Games,Critical Paths and Assignment Problems in Permutation Flow Shops and Cyclic Scheduling Flow Line Environments

In this paper we address the non-pre-emptive flow shop scheduling problem for makespan minimization in a new modelling framework. A lower bound generation scheme is developed by using appropriately defined linear assignment problems and, based on this new approach, a special class of permutation flow shop problems is identified. We present a game theoretic interpretation of our modelling approach which leads to an integer programming formulation of the scheduling problem. A new branch and bound scheme is developed based on these results. The major advantage of our modelling framework and branch-and- bound approach is that it can be easily extended to address a general class of cyclic scheduling problems for production flow lines with blocking. After a discussion of this extension, we report on computational experience that indicates the very satisfactory performance of the new optimal solution procedure for cyclic scheduling problems with finite capacity buffers.     

Stability,monotonicity and invariant quantities in general polling systems

Consider a polling system withK1 queues and a single server that visits the queues in a cyclic order. The polling discipline in each queue is of general gated-type or exhaustive-type. We assume that in each queue the arrival times form a Poisson process, and that the service times, the walking times, as well as the set-up times form sequences of independent and identically distributed random variables. For such a system, we provide a sufficient condition under which the vector of queue lengths is stable. We treat several criteria for stability: the ergodicity of the process, the geometric ergodicity, and the geometric rate of convergence of the first moment. The ergodicity implies the weak convergence of station times, intervisit times and cycle times. Next, we show that the queue lengths, station times, intervisit times and cycle times are stochastically increasing in arrival rates, in service times, in walking times and in setup times. The stability conditions and the stochastic monotonicity results are extended to the polling systems with additional customer routing between the queues, as well as bulk and correlated arrivals. Finally, we prove that the mean cycle time, the mean intervisit time and the mean station times are invariant under general service disciplines and general stationary arrival and service processes.     

Bone calcium, phosphorus detection by Auger electron spectroscopy

Auger electron spectroscopy was used to detect calcium and phosphorus of cortical bone from rat femoral neck and rear tibia. Spectra were taken from bone pieces as well as from disks prepared from grinded bone material. Experimental conditions were found whereby the samples could be analyzed without conductive coatings. The results of this preliminary investigation demonstrate that Auger electron spectroscopy can be used to study bone mineral elements.     

An explanation of the very low fluorescence and phosphorescence in pyridine: a CASSCF/CASMP2 study

In this work, we applied the multiconfigurational complete active space self-consistent field method and the multiconfigurational second-order perturbation theory CASMP2 to study the fundamental excited states of pyridine and its possible photophysical and photochemical transformations. Our calculations, which are in agreement with the experimental results corresponding to excitations around the 0–0 transition, showed that the very low experimentally observed fluorescence of pyridine is due to the presence of two almost isoenergetic crossings, one of triple character, S₁/T₁/S₀ and the other of S₁/S₀ character. Both crossings are below the minimum of S₁(nπ^*) and have a common transition state (S₁(TS)) with a very low energy barrier (1.85 kcal/mol or 0.08 eV at the CASMP2 level of theory) separating them. A third triple crossing of the type S₁/T₁/S₀ lying lower with respect to the other two elucidates the observed T₁→S₀ radiationless transition. This explains not only pyridine's very low fluorescence and phosphorescence but also its almost negligible photochemistry, showing that photophysics is the prevalent process in this molecule.     

Enhanced photon harvesting in silicon multicrystalline solar cells by new lanthanide complexes as light concentrators

Four europium complexes with enhanced luminescent properties have been synthesized. Thin transparent films of the complexes were prepared on glass panes and then were examined as efficient luminescent solar concentrators for full spectrum utilization in crystalline silicon photovoltaic cells. The complexes could behave as efficient solar concentrators since they absorb UV light, where the spectral response of the crystalline silicon solar cells is low and they emit at 615 nm where the spectral response is maximum. The glass panes covered with europium complexes act as planar waveguides of the emitted light that is collected by the solar cells, which are attached to the edges of the solar concentrators. The europium complexes as solar concentrators were examined in terms of the optimum concentrations and the number of coatings, which were determined in order to evaluate the maximum performance of the solar cells. The case of multiple glass panes with europium complexes was also examined while a 28% maximum increase in the photocurrent was finally established.     

Crude peroxidase from onion solid waste as a tool for organic synthesis. Part II: oxidative dimerization-cyclization of methyl p-coumarate, methyl caffeate and methyl ferulate

The ability of a crude onion peroxidase preparation to act as a biocatalyst for the oxidative dimerization-cyclization of methyl p-coumarate, methyl caffeate and methyl ferulate is presented. The products of the reaction have been fully characterized and were found to possess potent antioxidant activity in a ferric reducing antioxidant power (FRAP) assay.     

Invertible chaotic fragile watermarking for robust image authentication

Fragile watermarking is a popular method for image authentication. In such schemes, a fragile signal that is sensitive to manipulations is embedded in the image, so that it becomes undetectable after any modification of the original work. Most algorithms focus either on the ability to retrieve the original work after watermark detection (invertibility) or on detecting which image parts have been altered (localization). Furthermore, the majority of fragile watermarking schemes suffer from robustness flaws. We propose a new technique that combines localization and invertibility. Moreover, watermark dependency on the original image and the non-linear watermark embedding procedure guarantees that no malicious attacks will manage to create information leaks.