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  • 60001.
    Yu, Liang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Biogas upgrading by zeolite membranes2016Conference paper (Other academic)
  • 60002.
    Yu, Liang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Highly permeable CHA membranes prepared by fluoride synthesisfor efficient CO2/CH4 separation2018In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 16, p. 6847-6853Article in journal (Refereed)
    Abstract [en]

    All-silica CHA nanocrystals, much smaller (20–200 nm) than previously reported, were prepared by an improved method developed in the present work. The nanocrystals are prepared by adding milled crystals to a fluoride synthesis mixture and we observed that much smaller crystals are obtained by adding a much higher fraction of milled crystals. In the next step, CHA membranes with a thickness of ca. 1.3 μm were prepared by hydrothermal treatment of a monolayer of nanocrystals supported on porous graded alumina discs in a fluoride synthesis gel. Finally, the membranes were calcined at 480 °C. The highest measured single gas CO2 permeance was 172 × 10−7 mol m−2 s−1 Pa−1 at room temperature. The highly permeable membranes were evaluated for separation of CO2 from an equimolar mixture with CH4 at varying temperatures. The highest observed CO2 mixture permeance was 84 × 10−7 mol m−2 s−1 Pa−1 at 276 K with a separation selectivity of 47 at 9 bar feed pressure and atmospheric permeate pressure. At room temperature, the CO2 mixture permeance was also as high as 78 × 10−7 mol m−2 s−1 Pa−1 with a separation selectivity of 32. To the best of our knowledge, these CO2 permeances are by far the highest reported for CHA membranes, while the selectivity is similar to that reported previously at comparable test conditions.

  • 60003.
    Yu, Liang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Very High Flux MFI Membranes for Alcohol Recovery via Pervaporation at High Temperature and Pressure2015In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 153, p. 138-145Article in journal (Refereed)
    Abstract [en]

    Ultra-thin MFI membranes (0.5 μm) were evaluated for recovery of alcohols from dilute aqueous mixtures by pervaporation at high temperature and pressure for the first time. The feed pressure was sufficiently high to keep the feed in liquid state at high temperature, while the permeate pressure was kept at atmospheric and a low flow of sweep gas was used to reduce the partial pressure on the permeate side. Atmospheric pressure on the permeate side is more practical than vacuum. High feed temperature and pressure result in high fugacity in the liquid feed, which, in combination with lower permeate pressure, results in a large driving force. Consequently, the membrane exhibited very high fluxes for feeds comprised of 10 wt% ethanol/water and 5 wt% n-butanol/water mixtures at 110 °C and 140 °C, respectively. The flux observed for 10 wt% ethanol/water mixtures was as high as about 52 kg m-2 h-1, i.e., 6 times higher than the highest previously reported flux for this separation using zeolite membranes in pervaporation. For 5 wt% n-butanol/water mixtures, the flux was 40 kg m-2 h-1, which is 11 times higher than the highest previously reported flux for this separation by zeolite membranes. At these conditions, the membrane displayed separation factors for ethanol/water and n-butanol/water mixtures of 5 and 16, respectively. However, after about 6 hours of operation, the separation factor decreased significantly and the flux increased due to formation of defects in the membrane when the feed was saturated with silica. Lower membrane stability was observed for silica free feeds. The work has shown that it is possible to obtain high flux in pervporation by using ultra-thin membranes in combination with high feed temperature. The observed membrane selectivity was not excellent, due to pressure drop over the support as well as likely concentration polarization on the feed side resulting from the high flux. Membrane stability was also an issue at these conditions, however it was shown that stability could be improved by saturating the feed with silica.

  • 60004.
    Yu, Liang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Liu, Dong
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Yan, Baili
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Zeng, Changfeng
    College of Mechanic and Power Engineering, Nanjing Tech University.
    Wang, Chongqing
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    A Universal Biological-materials-assisted Hydrothermal Route to Prepare Various Inorganic Hollow Microcapsules in the Presence of Pollens2016In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 301, p. 26-33Article in journal (Refereed)
    Abstract [en]

    A universal bio-economical hydrothermal route has been developed to prepare various inorganic hollow microcapsules with the help of rapeseed pollens for the first time. The pollens were used without any modifications. TiO2, ZnO, zeolite ZSM-5, BaTiO3 and ZnS were prepared by this route using the regular synthesis solutions added with rapeseed pollens. The obtained products were examined by scanning and transmission electron microscopy, X-ray diffraction, FT-IR, N2 adsorption and thermogravimetric analysis. The hollow microcapsules are composed of inorganic particles around the derivations of pollens. And the diameter of the hollow has been demonstrated almost the same size as the derivations microspheres. The derivations were decomposed in high temperature crystallization procedure; therefore, no additional procedure is needed to remove the templates for the hollow structure. The hollow microcapsules prepared with rapeseeds have much higher specific surface area. The formation mechanism can be ascribed to the template effect of derivative microspheres formed from decomposition of these pollen grains. Furthermore, other pollens are also used in the preparation by the universal hydrothermal route. Still, inorganic hollow microcapsules but with different hollow diameters were obtained probably resulting from the different size of the derivations.

  • 60005.
    Yu, Liang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing, 210009, PR China.
    Zeng, Changfeng
    College of Mechanic and Power Engineering, Nanjing Tech University.
    Wang, Chongqing
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing.
    In situ impregnation−gelation−hydrothermal crystallization synthesis of hollow fiber zeolite NaA membrane2017In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 244, p. 278-283Article in journal (Refereed)
    Abstract [en]

    Chitosan-assisted in situ impregnation−gelation−hydrothermal (IGH) crystallization process has been developed for the preparation of hollow fiber zeolite NaA membranes. Firstly, chitosan-zeolite NaA composite hollow fibers were prepared successfully by assistance of a simple homemade tube-in-orifice spinneret. The composite hollow fibers were initially prepared by in situ impregnation–gelation–hydrothermal transformation of chitosan-silica hollow fibers in aluminate solution. Zeolite NaA membranes can be subsequently obtained on the outer surface of chitosan-zeolite NaA composite hollow fibers by in situ microwave hydrothermal treatment. The zeolite crystals in the composite hollow fibers serve as seeds for the growth of zeolite membrane. Moreover, the chitosan-silica hollow fibers were prepared by solidification of chitosan hollow fibers, which were formed in the tube-in-orifice spinneret from a chitosan-silica sol viscous aqueous solution, in the sodium hydroxide solution. Pervaporation for separation of 90 wt% ethanol aqueous solution was employed to examine the obtained membranes. The hollow fiber membranes showed high permeation flux and high stability.

  • 60006.
    Yu, Qiangliang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou.
    Wang, Yurong
    State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou.
    Huang, Guowei
    State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou.
    Ma, Zhengfeng
    State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Cai, Meirong
    State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou.
    Zhou, Feng
    State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou.
    Liu, Weimin
    State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou.
    Task-Specific Oil-Miscible Ionic Liquids Lubricate Steel/Light Metal Alloy: A Tribochemistry Study2018In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 5, no 19, article id 1800791Article in journal (Refereed)
    Abstract [en]

    In order to increase the solubility of ionic liquids in base oils and to improve the lubricating performance of light alloys, two new ionic liquids comprised of sulfonate base anion and phosphonium based cation are designed and synthesized. The difference between these two ionic liquids is the cation: One has only one organophosphate group (P88816DOSS) and the other has two organophosphate group (P888PDOSS). The copper strip corrosion test is used to evaluate the anticorrosion properties of new developed ionic liquids. Tribological properties of the ionic liquids are investigated by an optimal SRV-IV oscillating tribometer. The results indicate that the new designed ionic liquids show very good solubility in traditional mineral-based oils. P88816DOSS and P888PDOSS show excellent friction reduction, antiwear performance accompanied with effective anticorrosion properties for the mineral base oil. Surface analysis results show that the superior properties of P88816DOSS and P888PDOSS are attributed to surface chemical reactions between ionic liquids and light metal.

  • 60007.
    Yu, Qiangliang
    et al.
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.
    Zhang, Chaoyang
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.
    Dong, Rui
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China; University of Chinese Academy of Sciences, Beijing, China.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wang, Yurong
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China; University of Chinese Academy of Sciences, Beijing, China.
    Bai, Yanyan
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China; University of Chinese Academy of Sciences, Beijing, China.
    Zhang, Jiaying
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China; School of Materials Science and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China.
    Cai, Meirong
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.
    Zhou, Feng
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.
    Novel N, P-containing oil-soluble ionic liquids with excellent tribological and anti-corrosion performance2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 132, p. 118-129Article in journal (Refereed)
    Abstract [en]

    Two oil-soluble ionic liquids N, N-trimethyl-N-hexadecyl ammonium bis(2-ethylhexyl) phosphate (NP-16))and 1,2-bis-NN-dimethyl-N-cetylammonium bis (2-ethylhexyl) phosphate (NP-16-2-16) have been synthesized and investigated as a potential friction reduction and anti-wear lubricant additive with anti-corrosion properties. The results indicate that the addition of 1.0 wt % NP-16 into PAO10 can significantly reduce friction coefficient and improve its anti-wear performance under RT and 100 °C. The performance is obviously better than that of traditional additives ZDDP and tricresyl phosphate. PAO10 + 1.0 wt % NP-16 even outperformed the PAO10 with about 40% lower friction and 2 orders of magnitude less wear. The analysis results of SEM, EDS and XPS show that an FePO4 or nitrogen-containing tribofilm is formed on the friction interface when NP-16 and NP-16-2-16 are selected as additives, which play a key role in reducing friction and wear.

  • 60008. Yu, Wang
    Bimodal voice recognition based computer input2003Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the last few decades, the computer keyboards input device has received much attention in the past and is believed by many to be a prime factor in the etiology of upper extremity musculoskeletal disorders. And wide rang of voice input systems are proposed to allow persons to operate a computer without using a keyboard or mouse. This thesis reviewed both of acoustic–only and bimodal voice recognition system and compared their recognition accuracy in simulated noisy environments. Then, the voice recognition technique is adopted in keyboard design to fulfil keyboard ergonomic demands. Finally, the value analysis was performed to evaluate the redesigned voice input keyboards. The experiment results demonstrate, compared to conventional acoustic only based speech recognition, bimodal speech recognition scheme has a much improved recognition accuracy and using the visual features allows the development of a more practical and real-time recognition system. Through the redesigned voice input keyboard, computer users can get their hand free completely and partly at their own will, by which they are away from the upper extremity musculoskeletal disorders risk and vocal strain.

  • 60009.
    Yu, Xixun
    et al.
    The State Key Laboratory on Integrated Services Networks, School of Cyber Engineering, Xidian University, Xi’an.
    Yan, Zheng
    The State Key Laboratory on Integrated Services Networks, School of Cyber Engineering, Xidian University, Xi’an.
    Vasilakos, Athanasios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Survey of Verifiable Computation2017In: Mobile Networks and Applications, ISSN 1383-469X, Vol. 22, no 3, p. 438-453Article in journal (Refereed)
    Abstract [en]

    Internet of Things (IoT) has taken place to motivate various intelligent applications with the data collected by the things”. Meanwhile, Cloud computing offers an efficient and convenient way to store, process and analyze huge amount of data. Because a Cloud Service Provider (CSP) that is employed to store and process user private data is actually not in the trust domains of cloud users, data security becomes a serious issue in cloud computing. One crucial problem in cloud is the cloud data processing result may be incorrect, thus cannot be fully trusted. This calls for research to verify the correctness of data processing at the cloud in order to enhance its trustworthiness, especially for encrypted data processing. At present, various cryptosystems have been proposed to achieve verifiability with different characteristics and quality. However, the literature still lacks a thorough survey to review the current state of art in order to get a comprehensive view of this research field, named verifiable computation. In this paper, we review existing work of verifiable computation by comparing and discussing pros and cons according to performance requirements, highlight open research issues through serious review and analysis and propose a number of research directions in order to guide future research

  • 60010.
    Yu, Y.
    et al.
    Luleå tekniska universitet.
    Axelsson, Kennet
    Luleå tekniska universitet.
    Li, Z. Q.
    Interaction between soil and bored pile based on field tests1991In: Field measurements in geomechanics: proceedings of the 3rd international sysmposium Oslo / [ed] Geraldine Sorum, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1991, p. 799-808Conference paper (Refereed)
    Abstract [en]

    Three long instrumented bored piles have been tested in the ground of a multilayer soil of clay and sand. The shaft load transfer mechanism was investigated with regard to the soil type, pile geometry and test procedures. Additional pile tests of large displacement penetration have also been carried out to study the performance of tip resistance. Special attention is given to the installation procedure of piles, which may play a significant role in the performance of the bored piles.

  • 60011.
    Yu, Yan
    Luleå tekniska universitet.
    Silty landslides in the river valleys of northern Sweden1994In: Proceedings: Seventh International Congress, International Association of Engineering Geology, 5-9 September 1994, Lisboa Portugal / [ed] R. Oliveira, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1994, p. 1731-1740Conference paper (Refereed)
  • 60012.
    Yu, Yao
    Luleå tekniska universitet.
    Constitutive relations for soils and their verifications: a report on the level of development of geomaterial modelling : a state-of-the-art report1988Report (Other academic)
  • 60013.
    Yu, Yao
    Luleå tekniska universitet.
    Stability of embankments on sulphide-rich soils1994Report (Other academic)
  • 60014.
    Yu, Yao
    Luleå tekniska universitet.
    Testing and modelling of silty and sulphide-rich soils1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Silt and sulphide soil are two types of soil which are dominating in northern Sweden, especially in the coast area of the Baltic sea. The stress-strain and strength characteristics of these two soils have so far not been as much explored as those for e.g. Scandinavian clays. With increasing use of numerical methods in geotechnical engineering, better knowledge of the constitutive behaviour of soils is needed as well as more accurate models. The work reported in this thesis is an attempt to achieve such a knowledge for silt and sulphide soil. The drained and undrained stress-strain characteristics of silt have been investigated by means of triaxial compression and extension tests. The compressibility, the dual characteristic of contractancy and dilatancy during shearing, the effect of the clay content and the dependence of the failure surface on the Lode angle have been specially discussed. The drained and undrained stress-strain characteristics of sulphide soil were investigated by means of triaxial and CRS oedometer tests. The compressibility, the effect of the excess pore pressure and the anisotropy have been specially discussed. A plasticity model was proposed for modelling the constitutive behaviour of silt. Among others, the model takes into account the dual characteristic and the dependence of the yield criterion on the Lode angle. An analytical solution was carried out for the undrained triaxial state which links the dilatancy parameter to other parameters. Conditions of material stability were also derived for the triaxial stress state. A plasticity model was proposed for modelling the constitutive behaviour of sulphide soil. Among others, the model takes into account the cohesion and the initial and stress-induced anisotropy. An explicit relation was derived to relate failure or critical state parameters in the isotropic case to those in the anisotropic (K0) case. A calibration method based on optimization was designed to improve the overall quality of model parameters. By using this method, the two proposed models were then calibrated to experimental data from several sets of tests on silt and sulphide soil. Two boundary-value problems, with available data from field tests, were analyzed using a finite element code with the proposed models implemented to demonstrate the capability of the proposed models and of the numerical method.

  • 60015.
    Yu, Yao
    Luleå tekniska universitet.
    Three-dimensional finite element analyses of pile group foundations1993Report (Other academic)
  • 60016.
    Yu, Yao
    et al.
    Luleå tekniska universitet.
    Axelsson, Kennet
    Luleå tekniska universitet.
    A plasticity model for silt1992In: Numerical models in geomechanics: of the fourth International Symposium on Numerical Models in Geomechanics, NUMOG IV, Swansea, U.K., 24-27 August 1992 / [ed] G.N. Pande; S. Pietruszczak, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1992, Vol. 4, p. 37-45Conference paper (Refereed)
  • 60017.
    Yu, Yao
    et al.
    Luleå tekniska universitet.
    Axelsson, Kennet
    Luleå tekniska universitet.
    Constitutive driver for response behaviour of soils1992Report (Other academic)
  • 60018.
    Yu, Yao
    et al.
    Luleå tekniska universitet.
    Jacobsson, A.
    Geological and geotechnical characteristics of tills for road construction1994In: Proceedings: Seventh International Congress, International Association of Engineering Geology, 5-9 September 1994, Lisboa Portugal / [ed] R. Oliveira, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1994, p. 3235-3243Conference paper (Refereed)
  • 60019.
    Yu, Yong
    et al.
    Big Data Research Center, School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu.
    Xue, Liang
    Department of Computing, The Hong Kong Polytechnic University.
    Au, Man Ho
    Department of Computing, The Hong Kong Polytechnic University.
    Susilo, Willy
    Center for Computer and Information Security Research, School of Computing and Information Technology, University of Wollongong.
    Ni, Jianbin
    Big Data Research Center, School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu.
    Zhang, Yafang
    Big Data Research Center, School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu.
    Vasilakos, Athanasios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Shen, Jian
    School of Computer and Software at Nanjing University of Information Science and Technology, Nanjing.
    Cloud data integrity checking with an identity-based auditing mechanism from RSA2016In: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 62, p. 85-91Article in journal (Refereed)
    Abstract [en]

    Cloud data auditing is extremely essential for securing cloud storage since it enables cloud users to verify the integrity of their outsourced data efficiently. The computation overheads on both the cloud server and the verifier can be significantly reduced by making use of data auditing because there is no necessity to retrieve the entire file but rather just use a spot checking technique. A number of cloud data auditing schemes have been proposed recently, but a majority of the proposals are based on Public Key Infrastructure (PKI). There are some drawbacks in these protocols: (1) It is mandatory to verify the validity of public key certificates before using any public key, which makes the verifier incur expensive computation cost. (2) Complex certificate management makes the whole protocol inefficient. To address the key management issues in cloud data auditing, in this paper, we propose ID-CDIC, an identity-based cloud data integrity checking protocol which can eliminate the complex certificate management in traditional cloud data integrity checking protocols. The proposed concrete construction from RSA signature can support variable-sized file blocks and public auditing. In addition, we provide a formal security model for ID-CDIC and prove the security of our construction under the RSA assumption with large public exponents in the random oracle model. We demonstrate the performance of our proposal by developing a prototype of the protocol. Implementation results show that the proposed ID-CDIC protocol is very practical and adoptable in real life.

  • 60020.
    Yuan, Shengjuan
    et al.
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Chen, Yifeng
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Experimental study of CO2 absorption in aqueous cholinium-based ionic liquids2017In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 445, p. 14-24Article in journal (Refereed)
    Abstract [en]

    CO2 removal (or separation) is the key step for biogas upgrading. This research aims to investigate aqueous solutions of amino acid ionic liquids to achieve effective CO2 separation. In this work, three cholinium-based amino acid ionic liquids ([Cho][AA]s) (i.e. cholinium glycinate ([Cho][Gly]), cholinium alaninate ([Cho][Ala]) and cholinium prolinate ([Cho][Pro])) were synthesized and characterized. The effect of water on the viscosity, CO2 absorption loading (m and α) and apparent absorption rate constant was systematically studied. The CO2 absorption mechanism in the aqueous solution of [Cho][Gly] was explored by 13C Nuclear Magnetic Resonance (NMR). The results demonstrate that the absorption loading (m) and viscosity increase with increasing IL concentration, while the apparent absorption rate constant decreases. The absorption loading decreased with increasing temperature. The CO2 absorption mechanism in the aqueous [Cho][Gly] solution started with the chemical reaction to form carbamate at low absorption loading (α), and followed by the hydrolysis of carbamate and CO2 hydration reaction at high absorption loading (α). Moreover, the aqueous solution with 5 wt % [Cho][Gly] showed the highest regeneration efficiency, and the absorption and regeneration performance of the aqueous solution of [Cho][Gly] was compared with commercial CO2 absorbents with promising results.

  • 60021.
    Yuan, Shengjuan
    et al.
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Chen, Yifeng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Sun, Yunhao
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    CO2 absorption in mixed aqueous solution of MDEA and cholinium glycinate2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 7, p. 7325-7333Article in journal (Refereed)
    Abstract [en]

    A new mixed solvent system that consists of cholinium glycinate ([Cho][Gly]) and aqueous N-methyldiethanolamine (MDEA) solution was developed in this work to serve as CO2 absorbent. The equilibrium absorption was carried out to investigate the effect of solution composition, pressure and temperature on CO2 absorption performance. The effect of CO2 absorption on the viscosity of the aqueous solutions was studied, and the regeneration efficiency of the aqueous solutions was also investigated. The results showed that the CO2 absorption loading decreased with increasing [Cho][Gly] concentration and temperature, and the absorption loading strongly depended on CO2 partial pressure. The reactivity of MDEA was significantly enhanced with the addition of [Cho][Gly]. The aqueous solution with (10 wt % [Cho][Gly] + 20 wt % MDEA) showed an optimal CO2 absorption and high regeneration efficiency. Furthermore, the CO2 absorption mechanism in the aqueous [Cho][Gly]-MDEA solution was explored by 13C Nuclear Magnetic Resonance (NMR), which indicated that the CO2 absorption in the aqueous [Cho][Gly]-MDEA solution was zwitterion mechanism.

  • 60022.
    Yuan, Xuemin
    Luleå tekniska universitet.
    Action of gases in control of pulp chemistry and flotation selectivity for a complex sulphide ore1995Licentiate thesis, comprehensive summary (Other academic)
  • 60023.
    Yuan, Xuemin
    Luleå tekniska universitet.
    Flotation selectivity, process modelling and simulation for a complex sulphide ore1998Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis covers research with different methods on the same fine-grained complex sulphide ore - Petiknäs - from the Skellefte Field in Northern Sweden. Mineralogical research results demonstrate that the degree of liberation of galena, rather than the chemical factors under the current flotation conditions, is the dominant factor affecting Pb grade and recovery, since galena has the same flotation as chalcopyrite if having the same degree of liberation. A novel approach for liberation pattern recognition is proposed based on multivariate statistical modelling and a four-parameter liberation model developed in this study. This approach opens up the possibility to use automatic pattern recognition and identification, and provides us with a quicker and more illustrative way to visualise mineral liberation characteristics. It is found that the effect of oxidising and reducing gases is only significant if the ore has been ground in a mild steel environment. The combination of mild steel grinding and prolonged aeration produces a slightly better selectivity between the copper minerals and zinc or iron sulphides compared with stainless steel grinding. However, this is at the expence of a slower flotation kinetics. For mild steel grinding, it is found that the copper flotation shows a marked potential dependence with a flotation "edge" at approx. +75mV (SHE). The pulp chemistry data show that mild steel grinding increases the surface oxidation of sulphide minerals, mobilising more sulphur into the pulp liquid. A combination of a galvanic interaction mechanism and a ferric leaching effect is probably responsible for the increased oxidation of sulphides after mild steel grinding. Also, theoretical calculations support that the hydrophobic entity responsible for chalcopyrite flotation with dithiophosphate is probably a surface percipate similar to the stoichiometric copper-collector compound. In batch flotation experiments, the first-order kinetic model with rectangular distribution of floatability is best fitted to the test data after stainless steel grinding only. For mild steel grinding, no traditional kinetic models are applicable. Redox potential has a profound effect on the flotation kinetics of chalcopyrite. In research on industrial kinetics, a similar phenomenon to mild steel grinding in batch tests is observed, i.e., there is no traditional kinetic model suitable to the full-scale kinetic data. Instead, the first-order classical kinetic model modified with a zero- time factor is found to give a simpler form and the best fit to the industrial data.

  • 60024.
    Yuan, Xuemin
    et al.
    Luleå tekniska universitet.
    Pålsson, Bertil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Flotation of a complex sulphide ore I.: Cu/Zn selectivity control by adjusting pulp potential with different gases1996In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 46, no 3-4, p. 155-179Article in journal (Refereed)
    Abstract [en]

    To investigate the possibility of using gases with varying oxygen activity and their influence on copper-zinc selectivity, flotation tests were done in a mechanical laboratory cell on a fine-grained complex sulphide ore with high pyrite and pyrrhotite content. The pulp environment was modified by changing the grinding media and by using different gases in the pre-conditioning a flotation steps. A statistical design with two levels of grinding media, four levels of pre-conditioning, and three levels of flotation gas type, was used. It is found that the grinding environment is the most dominant variable influencing the flotation results. Strong interactions exist between the pre-conditioning type and the flotation gas for mild steel grinding. Such interactions, and even the direct influence of pre-conditioning and flotation gas type, are statistically insignificant for stainless steel grinding, which often gave good copper flotation. The Cu/Zn selectivity shows a strong dependence on the pre-conditioning type and flotation gases for mild steel grinding, but not for stainless steel grinding. The best Cu/Zn selectivity happens for the combination of 5% oxygen pre-conditioning and air flotation after mild steel grinding. It seems that galvanic reactions after or during the mild steel grinding facilitate surface oxidation of sulphides. A mechanism similar to ferric leaching is proposed. As expected, it was observed that the oxidising or reducing environment in the pulp, as measured by the pulp potential, has a strong influence on the flotation results.

  • 60025.
    Yuan, Xuemin
    et al.
    Luleå tekniska universitet.
    Pålsson, Bertil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Flotation of a complex sulphide ore. II.: Influence of grinding environments on Cu/Fe sulphide selectivity and pulp chemistry1996In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 46, no 3-4, p. 181-204Article in journal (Refereed)
    Abstract [en]

    To investigate the possibility of using gases with varying oxygen activity and their influence on copper-zinc selectivity, flotation tests were done in a mechanical laboratory cell on a fine-grained complex sulphide ore with high pyrite and pyrrhotite content. The pulp environment was modified by changing the grinding media and by using different gases in the pre-conditioning a flotation steps. A statistical design with two levels of grinding media, four levels of pre-conditioning, and three levels of flotation gas type, was used. It is found that the grinding environment is the most dominant variable influencing the flotation results. Strong interactions exist between the pre-conditioning type and the flotation gas for mild steel grinding. Such interactions, and even the direct influence of pre-conditioning and flotation gas type, are statistically insignificant for stainless steel grinding, which often gave good copper flotation. The Cu/Zn selectivity shows a strong dependence on the pre-conditioning type and flotation gases for mild steel grinding, but not for stainless steel grinding. The best Cu/Zn selectivity happens for the combination of 5% oxygen pre-conditioning and air flotation after mild steel grinding. It seems that galvanic reactions after or during the mild steel grinding facilitate surface oxidation of sulphides. A mechanism similar to ferric leaching is proposed. As expected, it was observed that the oxidising or reducing environment in the pulp, as measured by the pulp potential, has a strong influence on the flotation results.

  • 60026.
    Yuan, Xuemin
    et al.
    Luleå tekniska universitet.
    Pålsson, Bertil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Statistical intepretation of flotation kinetics in the flotation of a complex sulphide ore1995In: Konferens i mineralteknik: Luleå, 14-16 februari 1995 / [ed] Marianne Thomaeus; Eric Forssberg, MinFo , 1995, p. 51-61Conference paper (Other academic)
  • 60027.
    Yuan, Xuemin
    et al.
    Luleå tekniska universitet.
    Pålsson, Bertil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Statistical interpretation of flotation kinetics for a complex sulphide ore1996In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 9, no 4, p. 429-442Article in journal (Refereed)
    Abstract [en]

    Kinetic flotation models were applied to data from tests with reactive gases (hydrogen and sulphur dioxide) on a complex sulphide ore. The models were evaluated by statistical techniques, after non-linear regression on the model parameters. It is found that a first order model with rectangular distribution of floatability fits the test data very well. Statistical tests on copper, silver and lead kinetic data show that reactive gases have a greater influence on silver mineral flotation compared to copper-lead minerals. Sulphur dioxide generally gives higher ultimate silver recoveries than sodium bisulphite, and the magnitudes depend on the interactions between the modifiers and theflotation gases (5% H2 N2 and air). Correlation analysis suggests that silver flotation is probably determined by the floatability of a separate mineral such as tetrahedrite. Multivariate analysis on pulp chemistry data reveals that the pulp pH is the most significant variable among the pulp chemistry data, provided the grinding is iron free. The pH effect is attributed to the addition of sulphur dioxide. After autogenous or non-reducing grinding, the naturally-occurring variations in redox levels are too small to influence the flotation results, despite the tests being made with a complex sulphide ore.

  • 60028.
    Yuhua, Pan
    Luleå tekniska universitet.
    Mathematical modelling of fluid flow and heat transfer in steel ladles1999Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis work, three mathematical models, each of which is suitable for simulating a particular process in the operation of steel ladles, have been developed. Firstly, by using a finite-difference mathematical method (FDM), a one-dimensional numerical model for calculating heat transfer through ladle wall, bottom and top slag layer was established. This FDM model was used to provide transient and structure dependent heat loss fluxes for further modelling of fluid flow and heat transfer in steel ladles. Then, with a computational fluid dynamics (CFD) mathematical approach, a two-dimensional CFD model for simulating fluid flow and heat transfer in steel ladles during the holding period before teeming was developed. With this model the natural convection and thermal stratification phenomena occurring in steel ladles were investigated. Further, the two-dimensional CFD model was finally extended into a three-dimensional CFD model to include simulations on the fluid flow and heat transfer in steel ladles with drainage during teeming, so that the interaction between natural convection and drainage flow was examined. By using this three-dimensional CFD model, it is possible to predict the steel stream temperature during teeming which is important for further prediction and control of steel temperature in tundishes during continuous casting.

  • 60029. Yusuf Hassan, Abdiaziz
    Slitbanebetong för broar: Inventering och inverkan av krympning2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The use of direct mould concrete as material for the surfacing on bridges is an increasingly used coating option. But in order to implement this option at a larger scale, a change in the formula according to “bridge code 2004 part 62.323” for direct mould concrete has to be made. This is because the present formula gives too high volumes of steel fiber. Thus this report will be a part of improving the said formula.In this report the author makes an inventory in which, among others things, the amount of bridges that have been directly molded with concrete as surfacing. The inventory shows in what intervals in both runway length and the area of the surface that is direct moulded as well as where and when these bridges were built. There is also an inventory made of what kind of damage these bridges have been suffering. This is then presented in graphical format in order to get a grip on its scope.Another part of the research made in this report is to study the temperature and relative humidity’s effects on concrete shrinkage. This is done to simulate the concrete moulding in different seasons and locations in the country.The goal is to acquire an understanding on the extent of direct mould concrete usage in Sweden, as well as to find a favorable moulding-environment. If the shrinkage process is slow the grip between the main concrete construction and the surface coating is better, which in turn results into a smaller amount of required steel fibers in the concrete. It also leads to easier processing when moulding, and minimizes the surface roughness of the bridge way.

  • 60030.
    Yusupov, Khabib
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Functional Nanosystems and High-Temperature Materials National University of Science and Technology MISIS Moscow.
    Stumpf, Steffi
    Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena.
    You, Shujie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bogach, Aleksei
    Prokhorov General Physics Institute of the Russian Academy of Sciences.
    Martinez, Patricia M.
    NanoTech Institute University of Texas at Dallas Richardson .
    Zakhidov, Anvar
    Department of Functional Nanosystems and High-Temperature Materials National University of Science and Technology MISIS Moscow.
    Schubert, Ulrich S.
    Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena.
    Khovaylo, Vladimir V.
    Department of Functional Nanosystems and High-Temperature Materials National University of Science and Technology MISIS Moscow.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Flexible Thermoelectric Polymer Composites Based on a Carbon Nanotubes Forest2018In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 40, article id 1801246Article in journal (Refereed)
    Abstract [en]

    Polymer-based composites are of high interest in the field of thermoelectric (TE) materials because of their properties: abundance, low thermal conductivity, and nontoxicity. In applications, like TE for wearable energy harvesting, where low operating temperatures are required, polymer composites demonstrate compatible with the targeted specifications. The main challenge is reaching high TE efficiency. Fillers and chemical treatments can be used to enhance TE performance of the polymer matrix. The combined application of vertically aligned carbon nanotubes forest (VA-CNTF) is demonstrated as fillers and chemical post-treatment to obtain high-efficiency TE composites, by dispersing VA-CNTF into a poly (3,4-ethylenedioxythiophene) polystyrene sulfonate matrix. The VA-CNTF keeps the functional properties even in flexible substrates. The morphology, structure, composition, and functional features of the composites are thoroughly investigated. A dramatic increase of power factor is observed at the lowest operating temperature difference ever reported. The highest Seebeck coefficient and electrical conductivity are 58.7 μV K-1 and 1131 S cm-1, respectively. The highest power factor after treatment is twice as high in untreated samples. The results demonstrate the potential for the combined application of VA-CNTF and chemical post-treatment, in boosting the TE properties of composite polymers toward the development of high efficiency, low-temperature, flexible TEs.

  • 60031.
    Yusupov, Khabib
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Functional Nanosystems and High Temperature Materials, NUST MISiS, Moscow; Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Germany.
    Zakhidov, A.
    Department of Functional Nanosystems and High Temperature Materials, NUST MISiS, Moscow; NanoTech Institute, University of Texas at Dallas, USA.
    You, Shujie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Stumpf, S.
    Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Germany; Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Germany .
    Martinez, P.M.
    NanoTech Institute, University of Texas at Dallas, USA.
    Ishteev, A.
    Department of Functional Nanosystems and High Temperature Materials, NUST MISiS, Moscow.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Khovaylo, V.
    Department of Functional Nanosystems and High Temperature Materials, NUST MISiS, Moscow; National Research South Ural State University, Chelyabinsk, Russian Federation.
    Schubert, U.
    Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Germany; Center for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Germany; Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Germany.
    Influence of oriented CNT forest on thermoelectric properties of polymer-based materials2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 741, p. 392-397Article in journal (Refereed)
    Abstract [en]

    Thermoelectric (TE) materials are highly important due to their ability to convert wasted heat energy into electricity. Among the different TE materials, organic-based or polymer-based TE systems are among the most promising due to their sustainability, non-toxicity and good electrical properties. In our research, we have investigated for the first time the application of vertically aligned carbon nanotubes forest (VA-CNTF) as a filler for TE composite; compared to unconnected carbon nanotubes (CNT), which are typically used in polymer/CNT composites, dry pulled VA-CNTF sheets have more ordered structure, which is supposed to improve the TE efficiency of the material. VA-CNTF and short unoriented multiwalled carbon nanotubes (MWCNT) were used as fillers of a polymeric matrix, to prepare TE composites. Various stacking configurations were explored by using CNTF. All the samples were examined by scanning electron microscopy (SEM), micro-Raman spectroscopy, and four-point probe electrical measurements; MWCNT-based samples were used as benchmarking systems.

    The results revealed a dramatic increase of the Seebeck coefficient up to 46 μV/K for the VA-CNTF-based sample, while the best MWCNTs-based sample (MWCNT concentration 50 wt%) provided only 21.49, which is roughly the Seebeck coefficient of pure polymer. This research represents the first application of VA-CNTF as a promising material for TE systems and demonstrates that oriented nanoforests and related CNT sheets are a very perspective material for promising developments in the field.

  • 60032.
    Yuwawech, Kitti
    et al.
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology Thonburi(KMUTT), Bangkok.
    Wootthikanokkhan, Jatuphorn
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Tanpichai, Supachok
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Effects of Two Different Cellulose Nanofiber Types on Properties of Poly(vinyl alcohol) Composite Films2015In: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, Vol. 2015, article id 908689Article in journal (Refereed)
    Abstract [en]

    This work concerns a study on the effects of fiber types and content of cellulose nanofiber on mechanical, thermal, and optical properties polyvinyl alcohol (PVA) composites. Two different types of cellulose nanofibers, which are nanofibrillated cellulose (NFC) and bacterial cellulose (BC), were prepared under various mechanical treatment times and then incorporated into the PVA prior to the fabrication of composite films. It was found that tensile modulus of the PVA film increased with nanofibers content at the expense of its percentage elongation value. DSC thermograms indicate that percentage crystallinity of PVA increased after adding 2-4 wt% of the fibers. This contributed to the better mechanical properties of the composites. Tensile toughness values of the PVA/BC nanocomposite films were also superior to those of the PVA/NFC system containing the same fiber loading. SEM images of the composite films reveal that tensile fractured surface of PVA/BC experienced more ductile deformation than the PVA/NFC analogue. The above discrepancies were discussed in the light of differences between the two types of fibers in terms of diameter and their intrinsic properties. Lastly, percentage total visible light transmittance values of the PVA composite films were greater than 90%, regardless of the fiber type and content.

  • 60033.
    Yuwawech, Kitti
    et al.
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology Thonburi(KMUTT), Bangkok.
    Wootthikanokkhan, Jatuphorn
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Tanpichai, Supachok
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Enhancement of thermal, mechanical and barrier properties of EVA solar cell encapsulating films by reinforcing with esterified cellulose nanofibres2015In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 48, p. 12-22Article in journal (Refereed)
    Abstract [en]

    Solar cell encapsulating film based on ethylene vinyl acetate copolymer (EVA) was modified by using bacterial cellulose (BC) nanofibres. Bacterial cellulose was chemically modified with propionic anhydride prior to compounding with EVA in a twin screw extruder. The effects of fibre content on the mechanical, thermal, optical and barrier properties of the EVA composite films were investigated. Better mechanical and barrier properties of the EVA films were obtained when the modified BC nanofibres were used. The results were ascribed to the different chemical functional groups on the fibre surface, as verified by FTIR spectra. Deacetylation of the EVA was delayed and visible light transparency of the EVA films above 75% was retained. Overall, our study showed that it was possible to improve the barrier properties of EVA film without sacrificing much transparency by using a suitable type and content of cellulose nanofibres.

  • 60034.
    Yuwawech, Kitti
    et al.
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Wootthikanokkhan, Jatuphorn
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Wanwong, Sompit
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Tanpichai, Supachok
    School of EnergyEnvironment and Materials, King Mongkut's University of Technology Thonburi (KMUTT)Bangkok .
    Polyurethane/esterified cellulose nanocrystal composites as a transparent moisture barrier coating for encapsulation of dye sensitized solar cells2017In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 134, no 45, article id 45010Article in journal (Refereed)
    Abstract [en]

    This research work aims to investigate the effects of types and concentration of cellulose nanocrystals (CNCs) prepared from bacterial cellulose (BC) and nanofibrillated cellulose (NFC) on structure properties of polyurethane (PU) composites. Feasibility of applying the polymer composite for encapsulation of dye sensitized solar cells was of interest. Both CNCs were pretreated via esterification before mixing with the polyurethane by a solution process. Tensile strength and thermal stability of the PU/esterified CNCs were found to be superior to those of the systems reinforced with untreated CNCs. With the introduction of both untreated and esterified CNCs, water vapor transmission rates through the PU composite films were lowered while their visible light transmittance values were maintained to be above 80%. Also, better efficiency and stability of the solar cell were obtained when the PU was reinforced with CNCs, indicating its longer lifetime usage. The most suitable cell, described in terms of durability, was obtained when the PU was mixed with 2 wt % of esterified CNCs obtained from BC. Overall, this study shows that the surface modification of the CNCs is an important factor, affecting the reinforcing efficacy.

  • 60035. Yvling, Sofie
    Miljöriskanalys vid Smurfit Kappa Kraftliner Piteå2007Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 60036.
    Zabasta, Anatolijs
    et al.
    Institute of Industrial Electronics and Electrical Engineering, Riga Technical University, Riga, Latvia.
    Kunicina, Nadezda
    Institute of Industrial Electronics and Electrical Engineering, Riga Technical University, Riga, Latvia.
    Kondratjevs, Kaspars
    Institute of Industrial Electronics and Electrical Engineering, Riga Technical University, Riga, Latvia.
    Patlins, Antons
    Industrial Electronics and Electrical Engineering, Riga Technical University, Riga, Latvia.
    Ribickis, Leonids
    Institute of Industrial Electronics and Electrical Engineering, Riga Technical University, Riga, Latvia.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    MQTT Service Broker for Enabling the Interoperability of Smart City Systems2018Conference paper (Refereed)
    Abstract [en]

    Smart city offers a concept of interconnection of modern digital technologies in the context of a city that provides a solution to enhance the quality and performance of urban services. However, interconnection of the Smart city systems still is a challenging process due to incompatibility of systems that apply a plenty of appropriate technical solutions and protocols that cause collaboration between automation devices such as sensors, actuators, controllers. Introduction of Internet-of-Things (IoT) provides promising opportunities to develop new services and integrate different application domains. The Arrowhead Framework aims to apply Service Oriented Architecture to the embedded systems' world. This research is focused on the one of the Arrowhead Framework core systems - Event Handler. This system supports the handling of events, and enriches service-oriented applications with the capabilities of interacting via the publish/subscribe paradigm. We implemented the Event Handler system as a MQTT enabled service broker, and deployed data flow programming tool Node-RED for wiring together divergent hardware devices and nodes, and APIs for online services. A case study of the service broker implemented for control of utilities systems in urban environment is presented and discussed.

  • 60037. Zaccarini, Federica
    et al.
    Bakker, Ronald J.
    Garuti, Giorgio
    Aiglsperger, Thomas
    Thalhammer, Oskar A. R.
    Campos, Lolita
    Proenza, Joaquin A.
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    Lewis, John F.
    Department of Earth and Environmental Sciences, George Washington University, .
    Platinum group minerals in chromitite bodies of the Santa Elena Nappe, Costa Rica: mineralogical characterization by electron microprobe and Raman-spectroscopy2010In: Boletín de la Sociedad Geológica Mexicana, ISSN 1405-3322, Vol. 62, no 1, p. 161-171Article in journal (Refereed)
    Abstract [en]

    AbstractForty-seven grains of platinum group minerals (PGM) associated with small chromitite bodies of the Santa Elena ultramafic Nappe (Costa Rica) were mineralogically investigated with electron microscope, electron microprobe and Raman spectroscopy. The mineralogical assemblage includes sulfides of the laurite-erlichmanite series (RuS₂-OsS₂), irarsite (IrAsS), osmium, Ir-Rh sulfides containing relevant amounts of Ni, Fe and Cu, and a Ru-As-S compound, possibly ruarsite (RuAsS). Most platinum group element (PGE) sulfides and sulfarsenides represent primary magmatic phases entrapped in chromite at high temperatures, whereas native osmium is probably formed by subsolidus exsolution. The lack of primary PGE alloys suggests relatively high S-fugacity in the chromite forming system. This investigation emphasizes the efficiency of Raman spectroscopy in the identification of PGM of extremely small size, and shows how this technique can be used in revealing distinctive compositional differences among PGM of the laurite-erlichmanite series and irarsite.

  • 60038.
    Zaccarini, Frederica
    et al.
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Garuti, Giorgio
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Proenza, Joaquín A.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Campos, L.
    Escuela Centroamericana de Geología, University of Costa Rica.
    Thalhammer, O. A. R.
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Aiglsperger, Thomas
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona.
    Lewis, John F.
    Department of Earth and Environmental Sciences, George Washington University, .
    Chromite and platinum group elements mineralization in the Santa Elena Ultramafic Nappe (Costa Rica): Geodynamic implications2011In: Geologica Acta, ISSN 1695-6133, E-ISSN 1696-5728, Vol. 9, no 3-4, p. 407-423Article in journal (Refereed)
    Abstract [en]

    Chromitites associated with strongly altered peridotite from six distinct localities in the Santa Elena ultramaficnappe (Costa Rica) have been investigated for the first time. Santa Elena chromitites commonly display acompositional variation from extremely chromiferous (Cr/(Cr+Al)=0.81) to intermediate and aluminous(Cr/(Cr+Al)=0.54). This composition varies along a continuous trend, corresponding to calculated parental liquidswhich may have been derived from the differentiation of a single batch of boninitic magma with Cr-rich and(Al, Ti)-poor initial composition. Fractional precipitation of chromite probably occurred during differentiation ofthe boninitic melt and progressive metasomatic reaction with mantle peridotite. The distribution of platinum groupelements (PGE) displays the high (Os+Ir+Ru)/(Rh+Pt+Pd) ratio typical of ophiolitic chromitites and, consistently,the platinum group minerals (PGM) encountered are mainly Ru-Os-Ir sulfides and arsenides. Textural relations ofmost of the platinum group elements suggest crystallization at magmatic temperatures, possibly under relativelyhigh sulfur fugacity as indicated by the apparent lack of primary Os-Ir-Ru alloys.The chemical and mineralogical characteristics of chromitites from the Santa Elena ultramafic nappe have astrong affinity to podiform chromitites in the mantle section of supra-subduction-zone ophiolites. Calculatedparental melts of the chromitites are consistent with the differentiation of arc-related magmas, and do not supportthe oceanic spreading center geodynamic setting previously proposed by some authors.

  • 60039.
    Zaccarini, Frederica
    et al.
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Tredoux, Marian
    Department of Geology, University of the Free State, Bloemfontein.
    Miller, Duncan E.
    2Department of Geology, University of the Free State, Bloemfontein.
    Garuti, Giorgio
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Aiglsperger, Thomas
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    Proenza, Joaquin A.
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    The occurrence of platinum-group element and gold minerals in the Bon Accord Ni-oxide body, South Africa2014In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 99, no 8-9, p. 1774-1782Article in journal (Refereed)
    Abstract [en]

    Two samples from the enigmatic Ni-oxide body of Bon Accord (Barberton greenstone belt, South Africa) have been investigated with the hydroseparation technique to obtain heavy mineral concentrates. The concentrates contain abundant Pt, Pd, and gold minerals never reported before from the Bon Accord Ni-oxide body. The grains occur as: (1) minute inclusions (<3 μm) in trevorite (ideally NiFe3+O4) and (2) larger (5–70 μm) free aggregates liberated from the host phase. The first group comprises several PGM compounds of Pd-Sb, Pd-Sb-As, Pd-Cu-Sb, Pt-Sb, Pt-As-S, Ru-As-S, Ru-S, along with free grains of Ni-Fe-As. The second consists of sperrylite (PtAs2), members of the sobolevskite-kotulskite series, and electrum. These results are in good agreement with previous analyses of PGE-Au in bulk rock. Paragenetic relationships indicate that the PGM and electrum are of secondary origin, probably generated during low-temperature metamorphism of the Ni-rich mineralization. They have a terrestrial origin and are related with a low-sulfidation regime that usually accompanies hydrothermally driven serpentinization of mafic-ultramafic bodies. The ligands in the newly formed PGM (As, Sb, Bi, Te, and O) probably proceed from the same source of the hydrothermal solutions. In this model, the metals Ni-PGE-Au were original components of the primary mineral assemblage of the Bon Accord precursor, whereas As, Sb, Bi, Te, and O might have been contributed by the metasomatizing fluids, during near-surface evolution of the ore body. The data on the high-grade heavy mineral concentrates, obtained by hydroseparation, have provided new knowledge about the mineral deportment of Pd, Pt, and Au.

  • 60040.
    Zach, Ondrej
    et al.
    Department of Information Systems, University of Agder.
    Haddara, Moutaz
    Department of Information Systems, University of Agder.
    ERP systems in SMEs: A literature review2011In: 2011 44th Hawaii International Conference on System Sciences: (HICSS 2011); Kauai, Hawaii, USA, 4 - 7 January 2011 / [ed] Ralph H. Sprague, Piscataway, NJ: IEEE Communications Society, 2011, article id 5718924Conference paper (Refereed)
    Abstract [en]

    This review summarizes research on enterprise resource planning (ERP) systems in small and medium-size enterprises (SMEs). Due to the close-to-saturation of ERP adoptions in large enterprises (LEs), ERP vendors now focus more on SMEs. Moreover, because of globalization, partnerships, value networks, and the huge information flow across and within SMEs nowadays, more and more SMEs are adopting ERP systems. Risks of adoption rely on the fact that SMEs have limited resources and specific characteristics that make their case different from LEs. The main focus of this article is to shed the light on the areas that lack sufficient research within the ERP in SMEs domain, suggest future research avenues, as well as, present the current research findings that could aid practitioners, suppliers, and SMEs when embarking on ERP projects

  • 60041.
    Zachrisson, Anna
    et al.
    Department of Political Science, Umeå University.
    Lindahl, Karin Beland
    Department of Urban and Rural Development, Swedish University of Agricultural Sciences, Uppsala.
    Conflict resolution through collaboration: Preconditions and limitations in forest and nature conservation controversies2013In: Forest Policy and Economics, ISSN 1389-9341, E-ISSN 1872-7050, Vol. 33, p. 39-46Article in journal (Refereed)
    Abstract [en]

    Increasing competition over the world's forest resources will likely aggravate conflict, though conflict should not be seen as bad per se. As the challenge is to develop institutions and practices capable of handling conflict constructively, various collaborative approaches involving disputing actors are evolving worldwide. In Sweden, most such approaches pertain to protected areas and few involve commercial forestry. The reasons for the rise of different approaches to collaboration in protected areas and commercially managed forest lands are explored through a comparison of two conflicts embedded in different management regimes. The study suggests that actor interdependence is critical to how collaboration evolves. Interdependence is in turn affected by the institutions, discourses, and economic context in which the process is embedded. When contextual factors are unfavourable, power relations too unequal, and interdependencies between dominant and subordinated actors weak, the prospects for collaboration are slim. In an enabling context, in contrast, mobilization may alter power relations and interdependencies, making collaboration possible. This study suggests that the low occurrence of collaborative land use planning in many parts of Sweden may be related to the presence of strong economic land use interests, un-successful mobilization of weaker parties, and absence of enabling institutional and discursive factors

  • 60042. Zachrisson, Björn
    Extraction of free-space structures for path planning purposes2008Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    LKAB one of the world’s leading producers of upgraded iron ore products for the steel industry, uses autonomous Laud-Haul-Dump (LHD) machines for transportation of the iron ore at their underground mine located in Kiruna, Sweden. These machines are an essential part in the flow of ore transportation out of the mine and therefore the driving speed of these machines is very important. Today the drive paths for these machines are drawn by hand in computer software and this is a human-computer interaction that LKAB wants to remove because of the time consumption and also for the possibility to automatically generate faster and more optimized drive paths. Research has been conducted at Luleå University of Technology concerning optimization of drive paths for autonomous machines. This research resulted in a software prototype that integrated map-handling and path generation for the machines at LKAB. This prototype was based on a path generation algorithm with the unfortunately limitation of that the polygon must be monotone, and that is not the typical case for the drive paths that the machines are using. This thesis will show an implementation of an extension of this prototype that will improve the functionality so that polygons without constraints can be used in the calculations of optimized drive paths. In order to achieve this result triangulation of polygons and breadth first search has been used. Due to safety precautions a margin from the wall must exist on each side of the drive path to prevent the machine from colliding with the walls, this will affect the size of the polygon and the recalculation of the polygon is described in this thesis. It will show how optimizations for the inner and outer curves on the drive path will affect the final result of the optimization.

  • 60043. Zachrisson, Jan
    In situ detection and characterisation of phase transformations in weld metals2006Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The work presented in this thesis is concerned with the in situ detection of phase transformations in weld metals. In order to obtain favourable mechanical properties of a material it is useful to map its phase transformation behaviour. Cooling rate and chemical composition are factors of great influence to the transformation behaviour. For a given composition, a continuous cooling transformation (CCT) diagram can be used to illustrate this behaviour for a number of cooling rates. Usually these diagrams are constructed from data obtained through dilatometry, which is an expensive and, in the case of welding, not always accurate method. The aim of this work was to develop a new methodology and a set of tools for the construction of weld metal CCT-diagrams. The methodology is based on analysis of weld thermal histories acquired from temperature measurements in the fusion zone. The temperature was measured with thermocouples, logged with LabView and analysed numerically. The microstructure was characterised with light optical microscopy and field emission gun scanning electron microscopy. Hardness testing was performed using the Vickers technique. A description of the methodology is given and the results of an analysis of two low alloy weld metals are reported for the purpose of demonstration. Through the demonstration it becomes clear that the two central parts of the methodology, microstructural characterisation and thermal analysis, in combination offers the information needed to produce continuous cooling transformation diagrams.

  • 60044.
    Zackrisson, Jesper
    Luleå tekniska universitet.
    Produktivitet, kvalitet och arbetsmiljö: en fallstudie om lågskalig industri1994Licentiate thesis, comprehensive summary (Other academic)
  • 60045.
    Zackrisson, Jesper
    et al.
    Luleå tekniska universitet.
    Franzén, M.
    Umeå University, Department of Statistics.
    Melbin, M.
    ABB Railcar AB.
    Shahnavaz, Houshang
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    Quality by a step-by-step program in low scale industries1995In: International Journal of Production Economics, ISSN 0925-5273, E-ISSN 1873-7579, Vol. 41, no 1-3, p. 419-427Article in journal (Refereed)
    Abstract [en]

    This paper focuses on the effectiveness of the on-line QC in the low scale or experience industries. The basis of the study is the manufacturing process of trams in Sweden. The result indicates that the QC program demands a solid base to be effective from the beginning of its implementation. Empirical results show that during the off-line process the lead-time in the production was reduced by 50% and the mean cycle time of the storage is decreased by 33%. Formally, quality tools are investigated as regards the scale of the industry.

  • 60046.
    Zackrisson, Jesper
    et al.
    Luleå University of Technology.
    Melbin, M.
    ABB Railcar AB.
    Shahnavaz, Houshang
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    Quality assurance in low scale industry: advances in agile manufacturing1994In: Advances in agile manufacturing: integrating technology, organization and people : International Conference on Human Aspects of Advanced Manufacturing and Hybrid Automation / [ed] Paul T. Kidd; Waldemar Karwowski, IOS Press, 1994, p. 680-683Conference paper (Refereed)
  • 60047.
    Zackrisson, Jesper
    et al.
    Luleå University of Technology.
    Shahnavaz, Houshang
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    Från anställd till ägare: en studie om produktivitet, kvalitet och ergonomi1994In: Genomförandet av förändringar: NES 94 - Nordiska ergonomisällskapets årskonferens, 14-16 september 1994, Stenungsund, Sverige / [ed] Gunnar Palmerud, Göteborg: Nordiska ergonomisäl[l]skapet , 1994, p. 234-237Conference paper (Other academic)
  • 60048. Zackrisson, Pernilla
    Robotiserad fanpaketering: en förundersökning2003Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 60049.
    Zadorozhny, Vladimir
    et al.
    Department of Information Science and Telecommunication, University of Pittsburgh.
    Krishnamurthy, Prashant
    Department of Information Science and Telecommunication, University of Pittsburgh.
    Gunopulos, Dimitrios
    University of California, Riverside.
    Jensen, Christian
    Aalborg University.
    Wolfson, Ouri
    University of Illinois.
    Zaslavsky, Arkady
    Data intensive mobile sensornets: killer applications and grand deterrents2006In: 7th International Conference on Mobile Data Management: MDM 2006, Japan ; May 10 - 12, 2006, Nara, Japan ; proceedings, Piscataway, NJ: IEEE Computer Society Press , 2006Conference paper (Refereed)
  • 60050. Zafar, Ch. Naveed
    et al.
    Pilkjaer, Anthony
    E-Voting in Pakistan2007Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When we see today’s world, e-government has played an enormous role in the advancement of the services provided by the governments worldwide. Today each and every country is giving e-governance a go. There are different levels of implementation of the e-governance worldwide but it is more of an interest to find out this in the developing world. Pakistan is one the emerging countries in the world which is trying to make a difference in the developed world and is implementing e-government at an enormous rate. Hereby: we tried to find out what are the current issues as obstacles towards e-democracy and have tried to figure out what are the factors and measures the government should take to have e-voting as an electoral procedure rather than going through the previous traditional way of manual handling of the elections in which we see controversies. This research work is of more importance at this stage as Pakistan is reaching its election period and Government would be in need of such work to get hands on this through a fast and secure electoral process.

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