Stochastic tube MPC with state estimation

An output feedback Model Predictive Control (MPC) strategy for linear systems with additive stochastic disturbances and probabilistic constraints is proposed. Given the probability distributions of the disturbance input, the measurement noise and the initial state estimation error, the distributions of future realizations of the constrained variables are predicted using the dynamics of the plant and a linear state estimator. From these distributions, a set of deterministic constraints is computed for the predictions of a nominal model. The constraints are incorporated in a receding horizon optimization of an expected quadratic cost, which is formulated as a quadratic program. The constraints are constructed so as to provide a guarantee of recursive feasibility, and the closed loop system is stable in a mean-square sense. All uncertainties in this paper are taken to be bounded—in most control applications this gives a more realistic representation of process and measurement noise than the more traditional Gaussian assumption.     

Inhibition effect of honey on the adherence of Salmonella to intestinal epithelial cells in vitro

The aim of the study was to evaluate the antimicrobial effect and the ability of honey to prevent Salmonella interitidis adhering to intestinal epithelial cells in vitro. Antimicrobial activity was demonstrated. Bacterial adherence was assayed using S. interitidis cells that had been incubated first with honey and then with the intestinal epithelial cells. Results showed that honey at dilutions of up to 1:8 reduced bacterial adherence from 25.6+/-6.5 (control) to 6.7+/-3.3 bacteria per epithelial cell (P<0.001).     

The effect of rolling on the mechanical properties of polymers with phenylene groups in the main chain

The changes occurring, in mechanical properties particularly, when polymers with phenylene groups in the main chain are subjected to uniaxial rolling have been investigated. All properties can be enhanced by the process under the correct conditions. The anisotropy of the specimens at various reduction ratios have also been measured and an explanation of the behaviour on a molecular basis is suggested.     

Mullite/Alumina Particulate Composites by Infiltration Processing: IV, Residual Stress Profiles

Residual stress profiles through mullite/alumina bodies prepared by an infiltration process were determined. In one approach, residual stress profiles were predicted by obtaining concentration profiles and treating the bodies as laminates. In a second approach, a strain gage technique in which part of the sample was ground away while recording the resulting strain was used. The results showed that residual compressive stresses existed in the surface region of all composite samples. The strain gage approach indicated values of surface compression in the range of 176 to 291 MPa, which were higher than those predicted using the laminate approach. The results were compared with changes in the mechanical properties and found to be consistent with the increases in the strength and indentation fracture toughness which resulted when mullite was added to alumina by the infiltration technique.     

Mullite/Alumina Particulate Composites by Infiltration Processing: III, Mechanical Properties

The effect of incorporating mullite into alumina by an infiltration process on the mechanical properties was investigated. Data for Young's modulus, strength, and fracture toughness for various composite compositions were compared with those for the unreinforced matrix (alumina). Measurements of Young's modulus by a resonance technique showed that the addition of mullite decreased Young's modulus. Up to 14 vol%, these changes were close to those expected, but above this mullite content, the decrease was more dramatic and indicated specimen damage during processing. The addition of mullite led, in some cases, to increases of more than 60% in both the strength (biaxial flexure) and indentation fracture toughness. These increases have been attributed to the method of introducing mullite and the resulting residual compressive surface stresses. The strength of the indented composite bodies deviated from the ideal behavior, indicating the probability of R -curve behavior in these materials.     

Characteristics of bread and buns made with lard and vegetable oils of different iodine values

A good-quality white loaf of bread or rolls can be baked by substituting liquid vegetable oil (canola, soya and palm) for the standard shortening,i.e. lard, tallow or partially hydrogenated vegetable shortening. Canola oil and soya oil produced lower specific volumes of 5.56 and 5.55 cm³/g and higher softness indices when used with mono- and diglycerides only. Palm oil and lard produced specific volumes of 6.33 and 6.15 cm³/g and lower softness indices with mono- and diglycerides. When a blend of surfactants consisting of mono- and diglycerides and sodium stearyl lactylate (SSL) was used at 0.5% of flour weight, palm, canola, lard and soya gave comparable results in specific volume and compressibility. Rolls baked with the same fats and oils, and addition of ethoxylated stearic acid (MYRJ 45H) or a blend of MYRJ 45H and SSL, all gave good specific volumes ranging from 6.92 to 7.27 cm³/g and a softness index range of 0.71–0.86 and 0.68–0.86 after 48 and 96 h of storage. When a proper surfactant is used, good-quality bread and rolls can be baked with liquid vegetable oil. Furthermore, the usage level of liquid oil can be cut by approximately 30% in comparison to lard or shortening while still maintaining quality.     

Probabilistic tubes in linear stochastic model predictive control

This paper considers constrained control of linear systems with additive and multiplicative stochastic uncertainty and linear input/state constraints. Both hard and soft constraints are considered, and bounds are imposed on the probability of soft constraint violation. Assuming the plant parameters to be finitely supported, a method of constraint handling is proposed in which a sequence of tubes, corresponding to a sequence of confidence levels on the predicted future plant state, is constructed online around nominal state trajectories. A set of linear constraints is derived by imposing bounds on the probability of constraint violation at each point on an infinite prediction horizon through constraints on one-step-ahead predictions. A guarantee of the recursive feasibility of the online optimization ensures that the closed loop system trajectories satisfy both the hard and probabilistic soft constraints. The approach is illustrated by a numerical example.     

Denial of service detection using dynamic time warping

With the rapid growth of security threats in computer networks, the need for developing efficient security-warning systems is substantially increasing. Distributed denial-of-service (DDoS) and DoS attacks are still among the most effective and dreadful attacks that require robust detection. In this work, we propose a new method to detect TCP DoS/DDoS attacks. Since analyzing network traffic is a promising approach, our proposed method utilizes network traffic by decomposing the TCP traffic into control and data planes and exploiting the dynamic time warping (DTW) algorithm for aligning these two planes with respect to the minimum Euclidean distance. By demonstrating that the distance between the control and data planes is considerably small for benign traffic, we exploit this characteristic for detecting attacks as outliers. An adaptive thresholding scheme is implemented by adjusting the value of the threshold in accordance with the local statistics of the median absolute deviation (MAD) of the distances between the two planes. We demonstrate the efficacy of the proposed method for detecting DoS/DDoS attacks by analyzing traffic data obtained from publicly available datasets.     

A new approach to fuzzy estimation of Takagi-Sugeno model and its applications to optimal control for nonlinear systems

An efficient approach is presented to improve the local and global approximation and modelling capability of Takagi-Sugeno (T-S) fuzzy model. The main aim is obtaining high function approximation accuracy. The main problem is that T-S identification method cannot be applied when the membership functions are overlapped by pairs. This restricts the use of the T-S method because this type of membership function has been widely used during the last two decades in the stability, controller design and are popular in industrial control applications. The approach developed here can be considered as a generalized version of T-S method with optimized performance in approximating nonlinear functions. A simple approach with few computational effort, based on the well known parameters’ weighting method is suggested for tuning T-S parameters to improve the choice of the performance index and minimize it. A global fuzzy controller (FC) based Linear Quadratic Regulator (LQR) is proposed in order to show the effectiveness of the estimation method developed here in control applications. Illustrative examples of an inverted pendulum and Van der Pol system are chosen to evaluate the robustness and remarkable performance of the proposed method and the high accuracy obtained in approximating nonlinear and unstable systems locally and globally in comparison with the original T-S model. Simulation results indicate the potential, simplicity and generality of the algorithm.     

Improving the Management of Large Programs

ABSTRACT

The United States remains the world leader in managing large, complex programs such as the space shuttle program and major weapons systems. The challenges confronting the management of these programs and initiatives intended to meet these challenges are reviewed. This article asserts that these initiatives could be far more effective if they were structured around a unifying concept that could be easily convoyed to and retained by program personnel. A comprehensive quality concept can be used as this unifying framework. Observations about quality-oriented cultures in large programs are included.