Highly Oxidation-Resistant and Self-Healable MXene-Based Hydrogels for Wearable Strain Sensor

Very recently, MXene-based wearable hydrogels have emerged as promising candidates for epidermal sensors due to their tissue-like softness and unique electrical and mechanical properties. However, it remains a challenge to achieve MXene-based hydrogels with reliable sensing performance and prolonged service life, because MXene inevitably oxidizes in water-containing system of the hydrogels. Herein, catechol-functionalized poly(vinyl alcohol) (PVA-CA)-based hydrogels is proposed to inhibit the oxidation of MXene, leading to rapid self-healing and superior strain sensing behaviors. Sufficient interaction of hydrophobic catechol groups with the MXene surface reduces the oxidation-accessible sites in the MXene for reaction with water and eventually suppresses the oxidation of MXene in the hydrogel. Furthermore, the PVA-CA-MXene hydrogel is demonstrated for use as a strain sensor for real-time motion monitoring, such as detecting subtle human motions and handwriting. The signals of PVA-CA-MXene hydrogel sensor can be accurately classified using deep learning models.     

Effect of Annealing Conditions on the Texture and Normal Anisotropy of Al‐Killed Steels in Simulated Batch Annealing

Three commercial cold rolled Al‐killed steels were investigated to study the effect of annealing conditions on the crystallographic texture and the resulting plastic anisotropy. The heating rates, maximum temperatures and isothermal holding times were varied in 18 laboratory scale thermal cycles applied to all steels. The annealed and skin‐passed samples were tensile tested to determine mechanical properties and anisotropy parameters. Grain structures and average grain sizes were examined by an optical microscope and the textures were measured by X‐ray diffraction. It was found that the chemical composition of the steel had a significant effect on the texture and normal anisotropy obtained at certain heating rates. The differences between the current steels were discussed in the light of the competition between the kinetics of AIN precipitation and recrystallization. Excess heating rates led to a low normal anisotropy, which was not improved by extending the isothermal time of annealing. Pancake grain structure and the grain size larger than 20 mm were found to be indicators of the properly chosen heating rate and resulting in high normal anisotropy. At the proper heating rate high normal anisotropy was attained at low annealing temperatures and in short isothermal times, but a longer isothermal annealing was required to obtain a low yield strength.     

Rate-dependent compressive behavior of unidirectional carbon fiber composites

Unidirectional carbon fiber stitched composites were subjected to off-axis compression under static and low-velocity impact loading. Specimens were cut such that the fibers were at angles of 15°, 30°, 45° and 60° to the direction of loading. A modified compression fixture was used to carry out the tests. Static tests were carried out on a hydraulically activated MTS loading frame, where specimens were subjected to displacement controlled loading. Low-velocity impact tests were conducted on a drop tower facility. A three-strain-gauge rosette was used to measure global strains. Load was measured using a load cell. Owing to the unique microstructure of the specimens, a modified three-parameter characterization of the inelastic response was used, and the constants associated with this characterization were determined uniquely. Independently, Iosipescu shear tests were carried out to determine the shear response of the material under static and low-velocity impact conditions. The shear response so determined was checked against the off-axis test results. It is shown that rate-dependent interfacial effects are predominant in these materials. Polym. Compos. 25:397–406, 2004. © 2004 Society of Plastics Engineers.     

Entropy analysis of wet-surface cooling system for air flow

A wet-surface heat-exchanger, where the effluent air is moistened, is analysed according to a thermodynamic theory and data of experimental tests. An entropy generation function, which takes into account the changes of temperature and humidity of air, is derived. The analyses show that it is thermodynamically possible, without any cooling machine, to achieve extremely large temperature drops. With certain parameters the system results in a maximum rate of entropy generation which is used to analyse differences between two different methods of spraying the moistening water. Approximal limits for the efficient working fluid mass flow value are also given. © 1998 John Wiley & Sons, Ltd.     

Levels of selected polychlorinated biphenyl congeners in total diet samples from Aragón, Spain.

Six congeners of polychlorinated biphenyls (PCB 28, 52, 101, 138, 153, and 180) were investigated in 281 samples of different meals of the average diet consumed in Aragon, northeast Spain. PCB residues were extracted with organic solvents according to the techniques recommended by the U.S. Food and Drug Administration and the Netherlands' Ministry of Welfare, Health, and Cultural Affairs; the residues were cleaned up by gel permeation chromatography. Quantitation of analytes was carried out by capillary gas-liquid chromatography using electron capture detector. The identity of the peaks was confirmed by mass spectrometry. PCB residues were found only in fish meals (50% positive samples) with a mean level of 96.3 ng/g on a lipid basis. Congeners detected in fish meals were 138, 153, and 180, with mean values of 117.0, 122.3, and 36.2 ng/g on a lipid basis, respectively.     

Large-sample analysis of MUSIC and Min-Norm direction estimators in the presence of model errors

We analyze the large-sample mean square error (MSE) of MUSIC and Min-Norm direction-of-arrival (DOA) estimators under fairly general conditions, including mismodelling of the array response and the noise covariance. We separate the contributions to the MSE into a bias part caused by modelling errors and a variance part caused by finite (yet large) sample effects. The bias is simply evaluated by comparing the limiting estimate (corresponding to an infinite number of snapshots) with the true DOAs (which are known to the analyzer). To simplify the variance derivation we assume that the snapshots are complex i.i.d. Gaussian vectors and that the largest eigenvalues of their covariance matrix are distinct, but,otherwise, make none of the assumptions commonly used in previous analyses; in particular we do not constrain the snapshots to satisfy any model equation. The theoretical results obtained are illustrated by means of numerical examples using various modelling errors.The work of Petre Stoica was supported by the Swedish Research Council of Engineering Sciences under contract 91-676.     

Comprehensive computerized assessment of cognitive sequelae of a complete 12-16 hour fast.

Food deprivation has been shown to deleteriously affect human cognition, but findings are equivocal, and few studies have examined several cognitive domains. In this study, the authors used computerized testing to describe the profile of shifts in cognition attributable to short-term religious fasting. Multiple cognitive domains were evaluated at midday and late afternoon following complete abstention from eating and drinking beginning at midnight. Cross-domain, fasting-related deficits were found for tasks requiring perception of spatial relations. Fasting-related information processing deficits were found for response time but not accuracy for test levels of intermediate difficulty. Time-of-day effects often reflected poorer afternoon performance. These findings provide a detailed profile of cognitive consequences of food deprivation, affected by time of day, task demands, and type of outcome. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bandwidth allocation and pricing in multinode network

This paper presents adaptive resource sharing model that uses a revenue criterion to allocate network resources in the optimal way. The model ensures QoS requirements of data flows and, at the same time, maximizes the total revenue by adjusting parameters of the underlying scheduler. Besides, the adaptive model eliminates the need to find the optimal static weight values because they are calculated dynamically. The simulation consists of several cases that analyse the model and the way it provides the required QoS guarantees. The simulation reveals that the installation of the adaptive model increases the total revenue and ensures the QoS requirements for all service classes.     

Template Design for Cellular Nonlinear Networks With 1-Bit Weights

In this paper, we show how a cellular nonlinear network with 1-bit weight programmability can be used for processing black and white image data. When using such a binary-programmable network, some templates need to be processed algorithmically, in other words, divided into subtasks that are processed consecutively. We classify templates into groups based on their properties and give guidelines as to how the division into subtasks (when applicable) is performed. A large collection of templates suitable for the proposed model is shown. We also describe one possible cell structure that realizes the binary-programmable model. The cell is modeled with Matlab and selected template simulations are shown.     

Hygromechanical properties of composites of crosslinked allylglycidyl-ether modified starch reinforced by wood fibres

In a previous work a new family of thermoset composites of allylglycidyl ether modified starch as matrix, an ethylene glycol dimethacrylate as cross-linker and a wood fibre as reinforcement were prepared. The aim of the present work was to study the hygromechanical properties of the new composites including density, dimensional stability in water, water uptake, stiffness, and ultimate strength in three-point bending. It was shown that the samples with a starch matrix of a high degree of substitution (DS = 2.3), HDS, absorbed less water, were more stable in water and had also higher stiffness and strength than corresponding composite samples with a starch matrix of low degree of substitution (DS = 1.3), LDS. Overall, the fibre addition improved water stability. An increased fibre content from 40 to 70% by weight had a negligible impact on the water uptake. An increase in fibre content did, however, improve the mechanical properties. The HDS-sample with highest fibre content, 70% by weight showed the highest Young’s modulus (3700 MPa) and strength (130 MPa), which are markedly higher compared with the samples based on the pure HDS matrix (Young’s modulus of 360 MPa and strength of 15 MPa). The measured Young’s modulus and tensile strength values were roughly one order of magnitude higher than earlier reported cellulosic fibre reinforced natural polymer composites.