An experimental and kinetic modeling study of the autoignition of α-methylnaphthalene/air and α-methylnaphthalene/n-decane/air mixtures at elevated pressures

The autoignition of α-methylnaphthalene (AMN), the bicyclic aromatic reference compound for the cetane number (CN), and AMN/n-decane blends, potential diesel surrogate mixtures, was studied at elevated pressures for fuel/air mixtures in a heated high-pressure shock tube. Additionally, a comprehensive kinetic mechanism was developed to describe the oxidation of AMN and AMN/n-decane blends. Ignition delay times were measured in reflected shock experiments for Φ = 0.5, 1.0, and 1.5 AMN/air mixtures (CN = 0) for 1032-1445 K and 8-45 bar and for Φ = 1.0 30%-molar AMN/70%-molar n-decane/air (CN = 58) and 70%-molar AMN/30%-molar n-decane/air mixtures (CN = 28) for 848-1349 K and 14-62 bar. Kinetic simulations, based on the comprehensive AMN/n-decane mechanism, are in good agreement with measured ignition times, illustrating the emerging capability of comprehensive mechanisms for describing high molecular weight transportation fuels. Sensitivity and reaction flux analysis indicate the importance of reactions involving resonance stabilized phenylbenzyl radicals, the formation of which by H-atom abstractions with OH radicals has an important inhibiting effect on ignition.     

An experimental and kinetic investigation of premixed furan/oxygen/argon flames

The detailed chemical structures of three low-pressure (35 Torr) premixed laminar furan/oxygen/argon flames with equivalence ratios of 1.4, 1.8 and 2.2 have been investigated by using tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. About 40 combustion species including hydrocarbons and oxygenated intermediates have been identified by measurements of photoionization efficiency spectra. Mole fraction profiles of the flame species including reactants, intermediates and products have been determined by scanning burner position with some selected photon energies near ionization thresholds. Flame temperatures have been measured by a Pt–6%Rh/Pt–30%Rh thermocouple. A new mechanism involving 206 species and 1368 reactions has been proposed whose predictions are in reasonable agreement with measured species profiles for the three investigated flames. Rate-of-production and sensitivity analyses have been performed to track the key reaction paths governing furan consumption for different equivalence ratios. Both experimental and modeling results indicate that few aromatics could be formed in these flames. Furthermore, the current model has been validated against previous pyrolysis results of the literature obtained behind shock waves and the agreement is reasonable as well.     

Internal photoemission in Ge/sapphire/metal structures

Photoemission experiments on Ge/(single-crystal Al₂O₃)/metal structures are reported. The electronic barrier height between aluminium, silver or germanium and single-crystal Al₂O₃ were determined from the spectral response of the photoemission and were found to be 3.20 ± 0.03 eV, 3.81 ± 0.03 eV and 4.01 ± 0.03 eV respectively. Values for μτ (the product of the mobility and the lifetime) and the mean range of injected electrons in Al₂O₃ were determined from steady-state photocurrent-voltage characteristics measured on Ge/Al₂O₃/Al and Al/Al₂O₃/Al structures with a sapphire (Al₂O₃) thickness of 150–250 μm for electric fields in the range from 10² to 2 × 10⁴ V cm^-1. A mean value of 8.4 × 10^-6 cm² V^-1 was deduced for μτ from measurements made on several samples. Measurements made on samples with semitransparent aluminium electrodes of different thicknesses showed that the relative importance of a possible extrinsic photoconductivity component due to charges related to defect centres must be less than the 10% of the measured photocurrent.     

Stability analysis and gain-scheduled state feedback control for continuous-time systems with bounded parameter variations

The problems of robust stability analysis and state feedback control based on gain-scheduling for continuous-time systems with time-varying parameters that have bounded rates of variation and lie inside a polytope are addressed in this article. With respect to previous results in the literature, two main contributions of the article are: (i) the robust stability analysis conditions are less conservative and demand less computational effort than the existing ones; (ii) the conditions can be extended to cope with the problem of control design for this class of system. Parameter-dependent linear matrix inequality (LMI) conditions are given for the existence of a parameter-dependent Lyapunov function quadratic in the state and homogeneous polynomially of arbitrary degree in the parameter assuring robust stability. Two convex procedures based on LMIs exhibiting distinct complexities are proposed to solve the problem of robust stability. An extension to deal with the computation of a stabilising parameter-dependent state feedback gain for this class of time-varying systems is also provided, as a sequence of LMIs of increasing precision. Examples illustrate the results, including comparisons with other techniques from the literature.     

Effective strategic programming for Java developers

In object programming languages, the Visitor design pattern allows separation of algorithms and data structures. When applying this pattern to tree‐like structures, programmers are always confronted with the difficulty of making their code evolve. One reason is that the code implementing the algorithm is interwound with the code implementing the traversal inside the visitor. When implementing algorithms such as data analyses or transformations, encoding the traversal directly into the algorithm turns out to be cumbersome as this type of algorithm only focuses on a small part of the data‐structure model (e.g., program optimization). Unfortunately, typed programming languages like Java do not offer simple solutions for expressing generic traversals. Rewrite‐based languages like ELAN or Stratego have introduced the notion of strategies to express both generic traversal and rule application control in a declarative way. Starting from this approach, our goal was to make the notion of strategic programming available in a widely used language such as Java and thus to offer generic traversals in typed Java structures. In this paper, we present the strategy language SL that provides programming support for strategies in Java. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of nitridation on Fowler–Nordheim tunneling coefficients in SiO2 MOS capacitors with WSi2-polysilicon gate

In this work we have studied the influence of N₂O nitridation of thin EEPROM SiO₂ tunnel oxides on Fowler–Nordheim tunnel injection potential barrier heights in WSi₂-polysilicon gate MOS structures. In particular we have paid attention to the effect of the nitridation temperature by means of a comparison with standard (dry-wet-dry) oxides annealed in N₂ at the same temperature. The temperatures considered were 900 °C, 950 °C and 1000 °C. It has been shown that the Si/SiO₂ barrier is systematically smaller than the poly-Si/SiO₂ one (~0.05 eV) in the whole set of samples and that the nitridation in N₂O systematically decreases both the Si/SiO₂ and the poly-Si/SiO₂ barrier heights all the more as the nitridation temperature increases. The effects of neglecting the contribution of Si/SiO₂ interface states and of the gate depletion phenomenon in the evaluation of the oxide electric field and, as a consequence, in the evaluation of the tunnel injection potential barrier heights have also been considered. It has been shown that neglecting the polysilicon gate depletion phenomenon leads to a strongly over-evaluated value of the Si/SiO₂ barrier height while neglecting the interface states gives an error of approximately 1%. Moreover, we have shown that N₂O nitridation increases the oxide dielectric constant all the more as the nitridation temperature increases while fluorine incorporation into the oxide induced by the WSi₂ polycide deposition process decreases the same constant.     

Extension of Popov absolute stability criterion to non-autonomous systems with delays

This paper extends in a simple way the classical absolute stability Popov criterion to multivariable systems with delays and with time-varying memoryless non-linearities subject to sector conditions. The proposed sufficient conditions are expressed in the frequency domain, a form well-suited for robustness issues, and lead to simple graphical interpretations for scalar systems. Apart from the usual conditions, the results assume basically a generalized sector condition on the derivative of the non-linearities with respect to time. Results for local and global stability are given, the latter concerning in particular the linear time-varying ones. For rational transfers, the frequency conditions are equivalent to some easy-tocheck linear matrix inequalities:this leads to a tractable method of numerical resolution by rational approximation of the transfer. As an illustration, a numerical example is provided.     

Fuzzy multidimensional scaling

Multidimensional scaling (MDS) is a data analysis technique for representing measurements of (dis)similarity among pairs of objects as distances between points in a low-dimensional space. MDS methods differ mainly according to the distance model used to scale the proximities. The most usual model is the Euclidean one, although a spherical model is often preferred to represent correlation measurements. These two distance models are extended to the case where dissimilarities are expressed as intervals or fuzzy numbers. Each object is then no longer represented by a point but by a crisp or a fuzzy region in the chosen space. To determine these regions, two algorithms are proposed and illustrated using typical data sets. Experiments demonstrate the ability of the methods to represent both the structure and the vagueness of dissimilarity measurements.     

Characterization of the microheterogeneities of PIXY321, a genetically engineered granulocyte-macrophage colony-stimulating factor/interleukin-3 fusion protein expressed in yeast

PIXY321, a human cytokine analog genetically engineered by the fusion of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), was expressed in yeast under the control of the alcohol dehydrogenase 2 (ADH2) promoter and the alpha-mating factor expression system. To provide the material necessary for the evaluation of PIXY321 in clinical trials, the production was scaled up to the 1200-1 scale and the PIXY321 molecule isolated by four successive steps of ion-exchange chromatography. Multiple heterogeneities, due to the presence of different patterns of glycosylation as well as multiple amino acid sequences at both N and C termini, were characterized on the purified molecule using complementary analytical techniques including electrophoresis, liquid chromatography and electrospray mass spectrometry. Four different N-terminal sequences were identified but simplified to a reproducible ratio of two sequences, the mature form and a form starting at Ala3, by adjustment of the process conditions. Molecules lacking 1-6 residues at the C-terminus were identified and their relative frequencies quantified. Amino acid modifications, such as three oxidized Met residues at positions 79, 141 and 187 and one deamidated Asn residue at position 176, were detected at low level. Microheterogeneities in glycosylation were characterized on four different sites, one located in the GM-CSF portion and three in the IL-3 portion of the molecule. The sites were shown to be differentially occupied and to carry 0-10 mannose residues according to their location in the sequence. Precise measurement of the heterogeneities at the molecular level were used to tune the process conditions and ensure reproducibility of the clinical product between lots.