An exact method for a discrete multiobjective linear fractional optimization

Integer linear fractional programming problem with multiple objective MOILFP is an important field of research and has not received as much attention as did multiple objective linear fractional programming. In this work, we develop a branch and cut algorithm based on continuous fractional optimization, for generating the whole integer efficient solutions of the MOILFP problem. The basic idea of the computation phase of the algorithm is to optimize one of the fractional objective functions, then generate an integer feasible solution. Using the reduced gradients of the objective functions, an efficient cut is built and a part of the feasible domain not containing efficient solutions is truncated by adding this cut. A sample problem is solved using this algorithm, and the main practical advantages of the algorithm are indicated

An exact method for a discrete multiobjective linear fractional optimization

Integer linear fractional programming problem with multiple objective MOILFP is an important field of research and has not received as much attention as did multiple objective linear fractional programming. In this work, we develop a branch and cut algorithm based on continuous fractional optimization, for generating the whole integer efficient solutions of the MOILFP problem. The basic idea of the computation phase of the algorithm is to optimize one of the fractional objective functions, then generate an integer feasible solution. Using the reduced gradients of the objective functions, an efficient cut is built and a part of the feasible domain not containing efficient solutions is truncated by adding this cut. A sample problem is solved using this algorithm, and the main practical advantages of the algorithm are indicated.multiobjective programming, integer programming, linear fractional programming, branch and cut

Skew-symmetric matrices and their principal minors

Let $V$ be a nonempty finite set and $A=(a_{ij})_{i,j\in V}$ be a matrix with entries in a field $\mathbb{K}$. For a subset $X$ of $V$, we denote by $A[X]$ the submatrix of $A$ having row and column indices in $X$. We study the following problem. Given a positive integer $k$, what is the relationship between two matrices $A=(a_{ij})_{i,j\in V}$, $B=(b_{ij})_{i,j\in V}$ with entries in $\mathbb{K}$ and such that $\det(A\left[ X\right])=\det(B\left[ X\right])$ for any subset $X$ of $V$ of size at most $k$ ? The Theorem that we get in this Note is an improvement of a result of R. Loewy [5] for skew-symmetric matrices whose all off-diagonal entries are nonzero

Coupling of a high-energy excitation to superconducting quasiparticles in a cuprate from Coherent Charge Fluctuation Spectroscopy

Dynamical information on spin degrees of freedom of proteins or solids can be obtained by Nuclear Magnetic Resonance (NMR) and Electron Spin Resonance (ESR). A technique with similar versatility for charge degrees of freedom and their ultrafast correlations could move forward the understanding of systems like unconventional superconductors. By perturbing the superconducting state in a high-Tc cuprate using a femtosecond laser pulse, we generate coherent oscillations of the Cooper pair condensate which can be described by an NMR/ESR formalism. The oscillations are detected by transient broad-band reflectivity and found to resonate at the typical scale of Mott physics (2.6 eV), suggesting the existence of a non-retarded contribution to the pairing interaction, as in unconventional (non Migdal-Eliashberg) theories.Comment: Accepted for publication in the Proceedings of the National Academy of Sciences of the U.S.A. (PNAS

A microfluidic flow-cell for the study of the ultrafast dynamics of biological systems

The study of biochemical dynamics by ultrafast spectroscopic methods is often restricted by the limited amount of liquid sample available, while the high repetition rate of light sources can induce photodamage. In order to overcome these limitations, we designed a high flux, sub-ml, capillary flow-cell. While the 0.1 mm thin window of the 0.5 mm cross-section capillary ensures an optimal temporal resolution and a steady beam deviation, the cell-pump generates flows up to ∼0.35 ml/s that are suitable to pump laser repetition rates up to ∼14 kHz, assuming a focal spot-diameter of 100 μm. In addition, a decantation chamber efficiently removes bubbles and allows, via septum, for the addition of chemicals while preserving the closed atmosphere. The minimal useable amount of sample is ∼250 μl

Intelligent IT Governance Platform: Strategic level

The objective of this work is the implementation of a new IT governance platform adaptable to any type of Information system architecture and any kind of business. The proposed platform is intelligent and independent to understand the business needs continuously changing, is distributed to involve all stakeholders and heterogeneous components, and scalable to accumulate the know-how of the company's IT Governance through a learning asset

Ultrafast Electronic and Structural Phenomena in Graphite and Graphene

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 - August 5, 201