Abbas A. S. Al- Jeebori
Volume 1, Issue 1 , June 2008, Pages 1-15
Abstract
The surface selection method is the performance evaluation criteria (PEC) to reach an optimum surface selection. The method is not limited to surfaces found in the literature, but will accommodate any type of the heat transfer surfaces. The capability is demonstrated by the surface of selection of gas ...
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The surface selection method is the performance evaluation criteria (PEC) to reach an optimum surface selection. The method is not limited to surfaces found in the literature, but will accommodate any type of the heat transfer surfaces. The capability is demonstrated by the surface of selection of gas /gas plate-fin heat exchanger. A general methodology for plate-fin heat exchangers surface selection has been shown and applied for a specific illustration problems. The objective of the present work can be summarized as the selection of the plate-fin surfaces (high performance surfaces) depending on the qualitative and quantitive consideration for low Re.
Volume 1, Issue 1 , June 2008, Pages 1-14
Abstract
تم استخدام النتروجين السائل LN2 كمائع شغل لمحرك يعمل على أساس دورة رانكن المفتوحة Open .Rankine Cycle ان هذا المحرك تم تصميمه نظرياً بحيث يحقق اكبر عملية انتقال حرارة خلال شوط ...
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تم استخدام النتروجين السائل LN2 كمائع شغل لمحرك يعمل على أساس دورة رانكن المفتوحة Open .Rankine Cycle ان هذا المحرك تم تصميمه نظرياً بحيث يحقق اكبر عملية انتقال حرارة خلال شوط التمدد Expansion Stroke باستخدام مبادلات حرارية هوائية، حيث إن هذا المحرك لا يوجد فيه أي احتراق بل تمدد لضغط النتروجين السائل فقط .إذا كانت كمية الحرارة الداخلة خلال شوط التمدد كبيرة , فان هذا المحرك يعوض عن استخدام المحركات الكهربائية من ناحية القدرة الخارجة وكلفة التشغيل في حالة الإنتاج بالجملة. كل هذه التحديات الهندسية تم دراستها في هذا البحث. بالإضافة إلى العديد من الطرق اللازمة للحصول على التمدد الايزوثيرمي Isothermal Expansion
Volume 1, Issue 1 , June 2008, Pages 15-34
Abstract
The effect of footing closeness (of three parallel similar strip footings at equal distance from each other) on soil bearing capacity is studied using the finite element method. Flexible and Rigid (surface and buried) footings resting on clayey (under undrained conditions) and sandy soils, are analyzed. ...
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The effect of footing closeness (of three parallel similar strip footings at equal distance from each other) on soil bearing capacity is studied using the finite element method. Flexible and Rigid (surface and buried) footings resting on clayey (under undrained conditions) and sandy soils, are analyzed.
The effect on bearing capacity due to footings interference is expressed by the efficiency factor (Ef), which represents the ratio between the bearing capacity of the closely-spaced footings and that of a similar single footing under the same conditions.
The results show negligible effect of interference on the bearing capacity of flexible footings. The closeness of rigid strip footings, generally, results in increasing the soil bearing capacity. The embedment depth has a suppressing effect on interference when the footings are very close to each other.
Sallal R. Alowaisy; Muhaned A. Shallal
Volume 1, Issue 1 , June 2008, Pages 16-31
Abstract
Push-off tests were performed and a finite element model was adopted to study the influence of steel fibers on shear transfer strength of concrete. Nine push-off specimens were used. The specimens were divided into three groups each of a definable amount of steel fibers. Also, the amount of steel stirrups ...
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Push-off tests were performed and a finite element model was adopted to study the influence of steel fibers on shear transfer strength of concrete. Nine push-off specimens were used. The specimens were divided into three groups each of a definable amount of steel fibers. Also, the amount of steel stirrups crossing the shear plan was variable. The results show that the use of steel fibers in combination with steel stirrups can minimize the required amount of stirrups and improve strength and ductility. Comparing test and theoretical results with the provisions of ACI-05 Code, it is concluded the ACI-05 shear-friction method gives a very conservative estimate of shear transfer
Ali H. Abbar
Volume 1, Issue 1 , June 2008, Pages 32-45
Abstract
An electrochemical cell consisting of two electrodes (Lead-6%antimony alloy cathode and copper anode, (99.9%)) was used to study the electrolytic preparation of copper powder with particle size less than (63µm) directly as powdery form. Copper sulphate dissolved in sulfuric acid solution was used as ...
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An electrochemical cell consisting of two electrodes (Lead-6%antimony alloy cathode and copper anode, (99.9%)) was used to study the electrolytic preparation of copper powder with particle size less than (63µm) directly as powdery form. Copper sulphate dissolved in sulfuric acid solution was used as electrolyte. The produced powder was thoroughly washed with an acidified distilled water and absolute ethanol, then dried under an inert atmosphere at 80oC, and classified by screening. Samples of prepared powder were taken to determine their purity by atomic absorption. The effects of current density, metal ion concentration, sulfuric acid concentration, and electrolysis time on the weight percent of copper powder less than (63µm), yield and current efficiency were studied.It was found that copper powder with particle size less than (63µm) can be prepared at a weight percent (79.7% ) and current efficiency( 75%) using cathode current density (0.16 A/cm2),copper ion concentration(5gm/l),sulfuric acid concentration(100gm/l)temperature(25-30oC)and electrolysis time equal to(2hr). The prepared powder having an apparent density (2.24 gm/cm3) and specific surface area (421 X 103 cm2/gm). Its average particle size was (42 µm) and its purity was (99.7%)
Thulfikar Razzak Al- Husseini
Volume 1, Issue 1 , June 2008, Pages 46-59
Abstract
In this research, optimum hydraulic design for siphon has been studied depending on the method of optimization (Modified Hooke and Jeeves) with some modifications. Some modifications on this method have done. These modifications are: 1- Modification on the assumed initials base points 2- Modification ...
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In this research, optimum hydraulic design for siphon has been studied depending on the method of optimization (Modified Hooke and Jeeves) with some modifications. Some modifications on this method have done. These modifications are: 1- Modification on the assumed initials base points 2- Modification on the value of step length 3- Modification on the value of the reduced step length at each trial. The siphon shapes that used in this study are pipe, square, and rectangular. The materials that used are concrete and steel for designing inverted siphon. A computer program depending on the method of (Modified Hooke and Jeeves) has written for optimum hydraulic design of inverted siphon structure with "Quick- Basic" language. Many examples solved by using this program to make insure the accuracy of it.
Rehab Noor Mohammed; Ali Meer Ali Jasim; Ahmed Khadem
Volume 1, Issue 1 , June 2008, Pages 60-75
Abstract
In this research, we study the effect of the some parameters (gas turbine speed, power turbine speed, mass flow rate of air, mass flow rate of fuel, compression ratio, air to fuel ratio and inlet compressor temperature) on the overall system efficiency, alternator efficiency and the overall heat efficiency ...
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In this research, we study the effect of the some parameters (gas turbine speed, power turbine speed, mass flow rate of air, mass flow rate of fuel, compression ratio, air to fuel ratio and inlet compressor temperature) on the overall system efficiency, alternator efficiency and the overall heat efficiency of the two shaft gas turbine system, the working fluid was propane. Firstly we checked the experimental results by plotted the (T-S diagram) between the experimental and analytical solution and then we study the effect of the above parameters on the overall system efficiencies. Also we checked the effect of the inlet compressor temperature on the overall gas turbine performance .From these results, we can notes the increasing of the compression ratio and the power turbine speed will increase the overall efficiency, overall heat efficiency and decreasing the alternator efficiency, at the same time is increase the gas turbine efficiency
Ali Meer Ali Jasim Al-Zamily
Volume 1, Issue 1 , June 2008, Pages 76-94
Abstract
The effect of the environment (surrounding) conditions on the effectiveness of the heat exchanger for different working fluids are discussed here. The heat transfer between the heat exchanger external wall and environment are considered taken by radiation and convection. The convection heat transfer ...
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The effect of the environment (surrounding) conditions on the effectiveness of the heat exchanger for different working fluids are discussed here. The heat transfer between the heat exchanger external wall and environment are considered taken by radiation and convection. The convection heat transfer coefficient between the heat exchanger wall and the environment is taken as temperature dependence and the heat exchanger external wall is assumed a grey body. We analyzed the effect of the environment conditions on two type of heat exchanger working fluid, low viscid fluid (water) and medium viscid fluid (oil SAE-30). Because of the time is very effected factor on the heat transfer, then the unsteady state of the fluid inside the heat exchanger are assumed and analyzed in the present article. The increase of the emissivity, environment heat coefficient and environment temperature will decrease the hot fluid effectiveness and increase the entropy generation number. The fluid effectiveness is very effected by the environment specially when the working fluid has lower viscosity for same flow rate. The finite difference techniques is used to solve the unsteady state differential equations for the hot and cold fluid.
Adnan Flayih Hassan
Volume 1, Issue 1 , June 2008, Pages 95-108
Abstract
This study had been conducted to investigate the influence of magnetized water on the properties of cement mortars such as initial and final setting time, consistency and compressive strength with various water/cement ratios at the ages of 1 and 7 day. Results of (50) specimens with different shapes ...
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This study had been conducted to investigate the influence of magnetized water on the properties of cement mortars such as initial and final setting time, consistency and compressive strength with various water/cement ratios at the ages of 1 and 7 day. Results of (50) specimens with different shapes had been adopted, which represented mortars specimens having compressive strength ranging from (5.5) to (32.5) MPa, initial setting time ranging from (4) to ( 32) minutes and final setting time ranging from (303) to (546) minutes, by using two types of mixing water , first one is tap water , and the other is magnetized water.The results showed that the use of magnetized water in producing cement mortars lead to increase in the compressive strength and decreasing in the initial and final setting time with compare to use of tap water. Results also showed that the optimum water/cement ratio give best compressive strength under the conditions of this study was (0.45).
Haitham Ali Bady
Volume 1, Issue 1 , June 2008, Pages 109-125
Abstract
Design of steel tapered member under combined axial and flexural strength is somewhat complex if no approximations are made. However, recent Load Resistance Factor Design (LRFD) of the AISC code has treated the problem with sufficient accuracy and ease. The aim of this study is to present an algorithm ...
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Design of steel tapered member under combined axial and flexural strength is somewhat complex if no approximations are made. However, recent Load Resistance Factor Design (LRFD) of the AISC code has treated the problem with sufficient accuracy and ease. The aim of this study is to present an algorithm for the optimum design of steel frames composed of tapered beams and columns with I-section in which the width is taken as constant, together with the thickness of web and flange, while the depth is considered to be varying linearly between joints .The objective function which is taken as the weight of the steel frame is expressed in terms of the depth at each joint. Both the displacement and combined axial and flexural strength constraints are considered in the formulation of the design problem .The strength constraints are expressed as a nonlinear function of the depth variables. The optimality criteria method is then used to obtain a recursive relationship for the depth variable under the displacement and strength constraints. Numerical examples are presented to demonstrate the practical application of the algorithm
Ali I. Al-Mosawi
Volume 1, Issue 1 , June 2008, Pages 126-132
Abstract
This study aims to investigate possibility to increase the flame retardancy for composite materials by addition of a flame retardant material which represent the zinc borate as a coating layer of (4mm) thickness on the surface of composite material consist of araldite resin reinforced by hybrid fibers ...
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This study aims to investigate possibility to increase the flame retardancy for composite materials by addition of a flame retardant material which represent the zinc borate as a coating layer of (4mm) thickness on the surface of composite material consist of araldite resin reinforced by hybrid fibers from carbon and kevlar fibers as a consecutive layers which be as a woven roving (º 90 - º 0). Then, this system (flame retardant material and composite material) was exposed to a direct flame which generated from oxyacetylene flame (up to 3000ºC) and gas flame (2000ºC) under different exposure distances (10,15, and 20mm), and study the range of resistance of flame retardant material layer to the flames and protected the substrate where we used the method of measuring the surface temperature opposite to the flame where we obtained the better results with large exposed distance and large percentage from protective layer which is zinc borate (30%) for both types of flames , as well as the flame resistance will be increased with decrease the flame temperature .
