Tight Boundaries Research Articles

Topological recursion of the Weil–Petersson volumes of hyperbolic surfaces with tight boundaries

Topological recursion of the Weil–Petersson volumes of hyperbolic surfaces with tight boundaries

'Athletes', 'Talents', and 'Players': Conceptual Distinctions and Considerations for Researchers and Practitioners.

A clearer understanding of, and tighter boundaries between, terms are important for researchers designing studies as well as for other sport stakeholders creating evidence-informed policies. This article considers the terms 'athlete', 'talent', and 'player' from psychological and sociocultural perspectives and in different sporting communities to highlight the importance of terminological clarity in sport research. We present considerations to clarify the use of these terms within different contexts and how the use of specific terms may affect knowledge mobilization in diverse sporting populations. A conceptual discussion is provided to help operationalize development-related terminology and its associated stages, to better reflect contemporary academic thought, and enhance practical interpretations. Importantly, we also call for greater transparency from researchers when presenting findings and encourage practitioners to clearly define key terms when working in sport. Our intention in this paper is to energize readers to consider how we use language in athlete identification and development contexts, to stimulate deeper thought and discourse around the possible implications these terms may have at any point of an individual's development in sport. Greater deliberation, identification, and acknowledgment of the drawbacks accompanying these terms will be needed before more confident assertions can be made on how researchers and practitioners could (or even should) implement certain terminology across youth sport contexts moving forward. This paper adds to a growing literature on the importance of clarity in terminology and acts as an impetus for those working in specific sports to co-design key terms used by researchers, practitioners, and policy makers.

Addressing the elephant in the room: what’s the local in local government studies?

ABSTRACT Within the field of local government studies there has long been a tendency to conceive and engage with ‘the local’ in a normative way – focusing on its alleged inherently ‘good nature’ without interrogating what the local actually is and means. In this reflective provocation, drawing on the case of England, we contend that failure to address this existential question risks pushing local government studies into a cul-de-sac whereby its fails to benefit from the potential of multidisciplinary dialogues, drawing ever tighter boundaries around the field. In response, we shift attention to how we might harness the plurality of the local, suggesting that the real value of the local, both as a concept and practice, lies in its fuzzy and often problematic nature. We argue that embracing, rather than dismissing, this intrinsic character of the local is essential not just to capture its value, but also to open up new avenues in the way we study and conceive it.

Pivot, persist or perish? Knowledge problems and the extraordinarily tight boundary conditions of entrepreneurs as scientists

The characterization of entrepreneurs as scientists (EaS) has become increasingly popular among management scholars because it fits neatly with existing theories of entrepreneurial action grounded in the assumption that entrepreneurs form and test beliefs in an intendedly rational fashion, under conditions of uncertainty, while continually seeking to obtain and process new information. Recent scholarship breathes new life into the EaS paradigm by proposing a framework that builds upon pragmatism in developing a microfoundational perspective concerning causally inferential action and rationality-based heuristics. Yet, the drift towards EaS is not without controversy. Business venturing is rarely analyzable through the lens of natural laws and orderly structures. Moreover, uncertainty is not the only knowledge problem (KP) that entrepreneurs confront. As such, EaS may be ineffective in bringing resolution to these other challenging KPs – ambiguity, complexity, and equivocality – especially when entrepreneurs are entertaining decisions to pivot or persist. In this sense, our work underscores the importance of EaS while also asserting the need for clear boundary conditions.

Reaching Individually Stable Coalition Structures

The formal study of coalition formation in multi-agent systems is typically realized in the framework of hedonic games, which originate from economic theory. The main focus of this branch of research has been on the existence and the computational complexity of deciding the existence of coalition structures that satisfy various stability criteria. The actual process of forming coalitions based on individual behavior has received little attention. In this article, we study the convergence of simple dynamics leading to stable partitions in a variety of established classes of hedonic games, including anonymous, dichotomous, fractional, and hedonic diversity games. The dynamics we consider is based on individual stability: an agent will join another coalition if she is better off and no member of the welcoming coalition is worse off. Our results are threefold. First, we identify conditions for the (fast) convergence of our dynamics. To this end, we develop new techniques based on the simultaneous usage of multiple intertwined potential functions and establish a reduction uncovering a close relationship between anonymous hedonic games and hedonic diversity games. Second, we provide elaborate counterexamples determining tight boundaries for the existence of individually stable partitions. Third, we study the computational complexity of problems related to the coalition formation dynamics. In particular, we settle open problems suggested by Bogomolnaia and Jackson, Brandl et al., and Boehmer and Elkind.

Bijective enumeration of planar bipartite maps with three tight boundaries, or how to slice pairs of pants

We consider planar maps with three boundaries, colloquially called pairs of pants. In the case of bipartite maps with controlled face degrees, a simple expression for their generating function was found by Eynard and proved bijectively by Collet and Fusy. In this paper, we obtain an even simpler formula for \emph{tight} pairs of pants, namely for maps whose boundaries have minimal length in their homotopy class. We follow a bijective approach based on the slice decomposition, which we extend by introducing new fundamental building blocks called bigeodesic triangles and diangles, and by working on the universal cover of the triply punctured sphere. We also discuss the statistics of the lengths of minimal separating loops in (non necessarily tight) pairs of pants and annuli, and their asymptotics in the large volume limit.

3D radiative transfer modeling of structurally complex forest canopies through a lightweight boundary-based description of leaf clusters

Three-dimensional (3D) radiative transfer simulations are critical for studying the radiometric properties of canopies. Efficient and easy-to-use 3D radiative transfer models are required by remote sensing inversion and many validation applications. Extensive efforts have been made to improve the computational efficiency, accuracy, and useability of 3D radiative transfer models. This study focuses on the abstraction of canopies for 3D radiative transfer simulations by proposing a lightweight boundary-based description of leaf clusters (B-cluster) to ease the creation of 3D scenes while keeping the simulation as accurate as possible. B-cluster partitions a tree crown into sub-crown leaf clusters and abstracts each of them into a turbid medium enclosed by a complex and tight boundary, while terrain and branches are described with precise mesh surfaces. The radiative transfer simulation within B-cluster has been developed based on an efficient Monte Carlo path-tracing algorithm and implemented in the LargE-Scale remote sensing data and image Simulation framework (LESS) model by considering the presence of both turbid medium and surface scattering. The performance of the model was assessed by comparing with original LESS version, which describes all landscape elements with mesh surfaces (here called M-surface approach), and with a uniform voxel-based approach (U-voxel) in terms of the multiangle bidirectional reflectance factor (BRF) as well as with pixel-wise images. Results show that B-cluster is highly consistent with M-surface in abstract canopies (mean normalized absolute BRF differences δ¯ < 2%) and in realistic forest stand (δ¯ < 5% at 5-m resolution) with considerably reduced requirements for computational memory. Compared with U-voxel, B-cluster is also more robust and better at describing canopy structures with different levels of detail. B-cluster enables to quickly construct accurate 3D scenes with reduced requirements of computational resources. It is also a unified and scale-adaptive approach that can describe crowns as simple as geometric primitives and as complex as explicitly described meshes. The newly proposed approach has been released in new LESS versions at http://lessrt.org/.

A Supervoxel Segmentation Method With Adaptive Centroid Initialization for Point Clouds

Supervoxels find applications as a pre-processing step in many image processing problems due to their ability to present a regional representation of points by correlating them into a set of clusters. Besides reducing the overall computational time for subsequent algorithms, the desirable properties in supervoxels are adherence to object boundaries and compactness. Existing supervoxel segmentation methods define the size of a supervoxel based on a user inputted resolution value. A fixed resolution results in poor performance in point clouds with non-uniform density. Whereas, other methods, in their quest for better boundary adherence, produce supervoxels with irregular shapes and elongated boundaries. In this article, we propose a new supervoxel segmentation method, based on k-means algorithm, with dynamic cluster seed initialization to ensure uniform distribution of cluster seeds in point clouds with variable densities. We also propose a new cluster seed initialization strategy, based on histogram binning of surface normals, for better boundary adherence. Our algorithm is parameter-free and gives equal importance to the color, spatial location and orientation of the points resulting in compact supervoxels with tight boundaries. We test the efficacy of our algorithm on a publicly available point cloud dataset consisting of 1449 pairs of indoor RGB-D images, i.e., color (RGB) images coupled with depth information (D) mapped per pixel. Results are compared against three state-of-the-art algorithms based on four quality metrics. Results show that our method provides significant improvement over other methods in the undersegmentation error and compactness metrics and, performs equally well in the boundary recall and contour density metrics.

Predictive Machine Learning of Objective Boundaries for Solving COPs

Solving Constraint Optimization Problems (COPs) can be dramatically simplified by boundary estimation, that is providing tight boundaries of cost functions. By feeding a supervised Machine Learning (ML) model with data composed of the known boundaries and extracted features of COPs, it is possible to train the model to estimate the boundaries of a new COP instance. In this paper, we first give an overview of the existing body of knowledge on ML for Constraint Programming (CP), which learns from problem instances. Second, we introduce a boundary estimation framework that is applied as a tool to support a CP solver. Within this framework, different ML models are discussed and evaluated regarding their suitability for boundary estimation, and countermeasures to avoid unfeasible estimations that avoid the solver finding an optimal solution are shown. Third, we present an experimental study with distinct CP solvers on seven COPs. Our results show that near-optimal boundaries can be learned for these COPs with only little overhead. These estimated boundaries reduce the objective domain size by 60-88% and can help the solver find near-optimal solutions early during the search.

“Stone Steppers” and “Place Makers”: Community College Students’ Transfer Aspirations and Perceptions of Time

Background/Context Sociologists of education have studied how community colleges’ institutional authorities and organizational barriers stratify students’ postsecondary aspirations. Notions of how students might diverge in their pursuits are less understood. This study builds on imagined futures and postsecondary aspiration literature to demonstrate how students’ agency and institutional barriers interconnect, creating two different transfer approaches based on patterns in students’ sense of place and time. Research Questions (1) How do community college students who aspire to transfer perceive campus as a place? (2) How do students see their time at community college as part of their plans? Setting Tutoring center, campus events, classrooms, and surrounding areas at a community college in Southern California. Research Design Drawing on combined data from 11 months of participant observation (approximately 185 hours), eight semistructured interviews with key participants, and a novel timeline approach, this study analyzes how students’ mental boundary work and interactions with others reveal distinct interpretations of being a transfer-bound student. Findings/Results In noting patterns in students’ sense of place and time, I found two “lived pathways”: students act as “stone steppers” or “place makers.” Stone steppers had tighter boundaries around what on-campus activities they defined as academic or work and a detailed plan for their future. Place makers were less segmented in their view of academic or work activities and more open-ended in their plan for the future. Conclusions/Recommendations This study offers a contextual and process-focused examination of the pursuit of postsecondary aspirations based on students’ lived experiences and narratives. In focusing on the interplay between students’ agency and community college context, this study provides several key takeaways for community college personnel and other stakeholders to use in serving students and best connecting their goals to their pathways and movement through college.

Minimum Reload Cost Graph Factors

The concept of Reload cost in a graph refers to the cost that occurs while traversing a vertex via two of its incident edges. This cost is uniquely determined by the colors of the two edges. This concept has various applications in transportation networks, communication networks, and energy distribution networks. Various problems using this model are defined and studied in the literature. The problem of finding a spanning tree whose diameter with respect to the reload costs is smallest possible, the problems of finding a path, trail or walk with minimum total reload cost between two given vertices, problems about finding a proper edge coloring of a graph such that the total reload cost is minimized, the problem of finding a spanning tree such that the sum of the reload costs of all paths between all pairs of vertices is minimized, and the problem of finding a set of cycles of minimum reload cost, that cover all the vertices of a graph, are examples of such problems. In this work we focus on the last problem. Noting that a cycle cover of a graph is a 2-factor of it, we generalize the problem to the problem of finding an r-factor of minimum reload cost of an edge colored graph. We prove several NP-hardness results for special cases of the problem. Namely, bounded degree graphs, planar graphs, bounded total cost, and bounded number of distinct costs. For the special case of r = 2, our results imply an improved NP-hardness result. On the positive side, we present a polynomial-time solvable special case which provides a tight boundary between the polynomial and hard cases in terms of r and the maximum degree of the graph. We then investigate the parameterized complexity of the problem, prove W[1]-hardness results and present an FPT-algorithm.

A note on the autocovariance of p-series linear process

In this note, we provide tight boundaries for the autocovariance function of a stochastic linear process with p-series coefficients.

Revisiting a speciation classic: Comparative analyses support sharp but leaky transitions between Bombina toads

AbstractAimThe amount of gene flow between parapatric species can be greatly variable depending on how species boundaries are maintained in respect to numerous genetic and ecological factors that affect the strength of reproductive isolation. We quantified this variability to understand its effect on the genetic integrity of a well‐studied pair of hybridizing amphibians.LocationCentral and Eastern Europe.TaxaThe fire‐ and yellow‐bellied toads Bombina bombina and B. variegata.MethodsWe first complemented the mitochondrial phylogeography of European Bombina by barcoding additional populations and built MaxEnt species distribution models to identify the routes of post‐glacial colonization that led to hybrid zone formation. Second, we targeted the areas of parapatry in Poland and Ukraine to assess nuclear admixture by population genetics (PCA, Bayesian clustering) of allozyme and genomic markers (RAD‐seq). Third, we harvested the rich Bombina literature to thoroughly compare the extent of geographical introgression across 11 transitions altogether, using cline analyses when possible.ResultsWe found sharp (2–11 km wide) but leaky transitions (geographically extensive traces of introgression) in all parapatric areas, either measured from a few allozymes or thousands of species‐diagnostic SNPs, and irrespective of the intraspecific lineages involved or the relative ages since first contact.Main conclusionBombina species are permeable to gene flow despite selection against hybrids that retards but cannot ultimately prevent putatively neutral introgression into the parental gene pools. Although local hybrid swarms face genetic assimilation, the species’ integrities remain intact due to their large geographical ranges and ecological differentiation that enforces tight boundaries regardless of the biogeographical attributes of the contacts. Opposing the great variability of introgression patterns found between cryptic species, these results support that gene flow should not be viewed as a force of despeciation when reproductive isolation involves multiple intrinsic and extrinsic barriers.

Deriving power uncertainty intervals for low voltage grid state estimation using affine arithmetic

Pseudo-measurements are usually applied as substitutes for measurement data to obtain observability even in case of sparse measurement configurations. The quality of pseudo-measurements strongly affects the accuracy of state estimation results. Generating pseudo-measurements is not a straightforward task in particular for customers with highly stochastic behavior. This paper proposes a novel approach to obtain verified boundaries of pseudo-measurements, which are consistent to currently available measurement information. These boundaries allow to verify generated pseudo-measurements, whether they are compliant to current system conditions. Additionally, tight boundaries are suitable to generate pseudo-measurements on-line regardless of the customer’s structure. The proposed algorithm applies Affine Arithmetic - a self-validated numerical model - to the state estimation problem and treats pseudo-measurements as main source of uncertainty. The key properties of the algorithm are rigorous, iterative, linearizing and large-scale. These properties are demonstrated by numerical simulation of two benchmark grid models of different complexity. Computational and implementation issues are addressed in detail.

Accounting research boundaries, multiple centers and academic empathy

Abstract This commentary on the article “On the centrality of peripheral research and the dangers of tight boundary gatekeeping” is a personal reflection developed around four considerations. (1) Boundaries are defined according to the center we position ourselves in, which implies that multiple centers and boundaries are possible. (2) Although tension between multiple centers is typical across disciplines in their endeavor to create disciplinary identity, their existence is related to paradigmatic divides. (3) Problems related to excessive gatekeeping arise to protect the reputation of the dominant center. (4) The complexity of today’s societal and environmental challenges calls for an interdisciplinary approach. My concluding remarks develop the idea that, if bridges cannot be built across paradigmatic divides, tensions can be harnessed productively by nurturing academic empathy. Academic empathy, I argue, becomes key for the way in which we – as individual scholars – face today’s greatest challenges that are, in their nature, interdisciplinary and require us to rethink boundaries.

Periphery and centre in comparative perspective: Opportunities for accounting praxis

• Why the critical in critical accounting matters. • Expanding what we mean by ‘critical’ so we learn from the periphery. • What can critical accounting learn from ‘the culture wars’? • Critical Accounting and interdisciplinary teaching and learning. In their paper On the Centrality of Peripheral Research and the Dangers of Tight Boundary Objects, the authors call for a more ambitious accounting research programme. However, their call whilst is difficult is also perhaps hard to pin down. The article needs to be disseminated and debated, because it crystalizes for accounting research a fundamental moral position in knowledge production within a liberal capitalist society. As such. Different perspectives and indeed voices should be included and a certain egalitarianism sponsored. In a liberal capitalist society this is a good in itself (Rawls, 2009; Appiah, 2017). Surely many would argue this is the role indeed the essence of the University? We readily take up the paper’s invitation and are gratified by the professionalism and commitment of the authors. Accounting scholarship , like all parts of liberal capitalist society, requires constant vigilance and reform to approximate these liberal ideas of voice, inclusion, and equal participation. However, the paper is not merely for a liberal position ought to be. Rather the authors also insist that including voices from the periphery will lead to better scholarship. In other words, they argue that peripheral research possesses an intrinsic characteristic that can alter and improve accounting research. In this reply, we will set aside what makes it hard to resist – its appeal to a level playing field, fairness, inclusion, voice – and try to isolate this stronger claim if not for the superiority of peripheral scholarship, then at least for its salutary effects on central scholarship.

Grain Structure and Electrical Properties of Transparent Indium Oxide Thin Films Prepared by RF Magnetron Sputtering

Transparent conductive films of indium oxide (In2O3) are deposited on a glass substrate by RF magnetron sputtering and their electrical properties are investigated in relation to their microstructure. Sputtering deposition was carried out with variations of normalized substrate temperature (Ts/Tm where Tm is the melting temperature) and argon partial pressure (PAr). At a very low substrate temperature (Ts/Tm &lt; 0.1), the columnar grains with voided grain boundaries are observed in the In2O3 films, which are attributed to the low surface mobility and atomic shadowing effect. With an increase in the substrate temperature, tight grain boundaries are formed between the growing columnar grains. At high temperature (0.3 &lt; Ts/Tm &lt; 0.5), the grain surface is faceted, which is due to the high surface mobility of the sputtered atoms, and development of preferred orientation with grain growth is promoted. The growing morphology is also dependent on the argon partial pressure. At low PAr deposition, an inclined fibrous grain oriented to the target direction and a smooth surface structure is developed. As the PAr increases, a dome-shaped surface structure and columnar grains normal to the substrate are developed due to the scattering effect of the sputtered atoms. The growing morphology with substrate temperature and argon pressure coincides with the Thornton's Structure Zone Model (SZM). The lowest electrical resistivity (2.1×10-2 Ωcm) is observed in the In2O3 films with tight grain boundaries and faceted grains, which corresponds to zone II region of the SZM.

Genetic and substantive soil classifications and their applicability in geobotanical research

The first soil classifications dividing soils according to their individual properties and reflecting the resource value of soils were, in fact, substantive classifications. The appearance of soil science that studies soils as special natural bodies changing in space according to natural laws has led to the emergence of genetic soil classifications. The most detailed multilevel Classification of soils of the USSR (1977) is ecological genetic classification based on the relationship between soils and soil formation conditions, where the type of vegetation cover is the top hierarchy level. With the development of soil science, inconsistencies between the genetic classification and the growing volume of knowledge, difficulties in its formalization, and contradictions with the zonal approach have appeared. A paradigm of substantive classification has emerged based on modern measurable morphological and analytical indicators of soils. It is most fully implemented in the World reference base for soil resources (WRB); a compromise option is the substantive- genetic Soil Classification of Russia (2004). In these classifications, for the first time soils with strong human influence (Antrosols and Technosols) are included at a high classification level. The tasks of substantive classifications are the certainty of soil identification; however, discrete classification cells with tight boundaries do not correspond to the continual nature of soils. When using WRB 2014, geobotanical studies receive a certain “freedom” from soils, at the same time, the rigid framework of the parameters of soil properties makes it possible to more accurately identify soil-depended condition of the vegetation cover.

The Clever Shopper Problem

We investigate a variant of the so-called Internet Shopping problem introduced by Blazewicz et al. (Appl. Math. Comput. Sci. 20, 385–390, 2010), where a customer wants to buy a list of products at the lowest possible total cost from shops which offer discounts when purchases exceed a certain threshold. Although the problem is NP-hard, we provide exact algorithms for several cases, e.g. when each shop sells only two items, and an FPT algorithm for the number of items, or for the number of shops when all prices are equal. We complement each result with hardness proofs in order to draw a tight boundary between tractable and intractable cases. Finally, we give an approximation algorithm and hardness results for the problem of maximising the sum of discounts

A Clustering Algorithm for Block-Cave Production Scheduling

Production scheduling is one of the most important steps in the block-caving design process. Optimum production scheduling could add significant value to a mining project. The goal of long-term mine production scheduling is to determine the mining sequence, which optimizes the company’s strategic objectives while honouring the operational limitations over the mine life. Mathematical programming with exact solution methods is considered a practical tool to model block-caving production scheduling problems; this tool makes it possible to search for the optimum values while considering all of the constraints involved in the operation. This kind of model seeks to account for real-world conditions and must respond to all practical problems which extraction procedures face. Consequently, the number of subjected constraints is considerable and has tighter boundaries, solving the model is not possible or requires a lot of time. It is thus crucial to reduce the size of the problem meaningfully by using techniques which ensure that the absolute solution has less deviation from the original model. This paper presents a clustering algorithm to reduce the size of the large-scale models in order to solve the problem in a reasonable time. The results show a significant reduction in the size of the model and CPU time. Application and comparison of the production schedule based on the draw control system with the clustering technique is presented using 2,487 drawpoints to be extracted over 32 years.