996 research outputs found
Magnetoresistive sensors based on the elasticity of domain walls
Magnetic sensors based on the magnetoresistance effects have a promising
application prospect due to their excellent sensitivity and advantages in terms
of the integration. However, competition between higher sensitivity and larger
measuring range remains a problem. Here, we propose a novel mechanism for the
design of magnetoresistive sensors: probing the perpendicular field by
detecting the expansion of the elastic magnetic Domain Wall (DW) in the free
layer of a spin valve or a magnetic tunnel junction. Performances of devices
based on this mechanism, such as the sensitivity and the measuring range can be
tuned by manipulating the geometry of the device, without changing the
intrinsic properties of the material, thus promising a higher integration level
and a better performance. The mechanism is theoretically explained based on the
experimental results. Two examples are proposed and their functionality and
performances are verified via micromagnetic simulation.Comment: 4 figures, 13 page
Vibration measurement in a metro depot with trains running in the top story
Metro depots are places for subway train to get parked and maintained. To avoid the waste of large city areas occupied by depots, there is a need of developing depots for commercial and/or residential use as well, and in that case the train-induced vibrations become the major concern. This paper presents a unique case study on the vibration measurement in a 3-story metro depot, where the first two stories are developed for offices and shops and the third story is used as the maintenance garage with trains moving in/out through the connecting viaducts. Acceleration time histories of rails and floors in the three stories were measured. Amplitudes and frequency contents of the vibrations at different locations are compared through the corresponding frequency spectra and 1/3 octave band root-mean-square (RMS) spectra. The influence of track positions on floor vibration is investigated, and the vibration level of the building is evaluated using two indicators. Finally, numerical simulation is carried out so as to provide some references to the vibration control
Analysis of strength and microstructural characteristics of mine backfills containing fly ash and desulfurized gypsum
The utilization of solid wastes (SWs) as a potential resource for backfilling is not only conducive to environmental protection but also reduces the surface storage of waste. Two types of SWs, including fly ash (FA) and desulfurized gypsum (DG), were used to prepare cementitious backfilling materials for underground mined-out areas. Ordinary Portland cement (OPC) was used as cement in mine backfill. To better investigate the feasibility of preparing backfill materials, some laboratory tests, such as uniaxial compressive strength (UCS), scanning electron microscopy (SEM), and energy dissipation theory, were conducted to explore both strength and microstructural properties of backfilling. Results have demonstrated that the main components of FA and DG in this study are oxides, with few toxic and heavy metal components. The ideal ratio of OPC:FA:DG is 1:6:2 and the corresponding UCS values are 2.5 and 4.2 MPa when the curing time are 7 days and 14 days, respectively. Moreover, the average UCS value of backfilling samples gradually decreased when the proportion of DG in the mixture increased. The main failure modes of various backfilling materials are tensile and shearing cracks. In addition, the corresponding relations among total input energy, dissipated energy and strain energy, and stress-strain curve were investigated. The spatial distribution of oxygen, aluminum, silicon, calcium, iron and magnesium elements, and hydration product are explored from the microstructure's perspective. The findings of this study provide both invaluable information and industrial applications for the efficient management of solid waste, based on sustainable development and circular economy.National Natural Science Foundation of China (NSFC) 51804017
Fundamental Research Funds for the Central Universities FRF-TP-20-001A
Thermodynamic Analysis of Separating Synchronously Copper and Iron Components from Copper Smelting Slags
AbstractThe occurrence state changes and the possibility of synchronous separation of the components with copper and iron were researched by detailed calculation and derived, from the thermodynamics point of view in the oxidation modification process of copper smelting slag. The relationship between oxygen and sulfur potential of coexistence stage for metallic copper and the magnetite was concluded by analyzed the advantage area chart of Cu-Fe-S-O system. The Thermodynamic studies show that, there was a stability range of the oxygen and sulfur potential in Cu-Fe-S-O system, which made the metallic copper and the magnetite coexistence. The research will provide theoretical support for the synchronous separation between copper and iron components from copper smelting slag
Patterned nanofiber air filters with high optical transparency, robust mechanical strength, and effective PM_(2.5) capture capability
PM_(2.5), due to its small particle size, strong activity, ease of the attachment of toxic substances and long residence time in the atmosphere, has a great impact on human health and daily production. In this work, we have presented patterned nanofiber air filters with high optical transparency, robust mechanical strength and effective PM_(2.5) capture capability. Here, to fabricate a transparency air filter by a facile electrospinning method, we chose three kinds of patterned wire meshes with micro-structures as negative receiver substrates and directly electrospun polymer fibers onto the supporting meshes. Compared with randomly oriented nanofibers (named “RO NFs” in this paper) and commercially available facemasks, the patterned air filters showed great mechanical properties, and the water contact angles on their surfaces were about 122–143° (the water contact angle for RO NFs was 81°). In addition, the patterned nanofibers exhibited high porosity (>80%), and their mean pore size was about 0.5838–0.8686 μm (the mean pore size of RO NFs was 0.4374 μm). The results indicate that the transparent patterned air filters have the best PM_(2.5) filtration efficiency of 99.99% at a high transmittance of ∼69% under simulated haze pollution
Patterned nanofiber air filters with high optical transparency, robust mechanical strength, and effective PM_(2.5) capture capability
PM_(2.5), due to its small particle size, strong activity, ease of the attachment of toxic substances and long residence time in the atmosphere, has a great impact on human health and daily production. In this work, we have presented patterned nanofiber air filters with high optical transparency, robust mechanical strength and effective PM_(2.5) capture capability. Here, to fabricate a transparency air filter by a facile electrospinning method, we chose three kinds of patterned wire meshes with micro-structures as negative receiver substrates and directly electrospun polymer fibers onto the supporting meshes. Compared with randomly oriented nanofibers (named “RO NFs” in this paper) and commercially available facemasks, the patterned air filters showed great mechanical properties, and the water contact angles on their surfaces were about 122–143° (the water contact angle for RO NFs was 81°). In addition, the patterned nanofibers exhibited high porosity (>80%), and their mean pore size was about 0.5838–0.8686 μm (the mean pore size of RO NFs was 0.4374 μm). The results indicate that the transparent patterned air filters have the best PM_(2.5) filtration efficiency of 99.99% at a high transmittance of ∼69% under simulated haze pollution
- …