1,721,229 research outputs found
Computationof non conservative stability perturbation bounds for systems withnonlinearly correlated uncertainties
No full textRobustness in Identification and Control
No full textThis book comprises a selection of papers that were first presented at the Robustness in Identification and Control Workshop, held in Siena, July 30 - August 2, 1998. These are the latest contributions to the field, from leading researchers worldwide. The common theme underlying all of the contributions is the interplay between information, uncertainty and complexity in dealing with modelling, identification and control of dynamical systems. Papers cover recent developments in research areas such as identification for control and the classical area of robust control. There are a number of real-world case studies where the most advanced robustness analysis and synthesis techniques are applied to resolve previously unsolved problems. The relevance of the topic to the system engineering field, and the excellent scientific level of the contributions combine to make this book an important acquisition for engineers, control theorists and applied mathematicians
Convexity properties of polynomials with assigned root location
No full textThis paper presents some geometrical results on the domain of (generalized) stability for a family of nth order polynomials. Regions of root location such that the convex hull of the corresponding domain of stability in the coefficient space is a polyhedron are investigated, and specific regions for which the convex hull is an n+1 vertex polyhedron are derived. The discrete-time stability domain falls in the latter class of regions. Implications of the results for the design of filters solving the robust strict positive realness for families of rational transfer functions with uncertainty in the numerator are also developed
Clockwise property of the Nyquist plot with implications for absolute stability
No full textIn this paper the clockwise property of the Nyquist plot of stable transfer functions is addressed. The relationships between clockwise property and modulus and/or phase monotonicity are analyzed. Some necessary and sufficient conditions for a class of stable transfer functions to enjoy the clockwise property are obtained. These results are used to enlarge the class of systems for which the Kalman conjecture on absolute stability of nonlinear systems holds
GENE REGULATION BY MYC DURING B CELL ACTIVATION
Full text linkc-Myc is a transcriptional regulator required for the cellular response to proliferative stimuli. The gene expression programs regulated by Myc in physiological settings remain to be clarified. Here, we provide a complete characterization of Myc-dependent regulatory events in primary mouse B cells following activation by bacterial lipopolysaccharide (LPS). Taking advantage of cells homozygous for a conditional knockout allele of c-myc, we induced deletion before LPS stimulation, followed by genome wide profiling of mRNA levels and Myc-DNA interactions. In contrast with previous studies, in which Myc was proposed to directly drive transcriptional amplification at all active loci (Nie et al. 2012, Lin et al. 2012), our study revealed that Myc is required for the up- and down-regulation of distinct subsets of genes early after stimulation, occurring prior to the global increase in RNA production. These gene expression programs where partially overlapping with those regulated by Myc upon oncogenic activation, a distinction made not only in B-cells, but also in fibroblasts (Sabò et al., 2014, Perna et al. 2012). Our data also show that Myc dependent regulation can occur at the level of RNA Polymerase II loading, as well as elongation. Altogether these data provide an extensive picture of Myc' s action in response to a mitogenic stimulus, highlighting the importance of Myc-target genes in the remodeling of cellular physiology and metabolism. Systematic work will be needed to unravel which, among all the Myc-regulated genes, are critical in mediating this chain of events
Design criteria for robust strict positive realness in adaptive schemes
No full textDesign of filters ensuring convergence of recursive estimation algorithms in the presence of uncertainty in the plant model is a key problem in the area of identification and adaptive control. This paper addresses the problem of designing filters ensuring strict positive realness of a family of uncertain polynomials over an assigned region of the complex plane. The uncertainty is assumed to be both structured and unstructured. When the structured uncertainty of the family is represented through regions of root location of a certain shape (for instance, circles centered on the real axis), an optimal solution of the problem is provided. For more general uncertainty regions, a simple procedure for constructing sub-optimal solutions to the filter design problem is proposed. A numerical example is fully developed to show the effectiveness of the proposed approach
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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