209 research outputs found
The Effect of Oil Price Shocks on the Czech Economy
In the course of 2002 up to the end of 2007, very steep growth of oil prices, but no remarkable slowdown of either the world economy or the Czech economy, was observed. This phenomenon raises a question about the impact of oil prices on modern economies. Analyzing the available data we can conclude that notwithstanding the full dependence of the Czech economy on oil imports, its overall dependence on imported energy sources is relatively low. Compared to the EU15 level the energy intensity of the Czech economy is quite high. Nevertheless, further improvements in this area are expected. Furthermore, the appreciation of CZK and the set-up of the tax system significantly reduced the volatility of the consumer oil price between 2002 and 2007. Using a structural CGE model we quantify the impact of oil price changes on the Czech economy and demonstrate that it is not dramatic despite the oil price turmoil in the years 2000 to the end of 2007. We find that a 20% increase in the CZK oil price tends to decrease the GDP level by 1:5% and 0:8% in the short and long run, respectively. Short-run annual GDP growth decreases by 0:3 p.p. Concerning prices, inflation would accelerate by around 0:4 p.p. per annum in the short run.CGE, Czech Republic, oil price.
Optimization of graded multilayer designs for astronomical x-ray telescopes
We developed a systematic method for optimizing the design of depth-graded multilayers for astronomical hard-x-ray and soft-γ-ray telescopes based on the instrument’s bandpass and the field of view. We apply these methods to the design of the conical-approximation Wolter I optics employed by the balloon-borne High Energy Focusing Telescope, using W/Si as the multilayer materials. In addition, we present optimized performance calculations of mirrors, using other material pairs that are capable of extending performance to photon energies above the W K-absorption edge (69.5 keV), including Pt/C, Ni/C, Cu/Si, and Mo/Si
Progress toward a Soft X-ray Polarimeter
We are developing instrumentation for a telescope design capable of measuring
linear X-ray polarization over a broad-band using conventional spectroscopic
optics. Multilayer-coated mirrors are key to this approach, being used as Bragg
reflectors at the Brewster angle. By laterally grading the multilayer mirrors
and matching to the dispersion of a spectrometer, one may take advantage of
high multilayer reflectivities and achieve modulation factors over 50% over the
entire 0.2-0.8 keV band. We present progress on laboratory work to demonstrate
the capabilities of an existing laterally graded multilayer coated mirror pair.
We also present plans for a suborbital rocket experiment designed to detect a
polarization level of 12-17% for an active galactic nucleus in the 0.1-1.0 keV
band.Comment: 11 pages, 12 figures, to appear in the proceedings of the SPIE,
volume 8861, on Optics for EUV, X-Ray, and Gamma-Ray Astronom
MSWI bottom ash used as basement at two pilot-scale roads: Comparison of leachate chemistry and reactive transport modeling
International audienceThe recycling of municipal solid waste incineration bottom ash as aggregates for road basement requires assessing the long-term evolution of leachate chemistry. The Dåva (Sweden) and Hérouville (France) pilot-scale roads were monitored during 6 and 10 years, respectively. Calculated saturation indices were combined to batch test modeling to set a simplified geochemical model of the bottom ash materials. A common reactive transport model was then applied to both sites. At Hérouville, pH and the concentration of most elements quickly drop during the first two years to reach a set of minimum values over 10 years. The decrease is less pronounced at Dåva. The evolutions of pH and major element concentrations are fairly well related to the following pH-buffering sequence: portlandite, C-S-H phases or pseudo-wollastonite and, finally, calcite in equilibrium with atmospheric CO2. Al(OH)3, barite, ettringite and monohydrocalcite may also control leachate chemistry. Cu release is correctly modeled by DOM complexation and tenorite equilibrium. Temperature has no significant effect on the modeling of leachate chemistry in the range 5-30 C, except at high pH. Effects at road edges and roadside slopes are important for the release of the less reactive elements and, possibly, for carbonation processes
NASA advanced aeronautics design solar powered remotely piloted vehicle
Environmental problems such as the depletion of the ozone layer and air pollution demand a change in traditional means of propulsion that is sensitive to the ecology. Solar powered propulsion is a favorable alternative that is both ecologically harmless as well as cost effective. Integration of solar energy into designs ranging from futuristic vehicles to heating is beneficial to society. The design and construction of a Multi-Purpose Remotely Piloted Vehicle (MPRPV) seeks to verify the feasibility of utilizing solar propulsion as a primary fuel source. This task has been a year long effort by a group of ten students, divided into five teams, each dealing with different aspects of the design. The aircraft was designed to take-off, climb to the design altitude, fly in a sustained figure-eight flight path, and cruise for approximately one hour. This mission requires flight at Reynolds numbers between 150,000 and 200,000 and demands special considerations in the aerodynamic design in order to achieve flight in this regime. Optimal performance requires a light weight configuration with both structural integrity and maximum power availability. The structure design and choice of solar cells for the propulsion was governed by the weight, efficiency, and cost considerations. The final design is a MPRPV weighting 35 N which cruises 7 m/s at the design altitude of 50 m. The configuration includes a wing composed of balsa and foam NACA 6409 airfoil sections and carbon fiber spars, a tail of similar construction, and a truss structure fuselage. The propulsion system consists of 98 10 percent efficient solar cells donated by Mobil Solar, a NiCad battery for energy storage, and a folding propeller regulated by a lightweight and efficient control system. The airfoils and propeller chosen for the design were research and tested during the design process
Development of thermally formed glass optics for astronomical hard x-ray telescopes
The next major observational advance in hard X-ray/soft gamma-ray astrophysics will come with the implementation of telescopes capable of focusing 10-200 keV radiation. Focusing allows high signal-to-noise imaging and spectroscopic observations of many sources in this band for the first time. The recent development of depth-graded multilayer coatings has made the design of telescopes for this bandpass practical, however the ability to manufacture inexpensive substrates with appropriate surface quality and figure to achieve sub-arcminute performance has remained an elusive goal. In this paper, we report on new, thermally-formed glass micro-sheet optics capable of meeting the requirements of the next-generation of astronomical hard X-ray telescopes
W/SiC x-ray multilayers optimized for use above 100 keV
We have developed a new depth-graded multilayer system comprising W and SiC layers, suitable for use as hard x-ray reflective coatings operating in the energy range 100-200 keV. Grazing-incidence x-ray reflectance at E = 8 keV was used to characterize the interface widths, as well as the temporal and thermal stability in both periodic and depth-graded W/SiC structures, whereas synchrotron radiation was used to measure the hard x-ray reflectance of a depth-graded multilayer designed specifically for use in the range E ~150-170 keV. We have modeled the hard x-ray reflectance using newly derived optical constants, which we determined from reflectance versus incidence angle measurements also made using synchrotron radiation, in the range E = 120-180 keV. We describe our experimental investigation in detail, compare the new W/SiC multilayers with both W/Si and W/B4C films that have been studied previously, and discuss the significance of these results with regard to the eventual development of a hard x-ray nuclear line telescope
Evaluation and optimization of multilayer desigs for astronomical x-ray telescopes using a field-of-view- and energy-dependent figure of merit
The three most important quantities used to assess the performance of astronomical x-ray telescope optics are the
on-axis collecting area, the field of view, and the half-power diameter. The first two quantities depend on the mirror packing arrangement and the multilayer coating design. In order to optimize the coating design, we have developed a figure-of-merit (FOM) that accounts for the coating response over a specified range of energies and off-axis angles. We present an example where we have used this FOM to optimize a specific coating design for the High Energy Focusing Telescope (HEFT) and to understand tradeoffs between performance and coating thickness
Design of a soft gamma-ray focusing telescope for the study of nuclear lines
We have studied the design of astronomical multilayer telescopes optimized for performance from 5 to 200 keV. This region of the spectrum contains important nuclear lines that are observable in supernovae and their remnants. The study of these lines can help to differentiate currently competing theories of supernova explosion. Our telescope design will enable us to measure the spectral lines of isotopes such as Ni-56 in Type Ia supernovae and Ti-44 in core-collapse remnants, as well as to observe active galactic nuclei at gamma-ray energies. We considered the performances of multilayers of various material pairs, including W/Si, Pt/C and Ni93V7/Si, as employed in conical-approximation Wolter I optics. We experimented with dividing the energy band of interest into several sections, and optimizing different groups of mirror shells within a single telescope for each smaller energy band. Different material pairs are also used for different energy bands, in order to obtain a higher overall performance. We also consider the significance of the energy bandwidth on the effectiveness of Joensen's parametrization of the multilayer thickness profile, and on the mirror performance within the band
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