1,720,985 research outputs found
The Contribution of Harmful Traditional Practices to HIV Transmission Among Adolescent and Adult Females in Sub-Saharan Africa: a Victimological Approach,
No full textHarmful traditional practices are manifestations of gender-based discrimination caused by rooted unequal power relations between females and males and also represent a serious human rights violation affecting the rights of girls and women to health and safety. Although they are as diverse as the culture in which they occur, a common attribute of these practices is that they are related to female sexuality and are often enforced as a way of strengthening male domination. This study analyses the potential association between the harmful aspects of widow inheritance, virginity testing, female genital mutilation, and HIV transmission in adolescent and adult females. The main results of this analysis show how harmful traditional practices are mostly carried out without the consent of the victims involved and thus constitute a violation of international human rights laws. In general, this article significantly contributes to the multifaceted field of the victimology of human right
A defect-correction algorithm for quadratic matrix equations, with applications to quasi-Toeplitz matrices
No full textA defect correction formula for quadratic matrix equations of the kind (Formula presented.) is presented. This formula, expressed by means of an invariant subspace of a suitable pencil, allows us to introduce a modification of the Structure-preserving Doubling Algorithm (SDA), that enables refining an initial approximation to the sought solution. This modification provides substantial advantages, in terms of convergence acceleration, in the solution of equations coming from stochastic models, by choosing a stochastic matrix as the initial approximation. An application to solving random walks in the quarter plane is shown, where the coefficients (Formula presented.) are quasi-Toeplitz matrices of infinite size
Deflating subspaces of T-palindromic pencils and algebraic T-Riccati equations
No full textBy exploiting the connection between solving algebraic (Formula presented.) -Riccati equations and computing certain deflating subspaces of (Formula presented.) -palindromic matrix pencils, we obtain theoretical and computational results on both problems. Theoretically, we introduce conditions to avoid the presence of modulus-one eigenvalues in a (Formula presented.) -palindromic matrix pencil and conditions for the existence of solutions of a (Formula presented.) -Riccati equation. Computationally, we improve the palindromic QZ algorithm with a new ordering procedure and introduce new algorithms for computing deflating subspaces of the (Formula presented.) -palindromic pencil, based on quadraticizations of the pencil or on an integral representation of the projector on the sought deflating subspace
Relaxed fixed point iterations for matrix equations arising in Markov chain modeling
No full textWe present some accelerated variants of fixed point iterations for computing the minimal non-negative solution of the unilateral matrix equation associated with an M/G/1-type Markov chain. These variants derive from certain staircase regular splittings of the block Hessenberg M-matrix associated with the Markov chain. By exploiting the staircase profile, we introduce a two-step fixed point iteration. The iteration can be further accelerated by computing a weighted average between the approximations obtained at two consecutive steps. The convergence of the basic two-step fixed point iteration and of its relaxed modification is proved. Our theoretical analysis, along with several numerical experiments, shows that the proposed variants generally outperform the classical iterations
Palindromic linearization and numerical solution of nonsymmetric algebraic T -Riccati equations
Full text linkWe identify a relationship between the solutions of a nonsymmetric algebraic T-Riccati equation (T-NARE) and the deflating subspaces of a palindromic matrix pencil, obtained by arranging the coefficients of the T-NARE. The interplay between T-NAREs and palindromic pencils allows one to derive both theoretical properties of the solutions of the equation, and new methods for its numerical solution. In particular, we propose methods based on the (palindromic) QZ algorithm and the doubling algorithm, whose effectiveness is demonstrated by several numerical tests
Analytical performance evaluation of a two class DiffServ link
No full textThis paper provides an analytical model for the performance evaluation of a two class DiffServ link. It is applicable for the performance analysis of data traffic in the presence of higher priority Constant Bit Rate (CBR) encoded Voice and Video traffic. The DiffServ link is modeled as a single server queue in a Markovian environment. The queueing performance of data packets is evaluated by matrix geometric methods. The data generation process is assumed to follow a two state Markov modulated Poisson process (MMPP), and the service rate fluctuates based on the number of concurrent CBR sessions
A computational framework for two-dimensional random walks with restarts
Full text linkThe treatment of two-dimensional random walks in the quarter plane leads to Markov processes which involve semi-infinite matrices having Toeplitz or block Toeplitz structure plus a low-rank correction. We propose an extension of the framework introduced in [D. A. Bini, S. Massei, and B. Meini, Math. Comp., 87 (2018), pp. 2811-2830] which allows us to deal with more general situations such as processes involving restart events. This is motivated by the need for modeling processes that can incur in unexpected failures like computer system reboots. We present a theoretical analysis of an enriched Banach algebra that, combined with appropriate algorithms, enables the numerical treatment of these problems. The results are applied to the solution of bidimensional quasi-birth-death processes with infinitely many phases which model random walks in the quarter plane, relying on the matrix analytic approach. The reliability of our approach is confirmed by extensive numerical experimentation on several case studies
Traffic lights, clumping and QBDs
No full textIn discrete time, (Formula presented.) -blocks of red lights are separated by (Formula presented.) -blocks of green lights. Cars arrive at random. We seek the distribution of maximum line length of idle cars, and justify conjectured probabilistic asymptotics algebraically for (Formula presented.) and numerically for (Formula presented.)
Markov-Chain based centralities and Space Syntax’ Angular Analysis: an initial overview and application
No full textCentrality measures of Integration and Choice have performed a crucial role for Space Syntax in depicting complex relations among form, function, and movement within cities. However, while still relevant, those measures are unable to address certain innate network properties regarding the relative importance of certain road elements, essential for urban analyses focused on road-network resilience. The overreliance on Integration and Choice metrics to explain urban phenomena left several configurational patterns derived from connectivity rather unaddressed by Space Syntax and currently constitutes the methodology’s main limitation. With those points in consideration, this paper proposes an initial overview regarding the adaptation of Markov-based centrality measures to the Space Syntax framework and graph representation. These measures, often computable only in primal graphs, are adapted to the Road-Centre Line representation, in a first approach that aims to further integrate them into the Angular Analysis’ framework. We use the measures of Normalized PageRank Centrality and Normalized Kemeny-based centrality that estimate the connective relative importance of individual road-elements within the system. These measures are based on the notions of strong-ties and weak-ties, both well-known concepts in social networks; Weak-ties are important to establish bridges among interconnected communities of strong-tied individuals. In the urban configuration, weak-ties give information about crucial bridges among spaces characterized by strong-ties, areas that possess a high number of interconnected road elements – common pattern found in urban settlements. Results indicate that adapting Markov-based centralities to Space Syntax is feasible and maintains a configurational and spatial sense, hence it introduces new dimensions to be evaluated in urban-regional analysis
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