Quasi-total Roman Domination in Graphs

[EN] A quasi-total Roman dominating function on a graph G=(V,E) is a function f:V ->{0,1,2}satisfying the following: Every vertex for which u for which f(u) = 0 is adjacent to at least one vertex v for which f(v) = 2, and If x is an isolated vertex in the subgraph induced by the set of vertices labeled with 1 and 2, then f(x) = 1. The weight of a quasi-total Roman dominating function is the value omega(f) = f(V) = Sigma(u is an element of V) f(u). The minimum weight of a quasi-total Roman dominating function on a graph G is called the quasi-total Roman domination number of G. We introduce the quasi-total Roman domination number of graphs in this article, and begin the study of its combinatorial and computational properties.Cabrera García, S.; Cabrera Martínez, A.; Yero, IG. (2019). Quasi-total Roman Domination in Graphs. Results in Mathematics. 74(4):1-18. https://doi.org/10.1007/s00025-019-1097-5S11874

Further Results on the Total Roman Domination in Graphs

[EN] Let G be a graph without isolated vertices. A function f:V(G)-> {0,1,2} is a total Roman dominating function on G if every vertex v is an element of V(G) for which f(v)=0 is adjacent to at least one vertex u is an element of V(G) such that f(u)=2 , and if the subgraph induced by the set {v is an element of V(G):f(v)>= 1} has no isolated vertices. The total Roman domination number of G, denoted gamma tR(G) , is the minimum weight omega (f)=Sigma v is an element of V(G)f(v) among all total Roman dominating functions f on G. In this article we obtain new tight lower and upper bounds for gamma tR(G) which improve the well-known bounds 2 gamma (G)<= gamma tR(G)<= 3 gamma (G) , where gamma (G) represents the classical domination number. In addition, we characterize the graphs that achieve equality in the previous lower bound and we give necessary conditions for the graphs which satisfy the equality in the upper bound above.Cabrera Martínez, A.; Cabrera García, S.; Carrión García, A. (2020). Further Results on the Total Roman Domination in Graphs. Mathematics. 8(3):1-8. https://doi.org/10.3390/math8030349S1883Henning, M. A. (2009). A survey of selected recent results on total domination in graphs. Discrete Mathematics, 309(1), 32-63. doi:10.1016/j.disc.2007.12.044Henning, M. A., & Yeo, A. (2013). Total Domination in Graphs. Springer Monographs in Mathematics. doi:10.1007/978-1-4614-6525-6Henning, M. A., & Marcon, A. J. (2016). Semitotal Domination in Claw-Free Cubic Graphs. Annals of Combinatorics, 20(4), 799-813. doi:10.1007/s00026-016-0331-zHenning, M. . A., & Marcon, A. J. (2016). Vertices contained in all or in no minimum semitotal dominating set of a tree. Discussiones Mathematicae Graph Theory, 36(1), 71. doi:10.7151/dmgt.1844Henning, M. A., & Pandey, A. (2019). Algorithmic aspects of semitotal domination in graphs. Theoretical Computer Science, 766, 46-57. doi:10.1016/j.tcs.2018.09.019Cockayne, E. J., Dreyer, P. A., Hedetniemi, S. M., & Hedetniemi, S. T. (2004). Roman domination in graphs. Discrete Mathematics, 278(1-3), 11-22. doi:10.1016/j.disc.2003.06.004Stewart, I. (1999). Defend the Roman Empire! Scientific American, 281(6), 136-138. doi:10.1038/scientificamerican1299-136Chambers, E. W., Kinnersley, B., Prince, N., & West, D. B. (2009). Extremal Problems for Roman Domination. SIAM Journal on Discrete Mathematics, 23(3), 1575-1586. doi:10.1137/070699688Favaron, O., Karami, H., Khoeilar, R., & Sheikholeslami, S. M. (2009). On the Roman domination number of a graph. Discrete Mathematics, 309(10), 3447-3451. doi:10.1016/j.disc.2008.09.043Liu, C.-H., & Chang, G. J. (2012). Upper bounds on Roman domination numbers of graphs. Discrete Mathematics, 312(7), 1386-1391. doi:10.1016/j.disc.2011.12.021González, Y., & Rodríguez-Velázquez, J. (2013). Roman domination in Cartesian product graphs and strong product graphs. Applicable Analysis and Discrete Mathematics, 7(2), 262-274. doi:10.2298/aadm130813017gLiu, C.-H., & Chang, G. J. (2012). Roman domination on strongly chordal graphs. Journal of Combinatorial Optimization, 26(3), 608-619. doi:10.1007/s10878-012-9482-yAhangar Abdollahzadeh, H., Henning, M., Samodivkin, V., & Yero, I. (2016). Total Roman domination in graphs. Applicable Analysis and Discrete Mathematics, 10(2), 501-517. doi:10.2298/aadm160802017aAmjadi, J., Sheikholeslami, S. M., & Soroudi, M. (2019). On the total Roman domination in trees. Discussiones Mathematicae Graph Theory, 39(2), 519. doi:10.7151/dmgt.2099Cabrera Martínez, A., Montejano, L. P., & Rodríguez-Velázquez, J. A. (2019). Total Weak Roman Domination in Graphs. Symmetry, 11(6), 831. doi:10.3390/sym1106083

The total co-independent domination number of some graph operations

[EN] A set D of vertices of a graph G is a total dominating set if every vertex of G is adjacent to at least one vertex of D. The total dominating set D is called a total co-independent dominating set if the subgraph induced by V (G)- D is edgeless. The minimum cardinality among all total co-independent dominating sets of G is the total co-independent domination number of G. In this article we study the total co-independent domination number of the join, strong, lexicographic, direct and rooted products of graphs.I. Peterin was partially supported by ARRS Slovenia under grants P1-0297 and J1-9109; I. G. Yero was partially supported by Junta de Andalucia, FEDER-UPO Research and Development Call, reference number UPO-1263769.Cabrera Martinez, A.; Cabrera García, S.; Peterin, I.; Yero, IG. (2022). The total co-independent domination number of some graph operations. Revista de la Unión Matemática Argentina. 63(1):153-158. https://doi.org/10.33044/revuma.165215315863

Un método iterativo para el ajuste de curvas basado en la optimización en una variable y su aplicación al caso lineal en una variable independiente

[EN] An iterative method for the adjustment of curves is obtained by applying the least squares method reiteratively in functional subclasses, each defined by one parameter, after assigning values to the rest of the parameters which determine a previously determined general functional class. To find the minimum of the sum of the squared deviations, in each subclass, only techniques of optimization are used for real functions of a real variable.The value of the parameter which gives the best approximation in an iteration is substituted in the general functional class, to retake the variable character of the following parameter and repeat the process, getting a succession of functions. In the case of simple linear regression, the convergence of that succession to the least squares line is demonstrated, because the values of the parameters that define each approximation coincide with the values of the parameters obtained when applying the method of Gauss - Seidel to the normal system of equations. This approach contributes to the teaching objective of improving the treatment of the essential ideas of curve adjustment, which is a very important topic in applications, what gives major importance to the optimization of variable functions.[ES] Se obtiene un método iterativo para el ajuste de curvas al aplicar reiteradamente el método de los mínimos cuadrados en subclases funcionales, cada una definida por un parámetro, luego de asignar valores a los restantes parámetros que determinan una clase funcional general, seleccionada previamente. Para hallar el mínimo de la suma de las desviaciones cuadráticas, en cada subclase, solo se utilizan técnicas de optimización para funciones reales de una variable real. El valor del parámetro, que proporciona la mejor aproximación en una iteración, se sustituye en la clase funcional general, para retomar el carácter variable del siguiente parámetro y repetir el proceso, obteniéndose una sucesión de funciones. En el caso de la regresión lineal simple se demuestra la convergencia de esa sucesión a la recta mínimo cuadrática, pues coinciden los valores de los parámetros que definen cada aproximación con los que se obtienen al aplicar el método de Gauss - Seidel al sistema normal de ecuaciones. Este enfoque contribuye al objetivo docente de adelantar el tratamiento de las ideas esenciales del ajuste de curvas, temática muy importante en las aplicaciones, lo que le confiere mayor significación a la optimización de funciones de una variable.The authors acknowledge the financial support of AECID (Spain) under Project No A2/039476/11 - “Institutional Strengthening in the Teaching of Subjects of Statistics, Operative Investigation, Liability and Quality, and Scientific Application in Topics of Regional Interest”.Acosta, R.; Cabrera García, S.; Vega, LM.; Cabrera, A.; Acosta, N. (2014). An Iterative Method for Curve Adjustment Based on Optimization of a Variable and its Application. Revista Colombiana de Estadística. 37(1):111-125. https://doi.org/10.15446/rce.v37n1.44361S11112537

Total Roman Domination Number of Rooted Product Graphs

[EN] Let G be a graph with no isolated vertex and f:V(G)->{0,1,2} a function. If f satisfies that every vertex in the set {v is an element of V(G):f(v)=0} is adjacent to at least one vertex in the set {v is an element of V(G):f(v)=2}, and if the subgraph induced by the set {v is an element of V(G):f(v)>= 1} has no isolated vertex, then we say that f is a total Roman dominating function on G. The minimum weight omega(f)= n-ary sumation v is an element of V(G)f(v) among all total Roman dominating functions f on G is the total Roman domination number of G. In this article we study this parameter for the rooted product graphs. Specifically, we obtain closed formulas and tight bounds for the total Roman domination number of rooted product graphs in terms of domination invariants of the factor graphs involved in this product.Cabrera Martinez, A.; Cabrera García, S.; Carrión García, A.; Hernandez Mira, FA. (2020). Total Roman Domination Number of Rooted Product Graphs. Mathematics. 8(10):1-13. https://doi.org/10.3390/math8101850S11381

Relación entre las mediciones corporales y testiculares en búfalos jóvenes en Cuba

[EN] Background: appropriate selection of sires holds great importance in plans to genetically improve and raise buffalos. Objective: to obtain a statistical model that provides accurate associations between body and testicular measurements intended for selection of Bufalypso breed sires. Methods: measurements of body weight (BW), thoracic perimeter (TP), and scrotal circumference (SC) from 649 buffalos aged 2 to 36 months, were used to obtain the models corresponding to the associations between these traits. The statistical significance of the model and the model's parameters were evaluated using a one-way analysis of variance. The best-fit model was established by calculating determination coefficients (R2) and mean squared error (SE). Results: the most adequate regression model between thoracic perimeter and body weight was TP = 19.89* BW0.37, with 99% and 0.03 for R-2 and, SE, respectively. The best association between scrotal circumference and body weight was obtained with the model SC = 1.13* BW0.51, with values of 89% for R-2 and of 0.1 for SE. The model that best expressed the relationship between scrotal circumference and thoracic perimeter was SC = 0.02* TP0.89, with R-2 = 89% and SE = 0.01. Conclusion: nonlinear models described better the association between body and testicular measurements than the linear ones. These results suggest that nonlinear models are effective for selecting buffalo sires.[ES] Antecedentes: la selección de sementales tiene gran importancia en los planes de mejora genética y cría de búfalos. Objetivo: obtener los modelos estadísticos que mejor relacionan las mediciones corporales y testiculares en machos jóvenes de raza Bufalypso para su uso en la selección de futuros sementales. Métodos: se midió el peso corporal (BW), el perímetro torácico (TP) y la circunferencia escrotal (SC) a 649 búfalos, entre 2 y 36 meses de edad, obteniéndose los modelos correspondientes a las relaciones entre estas características. La significación estadística de los modelos y parámetros se evaluó mediante análisis de varianza de una vía. El mejor modelo de ajuste se determinó a partir de cálculos de los coeficientes de determinación (R2) y el error cuadrático medio (SE). Resultados: el modelo más adecuado entre el perímetro torácico y el peso corporal fue TP = 19,89*BW0.37, con valores de R2 de 99% y de 0,03 para SE. La mejor relación entre la circunferencia escrotal y el peso corporal se obtuvo con el modelo SC = 1,13*BW0.51, con un R2 igual al 89% y un SE de 0,1. El modelo que mejor expresó la relación entre la circunferencia escrotal y el perímetro torácico fue SC = 0,02*TP0.89, con valores de 89% para R2 de y de 0,01 para SE. Conclusión: los modelos no lineales describieron mejor la relación entre las mediciones corporales y testiculares que los modelos lineales. Los resultados sugieren que la selección de los sementales sería más efectiva utilizando modelos no lineales.[PT] Antecedentes: a seleção de reprodutores é muito importante nos programas de melhoramento e criação de búfalos. Objetivo: obter modelos estatísticos que melhor relacionem as medidas corporais e testiculares em machos jovens da raça Bufalypso, para serem usados na seleção de futuros reprodutores. Métodos: foi medido o peso corporal (BW), o perímetro torácico (TP) e a circunferência escrotal (SC) de uma amostra de 649 búfalos, com idades entre 2 e 36 meses. A significância estatística dos modelos e dos parâmetros foi avaliada pela análise de variância. O melhor modelo de ajuste foi determinado a partir do cálculo dos coeficientes de determinação (R2) e o quadrado médio do erro (SE). Resultados: o modelo mais adequado para o perímetro torácico e o peso corporal foi PT = 19,89*BW0,37 com R2 de 99% e SE de 0,03. A melhor relação entre circunferência escrotal e o peso corporal foi obtida com o modelo SC = 1,13*BW0,51 com R2 de 89% e SE de 0,1. O modelo que melhor representou a relação entre a circunferência escrotal e o perímetro torácico foi SC = 0,02*TP0,89 com valores de R2 de 89% e SE 0,01. Conclusão: os modelos não lineares descreveram melhor a relação entre as mensurações corporais e as testiculares do que os modelos lineares. Esses resultados sugerem que a seleção dos reprodutores seria mais eficaz utilizando os modelos não lineares.The authors acknowledge financial support from AECID (Spain) under Project No A2/039476/11, "Institutional strengthening of teaching the subjects of statistics, operations research and reliability and quality, and their scientific application to topics of regional interest."Almaguer, Y.; Font, H.; Cabrera García, S.; Arias, Y. (2017). Relationship between body and testicular measurements in young buffalo bulls in Cuba. Revista Colombiana de Ciencias Pecuarias. 30(2):138-146. https://doi.org/10.17533/udea.rccp.v30n2a05S13814630

On the Outer-Independent Roman Domination in Graphs

[EN] Let G be a graph with no isolated vertex and f:V(G)->{0,1,2} a function. Let V-i={v is an element of V(G):f(v)=i} for every i is an element of{0,1,2}. The function f is an outer-independent Roman dominating function on G if V0 is an independent set and every vertex in V-0 is adjacent to at least one vertex in V-2. The minimum weight omega(f)= Sigma v is an element of V(G)f(v) among all outer-independent Roman dominating functions f on G is the outer-independent Roman domination number of G. This paper is devoted to the study of the outer-independent Roman domination number of a graph, and it is a contribution to the special issue "Theoretical Computer Science and Discrete Mathematics" of Symmetry. In particular, we obtain new tight bounds for this parameter, and some of them improve some well-known results. We also provide closed formulas for the outer-independent Roman domination number of rooted product graphs.Cabrera Martínez, A.; Cabrera García, S.; Carrión García, A.; Grisales Del Rio, AM. (2020). On the Outer-Independent Roman Domination in Graphs. Symmetry (Basel). 12(11):1-12. https://doi.org/10.3390/sym12111846S1121211Goddard, W., & Henning, M. A. (2013). Independent domination in graphs: A survey and recent results. Discrete Mathematics, 313(7), 839-854. doi:10.1016/j.disc.2012.11.031Cockayne, E. J., Dreyer, P. A., Hedetniemi, S. M., & Hedetniemi, S. T. (2004). Roman domination in graphs. Discrete Mathematics, 278(1-3), 11-22. doi:10.1016/j.disc.2003.06.004Abdollahzadeh Ahangar, H., Chellali, M., & Samodivkin, V. (2017). Outer independent Roman dominating functions in graphs. International Journal of Computer Mathematics, 94(12), 2547-2557. doi:10.1080/00207160.2017.1301437Cabrera Martínez, A., Kuziak, D., & Yero, G. I. (2021). A constructive characterization of vertex cover Roman trees. Discussiones Mathematicae Graph Theory, 41(1), 267. doi:10.7151/dmgt.2179Godsil, C. D., & McKay, B. D. (1978). A new graph product and its spectrum. Bulletin of the Australian Mathematical Society, 18(1), 21-28. doi:10.1017/s000497270000776

Application of the Game Theory with Perfect Information to an agricultural company

[EN] This paper deals with the application of Game Theory with Perfect Information to an agricultural economics problem. The goal of this analysis is demonstrating the possibility of obtaining an equilibrium point, as proposed by Nash, in the case of an agricultural company that is considered together with its three sub-units in developing a game with perfect information. Production results in terms of several crops will be considered in this game, together with the necessary parameters to implement different linear programming problems. In the game with perfect information with the hierarchical structure established between the four considered players (a management center and three production units), a Nash equilibrium point is reached, since once the strategies of the rest of the players are known, if any of them would use a strategy different to the one proposed, their earnings would be less than the ones obtained by using the proposed strategies. When the four linear programming problems are solved, a particular case of equilibrium point is reached.Supported by the Spanish Agency for International Development Cooperation (AECID) (Projects No. A2/039476/11).Cabrera García, S.; Imbert Tamayo, JE.; Carbonell Olivares, J.; Pacheco Cabrera, Y. (2013). Application of the Game Theory with Perfect Information to an agricultural company. Agricultural Economics (AGRICECON). 59(1):1-7. http://hdl.handle.net/10251/66307S1759

Noise control by sonic crystal barriers made of recycled materials

A systematic study of noise barriers based on sonic crystals made of cylinders that use recycled materials like absorbing component is here reported. The barriers consist of only three rows of perforated metal shells filled with rubber crumb. Measurements of reflectance and transmittance by these barriers are reported. Their attenuation properties result from a combination of sound absorption by the rubber crumb and reflection by the periodic distribution of scatterers. It is concluded that porous cylinders can be used as building blocks whose physical parameters can be optimized in order to design efficient barriers adapted to different noisy environments

Total Roman {2}-domination in graphs

[EN] Given a graph G = (V, E), a function f: V -> {0, 1, 2} is a total Roman {2}-dominating function if every vertex v is an element of V for which f (v) = 0 satisfies that n-ary sumation (u)(is an element of N (v)) f (v) >= 2, where N (v) represents the open neighborhood of v, and every vertex x is an element of V for which f (x) >= 1 is adjacent to at least one vertex y is an element of V such that f (y) >= 1. The weight of the function f is defined as omega(f ) = n-ary sumation (v)(is an element of V) f (v). The total Roman {2}-domination number, denoted by gamma(t)({R2})(G), is the minimum weight among all total Roman {2}-dominating functions on G. In this article we introduce the concepts above and begin the study of its combinatorial and computational properties. For instance, we give several closed relationships between this parameter and other domination related parameters in graphs. In addition, we prove that the complexity of computing the value gamma(t)({R2})(G) is NP-hard, even when restricted to bipartite or chordal graphsCabrera García, S.; Cabrera Martinez, A.; Hernandez Mira, FA.; Yero, IG. (2021). Total Roman {2}-domination in graphs. Quaestiones Mathematicae. 44(3):411-444. https://doi.org/10.2989/16073606.2019.1695230S41144444