Stability analysis of systems with multiple nonlinearities

This paper shows a method for using describing functions in a control system with multiple nonlinearities. The linear system resulting after the proper describing functions have been inserted is analyzed using an "input dependent root locus" which is a modified root locus technique. The rules for construction of the input dependent locus and a proof of its applicability are given along with examples which illustrate the method. The technique shows the existence of limit cycles, their amplitude and frequency when they exist, and the stability of the limit cycle.     

A support vectors classifier approach to predicting the risk of progression of adolescent idiopathic scoliosis.

A support vector classifier (SVC) approach was employed in predicting the risk of progression of adolescent idiopathic scoliosis (AIS), a condition that causes visible trunk asymmetries. As the aetiology of AIS is unknown, its risk of progression can only be predicted from measured indicators. Previous studies suggest that individual indicators of AIS do not reliably predict its risk of progression. Complex indicators with better predictive values have been developed but are unsuitable for clinical use as obtaining their values is often onerous, involving much skill and repeated measurements taken over time. Based on the hypothesis that combining common indicators of AIS using an SVC approach would produce better prediction results more quickly, we conducted a study using three datasets comprising a total of 44 moderate AIS patients (30 observed, 14 treated with brace). Of the 44 patients, 13 progressed less than 5 degrees and 31 progressed more than 5 degrees. One dataset comprised all the patients. A second dataset comprised all the observed patients and a third comprised all the brace-treated patients. Twenty-one radiographic and clinical indicators were obtained for each patient. The result of testing on the three datasets showed that the system achieved 100% accuracy in training and 65%-80% accuracy in testing. It outperformed a "statistically equivalent" logistic regression model and a stepwise linear regression model on the said datasets. It took less than 20 min per patient to measure the indicators, input their values into the system, and produce the needed results, making the system viable for use in a clinical environment.     

Establishing a high-accuracy spectral response scale in the near infrared with digital filters

Spectrally invariant detectors are commonly used to interpolate or extrapolate the responsivity of InGaAs detectors in the infrared from absolute calibrations at a few wavelengths. The random noise in such detectors limits the accuracy that can be achieved in a narrowband, double-monochromator setup. We propose the application of a dedicated digital filter, which reduces the uncertainty by 30%, and combine it by calibrating a group of three detectors. The uncertainties are propagated from the observed variance in the relative measurement to the combined uncertainty of 0.4% (2sigma) in the responsivity values of the InGaAs detectors in the range of 1010-1640 nm.     

Properties of piperazine homopolyamide films

Properties of films prepared from the following poly(piperazine amides) were examined: poly(2-methylpiperazine fumaramide); poly(trans-2,5-dimethylpiperazine fumaramide); poly(trans-2,5-dimethylpiperazine mesaconamide); poly(trans-2,5-dimethylpiperazine terephthalamide); poly(trans-2,5-dimethylpiperazine isophthalamide); poly(trans-2,5-dimethylpiperazine adipamide). Mechanical properties of these films are good; they have in fact a high tensile strength and in accordance with the rigidity of the polymer chain, low elongations and a high modulus of elasticity. Optical properties are very good. Since the films have a high water absorption, permeability to water vapour is very high while treatment of the films in water causes lowering of mechanical properties. Resistance to thermal ageing in an atmosphere of nitrogen is good. Among the various films considered those obtained from polymers with an unsaturated acid (fumaric and mesaconic) seem to show the best properties.     

A review on ochratoxin A occurrence and effects of processing of cereal and cereal derived food products

Ochratoxin A (OTA) continues to grab global attention and concern for the hazard and impact that embody for both human and animals, based on its toxicity and occurrence. Despite OTA has been described in a myriad of foodstuffs, cereal and its derivatives remain the major contributors to OTA exposure. For that reason, a critical review on OTA occurrence reported by recent studies worldwide focusing on unprocessed and processed cereal foodstuffs is made in this work. Special attention is drawn to the major cereal derived products, namely flour, bread, breakfast cereals, baby/infant foods and the inherently involved technological food processing methods and its influence on the redistribution and chemical modification of OTA.     

The Influence of the Desulfovibrio desulfuricans 14 ATCC 27774 on the corrosion of mild steel

The involvement of sulphate‐reducing bacteria (SRB) in microbially influenced corrosion (MIC) of steel and the serious implications associated with their presence in industrial environments have long been known and extensively described. Desulfovibrio desulfuricans ATCC 27774 is an interesting metabolic case of SRB, as it can use both sulphate and nitrate as respiratory substrates during lactate oxidation. This strain has been extensively studied from both a biochemical and structural point of view but, so far, restricted information is available concerning its role in MIC. This work describes a comparative study of the corrosive aggressivity of ATCC 27774 strain towards mild steel when grown either in lactate/sulphate or lactate/nitrate media. The carbon source and electron acceptor's consumption rates were analysed and the metabolic features were correlated with weight loss measurements and SEM observations.