4,347 research outputs found
A quasiclassical method for calculating the density of states of ultracold collision complexes
We derive a quasiclassical expression for the density of states (DOS) of an
arbitrary, ultracold, -atom collision complex, for a general potential
energy surface (PES). We establish the accuracy of our quasiclassical method by
comparing to exact quantum results for the K-Rb and NaK-NaK systems, with
isotropic model PESs. Next, we calculate the DOS for an accurate NaK-NaK PES to
be 0.124~K, with an associated Rice-Ramsperger-Kassel-Marcus (RRKM)
sticking time of 6.0~s. We extrapolate the DOS and sticking times to all
other polar bialkali-bialkali collision complexes by scaling with atomic
masses, equilibrium bond lengths, dissociation energies, and dispersion
coefficients. The sticking times calculated here are two to three orders of
magnitude shorter than those reported by Mayle et al. [Phys. Rev. A 85, 062712
(2012)]. We estimate dispersion coefficients and collision rates between
molecules and complexes. We find that the sticking-amplified three-body loss
mechanism is not likely the cause of the losses observed in the experiments
Continuous production of glycerol by catalytic high pressure hydrogenolysis of sucrose
Several continuous reactor systems have been discussed for the catalytic high pressure hydrogenolysis of sucrose to glycerol. Theoretically and actually, continuous reactors lead to lower glycerol yields than in a batch process. Two continuous stirred tank reactors in cascade constitute a reasonable compromise. An economic evaluation of the sucrose route to glycerol in comparison with other synthetic glycerol processes based on allyl chloride and acrolein suggests that the sucrose process can be competitive if a sales potential is developed for the by-products propane-l,2-diol, ethylene glycol, and a mixture of higher polyhydric alcohols containing tetritol, pentitol, methyl fructoside, and hexitol
Mirrors of the World - Supporting Situational Awareness with Computer Screens
In this paper we develop a notion of support for social and situational awareness. Our initial ideas are based on the metaphor of using a mirror to see what you are not looking at. We provide two studies that, for different contexts, apply the metaphor to develop design ideas that fit the context of use
Photo-induced two-body loss of ultracold molecules
The lifetime of nonreactive ultracold bialkali gases was conjectured to be
limited by sticky collisions amplifying three-body loss. We show that the
sticking times were previously overestimated and do not support this
hypothesis. We find that electronic excitation of NaK+NaK collision complexes
by the trapping laser leads to the experimentally observed two-body loss. We
calculate the excitation rate with a quasiclassical, statistical model
employing ab initio potentials and transition dipole moments. Using longer
laser wavelengths or repulsive box potentials may suppress the losses
Time-Domain Measurement of Spontaneous Vibrational Decay of Magnetically Trapped NH
The v = 1 -> 0 radiative lifetime of NH (X triplet-Sigma-, v=1,N=0) is
determined to be tau_rad,exp. = 37.0 +/- 0.5 stat +2.0 / -0.8 sys miliseconds,
corresponding to a transition dipole moment of |mu_10| = 0.0540 + 0.0009 /
-0.0018 Debye. To achieve the long observation times necessary for direct
time-domain measurement, vibrationally excited NH (X triplet-Sigma-, v=1,N=0)
radicals are magnetically trapped using helium buffer-gas loading. Simultaneous
trapping and lifetime measurement of both the NH(v=1, N=0) and NH(v=0,N=0)
populations allows for accurate extraction of tau_rad,exp. Background helium
atoms are present during our measurement of tau_rad,exp., and the rate constant
for helium atom induced collisional quenching of NH(v=1,N=0) was determined to
be k_q < 3.9 * 10^-15 cm^3/s. This bound on k_q yields the quoted systematic
uncertainty on tau_rad,exp. Using an ab initio dipole moment function and an
RKR potential, we also determine a theoretical value of 36.99 ms for this
lifetime, in agreement with our experimental value. Our results provide an
independent determination of tau_rad,10, test molecular theory, and furthermore
demonstrate the efficacy of buffer-gas loading and trapping in determining
metastable radiative and collisional lifetimes.Comment: 10 pages + 3 figures (11 pages total) v2 has minor corrections and
explanations accepted for publication in PR
GTA: Groupware task analysis Modeling complexity
The task analysis methods discussed in this presentation stem from Human-Computer Interaction (HCI) and Ethnography (as applied for the design of Computer Supported Cooperative Work CSCW), different disciplines that often are considered conflicting approaches when applied to the same design problems. Both approaches have their strength and weakness, and an integration of them does add value to the early stages of design of cooperation technology. In order to develop an integrated method for groupware task analysis (GTA) a conceptual framework is presented that allows a systematic perspective on complex work phenomena. The framework features a triple focus, considering (a) people, (b) work, and (c) the situation. Integrating various task-modeling approaches requires vehicles for making design information explicit, for which an object oriented formalism will be suggested. GTA consists of a method and framework that have been developed during practical design exercises. Examples from some of these cases will illustrate our approach
Retirement Plans Limited to Salaried Employees: Tax Advantages and Qualification
Retirement plans are among the most effective tax saving devices available and can be extremely attractive, as will be shown, to the small corporation and the highly compensated employee, especially when it is considered that a properly designed plan can be integrated with Social Security so that larger benefits are provided on the salary in excess of that covered by Social Security than on the salary subject to Social Security
Double Greedy Algorithms: Reduced Basis Methods for Transport Dominated Problems
The central objective of this paper is to develop reduced basis methods for
parameter dependent transport dominated problems that are rigorously proven to
exhibit rate-optimal performance when compared with the Kolmogorov -widths
of the solution sets. The central ingredient is the construction of
computationally feasible "tight" surrogates which in turn are based on deriving
a suitable well-conditioned variational formulation for the parameter dependent
problem. The theoretical results are illustrated by numerical experiments for
convection-diffusion and pure transport equations. In particular, the latter
example sheds some light on the smoothness of the dependence of the solutions
on the parameters
HCI – the domain and the Education –coming of age, expanding territory, and marrying new domains
Podeu consultar el llibre complet a: http://hdl.handle.net/10459.1/64797Having developed academic HCI teaching in many countries, and being involved in professional societies from the start, we will show how the domain of HCI, and the related education, developed in different parts of the world, specifically in North America, Europe, and China. We observed local flavors and differences that in the last decades gradually related, merged, and moved the original domain to broader areas of application and to a larger population of users.
Usability was exchanged for experience, programming languages were replaced by service opportunities, interactive art, and cultural participation
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