Friction of linerboard based on recycled fiber

The purpose of this investigation was to study the origin of the differences in paper‐to‐paper friction of linerboards based on old corrugated containers (OCC). The sheets were subjected to two extraction stages and analyzed with respect to, surface roughness, and their content of low‐molecular‐mass lipophilic compounds (LLC). Friction was measured using a friction tester based on the horizontal plane principle. The surface roughness was measured using a Perthometer profiler and the low molecular mass lipophilic constituent of the paper sheets was determined by gas chromatography‐mass spectroscopy. The sheets were imaged using environmental scanning electron microscopy (ESEM), and the relative compositions of inorganic ions on the paper surfaces were determined by energy dispersive X‐ray spectroscopy (EDS). The results showed that a high amount of LLC in the sheets lead to low friction, due to lubrication. It was also observed that large CaCO₃ particles on the surface had a friction‐increasing effect, and that there was no relationship between the surface roughness and the friction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1511–1520, 2002     

A new view of anti‐windup design for uncertain linear systems in the frequency domain

This paper presents a new perspective on the stability problem for uncertain LTI feedback systems with actuator input amplitude saturation. The solution is obtained using the quantitative feedback theory and a 3 DoF non‐interfering control structure. Describing function (DF) analysis is used as a criterion for closed loop stability and limit cycle avoidance, but the circle or Popov criteria could also be employed. The novelty is the combination of a controller parameterization from the literature and describing function‐based limit cycle avoidance with margins for uncertain plants. Two examples are given. The first is a benchmark problem and a comparison is made with other proposed solutions. The second is an example that was implemented and tested on an X‐Y linear stage used for nano‐positioning applications. Design and implementation considerations are given. An example is given on how the method can be extended to amplitude and rate saturation with the help of the generalized describing function, and a novel anti‐windup compensation structure inspired by previous contributions. Copyright © 2015 John Wiley & Sons, Ltd.     

Clearance of iohexol, chromium-51-ethylenediaminetetraacetic acid, and creatinine for determining the glomerular filtration rate in pigs with normal renal function: comparison of different clearance techniques

RATIONALE AND OBJECTIVES: We wanted to improve determination of the glomerular filtration rate (GFR) with plasma clearance techniques because the alternative-renal clearance techniques-may involve inaccurate urine sampling or risk of urinary tract infection when bladder catheterization becomes necessary. Therefore, we compared the renal and plasma clearances of iohexol and chromium-51-ethylenediaminetetraacetic acid (51Cr-EDTA), as well as endogenous creatinine clearance, in 19 normal pigs using different techniques. METHODS: After an intravenous bolus injection of the GFR markers, 16 plasma samples were used to plot the marker concentrations versus time for 4.5 hr. Urine was collected during nine 30-min periods. Plasma clearance was calculated by dividing the dose of marker with the area under the plasma concentration curve (AUC) from the time of injection to infinity using one-compartment (ClAUC-slope) and three-compartment (ClAUC-3comp) models. The renal clearance was calculated by dividing the amount of marker excreted in the urine in a period with the AUC in the same period. This AUC was determined by integrating the total area in the period (Clren adv)--our reference method representing the "true" GFR--or by using the arithmetic mean of the plasma concentrations of the marker at the beginning and end of the urine collection period (Clren simple). Creatinine clearance was determined according to Clren simple. RESULTS: Renal clearances of iohexol and 51Cr-EDTA were significantly higher than creatinine clearance (P = .0002). There was no significant difference between the renal clearances of iohexol and 51Cr-EDTA or between their plasma clearances. The two mathematical methods of calculating the renal clearance of iohexol were highly correlated (rs = .99), as were the two methods of calculating its plasma clearance (rs = .95). Because of the extrarenal clearance of the markers, the plasma clearance methods for iohexol and 51Cr-EDTA always overestimated the true GFR. ClAUC-3comp was the method closest to the true GFR. For iohexol, the median overestimation of the GFR was higher with ClAUC-slope when early plasma samples (30-120 min) after injection of the marker were used (5.5 ml.min-1.10 kg-1) than when late samples (180-270 min) were used (4.0 ml.min-1.10 kg-1). After subtracting the median extrarenal clearances of iohexol and 51Cr-EDTA (previously determined in nephrectomized pigs) from their plasma clearances (ClAUC-3comp), the median overestimation of the true GFR was reduced from 2.0 to 1.1 ml.min-1.10 kg-1 with iohexol and from 2.1 to 1.3 ml.min-1.10 kg-1 with 51Cr-EDTA. CONCLUSION: GFR determination with plasma clearance techniques can be improved in three- and one-compartment models by taking late plasma samples and by subtracting the extrarenal plasma clearance of the species. One-compartment models can be improved by determining a correction formula in the species for the early parts of the decay curve of the plasma concentration of the marker.     

FETI‐DP,BDDC, and block Cholesky methods

The FETI‐DP and BDDC algorithms are reformulated using Block Cholesky factorizations, an approach which can provide a useful framework for the design of domain decomposition algorithms for solving symmetric positive definite linear system of equations. Instead of introducing Lagrange multipliers to enforce the coarse level, primal continuity constraints in these algorithms, a change of variables is used such that each primal constraint corresponds to an explicit degree of freedom. With the new formulation of these algorithms, a simplified proof is provided that the spectra of a pair of FETI‐DP and BDDC algorithms, with the same set of primal constraints, are essentially the same. Numerical experiments for a two‐dimensional Laplace's equation also confirm this result. Copyright © 2005 John Wiley & Sons, Ltd.     

Open Embedded Control

Embedded control devices today usually allow parameter changes, and possibly activation of different pre-implemented algorithms. Full reprogramming using the complete source code is not allowed for safety, efficiency, and proprietary reasons. For these reasons, embedded regulators are quite rigid and closed concerning the control structure. In several applications, like industrial robots, there is a need to tailor the low level control to meet specific application demands. In order to meet the efficiency and safety demands, a way of building more generic and open regulators has been developed. The key idea is to use pieces of compiled executable code as functional operators, which in the simplest case may appear as ordinary control parameters. In an object oriented framework, this means that new methods can be added to controller objects after implementation of the basic control, even at run-time. The implementation was carried out in industrially well accepted languages such as C and C++. The dynamic binding at run-time differs from ordinary dynamic linking in that only a subset of the symbols can be used. This subset is defined by the fixed part of the system. The safety demands can therefore still be fulfilled. Encouraged by results from fully implemented test cases, we believe that extensive use of this concept will admit more open, still efficient, embedded systems.     

Power-to-X im Kontext der Energiewende und des Klimaschutzes in Deutschland

In order to examine the impact of different Power-to-X technologies on the transformation of the German energy system and meeting the climate change mitigation goals, a cross-sectoral energy system model was developed. The results show that Power-to-X will be essential for a successful energy transition. Especially in applications where high energy densities are required and only few other options for defossilization exist, Power-to-X technologies become essential.     

Distributed dynamic load balancing with applications in radio access networks

Managing and balancing load in distributed systems remains a challenging problem in resource management, especially in networked systems where scalability concerns favour distributed and dynamic approaches. Distributed methods can also integrate well with centralised control paradigms if they provide high‐level usage statistics and control interfaces for supporting and deploying centralised policy decisions. We present a general method to compute target values for an arbitrary metric on the local system state and show that autonomous rebalancing actions based on the target values can be used to reliably and robustly improve the balance for metrics based on probabilistic risk estimates. To balance the trade‐off between balancing efficiency and cost, we introduce 2 methods of deriving rebalancing actuations from the computed targets that depend on parameters that directly affects the trade‐off. This enables policy level control of the distributed mechanism based on collected metric statistics from network elements. Evaluation results based on cellular radio access network simulations indicate that load balancing based on probabilistic overload risk metrics provides more robust balancing solutions with fewer handovers compared to a baseline setting based on average load.     

‘Green procurement’ of buildings: a study of Swedish clients' considerations

The results of a survey show that both public and private building clients in Sweden, to varying extents, include environmental requirements in their procurement documents. The requirements identified have been classified into six categories primarily related to building and demolition waste, building material, contractors' environmental work, ecological aspects, construction work and other. One conclusion is that requirements regarding the separation of waste and a contractor's environmental policy are considered important, since they are stipulated in the majority of projects. Another finding is that requirements related to operation and especially to energy use are not considered sufficiently. Structured interviews were conducted with three of the clients who at that time of the survey had developed the most complete procurement documents with regard to environmental requirements. The aim of the interviews was to investigate how the stipulation of requirements, the evaluation of environmental aspects and the verification of environmental requirements were carried out. The conclusion drawn is that Swedish clients find the stipulation of requirements relatively uncomplicated, but find the evaluation of environmental impact, mainly related to selection of materials, problematic due to inadequate evaluation models.     

Surface energy measurements from Griffith cracks in boron fibres

Journal of Materials Science -     

Analysis of Low Molecular Weight Lignin-Derived Sulphonates by Capillary Zone Electrophoresis

A fast and simple analytical procedure, based on capillary zone electrophoresis (CZE), for separation of underivatized low molecular weight lignin-derived sulphonates has been developed. Optimal CZE-operatipn conditions for the separation and detection of several lignin-derived sulphonic acids was found when using a low pH (pH 1.7) phosphate buffer system, an applied voltage of 20 kV and UV-detection at the anode-side. At these conditions the electroosmotic flow is negligible and the analytes are transported through the capillary column by electromigration. The sulphonation and subsequent degradation of the lignin-model compound 1-(4-hydroxy-3-methoxyphenyl)-2-O-(2-methoxyphenyl)-glycerol has been studied by CZE-analysis of aliquots taken from a sulphite reaction mixture No sample pretreatment was needed before analyzing the sulphite reaction mixture with CZE. The method has also been found to be useful for detection of sulphonic acids in samples from sulphite cooking. Crude extracts of a sulphite cooking liquor could be directly analysed by using the technique developed. Based on migration time data and comparison with an authentic sample, 1-(4-hydroxy-3-meth6xyphenyl)-prop-2-ene-1-sulphonate was identified as one of the sulphonic acids present in the sulphite cooking liquor.