RFID security

Radio Frequency Identification (RFID) systems have become popular for automated identification and supply chain applications. This article describes the technical fundamentals of RFID systems and the associated standards. Specifically, we address the security and privacy aspects of this relatively new and heterogeneous radio technology. We discuss the related security requirements, the threats and the implemented mechanisms. Then the current security and privacy proposals and their enhancements are presented. Finally we discuss the role of this technology in Ubiquitous Computing.     

Stability of linear systems with interval time delays excluding zero

The stability of linear systems with multiple, time-invariant, independent and uncertain delays is investigated. Each delay is assumed to reside within a known interval excluding zero. A delay-free sufficient comparison system is formed by replacing the delay elements with parameter-dependent filters, satisfying certain properties. It is shown that robust stability of this finite dimensional parameter-dependent comparison system, guarantees stability of the original time-delay system. This result is novel in the sense that it does not require any a priori knowledge regarding stability of the time-delay system for some fixed delay. When the parameter-dependent filters are formed in a particular manner using Pade approximations, an upper bound on the degree-of-conservatism of the comparison system may be obtained, which is independent of the time-delay system considered. With this, it is shown that the conservatism of this comparison system may be made arbitrarily small. A linear matrix ineqaulity (LMI) formulation is presented for analysis of the stability of the parameter-dependent comparison system. In the single-delay case, an eigenvalue criterion is also available for stability analysis which incurs no additional conservatism.     

Stability analysis of LPV time-delayed systems

This work provides one of the first attempts to derive computationally tractable criteria for analysing the stability of linear parameter varying (LPV) time-delayed systems. We present both delay-independent and delay-dependent stability conditions, which are derived using appropriately selected Lyapunov-Krasovskii functionals. According to the system parameter dependence, these functionals can be selected to obtain increasingly non-conservative results. Gridding techniques may be used to cast these tests as linear matrix inequalities (LMIs). In cases when the system matrices depend affinely or quadratically on the parameter, gridding may be avoided. These LMIs can be solved efficiently using available software. A numerical example of a time-delayed system motivated by a metal removal process is used to demonstrate the theoretical results.     

Vergütung von Kiefern- und Eichenholz durch Tränkung mit Harnstofformaldehydharz

Wood specimens of oak and pine have been impregnated with urea-formaldehyde-resin by the full-cell process. The treated wood was tested with respect to its water repellent and its strength properties as compared to untreated wood specimens. The hydrophobic effect in pine and oak was determined after a storage under water. Additionally, a possible increase of crushing and bending strength was measured with pine. As a result it can be stated that impregnation with a urea-formaldehyde-resin presents an effective system to protect wooden building elements.     

Reducing magnetic bearing currents via gain scheduled adaptivecontrol

A method for the reduction of an active magnetic bearing's speed-synchronous current is presented. The approach is based on research on adaptive vibration control for these systems. To minimize the memory and computational requirements imposed on the control system hardware, the gain matrix used is synthesized as functionally dependent upon the operating speed with only the diagonal elements varying linearly with speed. The resulting algorithm was experimentally tested on a high-speed spindle. Significant reductions in bearing currents were achieved over a wide range of operating speeds     

New results for the analysis of linear systems with time‐invariant delays

This paper presents a comparison system approach for the analysis of stability and ??_∞ performance of linear time‐invariant systems with unknown delays. The comparison system is developed by replacing the delay elements with certain parameter‐dependent Padé approximations. It is shown using the special properties of the Padé approximation to e^?s that the value sets of these approximations provide outer and inner coverings for that of each delay element and that the robust stability of the outer covering system is a sufficient condition for the stability of the original time delay system. The inner covering system, in turn, is used to provide an upper bound on the degree of conservatism of the delay margin established by the sufficient condition. This upper bound is dependent only upon the Padé approximation order and may be made arbitrarily small. In the single delay case, the delay margin can be calculated explicitly without incurring any additional conservatism. In the general case, this condition can be reduced with some (typically small) conservatism to finite‐dimensional LMIs. Finally, this approach is also extended to the analysis of ??_∞ performance for linear time‐delay systems with an exogenous disturbance. Copyright © 2003 John Wiley & Sons, Ltd.     

2-D Signal Representation, Interpolation, and a New Approach to Compression

The properties of certain elliptic functions are exploited for the representation and interpolation of functions over two-dimensional data. Also a new approach for the compression of two-dimensional data is given.     

Obesity as a metabolic risk factor

On the basis of the results of clinico-experimental examinations and of animal experiments the importance of obesity as metabolic factor of risk is confirmed and hereby the diabetes mellitus as well as cardiovascular effects are particularly taken into consideration. Conclusions are made relevant to practice and it is particularly referred to the central position of the B-cells for the pathogenesis of diabetes as well as to prophylactic and early therapeutic measures.