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131.
Solà C Burgos M Plazuelo A Toja J Plans M Prat N 《The Science of the total environment》2004,333(1-3):109-126
In the 1998 Aznalcóllar mining accident, 5 million cubic meters of toxic waste were spilled into the Guadiamar River (SW Spain). This paper describes the likely effects of metal pollution on the macroinvertebrate community in the first 15 km of the river adjacent to the mine, 2 years after the spill. The contents of Zn, Cu, Pb, As, Cd, Tl, and Sb in water, sediment, and in the caddisfly Hydropsyche were analysed, together with some physico-chemical parameters. From the results of physico-chemical and community parameters, the studied area was divided into three sections: the first section contained upstream control stations, not affected by current mining activities, and with a diverse macroinvertebrate community structure (mean number of families = 19); the second section, close to the mine, was severely polluted, with more than 50 mg l(-1) of Zn or 1.6 mg l(-1) of Cu in water, a pH of nearly 4, and a very diminished macroinvertebrate community (three families); in the last section, 6-15 km downstream from the mine, the water quality improved, metal concentrations decreased, pH reached neutrality and the macroinvertebrate community comprised eight families. We also determined metal concentrations in the larvae of Hydropsyche and found increases of 3- to 35-fold (for Cu and Cd, respectively) compared to control sites. As far as we are aware, these values are the highest concentrations so far detected in this caddisfly anywhere in the world. Different patterns of metal and pH tolerance were identified in macroinvertebrates. Most of the species were intolerant to present pollution levels and were only present in control sites. Others were tolerant to metal pollution but not to low pH and were present in the main river downstream of the mine, while a very few species managed to live in the most polluted section, with very low pH and high metal concentrations. 相似文献
132.
Fernandez Pantoja M. Rubio Bretones A. Garcia Ruiz F. Garcia S.G. Gomez Martin R. 《Antennas and Propagation Magazine, IEEE》2007,49(4):34-47
This paper presents a short tutorial and overview of optimization algorithms based on particle-swarm schemes, and their application to solving electromagnetic problems. As a practical example, a particle-swarm optimization (PSO) tool has been applied in conjunction with the Numerical Electromagnetics Code (NEC) to get the design curves of optimized log-periodic dipole arrays (LPDAs). The graphs show the performance of several radiation parameters (directive gain, front-to-back ratio, bandwidth, SWR, and half-power beamwidth in the E and H planes) as a function of typical design parameters of log-periodic dipole arrays (geometrical parameters and characteristics of the feed). Examples of optimized antennas are given, and their performance is compared to that of standard log-periodic dipole arrays. 相似文献
133.
Leonardo Augusto dos Santos Vieira Sergio Fernando Mayerle Carolina Luisa dos Santos Vieira Mônica Maria Mendes Luna 《Optimization and Engineering》2016,17(4):761-780
Available productive capacity is determinant of a company’s success once it allows meeting the current and future demand. This article proposes a quantitative model for determining long-term productive capacity in competitive oligopolistic markets, based on the Nash Equilibrium formulated as a Variational Inequality problem. Numerical examples enable an analytical evaluation of the economic equilibrium’s sensitivity to marginal costs, investment costs, hurdle rate, and market saturation. Results show that, in order to achieve a greater market share, it is important to adopt strategies that reduce marginal costs. On the other hand, variations in the hurdle rate may or may not reinforce the position of a competitor in the market and his interest in investing in capacity expansion. Additionally, market saturation may be achieved, beyond which investment becomes unattractive. Each of these is a positive outcome for society, triggering diversified investments and competition in economic sectors where competition is low and profits are high. 相似文献
134.
P. Trivero B. Fiscella F. Gomez P. Pavese 《International journal of remote sensing》2013,34(3):543-548
In this paper we demonstrate SAR system capability for detecting and characterizing marine surface slicks. During an aircraft measurement campaign over the Gulf of Genoa (Italy), a multi-frequency SAR system, operating in P-, L- and C-bands, explored a sea area heavily covered by slicks. At the same time in situ measurements were performed with an interferential microwave probe, installed on board a small boat, capable of measuring high resolution sea spectra up to frequencies of capillary waves. By plotting SAR pixel intensity versus sea wave Bragg frequency we obtained wide portions of the sea spectrum region affected by the surface film damping. Spectra derived from SAR imagery and from gauge data present comparable slopes and furthermore the ratio between clean to slicked water spectrum obtained with the two techniques were surprisingly similar. This demonstrates the multi-frequency SAR systems ability to detect and characterize sea surface films assuming the Bragg mechanism in the radar backscatter. The outlined analysis suggests a simple methodology to monitor coastal water quality by using airborne SAR. 相似文献
135.
136.
This paper examines the problem of decoupling designs for linear multivariable systems. Both partial and diagonal decoupling designs are considered. The development is based on an algebraic approach and the use of coprime factorizations, which provide a mechanism to account for key system properties including internal stability and decoupling invariants. The results obtained include necessary and sufficient conditions for decoupling and a parametrization of all decoupling controllers. 相似文献
137.
The purpose of this paper is to analyse inherent design limitations associated with systems that are linear and periodically time-varying. The contributions of the paper are (i) to relate frequency domain raising methods from signal processing literature to time-domain lifting used in control literature, and (ii) to develop extensions of the Poisson sensitivity and complementary sensitivity integral constraints. In particular, it is shown that there is generally an additional cost associated with having a time invariant target closed loop for a periodic open loop plant. It is also shown that design limitations due to unstable poles and/or non-minimum phase zeros of a discrete linear time-invariant plant remain even if a periodic time-varying controller is used. As a consequence, the utility of periodic control in circumventing design limitations is questioned. 相似文献
138.
Sukumaran Minu Amba Shetty Cécile Gomez 《International journal of remote sensing》2013,34(22):8246-8270
ABSTRACTVisible near-infrared and shortwave infrared data acquired by spaceborne sensors contain atmospheric noise, along with target reflectance that may affect its end applications, e.g. geological, vegetation, soil surface studies, etc. Several atmospheric correction algorithms have been already developed to remove unwanted atmospheric components of a spectral signature of Earth targets obtained from airborne/spaceborne hyperspectral image. In spite of this, choosing of an appropriate atmospheric correction algorithm is an ongoing research. In this study, two hybrid atmospheric correction (HAC) algorithms incorporating a modified empirical line (ELm) method were proposed. The first HAC model (named HAC_1) combines (i) a radiative transfer (RT) model based on the concepts of RT equations, which uses real-time in situ atmospheric and climatic data, and (ii) an ELm technique. The second one (named HAC_2) combines (i) the well-known ATmospheric CORrection (ATCOR) model and (ii) an ELm technique. Both HAC algorithms and their component single atmospheric correction algorithms (ATCOR, RT, and ELm) were applied to radiance data acquired by Hyperion satellite sensor over study sites in Australia. The performances of both HAC algorithms were analysed in two ways. First, the Hyperion reflectances obtained by five atmospheric correction algorithms were analysed and compared using spectral metrics. Second, the performance of each atmospheric correction algorithm was analysed for prediction of soil organic carbon (SOC) using Hyperion reflectances obtained from atmospheric correction algorithms. The prediction model of SOC was built using partial least square regression model. The results show that (i) both the hybrid models produce a good spectrum with lower Spectral Angle Mapper and Spectral Information Divergence values and (ii) both hybrid algorithms provided better SOC prediction accuracy, in terms of coefficient of determination (R2), residual prediction deviation (RPD), and ratio of performance to interquartile (RPIQ), with R2 ≥ 0.75, RPD ≥ 2, and RPIQ ≥ 2.58 than single algorithms. HAC algorithms, developed using ELm technique, may be recommended for atmospheric correction of Hyperion radiance data, when archived Hyperion reflectance data have to be used for SOC prediction mapping. 相似文献
139.
Carolina Tallon Monika Limacher George V. Franks 《Journal of the European Ceramic Society》2010,30(14):2819-2826
The effect of the nanometric-ranged particle size of the starting powder through a simple and well-established shaping method, slip casting, has been studied. Several alumina suspensions with the same viscosity (but different solid content suspensions) and different particle size (11, 44, 190 and 600 nm) were prepared and shaped into a dense body. The green and sintered densities ranged between 30–67% and 63–99% of the theoretical value, respectively. These values, together with the microstructure observations reveal the effect of the solid content of the suspensions and the characteristics of the ceramic powder, leading to the determination of an optimal particle size. Based on both processability (rheological behaviour) and microstructure (density and grain size) it has been determined that particles with sizes ranging 100–300 nm are the best for preparing concentrated suspensions with low viscosity and bodies with density close to the theoretical value when using conventional pressureless sintering densification. 相似文献
140.
Ana C. Lo Prete Clederson H. Dina Carolina H. Azevedo Camila G. Puk Neuza H. M. Lopes Whady A. Hueb Raul Cavalcante Maranhão 《Lipids》2009,44(10):917-924
The exchange of lipids with cells and other lipoproteins is a crucial process in HDL metabolism and for HDL antiatherogenic
function. Here, we tested a practical method to quantify the simultaneous transfer to HDL of phospholipids, free-cholesterol,
esterified cholesterol and triacylglycerols and to verify the lipid transfer in patients with coronary artery disease (CAD)
or undergoing statin treatment. Twenty-eight control subjects without CAD, 27 with CAD and 25 CAD patients under simvastatin
treatment were studied. Plasma samples were incubated with a donor nanoemulsion prepared by ultrasonication of the constituent
lipids and labeled with radioactive lipids; % lipids transferred to HDL were quantified in the HDL-containing supernatant
after chemical precipitation of non-HDL fractions and the nanoemulsion. The assay was precise and reproducible. Increase of
temperature (4–37 °C), of incubation period (5 min to 2 h), of HDL-cholesterol concentration (33–244 mg/dL) and of mass of
nanoemulsion lipids (0.075–0.3 mg/μL) resulted in increased lipid transfer from the nanoemulsion to HDL. In contrast, increasing
pH (6.5–8.5) and albumin concentration (3.5–7.0 g/dL) did not affect lipid transfer. There was no difference between CAD and
control non-CAD with regard to the lipid transfer, but statin treatment reduced the transfer to HDL of all four lipids. The
test herein described is a valid and practical tool for exploring an important aspect of HDL metabolism. 相似文献