1,569 research outputs found
Scenario-based modeling in industrial information systems
This manuscript addresses the creation of scenario-based models to reason about the behavior of existing industrial information systems. In our approach the system behavior is modeled in two steps that gradually introduce detail and formality. This manuscript addresses the first step, where text-based descriptions, in the form of structured rules, are used to specify how the system is or should be regulated. Those rules can be used to create behavioral snapshots, which are collections of scenario-based descriptions that represent different
instances of the system behavior. Snapshots are specified in an intuitive and graphical notation that considers the elements from the problem domain and permit designers to discuss and validate the externally observable behavior, together with the domain experts. In the second step (not fully covered in this manuscript), the system behavior is formalized with an executable model. This formal model, which in our approach is specified using the Colored Petri Net (CP-nets) language, allows the system internal behavior to be animated, simulated, and optimized.
The insights gained by experimenting with the formal model can be subsequently used for reengineering the existing system
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Laser induced recovery of deuterium or tritium from water
>A laser method for recovery of deuterium or tritium from water is proposed. The two-step photolysis method utilizes a known coincidencc of the P/ sub 1/(8) line of the DF laser with HDO and D/sub 2/O absorption lines coupled with a water filtered xenon flash lamp to selectively photolyze HDO and D/sub 2/O in the presence of H/sub 2/O. CO is to be added to the photolysis mixture to remove the O atom from the OH photolysis product. The isotopic material is to be collected as D/sub 2/. The reaction kinetics for this experiment has been modeled with a computer calculation based on rate processes. The dependence of isotopic selectivity on various vibrational energy transfer processes is discussed. (auth
Novel criticality in a model with absorbing states
We study a one-dimensional model which undergoes a transition between an
active and an absorbing phase. Monte Carlo simulations supported by some
additional arguments prompted as to predict the exact location of the critical
point and critical exponents in this model. The exponents and
follows from random-walk-type arguments. The exponents are found to be non-universal and encoded in the singular part of
reactivation probability, as recently discussed by H. Hinrichsen
(cond-mat/0008179). A related model with quenched randomness is also studied.Comment: 5 pages, 5 figures, generalized version with the continuously
changing exponent bet
Market Integration Shape Organic Farmers’ Organisation
Increasing consumption of organic products in globalised food chains will require the involvement of thousands more smallholder farmers in many regions of the world. A study of Egypt, China and Uganda identified the three key factors of property rights regimes, cultural differences and social organisation as determents of the supply chain organization and farmers’ degree of direct integration in the export markets. Patterns are emerging where smallholder farmers are being socially and economically linked to larger farmers who may do some processing before the raw materials are handed over to the contracting company. Where transactions costs are high, local communities may develop and contract out the land directly to exporting companies who farm using employees. Four organisational patterns are identified which each leads to different types of livelihood benefits for the producers; preliminary results indicate that income and a reliable market access is the dominant benefits
Spinning Strings, Black Holes and Stable Closed Timelike Geodesics
The existence and stability under linear perturbation of closed timelike
curves in the spacetime associated to Schwarzschild black hole pierced by a
spinning string are studied. Due to the superposition of the black hole, we
find that the spinning string spacetime is deformed in such a way to allow the
existence of closed timelike geodesics.Comment: 5 pages, RevTex4, some corrections and new material adde
Effect of FET geometry on charge ordering of transition metal oxides
We examine the effect of an FET geometry on the charge ordering phase diagram
of transition metal oxides using numerical simulations of a semiclassical model
including long-range Coulomb fields, resulting in nanoscale pattern formation.
We find that the phase diagram is unchanged for insulating layers thicker than
approximately twice the magnetic correlation length. For very thin insulating
layers, the onset of a charge clump phase is shifted to lower values of the
strength of the magnetic dipolar interaction, and intermediate diagonal stripe
and geometric phases can be suppressed. Our results indicate that, for
sufficiently thick insulating layers, charge injection in an FET geometry can
be used to experimentally probe the intrinsic charge ordering phases in these
materials.Comment: 4 pages, 4 postscript figure
Phase transition between synchronous and asynchronous updating algorithms
We update a one-dimensional chain of Ising spins of length with
algorithms which are parameterized by the probability for a certain site to
get updated in one time step. The result of the update event itself is
determined by the energy change due to the local change in the configuration.
In this way we interpolate between the Metropolis algorithm at zero temperature
for of the order of 1/L and for large , and a synchronous deterministic
updating procedure for . As function of we observe a phase transition
between the stationary states to which the algorithm drives the system. These
are non-absorbing stationary states with antiferromagnetic domains for ,
and absorbing states with ferromagnetic domains for . This means
that above this transition the stationary states have lost any remnants to the
ferromagnetic Ising interaction. A measurement of the critical exponents shows
that this transition belongs to the universality class of parity conservation.Comment: 5 pages, 3 figure
Impact of Intimate Partner Violence on Parenting and Children’s Externalizing Behaviors: Transactional Processes Over Time
This study used longitudinal data to examine the transactional associations between mothers’ spanking and mother–child relationship quality with children’s externalizing behaviors in the context of intimate partner violence (IPV). Data came from a sample of 1,152 low-income mothers with children age 10–14 years. Results showed that past-year IPV triggered transactional associations by increasing children’s externalizing behaviors which, in turn, increased spanking and subsequently more externalizing behaviors. Transactional associations were also found for relationship quality. All outcomes used were mothers-reported except relationship quality. Implications for practice include the importance of the mother–child dyad and their reciprocal processes in assessment and treatment
Study of the multi-species annihilating random walk transition at zero branching rate - cluster scaling behavior in a spin model
Numerical and theoretical studies of a one-dimensional spin model with
locally broken spin symmetry are presented. The multi-species annihilating
random walk transition found at zero branching rate previously is investigated
now concerning the cluster behaviour of the underlying spins. Generic power law
behaviors are found, besides the phase transition point, also in the active
phase with fulfillment of the hyperscaling law. On the other hand scaling laws
connecting bulk- and cluster exponents are broken - a possibility in no
contradiction with basic scaling assumptions because of the missing absorbing
phase.Comment: 7 pages, 6 figures, final form to appear in PRE Nov.200
Is nuclear matter perturbative with low-momentum interactions?
The nonperturbative nature of inter-nucleon interactions is explored by
varying the momentum cutoff of a two-nucleon potential. Conventional force
models, which have large cutoffs, are nonperturbative because of strong
short-range repulsion, the iterated tensor interaction, and the presence of
bound or nearly-bound states. But for low-momentum interactions with cutoffs
around 2 fm^{-1}, the softened potential combined with Pauli blocking leads to
corrections in nuclear matter in the particle-particle channel that are well
converged at second order in the potential, suggesting that perturbation theory
can be used in place of Brueckner resummations. Calculations of nuclear matter
using the low-momentum two-nucleon force V_{low k} with a corresponding
leading-order three-nucleon (3N) force from chiral effective field theory (EFT)
exhibit nuclear binding in the Hartree-Fock approximation, and become less
cutoff dependent with the inclusion of the dominant second-order contributions.
The role of the 3N force is essential to obtain saturation, and the
contribution to the total potential energy is compatible with EFT
power-counting estimates.Comment: 24 pages, 7 figures, references and attractive c4 contribution added,
figures updated, conclusions unchanged; minor additions, to appear in Nucl.
Phys.
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