Calibration of a TDR probe for low soil water content measurements

Time domain reflectometry (TDR) probes are increasingly used for field and laboratory estimation of soil water content. Usual calibration of TDR probes for the determination of soil water content uses two media: air for low and water for high values of dielectric permittivity, although the measured range of dielectric permittivity in soil is much smaller as compared to the range implied by the calibration media. The use of air for calibration of short TDR probes gives calibration errors due to overlapping incident and reflected pulses in the reflectogram, which result in their relative shift in time. This phenomenon, named the convolution effect, can be avoided by the application of selected calibration media. The presented approach minimizes of dielectric permittivity measurement errors by choosing the calibration media with dielectric permittivity values close to the limits of the measurement range and the possibility to use TDR probes of various lengths. The comparison of errors of TDR apparent dielectric permittivity measurement in three sandy soils, based on the probe calibrations in various media, is also presented.     

Abnormal Phenomena of Multi-Way Sodium Storage in Selenide Electrode

Transition-metal chalcogenides have gained special attention as potential anodes for Na-ion batteries due to their high capacities to originate from complex charge storage mechanisms. Although the sodium storage process in chalcogenides is still unclear, it is common to assume that it can occur via one of the following routes: intercalation, conversion, or alloying. In this paper, an anomalous multi-way mechanism in MoSe₂ electrode, including all three of the above scenarios, is reported. The intercyclic product of the discharge/charge process is a mixture of Se, Mo, and 1T-structured Na_xMoSe₂. An unexpected phenomena of Se precipitation leads to the additional alloying reaction, which is exclusive among all chalcogenides, and runs together with conversion and intercalation reactions in the same cycle. This new concept of sodium storage process includes two models, previously seemed to be mutually exclusive. Despite of complex electrode mechanisms, MoSe₂ retains high capacity and coulombic efficiency even after 50 cycles.     

On closed-form approximations for the free energy ofd-dimensional Ising model,II

It has been shown that it is possible to construct families of closed-form approximations lnZ* _d to lnZ _d for the anisotropic Ising model on ad-dimensional hypercubical lattice whose high- and low-temperature series expansions coincide with the corresponding exact expansions up to some order. For the isotropic case the density of zeros ofZ* _d near the critical pointK _c is found under the assumption that they behave like sinh2K=±(sinh2K _c +y±iy). It is shown that there exists a family of closed-form approximations such that ford3 the only possible densities of zeros arem(y)=|y|³ for=0 andm(y)=|y| for 0<||1, i.e., it contains the exact case ford5 corresponding to ||=1.     

Enhancement of math content accessibility in EPUB3 educational publications

ABSTRACT

The article presents methods of increasing mathematical content accessibility in educational e-publications using multimodal user interfaces (UI). Educational mathematical publications such as exercise notebooks and worksheets, require student's interactivity in problem solving. EPUB3, an open format for e-publications, has the possibilities of creating multimedia, interactive mathematics content. Among the programs that support EPUB3, only a few support the MathML format presenting formulas, and provides limited possibilities for user interactivity, insufficient in mathematical education. Our solutions in the PlatMat system increase the interactive accessibility of EPUB3 mathematical content for students with visual impairment. The solutions are based on concurrent multimodal alternative interfaces for exploring math content in EPUB3 publications. Students can read and modify formulas choosing preferred UI and device. Similarly, in different modes (visual, acoustic and touch) students can recognise function graphs and shapes of geometrical figures saved in scalable vector graphics (SVG) format. Teachers can create universal mathematical documents for all students. The system supports inclusive maths education and is designed according to the principles of universal design for learning (UDL). The article describes the system’s usefulness in relation to research conducted among maths teachers. Positive results have become the basis for the further development of the system.     

Analog integrator for the Korea superconducting tokamak advanced research magnetic diagnostics

An analog integrator, which automatically compensates an integrating drift, has been developed for the magnetic diagnostics in the Korea superconducting tokamak advanced research (KSTAR). The compensation of the drift is done by the analog to digital converter-register-digital to analog converter in the integrator. The integrator will be used in the equilibrium magnetic field measurements by using inductive magnetic sensors during a plasma discharge in the KSTAR machine. Two differential amplifiers are added to the signal path between each magnetic sensor and the integrator in order to improve the performance of the integrator because a long signal cable of 100 m will be used for the measurement in the KSTAR machine. In this work, the characteristics of the integrator with two differential amplifiers are experimentally investigated.     

Computer programs for the concordance correlation coefficient

The CCC macro is presented for computation of the concordance correlation coefficient (CCC), a common measure of reproducibility. The macro has been produced in both SAS and R, and a detailed presentation of the macro input and output for the SAS program is included. The macro provides estimation of three versions of the CCC, as presented by Lin [L.I.-K. Lin, A concordance correlation coefficient to evaluate reproducibility, Biometrics 45 (1989) 255-268], Barnhart et al. [H.X. Barnhart, J.L. Haber, J.L. Song, Overall concordance correlation coefficient for evaluating agreement among multiple observers, Biometrics 58 (2002) 1020-1027], and Williamson et al. [J.M. Williamson, S.B. Crawford, H.M. Lin, Resampling dependent concordance correlation coefficients, J. Biopharm. Stat. 17 (2007) 685-696]. It also provides bootstrap confidence intervals for the CCC, as well as for the difference in CCCs for both independent and dependent samples. The macro is designed for balanced data only. Detailed explanation of the involved computations and macro variable definitions are provided in the text. Two biomedical examples are included to illustrate that the macro can be easily implemented.     

Polynomial-Time Algorithms for the Ordered Maximum Agreement Subtree Problem

For a set of rooted, unordered, distinctly leaf-labeled trees, the NP-hard maximum agreement subtree problem (MAST) asks for a tree contained (up to isomorphism or homeomorphism) in all of the input trees with as many labeled leaves as possible. We study the ordered variants of MAST where the trees are uniformly or non-uniformly ordered. We provide the first known polynomial-time algorithms for the uniformly and non-uniformly ordered homeomorphic variants as well as the uniformly and non-uniformly ordered isomorphic variants of MAST. Our algorithms run in time , , , and , respectively, where n is the number of leaf labels and k is the number of input trees.     

Catalytic Oxidation of Sulfur Dioxide

The well-known industrial applications of sulfuric acid have made the oxidation of SO₂ to SO₃ a process of paramount practical importance. Nowadays vanadium catalysts are commonly used to catalyze the oxidation. Platinum and iron oxide catalysts, formerly employed in industrial practice, are no longer used.