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Andersons J.,University of Latvia | Joffe R.,Lule University of Technology
Composites Part A: Applied Science and Manufacturing | Year: 2011

Unidirectional orientation of natural fibers in a polymer composite ensures the highest efficiency of reinforcement. Flax fiber reinforcement is discontinuous due to limited fiber length and heterogeneous due to the presence of elementary fibers and their bundles. In order to assess the upper limit of tensile strength of such slightly misoriented, nominally UD natural fiber composite, a statistical strength model of continuous UD fiber reinforced composites is applied. It is found that the experimental strength of UD flax composites, produced from rovings or manually aligned fibers, approaches the theoretical limit only at relatively low fiber volume fraction ca. 0.2, being markedly below it at higher fiber content. © 2011 Elsevier Ltd. All rights reserved. Source

Borch D.Z.,Lule University of Technology | Sundberg J.,KTH Royal Institute of Technology
Journal of Voice | Year: 2011

This investigation aims at describing voice function of four nonclassical styles of singing, Rock, Pop, Soul, and Swedish Dance Band. A male singer, professionally experienced in performing in these genres, sang representative tunes, both with their original lyrics and on the syllable /pae/. In addition, he sang tones in a triad pattern ranging from the pitch Bb2 to the pitch C4 on the syllable /pae/ in pressed and neutral phonation. An expert panel was successful in classifying the samples, thus suggesting that the samples were representative of the various styles. Subglottal pressure was estimated from oral pressure during the occlusion for the consonant [p]. Flow glottograms were obtained from inverse filtering. The four lowest formant frequencies differed between the styles. The mean of the subglottal pressure and the mean of the normalized amplitude quotient (NAQ), that is, the ratio between the flow pulse amplitude and the product of period and maximum flow declination rate, were plotted against the mean of fundamental frequency. In these graphs, Rock and Swedish Dance Band assumed opposite extreme positions with respect to subglottal pressure and mean phonation frequency, whereas the mean NAQ values differed less between the styles. © 2011 The Voice Foundation. Source

Brchner J.,Chalmers University of Technology | Olofsson T.,Lule University of Technology
Journal of Construction Engineering and Management | Year: 2012

A 30-year retrospective analysis of resource use in a range of new construction and repair projects reveals insignificant productivity increase when applying traditional narrow measures, as shown in a case study of beam bridges. It appears as necessary to estimate hidden quality changes in both outputs and inputs. Changes in government regulations, in specifications, and the development of nonprice criteria for contract award emerge as important. Schemes for benchmarking the performance of construction projects as well as life-cycle analyses suggest that customer risk aversion and effects on customer productivity should be taken into account. The outcome is a set of measurements that can be applied to the selection of any type of proposed new construction or repair technology innovation according to their potential impact on industry productivity. © 2012 American Society of Civil Engineers. Source

Castano Arranz M.,Lule University of Technology | Birk W.,Lule University of Technology
Journal of Process Control | Year: 2012

The selection of the structure of a controller in large scale industry processes usually requires extensive process knowledge. The aim of this paper is to report new results on recently suggested methods for the analysis of complex processes. These methods aid the designers in comprehending a process by representing structural and functional relationships from actuators and process disturbances to measured or estimated variables. The methods are formulated in a flexible framework based on graph theory, which can also be used for closed-loop analysis. Additionally, the sensitivity of the methods to scaling and time delays are discussed and resolved. It is also proposed how filtering can be used to restrict the analysis to a frequency region of interest. The feasibility of the methods is shown by the use of three case studies. A quadruple tank process is used to exemplify the methods and their use. Then the methods are applied on a real-life process, the stock preparation plant of a pulp and paper mill. The third study case analyzes a previously published example in closed loop. It is shown that the methods can be used to take efficient decisions on decentralized and sparse control structures, as well as assessing the channel interactions in a closed-loop system. © 2011 Elsevier Ltd. All Rights Reserved. Source

Awe S.A.,Lule University of Technology | Sandstrom K.,Lule University of Technology
Minerals Engineering | Year: 2010

Removal of impurity elements in copper metallurgy is one of the major problems encountered today since pure copper ore reserves are becoming exhausted and the resources of unexploited ores often contain relatively high amounts of impurity elements like antimony, arsenic, mercury and bismuth, which need to be eliminated. The present work is aimed at pre-treating a tetrahedrite rich complex sulphide concentrate by selective dissolution of the impurities, therefore, upgrading it for pyrometallurgical processing. To accomplish this, dissolution of antimony and arsenic by an alkaline sulphide lixiviant from the concentrate were investigated. The lixiviant proved selective and effective to dissolve these impurity elements from the concentrate with good recoveries. Further investigations on the factors influencing the leaching efficiency of the lixiviant were studied. The parameters considered were sulphide ion and hydroxide ion concentrations, mineral particle size, reaction temperature and leaching time. Analysis of the leach residue indicates that copper content of tetrahedrite has transformed into copper sulphides with the average chemical formula Cu1.64S. The grade and economic value of the concentrate were improved greatly after sulphide treatment, and therefore, suitable as a feedstock for smelting. The impurities have been reduced to low levels which are tolerable in the smelting furnace and consequently reduce both the treatment and environmental problem encountered when such concentrate is processed pyrometallurgically. © 2010 Elsevier Ltd. All rights reserved. Source

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