200,488 research outputs found
Directional time-distance probing of model sunspot atmospheres
No full textA crucial feature not widely accounted for in local helioseismology is that surface magnetic regions actually open a window from the interior into the solar atmosphere, and that the seismic waves leak through this window, reflect high in the atmosphere, and then re-enter the interior to rejoin the seismic wave field normally confined there. In a series of recent numerical studies using translation invariant atmospheres, we utilized a ‘directional time–distance helioseismology’ measurement scheme to study the implications of the returning fast and Alfvén waves higher up in the solar atmosphere on the seismology at the photosphere (Cally & Moradi 2013; Moradi & Cally 2014). In this study, we extend our directional time–distance analysis to more realistic sunspot-like atmospheres to better understand the direct effects of the magnetic field on helioseismic travel-time measurements in sunspots. In line with our previous findings, we uncover a distinct frequency-dependent directional behaviour in the travel-time measurements, consistent with the signatures of magnetohydrodynamic mode conversion. We found this to be the case regardless of the sunspot field strength or depth of its Wilson depression. We also isolated and analysed the direct contribution from purely thermal perturbations to the measured travel times, finding that waves propagating in the umbra are much more sensitive to the underlying thermal effects of the sunspot
ADAPTED NUMERICAL METHODS FOR ADVECTION DIFFUSION PROBLEMS
No full textWe present exponentially fitted two step peer methods for the numerical solution of systems of ordinary differential equations having oscillatory solutions (2; 3). Such equations arise for example in the semi-discretization in space of advection-diffusion problems whose solution exhibits an oscillatory behaviour, such as the Boussinesq equation (1). Exponentially fitted methods are able to exploita-prioriknowninformationaboutthequalitativebehaviourofthesolutionin order to efficiently furnish an accurate solution. Moreover peer methods are very suitable for a parallel implementation, which may be necessary when the number ofspatialpointsincreases. Theeffectivenessofthisproblem-orientedapproachis shown through numerical tests on well-known problems.
References
[1] A. Cardone, R. D’Ambrosio, B. Paternoster. (2017). Exponentially fitted IMEX methods for advectiondiffusion problems, J. Comput. Appl. Math. (316), 100–108.
[2] D. Conte, R. D’Ambrosio, M. Moccaldi, B. Paternoster. (2018). Adapted explicit two-step peer methods, J. Numer. Math., in press.
[3] D. Conte, L. Moradi, B. Paternoster. (2017). Adapted implicit two-step peer methods, in preparation
Exponentially fitted peer methods for advection diffusion problems
No full textWe consider advection-diffusion problems whose solution exhibits an oscillatory behaviour, such as the Boussinesq equation [1]. The semi-discretization in space of such equation gives rise to a system of ordinary differential equations, whose dimension depends on the number of spatial points. We present a general class of exponentially fitted two step peer methods for the numerical integration of ordinary differential equations having oscillatory solutions [2, 3]. Such methods are able to exploit a-priori known information about the qualitative behaviour of the solution in order to efficiently furnish an accurate solution. Moreover peer methods are very suitable for a parallel implementation, which may be necessary when the number of spatial points increases. The effectiveness of this problemoriented approach is shown through numerical tests on well-known problems.
References
[1] A. Cardone, R. D’Ambrosio, B. Paternoster (2017). Exponentially fitted IMEX methods for advectiondiffusion problems, J. Comput. Appl. Math (316), 100–108.
[2] D. Conte, R. D’Ambrosio, M. Moccaldi, B. Paternoster (2018). Adapted explicit two-step peer methods, J. Numer. Math., in press.
[3] D. Conte, L. Moradi, B. Paternoster (2017). Adapted implicit two-step peer methods, in preparation
Size dependent effect on the buckling and vibration analysis of double-bonded nanocomposite piezoelectric plate reinforced by boron nitride nanotube based on modified couple stress theory
No full textIn this article, the buckling and vibration analysis of a double-bonded nanocomposite piezoelectric plate reinforced by a boron nitride nanotube based on the Eshelby-Mori-Tanaka approach is developed using modified couple stress theory under electro-thermo-mechanical loadings surrounded by an elastic foundation. Using Hamilton's principle, the governing equations of motion are obtained by applying a modified couple stress theory and the Eshelby-Mori-Tanaka approach for piezoelectric material and Kirchhoff plate. These equations are coupled for the double-layer plate using the Pasternak foundation and solved using Navier's type solution. Then the dimensionless frequencies and critical buckling load for simply-supported boundary conditions are obtained. The effects of material length scale parameter, elastic foundation coefficients, aspect ratio (a/b), length to thickness ratio (a/h), transverse and longitudinal wave numbers on the dimensionless natural are investigated. The dimensionless frequency of a double-bonded nanocomposite piezoelectric plate increases with increasing length to thickness ratio and decreases with increasing aspect ratio. In addition, the effect of the elastic foundation on the dimensionless frequency of double-bonded nanocomposite piezoelectric plates is more considerable for higher elastic medium parameters. The critical buckling load also decreases with an increase in the dimensionless material length scale parameter
Iranian and Exotic Horse Breeds Data
No full textGenome-wide analysis of population structure, effective population size and inbreeding in Iranian and exotic horsesRunning head: Genomic population structure and diversity of Iranian and exotic horsesB. Bazvand1, A. Rashidi1, M. B. Zandi2, M. H. Moradi*3, and J. Rostamzadeh1</p
Association of pituitary specific transcription factor-1 (POU1F1) gene polymorphism with growth and biometric traits and blood metabolites in Iranian Zel and Lori-Bakhtiari sheep
No full textThe pituitary-specific positive transcription factor 1 (POU1F1) gene has been the subject of many recent studies because of its important roles in growth and development of mammals. In this study, we investigated the single nucleotide polymorphisms (SNPs) at the third exon of POU1F1 gene and its association with growth and biometric traits and blood metabolites in two Iranian sheep breeds, Zel and Lori-Bakhtiari. Blood samples from 90 Lori-Bakhtiari and 90 Zel sheep were collected to extract DNA and the 295-bp fragment of the POU1F1 gene was amplified and the restriction fragment length polymorphism (RFLP) technique was adopted for genotyping. A SNP was identified in both Lori-Bakhtiari and Zel sheep breeds, which represents a non-synonymous single base mutation at restriction site for endonuclease AciI. The results revealed differential frequencies of alleles between the two studied breeds, where A allele was more frequent in Lori-Bakhtiari breed, while G allele was more frequent in Zel breed. When POU1F1 genotypes were tested, the animals with AA genotype had a higher weaning weight than those with GG genotype (p 0.05). These findings imply that the POU1F1 polymorphism may affect weaning weight, thus can be used as a molecular marker for this production trait
Acoustic emission dataset of single-stiffener composite panels subjected to impact and run-to-failure fatigue loading
No full textThis data article presents the AE measured from composite panels with a single stiffener during compression-compression fatigue loading until end-of-life. Different kinds of damage have occurred, especially induced by defects such as a pre-embedded disbond and impact at different locations. Low-level AE features were extracted from AE waveforms, including amplitude, rise time, duration, energy, counts, and RMS. Then, they were windowed according to different lengths (LW) and intervals (Int) in terms of the loading cycle. Moreover, diverse statistical features in time and frequency domains from each time window were extracted and are available. Both AE variables (low-level features) and statistical features can be utilized for research in prognostic and health management as well as composite structures. Ten different combinations of lengths (LW) and intervals (Int) were considered, including 100, 500, 1000, and 5000 cycles. Besides the AE low-level and statistical feature datasets, figures of the total number of events within each TW for different combinations of LW and Int are provided
Lipidomics unravels the role of leaf lipids in thyme plant response to drought stress
No full textThymus is one of the best known genera within the Labiatae (Lamiaceae) family, with more than 200 species and many medicinal and culinary uses. The effects of prolonged drought on lipid profile were investigated in tolerant and sensitive thyme plants (Thymus serpyllum L. and Thymus vulgaris L., respectively). Non-targeted non-polar metabolite profiling was carried out using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry with one-month-old plants exposed to drought stress, and their morpho-physiological parameters were also evaluated. Tolerant and sensitive plants exhibited clearly different responses at a physiological level. In addition, different trends for a number of non-polar metabolites were observed when comparing stressed and control samples, for both sensitive and tolerant plants. Sensitive plants showed the highest decrease (55%) in main lipid components such as galactolipids and phospholipids. In tolerant plants, the level of lipids involved in signaling increased, while intensities of those induced by stress (e.g., oxylipins) dramatically decreased (50-60%), in particular with respect to metabolites with m/z values of 519.3331, 521.3488, and 581.3709. Partial least square discriminant analysis separated all the samples into four groups: tolerant watered, tolerant stressed, sensitive watered and sensitive stressed. The combination of lipid profiling and physiological parameters represented a promising tool for investigating the mechanisms of plant response to drought stress at non-polar metabolome level
Acoustic emission dataset of single-stiffener composite panels subjected to impact and run-to-failure fatigue loading
No full textThis data article presents the AE measured from composite panels with a single stiffener during compression-compression fatigue loading until end-of-life. Different kinds of damage have occurred, especially induced by defects such as a pre-embedded disbond and impact at different locations. Low-level AE features were extracted from AE waveforms, including amplitude, rise time, duration, energy, counts, and RMS. Then, they were windowed according to different lengths (LW) and intervals (Int) in terms of the loading cycle. Moreover, diverse statistical features in time and frequency domains from each time window were extracted and are available. Both AE variables (low-level features) and statistical features can be utilized for research in prognostic and health management as well as composite structures. Ten different combinations of lengths (LW) and intervals (Int) were considered, including 100, 500, 1000, and 5000 cycles. Besides the AE low-level and statistical feature datasets, figures of the total number of events within each TW for different combinations of LW and Int are provided
The Numerical Study of the Gas-Solid Flow in a Conventional Cyclone Separator
No full textThis paper presents a numerical study of the gas–powder flow in a typical Lapple cyclone
with division of gas and particle flow in a vortex finder. The Navier-Stokes equations along
with the RNG k-ε turbulent model are solved numerically. The separation efficiency and the
trajectory of particles are simulated and the effects of the particle size on the separation
efficiency and the particle residence time are investigated. The effect of the particle density on
the particle size in the range which results 100% cyclone separation efficiency and particle
residence time is investigated. Large particles generally have a higher concentration in the
wall region and small particles have a higher concentration in the inner vortex region. The
particles enter from different sides give different separation efficiency and trajectory. A
particle with a size exceeding a critical diameter or a critical density would stagnate on the
wall of the cyclone’s cone. This phenomenon is regarded as a main reason for the deposition
on the inner conical surface in such cyclones used in the cement industry
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