A productivity signal feedback controller for continuous bioreactors

The control of continuous stirred bioreactors using productivity signal feedback consists of using the direct relation between the optimal static dilution rate and the optimal static productivity. This strategy drives the bioprocess to its optimal productivity point, irrespective of the feeding substrate concentration, and specific growth rate or substrate concentration estimates. While the algorithm covers a wide class of bioprocesses, explicit relations are given for the Monod and Haldane cases.     

Accurate junction detection and characterization in line-drawing images

In this paper, we present a new approach for junction detection and characterization in line-drawing images. We formulate this problem as searching for optimal meeting points of median lines. In this context, the main contribution of the proposed approach is three-fold. First, a new algorithm for the determination of the support region is presented using the linear least squares technique, making it robust to digitization effects. Second, an efficient algorithm is proposed to detect and conceptually remove all distorted zones, retaining reliable line segments only. These line segments are then locally characterized to form a local structure representation of each crossing zone. Finally, a novel optimization algorithm is presented to reconstruct the junctions. Junction characterization is then simply derived. The proposed approach is very highly robust to common geometry transformations and can resist a satisfactory level of noise/degradation. Furthermore, it works very efficiently in terms of time complexity and requires no prior knowledge of the document content. Extensive evaluations have been performed to validate the proposed approach using other baseline methods. An application of symbol spotting is also provided, demonstrating quite good results.     

Efficient prototyping of large-scale pdms and silicon nanofluidic devices using pdms-based phase-shift lithography

In this study, we explore the potential of poly-dimethylsiloxane (PDMS)-based phase-shift lithography (PPSL) for the fabrication of nanofluidic devices. We establish that this technology, which was already shown to allow for the generation of 100?nm linear or punctual features over squared centimeter surfaces with conventional photolithography systems, is readily adequate to produce some of the most popular nanofluidic systems, namely nanochannels and nanoposts arrays. We also demonstrate that PPSL technology enables to generate PDMS and silicon nanofluidic systems. This technological achievement allows us to perform single DNA molecule manipulation experiments in PDMS and silicon nanochannels, and we observe an unexpectedly slow migration of DNA in PDMS devices, which is independent on salt or pH conditions. Our data in fact hint to the existence of an anomalous response of DNA in PDMS nanofluidic devices, which is likely associated to transient nonspecific interactions of DNA with PDMS walls. Overall, our work demonstrates the efficiency and the performances of PPSL for prototyping nanofluidic systems.     

Statistical tolerance analysis of a hyperstatic mechanism,using system reliability methods

The quality level of a mechanism can be evaluated a posteriori after several months by following the number of warranty returns. However, it is more interesting to evaluate a predicted quality level in the design stage: this is one of the aims of statistical tolerance analysis. A possible method consists of computing the defect probability (P_D) expressed in ppm. It represents the probability that a functional requirement will not be satisfied in mass production. For assembly reasons, many hyperstatic mechanisms require gaps, which their functional requirements depend on. The defect probability assessment of such mechanisms is not straightforward, and requires advanced numerical methods. This problem particularly interests the VALEO W.S. company, which experiences problems with an assembly containing gaps. This paper proposes an innovative methodology to formulate and compute the defect probability of hyperstatic mechanisms with gaps in two steps. First, a complex feasibility problem is converted into a simpler problem. Then the defect probability is efficiently computed thanks to system reliability methods and the m-dimensional multivariate normal distribution Φ_m. Finally, a sensitivity analysis is provided to improve the original design. The whole approach is illustrated with an industrial case study, but can be adapted to other similar problems.     

A statistical tolerance analysis approach for over-constrained mechanism based on optimization and Monte Carlo simulation

Tolerancing decisions can profoundly impact the quality and cost of the mechanism. To evaluate the impact of tolerance on mechanism quality, designers need to simulate the influences of tolerances with respect to the functional requirements. This paper proposes a mathematical formulation of tolerance analysis which integrates the notion of quantifier: “For allacceptable deviations (deviations which are inside tolerances),there existsa gap configurationsuch asthe assembly requirements and the behavior constraints are verified” & “For allacceptable deviations (deviations which are inside tolerances), andfor alladmissible gap configurations, the assembly and functional requirements and the behavior constraints are verified”. The quantifiers provide a univocal expression of the condition corresponding to a geometrical product requirement. This opens a wide area for research in tolerance analysis. To solve the mechanical problem, an approach based on optimization is proposed. Monte Carlo simulation is implemented for the statistical analysis. The proposed approach is tested on an over-constrained mechanism.     

Mechanism of action of Melaleuca armillaris (Sol. Ex Gaertu) Sm. essential oil on six LAB strains as assessed by multiparametric flow cytometry and automated microtiter-based assay

Little is known concerning the effects of essential oils (EOs) against lactic acid bacteria (LAB), either of the human gastrointestinal microflora or those involved in industrial processes. GC and GC/MS analysis of Melaleuca armillaris EO resulted in the identification of 68 compounds comprising 99.6% of the oil. Eucalyptol (1,8-cineole) was the major compound (68.9%) and the composition was largely dominated by the oxygenated monoterpenes fraction (77.3%). The anti-LAB activities of the EO were first checked by the disc diffusion assay. In a second phase, time-survival kinetics of each strain incubated with increasing concentrations of the EO (0.25, 2.5, 5 and 25 μg/ml) were established using an automated microtiter assay (Bioscreen C). Bacteriostatic or bactericidal effects were noticed depending on the studied strain and on the applied concentration of the EO. The mathematical modelling of the kinetics showed that in presence of increasing concentrations of M. armillaris EO, the lag phases of growth were extended (0.69%–97.5%) and both the growth rate and final cell density were reduced. Variations depending on the strain were noticed.     

Effect of seed coat fragments on cotton yarn structure: impact of fragment size,attached fibres and position within yarn core

Seed coat fragments are a major source of cotton yarn imperfections. This article discusses the factors influencing the disruption caused by seed coat fragments in ring-spun yarn structure with a focus on three characteristics: the fragment's size, the amount of fibres attached to it and its position relative to the yarn core. The three characteristics were investigated through two experiments involving various types of yarn defects and a range of ring-spun yarn counts. Results presented in this article indicate that the three factors considered have a significant influence on the intensity of the disruption the seed coat fragment causes in the yarn structure, and are determinant of the type of defect that this disruption engenders (short/long defect).     

A variable neighborhood descent heuristic for arc routing problems with time-dependent service costs

This paper proposes a variable neighborhood descent heuristic for solving a capacitated arc routing problem with time-dependent service costs. The problem is motivated by winter gritting applications where the timing of each intervention is crucial. The variable neighborhood descent is based on neighborhood structures that manipulate arcs or sequences of arcs. Computational results are reported on problems derived from classical capacitated arc routing problem instances. A comparison is also provided with an alternative approach where the arc routing problem is solved after being transformed into an equivalent node routing problem.     

Nouveau type structural dans la chimie des phosphures : Le compose ternaire Ni20Zr6P13. Preparation,structure et proprietes

Two new compounds Ni₁₂Zr₂P₇ and Ni₂₀Zr₆P₁₃ were synthesized in the NiZrP system by reacting the constituent elements. Ni₁₂Zr₂P₇ is of the Fe₁₂Zr₂P₇-type while Ni₂₀Zr₆P₁₃ appears as a new structural type in the chemistry of transition metal phosphides. Its unit cell is hexagonal with space group P6̄ and contains one formula unit. The X-ray structure was studied from three-dimensional single-crystal counter data and was refined down to R = 0.040 for 221 independent reflections. The structure of Ni₂₀Zr₆P₁₃ can be described as built up by two groups of three phosphorus trigonal prisms occupied by the zirconium atoms. In each group, the |ZrP₆| prisms are linked together by common edges in order to generate triangular phosphorus sites occupied by nickel atoms. In addition, nickel atoms are also in tetrahedral and square-planar pyramidal phosphorus sites. A comparative study with the Fe₂P- and Co₄Hf₂P₃-type structures having the same metal/non metal ratio as in Ni₁₂Zr₂P₇ and Ni₂₀Zr₆P₁₃ is also discussed. A nearly temperature independent paramagetism and a metallic conduction deducted from magnetic and electrical measurements exhibit the metallic behavior for these new compounds.