Facultatea de Matematică şi Informatică / Faculty of Methematics and Informatics
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Item VARIETĂŢI ABSTRACTE MULTIDIMENSIONALE DEGENERATE(CEP USM, 2013) Cataranciuc, SergiuEste definită varietatea degenerată n -dimensională şi sunt studiate unele proprietăţi ale acesteia. Varietăţile sunt considerate închise, conexe, omogene şi fără găuri. Pornind de la complexul generalizat de relaţii multi-are, se face clasificarea varietăţilor degenerate. Rezultatele obţinute sunt similare celor cunoscute pentru varietăţile clasice de genul p [5,11,12], studiate prin intermediul complexului simplu de relaţii multi-are.Item MATRICELE DE RELAŢII MULTI-ARE ŞI NUMERELE PRIME ÎN CRIPTAREA INFORMAŢIEI(CEP USM, 2012) Cataranciuc, Sergiu; Zgureanu, AureliuSe propune un sistem simetric de criptare a informaţiei, numit Crypto 2. Acest sistem se bazează pe utilizarea numerelor prime mari şi pe dezvoltarea lor polinomială. Un rol deosebit revine matricelor multidimensionale, folositepentru reprezentarea mulţimilor de relaţii multi-are. Se descrie algoritmul de criptare/decriptare a informaţiei, Cripto 2,şi se demonstrează că acest algoritm are o complexitate liniară.Item ABOUT RATES OF CONVERGENCE IN THE LIMIT THEOREM(CEP USM, 2011) Munteanu, Bogdan Gheorghe; Leahu, Alexei; Cataranciuc, SergiuÎn lucrare se propune o estimare a ratei de convergenţă a densităţii sumei de variabile aleatoare în raport cu densitatea probabilităţii de repartiţie. Studii similare au fost făcute şi de către alţi matematicieni. Aici putem menţiona lucrarea lui W. Macht şi Wolf W. „On the local central limit theorem” [2], în care aproximarea densităţii probabilităţii unui şir de variabile aleatoare este făcută cu referire la densitatea probabilităţii distribuţiei normale standarde. Principalul rezultat al acestui articol se conţine în teorema 2.1, care stabileşte rata de convergenţă a densităţii probabilităţii unui şir de variabile aleatoare în raport cu densitatea probabilităţii de repartiţie a variantei cu una şi cu trei grade de libertate.Item THE CONVEXITY IN THE COMPLEX OF MULTI-ARY RELATIONS(Romanian Society of Applied & Industrial Mathematics Universitatea din Pitesti, 2015) Braguţă, Galina; Cataranciuc, SergiuFor a complex of multi-ary relations [12] it is defined the concept of (k,m)-chain which is a generalization of the concept of chain known from the graph theory. Using (k,m)- chains it is introduced the concept of the distance function and it is proved that this function generate a convexity in the complex of multi-ary relations. It is operating with the concepts of convexity and convex hull, axiomatically defined by F.Levi [29] and we describe the iterative procedure to construct a convex hull for a subset of elements from the complex of multi-ary relations. [ABSTRACT FROM AUTHOR]Item ON NONTRIVIAL COVERS AND PARTITIONS OF GRAPHS BY CONVEX SETS(Institutul de Matematică şi Informatică al Academiei de Ştiinţe a Moldovei, 2018) Buzatu, Radu; Cataranciuc, SergiuIn this paper we prove that it is NP-complete to decide whet- her a graph can be partitioned into nontrivial convex sets. We show that it can be verified in polynomial time whether a graph can be covered by nontrivial convex sets. Also, we propose a re- cursive formula that establishes the maximum nontrivial convex cover number of a tree.Item dm-CONVEX FUNCTIONS IN THE COMPLEX OF MULTI-ARY RELATIONS(2017) Cataranciuc, Sergiu; Braguța, GalinaIn the present work the notions of dm-convexity and dm convex function are defined. Some properties of these functions are mentioned. We study the complexes of multi-ary relations for which the median function is dm-convex.Item EULER CHARACTERISTIC OF ABSTRACT CUBES COMPLEX(Valines SRL, 2014) Cataranciuc, SergiuFormula for the Euler characteristics for the In complex is deduced. The formula is expressed by cardinals of the groups of the homologies and by a number of m-dimensional abstract cubes from In.Item DERIVATION OF BOOLEAN FUNCTIONS BY THE BLOCKS METHOD(Valines SRL, 2014) Bulat, Mihai; Cataranciuc, Sergiu; Ciobanu, Iacob; Izbas, Vladimir; Zgureanu, AureliuA method for calculating using blocks of the partial derivatives of the boolean function which are represented in algebraic form { a polynomial form, disjunctive normal form and conjunctive normal form is proposed. The method can be used success- fully for functions which depend on a large number of variables (tens and hundreds). This method can be applied to solve many problems from di®erent areas such as: elaborating of encryption system with variable keys, some problems from discrete mathematics (systems isomorphism problem, problem of determining of chromatic number in graphs ect.).Item LOCATION PROBLEMS ON d - CONVEX SIMPLE PLANAR GRAPHS(CEP USM, 2015) Cataranciuc, Sergiu; Macoveiciuc, EliseiThe article examines the center and median problems on graphs with special structure. In scientific works these are frequently called location problems on graphs. Although efficient solutions for graphs with some well-known properties have been found, in general case the problem remains complex. In this paper the structure of median and center in a d-convex simple planargraph Gis studied.We evaluate the connection between median/center of a graph Gwith mentioned properties and median/center of a tree, determined by G.Item COERENŢA ELEMENTELOR ÎNTR-UN COMPLEX DE RELAŢII MULTI-ARE(CEP USM, 2015) Cataranciuc, SergiuÎn articol este generalizată noţiunea de coerenţă simplă a elementelor unui complex de relaţii multi-are. Interpretând elementele complexului de relaţii ca simplexe abstracte, sunt introduse noţiunile de t-coerenţă şi (t q) coerenţă. Sunt demonstrate rezultate ce ţin de relaţia de coerenţă generalizată a simplexelor abstracte.