Experiments on anisotropic radial viscous fingering

We observe dendritic patterns in fluid flow in an anisotropic Hele-Shaw cell and measure the tip shapes and trajectories of individual dendritic branches under conditions where the pattern growth appears to be dominated by surface tension anisotropy and also under conditions where kinetic effects appear dominant. In each case, the tip position depends on a power law in the time, but the exponent of this power law can vary significantly among flow realizations. Averaging many growth exponents a yields a =0.640.09 in the surface tension dominated regime and a =0.660.09 in the kinetic regime. Restricting the analysis to realizations when a is very close to 0.6 shows great regularity across pattern regimes in the coefficient of the temporal dependence of the tip trajectory.

Out-of-sample forecast tests robust to the choice of window size

This paper proposes new methodologies for evaluating out-of-sample forecastingperformance that are robust to the choice of the estimation window size. The methodologies involve evaluating the predictive ability of forecasting models over a wide rangeof window sizes. We show that the tests proposed in the literature may lack the powerto detect predictive ability and might be subject to data snooping across differentwindow sizes if used repeatedly. An empirical application shows the usefulness of themethodologies for evaluating exchange rate models' forecasting ability.

The External validity in economic experiments

One of the most important questions regarding experimental economics is the external validity of laboratory experiments. This paper goes through a study that tests the generalizability of a Dictator Game as a laboratory analogue for a naturally occurringdecision-making context of teacher absenteeism. Because lab and naturally-occurring environments systematically differ we then discuss other factors that might strongly affect the choices that individuals make. We conclude that the dichotomy drawn between labexperiments and data collected from natural settings is a false one. A combination of the two would provide deeper and better insights than either separately.

Planning under partial observability by classical replanning: theory and experiments

Planning with partial observability can be formulated as a non-deterministic search problem in belief space. The problem is harder than classical planning as keeping track of beliefs is harder than keeping track of states, and searching for action policies is harder than searching for action sequences. In this work, we develop a framework for partial observability that avoids these limitations and leads to a planner that scales up to larger problems. For this, the class of problems is restricted to those in which 1) the non-unary clauses representing the uncertainty about the initial situation are nvariant, and 2) variables that are hidden in the initial situation do not appear in the body of conditional effects, which are all assumed to be deterministic. We show that such problems can be translated in linear time into equivalent fully observable non-deterministic planning problems, and that an slight extension of this translation renders the problem solvable by means of classical planners. The whole approach is sound and complete provided that in addition, the state-space is connected. Experiments are also reported.

MPRO-Spanish: development and experiments with a linguistic parser for Spanish texts

This paper describes the main features and present results of MPRO-Spanish, a parser for morphological and syntactic analysis of unrestricted Spanish text developed at the IAI1. This parser makes direct use of X-phrase structure rules to handle a variety of patterns from derivational morphology and syntactic structure. Both analyses, morphological and syntactic, are realised by two subsequent modules. One module analyses and disambiguates the source words at morphological level while the other consists of a series of programs and a deterministic, procedural and explicit grammar. The article explains the main features of MPRO and resumes some of the experiments on some of its applications, some of which still being implemented like the monolingual and bilingual term extraction while others need further work like indexing. The results and applications obtained so far with simple and relatively complex sentences give us grounds to believe in its reliability.

Relaxation and derelaxation of pure and hydrogenated amorphous silicon during thermal annealing experiments

The structural relaxation of pure amorphous silicon a-Si and hydrogenated amorphous silicon a-Si:H materials, that occurs during thermal annealing experiments, has been analyzed by Raman spectroscopy and differential scanning calorimetry. Unlike a-Si, the heat evolved from a-Si:H cannot be explained by relaxation of the Si-Si network strain but it reveals a derelaxation of the bond angle strain. Since the state of relaxation after annealing is very similar for pure and hydrogenated materials, our results give strong experimental support to the predicted configurational gap between a-Si and crystalline silicon.

Knowing What to Respond in the Future Does Not Cancel the Influence of Past Events

Everyday tasks seldom involve isolate actions but sequences of them. We can see whether previous actions influence the current one by exploring the response time to controlled sequences of stimuli. Specifically, depending on the response-stimulus temporal interval (RSI), different mechanisms have been proposed to explain sequential effects in two-choice serial response tasks. Whereas an automatic facilitation mechanism is thought to produce a benefit for response repetitions at short RSIs, subjective expectancies are considered to replace the automatic facilitation at longer RSIs, producing a cost-benefit pattern: repetitions are faster after other repetitions but they are slower after alternations. However, there is not direct evidence showing the impact of subjective expectancies on sequential effects. By using a fixed sequence, the results of the reported experiment showed that the repetition effect was enhanced in participants who acquired complete knowledge of the order. Nevertheless, a similar cost-benefit pattern was observed in all participants and in all learning blocks. Therefore, results of the experiment suggest that sequential effects, including the cost-benefit pattern, are the consequence of automatic mechanisms which operate independently of (and simultaneously with) explicit knowledge of the sequence or other subjective expectancies.

The determinants of contractual choice for private involvement in infrastructure projects in the United States

Reliance on private partners to help provide infrastructure investment and service delivery is increasing in the United States. Numerous studies have examined the determinants of the degree of private participation in infrastructure projects as governed by contract type. We depart from this simple public/private dichotomy by examining a rich set of contractual arrangements. We utilize both municipal and state-level data on 472 projects of various types completed between 1985 and 2008. Our estimates indicate that infrastructure characteristics, particularly those that reflect stand alone versus network characteristics, are key factors influencing the extent of private participation. Fiscal variables, such as a jurisdiction’s relative debt level, and basic controls, such as population and locality of government, increase the degree of private participation, while a greater tax burden reduces private participation.

Recovery Risk and Labor Costs in Public-Private Partnerships : Contractual Choice in the US Water industry

We use an ordered logistic model to empirically examine the factors that explain varying degrees of private involvement in the U.S. water sector through public-private partnerships. Our estimates suggest that a variety of factors help explain greater private participation in this sector. We find that the risk to private participants regarding cost recovery is an important driver of private participation. The relative cost of labor is also a key factor in determining the degree of private involvement in the contract choice. When public wages are high relative to private wages, private participation is viewed as a source of cost savings. We thus find two main drivers of greater private involvement: one encouraging private participation by reducing risk, and another encouraging government to seek out private participation in lowering costs.

Seguiment d'extremitats de ratolins en experiments optogenètics

L'objectiu principal d'aquest treball és aplicar tècniques de visió articial per aconseguir localitzar i fer el seguiment de les extremitats dels ratolins dins l'entorn de prova de les investigacions d'optogenètica del grup de recerca del Neuroscience Institute de la Universitat de Princeton, Nova Jersey.

Relaxation and derelaxation of pure and hydrogenated amorphous silicon during thermal annealing experiments

The structural relaxation of pure amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) materials, that occurs during thermal annealing experiments, has been analyzed by Raman spectroscopy and differential scanning calorimetry. Unlike a-Si, the heat evolved from a-Si:H cannot be explained by relaxation of the Si-Si network strain but it reveals a derelaxation of the bond angle strain. Since the state of relaxation after annealing is very similar for pure and hydrogenated materials, our results give strong experimental support to the predicted configurational gap between a-Si and crystalline silicon

Consumer valuation of energy-saving features of residential air conditioners with hedonic and choice models

The promotion of energy-efficient appliances is necessary to reduce the energetic and environmental burden of the household sector. However, many studies have reported that a typical consumer underestimates the benefits of energy-saving investment on the purchase of household electric appliances. To analyze this energy-efficiency gap problem, many scholars have estimated implicit discount rates that consumers use for energy-consuming durables. Although both hedonic and choice models have been used in previous studies, a comparison between two models has not yet been done. This study uses point of sale data about Japanese residential air conditioners and estimates implicit discounts rates with both hedonic and choice models. Both models demonstrate that a typical consumer underinvests in energy efficiency. Although choice models estimate a lower implicit discount rate than hedonic models, the latter models estimate the values of other product characteristics more consistently than choice models.

Effects of institutional environment and technology development on payment choice

The purpose of this paper is to analyze the combination of institutional factors and technology advances as determinants of payment systems choice. The theoretical set up suggests that countries entering into a new institutional environment approach accepting group attitudes towards payment choices as a consequence of institutional pressure and technology development. We apply the results of the model to 2004 European Union enlargement process. Results confirm the relevance of both institutional environment and technology development in retail payment system decisions of newly acceded countries.

Programming and analysing measurement experiments using the PicoCricket system

The aim of this project is to get used to another kind of programming. Since now, I used very complex programming languages to develop applications or even to program microcontrollers, but PicoCricket system is the evidence that we don’t need so complex development tools to get functional devices. PicoCricket system is the clear example of simple programming to make devices work the way we programmed it. There’s an easy but effective way to programs mall devices just saying what we want them to do. We cannot do complex algorithms and mathematical operations but we can program them in a short time. Nowadays, the easier and faster we produce, the more we earn. So the tendency is to develop fast, cheap and easy, and PicoCricket system can do it.