Time-resolved photometry of the nova remnants DM Gem, CP Lac, GI Mon, V400 Per, CT Ser and XX Tau

We present the first results of a photometric survey of poorly studied nova remnants in the Northern Hemisphere. The main results are as follows: DM Gem shows a modulation at 0.123 d (probably linked to the orbit) and rapid variations at ∼22 min. A moderate resolution spectrum taken at the time of the photometric observations shows intense He II λ4686 and Bowen emission, characteristic of an intermediate polar or a SW Sex star. Variability at 0.127 d and intense flickering (or quasi-periodic oscillations) are the main features of the light curve of CP Lac. A 0.1-mag dip lasting for ∼45 min is observed in GI Mon, which could be an eclipse. A clear modulation (probably related to the orbital motion) either at 0.179 d or 0.152 d is observed in the B-band light curve of V400 Per. The results for CT Ser point to an orbital period close to 0.16 d. Intense flickering is also characteristic of this old nova. Finally, XX Tau shows a possible periodic signal near 0.14 d and displays fast variability at ∼24 min. Its brightness seems to be modulated at ∼5 d. We relate this long periodicity to the motion of an eccentric/tilted accretion disc in the binary

Application of the Ring Theory in the Segmentation of Digital Images

Ring theory is one of the branches of the abstract algebra that has been broadly used in images. However, ring theory has not been very related with image segmentation. In this paper, we propose a new index of similarity among images using Zn rings and the entropy function. This new index was applied as a new stopping criterion to the Mean Shift Iterative Algorithm with the goal to reach a better segmentation. An analysis on the performance of the algorithm with this new stopping criterion is carried out. The obtained results proved that the new index is a suitable tool to compare images.Comment: Very interesting new index to compute the similarity among images. arXiv admin note: substantial text overlap with arXiv:1306.262

Following the yellow brick road? The Euro, the Czech Republic, Hungary and Poland.

This paper uses a combination of VAR and bootstrapping techniques to analyze whether the exchange rates of some New Member States of the EU have been used as output stabilizers (those of the Czech Republic, Hungary and Poland), during 1993-2004. This question is important because it provides a prior evaluation on the costs and benefits involved in entering the European Monetary Union (EMU). Joining the EMU is not optional for these countries but mandatory, although there is no definite deadline. Therefore, if the exchange rate works as a shock absorber, monetary independence could be retained for a longer period. Our main finding is that the exchange rate could be a stabilizing tool in Poland and the Czech Republic, although in Hungary it appears to act as a propagator of shocks. In addition, in these three countries, demand and monetary shocks account for most of the variability in both nominal and real exchange rates.EMU, exchange rate, Structural VAR, stationary bootstraps.

Technological sources of productivity growth in Japan, the U.S. and Germany

In this paper, we use a dynamic general equilibrium growth model to quantify the contribution of different technological sources to productivity growth in the three leading economies: Germany, Japan, and the U.S. The sources of technology are classified as representing either neutral progress or investment-specific progress. The latter can be split into two different types of equipment: information and communication technologies (ICT) and non-ICT equipment. We find that in the long run, neutral technological change is the main source of productivity growth in Germany. For Japan and the U.S., the main source of productivity growth is investment-specific technological change, mainly associated with ICT. We also find that a non negligible part of productivity growth has been due to technology specific to non-ICT equipment; this is mainly true after 1995.Productivity growth; Investment-specific progress; Neutral progress; Information and communication technology.

Following the yellow brick road? The Euro, the Czech Republic, Hungary and Poland

This paper uses a combination of VAR and bootstrapping techniques to analyze whether the exchange rates of some New Member States of the EU have been used as output stabilizers (those of the Czech Republic, Hungary and Poland), during 1993-2004. This question is important because it provides a prior evaluation on the costs and bene?ts involved in entering the European Monetary Union (EMU). Joining the EMU is not optional for these countries but mandatory, although there is no de?nite deadline. Therefore, if the exchange rate works as a shock absorber, monetary independence could be retained for a longer period. Our main ?nding is that the exchange rate could be a stabilizing tool in Poland and the Czech Republic, although in Hungary it appears to act as a propagator of shocks. In addition, in these three countries, demand and monetary shocks account for most of the variability in both nominal and real exchange rates.EMU, exchange rate, Structural VAR, stationary bootstraps

Productivity growth and technological change in Europe and the U.S.

This paper presents an evaluation on the technological sources of labor productivity growth across European countries and the US economy for the period 1980-2004. Assets of capital are divided into those related to the information and communication technologies (ICT), and non-ICT assets. Technological progress is divided into neutral change and investment specific change. Previous exercises have aimed at ICT as a serious contributor to the upsurge of US productivity from 1995 on. Contribution to productivity growth from each type of technological progress for the US and EU-15 countries is computed using two different approaches: a growth accounting and a general equilibrium. The US and Denmark are the countries with the larger contribution from ICT-technological progress. Overall, we find that Europe is well behind the US in terms of the effects of ICT technological change.Productivity growth, Investment-specific technological change, Neutral technological change

Hygroscopicity issues in powder and grain technology

The effect of hygroscopicity on flowability of powders and bulk solids with applications in the packaging industry is experimentally and numerically investigated. Firstly, four granular materials are tested at different water contents to study the impact of relative humidity on some hydro-mechanical properties, namely the hydraulic diffusivity on wetting, as well as the shear strength and compressibility properties of the materials. Next, a capillary model covering a wider water content range –compared to the previous tests– is applied to discrete element simulations of a granular column collapse set-up. These simulations give further insight into important aspects of grain hygroscopicity in packaging and other industrial applications (such as the kinematics of flow and flowability issues), which are outside the scope of conventional experimental testing.Postprint (published version

Factors that explain the use of ICT in secondary-education classrooms: the role of teacher characteristics and school infrastructure

Paradoxically, in Spain, schools have relatively ample information and communication technology (ICT)infrastructure but low levels of classroom ICT use. In this study, we analyse the role of school ICTinfrastructure and teacher characteristics to explain ICT use in education. We use data from the Spanishsample in the 2013 Teaching and Learning International Study (TALIS), which consists of 3339 teachersfrom 192 secondary education centres. The analysis was conducted using multilevel logistic regressionmodels. The principal results indicate that the availability of educational software, teacher ICT training,collaboration among teachers, perceived self-efficacy, and teaching concepts influence classroom ICT use.School hardware and internet-connection infrastructure are less significant. Based on thefindings,recommendations are presented to orient Spanish educational policy to encourage the use of ICT in classroom