Designing Paper Machine Headbox Using GA

A non-smooth biobjective optimization problem for designing the shape of a slice channel in a paper machine headbox is described. The conflicting goals defining the optimization problem are the ones determining important quality properties of produced paper: 1) basis weight should be even and 2) the wood fibers of paper should mainly be oriented to the machine direction across the width of the whole paper machine. The novelty of the considered approach is that maximum deviations are used instead of least squares when objective functions are formed. For the solution of this problem, a multiobjective genetic algorithm based on nondominated sorting is considered. The numerical results demonstrate the ability to obtain a large set of nondominated designs.     

Molecular reorganization in wood

Cyclical compression was applied to steamed Spruce wood in uniaxial strain under stress control. Molecular fatigue response was investigated in terms of thermoporosimetry. In accordance with classical Coffin–Manson theory, it was found that the creation of fatigue damage depends on plastic strain amplitude, not depending on the applied stress, applied strain, or the amount of dissipated energy as such. At a specified strain amplitude, molecular fatigue does not appear to be sensitive to loading frequency. However, it does appear to be related to decrement of dynamic stiffness in the course of dynamic loading. Molecular reorganization becomes more pronounced along with further energy application. Results for specimens loaded in the tangential material direction are rather consistent, whereas the molecular reaction varies widely along with the local strain amplitude in the case of specimens loaded in the radial material direction. This implies that the molecular fatigue process is essentially strain-controlled, rather than stress-controlled.     

Off-axis fatigue loading of steamed wood

Cyclical off-axis compression was applied to steamed Spruce wood in uniaxial strain under stress control. The strain level is a step function of stress level and test duration. Energy dissipation is negligible when the stress amplitude in relation to the greatest compressive stress is small, regardless of the applied stress level. There is a significant energy dissipation when the stress amplitude in relation to greatest applied compressive stress is large, regardless of stress level. Dynamic stiffness appearing during the dynamic loading strongly depends on applied stress and stress amplitude. Small-strain stiffness deteriorated during any dynamic loading experiment, apparently depending on the greatest compressive strain appearing during loading. Also plastic strain appears to depend on the strain appearing during loading. Thus stiffness decrement and plastic strain do not appear to reflect the variety of material reactions to fatigue treatments.     

Characterizing the evolving research on enterprise content management

Innovations in network technologies in the 1990's have provided new ways to store and organize information to be shared by people and various information systems. The term Enterprise Content Management (ECM) has been widely adopted by software product vendors and practitioners to refer to technologies used to manage the content of assets like documents, web sites, intranets, and extranets In organizational or inter-organizational contexts. Despite this practical interest ECM has received only little attention in the information systems research community. This editorial argues that ECM provides an important and complex subfield of Information Systems. It provides a framework to stimulate and guide future research, and outlines research issues specific to the field of ECM.     

Tacticity distribution of isotactic polypropylene prepared with heterogeneous Ziegler-Natta catalyst. 2. Application and analysis of SSA data for polypropylene

Accurate characterisation of the tacticity distribution in isotactic polypropylene is important for obtaining better structure property correlations and for the indirect investigation of the active sites in heterogeneous Ziegler-Natta catalysts. In this work, successive self-nucleation and annealing (SSA) DSC measurement is applied for the study of tacticity distribution in polypropylene fractions with varying isotacticity. The results are compared with ¹³C NMR and temperature rising elution fractionation (TREF). Analysis of the lamellar thicknesses and average meso sequence lengths (MSL) revealed that the fractions could be classified into three main groups according to the lamellar structure generated in SSA. The fractions with relatively low isotacticity crystallise mainly by the longest crystallisable sequence of the chain. In more isotactic fractions, the lamellar thicknesses are close to the average crystallisable sequence lengths of the chains. For the highest isotacticity fractions correlation was not found. Because of these differences the correlation between the melting temperature and isotacticity (meso diad-%) was non-linear. Good correspondence between the SSA melting curves and the TREF fractograms was observed.     

Determining the irradiance signal from an asymmetric source with directional detectors: application to calibrations of radiometers with diffusers

The energy transfer integral between radiating rectangular and detecting circular parallel plates having nonideal angular characteristics is solved for modeling the distance dependence of the irradiance signal. The equation derived for the irradiance signal, which is called the modified inverse-square law, depends on the position, shape, size, and angular characteristics of the light source and the detector. We apply the new model equation to the calibration of a spectroradiometer to determine accurately the distance offsets, which fix the positions of the effective receiving apertures of diffusers used in the entrance optics of spectroradiometers. Earlier measurement results, e.g., for solar UV irradiance, may include uncorrected effects and can be corrected reliably as diffuser offsets and other correction factors are determined with the modified inverse-square law. Simplifications of the modified inverse-square law for analyzing the distance offsets and the correction factors are studied. Simplified equations for the diffuser offset analysis may be used without losing the accuracy when the cosine response of the diffuser is reasonably good. However, for diffusers whose angular responsivities deviate much from the cosinusoidal angular responsivity, large approximation errors in the diffuser offset values may appear if the angular effects are not properly taken into account.     

Concentrations and leachability of chemical elements in estuarine sulfur-rich sediments, W. Finland

Concentrations, distributions and mobility of chemical elements were investigated in reduced sulfur-rich estuarine sediments located in western Finland. The main objective was to determine the possible extent of metal leaching when dredged masses of these sulfur-rich sediments are dumped on the land and thus exposed to air. When dredged, the reduced sulfur in the sediments oxidises resulting in a lowering of pH, which in turn is expected to leach metals. The study area is an artificial lake claimed from the Botnian sea in 1962. In this lake, several mass-kills of fish have occurred, believed partly to be due to dredging. Two sediment samples (0-50 and 50-100 cm) were taken from 39 sampling points in the lake. These samples were leached in aqua regia (2:2:2 HNO3/HCl/H2O1) and analysed for Fe, Al, Mg, Ca, K, P, Na, Mn, Zn, Ba, V, Sr, Cr, Ni, Cu, Co, As, Pb, B, Mo and Cd with ICP-AES. Sulfur and organic carbon were analysed with Leco. In a controlled laboratory experiment, the sediments were allowed to oxidise for 1 year while moisturised with deionised water every month. The pH and conductivity were determined in the beginning of the experiment (reduced state) and in the end (oxidised state). In the supernatants in the oxidised states the amount of leached metals (Na, Al, Mn, Zn, Sr, Co, Ni, Cu, Cd, Cr, Pb, U, Li, Rb and As) were determined with ICP-MS. The sediments were found to contain low levels of toxic metals but, as expected, high concentrations of sulfur. In the experiment, pH was lowered (down to 3.0) and the conductivity increased in all samples due to oxidation and release of metal ions. The extent of leaching varied between 0.03% for As and 12.3% for Na. Critical pH values, at which high amounts of metals begin to leach, were obtained graphically. These values varied between 4.8 (Ni) and 3.3 (Cr). Not all elements were controlled by pH, e.g. Mn correlated well with its aqua regia leachable concentration. In a planned dredging operation in the area some 23,300 t (10,500 m3) (dry wt.) of sediments will be dredged. The amounts of metals likely to be leached, according to the results from this study, are as follows (kg): Al (1710), Mn (1230), Zn (59), Sr (39), Co (13), Ni (12), Cu (2) and less than 1 kg of Cd-Cr-As-Pb.     

A new perspective on vegetable oil epoxidation modeling: Reaction and mass transfer in a liquid–liquid–solid system

A rigorous mathematical model was developed for a complex liquid–liquid–solid system in a batch reactor. The approach is general but well applicable for the indirect epoxidation of vegetable oils according to the concept of Nikolaj Prileschajew, implying in situ prepared percarboxylic acids as epoxidation agents. The model considers intra- and interfacial mass transfer effects coupled to reaction kinetics. The liquid phases were described with chemical approach (aqueous phase) and a reaction–diffusion approach (oil phase). The oil droplets were treated as rigid spheres, in which the overall reaction rate is influenced by chemical reactions and molecular diffusion. The model was tested with a generic example, where two reactions proceeded simultaneously in the aqueous and oil phases. The example (i.e., fatty acid epoxidation) illustrated the power of real multiphase model in epoxidation processes. The proposed modeling concept can be used for optimization purposes for applications, which comprise a complex water–oil–solid catalyst system.     

Zeroth-order complex-amplitude modulation with dielectric Fourier-type dififractive elements

Abstract

Diffraction by a lamellar grating with slowly modulated groove width and depth is considered. By mathematical design of the diffractive microstructure the zeroth diffraction order of the carrier grating may be modulated in amplitude and phase and thereby split into some specified on-axis far-zone diffraction pattern. The noise, which in diffractive optics normally appears in the immediate neighbourhood of the signal, is shifted angularly into the surroundings of the higher diffraction orders of the carrier grating. Therefore a large frame of virtually zero intensity can be formed around the original signal without brute force optimization. This is of interest in, for example, several space-invariant optical interconnection and photonic switching schemes that employ diffractive beam-splitter elements.     

Crystallographic Analysis of Isothermally Transformed Bainite in 0.2C-2.0Mn-1.55Si-0.6Cr Steel Using EBSD

The crystallography of bainite,transformed isothermally at 450℃in 0.2C-2.0Mn-1.5Si-0.6Cr steel,was investigated by electron backscatter diffraction(EBSD) analysis.The orientation relationship(OR) was found to be closer to Ntshiyama-Wassermann(N-W) than Kurdjumov—Sachs orientation relationship.Bainite microstructure consisted of parallel laths forming a morphological packet structure.Typically,there were three different lath orientations in a morphological packet.These orientations were dictated by a three specific N—W OR variants sharing the same {111} austenite plane.A packet of bainite laths with common {111} austenite plane was termed as crystallographic packet.Generally,the crystallographic packet size corresponded to the morphological packet size.Locally,crystallographic packets with only two dominant orientations were observed.This indicates strong local variant selection during isothermal bainite transformation.The relative orientation between the variants in crystallographic packets was found to be near 60°/<110>.This appears to explain the strong peak observed in the grain boundary misorientation distribution near 60°.Bainite also contained pronounced fraction of boundaries with their misorientation in the range of 2.5°—8°with quite widely dispersed rotation angles.Spatially these boundaries were found to locate inside the bainite laths,forming lath-like sub-grains.