Miracle-dz/UniFAR-FTUs huggingface dataset:
Caustics By Reflection And Their Application To Elastic-Plastic And Dynamic Fracture Mechanics

Applications of the method of reflected caustics to the measurement of the J integral in ductile materials are reviewed. It is demonstrated, both numerically and experimentally, that the conditions for accurate interpretation of caustics on the basis of plane stress small scale yielding analyses are often overrestrictive. To overcome these restrictions, we used a three-dimensional, elastic-plastic finite-element calculation to analyze caustics formed by reflection of light from a particular test specimen. Experimental measurements on the same specimen confirm the numerically obtained results. The out-of-plane surface displacements, measured experimentally by interferometry, are in excellent agreement with the corresponding numerical results. In addition, the experimentally obtained caustics agree well with the numerically generated caustics. The excellent agreement between experiment and calculations demonstrates the accuracy of the numerical model and establishes confidence in the interpretation of caustics in the presence of both extensive plasticity and three dimensionality. The analysis of caustics as based on the three-dimensional calculation is applied to the direct optical measurement of the time history of the J integral in a dynamically loaded specimen. The specimen was loaded in a drop weight tower, and the caustics were photographed with a high speed camera.
The interaction of an isotropic field of acoustic waves with a shock wave

Moore's (1954) inviscid linear analysis of the interaction of a shock wave with a plane acoustic wave is evaluated by comparison to computation. The analysis is then extended to study the interaction of an isotropic field of acoustic waves with a normal shock wave. The evolution of fluctuating kinetic energy, sound level and thermodynamic fluctuations across the shock wave are examined in detail. The interaction of acoustic fluctuations with the shock is notably different from that of vortical fluctuations. The kinetic energy of the acoustic fluctuations decreases across the shock wave for Mach numbers between 1.25 and 1.8. For Mach numbers exceeding 3, the kinetic energy amplifies by levels that significantly exceed those found in the interaction of vortical fluctuations with the shock. Upon interacting with the shock wave, the acoustic waves generate vortical fluctuations whose contribution to the far-field kinetic energy increases with increasing Mach number. The level of sound increases across the shock wave. The rise in the sound pressure level across the shock varies from 5 to 20 dB for Mach number varying from 1.5 to 5. The fluctuations behind the shock wave are nearly isentropic for Mach number less than 1.5, beyond which the generation of entropy fluctuations becomes significant.
Optical Field Effects and Band Structure of Some Perovskite-Type Ferroelectrics

Investigation of critical points in the band structure of some ferroelectric materials of the perovskite type has been carried out by the electroreflectance method (ER). Conducting samples of BaTi${\mathrm{O}}_{3}$, KTa${\mathrm{O}}_{3}$, and KTa${\mathrm{O}}_{3}$-KNb${\mathrm{O}}_{3}$ mixtures have been studied. The light was reflected at the interface between the samples and an electrolyte, where high electric fields could be achieved. Very large changes in the reflectivity have been measured upon application of the field. The observed behavior corresponds to shifts of the critical-point energies and splitting of the degenerate levels associated with the transition-metal-oxygen octahedra. The effect is interpreted in terms of a large lattice polarization induced by the external field. The dependence of the ER on sample orientation and light polarization has also been studied. Crystal-field symmetry considerations have allowed tentative assignments of the ER singularities to critical points in the band structure. The ER behavior in the photon range where the extinction coefficient is small compared to the refractive index is consistent with the electro-optic effect observed in the visible. It is suggested that a single mechanism accounts for both effects. In KTa${\mathrm{O}}_{3}$ the fundamental edge has been additionally investigated by electro-absorption. The data suggest that quantum-mechanical tunneling of the Franz-Keldysh type plays only a minor role in the optical field effects of ferroelectric crystals.
Study on the Ising Antiferromagnet in an External Magnetic Field

In an external magnetic field, the properties of an antiferromagnet are much less well understood than those of a ferromagnet are. An abnormal peak in the specific heat of matter at a low temperature, the so-called Schottky anomaly, is one of the most universal phenomena, and it is the most important concept in studying experimentally the low-energy structure of matter. We investigate the unknown properties of the Ising antiferromagnet in an external magnetic field B, in particular, the magnetic-field dependence of the Schottky anomaly of the Ising antiferromagnet systematically. We find three different kinds of Schottky anomalies for the Ising antiferromagnet. First, for B > Bc, where Bc is the critical magnetic field, both the maximum of the Schottky anomaly Cs(B) and the Schottky temperature Ts(B) increase as B increases. In particular, Ts(B) follows Ts(B) = 0.8336(B − Bc) only for B > Bc. Second, for B < Bc, both the maximum of the Schottky anomaly and the Schottky temperature decrease as B increases, in clear contrast to the increasing behaviors of the Schottky anomaly for B > Bc. Third, at B = Bc, the unusual Schottky anomaly appears due to the nonzero ground-state entropy, similar to real ice and spin glass. We expect that our results will play a vital role in measuring and understanding the properties of an antiferromagnet and related materials in an external magnetic field.
THE CRYSTAL DYNAMICS OF URANIUM DIOXIDE

The frequency/wave-vector dispersion relation for normal modes of vibration propagating along the [00ζ], [ζζ0], and [ζζζ] directions in uranium dioxide at 296 °K has been determined by studying the coherent one-phonon scattering of slow neutrons from a single-crystal specimen. Analysis of the results shows that a simple rigid-ion model of the crystal with axially symmetric forces between near-neighbor ions can provide qualitative agreement with experiment. A more complicated model, in which the ionic polarizabilities are taken into account, is needed to obtain quantitative agreement with the dispersion curves and with the known dielectric properties. Such a model provides an interpolation formula for computing the frequency distribution function and other related quantities, such as the Debye–Waller factors and lattice specific heat. Information concerning the anisotropy of the Debye–Waller factor for the oxygen ions and the configuration of the "magnetic" electrons in UO2 is derived by comparing these ca.
Conduction properties of microscopic gold contact surfaces

Electroplated gold surfaces of the type used for MEMS switches were surveyed by atomic force microscopy (AFM) to define the surface topographical features, and by x-ray photoelectron spectroscopy (XPS) to determine the chemical composition of the contact surface. The gold surfaces were contacted with electrochemically sharpened gold and tungsten probes using an interface force microscope (IFM), capable of simultaneously measuring contact currents from 10 fA to 10 mA and forces ranging from 0.01 to 100 uN. Both attractive and repulsive forces were observed, and attractive forces on the probe tip were found to exist at significant distances (greater than 5 nm) from the gold surface. The radius of the probe tip is on the order of a micron, making it a useful model system for a single-asperity contact on an actual MEMS switch-contact surface. The results of these single-contact measurement events are compared with contact measurements made with MEMS switches of various sizes and actuation schemes to understand the origins of contact resistance and switch failure.
Atomic force microscope cantilever based microcoordinate measuring probe for true three-dimensional measurements of microstructures

An atomic force microscope (AFM) cantilever based coordinate measuring probe applicable for true three dimensional measurements of microstructures is presented. The probe has a shaft glued to a commercial AFM cantilever and a probing sphere located at the free end of the shaft. A conventional optical lever method is applied to detect the bending, torsion, and the dynamic behavior of the AFM cantilever which will change dramatically when the probe sphere is in proximity to the object to be measured. The probe has advantages such as small probing force (<1μN), high probing sensitivity allowing nanometer measurement resolution, easy exchange of probing elements, and low cost. Measurements of a microgear and a fuel injection nozzle using the developed probe are demonstrated, indicating its promising application potential.
PHOTOELECTRIC PHOTOMETRY FROM A SPACE VEHICLE

For centuries astronomers have carried out their investigations of the cosmos from the bottom of an ocean of air. We are now entering the age of space astronomy. In-situ measurements within the solar system are now being carried out. Above the earth’s atmosphere the adverse effects of seeing scintillation, scattered light, and air glow are avoided and hold promise of extending measurements to objects 100 times fainter and increasing spatial resolution by more than an order of magnitude. Above all, observations above the earth’s atmosphere make it possible to make measurements in spectral regions unaccessible from the ground due to the opacity of the terrestrial atmosphere. The first of the major space observatories has been planned to carry out measurements in the vacuum ultraviolet. Future spacecrafts will provide facilities for expanded measurements in other spectral regions, such as X-rays. This paper describes some of the features of ultraviolet photometry from a space observatory. While the data are free of extinction and are not plagued by the seeing fluctuations so apparent in ground-based observations, the measurements from the Orbiting Astronomical Observatory require careful and unique observing techniques. The Orbiting Astronomical Observatory was launched on December 7, 1968 from Cape Kennedy into a 480-mile, 35-degree circle
Singaporean students' mathematical thinking in problem solving and problem posing: an exploratory study

This study explored Singaporean fourth, fifth, and sixth grade students' mathematical thinking in problem solving and problem posing. The results of this study showed that the majority of Singaporean fourth, fifth, and sixth graders are able to select appropriate solution strategies to solve these problems, and choose appropriate solution representations to clearly communicate their solution processes. Most Singaporean students are able to pose problems beyond the initial figures in the pattern. The results of this study also showed that across the four tasks, as the grade level advances, a higher percentage of students in that grade level show evidence of having correct answers. Surprisingly, the overall statistically significant differences across the three grade levels are mainly due to statistically significant differences between fourth and fifth grade students. Between fifth and sixth grade students, there are no statistically significant differences in most of the analyses. Compared to the findings concerning US and Chinese students' mathematical thinking, Singaporean students seem to be much more similar to Chinese students than to US students.
The relationship between the interdecadal variability of East Asian summer monsoon's movement and the spatial distribution pattern of the summer rainfall in East China

Using daily rainfall measurements from 740 stations across China and European Centre for Medium-Range Weather Forecasts (ECMWF) upper air reanalysis daily data (1958-2001), we give out climatically characters of East Asian summer monsoon's (EASM) movement with the definition of the EASM's front, finding out that the transfer of the rain belt over East China is consistent with the advance and retreat of the EASM. By the EOF (empirical orthogonal function) analysis of the gridded EASM's index (average for the 28th-45th pentad) from 1958 to 2001 in area (105°E-150°E,15°N-55°N), it is founded that, the second mode of the EOF analysis exhibits interdecadal variations and indicate that the movement of EASM has three interdecadal abrupt changes in 1965, 1980 and 1994, respectively. Therefore, the three interdecadal abrupt changes bring the different processes of the EASM's movement and lead to the obvious change of the spatial distribution pattern of summer rainfall in East China directly, especially prior to 1965, the rainfall in the mid-lower reaches of the Yangtze River is much less than normal, while the precipitation is much more in South China, North China and Northeast China but with decreasing continuously since 1965. However, the rainfall in the mid-lower Yangtze Valley increases continually from 1980, especially from 1994 the rainfall in South China and the Yangtze Valley increases rapidly while the precipitation over North China was much less than normal. Therefore, in East China underwent from the pattern of south- drought and northern- waterlog before 1979 to south-waterlog and north- drought.
Nondestructive Evaluation

The goal of this book is to provide engineers with a source of firm knowledge of the most frequently used non-destructive evaluation (NDE) techniques. The primary techniques (ultrasonics, acoustic emission, magnetics, eddy-current radiography, penetrants) are introduced from the fundamental laws of physics and described in depth in order to provide sufficient technical background. Typical examples are given which show usual NDE applications. At the end of each part of the book, a detailed bibliography is provided and problems are given which allow the reader to check his degree of understanding. Laboratory projects are suggested in the cases of magnetics and eddy currents. A list of names and addresses of the various organizations active in the area of NDE is supplied at the end of the book. This book is clear and very pedagogic and could be recommended for courses at undergraduate and graduate levels. I did, however, notice a few unfortunate omissions. In the overview of the probabilistic nature of failure and inspection, some helpful words concerning neural networks and artificial intelligence were left out. A classification of the different NDE techniques from the point of view of their frequency and their cost would have been useful. This would have allowed minor techniques to be introduced. There were also no descriptions of real NDE testing situations (e.g. nuclear plant or aeroplane) explaining the time and cost constraints which engineers and technicians have to cope with.
Energy dissipation in a thin polymer film by electron beam scattering

Monte Carlo calculations have been performed to determine the spatial distribution of energy dissipated in a 4000‐A‐thick film of polymethyl methacrylate (PMMA), due to an incident electron beam. The calculations were performed for 5‐, 10‐, and 20‐keV electrons on a silicon substrate and also for 20‐keV electrons on copper and gold substrates. The effect of varying the beam diameter from 250 to 3000 A was evaluated. A detailed comparison is made between the Monte Carlo results and analytic models used to predict the energy dissipated. The plural scattering model is found to be in good agreement with the Monte Carlo calculations, whereas discrepancies are found with the multiple scattering model. The large‐angle backscattering model is found to have several important limitations. Energy dissipation is calculated for the exposure of dots, isolated lines, and arrays of closely spaced lines—geometries that are of significance in electron beam lithography.
Implicit constitutive modelling for viscoplasticity using neural networks

Up to now, a number of models have been proposed and discussed to describe a wide range of inelastic behaviours of materials. The fatal problem of using such models is however the existence of model errors, and the problem remains inevitably as far as a material model is written explicitly. In this paper, the authors define the implicit constitutive model and propose an implicit viscoplastic constitutive model using neural networks. In their modelling, inelastic material behaviours are generalized in a state-space representation and the state-space form is constructed by a neural network using input–output data sets. A technique to extract the input–output data from experimental data is also described. The proposed model was first generated from pseudo-experimental data created by one of the widely used constitutive models and was found to replace the model well. Then, having been tested with the actual experimental data, the proposed model resulted in a negligible amount of model errors indicating its superiority to all the existing explicit models in accuracy. © 1998 John Wiley & Sons, Ltd.
Generation of Trees, Two-Trees, and Storage of Master Forests

A new method of listing all possible trees of any given graph without duplication or redundancy, using simple geometrical properties of the graph, is proposed. The procedure given is suitable for both manual and automatic computation, and any modifications to the given graph can be catered to by suitable interpolation and extrapolation. An alternate method for complete graphs, derived from it, gives the trees arranged in an order most suitable for their storage as master forest matrices and for directly obtaining trees and 2-trees of any given graph through simple modifications to them instead of starting from scratch every time. Some properties of master forest matrices are discussed, which. , inter alia, lead to a formula for the number of trees in a sub-graph of a complete graph. While an edge-numbering convention and a criterion for a tree play the key roles in systematic generation of trees, the storage technique makes it possible to obtain all the co-factors and determinants of a node-admittance matrix of any network (within the range of storage) by merely operating on one single master forest matrix.
Investigating nanoplastics toxicity using advanced stem cell-based intestinal and lung in vitro models

Plastic particles in the nanometer range–called nanoplastics–are environmental contaminants with growing public health concern. As plastic particles are present in water, soil, air and food, human exposure via intestine and lung is unavoidable, but possible health effects are still to be elucidated. To better understand the Mode of Action of plastic particles, it is key to use experimental models that best reflect human physiology. Novel assessment methods like advanced cell models and several alternative approaches are currently used and developed in the scientific community. So far, the use of cancer cell line-based models is the standard approach regarding in vitro nanotoxicology. However, among the many advantages of the use of cancer cell lines, there are also disadvantages that might favor other approaches. In this review, we compare cell line-based models with stem cell-based in vitro models of the human intestine and lung. In the context of nanoplastics research, we highlight the advantages that come with the use of stem cells. Further, the specific challenges of testing nanoplastics in vitro are discussed. Although the use of stem cell-based models can be demanding, we conclude that, depending on the research question, stem cells in combination with advanced exposure strategies might be a more suitable approach than cancer cell lines when it comes to toxicological investigation of nanoplastics.
Surface and curvature energies from jellium spheres: Density functional hierarchy and quantum Monte Carlo

Department of Physics and Center for Computational Physics, University of Coimbra, 3004-516 Coimbra, Portugal~Received 7 February 2002; published 20 August 2002! We consider spherical jellium clusters with up to 200 electrons as a testing ground for density functionalapproximations to the exchange-correlation energy of a many-electron ground state. As nearly-exact standards,we employ Hartree–Fock energies at the exchange-only level and the diffusion Monte Carlo~DMC! energiesof Sottile and Ballone ~2001! at the correlated level. The density functionals tested are the local spin density~LSD! , generalized gradient ~GGA! , and meta-generalized gradient ~meta-GGA! approximations; the lattergives the most accurate results. By ﬁtting the deviation from the LSD energy of closed-shell clusters to thepredictions of the liquid drop model, we extract the exchange-correlation surface energies and curvatureenergies of a semi-inﬁnite jellium from the energies of ﬁnite clusters. For the density functionals, the surfaceenergies so extracted agree closely with those calculated directly for a single planar surface. But for thediffusion Monte Carlo method, the surface energies so extracted are considerably lower ~and we suspect moreaccurate! than those extrapolated by Acioli and Ceperley ~1996! from their DMC supercell calculations. Theerrors of the LSD, GGA, and meta-GGA surface and curvature energies are estimated, and are found to beconsistently small for both properties only at the meta-GGA level. These errors are qualitatively related torelative performances of the various density functionals for the calculation of atomization energies: the properself-interaction correction to the LSD for a one-electron atom is in the curvature energy~as it is in meta-GGA! ,not in the surface energy ~as it is in GGA! Additionally, a formula is given for the interpolation and extrapo-lation of the surface energy s
Occupational engagement: some assumptions to inform occupational therapy

Abstract Occupational engagement has been conflated with other concepts, such as participation, active occupational performance, and therapeutic engagement. This critical review will discuss occupational engagement as a unique concept that describes a form of involvement in doing that does not require performance and foregrounds the subjective-affective and cognitive experiences of doing. We present some attributes of occupational engagement and the implications for the lack of clarity of this concept within the literature. The difference between occupational engagement and therapeutic engagement is discussed by comparing the foundational tenets of the Model of Human Occupation (MOHO) and the Canadian Model of Occupational Performance and Engagement (CMOP-E). Through one illustrative narrative, we discuss how occupational engagement can be understood as a phenomenon that is not performance-dependent and has different levels of engagement. To conclude, we point out some assumptions about occupational engagement that can inform occupational therapy research and practice.
Spatiotemporal analysis of propagation mechanism of positive primary streamer in water

Currently, further clarification of pre-breakdown phenomena in water such as propagation mechanisms of primary and secondary streamers are needed because applications of aqueous plasma to environmental and medical treatments are increasing. In this study, a series of primary streamer propagations in ultrapure water was visualized at 100-Mega frames per second (100 Mfps) in the range of 400 μm square using an ultra high-speed camera with a microscope lens when a single-shot pulsed positive voltage was applied to a needle electrode placed in a quartz cell. Every observation was synchronized with the waveforms of the applied voltage and the discharge current. The primary streamer, having many filamentary channels, started to propagate semi-spherically with a velocity of about 2 km/s when the pulsed currents occurred. Although most filamentary channels disappeared 400 ns after the beginning of the primary streamer, a few of them continued propagating with almost the same velocity (about 2 km/s) as long as the.