Permeable Boundaries Research Articles

On the Stability of Parallel Flow in a Vertical Porous Layer with Annular Cross Section

The linear stability of buoyant parallel flow in a vertical porous layer with an annular cross section is investigated. The vertical cylindrical boundaries are kept at different uniform temperatures, and they are assumed to be impermeable. The emergence of linear instability by convection cells is excluded on the basis of a numerical solution of the linearised governing equations. This result extends to the annular geometry the well-known Gill’s theorem regarding the impossibility of convective instability in a vertical porous plane slab whose boundaries are impermeable and isothermal with different temperatures. The extension of Gill’s theorem to the annular domain is approached numerically by evaluating the growth rate of normal mode perturbations and showing that its sign is negative, which means asymptotic stability of the basic flow. A concurring argument supporting the absence of linear instability arises from the investigation of cases where the impermeability condition at the vertical boundaries is relaxed and a partial permeability is modelled through Robin boundary conditions for the pressure. With partially permeable boundaries, an instability emerges which takes the form of axisymmetric normal modes. Then, as the boundary permeability is reduced towards zero, the critical Rayleigh number becomes infinite.

The Permeable Boundaries Between Theology, Science and Literature

The Permeable Boundaries Between Theology, Science and Literature

The Uncanny Afterlife of Dolls: Reconfiguring Personhood through Object Vivification in Gothic Film

This article proposes an investigation of the ways in which the figure of the non person in/animate body operates in Gothic cinema. It will focus on human-like objects, specifically dolls, in order to investigate the key narrative and aesthetic discourses they facilitate regarding hollowness and life. These entities establish a frightening dynamic between stasis and real or imagined (yet always unwanted) movement. In the process, they become haunting symbols of liminality that articulate particular ideas about identity and personhood, while also stressing the permeable boundaries between self and other. Gothic things undermine the normal subject-object relation and thus continually destabilize the demarcations between life and death or sanity and insanity. In so doing, they furthermore expose an irrational attitude towards existence and consciousness. Using an object-oriented approach that draws on Elaine Freedgood’s and Bill Brown’s thing theory, I explore the disruptive tendencies that in/animate agents foster in such films as Maria Lease’s Dolly Dearest (1991), Otto Preminger’s Bunny Lake is Missing (1965), and Robert Aldrich’s What Ever Happened to Baby Jane? (1962). I will focus on these case studies to examine the manner in which Gothic dolls activate uncanniness to represent subjectivity in crisis. In analyzing the figure of the doll to investigate the uneasy relationship between human beings and human-like things, this paper contributes to the growing interest surrounding the role of objects in Gothic cinema.

Buoyant flow and instability in a vertical cylindrical porous slab with permeable boundaries

The basic stationary buoyant flow in a vertical annular porous passage induced by a boundary temperature difference is investigated. The vertical cylindrical boundaries are considered both isothermal and permeable to external fluid reservoirs. There exists a stationary parallel velocity field with a zero flow rate and pure conduction heat transfer. Its linear stability is analysed with normal mode perturbations of the pressure and temperature fields. The transition to convective instability is caused by the basic horizontal temperature gradient. Hence, its nature differs from that of the usual Rayleigh–Bénard instability. The linear dynamics of the perturbed flow is formulated as an eigenvalue problem, solved numerically. Its solution provides the neutral stability curve at each fixed aspect ratio between the external radius and the internal radius. The critical Rayleigh number triggering the instability is evaluated for different aspect ratios. It is shown that the system becomes more an more unstable as the aspect ratio increases, with the critical Rayleigh number dropping to zero when the aspect ratio tends to infinity.

Power and Strategies in the External Stakeholder Management of Megaprojects: A Circuitry Framework

Infrastructure megaprojects can cause considerable inconvenience to external stakeholders such as project communities, stakeholders in lands and stakeholders in existing services. Managing these external stakeholders is difficult as they interact with the project across permeable boundaries, are unaccountable to the requirements of the project and cannot be governed with contractual instruments or conformance to standards, as is the case with internal stakeholders. Hence the project team must resort to other strategies to manage these stakeholders. There is at present little other than scattered accounts of the use of these strategies in the literature. What is missing is a framework to explain how such strategies work to manage external stakeholders. We use organizational power theories drawn from frameworks stressing both the dimensions and the circuits of power to understand how strategy and power interact in the process of managing external stakeholders. This research uses the case study of a metro rail project in India compiled from 30 semi-structured interviews, 168 news media articles along with their 446 user comments, and 640 social media tweets along with 435 community comments. Using a qualitative research methodology, we highlight relations of persuading, framing and hegemonizing strategies employed for managing the external stakeholders in the project. Covert power-based framing and hegemonizing strategies shape the visible overt power-based persuading strategies employed to manage external stakeholders.

Multidimensional Numerical Analysis of the Thermal Behavior and Pyrolysis Gas Flow Inside an Orthotropic Porous Material

Abstract This article describes a finite-volume fully implicit solver that simulates the transient thermal response and pyrolysis gas transport inside orthotropic charring ablators. Due to surface recession of ablators in the aeroheating environments, an arbitrary Lagrangian–Eulerian (ALE) formulation of the problem is presented. The governing equations (which consist of solid phase continuity, gas phase continuity, unsteady form of Darcy's law as gas momentum, and gas–solid mixture energy) are solved with an unstructured moving grid system. The boundary condition at the ablated surface is characterized by integrating the equilibrium thermochemical tables into the surface energy balance under assumption of a unity Lewis number. The developed computational scheme is verified using both analytical solution and code-to-code comparison. The simulations are performed on both cylindrical and iso-q shaped samples. The results show that the pyrolysis gas movement significantly influences the thermal response of the ablator. As the hot pyrolysis gas travels inside the porous ablator, it carries a great deal of energy, which enhances the solid temperature in the downstream region. Also, blowing the gas into the freestream has reduced the net convective heat flux, resulted in a decrease in the heat penetration area inside the ablator and char depth in the vicinity of permeable boundaries.

Permeable boundaries? Patient perspectives on space and time in general practice waiting rooms.

This paper considers an under-examined space in primary health care - the reception area/waiting room. This space can be challenging to negotiate, particularly for those who experience social marginalisation. We begin by situating the significance of the 'entry into the health care setting' in the patient journey in terms of time as well as space. Through an analysis of interview and focus group data gathered in a New Zealand study, we highlight ways that patients view these spaces as firmly bounded and confronting. In reflecting on the data, we then identify the potential for these spaces to be more permeable. We conclude that this spatio-temporal context need not be one of constraint. Rather, there are ways in which the boundaries of this space can be potentially enabling to those required to pause in the process of enacting patienthood.

Grain detachment and transport clogging during mineral dissolution in carbonate rocks with permeable grain boundaries

This paper explores the effect of permeable grain boundaries on carbonate rock dissolution in order to improve our understanding of grain detachment and migration during reactive flow. To do so we investigated the effects of grain size and enhanced reactivity along grain boundaries on global dissolution kinetics. Variations of permeability and porosity were calculated, and exponential relationships were observed in fractured rocks. Our model employed a reactive transport framework based on the Darcy-Brinkman equation to simulate calcite dissolution in carbonate rocks composed of microporous grains and, included fluid transport along grain boundaries. The model includes fluid flow, solute transport by advection–diffusion, heterogeneous reaction between fluid and minerals and grain detachment with subsequent grain transport in macropores. The migration of solid particles due to dissolution was based on cluster analysis and local movement, and the results show that grain detachment can lead to significant decreases in permeability due to the clogging of transport pathways. Microporous media with smaller grain sizes (fine grains in this study) showed a higher average reaction rate than those with coarser grains. In addition, as the overall rates of geochemical processes are commonly affected by the presence of texture heterogeneities such as fractures, a single fracture (macropore) introduced into a microporous matrix composed of permeable grains and grain boundaries was modelled as a large channel connecting the inlet and outlet of the simulation domain. It was found that macropore clogging by grain detachment temporary decreased permeability, lowering the long-term global reaction rates. We also observed that increases in flow rate can reduce detachment and fracture clogging by reducing local dissolution along grain boundaries.

Team Membership Change “Events”: A Review and Reconceptualization

Driven by views of teams as dynamic systems with permeable boundaries, scholars are increasingly seeking to better understand how team membership changes (i.e., team members joining and/or leaving) shape the functioning and performance of organizational teams. However, empirical studies of team membership change appear to be progressing in three largely independent directions as researchers consider: (a) how newcomers impact and are impacted by the teams they join; (b) how teams adapt to member departures; or (c) how teams function under conditions of high membership fluidity, with little theoretical integration or consensus across these three areas. To accelerate an integrative stream of research on team membership change, we advance a conceptual framework which depicts each team membership change as a discrete team-level “event” which shapes team functioning to the extent to which it is “novel,” “disruptive,” and “critical” for the team. We use this framework to guide our review and synthesis of empirical studies of team membership change published over the past 20 years. Our review reveals numerous factors, across conceptual levels of the organization, that determine the strength (i.e., novelty, disruptiveness, criticality) of a team membership change event and, consequently, its impact on team functioning and performance. In closing, we provide propositions for future research that integrate a multilevel, event-based perspective of team membership change and demonstrate how team membership change events may impact organizational systems over time and across levels of observation.

Thermohaline convective instability in an inclined porous layer with permeable boundaries

This study aims at investigating the onset of thermohaline convective instability in an inclined porous layer of finite width confined between two permeable boundaries. The instability in the flow is driven by the combined effect of temperature and solute concentration gradients acting vertically across the layer, and it depends on the angle of inclination at which that layer is inclined to the horizontal. This work complements previous studies on the double-diffusive convective instability by extensively discussing the effect of the solute concentration gradient for the case when the thermal and solutal buoyancy forces have comparable magnitudes and they act in the same and opposite directions. The investigation is illustrated by the results associated with the cases when the diffusivity ratio is thermally dominant, when the diffusivity ratio is thermally suppressed, and when the two components diffuse with the same intensity. A wide spectrum of the neutral stability curves are presented at different inclinations, which depict the instability in the basic state prevailing in the form of stationary and oscillatory modes. The neutral stability curves are seen to exhibit some exceptional behavior in the case when the thermal buoyancy and the solutal buoyancy act in the opposite directions. It is observed that the instability is always initiated by the non-traveling modes, except in the case when the thermal diffusivity is reasonably higher than the solutal diffusivity and when the two buoyant forces are acting in the opposite directions. The ratio of the two buoyant forces has an exceptionally non-monotonic impact on the instability, if considered in the vertical porous layer.

The design and development of a hybrid off-job crafting intervention to enhance needs satisfaction, well-being and performance: a study protocol for a randomized controlled trial

BackgroundEmployees dealing with job demands such as high workload and permeable work-life boundaries could benefit from bottom-up well-being strategies such as off-job crafting. We have developed a hybrid off-job crafting intervention to promote off-job crafting, a proactive pursuit to adjust one’s off-job time activities to satisfy one’s psychological needs. This hybrid intervention contains both on-site (two trainings) and online elements (smartphone app) to enhance employees’ well-being and performance within different life domains.MethodsThe study is designed as a randomized controlled trial with an intervention group and a waitlist control group. The study population will be Finnish knowledge workers. The intervention program focuses on six psychological needs (detachment, relaxation, autonomy, mastery, meaning, and affiliation) proposed by the DRAMMA model. The intervention will consist of the following components: 1) an on-site off-job crafting training, 2) an individual off-job crafting plan for the four-week intervention period, 3) Everydaily smartphone app usage, and 4) a training session for reflection. The study outcomes are assessed with online questionnaires once at baseline, weekly during the intervention period and twice after the intervention (two-week and six-week follow-up). Moreover, during the second training session, participants will participate in a process evaluation to shed light on the mechanisms that can affect the effectiveness of the intervention.DiscussionWe expect that the intervention will stimulate off-job crafting behaviors, which may in turn increase well-being and performance in both non-work and work domains during and after the intervention (compared to baseline and to the control group). The intervention may provide employees with additional resources to deal with various stressors in life. Furthermore, this off-job crafting intervention could also offer performance benefits for the employers such as increased organizational citizenship behaviors among employees.Trial registrationThe Netherlands Trial Register (NTR): NL8219, December 9, 2019. Registered retrospectively. https://www.trialregister.nl/trial/8219

In Auditory Absentia: Music(ology), Modern Art, and Aesthetic Experience

Inspired by recent interdisciplinary studies of music and the visual arts, this article is broadly based on the permeable boundaries between the two that are characteristic at thefin de siècle. I concentrate on scenes of music-making depicted on two painted canvases : Pierre Puvis de Chavannes’sLe Chant du berger(1891) and Henri Matisse’sLa Musique(1910). The principal aim is to suggest how these illustrations of music and musical performance, as well as critical responses to them, resonate with perspectives from some of the most prominent aesthetic and intellectual concerns of the day. An additional aim is to extend our understanding of live musical engagement, considering what it might mean to obstruct empathetic identification, deny the sensuous properties of sound, and negate aesthetic experience.

Impact of local thermal non-equilibrium on temporal thermo-hydro-mechanical processes in low permeable porous media

The thermo-hydraulic-mechanical (THM) response of low permeable media is of crucial significance in thermal fracturing for production of unconventional shale oil, enhanced geothermal systems, and waste disposal. During such processes, pore pressures and stresses change in a spatiotemporal manner due to hydraulic and thermal loadings. From the viewpoint of the energy balance equation, the available theoretical studies can be classified as local thermal equilibrium (LTE), and local thermal non-equilibrium (LTNE) models. LTE models consider identical temperature for different phase of the porous system. LTNE models allow different temperature variations in solid and fluid phases of a porous medium. Current LTNE studies are weakly-coupled – not incorporating thermo-osmosis. This paper presents novel coupled LTNE thermo-poroelastic solutions in a transversely isotropic saturated porous medium, incorporating thermo- osmosis effect. Solutions are obtained for permeable and impermeable boundaries. Thermo-osmosis is found to have a very different effect in case of LTNE versus LTE, resulting in a fundamentally different THM response. LTNE effect analysis reveals different THM responses under different heat transfer properties at the solid-fluid interface in low permeable strata.

The Progeny of Print: Manuscript Adaptations of John Speed’s Chaucer Engraving

John Speed’s engraved portrait of Chaucer, made for the 1598 edition of the Workes, relies rhetorically upon a manuscript tradition of Chaucerian portraiture to establish its authenticity. During the seventeenth century and onward, Speed’s printed plate exhibited a high degree of mobility, being removed from the editions and reappearing in other Chaucerian books and in later manuscript replicas. This essay tracks the movement of the portrait across the permeable boundaries of print and manuscript, arguing for the role of print culture in its dissemination and as the cause of its eventual reappropriation into hand-drawn and painted forms.

Early diversification and permeable species boundaries in the Mediterranean firs.

Inferring the evolutionary relationships of species and their boundaries is critical in order to understand patterns of diversification and their historical drivers. Despite Abies (Pinaceae) being the second most diverse group of conifers, the evolutionary history of Circum-Mediterranean firs (CMFs) remains under debate. We used restriction site-associated DNA sequencing (RAD-seq) on all proposed CMF taxa to investigate their phylogenetic relationships and taxonomic status. Based on thousands of genome-wide single nucleotide polymorphisms (SNPs), we present here the first formal test of species delimitation, and the first fully resolved, complete species tree for CMFs. We discovered that all previously recognized taxa in the Mediterranean should be treated as independent species, with the exception of Abies tazaotana and Abies marocana. An unexpectedly early pulse of speciation in the Oligocene-Miocene boundary is here documented for the group, pre-dating previous hypotheses by millions of years, revealing a complex evolutionary history encompassing both ancient and recent gene flow between distant lineages. Our phylogenomic results contribute to shed light on conifers' diversification. Our efforts to resolve the CMF phylogenetic relationships help refine their taxonomy and our knowledge of their evolution.

Editorial

This collection of papers has emerged from the Language Education across Borders conference held at the University of Graz, Austria in 2017 (see also Kostoulas, 2019). In the age of translanguaging, multilingualism, multiculturalism, globalization, international migration, transnationalism, and the blending of content and language education, there is an ever greater need in language education to reflect on the interconnections and overlap between languages, disciplines, constructs, and contexts that have traditionally been conceptualized in bounded ways. Instead, professional and personal domains have got increasingly permeable boundaries leading to emergent qualities that require new ways of theorizing, researching and teaching. The idea behind the conference was to promote interdisciplinary exchange and encourage people to challenge the notions of borders of all kinds. The aim was to promote discourse and exchange and re-think the fragmentation and separation imposed by borders – real or imagined. It was hoped that by prompting people to reflect on the kinds of borders that bound their research and practice, we would be challenged to think outside of these borders and find the rich, creative space that can lead to innovation and fresh perspectives on the familiar.

Effect of seepage flow on incipient motion of sand particles in a bed subjected to surface flow

Understanding the interaction of the groundwater seepage flow and sediment transport along permeable boundaries is essential for managing soil beds and bank erosion. A significant bank failure may occur due to sediment transport under the boiling condition. In the present study, an experiment is conducted to investigate the effects of injection or upward seepage on the critical shear stress of a cohesionless soil bed subjected to surface flow. The upward seepage force acting on the soil bed particles may reduce the virtual weight of the particles. In turn, it may also reduce the critical shear stress acting on the particles. A theoretical analysis examines how the upward seepage force acts to modify the critical shear stress for the sediment entrainment due to the increase in the hydraulic gradient of the seepage flow. A force analysis reveals that the ratio of the critical shear stress with seepage to that without seepage is dependent on the ratio of the hydraulic gradient of seepage to its value at the quicksand condition. A test apparatus was built, and the effects of injection on the critical shear stress of cohesionless soil bed particles were measured. An acrylic channel with a rectangular cross section was prepared, and a section of a cohesionless soil bed subjected to an upward seepage flow was installed at the bottom of the channel. The experiment demonstrates that the induced seepage affects the dynamics of the channel flow, even though the magnitude of the seepage flow velocity is significantly smaller than that of the free surface water flow. The test results show that the dimensionless critical shear stress of the cohesionless soil bed particles decreases slightly as the hydraulic gradient of the seepage flow is increased when critical shear stress is determined at the upstream edge of the seepage zone. Furthermore, the dimensionless critical shear stress decreases sharply with the increment of the hydraulic gradient of the seepage flow when critical shear stress is determined in the seepage zone. However, it does not decrease in either case, as was theoretically assumed, even when the hydraulic gradient approaches to the critical hydraulic gradient or the quicksand condition.

Effects of permeability conditions on time-dependent fracture of poroelastic media

The time-dependent fracture of fluid-infiltrated porous materials is known to be affected by fluid diffusion, which is strongly influenced by the initial pore pressure field attributed to loading and the permeability conditions on the boundaries. In this research, the concurrent solid deformation and fluid migration for a traction-free crack of finite length 2a in a poroelastic medium are analyzed. The remote boundaries of the medium are subjected to constant stress or constant stain in the direction perpendicular to crack faces. Without confining the range of the fluid diffusion to the neighborhood of the crack, four types of permeability conditions are considered on the boundaries: (I) the remote boundaries and the crack faces are both impermeable, (II) the remote boundaries are permeable to constant pore pressure, but the crack faces are impermeable, (III) the remote boundaries are impermeable, but the crack faces are permeable to constant pore pressure, and (IV) the remote boundaries and the crack faces are both permeable to constant pore pressure. The singularities of the stress and the pore pressure gradient at small flow times are obtained from finite element simulations and compared to asymptotic predictions. The instantaneous fracture energy J is evaluated using a method that uses the J-integral around the cohesive zone embedded ahead of the crack tip in the simulations. The numerical results of J are validated with the asymptotes predicted from stress intensities at small flow times. When there is a difference between the imposed pore pressure and the initial pore pressure caused by applying loading on the boundaries, the variation in J(t) is affected by short and long ranges of fluid flow, and J(t) reaches its drained limit at a time on the order of W2/c, where W is the dimensional size and c is the consolidation coefficient of porous materials. The drained limit may not be the maximum value of J, especially when the difference on the remote boundaries is positive under strain control. For stress-control cases, whether the maximum J occurs before the drained state depends not only on the difference in pore pressure but also on the location of the permeable boundaries.

Boundary effect on the hydraulic characteristics of gravelly soil slopes in physical model tests

The stability of a residual gravelly soil slope during heavy rainfall is closely related to the seepage field, which is directly affected by the seepage boundaries of the slope. To examine the boundary effect, a novel model flume that can implement permeable and impermeable boundary conditions was designed. With this flume, hydraulic model tests of a gravelly soil slope considering those two seepage boundaries were carried out. The results show that distinct spatial morphology of seepage fields is reflected by the hydraulic characteristics of the slope models with different seepage boundaries. The slope with permeable boundaries generally exhibits a larger average infiltration rate as well as a relatively smaller moving speed of wetting front in the lower part compared to the slope with impermeable boundaries. The residual moisture content in the deep-lower part of the slope with permeable boundaries is 6.6% cm3/cm3 smaller than that of the slope with impermeable boundaries. Nevertheless, the maximum pore water pressure in the middle part of the slope with permeable boundaries is 1.2 kPa higher than that in the corresponding part of the slope with impermeable boundaries. It is noted that regional pore water pressures in the shallow-lower and shallow-middle parts of the slope with impermeable boundaries exhibit large fluctuations with an amplitude over 0.5 kPa. The seepage field in the slope with permeable boundaries presents a multi-dimensional development, which may lead to a local failure of the slope. The results are of great significance in studying the similarity of seepage boundary condition in the field of similarity theory on landslide model tests and provide an experimental basis for establishing rainfall-induced landslide theory.

Boundary-work in management accounting: The case of hybrid professionalism

This paper investigates boundary-work in management accounting in the context of globalization and hybrid professionalism. The paper demonstrates how permeable symbolic boundaries of the management accounting field can be altered by employing expansion boundary-work. Contrasting boundary-work of IMA officials and IMA members in Russia, we show that IMA officials employ primarily monopolization boundary-work while IMA members employ primarily expansion boundary-work. Our findings illustrate how boundary-work is employed to exhibit organizational and occupational professionalism in the symbolic realm. The paper provides additional insight into the discursive domain of the accounting profession by linking boundary-work to globalization, two forms of professionalism, legitimacy, status and professional identity. This suggests that the professionalization process is influenced by the properties of professional boundaries.