Abstract The search for a reliable source of energy has been a challanging task to manking while conventional energy resorces are diminishing nuclear fusion, especially laser fusion, promises to be the source of the future. Experimental costs in laser fusion are astronomical and computer modeling drastically minimizes such costs and gives a chance for less fortunate Gauntries to gain insight into the scientific and technical aspects of the subject since a large portion of information involved is classified. This work deals with the spatial and temporal evolution of the laser fusion produced by different laser pulses It is based on a computer code called MEDUSA which takes into account the variation in the wavelength, power density pulse duration, target geometry and material. It assumes a target which is divided into 20 cells each of 24 urn width. Inverse-Bremsstrahlung and resonance absorption are the two main mechanisms responsible for absorption of energy from the incident laser pulse. Fusion takes place in the plasma as a result of ablation of the plasma corona where the formed shock waves compress the plasma cells and heat them. The rate of energy deposited into and radiated from the plasma ,which causes variation of the plasma internal energy, is expressed by the energy equation. This equation is transformed into a finite difference form and solved by Gauss Elimination Method to calculate the plasma parameters such as electron(T e) and ion ternperatures(Ti), pressure(P) and density(p) and the different processes of energy absorption and losses. The temporal evolution of these parameters is studied through the divisions of the pulse into chosen time steps at which the evolution is clear. The results have shown that by increasing laser power the energy deposited into and radiated from the plasma increases. The electron and ion temperatures the plasma pressure and density also increase. This is because of the geadual propagation of the shock wave from the surface of the pellet towards its center causing compression of the plasma cells. The optimum value of such parameters are obtained close to the end of the pulse where the incident laser power is maximum and so as the energy deposited into the plasma center where heating and compression causes the consumption of the whole target After the end of the pulse duration, the plasma cells coordinates expand and the plasma parameters decrease, a process known as diminishing of the plasma The effect of the laser parameters of four diffterent lasers namely CO2, KrF, Nd-glass and Ruby of 5ns, 15ns and 45ns pulse duration was studied. It was found that: (1) the maximum value of the plasma parameters decrease by increasing the pulse duration of a certain power and wavelength, (2) the maximum value of the plasma parameters increase by increasing the wavelength because of increasing the energy deposited into the plasma by resonance absorption process. At the optimum implosion time, the plasma parameters show a strong spatial variation. However, a strong temporal variation of the plasma parameters was observed at the pellet center.
هناء محمد حسن موسي (1994)

في هذا العمل قمنا بدراسة منظومة عناصر المجموعة الثانية (Be, Mg, Ca, Sr, Ba) باستخدام نظرية دالة الدالة للكثافة (DFT)، حيث تعتبر (DFT)من أهم النظريات التي ظهرت خلال العقود القليلة الماضية, وأثبتت نجاحها في اغلب الانظمة الفيزيائية. لقد أثبتت هذه النظرية أن خواص النظام الفيزيائية في حالته الأرضية دالة وحيدة فقط في كثافته الإلكترونية، وفي مقدمتها الخواص الكهربية، كما أن لعناصر المجموعة الثانية أهمية كبيرة في مجال العلوم والتكنولوجيا وتطبيقات عديدة في الصناعات الإستراتيجية المختلفة، وعليه فقد كانت مجال هده الدراسة. إن هدفين تم تحقيقهما في هده الدراسة: اختبار لنظرية دالة الدالة للكثافة (DFT) في الأنظمة المعقدة نسبيا، ودراسة عناصر المجموعة الثانية لأهميتها الصناعية والتقنية. تم تصميم نموذج نظري للكثافة الإلكترونية للعناصر المعدنية في الحالة المفردة (معدن واحد) والمزدوجة (الثنائيات المعدنية) سواء كانت متشابهة أو مختلفة، هذا النموذج في صورة دالة رياضية تصف ما يحدث للكثافة الإلكترونية وبالتالي الشحنة الكهربية الكلية في كل الفضاء الذي يشغله النظام استناداً إلى نموذج جيليوم. لقد حقق هذا النموذج كل الشروط اللازمة للتعبير عن النظام بما في ذلك الحدودية منها ويتوافق مع ما يحدث للأسطح البينية المعدنية بسبب التشابه أو الاختلاف وكذلك المسافة الفاصلة بينهما (2d)، واستجاب أيضا للعمليات التحليلية والحسابية العددية, بكفاءة عالية فقد تم حساب الكثافة الإلكترونية كدالة في المسافة العموديةعلى المستوياتفقط بسبب تماثل الشحنة الكهربية فيها, بالإضافة إلى ذلك فقد تم التوصل إلى صيغ للمجال الكهربي و الجهد الكهربي وكذلك طاقة النظام الكلية وبالتالي إلى حسابها.أظهرت نتائج هذه الحسابات دقة هذا النموذج وقدرته على التكيف مع ظروف النظام، وتميزه عن غيره من النماذج بأنه يعتمد على متغير واحد فقط وهو نصف قطر الحيز الذي يشغله الإلكترون في كل عنصر (rs) و كذلك صلاحيته لكل العناصر المعدنية بغض النظر عن المجموعة التي تنتمي لها. وبصفة عامة كانت نتائج حسابات الكثافة الالكترونية، كثافة الشحنة الكهربية، المجال الكهربي والجهد الكهربي متفقه مع الدراسات السابقة كمياً في حدود بينما كانت أكثر دقة من حيث الكيف، بإظهارها لتذبذبات فريدل والتسرب الميكانيكي الكمي للإلكترونات بوضوح، عليه أثبتت هذه الدراسة نجاح نظرية (DFT) بقوة في مثل هذه الأنظمة وأكدت أهمية استخدام عناصر المجموعة الثانية في مجالات العلوم والتكنولوجيا. Abstract In this work, we have studied Group IIA elements (Be, Mg, Ca, Sr, Ba) by using Density Functional Theory (DFT). DFT is the most important theories appeared during the near past decades, this theory proved clearly that the physical properties of the system in its ground state are a unique function of its electronic density, such as electric properties. The second group elements are of great importance in science and technology fields, it has many applications in various strategic industries, so it was the field of this study. Two goals have been defined for research in this study, first goal is to test DFT in these relative complex systems, and the second, is to provide important information on Group IIA elements, for its applications in science, industry and technology.Theoretical model of the electronic density has been designed of the metallic elements in a single case (One metal) and double case (Bimetallic), whether similar or different interfaces, mathematically this model is a function depends on some parameters, describing the electronic density for the whole space occupied and surrounding by the system and hence the total charge density based on the Julliem strategy. This model satisfied all necessary conditions and described the system perfectly, including, boundary conditions, and the electronic density profiles for both similar and different inter-metal surfaces and its interspacing (2d). It responded analytically, as well as numerically, to the computational processes with high efficiency. The electronic density for all suggested systems was calculated as a function of distance (z) only due to charge symmetry in (xy) planes. In additional to that, the electric field, electrostatic potential and the total energy formulas has been derived and calculated. Our results showed a high degree of accuracy and ability of this model, also its adaptation to the different conditions of the system. This model was distinguished from any other previous models by its dependency on only one variable, which defined for each element (rs), and its suitability for all metallic elements regardless of the group to which they belong. In general the results of the calculations of electronic and charge density, electric field and electric potential are agreed with previous studies quantitatively within while it was higher accuracy qualitatively; by showing clearly Friedl oscillations and the quantum mechanical leakage of electrons .However, this study strongly proves the success of DFT in such systems and confirmed the importance use of the second group elements in the science and technology fields.
أمنية موسى أحمد عليان (2009)

Abstract Laser surface treatment of materials is one of the most effective methods of improving properties and performance of metallic articles. This technique proved its capabilities and advantages in comparison with other methods of surface treatment As an example, it has been shown that the distortion caused by this type of treament is at least one order of magnitude smaller than by that due to other techniques. Moreeover, laser beam is capable of reaching practically any point of the surface whatever it is narrow or difficult to reach by other techniques. The current work investigates the possibility of improving certain mechanical properties of both technically pure aluminum and A1-4o/oSi alloy, using ruby laser of 3 xl 05 W/cm2 power density. The surface of the investigated materials has been impregnated by SiC particles of varying size ranges, with or without firrther alloying of the surface with Titanium powder addition to the impregnated mixture. The laser treatment included coating one surface of each specimen of SiC particles by means of a binder added at a certain ratio (with or without Ti additions to the mixture). The coated surface was then subjected to the laser beam, which melted a layer I OO-150Jilll thick. Due to hydrodynamic effects the melt mixes with SiC particles and dissolves some or all of the added Ti and rapidly solidifies forming a thin layer distinct in properties from the original surface. Two groups of specimens were used in this study. The first group was treated by impregnating SiC particles of one size range with or without Ti-additions. Various numbers of laser pulses have been applied increasmg in a geometrical progression (1-2-4-8 pulses). These specimens were used for the study of the effect of varying: 1) the chemical composition of the substrate materials ;2) the number of laser pulses :and 3) the effect of Ti additions to the impregnating mixture on the microstracture and microhardness of the treated zones. The specimens of the 2nd group were coated by a square network of laser treated zones each 1.5mm in diameter. These specimens have been used to study :1) the effect of the chemical composition of the substrate material ;2) the size of the SiC particles and 3) the effect of Ti addition to the mixture on the wear perfomance of the treated specimens. Identical specimens have been used to determine the solubility of Si into the aluminum phase during the test by means of x-ray diffraction. This dissolved Si is partly responsible for the increase ID microhardness and wear resistance of the investigated specimens. The results show the positive effect of the applied treatment on the properties and preformence of technically pure AI and A-4%Si alloy. The materials microhardness within the treated zones has been increased by a factor of 2.7 and 2.4 for pure Al and Al-4%Si substrates, respectively. The microstructure of the treated zones became more homogeneous and the penetration of SiC particles into them has been increased with increasing the number of the applied laser pulses. The wear resistance of pure Al has been increased by a factor of 73.6 due to laser assisted impregnation, while that of AI-4%Si by afactor of 42.5. Wear resistance was found to increase with I) Si addition to the base metal; 2) Ti addition to the impregnated mixture, and 3) increasing the SiC particle size. This thesis is a part of a wider study that deals with surface treatment of Al and AI-Si alloys undertaken in our laboratry. Such study proved how effective the laser alloying and impregnation of such alloys in improving some of their mechanical properties which are important in industrial application, especially in internal combustion engine design.
أسماء عبد الرزاق وهرة (2002)