Miracle-dz/UniFAR-FTUs huggingface dataset:
International comparative studies in mathematics education: are we obsessed with the international rankings of measured educational outcomes?

ABSTRACT Over the past few decades, researchers, policy makers, educators and the general public, who have an interest in mathematics education in different countries, pay a great deal of attention to the results from international comparative studies. Of great interest to the international studies is the results of Eastern students consistently achieving higher marks among the participating countries. In recent years, we have seen a climate of intense global economic competition and a growing belief in the key role of education, which have persuaded governments to become increasingly obsessed with the international rankings of measured educational outcomes. Accordingly, educational policy is increasingly driven by national attempts to “copy” the perceived advantage associated with the educational strategies and techniques of other countries. In this note, we present a discussion of the benefits and criticisms of one of these international comparative studies: Trends in International Mathematics and Science Study (TIMSS) studies. In so doing, we attempt to call attention to a continuously growing culture of “teaching to the test” in mathematics education.
Size and shape of shock waves and slipline for Mach reflection in steady flow

For Mach reflection in steady supersonic flow, the slipline and reflected shock wave from the triple point are disturbed by secondary Mach waves generated over the slipline and by the expansion fan from the rear wedge corner. Analytical expressions for the shape of the curved slipline and reflected shock wave are derived in this paper. It is found that, due to transmitted expansion waves from the expansion fan, the slipline has a slope discontinuity at the turning point, i.e., the intersection point of the slipline and the leading characteristics of the transmitted expansion wave. The hypothetical shock wave calculated by considering this slope discontinuity as flow deflection angle matches a similar wave observed in numerical results by computational fluid dynamics, suggesting the existence of a weak shock wave from this turning point. The effects of the secondary Mach waves upstream of the turning point and of the turning point weak shock wave mutually cancel out approximately so that the transmitted Mach waves can be approximated as straight characteristic lines. This simplification leads to a fast analytical model which can predict the Mach stem height and shape of the slipline and reflected shock wave with increasing accuracy for the decreasing deflection angle of the slipline at the triple point. The slipline slope discontinuity at the turning point and the hypothetical turning point weak shock wave are new phenomena found in this work.
Processing techniques for partial tree-pattern queries on xml data

In recent years, eXtensible Markup Language (XML) has become a de facto standard for exporting and exchanging data on the Web. XML structures data as trees. Querying capabilities are provided through patterns matched against the XML trees. Research on the processing of XML queries has focused mainly on tree-pattern queries. Tree-pattern queries are not appropriate for querying XML data sources whose structure is not fully known to the user, or for querying multiple data sources which structure information differently. Recently, a class of queries, called Partial Tree-Pattern Queries (PTPQs) was identified. A central feature of PTPQs is that the structure can be specified fully, partially, or not at all in a query. For this reason, PTPQs can be used for flexibly querying XML data sources. This thesis deals with processing techniques for PTPQs. In particular, it addresses the satisfiability, containment and minimization problems for PTPQs. In order to cope with structural expression derivation issues and to compare PTPQs, a set of inference rules is suggested and a canonical form for PTPQs that comprises all derived structural expressions is defined. This canonical form is used for determining necessary and sufficient conditions for PTPQ satisfiability. The containment problem is studied both in the absence and in the presence of structural summaries of data called dimension graphs. It is shown that this problem cannot be characterized by homomorphisms between PTPQs, even when PTPQs are put in canonical form. In both cases of the problem, necessary and sufficient conditions for PTPQ containment are provided in terms of homomorphisms between PTPQs and (a possibly exponential number of) tree-pattern queries. This result is used to identify a subclass of PTPQs that strictly contains tree-pattern queries for which the containment problem can be fully characterized through the existence of homomorphisms. To cope with the high complexity of PTPQ containment, heuristic approaches for this problem are designed that trade accuracy for speed. The heuristic approaches equivalently add structural expressions to PTPQs in order to increase the possibility for a homomorphism between two contained PTPQs to exist. An implementation and extensive experimental evaluation of these heuristics shows that they are useful in practice, and that they can be efficiently implemented in a query optimizer. The goal of PTPQ minimization is to produce an equivalent PTPQ which is syntactically smaller in size. This problem is studied in the absence of structural summaries. It is shown that PTPQs cannot be minimized by removing redundant parts as is the case with certain classes of tree-pattern queries. It is also shown that, in general, a PTPQ does not have a unique minimal equivalent PTPQ. Finally, sound, but not complete, heuristic approaches for PTPQ minimization are presented. These approaches gradually trade execution time for accuracy.
Assessing wind induced stay vibrations in bridges

Stay vibration events have been reported all over the world on cable-stayed bridges. Cable vibrations cause bridge users discomfort and may also lead to bridge collapse. Aim of this study is to investigate relevant cable vibration phenomena directly induced by wind, such as buffet -shedding, dry inclined galloping and rain wind induced vibrations. The results are presented in terms of required necessary damping to control the dynamic stability of stays for a significant case study. Keywords—cable-stayed bridge, cable vibrations, aerodynamics, bluff bodies
Multidimensional Gel'fand inverse boundary spectral problem: uniqueness and stability

A BSTR ACT Thc papcr is dcvoled lo lhc rcconstruct ion of a compact. Ricmannian manifold from the Gel'fand boundary spcclra l data. Thcsc data consist. of the cigeuvalue; and the boundary values of thc cigenfunctions of the Laplacc opcrator with the Neumaim boundnry condition. We provide the rccons tmction proccdure using thc gcometric V1lrin11t of t hc boundary cont rol mcthod. In addition to t hc uniqucness and rcconstruction rcsult.s, we ske tch rcccnt dcvclopmcnt.s in the condit ional stability in this problcm . T hcse conditions are formulatcd in tc.rins of somc gco· mctric rcstrictio11s t rndit ional for the thcory of gcometric convergenee.
Feedback-controlled and digitally processed coherent population trapping resonance conversion in 87Rb vapour to high-contrast resonant peak

This work reports on the study of a new approach to achievement of high-contrast resonant signals from coherent population trapping (CPT) resonances in 87Rb vapour based on feedback control and real-time digital processing of several measured parameters. This method consists in stabilisation of the value of a function depending on several system parameters measured as the frequency difference of the bichromatic pump radiation is scanned through adjustment of the pumping radiation power with a feedback loop. The present work made use of two such parameters: the pumping radiation power incident on and exiting from the optical cell. Exploration of the proposed method has shown that stabilisation of a linear combination of these two parameters results in a resonant peak whose contrast exceeds that of regular CPT resonance by more than two orders of magnitude at relatively slow CPT resonance scan rates, (scanning frequency of the frequency difference of the bichromatic field ∼1 Hz). When dynamically exciting the CPT resonance (the scan frequency of the frequency difference of the bichromatic field equal to 2 kHz), the resonant peak contrast was enhanced by over an order of magnitude.
On vortical disturbances in single and two-fluid boundary layers

The vortical disturbance environment surrounding a laminar boundary layer affects the proceedings of transition to turbulence. The exponentially growing Tollmien–Schlichting wave is observed under low free-stream turbulence levels, and is replaced by the algebraically growing streaks upon further increase in the turbulence intensity. This scenario is significantly affected by the presence of wall films which introduce additional instabilities and alter the amplification of the streaks. In this work, the effect of wall films on the linear stability of boundary layers is investigated using the Orr-Sommerfeld, Squire and the interface displacement equations. A modal analysis is conducted first, in order to identify all the unstable modes and their respective regimes of dominance. Furthermore, the physical mechanisms contributing to disturbance growth are studied using the kinetic energy equation. No unstable eigenvalues are found for wall films less viscous than the outer stream. Under such conditions, the streaks are likely to dominate; their amplification being dependent on the penetration of the free-stream vortical disturbances into the boundary layer. The ingestion of the free-stream vorticity in the mean shear is explained using the continuous spectrum of the Orr-Sommerfeld equation. A unique parameter is identified to distinguish three asymptotic regimes representing complete, partial and negligible penetration into the boundary layer, respectively. The physical mechanism is a competition between viscous diffusion and convection by the mean flow. The wall film affects the penetration into the boundary layer by modifying the wall-normal wavenumber across the interface. The penetrating free-stream disturbances efficiently generate streaks by tilting the mean vorticity. Their amplification is investigated using an initial value problem that describes the evolution of a linear perturbation. Lower viscosity wall films reduce the amplification of the streaks. However, another growth mechanism arising from the interfacial displacement dominates at long time and is enhanced for lower viscosity films.
Fast Track Colorectal Surgery

A ‘‘fast track’’ colon surgery program is the global package of perioperative care encompassing preoperative, operative, and postoperative techniques, which in aggregate result in fewer complications, a reduction in cost, less postoperative pain, a reduction in the hospital length of stay, and quicker return to work and normal activities. Results of fast track programs have shown signiﬁcant advantages; however, strong evidence is forth-coming. Implementation of a fast track program requires a signiﬁcant commitment and a multidisciplinary approach. Fast track principles may also be applied to anorectal surgery with good results.
Influence of the magnetic pole shape on the cogging torque of permanent magnet synchronous motor

ABSTRACT Aiming at the problem of the permanent magnet synchronous motor (PMSM) vibration, noise and poor control precision caused by the cogging torque, the influence of different pole shapes on the motor electromagnetic field was studied. Based on the FEM, the effects of two types of the magnetic poles with different eccentricity on the magnetic field and induced electromotive force (EMF) are studied. The relationship between the magnetic poles shapes, the magnetic field and the induced EMF is obtained. Secondly, based on the Fourier decomposition theory, the air gap flux density harmonic content and the induced EMF are studied. The influence mechanism of the magnetic pole shape on the air gap flux density and the induced EMF is revealed. Finally, the cogging torque of the PMSM with different magnetic poles is studied, and the influence of different magnetic pole shape on the cogging torque is obtained. By optimising the shape of the magnetic pole, the maximum fluctuation amplitude of the cogging torque is reduced by 80.4%. The motor cogging torque can be effectively weakened by the PM eccentric design. This work lays a theoretical foundation for the study of cogging torque.
Cyclandelate in the Treatment of Patients with Mild to Moderate Primary Degenerative Dementia of the Alzheimer Type or Vascular Dementia: Experience from a Placebo Controlled Multi-center Study

measurements for demented patients after 16 weeks of treatment with 1,600 mg/d cyclandelate. The present study was planned to gain further evidence supporting the efficacy of cyclandelate in the symptomatic treatmentofdementia,therebyobservingcurrentstandardsfor the clinical evaluation of nootropic drugs (CPMP, 1997; Kanowski et al.,1990; Kern & Menges ,1992). It was not intended to demonstrate etiopathogenetic specificity of an (cid:28)anti-demen-tia(cid:29) effect of cyclandelate, so patients with dementia of either vascular or primary degenerative origin were considered for inclusion in this 24-week trial of cyclandelate 800 mg bid against placebo. We will present the main results of this study and then discuss theefficacyoutcomeincludingadditionalexploratoryanalyses.
Naive Diversification Preferences and Their Representation

A widely applied diversification paradigm is the naive diversification choice heuristic. It stipulates that an economic agent allocates equal decision weights to given choice alternatives independent of their individual characteristics. This article provides mathematically and economically sound choice theoretic foundations for the naive approach to diversification. We axiomatize naive diversification by defining it as a preference for equality over inequality and derive its relationship to the classical diversification paradigm. In particular, we show that (i) the notion of permutation invariance lies at the core of naive diversification and that an economic agent is a naive diversifier if and only if his preferences are convex and permutation invariant; (ii) Schur-concave utility functions capture the idea of being inequality averse on top of being risk averse; and (iii) the transformations, which rebalance unequal decision weights to equality, are characterized in terms of their implied turnover.
Effect of Zn-impurity on T_c and its implication to pairing symmetry in under- and over-doped LaFeAsO1-xFx

The effect of non-magnetic Zn impurity on superconductivity in LaFe$_{1-y}$Zn$_y$AsO$_{1-x}$F$_x$ system is studied systematically. In the presence of Zn impurity, the superconducting transition temperature increases in the under-doped regime, remains unchanged in the optimally doped regime, and is severely suppressed in the over-doped regime. Our results suggest a switch of the symmetry of the superconducting order parameters from a s-wave to $s_{\pm}$ or d-wave states as the charge carrier doping increases in FeAs-based superconductors.
Abdominoperineal Resection: How Is It Done and What Are the Results?

Abdominoperineal resection (APR) for many years was the treatment of choice for most patients with rectal cancer. Recent advances in surgical technique and other treatment modalities have led to a marked increase in the rate of sphincter-sparing operations, with a concomitant decrease in APR. However, it is still necessary in selected patients, especially those with very distal tumors or poor sphincter function. This review will cover the history of APR, current operative strategy and complications, oncologic and quality of life results, as well as potential future advances.
Improving NCEP HWRF Simulations of Surface Wind and Inflow Angle in the Eyewall Area

This note describes a modification of the boundary layer parameterization scheme in the Hurricane Weather Research and Forecasting (HWRF) Model, which improves the simulations of low-level wind and surface inflow angle in the eyewall area and has been implemented in the HWRF system and used in the operational system since 2016. The modification is on an observation-based adjustment of eddy diffusivity previously implemented in the model. It is needed because the previous adjustment resulted in a discontinuity in the vertical distribution of eddy diffusivity near the surface-layer top, which increases the friction within the surface layer and compromises the surface-layer constant-flux assumption. The discontinuity affects the simulation of storm intensity and intensification, one of the main metrics of model performance, particularly in strong tropical cyclones. This issue is addressed by introducing a height-dependent adjustment so that the vertical profile of eddy diffusivity is continuous throughout the boundary layer. It is shown that the implementation of the modification results in low-level winds and surface inflow angles in the storm’s eyewall region closer to observations.
Temperature-dependent frictional properties of ultra-thin boron nitride nanosheets

We investigate the temperature-dependent frictional properties of mono- and few-layer hexagonal boron nitride nanosheets (BNNSs) by using atomic force microscopy (AFM). The measurements reveal that a modest increase in sample temperature results in a substantial decrease of the frictional force between a silicon AFM tip and a BNNS, and the frictional force change is modulated by the scan velocity of the AFM tip and the number of layers in the BNNS. The activation energy of the contact rupture for the examined BNNSs is found to be around 0.35 eV, which is substantially higher than the reported values for graphene. The observed high activation energy for the BNNS is ascribed to its electronically and topographically corrugated surface, which originates from the polarized nature of B-N bonds and the size difference of B and N atoms. The findings are useful to better understand the physical properties of hexagonal BNNS materials and in the pursuit of their applications, such as substrate materials in nano ele.
Two methods to improve location estimates—preliminary results

abstract Preliminary test results of two new seismic epicenter location methods show that the methods are quite effective in reducing location errors. The first method assumes that a large part of the travel-time residuals is caused by differences between the actual structures at source and receiver, and the standard structure used in the program. To correct for both regions, tables of the differences between the half-way travel times from source to bottoming layer using the Herrin model, and various regional models, were computed. In application, the total travel-time correction for each source-to-station path is the sum of the down-ray correction of the source region and the up-ray correction of the receiver region. Resulting location errors are much smaller (about half) than the errors using the ordinary location method. The second method considers the possibility that stations in close proximity may be measuring essentially the same travel-time residual, leading to a consistent stochastic bias. The assumption that the bias is stochastic can be modeled in terms of a correlation matrix for the residuals which varies according to the separation between two stations. The method adjusts the weighting of travel-time residuals in accordance with their overall intercorrelation matrix so that a large cluster of stations will not exert an inordinate effect on the estimated location. It thus becomes unnecessary to “balance” networks. Correlation coefficients estimated with 186 station residuals from LONGSHOT, were 0.7 for the O° to 5° distance range, 0.3 for the 5° to 10° range, and 0 for distances greater than 10°. For ease of computation, 184 stations were separated into nine geographical groupings. It was necessary to smooth the resulting correlation matrix to ensure a positive definite matrix. The LONGSHOT location error with the smoothed correlation matrix was reduced to 3.2 km, and the computational confidence intervals include the true location.
Tropical Cyclone Outflow and Warm Core Structure as Revealed by HS3 Dropsonde Data

AbstractDropsonde data collected during the NASA Hurricane and Severe Storm Sentinel (HS3) field campaign from 16 research missions spanning 6 tropical cyclones (TCs) are investigated, with an emphasis on TC outflow and the warm core. The Global Hawk (GH) AV-6 aircraft provided a unique opportunity to investigate the outflow characteristics due to a combination of 18+-h flight durations and the ability to release dropsondes from high altitudes above 100 hPa. Intensifying TCs are found to be associated with stronger upper-level divergence and radial outflow relative to nonintensifying TCs in the sample, regardless of current intensity. A layer of 2–4 m s−1 inflow 20–50 hPa deep is also observed 50–100 hPa above the maximum outflow layer, which appears to be associated with lower-stratospheric descent above the eye. The potential temperature of the outflow is found to be more strongly correlated with the equivalent potential temperature of the boundary layer inflow than to the present storm intensity, consi.
High Freestream Turbulence Effects on Endwall Heat Transfer for a Gas Turbine Stator Vane

High freestream turbulence along a gas turbine airfoil and strong secondary flows along the endwall have both been reported to significantly increase convective heat transfer. This study superimposes high freestream turbulence on the naturally occurring secondary flow vortices to determine the effects on the flowfield and the endwall convective heat transfer. Measured flowfield and heat transfer data were compared between low freestream turbulence levels (0.6%) and combustor simulated turbulence levels (19.5%) that were generated using an active grid. These experiments were conducted using a scaled-up, first stage stator vane geometry. Infrared thermography was used to measure surface temperatures on a constant heat flux plate placed on the endwall surface. Laser Doppler velocimeter (LDV) measurements were performed of all three components of the mean and fluctuating velocities of the leading edge horse-shoe vortex. The results indicate that the mean flowfields for the leading edge horseshoe vortex were similar between the low and high freestream turbulence cases. High turbulence levels in the leading edge-endwall juncture were attributed to a vortex unsteadiness for both the low and high freestream tubulence cases. While, in general, the high freestream turbulence increased the endwall heat transfer, low augmentations were found to coincide with the regions having the most intense vortex motions.Copyright © 2000 by ASME
Gastrointestinal Conditions during Pregnancy

Pregnancy causes anatomic and physiologic changes in the gastrointestinal tract. Pregnant women with intestinal disease such as Crohn disease or ulcerative colitis pose a management challenge in clinical diagnosis, radiologic evaluation, and treatment secondary to potential risk to the fetus. Heightened physician awareness on possible etiologies such as appendicitis, diverticulitis, and rarely colorectal cancer is required for rapid diagnosis and treatment to improve maternal/fetal outcome. A multidisciplinary approach to evaluation is a necessity because radiologic procedures and treatment medications commonly used in nonpregnant patients may have a potential harmful effect on the fetus. The authors review several gastrointestinal conditions encountered during pregnancy and address presentation, diagnosis, and treatment of each condition.