Miracle-dz/UniFAR-FTUs huggingface dataset:
An investigation of resonant waves in a numerical model of an observed sudden stratospheric warming

Abstract The major stratospheric sudden warming of February 1979 was characterized by the interaction of the zonal flow with a wavenumber 2 perturbation that was eastward traveling in the early stages of the warming, and slowed to stationary around the time of the wind reversal. Steady state calculations by Smith and Avery 1987 of wave 2 structure for the observed wind fields during this prewarming period indicate a sharp resonance of eastward traveling wave 2. The frequency range for which wave 2 is resonant shifts towards lower (stationary) values with increasing time. This suggests that resonant self-tuning may have played a role in the 1979 sudden warming. In self-tuning, a resonant, or near resonant wave, grows and interacts with the basic state; the change in the basic state modifies the conditions for resonance and the wave frequency then shifts in such a way that it continues to stay near the resonant frequency and to grow. A quasi-linear time-dependent model is used to investigate several questio.
Optimal control of a finite dam: average-cost case

We consider the problem of minimizing the long-run average cost per unit time of operating a finite dam in the class of the policies of the following type. Assume that the dam is initially empty, the release rate is kept at 0 until the dam storage increases to λ, and as soon as this occurs, water is released at rate M, then the output rate is kept at M as long as the dam storage is more than τ and it must be decreased to 0 if the dam storage becomes τ. We assume that the input of water into the finite dam is a Wiener process with non-negative drift μ and variance parameter σ 2. There is a cost in increasing the output rate from 0 to M as well as in decreasing the rate from M to 0 and whenever the dam storage is below level a, there is a penalty cost per unit time depending on the level. A reward is given for each unit of water released. In this paper, the long-run average cost per unit time is determined, and therefore the optimal policy can be found numerically.
Distribution-Free Statistical Methods

The preparation of several short courses on distribution-free statisti- cal methods for students at third and fourth year level in Australian universities led to the writing ofthis book. My criteria for the courses were, firstly, that the subject should have a clearly recognizable underlying common thread rather than appear to be a collection of isolated techniques. Secondly, some discussion of efficiency seemed essential, at a level where the students could appreciate the reasons for the types of calculations that are performed, and be able actually to do some of them. Thirdly, it seemed desirable to emphasize point and interval estimation rather more strongly than is the case in many of the fairly elementary books in this field. Randomization, or permutation, is the fundamental idea that connects almost all of the methods discussed in this book. Application of randomization techniques to original observations, or simple transformations of the observations, leads generally to conditionally distribution-free inference. Certain transformations, notably 'sign' and 'rank' transformations may lead to unconditionally distribution-free inference. An attendant advantage is that useful tabulations of null distributions of test statistics can be produced. In my experience students find the notion of asymptotic relative efficiency of testing difficult. Therefore it seemed worthwhile to give a rather informal introduction to the relevant ideas and to concentrate on the Pitman 'efficacy' as a measure of efficiency.
Preferred Representations of Middle School Algebra Students When Solving Problems

Preferences of middle school algebra students for certain representations were investigated in this research study. Previous studies reported that students from a wide range of ages and abilities have a preference for certain types of representation when solving algebraic problems. This study focused on representational preferences of middle school algebra students of different achievement levels when they solved problems involving linear relationships with one unknown. The study was conducted with a relatively large sample size (N = 443) of 7 th and 8 th grade students from one US urban district with low performance in mathematics. The students' achievement level was measured by the mathematics portion of the statewide Comprehensive Assessment System (sCAS). Analysis of the collected data generated explanations of the roots for their preferences and recommendations for teaching are provided.
Numerical simulation of annular flow boiling in microchannels

Flow boiling in microchannels has been researched for decades due to its potential for heat transfer applications in micro structured devices. The large number of existing experimental datasets and fitted correlations show considerable scatter and lack a mechanistic basis. The computational fluid dynamics (CFD) model developed here applies to boiling in the annular flow regime and provides insights into the underlying behaviour. Analysis of the heat transfer augmentation by interfacial waves is studied. Parametric investigations are performed using the model to understand the impact of important flow and system parameters. The calculated heat transfer coefficients are consistent with those from existing correlations, showing no more scatter than the data used to create them.
Larry Brown: Remembrance and Connections of His Work to Observational Studies

Statistics lost one of our giants when Larry Brown passed away in February, 2018 at the age of 77. Many lost a friend, a mentor and a teacher. I had the good fortune to be Larry’s colleague for the past 16 years. While I wasn’t as close to him as many others, Larry was my friend and I looked up to him. Larry loved thinking. When Larry got interested in something and scratched his head, I could see his enjoyment. Steam seemed to come out as Larry was thinking and then he happily shared his thoughts. Larry’s classes and talks were full of insights. After joining the faculty at Wharton, I attended Larry’s linear models first year PhD course even though I had seen the material before. I was glad I took the time to do so as I learned a lot, and seeing how Larry thought deeply through things from different perspectives (e.g., he often presented both a geometric and a statistical perspective) was memorable and inspiring. Larry often mentioned questions he had about methods or results, and directions of research he thought could be expanded upon, which I think motivated students to see statistics as a field full of open questions and research opportunities rather than a dead field. Larry was generous with his time. Whenever I had a student for whom it was unclear which other faculty members had the expertise to serve on their dissertation committee, I suggested asking Larry because I knew he would be willing to spend time talking with the student, read the dissertation seriously and have something thoughtful to say. A few days before Larry’s passing, when he knew his time was short, he was writing recommendation letters for students. Larry spent much time on public service, and he encouraged me about its value to society even though one may not get recognition for it. Larry worked hard. He was active in research, teaching and mentoring students and public service until his passing. The large number of Larry’s former students who traveled to his funeral from places far away at short notice (Hong Kong even! ) was a testament to Larry’s impact on their lives. Larry also made good time for family and friends. Besides the much time spent together with his wife Linda and their family, Larry made the time for trips over the summer alone with his sons. Larry treated people with respect and decency regardless of their status. At a time when I was the postdoctoral coordinator for our department, a PhD student from a little known university in India contacted Larry about a post doc opening in our department and
Groupes du ping-pong et géodésiques fermées en courbure -1

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storm observed by Cluster

dispersion of H + and O + and bouncing properties of H + ,w e show that the ions originate from a distant source located near 80 Re down tail. Our results show that the magnetotail is topographically stable to support multiple bouncing of H + ions during a storm period. Furthermore these results could suggest that the plasmasheet H + and O + ions have been accelerated to the same velocity in the vicinity of a reconnection region. INDEX TERMS: 2700 Magnetospheric Physics; 2744 Magnetospheric Physics: Magnetotail; 2748 Magnetospheric Physics: Magnetotail boundary layers; 2764 Magnetospheric Physics: Plasma sheet; 2788 Magnetospheric Physics: Storms and substorms. Citation: Korth, A. , et al. (2004), Ion injections at auroral latitude during the March 31, 2001 magnetic storm observed by Cluster, Geophys. Res. Lett. , 31, L20806, doi:10.1029/2004GL020356.
Influence of model parameters and the vane response method on a low-order prediction of fan broadband noise

The influence of modeling choices on a low-order method for predicting broadband interaction noise downstream of a fan stage in a turbofan engine is explored. The general method relies on experimentally or computationally obtained rotor-wake turbulence parameters as input. These parameters are used together with the Liepmann spectrum to define the inflow into the exit guide vane. Strip-theory allows the full 3D vane response to be constructed using a gust response model for a 2D vane. The sound power in the duct downstream of the exit guide vanes is calculated using the Green’s method for an annular duct. Comparison is made between the predictions obtained with a 2D flat-plate cascade gust response and a 2D flat-plate airfoil gust response. In addition, the effect of the inclusion of real vane geometry via an asymptotic gust response method is investigated. It is shown that for the current modeling method, a cascade response must be used and that the asymptotic method does not extend to high enough camber and angle of attack to be representative of modern vane geometries. It is concluded that the simpler flat-plate-based model is sufficient.
First determination of the 8 Li valence neutron asymptotic normalization coefficient using the 7 Li( 8 Li, 7 Li) 8 Li reaction

We report here a determination of the asymptotic normalization coefficient of the valence neutron in ${}^{8}$Li from a measurement of the angular distribution of the ${}^{7}$Li(${}^{8}$Li,${}^{7}$Li)${}^{8}$Li reaction at 11 MeV. Using isospin symmetry the ${}^{8}$B ANC has also been calculated and used to infer a value for ${S}_{17}(0)$ of 20.2 $\ifmmode\pm\else\textpm\fi{}$ 4.4 eV b.
New Internal-Wave Model in a Two-Layer Fluid

AbstractTo model internal waves, high-level Green-Naghdi (GN) equations that are strongly nonlinear were developed for a two-layer fluid with a rigid lid over the upper layer. The GN models were applied to two internal-solitary-wave cases: weakly dispersive and strongly dispersive. In the weakly dispersive case, the ratio between the upper and lower layers was 1:4.13. In the strongly dispersive case, the two depth ratios between the upper and lower layers were 1:24 and 10.13:1. For both the weakly and strongly dispersive test cases, the converged GN results for wave speed, wave profile, and velocity distribution agreed well with the experimental data and the solution of Euler equations, even for large-amplitude solitary waves. For the strongly nonlinear and strongly dispersive cases, the converged GN results showed better accuracy than some other strongly nonlinear models.
Improving crystallinity of femtosecond-laser hyperdoped silicon via co-doping with nitrogen

Laser hyperdoped silicon with high crystallinity in doped layer is obtained by method of femtosecond laser irradiation in NF3/SF6 gas mixture. SIMS measurement indicates nitrogen and sulfur dopants are incorporated into the top layer of about 300 nm at concentrations above 1019 cm−3, SAD and Raman Spectrum results show that there is approximately crystalline silicon in the doped layer. The crystallinity in doped layer of the laser co-hyperdoped silicon is almost same as that of the annealed sample at 800 K prepared in SF6. The improvement of crystallinity is attributed to the hyperdoped nitrogen, which is effectively on repairing the defects in the doped layer. The light absorption is more than 95% over the range of 300-1100 nm, and about 80% in the 1200-2500 nm wavelength range.
A CASE STUDY OF MATHEMATICS SELF-EFFICACY IN A FRESHMAN ENGINEERING MATHEMATICS COURSE

by Jacob Rowland Burnham, M.S. Washington State University May 2011 Chair: Shane A. Brown Student retention in engineering majors has become a cause for concern to the future of the science and technology industry in the United States. Researchers have since produced large bodies of evidence indicating a positive relationship between mathematics self-efficacy and students’ choice of science-related educational and career pathways (Betz and Hackett, 1983; Hackett and Betz, 1989; Lent et al., 1991). This study examined the effects of an introductory math course grounded in engineering context on the mathematics self-efficacy of 27 college freshman with the intent to pursue engineering. Surveys and interviews conducted before and after the course were triangulated to identify consistent, inconsistent, and contradictory findings of efficacy change for each student. Students were grouped based on the similarities in efficacy experiences that they demonstrated in their responses to each method. Following pattern coding of interviews, group analysis was performed to identify, within each group, common mechanisms/sources of efficacy as dictated by Bandura’s SelfEfficacy Theory. Results of a paired t-test analysis of a modified version of the Mathematics Self-Efficacy Survey (MSES) indicated a significant increase in students’ math problem solving
Some results on best L1-approximation of continuous functions

The chief purpose of this paper is to study the question of uniqueness of best L1-approximations for weighted approximation of continuous vector-valued functions and continuous functions of several variables by finite dimensional subspaces G. A uniqueness result for special subspaces G of the type G=G1, ×…×Gm is given. Moreover It is studied whether a sufficient condition for uniqueness introduced by DeVore and Strauss and in a more general context by Kroo is also necessary or not and a class of finite dimensional subspaces G for which a positive answer can be given is presented. Finally it is shown that subspaces of linear spline functions of two variables fail to have that sufficient property.
The emission structure between 11 and 13 µm across the Orion ionization front

Des observations spectrophotometriques dans la region 11-13 μm le long d'une ligne nord-sud a travers le front d'ionisation au sud-est du Trapeze dans Orion sont presentees. Les caracteristiques des emissions observees suggerent que les bandes d'emission sont produites par stimulation de molecules telles que les hydrocarbures polycycliques aromatiques, mais l'existence de deux bandes bien definies dans la region 11-13 μm indique preferentiellement un petit nombre d'especes dominantes
Three-dimensional effects on flag flapping dynamics

We examine three-dimensional (3D) effects on the flapping dynamics of a flag, modelled as a thin membrane, in uniform fluid inflow. We consider periodic spanwise variations of length $S$ (ignoring edge effects), so that the 3D effects are characterized by the dimensionless spanwise wavelength ${\it\gamma}=S/L$ , where $L$ is the chord length. We perform linear stability analysis (LSA) to show increase in stability with ${\it\gamma}$ , with the purely 2D mode being the most unstable. To confirm the LSA and to study nonlinear responses of 3D flapping, we obtain direct numerical simulations, up to Reynolds number 1000 based on $L$ , coupling solvers for the Navier–Stokes equations and that for a thin membrane structure undergoing arbitrarily large displacement. For nonlinear flapping evolution, we identify and characterize the effect of ${\it\gamma}$ on the distinct flag motions and wake vortex structures, corresponding to spanwise standing wave (SW) and travelling wave (TW) modes, in the absence and presence of cross-flow respectively. For both SW and TW, the response is characterized by an initial instability growth phase (I), followed by a nonlinear development phase (II) consisting of multiple unstable 3D modes, and tending, in long time, towards a quasi-steady limit-cycle response (III) dominated by a single (most unstable) mode. Phase I follows closely the predictions of LSA for initial instability and growth rates, with the latter increased for TW due to suppression of restoring forces by the cross-flow. Phase II is characterized by multiple competing flapping modes with energy cascading towards the more unstable mode(s). The wake is characterized by interwoven (SW) and oblique continuous (TW) shed vortices. For phase III, the persistent single dominant mode for SW is the (most unstable) 2D flag displacement with a continuous parallel wake structure; and for TW, the fundamental oblique travelling-wave flag displacement corresponding to the given ${\it\gamma}$ with continuous oblique shedding. The transition to phase III occurs slower for greater ${\it\gamma}$ . For the total forces, drag decreases for both SW and TW with decreasing ${\it\gamma}$ , while lift is negligible in phase I and II and comparable in magnitude to drag in phase III for any ${\it\gamma}$ .
Some Properties of Local Gaussian Correlation and Other Nonlinear Dependence Measures

This article consists of two parts. The first one contains a brief review of global and local dependence measures, including the local Gaussian correlation. For this, the local correlation at a point x is obtained by approximating the given bivariate density f at x by a bivariate Gaussian and then taking the correlation of that bivariate Gaussian as the definition of local Gaussian correlation. The second part consists in a bias study of the local Gaussian correlation. A small simulation experiment is performed. In the Appendix, the possibility of a neighbourhood‐free definition of local Gaussian correlation is explored.
Mad Mothering: Learning From the Intersections of Madness, Mothering, and Disability

Abstract:The article brings together the fields of mad studies (LeFrancois et al.), matricentric feminism (O'Reilly, Matricentric Feminism) and critical disability studies (Goodley, "Dis/entangling Critical Disability Studies"). The aim is to expose and challenge "relations of ruling" (Smith 79) that both produce and discipline "mad mothers of disabled children. " The analysis begins by exploring the un/commonalities of the emerging histories of the three disciplines. The article then identifies analytical points of intersection, including critiques of neoliberalism; troubling the "norm" (including radical resistance and activism); intersectionality, post-colonial and queer theory. Finally, the article turns to points of divergence and possible tensions between these theoretical approaches as it explores the absence of disability in matricentric feminism, the contested place of mothering in critical disability studies, and the absence of mothering in mad studies.
Study on the statistical method of wind direction

In the nuclear safety analysis and environmental impact assessment,hourly weather data must be used.However,the calculation method and the statistic method of hourly wind direction from automatic weather stations have not been defined as normal rules in the corresponding regulations similar to "ground observational criterion" and "nuclear safety guide" in China,so the statistical method of the hourly wind direction was discussed in this paper.Four methods were often used to the calculation of average wind direction,including the methods of an arithmetic mean,a sliding average,a vector average and a highest frequency.The first two methods were modified since they produce the error when wind direction across 0° was calculated.The results indicate that the modified method for wind direction across 0° is simple and accurate.The modified arithmetic mean method is more reliable when the data 10-min ahead normal hours are used as the hourly data of wind direction.However,it is easy to produce error using this method when wind speed is zero.Thus,a vector average method is recommended when the frequency of light wind and calm is high.The hourly wind direction statistic methods from "RG1.23 guide" presented by U.S and from "nuclear safety guide" and "ground observational criterion" in China differ each other,so the results from the above methods are compared with the observational data by using the same calculation algorithm.Using the wind direction with a 10-min average and a 15-min average before normal hours or other period of time as the hourly wind direction,the consistency of correlation matrix is 97.87%;using average of each 15-min value in one hour or average of each 10-min value in one hour as the hourly wind direction,their consistency is 99.96%. The consistency between the two classification methods and the method of average of a 10-min and a 15-min in one hour is only 86.00%. Using a 60-min average as the hourly wind direction,the consistency is the worst among all methods.
Hydrodynamics of swimming in stingrays: numerical simulations and the role of the leading-edge vortex

Stingrays, in contrast with many other aquatic animals, have flattened disk-shaped bodies with expanded pectoral ‘wings’, which are used for locomotion in water. To discover the key features of stingray locomotion, large-eddy simulations of a self-propelled stingray, modelled closely after the freshwater stingray, Potamotrygon orbignyi, are performed. The stingray’s body motion was prescribed based on three-dimensional experimental measurement of wing and body kinematics in live stingrays at two different swimming speeds of 1.5 and $2.5L~\text{s}^{-1}$ ( $L$ is the disk length of the stingray). The swimming speeds predicted by the self-propelled simulations were within 12 % of the nominal swimming speeds in the experiments. It was found that the fast-swimming stingray (Reynolds number $Re=23\,000$ and Strouhal number $St=0.27$ ) is approximately 12 % more efficient than the slow-swimming one ( $Re=13\,500$ , $St=0.34$ ). This is related to the wake of the fast- and slow-swimming stingrays, which was visualized along with the pressure on the stingray’s body. A horseshoe vortex was discovered to be present at the anterior margin of the stingray, creating a low-pressure region that enhances thrust for both fast and slow swimming speeds. Furthermore, it was found that a leading-edge vortex (LEV) on the pectoral disk of swimming stingrays generates a low-pressure region in the fast-swimming stingray, whereas the low- and high-pressure regions in the slow-swimming one are in the back half of the wing and not close to any vortical structures. The undulatory motion creates thrust by accelerating the adjacent fluid (the added-mass mechanism), which is maximized in the back of the wing because of higher undulations and velocities in the back. However, the thrust enhancement by the LEV occurs in the front portion of the wing. By computing the forces on the front half and the back half of the wing, it was found that the contribution of the back half of the wing to thrust in a slow-swimming stingray is several-fold higher than in the fast-swimming one. This indicates that the LEV enhances thrust in fast-swimming stingrays and improves the efficiency of swimming.