VMEXT: A Visualization Tool for Mathematical Expression Trees

Mathematical expressions can be represented as a tree consisting of terminal symbols, such as identifiers or numbers (leaf nodes), and functions or operators (non-leaf nodes). Expression trees are an important mechanism for storing and processing mathematical expressions as well as the most frequently used visualization of the structure of mathematical expressions. Typically, researchers and practitioners manually visualize expression trees using general-purpose tools. This approach is laborious, redundant, and error-prone. Manual visualizations represent a user's notion of what the markup of an expression should be, but not necessarily what the actual markup is. This paper presents VMEXT - a free and open source tool to directly visualize expression trees from parallel MathML. VMEXT simultaneously visualizes the presentation elements and the semantic structure of mathematical expressions to enable users to quickly spot deficiencies in the Content MathML markup that does not affect the presentation of the expression. Identifying such discrepancies previously required reading the verbose and complex MathML markup. VMEXT also allows one to visualize similar and identical elements of two expressions. Visualizing expression similarity can support support developers in designing retrieval approaches and enable improved interaction concepts for users of mathematical information retrieval systems. We demonstrate VMEXT's visualizations in two web-based applications. The first application presents the visualizations alone. The second application shows a possible integration of the visualizations in systems for mathematical knowledge management and mathematical information retrieval. The application converts LaTeX input to parallel MathML, computes basic similarity measures for mathematical expressions, and visualizes the results using VMEXT.Comment: 15 pages, 4 figures, Intelligent Computer Mathematics - 10th International Conference CICM 2017, Edinburgh, UK, July 17-21, 2017, Proceeding

DEM and experimental study of bi-directional simple shear

Stress–strain responses of granular material under bi-directional simple shear are comprehensively studied experimentally and numerically. The variable direction dynamic cyclic simple shear apparatus is used to test glass beads under various loading paths, and the DEM is used to reproduce experimental results. These two methods are complementary to each other. The glass beads are subject to the first shearing until a specified shear strain is reached, followed by the second shearing until the failure of samples, and the two shears are at various angles. The experimental results are in good agreement with the numerical results. Both experimental and numerical studies indicate that the development of shear stresses is dependent on the angle between the two shears in the early stage, and they approach the same ultimate values at the failure. The lateral stress, principal stress and non-coaxiality are also studied in the DEM simulation. While the lateral stress and principal stress are dependent on the angle, the orientations of principal stresses and plastic strain rate almost reach the same value at the failure. The contact force network and material fabric are also investigated to provide insight into the micro-scale responses and macro–micro relations regarding bi-directional simple shear

Linear and non-linear (non-)forecastability of high-frequency exchange rates

This paper forecasts Daily Sterling exchange rate returns using various naive, linear and non-linear univariate time-series models. The accuracy of the forecasts is evaluated using mean squared error and sign prediction criteria. These show only a very modest improvement over forecasts generated by a random walk model. The Pesaran–Timmerman test and a comparison with forecasts generated artificially shows that even the best models have no evidence of market timing ability

General approach for the determination of the magneto-angular dependence of the critical current of YBCO coated conductors

The physical understanding and numerical modelling of superconducting devices which exploit the high performance of second generation high temperature superconducting tapes (2G-HTS), is commonly hindered by the lack of accurate functions which allow the consideration of the in-field dependence of the critical current. This is true regardless of the manufacturer of the superconducting tape. In this paper, we present a general approach for determining a unified function I $_{c}$(B, θ), ultimately capable of describing the magneto-angular dependence of the in-field critical current of commercial 2G-HTS tapes in the Lorentz configuration. Five widely different superconducting tapes, provided by three different manufacturers, have been tested in a liquid nitrogen bath and external magnetic fields of up to 400 mT. The critical current was recorded at 90 different orientations of the magnetic field ranging from θ = 0°, i.e., with B aligned with the crystallographic ab-planes of the YBCO layer, towards ±90°, i.e., with B perpendicular to the wider surfaces of the 2G-HTS tape. The whole set of experimental data has been analysed using a novel multi-objective model capable of predicting a sole function I $_{c}$(B, θ). This allows an accurate validation of the experimental data regardless of the fabrication differences and widths of the superconducting tapes. It is shown that, in spite of the wide set of differences between the fabrication and composition of the considered tapes, at liquid nitrogen temperature the magneto-angular dependence of the in-field critical current of YBCO-based 2G-HTS tapes, can be described by a universal function I $_{c}$($\textit{f}$(B), θ), with a power law field dependence dominated by the Kim's factor B/B $_{0}$, and an angular dependence moderated by the electron mass anisotropy ratio of the YBCO layer.This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) project NMZF/064. X Zhang acknowledges a grant from the China Scholarship Council (No. 201408060080)

Dislocation network at InN/GaN interface revealed by scanning tunneling microscopy

For heteroepitaxy of InN on GaN(0001) by molecular-beam epitaxy, the lattice misfit strain is relieved by misfit dislocations (MDs) formed at the interface between InN and GaN. Imaging by scanning tunneling microscopy (STM) of the surfaces of thin InN epifilms reveals line feature parallel to 〈112 0〉. Their contrast becomes less apparent for thicker epifilms. From the interline spacing as well as a comparison with transmission electron microscopy studies, it is suggested that they correspond to the MDs beneath the surface. The STM contrast originates from both the surface distortion caused by the local strain at MDs and the electronic states of the defects. © 2008 American Institute of Physics.published_or_final_versio

Identification and characterization of the Bcl-2- associated athanogene (BAG) protein family in rice

The Bcl-2-associated athanogene (BAG) proteins are involved in the regulation of Hsp70/HSC70 in animals. There are six BAG genes in human that encode nine isoforms with different subcellular locations. Arabidopsis thaliana is reported to contain seven BAG proteins. We searched BAG proteins in Oryza sativa using profile-sequence (Pfam) and profile-profile (FFAS) algorithms and found six homologs. The BAG protein family in O. sativa can be grouped into two classes based on the presence of other conserved domains. Class I consists of four OsBAG genes (1 to 4) containing an additional ubiquitin-like domain, structurally similar to the human BAG1 proteins and might be BAG1 orthologs in plants. Class II consists of two OsBAG genes (5 and 6) containing calmodulin-binding domain. Multiple sequence alignment and structural models of O. sativa BAG proteins showed conservation of surface charge (except OsBAG5) and critical residues for the binding of BAG domain to Hsp70 nucleotide binding domain (NB). Meta analysis of microarray data showed that OsBAG genes are up or down regulated under different stresses (biotic and abiotic). Data obtained from real-time PCR of OsBAG genes under heat stress showed that maximum induction in the expression of all the genes occurred after one hour exposure to heat stress, while reduction in the expression was observed in the following time course and ultimately returned to the basal level at 24 h treatment. These results suggest that OsBAG genes might play important role at the onset of heat stress. A further detailed study may explore the exact function of the members of this gene family and help to make understanding of programmed cell death (PCD) mechanism in plants.Key words: Rice, ubiquitin-like domain, nucleotide-binding domain, real-time PCR

Experimental investigation of a solar collector integrated with a pulsating heat pipe and a compound parabolic concentrator

The paper reports an experimental investigation of a newly proposed solar collector that integrates a closed-end pulsating heat pipe (PHP) and a compound parabolic concentrator (CPC). The PHP is used as an absorber due to its simple structure and high heat transfer capacity. The CPC has a concentration ratio of 3.4 and can be readily manufactured by three-dimensional printing. The CPC can significantly increase the incident solar irradiation intensity to the PHP absorber and also reduce the heat loss due to the decrease in the area of the hot surface. A prototype of the solar collector has been built, consisting of a PHP absorber bent by 4 mm diameter copper tube, CPC arrayed by 10 × 2 CPC units with the collection area of 300 × 427.6 mm2, a hot water tank and a glass cover. HFE7100 was utilized as the working fluid at a filling ratio of 40%. The operating characteristics and thermal efficiency of the solar collector were experimentally studied. The steady and periodic temperature fluctuations of the evaporation and condensation sections of the PHP absorber indicate that the absorber works well with a thermal resistance of about 0.26 °C/W. It is also found that, as the main factor to the the thermal performance of the collector, thermal resistance of the PHP absorber decreases with increasing evaporation temperature. The collector apparently shows start-up, operational and shutdown stages at the starting and ending temperatures of 75 °C. When the direct normal irradiance is 800 W/m2, the instantaneous thermal efficiency of the solar collector can reach up to 50%.The work was financially supported by the National Natural Science Foundation of China (51506004), Beijing Natural Science Foundation (3162009), Scientific Research Project of Beijing Educational Committee (KM201410016001) and Research Fund of Beijing University of Civil Engineering and Architecture

Network coding for wireless communication networks

This special issue includes a collection of 19 outstanding research papers which cover a diversity of topics on the application of network coding in wireless communication networks.published_or_final_versio

Investigation of demagnetization in HTS stacked tapes implemented in electric machines as a result of crossed magnetic field

This paper investigates the practical effectiveness of employing superconducting stacked tapes to superconducting electric machinery. The use of superconducting bulks in various practical applications has been addressed extensively in the literature. However, in practice, dramatic decrease in magnetization would occur on superconducting bulks due to the crossed field effect. In our study, we employed the superconducting stacked tapes in a synchronous superconducting motor, which was designed and fabricated in our laboratory, aiming to lessen demagnetization due to crossed field effect in comparison with superconducting bulks. Applying the transverse AC field, the effects of frequency, amplitude, and number of cycles of the transverse magnetic field are discussed. Furthermore, a stack of 16 layers of superconducting tapes is modelled and the consequences of applying the crossed magnetic field on the sample are evaluated. The confrontation between experiments and simulation allows us to thoroughly understand the crossed field effects on stacked tapes. At the end, a preventive treatment, based on the shielding characteristic of superconductor and materials with high permeability, i.e. -metal and metalic glass, is suggested. On the other hand, the shielding feature of aforementioned materials will hinder the penetration of magnetic field and, consequently, reduction of the demagnetization will be attained.This is the accepted manuscript. The final version is available from IEEE at https://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6965587&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_Publication_Number%3A77%29%26pageNumber%3D16

Multi-decadal trends in global terrestrial evapotranspiration and its components

Evapotranspiration (ET) is the process by which liquid water becomes water vapor and energetically this accounts for much of incoming solar radiation. If this ET did not occur temperatures would be higher, so understanding ET trends is crucial to predict future temperatures. Recent studies have reported prolonged declines in ET in recent decades, although these declines may relate to climate variability. Here, we used a well-validated diagnostic model to estimate daily ET during 1981–2012, and its three components: transpiration from vegetation (Et), direct evaporation from the soil (Es) and vaporization of intercepted rainfall from vegetation (Ei). During this period, ET over land has increased significantly (p < 0.01), caused by increases in Et and Ei, which are partially counteracted by Es decreasing. These contrasting trends are primarily driven by increases in vegetation leaf area index, dominated by greening. The overall increase in Et over land is about twofold of the decrease in Es. These opposing trends are not simulated by most Coupled Model Intercomparison Project phase 5 (CMIP5) models, and highlight the importance of realistically representing vegetation changes in earth system models for predicting future changes in the energy and water cycle