Compressible flow in a plate/plate rheometer: application to the experimental determination of reactive expansion’s models parameters for polyurethane foam

The quality of polyurethane foam’s structure mainly depends on the manufacturing process, during what two concomitant principal exothermic chemical reactions take place: the first one creates CO₂ dissolved into the fluid matrix (initiating micro-bubbles, expansion and coarsening of the foam) and the second one leads to the polymerization. In order to follow the rheological evolution of the PU foam during the process, the evolutions of the rheological properties of the foam during the process have been measured in a plate/plate rheometer with imposed deformation (RMS 800) and imposed stress (Stresstech). An analytical solution of the mechanical balance equation for viscoelastic compressible fluid has been proposed to describe the flow in this plate/plate rheometer with radial expansion. The trace of the elastic modulus G′ and the loss modulus G′′ as a function of time highlights the different steps of the foaming and polymerization process. The temperature dependence of both reactions follows Arrhenius’ laws. The recording of G′ and G′′ allows to identify kinetic parameters of numerical models for describing the expansion of a polymer foam and taking into account both chemical reactions.     

An extension of the noncommutative Bergman’s ring with a large number of noninvertible elements

For a prime number \(p\) , Bergman (Israel J Math 18:257–277, 1974) established that \(\mathrm {End}(\mathbb {Z}_{p} \times \mathbb {Z}_{p^{2}})\) is a semilocal ring with \(p^{5}\) elements that cannot be embedded in matrices over any commutative ring. In an earlier paper Climent et al. (Appl Algebra Eng Commun Comput 22(2):91–108, 2011), the authors presented an efficient implementation of this ring, and introduced a key exchange protocol based on it. This protocol was cryptanalyzed by Kamal and Youssef (Appl Algebra Eng Commun Comput 23(3–4):143–149, 2012) using the invertibility of most elements in this ring. In this paper we introduce an extension of Bergman’s ring, in which only a negligible fraction of elements are invertible, and propose to consider a key exchange protocol over this ring.     

Dispersion in a two-zone packed tube: An extended Taylor’s analysis

Taylor’s classical analysis for scalar dispersion in a single phase fluid flow is rigorously generalized for an instantaneous release of scalar substances into a fully developed flow through a long tube of two zones distinctively packed with porous media. A formulation for the dispersion is presented by cross-sectionally averaging the concentration transport equations and introducing a closure model for the concentration deviation terms produced in the averaging procedure. The velocity distribution of the flow through the tube is derived, with existing solution for a single zone tube flow included as a special case. Corresponding dispersivity is analytically determined, and Taylor’s well-known result for a single phase flow in a single-zone tube is recovered by setting corresponding parameters as unity. The effects of relevant parameters on both velocity profile and Taylor dispersivity are illustrated.     

Radial basis functions–finite differences collocation and a Unified Formulation for bending,vibration and buckling analysis of laminated plates,according to Murakami’s zig-zag theory

In this paper, we propose to use the Murakami’s zig-zag theory for the static and vibration analysis of laminated plates, by local collocation with radial basis functions in a finite differences framework. The equations of motion and the boundary conditions are obtained by the Carrera’s Unified Formulation, and further interpolated by a local collocation with radial basis functions and finite differences. This paper considers the analysis of static deformations, free vibrations and buckling loads on laminated composite plates.     

India’s contribution on antioxidants: a bibliometric analysis, 2001–10

The study examines India’s performance on antioxidants using several quantitative measures such as India’s global publication share, rank, growth rate and citation quality, its publication share in various sub-fields in terms of national share utilising last 10 year’s (2001–10) publications data obtained from the Scopus database. We have also determined Indian share with international collaborative papers at the national level as well as is major international collaborative partners, besides analysing the characteristics of its high productivity institutions, authors and high-cited papers, etc.     

Historical roots of Judit Bar-Ilan’s research: a cited-references analysis using CRExplorer

Scientometrics - Judit Bar-Ilan (JB) was an influential researcher in information science and scientometrics. She published more than 100 papers about different topics. We used the CRExplorer (see...     

Eshelby’s tensors for plane strain and cylindrical inclusions based on a simplified strain gradient elasticity theory

The Eshelby tensor for a plane strain inclusion of arbitrary cross-sectional shape is first presented in a general form, which has 15 independent non-zero components (as opposed to 36 such components for a three-dimensional inclusion of arbitrary shape). It is based on a simplified strain gradient elasticity theory that involves one material length scale parameter. The Eshelby tensor for an infinitely long cylindrical inclusion is then derived using the general form, with its components obtained in explicit (closed-form) expressions for the two regions inside and outside the inclusion for the first time based on a higher-order elasticity theory. This Eshelby tensor is separated into a classical part and a gradient part. The latter depends on the position, the inclusion size, the length scale parameter, and Poisson’s ratio. As a result, the new Eshelby tensor is non-uniform even inside the cylindrical inclusion and captures the size effect. When the strain gradient effect is not considered, the gradient part vanishes and the newly obtained Eshelby tensor reduces to its counterpart based on classical elasticity. The numerical results quantitatively show that the components of the new Eshelby tensor vary with the position, the inclusion size, and the material length scale parameter, unlike their classical elasticity-based counterparts. When the inclusion radius is comparable to the material length scale parameter, it is found that the gradient part is too large to be ignored. In view of the need for homogenization analyses of fiber-reinforced composites, the volume average of the newly derived Eshelby tensor over the cylindrical inclusion is obtained in a closed form. The components of the average Eshelby tensor are observed to depend on the inclusion size: the smaller the inclusion radius, the smaller the components. However, as the inclusion size becomes sufficiently large, these components are seen to approach from below the values of their classical elasticity-based counterparts.     

Bioinspired Multifunctional Cellular Plastics with a Negative Poisson’s Ratio for High Energy Dissipation

Cellular plastics have been widely used in transportation, aerospace, and personal safety applications owing to their excellent mechanical, thermal, and acoustic properties. It is highly desirable to impart them with a complex porous structure and composition distribution to obtain specific functionality for various engineering applications, which is challenging with conventional foaming technologies. Herein, it is demonstrated that this can be achieved through the controlled freezing process of a monomer/water emulsion, followed by cryopolymerization and room temperature thawing. As ice is used as a template, this method is environmentally friendly and capable of producing cellular plastics with various microstructures by harnessing the numerous morphologies of ice crystals. In particular, a cellular plastic with a radially aligned structure shows a negative Poisson’s ratio under compression. The rigid plastic shows a much higher energy dissipation capability compared to other materials with similar negative Poisson’s ratios. Additionally, the simplicity and scalability of this approach provides new possibilities for fabricating high-performance cellular plastics with well-defined porous structures and composition distributions.     

Melnikov’s method for controlled stochastic oscillations of a rocking block with fractional derivative

The problem of controlling a rocking block with fractional dissipation so as to prevent it from leaving a prescribed set of bounded oscillations has a number of interesting applications in many scientific and technological fields. This work develops an analytical framework to describe the influence of control on the behavior of a fractionally dissipative rocking block subject to random acceleration of the ground. Control equations are developed and control strategies leading to optimal suppression of instability are asymptotically described under the assumptions of weak dissipation along with a small energy noise. Under these assumptions, the behavior of the block is interpreted as weakly perturbed rocking oscillations close to a generic periodic solution, and the Melnikov approximations are considered as the necessary conditions of instability. The stochastic Melnikov criterion derived in this paper allows for an approximate calculation of an upper bound to the overturning probability as well as to the representation of an optimal control strategy. The Melnikov criterion for stochastic rocking oscillations in the presence of convenient control strategies are derived explicitly for the first time, using an extension of the Melnikov theory to a model with fractional derivative.     

The Journal’s Integrated Impact Index: a new indicator for journal evaluation

Journal impact factor (JIF) has been used for journal evaluation over a long time, but also accompanied by the continuing controversy. In this study, a new indicator, the Journal’s Integrated Impact Index (JIII) has been proposed for journal evaluation. In the JIII, one journal’s average citations per paper, total citations, and all journals’ average level of average citations per paper and total citations have been used to characterize the integrated impact of journals. Some contrastive analyses were carried out between JIII and JIF. The results show some interesting properties of the new indicator, and also reveal some relevant relationships among JIII, JIF, and other bibliometric indicators.     

Organization-oriented technology opportunities analysis based on predicting patent networks: a case of Alzheimer’s disease

Scientometrics - This study aims to investigate how to test and assess the dichotomy of roles from an organization-oriented perspective for technology opportunity analysis, in context of the...     

Developing a tailored strategy for mobile applications’ adoption across diffusion levels: A panel data analysis

This paper proposes that there should be contextual strategy development of applications’ diffusion based on the stage of mobile applications (apps) adoption already reached in a country. This is because as apps diffusion grows, the demand and supply constraints challenging the adoption of apps will change accordingly. A total of 77 countries are categorized into three clusters, Initial, Fast-Adoption, and Maturity, grouped by their adoption rates and the speeds over four-years from 2014 to 2017. With pooled and fixed-effect panel data models, this paper examines which variables out of 22 independent variables are effective in enhancing apps adoption globally. Further, by interacting two dummy clusters, Initial and Maturity with determinant variables, the study identifies the differential policy effectiveness of each determinant factor on apps adoption. The paper concludes that the three stages of apps diffusion levels have their respective effective strategy choice sets: 11 for Initial stage, 12 for Fast-adoption stage, and 13 for Maturity stage, suggesting that countries should develop their mobile apps inclusiveness strategy tailored to their context of apps adoption.     

Proposing integrated Shannon’s entropy–inverse data envelopment analysis methods for resource allocation problem under a fuzzy environment

In this study, a two-phase methodology for resource allocation problems under a fuzzy environment is proposed. In the first phase, the imprecise Shannon’s entropy method and the acceptability index are suggested, for the first time in the literature, to select input and output variables to be used in the data envelopment analysis (DEA) application. In the second step, an interval inverse DEA model is executed for resource allocation in a short run. In an effort to exemplify the practicality of the proposed fuzzy model, a real case application has been conducted involving 16 cement firms listed in Borsa Istanbul. The results of the case application indicated that the proposed hybrid model is a viable procedure to handle input–output selection and resource allocation problems under fuzzy conditions. The presented methodology can also lend itself to different applications such as multi-criteria decision-making problems.     

Nanocellulose as a natural source for groundbreaking applications in materials science: Today’s state

Nanocelluloses are natural materials with at least one dimension in the nano-scale. They combine important cellulose properties with the features of nanomaterials and open new horizons for materials science and its applications. The field of nanocellulose materials is subdivided into three domains: biotechnologically produced bacterial nanocellulose hydrogels, mechanically delaminated cellulose nanofibers, and hydrolytically extracted cellulose nanocrystals. This review article describes today’s state regarding the production, structural details, physicochemical properties, and innovative applications of these nanocelluloses. Promising technical applications including gels/foams, thickeners/stabilizers as well as reinforcing agents have been proposed and research from last five years indicates new potential for groundbreaking innovations in the areas of cosmetic products, wound dressings, drug carriers, medical implants, tissue engineering, food and composites. The current state of worldwide commercialization and the challenge of reducing nanocellulose production costs are also discussed.     

Polyoxometalate-based nanozyme: Design of a multifunctional enzyme for multi-faceted treatment of Alzheimer’s disease

Proteolytic degradation of amyloid-β (Aβ) aggregates and clearance of Aβ-induced reactive oxygen species (ROS) have received significant attention for the treatment of Alzheimer’s disease (AD). However, it is difficult, and often unfeasible, to directly upregulate or transport intracellular native enzymes. More importantly, penetration of the blood-brain barrier (BBB) has presented a major impediment. Herein, we report on the rational design of a polyoxometalatebased nanozyme with both protease-like activity for depleting Aβ aggregates, and superoxide dismutase (SOD)-like activity for scavenging Aβ-mediated ROS. Furthermore, this nanozyme acts as a metal chelator to remove Cu from Cu-induced Aβ oligomers. More intriguingly, the nanozyme can cross the BBB and exhibits low toxicity. This work provides new insights into the design and synthesis of inorganic nanozymes as multifunctional therapeutic agents in the treatment of AD.

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Young’s modulus of low-pressure cold sprayed composites: an analysis based on a minimum contact area model

A theoretical and mathematical model based on minimum contact area (MCA) is developed to explain the bonding that takes place in the low-pressure gas dynamic spray (LPGDS) process. It is shown that by normalizing this MCA it is possible to compare the relative elastic modulus as a function of porosity. Theoretical predictions of relative elastic modulus are compared against results obtained through acoustic analysis and it is found that the correlation between is dependent on the porosity. For low porosity, the experimental and theoretical results differ substantially, while for higher porosity there seems to be good agreement between the two. To explain this behaviour it is theorized that full adiabatic shear bands (ASB) are created between only some of the particles. The higher porosity causes higher strain in the samples and thus more local deformation of the particles. This, in turn, causes more actual ASB formation. Since the theoretical model assumes full ASB formation, only the higher porosities cause enough strain to have a comparable relative elastic modulus. For the lower porosities, the local strain is less, and some of the bonds will not achieve full ASB formation. For these cases, the relative elastic modulus will be lower than that predicted.     

Multiple regression analysis of a patent’s citation frequency and quantitative characteristics: the case of Japanese patents

Although many studies have been conducted to clarify the factors that affect the citation frequency of “academic papers,” there are few studies where the citation frequency of “patents” has been predicted on the basis of statistical analysis, such as regression analysis. Assuming that a patent based on a variety of technological bases tends to be an important patent that is cited more often, this study examines the influence of the number of cited patents’ classifications and compares it with other factors, such as the numbers of inventors, classifications, pages, and claims. Multiple linear, logistic, and zero-inflated negative binomial regression analyses using these factors are performed. Significant positive correlations between the number of classifications of cited patents and the citation frequency are observed for all the models. Moreover, the multiple regression analyses demonstrate that the number of classifications of cited patents contributes more to the regression than do other factors. This implies that, if confounding between factors is taken into account, it is the diversity of classifications assigned to backward citations that more largely influences the number of forward citations.     

Citation of retracted research: a case-controlled,ten-year follow-up scientometric analysis of Scott S. Reuben’s malpractice

Scientometrics - A major problem in scientific literature is the citation of retracted research. Until now, no long-term follow-up of the course of citations of such articles has been published. In...     

An overview of the inequality in China’s carbon intensity 1997–2016: a Theil index decomposition analysis

Clean Technologies and Environmental Policy - Although China has experienced an overall decline in CO2 emissions intensity from 2009 to 2016, the intensity from one province to another varies...     

Mathematical modeling of sway, roll and yaw motions: order-wise analysis to determine coupled characteristics and numerical simulation for restoring moment’s sensitivity analysis

This paper investigates sway, roll and yaw motions of a floating body with the aim to determine coupled motion characteristics based on the order-wise analysis of hydrodynamic coefficients. To compute the hydrodynamic coefficients and wave force exerted on the floating body, we employ speed-dependent strip theory. The governing equations are solved analytically for linear restoring moment. For nonlinear restoring moment which is expressed as an odd-order polynomial of fifth degree in roll angle, we apply the Runge–Kutta–Gill method to solve the coupled equations. To investigate the effect of initial disturbances on sway, roll, yaw and speed of the body, numerical experiments have been carried out for a Panamax Container ship under the action of a sinusoidal wave of periodicity 11.2 s with varying wave height and speed. For the linear restoring moment, we first derive associated motion equations for various cases based on the relative magnitude of the hydrodynamic coefficients. The order-wise analysis leads to the classification of coupled characteristics exhibiting the nature of coupling. For the nonlinear restoring moment, we notice that the initial disturbance plays an important role in the ship’s stability. The effects of forward speed and variation in wave heights are illustrated through typical numerical experiments.