140,757 research outputs found
Corrigendum to “Reliability assessment of generic geared wind turbines by GTST-MLD model and Monte Carlo simulation” (Renewable Energy (2015) 83 (222–233), (S0960148115003158), (10.1016/j.renene.2015.04.035))
No full textThe authors regret that the Order of Authors in this article published in November 2015 is incorrect. Thus, the objective of this Corrigendum is to re-establish the originally agreed Order of Authors, as described below. Order of Authors from published Article: Yan-Fu Li, PhD; Sebastien Valla; Enrico Zio, PhD. Corrected Order of Authors to implement with this Corrigendum: Sebastien Valla, Yan-Fu Li, PhD; Enrico Zio, PhD. The Corresponding author to contact for these changes are the Primary Author, Sebastien Valla (email below). The authors would like to apologise for any inconvenience caused
Li–Yorke and distributionally chaotic operators
No full textWe study Li-Yorke chaos and distributional chaos for operators on Banach spaces. More precisely, we characterize Li-Yorke chaos in terms of the existence of irregular vectors. Sufficient "computable" criteria for distributional and Li-Yorke chaos are given, together with the existence of dense scrambled sets under some additional conditions. We also obtain certain spectral properties. Finally, we show that every infinite dimensional separable Banach space admits a distributionally chaotic operator which is also hypercyclic. © 2010 Elsevier Inc.The second author is supported in part by MEC and FEDER, Project MTM2008-05891. The third and fourth authors are supported in part by MEC and FEDER, Projects MTM2007-64222, MTM2010-14909 and by Generalitat Velenciana. Project PROMETEO/2008/101. We want to thank the referee for the suggestions.Bermúdez, T.; Bonilla, A.; Martínez Jiménez, F.; Peris Manguillot, A. (2011). Li–Yorke and distributionally chaotic operators. Journal of Mathematical Analysis and Applications. 373:83-93. https://doi.org/10.1016/j.jmaa.2010.06.011S839337
Reliability Analysis, Safety Assessment and Optimization: Methods and Applications in Energy Systems and Other Applications
No full textThis book offers a comprehensive overview of recently developed methods for assessing and optimizing system reliability. It consists of two main parts, for treating assessment methods and optimization methods, respectively. The first part covers methods of multi-state system reliability modelling and evaluation, Markov processes, Monte Carlo simulation and uncertainty analysis. The methods considered range from piecewise-deterministic Markov processes to belief function analysis. The second part covers optimization methods of mathematical programming and evolutionary algorithms, and problems of multi-objective optimization and optimization under uncertainty. The methods of this part range from non-dominated sorting genetic algorithm to robust optimization. The book also includes the application of the assessment and optimization methods considered on real case studies, particularly with respect to the reliability assessment and optimization of renewable energy systems, and bridges the gap between theoretical method development and engineering practice
Visual and olfactory preferences of Frankliniella occidentalis (Thysanoptera: Thripidae) for color and volatiles of different Rosa chinensis (Rosales: Rosaceae) cultivars
No full textThe free choice of Frankliniella occidentalis to the paper color simu- lative to Rosa chinensis cultivars (Ruby, Love,Parade,Mohana, Pink Peace, and Spectra) was tested in Petri dishes, and their behavioral responses to the volatiles of different these R. chinensis cultivars was tested in a Y-tube olfactometer. The results showed that F. occiden- talis exhibited color preference for yellow (Mohana ≈ Spectra) > red (Ruby ≈ Love) > pink (Parade ≈ Pink Peace), whereas the preference for plant flower volatiles was Ruby > Love > Parade > Mohana > Pink Peace > Spectra. Gas chromatography mass spectrometry analysis showed that benzeneethanol was the single most abundant compo- nent in the volatile profiles of Ruby, Love, and Mohana, with contents of 37.03, 25.25, and 33.13%, respectively. (Z)-3-Hexenyl acetate was the most abundant component in the volatile profiles of Parade and Spectra, with contents of 39.87 and 22.62%, respectively. Geraniol (16.07%) was the most abundant component of the Pink Peace volatiles. Therefore, future mitigation approaches, e.g., color sticky traps or/and attractants, could be still used for the key monitoring and control of F. occidentalis on a particular cultivar when different varieties of certain crops were grown together on a large scale
Drag reduction in a turbulent boundary layer using periodic blowing through one array of streamwise slits
No full textActive drag reduction of a turbulent boundary layer has been experimentally investigated using periodic blowing through one array of streamwise slits. Local skin-friction drag exhibits a strong dependence on control parameters, including the blowing amplitude A+ and frequency f +. A maximum drag reduction of almost 70% has been achieved at x+=33 downstream of the actuators. The near-wall structure under control are measured using smoke-wire flow visualization, hot-wire and PIV techniques. All the results point to a pronounced change in the structure of the boundary layer and a significant increase of the mean energy dissipation rate
The generalized Liénard polynomial differential systems x'=y,y'= -g(x) - f (x)y with deg g = deg f 1 are not Liouvillian integrable
No full textAgraïments: The second author was supported by Portuguese National Funds through FCT - Fundação para a Ciência e a Tecnologia within the project PTDC/MAT/117106/2010 and by CAMGSD (PEst-OE/EEI/LA0009/2013)We prove the nonexistence of Liouvillian first integrals for the generalized Li\'enard polynomial differential systems of the form x' = y, y'=-g(x)-f(x)y, where g(x) and f(x) are arbitrary polynomials such that g = f 1
A Study of the Thermodynamics and Kinetics of LiₓFePO₄ as a Cathode Material for Li Batteries
No full textOlivine-type LiFePO4 has been recognized as one of the most promising cathode materials for rechargeable Li batteries. Its advantages include high capacity, high stability, nontoxicity, and low cost. Our methods for synthesizing nanocrystalline LixFePO4 with the olivine structure are described. Solid-state reactions and precipitation reactions were both successful, and ball milling was especially effective at reducing crystallite sizes. Diffractometry and microscopy were used to characterize these materials, and results of impurity phases, excess Fe3+, and internal stresses are reported for the different types of synthesis.
Applications of lithium-ion batteries, including automotive applications, require fast kinetics and high conductivity of ions and electrons. Unfortunately, LixFePO4 has the electronic structure of an insulator, an entirely unsatisfactory situation if it is to be used as a battery electrode. Electrical conductivity in LixFePO4 occurs by the motion of small polarons, which are valence electrons at Fe atoms plus their distorted local environments. Electrical conductivity of LixFePO4 is interpreted in terms of small polaron hopping. There are other factors of importance in these measurements, such as impurities or defects that block the one-dimensional conduction channels of the olivine structure of LixFePO4.
We studied the polaron hopping directly, which allows us to understand the intrinsic electrical conductivity, and how it depends on microstructure and composition of LixFePO4. The experimental technique was Mossbauer spectrometry, which has been used for many years as a means for determining the fractions of Fe2+ and Fe3+ in a material. Usually the spectral signatures of Fe2+ and Fe3+ are distinct. When valence electrons hop between Fe2+ and Fe3+ at a frequency of 108 Hz or higher, however, the valence changes during the timescale of the Mossbauer measurement and the spectrum is blurred. By measuring Mossbauer spectra at elevated temperatures, we can determine the fractions of Fe atoms participating in polaron hopping, and determine the activation energy of the process. From this we estimate intrinsic electrical conductivities of 10-7S/cm at room temperature for nanocrystalline Li0.5FePO4, for example. We find a comparable conductivity for LixFePO4 prepared as a solid solution, but the conductivity of conventional LixFePO4 is much lower.
There has been much discussion about how surface area might thermodynamically stabilize the solid solution phase of nanocrystalline LixFePO4. In a series of X-ray diffraction measurements, some at elevated temperatures, we found the solid solution phase of LixFePO4 to be especially robust at room temperature when the material was prepared in nanocrystalline form. Moreover, the consistent phase transition temperature around 200°C was observed, as evidence for the unchanged equilibrium phase diagram by crystallite size. This is consistent with our evaluation on the boundaries of the two-phase mixture of triphylite and heterosite during Li insertion and extraction. Profiles of entropy and enthalpy changes were evaluated by open-circuit voltage measurements. The boundaries were found at x=0.05 and 0.95 in the LixFePO4 with crystal size of 70 nm, similar to the reported values on bulk-LixFePO4. These are important in practice, because electrochemical lithiation and delithiation at room temperature should remain as a two-phase transformation, even if a solid solution of lithium is present in the initial electrode material.</p
The generalized Liénard polynomial differential systems x'=y,y'= -g(x) - f (x)y with deg g = deg f 1 are not Liouvillian integrable
No full textAgraïments: The second author was supported by Portuguese National Funds through FCT - Fundação para a Ciência e a Tecnologia within the project PTDC/MAT/117106/2010 and by CAMGSD (PEst-OE/EEI/LA0009/2013)We prove the nonexistence of Liouvillian first integrals for the generalized Li\'enard polynomial differential systems of the form x' = y, y'=-g(x)-f(x)y, where g(x) and f(x) are arbitrary polynomials such that g = f 1
Interfacial “Single-Atom-in-Defects” Catalysts Accelerating Li+ Desolvation Kinetics for Long-Lifespan Lithium-Metal Batteries
No full textThe lithium-metal anode is a promising candidate for realizing high-energy-density batteries owing to its high capacity and low potential. However, several rate-limiting kinetic obstacles, such as the desolvation of Li+ solvation structure to liberate Li+, Li0 nucleation, and atom diffusion, cause heterogeneous spatial Li-ion distribution and fractal plating morphology with dendrite formation, leading to low Coulombic efficiency and depressive electrochemical stability. Herein, differing from pore sieving effect or electrolyte engineering, atomic iron anchors to cation vacancy-rich Co1−xS embedded in 3D porous carbon (SAFe/CVRCS@3DPC) is proposed and demonstrated as catalytic kinetic promoters. Numerous free Li ions are electrocatalytically dissociated from the Li+ solvation complex structure for uniform lateral diffusion by reducing desolvation and diffusion barriers via SAFe/CVRCS@3DPC, realizing smooth dendrite-free Li morphologies, as comprehensively understood by combined in situ/ex situ characterizations. Encouraged by SAFe/CVRCS@3DPC catalytic promotor, the modified Li-metal anodes achieve smooth plating with a long lifespan (1600 h) and high Coulombic efficiency without any dendrite formation. Paired with the LiFePO4 cathode, the full cell (10.7 mg cm−2) stabilizes a capacity retention of 90.3% after 300 cycles at 0.5 C, signifying the feasibility of using interfacial catalysts for modulating Li behaviors toward practical applications
- …
