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Sökning: db:Swepub > (2010-2011) > Umeå universitet > Teknik

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1.
  • Johansson, Kristin, et al. (författare)
  • Oxygen scavenging enzymes in coatings : Effect of coating procedures on enzyme activity
  • 2011
  • Ingår i: Nordic Pulp & Paper Research Journal. - Stockholm : Mittuniversitetet. - 0283-2631 .- 2000-0669. ; 26:2, s. 197-204
  • Tidskriftsartikel (refereegranskat)abstract
    • The oxygen content in food packaging may be reduced by attaching oxygen scavengers to the packaging material. The critical parameters that determine the oxygen-scavenging ability of an enzyme-based coating i.e. pH, heat and coating color formulation were evaluated. Glucose oxidase, catalase and glucose were added to latex dispersions in the preparation of the coating colors. The enzymes were entrapped in the coating layers after coating and drying. The clay concentration and drying conditions were varied and the enzymatic activity of the coated layer was evaluated. The need for a pH-buffered system was also studied and the results indicated that, when using a carboxylated latex of a standard coating grade, a buffered system was not needed. A rapid drying at a high temperature was preferred over a slow drying at a low temperature in order to prevent pre-oxidation of the substrate in the wet coating color. The scavenging capacity of the coating was dependent on the amount of substrate for the enzyme reaction left after complete drying. The concentration of clay in the coating formulation was shown to have a marked impact on the oxygen-scavenging ability of the coated layer. The enzyme activity was increased by the addition of clay up to a pigment volume concentration (PVC) of ca. 10%. At higher concentrations of clay, the enzyme activity decreased until the critical pigment volume concentration (CPVC) was reached, probably due to the prevention of diffusion of oxygen and consumption of glucose in the coating process before the layer was completely dried. Further additions of clay above the CPVC resulted in an increased enzyme activity, probably due to the creation of a porous structure.
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2.
  • Vaziri, Mojgan, et al. (författare)
  • Magnetic resonance imaging of water distribution in welded woods
  • 2011
  • Ingår i: Journal of Adhesion Science and Technology. - Utrecht : VSP. - 0169-4243 .- 1568-5616. ; 25:16, s. 1997-2003
  • Tidskriftsartikel (refereegranskat)abstract
    • This study was performed for a better understanding of water effect on welded wood and improving its water resistance. In this article, we have also attempted to demonstrate the feasibility of using Magnetic Resonance Imaging technology to study water movement in welded woods. Water distribution in welded woods of Scots pine (Pinus sylvestris) and beech (Fagus sylvatica) was investigated by Magnetic Resonance Imaging. Axial specimens were cut from beech and sapwood of Scots pine in longitudinal direction of wood grain. Two pieces of each wood species were welded together by a linear vibration machine. Sub-samples measuring 30 mm x 20 mm x 100 mm were cut from the welded specimens for Magnetic Resonance Imaging. The results showed that weldline of Scots pine was more resistant to water than weldline of beech. Pine joint was still holding after 40 h immersion in water, while a rapid wetting of the beech joint resulted in breakage of the joint in even less than an hour. This preliminary study also showed that MRI is a powerful tool to measure water distribution in welded woods and highlighted the potential of this technique to enhance understanding of wood welding. (C) Koninklijke Brill NV, Leiden, 2011
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3.
  • Gustavsson, Leif, 1954-, et al. (författare)
  • Implementering av energieffektiviseringsåtgärder i befintlig bebyggelse : Report prepared for the Swedish Energy Agency
  • 2010
  • Rapport (populärvet., debatt m.m.)abstract
    • There is great potential to improve energy efficiency in existing Swedish residential buildings. However, the successful implementation of efficiency measures depends on economical and technical factors, as well as on the attitudes and perceptions of the relevant actors. A better understanding of their attitudes and perceptions may influence the design of suitable policy measures that increase the adoption of energy efficiency measures. In this context, we conducted mail-in surveys completed by owners of detached houses, chairmen of co-operative housing associations (bostadsrättsförening) and municipality energy advisers in Sweden. We also interviewed window sellers/installers in Jämtland.Results show that it was important for the majority of homeowners to reduce their household energy use, with most undertaking no-cost measures (e.g., switching off lights). However, 70–90% of the responding homeowners had no intention of adopting building envelope measures over the next 10 years. The main reason for non-adoption was that homeowners were satisfied with the physical condition and thermal performance of their existing building envelope components. Homeowners who thought their energy cost was high were more likely to adopt an investment measure compared to those who thought their energy cost was low. Investment costs and annual energy cost savings were the most important factors in adoption of energy efficient building envelope measures. Therefore, economic incentives may induce homeowners to adopt energy efficiency investment measures. However, a large percentage (64%) of homeowners was unaware of the existence of government support for reducing household energy use. Information campaigns announcing the availability of economic incentives and the cost advantages of energy efficiency measures may be helpful in the adoption decision.Homeowners‘ considered interpersonal sources, builders, installers and energy advisers as important sources of information for their adoption of energy efficiency measures. Though a large percentage of respondents considered energy advisers as an important source of information, only 14% of homeowners had contacted an energy adviser in the past. Our findings suggest that the energy advice service is important for homeowners, but more efforts are needed to increase homeowners‘ awareness of and satisfaction with such services. The majority of municipal energy advisers were of the opinion that more training in technical aspects of energy issues and increased financial support could improve their performance.Installers and material suppliers are important actors in homeowners‘ adoption of energy efficiency measures. For example, approximately 53% of responding homeowners to a survey in Jämtland/Västernorrland stated that the window seller/installer from whom they had bought windows had recommended a particular type of window, and 97% had installed the windows that were recommended. The window sellers/installers in Jämtland prefer a window that is ―reasonably‖ energy efficient. They believe that windows with a U-value of 1.2 W/m2K are good and there is no reason to further improve the energy efficiency. The majority did not recommend windows with U-value <1.2 W/m2K. They were concerned about the condensation issues and high prices of such windows. This may influence the diffusion of very energy efficient windows in Swedish detached houses.About 80-95% of chairmen in co-operative housing associations who responded to our survey had no intention of adopting building envelope measures over the next 10 years. They were satisfied with the existing building envelope components, which may be one of the reasons for this lack of intention. As in the case of owners of detached houses, economic factors, like annual energy cost savings and investment costs, guide the implementation of energy efficiency investment measures in co-operative housing associations. However, about 66% of the responding chairmen did not consider financial constraint as a barrier to implementing investment intensive energy efficiency measures. For 54% of the respondents limited in-house competency to evaluate the benefits of energy efficiency measures was the main barrier.The majority of owners of detached houses (80%) and chairmen of co-operative housing associations (70%) perceived that economic policy instruments, such as investment subsidies and tax deductions, would encourage them to implement energy efficiency measures. Other policy instruments, especially information instruments, were perceived as less effective. Among various information policies, increasing the frequency of meter reading received the highest approval with 38% of homeowners, whereas approximately 41% of housing association chairmen thought that individual metering of heating and hot water use could be effective. Approximately 30% of homeowners and housing association chairmen thought that energy declaration was effective.
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4.
  • Gacanin, Haris, et al. (författare)
  • On Channel Estimation for Analog Network Coding in a Frequency-Selective Fading Channel
  • 2011
  • Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer. - 1687-1472 .- 1687-1499.
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, broadband analog network coding (ANC) was introduced for high-speed transmission over the wireless (frequency-selective fading) channel. However, ANC requires the knowledge of channel state information (CSI) for self-information removal and coherent signal detection. In ANC, the users' pilot signals interfere during the first slot, which renders the relay unable to estimate CSIs of different users, and, consequently, four time-slot pilot-assisted channel estimation (CE) is required to avoid interference. Naturally, this will reduce the capacity of ANC scheme. In this paper, we theoretically analyze the bit error rate (BER) performance of bi-directional broadband ANC communication based on orthogonal frequency division multiplexing (OFDM) radio access. We also theoretically analyze the performance of the channel estimator's mean square error (MSE). The analysis is based on the assumption of perfect timing and frequency synchronization. The achievable BER performance and the estimator's MSE for broadband ANC is evaluated by numerical and computer simulation. We discuss how, and by how much, the imperfect knowledge of CSI affects the BER performance of broadband ANC. It is shown that the CE scheme achieves a slightly higher BER in comparison with ideal CE case for a low and moderate mobile terminal speed in a frequency-selective fading channel.
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5.
  • Wang, Da, et al. (författare)
  • Outlet design optimization based on large-scale nonsmooth DEM simulation
  • 2011
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • We consider the application of a nonsmooth discrete element method (NDEM) [1-3] to geometricdesign optimization of a balling drum outlet used in production of iron ore pellets. The geometricdesign optimization problem is based on the need for spatially and temporally homogeneous flow ofpellets from the balling drum onto a wide belt conveyor feeding a roller sieve. Homogeneous pelletflow makes sieving most efficient and facilitates good control in the hardening furnace. The model ofthe pellet material and balling drum are specified in a NDEM framework. The simulation andanalysis procedure is described. A material flow profile in terms of design parameters is computedfrom simulation data and used for solving the design optimization problem. The solution is comparedwith different designs used in a real production plants. It is demonstrated that the method can clearlydistinguish between the original and improved design in that plant. The uncertainty in the optimaldesign parameters is discussed and put in relation to the assumptions and approximations behind the particular NDEM that is used. Proposal for how to improve and validate the material and ballingdrum model is given.The particular NDEM is described in more detail in an accompanying paper [4] where the method isalso contrasted to the more conventional smooth discrete element method (DEM) [5]. The nonsmoothapproach allows for time integration using time-steps much larger than the characteristic elasticresponse time. Given an efficient solver and that the system and application justifies the nonsmoothapproximation a considerable speed-up can be achieved, though it should be recognized that this issignificantly problem dependent. The current paper includes analysis of the computational efficiencyof the NDEM approach to the particular case of balling drum outlet flow analysis with a given errortolerance. Time estimates of a corresponding smooth DEM approach is provided for comparison.
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6.
  • Berge, John, 1979, et al. (författare)
  • Design considerations for tunable bulk acoustic wave resonators based on paraelectric phase BaxSr1-xTiO3 thin films
  • 2010
  • Ingår i: 19th International Symposium on the Applications of Ferroelectrics.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Paraelectric phase BaxSr1-xTiO3 (BSTO) is due to the pronounced field induced piezoelectric effect a promising candidate to realize hysteresis-free tunable thin film bulk acoustic wave resonators (TFBARs) at GHz frequencies. Compared to the conventional fixed-frequency TFBAR technology, mainly based on piezoelectric AlN films, the design of tunable BSTO based resonators require additional considerations due to the demanding conditions necessary for the growth of the BSTO active layer (high temperature, O2 ambient). In this work a number of problems and possible solutions are presented for the specific case of solidly mounted resonators based on an acoustic Bragg reflector structure. Simulation results for a proposed tunable resonator based on a BSTO film and a SiO2/HfO2 reflector stack co-optimized for both longitudinal and shear waves are presented and compared to simulations and existing experimental data from other structures.
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7.
  • Bätz, Georg, et al. (författare)
  • Ball dribbling with an underactuated continuous-time control phase : Theory & experiments
  • 2010
  • Ingår i: 2010 IEEE/RSJ International Conference on Intelligent Robots and Systems. - : IEEE. - 9781424466757 - 9781424466764 - 9781424466740 ; , s. 2890-2895
  • Konferensbidrag (refereegranskat)abstract
    • Ball dribbling is a central element of basketball. One main challenge for realizing basketball robots is to stabilize periodic motion of the ball. The task is nontrivial due to the discrete-continuous nature of the corresponding dynamics. This paper proposes to add an elastic element to the manipulator so the ball can be controlled in a continuous-time phase instead of an intermittent contact. Optimal catching and pushing trajectories are planned for the underactuated system based on the virtual holonomic constraints approach. First experimental studies are presented to evaluate the approach. 
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8.
  • Enestam, Sonja, et al. (författare)
  • Occurrence of Zinc and Lead in Aerosols and Deposits in the Fluidized-Bed Combustion of Recovered Waste Wood. Part 2: Thermodynamic Considerations
  • 2011
  • Ingår i: Energy & Fuels. - : ACS publications. - 0887-0624 .- 1520-5029. ; 25:4, s. 1970-1977
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, which is the second part in a series of two, multi-phase, multi-component equilibrium calculations were used to study the chemistry and deposition behavior of lead and zinc in the combustion of recovered waste wood (RWW). Particular attention was paid to the deposition behavior in different parts of the boiler under varying flue gas and material temperature conditions. In addition, the influence of fuel composition was considered by studying three different fuel compositions. The results from the calculations were compared to experimental results from two measurement campaigns, whose goal was to experimentally determine the distribution and speciation of zinc and lead compounds in aerosol particles and deposits in the fluidized-bed combustion of RWW. The results from the experimental work are presented in part 1 (10.1021/ef101478n) of this work.
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9.
  • Halawani, Alaa, et al. (författare)
  • Building eye contact in e-learning through head-eye coordination
  • 2011
  • Ingår i: International Journal of Social Robotics. - Dordrecht : Springer. - 1875-4791 .- 1875-4805. ; 3:1, s. 95-106
  • Tidskriftsartikel (refereegranskat)abstract
    • Video conferencing is a very effective tool to use for e-learning. Most of the available video conferencing systems suffer a main drawback represented by the lack of eye contact between participants. In this paper we present a new scheme for building eye contact in e-learning sessions. The scheme assumes a video conferencing session with “one teacher many students” arrangement. In our system, eye contact is achieved without the need for any gaze estimation technique. Instead, we “generate the gaze” by allowing the user communicate his visual attention to the system through head-eye coordination. To enable real time and precise headeye coordination, a head motion tracking technique is required. Unlike traditional head tracking systems, our procedure suggests mounting the camera on the user’s head rather than in front of it. This configuration achieves much better resolution and thus leads to better tracking results. Promising results obtained from both demo and real time experiments demonstrate the effectiveness and efficiency of the proposed scheme. Although this paper concentrates on elearning, the proposed concept can be easily extended to the world of interaction with social robotics, in which introducing eye contact between humans and robots would be of great advantage.
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10.
  • Li, Fei, et al. (författare)
  • A novel neural network optimized by quantum genetic algorithm for signal detection in MIMO-OFDM systems
  • 2011
  • Ingår i: Computational Intelligence in Control and Automation (CICA). - : IEEE. - 9781424499038 - 9781424499021 ; , s. 170-177
  • Konferensbidrag (refereegranskat)abstract
    • Neural networks can easily fall into a local extremum and have slow convergence rate. Quantum Genetic Algorithm (QGA) has features of small population size and fast convergence. Based on the investigation of QGA, we propose a novel neural network model, Radial Basis Function (RBF) networks optimized by Quantum Genetic Algorithm (QGA-RBF model). Then we investigate the performance of the proposed QGA-RBF on solving MIMO-OFDM signal detection problem. A novel signal detector based on QGA-RBF for MIMO-OFDM system is also proposed. The simulation results show that the proposed detector has more powerful properties in bit error rate than QGA based detector, RBF based detector and MMSE algorithm based detector, namely a 4-6 dB gain in performance can be achieved. The performance of the proposed detector is closer to optimal, compared with the other detectors. 
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