A three-phase to single-phase matrix converter for high-frequency induction heating

The paper describes a new three-phase to single-phase matrix converter featuring unity input power factor, very low input total harmonic distortion, and soft-switching over the full power range, for high frequency induction heating applications. A variable output pulse density modulation scheme has been proposed for stable operation of the converter, with the notable feature of requiring no on-line calculations for the synthesis of three-phase input current system. Practical issues in realising the converter, viz. line frequency synchronisation and output current circulation, are described. Good agreement between simulation and experimental results confirm the benefits of the proposed converter

Comparison of single-phase matrix converter and H-bridge converter for radio frequency induction heating

This paper compares the newly developed single-phase matrix converter and the more conventional H- bridge converter for radio frequency induction heating. Both the converters exhibit unity power factor, very low total harmonic distortion at the utility supply interface, good controllability under soft switching condition for a wide range of power, and high efficiencies, whilst still having simple structures. A novel switching control pattern has been proposed for the matrix converter in order to maintain the comparable performance to the H-bridge converter. Simulation and experimental results for both converters are presented. Comparisons between two converters have confirmed the excellent performance of the proposed matrix converter

Single phase matrix converter for radio frequency induction heating

Conventional converters for radio frequency induction heating usually follow an AC-DC-AC structure, which can exhibit non-unity power factor and introduce large harmonic currents into the utility supply. The need for a direct converter for radio frequency induction heating, featuring unity power factor, and sinusoidal input current, has motivated the development of a single phase matrix converter as an induction heater. A novel commutation strategy is therefore required to ensure smooth operation of the converter whilst creating a high frequency output under soft switching conditions. The operating principle and features of the proposed converter are described here, and experimentally verifie

The weak Lefschetz property of artinian algebras associated to paths and cycles

Given a base field $\Bbbk$ of characteristic zero, for each graph $G$, we associate the artinian algebra $A(G)$ defined by the edge ideal of $G$ and the squares of the variables. We study the weak Lefschetz property of $A(G)$. We classify some classes of graphs with relatively few edges, including paths and cycles, such that its associated artinian ring has the weak Lefschetz property.Comment: 21 pages. Comments are welcome

Sound-Dr: Reliable Sound Dataset and Baseline Artificial Intelligence System for Respiratory Illnesses

As the burden of respiratory diseases continues to fall on society worldwide, this paper proposes a high-quality and reliable dataset of human sounds for studying respiratory illnesses, including pneumonia and COVID-19. It consists of coughing, mouth breathing, and nose breathing sounds together with metadata on related clinical characteristics. We also develop a proof-of-concept system for establishing baselines and benchmarking against multiple datasets, such as Coswara and COUGHVID. Our comprehensive experiments show that the Sound-Dr dataset has richer features, better performance, and is more robust to dataset shifts in various machine learning tasks. It is promising for a wide range of real-time applications on mobile devices. The proposed dataset and system will serve as practical tools to support healthcare professionals in diagnosing respiratory disorders. The dataset and code are publicly available here: https://github.com/ReML-AI/Sound-Dr/.Comment: 9 pages, PHMAP2023, PH

Image rectification tool for evaluation of gusset plate connections in steel truss bridges

A methodology was developed to permit rectification and metrification of digital images of steel truss gusset plate connections. The approach will enable rapid and accurate collection of field measurements as compared to traditional methods to enable structural evaluation of gusset plate connections. The program enables the operator to quickly create AutoCAD drawings by collecting dimensional information about the gusset plate and connectors from the scaled orthographic photograph (orthophoto), thereby limiting data entry errors and redundant efforts. The availability of scaled orthophotos provides a useful record of field conditions and can be compared with subsequent field inspection results to identify long term changes in visual characteristics. The methodology uses the direct linear transformation (DLT) algorithm to remove image perspective. This transformation requires that certain geometrical characteristics be established between the real world image and the image plane so that the image can be rectified. For the present research, reference targets were developed that can be placed on a gusset plate that establish 9 control points. The control points are ideally spread throughout the image. A mock gusset plate was developed to demonstrate the rectification and metrification techniques. The gusset plate was modeled after a connection in a steel truss bridge located on an interstate highway in Oregon. A series of 10 images were used to demonstrate methodology and to compare resulting measurements of gusset plate geometry from the orthophotos. Overall, images taken with greater skew angles had larger errors than those which were more orthogonal to the mock gusset plate. The largest percentage errors were found using Camera 3 due to more radial distortion inherent in the built-in camera lens. When the gusset plate filled a larger proportion of the overall image, the camera had higher resolution, and a sharp well focused image was taken, and results were improved. Typical absolute measurement errors were 0.27 in