Sensitivity analysis for the dynamic response of viscoplastic shells of revolution

A computational procedure is presented for evaluating the sensitivity coefficients of the dynamic axisymmetric response of viscoplastic shells of revolution. The analytical formulation is based on Reissner's large deformation shell theory with the effects of transverse shear deformation, rotatory inertia and moments turning around the normal to the middle surface included. The material model is chosen to be isothermal viscoplasticity, and an associated flow rule is used with a von Mises effective stress. A mixed formulation is used with the fundamental unknowns consisting of six stress resultants, three generalized displacements and three velocity components. Spatial discretization is performed using finite elements, with discontinuous stress resultants across element interfaces. The temporal integration is performed by using an explicit central difference scheme (leap-frog method) with an implicit constitutive update. The sensitivity coefficients are evaluated using a direct differentiation approach. Numerical results are presented for a spherical cap subjected to step loading, and a circular plate subjected to impulsive loading. The sensitivity coefficients are generated by evaluating the derivatives of the response quantities with respect to thickness, mass density, Young's modulus, and two of the material parameters characterizing the viscoplastic response. Time histories of the response and sensitivity coefficients are presented, along with spatial distributions of these quantities at selected times

An Expert Based Methodology for Cost Oriented Analysis of Machine Tool Reliability

Abstract: This paper proposes an improved methodology for machine tool reliability analysis. The overall objective of the proposed methodology is to provide the machine tool manufacturers with the approach that will help them in making cost driven decisions while improving the performance of their machines in the field. The methodology consists of three parts viz., modified fault tree diagram, simulation based data analysis and cost based Failure Modes and Effects Analysis (FMEA). Modified fault tree diagram found useful in providing better insight into the failures and their impact. The simulation based approach helps in obtaining time to failure distribution parameters for each failure events using expert's judgements. The effect of uncertainty in the experts' judgements is also quantified in terms of 90 per cent confidence interval values of the parameters. Finally, the cost based FMEA proposed in this paper will help the manufacturer in identifying the critical failure events based on actual cost of failures to the users. The methodology is illustrated with the help of an example of a CNC grinding machine

A Novel Class of Pyrazoline Analogue of Combretastatin-A4 (CA-4): Synthesis Characterization and in-vitro Biological Testing

A series of pyrazoline bridged combretastatin analogues were designed and synthesised from their precursor chalcone analogues, and all these compounds were ascertained by IR, 1H NMR, and mass spectral analysis. Subsequently, all these compounds were evaluated for anticancer activities against breast cancer (MCF-7) and normal Vero (Monkey Kidney) cell lines, and five selected compounds from the series were evaluated against Hela (Human Cervical), MDA-MB-231 (Breast), and A-549 (Lung cancer) cell lines using the Sulforhodamine B (SRB) assay method. Compounds 3a, 6a, 6e, 5b, 7a, 5a, and 7d were found to be the most potent in the series, with a GI50 value of 10 to 30 M in the MCF-7 cell line. Moreover, the same compounds 6a and 7a showed remarkable cytotoxicity against the A-549 (Lung) cell line with a GI50 value ranging from 10 to 30 M, while compound 3a displayed moderate cytotoxicity against the Hela (Human Cervical) cell line. All these compounds were found nontoxic to the Vero (Monkey Kidney) normal cell line

Potassium phosphate catalyzed highly efficient synthesis of structurally diverse thioethers at ambient temperature

154-158Commercially available potassium phosphate has been demonstrated to be a highly efficient catalyst for the synthesis of thioethers employing two different routes viz. alkylation of thiols with alkyl/aralkyl halides and by Michael addition of thiols to conjugated alkenes

Evaluation of the Amphibian Fauna of the Semi-arid and Arid Grassland Habitats in and around the Mayureshwar, Rehekuri, and Karmala Wildlife Sanctuaries in Maharashtra, India

Few studies document amphibian species composition from arid and semiarid environments. Scatteredbodies of water in the semi-arid and arid landscape around Pune, Maharashtra, India, could be viable amphibian habitats; however; information on amphibians using these bodies of water is not available. In a preliminary study, we assessed the amphibian diversity and population status in three wildlife sanctuaries and surrounding areas near Pune. We also compared the use of artificial and natural ponds by amphibians and surveyed the amphibians for the presence of the chytrid fungus

Intracranial hypotension secondary to spinal arachnoid cyst rupture presenting with acute severe headache: a case report

<p>Abstract</p> <p>Introduction</p> <p>Headache is a common presenting complaint and has a wide differential diagnosis. Clinicians need to be alert to clues that may suggest an underlying secondary aetiology. We describe a novel case of headache secondary to intracranial hypotension which was precipitated by the rupture of a spinal arachnoid cyst.</p> <p>Case report</p> <p>A 51-year-old Indian female presented with sudden onset severe headache suggestive of a subarachnoid haemorrage. Investigations including a computed tomography brain scan, cerebrospinal fluid examination and a magnetic resonance angiogram were normal. The headache persisted and magnetic resonance imaging revealed bilateral thin subdural collections, a spinal subarachnoid cyst and a right-sided pleural effusion. This was consistent with a diagnosis of headache secondary to intracranial hypotension resulting from spinal arachnoid cyst rupture.</p> <p>Conclusions</p> <p>Spinal arachnoid cyst rupture is a rare cause of spontaneous intracranial hypotension. Spontaneous intracranial hypotension is a common yet under-diagnosed heterogeneous condition. It should feature significantly in the differential diagnosis of patients with new-onset daily persistent headache.</p

Fetal diastematomyelia: MR imaging: A case report

MRI is increasingly being used in the diagnosis of fetal anomalies suspected on USG. The USG evaluation of fetal spinal anomalies is limited by acoustic shadowing, fetal position and the amount of liquor. Fetal MRI is able to show spinal anomalies well, as in our case of fetal diastematomyelia with a dorsal dermal sinus, suspected on USG at 28 weeks gestation