Al-Nahrain Journal for Engineering Sciences

Transient solutions will be developed for laminated
simply supported closed cylindrical shells subjected
to a uniform dynamic pressure at the outer surface
of the cylinder. These solutions are obtained by
using General Third Shell Theory (G.T.T.).
Rectangular pulse, triangular pulse, sinusoidal
pulse and (ramp-constant) load-time varying
functions are studied and the required equilibrium
equations are developed. The central deformation
and principle stresses are investigated for different
cross-ply laminates.

In this paper, a comprehensive study of friction
damper stiffness effects on the response
characteristics of a typical turbine blade executing
steady-state motion, is explored. The damper is
modeled as a one-bar microslip type assembled in
the intermediate platform attachment of the blade
leaving the other attachment of a shroud mass at
the blade tip to be free. A discrete lumped mass
approach, previously theorized in another paper, is
employed to predict the response amplitudes as well
as the slip length parameter at any state of the
forced
frequency including the resonance
condition. The analysis covers a practical range of
damper stiffness values adapted from relevant
studies in this field. The present main outputs show
that a magnificent rising of the response occurs
with the increase in the stiffness, the characteristic
behavior varies appreciably and the resonant
amplitudes tend to increase linearly at high levels of
damper stiffness, whereas the corresponding
frequency and slip length show almost uniform
trend. The results can serve very well for design and
control purposes in the pre-manufacture stages of
the given blade-damper system.

The oxidation of Al-Li base alloy containing small
amounts of rare earth (RE) oxides such as Y2O3 and
Nd2O3 particles has been studied at temperatures
between 300°Cand 550°C. The lithium is selectively
oxidized in Al-Li alloys and the parabolic rate
constants for the growth of the resulting oxides layer
Li2O, LiAl5O8, Li2CO3 and Li5AlO4 are about an
order of magnitude higher than those for growth of
oxides on alloy (Al-Li) with RE oxides. Alloys used
in this study were prepared by melting and casting in
a permanent steel mould under controlled
atmosphere.
It was found that 0.2%Y2O3 containing alloys
possess the lowest oxidation rate and show great
improvements in oxidation resistance compared to
the base alloy.
Oxides found on base alloy are subjected to
cracking and spalling during thermal shock at high
temperature i.e. 500°Cand 550°C. Identification of
oxidation kinetics was carried out by using weight
gain measurements while scanning electron
microscopy (SEM) and x-ray diffraction analysis
were used for microstructural morphologies and
phase identification of the oxide scales. The weight
gain measurement results suggest that the oxidation
kinetic of all studied alloys follows the parabolic law
in most experimental tests under the different
temperatures except at 300°C oxidation kinetic
follows almost a logarithmic rate law.

A theoretical study is performed to determine the
turbulent Prandtl number (Prt ) for liquids of wide
range of molecular Prandtl number (Pr=1 to 600)
under turbulent flow conditions of Reynolds number
range 10000- 100000 by analysis of experimental
momentum and heat transfer data of other authors. A
semi empirical correlation for Prt is obtained and
employed to predict the heat transfer coefficient for
the investigated range of Re and molecular Prandtl
number (Pr). Also an expression for momentum eddy
diffusivity is developed. The results revealed that the
Prt is less than 0.7 and is function of both Re and Pr
according to the following relation:
Prt=6.374Re-0.238 Pr-0.161
The capability of many previously proposed models of
Prt in predicting the heat transfer coefficient is
examined. Cebeci [1973] model is found to give good
accuracy when used with the momentum eddy
diffusivity developed in the present analysis. The
thickness of thermal sublayer decreases with
Reynolds number and molecular Prandtl number.

An experimental Michelson interferometer
arrangement has been implemented utilizing the
principle of laser Doppler vibrometry. He-Ne laser
has been used as a coherent light source. The
circuit for heterodyne detection has been built to
detect and record Doppler signals. Two types of
materials have been used as vibrating panel, which
are excited by acoustic waves applied from a
loudspeaker connected to a function generator.
The applied waves were in frequency range of 10
100Hz. The recorded results of the experimental
work demonstrate that the vibration frequency of
the panel conforms to the applied frequency when
the ratio between the applied and natural
frequencies is greater than two (or less than one
half).

Hemodialysis is a technique of removing, or clearing ,
solutes from the blood and removal of extra fluid from
the body, by using dialyzing machine and a dialyzer
which is also known as (artificial kidney). The principle
of hemodialysis is, primarily, the diffusion of solutes
across a semipermeable membrane and ultrafiltration
for removal of extra fluid.
The purpose of this study is to demonstrate the effect of
increasing nominal dialysate flow rate from 500 ml/min
to 800 ml/min on the amount of the small solutes (urea)
removed from the blood and examine its effect on the
amount of dialysis delivered.
In this study the in vivo effects of increase in dialysate
flow rate on the delivered dose of dialysis studied on 28
maintenance hemodialysis patients.
Hemodialysis was performed at dialysate flow rates 500
and 800 ml/min. The patients treated two times per week
for 3 hours. The results show increase in urea clearance
and dialysis adequacy, and a significant increase in the
urea difference between pre- and post-blood urea
concentration by increasing dialysate flow rate from 500
to 800 ml/min.
It can be concluded that hemodialysis with dialysate
flow rate 800 ml/min should be considered in selected
patients not achieving adequacy despite extended
treatment times and optimized blood flow rate. And
increasing nominal dialysate flow rate from 500 ml/min
to 800 ml/min alters the mass transfer characteristics of
hollow fiber hemodialyzer and results in a larger
increase in urea clearance.