Dependence of Granular Matrix Demagnetizing Factor on the Matrix Relative Size

We note that for a wide range of porous, especially granular, ferromagnetics used as matrices of magnetic filter-separators, there is still an issue of defining their demagnetizing factor N which has a dramatic effect on the values of average magnetic permeability of these operating units of filter-separators. The work aims at filling the existent gaps in the issue, we supply N values depending on the relative size of such magnets as well as a respective generalizing phenomenological dependence which is characterized by an exponential realtion between the demagnetizing factor and relative size radical. The established relation allows obtaining real values of magnetic permeability of a short filter matrix thus providing an unbiased comparative estimate of its technological workability.

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Influence of Alumina Nanofibers Sintered by the Spark Plasma Method on Nickel Mechanical Properties

Metals ◽

10.3390/met11040548 ◽

2021 ◽

Vol 11 (4) ◽

pp. 548 ◽

Cited By ~ 1

Author(s):

Leonid Agureev ◽

Valeriy Kostikov ◽

Zhanna Eremeeva ◽

Svetlana Savushkina ◽

Boris Ivanov ◽

...

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Elastic Modulus ◽

Strength Properties ◽

Alumina Nanoparticles ◽

Metal Powders ◽

Wide Range ◽

The Matrix ◽

Spark Plasma ◽

Average Size

The article presents the study of alumina nanoparticles’ (nanofibers) concentration effect on the strength properties of pure nickel. The samples were obtained by spark plasma sintering of previously mechanically activated metal powders. The dependence of the grain size and the relative density of compacts on the number of nanofibers was investigated. It was found that with an increase in the concentration of nanofibers, the average size of the matrix particles decreased. The effects of the nanoparticle concentration (0.01–0.1 wt.%) on the elastic modulus and tensile strength were determined for materials at 25 °C, 400 °C, and 750 °C. It was shown that with an increase in the concentration of nanofibers, a 10–40% increase in the elastic modulus and ultimate tensile strength occurred. A comparison of the mechanical properties of nickel in a wide range of temperatures, obtained in this work with materials made by various technologies, is carried out. A description of nanofibers’ mechanisms of influence on the structure and mechanical properties of nickel is given. The possible impact of impurity phases on the properties of nickel is estimated. The tendency of changes in the mechanical properties of nickel, depending on the concentration of nanofibers, is shown.

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Estimating the number of usability problems affecting medical devices: modelling the discovery matrix

BMC Medical Research Methodology ◽

10.1186/s12874-020-01091-y ◽

2020 ◽

Vol 20 (1) ◽

Author(s):

Vincent Vandewalle ◽

Alexandre Caron ◽

Coralie Delettrez ◽

Renaud Périchon ◽

Sylvia Pelayo ◽

...

Keyword(s):

Medical Devices ◽

Market Access ◽

Real Life ◽

Usability Testing ◽

Probability Of Detection ◽

Usability Problems ◽

Usability Problem ◽

Wide Range ◽

The Matrix ◽

Problem Detection

Abstract Background Usability testing of medical devices are mandatory for market access. The testings’ goal is to identify usability problems that could cause harm to the user or limit the device’s effectiveness. In practice, human factor engineers study participants under actual conditions of use and list the problems encountered. This results in a binary discovery matrix in which each row corresponds to a participant, and each column corresponds to a usability problem. One of the main challenges in usability testing is estimating the total number of problems, in order to assess the completeness of the discovery process. Today’s margin-based methods fit the column sums to a binomial model of problem detection. However, the discovery matrix actually observed is truncated because of undiscovered problems, which corresponds to fitting the marginal sums without the zeros. Margin-based methods fail to overcome the bias related to truncation of the matrix. The objective of the present study was to develop and test a matrix-based method for estimating the total number of usability problems. Methods The matrix-based model was based on the full discovery matrix (including unobserved columns) and not solely on a summary of the data (e.g. the margins). This model also circumvents a drawback of margin-based methods by simultaneously estimating the model’s parameters and the total number of problems. Furthermore, the matrix-based method takes account of a heterogeneous probability of detection, which reflects a real-life setting. As suggested in the usability literature, we assumed that the probability of detection had a logit-normal distribution. Results We assessed the matrix-based method’s performance in a range of settings reflecting real-life usability testing and with heterogeneous probabilities of problem detection. In our simulations, the matrix-based method improved the estimation of the number of problems (in terms of bias, consistency, and coverage probability) in a wide range of settings. We also applied our method to five real datasets from usability testing. Conclusions Estimation models (and particularly matrix-based models) are of value in estimating and monitoring the detection process during usability testing. Matrix-based models have a solid mathematical grounding and, with a view to facilitating the decision-making process for both regulators and device manufacturers, should be incorporated into current standards.

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Ni Content Surface Layer Produced by Laser Surface Treatment on Amorphisable Cu Base Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.649.101 ◽

2010 ◽

Vol 649 ◽

pp. 101-106

Author(s):

Mária Svéda ◽

Dóra Janovszky ◽

Kinga Tomolya ◽

Jenő Sólyom ◽

Zoltán Kálazi ◽

...

Keyword(s):

Surface Layer ◽

Surface Treatment ◽

Laser Cladding ◽

Base Alloy ◽

Laser Surface ◽

Laser Alloying ◽

Laser Surface Treatment ◽

Ni Content ◽

Wide Range ◽

The Matrix

The aim of our research was to comparatively examine Ni content surface layers on amorphisable Cu base alloy produced by different laser surface treatments. Laser surface treatment (LST) techniques, such as laser surface melting, laser alloying and laser cladding, provide a wide range of interesting solutions for the production of wear and corrosion resistant surfaces. [1,2] With LST techniques, the surface can be: i) coated with a layer of another material by laser cladding, ii) the composition of the matrix can be modified by laser alloying. [3] Two kinds of laser surface treatment technologies were used. In the case of coating-melting technology a Ni content surface layer was first developed by galvanization, and then the Ni content layer was melted together with the matrix. In the case of powder blowing technology Ni3Al powder was blown into the layer melted by laser beam and Argon gas. LST was performed using an impulse mode Nd:YAG laser. The laser power and the interaction time were 2 kW and 20÷60 ms. The characterization of the surface layer microstructure was performed by XRD, scanning electron microscopy and microhardness measurements.

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Unravelling the impact of harvesting pressure on canopy-forming macroalgae

Marine and Freshwater Research ◽

10.1071/mf14198 ◽

2016 ◽

Vol 67 (1) ◽

pp. 153 ◽

Cited By ~ 7

Author(s):

Doriane Stagnol ◽

Renaud Michel ◽

Dominique Davoult

Keyword(s):

Habitat Characteristics ◽

Spatiotemporal Variability ◽

Macrobenthic Assemblages ◽

Wide Range ◽

The Matrix ◽

Commercial Species ◽

Canopy Removal ◽

The Impact ◽

Relevant Finding

Canopy-forming macroalgae create a specific surrounding habitat (the matrix) with their own ecological properties. Previous studies have shown a wide range of responses to canopy removal. Magnitude and strength of the effects of harvesting are thought to be context-dependent, with the macroalgal matrix that can either soften or exacerbate the impact of harvesting. We experimentally examined in situ the effect of harvesting on targeted commercial species, and how these potential impacts might vary in relation to its associated matrix. We found that patterns of recovery following the harvesting disturbance were variable and matrix specific, suggesting that local factors and surrounding habitat characteristics mediated the influence of harvesting. The greatest and longest effects of harvesting were observed for the targeted species that created a dominant and monospecific canopy on their site prior to the disturbance. Another relevant finding was the important natural spatiotemporal variability of macrobenthic assemblages associated with canopy-forming species, which raises concern about the ability to discriminate the natural variability from the disturbance impact. Finally, our results support the need to implement ecosystem-based management, assessing both the habitat conditions and ecological roles of targeted commercial species, in order to insure the sustainability of the resource.

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Research and Modeling of Viscoelastic Behavior of Elastomeric Nanocomposites

PNRPU Mechanics Bulletin ◽

10.15593/perm.mech/2021.2.08 ◽

2021 ◽

pp. 76-87

Author(s):

V. D Kislitsyn ◽

K. A Mokhireva ◽

V. V Shadrin ◽

A. L Svistkov

Keyword(s):

Constitutive Relations ◽

Viscoelastic Behavior ◽

Polymer Materials ◽

Material Structure ◽

Softening Effect ◽

Single Walled Nanotubes ◽

Wide Range ◽

Significant Difference ◽

The Matrix ◽

Entire History

The paper presents results of studying mechanical properties of polymer composites depending on types of filler particles (granular - carbon black, nanodiamonds; layered - graphene plates; fibrous - single-walled nanotubes). These nanofillers differ greatly from each other in their structure and geometry. A significant difference in behavior of nanocomposites was revealed even with little introduction of particles into the elastomer. The highest level of reinforcement of the matrix was obtained when single-wall nanotubes and detonation nanodiamonds were used as fillers. The viscoelastic properties and the Mullins softening effect [1-4] were investigated in experiments performed with material samples subjected to complex uniaxial cyclic deformation. In these experiments, the amplitude of deformations was changed step by step; and at each step a time delay was specified to complete rearrangement processes of the material structure. It was found that a pronounced softening effect after the first cycle of deformation and significant hysteresis losses occur in the material filled with single-walled nanotubes. These characteristics are insignificant for the rest of nanocomposites until elongation increases twofold. In accordance with the obtained results, a new version of the mathematical model to describe properties of the viscoelastic polymer materials was proposed. The constants of the constitutive relations were calculated for each material; the theoretical and experimental load curves were compared. As a result, the introduced model is able to describe the behavior of elastomeric nanocomposites with a high accuracy. Moreover, this model is relatively easy to use, suitable for a wide range of strain rates and stretch ratios and does not require the entire history of deformation as needed for integral models of viscoelasticity.

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An induced real quaternion spherical ensemble of random matrices

Random Matrices Theory and Application ◽

10.1142/s2010326317500010 ◽

2017 ◽

Vol 06 (01) ◽

pp. 1750001

Author(s):

Anthony Mays ◽

Anita Ponsaing

Keyword(s):

Real Line ◽

Relative Size ◽

Functional Differentiation ◽

The Real ◽

Real Quaternion ◽

Large Matrix ◽

Wall Boundary Conditions ◽

The Matrix ◽

Soft Wall ◽

Point Correlation

We study the induced spherical ensemble of non-Hermitian matrices with real quaternion entries (considering each quaternion as a [Formula: see text] complex matrix). We define the ensemble by the matrix probability distribution function that is proportional to [Formula: see text] These matrices can also be constructed via a procedure called ‘inducing’, using a product of a Wishart matrix (with parameters [Formula: see text]) and a rectangular Ginibre matrix of size [Formula: see text]. The inducing procedure imposes a repulsion of eigenvalues from [Formula: see text] and [Formula: see text] in the complex plane with the effect that in the limit of large matrix dimension, they lie in an annulus whose inner and outer radii depend on the relative size of [Formula: see text], [Formula: see text] and [Formula: see text]. By using functional differentiation of a generalized partition function, we make use of skew-orthogonal polynomials to find expressions for the eigenvalue [Formula: see text]-point correlation functions, and in particular the eigenvalue density (given by [Formula: see text]). We find the scaled limits of the density in the bulk (away from the real line) as well as near the inner and outer annular radii, in the four regimes corresponding to large or small values of [Formula: see text] and [Formula: see text]. After a stereographic projection, the density is uniform on a spherical annulus, except for a depletion of eigenvalues on a great circle corresponding to the real axis (as expected for a real quaternion ensemble). We also form a conjecture for the behavior of the density near the real line based on analogous results in the [Formula: see text] and [Formula: see text] ensembles; we support our conjecture with data from Monte Carlo simulations of a large number of matrices drawn from the [Formula: see text] induced spherical ensemble. This ensemble is a quaternionic analog of a model of a one-component charged plasma on a sphere, with soft wall boundary conditions.

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Iron Deficiency: The Problem and Approaches to its Solution

Food and Nutrition Bulletin ◽

10.1177/156482659601700108 ◽

1996 ◽

Vol 17 (1) ◽

pp. 1-4 ◽

Cited By ~ 2

Author(s):

Clive E. West

Keyword(s):

Iron Deficiency ◽

Vitamin A ◽

Work Performance ◽

Nutrient Status ◽

Related Factors ◽

Number Of Factors ◽

Wide Range ◽

The Matrix ◽

Intractable Problem ◽

Year 2000

Anaemia is associated with increased perinatal mortality, increased child morbidity and mortality, behavioural changes and impaired mental development, decreased work performance, increased susceptibility to lead poisoning, and impaired immune competence. Iron-deficiency anaemia is an intractable problem, as indicated by the goal set by world leaders of reducing nutritional anaemia to one-third of 1990 levels by the year 2000, compared with the goals of virtually eliminating deficiencies of vitamin A and of iodine during the same period. To a large extent, this is because intake is less associated with status for iron than for iodine and vitamin A. The demand for iron varies throughout the life cycle, and the bioavailability of iron varies over a wide range because of a number of factors, such as the species of iron compound, the molecular linkage, the amount of nutrient consumed in a meal, the matrix in which the nutrient is incorporated, the absorption modifiers, the nutrient status of the host, genetic factors, other host-related factors, and interactions among factors.

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Improved Method for Measuring the Permeability of Nanoporous Material and Its Application to Shale Matrix with Ultra-Low Permeability

Materials ◽

10.3390/ma12091567 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1567 ◽

Cited By ~ 2

Author(s):

Taojie Lu ◽

Ruina Xu ◽

Bo Zhou ◽

Yichuan Wang ◽

Fuzhen Zhang ◽

...

Keyword(s):

High Pressure ◽

Fluid Transport ◽

Effective Means ◽

Clean Energy ◽

Nanoporous Materials ◽

Environmental Research ◽

Low Permeability ◽

Matrix Permeability ◽

Wide Range ◽

The Matrix

Nanoporous materials have a wide range of applications in clean energy and environmental research. The permeability of nanoporous materials is low, which affects the fluid transport behavior inside the nanopores and thus also affects the performance of technologies based on such materials. For example, during the development of shale gas resources, the permeability of the shale matrix is normally lower than 10−3 mD and has an important influence on rock parameters. It is challenging to measure small pressure changes accurately under high pressure. Although the pressure decay method provides an effective means for the measurement of low permeability, most apparatuses and experiments have difficulty measuring permeability in high pressure conditions over 1.38 MPa. Here, we propose an improved experimental method for the measurement of low permeability. To overcome the challenge of measuring small changes in pressure at high pressure, a pressure difference sensor is used. By improving the constant temperature accuracy and reducing the helium leakage rate, we measure shale matrix permeabilities ranging from 0.05 to 2 nD at pore pressures of up to 8 MPa, with good repeatability and sample mass irrelevance. The results show that porosity, pore pressure, and moisture conditions influence the matrix permeability. The permeability of moist shale is lower than that of dry shale, since water blocks some of the nanopores.

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Polyethylene and Polyvinyl Chloride-Blended Polystyrene Nanofibrous Sorbents and Their Application in the Removal of Various Oil Spills

Advances in Polymer Technology ◽

10.1155/2020/4097520 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Mohamed. A. Alnaqbi ◽

Afra G. Al Blooshi ◽

Yaser E. Greish

Keyword(s):

Crude Oil ◽

Oil Spills ◽

Aqueous Media ◽

Electrospun Fibers ◽

Motor Oil ◽

Polymer Blending ◽

Hydrophobic Polymers ◽

Poly Vinyl Chloride ◽

Wide Range ◽

The Matrix

Polymers provide a wide range of properties, and these properties can be greatly enhanced and modified through polymer blending. Polymer blending combines the properties and advantages of their original polymers. This paper showcases hydrophobic polymers prepared through polymer blending; these blends are characterized and evaluated for their efficiency in the removal of crude oil spills from aqueous media. The application of these blends holds a great deal of importance in preserving the environment and the recovery of lost oil in spills. The blends are produced using polystyrene (PS) as the matrix polymer and individually blending poly(vinyl chloride) (PVC) and polyethylene (PE) with the PS consisting of proportions of 5–20 wt.% each. The blends are then electrospun into bead-free microfibers with interconnected porosities as shown by their respective scanned electron micrographs. All fibrous sorbents showed a high affinity towards the removal of crude oil, motor oil, and diesel spills. The highly viscous motor spill showed a different pattern of sorption onto fibers than that of crude oil and diesel spills. Upon comparing all the studied electrospun fibers to commercially available polypropylene fibrous sorbents, results show that the sorption efficiency of the electrospun fibers is superior. Most notably, both PS-PE5 and PS-PVC5 fibers showed to be highly more effective than commercially available polypropylene (PP) sorbents towards all types of oil spills.

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Cellulose Nanofibrils Filled Poly(Lactic Acid) Biocomposite Filament for FDM 3D Printing

Molecules ◽

10.3390/molecules25102319 ◽

2020 ◽

Vol 25 (10) ◽

pp. 2319 ◽

Cited By ~ 1

Author(s):

Qianqian Wang ◽

Chencheng Ji ◽

Lushan Sun ◽

Jianzhong Sun ◽

Jun Liu

Keyword(s):

Thermal Stability ◽

3D Printing ◽

Fused Deposition Modeling ◽

Mechanical Performance ◽

Cellulose Nanofibrils ◽

Poly Lactic Acid ◽

Fused Deposition ◽

Wide Range ◽

The Matrix ◽

Direct Digital Manufacturing

As direct digital manufacturing, 3D printing (3DP) technology provides new development directions and opportunities for the high-value utilization of a wide range of biological materials. Cellulose nanofibrils (CNF) and polylactic acid (PLA) biocomposite filaments for fused deposition modeling (FDM) 3DP were developed in this study. Firstly, CNF was isolated by enzymatic hydrolysis combined with high-pressure homogenization. CNF/PLA filaments were then prepared by melt-extrusion of PLA as the matrix and CNF as the filler. Thermal stability, mechanical performance, and water absorption property of biocomposite filaments and 3D-printed objects were analyzed. Findings showed that CNF increased the thermal stability of the PLA/PEG600/CNF composite. Compared to unfilled PLA FDM filaments, the CNF filled PLA biocomposite filament showed an increase of 33% in tensile strength and 19% in elongation at break, suggesting better compatibility for desktop FDM 3DP. This study provided a new potential for the high-value utilization of CNF in 3DP in consumer product applications.

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