1,721,573 research outputs found
A derivative-free method for structured optimization problems
Full text linkStructured optimization problems are ubiquitous in fields like data science and engineering. The goal in structured optimization is using a prescribed set of points, called atoms, to build up a solution that minimizes or maximizes a given function. In the present paper, we want to minimize a black-box function over the convex hull of a given set of atoms, a problem that can be used to model a number of real-world applications. We focus on problems whose solutions are sparse, i.e., solutions that can be obtained as a proper convex combination of just a few atoms in the set, and propose a suitable derivative-free inner approximation approach that nicely exploits the structure of the given problem. This enables us to properly handle the dimensionality issues usually connected with derivative-free algorithms, thus getting a method that scales well in terms of both the dimension of the problem and the number of atoms. We analyze global convergence to stationary points. Moreover, we show that, under suitable assumptions, the proposed algorithm identifies a specific subset of atoms with zero weight in the final solution after finitely many iterations. Finally, we report numerical results showing the effectiveness of the proposed method
A zeroth order method for stochastic weakly convex optimization
Full text linkIn this paper, we consider stochastic weakly convex optimization problems, however without the existence of a stochastic subgradient oracle. We present a derivative free algorithm that uses a two point approximation for computing a gradient estimate of the smoothed function. We prove convergence at a similar rate as state of the art methods, however with a larger constant, and report some numerical results showing the effectiveness of the approach
Razionali emozioni
No full textArticolo di introduzione ad altro articolo sul tema della Human Resources Managemen
Codex Atlanticus. Leonardo e la sua bottega: disegni di figura e di animali
No full textCatalogo della Mostra tenutasi nella Biblioteca Ambrosiana e nella Sacrestia del Bramante ( 14 marzo-11 giugno 2011
Structure-based approaches in synthetic lethality strategies
No full textEvolution has fostered robust DNA damage response (DDR)
mechanisms to combat DNA lesions. However, disruptions in
this intricate machinery can render cells overly reliant on the
remaining functional but often less accurate DNA repair pathways. This increased dependence on error-prone pathways
may result in improper repair and the accumulation of mutations, fostering genomic instability and facilitating the uncontrolled cell proliferation characteristic of cancer initiation and
progression. Strategies based on the concept of synthetic
lethality (SL) leverage the inherent genomic instability of
cancer cells by targeting alternative pathways, thereby
inducing selective death of cancer cells. This review emphasizes recent advancements in structural investigations of
pivotal SL targets. The significant contribution of structurebased methodologies to SL research underscores their potential impact in characterizing the growing number of SL targets, largely due to advances in next-generation sequencing.
Harnessing these approaches is essential for advancing the
development of precise and personalized SL therapeutic
strategies
Solving l0-penalized problems with simple constraints via the Frank–Wolfe reduced dimension method
No full textl0-penalized problems arise in a number of applications in engineering, machine learning and statistics, and, in the last decades, the design of algorithms for these problems has attracted the interest of many researchers. In this paper, we are concerned with the definition of a first-order method for the solution of l0-penalized problems with simple constraints. We use a reduced dimension Frank–Wolfe algorithm Rinaldi (Optim Methods Softw, 26, 2011) and show that the subproblem related to the computation of the Frank–Wolfe direction can be solved analytically at least for some sets of simple constraints. This gives us a very easy to implement and quite general tool for dealing with l0-penalized problems. The proposed method is then applied to the numerical solution of two practical optimization problems, namely, the Sparse Principal Component Analysis and the Sparse Reconstruction of Noisy Signals. In both cases, the reported numerical performances and comparisons with state-of-the-art solvers show the efficiency of the proposed method
Oderzo, via delle Grazie 5-7.Una domus con pavimentazioni a mosaico.
No full textPresentazione di un contesto di scavo relativo al municipium di Oderzo con identificazione di una domus con tappeti musivi in relazione alla identificazione dei quartieri della città di epoca romana
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