research centers


Search results: Found 18

Listing 1 - 10 of 18 << page
of 2
>>
Sort by

Article
Feasibility and Optimization of Electrochemical Machining for 6061 Aluminum alloy

Author: Dhia Ahmed Alazawi
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2018 Volume: 11 Issue: 1 Pages: 44-53
Publisher: Diyala University جامعة ديالى

Loading...
Loading...
Abstract

The request depending on electrochemical machining (ECM) technique has progressed in a large scale according to different points of view such that; cost or energy consuming, environment protection, reliable performance etc. This work aims to predict and optimize ECM process parameters for important, economic and applicable material (6061 aluminum) by employing L9 Taguchi method as a design of experiment (DOE) approach. This has led to experimental designing, developing a mathematical model and optimizing the entire ECM operation. This was carried out by controlling the chosen process variables (voltage, flow rate speed and electrolyte concentration) in order to optimize and predict the responses namely material removal rate (MRR) and dissolution rate. ANOVA, 3D contour graphs and perturbation plots have been employed to identify the analysis of variance of each response as well as to show the significant model terms. The process parameters i.e. voltage, flow rate speed and electrolyte concentration have been ranged to be 15-25V, 8-12 l/min and 3.36-7 % respectively. In both cases of MRR and dissolution rate the voltage parameter has seen to be the prominent factor that affects the responses so as to investigate highest value of MRR and dissolution rate, 0.477 g/min and 2.149 mm/min, respectively. This has been confirmed due to the results obtained from the ANOVA analysis which shows maximum F-valu for the voltage in the MRR and dissolution rate such that; 921.91 and 1608.34 respectively. But, still there was a considerable enhancement in the MRR and dissolution rate due to the increment in the flow rate speed and electrolyte concentration. Model validation has been carried out and thus the results invistigated that all the considered models were adequate since the residuals in prediction of each response were ignored, because the residuals were semi-matched with the diagonal line. Optimizations of responses were performed in this work numerically by using two types of criteria (restricted and non-restricted). According to these criteria, important increment in the MRR can be obtained which reaches 37%. A considerable enhancement has been obtained in the dissolution rate due to the comparison between the two criteria which results in increment by around 11% as well.


Article
Analysis and Optimization of Resistance Spot Welding Parameter of Dissimilar Metals Mild Steel and Aluminum Using Design of Experiment Method
تحليل وأمثلة متغيرات لحام المقاومة النقطي للمعادن المختلفة حديد المطاوع والألمنيومباستخدام طريقة تصميم التجارب

Author: Sabah Khammass Hussein
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2015 Volume: 33 Issue: 8 Part (A) Engineering Pages: 1999-1011
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

This research aims to study the effect of parameters of the resistance spot welding (RSW) on the shear strength of the spot weld for different metals {AA 6061-T6and AISI 1010}using (0.5 and 0.7 mm) thickness.Three values for each welding parameters (welding current, electrode force, squeeze time and welding time) are to be used. The effect of those parameters have been analyzed by Minitab program by design of experiments (DOE) in order to determine and reduce the number of specimens required to achieve the tests. The design of experiment method which used was Taguchi methodThe experimental tests that had been done are shear, Microhardness and microstructure tests.It was found that the maximum shear force in welding of dissimilar metals(AA 6061-T6 with AISI 1010)is (F = 1.14 KN for t = 0.7 mm ).This value has been optimized to reach (F =1.24KN) using DOE. The minimum shear force was(F = 0.25 KN in t = 0.5 mm).In general, increasing the welding current and sample thickness gave an increase in the shear force, but at the same time the reduction in shear force have occurred during the increasing in electrode force, squeeze time and welding time.From Microhardness tests, the maximum value of hardness is found at the center of nugget zone (NZ) and it reduces slightly until reaching constant values away from NZ.

هذا البحث يهدف لدراسة تأثير متغيرات لحام المقاومة النقطي على مقاومة القص لنقطة اللحام لمواد مختلفة{AA 6061-T6and AISI 1010 } باستخدام سمك (0.5 , 0.7) ملم.استخدمت ثلاث قيم من متغيرات اللحام ( تيار اللحام , قوة القطب , زمن الضغط وزمن اللحام ).تم تحليل تأثير هذه المتغيرات باستخدام برنامج (Minitab) بطريقة تصميم التجارب (DOE) لغرض حساب وتقليل عدد العينات اللازمة في الاختبارات.طريقة تصميم التجربة التي استخدمت هي طريقة تاكوشيالتجارب العملية المنجزة هي (اختبار الشد القصي , الصلادة الدقيقة وفحص البنية المجهرية ).وجد ان أقصى قوة قص في لحام المواد المختلفة {AA 6061-T6 and AISI 1010 }هي ( F = 1.14 KN بسمك t = 0.7 mm ). تم تحسين هذه القيمة الى ( F = 1.24 KN) باستخدام طريقة تصميم التجارب (DOE). اقل قيمة قوة قص كانت (F = 0.25 KN بسمك t = 0.5 mm).بصورة عامة , زيادة تيار الحام وسمك المعدن اعطى زيادة في قوة القص , ولكن بنفس الوقت النقصان في قوة القص حصل خلال زيادة قوة القطب وزمن الضغط وزمن اللحام.من خلال تجربة الصلادة (المجهرية) أقصى قيمة للصلادة لوحظت في مركز المنطقة الصلبة وتقل تدريجيا حتى تصل قيمة ثابتة بعيدا عن هذه المنطقة.


Article
Optimization the Resistance Spot Welding Parameters of Austenitic Stainless Steel and Aluminum Alloy Using Design of Experiment Method

Authors: Sabah Khammass Hussein --- Osamah Sabah Barrak
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2016 Volume: 34 Issue: 7 Part (A) Engineering Pages: 1383-1401
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

This research aims to study the effect of RSW parameters on the sheerforce of the spot weldedfor two materials {AISI 304L and AA 6061-T6}with (0.5 and 0.7 mm) thickness. Three values for each welding parameters (welding current, electrode force, squeeze time and welding time) are to be used. The effect of those parameters has been analyzed by using design of experiments (DOE) in order to determine and reduce the number of the tested specimens.The experimental tests have been donethat are;shear, micro hardness tests and microstructure examination. It was found that the maximum shear force in welding of similar material AISI 304L is (F = 4.78 KN for t = 0.7 mm), while in the joint of dissimilar material (AA 6061-T6 with AISI 304L), the maximum shear force is (F = 1.42 KN for t = 0.7 mm). These values have been optimized to reach (F =5.13 KN & F =1.54 KN) respectively by using DOE. The minimum shear force was (F = 0.07 KN in t = 0.5 mm).It was found that, increasing the welding current and sheet thickness gave an increase in the shear force, but at the same time the reduction in shear force has occurred during the increasing in electrode force, squeeze time and welding time. From micro hardness tests, it was found that the maximum value of hardness was at the center of nugget zone (NZ) and it reduces slightly until reaching constant values away from nugget zone.


Article
Effect of Different Tool Geometries in Friction Stir Welding of AA 2024-T3 using Design of Experiments
تأثير الاشكال المختلفة للعُدة في لحام المزج الاحتكاكي لسبيكة المنيوم AA2024-T3 بإستخدام طريقة تصميم التجارب

Authors: Moneer H. Al-Saadi منير حميد السعدي --- Sabah Khammass Hussein صباح خماس حسين --- Mursal Luaibi Saad مرسل لعيبي سعد
Journal: AL-NAHRAIN JOURNAL FOR ENGINEERING SCIENCES مجلة النهرين للعلوم الهندسية ISSN: 25219154 / eISSN 25219162 Year: 2017 Volume: 20 Issue: 1 Pages: 19-26
Publisher: Al-Nahrain University جامعة النهرين

Loading...
Loading...
Abstract

In this work, Aluminum alloy (AA2024-T3) was welded by friction stir (FSW) method using different pin profile design types; straight cylinder, threaded cylinder, tapered cylinder hexagonal, square, and threaded taper. For each type, a flat and concave shoulder was used, as well as, the welding process was single and double. The results of mechanical tests are analyzed using design of experiments method (DOE). The best and weaken mechanical properties (tensile strength, bending force and hardness) are observed when the welding is achieved by hexagonal and straight cylinder pin profile respectively. A concave shoulder gave higher mechanical properties as compared with flat shoulder. The change in welding process type presented a sensible effect. Nugget zone hardness is higher than that of base metal for all specimens. The optimum hardness result is recorded by hexagonal pin with concave shoulder profile.

في هذا البحث، تم لحام سبيكة الالمنيوم (AA2024-T3) بطريقة المزج الاحتكاكي باستخدام انواع مختلفة التصميم لشكل النتوء؛ اسطوانة مستوية, اسطوانة مسننة، اسطوانة مغزلية، سداسي، مربع ومغزل مسنن. استُخدم لكل نوع كتف مسطح ومقعر، بالاضافة الى ذلك، كانت عملية اللحام منفردة ومزدوجة. تم تحليل نتائج الاختبارات الميكانيكية بأستخدام طريقة تصميم التجارب. افضل واضعف الخواص الميكانيكية ( مقاومة الشد، قوة الانحناء والصلادة) لوحظت عندما يُنجز اللحام بأستخدام النتوء ذو الشكل السداسي والاسطواني المستوي على التوالي. اعطى الكتف المقعر اعلى الخواص الميكانيكية مقارنة مع الكتف المسطح. اعطى التغيير في نوع عملية اللحام تأثير محسوس. صلادة منطقة خط اللحام اعلى من المعدن الاساس لكافة العينات. سُجلت امثل نتيجة صلادة بإستخدام النتوء السداسي ذو الكتف المقعر.


Article
Study the Effect of Welding Parameters on the Residual Stresses Induced by Submerged Arc Welding process

Authors: Samir Ali Amin --- Sadeq Hussein Bakhy --- Fouad Ali Abdullah
Journal: AL-NAHRAIN JOURNAL FOR ENGINEERING SCIENCES مجلة النهرين للعلوم الهندسية ISSN: 25219154 / eISSN 25219162 Year: 2017 Volume: 20 Issue: 4 Pages: 945-951
Publisher: Al-Nahrain University جامعة النهرين

Loading...
Loading...
Abstract

Welding residual stress has influences on fatigue, fracture, and corrosion. It is therefore important to explore the welding factors effect on the residual stresses. In this work, four welding factors (current, arc voltage, welding travel speed and included angle) were used to weld low carbon steel (ASTM A516 Grade 60).The experiments included welding of (60) pieces with dimensions of (300 x 150) mm and 10 mm thickness that were conducted based on the design matrix founded by using design of experiment (DOE) software (DESIGN EXPERT 10) with response surface methodology (RSM) technique. The X-Ray diffraction (XRD) method was used to measure the residual stress, which was then modeled and optimized in terms of the welding factors using (RSM) technique. The data showed that the welding travel speed and arc voltage have a significant influence on the residual stress. It was found that the optimum solution for minimum residual stress was at 450 Amp welding current, 34 volt arc voltage, 38 cpm welding speed, and 60⁰ included angle. Where, the optimum value of residual stress was (-88.4 MPa). Finally, the predicted and experimental results of residual stress were in agreement with a maximum error of 1.8%.

تؤثر الأجهادات المتبقية المتولدة من عملية اللحام على كل من الكلل والتآكل والكسر الميكانيكي. لذلك فمن المهم دراسة تأثير عوامل اللحام على تولد الاجهادات المتبقية. في هذه الدراسة تم تم دراسة حالة الاجهادات المتبقية المتولدة من اللحام بطريقة القوس المغمور لصلب واطيء الكاربون نوع (A516 Gr 60), حيث تم استخدام اربعة عوامل لحام هي التيار والفولطية وسرعة اللحام وزاوية اخدود اللحام, ان ابعاد القطع المعدنية المعدة للحام هي (300x150x10 mm). تم بعد ذلك قياس الاجهادات المتبقية المتولدة بطريقة حيود الاشعة السينية (XRD) ثم عمل موديل رياضي وحساب القيمة المثلى بوصفها دالة لعوامل اللحام المستخدمة بواسطة تقنية تصميم التجارب (DOE) مع منهجية الاستجابة السطحية (RSM). حيث اظهرت النتائج ان التأثير الاكبر على تولد الاجهادات المتبقية كان لفولطية القوس وسرعة اللحام, كذلك وجد ان الظروف المثلى التي تعطي اقل اجهادات متبقية هي (450 Amperes, 34 Volt, 38 cpm and 60⁰ Included Angle) حيث تكون القيمة المثلى للاجهادات المتبقية عند هذه الظروف هي (-88.4). واخيراً كان هنالك توافق كبير بين النتائج المتوقعة والعملية للاجهادات المتبقية مع نسبة خطاء قليلة جداً لا تتجاوز 1.8%.

Keywords

: SAW --- Residual Stress --- Welding parameters --- DOE --- RSM


Article
Influence of SAW Welding Parameters on Microhardness of Steel A516-Gr60

Authors: Sadeq H. Bakhy --- Samir A. Amin --- Fouad A. Abdullah
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 10 Part (A) Engineering Pages: 1039-1047
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

Submerged Arc Welding (SAW) process is generally used for industries, such as petroleum storage tanks, pressure vessels, and structural components.Good mechanical properties of welded joint lead to crack-free strong joints. In this research, included angle, current, welding travel speed and arc voltage were utilized as welding parameters to weld ASTM A516 Grade 60 (low carbon steel). The experiments were carried out according to a design matrix that established by DOE (Version10) with RSM technique. Microhardness of welded samples was measured by a Digital Microhardness Tester, and then RSM technique was used to model and optimize the microhardness based on the welding parameters. The results showed that the including angle and welding current have a great effect on the microhardness. The optimum solution for minimum microhardness was found at 450 Amp welding current, 38 cpm welding speed, 34-volt arc voltage and included angle of 60⁰. The optimum value of microhardness was (186.7 HV). Eventually, the experimental and predicted results of microhardness were found in good agreement with 4.6%. maximum error.

Keywords

SAW --- Microhardness --- Welding parameters --- DOE --- RSM


Article
Determination of Optimum Welding Parameters for FSW AA2024-T351
تحديد معاملات اللحام المثالية لسبائك الالمنيوم (AA2024-T351) الملحومة بواسطة لحام الخلط الاحتكاكي

Authors: Zuhair Altaher زهير الطاهر --- Qasim Abbas Atiah قاسم عباس عطية --- Samir Ali Amin Al-Rubaie سمير علي أمين الربيعي
Journal: Al-Khwarizmi Engineering Journal مجلة الخوارزمي الهندسية ISSN: 18181171 23120789 Year: 2015 Volume: 11 Issue: 1 Pages: 51-64
Publisher: Baghdad University جامعة بغداد

Loading...
Loading...
Abstract

Friction stir welding is a relatively new joining process, which involves the joining of metals without fusion or filler materials. In this study, the effect of welding parameters on the mechanical properties of aluminum alloys AA2024-T351 joints produced by FSW was investigated.Different ranges of welding parameters, as input factors, such as welding speed (6 - 34 mm/min) and rotational speed (725 - 1235 rpm) were used to obtain their influences on the main responses, in terms of elongation, tensile strength, and maximum bending force. Experimental measurements of main responses were taken and analyzed using DESIGN EXPERT 8 experimental design software which was used to develop the response surface methodology (RSM) models. Mathematical model of responses, as functions of used welding conditions, were obtained and analyzed by ANOVA variance to verify the adequacy of these models. The resultant quadratic models showed that as the rotation speed or welding speed increases, the tensile strength and elongation of the joint firstly increase to a maximum value and then decrease more likely due to the occurrence of void defect. Increasing both welding speed and rotational speed leads to increase the maximum bending force firstly to a maximum value and then decreases. However, the welding speed was found more significant than rotational speed. A good agreement was found between the results of these models and optimization with the experimental ones with confidence level of 95%.

اللحام بالخلط الاحتكاكي هو عملية لحام جديدة نسبياً، و الذي يستلزم لحام المعادن بدون استخدام الانصهار او المواد المالئة. في هذه الدراسة، تم التحقق من تاثير معاملات اللحام على الخواص الميكانيكية لسبائك الالمنيوم (AA2024-T351) الملحومة بطريقة لحام الخلط الاحتكاكي.تم استخدام مديات مختلفة لمعاملات اللحام، بوصفها عوامل إدخال، مثل سرعة اللحام (6-34 mm/min) و السرعة الدورانية (725-1235 rpm) للحصول على تاثيرها على الاستجابات الرئيسة، بدلالة الاستطالة و مقاومة الشد، و قوة الانحناء العظمى. كما قد تم إستخدام و تحليل قياسات تجريبية للاستطالة، مقاومة الشد، وقوة الانحناء العظمى بإستعمال برنامج التصميم التجريبي (DESIGN EXPERT 8) للحصول على نماذج منهجية للاستجابة السطحية (RSM). كما تم إستحصال و تحليل النموذج الرياضي للإستجابات (الاستطالة، مقاومةالشد، وقوةالانحناءالعظمى) كدوال لضروف اللحام المستعملة باستعمال تباين ANOVA للتحقق من ملائمة هذه النماذج. النماذج المربعة الناتجة بينت بانه بزيادة سرعة اللحام و السرعة الدورانية، فانه تزداد مقاومة الشد و الاستطالة الى قيمة عظمى في البداية ثم تتناقص بسبب حدوث العيوب الفراغية. كما ان زيادة كلا من سرعة اللحام والسرعة الدورانية تؤدي الى زيادة قوة الانحناء العظمى اولاً الى قيمة عظمى ثم تتناقص. ومهما يكن من امر، فقد وجد بان سرعة اللحام تكون اكثر تاثيرا من السرعة الدورانية. و وجد توافق جيد بين نتائج هذه النماذج و الامثلية مع النتائج العملية بمستوى ثقة (95%).


Article
Spot Welding of Galvanized Steel ASTM A653 Using Oxygen Free High Conductivity Copper Interlayer
اللحام النقطي للفولاذ الكاربوني (ASTM A653) باستخدام نحاس عالي النقاوة كطبقة وسطية

Author: Mohammed Hillan Sar
Journal: journal of kerbala university مجلة جامعة كربلاء ISSN: 18130410 Year: 2016 Volume: 14 Issue: 1 Pages: 63-72
Publisher: Kerbala University جامعة كربلاء

Loading...
Loading...
Abstract

The effect of spot welding parameters (Current and Applied Load) are studied in welding of galvanized steel specimens. Three values of current 9600, 11000 and 12300 AMP and load of 350, 400, 450 kg are used. The results indicate that the shear force improve with increasing the current and decreasing the load. The optimum shear force is achieved with current of 12300 AMP and load of 350 kg. Those parameters is used to weld steel (with and without galvanize layer) using the OFHC copper as interlayer with different thickness (0.1, 0.2 and 0.3mm). The results show that OFHC as interlayer reduce the shear force.

تم دراسة تأثير متغيرات لحام النقطة (التيار وحمل مسلط ) على عينات من الفولاذ المغلون . اختيرت ثلاث قيم من التيار ( 9600, 11000، 12300 أمبير) وثلاث قيم من حمل مسلط ( 350 , 400 ، 450 كغم ) للحام العينات . اظهرت النتائج ازدياد قوة القص بزيادة التيار وصولا الى 12300 امبير وحملا مسلطاً عند 350 كغم. استخدمت هذه المتغيرات للحام العينات المغلونة وغير المغلونة ( بعد ازالة طبقة الزنك) باستعمال طبقة رقيقة من النحاس عالي النقاوة كمعدن حشو وباسماك (0.1، 0.2 ، 0.3 ملم ). بينت النتائج ان استخدام معدن الحشو ساعد على خفض قوة القص.


Article
MINIMIZATION THE DEFLECTION AND COST OF REINFORCEMENT FRAME USING DOE
تقليل انحراف وكلفة الهياكل المقواة بأستخدام طريقة تصميم التجارب

Author: Sabah Khammass Hussein
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2015 Volume: 19 Issue: 6 Pages: 59-76
Publisher: Al-Mustansyriah University الجامعة المستنصرية

Loading...
Loading...
Abstract

The stiffening of a rectangular frame is taking place by using bars. Those bars are distributed longitudinally, transversely, inclined and mixed shape. The theoretical deflection of frame free edge is calculated and compared with the (FEM) using MATLAB and ANSYS software programs. A good agreement is found from the (FEM) model as compared with the theoretical and ANSYS results. Different bar distributions gave a different torsional resistance and deflection. A higher torsional resistance is found in the transverse and cross shape of bar distributions. Minitab program is used to analyze the results and minimize the deflection and cost by (DOE). In which, the effect of input factors and their interactions has been studied. The main effect on the deflection and cost has been observed in the inclined bars. A higher reduction in the deflection and cost has been observed in the existence of longitudinal and transverse bars, respectively.

هذه الوثيقة هي قالب حي. المكونات المختلفة من البحث ]العنوان، النص، الحاشيات، إلخ[ قد تم تعريفها بالفعل على الورقة النمطية تتمتقوية الهيكل المستطيل بأستخدام قضبان. وزِعت هذه القضبان بشكل طولي، عرضي، مائل ومدموج. الانحراف النظري لحافة الهيكل الحرة حٌسِ بوقٌورِن مع طريقة العناصر المحددة باستخدام برنامجي ال ) MATLAB ( و ال) ANSYS (. لاحظنا توافق جيد لنموذج طريقة العناصر المحددةمقارنة مع نتائج الجزء النظري وال) ANSYS (. التوزيعات المختلفة للقضيب اعطت اختلاف بمقاومة الألتواء والانحراف. اعلى مقاومة التواءوجدت في توزيع القضبان بشكل عرضي ومتقاطع. استخدم برنامج ال) Minitab ( لتحليل النتائج وتقليل الانحراف والكلفة بطريقة ال ) DOE .)حيث دُرِس تأثير العوامل الداخلة وتداخلاتها. لوحظ التأثير الرئيسي على الانحراف والكلفة في القضبان المائلة. اعلى نسبة تخفيض في الانحرافوالكلفة لٌوحظت بوجود القضبان بالشكل الطولي والعرضي على التوالي.ِ


Article
Studying the Efficiency of Lime-Soda Sinter Process to Extract Alumina from Colored Kaolinite Ores Using Factorial Technique of Design of Experiments

Authors: Hijran Z. Toama --- Abdul-Wahab A. Al-Ajeel --- Ajheen H. Jumaah
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 5 Part (A) Engineering Pages: 500-508
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

As the increasing demand for alumina in recent years with the result diminishing reserve of bauxite, the need to secure a domestic raw material base is driving research in new technologies to process low grade ores into alumina, with the intention that these technologies will lead to a significant reduction of bauxite and alumina transportation costs, allow the extraction of more valuable components from the ore and reduce environmental impact. Clays are types of the low-grade aluminum ores, they're also well abundant which make them a potential substitutes for Bauxite. In this work, lime soda sinter process was adopted for extracting alumina from kaolinitic claystone from Al-Ga'ara formation (Duekhla) quarry in western Iraq. The operation efficiency of sintering was studied in which the whole process has been done with three stages: the sintering process for the raw materials, leaching and carbonizing processes to precipitate and separate the alumina from the leach pregnant solution . Factorial technique of Design of Experiments (DOE) module in Minitab was used as a principal methodology to examine the sintering efficiency over alumina extraction. The results obtained showed that the optimum parameters for the sintering operation were CaO/SiO2 molar ratio of 2.2, Na2O/Al2O3 molar ratio of 1.2, sintering temperature at 1213 °C for 90 min. The sintered materials were leached with sodium carbonate solution, and sodium aluminate solution was obtained. By bubbling carbon dioxide gas into this extract solution aluminum hydroxide [Al(OH)3] has been precipitated and on calcination at 1200 °C for 2 hrs, alpha alumina (α-Al2O3) was obtained with purity of 98.5 %.

Listing 1 - 10 of 18 << page
of 2
>>
Sort by
Narrow your search

Resource type

article (18)


Language

English (13)

Arabic and English (3)

Arabic (2)


Year
From To Submit

2018 (6)

2017 (3)

2016 (2)

2015 (5)

2013 (1)

More...