Dec 2009, Volume 4 Issue 4
    

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  • Research articles
    Computational evidence of A-to-I RNA editing in nucleus transcriptome of Arabidopsis thaliana
    Pufeng DU, Yang CHEN, Yanda LI,
    2009, 4(4): 349-361. https://doi.org/10.1007/s11460-009-0053-7
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    RNA editing is a mechanism that can increase the complexity of the transcriptome via the insertion, deletion, or substitution of single or multiple nucleotides of mRNA sequences. In the last two decades, A-to-I RNA editing, which is catalyzed by the ADAR family enzymes, was discovered in many metazoans. C-to-U and U-to-C RNA editing were found in the mitochondria and plastids of plants. However, there is no report about RNA editing in plant nucleus transcriptome yet. Here, by integrating resources from public databases with computational methods, this paper proposes that A-to-I RNA editing mechanism may exist in the nucleus of Arabidopsis thaliana. Some characteristics of the potential A-to-I RNA editing sites in Arabidopsis thaliana are similar to those we have known in animals.
  • Research articles
    Shared-p-cycles method for design of survivable WDM networks
    Zhenrong ZHANG, Lixin ZHU, Zhengbin LI, Anshi XU,
    2009, 4(4): 362-370. https://doi.org/10.1007/s11460-009-0057-3
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    In future high-capacity wavelength division multiplexed (WDM) optical networks, the failure of a network component such as a fiber link can lead to severe disruption in the networks’ traffic. Hence, it is imperatively important to provide fast and full protection in WDM optical networks. In this paper, we propose a new approach, called shared preconfigured protection cycles (shared-p-cycles), for the design of survivable WDM networks. We develop an integer linear program (ILP) formulation to solve the problem of shared-p-cycles design for WDM networks with and without wavelength conversion. Numerical results show that the shared-p-cycles design is more efficient in the use of spare capacity and requires much less spare capacity than the conventional p-cycles design.
  • Research articles
    A novel rate-2 full diversity algebraic space-time code
    Xiufeng JIN, Guangguo BI,
    2009, 4(4): 371-377. https://doi.org/10.1007/s11460-009-0059-1
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    Orthogonal space-time block codes (OSTBCs) have attracted considerable attention due to their low complexity linear decoding and full diversity in Rayleigh fading channels. However, OSTBCs exist only for certain numbers of transmit antennas and do not provide full code rate when more than two transmit antennas are used. In this paper, a novel rate-2 algebraic space-time code that combines coordinate-interleaving and group precoding is proposed. By properly choosing the designed parameters, the coding scheme can achieve full diversity order and high coding gain. The receiver adopts polynomial complexity sphere decoding algorithm to get maximum likelihood (ML) performance. Analysis and simulations illustrate that the new code exhibits significant performance gain over the conventional OSTBCs and diagonal algebraic space-time code.
  • Research articles
    New approaches to delay-dependent robust H ∞ control of uncertain discrete-time T-S fuzzy systems with time-varying delay
    Jianbin QIU, Gang FENG, Jie YANG,
    2009, 4(4): 378-391. https://doi.org/10.1007/s11460-009-0058-2
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    This paper investigates the problem of delay-dependent robust H∞ state-feedback control for a class of uncertain discrete-time state-delayed T-S fuzzy systems. The state delay is assumed to be time-varying and of an interval-like type with the lower and upper bounds. The parameter uncertainties are assumed to have a structured linear-fractional form. Based on a novel fuzzy-basis-dependent Lyapunov-Krasovskii functional incorporating a free-weighting matrix approach, some new delay-dependent sufficient conditions for robust H∞ performance analysis and controller synthesis are derived in terms of linear matrix inequalities (LMIs). Numerical examples are also provided to illustrate the effectiveness of the proposed approaches.
  • Research articles
    Complexity of comparing expressions in max-plus algebra
    Qianchuan ZHAO,
    2009, 4(4): 392-396. https://doi.org/10.1007/s11460-009-0055-5
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    Max-plus algebra has been widely used in the study of discrete-event dynamic systems. Using max-plus algebra makes it easy to specify safety constraints on events since they can be described as a set of inequalities of state variables, i.e., firing times of relevant events. This paper proves that the problem of solving max-plus inequalities in a cube (MAXINEQ) is nondeterministic polynomial-time hard (NP-hard) in strong sense and the problem of verifying max-plus inequalities (VERMAXINEQ) is co-NP. As a corollary, the problem of solving a system of multivariate max-algebraic polynomial equalities and inequalities (MPEI) is shown to be NP-hard in strong sense. The results indicate the difficulties in comparing max-plus formulas in general. Problem structures of specific systems have to be explored to enable the development of efficient algorithms.
  • Research articles
    Distributed cooperative formation of multiple mobile agents with preserved connectivity
    Xiaoli LI, Yugeng XI,
    2009, 4(4): 397-408. https://doi.org/10.1007/s11460-009-0060-8
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    This paper investigates distributed cooperative formation control of a group of multiple mobile agents with a virtual leader, where information exchange among agents is modeled by the group topology, and the states of the virtual leader are known only by parts of the agents. We develop a class of distributed formation control laws with similar form. The steered group is proved to achieve the desired formation objectives as long as the intersection of the initial communication topology and the formation goal topology is connected. This requirement of connectivity can be easily achieved by many practical applications; consequently, our developed distributed control laws are effective and feasible. Furthermore, for the developed control laws, we show the influence of different information flow graph of agents on the convergence rate and robustness to node and connection failures.
  • Research articles
    Convergence analysis of self-tuning Riccati equation for systems with correlation noises
    Chenjian RAN, Zili DENG, Guili TAO, Jinfang LIU,
    2009, 4(4): 409-416. https://doi.org/10.1007/s11460-009-0056-4
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    For linear discrete time-invariant stochastic system with correlated noises, and with unknown state transition matrix and unknown noise statistics, substituting the online consistent estimators of the state transition matrix and noise statistics into steady-state optimal Riccati equation, a new self-tuning Riccati equation is presented. A dynamic variance error system analysis (DVESA) method is presented, which transforms the convergence problem of self-tuning Riccati equation into the stability problem of a time-varying Lyapunov equation. Two decision criterions of the stability for the Lyapunov equation are presented. Using the DVESA method and Kalman filtering stability theory, it proves that with probability 1, the solution of self-tuning Riccati equation converges to the solution of the steady-state optimal Riccati equation or time-varying optimal Riccati equation. The proposed method can be applied to design a new self-tuning information fusion Kalman filter and will provide the theoretical basis for solving the convergence problem of self-tuning filters. A numerical simulation example shows the effectiveness of the proposed method.
  • Research articles
    Controller design for 2-DOF underactuated mechanical systems based on controlled Lagrangians and application to Acrobot control
    Maoqing LI,
    2009, 4(4): 417-439. https://doi.org/10.1007/s11460-009-0063-5
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    On the basis of controlled Lagrangians, a controller design is proposed for underactuated mechanical systems with two degrees of freedom. A new kinetic energy equation (K-equation) independent of the gyroscopic forces is found due to the use of their property. As a result, the necessary and sufficient matching condition comprises the new K-equation and the potential energy equation (P-equation) cascaded, the regular condition, and the explicit gyroscopic forces. Further, for two classes of input decoupled systems that cover the main benchmark examples, the new K-equation, respectively, degenerates from a quasilinear partial differential equation (PDE) into an ordinary differential equation (ODE) under some choice and into a homogeneous linear PDE with two kinds of explicit general solutions. Benefiting from one of the general solutions, the obtained smooth state feedback controller for the Acrobots is of a more general form. Specifically, a constant fixed in a related paper by the system parameters is converted into a controller parameter ranging over an open interval along with some new nonlinear terms involved. Unlike what is mentioned in the related paper, some categories of the Acrobots cannot be stabilized with the existing interconnection and damping assignment passivity based control (IDA-PBC) method. As a contribution, the system can be locally asymptotically stabilized by the selection of the new controller parameter except for only one special case.
  • Research articles
    Study on a 60?kV/5?A magnetron injection gun for 200?GHz electron cyclotron master
    Wenjie FU, Yang YAN, Shenggang LIU,
    2009, 4(4): 440-445. https://doi.org/10.1007/s11460-009-0061-7
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    To develop 200GHz electron cyclotron maser (ECM) in University of Electronic Science and Technology of China, a magnetron injection gun (MIG) with 60kV/5A has been designed. The behavior of the designed magnetron injection gun with variations of relevant parameters is given in detail by means of computer simulations. The preliminary and operation parameters of the gun are reported. The optimization by using the EGUN code shows that the ratio of the perpendicular velocity to the parallel velocity of the electron beam is 1.63, and the perpendicular and parallel velocities spread are 2.62% and 6.63%, respectively.
  • Research articles
    Plastic wastes recovery using electrostatic forces
    A. TILMATINE, S. BENDIMERAD,
    2009, 4(4): 446-450. https://doi.org/10.1007/s11460-009-0062-6
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    Among the separation techniques used in industry, the triboelectric separation of insulating particles using rotary tube is an efficient technology employed in waste recovery and mineral industries. This process, also called free-fall triboelectric separation, is widely used for the sorting and the purification of granular materials resulting from industrial plastic wastes. This paper aims at the achievement of a comprehensive description of a laboratory triboelectric separator built up by the authors and its utilization for an experimental study carried out on granular samples containing particles of polyvinyl chloride (PVC) and polyethylene (PE). Thus, among the variable factors of the process, we analyzed the influence of the most important ones, i.e., the rotational speed of the cylinder n (rpm), the applied high voltage U (kV), the charging time of the particles t (s), the mass of the sample m (g), and the composition percentage of the sample Cp (%).