Investigation into the formation of charge packets in polyethylene: experiment and simulation

The phenomenon of charge packet has been reported in polymeric insulation materials under the application of dc electric fields in recent decades. It is noted that such charge packets could lead to substantial modification of local electric stress, which increases the possibility of failure of insulating materials. The physics of charge packets has not yet been revealed clearly. In this paper, the dynamics of positive charge packets in polyethylene is observed using the pulsed electro-acoustic technique. Negative differential mobility of positive charge carrier is found, which is believed to be crucial to the formation of charge packets. This negative differential mobility is introduced into a bipolar charge transport model to simulate the packet-like space charge in polymers. Simulation results show that not only the negative differential mobility but also weaker trapping characteristic are required to generate a positive charge packet in polyethylene under dc stress believed to be crucial to the formation of charge packets. This negative differential mobility is introduced into a bipolar charge transport model to simulate the packet-like space charge in polymers. Simulation results show that not only the negative differential mobility but also weaker trapping characteristic are required to generate a positive charge packet in polyethylene under dc stress

Stock Optimization in Emergency Resupply Networks under Stuttering Poisson Demand

We consider a network in which field stocking locations (FSLs) manage multiple parts according to an (S-1,S) policy. Demand processes for the parts are assumed to be independent stuttering Poisson processes. Regular replenishments to an FSL occur from a regional stocking location (RSL) that has an unlimited supply of each part type. Demand in excess of supply at an FSL is routed to an emergency stocking location (ESL), which also employs an (S-1,S) policy to manage its inventory. Demand in excess of supply at the ESL is backordered. Lead time from the ESL to each FSL is assumed to be negligible compared to the RSL-ESL resupply time. In companion papers we have shown how to approximate the joint probability distributions of units on hand, units in regular resupply, and units in emergency resupply. In this paper, we focus on the problem of determining the stock levels at the FSLs and ESL across all part numbers that minimize backorder, and emergency resupply costs subject to an inventory investment budget constraint. The problem is shown to be a nonconvex integer programming problem, and we explore a collection of heuristics for solving the optimization problem

A New Semantic-Based Tool Detection Method for Robots

Home helper robots have become more acceptable due to their excellent image recognition ability. However, some common household tools remain challenging to recognize, classify, and use by robots. We designed a detection method for the functional components of common household tools based on the mask regional convolutional neural network (Mask-R-CNN). This method is a multitask branching target detection algorithm that includes tool classification, target box regression, and semantic segmentation. It provides accurate recognition of the functional components of tools. The method is compared with existing algorithms on the dataset UMD Part Affordance dataset and exhibits effective instance segmentation and key point detection, with higher accuracy and robustness than two traditional algorithms. The proposed method helps the robot understand and use household tools better than traditional object detection algorithms

Investigation of charge injection threshold field in epoxy resin

In this paper, space charge formation in epoxy resin has been measured at different applied electric fields using the pulsed electroacoustic technique to reveal the charge injection threshold field. The influence of electrode material on the charge injection has also been investigated. It has been found that the threshold field value for negative charge injection is much lower than that of positive charges, and electrons are the dominant type of charge carrier in epoxy resin. Compared with aluminium, the sample with gold electrode shows a higher threshold field value and lower amount of charge injection. This observation can be attributed to a higher work function of the gold

Universal Susceptibility Variations in 1+1 Dimensional Vortex Glass

We model a planar array of fluxlines as a discrete solid-on-solid model with quenched disorder. Simulations at finite temperatures are made possible by a new algorithm which circumvents the slow glassy dynamics encountered by traditional Metropolis Monte Carlo algorithms. Numerical results on magnetic susceptibility variations support analytic predictions.Comment: 6 pages, elsart file enclosed, 4 figures. Comments can be sent to [email protected]

Blow up criterion for compressible nematic liquid crystal flows in dimension three

In this paper, we consider the short time strong solution to a simplified hydrodynamic flow modeling the compressible, nematic liquid crystal materials in dimension three. We establish a criterion for possible breakdown of such solutions at finite time in terms of the temporal integral of both the maximum norm of the deformation tensor of velocity gradient and the square of maximum norm of gradient of liquid crystal director field.Comment: 22 page

An arginine-to-proline mutation in a domain with undefined functions within the helicase protein (Nsp13) is lethal to the coronavirus infectious bronchitis virus in cultured cells

AbstractGenetic manipulation of the RNA genomes by reverse genetics is a powerful tool to study the molecular biology and pathogenesis of RNA viruses. During construction of an infectious clone from a Vero cell-adapted coronavirus infectious bronchitis virus (IBV), we found that a G–C point mutation at nucleotide position 15526, causing Arg-to-Pro mutation at amino acid position 132 of the helicase protein, is lethal to the infectivity of IBV on Vero cells. When the in vitro-synthesized full-length transcripts containing this mutation were introduced into Vero cells, no infectious virus was rescued. Upon correction of the mutation, infectious virus was recovered. Further characterization of the in vitro-synthesized full-length transcripts containing the G15526C mutation demonstrated that this mutation may block the transcription of subgenomic RNAs. Substitution mutation of the Arg132 residue to a positively charged amino acid Lys affected neither the infectivity of the in vitro-synthesized transcripts nor the growth properties of the rescued virus. However, mutation of the Arg132 residue to Leu, a conserved residue in other coronaviruses at the same position, reduced the recovery rate of the in vitro-synthesized transcripts. The recovered mutant virus showed much smaller-sized plaques. On the contrary, a G–C and a G–A point mutations at nucleotide positions 4330 and 9230, respectively, causing Glu–Gln and Gly–Glu mutations in or near the catalytic centers of the papain-like (Nsp3) and 3C-like (Nsp5) proteinases, did not show detectable detrimental effect on the rescue of infectious viruses and the infectivity of the rescued viruses

Intrinsic ferromagnetic impurity phases in SmFeAsO1-xFx detected by muSR

We report about muSR measurements on SmFeAsO1-xFx which helped us to identify the signature of diluted ferromagnetic inclusions, ubiquitous in the iron pnictides. These impurities are characterized by a Curie temperature close to room temperature and they seem responsible for a non negligible magnetic relaxation of the implanted muons, that should not be confused with intrinsic pnictide properties.Comment: The International Conference on FeAs High Tc Superconducting Multilayers and Related Phenomena (Superstripes2008), Rome, Italy, December 9-13, 200

Lattice-Boltzmann Method for Geophysical Plastic Flows

We explore possible applications of the Lattice-Boltzmann Method for the simulation of geophysical flows. This fluid solver, while successful in other fields, is still rarely used for geotechnical applications. We show how the standard method can be modified to represent free-surface realization of mudflows, debris flows, and in general any plastic flow, through the implementation of a Bingham constitutive model. The chapter is completed by an example of a full-scale simulation of a plastic fluid flowing down an inclined channel and depositing on a flat surface. An application is given, where the fluid interacts with a vertical obstacle in the channel.Comment: in W. Wu, R.I. Borja (Edts.) Recent advances in modelling landslides and debris flow, Springer Series in Geomechanics and Geoengineering (2014), ISBN 978-3-319-11052-3, pp. 131-14

On 2D Viscoelasticity with Small Strain

An exact two-dimensional rotation-strain model describing the motion of Hookean incompressible viscoelastic materials is constructed by the polar decomposition of the deformation tensor. The global existence of classical solutions is proved under the smallness assumptions only on the size of initial strain tensor. The proof of global existence utilizes the weak dissipative mechanism of motion, which is revealed by passing the partial dissipation to the whole system.Comment: Different contributions of strain and rotation of the deformation are studied for viscoelastic fluids of Oldroyd-B type in 2