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Engineering
Adaptive Delaunay triangulation for steady-state and transient heat transfer analyses	245
Sutthisak Phongthanapanich & Pramote Dechaumphai

Characterization of slug flow in horizontal channels	261
A M Surendrakumar & Kannan Iyer

A modified version of potentiometer	265
R N Pathak & Archana Maurya

Breakage parameters of some minerals and coals ground in a laboratory size ceramic mill	269
A Ozkan, M Yekeler & S Aydogan

Ferrofluid lubrication equation for porous bearings considering anisotropic permeability and slip velocity	277
Rajesh C Shah & M V Bhat

Thermo-magnetic convection in ferrofluids with gravity-modulation reference	282
Renu Bajaj

Materials Science
Comparative studies on Al₂O₃ based nanocomposites of some speciality polymers and binary polymers with the corresponding SiO₂, MnO₂ and ZrO₂ based nanocomposites	292
Nirmalya Ballav, Arjun Maity & Mukul Biswas

Effect of particle inclusions on the mechanical properties of composites fabricated by liquid metallurgy	301
S Charles & V P Arunachalam

Power injection molding and sintering of austenitic stainless steel	306
A K Mishra, S Paul, A Upadhyaya, T Barriere & J C Gelin

Naturally occurring biopolymer as ion conducting material: Water uptake, swelling and conductivity studies	314
Harinder Pal Singh, Ranjit Kaur & S S Sekhon

A new brightener for zinc plating from non-cyanide alkaline bath	318
Y Arthoba Naik & T V Venkatesha

Effect of bandwidth and size disorder on the electrical and magnetotransport properties of doped LaMnO₃ perovskite	324
C M Thaker, D S Rana, Krushna Mavani, S I Patil, M Sahasrabudhe & D G Kuberkar

Preparation and characterization of silver doped (ZnCd)S mixed mechanoluminophors	329
Sanjay Tiwari, Shikha Tiwari & B P Chandra

Adaptive Delaunay triangulation for steady-state and
transient heat transfer analyses

A finite element method is combined with the Delaunay triangulation and the adaptive remeshing technique to find solutions of both steady-state and transient heat transfer problems. The Delaunay triangulation and the adaptive remeshing technique are explained in detail. The solution accuracy and the effectiveness of the combined procedure are evaluated by heat transfer problems that have exact solutions. These problems include steady-state heat conduction in a square plate subjected to a highly localized surface heating, and a transient heat conduction in a long plate subjected to a moving heat source.

Characterization of slug flow in horizontal channels

A brief study of slug characteristics is reported here. The aim of the present work is to perform in depth analysis of the characteristics of slug flow in horizontal channels. A brief explanation of the experimental set up with instrumentation is reviewed. The data reduction procedure is employed to obtain different characteristics by experimental set up and the corresponding results are also discussed.

A modified version of potentiometer

The simple potentiometer circuit for emf measurements based on poggendorf’s compensation principle has been, successfully, modified by introducing four Push Buttons (each containing six-base pins) in place of simple on/off keys. The modified circuit enables one to compare the emf of 1:1 or 1:2 cells putting them parallel to meter wire without the botheration of connecting and disconnecting several electrical wires. In fact, it is the circuit which is a resultant obtained by coupling different stages of measurements into one circuit. Just press a button and the circuit changes to another one.

Breakage parameters of some minerals and

coals ground in a laboratory size ceramic mill

The kinetics of batch dry and wet grindings of calcite, barite, quartz, lignite and anthracite from feeds of sieve size -425+300 µm has been determined using a laboratory scale ceramic ball mill. The S₁ values obtained were the highest (0.294 min^-1) for anthracite and the lowest (0.071 min^-1) for quartz when ground dry. However, the wet grinding of these materials gave higher S₁ values by a factor of 1.28 for calcite, 1.15 for barite, 1.25 for quartz, 1.11 for lignite and 1.07 for anthracite comparing to the dry S₁ values. The B_i,j values also changed for all the materials ground as dry and wet. The simulations of the product size distributions for both first-order and non-first order breakage of the materials ground were in good agreement with the experimental size distributions. There is a relationship between the S₁ values and the g value of B_i,j parameter; i.e., S₁ values increase when g values decrease, indicating that faster breakage rates of top sizes produce more fines in the finer size distribution region (–150 µm).

Ferrofluid lubrication equation for porous bearings considering anisotropic permeability and slip velocity

A Reynolds type equation was derived for the lubrication of porous bearings considering slip velocity at the porous-film interface and anisotropic permeability in the porous matrix. A ferrofluid lubricant flowing as per Jenkins model was used with an oblique magnetic field. Various special cases were deduced from the lubrication equation.

Thermo-magnetic convection in ferrofluids with gravity-modulation

Convection in magnetic fluids is considered in the presence of vertical magnetic field and periodically modulated gravitational field. Depending upon the different physical parameters, modulation may have destabilizing effect on the unmodulated stable system. Also, the unstable system may get stabilized with modulation. Instability may occur either as subharmonic instability or harmonic instability. Using Floquet theory, the regions of parametric instability have been obtained.

Comparative studies on Al₂O₃ based nanocomposites of some speciality polymers and binary polymers with the corresponding SiO₂, MnO₂ and ZrO₂ based nanocomposites

Al₂O₃ based nanocomposites of speciality polymers such as poly-N-vinylcarbazole (PNVC), polypyrrole (PPY) and polythiophene (PTP) and of binary polymers PNVC-PPY, PNVC-PTP or PNVC-PANI were prepared and characterized by FTIR spectroscopic analyses. General bulk properties such as thermogravimetric stability, morphological features (SEM) and particle sizes (TEM) were investigated and compared with those reported with other nano-oxide (SiO₂, ZrO₂, MnO₂) based polymers prepared by similar procedures. Thermal stabilities of the polymer-metal oxidecomposites and of the binary polymer-Al₂O₃ based composites were appreciably improved compared to the same for the unmodified base polymers. SEM analyses revealed the presence of lumpy aggregates of smaller particles forming a ‘raspberry’ morphology pattern. TEM studies showed formation of spherical particles of sizes varying between 24-500 nm depending on the nature of the oxides and monomers used. The d.c. conductivities of the composites were in the range of 10^-5-10^-7 S/cm for the PNVC based systems including the binary copolymer composites, 10^-2-10^-4 S/cm for PPY-based systems, 10^-3 S/cm for PTP-based systems and (0.03-6.1)´10^-2 S/cm for PANI-based systems. The nature of the metal oxide counterpart did not influence the conductivity values. These composites were dispersible in aqueous medium- the dispersion stabilities being different from system-to-system depending on the polymers and the nature of the oxide counterpart.

Effect of particle inclusions on the mechanical properties of composites fabricated by liquid metallurgy

Metal Matrix composites refer to a family of metal-based materials reinforced with fiber, whisker or particulate, which can produce considerable alteration in the physical and mechanical properties of the base alloy. The present work investigates the influence of particle additions in the basic properties of the composite. Adding dispersoids such as quartz, magnesium and silicon carbide to the matrix increases their strength and hardness. Wear resistance is found to increase with increase in percentage composition. Microstructural examination of the specimens shows fairly uniform distribution of the dispersoids.

Powder injection molding and sintering of

austenitic stainless steel

This paper describes powder metallurgy (P/M) processing approach to consolidate ferrous alloys for automotive applications. The net shape and corrosion/oxidation requirements in automotive components, such as exhaust flanges, necessitate P/M processing route giving the advantage of alloying flexibility and precision manufacturing. One variant of P/M processing is powder injection molding (PIM) where complex-shaped components on a large scale are fabricated.

In this study, experiments were performed on 316L stainless steels using compacts shaped by pressing and powder injection molding (PIM). In the conventional process, the austenitic stainless steel compacts were solid-state sintered at 1250°C and supersolidus liquid phase sintered (SLPS) at 1400°C. The injection molded 316L stainless steel feedstock were injected, thermally debound and sintered. The rheological behavior of the binder was investigated through in situ imaging. Density of the stainless steel samples sintered by supersolidus liquid phase sintering was higher than the solid-state sintered samples. The effect of sintering temperature on the microstructural evolution was characterized. The PIM stainless steel components attained nearly full density with a uniform shrinkage.

Naturally occurring biopolymer as ion conducting material: Water uptake, swelling and conductivity studies

Naturally occurring biopolymer – gum arabica, which is obtained from acacia tree, is being used for its excellent medicinal properties and has been found to be an ionic conductor. This biopolymer has been found to show high value of ionic conductivity after swelling and conductivity of the order of 10^-3 S/cm at room temperature has been observed. Water uptake study shows this polymer to be superabsorbant in nature and has been found to reach a saturation level in about five hours. The conductivity of this biopolymer has been found to increase with swelling which suggests that the biopolymer releases ions during swelling which take part in the conduction process.

A new brightener for zinc plating from

non-cyanide alkaline bath

Zinc electrodeposition from non-cyanide alkaline solution was carried out in presence of salicylaldehyde, a new brightener. The bath constituents and bath variables were optimized through standard Hull cell experiments. Current efficiency and throwing power of the developed bath were measured. Polarization study revealed the shifting of potential towards more cathodic direction in presence of addition agents. Corrosion resistance test on zinc coated steel revealed good protection of the base metal by the zinc coating. SEM photomicrographs of the deposits showed fine-grained crystal growth in the presence of salicylaldehyde. The consumption of brightener was 0.4 mLL^-1 for 1000 A-h.

Effect of bandwidth and size disorder on the electrical and magnetotransport properties of doped LaMnO₃ perovskite

Structural, electrical, magnetic and magnetotransport measurements have been carried out on La_1-2xPr_xCa_xMnO₃; x = 0.20 and 0.30 manganite compounds. These samples form in a distorted orthorhombic structure and behave as nearly low bandwidth systems. Both these samples exhibit insulator-metal transition below 120 K with a large colossal magnetoresistance (CMR) effect at relatively weaker fields (MR=75% at 1 Tesla for x = 0.30 sample). We have also studied the structural, transport and magnetotransport properties of a larger size cation, Sr²⁺, substituted La_0.5Pr_0.2Ca_0.3-xSr_xMnO₃ (0.0£x£0.20) compounds. It is observed that increasing Sr²⁺ substitution results in an enhancement in transition temperature with a subsequent fall in MR%. The insulator-metal transition temperature for these samples increases from 138 K for x=0.0 to 252 K for x=0.20. The CMR effect fall from 46% for x=0.0 to less than 10% for x=0.20 at a field of 1 Tesla. Also, for samples with higher Sr content the MR% at low temperature is comparable to the MR% in the vicinity of peak resistance. The resistance data in the semiconducting region of all the samples obeys the Mott’s Variable Range Hopping type
(lnR µ T^-0.25) of conduction mechanism.

Preparation and characterization of silver doped (ZnCd)S mixed mechanoluminophors

Mechanoluminescence (ML) in silver doped (ZnCd)S phosphors is reported. Considering the basic processes involved in (ML), a theoretical approach is made to understand the mechanical characteristics of ML. The expressions derived are able to explain the dependence of ML intensity on several parameters like temperature, time, area of newly created surfaces and surface charge density. Spectroscopic studies of ML are made. The wavelength corresponding to the peak of both the ML and photoluminescence (PL) spectra shift towards longer wavelength with increasing CdS contents. The mechanism of ML is discussed and it is concluded that the impulsive deformation of these phosphors may be due to piezo-electrification of newly created surfaces. The similarity of ML spectra with electroluminescence (EL) and photoluminescence (PL) spectra suggests that although there is a difference in the process of excitation of electrons whereas the relaxation with the emission of photons involves the same process.

ISSN : 0971-4588		CODEN : IEMSEW
VOLUME 10	NUMBER 4	AUGUST 2003

Indian Journal of Engineering & Materials Sciences

Engineering

Materials Science

Adaptive Delaunay triangulation for steady-state and transient heat transfer analyses