Robust observer based control for plasma glucose regulation in type 1 diabetes patient using attractive ellipsoid method

This paper deals with the design of robust observer based output feedback control law for the stabilisation of an uncertain nonlinear system and subsequently apply the developed method for the regulation of plasma glucose concentration in Type 1 diabetes (T1D) patients. The principal objective behind the proposed design is to deal with the issues of intra‐patient parametric variation and non‐availability of all state variables for measurement. The proposed control technique for the T1D patient model is based on the attractive ellipsoid method (AEM). The observer and controller conditions are obtained in terms of linear matrix inequality (LMI), thus allowing to compute easily both the observer and controller gains. The closed‐loop response obtained using the designed controller avoids adverse situations of hypoglycemia and post‐prandial hyperglycemia under uncertain conditions. Further to validate the robustness of the design, closed‐loop simulations of random 200 virtual T1D patients considering parameters within the considered ranges are presented. The results indicate that hypoglycemia and post‐prandial hyperglycemia are significantly reduced in the presence of bounded (±30% ) parametric variability and uncertain exogenous meal disturbance.Inspec keywords: medical control systems, observers, uncertain systems, nonlinear control systems, robust control, control system synthesis, linear matrix inequalities, feedback, sugar, closed loop systems, diseasesOther keywords: virtual T1D patients, type 1 diabetes patients, closed‐loop simulations, uncertain conditions, post‐prandial hyperglycemia, designed controller, closed‐loop response, controller gains, linear matrix inequality, controller conditions, T1D patient model, control technique, intra‐patient parametric variation, principal objective, plasma glucose concentration, uncertain nonlinear system, robust observer based output feedback control law, attractive ellipsoid method, plasma glucose regulation     

A hygrometer comprising a porous silicon humidity sensor with phase-detection electronics

A novel hygrometer is presented, comprising a capacitive humidity sensor with a porous silicon (PS) dielectric and electronics. The adsorption of water vapor by the PS layer leading to change of its effective dielectric constant is modeled with an effective medium approximation (EMA). A simple, but precise, phase-sensitive electronic circuit has been developed. This detects any change of phase of a sinusoidal signal transmitted through the PS dielectric and correlates to ambient humidity. It is outlined how the nonlinear response of the sensor is compensated through piecewise linearization. The sensor is tested in combination with the phase detection circuitry. Excellent linearity over the entire range of relative humidity is achieved. Experimental results show a resolution better than 0.1% and an accuracy of 2% (near the transition region) and better than 0.1% (otherwise). The response time is less than 10 s with good stability.     

Quality of service provisioning in 802.11e networks: challenges, approaches, and future directions

In order to support diverse application requirements, a new standard called IEEE 802.11e is being proposed to improve quality of service in wireless LAN networks. There are, however, a few remaining challenges that need to be addressed in order to enable comprehensive QoS support using 802.11e. In this article we provide an overview of a few of these challenges, describe their possible impact on QoS, and provide a survey of techniques that potentially could be used to address the identified challenges. Specifically, we focus on three challenges: handling time-varying network conditions, adapting to varying application profiles, and managing link layer resources. Additionally, we present several potential future directions toward improved QoS in wireless networks.     

Dependence of bacterial growth rate on dynamic temperature changes

Temperature is an important determinant of bacterial growth. While the dependence of bacterial growth on different temperatures has been well studied for many bacterial species, prediction of bacterial growth rate for dynamic temperature changes is relatively unclear. Here, the authors address this issue using a combination of experimental measurements of the growth, at the resolution of 5 min, of Escherichia coli and mathematical models. They measure growth curves at different temperatures and estimate model parameters to predict bacterial growth profiles subject to dynamic temperature changes. They compared these predicted growth profiles for various step‐like temperature changes with experimental measurements using the coefficient of determination and mean square error and based on this comparison, ranked the different growth models, finding that the generalised logistic growth model gave the smallest error. They note that as the maximum specific growth increases the duration of this growth predominantly decreases. These results provide a basis to compute the dependence of the growth rate parameter in biomolecular circuits on dynamic temperatures and may be useful for designing biomolecular circuits that are robust to temperature.Inspec keywords: microorganisms, temperature, environmental factors, mean square error methods, parameter estimationOther keywords: bacterial growth rate, dynamic temperature changes, bacterial species, bacterial growth profiles, generalised logistic growth model, escherichia coli, model parameter estimation, coefficient of determination, mean square error, environmental conditions     

Rough-granular Approach for Impulse Fault Classification of Transformers using Cross-wavelet Transform

A novel approach based on information granulation using Rough sets for impulse fault identification of transformers has been proposed. It is found that the location and type of fault within a transformer winding can be classified efficiently by the features extracted from cross-wavelet spectra of current waveforms, obtained from impulse test. Results show that the proposed methodology can localize the fault within 5% of the winding length with a high degree of accuracy. The basic concepts of feature extraction using cross-wavelet transform and the method of classification of those features by rough-granular method are also explained.     

Textural and microstructural developments during fabrication of Zr-2.5Nb pressure tubes

Zr-2.5wt%Nb pressure tubes, as used in the Indian pressurized heavy water reactors (PHWR), are fabricated through a combination of hot extrusion followed by two stages of cold pilgering and annealing. The present study makes an effort to systematically characterize the textural changes during the fabrication stages. The starting single-phase hcp martensitic structure was textured to start with and it also went through strong texture developments during hot extrusion. First and especially the second pilgering modified the texture. Such modifications were related to local discontinuity of the softer second phase, as an apparent continuity restricted lattice rotation in the primary hcp phase. Annealing caused discontinuity or spherodization of the bcc phase, but did not create recrystallization in the hcp matrix. The combination of two pilgering plus annealing operations, though the latter did not cause noticeable texture changes, however, reverted the final texture close to the parent hot-extruded texture.     

Effect of Gravity and Initial Stress on Torsional Surface Waves in Dry Sandy Medium

This problem studies the effect of gravity and initial stress on the propagation of torsional surface waves in dry sandy medium. The mathematical analysis of the problem has been dealt with the Whittaker function. Assuming the expansion of the Whittaker function up to linear term, it is concluded that the gravity field will always allow torsional waves to propagate. The expansion of the Whittaker function up to quadratic terms shows that two such wave fronts may exist in the medium. Finally, it is concluded that the sandy medium without support of a gravity field cannot allow the propagation of torsional surface waves, where as the presence of a gravity field always supports the propagation of torsional surface waves regardless of whether the medium is elastic or dry sandy.     

LI-BIST: A Low-Cost Self-Test Scheme for SoC Logic Cores and Interconnects

For system-on-chips (SoC) using deep submicron (DSM) technologies, interconnects are becoming critical determinants for performance, reliability and power. Buses and long interconnects being susceptible to crosstalk noise, may lead to functional and timing failures. Existing at-speed interconnect crosstalk test methods propose inserting dedicated interconnect self-test structures in the SoC to generate vectors which have high crosstalk defect coverage. However, these methods may have a prohibitively high area overhead. To reduce this overhead, existing logic BIST structures like LFSRs could be reused to deliver interconnect tests. But, as shown by our experiments, use of LFSR tests achieve poor crosstalk defect coverage. Additionally, it has been shown that the power consumed during testing can potentially become a significant concern.In this paper, we present Logic-Interconnect BIST (LI-BIST), a comprehensive self-test solution for both the logic of the cores and the SoC interconnects. LI-BIST reuses existing logic BIST structures but generates high-quality tests for interconnect crosstalk defects, while minimizing the area overhead and interconnect power consumption. The application of the LI-BIST methodology on example SoCs indicates that LI-BIST is a viable, low-cost, yet comprehensive solution for testing SoCs.