Miracle-dz/UniFAR-FTUs huggingface dataset:
Structural properties of hydrogenated silicon nanocrystals and nanoclusters

The structures of fully and partially hydrogenated Si nanocrystals and nanoclusters are studied by geometric optimizations and molecular dynamics simulations based on an empirical tight-binding approach. It is shown that the structural properties of the hydrogen saturated Si nanocrystals have little size effect, contrary to their electronic properties. The surface relaxation is quite small in the fully hydrogen saturated Si nanocrystals, with a lattice contraction of 0.01 to 0.02 A residing in the outermost two or three layers. Inside the hydrogenated Si nanocrystals, there is only very small strain (lattice expansion) of the order 10−4 to 10−3, in agreement with the x-ray diffraction measurement. The fully hydrogenated Si nanocrystals are the most stable structures compared to those partially hydrogenated. For the smaller SimHx (m⩽151) nanocrystals, removing up to 50% of the surface terminating H atoms only causes distortions to the crystal structure, with the basic tetrahedral structural features still .
Transformation of internal waves passing over a bottom step

The transformation of small-amplitude internal waves on the oceanic shelf is studied numerically. The transmission and reflection coefficients are found for the simplified step-wise model of the oceanic shelf in a two-layer fluid. The approximate formulae are proposed for the transformation coefficients as functions of incident wavenumber, density ratio of layers, depth of the pycnocline and height of the bottom step. Results of direct numerical modelling of internal wave transformation are obtained and presented as functions of all aforementioned parameters. It is shown that there is a good agreement between the outcomes of approximate theory and numerical data. Both the theoretical and the numerical results agree well with the law of energy flux conservation.
Application of space–time duality to ultrahigh-speed optical signal processing

Manipulation and characterization of information using ultrafast optical signals is critical for numerous applications in telecommunications, biology, quantum information science, spectroscopy, and atomic and molecular physics. Femtosecond pulsed laser sources are available over a wide range of wavelengths and repetition rates, which enable the generation, transmission, and characterization of information at bandwidths beyond 1 THz. In this article, we review the concept of space–time duality as a system design tool for ultrafast optical processing and characterization. The combination of this design framework with recent advances in nonlinear optical devices enables the realization of highly complex signal processing systems that can generate, characterize, and manipulate arbitrary and non-repetitive optical waveforms at unprecedented processing speeds.
A Numerical Simulation of Cooling Coronal Flare Plasma

We have simulated the cooling of coronal flare plasma (T/sub e/>10/sup 7/ K) using a numerical model of a vertical magnetic flux tube containing an idealized flare chromosphere, transition region, and corona. The model solves the set of one-dimensional, two-fluid hydrodynamic equations. The cooling of the flux tube is calculated for a specific case beginning with an initial atmosphere in hydrostatic equilibrium and a maximum temperature of about 18 x 10/sup 6/ K. The behavior of temperature, density, and velocity is calculated as a function of height as the system cools. Early in the cooling energy is transported by conduction into the transition region and chromosphere where it is radiated away. Later, the transition region-corona interface moves upward into the tube at velocities of about 20 km s/sup -1/, while the chromosphere cools and the coronal component cools by both conduction and radiation. Coronal downflow velocities of about 60 km s/sup -1/ are evident during this phase. The expected spectral line emission from the system in X-ray lines of Fe XXV, Fe XXIV, Fe XXII, O VIII, and O VII is also calculated and compared to recent observational results. Some observational results can be explained as a consequence of simplemore » cooling of flare flux tubes. The expected spectral line emission from certain transition region lines is also briefly considered. The dependence of our results on flare size is discussed, and our results are compared with similar previous work. « less
Spaceborne along-track SAR interferometry: performance analysis and mission scenarios

A system study of a spaceborne along-track synthetic aperture radar (SAR) interferometer is presented. This sensor has been successfully experienced for detecting moving targets by using only airborne installations. Several key issues must be addressed when spaceborne configurations are envisaged. To this end, a quantitative evaluation of system performance and measurement accuracy has been conducted. First, the identification of possible space configurations has been accomplished. In particular, the two antennas can operate on a single satellite or they can be carried along appropriate trajectories by two spacecrafts. Then, an error budget of radial velocity measurement accuracy has been performed. Finally, two possible mission scenarios are dealt in details, and numerical results are reported.
A rationale for 'edge-elements' in 3-D fields computations

A justification for the use of finite elements with edge-attached degrees of freedom (edge-elements) is sought in some mathematical structures that underlie eddy-current theory. An introduction to so-called mixed methods in magnetostatics is given, and two dual methods for eddy-current computations, both making use of edge elements, are shown to derive from these considerations. >
Homogenization of Reticulated Structures

Materials science is an area of growing research as composite materials become widely used in such areas as civil engineering, electrotechnics, and the aerospace industry. This mathematically rigorous treatment of lattice-type structures will appeal to both applied mathematicians, as well as engineers looking for a solid mathematical foundation of the methodology.
Helping Hands? Experts Examine Curricular Alignment at Kentridge High School

ducation reform is nothing new; however, from our point of view, the tension between assessment and accountability is at an all-time high. Currently, 48 states administer state-mandated tests and 36 states publish annual report cards on school performance (Olson, 1999). Kentucky, for example, links student achievement on standardized assessments to teacher pay (Din, 1996). This link has contributed to an increasingly volatile situation, where some teachers refuse to administer high-stakes tests. They end up serving lengthy suspensions and battling administrators over the validity of such tests (http://www.pdkintl.org! kappan/kohaO101.htm). As a nation, we are faced with a political and educational situation in which assessment and accountability are colliding. Accountability is a key word in all educational circles and permeates educational debates from the national level down to the individual classroom level. In February 1990, several national educational goals were adopted after a landmark educational summit in late 1989. Chief among them was the goal that by the year 2000, students from the United States would be ranked first in the world in math and science (Doran et al., 1994). After the adoption of this goal, national and state standards were developed, including the National Science Education Standards (NRC, 1996). The wave of educational reform continues to the present day, even though practitioners and researchers warn of the "perils associated with rigid standards that stress testing and teacher accountability" (Biddle, 1998, p. 165). Two current examples of this national-to-local trickle down effect include the Washington State Essential Academic Learning Requirements (EALRs: Washington Commission on Student Learning, 1998) and the Oregon State Standards (Conly & Goldman, 1998).
Low-frequency robust control for singularly perturbed system

This study is concerned with the low-frequency (LF) integral quadratic constraints (IQC) of the linear singularly perturbed model (SPM). The conditions satisfying LF IQC are derived in terms of linear matrix inequalities by using the generalised Kalman–Yakubovich–Popov lemma. As special cases of LF IQC, LF bounded realness and LF positive realness are exploited in detail. In addition, upper bound of the small perturbation parameter, which relates to the robustness of SPM, can be estimated. Numerical simulations demonstrate that the proposed method can reduce the conservatism and characterise the SPM more specifically by ignoring the unrelated frequency range.
High-resolution VLA survey of the alpha = 08h52m15s, delta = +17 deg 16 arcmin field

A single primary beam area centered on alpha = 08h52m15s, delta = +17 deg 16 arcmin was mapped with the VLA at 5.8-arcsec resolution to investigate the angular sizes of very faint radio sources at 1465 MHz. Previously, this field (approximately one square degree) was mapped with 19-arcsec resolution to a 6.3 sigma flux density limit of 84 micro Jy. The rms noise in the high resolution map is sigma equal to about 21 micro Jy; hence all previously detected point sources should be present at a confidence level of four sigma. The low resolution map was used to verify that sources were not resolved away by the high resolution observations. The median angular size (theta med) found for the faintest sources (greater than or equal to 84 and less than 400 micro Jy) is less than or equal to 3 arcsec. It is significantly lower than the extrapolation of earlier data and models in which theta med remains constant in the range 7-10 arcsec for sources brighter than about 1 mJy and fainter than 100 mJy. The observed dropoff in angular size is consistent with most stronger sources being produced by elliptical galaxies, while the fainter sources reside inmore » spiral or Seyfert galaxies. Thus a simple model can fit the new data without requiring size evolution of radio sources. 15 references. « less
Resolving power and information theory in signal recovery

We develop a probabilistic approach to the problem of signal recovery from noisy data. In particular, in constructing the approximation, we introduce a truncation method that is related to an order–disorder transition point of the Fourier coefficients of the data. Through a statistical method we show how to determine this truncation point without using any prior information.
Covering of heating load of object by using ground heat as a renewable energy source

Rational use of energy, improving energy performance of buildings and use of renewable energy sources are the most important measures for reducing consumption of non-renewable primary energy (solid, liquid, and gaseous fuels), environmental protection and for the future sustainable development of mankind. In the total primary energy consumption great part is related to building industry, for heating spaces in which people stay and live. Renewable energy sources (RES) present natural resources and they are one of the alternatives that allow obtaining heat for heating buildings, and by that they provide a significant contribution to the energy balance of a country. This paper analyzes the participation of ground source as RES, when the vertical (the probe in the ground) and horizontal (registry in the ground) heat exchangers are used for covering heating load of the building.
Total reflection high-energy positron diffraction (TRHEPD)

Total reflection high-energy positron diffraction (TRHEPD) promises to be an ideal technique for determining the atomic arrangement of solid surfaces. TRHEPD makes full use of the total reflection of the positron beam from a surface in reflection high-energy positron diffraction (RHEPD), the positron counterpart of reflection high-energy electron diffraction (RHEED). Owing to the development and use of a brightness-enhanced intense positron beam at KEK, it is now possible to obtain clear TRHEPD patterns. It is shown that the TRHEPD pattern from a Si(111)-7×7 reconstructed surface for the total reflection condition does not contain contributions from atoms in the bulk.
Circular Flow and Circular Chromatic Number in the Matroid Context

This thesis considers circular flow-type and circular chromatic-type parameters ($ and X, respectively) for matroids. In particular we focus on orientable matroids and fi-matroids. These parameters are obtained via two approaches: algebraic and orientation-based. The general questions we discuss are: bounds for flow number; characterizations of Eulerian and bipartite matroids; and possible connections between the two possible extensions of $: algebraic and orientation. In the case of orientable matroids, we obtain characterizations of bipartite rank-3 matroids and Eulerian uniform, rank-3 matroids; an asymptotic result regarding the flow number of uniform matroids; and an improvement on the known bound for flow number of matroids of arbitrary rank. This bound is further improved for the uniform case. For fi-matroids, we examine an algebraic extension of the parameters x and $. We also introduce a notion of orientation and the corresponding flow and chromatic numbers applicable to this class. We investigate the possibility of a connection between the algebraic and orientation-based parameters, akin to that established for regular matroids by Hoffman's Circulation Lemma and we obtain a partial connection. We extend the notion of "Eulerian" to fi-matroids. We call such matroids hex-Eulerian. We show that every maximum-sized $'i-matroid, of fixed rank, is hexEulerian. We also show that a regular matroid is hex-Eulerian if and only if it admits a nowhere-zero 3-flow. We include an extension of Tutte's chain groups, which characterize regular matroids, to what we term hex-chain modules which describe $'i-matroids.
Identification of parameters in multilayer media

Multilayer media are of increasing importance as magneto-optic and perpendicular media. The properties of successive layers evolve as the layers are epitaxially deposited. This complicates both the model for these media and the identification of the model parameters. In this paper, the effect of the variation of the Preisach model parameters is discussed and an identification procedure is outlined. Reentrant-type hysteresis behavior, which is found to be necessary in order to accurately fit both major loop and first-order reversal curves in these multilayer materials, is also considered.
Topological bifurcation for the double cusp polynomial

In his work on elementary catastrophes Zeeman(1) has considered what he has named as the double cusp catastrophe. This catastrophe is defined by the unfolding of the two variable polynomial x4 + y4. Using Mather's results (2) on stability of singular germs of C∞ maps we can find an expression for the unfolding. The eight dimensional unfolding can then be considered as a polynomial in two variables with eight parameters.
Evidence of non-bolometric mixing in the bandwidth of a hot-electron bolometer

The gain bandwidth of a superconducting NbN hot-electron mixer was measured at local oscillator (LO) frequencies 2.5, 0.6 and 0.3 THz and compared to values from presently known bolometric mixer models. At 2.5 THz variations of the bandwidth with the LO power agree rather with the hot-spot mixer model than with any of the homogeneous bolometric models, whereas an increase of the bandwidth at low LO frequencies plausibly evidences non-bolometric direct interaction of magnetic vortices with the radiation field.
Effects of Pyrogenic Reoxidation Annealing on Inversion Channel Mobility of 4H–SiC Metal-Oxide-Semiconductor Field-Effect Transistor Fabricated on (112̄0) Face

The interface properties of 4H-silicon carbide (SiC) metal-oxide-semiconductor (MOS) capacitors and the electrical properties of MOS field-effect transistors (MOSFETs) on the (112̄0) face fabricated using pyrogenic reoxidation annealing (pyrogenic ROA) have been characterized. Pyrogenic ROA reduces the interface-state density near the conduction band, resulting in an increase in the inversion channel mobility and a decrease of the threshold voltage for the MOSFETs with both dry and wet gate-oxides. Eventually, a high channel mobility of 68 cm2/(V·s) was successfully achieved in a MOSFET with wet gate-oxide using the pyrogenic ROA. On the (112̄0) face, the channel mobility of MOSFETs strongly depends on the interface-state density near the conduction band.
Reaching Li 7 quantum degeneracy with a minitrap

A millimeter-scale Ioffe-Pritchard trap is used to achieve quantum degeneracy in $^{7}\mathrm{Li}$. The trap employs freestanding copper coils integrated onto a direct-bond copper surface-electrode structure. The trap achieves a radial magnetic gradient of $420\phantom{\rule{0.3em}{0ex}}\mathrm{G}∕\mathrm{cm}$, an axial oscillation frequency of $50\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}$, and a trap depth of $66\phantom{\rule{0.3em}{0ex}}\mathrm{G}$ with a $100\phantom{\rule{0.3em}{0ex}}\mathrm{A}$ drive current and $7\phantom{\rule{0.3em}{0ex}}\mathrm{W}$ total power dissipation.
On photo‐electron angular distributions from clusters

The distributions of electrons emitted from a metal cluster after laser excitation are analyzed from a theoretical perspective. The focus is laid on the angular distributions of the emitted electrons taking, in particular, the anisotropy as measure for the basic shape. This observable is discussed at various levels of sophistication, from stationary perturbation theory to a fully dynamical simulation of the electron dynamics using time‐dependent density‐functional theory. The simple most approach, perturbation theory with outgoing plane waves, can be treated mostly analytically which provides useful, qualitative insights into the mechanisms determining the angular distributions. Comparing the model, an extreme sensitivity of the results to all details of the cluster has been found. This requires a theoretical description without compromises. Using a fully dynamical simulation with detailed ionic background yields generally smooth trends for the frequency dependence of the anisotropy, with emission preferably along the laser polarization plus some isotropic background. Weakly bound cluster ions make an exception for frequencies near emission threshold where a generic tendency to sidewards emission prevails.
Water quality studies of combined optical, thermal infrared, and microwave remote sensing

Two major water quality parameters can be estimated from optical, thermal infrared (IR), and microwave remotely sensed data. The results show that these data combined can result in better estimated accuracy than the optical retrieval of water quality observations. However, the technique still needs to be refined in future studies. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 281–285, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10438
Estimates on Invariant Tori near an Elliptic Equilibrium Point of a Hamiltonian System

Abstract We give a precise statement for the KAM theorem in a neighbourhood of an elliptic equilibrium point of a Hamiltonian system. If the frequencies of the elliptic point are nonresonant up to a certain order K ⩾4, and a nondegeneracy condition is fulfilled, we get an estimate for the measure of the complement of the KAM tori in a neighbourhood of given radius. Moreover, if the frequencies satisfy a Diophantine condition, with exponent τ , we show that in a neighbourhood of radius r the measure of the complement is exponentially small in (1/ r ) 1/( τ +1) . We also give a related result for quasi-Diophantine frequencies, which is more useful for practical purposes. The results are obtained by putting the system in Birkhoff normal form up to an appropiate order, and the key point relies on giving accurate bounds for its terms.
Regional Climate Projections of Extreme Heat Events in Nine Pilot Canadian Communities for Public Health Planning

AbstractPublic health planning needs the support of evidence-based information on current and future climate, which could be used by health professionals and decision makers to better understand and respond to the health impacts of extreme heat. Climate models provide information regarding the expected increase in temperatures and extreme heat events with climate change and can help predict the severity of future health impacts, which can be used in the public health sector for the development of adaptation strategies to reduce heat-related morbidity and mortality. This study analyzes the evolution of extreme temperature indices specifically defined to characterize heat events associated with health risks, in the context of a changing climate. The analysis is performed by using temperature projections from the Canadian Regional Climate Model. A quantile-based statistical correction is applied to the projected temperatures, in order to reduce model biases and account for the representativeness error. Moreo.
Forecasting with EC-VARMA Models

This article studies error correction vector autoregressive moving average (ECVARMA) models. A complete procedure for identifying and estimating EC-VARMA models is proposed. The cointegrating rank is estimated in the first stage using an extension of the non-parametric method of Poskitt (2000). Then, the structure of the VARMA model for variables in levels is identified using the scalar component model (SCM) methodology developed in Athanasopoulos and Vahid (2008), which leads to a uniquely identifiable VARMA model. In the last stage, the VARMA model is estimated in its error correction form. Monte Carlo simulation is conducted using a 3-dimensional VARMA(1,1) DGP with cointegrating rank 1, in order to evaluate the forecasting performances of the EC-VARMA models. This algorithm is illustrated further using an empirical example of the term structure of U.S. interest rates. The results reveal that the out-of-sample forecasts of the EC-VARMA model are superior to those produced by error correction vector autoregressions (VARs) of finite order, especially in short horizons.
Large deformation and amorphization of Ni nanowires under uniaxial strain: A molecular dynamics study

Molecular-dynamics simulations were employed to study deformations on nickel nanowires subjected to uniaxial strain at 300 K using a recently reported embedded-atom (many body) model potential. This embedded-atom model can reproduce exactly the experimental second-order and third-order elastic moduli as well as the phase stability, equation of state and phonon frequency spectra are also in good agreement with experiments. Strong influence was observed in the Young modulus and force constant due to surface effects when considering nanowires with different cross sections. Applying strain rates, from 0.05 to $15%{\mathrm{ps}}^{\ensuremath{-}1},$ we found elastic behavior up to 11.5% strain with corresponding stress of 9.4 GPa. At low strain rates $(l0.05%{\mathrm{ps}}^{\ensuremath{-}1})$ the system passes through plastic deformations although keeping the crystalline structure. This ductile process is showed by several snapshots. At this low strain rate regime we observed that the nanowires shows superplasticity. For high strain rates $(g~7%{\mathrm{ps}}^{\ensuremath{-}1})$ the system changes continuously from crystalline to amorphous phase. Although this amorphization occurs with no use of liquid quenching or introduction of chemical or physical disorder, so being a different and interesting process, the amorphous resulted is unstable. We studied this instability monitoring the recrystallization process.