Control of nonlinear chained systems: from the Routh-Hurwitzstability criterion to time-varying exponential stabilizers

We show how any linear feedback that stabilizes the origin of a linear chain of integrators induces a simple, continuous time-varying feedback that exponentially stabilizes the origin of a nonlinear chained-form system. The design method is related to a method developed by M'Closkey and Murray (1997) to transform smooth feedback yielding slow polynomial convergence into continuous homogeneous ones that give exponential convergence     

MIQR Active Learning on a Continuous Function and a Discontinuous Function

Active learning balances the cost of data acquisition against its usefulness for training. We select only those data points which are the most informative about the system being modelled. The MIQR (Maximum Inter-Quartile Range) criterion is defined by computing the inter-quartile range of the outputs of an ensemble of networks, and finding the input parameter values for which this is maximal. This method ensures data selection is not unduly influenced by ‘outliers’, but is principally dependent upon the ‘mainstream’ state of the ensemble. MIQR is more effective and efficient than contending methods¹ . The algorithm automatically regulates the training threshold and the network architecture as necessary. We compare active learning methods by applying them to a continuous function and a discontinuous function. Training is more difficult for a discontinuous function than a continuous function, and the volume of data for active learning is substantially less than for passive learning.     

Progress of quantum electronics and the future of wireless technologies

Research in quantum electronics over several decades has fueled the creation and rapid growth of today's wireless communications market. Sales of electronic components into this market exceeded $25 billion in 2006. Nearly all cellular handsets sold today include integrated circuits (ICs) based on energy gap engineered transistors—high-electron mobility transistors (HEMTs) and heterojunction base transistors (HBTs). The success of these technologies notwithstanding, future wireless communications systems will require even more demanding IC performance, especially in the areas of linearity and low noise. We propose that a new concept in transistor design, wave-function engineering, offers un-tapped opportunities to realize these needed performance improvements.     

Usage-based comparison of ESI techniques

A comparative study of equivalent-step-index (ESI) techniques is performed on the basis of the ESI fiber's ability to predict the bend, transition, microbending and splice loss, waveguide dispersion, launching efficiency, and second-mode cutoff wavelength. Theoretical and experimental investigations were performed to determine the accuracy of the predictions. It was found that none of the present ESI techniques can be used to characterize all features of interest for a single-mode fiber with great accuracy. However, for the purpose of producing specifications on the behavior of single-mode fiber systems, it may be adequate to specify bounds on parameters such as bend loss within a factor of two.