49,260 research outputs found

    Location of leaks in pipelines using parameter identification tools

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    This work proposes an approach to locate leaks by identifying the parameters of finite models associated with these fault events. The identification problem is attacked by using well-known identification methods such as the Prediction Error Method and extended Kalman filters. In addition, a frequency evaluation is realized to check the conditions for implementing any method which require an excitation condition.Comment: This paper has some error

    On Chow Stability for algebraic curves

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    In the last decades there have been introduced different concepts of stability for projective varieties. In this paper we give a natural and intrinsic criterion of the Chow, and Hilbert, stability for complex irreducible smooth projective curves C⊂PnC\subset \mathbb P ^n. Namely, if the restriction TP∣CnT\mathbb P_{|C} ^n of the tangent bundle of Pn\mathbb P ^n to CC is stable then C⊂PnC\subset \mathbb P ^n is Chow stable, and hence Hilbert stable. We apply this criterion to describe a smooth open set of the irreducible component HilbChP(t),sHilb^{P(t),s}_{{Ch}} of the Hilbert scheme of Pn\mathbb{P} ^n containing the generic smooth Chow-stable curve of genus gg and degree d>g+n−⌊gn+1⌋.d>g+n-\left\lfloor\frac{g}{n+1}\right\rfloor. Moreover, we describe the quotient stack of such curves. Similar results are obtained for the locus of Hilbert stable curves.Comment: Minor corrections and improvements to presentation. We add Theorem 4.

    Genus and spot density in the COBE DMR first year anisotropy maps

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    A statistical analysis of texture on the {\it COBE}-DMR first year sky maps based on the genus and spot number is presented. A generalized χ2\chi^2 statistic is defined in terms of ``observable'' quantities: the genus and spot density that would be measured by different cosmic observers. This strategy together with the use of Monte Carlo simulations of the temperature fluctuations, including all the relevant experimental parameters, represent the main difference with previous analyses. Based on the genus analysis we find a strong anticorrelation between the quadrupole amplitude Qrms−PSQ_{rms-PS} and the spectral index nn of the density fluctuation power spectrum at recombination of the form Qrms−PS=22.2±1.7−(4.7±1.3)×n μQ_{rms-PS}= 22.2 \pm 1.7 - (4.7 \pm 1.3) \times n\ \muK for fixed nn, consistent with previous works. The result obtained based on the spot density is consistent with this Qrms−PS(n)Q_{rms-PS} (n) relation. In addition to the previous results we have determined, using Monte Carlo simulations, the minimum uncertainty due to cosmic variance for the determination of the spectral index with the genus analysis. This uncertainty is δn≈0.2\delta n\approx 0.2.Comment: 5 pages, uuencode file containing text and 1 figure. MNRAS in press

    KΛ(1405)K\Lambda(1405) configuration of the KKˉNK\bar{K}N system

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    We study the KΛ(1405)K\Lambda(1405) configuration of the KKˉNK\bar{K}N system by considering KπΣK\pi\Sigma as a coupled channel. We solve the Faddeev equations for these systems and find confirmation of the existence of a new N∗N^{*} resonance around 1920 MeV with Jπ=1/2+J^{\pi}=1/2^{+} predicted in a single-channel potential model and also found in a Faddeev calculation as an a0(980)Na_{0}(980)N state, with the a0(980)a_{0}(980) generated in the KKˉK\bar{K}, πη\pi\eta interaction.Comment: Published versio
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