12,024 research outputs found
Pairs of Noncrossing Free Dyck Paths and Noncrossing Partitions
Using the bijection between partitions and vacillating tableaux, we establish
a correspondence between pairs of noncrossing free Dyck paths of length
and noncrossing partitions of with blocks. In terms of the
number of up steps at odd positions, we find a characterization of Dyck paths
constructed from pairs of noncrossing free Dyck paths by using the Labelle
merging algorithm.Comment: 9 pages, 5 figures, revised version, to appear in Discrete
Mathematic
A refined invariant subspace method and applications to evolution equations
The invariant subspace method is refined to present more unity and more
diversity of exact solutions to evolution equations. The key idea is to take
subspaces of solutions to linear ordinary differential equations as invariant
subspaces that evolution equations admit. A two-component nonlinear system of
dissipative equations was analyzed to shed light on the resulting theory, and
two concrete examples are given to find invariant subspaces associated with
2nd-order and 3rd-order linear ordinary differential equations and their
corresponding exact solutions with generalized separated variables.Comment: 16 page
Determination of alkylamine carbonate nonionic-anion oil displacement agent in oil-field water using HPLC after derivatization with 4- methoxybenzenesulfonyl fluoride
In this study, a method for the determination of alkylamine carbonate (AAC) nonionic-anion oil displacement agent in oil-field water was developed for the first time, involving pre-column derivatization using a novel labeling agent and HPLC with diode-array detection. The derivatization and chromatographic separation conditions were investigated thoroughly. The analyte was labeled with 4-methoxybenzenesulfonyl fluoride at 50 °C for 20 min. When the method was applied in the determination of C18A5C (an AAC oil displacement agent containing eighteen alkyl and five amino groups) a linear calibration curve was obtained from 1.0 to 100.0 μg mL-1 with a correlation coefficient of more than 0.999 and a detection limit of 0.05 μg mL-1. In the determination of real oil-field water samples, the recovery range of C18A5C was 91.8% to 96.2%, and the intra-day and inter-day relative standard deviations were 2.9-3.5% and 3.8-4.3%, respectively. The experimental results demonstrate that this method, with its merits of simplicity in pretreatment, rapidity in derivatization, and stability of the derivatives, can be employed in the analysis of C18A5C and has potential application in the detection of other oil displacement surfactants containing amino groups. It is of great significance to develop a fast, easy-to-operate, sensitive and reliable method for environmental impact assessment. © The Royal Society of Chemistry 2013
An advanced fuzzy Bayesian-based FMEA approach for assessing maritime supply chain risks
This paper aims to develop a novel model to assess the risk factors of maritime supply chains by incorporating a fuzzy belief rule approach with Bayesian networks. The new model, compared to traditional risk analysis methods, has the capability of improving result accuracy under a high uncertainty in risk data. A real case of a world leading container shipping company is investigated, and the research results reveal that among the most significant risk factors are transportation of dangerous goods, fluctuation of fuel price, fierce competition, unattractive markets, and change of exchange rates in sequence. Such findings will provide useful insights for accident prevention
Facile Fabrication of Superhydrophobic Surface from Fluorinated POSS Acrylate Copolymer via One-Step Breath Figure Method and Its Anti-Corrosion Property
Novel fluorinated polyhedral oligomeric silsesquioxane (POSS) acrylic copolymers were synthesized by the radical solution polymerization. The superhydrophobic coating was prepared using a one-step breath figure method. Chemical constitution, morphology, hydrophobicity, and anticorrosion ability of as-prepared coatings were investigated by the corresponding equipment. The addition of proper fluorinated POSS can synchronously promote the formation of the micro-nano convex structure and the enrichment of fluorinated groups on the surface. Compared to commercial acrylic coating, the fluorinated POSS coating presented enhanced anticorrosion performance. The impedance was the highest and the corrosion current density was the lowest for superhydrophobic coating with 25 wt % fluorinated POSS.</jats:p
Anomalous thermoelectric effects of ZrTe in and beyond the quantum limit
Thermoelectric effects are more sensitive and promising probes to topological
properties of emergent materials, but much less addressed compared to other
physical properties. Zirconium pentatelluride (ZrTe) has inspired active
investigations recently because of its multiple topological nature. We study
the thermoelectric effects of ZrTe in a magnetic field and find several
anomalous behaviors. The Nernst response has a steplike profile near zero field
when the charge carriers are electrons only, suggesting the anomalous Nernst
effect arising from a nontrivial profile of Berry curvature. Both the
thermopower and Nernst signal exhibit exotic peaks in the strong-field quantum
limit. At higher magnetic fields, the Nernst signal has a sign reversal at a
critical field where the thermopower approaches to zero. We propose that these
anomalous behaviors can be attributed to the Landau index inversion, which is
resulted from the competition of the dependence of the Dirac-type
Landau bands and linear- dependence of the Zeeman energy ( is the
magnetic field). Our understanding to the anomalous thermoelectric properties
in ZrTe opens a new avenue for exploring Dirac physics in topological
materials.Comment: 6 pages, 4 figure
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