59,211 research outputs found
Luther and the Mystics
Hoffman, Bengt R. Luther and the Mystics. [S.l.]: Augsburg Publishing House, 1976
Solving the Vlasov equation for one-dimensional models with long range interactions on a GPU
We present a GPU parallel implementation of the numeric integration of the
Vlasov equation in one spatial dimension based on a second order time-split
algorithm with a local modified cubic-spline interpolation. We apply our
approach to three different systems with long-range interactions: the
Hamiltonian Mean Field, Ring and the self-gravitating sheet models. Speedups
and accuracy for each model and different grid resolutions are presented
Solving constraints within a graph based dependency model by digitising a new process of incrementally casting concrete structures
The mechanisation of incrementally casting concrete structures can reduce the economic and environmental cost of the formwork which produces them. Low-tech versions of these forms have been designed to produce structures with cross-sectional continuity, but the design and implementation of complex adaptable formworks remains untenable for smaller projects. Addressing these feasibility issues by digitally modelling these systems is problematic because constraint solvers are the obvious method of modelling the adaptable formwork, but cannot acknowledge the hierarchical relationships created by assembling multiple instances of the system. This thesis hypothesises that these opposing relationships may not be completely disparate and that simple dependency relationships can be used to solve constraints if the real procedure of constructing the system is replicated digitally. The behaviour of the digital model was correlated with the behaviour of physical prototypes of the system which were refined based on digital explorations of its possibilities. The generated output is assessed physically on the basis of its efficiency and ease of assembly and digitally on the basis that permutations can be simply described and potentially built in reality. One of the columns generated by the thesis will be cast by the redesigned system in Lyon at the first F2F (file to factory) continuum workshop
Abundances in metal-rich stars - Detailed abundance analysis of 47 G and K dwarf stars with [Me/H] 0.10 dex
We have derived elemental abundances of O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn,
Fe, Co, Ni for 47 G and K dwarf, with [Me/H]>0.1 dex. The selection of stars
was based on their kinematics as well as on their uvby-photometry. One sample
of stars on rather eccentric orbits traces the chemical evolution interior to
the solar orbit and another, on circular orbits, the evolution around the solar
orbit. A few Extreme Pop I stars were included in the latter sample. The stars
have -0.1<Fe/H]<0.42 dex. We find that the elemental abundances of Mg, Al, Si,
Ca, Ti, Cr and Ni all follow [Fe/H]. Our data put further constraints on models
of galactic chemical evolution, in particular of Cr, Mn and Co which has not
previously been studied for dwarf stars with [Me/H]>0.1 dex. The increase in
[Na/Fe] and [Al/Fe] as a function of [Fe/H] found previously by Edvardsson et
al. (1993a) has been confirmed for [Na/Fe]. This upturning relation, and the
scatter around it, are shown not to be due to a mixture of populations with
different mean distances to the galactic centre. We have not been able to trace
any tendency for relative abundances of O, Si, and Ti relative to Fe to vary
with the stellar velocities, i.e. the stars present mean distance to the
galactic centre. These results imply that there is no significant difference in
the chemical evolution of the different stellar populations for stars with
[Me/H]>0.1 dex. SMR stars on highly eccentric orbits, alleged to trace the
evolution of the chemical evolution in the galactic Bulge, have previously been
found overabundant in O, Mg and Si. We have included 3 such stars from the
study by Barbuy & Grenon (1990). We find them to be less metal rich and the
other elemental abundances remain puzzling. Our study includes 5 K dwarf stars
and reveal a striking example of overionization.Comment: Accepted for publication in Astronomy and Astrophysics Supplement
Series. RGO preprint No. 28
The ISO-LWS map of the Serpens cloud core. II. The line spectra
We present spectrophotometric ISO imaging with the LWS and the CAM-CVF of the
Serpens molecular cloud core. The LWS map is centred on the far infrared and
submillimetre source SMM1 and its size is 8' x 8'. The fine structure line
emission in [OI] and [CII] is extended and can be successfully modelled to
originate in a PDR with G_0 = 15 and n(H2) about 10^4 - 10^5 cm^-3. Extended
emission is also observed in the rotational line emission of H2O and high-J CO.
However, lack of sufficient angular resolution prevents us from excluding the
possibility that the emssion regions of these lines are point like, which could
be linked to the embedded objects SMM9 and SMM4. Toward the Class0 source SMM1,
the LWS observations reveal, in addition to fine structure line emission, a
rich spectrum of molecular lines. The sub-thermally excited and optically thick
CO, H2O and OH lines are tracing an about 10^3 AU source with temperatures
higher than 300 K and densities above 10^6 cm^-3. We show that geometry is of
concern for the correct interpretation of the data and based on 2D-radiative
transfer modelling of the disk/torus around SMM1, which successfully reproduces
the entire observed SED and the observed line profiles of CO isotopomers, we
can exclude the disk to be the source of the LWS-molecular line emission. The
CAM-CVF permits us to see a region of rotational H2 emission. This H2 gas has a
temperature of 10^3 K, which suggests that the heating of the gas is achieved
through relatively slow shocks. Although we are not able to establish any firm
conclusion regarding the detailed nature of the shock waves, our observations
of the molecular line emission from SMM1 can be explainable in terms of an
admixture of J-shocks and of C-shocks.Comment: 20 pages, 20 figures, accepted for publication in A&
Probing the QCD phase diagram with fluctuations
The relevance of higher order cumulants of conserved charges for the analysis
of freeze-out and critical conditions in heavy ion collisions at LHC and RHIC
is discussed. Using properties of scaling functions, the generic
structure of these higher cumulants at vanishing baryon chemical potential is
discussed. Chiral model calculations are then used to study their properties at
non-zero baryon chemical potential. It is argued that the rapid variation of
sixth and higher order cumulants at the phase boundary may be used to explore
the QCD phase diagram in experiment. Moreover, results for the Polyakov loop
susceptibilities in SU(3) lattice gauge theory as well as in (2+1) flavor
lattice QCD are discussed. An analysis of the ratios of susceptibilities
indicates that the deconfinement transition is reflected in characteristic
modifications of these ratios.Comment: 14 pages, 6 figures. To appear in the G.E. Brown memorial volume in
NP
- …