Lower Bounds from State Space Relaxations for Concave Cost Network Flow Problems

In this paper we obtain Lower Bounds (LBs) to concave cost network flow problems. The LBs are derived from state space relaxations of a dynamic programming formulation, which involve the use of non-injective mapping functions guaranteing a reduction on the cardinality of the state space. The general state space relaxation procedure is extended to address problems involving transitions that go across several stages, as is the case of network flow problems. Applications for these LBs include: estimation of the quality of heuristic solutions; local search methods that use information of the LB solution structure to find initial solutions to restart the search (Fontes et al., 2003, Networks, 41, 221–228); and branch-and-bound (BB) methods having as a bounding procedure a modified version of the LB algorithm developed here, (see Fontes et al., 2005a). These LBs are iteratively improved by penalizing, in a Lagrangian fashion, customers not exactly satisfied or by performing state space modifications. Both the penalties and the state space are updated by using the subgradient method. Additional constraints are developed to improve further the LBs by reducing the searchable space. The computational results provided show that very good bounds can be obtained for concave cost network flow problems, particularly for fixed-charge problems.     

Synthesis of enantiopure β-amino amides via a practical reductive amination of the corresponding β-keto amides

A convenient and efficient reductive amination for the preparation of chiral β-amino amides is developed utilizing microwave heating. A variety of chiral β-keto amides react with ammonium acetate and sodium cyanoborohydride to afford the desired functionalized amines in good yields. This improved procedure takes advantage of microwave heating to significantly accelerate the reaction and offers a convenient and effective method to access some interesting molecules containing primary amine functionalities.     

Optimal Control of an Evolution Problem Involving Time-Dependent Maximal Monotone Operators

Journal of Optimization Theory and Applications - We consider a control problem in a finite-dimensional setting, which consists in finding a minimizer for a standard functional defined by way of...     

Scatter Search and Genetic Algorithms for MAX-SAT Problems

In this paper, both scatter search (SS) and genetic algorithms (GAs) are studied for the NP-Hard optimization variant of the satisfiability problem, namely MAX-SAT. First, we investigate a new selection strategy based on both fitness and diversity to choose individuals to participate in the reproduction phase of a genetic algorithm. The resulting algorithm is enhanced in two ways leading to two genetic algorithm variants: the first one uses a uniform crossover. The second one uses a specific crossover operator (to MAX-SAT). The crossover operator is combined with an improved stochastic local search (SLS). The crossover operator is used to identify promising regions while the stochastic local search performs an intensified search of solutions around these regions. Secondly, we propose a scatter search variant for MAX-SAT. Both the SS and the GAs implementations share the solution selection strategy, the improved SLS method and the combination operator. Experiments on several instances from MAX-SAT libraries are performed to show and compare the effectiveness of our approaches. The computational experiments show that both (SS) and (GAs) with a stochastic local search (SLS) improvement technique outperform a classical genetic algorithm (without SLS). The two metaheuristics are able of balancing search diversification and intensification which leads to good results. In general, the specific genetic algorithm with a (SLS) improvement technique and a specific combination method provides competitive results and finds solutions of a higher quality than a scatter search.     

Théorèmes d'existence pour des inclusions différentielles du second ordre

We prove several existence theorems for second order differential inclusions of the form $\text{x}\text{?}\text{(t)∈K(x(t))}$, $\text{x}\text{?}\text{(t)∈?N(K(x(t));}\text{x}\text{?}\text{(t))+F(t,}\text{x}\text{?}\text{(t)),}$ when K and F are set-valued mappings taking nonconvex and convex values, respectively, in a Hilbert space H. To cite this article: M. Bounkhel, D. Laouir-Azzam, C. R. Acad. Sci. Paris, Ser. I 336 (2003).     

Highly hydrophilic surfaces from polyglycidol grafts with dual antifouling and specific protein recognition properties

Homopolymer grafts from α-tert-butoxy-ω-vinylbenzyl-polyglycidol (PGL) were prepared on gold and stainless steel (SS) substrates modified by 4-benzoyl-phenyl (BP) moieties derived from the electroreduction of the parent salt 4-benzoyl benzene diazonium tetrafluoroborate. The grafted BP aryl groups efficiently served to surface-initiate photopolymerization (SIPP) of PGL. In similar conditions, SIPP of hydroxyethyl methacrylate (HEMA) permitted the production of PHEMA grafts as model surfaces. Water contact angles were found to be 66°, 15°, and 0° for SS-BP, SS-PHEMA, and SS-PPGL, respectively. The spontaneous spreading of water drops on SS-PPGL was invariably observed with 1.5 μL water drops. PPGL thus appears as a superhydrophilic polymer. Resistance to nonspecific adsorption of proteins of PPGL and PHEMA grafts on gold was evaluated by surface plasmon resonance (SPR) using antibovine serum albumin (anti-BSA). The results conclusively show that PPGL-grafts exhibit enhanced resistance to anti-BSA adsorption compared to the well-known hydrophilic PHEMA. PPGL grafts were further modified with BSA through the carbonyldiimidazole activation of the OH groups providing immunosensing surfaces. The so-prepared PPGL-grafted BSA hybrids specifically interacted with anti-BSA in PBS as compared to antimyoglobin. It is clear that the superhydrophilic character of PPGL grafts opens new avenues for biomedical applications where surfaces with dual functionality, namely, specific protein grafting together with resistance to biofouling, are required.     

Thermodynamic Study of the Solid-Liquid Equilibria in the Systems MIPO3-Pr(PO3)3 (MI=Na,Rb, Cs OR Ag)

A previously established equation of a stoichiometric phase liquidus curve was applied to determination of the phase diagrams of the systems M^IPO₃-Pr(PO₃)₃ (with M^I=Na, Rb, Cs or Ag). The temperature, enthalpy and entropy of fusion were calculated for each solid phase with the exception of silver polyphosphate, the crystallization field of which was very limited. The enthalpy of fusion of the polyphosphate Pr(PO₃)₃ was determined from the DTA curve. The melting enthalpy of Pr(PO₃)₃ calculated from the different binary systems was approximately equal to the measured value. The calculated temperatures and compositions were in good agreement with those determined experimentally. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectroscopical Observation of a Relaxing High Speed Nitrogen Plasma Jet

A near sonic nitrogen plasma jet operating at pressures between 100 Torr and 1 atm has been investigated spectroscopically. From the absolute emission coefficient of a NI spectral line, local values for the electron temperature T_e have been derived. For pressures above 200 Torr, T_g was found to coincide within the limits of experimental error with the gas temperature T_g. The latter quantity has been determined via the relative emission coefficient of selected rotational line components of the N₂⁺ molecular band at 3914 Å. The results of these measurements together with control data for the electron density derived from the continuous emission coefficient indicate that at pressures above 200 Torr the existence of a thermal equilibrium between the degrees of freedom corresponding to particle translation, electron excitation, and ionization can be accepted, at least for the inner zone of the plasma jet. To the contrary, the data for the absolute emission coefficient of N₂⁺ molecular band lines show that the degree of dissociation in the plasma jet is much in excess of that corresponding to equilibrium. This phenomenon can be explained as a result of the rapid temperature decay in the plasma from initially 13000 K in the arc heating zone to T ≦ 9000 K in the plasma jet zone proceeding in a time interval of 10^?5 s which is much shorter than the time necessary for adjustment of dissociation equilibrium. In the outer cool zone of the plasma jet, an unusual high intensity of the N₂⁺ radiation was found thus indicating the existence of a nonequilibrium excitation mechanism typical for a decaying nitrogen plasma. From the supernormal high degree of dissociation in the high-speed subatmospheric nitrogen plasma jet, conclusions are drawn with respect to its applicability as source of reactive particles in plasma-chemical experiments.     

Untersuchungen der kontrahierten Edelgassäule bei mittleren Drücken II. Meßergebnisse in Argon

In this work plasma parameters of the constricted argon discharge have been determined by an iterative method. For the conditions 20 ? Rp ? 300 cm Torr and 0,05 ? i/R ? 2,5 A/cm the electron density, the electron temperature, and the gas temperature are obtained. These results are compared with measurements and calculated values of other authors. With the exception of the determination of gas temperatures at 2,5 A/cm the agreement between our results and the measurements of some other authors is satisfactory.