550 research outputs found
The Effect of Inter-bundle Resistive Barriers on Coupling Loss, Current Distribution and DC Performance in ITER Conductors
The role of inter-bundle resistive barriers (metal sheet wraps), introduced to reduce the inter-bundle coupling loss in multistage cabled Cable-In-Conduit Conductors (CICC) for the International Thermonuclear Experimental Reactor (ITER) is evaluated, based on results gained recently on short sample experiments in the Twente Cable Press and SULTAN. The obvious benefit of limiting the inter bundle coupling loss unavoidably goes together with impeding the redistribution of nonuniform currents in the coil winding introduced at the terminations, as well as reduction of the heat exchange between the bundles. Six-element numerical electromagnetic code simulations are presented that qualitatively explain the effect of wraps on the DC performance, strongly depending on the testing geometry. The computations illustrate that wraps can reduce the DC performance in short sample tests. At the same time simulations of the Poloidal Field Coil Insert (PFCI), with a winding length of 50 m, have shown that omitting sub-stage wraps, can even degrade the DC performance of coils due to the short current transfer length in combination with current nonuniformity causing peak voltages in the most overloaded petals
Chemical Composition of the RS CVn-TYPE Star Lambda Andromedae
Photospheric parameters and chemical composition are determined for the
single-lined chromospherically active RS CVn-type star {\lambda} And (HD
222107). From the high resolution spectra obtained on the Nordic Optical
Telescope, abundances of 22 chemical elements and isotopes, including such key
elements as 12C, 13C, N and O, were investigated. The differential line
analysis with the MARCS model atmospheres gives T eff=4830 K, log g=2.8,
[Fe/H]=-0.53, [C/Fe]=0.09, [N/Fe]=0.35, [O/Fe]=0.45, C/N=2.21, 12C/13C = 14.
The value of 12C/13C ratio for a star of the RS CVn-type is determined for the
first time, and its low value gives a hint that extra-mixing processes may
start acting in low-mass chromospherically active stars below the bump of the
luminosity function of red giants
Chemical Composition of the RS CVn-type Star 29 Draconis
Photospheric parameters and chemical composition are determined for the
single-lined chromospherically active RS CVn-type star 29 Draconis (HD 160538).
From the high resolution spectra obtained on the Nordic Optical Telescope,
abundances of 22 chemical elements, including the key elements such as 12C,
13C, N and O, were investigated. The differential line analysis with the MARCS
model atmospheres gives Teff=4720 K, log g=2.5, Fe/H]=-0.20, [C/Fe]=-0.14,
[N/Fe]=0.08, [O/Fe]=-0.04, C/N=2.40, 12C/13C=16. The low value of the 12C/13C
ratio gives a hint that extra mixing processes in low-mass chromospherically
active stars may start earlier than the theory of stellar evolution predicts
Seasonal and interannual variability of the water exchange in the Turkish Straits System estimated by modelling
A chain of simple linked models is used to simulate the seasonal and interannual variability of the Turkish Straits System. This chain includes two-layer hydraulic models of the Bosphorus and Dardanelles straits simulating the exchange in terms of level and density difference along each strait, and a one-dimensional area averaged layered model of the Marmara Sea. The chain of models is complemented also by the similar layered model of the Black Sea proper and by a one-layer Azov Sea model with the Kerch Strait. This linked chain of models is used to study the seasonal and interannual variability of the system in the period 1970-2009. The salinity of the Black Sea water flowing into the Aegean Sea increases by approximately 1.7 times through entrainment from the lower layer. The flow entering into the lower layer of the Dardanelles Strait from the Aegean Sea is reduced by nearly 80% when it reaches the Black Sea. In the seasonal scale, a maximal transport in the upper layer and minimal transport in the bottom layer are during winter/spring for the Bosphorus and in spring for the Dardanelles Strait, whereas minimal transport in upper layer and maximal undercurrent are during the summer for the Bosphorus Strait and autumn for the Dardanelles Strait. The increase of freshwater flux into the Black Sea in interannual time scales (41 m3s-1 per year) is accompanied by a more than twofold growth of the Dardanelles outflow to the North Aegean (102 m3s-1 per year)
Structure And Properties of Nanoparticles Formed under Conditions of Wire Electrical Explosion
Structure and properties of nanoparticles formed under conditions of wire
electrical explosion were studied. It was shown that the state of WEE power
particles can be characterized as a metastable state. It leads to an increased
stability of nanopowders at normal temperatures and an increased reactivity
during heating, which is revealed in the form of threshold phenomena.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Spectral scaling of the Leray- model for two-dimensional turbulence
We present data from high-resolution numerical simulations of the
Navier-Stokes- and the Leray- models for two-dimensional
turbulence. It was shown previously (Lunasin et al., J. Turbulence, 8, (2007),
751-778), that for wavenumbers such that , the energy
spectrum of the smoothed velocity field for the two-dimensional
Navier-Stokes- (NS-) model scales as . This result is
in agreement with the scaling deduced by dimensional analysis of the flux of
the conserved enstrophy using its characteristic time scale. We therefore
hypothesize that the spectral scaling of any -model in the sub-
spatial scales must depend only on the characteristic time scale and dynamics
of the dominant cascading quantity in that regime of scales. The data presented
here, from simulations of the two-dimensional Leray- model, confirm our
hypothesis. We show that for , the energy spectrum for the
two-dimensional Leray- scales as , as expected by the
characteristic time scale for the flux of the conserved enstrophy of the
Leray- model. These results lead to our conclusion that the dominant
directly cascading quantity of the model equations must determine the scaling
of the energy spectrum.Comment: 11 pages, 4 figure
High resolution spectroscopic study of red clump stars in the Galaxy: iron group elements
The main atmospheric parameters and abundances of the iron group elements
(vanadium, chromium, iron, cobalt and nickel) are determined for 62 red giant
"clump" stars revealed in the Galactic field by the Hipparcos orbiting
observatory. The stars form a homogeneous sample with the mean value of
temperature T=4750 +- 160K, of surface gravity log g = 2.41 +- 0.26 and the
mean value of metallicity [Fe/H] = -0.04 +- 0.15 dex. A Gaussian fit to the
[Fe/H] distribution produces the mean [Fe/H] = -0.01 dex and dispersion of
[Fe/H] = 0.08 dex. The near-solar metallicity and small dispersion of [Fe/H] of
clump stars of the Galaxy obtained in this work confirm the theoretical model
of the Hipparcos clump by Girardi & Salaris (2001). This suggests that nearby
clump stars are (in the mean) relatively young objects, reflecting mainly the
near-solar metallicities developed in the local disk during the last few Gyrs
of its history. We find iron group element to iron abundance ratios in clump
giants to be close to solar.Comment: 9 pages, 7 figures, accepted for publication in MNRA
- …