Nanostructure characterization of mechanical alloyed and consolidated iron alloys

High-energy ball milling (which is readily adoptable to commercial application) was used to develop sufficient quantities of nanostructured material to produce compacts capable of being measured for macroscopic properties. Characterization of the ball-milled powders show that grain boundary properties play a significant role in the overall properties of the milled powder. Nearly full-dense compacts were produced by hot-pressing. Characterization of the strength properties of these compacts show that there was little influence of hardness, density, or alloy composition on the failure properties. The range of failure stress was large and when fitted to a Weibull distribution suggest that failure was the result of flaws or cracks resulting from the hot-pressing. Hardness data, commonly used to evaluate the strength of nanostructured materials, showed no correlation to tensile strength, but correlated highly to compression maximum stress.     

Fractionation of potato juice proteins into acid-soluble and acid-coagulable fractions

Potato juice proteins were fractionated by acidification to pH 3 into acid-coagulable and acid-soluble fractions. Both fractions are heterogeneous. They differ in molecular weight, conformation in solution and composition of amino acids. The acid-coagulable fraction consists of units of molecular weight between 32,000 and 87,000, while the acid-soluble fraction consists of units of molecular weight between 17,000 and 27,000. Circular dichroism measurements show that the acid-coagulable fraction is in helical and beta conformations whilst, for the acid-soluble fraction, a substantial contribution of the random conformation is observed. The acid-coagulable fraction has a higher content of methionine than the acid-soluble fraction. It is shown that this type of fractionation is more meaningful than fractionation in terms of albumins and globulins by solubility in water or dilute salt solutions.     

Film and penetration theories for a first-order reaction in exothermic gas absorption

Film and penetration models for simultaneous heat and mass transfer are developed for the absorption of gas with a first-order chemical reaction in the liquid phase with temperature-dependent solubility and reaction rate coefficient. These two models represent two extreme conditions of interfacial temperature rise and gas solubility and they are compared with some previous models (Allan and Mann, 1979; Asai et al., 1985). The approximate analytical expressions of the penetration model of Asai et al. (1985) are in good agreement with the numerical results of this work. The results reveal that under many practical circumstances the gas-liquid interfacial temperature may be several degrees Kelvin higher than the bulk liquid temperature. The degree of deviation of the enhancement factor from its isothermal value at the bulk liquid temperature depends on the degree of difference of a certain dimensionless activation energy group from zero, which confirms the previous finding of Asai et al. (1985).     

Engineering yeast alcohol dehydrogenase. Replacing Trp54 by Leu broadens substrate specificity

Analysis of a crystal structure of alcohol dehydrogenase (Adh)from horse liver suggests that Trp54 in the homologous yeastalcohol dehydrogenase prevents the yeast enzyme from efficientlycatalysing the oxidation of long-chain primary alcohols withbranching at the 4 position (e.g. 4-methyl-1-pentanol, cinnamylalcohol). This residue has been altered to Leu by site-directedmutagenesis. The alteration yields an enzyme that serves asan effective catalyst for both longer straight-chain primaryalcohols and branched chain alcohols.     

Atmospheric spouted bed combustion: The role of hydrodynamics in emissions generation and control

Recent studies have reaffirmed the utility of spouted beds as potential combustion devices for a variety of fuels: solid, liquid and gaseous fuels (Arbib and Levy, 1982; Weinberg et al., 1988; Zhao et al., 1987; Altwicker et al., 1989; Altwicker and Lin, 1991; Altwicker et al., 1993; Konduri et al., 1994). In this study, the role of annulus residence time on the performance of such a spouted bed combustor is investigated. The experiments presented here show that fluid hydrodynamics in the annulus of a spouted bed combustor can significantly influence the overall performance; changing the residence time in the annulus significantly affects the concentrations of products due to incomplete combustion at the exit of the combustor. The annular residence time is varied by changing the shape of the bottom of the reactor, by introducing a draft tube and by changing the bed heighn. Propane is used as the fuel and sand as the bed medium. Inferences from the combustion results are supported by pressure and temperature profiles. A streamtube model (Lim and Mathur, 1976) was used to obtain an estimate of the residence time in the annulus. It is concluded that the flame processes taking place at the top of the annulus play a critical role in the emission generation and that more information is needed to understand the annulus-flame.     

Vergleichende Untersuchung raumakustischer Konzepte von Mehrpersonenbüros hinsichtlich Sprachverständlichkeit,Arbeitsgedächtnisleistung und Arbeitsbehaglichkeit durch Hörversuche

Comparative studies of room‐acoustic concepts for open‐plan offices with regard to speech intelligibility, short‐term memory perfomance and acoustic comfort. Increasing use of tempering the core of reeinforced concrete ceilings of open‐plan offices for cooling and if necessary for heating strongly limits the implementation of sound‐absorbing ceilings. In these cases the classic concept for offices with fully sound‐absorbing ceilings and screen barriers is not applicable anymore. As an alternative to this concept of screen barriers a so‐called partition wall concept is going to be implemented in these open‐plan offices. In this case a sound‐absorbing ceiling is not used anymore; instead room‐high partition walls are mounted, which are highly sound‐absorbing on both sides. The objective of the study was to compare these two concepts for open‐plan offices regarding speech intelligibility on the phone, ability to concentrate and acoustic comfort. In addition to that the effect of low‐frequency absorbers was investigated. To evaluate the acoustic concepts of theses offices audibility tests were conducted. For this purpose the room‐acoustic conditions of the office situations were auralized with the help of measured binaural room impulse responses of original open‐plan offices. For comparison an open‐plan office without room‐acoustic measures was included. With this procedure different office situations are directly comparable.     

Functional Adhesive Surfaces with “Gecko” Effect: The Concept of Contact Splitting

Nature has developed reversibly adhesive surfaces whose stickiness has attracted much research attention over the last decade. The central lesson from nature is that “patterned” or “fibrillar” surfaces can produce higher adhesion forces to flat and rough substrates than smooth surfaces. This paper critically examines the principles behind fibrillar adhesion from a contact mechanics perspective, where much progress has been made in recent years. The benefits derived from “contact splitting” into fibrils are separated into extrinsic/intrinsic contributions from fibril deformation, adaptability to rough surfaces, size effects due to surface‐to‐volume ratio, uniformity of stress distribution, and defect‐controlled adhesion. Another section covers essential considerations for reliable and reproducible adhesion testing, where better standardization is still required. It is argued that, in view of the large number of parameters, a thorough understanding of adhesion effects is required to enable the fabrication of reliable adhesive surfaces based on biological examples.     

Failure of fibrous anisotropic materials under combined loading

A failure criterion for anisotropic materials under combined stress is developed and demonstrated. The generality and accuracy of the present theory are illustrated by examination through the use of material systems under various loading conditions. Calculated results are compared with the experimental data throughout four quadrants. It agrees with observation quite well at high values of shear stress, where the Tsai–Hill theory becomes too conservative. The present criterion is also compared with other criteria. The comparison shows that this criterion has a good agreement with the experimental data even when the shear stress component is greater than the shear strength.     

Modeling mobility in disaster area scenarios

This paper provides a model that realistically represents the movements in a disaster area scenario. The model is based on an analysis of tactical issues of civil protection. This analysis provides characteristics influencing network performance in public safety communication networks like heterogeneous area-based movement, obstacles, and joining/leaving of nodes. As these characteristics cannot be modeled with existing mobility models, we introduce a new disaster area mobility model. To examine the impact of our more realistic modeling, we compare it to existing ones (modeling the same scenario) using different pure movement and link-based metrics. The new model shows specific characteristics like heterogeneous node density. Finally, the impact of the new model is evaluated in an exemplary simulative network performance analysis. The simulations show that the new model discloses new information and has a significant impact on performance analysis.     

A Survey on Gradient‐Domain Rendering

Monte Carlo methods for physically‐based light transport simulation are broadly adopted in the feature film production, animation and visual effects industries. These methods, however, often result in noisy images and have slow convergence. As such, improving the convergence of Monte Carlo rendering remains an important open problem. Gradient‐domain light transport is a recent family of techniques that can accelerate Monte Carlo rendering by up to an order of magnitude, leveraging a gradient‐based estimation and a reformulation of the rendering problem as an image reconstruction. This state of the art report comprehensively frames the fundamentals of gradient‐domain rendering, as well as the pragmatic details behind practical gradient‐domain uniand bidirectional path tracing and photon density estimation algorithms. Moreover, we discuss the various image reconstruction schemes that are crucial to accurate and stable gradient‐domain rendering. Finally, we benchmark various gradient‐domain techniques against the state‐of‐the‐art in denoising methods before discussing open problems.