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The vulnerability of the Amazon has widely increased with the COVID-19 global pandemic and with the dismantlement of environmental protection policies in Brazil during the Bolsonaro administration. By contrast, local initiatives focusing on sustainable production, conservation, enhancing local people’s quality of life, and supporting a more inclusive economy have emerged throughout the region and are building resilience in face of these disruptions. They represent seeds for transformation towards more sustainable trajectories from the ground up. In this context, women play a significant role, but their actions and voices are poorly understood, studied, or even considered. In this article, we use a novel approach to engage and highlight women’s experiences by connecting decolonial and process-relational perspectives. Decolonial and process-relational thinking are closely linked in many ways, including in that they embrace difference as a mode of experiencing social-ecological relations. One particular aspect of this link is the shared focus on liminal thinking or thinking from the borders, what we call ‘betweenness’. In our decolonial praxis, we highlight women’s perspectives on their particular and diverse ways of life in the Amazon as they confront diverse pressures. To this end, we collaborated with 39 women from Santarém and neighboring towns in western Pará through participant observation, semi-structured interviews and facilitated dialogues. We discuss their perspectives on regional transformation, particularly the expansion of large-scale agribusiness around rural communities, and their understanding and responses to these changes. We reflect on the mutual learning experience resulting from the transdisciplinary engagement between researchers and collaborators.

Köszegi and Rabin (2006, 2007) formulate loss-aversion models called Preferred Personal Equilibrium (PPE) and Choice-acclimating Personal Equilibrium (CPE) so successfully that many papers have been applied their models to a variety of economic fields in this decade. In this paper, without assuming any specific functional form, I show that these two loss-aversion models satisfy strong mixture aversion in the sense that a non-degenerate lottery is strictly preferred to any mixture between the lottery and its certainty equivalent. This property distinguishes these loss-aversion models from many other standard models such as the expected utility theory and disappointment aversion so that this result allows experimental economists to test a class of these models in a simple setting.

The rapid growth of the digital economy has driven economic development, but the massive demand for elec-tricity from digital reforms, coupled with China's coal-based power generation, has created a significant CO2 emission problem. Previous studies have assessed digital economy sectors with an incomplete scope and a lack of carbon emissions assessment at the intermediary-side. To fill these gaps, this study assessed CO2 emissions using input-output modeling of the core industry sector of the digital economy and the industrial digitalization sector at the production, intermediary, and demand sides, and identified key CO2 transmission centers. The results show the following: (1) Digital economy sectors had a high betweenness and were important CO2 transmission centers in the economic system, transmitting more than 4.08 billion tonnes of betweenness-based CO2 emissions; (2) specifically, the industrial digitalization sector transmitted the most CO2 in the economic system, and the digital product manufacturing sector was the core industry sector with the highest betweenness and a strong trans-mission effect on the CO2 emissions in the supply chain; (3) digital economy sectors had large CO2 emissions on the production, intermediary, and demand sides, and transmitted CO2 more through the demand-side and key transmission centers. These results suggest that digital economy sectors can decarbonize and reduce CO2 emissions by (1) improving material use efficiency in the digital product manufacturing sector, (2) reducing the use of carbon-intensive energy and materials in the digital economy sectors, and (3) establishing CO2 emission disclosure rules, incentives, and penalties.

Köszegi and Rabin (2006, 2007) formulate loss-aversion models called Preferred Personal Equilibrium (PPE) and Choice-acclimating Personal Equilibrium (CPE) so successfully that many papers have been applied their models to a variety of economic fields in this decade. In this paper, without assuming any specific functional form, I show that these two loss-aversion models satisfy strong mixture aversion in the sense that a non-degenerate lottery is strictly preferred to any mixture between the lottery and its certainty equivalent. This property distinguishes these loss-aversion models from many other standard models such as the expected utility theory and disappointment aversion so that this result allows experimental economists to test a class of these models in a simple setting.

The vulnerability of the Amazon has widely increased with the COVID-19 global pandemic and with the dismantlement of environmental protection policies in Brazil during the Bolsonaro administration. By contrast, local initiatives focusing on sustainable production, conservation, enhancing local people’s quality of life, and supporting a more inclusive economy have emerged throughout the region and are building resilience in face of these disruptions. They represent seeds for transformation towards more sustainable trajectories from the ground up. In this context, women play a significant role, but their actions and voices are poorly understood, studied, or even considered. In this article, we use a novel approach to engage and highlight women’s experiences by connecting decolonial and process-relational perspectives. Decolonial and process-relational thinking are closely linked in many ways, including in that they embrace difference as a mode of experiencing social-ecological relations. One particular aspect of this link is the shared focus on liminal thinking or thinking from the borders, what we call ‘betweenness’. In our decolonial praxis, we highlight women’s perspectives on their particular and diverse ways of life in the Amazon as they confront diverse pressures. To this end, we collaborated with 39 women from Santarém and neighboring towns in western Pará through participant observation, semi-structured interviews and facilitated dialogues. We discuss their perspectives on regional transformation, particularly the expansion of large-scale agribusiness around rural communities, and their understanding and responses to these changes. We reflect on the mutual learning experience resulting from the transdisciplinary engagement between researchers and collaborators.

Identifying influential nodes in a network is arguably one of the most important tasks in graph mining and network analysis. A large variety of centrality measures, all aiming at correctly quantifying a node’s importance in the network, have been formulated in the literature. One of the most cited ones is the betweenness centrality, formally introduced by Freeman (Sociometry, 1977). On the other hand, researchers have recently been very interested in capturing the dynamic nature of real-world networks by studying temporal graphs, rather than static ones. Clearly, centrality measures, including the betweenness centrality, have also been extended to temporal graphs. Buß et al. (KDD, 2020) gave algorithms to compute various notions of temporal betweenness centrality, including the perhaps most natural one - shortest temporal betweenness. Their algorithm computes centrality values of all nodes in time O(n³ T²), where n is the size of the network and T is the total number of time steps. For real-world networks, which easily contain tens of thousands of nodes, this complexity becomes prohibitive. Thus, it is reasonable to consider proxies for shortest temporal betweenness rankings that are more efficiently computed, and, therefore, allow for measuring the relative importance of nodes in very large temporal graphs. In this paper, we compare several such proxies on a diverse set of real-world networks. These proxies can be divided into global and local proxies. The considered global proxies include the exact algorithm for static betweenness (computed on the underlying graph), prefix foremost temporal betweenness of Buß et al., which is more efficiently computable than shortest temporal betweenness, and the recently introduced approximation approach of Santoro and Sarpe (WWW, 2022). As all of these global proxies are still expensive to compute on very large networks, we also turn to more efficiently computable local proxies. Here, we consider temporal versions of the ego-bet

Recent evidence underscores the importance of greenspace exposure in promoting physical activity, and in having a positive impact on mental health and cognitive development. Accessibility has been identified to be the primary motivating factor when it comes to encouraging greenspace use and, correspondingly, exposure. Existing quantitative approaches to measuring greenspace accessibility predominantly focus on the areas surrounding home locations, often disregarding access from other settings such as schools or workplaces, exposures while on the move, and mobility differences among different population age groups. This article introduces a novel method to measure greenspace accessibility that considers access from different activity settings (i.e., homes, schools, and the commutes between them) for children and adolescents, while accounting for the dependency of human access on the road network. We use Amsterdam, Rotterdam, and The Hague in the Netherlands as case studies to illustrate the utility of our method. Compared to conventional measures of greenspace accessibility, we show that accounting for school and commuting settings, in addition to residences, captures previously untapped accessibility aspects for both children and adolescents. Our approach can be replicated in other cities worldwide, with the aspiration to provide planners and public health policy-makers with a methodological tool that can help in evaluating access and use of greenspaces when designing health-promoting interventions., Human-Centred Artificial Intelligence, Internet of Things

[EN] In light of the ongoing global change, a better understanding of global wildfire activity is the key to anticipate future impacts and minimize, as much as possible, their negative consequences on natural ecosystems and human economy, in order to adequately guide management practices, preparedness and mitigation policies at the different stages of the decision-making process. This master's thesis presents a global-scale analysis of the inter-annual synchronicity of wildfires using two types of probabilistic networks, able to capture the underlying structures in the data from two different approaches: correlation-based and bayesian networks. By studying their properties through centrality measures and community detection for the complex network, and inference from the Bayesian network, we seek to gain a better understanding of the interrelationships between fire activity in different regions of the planet, highlighting the most important teleconnection patterns, helping to develop and test plausible hypothesis about the underlying mechanisms supporting these relationships., [ES] En vista del actual cambio global, una mejor comprensión del fenómeno de los incendios puede resultar clave para anticipar futuros impactos y minimizar, en la medida de lo posible, las consecuencias negativas sobre los sistemas naturales y la economía humana, orientando adecuadamente las políticas de gestión, preparación y mitigación a diferentes niveles del proceso de toma de decisiones. En este trabajo se presenta un análisis a escala global de la sincronicidad anual del fenómeno de los incendios, a través de la construcción de dos tipos de redes complejas que reflejan las estructuras subyacentes en los datos desde enfoques distintos: redes de correlación y redes bayesianas. Estudiando sus propiedades a través de medidas de centralidad y detección de comunidades para la red compleja y de inferencia para la red bayesiana se logra una mejor comprensión de la interrelacion entre la actividad de los incendios en diferentes regiones del planeta, destacando aquellos patrones de teleconexión más relevantes que pueden dar lugar a análisis posteriores más detallados sobre la causalidad de dichas relaciones.

Cognitive grounding of formal models of qualitative spatial relations is important to bridge between spatial data and human perceptions of spatial arrangements. Here, we report on an experimental verification of the cognitive alignment of the recently proposed Ray Intersection Model (RIM) capturing qualitative relationships between three spatial objects, and human perceptions of spatial arrangements through a grouping task. Further, we explore arrangements with an object positioned "between" two other objects. We show that RIM has sufficient expressive power and aligns well with human perceptions of ternary spatial relationships.

Analysis of large dataset of soccer can be extremely difficult if it is not represented graphically. This paper proposes SoccerMetrics, an interactive, open source data visualization system for predicting the individual and team performance. The effectiveness of SoccerMetrics is demonstrated by the available dataset and its visualization. © 2021 IEEE.

Analysis of large dataset of soccer can be extremely difficult if it is not represented graphically. This paper proposes SoccerMetrics, an interactive, open source data visualization system for predicting the individual and team performance. The effectiveness of SoccerMetrics is demonstrated by the available dataset and its visualization. © 2021 IEEE.

Analysis of large dataset of soccer can be extremely difficult if it is not represented graphically. This paper proposes SoccerMetrics, an interactive, open source data visualization system for predicting the individual and team performance. The effectiveness of SoccerMetrics is demonstrated by the available dataset and its visualization. © 2021 IEEE.

Betweenness is a project questioning the relation between us and what we surround us with. To reveal our assumptions around artifacts and by doing so create an conversation between us viewers/ users and the objects themselves. Who owns the dialogue: the object or the viewer? Taking a deeper dive into the symbols and languages of objects, the quiet voices they posses and the functions surfaces, the visualization circle around words such as visual function, ornamentation, material displacement and attraction. By trying to convey the objects “inner thoughts” and creating a dialogue it pushes our ideas of what is desirable, what is strange, what is useful or even beautiful. The trick is in the contrast between what we see and what we know, bordering into imaginary, creating voices for ambiguous objects.

The pursuit-evasion game with two persons is considered. Both players are moving in a metric space, have equal maximum speeds and complete information about the location of each other. We study the sufficient conditions for a capture (with a positive capture radius). We assume that Lion wins if he manages the capture independently of the initial positions of the players and the evader’s strategy. We prove that the discrete-time simple pursuit strategy is a Lion’s winning strategy in a compact geodesic space satisfying the betweenness property. In particular, it means that Lion wins in compact CAT(0)-spaces, Ptolemy spaces, Buseman convex spaces, or any geodesic space with convex metric. We also do not need to use such properties as finite dimension, smoothness, boundary regularity, or contractibility of the loops. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

Betweenness is a project questioning the relation between us and what we surround us with. To reveal our assumptions around artifacts and by doing so create an conversation between us viewers/ users and the objects themselves. Who owns the dialogue: the object or the viewer? Taking a deeper dive into the symbols and languages of objects, the quiet voices they posses and the functions surfaces, the visualization circle around words such as visual function, ornamentation, material displacement and attraction. By trying to convey the objects “inner thoughts” and creating a dialogue it pushes our ideas of what is desirable, what is strange, what is useful or even beautiful. The trick is in the contrast between what we see and what we know, bordering into imaginary, creating voices for ambiguous objects.

El 54% de la población mundial vive ya en torno a núcleos de población que llamamos ciudades, por lo que su estudio nos enseña la forma en que piensa y se desarrolla el propio ser humano. Un análisis de las relaciones espaciales que se producen en entornos urbanos reales requieren un procesamiento de dichas relaciones en paralelo. Con el fin de representar y analizar estas relaciones espaciales complejas, los especialistas en urbanismo han empezado a utilizar modelos basados en redes complejas. Las redes emergen como un nuevo modelo más acorde con el problema de la complejidad organizada que es una ciudad. Otro aspecto esencial unido a las ciudades es que se han convertido en unas entidades productoras y creadoras de datos, tanto físicos como virtuales. Un estudio serio de la ciudad significa, por tanto, un estudio de los datos que en ella se generan o se encuentran. Dentro de la moderna teoría de redes, un concepto fundamental y muy estudiado en la bibliografía en las últimas décadas es el de la centralidad de la red. La centralidad consiste en determinar cuantitativamente la importancia de cada nodo dentro de la red, dependiendo del criterio que se adopte en cuanto a lo que consideramos por “importante”. Existen unas medidas clásicas de centralidad en redes complejas, como son la centralidad de grado, de cercanía, de intermediación y basadas en el vector propio. Todas estas medidas solo tienen en cuenta la topología de la red para determinar un valor y una clasificación de los nodos en orden de importancia. Cuando aplicamos estas centralidades a las redes urbanas nos encontramos con el problema de la densidad de grado uniforme que tienen estas redes, lo que hace que no sean adecuadas para la realidad que representan las ciudades. En esta memoria, se han implementado un conjunto de medidas de centralidad para redes urbanas, con la principal característica que tienen en cuenta no solo la topología de la red sino la influencia de la cuantía de los datos presentes en

El 54% de la población mundial vive ya en torno a núcleos de población que llamamos ciudades, por lo que su estudio nos enseña la forma en que piensa y se desarrolla el propio ser humano. Un análisis de las relaciones espaciales que se producen en entornos urbanos reales requieren un procesamiento de dichas relaciones en paralelo. Con el fin de representar y analizar estas relaciones espaciales complejas, los especialistas en urbanismo han empezado a utilizar modelos basados en redes complejas. Las redes emergen como un nuevo modelo más acorde con el problema de la complejidad organizada que es una ciudad. Otro aspecto esencial unido a las ciudades es que se han convertido en unas entidades productoras y creadoras de datos, tanto físicos como virtuales. Un estudio serio de la ciudad significa, por tanto, un estudio de los datos que en ella se generan o se encuentran. Dentro de la moderna teoría de redes, un concepto fundamental y muy estudiado en la bibliografía en las últimas décadas es el de la centralidad de la red. La centralidad consiste en determinar cuantitativamente la importancia de cada nodo dentro de la red, dependiendo del criterio que se adopte en cuanto a lo que consideramos por “importante”. Existen unas medidas clásicas de centralidad en redes complejas, como son la centralidad de grado, de cercanía, de intermediación y basadas en el vector propio. Todas estas medidas solo tienen en cuenta la topología de la red para determinar un valor y una clasificación de los nodos en orden de importancia. Cuando aplicamos estas centralidades a las redes urbanas nos encontramos con el problema de la densidad de grado uniforme que tienen estas redes, lo que hace que no sean adecuadas para la realidad que representan las ciudades. En esta memoria, se han implementado un conjunto de medidas de centralidad para redes urbanas, con la principal característica que tienen en cuenta no solo la topología de la red sino la influencia de la cuantía de los datos presentes en

Street traders operate in and around spaces that facilitate optimal interactions with potential customers - a distribution pattern which coincides with the busiest and most central parts of a city. In Lagos, street trading is ubiquitous and its appropriation of public space is contentious for spatial governance. Attempts at regulation exacerbate the precarious status of street traders and are mostly unsuccessful, and this is due to the limited understanding of the spatiality of street trading. The locations where street trading thrives are thus investigated in this thesis to unravel what aspects of spatiality creates the milieu that encourages their activities - an area of research that has received little attention in recent years. The aim is to contribute to the discourse on inclusive urban practices and policies in developing country cities. In literature, the determinants of street traders workplace locations are referenced to externalities from locational centrality and potent human activity (Dewar and Watson 1990; Monnet et al. 2007; Skinner 2008b; Skinner 2008a; Dobson et al. 2009). However, this body of work has not employed a systematic analysis in the study of such locations. This gap in research is addressed by using a novel methodological framework known as ‘Spatial Design Network Analysis for Street-Based Enterprises’ (sDNA-sBEL), which combines the systematic analyses of multi-scale network accessibility distribution with morphological properties of urban form. As a principle of sDNA-sBEL, open-source data and freeware applications were used to ensure replicability and accessibility to a broader audience. The sDNA-sBEL analyses identified that the most prolific street trading locations in Lagos have high values of macro-scale betweenness – spaces traversed most frequently while Lagosians take the shortest routes for long distance (inter-city) vehicular journeys. However, other compositional spatial factors must coincide with m

We rethink and extend the concepts of position and role in a network, basing them on various well-known measures that were not previously associated with these concepts, such as geodesic distance and modularity. The effectiveness of our new role and position detection algorithms is evaluated both qualitatively and quantitatively, on synthetic and real data, showing that we can identify new types of meaningful patterns in networks.

The final publication is available at Springer via http://dx.doi.org/10.1007/s13278-016-0346-9., We rethink and extend the concepts of position and role in a network, basing them on various well-known measures that were not previously associated with these concepts, such as geodesic distance and modularity. The effectiveness of our new role and position detection algorithms is evaluated both qualitatively and quantitatively, on synthetic and real data, showing that we can identify new types of meaningful patterns in networks., Peer Reviewed, Postprint (published version)

We show improved NP-hardness of approximating Ordering Constraint Satis-faction Problems (OCSPs). For the two most well-studied OCSPs, Maximum Acyclic Subgraph and Maximum Betweenness, we prove NP-hard approximation factors of 14/15+ε and 1/2+ε. When it is hard to approximate an OCSP by a constant better than takinga uniformly-at-random ordering, then the OCSP is said to be approximation resistant. We show that the Maximum Non-Betweenness Problem is approximation resistant and that there are width-m approximation-resistant OCSPs accepting only a fraction 1/(m/2)! of assignments. These results provide the first examples of approximation-resistant OCSPs only to P != NP., ApproxNP

We show improved NP-hardness of approximating Ordering Constraint Satis-faction Problems (OCSPs). For the two most well-studied OCSPs, Maximum Acyclic Subgraph and Maximum Betweenness, we prove NP-hard approximation factors of 14/15+ε and 1/2+ε. When it is hard to approximate an OCSP by a constant better than takinga uniformly-at-random ordering, then the OCSP is said to be approximation resistant. We show that the Maximum Non-Betweenness Problem is approximation resistant and that there are width-m approximation-resistant OCSPs accepting only a fraction 1/(m/2)! of assignments. These results provide the first examples of approximation-resistant OCSPs only to P != NP., ApproxNP

We show improved NP-hardness of approximating Ordering Constraint Satis-faction Problems (OCSPs). For the two most well-studied OCSPs, Maximum Acyclic Subgraph and Maximum Betweenness, we prove NP-hard approximation factors of 14/15+ε and 1/2+ε. When it is hard to approximate an OCSP by a constant better than takinga uniformly-at-random ordering, then the OCSP is said to be approximation resistant. We show that the Maximum Non-Betweenness Problem is approximation resistant and that there are width-m approximation-resistant OCSPs accepting only a fraction 1/(m/2)! of assignments. These results provide the first examples of approximation-resistant OCSPs only to P != NP., ApproxNP

We show improved NP-hardness of approximating Ordering Constraint Satis-faction Problems (OCSPs). For the two most well-studied OCSPs, Maximum Acyclic Subgraph and Maximum Betweenness, we prove NP-hard approximation factors of 14/15+ε and 1/2+ε. When it is hard to approximate an OCSP by a constant better than takinga uniformly-at-random ordering, then the OCSP is said to be approximation resistant. We show that the Maximum Non-Betweenness Problem is approximation resistant and that there are width-m approximation-resistant OCSPs accepting only a fraction 1/(m/2)! of assignments. These results provide the first examples of approximation-resistant OCSPs only to P != NP., ApproxNP

Problem solving is an integral aspect of modern society and includes such tasks as picking the fastest route to work, optimizing a production line, scheduling computer tasks, placing new bus stops, or picking a meal from available ingredients.We study the hardness of solving Constraint Satisfaction Problems (CSPs). In these, one is given a collection of constraints on variables with the task of finding an assignment satisfying the greatest number of constraints. In particular, parity constraints dictate that an odd (alt. even) number of variables are assigned a certain value.Satisfiable collections of parity constraints are easy in the sense that they can be efficiently solved via Gaussian elimination. We prove the threshold phenomenon that when constraints accept even one more assignment besides parities, then it is hard to find approximate solutions which are essentially better than random assignments.We also investigate the uselessness of predicates. Uselessness is a stronger hardness property in the sense that even if one was permitted to choose the acceptance criteria for given constraints, it is NP-hard to find solutions beating random assignments. We provide the first examples of predicates which are useless even when all variables appear unnegated.Finally, in an Ordering CSP (OCSP), one receives a set of items to order and constraints specifying how the items should be ordered relative to one another. For example, in the problem Maximum Betweenness, we have constraints of the form "order x between y and z". Our contribution is to significantly improve the approximation hardness of various OCSPs and provide the first unconditional direct Probabilistically Checkable Proofs for OCSPs.Notably, all results were previously known assuming the Unique Games Conjecture and the d-to-1 Conjecture. Our unconditional analogues of the same theorems involve developments for dealing with various obstacles faced by conventional techniques., QC 20140929, Approximation of NP-hard optimization problems

One of the better studied topology metrics of complex networks is the second smallest eigenvalue of the Laplacian matrix of a network’s graph, referred to as the algebraic connectivity mN-1. This spectral metric plays a decisive role in synchronization of coupled oscillators, network robustness, consensus problems, belief propagation, graph partitioning, and distributed filtering in sensor networks. However, computing the graph spectra is computationally slow and its convergence greatly depends on the topology, thus a number of lower bounds have been proposed over the years in order to find good approximations. To date, the closest bound is the one proposed by Rad et al. [21] in 2009. The current paper proposes new approximations for the algebraic connectivity based on three variations of the betweenness centrality, a popular centrality score often used in social studies to characterize the importance of a node or link within a network. Based on numerical and a partly analytic analysis, we show that our approximations provide accurate lower bounds for the algebraic connectivity for a wide range of graphs, including random, power-law, small-world, and lattice graphs. In particular, we numerically show that the average weighted Brandes betweenness can be treated as a lower bound for large enough networks, which greatly improves state-of-the-art bounds., Network Architectures & Services (NAS), Electrical Engineering, Mathematics and Computer Science

We propose and discuss a new centrality index for urban street patterns represented as networks in geographical space. This centrality measure, that we call ranking-betweenness centrality, combines the idea behind the random-walk betweenness centrality measure and the idea of ranking the nodes of a network produced by an adapted PageRank algorithm. We initially use a PageRank algorithm in which we are able to transform some information of the network that we want to analyze into numerical values. Numerical values summarizing the information are associated to each of the nodes by means of a data matrix. After running the adapted PageRank algorithm, a ranking of the nodes is obtained, according to their importance in the network. This classification is the starting point for applying an algorithm based on the random-walk betweenness centrality. A detailed example of a real urban street network is discussed in order to understand the process to evaluate the ranking-betweenness centrality proposed, performing some comparisons with other classical centrality measures.

We propose and discuss a new centrality index for urban street patterns represented as networks in geographical space. This centrality measure, that we call ranking-betweenness centrality, combines the idea behind the random-walk betweenness centrality measure and the idea of ranking the nodes of a network produced by an adapted PageRank algorithm. We initially use a PageRank algorithm in which we are able to transform some information of the network that we want to analyze into numerical values. Numerical values summarizing the information are associated to each of the nodes by means of a data matrix. After running the adapted PageRank algorithm, a ranking of the nodes is obtained, according to their importance in the network. This classification is the starting point for applying an algorithm based on the random-walk betweenness centrality. A detailed example of a real urban street network is discussed in order to understand the process to evaluate the ranking-betweenness centrality proposed, performing some comparisons with other classical centrality measures.

One of the better studied topology metrics of complex networks is the second smallest eigenvalue of the Laplacian matrix of a network’s graph, referred to as the algebraic connectivity mN-1. This spectral metric plays a decisive role in synchronization of coupled oscillators, network robustness, consensus problems, belief propagation, graph partitioning, and distributed filtering in sensor networks. However, computing the graph spectra is computationally slow and its convergence greatly depends on the topology, thus a number of lower bounds have been proposed over the years in order to find good approximations. To date, the closest bound is the one proposed by Rad et al. [21] in 2009. The current paper proposes new approximations for the algebraic connectivity based on three variations of the betweenness centrality, a popular centrality score often used in social studies to characterize the importance of a node or link within a network. Based on numerical and a partly analytic analysis, we show that our approximations provide accurate lower bounds for the algebraic connectivity for a wide range of graphs, including random, power-law, small-world, and lattice graphs. In particular, we numerically show that the average weighted Brandes betweenness can be treated as a lower bound for large enough networks, which greatly improves state-of-the-art bounds., Network Architectures & Services (NAS), Electrical Engineering, Mathematics and Computer Science

Problem solving is an integral aspect of modern society and includes such tasks as picking the fastest route to work, optimizing a production line, scheduling computer tasks, placing new bus stops, or picking a meal from available ingredients.We study the hardness of solving Constraint Satisfaction Problems (CSPs). In these, one is given a collection of constraints on variables with the task of finding an assignment satisfying the greatest number of constraints. In particular, parity constraints dictate that an odd (alt. even) number of variables are assigned a certain value.Satisfiable collections of parity constraints are easy in the sense that they can be efficiently solved via Gaussian elimination. We prove the threshold phenomenon that when constraints accept even one more assignment besides parities, then it is hard to find approximate solutions which are essentially better than random assignments.We also investigate the uselessness of predicates. Uselessness is a stronger hardness property in the sense that even if one was permitted to choose the acceptance criteria for given constraints, it is NP-hard to find solutions beating random assignments. We provide the first examples of predicates which are useless even when all variables appear unnegated.Finally, in an Ordering CSP (OCSP), one receives a set of items to order and constraints specifying how the items should be ordered relative to one another. For example, in the problem Maximum Betweenness, we have constraints of the form "order x between y and z". Our contribution is to significantly improve the approximation hardness of various OCSPs and provide the first unconditional direct Probabilistically Checkable Proofs for OCSPs.Notably, all results were previously known assuming the Unique Games Conjecture and the d-to-1 Conjecture. Our unconditional analogues of the same theorems involve developments for dealing with various obstacles faced by conventional techniques., QC 20140929, Approximation of NP-hard optimization problems

We show improved NP-hardness of approximating Ordering Constraint Satisfaction Problems (OCSPs). For the two most well-studied OCSPs, Maximum Acyclic Subgraph and Maximum Betweenness, we prove inapproximability of 14/15 + ε and 1/2 + ε. An OCSP is said to be approximation resistant if it is hard to approximate better than taking a uniformly random ordering. We prove that the Maximum Non- Betweenness Problem is approximation resistant and that there are width-m approximation-resistant OCSPs accepting only a fraction 1/(m/2)! of assignments. These results provide the first examples of approximation-resistant OCSPs subject only to P ≠ NP. Our reductions from Label Cover differ from previous works in two ways. First, we establish a somewhat general bucketing lemma permitting us to reduce the analysis of ordering predicates to that of classical predicates. Second, instead of "folding", which is not available for ordering predicates, we employ permuted instantiations of the predicates to limit the value of poorly correlated strategies., QC 20131204

Quite recently certification systems for sustainable development of neighborhoods and communities, such as L EED ND and BREEAM for Communities, came to the market. These systems try to define urban sustainability through sets of criteria that in a variety of ways measure aspects in urban developments that have an influence on environmental, social and economical issues on a local level. This paper investigates the monetary values on these criteria, derived from property prices from apartments and single family houses in Copenhagen. In order to make proper estimates on the monetary values for certification criteria a hedonic price model is used. The model holds property prices from about 20 000 sales as dependent variable which is then correlated, through multiple regressions, with variables made out of the criteria through GIS-analyses. Translation from certification criteria into measurable variables is done with great consideration to contemporary urban theory. These variables are results from spatial analyses based on space syntax and other more standard spatial measures. The certification systems focuses on neighborhoods and communities, which is considered in the radiuses used for analyzing. It turns out that 19 of the 30 measured criterions are statistically significant, but a majority shows negative correlations to price. It is also acknowledged that space syntax measures like integration and betweenness have an influence on prices. Local integration, used as a proxy for various urban qualities, is shown to have a negative impact on prices. Qn the contrary, betweenness on a global scale is valued as positive. From these results the conclusion is that people are generally not willing to pay for urban sustainability on the local scale, as defined in LEED and BREEAM certification systems. However, it is furthermore argued that this is a question of measure and definition. Previous studies, e.g. (Spacescape and Evidens 2011) and (Sjaastad et al. 2007), imply that, QC 20170307

Social Network Analysis (SNA), the study of social interactions within a group, spans many different fields of study, ranging from psychology to biology to information sciences. Over the past half century, many analysts outside of the social science field have taken SNA concepts and theories and have applied them to an array of networks in the hope of formulating mathematical descriptions of the relations within the network of interest. More than 50 measures of networks have been identified across these fields; however, little research has examined the findings of these measures for possible relationships. This thesis tests a set of widely accepted SNA measures for correlation and redundancies with respect to the most accepted network structural properties: size, clustering coefficients, and scale-free parameters. The goal of the thesis is to investigate the SNA measures' ability to discriminate and identify different actors in a network. As a result, the study not only identifies high correlation amongst many of the measures, it also aids analysts in identifying which measure best suits a network with specific structural properties, and the measure's efficiency for a given analysis goal., The original document contains color images.

Hexは簡単なルールの2人用ボードゲームであり，チェスや囲碁のように戦略的な奥深さがあるゲームとして知られ，コンピュータAIの研究もされている．Hexの任意の盤面の状態は自分と相手のネットワークとして表現でき，勝利条件は辺ノードを直接接続することへ変化する．本研究では，熟練者の手筋に現れるネットワークの特徴を，ノード間の媒介性の指標であるk-寄与度を提案し，それを用いた解析により得られた特徴を反映させた，最短経路以外の経路も考慮する，Hexの局面の新たな評価手法を提案する．

In this paper we investigate the structural properties of betweenness centrality and determine some cases in which betweenness reaches its extremal values. Special attention is paid to Star(G), the set of vertices adjacent to all other vertices in a graph and we prove several results about the betweenness of the elements of this set. We introduce the new concept of total betweenness and relate it to group betweenness. We prove a necessary and sufficient condition for the two measures to coincide. Next we consider cutsets and cutvertices and we find a lower bound for their betweenness; in particular for a cutvertex this lower bound is the cutting number. Finally we apply the previous results to trees, proving an alternative formula for betweenness based oil cutvertex properties.

The rise of the 21st Century Islamic extremist movement, which was mobilised by the al-Qaeda attacks of and responses to September 11, 2001, heralds a new period in the history of terrorism. The increased frequency and intensity of this type of terrorism affects every nation in the world, not least Australia. Rising to meet the challenges posed by terrorism is the field of terrorism studies, the field which aims at understanding, explaining, and countering terrorism. Despite the importance of the field, it has been beleaguered with criticisms since its inception as a response to the rise of international terrorism. These criticisms specifically aim at the field's lack of objectivity, abstraction, levels of research, and levels of analysis. These criticisms were the impetus behind the adoption of the methodology of this thesis, which offers the distinct ability to understand, explain, and forecast the way in which terrorists interact within covert cells. Through social network analysis, this thesis examines four terrorist cells that have operated in or against Australia. These cells are from the groups Hrvatsko Revolucionarno Bratstvo (Croatian Revolutionary Brotherhood), Aum Shinrikyo (Supreme Truth), Lashkar-e-Taiba (Army of the Pure), and Jemaah Islamiyah (Islamic Community) and operated between 1963 and 2003. Essentially, this methodology attempts to discover, map, and analyse the interaction within the cells during the covert stage of their respective operations. Following this, the results are analysed through the traditional social network analysis frameworks to discover the internal dynamics of the cell and identify the critical nodes (leaders) within the cells. Destabilisation techniques are subsequently employed, targeting these critical nodes to establish the most effective disruption techniques from a counter-terrorism point of view. The major findings of this thesis are: (1) that cells with a focus on efficiency rather than covertness were more successfu

The notion of transit function is introduced to present a unifying approach for results and ideas on intervals, convexities and betweenness in graphs and posets. Prime examples of such transit functions are the interval function I and the induced path function J of a connected graph. Another transit function is the all-paths function. New transit functions are introduced, such as the cutvertex transit function and the longest path function. The main idea of transit functions is that of ‘transferring’ problems and ideas of one transit function to the other. For instance, a result on the interval function I might suggest similar problems for the induced path function J. Examples are given of how fruitful this transfer can be. A list of Prototype Problems and Questions for this transferring process is given, which suggests many new questions and open problems.

A measure of the centrality of a vertex of a graph is the portion of shortest paths crossing through it between other vertices of the graph. This is called betweenness centrality and here we study some of its general properties, relations with distance parameters (diameter, mean distance), local parameters, symmetries, etc. Some bounds for this parameter are obtained, using them to improve known bounds for the mean distance of the graph.

The induced path function $J(u, v)$ of a graph consists of the set of all vertices lying on the induced paths between vertices $u$ and $v$. This function is a special instance of a transit function. The function $J$ satisfies betweenness if $w \\in J(u, v)$ implies $u \\notin J(w, v)$ and $x \\in J(u, v)$ implies $J(u, x \\subseteq J(u, v)$, and it is monotone if $x, y \\in J(u, v)$ implies $J(x, y) \\subseteq J(u, v)$. The induced path function of a connected graph satisfying the betweenness and monotone axioms are characterized by transit axioms.

The paper provides an axiomatization in a multi-valued language of some basic predicates of utility theory. This axiomatization is based on deductions interpreted so that assertions which are theoretically error-free can be treated in an approximate way in actual structures for the language. (Author), This article is from 'Proceedings of the International Symposium on Multiple-Valued Logic (13th) Held at Kyoto, Japan on May 23-25, 1983,' AD-A136 457, p219-221.

Köszegi and Rabin (2006, 2007) formulate loss-aversion models called Preferred Personal Equilibrium (PPE) and Choice-acclimating Personal Equilibrium (CPE) so successfully that many papers have been applied their models to a variety of economic fields in this decade. In this paper, without assuming any specific functional form, I show that these two loss-aversion models satisfy strong mixture aversion in the sense that a non-degenerate lottery is strictly preferred to any mixture between the lottery and its certainty equivalent. This property distinguishes these loss-aversion models from many other standard models such as the expected utility theory and disappointment aversion so that this result allows experimental economists to test a class of these models in a simple setting.

Köszegi and Rabin (2006, 2007) formulate loss-aversion models called Preferred Personal Equilibrium (PPE) and Choice-acclimating Personal Equilibrium (CPE) so successfully that many papers have been applied their models to a variety of economic fields in this decade. In this paper, without assuming any specific functional form, I show that these two loss-aversion models satisfy strong mixture aversion in the sense that a non-degenerate lottery is strictly preferred to any mixture between the lottery and its certainty equivalent. This property distinguishes these loss-aversion models from many other standard models such as the expected utility theory and disappointment aversion so that this result allows experimental economists to test a class of these models in a simple setting.