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Article
Consolidation Characteristics of Unsaturated Soil
خصائص الانضمام في الترب غير المشبعة

Authors: Firas J. Kadhim --- Mohammed Y. Fattah
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2009 Volume: 27 Issue: 10 Pages: 2027-2046
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

The most common three-phase problem in porous media is the flow of air and water. This is for example found in the unsaturated zone, where water infiltrates through partly saturated pores to the groundwater. Liquid flow in the unsaturated zone is controlled by a combination of gravitational, capillary, and viscous forces. The mechanical behaviour of partially saturated soils can be very different from that of fully saturated soils. It has long been established that for such soils, changes in suction do not have the same effect as changes in the applied stresses, and consequently the effective stress principle is not applicable. Conventional constitutive models, which are based on this principle, are therefore of limited use when analyzinggeotechnical problems that involve the presence of partially saturated soil zones. In this paper, Al-Mdaina trial embankment was the problem analysed. The finite element programs SIGMA/W and SEEP/W were used, and eight noded isoparametric quadrilateral elements were used for modelling both the soil skeleton and pore water pressure. Parametric study was carried out and different parameters were changed to find their effects on the behaviour of partially saturated soil. Theparameters include the modulus of elasticity and permeability of the soil. It was concluded that the effect of modulus of elasticity on the behaviour of unsaturated soil is apparent at early stages of consolidation and diminishes when the time proceeds. When the clay layer consists of soft clay (Esoil <10000 kN/m2), the effect of unsaturated soil is apparent, while the effect of the modulus of elasticity diminishes when the soil is stiff.

المسالة ثلاثية الطور الأكثر شيوعا في الأوساط المسامية هي جريان الهواء والماء. وهذا على سبيل المثال يوجد في المناطق غير المشبعة، عندما ينفذ الماء خلال مسامات مشبعة جزئيا إلى الماء الأرضي. جريان السائل في المنطقة غير المشبعة يسيطر عليه بواسطة علاقة مركبة من قوى الجاذبية والخاصية الشعرية وقوى اللزوجة. يمكن أن يكون السلوك الميكانيكي للترب المشبعة جزئيا مختلفا جدا عن سلوك الترب المشبعة كليا. لقد ثبت منذ زمن طويل انه لمثل هذه الترب لا يكون التغير في الامتصاص له نفس تأثير التغير في الإجهاد المسلط، وكنتيجة لذلك فان مبدأ الجهاد الفعال لا يكون قابلا للتطبيق. لذلكتكون العلاقات التكوينية التقليدية والتي تستند على هذا المبدأ محدودة الاستخدام عند تحليل المسائل الجيوتكنيكية المتضمنة وجود مناطق تربة مشبعة جزئيا. في هذا البحث تم تحليل مسألة سدة المدينة التجريبية. استخدم برنامجا العناصر المحددة وتم استخدام عناصر رباعية الأضلاع بثماني عقد لتمثيل هيكل ،( SEEP/W) و ( SIGMA/W) التربة و ضغط ماء المسام. أجريت دراسة معاملات و غيرت قيم معاملات متعددة لإيجاد تأثير هذه و معامل (E) العوامل على سلوك التربة المشبعة جزئيا.و تتضمن هذه العوامل معامل مرونة التربة .(k) النفاذية توصل البحث إلى أن تأثير معامل المرونة على سلوك التربة غير المشبعة يظهر في المراحل الأولى من عملية الانضمام ويتلاشى مع تقدم الزمن. وعندما تتكون طبقة التربة من طين رخو يكون تأثيره واضح في التربة غير المشبعة بينما يتلاشى هذا التأثير عندما تكون التربة قوية


Article
Structural Characteristics of Nickel Ferrite Nanoparticles Synthesized by New Arrangement of Concentric Targets in DC Reactive Magnetron Sputtering

Authors: Firas J. Kadhim --- Ruaa A. Mohammed
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2016 Volume: 12 Issue: 4 Pages: 9-12
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

Nickel ferrite (NiFe2O4) nanostructures were synthesized by co-sputtering of Ni and Fe targets in presence of oxygen. A dc plasma sputtering system employing closed-field unbalanced magnetron at the anode was used for the preparation of these films. The structural characteristics of the prepared films were determined and the results showed that these films are polycrystalline, highly pure, with average particle size of 20-25nm and average surface roughness of 0.465nm. These nickel ferrite nanostructures were prepared at low production cost, high reliability and reasonable structural purity.


Article
Effect of Adding Nitrogen to the Gas Mixture on Plasma Characteristics of a Closed-Field Unbalanced DC Magnetron Sputtering System

Authors: Firas J. Kadhim --- Mohammed K. Khalaf --- Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2014 Volume: 10 Issue: 1 Pages: 27-31
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, the role of adding nitrogen gas to the discharge gas mixture containing argon was studied by introducing the electrical characteristics of plasma generated between two closed-field unbalanced magnetron electrodes. This role was also related to the presence and absence of magnetron at the electrodes in the fundamental design of such sputtering system. The role of nitrogen gas added to the gas mixture was reasonably observed by enhancing the electrical characteristics of the glow discharge plasma generated between the dual CFUBM electrodes. Adding nitrogen caused to increase the concentration of the charged particles produced by collisional ionization in discharge volume as the mean free path of primary discharge electrons was reduced. A relative reduction in electron temperature was observed as a result of adding nitrogen with increase in electron and ion densities while no observed difference was observed in the ion temperature due to their larger masses compared to those of electrons.


Article
Current-Voltage Characteristics of DC Plasma Discharges Employed in Sputtering Techniques
خصائص تيار-جهد لتفريغ البلازما المستمر المستخدم في تقنيات الترذيذ

Authors: Mohammed K. Khalaf --- Oday A. Hammadi --- Firas J. Kadhim
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2016 Volume: 12 Issue: 3 Pages: 11-16
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, the current-voltage characteristics of dc plasma discharges were studied. The current-voltage characteristics of argon gas discharge at different inter-electrode distances and working pressure of 0.7mbar without magnetrons were introduced. Then the variation of discharge current with inter-electrode distance at certain discharge voltages without using magnetron was determined. The current-voltage characteristics of discharge plasma at inter-electrode distance of 4cm without magnetron, with only one magnetron and with dual magnetrons were also determined. The variation of discharge current with inter-electrode distance at certain discharge voltage (400V) for the cases without magnetron, using one magnetron and dual magnetrons were studied. Finally, the discharge current-voltage characteristics for different argon/nitrogen mixtures at total gas pressure of 0.7mbar and inter-electrode distance of 4cm were presented.


Article
Structural Properties of Nickel Oxide Nanostructures Prepared by Closed-Field Unbalanced Dual Magnetron Sputtering Technique

Authors: Firas J. Kadhim --- Oday A. Hammadi --- Mohammed K. Khalaf
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2017 Volume: 13 Issue: 2 Pages: 3-10
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, nickel oxide nanostructures were prepared by a closed-field unbalanced dual magnetron plasma sputtering technique. The structural characterizations performed on the prepared samples showed that they were polycrystalline and the optimization of preparation conditions, only two crystal planes; (111) and (012), were observed in the final product. The surface roughness of the nanostructures can be varied by controlling the inter-electrode distance. Minimum particle size of 25nm was determined for the samples prepared at inter-electrode distance of 6cm.


Article
Preparation and Characterization of Silicon Nitride Nanostructures Prepared by DC Reactive Sputtering Technique with Novel Design of Closed-Field Unbalanced Dual Magnetron Assembly

Authors: Firas J. Kadhim --- Mohammed K. Khalaf --- Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2017 Volume: 13 Issue: 3 Pages: 3-12
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, novel design of closed-field unbalanced dual magnetrons system was employed in a DC reactive sputtering system to prepare silicon nitride nanostructures. Two types of silicon wafers (n- and p-type) were sputtered in presence of nitrogen gas to deposit nanostructured silicon nitride thin films on glass substrates. The prepared nanostructured were polycrystalline with six dominant crystal planes: (101), (110), (200), (232), (301) and (321). The surface roughness of the sample prepared at inter-electrode distance of 4cm was higher than other samples prepared at smaller or larger distances and the average and R.M.S roughness were 0.777 and 1.03 nm, respectively. The nanoparticles of minimum size of 30nm were formed and recognized as individual accumulated particles. Two bands of significant absorption were observed around 960 and 1086 cm-1, those are attributed to the Si-N-Si vibration mode in Si3N4 molecule. An absorption peak was observed at 389nm, which is attributed to the quantum size effect of nanostructures. The refractive index of the prepared Si3N4 samples was determined to be 1.38-2.1 and the energy band gap was ranging in 5.1-5.2 eV. The energy band gap was found to increase with decreasing thickness of the prepared film. The wide energy band gap of Si3N4 nanostructures makes them good candidate, as similar as AlN, BN and GaN, for power electronics and optoelectronics operating at high temperatures.


Article
Key Mechanisms of Low-Pressure Glow Discharge in Magnetized Plasmas
الاليات الاساسية للتفريغ التوهجي ذي الضغط الواطيء في البلازما الممغنطة

Authors: Oday A. Hammadi --- Mohammed K. Khalaf --- Firas J. Kadhim --- Bahaa T. Chiad
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2016 Volume: 12 Issue: 3 Pages: 3-10
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this article, the key mechanisms of glow discharge in low-pressure gas mixtures were presented and discussed. The particle motions – mainly collisions – in discharge plasma those considered in most applications of plasma were presented. The regions of glow discharge were identified and their main characteristics were highlighted. These mechanisms were supported by experimental results obtained from a homemade dc plasma sputtering system. The experimental parameters, such as inter-electrode distance, using magnetrons and adding nitrogen to the gas mixture, and their effects on the Paschen’s curve of glow discharge were introduced.


Article
Langmuir Probe Diagnostics of Low-Pressure Glow Discharge Plasma Using Argon-Nitrogen Mixtures
التشخيص باستخدام مجس لانجمور لبلازما التفريغ ذي الضغط الواطئ باستخدام خلائط غازي الاركون والنتروجين

Authors: Bahaa T. Chiad --- Oday A. Hammadi --- Firas J. Kadhim --- Mohammed K. Khalaf
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2016 Volume: 12 Issue: 3 Pages: 17-26
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, experimental results on Langmuir probe diagnostics of low-pressure glow discharge plasma using argon-nitrogen mixtures are presented. The effect of variation in working pressure on the current-voltage characteristics of Langmuir probe diagnostics in unmagnetized glow-discharge plasma was introduced. The current-voltage characteristics of Langmuir probe diagnostics in glow-discharge plasma were studied at working pressure of 0.7mbar and three different cases (no magnetron, using one magnetron at the cathode, and using dual magnetrons). Similarly, the current-voltage characteristics of Langmuir probe in glow-discharge plasma at three different positions of the Langmuir probe inside plasma volume were presented. The variation of electron temperature and density in plasma with working gas pressure at the center point between the electrodes when dual magnetrons were used was determined. As well, the effect of mixing nitrogen with argon on the Langmuir probe characteristics at total working pressure of 0.7mbar and inter-electrode distance of 4cm was studied.


Article
Preparation of Highly Pure Nanostructures by Reactive DC Magnetron Sputtering Technique
تحضير تراكيب نانوية عالية النقاوة باستخدام تقنية الترذيذ التفاعلي المستمر

Authors: Firas J. Kadhim --- Oday A. Hammadi --- Mohammed K. Khalaf --- Bahaa T. Chiad
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2016 Volume: 12 Issue: 3 Pages: 27-34
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, metal oxide and nitride nanostructures were prepared by reactive dc magnetron sputtering technique. These nanostructures were synthesized from metal oxide such as NiO and nitride such as Si3N4 for functional materials applications. The prepared nanostructures were diagnosed by x-ray diffraction (XRD) patterns and Fourier-transform infrared (FTIR) spectroscopy. The results showed that the prepared nanostructures are highly pure, which is ascribed to the featured characteristics of magnetron sputtering technique for such purposes.


Article
A study of the solvent effect on the low temperature spectra of benzoanthracene molecules
دراسة تاثير المذيب على اطياف درجات الحرارة الواطئة لجزيئات البنزوانثراسين

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Abstract

Low temperature spectroscopy of benzoanthracene solutions at fixed molar concentration has been studied. The temperature range has been taken at room temperature down to liquid nitrogen temperature (77K). Polar and nonpolar solvents have been used to study the solvent effect on the absorption and fluorescence spectra of solute molecules. Some of the spectroscopic parameters have been determined as functions of solvent polarity and temperature. The results indicate that the band width FWHM increases with increasing the solvent polarity and temperature, while the peak emission cross section decreases with increasing of solvent polarity and decreases with increasing the temperatures. Clear vibrational structure spectra of benzoanthracene molecules have been observed in Nonane and Hexane solvents at 77K.

في العمل الحالي تم دراسة مطيافية درجات الحرارة الواطئة لجزيئة البنزوانثراسين المحضرة بالطور السائل عند تركيز مولاري ثابت. مديات درجات الحرارة بدات من درجة حرارة الغرفة وصولا الى درجة سائل النتروجين (77كلفن). تم استخدام عدة مذيبات قطبية وغير قطبية لتحضيرمحاليل جزيئة البنزوانثراسين لغرض دراسة تاثير المذيب على اطياف الامتصاص والفلورة لهذه الجزيئة. تم تحديد بعض المعلمات الطيفية من الاطياف المستحصلة كدالة لكل من قطبية المذيب ودرجة الحرارة. اظهرت النتائج ان عرض الحزمة عند منتصف القمة يزداد بزيادة قطبية المذيب ودرجة الحرارة بينما يقل المقطع العرضي لقمة الانبعاث مع زيادة قطبية المذيب ودرجة الحرارة. التركيب الدقيق لاطياف لجزيئات البنزوانثراسين ظهر بوضوح مع مذيب النونان والهيكسان عند 77كلفن.

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