Reynolds stresses and mean fields generated by pure waves: applications to shear flows and convection in a rotating shell

A general reformulation of the Reynolds stresses created by two-dimensional waves breaking a translational or a rotational invariance is described. This reformulation emphasizes the importance of a geometrical factor: the slope of the separatrices of the wave flow. Its physical relevance is illustrated by two model systems: waves destabilizing open shear flows; and thermal Rossby waves in spherical shell convection with rotation. In the case of shear-flow waves, a new expression of the Reynolds–Orr amplification mechanism is obtained, and a good understanding of the form of the mean pressure and velocity fields created by weakly nonlinear waves is gained. In the case of thermal Rossby waves, results of a three-dimensional code using no-slip boundary conditions are presented in the nonlinear regime, and compared with those of a two-dimensional quasi-geostrophic model. A semi-quantitative agreement is obtained on the flow amplitudes, but discrepancies are observed concerning the nonlinear frequency shifts. With the quasi-geostrophic model we also revisit a geometrical formula proposed by Zhang to interpret the form of the zonal flow created by the waves, and explore the very low Ekman-number regime. A change in the nature of the wave bifurcation, from supercritical to subcritical, is found

Trade, environmental regulations and the World Trade Organization : new empirical evidence

The paper empirically explores the linkages between environmental regulations and international trade flows. So far, empirical studies either have failed to find any close statistical relationship or have delivered questionable results due to data limitations. Using a comprehensive new database for environmental regulations across countries, a thorough empirical investigation of that linkage for 119 countries and five high-polluting industries is performed. No evidence is found to support the pollution hypothesis that industries facing above-average abatement costs with environmental regulations would prefer pollution havens and relocate their activities. The exception is iron and steel products, where a negative and statistically significant link is established, implying that higher compliance with international treaties and conventions and more stringent regulations are associated with reduced net exports. High-income countries, where environmental regulations are usually more stringent in comparison to middle or low income countries, have experienced a considerable decline in the export-import ratio of iron and steel products since the late 1970s. There is no clear evidence that national governments choose sub-optimal policies that result in insufficient regulations, so the case for environmental standards within the WTO framework is relatively weak.Water and Industry,Environmental Economics&Policies,Public Health Promotion,Economic Theory&Research,Administrative&Regulatory Law,Environmental Economics&Policies,Economic Theory&Research,Water and Industry,Administrative&Regulatory Law,Trade and Services

Tariffs, Transport Costs and the WTO Doha Round: The Case of Developing Countries

The WTO Doha Round of multinational trade negotiations is labelled the “development round” to highlight the fact that progress could be achieved through the enhanced integration of the poor countries into the world economy. Since the trade agenda focuses to a large extent on the levels of direct and indirect trade barriers as well as other aspects of trade and competition policy, an important aspect of the relative trade performance of developing countries has been neglected somewhat. This paper argues that, in addition to trade barriers, other trade costs, such as communications and transport costs, have to be taken into account. These other costs can be significantly higher in developing countries, which impedes their successful integration into world markets.developing countries, transport costs, WTO Doha Round, International Relations/Trade,

Knowledge representation in space flight operations

In space flight operations rapid understanding of the state of the space vehicle is essential. Representation of knowledge depicting space vehicle status in a dynamic environment presents a difficult challenge. The NASA Jet Propulsion Laboratory has pursued areas of technology associated with the advancement of spacecraft operations environment. This has led to the development of several advanced mission systems which incorporate enhanced graphics capabilities. These systems include: (1) Spacecraft Health Automated Reasoning Prototype (SHARP); (2) Spacecraft Monitoring Environment (SME); (3) Electrical Power Data Monitor (EPDM); (4) Generic Payload Operations Control Center (GPOCC); and (5) Telemetry System Monitor Prototype (TSM). Knowledge representation in these systems provides a direct representation of the intrinsic images associated with the instrument and satellite telemetry and telecommunications systems. The man-machine interface includes easily interpreted contextual graphic displays. These interactive video displays contain multiple display screens with pop-up windows and intelligent, high resolution graphics linked through context and mouse-sensitive icons and text

An expert system for satellite and instrument data anomaly and fault isolation

A prototype Generic Payload Operations Control System (GPOCC) is being developed at the NASA Jet Propulsion Laboratory to provide a low-cost command and control processing center for science instruments and small payloads. The GPOCC supports the difficult transition from integration and test to flight operations. The prototype will incorporate four expert systems to perform telemetry, command, and mission planning functions as well as telecommunications scheduling. The first of these expert systems to be developed will perform telemetry data analysis and fault isolation, as well as propose corrective action. This Data Analysis Module (DAM) will monitor telemetry data and perform continual data monitoring and trend analysis based on a knowledge base and historic data archived on an optical disk storage device. The system maintains a continuous knowledge database of past system performance characteristics. The goal of the Data Analysis Module is to achieve consistent, dependable and validatable performance, to demonstrate thorough, reliable and fast reasoning, and to reduce the concentration demanded of flight analysis personnel

Improved variational principle for bounds on energy dissipation in turbulent shear flow

We extend the Doering-Constantin approach to upper bounds on energy dissipation in turbulent flows by introducing a balance parameter into the variational principle. This parameter governs the relative weight of different contributions to the dissipation rate. Its optimization leads to improved bounds without entailing additional technical difficulties. For plane Couette flow, the high-Re-bounds obtainable with one-dimensional background flows are methodically lowered by a factor of 27/32.Comment: 15 pages, RevTeX, 3 postscript figure

Bistability and hysteresis of dipolar dynamos generated by turbulent convection in rotating spherical shells

Bistability and hysteresis of magnetohydrodynamic dipolar dynamos generated by turbulent convection in rotating spherical fluid shells is demonstrated. Hysteresis appears as a transition between two distinct regimes of dipolar dynamos with rather different properties including a pronounced difference in the amplitude of the axisymmetric poloidal field component and in the form of the differential rotation. The bistability occurs from the onset of dynamo action up to about 9 times the critical value of the Rayleigh number for onset of convection and over a wide range of values of the ordinary and the magnetic Prandtl numbers including the value unity

Pointer basis induced by collisional decoherence

We study the emergence and dynamics of pointer states in the motion of a quantum test particle affected by collisional decoherence. These environmentally distinguished states are shown to be exponentially localized solitonic wave functions which evolve according to the classical equations of motion. We explain their formation using the orthogonal unraveling of the master equation, and we demonstrate that the statistical weights of the arising mixture are given by projections of the initial state onto the pointer basis.Comment: 26 pages, 9 figures; v2: minimal corrections, corresponds to published versio

spotlight europe #2013/05 - December 2013: Unblocking the lifeline of talent

Against the background of demographic decline and growing economic competitiveness from emerging economies, this Spotlight published in cooperation with the Centre for European Policy Studies looks into the potential of increased intra-EU labour mobility. It will examine the ‘German case’ on EU labour mobility. It proposes ideas on how to better foster a European fair deal on talent, one that would benefit the EU as a whole. It concludes with a proposal on how to increase the benefits of the freedom of movement