Engineering and Technology Journal

The study is carried out to investigate the behavior of tunnel lining in sandy soil by
evaluating the magnitudes of the generated stresses that are generally required to ensure the
safety of tunnel construction. The testing program comprised different factors, i.e., sand
depth, density with and without the effect of surface loading. The experimental work was
accomplished through an instrumented (strain gauged) circular tunnel model. It was shown
that the generated stresses, for different loading types, i, e., surcharge, circular or strip
loading, decreased as the sand density increases for all regions (Crown, Shoulder & Springline)
and they increase as the sand depth increases. The results are presented in the form of
design charts.

Since Low Earth Orbit (LEO) satellites provide short round trip delays, they are
becoming increasingly important for real-time applications such as voice and video traffic.
Several strategies have been proposed for routing in a LEO satellite system. Some of them
are based on the Internet Protocol (IP), the Asynchronous Transfer Mode (ATM) switching,
and the Routing Sets (RS).
This paper will introduce an improving for the new packet routing mechanism over
inter-connected satellite networks that is the Minimum Flow Maximum Residual (MFMR)
algorithm that will be based on RS concept and will give simulation results of a certain
scenario. Our proposed algorithm is based on the Hybrid mesh topology (one of many mesh
topologies used in LEO satellite routing). The algorithm is developed and implemented
using a software simulation in Matlab. The proposed algorithm tries to minimize the
maximum flow over a given set of shortest paths from the source to destination, and also,
generates minimum propagation delay paths. The propagation delay we get is less than that
of MFMR algorithm, i.e., improving the performance of the LEO satellite network by using
Hybrid topology.

The optical response characteristics of Se/Sb thin film heterojunction deposited on
a p-type silicon substrate were studied. Results indicated that the obtained isotype
heterojunction is linearly graded and has 0.8V built-in potential. Also, the maximum
spectral responsivity and maximum quantum efficiency were obtained at the region of (600-
650) nm and the detectivity was about 7.77x1010 cm.Hz 1/2.W-1. Response time of the
manufactured detector was about 225ns. This work is a good attempt to manufacture the
heterojunction detector from V and VI elements.

This work include prepare five alloys of bronze (Cu-5wt.%Sn, Cu-10wt.%Sn, Cu-
15wt.%Sn, Cu-20wt.%Sn, Cu-25wt.%Sn).These alloys were then subjected to tensile
tests to determine the tensile strength (MPa) and elongation(%) for each alloy. Tensile
tests were performed according to ASTM-E8.MATLAB language was used to determine
the mathematical model for tensile strength and elongation with respect to alloy
composition.MATLAB results showed that there is a multiple linear model between
tensile results and alloy composition.

Cathodic protection is an effective electrochemical technique for preventing
corrosion of metallic structures. It has widespread applications on various structures,
suffering serious problems of corrosion in the environments.
The main problem with this protection method is to determine the parameters
(current density and potential). The previous works in this area used classical statistical
methods to determine these parameters.
In order to determine the cathodic protection potential, it is important to deal with
the electrochemical studies of open circuit potential (OCP) and polarization
investigations of low carbon steel used in pipeline application in 3.5 % NaCl solution at
temperature range( 30- 50°C).These studies define the corrosion potential and also help
one to understand the corrosion behavior of the used metal (low carbon steel ). This
system was used to investigate the influence of various conditions on the minimum
cathodic protection current that would provide a full cathodic protection for steel tube
immersed in sea water. The variable conditions studied are concentration of (0.01 – 3.5)
% NaCl , temperature (30- 50°C), distance between pipe (cathode) and graphite
electrode ( anode ) of (10 – 20) cm and pH solution of (5.0 – 9.0) using a selected range
of these conditions, the experimental results for the minimum cathodic protection current
were obtained and recorded.
The electrochemical results show that cathodic protection current density increases
with increasing temperature and concentration. The current density also slightly
increases with increase distance between cathode and anode.
The effective sequence of these parameters on cathodic current density is as follows:
Temperature > concentration > pH solution > cathode – anode distance .

The study was devoted to test the effect of the process variables on the desublimator
(cold trap) efficiency under vacuum technique. Since several intermediate process
parameters could not be measured or inspected, then it was necessary to predict them by
the gray model. Although the novel approach (tendency model) for the desublimator was
less accurate than the detailed one, but it showed agreement results when compared with
the experimental data. The accuracy of model could be increased by increasing the
process variable monitors. The tendency model was more effective to deal with the lack
of knowledge about the process when implemented with the optimal control system.

This paper represents new method to determine the optimum switching angles for
Selective Harmonic Eliminated PWM (SHEPWM) inverter. Such switching angles are
defined by a set of nonlinear equations to be solved using the Resultant method. This is
done by first converting these equations that specify the harmonic elimination problem into
an equivalent set of polynomial equations. Then, using the mathematical theory of
Resultants, all solutions to this equivalent problem can be found without the need for any
initial guess. The complete solutions for unipolar SHEPWM switching pattern which
produce the fundamental while not generating specifically chosen harmonics are
investigated.

A numerical study of two-dimensional turbulent buoyant rcirculating flow within
mechanically ventilated rooms is reported. The study involves the solution of elliptic partial
differential equations for the conservation of mass, momentum, energy, turbulent energy and
its dissipation rate in a finite difference form. These equations were solved together with
algebraic expressions for the turbulent viscosity and heat diffusivity, using (K-ε) turbulence
model. A modified version of a two-dimensional elliptic computer code was used to
simulate the complex flows inside a slot-ventilated room. The present study demonstrates
that the flow behavior depends on several parameters, such as airflow rate, size and
temperature of the heated obstruction. Each of these parameters was modeled separately to
understand their affects on the airflow characteristic inside ventilated room.

This paper describes the investigation of a corrosion behavior of bottom Plates of a
potable water storage tank . The tank was internally inspected for the first time after
fourteen years of service. Paint blisters and rust spots were observed on the bottom
plates. Sand blasting and repainting the bottom plates and shell plates were to be used
as a remedial work .
However, during the sand blasting, holes and deep pitting were observed on the
bottom plates. On-site visual inspection, magnetic flux leakage (MFL) inspection,
ultrasonic testing (UT), and evaluation of the external cathodic protection (CP) system
were used in the failure analysis. The failure is attributed to the ingress of water and its
impoundment under the tank bottom along the periphery inside the ring wall and failure
of water side epoxy coating.

Zn–Ni alloy based coatings have high corrosion resistance, good adherence and
unique physical as well as mechanical properties. In the present work, nickel was
dispersed in the under layer of hot dip zinc coating (Galvanizing). showed substantial
improvement in physical as well as galvanic performance. The presence of nickel in the
under layer was found to result in good adherence, less porosity and better hardness .The
presence of nickel decreases the thickness of the coating and enhances the corrosion
resistance character.

Diffusion coating was carried out at 1050 oC for 6 h under argon atmosphere by
simultaneous Ge-doped chromizing-siliconizing process on low alloy steel type-T22.
Cyclic oxidation tests were conducted for the uncoated and for the chromizing –
Siliconizing coated steel-T22 alloy at 800 oC . For the Ge-dopded chromizingsiliconizing
coated steel, the cyclic oxidation was carried out in the temperature range
600-800 oC in air for 100 h at 5 h cycle. The results showed that the oxidation kinetics
for uncoated steel-T22 alloy in air at 800 oC follow a breakaway oxidation and the
phases present are FeO (Wustite), Fe3O4 (Magnetite) and Fe2O3 (Haematite).
The oxidation kinetics for chromizing –Siliconizing coated system in air at 800 oC
was found to be parabolic. Oxide phases that formed on coated system are SiO2 and
Cr2O3. The oxidation kinetics Ge-doped chromizing –Siliconizing coated system in air in
the temperature range 600-800 oC was found to be parabolic .Oxide phases that formed
on coated system are SiO2 and Cr2O3. The Ge addition improves the oxidation resistance
of low alloy steel.

Abstract- The harmonic distortion in the power system is increasing with wide use of
nonlinear loads such as wave rectifiers, static VAR compensator, and solid-state controlled
devices.Thus, it is important to analyze and evaluate the various harmonic problems in the
power system prior to their occurrence. This paper presents a technique to analyze
propagation of harmonic current and voltage in power system networks, and determine the
location and magnitude of the maximum harmonic current and voltage in the network
.Frequency dependent models of a power system elements and loads have been developed
for the appropriate range of frequency. The harmonic source representation is described.
The location of harmonic source, and the system loads are all found to be factors in
determining the magnitude of harmonic currents and voltages flow in the system.

The design aspect of cathodic protection of steel reinforcement embedded in
concrete; still implies a great deal of uncertainties, assumptions and specifications.
Important features, such as design criteria, current distribution, and others are, as yet
beyond standardization.
The main aim of this research is to study relationship between the induced level
of polarization and the area of the embedded steel, area of anode, the distance between
the cathode and anode and the level of applied external voltage. The experimental
program included preparing 12 reinforced concrete specimens with dimensions 20 x 30 x
60 cm. The specimens were partially submerged in 3.5% sodium chloride solution.
Various electrochemical and electrical measurement were carried out on polarized the
specimen using different external voltages.
The results indicate differential moisture content within each specimen has
produced different potentials along the steel bars. Greater polarization has always been
associated with the submerged portion of the specimen.
The results show that to achieve efficient design, the protected area should be
divided into discrete electrochemical zones depending on the concrete resistance and
steel potential.