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.     

On “uniformity” in definitions of global asymptotic stability for time-varying nonlinear systems

We discuss the lack of “uniformity” in definitions of uniform global asymptotic stability (UGAS) that have been used in various textbooks, monographs, and papers over the years. Sometimes UGAS is taken to be the combination of uniform local stability (ULS) and uniform global attractivity (UGA). Other times it also encompasses uniform global boundedness (UGB). This paper contains an explicit, smooth scalar example that shows that these definitions do not agree in general, even when the right-hand side is locally Lipschitz in the state uniformly in time (and thus bounded in time). We also discuss various notions of global asymptotic stability with relaxed uniformity (with respect to the initial time) requirements for the behavior of the solutions. In particular, we consider class- estimates and Lyapunov characterizations.     

Corrigendum to “Exponential state estimation for recurrent neural networks with distributed delays” [Neurocomputing 71(1–3) (2007) 428–438]

In the letter [Neurocomputing 71(1–3) (2007) 428–438], there exists one minor error in computing the derivative of V₂((t)) and thus, the proof of Theorem 1 needs some improvement.     

Assessment of potential noise-induced hearing loss with commercial “Karaoke” noise

A study was conducted to assess the noise levels of popular Karaoke environments in Korea and the degree of potential noise-induced hearing loss due to commercial Karaoke noise. Using 18 subjects with normal hearing, a two-way, mixed-factors experimental design was used with two independent variables of “noise source” (no-singer, one-singer, and two-singer conditions) and “music type” (Trot, Ballad, and Rock music). For each experimental condition, average sound pressure levels and maximum sound pressure levels were measured. For assessing amount of temporary hearing threshold shift as a measure of potential hearing loss index, pure-tone audiometry was applied for measuring subjects’ hearing threshold levels of both ears before and after 100 min exposure to Karaoke noise. Questionnaires from 155 actual Karaoke users were also obtained to evaluate realistic user subjective perception on the Karaoke environment. Results showed that noise levels of typical Karaoke singing environments were higher than 95 dBA, with maximum noise levels often exceeded the US OSHA's non-permissible 115 dBA level. Further statistical analysis of hearing threshold shift revealed that up to 8 dB of significant hearing loss was found at the most important human hearing frequency band, centered at 4000 Hz, after about less than 2 h of Karaoke noise exposure, indicating that Karaoke facilities may pose a serious threat to noise-induced hearing loss. Along with some ergonomic/safety issues, practical hearing protection strategies are suggested and discussed.

Relevance to industry

Since noise levels from popular commercial Karaoke facilities are found to be potentially dangerous, the Karaoke-related industries, of supporting a big consumer market of entertainment, need to provide safer environments to protect naive users from potential hearing loss. Providing better design of Karaoke facilities with some ergonomic intervention strategies (such as proper sound absorptive treatment in Karaoke rooms, displaying warning signs of potential hearing loss, and setting up an upper safety volume limit in the Karaoke machine, etc.) may help those industries not only contribute for consumer protection but also develop better market with strong ethical and legal support in the future.     

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.     

Transformation ratio of “ring-dot” planar piezoelectric transformer

A piezoelectric transformer (PT) is a device, which can be used for transforming an ac voltage via ultrasonic vibrations. The best characteristics are achieved in the vicinity of mechanical vibration resonance. “Ring-dot” type design of homogeneously poled disk PT was originally proposed by Berlincourt. Only experimental data were published in preceding studies. An analytical continuum model is presented in this work. The effects of dimensions, material properties and electrical load on the voltage gain as well as on the efficiency are calculated. Hard lead zirconate titanate ceramics (PZT, APC841 type) was used for sample fabrication. Studied PTs typically attain transformation ratio equal 20 without load. For load impedance around 5 kΩ, the observed efficiency was above 90%, whereas the transformation ratio dropped down to the values around 2. The model correspondence with experiment is limited by employed approximations. Model limitations are discussed with respect to experimental data.     

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.      

Construction of a hermite rational “Wachspress type” finite element

This paper concerns the construction of a quadrilateral finite element whose interpolation space admits of rational fractions for basis functions of “Wachspress type” [1, 2]. The construction of this finite element, which is in a way the “rational” equivalent of the ADINI finite element[3, 4], is founded on a method analogous to the one used for Serendip degree-two finite element construction in[2]. The study of interpolation error is dealt with in a paper by Apprato, Arcangeli and Gout in this journal “Rational interpolation of Wachspress error estimates”.     

Visualizing “typical” and “exotic” Internet traffic data

The threat of cyber attacks motivates the need to monitor Internet traffic data for potentially abnormal behavior. Due to the enormous volumes of such data, statistical process monitoring tools, such as those traditionally used on data in the product manufacturing arena, are inadequate. “Exotic” data may indicate a potential attack; detecting such data requires a characterization of “typical” data. We devise some new graphical displays, including a “skyline plot,” that permit ready visual identification of unusual Internet traffic patterns in “streaming” data, and use appropriate statistical measures to help identify potential cyberattacks. These methods are illustrated on a moderate-sized data set (135,605 records) collected at George Mason University.     

“Paraprogramming” manufacturing information systems

Computer integrated manufacturing (CIM) is creating unexpected problems for a growing number of manufacturing companies. Manufacturers are finding it especially difficult to attract programmers who are both willing and able to develop the highly complex software that integrates existing accounting, sales, production, engineering, and quality control information subsystems. Consequently, many companies abdicate their responsibility for manufacturing information systems and seek third party support ranging from consulting assistance to a total takeover of the company's information resources and operations. Companies that “give away” their internal information system capabilities to third parties will ultimately lose control of their enterprise information, a danger to be avoided. Off-the-shelf software for desktop computers has become sufficiently powerful to help solve a major portion of this serious problem. We hypothesize that manufacturing engineers (and others) can be trained to use packaged software to leverage their company's systems programming capabilities. In effect they would become “paraprogrammers” who would help design, develop, and maintain manufacturing information systems. This new type of professional would not require a computer science or similar educational background, but could be trained to satisfy many specialized programming needs in a manner similar to how paramedics and paralegals are trained and used in the medical and legal professions, respectively. This paper reports on the early stages of research to determine whether or not product design engineers can use a desktop relational database management system and its various command languages to develop a master bill of material information system (BOMIS). The purpose of the research is to evaluate the amount of programming complexity reduction and increased operational effectiveness that can be achieved through paraprogramming by manufacturing engineers.     

A Calculus for “environment-aware” computation

We present a calculus for modelling “environment-aware” computations, that is computations that adapt their behaviour according to the capabilities of the environment. The calculus is an imperative, object-based language with extensible objects, equipped with a labelled transition semantics. A notion of bisimulation, lifting to computations a correspondence between the capabilities of different environments, is provided. Bisimulation can be used to prove that a program is “cross-environment”, i.e., it has the same behaviour when run in different environments.     

H∞ identification of “soft” uncertainty models

The paper investigates the problem of identifying uncertainty models of causal, SISO, LTI, discrete-time, BIBO stable, unknown systems, using frequency domain measurements corrupted by Gaussian noise of known covariance. Additive uncertainty models are looked for, consisting of a nominal model and an additive dynamic perturbation accounting for the modeling error. The nominal model is chosen within a class of affinely parametrized models with transfer function of given (possibly low) order. An estimate of the parameters minimizing the H_∞ modeling error is obtained by minimizing an upper bound of the worst-case (with respect to the modeling error) second moment of the estimation error. Then, a bound in the frequency domain guaranteeing to include, with probability α, the frequency response error between the estimated nominal model and the unknown system is derived.     

A search space “cartography” for guiding graph coloring heuristics

We present a search space analysis and its application in improving local search algorithms for the graph coloring problem. Using a classical distance measure between colorings, we introduce the following clustering hypothesis: the high quality solutions are not randomly scattered in the search space, but rather grouped in clusters within spheres of specific diameter. We first provide intuitive evidence for this hypothesis by presenting a projection of a large set of local minima in the 3D space. An experimental confirmation is also presented: we introduce two algorithms that exploit the hypothesis by guiding an underlying Tabu Search (TS) process. The first algorithm (TS-Div) uses a learning process to guide the basic TS process toward as-yet-unvisited spheres. The second algorithm (TS-Int) makes deep investigations within a bounded region by organizing it as a tree-like structure of connected spheres. We experimentally demonstrate that if such a region contains a global optimum, TS-Int does not fail in eventually finding it. This pair of algorithms significantly outperforms the underlying basic TS algorithm; it can even improve some of the best-known solutions ever reported in the literature (e.g. for dsjc1000.9).     

Alias types for “environment-aware” computations

In previous work with Bono we introduced a calculus for modelling “environment-aware” computations, that is computations that adapt their behavior according to the capabilities of the environment. The calculus is an imperative, object-based language (with extensible objects and primitives for discriminating the presence or absence of attributes of objects) equipped with a small-step operational semantics.In this paper we define a type and effect system for the calculus. The typing judgements specify, via constraints, the shape of environments which guarantees the correct execution of expressions and the typing rules track the effect of expression evaluation on the environment. The type and effect system is sound w.r.t. the operational semantics of the language.     

A broadband inverted umbrella shaped cylindrical dielectric resonator antenna for “WLAN” and “C” band applications

The main objective of the present article is to improve the bandwidth of a low profile Cylindrical Dielectric Resonator Antenna (CDRA) and operate it for WLAN and “C” band applications. An inverted umbrella shaped CDRA excited by a microstrip feedline with single stub is proposed here. Efficient coupling has been achieved by means of a single stub microstrip feed between DRA and the feed. The new shape of DRA and a single stub microstrip feed improves the bandwidth significantly as high as 28% from 5 to 6.67 GHz which is quite useful for both WLAN and “C” band applications. The proposed antenna is simple in construction, easy to fabricate, low profile and thickness of CDRA is only 5 mm. A parametric study is performed using Ansoft HFSS simulation software to optimize the antenna performance. The proposed CDRA is fabricated and the characteristics of the antenna are measured.     

Information retrieval expert system “matchmaker”

This paper describes the information system used to search for a potential matrimonial partner. The search is based on comparison of the subject's record, which consists of his/her answers to about 400 items of a specially designed questionnaire, to the records of the potential partners. The basic principle of the system is representation of the set of candidates for the client with psychological warnings about potential “conflict zones” in relationships between client and candidate rather than a ranking of candidates based on hypothetical “psychological compatibility” indices.     

“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.      

The depth of monotone Boolean functions with multi input “AND” and “OR” gates

The problem of maximum depth of monotone Boolean functions is investigated when k-input AND and OR gates are used for realisation.     

Robot control system using “intelligent” integrators

Integral control is important in practice, but in many applications for robot systems this control is unsatisfactory, due to large initial conditions or disturbances. The overshoot becomes large, the speed of response not fast enough, and path tracking is needed. One cure for this problem is the use of the intelligent integral controller, which is very simple in implementation. This control scheme, as part of a PID controller, is applied to a robot system and its superiority, from the conventional one, becomes clear. The main advantage of this controller is that it gives very satisfactory results, while being rather simple.