Vol.
9, April 2002, pp. 91-97
Neutron sensitivity
improvement in boron-lined proportional counters
P M Dighe, K R Prasad & S K Kataria
Various techniques
have been employed to improve the neutron sensitivity of boron-coated
proportional counters developed indigenously. A boron-lined proportional
counter (67 mm ID ´ 750 mm length) of 17 cps/nv thermal neutron
sensitivity is developed by coating 92% enriched 10B on the inner
wall of the counter. This counter can be used for low thermal neutron flux
(~0.2 nv) at various applications such as neutron area monitoring, reactor
start-up instrumentation, assay of fissile materials and detection of fuel
failure. An improvement in sensitivity was also achieved by summing the output
signals from four 10B lined counters and two BF3
proportional counters. The summation did not change the susceptibility of the
device to gamma interference. In view of the scarcity of enriched 10B
isotope, indigenously available natural boron coated two prototype proportional
counters are developed of 0.8 cps/nv and 1.1 cps/nv thermal neutron
sensitivity. Efforts have been made to improve the sensitivity with boron
coated 3-dimensional structures introduced into the sensitive volume. Tests in
thermal neutron flux showed 50% improvement in the sensitivity due to the
introduction of additional boron coated wires. Another counter with 51
boron-coated annular discs (23 mm OD ´ 10 mm ID ´ 1 mm thick)
mounted perpendicular to the axis of the cathode showed 1.7 cps/nv neutron
sensitivity, an improvement by a factor of 2.5.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, April 2002, pp. 98-102
Elegant
and accurate closed form solutions to predict vibration and buckling behaviour
of slender beams on Pasternak foundation
G Venkateswara Rao & K Kanaka Raju
Elegant and accurate closed form solutions to
predict the vibration and buckling of slender beams on Pasternak (two parameter
elastic) foundation have been derived using simple single term trigonometric
functions which satisfy the geometric boundary conditions in conjunction with
the Rayleigh-Ritz method. Bernoulli-Euler beam theory is used for the analysis.
Simply supported, cantilever and clamped boundary conditions are considered in
the present study. Numerical results for the fundamental frequency and buckling
load parameters are presented in the form of Tables. The present results show
an excellent agreement when compared with those obtained by the versatile
finite element method. An anomaly observed in the case of the buckling problem
for very high first foundation stiffness parameter, is explained clearly for
the case of a simply supported beam and corrective measure in terms of the mode
of buckling is provided.
Vibration analysis
of visco-elastic clamped circular plates subjected to
thermal gradient
S B Singha & M Arifb
An analysis of
vibration of visco-elastic circular plate of variable thickness subjected to
thermal gradient is presented here. The governing differential equation has
been solved for free vibrations of visco-elastic circular plate, which is
clamped along the boundary. Galerkins technique has been applied to obtain
corresponding natural frequencies in the form of explicit formulae. Deflection,
time period and logarithmic decrement at different points for the first two
modes of vibration are calculated for various types of thermal gradient and
taper constant and are illustrated with tables and graphs.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, April 2002, pp. 109-114
Prediction of strength and workability of high performance
concrete composites using artificial neural networks
S Rajasekaran & R Amalraj
A model based on an Artificial Neural
Network for predicting the compressive strength and workability for various
mixes of High Performance Concrete (HPC) from M80 to M150 is presented. It is
felt that the conventional methods of design of concrete mixes may not be
suitable for HPC because, with the addition of silica fume, more water content
is needed that can be eliminated by using high range water reducing admixtures
for achieving the same workability. Further, the compressive strength and
workability properties of HPC mixes are greatly influenced by several
parameters, viz. fine aggregate, coarse aggregate, water-cement ratios, and
percentage of silicafume and super-plasticizer. Consequently, developing a
standard mix design procedure for HPC mixes requires an extensive understanding
of relation between these parameters and the properties of the resulting mix.
Developing an empirical formula for predicting the compressive strength and
workability of HPC is extremely difficult because of non-linear interaction
among the various parameters.
A numerical study on
the physics of mixing in two-dimensional supersonic stream
Mohammad Alia, Toshi Fujiwarab
& Anwar Pervezc
A numerical
investigation has been performed on the physics of mixing for better
understanding about the penetration and mixing mechanism, and eventually to
find out the means of increasing the mixing efficiency. The two-dimensional
full Navier-Stokes equations with an explicit Harten-Yee Mon-MUSCL
Modified-flux-type Total Variation Diminishing (TVD) scheme have been used. A
zero-equation algebraic turbulence model has been used to calculate the eddy
viscosity coefficient. For this study the air of Mach number 5.0 is considered
as main flow. Hydrogen gas at sonic condition is injected perpendicularly into
it. The effects of molecular and turbulent diffusion coefficients, and that of
boundary layer on mixing have been analyzed and discussed. The results show
that upstream re-circulation plays an important role to increase the mixing of
side jet with the main flow of high Mach number. It has been found that the
mixing is only possible by incorporating the molecular diffusion terms in the
Navier-Stokes equations. The use of turbulence model increases the penetration
height of hydrogen in the mixing field.
Treatment of phenol rich aqueous solutions using surface
modified pillared clay
V P Vinod & T S Anirudhan*
The efficacy of
humic acid treated zirconium pillared clay (HA-PILC) in the removal of phenol
from aqueous solution has been investigated using batch adsorption technique at
different sorbate concentrations, rate of agitation, pH and temperature. The maximum removal of
98.0, 84.0 and 73.2 % has been noted at pH 5.0 for an initial concentration of 25,
50 and 100 mg/L respectively. The maximum adsorption capacity has been observed
at pH
5.0. The process of uptake follows a first-order reversible kinetic expression.
The removal process has also been found to be diffusion controlled. The
adsorption capacity has been increased from 78.2 to 92.6 % with an increase in
agitation speed from 100 to 400 rpm at an initial concentration of 50 mg/L. The
adsorption isotherm for phenol removal may be classified as L-type of the Giles
classification, which suggests a favourable adsorption, and the adsorbent has a
high affinity for phenol. The adsorption data points have been fitted to both
Langmuir and Freundlich isotherm equations. The maximum adsorption capacity (Q0) decreases from 179.86 mg/g at 10°C to 126.69
mg/g at 40°C. Lower temperature has been found to be more
effective in the removal of phenol. Thermodynamic parameters such as DG0, DH0 and DS0 for the adsorption process have been
calculated to predict the nature of adsorption process. Cost of the HA-PILC and
its adsorption capacity with other adsorbent materials reported in the
literature, have also been presented.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, April 2002, pp. 137-140
Nanocrystalline lead ruthenium
pyrochlore as oxygen reduction electrode
V Raghuveer, Keshav kumar & B Viswanathan*
The synthesis of nanocrystalline Pb-Ru
pyrochlore of composition Pb2Ru1.95Pb0.05O7-d was studied for the potential usage
in the electrochemical reduction of oxygen. The nanocrystalline pyrochlore was
synthesized by reverse micellar method. The single phase oxide formation and
crystallite size determination (1-20 nm) were carried out using X-ray
diffraction and transmission electron microscopic studies respectively. The
electrocatalytic activity for oxygen reduction and its comparison with the
oxide prepared by conventional ceramic method are also reported here.
Inhibition of corrosion
of mild steel by nitrite, hydrogen phosphate and molybdate ions in aqueous
solution of sodium chloride
Rita Mehra & Aditi Soni
Inhibition of mild
steel in aqueous sodium chloride by sodium nitrite, disodium hydrogen phosphate
and sodium molybdate with respect to the inhibitor concentration and
temperature is reported here. Na2MoO4 shows highest
efficiency (90.00%) followed by NaNO2 (87.56%) and Na2HPO4
(85.36%). As such, the order of inhibition observed is Na2MoO4>NaNO2>Na2HPO4.
Thermodynamic as well as kinetic parameters including activation energy (Ea),
change in free energy of adsorption (DG), entropy of adsorption (DS), corrosion
current (Icorr), open circuit potential (OCP), Tafel slopes (ba, bc) and threshold limiting value (TLV) for protective
film formation have also been calculated from weight loss and potentiostatic
polarisation methods.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, April 2002, pp. 147-152
Influence of altered basalt on the burnability
of portland cement clinker
El- Sayed
Ali El-Alfi
Synthesis of portland cement clinker from
cement raw mixes containing altered basalt was studied. The clay of the raw mix
of portland cement was substituted by basalt in ratios 0, 15, 30, 45 and 60
wt.%. The ingredients of the mixes were intimately homogenized, mixed, moulded
into a compact mass and fired at 1200, 1250, 1300, 1350 and 1375ēC for two
hours soaking time. The burnability of each raw mix was investigated by the
determination of insoluble residue, free lime contents and the phase
composition of the fired products. The results show that the clinker formation
was completed at 1300ēC in the presence of 30-60 wt.% basalt.
Effect of ambient H2S
atmosphere on the optical, structural and electrical properties of vacuum
deposited
thin films of cadmium sulphide
Virendra Singh*a, Beer Pal Singha,
Kasturi Lalb, R C Tyagia & T P Sharmaa
Evaporated thin
films of cadmium sulphide have been deposited in a low ambient atmosphere of H2S
(~10-4 torr). The H2S atmosphere was obtained by
controlled thermal decomposition of thiourea inside the vacuum chamber. Keeping
the substrates at an elevated temperature of about 200ēC helps eject any
sulphur atoms deposited due to thermal decomposition of CdS during evaporation.
The cadmium ions promptly recombined with the H2S to give better
stoichiometry of the deposited films. The films grown by this technique have
better uniformity and have better crystallinity. Apart from being more adherent
to the substrates, such films are pin-holes free, which is a very vital factor
in any device fabrication. The technique is applicable for all sulphide films
including ZnS, PbS, CuS. Optical, electrical conductivity, X-ray diffraction
and scanning electron microscope patterns are presented to show the better
quality of the sulphide films deposited by this technique.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, April 2002, pp. 156-158
Performance
evaluation of Ogwasi lignite coal under adiabatic condition
J Soji Adeyinkaa* & F O
Akinbodeb
Adiabatic condition was used to evaluate
gasification of a low-grade lignite coal. Carbon boundary theory was used to
evaluate CO2:CO and C:CO conversion in the bed. Temperature analysis
conformed to CO:CO2 yield at 90% air factor and a carbon to carbon
monoxide yield was improved by converting CO2 at the carbon
boundary.