A Semantic Grid Service for Experimentation with an Agent-Based Model of Land-Use Change

Agent-based models, perhaps more than other models, feature large numbers of parameters and potentially generate vast quantities of results data. This paper shows through the FEARLUS-G project (an ESRC e-Social Science Initiative Pilot Demonstrator Project) how deploying an agent-based model on the Semantic Grid facilitates international collaboration on investigations using such a model, and contributes to establishing rigorous working practices with agent-based models as part of good science in social simulation. The experimental workflow is described explicitly using an ontology, and a Semantic Grid service with a web interface implements the workflow. Users are able to compare their parameter settings and results, and relate their work with the model to wider scientific debate.Agent-Based Social Simulation, Experiments, Ontologies, Replication, Semantic Grid

Balmer and Metal Absorption Feature Gradients in M32

Spectra from MDM Observatory are used to assess Lick/IDS feature strength gradients inside the half-light radius of the compact Local Group elliptical galaxy M32. All but a few (of 24 measured) indices show a statistically significant gradient. Comparing with models, the index gradients indicate a mean age and abundance gradient in the sense that the nucleus is a factor of 2.5 younger and a factor of 0.3 dex more metal-rich than at 1 effective radius. This conclusion is only weakly dependent on which index combinations are used and is robust to high accuracy. Stars near the M32 nucleus have a mean age and heavy element abundance [M/H] of (4.7 Gyr, +0.02), judging from models by Worthey with variable abundance ratios. This result has very small formal random errors, although, of course, there is significant age-metallicity degeneracy along an (age, abundance) line segment from (5.0 Gyr, 0.00) to (4.5 Gyr, +0.05). An abundance pattern of [C/M]=+0.077, [N/M]=-0.13, [Mg/M]=-0.18, [Fe/M]~0.0, and [Na/M]=+0.12 is required to fit the feature data, with a fitting precision of about 0.01 dex. Model uncertainties make the accuracies of these values at least twice the magnitude of the precision. Forcing scaled-solar abundances does not change the age very much, but it increases the rms goodness of model-data fit by a factor of 3 and broadens the allowed range of age to $\pm 1$ Gyr. The overall abundance pattern contrasts with larger elliptical galaxies, in which all measurable lighter elements are enhanced relative to iron and calcium.Comment: 23 pages, 9 figures, Astronomical Journal, in pres

Are monetarists an endangered species?

Monetary policy

Errors and Artefacts in Agent-Based Modelling

The objectives of this paper are to define and classify different types of errors and artefacts that can appear in the process of developing an agent-based model, and to propose activities aimed at avoiding them during the model construction and testing phases. To do this in a structured way, we review the main concepts of the process of developing such a model – establishing a general framework that summarises the process of designing, implementing, and using agent-based models. Within this framework we identify the various stages where different types of errors and artefacts may appear. Finally we propose activities that could be used to detect (and hence eliminate) each type of error or artefact.Verification, Replication, Artefact, Error, Agent-Based Modelling, Modelling Roles

CHIN MUSIC: A STATISTICAL ANALYSIS OF RETALIATION PITCHES IN MAJOR LEAGUE BASEBALL

This paper is focused on hit batsmen in Major League Baseball from the 2008 season through August 20th of the 2013 season. More specifically, this paper examines the characteristics of retaliation pitches and attempts to determine the intent of the pitcher. The paper also takes into account moral hazard and cost-benefit analysis of hitting an opposing batsman. There has been a vast amount of literature in economics with regard to hit batsmen in Major League Baseball. However, very few of these papers have been able to evaluate economic theories in Major League Baseball using Pitchf/x data. Pitchf/x technology became fully implemented into all thirty Major League ballparks prior to the 2008 season. Pitchf/x provides us with intricate details of every pitch, which include velocity, movement, and pitch location. Using Pitchf/x data, this paper presents a very detailed statistical analysis with regard to hit batsmen under a variety of scenarios. A probit model is used to test for the probability of an intentional retaliation pitch based on a variety of predictor variables. The most important conclusion we are able to draw from the two regression models presented in this paper is that, holding all other factors constant, retaliation pitches that are fastballs increase the probability of being intentional by roughly 17%

Techniques to Understand Computer Simulations: Markov Chain Analysis

The aim of this paper is to assist researchers in understanding the dynamics of simulation models that have been implemented and can be run in a computer, i.e. computer models. To do that, we start by explaining (a) that computer models are just input-output functions, (b) that every computer model can be re-implemented in many different formalisms (in particular in most programming languages), leading to alternative representations of the same input-output relation, and (c) that many computer models in the social simulation literature can be usefully represented as time-homogeneous Markov chains. Then we argue that analysing a computer model as a Markov chain can make apparent many features of the model that were not so evident before conducting such analysis. To prove this point, we present the main concepts needed to conduct a formal analysis of any time-homogeneous Markov chain, and we illustrate the usefulness of these concepts by analysing 10 well-known models in the social simulation literature as Markov chains. These models are: • Schelling\'s (1971) model of spatial segregation • Epstein and Axtell\'s (1996) Sugarscape • Miller and Page\'s (2004) standing ovation model • Arthur\'s (1989) model of competing technologies • Axelrod\'s (1986) metanorms models • Takahashi\'s (2000) model of generalized exchange • Axelrod\'s (1997) model of dissemination of culture • Kinnaird\'s (1946) truels • Axelrod and Bennett\'s (1993) model of competing bimodal coalitions • Joyce et al.\'s (2006) model of conditional association In particular, we explain how to characterise the transient and the asymptotic dynamics of these computer models and, where appropriate, how to assess the stochastic stability of their absorbing states. In all cases, the analysis conducted using the theory of Markov chains has yielded useful insights about the dynamics of the computer model under study.Computer Modelling, Simulation, Markov, Stochastic Processes, Analysis, Re-Implementation

A deception based framework for the application of deceptive countermeasures in 802.11b wireless networks

The advance of 802.11 b wireless networking has been beset by inherent and in-built security problems. Network security tools that are freely available may intercept network transmissions readily and stealthily, making organisations highly vulnerable to attack. Therefore, it is incumbent upon defending organisations to take initiative and implement proactive defences against common network attacks. Deception is an essential element of effective security that has been widely used in networks to understand attack methods and intrusions. However, little thought has been given to the type and the effectiveness of the deception. Deceptions deployed in nature, the military and in cyberspace were investigated to provide an understanding of how deception may be used in network security. Deceptive network countermeasures and attacks may then be tested on a wireless honeypot as an investigation into the effectiveness of deceptions used in network security. A structured framework, that describes the type of deception and its modus operandi, was utilised to deploy existing honeypot technologies for intrusion detection. Network countermeasures and attacks were mapped to deception types in the framework. This enabled the honeypot to appear as a realistic network and deceive targets in varying deceptive conditions. The investigation was to determine if particular deceptive countermeasures may reduce the effectiveness of particular attacks. The effectiveness of deceptions was measured, and determined by the honeypot\u27s ability to fool the attacking tools used. This was done using brute force network attacks on the wireless honeypot. The attack tools provided quantifiable forensic data from network sniffing, scans, and probes of the wireless honeypot. The aim was to deceive the attack tools into believing a wireless network existed, and contained vulnerabilities that may be further exploited by the naive attacker

Emotion regulation and executive functioning as predictors of theory of mind competence during early childhood.

The linkage between emotion regulation (ER) skills and executive functioning (EF) abilities as predictors of theory of mind skills (ToM) was examined. 263 3.5-year-old children that participated in an on-going longitudinal study were administered various executive function, emotion regulation, and theory of mind tasks; maternal reports of emotion regulation abilities were also obtained. It was predicted that children who score higher on ER measures will better be able to perform on EF tasks and in turn have a superior ToM ability; superior EF skills would mediate the relation between ER skills and ToM abilities. Results showed no relationship between ER, EF, and ToM after controlling for demographic variables such as maternal education, race, language, gender, and maternal marital status; the mediation hypothesis was not supported. But associations between some EF tasks and ToM tasks were found. Results are discussed in terms of limitations and possible implications for supporting the development of cognitive, regulatory, and social skills in young children