In this paper, inspired from our previous algorithm, which was
based on the theory of Tsallis statistical mechanics, we develop a
new evolving stochastic learning algorithm for neural networks.
The new algorithm combines deterministic and stochastic search
steps by employing a different adaptive stepsize for each network
weight, and applies a form of noise that is characterized by the
nonextensive entropic index q, regulated by a weight decay term.
The behavior of the learning algorithm can be made more stochastic
or deterministic depending on the trade off between the
temperature T and the q values. This is achieved by
introducing a formula that defines a time-dependent relationship
between these two important learning parameters. Our experimental
study verifies that there are indeed improvements in the
convergence speed of this new evolving stochastic learning
algorithm, which makes learning faster than using the original
Hybrid Learning Scheme (HLS). In addition, experiments are
conducted to explore the influence of the entropic index q and
temperature T on the convergence speed and stability of the
proposed method. 相似文献
Two types of Equations of State (EoS), which are characterized here as “simple” and “complex” EoS, are evaluated in this study. The “simple” type involves two versions of the Peng–Robinson (PR) EoS: the traditional one that utilizes the experimental critical properties and the acentric factor and the other, referred to as PR-fitted (PR-f), where these parameters are determined by fitting pure compound vapor pressure and saturated liquid volume data. As “complex” EoS in this study are characterized the EoS derived from statistical mechanics considerations and involve the Sanchez–Lacombe (SL) EoS and two versions of the Statistical Associating Fluid Theory (SAFT) EoS, the original and the Perturbed-Chain SAFT (PC-SAFT).
The evaluation of these two types of EoS is carried out with respect to their performance in the prediction and correlation of vapor liquid equilibria in binary and multicomponent mixtures of methane or ethane with alkanes of various degree of asymmetry. It is concluded that for this kind of systems complexity offers no significant advantages over simplicity. Furthermore, the results obtained with the PR-f EoS, especially those for multicomponent systems that are encountered in practice, even with the use of zero binary interaction parameters, indicate that this EoS may become a powerful tool for reservoir fluid phase equilibria modeling. 相似文献
Microalgae are well-known for their high-added value compounds and their recovery is currently of great interest. The aim of this work is the recovery of such components from Chlorella vulgaris through supercritical fluid extraction (SFE) with CO2. The effect of the extraction temperature (40–60 °C), pressure (110–250 bar), and solvent flow rate (20–40 g/min) was tested on yield, the extract’s antioxidant activity, and the phenolic, chlorophyll and carotenoid content. Thus, data analysis indicated that the yield was mainly affected by temperature, carotenoids by pressure, while the extract’s phenolics and antioxidant activity were affected by the synergy of temperature and pressure. Moreover, SFE’s kinetic study was performed and experimental data were correlated using Sovová’s mass transfer-based model. SFE optimization (60 °C, 250 bar, 40 g/min) led to 3.37% w/w yield, 44.35 mgextr/mgDPPH antioxidant activity (IC50), 18.29 mgGA/gextr total phenolic content, 35.55, 21.14 and 10.00 mg/gextr total chlorophyll, carotenoid and selected carotenoid content (astaxanthin, lutein and β-carotene), respectively. A comparison of SFE with conventional aq. ethanol (90% v/v) extraction proved SFE’s superiority regarding extraction duration, carotenoids, antioxidant activity and organoleptic characteristics of color and odor despite the lower yield. Finally, cosolvent addition (ethanol 10% w/w) at optimum SFE conditions improved the extract’s antioxidant activity (19.46%) as well as yield (101.81%). 相似文献
Analytical work, especially for environmental purposes, involves in the typical case determination of organic compounds in
compartments, where their presence is very small. Identification of the appropriate experimental technique, whose range of
applicability covers the concentration value involved, requires an estimate of this value. To this purpose, we present in
this study a methodology for the prediction of the concentration of organic pollutants in the various environmental compartments
(aquatic biota, air, sediment and soil) from the knowledge of the concentration in one of them. In case where the pollutant’s
concentration is not available for any of the compartments, the proposed methodology can be used to estimate the maximum expected
concentration in each one of them assuming that the water phase is saturated with the pollutant. The latter value can be obtained
from a simple correlation presented here.
The methodology is based on the correlation of the partition coefficients of pollutants among the various environmental compartments
with two important thermodynamic quantities of pollutants: the octanol/water partition coefficient and the Henry’s law coefficient,
which can be easily predicted by simple models presented here. Application of the methodology to field experimental data gives
very satisfactory results at least for identifying the appropriate experimental technique. 相似文献
In this paper we propose a nonmonotone approach to recurrent neural networks training for temporal sequence processing applications. This approach allows learning performance to deteriorate in some iterations, nevertheless the network’s performance is improved over time. A self-scaling BFGS is equipped with an adaptive nonmonotone technique that employs approximations of the Lipschitz constant and is tested on a set of sequence processing problems. Simulation results show that the proposed algorithm outperforms the BFGS as well as other methods previously applied to these sequences, providing an effective modification that is capable of training recurrent networks of various architectures. 相似文献
The narrow escape problem consists in deriving the asymptotic expansion of the solution of a drift-diffusion equation with the Dirichlet boundary condition on a small absorbing part of the boundary and the Neumann boundary condition on the remaining reflecting boundaries. Using layer potential techniques, we rigorously find high-order asymptotic expansions of such solutions. The asymptotic formula explicitly exhibits the nonlinear interaction of many small absorbing targets. Based on the asymptotic theory for eigenvalue problems developed in Ammari et al. (2009) [3], we also construct high-order asymptotic formulas for the perturbation of eigenvalues of the Laplace and the drifted Laplace operators for mixed boundary conditions on large and small pieces of the boundary. 相似文献
A library of seventeen novel ether phospholipid analogues, containing 5-membered heterocyclic rings (1,2,3-triazolyl, isoxazolyl, 1,3,4-oxadiazolyl and 1,2,4-oxadiazolyl) in the lipid portion were designed and synthesized aiming to identify optimised miltefosine analogues. The compounds were evaluated for their in vitro antiparasitic activity against Leishmania infantum and Leishmania donovani intracellular amastigotes, against Trypanosoma brucei brucei and against different developmental stages of Trypanosoma cruzi. The nature of the substituents of the heterocyclic ring (tail) and the oligomethylene spacer between the head group and the heterocyclic ring was found to affect the activity and toxicity of these compounds leading to a significantly improved understanding of their structure–activity relationships. The early ADMET profile of the new derivatives did not reveal major liabilities for the potent compounds. The 1,2,3-triazole derivative 27 substituted by a decyl tail, an undecyl spacer and a choline head group exhibited broad spectrum antiparasitic activity. It possessed low micromolar activity against the intracellular amastigotes of two L. infantum strains and T. cruzi Y strain epimastigotes, intracellular amastigotes and trypomastigotes, while its cytotoxicity concentration (CC50) against THP-1 macrophages ranged between 50 and 100 μM. Altogether, our work paves the way for the development of improved ether phospholipid derivatives to control neglected tropical diseases. 相似文献
We report on the fabrication of porous hot-wire deposited WOx (hwWOx) films with omnidirectional antireflective properties coming from in-depth variation of both (i) void fraction from 0% at the Si substrate/hwWOx interface to 30% within less than 7 nm and to higher than 50% at the hwWOx/air interface, and (ii) x, namely hwWOx stoichiometry, from 2.5 at the Si/hwWOx to 3 within less than 7 nm. hwWOx films were deposited by means of hw deposition at rough vacuum and controlled chamber environment. The films were analyzed by Spectroscopic Ellipsometry to extract the graded refractive index profile, which was then used in a rigorous coupled wave analysis (RCWA) model to simulate the antireflective properties. RCWA followed reasonably the experimental reflection measurements. Void fraction and x in-depth variation, controlled by the hw process, greatly affect the antireflective properties, and improve the omnidirectional and broadband characteristics. The reflection suppression below 10% within the range of 500-1000 nm for angles of incidence up to more than 60° is demonstrated. 相似文献