Al-Nahrain Journal for Engineering Sciences

Two dimensional numerical study of the effect of high thermal conductive baffles on natural convection
heat transfer in saturated porous medium inside enclosure. The top and bottom surface of the enclosure are
insulated, the two vertical walls of the enclosure have different constant temperature, high conductive thin
baffles are attached on the two vertical walls. The governing equations were solved by finite difference method.
The results inserted for different value of Rayleigh number and different position s of the baffles with change in
length of baffles, when the baffles attached to the hot and cold walls in distances (0.25,0.75) respectively from
bottom surface, also when the baffles attached to the hot and cold walls in distance ( 0.75 , 0.25 ) respectively
from bottom surface. The length of baffles in the two cases changed in range ( 0.2 0.8 ). For the above cases
The Rayleigh number changed in range ( 150 750 ). The results are represented by streamlines and isotherm
lines to show the behavior of the fluid circulation and temperature distribution. Also some graphics had been
obtained which represent the relationship between Nusselt and Rayleigh numbers with the position and length of
baffles. The results show that increasing Rayleigh number leads to increase in the Nusselt number for two
cases. But in the two cases the increasing in the baffles length results a decreases in Nusselt number.
(Key words: natural convection, porous medium, Baffle, Enclosure)

This research investigates the influence of solid loading ratio , Reynolds number & angle of flow
direction change on minor losses coefficient for two-phase flow type gas-solid through an orifice by
manufacturing a special apparatus with solving the equations mathematically .
Three different angles of elbow 15 , 30 & 45 deg. was chosen to study this effect on minor losses head
and minor losses coefficient for a solid loading ratio range 0 to 1.9 , Reynolds number range 36209 to
78078 .
It is found that the minor losses head decrease with increase of mixture velocity and Reynolds number
with relationship of elbow angle increasing linearly with solid loading ratio increment . also the minor
losses coefficient increasing with minor losses head increment and linearly with mixture velocity ,
Reynolds number as same as solid loading ratio . fig.(1) shows the apparatus which used in this research .

In this study a new criteria is adopted by
the use of Rectilinear Diameter principle to
express the saturated vapor and liquid enthalpies
at the coexisting phases for pure substances and
mixtures, this requires another relation that used
to calculate enthalpies of vaporization at the
corresponding temperatures.
The relationships between saturated
vapor enthalpy, saturated liquid enthalpy and
pressure are investigated for many pure
substances. These investigations show that the
saturated vapor and liquid enthalpies cannot be
described by pressure as a simple general relation.

Experimental investigation was conducted to
study the dynamics of double-pipe heat exchanger
using step change in flow rate of hot water and
observe its effect on the temperature of cold water
and it was found that the transfer function can be
represented by first order system plus dead time
(FOPDT).
MATLAB 7.4 simulation and programming was
used to show the response of close-loop system
using P, PI, PID and fuzzy logic control.
The Smith predictor was used to remove the
effect of transport delay on the process and it was
found that this method greatly improve the
response of the system. The stability of the overall
closed loop system was proved by using Bod plot
diagram.

The basic approach taken here works
by finding predictable higher-order statistics of
natural images within a multi-scale
decomposition, and then showing that
embedded messages alter these statistics. A
Fisher linear discriminant analysis is then used
to discriminate between untouched and
adulterated images. Detection system
suggested here is used to detect seven systems
these are: hiding in LSB, hiding in palette,
hiding in DCT simple level security, and
hiding in wavelet simple level security. In
addition, highly-secret systems were
constructed, i.e. systems that integrate
Cryptography with Steganography in both
domains, DCT and Wavelet. Moreover,
system of hiding in multiwavelet was used
with cryptography.

The basic approach taken here works
by finding predictable higher-order statistics of
natural images within a multi-scale
decomposition, and then showing that
embedded messages alter these statistics. A
Fisher linear discriminant analysis is then used
to discriminate between untouched and
adulterated images. Detection system
suggested here is used to detect seven systems
these are: hiding in LSB, hiding in palette,
hiding in DCT simple level security, and
hiding in wavelet simple level security. In
addition, highly-secret systems were
constructed, i.e. systems that integrate
Cryptography with Steganography in both
domains, DCT and Wavelet. Moreover,
system of hiding in multiwavelet was used
with cryptography.

In this paper a possible way of MIMO
technique is used to exploit the multipath
scattering properly, it is the Spatial
Multiplexing, where the parallel streams of
data are mixed up in the air but can be
recovered at the receiver by using different
Vertical Bell Labs Layered Space- Time
(VBLAST algorithms like, Zero Forcing (ZF),
Minimum Mean Square Error (MMSE), and
QR-decomposition decoding methods.
This paper focused in performance
evaluation between these different algorithms
in terms of Bit Error Rate (BER) performance
using different modulation schemes (4PSK,
8PSK, 16PSK, and 16QAM), and different
numbers of antennas. The results derived have
shown that 4PSK has the best performance and
16PSK has the worst for all different types of
receiver algorithms, with 16QAM constellation
performance better than 16PSK, although they
use the same bit rate. The BER performance
degrades when the constellation size increases.
Also the VBLAST receivers with VBLASTMMSE
perform better than VBLAST-ZF and
VBLAST-QR receiver in terms of BER when
2X2 antennas are used. Also, it is noted that
with increasing modulation constellation the
curves of BER are shifted to right due to the
higher data rate that is transmitted. MMSE
loses the advantage over ZF that is observed
for lower constellations, and VBLAST-QR
performs better than lower constellations.
Finally it is noticed that the BER performance
degrades with increasing the number of
antennas.

Segmentation of a color image composed
of different kinds of regions can be a hard
problem, namely to compute for an exact
texture fields and make a decision of the
optimum number of segmentation areas in an
image when it contains similar and/or
unstationary texture fields. A local novel
neighborhood-based segmentation approach is
proposed. Genetic algorithm is used in the
proposed limited segment-pass optimization
process. In this pass, an energy function, which
is defined based on Markov Random Fields, is
minimized. The proposed system uses an
adaptive threshold estimation method for
image thresholding in the wavelet domain
based on the Generalized Gaussian
Distribution (GGD) modeling of sub band
coefficients. This method called Normal
Shrink is computationally more efficient and
adaptive because the parameters required for
estimating the threshold depend on sub band
data energy that used in the pre-stage of
segmentation. A quadtree is utilized to
implement the fast clustering segments for
multiresolution framework analysis, which
enables the use of different strategies at
different resolution levels, and hence, the
computation can be accelerated. The
experimental results of the proposed
segmentation approach are very encouraging.