370 research outputs found
Status of ultrachemical analysis for semiconductors
Status of ultratrace chemical analyses of materials for semiconductors was studied. This study covered atomic absorption spectroscopy, emission spectroscopy, and activation analyses. It makes recommendations to improve sensitivity, reliability and versatility for ultratrace chemical analysis
Consistent thermodynamic derivative estimates for tabular equations of state
Numerical simulations of compressible fluid flows require an equation of
state (EOS) to relate the thermodynamic variables of density, internal energy,
temperature, and pressure. A valid EOS must satisfy the thermodynamic
conditions of consistency (derivation from a free energy) and stability
(positive sound speed squared). When phase transitions are significant, the EOS
is complicated and can only be specified in a table. For tabular EOS's such as
SESAME from Los Alamos National Laboratory, the consistency and stability
conditions take the form of a differential equation relating the derivatives of
pressure and energy as functions of temperature and density, along with
positivity constraints. Typical software interfaces to such tables based on
polynomial or rational interpolants compute derivatives of pressure and energy
and may enforce the stability conditions, but do not enforce the consistency
condition and its derivatives. We describe a new type of table interface based
on a constrained local least squares regression technique. It is applied to
several SESAME EOS's showing how the consistency condition can be satisfied to
round-off while computing first and second derivatives with demonstrated
second-order convergence. An improvement of 14 orders of magnitude over
conventional derivatives is demonstrated, although the new method is apparently
two orders of magnitude slower, due to the fact that every evaluation requires
solving an 11-dimensional nonlinear system.Comment: 29 pages, 9 figures, 16 references, submitted to Phys Rev
âThe Queen of Decadence': Rachilde and Sado-Masochistic Feminism
In 1884, the novel Monsieur VĂ©nus took the French literary world by storm, and inaugurated its controversial female author, Rachilde, the âqueen of decadence.â Many critics did not believe that a young, aristocratic woman could possibly have devised such a salacious story. A literary press which specialized in erotica first published the book, but it was banned regardless, and Rachilde was even condemned to prison for pornographic writing. Subsequent editions therefore required fake male co-authors and introductions by famous male writers that consigned the novel not literature at all, but the case study of a hysterical woman. Rachilde also publicly denounced the feminism of her moment, a proclamation that affected the twentieth-century reception of her writing. Yet, following new French and English editions published in 2004, Monsieur VĂ©nus has been hailed a queer forerunner in contemporary academic circles, even while questions about Rachildeâs feminist affiliations persist. This paper goes beyond the biographical details that have dominated conversation about Rachildeâs writing to closely interrogate the use of sexual violence in Monsieur VĂ©nus, and in her much lesser-known novel, La Marquise de Sade (1887). Based on the definition of sadomasochism Gilles Deleuze outlines in his book, Masochism: Coldness and Cruelty (1991), the respective use of masochism in Monsieur VĂ©nus and of sadism in La Marquise de Sade places its female characters in the unlikely positions of masochist and sadist to offer a provocative critique of the decadent moment, and its representations of sexuality, the body, and even nationalism
Apographs of lost codex r for Demosthenis in Timocratem
The study of the five apographs of the lost codex r is still partial. It can be shown that the scholia in R, Fi, Vf, Mk, Lb come down from r. Discussion on the sources of r and an inquiry about its readings. This lost ms. was probably copied during the Paleologean age. The scholia in Vf, Mk and Lb were copied from still extant mss. And R and Fi, although they are the first copies of r, are useless to establish a new text of the scholia on Demosthenesâ Or. 24
Solving One Dimensional Scalar Conservation Laws by Particle Management
We present a meshfree numerical solver for scalar conservation laws in one
space dimension. Points representing the solution are moved according to their
characteristic velocities. Particle interaction is resolved by purely local
particle management. Since no global remeshing is required, shocks stay sharp
and propagate at the correct speed, while rarefaction waves are created where
appropriate. The method is TVD, entropy decreasing, exactly conservative, and
has no numerical dissipation. Difficulties involving transonic points do not
occur, however inflection points of the flux function pose a slight challenge,
which can be overcome by a special treatment. Away from shocks the method is
second order accurate, while shocks are resolved with first order accuracy. A
postprocessing step can recover the second order accuracy. The method is
compared to CLAWPACK in test cases and is found to yield an increase in
accuracy for comparable resolutions.Comment: 15 pages, 6 figures. Submitted to proceedings of the Fourth
International Workshop Meshfree Methods for Partial Differential Equation
CoSyR: a novel beam dynamics code for the modeling of synchrotron radiation effects
The self-consistent nonlinear dynamics of a relativistic charged particle
beam interacting with its complete self-fields is a fundamental problem
underpinning many of the accelerator design issues in high brightness beam
applications, as well as the development of advanced accelerators.
Particularly, synchrotron radiation induced effects in a magnetic dispersive
beamline element can lead to collective beam instabilities and emittance
growth. A novel beam dynamic code is developed based on a Lagrangian method for
the calculation of the particles' radiation near-fields using wavefront/wavelet
meshes via the Green's function of the Maxwell equations. These fields are then
interpolated onto a moving mesh for dynamic update of the beam. This method
allows radiation co-propagation and self-consistent interaction with the beam
in the simulation at greatly reduced numerical errors. Multiple levels of
parallelisms are inherent in this method and implemented in our code CoSyR to
enable at-scale simulations of nonlinear beam dynamics on modern computing
platforms using MPI, multi-threading, and GPUs. CoSyR has been used to evaluate
the transverse and longitudinal coherent radiation effects on the beam and to
investigate beam optics designs proposed for mitigation of beam brightness
degradation in a magnetic bunch compressor. In this paper, the design of CoSyR,
as well as the benchmark with other coherent synchrotron radiation models, are
described and discussed.Comment: 17 pages, 14 figure
Improving smoothed particle hydrodynamics with an integral approach to calculating gradients
In this paper we develop and test a fully conservative SPH scheme based on a
tensor formulation that can be applied to simulate astrophysical systems. In
the proposed scheme, derivatives are calculated from an integral expression
that leads to a tensor (instead of a vectorial) estimation of gradients and
reduces to the standard formulation in the continuum limit. The new formulation
improves the interpolation of physical magnitudes, leading to a set of
conservative equations that resembles those of standard SPH. The resulting
scheme is verified using a variety of well-known tests, all of them simulated
in two dimensions. We also discuss an application of the proposed tensor method
to astrophysics by simulating the stability of a Sun-like polytrope calculated
in three dimensions.Comment: 15 pages, 12 figures, accepted for publication in Astronomy and
Astrophysics; minor changes due to language editin
Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Comparison
Knowledge of the relative stabilities of alane (AlH3) complexes with electron
donors is essential for identifying hydrogen storage materials for vehicular
applications that can be regenerated by off-board methods; however, almost no
thermodynamic data are available to make this assessment. To fill this gap, we
employed the G4(MP2) method to determine heats of formation, entropies, and
Gibbs free energies of formation for thirty-eight alane complexes with NH3-nRn
(R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA),
quinuclidine, OH2-nRn (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran
(THF). Monomer, bis, and selected dimer complex geometries were considered.
Using these data, we computed the thermodynamics of the key formation and
dehydrogenation reactions that would occur during hydrogen delivery and alane
regeneration, from which trends in complex stability were identified. These
predictions were tested by synthesizing six amine-alane complexes involving
trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and
hexamine, and obtaining upper limits of delta G for their formation from
metallic aluminum. Combining these computational and experimental results, we
establish a criterion for complex stability relevant to hydrogen storage that
can be used to assess potential ligands prior to attempting synthesis of the
alane complex. Based on this, we conclude that only a subset of the tertiary
amine complexes considered and none of the ether complexes can be successfully
formed by direct reaction with aluminum and regenerated in an alane-based
hydrogen storage system.Comment: Accepted by the Journal of Physical Chemistry
Recommended from our members
Visuo-spatial cognition in Williams syndrome: Reviewing and accounting for the strengths and weaknesses in performance
Individuals with Williams syndrome typically show relatively poor visuo-spatial abilities in comparison to stronger verbal skills. However, individuals' level of performance is not consistent across all visuo-spatial tasks. The studies assessing visuo-spatial functioning in Williams syndrome are critically reviewed, in order to provide a clear pattern of the relative difficulty of these tasks. This prompts a possible explanation of the variability in performance seen which focuses on the processing demands of some of these tasks. Individuals with Williams syndrome show an atypical processing style on tests of construction, which does not affect tests of perception
- âŠ