2,017 research outputs found
Root Locus Techniques With Nonlinear Gain Parameterization
No full textThis thesis presents rules that characterize the root locus for polynomials that are nonlinear in the root-locus parameter k. Classical root locus applies to polynomials that are affine in k. In contrast, this thesis considers polynomials that are quadratic or cubic in k. In particular, we focus on constructing the root locus for linear feedback control systems, where the closed-loop denominator polynomial is quadratic or cubic in k. First, we present quadratic root-locus rules for a controller class that yields a closed-loop denominator polynomial that is quadratic in k. Next, we develop cubic root-locus rules for a controller class that yields a closed-loop denominator polynomial that is cubic in k. Finally, we extend the quadratic root-locus rules to accommodate a larger class of controllers. We also provide controller design examples to demonstrate the quadratic and cubic root locus. For example, we show that the triple integrator can be high-gain stabilized using a controller that yields a closed-loop denominator polynomial that is quadratic in k. Similarly, we show that the quadruple integrator can be high-gain stabilized using a controller that yields a closed-loop denominator polynomial that is cubic in k
Estimation in threshold autoregressive models with a stationary and a unit root regime
No full textThis paper treats estimation in a class of new nonlinear threshold autoregressive models with both a stationary and a unit root regime. Existing literature on nonstationary threshold models have basically focused on models where the nonstationarity can be removed by differencing and/or where the threshold variable is stationary. This is not the case for the process we consider, and nonstandard estimation problems are the result. This paper proposes a parameter estimation method for such nonlinear threshold autoregressive models using the theory of null recurrent Markov chains. Under certain assumptions, we show that the ordinary least squares (OLS) estimators of the parameters involved are asymptotically consistent. Furthermore, it can be shown that the OLS estimator of the coefficient parameter involved in the stationary regime can still be asymptotically normal while the OLS estimator of the coefficient parameter involved in the nonstationary regime has a nonstandard asymptotic distribution. In the limit, the rate of convergence in the stationary regime is asymptotically proportional to n-1/4, whereas it is n-1 in the nonstationary regime. The proposed theory and estimation method are illustrated by both simulated data and a real data example.Autoregressive process; null-recurrent process; semiparametric model; threshold time series; unit root structure.
A decision theoretic analysis of the unit root hypothesis using mixtures of elliptical models
No full textTime Series;Unit Root
Measuring (KSK +/-)-K-0 interactions using Pb-Pb collisions at root S-NN=2.76 TeV
No full textWe present the first ever measurements of femtoscopic correlations between the K-S(0) and K-+/- particles. The analysis was performed on the data from Pb-Pb collisions at root S-NN = 2.76 TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding via the a(0)(980) resonance. The extracted kaon source radius and correlation strength parameters for (KSK-)-K-0 are found to be equal within the experimental uncertainties to those for (KSK+)-K-0. Comparing the results of the present study with those from published identical-kaon femtoscopic studies by ALICE, mass and coupling parameters for the a(0) resonance are tested. Our results are also compatible with the interpretation of the a(0) having a tetraquark structure instead of that of a diquark. (c) 2017 The Author. Published by Elsevier B.V
Responses of nutrient capture and fine root morphology of subalpine coniferous tree Picea asperata to nutrient heterogeneity and competition
No full textInvestigating the responses of trees to the heterogeneous distribution of nutrients in soil and simultaneous presence of neighboring roots could strengthen the understanding of an influential mechanism on tree growth and provide a scientific basis for forest management. Here, we conducted two split-pot experiments to investigate the effects of nutrient heterogeneity and intraspecific competition on the fine root morphology and nutrient capture of Picea asperata. The results showed that P. asperata efficiently captured nutrients by increasing the specific root length (SRL) and specific root area (SRA) of first-and second-order roots and decreasing the tissue density of first-order roots to avoid competition for resources and space with neighboring roots. The nutrient heterogeneity and addition of fertilization did not affect the fine root morphology, but enhanced the P and K concentrations in the fine roots in the absence of a competitor. On the interaction between nutrient heterogeneity and competition, competition decreased the SRL and SRA but enhanced the capture of K under heterogeneous soil compared with under homogeneous soil. Additionally, the P concentration, but not the K concentration, was linearly correlated to root morphology in heterogeneous soil, even when competition was present. The results suggested that root morphological features were only stimulated when the soil nutrients were insufficient for plant growth and the nutrients accumulations by root were mainly affected by the soil nutrients more than the root morphology
K-core in random graphs
No full textA graph G=(V,E) is a mathematical model for a network with vertex set V and edge set E. A Random Graph model is a probabilistic graph. A Random Geometric Graph is a Random Graph were each vertex has a location in a space χ. We compare the Erdos-Rényi random graph, G(n,p), to the Random Geometric Graph model, RGG(n,r) where, in general we use r=c / (n^(-1/d)), with dimension d. It is known that for p = λ*/n the k-core has a first-order phase transition in G(n,p) where λ* is the critical value for the k-core. The k-core is a global property of a graph. The k-core is the largest induced subgraph where each vertex has at least degree k. We suggest by simulations and a supportive proof that for the RGG-model a first-order phase transition not plausible. A inhomogeneous extension of the RGG-model with a vertex weight distribution T is a Geometric Inhomogeneous Random Graph model (GIRG). We also prove why some heavy-tailed (i.e. power-law) distributions almost surely have a k-core, when the amount of vertices v, which have weights greater than the square root of n, is greater than k. Furthermore, we rephrase from known literature how using a fixed equation for a branching process is a useful tool for analysing the existence of a k-core. In particular, the critical value for the 3-core is recovered using the probability of a binary tree embedding in branching processes, with the root having at least 3 children.Applied Mathematic
Salt priming improved salt tolerance in sweet sorghum by enhancing osmotic resistance and reducing root Na+ uptake
No full textThis study attempted to explore how salt priming affected salt tolerance in sweet sorghum with emphasis on root Na+ uptake. After 10 days of pretreatment with 150 mM NaCl, plants were stressed with 300 mM NaCl. After salt stress for 7 days, dry matter of root and shoot decreased by 58.7 and 69.7 % in non-pretreated plants and by 37.9 and 41.3 % in pretreated plants. Consistently, pretreated plants maintained higher photosynthetic rate during salt stress, suggesting the enhanced tolerance by salt priming. Salt priming enhanced osmotic resistance, as proline and relative water contents in the leaf were higher in pretreated plants under salt stress. Salt priming alleviated salt-induced oxidative damage not by improving antioxidant protection due to lower increase in leaf malondialdehyde content and no extra induction on ascorbate peroxidase, catalase, superoxide dismutase, ascorbic acid and reduced glutathione in pretreated plants. After 7 days of salt stress, root Na+ efflux increased by 8.5- and 3.9-folds in pretreated and non-pretreated plants, suggesting that salt priming reduced root Na+ uptake, and then root and leaf Na+ accumulation were mitigated in pretreated plants. However, root Na+ extrusion became indifferent between pretreated and non-pretreated plants under salt stress after inhibiting plasma membrane (PM) Na+/H+ antiporter. Thus, the greater Na+ extrusion induced by salt priming had relation to PM Na+/H+ antiporter. Overall, salt priming improved salt tolerance in sweet sorghum by enhancing osmotic resistance and reducing root Na+ uptake
Measurement of e(+) e(-) -> K+ K- cross section at root s=2.00-3.08 GeV
No full textOnur Buğra Kolcu (Arel Author)The cross section of the process e(+) e(-) -> K+ K- is measured at a number of center-of-mass energies root s from 2.00 to 3.08 GeV with the BESIII detector at the Beijing Electron Positron Collider (BEPCII). The results provide the best precision achieved so far. A resonant structure around 2.2 GeV is observed in the cross section line shape. A Breit-Wigner fit yields a mass of M = 2239.2 +/- 7.1 +/- 11.3 MeV/c(2) and a width of Gamma = 139.8 +/- 12.3 +/- 20.6 MeV, where the first uncertainties are statistical and the second ones are systematic. In addition, the timelike electromagnetic form factor of the kaon is determined at the individual center-of-mass energy points
On the Order of Convergence of a Determinantal Family of Root-finding Methods
No full textFor each natural number m greater than one, and each natural number k less than or equal to m, there exists a root-finding iteration function, dened as the ratio of two determinants that depend on the rst m k derivatives of the given function, and for k = 1 are Toeplitz determinants. In this paper we analyze the order of convergence of this fundamental family. For xed m, as k increases, the order decreases from m to the positive root of the characteristic polynomial of generalized Fibonacci numbers of order m. For xed k, the order increases in m. The asymptotic error constant is defined in terms of Toeplitz determinants. Newton's method, Halley's method, and their multipoint versions are members of the family.Technical report DCS-TR-32
Observation of the decay B+ -> psi(2S)phi(1020)K+ in pp collisions at root s=8 TeV
No full textThe decay B+ -> psi(2S) phi(1020) K+ is observed for the first time using data collected from pp collisions at root S = 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb(-1). The branching fraction of this decay is measured, using the mode B+ -> psi(2S) K+ as normalization, to be (4.0 +/- 0.4 (stat)+/- 0.6 (syst)+/- 0.2 (B)) x 10(-6), where the third uncertainty is from the measured branching fraction of the normalization channel. (C) 2016 The Author(s). Published by Elsevier B.V
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