4,595 research outputs found
Fractal analysis of weld defect patterns obtained by radiographic tests
This paper presents a fractal analysis of radiographic patterns obtained from
specimens with three types of inserted welding defects: lack of fusion, lack of
penetration, and porosity. The study focused on patterns of carbon steel beads
from radiographs of the International Institute of Welding (IIW). The
radiographs were scanned using a greyscale with 256 levels, and the fractal
features of the surfaces constructed from the radiographic images were
characterized by means of Hurst, detrended-fluctuation, and minimal-cover
analyses. A Karhunen-Loeve transformation was then used to classify the curves
obtained from the fractal analyses of the various images, and a study of the
classification errors was performed. The obtained results indicate that fractal
analyses can be an effective additional tool for pattern recognition of weld
defects in radiographic tests.Comment: 7 pages, 2 figures. To appear AIP Conference Proceedings - QNDE 200
Student and AI responses to physics problems examined through the lenses of sensemaking and mechanistic reasoning
Several reports in education have called for transforming physics learning
environments by promoting sensemaking of real-world scenarios in light of
curricular ideas. Recent advancements in Generative-Artificial Intelligence has
garnered increasing traction in educators' community by virtue of its potential
in transforming STEM learning. In this exploratory study, we adopt a
mixed-methods approach in comparatively examining student- and AI-generated
responses to two different formats of a physics problem through the cognitive
lenses of sensemaking and mechanistic reasoning. The student data is derived
from think-aloud interviews of introductory students and the AI data comes from
ChatGPT's solutions collected using Zero shot approach. The results highlight
AI responses to evidence most features of the two processes through
well-structured solutions and student responses to effectively leverage
representations in their solutions through iterative refinement of arguments.
In other words, while AI responses reflect how physics is talked about, the
student responses reflect how physics is practiced. Implications of these
results in light of development and deployment of AI systems in physics
pedagogy are discussed
Identifying sustainable nitrogen management practices for tea plantations
Tea (Camellia sinensis L.) is the most widely consumed beverage in the world. It is mostly grown in the tropics with a heavy dependence on mineral nitrogen (N) fertilisers to maintain high yields while minimising the areas under cultivation. However, N is often applied in excess of crop requirements, resulting in substantial adverse environmental impacts. We conducted a systematic literature review, synthesising the findings from 48 studies to assess the impacts of excessive N application on soil health, and identify sustainable, alternative forms of N management. High N applications lead to soil acidification, N leaching to surface and groundwater, and the emission of greenhouse gases including nitrous oxide (N2O). We identified a range of alternative N management practices, the use of organic fertilisers, a mixture of organic and inorganic fertilisers, controlled release fertilisers, nitrification inhibitors and soil amendments including biochar. While many practices result in reduced N loading or mitigate some adverse impacts, major trade-offs include lower yields, and in some instances increased N2O emissions. Practices are also frequently trialled in isolation, meaning there may be a missed opportunity from assessing synergistic effects. Moreover, adoption rates of alternatives are low due to a lack of knowledge amongst farmers, and/or financial barriers. The use of site-specific management practices which incorporate local factors (for example climate, tea variety, irrigation requirements, site slope, and fertiliser type) are therefore recommended to improve sustainable N management practices in the long term.Innovate UK (Grant number 47864) and HEIF
Friendship as conceptual landscape and friend as conceptual character, according to Deleuze e Guattari
ABSTRACT This essay begins with the proposal of the "pedagogy of the concept" according to Deleuze and Guattari. On this basis, I emphasize and explore the assertion that every Philosophy demands, as its internal condition, "relationary traces". Among the relationary traces defined by this pedagogy of the concept, I choose the "friend" as a feature who characterizes a given philosophical thought. I attempt, after that, to define, in a general way, the friend and the landscape of friendship in the Plato's, Nietzsche's, Heidegger's and Foucault's philosophies
Heat capacity, thermal expansion and heat transport in the Han Blue (BaCuSi 4 O 10 ): Observation of structural phase transitions
a b s t r a c t Structural phase transitions at 87 K and 103 K are reported for single-crystalline Han Blue (BaCuSi 4 O 10 ) by means of high-resolution thermal-expansion, thermal conductivity and heat capacity measurements. The phase transition at 103 K results in differing lengths of the a and b lattice parameters, and thus a lowering of the crystallographic symmetry. Negative thermal-expansion coefficients are observed perpendicular to the c-axis over a wide temperature range The thermal conductivity is small, and decreases with temperature, both of which suggest strong scattering of heat-carrying phonons. The principle Grüneisen parameter within the plane and perpendicular to it was determined to be γ 1 ¼ À1.09 and γ 3 ¼1.06 at room temperature; the bulk Grüneisen parameter is γ¼0.10. The results are consistent with the presence of low-energy vibrations associated with the collective motions of CuO 4 and Si 4 O 10 polyhedral subunits
Electron transport in quantum dot chains: Dimensionality effects and hopping conductance
Detailed experimental and theoretical studies of lateral electron transport in a system of quantum dot chains demonstrate the complicated character of the conductance within the chain structure due to the interaction of conduction channels with different dimensionalities. The one-dimensional character of states in the wetting layer results in an anisotropic mobility, while the presence of the zero-dimensional states of the quantum dots leads to enhanced hopping conductance, which affects the low-temperature mobility and demonstrates an anisotropy in the conductance. These phenomena were probed by considering a one-dimensional model of hopping along with band filling effects. Differences between the model and the experimental results indicate that this system does not obey the simple one-dimensional Mott\u27s law of hopping and deserves further experimental and theoretical considerations
A Real Space Description of Field Induced Melting in the Charge Ordered Manganites: II. the Disordered Case
We study the effect of A site disorder on magnetic field induced melting of
charge order (CO) in half doped manganites using a Monte-Carlo technique.
Strong A-site disorder destroys CO even without an applied field. At moderate
disorder, the zero field CO state survives but has several intriguing features
in its field response. Our spatially resolved results track the broadening of
the field melting transition due to disorder and explain the unusual dependence
of the melting scales on bandwidth and disorder. In combination with our
companion paper on field melting of charge order in clean systems we provide an
unified understanding of CO melting across all half doped manganites.Comment: 9 pages, pdflatex, 10 embedded png fig
A Real Space Description of Magnetic Field Induced Melting in the Charge Ordered Manganites: I. The Clean Limit
We study the melting of charge order in the half doped manganites using a
model that incorporates double exchange, antiferromagnetic superexchange, and
Jahn-Teller coupling between electrons and phonons. We primarily use a real
space Monte Carlo technique to study the phase diagram in terms of applied
field and temperature , exploring the melting of charge order with
increasing and its recovery on decreasing . We observe hysteresis in
this response, and discover that the `field melted' high conductance state can
be spatially inhomogeneous even without extrinsic disorder. The hysteretic
response plays out in the background of field driven equilibrium phase
separation. Our results, exploring , , and the electronic parameter
space, are backed up by analysis of simpler limiting cases and a Landau
framework for the field response. This paper focuses on our results in the
`clean' systems, a companion paper studies the effect of cation disorder on the
melting phenomena.Comment: 16 pages, pdflatex, 11 png fig
Observações preliminares sobre o "declínio" da seringueira.
A partir de 1983, uma enfermidade aparentemente nova vem sendo observada em seringais de cultivo no Estado do Amazonas, constituida pela reducao da taxa de crescimento e/ou definhamento das plantas. Estao sendo feitos ensaios para se identificar um possivel agente infeccioso, bem como selecao de clones tolerantes, ensaios de adubacao e avaliacao de comportamento das plantas afetadas.bitstream/item/76995/1/CPAA-PESQ.-AND.-44-86.pd
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