Design of a Phase Locked Loop for a Low Power Transceiver

ope

The Synthesis and Characterization of RuII(bpy){(bpyrm)RuII(NH3)4}2](PF6)6 and [RuII(bpy)2(bpyrm)RuII(NH3)4](PF6)4

This thesis describes the synthesis of a trimetallic RuII complex [RuII(bpy){(bpyrm)RuII(NH3)4}2](PF6)6 and its bimetallic analog [RuII(bpy)2(bpyrm)RuII(NH3)4](PF6)4. The trimetallic species was designed to be the first in a series of complexes where the reduction potential of the bridging complex could be varied (relative to the terminal sites) through systematic variation in the metal (M) and/or ligand (LL) … Generation of the [RuII-MII-RuIII] mixed-valence complex would then allow observation of end-to-end intervalence charge transfer (IVCT) as a function of bridge potential. The initial bi- and trimetallic complexes were synthesized and characterized. In addition, the [2,3] and [3,2,3] mixed-valence forms of these complexes were generated and studied. However, a persistent impurity, originating from a side reaction of one of the starting materials, made it difficult to generate the target [2,2,3] mixed-valence form of the trimetallic species. Rigorous attempts to purify the complexes are described in detail

Design and Development of a Digital Radio Frequency Control System for Linear Accelerators

The new control system for Radio Frequency (RF) structures at Legnaro National Laboratories (LNL) is presented in this document. LNL is one of the four national laboratories of the National Institute for Nucler Physics (INFN) and it is devoted to basic research in nuclear physics and nuclear-astrophysics, together with applications of nuclear technologies. The subject of this Ph.D. thesis is indeed the development of a fully digital RF feedback system, focusing on the validation of the RF controller, its programming and its integration in the particle accelerator control system. The RF controller interacts directly with the cavities and it works in a real-time closed loop. It is a set of analog and digital electronics which provides phase, amplitude and frequency corrections to stabilize the RF field in presence of disturbances and vibrations due to other subsystems of the accelerator. The control algorithm is implemented via a programmable device as an FPGA. This increases dramatically the flexibility and the programmability of the controller. The digital board of the RF controller can work in a wide range of the RF spectrum. It is a versatile tool, easy to adapt to 40/80/160/352 MHz resonators, thus spanning all types of cavities of the final SPES configuration. At LNL, it may be used to control RF cavities like bunchers to pulse the beam, superconducting cavities to accelerate the beam and RF quadrupoles (RFQ) to both accelerate and focus the beam. Most of them work in superconducting condition, while the other ones in normal condition. The controlling and the monitoring of the RF controller is done by the particle accelerator control system based on EPICS (Experimental Physics and Industrial Control System). It is a widely adopted software framework for control systems. EPICS is a set of tools, libraries and applications developed collaboratively and used worldwide to create distributed soft real-time control systems for scientific instruments such as particle accelerators. Beam transport was carried out with the 8 cavities working in superconducting mode with the new instruments. The controller kept locked the cavities for few days. In this time the controller has proven to be more stable and reliable than the precedent system. The first chapter of the document introduces the SPES and ALPI facility and the RF subsystem to a certain level of details: RF acceleration concepts and Low Level RF (LLRF) control for an optimum energy gain of the particle beam. In order to better understand the issues faced during the design of the control system it is useful to derive mathematical models of the RF cavities. This is the subject of the second chapter. In the third chapter the disturbance sources of the accelerating field are listed, besides clarifying the stability requirements, the frequency tuning of the cavities and their driving modes. Furthermore, the choice of the frequency sampling is outlined. The fourth chapter introduces the controller in detail. The boards functionalities are highlighted, the fundamental elements of the boards are described as well as the communication between components and boards. The fifth, sixth and seventh chapters describe the main contribution of this Ph.D. thesis. The firmware development for the Field Programmable Field Array, that is the heart of the RF controller, is covered in chapter five, emphasizing the module for the communication with the accelerator control system and the module that implements the control algorithms. The sixth chapter gives an overview of the EPICS framework, focusing on the driver support, the integration of the RF controller with the EPICS based control system is further expanded while in the last section the RF cavity tuning is explained. The seventh chapter is split in two sections. The first section lists the tests performed in order to qualify the boards of the RF controller. The second section analyzes some key parameters acquired during a successful beam test in real working conditions, where the performance of the new controller has been evaluated. Finally, a concluding chapter summarizes the results obtained so far and outlines improvements and future upgrades that can implement new functionalities in the Radio Frequency control system

Additives incorporated into urea to reduce nitrogen losses after application to the soil.

The objective of this work was to develop urea-based fertilizers with internal incorporation of urease inhibitors and other additives in the granule. The effects of the incorporation of NBPT, copper (Cu+2), boric acid (H3BO3), elemental sulphur (Sº), and a clay mineral from the zeolite group in powder urea - with ten different combinations of these additives - were evaluated as to N losses by volatilization and leaching. The losses in laboratory-developed formulations were compared with those of commercial fertilizers coated with the same additives (Super N, FH Nitro Mais, and FH Nitro Gold). The evaluations were made in greenhouse conditions, using a Ultisol accommodated in PVC columns. Nitrate and ammonium leaching was evaluated in the solution percolated through the soil columns. Ammonia volatilization was measured with a semi-open static chamber. The incorporation of urease inhibitors (NBPT, H3BO3, and Cu+2) into the urea granules was efficient to reduce N volatilization. Ammonia volatilization in the laboratory-developed ureas was lower than in commercial fertilizers coated with the same additives, while ammonium sulfate losses by leaching were similar. The addition of zeolite does not reduce N volatilization. Mineral N leaching in the soil profile is not affected by urease inhibitors.Título em português: Aditivos incorporados à ureia para reduzir perdas de nitrogênio após aplicação ao solo

Cover crop species and mycorrhizal colonization on soil phosphorus dynamics

Phosphorus (P) plays an important role in the physiological plant processes; however, in tropical soils, P is one of the most limiting nutrients for crop yield due to its low mobility, determined by the adsorption of this element to the soil. To enhance P-use and P-acquisition efficiency, this research aimed to evaluate the effect of cover crops and mycorrhizal colonization on changing soil P fractions, both organic and inorganic. A complete randomized block design was adopted in a field experiment, with four replications using four cover crops: i) pigeon pea (Cajanus cajan); ii) crotalaria (Crotalaria juncea); iii) millet (Pennisetum glaucum); iv) brachiaria (Brachiaria ruziziensis) and v) fallow, as control. The arbuscular mycorrhizal fungus colonization, the fungal spore density, soil P fractionation, and N, P, and K uptake were assessed. Our results show that cover crops affected the soil P cycling in deeper soil layers. Cover crops may increase arbuscular mycorrhizal inoculum potential for the succeeding crop in rotation or intercropping, when used as a green manure.El fósforo (P) juega un papel importante en los procesos fisiológicos de las plantas; sin embargo, en suelos tropicales, el P es uno de los nutrientes más limitantes para el rendimiento de los cultivos debido a su baja movilidad, determinada por la adsorción de este elemento al suelo. Para mejorar la eficiencia de uso y adquisición de P, esta investigación tuvo como objetivo evaluar el efecto de los cultivos de cobertura y la colonización de micorrizas en el cambio de las fracciones de P del suelo, tanto orgánicas como inorgánicas. Se adoptó un diseño de bloques completos al azar en un experimento de campo, con cuatro repeticiones utilizando cuatro cultivos de cobertura: i) guandú (Cajanus cajan); ii) crotalaria (Crotalaria juncea); iii) mijo (Pennisetum glaucum); iv) brachiaria (Brachiaria ruziziensis) yv) barbecho, como testigo. Se evaluó la colonización de hongos micorrízicos arbusculares, la densidad de esporas fúngicas, el fraccionamiento de P del suelo y la absorción de N, P y K. Nuestros resultados muestran que los cultivos de cobertura afectaron el ciclo del P del suelo en las capas más profundas del suelo. Los cultivos de cobertura pueden aumentar el potencial de inóculo de micorrizas arbusculares para el cultivo siguiente en rotación o cultivos intercalados, cuando se utilizan como abono verde