Preliminary Experiments using Subjective Logic for the Polyrepresentation of Information Needs

According to the principle of polyrepresentation, retrieval accuracy may improve through the combination of multiple and diverse information object representations about e.g. the context of the user, the information sought, or the retrieval system. Recently, the principle of polyrepresentation was mathematically expressed using subjective logic, where the potential suitability of each representation for improving retrieval performance was formalised through degrees of belief and uncertainty. No experimental evidence or practical application has so far validated this model. We extend the work of Lioma et al. (2010), by providing a practical application and analysis of the model. We show how to map the abstract notions of belief and uncertainty to real-life evidence drawn from a retrieval dataset. We also show how to estimate two different types of polyrepresentation assuming either (a) independence or (b) dependence between the information objects that are combined. We focus on the polyrepresentation of different types of context relating to user information needs (i.e. work task, user background knowledge, ideal answer) and show that the subjective logic model can predict their optimal combination prior and independently to the retrieval process

Evaluating Maximum Likelihood Estimation Methods to Determine the Hurst Coefficient

A maximum likelihood estimation method implemented in S-PLUS (S-MLE) to estimate the Hurst coefficient (H) is evaluated. The Hurst coefficient, with 0.5\u3cHS-MLE was developed to estimate H for fractionally differenced (fd) processes. However, in practice it is difficult to distinguish between fd processes and fractional Gaussian noise (fGn) processes. Thus, the method is evaluated for estimating H for both fd and fGn processes. S-MLE gave biased results of H for fGn processes of any length and for fd processes of lengths less than 210. A modified method is proposed to correct for this bias. It gives reliable estimates of H for both fd and fGn processes of length greater than or equal to 211

Fiscal Policy and Growth: Do Financial Crises make a Difference?

In this paper we assess to what extent in the existence of a financial crisis, government spending can contribute to mitigate economic downturns in the short run and whether such impact differs in crisis and non crisis times. We use panel analysis for a set of OECD and non-OECD countries for the period 1981-2007. The fiscal multiplier for the full sample for instrumented regular and crisis spending is about 0.6-0.8 considering the sample average government spending share of GDP of about one third. Altogether, we cannot reject the hypothesis that crisis spending and regular spending have the same impact using a variation of controls, sub-samples and specifications.fiscal policy, financial crisis, growth, OECD, EU, panel analysis.

Fiscal policy and growth: do financial crises make a difference?

In this paper we assess to what extent in the existence of a financial crisis, government spending can contribute to mitigate economic downturns in the short run and whether such impact differs in crisis and non crisis times. We use panel analysis for a set of OECD and non-OECD countries for the period 1981-2007. The fiscal multiplier for the full sample for instrumented regular and crisis spending is about 0.6-0.8 considering the sample average government spending share of GDP of about one third. Altogether, we cannot reject the hypothesis that crisis spending and regular spending have the same impact using a variation of controls, sub-samples and specifications. JEL Classification: C23, E62, E44, F43, H50EU, financial crisis, Fiscal Policy, Growth, oecd, panel analysis

Media Coverage as Mirror or Molder? An Inference-Based Framework

Many communication theories in the context of political communication are based on the premise that humans are social beings affected by their perception of what others think, do, or say. For example, the spiral of silence theory predicts that individuals publically speaking their mind on certain issues is dependent on whether they perceive their opinion to be that of the majority or minority, and that the media is a core source for gauging public opinion. Yet, communication research has produced contradictory findings regarding the relationship between media coverage, perceived public opinion, personal opinion, and behavior. We argue that these contradictory findings can be explained by different inference hypotheses that people apply when inferring the opinion and behaviors of others from media coverage. There are two competing inference hypotheses discussed in the literature: While the reflection hypothesis assumes that the audience sees media content as a mirror of what the public thinks, persuasive press inference postulates that individuals perceive media as an influence on public opinion. Drawing on different research strands such as the spiral of silence theory, hostile media, persuasive press inference, and corrective action, several propositions are put forward that link these inference hypotheses to the media coverage and its effects on individual outcomes, and potential drivers are discussed. The propositions are then put to an initial test using an existing data set

Particle Detection Algorithms for Complex Plasmas

In complex plasmas, the behavior of freely floating micrometer sized particles is studied. The particles can be directly visualized and recorded by digital video cameras. To analyze the dynamics of single particles, reliable algorithms are required to accurately determine their positions to sub-pixel accuracy from the recorded images. Typically, straightforward algorithms are used for this task. Here, we combine the algorithms with common techniques for image processing. We study several algorithms and pre- and post-processing methods, and we investigate the impact of the choice of threshold parameters, including an automatic threshold detection. The results quantitatively show that each algorithm and method has its own advantage, often depending on the problem at hand. This knowledge is applicable not only to complex plasmas, but useful for any kind of comparable image-based particle tracking, e.g. in the field of colloids or granular matter

Measuring perceived 3D shape at multiple spatial scales

We present and test a novel multiscale representation of perceived 3D surface orientation: the orientation path. Using a multiscale probe, we measure perceived surface orientation at multiple spatial scales: linking the measurements for a given surface location yields that location's orientation path. The multiscale data obtained show that observers consistently see different surface orientations at different spatial scales. We demonstrate that such multiscale data can reveal multiscale differences between observers' percepts of a stimulus and the stimulus geometry. We also demonstrate the use of the orientation path in evaluating the multiscale effects of adding a depth cue to a 3D display