999 research outputs found
Technical note: Design flood under hydrological uncertainty
Planning and verification of hydraulic infrastructures require a
design estimate of hydrologic variables, usually provided by frequency
analysis, and neglecting hydrologic uncertainty. However, when hydrologic
uncertainty is accounted for, the design flood value for a specific return
period is no longer a unique value, but is represented by a distribution of
values. As a consequence, the design flood is no longer univocally defined,
making the design process undetermined.
The Uncertainty Compliant Design Flood Estimation (UNCODE) procedure is a
novel approach that, starting from a range of possible design flood estimates
obtained in uncertain conditions, converges to a single design value. This is
obtained through a cost–benefit criterion with additional constraints that
is numerically solved in a simulation framework. This paper contributes to
promoting a practical use of the UNCODE procedure without resorting to
numerical computation. A modified procedure is proposed by using a correction
coefficient that modifies the standard (i.e., uncertainty-free) design value
on the basis of sample length and return period only. The procedure is robust
and parsimonious, as it does not require additional parameters with respect
to the traditional uncertainty-free analysis.
Simple equations to compute the correction term are provided for a number of
probability distributions commonly used to represent the flood frequency
curve. The UNCODE procedure, when coupled with this simple correction factor,
provides a robust way to manage the hydrologic uncertainty and to go beyond
the use of traditional safety factors. With all the other parameters being
equal, an increase in the sample length reduces the correction factor, and
thus the construction costs, while still keeping the same safety level
Affine actions on non-archimedean trees
We initiate the study of affine actions of groups on -trees for a
general ordered abelian group ; these are actions by dilations rather
than isometries. This gives a common generalisation of isometric action on a
-tree, and affine action on an -tree as studied by I. Liousse. The
duality between based length functions and actions on -trees is
generalised to this setting. We are led to consider a new class of groups:
those that admit a free affine action on a -tree for some .
Examples of such groups are presented, including soluble Baumslag-Solitar
groups and the discrete Heisenberg group.Comment: 27 pages. Section 1.4 expanded, typos corrected from previous versio
Sensor fault tolerant architecture for irrigation canals
10th Portuguese Conference on Automatic Control, 2012, Funchal, Portugalinfo:eu-repo/semantics/publishedVersio
C1q acts in the tumour microenvironment as a cancer-promoting factor independently of complement activation
Complement C1q is the activator of the classical pathway. However, it is now recognized that C1q can exert functions unrelated to complement activation. Here we show that C1q, but not C4, is expressed in the stroma and vascular endothelium of several human malignant tumours. Compared with wild-type (WT) or C3- or C5-deficient mice, C1q-deficient (C1qa(-/-)) mice bearing a syngeneic B16 melanoma exhibit a slower tumour growth and prolonged survival. This effect is not attributable to differences in the tumour-infiltrating immune cells. Tumours developing in WT mice display early deposition of C1q, higher vascular density and an increase in the number of lung metastases compared with C1qa(-/-) mice. Bone marrow (BM) chimeras between C1qa(-/-) and WT mice identify non-BM-derived cells as the main local source of C1q that can promote cancer cell adhesion, migration and proliferation. Together these findings support a role for locally synthesized C1q in promoting tumour growth
Nonlinear dynamic analysis of gas turbine combustor leaf seal
The leaf seals are one of the typical sealing systems in gas turbine and jet engines. In Baker Hughes LT family gas turbines, they are used to create sealing between the combustion chamber and the first stage nozzle. The leaf seals are thin metallic plates and subjected to dynamic loads and high temperatures. They have curved contacts, and depending on the inclination, they can experience partial contact. Furthermore, when excited by dynamic loads, the leaf seal can be subject to intermittent contact, possibly triggering wear out or vibratory phenomena. Due to its flexibility and its partial seating, it exhibits a complex nonlinear dynamic behaviour, strongly variable with the operating conditions. This study presents a numerical investigation using coupled static/dynamic harmonic balance method (HBM) frequency-based solution technique. The reported solutions include nonlinear forced response and contact studies for various operating and kinematic conditions along with brief insights
Model and Design of a Power Driver for Piezoelectric Stack Actuators
A power driver has been developed to control piezoelectric stack actuators used in automotive application. An FEM model of the actuator has been implemented starting from experimental characterization of the stack and mechanical and piezoelectric parameters. Experimental results are reported to show a correct piezoelectric actuator driving method and the possibility to obtain a sensorless positioning control
Data based modeling of a large scale water delivery system
Trabalho apresentado em 12th Portuguese Conference on Automatic Control, 2016, GuimarĂŁes, Portugalinfo:eu-repo/semantics/publishedVersio
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