Showing papers by "Northeastern University (China) published in 2011"
TL;DR: In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-Capacitance have been explored and show not only enhanced capacitance, but as well good cyclability.
Abstract: Carbon materials have attracted intense interests as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost. Activated carbons produced by different activation processes from various precursors are the most widely used electrodes. Recently, with the rapid growth of nanotechnology, nanostructured electrode materials, such as carbon nanotubes and template-synthesized porous carbons have been developed. Their unique electrical properties and well controlled pore sizes and structures facilitate fast ion and electron transportation. In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-capacitance have been explored. They show not only enhanced capacitance, but as well good cyclability. In this review, recent progresses on carbon-based electrode materials are summarized, including activated carbons, carbon nanotubes, and template-synthesized porous carbons, in particular mesoporous carbons. Their advantages and disadvantages as electrochemical capacitors are discussed. At the end of this review, the future trends of electrochemical capacitors with high energy and power are proposed.
2,497 citations
TL;DR: This work proposes an image cryptosystem employing the Arnold cat map for bit-level permutation and the logistic map for diffusion, demonstrating the superior security and high efficiency of this algorithm.
596 citations
TL;DR: This article proposes new filtering techniques by exploiting the token ordering information and drastically reduce the candidate sizes and hence improve the efficiency of existing algorithms to find a pair of records such that their similarities are no less than a given threshold.
Abstract: With the increasing amount of data and the need to integrate data from multiple data sources, one of the challenging issues is to identify near-duplicate records efficiently. In this article, we focus on efficient algorithms to find a pair of records such that their similarities are no less than a given threshold. Several existing algorithms rely on the prefix filtering principle to avoid computing similarity values for all possible pairs of records. We propose new filtering techniques by exploiting the token ordering information; they are integrated into the existing methods and drastically reduce the candidate sizes and hence improve the efficiency. We have also studied the implementation of our proposed algorithm in stand-alone and RDBMS-based settings. Experimental results show our proposed algorithms can outperform previous algorithms on several real datasets.
546 citations
TL;DR: A novel data-driven robust approximate optimal tracking control scheme is proposed for unknown general nonlinear systems by using the adaptive dynamic programming (ADP) method and a robustifying term is developed to compensate for the NN approximation errors introduced by implementing the ADP method.
Abstract: In this paper, a novel data-driven robust approximate optimal tracking control scheme is proposed for unknown general nonlinear systems by using the adaptive dynamic programming (ADP) method. In the design of the controller, only available input-output data is required instead of known system dynamics. A data-driven model is established by a recurrent neural network (NN) to reconstruct the unknown system dynamics using available input-output data. By adding a novel adjustable term related to the modeling error, the resultant modeling error is first guaranteed to converge to zero. Then, based on the obtained data-driven model, the ADP method is utilized to design the approximate optimal tracking controller, which consists of the steady-state controller and the optimal feedback controller. Further, a robustifying term is developed to compensate for the NN approximation errors introduced by implementing the ADP method. Based on Lyapunov approach, stability analysis of the closed-loop system is performed to show that the proposed controller guarantees the system state asymptotically tracking the desired trajectory. Additionally, the obtained control input is proven to be close to the optimal control input within a small bound. Finally, two numerical examples are used to demonstrate the effectiveness of the proposed control scheme.
530 citations
TL;DR: A trust and reputation model TRM-IoT is presented to enforce the cooperation between things in a network of IoT/CPS based on their behaviors and the accuracy, robustness and lightness of the proposed model is validated through a wide set of simulations.
Abstract: Since a large scale Wireless Sensor Network (WSN) is to be completely
integrated into Internet as a core part of Internet of Things (IoT) or Cyber
Physical System (CPS), it is necessary to consider various security
challenges that come with IoT/CPS, such as the detection of malicious
attacks. Sensors or sensor embedded things may establish direct communication
between each other using 6LoWPAN protocol. A trust and reputation model is
recognized as an important approach to defend a large distributed sensor
networks in IoT/CPS against malicious node attacks, since trust establishment
mechanisms can stimulate collaboration among distributed computing and
communication entities, facilitate the detection of untrustworthy entities,
and assist decision-making process of various protocols. In this paper, based
on in-depth understanding of trust establishment process and quantitative
comparison among trust establishment methods, we present a trust and
reputation model TRM-IoT to enforce the cooperation between things in a
network of IoT/CPS based on their behaviors. The accuracy, robustness and
lightness of the proposed model is validated through a wide set of
simulations.
470 citations
TL;DR: The recent progress in the synthesis and surface modification of rare-earth doped UCNPs with a specific focus on their biological applications is discussed.
448 citations
TL;DR: A new iterative adaptive dynamic programming (ADP) method is proposed to solve a class of continuous-time nonlinear two-person zero-sum differential games and the convergence property of the performance index function is proved.
365 citations
TL;DR: A brief introduction of the historical background of grain boundary engineering for structural and functional polycrystalline materials is presented in this article, where a new approach in terms of the grain boundary and interface engineering is discussed for the design and development of high performance materials with desirable bulk properties.
Abstract: A brief introduction of the historical background of grain boundary engineering for structural and functional polycrystalline materials is presented herewith. It has been emphasized that the accumulation of fundamental knowledge about the structure and properties of grain boundaries and interfaces has been extensively done by many researchers during the past one century. A new approach in terms of the concept of grain boundary and interface engineering is discussed for the design and development of high performance materials with desirable bulk properties. Recent advancements based on these concepts clearly demonstrate the high potential and general applicability of grain boundary engineering for various kinds of structural and functional materials. Future prospects of the grain boundary and interface engineering have been outlined, hoping that a new dimension will emerge pertaining to the discovery of new materials and the generation of a new property originating from the presence of grain boundaries and interfaces in advanced polycrystalline materials.
341 citations
TL;DR: In this article, a mesoporous carbon material with hierarchical foam-like pore structures was synthesized by a dual-templating strategy using phenolic resol as a carbon source, Pluronic F127 and spherical silica mesocellular foams (Si-MCFs) as the soft and hard template, respectively.
298 citations
TL;DR: It is proved that the two proposed control approaches can guarantee that all the signals of the closed-loop system are semi-globally uniformly ultimately bounded, and the observer errors and the tracking errors converge to a small neighborhood of the origin.
Abstract: In this paper, two adaptive neural network (NN) decentralized output feedback control approaches are proposed for a class of uncertain nonlinear large-scale systems with immeasurable states and unknown time delays. Using NNs to approximate the unknown nonlinear functions, an NN state observer is designed to estimate the immeasurable states. By combining the adaptive backstepping technique with decentralized control design principle, an adaptive NN decentralized output feedback control approach is developed. In order to overcome the problem of “explosion of complexity” inherent in the proposed control approach, the dynamic surface control (DSC) technique is introduced into the first adaptive NN decentralized control scheme, and a simplified adaptive NN decentralized output feedback DSC approach is developed. It is proved that the two proposed control approaches can guarantee that all the signals of the closed-loop system are semi-globally uniformly ultimately bounded, and the observer errors and the tracking errors converge to a small neighborhood of the origin. Simulation results are provided to show the effectiveness of the proposed approaches.
286 citations
TL;DR: A novel chaos-based bit-level permutation scheme for secure and efficient image cipher is proposed that is competitive with that of permutation–diffusion type image cipher, while the computational complexity is much lower and is a good candidate for real-time secure image communication applications.
25 Nov 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors investigated the correlation of microstructural characteristics and toughness of the simulated coarse grained heat affected zone (CGHAZ) of low carbon bainitic steel.
Abstract: The correlation of microstructural characteristics and toughness of the simulated coarse grained heat affected zone (CGHAZ) of low carbon bainitic steel was investigated in this study. The toughness of simulated specimens was examined by using an instrumented Charpy impact tester after the simulation welding test was conducted with different cooling times. Microstructure observation and crystallographic feature analysis were conducted by means of optical microscope and scanning electron microscope equipped with electron back scattered diffraction (EBSD) system, respectively. The main microstructure of simulated specimen changes from lath martensite to coarse bainite with the increase in cooling time. The deterioration of its toughness occurs when the cooling time ranges from 10 to 50 s compared with base metal toughness, and the toughness becomes even worse when the cooling time increases to 90 s or more. The MA (martensite–austenite) constituent is primary responsible for the low toughness of simulated CGHAZ with high values of cooling time because the large MA constituent reduces the crack initiation energy significantly. For crack propagation energy, the small effective grain size of lath martensite plays an important role in improving the crack propagation energy. By contrast, high misorientation packet boundary in coarse bainite seems to have few contributions to the improvement of the toughness because cleavage fracture micromechanism of coarse bainite is mainly controlled by crack initiation.
TL;DR: It is found that the fluorescence of BSA at λ(ex) 230 nm arising from aromatic amino acids Trp and Tyr is almost as sensitive as that achieved at η 280 nm for elucidating the protein conformational changes, which provides a valid and new probe for the investigation of binding kinetics between molecules/ions and proteins.
Abstract: The interactions of imidazolium ionic liquids (ILs), i.e., dibutylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-butyl-3-methylimidazolium nitrate, with bovine serum albumin (BSA) were studied by monitoring the spectral behaviors of IL-BSA aqueous systems. The intrinsic fluorescence of BSA at 340 nm excited at 230 nm is obviously quenched by these ILs due to complex dynamic collision and their quenching constants are at the order of 10(2) L mol(-1). However, no fluorescence quenching is observed within the same region when excited at 280 nm, which is widely used for probing protein conformations. Thermodynamic investigations reveal that the combination between ILs and BSA is entropy driven by predominantly hydrophobic and electrostatic interactions, leading to the unfolding of polypeptides within BSA. The influence of the ILs on the conformation of BSA follows a sequence of BmimNO(3) > BmimCl ≈ BbimCl. Molecular docking shows that cationic imidazolium moieties of ILs enter the subdomains of protein and interact with the hydrophobic residues of domain III. An agreement between fluorescence spectroscopic investigations and molecular docking is reached. It is found that the fluorescence of BSA at λ(ex) 230 nm arising from aromatic amino acids Trp and Tyr is almost as sensitive as that achieved at λ(ex) 280 nm for elucidating the protein conformational changes, which provides a valid and new probe for the investigation of binding kinetics between molecules/ions and proteins.
01 Mar 2011
TL;DR: Computational experiments with a set of large-scale instances show that the NGHS can be an efficient alternative for solving 0-1 knapsack problems.
Abstract: This paper proposes a novel global harmony search algorithm (NGHS) to solve 0-1 knapsack problems. The proposed algorithm includes two important operations: position updating and genetic mutation with a small probability. The former enables the worst harmony of harmony memory to move to the global best harmony rapidly in each iteration, and the latter can effectively prevent the NGHS from trapping into the local optimum. Computational experiments with a set of large-scale instances show that the NGHS can be an efficient alternative for solving 0-1 knapsack problems.
TL;DR: The resilience and friability of the railway network within the Chinese mainland is evaluated and analyzed, and a structure optimization model with a computational algorithm for transportation network design is recommended.
Abstract: To analyze the resilience of transportation networks, it is proposed to use a quantifiable resilience evaluation approach. First, we represent transportation networks by an undirected graph with the nodes as cities and edges as traffic roads. Because the survivability of transportation of a pair of cities depends on the number of passageways between them, the resilience of a city node can be evaluated by the weighted average number of reliable passageways with all other city nodes in the network. The network resilience can then be calculated by the weighted sum of the resilience of all nodes. To identify critical road lines or hub cities in networks, the concept of friability is proposed. This is defined as the reduction in total resilience upon removing an edge or hub city. Following the resilience and friability evaluation, a structure optimization model with a computational algorithm for transportation network design is recommended. Based on the recommended approaches, the resilience and friability of the railway network within the Chinese mainland is evaluated and analyzed. Several interesting conclusions are drawn from the computational results. The friability value of the railway lines in the Sichuan Basin which was damaged by the recent earthquake in China was also calculated.
TL;DR: This paper proposes a distributed multi-agent-based load shedding algorithm, which can make efficient load shedding decision based on discovered global information, and according to rigorous stability analysis, convergence of the designed algorithm can be guaranteed.
Abstract: If generation in a power system is insufficient to power all loads, efficient load shedding operations may need to be deployed to maintain the supply-demand balance. This paper proposes a distributed multi-agent-based load shedding algorithm, which can make efficient load shedding decision based on discovered global information. During the information discovery process, only communications between immediate neighboring agents are used. The information discovery algorithm is represented as a discrete time linear system and the stability of which is analyzed according to average-consensus theorem. According to rigorous stability analysis, convergence of the designed algorithm can be guaranteed. To improve the speed of the algorithm, particle swarm optimization (PSO) is used to optimize the coefficients for information exchange so that the second largest eigenvalue of the iteration matrix is minimized. According to the designed algorithm, total net active power and operating status of loads can be discovered accurately even with faults. Based on the discovered information, coordinated load shedding decision can be made.
TL;DR: By using the quadratic Lyapunov function approach and adding slack matrix variables, sufficient conditions for designing the nonfragile H⩽∞ filter are proposed in terms of solutions to a set of linear matrix inequalities (LMIs).
Abstract: This paper is concerned with the problem of nonfragile H∞ filtering for a class of continuous-time fuzzy systems. Attention is focused on the design of a filter such that the filtering error system preserves a prescribed H∞ performance, where the filter to be designed is assumed to have gain variations. By using the quadratic Lyapunov function approach and adding slack matrix variables, sufficient conditions for designing the nonfragile H∞ filter are proposed in terms of solutions to a set of linear matrix inequalities (LMIs). Finally, a simulation example will be given to show the efficiency of the proposed design methods.
TL;DR: Extraordinarily high reversible capacity of lithium-ion battery anodes is realized from SnO(2)/α-MoO(3) core-shell nanobelts that makes extra Li(2)O reversibly convert to Li(+).
TL;DR: This paper primarily aims to highlight the major security, privacy and trust issues in current existing cloud computing environments and help users recognize the tangible and intangible threats associated with their uses, and analyze the way that may be addressed to eliminate these potential privacy, security and trust threats.
TL;DR: A new type of state-feedback controller, namely, the homogeneous polynomially nonquadratic control law (HPNQCL), is developed to conceive less-conservative stabilization conditions and the obtained stability and stabilization conditions are further relaxed by using the proposed right-hand-side slack variables technique.
Abstract: This paper is concerned with the problem of developing an advanced strategy to reduce the conservatism in stability analysis and control synthesis of continuous-time Takagi-Sugeno (T-S) fuzzy systems. A novel augmented multi-indexed matrix approach is proposed to implement new right-hand-side slack variables technique for the homogenous polynomial setting. Combining with the Finsler lemma with homogenous-matrix Lagrange multipliers, convergent linear-matrix-inequality (LMI) relaxations for stability analysis are proposed by using the generalization of the Polya theorem for the case of positive polynomials with matrix-valued coefficients. A new type of state-feedback controller, namely, the homogeneous polynomially nonquadratic control law (HPNQCL), is developed to conceive less-conservative stabilization conditions. The obtained stability and stabilization conditions are further relaxed by using the proposed right-hand-side slack variables technique. Moreover, the advantages over the existing control schemes are certificated in theory. Three numerical examples are also provided to illustrate the effectiveness of the proposed methods.
TL;DR: In this paper, a fully coupled model of coal deformation, gas transport, and thermal transport is developed and solved using the finite element method, which represents important nonlinear responses due to the effective stress effects that cannot be recovered where mechanical influences are not rigorously coupled with the gas and the thermal transport systems.
TL;DR: Ultrafast charging/discharging of lithium-ion battery anodes is realized from porous Co(3)O(4) nanoneedle arrays growing on copper foils, implying that nano-arrays growing directly on copperfoils are good candidates for anodes.
TL;DR: A novel heuristic dynamic programming (HDP) iteration algorithm is proposed to solve the optimal tracking control problem for a class of nonlinear discrete-time systems with time delays.
Abstract: In this paper, a novel heuristic dynamic programming (HDP) iteration algorithm is proposed to solve the optimal tracking control problem for a class of nonlinear discrete-time systems with time delays. The novel algorithm contains state updating, control policy iteration, and performance index iteration. To get the optimal states, the states are also updated. Furthermore, the “backward iteration” is applied to state updating. Two neural networks are used to approximate the performance index function and compute the optimal control policy for facilitating the implementation of HDP iteration algorithm. At last, we present two examples to demonstrate the effectiveness of the proposed HDP iteration algorithm.
TL;DR: In this article, the authors investigated the performance of the power grid of the western United States subject to three intentional attacks and showed that the effects of different attacks for the network robustness against cascading failures have close relations with the tunable parameter [theta].
TL;DR: In this article, the consensus of second-order multi-agent dynamical systems with exogenous disturbances is studied and a pinning control strategy is designed for a part of agents without disturbances, and this pinning controller can bring multiple agents' states to reaching an expected consensus track.
Abstract: In this paper, the consensus of second-order multi-agent dynamical systems with exogenous disturbances is studied. A pinning control strategy is designed for a part of agents of the multi-agent systems without disturbances, and this pinning control can bring multiple agents' states to reaching an expected consensus track. Under the influence of the disturbances, disturbance observers-based control (DOBC) is developed for disturbances generated by an exogenous system to estimate the disturbances. Asymptotical consensus of the multi-agent systems with disturbances under the composite controller can be achieved for fixed and switching topologies. Finally, by applying an example of multi-agent systems with switching topologies and exogenous disturbances, the consensus of multi-agent systems is reached under the DOBC with the designed parameters. Copyright © 2010 John Wiley & Sons, Ltd.
26 Oct 2011
TL;DR: This paper develops a distributed computing framework, PrIter, which supports the prioritized execution of iterative computations, and shows that PrIter achieves up to 50 × speedup over Hadoop for a series ofIterative algorithms.
Abstract: Iterative computations are pervasive among data analysis applications in the cloud, including Web search, online social network analysis, recommendation systems, and so on. These cloud applications typically involve data sets of massive scale. Fast convergence of the iterative computation on the massive data set is essential for these applications. In this paper, we explore the opportunity for accelerating iterative computations and propose a distributed computing framework, PrIter, which enables fast iterative computation by providing the support of prioritized iteration. Instead of performing computations on all data records without discrimination, PrIter prioritizes the computations that help convergence the most, so that the convergence speed of iterative process is significantly improved. We evaluate PrIter on a local cluster of machines as well as on Amazon EC2 Cloud. The results show that PrIter achieves up to 50x speedup over Hadoop for a series of iterative algorithms.
TL;DR: This paper presents a framework for global synchronization of dynamical networks with nonidentical nodes using free matrices for both cases of synchronizing to a common equilibrium solution of all isolated nodes and synchronize to the average state trajectory.
Abstract: This paper presents a framework for global synchronization of dynamical networks with nonidentical nodes. Several criteria for synchronization are given using free matrices for both cases of synchronizing to a common equilibrium solution of all isolated nodes and synchronizing to the average state trajectory. These criteria can be viewed as generalizations of the master stability function method for local synchronization of networks with identical nodes to the case of nonidentical nodes. The controlled synchronization problem is also studied. The control action, which is subject to certain constraints, is viewed as reorganization of the connection topology of the network. Synchronizability conditions via control are put forward. The synchronizing controllers can be obtained by solving an optimization problem.
TL;DR: This paper studies aspect-based opinion polling from unlabeled free-form textual customer reviews without requiring customers to answer any questions, using a multi-aspect bootstrapping method and an aspect- based segmentation model.
Abstract: Opinion polling has been traditionally done via customer satisfaction studies in which questions are carefully designed to gather customer opinions about target products or services. This paper studies aspect-based opinion polling from unlabeled free-form textual customer reviews without requiring customers to answer any questions. First, a multi-aspect bootstrapping method is proposed to learn aspect-related terms of each aspect that are used for aspect identification. Second, an aspect-based segmentation model is proposed to segment a multi-aspect sentence into multiple single-aspect units as basic units for opinion polling. Finally, an aspect-based opinion polling algorithm is presented in detail. Experiments on real Chinese restaurant reviews demonstrated that our approach can achieve 75.5 percent accuracy in aspect-based opinion polling tasks. The proposed opinion polling method does not require labeled training data. It is thus easy to implement and can be applicable to other languages (e.g., English) or other domains such as product or movie reviews.
TL;DR: Ordered mesoporous carbon/nanoparticle nickel composites have been synthesized via multi-component co-assembly strategy associated with a direct carbonization process from resol, tetraethyl orthosilicate, Ni(NO 3 ) 2 ·6H 2 O and subsequent silicates removal with NaOH solution as discussed by the authors.
TL;DR: The exceptional sensitivity, selectivity, and reusability of this folding-based electrochemical DNA aptasensor platform suggest it may be a promising strategy for a wide variety of sensing applications.