On the “Uniform” Observability of Discrete-Time Nonlinear Systems

In constructing an observer for a discrete-time nonlinear system, the system is commonly required to satisfy a certain kind of uniform observability condition, that is, the state should always be reconstructible from observation windows of a specific length, irrespective of the values of the state and inputs. In this technical note, it is proved that this uniform requirement is unnecessary in the sense that if the initial state and inputs are on a compact set, then the uniform observability is derived from its non-uniform counterpart.     

Comments on “The Extreme Learning Machine”

This comment letter points out that the essence of the “extreme learning machine (ELM)” recently appeared has been proposed earlier by Broomhead and Lowe and Pao , and discussed by other authors. Hence, it is not necessary to introduce a new name “ELM.”      

Attack on “Watermarking Method Based on Significant Difference of Wavelet Coefficient Quantization”

This letter describes an attack on the recently proposed ldquowatermarking method based on significant difference of wavelet coefficient quantizationrdquo by Lin While the method is shown to be robust against many signal processing operations, security of the watermarking scheme under intentional attack exploiting knowledge of the implementation has been neglected. We demonstrate a straightforward attack which retains the fidelity of the image. The method is therefore not suitable for copyright protection applications. Further, we propose a countermeasure which mitigates the shortcoming.     

Comments on “Controller Synthesis of Fuzzy-Dynamic Systems Based on Piecewise Lyapunov Functions”

This comment tries to describe a theoretical mistake made in the aforementioned paper [G. Feng, IEEE Trans. Fuzzy Syst., vol. 11, no. 5, pp. 605–612, Oct. 2003] to formulate the inverse of matrices used to construct the piecewise-quadratic Lyapunov functions. Derivation of these inverse matrices is the most critical step toward transforming the design constraints into linear matrix inequalities (LMIs). Therefore, the erroneous formulation essentially affects the validity of the approach and final results. Unfortunately, it seems that there is no simple correction for this problem. However, some close alternative approaches are suggested by the same authors in their other works.      

“Vague-to-Crisp” Neural Mechanism of Perception

This brief describes neural modeling fields (NMFs) for object perception, a bio-inspired paradigm. We discuss previous difficulties in object perception algorithms encountered since the 1950s, and describe how NMF overcomes these difficulties. NMF mechanisms are compared to recent experimental neuroimaging observations, which have demonstrated that initial top-down signals are vague and during perception they evolve into crisp representations matching the bottom-up signals from observed objects. Neural and mathematical mechanisms are described and future research directions outlined.      

Remarks on “Measuring Ambiguity in the Evidence Theory”

In a recent paper, a functional AM (ambiguity measure) is introduced and an attempt is made to show that this functional qualifies as a measure of total aggregated uncertainty in the Dempster-Shafer theory. We show that this attempt fails due to a particular error in the proof of one of the principal theorems in the paper. Some additional remarks are made regarding recent research pertaining to the subject of the discussed paper.     

Comment on “On Siphon Computation for Deadlock Control in a Class of Petri Nets”

It was claimed recently in the paper by Li and Zhou that ldquoa polynomial time algorithm for finding the set of elementary siphons in S³PRs is proposed, which avoids complete siphon enumerationrdquo. However, this is incorrect because Proposition 1 and Corollary 6 of the aforementioned paper, which lead to the claim, are both incorrect. In this correspondence paper, Proposition 1 and Corollary 6 are disproved. As a consequence, some claims of the aforesaid paper are denied. Two examples are presented to disprove some claims of the previously mentioned paper.     

A “Globally” Convergent Controller for Multi-Machine Power Systems Using Structure-Preserving Models

The design of excitation controllers to improve transient stabilization of power systems is a topic of renewed interest in the control community. Existence of a state-feedback stabilizing law for multi-machine aggregated reduced network models has recently been established. In this paper we extend this result in two directions: first, in contrast with aggregated models, we consider the more natural and widely popular structure-preserving models that preserve the identity of the network components (generators, loads and lines) and allow for a more realistic treatment of the loads. Second, we explicitly compute a control law that, under a detectability assumption, ensures that all trajectories converge to the desired equilibrium point, provided that they start and remain in the region where the model makes physical sense.     

Comments on “Scalable Services via Egress Admission Control”

In the recent paper by Cetinkaya et al , admission control tests are derived by approximating the sum of two Gumbel distributed random variables by a Gumbel distributed random variable. In fact, the sum of two Gumbel distributed random variables does not follow a Gumbel distribution. Here, explicit expressions are derived for the probability density function (pdf) and the cumulative distribution function (cdf) of the exact distribution of the sum. The discrepancy between the exact and the approximate distributions is studied numerically.     

Comments on “Backpropagation Algorithms for a Broad Class of Dynamic Networks”

In a recent paper, De JesÚs proposed a general framework for describing dynamic neural networks. Gradient and Jacobian calculations were discussed based on backpropagation-through-time (BPTT) algorithm and real-time recurrent learning (RTRL). Some errors in the paper of De JesÚs bring difficulties for other researchers who want to implement the algorithms. This comments paper shows the critical parts of the publication and gives errata to facilitate understanding and implementation.      

Notes on “Reducing Algorithm Complexity for Computing an Aggregate Uncertainty Measure”

In a recent paper, Liu have proposed the so-called F -algorithm which conditionally reduces the computational complexity of the Meyerowitz-Richman-Walker algorithm for the computation of the aggregate-uncertainty measure in the Dempster-Shafer theory of evidence, along with an illustration of its application in a practical scenario of target identification. In this correspondence, we will point out several technical mistakes, which some of them lead to some inexact or incomplete statements in the paper of Liu The corrections of these mistakes will be made, and some further improvement and results will be derived.     

A New Security Evaluation for Steganographic System Based on Vague Set Similarity Measure

由于图像隐写所引起的各种统计特征变化是不确定的,文中将Vague集相似度量引人隐写系统的安全性评价中.从图像的一阶统计特征和二阶统计特征两方面,定义了基于载体数据及载密数据相关Vague集相似度量的隐写系统一阶和二阶安全性测度,证明了该安全性测度的有界性,对称性和一致性.在假设图像满足独立同分布的条件下,证明了所提出的两种安全性测度是等价的.结果表明,所提出的二阶安全性比一阶安全性能更好地反映隐写引起的载体统计分布变化.与确定模式下的安全性测度相比,当嵌入率低于0.5比特／像素,新的测度可更好地度量隐写系统安全性,因此该测度对小容量的隐写及隐写分析算法设计具有更好的指导作用.     

一种基于分布式系统的安全广播方案

该文基于分布式系统给出了一种安全广播方案。与已有广播方案相比,该方案有效地减少了发送者所产生的广播信息并能防止攻击;另外,当一个新用户/已有用户要插入/退出分布式系统时,该方案不需要修改任何已有的保密密钥和公开密钥。     

Erratum to “On the Synthesis of Haptic Textures” [Jun 08 527-536]

In the above titled paper (ibid., vol. 24, no. 3, pp. 527-536, Jun 08), it is stated in Sec. IV-D3 that the characteristic number of the first variant of the god object method applied to texture synthesis is 1. This statement is not always true, and clarification of this issue is presented here.     

Comments on “Discrete-Time Adaptive Backstepping Nonlinear Control via High-Order Neural Networks”

The purpose of this comment is to point out some mistakes in the above paper. It is shown that the main results of the paper cannot stand in general. Also, it is pointed out that after some corrections, the proposed control algorithm is still applicable to a more simple system. For simplicity, all the symbols in this comment are the same as those in the above paper.     

“Communication to: A Closed-Form Expression for the Uncertainty in Odometry Position Estimate of an Autonomous Vehicle”

The uncertainty of the odometry position estimate for a given vehicle can be obtained from the definition of the covariance matrix by using its kinematic model as well as its sensory system data. This communication item extends a previous work in by giving the appropriate guidelines so as to compute the cross-covariance terms between the previous position estimate and the actual increments of position. This is necessary in general because the orientation errors on the robot's previous position will affect the calculation of the actual increments of position.      

Further Comment on “Optimal Fuzzy Controller Design: Local Concept Approach”

Stability analysis and optimality are important in any systems. In the paper, optimal fuzzy controller design: local concept approach, optimal fuzzy controller is design for Takagi-Sugeno fuzzy model. Unfortunately, it seems that some errors are happen and no simple correction can be done. In this paper, we show that some errors exit in the aforementioned paper with simple and clear examples.