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111.
We use quantum Monte Carlo simulations to determine the finite temperature phase diagram and to investigate the thermal and quantum melting of stripe phases in a two-dimensional hard-core boson model. At half filling and low temperatures the stripes melt at a first order transition. In the doped system, the melting transitions of the smectic phase at high temperatures and the superfluid smectic (supersolid) phase at low temperatures are either very weakly first order, or of second order with no clear indications for an intermediate nematic phase. 相似文献
112.
L. Cultrera D. Guido A. Perrone M.I. Zeifman 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1181-1184
The results of a new geometrical configuration of pulsed laser ablation deposition technique that uses a hemi-cylindrical transparent plastic substrate are presented and discussed. With the new arrangement, two distinct components with different material compositions have been clearly observed. While the first component comprises atoms, ions and molecules and constitutes visible or the so-called luminous plume, the second component is formed of fragments, clusters and liquid droplets and is invisible to the naked eye. The latter component constitutes a major part of the ablated material. The luminous plume symmetry axis does not coincide with the mass distribution symmetry axis. In the case of Si ablation and 45° incident beam angle, the maximum deflection angle of the luminous plume reaches 30° with respect to the normal to the target surface, while the deflection angle of the second component is higher than 40°. The change in the target morphology and the dependence of the composition of the ablated material on local fluence, along with the hydrodynamic effects, is sought to explain this previously unexpected and unreported phenomenon. PACS 61.80.Ba; 47.35.+i; 52.38.Mf; 81.15.Fg 相似文献
113.
The German bakery waste incident; use of a combined approach of screening and confirmation for dioxins in feed and food 总被引:1,自引:0,他引:1
During the last six years several incidents have occurred with dioxins in feed, stressing the need for rapid screening methods for these compounds. The most recent incident was the contamination of bakery waste used for animal feed due to the use of waste wood for drying of the material. In addition to Germany, the material was also shipped to the Netherlands. Levels up to 12 ng TEQ/kg have been detected, being about 15 times over the current limit of 0.75 ng TEQ/kg. In the Netherlands a combined strategy of screening with the CALUX-bioassay and the HRGC/HRMS confirmatory method was used to rapidly control the incident. Pigs were contaminated by the incident but only to a very limited extent. Despite the rather low limits for pig meat, the CALUX bioassay showed excellent performance, once again confirming the value of this assay. 相似文献
114.
Guido Gentile 《Communications in Mathematical Physics》2003,242(1-2):221-250
We consider the Schrödinger equation for a class of two-level atoms in a quasi-periodic external field in the case in which the spacing 2 between the two unperturbed energy levels is small, and we study the problem of finding quasi-periodic solutions of a related generalized Riccati equation. We prove the existence of quasi-periodic solutions of the latter equation for a Cantor set of values of around the origin which is of positive Lebesgue measure: such solutions can be obtained from the formal power series by a suitable resummation procedure. The set can be characterized by requesting infinitely many Diophantine conditions of Melnikov type. 相似文献
115.
The dynamics of an electronic Dirac wave packet evolving under the influence of an ultraintense laser pulse and an ensemble of highly charged ions is investigated numerically. Special emphasis is placed on the evolution of quantum signatures from single to multiple scattering events. We quantify the occurrence of quantum relativistic interference fringes in various situations and stress their significance in multiple-particle systems, even in the relativistic range of laser-matter interaction. 相似文献
116.
117.
118.
Guido Schneider Hannes Uecker 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2003,173(1):677-712
Modulating pulse solutions play a big rôle in modern long distance high speed communication.
Such solutions consist of a traveling pulse-like envelope modulating an underlying
electromagnetic wave. In this paper we show that under certain assumptions such solutions exist
and are dynamically stable for the associated nonlinear partial differential equations, namely
Maxwells integro-differential equations describing nonlinear optics. The analysis is worked out
in detail for bulk media, and we discuss how the results extend to optical fibers and to parametrically forced systems. 相似文献
119.
Guido Van Oost James P. Gunn Alexander Melnikov Jan Stöckel Michael Tendler 《Czechoslovak Journal of Physics》2001,51(10):957-975
Radial electric fields (E
r) and their role in the establishment of edge transport barriers and improved confinement have been studied in the tokamaks TEXTOR-94 and CASTOR, where E
r is externally applied to the plasma in a controlled way using a biased electrode, as well as in the tokamak T-10 where an edge transport barrier (H-mode) is obtained during electron-cyclotron resonance heating (ECRH) of the plasma.The physics of radial currents was studied and the radial conductivity in the edge of TEXTOR-94 (R = 1.75 m, a = 0.46 m) was found to be dominated by recycling (ion-neutral collisions) at the last closed flux surface (LCFS) and by parallel viscosity inside the LCFS. From a performance point of view (edge engineering), such electrode biasing was shown to induce a particle transport barrier, a reduction of particle transport, and a concomitant increase in energy confinement. An H-mode-like behaviour can be induced both with positive and negative electric fields. Positive as well as negative electric fields were shown to strongly affect the exhaust of hydrogen, helium, and impurities, not only in the H-mode-like regime.The impact of sheared radial electric fields on turbulent structures and flows at the plasma edge is investigated on the CASTOR tokamak (R = 0.4 m, a = 0.085 m). A non-intrusive biasing scheme that we call "separatrix biasing" is applied whereby the electrode is located in the scrape-off layer (SOL) with its tip just touching the LCFS. There is evidence of strongly sheared radial electric field and E×B flow, resulting in the formation of a transport barrier at the separatrix. Advanced probe diagnosis of the edge region has shown that the E×B shear rate that arises during separatrix biasing is larger than for standard edge plasma biasing. The plasma flows, especially the poloidal E×B drift velocity, are strongly modified in the sheared region, reaching Mach numbers as high as half the sound speed. The corresponding shear rates ( 5×106 s-1) derived from both the flow and electric field profiles are in excellent agreement and are at least an order of magnitude higher than the growth rate of unstable turbulent modes as estimated from fluctuation measurements.During ECRH in the tokamak T-10 (R = 1.5 m, a = 0.3 m), a regime of improved confinement is obtained with features resembling those in the H-mode in other tokamaks. Using a heavy ion beam probe, a narrow potential well is observed near the limiter together with the typical features of the L-H transition. The time evolution of the plasma profiles during L-H and H-L transitions is clearly correlated with that of the density profile and the formation of a transport barrier near the limiter. The edge electric field is initially positive after the onset of ECRH. It changes its sign during the L-H transition and grows till a steady condition is reached. Similar to the biasing experiments in TEXTOR-94 and CASTOR, the experimentally observed transport barrier is a barrier for particles. 相似文献
120.
Monotone iterative scheme for nonlinear hyperbolic boundary value problem is established. 相似文献