Abstract Volkov–Pankratov (VP) states are a family of sub-gap states that appear at the smooth interface/domain wall between topologically distinct gaped states. We carry out quantum transport ...simulations on one- and two-dimensional lattice models to demonstrate the emergence of such states in the edge spectrum of a quantum spin Hall system subjected to a smoothly varying exchange field that switches its sign at a given spatial point. We show the VP states possess non-trivial spin textures that can be characterized by a winding number in real space. It is further demonstrated that the application of an electric field along the edge provides control of this spin texture without altering the winding number. Finally, we illuminate how these spin textures can be read off via the local tunnel magnetoresistance (TMR) response of spin-polarized tunnel probes attached to the edge and the TMR can be controlled by purely electrical means akin to a Datta–Das type spin transistor.
This paper reports some recent results related to active monitoring of powder bed fusion (PBF-LB) processes through analysis of layer-by-layer surface profile data. Estimation of fault probability ...was carried out experimentally in a Renishaw AM250 machine, by collecting Fe3Si powder bed height data, in situ, during the metal additive manufacturing of a heat exchanger section, comprised a series of conformal channels. Specifically, high-resolution powder bed surface height data from a laser profilometer was linked to post-print ground-truth labels (faulty or nominal) for each site from computed tomography (CT) scans, by training a shallow artificial neural net (ANN). The ANN demonstrated interesting capabilities for discovering correlations between surface roughness characteristics and the presence and size of faults. Strong performance was achieved with respect to several standard metrics for classifying faulty and nominal sites. These developments can potentially enable active monitoring processes to become a future component of a layer-by-layer feedback system for better control of PBF-LB processes.
Hyperbranched polyesters with polyionic character and high hydrodynamic sizes were synthesized at four different monomer mole ratios (A
n
/B
3
= 1:0.5, 1:1, 1: 3 and 1:5) by melt condensation of ...ecofriendly Poly (ethylene glycol) or PEG and Aconitic acid or AA via A
n
+ B
3
approach. The products were characterized by FTIR,
1
H NMR, FESEM, TEM and DSC techniques to establish the microstructure as well as the hyperbranched architecture. The degree of branching was estimated to be within 89%-33% by
1
H NMR measurements. Polyesters synthesized from 1:3 and 1:5 contained low (12%) to moderately high (40%) crosslinked structure as well. Gelation was effectively avoided at 1:0.5 and 1:3 mol compositions by keeping the AA content at lower values than PEG. The most soluble hyperbranched polyester was spherical having a dense core and a higher shell morphology. Whereas, the more crosslinked molecule was spherical but uniformly dense. Due to of the polyelectrolytic nature, the polyesters were used as flocculant to unsettle highly stable kaolin suspension at low suspension concentration maintained at 0.25% concentration by weight. The highest hydrodynamic size of the sample synthesized from 1:1 mole composition, was able to flocculate at the fastest rate (39 s) at pH 2.0 than at the iso-electric point (pH 4.2) of kaolin as well as reproduced the pure water with highest clarity (turbidity: 4 NTU).
Non-traditional polyesters from low molecular weight Poly (ethylene glycol) (PEG, M
n
4000) and biocompatible Trimesic acid (TMA) were synthesised through stoichiometric feeding of PEG and TMA in the ...mole ratios starting from 1:0.5 to 1:5. The melt condensation was carried out under catalytic condition for a limited period of 6 h to prohibit gelation of the entire mass due to over-abundance of the functional groups. The polyesters were formed with substantial soluble yield; at lower acid concentration in the feed e.g. 1:0.5, 1:1 and 1:2-they were mostly branched while at higher concentration e.g. 1:3 and 1:5-they were significantly crosslinked. Nearly all the specimens contained partially reacted TMA molecules in the branch ends which made them pH responsive (the hydrodynamic sizes altered with change in pH). The polymers were characterized using solubility, spectroscopy, viscometry and particle size measurements to establish the microstructure, formation kinetics and branched topology. Nuclear magnetic resonance (
1
H NMR) established the maximum extent of branching (65%) at 1:5 mol composition. Suitability for bioapplication of the polyesters was examined from surface texture study and cell cytotoxicity analysis. The scanning electron microscopic (SEM) images portrayed adequate micro voids on the surface, on the other hand, the cytotoxicity study depicted those surfaces could adhere and support the growth of mammalian cells and also successfully survive the MTT assay.
Liquid water saturation profiles were determined using high resolution neutron radiography for commercially available fuel cell materials and hardware. Temperature, pressure, and relative humidity ...(concentration) gradients were imposed on the cell to determine individual influences on water content for each gradient. The asymmetric anode/cathode channel/land architecture used in this work results in significant water accumulation in the anode diffusion media with saturation values of up to ∼50%. Anode water content was found to change substantially with imposed pressure or concentration gradient, whereas the cathode saturation profile remained relatively consistent, indicating the channel/land ratio and thickness have a determinant role in diffusion media retention. The data generated in this work has been made publicly available through www.pemfcdata.org, and should be useful for computational modelers seeking validation data.
•High resolution neutron radiography used to determine through-plane water content.•Test conditions chosen to push limitations of multi-phase models.•Online database provides rich validation data for multiphase models.•Flow field geometry significantly influences diffusion media saturation levels.•Anode was more sensitive to water content with asymmetric flow field.
There have been 130 mass shootings in the United States from 1982 to June, 2022 according to the Mother Jones database of active shooter events. In these critical scenarios, making the right ...decisions while evacuating can be the difference between life and death. However, emergency evacuation is intensely stressful, which along with lack of verifiable real-time information may lead to costly incorrect decisions. In this paper, we demonstrate the effectiveness of a non-homogeneous semi-Markov-Decision-Process (NHSMDP) based naive algorithm that relies on prior knowledge about the layout of a building and uses recurring updates of the shooter's location (based on automatic processing of images from a camera network) to provide an optimized egress plan for evacuees. While emergency evacuations due to fire and natural disasters are well researched, the novelty of this work is in the response to a threat that moves either purposefully or randomly through the building and in incorporating the ability for an evacuee to wait for danger to pass before beginning egress and during the process of evacuation. This ability to include sojourn times in the optimized scheme is due to the NHSMDP formulation and is a notable augmentation to the current state-of-the-art. We show that following this algorithm can reduce casualties by 56% and the time spent by evacuees in the shooter's line of sight by 52% compared to an intuitive natural response guided by expert advice.
This work presents a heuristic for describing the next best view location for an autonomous agent exploring an unknown environment. The approach considers each robot as a point mass with ...omnidirectional and unrestricted vision of the environment and line-of-sight communication operating in a polygonal environment which may contain holes. The number of robots in the team is always sufficient for full visual coverage of the space. The technique employed falls in the category of distributed visibility-based deployment algorithms which seek to segment the space based on each agent's field of view with the goal of deploying each agent into the environment to create a visually connected series of agents which fully observe the previously unknown region. The contributions made to this field are a technique for utilizing linear programming methods to determine the solution to the next best observation (NBO) problem as well as a method for calculating multiple NBO points simultaneously. Both contributions are incorporated into an algorithm and deployed in a simulated environment built with MATLAB for testing. The algorithm successfully deployed agents into polygons which may contain holes. The efficiency of the deployment method was compared with random deployment methods to establish a performance metric for the proposed tactic. It was shown that the heuristic presented in this work performs better the other tested strategies.
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