Effect of anodization on corrosion behaviour and biocompatibility of Cp-titanium in simulated body fluid

The objective of this investigation is to study the effectiveness of anodized surface of commercial purity titanium (Cp-Ti) on its corrosion behaviour in simulated body fluid (SBF) and proliferation of osteoblast cells on it, to assess its potentiality as a process of surface modification in enhancing corrosion resistance and osseointegration of dental implants. Highly ordered nano-porous oxide layer, with nano-sized pores, is developed on the surface of Cp-Ti through electrochemical anodization in the electrolyte of aqueous solution of 0·5% HF at 15 V for 30 min at 24 °C. The nano-porous feature of the anodized surface is characterized by field-emission scanning electron microscope (FESEM). Pores of some anodized samples are sealed by exposing the anodized surface in boiling water. Corrosion behaviour of the anodized specimen is studied in Ringer’s solution at 30 ± 2 °C, using electrochemical impedance and cyclic polarization technique. Biocompatibility of the anodized surface is accessed using MG63 osteoblast cells. Both corrosion as well as pitting resistance of Cp-Ti in simulated body fluid are found to be highest in the anodized and sealed condition and followed in decreasing order by those of anodized and unanodized ones. Significantly higher MG63 osteoblast cell proliferations are found on the anodized surface than that on the unanodized one. Anodized Cp-Ti develops nano-size surface pores, like that of natural bone. It enhances corrosion and pitting resistance and also the process of osteoblast cell proliferation on Cp-Ti.     

EFFECT OF DIFFERENT PREMILLING TREATMENTS ON DEHULLING OF BLACK GRAM (PHASEOLUS MUNGO L.)

Black gram is mainly used after dehulling. Various types of premilling treatments are applied for proper dehulling. In this study, premilling treatments such as the dry method, chemical and hydrothermal treatments were carried out. It was found that premilling treatments with certain chemicals such as sodium bicarbonate, acetic acid and alcohol were found effective in dehulling black gram. Several vegetable oils at varying concentrations (0.2, 0.4, 0.6, 0.8 and 1.0%) were used; it was found that 0.6% was optimal, except that sesame oil was effective even at 0.2%. Oil treatment gave dhal suitable for use in many traditional products. Although chemicals were effective, they had to be used at relatively high concentrations of approximately 5%. It was also found that a steaming time of 10–15 min was adequate to loosen the hull, resulting in easy dehulling. It was concluded that hydrothermal treatment could be used for dehulling black gram. However, hydrothermally pretreated dhal was not suitable for fermented products, in which case a conventional oil pretreatment method should be used with sesame oil preferred.

PRACTICAL APPLICATIONS

This study shows the effects of different premilling treatments on dehulling black gram. Black gram dehulling efficiency can be enhanced by premilling treatments such as dry method, chemical method or hydrothermal treatment. For practical application, it is important to give due consideration to the end product use of dehulled black gram. Hydrothermal treatment for 10 min is suitable for dehulling black gram if the finished product is used for nonfermented products, and dry method with sesame oil concentration of 0.4% w/w would suit both fermented as well as nonfermented products. This study could be used by black gram processors for optimizing process conditions and premilling treatment.     

Numerical simulation for determination of limit strains of a cold rolled and solution treated Nimonic C-263 alloy sheet

Nimonic alloys are Ni-base superalloys used for several high temperature applications, notable among them are the components in space vehicles, rocket engines, submarines, nuclear reactors, chemical processing vessels and heat exchange tubing as they exhibit excellent mechanical strength and creep resistance at high temperatures. Hence, evaluation of their formability characteristics is of utmost importance to make them into several useful components. Limit strains or forming limit curve is one of the parameters that indicates the formability, especially the drawability of sheet metal for deep drawing applications. In this paper, the limit strains of Nimonic C-263 alloy is investigated and presented using an explicit finite element code LSDYNA 3D. The material properties and the material model are evaluated by conducting tensile tests. The limit strains obtained from the simulation are verified by the analytical equations developed using vertex theory. The results tally within ±10% error.     

Corrosion of Phosphorus Oxynitride Glasses in Water and Humid Air

Phosphorus oxynitride (PON) glasses, prepared by remelting phosphate glasses in anhydrous ammonia vapor, are more resistant to dissolution in water and corrosion in humid environments than the parent phosphate glasses. The chemical durability of PON glasses is directly related to their nitrogen content. Solution analyses, pH stat titrations, and hydrogen depth profiles suggest that nitrogen improves the durability of phosphate glasses by cross-linking the polymeric phosphate chains in the network structure.     

Radiation Effects on the Physical Properties of Low-Expansion-Coefficient Glasses and Ceramics

The effects of irradiation on the coefficient of thermal expansion (CTE), the density, and the elastic moduli of low-CTE materials such as amorphous SiO₂, ultra-low-expansion glass, β-SiC, Astrositall, and Zerodur were surveyed. It was found that the properties of all of these materials were affected by radiation exposures up to 2 × 10⁹ rd; SiO₂ and SiC were the most radiation-resistant of the materials studied.     

Analytical Study of Pure and Extended Portland Cement Pastes: II, Fly Ash- and Slag-Cement Pastes

A range of pastes of portland cement interground with low-calcium fly ash or granulated blast furnace slag was studied by X-ray diffraction, analytical electron microscopy, thermo-gravimetry, and determinations of CO₂ and of unreacted fly ash or slag. Partial replacement of clinker by fly ash results in increased reaction of the alite from at least as early as 3 d. The amount of Ca(OH)₂ formed from a given weight of clinker increases at 3 d due to the enhanced reaction, but from 28 d onward, it decreases due to the pozzolanic reaction. The mean Ca/SI ratio of the C-S-H decreases with time or fly ash content, toward a lower limit of ∼1.4. Partial replacement of clinker by slag also decreases both the amount of Ca(OH)₂ formed from a given weight of clinker and the mean Ca/Si ratio of the C-S-H, but to a lesser extent. Using the methods described in Part I of this paper, the results of the experimental methods were tested for mutual consistency, and volume percents of phases, porosities, and related quantities were calculated.     

Determination of Base Spreading Resistance and Junction Temperature of Uniform-base Junction Transistors†

The propagation of waves in incompressible beam-plasma systems is investigated on the basis of linear fluid equations. The pressure is assumed scalar and the incompressibility condition is chosen to illustrate a class of non-barotropic plasmas. The dispersion law For these linear waves is derived, and is generally discussed. The case of oblique propagation differs appreciably from results obtained for barotropic plasmas, mainly because compressional longitudinal waves are absent. Alfvén. waves in beam-plasma systems are then denned as low-frequency waves, with wave and drift frequencies small compared to gyrofrequencies. The Alfvén approximation of the dispersion law shows that the wave frequency at fixed wave-number is lower than if no streaming were applied.     

USE OF PUMPED-HYDRO AS PEAK-LOAD MANAGEMENT PLANT IN OPTIMAL SCHEDULING OF POWER SYSTEMS

ABSTRACT

The system demand, during some intervals of a day, may exceed the available system generation (excluding the pumped-hydro generation). A pumped-hydro plant may then, be used as a peak-load management unit to safeguard the power system by minimizing the power blackout in order to avoid large deviation in system frequency. In this paper, an algorithm is presented to obtain the optimal schedule for hydro, thermal plants including the pumped-hydro unit by proper selection of initial feasible trajectory for the pumped-hydro plant. An additional constraint is introduced to ensure the power balance in each time interval during the perturbation of water storage trajectory. The proposed method decomposes the problem into hydro and thermal subproblems and solves them alternately. The hydro subproblem is solved using a search procedure namely, the local variation method and the thermal subproblem is solved using a judicious combination of participation factors/linear programming method. Optimal scheduling was conducted on a 9-bus system and a 66-bus Utility system. The results obtained for the above two systems demonstrate the effectiveness of the algorithm proposed.