LEXTALE_CH: A quick, character-based proficiency test for Mandarin Chinese

Research in second language acquisition suggests that objective performance-based assessments may provide more reliable and valid measures of second language proficiency than subjective self-ratings. To measure proficiency in English as a second language, a quick, vocabulary-based test called LexTALE (Lexical Test for Advanced Learners of English) was developed and shown to be able to differentiate between various levels of English proficiency. Following in the line of adaptations of this test for other languages, we created a character-based adaptation for Mandarin Chinese: LEXTALE_CH. In this paper, we discuss the development and validation of LEXTALE_CH in detail. In short, LEXTALE_CH can discriminate between high and low levels of Mandarin proficiency and is sensitive to the significant differences in vocabulary size between native speakers and second language learners of Mandarin; further, it takes only a few minutes to administer and is simple to score, making it a practical tool for low-stakes estimation of Mandarin proficiency.http://www.lingref.com/bucld/42/BUCLD42-09.pdfPublished versio

Global and Local Two-Sample Tests via Regression

Two-sample testing is a fundamental problem in statistics. Despite its long history, there has been renewed interest in this problem with the advent of high-dimensional and complex data. Specifically, in the machine learning literature, there have been recent methodological developments such as classification accuracy tests. The goal of this work is to present a regression approach to comparing multivariate distributions of complex data. Depending on the chosen regression model, our framework can efficiently handle different types of variables and various structures in the data, with competitive power under many practical scenarios. Whereas previous work has been largely limited to global tests which conceal much of the local information, our approach naturally leads to a local two-sample testing framework in which we identify local differences between multivariate distributions with statistical confidence. We demonstrate the efficacy of our approach both theoretically and empirically, under some well-known parametric and nonparametric regression methods. Our proposed methods are applied to simulated data as well as a challenging astronomy data set to assess their practical usefulness

Energy Transfer Rate in Double-Layer Graphene Systems: Linear Regime

We investigate theoretically the energy transfer phenomenon in a double-layer graphene (DLG) system in which two layers are coupled due to the Coulomb interlayer interaction without appreciable interlayer tunneling. We use the balance equation approach and the dynamic and temperature dependent random phase approximation (RPA) screening function in our calculations to obtain the rates of energy transfer between two graphene layers at different layer electron temperatures, densities and interlayer spacings and compare the results with those calculated for the conventional double-layer two-dimensional electron gas (2DEG) systems. In addition, we study the effect of changing substrate dielectric constant on the rate of energy transfer. The general behavior of the energy transfer rate in the DLG is qualitatively similar to that obtained in the double-layer 2DEG but quantitatively its DLG values are an order of magnitude greater. Also, at large electron temperature differences between two layers, the electron density dependence of the energy transfer for the DLG system is significantly different from that found for the double-layer 2DEG system, particularly in case of unequal layer electron densities.Comment: 12 pages,4 figure

The Role of Oceanic Processes in the Initiation of Boreal Winter Intraseasonal Oscillations over the Indian Ocean

Observational analyses and a hierarchy of ocean general circulation model (OGCM) experiments were performed to understand the influence of oceanic processes on the warm sea surface temperature anomalies (SSTAs) prior to the convection initiation of boreal winter intraseasonal oscillations (ISOs), including the Madden-Julian Oscillation (MJO), in the equatorial Indian Ocean. We found 39 strong ISOs that passed over the Indian Ocean Warm Pool region during the November-April season of the 2001-2012 period. 17/39 ISO events initiated in the Seychelles-Chagos Thermocline Ridge (SCTR) before propagating eastward; the remaining events initiated in the southern Arabian Sea (6) or Warm Pool (16) regions. The SCTR event set was notable in that it contained more global-scale MJOs (71-76%), as defined by the RMM and OMI indices, than the WP events (25-44%). Additionally, ~24% (44%) of the SCTR (Warm Pool) events were preceded by strong oceanic process-induced SSTAs of similar magnitude to those of shortwave radiative and turbulent heat fluxes. The Arabian Sea events, however, were not associated with statistically significant SSTA signals prior to convection. Based on a mixed layer heat budget analysis, entrainment and upwelling reduction were the dominant oceanic processes contributing to the warming, in contrast with boreal summer, when horizontal advection dominated. We examined several case studies, including primary MJO events, where oceanic Rossby waves were associated with the entrainment and upwelling reduction. Two simple atmospheric boundary layer convergence models revealed that the SSTAs contributed at least half of the total convergence and suggested that the ocean dynamical effect was responsible for the majority of SSTA-forced convergence for those case studies. These results underscore the need for climate prediction models to accurately represent the ocean structure and processes to include the effects of oceanic predictors

On methods to determine bounds on the Q-factor for a given directivity

This paper revisit and extend the interesting case of bounds on the Q-factor for a given directivity for a small antenna of arbitrary shape. A higher directivity in a small antenna is closely connected with a narrow impedance bandwidth. The relation between bandwidth and a desired directivity is still not fully understood, not even for small antennas. Initial investigations in this direction has related the radius of a circumscribing sphere to the directivity, and bounds on the Q-factor has also been derived for a partial directivity in a given direction. In this paper we derive lower bounds on the Q-factor for a total desired directivity for an arbitrarily shaped antenna in a given direction as a convex problem using semi-definite relaxation techniques (SDR). We also show that the relaxed solution is also a solution of the original problem of determining the lower Q-factor bound for a total desired directivity. SDR can also be used to relax a class of other interesting non-convex constraints in antenna optimization such as tuning, losses, front-to-back ratio. We compare two different new methods to determine the lowest Q-factor for arbitrary shaped antennas for a given total directivity. We also compare our results with full EM-simulations of a parasitic element antenna with high directivity.Comment: Correct some minor typos in the previous versio