A Cost-Regular Based Hybrid Column Generation Approach

Constraint Programming (CP) offers a rich modeling language of constraints embedding efficient algorithms to handle complex and heterogeneous combinatorial problems. To solve hard combinatorial optimization problems using CP alone or hybrid CP-ILP decomposition methods, costs also have to be taken into account within the propagation process. Optimization constraints, with their cost-based filtering algorithms, aim to apply inference based on optimality rather than feasibility. This paper introduces a new optimization constraint, cost-regular. Its filtering algorithm is based on the computation of shortest and longest paths in a layered directed graph. The support information is also used to guide the search for solutions. We believe this constraint to be particularly useful in modeling and solving Column Generation subproblems and evaluate its behaviour on complex Employee Timetabling Problems through a flexible CP-based column generation approach. Computational results on generated benchmark sets and on a complex real-world instance are given.A preliminary version of this paper appeared as [7]. This research was supported by the Mathematics of Information Technology and Complex Systems (MITACS) Internship program in association with Omega Optimisation Inc. (CA).     

Tight LP bounds for resource constrained project scheduling

The best lower bound for the Resource Constrained Project Scheduling Problem is currently based on the resolution of several large Linear Programs (Brucker & Knust, EJOR, 107: 272-288, 1998). In this paper, we show that (1) intensive constraint propagation can be used to tighten the initial formulation of the linear programs and (2) we introduce several sets of valid cutting planes. These improvements allow us to close 16 new instances of the PSPLIB with 60 activities and to improve the best known lower bounds of 64 instances.Correspondence to:Philippe BaptisteThe authors would like to thank Peter Brucker and Sigrid Knust for providing their source code as well as Christian Artigues, Jacques Carlier and Philippe Michelon for enlightening discussions on project scheduling.     

Diffusional fluorescence quenching of aromatic hydrocarbons

The quenching of the fluorescence of five aromatic hydrocarbons by three halogenated organics and by molecular oxygen has been measured. Both fluorescence intensity and fluorescence lifetime measurements have been employed to validate results and interpretation; linear Stern-Volmer analyses are shown to apply throughout. The fluorescence quenching rate constant of molecular oxygen for the five aromatic hydrocarbons is essentially equivalent to the diffusion rate constant independent of the fluorophore excitation energy. The halogenated organic-fluorophore rate constants vary by a factor of 965 and are shown to correlate roughly with the energy difference between the quencher and fluorophore excited electronic states in accord with a standard model of quantum two-level mixing. The value of the coupling interaction energy is approximately 2500 cm(-1).     

High pass filter with above IC integrated SrTiO3 high K MIM capacitors

This paper describes realization and characterization of SrTiO₃ (STO) high K MIM capacitors above BiCMOS integrated circuit (IC). These capacitances are connected to IC and are used as coupling capacitors in order to realize a high pass filter. Surface capacitance achieved is 10 nF/mm² with capacitance value of 1.2 nF. The process for STO MIM fabrication does not exceed 400 °C, which is compatible with interconnections. Typical K and dielectric losses values obtained are, respectively 110% and 2%. Yield obtained reaches 83% for capacitors. A functional high pass filter using these STO capacitors was realized in this study. It exhibits a cut-off frequency at 6.5 kHz and a constant gain at higher frequencies of −1.3 dB.     

Optimization of LED‐based light blendings for object presentation

This study looks at the perceived quality of light‐emitting diode (LED)‐based lighting of various colors. The objective was to find out whether LEDs could provide better (i.e., more relevant and acceptable) lighting than that which is obtained with standard halogen or fluorescent sources. The perception of objects was assessed under different lighting schemes. Subjects were invited to add red, cyan and/or amber to white LED‐based light to match the halogen and fluorescence rendering on specific targets: a color chart and a painting. They were also asked to rate the difference between the two, and to express their preference. The results obtained for the perception of LED‐based lighting were quite positive. Color blendings of LED light were found to provide illuminated situations similar to halogens or fluorescent sources. These blendings were well accepted, and indeed often preferred, although the color rendering index (CRI) was always low. This indicates that the CRI as it stands is inadequate to characterize the color rendering of solid‐state light sources, and needs to be updated. LED‐based lighting systems seem to have considerable potential for use in shops and display units, where they may well outperform existing lighting systems. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 310–320, 2009     

Iron compounds electrodeposited onto a transparent semiconductor: Synthesis and characterisation by UV-vis spectroscopy

Homogeneous thin layers of lepidocrocite, green rust incorporating chloride anions (GRCl-GR1) and green rust incorporating sulphate anions (GRSO₄-GR2) were successfully electrodeposited onto tin dioxide substrate (SnO₂). The UV-vis spectroscopy absorbance, measured just after synthesis, increases linearly with the amount of iron compounds confirming that the electrodeposition is a homogeneous process. From the spectra, the absorption coefficients were determined for the three compounds. The monitoring by UV-vis spectroscopy measurements in real time of the oxidation in the air of the two unstable compounds, GRCl and GRSO₄, shows that the two green rusts have a different behaviour due to their own structure. The presence of an isobestic point in the case of GRSO₄ translates one equilibrium with its oxidised compound. This phenomenon is not observed for GRCl, however, the characteristic variation of the absorbance in the high wavelengths gives information on its oxidation reaction. From simple measurements, fruitful information on green rusts is obtained and this experimental system may be applied to other unstable solid compounds.     

Fabrication and evaluation of solid-oxide fuel cell anodes employing reaction-sintered yttria-stabilized zirconia

This paper reports on the fabrication and performance of solid-oxide fuel cell (SOFC) anodes utilizing yttria reaction-sintered zirconia (YRSZ). Through the reaction-sintering process, the technical-grade YSZ commonly used in the Ni-YSZ anode cermet is replaced with lower-cost ZrO₂ and Y₂O₃ materials. When sintered in the presence of nickel oxide, ZrO₂ and Y₂O₃ form cubic-phase YSZ at temperatures characteristic of SOFC processing (1400-1550 °C). Reaction sintering enables the formation of YSZ during cell fabrication, reducing SOFC anode raw-materials cost and the number of SOFC-fabrication processes. This paper reports the results of a broad range of characterization and performance measurements to evaluate the YRSZ material, including (1) crystal structure, (2) morphology, (3) pore-size distribution, (4) electronic resistivity, (5) fracture strength, (6) gas transport and catalytic activity, and (7) electrochemical performance. Material properties and performance are found to be comparable to or better than equivalent materials fabricated by conventional processes.     

拉拉君堡的采收之旅

9月我从上海出发，坐了十多个小时的飞机经巴黎辗转到达波尔多，从机场驱车沿着齐隆河（Gironde）左岸北上高梅多克（Haut Medoc），20分钟后司机提醒我到达了这条公路上的第一家列级酒店。