Miracle-dz/UniFAR-FTUs huggingface dataset:
Attenuation of short period seismic waves due to scattering

We point out first the inadequacy of the two widely used approaches in calculating the amplitude attenuation of seismic waves in a random medium, the formulation of mean field attenuation and that of the scattering coefficient under the single-scattering approximation. Then we calculate the average amplitude attenuation due to scattering in an infinite random slab. We slice the random slab into layers of thickness a correlation length and use the Born approximation for each slice to calculate the scattered field. To include the effect of multiple scattering, we take the back-halfspace integration of the scattered energy as the energy loss and do energy correction for each successive slice. Taking scalar wave approximation for seismic waves, we get a formula for average amplitude attenuation essentially valid for high frequency range (ka»1). The attenuation depends strongly on the form of correlation function of the random inhomogeneities. We derive the formulas for Gaussian, exponential and Von Karman correlation functions. The frequency dependence of attenuation by our formulation agrees well with experiments.
Exact solutions for the unsteady plane Couette flow of a dipolar fluid

The Laplace transform is used to determine two forms of the exact solution for the unsteady, isothermal, one–dimensional plane Couette flow of an incompressible dipolar fluid set in motion by the sudden acceleration from rest of the top plate. The solutions are found for arbitrary values of the dipolar constants d (⩾ 0) and l (> 0). In considering special/limiting cases of the dipolar constants, exact solutions are also determined for Rivlin–Ericksen fluids, fluids with couple stresses, and viscous Newtonian fluids. Specifically, steady–state development time, mass flux and the skinfriction coefficient are determined for all fluid types. The results obtained are then compared with those of dipolar fluids. The influence of the dipolar constants and the other physical parameters on the velocity field is also examined, as well as the effects of start–stop plate motion. Most significantly, it is shown that when d > 0 the velocity field suffers a jump discontinuity on start–up, a transient back–flow condition is possible when l > d, and for special values of the physical parameters the flow instantly attains a steady state. Lastly, numerical results are presented graphically, conclusions are stated and closing remarks follow.
Use of WhatsApp as a Platform to Promote English Oral Fluency and Accuracy: A Task Repetition Approach

Nowadays, English as a foreign language (EFL) teachers needed to adapt their practices to continue teaching the foreign language with the use of different emerging technologies and online platforms. This required them to develop a greater number of digital skills to promote students’ language production and achievement. Drawing on evidence which suggests that task repetition is beneficial for developing oral production in speaking and writing tasks, this exploratory study investigates the fluency and accuracy demonstrated by seven Mexican EFL students from a state university in a monologue narrative task performed on WhatsApp following a task repetition design. Fluency and accuracy metrics show that these skills appear to fluctuate in the students during the performance of the task. Interestingly, they also suggest that only fluency increased as the weeks went by, while accuracy development was limited. These results raise questions about the dynamic nature of fluency and how it may interact with accuracy, other language dimensions, student-related factors, and the online environment.
Gorenstein homological algebra

In basic homological algebra, the projective, injective and flat dimensions of modules play an important and fundamental role. In this paper, the closely related Gorenstein projective, Gorenstein injective and Gorenstein flat dimensions are studied. There is a variety of nice results about Gorenstein dimensions over special commutative noetherian rings; very often local Cohen–Macaulay rings with a dualizing module. These results are done by Avramov, Christensen, Enochs, Foxby, Jenda, Martsinkovsky and Xu among others. The aim of this paper is to generalize these results, and to give homological descriptions of the Gorenstein dimensions over arbitrary associative rings. Introduction Throughout this paper, R denotes a non-trivial associative ring. All modules are—if not specified otherwise—left R–modules. When R is two-sided and noetherian, Auslander and Bridger [2] introduced in 1969 the G-dimension, G-dimRM , for every finite, that is, finitely generated, R–module M (see also [1] from 1966/67). They proved the inequality G-dimRM 6 pdRM , with equality G-dimRM = pdRM when pdRM is finite. Furthermore they showed the generalized Auslander–Buchsbaum formula (sometimes known as the AuslanderBridger formula) for the G-dimension. Over a general ring R, Enochs and Jenda defined in [9] a homological dimension, namely the Gorenstein projective dimension, GpdR(−), for arbitrary (non–finite) modules. It is defined via resolutions with (the so-called) Gorenstein projective modules. Avramov, Buchweitz, Martsinkovsky and Reiten prove that a finite module over a noetherian ring is Gorenstein projective if and only if G-dimRM = 0 (see the remark following [7, Theorem (4.2.6)]). Section 2 deals with this Gorenstein projective dimension, GpdR(−). First we establish the following fundamental. Theorem. The class of all Gorenstein projective modules is resolving, in the sense that if 0 → M ′ → M → M ′′ → 0 is a short exact sequence of R–modules, where M ′′ is Gorenstein projective, then M ′ is Gorenstein projective if and only if M is Gorenstein projective. 2000 Mathematics Subject Classification. 13D02, 13D05, 13D07, 16E05, 16E10, 16E30.
Effects of positive reappraisal and self-distancing on the meaningfulness of everyday negative events

Current work on meaning-making has primarily focused on major negative life events such as trauma and loss, leaving common daily adversities unexplored. This study aimed to examine how utilizing meaning-making strategies such as positive reappraisal and self-distancing (in isolation or in combination) can facilitate an adaptive processing of these daily negative experiences. Overall meaning and facets of meaning (coherence, purpose, and significance/mattering) were assessed at both global and situational levels. Results suggested that positive reappraisal was generally effective for enhancing situational meaning but not under all conditions. Specifically, when negative experiences were high on emotional intensity, reflecting on the experience from a distanced (third-person) perspective enhanced coherence and existential mattering more than engaging in positive reappraisal. However, when negative experiences were low on intensity, distanced reflection led to less coherence and mattering than positive reappraisal. The findings of this study elucidated the importance of examining the multidimensional construct of meaning at the facet level and highlighted the importance of applying different coping strategies to effectively make meaning out of daily negative experiences.
Convex stochastic control problems

The solution of the infinite horizon stochastic control problem under certain criteria, the functional characterization and computation of optimal values and policies, is related to two dynamic programming-like functional equations: the discounted cost optimality equation (DCOE) and the average cost optimality equation (ACOE). The authors consider what useful properties, shared by large and important problem classes, can be used to show that an ACOE holds, and how these properties can be exploited to aid in the development of tractable algorithmic solutions. They address this issue by concentrating on structured solutions to stochastic control models. By a structured solution is meant a model for which value functions and/or optimal policies have some special dependence on the (initial) state. The focus is on convexity properties of the value function. <<ETX>>
Dipole Radiation From a Cylindrical Hole in the Earth

This report examines the problem of an antenna radiating from a cylindrical hole in the earth and the subsequent far-zone field produced in the upper air half space. The approach used for this analysis was to first examine propagation characteristics along the hole for surrounding geologic material properties. Three cases of sand with various levels of moisture content were considered as the surrounding material to the hole. For the hole diameters and sand cases examined, the radiation through the earth medium was found to be the dominant contribution to the radiation transmitted through to the upper half-space. In the analysis presented, the radiation from a vertical and a horizontal dipole source within the hole is used to determine a closed-form expression for the radiation in the earth medium which represents a modified element factor for the source and hole combination. As the final step, the well-known results for a dipole below a half space, in conjunction with the use of Snell's law to transform the modified element factor to the upper half space, determine closed-form expressions for the far-zone radiated fields in the air region above the earth.
COMPUTATION OF OPTIMAL COPLANAR ORBIT TRANSFERS

The use of simplified equations of motion ‘is the reason why nearly circular orbit transfers are singular for both impulsive optimization and optimal control since the eccentricity is a factor in the equation governing the location of the burns. A more detailed analysis of the change of the costate during the burns and during the coasting phase enables us to define . a preliminary analytic guess of the initial costate for coplanar orbit transfer with free final time. A classical trajectory optimization tool is used to improve the estimate ofthe costate and to find the solution of the optimal transfer. The presentation is restricted to minimum fuel criterion and constant thrust case. The results obtained in the last section . demonstrate the performance of the preliminary algorithm and propose some further improvements.
Singularities in the nilpotent scheme of a classical group

If (X, x) is a pointed scheme over a ring k, we introduce a (generalized) partition ord(x, X/k). If G is a reductive group scheme over k, the existence of a nilpotent subscheme N(G) of Lie(G) is discussed. We prove that ord(x, N(G)/k) characterizes the orbits in N(G), their codimension and their adjacency structure, provided that G is Gln, or SPn and 1/2 E k. For SOn only partial results are obtained. We give presentations of some singularities of N(G). Tables for its orbit structure are added. Introduction. Let G be a reductive algebraic group over a field of characteristic p. Let g be its Lie-algebra and N(G) the closed subset of the nilpotent elements of g, cf. [19]. The G-orbits in N(G) are characterized by weighted Dynkin diagrams,cf. [20, III]. Consider the following question. Is it possible to classify the orbits in N(G) using only the local structure of the variety N(G)? We prove in (4.3) that the answer is positive if G is Gln or if G is SPn and p * 2. To this end we introduce a local invariant "ord" for any pointed scheme in ? 1. We develop the theory of N(G) over an arbitrary ground ring k in ? 2. In ? 3 we restrict our attention to the classical group schemes. Using a cross section we obtain information about the orbit structure of N(G). Our main theorem (4.2) relates ord(x, N(G)/k) to the Jordan normal form of the nilpotent endomorphism induced by x in the classical representation. This paper is a condensed version of [13]. The author wishes to express his gratitude to his thesis adviser, Professor T. A. Springer. Conventions and notations. The cardinality of a set V is denoted by # V Any infinite cardinal is represented by oo. If x is a real number then [x] is thc greatest integer in x. All rings are commutative with 1. Let M be a module over a ring A. If M is free the rank of M is denoted by rgAM. An element r E A is called M-regular if a: M M is injective. Let a = (a,, . . , ar) be a Received by the editors March 18, 1975. AMS (MOS) subject classifications (1970). Primary 14B05, 14L15; Secondary 05A17, 10C30, 13H15, 20G35.
Reflection at a Curved Dielectric Lnterface--- Electromagnetic Tunneling

The reflection of a locally plane wave from a curved interface between two nonabsorbing dielectric media is investigated. Our analysis is applicable to an interface of general shape, defined at each point by the two principal radii of curvature. When the wave is incident from the denser medium at angles greater than the critical angle it is only partially reflected, due to a form of electromagnetic tunneling. Generalized Fresnel transmission coefficients and an extension of Snell's law are derived to account for this transmission into the less dense medium. Ray tracing can then be applied to determine such phenomena as the bending losses in optical slab waveguides, and the curvature loss of skew rays within straight optical waveguides of circular cross section.
Spectral signature of uncombed penumbral magnetic fields - Reply

The uncombed penumbral model proposed by Solanki & Montavon (1993) is used to understand some recent observational results found in penumbrae. This model uses a penumbral magnetic field structured into horizontal flux tubes embedded in a more vertical background field. A modified version of this model, with a weaker field strength in the horizontal tubes, is used to explain the gradient with height of field strength and inclination found in studies using inversion techniques. These studies have found that over a range of 300 km, the field strength of the outer penumbra increases with height by more than 500 G. Similarly, the field inclination decreases with height by 30◦ in the same range of heights. We show that spectra generated by the uncombed model can give rise to these two effects as long as the horizontal tubes (of ∼100 km diameter) remain unresolved. We also study the linear, quadratic and rms fluctuations of the inclination gradients that can be generated by the uncombed model. These gradients are found to be compatible with those obtained from the null divergence condition and those derived from observations of net circular polarization. A key ingredient to explain these gradients is the contribution of the two boundary layers that enclose the horizontal magnetic tubes as seen by the line-of-sight. Our realization of the uncombed model also predicts values of the net circular polarization observed with the Advanced Stokes Polarimeter. The existence of a pure background penumbral field as proposed by the model is, however, put into question.
The timing of vortex shedding in a cylinder wake imposed by periodic inflow perturbations

The interaction of vortex shedding from a circular cylinder with an inflow which has low-amplitude periodic velocity oscillations (perturbations) superimposed upon it, was investigated experimentally by means of particle image velocimetry. The experiments were made at three perturbation frequencies across the lock-on range in which the vortex shedding frequency is synchronized with the subharmonic of the imposed frequency. The basic wake pattern in this range is antisymmetric vortex shedding, i.e. the familiar 2S mode. The timing of vortex shedding is defined with respect to the cross-flow oscillation of the wake which is found to play a critical role. Quantitative analysis of the phase-referenced patterns of vorticity distribution in the wake shows that a vortex is actually shed from the cylinder when the cross-flow oscillation of the wake is strongest, marked by a sudden drop in the computed vortex strength. At the middle of the lock-on range, shedding occurs near the minimum inflow velocity in the cycle or, equivalently, during the forward stroke of a cylinder oscillating in-line with the flow. It is argued that the imposed timing of vortex shedding relative to the cylinder motion induces a negative excitation from the fluid, which might explain why the in-line response of a freely vibrating cylinder exhibits two positive excitation regions separated by the lock-on region found in forced oscillations.
How YouTubers Make Popular Marketing Videos? Speech Acts, Move Structure, and Audience Response in YouTube Influencer Marketing Videos

In recent years, the promotional discourse has grown more versatile due to the emergence of new social media. YouTube influencer marketing is of increasing significance for brands’ promotion, especially in the beauty category. Many studies on the effect of influencer marketing used self-reported surveys, the results of which provide limited help in formulating effective videos. The current study aims to characterize YouTube influencer marketing videos through speech act analysis and genre analysis and then determine the features significantly associated with audience response through correlation analysis. The study collects 12 videos from 8 YouTubers in the beauty category and finds that the overall speech act composition is 56% assertives, 26% expressives, 10.1% commissives, and 7.4% directives. The study also proposes a 10-move structure. Significant positive correlations are reported between audience response and the percentage of directives and three moves, advising YouTubers to utilize more directive speech acts, share more personal experience, and spend more time preparing the audience in the opening of videos soliciting subscription.
Addressing Cognitive Function and Psychological Well-Being in Chronic Kidney Disease: A Systematic Review on the Use of Technology-Based Interventions

Patients with chronic kidney disease (CKD) are at risk of both a gradual decline in cognitive function and an increase in psychological distress. This includes symptoms of anxiety, depression, and sleep disturbances, all of which are factors that have been associated with increased morbidity and mortality. In response, we are now seeing that interventions based on new digital technologies are increasingly used in order to optimize patients’ quality of life. Systematic research of the literature on electronic databases (MEDLINE/PubMed, Scopus, Web of Science, and PsycInfo/ProQuest) covering the period from 2012 to 2022 was conducted in order to methodically review the existing evidence regarding the implementation and effectiveness of technology-based interventions in the management of cognitive and psychological well-being symptoms in patients with CKD. A total of 739 articles were retrieved, 13 of which are included in the present review. All the studies focused on the usability, acceptability, and feasibility of technology-based interventions aimed at psychological symptoms, with no studies targeting cognitive functioning. Technology-based interventions offer feelings of safety, fun, and satisfaction, and they also have the potential to improve CKD patients’ health outcomes regarding their psychological well-being. The diverseness of technologies allows an approximation towards the identification of those types of technologies most frequently used, as well as the symptoms targeted. There was considerable heterogeneity in the types of technologies used for interventions in so few studies, making it difficult to draw conclusive findings with regard to their efficiency. In order to adequately assess the technology-based health interventions effect, future lines of research should consider designing non-pharmacological treatments for the improvement of cognitive and psychological symptoms in this type of patient.
Modulation of a semicondutor‐to‐semimetal transition at 7 THz via coherent lattice vibrations

This letter introduces the general notion of significantly modulating the physical characteristics of a solid on a terahertz time scale with coherent lattice vibrations. We show, as an example, experiments in which coherent phonons are optically excited in single‐crystal Ti2O3, which is a narrow‐gap semiconductor at 300 K and gradually transforms into a semimetal at 600 K. Quantitative comparison of previous equilibrium measurements to our new transient measurements suggests that the induced coherent lattice vibration is significantly modulating the semiconductor‐to‐semimetal transition at 7 THz.
A General Necessary Condition for Exact Observability

Suppose $A$ generates an exponentially stable strongly continuous semigroup on the Hilbert space $X,Y$ is another Hilbert space, and $C : D(A) \rightarrow Y$ is an admissible observation operator for this semigroup. (This means that to any initial state in $X$ we can associate an output function in $L^{2}([0,\infty),Y)$. ) This paper gives a necessary condition for the exact observability of the system defined by $A$ and $C$. This condition, called (${\bf E}$), is related to the Hautus Lemma from finite dimensional systems theory. It is an estimate in terms of the operators $A$ and $C$ alone (in particular, it makes no reference to the semigroup). This paper shows that (${\bf E}$) implies approximate observability and, if $A$ is bounded, it implies exact observability. This paper conjectures that (${\bf E}$) is in fact equivalent to exact observability. The paper also shows that for diagonal semigroups, (${\bf E}$) takes on a very simple form, and applies the results to sequences of complex exponential functions.
The effect of a mesenteric traction syndrome on internal carotid artery blood flow

Purpose During abdominal surgery, manipulation of internal organs may induce a “mesenteric traction syndrome” (MTS) including a triad of flushing, hypotension, and tachycardia that lasts for approximately 30 min. We evaluated whether MTS affects internal carotid artery blood flow. Methods This prospective cohort study included 27 patients aged 65 ± 11 years (mean ± SD) undergoing stomach resection (n = 12), esophageal resection (n = 14), or gastro-entero anastomosis (n = 1) during propofol-remifentanil and thoracic epidural anesthesia. Duplex ultrasound determined internal carotid artery blood flow, laser Doppler flowmetry assessed forehead skin blood flow, and near-infrared spectroscopy determined cerebral oxygenation. Development of MTS was defined by flushing within 60 min after incision. Results Seven patients developed MTS 22 [20–26; median (IQR)] min after incision and at that time the change in heart rate (to 87 ± 13 vs. 70 ± 11 bpm; P = 0.0007) and skin blood flow (to 214 (134–269) vs. 84 (59-112 PU; P = 0.0044) was higher in the patients who developed MTS as compared to those who did not, while mean arterial pressure (63 ± 13 vs. 64 ± 14 mmHg; P = 0.1433), cerebral oxygenation (69 ± 9% vs. 63 ± 10%; P = 0.2485), and internal carotid artery flow (225 ± 53 vs. 203 ± 69 ml/min; P = 0.9529) were similar. Conclusion Hemodynamic perturbations are observed in some patients in response to manipulation of the viscera, but the development of MTS appears not to influence internal carotid artery flow. Clinical trial registration https://clinicaltrials.gov/ct2/show/NCT02951273? term=NCT02951273&rank=1, identifier: NCT02951273.
Success run statistics defined on an urn model

Statistics denoting the numbers of success runs of length exactly equal and at least equal to a fixed length, as well as the sum of the lengths of success runs of length greater than or equal to a specific length, are considered. They are defined on both linearly and circularly ordered binary sequences, derived according to the Pólya-Eggenberger urn model. A waiting time associated with the sum of lengths statistic in linear sequences is also examined. Exact marginal and joint probability distribution functions are obtained in terms of binomial coefficients by a simple unified combinatorial approach. Mean values are also derived in closed form. Computationally tractable formulae for conditional distributions, given the number of successes in the sequence, useful in nonparametric tests of randomness, are provided. The distribution of the length of the longest success run and the reliability of certain consecutive systems are deduced using specific probabilities of the studied statistics. Numerical examples are given to illustrate the theoretical results.