Feedback linearization based control of a rotational hydraulic drive

The technique of feedback linearization is used to design controllers for displacement, velocity and differential pressure control of a rotational hydraulic drive. The controllers, which take into account the square-root nonlinearity in the system's dynamics, are implemented on an experimental test bench and results of performance evaluation tests are presented. The objective of this research is twofold: firstly, to present a unified method for tracking control of displacement, velocity and differential pressure; and secondly, to experimentally address the issue of whether the system can be modeled with sufficient accuracy to effectively cancel out the nonlinearities in a real-world system.     

Herbally derived polymeric nanofibrous scaffolds for bone tissue regeneration

Hydroxyapatite (HA), the bone mineral and Cissus quadrangularis (CQ), a medicinal plant with osteogenic activity, are attaining increasing interest as a potential therapeutic agent for enhanced bone tissue regeneration. In the present study a synergistic effect of these two agents were analyzed by fabricating PCL‐CQ‐HA nanofibrous scaffolds by electrospinning and compared with PCL‐CQ and PCL (control) nanofibrous scaffolds. Morphology, composition, hydrophilicity, and mechanical properties of the electrospun PCL, PCL‐CQ, PCL‐CQ‐HA nanofibrous scaffolds were examined by Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Contact angle and Tensile tests, respectively. The response of human foetal osteoblast cells on these scaffolds were evaluated using MTS assay, alkaline phosphatase activity, alizarin red staining, and osteocalcin expression for bone tissue regeneration. While the observed cellular response to both groups of scaffolds was better than for the control PCL scaffold, the PCL‐CQ‐HA nanofibrous scaffolds provided the most favorable substrate for cell proliferation and mineralization. The results showed that PCL‐CQ‐HA nanofibrous scaffolds had appropriate surface roughness for the osteoblast adhesion, proliferation, and mineralization comparing with other scaffolds. The observed investigation of physicochemical and biological properties suggests that the CQ‐HA loaded PCL nanofibrous scaffolds serve as a potential biocomposite material for bone tissue engineering. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39835.     

Low frequency magnetic force augments hepatic differentiation of mesenchymal stem cells on a biomagnetic nanofibrous scaffold

Liver tissue engineering using polymeric nanofibrous scaffold and stem cells holds great promises for treating end-stage liver failures. The aim of this study was to evaluate hepatic trans-differentiation potential of human mesenchymal stem cells (hMSCs) on a biomagnetic electrospun nanofibrous scaffold fabricated from a blend of poly-l-lactide (PLLA), collagen and fibrin-rich blood clot, under the influence of a low frequency magnetic field. The scaffold was characterized for surface properties, biochemical and biomechanical parameters and bio-magnetic behaviour. Cell proliferation assay revealed that the scaffold was suitable for hMSCs adhesion and proliferation. Hepatic trans-differentiation potential of hMSCs was augmented on nanofibrous scaffold in magnetic field exposure group compared to control groups, as evident by strong expression of hepatocyte specific markers, albumin release, urea synthesis and presence of an inducible cytochrome P450 system. Our results conclude that biomagnetic scaffold of PLLA/collagen/blood clot augments hepatic trans-differentiation of hMSCs under magnetic field influence.     

Studies on stabilised zirconia as host phase for the fixation of actinides, rare-earths and sodium

Titania, zirconia and alumina based ceramic materials are potential solid waste forms being assessed to determine their suitability for long term immobilisation of radionuclides. The preparation, characterisation, solid solubilities and leachability studies on stabilised zirconia containing actinides, rare earths and sodium are reported. The range of solid solubilities of cerium, uranium, neodymium, plutonium and sodium was established in stabilised zirconia. Leaching studies in water and 0.1 M HCl at room temperature and 70°C showed very low leachabilities of uranium, plutonium and rare earths.     

Constitutive equations to predict high temperature flow stress in a Ti-modified austenitic stainless steel

The experimental stress–strain data from isothermal hot compression tests, in a wide range of temperatures (1123–1523 K) and strain rates (10⁻³–10² s⁻¹), were employed to develop constitutive equations in a Ti-modified austenitic stainless steel. The effects of temperature and strain rate on deformation behaviors were represented by Zener-Holloman parameter in an exponent type equation. The influence of strain was incorporated in the constitutive analysis by considering the effect of strain on material constants. The constitutive equation (considering the compensation of strain) could precisely predict the flow stress only at 0.1 and 1 s⁻¹ strain rates. A modified constitutive equation (incorporating both the strain and strain rate compensation), on the other hand, could predict the flow stress throughout the entire temperatures and strain rates range except at 1123 K in 10 and 100 s⁻¹. The breakdown of the constitutive equation at these processing conditions is possibly due to adiabatic temperature rise during high strain rate deformation.     

Predictive Control of a Circulating Fluidized Bed Combustor

The acceptance of CFB combustion in process and utility industries for generating steam has been increasing because of its ability to burn a wide variety of fuels efficiently and in an environmentally acceptable manner. Work on control of this emerging technology is beginning to appear. This paper evaluates the performance of two predictive control algorithms (the Dynamic Matrix Control and a simplified version) for control of temperature and pressure drop in a pilot scale CFB combustor. The robustness of the algorithms is studied on a model of the CFB combustor. The experimental and simulation results show the suitability of the two control algorithms for control of the CFB combustor.     

Sinus of Valsalva aneurysms: 20 years' experience

BACKGROUND: Aneurysms of sinus of Valsalva are rare. Here, we analyze retrospectively patients operated on at our center during the last 20 years. PATIENTS AND METHODS: One hundred four cases of congential aneurysm of sinus of Valsalva were operated upon between January 1977 and April 1996. Only 12 aneurysms were unruptured. The majority (76.9%) arose from the right coronary sinus. The right ventricle was the most common chamber of rupture (58.6%). Ventricular septal defect was associated in 46 patients (44.2%), of which 28 (60.9%) were supracristal. Ventricular septal defect was more common in aneurysms arising from the right coronary sinus (91.3%). Aortic incompetence was found in 45 patients (43.3%). The defect was closed through the aortic root alone in 24 patients (23.1%) and through both the aortic root and the chamber of rupture in the remaining 80 patients. Six patients underwent aortic valve repair, and 21 an aortic valve replacement. RESULTS: There were two hospital deaths (1.92%). Morbidities were few. Follow-up ranged from 1 to 20 years (mean 8.2 +/- 1.1). There was one late noncardiac death, and in the majority, the long-term follow-up was uneventful. CONCLUSION: Surgery for aneurysm of sinus of Valsalva yields gratifying results, and it should be undertaken as soon as the condition is diagnosed.     

Smart Proxies for Accessing Replicated Web Services

According to Wikipedia (http://en.wikipedia.Org/wiki/Web_2.0), Web 2.0 refers to "a perceived second generation of Web-based communities and hosted services-such as social networking sites, wikis, and folksonomies-rdquowhich aim to facilitate collaboration and sharing between users." Web 2.0 is especially widely used in the consumer space for those people who are their own IT administrators. However, this paper focus on enterprise IT.     

Lyapunov‐based backward‐horizon adaptive stabilization

In this paper we develop a discrete‐time adaptive stabilization algorithm based on a one‐step backward‐horizon cost criterion. By optimizing the cost with respect to the update step size, we obtain a gain update law that guarantees convergence of the plant states. The convergence proof is based on a modified Lyapunov technique. We extend the algorithm to include integral control for rejecting constant disturbances and we present an experimental application to DC motor positioning system. Copyright © 2003 John Wiley & Sons, Ltd.