Integrated fault estimation and fault‐tolerant control for uncertain Lipschitz nonlinear systems

This paper proposes an integrated fault estimation and fault‐tolerant control (FTC) design for Lipschitz non‐linear systems subject to uncertainty, disturbance, and actuator/sensor faults. A non‐linear unknown input observer without rank requirement is developed to estimate the system state and fault simultaneously, and based on these estimates an adaptive sliding mode FTC system is constructed. The observer and controller gains are obtained together via H_∞ optimization with a single‐step linear matrix inequality (LMI) formulation so as to achieve overall optimal FTC system design. A single‐link manipulator example is given to illustrate the effectiveness of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.     

Buckling of fixed-ended concrete-filled steel columns under axial compression

In recent years, due to a relatively high price increase of nickel alloys, there is an increase in demand for lean duplex stainless steel (LDSS) with a low nickel content of ~1.5%, such as grade EN 1.4162. LDSS offers roughly twice the strength compared to austenitic stainless steels and has great potential for expanding future structural possibilities, enabling a reduction in the section sizes leading to lighter structures. This paper reports the buckling behavior of fixed-ended concrete-filled LDSS tubular (CFDSST) columns with L-, T-, and +-shape (Non-Rectangular Sections or NRSs) sections and a representative square section with varying lengths through Finite Element (FE) analysis. The purpose is to compare and assess the strength and deformation characteristics as well as the failure modes of such columns. It is seen that concrete-filled tubular columns with NRSs offered a better performance for all lengths considered, especially the T-shaped and +-shaped sections, in terms of strength. The influence of the cross-sectional shapes on the ε _u becomes less significant with increasing λ, but becomes increasingly significant with decreasing λ. The design standards show over conservative results for square and L-shape sections and conservative for T-shape and +-shape sections.     

Chromatographic separation of lactone precursors and tentative identification of the γ-lactones of 4-hydroxy octanoic and 4-hydroxy nonanoic acids in butterfat

A combination of silicic acid column and thin layer chromatography which separates γ- and δ-hydroxy acid containing glycerides from butterfat is described. This procedure facilitates the isolation of the γ- and δ-hydroxy acids (lactone precursors) while avoiding lactonization. The method indicated that the hydroxy acids are entirely esterified to the glyceride in fresh butterfat. Hydrolysis, using pancreatic lipase, showed that these polar acids are located on the α-positions of the glycerides. The γ-lactones of 4-hydroxy octanoic and 4-hydroxy nonanoic acids were tentatively identified by gas liquid chromatography. These occurred in quantities of 0.25–0.5 ppm and approximately 0.2 ppm respectively in the butterfat samples investigated. Authorized for publication on June 22, 1966, as Paper No. 3156 in the journal series of the Pennsylvania Agricultural Experiment Station.     

Structural behaviour of stainless steel stub column under axial compression: a FE study

This paper presents a Finite Element (FE) study on Lean Duplex Stainless Steel stub column with built-up sections subjected to pure axial compression with column web spacing varied at different position across the column flanges. The thicknesses of the steel sections were from 2 to 7 mm to encompass a range of section slenderness. The aim is to study and compare the strength and deformation capacities as well as the failure modes of the built-up stub columns. The FE results have been compared with the un-factored design strengths predicted through EN1993-1-4 (2006)?+?A1 (2015) and ASCE8-02 standards, Continuous Strength Method (CSM) and Direct Strength Method (DSM). The results showed that the design rules generally under predict the bearing capacities of the specimens. It’s been observed that the CSM method offers improved mean resistance and reduced scatter for both classes of cross-sections (i.e. slender and stocky sections) compared to the EN1993-1-4 (2006)?+?A1 (2015) and ASCE 8-02 design rules which are known to be conservative for stocky cross-sections.     

Influence of punctures, cuts, and surface morphologies of golden delicious apples on penetration and growth of Escherichia coli O157:H7

The ability of Escherichia coli O157:H7 to penetrate and grow within punctures, fresh-cut surfaces, and calyces of Golden Delicious apples was investigated. A three-strain cocktail of E. coli O157:H7 resistant to ampicillin was used to inoculate fresh and 48-h-old punctures, fresh-cut surfaces, and open or closed calyces. A concentric cutting procedure was used to evaluate depth of penetration within punctures and prevent cross contamination during sampling. Within 2 h, E. coli O157:H7 penetrated vertically through the fresh punctures and 3.4 mm within the underlying parenchyma. After 48 h, E. coli O157: H7 cells penetrated up to 5.5 mm within the punctures and >2.6 mm horizontally away from fresh punctures. However, 48-h-old punctures did not permit penetration beyond their boundaries. Fresh-cut surfaces permitted up to 2.8 mm penetration after 24 h. Onset of growth of E. coli O157:H7 occurred 4 to 8 h postinoculation on fresh punctures and fresh-cut surfaces with populations increasing by 3 logs after 48 h. E. coli O157:H7 penetrated within calyces regardless of the extent of opening or method of inoculation. However, E. coli O157:H7 was never recovered from the inner core of apples. Computed tomography scan imaging revealed that closed calyces effectively prevented penetration of sodium iodide solutions within the calyx cavity. Lack of solution penetration may explain why sanitizing treatments are ineffective in inactivating microbial cells within the calyx. Understanding the role of morphological differences in permitting or restricting bacterial penetration may lead to development of more effective strategies to enhance the safety of fresh horticultural products.     

Differences in the expression of genes involved in the somatotropic axis in divergent strains of Holstein-Friesian dairy cows during early and mid lactation

Differences in genetic selection criteria for dairy cows internationally have led to divergence in the Holstein-Friesian breed. The objective of this study was to compare hepatic expression of genes of the somatotropic axis in the North American Holstein-Friesian and the New Zealand Holstein-Friesian strains of dairy cow at early and mid lactation. Mature cows of both the North American Holstein-Friesian (n = 10) and New Zealand Holstein-Friesian (n = 10) strains were selected. Liver tissue was collected by percutaneous punch biopsy from all cows at 35 and 140 d postpartum, representing early and mid lactation, respectively. Total RNA was extracted and the hepatic expression of genes involved in the control of the somatotropic axis was examined. Abundance of insulin-like growth factor (IGF)-1 mRNA was greater in the New Zealand strain, concomitant with a tendency for increased expression of acid-labile subunit mRNA. Across strains, mRNA abundance of IGF-binding protein-1, IGF-binding protein-2, and growth hormone receptor 1A decreased from d 35 to 140 postpartum, whereas expression of IGF-1 and acid-labile subunit tended to increase. Abundance of suppressor of cytokine signaling-3 mRNA was increased at d 140 postpartum. Both the strain of Holstein-Friesian cow and the stage of lactation influenced expression of genes controlling the somatotropic axis in hepatic tissue.     

Finite element modelling of concrete-filled lean duplex stainless steel tubular stub columns

This paper presents a finite element (FE) study on concrete-filled lean duplex slender stainless steel tubular (CFDSST) stub columns of square and L-, T-, and +-shape (Non-Rectangular Sections or NRSs) sections under pure axial compression. The effect of cross-sectional shape and concrete compressive strength, by considering equal steel consumption (i.e. equal cross-sectional area) for all the square and NRSs sections have been reported. In CFDSST stub columns, the axial deformation (δ _u ) at ultimate load (P _u ) decreases with increasing concrete strengths, but increases as the sections changes from Square→L→T→+-shape. For normal concrete strength (≤40 MPa), NRSs appear to have similar or slightly enhanced P _u , in comparison with the representaive square section. But in the case of a high strength concrete core (i.e. >40 MPa), NRSs are clearly at a disadvantage as far as the values of P _u is concerned, however as the NRSs are lighter by 37%, they still offer an attractive option for the designers. The FE strengths over predicts the EN 1994-1-1 (2004) specification by about an average of 21, 19, 14, and 4% for the square, L, T, and +-shape sections, respectively.     

Conduction and Gas–Surface Reaction Modeling in Metal Oxide Gas Sensors

A phenomenological approach to the operation of metal oxide gas sensors, the Integrated Reaction Conduction (IRC) model, is proposed which integrates the gas-surface reactions with the electrical conduction process in a weakly sintered, porous metal oxide. An effective medium approximation is employed to relate the mesoscopic microstructure and the carrier depletion at the granular surface to the macroscopic electrical conduction. For a given ambient gas concentration and temperature, the electron concentration in the depletion layer is calculated from the gas-surface reaction kinetics. The adsorption and oxidation reaction energies of the gas sensing reactions are extracted for a TiO_2-x CO sensor by comparing experimental data with three-dimensional plots of IRC model resistance as a function of the ambient [CO(g)] and temperature. The IRC model predicts novel properties of the gas sensor, including the sensitivity and the response range, which depend on the doping of the sensor material, the temperature, the grain size, and the geometry of the necks between grains.     

Worsening enterocolitis in neonates: diagnosis by CT examination of urine after enteral administration of iohexol

Perforation, a severe complication of necrotizing enterocolitis (NEC), has a high mortality rate. Recently, we presented a new technique for evaluation of NEC: measuring the CT attenuation coefficient of urine after oral administration of iohexol. We present three cases of neonates with NEC who demonstrated serial increases in urine CT attenuation coefficients, all of whom subsequently deteriorated clinically and radiographically. Surgery in all three cases confirmed severe necrosis and/or perforation. These three cases suggest that the CT attenuation coefficient of urine after oral administration of iohexol may be a more sensitive indicator of NEC severity, progression, and perforation than clinical evaluation and radiography. More investigation is necessary, but eventually, this noninvasive technique may be able to decrease morbidity and mortality by predicting the need for surgical intervention or more aggressive medical management of NEC before perforation occurs.