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991.
This paper considers the one-dimensional advection and diffusion of a passive scalar in the context of baker's maps of the unit interval. Our main interest is the thermal transport between two points held at fixed temperatures, when a deterministic sequence of maps of various scales are involved. Molecular diffusion occurs during the periods of rest between maps. We focus on the behavior of the transport in the limit of infinite Péclet number (or small molecular diffusion). Various asymptotic results are presented and compared with numerical calculations. Convergence to turbulent transport independent of molecular diffusion is observed as the number of scales is increased.This paper is dedicated to Jerry Percus on the occasion of his 65th birthday. 相似文献
992.
HARMIT SINGH RAVINDERJIT KAUR 《Journal of inclusion phenomena and macrocyclic chemistry》1997,28(2):105-116
The transportation of neutral arenes such as benzene, toluene, o,m,p-xylene, durene,biphenyl, anthracene and phenanthrene through an aqueous medium using the crownconformation of tetrameric cyclophane hosts 1 and 2 has been studied. In general,transportation of all arenes increases with time, exceptfor toluene, which showssaturation behaviour with both hosts 1 and 2.Among the larger arenes, transportationof biphenyl is a maximum with 1; with host 2,transportation of anthracene is a maximumdue to its larger association constant. In the case ofsmaller arenes, 1 transportsbenzene most effectively, and transportation decreases asthe number of methyl groups onbenzene increases, showing that stereoelectronic factors affecttransportation. With 2toluene is transported most effectively due tothe change in the shape of the binding cavitycaused by a change in bridging groups. A comparison oftransportation for 1 h with 1 and 2shows that for all arenes transportation is greater withhost 2 than with 1 due to thehydrophobic nature of 2. 相似文献
993.
J. Rieger M. Leghissa J. Wiezoreck H. -P. Krmer G. Ries H. -W. Neumüller 《Physica C: Superconductivity and its Applications》1998,310(1-4):225-230
To demonstrate the possibility of manufacturing a HTS power transmission cable with low AC losses, we fabricated a 10 m long cable conductor and a cryosystem. The conductor was wound in a four-layer design out of 2 km Ag/Bi-2223 tapes. We determined a critical current of 5000 A. Loss measurements were performed with an electric method which detects the voltage drop along the conductor with a lock-in technique and a calorimetric method which measures the temperature rise along the conductor. Both methods yield the same low loss values of only 0.8 W/m at 77 K and 2000 Arms/50 Hz. This is due to the low loss winding scheme we used which assures an equal current distribution in all four layers through transformatoric coupling. We applied the uniform current distribution model and added the nonlinear V–I curve to describe quantitatively the obtained results. 相似文献
994.
O. A. Shevchenko J. J. Rabbers A. Godeke B. ten Haken H. H. J. ten Kate 《Physica C: Superconductivity and its Applications》1998,310(1-4):106-110
In a typical superconducting coil made of BSCCO/Ag tape, both amplitude and direction of the magnetic field determine the critical current, resistive voltage and AC loss. The distribution of the magnetic field along and across the superconducting tape in a coil is rather complex. This gives rise to the question: how accurate can one predict the critical current, V–I characteristic and AC loss of the AC coil from results of short sample measurements? To answer this question, we have measured and compared the characteristics of a short sample and a small coil employing 14 m of the same tape at 77 K. The comparison is performed as follows. First, a short sample is characterised with regard to the field dependence of the critical current, V–I characteristic and the AC loss. Second, the distribution of the magnetic field along the tape in a coil is accurately calculated. From the data, the voltage along the tape and the loss of the tape in the coil are found. Finally, the resistive voltage and the AC loss of the complete coil are calculated and compared to measured AC losses in the frequency range of 0 to 160 Hz, typical for power applications. 相似文献
995.
996.
The steady state of a system of independent particles which undergo elastic collisions can be expressed in terms of the absorption probabilities of the associated Markov process. For the slab albedo problem, this representation enables the application of probabilistic methods to obtain explicit upper and lower bounds on the steady-state density. In particular, the bounds prove the 1/L, decrease of the steady-state flux as a function of the slab widthL (Fick's law).Supported in part by U.S. National Science Foundation grant MCS 75-21684 A02.On leave of absence from Fachbereich Physik, UniversitÄt Mönchen. Work supported by a DFG research fellowship. 相似文献
997.
Within a transport model it is shown that the neutron/proton ratio of squeezed-out nucleons perpendicular to the reaction plane, especially at high transverse momenta, in heavy-ion reactions induced by high energy neutron-rich nuclei can be a useful tool for studying the high density behavior of the nuclear symmetry energy. 相似文献
998.
The effect of a plasticizer dimethyl formamide (DMF) on the properties of a potassium ion conducting electrolyte based on
polyvinyl chloride (PVC) complexed with potassium bromate (KBrO3) prepared using solution-cast technique was investigated. Various experimental techniques, such as electrical conductivity
(composition and temperature dependence) and transport number measurements, were used to characterize these polymer electrolyte
films. It was found that the addition of plasticizer (DMF) significantly improved the ionic conductivity. Transport number
for K+ ion ranged from 0.95 to 0.97 depending on the composition and temperature. Electrochemical cells of configuration K/PVC+KBrO3/(I2+C+electrolyte) and K/PVC+KBrO3+plasticizer/(I2+C+electrolyte) were fabricated. The discharge characteristics of the cells were studied under a constant load of 100 kΩ.
The open-circuit voltage, short-circuit current, and discharge time for the plateau region were measured. The PVC+KBrO3 polymer electrolyte system with added plasticizer showed an increased discharge time with respect to pure PVC+KBrO3 electrolyte system. The features of complexation of the electrolytes were studied by X-ray diffraction. 相似文献
999.
M. Potoczek 《Journal of Physics and Chemistry of Solids》2007,68(4):564-569
Ceramic molybdenum disulphide (MoS2) was equilibrated at an ambient sulphur vapour partial pressure p(S2), 10 Pa<p(S2)<1000 Pa. After the step change of p(S2) to a new value, the equilibration kinetics was monitored by measuring electrical conductivity. The application of the solution of Fick's second law (with the initial condition: no concentration gradient in specimen and the boundary condition: surface concentration constant) to the kinetic data gave the chemical diffusion coefficient. The chemical diffusion coefficient, Dchem, determined at 1273 K, was Dchem=(3.20±0.32)*10−7 cm2 s−1 and was found to be independent of sulphur vapour partial pressure. The usefulness of transient electrical conductivity method for determining real values of diffusion data was discussed in terms of defect structure of the studied material. 相似文献
1000.
D. H.H. Hoffmann A. Blazevic O. N. Rosmej P. Spiller N. A. Tahir K. Weyrich T. Dafni M. Kuster P. Ni M. Roth S. Udrea D. Varentsov J. Jacoby V. Kain R. Schmidt K. Zioutas V. Mintsev V. E. Fortov B. Yu. Sharkov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):293-300
Interaction phenomena of intense ion- and laser radiation with matter have a
large range of application in different fields of science, extending from
basic research of plasma properties to applications in energy science,
especially in inertial fusion. The heavy ion synchrotron at GSI now
routinely delivers intense uranium beams that deposit about 1 kJ/g of
specific energy in solid matter, e.g. solid lead. Our simulations show that
the new accelerator complex FAIR (Facility for Antiproton and Ion Research)
at GSI as well as beams from the CERN large hadron collider (LHC) will
vastly extend the accessible parameter range for high energy density states.
A natural example of hot dense plasma is provided by our neighbouring star
the sun, and allows a deep insight into the physics of fusion, the
properties of matter at high energy density, and is moreover an excellent
laboratory for astroparticle physics. As such the sun's interior plasma can
even be used to probe the existence of novel particles and dark matter
candidates. We present an overview on recent results and developments of
dense plasma physics addressed with heavy ion and laser beams combined with
accelerator- and nuclear physics technology. 相似文献