A smoke-filling simulation model and its engineering applications

A brief presentation of the computer model DSLAY1, which describes the smoke-filling process in a single enclosure, is first given in this paper. Also some computed data of the model are compared with experimental results to show the agreement between theory and experiment. In the latter part of the paper computed results are presented for areas where the model has been used for different fire engineering applications. The main purpose is to show that zone models like DSLAY1 are useful tools to predict the heat and smoke conditions in single enclosures as a result of growing fires. DSLAY1 is an interactive computer program. The user converses with the program via a terminal connected to the computer. The dialogue is governed by commands adapted to the concepts of the user. Reference: Staffan Bengtson and Bengt Hägglund, A Smoke-Filling Simulation Model and Its Engineering Applications,Fire Technology, Vol. 22, No. 2, May 1986, p. 92.     

Textured surfaces for improved lubrication at high pressure and low sliding speed of roller/piston in hydraulic motors

The present study investigates the potential of surface textures to improve the friction situation of the piston/roller contact in hydraulic motors at low speed and high pressure. A self-adjusting flat on flat rig, with conditions representative of an actual hydraulic motor, is used in a reciprocating sliding motion. The samples are made out of the same materials and the surface finishing operations are the same as used in the motor.The piston surfaces are textured using newly developed embossing tools comprising micromechanically formed all-diamond surfaces. The textured surfaces involve parallel grooves and crossed grooves, each of four different spacings. Also polished surfaces were tested. Un-textured—as tumbled—surfaces are used as reference.Generally, it was found that the friction level was only marginally influenced by the textures. However, the friction fluctuations were reduced. SEM investigations disclosed rather severe modifications of the surfaces during use, primarily caused by plastic deformation of the surface layer. The results and their practical implications are discussed.     

Equilibrium approaches to natural water systems—6. Acid-base properties of a concentrated bog-water and its complexation reactions with aluminium(III)

A filtered bog-water, concentrated by means of a freezing technique, has been studied with respect to acid-base properties and aluminium(III) complexation reactions. Sampling was performed during autumn and winter periods with a resulting acidity or alkalinity due to oxic (autumn) or anoxic (winter) conditions. The measurements were performed as potentiometric titrations in constant ionic media (0.02, 0.1 and 0.6 M NaCl) with the use of a glass electrode. The samples show buffer ranges at 3 pH 5 and pH 7.5. The first is ascribed to the presence of carboxylate groups and is characterized by fast equilibria. The second is due to phenolic OH⁻ groups and precipitation reactions with resulting sluggish equilibria. For one sampling period comprehensive measurements were undertaken to study the possible polyelectrolytic character of the organic acids. Due to the small increase in apparent carboxylate pKa-values with the degree of dissociation at low (0.02 M) as well as at high (0.6 M) ionic strength, the possible polyelectrolytic feature of the acids was neglected. Instead, a good fit to data was obtained by introducing a di-protic acid (H₂L) as a model compound. Furthermore the medium dependence of the two acidity constants could satisfactorily be fitted to the expression:

Full-size image (1K)

, where K is the constant at infinite dilution, a and b parameters of which b has been adjusted to present data. The following K values were obtained: pK₁ = 3.65 and pK₂ = 4.30. The complexation with Al(III) could be described by the formation of AlL⁺, AlL₂⁻ and the ternary species AlLH₋₁. The stability constants (log k₁ = 4.4 (winter), 4.2 (autumn); log k₂ = 4.2, 4.7; pKa (AlL⁺) = 4.2, 4.2) show no significant trend with sampling period but indicate a stability of the complexes greater than for phtalic acid but lower than for oxalic acid. Finally, the theoretical solubility of the clay mineral kaolinite in the presence of bog-water was computer modelled. The calculations show up on a 10-fold increase with respect to soluble aluminium at pH = 5.     

Numerical derivation of dispersion coefficients for flow through three‐dimensional randomly packed beds of monodisperse spheres

The longitudinal (D_L) and transverse (D_T) dispersion coefficients for flow through randomly packed beds of discrete monosized spherical particles are studied. The three‐dimensional (3‐D) porous‐medium model consists of thousands of spherical particles that are divided into cells using Voronoi diagrams. The relationship between the variation of the dual stream function and the vorticity between neighboring particles is derived using Laurent series. The whole flow pattern at low particle Reynolds number is then obtained by minimization of the dissipation rate of energy with respect to the dual stream function. The D_L is obtained by fitting the resulting effluent curve to a 1‐D solution of a continuous model. The D_T is obtained by fitting the numerical concentration profile to an approximate 2‐D solution. The derived D_L and D_T values are in agreement with 3‐D experimental data from the literature enabling a study of the effects of pore structure and porosity on D_L and D_T. © 2013 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J 60: 749–761, 2014     

A Chain‐Elongated Oligophenylenevinylene Electrolyte Increases Microbial Membrane Stability

A novel conjugated oligoelectrolyte (COE) material, named S6 , is designed to have a lipid‐bilayer stabilizing topology afforded by an extended oligophenylenevinylene backbone. S6 intercalates biological membranes acting as a hydrophobic support for glycerophospholipid acyl chains. Indeed, Escherichia coli treated with S6 exhibits a twofold improvement in butanol tolerance, a relevant feature to achieve within the general context of modifying microorganisms used in biofuel production. Filamentous growth, a morphological stress response to butanol toxicity in E. coli, is observed in untreated cells after incubation with 0.9% butanol (v/v), but is mitigated by S6 treatment. Real‐time fluorescence imaging using giant unilamellar vesicles reveals the extent to which S6 counters membrane instability. Moreover, S6 also reduces butanol‐induced lipopolysaccharide release from the outer membrane to further maintain cell integrity. These findings highlight a deliberate effort in the molecular design of a chain‐elongated COE to stabilize microbial membranes against environmental challenges.     

Simultaneous extraction and fractionation of polycyclic aromatic hydrocarbons and their oxygenated derivatives in soil using selective pressurized liquid extraction

In this study, a selective pressurized liquid extraction (PLE) method which can extract polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives (oxy-PAHs) from contaminated soil and simultaneously separate them into two fractions was developed. The method uses extraction cells packed with a chromatographic adsorbent and extraction solvents of increasing polarity. Several experiments were conducted on both spiked and authentic contaminated soil samples. Different types of adsorbents, combinations of extraction solvents, and extraction temperatures were tested in order to find a method that could fulfill the purpose of the study. The final method was based on extraction cells packed with 2% deactivated silica gel. The PAHs were extracted with cyclohexane/dichloromethane (9:1) at 120 degrees C, after which the oxy-PAHs where extracted with cyclohexane/dichloromethane (1:3) at 150 degrees C. The PAHs and oxy-PAHs were efficiently separated into two fractions, and only trace amounts of some compounds were found in the inappropriate fraction. The recoveries of the PAHs were mostly above 70% and of the oxy-PAHs, above 90%. The linearity of the method was good, and the calibration curves for most compounds had a regression coefficient better than 0.99 and an intercept close to the origin of coordinates. When the selective PLE method was applied to seven authentic soil samples, the results were found to be in good agreement with those of a reference method based on Soxhlet extraction and silica gel cleanup and also in good agreement with the certified reference values available for one of the soils. The selective PLE method is faster and consumes less solvent than a traditional method based on separate extraction and fractionation steps. The selective PLE method is, therefore, suitable for the concurrent analysis of PAHs and oxy-PAHs during large-scale soil contamination studies. This will provide more information about the soil contamination and the levels of toxicity than an ordinary PAH analysis.     

Children's event-related potentials of auditory selective attention vary with their socioeconomic status.

Past research suggests a link between socioeconomic status (SES) and brain processes in children, but direct evidence from neuroimaging is scarce. The authors investigated the relationships among SES, performance, and the neural correlates of auditory selective attention, by comparing event-related potentials (ERPs) in lower- and higher-SES preadolescent children during a task in which they attended to two types of pure tones but ignored two other types. Our hypothesis was that, at comparable performance levels, higher-SES children ignore distracters (the unattended, irrelevant tones) while lower-SES children attend equally to distracters and to targets (the attended, relevant tones). The authors found that ERP waveform differences between attended and unattended tones (Nd, difference negativity) were significant in the higher-SES but not in the lower-SES group. However, the groups did not differ in reaction times or accuracy. Electroencephalographic power analysis revealed a differential pattern of theta activity concomitant with irrelevant tones for the two groups, indicating that although they performed similarly the children from these groups recruited different neural processes. Lower-SES children, the authors suggest, deployed supplementary resources to also attend to irrelevant information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context adaptable driver information – Or,what do whom need and want when?

This study deals with a first step towards context adaptive functionality of a Driver Information System.