Scenes of a fight

Panel: Note to Self: Why I Write What I Write (2

Analysis And Design Of A Modular Solar-fed Fault-tolerant Power System With Maximum Power Point Tracking

Solar power is becoming ever more popular in a variety of applications. It is particularly attractive because of its abundance, renewability, and environment friendliness. Solar powered spacecraft systems have ever-expanding loads with stringent power regulation specifications. Moreover, they require a light and compact design of their power system. These constraints make the optimization of power harvest from solar arrays a critical task. Florida Power Electronics Center (FPEC) at UCF set to develop a modular fault-tolerant power system architecture for space applications. This architecture provides a number of very attractive features including Maximum Power Point Tracking (MPPT) and uniform power stress distribution across the system. MPPT is a control technique that leads the system to operate its solar sources at the point where they provide maximum power. This point constantly moves following changes in ambient operating conditions. A digital controller is setup to locate it in real time while optimizing other operating parameters. This control scheme can increase the energy yield of the system by up to 45%, and thus significantly reduces the size and weight of the designed system. The modularity of the system makes it easy to prototype and expand. It boosts its reliability and allows on-line reconfiguration and maintenance, thus reducing down-time upon faults. This thesis targets the analysis and optimization of this architecture. A new modeling technique is introduced for MPPT in practical environments, and a novel digital power stress distribution scheme is proposed in order to properly distribute peak and thermal stress and improve reliability. A 2kW four-channel prototype of the system was built and tested. Experimental results confirm the theoretical improvements, and promise great success in the field

Libya and regional security

In theory and practice, there is a consensus that the question of regional security is becoming of great importance. This largely due to the fact that the level of international security is interlocked and heavily pending on the extent of micro-security: i.e. regional, subregional, national, local and personal. Accordingly, we will examine how Libya deals with the security issue within its regional settings. Initially, this requires throwing light on the underlying factors that heavily determine the preference and priority of which regional security arrangement to adhere. In the Libya case, there are a number of alternatives. This include: the Arab world, the Middle East, North Africa, the Arab Maghreb and the Mediterranean Region.Mesa Seguridad Internacional: La seguridad regional: estructura y coyunturaInstituto de Relaciones Internacionale

Rethinking Frantz Fanon's "On national culture" within the context of Native American and Palestinian literature

Thesis (M.A.)--University of Oklahoma, 2003.Includes bibliographical references (leaves 90-94)

Integrated Topologies And Digital Control For Satellite Power Management And Distribution Systems

This work is focused on exploring advanced solutions for space power management and distribution (PMAD) systems. As spacecraft power requirements continue to increase, paralleled by the pressures for reducing cost and overall system weight, power electronics engineers will continue to face major redesigns of the space power systems in order to meet such challenges. Front-end PMAD systems, used to interface the solar sources and battery backup to the distribution bus, need to be designed with increased efficiency, reliability, and power density. A new family of integrated single-stage power converter structures is introduced here. This family allows the interface and control of multiple power sources and storage devices in order to optimize utilization of available resources. Employing single-stage power topologies, these converters control power flow efficiently and cost-effectively. This is achieved by modifying the operation and control strategies of isolated soft-switched half-bridge and full-bridge converters--two of the most popular two-port converter topologies. These topologies are reconfigured and utilized to realize three power processing paths. These paths simultaneously utilize the power devices, allowing increased functionality while promising reduced losses and enhanced power densities. Each of the proposed topologies is capable of performing simultaneous control of two of its three ports. Control objectives include battery or ultra-capacitor charge regulation, solar array maximum power point tracking (MPPT), and/or bus voltage regulation. Another advantage of the proposed power structure is that current engineering design concepts can be used to optimize the new topologies in a fashion similar to the mother topologies. This includes component selection and magnetic design procedures, as well as achieving soft-switching for increased efficiency at higher switching frequencies. Galvanic isolation of the load port through high-frequency transformers provides design flexibility for high step-up/step-down conversion ratios. It further allows the converters to be used as power electronics building blocks (PEBB) with outputs connected in different series/parallel combinations to meet different load requirements. Utilizing such converters promises significant savings in size, weight, and costs of the power management system as well as the devices it manages. Chapter 1 of this dissertation provides an introduction to the requirements, challenges, and trends of space PMAD. A review of existing multi-port converter technologies and digital control techniques is given in Chapter 2. Chapter 3 discusses different PMAD system architectures. It outlines the basic concepts used for PMAD integration and discusses the potential for improvement. Chapters 4 and 5 present and discuss the operation and characteristics of three different integrated multi-port converters. Chapter 6 presents improved methods for practical digital control of switching converters, which are especially useful in complex multi-objective controllers used for PMAD. This is followed by conclusions and suggested future work

Libya and regional security

In theory and practice, there is a consensus that the question of regional security is becoming of great importance. This largely due to the fact that the level of international security is interlocked and heavily pending on the extent of micro-security: i.e. regional, subregional, national, local and personal. Accordingly, we will examine how Libya deals with the security issue within its regional settings. Initially, this requires throwing light on the underlying factors that heavily determine the preference and priority of which regional security arrangement to adhere. In the Libya case, there are a number of alternatives. This include: the Arab world, the Middle East, North Africa, the Arab Maghreb and the Mediterranean Region.Mesa Seguridad Internacional: La seguridad regional: estructura y coyunturaInstituto de Relaciones Internacionale

Novel Immunotherapy Targets Cathepsin G in Solid Tumors

https://openworks.mdanderson.org/sumexp21/1221/thumbnail.jp

Evaluation of newly generated LRP1 antibodies in different cell types: THP1 cancer cell line, human and mouse immune cells

https://openworks.mdanderson.org/sumexp22/1008/thumbnail.jp

Soil yeast abundance and diversity assessment in a hot climatic region, semi-arid ecosystem

ABSTRACT Background and Objectives: Yeasts are an important portion of microbial communities of soil due to their bioactivity  for ecosystem safety. Soil yeast abundance and diversity are likely to be affected under harsh environmental and climatic conditions. In Iraq, human activity and climatic changes especially high temperature which may alter microbial communities in soil. Very little is known about yeast abundance and diversity in a hot climatic region. Materials and Methods: By PCR technique, soil yeast abundance and diversity were investigated under extreme environmental and climatic conditions , as well as the effects of soil properties and vegetation cover in semi-arid lands. Results: In all, 126 yeast strains were isolated and identified as belonging to 13 genera and 26 known species. The maximum quantity of yeast was 0.8 X 102 CFU g-1 of soil, with significantly varied in abundance and diversity depending on soil properties and presence of vegetation. Conclusion: The results show that soil yeast abundance in these regions was significantly decreased. However, semi-arid lands are still rich in yeast diversity, and many species have adapted to survive in such conditions