The turbomachine blading design using S2-S1 approach

The boundary conditions corresponding to the design problem when the blades being simulated by the bound vorticity distribution are presented. The 3D flow is analyzed by the two steps S2 - S1 approach. In the first step, the number of blades is supposed to be infinite, the vortex distribution is transformed into an axisymmetric one, so that the flow field can be analyzed in a meridional plane. The thickness distribution of the blade producing the flow channel striction is taken into account by the modification of metric tensor in the continuity equation. Using the meridional stream function to define the flow field, the mass conservation is satisfied automatically. The governing equation is deduced from the relation between the azimuthal component of the vorticity and the meridional velocity. The value of the azimuthal component of the vorticity is provided by the hub to shroud equilibrium condition. This step leads to the determination of the axisymmetric stream sheets as well as the approximate camber surface of the blade. In the second step, the finite number of blades is taken into account, the inverse problem corresponding to the blade to blade flow confined in each stream sheet is analyzed. The momentum equation implies that the free vortex of the absolute velocity must be tangential to the stream sheet. The governing equation for the blade to blade flow stream function is deduced from this condition. At the beginning, the upper and the lower surfaces of the blades are created from the camber surface obtained from the first step with the assigned thickness distribution. The bound vorticity distribution and the penetrating flux conservation applied on the presumed blade surface constitute the boundary conditions of the inverse problem. The detection of this flux leads to the rectification of the geometry of the blades

an extensible tuplespace as XML-middleware

XMLSpaces.NET implements the Linda concept as a middleware for XML documents. It introduces an extended matching flexibility on nested tuples and richer data types for fields, including objects and XML documents. It is completely XML-based since data, tuples and tuplespaces are seen as trees represented as XML documents. XMLSpaces.NET is extensible in that it supports a hierarchy of matching relations on tuples and an open set of matching amongst data, documents and objects. It is currently being implemented on the .NET platform

What explains the short-term dynamics of the prices of CO2 emissions?

Using the vector auto-regression (VAR) and the vector error-correction Models (VECM), this paper analyzes the short-term dynamics of the prices of CO2 emissions in response to changes in the prices of oil, coal, natural gas, electricity and carbon emission allowances. The results show that: (i) a positive shock to the crude oil prices has a negative effect on the CO2 allowance prices; (ii) an unexpected increase in the natural gas prices raises the price of CO2 emissions; (iii) a positive shock to the prices of the fuel of choice, coal, has virtually no significant impact on the CO2 prices; (iv) there is a clear positive effect of the coal prices on the CO2 allowance prices when the electricity prices are excluded from the VAR system; and (v) a positive shock to the electricity prices reduces the price of the CO2 allowances. We also find that the energy price shocks have a persistent impact on the CO2 allowance prices, with the largest effect occurring six months after a shock strikes. The effect is particularly strong in the case of the natural gas price shocks. Additionally, we estimate that it takes between 7.3 and 9.6 months to halve the gap between the actual and the equilibrium prices of the CO2 allowances, i.e., to erase any price over- or undervaluations after a shock strikes. Finally, the empirical findings suggest an important degree of substitution between the three primary sources of energy (i.e., crude oil, natural gas and coal), particularly, when electricity prices are excluded from the VAR system.COMPETE, QREN, FEDER, Fundação para a Ciência e a Tecnologia (FCT

Energy prices and CO2 emission allowance prices : a quantile regression approach

We use a quantile regression framework to investigate the impact of changes in crude oil prices, natural gas prices, coal prices, and electricity prices on the distribution of the CO2 emission allowance prices in the United States. We find that: (i) an increase in the crude oil price generates a substantial drop in the carbon prices when the latter is very high; (ii) changes in the natural gas prices have a negative effect on the carbon prices when they are very low but have a positive effect when they are quite high; (iii) the impact of the changes in the electricity prices on the carbon prices can be positive in the right tail of the distribution; and (iv) the coal prices exert a negative effect on the carbon prices.COMPETE, QREN, FEDER, Fundação para a Ciência e a Tecnologia (FCT

Asymmetric and nonlinear pass-through of energy prices to CO2 emission allowance prices

We use the recently developed nonlinear autoregressive distributed lags (NARDL) model to examine the pass-through of changes in crude oil prices, natural gas prices, coal prices and electricity prices to the CO2 emission allowance prices. This approach allows one to simultaneously test the short- and long-run nonlinearities through the positive and negative partial sum decompositions of the predetermined explanatory variables. It also offers the possibility to quantify the respective responses of the CO2 emission prices to positive and negative shocks to the prices of their determinants from the asymmetric dynamic multipliers. We find that: (i) the crude oil prices have a long-run negative and asymmetric effect on the CO2 allowance prices; (ii) the falls in the coal prices have a stronger impact on the carbon prices in the short-run than the increases; (iii) the natural gas prices and electricity prices have a symmetric effect on the carbon prices, but this effect is negative for the former and positive for the latter. Policy implications are provided.COMPETE, QREN, FEDER, Fundação para a Ciência e a Tecnologia (FCT

Design and characterization of SiON integrated optics components for optical coherence tomography

Optical coherence tomography (OCT) is a technique for high resolution imaging of biological tissues with a depth range of a few millimeters. OCT is based on interferometry to enable depth ranging. Currently, optical components for OCT are rather bulky and expensive; the use of integrated optical circuits presents a great opportunity to reduce costs and enhance system functionality and performance. We present the design and characterization of SiON-based integrated optics waveguides, splitters, couplers and interferometers for OCT operating at a wavelength of 1.3 um