Two Types of Compact UHF Antennas for Partial Discharge Measurement

To investigate the partial discharge (PD) online monitoring of transformers by ultra-high-frequency (UHF) approaches,high-qualified UHF antennas are focused on as one key technique. The size of UHF sensor used for PD UHF online monitoring in transformer is excessively large,therefore,it is not convenient for internal installation of transformer. Two types of compact UHF antennas with small sizes,a Hilbert fractal antenna and a small loop antenna are presented. PD experiments of three typically artificial insulation defects are executed and both antennas are used for PD measurement. The spectra of power via frequency of detected PD signals are analyzed and compared. The experimental results show that the Hilbert fractal antenna and small loop antenna are qualified for PD online UHF monitoring.

Dimethyl ether as circular hydrogen carrier:Catalytic aspects of hydrogenation/dehydrogenation steps

The intermittent nature of renewable resources requires for most applications the development of efficient and cost-effective technologies for steady supply of electrical energy.The storage of energy in the form of hydrogen chemically bound within organic molecules(rather than physically as compressed gas or cooled liquid)represents an alternative approach that is attracting great research interest.Compared to other liquid organic hydrogen carriers(LOHCs),dimethyl ether(DME)appears to have the largest potential impact on society,especially if inserted in technological chains of CO_(2) sequestration and utilization,so to determine an effective mitigation of environmental issues,without any net effect on the carbon footprint.Specifically,the steps of H2 storage and H2 release can take place in two coupled chemical processes,constituted by the exothermic synthesis of DME via CO_(2) hydrogenation and the endothermic steam reforming of DME,respectively.Herein,the latest advances in the development of heterogeneous bifunctional and hybrid catalysts for the direct hydrogenation of CO_(2) to DME are thoroughly reviewed,with special emphasis on thermodynamics,catalyst design and process feasibility.Despite many aspects behind the mechanism of DME synthesis from H2-CO_(2) streams are still to be uncovered,the recent progress in the research on H2 release by DME steam reforming is increasing the interest for effectively closing this binary H2 loop,in view of future green deals and sustainable research developments.

Effect of Heat Treatment on Microstructure and Mechanical Properties of Quenching and Partitioning Steel

In order to investigate the effect of microstructural characterization on the mechanical properties and retained austenite stability, a different type of quenching and partitioning steel（I-Q＆P） through intercritical annealing before the quenching and partitioning process was designed, which can realize lamellar intercritical microstructure compared to the conventional quenching and partitioning（Q＆P） process. The morphology of ferrite and martensite/retained austenite is lamellar in the I-Q＆P steel while it is equiaxed after being heat-treated by conventional Q＆P process. The I-Q＆P steel is proved to have better formability and mechanical properties than conventional Q＆P steel, which is due to the highervolume fraction of retained austenite in the I-Q＆P steel and confirmed by electron backscattering diffraction patterns and X-ray diffraction. Furthermore, the stability of retained austenite in I-Q＆P steel is also higher than that in conventional Q＆P steel, which is investigated by tensile tests and differential scanning calorimetry.