Experimental Evaluation of Branching Schemes for the CSP

The search strategy of a CP solver is determined by the variable and value ordering heuristics it employs and by the branching scheme it follows. Although the effects of variable and value ordering heuristics on search effort have been widely studied, the effects of different branching schemes have received less attention. In this paper we study this effect through an experimental evaluation that includes standard branching schemes such as 2-way, d-way, and dichotomic domain splitting, as well as variations of set branching where branching is performed on sets of values. We also propose and evaluate a generic approach to set branching where the partition of a domain into sets is created using the scores assigned to values by a value ordering heuristic, and a clustering algorithm from machine learning. Experimental results demonstrate that although exponential differences between branching schemes, as predicted in theory between 2-way and d-way branching, are not very common, still the choice of branching scheme can make quite a difference on certain classes of problems. Set branching methods are very competitive with 2-way branching and outperform it on some problem classes. A statistical analysis of the results reveals that our generic clustering-based set branching method is the best among the methods compared.Comment: To appear in the 3rd workshop on techniques for implementing constraint programming systems (TRICS workshop at the 16th CP Conference), St. Andrews, Scotland 201

Comparative studies on energy efficiency and GHG emissions between conventional and organic olive groves in Greece and Portugal

Nowadays, traditional farming based on achieving high yields using high inputs, shifts gradu-ally towards maximum possible crop yield using minimal inputs in an optimized way or to-wards organic farming. This is usually accomplishing by low yield of high quality products without using conventional agrochemicals (i.e. fertilizers, pesticides). In general, this last ap-proach leads to lower energy consumption per unit area of land, therefore lower cost and reduced greenhouse gas (GHG) emissions. However, in a global perspective it has the risk of significant total production reduction. Hence, it is vital to consider energy efficiency im-provement, namely the decrease of primary energy consumption for the production of a unit of agricultural product (expressed in weight or volume units), within the farm boundaries. Im-provement of energy efficiency is a key parameter affecting positively the overall efficiency of crop farming systems in terms of energy and GHG emissions. In the present paper, two show cases of olive groves in Greece (“Sterea Ellada” region) and Portugal (“Alentejo” re-gion) were compared to illustrate the effect on energy efficiency and GHG emissions when moving from conventional to organic olive grove cultivations in these different locations. The analysis was based on two simple framework models using information provided by farmers and literature data regarding the inputs and outputs of each olive grove. The models were adjusted according to the olives’ variety, the agricultural practices followed and the location of the production system. Considering the specific energy consumption per unit of product, in the case of the Greek olive grove, organic farming reduces energy consumption by 13.9%, while the final yield is reduced by 30%. GHG emissions are reduced by 58%. In the case of the Portuguese olive grove, organic farming significantly reduces crop yield (54.5%), while, energy efficiency is improved by 9.7% and GHG emissions are reduced by 26%

Assessing the confidence of sociology students on using quantitative research methods through Technology Enhanced Learning

This research aims to investigate the ways Technology Enhanced Learning can facilitate the learning of quantitative research methods in social sciences degrees. Specifically, how sociologists tend to avoid statistical modules due to anxiety and inadequate teaching methods. Digital competency of sociologists is a crucial debate in the literature and technological developments provide a useful tool for learning, which however in not being exploited enough. This study explores how Computer Based Learning, Computer Assisted Learning and Computer Supported Collaborative learning sessions can address the increased statistics anxiety observed in students that study social sciences.   The analyses corroborated the main assumptions drawn in the relevant literature. Students in social sciences tend to present social anxiety and dissociate from quantitative methods, lacking a crucial tool for their future as social scientists. Technology enhanced learning methods were found to be effective in the acquisition of knowledge and understanding of quantitative methods. Participants highlighted the need of technology to be an integral part in learning, that extended communication between students and teachers is beneficial, that future technologies must be an ongoing part of curriculums and institutions should focus on equipping students with the ability to use digital tools for their future employment.    Consequently, further research is recommended on the ways institutions should respond to the digital transformation of the social sciences and education, on how to integrate new technologies without ignoring the beneficial contribution of current and established methods, and on what the future brings for contemporary social sciences in the dawn of artificial intelligence

Comparative Analysis of Energy Efficiency in Wheat Production in Different Climate Conditions of Europe

This paper presents results concerning energy efficiency of wheat production considered in the context of specific energy input variation in different climatic conditions of Europe as well as case studies on implementation of selected energy saving measures in practice. The source data collected from the six european union (EU) countries represent five agricultural regions of continental Europe and three climates: continental, temperate and Mediterranean. The life cycle assessment (LCA) methodology was applied to analyze the data excluding of pre-farm gate activities. The total primary energy consumption was decomposed into main energy input streams and it was regressed to yield. In order to compare energy efficiency of wheat production across the geographical areas, the data envelopment analysis (DEA) was applied. It was shown that the highest wheat yield (6.7 t/ha to 8.7 t/ha) at the lowest specific energy input (2.08 GJ/t to 2.56 GJ/t) is unique for temperate climate conditions. The yield in continental and Mediterranean climatic conditions is on average lower by 1.3 t/ha and 2.7 t/ha and energy efficiency lower by 14% and 38%, respectively. The case studies have shown that the energy saving activities in wheat production may be universal for the climatic zones or specific for a given geographical location. It was stated that trade-offs between energy, economic, and environmental effects, which are associated with implementation of a given energy saving measure or a set of measures to a great extent depend on the current energy efficiency status of the farm and opportunity for investment, which varies substantially across Europe

Case studies and comparative analysis of energy efficiency in wheat production in different climatic conditions of Europe

The paper presents results concerning energy efficiency of wheat production considered in the context of specific energy input variation in different climatic conditions of Europe as well as case studies on implementation of selected energy saving measures in practice. It was shown that the highest wheat yield (6.7-8.7 t·ha-1) at the lowest specific energy input (2.08-2.56 GJ·t-1) is unique for temperate climate conditions. The yield in continental and Mediter-ranean climatic conditions is on average lower by 1.3 t·ha-1 and 2.7 t·ha-1 and energy effi-ciency lower by 14% and 38%, respectively. The case studies have shown that the energy saving activities in wheat production may be universal for the climatic zones or specific for a given geographical location. It was stated that trade-offs between energy, economic and en-vironmental effects, which are associated with implementation of a given energy saving measure or a set of measures to a great extent depend on the current energy efficiency sta-tus of the farm and opportunity for investment, which varies substantially across Europe

OROGRAPHIC EFFECT ON HEAVY RAINFALL IN CHALKIDIKI PENINSULA (GREECE) INDUCED BY A MEDITERRANEAN COLD FRONT: A CASE STUDY ON 7 to 8 OF OCTOBER 2000

Abstract. The exceptional heavy rainfall, in Chalkidiki peninsula-Greece, of 240 mm in a very short time period of 6 hours (380 mm in 24 hours) is analyzed. This area geographically located in the NW shores of the Aegean Sea, commonly has not the experience of frequent heavy rainfall events, and consequently the natural hydrographic network was not able to restrain this strong rainfall shock. Thus the result of the impact of this phenomenon was floods and damages in the properties of the residents with a very significant cost of hundredths thousands of Euros. This heavy rain phenomenon has been analyzed studying the role of the topography, the role of the nearby warm sea and the prevailing meteorological conditions resulting from the passage of the cold frond. This front was moving almost from south to north passing at first above the warm Aegean Sea surface, where it was supplied with huge amounts of water vapors, giving a total precipitable water value up to 32,0 mm. Then the very humid air forced uplifting, due to the intense relief of the mountainous peninsula, resulting to this torrential rainfall. All the relevant meteorological data and information about atmospheric instability, instability indexes and precipitable water available arising to from five upper air stations and the synoptic charts of surface, 850, 700, 500 and 300 hPa were analyzed in order to describe in details this heavy rain phenomenon