Print ISSN: 1813-162X

Online ISSN: 2312-7589

Volume 18, Issue 3

Volume 18, Issue 3, Summer 2011, Page 1-104

Chemical Acidic Attack Resistance of Lightweight Concrete with Additives

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 16-29

تم في هذا البحث دراسة تأثير حامضي الكبريتيك H2SO4 بتركيز (8%) والهيدروكلوريك HCl بتركيز (8%) ومياه الفضلات الصناعية من معمل البان جامعة تكريت (pH= 5.1 ,= 850mg/L SO4=, Cl-=750 mg/L , TDS = 2500 mg/L ) على الخرسانة خفيفة الوزن باستخدام الحجر الجيري (Limestone) كركام خفيف الوزن أو بأستخدام المادة الرغوية. كما استخدمت الملدنات الفائقة (SP) لتحسين خواص الخرسانة خفيفة الوزن. حيث تم قياس تأثير الحوامض ومياه الفضلات عن طريق احتساب النسبة المئوية للنقصان بالوزن ومقاومة الانضغاط بأستخدام مواشير خرسانية بأبعاد (010*010*400) ملم والمعدة أصلا لفحص معامل الكسر حيث تم اخذ قطعتي كل موشور بعد اجراء فحص معامل الكسر ليتم غمر الجزء الاصغر من الموشور كلياً في المحاليل اعلاه و مراقبة صعود الاملاح عن طريق غمر (100) ملم من الجزء الثاني من الموشور في المحلولين الحامضيين, أظهرت نتائج الفحوصات ان H2SO4 يكون تأثيره اكثر من HCl بالنسبة للنقصان بالوزن على الخرسانة الاعتيادية بينما يكون تأثير HCl كبيرا على الخرسانة خفيفة الوزن بأستخدام الركام خفيف الوزن (Limestone) وتأثيره اقل من H2SO4 بالنسبة للخرسانة خفيفة الوزن عند استخدام المادة الرغوية . كذلك تبين بأن تأثير H2SO4 على الخرسانة الاعتيادية بالنسبة للنقصان بالمقاومة يكون اقل من تاثير HCl , بينما يكون تاثير H2SO4 كبير على الخرسانة خفيفة الوزن الحاوية على المادة الرغوية وتاثيره اقل على الخرسانة خفيفة الوزن الحاوية على SP و Limestone . اما بالنسبة لمياه الفضلات فقد تم غمر المواشير كلياً فيها ولوحظ بانها لم تؤثر كثيرا على النسبة المئوية للنقصان بالوزن بسبب قلة تركيز الكبريتات والكلوريدات في مياه الفضلات المستخدمة , اما بالنسبة للفقدان بالمقاومة فقد اظهرت النتائج بان مياه الفضلات لا تؤثر كثيرا على مقاومة الخرسانة الاعتيادية والخرسانة خفيفة الوزن الحاوية على الحجر الجيري Limestone كركام خشن , بينما يكون تاثيرها كبير على الخرسانة خفيفة الوزن الحاوية على SP و Limestone معا كركام ناعم وخشن وعلى الخرسانة الحاوية على المادة الرغوية .

Gas Holdup and Liquid-Phase Dispersion in Packed Bubble Columns

Dr. Burhan Sadeq Abdulrazzaq

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 13-22

The gas holdup and liquid phase axial dispersion coefficient are measured in two semi batch packed bubble columns, 10 and 15 cm diameter for an air–water system, at atmospheric conditions. The experiments were carried out using a transient method (the tracer response method). The dispersion coefficient was obtained by adjusting the experimental profiles of tracer concentration with the predictions of the model. Experiment results of packed bubble column, shows a considerable reduction of the backmixing. The investigations have been carried out using RTD measurements and the backmixing is usually characterized by the axial dispersion coefficient obtained from the one-dimensional axial dispersion model. Also, a decrease in superficial gas velocity reduces the liquid backmixing. It is observed that the liquid circulation comprises an upward flow in the column core and a downward flow along the wall. It also seen that the transition from the bubbly flow to the pulsation flow regime occurred at 5-6 cm/s superficial gas velocity. Keywords: Packed Bubble columns, Gas holdup, Liquid dispersion, Liquid circulation

Specific Energy Absorbed Study Of Aluminum (2024-351T) Tubes Alloy Under Lateral Crush

Ayad Arab Ghaidan

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 52-60

This paper aims to find SEA (Specific Energy Absorber) for lateral crushing (statically) behavior for Aluminum (2024-T351) alloy with difference lengths (10, 20, and 30 mm). An experimental, finite element simulation, and theoretical models present to find force-deformation curves and then find SEA for difference lengths. Experimental results more agreements with finite elements simulation and theoretical when length of tubes is increase for load deformation curve, because when the length increases the plastic region increase with initial plastic collapse load (Pc). The experimental, ANSYS simulation and theoretical results have plotted and it has seen that the theory also underestimates the ANSYS results because in theoretical model, is customary to assume that the material is perfectly plastic, therefore, the finite element simulation might predict the experimental results better than the theoretical one. The results show that light density Aluminum alloy is suitable for SEA.Keywords: SEA, Lateral crushing, Finite element method by Ansys.

Hardware Implementation Of Line Clipping A lgorithm By Using FPGA

Amar I. Dawod

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 88-104

The computer graphics system performance is increasing faster than any other computing application. Algorithms for line clipping against convex polygons and lines have been studied for a long time and many research papers have been published so far. In spite of the latest graphical hardware development and significant increase of performance the clipping is still a bottleneck of any graphical system. So its implementation in hardware is essential for real time applications. In this paper clipping operation is discussed and a hardware implementation of the line clipping algorithm is presented and finally formulated and tested using Field Programmable Gate Arrays (FPGA). The designed hardware unit consists of two parts : the first is positional code generator unit and the second is the clipping unit. Finally it is worth mentioning that the designed unit is capable of clipping (232524 ) line segments per second. Keywords: Clipping, Graphical Pipeline, Real time, FPGA.

Minimizing the Moisture Damage and Drain down of Iraqi SMA Mixtures Using Waste Additives

Ayman Talib Hameed; Ali Al-Hadidy

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 68-80

This research deals with the viability of using polyester fiber (PF), crumb rubber tire (CRT) and cellulose fiber (CF) as stabilizing waste additives in producing Iraqi SMA mixtures that sustain drain down phenomenon and moisture damage sensitivity. Different ratios of these additives (0.1, 0.2, and 0.3% by weight of aggregate and filler) were mixed with 40/50 paving asphalt by means of dry process. Unmodified and modified SMA mixtures were subjected to drain down, Marshall, static indirect tensile strength, tensile stiffness modulus, static compressive strength, tensile strength ratio and index of retained strength tests. A set of regression equations between these tests were established. In addition, an optimization table based on these tests, which can be used to select the type or amount of additive for any field applications has been determined and reported. The results indicated that the inclusion of these additives in SMA mixtures can satisfy the performance requirement of high temperature and much rain zone.Keywords: Additives; Stone matrix asphalt; Waste materials; Scrap tires; Optimization.

Design Of A Doherty Power Amplifier For GSM Systems

Saad Wasmi Osman Luhaib

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 61-67

This paper presents the design and analysis of Doherty power amplifier. The Doherty amplifier is used in a base station for mobile system because of its high efficiency. The class AB power amplifier used in the configuration of the main and auxiliary amplifier. The result obtained shows that the Doherty power amplifier can be used on a wide band spectrum, the amplifier works at 900MHz and has very good power added efficiency (PAE) and gain. The amplifier can also work at 1800MHz at input power greater than 20dBm.

Effect Of Climatic Conditions On DurabilityOf Clayey Soil Stabilized With Lime

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 1-15

يعد تثبيت التربة من الأمور المهمة، إلا انه من الأمور الأهم معرفة ديمومة التربة المثبتة. ونظراً لعدم وجود مواصفات خاصة لدراسة ديمومة الترب المثبتة بالنورة، عليه تم اقتراح عدة فحوصات لمعرفة ديمومة تربة طينية مأخوذة من إحدى مناطق مدينة الموصل ومثبتة بنسبة (5%) نورة باعتبارها النسبة المثلى لهذه التربة بأخذ دورات مختلفة ومتعاقبة من (الترطيب أو الغمر، تجفيف أو ذوبان وانجماد). أظهرت الدراسة أن كل من الغمر أو التجميد يقلل من مقاومة الانضغاط غير المحصور للتربة، في حين بينت نتائج فحص التقشر للتربة المعاملة بنسب نورة مختلفة زيادة في مقاومة التربة للتقشر مع زيادة نسبة النورة المضافة. كما بينت الدراسة تردي خصائص التربة الهندسية (قوة تحمل، الفقدان بالوزن والتغير ألحجمي) للنماذج المعرضة لثلاثة ظروف بيئية (انجماد، تجفيف وترطيب) أكثر من تلك المعرضة لظرفين فقط، وان الظرف الأول للدورة له التأثير الأكبر في ديمومة التربة بالنسبة للنماذج المعرضة لظرفين إضافةً إلى الظرف الذي يليه بالنسبة للنماذج المعرضة لثلاثة ظروف وان لكل ظرف من ظروف الديمومة له تأثير يختلف عن الأخر سلباً أو ايجاباً (نوعاً ومقداراً) وهذا له أهمية كبيرة من الناحية العملية لتحديد توقيت بداية العمل حقلياً لتفادي مشاكل الظروف المناخية.الكلمات الدالة: التربة الطينية، التثبيت بالنورة، الديمومة، مقاومة القص، الظروف المناخية.

Using of Glass Wastes as a Fine Aggregate in Concrete Mixture

Abbas Hadi Abbas; Raed M. Abdulah; Mohammad F. Al-Deen

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 81-87

In this study, the waste glass (WG) is considered as a fine aggregate in the concrete mixture. WG is used after grinding to size according to Iraqi sand specifications No.45. The waste glass has been used instead of sand in different proportions which are 0%, 33%, 66% and 100%. The effects of WG on compressive strength of the concrete and unit weight are analysed. As results of this study, WG is determined to have a significant effect upon the reduction of its compressive strength and there is a significant decreasing of its unit weight. As for cost analysis, it was determined to lower the cost of concrete production. This study was an environmental one in consideration of the fact that WG could be used in the concrete as fine aggreagates without the need for a high cost or rigorous energy.

Effect of Static Soaking Under Different Temperatures on the Lime Stabilized Gypseous Soil

Abdulrahman H. T. Al-Zubaydi

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 42-51

This study concerns with the effect of long-term soaking on the unconfined compressive strength, loss in weight and gypsum dissolution of gypseous soil stabilized with (4%) lime, take into account the following variables: initial water content, water temperature, soaking duration. The results reveals that, the unconfined compressive strength was dropped, and the reduction in values was different according to the initial water content and water temperature, so that the reduction of the unconfined compressive strength of samples soaked in water at low temperatures (50 and 250 C) was greater than those soaked in water temperatures at (490 and 600 C). The results obtained shows that the increase in soaking period decreases the percentage amount of gypsum and loss in weight for all water temperatures and soaking durations.Key Words: Gypseous soil, Lime stabilization, Strength, Loss in weight.

Axial Dispersion and Back-mixing of Gas Phase in Pebble Bed Reactor

Dr. Rahman Shnain Abdulmohsin Al-Musafir

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 1-12

Despite the worldwide attended of pebble bed reactors (PBRs), there is a lack of fundamental understanding of the complex flow pattern. In this work, the non-ideal flow behavior of the gas phase which is used for cooling has been investigated experimentally in a 0.3 m diameter pebble bed. The extent of mixing and dispersion of the gas phase has been qualified. The effect of gas velocity on the axial dispersion has been investigated with range from 0.05 to 0.6 m/s covering both the laminar and turbulent flow regimes. Glass bead particles of 1.2 cm diameter and 2.5 gm/cm3 which is randomly and closely packed have been used to mimic the pebbles. An advanced gas tracer technique was applied to measure the residence time distribution (RTD) of gas phase using impulse tracer. The axial dispersion coefficients of gas phase in the studied pebble bed have been estimated using the axial dispersion model (ADM). It was found that the flow pattern of the gas phase deviates from plug flow depending on the superficial gas velocity. The results showed that the dispersion of the gas reduces as the gas velocity and Reynolds numbers increased. Keywords: Pebble bed; gas phase mixing, axial dispersion; packed bed; dispersion flow model

Influence Of Cement Kiln Dust As Partial Replacement On Some Properties Of Ordinary And White Portland Cement

Dr. Salah Farhan A. Sharif

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 23-32

Cement Kiln Dust (CKD) is produced as a solid waste with large quantities during manufacturing of Portland cement clinker. The possibility of utilizing CKD as partial replacement for Ordinary Portland Cement (OPC) and White Portland Cement (WPC) produced in factories of the Iraqi cement state company has been examined in this study to fulfil the environmental and economical aims. Different percentages of CKD were blended with OPC and WPC mixes. The results show that the amount of water for normal consistency were increased with about 39 % and 31 % for OPC and WPC blended with 25 % CKD. The setting time (initial and final) decreases with increasing percent of CKD added. Compressive strength decreases slightly with increasing CKD content up to 10 %. For 7- day curing time, it decreases 7 % and 9 % for OPC and WPC mixes, respectively. As percent of added CKD increases to more than 10 %, the compressive strength and other parameters where affected significantly. Overall results proved that OPC and WPC blended with up to 10 % CKD are admissible for passing relevant specification requirements.

Finite Element Analysis for Bearing Capacity of Rectangular Footing Resting Near Sloped Cohesive soil

Ayad S. Sabbar; Dr. Jawdat K. Abbas

Tikrit Journal of Engineering Sciences, Volume 18, Issue 3, Pages 33-41

Finite element method is used to investigate the ultimate bearing capacity of rectangular footing resting on cohesive soil near slope. The effect of footing aspect ratio (L/B), distance ratio (b/B), and slope angle (β) on the bearing capacity are calculated. A new reduction factor (Rs) is proposed to compute the ultimate bearing capacity for rectangular footing adjacent to slope of cohesive soil from ultimate bearing capacity for similar rectangular footing resting on ground level of cohesive soils. This study shows that the ultimate bearing capacity for rectangular footing adjacent to slope of cohesive soils decreases when slope angle (β) and aspect ratio (L/B) increases. Also the ultimate bearing capacity increases when the distance ratio (b/B) increases. Finally The effect of slope diminishes as the distance ratio (b/B) equal, or exceeds 0.75