Popular Ensemble Methods: An Empirical Study

An ensemble consists of a set of individually trained classifiers (such as neural networks or decision trees) whose predictions are combined when classifying novel instances. Previous research has shown that an ensemble is often more accurate than any of the single classifiers in the ensemble. Bagging (Breiman, 1996c) and Boosting (Freund and Shapire, 1996; Shapire, 1990) are two relatively new but popular methods for producing ensembles. In this paper we evaluate these methods on 23 data sets using both neural networks and decision trees as our classification algorithm. Our results clearly indicate a number of conclusions. First, while Bagging is almost always more accurate than a single classifier, it is sometimes much less accurate than Boosting. On the other hand, Boosting can create ensembles that are less accurate than a single classifier -- especially when using neural networks. Analysis indicates that the performance of the Boosting methods is dependent on the characteristics of the data set being examined. In fact, further results show that Boosting ensembles may overfit noisy data sets, thus decreasing its performance. Finally, consistent with previous studies, our work suggests that most of the gain in an ensemble's performance comes in the first few classifiers combined; however, relatively large gains can be seen up to 25 classifiers when Boosting decision trees

Options for transporting Russian gas to Western Europe: A game-theoretic simulation analysis

This paper examines the perspectives of Russian gas exports to Western Europe and the strategic options of the CIS gas transiting countries, namely Ukraine and Belarus. The development of a new transit corridor through Belarus (the Yamal-Europe pipeline), depriving Ukraine of its former monopoly, has modified the situation profoundly. The thrust of the paper is an analysis of nthe strategies that Ukraine and Belarus may pursue in transiting Russian gas: non-cooperative duopoly, cooperative duopoly, and individual or collective cooperation with Russia. Using a demand function for Western European gas imports from Russia, we estimate prices and quantities for gas transit, the expected profits for Russia, Ukraine, and Belarus, and the resulting import prices for Western Europe. The results indicate that Ukraine suffers a loss of several hundred million USD annually from the market entry of Belarus, Belarus has an incentive to increase its gas transit capacity to at least 56 billion cubic meters, and Russia's profits increase, in particular when it unites its gas sector with Belarus and Ukraine. For Western Europe, all scenarios indicate an increase in welfare through the new pipeline, but also an increasing importance of gas imports from Russia. -- Der Beitrag untersucht die Perspektiven russischer Gasexporte nach Westeuropa und die strategischen Optionen der Gastransitländer Ukraine und Belarus. Durch den Neu- und Ausbau eines Gastransitkorridors durch Belarus (die Jamal-Europa-Pipeline) geht die bisherige Monopolstellung der Ukraine als Transitland verloren. Ziel der Arbeit ist die Modellierung und Quantifizierung unterschiedlicher Wettbewerbsstrategien, wie das nichtkooperative Duopol, das kooperative Duopol, oder die individuelle bzw. kollektive Kooperation der Transitländer mit Russland. Hierfür werden Exportpreise und mengen sowie die resultierenden Gewinne der Spieler geschätzt. Durch den Markteintritt von Belarus ergeben sich erhebliche Verluste für die Ukraine, während sich Belarus mit einem Ausbau seiner Kapazitäten auf 56 Mrd. m3 noch besser stellt. Russlands Gewinne steigen insbesondere durch die vertikale Integration der belarussischen und ukrainischen Gassektoren. Für Westeuropa legen die Ergebnisse erhebliche Wohlfahrtsgewinne durch den Pipelineausbau nahe, gleichzeitig aber auch eine gestiegene Abhängigkeit von Gasimporten aus Russland.Gas,pipelines,strategic behavior,CIS,Russia

Power utility re-regulation in East European and CIS transformation countries (1990-1999) : an institutional interpretation

This paper analyzes the process of power utility re-regulation in Eastern Europe and the CIS during the decade of systemic transformation (1990-1999); in particular, it explores reasons why early attempts to introduce competition-oriented reform models have not succeeded. We discuss advantages and disadvantages of various reform models from an institutional economic perspective. The approaches to and results of power sector reform in Eastern Europe are assessed; quantitative indicators are wholesale and retail prices, cost coverage ratios, investment levels, and the degree of unbundling and privatization. The paper concludes that a gradual approach to reforms may have been appropriate for the first years of systemic transformation, but that today, ten years later, there is no reason to delay market-oriented reforms any longer.Der Beitrag untersucht die Re-Regulierung der Stromwirtschaften in den osteuropäischen Transformationsländern zwischen 1990 und 1999; insbesondere wird geprüft, warum frühe marktorientierte Reformansätze gescheitert sind. Nach einem Vergleich alternativer Reformmodelle werden der Prozess und die Ergebnisse der Re-Regulierung analysiert; quantitative Indikatoren sind die absoluten und relativen Preise, Kostendeckungsgrade, die Höhe der Investitionen und da Ausmaß der Liberalisierung und Privatisierung. Die vorliegende Evidenz legt nahe, dass aufgrund technischer und institutioneller Schwierigkeiten eine umgehende Marktöffnung nicht möglich war; andererseits gibt es heute, 10 Jahre später, keinen Grund mehr, die Liberalisierung und Privatisierung der Stromwirtschaft weiter zu verzögern

Nanofriction mechanisms derived from the dependence of friction on load and sliding velocity from air to UHV on hydrophilic silicon

This paper examines friction as a function of the sliding velocity and applied normal load from air to UHV in a scanning force microscope (SFM) experiment in which a sharp silicon tip slides against a flat Si(100) sample. Under ambient conditions, both surfaces are covered by a native oxide, which is hydrophilic. During pump-down in the vacuum chamber housing the SFM, the behavior of friction as a function of the applied normal load and the sliding velocity undergoes a change. By analyzing these changes it is possible to identify three distinct friction regimes with corresponding contact properties: (a) friction dominated by the additional normal forces induced by capillarity due to the presence of thick water films, (b) higher drag force from ordering effects present in thin water layers and (c) low friction due to direct solid-solid contact for the sample with the counterbody. Depending on environmental conditions and the applied normal load, all three mechanisms may be present at one time. Their individual contributions can be identified by investigating the dependence of friction on the applied normal load as well as on the sliding velocity in different pressure regimes, thus providing information about nanoscale friction mechanisms

Power utility re-regulation in East European and CIS transformation countries (1990 - 1999): An institutional interpretation

This paper analyzes the process of power utility re-regulation in Eastern Europe and the CIS during the decade of systemic transformation (1990-1999); in particular, it explores reasons why early attempts to introduce competition-oriented reform models have not succeeded. We discuss advantages and disadvantages of various reform models from an institutional economic perspective. The approaches to and results of power sector reform in Eastern Europe are assessed; quantitative indicators are wholesale and retail prices, cost coverage ratios, investment levels, and the degree of unbundling and privatization. The paper concludes that a gradual approach to reforms may have been appropriate for the first years of systemic transformation, but that today, ten years later, there is no reason to delay market-oriented reforms any longer.Der Beitrag untersucht die Re-Regulierung der Stromwirtschaften in den osteuropäischen Transformationsländern zwischen 1990 und 1999; insbesondere wird geprüft, warum frühe marktorientierte Reformansätze gescheitert sind. Nach einem Vergleich alternativer Reformmodelle werden der Prozess und die Ergebnisse der Re-Regulierung analysiert; quantitative Indikatoren sind die absoluten und relativen Preise, Kostendeckungsgrade, die Höhe der Investitionen und da Ausmaß der Liberalisierung und Privatisierung. Die vorliegende Evidenz legt nahe, dass aufgrund technischer und institutioneller Schwierigkeiten eine umgehende Marktöffnung nicht möglich war; andererseits gibt es heute, 10 Jahre später, keinen Grund mehr, die Liberalisierung und Privatisierung der Stromwirtschaft weiter zu verzögern

Options for transporting Russian gas to Western Europe: A game-theoretic simulation analysis

This paper examines the perspectives of Russian gas exports to Western Europe and the strategic options of the CIS gas transiting countries, namely Ukraine and Belarus. The development of a new transit corridor through Belarus (the Yamal-Europe pipeline), depriving Ukraine of its former monopoly, has modified the situation profoundly. The thrust of the paper is an analysis of nthe strategies that Ukraine and Belarus may pursue in transiting Russian gas: non-cooperative duopoly, cooperative duopoly, and individual or collective cooperation with Russia. Using a demand function for Western European gas imports from Russia, we estimate prices and quantities for gas transit, the expected profits for Russia, Ukraine, and Belarus, and the resulting import prices for Western Europe. The results indicate that Ukraine suffers a loss of several hundred million USD annually from the market entry of Belarus, Belarus has an incentive to increase its gas transit capacity to at least 56 billion cubic meters, and Russia's profits increase, in particular when it unites its gas sector with Belarus and Ukraine. For Western Europe, all scenarios indicate an increase in welfare through the new pipeline, but also an increasing importance of gas imports from Russia.Der Beitrag untersucht die Perspektiven russischer Gasexporte nach Westeuropa und die strategischen Optionen der Gastransitländer Ukraine und Belarus. Durch den Neu- und Ausbau eines Gastransitkorridors durch Belarus (die Jamal-Europa-Pipeline) geht die bisherige Monopolstellung der Ukraine als Transitland verloren. Ziel der Arbeit ist die Modellierung und Quantifizierung unterschiedlicher Wettbewerbsstrategien, wie das nichtkooperative Duopol, das kooperative Duopol, oder die individuelle bzw. kollektive Kooperation der Transitländer mit Russland. Hierfür werden Exportpreise und -mengen sowie die resultierenden Gewinne der Spieler geschätzt. Durch den Markteintritt von Belarus ergeben sich erhebliche Verluste für die Ukraine, während sich Belarus mit einem Ausbau seiner Kapazitäten auf 56 Mrd. m3 noch besser stellt. Russlands Gewinne steigen insbesondere durch die vertikale Integration der belarussischen und ukrainischen Gassektoren. Für Westeuropa legen die Ergebnisse erhebliche Wohlfahrtsgewinne durch den Pipelineausbau nahe, gleichzeitig aber auch eine gestiegene Abhängigkeit von Gasimporten aus Russland

Limb imaging of the Venus O2 visible nightglow with the Venus Monitoring Camera

We investigated the Venus O2 visible nightglow with imagery from the Venus Monitoring Camera on Venus Express. Drawing from data collected between April 2007 and January 2011, we study the global distribution of this emission, discovered in the late 70s by the Venera 9 and 10 missions. The inferred limb-viewing intensities are on the order of 150 kiloRayleighs at the lower latitudes and seem to drop somewhat towards the poles. The emission is generally stable, although there are episodes when the intensities rise up to 500 kR. We compare a set of Venus Monitoring Camera observations with coincident measurements of the O2 nightglow at 1.27 {\mu}m made with the Visible and Infrared Thermal Imaging Spectrometer, also on Venus Express. From the evidence gathered in this and past works, we suggest a direct correlation between the instantaneous emissions from the two O2 nightglow systems. Possible implications regarding the uncertain origin of the atomic oxygen green line at 557.7 nm are noted.Comment: 7 pages, 3 figure

Применение программного продукта Eclipse для оптимизации разработки нефтяных месторождений Западно-Сибирского региона

Применение программного продукта Eclipse для оптимизации разработки нефтяных месторождений Западно-Сибирского регионаApplication software Eclipse to optimize the development of oil fields of West Siberi

Using airborne LiDAR Survey to explore historic-era archaeological landscapes of Montserrat in the eastern Caribbean

This article describes what appears to be the first archaeological application of airborne LiDAR survey to historic-era landscapes in the Caribbean archipelago, on the island of Montserrat. LiDAR is proving invaluable in extending the reach of traditional pedestrian survey into less favorable areas, such as those covered by dense neotropical forest and by ashfall from the past two decades of active eruptions by the Soufrière Hills volcano, and to sites in localities that are inaccessible on account of volcanic dangers. Emphasis is placed on two aspects of the research: first, the importance of ongoing, real-time interaction between the LiDAR analyst and the archaeological team in the field; and second, the advantages of exploiting the full potential of the three-dimensional LiDAR point cloud data for purposes of the visualization of archaeological sites and features

Options for transporting Russian gas to Western Europe : a game-theoretic simulation analysis

This paper examines the perspectives of Russian gas exports to Western Europe and the strategic options of the CIS gas transiting countries, namely Ukraine and Belarus. The development of a new transit corridor through Belarus (the Yamal-Europe pipeline), depriving Ukraine of its former monopoly, has modified the situation profoundly. The thrust of the paper is an analysis of the strategies that Ukraine and Belarus may pursue in transiting Russian gas: non-cooperative duopoly, cooperative duopoly, and individual or collective cooperation with Russia. Using a demand function for Western European gas imports from Russia, we estimate prices and quantities for gas transit, the expected profits for Russia, Ukraine, and Belarus, and the resulting import prices for Western Europe. The results indicate that Ukraine suffers a loss of several hundred million USD annually from the market entry of Belarus, Belarus has an incentive to increase its gas transit capacity to at least 56 billion cubic meters, and Russia's profits increase, in particular when it unites its gas sector with Belarus and Ukraine, a strategy pursued by Russia's Gazprom presently. For Western Europe, all scenarios indicate an increase in welfare through the new pipeline, but also an increasing importance of gas imports from Russia