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31.
Taguchi method is the usual strategy in robust design and involves conducting experiments using orthogonal arrays and estimating the combination of factor levels that optimizes a given performance measure, typically a signal-to-noise ratio. The problem is more complex in the case of multiple responses since the combinations of factor levels that optimize the different responses usually differ. In this paper, an Artificial Neural Network, trained with the experiments results, is used to estimate the responses for all factor level combinations. After that, Data Envelopment Analysis (DEA) is used first to select the efficient (i.e. non-dominated) factor level combinations and then for choosing among them the one which leads to a most robust quality loss penalization. Mean Square Deviations of the quality characteristics are used as DEA inputs. Among the advantages of the proposed approach over traditional Taguchi method are the non-parametric, non-linear way of estimating quality loss measures for unobserved factor combinations and the non-parametric character of the performance evaluation of all the factor combinations. The proposed approach is applied to a number of case studies from the literature and compared with existing approaches. 相似文献
32.
33.
Vincenzo Ferone Ester Giarrusso Basilio Messano M. Rosaria Posteraro 《Calculus of Variations and Partial Differential Equations》2013,46(3-4):749-768
In this paper we deal with blow-up solutions to an elliptic equation with a nonlinear gradient term. The problem under consideration can be seen as the ergodic limit of a stochastic control problem with state constraints. It is well known that it has a solution only when a parameter which appears in the equation assumes a particular value known as ergodic constant. For such a constant many properties similar to those of an eigenvalue hold true. We show that a Faber–Krahn inequality can be stated for the ergodic constant and that for the corresponding solution a comparison result in terms of the solution to a symmetrized problem can be proved. 相似文献
34.
In this paper, a directional distance approach is proposed to deal with network DEA problems in which the processes may generate not only desirable final outputs but also undesirable outputs. The proposed approach is applied to the problem of modelling and benchmarking airport operations. The corresponding network DEA model considers two process (Aircraft Movement and Aircraft Loading) with two final outputs (Annual Passenger Movement and Annual Cargo handled), one intermediate product (Aircraft Traffic Movements) and two undesirable outputs (Number of Delayed Flights and Accumulated Flight Delays). The proposed approach has been applied to Spanish airports data for year 2008 comparing the computed directional distance efficiency scores with those obtained using a conventional, single-process directional distance function approach. From this comparison, it can be concluded that the proposed network DEA approach has more discriminatory power than its single-process counterpart, uncovering more inefficiencies and providing more valid results. 相似文献
35.
36.
We consider the asymptotic method designed by Olver (Asymptotics and special functions. Academic Press, New York, 1974) for linear differential equations of the second order containing a large (asymptotic) parameter \(\Lambda \): \(x^my''-\Lambda ^2y=g(x)y\), with \(m\in \mathbb {Z}\) and g continuous. Olver studies in detail the cases \(m\ne 2\), especially the cases \(m=0, \pm 1\), giving the Poincaré-type asymptotic expansions of two independent solutions of the equation. The case \(m=2\) is different, as the behavior of the solutions for large \(\Lambda \) is not of exponential type, but of power type. In this case, Olver’s theory does not give many details. We consider here the special case \(m=2\). We propose two different techniques to handle the problem: (1) a modification of Olver’s method that replaces the role of the exponential approximations by power approximations, and (2) the transformation of the differential problem into a fixed point problem from which we construct an asymptotic sequence of functions that converges to the unique solution of the problem. Moreover, we show that this second technique may also be applied to nonlinear differential equations with a large parameter. 相似文献
37.
Guimarães RL Lima DJ Barros ME Cavalcanti LN Hallwass F Navarro M Bieber LW Malvestiti I 《Molecules (Basel, Switzerland)》2007,12(9):2089-2105
The aqueous tin-mediated Barbier reaction affords good to excellent yields and moderate syn diastereoselectivity under basic and acidic conditions. The high yields and stereoselectivity observed in the case of o-substituted aldehydes suggest a cyclic organotin intermediate or transition state in K2HPO4 solution. A practical and efficient aqueous tin allylation of methoxy- and hydroxybenzaldehydes can be carried out in HCl solution in 15 minutes to afford the corresponding homoallylic alcohols in high yields. Aliphatic aldehydes give moderate to excellent yields with reaction times ranging from 30 to 60 minutes. Under these conditions, crotylation gives exclusively the gamma-product and the syn isomer is formed preferentially. For 2-methoxybenzaldehyde, an equilibration of the isomers to a syn/anti ratio of 1:1 can be observed after several hours. Control experiments with radical sources or scavengers give no support for radical intermediates. NMR studies suggest a mechanism involving an organotin intermediate. The major organotin species formed depends on the reaction medium and the reaction time. The use of acidic solution reduces the reaction times, due to the acceleration of the formation of the allyltin(IV) species. 相似文献
38.
Consumption of non-steroidal anti-inflammatory drugs (NSAIDs) is increasing and with it the danger of environmental pollution
by pharmaceutical residues. Publications regarding NSAIDs in the environment not only show that they are toxic to many animal
species, but also highlight the need for robust analytical methods for monitoring the level of such contaminants in environmental
matrices. In our study we selected the four most widely used NSAIDs in Slovenia and Central Europe, ibuprofen, naproxen, ketoprofen
and diclofenac, and studied their extraction from sediment samples. We examined several extraction techniques (ultrasonic
extraction, Soxhlet extraction, pressurized liquid extraction, supercritical fluid extraction and microwave-assisted extraction)
using a spiked sediment sample and determined optimal extraction conditions. After extraction we applied a clean-up step,
derivatisation of the analytes and gas chromatography with mass spectrometric detection (GC-MSD) and selected the most appropriate
extraction procedure. The optimised analytical method chosen for analysis of sediment samples consisted of microwave-assisted
extraction, clean-up of the extract with SPE, derivatisation with MSTFA and determination with GC-MSD. The optimised procedure
was applied to the analysis of two environmental river samples taken from the vicinity of Novo mesto, the biggest town in
the south eastern part of Slovenia with 62,000 inhabitants, a hospital and a pharmaceutical factory in its vicinity. While
analysis of the sample taken upstream of the town showed no detectable amounts of NSAIDs, analysis of samples taken downstream
showed quantifiable levels of two of the studied NSAIDs (naproxen and ketoprofen). Besides these two NSAIDs, river water samples
sampled at the same time and location on the River Krka also showed the presence of diclofenac. Sampling on the River Krka
and other Slovene rivers will in the future be repeated at different sampling points in order to track down the main sources
of pollution. 相似文献
39.
Concern is growing over the contamination of the environment with pharmaceutical residues, among which non-steroidal anti-inflammatory
drugs (NSAIDs) are one of the most abundant groups. Their widespread appearance in the aquatic environment is because of their
high consumption and their incomplete removal during wastewater treatment. Because effective operation of wastewater-treatment
plants is important for minimising the release of xenobiotic compounds, for example pharmaceutical products, into the aquatic
environment, our study focuses on removal of commonly used NSAIDs (ibuprofen, naproxen, ketoprofen, diclofenac) and clofibric
acid in a specially designed small-scale pilot wastewater treatment plant (PWWTP). This study shows that, except for diclofenac,
steady-rate removal of NSAIDs over a two-year monitoring period has been achieved. Elimination of the compounds in the PWWTP
was ≥87% for ibuprofen, naproxen and ketoprofen but only 49–59% for diclofenac. We also studied clofibric acid. Results after
one month of operation revealed 30% elimination with no sign of adaptation by the biomass. Also described are degradation
products of diclofenac, which we were able to identify because of the similarity of their mass spectra with those in the NIST
library and by comparing the retention times of different compounds. Although the structures of these compounds were confirmed
with a high probability (99%), we still need to compare the fragmentation of authentic compounds with degradation products
formed under our experimental conditions. Degradation products of ibuprofen, naproxen, ketoprofen, and clofibric acid were
found but these must be identified by use of high-resolution mass spectrometry and analysis of authentic compounds. 相似文献
40.
León IR Neves-Ferreira AG Valente RH Mota EM Lenzi HL Perales J 《Journal of mass spectrometry : JMS》2007,42(10):1363-1374
Matrix-assisted laser desorption ionization (MALDI), Peptide Mass Fingerprinting (PMF) and MALDI-MS/MS ion search (using MASCOT) have become the preferred methods for high-throughput identification of proteins. Unfortunately, PMF can be ambiguous, mainly when the genome of the organism under investigation is unknown and the quality of spectra generated is poor and does not allow confident identification. The post-source decay (PSD) fragmentation of singly charged tryptic peptide ions generated by MALDI-TOF/TOF typically results in low fragmentation efficiency and/or complex spectra, including backbone fragmentation ions (series b and y), internal fragmentation etc. Interpreting these data either manually and/or using de novo sequencing software can frequently be a challenge. To overcome this limitation when studying the proteome of adult Angiostrongylus costaricensis, a nematode with unknown genome, we have used chemical N-terminal derivatization of the tryptic peptides with 4-sulfophenyl isothiocyanate (SPITC) prior to MALDI-TOF/TOF MS. This methodology has recently been reported to enhance the quality of MALDI-TOF/TOF-PSD data, allowing the obtainment of complete sequence of most of the peptides and thus facilitating de novo peptide sequencing. Our approach, consisting of SPITC derivatization along with manual spectra interpretation and Blast analysis, was able to positively identify 76% of analyzed samples, whereas MASCOT analysis of derivatized samples, MASCOT analysis of nonderivatized samples and PMF of nonderivatized samples yielded only 35, 41 and 12% positive identifications, respectively. Moreover, de novo sequencing of SPITC modified peptides resulted in protein sequences not available in NCBInr database paving the way to the discovery of new protein molecules. 相似文献