Journal of Engineering

Shell-and-double concentric tube heat exchanger is one of the new designs that enhance the heat transfer process. Entransy dissipation is a recent development that incorporates thermodynamics in the design and optimization of heat exchangers. In this paper the concept of entransy dissipation is related to the shell-and-double concentric tube heat exchanger for the first time, where the experiments were conducted using hot oil with temperature of 80, 100 and 120°C, flow rate of cold water was 0.667, 1, and 1.334 kg/m3 respectively and the temperature of inlet cold water was 20°C. The entransy dissipation rate due to heat transfer and to fluid friction or pressure drop was studied.

With the development of computer architecture and its technologies in recent years, applications like e-commerce, e-government, e-governance and e-finance are widely used, and they act as active research areas. In addition, in order to increase the quality and quantity of the ordinary everyday transactions, it is desired to migrate from the paper-based environment to a digital-based computerized environment. Such migration increases efficiency, saves time, eliminates paperwork, increases safety and reduces the cost in an organization. Digital signatures are playing an essential role in many electronic and automatic based systems and facilitate this migration. The digital signatures are used to provide many services and solutions that would not have been possible by the conventional hand-written signature.


In the educational environment, the process of issuing the graduation certificates can no longer be restricted to the traditional methods. Hence, a computerized system for issuing certificates of graduation in an electronic form is needed and desired. This paper proposes a Graduation Certificates Issuing System (GCIS) based on digital signature technology. In doing so, this research highlights the state-of-the-art and the art-of-the-practice for some existing digital signature-based systems in the literatures. In addition, eight intertwined elected services are identified, namely: message authentication, entity authentication, integrity, non-repudiation, time stamping, distinguished signing authorities, delegating signing capability and supporting workflow systems. Moreover, this research examines nine existing systems, showing their merits and demerits in terms of these elected services. Furthermore, the research describes the architectural design using the Unified Modeling Language (UML) and provides the concrete implementation of the proposed GCIS. The GCIS is implemented using Visual Basic.Net programming language and SQL Server database management system.

Phase change materials (PCMs) such as paraffin wax can be used to store or release large amount of energy at certain temperature at which their solid-liquid phase changes occurs. Paraffin wax that used in latent heat thermal energy storage (LHTES) has low thermal conductivity. In this study, the thermal conductivity of paraffin wax has been enhanced by adding different mass concentration (1wt.%, 3wt.%, 5wt.%) of (TiO2) nano-particles with about (10nm) diameter. It is found that the phase change temperature varies with adding (TiO2) nanoparticles in to the paraffin wax. The thermal conductivity of the composites is found to decrease with increasing temperature. The increase in thermal conductivity has been found to increase by about (10%) at nanoparticles loading (5wt.% and 15oC).

The different parameters on mechanical and microstructural properties of aluminium alloy 6061-T6 Friction stir-welded (FSW) joints were investigated in the present study. Different welded specimens were produced by employing variable rotating speeds and welding speeds. Tensile strength of the produced joints was tested at room temperature and the the effecincy was assessed, it was 75% of the base metal at rotational speed 1500 rpm and weld speed 50 mm/min. Hardness of various zones of FSW welds are presented and analyzed by means of brinell hardness number . Besides to thess tests the bending properties investigated and showed good results in some specimen and not in onother the mamximum stress was 240 N/mm2 at rotational speed 1500 rpm and weld speed 50 mm/min , while the maximum stress at 1250 rpm and 75 mm/min 94 N/mm2 , hardness results shwed lower values in heat affected and nugget zones than the base metal with improving of hardness at 1500 rpm, 75 mm/min .

In many industries especially oil companies in Iraq consumed large quantities of water which will produce oil-contaminated water which can cause major pollution in agricultural lands and rivers. The aim of the present work is to enhance the efficiency of dispersed air flotation technique by using highly effective and cost-efficient coagulant to treating gas oil emulsion. The experimental work was carried out using bubble column made of Perspex glass (5cm I.D, 120cm height). A liquid was at depth of 60cm. Different dosage of sawdust +bentonite at ratio 2:1 (0.5+ 0.25; 1+ 0.5 and 2+1) gm and alum at concentration (10,20and30mg/l) at different pH ( 4 and 7) were used to determine optimum dosages of coagulant. Jar test experiment has showed that optimum dosage of (sawdust +bentonite) was (1+0.5gm) and alum concentration was 30 mg/l at pH=4.


The present study was conducted to evaluate the effect of various parameters pH (3, 4,7and 9); air flow rate (300, 500, 1000, and 1500 cc/min); initial oil concentration (300 up to 1000 ppm); concentration of Sodium dodecylsulphat surfactants ,SDS (25, 75and 150mg/l); and the effect of the addition coagulant (sawdust + bentonite at ratio 2:1) and alum (30mg/l) in the removal efficiency of oil from wastewater by coagulation –flotation process.


The study has showed that the removal efficiency of COD, oil content and turbidity were related to the initial oil concentration; additive concentration of SDS and dosage of coagulants. It was found that the flotation rate increases when using coagulants, the fastest removal rate was obtained when pH 4 and also the higher removal efficiency achieved was for flotation (87%) and (95.7%) sawdust +bentonite; (97%) for alum in coagulation – flotation process.

The variation of compression index Cc and swelling index Cs with the degree of saturation S was studied on unsaturated and fully saturated soils for different degrees of saturation (100%, 91%, 85%, 75%, 60%), several mathematical equations were found to describe these relationships, these equations can be used to predict settlement during the consolidation process in unsaturated and fully saturated soils.

Active Magnetic Bearings (AMBs) are progressively being implemented in a wide variety of applications. Their exclusive appealing features make them suitable for solving traditional rotor-bearing problems using novel design approaches for rotating machinery. In this paper, a linearized uncertain model of AMBs is utilized to develop a nonlinear sliding mode controller based on Lyapunov function for the electromechanical system. The controller requires measurements of the rotor displacements and their derivatives. Since the control law is discontinuous, the proposed controller can achieve a finite time regulation but with the drawback of the chattering problem. To reduce the effect of this problem, the gain of the unite vector term is evaluated as a function to state variables. As a result the proposed discontinuous controller regulates the state to the origin in a finite time in spite of the uncertainty in system model and the presence of external disturbances. These results are demonstrated via numerical simulations. In addition the chattering in system response in these results is within the acceptable range.

This paper presents a numerical analysis using ANSYS finite element program to simulate the reinforced concrete slabs with spherical voids. Six full-scale one way bubbled slabs of (3000mm) length with rectangular cross-sectional area of (460mm) width and (150mm) depth are tested as simply supported under two-concentrated load. The results of the finite element model are presented and compared with the experimental data of the tested slabs. Material nonlinearities due to cracking and crushing of concrete and yielding of reinforcement are considered. The general behavior of the finite element models represented by the load-deflection curves at midspan, crack pattern, ultimate load, load-concrete strain curves and failure modes shows good agreement with the experimental data.

Health and environmental factors as well as operational difficulties are major challenges facing the development of an anaerobic digestion process. Some of these problems relate to the use of sludge collected from primary and secondary clarifier units in wastewater treatment plants for laboratory purposes.


The present study addresses the preparation of sludge for laboratory purposes by using a mixture that consists of the digested sludge, which is less pathogenic, compared to the collected sludge from the primary or secondary clarifier, and food wastes. The sludge has been tested experimentally for 19 and 32 days under mesophilic conditions. The results show a steady methane production rate from the anaerobic digester which used sludge with a rate of 1.5 l/day and concentration around 60%, with comparatively low H2S gas content (10 ppm). The methane produced from the digester that used only digested sludge decreases during the experimental period.

Hot mix recycling of asphalt pavements is increasingly being used as one of the major rehabilitation methods by various highway agencies. Besides general savings in costs and energy expended, it also saves our natural resources and environment. Recycling process presents a sustainable pavement by using the old materials that could be reclaimed from the pavement; these materials could be mixed with recycling agents to produce recycled mixtures. The important expected benefits of recycling process are the conservation of natural resources and reduction of environmental impact. The primary objectives of this work are evaluating the Tensile and Shear Properties of recycled asphalt concrete mixtures, In addition to the resistance to moisture damage. The impact of implementing three types of recycling agents on asphalt concrete properties was also investigated. For this purpose, old materials reclaimed from field, (100% RAP), virgin filler at 3 percent content by weight of mixture and three types of recycling agents ( soft asphalt cement of penetration grade 200-300, soft asphalt cement of penetration grade 200-300 blended with 4% silica fumes and soft asphalt cement of penetration grade 200-300 blended with 6% fly ash ) at 1.5% content by weight of mixture have been implemented and used to prepare recycled mixtures. Mixtures were subjected to the following tests: Marshall Test (12 specimens), indirect tensile strength test at 20ºC, 25ºC, 40ºC, and 60ºC (48 specimens), indirect tensile ratio ( 12 specimens), double punch shear test (12 specimens).


It was found that using (soft asphalt cement blended with silica fumes) as a recycling agent revealed better performance results than the other type of recycling agent. The percentages of variation for recycled mixtures with recycling agent of (soft asphalt cement blended with silica fume) when compared to aged mixture were ( -13.8%, -25.05%, 229.5%, -47.67%, ) for properties of ( Marshall stability, indirect tensile strength at 60ºC, tensile strength ratio, double punch test,), respectively.

The study aims to predict Total Dissolved Solids (TDS) as a water quality indicator parameter at spatial and temporal distribution of the Tigris River, Iraq by using Artificial Neural Network (ANN) model. This study was conducted on this river between Mosul and Amarah in Iraq on five positions stretching along the river for the period from 2001to 2011. In the ANNs model calibration, a computer program of multiple linear regressions is used to obtain a set of coefficient for a linear model. The input parameters of the ANNs model were the discharge of the Tigris River, the year, the month and the distance of the sampling stations from upstream of the river. The sensitivity analysis indicated that the distance and discharge have the most significant affect on the predicted TDS concentrations. The results showed that a network with (8) hidden neurons was highly accurate in predicting TDS concentration. The correlation coefficient (r), root mean square error (RMSE) and mean absolute percentage error (MAPE) between measured data and model outputs were calculated as 0.975, 113.9 and 11.51%, respectively for testing data sets. Comparisons between final results of ANNs and multiple linear regressions (MLR) showed that the ANNs model could be successfully applied and provides high accuracy to predict TDS concentrations as a water quality parameter.

In the period of the marked urban decline that the country undergoes now, which urges us toward making a comparison between the beginning of the modern Iraqi architecture and its ascending path up to its peak and the periods of its decline until it reached a very bad condition which has been referred to by many critics and specialists. In order not to have solutions that are subject to action-and-reaction principle, it is necessary to search for the intact origins of this architecture and its construction, define its concepts and achievements and the methods adopted by its pioneers to scaffold the urban status of Iraq and to find a pure Iraqi touch full of modernity and innovation. Dr. Qahtan Al-Madfa’i is one of those distinguished pioneers whose works and urban outcome can take as excellent examples of that period and to deduce from him and from his work many things that cannot be ignored.


All of this will be done through the illustration and analysis of selected group of Al-Madfa’i’s buildings, designed and implemented, and to be compared with the works of his international architects and thereby reaching the goal of the research.