A Solar Cell Based Coarse Sun Sensor for a Small LEO Satellite Attitude Determination

Zahran, Mohamed,Aly, Mohamed The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.4

The sun is a useful reference direction because of its brightness relative to other astronomical objects and its relatively small apparent radius as viewed by spacecrafts near the Earth. Most satellites use solar power as a source of energy, and so need to make sure that solar panels are oriented correctly with respect to the sun. Also, some satellites have sensitive instruments that must not be exposed to direct sunlight. For all these reasons, sun sensors are important components in spacecraft attitude determination and control systems. To minimize components and structural mass, some components have multiple purposes. The solar cells will provide power and also be used as coarse sun sensors. A coarse Sun sensor is a low-cost attitude determination sensor suitable for a wide range of space missions. The sensor measures the sun angle in two orthogonal axes. The Sun sensor measures the sun angle in both azimuth and elevation. This paper presents the development of a model to determine the attitude of a small cube-shaped satellite in space relative to the sun's direction. This sensor helps small cube-shaped Pico satellites to perform accurate attitude determination without requiring additional hardware.

Design, Implementation and Testing of HF transformers for Satellite EPS Applications

Zahran, Mohamed The Korean Institute of Power Electronics 2008 JOURNAL OF POWER ELECTRONICS Vol.8 No.3

The electric power subsystems (EPS) of most remote sensing satellites consist of a solar array as a source of energy, a storage battery, a power management and control (PMC) unit and a charge equalization unit (CEU) for the storage battery. The PMC and CEU use high frequency transformers in their power modules. This paper presents a design, implementation and testing results of a high frequency transformer for the EPS of satellite applications. Two approaches are used in the design process of the transformer based on the pre-determined transformer specifications. The transformer is designed based on an ETD 29 ferrite core. The implemented transformer consists of one center-tapped primary coil with eleven center-tapped secondary coils. The offline calculation results and measured values of R, L for transformer coils are convergence. A test circuit for measuring the transformer parameters like voltage, current and B-H hysteresis was implemented and applied. The test results confirm that the voltage waveforms of both primary and secondary coils were as desired. No overlapping occurred between the control signal and the transformer, which was not saturated during testing even during a short circuit test of the secondary channels. The dynamic B-H loop characteristics of the used transformer cores were measured. The sample test results are given in this paper.

Design and Implementation of a Digital Control Unit for an Oxygenaire Servo Baby Incubator

Zahran, Mohamed,Salem, Mahmoud,Attia, Yousry,Eliwa, Aref The Korean Institute of Power Electronics 2008 JOURNAL OF POWER ELECTRONICS Vol.8 No.2

This paper introduces a design and implementation of a digital control unit for an Oxygenaire Servo Baby Incubator. The control unit is designed and implemented according to international standards. The control unit is based on an AVR Atmel microcontroller unit. It is built for monitoring and control and displays the three main temperature values: set point temperature, baby skin temperature and air temperature. User friendly software is implemented. The implemented control unit was tested in the laboratory as well as in the field. The control unit is sensitive to change of $0.1^{\circ}C$. At startup, based on a unique control strategy, the incubator reaches its steady state in about 14 minutes. The system schematic diagrams are shown in the paper. Also, programs flow charts are presented. The control unit was designed and implemented based on a contract between the Electronics Research Institute (ERI) and ENGIMED Company. The authors would like to thank ERI and ENGIMED for introducing all required finance and shoring to complete this work.

Photovoltaic Hybrid Systems Reliability and Availability

Mohamed B.A. Zahran 전력전자학회 2003 JOURNAL OF POWER ELECTRONICS Vol.3 No.3

Reliability, availability, and cost have been the major concerns for photovoltaic hybrid systems since their beginning as primary sources for much critical applications like communication units and repeaters. This paper descnbes the performance of two hybrid systems, photovoltaic-battery, wind-turbine coupled with the public-grid (PVBWG) hybrid system and photovoltaic-battery, wind-turbine coupled With the diesel generator (PVBWD) hybrid system The systems are sized to power a typical 300W/48V de telecommunication load continuously throughout the year Such hybrid systems consist of subsystems, which in turn consist of components Failure of anyone of these components may cause failure of the entire system. The reliability and availability basics, and estimation procedure for the two proposals are introduced also in this paper. The PVBWG and PVBWD system configurations are shown with the relevant mean-time-between-faIlure (MTBF) and failure rate (λ) of each component. The characteristics equations of the two systems are deduced as a function of operating hours and the percentage of sun and wind availabilities per day. The system probability failure as well as the reliability is estimated based on the fault tree analysis technique. The results show that, by using standard or normal components MTBF, the PVBWG is more reliable and the time of periodic maintenance period is more than one year especially in the rich sites of both sun and wind, but PVBWD competes else Also, in the first five years from the system installation, the system is quit reliable and may not require any maintenance. The results show also, as the sun and wind are available, as the system reliable and available

A Solar Cell Based Coarse Sun Sensor for a Small LEO Satellite Attitude Determination

Mohamed Zahran,Mohamed Aly 전력전자학회 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.4

The sun is a useful reference direction because of its brightness relative to other astronomical objects and its relatively small apparent radius as viewed by spacecrafts near the Earth. Most satellites use solar power as a source of energy, and so need to make sure that solar panels are oriented correctly with respect to the sun. Also, some satellites have sensitive instruments that must not be exposed to direct sunlight. For all these reasons, sun sensors are important components in spacecraft attitude determination and control systems. To minimize components and structural mass, some components have multiple purposes. The solar cells will provide power and also be used as coarse sun sensors. A coarse Sun sensor is a low-cost attitude determination sensor suitable for a wide range of space missions. The sensor measures the sun angle in two orthogonal axes. The Sun sensor measures the sun angle in both azimuth and elevation. This paper presents the development of a model to determine the attitude of a small cube-shaped satellite in space relative to the sun’s direction. This sensor helps small cube-shaped Pico satellites to perform accurate attitude determination without requiring additional hardware [1].

Photovoltaic Hybrid Systems Reliability and Availability

Zahran, Mohamed B.A. The Korean Institute of Power Electronics 2003 JOURNAL OF POWER ELECTRONICS Vol.3 No.3

Reliability, availability, and cost have been the major concerns for photovoltaic hybrid systems since their beginning as primary sources for much critical applications like communication units and repeaters. This paper descnbes the performance of two hybrid systems, photovoltaic-battery, wind-turbine coupled with the public-grid (PVBWG) hybrid system and photovoltaic-battery, wind-turbine coupled With the diesel generator (PVBWD) hybrid system The systems are sized to power a typical 300W/48V de telecommunication load continuously throughout the year Such hybrid systems consist of subsystems, which in turn consist of components Failure of anyone of these components may cause failure of the entire system. The reliability and availability basics, and estimation procedure for the two proposals are introduced also in this paper. The PVBWG and PVBWD system configurations are shown with the relevant mean-time-between-faIlure (MTBF) and failure rate (${\lambda}$) of each component. The characteristics equations of the two systems are deduced as a function of operating hours and the percentage of sun and wind availabilities per day. The system probability failure as well as the reliability is estimated based on the fault tree analysis technique. The results show that, by using standard or normal components MTBF, the PVBWG is more reliable and the time of periodic maintenance period is more than one year especially in the rich sites of both sun and wind, but PVBWD competes else Also, in the first five years from the system installation, the system is quit reliable and may not require any maintenance. The results show also, as the sun and wind are available, as the system reliable and available.

Design, Implementation and Testing of HF transformers for Satellite EPS Applications

Mohamed Zahran 전력전자학회 2008 JOURNAL OF POWER ELECTRONICS Vol.8 No.3

The electric power subsystems (EPS) of most remote sensing satellites consist of a solar array as a source of energy, a storage battery, a power management and control (PMC) unit and a charge equalization unit (CEU) for the storage battery. The PMC and CEU use high frequency transformers in their power modules. This paper presents a design, implementation and testing results of a high frequency transformer for the EPS of satellite applications. Two approaches are used in the design process of the transformer based on the pre-determined transformer specifications. The transformer is designed based on an ETD 29 ferrite core. The implemented transformer consists of one center-tapped primary coil with eleven center-tapped secondary coils. The offline calculation results and measured values of R, L for transformer coils are convergence. A test circuit for measuring the transformer parameters like voltage, current and B-H hysteresis was implemented and applied. The test results confirm that the voltage waveforms of both primary and secondary coils were as desired. No overlapping occurred between the control signal and the transformer, which was not saturated during testing even during a short circuit test of the secondary channels. The dynamic B-H loop characteristics of the used transformer cores were measured. The sample test results are given in this paper.

Design and Implementation of a Digital Control Unit for an Oxygenaire Servo Baby Incubator

Mohamed Zahran,Mahmoud Salem,Yousry Attia,Aref Eliwa 전력전자학회 2008 JOURNAL OF POWER ELECTRONICS Vol.8 No.2

This paper introduces a design and implementation of a digital control unit for an Oxygenaire Servo Baby Incubator. The control unit is designed and implemented according to international standards. The control unit is based on an AVR Atmel microcontroller unit. It is built for monitoring and control and displays the three main temperature values: set point temperature, baby skin temperature and air temperature. User friendly software is implemented. The implemented control unit was tested in the laboratory as well as in the field. The control unit is sensitive to change of 0.1OC. At startup, based on a unique control strategy, the incubator reaches its steady state in about 14 minutes. The system schematic diagrams are shown in the paper. Also, programs flow charts are presented. The control unit was designed and implemented based on a contract between the Electronics Research Institute (ERI) and ENGIMED Company. The authors would like to thank ERI and ENGIMED for introducing all required finance and shoring to complete this work.

Decomposition of fuzzy ideal continuity via fuzzy idealization

Zahran, Ahmed M.,El-Baki, S. Ahmed Abd,Saber, Yaser Mohammed Korean Institute of Intelligent Systems 2009 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.9 No.2

Recently, El-Naschie has shown that the notion of fuzzy topology may be relevant to quantum paretical physics in connection with string theory and E-infinity space time theory. In this paper, we study the concepts of r-fuzzy semi-I-open, r-fuzzy pre-I-open, r-fuzzy $\alpha$-I-open and r-fuzzy $\beta$-I-open sets, which is properly placed between r-fuzzy openness and r-fuzzy $\alpha$-I-openness (r-fuzzy pre-I-openness) sets regardless the fuzzy ideal topological space in Sostak sense. Moreover, we give a decomposition of fuzzy continuity, fuzzy ideal continuity and fuzzy ideal $\alpha$-continuity, and obtain several characterization and some properties of these functions. Also, we investigate their relationship with other types of function.

Histological and Physiological Studies of the Effect of Bone Marrow-Derived Mesenchymal Stem Cells on Bleomycin Induced Lung Fibrosis in Adult Albino Rats

Zakaria Dina Mohamed,Zahran Noha Mahmoud,Arafa Samia Abdel Aziz,Mehanna Radwa Ali,Abdel-Moneim Rehab Ahmed 한국조직공학과 재생의학회 2021 조직공학과 재생의학 Vol.18 No.1

Background: Lung fibrosis is considered as an end stage for many lung diseases including lung inflammatory disease, autoimmune diseases and malignancy. There are limited therapeutic options with bad prognostic outcome. The aim of this study was to explore the effect of mesenchymal stem cells (MSCs) derived from bone marrow on Bleomycin (BLM) induced lung fibrosis in albino rats. Methods: 30 adult female albino rats were distributed randomly into 4 groups; negative control group, Bleomycin induced lung fibrosis group, lung fibrosis treated with bone marrow-MSCs (BM-MSCs) and lung fibrosis treated with cell free media. Lung fibrosis was induced with a single dose of intratracheal instillation of BLM. BM-MSCs or cell free media were injected intravenously 28 days after induction and rats were sacrificed after another 28 days for assessment. Minute respiratory volume (MRV), forced vital capacity (FVC) and forced expiratory volume 1 (FEV1) were recorded using spirometer (Power lab data acquisition system). Histological assessment was performed by light microscopic examination of H&E, and Masson’s trichrome stained sections and was further supported by morphometric studies. In addition, electron microscopic examination to assess ultra-structural changes was done. Confocal Laser microscopy and PCR were used as tools to ensure MSCs homing in the lung. Results: Induction of lung fibrosis was confirmed by histological examination, which revealed disorganized lung architecture, thickened inter-alveolar septa due excessive collagen deposition together with inflammatory cellular infiltration. Moreover, pneumocytes depicted variable degenerative changes. Reduction in MRV, FVC and FEV1 were recorded. BM-MSCs treatment showed marked structural improvement with minimal cellular infiltration and collagen deposition and hence restored lung architecture, together with lung functions. Conclusion: MSCs are promising potential therapy for lung fibrosis that could restore the normal structure and function of BLM induced lung fibrosis. Background: Lung fibrosis is considered as an end stage for many lung diseases including lung inflammatory disease, autoimmune diseases and malignancy. There are limited therapeutic options with bad prognostic outcome. The aim of this study was to explore the effect of mesenchymal stem cells (MSCs) derived from bone marrow on Bleomycin (BLM) induced lung fibrosis in albino rats. Methods: 30 adult female albino rats were distributed randomly into 4 groups; negative control group, Bleomycin induced lung fibrosis group, lung fibrosis treated with bone marrow-MSCs (BM-MSCs) and lung fibrosis treated with cell free media. Lung fibrosis was induced with a single dose of intratracheal instillation of BLM. BM-MSCs or cell free media were injected intravenously 28 days after induction and rats were sacrificed after another 28 days for assessment. Minute respiratory volume (MRV), forced vital capacity (FVC) and forced expiratory volume 1 (FEV1) were recorded using spirometer (Power lab data acquisition system). Histological assessment was performed by light microscopic examination of H&E, and Masson’s trichrome stained sections and was further supported by morphometric studies. In addition, electron microscopic examination to assess ultra-structural changes was done. Confocal Laser microscopy and PCR were used as tools to ensure MSCs homing in the lung. Results: Induction of lung fibrosis was confirmed by histological examination, which revealed disorganized lung architecture, thickened inter-alveolar septa due excessive collagen deposition together with inflammatory cellular infiltration. Moreover, pneumocytes depicted variable degenerative changes. Reduction in MRV, FVC and FEV1 were recorded. BM-MSCs treatment showed marked structural improvement with minimal cellular infiltration and collagen deposition and hence restored lung architecture, together with lung functions. Conclusion: MSCs are promising potential therapy for lung fibrosis that could restore the normal structure and function of BLM induced lung fibrosis.