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49,327 Research products, page 1 of 4,933

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  • 2017-2021
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  • Open Access
    Authors: 
    Fangong Kong; Shoujuan Wang; Weijue Gao; Pedram Fatehi;
    Publisher: Royal Society of Chemistry (RSC)
    Project: NSERC

    Kraft lignin (KL) produced in kraft pulping process has a low molecular weight and solubility, which limits its application in industry. For the first time, KL was polymerized with acrylic acid (AA) in an acidic aqueous suspension system to produce a water soluble lignin–AA polymer with a high molecular weight in this work. The polymerization reaction was carried out using K2S2O8 as an initiator, and the influence of reaction conditions on the carboxylate group content and molecular weight of resultant lignin polymers was systematically investigated. The mechanism of polymerization of KL and AA was discussed fundamentally. The resulting lignin–AA polymer was characterized by Fourier Transform Infrared spectrophotometry (FTIR), proton nuclear magnetic resonance (1H-NMR) and elemental analyses. The results showed that the phenolic hydroxyl group (Ph-OH) content of KL promoted the polymerization under an acidic environment. Under the conditions of 1.5 wt% of initiator, 3.5 of pH, 10.0 of AA/lignin molar ratio, 0.15 mol L−1 of lignin concentration, 3 h and 80 °C, the carboxylate group content and the molecular weight of the polymer were 7.37 mmol g−1 and 7.4 × 105 g mol−1, respectively. The lignin–AA polymer was water soluble at a 10 g L−1 concentration and a pH higher than 4.5. Furthermore, the flocculation performance of lignin–AA polymer in an aluminium oxide suspension was evaluated. Compared with polyAA, the lignin–AA polymer was a more efficient flocculant for aluminium oxide suspension, which shows its potential to be used as a green flocculant in industry.

  • Closed Access
    Authors: 
    Tingting Yu; Yishuai Xu; Yifan Liu; Puren Ouyang; M.M. Gupta; W.J. Zhang; W.J. Zhang;
    Publisher: IEEE

    This paper reports a work on developing a novel charge control circuit for control of the piezoelectric actuator to overcome its hysteresis nonlinearity when the actuator is driven at high voltage (as opposed to low voltage reported in literature). The charge control circuit also includes a balancing resistor. A test-bed for a piezoelectric actuator was established and an experiment was conducted. The result showed that the hysteresis nonlinearity of the piezoelectric actuator was reduced by 82% under the proposed charge control circuit. This charge control circuit can be used for control of piezoelectric inertia-friction actuator, in which the piezoelectric actuator is part of the whole actuator system.

  • Publication . Other literature type . Article . 2021
    Open Access
    Authors: 
    Shengnan Ke; Jun Gong; Songnian Li; Qing Zhu; Xintao Liu; Yeting Zhang;
    Publisher: Ryerson University Library and Archives

    In recent years, there has been tremendous growth in the field of indoor and outdoor positioning sensors continuously producing huge volumes of trajectory data that has been used in many fields such as location-based services or location intelligence. Trajectory data is massively increased and semantically complicated, which poses a great challenge on spatio-temporal data indexing. This paper proposes a spatio-temporal data indexing method, named HBSTR-tree, which is a hybrid index structure comprising spatio-temporal R-tree, B*-tree and Hash table. To improve the index generation efficiency, rather than directly inserting trajectory points, we group consecutive trajectory points as nodes according to their spatio-temporal semantics and then insert them into spatio-temporal R-tree as leaf nodes. Hash table is used to manage the latest leaf nodes to reduce the frequency of insertion. A new spatio-temporal interval criterion and a new node-choosing sub-algorithm are also proposed to optimize spatio-temporal R-tree structures. In addition, a B*-tree sub-index of leaf nodes is built to query the trajectories of targeted objects efficiently. Furthermore, a database storage scheme based on a NoSQL-type DBMS is also proposed for the purpose of cloud storage. Experimental results prove that HBSTR-tree outperforms TB*-tree in some aspects such as generation efficiency, query performance and query type.

  • Open Access English
    Authors: 
    Nan Zhao; Fen Cheng; F. Richard Yu; Jie Tang; Yunfei Chen; Guan Gui; Hikmet Sari;
    Publisher: IEEE
    Country: United Kingdom

    Unmanned aerial vehicles (UAVs) can help smallcell base stations (SBSs) offload traffic via wireless backhaul to improve coverage and increase rate. However, the capacity of backhaul is limited. In this paper, UAV assisted secure transmission for scalable videos in hyper-dense networks via caching is studied. In the proposed scheme, UAVs can act as SBSs to provide videos to mobile users in some small cells. To reduce the pressure of wireless backhaul, UAVs and SBSs are both equipped with caches to store videos at off-peak time. To facilitate UAVs, a single antenna is equipped at each UAV and thus, only the precoding matrices of SBSs should be cooperatively designed to manage interference by exploiting the principle of interference alignment. On the other hand, the SBSs replaced by UAVs will be idle. Thus, in order to guarantee secure transmission, the idle SBSs can be further exploited to generate jamming signal to disrupt eavesdropping. The jamming signal is zero-forced at the legitimate users through the precoding of the idle SBSs, without affecting the legitimate transmission. The feasibility conditions of the proposed scheme are derived, and the secrecy performance is analyzed. Finally, simulation results are presented to verify the effectiveness of the proposed scheme.\ud

  • Authors: 
    Ling Cen; Feng Chen; Yu Hou; Gordon D. Richardson;
    Publisher: American Accounting Association

    ABSTRACT In the presence of litigation-facing suppliers, the supply chain relationship is at risk. Suppliers with principal customers (dependent suppliers) have a higher concentration of sales to customers, and they are more at risk relative to suppliers without principal customers (non-dependent suppliers). As a result, we predict and find that litigation disclosure patterns differ for the two supplier types: dependent suppliers are more likely to delay bad news and accelerate good news related to litigation outcomes, compared to non-dependent suppliers. Such strategic disclosure patterns in our end-game setting are opposite to those documented in the existing supply chain literature for the repeated-game setting (for example, Hui, Klasa, and Yeung 2012). JEL Classifications: M41; M48; K22.

  • Open Access English
    Authors: 
    Ruilong Sheng; Zhao Wang; Ting Luo; Amin Cao; Jingjing Sun; Joseph M. Kinsella;
    Publisher: Multidisciplinary Digital Publishing Institute

    Using renewable and biocompatible natural-based resources to construct functional biomaterials has attracted great attention in recent years. In this work, we successfully prepared a series of steroid-based cationic lipids by integrating various steroid skeletons/hydrophobes with (l-)-arginine headgroups via facile and efficient synthetic approach. The plasmid DNA (pDNA) binding affinity of the steroid-based cationic lipids, average particle sizes, surface potentials, morphologies and stability of the steroid-based cationic lipids/pDNA lipoplexes were disclosed to depend largely on the steroid skeletons. Cellular evaluation results revealed that cytotoxicity and gene transfection efficiency of the steroid-based cationic lipids in H1299 and HeLa cells strongly relied on the steroid hydrophobes. Interestingly, the steroid lipids/pDNA lipoplexes inclined to enter H1299 cells mainly through caveolae and lipid-raft mediated endocytosis pathways, and an intracellular trafficking route of "lipid-raft-mediated endocytosis→lysosome→cell nucleic localization" was accordingly proposed. The study provided possible approach for developing high-performance steroid-based lipid gene carriers, in which the cytotoxicity, gene transfection capability, endocytosis pathways, and intracellular trafficking/localization manners could be tuned/controlled by introducing proper steroid skeletons/hydrophobes. Noteworthy, among the lipids, Cho-Arg showed remarkably high gene transfection efficacy, even under high serum concentration (50% fetal bovine serum), making it an efficient gene transfection agent for practical application.

  • Authors: 
    Asatur Zh. Khurshudyan;
    Publisher: World Scientific Pub Co Pte Lt

    In this paper, we consider a nonlinear control problem for one-dimensional viscous Burgers’ equation associated with a controlled linear heat equation by means of the Hopf–Cole transformation. The control is carried out by the time-dependent intensity of a distributed heat source influencing the heat equation. The set of admissible controls consists of compactly supported [Formula: see text] functions. Using the Green’s function approach, we analyze the possibilities of exact and approximate establishment of a given terminal state for the associated nonlinear Burgers’ equation within a desired amount of time. It is shown that the exact controllability of the associated Burgers’ equation and the heat equation are equivalent. Furthermore, sufficient conditions for the approximate controllability are derived. The set of resolving controls is constructed in both cases. The determination of the resolving controls providing exact controllability is reduced to an infinite-dimensional system of linear algebraic equations. By means of the heuristic method of resolving control determination, parametric hierarchies of solutions providing approximate controllability are constructed. The results of a numerical simulation supporting the theoretical derivations are discussed.

  • Authors: 
    Pengwen Xiong; Xiaodong Zhu; Aiguo Song; Lingyan Hu; Xiaoping P. Liu; Lihang Feng;
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)

    Most target grabbing problems have been dealt with by computer vision system, however, computer vision method is not always enough when it comes to the precision contact grabbing problems during the teleoperation process, and need to be combined with the stiffness display to provide more effective information to the operator on the remote side. Therefore, in this paper a more portable stiffness display device with a small volume and extended function is developed based on our previous work. A new static load calibration of the improved stiffness display device is performed to detect its accuracy, and the relationship between the stiffness and the position is given. An effective target grabbing strategy is presented to help operator on the remote side to judge and control and the target is classified by multi-class SVM U+0028 supporter vector machine U+0029. The teleoperation system is established to test and verify the feasibility. A special experiment is designed and the results demonstrate that the improved stiffness display device could greatly help operator on the remote side control the telerobot to grab target and the target grabbing strategy is effective.

  • Closed Access
    Authors: 
    Qibing Jin; Qie Liu; Biao Huang;
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)

    This paper is concerned with control of processes with uncertain delays for disturbance rejection. The effect of the uncertain delays on the stability is studied. First, the method to compute the maximum uncertain delay that a given controller can tolerate is described. Second, in the case of PI/PID controller, all of the admissible controller parameters stabilizing a system with uncertain but bounded delays are determined. Meanwhile, we propose a simple method to construct the parameter space satisfying a given robustness index for the nominal model. In the admissible regions satisfying various objectives, the global optimum controller is achieved for disturbance rejection in the presence of uncertain delay. As a result, the MIGO ( ${{M}_{s}}$ -constrained Integral Gain Optimization) method is revisited in the case of uncertain delay, and the rule of selecting the value of maximum sensitivity function is proposed in terms of the bound on the uncertain delay. Two simulation examples and an experiment are given to demonstrate the effectiveness and advantage of the proposed method.

  • Closed Access
    Authors: 
    Weihong Li; Yuanyuan Shao; Jingxu Zhu; Haiping Zhang; Hui Zhang;
    Publisher: Elsevier BV

    Abstract Air classifier mill (ACM) is widely used in powder coating and mineral comminution process. One of the problems typically presenting in ACM is over-grinding, which leads to high energy consumption and broad particle size distribution (PSD). To decrease the excessive amount of fine particles in the products, 6 configurations of grinding pins with ditches in the impact surface were used in the experiments. The width and depth of ditches varied from 1.35 mm and 1 mm to 4.75 mm and 3 mm, respectively, while the interior angles in the ditches are the same. The particle size and PSD show that the ditches on the grinding pins have significant effect on the D10 values and the particle size span. The deepest and widest ditches (P4) result in largest D10 and smallest span in this study. The D10s of products ground by P4 increase by 24.1% for fine powder (D50 = 25 μm) and 16.0% for coarse powder (D50 = 33 μm), while the span decreases by 6.9% (D50 = 25 μm) and 6.4% (D50 = 33 μm) compared to regular cylindrical pins (PC), respectively. Meanwhile, it is found that the P4 configuration improves the energy utilization efficiency by 7.6% (D50 = 25 μm) and 3.4% (D50 = 33 μm), compared to that of the original PC pins.

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Include:
The following results are related to Canada. Are you interested to view more results? Visit OpenAIRE - Explore.
49,327 Research products, page 1 of 4,933
  • Open Access
    Authors: 
    Fangong Kong; Shoujuan Wang; Weijue Gao; Pedram Fatehi;
    Publisher: Royal Society of Chemistry (RSC)
    Project: NSERC

    Kraft lignin (KL) produced in kraft pulping process has a low molecular weight and solubility, which limits its application in industry. For the first time, KL was polymerized with acrylic acid (AA) in an acidic aqueous suspension system to produce a water soluble lignin–AA polymer with a high molecular weight in this work. The polymerization reaction was carried out using K2S2O8 as an initiator, and the influence of reaction conditions on the carboxylate group content and molecular weight of resultant lignin polymers was systematically investigated. The mechanism of polymerization of KL and AA was discussed fundamentally. The resulting lignin–AA polymer was characterized by Fourier Transform Infrared spectrophotometry (FTIR), proton nuclear magnetic resonance (1H-NMR) and elemental analyses. The results showed that the phenolic hydroxyl group (Ph-OH) content of KL promoted the polymerization under an acidic environment. Under the conditions of 1.5 wt% of initiator, 3.5 of pH, 10.0 of AA/lignin molar ratio, 0.15 mol L−1 of lignin concentration, 3 h and 80 °C, the carboxylate group content and the molecular weight of the polymer were 7.37 mmol g−1 and 7.4 × 105 g mol−1, respectively. The lignin–AA polymer was water soluble at a 10 g L−1 concentration and a pH higher than 4.5. Furthermore, the flocculation performance of lignin–AA polymer in an aluminium oxide suspension was evaluated. Compared with polyAA, the lignin–AA polymer was a more efficient flocculant for aluminium oxide suspension, which shows its potential to be used as a green flocculant in industry.

  • Closed Access
    Authors: 
    Tingting Yu; Yishuai Xu; Yifan Liu; Puren Ouyang; M.M. Gupta; W.J. Zhang; W.J. Zhang;
    Publisher: IEEE

    This paper reports a work on developing a novel charge control circuit for control of the piezoelectric actuator to overcome its hysteresis nonlinearity when the actuator is driven at high voltage (as opposed to low voltage reported in literature). The charge control circuit also includes a balancing resistor. A test-bed for a piezoelectric actuator was established and an experiment was conducted. The result showed that the hysteresis nonlinearity of the piezoelectric actuator was reduced by 82% under the proposed charge control circuit. This charge control circuit can be used for control of piezoelectric inertia-friction actuator, in which the piezoelectric actuator is part of the whole actuator system.

  • Publication . Other literature type . Article . 2021
    Open Access
    Authors: 
    Shengnan Ke; Jun Gong; Songnian Li; Qing Zhu; Xintao Liu; Yeting Zhang;
    Publisher: Ryerson University Library and Archives

    In recent years, there has been tremendous growth in the field of indoor and outdoor positioning sensors continuously producing huge volumes of trajectory data that has been used in many fields such as location-based services or location intelligence. Trajectory data is massively increased and semantically complicated, which poses a great challenge on spatio-temporal data indexing. This paper proposes a spatio-temporal data indexing method, named HBSTR-tree, which is a hybrid index structure comprising spatio-temporal R-tree, B*-tree and Hash table. To improve the index generation efficiency, rather than directly inserting trajectory points, we group consecutive trajectory points as nodes according to their spatio-temporal semantics and then insert them into spatio-temporal R-tree as leaf nodes. Hash table is used to manage the latest leaf nodes to reduce the frequency of insertion. A new spatio-temporal interval criterion and a new node-choosing sub-algorithm are also proposed to optimize spatio-temporal R-tree structures. In addition, a B*-tree sub-index of leaf nodes is built to query the trajectories of targeted objects efficiently. Furthermore, a database storage scheme based on a NoSQL-type DBMS is also proposed for the purpose of cloud storage. Experimental results prove that HBSTR-tree outperforms TB*-tree in some aspects such as generation efficiency, query performance and query type.

  • Open Access English
    Authors: 
    Nan Zhao; Fen Cheng; F. Richard Yu; Jie Tang; Yunfei Chen; Guan Gui; Hikmet Sari;
    Publisher: IEEE
    Country: United Kingdom

    Unmanned aerial vehicles (UAVs) can help smallcell base stations (SBSs) offload traffic via wireless backhaul to improve coverage and increase rate. However, the capacity of backhaul is limited. In this paper, UAV assisted secure transmission for scalable videos in hyper-dense networks via caching is studied. In the proposed scheme, UAVs can act as SBSs to provide videos to mobile users in some small cells. To reduce the pressure of wireless backhaul, UAVs and SBSs are both equipped with caches to store videos at off-peak time. To facilitate UAVs, a single antenna is equipped at each UAV and thus, only the precoding matrices of SBSs should be cooperatively designed to manage interference by exploiting the principle of interference alignment. On the other hand, the SBSs replaced by UAVs will be idle. Thus, in order to guarantee secure transmission, the idle SBSs can be further exploited to generate jamming signal to disrupt eavesdropping. The jamming signal is zero-forced at the legitimate users through the precoding of the idle SBSs, without affecting the legitimate transmission. The feasibility conditions of the proposed scheme are derived, and the secrecy performance is analyzed. Finally, simulation results are presented to verify the effectiveness of the proposed scheme.\ud

  • Authors: 
    Ling Cen; Feng Chen; Yu Hou; Gordon D. Richardson;
    Publisher: American Accounting Association

    ABSTRACT In the presence of litigation-facing suppliers, the supply chain relationship is at risk. Suppliers with principal customers (dependent suppliers) have a higher concentration of sales to customers, and they are more at risk relative to suppliers without principal customers (non-dependent suppliers). As a result, we predict and find that litigation disclosure patterns differ for the two supplier types: dependent suppliers are more likely to delay bad news and accelerate good news related to litigation outcomes, compared to non-dependent suppliers. Such strategic disclosure patterns in our end-game setting are opposite to those documented in the existing supply chain literature for the repeated-game setting (for example, Hui, Klasa, and Yeung 2012). JEL Classifications: M41; M48; K22.

  • Open Access English
    Authors: 
    Ruilong Sheng; Zhao Wang; Ting Luo; Amin Cao; Jingjing Sun; Joseph M. Kinsella;
    Publisher: Multidisciplinary Digital Publishing Institute

    Using renewable and biocompatible natural-based resources to construct functional biomaterials has attracted great attention in recent years. In this work, we successfully prepared a series of steroid-based cationic lipids by integrating various steroid skeletons/hydrophobes with (l-)-arginine headgroups via facile and efficient synthetic approach. The plasmid DNA (pDNA) binding affinity of the steroid-based cationic lipids, average particle sizes, surface potentials, morphologies and stability of the steroid-based cationic lipids/pDNA lipoplexes were disclosed to depend largely on the steroid skeletons. Cellular evaluation results revealed that cytotoxicity and gene transfection efficiency of the steroid-based cationic lipids in H1299 and HeLa cells strongly relied on the steroid hydrophobes. Interestingly, the steroid lipids/pDNA lipoplexes inclined to enter H1299 cells mainly through caveolae and lipid-raft mediated endocytosis pathways, and an intracellular trafficking route of "lipid-raft-mediated endocytosis→lysosome→cell nucleic localization" was accordingly proposed. The study provided possible approach for developing high-performance steroid-based lipid gene carriers, in which the cytotoxicity, gene transfection capability, endocytosis pathways, and intracellular trafficking/localization manners could be tuned/controlled by introducing proper steroid skeletons/hydrophobes. Noteworthy, among the lipids, Cho-Arg showed remarkably high gene transfection efficacy, even under high serum concentration (50% fetal bovine serum), making it an efficient gene transfection agent for practical application.

  • Authors: 
    Asatur Zh. Khurshudyan;
    Publisher: World Scientific Pub Co Pte Lt

    In this paper, we consider a nonlinear control problem for one-dimensional viscous Burgers’ equation associated with a controlled linear heat equation by means of the Hopf–Cole transformation. The control is carried out by the time-dependent intensity of a distributed heat source influencing the heat equation. The set of admissible controls consists of compactly supported [Formula: see text] functions. Using the Green’s function approach, we analyze the possibilities of exact and approximate establishment of a given terminal state for the associated nonlinear Burgers’ equation within a desired amount of time. It is shown that the exact controllability of the associated Burgers’ equation and the heat equation are equivalent. Furthermore, sufficient conditions for the approximate controllability are derived. The set of resolving controls is constructed in both cases. The determination of the resolving controls providing exact controllability is reduced to an infinite-dimensional system of linear algebraic equations. By means of the heuristic method of resolving control determination, parametric hierarchies of solutions providing approximate controllability are constructed. The results of a numerical simulation supporting the theoretical derivations are discussed.

  • Authors: 
    Pengwen Xiong; Xiaodong Zhu; Aiguo Song; Lingyan Hu; Xiaoping P. Liu; Lihang Feng;
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)

    Most target grabbing problems have been dealt with by computer vision system, however, computer vision method is not always enough when it comes to the precision contact grabbing problems during the teleoperation process, and need to be combined with the stiffness display to provide more effective information to the operator on the remote side. Therefore, in this paper a more portable stiffness display device with a small volume and extended function is developed based on our previous work. A new static load calibration of the improved stiffness display device is performed to detect its accuracy, and the relationship between the stiffness and the position is given. An effective target grabbing strategy is presented to help operator on the remote side to judge and control and the target is classified by multi-class SVM U+0028 supporter vector machine U+0029. The teleoperation system is established to test and verify the feasibility. A special experiment is designed and the results demonstrate that the improved stiffness display device could greatly help operator on the remote side control the telerobot to grab target and the target grabbing strategy is effective.

  • Closed Access
    Authors: 
    Qibing Jin; Qie Liu; Biao Huang;
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)

    This paper is concerned with control of processes with uncertain delays for disturbance rejection. The effect of the uncertain delays on the stability is studied. First, the method to compute the maximum uncertain delay that a given controller can tolerate is described. Second, in the case of PI/PID controller, all of the admissible controller parameters stabilizing a system with uncertain but bounded delays are determined. Meanwhile, we propose a simple method to construct the parameter space satisfying a given robustness index for the nominal model. In the admissible regions satisfying various objectives, the global optimum controller is achieved for disturbance rejection in the presence of uncertain delay. As a result, the MIGO ( ${{M}_{s}}$ -constrained Integral Gain Optimization) method is revisited in the case of uncertain delay, and the rule of selecting the value of maximum sensitivity function is proposed in terms of the bound on the uncertain delay. Two simulation examples and an experiment are given to demonstrate the effectiveness and advantage of the proposed method.

  • Closed Access
    Authors: 
    Weihong Li; Yuanyuan Shao; Jingxu Zhu; Haiping Zhang; Hui Zhang;
    Publisher: Elsevier BV

    Abstract Air classifier mill (ACM) is widely used in powder coating and mineral comminution process. One of the problems typically presenting in ACM is over-grinding, which leads to high energy consumption and broad particle size distribution (PSD). To decrease the excessive amount of fine particles in the products, 6 configurations of grinding pins with ditches in the impact surface were used in the experiments. The width and depth of ditches varied from 1.35 mm and 1 mm to 4.75 mm and 3 mm, respectively, while the interior angles in the ditches are the same. The particle size and PSD show that the ditches on the grinding pins have significant effect on the D10 values and the particle size span. The deepest and widest ditches (P4) result in largest D10 and smallest span in this study. The D10s of products ground by P4 increase by 24.1% for fine powder (D50 = 25 μm) and 16.0% for coarse powder (D50 = 33 μm), while the span decreases by 6.9% (D50 = 25 μm) and 6.4% (D50 = 33 μm) compared to regular cylindrical pins (PC), respectively. Meanwhile, it is found that the P4 configuration improves the energy utilization efficiency by 7.6% (D50 = 25 μm) and 3.4% (D50 = 33 μm), compared to that of the original PC pins.