Print ISSN: 1813-0526

Online ISSN: 2220-1270

Volume 17, Issue 5

Volume 17, Issue 5, Summer and Autumn 2009, Page 1-153

A Study on the Effects of Servovalve Lap on the Performance of a Closed - Loop Electrohydraulic Position Control System

Rawand E. J. Talabani; Yahya A. Faraj; Rafa A. H. AL-Baldawi

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 1-14
DOI: 10.33899/rengj.2009.43375


This 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.

Keywords: Zerolap, Underlap, EHSV, Steady-State Characteristics, Dynamic Response, Position Control, Modeling, Simulation.

Active Control Of Vibration For Aflixibly Supported Rigid Rotor On Oil Film Bearings

Ikhlas A. Basheer; Zakariya Y. Mohammad

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 1-18
DOI: 10.33899/rengj.2009.43384

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.
For 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 %.
Key words: Rotor vibration, rotor bearing system, Active vibration control.

THD Reduction Using Series Transformer Connection In A STATCOM Within Mosul Ring System

Yasser A. Mahmood; Majed S. Al-Hafid; Dhaiya A. Al-Nimma

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 15-22
DOI: 10.33899/rengj.2009.43378

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.

Keywords :STATCOM, Harmonic reduction, Transformer connection in STATCOM, Mosul distribution ring.

Numerical Study of Natural Convection Heat Transfer of Porous Cavity contains Partitions and Square body by Using Thermal Non-Equilibrium Model

Ramiz Ibraheem Saeed Al-Abushi

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 19-33
DOI: 10.33899/rengj.2009.43385

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≤H≤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 .

Applying Direct Sequence Spread Spectrum to Improve the Throughput of Aloha Protocols

A. I. A. Jabbar

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 23-31
DOI: 10.33899/rengj.2009.43379

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.

Keywords: Aloha, Slotted Aloha, Direct Sequence, Spread Spectrum.

Wavelet-Based Homomorphic De-Speckling Technique With Directional Weighted-Averaging Stage

Jassim M. Abdul-Jabbar

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 32-43
DOI: 10.33899/rengj.2009.43380

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 log-transformed pixel values in the neighborhood of that pixel. The weighted averaged log-transformed 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.

Keywords: Speckle noise, homomorphic environment, weighted-average, wavelet thresholding

The Effect of Power Swing on Distance Relays Performance

Atheer Habash Abosh; Abdul Ghani A. Abdul Ghafoor

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 43-48
DOI: 10.33899/rengj.2009.43386

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.
Key Word: Power swing, Distance relay , Out of step protection technique.

The Effect Of A Variable Percentage Of Limestone Filler On Some Mechanical Properties Of Self-Compacting Concrete

Ashtar S. Al-Luhybi

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 44-58
DOI: 10.33899/rengj.2009.43381

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.
Key words: Concrete mechanical Strength, Limestone Filler, Self-Compacting Concrete.

Wastewater Treatment of Khanssa Hospital by Using Some Types of Muds

Halla Nabeel Elea; Soad Abid Abawee

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 49-59
DOI: 10.33899/rengj.2009.43388

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%).
Key Words: Bentonite Clay, Ninavite Clay, Kaoline Clay, Coagulation,Hospital Wastewater Treatment.

Predicting The Relationship Between The Modulus Of Rupture And Compressive Strength Of Cement Mortar

Sura A. Majeed

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 59-68
DOI: 10.33899/rengj.2009.43383

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.
Keywords: compressive strength, modulus of rupture, mortar, sand.

Laboratory Comparison Study of Scour Downstream Weirs and Communed Gates

Ahmad A. A. Alkatan; Mwafaq Y. M. Aljubori; Bahzad M. A. Noori

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 60-75
DOI: 10.33899/rengj.2009.43392

In the present investigation , a laboratory study of scour characteristics downstream weirs , compound 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 (ΔHw/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),(ΔHw/P),(h0/ΔHt) 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 .

Statistical Study for Free Evaporation at Mosul Area by Kernel Estimation Method

Alaa Emad Hameed; Basil Khether Dawood; Basil Younis Thanoon

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 76-90
DOI: 10.33899/rengj.2009.43396


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 .

Key words : free evaporation , Mosul area , kernel estimation, statistical study for evaporation.

Spatial Configuration properties of Islamic Palaces

Raeed S. A. Al-numman

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 91-108
DOI: 10.33899/rengj.2009.43401

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 .
Keyword : Islamic architecture , palaces , spatial configuration

Visual Sequences in Mosul City Paths A comparative Study for formal characteristics

Niam .Behnam Manona

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 109-126
DOI: 10.33899/rengj.2009.43404

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.
Key word : Visual Sequences , Urban Path

The Rhythm and Heritage Continuity in Contemporary Mosul Architectural Product

Nasma M. Thabit

AL-Rafdain Engineering Journal (AREJ), Volume 17, Issue 5, Pages 127-153
DOI: 10.33899/rengj.2009.43409

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.
Keywords: Rhythm, Heritage Continuity, Contemporary Mosul Architecture