AL-Rafidain Engineering Journal (AREJ)

The influence of a transverse crack upon the dynamic behavior of a rotating
shaft is studied. Introduction of such a crack results in lower transverse natural
frequencies due to the added local flexibility. The strain energy release function is
related to the compliance of the cracked shaft that is to the local flexibility due to
introduction of crack. This function is related to the stress intensity factor, which for
transverse of a shaft with a crack has a known expression. As a result, the local
flexibility of the shaft due to the presence of the crack has been computed. This result,
can be further utilized to yield the dynamic response of a shaft with complex geometry.
Starting from the equation of motion for the shaft under bending to derive the
expression of calculating the natural frequency of the shaft.
Two cases of fixing the shaft are suggested in this study to investigate and
analyze the vibration characteristics of the shaft with and without cracks. The
fundamental natural frequency showed strong dependence on the crack depth, This
dependence is smaller as the order of the frequency increase. Experimental results are in
close agreement with those practical from the theoretical analysis. Finally, the results
showed that the change in dynamic response due to the crack is high enough to allow
the detection of the crack and estimation of its magnitude.

Good regulation and stability are important factors to be considered in
designing of the uninterruptible power supplies systems, which depend on the load
requirements. On the other side, the cost factor roles the proper design selection of
the uninterruptible power supply, especially for the commercial applications. A pulse
width modulation uninterruptible power supplies are considered to have good
features over the rival one.
This paper presents a suggested method for the controlling of the
uninterruptible power supplies to regulate the output voltage, by using an easy
practicable, low cost, and one-sensor, microprocessor-based regulator. This
regulator circuit depends on minimizing the hardware complicity with efficient
software. The practical results show that a good and reliable regulation performance
in the applications when the fluctuation in both input DC voltage and load occurred,
such as the applications using the solar cells or batteries as the input voltage source
supplying variable load conditions.

In this chapter the various kinds of charge storage cells are discussed
as a result of examining many samples with different structures. The C-V, I-V and R-V
measurements of the structures confirm the memorization capability of MIOS devices.
The examined structures reveal three kinds of memory actions. The first one is the
charge storage capability which can be shown through (C-V) curve shifting as the device
was exposed to certain stress for a certain time. The second is the electronic switching
that is demonstrated by the fact that the switching between ON and OFF states and
back to original state can only be obtained by inverting the polarity of the applied bias
voltage. The third kind of memorization action is that the device can be switched into a
variety of stable intermediate resistance states. The new resistance state is determined
by the height of the programming pulse applied to the device. This memory action is
noticed from R-V characteristic and known as a nonvolatile analogue memory behavior.

In this research it has been studied the effect of the rail materials and the
superconducting coils on the lifting force of the magnetically leviated trains.
Concentration on the Super-conducting coils for creation of the lifting force was
done also, in order to minimize the current without decreasing the lifting force a
new frame coil was designed such that we take benefit of all the allowed area of
the base.
The rail is a material tape in which lifting force is formed when a magnet
is moved over it. Detailed study of the rail materials which can be used as rails
was done, lifting force of the Aluminum and Copper was studied. The lifting for the copper alloy was studied also, like brass (Cu-Zn), with different content of
Zn in it. Also studied the lifting force for the alloy (Al-Cu-Mg) and this is one of
the very strong alloys from which car wheels are madeforce

Voltage stability is indeed a dynamic problem. Dynamic analysis is
important for a better understanding of voltage instability process. In this work
an analysis of voltage stability from bifurcation and voltage collapse point of
view based on a center manifold voltage collapse model. A static and dynamic
load models were used to explain voltage collapse. The basic equations of a
simple power system and load used to demonstrate voltage collapse dynamics
and bifurcation theory. These equations are also developed in a manner, which is
suitable for the Matlab-Simulink application. As a result detection of voltage
collapse before it reach the critical collapse point was obtained as original point.

A computerized model with (Microsoft QuickBasic version 1.1) was proposed
for simulating the effect of deficit irrigation for maize crop during spring and autumn
seasons in Mosul region. The simulation is based on 16 years of climatological data
for the period ( 1985-2000 ) for Mosul meteorological station , which includes daily
maximum and minimum temperatures , maximum and minimum relative humidity ,
wind speed at 2m height , and sunshine hours , which is used to calculate daily
reference evapotranspiration with Penman-Monteith equation .The model predicts
yield reduction by changing irrigation depth for three different irrigation methods
(sprinkler , furrow and drip) .The rainfall is divided into three classes which represent
three regions (wet ,semi- arid and arid ).

In this investigation, the characteristics of free flow over normal and oblique
weirs with semicircular crests are studied experimentally. For this purpose, forty eight
weir models were constructed and tested. The first twelve models were normal weirs in
which the crest radius was varied three times; 5cm, 7.5cm and 10cm. For each crest
radius, the weir height was varied four times; 35cm, 30cm, 25cm and 20cm. The
remaining models were oblique weirs. The oblique angle was varied three times; 60????, 45????
and 30????. In weirs of the same oblique angle, the crest radius and weir height were varied
similarly to those of normal weirs.The experimental results showed that for normal weirs,
the discharge coefficient (Cdw) increases with the increase of head to crest height ratio
(h/P) for the same height of weir. In case of oblique weirs, it was found that (Cdw)
decreases with the increase of (h/P) values and weirs of small oblique angle (???? ) give high
values of (Cdw ).For normal weirs, the discharge magnification factor (QNC /QNS) and
performance increase as values of (h/P) increase. Normal weirs of semicircular crests
perform better than those of sharp crested weirs for all values of weir height and crest
radius tested in this study. While, for oblique weirs the discharge magnification factor
(QOB/QNS) and performance increased with the decrease of (h/P) values. As (h/P) value
approaches zero, the discharge magnification factor approaches the length magnification
of the weir. Weirs of small oblique angles give high discharge magnification factor and
high performance.A simple procedure was applied for the hydraulic design of oblique
weirs. The design method yields the final dimensions of a weir and predicts its headdischarge
curve for the whole range of operation

The main objective of this investigation is to study experimentally the water surface
profiles and to obtain convenient expressions for the estimation of discharge
coefficients (Cd) for free flow over chimney weir and the discharge factor (q/q1) for
submerged flow. Four chimney weir models with different vertex angles were
constructed and tested, the surface water profiles, for all models were smooth upstream
and fall suddenly downstream the model and at a high discharge it become concave
while at law discharge the water surface profile become convex. The coefficient of
discharge for free flow increase with the decrease of the upstream head and with the
decrease of half vertex angle (???? ). While the discharge factor for submerged flow
increase with the decrease of the submergence ratio (h2/h1). Two general expressions
were optioned, one, for the estimation of Cd with respect of (h/p),(w/p) and ???? for free
flow conditions and the other for estimation of the coefficient factor (q/q1) with respect
to (h2/h1) and (h1/p).