13,257 research outputs found
Thermochemical generation of hydrogen
The direct fluid contact heat exchange with H2SO4 at about 330 C prior to high temperature decomposition at about 830 C in the oxygen release step of several thermochemical cycles for splitting water into hydrogen and oxygen provides higher heat transfer rates, savings in energy and permits use of cast vessels rather than expensive forged alloy indirect heat exchangers. Among several candidate perfluorocarbon liquids tested, only perfluoropropylene oxide polymers having a degree of polymerization from about 10 to 60 were chemically stable, had low miscibility and vapor pressure when tested with sulfuric acid at temperatures from 300 C to 400 C
Improved gas ring laser
Minimizing mode coupling improves sensing resolution of a gas ring laser in a gimballess gyroscope system or inertial rotation sensor. The piezoelectric-driven corner mirrors of the ring laser are oscillated in a direction parallel to their surfaces and the plane of rotation
Potential heat exchange fluids for use in sulfuric acid vaporizers
A series of perhalocarbons are proposed as candidate heat exchange fluids for service in thermochemical cycles for hydrogen production that involve direct contact of the fluid with sulfuric acid and vaporization of the acid. The required chemical and physical criteria of the liquids are described and the results of some preliminary high temperature test data are presented
The platinum nuclei: concealed configuration mixing and shape coexistence
The role of configuration mixing in the Pt region is investigated. For this
chain of isotopes, the nature of the ground state changes smoothly, being
spherical around mass and and deformed around the
mid-shell N=104 region. This has a dramatic effect on the systematics of the
energy spectra as compared to the systematics in the Pb and Hg nuclei.
Interacting Boson Model with configuration mixing calculations are presented
for gyromagnetic factors, -decay hindrance factors, and isotope shifts.
The necessity of incorporating intruder configurations to obtain an accurate
description of the latter properties becomes evident.Comment: Accepted in Physical Review
Composite fermions from the algebraic point of view
Composite fermion wavefuctions have been used to describe electrons in a
strong magnetic field. We show that the polynomial part of these wavefunctions
can be obtained by applying a normal ordered product of suitably defined
annihilation and creation operators to an even power of the Vandermonde
determinant, which can been considered as a kind of a non-trivial Fermi sea. In
the case of the harmonic interaction we solve the system exactly in the lowest
Landau level. The solution makes explicit the boson-fermion correspondence
proposed recently.Comment: 11 pages 1 figur
Safety hazards associated with the charging of lithium/sulfur dioxide cells
A continuing research program to assess the responses of spirally wound, lithium/sulfur dioxide cells to charging as functions of charging current, temperature, and cell condition prior to charging is described. Partially discharged cells that are charged at currents greater than one ampere explode with the time to explosion inversely proportional to the charging current. Cells charged at currents of less than one ampere may fail in one of several modes. The data allows an empirical prediction of when certain cells will fail given a constant charging current
Numerical Quantum Field Theory on the Continuum and a New Look at Perturbation Theory
The Source Galerkin method finds approximate solutions to the functional
differential equations of field theories in the presence of external sources.
While developing this process, it was recognized that approximations of the
spectral representations of the Green's functions by Sinc function expansions
are an extremely powerful calculative tool. Specifically, this understanding
makes it not only possible to apply the Source Galerkin method to higher
dimensional field theories, but also leads to a new approach to perturbation
theory calculations in scalar and fermionic field theories. This report
summarizes the methodologies for solving quantum field theories with the Source
Galerkin method and for performing perturbation theory calculations using Sinc
approximations.Comment: Lattice2001(theorydevelop
Basic linear algebra subprograms for FORTRAN usage
A package of 38 low level subprograms for many of the basic operations of numerical linear algebra is presented. The package is intended to be used with FORTRAN. The operations in the package are dot products, elementary vector operations, Givens transformations, vector copy and swap, vector norms, vector scaling, and the indices of components of largest magnitude. The subprograms and a test driver are available in portable FORTRAN. Versions of the subprograms are also provided in assembly language for the IBM 360/67, the CDC 6600 and CDC 7600, and the Univac 1108
Manifestation of three-body forces in f7/2-shell nuclei
The traditional nuclear shell model approach is extended to include many-body
forces. The empirical Hamiltonian with a three-body force is constructed for
the identical nucleons on the 0f7/2 shell. Manifestations of the three-body
force in spectra, binding energies, seniority mixing, particle-hole symmetry,
electromagnetic and particle transition rates are investigated. It is shown
that in addition to the usual expansion of the valence space within the
tranditional two-body shell model, the three-body component in the Hamiltonian
can be an important part improving the quality of the theoretical approach.Comment: 5 pages, 1 figur
Episodic disk accretion in the halo of the 'old' Pre-Main Sequence cluster Eta Chamaeleontis
We present multi-epoch medium-resolution observations of two M4.5 candidate
members in the halo of the ~8 Myr Eta Chamaeleontis open cluster. Over six
months of observations both stars exhibited variations in their H-alpha line
profiles on timescales of days to months, with at least one episode of
substantial activity attributable to accretion from a circumstellar disk. We
derive an accretion rate ~10^-8.7 Msun/yr for this event, with a rate of
~10^-10.6 Msun/yr in quiescence. Episodic accretion like that observed here
means existing surveys of accreting Weak-lined T-Tauri Stars in young clusters
are likely incomplete and that gas dissipation timescales calculated from the
fraction of accreting objects are underestimates.Comment: 5 pages, 5 figures, 1 table. Accepted for publication in MNRAS
Letter
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