane problem, the solution given as a monogenous surface, we obtain the solution of Neumann’s plane problem through the rotation of the quater- nion associated to the solution of Dirichlet’s problem.
No. of downloads: 202 Full access PDF |
Automata-Based Compositional Analysis of Component Systems. Design and Implementation Issues
Author: Bazil Pârv / Simona Motogna / Dragoș Petrașcu
Abstract: Specifying a real-world component system is a complex manual process. It is essential to be able to verify the correctness and robustness of its behavior, before it becomes operational. We propose a new way of specifying a component system, based on the concept of interface, that can be seen as a tool from analysis and design to programming and for type specification. We construct an algorithm that constructs the model, and can be used to deduct properties about the system: correctness, termination, deadlock free.
No. of downloads: 196 Full access PDF |
On a matrix representation of molecular structures
Author: Zoița Berinde / Mădălina Berinde
Abstract: In order to discriminate molecular structures containing multiple bonds and het- eroatoms, the paper considers the weighted electronic connectivity matrix (CEP). This matrix is obtained by replacing the classical topological distance by the so called weighted electronic distance (w.e.d). The CEP matrix can be then used for obtaining several topological indices [10].
No. of downloads: 225 Full access PDF |
Stability Prediction in C40 Fullerenes
Author: Marcela F. Dinca / Simona Ciger / Monica Stefu / F. Gherman / Katalin Miklos / Csaba L. N
Abstract: The well-known “isolated pentagon rule” IPR is described in quantitative terms provided by the layer matrix of valences, constructed on the dual of the associate molecular graph of fullerenes. The derived pentagon valence pv parameter correlates well (it describes more than 90% of variance) with the PM3 heat of formation of small fullerenes C40. The equivalence classes of their vertices, edges and faces are also deducible from some layer matrix invariants. They are important in simulating the 13C NMR spectrum and/or in predicting the products of addition reactions of fullerenes.1
No. of downloads: 254 Full access PDF |
Topology Counting in Nanostructures
Author: Mircea V. Diudea / Duanska Janeie / Ante Graovac
Abstract: Tubulenes are capped nanotubes built up from two caps and a distancing nanotube/neck of diverse decoration. Ways of “in silico” construction of several finite nanostructures, classified by their neck and/or caps, are presented. Topological periodicity is presented as constitutive typing enumeration. Semiempirical calculations support the idea that new, relatively stable molecules may appear in the soot of vaporized graphite.
No. of downloads: 221 Full access PDF |
The Second Path Matrix of the Graph and its Characteristic Polynomial
Author: Peter E. John / Mircea V. Diudea
Abstract: The second path matrix S(G) collects all the second paths in the graph G. Its characteristic polynomial shows some regularity in several particular graphs, such as paths, cycles, stars and complete graphs, as well as in bipartite graphs. Formulas for calculating the characteristic polynomials in these graphs are given. The first eigenvalue of S(G) showed an excellent correlating ability.
No. of downloads: 223 Full access PDF |
Theoretical Study on Phosphorus Substitutionally Doped Fullerenes
Author: Liliana Pacureanu / Mircea V. Diudea / Mircea Mracec
Abstract: Since Karfunkel predicted the stability of azafullerenes by semiempirical calculation, a sustaining effort was paid to quantum-chemical calculation of substitutionally dopped fullerenes. While the N and B hetero-fullerenes are the most known, in the last years Si, Co, Ni, Fe, Rh, Ir dopped C60 have been modeled.4-6 This paper reports semiempirical PM3 calculations of phosphorus substituted fullerenes C60- nPn, n = 1-6. The C by P replacement appears to not dramatically influence the thermal stability of substituted C60 but electronic structure is changed. The degeneracy of HOMO and LUMO levels is reduced or destroyed while the HOMO-LUMO gap is, in some cases, as high as in the parent C60 and consistent with a good kinetic stability. The difference between C and P electronegativity determines the partial positive charge at phosphorus and a negative charge at the neighboring C atoms. The displacement of a number of phosphorus atoms on the same polygon diminishes the positive charge at phosphorus. Angles at phosphorus are larger when phosphorus is on a hexagon. The reverse situation is found for bond length that increases for P-C [5,6] with respect to [6,6] bonds. The bonding energy of P-dopped fullerenes decrease with increasing the number of phosphorus atoms, as the strength of P-C bonds decreases with respect to C-C bonds. From energetic considerations, we can draw the conclusion that phosphorus dopped fullerenes may be stable molecules.
No. of downloads: 215 Full access PDF |
From Nano-Peapods through DWNTs to Elongated Tori
Author: Csaba L. Nagy / Mircea V. Diudea
Abstract: The encapsulation of fullerene cages inside single-walled nanotubes SWNT can be performed very efficiently in both vapor phase and in solution. In the inner space of SWNT, zero dimensional molecules, like C60, are ordered in one-dimensional arrays. Such structures are called nanopeapods. Annealing peapods over 800oC, results in double-walled carbon nanotubes DWNT. We propose that controlled irradiation at the tip of nano-peapods could initiate the fusion between the inner and parent nanotube, resulting a torus.1
No. of downloads: 204 Full access PDF |
Detection Method of Function Site of Proteins by Using a Graph-Theoretic Algorithm
Author: Shin-Ichi Nakayama / Yoshihiro Kawasaki / Shiho Matsuda / Akiko Kamiya / Tetsuya Maeshiro
Abstract: We present a new detection method of amino acid residues, which play the role of the protein functional activities. The principle of the method is that proteins with the same function have similar amino acid residues at the similar 3D positions. Thus we assume that maximal amino acid residues existing in the similar 3D positions of proteins are their function site residues. The method first constructs the graph describing relations of 3D positions of all possible pairs of amino acid residues in two proteins and then extracts its maximal complete subgraph, which means the maximal amino acid residues at the similar three dimensional positions, by the algorithm of Carraghan and Pardalos. The method was tested using electron transport proteins: azurin and plastocyanin, and 6 reasonable amino acid residues as the function site residues of those proteins, were obtained. The method was also applied to acid proteases: porcine pepsin and Rhizopus pepsin. In this investigation, we restricted the formation of amino acid pairs only to the same ones, because of the limitation of computer memory. The result gave 11 amino acid residues, consisting in some active site residues, as the function residues of acid proteases. The results indicate the effectiveness of this new method.
No. of downloads: 208 Full access PDF |
QSARs of some Novel Isosteric Heterocyclic with Antifungal Activity
Author: Oleg Ursu / Adina Costescu / Mircea V. Diudea / Bazil Parv
Abstract: QSAR analysis of a set of 2,5,6-trisubstituted benzoxazoles, benzimidazoles and 2- substituted oxazolo(4,5-b)pyridines, tested for growth inhibitory activity against Candida albicans, was performed by using a multiple regression procedure. The activity contributions for either heterocyclic ring systems or substituent effects of these compounds were determined from the correlation equations and the lead optimization is described. The obtained QSAR revealed that the oxazolo(4,5-b)pyridine ring, substituted by a benzyl moiety at position 2, was the most favorable structure among the heterocyclic nuclei. Moreover, the fifth position in the fused ring system is found more significant than the other positions in rising up the activity.
No. of downloads: 233 Full access PDF |
Qsar Study On Dipeptide Ace Inhibitors
Author: Oleg Ursu / Marinela Don / Gabriel Katona / Lorentz Jantschi / Mircea V. Diudea
Abstract: Quantitative Structure-Activity Relationships (QSARs) establish a mathematical relation between the biological activity of chemical compounds and their molecular structure. They provide quantitative models aimed to accurately predict a certain activity from the structural attributes. This topic has become a well-delimited branch in chemistry and was favored by the progress in computer science. Cluj property indices are used for modeling the ACE inhibition biological activity of a set of 58 dipeptides, taken from the literature. Description of dipeptide molecules is made by using the fragmental property Cluj indices. Four models were taken into consideration: two of them topological (dense topological and rare topological) and two others geometric (dense geometric and rare geometric). In these models, a weak dependence on distance for the potential function (gravitational and Coulombian), in uniform field, and a strong dependence on distance for the potential, that generates a non-uniform field, were considered. The indices are calculated as local descriptors of some fragments of the molecule and, a global index is then obtained by summing the fragmental contributions. The statistics were performed by STATISTICA software package. The results are compared to those reported in some previous works.
No. of downloads: 204 Full access PDF |
Quantitative Structure-Activity Relationship Study of COX-2 Inhibitors
Author: Oleg Ursu / Mircea V. Diudea / Shin-Ichi Nakayma
Abstract: Quantitative Structure-Activity Relationship (QSAR) is a tool used with success to model biological activity of series of compounds. There is a serious limitation in the use of this method – it works well only on series of highly homogenous compounds. To furnish such sets of structures, several similarity classification schemes have been proposed: Naïve Bayesian classifier, artificial neural networks, molecular fingerprints, and maximum overlapping structures method, MOS. The most accurate classifier MOS is the most computationally demanding as well, and until recently its use was limited. Recent development of the algorithm introduced a series of heuristics and a new rapid clique detection procedure led to significant improvements in the speed of MOS, thus making it suitable for virtual screening of large databases of molecules. In the present study we make use of the MOS method to classify unknowns according to their structural features into classes of structurally homogeneous compounds suitable for further analysis by classical QSAR approaches.
No. of downloads: 210 Full access PDF |
Image processing based on the wavelet transform
Author: Ovidiu Cosma
Abstract: This article presents a method for adjusting the contrast of images, based entirely on the Discrete Wavelet Transform.
No. of downloads: Full access PDF |
Evaluation of the DWT filters for image compression
Author: Ovidiu Cosma
Abstract: The characteristics of the digital filter used for computing the Discrete Wavelet Transform (DWT) determine the performance of the compression scheme. This article presents an evaluation of the DWT filters, from an image compression point of view.
No. of downloads: Full access PDF |

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