175 research outputs found
Understanding Lean Manufacturing According to Axiomatic Design Principles
In this paper, a sequence of implementation steps will be developed through the application of axiomatic design. This sequence will provide a design methodology for lean production which connects manufacturing system design objectives to operation design parameters.Lean Aerospace Initiativ
Axiomatic Design of Manufacturing Systems
This paper introduces the use of axiomatic design in the design of manufacturing systems. The two
primary functional requirements of any manufacturing system are developed. These functional requirements
are used to analyze the design of four manufacturing systems in terms of system performance. The purpose
of this work is to provide a new foundation for describing, determining and rationalizing the design of any
new manufacturing system
Spin transport in magnetic multilayers
We study by extensive Monte Carlo simulations the transport of itinerant
spins travelling inside a multilayer composed of three ferromagnetic films
antiferromagnetically coupled to each other in a sandwich structure. The two
exterior films interact with the middle one through non magnetic spacers. The
spin model is the Ising one and the in-plane transport is considered. Various
interactions are taken into account. We show that the current of the itinerant
spins going through this system depends strongly on the magnetic ordering of
the multilayer: at temperatures below (above) the transition temperature
, a strong (weak) current is observed. This results in a strong jump of
the resistance across . Moreover, we observe an anomalous variation,
namely a peak, of the spin current in the critical region just above . We
show that this peak is due to the formation of domains in the temperature
region between the low- ordered phase and the true paramagnetic disordered
phase. The existence of such domains is known in the theory of critical
phenomena. The behavior of the resistance obtained here is compared to a recent
experiment. An excellent agreement with our physical interpretation is
observed. We also show and discuss effects of various physical parameters
entering our model such as interaction range, strength of electric and magnetic
fields and magnetic film and non magnetic spacer thicknesses.Comment: 8 pages, 17 figures, submitted to J. Phys.: Cond Matte
First-Order Phase Transition in Potts Models with finite-range interactions
We consider the -state Potts model on , , ,
with Kac ferromagnetic interactions and scaling parameter \ga. We prove the
existence of a first order phase transition for large but finite potential
ranges. More precisely we prove that for \ga small enough there is a value of
the temperature at which coexist Gibbs states. The proof is obtained by a
perturbation around mean-field using Pirogov-Sinai theory. The result is valid
in particular for , Q=3, in contrast with the case of nearest-neighbor
interactions for which available results indicate a second order phase
transition. Putting both results together provides an example of a system which
undergoes a transition from second to first order phase transition by changing
only the finite range of the interaction.Comment: Soumis pour publication a Journal of statistical physics - version
r\'{e}vis\'{e}
Reexamination of the long-range Potts model: a multicanonical approach
We investigate the critical behavior of the one-dimensional q-state Potts
model with long-range (LR) interaction , using a multicanonical
algorithm. The recursion scheme initially proposed by Berg is improved so as to
make it suitable for a large class of LR models with unequally spaced energy
levels. The choice of an efficient predictor and a reliable convergence
criterion is discussed. We obtain transition temperatures in the first-order
regime which are in far better agreement with mean-field predictions than in
previous Monte Carlo studies. By relying on the location of spinodal points and
resorting to scaling arguments, we determine the threshold value
separating the first- and second-order regimes to two-digit precision within
the range . We offer convincing numerical evidence supporting
$\sigma_c(q)Comment: 18 pages, 18 figure
Unravelling the effect of charge dynamics at the plasmonic metal/semiconductor interface for CO2 photoreduction
Sunlight plays a critical role in the development of emerging sustainable energy conversion and storage technologies. Light-induced CO2 reduction by artificial photosynthesis is one of the cornerstones to produce renewable fuels and environmentally friendly chemicals. Interface interactions between plasmonic metal nanoparticles and semiconductors exhibit improved photoactivities under a wide range of the solar spectrum. However, the photo-induced charge transfer processes and their influence on photocatalysis with these materials are still under debate, mainly due to the complexity of the involved routes occurring at different timescales. Here, we use a combination of advanced in situ and time-resolved spectroscopies covering different timescales, combined with theoretical calculations, to unravel the overall mechanism of photocatalytic CO2 reduction by Ag/TiO2 catalysts. Our findings provide evidence of the key factors determining the enhancement of photoactivity under ultraviolet and visible irradiation, which have important implications for the design of solar energy conversion materials
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