Search results for "complex"
showing 10 items of 5889 documents
Nature log-analytique du volume des sous-analytiques
2000
Using a preparation theorem for subanalytic functions and Lipschitz stratification for compact subanalytic sets we prove that volumes of slices of globally subanalytic sets and density have a log-analytic nature. We also prove that the set of parameters for which the volume of fiber is finite is globally subanalytic.
Nonlocal Minimal Surfaces and Nonlocal Curvature
2019
Recall that if a set E has minimal local perimeter in a bounded set Ω, then it has zero mean curvature at each point of ∂E ∩ Ω (see [51]), and the equation that says that the curvature is equal to zero is the Euler–Lagrange equation associated to the minimization of the perimeter of a set.
Regression with Imputed Covariates: A Generalized Missing Indicator Approach
2011
A common problem in applied regression analysis is that covariate values may be missing for some observations but imputed values may be available. This situation generates a trade-off between bias and precision: the complete cases are often disarmingly few, but replacing the missing observations with the imputed values to gain precision may lead to bias. In this paper we formalize this trade-off by showing that one can augment the regression model with a set of auxiliary variables so as to obtain, under weak assumptions about the imputations, the same unbiased estimator of the parameters of interest as complete-case analysis. Given this augmented model, the bias-precision trade-off may then…
An Introduction to Computational Complexity
2016
This chapter is not strictly about algebra. However, this chapter offers a set of mathematical and computational instruments that will allow us to introduce several concepts in the following chapters. Moreover, the contents of this chapter are related to algebra as they are ancillary concepts that help (and in some cases allow) the understanding of algebra.
Setpoints compensation in industrial processes via multirate output feedback control
2013
This paper investigates the setpoints compensation for a class of complex industrial processes. Plants at the device layer are controlled by the local regulation controllers, and a multirate output feedback control approach for setpoint compensation is proposed such that the subsystems can reach the dynamically changed setpoints and the given economic objective can also be tracked via certain economic performance index (EPI). First, a sampled-data multivariable direct output feedback proportional integral (PI) controller is designed to regulate the performance of the subsystems. Second, the outputs and control inputs of the plants at the device layer are sampled at operation layer sampling …
Grassland fire effect on soil organic carbon reservoirs in a semiarid environment
2013
Abstract. The aim of this work was to investigate the effect of an experimental fire used for grassland management on soil organic carbon (SOC) stocks. The study was carried out on Hyparrhenia hirta (L.) Stapf (Hh) grassland and Ampelodesmos mauritanicus (Desf.) T. Durand & Schinz (Am) grasslands located in the north of Sicily. Soil samples were collected at 0–5 cm before and after the experimental fire, and SOC was measured. During the grassland fire, soil surface temperature was monitored. Biomass of both grasses was analysed in order to determine dry weight and its chemical composition. The results showed that SOC varied significantly with vegetation type, while it is not affecte…
Effects of Humic Substances and Soya Lecithin on the Aerobic Bioremediation of a Soil Historically Contaminated by Polycyclic Aromatic Hydrocarbons (…
2004
The high hydrophobicity of polycyclic aromatic hydrocarbons (PAHs) strongly reduces their bioavailability in aged contaminated soils, thus limiting their bioremediation. The biodegradation of PAHs in soils can be enhanced by employing surface-active agents. However, chemical surfactants are often recalcitrant and exert toxic effects in the amended soils. The effects of two biogenic materials as pollutant-mobilizing agents on the aerobic bioremediation of an aged-contaminated soil were investigated here. A soil historically contaminated by about 13 g kg(-1) of a large variety of PAHs, was amended with soya lecithin (SL) or humic substances (HS) at 1.5% w/w and incubated in aerobic solid-phas…
First assessment of the vermetid reefs along the coasts of Favignana Island (Southern Tyrrhenian Sea)
2015
Intertidal vermetid reefs, particularly vulnerable to environmental changes and human activities, are now experiencing high mortality in several areas of the Mediterranean Sea. Since the increase of knowledge on this habitat is important for conservation purposes, we provide a first baseline assessment of the vermetid reefs along the coasts of the Favignana Island (Marine Protected Area “Egadi Islands”). Preliminary results showed the presence of a true reef, similar to a fringing reef, displaying at least three local patterns, distinguishable for width (from 2.3 to 15.5 m), height of the outer and of the inner margin (from 5.6 to 18 cm and from 8.3 to 26 cm, respectively) and number, width…
Polymer aging affects the bioavailability of microplastics-associated contaminants in sea urchin embryos
2022
Microplastics (MPs) in the marine environment undergo complex weathering factors that can affect their ability to interact with different coexisting environmental contaminants (termed here co-contaminants). In this study, the influence of artificially aging using UV on the sorption of a complex mixture of co-contaminants onto MPs was investigated in order to provide meaningful hypotheses on their individual and combined toxicities on sea urchin embryos. A mixture of artificially aged MPs (PS particles and PA microfibers) combined with 2,2′ ,4,4′ - tetrabromodiphenyl ether (BDE-47), or Cd or Cu, both alone and in a mix, were used to expose embryos of Paracentrotus lividus. The effects of pol…
RESULTS OF DIFFERENT ANTHROPIC USES ON THE STRUCTURE OF VERMETID REEFS
2014
The biogenic vermetid reef is a key habitat of coastal ecosystems that modifies the shoreline morphology and increases the local biodiversity. Despite its ecological relevance, rarely it is subjected to an accurate management and is often exposed to several human activities. This study aims to distinguish between the effects of different typologies of anthropic uses on the physical structure of the vermetid reef. A comparison between totally protected, partially protected and strongly anthropized reefs has been done and two variables have been analysed: the substratum complexity and the density of reef-building organism. Both the variables show higher values in totally and partially protect…