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[en] COMPTRA04 is a Fortran 90 program package developed for the calculation of composition and transport coefficients within the partially ionized plasma model. This paper summarizes the theoretical background and gives instructions on how to implement and use the package. Results obtained by using COMPTRA04 are given for Be plasma in order to allow for a test of the package. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
[en] The FINESSE code (finite element solver for stationary equilibria) computes axisymmetric magnetohydrodynamic equilibria in poloidal elliptic flow regimes for a variety of astrophysical and laboratory plasma configurations. The obtained equilibria are accurate and are used to study the spectral characteristics of such flowing equilibria. The nonlinear partial differential equation for the poloidal magnetic flux is solved in a weak form via Picard iteration, resulting in a large-scale linear problem. The algebraic Bernoulli equation for the poloidal Alfven Mach number is solved with a nonlinear root finder. Converged solutions are obtained by iterating on these two equations
[en] This paper reports on wind powered hydrogen production which is promising for Hawaii because Hawaii's wind energy potential exceeds the state's current electrical energy requirements by more than twenty-fold. Wind energy costs are now approaching $0.06 to $0.08/kWh, and the U.S. Department of Energy has set a goal of $0.04/kWh. These conditions make wind power a good source for electrolytic production of hydrogen. HNEI's wind-hydrogen program, at the HNEI-Kahua Wind Energy Storage Test facility on the island of Hawaii, is developing energy storage and power electronic systems for intermittent wind and solar devices to provide firm power to the utility or to a stand-alone hybrid system. In mid 1990, the first wind-hydrogen production/storage/ generation system is scheduled for installation. HNEI's wind- hydrogen program will provide research, development, demonstration, and education on the great potential and benefits of hydrogen
[en] In most cases a saccular aneurysm is the cause of acute subarachnoidal hemorrhage (SAH). The usual symptoms are severe headache and meningism. Due to the high mortality rate caused by rebleeding an early occlusion of the aneurysm should be strived for. For this early diagnosis an exact identification of the aneurysm and its configuration is essential. (orig.)
[de]Ursache einer Subarachnoidalblutung (SAB) ist meist ein sackfoermiges Aneurysma. Die SAB aeussert sich durch einen ploetzlich auftretenden Kopfschmerz, meist verbunden mit Meningismus. Die Mortalitaetsrate bei unbehandelten Aneurysmablutungen ist hoch. Ziel ist somit eine fruehe Diagnosestellung mit dann raschem Verschluss der Blutungsquelle. (orig.)
[en] We present theoretical results for the equation of state of hydrogen and helium applying the chemical picture which treats the elementary charged particles (electrons, ions) and neutral bound states (atoms, molecules) on an equal footing. The chemical equilibrium for dissociation and ionization processes is solved accounting for nonideality corrections. We compare our results with experiments and other theoretical models and calculate pressures and temperatures in jupiter's interior
[en] Complete text of publication follows. The behavior of warm dense matter (pressures of several megabar and temperatures of several eV) is of paramount importance for interior models of giant planets such as Jupiter and Saturn. Coulomb systems under those conditions are strongly correlated and quantum effects are important so that they can be used to check methods of many particle theory. Challenging problems in warm dense matter physics are, e.g., the highpressure phase diagram of the simplest and most abundant elements hydrogen and helium. Furthermore, novel phenomena such as proton conduction and demixing are expected in oxygen, carbon, nitrogen, their hydrides and mixtures at high pressures which are relevant for, e.g., Uranus and Neptune. Therefore, solar and extrasolar giant planets are perfect laboratories for the study of warm dense matter. We apply ab initio molecular dynamics simulations based on finite-temperature density functional theory to calculate the thermophysical properties of H, He, their mixtures and of H2O for a wide range of densities and temperatures. For instance, equation of state data for hydrogen indicate a first-order liquid-liquid phase transition which is closely connected with a nonmetal-to-metal transition. Our results yield a critical point at 1400 K, 1.32 Mbar and 0.79 g/cm3 - i.e. at much lower temperatures than chemical models have predicted for the plasma phase transition. The behavior of the electrical and thermal conductivity, thermopower, and Lorenz number is analyzed along this transition, especially deviations from the Wiedemann-Franz relation. We have identified the parameters for demixing of helium from hydrogen which match the conditions in the interior of Saturn as long has been predicted. The high-pressure phase diagram of water has been calculated including the location of a superionic phase. We have determined the interior structure and composition of Jupiter and Saturn based on this ab initio equation of state data within three-layer models. We give results for the metallicity, the size of the core, and the cooling time. Corresponding interior models for Uranus and Neptune are in striking agreement with assumptions of dynamo simulations that reproduce their unusual magnetic field structure. Predictions for possible interior structures of extrasolar giant planets can be given as well, see e.g.
[en] Matter-wave interferometry has been used extensively over the last few years to demonstrate the quantum-mechanical wave nature of increasingly larger and more massive particles. We have recently suggested the use of the historical Poisson spot setup to test the diffraction properties of larger objects. In this paper, we present the results of a classical particle van der Waals (vdW) force model for a Poisson spot experimental setup and compare these to Fresnel diffraction calculations with a vdW phase term. We include the effect of disc-edge roughness in both models. Calculations are performed with D2 and with C70 using realistic parameters. We find that the sensitivity of the on-axis interference/focus spot to disc-edge roughness is very different in the two cases. We conclude that by measuring the intensity on the optical axis as a function of disc-edge roughness, it can be determined whether the objects behave as de Broglie waves or classical particles. The scaling of the Poisson spot experiment to larger molecular masses is, however, not as favorable as in the case of near-field light-grating-based interferometers. Instead, we discuss the possibility of studying the Casimir-Polder potential using the Poisson spot setup.
[en] The amount and distribution of heavy elements in Jupiter gives indications on the process of its formation and evolution. Core mass and metallicity predictions, however, depend on the equations of state (EOSs) used and on model assumptions. We present an improved ab initio hydrogen EOS, H-REOS.2, and compute the internal structure and thermal evolution of Jupiter within the standard three-layer approach. The advance over our previous Jupiter models with H-REOS.1 by Nettelmann et al. is that the new models are also consistent with the observed ∼> 2 times solar heavy element abundances in Jupiter's atmosphere. Such models have a rock core mass Mc = 0-8 M⊕, total mass of heavy elements MZ = 28-32 M⊕, a deep internal layer boundary at ≥4 Mbar, and a cooling time of 4.4-5.0 Gyr when assuming homogeneous evolution. We also calculate two-layer models in the manner of Militzer et al. and find a comparable large core of 16-21 M⊕, out of which ∼11 M⊕ is helium, but a significantly higher envelope metallicity of 4.5 times solar. According to our preferred three-layer models, neither the characteristic frequency (ν0 ∼ 156 μHz) nor the normalized moment of inertia (λ ∼0.276) is sensitive to the core mass but accurate measurements could well help to rule out some classes of models.
[en] We present simulations of coronal mass ejections (CMEs) performed with a new two-temperature coronal model developed at the University of Michigan, which is able to address the coupled thermodynamics of the electron and proton populations in the context of a single fluid. This model employs heat conduction for electrons, constant adiabatic index (γ = 5/3), and includes Alfvén wave pressure to accelerate the solar wind. The Wang-Sheeley-Arge empirical model is used to determine the Alfvén wave pressure necessary to produce the observed bimodal solar wind speed. The Alfvén waves are dissipated as they propagate from the Sun and heat protons on open magnetic field lines to temperatures above 2 MK. The model is driven by empirical boundary conditions that includes GONG magnetogram data to calculate the coronal field, and STEREO/EUVI observations to specify the density and temperature at the coronal boundary by the Differential Emission Measure Tomography method. With this model, we simulate the propagation of fast CMEs and study the thermodynamics of CME-driven shocks. Since the thermal speed of the electrons greatly exceeds the speed of the CME, only protons are directly heated by the shock. Coulomb collisions low in the corona couple the protons and electrons allowing heat exchange between the two species. However, the coupling is so brief that the electrons never achieve more than 10% of the maximum temperature of the protons. We find that heat is able to conduct on open magnetic field lines and rapidly propagates ahead of the CME to form a shock precursor of hot electrons.
[en] Equilibrium, waves, and instabilities of tokamaks and accretion disks that are rotating with arbitrary transonic velocities have been solved by means of advanced numerical and analytical techniques. The different transonic flow regimes yield a surprisingly large number of new MHD waves and instabilities that (1) are relevant for turbulent processes in accretion disks, (2) provide a clear correspondence between tokamaks and accretion disk dynamics, with different influence of rotation profiles, gravity, and magnetic pressure, (3) provide a new angle on rapid transition phenomena in transonic MHD flows of rotating astrophysical plasmas. The new angle entails a complete revision of all previously obtained spectral results. The reason is that transonic flows upset the standard theoretical approach to plasma dynamics, consisting of a separate study of the equilibrium state and of the perturbations of this background. We will discuss a new approach to this dichotomy consisting of a study of the similarities of the nonlinear stationary flow patterns and the different linear wave structures that occur when the background speed traverses the full range of critical speeds (from 'slow magnetosonic' to 'Alfven' to 'fast magnetosonic'). This has required the development of new computational tools that yield the mentioned plethora of new waves and instabilities