Boundary Tension Research Articles

The fallacy of uti possidetis juris: transboundary fishing in disputed maritime boundaries as a threat to Africa’s peace and security

ABSTRACT Africa’s oceans and seas and their resources are crucial for the economic and food security of Coastal States and Small Island Developing States (SIDS). However, sustaining these contributions is undermined by depleting resources and other security threats at sea. Given the transboundary nature of oceans resources and the threats that pervade them, maritime boundary disputes further complicate the situation, by making maritime security cooperation difficult for African countries, especially against illegal fishing. Our transdisciplinary paper draws evidence from legal, security, and development literature, policy documents, and expert insights to highlight the impact of maritime boundary disputes on maritime cooperation and security. Our argument is threefold: first, the principle of uti possidetis juris has resulted in artificial boundaries, propelling maritime boundary tensions and, arguably, in some cases, inflaming them. Second, delimitation exercises, often the outcome of applying the uti possidetis juris principle, limit opportunities for cooperation in managing shared resources and security. Third, irrespective of boundary disputes, the ambulatory nature of fish forces fishers to encroach into neighbouring waters. This paper concludes that addressing these challenges requires a comprehensive approach to oceans governance, acknowledging the transboundary nature of threats and promoting joint management arrangements as a mechanism for settling boundary disputes.

Physics Informed Gaussian Process for Bolt Tension Estimation

Bolted joints are fundamental components in many engineering applications. Therefore, the need for monitoring their tension over their life span is an essential for securing their integrity. Modelling of the dynamics of a bolt has shown success through Euler-Bernoulli beam theory where a relationship of boundary conditions and tension allows determining the changes in the modal parameters. However, the widespread adoption of this approach has faces challenges, as obtaining high-fidelity data for bolts under all tension phases is often unfeasible in practice, particularly for those in low tension. Nevertheless, merging data and prior physics knowledge can provide practical constraints for bolt tension estimation in areas lacking observational data. This study establishes its foundation by developing a stochastic model for bolt tension estimation through the integration of bolt data-driven and physics-based predictions using Gaussian Process Regression (GPR). The core concept of this approach involves predicting data observations through a stochastic simulation using a physics-based model, particularly in scenarios where observational data is absent. The proposed methodology is validated with experimental data to critically evaluate its performance.

Fractal Characteristics of Overburden Rock Fractures and Their Impact on Ground Fissures in Longwall Coal Mining

Ground fissures are generated during the coal mining process due to overlying strata migration, which provides gas and water seepage channels and usually contributes to coal mining accidents in shallow buried coal seams with larger mining height working faces. Thus, the evolution features of ground fissures in large mining height working faces and shallow buried coal seams were explored by considering field observation data, similar simulation, and numerical simulations. The results show that the weathered rock layer above the thin bedrock inhibits fracture growth caused by coal mining. Overlying strata fracture expansion can be quantitatively divided into three stages based on fractal dimension: the overburden fracture formation stage, the overburden deformation fracture expansion stage, and the overburden fracture stable development stage. The movement deformation region of the ground fissure can be described by three characteristic zones: the boundary tension zone, the central compression zone, and the central dynamic tension and compression zone. Central dynamic fissures usually have 3–5 fissure counts with 2–5 m intervals between each group of fissures; central fissures develop twice from open to closed widths; the time period for two central fissures to reach their with maximum widths is 11–20 days; and border fissures expand rapidly with maximum values in a time period of 5–6 days.

Role of turgor-pressure induced boundary tension in the maintenance of the shoot apical meristem of Arabidopsis thaliana.

In plants, the robust maintenance of tissue structure is crucial to supporting its functionality. The multi-layered shoot apical meristem (SAM) of Arabidopsis, containing stem cells, is an approximately radially symmetric tissue whose shape and structure is maintained throughout the life of the plant. In this paper, a new biologically calibrated pseudo-three-dimensional (P3D) computational model of a longitudinal section of the SAM is developed. It includes anisotropic expansion and division of cells out of the cross-section plane, as well as representation of tension experienced by the SAM epidermis. Results from the experimentally calibrated P3D model provide new insights into maintenance of the structure of the SAM epidermal cell monolayer under tension and quantify dependence of epidermal and subepidermal cell anisotropy on the amount of tension. Moreover, the model simulations revealed that out-of-plane cell growth is important in offsetting cell crowding and regulating mechanical stresses experienced by tunica cells. Predictive model simulations show that tension-determined cell division plane orientation in the apical corpus may be regulating cell and tissue shape distributions needed for maintaining structure of the wild-type SAM. This suggests that cells' responses to local mechanical cues may serve as a mechanism to regulate cell- and tissue-scale patterning.

Phase transitions and droplet shapes above a wetting stripe

We consider fluid adsorption on a planar wall patterned by a single stripe of width L of a wet material imbedded within a partially wet surface. If L were infinite we suppose that the wall would exhibit a first-order wetting transition at temperature Tw, and an associated line of pre-wetting transitions extending off bulk-coexistence. For finite widths L, we a) determine the finite-size scaling shift of the wetting temperature Tw(L), b) derive an equation, analogous to the Kelvin equation for capillary condensation, for the shift of the pre-wetting line but involving boundary tensions and a boundary contact angle and c) highlight the scaling and conformally invariant properties of condensed liquid drops lying above the stripe at bulk coexistence. We point out analogies between these predictions and those for capillary condensation and criticality in a parallel plate geometry and test them against numerical results obtained from a microscopic non-local classical density functional theory.

Independent prescribing in the UK: insights from the Department of Health Allied Health Professions Medicines Project team

BackgroundThe UK medicines legislation was amended ten years ago (2013) to allow podiatrists and physiotherapists independent prescribing rights, the first of the allied health professions to do so. Non-medical prescribing formed one part of a broader policy agenda promoting role flexibility in response to the challenge of an ageing population and the need to maintain effective health provision in the face of a contracting workforce.AimThe aim of this study was to outline the experiences of the Department of Health AHP medicines project board team in working towards independent prescribing for podiatry and physiotherapy, with a particular focus on the challenges encountered.MethodsIn depth, open-ended interviews were conducted with eight of the core members of the project team, drawn from those individuals who served throughout the duration of the project (2010–2013). Included were the former Department of Health Chief and Deputy Chief Allied Health Professions Officers; the Department of Health Engagement and Communications Officer; representatives of the Health and Care Professions Council; the Medicines and Healthcare products Regulatory Agency; the Council of Deans of Health; the Royal College of Podiatry and the Chartered Society of Physiotherapy (The team also included the representative of the Allied Health Professions Federation. However, as that representative is also a researcher in this study, he has recused himself from any role as a participant.). Data were transcribed and subject to a thematic analysis.ResultsA complex picture of the project emerged revealing a range of obstacles and challenges, including inter-professional role boundary tensions and negative prior assumptions about the two professions. Success hinged upon the adoption of a dual strategy involving submission of a robust case of need focused on patient benefit coupled with the careful management of professional expectations. Underpinning theory from the sociology of the professions offers a supportive explanatory framework for understanding the relationships between the various stakeholders involved.ConclusionsUltimately, success depended upon aligning the project aims with healthcare policy through a clear focus on patient benefit. Balancing competing professional and policy demands through a continual emphasis on improved patient care laid the foundations for future projects by other allied health professions.

Interstitial Institutions

Lately, cultural sociologists have been engaged in theorizing the complexity and ambiguities of border-crossing translations from a variety of research strings. This article contributes to this theorizing by developing the concept of interstitial institutions as ongoing sites of translations. Building on the history of gift-giving practices of Danish philanthropic organizations from the enactment of the Danish constitution in 1849 till today, the article broadens and expands on civil sphere theory (CST) in three ways. First, it shows how interstitial institutions are an important site of translation because they work as a lock on the border between the non-civil and civil spheres, and this dual membership inevitably leads to ongoing boundary tensions. Second, the study of interstitial institutions provides insights into how civil repair is molded by cultural-historical contexts and narratives and consequently fertilizes particular ways of mobilizing cultural codes. Third, studying interstitial institutions and their translation practices emphasizes and strengthens CST’s processual ground.

Structural stability of a lightsail for laser-driven interstellar flight

The structural stability of a lightsail under the intense laser flux necessary for interstellar flight is studied analytically and numerically. A sinusoidal perturbation is introduced into a two-dimensional thin-film sail to determine if the sail remains stable or if the perturbations grow in amplitude. A perfectly reflective sail material that gives specular reflection of the laser illumination is assumed in determining the resulting loading on the sail, although other reflection models can be incorporated as well. The quasi-static solution of the critical point between shape stability and instability is found by equating the bending moments induced on the sail due to radiation pressure with the restoring moments caused by the strength of the sail material and the tension applied at the edges of the sail. From this quasi-static solution, analytical expressions for the critical value of elastic modulus and boundary tension magnitude are found as a function of sail properties (e.g., thickness) and the amplitude and wave number of the initial sinusoidal perturbation. These same expressions are also derived from a more formal variational energy (virtual work) approach. A numerical model of the complete lightsail dynamics is developed by discretizing the lightsail into rectangular finite elements. By introducing torsional and rectilinear springs between the elements into the numerical model, a hierarchy of models is produced that can incorporate the effects of bending and applied tension. The numerical models permit the transient dynamics of a perturbed lightsail to be compared to the analytic results of the quasi-static analysis, visualized as stability maps that show the rate of perturbation growth as a function of sail thickness, elastic modulus, and applied tension. The analytic theory is able to correctly predict the stability boundary found in the numerical simulations. The stiffness required to make a thin lightsail stable against uncontrolled perturbation growth appears to be unfeasible for known materials, however, a relatively modest tensioning of the sail (e.g., via an inflatable structure or spinning of the sail) is able to maintain the sail shape under all wavelengths and amplitudes of perturbations.

Estimation Based Adaptive Constraint Control for a Class of Coupled String Systems

Dear editor, In this letter, the boundary tension constraint-based adaptive boundary control problem is investigated for a class of flexible string systems with unknown boundary disturbances and unknown parameters, with the purpose of suppressing transverse and longitudinal vibrations. Firstly, on the basis of the Hamiltonian principle, two partial differential equations for a transverse-longitudinal coupled string with spatiotemporally varying tension are derived. Secondly, the transverse and longitudinal adaptive boundary controllers are designed by constructing Lyapunov functions. A barrier Lyapunov function is adopted to confine the boundary tension within the constraint and disturbance observers are designed to estimate the unknown boundary disturbances. Finally, stability analysis of the closed-loop system is performed. The simulation results further illustrate the effectiveness of the proposed method.

The study of the effect of clay type in the reservoir composition on the oil replacement coefficient and change of physical-chemi- cal properties of water in the treatment by electrical field

The paper considers the impact of direct electrical current and clay type in the reservoir composition on the replacement coefficient of oil with water, on the changing of boundary tension and the hydrogen value of oil replacing water. The formation models were developed from clean quartz sand with separate addition of 10–20 % monmorillonitic or kaolinite type of clay. Alkali produced water was used as an electrolyte, by means of which Girmaki oil was replaced. It was defined that significant impact of electric current field on the parameters of oil replacement with water occurs in the presence of the montmorillonitic clay in the composition of formation model. In the presence of the kaolinite less than 10 % oil was recovered compared to the initial oil saturation. Thermal energy appearing in the impact with electric current has a specific effect on the changing of parameters of coefficient of oil replacement with water. It was revealed that the field of direct electric current contributes to the interrelation between water electrolytes and oxygen compounds of oil, intensifies ion exchange processes between the alkali water replacing the oil and clay particles of the skeleton of porous medium.

Contesting issues between Ethiopia and Sudan over the Gwynn Line: Authorisation and irregularities in the demarcation of the boundary

AbstractAs two old countries in Africa sharing a long stretch of boundary, Ethiopia and Sudan have been acting as strategic partners in maintaining a neighbourhood and regional security complex. Irrespective, the boundary problem has continued for more than a century and is still point of cooperation and dispute between the two countries. This paper examines the roots of the boundary tensions between Ethiopia and Sudan, divergent views between them over the demarcation made by Gwynn in 1903 and 1909, issues of authorisation, and limitations of the boundary line especially from the River Setit in the North to Mount Daglish, Quara. On the Ethiopian side, divergent views emanated from the territories left to the Sudanese side by Gwynn deflecting the line from the east to the west, disregarding terms signed between Menelik II and Harrington in May 1902. Successive regimes in Ethiopia have declined to recognise Gwenn's demarcation, arguing that the demarcation was unilaterally carried out by one side leaving resource‐rich areas to the Sudanese side. On contrary, the Sudanese have contradicting positions and argue for validation of the Gwynn line. Evidence for this study was collected from different state offices; in addition, elders who have been cultivating in the frontier territories for many years were exhaustively interviewed.

Nonlinear truss models for strain‐based seismic evaluation of planar RC walls

AbstractThis paper introduces a new approach for the seismic performance evaluation of planar RC walls. Compared to existing assessment guidelines, such as those in ASCE/SEI 41‐17, where performance limits are described by plastic rotation or lateral drift, the proposed method uses local (strain) quantities, obtained from computational models. The analyses rely on a user‐friendly implementation of the nonlinear truss model for RC structures, which eliminates the need to manually create a line‐element representation of a wall and includes a material law for steel accounting for buckling and rupture of reinforcement. The capability of the models to capture common failure patterns for planar walls is validated for a set of six previously tested wall components which experienced a variety of damage modes (bar rupture, boundary element failure, diagonal compression and tension failures). The analytical models accurately predict the lateral strength, deformation capacity and failure modes observed in the tests. A set of acceptance criteria, based on the analytically obtained concrete and steel strains, is then established for the immediate occupancy, life safety and collapse prevention levels, consistent with different levels and types of damage. An initial calibration of the limit values associated with these criteria is proposed and verified using the analytical results for the six walls considered. The results of the proposed assessment methodology applied to the six walls are compared to those obtained using the nonlinear procedures in ASCE/SEI 41‐17. The results indicate that ASCE/SEI 41‐17 may not accurately describe the deformability of walls exhibiting mixed flexure‐shear inelastic deformations.

Stress analysis of riveted and bolted joints using analytical and experimental approach

Abstract The riveted and bolted joints are more commonly used for joining mild steel body structures for boilers, bridges and automobile industry, etc. These two main joining technologies is investigated and a comparison of mechanical behaviour is documented for joints under loading conditions. Joint efficiency increases as thickness increases. This research also deals with collaborative study using ANSYS software version 17.2. The finite element technique was used in present work study. Joint analysis was conducted through analytical and experimental approaches. IS 2062 were selected for bolted joints and IS 513 D were selected for rivets. By applying appropriate boundary conditions, stress analysis and tension test were conducted for both approaches and is compared with single-lap riveted and bolted joints. For different pitch dimensions of 27 mm, 37 mm and 47 mm for the applied boundary conditions, riveted joints have more endurance than bolted joints.

Boundary viscoelasticity theory at finite deformations and computational implementation using isogeometric analysis

Use of surface elasticity theory has experienced a prolific growth recently due to its utility in understanding the mechanics of nanomaterials and soft solids at small scales. Various extensions of surface elasticity theory have been proposed. The main objective of this contribution is to formulate a finite deformation theory for boundary viscoelasticity in principal stretches by accounting for strain-dependent boundary stresses. We present a model that utilizes a nonlinear evolution law and thus is not restricted to the states that are close to the thermodynamic equilibrium. Boundary contributions include both surface and curve effects wherein boundary elasticity as well as boundary tension are accounted for. The boundary constitutive models are formulated such that fluid-like and solid-like viscoelastic behavior of boundaries are considered. A geometrically exact computational framework using isogeometric analysis inherently suited to account for boundaries is developed. Equipped with the theoretical and computational framework, the influence of boundary viscoelasticity on the material response is illustrated. Non-equilibrium counterpart of surface tension is introduced and its effects are elucidated via examples. Through numerical examples, various applications of the bulk–boundary coupled formulation which require further investigation are highlighted.

Analytic description of grain boundary segregation, tension, and formation energy in the copper–nickel system

In this theoretical study, a recently proposed segregation model is applied to segregation data of an exemplary Σ5 grain boundary (GB), which is investigated using a copper–nickel embedded-atom method potential. Segregation in the semi-grandcanonical ensemble is systematically studied by varying the chemical potential in order to explore the full composition range for temperatures from 500 K to 1000 K. As a major thermodynamic feature, the mentioned segregation model avoids the usage of interface compositions, for which an arbitrary volume must be defined, but rather models the thermodynamically unambiguous solute excess. It was shown that the solute excess and the interface formation energy could be described very accurately over a wide range of temperatures and over the entire composition range based on a composition-dependent, but temperature-independent effective energy of segregation. However, the model was initially derived for systems without lattice mismatch so that interface tensions were neglected. Since the copper–nickel system exhibits a moderate lattice mismatch of roughly 2.7%, the copper–nickel system is chosen in this study to further extend the segregation model by a linear-elastic theory to also account for the interface tensions. Using this extended model, it will be shown that the solute excess, GB tensions, and GB formation energies can be derived from the effective energy of segregation for all temperatures and over the whole composition range. As in principle only one single segregation isotherm is sufficient to determine the effective energy of segregation and derived thermodynamic interface quantities, the application of this model is especially interesting for experimental evaluations.

On the existence of L2-valued thermodynamic entropy solutions for a hyperbolic system with boundary conditions

We prove existence of L2-weak solutions of a quasilinear wave equation with boundary conditions. This describes the isothermal evolution of a one dimensional non-linear elastic material, attached to a fixed point on one side and subject to a force (tension) applied to the other side. The L2-valued solutions appear naturally when studying the hydrodynamic limit from a microscopic dynamics of a chain of anharmonic springs connected to a thermal bath. The proof of the existence is done using a vanishing viscosity approximation with extra Neumann boundary conditions added. In this setting we obtain a uniform a priori estimate in L2, allowing us to use L2 Young measures, together with the classical tools of compensated compactness. We then prove that the viscous solutions converge to weak solutions of the quasilinear wave equation strongly in Lp, for any that satisfy, in a weak sense, the boundary conditions. Furthermore, these solutions satisfy, beside the local Lax entropy condition, the Clausius inequality: the change of the free energy is bounded by the work done by the boundary tension. In this sense they are the correct thermodynamic solutions, and we conjecture their uniqueness.

A009 Rethinking Cardiac Rehabilitation

The nature of Cardiac Rehabilitation (CR) and healthcare have changed dramatically in recent years. Most evidence relating to the change in rehabilitation practices point to growing disruptions in traditional health service systems and structures, ways of working, forms of technologically-mediated care, and prognoses for people recovering from major cardiovascular illness. It is argued that integrated care is key to contemporary healthcare policy, and healthcare providers are moving away from care centered around discipline specialisation towards multi-disciplinary teams (MDT) (Liberati, Gorli, & Scaratti, 2016). Foucauldian discourse analysis was used in this study to interrogate the many competing and contested truths and power relations inherent in everyday CR practice. New approaches to clinical practice, healthcare budgets and societal expectations are changing in the way cardiac disease, patients and health professionals now view the role of CR. 1.The growth of interdependent practice systems raises concerns of power, boundary tensions and control amongst health professionals. Such changes pose significant challenges for cardiac physiotherapists practicing within a traditional healthcare paradigm.2.Furthermore, CR is a comprehensive programme that was traditionally colonised by physiotherapists. However, physiotherapists' monopoly over the care of patients in CR has been challenged by professions such as the clinical exercise physiologists with overlapping skills and roles and physiotherapists are under threat of losing it. Boundary tensions have been under-theorised and this study uses ruptures and key events to understand the boundary tensions within CR.

Analytic Description of Grain Boundary Segregation, Tension, and Formation Energy in the Copper-Nickel System

Analytic Description of Grain Boundary Segregation, Tension, and Formation Energy in the Copper-Nickel System

Ultrathin Tunable Lens Based on Boundary Tension Effect.

Solid and liquid lenses are commonly used in optical design. Such lenses have suitable thicknesses due to their working principle and processing mode. Thus, zoom optical systems comprising solid and liquid lenses are extremely large. This work presents a new ultrathin tunable lens (UTL) comprising two liquid film lenses (LFLs) obtained through aspheric deformation and produced from the surface of a micro-liquid under gravity and boundary tension. The UTL can flexibly change focal lengths between positive and negative lenses when the device thickness is merely 2.15 mm. The proposed lens has the advantages of small volume, light weight, simple fabrication, and independence from external force during zooming. This research makes up for the drawback that traditional solid and liquid lenses cannot further reduce their thicknesses. The proposed UTL provides a new lens form and fabrication method, and can be used to replace solid and liquid lenses for designing miniature zoom optical systems.

Minimization of Cable-Net Reflector Shape Error by Machine Learning

During assembly of a cable-net reflector, surface adjustments must be made to meet the stick accuracy requirement of a space mission by changing the lengths of adjustable cables. It is desirable to find the optimum adjustment amount based on the current state of the cable-net reflector. However, all data needed to establish an accurate simulation model for the cable-net reflector cannot be measured. Therefore, the cable-net reflector is treated as a black box, and a machine learning algorithm (support vector machine) is used to develop a prediction model to establish the relationship between cable length adjustments and surface accuracy. The -fold cross-validation method is used to estimate the generalization error. The simulated annealing and grid search are combined to get the optimum hyperparameters for the prediction model. Next, a surface adjustment method is developed to calculate the optimal cable lengths. A tension truss reflector example is used to demonstrate the support vector machine prediction model and the adjustment method. The machine learning algorithm identified the relationships between cable lengths and surface accuracy. Both surface accuracy and tension uniformity can be improved by adjusting the boundary cables and tension ties with this method using only information from the front-side nodes.