Abstract: For gamma radiation detection, assemblies having
scintillation crystals and a photomultiplier tube, also there is a
preamplifier connected to the detector because the signals from
photomultiplier tube are of small amplitude. After pre-amplification
the signals are sent to the amplifier and then to the multichannel
analyser. The multichannel analyser sorts all incoming electrical
signals according to their amplitudes and sorts the detected photons
in channels covering small energy intervals. The energy range of
each channel depends on the gain settings of the multichannel
analyser and the high voltage across the photomultiplier tube. The
exit spectrum data of the two main isotopes studied ,putting data in
biomass program ,process it by Matlab program to get the solid
holdup image (solid spherical nuclear fuel)
Abstract: Coronary artery bypass grafts (CABG) are widely
studied with respect to hemodynamic conditions which play
important role in presence of a restenosis. However, papers which
concern with constitutive modeling of CABG are lacking in the
literature. The purpose of this study is to find a constitutive model for
CABG tissue. A sample of the CABG obtained within an autopsy
underwent an inflation–extension test. Displacements were
recoredered by CCD cameras and subsequently evaluated by digital
image correlation. Pressure – radius and axial force – elongation
data were used to fit material model. The tissue was modeled as onelayered
composite reinforced by two families of helical fibers. The
material is assumed to be locally orthotropic, nonlinear,
incompressible and hyperelastic. Material parameters are estimated
for two strain energy functions (SEF). The first is classical
exponential. The second SEF is logarithmic which allows
interpretation by means of limiting (finite) strain extensibility.
Presented material parameters are estimated by optimization based
on radial and axial equilibrium equation in a thick-walled tube. Both
material models fit experimental data successfully. The exponential
model fits significantly better relationship between axial force and
axial strain than logarithmic one.
Abstract: The present paper deals with the experimental and
computational study of axial collapse of the aluminum metallic shells
having combined tube-frusta geometry between two parallel plates.
Shells were having bottom two third lengths as frusta and remaining
top one third lengths as tube. Shells were compressed to recognize
their modes of collapse and associated energy absorption capability.
An axisymmetric Finite Element computational model of collapse
process is presented and analysed, using a non-linear FE code
FORGE2. Six noded isoparametric triangular elements were used to
discretize the deforming shell. The material of the shells was
idealized as rigid visco-plastic. To validate the computational model
experimental and computed results of the deformed shapes and their
corresponding load-compression and energy-compression curves
were compared. With the help of the obtained results progress of the
axisymmetric mode of collapse has been presented, analysed and
discussed.
Abstract: This paper presents the effect of corrugation profile
geometry on the crushing behavior, energy absorption, failure
mechanism, and failure mode of woven roving glass fibre/epoxy
laminated composite tube. Experimental investigations were carried
out on composite tubes with three different profile shapes: sinusoidal,
triangular and trapezoidal. The tubes were subjected to lateral
compressive loading. On the addition to a radial corrugated
composite tube, cylindrical composite tube, were fabricated and
tested under the same condition in order to know the effect of
corrugation geometry. Typical histories of their deformation are
presented. Behavior of tubes as regards the peak crushing load,
energy absorbed and mode of crushing has been discussed. The
results show that the behavior of the tube under lateral compression
load is influenced by the geometry of the tube itself.
Abstract: Thermal water hammer is a special type of water
hammer which rarely occurs in heat exchangers. In biphasic fluids, if
steam bubbles are surrounded by condensate, regarding lower
condensate temperature than steam, they will suddenly collapse. As a
result, the vacuum caused by an extreme change in volume lead to
movement of the condensates in all directions and their collision the
force produced by this collision leads to a severe stress in the pipe
wall. This phenomenon is a special type of water hammer. According
to fluid mechanics, this phenomenon is a particular type of transient
flows during which abrupt change of fluid leads to sudden pressure
change inside the tube. In this paper, the mechanism of abrupt failure
of 80 tubes of 481 tubes of a methanol heat exchanger is discussed.
Initially, due to excessive temperature differences between heat
transfer fluids and simultaneous failure of 80 tubes, thermal shock
was presupposed as the reason of failure. Deeper investigation on
cross-section of failed tubes showed that failure was, ductile type of
failure, so the first hypothesis was rejected. Further analysis and more
accurate experiments revealed that failure of tubes caused by thermal
water hammer. Finally, the causes of thermal water hammer and
various solutions to avoid such mechanism are discussed.
Abstract: This work has been carried out in order to provide an understanding of the physical behaviors of the flow variation of pressure and temperature in a vortex tube. A computational fluid dynamics model is used to predict the flow fields and the associated temperature separation within a Ranque–Hilsch vortex tube. The CFD model is a steady axisymmetric model (with swirl) that utilizes the standard k-ε turbulence model. The second–order numerical schemes, was used to carry out all the computations. Vortex tube with a circumferential inlet stream and an axial (cold) outlet stream and a circumferential (hot) outlet stream was considered. Performance curves (temperature separation versus cold outlet mass fraction) were obtained for a specific vortex tube with a given inlet mass flow rate. Simulations have been carried out for varying amounts of cold outlet mass flow rates. The model results have a good agreement with experimental data.
Abstract: In this paper, computational fluid dynamics (CFD) is utilized to characterize a prototype biolistic delivery system, the biomedical device based on the contoured-shock-tube design (CST), with the aim at investigating shocks induced flow instabilities within the contoured shock tube. The shock/interface interactions, the growth of perturbation at an interface between two fluids of different density are interrogated. The key features of the gas dynamics and gas-particle interaction are discussed