Thermal-mechanical fatigue crack growth in Inconel X-750

Thermal-mechanical fatigue crack growth (TMFCG) was studied in a gamma-gamma' nickel base superalloy Inconel X-750 under controlled load amplitude in the temperature range from 300 to 650 C. In-phase (T sub max at sigma sub max), out-of-phase (T sub min at sigma sub max), and isothermal tests at 650 C were performed on single-edge notch bars under fully reversed cyclic conditions. A dc electrical potential method was used to measure crack length. The electrical potential response obtained for each cycle of a given wave form and R value yields information on crack closure and crack extension per cycle. The macroscopic crack growth rates are reported as a function of delta k and the relative magnitude of the TMFCG are discussed in the light of the potential drop information and of the fractographic observations

Equalization and the Decentralization of Revenue-Raising in a Federation

We study federal economies in which regional governments have responsibility for delivering public services and redistributive objectives apply. The implications of these for the assignment of revenue-raising instruments and fiscal transfers, both vertical and horizontal, are considered. Models of heterogenous regions of varying degrees of complexity and generality are constructed. For each case, we determine what fiscal instruments must be given to the regions and what inter-governmental transfers must be made in order that the social optimum is achieved. With heterogenous households and regions, the social optimum can be decentralized by making regions responsible for redistribution and implementing equalization transfers that depend on the number of households of each type.

La contamination des eaux continentales par les micropolluants organiques

Il y a environ 50 000 à 60 000 composés chimiques utilisés communément à des fins techniques. Certains d'entre eux sont toxiques et leur rejet dans l'environnement peut constituer une menace pour l'équilibre des écosystèmes aquatiques et pour la santé humaine. Plusieurs listes de substances dangereuses, appelées également polluants chimiques prioritaires, ont ainsi été établies par des organismes nationaux ou internationaux, notamment par l'EPA aux Etats-Unis, la CEE en Europe, l'Organisation Mondiale de la Santé (OMS). La nécessité de protéger les milieux aquatiques et la santé humaine a par ailleurs amené le développement de standards, de critères de qualité des eaux naturelles et des eaux potables, vis-à-vis de ces contaminants chimiques.Les sources de pollution sont diverses, se partageant entre les sources localisées comme les effluents urbains et industriels et les sources diffuses comme les eaux de ruissellement en zones rurales et en zones urbaines et les retombées atmosphériques. Différentes processus biogéochimiques déterminent les mécanismes de transport et de transformation des polluants organiques dans le milieu aquatique, et la bioaccumutation dans les organismes vivants représente un important aspect de ce comportement.Une première évaluation de la qualité des eaux continentales (rivières, lacs, eaux souterraines) est effectuée en examinant les données recueillies à travers le réseau de surveillance mondiale de la qualité de l'eau (GENS/EAUX) mis en place par deux organismes des Nations Unies, l'OMS et le PNUE. D'autres sources d'informations, publiées dans la littérature scientifique, ont été également utilisées pour évaluer les niveaux de concentrations observés pour différents groupes de polluants organiques dans les eaux naturelles et les eaux potables. La plupart des données disponibles proviennent d'un nombre limité de pays industriels d'Amérique du Nord, d'Europe et du Japon. Il y a une dramatique absence d'informations concernant la qualité chimique des eaux continentales dans les pays les moins développés d'Afrique, d'Amérique Latine et d'Asie. A l'heure actuelle, la stratégie de surveillance des polluants chimiques à l'échelle mondiale est donc loin d'être réellement satisfaisante.There are about 50,000 to 60,000 chemical compounds used for technical purposes. Some are toxic and the discharge of these substances in the environment can be a threat to the balance of aquatic ecosystems and to human health. Several lists of dangerous substances, also called major chemical pollutants, have been drawn up by various national or international bodies such as the EPA in the United States, the EEC in Europe or the World Health Organization (WHO). The need to protect the aquatic environment and human health has also led to the establishment of standards and of quality criteria for natural and drinking water subject to these chemical contaminants.There are several sources of pollution, punctual sources such as urban and industrial effluents and diffuse sources such as run-offs from agricultural land and urban areas and atmosphere fallout. Various biogeochemical processes determine the mechanisms by which organic pollutants are transported and transformed in the aquatic environment. Bioaccumulation in living organisms represents an important aspect of their behaviour.A first assessment of the quality of continental waters (rivers, lakes and groundwater) is made by examining the data collected by the international GEMS/WATER surveillance network carried out by two United Nations Agencies, WHO and UNEP. Other sources of information, published in the literature, were also used in order to determine the level of concentration of different groups of organic pollutants found in natural waters and in drinking water. Most of the data collected come from a limited number of industrial countries : North America, Europe and Japan. There is a serious lack of informations concerning the quality of continental waters in numerous countries in Africa, South America and Asia. At present, the procedure of global chemical pollution surveillance is far from satisfactory

Les PCB dans l'environnement marin. Aspects géochimiques d'apports et de distribution. Cas du littoral français

Les PCB représentent un groupe de substances chimiques chlorées particulièrement rémanent dans l'environnement. La production mondiale cumulée est évaluée à 1 200 000 tonnes et environ 30 % de cette production sont dispersés dans l'environnement, essentiellement dans le milieu océanique. La distribution de ces substances dans l'environnement aquatique est fonction des mécanismes d'échanges aux interfaces eau/atmosphère, eau/sédiment, aux processus de transformation abiotiques et biotiques, et aux processus de bioconcentration dans les organismes vivants. Les travaux réalisés depuis une vingtaine d'années permettent de décrire assez précisément le cycle biogéochimique des PCB dans le milieu océanique. La contamination du milieu marin côtier français est examinée plus particulièrement. La production totale des PCB en France est estimée à 123 000 tonnes et les apports polluants vers le milieu marin côtier, par les fleuves et l'atmosphère, sont évalués entre 2,5 et 3,0 tonnes par an. Les zones côtières les moins touchées par la contamination des PCB sont localisées en Manche sur le littoral nord de la Bretagne jusqu'en Normandie (Ouest Contentin) et en Méditerranée sur le littoral est de la Corse. La zone la plus contaminée est l'estuaire et la baie de Seine qui reçoivent les apports contaminants fluviaux de la Seine. De fortes contaminations sont également observées dans les zones industrielles et urbaines, et dans les secteurs qui reçoivent les effluents urbains non traités (ex : Marseille).Plusieurs études réalisées régulièrement suggèrent une décroissance générale des niveaux de contamination le long du littoral français depuis une décennie.PCB's are a group of chlorinated chemicals particularly persistent in the environment. The total global production of PCB compounds is evaluated at 1 200 000 tons and about 30 % are dispersed in the environment, mainly in the oceans. Distribution of these substances in the aquatic environment depends on exchange mechanisms at seawater/atmosphere and seawater/sediment interfaces, at abiotic and biotic transformation processes and at bioconcentration processes in the biota. Twenty years of research work allow us to describe with sufficient precision the biogeochemical cycle of PCB's in the marine environment. The PCB contamination of the French coastal marine environment is investigated more closely. Total PCB production in France is evaluated at 123 000 tons and pollutant inputs to the coastal marine environment, via rivers and atmosphere, are estimated between 2.5 and 3.0 tons/years. The Least polluted zones are in the English Channel along the north coast of Brittany till Normandy (West Cotentin) and in the Mediterranean along the east coast of Corsica. The most highly polluted area is constituted by the estuary and the bay of the Seine which receive river pollutant inputs. High PCB contaminations are also observed in industrial and urban zones, and in areas which receive untreated urban sewage (ex. Marseille). Several short-term surveys let us suppose there has been a general decrease in PCB levels along the French coastal marine environment in the last decade

Ranking Inequality: Applications of Multivariate Subset Selection

Inequality measures are often presented in the form of a rank ordering to highlight their relative magnitudes. However, a rank ordering may produce misleading inference, because the inequality measures themselves are statistical estimators with different standard errors, and because a rank ordering necessarily implies multiple comparisons across all measures. Within this setting, if differences between several inequality measures are simultaneously and statistically insignificant, the interpretation of the ranking is changed. This study uses a multivariate subset selection procedure to make simultaneous distinctions across inequality measures at a pre-specified confidence level. Three applications of this procedure are explored using country-level data from the Luxembourg Income Study. The findings show that simultaneous precision plays an important role in relative inequality comparisons and should not be ignored.Income distribution, Inference, Poverty, Subset Selection

Comparitive assessment of the vulnerability and resilience of 10 deltas, synthesis report

The proposed framework for delta assessment and especially the scorecards are intended to enhance awareness raising, discussion and prioritization on most relevant delta issues, in each delta but also in comparison with other deltas. This should lead to more efficient and effective (multi-sectoral) policy formulation, management design and implementation, in concrete Delta plans, pilot-projects and (research) programmes. The target groups are all stakeholders who are involved in delta management at different levels and with different interests (government, private companies, NGOs, public), and who wish to contribute to the resilience of their own delta and other deltas worldwide

Comparative assessment of the vulnerability and resilience of 10 deltas : work document

Background information about: Nile delta (Egypt), Incomati delta (Mozambique), Ganges-Brahmaputra-Meghna (Bangladesh), Yangtze (China), Ciliwung (Indonesia), Mekong (Vietnam), Rhine-Meuse (The Netherlands), Danube (Romania), California Bay-Delta, Mississippi River Delta (USA

Under Ice Operations

The oceans of the world, and the myriad of mysteries they contain, have long been described as Inner Space

Flood risk analysis for the river Scheldt estuary

This report gives an overview of the history of flood risk management along the Scheldt estuary. Thepurpose of this overview is twofold. It documents the results obtained in the first activity of the Task25 Pilot, being focused on flood risk analysis, both in historical perspective and with regard to currentpolicies. Secondly, it provides an introduction to the Scheldt estuary for other partners in theFLOODsite project which will use the Scheldt Pilot for their own tasks and activities.The Scheldt estuary is a clear example where integrated water management is required. Integratedmeans in this case: meeting the objectives for 3 major basic functions and values of the estuary: safety,accessibility (navigation) and ecology. Recently finalised and ongoing projects, such as Proses and theSIGMA plan show a highly multidisciplinary approach in order to fulfil these objectives.From the perspective of flood risk management we see a significant difference in approach betweenBelgium and the Netherlands. The Belgian New Sigma Plan has used an approach that is strikinglysimilar to the FLOODsite methodology, i.e. going through the three phases Risk Analysis, RiskAssessment and Flood Management Strategy formulation. In contrast, the Dutch flood riskmanagement was developed over a long historical period, with the Delta Plan as the final apotheosis.In the time the Delta Plan was formulated, there was hardly any attention and technology available todetermine flood probability and flood damage