Selection application of material to be used in hip prosthesis production with analytic hierarchy process

Metallic biomaterials used in making hip prosthesis are required to meet expectations in terms of fatigue strength, corrosion resistance, wear resistance, cost and biocompatibility. It is also desirable that the modulus of elasticity they possess is close to the level of the possible bone. Metallic biomaterials face the problem of ion release even though they meet the criteria mentioned above. As a result, the choice of metallic material to be preferred in the manufacture of hip prosthesis can be made by evaluating all these criteria among themselves and by the performances of biomaterials to be compared according to these criteria. In this study, firstly the criteria expected from the metals to be used as biomaterials have been determined. Expert opinions about the subject and criteria determined in accordance with the studies in the literature by using analytical hierarchy process have been graded according to each other. Afterwards, selection of the most appropriate material was ensured by making the order of importance according to the criteria of the candidate materials.     

Robust multivariable-cascade governors for hydroturbine controls

This paper proposes a new robust multivariable-cascade governor that is based on the polynomial H_X optimisation method for hydroturbine speed controls. Only the bound of uncertainty is required to design a robust governor. Impacts of disturbance and uncertainties are briefly discussed to investigate robustness and performance measures of the system. A non-linear turbine model that includes effects of water hammer, travelling waves and inelastic water penstocks, and disturbance models is considered in the robust design procedure. The robust governor ensures that the overall system remains asymptotically stable for all permissible norm-bounded uncertainties and for system oscillations. Simulation results illustrated in time and frequency domains show the feasibility of the approach and the factors involved in design such that the proposed robust governor even in the presence of norm-bounded uncertainties improves the performance significantly.     

Kinetic Studies on Karlıova Coal

In this study, reaction kinetics of the liquefaction of Karlova coal in a process development unit having three reactors in series have been studied at temperatures of 530–570°C and pressures of 15–25 MPa. It is shown that the rate of hydrogen consumption can be expressed as a function of the concentrations of coal and catalyst, hydrogen partial pressure, reaction temperature, and residence time, and is controlled by the rates of hydrogenation of polynuclear aromatic components and the rates of formation and stabilization of radicals. The relative contribution of these reactions, at any temperature, determines the influence of the hydrogen partial pressure on the rate of the hydrogen consumption. The kinetics of the decomposition reactions of coal to preasphaltene, asphaltene, and oil also have been studied. The apparent activation energies determined are 20 kJ/mol for coal to preasphaltene, 40 kJ/mol for preasphaltene, 66 kJ/mol for asphaltene to oil, and 174 kJ/mol for oil to gases.     

Agglomeration and refragmentation in microscale granular flows

A model is developed to describe dendritic agglomeration in microscale granular flows. The individual particulate grains under consideration are approximated as being spheres that remain spherical after impact. The spheres may adhere to one another, forming branched aggregates (dendrites), based upon an empirical contact pressure relation. The possibility for fragmentation is also included in the analysis. The computational model developed is used to demonstrate agglomeration behavior in granular flows for a range of control parameters. The results indicate that there is a transition from size-unstable agglomeration to size-stable agglomeration; which is controlled by the velocity field and the material properties.     

A large deformation frictional contact formulation using NURBS‐based isogeometric analysis

This paper focuses on the application of NURBS‐based isogeometric analysis to Coulomb frictional contact problems between deformable bodies, in the context of large deformations. A mortar‐based approach is presented to treat the contact constraints, whereby the discretization of the continuum is performed with arbitrary order NURBS, as well as C⁰‐continuous Lagrange polynomial elements for comparison purposes. The numerical examples show that the proposed contact formulation in conjunction with the NURBS discretization delivers accurate and robust predictions. Results of lower quality are obtained from the Lagrange discretization, as well as from a different contact formulation based on the enforcement of the contact constraints at every integration point on the contact surface. Copyright © 2011 John Wiley & Sons, Ltd.     

Degradation of Superconducting Properties in MgB2 by Formation of the MgB4 Phase

Superconducting MgB₂ polycrystalline samples have been fabricated under two different conditions in order to determine the effect of MgB₄ phase. A series of samples was placed in an α-alumina container closed with a cup and fired under high purity argon gas. The other series of samples was placed in an α-alumina boot without any lid and fired under similar conditions. For the first series of samples, we have found pure MgB₂ phase formation and a narrow transition width at 0.4 K. For the second series of samples, significant amount of MgB₄ phase were formed and the T _zero was decreased to 27 K. For both the group of samples magnetization hysteresis loops obtained at various temperature range and applied field up to 2 T. The best J _cmag for the first series of samples was 1.9 × 10⁵ A/cm² at 10 K and 0 T, and for the second series of samples was 0.7 × 10⁴ A/cm² at 10 K and 0 T.     

A comparative study on some physical and mechanical properties of Laminated Veneer Lumber (LVL) produced from Beech (Fagus orientalis Lipsky) and Eucalyptus (Eucalyptus camaldulensis Dehn.) veneers

Laminated Veneer Lumber (LVL) panels made from eucalyptus (Eucalyptus camaldulensis Dehn.) and beech (Fagus orientalis Lipsky.) veneers were tested for physical and mechanical strength properties in this study. Urea formaldehyde (UF) and Polyvinyl acetate (PVA) adhesives were used for eucalyptus LVL panels and UF adhesive for beech LVL panels. The effect of veneer wood species on some physical and mechanical properties was found statistically significant. Also, different glue species caused the differences in strength properties of LVL panels.

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Über einige Eigenschaften von Furnierschichtholzplatten hergestellt aus Buchen- und Eukalyptusfurnieren

Zusammenfassung In diesem Beitrag werden einige physikalische und mechanische Eigenschaften von Schichtholzplatten, hergestellt aus Buchen- (Fagus orientalis Lipsky.) und Eukalyptusfurnieren (Eucalyptus camaldulensis Dehn.) untersucht. Für die Herstellung von Schichtholzplatten wurden die Buchenfurniere mit UF und die Eukalyptusfurniere mit UF und PVA verleimt. Die Ergebnisse zeigen, dass sowohl die Art des Bindemittels als auch die Holzart der Furniere die Eigenschaften der Schichtholzplatten signifikant beeinflussen.

     

Corrosion inhibition performance of polymer-alloy bilayer coatings: electropolymerised polyaniline and electrodeposited ZnNi with different layer orders

Polyaniline (PANI) conducting polymer coatings have been obtained galvanostatically with various current densities (from 0·1 to 0·4 mA cm^?2) and ZnNi alloy coatings have been obtained galvanostatically at 30 mA cm^?2 current density. Corrosion protection performances of monolayered PANI and ZnNi alloy coatings and multi-layered ZnNi/PANI and PANI/ZnNi coatings on st-37 low carbon mild steel (MS) have been investigated by an open circuit potential method, Tafel extrapolation method and electrochemical impedance method in 3·5 wt-% NaCl solution. In addition, the surface morphology of the coatings has been characterised by using scanning electron microscopy (SEM). Synthesising PANI films between two metal layers provided better corrosion protection to the steel. MS/PANI/ZnNi layer formation exhibited the biggest corrosion protection performance among all layer formations of the films and protected MS for up to 72 h.     

Development of a 635 nm-Laser Diode Spectrometer for Continuous Monitoring of Amino Nitrogen in the Beet Sugar Industry

Abstract

The quality of sugar beet is affected by harmful nitrogen compounds. Although nitrogen is one of the essential elements for plants, introduction of excess nitrogen as fertilizer to the soil increases the nitrogen containing compounds in beet which deteriorates the quality of sugar production. Hence, the concentration of soluble nitrogen in beets was monitored as a routine process in the sugar industry. In this work, a low cost, but very long life time laser diode spectrometer, was developed for continuous monitoring of amino nitrogen compounds in sugar beets. A laser diode source emits monochromatic light at 635 nm which is the maximum of absorption spectrum of Cu(II)-glutamine complex. A standard solution of Cu(II) ion and glutamine was prepared at pH = 6.0 to calibrate the laser diode spectrometer. The formation of Cu(II)-glutamine complex was examined at pH = 5.0, 6.0, and 7.0 by a continuous variations method and we found a monovalent complex, Cu(II)(glutamine) at pH = 6.0, and a divalent complex, Cu(II)(glutamine)₂ at pH = 7.0. A continuous mixing system with a peristaltic pump and tubing was set for monitoring of harmful nitrogen in beets, besides sugar determination with a polarimeter and Na and K measurement with a flame photometer, synchronously. The calibration of the laser diode spectrometer yielded a linear correlation coefficient of R² = 0.999. A negative correlation between sugar digestion and amino nitrogen content of sugar beets was found, with a correlation coefficient of R² = 0.807.