AL-Rafidain Engineering Journal (AREJ)

T his paper deals with a closed–loop position control of a double acting and double–rod
actuator using an electrohydraulic servovalve (EHSV). This system is studied by using
symmetric critical center spool valve (zerolapped) and open center spool valve (underlapped).
The nonlinear dynamic behavior of each case is undertaken and simulated. The system is
modeled by using five state variables (piston position, piston velocity, actuator pressures, and
servovalve spool displacement) and is tested under different step inputs. The EHSV is modeled
with a first order differential equation. The closed-loop system stability is investigated by
introducing equilibrium state into Jacobian matrix and determining the eignvalues. Viscous
friction and compressibility of oil are included in the modeling of the system. Because the
electrohydraulic position servo system is not very sensitive to coulomb friction and piston
leakage they are neglected. The work showed that when the underlapped servovalve operates in
the underlap region, the hydraulic position control system has more stable operation and better
transient responses.

Vibrations in rotating system are considered as one of the major operating problems
since they have adverse effects on the performance of rotating system, which result in
operating life reduction.
In this research, the active control of vibration, as a response to mass unbalance, in a
rigid rotor symmetrically supported by an oil film bearing is considered.
A model of rigid rotor is considered in this study, in which the unbalance mass is
positioned out of the plane of the geometrical center of the system.
F or the cases studied, the active control of system vibration was achieved by the
Application of two techniques, namely, pole placement and optimal control techniques,
the system dynamics is represented by mathematical models and the system is simulated
by a digital computer using Matlab programs.
The results obtained showed a high reduction in vibration amplitude, This reduction was
more than 80 % and in some situations it raises to more than 90 %.

The static synchronous compensator (STATCOM) is one of the components of Flexible
AC Transmission System (FACT). STATCOM is used to compensate the reactive power with
fast response. It consist of power electronic devices. The main drawback of STATCOM is
harmonics injection to the system. Different techniques can be used to reduce harmonic
injection, such as the use of 12-pulse STATCOM with Pulse Width Modulation (PWM) to
control the operation of power electronic devices.
In this work the series connection of transformers is studied and compared with parallel
connection. The study is applied to the suggested STATCOM in the ring system around Mosul
city. Matlab / Simulink is used to analyze the two systems. The results are given and discussed
in the paper. Also it is found that the Total Harmonic Distortion (THD) can be further reduced
by using series connection of transformers secondary rather than shunt connection

In this research, natural cnvective heat transfer between hot walls of cavity and a cold
body with square section concentric in cavity is studied numerically. The cavity is filled with a
saturated porous medium with thermally non-equilibrium between the solid and fluid phases.
Two adiabatic partitions attached to the walls of cavity .The governing equations include
continuity, momentum and energy equations are solved by using finite deference method with
Gauss-Seidle iterative method.
This investigation was performed under the effect of four non-dimensional groups which
defined as : modified Rayleigh number (100????Ra*????1000), scaled heat transfer coefficient
(0.1????????????100), thermal conductivity ratio (0.1????Kr????100) and the location of the partitions with
respect to the length of the cavity (Yp*=0.25,0.5,0.75). The results were presented in terms of
streamlines and isotherms of fluid and solid phases and the relations between Nusselt number
variation with modified Rayleigh number .The Nusselt number in each phases(solid and liquid)
and total Nusselt number are found to be increased proportionally due to the increasing in
modified Rayleigh number. The effect of thermal conductivity ratio on Nusselt number was
comprehensive while scaled heat transfer coefficient was confined to solid phase Nusselt number.
Also the results showed that when the two partitions moved towards upper part of cavity , the
quantity of heat transfer is to be larger and the maximum heat transfer is to be when the
horizontal partitions in the upper part of the cavity in all cases .

Aloha protocols are characterized by their easy performance and relatively
simple hardware requirement as compared with other protocols like CSMA/CA.
The main disadvantages of Aloha protocols are the low throughput and long delays
as the offered load increases. In this paper, direct sequence spread spectrum is
introduced to increase the throughput of Aloha protocols. This can be achieved by
increasing the auto correlation and minimizing the cross correlation and as a
consequence decreasing the rate of contention between the transmitted packets

In this paper, a new homomorphic wavelet-based de-speckling technique is proposed.
The technique combines a spatial domain processing with another transform domain processing
in a homomorphic environment. The spatial domain nonlinear processing is based on replacing
each log-transformed pixel value of the speckled image by a weighted-average of the logtransformed
pixel values in the neighborhood of that pixel. The weighted averaged logtransformed
image is then subjected to wavelet thresholding for further nonlinear transform
domain processing. An exponential operation on the filtered output is used to simulate the final
homomorphic antilog-transformation stage and to obtain the de-speckled image. Quantitative
and qualitative measures prove the superiority of the proposed technique for the applications of
image classification and recognition in ultrasonic and SAR systems.

The distance relay is suffering from under-reach in its performance. This is because of some
transient disturbance, which may happen when the power flows and swings. Besides that the
power swings as a consequence of some fault cases. In this paper a new distance relay has been
suggested and modeled for detecting stable and unstable power swings.
This relay is known as out of step relay (OOS). The method employed is to measure the rate
of change of the positive sequence impedance of the relay which supervise the trip signal that
comes out of the distance relay. It allows the distance relay to work, if it detects an unstable
power swing or a fault. On the other hand it blocks it if the power swing is stable. The new relay
have been modeled and simulated using MATLAB-SIMULINK software programs.
The performance of this relay has been tested on an equivalent two sources system. The
results prove that the suggested relay is active and fast. Thus overcoming the limitation of the
distance relay in case of under-reach. The results also show that the new relay has the ability in
discriminating between the types of faults, that occur during power swings.

The first aim of this experimental program is to produce and evaluate Self-Consolidating
Concrete (SCC); the second aim is to replace part of cement by predetermined percentages of
limestone powder CaCo3 (LSP) to find out the effect of a variable percentage of LSP on some
mechanical properties of SCC. The study also takes into account the difference between using the
LSP as a replacement or as an additive of cement to the mix. Six concrete mixes were prepared.
The first one was without LSP (0%), second, third and fourth ones contained LSP as percentage
replacement of cement in the order of 20,30,40% respectively, fifth and sixth mixes contained
20,30% LSP but as an additive to the cement. Results showed that using LSP as replacement of
cement led to the production of SCC. Using LSP as replacement also led to economical
advantages due to the decrease in plasticizer content, with no noticeable differences in
mechanical properties of SCC, but causing a fluidity increase of SCC when using LSP as an
additive.

This study aimed to treat the wastewater of Khansaa Hospital in Mosul city by using mud of
( Bentonite , Ninavite & Kaoline ) the experiments were conducted by using the Jar-Test as
laboratory scale .The efficiency had been calculated by the following characteristics :-( Chemical
Oxygen Demand ( COD ) , Biochemical Oxygen Demand ( BOD5 ) , Oil and grease , Chloride ,
Sulphate ,Turbidity ,Total Hardness , Calcium , magnesium , Phosphate , Nitrate, Electrical
conductivity ( Ec ) & ( pH ) ) . Bentonite showed the best removal efficiency , followed by
Ninavite and Kaoline respectively . The removal efficiency was shown at the optimum doses for
Bentonite then Ninavite and Kaoline at doses ( 40 , 50 & 60 ) mg/l respectively .Removal of
COD give (62%,58%,51%) and (55%,50%,45%) for BOD5 at optimum doses , while oil and
grease removal efficiency was (56%,51%&44%).Phosphate removal was (48%,42% & 39%) and
efficiency of sulphate removal (46%,41.6% & 38) , while chloride removal efficiency (22%,20%
& 17.2%).

The present paper deals with studying the effect of sand/cement (s/c) ratio and
water/cement (w/c) ratio on the mechanical properties of cement mortar and to predict a
relationship between modulus of rupture and compressive strength for the cement mortar. In the
present work seventy two sample of cubes and prisms were tested for compressive strength and
modulus of rupture. All the tests were carried out in accordance to the ASTM specification C109
using twelve different mix proportions of cement/sand ratio and water/cement ratio. From the test results and based on regression analysis a best power relation between modulus of rupture and compressive strength are proposed.

ound gates has been conducted . The study included the measurement of maximum scour
depth and the length of scour hole downstream these structures . Also , the effects of structure
height , undersluice opening height , discharge variation and bed material size on the depth and
length of scour hole , Two hundred eighty eight Experiments were conducted in a concrete
laboratory channel Three sizes of rocks were used are in range of (1.43-2.21) cm and three of
15,20 and 30cm and Three under gate opening heights of 1,2 and 3cm were tested Experimental.
Results of this study showed a good direct relationships between relative scour depth (Ds/D50)
with Froud Number (Fro) of correlation factor (R2) between (0.9729-0.9911) and other between
relative scour length (Ls/D50) with (Fro) of correlation factor (R2) between (0.9636-0.9947) for
weirs and another good direct relationships between (Ds/D50) with (Fr0) of correlation factor (R2)
between (0.972-0.9866) and with (qu/qd) of correlation factor (R2) between (0.9608-0.9904) and
other relationship between (Ls/D50) with (Fro) of correlation factor (R2) between (0.9861-0.9985)
and with (qu/qd) of correlation factor (R2) between (0.9847-0.9955), many relationships were
obtained the first to estimate (Ds/D50) of correlation factor (R2=0.9311) , the second for (Ls/D50)
of correlation factor (R2=0.9421) downstream weirs each of them in terms of (Fr0) and (????Hw/P) ,
the third to estimate (Ds/D50) of correlation factor (R2=0.8989) and the forth for (Ls/D50) of
correlation factor (R2=0.9212) downstream compound gates each of them in terms of
(Fr0),(????Hw/P),(h0????????Ht) and (qu/qd) . It was also shown that the scour depth and length
downstream compound gates are less than those downstream weirs but the percentage decrement
will decrease if the opening of compound gate is increased

Meteorological phenomena like temperature, humidity, radiation, wind speed play an
important role in the determining the quantity of evaporation. In this study one of the advanced
methods in the statistical analysis by computer has been applied to find relation between the
present and antecedent evaporation and other meteorological phenomena. Monthly historical data for each phenomenas are collected for the period (1980-2000). The kernel estimation, according to the established computer programs , gives an estimator which depends on the time and nature of the variable .

In recent years, trends focusing on exploration the architectural identity through the study of the
domestic architecture properties, have emerged in order to find an appropriate architecture therefore many
studies have recently talked this topic including Arabic – Islamic societies . some of them have focused
on studying the compositional relation of architectural products . others have focused on studying limited
properties and phenomena and others , including this paper , have focused on studying the properties of
specific buildings (Islamic palaces) for limited design aspects (architectural palaces) in the Islamic
architecture .
The literature review of the concept of Special Configuration in Islamic building shows the absence of
the clear and specific limitation of the properties of the special Configuration of the Islamic buildings . the
paper has taken this problem to be the problem of the research . The aim of the research is to give a clear
and specific limitation of the properties of the Special Configuration of the Islamic palaces by comparing
them with their counterpart in the palaces of Mesopotamia and the adjacent regions . Space Syntax
analysis has been applied to assess the characteristic of the building type .
The conclusion solved that there is clear idiosyncrasy of the Special Configuration of Islamic palaces
due to the effect of Islamic belief . Some of these palaces have similar properties of these of Mesopotamia
because of social values , others because of the environmental effect .

The urban environment is a spatial organization synthesized from different types of
spaces, it’s characteristics are the key factor of it’s use because spatial relationship usually affect
human behavior within the environment by affecting the ways he perceives, cognized and
evaluates it.
This research is a comparative study concerning the differences of the visual composition
of the urban paths of tradional and modern parts in the city of Mosul. It’s objective is to describe
and define the characteristics of those paths in terms of their identity, spatial formulation, the
meaning of their composition and the richness of their visual sequence.
By adopting a clear methodology and simplified objective measures, the research
concluded the visual richness of the patgs under, study, in addition to suggesting the possibility
of using the measures used in it to evaluate future designs of urban paths.

The present study defines the research problem as a reformulation of a scientific
aspect to study of the relations between heritage and rhythm under influence of continuity,
and discusses the studies about the relations of rhythm with heritage continuity, this research
clarifies how strategically usage for concept rhythm in architecture in achieving the
communicated for architectural product depending heritage usage on different levels
mentally,formally and specially, research contains four axes: discussing the relation between
rhythm and heritage continuity, firstly, and discussing studies about rhythm,secondly, then
differentiation the theoretical framework, thirdly, at last concluding the applying operations
are submitted which represented by electing four main items of detailed theoretical field as
the following:(Nature of rhythm aims, Rhythm greation forms, What the resources of rhythm
is, Rhythm formal properties) which limit the concept in architecture, firstly,and the
application of the items by electing two important projects in Mosul architecture(as models)
and crystallized the hypothesis,secondly, at last discussing the results to submit the
conclusions in the end.