Bayesian Analysis in Partially Accelerated Life Tests for Weighted Lomax Distribution

Accelerated life testing has been widely used in product life testing experiments because it can quickly provide information on the lifetime distributions by testing products or materials at higher than basic conditional levels of stress, such as pressure, temperature, vibration, voltage, or load to induce early failures. In this paper, a step stress partially accelerated life test (SS-PALT) is regarded under the progressive type-II censored data with random removals. The removals from the test are considered to have the binomial distribution. The life times of the testing items are assumed to follow length-biased weighted Lomax distribution. The maximum likelihood method is used for estimating the model parameters of length-biased weighted Lomax. The asymptotic confidence interval estimates of the model parameters are evaluated using the Fisher information matrix. The Bayesian estimators cannot be obtained in the explicit form, so the Markov chain Monte Carlo method is employed to address this problem, which ensures both obtaining the Bayesian estimates as well as constructing the credible interval of the involved parameters. The precision of the Bayesian estimates and the maximum likelihood estimates are compared by simulations. In addition, to compare the performance of the considered confidence intervals for different parameter values and sample sizes. The Bootstrap confidence intervals give more accurate results than the approximate confidence intervals since the lengths of the former are less than the lengths of latter, for different sample sizes, observed failures, and censoring schemes, in most cases. Also, the percentile Bootstrap confidence intervals give more accurate results than Bootstrap-t since the lengths of the former are less than the lengths of latter for different sample sizes, observed failures, and censoring schemes, in most cases. Further performance comparison is conducted by the experiments with real data.     

Gait Pattern Based on CMAC Neural Network for Robotic Applications

The main goal of this paper is to provide a general methodology and a practical approach for the design of gait pattern for biped robotic applications directly usable by researchers and engineers. This approach, which is based on CMAC neural network, is an alternative way in comparison to the traditional Central Pattern Generator. In the proposed method, the CMAC neural networks are used to learn basic motions (e.g. reference gait) and a Fuzzy Inference System allows to merge these reference motions in order to built more complex gaits. The results of our biped robotic applications show how to design a self-adaptive gait pattern according to average velocity and external perturbations.     

A Relative Representation of Trajectories in Geogaphical Spaces

The research presented in this paper introduces a relative representation of trajectories in space and time. The objective is to represent space the way it is perceived by a moving observer acting in the environment, and to provide a complementary view to the usual absolute vision of space. Trajectories are characterized from the perception of a moving observer where relative positions and relative velocities are the basic primitives. This allows for a formal identification of elementary trajectory configurations, and their relationships with the regions that compose the environment. The properties of the model are studied, including transitions and composition tables. These properties characterize trajectory transitions by the underlying processes that semantically qualify them. The approach provides a representation that might help the understanding of trajectory patterns in space and time.

Kinetics analysis of the curing of a diepoxy-diamine system

The reaction between the diglycidylether of bisphenol A (DGEBA) and 4,9-dioxa-1,12-dodecanediamine (DDDD) has been studied by means of isothermal and dynamic differential scanning calorimetry. The enthalpy of the reaction of an epoxy group with an amino-hydrogen has been determined to be 112 ± 5 kJ/mol. A kinetic model has been validated. It involves two competitive mechanisms: one is catalysed by the hydroxy groups initially present on the epoxy chain or generated during the reaction (activation energy 77 ± 5 kJ/mol), the other is not catalysed with a higher activation energy (103 ± 3 kJ/mol). For each isothermal curing, the kinetics are not modified by gelation. Evaluated from the gel times, the overall activation energy of the reaction is equal to 62 ± 2 kJ/mol.     

Lipid composition of normal and hypertrophic bovine thyroids

The phospholipid content of bovine thyroid tissue amounts to 70% of total lipid. Triglycerides and cholesterol are the main neutral lipids. Only trace amounts of free fatty acid and esterified cholesterol are found, while two not yet identified components also are present. The distribution of lipid phosphorus in the different phospholipid classes is as follows: phosphatidyl choline, 43.0%; phosphatidyl ethanolamine, 25.2%; phosphatidyl serine, 5.6%; phosphatidyl inositol, 6.5%; sphingomyelin, 14.0%; cardiolipin, 2.8%; lysophosphatidyl choline, <1%; and phosphatidic acid, <1%. The phosphatidyl ethanolamines are rich in plasmalogens. The fatty acid patterns in the different lipid classes are reported. The essential differences between normal and hypertrophic bovine thyroid tissue are higher water content and lower triglyceride and sphingomyelin values for hypertrophic tissue.     

A glance at violet LED sensitive photoinitiators based on the spiroxanthene scaffold

A novel photoinitiator based on a spiroxanthene scaffold in the presence of an iodonium salt is proposed for the cationic ring‐opening polymerization of a diepoxide, as well as for the free‐radical polymerization of an acrylate upon violet LED exposure (385 and 405 nm). Good‐to‐excellent rates of polymerization and final conversions are obtained. These systems are characterized by a higher reactivity compared with that of anthracene/iodonium salt used as reference for cationic near UV polymerization. The addition of a poly(ionic liquid) improves the cationic polymerization profiles. The photochemical mechanisms are studied by steady‐state photolysis, fluorescence, and electron spin resonance spin‐trapping techniques. Molecular orbital calculations give an insight into the light absorption properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43213.     

Retro‐1 Analogues Differentially Affect Oligonucleotide Delivery and Toxin Trafficking

Retro‐1 is a small molecule that displays two important biological activities: First, it blocks the actions of certain toxins by altering their intracellular trafficking. Second, it enhances the activity of oligonucleotides by releasing them from entrapment in endosomes. This raises the question of whether the two actions involve the same cellular target. Herein we report the effects of several Retro‐1 analogues on both toxins and oligonucleotides. We found analogues that affect toxins but not oligonucleotides and vice‐versa, while Retro‐1 is the only compound that affects both. This indicates that the molecular target(s) involved in the two processes are distinct.     

Modeling of the chemical behavior of sodium fire aerosols during atmospheric dispersion

The use of liquid sodium as a coolant in sodium-cooled fast reactors (SFR) circuits requires studying the consequences of a sodium fire for safety analysis, and particularly the toxicological impact of sodium fire aerosols. More particularly, the carbonation of sodium fire aerosols from sodium hydroxide (NaOH) to sodium carbonate (Na₂CO₃) is investigated. A new kinetic model, based on the CO₂ reactive absorption and the two-film theory, is developed to describe the carbonation process of NaOH solutions, taking into account the NaOH aerosols' initial characteristics in equilibrium with the atmosphere. This model is applied for the case of NaOH aerosols considering the CO₂ absorption at the particle external surface. The estimation for the model parameters is detailed as function of NaOH degree of conversion, relative humidity (RH), and temperature. By comparisons with available experimental data, the absorption interfacial area is empirically estimated over the studied range of RH and initial particle diameter. The global sensitivity study of the model confirms its capabilities to describe NaOH aerosols' carbonation, waiting for new experimental data for validation.

© 2016 American Association for Aerosol Research     

Filtration performances of HVAC filters for PM10 and microbial aerosols— Influence of management in a lab-scale air handling unit

Filtration performances of air handling unit (AHU) filters for particles and microbial aerosols were investigated. The influence of the AHU operational conditions on the behavior of microorganisms collected on the filters was also studied. A lab-scale AHU with two filtration stages was developed and validated for the study of downsized filters with industrial geometries. Three types of filters of different efficiency were considered: G4, F7, and F9, according to European standard EN 779. Two configurations of filters were studied: G4 pleated/F7 bag and F7/F9 bag. Filters were sequentially clogged by alumina particles, which provided a mineral fraction in the particulate cake, and then by micronized rice particles, which provided the fungus Penicillium chrysogenum and an organic fraction that acts as a substrate for microorganisms. Finally, a microbial aerosol composed of endospores of Bacillus subtilis and spores of Aspergillus niger was nebulized to contaminate filters. After clogging, periods of 5 days on and 2 day weekend stops with restarts of ventilation were simulated for 6 weeks. The results showed that the filter efficiency for particles was quite comparable to that for microbial aerosols expressed in cultivable concentration. The particulate cake composed of alumina and micronized rice particles enabled the growth of the endogenous species P. chrysogenum and the survival of exogenous species B. subtilis and A. niger on filters. During restarts of ventilation, low particle concentrations were detected downstream of the second filtration stages by release but the microbial concentration from the fraction of air sampled was below the detection limit.

© 2016 American Association for Aerosol Research