The Effect of Electronic Markets on Forecasts of New Product Success

In this paper, we extend field experiments of real money prediction markets to the problem of forecasting the success of a new product. We collect forecasts using a traditional survey mechanism and a market mechanism. Our results suggest that market prices summarize the information contained in survey forecasts and improve those forecasts by reducing the variability of the forecast. However, we find no evidence of a crystal ball equilibrium. Our markets have considerable variability and predict only as well as the public signal provided by the HSX movie market game.     

The instantaneous frequency of cardiovascular time series: a comparison of methods

The instantaneous frequency (IF) of cardiovascular time series is used to describe the time-varying spectral contents of the characteristic frequency bands that are of interest for psychophysiological and cardiovascular research. Four methods to compute IF of band-limited, monocomponent, and analytical cardiovascular time series were compared by means of simulated time series contaminated with additive noise. These four methods are: the method using the inverse Fourier transform of uncorrelated time-slices of the Wigner-Ville distribution, the discrete time-frequency transform, the circular mean direction of the time-slices of the Wigner-Ville distribution, and the central finite difference of the phase. The time resolution of the estimates is optimal and is inversely related to the bandwidth of the frequency components, as given by the uncertainty principle of Gabor. At periods in time where the signal fulfills the requirements of the model signal, the four estimates of IF are numerically equal; only the circular mean direction showed a slight deviation from the other estimates. Although the estimates of IF differ at sudden phase shifts at low amplitude, i.e. at points where the signal locally does not comply with the requirements of the model signal, overall the four methods produce comparable estimates of IF of a cardiovascular time series at an optimal time resolution.     

Minimum‐Displacement Overlap Removal for Geo‐referenced Data Visualization

Given a set of rectangles embedded in the plane, we consider the problem of adjusting the layout to remove all overlap while preserving the orthogonal order of the rectangles. The objective is to minimize the displacement of the rectangles. We call this problem Minimum -Displacement Overlap Removal (mdor ). Our interest in this problem is motivated by the application of displaying metadata of archaeological sites. Because most existing overlap removal algorithms are not designed to minimize displacement while preserving orthogonal order, we present and compare several approaches which are tailored to our particular usecase. We introduce a new overlap removal heuristic which we call re Arrange . Although conceptually simple, it is very effective in removing the overlap while keeping the displacement small. Furthermore, we propose an additional procedure to repair the orthogonal order after every iteration, with which we extend both our new heuristic and PRISM, a widely used overlap removal algorithm. We compare the performance of both approaches with and without this order repair method. The experimental results indicate that re Arrange is very effective for heterogeneous input data where the overlap is concentrated in few dense regions.     

A GF miniature resource grammar for Tswana: modelling the proper verb

The Grammatical Framework (GF) not only offers state of the art grammar-based machine translation support between an increasing number of languages through its so-called Resource Grammar Library, but is also fast becoming a de facto framework for developing multilingual controlled natural languages (CNLs). For a natural language to share maximally in the opportunities that GF-based multilingual CNL support presents, it has to have a GF resource grammar. Tswana, an agglutinating Bantu language, spoken in Southern Africa as one of the eleven official languages of South Africa, does not yet have such a grammar. This article reports on the development of a so-called miniature resource grammar, a first step towards a full resource grammar for Tswana. The focus is on the modelling of the Tswana proper verb as it occurs in simple sentences. The (proper) verb is the morphologically most complex word category in Tswana, and therefore constitutes a notable contribution towards the development of a GF resource grammar for Tswana. The computational model is discussed in some detail, implemented and tested on a systematically constructed treebank.     

When do agents outperform centralized algorithms?

Multi-agent systems (MAS) literature often assumes decentralized MAS to be especially suited for dynamic and large scale problems. In operational research, however, the prevailing paradigm is the use of centralized algorithms. Present paper empirically evaluates whether a multi-agent system can outperform a centralized algorithm in dynamic and large scale logistics problems. This evaluation is novel in three aspects: (1) to ensure fairness both implementations are subject to the same constraints with respect to hardware resources and software limitations, (2) the implementations are systematically evaluated with varying problem properties, and (3) all code is open source, facilitating reproduction and extension of the experiments. Existing work lacks a systematic evaluation of centralized versus decentralized paradigms due to the absence of a real-time logistics simulator with support for both paradigms and a dataset of problem instances with varying properties. We extended an existing logistics simulator to be able to perform real-time experiments and we use a recent dataset of dynamic pickup-and-delivery problem with time windows instances with varying levels of dynamism, urgency, and scale. The OptaPlanner constraint satisfaction solver is used in a centralized way to compute a global schedule and used as part of a decentralized MAS based on the dynamic contract-net protocol (DynCNET) algorithm. The experiments show that the DynCNET MAS finds solutions with a relatively lower operating cost when a problem has all following three properties: medium to high dynamism, high urgency, and medium to large scale. In these circumstances, the centralized algorithm finds solutions with an average cost of 112.3% of the solutions found by the MAS. However, averaged over all scenario types, the average cost of the centralized algorithm is 94.2%. The results indicate that the MAS performs best on very urgent problems that are medium to large scale.     

A test of the design of a video tutorial for software training

The effectiveness of a video tutorial versus a paper‐based tutorial for software training has yet to be established. Mixed outcomes from the empirical studies to date suggest that for a video tutorial to outperform its paper‐based counterpart, the former should be crafted so that it addresses the strengths of both designs. This was attempted in the present study. Two consecutive experiments were conducted to examine the effect of tutorial type (video vs. paper based) on task relevance, self‐efficacy, mood, flow and task performance. Participants were students from junior high school. Both studies reported significant, positive contributions of the tutorials to task relevance, self‐efficacy, mood and flow. Both studies also found significant and substantial effects on task performance. A learning gain of about 30% was achieved in both studies. A retention task, completed only in Study 2, further revealed that the learning effect was stable. More importantly, performance on this task also indicated a significant interaction with tutorial type, favouring the video. The success of the video tutorial is ascribed to its design, which attended to and even incorporated key qualities of paper‐based tutorials, while also capitalizing on the strengths of video.     

Identifying multiple roles of ICT coordinators

This study reports on the development and validation of measurement scales to study the different roles fulfilled by ICT coordinators. Based on a review of the literature, a 24 item questionnaire was constructed and administered to a sample of 177 Flemish ICT coordinators working in primary education. Exploratory factor analysis revealed a four-factor solution: the ICT coordinator as a planner, a budgeter, a technician, and an educationalist. Qualitative data corroborated these roles. This study provides a quantitative measure of the different roles assumed by ICT coordinators in practice. The implications of our findings for schools, researchers and policy makers are discussed.     

On the adjoint-consistent formulation of interface conditions in goal-oriented error estimation and adaptivity for fluid–structure interaction

The numerical solution of fluid–structure-interaction problems poses a paradox in that most of the computational resources are consumed by the subsystem of least practical interest, viz., the fluid. Goal-oriented adaptive discretization methods provide a paradigm to bypass this paradox. Based on the solution of a dual problem, the contribution of local residuals to the error in a specific goal functional is estimated, and only the regions that yield a dominant contribution are refined. In the present work, we address a fundamental complication in the application of goal-oriented adaptivity to fluid–structure-interaction problems, namely, that the treatment of the interface conditions has nontrivial consequences for the properties of the dual problem. In the context of a linearized model problem, we consider two equivalent discretizations differing only on the formulation of the interface coupling terms. By means of an adjoint consistency analysis, we show that only one of these discretizations is adjoint consistent. Numerical experiments convey that the two discretizations behave very differently for the dual problem, and that the adjoint-consistent discretization yields more reliable error estimates. Based on the adjoint-consistent discretization, we finally present some h- and hp-adaptive results, confirming that tremendous savings in computational cost can be realized through the use of goal-oriented refinement strategies. The numerical experiments illustrate that the goal-oriented approach effectively equilibrates the error contributions of the fluid and structure subsystems, which is imperative for efficiently resolving the coupled fluid–structure-interaction problem, and which cannot be accomplished by uniform or residual-based refinement strategies.