Miracle-dz/UniFAR-FTUs huggingface dataset:
A statistical development of entropy for the introductory physics course

Many introductory physics texts introduce the statistical basis for the definition of entropy in addition to the Clausius definition, ΔS=q/T. We use a model based on equally spaced energy levels to present a way that the statistical definition of entropy can be developed at the introductory level. In addition to motivating the statistical definition of entropy, we also develop statistical arguments to answer the following questions: (i) Why does a system approach a state of maximum number of microstates? (ii) What is the equilibrium distribution of particles? (iii) What is the statistical basis of temperature? (iv) What is the statistical basis for the direction of spontaneous energy transfer? Finally, a correspondence between the statistical and the classical Clausius definitions of entropy is made.
Monitoring and modeling silicon homoepitaxy breakdown with real-time spectroscopic ellipsometry

Real-time spectroscopic ellipsometry (RTSE) is used to monitor the breakdown of low-temperature homoepitaxial growth of silicon on silicon wafers in a hot-wire chemical-vapor deposition reactor. We develop and evaluate two optical models to interpret the RTSE data, revealing the progression of epitaxy and its eventual breakdown into amorphous silicon growth. Comparison of the RTSE analysis with cross-sectional transmission electron microscopy, ex situ variable-angle spectroscopic ellipsometry, and Raman spectroscopy measurements shows that RTSE provides accurate and fast quantitative feedback about the progression of epitaxy.
Point defect calculations in diamond-type crystals by the extended Huckel method 1: General theory and the vacancy problem

The applicability of the extended Huckel method for the calculation of the electronic properties of point defects in diamond-type crystals is discussed. A detailed study of the isolated vacancy in both the diamond and silicon lattice shows that the results obtained depend upon the size of the cluster chosen and the approximations made at the boundary of the system. Clusters with up to 47 host lattice atoms are considered. A cluster of 41 atoms, which includes all atoms directly bonded to the second neighbours from the point defect, is considered to be the most suitable system. On the basis of a comparison of ab initio and extended Huckel calculations for small molecules, it is argued that studies involving distortions are beyond the validity of the simple method used here. At best, the results from extended Huckel studies for point defects in diamond type crystal should be considered to be semiquantitative.
Illustrating the Law of Large Numbers (and Confidence Intervals)

Instructors of introductory statistics classes tend to separate out abstract probability concepts because of the level of mathematics required to present them. The Law of Large Numbers, which explains why making repeated observations on a population is informative, seems especially vulnerable to this tendency. This is unfortunate because the Law validates students' intuitive understanding about why statistics works and reinforces the notion that abstract probability concepts have important, real-life consequences. Instead of presenting the Law in a mathematical fashion, we propose a graphical presentation designed to communicate and emphasize the Law's importance. Specifically, we illustrate the effect that the Law of Large Numbers has on a sequence of sample means by plotting a randomly generated sequence of sample means versus their sample size. Students can then observe (1) how the sample mean approaches the population mean as the sample size grows large, (2) the variability associated with that process, and (3) the implied mathematical result. The corresponding sequence of probability intervals for the sample mean can then be superimposed on the plot to show how the sample mean's variability is reduced as the sample size grows. Furthermore, the sequence of confidence intervals can also be superimposed on the plot to demonstrate that the concept of coverage probability applies only to the procedure for setting confidence intervals (which we refer to as a random probability interval) and not to the observed confidence interval itself.
Area dependent efficiency of organic solar cells

Efficiency estimations of organic solar cells are observed to be dependent on the dimensions of electrode defining the active area. We address this issue and explore the manner in which efficiency scales in polymer solar cells by studying these devices as a function of electrode area and incident beam size. The increase in efficiency for smaller active areas can be explained by the reduced electrical resistive loss, the enhanced optical effects, and the finite additional fraction of photogenerated carriers in the vicinity of the perimeter defined by the metal electrode
On the Relation Between Spherical Harmonics and Simplified Spherical Harmonics Methods

The purpose of the paper is, first, to recall the proof that the AN method and, therefore, the SP2N−1 method (of which AN was shown to be a variant) are equivalent to the odd order P2N−1, at least for a particular class of multi-region problems; namely the problems for which the total cross section has the same value for all the regions and the scattering is supposed to be isotropic. By virtue of the introduction of quadrature formulas representing first collision probabilities, this class is then enlarged in order to encompass the systems in which the regions may have different total cross sections. Some examples are reported to numerically validate the procedure.
Resonance frequency estimation of a bridged loop‐gap resonator used for magnetic resonance measurements

This paper presents a method for estimating the resonance frequency of a bridged loop‐gap resonator (BLGR). It first describes the structure of the BLGR and its equivalent electrical circuit, and then a procedure for calculating the resonance frequency is revealed. In this procedure, node analysis, which is a circuit theory, is applied to calculate the branch voltages of the equivalent circuit. Finally, this paper reports on the calculations and measurements of the resonance frequency, and the validity of the method for estimating resonance frequency.
Large‐area, free‐standing gratings for atom interferometry produced using holographic lithography

Interferometers based on matter waves promise orders‐of‐magnitude improvements in metrology over laser‐based systems by virtue of the fact that the de Broglie wavelengths of atoms are about 104 times shorter. To date, the required matched set of four aligned gratings for such atom interferometers has been made using electron beam lithography and, as a result, such gratings suffer from a lack of spatial‐phase coherence. We report on processes we have developed for fabricating free‐standing gratings over large areas using conventional holographic lithography and achromatic holographic lithography to achieve spatial periods of 200 and 100 nm, respectively (i.e., nominal linewidths of 100 and 50 nm, respectively).
On record statistics from a mixture of two exponential distributions

This article is concerned with the problem of estimating the parameters of the finite mixture of two exponential distributions based on record statistics. The maximum likelihood and Bayes methods of estimation are used for this purpose. Bayes estimators for the parameters of the mixture model are obtained by using the approximation form of Lindley (1980). The Bayes estimates are compared with their corresponding maximum likelihood estimates based on a Monte Carlo simulation study. Email: zjaheen@hotmail.com
Optical interstellar lines in southern supergiants

Photoelectric photometry of 35 southern supergiants reveals a good correlation of the central residual in- tensity of the diffuse interstellar line at 4430 Â with color excess. From spectra of the brighter southern supergiants, I have derived column densities of Na i and Ca n, and, in a few cases, of CH and CH + . These results are averaged and compared with previous studies of the interstellar medium at high galactic latitudes and in the denser regions of the plane. The basic peculiarities of the interstellar lines in these two regions, as discussed in Papers I and II, are more sharply delineated by this comparison. Models for the gas in the halo are derived, and I obtained the mass of gas in the halo (from 1 x 10 7 to 6 x 10 7 M©) and a maximum value of the metal depletion of the halo gas relative to the disk gas (from 300 to 90, depending on whether grains exist in the halo). This maximum value implies that the gas in the halo has been significantly contaminated by material which has undergone nuclear processing.
Comparison of induced current and aperture field integrations for an offset parabolic reflector

The fields predicted by integration of the physical optics induced currents on the reflector (ICM) and the geometrical optics aperture fields (AFM) on the surface that caps the reflector are compared numerically for offset parabolic reflectors. It is found that the AFM solutions are very close to ICM solutions for the main beam and the first few sidelobes but discrepancy remains for the far-out sidelobes. This discrepancy is found to come mainly from the difference of polarization matrix for each method.
Physics-based modeling of computed tomography systems

We present a theoretical framework describing projections obtained from computed tomography systems considering physics of each component consisting of the systems. The projection model mainly consists of the attenuation of x-ray photons through objects including x-ray scatter and the detection of attenuated/scattered x-ray photons at pixel detector arrays. X-ray photons are attenuated by the Beers-Lambert law and scattered by using the Klein-Nishina formula. The cascaded signal-transfer model for the detector includes x-ray photon detection and light photon conversion/spreading in scintillators, light photon detection in photodiodes, and the addition of electronic noise quanta. On the other hand, image noise is considered by re-distributing the pixel signals in pixel-by-pixel ways at each image formation stage using the proper distribution functions. Instead of iterating the ray tracing over each energy bin in the x-ray spectrum, we first perform the ray tracing for an object only considering the thickness of each component. Then, we assign energy-dependent linear attenuation coefficients to each component in the projected images. This approach reduces the computation time by a factor of the number of energy bins in the x-ray spectrum divided by the number of components in the object compared with the conventional ray-tracing method. All the methods developed in this study are validated in comparisons with the measurements or the Monte Carlo simulations.
Contacts to p-type ZnMgO

Ohmic and Schottky contacts to p-type Zn0.9Mg0. 1O are reported. The lowest specific contact resistivity of 3×10−3 Ω cm2 was obtained for Ti/Au annealed at 600 °C for 30 s. Ni/Au was less thermally stable and showed severe degradation of contact morphology at this annealing temperature. Both Pt and Ti with Au overlayers showed rectifying characteristics on p-ZnMgO, with barrier heights of ∼0.55–0.56 eV and ideality factors of ∼1.9. Comparison of these results with the same metals on n-type ZnO indicates that high surface state densities play a significant role in determining the effective barrier height.
ON LIFTINGS OF POWERS OF IRREDUCIBLE POLYNOMIALS

Let v be a henselian valuation of arbitrary rank of a field K with valuation ring Rv having maximal ideal Mv. Using the canonical homomorphism from Rv onto Rv/Mv, one can lift any monic irreducible polynomial with coefficients in Rv/Mv to yield monic irreducible polynomials over Rv. Popescu and Zaharescu extended this approach and introduced the notion of lifting with respect to a residually transcendental prolongation w of v to a simple transcendental extension K(x) of K. As it is well known, the residue field of such a prolongation w is , where is the residue field of the unique prolongation of v to a finite simple extension L of K and Y is transcendental over (see [V. Alexandru, N. Popescu and A. Zaharescu, A theorem of characterization of residual transcendental extension of a valuation, J. Math. Kyoto Univ.28 (1988) 579–592]). It is known that a lifting of an irreducible polynomial belonging to with respect to w, is irreducible over K. In this paper, we give some sufficient conditions to ensure that a given polynomial in K[x] satisfying these conditions which is a lifting of a power of some irreducible polynomial belonging to with respect to w, is irreducible over K. Our results extend Eisenstein–Dumas and generalized Schonemann irreducibility criteria.
High transmission LiF prism monochromator for separation of VUV wavelengths in frequency mixing experiments

Abstract We describe a simple, high throughput, LiF prism monochromator for the vacuum ultraviolet (VUV). The instrument throughput is 30% at 145 nm and the output can be tuned within the range 120–185 nm. The very high dispersion of LiF in the VUV means that neither narrow slits nor high precision are required. The suitability of this instrument for separation of coherent VUV radiation, generated by four-wave mixing, from the intense fundamental laser radiation (at 212 nm and the visible) is demonstrated. General advantages in throughput, polarization and resistance to radiation damage of such a prism instrument compared to a diffraction grating monochromator are discussed.
C and L band transionospheric scintillation experiment: Some results for applications to satellite radio systems

Satellite radio systems suffer loss of information in a wide band of frequencies during periods of intense ionospheric scintillation activity when the received signal undergoes rapid and deep fading. In order to assess the problem and to determine a proper fade margin for an Earth-space link, system engineers require information on signal statistics as well as on the morphological aspects of scintillations. Our observations near the northern boundary of the equatorial scintillation belt at (18.9° N geomagnetic) within the Indian zone show that the signal at 4/1.5 Ghz has faded often beyond 10 dB pp, and at times beyond 24 dB pp at 4 Ghz during equinoctial months of high solar activity during the years of 1989–1990. In addition to the morphology at 4 Ghz, information on signal statistics, such as cumulative amplitude distribution function, fade rate distribution, and signal reliability for different message lengths for some events of scintillations, both at C and L band, has been presented. The theoretical Nakagami m distribution has been found to be the best for describing various levels of fade. Autocorrelation and power-spectrum analysis have been used to estimate average fade rates and ground correlation distances. Performance evaluation of satellite Earth terminals using small antennas has been carried out to show the vulnerability of the system in the hostile ionospheric environment notwithstanding the advanced modulation systems being employed.
Shot boundary detection using scale invariant feature matching

This paper presents a shot boundary detection (SBD) method that finds boundaries between shots using the changes in visual content elements such as objects, actors, and background. Our work presented in this paper is based on the property that the features do not change significantly within a shot whereas they change substantially across a shot boundary. Noticing this characteristic of shot boundaries, we propose a SBD algorithm using the scale- and rotationinvariant local image descriptors. To obtain information of the content elements, we employ the scale invariant feature transform (SIFT) that has been commonly used in object recognition. The number of matched points is large within the same shot whereas zero or the small number of matched points is detected at the shot boundary because all the elements in the previous shot change abruptly in the next shot. Thus we can determine the existence of shot boundaries by the number of matched points. We identify two types of shot boundaries (hard-cut and gradual-transition such as tiling, panning, and fade in/out) with a adjustable frame distance between consecutive frames. Experimental results with four test videos show the effectiveness of the proposed SBD algorithm using scale invariant feature matching.
Improving E-Bike Safety on Urban Highways in China

This paper aims to examine characteristics of e-bike fatal crashes on urban highways in China. Crash data were retrieved from the three-year crash reports (2010–2012) of Taixing City. Descriptive analysis was conducted to examine characteristics of e-bike riders, drivers, and crashes. The important findings include the following: (1) most fatal crashes were related to e-bike riders’ aberrant driving behaviors, including driving in motorized lanes, red-light running, driving against the direction of traffic, inattentive driving, and drunk driving; (2) e-bike riders with lower educational background tended to perform illegal or inattentive driving behaviors in fatal crashes; (3) most drivers were not found to commit any faults and very few drivers were found to commit drunk driving offences; (4) most nighttime fatal crashes were related to absence of street lightings; (5) heavy good vehicles (HGVs) and small passenger cars were the two vehicle types that were mostly involved in the e-bike fatal crashes. This study provides useful information that can help traffic engineers better understand e-bike safety in China and develop safety countermeasures.
Statistical analysis of nonlinear factor analysis models

This paper presents a Bayesian analysis of a general nonlinear factor analysis model. Both the non-informative and conjugate prior distributions are considered. A hybrid algorithm that combines the Metropolis-Hastings algorithm and the Gibbs sampler is implemented to produce direct estimates of the latent factor scores and the structural parameters. Standard errors estimates as well as a goodness-of-fit statistic for assessing the posited model are presented. To illustrate the methodology, results from a simulation study and a real example are reported.
Complex flow characterisation of a porous tissue scaffold measured by Doppler optical coherence tomography

The flow of culture medium through a mechanically stimulated cell-seeded tissue scaffold is a factor influencing not only the transport of essential nutrients and waste product removal but also impacting on the degradation kinetics of the scaffold. Being able to map spatial and temporal changes in fluid flow behaviour is key to the development of improved bioreactors and tissue scaffold designs, especially for the new generation of multiple tissue reactors. In this paper we demonstrate the excellent metrological benefits of fast Doppler optical coherence tomography for time-lapse characterisation of tissue scaffolds placed in a dynamic flow environment.
Radial Tracing Method of Cytoplasm Segmentation in Overlapped Cervical Cell Images

ABSTRACT This paper proposes a new method to trace the obscure boundary of the cytoplasm in stained microscopic cervical cell images because of low intensity contrast with the background and the contaminations caused by inflammatory cells, blood stains, etc. A Gaussian filter is used for smoothing the image for suppressing the high frequencies. A bi-group enhancer is used to suppress the noise and to improve the contrast between the weak boundaries of the objects of nuclei and cytoplasm of cervical cells. The binarized bi-group image is used for nuclei segmentation. But the segmentation of cytoplasm in overlapped cervical cell images is really a very tedious task because of the fuzzy boundaries existing between cell images and the vague boundary which separates the cytoplasm and background. Hence, a gradient map is generated which is used as a base to radial trace the boundary of the cytoplasm to locate ambiguous boundaries. Once the true boundary of nuclei and cytoplasm is located, the quantitative metrics (e.g. nuclei area, cytoplasm area, the nucleus–cytoplasm ratio, etc.) can be calculated since cells in cancers and pre-cancers are characterized by many morphologic and architectural alterations, including shape and size of the cytoplasm and nucleus, an increasing nuclear–cytoplasmic ratio, etc.
The connection between centrifugal instability and Tollmien–Schlichting-like instability for spiral Poiseuille flow

For spiral Poiseuille flow with radius ratio $\eta\,{\equiv}\,R_i\slash R_o\,{=}\,0.5$, we have computed complete linear stability boundaries for several values of the rotation rate ratio $\mu\equiv{\it\Omega}_o\slash{\it\Omega}_i$}, where $R_i$ and $R_o$ are the inner and outer cylinder radii, respectively, and ${\it \Omega}_i$ and ${\it \Omega}_o$ are the corresponding (signed) angular speeds. The analysis extends the previous range of Reynolds number $Re$ studied computationally by more than eightyfold, and accounts for arbitrary disturbances of infinitesimal amplitude over the entire range of $Re$ for which spiral Poiseuille flow is stable for some range of the Taylor number $Ta$. We show how the centrifugally driven instability (beginning with steady or azimuthally travelling-wave bifurcation of circular Couette flow at $Re\,{=}\,0$ when $\mu\,{<}\,\eta^2$) connects, as conjectured by Reid (1961) in the narrow-gap limit, to a non-axisymmetric Tollmien–Schlichting-like instability of non-rotating annular Poiseuille flow at $Ta\,{=}\,0$. For $\mu\,{>}\,\eta^2$, we show that there is no instability for $0\,{\leq}\,Re\,{\leq}\,Re_{min}$. For $\mu\,{=}\,0.5$, $Re_{min}$ corresponds to a turning point, beyond which exists a range of $Re$ for which there are two critical values of $Ta$, with spiral Poiseuille flow being stable below the lower one and above the upper one, and unstable in between. For the special case $\mu\,{=}\,1$, with the two cylinders having the same angular velocity, $Re_{min}$ corresponds to a vertical asymptote smaller than found by Meseguer & Marques (2002), whose results for $\mu\,{>}\,\eta^2$ fail to account for disturbances with a sufficiently wide range of azimuthal wavenumbers.
Errors in Estimating Raindrop Size Distribution Parameters Employing Disdrometer and Simulated Raindrop Spectra

Abstract There have been debates and differences of opinion over the validity of using drop size distribution (DSD) models to characterize precipitation microphysics and to retrieve DSD parameters from multiparameter radar measurements. In this paper, simulated and observed rain DSDs are used to evaluate moment estimators. Seven estimators for gamma DSD parameters are evaluated in terms of the biases and fractional errors of five integral parameters: radar reflectivity (ZH), differential reflectivity (ZDR), rainfall rate (R), mean volume diameter (Dm), and total number concentration (NT). It is shown that middle-moment estimators such as M234 (using the second-third-fourth moments) produce smaller errors than lower- and higher-moment estimators if the DSD follows the gamma distribution. However, if there are model errors, the performance of M234 degrades. Even though the DSD parameters can be biased in moment estimators, integral parameters are usually not. Maximum likelihood (ML) and L-moment (LM) estima.