Soft computing approach to fault diagnosis of centrifugal pump

Fault detection and isolation in rotating machinery is very important from an industrial viewpoint as it can help in maintenance activities and significantly reduce the down-time of the machine, resulting in major cost savings. Traditional methods have been found to be not very accurate. Soft computing based methods are now being increasingly employed for the purpose. The proposed method is based on a genetic programming technique which is known as gene expression programming (GEP). GEP is somewhat a new member of the genetic programming family. The main objective of this paper is to compare the classification accuracy of the proposed evolutionary computing based method with other pattern classification approaches such as support vector machine (SVM), Wavelet-GEP, and proximal support vector machine (PSVM). For this purpose, six states viz., normal, bearing fault, impeller fault, seal fault, impeller and bearing fault together, cavitation are simulated on centrifugal pump. Decision tree algorithm is used to select the features. The results obtained using GEP is compared with the performance of Wavelet-GEP, support vector machine (SVM) and proximal support vector machine (PSVM) based classifiers. It is observed that both GEP and SVM equally outperform the other two classifiers (PSVM and Wavelet-GEP) considered in the present study.     

Electrical resistivity of plasma-sprayed titanium diboride coatings

Plasma-sprayed TiB₂ coatings (50–600 m thick) on alumina substrates have been developed and characterized. X-ray diffraction studies, thermal analysis and oxygen analysis of the coatings show that there is appreciable oxidation of TiB₂ during the spray process. Partial oxidation of the boride during spraying strongly influences the electrical conductivity of the coatings, which is found to be 100–1000 times less than that of pure TiB₂. Although use of argon as shield gas during the spray process brings down the resisitivity substantially, partial oxidation of TiB₂ could not be totally avoided.     

The influence of the motion of a rotor grid on a stator grid

Summary In this paper we have used the method of characteristics developed for two dimensional unsteady flow problems to study a simplified axial turbine problem. The system consists of two sets of blades —the guiding vanes which are fixed and the rotor blades which move perpendicular to these vanes. The initial undisturbed constant flow in the system is perturbed by introducing a small velocity normal to the rotor blades to simulate a slight constant inclination. The resulting perturbed flow is periodic after the first three cycles. We have studied the perturbed density distribution throughout the system during a period.

---

Der Einfluß der Bewegung eines Laufschaufelgitters auf ein Leitschaufelgitter

Zusammenfassung In der vorliegenden Arbeit wird das Charakteristikenverfahren für zweidimensionale instationäre Strömungen auf ein Problem der Axialturbinen angewandt. Das System besteht aus zwei Gitterreihen, den feststehenden Leitschaufeln und den hierzu senkrecht bewegten Laufschaufeln. Die anfangs ungestörte konstante Strömung wird gestört, indem den Laufschaufeln eine geringe Normalgeschwindigkeit erteilt wird, um eine konstante Anstellung zu simulieren. Die gestörte Strömung ist periodisch nach den ersten drei Perioden. Berechnet wurde das gestörte Dichtefeld während einer Periode.

---

List of Symbols d distance between guide vanes - angle of inclination of rotor blades - W ₀ constant velocity of rotor blades perpendicular to the guide vanes - U ₀ initial steady streaming parallel flow between the guiding vanes - V _p velocity perpendicular to the rotor blades to simulate inclination of the blades - x coordinate parallel to the guide vanes - y coordinate perpendicular to the guide vanes - t time - u, v velocity componente inx, y directions, respectively - a ₀ undisturbed sound velocity in the system - a perturbed sound velocity - M ₀=U ₀/a ₀ nondimensional quantity corresponding toU ₀ - N ₀=W ₀/a ₀ nondimensional quantity corresponding toW ₀ - V ₀=V _p0/a ₀ nondimensional quantity corresponding toV _p0 - nondimensional coordinates corresponding tox, y, t, respectively - nondimensional quantity corresponding toa - nondimensional quantities corresponding tou, v respectively With 5 FiguresThis work was done during the award of an Alexander Von Humboldt Fellowship at the DFVLR-Aerodynamische Versuchsanstalt, Institut für Strömungsmechanik, Göttingen, Federal Republic of Germany.     

Dynamics of a thin film with temperature-dependent viscosity on a rotating disk

Summary The thermal effects on the dynamics of an axisymmetric flow of a non-volatile incompressible viscous thin liquid film on a rotating disk due to viscosity variation depending exponentially on temperature are considered. The nonlinear evolution equation is solved numerically. The numerical results reveal that heating the film from below enhances the rate of thinning. The increase in Biot number increases the film thickness, when the film is heated from below. Further, the relative amount of fluid retained on the substrate decreases as the film is heated from below. The results are reversed for the case of a film which is cooled from below. The rate of thinning of the film is more (less) for the case of temperature dependent viscosity when the film is heated (cooled) from below than for the case of constant viscosity of the fluid.     

A formally verified application-level framework for real-time scheduling on POSIX real-time operating systems

We present a framework, called meta scheduler, for implementing real-time scheduling algorithms. The meta scheduler is a portable middleware layer component designed for implementations over POSIX-compliant operating systems. It accommodates pluggable real-time scheduling algorithms while offering the flexibility of platform independence - the singular underlying OS requirement is the now nearly ubiquitous POSIX compliance. The versatility of pluggable schedulers positions the meta scheduler for deployment in an interoperable heterogeneous real-time environment. We present the design of the meta scheduler and outline its implementation. Furthermore, we present a mechanized correctness verification using the UPPAAL model checker. Prototype implementation of the meta scheduler over QNX Neutrino real-time operating system demonstrates high performance and a small footprint.     

A hybridisation of metaheuristics for flow shop scheduling

The present paper deals with the formation of an optimal sequence of flow shop scheduling (FSS) for efficient operation. The primary concern of FSS is to obtain the optimal sequence, which minimises the idle time, tardiness, makespan, etc. Among these, the criteria of minimising the makespan plays a vital part. Thus, in this paper, the sequencing of the FSS for minimising the makespan is addressed. An effective hybrid has been formed with the metaheuristics, namely an ant system and a genetic algorithm (GA). A number of illustrative examples with different combinations of machines and jobs have been solved using the proposed hybrid method.     

Experimental characterization of meso‐scale deformation mechanisms and the RVE size in plastically deformed carbon steel

The local deformation response of low carbon steel subjected to uniaxial tensile loading is investigated, and the local strain field at sub‐grain scale is obtained using high‐spatial‐resolution digital image correlation. The implemented digital image correlation method enables the observation and study of inhomogeneous deformation response at microstructural levels. Detailed local deformation mechanisms including mesoscopic slip bands are captured. Furthermore, the local information is used for the determination of representative volume element size in polycrystalline low carbon steel. To obtain the representative volume element size, we proposed and successfully implemented a strain variation method. Further, the influence of global strain on the local deformation mechanisms and representative volume element size is discussed. The challenges associated with the local strain measurement using digital image correlation are also discussed.     

Synthesis and phase stability of precursor derived HfO2/Si-C-N-O nanocomposites

Hafnium alkoxide modified polysilazane was synthesized by the drop-wise addition of hafnium tetra(n-butoxide) to polysilazane. The solid state thermolysis (SST) temperature and the ceramic yield for both the polysilazane and modified polysilazane were determined by performing thermogravimetry. Fourier transform infrared spectroscopy was performed to understand the polymer to ceramic conversion as well as the bonding characteristics of the ceramics. The modified polymer after crosslinking was subjected to SST at 800 °C at a constant heating rate of 5 °C/min for a dwell time of 2 h in atmospheric ambience. From the X-ray diffractograms, the as-thermolysed ceramics were observed to remain X-ray amorphous and on heat-treatment resulted in the crystallization of tetragonal hafnia. However, on heat-treatment at 1500 °C, reverse phase transformation from tetragonal to monoclinic hafnia was observed. Raman spectroscopy and transmission electron microscopy were employed to further understand the phase evolution. The thermal stability and the influence of amorphous matrix on the coarsening of HfO₂ were also evaluated.     

Characterization and Low Temperature Study of Iron Telluride Thin Films Upon Ageing and Oxygen Ion Irradiation

The occurrence of superconductivity in iron telluride thin films has been observed upon ageing. The superconducting transition is found to be very robust under an application of magnetic fields up to 10 T. Infrared and Raman spectroscopic characterization of the aged films reveal the formation of Fe_1+δTeO _x upon ageing. As an alternative method of introducing oxygen in FeTe thin film, oxygen ion irradiation has also been carried out It is found that the irradiated film becomes increasingly disordered and ultimately transforms to an amorphous phase upon increasing the irradiation dose. Investigation of electrical resistivity and optical reflectivity of the irradiated FeTe films indicates an interesting possibility of an ion irradiationinduced phase change memory material in analogy to the phase change characteristics of laserirradiated FeTe films.