Permanent Set Research Articles

The Elgar companion to innovation and knowledge creation

This handbook provides a timely and comprehensive assessment of the state of the art of innovation research. Acknowledging the multidisciplinary nature of innovation and the central role played by knowledge and creativity in sustaining and propelling innovation development, the book draws on numerous perspectives to discuss why innovation has become so relevant in today’s economy and to shed light on the mechanisms whereby it develops over time and across space. Despite building on multiple disciplines such as economics, geography, management and sociology, the book provides a unitary and coherent narrative that the reader can easily follow. Although providing an overview of the numerous book chapters would be impossible through this review, there are a few highlights from each section that are worth the reader’s consideration. The first part of the book ‘Innovation as a Concept’ is mostly used by the authors to clarify the meaning of innovation and explain how its understanding has evolved over time. Part II ‘Innovation and Institutions’ offers a critical analysis of the role that institutions can play in support of innovation development, whereas Part III ‘Innovation and Creativity’ explores the interconnection between innovation and creativity and highlights the need to expand our understanding of the innovation’s underlying dynamics. Part IV ‘Innovation in Permanent Spatial Settings’ focuses on the importance of relationships in innovation, whether in the form of network or community linkages and interdependencies.

A balanced evaluation of the evidence for adult neurogenesis in humans: implication for neuropsychiatric disorders.

There is a widespread belief that neurogenesis exists in adult human brain, especially in the dentate gyrus, and it is to be maintained and, if possible, augmented with different stimuli including exercise and certain drugs. Here, we examine the evidence for adult human neurogenesis and note important limitations of the methodologies used to study it. A balanced review of the literature and evaluation of the data indicate that adult neurogenesis in human brain is improbable. In fact, in several high-quality recent studies in adult human brain, unlike in adult brains of other species, neurogenesis was not detectable. These findings suggest that the human brain requires a permanent set of neurons to maintain acquired knowledge for decades, which is essential for complex high cognitive functions unique to humans. Thus, stimulation and/or injection of neural stem cells into human brains may not only disrupt brain homeostatic systems, but also disturb normal neuronal circuits. We propose that the focus of research should be the preservation of brain neurons by prevention of damage, not replacement.

The Environmental Assessment of Urban Agglomerations on the Basis of Sustainable Development Indicators

The article discusses the indicators of sustainable development given from the standpoint of the classical concept of sustainable development. The methods used are analyzed to identify criteria for sustainable development. The indicators of sustainable development have been known and developed for a long time. However, their development did not take into account the regional fix, which would allow creating a permanent set of the most representative indicators for a certain territory. Volgograd and Rostov agglomerations are chosen as objects. A complex analysis of the regional indicators of sustainable development is carried out taking into account physiographic, climatic, sectoral features, the economic potential and ecological well-being of Volgograd and Rostov agglomerations. The work assesses the ecological and economic sustainability of the agglomerations under study, which allows to give the comparative analysis of the territory development predictive models. Today, it is still too early to talk about the effectiveness of achieving criteria for sustainable development in urban agglomerations. The accepted methods cannot be considered effective due to the fact that the efforts of all areas of management are needed. In the forecast, we can talk about a slight increase in the stability of Rostov agglomeration due to capital inflows. Taking into account current trends, Volgograd agglomeration can face a gradual decrease in sustainability requiring an immediate intervention.

Viscoelastic stability of pre-cured resin-composite CAD/CAM structures

ObjectivesTo study the effect of water storage (3 months) on the creep deformation and recovery of CAD/CAM composite materials to determine their viscoelastic stability. Materials and methodsFive CAD/CAM composite blocks, with increasing filler loading, and one polymer-infiltrated ceramic network (PICN) were studied. Six specimens of each material were separated into two groups (n=3) according to their storage conditions (24 h dry storage at 23°C versus 3 months storage in 37°C distilled water). A constant static compressive stress of 20 MPa was applied on each specimen via a loading pin for 2 h followed by unloading and monitoring strain recovery for a further period of 2 h. The maximum creep-strain (%) and permanent set (%) were recorded. Data were analysed via two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests (<0.05) for comparisons between the materials. Homogeneity of variance was calculated via Levene’s statistics. ResultsThe maximum creep strain after 24 h dry ranged from 0.45% to 1.09% and increased after 3-month storage in distilled water to between 0.71% and 1.85%. The permanent set after 24 h dry storage ranged from 0.033% to 0.15% and increased after 3-month water storage to between 0.087% and 0.18%. The maximum creep strain also reduced with increasing filler loading. SignificanceThe PICN material exhibited superior dimensional stability to all of the pre-cured resin composite blocks in both storage conditions with deformation being predominantly elastic rather than viscoelastic. Notwithstanding, two of the resin-matrix composite blocks approached the PICN performance, when dry, but less so after water storage.

Mechanical properties of doubly crosslinked gels

We fabricated the doubly crosslinked gel, with internal stress by stretching the gel during the gelation reaction using tetra-PEG gels, which are formed by the AB type crosslink-coupling of two mutually reactive tetra-arm polyethylene glycol (PEG). In a doubly crosslinked gel, two networks having different reference states coexist with and balance each other, resulting in enhanced Young’s modulus and residual strain. We investigated these properties by tuning the time for the imposition of the stretching of the gels and the stretching ratio. The residual strain increased with increase in the time for the imposition of stretching and the stretching ratio. On the other hand, the Young’s modulus had a maximum value at a certain time for the imposition of the stretching of the gels and increased with increasing stretching ratio. These results were well explained by the balance between the strain energies of the first and second networks under the framework of the classical two-network theory, where the total strain energy is described as a simple sum of the energies of the first and second networks. We fabricated the doubly crosslinked gel by stretching the gel during the gelation using tetra-PEG gels. In this gel, two networks having different reference states coexist with and balance each other, influencing Young’s modulus (E) and permanent set (λs). We tuned the time for the stretching imposition on the gels, which influences the 1st network fraction (g1/g0). λs increased with increasing the 1st network fraction, while E had a maximum value against g1/g0, which were explained by the balance between the strain energies of the first and second networks.

A physically-based damage model for soft elastomeric materials with anisotropic Mullins effect

In this paper, we develop a new physically-based damage model to describe the anisotropic Mullins effect of elastomeric materials. The damage model is based on our previous hyperelastic model (Xiang et al., 2018), which has a strain energy density function composed of the crosslinked part and the entangled part. We describe the damage of the crosslinked network using a network alteration theory. Chains along various directions suffer from different degrees of damage and thus cause the anisotropy. The irreversible degradation on constraints for entanglement leads to the reduction of the entangled modulus with the increasing of historical maximal stretch. This model can well capture the stress-softening, anisotropy and residual deformation (permanent set) with only five parameters that have definite physical meanings. It also predicts the damage behaviors under various states of deformation, for both unfilled and filled elastomers. We use the model to fit the experiment data of VHB 4905, silicon rubber, carbon-black filled styrene butadiene rubber (SBR) and carbon-black filled nature rubber (NR). The damage induced anisotropy, which is validated by directional loading experiments of silicon rubber and carbon-black filled NR, can be characterized. We compare this model with other existing similar ones, and show its competitive advantages in characterizing the comprehensive Mullins effect with concise and explicit mathematical expression and physical meaning.

Antimicrobial wound dressings with high mechanical conformability prepared through thiol-yne click photopolymerization reaction

Radical mediated photochemical thiol-yne click polymerization of thiol-terminated polyurethane prepolymers, with poly(ethylene glycol) soft segment at two different molecular weights, a propargyl terminated urethane crosslinker and silver salt was utilized to prepare versatile wound dressings containing well-dispersed Ag° nanoparticles produced via in situ reduction of Ag+ ions. The dressings with optimized chemical structure showed desirable fluid handling capacity (up to 4.84 g/10 cm2 d−1) to provide moist environment over damaged tissue. They were permeable to oxygen and carbon dioxide, therefore, the processes related to tissue regeneration of wound bed could be continued without problem. Their appropriate tensile strength (up to 3.87 MPa) and suitable conformability (less than 0.1% permanent set) enabled protection of damaged skin tissue from external physical forces during the healing process, even for wounds present at organs with a high degree of freedom. The proper cytocompatibility of the prepared dressings and their ability to support growth and proliferation of fibroblast cells as determined by wound scratch healing assay showed the potential utility of the dressings to motivate wound healing progression by migration of cells to the damaged area. In addition, these dressings with in situ formed silver nanoparticles exhibited promising antimicrobial activity against different bacterial and fungal strains, and consequently could encourage wound healing process by prevention from infection in the wound site.

Health needs of refugees: port of arrival versus permanent camp settings

The world's refugee population has surpassed 21 million, the large majority of which resides in developing countries. Refugees have relatively high rates of healthcare utilization for management of both long-term needs, such as diabetes, and acute conditions, such as scabies. Using interviews of stakeholders in disparate healthcare settings, we aim to elucidate both common themes and areas of difference that should be recognized and addressed as the refugee crisis continues. This qualitative interview study compares and contrasts two settings for healthcare provision for refugees: the permanent setting of Za'atari, a camp in Jordan, versus the transitory arrival location of Lampedusa, Italy. We present data from 12 semi-structured interviews with experts in refugee healthcare that have experience in these two locations. We focus on issues of disease burden and health screening, organizational structures and services, cultural competency, and international response. We compiled recommendations to improve healthcare for refugees include recognizing differing health needs of refugees in Za'atari and Lampedusa, training providers in culturally-competent care, screening for and treating psychiatric disorders, and prioritizing agency coordination, documentation, and advocacy.

High‐molecular‐weight polyisobutylenes (PIBs) and PIB networks from liquid PIBs by thiol‐ene clicking

ABSTRACTWe report the synthesis of high‐molecular‐weight linear polyisobutylenes (PIBs) and PIB networks from low‐molecular‐weight PIB by thiol‐ene click chemistry. Thus, liquid allyl‐telechelic PIB was reacted with small di‐ and tri‐thiols, and the thiolated intermediates chain‐extended by UV‐ or thermally induced free radical initiation to linear and crosslinked products. PIB networks were also prepared by crosslinking SH‐telechelic PIB with a small triallyl compound. Linear products were characterized by 1H NMR spectroscopy and GPC, and networks by FTIR spectroscopy, extractables, swelling, and permanent set. The effect of reaction conditions (nature of thiol chain extender, concentration of photo‐ and thermal initiators, UV radiation time, and reagent concentrations) on chain extension and crosslinking was investigated. Under well‐defined conditions high‐molecular‐weight PIBs and tight PIB networks were prepared. Thiol‐ene click chemistry provides novel thiolated PIB derivatives and is a useful strategy for the convenient preparation of high‐molecular‐weight rubbery PIBs and tight PIB networks from low‐molecular‐weight PIB precursors. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019

Coupled thermal- and deformation-induced degradation in planar rubber membranes under radial loading

Elastomers at elevated temperatures can undergo microstructural changes owing to the scission, re-coiling, and re-crosslinking in their macromolecular network. These result in chemically based stress relaxation and permanent set. In previous work, a constitutive equation was developed for the thermo-mechanical response of such elastomers that generalized the Tobolsky two-network theory and incorporated results from an experimental program. One experimental result was that the scission process appeared to be unaffected by stretch, to within moderate stretches. There are indications that larger deformations affect the scission process. The purpose of the present work is to modify the previously developed constitutive theory to allow for this. The constitutive theory contains material properties, representing the chemical kinetics of scission, re-coiling, and re-crosslinking, that are expressed in terms of activation energies. The premise considered here, motivated by the mechano-chemical discussion in the literature, is that an increasing deformation decreases the activation energy and results in faster chemical stress relaxation. A method for accounting for this is introduced. The resultant constitutive theory is then used in the simulation of the radial planar deformation of a planar annular sheet by tractions at its outer boundary. This particular geometry is chosen for two reasons: (1) its convenience for experimental study; (2) the stretch concentration near the inner circular boundary will cause faster chemically based stress relaxation there, which could be readily observable.

Minor amounts of glycerol improve the properties of polyisobutylene‐based polyurethane and its nanocomposites

ABSTRACTThe synthesis of primary hydroxyl‐telechelic polyisobutylene, HOCH2‐PIB‐CH2OH, often yields product the number average terminal functionality () of which is less than theoretical 2.0, typically = 1.75–1.95. Polyurethane (PU) prepared with such low‐cost imperfect PIB‐diols, unsurprisingly, exhibit poor overall properties. Herein we report that mechanical, rheological, and thermal properties of polyisobutylene‐based polyurethane (PIB‐PU) and PIB‐PU reinforced with organically modified montmorillonite (OmMMT) prepared with PIB‐diol of = 1.85 are significantly enhanced by glycerol. Specifically, we document that calculated minor amounts of glycerol substantially improves tensile strength, ultimate elongation, elastic modulus, toughness, rubbery plateau, flow temperature, creep, permanent set, rate of recovery after loading, and thermal properties of PIB‐PU and OmMMT‐reinforced PIB‐PU prepared with PIB‐diol of = 1.85. The observations are summarized and discussed in terms of chemistry, micromorphology, and viscoelasticity. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 929–935

Elastic and Irreversible Bending of Tree and Shrub Branches Under Cantilever Loads.

Tree and shrub branches subjected to cantilever loads such as intercepted snowfall undergo, in addition to the familiar instantaneous elastic bending, a conspicuous retarded-elastic bending, which is commonly 30–50% of their instantaneous bending and occasionally even more. The resultant bending creep that occurs after loading also often includes a slow, time-dependent irreversible bending. These phenomena occur quite generally among woody plants of different major biomes, taxonomic groups, and structural types. We give some of branch bending viscoelasticity’s basic physical properties such as load dependence and stress relaxation. These properties belong to the secondary walls of branches’ xylem (wood) cells; some properties differ notably from those reported for primary cell walls, a difference for which we propose explanations. A method for separating the overlapping time courses of retarded-elastic and time-dependent irreversible bending shows that multiple retarded-elastic (“Kelvin”) elements of branches span a wide range of retardation times (a retardation spectrum, approximate examples of which we calculate), and that irreversible bending can occur in different cases either only in the first few h after loading, or more extensively through 24 h, or (rarely) for several days. A separate time-independent irreversible bending, permanent set, involving a substantial yield stress, also occurs. In three species of shrubs rapid irreversible bending began only several (up to 24) h after loading, implying an unusual kind of viscoelasticity. Deductions from the dynamics of bending suggest that retarded elasticity can help protect branches against breakage by wind gusts during storms. Irreversible bending probably contributes both to the form that tree and shrub crowns develop over the long term, involving progressive increase in the downward curvature and/or inclination of branches, and also to certain other, more specialized, developmental changes.

The Journey, Not the Destination.

The Journey, Not the Destination.

Pseudo-Elastic Analysis with Permanent Set in Carbon-Filled Rubber

Via cyclic loading and unloading tests of natural/styrene-butadiene rubber (NSBR) blends at room temperature, the effects of the stretching, rate, temperature, and volume fraction of carbon black in the filled rubber on a permanent set (residual strain) were studied. The results showed that increasing the stretching, rate, and volume fraction of carbon black and reducing the temperature yielded greater residual strain. The uniaxial tensile behaviors of composites with the Mullins effect and residual strain were simulated using the ABAQUS software according to the aforementioned data. An Ogden-type constitutive model was derived, and the theory of pseudo-elasticity proposed by Ogden and Roxburgh was used in the model. It was found that the theory of pseudo-elasticity and the Ogden constitutive model are applicable to this composite, and if combined with plastic deformation, the models are more accurate for calculating the residual strain after unloading.

MODULAR PLATFORM TO MODEL PARALLEL INELASTIC MECHANISMS IN RUBBER-LIKE MATERIALS

ABSTRACT Cross-linked rubber-like materials exhibit an elastic behavior with several inelastic features such as the Mullins effect, Payne effect, permanent set, deformation-induced anisotropy, and hysteresis. Although these features are being modeled individually, few attempts have been made toward systematic integration of these models into one model to consider damage accumulation in rubber-like materials. A new platform is presented to couple constitutive models of different inelastic mechanisms into one generalized model that can simultaneously consider them all. The kinematic structure of the proposed approach is based on two concepts: (1) the concept of microsphere and (2) the concept of network decomposition. The polymer matrix is decomposed into a number of parallel networks, in which each network describes one inelastic feature and is represented by one microsphere. Accordingly, the energy of the polymer matrix, $\Psi$, is the summation of the energies of the parallel networks. A network is considered as a three-dimensional (3D) assembly of unidirectional subnetwork elements distributed in all spatial directions represented by one microsphere. Such structural breakdown allows us to simplify different inelastic mechanisms as 3D assemblies of one-dimensional (1D) elements that host simplified 1D inelastic mechanisms. This concept replaces the complex 3D formulations of finite inelasticity based on the multiplicative decomposition of the F by a simple solution that can be further scaled up and integrates other models. The microsphere enables us to derive the stretch and the deformation history for each direction. Modular design of the platform allows models to be replaced anytime. Any ill-performing or expensive model can be later substituted by an improved version or temporarily deactivated. To validate the concept, a platform is proposed that can host models of permanent set, hysteresis, and Mullins effect. The accuracy of the platform is evaluated in comparison with experimental data and with respect to different models.

Design and Evaluation of Solid Set Canopy Delivery System for Spray Application in High-density Apple Orchards

Abstract. Permanent or solid set canopy delivery (SSCD) system with certain types of emitters placed along the tree rows have shown promise in the past for foliar application in tree fruit orchards. However, limited knowledge exists in terms of designing a SSCD system for uniform canopy spray coverage in tree fruit orchards. This study examined the spray coverage in high-density, super spindle apple orchards created by different nozzles and their configuration within a canopy on a SSCD system. Three different types of emitters (sprinkler, full cone, and hollow cone) and two different design configurations were evaluated in the orchard using three consecutive tree fruit rows that were 9 m long. Application pressures were 241, 379, and 517 kPa. Coverage analysis on the upper- and under-side of leaves was determined using water sensitive cards (WSC) on three randomly selected trees (23= cards/tree). The results indicated that the design configuration with two 80° hollow-cone nozzles, installed at three different canopy heights, and spray application pressure of 379 kPa provided greater coverage on upper-side (87%) and on the under-side (50%) of tree leaves. Additional studies would have to be conducted for other fruit crops and training systems to optimize system design for intended spray coverage. Keywords: Application pressure, Emitter, Solid set canopy delivery, Spray nozzle, Spray coverage.

A micro-mechanical approach to model thermal induced aging in elastomers

This paper presents a micro-mechanical approach to describe the effects of thermal induced aging on the constitutive behavior of aged elastomers for long-range timescales. In particular, this model focuses on the effects of thermal induced aging on the quasi-static mechanical response of elastomers and their inelastic responses such as Mullins effect and permanent set over time. The model describes the aging induced damage with respect to experimental studies on the process of chemical aging which suggests high detachment of original covalent bonds and formation of new bonds. Accordingly, in the course of aging, the strain energy of the polymer matrix is divided from two independent sources, (i) a decomposing original matrix cross-linked by a small number of strong original bonds, (ii) a newly formed matrix cross-linked by a high number of weak reformed bonds. Each network has its own damage mechanisms which are induced based on the applied deformation and time. The proposed mechanism satisfies the Clausius–Planck inequality and is thus physically feasible. The model is validated with respect to a comprehensive set of experimental data designed by Johlitz et al. [38]. to capture thermal induced aging effect on constitutive behavior of elastomers. Besides accuracy, the model is relatively simple and easy to fit. It requires ten material parameters, all with clear physical meaning, which can be identified from only one set of experiment.

THE PHENOMENON OF ETIQUETTE SPACE AND ITS STRUCTURE

The article considers the phenomenon of etiquette space and defines its structural elements. Etiquette space consists of communicators, a stable set of etiquette situations, a permanent set of etiquette signs, etiquette norms and communicative values. Special attention is paid to every element of the etiquette space, which has its own specificity and its functional value in the whole system. The form of etiquette communication and its verbal / non-verbal content is determined by the communicators depending on their social status. Frequency of use, the communicative orientation of the etiquette expression and the degree of ritualization allow us to establish different types of etiquette situations. The etiquette situation is always regulated and follow a certain script. The article emphasizes the existence of a set of etiquette signs that is implemented within the script. The communicative values, which are formed on the basis of culture dominantes, create stable unique communication genres. Ignoring a certain value in etiquette interaction is evaluated negatively. The article reveals the expediency of all-round study of etiquette space, which involves a combination of linguo-cognitive, culturological, semiotic and linguistic approaches. The linguo-cognitive aspect of the study allows us to identify the peculiarities of mental structures of communicators and to identify the unique features of the frame-scripts within a specific culture. Cultural-specific communicative values, which communicators are guided by in etiquette interaction, can be defined within the culturological aspect of the research. The analysis of etiquette signs can be done within the semiotic aspect of the study of etiquette space.

Towards understanding the role of peroxide initiators on compatibilization efficiency of thermoplastic elastomers highly filled with reclaimed GTR

Thermoplastic elastomers based on recycled high density polyethylene (rHDPE) and styrene-butadiene-styrene (SBS) block copolymer were highly filled with reclaimed ground tire rubber (RR). The impact of various organic peroxides (dicumyl peroxide (DCP), benzoyl peroxide (BP) and di-tert-butyl peroxide (DB)), applied as free-radical initiators, on the processing, structure and performance properties of rHDPE/SBS/RR blends was investigated. It was found that, regardless of peroxide type, their application resulted in decrease of the sol fraction, which indicated increase of cross-link density. This was confirmed by the reduced flowability of material, expressed by noticeable changes in melt flow index that decreased in the order BP > DB > DCP. The most beneficial changes were observed for application of DCP, which led to 80% increase of tensile strength, 40% reduction of permanent set and 25% increase of hardness. Moreover, thermal stability of analyzed thermoplastic elastomers was significantly improved with onset of thermal decomposition shifted by over 40 °C. Scanning electron microscope images revealed enhancement of interactions at the interphase due to increased cross-link density, which had direct influence on the mechanical properties of thermoplastic elastomers. The results showed that processing and mechanical performance of obtained thermoplastic elastomers can be easily engineered by suitable selection of organic peroxide.

Modelling and optimisation of energy-efficient U-shaped robotic assembly line balancing problems

Within U-shaped assembly lines, the increase of labour costs and subsequent utilisation of robots has led to growing energy consumption, which is the current main expense of auto and electronics industries. However, there are limited researches concerning both energy consumption reduction and productivity improvement on U-shaped robotic assembly lines. This paper first develops a nonlinear multi-objective mixed-integer programming model, reformulates it into a linear form by linearising the multiplication of two binary variables, and then refines the weight of multiple objectives so as to achieve a better approximation of true Pareto frontiers. In addition, Pareto artificial bee colony algorithm (PABC) is extended to tackle this new complex problem. This algorithm stores all the non-dominated solutions into a permanent archive set to keep all the good genes, and selects one solution from this set to overcome the strong local minima. Comparative experiments based on a set of newly generated benchmarks verify the superiority of the proposed PABC over four multi-objective algorithms in terms of generation distance, maximum spread, hypervolume ratio and the ratio of non-dominated solution.