البحث — المستودع الرقمي العراقي

المستخلص: Widespread wireless communications system in the last few years, leads people to ask many questions about the advantages and disadvantages of those systems, especially about electromagnetic waves pollution and their effect on human health.The mobile device is frequently used by the general public from adult to child, one of the main sources of electromagnetic waves and very close to the human head. Therefore the focus of this research on the impact of electromagnetic waves from mobile to human health by measuring the Specific Absorption Rate (SAR), at the human head and the hand through SEMCAD - X that uses the Finite Different Time Domain (FDTD). SAR computation uses (FDTD) in the way the limited space of time, to calculate the specific absorption rate. The results have been compared with standards averaged over any 1 g of tissue and averaged over any 10 g of tissue. It didn't exceed the applicable standard.This work evaluates specific absorption rate (SAR) at different ages of three people. Firstly, old man, who was estimated to head 100% size of header used in the program SEMCAD - X. Secondly Adult man was estimated his head by 85% size of header used in program, and finally the child who was estimated his head by 65% size of header used in the program SEMCAD - X, the design hand has been used with all cases.The design of the mobile phone software works in four different packages of frequencies; the packets are the center frequencies 900MHz 1800MHz, 2100MHz and 2400MHz, when increased frequency the SAR increased but in the some state and frequency decreasing.The Evaluation of SAR in the head and the hand of the user device and the generic phone, the highest value of SAR decreases with increasing distance between the generic phone and the user's head and reducing the proportion was 50% for the old man, 40% for adult man and 35% for child. It can be noted that the angle of the rotation of the various frequencies is not fixed, while the ratio approximately is 25% for each angle of rotation.Also, it can be noted that for fixed frequency, the input power is increased to a double and the SAR have been used increased almost to a double.The different positions show that the methods of holding generic phone have a significant impact on the value of SAR. Therefore, the value of SAR can be reduced into 90% when using the correct method.The evaluation of SAR in these cases shows their influence on children and it was much greater than the adult human or old human by parentage 40% old man and 35% adult man.

تمييز الحروف العربية المعزولة المكتوبة بخط اليد باستخدام الشبكات العصبية Recognition Of Isolated Handwritten Arabic Letters Using Neural Networks

اسم المؤلف: نهلة ظاهر حبيب بهية

اسم المشرف: منذر نعمان التكريتي

الموضوع العام: هندسة الكهرباء والالكترون والاتصالات

السنة: 2004

الموضوع الدقيق: هندسة الكهرباء

الدرجة: ماجستير

الجامعة: الجامعة المستنصرية - كلية الهندسة - قسم الهندسة الكهربائية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

استراتيجية السيطرة على المقوم ثلاثي الاطوار المضمن بعرض النبضة (PWM) نوع رافع للجهد ولمصدر تغذية متغير الحالات

اسم المؤلف: منتظر كاظم عبد الله

اسم المشرف: تركي كحيوش حسن

الموضوع العام: هندسة الكهرباء والالكترون والاتصالات

السنة: 2014

الموضوع الدقيق: هندسة الكهرباء

الدرجة: ماجستير

الجامعة: الجامعة المستنصرية - كلية الهندسة - قسم الهندسة الكهربائية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: In this thesis, a proposed control strategy is presented to improve the performance of the PWM boost type rectifier when operating under different supply voltage conditions (balanced, unbalanced, and distorted three - phase supply voltages). The proposed control strategy is classified into two parts, the first part is voltage controller and the second part is current controller. In the voltage controller, Repetitive Controller (RC) is used to reduce the even order harmonics in the regulated output dc voltage (5.62V (P.P.)) so small output capacitor (480µF) is used instead of large capacitor (920µF) that is used with the conventional controller (PI controller connected in series with a LPF). RC also reduces the even order harmonics (0.014A (P.P)) which appears in the reflected dc current (IMAX), this leads to reduce the odd order harmonics (0.01A) which appears in the input currents. While in the current controller, enhanced Phase Locked Loop (EPLL) technique is used to obtain sinusoidal and balanced three phases, to construct the reference currents, which are in phase with the fundamental supply voltages Therefore, the supply - side power factor is kept close to unity (0.9036 for extremely distorting case). As a result the calculations of the reference currents in the proposed control strategy does not require Clarke or Park transformations, the same for the calculations of the positive or negative sequence components. A proportional controller is used to give excellent tracking between the line and the reference currents. Using this approach makes the control strategy easy to understand and also it saves calculation time of the control algorithms if implements in real time. The complete system with the proposed control strategy is simulated using Matlab/Simulink (Version 2012). The obtained results for the complete system using repetitive voltage controller are compared to the results of the system with using the conventional voltage controller. The results with the repetitive controller show better responses and stable operation in the steady state under different input voltage conditions, as well as in the transient response under different disturbances.

مبدل فوتوفولطائي مايكروي احادي المرحلة نوع فلايباك المغذي للشبكة Single Stage Grid - Connected Flyback Photovoltaic Microinverter

اسم المؤلف: مصطفى عباس فضل

اسم المشرف: تركي كحیوش حسن

الموضوع العام: هندسة الكهرباء والالكترون والاتصالات

السنة: 2016

الموضوع الدقيق: هندسة الكهرباء - قدرة ومكائن

الدرجة: ماجستير

الجامعة: الجامعة المستنصرية - كلية الهندسة - قسم الهندسة الكهربائية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى: