Some methodological issues in the design of CIAO - A generic, parallel concurrent constraint system

We informally discuss several issues related to the parallel execution of logic programming systems and concurrent logic programming systems, and their generalization to constraint programming. We propose a new view of these systems, based on a particular definition of parallelism. We argüe that, under this view, a large number of the actual systems and models can be explained through the application, at different levéis of granularity, of only a few basic principies: determinism, non-failure, independence (also referred to as stability), granularity, etc. Also, and based on the convergence of concepts that this view brings, we sketch a model for the implementation of several parallel constraint logic programming source languages and models based on a common, generic abstract machine and an intermedíate kernel language.

Some methodological issues in the design of CIAO, a generic, parallel concurrent constraint system

We informally discuss several issues related to the parallel execution of logic programming systems and concurrent logic programming systems, and their generalization to constraint programming. We propose a new view of these systems, based on a particular definition of parallelism. We argüe that, under this view, a large number of the actual systems and models can be explained through the application, at different levéis of granularity, of only a few basic principies: determinism, non-failure, independence (also referred to as stability), granularity, etc. Also, and based on the convergence of concepts that this view brings, we sketch a model for the implementation of several parallel constraint logic programming source languages and models based on a common, generic abstract machine and an intermedíate kernel language.

Methodological issues of LCA application to building sector: challenges, risks and opportunities

Methodological issues of LCA application to building sector: challenges, risks and opportunities

Remarks on Compositionality (with reference to Gennadij Zeldoviè's article “On Russian Dative Reflexive Constructions: Accidental or Compositional”)

Zeldovič’s article “On Russian Dative Reflexive Constructions: Accidental or Compositional” is very interesting. It contains a good deal of insightful observations and is painstakingly argued. Its research object is the Russian dative reflexive construction (DRC) like Ивану не работается ‘Ivan does not feel like reading’. The aim of the article is to show that the DRC is fully compositional. Like many other works by Zeldovič, the article is written from the radical-pragmatic perspective and constitutes a very good illustration of this trend in linguistic research. The language material that it analyzes has often been investigated within more traditional frameworks, especially in Russian linguistics, which makes Zeldovič’s novel approach to the old problem particularly interesting. In this short note I would like (by way of discussion) to address two problems connected not so much with the DRC itself as with methodological issues concerning compositionality. I will dwell on two aspects: on the question of how we understand the very concept of compositionality, and what instruments we employ to demonstrate it.

Comparasion of road traffic emission models in Madrid (Spain)

Many cities in Europe have difficulties to meet the air quality standards set by the European legislation, most particularly the annual mean Limit Value for NO2. Road transport is often the main source of air pollution in urban areas and therefore, there is an increasing need to estimate current and future traffic emissions as accurately as possible. As a consequence, a number of specific emission models and emission factors databases have been developed recently. They present important methodological differences and may result in largely diverging emission figures and thus may lead to alternative policy recommendations. This study compares two approaches to estimate road traffic emissions in Madrid (Spain): the COmputer Programme to calculate Emissions from Road Transport (COPERT4 v.8.1) and the Handbook Emission Factors for Road Transport (HBEFA v.3.1), representative of the ‘average-speed’ and ‘traffic situation’ model types respectively. The input information (e.g. fleet composition, vehicle kilometres travelled, traffic intensity, road type, etc.) was provided by the traffic model developed by the Madrid City Council along with observations from field campaigns. Hourly emissions were computed for nearly 15 000 road segments distributed in 9 management areas covering the Madrid city and surroundings. Total annual NOX emissions predicted by HBEFA were a 21% higher than those of COPERT. The discrepancies for NO2 were lower (13%) since resulting average NO2/NOX ratios are lower for HBEFA. The larger differences are related to diesel vehicle emissions under “stop & go” traffic conditions, very common in distributor/secondary roads of the Madrid metropolitan area. In order to understand the representativeness of these results, the resulting emissions were integrated in an urban scale inventory used to drive mesoscale air quality simulations with the Community Multiscale Air Quality (CMAQ) modelling system (1 km2 resolution). Modelled NO2 concentrations were compared with observations through a series of statistics. Although there are no remarkable differences between both model runs, the results suggest that HBEFA may overestimate traffic emissions. However, the results are strongly influenced by methodological issues and limitations of the traffic model. This study was useful to provide a first alternative estimate to the official emission inventory in Madrid and to identify the main features of the traffic model that should be improved to support the application of an emission system based on “real world” emission factors.

Residential self-selection and geographical scales in trip frequency.

Neighbourhood representation and scale used to measure the built environment have been treated in many ways. However, it is anything but clear what representation of neighbourhood is the most feasible in the existing literature. This paper presents an exhaustive analysis of built environment attributes through three spatial scales. For this purpose multiple data sources are integrated, and a set of 943 observations is analysed. This paper simultaneously analyses the influence of two methodological issues in the study of the relationship between built environment and travel behaviour: (1) detailed representation of neighbourhood by testing different spatial scales; (2) the influence of unobserved individual sensitivity to built environment attributes. The results show that different spatial scales of built environment attributes produce different results. Hence, it is important to produce local and regional transport measures, according to geographical scale. Additionally, the results show significant sensitivity to built environment attributes depending on place of residence. This effect, called residential sorting, acquires different magnitudes depending on the geographical scale used to measure the built environment attributes. Spatial scales risk to the stability of model results. Hence, transportation modellers and planners must take into account both effects of self-selection and spatial scales.

Territorial cohesion impacts of high-speed rail under different zoning systems

Large-scale transport infrastructure projects such as high-speed rail (HSR) produce significant effects on the spatial distribution of accessibility. These effects, commonly known as territorial cohesion effects, are receiving increasing attention in the research literature. However, there is little empirical research into the sensitivity of these cohesion results to methodological issues such as the definition of the limits of the study area or the zoning system. In a previous paper (Ortega et al., 2012), we investigated the influence of scale issues, comparing the cohesion results obtained at four different planning levels. This paper makes an additional contribution to our research with the investigation of the influence of zoning issues. We analyze the extent to which changes in the size of the units of analysis influence the measurement of spatial inequalities. The methodology is tested by application to the Galician (north-western) HSR corridor, with a length of nearly 670 km, included in the Spanish PEIT (Strategic Transport and Infrastructure Plan) 2005-2020. We calculated the accessibility indicators for the Galician HSR corridor and assessed their corresponding territorial distribution. We used five alternative zoning systems depending on the method of data representation used (vector or raster), and the level of detail (cartographic accuracy or cell size). Our results suggest that the choice between a vector-based and raster-based system has important implications. The vector system produces a higher mean accessibility value and a more polarized accessibility distribution than raster systems. The increased pixel size of raster-based systems tends to give rise to higher mean accessibility values and a more balanced accessibility distribution. Our findings strongly encourage spatial analysts to acknowledge that the results of their analyses may vary widely according to the definition of the units of analysis.

Social issues in sustainable supply chain networks: state of the art and further research directions

The study of supply networks sustainability is a field with a long path behind. Nonetheless, most studies to date are focused on the environmental sub dimension of sustainability, while the social perspective in supply chain networks research still shows a potential for pioneering contri butions. Moreover, from the development standpoint we have observed a paradigm shift advancing from a narrow concept of development, centered on purely economic dimensions, towards more refined issues such as inclusive business, shared value or poverty footprint, all of which are highly related to supply chain activities. In this paper we present a review of the current state of the art on social sustainability of supply chains and we identify the main existing trends in this field. After conducting this study, we can state that a new sphere of knowledge is emerging at the interface between sustainable supply chain networks and development research. The academic community is called to play an important dovetailing role in this scenario by advancing both conceptual and methodological contributions.

Identifying wind power ramp causes from multivariate datasets: a methodological proposal and its application to reanalysis data.

Forecasting abrupt variations in wind power generation (the so-called ramps) helps achieve large scale wind power integration. One of the main issues to be confronted when addressing wind power ramp forecasting is the way in which relevant information is identified from large datasets to optimally feed forecasting models. To this end, an innovative methodology oriented to systematically relate multivariate datasets to ramp events is presented. The methodology comprises two stages: the identification of relevant features in the data and the assessment of the dependence between these features and ramp occurrence. As a test case, the proposed methodology was employed to explore the relationships between atmospheric dynamics at the global/synoptic scales and ramp events experienced in two wind farms located in Spain. The achieved results suggested different connection degrees between these atmospheric scales and ramp occurrence. For one of the wind farms, it was found that ramp events could be partly explained from regional circulations and zonal pressure gradients. To perform a comprehensive analysis of ramp underlying causes, the proposed methodology could be applied to datasets related to other stages of the wind-topower conversion chain.