Electrical Power

—Conquest of the space spreads with small educational projects that aim to explore the capabilities and the potentials that the mankind have. This paper concludes our experiments that led to launching the second Can-Sat form Alexandria, Egypt under affiliation of Space and Technology Program in Bibliotecha Alexandrina. Here we presents our satellite system and the communication system that connects the ground station to the flying system, as well it represents the launching procedure, and some of the problems we overboard during our project duration

Under the scenario of an underlay cognitive radio network, we propose in this paper two adaptive schemes using switched transmit diversity and adaptive modulation in order to increase the spectral efficiency of the secondary link and maintain a desired performance for the primary link. The proposed switching efficient scheme (SES) and bandwidth efficient scheme (BES) use the scan and wait combining technique (SWC) where a transmission occurs only when a branch with an acceptable performance is found, otherwise data is buffered. In these schemes, the modulation constellation size and the used transmit branch are determined to minimize the average number of switched branches and to achieve the highest spectral efficiency given the fading channel conditions, the required error rate performance, and a peak interference constraint to the primary receiver (PR). For delay-sensitive applications, we also propose two variations of the SES and BES schemes using power control (SES-PC and BES-PC) where the secondary transmitter (ST) starts sending data using a nominal power level which is selected in order to minimize the average delay introduced by the SWC technique. We demonstrate through numerical examples that the BES scheme increases the capacity of the secondary link when compared to the SES scheme. This spectral efficiency improvement comes at the expense of an increased average number of switched branches and thus an increased average delay. We also show that the SES-PC and the BES-PC schemes minimize the average delay while satisfying the same spectral efficiency as the SES and BES schemes, respectively.

Twelve-Switch Nine-Phase Inverter (TSNPI) can be used to feed three independent three-phase loads or nine-phase load such as nine-phase machines. It provides dc-ac conversion with a reduced number of switches, as only twelve switches are employed to feed the load instead of employing conventional ninephase voltage source inverter with eighteen switches. In this paper, optimum sinusoidal modulating signals are extracted to enable operating with enhanced utilization of the dc input voltage while feeding symmetrical/asymmetrical nine-phase loads. Simulation and experimental results are presented to validate the proposed approach.

Harmonics distortion is a crucial problem in microgrid. Harmonic sources can be categorized as two main factors: renewable energy integration and nonlinear loads. Both factors are investigated in this thesis. For renewbale energy, photovoltaic (PV) power is one of the most effective solutions for energy crisis and it is showing great potential for serving customers in microgrid. A three phase PV source model is established from both mathematical equations and power electronic control schemes. A composite load model by Crossed Frequency Admittance Matrix theory is illustrated and built as well. Due to the fact that microgrid should be able to run under two different operating modes: gridconnected and stand-alone, energy storage devices are considered as neccesity. Therefore the energy storage with droop control is included in this thesis. A practicdal microgrid loacated at GA, USA is used as a study system. Instead of making the ideal assumption, the unbalanced feeder structure and historical meteorological data are considered in the study. The microgrid, PV model, nonlinear load model and energy storage are simulated in MATLAB/Simulink environment. Multiple PV sources are integrated at different locations in order to observe the impact of harmonics on the microgrid and power quality (PQ). The results show the impact of installing PV sources in both grid-connected mode and stand-alone mode considering linear and composite nonlinear loads. In addition, three PQ indices are discussed to demonstrate the numerical impacts with various perspectives. Furthermore, the mitgation of harmonics is developed by adding a active power filter on energy storage devices in the stand-alone mode.

Seeds of Pisum sativum and Vicia faba were pre-soaked in either 1.0, 2.0 or 4.0 mM of sodium azide (NaN3) for 30 min, 1 h or 2 hs then, sown in clay soil in plastic pots under conditions of 25/18°C day/night and natural light (16/8 h day/night) and the seedlings were harvested after 21 days. The results revealed that total phenols, H2O2, malondialdehyde and the activities of catalase, peroxidase and DPPH scavenging activity in both plant were gradually increased with the increase in NaN3 concentration and soaking time. The isozymes of α- and β- esterases and α-amylase had number of loci ranged from two (α-amylase) to four (α-esterase) in pea, while in bean, it was three for the three investigated enzymes. The ISSR analysis revealed that both plants showed highly significant increase in the appearance of bands by the highest treatment of NaN3, especially with the longest duration. Pea produced 14 polymorphic, 9 monomorphic and 4 unique bands, while bean produced 14 polymorphic, 8 mon...