Miracle-dz/UniFAR-FTUs huggingface dataset:
Precision Tests of Theories of Gravity Using Pulsars

In the quest of understanding gravity, binary pulsars provide indispensable laboratories for precision tests of gravity. Effects that can be studied in great detail include the emission of gravitational waves, Shapiro delay, orbital precession and more. But also fundamental differences between general relativity and alternative theories of gravity can be probed, such as possible violations of the strong equivalence principle, preferred frame effects or the existence of gravitational dipole radiation or scalar fields. Also the effects of spin precession in strongly self-gravitating bodies can be studied by observing effects of geodetic precession.
Damage Detection for Composite Plates Using Lamb Waves and Projection Genetic Algorithm

A method of damage detection for composite plates using Lamb waves and a projection genetic algorithm is investigated in this study. This method first formulates the damage detection as an optimization problem of minimizing the error between the measured and calculated surface displacement response derived from Lamb waves. The calculated response is obtained by using the strip element method with the trial crack parameters (location, size). Then a projection genetic algorithm is used to solve the optimization problem and thus identify the actual crack parameters. The projection genetic algorithm is developed from the hybridization of the modified micro-genetic algorithm with a projection operator. It has an excellent convergence performance, taking only 9.9 ∼ 14.2% of the number of function evaluations required by the conventional micro-genetic algorithm to obtain the global optima for six benchmark functions. Numerical examples are presented to verify the proposed method for detection of cracks inside composite plates. The maximal error of detected crack parameters is -4.3% for four simulated cases, which is achieved by running only 60 generations of projection genetic algorithm.
Pfirsch–Schlüter neoclassical heavy impurity transport in a rotating plasma

In this work, we extend previous analytic theories for the neoclassical transport of a trace heavy impurity in a rotating plasma in the Pfirsch–Schlüter regime. The complete diffusive and convective components of the ambipolar particle flux are derived. The solution is valid for arbitrary impurity charge and impurity Mach number and for general geometry. Inclusion of finite main-ion temperature gradient effects is shown in the small ion Mach number limit. A simple interpolation formula is derived for the case of high impurity charge and circular geometry. While an enhancement of the diffusion coefficient is found for order one impurity Mach number, a reduction due to the rotation-driven poloidal asymmetry in the density occurs for very large Mach number.
Transient characterization of the electroforming process in TiO2 based resistive switching devices

The transient electroforming process of TiO2-based resistive switching devices is investigated using a pulsed voltage method, and the electroforming time is found to vary from 10−8 s to 10−1 s as function of pulse magnitude (3–8 V) and ambient temperature (25–100 °C). Pulsed experiments and thermal simulations reveal that Joule self-heating has a significant effect on the electroforming dynamics, specially for electroforming voltages above 5.5 V where there is little dependence on ambient temperature and the electroforming time (10–100 ns) is much shorter than the device thermal time constant (≈2 μs).
Miura-Base Rigid Origami: Parameterizations of First-Level Derivative and Piecewise Geometries

Miura and Miura-derivative rigid origami patterns are increasingly used for engineering and architectural applications. However, geometric modelling approaches used in existing studies are generally haphazard, with pattern identifications and parameterizations varying widely. Consequently, relationships between Miura-derivative patterns are poorly understood, and widespread application of rigid patterns to the design of folded plate structures is hindered. This paper explores the relationship between the Miura pattern, selected because it is a commonly used rigid origami pattern, and first-level derivative patterns, generated by altering a single characteristic of the Miura pattern. Five alterable characteristics are identified in this paper: crease orientation, crease alignment, developability, flat-foldability, and rectilinearity. A consistent parameterization is presented for five derivative patterns created by modifying each characteristic, with physical prototypes constructed for geometry validation. It is also shown how the consistent parameterization allows first-level derivative geometries to be combined into complex piecewise geometries. All parameterizations presented in this paper have been compiled into a matlab Toolbox freely available for research purposes.
The first crossing-time density for Brownian motion with a perturbed linear boundary

An expansion is derived for the density of the first time a Brownian path crosses a perturbed linear boundary a + Ef(t). When the perturbation f(t) is a finite mixture of negative exponentials of either sign the expansion is shown to converge for all values of the perturbation parameter E. Numerical examples suggest that the technique works well for a wider choice of f(t), including cases where f(t) is periodic.
Efficient third-harmonic generation of a picosecond laser pulse with time delay

A new configuration based on the polarization-mismatching scheme with time delay for efficient frequency tripling conversion is proposed in this paper. The calculated results showed that the requirement for the efficient frequency tripling conversion of a 1-ps laser pulse is not only the optimization of peak intensity of the second-harmonic pulse, but also the optimization of the pulse duration ratio and temporal difference between the o-polarization second-harmonic pulse and the e-polarization first-harmonic pulse due to group-velocity mismatch among the interacting pulses. With the proposed scheme the group velocity mismatch can be compensated. Overall energy conversion efficiency increases from 55% to 75% under the optimized conditions at the intensity of 6 GW/cm/sup 2/. The temporal shape of the third-harmonic pulse with 1 ps pulse duration has no subpulses. The optimization of the efficient frequency tripling conversion for intensities of over 75 GW/cm/sup 2/ is also described. The results showed that the maximum tripling energy conversion efficiency is close to 80% with the optimized doubler and tripler.
Analytical Solutions for the Pencil-Beam Equation with Energy Loss and Straggling

In this article, we derive equations approximating the Boltzmann equation for charged particle transport under the continuous slowing down assumption. The objective is to obtain analytical expressions that approximate the solution to the Boltzmann equation. The analytical expressions found are based on the Fermi-Eyges solution, but include correction factors to account for energy loss and spread. Numerical tests are also performed to investigate the validity of the approximations.
Components of Environmental Literacy in Elementary Science Education Curriculum in Bulgaria and Turkey.

The purpose of this study was to analyze the extent to which science education objectives in elementary schools addressed to the six basic components of environmental literacy (EL), and how this attention differed from Bulgaria to Turkey. The main method in the study involved comparative content analysis of these objectives. The courses sampled for Bulgaria include “The Human Being and Nature”, “Biology and Health Education”, “Chemistry and Environmental Protection” and “Physics and Astronomy”. The course sampled for Turkey is “Science and Technology Education”. Content analysis of these objectives reveals that all components of environmental literacy did not receive the same attention. For example in both countries most attention was given to knowledge, less to skills and attitudes, and little to environmentally responsible behavior (ERB).
Perceptual motion transparency : the role of geometrical information

Perceptual motion transparency occurs whenever two or more patterns are seen moving at different depth levels, such that we can see one pattern move across the others, and perceptual motion coherence occurs when we see a single motion. We present here a model of perceptual motion transparency and coherence that consists of three stages: (i) measure the normal velocity along contours or the velocity of features such as corners or line end points; (ii) take the intersection, in velocity space, of all possible pairs of constraint lines associated with the normal velocity components; and (iii) combine the results of steps (i) and (ii) in the velocity histogram, which is the plot of the total number of votes for each velocity in velocity space. For two patterns we perceive motion coherence, transparency, or a mixture of both types of motion depending on whether the velocity histogram is unimodal, bimodal, or trimodal. According to our model we perceive motion transparency or coherence depending on the total number of prominent peaks of the velocity histogram, where each peak is located at the position corresponding to the velocity of one of the patterns or of coherent motion. We show that the number of prominent peaks in the velocity histogram depends on the error in the measurement of the local velocity and on the relative orientation of the local velocities along contours; this relative orientation encodes contour shape. Our model differs from current motion theories in that it describes the perception of motion not as a result of local velocity extraction but instead as the result of the integration of local velocity and geometrical shape information across different points of the image and across superimposed patterns. This model allows for the occurrence of mixed motion perception, which arises from the combination of the velocity information associated with motion transparency and coherence. We have tested this model through computational and psychophysical experiments done with line patterns. As a result of these experiments we conjecture that the human visual system may use at least three stages to process image velocity.
Current and emerging laser sensors for greenhouse gas sensing and leak detection

To reduce atmospheric accumulation of the greenhouse gases methane and carbon dioxide, networks of continuously operating sensors that monitor and map their sources are desirable. In this paper, we discuss advances in laser-based open-path leak detectors, as well as technical and economic challenges inhibiting widespread sensor deployment for “ubiquitous monitoring”. We describe permanently-installed, wireless, solar-powered sensors that overcome previous installation and maintenance difficulties while providing autonomous real-time leak reporting without false alarms.
Directivity of the radio emission from the K1 dwarf star AB Doradus

We present measurements of the spectrum and polarization of the flaring radio emission from the K1 dwarf star AB Doradus, together with previously reported single frequency measurements (with no polarization information) on 3 other days. On all 4 days spanning a 6 month period, the emission was strong and, when folded with the stellar rotation period, showed similar time variations with two prominant peaks at phase 0.35 and 0.75. These peaks coincide in longitude with two large starspots identified from the stellar optical light curve and have half-powe widths as small as 0.1 rotations and no larger than 0.2 rotations. The modulated emission shows no measurable circular polarization, and its two peaks have different turnover frequencies.
Alpha particle detection with GaN Schottky diodes

Ni/GaN Schottky diode radiation detectors were fabricated on 3-μm-thick unintentionally doped n-GaN films grown by molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) and on 12-μm-thick undoped n-GaN layers prepared by epitaxial lateral overgrowth (ELOG). The reverse current of all detector structures was <10−9 A for bias voltages necessary for detector operation, with the level of background donor doping of <1015 cm−3. With this doping level the space charge region of the Schottky diode could be extended to the entire thickness of the films. The charge collection efficiency of the detectors was close to 100% for MOCVD and ELOG detectors for α-particles with range comparable to the thickness of the layer. Electrical properties and deep trap spectra were also studied. The collection efficiency decreased when the concentra-tion of deep electron traps, particularly Ec-0.6 eV traps, increased in MBE grown films.
Superhumps in Cataclysmic Binaries. XV. EG Cancri, King of the Echo Outbursts

We report photometry and spectroscopy of the dwarf nova EG Cancri in its 1996/1997 episode of eruptions. The main eruption was clearly a superoutburst featuring common superhumps with a period of 0.06036(2) days, establishing the star as a new member of the SU UMa class of dwarf novae. At the end of the main eruption, the superhumps were replaced by another wave of slightly longer period (0.06045 days), which endured for at least another 90 days. The properties of the latter wave suggest identification as a “late superhump. ” The recurrence time for superoutbursts is long, probably in the range 7–20 yr. After the 15 day superoutburst, the star displayed six remarkable surges in light, with an average interval of 7 days; these “echo outbursts” strongly resemble ordinary dwarf nova eruptions. This suggests that a high accretion rate persisted in the disk for ∼40 days after the main superoutburst. By a year after outburst, the star faded to V = 18.7, with most of the continuum light from a white dwarf of T∼15,000 K. We estimate a distance of 320 pc and a 〈Mv〉 = +11.5 for accretion light. The extreme faintness, the rarity of eruptions, the enormous duration of superhumps, and the quiescent spectrum together establish membership in the WZ Sge subclass, the most sluggish of dwarf novae. Spectroscopy at quiescence and a transient wave in early outburst establish an orbital period of 0.05997(9) days. This suggests a secondary star with M∼0.02 M⊙, yet R∼0.08 R⊙. A binary can reach such a state after the secondary is forced to lose mass on a timescale shorter than its Kelvin‐Helmholtz timescale.
Atmospheric Effects on the Speed of Sound

Abstract : The small-signal speed of sound in humid air is calculated from a model which includes the real-gas effects from the equation of state for humid air and the vibrational dispersion due to N2, O2, and CO2 relaxation. Other atmospheric effects such as dispersion due to viscothermal and rotational relaxation, heat radiation, propagation along the air-ground boundary, the density gradient, turbulence, aerosols and fogs are considered and found to be unimportant for frequencies between 1 Hz and 5 MHz (at one atmosphere). The uncertainty in predicting the sound speed varies between 0.22 m/sec at -90 C to 0.05 m/sec at 90 C. Experimental results in humid air at 20 C and 30 C are in excellent agreement with the model. For the propagation frequency of 20 Hz, it is found that the presently used sound-ranging formula, c = 20.06 x square root of T sub s, where T sub s = . 75t sub v + . 25t + 273.2 (t sub v = virtual temperature), differs by up to 0.5 m/sec over the range -60 C to 60 C. A correction to the 'sonic' temperature determination is suggested which results in deviations of less than 0.05 m/sec over the temperature range from -60 C to 50 C and for relative humidities from 5% to 100%. (Author)
Affine smoothing of the Wigner-Ville distribution

A formalism of signal energy representations depending on time and scale is presented. Precise links between time-frequency and time-scale energy distributions are provided. It is known that a full description of the former is given by Cohen's class, which can be described as a generalization of the spectrogram appropriately parameterized by a smoothing function acting on the Wigner-Ville distribution. A full description of the latter is given, resulting in a class of representations in which the smoothing of the Wigner-Ville distribution is scale-dependent. Through proper choice of the smoothing function, interesting properties may be imposed on the representation, which makes it a versatile tool for the analysis of nonstationary signals. Also, specific choices allow known definitions to be recovered (including the Bertrands' and the energetic version of the wavelet transform, referred to as the scalogram). Another very flexible choice uses separable smoothing functions. It is shown, in particular, that Gaussian kernels provide a continuous transition between spectrograms and scalograms by means of the Wigner-Ville distribution. <<ETX>>
The potential for asteroseismology of DB white dwarf stars

We present the results of a parametric survey of evolutionary models of compositionally stratified white dwarfs with helium surface layers (DB white dwarfs). Because white dwarfs are the most common final end state of stellar evolution, determining their internal structure will offer us many clues about stellar evolution and the physics of matter under extreme conditions. As a first step towards determining the internal structure of DB white dwarf stars, we provide a comprehensive set of theoretical g-mode pulsation periods for comparison to observations of pulsating DB white dwarfs
PVDF transducers-a performance comparison of single layer and multilayer structures

To improve the pulse-echo sensitivity of a piezopolymer transducer while preserving its broad bandwidth property, several multilayer transducer design approaches have been suggested. This paper presents formulae describing three types of multilayer transducers-a Barker code multilayer-, folded multilayer and switchable Barker code multilayer transducer. Based on the formulae derived, the pulse-echo responses of the multilayer transducers under various excitation signals were calculated and compared with those achievable with an equivalent PZT transducer. Also, the influence of a tissue layer on the transducer responses was examined. The simulation results indicated that the switchable Barker code transducer design outperforms all other transducer designs analyzed with respect to the axial resolution and overall sensitivity in the medical imaging frequency range. To verify the simulation results, several prototypes of multilayer transducers were fabricated and tested in water. A good agreement between the experimental results and the corresponding computer predictions was achieved.
A simple model of the adhesive failure of a layer: Cohesive effects

A fine-scale model is developed for the removal of an adhesive layer by a uniform stress. The initial motivation of this modeling project was a description of the removal of a layer of filter cake from cylindrical filters by backpulse cleaning. The model includes the bonding forces of adhesion between the layer and a substrate, as well as the forces of cohesion between imaginary “gridblocks’’ within the layer. For stresses greater than a threshold value, some of the layer is removed, with the fraction removed depending upon the stress, the average adhesive and cohesive forces, and the distribution of these forces about their average. The cohesive forces reduce the threshold well below the average strength of the adhesive force, because they increase the stress near broken adhesive bonds. The cohesive forces also sharpen the threshold in the cleaning pressure significantly, so that the threshold is very much sharper than the distribution of adhesive strengths. For moderate filter cake thickness (moderately.
Generalized inverses modulo ℋ in semigroups and rings

The definition of the inverse along an element was very recently introduced, and it contains known generalized inverses such as the group, Drazin and Moore–Penrose inverses. In this article, we first prove a simple existence criterion for this inverse in a semigroup, and then relate the existence of such an inverse in a ring to the ring units.
On the possible effect of pedestal pulse on material removal by ultrahigh intensity laser pulses

The results of the interaction of 200 fs and 4 ns laser pulses produced by a Ti : Sapphire commercial laser system with various materials are reported. The drilling rates were measured as a function of laser pulse energy and material thickness. Saturation of the material removal rate was observed for high laser pulse energy. The dependence of the material removal rate on the sample thickness was measured. The results of numerical simulation of laser drilling with femtosecond and nanosecond laser pulses using a theoretical model which includes phase transition at the critical temperature are reported. The computed drilling rates are in agreement with the data of measurements. The effect of a suspected nanosecond pedestal pulse containing approximately 30% of total pulse energy on the rate of drilling with femtosecond laser pulses is numerically simulated and the computed results are discussed.
65 years of ZnO research – old and very recent results

The research on ZnO has a long history but experiences an extremely vivid revival during the last 10 years. We critically discuss in this didactical review old and new results concentrating on optical properties but presenting shortly also a few aspects of other fields like transport or magnetic properties. We start generally with the properties of bulk samples, proceed then to epitaxial layers and nanorods, which have in many respects properties identical to bulk samples and end in several cases with data on quantum wells or nano crystallites. Since it is a didactical review, we present explicitly misconceptions found frequently in submitted or published papers, with the aim to help young scientists entering this field to improve the quality of their submitted manuscripts. We finish with an appendix on quasi two‐ and one‐dimensional exciton cavity polaritons.
Least mean square error difference minimum criterion for adaptive chaotic noise canceller

The least mean square error difference (LMS-ED) minimum criterion for an adaptive chaotic noise canceller is proposed in this paper. Different from traditional least mean square error minimum criterion in which the error is uncorrelated with the input vector, the proposed LMS-ED minimum criterion tries to minimize the correlation between the error difference and input vector difference. The novel adaptive LMS-ED algorithm is then derived to update the weights of adaptive noise canceller. A comparison between cancelling performances of adaptive least mean square (LMS), normalized LMS (NLMS) and proposed LMS-ED algorithms is simulated by using three kinds of chaotic noises. The simulation results clearly show that the proposed algorithm outperforms the LMS and NLMS algorithms in achieving small values of steady-state excess mean square error. Moreover, the computational complexity of the proposed LMS-ED algorithm is the same as that of the standard LMS algorithms.