363 research outputs found
Distribution of some elements in Veronica scutellata L. from Bolu,Turkey: soil-plant interactions
Veronica scutellata L. occurs in moist and wet habitats, such as ponds, marshes and other wetlands. This study was conducted on this species to examine its mineral element uptake status in terms of interactions between soil and plant. Experimental materials were taken from the Southern coast of Black Sea at coordinates 40º36’N and 31º16’E at an altitude of 1400 m above sea level from Bolu – Turkey; using standard methods and plant (root, stem and leaf parts) and soil mineral element measurements (Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, Ni and Zn) were done. During the study, ICP-OES was employed for the measurement of mineral elements. It was observed that considerable amounts of B, Ca, K, Mg, Mn, Na and Zn are accumulated by the plant
Inverse problem by Cauchy data on arbitrary subboundary for system of elliptic equations
We consider an inverse problem of determining coefficient matrices in an
-system of second-order elliptic equations in a bounded two dimensional
domain by a set of Cauchy data on arbitrary subboundary. The main result of the
article is as follows: If two systems of elliptic operators generate the same
set of partial Cauchy data on an arbitrary subboundary, then the coefficient
matrices of the first-order and zero-order terms satisfy the prescribed system
of first-order partial differential equations. The main result implies the
uniqueness of any two coefficient matrices provided that the one remaining
matrix among the three coefficient matrices is known
Development Of Al-B-C Master Alloy Under External Fields
This study investigates the application of external fields in the development of an Al-B-C alloy, with the aim of synthesizing in situ Al3BC particles. A combination of ultrasonic cavitation and distributive mixing was applied for uniform dispersion of insoluble graphite particles in the Al melt, improving their wettability and its subsequent incorporation into the Al matrix. Lower operating temperatures facilitated the reduction in the amount of large clusters of reaction phases, with Al3BC being identified as the main phase in XRD analysis. The distribution of Al3BC particles was quantitatively evaluated. Grain refinement experiments reveal that Al-B-C alloy can act as a master alloy for Al-4Cu and AZ91D alloys, with average grain size reduction around 50% each at 1wt%Al-1.5B-2C additions
Comparison of cavitation intensity in water and in molten aluminium using a high-temperature cavitometer
The application of ultrasound to industrial casting processes has attracted research interest during the last 50 years. However, the transfer and scale-up of this advanced and promising technology to the industry have been hindered by difficulties in treating large volumes of liquid metal due to the lack of understanding of certain fundamentals. In the current study, experimental results on ultrasonic processing in deionised water and in liquid aluminium (Al) are reported. Cavitation activity was determined in both liquid environments using an advanced high-temperature cavitometer sensor. In water, the highest cavitation activity is obtained for the lowest sonotrode tip amplitudes. Below the sonotrode, the cavitation intensity in liquid aluminium is found to be four times higher than in water.Ultramelt Project financially supported by the EPSRC grants EP/K005804/1 and EP/K00588X/
Sum of Lyapunov exponents of the Hodge bundle with respect to the Teichmuller geodesic flow
We compute the sum of the positive Lyapunov exponents of the Hodge bundle
with respect to the Teichmuller geodesic flow. The computation is based on the
analytic Riemann-Roch Theorem and uses a comparison of determinants of flat and
hyperbolic Laplacians when the underlying Riemann surface degenerates.Comment: Minor corrections. To appear in Publications mathematiques de l'IHE
Comparison between low-order and high-order acoustic pressure solvers for bubbly media computations
Numerical modelling is a useful tool for the fundamental study of acoustic cavitation treatment in liquid metals. This treatment, also known as ultrasonic melt processing, significantly improves the properties and quality of metallic materials. However, the mechanisms leading to these observed improvements are still unclear and a fundamental study of cavitation treatment is required to understand this process. In this endeavour, this paper compares the use of high-order discretization schemes for solving acoustic pressures in cavitating liquids with its low-order counterpart. A fourth order scheme is shown to be more stable and accurate than a second order scheme when taking into account the acceleration of bubbles before their collapse, and is recommended for the full cavitation modelling of acoustic treatment of liquid metals.UK Engineering and Physical Sciences Research Council (EPSRC
Square-tiled cyclic covers
A cyclic cover of the complex projective line branched at four appropriate
points has a natural structure of a square-tiled surface. We describe the
combinatorics of such a square-tiled surface, the geometry of the corresponding
Teichm\"uller curve, and compute the Lyapunov exponents of the determinant
bundle over the Teichm\"uller curve with respect to the geodesic flow. This
paper includes a new example (announced by G. Forni and C. Matheus in
\cite{Forni:Matheus}) of a Teichm\"uller curve of a square-tiled cyclic cover
in a stratum of Abelian differentials in genus four with a maximally degenerate
Kontsevich--Zorich spectrum (the only known example found previously by Forni
in genus three also corresponds to a square-tiled cyclic cover
\cite{ForniSurvey}).
We present several new examples of Teichm\"uller curves in strata of
holomorphic and meromorphic quadratic differentials with maximally degenerate
Kontsevich--Zorich spectrum. Presumably, these examples cover all possible
Teichm\"uller curves with maximally degenerate spectrum. We prove that this is
indeed the case within the class of square-tiled cyclic covers.Comment: 34 pages, 6 figures. Final version incorporating referees comments.
In particular, a gap in the previous version was corrected. This file uses
the journal's class file (jmd.cls), so that it is very similar to published
versio
Discrete singular integrals in a half-space
We consider Calderon -- Zygmund singular integral in the discrete half-space
, where is entire lattice () in ,
and prove that the discrete singular integral operator is invertible in
) iff such is its continual analogue. The key point for
this consideration takes solvability theory of so-called periodic Riemann
boundary problem, which is constructed by authors.Comment: 9 pages, 1 figur
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Effect of water temperature and induced acoustic pressure on cavitation erosion behaviour of aluminium alloys
Data availability: The raw/processed data required to reproduce these findings are available from the corresponding author on request.Copyright © 2023 The Author(s). Cavitation erosion is a major challenge for marine and fluid machinery systems. This study investigated the erosion performance of two as-cast aluminium alloys exposed to acoustic cavitation in water at temperatures of 10–50 °C and those were then compared with an extruded wrought alloy tested specifically at the temperature of maximum erosion. The results showed that the as-cast A380 alloy displayed exceptional resistance to cavitation erosion, with the lowest mass loss and surface roughness. This finding suggests that the as-cast A380 alloy is a suitable choice for lightweight, high-performance components in applications where cavitation resistance is critical.This work was financially sponsored by the PAAM (grants EP/W006774/1, EP/W00593X/1 and EP/W006154/1), UltraMelt2 (grants EP/R011001/1, EP/R011095/1 and EP/R011044/1) and EcoUltra2D (grants EP/R031401/1, EP/R031665/1, EP/R031819/1, EP/R031975/1) projects funded by the UK Engineering and Physical Sciences Research Council (EPSRC)
Effect of input power and temperature on the cavitation intensity during the ultrasonic treatment of molten aluminium
Experimental results of ultrasonic processing of liquid aluminium with a 5 kW magnetostrictive transducer and a 20 mm titanium sonotrode excited at 17 kHz are reported in this study. A unique high-temperature cavitometer sensor, placed at various locations in the liquid melt, measured cavitation activity at various acoustic power levels and different temperature ranges. The highest cavitation intensity in the liquid bulk is achieved below the surface of the sonotrode, at the lowest temperature and with an applied power of 3.5 kW. This two-fold mechanism is related to (a) acoustic shielding and (b) the tendency of liquid aluminium to release hydrogen when the temperature drops, thus promoting multiple cavitation events. Understanding these mechanisms in liquid metals can result in a major breakthrough for the optimization of ultrasound applications to liquid metal processing.This work is performed within the Ultramelt Project supported by the EPSRC Grants EP/K005804/1 and EP/K00588X/1
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