7,975 research outputs found
Perverse sheaves on Artin stacks
In this paper we develop the theory of perverse sheaves on Artin stacks
continuing the study in "The six operations for sheaves on Artin stacks I:
Finite Coefficients" and "The six operations for sheaves on Artin stacks II:
Adic Coefficients" (math.AG/0512097 and math.AG/0603680
Linear Inequality Measures and the Redistribution of Income
A class of inequality measures that is a natural companion to the popular Lorenz curve is the class of measures that are linear in incomes. These measures, which include the Gini and S-Gini coefficients, can be interpreted as ethical means of relative deprivation feelings. Their change through the tax and benefit system can be decomposed simply as a sum of progressivity indices for individual taxes and benefits, minus an index of horizontal inequity measured by the extent of reranking in the population. These progressivity and horizontal inequity indices can also be interpreted as ethical means of perceptions of fiscal harshness and ill-performance. We furthermore derive the asymptotic sampling distribution of these classes of indices of redistribution, progressivity, and horizontal inequity, which enables their use with micro-data on a population. We illustrate the theoretical and statistical results through an application on the distribution and redistribution of income in Canada in 1981 and in 1990.
Virtual manufacturing: prediction of work piece geometric quality by considering machine and set-up
Lien vers la version Ă©diteur: http://www.tandfonline.com/doi/full/10.1080/0951192X.2011.569952#.U4yZIHeqP3UIn the context of concurrent engineering, the design of the parts, the production planning and the manufacturing facility must be considered simultaneously. The design and development cycle can thus be reduced as manufacturing constraints are taken into account as early as possible. Thus, the design phase takes into account the manufacturing constraints as the customer requirements; more these constraints must not restrict the creativity of design. Also to facilitate the choice of the most suitable system for a specific process, Virtual Manufacturing is supplemented with developments of numerical computations (Altintas et al. 2005, Bianchi et al. 1996) in order to compare at low cost several solutions developed with several hypothesis without manufacturing of prototypes. In this context, the authors want to predict the work piece geometric more accurately by considering machine defects and work piece set-up, through the use of process simulation. A particular case study based on a 3 axis milling machine will be used here to illustrate the authorsâ point of view. This study focuses on the following geometric defects: machine geometric errors, work piece positioning errors due to fixture system and part accuracy
Manufacturing Process Modeling and Simulation
This paper presents a methodology to be employed in the whole process design phase including first and second processing. This methodology consists of a set of steps which are characterised by an independent model. This paperâs objective is to analyse the coherence between the different models and the coherence between the model and the objectives of each step. The final stage is to develop the production plans. The casting process was the first one to be analyzed. Casting models were created using CAD software (Catia V5R17) and imported into the casting simulation environment (Magmasoft). Filling and solidifying processes have been simulated using different casting models in order to optimize the final configuration. The machining process was modeled using the machining features concept and it was simulated using Catiaâs Advanced Machining environment. Two machining strategies have been analyzed according to positioning strategies. Process engineering software was used to create the process plans and to analyze the resource allocation
Quadratization of Symmetric Pseudo-Boolean Functions
A pseudo-Boolean function is a real-valued function
of binary variables; that is, a mapping from
to . For a pseudo-Boolean function on
, we say that is a quadratization of if is a
quadratic polynomial depending on and on auxiliary binary variables
such that for
all . By means of quadratizations, minimization of is
reduced to minimization (over its extended set of variables) of the quadratic
function . This is of some practical interest because minimization of
quadratic functions has been thoroughly studied for the last few decades, and
much progress has been made in solving such problems exactly or heuristically.
A related paper \cite{ABCG} initiated a systematic study of the minimum number
of auxiliary -variables required in a quadratization of an arbitrary
function (a natural question, since the complexity of minimizing the
quadratic function depends, among other factors, on the number of
binary variables). In this paper, we determine more precisely the number of
auxiliary variables required by quadratizations of symmetric pseudo-Boolean
functions , those functions whose value depends only on the Hamming
weight of the input (the number of variables equal to ).Comment: 17 page
Charles-Philippe Courtois, La ConquĂȘte. Une anthologie, MontrĂ©al, Les Ăditions Typo, 2009, 488 p. (Anthologie.)
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