Conventional Theory Research Articles

Modified double cantilever beam test method for mode-I energy release rate of elastic adhesive layers

This study proposes a Mode I double cantilever beam (DCB) test method for debonding thick elastic adhesive layers. The approach integrates Bernoulli–Euler beams connected via spring elements akin to Winkler’s foundation. Energy release rate determination considers crack length correlation with elastic deformation in the crack-front region, accounting for both beam rotation and lateral movement. Evaluation of Ti6Al4V samples bonded with FM 309 adhesive revealed higher initial energy release rates with the conventional beam theory and conservative values with the modified beam theory. The proposed method offered improved consistency, and less conservative energy release rate values compared to the modified theory.

Elastohydrodynamic Traction and Film Thickness at High Speeds

A renewed interest in elastohydrodynamic lubrication (EHL) phenomena at high speeds, for which thermal effects strongly influence both traction and film thickness, has grown out of the challenges presented by high-speed geared transmissions in electric vehicles. This study uses a new ball-on-disc set-up employing the well-known ultra-thin-film interferometry technique to simultaneously measure EHL film thickness and traction at entrainment speeds up to 20 m/s and slide-roll ratios up to 100%. The effect of fluid composition is examined for Group I, II and III mineral oils, for two polyalphaolefins in Group IV, and for the traction fluid Santotrac 50. The effect of viscosity in the range 4–180 mPa.s is investigated by varying bulk fluid temperature. At high speeds, both film thickness and traction are considerably lower than predicted by conventional EHL theory. The contact is seen to be fully-flooded for all conditions tested. The widely-used thermal EHL correction of Gupta is shown to overcorrect for the film thickness reduction even at modest SRRs. Finally, the influence of the sliding direction on traction and film thickness is discussed for this set-up, and a thermal model is proposed to explain the observed behaviour.Graphical abstract

Capital structure in Latin America: institutional and macroeconomic effects

PropósitoEste estudio analiza la influencia de los factores institucionales y macroeconómicos, además de los factores a nivel de empresa, en la estructura de capital de las empresas industriales cotizadas latinoamericanas (LATAM). El objetivo es proporcionar evidencia empírica sobre las empresas latinoamericanas desde (1) la perspectiva de las teorías tradicionales trade-off y pecking order, y (2) desde los enfoques que introducen el impacto de los factores institucionales y macroeconómicos en el análisis.Diseño/metodología/enfoqueEl análisis empírico adopta una metodología econométrica, utilizando datos de panel de empresas de Argentina, Brasil, Chile, Colombia, México y Perú, de 2008 a 2018.HallazgosLos resultados indican que, además de las características a nivel de empresa, las características institucionales y macroeconómicas de los países influyen en la estructura de capital de las empresas latinoamericanas.Limitaciones/implicaciones de la investigaciónEl estudio presenta algunas limitaciones, principalmente se centra en empresas cotizadas provenientes de solo seis países de LATAM, debido a la falta de datos. Sería recomendable realizar estudios similares con factores de gobierno corporativo, con empresas familiares y PYMES.Implicaciones prácticasLos resultados pueden servir de referencia para los agentes económicos y profesionales, animándolos a considerar la evolución de las variables institucionales y macroeconómicas a la hora de tomar decisiones. Académicamente, nuestros hallazgos verifican la validez de las teorías convencionales y la relevancia de incorporar variables institucionales externas en el marco de la estructura de capital.Originalidad/valorLa importancia de esta investigación radica en analizar la estructura de capital de empresas en un área geográfica poco explorada, LATAM, incluyendo factores institucionales y macroeconómicos y utilizando la nueva base de datos Orbis.

Unraveling the dynamics of password manager adoption: a deeper dive into critical factors

Purpose The purpose of this study is to comprehensively explore the password manager adoption landscape, delving into crucial factors such as performance, trust, social influence, self-efficacy, risk perception, security concerns, enjoyment and facilitating conditions. It also aims to contribute meaningful insights to security product research and practice. Design/methodology/approach A survey was used to investigate the characteristics of adoption intention for password managers. In total, 156 participants from a public university located in the Midwest region of the USA voluntarily completed the survey. Partial least squares structural equation modeling was used to estimate and validate causal relationships and the proposed research model. Findings Through empirical validation, this study demonstrates that constructs such as social influence, web-specific self-efficacy and perceived risk directly impact trust in password managers. Facilitating conditions and perceived security controls are identified as direct influencers on performance expectancy, deviating from the pathways of the traditional framework. Moreover, the model introduces novel elements crucial for comprehending password manager adoption, including “web-specific self-efficacy” and “perceived security control.” Originality/value The paper systematically reviews existing research on password managers, shedding light on crucial factors significantly influencing adoption behavior. By introducing deviations from conventional frameworks and theories, the study emphasizes the innovative nature of its model. It also formulates strategies to catalyze wider adoption and promote effective design of password managers, increasing user engagement rates.

Surface‐Like Diffusion of Fast Ions in Framework Energy Materials for Li‐ and Na‐Ion Batteries

AbstractThe rate performance, power density, and energy efficiency of electrochemical devices are often limited by ionic conductivities in electrolyte and electrode materials. Framework Prussian blue analogs and dense niobium oxides have been identified as high‐rate electrodes for sodium‐ and lithium‐ion batteries, respectively, yet the origin of the extremely high solid‐state Na+/Li+ transport is not fully understood. Of critical importance is the fact that their ultra‐low activation energy and anomalous pre‐exponent factor cannot be satisfactorily rationalized from conventional theory of solid‐state diffusion in the crystal lattice. Here, assisted by density‐functional‐theory calculations, we argued that the true origin is a unique surface‐like diffusion mechanism of the intercalation ions. In a surface‐like migration event, a mobile ion moves along the channel wall via a low coordination number and low migration barrier experiencing minimal steric hindrance. It is similar to surface diffusion in the conventional picture and contrasts with lattice diffusion from one interstitial/vacancy site to another one with high coordination number, crowded saddle‐point geometry and high migration barrier. We found that the shifting from solid‐state lattice diffusion to surface‐like diffusion is determined by the size difference between the mobile ion and the diffusion channel, and a lowest migration energy barrier can be reached by mediating the channel size. The analogy to gas diffusion in molecular sieves shall be discussed. Additionally, the effects of defects and crystal water in Prussian blue analogs were also discussed for better understanding their rate performances in experimental scenarios.

Surface-Like Diffusion of Fast Ions in Framework Energy Materials for Li- and Na-Ion Batteries.

The rate performance, power density, and energy efficiency of electrochemical devices are often limited by ionic conductivities in electrolyte and electrode materials. Framework Prussian blue analogs and dense niobium oxides have been identified as high-rate electrodes for sodium- and lithium-ion batteries, respectively, yet the origin of the extremely high solid-state Na+/Li+ transport is not fully understood. Of critical importance is the fact that their ultra-low activation energy and anomalous pre-exponent factor cannot be satisfactorily rationalized from conventional theory of solid-state diffusion in the crystal lattice. Here, assisted by density-functional-theory calculations, we argued that the true origin is a unique surface-like diffusion mechanism of the intercalation ions. In a surface-like migration event, a mobile ion moves along the channel wall via a low coordination number and low migration barrier experiencing minimal steric hindrance. It is similar to surface diffusion in the conventional picture and contrasts with lattice diffusion from one interstitial/vacancy site to another one with high coordination number, crowded saddle-point geometry and high migration barrier. We found that the shifting from solid-state lattice diffusion to surface-like diffusion is determined by the size difference between the mobile ion and the diffusion channel, and a lowest migration energy barrier can be reached by mediating the channel size. The analogy to gas diffusion in molecular sieves shall be discussed. Additionally, the effects of defects and crystal water in Prussian blue analogs were also discussed for better understanding their rate performances in experimental scenarios.

Group Theory on Quasisymmetry and Protected Near Degeneracy.

In solid state systems, group representation theory is powerful in characterizing the behavior of quasiparticles, notably the energy degeneracy. While conventional group theory is effective in answering yes-or-no questions related to symmetry breaking, its application to determining the magnitude of energy splitting resulting from symmetry lowering is limited. Here, we propose a theory on quasisymmetry and near degeneracy, thereby expanding the applicability of group theory to address questions regarding large-or-small energy splitting. Defined within the degenerate subspace of an unperturbed Hamiltonian, quasisymmetries form an enlarged symmetry group eliminating the first-order splitting. This framework ensures that the magnitude of splitting arises as a second-order effect of symmetry-lowering perturbations, such as external fields and spin-orbit coupling. We systematically tabulate the quasisymmetry groups within 32 crystallographic point groups and find all the possible unitary quasisymmetry group structures regarding double degeneracy. Applying our theory to the realistic material AgLa, we predict a "quasi-Dirac semimetal" phase characterized by two tiny-gap band anticrossings.

Business education and its paradoxes: Linking business and biodiversity through critical pedagogy curriculum

AbstractThe Kunming‐Montreal Global Biodiversity Framework, launched during the United Nations Biodiversity Conference in December 2022, encourages governments, companies and investors to publish data on their nature‐related risks, dependencies and impacts. These disclosures are intended to drive businesses to recognise, manage and mitigate their reliance on ecosystem goods and services. However, there is a ‘biodiversity blind spot’ that is evident for most organisations and business schools. Business education rarely addresses the root causes of biodiversity loss, such as the unsustainable exploitation of natural resources. As the dominant positioning of Education for Sustainable Development Goals (ESDG) presents biodiversity in anthropocentric instrumental terms inadequate for addressing ecosystem decline, we posit that a more progressive and transformative ecocentric education through ecopedagogy and ecoliteracy is needed. Both approaches include the development of critical thinking about degrowth, the circular economy and conventional stakeholder theory to include non‐human stakeholders. Using comparative case studies from Northumbria University, the University of Hong Kong and Amsterdam University of Applied Sciences, we illustrate how business education can be transformed to address biodiversity loss, providing theoretical guidance and practical recommendations to academic practitioners and future business leaders.

On testing the changes in trends of stock market index and rates

Calibration of interest rate models benefits from grouping data to homogenous classes. Such an approach is typical in many financial time series. Preliminaries have been developed for Cox–Ingersoll–Ross models but this issue remains an open problem for many more realistic interest rate models. Here we develop such a strategy for general class interest rate and classes are based on p-value thresholds for testing for normality and gamma distributions. We use as the benchmark financial series of Chilean stock market index IPSA (Indice de precios selectivo de acciones) and its log-returns. We also study the relationship between interest rate and the market returns represented by the IPSA indicator, with positive correlation in some lags which reveals some interesting facts in the contrary to the conventional theory.

Analysis of the temperature-dependent plastic deformation of single crystals of quinary, quaternary and ternary equiatomic high- and medium-entropy alloys of the Cr-Mn-Fe-Co-Ni system

ABSTRACT Temperature-dependent plastic deformation behaviors of single crystals of quaternary and ternary equiatomic medium-entropy alloys (MEAs) belonging to the Cr-Mn-Fe-Co-Ni system were investigated in compression at temperatures in the range 9 K to 1373 K. Their critical resolved shear stresses (CRSSs) increase with decreasing temperature below room temperature. There is also a dulling of the temperature dependence of CRSS below 77 K due to dislocation inertial effects that we attribute to a decrease in the phonon drag coefficient. These behaviors were compared with those of previously investigated single crystals of the equiatomic Cr-Co-Ni and Cr-Fe-Co-Ni MEAs, and the equiatomic Cr-Mn-Fe-Co-Ni high-entropy alloy (HEA). The temperature dependence of CRSS and the apparent activation volumes below room temperature can be well described by conventional thermal activation theories of face-centered cubic (FCC) alloys. Above 673 K, there is a small increase in CRSS, which we believe is due to elastic interactions between solutes and mobile dislocations, the so-called Portevin-Le Chatelier (PL) effect. The CRSS at 0 K was obtained by extrapolation of fitted CRSS vs. temperature curves and compared with predictions from solid solution strengthening models of HEA and MEAs.

Strategic justice, conventions, and game theory: introduction to a Synthese topical collection

Evolutionary, game-theoretic approaches to justice and the social contract have become increasingly popular in contemporary moral and political philosophy. (Vanderschraaf, Strategic justice: convention and problems of balancing divergent interests, Oxford University Press, 2019) theory of strategic justice represents the most recent contribution to this tradition and, in many ways, can be viewed as a culmination of it. This article discusses some of the central features of Vanderschraaf’s theory and relates them to the contributions in this collection. Some of the contributions directly address Vanderschraaf’s work, while others explore related topics in game theory, bargaining theory, formal philosophy, rationality, equality, justice, and the theory of conventions. This collection aims to bridge a gap between disjoint but closely related literature spanning a wide range of disciplines. The contributions allow readers to systematically engage with the topic of strategic justice, advance dialogue, and more easily follow this rich and expanding field of study.

Promote or inhibit? Examining the influence of youth digital advocacy on digital social entrepreneurship

PurposeThis study aims to investigates the impact of felt obligation for constructive change, constructive voices on social media and social media knowledge competence on digital social entrepreneurship among Indonesian youth.Design/methodology/approachThis study uses Hayes’ process model to assess the stated hypotheses using survey data gathered from 489 Indonesian youth.FindingsYouth with elevated social media knowledge competency might display diminished motivation to participate in digital social entrepreneurship, even when their felt obligation for constructive change remains robust. While promotive voice on social media mediates the relationship between felt obligation and digital social entrepreneurship, the notable absence of a mediating role for prohibitive voice on social media contradicts traditional Positive Youth Development (PYD) theoryResearch limitations/implicationsThis research challenges conventional PYD theory by suggesting that youth with high social media knowledge competence may have reduced motivation for digital social entrepreneurship, despite a strong commitment to positive change. While promotive voice behavior mediates the relationship between felt obligation and digital entrepreneurship, the absence of mediation by prohibitive voice contradicts traditional PYD principles. This study expands the PYD framework, highlighting the challenges related to social media knowledge competence and prohibitive voice in engaging youth advocates for digital social entrepreneurship. It emphasizes the need to adapt PYD theory to address the complexities of the digital age effectively.Practical implicationsThe findings offer valuable insights for students, aspiring young entrepreneurs, educators and policymakers interested in advancing the development of digital social entrepreneurship in a developing nation.Social implicationsThis research offers valuable practical implications for policymakers, educators and society. It suggests the importance of nurturing a sense of responsibility among young individuals, enabling their active involvement in addressing issues like environmental degradation and discrimination. Creating supportive online communities for collaboration and constructive voice behavior on social media can provide judgment-free environments. Additionally, advocating for partnerships between youth and various stakeholders can boost resources, mentorship and funding opportunities, enhancing the prospects for impactful digital social entrepreneurship.Originality/valueThis study contributes to an underexplored area in the field of social entrepreneurship by investigating the intersection of youth, digital advocacy and digital social entrepreneurship. The incorporation of the PYD theory introduces a novel dimension to recent research in this domain

Overview of welding defect detection utilising metal magnetic memory technology

Welded joints frequently endure the composite stress of steel components. The presence of defects within these welded joints can significantly jeopardise the safety and performance of the welded structure. Magnetic memory testing technology has garnered substantial attention due to its ability to evaluate welding defects. However, the conventional zero-point pole theory, which serves as the foundation for defect assessment in practical detection, may lead to defect location and omission errors. In response to this challenge, scholars have conducted extensive research to accurately pinpoint the location and identify the types of defect within welds. This paper systematically reviews the mechanisms of magnetic memory welding defect detection, the factors that influence it, signal characteristic parameters, noise reduction in magnetic memory signals and the application of machine learning for quantitative assessment. By summarising these research advancements, this paper aims to address the current issues and provide guidance for the precise quantitative evaluation of welding defects in the future using metal magnetic memory technology.

Prescribed-time command filtered control for a class uncertain nonlinear systems

This article delves into the intricate challenge of implementing prescribed-time command filtered control in the context of uncertain nonlinear systems. Firstly, a prescribed-time function is defined to lay the groundwork for subsequent controller design. Subsequently, a novel prescribed-time command Filtered controller is proposed for high-order nonlinear systems featuring unknown parameters. This controller guarantees swift error convergence within a predefined time range, with the added capability of periodic error convergence to zero during subsequent controller operations. A pivotal innovation in this study lies in the controller’s design, which remains unaffected by the system’s initial conditions. This unique feature enables the prescribed time to be flexibly set within physical constraints, diverging markedly from conventional finite-time control theory. Theoretical analysis has conclusively shown that the controller achieves full-state tracking error convergence within the specified time frame. The efficacy of the research findings is substantiated through two simulation cases, underscoring a substantial contribution to the refinement and adaptability of nonlinear system control theory.

Analytical insight into local defect resonance using a two-step method

Local defect resonance (LDR) has gained increasing attention in the field of non-destructive testing due to its capacity to selectively amplify vibrations within the defect regions and to enable defect-selective and high-resolution imaging. How-ever, the conventional theory based on vibration method adopted for analyzing the fundamental frequencies of LDR deviates from experimental results when dealing with relatively thick defects. To tackle this deficiency, this study presents a two-step analytical methodology designed to precisely evaluate the local reso-nance effects of thick planar defects. In the first step, the normal-mode expansion method is employed to calculate the phase shift of the reflected elastic wave. In the second step, by using the standing wave's wavelength obtained in the first step, the Rayleigh method is taken into account to calculate LDR frequencies for various defect shapes. The refined theory is subsequently validated through finite element analysis and experimental measurement. The results clearly demonstrate that the LDR frequencies calculated using the refined theory exhibit a better agreement with experimental and simulated data.

NSSF Social Health Insurance Benefit (SHIB) and Health Care Services: Accessibility and Availability in Tanzania

This study is about “Social Health Insurance and accessibility of health care services through National Social Security Fund (NSSF) Health Insurance service in Kinondoni Municipality. The focus of this study was on the ease of accessing health services using the NSSF health insurance, and the beneficiaries’ awareness level since people knew about NHIF and ICHF only. The objective of the study is to examine the accessibility of Social Health Insurance Benefits on health care service to people at Kinondoni Municipality. The study used a qualitative research approach to gather and analyze data from informants. In-depth interview was used to capture information from the key informants; observation was used to supplement and understand information gathered from the perspective group studied. This study used conventional theory to signify that any additional health care that consumers purchased through insurance coverage was not worth the real cost of producing it. The results indicated that Health Insurance users have failed to use it due to its accessibility and ignorance of community members and insufficient funds released by the National Social Security Fund (NSSF) to cover all the services required by their customers. This paper recommends that it is important to maintain the quality of healthcare services that NSSF receives from its customers. Also, NSSF should be accessible and reliable to all its customers.

Modelling laser modified secondary electron yield response of surfaces

Electron clouds hinder the operation of particle accelerators. In the Large Hadron Collider (LHC), the copper beam screens are located within close proximity to the beam path, resulting in beam-induced electron multipacting, which is the main source of electron cloud formation. Conditions for multipacting are encountered when such surfaces have a secondary electron yield (SEY) greater than unity. Roughening the surface through laser processing offers an effective solution for reducing secondary electrons. Laser ablation leaves behind a complex rough, multi-scale geometrical surface with an altered chemical composition. Current models often over-simplify the geometry, do not have sufficient experimental data to derive input parameters, and exclude SEY-reducing mechanisms such as the surface chemistry. Leading to electron-matter interactions which do not resemble that of a real surface. Here, this complex surface is studied on copper used in the LHC, and the influence of microgeometry, inhomogeneous nanostructure and complex surface chemistry on the SEY is investigated. A novel, improved model is proposed that characterises these sophisticated structures, enabling the efficient design of surfaces to reduce SEY. To validate the model, samples were made using a variety of laser parameters. Modelling insights revealed that secondary electron suppression is not only caused by the microgeometry but also the nanostructure and chemical modification play a role. Contrary to the conventional theory, high aspect ratio structures are not necessarily required for effective SEY reduction. Currently, the model is applicable to a variety of surface morphologies and could be employed for other materials.

Pre-contact Indigenous fire stewardship: a research framework and application to a Pacific Northwest temperate rainforest

Fire is a key disturbance process that shapes the structure and function of montane temperate rainforest in the Pacific Northwest (PNW). Recent research is revealing more frequent historical fire activity in the western central Cascades than expected by conventional theory. Indigenous peoples have lived in the PNW for millennia. However, Indigenous people's roles in shaping vegetation mosaics in montane temperate forests of the PNW has been overlooked, despite archaeological evidence of long-term, continuous human use of these landscapes. In this paper, we present a generalizable research framework for overcoming biases often inherent in historical fire research. The framework centers Indigenous perspectives and ethnohistory, leveraging theory in human ecology and archaeology to interpret fire histories. We apply this framework to place-based, empirical evidence of Indigenous land use and dendroecological fire history. Our framework leads us to conclude that the most parsimonious explanation for the occurrence of historical high fire frequency in the western Cascades is Indigenous fire stewardship. Further, our case study makes apparent that scholars can no longer ignore the role of Indigenous people in driving montane forest dynamics in the PNW.

Absolutely Fuzzy Lipschitz p-summing Maps between Fuzzy Pointed Metric Spaces

Motivated by Lipschitz ideals in the conventional (crisp) theory, we are constructing a new Lipschitz ideal in fuzzy theory. We introduce the notion of fuzzy Lipschitz ideals and give some elementary illustrations. The class of absolutely fuzzy Lipschitz -summing maps between arbitrary fuzzy pointed metric spaces is a significant category of fuzzy Lipschitz ideals. It is a logical extension of the concept of absolutely (crisp) Lipschitz p-summing maps between arbitrary pointed metric spaces, as established by Farmer Jeffrey and William Johnson. We establish that the fuzzy Lipschitz norm of the previously specified concept is a fuzzy real number. We demonstrate that a complete fuzzy normed fuzzy operator ideal is the resulting class of fuzzy Lipschitz operators between arbitrary fuzzy pointed metric spaces and complete fuzzy normed spaces. Next, we define a basic characterisation of a Lipschitz p-summing map that is completely fuzzy. By demonstrating a fuzzy variant of the nonlinear Pietsch Domination Theorem, this is accomplished. Lastly, we bring forth a few unsolved problems that we find intriguing.

Partial melting nature of phase-change memory Ge-Sb-Te superlattice uncovered by large-scale machine learning interatomic potential molecular dynamics

[GeTe]m-[Sb2Te3]n superlattice (GST-SL) is a promising material candidate to solve the critical problem of high-power consumption for phase-change memory technology. However, the switching mechanism is still under strong debate during the last decade. A key controversial question is that whether melting in GST-SL is possible. In this work, a large-scale machine learning interatomic potential (MLIP) molecular dynamics (MD) simulation with a one-order-of-magnitude larger atom number than that of conventional density functional theory (DFT) MD captures a unique partial melting behavior in GST-SL, where a sparse-nucleation-and-growth governed melting behavior is triggered by the flipping of atoms into van der Waals (vdW) gaps and forming cation-in-vdW-gap (CiV) defect as starting point, and then is slowly developed via propagating liquid-crystalline interfaces. In great contrast, the traditional melting of rock salt (RS)-GST occurs very fast due to instant homogeneous nucleation from high-density intrinsic vacancies distributed randomly in its cubic lattice. Therefore, the melting regions in GST-SL can be spatially localized in form of partial melting and are readily controlled. Moreover, the atomic distribution after melting in GST-SL is more chemical ordering than that in RS-GST. By the large-scale MLIP-MD, the present study provides a critical atomic insight into GST-SL phase-change behaviors that conventional DFT-MDs hardly achieve. This partial-melting nature in GST-SL helps explain the long-term-confused working principle of GST-SL-based phase-change memory, which will accelerate its application in the big-data era.