The Economics of Small Worlds

We examine a simple economic model of network formation where agents benefit from indirect relationships. We show that small-world features—short path lengths between nodes together with highly clustered link structures—necessarily emerge for a wide set of parameters

The Economics of Small Worlds

We examine a simple economic model of network formation where agents benefit from indirect relationships. We show that small-world features - -- short path lengths between nodes together with highly clustered link structures --- necessarily emerge for a wide set of parameters.networks, small worlds

Homophily and Long-Run Integration in Social Networks

We model network formation when heterogeneous nodes enter sequentially and form connections through both random meetings and network-based search, but with type-dependent biases. We show that there is "long-run integration," whereby the composition of types in sufficiently old nodes' neighborhoods approaches the global type distribution, provided that the network-based search is unbiased. However, younger nodes' connections still reflect the biased meetings process. We derive the type-based degree distributions and group-level homophily patterns when there are two types and location-based biases. Finally, we illustrate aspects of the model with an empirical application to data on citations in physics journals.Comment: 39 pages, 2 figure

Stiffness behaviour of trial road foundations.

This paper reports the results of two full-scale field trials to determine the stiffness and density of granular materials receiving different levels of compaction energy and support. The research showed that there were greater improvements in density with initial input of compaction energy, and yet little change in density, but significant increases in stiffness, with the final applications of compaction energy. Density is thus an inappropriate indicator of performance (i.e. resilient elastic stiffness

Performance parameters and target values for construction of UK road foundations

There is impetus in the UK to move away from empirical design of road foundations and method specification towards analytical design assured by end product testing during construction. Current research at Loughborough University, sponsored by the Highways Agency, is aimed at introducing such a performance based specification. This paper introduces the philosophy behind the research and explains the primary objectives. Selective results are presented from a full-scale field trial construction of a road foundation on a soft subgrade, which was characterised by a variety of field devices and subsequently trafficked. This paper focuses on insitu stiffness modulus (ER), measured by several devices for comparison. The setting of suitable target values for field ER is seen as a key factor and the influence of inherent variability in material response a concern. The discrepancy between devices and the problem of long-term stability are discussed and highlighted as a key focus for the remainder of the work

Threshold stress and asymptotic stiffness of UK clays in the repeated load triaxial test.

Recent research at Loughborough University has produced a draft performance specification for pavement foundations. To assess the performance parameters of stiffness and resistance to permanent deformation of the subgrade, an extensive series of repeated load triaxial tests has been performed on a range of fine grained subgrades. Assessment of the data has shown that the deviator stress at which the cumulative permanent deformation starts to increase significantly (i.e. the threshold stress) is equal to half that at failure (and occurs at approximately 1% permanent strain). The resilient stiffness of the materials tends to low asymptotic values at higher deviator stress. Comparison between the elastic and plastic behaviour has shown that the deviator stress at ‘threshold’ is coincident with the stiffness asymptote. This paper presents a suggested simplified mechanistic design approach for pavement foundations based on these findings

How Captain Amerika uses neural networks to fight crime

Artificial neural network models can make amazing computations. These models are explained along with their application in problems associated with fighting crime. Specific problems addressed are identification of people using face recognition, speaker identification, and fingerprint and handwriting analysis (biometric authentication)

Subgrade equilibrium water content and resilient modulus for UK clays

The main functional requirement of the subgrade is to resist excessive deformations during construction and in service. Deformation is controlled by ensuring adequate foundation resilient modulus. UK pavement design currently relies upon the determination of long-term CBR values for subgrades, which results in conservative pavement foundation design. To allow more realistic design an analytical approach is required, including measured values of resilient modulus at anticipated short- and long-term equilibrium subgrade water contents. Resilient modulus is determined from repeated load triaxial tests with on-sample strain measurement. Results from these tests on samples adjusted to model the subgrade behaviour at various design conditions are presented. These results are discussed, highlighting problems both with measuring small strains on undisturbed soils and in predicting and modelling accurately long-term soil behaviour. RÉSUMÉ: Le critère principal d’une sous-couche est de résister à des déformations excessives en construction puis en service. La conception des chaussées au Royaume-Uni est actuellement basée sur la détermination de l'indice portant Californien (CBR) à longterme des sous-couches. Pour une conception plus réaliste, il est nécessaire d'adopter une approche prenant en compte des valeurs de module de résilience mesurées à des degrés d'humidité de sous-couches à l'équilibre simulés à court et long-terme. Le module de résilience est déterminé à partir d'essais répétés en charge triaxiale avec mesure des contraintes sur l'échantillon. Dans cet article les résultats de ces tests sur des échantillons simulant le comportement de la sous-couche sous diverses conditions de conception sont présentés. Ces résultats sont discutés, en soulignant les problèmes résultant de la mesure de faibles contraintes sur des sols non-perturbés, et dus à la prédiction et à la modélisation du comportement des sols à long-terme

Knee Osteoarthritis and the Efficacy of Kinesthesia, Balance & Agility Exercise Training: A Pilot Study

Kinesthesia, balance and agility (KBA) neuromuscular exercises are commonly used for rehabilitation of lower extremity injuries. KBA combined with strength training (ST) reportedly improves function among persons with knee osteoarthritis (OA), but independent effects of KBA are unknown. The purpose of this study was to determine the efficacy of KBA exercises, independent of ST, to improve function among persons with knee OA. Twenty participants (69.3, SD 11.4 y) were randomized to 8 weeks, 3-days per week, instructor-lead KBA or ST groups. Self-reported physical function (difficulty with daily living activities such as walking, bending, stair climbing, etc.) was measured at baseline and every two weeks. Community physical activity level, negative and positive outcome expectancies for exercise, self-reported knee stability, and timed 10-stair climb, 10-stair descent, and ‘get up and go’ 15 m walk were measured at baseline and follow-up. Physical function improved 59% (p = 0.02) with KBA and 40% (p = 0.02) with ST at 8 weeks. Community physical activity level improved only in KBA (p = 0.04); knee stability improved in both KBA (p = 0.04) and ST (p = 0.01). There were no significant between-group differences (p \u3e 0.05). In conclusion, both interventions appear to improve function and knee stability among persons with symptomatic knee OA. As KBA has never been studied as an independent treatment program, our results indicate it is a promising stand-alone intervention worthy of further study